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Linux/kernel/sched/core.c

  1 /*
  2  *  kernel/sched/core.c
  3  *
  4  *  Kernel scheduler and related syscalls
  5  *
  6  *  Copyright (C) 1991-2002  Linus Torvalds
  7  *
  8  *  1996-12-23  Modified by Dave Grothe to fix bugs in semaphores and
  9  *              make semaphores SMP safe
 10  *  1998-11-19  Implemented schedule_timeout() and related stuff
 11  *              by Andrea Arcangeli
 12  *  2002-01-04  New ultra-scalable O(1) scheduler by Ingo Molnar:
 13  *              hybrid priority-list and round-robin design with
 14  *              an array-switch method of distributing timeslices
 15  *              and per-CPU runqueues.  Cleanups and useful suggestions
 16  *              by Davide Libenzi, preemptible kernel bits by Robert Love.
 17  *  2003-09-03  Interactivity tuning by Con Kolivas.
 18  *  2004-04-02  Scheduler domains code by Nick Piggin
 19  *  2007-04-15  Work begun on replacing all interactivity tuning with a
 20  *              fair scheduling design by Con Kolivas.
 21  *  2007-05-05  Load balancing (smp-nice) and other improvements
 22  *              by Peter Williams
 23  *  2007-05-06  Interactivity improvements to CFS by Mike Galbraith
 24  *  2007-07-01  Group scheduling enhancements by Srivatsa Vaddagiri
 25  *  2007-11-29  RT balancing improvements by Steven Rostedt, Gregory Haskins,
 26  *              Thomas Gleixner, Mike Kravetz
 27  */
 28 
 29 #include <linux/kasan.h>
 30 #include <linux/mm.h>
 31 #include <linux/module.h>
 32 #include <linux/nmi.h>
 33 #include <linux/init.h>
 34 #include <linux/uaccess.h>
 35 #include <linux/highmem.h>
 36 #include <linux/mmu_context.h>
 37 #include <linux/interrupt.h>
 38 #include <linux/capability.h>
 39 #include <linux/completion.h>
 40 #include <linux/kernel_stat.h>
 41 #include <linux/debug_locks.h>
 42 #include <linux/perf_event.h>
 43 #include <linux/security.h>
 44 #include <linux/notifier.h>
 45 #include <linux/profile.h>
 46 #include <linux/freezer.h>
 47 #include <linux/vmalloc.h>
 48 #include <linux/blkdev.h>
 49 #include <linux/delay.h>
 50 #include <linux/pid_namespace.h>
 51 #include <linux/smp.h>
 52 #include <linux/threads.h>
 53 #include <linux/timer.h>
 54 #include <linux/rcupdate.h>
 55 #include <linux/cpu.h>
 56 #include <linux/cpuset.h>
 57 #include <linux/percpu.h>
 58 #include <linux/proc_fs.h>
 59 #include <linux/seq_file.h>
 60 #include <linux/sysctl.h>
 61 #include <linux/syscalls.h>
 62 #include <linux/times.h>
 63 #include <linux/tsacct_kern.h>
 64 #include <linux/kprobes.h>
 65 #include <linux/delayacct.h>
 66 #include <linux/unistd.h>
 67 #include <linux/pagemap.h>
 68 #include <linux/hrtimer.h>
 69 #include <linux/tick.h>
 70 #include <linux/ctype.h>
 71 #include <linux/ftrace.h>
 72 #include <linux/slab.h>
 73 #include <linux/init_task.h>
 74 #include <linux/context_tracking.h>
 75 #include <linux/compiler.h>
 76 #include <linux/frame.h>
 77 #include <linux/prefetch.h>
 78 
 79 #include <asm/switch_to.h>
 80 #include <asm/tlb.h>
 81 #include <asm/irq_regs.h>
 82 #include <asm/mutex.h>
 83 #ifdef CONFIG_PARAVIRT
 84 #include <asm/paravirt.h>
 85 #endif
 86 
 87 #include "sched.h"
 88 #include "../workqueue_internal.h"
 89 #include "../smpboot.h"
 90 
 91 #define CREATE_TRACE_POINTS
 92 #include <trace/events/sched.h>
 93 
 94 DEFINE_MUTEX(sched_domains_mutex);
 95 DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
 96 
 97 static void update_rq_clock_task(struct rq *rq, s64 delta);
 98 
 99 void update_rq_clock(struct rq *rq)
100 {
101         s64 delta;
102 
103         lockdep_assert_held(&rq->lock);
104 
105         if (rq->clock_skip_update & RQCF_ACT_SKIP)
106                 return;
107 
108         delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
109         if (delta < 0)
110                 return;
111         rq->clock += delta;
112         update_rq_clock_task(rq, delta);
113 }
114 
115 /*
116  * Debugging: various feature bits
117  */
118 
119 #define SCHED_FEAT(name, enabled)       \
120         (1UL << __SCHED_FEAT_##name) * enabled |
121 
122 const_debug unsigned int sysctl_sched_features =
123 #include "features.h"
124         0;
125 
126 #undef SCHED_FEAT
127 
128 /*
129  * Number of tasks to iterate in a single balance run.
130  * Limited because this is done with IRQs disabled.
131  */
132 const_debug unsigned int sysctl_sched_nr_migrate = 32;
133 
134 /*
135  * period over which we average the RT time consumption, measured
136  * in ms.
137  *
138  * default: 1s
139  */
140 const_debug unsigned int sysctl_sched_time_avg = MSEC_PER_SEC;
141 
142 /*
143  * period over which we measure -rt task cpu usage in us.
144  * default: 1s
145  */
146 unsigned int sysctl_sched_rt_period = 1000000;
147 
148 __read_mostly int scheduler_running;
149 
150 /*
151  * part of the period that we allow rt tasks to run in us.
152  * default: 0.95s
153  */
154 int sysctl_sched_rt_runtime = 950000;
155 
156 /* cpus with isolated domains */
157 cpumask_var_t cpu_isolated_map;
158 
159 /*
160  * this_rq_lock - lock this runqueue and disable interrupts.
161  */
162 static struct rq *this_rq_lock(void)
163         __acquires(rq->lock)
164 {
165         struct rq *rq;
166 
167         local_irq_disable();
168         rq = this_rq();
169         raw_spin_lock(&rq->lock);
170 
171         return rq;
172 }
173 
174 /*
175  * __task_rq_lock - lock the rq @p resides on.
176  */
177 struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf)
178         __acquires(rq->lock)
179 {
180         struct rq *rq;
181 
182         lockdep_assert_held(&p->pi_lock);
183 
184         for (;;) {
185                 rq = task_rq(p);
186                 raw_spin_lock(&rq->lock);
187                 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
188                         rf->cookie = lockdep_pin_lock(&rq->lock);
189                         return rq;
190                 }
191                 raw_spin_unlock(&rq->lock);
192 
193                 while (unlikely(task_on_rq_migrating(p)))
194                         cpu_relax();
195         }
196 }
197 
198 /*
199  * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
200  */
201 struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
202         __acquires(p->pi_lock)
203         __acquires(rq->lock)
204 {
205         struct rq *rq;
206 
207         for (;;) {
208                 raw_spin_lock_irqsave(&p->pi_lock, rf->flags);
209                 rq = task_rq(p);
210                 raw_spin_lock(&rq->lock);
211                 /*
212                  *      move_queued_task()              task_rq_lock()
213                  *
214                  *      ACQUIRE (rq->lock)
215                  *      [S] ->on_rq = MIGRATING         [L] rq = task_rq()
216                  *      WMB (__set_task_cpu())          ACQUIRE (rq->lock);
217                  *      [S] ->cpu = new_cpu             [L] task_rq()
218                  *                                      [L] ->on_rq
219                  *      RELEASE (rq->lock)
220                  *
221                  * If we observe the old cpu in task_rq_lock, the acquire of
222                  * the old rq->lock will fully serialize against the stores.
223                  *
224                  * If we observe the new cpu in task_rq_lock, the acquire will
225                  * pair with the WMB to ensure we must then also see migrating.
226                  */
227                 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
228                         rf->cookie = lockdep_pin_lock(&rq->lock);
229                         return rq;
230                 }
231                 raw_spin_unlock(&rq->lock);
232                 raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags);
233 
234                 while (unlikely(task_on_rq_migrating(p)))
235                         cpu_relax();
236         }
237 }
238 
239 #ifdef CONFIG_SCHED_HRTICK
240 /*
241  * Use HR-timers to deliver accurate preemption points.
242  */
243 
244 static void hrtick_clear(struct rq *rq)
245 {
246         if (hrtimer_active(&rq->hrtick_timer))
247                 hrtimer_cancel(&rq->hrtick_timer);
248 }
249 
250 /*
251  * High-resolution timer tick.
252  * Runs from hardirq context with interrupts disabled.
253  */
254 static enum hrtimer_restart hrtick(struct hrtimer *timer)
255 {
256         struct rq *rq = container_of(timer, struct rq, hrtick_timer);
257 
258         WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
259 
260         raw_spin_lock(&rq->lock);
261         update_rq_clock(rq);
262         rq->curr->sched_class->task_tick(rq, rq->curr, 1);
263         raw_spin_unlock(&rq->lock);
264 
265         return HRTIMER_NORESTART;
266 }
267 
268 #ifdef CONFIG_SMP
269 
270 static void __hrtick_restart(struct rq *rq)
271 {
272         struct hrtimer *timer = &rq->hrtick_timer;
273 
274         hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED);
275 }
276 
277 /*
278  * called from hardirq (IPI) context
279  */
280 static void __hrtick_start(void *arg)
281 {
282         struct rq *rq = arg;
283 
284         raw_spin_lock(&rq->lock);
285         __hrtick_restart(rq);
286         rq->hrtick_csd_pending = 0;
287         raw_spin_unlock(&rq->lock);
288 }
289 
290 /*
291  * Called to set the hrtick timer state.
292  *
293  * called with rq->lock held and irqs disabled
294  */
295 void hrtick_start(struct rq *rq, u64 delay)
296 {
297         struct hrtimer *timer = &rq->hrtick_timer;
298         ktime_t time;
299         s64 delta;
300 
301         /*
302          * Don't schedule slices shorter than 10000ns, that just
303          * doesn't make sense and can cause timer DoS.
304          */
305         delta = max_t(s64, delay, 10000LL);
306         time = ktime_add_ns(timer->base->get_time(), delta);
307 
308         hrtimer_set_expires(timer, time);
309 
310         if (rq == this_rq()) {
311                 __hrtick_restart(rq);
312         } else if (!rq->hrtick_csd_pending) {
313                 smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd);
314                 rq->hrtick_csd_pending = 1;
315         }
316 }
317 
318 #else
319 /*
320  * Called to set the hrtick timer state.
321  *
322  * called with rq->lock held and irqs disabled
323  */
324 void hrtick_start(struct rq *rq, u64 delay)
325 {
326         /*
327          * Don't schedule slices shorter than 10000ns, that just
328          * doesn't make sense. Rely on vruntime for fairness.
329          */
330         delay = max_t(u64, delay, 10000LL);
331         hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay),
332                       HRTIMER_MODE_REL_PINNED);
333 }
334 #endif /* CONFIG_SMP */
335 
336 static void init_rq_hrtick(struct rq *rq)
337 {
338 #ifdef CONFIG_SMP
339         rq->hrtick_csd_pending = 0;
340 
341         rq->hrtick_csd.flags = 0;
342         rq->hrtick_csd.func = __hrtick_start;
343         rq->hrtick_csd.info = rq;
344 #endif
345 
346         hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
347         rq->hrtick_timer.function = hrtick;
348 }
349 #else   /* CONFIG_SCHED_HRTICK */
350 static inline void hrtick_clear(struct rq *rq)
351 {
352 }
353 
354 static inline void init_rq_hrtick(struct rq *rq)
355 {
356 }
357 #endif  /* CONFIG_SCHED_HRTICK */
358 
359 /*
360  * cmpxchg based fetch_or, macro so it works for different integer types
361  */
362 #define fetch_or(ptr, mask)                                             \
363         ({                                                              \
364                 typeof(ptr) _ptr = (ptr);                               \
365                 typeof(mask) _mask = (mask);                            \
366                 typeof(*_ptr) _old, _val = *_ptr;                       \
367                                                                         \
368                 for (;;) {                                              \
369                         _old = cmpxchg(_ptr, _val, _val | _mask);       \
370                         if (_old == _val)                               \
371                                 break;                                  \
372                         _val = _old;                                    \
373                 }                                                       \
374         _old;                                                           \
375 })
376 
377 #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
378 /*
379  * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
380  * this avoids any races wrt polling state changes and thereby avoids
381  * spurious IPIs.
382  */
383 static bool set_nr_and_not_polling(struct task_struct *p)
384 {
385         struct thread_info *ti = task_thread_info(p);
386         return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG);
387 }
388 
389 /*
390  * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
391  *
392  * If this returns true, then the idle task promises to call
393  * sched_ttwu_pending() and reschedule soon.
394  */
395 static bool set_nr_if_polling(struct task_struct *p)
396 {
397         struct thread_info *ti = task_thread_info(p);
398         typeof(ti->flags) old, val = READ_ONCE(ti->flags);
399 
400         for (;;) {
401                 if (!(val & _TIF_POLLING_NRFLAG))
402                         return false;
403                 if (val & _TIF_NEED_RESCHED)
404                         return true;
405                 old = cmpxchg(&ti->flags, val, val | _TIF_NEED_RESCHED);
406                 if (old == val)
407                         break;
408                 val = old;
409         }
410         return true;
411 }
412 
413 #else
414 static bool set_nr_and_not_polling(struct task_struct *p)
415 {
416         set_tsk_need_resched(p);
417         return true;
418 }
419 
420 #ifdef CONFIG_SMP
421 static bool set_nr_if_polling(struct task_struct *p)
422 {
423         return false;
424 }
425 #endif
426 #endif
427 
428 void wake_q_add(struct wake_q_head *head, struct task_struct *task)
429 {
430         struct wake_q_node *node = &task->wake_q;
431 
432         /*
433          * Atomically grab the task, if ->wake_q is !nil already it means
434          * its already queued (either by us or someone else) and will get the
435          * wakeup due to that.
436          *
437          * This cmpxchg() implies a full barrier, which pairs with the write
438          * barrier implied by the wakeup in wake_up_q().
439          */
440         if (cmpxchg(&node->next, NULL, WAKE_Q_TAIL))
441                 return;
442 
443         get_task_struct(task);
444 
445         /*
446          * The head is context local, there can be no concurrency.
447          */
448         *head->lastp = node;
449         head->lastp = &node->next;
450 }
451 
452 void wake_up_q(struct wake_q_head *head)
453 {
454         struct wake_q_node *node = head->first;
455 
456         while (node != WAKE_Q_TAIL) {
457                 struct task_struct *task;
458 
459                 task = container_of(node, struct task_struct, wake_q);
460                 BUG_ON(!task);
461                 /* task can safely be re-inserted now */
462                 node = node->next;
463                 task->wake_q.next = NULL;
464 
465                 /*
466                  * wake_up_process() implies a wmb() to pair with the queueing
467                  * in wake_q_add() so as not to miss wakeups.
468                  */
469                 wake_up_process(task);
470                 put_task_struct(task);
471         }
472 }
473 
474 /*
475  * resched_curr - mark rq's current task 'to be rescheduled now'.
476  *
477  * On UP this means the setting of the need_resched flag, on SMP it
478  * might also involve a cross-CPU call to trigger the scheduler on
479  * the target CPU.
480  */
481 void resched_curr(struct rq *rq)
482 {
483         struct task_struct *curr = rq->curr;
484         int cpu;
485 
486         lockdep_assert_held(&rq->lock);
487 
488         if (test_tsk_need_resched(curr))
489                 return;
490 
491         cpu = cpu_of(rq);
492 
493         if (cpu == smp_processor_id()) {
494                 set_tsk_need_resched(curr);
495                 set_preempt_need_resched();
496                 return;
497         }
498 
499         if (set_nr_and_not_polling(curr))
500                 smp_send_reschedule(cpu);
501         else
502                 trace_sched_wake_idle_without_ipi(cpu);
503 }
504 
505 void resched_cpu(int cpu)
506 {
507         struct rq *rq = cpu_rq(cpu);
508         unsigned long flags;
509 
510         if (!raw_spin_trylock_irqsave(&rq->lock, flags))
511                 return;
512         resched_curr(rq);
513         raw_spin_unlock_irqrestore(&rq->lock, flags);
514 }
515 
516 #ifdef CONFIG_SMP
517 #ifdef CONFIG_NO_HZ_COMMON
518 /*
519  * In the semi idle case, use the nearest busy cpu for migrating timers
520  * from an idle cpu.  This is good for power-savings.
521  *
522  * We don't do similar optimization for completely idle system, as
523  * selecting an idle cpu will add more delays to the timers than intended
524  * (as that cpu's timer base may not be uptodate wrt jiffies etc).
525  */
526 int get_nohz_timer_target(void)
527 {
528         int i, cpu = smp_processor_id();
529         struct sched_domain *sd;
530 
531         if (!idle_cpu(cpu) && is_housekeeping_cpu(cpu))
532                 return cpu;
533 
534         rcu_read_lock();
535         for_each_domain(cpu, sd) {
536                 for_each_cpu(i, sched_domain_span(sd)) {
537                         if (cpu == i)
538                                 continue;
539 
540                         if (!idle_cpu(i) && is_housekeeping_cpu(i)) {
541                                 cpu = i;
542                                 goto unlock;
543                         }
544                 }
545         }
546 
547         if (!is_housekeeping_cpu(cpu))
548                 cpu = housekeeping_any_cpu();
549 unlock:
550         rcu_read_unlock();
551         return cpu;
552 }
553 /*
554  * When add_timer_on() enqueues a timer into the timer wheel of an
555  * idle CPU then this timer might expire before the next timer event
556  * which is scheduled to wake up that CPU. In case of a completely
557  * idle system the next event might even be infinite time into the
558  * future. wake_up_idle_cpu() ensures that the CPU is woken up and
559  * leaves the inner idle loop so the newly added timer is taken into
560  * account when the CPU goes back to idle and evaluates the timer
561  * wheel for the next timer event.
562  */
563 static void wake_up_idle_cpu(int cpu)
564 {
565         struct rq *rq = cpu_rq(cpu);
566 
567         if (cpu == smp_processor_id())
568                 return;
569 
570         if (set_nr_and_not_polling(rq->idle))
571                 smp_send_reschedule(cpu);
572         else
573                 trace_sched_wake_idle_without_ipi(cpu);
574 }
575 
576 static bool wake_up_full_nohz_cpu(int cpu)
577 {
578         /*
579          * We just need the target to call irq_exit() and re-evaluate
580          * the next tick. The nohz full kick at least implies that.
581          * If needed we can still optimize that later with an
582          * empty IRQ.
583          */
584         if (cpu_is_offline(cpu))
585                 return true;  /* Don't try to wake offline CPUs. */
586         if (tick_nohz_full_cpu(cpu)) {
587                 if (cpu != smp_processor_id() ||
588                     tick_nohz_tick_stopped())
589                         tick_nohz_full_kick_cpu(cpu);
590                 return true;
591         }
592 
593         return false;
594 }
595 
596 /*
597  * Wake up the specified CPU.  If the CPU is going offline, it is the
598  * caller's responsibility to deal with the lost wakeup, for example,
599  * by hooking into the CPU_DEAD notifier like timers and hrtimers do.
600  */
601 void wake_up_nohz_cpu(int cpu)
602 {
603         if (!wake_up_full_nohz_cpu(cpu))
604                 wake_up_idle_cpu(cpu);
605 }
606 
607 static inline bool got_nohz_idle_kick(void)
608 {
609         int cpu = smp_processor_id();
610 
611         if (!test_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu)))
612                 return false;
613 
614         if (idle_cpu(cpu) && !need_resched())
615                 return true;
616 
617         /*
618          * We can't run Idle Load Balance on this CPU for this time so we
619          * cancel it and clear NOHZ_BALANCE_KICK
620          */
621         clear_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu));
622         return false;
623 }
624 
625 #else /* CONFIG_NO_HZ_COMMON */
626 
627 static inline bool got_nohz_idle_kick(void)
628 {
629         return false;
630 }
631 
632 #endif /* CONFIG_NO_HZ_COMMON */
633 
634 #ifdef CONFIG_NO_HZ_FULL
635 bool sched_can_stop_tick(struct rq *rq)
636 {
637         int fifo_nr_running;
638 
639         /* Deadline tasks, even if single, need the tick */
640         if (rq->dl.dl_nr_running)
641                 return false;
642 
643         /*
644          * If there are more than one RR tasks, we need the tick to effect the
645          * actual RR behaviour.
646          */
647         if (rq->rt.rr_nr_running) {
648                 if (rq->rt.rr_nr_running == 1)
649                         return true;
650                 else
651                         return false;
652         }
653 
654         /*
655          * If there's no RR tasks, but FIFO tasks, we can skip the tick, no
656          * forced preemption between FIFO tasks.
657          */
658         fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running;
659         if (fifo_nr_running)
660                 return true;
661 
662         /*
663          * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left;
664          * if there's more than one we need the tick for involuntary
665          * preemption.
666          */
667         if (rq->nr_running > 1)
668                 return false;
669 
670         return true;
671 }
672 #endif /* CONFIG_NO_HZ_FULL */
673 
674 void sched_avg_update(struct rq *rq)
675 {
676         s64 period = sched_avg_period();
677 
678         while ((s64)(rq_clock(rq) - rq->age_stamp) > period) {
679                 /*
680                  * Inline assembly required to prevent the compiler
681                  * optimising this loop into a divmod call.
682                  * See __iter_div_u64_rem() for another example of this.
683                  */
684                 asm("" : "+rm" (rq->age_stamp));
685                 rq->age_stamp += period;
686                 rq->rt_avg /= 2;
687         }
688 }
689 
690 #endif /* CONFIG_SMP */
691 
692 #if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
693                         (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))
694 /*
695  * Iterate task_group tree rooted at *from, calling @down when first entering a
696  * node and @up when leaving it for the final time.
697  *
698  * Caller must hold rcu_lock or sufficient equivalent.
699  */
700 int walk_tg_tree_from(struct task_group *from,
701                              tg_visitor down, tg_visitor up, void *data)
702 {
703         struct task_group *parent, *child;
704         int ret;
705 
706         parent = from;
707 
708 down:
709         ret = (*down)(parent, data);
710         if (ret)
711                 goto out;
712         list_for_each_entry_rcu(child, &parent->children, siblings) {
713                 parent = child;
714                 goto down;
715 
716 up:
717                 continue;
718         }
719         ret = (*up)(parent, data);
720         if (ret || parent == from)
721                 goto out;
722 
723         child = parent;
724         parent = parent->parent;
725         if (parent)
726                 goto up;
727 out:
728         return ret;
729 }
730 
731 int tg_nop(struct task_group *tg, void *data)
732 {
733         return 0;
734 }
735 #endif
736 
737 static void set_load_weight(struct task_struct *p)
738 {
739         int prio = p->static_prio - MAX_RT_PRIO;
740         struct load_weight *load = &p->se.load;
741 
742         /*
743          * SCHED_IDLE tasks get minimal weight:
744          */
745         if (idle_policy(p->policy)) {
746                 load->weight = scale_load(WEIGHT_IDLEPRIO);
747                 load->inv_weight = WMULT_IDLEPRIO;
748                 return;
749         }
750 
751         load->weight = scale_load(sched_prio_to_weight[prio]);
752         load->inv_weight = sched_prio_to_wmult[prio];
753 }
754 
755 static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
756 {
757         update_rq_clock(rq);
758         if (!(flags & ENQUEUE_RESTORE))
759                 sched_info_queued(rq, p);
760         p->sched_class->enqueue_task(rq, p, flags);
761 }
762 
763 static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
764 {
765         update_rq_clock(rq);
766         if (!(flags & DEQUEUE_SAVE))
767                 sched_info_dequeued(rq, p);
768         p->sched_class->dequeue_task(rq, p, flags);
769 }
770 
771 void activate_task(struct rq *rq, struct task_struct *p, int flags)
772 {
773         if (task_contributes_to_load(p))
774                 rq->nr_uninterruptible--;
775 
776         enqueue_task(rq, p, flags);
777 }
778 
779 void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
780 {
781         if (task_contributes_to_load(p))
782                 rq->nr_uninterruptible++;
783 
784         dequeue_task(rq, p, flags);
785 }
786 
787 static void update_rq_clock_task(struct rq *rq, s64 delta)
788 {
789 /*
790  * In theory, the compile should just see 0 here, and optimize out the call
791  * to sched_rt_avg_update. But I don't trust it...
792  */
793 #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
794         s64 steal = 0, irq_delta = 0;
795 #endif
796 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
797         irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
798 
799         /*
800          * Since irq_time is only updated on {soft,}irq_exit, we might run into
801          * this case when a previous update_rq_clock() happened inside a
802          * {soft,}irq region.
803          *
804          * When this happens, we stop ->clock_task and only update the
805          * prev_irq_time stamp to account for the part that fit, so that a next
806          * update will consume the rest. This ensures ->clock_task is
807          * monotonic.
808          *
809          * It does however cause some slight miss-attribution of {soft,}irq
810          * time, a more accurate solution would be to update the irq_time using
811          * the current rq->clock timestamp, except that would require using
812          * atomic ops.
813          */
814         if (irq_delta > delta)
815                 irq_delta = delta;
816 
817         rq->prev_irq_time += irq_delta;
818         delta -= irq_delta;
819 #endif
820 #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
821         if (static_key_false((&paravirt_steal_rq_enabled))) {
822                 steal = paravirt_steal_clock(cpu_of(rq));
823                 steal -= rq->prev_steal_time_rq;
824 
825                 if (unlikely(steal > delta))
826                         steal = delta;
827 
828                 rq->prev_steal_time_rq += steal;
829                 delta -= steal;
830         }
831 #endif
832 
833         rq->clock_task += delta;
834 
835 #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
836         if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY))
837                 sched_rt_avg_update(rq, irq_delta + steal);
838 #endif
839 }
840 
841 void sched_set_stop_task(int cpu, struct task_struct *stop)
842 {
843         struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
844         struct task_struct *old_stop = cpu_rq(cpu)->stop;
845 
846         if (stop) {
847                 /*
848                  * Make it appear like a SCHED_FIFO task, its something
849                  * userspace knows about and won't get confused about.
850                  *
851                  * Also, it will make PI more or less work without too
852                  * much confusion -- but then, stop work should not
853                  * rely on PI working anyway.
854                  */
855                 sched_setscheduler_nocheck(stop, SCHED_FIFO, &param);
856 
857                 stop->sched_class = &stop_sched_class;
858         }
859 
860         cpu_rq(cpu)->stop = stop;
861 
862         if (old_stop) {
863                 /*
864                  * Reset it back to a normal scheduling class so that
865                  * it can die in pieces.
866                  */
867                 old_stop->sched_class = &rt_sched_class;
868         }
869 }
870 
871 /*
872  * __normal_prio - return the priority that is based on the static prio
873  */
874 static inline int __normal_prio(struct task_struct *p)
875 {
876         return p->static_prio;
877 }
878 
879 /*
880  * Calculate the expected normal priority: i.e. priority
881  * without taking RT-inheritance into account. Might be
882  * boosted by interactivity modifiers. Changes upon fork,
883  * setprio syscalls, and whenever the interactivity
884  * estimator recalculates.
885  */
886 static inline int normal_prio(struct task_struct *p)
887 {
888         int prio;
889 
890         if (task_has_dl_policy(p))
891                 prio = MAX_DL_PRIO-1;
892         else if (task_has_rt_policy(p))
893                 prio = MAX_RT_PRIO-1 - p->rt_priority;
894         else
895                 prio = __normal_prio(p);
896         return prio;
897 }
898 
899 /*
900  * Calculate the current priority, i.e. the priority
901  * taken into account by the scheduler. This value might
902  * be boosted by RT tasks, or might be boosted by
903  * interactivity modifiers. Will be RT if the task got
904  * RT-boosted. If not then it returns p->normal_prio.
905  */
906 static int effective_prio(struct task_struct *p)
907 {
908         p->normal_prio = normal_prio(p);
909         /*
910          * If we are RT tasks or we were boosted to RT priority,
911          * keep the priority unchanged. Otherwise, update priority
912          * to the normal priority:
913          */
914         if (!rt_prio(p->prio))
915                 return p->normal_prio;
916         return p->prio;
917 }
918 
919 /**
920  * task_curr - is this task currently executing on a CPU?
921  * @p: the task in question.
922  *
923  * Return: 1 if the task is currently executing. 0 otherwise.
924  */
925 inline int task_curr(const struct task_struct *p)
926 {
927         return cpu_curr(task_cpu(p)) == p;
928 }
929 
930 /*
931  * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock,
932  * use the balance_callback list if you want balancing.
933  *
934  * this means any call to check_class_changed() must be followed by a call to
935  * balance_callback().
936  */
937 static inline void check_class_changed(struct rq *rq, struct task_struct *p,
938                                        const struct sched_class *prev_class,
939                                        int oldprio)
940 {
941         if (prev_class != p->sched_class) {
942                 if (prev_class->switched_from)
943                         prev_class->switched_from(rq, p);
944 
945                 p->sched_class->switched_to(rq, p);
946         } else if (oldprio != p->prio || dl_task(p))
947                 p->sched_class->prio_changed(rq, p, oldprio);
948 }
949 
950 void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
951 {
952         const struct sched_class *class;
953 
954         if (p->sched_class == rq->curr->sched_class) {
955                 rq->curr->sched_class->check_preempt_curr(rq, p, flags);
956         } else {
957                 for_each_class(class) {
958                         if (class == rq->curr->sched_class)
959                                 break;
960                         if (class == p->sched_class) {
961                                 resched_curr(rq);
962                                 break;
963                         }
964                 }
965         }
966 
967         /*
968          * A queue event has occurred, and we're going to schedule.  In
969          * this case, we can save a useless back to back clock update.
970          */
971         if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
972                 rq_clock_skip_update(rq, true);
973 }
974 
975 #ifdef CONFIG_SMP
976 /*
977  * This is how migration works:
978  *
979  * 1) we invoke migration_cpu_stop() on the target CPU using
980  *    stop_one_cpu().
981  * 2) stopper starts to run (implicitly forcing the migrated thread
982  *    off the CPU)
983  * 3) it checks whether the migrated task is still in the wrong runqueue.
984  * 4) if it's in the wrong runqueue then the migration thread removes
985  *    it and puts it into the right queue.
986  * 5) stopper completes and stop_one_cpu() returns and the migration
987  *    is done.
988  */
989 
990 /*
991  * move_queued_task - move a queued task to new rq.
992  *
993  * Returns (locked) new rq. Old rq's lock is released.
994  */
995 static struct rq *move_queued_task(struct rq *rq, struct task_struct *p, int new_cpu)
996 {
997         lockdep_assert_held(&rq->lock);
998 
999         p->on_rq = TASK_ON_RQ_MIGRATING;
1000         dequeue_task(rq, p, 0);
1001         set_task_cpu(p, new_cpu);
1002         raw_spin_unlock(&rq->lock);
1003 
1004         rq = cpu_rq(new_cpu);
1005 
1006         raw_spin_lock(&rq->lock);
1007         BUG_ON(task_cpu(p) != new_cpu);
1008         enqueue_task(rq, p, 0);
1009         p->on_rq = TASK_ON_RQ_QUEUED;
1010         check_preempt_curr(rq, p, 0);
1011 
1012         return rq;
1013 }
1014 
1015 struct migration_arg {
1016         struct task_struct *task;
1017         int dest_cpu;
1018 };
1019 
1020 /*
1021  * Move (not current) task off this cpu, onto dest cpu. We're doing
1022  * this because either it can't run here any more (set_cpus_allowed()
1023  * away from this CPU, or CPU going down), or because we're
1024  * attempting to rebalance this task on exec (sched_exec).
1025  *
1026  * So we race with normal scheduler movements, but that's OK, as long
1027  * as the task is no longer on this CPU.
