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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 <asm/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/debugfs.h>
 71 #include <linux/ctype.h>
 72 #include <linux/ftrace.h>
 73 #include <linux/slab.h>
 74 #include <linux/init_task.h>
 75 #include <linux/binfmts.h>
 76 #include <linux/context_tracking.h>
 77 #include <linux/compiler.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 #ifdef CONFIG_SCHED_DEBUG
129 #define SCHED_FEAT(name, enabled)       \
130         #name ,
131 
132 static const char * const sched_feat_names[] = {
133 #include "features.h"
134 };
135 
136 #undef SCHED_FEAT
137 
138 static int sched_feat_show(struct seq_file *m, void *v)
139 {
140         int i;
141 
142         for (i = 0; i < __SCHED_FEAT_NR; i++) {
143                 if (!(sysctl_sched_features & (1UL << i)))
144                         seq_puts(m, "NO_");
145                 seq_printf(m, "%s ", sched_feat_names[i]);
146         }
147         seq_puts(m, "\n");
148 
149         return 0;
150 }
151 
152 #ifdef HAVE_JUMP_LABEL
153 
154 #define jump_label_key__true  STATIC_KEY_INIT_TRUE
155 #define jump_label_key__false STATIC_KEY_INIT_FALSE
156 
157 #define SCHED_FEAT(name, enabled)       \
158         jump_label_key__##enabled ,
159 
160 struct static_key sched_feat_keys[__SCHED_FEAT_NR] = {
161 #include "features.h"
162 };
163 
164 #undef SCHED_FEAT
165 
166 static void sched_feat_disable(int i)
167 {
168         static_key_disable(&sched_feat_keys[i]);
169 }
170 
171 static void sched_feat_enable(int i)
172 {
173         static_key_enable(&sched_feat_keys[i]);
174 }
175 #else
176 static void sched_feat_disable(int i) { };
177 static void sched_feat_enable(int i) { };
178 #endif /* HAVE_JUMP_LABEL */
179 
180 static int sched_feat_set(char *cmp)
181 {
182         int i;
183         int neg = 0;
184 
185         if (strncmp(cmp, "NO_", 3) == 0) {
186                 neg = 1;
187                 cmp += 3;
188         }
189 
190         for (i = 0; i < __SCHED_FEAT_NR; i++) {
191                 if (strcmp(cmp, sched_feat_names[i]) == 0) {
192                         if (neg) {
193                                 sysctl_sched_features &= ~(1UL << i);
194                                 sched_feat_disable(i);
195                         } else {
196                                 sysctl_sched_features |= (1UL << i);
197                                 sched_feat_enable(i);
198                         }
199                         break;
200                 }
201         }
202 
203         return i;
204 }
205 
206 static ssize_t
207 sched_feat_write(struct file *filp, const char __user *ubuf,
208                 size_t cnt, loff_t *ppos)
209 {
210         char buf[64];
211         char *cmp;
212         int i;
213         struct inode *inode;
214 
215         if (cnt > 63)
216                 cnt = 63;
217 
218         if (copy_from_user(&buf, ubuf, cnt))
219                 return -EFAULT;
220 
221         buf[cnt] = 0;
222         cmp = strstrip(buf);
223 
224         /* Ensure the static_key remains in a consistent state */
225         inode = file_inode(filp);
226         inode_lock(inode);
227         i = sched_feat_set(cmp);
228         inode_unlock(inode);
229         if (i == __SCHED_FEAT_NR)
230                 return -EINVAL;
231 
232         *ppos += cnt;
233 
234         return cnt;
235 }
236 
237 static int sched_feat_open(struct inode *inode, struct file *filp)
238 {
239         return single_open(filp, sched_feat_show, NULL);
240 }
241 
242 static const struct file_operations sched_feat_fops = {
243         .open           = sched_feat_open,
244         .write          = sched_feat_write,
245         .read           = seq_read,
246         .llseek         = seq_lseek,
247         .release        = single_release,
248 };
249 
250 static __init int sched_init_debug(void)
251 {
252         debugfs_create_file("sched_features", 0644, NULL, NULL,
253                         &sched_feat_fops);
254 
255         return 0;
256 }
257 late_initcall(sched_init_debug);
258 #endif /* CONFIG_SCHED_DEBUG */
259 
260 /*
261  * Number of tasks to iterate in a single balance run.
262  * Limited because this is done with IRQs disabled.
263  */
264 const_debug unsigned int sysctl_sched_nr_migrate = 32;
265 
266 /*
267  * period over which we average the RT time consumption, measured
268  * in ms.
269  *
270  * default: 1s
271  */
272 const_debug unsigned int sysctl_sched_time_avg = MSEC_PER_SEC;
273 
274 /*
275  * period over which we measure -rt task cpu usage in us.
276  * default: 1s
277  */
278 unsigned int sysctl_sched_rt_period = 1000000;
279 
280 __read_mostly int scheduler_running;
281 
282 /*
283  * part of the period that we allow rt tasks to run in us.
284  * default: 0.95s
285  */
286 int sysctl_sched_rt_runtime = 950000;
287 
288 /* cpus with isolated domains */
289 cpumask_var_t cpu_isolated_map;
290 
291 /*
292  * this_rq_lock - lock this runqueue and disable interrupts.
293  */
294 static struct rq *this_rq_lock(void)
295         __acquires(rq->lock)
296 {
297         struct rq *rq;
298 
299         local_irq_disable();
300         rq = this_rq();
301         raw_spin_lock(&rq->lock);
302 
303         return rq;
304 }
305 
306 #ifdef CONFIG_SCHED_HRTICK
307 /*
308  * Use HR-timers to deliver accurate preemption points.
309  */
310 
311 static void hrtick_clear(struct rq *rq)
312 {
313         if (hrtimer_active(&rq->hrtick_timer))
314                 hrtimer_cancel(&rq->hrtick_timer);
315 }
316 
317 /*
318  * High-resolution timer tick.
319  * Runs from hardirq context with interrupts disabled.
320  */
321 static enum hrtimer_restart hrtick(struct hrtimer *timer)
322 {
323         struct rq *rq = container_of(timer, struct rq, hrtick_timer);
324 
325         WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
326 
327         raw_spin_lock(&rq->lock);
328         update_rq_clock(rq);
329         rq->curr->sched_class->task_tick(rq, rq->curr, 1);
330         raw_spin_unlock(&rq->lock);
331 
332         return HRTIMER_NORESTART;
333 }
334 
335 #ifdef CONFIG_SMP
336 
337 static void __hrtick_restart(struct rq *rq)
338 {
339         struct hrtimer *timer = &rq->hrtick_timer;
340 
341         hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED);
342 }
343 
344 /*
345  * called from hardirq (IPI) context
346  */
347 static void __hrtick_start(void *arg)
348 {
349         struct rq *rq = arg;
350 
351         raw_spin_lock(&rq->lock);
352         __hrtick_restart(rq);
353         rq->hrtick_csd_pending = 0;
354         raw_spin_unlock(&rq->lock);
355 }
356 
357 /*
358  * Called to set the hrtick timer state.
359  *
360  * called with rq->lock held and irqs disabled
361  */
362 void hrtick_start(struct rq *rq, u64 delay)
363 {
364         struct hrtimer *timer = &rq->hrtick_timer;
365         ktime_t time;
366         s64 delta;
367 
368         /*
369          * Don't schedule slices shorter than 10000ns, that just
370          * doesn't make sense and can cause timer DoS.
371          */
372         delta = max_t(s64, delay, 10000LL);
373         time = ktime_add_ns(timer->base->get_time(), delta);
374 
375         hrtimer_set_expires(timer, time);
376 
377         if (rq == this_rq()) {
378                 __hrtick_restart(rq);
379         } else if (!rq->hrtick_csd_pending) {
380                 smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd);
381                 rq->hrtick_csd_pending = 1;
382         }
383 }
384 
385 static int
386 hotplug_hrtick(struct notifier_block *nfb, unsigned long action, void *hcpu)
387 {
388         int cpu = (int)(long)hcpu;
389 
390         switch (action) {
391         case CPU_UP_CANCELED:
392         case CPU_UP_CANCELED_FROZEN:
393         case CPU_DOWN_PREPARE:
394         case CPU_DOWN_PREPARE_FROZEN:
395         case CPU_DEAD:
396         case CPU_DEAD_FROZEN:
397                 hrtick_clear(cpu_rq(cpu));
398                 return NOTIFY_OK;
399         }
400 
401         return NOTIFY_DONE;
402 }
403 
404 static __init void init_hrtick(void)
405 {
406         hotcpu_notifier(hotplug_hrtick, 0);
407 }
408 #else
409 /*
410  * Called to set the hrtick timer state.
411  *
412  * called with rq->lock held and irqs disabled
413  */
414 void hrtick_start(struct rq *rq, u64 delay)
415 {
416         /*
417          * Don't schedule slices shorter than 10000ns, that just
418          * doesn't make sense. Rely on vruntime for fairness.
419          */
420         delay = max_t(u64, delay, 10000LL);
421         hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay),
422                       HRTIMER_MODE_REL_PINNED);
423 }
424 
425 static inline void init_hrtick(void)
426 {
427 }
428 #endif /* CONFIG_SMP */
429 
430 static void init_rq_hrtick(struct rq *rq)
431 {
432 #ifdef CONFIG_SMP
433         rq->hrtick_csd_pending = 0;
434 
435         rq->hrtick_csd.flags = 0;
436         rq->hrtick_csd.func = __hrtick_start;
437         rq->hrtick_csd.info = rq;
438 #endif
439 
440         hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
441         rq->hrtick_timer.function = hrtick;
442 }
443 #else   /* CONFIG_SCHED_HRTICK */
444 static inline void hrtick_clear(struct rq *rq)
445 {
446 }
447 
448 static inline void init_rq_hrtick(struct rq *rq)
449 {
450 }
451 
452 static inline void init_hrtick(void)
453 {
454 }
455 #endif  /* CONFIG_SCHED_HRTICK */
456 
457 /*
458  * cmpxchg based fetch_or, macro so it works for different integer types
459  */
460 #define fetch_or(ptr, val)                                              \
461 ({      typeof(*(ptr)) __old, __val = *(ptr);                           \
462         for (;;) {                                                      \
463                 __old = cmpxchg((ptr), __val, __val | (val));           \
464                 if (__old == __val)                                     \
465                         break;                                          \
466                 __val = __old;                                          \
467         }                                                               \
468         __old;                                                          \
469 })
470 
471 #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
472 /*
473  * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
474  * this avoids any races wrt polling state changes and thereby avoids
475  * spurious IPIs.
476  */
477 static bool set_nr_and_not_polling(struct task_struct *p)
478 {
479         struct thread_info *ti = task_thread_info(p);
480         return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG);
481 }
482 
483 /*
484  * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
485  *
486  * If this returns true, then the idle task promises to call
487  * sched_ttwu_pending() and reschedule soon.
488  */
489 static bool set_nr_if_polling(struct task_struct *p)
490 {
491         struct thread_info *ti = task_thread_info(p);
492         typeof(ti->flags) old, val = READ_ONCE(ti->flags);
493 
494         for (;;) {
495                 if (!(val & _TIF_POLLING_NRFLAG))
496                         return false;
497                 if (val & _TIF_NEED_RESCHED)
498                         return true;
499                 old = cmpxchg(&ti->flags, val, val | _TIF_NEED_RESCHED);
500                 if (old == val)
501                         break;
502                 val = old;
503         }
504         return true;
505 }
506 
507 #else
508 static bool set_nr_and_not_polling(struct task_struct *p)
509 {
510         set_tsk_need_resched(p);
511         return true;
512 }
513 
514 #ifdef CONFIG_SMP
515 static bool set_nr_if_polling(struct task_struct *p)
516 {
517         return false;
518 }
519 #endif
520 #endif
521 
522 void wake_q_add(struct wake_q_head *head, struct task_struct *task)
523 {
524         struct wake_q_node *node = &task->wake_q;
525 
526         /*
527          * Atomically grab the task, if ->wake_q is !nil already it means
528          * its already queued (either by us or someone else) and will get the
529          * wakeup due to that.
530          *
531          * This cmpxchg() implies a full barrier, which pairs with the write
532          * barrier implied by the wakeup in wake_up_list().
533          */
534         if (cmpxchg(&node->next, NULL, WAKE_Q_TAIL))
535                 return;
536 
537         get_task_struct(task);
538 
539         /*
540          * The head is context local, there can be no concurrency.