1028  */
1029 static struct rq *__migrate_task(struct rq *rq, struct task_struct *p, int dest_cpu)
1030 {
1031         if (unlikely(!cpu_active(dest_cpu)))
1032                 return rq;
1033 
1034         /* Affinity changed (again). */
1035         if (!cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p)))
1036                 return rq;
1037 
1038         rq = move_queued_task(rq, p, dest_cpu);
1039 
1040         return rq;
1041 }
1042 
1043 /*
1044  * migration_cpu_stop - this will be executed by a highprio stopper thread
1045  * and performs thread migration by bumping thread off CPU then
1046  * 'pushing' onto another runqueue.
1047  */
1048 static int migration_cpu_stop(void *data)
1049 {
1050         struct migration_arg *arg = data;
1051         struct task_struct *p = arg->task;
1052         struct rq *rq = this_rq();
1053 
1054         /*
1055          * The original target cpu might have gone down and we might
1056          * be on another cpu but it doesn't matter.
1057          */
1058         local_irq_disable();
1059         /*
1060          * We need to explicitly wake pending tasks before running
1061          * __migrate_task() such that we will not miss enforcing cpus_allowed
1062          * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
1063          */
1064         sched_ttwu_pending();
1065 
1066         raw_spin_lock(&p->pi_lock);
1067         raw_spin_lock(&rq->lock);
1068         /*
1069          * If task_rq(p) != rq, it cannot be migrated here, because we're
1070          * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
1071          * we're holding p->pi_lock.
1072          */
1073         if (task_rq(p) == rq) {
1074                 if (task_on_rq_queued(p))
1075                         rq = __migrate_task(rq, p, arg->dest_cpu);
1076                 else
1077                         p->wake_cpu = arg->dest_cpu;
1078         }
1079         raw_spin_unlock(&rq->lock);
1080         raw_spin_unlock(&p->pi_lock);
1081 
1082         local_irq_enable();
1083         return 0;
1084 }
1085 
1086 /*
1087  * sched_class::set_cpus_allowed must do the below, but is not required to
1088  * actually call this function.
1089  */
1090 void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask)
1091 {
1092         cpumask_copy(&p->cpus_allowed, new_mask);
1093         p->nr_cpus_allowed = cpumask_weight(new_mask);
1094 }
1095 
1096 void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
1097 {
1098         struct rq *rq = task_rq(p);
1099         bool queued, running;
1100 
1101         lockdep_assert_held(&p->pi_lock);
1102 
1103         queued = task_on_rq_queued(p);
1104         running = task_current(rq, p);
1105 
1106         if (queued) {
1107                 /*
1108                  * Because __kthread_bind() calls this on blocked tasks without
1109                  * holding rq->lock.
1110                  */
1111                 lockdep_assert_held(&rq->lock);
1112                 dequeue_task(rq, p, DEQUEUE_SAVE);
1113         }
1114         if (running)
1115                 put_prev_task(rq, p);
1116 
1117         p->sched_class->set_cpus_allowed(p, new_mask);
1118 
1119         if (queued)
1120                 enqueue_task(rq, p, ENQUEUE_RESTORE);
1121         if (running)
1122                 set_curr_task(rq, p);
1123 }
1124 
1125 /*
1126  * Change a given task's CPU affinity. Migrate the thread to a
1127  * proper CPU and schedule it away if the CPU it's executing on
1128  * is removed from the allowed bitmask.
1129  *
1130  * NOTE: the caller must have a valid reference to the task, the
1131  * task must not exit() & deallocate itself prematurely. The
1132  * call is not atomic; no spinlocks may be held.
1133  */
1134 static int __set_cpus_allowed_ptr(struct task_struct *p,
1135                                   const struct cpumask *new_mask, bool check)
1136 {
1137         const struct cpumask *cpu_valid_mask = cpu_active_mask;
1138         unsigned int dest_cpu;
1139         struct rq_flags rf;
1140         struct rq *rq;
1141         int ret = 0;
1142 
1143         rq = task_rq_lock(p, &rf);
1144 
1145         if (p->flags & PF_KTHREAD) {
1146                 /*
1147                  * Kernel threads are allowed on online && !active CPUs
1148                  */
1149                 cpu_valid_mask = cpu_online_mask;
1150         }
1151 
1152         /*
1153          * Must re-check here, to close a race against __kthread_bind(),
1154          * sched_setaffinity() is not guaranteed to observe the flag.
1155          */
1156         if (check && (p->flags & PF_NO_SETAFFINITY)) {
1157                 ret = -EINVAL;
1158                 goto out;
1159         }
1160 
1161         if (cpumask_equal(&p->cpus_allowed, new_mask))
1162                 goto out;
1163 
1164         if (!cpumask_intersects(new_mask, cpu_valid_mask)) {
1165                 ret = -EINVAL;
1166                 goto out;
1167         }
1168 
1169         do_set_cpus_allowed(p, new_mask);
1170 
1171         if (p->flags & PF_KTHREAD) {
1172                 /*
1173                  * For kernel threads that do indeed end up on online &&
1174                  * !active we want to ensure they are strict per-cpu threads.
1175                  */
1176                 WARN_ON(cpumask_intersects(new_mask, cpu_online_mask) &&
1177                         !cpumask_intersects(new_mask, cpu_active_mask) &&
1178                         p->nr_cpus_allowed != 1);
1179         }
1180 
1181         /* Can the task run on the task's current CPU? If so, we're done */
1182         if (cpumask_test_cpu(task_cpu(p), new_mask))
1183                 goto out;
1184 
1185         dest_cpu = cpumask_any_and(cpu_valid_mask, new_mask);
1186         if (task_running(rq, p) || p->state == TASK_WAKING) {
1187                 struct migration_arg arg = { p, dest_cpu };
1188                 /* Need help from migration thread: drop lock and wait. */
1189                 task_rq_unlock(rq, p, &rf);
1190                 stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
1191                 tlb_migrate_finish(p->mm);
1192                 return 0;
1193         } else if (task_on_rq_queued(p)) {
1194                 /*
1195                  * OK, since we're going to drop the lock immediately
1196                  * afterwards anyway.
1197                  */
1198                 lockdep_unpin_lock(&rq->lock, rf.cookie);
1199                 rq = move_queued_task(rq, p, dest_cpu);
1200                 lockdep_repin_lock(&rq->lock, rf.cookie);
1201         }
1202 out:
1203         task_rq_unlock(rq, p, &rf);
1204 
1205         return ret;
1206 }
1207 
1208 int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
1209 {
1210         return __set_cpus_allowed_ptr(p, new_mask, false);
1211 }
1212 EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
1213 
1214 void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
1215 {
1216 #ifdef CONFIG_SCHED_DEBUG
1217         /*
1218          * We should never call set_task_cpu() on a blocked task,
1219          * ttwu() will sort out the placement.
1220          */
1221         WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
1222                         !p->on_rq);
1223 
1224         /*
1225          * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
1226          * because schedstat_wait_{start,end} rebase migrating task's wait_start
1227          * time relying on p->on_rq.
1228          */
1229         WARN_ON_ONCE(p->state == TASK_RUNNING &&
1230                      p->sched_class == &fair_sched_class &&
1231                      (p->on_rq && !task_on_rq_migrating(p)));
1232 
1233 #ifdef CONFIG_LOCKDEP
1234         /*
1235          * The caller should hold either p->pi_lock or rq->lock, when changing
1236          * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
1237          *
1238          * sched_move_task() holds both and thus holding either pins the cgroup,
1239          * see task_group().
1240          *
1241          * Furthermore, all task_rq users should acquire both locks, see
1242          * task_rq_lock().
1243          */
1244         WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
1245                                       lockdep_is_held(&task_rq(p)->lock)));
1246 #endif
1247 #endif
1248 
1249         trace_sched_migrate_task(p, new_cpu);
1250 
1251         if (task_cpu(p) != new_cpu) {
1252                 if (p->sched_class->migrate_task_rq)
1253                         p->sched_class->migrate_task_rq(p);
1254                 p->se.nr_migrations++;
1255                 perf_event_task_migrate(p);
1256         }
1257 
1258         __set_task_cpu(p, new_cpu);
1259 }
1260 
1261 static void __migrate_swap_task(struct task_struct *p, int cpu)
1262 {
1263         if (task_on_rq_queued(p)) {
1264                 struct rq *src_rq, *dst_rq;
1265 
1266                 src_rq = task_rq(p);
1267                 dst_rq = cpu_rq(cpu);
1268 
1269                 p->on_rq = TASK_ON_RQ_MIGRATING;
1270                 deactivate_task(src_rq, p, 0);
1271                 set_task_cpu(p, cpu);
1272                 activate_task(dst_rq, p, 0);
1273                 p->on_rq = TASK_ON_RQ_QUEUED;
1274                 check_preempt_curr(dst_rq, p, 0);
1275         } else {
1276                 /*
1277                  * Task isn't running anymore; make it appear like we migrated
1278                  * it before it went to sleep. This means on wakeup we make the
1279                  * previous cpu our target instead of where it really is.
1280                  */
1281                 p->wake_cpu = cpu;
1282         }
1283 }
1284 
1285 struct migration_swap_arg {
1286         struct task_struct *src_task, *dst_task;
1287         int src_cpu, dst_cpu;
1288 };
1289 
1290 static int migrate_swap_stop(void *data)
1291 {
1292         struct migration_swap_arg *arg = data;
1293         struct rq *src_rq, *dst_rq;
1294         int ret = -EAGAIN;
1295 
1296         if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu))
1297                 return -EAGAIN;
1298 
1299         src_rq = cpu_rq(arg->src_cpu);
1300         dst_rq = cpu_rq(arg->dst_cpu);
1301 
1302         double_raw_lock(&arg->src_task->pi_lock,
1303                         &arg->dst_task->pi_lock);
1304         double_rq_lock(src_rq, dst_rq);
1305 
1306         if (task_cpu(arg->dst_task) != arg->dst_cpu)
1307                 goto unlock;
1308 
1309         if (task_cpu(arg->src_task) != arg->src_cpu)
1310                 goto unlock;
1311 
1312         if (!cpumask_test_cpu(arg->dst_cpu, tsk_cpus_allowed(arg->src_task)))
1313                 goto unlock;
1314 
1315         if (!cpumask_test_cpu(arg->src_cpu, tsk_cpus_allowed(arg->dst_task)))
1316                 goto unlock;
1317 
1318         __migrate_swap_task(arg->src_task, arg->dst_cpu);
1319         __migrate_swap_task(arg->dst_task, arg->src_cpu);
1320 
1321         ret = 0;
1322 
1323 unlock:
1324         double_rq_unlock(src_rq, dst_rq);
1325         raw_spin_unlock(&arg->dst_task->pi_lock);
1326         raw_spin_unlock(&arg->src_task->pi_lock);
1327 
1328         return ret;
1329 }
1330 
1331 /*
1332  * Cross migrate two tasks
1333  */
1334 int migrate_swap(struct task_struct *cur, struct task_struct *p)
1335 {
1336         struct migration_swap_arg arg;
1337         int ret = -EINVAL;
1338 
1339         arg = (struct migration_swap_arg){
1340                 .src_task = cur,
1341                 .src_cpu = task_cpu(cur),
1342                 .dst_task = p,
1343                 .dst_cpu = task_cpu(p),
1344         };
1345 
1346         if (arg.src_cpu == arg.dst_cpu)
1347                 goto out;
1348 
1349         /*
1350          * These three tests are all lockless; this is OK since all of them
1351          * will be re-checked with proper locks held further down the line.
1352          */
1353         if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu))
1354                 goto out;
1355 
1356         if (!cpumask_test_cpu(arg.dst_cpu, tsk_cpus_allowed(arg.src_task)))
1357                 goto out;
1358 
1359         if (!cpumask_test_cpu(arg.src_cpu, tsk_cpus_allowed(arg.dst_task)))
1360                 goto out;
1361 
1362         trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu);
1363         ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg);
1364 
1365 out:
1366         return ret;
1367 }
1368 
1369 /*
1370  * wait_task_inactive - wait for a thread to unschedule.
1371  *
1372  * If @match_state is nonzero, it's the @p->state value just checked and
1373  * not expected to change.  If it changes, i.e. @p might have woken up,
1374  * then return zero.  When we succeed in waiting for @p to be off its CPU,
1375  * we return a positive number (its total switch count).  If a second call
1376  * a short while later returns the same number, the caller can be sure that
1377  * @p has remained unscheduled the whole time.
1378  *
1379  * The caller must ensure that the task *will* unschedule sometime soon,
1380  * else this function might spin for a *long* time. This function can't
1381  * be called with interrupts off, or it may introduce deadlock with
1382  * smp_call_function() if an IPI is sent by the same process we are
1383  * waiting to become inactive.
1384  */
1385 unsigned long wait_task_inactive(struct task_struct *p, long match_state)
1386 {
1387         int running, queued;
1388         struct rq_flags rf;
1389         unsigned long ncsw;
1390         struct rq *rq;
1391 
1392         for (;;) {
1393                 /*
1394                  * We do the initial early heuristics without holding
1395                  * any task-queue locks at all. We'll only try to get
1396                  * the runqueue lock when things look like they will
1397                  * work out!
1398                  */
1399                 rq = task_rq(p);
1400 
1401                 /*
1402                  * If the task is actively running on another CPU
1403                  * still, just relax and busy-wait without holding
1404                  * any locks.
1405                  *
1406                  * NOTE! Since we don't hold any locks, it's not
1407                  * even sure that "rq" stays as the right runqueue!
1408                  * But we don't care, since "task_running()" will
1409                  * return false if the runqueue has changed and p
1410                  * is actually now running somewhere else!
1411                  */
1412                 while (task_running(rq, p)) {
1413                         if (match_state && unlikely(p->state != match_state))
1414                                 return 0;
1415                         cpu_relax();
1416                 }
1417 
1418                 /*
1419                  * Ok, time to look more closely! We need the rq
1420                  * lock now, to be *sure*. If we're wrong, we'll
1421                  * just go back and repeat.
1422                  */
1423                 rq = task_rq_lock(p, &rf);
1424                 trace_sched_wait_task(p);
1425                 running = task_running(rq, p);
1426                 queued = task_on_rq_queued(p);
1427                 ncsw = 0;
1428                 if (!match_state || p->state == match_state)
1429                         ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
1430                 task_rq_unlock(rq, p, &rf);
1431 
1432                 /*
1433                  * If it changed from the expected state, bail out now.
1434                  */
1435                 if (unlikely(!ncsw))
1436                         break;
1437 
1438                 /*
1439                  * Was it really running after all now that we
1440                  * checked with the proper locks actually held?
1441                  *
1442                  * Oops. Go back and try again..
1443                  */
1444                 if (unlikely(running)) {
1445                         cpu_relax();
1446                         continue;
1447                 }
1448 
1449                 /*
1450                  * It's not enough that it's not actively running,
1451                  * it must be off the runqueue _entirely_, and not
1452                  * preempted!
1453                  *
1454                  * So if it was still runnable (but just not actively
1455                  * running right now), it's preempted, and we should
1456                  * yield - it could be a while.
1457                  */
1458                 if (unlikely(queued)) {
1459                         ktime_t to = ktime_set(0, NSEC_PER_SEC/HZ);
1460 
1461                         set_current_state(TASK_UNINTERRUPTIBLE);
1462                         schedule_hrtimeout(&to, HRTIMER_MODE_REL);
1463                         continue;
1464                 }
1465 
1466                 /*
1467                  * Ahh, all good. It wasn't running, and it wasn't
1468                  * runnable, which means that it will never become
1469                  * running in the future either. We're all done!
1470                  */
1471                 break;
1472         }
1473 
1474         return ncsw;
1475 }
1476 
1477 /***
1478  * kick_process - kick a running thread to enter/exit the kernel
1479  * @p: the to-be-kicked thread
1480  *
1481  * Cause a process which is running on another CPU to enter
1482  * kernel-mode, without any delay. (to get signals handled.)
1483  *
1484  * NOTE: this function doesn't have to take the runqueue lock,
1485  * because all it wants to ensure is that the remote task enters
1486  * the kernel. If the IPI races and the task has been migrated
1487  * to another CPU then no harm is done and the purpose has been
1488  * achieved as well.
1489  */
1490 void kick_process(struct task_struct *p)
1491 {
1492         int cpu;
1493 
1494         preempt_disable();
1495         cpu = task_cpu(p);
1496         if ((cpu != smp_processor_id()) && task_curr(p))
1497                 smp_send_reschedule(cpu);
1498         preempt_enable();
1499 }
1500 EXPORT_SYMBOL_GPL(kick_process);
1501 
1502 /*
1503  * ->cpus_allowed is protected by both rq->lock and p->pi_lock
1504  *
1505  * A few notes on cpu_active vs cpu_online:
1506  *
1507  *  - cpu_active must be a subset of cpu_online
1508  *
1509  *  - on cpu-up we allow per-cpu kthreads on the online && !active cpu,
1510  *    see __set_cpus_allowed_ptr(). At this point the newly online
1511  *    cpu isn't yet part of the sched domains, and balancing will not
1512  *    see it.
1513  *
1514  *  - on cpu-down we clear cpu_active() to mask the sched domains and
1515  *    avoid the load balancer to place new tasks on the to be removed
1516  *    cpu. Existing tasks will remain running there and will be taken
1517  *    off.
1518  *
1519  * This means that fallback selection must not select !active CPUs.
1520  * And can assume that any active CPU must be online. Conversely
1521  * select_task_rq() below may allow selection of !active CPUs in order
1522  * to satisfy the above rules.
1523  */
1524 static int select_fallback_rq(int cpu, struct task_struct *p)
1525 {
1526         int nid = cpu_to_node(cpu);
1527         const struct cpumask *nodemask = NULL;
1528         enum { cpuset, possible, fail } state = cpuset;
1529         int dest_cpu;
1530 
1531         /*
1532          * If the node that the cpu is on has been offlined, cpu_to_node()
1533          * will return -1. There is no cpu on the node, and we should
1534          * select the cpu on the other node.
1535          */
1536         if (nid != -1) {
1537                 nodemask = cpumask_of_node(nid);
1538 
1539                 /* Look for allowed, online CPU in same node. */
1540                 for_each_cpu(dest_cpu, nodemask) {
1541                         if (!cpu_active(dest_cpu))
1542                                 continue;
1543                         if (cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p)))
1544                                 return dest_cpu;
1545                 }
1546         }
1547 
1548         for (;;) {
1549                 /* Any allowed, online CPU? */
1550                 for_each_cpu(dest_cpu, tsk_cpus_allowed(p)) {
1551                         if (!(p->flags & PF_KTHREAD) && !cpu_active(dest_cpu))
1552                                 continue;
1553                         if (!cpu_online(dest_cpu))
1554                                 continue;
1555                         goto out;
1556                 }
1557 
1558                 /* No more Mr. Nice Guy. */
1559                 switch (state) {
1560                 case cpuset:
1561                         if (IS_ENABLED(CONFIG_CPUSETS)) {
1562                                 cpuset_cpus_allowed_fallback(p);
1563                                 state = possible;
1564                                 break;
1565                         }
1566                         /* fall-through */
1567                 case possible:
1568                         do_set_cpus_allowed(p, cpu_possible_mask);
1569                         state = fail;
1570                         break;
1571 
1572                 case fail:
1573                         BUG();
1574                         break;
1575                 }
1576         }
1577 
1578 out:
1579         if (state != cpuset) {
1580                 /*
1581                  * Don't tell them about moving exiting tasks or
1582                  * kernel threads (both mm NULL), since they never
1583                  * leave kernel.
1584                  */
1585                 if (p->mm && printk_ratelimit()) {
1586                         printk_deferred("process %d (%s) no longer affine to cpu%d\n",
1587                                         task_pid_nr(p), p->comm, cpu);
1588                 }
1589         }
1590 
1591         return dest_cpu;
1592 }
1593 
1594 /*
1595  * The caller (fork, wakeup) owns p->pi_lock, ->cpus_allowed is stable.
1596  */
1597 static inline
1598 int select_task_rq(struct task_struct *p, int cpu, int sd_flags, int wake_flags)
1599 {
1600         lockdep_assert_held(&p->pi_lock);
1601 
1602         if (tsk_nr_cpus_allowed(p) > 1)
1603                 cpu = p->sched_class->select_task_rq(p, cpu, sd_flags, wake_flags);
1604         else
1605                 cpu = cpumask_any(tsk_cpus_allowed(p));
1606 
1607         /*
1608          * In order not to call set_task_cpu() on a blocking task we need
1609          * to rely on ttwu() to place the task on a valid ->cpus_allowed
1610          * cpu.
1611          *
1612          * Since this is common to all placement strategies, this lives here.
1613          *
1614          * [ this allows ->select_task() to simply return task_cpu(p) and
1615          *   not worry about this generic constraint ]
1616          */
1617         if (unlikely(!cpumask_test_cpu(cpu, tsk_cpus_allowed(p)) ||
1618                      !cpu_online(cpu)))
1619                 cpu = select_fallback_rq(task_cpu(p), p);
1620 
1621         return cpu;
1622 }
1623 
1624 static void update_avg(u64 *avg, u64 sample)
1625 {
1626         s64 diff = sample - *avg;
1627         *avg += diff >> 3;
1628 }
1629 
1630 #else
1631 
1632 static inline int __set_cpus_allowed_ptr(struct task_struct *p,
1633                                          const struct cpumask *new_mask, bool check)
1634 {
1635         return set_cpus_allowed_ptr(p, new_mask);
1636 }
1637 
1638 #endif /* CONFIG_SMP */
1639 
1640 static void
1641 ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
1642 {
1643         struct rq *rq;
1644 
1645         if (!schedstat_enabled())
1646                 return;
1647 
1648         rq = this_rq();
1649 
1650 #ifdef CONFIG_SMP
1651         if (cpu == rq->cpu) {
1652                 schedstat_inc(rq->ttwu_local);
1653                 schedstat_inc(p->se.statistics.nr_wakeups_local);
1654         } else {
1655                 struct sched_domain *sd;
1656 
1657                 schedstat_inc(p->se.statistics.nr_wakeups_remote);
1658                 rcu_read_lock();
1659                 for_each_domain(rq->cpu, sd) {
1660                         if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
1661                                 schedstat_inc(sd->ttwu_wake_remote);
1662                                 break;
1663                         }
1664                 }
1665                 rcu_read_unlock();
1666         }
1667 
1668         if (wake_flags & WF_MIGRATED)
1669                 schedstat_inc(p->se.statistics.nr_wakeups_migrate);
1670 #endif /* CONFIG_SMP */
1671 
1672         schedstat_inc(rq->ttwu_count);
1673         schedstat_inc(p->se.statistics.nr_wakeups);
1674 
1675         if (wake_flags & WF_SYNC)
1676                 schedstat_inc(p->se.statistics.nr_wakeups_sync);
1677 }
1678 
1679 static inline void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
1680 {
1681         activate_task(rq, p, en_flags);
1682         p->on_rq = TASK_ON_RQ_QUEUED;
1683 
1684         /* if a worker is waking up, notify workqueue */
1685         if (p->flags & PF_WQ_WORKER)
1686                 wq_worker_waking_up(p, cpu_of(rq));
1687 }
1688 
1689 /*
1690  * Mark the task runnable and perform wakeup-preemption.
1691  */
1692 static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags,
1693                            struct pin_cookie cookie)
1694 {
1695         check_preempt_curr(rq, p, wake_flags);
1696         p->state = TASK_RUNNING;
1697         trace_sched_wakeup(p);
1698 
1699 #ifdef CONFIG_SMP
1700         if (p->sched_class->task_woken) {
1701                 /*
1702                  * Our task @p is fully woken up and running; so its safe to
1703                  * drop the rq->lock, hereafter rq is only used for statistics.
1704                  */
1705                 lockdep_unpin_lock(&rq->lock, cookie);
1706                 p->sched_class->task_woken(rq, p);
1707                 lockdep_repin_lock(&rq->lock, cookie);
1708         }
1709 
1710         if (rq->idle_stamp) {
1711                 u64 delta = rq_clock(rq) - rq->idle_stamp;
1712                 u64 max = 2*rq->max_idle_balance_cost;
1713 
1714                 update_avg(&rq->avg_idle, delta);
1715 
1716                 if (rq->avg_idle > max)
1717                         rq->avg_idle = max;
1718 
1719                 rq->idle_stamp = 0;
1720         }
1721 #endif
1722 }
1723 
1724 static void
1725 ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
1726                  struct pin_cookie cookie)
1727 {
1728         int en_flags = ENQUEUE_WAKEUP;
1729 
1730         lockdep_assert_held(&rq->lock);
1731 
1732 #ifdef CONFIG_SMP
1733         if (p->sched_contributes_to_load)
1734                 rq->nr_uninterruptible--;
1735 
1736         if (wake_flags & WF_MIGRATED)
1737                 en_flags |= ENQUEUE_MIGRATED;
1738 #endif
1739 
1740         ttwu_activate(rq, p, en_flags);
1741         ttwu_do_wakeup(rq, p, wake_flags, cookie);
1742 }
1743 
1744 /*
1745  * Called in case the task @p isn't fully descheduled from its runqueue,
1746  * in this case we must do a remote wakeup. Its a 'light' wakeup though,
1747  * since all we need to do is flip p->state to TASK_RUNNING, since
1748  * the task is still ->on_rq.
1749  */
1750 static int ttwu_remote(struct task_struct *p, int wake_flags)
1751 {
1752         struct rq_flags rf;
1753         struct rq *rq;
1754         int ret = 0;
1755 
1756         rq = __task_rq_lock(p, &rf);
1757         if (task_on_rq_queued(p)) {
1758                 /* check_preempt_curr() may use rq clock */
1759                 update_rq_clock(rq);
1760                 ttwu_do_wakeup(rq, p, wake_flags, rf.cookie);
1761                 ret = 1;
1762         }
1763         __task_rq_unlock(rq, &rf);
1764 
1765         return ret;
1766 }
1767 
1768 #ifdef CONFIG_SMP
1769 void sched_ttwu_pending(void)
1770 {
1771         struct rq *rq = this_rq();
1772         struct llist_node *llist = llist_del_all(&rq->wake_list);
1773         struct pin_cookie cookie;
1774         struct task_struct *p;
1775         unsigned long flags;
1776 
1777         if (!llist)
1778                 return;
1779 
1780         raw_spin_lock_irqsave(&rq->lock, flags);
1781         cookie = lockdep_pin_lock(&rq->lock);
1782 
1783         while (llist) {
1784                 int wake_flags = 0;
1785 
1786                 p = llist_entry(llist, struct task_struct, wake_entry);
1787                 llist = llist_next(llist);
1788 
1789                 if (p->sched_remote_wakeup)
1790                         wake_flags = WF_MIGRATED;
1791 
1792                 ttwu_do_activate(rq, p, wake_flags, cookie);
1793         }
1794 
1795         lockdep_unpin_lock(&rq->lock, cookie);
1796         raw_spin_unlock_irqrestore(&rq->lock, flags);
1797 }
1798 
1799 void scheduler_ipi(void)
1800 {
1801         /*
1802          * Fold TIF_NEED_RESCHED into the preempt_count; anybody setting
1803          * TIF_NEED_RESCHED remotely (for the first time) will also send
1804          * this IPI.
1805          */
1806         preempt_fold_need_resched();
1807 
1808         if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick())
1809                 return;
1810 
1811         /*
1812          * Not all reschedule IPI handlers call irq_enter/irq_exit, since
1813          * traditionally all their work was done from the interrupt return
1814          * path. Now that we actually do some work, we need to make sure
1815          * we do call them.
1816          *
1817          * Some archs already do call them, luckily irq_enter/exit nest
1818          * properly.
1819          *
1820          * Arguably we should visit all archs and update all handlers,
1821          * however a fair share of IPIs are still resched only so this would
1822          * somewhat pessimize the simple resched case.
1823          */
1824         irq_enter();
1825         sched_ttwu_pending();
1826 
1827         /*
1828          * Check if someone kicked us for doing the nohz idle load balance.
1829          */
1830         if (unlikely(got_nohz_idle_kick())) {
1831                 this_rq()->idle_balance = 1;
1832                 raise_softirq_irqoff(SCHED_SOFTIRQ);
1833         }
1834         irq_exit();
1835 }
1836 
1837 static void ttwu_queue_remote(struct task_struct *p, int cpu, int wake_flags)
1838 {
1839         struct rq *rq = cpu_rq(cpu);
1840 
1841         p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED);
1842 
1843         if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list)) {
1844                 if (!set_nr_if_polling(rq->idle))
1845                         smp_send_reschedule(cpu);
1846                 else
1847                         trace_sched_wake_idle_without_ipi(cpu);
1848         }
1849 }
1850 
1851 void wake_up_if_idle(int cpu)
1852 {
1853         struct rq *rq = cpu_rq(cpu);
1854         unsigned long flags;
1855 
1856         rcu_read_lock();
1857 
1858         if (!is_idle_task(rcu_dereference(rq->curr)))
1859                 goto out;
1860 
1861         if (set_nr_if_polling(rq->idle)) {
1862                 trace_sched_wake_idle_without_ipi(cpu);
1863         } else {
1864                 raw_spin_lock_irqsave(&rq->lock, flags);
1865                 if (is_idle_task(rq->curr))
1866                         smp_send_reschedule(cpu);
1867                 /* Else cpu is not in idle, do nothing here */
1868                 raw_spin_unlock_irqrestore(&rq->lock, flags);
1869         }
1870 
1871 out:
1872         rcu_read_unlock();
1873 }
1874 
1875 bool cpus_share_cache(int this_cpu, int that_cpu)
1876 {
1877         return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
1878 }
1879 #endif /* CONFIG_SMP */
1880 
1881 static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags)
1882 {
1883         struct rq *rq = cpu_rq(cpu);
1884         struct pin_cookie cookie;
1885 
1886 #if defined(CONFIG_SMP)
1887         if (sched_feat(TTWU_QUEUE) && !cpus_share_cache(smp_processor_id(), cpu)) {
1888                 sched_clock_cpu(cpu); /* sync clocks x-cpu */
1889                 ttwu_queue_remote(p, cpu, wake_flags);
1890                 return;
1891         }
1892 #endif
1893 
1894         raw_spin_lock(&rq->lock);
1895         cookie = lockdep_pin_lock(&rq->lock);
1896         ttwu_do_activate(rq, p, wake_flags, cookie);
1897         lockdep_unpin_lock(&rq->lock, cookie);
1898         raw_spin_unlock(&rq->lock);
1899 }
1900 
1901 /*
1902  * Notes on Program-Order guarantees on SMP systems.
1903  *
1904  *  MIGRATION
1905  *
1906  * The basic program-order guarantee on SMP systems is that when a task [t]
1907  * migrates, all its activity on its old cpu [c0] happens-before any subsequent
1908  * execution on its new cpu [c1].
1909  *
1910  * For migration (of runnable tasks) this is provided by the following means:
1911  *
1912  *  A) UNLOCK of the rq(c0)->lock scheduling out task t
1913  *  B) migration for t is required to synchronize *both* rq(c0)->lock and
1914  *     rq(c1)->lock (if not at the same time, then in that order).
1915  *  C) LOCK of the rq(c1)->lock scheduling in task
1916  *
1917  * Transitivity guarantees that B happens after A and C after B.
1918  * Note: we only require RCpc transitivity.
1919  * Note: the cpu doing B need not be c0 or c1
1920  *
1921  * Example:
1922  *
1923  *   CPU0            CPU1            CPU2
1924  *
1925  *   LOCK rq(0)->lock
1926  *   sched-out X
1927  *   sched-in Y
1928  *   UNLOCK rq(0)->lock
1929  *
1930  *                                   LOCK rq(0)->lock // orders against CPU0
1931  *                                   dequeue X
1932  *                                   UNLOCK rq(0)->lock
1933  *
1934  *                                   LOCK rq(1)->lock
1935  *                                   enqueue X
1936  *                                   UNLOCK rq(1)->lock
1937  *
1938  *                   LOCK rq(1)->lock // orders against CPU2
1939  *                   sched-out Z
1940  *                   sched-in X
1941  *                   UNLOCK rq(1)->lock
1942  *
1943  *
1944  *  BLOCKING -- aka. SLEEP + WAKEUP
1945  *
1946  * For blocking we (obviously) need to provide the same guarantee as for
1947  * migration. However the means are completely different as there is no lock
1948  * chain to provide order. Instead we do:
1949  *
1950  *   1) smp_store_release(X->on_cpu, 0)
1951  *   2) smp_cond_load_acquire(!X->on_cpu)
1952  *
1953  * Example:
1954  *
1955  *   CPU0 (schedule)  CPU1 (try_to_wake_up) CPU2 (schedule)
1956  *
1957  *   LOCK rq(0)->lock LOCK X->pi_lock
1958  *   dequeue X
1959  *   sched-out X
1960  *   smp_store_release(X->on_cpu, 0);
1961  *
1962  *                    smp_cond_load_acquire(&X->on_cpu, !VAL);
1963  *                    X->state = WAKING
1964  *                    set_task_cpu(X,2)
1965  *
1966  *                    LOCK rq(2)->lock
1967  *                    enqueue X
1968  *                    X->state = RUNNING
1969  *                    UNLOCK rq(2)->lock
1970  *
1971  *                                          LOCK rq(2)->lock // orders against CPU1
1972  *                                          sched-out Z
1973  *                                          sched-in X
1974  *                                          UNLOCK rq(2)->lock
1975  *
1976  *                    UNLOCK X->pi_lock
1977  *   UNLOCK rq(0)->lock
1978  *
1979  *
1980  * However; for wakeups there is a second guarantee we must provide, namely we
1981  * must observe the state that lead to our wakeup. That is, not only must our
1982  * task observe its own prior state, it must also observe the stores prior to
1983  * its wakeup.
1984  *
1985  * This means that any means of doing remote wakeups must order the CPU doing
1986  * the wakeup against the CPU the task is going to end up running on. This,
1987  * however, is already required for the regular Program-Order guarantee above,
1988  * since the waking CPU is the one issueing the ACQUIRE (smp_cond_load_acquire).
1989  *
1990  */
1991 
1992 /**
1993  * try_to_wake_up - wake up a thread
1994  * @p: the thread to be awakened
1995  * @state: the mask of task states that can be woken
1996  * @wake_flags: wake modifier flags (WF_*)
1997  *
1998  * Put it on the run-queue if it's not already there. The "current"
1999  * thread is always on the run-queue (except when the actual
2000  * re-schedule is in progress), and as such you're allowed to do
2001  * the simpler "current->state = TASK_RUNNING" to mark yourself
2002  * runnable without the overhead of this.
2003  *
2004  * Return: %true if @p was woken up, %false if it was already running.
2005  * or @state didn't match @p's state.
2006  */
2007 static int
2008 try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
2009 {
2010         unsigned long flags;
2011         int cpu, success = 0;
2012 
2013         /*
2014          * If we are going to wake up a thread waiting for CONDITION we
2015          * need to ensure that CONDITION=1 done by the caller can not be
2016          * reordered with p->state check below. This pairs with mb() in
2017          * set_current_state() the waiting thread does.
2018          */
2019         smp_mb__before_spinlock();
2020         raw_spin_lock_irqsave(&p->pi_lock, flags);
2021         if (!(p->state & state))
2022                 goto out;
2023 
2024         trace_sched_waking(p);
2025 
2026         success = 1; /* we're going to change ->state */
2027         cpu = task_cpu(p);
2028 
2029         /*
2030          * Ensure we load p->on_rq _after_ p->state, otherwise it would
2031          * be possible to, falsely, observe p->on_rq == 0 and get stuck
2032          * in smp_cond_load_acquire() below.
2033          *
2034          * sched_ttwu_pending()                 try_to_wake_up()
2035          *   [S] p->on_rq = 1;                  [L] P->state
2036          *       UNLOCK rq->lock  -----.
2037          *                              \
2038          *                               +---   RMB
2039          * schedule()                   /
2040          *       LOCK rq->lock    -----'
2041          *       UNLOCK rq->lock
2042          *
2043          * [task p]
2044          *   [S] p->state = UNINTERRUPTIBLE     [L] p->on_rq
2045          *
2046          * Pairs with the UNLOCK+LOCK on rq->lock from the
2047          * last wakeup of our task and the schedule that got our task
2048          * current.
2049          */
2050         smp_rmb();
2051         if (p->on_rq && ttwu_remote(p, wake_flags))
2052                 goto stat;
2053 
2054 #ifdef CONFIG_SMP
2055         /*
2056          * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
2057          * possible to, falsely, observe p->on_cpu == 0.
2058          *
2059          * One must be running (->on_cpu == 1) in order to remove oneself
2060          * from the runqueue.
2061          *
2062          *  [S] ->on_cpu = 1;   [L] ->on_rq
2063          *      UNLOCK rq->lock
2064          *                      RMB
2065          *      LOCK   rq->lock
2066          *  [S] ->on_rq = 0;    [L] ->on_cpu
2067          *
2068          * Pairs with the full barrier implied in the UNLOCK+LOCK on rq->lock
2069          * from the consecutive calls to schedule(); the first switching to our
2070          * task, the second putting it to sleep.
2071          */
2072         smp_rmb();
2073 
2074         /*
2075          * If the owning (remote) cpu is still in the middle of schedule() with
2076          * this task as prev, wait until its done referencing the task.
2077          *
2078          * Pairs with the smp_store_release() in finish_lock_switch().
2079          *
2080          * This ensures that tasks getting woken will be fully ordered against
2081          * their previous state and preserve Program Order.
2082          */
2083         smp_cond_load_acquire(&p->on_cpu, !VAL);
2084 
2085         p->sched_contributes_to_load = !!task_contributes_to_load(p);
2086         p->state = TASK_WAKING;
2087 
2088         cpu = select_task_rq(p, p->wake_cpu, SD_BALANCE_WAKE, wake_flags);
2089         if (task_cpu(p) != cpu) {
2090                 wake_flags |= WF_MIGRATED;
2091                 set_task_cpu(p, cpu);
2092         }
2093 #endif /* CONFIG_SMP */
2094 
2095         ttwu_queue(p, cpu, wake_flags);
2096 stat:
2097         ttwu_stat(p, cpu, wake_flags);
2098 out:
2099         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2100 
2101         return success;
2102 }
2103 
2104 /**
2105  * try_to_wake_up_local - try to wake up a local task with rq lock held
2106  * @p: the thread to be awakened
2107  * @cookie: context's cookie for pinning
2108  *
2109  * Put @p on the run-queue if it's not already there. The caller must
2110  * ensure that this_rq() is locked, @p is bound to this_rq() and not
2111  * the current task.
2112  */
2113 static void try_to_wake_up_local(struct task_struct *p, struct pin_cookie cookie)
2114 {
2115         struct rq *rq = task_rq(p);
2116 
2117         if (WARN_ON_ONCE(rq != this_rq()) ||
2118             WARN_ON_ONCE(p == current))
2119                 return;
2120 
2121         lockdep_assert_held(&rq->lock);
2122 
2123         if (!raw_spin_trylock(&p->pi_lock)) {
2124                 /*
2125                  * This is OK, because current is on_cpu, which avoids it being
2126                  * picked for load-balance and preemption/IRQs are still
2127                  * disabled avoiding further scheduler activity on it and we've
2128                  * not yet picked a replacement task.
2129                  */
2130                 lockdep_unpin_lock(&rq->lock, cookie);
2131                 raw_spin_unlock(&rq->lock);
2132                 raw_spin_lock(&p->pi_lock);
2133                 raw_spin_lock(&rq->lock);
2134                 lockdep_repin_lock(&rq->lock, cookie);
2135         }
2136 
2137         if (!(p->state & TASK_NORMAL))
2138                 goto out;
2139 
2140         trace_sched_waking(p);
2141 
2142         if (!task_on_rq_queued(p))
2143                 ttwu_activate(rq, p, ENQUEUE_WAKEUP);
2144 
2145         ttwu_do_wakeup(rq, p, 0, cookie);
2146         ttwu_stat(p, smp_processor_id(), 0);
2147 out:
2148         raw_spin_unlock(&p->pi_lock);
2149 }
2150 
2151 /**
2152  * wake_up_process - Wake up a specific process
2153  * @p: The process to be woken up.
2154  *
2155  * Attempt to wake up the nominated process and move it to the set of runnable
2156  * processes.
2157  *
2158  * Return: 1 if the process was woken up, 0 if it was already running.
2159  *
2160  * It may be assumed that this function implies a write memory barrier before
2161  * changing the task state if and only if any tasks are woken up.
2162  */
2163 int wake_up_process(struct task_struct *p)
2164 {
2165         return try_to_wake_up(p, TASK_NORMAL, 0);
2166 }
2167 EXPORT_SYMBOL(wake_up_process);
2168 
2169 int wake_up_state(struct task_struct *p, unsigned int state)
2170 {
2171         return try_to_wake_up(p, state, 0);
2172 }
2173 
2174 /*
2175  * This function clears the sched_dl_entity static params.
2176  */
2177 void __dl_clear_params(struct task_struct *p)
2178 {
2179         struct sched_dl_entity *dl_se = &p->dl;
2180 
2181         dl_se->dl_runtime = 0;
2182         dl_se->dl_deadline = 0;
2183         dl_se->dl_period = 0;
2184         dl_se->flags = 0;
2185         dl_se->dl_bw = 0;
2186 
2187         dl_se->dl_throttled = 0;
2188         dl_se->dl_yielded = 0;
2189 }
2190 
2191 /*
2192  * Perform scheduler related setup for a newly forked process p.
2193  * p is forked by current.
2194  *
2195  * __sched_fork() is basic setup used by init_idle() too:
2196  */
2197 static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
2198 {
2199         p->on_rq                        = 0;
2200 
2201         p->se.on_rq                     = 0;
2202         p->se.exec_start                = 0;
2203         p->se.sum_exec_runtime          = 0;
2204         p->se.prev_sum_exec_runtime     = 0;
2205         p->se.nr_migrations             = 0;
2206         p->se.vruntime                  = 0;
2207         INIT_LIST_HEAD(&p->se.group_node);
2208 
2209 #ifdef CONFIG_FAIR_GROUP_SCHED
2210         p->se.cfs_rq                    = NULL;
2211 #endif
2212 
2213 #ifdef CONFIG_SCHEDSTATS
2214         /* Even if schedstat is disabled, there should not be garbage */
2215         memset(&p->se.statistics, 0, sizeof(p->se.statistics));
2216 #endif
2217 
2218         RB_CLEAR_NODE(&p->dl.rb_node);
2219         init_dl_task_timer(&p->dl);
2220         __dl_clear_params(p);
2221 
2222         INIT_LIST_HEAD(&p->rt.run_list);
2223         p->rt.timeout           = 0;
2224         p->rt.time_slice        = sched_rr_timeslice;
2225         p->rt.on_rq             = 0;
2226         p->rt.on_list           = 0;
2227 
2228 #ifdef CONFIG_PREEMPT_NOTIFIERS
2229         INIT_HLIST_HEAD(&p->preempt_notifiers);
2230 #endif
2231 
2232 #ifdef CONFIG_NUMA_BALANCING
2233         if (p->mm && atomic_read(&p->mm->mm_users) == 1) {
2234                 p->mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2235                 p->mm->numa_scan_seq = 0;
2236         }
2237 
2238         if (clone_flags & CLONE_VM)
2239                 p->numa_preferred_nid = current->numa_preferred_nid;
2240         else
2241                 p->numa_preferred_nid = -1;
2242 
2243         p->node_stamp = 0ULL;
2244         p->numa_scan_seq = p->mm ? p->mm->numa_scan_seq : 0;
2245         p->numa_scan_period = sysctl_numa_balancing_scan_delay;
2246         p->numa_work.next = &p->numa_work;
2247         p->numa_faults = NULL;
2248         p->last_task_numa_placement = 0;
2249         p->last_sum_exec_runtime = 0;
2250 
2251         p->numa_group = NULL;
2252 #endif /* CONFIG_NUMA_BALANCING */
2253 }
2254 
2255 DEFINE_STATIC_KEY_FALSE(sched_numa_balancing);
2256 
2257 #ifdef CONFIG_NUMA_BALANCING
2258 
2259 void set_numabalancing_state(bool enabled)
2260 {
2261         if (enabled)
2262                 static_branch_enable(&sched_numa_balancing);
2263         else
2264                 static_branch_disable(&sched_numa_balancing);
2265 }
2266 
2267 #ifdef CONFIG_PROC_SYSCTL
2268 int sysctl_numa_balancing(struct ctl_table *table, int write,
2269                          void __user *buffer, size_t *lenp, loff_t *ppos)
2270 {
2271         struct ctl_table t;
2272         int err;
2273         int state = static_branch_likely(&sched_numa_balancing);
2274 
2275         if (write && !capable(CAP_SYS_ADMIN))
2276                 return -EPERM;
2277 
2278         t = *table;
2279         t.data = &state;
2280         err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2281         if (err < 0)
2282                 return err;
2283         if (write)
2284                 set_numabalancing_state(state);
2285         return err;
2286 }
2287 #endif
2288 #endif
2289 
2290 #ifdef CONFIG_SCHEDSTATS
2291 
2292 DEFINE_STATIC_KEY_FALSE(sched_schedstats);
2293 static bool __initdata __sched_schedstats = false;
2294 
2295 static void set_schedstats(bool enabled)
2296 {
2297         if (enabled)
2298                 static_branch_enable(&sched_schedstats);
2299         else
2300                 static_branch_disable(&sched_schedstats);
2301 }
2302 
2303 void force_schedstat_enabled(void)
2304 {
2305         if (!schedstat_enabled()) {
2306                 pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n");
2307                 static_branch_enable(&sched_schedstats);
2308         }
2309 }
2310 
2311 static int __init setup_schedstats(char *str)
2312 {
2313         int ret = 0;
2314         if (!str)
2315                 goto out;
2316 
2317         /*
2318          * This code is called before jump labels have been set up, so we can't
2319          * change the static branch directly just yet.  Instead set a temporary
2320          * variable so init_schedstats() can do it later.
2321          */
2322         if (!strcmp(str, "enable")) {
2323                 __sched_schedstats = true;
2324                 ret = 1;
2325         } else if (!strcmp(str, "disable")) {
2326                 __sched_schedstats = false;
2327                 ret = 1;
2328         }
2329 out:
2330         if (!ret)
2331                 pr_warn("Unable to parse schedstats=\n");
2332 
2333         return ret;
2334 }
2335 __setup("schedstats=", setup_schedstats);
2336 
2337 static void __init init_schedstats(void)
2338 {
2339         set_schedstats(__sched_schedstats);
2340 }
2341 
2342 #ifdef CONFIG_PROC_SYSCTL
2343 int sysctl_schedstats(struct ctl_table *table, int write,
2344                          void __user *buffer, size_t *lenp, loff_t *ppos)
2345 {
2346         struct ctl_table t;
2347         int err;
2348         int state = static_branch_likely(&sched_schedstats);
2349 
2350         if (write && !capable(CAP_SYS_ADMIN))
2351                 return -EPERM;
2352 
2353         t = *table;
2354         t.data = &state;
2355         err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2356         if (err < 0)
2357                 return err;
2358         if (write)
2359                 set_schedstats(state);
2360         return err;
2361 }
2362 #endif /* CONFIG_PROC_SYSCTL */
2363 #else  /* !CONFIG_SCHEDSTATS */
2364 static inline void init_schedstats(void) {}
2365 #endif /* CONFIG_SCHEDSTATS */
2366 
2367 /*
2368  * fork()/clone()-time setup:
2369  */
2370 int sched_fork(unsigned long clone_flags, struct task_struct *p)
2371 {
2372         unsigned long flags;
2373         int cpu = get_cpu();
2374 
2375         __sched_fork(clone_flags, p);
2376         /*
2377          * We mark the process as NEW here. This guarantees that
2378          * nobody will actually run it, and a signal or other external
2379          * event cannot wake it up and insert it on the runqueue either.
2380          */
2381         p->state = TASK_NEW;
2382 
2383         /*
2384          * Make sure we do not leak PI boosting priority to the child.
2385          */
2386         p->prio = current->normal_prio;
2387 
2388         /*
2389          * Revert to default priority/policy on fork if requested.
2390          */
2391         if (unlikely(p->sched_reset_on_fork)) {
2392                 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
2393                         p->policy = SCHED_NORMAL;
2394                         p->static_prio = NICE_TO_PRIO(0);
2395                         p->rt_priority = 0;
2396                 } else if (PRIO_TO_NICE(p->static_prio) < 0)
2397                         p->static_prio = NICE_TO_PRIO(0);
2398 
2399                 p->prio = p->normal_prio = __normal_prio(p);
2400                 set_load_weight(p);
2401 
2402                 /*
2403                  * We don't need the reset flag anymore after the fork. It has
2404                  * fulfilled its duty:
2405                  */
2406                 p->sched_reset_on_fork = 0;
2407         }
2408 
2409         if (dl_prio(p->prio)) {
2410                 put_cpu();
2411                 return -EAGAIN;
2412         } else if (rt_prio(p->prio)) {
2413                 p->sched_class = &rt_sched_class;
2414         } else {
2415                 p->sched_class = &fair_sched_class;
2416         }
2417 
2418         init_entity_runnable_average(&p->se);
2419 
2420         /*
2421          * The child is not yet in the pid-hash so no cgroup attach races,
2422          * and the cgroup is pinned to this child due to cgroup_fork()
2423          * is ran before sched_fork().
2424          *
2425          * Silence PROVE_RCU.
2426          */
2427         raw_spin_lock_irqsave(&p->pi_lock, flags);
2428         /*
2429          * We're setting the cpu for the first time, we don't migrate,
2430          * so use __set_task_cpu().
2431          */
2432         __set_task_cpu(p, cpu);
2433         if (p->sched_class->task_fork)
2434                 p->sched_class->task_fork(p);
2435         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2436 
2437 #ifdef CONFIG_SCHED_INFO
2438         if (likely(sched_info_on()))
2439                 memset(&p->sched_info, 0, sizeof(p->sched_info));
2440 #endif
2441 #if defined(CONFIG_SMP)
2442         p->on_cpu = 0;
2443 #endif
2444         init_task_preempt_count(p);
2445 #ifdef CONFIG_SMP
2446         plist_node_init(&p->pushable_tasks, MAX_PRIO);
2447         RB_CLEAR_NODE(&p->pushable_dl_tasks);
2448 #endif
2449 
2450         put_cpu();
2451         return 0;
2452 }
2453 
2454 unsigned long to_ratio(u64 period, u64 runtime)
2455 {
2456         if (runtime == RUNTIME_INF)
2457                 return 1ULL << 20;
2458 
2459         /*
2460          * Doing this here saves a lot of checks in all
2461          * the calling paths, and returning zero seems
2462          * safe for them anyway.
2463          */
2464         if (period == 0)
2465                 return 0;
2466 
2467         return div64_u64(runtime << 20, period);
2468 }
2469 
2470 #ifdef CONFIG_SMP
2471 inline struct dl_bw *dl_bw_of(int i)
2472 {
2473         RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
2474                          "sched RCU must be held");
2475         return &cpu_rq(i)->rd->dl_bw;
2476 }
2477 
2478 static inline int dl_bw_cpus(int i)
2479 {
2480         struct root_domain *rd = cpu_rq(i)->rd;
2481         int cpus = 0;
2482 
2483         RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
2484                          "sched RCU must be held");
2485         for_each_cpu_and(i, rd->span, cpu_active_mask)
2486                 cpus++;
2487 
2488         return cpus;
2489 }
2490 #else
2491 inline struct dl_bw *dl_bw_of(int i)
2492 {
2493         return &cpu_rq(i)->dl.dl_bw;
2494 }
2495 
2496 static inline int dl_bw_cpus(int i)
2497 {
2498         return 1;
2499 }
2500 #endif
2501 
2502 /*
2503  * We must be sure that accepting a new task (or allowing changing the
2504  * parameters of an existing one) is consistent with the bandwidth
2505  * constraints. If yes, this function also accordingly updates the currently
2506  * allocated bandwidth to reflect the new situation.
2507  *
2508  * This function is called while holding p's rq->lock.
2509  *
2510  * XXX we should delay bw change until the task's 0-lag point, see
2511  * __setparam_dl().
2512  */
2513 static int dl_overflow(struct task_struct *p, int policy,
2514                        const struct sched_attr *attr)
2515 {
2516 
2517         struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
2518         u64 period = attr->sched_period ?: attr->sched_deadline;
2519         u64 runtime = attr->sched_runtime;
2520         u64 new_bw = dl_policy(policy) ? to_ratio(period, runtime) : 0;
2521         int cpus, err = -1;
2522 
2523         /* !deadline task may carry old deadline bandwidth */
2524         if (new_bw == p->dl.dl_bw && task_has_dl_policy(p))
2525                 return 0;
2526 
2527         /*
2528          * Either if a task, enters, leave, or stays -deadline but changes
2529          * its parameters, we may need to update accordingly the total
2530          * allocated bandwidth of the container.
2531          */
2532         raw_spin_lock(&dl_b->lock);
2533         cpus = dl_bw_cpus(task_cpu(p));
2534         if (dl_policy(policy) && !task_has_dl_policy(p) &&
2535             !__dl_overflow(dl_b, cpus, 0, new_bw)) {
2536                 __dl_add(dl_b, new_bw);
2537                 err = 0;
2538         } else if (dl_policy(policy) && task_has_dl_policy(p) &&
2539                    !__dl_overflow(dl_b, cpus, p->dl.dl_bw, new_bw)) {
2540                 __dl_clear(dl_b, p->dl.dl_bw);
2541                 __dl_add(dl_b, new_bw);
2542                 err = 0;
2543         } else if (!dl_policy(policy) && task_has_dl_policy(p)) {
2544                 __dl_clear(dl_b, p->dl.dl_bw);
2545                 err = 0;
2546         }
2547         raw_spin_unlock(&dl_b->lock);
2548 
2549         return err;
2550 }
2551 
2552 extern void init_dl_bw(struct dl_bw *dl_b);
2553 
2554 /*
2555  * wake_up_new_task - wake up a newly created task for the first time.
2556  *
2557  * This function will do some initial scheduler statistics housekeeping
2558  * that must be done for every newly created context, then puts the task
2559  * on the runqueue and wakes it.
2560  */
2561 void wake_up_new_task(struct task_struct *p)
2562 {
2563         struct rq_flags rf;
2564         struct rq *rq;
2565 
2566         raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
2567         p->state = TASK_RUNNING;
2568 #ifdef CONFIG_SMP
2569         /*
2570          * Fork balancing, do it here and not earlier because:
2571          *  - cpus_allowed can change in the fork path
2572          *  - any previously selected cpu might disappear through hotplug
2573          *
2574          * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq,
2575          * as we're not fully set-up yet.
2576          */
2577         __set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0));
2578 #endif
2579         rq = __task_rq_lock(p, &rf);
2580         post_init_entity_util_avg(&p->se);
2581 
2582         activate_task(rq, p, 0);
2583         p->on_rq = TASK_ON_RQ_QUEUED;
2584         trace_sched_wakeup_new(p);
2585         check_preempt_curr(rq, p, WF_FORK);
2586 #ifdef CONFIG_SMP
2587         if (p->sched_class->task_woken) {
2588                 /*
2589                  * Nothing relies on rq->lock after this, so its fine to
2590                  * drop it.
2591                  */
2592                 lockdep_unpin_lock(&rq->lock, rf.cookie);
2593                 p->sched_class->task_woken(rq, p);
2594                 lockdep_repin_lock(&rq->lock, rf.cookie);
2595         }
2596 #endif
2597         task_rq_unlock(rq, p, &rf);
2598 }
2599 
2600 #ifdef CONFIG_PREEMPT_NOTIFIERS
2601 
2602 static struct static_key preempt_notifier_key = STATIC_KEY_INIT_FALSE;
2603 
2604 void preempt_notifier_inc(void)
2605 {
2606         static_key_slow_inc(&preempt_notifier_key);
2607 }
2608 EXPORT_SYMBOL_GPL(preempt_notifier_inc);
2609 
2610 void preempt_notifier_dec(void)
2611 {
2612         static_key_slow_dec(&preempt_notifier_key);
2613 }
2614 EXPORT_SYMBOL_GPL(preempt_notifier_dec);
2615 
2616 /**
2617  * preempt_notifier_register - tell me when current is being preempted & rescheduled
2618  * @notifier: notifier struct to register
2619  */
2620 void preempt_notifier_register(struct preempt_notifier *notifier)
2621 {
2622         if (!static_key_false(&preempt_notifier_key))
2623                 WARN(1, "registering preempt_notifier while notifiers disabled\n");
2624 
2625         hlist_add_head(&notifier->link, &current->preempt_notifiers);
2626 }
2627 EXPORT_SYMBOL_GPL(preempt_notifier_register);
2628 
2629 /**
2630  * preempt_notifier_unregister - no longer interested in preemption notifications
2631  * @notifier: notifier struct to unregister
2632  *
2633  * This is *not* safe to call from within a preemption notifier.
2634  */
2635 void preempt_notifier_unregister(struct preempt_notifier *notifier)
2636 {
2637         hlist_del(&notifier->link);
2638 }
2639 EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
2640 
2641 static void __fire_sched_in_preempt_notifiers(struct task_struct *curr)
2642 {
2643         struct preempt_notifier *notifier;
2644 
2645         hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
2646                 notifier->ops->sched_in(notifier, raw_smp_processor_id());
2647 }
2648 
2649 static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
2650 {
2651         if (static_key_false(&preempt_notifier_key))
2652                 __fire_sched_in_preempt_notifiers(curr);
2653 }
2654 
2655 static void
2656 __fire_sched_out_preempt_notifiers(struct task_struct *curr,
2657                                    struct task_struct *next)
2658 {
2659         struct preempt_notifier *notifier;
2660 
2661         hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
2662                 notifier->ops->sched_out(notifier, next);
2663 }
2664 
2665 static __always_inline void
2666 fire_sched_out_preempt_notifiers(struct task_struct *curr,
2667                                  struct task_struct *next)
2668 {
2669         if (static_key_false(&preempt_notifier_key))
2670                 __fire_sched_out_preempt_notifiers(curr, next);
2671 }
2672 
2673 #else /* !CONFIG_PREEMPT_NOTIFIERS */
2674 
2675 static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
2676 {
2677 }
2678 
2679 static inline void
2680 fire_sched_out_preempt_notifiers(struct task_struct *curr,
2681                                  struct task_struct *next)
2682 {
2683 }
2684 
2685 #endif /* CONFIG_PREEMPT_NOTIFIERS */
2686 
2687 /**
2688  * prepare_task_switch - prepare to switch tasks
2689  * @rq: the runqueue preparing to switch
2690  * @prev: the current task that is being switched out
2691  * @next: the task we are going to switch to.
2692  *
2693  * This is called with the rq lock held and interrupts off. It must
2694  * be paired with a subsequent finish_task_switch after the context
2695  * switch.
2696  *
2697  * prepare_task_switch sets up locking and calls architecture specific
2698  * hooks.
2699  */
2700 static inline void
2701 prepare_task_switch(struct rq *rq, struct task_struct *prev,
2702                     struct task_struct *next)
2703 {
2704         sched_info_switch(rq, prev, next);
2705         perf_event_task_sched_out(prev, next);
2706         fire_sched_out_preempt_notifiers(prev, next);
2707         prepare_lock_switch(rq, next);
2708         prepare_arch_switch(next);
2709 }
2710 
2711 /**
2712  * finish_task_switch - clean up after a task-switch
2713  * @prev: the thread we just switched away from.
2714  *
2715  * finish_task_switch must be called after the context switch, paired
2716  * with a prepare_task_switch call before the context switch.
2717  * finish_task_switch will reconcile locking set up by prepare_task_switch,
2718  * and do any other architecture-specific cleanup actions.
2719  *
2720  * Note that we may have delayed dropping an mm in context_switch(). If
2721  * so, we finish that here outside of the runqueue lock. (Doing it
2722  * with the lock held can cause deadlocks; see schedule() for
2723  * details.)
2724  *
2725  * The context switch have flipped the stack from under us and restored the
2726  * local variables which were saved when this task called schedule() in the
2727  * past. prev == current is still correct but we need to recalculate this_rq
2728  * because prev may have moved to another CPU.
2729  */
2730 static struct rq *finish_task_switch(struct task_struct *prev)
2731         __releases(rq->lock)
2732 {
2733         struct rq *rq = this_rq();
2734         struct mm_struct *mm = rq->prev_mm;
2735         long prev_state;
2736 
2737         /*
2738          * The previous task will have left us with a preempt_count of 2
2739          * because it left us after:
2740          *
2741          *      schedule()
2742          *        preempt_disable();                    // 1
2743          *        __schedule()
2744          *          raw_spin_lock_irq(&rq->lock)        // 2
2745          *
2746          * Also, see FORK_PREEMPT_COUNT.
2747          */
2748         if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET,
2749                       "corrupted preempt_count: %s/%d/0x%x\n",
2750                       current->comm, current->pid, preempt_count()))
2751                 preempt_count_set(FORK_PREEMPT_COUNT);
2752 
2753         rq->prev_mm = NULL;
2754 
2755         /*
2756          * A task struct has one reference for the use as "current".
2757          * If a task dies, then it sets TASK_DEAD in tsk->state and calls
2758          * schedule one last time. The schedule call will never return, and
2759          * the scheduled task must drop that reference.
2760          *
2761          * We must observe prev->state before clearing prev->on_cpu (in
2762          * finish_lock_switch), otherwise a concurrent wakeup can get prev
2763          * running on another CPU and we could rave with its RUNNING -> DEAD
2764          * transition, resulting in a double drop.
2765          */
2766         prev_state = prev->state;
2767         vtime_task_switch(prev);
2768         perf_event_task_sched_in(prev, current);
2769         finish_lock_switch(rq, prev);
2770         finish_arch_post_lock_switch();
2771 
2772         fire_sched_in_preempt_notifiers(current);
2773         if (mm)
2774                 mmdrop(mm);
2775         if (unlikely(prev_state == TASK_DEAD)) {
2776                 if (prev->sched_class->task_dead)
2777                         prev->sched_class->task_dead(prev);
2778 
2779                 /*
2780                  * Remove function-return probe instances associated with this
2781                  * task and put them back on the free list.
2782                  */
2783                 kprobe_flush_task(prev);
2784 
2785                 /* Task is done with its stack. */
2786                 put_task_stack(prev);
2787 
2788                 put_task_struct(prev);
2789         }
2790 
2791         tick_nohz_task_switch();
2792         return rq;
2793 }
2794 
2795 #ifdef CONFIG_SMP
2796 
2797 /* rq->lock is NOT held, but preemption is disabled */
2798 static void __balance_callback(struct rq *rq)
2799 {
2800         struct callback_head *head, *next;
2801         void (*func)(struct rq *rq);
2802         unsigned long flags;
2803 
2804         raw_spin_lock_irqsave(&rq->lock, flags);
2805         head = rq->balance_callback;
2806         rq->balance_callback = NULL;
2807         while (head) {
2808                 func = (void (*)(struct rq *))head->func;
2809                 next = head->next;
2810                 head->next = NULL;
2811                 head = next;
2812 
2813                 func(rq);
2814         }
2815         raw_spin_unlock_irqrestore(&rq->lock, flags);
2816 }
2817 
2818 static inline void balance_callback(struct rq *rq)
2819 {
2820         if (unlikely(rq->balance_callback))
2821                 __balance_callback(rq);
2822 }
2823 
2824 #else
2825 
2826 static inline void balance_callback(struct rq *rq)
2827 {
2828 }
2829 
2830 #endif
2831 
2832 /**
2833  * schedule_tail - first thing a freshly forked thread must call.
2834  * @prev: the thread we just switched away from.
2835  */
2836 asmlinkage __visible void schedule_tail(struct task_struct *prev)
2837         __releases(rq->lock)
2838 {
2839         struct rq *rq;
2840 
2841         /*
2842          * New tasks start with FORK_PREEMPT_COUNT, see there and
2843          * finish_task_switch() for details.
2844          *
2845          * finish_task_switch() will drop rq->lock() and lower preempt_count
2846          * and the preempt_enable() will end up enabling preemption (on
2847          * PREEMPT_COUNT kernels).
2848          */
2849 
2850         rq = finish_task_switch(prev);
2851         balance_callback(rq);
2852         preempt_enable();
2853 
2854         if (current->set_child_tid)
2855                 put_user(task_pid_vnr(current), current->set_child_tid);
2856 }
2857 
2858 /*
2859  * context_switch - switch to the new MM and the new thread's register state.