541          */
542         *head->lastp = node;
543         head->lastp = &node->next;
544 }
545 
546 void wake_up_q(struct wake_q_head *head)
547 {
548         struct wake_q_node *node = head->first;
549 
550         while (node != WAKE_Q_TAIL) {
551                 struct task_struct *task;
552 
553                 task = container_of(node, struct task_struct, wake_q);
554                 BUG_ON(!task);
555                 /* task can safely be re-inserted now */
556                 node = node->next;
557                 task->wake_q.next = NULL;
558 
559                 /*
560                  * wake_up_process() implies a wmb() to pair with the queueing
561                  * in wake_q_add() so as not to miss wakeups.
562                  */
563                 wake_up_process(task);
564                 put_task_struct(task);
565         }
566 }
567 
568 /*
569  * resched_curr - mark rq's current task 'to be rescheduled now'.
570  *
571  * On UP this means the setting of the need_resched flag, on SMP it
572  * might also involve a cross-CPU call to trigger the scheduler on
573  * the target CPU.
574  */
575 void resched_curr(struct rq *rq)
576 {
577         struct task_struct *curr = rq->curr;
578         int cpu;
579 
580         lockdep_assert_held(&rq->lock);
581 
582         if (test_tsk_need_resched(curr))
583                 return;
584 
585         cpu = cpu_of(rq);
586 
587         if (cpu == smp_processor_id()) {
588                 set_tsk_need_resched(curr);
589                 set_preempt_need_resched();
590                 return;
591         }
592 
593         if (set_nr_and_not_polling(curr))
594                 smp_send_reschedule(cpu);
595         else
596                 trace_sched_wake_idle_without_ipi(cpu);
597 }
598 
599 void resched_cpu(int cpu)
600 {
601         struct rq *rq = cpu_rq(cpu);
602         unsigned long flags;
603 
604         if (!raw_spin_trylock_irqsave(&rq->lock, flags))
605                 return;
606         resched_curr(rq);
607         raw_spin_unlock_irqrestore(&rq->lock, flags);
608 }
609 
610 #ifdef CONFIG_SMP
611 #ifdef CONFIG_NO_HZ_COMMON
612 /*
613  * In the semi idle case, use the nearest busy cpu for migrating timers
614  * from an idle cpu.  This is good for power-savings.
615  *
616  * We don't do similar optimization for completely idle system, as
617  * selecting an idle cpu will add more delays to the timers than intended
618  * (as that cpu's timer base may not be uptodate wrt jiffies etc).
619  */
620 int get_nohz_timer_target(void)
621 {
622         int i, cpu = smp_processor_id();
623         struct sched_domain *sd;
624 
625         if (!idle_cpu(cpu) && is_housekeeping_cpu(cpu))
626                 return cpu;
627 
628         rcu_read_lock();
629         for_each_domain(cpu, sd) {
630                 for_each_cpu(i, sched_domain_span(sd)) {
631                         if (!idle_cpu(i) && is_housekeeping_cpu(cpu)) {
632                                 cpu = i;
633                                 goto unlock;
634                         }
635                 }
636         }
637 
638         if (!is_housekeeping_cpu(cpu))
639                 cpu = housekeeping_any_cpu();
640 unlock:
641         rcu_read_unlock();
642         return cpu;
643 }
644 /*
645  * When add_timer_on() enqueues a timer into the timer wheel of an
646  * idle CPU then this timer might expire before the next timer event
647  * which is scheduled to wake up that CPU. In case of a completely
648  * idle system the next event might even be infinite time into the
649  * future. wake_up_idle_cpu() ensures that the CPU is woken up and
650  * leaves the inner idle loop so the newly added timer is taken into
651  * account when the CPU goes back to idle and evaluates the timer
652  * wheel for the next timer event.
653  */
654 static void wake_up_idle_cpu(int cpu)
655 {
656         struct rq *rq = cpu_rq(cpu);
657 
658         if (cpu == smp_processor_id())
659                 return;
660 
661         if (set_nr_and_not_polling(rq->idle))
662                 smp_send_reschedule(cpu);
663         else
664                 trace_sched_wake_idle_without_ipi(cpu);
665 }
666 
667 static bool wake_up_full_nohz_cpu(int cpu)
668 {
669         /*
670          * We just need the target to call irq_exit() and re-evaluate
671          * the next tick. The nohz full kick at least implies that.
672          * If needed we can still optimize that later with an
673          * empty IRQ.
674          */
675         if (tick_nohz_full_cpu(cpu)) {
676                 if (cpu != smp_processor_id() ||
677                     tick_nohz_tick_stopped())
678                         tick_nohz_full_kick_cpu(cpu);
679                 return true;
680         }
681 
682         return false;
683 }
684 
685 void wake_up_nohz_cpu(int cpu)
686 {
687         if (!wake_up_full_nohz_cpu(cpu))
688                 wake_up_idle_cpu(cpu);
689 }
690 
691 static inline bool got_nohz_idle_kick(void)
692 {
693         int cpu = smp_processor_id();
694 
695         if (!test_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu)))
696                 return false;
697 
698         if (idle_cpu(cpu) && !need_resched())
699                 return true;
700 
701         /*
702          * We can't run Idle Load Balance on this CPU for this time so we
703          * cancel it and clear NOHZ_BALANCE_KICK
704          */
705         clear_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu));
706         return false;
707 }
708 
709 #else /* CONFIG_NO_HZ_COMMON */
710 
711 static inline bool got_nohz_idle_kick(void)
712 {
713         return false;
714 }
715 
716 #endif /* CONFIG_NO_HZ_COMMON */
717 
718 #ifdef CONFIG_NO_HZ_FULL
719 bool sched_can_stop_tick(void)
720 {
721         /*
722          * FIFO realtime policy runs the highest priority task. Other runnable
723          * tasks are of a lower priority. The scheduler tick does nothing.
724          */
725         if (current->policy == SCHED_FIFO)
726                 return true;
727 
728         /*
729          * Round-robin realtime tasks time slice with other tasks at the same
730          * realtime priority. Is this task the only one at this priority?
731          */
732         if (current->policy == SCHED_RR) {
733                 struct sched_rt_entity *rt_se = &current->rt;
734 
735                 return list_is_singular(&rt_se->run_list);
736         }
737 
738         /*
739          * More than one running task need preemption.
740          * nr_running update is assumed to be visible
741          * after IPI is sent from wakers.
742          */
743         if (this_rq()->nr_running > 1)
744                 return false;
745 
746         return true;
747 }
748 #endif /* CONFIG_NO_HZ_FULL */
749 
750 void sched_avg_update(struct rq *rq)
751 {
752         s64 period = sched_avg_period();
753 
754         while ((s64)(rq_clock(rq) - rq->age_stamp) > period) {
755                 /*
756                  * Inline assembly required to prevent the compiler
757                  * optimising this loop into a divmod call.
758                  * See __iter_div_u64_rem() for another example of this.
759                  */
760                 asm("" : "+rm" (rq->age_stamp));
761                 rq->age_stamp += period;
762                 rq->rt_avg /= 2;
763         }
764 }
765 
766 #endif /* CONFIG_SMP */
767 
768 #if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
769                         (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))
770 /*
771  * Iterate task_group tree rooted at *from, calling @down when first entering a
772  * node and @up when leaving it for the final time.
773  *
774  * Caller must hold rcu_lock or sufficient equivalent.
775  */
776 int walk_tg_tree_from(struct task_group *from,
777                              tg_visitor down, tg_visitor up, void *data)
778 {
779         struct task_group *parent, *child;
780         int ret;
781 
782         parent = from;
783 
784 down:
785         ret = (*down)(parent, data);
786         if (ret)
787                 goto out;
788         list_for_each_entry_rcu(child, &parent->children, siblings) {
789                 parent = child;
790                 goto down;
791 
792 up:
793                 continue;
794         }
795         ret = (*up)(parent, data);
796         if (ret || parent == from)
797                 goto out;
798 
799         child = parent;
800         parent = parent->parent;
801         if (parent)
802                 goto up;
803 out:
804         return ret;
805 }
806 
807 int tg_nop(struct task_group *tg, void *data)
808 {
809         return 0;
810 }
811 #endif
812 
813 static void set_load_weight(struct task_struct *p)
814 {
815         int prio = p->static_prio - MAX_RT_PRIO;
816         struct load_weight *load = &p->se.load;
817 
818         /*
819          * SCHED_IDLE tasks get minimal weight:
820          */
821         if (idle_policy(p->policy)) {
822                 load->weight = scale_load(WEIGHT_IDLEPRIO);
823                 load->inv_weight = WMULT_IDLEPRIO;
824                 return;
825         }
826 
827         load->weight = scale_load(sched_prio_to_weight[prio]);
828         load->inv_weight = sched_prio_to_wmult[prio];
829 }
830 
831 static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
832 {
833         update_rq_clock(rq);
834         if (!(flags & ENQUEUE_RESTORE))
835                 sched_info_queued(rq, p);
836         p->sched_class->enqueue_task(rq, p, flags);
837 }
838 
839 static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
840 {
841         update_rq_clock(rq);
842         if (!(flags & DEQUEUE_SAVE))
843                 sched_info_dequeued(rq, p);
844         p->sched_class->dequeue_task(rq, p, flags);
845 }
846 
847 void activate_task(struct rq *rq, struct task_struct *p, int flags)
848 {
849         if (task_contributes_to_load(p))
850                 rq->nr_uninterruptible--;
851 
852         enqueue_task(rq, p, flags);
853 }
854 
855 void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
856 {
857         if (task_contributes_to_load(p))
858                 rq->nr_uninterruptible++;
859 
860         dequeue_task(rq, p, flags);
861 }
862 
863 static void update_rq_clock_task(struct rq *rq, s64 delta)
864 {
865 /*
866  * In theory, the compile should just see 0 here, and optimize out the call
867  * to sched_rt_avg_update. But I don't trust it...
868  */
869 #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
870         s64 steal = 0, irq_delta = 0;
871 #endif
872 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
873         irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
874 
875         /*
876          * Since irq_time is only updated on {soft,}irq_exit, we might run into
877          * this case when a previous update_rq_clock() happened inside a
878          * {soft,}irq region.
879          *
880          * When this happens, we stop ->clock_task and only update the
881          * prev_irq_time stamp to account for the part that fit, so that a next
882          * update will consume the rest. This ensures ->clock_task is
883          * monotonic.
884          *
885          * It does however cause some slight miss-attribution of {soft,}irq
886          * time, a more accurate solution would be to update the irq_time using
887          * the current rq->clock timestamp, except that would require using
888          * atomic ops.
889          */
890         if (irq_delta > delta)
891                 irq_delta = delta;
892 
893         rq->prev_irq_time += irq_delta;
894         delta -= irq_delta;
895 #endif
896 #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
897         if (static_key_false((&paravirt_steal_rq_enabled))) {
898                 steal = paravirt_steal_clock(cpu_of(rq));
899                 steal -= rq->prev_steal_time_rq;
900 
901                 if (unlikely(steal > delta))
902                         steal = delta;
903 
904                 rq->prev_steal_time_rq += steal;
905                 delta -= steal;
906         }
907 #endif
908 
909         rq->clock_task += delta;
910 
911 #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
912         if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY))
913                 sched_rt_avg_update(rq, irq_delta + steal);
914 #endif
915 }
916 
917 void sched_set_stop_task(int cpu, struct task_struct *stop)
918 {
919         struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
920         struct task_struct *old_stop = cpu_rq(cpu)->stop;
921 
922         if (stop) {
923                 /*
924                  * Make it appear like a SCHED_FIFO task, its something
925                  * userspace knows about and won't get confused about.
926                  *
927                  * Also, it will make PI more or less work without too
928                  * much confusion -- but then, stop work should not
929                  * rely on PI working anyway.
930                  */
931                 sched_setscheduler_nocheck(stop, SCHED_FIFO, &param);
932 
933                 stop->sched_class = &stop_sched_class;
934         }
935 
936         cpu_rq(cpu)->stop = stop;
937 
938         if (old_stop) {
939                 /*
940                  * Reset it back to a normal scheduling class so that
941                  * it can die in pieces.
942                  */
943                 old_stop->sched_class = &rt_sched_class;
944         }
945 }
946 
947 /*
948  * __normal_prio - return the priority that is based on the static prio
949  */
950 static inline int __normal_prio(struct task_struct *p)
951 {
952         return p->static_prio;
953 }
954 
955 /*
956  * Calculate the expected normal priority: i.e. priority
957  * without taking RT-inheritance into account. Might be
958  * boosted by interactivity modifiers. Changes upon fork,
959  * setprio syscalls, and whenever the interactivity
960  * estimator recalculates.
961  */
962 static inline int normal_prio(struct task_struct *p)
963 {
964         int prio;
965 
966         if (task_has_dl_policy(p))
967                 prio = MAX_DL_PRIO-1;
968         else if (task_has_rt_policy(p))
969                 prio = MAX_RT_PRIO-1 - p->rt_priority;
970         else
971                 prio = __normal_prio(p);
972         return prio;
973 }
974 
975 /*
976  * Calculate the current priority, i.e. the priority
977  * taken into account by the scheduler. This value might
978  * be boosted by RT tasks, or might be boosted by
979  * interactivity modifiers. Will be RT if the task got
980  * RT-boosted. If not then it returns p->normal_prio.
981  */
982 static int effective_prio(struct task_struct *p)
983 {
984         p->normal_prio = normal_prio(p);
985         /*
986          * If we are RT tasks or we were boosted to RT priority,
987          * keep the priority unchanged. Otherwise, update priority
988          * to the normal priority:
989          */
990         if (!rt_prio(p->prio))
991                 return p->normal_prio;
992         return p->prio;
993 }
994 
995 /**
996  * task_curr - is this task currently executing on a CPU?
997  * @p: the task in question.
998  *
999  * Return: 1 if the task is currently executing. 0 otherwise.
1000  */
1001 inline int task_curr(const struct task_struct *p)
1002 {
1003         return cpu_curr(task_cpu(p)) == p;
1004 }
1005 
1006 /*
1007  * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock,
1008  * use the balance_callback list if you want balancing.
1009  *
1010  * this means any call to check_class_changed() must be followed by a call to
1011  * balance_callback().
1012  */
1013 static inline void check_class_changed(struct rq *rq, struct task_struct *p,
1014                                        const struct sched_class *prev_class,
1015                                        int oldprio)
1016 {
1017         if (prev_class != p->sched_class) {
1018                 if (prev_class->switched_from)
1019                         prev_class->switched_from(rq, p);
1020 
1021                 p->sched_class->switched_to(rq, p);
1022         } else if (oldprio != p->prio || dl_task(p))
1023                 p->sched_class->prio_changed(rq, p, oldprio);
1024 }
1025 
1026 void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
1027 {
1028         const struct sched_class *class;
1029 
1030         if (p->sched_class == rq->curr->sched_class) {
1031                 rq->curr->sched_class->check_preempt_curr(rq, p, flags);
1032         } else {
1033                 for_each_class(class) {
1034                         if (class == rq->curr->sched_class)
1035                                 break;
1036                         if (class == p->sched_class) {
1037                                 resched_curr(rq);
1038                                 break;
1039                         }
1040                 }
1041         }
1042 
1043         /*
1044          * A queue event has occurred, and we're going to schedule.  In
1045          * this case, we can save a useless back to back clock update.
1046          */
1047         if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
1048                 rq_clock_skip_update(rq, true);
1049 }
1050 
1051 #ifdef CONFIG_SMP
1052 /*
1053  * This is how migration works:
1054  *
1055  * 1) we invoke migration_cpu_stop() on the target CPU using
1056  *    stop_one_cpu().
1057  * 2) stopper starts to run (implicitly forcing the migrated thread
1058  *    off the CPU)
1059  * 3) it checks whether the migrated task is still in the wrong runqueue.
1060  * 4) if it's in the wrong runqueue then the migration thread removes
1061  *    it and puts it into the right queue.
1062  * 5) stopper completes and stop_one_cpu() returns and the migration
1063  *    is done.
1064  */
1065 
1066 /*
1067  * move_queued_task - move a queued task to new rq.
1068  *
1069  * Returns (locked) new rq. Old rq's lock is released.
1070  */
1071 static struct rq *move_queued_task(struct rq *rq, struct task_struct *p, int new_cpu)
1072 {
1073         lockdep_assert_held(&rq->lock);
1074 
1075         p->on_rq = TASK_ON_RQ_MIGRATING;
1076         dequeue_task(rq, p, 0);
1077         set_task_cpu(p, new_cpu);
1078         raw_spin_unlock(&rq->lock);
1079 
1080         rq = cpu_rq(new_cpu);
1081 
1082         raw_spin_lock(&rq->lock);
1083         BUG_ON(task_cpu(p) != new_cpu);
1084         enqueue_task(rq, p, 0);
1085         p->on_rq = TASK_ON_RQ_QUEUED;
1086         check_preempt_curr(rq, p, 0);
1087 
1088         return rq;
1089 }
1090 
1091 struct migration_arg {
1092         struct task_struct *task;
1093         int dest_cpu;
1094 };
1095 
1096 /*
1097  * Move (not current) task off this cpu, onto dest cpu. We're doing
1098  * this because either it can't run here any more (set_cpus_allowed()
1099  * away from this CPU, or CPU going down), or because we're
1100  * attempting to rebalance this task on exec (sched_exec).
1101  *
1102  * So we race with normal scheduler movements, but that's OK, as long
1103  * as the task is no longer on this CPU.
1104  */
1105 static struct rq *__migrate_task(struct rq *rq, struct task_struct *p, int dest_cpu)
1106 {
1107         if (unlikely(!cpu_active(dest_cpu)))
1108                 return rq;
1109 
1110         /* Affinity changed (again). */
1111         if (!cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p)))
1112                 return rq;
1113 
1114         rq = move_queued_task(rq, p, dest_cpu);
1115 
1116         return rq;
1117 }
1118 
1119 /*
1120  * migration_cpu_stop - this will be executed by a highprio stopper thread
1121  * and performs thread migration by bumping thread off CPU then
1122  * 'pushing' onto another runqueue.
1123  */
1124 static int migration_cpu_stop(void *data)
1125 {
1126         struct migration_arg *arg = data;
1127         struct task_struct *p = arg->task;
1128         struct rq *rq = this_rq();
1129 
1130         /*
1131          * The original target cpu might have gone down and we might
1132          * be on another cpu but it doesn't matter.
1133          */
1134         local_irq_disable();
1135         /*
1136          * We need to explicitly wake pending tasks before running
1137          * __migrate_task() such that we will not miss enforcing cpus_allowed
1138          * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
1139          */
1140         sched_ttwu_pending();
1141 
1142         raw_spin_lock(&p->pi_lock);
1143         raw_spin_lock(&rq->lock);
1144         /*
1145          * If task_rq(p) != rq, it cannot be migrated here, because we're
1146          * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
1147          * we're holding p->pi_lock.
1148          */
1149         if (task_rq(p) == rq && task_on_rq_queued(p))
1150                 rq = __migrate_task(rq, p, arg->dest_cpu);
1151         raw_spin_unlock(&rq->lock);
1152         raw_spin_unlock(&p->pi_lock);
1153 
1154         local_irq_enable();
1155         return 0;
1156 }
1157 
1158 /*
1159  * sched_class::set_cpus_allowed must do the below, but is not required to
1160  * actually call this function.
1161  */
1162 void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask)
1163 {
1164         cpumask_copy(&p->cpus_allowed, new_mask);
1165         p->nr_cpus_allowed = cpumask_weight(new_mask);
1166 }
1167 
1168 void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
1169 {
1170         struct rq *rq = task_rq(p);
1171         bool queued, running;
1172 
1173         lockdep_assert_held(&p->pi_lock);
1174 
1175         queued = task_on_rq_queued(p);
1176         running = task_current(rq, p);
1177 
1178         if (queued) {
1179                 /*
1180                  * Because __kthread_bind() calls this on blocked tasks without
1181                  * holding rq->lock.
1182                  */
1183                 lockdep_assert_held(&rq->lock);
1184                 dequeue_task(rq, p, DEQUEUE_SAVE);
1185         }
1186         if (running)
1187                 put_prev_task(rq, p);
1188 
1189         p->sched_class->set_cpus_allowed(p, new_mask);
1190 
1191         if (running)
1192                 p->sched_class->set_curr_task(rq);
1193         if (queued)
1194                 enqueue_task(rq, p, ENQUEUE_RESTORE);
1195 }
1196 
1197 /*
1198  * Change a given task's CPU affinity. Migrate the thread to a
1199  * proper CPU and schedule it away if the CPU it's executing on
1200  * is removed from the allowed bitmask.
1201  *
1202  * NOTE: the caller must have a valid reference to the task, the
1203  * task must not exit() & deallocate itself prematurely. The
1204  * call is not atomic; no spinlocks may be held.
1205  */
1206 static int __set_cpus_allowed_ptr(struct task_struct *p,
1207                                   const struct cpumask *new_mask, bool check)
1208 {
1209         unsigned long flags;
1210         struct rq *rq;
1211         unsigned int dest_cpu;
1212         int ret = 0;
1213 
1214         rq = task_rq_lock(p, &flags);
1215 
1216         /*
1217          * Must re-check here, to close a race against __kthread_bind(),
1218          * sched_setaffinity() is not guaranteed to observe the flag.
1219          */
1220         if (check && (p->flags & PF_NO_SETAFFINITY)) {
1221                 ret = -EINVAL;
1222                 goto out;
1223         }
1224 
1225         if (cpumask_equal(&p->cpus_allowed, new_mask))
1226                 goto out;
1227 
1228         if (!cpumask_intersects(new_mask, cpu_active_mask)) {
1229                 ret = -EINVAL;
1230                 goto out;
1231         }
1232 
1233         do_set_cpus_allowed(p, new_mask);
1234 
1235         /* Can the task run on the task's current CPU? If so, we're done */
1236         if (cpumask_test_cpu(task_cpu(p), new_mask))
1237                 goto out;
1238 
1239         dest_cpu = cpumask_any_and(cpu_active_mask, new_mask);
1240         if (task_running(rq, p) || p->state == TASK_WAKING) {
1241                 struct migration_arg arg = { p, dest_cpu };
1242                 /* Need help from migration thread: drop lock and wait. */
1243                 task_rq_unlock(rq, p, &flags);
1244                 stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
1245                 tlb_migrate_finish(p->mm);
1246                 return 0;
1247         } else if (task_on_rq_queued(p)) {
1248                 /*
1249                  * OK, since we're going to drop the lock immediately
1250                  * afterwards anyway.
1251                  */
1252                 lockdep_unpin_lock(&rq->lock);
1253                 rq = move_queued_task(rq, p, dest_cpu);
1254                 lockdep_pin_lock(&rq->lock);
1255         }
1256 out:
1257         task_rq_unlock(rq, p, &flags);
1258 
1259         return ret;
1260 }
1261 
1262 int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
1263 {
1264         return __set_cpus_allowed_ptr(p, new_mask, false);
1265 }
1266 EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
1267 
1268 void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
1269 {
1270 #ifdef CONFIG_SCHED_DEBUG
1271         /*
1272          * We should never call set_task_cpu() on a blocked task,
1273          * ttwu() will sort out the placement.
1274          */
1275         WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
1276                         !p->on_rq);
1277 
1278         /*
1279          * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
1280          * because schedstat_wait_{start,end} rebase migrating task's wait_start
1281          * time relying on p->on_rq.
1282          */
1283         WARN_ON_ONCE(p->state == TASK_RUNNING &&
1284                      p->sched_class == &fair_sched_class &&
1285                      (p->on_rq && !task_on_rq_migrating(p)));
1286 
1287 #ifdef CONFIG_LOCKDEP
1288         /*
1289          * The caller should hold either p->pi_lock or rq->lock, when changing
1290          * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
1291          *
1292          * sched_move_task() holds both and thus holding either pins the cgroup,
1293          * see task_group().
1294          *
1295          * Furthermore, all task_rq users should acquire both locks, see
1296          * task_rq_lock().
1297          */
1298         WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
1299                                       lockdep_is_held(&task_rq(p)->lock)));
1300 #endif
1301 #endif
1302 
1303         trace_sched_migrate_task(p, new_cpu);
1304 
1305         if (task_cpu(p) != new_cpu) {
1306                 if (p->sched_class->migrate_task_rq)
1307                         p->sched_class->migrate_task_rq(p);
1308                 p->se.nr_migrations++;
1309                 perf_event_task_migrate(p);
1310         }
1311 
1312         __set_task_cpu(p, new_cpu);
1313 }
1314 
1315 static void __migrate_swap_task(struct task_struct *p, int cpu)
1316 {
1317         if (task_on_rq_queued(p)) {
1318                 struct rq *src_rq, *dst_rq;
1319 
1320                 src_rq = task_rq(p);
1321                 dst_rq = cpu_rq(cpu);
1322 
1323                 p->on_rq = TASK_ON_RQ_MIGRATING;
1324                 deactivate_task(src_rq, p, 0);
1325                 set_task_cpu(p, cpu);
1326                 activate_task(dst_rq, p, 0);
1327                 p->on_rq = TASK_ON_RQ_QUEUED;
1328                 check_preempt_curr(dst_rq, p, 0);
1329         } else {
1330                 /*
1331                  * Task isn't running anymore; make it appear like we migrated
1332                  * it before it went to sleep. This means on wakeup we make the
1333                  * previous cpu our targer instead of where it really is.