2860  */
2861 static __always_inline struct rq *
2862 context_switch(struct rq *rq, struct task_struct *prev,
2863                struct task_struct *next, struct pin_cookie cookie)
2864 {
2865         struct mm_struct *mm, *oldmm;
2866 
2867         prepare_task_switch(rq, prev, next);
2868 
2869         mm = next->mm;
2870         oldmm = prev->active_mm;
2871         /*
2872          * For paravirt, this is coupled with an exit in switch_to to
2873          * combine the page table reload and the switch backend into
2874          * one hypercall.
2875          */
2876         arch_start_context_switch(prev);
2877 
2878         if (!mm) {
2879                 next->active_mm = oldmm;
2880                 atomic_inc(&oldmm->mm_count);
2881                 enter_lazy_tlb(oldmm, next);
2882         } else
2883                 switch_mm_irqs_off(oldmm, mm, next);
2884 
2885         if (!prev->mm) {
2886                 prev->active_mm = NULL;
2887                 rq->prev_mm = oldmm;
2888         }
2889         /*
2890          * Since the runqueue lock will be released by the next
2891          * task (which is an invalid locking op but in the case
2892          * of the scheduler it's an obvious special-case), so we
2893          * do an early lockdep release here:
2894          */
2895         lockdep_unpin_lock(&rq->lock, cookie);
2896         spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
2897 
2898         /* Here we just switch the register state and the stack. */
2899         switch_to(prev, next, prev);
2900         barrier();
2901 
2902         return finish_task_switch(prev);
2903 }
2904 
2905 /*
2906  * nr_running and nr_context_switches:
2907  *
2908  * externally visible scheduler statistics: current number of runnable
2909  * threads, total number of context switches performed since bootup.
2910  */
2911 unsigned long nr_running(void)
2912 {
2913         unsigned long i, sum = 0;
2914 
2915         for_each_online_cpu(i)
2916                 sum += cpu_rq(i)->nr_running;
2917 
2918         return sum;
2919 }
2920 
2921 /*
2922  * Check if only the current task is running on the cpu.
2923  *
2924  * Caution: this function does not check that the caller has disabled
2925  * preemption, thus the result might have a time-of-check-to-time-of-use
2926  * race.  The caller is responsible to use it correctly, for example:
2927  *
2928  * - from a non-preemptable section (of course)
2929  *
2930  * - from a thread that is bound to a single CPU
2931  *
2932  * - in a loop with very short iterations (e.g. a polling loop)
2933  */
2934 bool single_task_running(void)
2935 {
2936         return raw_rq()->nr_running == 1;
2937 }
2938 EXPORT_SYMBOL(single_task_running);
2939 
2940 unsigned long long nr_context_switches(void)
2941 {
2942         int i;
2943         unsigned long long sum = 0;
2944 
2945         for_each_possible_cpu(i)
2946                 sum += cpu_rq(i)->nr_switches;
2947 
2948         return sum;
2949 }
2950 
2951 unsigned long nr_iowait(void)
2952 {
2953         unsigned long i, sum = 0;
2954 
2955         for_each_possible_cpu(i)
2956                 sum += atomic_read(&cpu_rq(i)->nr_iowait);
2957 
2958         return sum;
2959 }
2960 
2961 unsigned long nr_iowait_cpu(int cpu)
2962 {
2963         struct rq *this = cpu_rq(cpu);
2964         return atomic_read(&this->nr_iowait);
2965 }
2966 
2967 void get_iowait_load(unsigned long *nr_waiters, unsigned long *load)
2968 {
2969         struct rq *rq = this_rq();
2970         *nr_waiters = atomic_read(&rq->nr_iowait);
2971         *load = rq->load.weight;
2972 }
2973 
2974 #ifdef CONFIG_SMP
2975 
2976 /*
2977  * sched_exec - execve() is a valuable balancing opportunity, because at
2978  * this point the task has the smallest effective memory and cache footprint.
2979  */
2980 void sched_exec(void)
2981 {
2982         struct task_struct *p = current;
2983         unsigned long flags;
2984         int dest_cpu;
2985 
2986         raw_spin_lock_irqsave(&p->pi_lock, flags);
2987         dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), SD_BALANCE_EXEC, 0);
2988         if (dest_cpu == smp_processor_id())
2989                 goto unlock;
2990 
2991         if (likely(cpu_active(dest_cpu))) {
2992                 struct migration_arg arg = { p, dest_cpu };
2993 
2994                 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2995                 stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
2996                 return;
2997         }
2998 unlock:
2999         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
3000 }
3001 
3002 #endif
3003 
3004 DEFINE_PER_CPU(struct kernel_stat, kstat);
3005 DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat);
3006 
3007 EXPORT_PER_CPU_SYMBOL(kstat);
3008 EXPORT_PER_CPU_SYMBOL(kernel_cpustat);
3009 
3010 /*
3011  * The function fair_sched_class.update_curr accesses the struct curr
3012  * and its field curr->exec_start; when called from task_sched_runtime(),
3013  * we observe a high rate of cache misses in practice.
3014  * Prefetching this data results in improved performance.
3015  */
3016 static inline void prefetch_curr_exec_start(struct task_struct *p)
3017 {
3018 #ifdef CONFIG_FAIR_GROUP_SCHED
3019         struct sched_entity *curr = (&p->se)->cfs_rq->curr;
3020 #else
3021         struct sched_entity *curr = (&task_rq(p)->cfs)->curr;
3022 #endif
3023         prefetch(curr);
3024         prefetch(&curr->exec_start);
3025 }
3026 
3027 /*
3028  * Return accounted runtime for the task.
3029  * In case the task is currently running, return the runtime plus current's
3030  * pending runtime that have not been accounted yet.
3031  */
3032 unsigned long long task_sched_runtime(struct task_struct *p)
3033 {
3034         struct rq_flags rf;
3035         struct rq *rq;
3036         u64 ns;
3037 
3038 #if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
3039         /*
3040          * 64-bit doesn't need locks to atomically read a 64bit value.
3041          * So we have a optimization chance when the task's delta_exec is 0.
3042          * Reading ->on_cpu is racy, but this is ok.
3043          *
3044          * If we race with it leaving cpu, we'll take a lock. So we're correct.
3045          * If we race with it entering cpu, unaccounted time is 0. This is
3046          * indistinguishable from the read occurring a few cycles earlier.
3047          * If we see ->on_cpu without ->on_rq, the task is leaving, and has
3048          * been accounted, so we're correct here as well.
3049          */
3050         if (!p->on_cpu || !task_on_rq_queued(p))
3051                 return p->se.sum_exec_runtime;
3052 #endif
3053 
3054         rq = task_rq_lock(p, &rf);
3055         /*
3056          * Must be ->curr _and_ ->on_rq.  If dequeued, we would
3057          * project cycles that may never be accounted to this
3058          * thread, breaking clock_gettime().
3059          */
3060         if (task_current(rq, p) && task_on_rq_queued(p)) {
3061                 prefetch_curr_exec_start(p);
3062                 update_rq_clock(rq);
3063                 p->sched_class->update_curr(rq);
3064         }
3065         ns = p->se.sum_exec_runtime;
3066         task_rq_unlock(rq, p, &rf);
3067 
3068         return ns;
3069 }
3070 
3071 /*
3072  * This function gets called by the timer code, with HZ frequency.
3073  * We call it with interrupts disabled.
3074  */
3075 void scheduler_tick(void)
3076 {
3077         int cpu = smp_processor_id();
3078         struct rq *rq = cpu_rq(cpu);
3079         struct task_struct *curr = rq->curr;
3080 
3081         sched_clock_tick();
3082 
3083         raw_spin_lock(&rq->lock);
3084         update_rq_clock(rq);
3085         curr->sched_class->task_tick(rq, curr, 0);
3086         cpu_load_update_active(rq);
3087         calc_global_load_tick(rq);
3088         raw_spin_unlock(&rq->lock);
3089 
3090         perf_event_task_tick();
3091 
3092 #ifdef CONFIG_SMP
3093         rq->idle_balance = idle_cpu(cpu);
3094         trigger_load_balance(rq);
3095 #endif
3096         rq_last_tick_reset(rq);
3097 }
3098 
3099 #ifdef CONFIG_NO_HZ_FULL
3100 /**
3101  * scheduler_tick_max_deferment
3102  *
3103  * Keep at least one tick per second when a single
3104  * active task is running because the scheduler doesn't
3105  * yet completely support full dynticks environment.
3106  *
3107  * This makes sure that uptime, CFS vruntime, load
3108  * balancing, etc... continue to move forward, even
3109  * with a very low granularity.
3110  *
3111  * Return: Maximum deferment in nanoseconds.
3112  */
3113 u64 scheduler_tick_max_deferment(void)
3114 {
3115         struct rq *rq = this_rq();
3116         unsigned long next, now = READ_ONCE(jiffies);
3117 
3118         next = rq->last_sched_tick + HZ;
3119 
3120         if (time_before_eq(next, now))
3121                 return 0;
3122 
3123         return jiffies_to_nsecs(next - now);
3124 }
3125 #endif
3126 
3127 #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
3128                                 defined(CONFIG_PREEMPT_TRACER))
3129 /*
3130  * If the value passed in is equal to the current preempt count
3131  * then we just disabled preemption. Start timing the latency.
3132  */
3133 static inline void preempt_latency_start(int val)
3134 {
3135         if (preempt_count() == val) {
3136                 unsigned long ip = get_lock_parent_ip();
3137 #ifdef CONFIG_DEBUG_PREEMPT
3138                 current->preempt_disable_ip = ip;
3139 #endif
3140                 trace_preempt_off(CALLER_ADDR0, ip);
3141         }
3142 }
3143 
3144 void preempt_count_add(int val)
3145 {
3146 #ifdef CONFIG_DEBUG_PREEMPT
3147         /*
3148          * Underflow?
3149          */
3150         if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
3151                 return;
3152 #endif
3153         __preempt_count_add(val);
3154 #ifdef CONFIG_DEBUG_PREEMPT
3155         /*
3156          * Spinlock count overflowing soon?
3157          */
3158         DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
3159                                 PREEMPT_MASK - 10);
3160 #endif
3161         preempt_latency_start(val);
3162 }
3163 EXPORT_SYMBOL(preempt_count_add);
3164 NOKPROBE_SYMBOL(preempt_count_add);
3165 
3166 /*
3167  * If the value passed in equals to the current preempt count
3168  * then we just enabled preemption. Stop timing the latency.
3169  */
3170 static inline void preempt_latency_stop(int val)
3171 {
3172         if (preempt_count() == val)
3173                 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
3174 }
3175 
3176 void preempt_count_sub(int val)
3177 {
3178 #ifdef CONFIG_DEBUG_PREEMPT
3179         /*
3180          * Underflow?
3181          */
3182         if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
3183                 return;
3184         /*
3185          * Is the spinlock portion underflowing?
3186          */
3187         if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
3188                         !(preempt_count() & PREEMPT_MASK)))
3189                 return;
3190 #endif
3191 
3192         preempt_latency_stop(val);
3193         __preempt_count_sub(val);
3194 }
3195 EXPORT_SYMBOL(preempt_count_sub);
3196 NOKPROBE_SYMBOL(preempt_count_sub);
3197 
3198 #else
3199 static inline void preempt_latency_start(int val) { }
3200 static inline void preempt_latency_stop(int val) { }
3201 #endif
3202 
3203 /*
3204  * Print scheduling while atomic bug:
3205  */
3206 static noinline void __schedule_bug(struct task_struct *prev)
3207 {
3208         /* Save this before calling printk(), since that will clobber it */
3209         unsigned long preempt_disable_ip = get_preempt_disable_ip(current);
3210 
3211         if (oops_in_progress)
3212                 return;
3213 
3214         printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
3215                 prev->comm, prev->pid, preempt_count());
3216 
3217         debug_show_held_locks(prev);
3218         print_modules();
3219         if (irqs_disabled())
3220                 print_irqtrace_events(prev);
3221         if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
3222             && in_atomic_preempt_off()) {
3223                 pr_err("Preemption disabled at:");
3224                 print_ip_sym(preempt_disable_ip);
3225                 pr_cont("\n");
3226         }
3227         if (panic_on_warn)
3228                 panic("scheduling while atomic\n");
3229 
3230         dump_stack();
3231         add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
3232 }
3233 
3234 /*
3235  * Various schedule()-time debugging checks and statistics:
3236  */
3237 static inline void schedule_debug(struct task_struct *prev)
3238 {
3239 #ifdef CONFIG_SCHED_STACK_END_CHECK
3240         if (task_stack_end_corrupted(prev))
3241                 panic("corrupted stack end detected inside scheduler\n");
3242 #endif
3243 
3244         if (unlikely(in_atomic_preempt_off())) {
3245                 __schedule_bug(prev);
3246                 preempt_count_set(PREEMPT_DISABLED);
3247         }
3248         rcu_sleep_check();
3249 
3250         profile_hit(SCHED_PROFILING, __builtin_return_address(0));
3251 
3252         schedstat_inc(this_rq()->sched_count);
3253 }
3254 
3255 /*
3256  * Pick up the highest-prio task:
3257  */
3258 static inline struct task_struct *
3259 pick_next_task(struct rq *rq, struct task_struct *prev, struct pin_cookie cookie)
3260 {
3261         const struct sched_class *class = &fair_sched_class;
3262         struct task_struct *p;
3263 
3264         /*
3265          * Optimization: we know that if all tasks are in
3266          * the fair class we can call that function directly:
3267          */
3268         if (likely(prev->sched_class == class &&
3269                    rq->nr_running == rq->cfs.h_nr_running)) {
3270                 p = fair_sched_class.pick_next_task(rq, prev, cookie);
3271                 if (unlikely(p == RETRY_TASK))
3272                         goto again;
3273 
3274                 /* assumes fair_sched_class->next == idle_sched_class */
3275                 if (unlikely(!p))
3276                         p = idle_sched_class.pick_next_task(rq, prev, cookie);
3277 
3278                 return p;
3279         }
3280 
3281 again:
3282         for_each_class(class) {
3283                 p = class->pick_next_task(rq, prev, cookie);
3284                 if (p) {
3285                         if (unlikely(p == RETRY_TASK))
3286                                 goto again;
3287                         return p;
3288                 }
3289         }
3290 
3291         BUG(); /* the idle class will always have a runnable task */
3292 }
3293 
3294 /*
3295  * __schedule() is the main scheduler function.
3296  *
3297  * The main means of driving the scheduler and thus entering this function are:
3298  *
3299  *   1. Explicit blocking: mutex, semaphore, waitqueue, etc.
3300  *
3301  *   2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
3302  *      paths. For example, see arch/x86/entry_64.S.
3303  *
3304  *      To drive preemption between tasks, the scheduler sets the flag in timer
3305  *      interrupt handler scheduler_tick().
3306  *
3307  *   3. Wakeups don't really cause entry into schedule(). They add a
3308  *      task to the run-queue and that's it.
3309  *
3310  *      Now, if the new task added to the run-queue preempts the current
3311  *      task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
3312  *      called on the nearest possible occasion:
3313  *
3314  *       - If the kernel is preemptible (CONFIG_PREEMPT=y):
3315  *
3316  *         - in syscall or exception context, at the next outmost
3317  *           preempt_enable(). (this might be as soon as the wake_up()'s
3318  *           spin_unlock()!)
3319  *
3320  *         - in IRQ context, return from interrupt-handler to
3321  *           preemptible context
3322  *
3323  *       - If the kernel is not preemptible (CONFIG_PREEMPT is not set)
3324  *         then at the next:
3325  *
3326  *          - cond_resched() call
3327  *          - explicit schedule() call
3328  *          - return from syscall or exception to user-space
3329  *          - return from interrupt-handler to user-space
3330  *
3331  * WARNING: must be called with preemption disabled!
3332  */
3333 static void __sched notrace __schedule(bool preempt)
3334 {
3335         struct task_struct *prev, *next;
3336         unsigned long *switch_count;
3337         struct pin_cookie cookie;
3338         struct rq *rq;
3339         int cpu;
3340 
3341         cpu = smp_processor_id();
3342         rq = cpu_rq(cpu);
3343         prev = rq->curr;
3344 
3345         schedule_debug(prev);
3346 
3347         if (sched_feat(HRTICK))
3348                 hrtick_clear(rq);
3349 
3350         local_irq_disable();
3351         rcu_note_context_switch();
3352 
3353         /*
3354          * Make sure that signal_pending_state()->signal_pending() below
3355          * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
3356          * done by the caller to avoid the race with signal_wake_up().
3357          */
3358         smp_mb__before_spinlock();
3359         raw_spin_lock(&rq->lock);
3360         cookie = lockdep_pin_lock(&rq->lock);
3361 
3362         rq->clock_skip_update <<= 1; /* promote REQ to ACT */
3363 
3364         switch_count = &prev->nivcsw;
3365         if (!preempt && prev->state) {
3366                 if (unlikely(signal_pending_state(prev->state, prev))) {
3367                         prev->state = TASK_RUNNING;
3368                 } else {
3369                         deactivate_task(rq, prev, DEQUEUE_SLEEP);
3370                         prev->on_rq = 0;
3371 
3372                         /*
3373                          * If a worker went to sleep, notify and ask workqueue
3374                          * whether it wants to wake up a task to maintain
3375                          * concurrency.
3376                          */
3377                         if (prev->flags & PF_WQ_WORKER) {
3378                                 struct task_struct *to_wakeup;
3379 
3380                                 to_wakeup = wq_worker_sleeping(prev);
3381                                 if (to_wakeup)
3382                                         try_to_wake_up_local(to_wakeup, cookie);
3383                         }
3384                 }
3385                 switch_count = &prev->nvcsw;
3386         }
3387 
3388         if (task_on_rq_queued(prev))
3389                 update_rq_clock(rq);
3390 
3391         next = pick_next_task(rq, prev, cookie);
3392         clear_tsk_need_resched(prev);
3393         clear_preempt_need_resched();
3394         rq->clock_skip_update = 0;
3395 
3396         if (likely(prev != next)) {
3397                 rq->nr_switches++;
3398                 rq->curr = next;
3399                 ++*switch_count;
3400 
3401                 trace_sched_switch(preempt, prev, next);
3402                 rq = context_switch(rq, prev, next, cookie); /* unlocks the rq */
3403         } else {
3404                 lockdep_unpin_lock(&rq->lock, cookie);
3405                 raw_spin_unlock_irq(&rq->lock);
3406         }
3407 
3408         balance_callback(rq);
3409 }
3410 
3411 void __noreturn do_task_dead(void)
3412 {
3413         /*
3414          * The setting of TASK_RUNNING by try_to_wake_up() may be delayed
3415          * when the following two conditions become true.
3416          *   - There is race condition of mmap_sem (It is acquired by
3417          *     exit_mm()), and
3418          *   - SMI occurs before setting TASK_RUNINNG.
3419          *     (or hypervisor of virtual machine switches to other guest)
3420          *  As a result, we may become TASK_RUNNING after becoming TASK_DEAD
3421          *
3422          * To avoid it, we have to wait for releasing tsk->pi_lock which
3423          * is held by try_to_wake_up()
3424          */
3425         smp_mb();
3426         raw_spin_unlock_wait(&current->pi_lock);
3427 
3428         /* causes final put_task_struct in finish_task_switch(). */
3429         __set_current_state(TASK_DEAD);
3430         current->flags |= PF_NOFREEZE;  /* tell freezer to ignore us */
3431         __schedule(false);
3432         BUG();
3433         /* Avoid "noreturn function does return".  */
3434         for (;;)
3435                 cpu_relax();    /* For when BUG is null */
3436 }
3437 
3438 static inline void sched_submit_work(struct task_struct *tsk)
3439 {
3440         if (!tsk->state || tsk_is_pi_blocked(tsk))
3441                 return;
3442         /*
3443          * If we are going to sleep and we have plugged IO queued,
3444          * make sure to submit it to avoid deadlocks.
3445          */
3446         if (blk_needs_flush_plug(tsk))
3447                 blk_schedule_flush_plug(tsk);
3448 }
3449 
3450 asmlinkage __visible void __sched schedule(void)
3451 {
3452         struct task_struct *tsk = current;
3453 
3454         sched_submit_work(tsk);
3455         do {
3456                 preempt_disable();
3457                 __schedule(false);
3458                 sched_preempt_enable_no_resched();
3459         } while (need_resched());
3460 }
3461 EXPORT_SYMBOL(schedule);
3462 
3463 #ifdef CONFIG_CONTEXT_TRACKING
3464 asmlinkage __visible void __sched schedule_user(void)
3465 {
3466         /*
3467          * If we come here after a random call to set_need_resched(),
3468          * or we have been woken up remotely but the IPI has not yet arrived,
3469          * we haven't yet exited the RCU idle mode. Do it here manually until
3470          * we find a better solution.
3471          *
3472          * NB: There are buggy callers of this function.  Ideally we
3473          * should warn if prev_state != CONTEXT_USER, but that will trigger
3474          * too frequently to make sense yet.
3475          */
3476         enum ctx_state prev_state = exception_enter();
3477         schedule();
3478         exception_exit(prev_state);
3479 }
3480 #endif
3481 
3482 /**
3483  * schedule_preempt_disabled - called with preemption disabled
3484  *
3485  * Returns with preemption disabled. Note: preempt_count must be 1
3486  */
3487 void __sched schedule_preempt_disabled(void)
3488 {
3489         sched_preempt_enable_no_resched();
3490         schedule();
3491         preempt_disable();
3492 }
3493 
3494 static void __sched notrace preempt_schedule_common(void)
3495 {
3496         do {
3497                 /*
3498                  * Because the function tracer can trace preempt_count_sub()
3499                  * and it also uses preempt_enable/disable_notrace(), if
3500                  * NEED_RESCHED is set, the preempt_enable_notrace() called
3501                  * by the function tracer will call this function again and
3502                  * cause infinite recursion.
3503                  *
3504                  * Preemption must be disabled here before the function
3505                  * tracer can trace. Break up preempt_disable() into two
3506                  * calls. One to disable preemption without fear of being
3507                  * traced. The other to still record the preemption latency,
3508                  * which can also be traced by the function tracer.
3509                  */
3510                 preempt_disable_notrace();
3511                 preempt_latency_start(1);
3512                 __schedule(true);
3513                 preempt_latency_stop(1);
3514                 preempt_enable_no_resched_notrace();
3515 
3516                 /*
3517                  * Check again in case we missed a preemption opportunity
3518                  * between schedule and now.
3519                  */
3520         } while (need_resched());
3521 }
3522 
3523 #ifdef CONFIG_PREEMPT
3524 /*
3525  * this is the entry point to schedule() from in-kernel preemption
3526  * off of preempt_enable. Kernel preemptions off return from interrupt
3527  * occur there and call schedule directly.
3528  */
3529 asmlinkage __visible void __sched notrace preempt_schedule(void)
3530 {
3531         /*
3532          * If there is a non-zero preempt_count or interrupts are disabled,
3533          * we do not want to preempt the current task. Just return..
3534          */
3535         if (likely(!preemptible()))
3536                 return;
3537 
3538         preempt_schedule_common();
3539 }
3540 NOKPROBE_SYMBOL(preempt_schedule);
3541 EXPORT_SYMBOL(preempt_schedule);
3542 
3543 /**
3544  * preempt_schedule_notrace - preempt_schedule called by tracing
3545  *
3546  * The tracing infrastructure uses preempt_enable_notrace to prevent
3547  * recursion and tracing preempt enabling caused by the tracing
3548  * infrastructure itself. But as tracing can happen in areas coming
3549  * from userspace or just about to enter userspace, a preempt enable
3550  * can occur before user_exit() is called. This will cause the scheduler
3551  * to be called when the system is still in usermode.
3552  *
3553  * To prevent this, the preempt_enable_notrace will use this function
3554  * instead of preempt_schedule() to exit user context if needed before
3555  * calling the scheduler.
3556  */
3557 asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
3558 {
3559         enum ctx_state prev_ctx;
3560 
3561         if (likely(!preemptible()))
3562                 return;
3563 
3564         do {
3565                 /*
3566                  * Because the function tracer can trace preempt_count_sub()
3567                  * and it also uses preempt_enable/disable_notrace(), if
3568                  * NEED_RESCHED is set, the preempt_enable_notrace() called
3569                  * by the function tracer will call this function again and
3570                  * cause infinite recursion.
3571                  *
3572                  * Preemption must be disabled here before the function
3573                  * tracer can trace. Break up preempt_disable() into two
3574                  * calls. One to disable preemption without fear of being
3575                  * traced. The other to still record the preemption latency,
3576                  * which can also be traced by the function tracer.
3577                  */
3578                 preempt_disable_notrace();
3579                 preempt_latency_start(1);
3580                 /*
3581                  * Needs preempt disabled in case user_exit() is traced
3582                  * and the tracer calls preempt_enable_notrace() causing
3583                  * an infinite recursion.
3584                  */
3585                 prev_ctx = exception_enter();
3586                 __schedule(true);
3587                 exception_exit(prev_ctx);
3588 
3589                 preempt_latency_stop(1);
3590                 preempt_enable_no_resched_notrace();
3591         } while (need_resched());
3592 }
3593 EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
3594 
3595 #endif /* CONFIG_PREEMPT */
3596 
3597 /*
3598  * this is the entry point to schedule() from kernel preemption
3599  * off of irq context.
3600  * Note, that this is called and return with irqs disabled. This will
3601  * protect us against recursive calling from irq.
3602  */
3603 asmlinkage __visible void __sched preempt_schedule_irq(void)
3604 {
3605         enum ctx_state prev_state;
3606 
3607         /* Catch callers which need to be fixed */
3608         BUG_ON(preempt_count() || !irqs_disabled());
3609 
3610         prev_state = exception_enter();
3611 
3612         do {
3613                 preempt_disable();
3614                 local_irq_enable();
3615                 __schedule(true);
3616                 local_irq_disable();
3617                 sched_preempt_enable_no_resched();
3618         } while (need_resched());
3619 
3620         exception_exit(prev_state);
3621 }
3622 
3623 int default_wake_function(wait_queue_t *curr, unsigned mode, int wake_flags,
3624                           void *key)
3625 {
3626         return try_to_wake_up(curr->private, mode, wake_flags);
3627 }
3628 EXPORT_SYMBOL(default_wake_function);
3629 
3630 #ifdef CONFIG_RT_MUTEXES
3631 
3632 /*
3633  * rt_mutex_setprio - set the current priority of a task
3634  * @p: task
3635  * @prio: prio value (kernel-internal form)
3636  *
3637  * This function changes the 'effective' priority of a task. It does
3638  * not touch ->normal_prio like __setscheduler().
3639  *
3640  * Used by the rt_mutex code to implement priority inheritance
3641  * logic. Call site only calls if the priority of the task changed.
3642  */
3643 void rt_mutex_setprio(struct task_struct *p, int prio)
3644 {
3645         int oldprio, queued, running, queue_flag = DEQUEUE_SAVE | DEQUEUE_MOVE;
3646         const struct sched_class *prev_class;
3647         struct rq_flags rf;
3648         struct rq *rq;
3649 
3650         BUG_ON(prio > MAX_PRIO);
3651 
3652         rq = __task_rq_lock(p, &rf);
3653 
3654         /*
3655          * Idle task boosting is a nono in general. There is one
3656          * exception, when PREEMPT_RT and NOHZ is active:
3657          *
3658          * The idle task calls get_next_timer_interrupt() and holds
3659          * the timer wheel base->lock on the CPU and another CPU wants
3660          * to access the timer (probably to cancel it). We can safely
3661          * ignore the boosting request, as the idle CPU runs this code
3662          * with interrupts disabled and will complete the lock
3663          * protected section without being interrupted. So there is no
3664          * real need to boost.
3665          */
3666         if (unlikely(p == rq->idle)) {
3667                 WARN_ON(p != rq->curr);
3668                 WARN_ON(p->pi_blocked_on);
3669                 goto out_unlock;
3670         }
3671 
3672         trace_sched_pi_setprio(p, prio);
3673         oldprio = p->prio;
3674 
3675         if (oldprio == prio)
3676                 queue_flag &= ~DEQUEUE_MOVE;
3677 
3678         prev_class = p->sched_class;
3679         queued = task_on_rq_queued(p);
3680         running = task_current(rq, p);
3681         if (queued)
3682                 dequeue_task(rq, p, queue_flag);
3683         if (running)
3684                 put_prev_task(rq, p);
3685 
3686         /*
3687          * Boosting condition are:
3688          * 1. -rt task is running and holds mutex A
3689          *      --> -dl task blocks on mutex A
3690          *
3691          * 2. -dl task is running and holds mutex A
3692          *      --> -dl task blocks on mutex A and could preempt the
3693          *          running task
3694          */
3695         if (dl_prio(prio)) {
3696                 struct task_struct *pi_task = rt_mutex_get_top_task(p);
3697                 if (!dl_prio(p->normal_prio) ||
3698                     (pi_task && dl_entity_preempt(&pi_task->dl, &p->dl))) {
3699                         p->dl.dl_boosted = 1;
3700                         queue_flag |= ENQUEUE_REPLENISH;
3701                 } else
3702                         p->dl.dl_boosted = 0;
3703                 p->sched_class = &dl_sched_class;
3704         } else if (rt_prio(prio)) {
3705                 if (dl_prio(oldprio))
3706                         p->dl.dl_boosted = 0;
3707                 if (oldprio < prio)
3708                         queue_flag |= ENQUEUE_HEAD;
3709                 p->sched_class = &rt_sched_class;
3710         } else {
3711                 if (dl_prio(oldprio))
3712                         p->dl.dl_boosted = 0;
3713                 if (rt_prio(oldprio))
3714                         p->rt.timeout = 0;
3715                 p->sched_class = &fair_sched_class;
3716         }
3717 
3718         p->prio = prio;
3719 
3720         if (queued)
3721                 enqueue_task(rq, p, queue_flag);
3722         if (running)
3723                 set_curr_task(rq, p);
3724 
3725         check_class_changed(rq, p, prev_class, oldprio);
3726 out_unlock:
3727         preempt_disable(); /* avoid rq from going away on us */
3728         __task_rq_unlock(rq, &rf);
3729 
3730         balance_callback(rq);
3731         preempt_enable();
3732 }
3733 #endif
3734 
3735 void set_user_nice(struct task_struct *p, long nice)
3736 {
3737         bool queued, running;
3738         int old_prio, delta;
3739         struct rq_flags rf;
3740         struct rq *rq;
3741 
3742         if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
3743                 return;
3744         /*
3745          * We have to be careful, if called from sys_setpriority(),
3746          * the task might be in the middle of scheduling on another CPU.
3747          */
3748         rq = task_rq_lock(p, &rf);
3749         /*
3750          * The RT priorities are set via sched_setscheduler(), but we still
3751          * allow the 'normal' nice value to be set - but as expected
3752          * it wont have any effect on scheduling until the task is
3753          * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
3754          */
3755         if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
3756                 p->static_prio = NICE_TO_PRIO(nice);
3757                 goto out_unlock;
3758         }
3759         queued = task_on_rq_queued(p);
3760         running = task_current(rq, p);
3761         if (queued)
3762                 dequeue_task(rq, p, DEQUEUE_SAVE);
3763         if (running)
3764                 put_prev_task(rq, p);
3765 
3766         p->static_prio = NICE_TO_PRIO(nice);
3767         set_load_weight(p);
3768         old_prio = p->prio;
3769         p->prio = effective_prio(p);
3770         delta = p->prio - old_prio;
3771 
3772         if (queued) {
3773                 enqueue_task(rq, p, ENQUEUE_RESTORE);
3774                 /*
3775                  * If the task increased its priority or is running and
3776                  * lowered its priority, then reschedule its CPU:
3777                  */
3778                 if (delta < 0 || (delta > 0 && task_running(rq, p)))
3779                         resched_curr(rq);
3780         }
3781         if (running)
3782                 set_curr_task(rq, p);
3783 out_unlock:
3784         task_rq_unlock(rq, p, &rf);
3785 }
3786 EXPORT_SYMBOL(set_user_nice);
3787 
3788 /*
3789  * can_nice - check if a task can reduce its nice value
3790  * @p: task
3791  * @nice: nice value
3792  */
3793 int can_nice(const struct task_struct *p, const int nice)
3794 {
3795         /* convert nice value [19,-20] to rlimit style value [1,40] */
3796         int nice_rlim = nice_to_rlimit(nice);
3797 
3798         return (nice_rlim <= task_rlimit(p, RLIMIT_NICE) ||
3799                 capable(CAP_SYS_NICE));
3800 }
3801 
3802 #ifdef __ARCH_WANT_SYS_NICE
3803 
3804 /*
3805  * sys_nice - change the priority of the current process.