1334                  */
1335                 p->wake_cpu = cpu;
1336         }
1337 }
1338 
1339 struct migration_swap_arg {
1340         struct task_struct *src_task, *dst_task;
1341         int src_cpu, dst_cpu;
1342 };
1343 
1344 static int migrate_swap_stop(void *data)
1345 {
1346         struct migration_swap_arg *arg = data;
1347         struct rq *src_rq, *dst_rq;
1348         int ret = -EAGAIN;
1349 
1350         if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu))
1351                 return -EAGAIN;
1352 
1353         src_rq = cpu_rq(arg->src_cpu);
1354         dst_rq = cpu_rq(arg->dst_cpu);
1355 
1356         double_raw_lock(&arg->src_task->pi_lock,
1357                         &arg->dst_task->pi_lock);
1358         double_rq_lock(src_rq, dst_rq);
1359 
1360         if (task_cpu(arg->dst_task) != arg->dst_cpu)
1361                 goto unlock;
1362 
1363         if (task_cpu(arg->src_task) != arg->src_cpu)
1364                 goto unlock;
1365 
1366         if (!cpumask_test_cpu(arg->dst_cpu, tsk_cpus_allowed(arg->src_task)))
1367                 goto unlock;
1368 
1369         if (!cpumask_test_cpu(arg->src_cpu, tsk_cpus_allowed(arg->dst_task)))
1370                 goto unlock;
1371 
1372         __migrate_swap_task(arg->src_task, arg->dst_cpu);
1373         __migrate_swap_task(arg->dst_task, arg->src_cpu);
1374 
1375         ret = 0;
1376 
1377 unlock:
1378         double_rq_unlock(src_rq, dst_rq);
1379         raw_spin_unlock(&arg->dst_task->pi_lock);
1380         raw_spin_unlock(&arg->src_task->pi_lock);
1381 
1382         return ret;
1383 }
1384 
1385 /*
1386  * Cross migrate two tasks
1387  */
1388 int migrate_swap(struct task_struct *cur, struct task_struct *p)
1389 {
1390         struct migration_swap_arg arg;
1391         int ret = -EINVAL;
1392 
1393         arg = (struct migration_swap_arg){
1394                 .src_task = cur,
1395                 .src_cpu = task_cpu(cur),
1396                 .dst_task = p,
1397                 .dst_cpu = task_cpu(p),
1398         };
1399 
1400         if (arg.src_cpu == arg.dst_cpu)
1401                 goto out;
1402 
1403         /*
1404          * These three tests are all lockless; this is OK since all of them
1405          * will be re-checked with proper locks held further down the line.
1406          */
1407         if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu))
1408                 goto out;
1409 
1410         if (!cpumask_test_cpu(arg.dst_cpu, tsk_cpus_allowed(arg.src_task)))
1411                 goto out;
1412 
1413         if (!cpumask_test_cpu(arg.src_cpu, tsk_cpus_allowed(arg.dst_task)))
1414                 goto out;
1415 
1416         trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu);
1417         ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg);
1418 
1419 out:
1420         return ret;
1421 }
1422 
1423 /*
1424  * wait_task_inactive - wait for a thread to unschedule.
1425  *
1426  * If @match_state is nonzero, it's the @p->state value just checked and
1427  * not expected to change.  If it changes, i.e. @p might have woken up,
1428  * then return zero.  When we succeed in waiting for @p to be off its CPU,
1429  * we return a positive number (its total switch count).  If a second call
1430  * a short while later returns the same number, the caller can be sure that
1431  * @p has remained unscheduled the whole time.
1432  *
1433  * The caller must ensure that the task *will* unschedule sometime soon,
1434  * else this function might spin for a *long* time. This function can't
1435  * be called with interrupts off, or it may introduce deadlock with
1436  * smp_call_function() if an IPI is sent by the same process we are
1437  * waiting to become inactive.
1438  */
1439 unsigned long wait_task_inactive(struct task_struct *p, long match_state)
1440 {
1441         unsigned long flags;
1442         int running, queued;
1443         unsigned long ncsw;
1444         struct rq *rq;
1445 
1446         for (;;) {
1447                 /*
1448                  * We do the initial early heuristics without holding
1449                  * any task-queue locks at all. We'll only try to get
1450                  * the runqueue lock when things look like they will
1451                  * work out!
1452                  */
1453                 rq = task_rq(p);
1454 
1455                 /*
1456                  * If the task is actively running on another CPU
1457                  * still, just relax and busy-wait without holding
1458                  * any locks.
1459                  *
1460                  * NOTE! Since we don't hold any locks, it's not
1461                  * even sure that "rq" stays as the right runqueue!
1462                  * But we don't care, since "task_running()" will
1463                  * return false if the runqueue has changed and p
1464                  * is actually now running somewhere else!
1465                  */
1466                 while (task_running(rq, p)) {
1467                         if (match_state && unlikely(p->state != match_state))
1468                                 return 0;
1469                         cpu_relax();
1470                 }
1471 
1472                 /*
1473                  * Ok, time to look more closely! We need the rq
1474                  * lock now, to be *sure*. If we're wrong, we'll
1475                  * just go back and repeat.
1476                  */
1477                 rq = task_rq_lock(p, &flags);
1478                 trace_sched_wait_task(p);
1479                 running = task_running(rq, p);
1480                 queued = task_on_rq_queued(p);
1481                 ncsw = 0;
1482                 if (!match_state || p->state == match_state)
1483                         ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
1484                 task_rq_unlock(rq, p, &flags);
1485 
1486                 /*
1487                  * If it changed from the expected state, bail out now.
1488                  */
1489                 if (unlikely(!ncsw))
1490                         break;
1491 
1492                 /*
1493                  * Was it really running after all now that we
1494                  * checked with the proper locks actually held?
1495                  *
1496                  * Oops. Go back and try again..
1497                  */
1498                 if (unlikely(running)) {
1499                         cpu_relax();
1500                         continue;
1501                 }
1502 
1503                 /*
1504                  * It's not enough that it's not actively running,
1505                  * it must be off the runqueue _entirely_, and not
1506                  * preempted!
1507                  *
1508                  * So if it was still runnable (but just not actively
1509                  * running right now), it's preempted, and we should
1510                  * yield - it could be a while.
1511                  */
1512                 if (unlikely(queued)) {
1513                         ktime_t to = ktime_set(0, NSEC_PER_SEC/HZ);
1514 
1515                         set_current_state(TASK_UNINTERRUPTIBLE);
1516                         schedule_hrtimeout(&to, HRTIMER_MODE_REL);
1517                         continue;
1518                 }
1519 
1520                 /*
1521                  * Ahh, all good. It wasn't running, and it wasn't
1522                  * runnable, which means that it will never become
1523                  * running in the future either. We're all done!
1524                  */
1525                 break;
1526         }
1527 
1528         return ncsw;
1529 }
1530 
1531 /***
1532  * kick_process - kick a running thread to enter/exit the kernel
1533  * @p: the to-be-kicked thread
1534  *
1535  * Cause a process which is running on another CPU to enter
1536  * kernel-mode, without any delay. (to get signals handled.)
1537  *
1538  * NOTE: this function doesn't have to take the runqueue lock,
1539  * because all it wants to ensure is that the remote task enters
1540  * the kernel. If the IPI races and the task has been migrated
1541  * to another CPU then no harm is done and the purpose has been
1542  * achieved as well.
1543  */
1544 void kick_process(struct task_struct *p)
1545 {
1546         int cpu;
1547 
1548         preempt_disable();
1549         cpu = task_cpu(p);
1550         if ((cpu != smp_processor_id()) && task_curr(p))
1551                 smp_send_reschedule(cpu);
1552         preempt_enable();
1553 }
1554 EXPORT_SYMBOL_GPL(kick_process);
1555 
1556 /*
1557  * ->cpus_allowed is protected by both rq->lock and p->pi_lock
1558  */
1559 static int select_fallback_rq(int cpu, struct task_struct *p)
1560 {
1561         int nid = cpu_to_node(cpu);
1562         const struct cpumask *nodemask = NULL;
1563         enum { cpuset, possible, fail } state = cpuset;
1564         int dest_cpu;
1565 
1566         /*
1567          * If the node that the cpu is on has been offlined, cpu_to_node()
1568          * will return -1. There is no cpu on the node, and we should
1569          * select the cpu on the other node.
1570          */
1571         if (nid != -1) {
1572                 nodemask = cpumask_of_node(nid);
1573 
1574                 /* Look for allowed, online CPU in same node. */
1575                 for_each_cpu(dest_cpu, nodemask) {
1576                         if (!cpu_online(dest_cpu))
1577                                 continue;
1578                         if (!cpu_active(dest_cpu))
1579                                 continue;
1580                         if (cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p)))
1581                                 return dest_cpu;
1582                 }
1583         }
1584 
1585         for (;;) {
1586                 /* Any allowed, online CPU? */
1587                 for_each_cpu(dest_cpu, tsk_cpus_allowed(p)) {
1588                         if (!cpu_online(dest_cpu))
1589                                 continue;
1590                         if (!cpu_active(dest_cpu))
1591                                 continue;
1592                         goto out;
1593                 }
1594 
1595                 /* No more Mr. Nice Guy. */
1596                 switch (state) {
1597                 case cpuset:
1598                         if (IS_ENABLED(CONFIG_CPUSETS)) {
1599                                 cpuset_cpus_allowed_fallback(p);
1600                                 state = possible;
1601                                 break;
1602                         }
1603                         /* fall-through */
1604                 case possible:
1605                         do_set_cpus_allowed(p, cpu_possible_mask);
1606                         state = fail;
1607                         break;
1608 
1609                 case fail:
1610                         BUG();
1611                         break;
1612                 }
1613         }
1614 
1615 out:
1616         if (state != cpuset) {
1617                 /*
1618                  * Don't tell them about moving exiting tasks or
1619                  * kernel threads (both mm NULL), since they never
1620                  * leave kernel.
1621                  */
1622                 if (p->mm && printk_ratelimit()) {
1623                         printk_deferred("process %d (%s) no longer affine to cpu%d\n",
1624                                         task_pid_nr(p), p->comm, cpu);
1625                 }
1626         }
1627 
1628         return dest_cpu;
1629 }
1630 
1631 /*
1632  * The caller (fork, wakeup) owns p->pi_lock, ->cpus_allowed is stable.
1633  */
1634 static inline
1635 int select_task_rq(struct task_struct *p, int cpu, int sd_flags, int wake_flags)
1636 {
1637         lockdep_assert_held(&p->pi_lock);
1638 
1639         if (p->nr_cpus_allowed > 1)
1640                 cpu = p->sched_class->select_task_rq(p, cpu, sd_flags, wake_flags);
1641 
1642         /*
1643          * In order not to call set_task_cpu() on a blocking task we need
1644          * to rely on ttwu() to place the task on a valid ->cpus_allowed
1645          * cpu.
1646          *
1647          * Since this is common to all placement strategies, this lives here.