3806  * @increment: priority increment
3807  *
3808  * sys_setpriority is a more generic, but much slower function that
3809  * does similar things.
3810  */
3811 SYSCALL_DEFINE1(nice, int, increment)
3812 {
3813         long nice, retval;
3814 
3815         /*
3816          * Setpriority might change our priority at the same moment.
3817          * We don't have to worry. Conceptually one call occurs first
3818          * and we have a single winner.
3819          */
3820         increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH);
3821         nice = task_nice(current) + increment;
3822 
3823         nice = clamp_val(nice, MIN_NICE, MAX_NICE);
3824         if (increment < 0 && !can_nice(current, nice))
3825                 return -EPERM;
3826 
3827         retval = security_task_setnice(current, nice);
3828         if (retval)
3829                 return retval;
3830 
3831         set_user_nice(current, nice);
3832         return 0;
3833 }
3834 
3835 #endif
3836 
3837 /**
3838  * task_prio - return the priority value of a given task.
3839  * @p: the task in question.
3840  *
3841  * Return: The priority value as seen by users in /proc.
3842  * RT tasks are offset by -200. Normal tasks are centered
3843  * around 0, value goes from -16 to +15.
3844  */
3845 int task_prio(const struct task_struct *p)
3846 {
3847         return p->prio - MAX_RT_PRIO;
3848 }
3849 
3850 /**
3851  * idle_cpu - is a given cpu idle currently?
3852  * @cpu: the processor in question.
3853  *
3854  * Return: 1 if the CPU is currently idle. 0 otherwise.
3855  */
3856 int idle_cpu(int cpu)
3857 {
3858         struct rq *rq = cpu_rq(cpu);
3859 
3860         if (rq->curr != rq->idle)
3861                 return 0;
3862 
3863         if (rq->nr_running)
3864                 return 0;
3865 
3866 #ifdef CONFIG_SMP
3867         if (!llist_empty(&rq->wake_list))
3868                 return 0;
3869 #endif
3870 
3871         return 1;
3872 }
3873 
3874 /**
3875  * idle_task - return the idle task for a given cpu.
3876  * @cpu: the processor in question.
3877  *
3878  * Return: The idle task for the cpu @cpu.
3879  */
3880 struct task_struct *idle_task(int cpu)
3881 {
3882         return cpu_rq(cpu)->idle;
3883 }
3884 
3885 /**
3886  * find_process_by_pid - find a process with a matching PID value.
3887  * @pid: the pid in question.
3888  *
3889  * The task of @pid, if found. %NULL otherwise.
3890  */
3891 static struct task_struct *find_process_by_pid(pid_t pid)
3892 {
3893         return pid ? find_task_by_vpid(pid) : current;
3894 }
3895 
3896 /*
3897  * This function initializes the sched_dl_entity of a newly becoming
3898  * SCHED_DEADLINE task.
3899  *
3900  * Only the static values are considered here, the actual runtime and the
3901  * absolute deadline will be properly calculated when the task is enqueued
3902  * for the first time with its new policy.
3903  */
3904 static void
3905 __setparam_dl(struct task_struct *p, const struct sched_attr *attr)
3906 {
3907         struct sched_dl_entity *dl_se = &p->dl;
3908 
3909         dl_se->dl_runtime = attr->sched_runtime;
3910         dl_se->dl_deadline = attr->sched_deadline;
3911         dl_se->dl_period = attr->sched_period ?: dl_se->dl_deadline;
3912         dl_se->flags = attr->sched_flags;
3913         dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime);
3914 
3915         /*
3916          * Changing the parameters of a task is 'tricky' and we're not doing
3917          * the correct thing -- also see task_dead_dl() and switched_from_dl().
3918          *
3919          * What we SHOULD do is delay the bandwidth release until the 0-lag
3920          * point. This would include retaining the task_struct until that time
3921          * and change dl_overflow() to not immediately decrement the current
3922          * amount.
3923          *
3924          * Instead we retain the current runtime/deadline and let the new
3925          * parameters take effect after the current reservation period lapses.
3926          * This is safe (albeit pessimistic) because the 0-lag point is always
3927          * before the current scheduling deadline.
3928          *
3929          * We can still have temporary overloads because we do not delay the
3930          * change in bandwidth until that time; so admission control is
3931          * not on the safe side. It does however guarantee tasks will never
3932          * consume more than promised.
3933          */
3934 }
3935 
3936 /*
3937  * sched_setparam() passes in -1 for its policy, to let the functions
3938  * it calls know not to change it.
3939  */
3940 #define SETPARAM_POLICY -1
3941 
3942 static void __setscheduler_params(struct task_struct *p,
3943                 const struct sched_attr *attr)
3944 {
3945         int policy = attr->sched_policy;
3946 
3947         if (policy == SETPARAM_POLICY)
3948                 policy = p->policy;
3949 
3950         p->policy = policy;
3951 
3952         if (dl_policy(policy))
3953                 __setparam_dl(p, attr);
3954         else if (fair_policy(policy))
3955                 p->static_prio = NICE_TO_PRIO(attr->sched_nice);
3956 
3957         /*
3958          * __sched_setscheduler() ensures attr->sched_priority == 0 when
3959          * !rt_policy. Always setting this ensures that things like
3960          * getparam()/getattr() don't report silly values for !rt tasks.
3961          */
3962         p->rt_priority = attr->sched_priority;
3963         p->normal_prio = normal_prio(p);
3964         set_load_weight(p);
3965 }
3966 
3967 /* Actually do priority change: must hold pi & rq lock. */
3968 static void __setscheduler(struct rq *rq, struct task_struct *p,
3969                            const struct sched_attr *attr, bool keep_boost)
3970 {
3971         __setscheduler_params(p, attr);
3972 
3973         /*
3974          * Keep a potential priority boosting if called from
3975          * sched_setscheduler().
3976          */
3977         if (keep_boost)
3978                 p->prio = rt_mutex_get_effective_prio(p, normal_prio(p));
3979         else
3980                 p->prio = normal_prio(p);
3981 
3982         if (dl_prio(p->prio))
3983                 p->sched_class = &dl_sched_class;
3984         else if (rt_prio(p->prio))
3985                 p->sched_class = &rt_sched_class;
3986         else
3987                 p->sched_class = &fair_sched_class;
3988 }
3989 
3990 static void
3991 __getparam_dl(struct task_struct *p, struct sched_attr *attr)
3992 {
3993         struct sched_dl_entity *dl_se = &p->dl;
3994 
3995         attr->sched_priority = p->rt_priority;
3996         attr->sched_runtime = dl_se->dl_runtime;
3997         attr->sched_deadline = dl_se->dl_deadline;
3998         attr->sched_period = dl_se->dl_period;
3999         attr->sched_flags = dl_se->flags;
4000 }
4001 
4002 /*
4003  * This function validates the new parameters of a -deadline task.
4004  * We ask for the deadline not being zero, and greater or equal
4005  * than the runtime, as well as the period of being zero or
4006  * greater than deadline. Furthermore, we have to be sure that
4007  * user parameters are above the internal resolution of 1us (we
4008  * check sched_runtime only since it is always the smaller one) and
4009  * below 2^63 ns (we have to check both sched_deadline and
4010  * sched_period, as the latter can be zero).
4011  */
4012 static bool
4013 __checkparam_dl(const struct sched_attr *attr)
4014 {
4015         /* deadline != 0 */
4016         if (attr->sched_deadline == 0)
4017                 return false;
4018 
4019         /*
4020          * Since we truncate DL_SCALE bits, make sure we're at least
4021          * that big.
4022          */
4023         if (attr->sched_runtime < (1ULL << DL_SCALE))
4024                 return false;
4025 
4026         /*
4027          * Since we use the MSB for wrap-around and sign issues, make
4028          * sure it's not set (mind that period can be equal to zero).
4029          */
4030         if (attr->sched_deadline & (1ULL << 63) ||
4031             attr->sched_period & (1ULL << 63))
4032                 return false;
4033 
4034         /* runtime <= deadline <= period (if period != 0) */
4035         if ((attr->sched_period != 0 &&
4036              attr->sched_period < attr->sched_deadline) ||
4037             attr->sched_deadline < attr->sched_runtime)
4038                 return false;
4039 
4040         return true;
4041 }
4042 
4043 /*
4044  * check the target process has a UID that matches the current process's
4045  */
4046 static bool check_same_owner(struct task_struct *p)
4047 {
4048         const struct cred *cred = current_cred(), *pcred;
4049         bool match;
4050 
4051         rcu_read_lock();
4052         pcred = __task_cred(p);
4053         match = (uid_eq(cred->euid, pcred->euid) ||
4054                  uid_eq(cred->euid, pcred->uid));
4055         rcu_read_unlock();
4056         return match;
4057 }
4058 
4059 static bool dl_param_changed(struct task_struct *p,
4060                 const struct sched_attr *attr)
4061 {
4062         struct sched_dl_entity *dl_se = &p->dl;
4063 
4064         if (dl_se->dl_runtime != attr->sched_runtime ||
4065                 dl_se->dl_deadline != attr->sched_deadline ||
4066                 dl_se->dl_period != attr->sched_period ||
4067                 dl_se->flags != attr->sched_flags)
4068                 return true;
4069 
4070         return false;
4071 }
4072 
4073 static int __sched_setscheduler(struct task_struct *p,
4074                                 const struct sched_attr *attr,
4075                                 bool user, bool pi)
4076 {
4077         int newprio = dl_policy(attr->sched_policy) ? MAX_DL_PRIO - 1 :
4078                       MAX_RT_PRIO - 1 - attr->sched_priority;
4079         int retval, oldprio, oldpolicy = -1, queued, running;
4080         int new_effective_prio, policy = attr->sched_policy;
4081         const struct sched_class *prev_class;
4082         struct rq_flags rf;
4083         int reset_on_fork;
4084         int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE;
4085         struct rq *rq;
4086 
4087         /* may grab non-irq protected spin_locks */
4088         BUG_ON(in_interrupt());
4089 recheck:
4090         /* double check policy once rq lock held */
4091         if (policy < 0) {
4092                 reset_on_fork = p->sched_reset_on_fork;
4093                 policy = oldpolicy = p->policy;
4094         } else {
4095                 reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK);
4096 
4097                 if (!valid_policy(policy))
4098                         return -EINVAL;
4099         }
4100 
4101         if (attr->sched_flags & ~(SCHED_FLAG_RESET_ON_FORK))
4102                 return -EINVAL;
4103 
4104         /*
4105          * Valid priorities for SCHED_FIFO and SCHED_RR are
4106          * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
4107          * SCHED_BATCH and SCHED_IDLE is 0.
4108          */
4109         if ((p->mm && attr->sched_priority > MAX_USER_RT_PRIO-1) ||
4110             (!p->mm && attr->sched_priority > MAX_RT_PRIO-1))
4111                 return -EINVAL;
4112         if ((dl_policy(policy) && !__checkparam_dl(attr)) ||
4113             (rt_policy(policy) != (attr->sched_priority != 0)))
4114                 return -EINVAL;
4115 
4116         /*
4117          * Allow unprivileged RT tasks to decrease priority:
4118          */
4119         if (user && !capable(CAP_SYS_NICE)) {
4120                 if (fair_policy(policy)) {
4121                         if (attr->sched_nice < task_nice(p) &&
4122                             !can_nice(p, attr->sched_nice))
4123                                 return -EPERM;
4124                 }
4125 
4126                 if (rt_policy(policy)) {
4127                         unsigned long rlim_rtprio =
4128                                         task_rlimit(p, RLIMIT_RTPRIO);
4129 
4130                         /* can't set/change the rt policy */
4131                         if (policy != p->policy && !rlim_rtprio)
4132                                 return -EPERM;
4133 
4134                         /* can't increase priority */
4135                         if (attr->sched_priority > p->rt_priority &&
4136                             attr->sched_priority > rlim_rtprio)
4137                                 return -EPERM;
4138                 }
4139 
4140                  /*
4141                   * Can't set/change SCHED_DEADLINE policy at all for now
4142                   * (safest behavior); in the future we would like to allow
4143                   * unprivileged DL tasks to increase their relative deadline
4144                   * or reduce their runtime (both ways reducing utilization)
4145                   */
4146                 if (dl_policy(policy))
4147                         return -EPERM;
4148 
4149                 /*
4150                  * Treat SCHED_IDLE as nice 20. Only allow a switch to
4151                  * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
4152                  */
4153                 if (idle_policy(p->policy) && !idle_policy(policy)) {
4154                         if (!can_nice(p, task_nice(p)))
4155                                 return -EPERM;
4156                 }
4157 
4158                 /* can't change other user's priorities */
4159                 if (!check_same_owner(p))
4160                         return -EPERM;
4161 
4162                 /* Normal users shall not reset the sched_reset_on_fork flag */
4163                 if (p->sched_reset_on_fork && !reset_on_fork)
4164                         return -EPERM;
4165         }
4166 
4167         if (user) {
4168                 retval = security_task_setscheduler(p);
4169                 if (retval)
4170                         return retval;
4171         }
4172 
4173         /*
4174          * make sure no PI-waiters arrive (or leave) while we are
4175          * changing the priority of the task:
4176          *
4177          * To be able to change p->policy safely, the appropriate
4178          * runqueue lock must be held.
4179          */
4180         rq = task_rq_lock(p, &rf);
4181 
4182         /*
4183          * Changing the policy of the stop threads its a very bad idea
4184          */
4185         if (p == rq->stop) {
4186                 task_rq_unlock(rq, p, &rf);
4187                 return -EINVAL;
4188         }
4189 
4190         /*
4191          * If not changing anything there's no need to proceed further,
4192          * but store a possible modification of reset_on_fork.
4193          */
4194         if (unlikely(policy == p->policy)) {
4195                 if (fair_policy(policy) && attr->sched_nice != task_nice(p))
4196                         goto change;
4197                 if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
4198                         goto change;
4199                 if (dl_policy(policy) && dl_param_changed(p, attr))
4200                         goto change;
4201 
4202                 p->sched_reset_on_fork = reset_on_fork;
4203                 task_rq_unlock(rq, p, &rf);
4204                 return 0;
4205         }
4206 change:
4207 
4208         if (user) {
4209 #ifdef CONFIG_RT_GROUP_SCHED
4210                 /*
4211                  * Do not allow realtime tasks into groups that have no runtime
4212                  * assigned.
4213                  */
4214                 if (rt_bandwidth_enabled() && rt_policy(policy) &&
4215                                 task_group(p)->rt_bandwidth.rt_runtime == 0 &&
4216                                 !task_group_is_autogroup(task_group(p))) {
4217                         task_rq_unlock(rq, p, &rf);
4218                         return -EPERM;
4219                 }
4220 #endif
4221 #ifdef CONFIG_SMP
4222                 if (dl_bandwidth_enabled() && dl_policy(policy)) {
4223                         cpumask_t *span = rq->rd->span;
4224 
4225                         /*
4226                          * Don't allow tasks with an affinity mask smaller than
4227                          * the entire root_domain to become SCHED_DEADLINE. We
4228                          * will also fail if there's no bandwidth available.
4229                          */
4230                         if (!cpumask_subset(span, &p->cpus_allowed) ||
4231                             rq->rd->dl_bw.bw == 0) {
4232                                 task_rq_unlock(rq, p, &rf);
4233                                 return -EPERM;
4234                         }
4235                 }
4236 #endif
4237         }
4238 
4239         /* recheck policy now with rq lock held */
4240         if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
4241                 policy = oldpolicy = -1;
4242                 task_rq_unlock(rq, p, &rf);
4243                 goto recheck;
4244         }
4245 
4246         /*
4247          * If setscheduling to SCHED_DEADLINE (or changing the parameters
4248          * of a SCHED_DEADLINE task) we need to check if enough bandwidth
4249          * is available.
4250          */
4251         if ((dl_policy(policy) || dl_task(p)) && dl_overflow(p, policy, attr)) {
4252                 task_rq_unlock(rq, p, &rf);
4253                 return -EBUSY;
4254         }
4255 
4256         p->sched_reset_on_fork = reset_on_fork;
4257         oldprio = p->prio;
4258 
4259         if (pi) {
4260                 /*
4261                  * Take priority boosted tasks into account. If the new
4262                  * effective priority is unchanged, we just store the new
4263                  * normal parameters and do not touch the scheduler class and
4264                  * the runqueue. This will be done when the task deboost
4265                  * itself.
4266                  */
4267                 new_effective_prio = rt_mutex_get_effective_prio(p, newprio);
4268                 if (new_effective_prio == oldprio)
4269                         queue_flags &= ~DEQUEUE_MOVE;
4270         }
4271 
4272         queued = task_on_rq_queued(p);
4273         running = task_current(rq, p);
4274         if (queued)
4275                 dequeue_task(rq, p, queue_flags);
4276         if (running)
4277                 put_prev_task(rq, p);
4278 
4279         prev_class = p->sched_class;
4280         __setscheduler(rq, p, attr, pi);
4281 
4282         if (queued) {
4283                 /*
4284                  * We enqueue to tail when the priority of a task is
4285                  * increased (user space view).
4286                  */
4287                 if (oldprio < p->prio)
4288                         queue_flags |= ENQUEUE_HEAD;
4289 
4290                 enqueue_task(rq, p, queue_flags);
4291         }
4292         if (running)
4293                 set_curr_task(rq, p);
4294 
4295         check_class_changed(rq, p, prev_class, oldprio);
4296         preempt_disable(); /* avoid rq from going away on us */
4297         task_rq_unlock(rq, p, &rf);
4298 
4299         if (pi)
4300                 rt_mutex_adjust_pi(p);
4301 
4302         /*
4303          * Run balance callbacks after we've adjusted the PI chain.
4304          */
4305         balance_callback(rq);
4306         preempt_enable();
4307 
4308         return 0;
4309 }
4310 
4311 static int _sched_setscheduler(struct task_struct *p, int policy,
4312                                const struct sched_param *param, bool check)
4313 {
4314         struct sched_attr attr = {
4315                 .sched_policy   = policy,
4316                 .sched_priority = param->sched_priority,
4317                 .sched_nice     = PRIO_TO_NICE(p->static_prio),
4318         };
4319 
4320         /* Fixup the legacy SCHED_RESET_ON_FORK hack. */
4321         if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) {
4322                 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
4323                 policy &= ~SCHED_RESET_ON_FORK;
4324                 attr.sched_policy = policy;
4325         }
4326 
4327         return __sched_setscheduler(p, &attr, check, true);
4328 }
4329 /**
4330  * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
4331  * @p: the task in question.
4332  * @policy: new policy.
4333  * @param: structure containing the new RT priority.
4334  *
4335  * Return: 0 on success. An error code otherwise.
4336  *
4337  * NOTE that the task may be already dead.
4338  */
4339 int sched_setscheduler(struct task_struct *p, int policy,
4340                        const struct sched_param *param)
4341 {
4342         return _sched_setscheduler(p, policy, param, true);
4343 }
4344 EXPORT_SYMBOL_GPL(sched_setscheduler);
4345 
4346 int sched_setattr(struct task_struct *p, const struct sched_attr *attr)
4347 {
4348         return __sched_setscheduler(p, attr, true, true);
4349 }
4350 EXPORT_SYMBOL_GPL(sched_setattr);
4351 
4352 /**
4353  * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
4354  * @p: the task in question.
4355  * @policy: new policy.
4356  * @param: structure containing the new RT priority.
4357  *
4358  * Just like sched_setscheduler, only don't bother checking if the
4359  * current context has permission.  For example, this is needed in
4360  * stop_machine(): we create temporary high priority worker threads,
4361  * but our caller might not have that capability.
4362  *
4363  * Return: 0 on success. An error code otherwise.
4364  */
4365 int sched_setscheduler_nocheck(struct task_struct *p, int policy,
4366                                const struct sched_param *param)
4367 {
4368         return _sched_setscheduler(p, policy, param, false);
4369 }
4370 EXPORT_SYMBOL_GPL(sched_setscheduler_nocheck);
4371 
4372 static int
4373 do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
4374 {
4375         struct sched_param lparam;
4376         struct task_struct *p;
4377         int retval;
4378 
4379         if (!param || pid < 0)
4380                 return -EINVAL;
4381         if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
4382                 return -EFAULT;
4383 
4384         rcu_read_lock();
4385         retval = -ESRCH;
4386         p = find_process_by_pid(pid);
4387         if (p != NULL)
4388                 retval = sched_setscheduler(p, policy, &lparam);
4389         rcu_read_unlock();
4390 
4391         return retval;
4392 }
4393 
4394 /*
4395  * Mimics kernel/events/core.c perf_copy_attr().
4396  */
4397 static int sched_copy_attr(struct sched_attr __user *uattr,
4398                            struct sched_attr *attr)
4399 {
4400         u32 size;
4401         int ret;
4402 
4403         if (!access_ok(VERIFY_WRITE, uattr, SCHED_ATTR_SIZE_VER0))
4404                 return -EFAULT;
4405 
4406         /*
4407          * zero the full structure, so that a short copy will be nice.
4408          */
4409         memset(attr, 0, sizeof(*attr));
4410 
4411         ret = get_user(size, &uattr->size);
4412         if (ret)
4413                 return ret;
4414 
4415         if (size > PAGE_SIZE)   /* silly large */
4416                 goto err_size;
4417 
4418         if (!size)              /* abi compat */
4419                 size = SCHED_ATTR_SIZE_VER0;
4420 
4421         if (size < SCHED_ATTR_SIZE_VER0)
4422                 goto err_size;
4423 
4424         /*
4425          * If we're handed a bigger struct than we know of,
4426          * ensure all the unknown bits are 0 - i.e. new
4427          * user-space does not rely on any kernel feature
4428          * extensions we dont know about yet.
4429          */
4430         if (size > sizeof(*attr)) {
4431                 unsigned char __user *addr;
4432                 unsigned char __user *end;
4433                 unsigned char val;
4434 
4435                 addr = (void __user *)uattr + sizeof(*attr);
4436                 end  = (void __user *)uattr + size;
4437 
4438                 for (; addr < end; addr++) {
4439                         ret = get_user(val, addr);
4440                         if (ret)
4441                                 return ret;
4442                         if (val)
4443                                 goto err_size;
4444                 }
4445                 size = sizeof(*attr);
4446         }
4447 
4448         ret = copy_from_user(attr, uattr, size);
4449         if (ret)
4450                 return -EFAULT;
4451 
4452         /*
4453          * XXX: do we want to be lenient like existing syscalls; or do we want
4454          * to be strict and return an error on out-of-bounds values?
4455          */
4456         attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE);
4457 
4458         return 0;
4459 
4460 err_size:
4461         put_user(sizeof(*attr), &uattr->size);
4462         return -E2BIG;
4463 }
4464 
4465 /**
4466  * sys_sched_setscheduler - set/change the scheduler policy and RT priority
4467  * @pid: the pid in question.
4468  * @policy: new policy.
4469  * @param: structure containing the new RT priority.
4470  *
4471  * Return: 0 on success. An error code otherwise.
4472  */
4473 SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy,
4474                 struct sched_param __user *, param)
4475 {
4476         /* negative values for policy are not valid */
4477         if (policy < 0)
4478                 return -EINVAL;
4479 
4480         return do_sched_setscheduler(pid, policy, param);
4481 }
4482 
4483 /**
4484  * sys_sched_setparam - set/change the RT priority of a thread
4485  * @pid: the pid in question.
4486  * @param: structure containing the new RT priority.
4487  *
4488  * Return: 0 on success. An error code otherwise.
4489  */
4490 SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
4491 {
4492         return do_sched_setscheduler(pid, SETPARAM_POLICY, param);
4493 }
4494 
4495 /**
4496  * sys_sched_setattr - same as above, but with extended sched_attr
4497  * @pid: the pid in question.
4498  * @uattr: structure containing the extended parameters.
4499  * @flags: for future extension.
4500  */
4501 SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
4502                                unsigned int, flags)
4503 {
4504         struct sched_attr attr;
4505         struct task_struct *p;
4506         int retval;
4507 
4508         if (!uattr || pid < 0 || flags)
4509                 return -EINVAL;
4510 
4511         retval = sched_copy_attr(uattr, &attr);
4512         if (retval)
4513                 return retval;
4514 
4515         if ((int)attr.sched_policy < 0)
4516                 return -EINVAL;
4517 
4518         rcu_read_lock();
4519         retval = -ESRCH;
4520         p = find_process_by_pid(pid);
4521         if (p != NULL)
4522                 retval = sched_setattr(p, &attr);
4523         rcu_read_unlock();
4524 
4525         return retval;
4526 }
4527 
4528 /**
4529  * sys_sched_getscheduler - get the policy (scheduling class) of a thread
4530  * @pid: the pid in question.
4531  *
4532  * Return: On success, the policy of the thread. Otherwise, a negative error
4533  * code.
4534  */
4535 SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
4536 {
4537         struct task_struct *p;
4538         int retval;
4539 
4540         if (pid < 0)
4541                 return -EINVAL;
4542 
4543         retval = -ESRCH;
4544         rcu_read_lock();
4545         p = find_process_by_pid(pid);
4546         if (p) {
4547                 retval = security_task_getscheduler(p);
4548                 if (!retval)
4549                         retval = p->policy
4550                                 | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0);
4551         }
4552         rcu_read_unlock();
4553         return retval;
4554 }
4555 
4556 /**
4557  * sys_sched_getparam - get the RT priority of a thread
4558  * @pid: the pid in question.
4559  * @param: structure containing the RT priority.
4560  *
4561  * Return: On success, 0 and the RT priority is in @param. Otherwise, an error
4562  * code.
4563  */
4564 SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
4565 {
4566         struct sched_param lp = { .sched_priority = 0 };
4567         struct task_struct *p;
4568         int retval;
4569 
4570         if (!param || pid < 0)
4571                 return -EINVAL;
4572 
4573         rcu_read_lock();
4574         p = find_process_by_pid(pid);
4575         retval = -ESRCH;
4576         if (!p)
4577                 goto out_unlock;
4578 
4579         retval = security_task_getscheduler(p);
4580         if (retval)
4581                 goto out_unlock;
4582 
4583         if (task_has_rt_policy(p))
4584                 lp.sched_priority = p->rt_priority;
4585         rcu_read_unlock();
4586 
4587         /*
4588          * This one might sleep, we cannot do it with a spinlock held ...
4589          */
4590         retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
4591 
4592         return retval;
4593 
4594 out_unlock:
4595         rcu_read_unlock();
4596         return retval;
4597 }
4598 
4599 static int sched_read_attr(struct sched_attr __user *uattr,
4600                            struct sched_attr *attr,
4601                            unsigned int usize)
4602 {
4603         int ret;
4604 
4605         if (!access_ok(VERIFY_WRITE, uattr, usize))
4606                 return -EFAULT;
4607 
4608         /*
4609          * If we're handed a smaller struct than we know of,
4610          * ensure all the unknown bits are 0 - i.e. old
4611          * user-space does not get uncomplete information.
4612          */
4613         if (usize < sizeof(*attr)) {
4614                 unsigned char *addr;
4615                 unsigned char *end;
4616 
4617                 addr = (void *)attr + usize;
4618                 end  = (void *)attr + sizeof(*attr);
4619 
4620                 for (; addr < end; addr++) {
4621                         if (*addr)
4622                                 return -EFBIG;
4623                 }
4624 
4625                 attr->size = usize;
4626         }
4627 
4628         ret = copy_to_user(uattr, attr, attr->size);
4629         if (ret)
4630                 return -EFAULT;
4631 
4632         return 0;
4633 }
4634 
4635 /**
4636  * sys_sched_getattr - similar to sched_getparam, but with sched_attr
4637  * @pid: the pid in question.
4638  * @uattr: structure containing the extended parameters.
4639  * @size: sizeof(attr) for fwd/bwd comp.
4640  * @flags: for future extension.
4641  */
4642 SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
4643                 unsigned int, size, unsigned int, flags)
4644 {
4645         struct sched_attr attr = {
4646                 .size = sizeof(struct sched_attr),
4647         };
4648         struct task_struct *p;
4649         int retval;
4650 
4651         if (!uattr || pid < 0 || size > PAGE_SIZE ||
4652             size < SCHED_ATTR_SIZE_VER0 || flags)
4653                 return -EINVAL;
4654 
4655         rcu_read_lock();
4656         p = find_process_by_pid(pid);
4657         retval = -ESRCH;
4658         if (!p)
4659                 goto out_unlock;
4660 
4661         retval = security_task_getscheduler(p);
4662         if (retval)
4663                 goto out_unlock;
4664 
4665         attr.sched_policy = p->policy;
4666         if (p->sched_reset_on_fork)
4667                 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
4668         if (task_has_dl_policy(p))
4669                 __getparam_dl(p, &attr);
4670         else if (task_has_rt_policy(p))
4671                 attr.sched_priority = p->rt_priority;
4672         else
4673                 attr.sched_nice = task_nice(p);
4674 
4675         rcu_read_unlock();
4676 
4677         retval = sched_read_attr(uattr, &attr, size);
4678         return retval;
4679 
4680 out_unlock:
4681         rcu_read_unlock();
4682         return retval;
4683 }
4684 
4685 long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
4686 {
4687         cpumask_var_t cpus_allowed, new_mask;
4688         struct task_struct *p;
4689         int retval;
4690 
4691         rcu_read_lock();
4692 
4693         p = find_process_by_pid(pid);
4694         if (!p) {
4695                 rcu_read_unlock();
4696                 return -ESRCH;
4697         }
4698 
4699         /* Prevent p going away */
4700         get_task_struct(p);
4701         rcu_read_unlock();
4702 
4703         if (p->flags & PF_NO_SETAFFINITY) {
4704                 retval = -EINVAL;
4705                 goto out_put_task;
4706         }
4707         if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
4708                 retval = -ENOMEM;
4709                 goto out_put_task;
4710         }
4711         if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
4712                 retval = -ENOMEM;
4713                 goto out_free_cpus_allowed;
4714         }
4715         retval = -EPERM;
4716         if (!check_same_owner(p)) {
4717                 rcu_read_lock();
4718                 if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
4719                         rcu_read_unlock();
4720                         goto out_free_new_mask;
4721                 }
4722                 rcu_read_unlock();
4723         }
4724 
4725         retval = security_task_setscheduler(p);
4726         if (retval)
4727                 goto out_free_new_mask;
4728 
4729 
4730         cpuset_cpus_allowed(p, cpus_allowed);
4731         cpumask_and(new_mask, in_mask, cpus_allowed);
4732 
4733         /*
4734          * Since bandwidth control happens on root_domain basis,
4735          * if admission test is enabled, we only admit -deadline
4736          * tasks allowed to run on all the CPUs in the task's
4737          * root_domain.
4738          */
4739 #ifdef CONFIG_SMP
4740         if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {
4741                 rcu_read_lock();
4742                 if (!cpumask_subset(task_rq(p)->rd->span, new_mask)) {
4743                         retval = -EBUSY;
4744                         rcu_read_unlock();
4745                         goto out_free_new_mask;
4746                 }
4747                 rcu_read_unlock();
4748         }
4749 #endif
4750 again:
4751         retval = __set_cpus_allowed_ptr(p, new_mask, true);
4752 
4753         if (!retval) {
4754                 cpuset_cpus_allowed(p, cpus_allowed);
4755                 if (!cpumask_subset(new_mask, cpus_allowed)) {
4756                         /*
4757                          * We must have raced with a concurrent cpuset
4758                          * update. Just reset the cpus_allowed to the
4759                          * cpuset's cpus_allowed
4760                          */
4761                         cpumask_copy(new_mask, cpus_allowed);
4762                         goto again;
4763                 }
4764         }
4765 out_free_new_mask:
4766         free_cpumask_var(new_mask);
4767 out_free_cpus_allowed:
4768         free_cpumask_var(cpus_allowed);
4769 out_put_task:
4770         put_task_struct(p);
4771         return retval;
4772 }
4773 
4774 static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
4775                              struct cpumask *new_mask)
4776 {
4777         if (len < cpumask_size())
4778                 cpumask_clear(new_mask);
4779         else if (len > cpumask_size())
4780                 len = cpumask_size();
4781 
4782         return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
4783 }
4784 
4785 /**
4786  * sys_sched_setaffinity - set the cpu affinity of a process
4787  * @pid: pid of the process
4788  * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4789  * @user_mask_ptr: user-space pointer to the new cpu mask
4790  *
4791  * Return: 0 on success. An error code otherwise.