1648          *
1649          * [ this allows ->select_task() to simply return task_cpu(p) and
1650          *   not worry about this generic constraint ]
1651          */
1652         if (unlikely(!cpumask_test_cpu(cpu, tsk_cpus_allowed(p)) ||
1653                      !cpu_online(cpu)))
1654                 cpu = select_fallback_rq(task_cpu(p), p);
1655 
1656         return cpu;
1657 }
1658 
1659 static void update_avg(u64 *avg, u64 sample)
1660 {
1661         s64 diff = sample - *avg;
1662         *avg += diff >> 3;
1663 }
1664 
1665 #else
1666 
1667 static inline int __set_cpus_allowed_ptr(struct task_struct *p,
1668                                          const struct cpumask *new_mask, bool check)
1669 {
1670         return set_cpus_allowed_ptr(p, new_mask);
1671 }
1672 
1673 #endif /* CONFIG_SMP */
1674 
1675 static void
1676 ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
1677 {
1678 #ifdef CONFIG_SCHEDSTATS
1679         struct rq *rq = this_rq();
1680 
1681 #ifdef CONFIG_SMP
1682         int this_cpu = smp_processor_id();
1683 
1684         if (cpu == this_cpu) {
1685                 schedstat_inc(rq, ttwu_local);
1686                 schedstat_inc(p, se.statistics.nr_wakeups_local);
1687         } else {
1688                 struct sched_domain *sd;
1689 
1690                 schedstat_inc(p, se.statistics.nr_wakeups_remote);
1691                 rcu_read_lock();
1692                 for_each_domain(this_cpu, sd) {
1693                         if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
1694                                 schedstat_inc(sd, ttwu_wake_remote);
1695                                 break;
1696                         }
1697                 }
1698                 rcu_read_unlock();
1699         }
1700 
1701         if (wake_flags & WF_MIGRATED)
1702                 schedstat_inc(p, se.statistics.nr_wakeups_migrate);
1703 
1704 #endif /* CONFIG_SMP */
1705 
1706         schedstat_inc(rq, ttwu_count);
1707         schedstat_inc(p, se.statistics.nr_wakeups);
1708 
1709         if (wake_flags & WF_SYNC)
1710                 schedstat_inc(p, se.statistics.nr_wakeups_sync);
1711 
1712 #endif /* CONFIG_SCHEDSTATS */
1713 }
1714 
1715 static inline void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
1716 {
1717         activate_task(rq, p, en_flags);
1718         p->on_rq = TASK_ON_RQ_QUEUED;
1719 
1720         /* if a worker is waking up, notify workqueue */
1721         if (p->flags & PF_WQ_WORKER)
1722                 wq_worker_waking_up(p, cpu_of(rq));
1723 }
1724 
1725 /*
1726  * Mark the task runnable and perform wakeup-preemption.
1727  */
1728 static void
1729 ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
1730 {
1731         check_preempt_curr(rq, p, wake_flags);
1732         p->state = TASK_RUNNING;
1733         trace_sched_wakeup(p);
1734 
1735 #ifdef CONFIG_SMP
1736         if (p->sched_class->task_woken) {
1737                 /*
1738                  * Our task @p is fully woken up and running; so its safe to
1739                  * drop the rq->lock, hereafter rq is only used for statistics.
1740                  */
1741                 lockdep_unpin_lock(&rq->lock);
1742                 p->sched_class->task_woken(rq, p);
1743                 lockdep_pin_lock(&rq->lock);
1744         }
1745 
1746         if (rq->idle_stamp) {
1747                 u64 delta = rq_clock(rq) - rq->idle_stamp;
1748                 u64 max = 2*rq->max_idle_balance_cost;
1749 
1750                 update_avg(&rq->avg_idle, delta);
1751 
1752                 if (rq->avg_idle > max)
1753                         rq->avg_idle = max;
1754 
1755                 rq->idle_stamp = 0;
1756         }
1757 #endif
1758 }
1759 
1760 static void
1761 ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags)
1762 {
1763         lockdep_assert_held(&rq->lock);
1764 
1765 #ifdef CONFIG_SMP
1766         if (p->sched_contributes_to_load)
1767                 rq->nr_uninterruptible--;
1768 #endif
1769 
1770         ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_WAKING);
1771         ttwu_do_wakeup(rq, p, wake_flags);
1772 }
1773 
1774 /*
1775  * Called in case the task @p isn't fully descheduled from its runqueue,
1776  * in this case we must do a remote wakeup. Its a 'light' wakeup though,
1777  * since all we need to do is flip p->state to TASK_RUNNING, since
1778  * the task is still ->on_rq.
1779  */
1780 static int ttwu_remote(struct task_struct *p, int wake_flags)
1781 {
1782         struct rq *rq;
1783         int ret = 0;
1784 
1785         rq = __task_rq_lock(p);
1786         if (task_on_rq_queued(p)) {
1787                 /* check_preempt_curr() may use rq clock */
1788                 update_rq_clock(rq);
1789                 ttwu_do_wakeup(rq, p, wake_flags);
1790                 ret = 1;
1791         }
1792         __task_rq_unlock(rq);
1793 
1794         return ret;
1795 }
1796 
1797 #ifdef CONFIG_SMP
1798 void sched_ttwu_pending(void)
1799 {
1800         struct rq *rq = this_rq();
1801         struct llist_node *llist = llist_del_all(&rq->wake_list);
1802         struct task_struct *p;
1803         unsigned long flags;
1804 
1805         if (!llist)
1806                 return;
1807 
1808         raw_spin_lock_irqsave(&rq->lock, flags);
1809         lockdep_pin_lock(&rq->lock);
1810 
1811         while (llist) {
1812                 p = llist_entry(llist, struct task_struct, wake_entry);
1813                 llist = llist_next(llist);
1814                 ttwu_do_activate(rq, p, 0);
1815         }
1816 
1817         lockdep_unpin_lock(&rq->lock);
1818         raw_spin_unlock_irqrestore(&rq->lock, flags);
1819 }
1820 
1821 void scheduler_ipi(void)
1822 {
1823         /*
1824          * Fold TIF_NEED_RESCHED into the preempt_count; anybody setting
1825          * TIF_NEED_RESCHED remotely (for the first time) will also send
1826          * this IPI.
1827          */
1828         preempt_fold_need_resched();
1829 
1830         if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick())
1831                 return;
1832 
1833         /*
1834          * Not all reschedule IPI handlers call irq_enter/irq_exit, since
1835          * traditionally all their work was done from the interrupt return
1836          * path. Now that we actually do some work, we need to make sure
1837          * we do call them.
1838          *
1839          * Some archs already do call them, luckily irq_enter/exit nest
1840          * properly.
1841          *
1842          * Arguably we should visit all archs and update all handlers,
1843          * however a fair share of IPIs are still resched only so this would
1844          * somewhat pessimize the simple resched case.
1845          */
1846         irq_enter();
1847         sched_ttwu_pending();
1848 
1849         /*
1850          * Check if someone kicked us for doing the nohz idle load balance.
1851          */
1852         if (unlikely(got_nohz_idle_kick())) {
1853                 this_rq()->idle_balance = 1;
1854                 raise_softirq_irqoff(SCHED_SOFTIRQ);
1855         }
1856         irq_exit();
1857 }
1858 
1859 static void ttwu_queue_remote(struct task_struct *p, int cpu)
1860 {
1861         struct rq *rq = cpu_rq(cpu);
1862 
1863         if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list)) {
1864                 if (!set_nr_if_polling(rq->idle))
1865                         smp_send_reschedule(cpu);
1866                 else
1867                         trace_sched_wake_idle_without_ipi(cpu);
1868         }
1869 }
1870 
1871 void wake_up_if_idle(int cpu)
1872 {
1873         struct rq *rq = cpu_rq(cpu);
1874         unsigned long flags;
1875 
1876         rcu_read_lock();
1877 
1878         if (!is_idle_task(rcu_dereference(rq->curr)))
1879                 goto out;
1880 
1881         if (set_nr_if_polling(rq->idle)) {
1882                 trace_sched_wake_idle_without_ipi(cpu);
1883         } else {
1884                 raw_spin_lock_irqsave(&rq->lock, flags);
1885                 if (is_idle_task(rq->curr))
1886                         smp_send_reschedule(cpu);
1887                 /* Else cpu is not in idle, do nothing here */
1888                 raw_spin_unlock_irqrestore(&rq->lock, flags);
1889         }
1890 
1891 out:
1892         rcu_read_unlock();
1893 }
1894 
1895 bool cpus_share_cache(int this_cpu, int that_cpu)
1896 {
1897         return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
1898 }
1899 #endif /* CONFIG_SMP */
1900 
1901 static void ttwu_queue(struct task_struct *p, int cpu)
1902 {
1903         struct rq *rq = cpu_rq(cpu);
1904 
1905 #if defined(CONFIG_SMP)
1906         if (sched_feat(TTWU_QUEUE) && !cpus_share_cache(smp_processor_id(), cpu)) {
1907                 sched_clock_cpu(cpu); /* sync clocks x-cpu */
1908                 ttwu_queue_remote(p, cpu);
1909                 return;
1910         }
1911 #endif
1912 
1913         raw_spin_lock(&rq->lock);
1914         lockdep_pin_lock(&rq->lock);
1915         ttwu_do_activate(rq, p, 0);
1916         lockdep_unpin_lock(&rq->lock);
1917         raw_spin_unlock(&rq->lock);
1918 }
1919 
1920 /*
1921  * Notes on Program-Order guarantees on SMP systems.
1922  *
1923  *  MIGRATION
1924  *
1925  * The basic program-order guarantee on SMP systems is that when a task [t]
1926  * migrates, all its activity on its old cpu [c0] happens-before any subsequent
1927  * execution on its new cpu [c1].
1928  *
1929  * For migration (of runnable tasks) this is provided by the following means:
1930  *
1931  *  A) UNLOCK of the rq(c0)->lock scheduling out task t
1932  *  B) migration for t is required to synchronize *both* rq(c0)->lock and
1933  *     rq(c1)->lock (if not at the same time, then in that order).
1934  *  C) LOCK of the rq(c1)->lock scheduling in task
1935  *
1936  * Transitivity guarantees that B happens after A and C after B.
1937  * Note: we only require RCpc transitivity.
1938  * Note: the cpu doing B need not be c0 or c1
1939  *
1940  * Example:
1941  *
1942  *   CPU0            CPU1            CPU2
1943  *
1944  *   LOCK rq(0)->lock
1945  *   sched-out X
1946  *   sched-in Y
1947  *   UNLOCK rq(0)->lock
1948  *
1949  *                                   LOCK rq(0)->lock // orders against CPU0
1950  *                                   dequeue X
1951  *                                   UNLOCK rq(0)->lock
1952  *
1953  *                                   LOCK rq(1)->lock
1954  *                                   enqueue X
1955  *                                   UNLOCK rq(1)->lock
1956  *
1957  *                   LOCK rq(1)->lock // orders against CPU2
1958  *                   sched-out Z
1959  *                   sched-in X
1960  *                   UNLOCK rq(1)->lock
1961  *
1962  *
1963  *  BLOCKING -- aka. SLEEP + WAKEUP
1964  *
1965  * For blocking we (obviously) need to provide the same guarantee as for
1966  * migration. However the means are completely different as there is no lock
1967  * chain to provide order. Instead we do:
1968  *
1969  *   1) smp_store_release(X->on_cpu, 0)
1970  *   2) smp_cond_acquire(!X->on_cpu)
1971  *
1972  * Example:
1973  *
1974  *   CPU0 (schedule)  CPU1 (try_to_wake_up) CPU2 (schedule)
1975  *
1976  *   LOCK rq(0)->lock LOCK X->pi_lock
1977  *   dequeue X
1978  *   sched-out X
1979  *   smp_store_release(X->on_cpu, 0);
1980  *
1981  *                    smp_cond_acquire(!X->on_cpu);
1982  *                    X->state = WAKING
1983  *                    set_task_cpu(X,2)
1984  *
1985  *                    LOCK rq(2)->lock
1986  *                    enqueue X
1987  *                    X->state = RUNNING
1988  *                    UNLOCK rq(2)->lock
1989  *
1990  *                                          LOCK rq(2)->lock // orders against CPU1
1991  *                                          sched-out Z
1992  *                                          sched-in X
1993  *                                          UNLOCK rq(2)->lock
1994  *
1995  *                    UNLOCK X->pi_lock
1996  *   UNLOCK rq(0)->lock
1997  *
1998  *
1999  * However; for wakeups there is a second guarantee we must provide, namely we
2000  * must observe the state that lead to our wakeup. That is, not only must our
2001  * task observe its own prior state, it must also observe the stores prior to
2002  * its wakeup.
2003  *
2004  * This means that any means of doing remote wakeups must order the CPU doing
2005  * the wakeup against the CPU the task is going to end up running on. This,
2006  * however, is already required for the regular Program-Order guarantee above,
2007  * since the waking CPU is the one issueing the ACQUIRE (smp_cond_acquire).
2008  *
2009  */
2010 
2011 /**
2012  * try_to_wake_up - wake up a thread
2013  * @p: the thread to be awakened
2014  * @state: the mask of task states that can be woken
2015  * @wake_flags: wake modifier flags (WF_*)
2016  *
2017  * Put it on the run-queue if it's not already there. The "current"
2018  * thread is always on the run-queue (except when the actual
2019  * re-schedule is in progress), and as such you're allowed to do
2020  * the simpler "current->state = TASK_RUNNING" to mark yourself
2021  * runnable without the overhead of this.
2022  *
2023  * Return: %true if @p was woken up, %false if it was already running.
2024  * or @state didn't match @p's state.
2025  */
2026 static int
2027 try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
2028 {
2029         unsigned long flags;
2030         int cpu, success = 0;
2031 
2032         /*
2033          * If we are going to wake up a thread waiting for CONDITION we
2034          * need to ensure that CONDITION=1 done by the caller can not be
2035          * reordered with p->state check below. This pairs with mb() in
2036          * set_current_state() the waiting thread does.
2037          */
2038         smp_mb__before_spinlock();
2039         raw_spin_lock_irqsave(&p->pi_lock, flags);
2040         if (!(p->state & state))
2041                 goto out;
2042 
2043         trace_sched_waking(p);
2044 
2045         success = 1; /* we're going to change ->state */
2046         cpu = task_cpu(p);
2047 
2048         if (p->on_rq && ttwu_remote(p, wake_flags))
2049                 goto stat;
2050 
2051 #ifdef CONFIG_SMP
2052         /*
2053          * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
2054          * possible to, falsely, observe p->on_cpu == 0.
2055          *
2056          * One must be running (->on_cpu == 1) in order to remove oneself
2057          * from the runqueue.
2058          *
2059          *  [S] ->on_cpu = 1;   [L] ->on_rq
2060          *      UNLOCK rq->lock
2061          *                      RMB
2062          *      LOCK   rq->lock
2063          *  [S] ->on_rq = 0;    [L] ->on_cpu
2064          *
2065          * Pairs with the full barrier implied in the UNLOCK+LOCK on rq->lock
2066          * from the consecutive calls to schedule(); the first switching to our
2067          * task, the second putting it to sleep.
2068          */
2069         smp_rmb();
2070 
2071         /*
2072          * If the owning (remote) cpu is still in the middle of schedule() with
2073          * this task as prev, wait until its done referencing the task.
2074          *
2075          * Pairs with the smp_store_release() in finish_lock_switch().
2076          *
2077          * This ensures that tasks getting woken will be fully ordered against
2078          * their previous state and preserve Program Order.
2079          */
2080         smp_cond_acquire(!p->on_cpu);
2081 
2082         p->sched_contributes_to_load = !!task_contributes_to_load(p);
2083         p->state = TASK_WAKING;
2084 
2085         if (p->sched_class->task_waking)
2086                 p->sched_class->task_waking(p);
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);
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  *
2108  * Put @p on the run-queue if it's not already there. The caller must
2109  * ensure that this_rq() is locked, @p is bound to this_rq() and not
2110  * the current task.
2111  */
2112 static void try_to_wake_up_local(struct task_struct *p)
2113 {
2114         struct rq *rq = task_rq(p);
2115 
2116         if (WARN_ON_ONCE(rq != this_rq()) ||
2117             WARN_ON_ONCE(p == current))
2118                 return;
2119 
2120         lockdep_assert_held(&rq->lock);
2121 
2122         if (!raw_spin_trylock(&p->pi_lock)) {
2123                 /*
2124                  * This is OK, because current is on_cpu, which avoids it being
2125                  * picked for load-balance and preemption/IRQs are still
2126                  * disabled avoiding further scheduler activity on it and we've
2127                  * not yet picked a replacement task.
2128                  */
2129                 lockdep_unpin_lock(&rq->lock);
2130                 raw_spin_unlock(&rq->lock);
2131                 raw_spin_lock(&p->pi_lock);
2132                 raw_spin_lock(&rq->lock);
2133                 lockdep_pin_lock(&rq->lock);
2134         }
2135 
2136         if (!(p->state & TASK_NORMAL))
2137                 goto out;
2138 
2139         trace_sched_waking(p);
2140 
2141         if (!task_on_rq_queued(p))
2142                 ttwu_activate(rq, p, ENQUEUE_WAKEUP);
2143 
2144         ttwu_do_wakeup(rq, p, 0);
2145         ttwu_stat(p, smp_processor_id(), 0);
2146 out:
2147         raw_spin_unlock(&p->pi_lock);
2148 }
2149 
2150 /**
2151  * wake_up_process - Wake up a specific process
2152  * @p: The process to be woken up.
2153  *
2154  * Attempt to wake up the nominated process and move it to the set of runnable
2155  * processes.
2156  *
2157  * Return: 1 if the process was woken up, 0 if it was already running.
2158  *
2159  * It may be assumed that this function implies a write memory barrier before
2160  * changing the task state if and only if any tasks are woken up.
2161  */
2162 int wake_up_process(struct task_struct *p)
2163 {
2164         return try_to_wake_up(p, TASK_NORMAL, 0);
2165 }
2166 EXPORT_SYMBOL(wake_up_process);
2167 
2168 int wake_up_state(struct task_struct *p, unsigned int state)
2169 {
2170         return try_to_wake_up(p, state, 0);
2171 }
2172 
2173 /*
2174  * This function clears the sched_dl_entity static params.
2175  */
2176 void __dl_clear_params(struct task_struct *p)
2177 {
2178         struct sched_dl_entity *dl_se = &p->dl;
2179 
2180         dl_se->dl_runtime = 0;
2181         dl_se->dl_deadline = 0;
2182         dl_se->dl_period = 0;
2183         dl_se->flags = 0;
2184         dl_se->dl_bw = 0;
2185 
2186         dl_se->dl_throttled = 0;
2187         dl_se->dl_new = 1;
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         memset(&p->se.statistics, 0, sizeof(p->se.statistics));
2215 #endif
2216 
2217         RB_CLEAR_NODE(&p->dl.rb_node);
2218         init_dl_task_timer(&p->dl);
2219         __dl_clear_params(p);
2220 
2221         INIT_LIST_HEAD(&p->rt.run_list);
2222 
2223 #ifdef CONFIG_PREEMPT_NOTIFIERS
2224         INIT_HLIST_HEAD(&p->preempt_notifiers);
2225 #endif
2226 
2227 #ifdef CONFIG_NUMA_BALANCING
2228         if (p->mm && atomic_read(&p->mm->mm_users) == 1) {
2229                 p->mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2230                 p->mm->numa_scan_seq = 0;
2231         }
2232 
2233         if (clone_flags & CLONE_VM)
2234                 p->numa_preferred_nid = current->numa_preferred_nid;
2235         else
2236                 p->numa_preferred_nid = -1;
2237 
2238         p->node_stamp = 0ULL;
2239         p->numa_scan_seq = p->mm ? p->mm->numa_scan_seq : 0;
2240         p->numa_scan_period = sysctl_numa_balancing_scan_delay;
2241         p->numa_work.next = &p->numa_work;
2242         p->numa_faults = NULL;
2243         p->last_task_numa_placement = 0;
2244         p->last_sum_exec_runtime = 0;
2245 
2246         p->numa_group = NULL;
2247 #endif /* CONFIG_NUMA_BALANCING */
2248 }
2249 
2250 DEFINE_STATIC_KEY_FALSE(sched_numa_balancing);
2251 
2252 #ifdef CONFIG_NUMA_BALANCING
2253 
2254 void set_numabalancing_state(bool enabled)
2255 {
2256         if (enabled)
2257                 static_branch_enable(&sched_numa_balancing);
2258         else
2259                 static_branch_disable(&sched_numa_balancing);
2260 }
2261 
2262 #ifdef CONFIG_PROC_SYSCTL
2263 int sysctl_numa_balancing(struct ctl_table *table, int write,
2264                          void __user *buffer, size_t *lenp, loff_t *ppos)
2265 {
2266         struct ctl_table t;
2267         int err;
2268         int state = static_branch_likely(&sched_numa_balancing);
2269 
2270         if (write && !capable(CAP_SYS_ADMIN))
2271                 return -EPERM;
2272 
2273         t = *table;
2274         t.data = &state;
2275         err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2276         if (err < 0)
2277                 return err;
2278         if (write)
2279                 set_numabalancing_state(state);
2280         return err;
2281 }
2282 #endif
2283 #endif
2284 
2285 /*
2286  * fork()/clone()-time setup:
2287  */
2288 int sched_fork(unsigned long clone_flags, struct task_struct *p)
2289 {
2290         unsigned long flags;
2291         int cpu = get_cpu();
2292 
2293         __sched_fork(clone_flags, p);
2294         /*
2295          * We mark the process as running here. This guarantees that
2296          * nobody will actually run it, and a signal or other external
2297          * event cannot wake it up and insert it on the runqueue either.
2298          */
2299         p->state = TASK_RUNNING;
2300 
2301         /*
2302          * Make sure we do not leak PI boosting priority to the child.
2303          */
2304         p->prio = current->normal_prio;
2305 
2306         /*
2307          * Revert to default priority/policy on fork if requested.
2308          */
2309         if (unlikely(p->sched_reset_on_fork)) {
2310                 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
2311                         p->policy = SCHED_NORMAL;
2312                         p->static_prio = NICE_TO_PRIO(0);
2313                         p->rt_priority = 0;
2314                 } else if (PRIO_TO_NICE(p->static_prio) < 0)
2315                         p->static_prio = NICE_TO_PRIO(0);
2316 
2317                 p->prio = p->normal_prio = __normal_prio(p);
2318                 set_load_weight(p);
2319 
2320                 /*
2321                  * We don't need the reset flag anymore after the fork. It has
2322                  * fulfilled its duty:
2323                  */
2324                 p->sched_reset_on_fork = 0;
2325         }
2326 
2327         if (dl_prio(p->prio)) {
2328                 put_cpu();
2329                 return -EAGAIN;
2330         } else if (rt_prio(p->prio)) {
2331                 p->sched_class = &rt_sched_class;
2332         } else {
2333                 p->sched_class = &fair_sched_class;
2334         }
2335 
2336         if (p->sched_class->task_fork)
2337                 p->sched_class->task_fork(p);
2338 
2339         /*
2340          * The child is not yet in the pid-hash so no cgroup attach races,
2341          * and the cgroup is pinned to this child due to cgroup_fork()
2342          * is ran before sched_fork().
2343          *
2344          * Silence PROVE_RCU.
2345          */
2346         raw_spin_lock_irqsave(&p->pi_lock, flags);
2347         set_task_cpu(p, cpu);
2348         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2349 
2350 #ifdef CONFIG_SCHED_INFO
2351         if (likely(sched_info_on()))
2352                 memset(&p->sched_info, 0, sizeof(p->sched_info));
2353 #endif
2354 #if defined(CONFIG_SMP)
2355         p->on_cpu = 0;
2356 #endif
2357         init_task_preempt_count(p);
2358 #ifdef CONFIG_SMP
2359         plist_node_init(&p->pushable_tasks, MAX_PRIO);
2360         RB_CLEAR_NODE(&p->pushable_dl_tasks);
2361 #endif
2362 
2363         put_cpu();
2364         return 0;
2365 }
2366 
2367 unsigned long to_ratio(u64 period, u64 runtime)
2368 {
2369         if (runtime == RUNTIME_INF)
2370                 return 1ULL << 20;
2371 
2372         /*
2373          * Doing this here saves a lot of checks in all
2374          * the calling paths, and returning zero seems
2375          * safe for them anyway.
2376          */
2377         if (period == 0)
2378                 return 0;
2379 
2380         return div64_u64(runtime << 20, period);
2381 }
2382 
2383 #ifdef CONFIG_SMP
2384 inline struct dl_bw *dl_bw_of(int i)
2385 {
2386         RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
2387                          "sched RCU must be held");
2388         return &cpu_rq(i)->rd->dl_bw;
2389 }
2390 
2391 static inline int dl_bw_cpus(int i)
2392 {
2393         struct root_domain *rd = cpu_rq(i)->rd;
2394         int cpus = 0;
2395 
2396         RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
2397                          "sched RCU must be held");
2398         for_each_cpu_and(i, rd->span, cpu_active_mask)
2399                 cpus++;
2400 
2401         return cpus;
2402 }
2403 #else
2404 inline struct dl_bw *dl_bw_of(int i)
2405 {
2406         return &cpu_rq(i)->dl.dl_bw;
2407 }
2408 
2409 static inline int dl_bw_cpus(int i)
2410 {
2411         return 1;
2412 }
2413 #endif
2414 
2415 /*
2416  * We must be sure that accepting a new task (or allowing changing the
2417  * parameters of an existing one) is consistent with the bandwidth
2418  * constraints. If yes, this function also accordingly updates the currently
2419  * allocated bandwidth to reflect the new situation.
2420  *
2421  * This function is called while holding p's rq->lock.
2422  *
2423  * XXX we should delay bw change until the task's 0-lag point, see
2424  * __setparam_dl().