4792  */
4793 SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
4794                 unsigned long __user *, user_mask_ptr)
4795 {
4796         cpumask_var_t new_mask;
4797         int retval;
4798 
4799         if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
4800                 return -ENOMEM;
4801 
4802         retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
4803         if (retval == 0)
4804                 retval = sched_setaffinity(pid, new_mask);
4805         free_cpumask_var(new_mask);
4806         return retval;
4807 }
4808 
4809 long sched_getaffinity(pid_t pid, struct cpumask *mask)
4810 {
4811         struct task_struct *p;
4812         unsigned long flags;
4813         int retval;
4814 
4815         rcu_read_lock();
4816 
4817         retval = -ESRCH;
4818         p = find_process_by_pid(pid);
4819         if (!p)
4820                 goto out_unlock;
4821 
4822         retval = security_task_getscheduler(p);
4823         if (retval)
4824                 goto out_unlock;
4825 
4826         raw_spin_lock_irqsave(&p->pi_lock, flags);
4827         cpumask_and(mask, &p->cpus_allowed, cpu_active_mask);
4828         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
4829 
4830 out_unlock:
4831         rcu_read_unlock();
4832 
4833         return retval;
4834 }
4835 
4836 /**
4837  * sys_sched_getaffinity - get the cpu affinity of a process
4838  * @pid: pid of the process
4839  * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4840  * @user_mask_ptr: user-space pointer to hold the current cpu mask
4841  *
4842  * Return: size of CPU mask copied to user_mask_ptr on success. An
4843  * error code otherwise.
4844  */
4845 SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
4846                 unsigned long __user *, user_mask_ptr)
4847 {
4848         int ret;
4849         cpumask_var_t mask;
4850 
4851         if ((len * BITS_PER_BYTE) < nr_cpu_ids)
4852                 return -EINVAL;
4853         if (len & (sizeof(unsigned long)-1))
4854                 return -EINVAL;
4855 
4856         if (!alloc_cpumask_var(&mask, GFP_KERNEL))
4857                 return -ENOMEM;
4858 
4859         ret = sched_getaffinity(pid, mask);
4860         if (ret == 0) {
4861                 size_t retlen = min_t(size_t, len, cpumask_size());
4862 
4863                 if (copy_to_user(user_mask_ptr, mask, retlen))
4864                         ret = -EFAULT;
4865                 else
4866                         ret = retlen;
4867         }
4868         free_cpumask_var(mask);
4869 
4870         return ret;
4871 }
4872 
4873 /**
4874  * sys_sched_yield - yield the current processor to other threads.
4875  *
4876  * This function yields the current CPU to other tasks. If there are no
4877  * other threads running on this CPU then this function will return.
4878  *
4879  * Return: 0.
4880  */
4881 SYSCALL_DEFINE0(sched_yield)
4882 {
4883         struct rq *rq = this_rq_lock();
4884 
4885         schedstat_inc(rq->yld_count);
4886         current->sched_class->yield_task(rq);
4887 
4888         /*
4889          * Since we are going to call schedule() anyway, there's
4890          * no need to preempt or enable interrupts:
4891          */
4892         __release(rq->lock);
4893         spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
4894         do_raw_spin_unlock(&rq->lock);
4895         sched_preempt_enable_no_resched();
4896 
4897         schedule();
4898 
4899         return 0;
4900 }
4901 
4902 #ifndef CONFIG_PREEMPT
4903 int __sched _cond_resched(void)
4904 {
4905         if (should_resched(0)) {
4906                 preempt_schedule_common();
4907                 return 1;
4908         }
4909         return 0;
4910 }
4911 EXPORT_SYMBOL(_cond_resched);
4912 #endif
4913 
4914 /*
4915  * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
4916  * call schedule, and on return reacquire the lock.
4917  *
4918  * This works OK both with and without CONFIG_PREEMPT. We do strange low-level
4919  * operations here to prevent schedule() from being called twice (once via
4920  * spin_unlock(), once by hand).
4921  */
4922 int __cond_resched_lock(spinlock_t *lock)
4923 {
4924         int resched = should_resched(PREEMPT_LOCK_OFFSET);
4925         int ret = 0;
4926 
4927         lockdep_assert_held(lock);
4928 
4929         if (spin_needbreak(lock) || resched) {
4930                 spin_unlock(lock);
4931                 if (resched)
4932                         preempt_schedule_common();
4933                 else
4934                         cpu_relax();
4935                 ret = 1;
4936                 spin_lock(lock);
4937         }
4938         return ret;
4939 }
4940 EXPORT_SYMBOL(__cond_resched_lock);
4941 
4942 int __sched __cond_resched_softirq(void)
4943 {
4944         BUG_ON(!in_softirq());
4945 
4946         if (should_resched(SOFTIRQ_DISABLE_OFFSET)) {
4947                 local_bh_enable();
4948                 preempt_schedule_common();
4949                 local_bh_disable();
4950                 return 1;
4951         }
4952         return 0;
4953 }
4954 EXPORT_SYMBOL(__cond_resched_softirq);
4955 
4956 /**
4957  * yield - yield the current processor to other threads.
4958  *
4959  * Do not ever use this function, there's a 99% chance you're doing it wrong.
4960  *
4961  * The scheduler is at all times free to pick the calling task as the most
4962  * eligible task to run, if removing the yield() call from your code breaks
4963  * it, its already broken.
4964  *
4965  * Typical broken usage is:
4966  *
4967  * while (!event)
4968  *      yield();
4969  *
4970  * where one assumes that yield() will let 'the other' process run that will
4971  * make event true. If the current task is a SCHED_FIFO task that will never
4972  * happen. Never use yield() as a progress guarantee!!
4973  *
4974  * If you want to use yield() to wait for something, use wait_event().
4975  * If you want to use yield() to be 'nice' for others, use cond_resched().
4976  * If you still want to use yield(), do not!
4977  */
4978 void __sched yield(void)
4979 {
4980         set_current_state(TASK_RUNNING);
4981         sys_sched_yield();
4982 }
4983 EXPORT_SYMBOL(yield);
4984 
4985 /**
4986  * yield_to - yield the current processor to another thread in
4987  * your thread group, or accelerate that thread toward the
4988  * processor it's on.
4989  * @p: target task
4990  * @preempt: whether task preemption is allowed or not
4991  *
4992  * It's the caller's job to ensure that the target task struct
4993  * can't go away on us before we can do any checks.
4994  *
4995  * Return:
4996  *      true (>0) if we indeed boosted the target task.
4997  *      false (0) if we failed to boost the target.
4998  *      -ESRCH if there's no task to yield to.
4999  */
5000 int __sched yield_to(struct task_struct *p, bool preempt)
5001 {
5002         struct task_struct *curr = current;
5003         struct rq *rq, *p_rq;
5004         unsigned long flags;
5005         int yielded = 0;
5006 
5007         local_irq_save(flags);
5008         rq = this_rq();
5009 
5010 again:
5011         p_rq = task_rq(p);
5012         /*
5013          * If we're the only runnable task on the rq and target rq also
5014          * has only one task, there's absolutely no point in yielding.
5015          */
5016         if (rq->nr_running == 1 && p_rq->nr_running == 1) {
5017                 yielded = -ESRCH;
5018                 goto out_irq;
5019         }
5020 
5021         double_rq_lock(rq, p_rq);
5022         if (task_rq(p) != p_rq) {
5023                 double_rq_unlock(rq, p_rq);
5024                 goto again;
5025         }
5026 
5027         if (!curr->sched_class->yield_to_task)
5028                 goto out_unlock;
5029 
5030         if (curr->sched_class != p->sched_class)
5031                 goto out_unlock;
5032 
5033         if (task_running(p_rq, p) || p->state)
5034                 goto out_unlock;
5035 
5036         yielded = curr->sched_class->yield_to_task(rq, p, preempt);
5037         if (yielded) {
5038                 schedstat_inc(rq->yld_count);
5039                 /*
5040                  * Make p's CPU reschedule; pick_next_entity takes care of
5041                  * fairness.
5042                  */
5043                 if (preempt && rq != p_rq)
5044                         resched_curr(p_rq);
5045         }
5046 
5047 out_unlock:
5048         double_rq_unlock(rq, p_rq);
5049 out_irq:
5050         local_irq_restore(flags);
5051 
5052         if (yielded > 0)
5053                 schedule();
5054 
5055         return yielded;
5056 }
5057 EXPORT_SYMBOL_GPL(yield_to);
5058 
5059 /*
5060  * This task is about to go to sleep on IO. Increment rq->nr_iowait so
5061  * that process accounting knows that this is a task in IO wait state.
5062  */
5063 long __sched io_schedule_timeout(long timeout)
5064 {
5065         int old_iowait = current->in_iowait;
5066         struct rq *rq;
5067         long ret;
5068 
5069         current->in_iowait = 1;
5070         blk_schedule_flush_plug(current);
5071 
5072         delayacct_blkio_start();
5073         rq = raw_rq();
5074         atomic_inc(&rq->nr_iowait);
5075         ret = schedule_timeout(timeout);
5076         current->in_iowait = old_iowait;
5077         atomic_dec(&rq->nr_iowait);
5078         delayacct_blkio_end();
5079 
5080         return ret;
5081 }
5082 EXPORT_SYMBOL(io_schedule_timeout);
5083 
5084 /**
5085  * sys_sched_get_priority_max - return maximum RT priority.
5086  * @policy: scheduling class.
5087  *
5088  * Return: On success, this syscall returns the maximum
5089  * rt_priority that can be used by a given scheduling class.
5090  * On failure, a negative error code is returned.
5091  */
5092 SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
5093 {
5094         int ret = -EINVAL;
5095 
5096         switch (policy) {
5097         case SCHED_FIFO:
5098         case SCHED_RR:
5099                 ret = MAX_USER_RT_PRIO-1;
5100                 break;
5101         case SCHED_DEADLINE:
5102         case SCHED_NORMAL:
5103         case SCHED_BATCH:
5104         case SCHED_IDLE:
5105                 ret = 0;
5106                 break;
5107         }
5108         return ret;
5109 }
5110 
5111 /**
5112  * sys_sched_get_priority_min - return minimum RT priority.
5113  * @policy: scheduling class.
5114  *
5115  * Return: On success, this syscall returns the minimum
5116  * rt_priority that can be used by a given scheduling class.
5117  * On failure, a negative error code is returned.
5118  */
5119 SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
5120 {
5121         int ret = -EINVAL;
5122 
5123         switch (policy) {
5124         case SCHED_FIFO:
5125         case SCHED_RR:
5126                 ret = 1;
5127                 break;
5128         case SCHED_DEADLINE:
5129         case SCHED_NORMAL:
5130         case SCHED_BATCH:
5131         case SCHED_IDLE:
5132                 ret = 0;
5133         }
5134         return ret;
5135 }
5136 
5137 /**
5138  * sys_sched_rr_get_interval - return the default timeslice of a process.
5139  * @pid: pid of the process.
5140  * @interval: userspace pointer to the timeslice value.
5141  *
5142  * this syscall writes the default timeslice value of a given process
5143  * into the user-space timespec buffer. A value of '' means infinity.
5144  *
5145  * Return: On success, 0 and the timeslice is in @interval. Otherwise,
5146  * an error code.
5147  */
5148 SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
5149                 struct timespec __user *, interval)
5150 {
5151         struct task_struct *p;
5152         unsigned int time_slice;
5153         struct rq_flags rf;
5154         struct timespec t;
5155         struct rq *rq;
5156         int retval;
5157 
5158         if (pid < 0)
5159                 return -EINVAL;
5160 
5161         retval = -ESRCH;
5162         rcu_read_lock();
5163         p = find_process_by_pid(pid);
5164         if (!p)
5165                 goto out_unlock;
5166 
5167         retval = security_task_getscheduler(p);
5168         if (retval)
5169                 goto out_unlock;
5170 
5171         rq = task_rq_lock(p, &rf);
5172         time_slice = 0;
5173         if (p->sched_class->get_rr_interval)
5174                 time_slice = p->sched_class->get_rr_interval(rq, p);
5175         task_rq_unlock(rq, p, &rf);
5176 
5177         rcu_read_unlock();
5178         jiffies_to_timespec(time_slice, &t);
5179         retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
5180         return retval;
5181 
5182 out_unlock:
5183         rcu_read_unlock();
5184         return retval;
5185 }
5186 
5187 static const char stat_nam[] = TASK_STATE_TO_CHAR_STR;
5188 
5189 void sched_show_task(struct task_struct *p)
5190 {
5191         unsigned long free = 0;
5192         int ppid;
5193         unsigned long state = p->state;
5194 
5195         if (!try_get_task_stack(p))
5196                 return;
5197         if (state)
5198                 state = __ffs(state) + 1;
5199         printk(KERN_INFO "%-15.15s %c", p->comm,
5200                 state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?');
5201         if (state == TASK_RUNNING)
5202                 printk(KERN_CONT "  running task    ");
5203 #ifdef CONFIG_DEBUG_STACK_USAGE
5204         free = stack_not_used(p);
5205 #endif
5206         ppid = 0;
5207         rcu_read_lock();
5208         if (pid_alive(p))
5209                 ppid = task_pid_nr(rcu_dereference(p->real_parent));
5210         rcu_read_unlock();
5211         printk(KERN_CONT "%5lu %5d %6d 0x%08lx\n", free,
5212                 task_pid_nr(p), ppid,
5213                 (unsigned long)task_thread_info(p)->flags);
5214 
5215         print_worker_info(KERN_INFO, p);
5216         show_stack(p, NULL);
5217         put_task_stack(p);
5218 }
5219 
5220 void show_state_filter(unsigned long state_filter)
5221 {
5222         struct task_struct *g, *p;
5223 
5224 #if BITS_PER_LONG == 32
5225         printk(KERN_INFO
5226                 "  task                PC stack   pid father\n");
5227 #else
5228         printk(KERN_INFO
5229                 "  task                        PC stack   pid father\n");
5230 #endif
5231         rcu_read_lock();
5232         for_each_process_thread(g, p) {
5233                 /*
5234                  * reset the NMI-timeout, listing all files on a slow
5235                  * console might take a lot of time:
5236                  * Also, reset softlockup watchdogs on all CPUs, because
5237                  * another CPU might be blocked waiting for us to process
5238                  * an IPI.
5239                  */
5240                 touch_nmi_watchdog();
5241                 touch_all_softlockup_watchdogs();
5242                 if (!state_filter || (p->state & state_filter))
5243                         sched_show_task(p);
5244         }
5245 
5246 #ifdef CONFIG_SCHED_DEBUG
5247         if (!state_filter)
5248                 sysrq_sched_debug_show();
5249 #endif
5250         rcu_read_unlock();
5251         /*
5252          * Only show locks if all tasks are dumped:
5253          */
5254         if (!state_filter)
5255                 debug_show_all_locks();
5256 }
5257 
5258 void init_idle_bootup_task(struct task_struct *idle)
5259 {
5260         idle->sched_class = &idle_sched_class;
5261 }
5262 
5263 /**
5264  * init_idle - set up an idle thread for a given CPU
5265  * @idle: task in question
5266  * @cpu: cpu the idle task belongs to
5267  *
5268  * NOTE: this function does not set the idle thread's NEED_RESCHED
5269  * flag, to make booting more robust.
5270  */
5271 void init_idle(struct task_struct *idle, int cpu)
5272 {
5273         struct rq *rq = cpu_rq(cpu);
5274         unsigned long flags;
5275 
5276         raw_spin_lock_irqsave(&idle->pi_lock, flags);
5277         raw_spin_lock(&rq->lock);
5278 
5279         __sched_fork(0, idle);
5280         idle->state = TASK_RUNNING;
5281         idle->se.exec_start = sched_clock();
5282 
5283         kasan_unpoison_task_stack(idle);
5284 
5285 #ifdef CONFIG_SMP
5286         /*
5287          * Its possible that init_idle() gets called multiple times on a task,
5288          * in that case do_set_cpus_allowed() will not do the right thing.
5289          *
5290          * And since this is boot we can forgo the serialization.
5291          */
5292         set_cpus_allowed_common(idle, cpumask_of(cpu));
5293 #endif
5294         /*
5295          * We're having a chicken and egg problem, even though we are
5296          * holding rq->lock, the cpu isn't yet set to this cpu so the
5297          * lockdep check in task_group() will fail.
5298          *
5299          * Similar case to sched_fork(). / Alternatively we could
5300          * use task_rq_lock() here and obtain the other rq->lock.
5301          *
5302          * Silence PROVE_RCU
5303          */
5304         rcu_read_lock();
5305         __set_task_cpu(idle, cpu);
5306         rcu_read_unlock();
5307 
5308         rq->curr = rq->idle = idle;
5309         idle->on_rq = TASK_ON_RQ_QUEUED;
5310 #ifdef CONFIG_SMP
5311         idle->on_cpu = 1;
5312 #endif
5313         raw_spin_unlock(&rq->lock);
5314         raw_spin_unlock_irqrestore(&idle->pi_lock, flags);
5315 
5316         /* Set the preempt count _outside_ the spinlocks! */
5317         init_idle_preempt_count(idle, cpu);
5318 
5319         /*
5320          * The idle tasks have their own, simple scheduling class:
5321          */
5322         idle->sched_class = &idle_sched_class;
5323         ftrace_graph_init_idle_task(idle, cpu);
5324         vtime_init_idle(idle, cpu);
5325 #ifdef CONFIG_SMP
5326         sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu);
5327 #endif
5328 }
5329 
5330 int cpuset_cpumask_can_shrink(const struct cpumask *cur,
5331                               const struct cpumask *trial)
5332 {
5333         int ret = 1, trial_cpus;
5334         struct dl_bw *cur_dl_b;
5335         unsigned long flags;
5336 
5337         if (!cpumask_weight(cur))
5338                 return ret;
5339 
5340         rcu_read_lock_sched();
5341         cur_dl_b = dl_bw_of(cpumask_any(cur));
5342         trial_cpus = cpumask_weight(trial);
5343 
5344         raw_spin_lock_irqsave(&cur_dl_b->lock, flags);
5345         if (cur_dl_b->bw != -1 &&
5346             cur_dl_b->bw * trial_cpus < cur_dl_b->total_bw)
5347                 ret = 0;
5348         raw_spin_unlock_irqrestore(&cur_dl_b->lock, flags);
5349         rcu_read_unlock_sched();
5350 
5351         return ret;
5352 }
5353 
5354 int task_can_attach(struct task_struct *p,
5355                     const struct cpumask *cs_cpus_allowed)
5356 {
5357         int ret = 0;
5358 
5359         /*
5360          * Kthreads which disallow setaffinity shouldn't be moved
5361          * to a new cpuset; we don't want to change their cpu
5362          * affinity and isolating such threads by their set of
5363          * allowed nodes is unnecessary.  Thus, cpusets are not
5364          * applicable for such threads.  This prevents checking for
5365          * success of set_cpus_allowed_ptr() on all attached tasks
5366          * before cpus_allowed may be changed.
5367          */
5368         if (p->flags & PF_NO_SETAFFINITY) {
5369                 ret = -EINVAL;
5370                 goto out;
5371         }
5372 
5373 #ifdef CONFIG_SMP
5374         if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span,
5375                                               cs_cpus_allowed)) {
5376                 unsigned int dest_cpu = cpumask_any_and(cpu_active_mask,
5377                                                         cs_cpus_allowed);
5378                 struct dl_bw *dl_b;
5379                 bool overflow;
5380                 int cpus;
5381                 unsigned long flags;
5382 
5383                 rcu_read_lock_sched();
5384                 dl_b = dl_bw_of(dest_cpu);
5385                 raw_spin_lock_irqsave(&dl_b->lock, flags);
5386                 cpus = dl_bw_cpus(dest_cpu);
5387                 overflow = __dl_overflow(dl_b, cpus, 0, p->dl.dl_bw);
5388                 if (overflow)
5389                         ret = -EBUSY;
5390                 else {
5391                         /*
5392                          * We reserve space for this task in the destination
5393                          * root_domain, as we can't fail after this point.
5394                          * We will free resources in the source root_domain
5395                          * later on (see set_cpus_allowed_dl()).
5396                          */
5397                         __dl_add(dl_b, p->dl.dl_bw);
5398                 }
5399                 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
5400                 rcu_read_unlock_sched();
5401 
5402         }
5403 #endif
5404 out:
5405         return ret;
5406 }
5407 
5408 #ifdef CONFIG_SMP
5409 
5410 static bool sched_smp_initialized __read_mostly;
5411 
5412 #ifdef CONFIG_NUMA_BALANCING
5413 /* Migrate current task p to target_cpu */
5414 int migrate_task_to(struct task_struct *p, int target_cpu)
5415 {
5416         struct migration_arg arg = { p, target_cpu };
5417         int curr_cpu = task_cpu(p);
5418 
5419         if (curr_cpu == target_cpu)
5420                 return 0;
5421 
5422         if (!cpumask_test_cpu(target_cpu, tsk_cpus_allowed(p)))
5423                 return -EINVAL;
5424 
5425         /* TODO: This is not properly updating schedstats */
5426 
5427         trace_sched_move_numa(p, curr_cpu, target_cpu);
5428         return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);
5429 }
5430 
5431 /*
5432  * Requeue a task on a given node and accurately track the number of NUMA
5433  * tasks on the runqueues
5434  */
5435 void sched_setnuma(struct task_struct *p, int nid)
5436 {
5437         bool queued, running;
5438         struct rq_flags rf;
5439         struct rq *rq;
5440 
5441         rq = task_rq_lock(p, &rf);
5442         queued = task_on_rq_queued(p);
5443         running = task_current(rq, p);
5444 
5445         if (queued)
5446                 dequeue_task(rq, p, DEQUEUE_SAVE);
5447         if (running)
5448                 put_prev_task(rq, p);
5449 
5450         p->numa_preferred_nid = nid;
5451 
5452         if (queued)
5453                 enqueue_task(rq, p, ENQUEUE_RESTORE);
5454         if (running)
5455                 set_curr_task(rq, p);
5456         task_rq_unlock(rq, p, &rf);
5457 }
5458 #endif /* CONFIG_NUMA_BALANCING */
5459 
5460 #ifdef CONFIG_HOTPLUG_CPU
5461 /*
5462  * Ensures that the idle task is using init_mm right before its cpu goes
5463  * offline.
5464  */
5465 void idle_task_exit(void)
5466 {
5467         struct mm_struct *mm = current->active_mm;
5468 
5469         BUG_ON(cpu_online(smp_processor_id()));
5470 
5471         if (mm != &init_mm) {
5472                 switch_mm_irqs_off(mm, &init_mm, current);
5473                 finish_arch_post_lock_switch();
5474         }
5475         mmdrop(mm);
5476 }
5477 
5478 /*
5479  * Since this CPU is going 'away' for a while, fold any nr_active delta
5480  * we might have. Assumes we're called after migrate_tasks() so that the
5481  * nr_active count is stable. We need to take the teardown thread which
5482  * is calling this into account, so we hand in adjust = 1 to the load
5483  * calculation.
5484  *
5485  * Also see the comment "Global load-average calculations".
5486  */
5487 static void calc_load_migrate(struct rq *rq)
5488 {
5489         long delta = calc_load_fold_active(rq, 1);
5490         if (delta)
5491                 atomic_long_add(delta, &calc_load_tasks);
5492 }
5493 
5494 static void put_prev_task_fake(struct rq *rq, struct task_struct *prev)
5495 {
5496 }
5497 
5498 static const struct sched_class fake_sched_class = {
5499         .put_prev_task = put_prev_task_fake,
5500 };
5501 
5502 static struct task_struct fake_task = {
5503         /*
5504          * Avoid pull_{rt,dl}_task()
5505          */
5506         .prio = MAX_PRIO + 1,
5507         .sched_class = &fake_sched_class,
5508 };
5509 
5510 /*
5511  * Migrate all tasks from the rq, sleeping tasks will be migrated by
5512  * try_to_wake_up()->select_task_rq().
5513  *
5514  * Called with rq->lock held even though we'er in stop_machine() and
5515  * there's no concurrency possible, we hold the required locks anyway
5516  * because of lock validation efforts.
5517  */
5518 static void migrate_tasks(struct rq *dead_rq)
5519 {
5520         struct rq *rq = dead_rq;
5521         struct task_struct *next, *stop = rq->stop;
5522         struct pin_cookie cookie;
5523         int dest_cpu;
5524 
5525         /*
5526          * Fudge the rq selection such that the below task selection loop
5527          * doesn't get stuck on the currently eligible stop task.
5528          *
5529          * We're currently inside stop_machine() and the rq is either stuck
5530          * in the stop_machine_cpu_stop() loop, or we're executing this code,
5531          * either way we should never end up calling schedule() until we're
5532          * done here.
5533          */
5534         rq->stop = NULL;
5535 
5536         /*
5537          * put_prev_task() and pick_next_task() sched
5538          * class method both need to have an up-to-date
5539          * value of rq->clock[_task]
5540          */
5541         update_rq_clock(rq);
5542 
5543         for (;;) {
5544                 /*
5545                  * There's this thread running, bail when that's the only
5546                  * remaining thread.
5547                  */
5548                 if (rq->nr_running == 1)
5549                         break;
5550 
5551                 /*
5552                  * pick_next_task assumes pinned rq->lock.
5553                  */
5554                 cookie = lockdep_pin_lock(&rq->lock);
5555                 next = pick_next_task(rq, &fake_task, cookie);
5556                 BUG_ON(!next);
5557                 next->sched_class->put_prev_task(rq, next);
5558 
5559                 /*
5560                  * Rules for changing task_struct::cpus_allowed are holding
5561                  * both pi_lock and rq->lock, such that holding either
5562                  * stabilizes the mask.
5563                  *
5564                  * Drop rq->lock is not quite as disastrous as it usually is
5565                  * because !cpu_active at this point, which means load-balance
5566                  * will not interfere. Also, stop-machine.
5567                  */
5568                 lockdep_unpin_lock(&rq->lock, cookie);
5569                 raw_spin_unlock(&rq->lock);
5570                 raw_spin_lock(&next->pi_lock);
5571                 raw_spin_lock(&rq->lock);
5572 
5573                 /*
5574                  * Since we're inside stop-machine, _nothing_ should have
5575                  * changed the task, WARN if weird stuff happened, because in
5576                  * that case the above rq->lock drop is a fail too.