2425  */
2426 static int dl_overflow(struct task_struct *p, int policy,
2427                        const struct sched_attr *attr)
2428 {
2429 
2430         struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
2431         u64 period = attr->sched_period ?: attr->sched_deadline;
2432         u64 runtime = attr->sched_runtime;
2433         u64 new_bw = dl_policy(policy) ? to_ratio(period, runtime) : 0;
2434         int cpus, err = -1;
2435 
2436         if (new_bw == p->dl.dl_bw)
2437                 return 0;
2438 
2439         /*
2440          * Either if a task, enters, leave, or stays -deadline but changes
2441          * its parameters, we may need to update accordingly the total
2442          * allocated bandwidth of the container.
2443          */
2444         raw_spin_lock(&dl_b->lock);
2445         cpus = dl_bw_cpus(task_cpu(p));
2446         if (dl_policy(policy) && !task_has_dl_policy(p) &&
2447             !__dl_overflow(dl_b, cpus, 0, new_bw)) {
2448                 __dl_add(dl_b, new_bw);
2449                 err = 0;
2450         } else if (dl_policy(policy) && task_has_dl_policy(p) &&
2451                    !__dl_overflow(dl_b, cpus, p->dl.dl_bw, new_bw)) {
2452                 __dl_clear(dl_b, p->dl.dl_bw);
2453                 __dl_add(dl_b, new_bw);
2454                 err = 0;
2455         } else if (!dl_policy(policy) && task_has_dl_policy(p)) {
2456                 __dl_clear(dl_b, p->dl.dl_bw);
2457                 err = 0;
2458         }
2459         raw_spin_unlock(&dl_b->lock);
2460 
2461         return err;
2462 }
2463 
2464 extern void init_dl_bw(struct dl_bw *dl_b);
2465 
2466 /*
2467  * wake_up_new_task - wake up a newly created task for the first time.
2468  *
2469  * This function will do some initial scheduler statistics housekeeping
2470  * that must be done for every newly created context, then puts the task
2471  * on the runqueue and wakes it.
2472  */
2473 void wake_up_new_task(struct task_struct *p)
2474 {
2475         unsigned long flags;
2476         struct rq *rq;
2477 
2478         raw_spin_lock_irqsave(&p->pi_lock, flags);
2479         /* Initialize new task's runnable average */
2480         init_entity_runnable_average(&p->se);
2481 #ifdef CONFIG_SMP
2482         /*
2483          * Fork balancing, do it here and not earlier because:
2484          *  - cpus_allowed can change in the fork path
2485          *  - any previously selected cpu might disappear through hotplug
2486          */
2487         set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0));
2488 #endif
2489 
2490         rq = __task_rq_lock(p);
2491         activate_task(rq, p, 0);
2492         p->on_rq = TASK_ON_RQ_QUEUED;
2493         trace_sched_wakeup_new(p);
2494         check_preempt_curr(rq, p, WF_FORK);
2495 #ifdef CONFIG_SMP
2496         if (p->sched_class->task_woken) {
2497                 /*
2498                  * Nothing relies on rq->lock after this, so its fine to
2499                  * drop it.
2500                  */
2501                 lockdep_unpin_lock(&rq->lock);
2502                 p->sched_class->task_woken(rq, p);
2503                 lockdep_pin_lock(&rq->lock);
2504         }
2505 #endif
2506         task_rq_unlock(rq, p, &flags);
2507 }
2508 
2509 #ifdef CONFIG_PREEMPT_NOTIFIERS
2510 
2511 static struct static_key preempt_notifier_key = STATIC_KEY_INIT_FALSE;
2512 
2513 void preempt_notifier_inc(void)
2514 {
2515         static_key_slow_inc(&preempt_notifier_key);
2516 }
2517 EXPORT_SYMBOL_GPL(preempt_notifier_inc);
2518 
2519 void preempt_notifier_dec(void)
2520 {
2521         static_key_slow_dec(&preempt_notifier_key);
2522 }
2523 EXPORT_SYMBOL_GPL(preempt_notifier_dec);
2524 
2525 /**
2526  * preempt_notifier_register - tell me when current is being preempted & rescheduled
2527  * @notifier: notifier struct to register
2528  */
2529 void preempt_notifier_register(struct preempt_notifier *notifier)
2530 {
2531         if (!static_key_false(&preempt_notifier_key))
2532                 WARN(1, "registering preempt_notifier while notifiers disabled\n");
2533 
2534         hlist_add_head(&notifier->link, &current->preempt_notifiers);
2535 }
2536 EXPORT_SYMBOL_GPL(preempt_notifier_register);
2537 
2538 /**
2539  * preempt_notifier_unregister - no longer interested in preemption notifications
2540  * @notifier: notifier struct to unregister
2541  *
2542  * This is *not* safe to call from within a preemption notifier.
2543  */
2544 void preempt_notifier_unregister(struct preempt_notifier *notifier)
2545 {
2546         hlist_del(&notifier->link);
2547 }
2548 EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
2549 
2550 static void __fire_sched_in_preempt_notifiers(struct task_struct *curr)
2551 {
2552         struct preempt_notifier *notifier;
2553 
2554         hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
2555                 notifier->ops->sched_in(notifier, raw_smp_processor_id());
2556 }
2557 
2558 static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
2559 {
2560         if (static_key_false(&preempt_notifier_key))
2561                 __fire_sched_in_preempt_notifiers(curr);
2562 }
2563 
2564 static void
2565 __fire_sched_out_preempt_notifiers(struct task_struct *curr,
2566                                    struct task_struct *next)
2567 {
2568         struct preempt_notifier *notifier;
2569 
2570         hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
2571                 notifier->ops->sched_out(notifier, next);
2572 }
2573 
2574 static __always_inline void
2575 fire_sched_out_preempt_notifiers(struct task_struct *curr,
2576                                  struct task_struct *next)
2577 {
2578         if (static_key_false(&preempt_notifier_key))
2579                 __fire_sched_out_preempt_notifiers(curr, next);
2580 }
2581 
2582 #else /* !CONFIG_PREEMPT_NOTIFIERS */
2583 
2584 static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
2585 {
2586 }
2587 
2588 static inline void
2589 fire_sched_out_preempt_notifiers(struct task_struct *curr,
2590                                  struct task_struct *next)
2591 {
2592 }
2593 
2594 #endif /* CONFIG_PREEMPT_NOTIFIERS */
2595 
2596 /**
2597  * prepare_task_switch - prepare to switch tasks
2598  * @rq: the runqueue preparing to switch
2599  * @prev: the current task that is being switched out
2600  * @next: the task we are going to switch to.
2601  *
2602  * This is called with the rq lock held and interrupts off. It must
2603  * be paired with a subsequent finish_task_switch after the context
2604  * switch.
2605  *
2606  * prepare_task_switch sets up locking and calls architecture specific
2607  * hooks.
2608  */
2609 static inline void
2610 prepare_task_switch(struct rq *rq, struct task_struct *prev,
2611                     struct task_struct *next)
2612 {
2613         sched_info_switch(rq, prev, next);
2614         perf_event_task_sched_out(prev, next);
2615         fire_sched_out_preempt_notifiers(prev, next);
2616         prepare_lock_switch(rq, next);
2617         prepare_arch_switch(next);
2618 }
2619 
2620 /**
2621  * finish_task_switch - clean up after a task-switch
2622  * @prev: the thread we just switched away from.
2623  *
2624  * finish_task_switch must be called after the context switch, paired
2625  * with a prepare_task_switch call before the context switch.
2626  * finish_task_switch will reconcile locking set up by prepare_task_switch,
2627  * and do any other architecture-specific cleanup actions.
2628  *
2629  * Note that we may have delayed dropping an mm in context_switch(). If
2630  * so, we finish that here outside of the runqueue lock. (Doing it
2631  * with the lock held can cause deadlocks; see schedule() for
2632  * details.)
2633  *
2634  * The context switch have flipped the stack from under us and restored the
2635  * local variables which were saved when this task called schedule() in the
2636  * past. prev == current is still correct but we need to recalculate this_rq
2637  * because prev may have moved to another CPU.
2638  */
2639 static struct rq *finish_task_switch(struct task_struct *prev)
2640         __releases(rq->lock)
2641 {
2642         struct rq *rq = this_rq();
2643         struct mm_struct *mm = rq->prev_mm;
2644         long prev_state;
2645 
2646         /*
2647          * The previous task will have left us with a preempt_count of 2
2648          * because it left us after:
2649          *
2650          *      schedule()
2651          *        preempt_disable();                    // 1
2652          *        __schedule()
2653          *          raw_spin_lock_irq(&rq->lock)        // 2
2654          *
2655          * Also, see FORK_PREEMPT_COUNT.
2656          */
2657         if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET,
2658                       "corrupted preempt_count: %s/%d/0x%x\n",
2659                       current->comm, current->pid, preempt_count()))
2660                 preempt_count_set(FORK_PREEMPT_COUNT);
2661 
2662         rq->prev_mm = NULL;
2663 
2664         /*
2665          * A task struct has one reference for the use as "current".
2666          * If a task dies, then it sets TASK_DEAD in tsk->state and calls
2667          * schedule one last time. The schedule call will never return, and
2668          * the scheduled task must drop that reference.
2669          *
2670          * We must observe prev->state before clearing prev->on_cpu (in
2671          * finish_lock_switch), otherwise a concurrent wakeup can get prev
2672          * running on another CPU and we could rave with its RUNNING -> DEAD
2673          * transition, resulting in a double drop.
2674          */
2675         prev_state = prev->state;
2676         vtime_task_switch(prev);
2677         perf_event_task_sched_in(prev, current);
2678         finish_lock_switch(rq, prev);
2679         finish_arch_post_lock_switch();
2680 
2681         fire_sched_in_preempt_notifiers(current);
2682         if (mm)
2683                 mmdrop(mm);
2684         if (unlikely(prev_state == TASK_DEAD)) {
2685                 if (prev->sched_class->task_dead)
2686                         prev->sched_class->task_dead(prev);
2687 
2688                 /*
2689                  * Remove function-return probe instances associated with this
2690                  * task and put them back on the free list.
2691                  */
2692                 kprobe_flush_task(prev);
2693                 put_task_struct(prev);
2694         }
2695 
2696         tick_nohz_task_switch();
2697         return rq;
2698 }
2699 
2700 #ifdef CONFIG_SMP
2701 
2702 /* rq->lock is NOT held, but preemption is disabled */
2703 static void __balance_callback(struct rq *rq)
2704 {
2705         struct callback_head *head, *next;
2706         void (*func)(struct rq *rq);
2707         unsigned long flags;
2708 
2709         raw_spin_lock_irqsave(&rq->lock, flags);
2710         head = rq->balance_callback;
2711         rq->balance_callback = NULL;
2712         while (head) {
2713                 func = (void (*)(struct rq *))head->func;
2714                 next = head->next;
2715                 head->next = NULL;
2716                 head = next;
2717 
2718                 func(rq);
2719         }
2720         raw_spin_unlock_irqrestore(&rq->lock, flags);
2721 }
2722 
2723 static inline void balance_callback(struct rq *rq)
2724 {
2725         if (unlikely(rq->balance_callback))
2726                 __balance_callback(rq);
2727 }
2728 
2729 #else
2730 
2731 static inline void balance_callback(struct rq *rq)
2732 {
2733 }
2734 
2735 #endif
2736 
2737 /**
2738  * schedule_tail - first thing a freshly forked thread must call.
2739  * @prev: the thread we just switched away from.
2740  */
2741 asmlinkage __visible void schedule_tail(struct task_struct *prev)
2742         __releases(rq->lock)
2743 {
2744         struct rq *rq;
2745 
2746         /*
2747          * New tasks start with FORK_PREEMPT_COUNT, see there and
2748          * finish_task_switch() for details.
2749          *
2750          * finish_task_switch() will drop rq->lock() and lower preempt_count
2751          * and the preempt_enable() will end up enabling preemption (on
2752          * PREEMPT_COUNT kernels).
2753          */
2754 
2755         rq = finish_task_switch(prev);
2756         balance_callback(rq);
2757         preempt_enable();
2758 
2759         if (current->set_child_tid)
2760                 put_user(task_pid_vnr(current), current->set_child_tid);
2761 }
2762 
2763 /*
2764  * context_switch - switch to the new MM and the new thread's register state.