5577                  */
5578                 if (WARN_ON(task_rq(next) != rq || !task_on_rq_queued(next))) {
5579                         raw_spin_unlock(&next->pi_lock);
5580                         continue;
5581                 }
5582 
5583                 /* Find suitable destination for @next, with force if needed. */
5584                 dest_cpu = select_fallback_rq(dead_rq->cpu, next);
5585 
5586                 rq = __migrate_task(rq, next, dest_cpu);
5587                 if (rq != dead_rq) {
5588                         raw_spin_unlock(&rq->lock);
5589                         rq = dead_rq;
5590                         raw_spin_lock(&rq->lock);
5591                 }
5592                 raw_spin_unlock(&next->pi_lock);
5593         }
5594 
5595         rq->stop = stop;
5596 }
5597 #endif /* CONFIG_HOTPLUG_CPU */
5598 
5599 static void set_rq_online(struct rq *rq)
5600 {
5601         if (!rq->online) {
5602                 const struct sched_class *class;
5603 
5604                 cpumask_set_cpu(rq->cpu, rq->rd->online);
5605                 rq->online = 1;
5606 
5607                 for_each_class(class) {
5608                         if (class->rq_online)
5609                                 class->rq_online(rq);
5610                 }
5611         }
5612 }
5613 
5614 static void set_rq_offline(struct rq *rq)
5615 {
5616         if (rq->online) {
5617                 const struct sched_class *class;
5618 
5619                 for_each_class(class) {
5620                         if (class->rq_offline)
5621                                 class->rq_offline(rq);
5622                 }
5623 
5624                 cpumask_clear_cpu(rq->cpu, rq->rd->online);
5625                 rq->online = 0;
5626         }
5627 }
5628 
5629 static void set_cpu_rq_start_time(unsigned int cpu)
5630 {
5631         struct rq *rq = cpu_rq(cpu);
5632 
5633         rq->age_stamp = sched_clock_cpu(cpu);
5634 }
5635 
5636 static cpumask_var_t sched_domains_tmpmask; /* sched_domains_mutex */
5637 
5638 #ifdef CONFIG_SCHED_DEBUG
5639 
5640 static __read_mostly int sched_debug_enabled;
5641 
5642 static int __init sched_debug_setup(char *str)
5643 {
5644         sched_debug_enabled = 1;
5645 
5646         return 0;
5647 }
5648 early_param("sched_debug", sched_debug_setup);
5649 
5650 static inline bool sched_debug(void)
5651 {
5652         return sched_debug_enabled;
5653 }
5654 
5655 static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,
5656                                   struct cpumask *groupmask)
5657 {
5658         struct sched_group *group = sd->groups;
5659 
5660         cpumask_clear(groupmask);
5661 
5662         printk(KERN_DEBUG "%*s domain %d: ", level, "", level);
5663 
5664         if (!(sd->flags & SD_LOAD_BALANCE)) {
5665                 printk("does not load-balance\n");
5666                 if (sd->parent)
5667                         printk(KERN_ERR "ERROR: !SD_LOAD_BALANCE domain"
5668                                         " has parent");
5669                 return -1;
5670         }
5671 
5672         printk(KERN_CONT "span %*pbl level %s\n",
5673                cpumask_pr_args(sched_domain_span(sd)), sd->name);
5674 
5675         if (!cpumask_test_cpu(cpu, sched_domain_span(sd))) {
5676                 printk(KERN_ERR "ERROR: domain->span does not contain "
5677                                 "CPU%d\n", cpu);
5678         }
5679         if (!cpumask_test_cpu(cpu, sched_group_cpus(group))) {
5680                 printk(KERN_ERR "ERROR: domain->groups does not contain"
5681                                 " CPU%d\n", cpu);
5682         }
5683 
5684         printk(KERN_DEBUG "%*s groups:", level + 1, "");
5685         do {
5686                 if (!group) {
5687                         printk("\n");
5688                         printk(KERN_ERR "ERROR: group is NULL\n");
5689                         break;
5690                 }
5691 
5692                 if (!cpumask_weight(sched_group_cpus(group))) {
5693                         printk(KERN_CONT "\n");
5694                         printk(KERN_ERR "ERROR: empty group\n");
5695                         break;
5696                 }
5697 
5698                 if (!(sd->flags & SD_OVERLAP) &&
5699                     cpumask_intersects(groupmask, sched_group_cpus(group))) {
5700                         printk(KERN_CONT "\n");
5701                         printk(KERN_ERR "ERROR: repeated CPUs\n");
5702                         break;
5703                 }
5704 
5705                 cpumask_or(groupmask, groupmask, sched_group_cpus(group));
5706 
5707                 printk(KERN_CONT " %*pbl",
5708                        cpumask_pr_args(sched_group_cpus(group)));
5709                 if (group->sgc->capacity != SCHED_CAPACITY_SCALE) {
5710                         printk(KERN_CONT " (cpu_capacity = %d)",
5711                                 group->sgc->capacity);
5712                 }
5713 
5714                 group = group->next;
5715         } while (group != sd->groups);
5716         printk(KERN_CONT "\n");
5717 
5718         if (!cpumask_equal(sched_domain_span(sd), groupmask))
5719                 printk(KERN_ERR "ERROR: groups don't span domain->span\n");
5720 
5721         if (sd->parent &&
5722             !cpumask_subset(groupmask, sched_domain_span(sd->parent)))
5723                 printk(KERN_ERR "ERROR: parent span is not a superset "
5724                         "of domain->span\n");
5725         return 0;
5726 }
5727 
5728 static void sched_domain_debug(struct sched_domain *sd, int cpu)
5729 {
5730         int level = 0;
5731 
5732         if (!sched_debug_enabled)
5733                 return;
5734 
5735         if (!sd) {
5736                 printk(KERN_DEBUG "CPU%d attaching NULL sched-domain.\n", cpu);
5737                 return;
5738         }
5739 
5740         printk(KERN_DEBUG "CPU%d attaching sched-domain:\n", cpu);
5741 
5742         for (;;) {
5743                 if (sched_domain_debug_one(sd, cpu, level, sched_domains_tmpmask))
5744                         break;
5745                 level++;
5746                 sd = sd->parent;
5747                 if (!sd)
5748                         break;
5749         }
5750 }
5751 #else /* !CONFIG_SCHED_DEBUG */
5752 
5753 # define sched_debug_enabled 0
5754 # define sched_domain_debug(sd, cpu) do { } while (0)
5755 static inline bool sched_debug(void)
5756 {
5757         return false;
5758 }
5759 #endif /* CONFIG_SCHED_DEBUG */
5760 
5761 static int sd_degenerate(struct sched_domain *sd)
5762 {
5763         if (cpumask_weight(sched_domain_span(sd)) == 1)
5764                 return 1;
5765 
5766         /* Following flags need at least 2 groups */
5767         if (sd->flags & (SD_LOAD_BALANCE |
5768                          SD_BALANCE_NEWIDLE |
5769                          SD_BALANCE_FORK |
5770                          SD_BALANCE_EXEC |
5771                          SD_SHARE_CPUCAPACITY |
5772                          SD_ASYM_CPUCAPACITY |
5773                          SD_SHARE_PKG_RESOURCES |
5774                          SD_SHARE_POWERDOMAIN)) {
5775                 if (sd->groups != sd->groups->next)
5776                         return 0;
5777         }
5778 
5779         /* Following flags don't use groups */
5780         if (sd->flags & (SD_WAKE_AFFINE))
5781                 return 0;
5782 
5783         return 1;
5784 }
5785 
5786 static int
5787 sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
5788 {
5789         unsigned long cflags = sd->flags, pflags = parent->flags;
5790 
5791         if (sd_degenerate(parent))
5792                 return 1;
5793 
5794         if (!cpumask_equal(sched_domain_span(sd), sched_domain_span(parent)))
5795                 return 0;
5796 
5797         /* Flags needing groups don't count if only 1 group in parent */
5798         if (parent->groups == parent->groups->next) {
5799                 pflags &= ~(SD_LOAD_BALANCE |
5800                                 SD_BALANCE_NEWIDLE |
5801                                 SD_BALANCE_FORK |
5802                                 SD_BALANCE_EXEC |
5803                                 SD_ASYM_CPUCAPACITY |
5804                                 SD_SHARE_CPUCAPACITY |
5805                                 SD_SHARE_PKG_RESOURCES |
5806                                 SD_PREFER_SIBLING |
5807                                 SD_SHARE_POWERDOMAIN);
5808                 if (nr_node_ids == 1)
5809                         pflags &= ~SD_SERIALIZE;
5810         }
5811         if (~cflags & pflags)
5812                 return 0;
5813 
5814         return 1;
5815 }
5816 
5817 static void free_rootdomain(struct rcu_head *rcu)
5818 {
5819         struct root_domain *rd = container_of(rcu, struct root_domain, rcu);
5820 
5821         cpupri_cleanup(&rd->cpupri);
5822         cpudl_cleanup(&rd->cpudl);
5823         free_cpumask_var(rd->dlo_mask);
5824         free_cpumask_var(rd->rto_mask);
5825         free_cpumask_var(rd->online);
5826         free_cpumask_var(rd->span);
5827         kfree(rd);
5828 }
5829 
5830 static void rq_attach_root(struct rq *rq, struct root_domain *rd)
5831 {
5832         struct root_domain *old_rd = NULL;
5833         unsigned long flags;
5834 
5835         raw_spin_lock_irqsave(&rq->lock, flags);
5836 
5837         if (rq->rd) {
5838                 old_rd = rq->rd;
5839 
5840                 if (cpumask_test_cpu(rq->cpu, old_rd->online))
5841                         set_rq_offline(rq);
5842 
5843                 cpumask_clear_cpu(rq->cpu, old_rd->span);
5844 
5845                 /*
5846                  * If we dont want to free the old_rd yet then
5847                  * set old_rd to NULL to skip the freeing later
5848                  * in this function:
5849                  */
5850                 if (!atomic_dec_and_test(&old_rd->refcount))
5851                         old_rd = NULL;
5852         }
5853 
5854         atomic_inc(&rd->refcount);
5855         rq->rd = rd;
5856 
5857         cpumask_set_cpu(rq->cpu, rd->span);
5858         if (cpumask_test_cpu(rq->cpu, cpu_active_mask))
5859                 set_rq_online(rq);
5860 
5861         raw_spin_unlock_irqrestore(&rq->lock, flags);
5862 
5863         if (old_rd)
5864                 call_rcu_sched(&old_rd->rcu, free_rootdomain);
5865 }
5866 
5867 static int init_rootdomain(struct root_domain *rd)
5868 {
5869         memset(rd, 0, sizeof(*rd));
5870 
5871         if (!zalloc_cpumask_var(&rd->span, GFP_KERNEL))
5872                 goto out;
5873         if (!zalloc_cpumask_var(&rd->online, GFP_KERNEL))
5874                 goto free_span;
5875         if (!zalloc_cpumask_var(&rd->dlo_mask, GFP_KERNEL))
5876                 goto free_online;
5877         if (!zalloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))
5878                 goto free_dlo_mask;
5879 
5880         init_dl_bw(&rd->dl_bw);
5881         if (cpudl_init(&rd->cpudl) != 0)
5882                 goto free_dlo_mask;
5883 
5884         if (cpupri_init(&rd->cpupri) != 0)
5885                 goto free_rto_mask;
5886         return 0;
5887 
5888 free_rto_mask:
5889         free_cpumask_var(rd->rto_mask);
5890 free_dlo_mask:
5891         free_cpumask_var(rd->dlo_mask);
5892 free_online:
5893         free_cpumask_var(rd->online);
5894 free_span:
5895         free_cpumask_var(rd->span);
5896 out:
5897         return -ENOMEM;
5898 }
5899 
5900 /*
5901  * By default the system creates a single root-domain with all cpus as
5902  * members (mimicking the global state we have today).
5903  */
5904 struct root_domain def_root_domain;
5905 
5906 static void init_defrootdomain(void)
5907 {
5908         init_rootdomain(&def_root_domain);
5909 
5910         atomic_set(&def_root_domain.refcount, 1);
5911 }
5912 
5913 static struct root_domain *alloc_rootdomain(void)
5914 {
5915         struct root_domain *rd;
5916 
5917         rd = kmalloc(sizeof(*rd), GFP_KERNEL);
5918         if (!rd)
5919                 return NULL;
5920 
5921         if (init_rootdomain(rd) != 0) {
5922                 kfree(rd);
5923                 return NULL;
5924         }
5925 
5926         return rd;
5927 }
5928 
5929 static void free_sched_groups(struct sched_group *sg, int free_sgc)
5930 {
5931         struct sched_group *tmp, *first;
5932 
5933         if (!sg)
5934                 return;
5935 
5936         first = sg;
5937         do {
5938                 tmp = sg->next;
5939 
5940                 if (free_sgc && atomic_dec_and_test(&sg->sgc->ref))
5941                         kfree(sg->sgc);
5942 
5943                 kfree(sg);
5944                 sg = tmp;
5945         } while (sg != first);
5946 }
5947 
5948 static void destroy_sched_domain(struct sched_domain *sd)
5949 {
5950         /*
5951          * If its an overlapping domain it has private groups, iterate and
5952          * nuke them all.
5953          */
5954         if (sd->flags & SD_OVERLAP) {
5955                 free_sched_groups(sd->groups, 1);
5956         } else if (atomic_dec_and_test(&sd->groups->ref)) {
5957                 kfree(sd->groups->sgc);
5958                 kfree(sd->groups);
5959         }
5960         if (sd->shared && atomic_dec_and_test(&sd->shared->ref))
5961                 kfree(sd->shared);
5962         kfree(sd);
5963 }
5964 
5965 static void destroy_sched_domains_rcu(struct rcu_head *rcu)
5966 {
5967         struct sched_domain *sd = container_of(rcu, struct sched_domain, rcu);
5968 
5969         while (sd) {
5970                 struct sched_domain *parent = sd->parent;
5971                 destroy_sched_domain(sd);
5972                 sd = parent;
5973         }
5974 }
5975 
5976 static void destroy_sched_domains(struct sched_domain *sd)
5977 {
5978         if (sd)
5979                 call_rcu(&sd->rcu, destroy_sched_domains_rcu);
5980 }
5981 
5982 /*
5983  * Keep a special pointer to the highest sched_domain that has
5984  * SD_SHARE_PKG_RESOURCE set (Last Level Cache Domain) for this
5985  * allows us to avoid some pointer chasing select_idle_sibling().
5986  *
5987  * Also keep a unique ID per domain (we use the first cpu number in
5988  * the cpumask of the domain), this allows us to quickly tell if
5989  * two cpus are in the same cache domain, see cpus_share_cache().
5990  */
5991 DEFINE_PER_CPU(struct sched_domain *, sd_llc);
5992 DEFINE_PER_CPU(int, sd_llc_size);
5993 DEFINE_PER_CPU(int, sd_llc_id);
5994 DEFINE_PER_CPU(struct sched_domain_shared *, sd_llc_shared);
5995 DEFINE_PER_CPU(struct sched_domain *, sd_numa);
5996 DEFINE_PER_CPU(struct sched_domain *, sd_asym);
5997 
5998 static void update_top_cache_domain(int cpu)
5999 {
6000         struct sched_domain_shared *sds = NULL;
6001         struct sched_domain *sd;
6002         int id = cpu;
6003         int size = 1;
6004 
6005         sd = highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES);
6006         if (sd) {
6007                 id = cpumask_first(sched_domain_span(sd));
6008                 size = cpumask_weight(sched_domain_span(sd));
6009                 sds = sd->shared;
6010         }
6011 
6012         rcu_assign_pointer(per_cpu(sd_llc, cpu), sd);
6013         per_cpu(sd_llc_size, cpu) = size;
6014         per_cpu(sd_llc_id, cpu) = id;
6015         rcu_assign_pointer(per_cpu(sd_llc_shared, cpu), sds);
6016 
6017         sd = lowest_flag_domain(cpu, SD_NUMA);
6018         rcu_assign_pointer(per_cpu(sd_numa, cpu), sd);
6019 
6020         sd = highest_flag_domain(cpu, SD_ASYM_PACKING);
6021         rcu_assign_pointer(per_cpu(sd_asym, cpu), sd);
6022 }
6023 
6024 /*
6025  * Attach the domain 'sd' to 'cpu' as its base domain. Callers must
6026  * hold the hotplug lock.
6027  */
6028 static void
6029 cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
6030 {
6031         struct rq *rq = cpu_rq(cpu);
6032         struct sched_domain *tmp;
6033 
6034         /* Remove the sched domains which do not contribute to scheduling. */
6035         for (tmp = sd; tmp; ) {
6036                 struct sched_domain *parent = tmp->parent;
6037                 if (!parent)
6038                         break;
6039 
6040                 if (sd_parent_degenerate(tmp, parent)) {
6041                         tmp->parent = parent->parent;
6042                         if (parent->parent)
6043                                 parent->parent->child = tmp;
6044                         /*
6045                          * Transfer SD_PREFER_SIBLING down in case of a
6046                          * degenerate parent; the spans match for this
6047                          * so the property transfers.
6048                          */
6049                         if (parent->flags & SD_PREFER_SIBLING)
6050                                 tmp->flags |= SD_PREFER_SIBLING;
6051                         destroy_sched_domain(parent);
6052                 } else
6053                         tmp = tmp->parent;
6054         }
6055 
6056         if (sd && sd_degenerate(sd)) {
6057                 tmp = sd;
6058                 sd = sd->parent;
6059                 destroy_sched_domain(tmp);
6060                 if (sd)
6061                         sd->child = NULL;
6062         }
6063 
6064         sched_domain_debug(sd, cpu);
6065 
6066         rq_attach_root(rq, rd);
6067         tmp = rq->sd;
6068         rcu_assign_pointer(rq->sd, sd);
6069         destroy_sched_domains(tmp);
6070 
6071         update_top_cache_domain(cpu);
6072 }
6073 
6074 /* Setup the mask of cpus configured for isolated domains */
6075 static int __init isolated_cpu_setup(char *str)
6076 {
6077         int ret;
6078 
6079         alloc_bootmem_cpumask_var(&cpu_isolated_map);
6080         ret = cpulist_parse(str, cpu_isolated_map);
6081         if (ret) {
6082                 pr_err("sched: Error, all isolcpus= values must be between 0 and %d\n", nr_cpu_ids);
6083                 return 0;
6084         }
6085         return 1;
6086 }
6087 __setup("isolcpus=", isolated_cpu_setup);
6088 
6089 struct s_data {
6090         struct sched_domain ** __percpu sd;
6091         struct root_domain      *rd;
6092 };
6093 
6094 enum s_alloc {
6095         sa_rootdomain,
6096         sa_sd,
6097         sa_sd_storage,
6098         sa_none,
6099 };
6100 
6101 /*
6102  * Build an iteration mask that can exclude certain CPUs from the upwards
6103  * domain traversal.
6104  *
6105  * Asymmetric node setups can result in situations where the domain tree is of
6106  * unequal depth, make sure to skip domains that already cover the entire
6107  * range.
6108  *
6109  * In that case build_sched_domains() will have terminated the iteration early
6110  * and our sibling sd spans will be empty. Domains should always include the
6111  * cpu they're built on, so check that.
6112  *
6113  */
6114 static void build_group_mask(struct sched_domain *sd, struct sched_group *sg)
6115 {
6116         const struct cpumask *span = sched_domain_span(sd);
6117         struct sd_data *sdd = sd->private;
6118         struct sched_domain *sibling;
6119         int i;
6120 
6121         for_each_cpu(i, span) {
6122                 sibling = *per_cpu_ptr(sdd->sd, i);
6123                 if (!cpumask_test_cpu(i, sched_domain_span(sibling)))
6124                         continue;
6125 
6126                 cpumask_set_cpu(i, sched_group_mask(sg));
6127         }
6128 }
6129 
6130 /*
6131  * Return the canonical balance cpu for this group, this is the first cpu
6132  * of this group that's also in the iteration mask.
6133  */
6134 int group_balance_cpu(struct sched_group *sg)
6135 {
6136         return cpumask_first_and(sched_group_cpus(sg), sched_group_mask(sg));
6137 }
6138 
6139 static int
6140 build_overlap_sched_groups(struct sched_domain *sd, int cpu)
6141 {
6142         struct sched_group *first = NULL, *last = NULL, *groups = NULL, *sg;
6143         const struct cpumask *span = sched_domain_span(sd);
6144         struct cpumask *covered = sched_domains_tmpmask;
6145         struct sd_data *sdd = sd->private;
6146         struct sched_domain *sibling;
6147         int i;
6148 
6149         cpumask_clear(covered);
6150 
6151         for_each_cpu(i, span) {
6152                 struct cpumask *sg_span;
6153 
6154                 if (cpumask_test_cpu(i, covered))
6155                         continue;
6156 
6157                 sibling = *per_cpu_ptr(sdd->sd, i);
6158 
6159                 /* See the comment near build_group_mask(). */
6160                 if (!cpumask_test_cpu(i, sched_domain_span(sibling)))
6161                         continue;
6162 
6163                 sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(),
6164                                 GFP_KERNEL, cpu_to_node(cpu));
6165 
6166                 if (!sg)
6167                         goto fail;
6168 
6169                 sg_span = sched_group_cpus(sg);
6170                 if (sibling->child)
6171                         cpumask_copy(sg_span, sched_domain_span(sibling->child));
6172                 else
6173                         cpumask_set_cpu(i, sg_span);
6174 
6175                 cpumask_or(covered, covered, sg_span);
6176 
6177                 sg->sgc = *per_cpu_ptr(sdd->sgc, i);
6178                 if (atomic_inc_return(&sg->sgc->ref) == 1)
6179                         build_group_mask(sd, sg);
6180 
6181                 /*
6182                  * Initialize sgc->capacity such that even if we mess up the
6183                  * domains and no possible iteration will get us here, we won't
6184                  * die on a /0 trap.
6185                  */
6186                 sg->sgc->capacity = SCHED_CAPACITY_SCALE * cpumask_weight(sg_span);
6187 
6188                 /*
6189                  * Make sure the first group of this domain contains the
6190                  * canonical balance cpu. Otherwise the sched_domain iteration
6191                  * breaks. See update_sg_lb_stats().
6192                  */
6193                 if ((!groups && cpumask_test_cpu(cpu, sg_span)) ||
6194                     group_balance_cpu(sg) == cpu)
6195                         groups = sg;
6196 
6197                 if (!first)
6198                         first = sg;
6199                 if (last)
6200                         last->next = sg;
6201                 last = sg;
6202                 last->next = first;
6203         }
6204         sd->groups = groups;
6205 
6206         return 0;
6207 
6208 fail:
6209         free_sched_groups(first, 0);
6210 
6211         return -ENOMEM;
6212 }
6213 
6214 static int get_group(int cpu, struct sd_data *sdd, struct sched_group **sg)
6215 {
6216         struct sched_domain *sd = *per_cpu_ptr(sdd->sd, cpu);
6217         struct sched_domain *child = sd->child;
6218 
6219         if (child)
6220                 cpu = cpumask_first(sched_domain_span(child));
6221 
6222         if (sg) {
6223                 *sg = *per_cpu_ptr(sdd->sg, cpu);
6224                 (*sg)->sgc = *per_cpu_ptr(sdd->sgc, cpu);
6225                 atomic_set(&(*sg)->sgc->ref, 1); /* for claim_allocations */
6226         }
6227 
6228         return cpu;
6229 }
6230 
6231 /*
6232  * build_sched_groups will build a circular linked list of the groups
6233  * covered by the given span, and will set each group's ->cpumask correctly,
6234  * and ->cpu_capacity to 0.
6235  *
6236  * Assumes the sched_domain tree is fully constructed
6237  */
6238 static int
6239 build_sched_groups(struct sched_domain *sd, int cpu)
6240 {
6241         struct sched_group *first = NULL, *last = NULL;
6242         struct sd_data *sdd = sd->private;
6243         const struct cpumask *span = sched_domain_span(sd);
6244         struct cpumask *covered;
6245         int i;
6246 
6247         get_group(cpu, sdd, &sd->groups);
6248         atomic_inc(&sd->groups->ref);
6249 
6250         if (cpu != cpumask_first(span))
6251                 return 0;
6252 
6253         lockdep_assert_held(&sched_domains_mutex);
6254         covered = sched_domains_tmpmask;
6255 
6256         cpumask_clear(covered);
6257 
6258         for_each_cpu(i, span) {
6259                 struct sched_group *sg;
6260                 int group, j;
6261 
6262                 if (cpumask_test_cpu(i, covered))
6263                         continue;
6264 
6265                 group = get_group(i, sdd, &sg);
6266                 cpumask_setall(sched_group_mask(sg));
6267 
6268                 for_each_cpu(j, span) {
6269                         if (get_group(j, sdd, NULL) != group)
6270                                 continue;
6271 
6272                         cpumask_set_cpu(j, covered);
6273                         cpumask_set_cpu(j, sched_group_cpus(sg));
6274                 }
6275 
6276                 if (!first)
6277                         first = sg;
6278                 if (last)
6279                         last->next = sg;
6280                 last = sg;
6281         }
6282         last->next = first;
6283 
6284         return 0;
6285 }
6286 
6287 /*
6288  * Initialize sched groups cpu_capacity.
6289  *
6290  * cpu_capacity indicates the capacity of sched group, which is used while
6291  * distributing the load between different sched groups in a sched domain.
6292  * Typically cpu_capacity for all the groups in a sched domain will be same
6293  * unless there are asymmetries in the topology. If there are asymmetries,
6294  * group having more cpu_capacity will pickup more load compared to the
6295  * group having less cpu_capacity.
6296  */
6297 static void init_sched_groups_capacity(int cpu, struct sched_domain *sd)
6298 {
6299         struct sched_group *sg = sd->groups;
6300 
6301         WARN_ON(!sg);
6302 
6303         do {
6304                 sg->group_weight = cpumask_weight(sched_group_cpus(sg));
6305                 sg = sg->next;
6306         } while (sg != sd->groups);
6307 
6308         if (cpu != group_balance_cpu(sg))
6309                 return;
6310 
6311         update_group_capacity(sd, cpu);
6312 }
6313 
6314 /*
6315  * Initializers for schedule domains
6316  * Non-inlined to reduce accumulated stack pressure in build_sched_domains()
6317  */
6318 
6319 static int default_relax_domain_level = -1;
6320 int sched_domain_level_max;
6321 
6322 static int __init setup_relax_domain_level(char *str)
6323 {
6324         if (kstrtoint(str, 0, &default_relax_domain_level))
6325                 pr_warn("Unable to set relax_domain_level\n");
6326 
6327         return 1;
6328 }
6329 __setup("relax_domain_level=", setup_relax_domain_level);
6330 
6331 static void set_domain_attribute(struct sched_domain *sd,
6332                                  struct sched_domain_attr *attr)
6333 {
6334         int request;
6335 
6336         if (!attr || attr->relax_domain_level < 0) {
6337                 if (default_relax_domain_level < 0)
6338                         return;
6339                 else
6340                         request = default_relax_domain_level;
6341         } else
6342                 request = attr->relax_domain_level;
6343         if (request < sd->level) {
6344                 /* turn off idle balance on this domain */
6345                 sd->flags &= ~(SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
6346         } else {
6347                 /* turn on idle balance on this domain */
6348                 sd->flags |= (SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
6349         }
6350 }
6351 
6352 static void __sdt_free(const struct cpumask *cpu_map);
6353 static int __sdt_alloc(const struct cpumask *cpu_map);
6354 
6355 static void __free_domain_allocs(struct s_data *d, enum s_alloc what,
6356                                  const struct cpumask *cpu_map)
6357 {
6358         switch (what) {
6359         case sa_rootdomain:
6360                 if (!atomic_read(&d->rd->refcount))
6361                         free_rootdomain(&d->rd->rcu); /* fall through */
6362         case sa_sd:
6363                 free_percpu(d->sd); /* fall through */
6364         case sa_sd_storage:
6365                 __sdt_free(cpu_map); /* fall through */
6366         case sa_none:
6367                 break;
6368         }
6369 }
6370 
6371 static enum s_alloc __visit_domain_allocation_hell(struct s_data *d,
6372                                                    const struct cpumask *cpu_map)
6373 {
6374         memset(d, 0, sizeof(*d));
6375 
6376         if (__sdt_alloc(cpu_map))
6377                 return sa_sd_storage;
6378         d->sd = alloc_percpu(struct sched_domain *);
6379         if (!d->sd)
6380                 return sa_sd_storage;
6381         d->rd = alloc_rootdomain();
6382         if (!d->rd)
6383                 return sa_sd;
6384         return sa_rootdomain;
6385 }
6386 
6387 /*
6388  * NULL the sd_data elements we've used to build the sched_domain and
6389  * sched_group structure so that the subsequent __free_domain_allocs()
6390  * will not free the data we're using.
6391  */
6392 static void claim_allocations(int cpu, struct sched_domain *sd)
6393 {
6394         struct sd_data *sdd = sd->private;
6395 
6396         WARN_ON_ONCE(*per_cpu_ptr(sdd->sd, cpu) != sd);
6397         *per_cpu_ptr(sdd->sd, cpu) = NULL;
6398 
6399         if (atomic_read(&(*per_cpu_ptr(sdd->sds, cpu))->ref))
6400                 *per_cpu_ptr(sdd->sds, cpu) = NULL;
6401 
6402         if (atomic_read(&(*per_cpu_ptr(sdd->sg, cpu))->ref))
6403                 *per_cpu_ptr(sdd->sg, cpu) = NULL;
6404 
6405         if (atomic_read(&(*per_cpu_ptr(sdd->sgc, cpu))->ref))
6406                 *per_cpu_ptr(sdd->sgc, cpu) = NULL;
6407 }
6408 
6409 #ifdef CONFIG_NUMA
6410 static int sched_domains_numa_levels;
6411 enum numa_topology_type sched_numa_topology_type;
6412 static int *sched_domains_numa_distance;
6413 int sched_max_numa_distance;
6414 static struct cpumask ***sched_domains_numa_masks;
6415 static int sched_domains_curr_level;
6416 #endif
6417 
6418 /*
6419  * SD_flags allowed in topology descriptions.
6420  *
6421  * These flags are purely descriptive of the topology and do not prescribe
6422  * behaviour. Behaviour is artificial and mapped in the below sd_init()
6423  * function:
6424  *
6425  *   SD_SHARE_CPUCAPACITY   - describes SMT topologies
6426  *   SD_SHARE_PKG_RESOURCES - describes shared caches
6427  *   SD_NUMA                - describes NUMA topologies
6428  *   SD_SHARE_POWERDOMAIN   - describes shared power domain
6429  *   SD_ASYM_CPUCAPACITY    - describes mixed capacity topologies
6430  *
6431  * Odd one out, which beside describing the topology has a quirk also
6432  * prescribes the desired behaviour that goes along with it:
6433  *
6434  *   SD_ASYM_PACKING        - describes SMT quirks
6435  */
6436 #define TOPOLOGY_SD_FLAGS               \
6437         (SD_SHARE_CPUCAPACITY |         \
6438          SD_SHARE_PKG_RESOURCES |       \
6439          SD_NUMA |                      \
6440          SD_ASYM_PACKING |              \
6441          SD_ASYM_CPUCAPACITY |          \
6442          SD_SHARE_POWERDOMAIN)
6443 
6444 static struct sched_domain *
6445 sd_init(struct sched_domain_topology_level *tl,
6446         const struct cpumask *cpu_map,
6447         struct sched_domain *child, int cpu)
6448 {
6449         struct sd_data *sdd = &tl->data;
6450         struct sched_domain *sd = *per_cpu_ptr(sdd->sd, cpu);
6451         int sd_id, sd_weight, sd_flags = 0;
6452 
6453 #ifdef CONFIG_NUMA
6454         /*
6455          * Ugly hack to pass state to sd_numa_mask()...
6456          */
6457         sched_domains_curr_level = tl->numa_level;
6458 #endif
6459 
6460         sd_weight = cpumask_weight(tl->mask(cpu));
6461 
6462         if (tl->sd_flags)
6463                 sd_flags = (*tl->sd_flags)();
6464         if (WARN_ONCE(sd_flags & ~TOPOLOGY_SD_FLAGS,
6465                         "wrong sd_flags in topology description\n"))
6466                 sd_flags &= ~TOPOLOGY_SD_FLAGS;
6467 
6468         *sd = (struct sched_domain){
6469                 .min_interval           = sd_weight,
6470                 .max_interval           = 2*sd_weight,
6471                 .busy_factor            = 32,
6472                 .imbalance_pct          = 125,
6473 
6474                 .cache_nice_tries       = 0,
6475                 .busy_idx               = 0,
6476                 .idle_idx               = 0,
6477                 .newidle_idx            = 0,
6478                 .wake_idx               = 0,
6479                 .forkexec_idx           = 0,
6480 
6481                 .flags                  = 1*SD_LOAD_BALANCE
6482                                         | 1*SD_BALANCE_NEWIDLE
6483                                         | 1*SD_BALANCE_EXEC
6484                                         | 1*SD_BALANCE_FORK
6485                                         | 0*SD_BALANCE_WAKE
6486                                         | 1*SD_WAKE_AFFINE
6487                                         | 0*SD_SHARE_CPUCAPACITY
6488                                         | 0*SD_SHARE_PKG_RESOURCES
6489                                         | 0*SD_SERIALIZE
6490                                         | 0*SD_PREFER_SIBLING
6491                                         | 0*SD_NUMA
6492                                         | sd_flags
6493                                         ,
6494 
6495                 .last_balance           = jiffies,
6496                 .balance_interval       = sd_weight,
6497                 .smt_gain               = 0,
6498                 .max_newidle_lb_cost    = 0,
6499                 .next_decay_max_lb_cost = jiffies,
6500                 .child                  = child,
6501 #ifdef CONFIG_SCHED_DEBUG
6502                 .name                   = tl->name,
6503 #endif
6504         };
6505 
6506         cpumask_and(sched_domain_span(sd), cpu_map, tl->mask(cpu));
6507         sd_id = cpumask_first(sched_domain_span(sd));
6508 
6509         /*
6510          * Convert topological properties into behaviour.
6511          */
6512 
6513         if (sd->flags & SD_ASYM_CPUCAPACITY) {
6514                 struct sched_domain *t = sd;
6515 
6516                 for_each_lower_domain(t)
6517                         t->flags |= SD_BALANCE_WAKE;
6518         }
6519 
6520         if (sd->flags & SD_SHARE_CPUCAPACITY) {
6521                 sd->flags |= SD_PREFER_SIBLING;
6522                 sd->imbalance_pct = 110;
6523                 sd->smt_gain = 1178; /* ~15% */
6524 
6525         } else if (sd->flags & SD_SHARE_PKG_RESOURCES) {
6526                 sd->imbalance_pct = 117;
6527                 sd->cache_nice_tries = 1;
6528                 sd->busy_idx = 2;
6529 
6530 #ifdef CONFIG_NUMA
6531         } else if (sd->flags & SD_NUMA) {
6532                 sd->cache_nice_tries = 2;
6533                 sd->busy_idx = 3;
6534                 sd->idle_idx = 2;
6535 
6536                 sd->flags |= SD_SERIALIZE;
6537                 if (sched_domains_numa_distance[tl->numa_level] > RECLAIM_DISTANCE) {
6538                         sd->flags &= ~(SD_BALANCE_EXEC |
6539                                        SD_BALANCE_FORK |
6540                                        SD_WAKE_AFFINE);
6541                 }
6542 
6543 #endif
6544         } else {
6545                 sd->flags |= SD_PREFER_SIBLING;
6546                 sd->cache_nice_tries = 1;
6547                 sd->busy_idx = 2;
6548                 sd->idle_idx = 1;
6549         }
6550 
6551         /*
6552          * For all levels sharing cache; connect a sched_domain_shared
6553          * instance.
6554          */
6555         if (sd->flags & SD_SHARE_PKG_RESOURCES) {
6556                 sd->shared = *per_cpu_ptr(sdd->sds, sd_id);
6557                 atomic_inc(&sd->shared->ref);
6558                 atomic_set(&sd->shared->nr_busy_cpus, sd_weight);
6559         }
6560 
6561         sd->private = sdd;
6562 
6563         return sd;
6564 }
6565 
6566 /*
6567  * Topology list, bottom-up.
6568  */
6569 static struct sched_domain_topology_level default_topology[] = {
6570 #ifdef CONFIG_SCHED_SMT
6571         { cpu_smt_mask, cpu_smt_flags, SD_INIT_NAME(SMT) },
6572 #endif
6573 #ifdef CONFIG_SCHED_MC
6574         { cpu_coregroup_mask, cpu_core_flags, SD_INIT_NAME(MC) },
6575 #endif
6576         { cpu_cpu_mask, SD_INIT_NAME(DIE) },
6577         { NULL, },
6578 };
6579 
6580 static struct sched_domain_topology_level *sched_domain_topology =
6581         default_topology;
6582 
6583 #define for_each_sd_topology(tl)                        \
6584         for (tl = sched_domain_topology; tl->mask; tl++)
6585 
6586 void set_sched_topology(struct sched_domain_topology_level *tl)
6587 {
6588         if (WARN_ON_ONCE(sched_smp_initialized))
6589                 return;
6590 
6591         sched_domain_topology = tl;
6592 }
6593 
6594 #ifdef CONFIG_NUMA
6595 
6596 static const struct cpumask *sd_numa_mask(int cpu)
6597 {
6598         return sched_domains_numa_masks[sched_domains_curr_level][cpu_to_node(cpu)];
6599 }
6600 
6601 static void sched_numa_warn(const char *str)
6602 {
6603         static int done = false;
6604         int i,j;
6605 
6606         if (done)
6607                 return;
6608 
6609         done = true;
6610 
6611         printk(KERN_WARNING "ERROR: %s\n\n", str);
6612 
6613         for (i = 0; i < nr_node_ids; i++) {
6614                 printk(KERN_WARNING "  ");
6615                 for (j = 0; j < nr_node_ids; j++)
6616                         printk(KERN_CONT "%02d ", node_distance(i,j));
6617                 printk(KERN_CONT "\n");
6618         }
6619         printk(KERN_WARNING "\n");
6620 }
6621 
6622 bool find_numa_distance(int distance)
6623 {
6624         int i;
6625 
6626         if (distance == node_distance(0, 0))
6627                 return true;
6628 
6629         for (i = 0; i < sched_domains_numa_levels; i++) {
6630                 if (sched_domains_numa_distance[i] == distance)
6631                         return true;
6632         }
6633 
6634         return false;
6635 }
6636 
6637 /*
6638  * A system can have three types of NUMA topology:
6639  * NUMA_DIRECT: all nodes are directly connected, or not a NUMA system
6640  * NUMA_GLUELESS_MESH: some nodes reachable through intermediary nodes
6641  * NUMA_BACKPLANE: nodes can reach other nodes through a backplane
6642  *
6643  * The difference between a glueless mesh topology and a backplane
6644  * topology lies in whether communication between not directly
6645  * connected nodes goes through intermediary nodes (where programs
6646  * could run), or through backplane controllers. This affects
6647  * placement of programs.
6648  *
6649  * The type of topology can be discerned with the following tests:
6650  * - If the maximum distance between any nodes is 1 hop, the system
6651  *   is directly connected.
6652  * - If for two nodes A and B, located N > 1 hops away from each other,
6653  *   there is an intermediary node C, which is < N hops away from both
6654  *   nodes A and B, the system is a glueless mesh.
6655  */
6656 static void init_numa_topology_type(void)
6657 {
6658         int a, b, c, n;
6659 
6660         n = sched_max_numa_distance;
6661 
6662         if (sched_domains_numa_levels <= 1) {
6663                 sched_numa_topology_type = NUMA_DIRECT;
6664                 return;
6665         }
6666 
6667         for_each_online_node(a) {
6668                 for_each_online_node(b) {
6669                         /* Find two nodes furthest removed from each other. */
6670                         if (node_distance(a, b) < n)
6671                                 continue;
6672 
6673                         /* Is there an intermediary node between a and b? */
6674                         for_each_online_node(c) {
6675                                 if (node_distance(a, c) < n &&
6676                                     node_distance(b, c) < n) {
6677                                         sched_numa_topology_type =
6678                                                         NUMA_GLUELESS_MESH;
6679                                         return;
6680                                 }
6681                         }
6682 
6683                         sched_numa_topology_type = NUMA_BACKPLANE;
6684                         return;
6685                 }
6686         }
6687 }
6688 
6689 static void sched_init_numa(void)
6690 {
6691         int next_distance, curr_distance = node_distance(0, 0);
6692         struct sched_domain_topology_level *tl;
6693         int level = 0;
6694         int i, j, k;
6695 
6696         sched_domains_numa_distance = kzalloc(sizeof(int) * nr_node_ids, GFP_KERNEL);
6697         if (!sched_domains_numa_distance)
6698                 return;
6699 
6700         /*
6701          * O(nr_nodes^2) deduplicating selection sort -- in order to find the
6702          * unique distances in the node_distance() table.
6703          *
6704          * Assumes node_distance(0,j) includes all distances in
6705          * node_distance(i,j) in order to avoid cubic time.
6706          */
6707         next_distance = curr_distance;
6708         for (i = 0; i < nr_node_ids; i++) {
6709                 for (j = 0; j < nr_node_ids; j++) {
6710                         for (k = 0; k < nr_node_ids; k++) {
6711                                 int distance = node_distance(i, k);
6712 
6713                                 if (distance > curr_distance &&
6714                                     (distance < next_distance ||
6715                                      next_distance == curr_distance))
6716                                         next_distance = distance;
6717 
6718                                 /*
6719                                  * While not a strong assumption it would be nice to know
6720                                  * about cases where if node A is connected to B, B is not
6721                                  * equally connected to A.
6722                                  */
6723                                 if (sched_debug() && node_distance(k, i) != distance)
6724                                         sched_numa_warn("Node-distance not symmetric");
6725 
6726                                 if (sched_debug() && i && !find_numa_distance(distance))
6727                                         sched_numa_warn("Node-0 not representative");
6728                         }
6729                         if (next_distance != curr_distance) {
6730                                 sched_domains_numa_distance[level++] = next_distance;
6731                                 sched_domains_numa_levels = level;
6732                                 curr_distance = next_distance;
6733                         } else break;
6734                 }
6735 
6736                 /*
6737                  * In case of sched_debug() we verify the above assumption.
6738                  */
6739                 if (!sched_debug())
6740                         break;
6741         }
6742 
6743         if (!level)
6744                 return;
6745 
6746         /*
6747          * 'level' contains the number of unique distances, excluding the
6748          * identity distance node_distance(i,i).
6749          *
6750          * The sched_domains_numa_distance[] array includes the actual distance
6751          * numbers.
6752          */
6753 
6754         /*
6755          * Here, we should temporarily reset sched_domains_numa_levels to 0.
6756          * If it fails to allocate memory for array sched_domains_numa_masks[][],
6757          * the array will contain less then 'level' members. This could be
6758          * dangerous when we use it to iterate array sched_domains_numa_masks[][]
6759          * in other functions.
6760          *
6761          * We reset it to 'level' at the end of this function.
6762          */
6763         sched_domains_numa_levels = 0;
6764 
6765         sched_domains_numa_masks = kzalloc(sizeof(void *) * level, GFP_KERNEL);
6766         if (!sched_domains_numa_masks)
6767                 return;
6768 
6769         /*
6770          * Now for each level, construct a mask per node which contains all
6771          * cpus of nodes that are that many hops away from us.
6772          */
6773         for (i = 0; i < level; i++) {
6774                 sched_domains_numa_masks[i] =
6775                         kzalloc(nr_node_ids * sizeof(void *), GFP_KERNEL);
6776                 if (!sched_domains_numa_masks[i])
6777                         return;
6778 
6779                 for (j = 0; j < nr_node_ids; j++) {
6780                         struct cpumask *mask = kzalloc(cpumask_size(), GFP_KERNEL);
6781                         if (!mask)
6782                                 return;
6783 
6784                         sched_domains_numa_masks[i][j] = mask;
6785 
6786                         for_each_node(k) {
6787                                 if (node_distance(j, k) > sched_domains_numa_distance[i])
6788                                         continue;
6789 
6790                                 cpumask_or(mask, mask, cpumask_of_node(k));
6791                         }
6792                 }
6793         }
6794 
6795         /* Compute default topology size */
6796         for (i = 0; sched_domain_topology[i].mask; i++);
6797 
6798         tl = kzalloc((i + level + 1) *
6799                         sizeof(struct sched_domain_topology_level), GFP_KERNEL);
6800         if (!tl)
6801                 return;
6802 
6803         /*
6804          * Copy the default topology bits..
6805          */
6806         for (i = 0; sched_domain_topology[i].mask; i++)
6807                 tl[i] = sched_domain_topology[i];
6808 
6809         /*
6810          * .. and append 'j' levels of NUMA goodness.
6811          */
6812         for (j = 0; j < level; i++, j++) {
6813                 tl[i] = (struct sched_domain_topology_level){
6814                         .mask = sd_numa_mask,
6815                         .sd_flags = cpu_numa_flags,
6816                         .flags = SDTL_OVERLAP,
6817                         .numa_level = j,
6818                         SD_INIT_NAME(NUMA)
6819                 };
6820         }
6821 
6822         sched_domain_topology = tl;
6823 
6824         sched_domains_numa_levels = level;
6825         sched_max_numa_distance = sched_domains_numa_distance[level - 1];
6826 
6827         init_numa_topology_type();
6828 }
6829 
6830 static void sched_domains_numa_masks_set(unsigned int cpu)
6831 {
6832         int node = cpu_to_node(cpu);
6833         int i, j;
6834 
6835         for (i = 0; i < sched_domains_numa_levels; i++) {
6836                 for (j = 0; j < nr_node_ids; j++) {
6837                         if (node_distance(j, node) <= sched_domains_numa_distance[i])
6838                                 cpumask_set_cpu(cpu, sched_domains_numa_masks[i][j]);
6839                 }
6840         }
6841 }
6842 
6843 static void sched_domains_numa_masks_clear(unsigned int cpu)
6844 {
6845         int i, j;
6846 
6847         for (i = 0; i < sched_domains_numa_levels; i++) {
6848                 for (j = 0; j < nr_node_ids; j++)
6849                         cpumask_clear_cpu(cpu, sched_domains_numa_masks[i][j]);
6850         }
6851 }
6852 
6853 #else
6854 static inline void sched_init_numa(void) { }
6855 static void sched_domains_numa_masks_set(unsigned int cpu) { }
6856 static void sched_domains_numa_masks_clear(unsigned int cpu) { }
6857 #endif /* CONFIG_NUMA */
6858 
6859 static int __sdt_alloc(const struct cpumask *cpu_map)
6860 {
6861         struct sched_domain_topology_level *tl;
6862         int j;
6863 
6864         for_each_sd_topology(tl) {
6865                 struct sd_data *sdd = &tl->data;
6866 
6867                 sdd->sd = alloc_percpu(struct sched_domain *);
6868                 if (!sdd->sd)
6869                         return -ENOMEM;
6870 
6871                 sdd->sds = alloc_percpu(struct sched_domain_shared *);
6872                 if (!sdd->sds)
6873                         return -ENOMEM;
6874 
6875                 sdd->sg = alloc_percpu(struct sched_group *);
6876                 if (!sdd->sg)
6877                         return -ENOMEM;
6878 
6879                 sdd->sgc = alloc_percpu(struct sched_group_capacity *);
6880                 if (!sdd->sgc)
6881                         return -ENOMEM;
6882 
6883                 for_each_cpu(j, cpu_map) {
6884                         struct sched_domain *sd;
6885                         struct sched_domain_shared *sds;
6886                         struct sched_group *sg;
6887                         struct sched_group_capacity *sgc;
6888 
6889                         sd = kzalloc_node(sizeof(struct sched_domain) + cpumask_size(),
6890                                         GFP_KERNEL, cpu_to_node(j));
6891                         if (!sd)
6892                                 return -ENOMEM;
6893 
6894                         *per_cpu_ptr(sdd->sd, j) = sd;
6895 
6896                         sds = kzalloc_node(sizeof(struct sched_domain_shared),
6897                                         GFP_KERNEL, cpu_to_node(j));
6898                         if (!sds)
6899                                 return -ENOMEM;
6900 
6901                         *per_cpu_ptr(sdd->sds, j) = sds;
6902 
6903                         sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(),
6904                                         GFP_KERNEL, cpu_to_node(j));
6905                         if (!sg)
6906                                 return -ENOMEM;
6907 
6908                         sg->next = sg;
6909 
6910                         *per_cpu_ptr(sdd->sg, j) = sg;
6911 
6912                         sgc = kzalloc_node(sizeof(struct sched_group_capacity) + cpumask_size(),
6913                                         GFP_KERNEL, cpu_to_node(j));
6914                         if (!sgc)
6915                                 return -ENOMEM;
6916 
6917                         *per_cpu_ptr(sdd->sgc, j) = sgc;
6918                 }
6919         }
6920 
6921         return 0;
6922 }
6923 
6924 static void __sdt_free(const struct cpumask *cpu_map)
6925 {
6926         struct sched_domain_topology_level *tl;
6927         int j;
6928 
6929         for_each_sd_topology(tl) {
6930                 struct sd_data *sdd = &tl->data;
6931 
6932                 for_each_cpu(j, cpu_map) {
6933                         struct sched_domain *sd;
6934 
6935                         if (sdd->sd) {
6936                                 sd = *per_cpu_ptr(sdd->sd, j);
6937                                 if (sd && (sd->flags & SD_OVERLAP))
6938                                         free_sched_groups(sd->groups, 0);
6939                                 kfree(*per_cpu_ptr(sdd->sd, j));
6940                         }
6941 
6942                         if (sdd->sds)
6943                                 kfree(*per_cpu_ptr(sdd->sds, j));
6944                         if (sdd->sg)
6945                                 kfree(*per_cpu_ptr(sdd->sg, j));
6946                         if (sdd->sgc)
6947                                 kfree(*per_cpu_ptr(sdd->sgc, j));
6948                 }
6949                 free_percpu(sdd->sd);
6950                 sdd->sd = NULL;
6951                 free_percpu(sdd->sds);
6952                 sdd->sds = NULL;
6953                 free_percpu(sdd->sg);
6954                 sdd->sg = NULL;
6955                 free_percpu(sdd->sgc);
6956                 sdd->sgc = NULL;
6957         }
6958 }
6959 
6960 struct sched_domain *build_sched_domain(struct sched_domain_topology_level *tl,
6961                 const struct cpumask *cpu_map, struct sched_domain_attr *attr,
6962                 struct sched_domain *child, int cpu)
6963 {
6964         struct sched_domain *sd = sd_init(tl, cpu_map, child, cpu);
6965 
6966         if (child) {
6967                 sd->level = child->level + 1;
6968                 sched_domain_level_max = max(sched_domain_level_max, sd->level);
6969                 child->parent = sd;
6970 
6971                 if (!cpumask_subset(sched_domain_span(child),
6972                                     sched_domain_span(sd))) {
6973                         pr_err("BUG: arch topology borken\n");
6974 #ifdef CONFIG_SCHED_DEBUG
6975                         pr_err("     the %s domain not a subset of the %s domain\n",
6976                                         child->name, sd->name);
6977 #endif
6978                         /* Fixup, ensure @sd has at least @child cpus. */
6979                         cpumask_or(sched_domain_span(sd),
6980                                    sched_domain_span(sd),
6981                                    sched_domain_span(child));
6982                 }
6983 
6984         }
6985         set_domain_attribute(sd, attr);
6986 
6987         return sd;
6988 }
6989 
6990 /*
6991  * Build sched domains for a given set of cpus and attach the sched domains
6992  * to the individual cpus
6993  */
6994 static int build_sched_domains(const struct cpumask *cpu_map,
6995                                struct sched_domain_attr *attr)
6996 {
6997         enum s_alloc alloc_state;
6998         struct sched_domain *sd;
6999         struct s_data d;
7000         struct rq *rq = NULL;
7001         int i, ret = -ENOMEM;
7002 
7003         alloc_state = __visit_domain_allocation_hell(&d, cpu_map);
7004         if (alloc_state != sa_rootdomain)
7005                 goto error;
7006 
7007         /* Set up domains for cpus specified by the cpu_map. */
7008         for_each_cpu(i, cpu_map) {
7009                 struct sched_domain_topology_level *tl;
7010 
7011                 sd = NULL;
7012                 for_each_sd_topology(tl) {
7013                         sd = build_sched_domain(tl, cpu_map, attr, sd, i);
7014                         if (tl == sched_domain_topology)
7015                                 *per_cpu_ptr(d.sd, i) = sd;
7016                         if (tl->flags & SDTL_OVERLAP || sched_feat(FORCE_SD_OVERLAP))
7017                                 sd->flags |= SD_OVERLAP;
7018                         if (cpumask_equal(cpu_map, sched_domain_span(sd)))
7019                                 break;
7020                 }
7021         }
7022 
7023         /* Build the groups for the domains */
7024         for_each_cpu(i, cpu_map) {
7025                 for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
7026                         sd->span_weight = cpumask_weight(sched_domain_span(sd));
7027                         if (sd->flags & SD_OVERLAP) {
7028                                 if (build_overlap_sched_groups(sd, i))
7029                                         goto error;
7030                         } else {
7031                                 if (build_sched_groups(sd, i))
7032                                         goto error;
7033                         }
7034                 }
7035         }
7036 
7037         /* Calculate CPU capacity for physical packages and nodes */
7038         for (i = nr_cpumask_bits-1; i >= 0; i--) {
7039                 if (!cpumask_test_cpu(i, cpu_map))
7040                         continue;
7041 
7042                 for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
7043                         claim_allocations(i, sd);
7044                         init_sched_groups_capacity(i, sd);
7045                 }
7046         }
7047 
7048         /* Attach the domains */
7049         rcu_read_lock();
7050         for_each_cpu(i, cpu_map) {
7051                 rq = cpu_rq(i);
7052                 sd = *per_cpu_ptr(d.sd, i);
7053 
7054                 /* Use READ_ONCE()/WRITE_ONCE() to avoid load/store tearing: */
7055                 if (rq->cpu_capacity_orig > READ_ONCE(d.rd->max_cpu_capacity))
7056                         WRITE_ONCE(d.rd->max_cpu_capacity, rq->cpu_capacity_orig);
7057 
7058                 cpu_attach_domain(sd, d.rd, i);
7059         }
7060         rcu_read_unlock();
7061 
7062         if (rq && sched_debug_enabled) {
7063                 pr_info("span: %*pbl (max cpu_capacity = %lu)\n",
7064                         cpumask_pr_args(cpu_map), rq->rd->max_cpu_capacity);
7065         }
7066 
7067         ret = 0;
7068 error:
7069         __free_domain_allocs(&d, alloc_state, cpu_map);
7070         return ret;
7071 }
7072 
7073 static cpumask_var_t *doms_cur; /* current sched domains */
7074 static int ndoms_cur;           /* number of sched domains in 'doms_cur' */
7075 static struct sched_domain_attr *dattr_cur;
7076                                 /* attribues of custom domains in 'doms_cur' */
7077 
7078 /*
7079  * Special case: If a kmalloc of a doms_cur partition (array of
7080  * cpumask) fails, then fallback to a single sched domain,
7081  * as determined by the single cpumask fallback_doms.
7082  */
7083 static cpumask_var_t fallback_doms;
7084 
7085 /*
7086  * arch_update_cpu_topology lets virtualized architectures update the
7087  * cpu core maps. It is supposed to return 1 if the topology changed
7088  * or 0 if it stayed the same.
7089  */
7090 int __weak arch_update_cpu_topology(void)
7091 {
7092         return 0;
7093 }
7094 
7095 cpumask_var_t *alloc_sched_domains(unsigned int ndoms)
7096 {
7097         int i;
7098         cpumask_var_t *doms;
7099 
7100         doms = kmalloc(sizeof(*doms) * ndoms, GFP_KERNEL);
7101         if (!doms)
7102                 return NULL;
7103         for (i = 0; i < ndoms; i++) {
7104                 if (!alloc_cpumask_var(&doms[i], GFP_KERNEL)) {
7105                         free_sched_domains(doms, i);
7106                         return NULL;
7107                 }
7108         }
7109         return doms;
7110 }
7111 
7112 void free_sched_domains(cpumask_var_t doms[], unsigned int ndoms)
7113 {
7114         unsigned int i;
7115         for (i = 0; i < ndoms; i++)
7116                 free_cpumask_var(doms[i]);
7117         kfree(doms);
7118 }
7119 
7120 /*
7121  * Set up scheduler domains and groups. Callers must hold the hotplug lock.
7122  * For now this just excludes isolated cpus, but could be used to
7123  * exclude other special cases in the future.
7124  */
7125 static int init_sched_domains(const struct cpumask *cpu_map)
7126 {
7127         int err;
7128 
7129         arch_update_cpu_topology();
7130         ndoms_cur = 1;
7131         doms_cur = alloc_sched_domains(ndoms_cur);
7132         if (!doms_cur)
7133                 doms_cur = &fallback_doms;
7134         cpumask_andnot(doms_cur[0], cpu_map, cpu_isolated_map);
7135         err = build_sched_domains(doms_cur[0], NULL);
7136         register_sched_domain_sysctl();
7137 
7138         return err;
7139 }
7140 
7141 /*
7142  * Detach sched domains from a group of cpus specified in cpu_map
7143  * These cpus will now be attached to the NULL domain
7144  */
7145 static void detach_destroy_domains(const struct cpumask *cpu_map)
7146 {
7147         int i;
7148 
7149         rcu_read_lock();
7150         for_each_cpu(i, cpu_map)
7151                 cpu_attach_domain(NULL, &def_root_domain, i);
7152         rcu_read_unlock();
7153 }
7154 
7155 /* handle null as "default" */
7156 static int dattrs_equal(struct sched_domain_attr *cur, int idx_cur,
7157                         struct sched_domain_attr *new, int idx_new)
7158 {
7159         struct sched_domain_attr tmp;
7160 
7161         /* fast path */
7162         if (!new && !cur)
7163                 return 1;
7164 
7165         tmp = SD_ATTR_INIT;
7166         return !memcmp(cur ? (cur + idx_cur) : &tmp,
7167                         new ? (new + idx_new) : &tmp,
7168                         sizeof(struct sched_domain_attr));
7169 }
7170 
7171 /*
7172  * Partition sched domains as specified by the 'ndoms_new'
7173  * cpumasks in the array doms_new[] of cpumasks. This compares
7174  * doms_new[] to the current sched domain partitioning, doms_cur[].
7175  * It destroys each deleted domain and builds each new domain.
7176  *
7177  * 'doms_new' is an array of cpumask_var_t's of length 'ndoms_new'.
7178  * The masks don't intersect (don't overlap.) We should setup one
7179  * sched domain for each mask. CPUs not in any of the cpumasks will
7180  * not be load balanced. If the same cpumask appears both in the
7181  * current 'doms_cur' domains and in the new 'doms_new', we can leave
7182  * it as it is.
7183  *
7184  * The passed in 'doms_new' should be allocated using
7185  * alloc_sched_domains.  This routine takes ownership of it and will
7186  * free_sched_domains it when done with it. If the caller failed the
7187  * alloc call, then it can pass in doms_new == NULL && ndoms_new == 1,
7188  * and partition_sched_domains() will fallback to the single partition
7189  * 'fallback_doms', it also forces the domains to be rebuilt.
7190  *
7191  * If doms_new == NULL it will be replaced with cpu_online_mask.
7192  * ndoms_new == 0 is a special case for destroying existing domains,
7193  * and it will not create the default domain.
7194  *
7195  * Call with hotplug lock held
7196  */
7197 void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
7198                              struct sched_domain_attr *dattr_new)
7199 {
7200         int i, j, n;
7201         int new_topology;
7202 
7203         mutex_lock(&sched_domains_mutex);
7204 
7205         /* always unregister in case we don't destroy any domains */
7206         unregister_sched_domain_sysctl();
7207 
7208         /* Let architecture update cpu core mappings. */
7209         new_topology = arch_update_cpu_topology();
7210 
7211         n = doms_new ? ndoms_new : 0;
7212 
7213         /* Destroy deleted domains */
7214         for (i = 0; i < ndoms_cur; i++) {
7215                 for (j = 0; j < n && !new_topology; j++) {
7216                         if (cpumask_equal(doms_cur[i], doms_new[j])
7217                             && dattrs_equal(dattr_cur, i, dattr_new, j))
7218                                 goto match1;
7219                 }
7220                 /* no match - a current sched domain not in new doms_new[] */
7221                 detach_destroy_domains(doms_cur[i]);
7222 match1:
7223                 ;
7224         }
7225 
7226         n = ndoms_cur;
7227         if (doms_new == NULL) {
7228                 n = 0;
7229                 doms_new = &fallback_doms;
7230                 cpumask_andnot(doms_new[0], cpu_active_mask, cpu_isolated_map);
7231                 WARN_ON_ONCE(dattr_new);
7232         }
7233 
7234         /* Build new domains */
7235         for (i = 0; i < ndoms_new; i++) {
7236                 for (j = 0; j < n && !new_topology; j++) {
7237                         if (cpumask_equal(doms_new[i], doms_cur[j])
7238                             && dattrs_equal(dattr_new, i, dattr_cur, j))
7239                                 goto match2;
7240                 }
7241                 /* no match - add a new doms_new */
7242                 build_sched_domains(doms_new[i], dattr_new ? dattr_new + i : NULL);
7243 match2:
7244                 ;
7245         }
7246 
7247         /* Remember the new sched domains */
7248         if (doms_cur != &fallback_doms)
7249                 free_sched_domains(doms_cur, ndoms_cur);
7250         kfree(dattr_cur);       /* kfree(NULL) is safe */
7251         doms_cur = doms_new;
7252         dattr_cur = dattr_new;
7253         ndoms_cur = ndoms_new;
7254 
7255         register_sched_domain_sysctl();
7256 
7257         mutex_unlock(&sched_domains_mutex);
7258 }
7259 
7260 static int num_cpus_frozen;     /* used to mark begin/end of suspend/resume */
7261 
7262 /*
7263  * Update cpusets according to cpu_active mask.  If cpusets are
7264  * disabled, cpuset_update_active_cpus() becomes a simple wrapper
7265  * around partition_sched_domains().
7266  *
7267  * If we come here as part of a suspend/resume, don't touch cpusets because we
7268  * want to restore it back to its original state upon resume anyway.
7269  */
7270 static void cpuset_cpu_active(void)
7271 {
7272         if (cpuhp_tasks_frozen) {
7273                 /*
7274                  * num_cpus_frozen tracks how many CPUs are involved in suspend
7275                  * resume sequence. As long as this is not the last online
7276                  * operation in the resume sequence, just build a single sched
7277                  * domain, ignoring cpusets.
7278                  */
7279                 num_cpus_frozen--;
7280                 if (likely(num_cpus_frozen)) {
7281                         partition_sched_domains(1, NULL, NULL);
7282                         return;
7283                 }
7284                 /*
7285                  * This is the last CPU online operation. So fall through and
7286                  * restore the original sched domains by considering the
7287                  * cpuset configurations.
7288                  */
7289         }
7290         cpuset_update_active_cpus(true);
7291 }
7292 
7293 static int cpuset_cpu_inactive(unsigned int cpu)
7294 {
7295         unsigned long flags;
7296         struct dl_bw *dl_b;
7297         bool overflow;
7298         int cpus;
7299 
7300         if (!cpuhp_tasks_frozen) {
7301                 rcu_read_lock_sched();
7302                 dl_b = dl_bw_of(cpu);
7303 
7304                 raw_spin_lock_irqsave(&dl_b->lock, flags);
7305                 cpus = dl_bw_cpus(cpu);
7306                 overflow = __dl_overflow(dl_b, cpus, 0, 0);
7307                 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
7308 
7309                 rcu_read_unlock_sched();
7310 
7311                 if (overflow)
7312                         return -EBUSY;
7313                 cpuset_update_active_cpus(false);
7314         } else {
7315                 num_cpus_frozen++;
7316                 partition_sched_domains(1, NULL, NULL);
7317         }
7318         return 0;
7319 }
7320 
7321 int sched_cpu_activate(unsigned int cpu)
7322 {
7323         struct rq *rq = cpu_rq(cpu);
7324         unsigned long flags;
7325 
7326         set_cpu_active(cpu, true);
7327 
7328         if (sched_smp_initialized) {
7329                 sched_domains_numa_masks_set(cpu);
7330                 cpuset_cpu_active();
7331         }
7332 
7333         /*
7334          * Put the rq online, if not already. This happens:
7335          *
7336          * 1) In the early boot process, because we build the real domains
7337          *    after all cpus have been brought up.
7338          *
7339          * 2) At runtime, if cpuset_cpu_active() fails to rebuild the
7340          *    domains.
7341          */
7342         raw_spin_lock_irqsave(&rq->lock, flags);
7343         if (rq->rd) {
7344                 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
7345                 set_rq_online(rq);
7346         }
7347         raw_spin_unlock_irqrestore(&rq->lock, flags);
7348 
7349         update_max_interval();
7350 
7351         return 0;
7352 }
7353 
7354 int sched_cpu_deactivate(unsigned int cpu)
7355 {
7356         int ret;
7357 
7358         set_cpu_active(cpu, false);
7359         /*
7360          * We've cleared cpu_active_mask, wait for all preempt-disabled and RCU
7361          * users of this state to go away such that all new such users will
7362          * observe it.
7363          *
7364          * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
7365          * not imply sync_sched(), so wait for both.
7366          *
7367          * Do sync before park smpboot threads to take care the rcu boost case.
7368          */
7369         if (IS_ENABLED(CONFIG_PREEMPT))
7370                 synchronize_rcu_mult(call_rcu, call_rcu_sched);
7371         else
7372                 synchronize_rcu();
7373 
7374         if (!sched_smp_initialized)
7375                 return 0;
7376 
7377         ret = cpuset_cpu_inactive(cpu);
7378         if (ret) {
7379                 set_cpu_active(cpu, true);
7380                 return ret;
7381         }
7382         sched_domains_numa_masks_clear(cpu);
7383         return 0;
7384 }
7385 
7386 static void sched_rq_cpu_starting(unsigned int cpu)
7387 {
7388         struct rq *rq = cpu_rq(cpu);
7389 
7390         rq->calc_load_update = calc_load_update;
7391         update_max_interval();
7392 }
7393 
7394 int sched_cpu_starting(unsigned int cpu)
7395 {
7396         set_cpu_rq_start_time(cpu);
7397         sched_rq_cpu_starting(cpu);
7398         return 0;
7399 }
7400 
7401 #ifdef CONFIG_HOTPLUG_CPU
7402 int sched_cpu_dying(unsigned int cpu)
7403 {
7404         struct rq *rq = cpu_rq(cpu);
7405         unsigned long flags;
7406 
7407         /* Handle pending wakeups and then migrate everything off */
7408         sched_ttwu_pending();
7409         raw_spin_lock_irqsave(&rq->lock, flags);
7410         if (rq->rd) {
7411                 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
7412                 set_rq_offline(rq);
7413         }
7414         migrate_tasks(rq);
7415         BUG_ON(rq->nr_running != 1);
7416         raw_spin_unlock_irqrestore(&rq->lock, flags);
7417         calc_load_migrate(rq);
7418         update_max_interval();
7419         nohz_balance_exit_idle(cpu);
7420         hrtick_clear(rq);
7421         return 0;
7422 }
7423 #endif
7424 
7425 #ifdef CONFIG_SCHED_SMT
7426 DEFINE_STATIC_KEY_FALSE(sched_smt_present);
7427 
7428 static void sched_init_smt(void)
7429 {
7430         /*
7431          * We've enumerated all CPUs and will assume that if any CPU
7432          * has SMT siblings, CPU0 will too.
7433          */
7434         if (cpumask_weight(cpu_smt_mask(0)) > 1)
7435                 static_branch_enable(&sched_smt_present);
7436 }
7437 #else
7438 static inline void sched_init_smt(void) { }
7439 #endif
7440 
7441 void __init sched_init_smp(void)
7442 {
7443         cpumask_var_t non_isolated_cpus;
7444 
7445         alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL);
7446         alloc_cpumask_var(&fallback_doms, GFP_KERNEL);
7447 
7448         sched_init_numa();
7449 
7450         /*
7451          * There's no userspace yet to cause hotplug operations; hence all the
7452          * cpu masks are stable and all blatant races in the below code cannot
7453          * happen.
7454          */
7455         mutex_lock(&sched_domains_mutex);
7456         init_sched_domains(cpu_active_mask);
7457         cpumask_andnot(non_isolated_cpus, cpu_possible_mask, cpu_isolated_map);
7458         if (cpumask_empty(non_isolated_cpus))
7459                 cpumask_set_cpu(smp_processor_id(), non_isolated_cpus);
7460         mutex_unlock(&sched_domains_mutex);
7461 
7462         /* Move init over to a non-isolated CPU */
7463         if (set_cpus_allowed_ptr(current, non_isolated_cpus) < 0)
7464                 BUG();
7465         sched_init_granularity();
7466         free_cpumask_var(non_isolated_cpus);
7467 
7468         init_sched_rt_class();
7469         init_sched_dl_class();
7470 
7471         sched_init_smt();
7472 
7473         sched_smp_initialized = true;
7474 }
7475 
7476 static int __init migration_init(void)
7477 {
7478         sched_rq_cpu_starting(smp_processor_id());
7479         return 0;
7480 }
7481 early_initcall(migration_init);
7482 
7483 #else
7484 void __init sched_init_smp(void)
7485 {
7486         sched_init_granularity();
7487 }
7488 #endif /* CONFIG_SMP */
7489 
7490 int in_sched_functions(unsigned long addr)
7491 {
7492         return in_lock_functions(addr) ||
7493                 (addr >= (unsigned long)__sched_text_start
7494                 && addr < (unsigned long)__sched_text_end);
7495 }
7496 
7497 #ifdef CONFIG_CGROUP_SCHED
7498 /*
7499  * Default task group.
7500  * Every task in system belongs to this group at bootup.
7501  */
7502 struct task_group root_task_group;
7503 LIST_HEAD(task_groups);
7504 
7505 /* Cacheline aligned slab cache for task_group */
7506 static struct k