2765  */
2766 static inline struct rq *
2767 context_switch(struct rq *rq, struct task_struct *prev,
2768                struct task_struct *next)
2769 {
2770         struct mm_struct *mm, *oldmm;
2771 
2772         prepare_task_switch(rq, prev, next);
2773 
2774         mm = next->mm;
2775         oldmm = prev->active_mm;
2776         /*
2777          * For paravirt, this is coupled with an exit in switch_to to
2778          * combine the page table reload and the switch backend into
2779          * one hypercall.
2780          */
2781         arch_start_context_switch(prev);
2782 
2783         if (!mm) {
2784                 next->active_mm = oldmm;
2785                 atomic_inc(&oldmm->mm_count);
2786                 enter_lazy_tlb(oldmm, next);
2787         } else
2788                 switch_mm(oldmm, mm, next);
2789 
2790         if (!prev->mm) {
2791                 prev->active_mm = NULL;
2792                 rq->prev_mm = oldmm;
2793         }
2794         /*
2795          * Since the runqueue lock will be released by the next
2796          * task (which is an invalid locking op but in the case
2797          * of the scheduler it's an obvious special-case), so we
2798          * do an early lockdep release here:
2799          */
2800         lockdep_unpin_lock(&rq->lock);
2801         spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
2802 
2803         /* Here we just switch the register state and the stack. */
2804         switch_to(prev, next, prev);
2805         barrier();
2806 
2807         return finish_task_switch(prev);
2808 }
2809 
2810 /*
2811  * nr_running and nr_context_switches:
2812  *
2813  * externally visible scheduler statistics: current number of runnable
2814  * threads, total number of context switches performed since bootup.
2815  */
2816 unsigned long nr_running(void)
2817 {
2818         unsigned long i, sum = 0;
2819 
2820         for_each_online_cpu(i)
2821                 sum += cpu_rq(i)->nr_running;
2822 
2823         return sum;
2824 }
2825 
2826 /*
2827  * Check if only the current task is running on the cpu.
2828  *
2829  * Caution: this function does not check that the caller has disabled
2830  * preemption, thus the result might have a time-of-check-to-time-of-use
2831  * race.  The caller is responsible to use it correctly, for example:
2832  *
2833  * - from a non-preemptable section (of course)
2834  *
2835  * - from a thread that is bound to a single CPU
2836  *
2837  * - in a loop with very short iterations (e.g. a polling loop)
2838  */
2839 bool single_task_running(void)
2840 {
2841         return raw_rq()->nr_running == 1;
2842 }
2843 EXPORT_SYMBOL(single_task_running);
2844 
2845 unsigned long long nr_context_switches(void)
2846 {
2847         int i;
2848         unsigned long long sum = 0;
2849 
2850         for_each_possible_cpu(i)
2851                 sum += cpu_rq(i)->nr_switches;
2852 
2853         return sum;
2854 }
2855 
2856 unsigned long nr_iowait(void)
2857 {
2858         unsigned long i, sum = 0;
2859 
2860         for_each_possible_cpu(i)
2861                 sum += atomic_read(&cpu_rq(i)->nr_iowait);
2862 
2863         return sum;
2864 }
2865 
2866 unsigned long nr_iowait_cpu(int cpu)
2867 {
2868         struct rq *this = cpu_rq(cpu);
2869         return atomic_read(&this->nr_iowait);
2870 }
2871 
2872 void get_iowait_load(unsigned long *nr_waiters, unsigned long *load)
2873 {
2874         struct rq *rq = this_rq();
2875         *nr_waiters = atomic_read(&rq->nr_iowait);
2876         *load = rq->load.weight;
2877 }
2878 
2879 #ifdef CONFIG_SMP
2880 
2881 /*
2882  * sched_exec - execve() is a valuable balancing opportunity, because at
2883  * this point the task has the smallest effective memory and cache footprint.
2884  */
2885 void sched_exec(void)
2886 {
2887         struct task_struct *p = current;
2888         unsigned long flags;
2889         int dest_cpu;
2890 
2891         raw_spin_lock_irqsave(&p->pi_lock, flags);
2892         dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), SD_BALANCE_EXEC, 0);
2893         if (dest_cpu == smp_processor_id())
2894                 goto unlock;
2895 
2896         if (likely(cpu_active(dest_cpu))) {
2897                 struct migration_arg arg = { p, dest_cpu };
2898 
2899                 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2900                 stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
2901                 return;
2902         }
2903 unlock:
2904         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2905 }
2906 
2907 #endif
2908 
2909 DEFINE_PER_CPU(struct kernel_stat, kstat);
2910 DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat);
2911 
2912 EXPORT_PER_CPU_SYMBOL(kstat);
2913 EXPORT_PER_CPU_SYMBOL(kernel_cpustat);
2914 
2915 /*
2916  * Return accounted runtime for the task.
2917  * In case the task is currently running, return the runtime plus current's
2918  * pending runtime that have not been accounted yet.
2919  */
2920 unsigned long long task_sched_runtime(struct task_struct *p)
2921 {
2922         unsigned long flags;
2923         struct rq *rq;
2924         u64 ns;
2925 
2926 #if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
2927         /*
2928          * 64-bit doesn't need locks to atomically read a 64bit value.
2929          * So we have a optimization chance when the task's delta_exec is 0.
2930          * Reading ->on_cpu is racy, but this is ok.
2931          *
2932          * If we race with it leaving cpu, we'll take a lock. So we're correct.
2933          * If we race with it entering cpu, unaccounted time is 0. This is
2934          * indistinguishable from the read occurring a few cycles earlier.
2935          * If we see ->on_cpu without ->on_rq, the task is leaving, and has
2936          * been accounted, so we're correct here as well.
2937          */
2938         if (!p->on_cpu || !task_on_rq_queued(p))
2939                 return p->se.sum_exec_runtime;
2940 #endif
2941 
2942         rq = task_rq_lock(p, &flags);
2943         /*
2944          * Must be ->curr _and_ ->on_rq.  If dequeued, we would
2945          * project cycles that may never be accounted to this
2946          * thread, breaking clock_gettime().
2947          */
2948         if (task_current(rq, p) && task_on_rq_queued(p)) {
2949                 update_rq_clock(rq);
2950                 p->sched_class->update_curr(rq);
2951         }
2952         ns = p->se.sum_exec_runtime;
2953         task_rq_unlock(rq, p, &flags);
2954 
2955         return ns;
2956 }
2957 
2958 /*
2959  * This function gets called by the timer code, with HZ frequency.
2960  * We call it with interrupts disabled.
2961  */
2962 void scheduler_tick(void)
2963 {
2964         int cpu = smp_processor_id();
2965         struct rq *rq = cpu_rq(cpu);
2966         struct task_struct *curr = rq->curr;
2967 
2968         sched_clock_tick();
2969 
2970         raw_spin_lock(&rq->lock);
2971         update_rq_clock(rq);
2972         curr->sched_class->task_tick(rq, curr, 0);
2973         update_cpu_load_active(rq);
2974         calc_global_load_tick(rq);
2975         raw_spin_unlock(&rq->lock);
2976 
2977         perf_event_task_tick();
2978 
2979 #ifdef CONFIG_SMP
2980         rq->idle_balance = idle_cpu(cpu);
2981         trigger_load_balance(rq);
2982 #endif
2983         rq_last_tick_reset(rq);
2984 }
2985 
2986 #ifdef CONFIG_NO_HZ_FULL
2987 /**
2988  * scheduler_tick_max_deferment
2989  *
2990  * Keep at least one tick per second when a single
2991  * active task is running because the scheduler doesn't
2992  * yet completely support full dynticks environment.
2993  *
2994  * This makes sure that uptime, CFS vruntime, load
2995  * balancing, etc... continue to move forward, even
2996  * with a very low granularity.
2997  *
2998  * Return: Maximum deferment in nanoseconds.
2999  */
3000 u64 scheduler_tick_max_deferment(void)
3001 {
3002         struct rq *rq = this_rq();
3003         unsigned long next, now = READ_ONCE(jiffies);
3004 
3005         next = rq->last_sched_tick + HZ;
3006 
3007         if (time_before_eq(next, now))
3008                 return 0;
3009 
3010         return jiffies_to_nsecs(next - now);
3011 }
3012 #endif
3013 
3014 notrace unsigned long get_parent_ip(unsigned long addr)
3015 {
3016         if (in_lock_functions(addr)) {
3017                 addr = CALLER_ADDR2;
3018                 if (in_lock_functions(addr))
3019                         addr = CALLER_ADDR3;
3020         }
3021         return addr;
3022 }
3023 
3024 #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
3025                                 defined(CONFIG_PREEMPT_TRACER))
3026 
3027 void preempt_count_add(int val)
3028 {
3029 #ifdef CONFIG_DEBUG_PREEMPT
3030         /*
3031          * Underflow?
3032          */
3033         if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
3034                 return;
3035 #endif
3036         __preempt_count_add(val);
3037 #ifdef CONFIG_DEBUG_PREEMPT
3038         /*
3039          * Spinlock count overflowing soon?
3040          */
3041         DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
3042                                 PREEMPT_MASK - 10);
3043 #endif
3044         if (preempt_count() == val) {
3045                 unsigned long ip = get_parent_ip(CALLER_ADDR1);
3046 #ifdef CONFIG_DEBUG_PREEMPT
3047                 current->preempt_disable_ip = ip;
3048 #endif
3049                 trace_preempt_off(CALLER_ADDR0, ip);
3050         }
3051 }
3052 EXPORT_SYMBOL(preempt_count_add);
3053 NOKPROBE_SYMBOL(preempt_count_add);
3054 
3055 void preempt_count_sub(int val)
3056 {
3057 #ifdef CONFIG_DEBUG_PREEMPT
3058         /*
3059          * Underflow?
3060          */
3061         if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
3062                 return;
3063         /*
3064          * Is the spinlock portion underflowing?
3065          */
3066         if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
3067                         !(preempt_count() & PREEMPT_MASK)))
3068                 return;
3069 #endif
3070 
3071         if (preempt_count() == val)
3072                 trace_preempt_on(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
3073         __preempt_count_sub(val);
3074 }
3075 EXPORT_SYMBOL(preempt_count_sub);
3076 NOKPROBE_SYMBOL(preempt_count_sub);
3077 
3078 #endif
3079 
3080 /*
3081  * Print scheduling while atomic bug:
3082  */
3083 static noinline void __schedule_bug(struct task_struct *prev)
3084 {
3085         if (oops_in_progress)
3086                 return;
3087 
3088         printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
3089                 prev->comm, prev->pid, preempt_count());
3090 
3091         debug_show_held_locks(prev);
3092         print_modules();
3093         if (irqs_disabled())
3094                 print_irqtrace_events(prev);
3095 #ifdef CONFIG_DEBUG_PREEMPT
3096         if (in_atomic_preempt_off()) {
3097                 pr_err("Preemption disabled at:");
3098                 print_ip_sym(current->preempt_disable_ip);
3099                 pr_cont("\n");
3100         }
3101 #endif
3102         dump_stack();
3103         add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
3104 }
3105 
3106 /*
3107  * Various schedule()-time debugging checks and statistics:
3108  */
3109 static inline void schedule_debug(struct task_struct *prev)
3110 {
3111 #ifdef CONFIG_SCHED_STACK_END_CHECK
3112         BUG_ON(task_stack_end_corrupted(prev));
3113 #endif
3114 
3115         if (unlikely(in_atomic_preempt_off())) {
3116                 __schedule_bug(prev);
3117                 preempt_count_set(PREEMPT_DISABLED);
3118         }
3119         rcu_sleep_check();
3120 
3121         profile_hit(SCHED_PROFILING, __builtin_return_address(0));
3122 
3123         schedstat_inc(this_rq(), sched_count);
3124 }
3125 
3126 /*
3127  * Pick up the highest-prio task:
3128  */
3129 static inline struct task_struct *
3130 pick_next_task(struct rq *rq, struct task_struct *prev)
3131 {
3132         const struct sched_class *class = &fair_sched_class;
3133         struct task_struct *p;
3134 
3135         /*
3136          * Optimization: we know that if all tasks are in
3137          * the fair class we can call that function directly:
3138          */
3139         if (likely(prev->sched_class == class &&
3140                    rq->nr_running == rq->cfs.h_nr_running)) {
3141                 p = fair_sched_class.pick_next_task(rq, prev);
3142                 if (unlikely(p == RETRY_TASK))
3143                         goto again;
3144 
3145                 /* assumes fair_sched_class->next == idle_sched_class */
3146                 if (unlikely(!p))
3147                         p = idle_sched_class.pick_next_task(rq, prev);
3148 
3149                 return p;
3150         }
3151 
3152 again:
3153         for_each_class(class) {
3154                 p = class->pick_next_task(rq, prev);
3155                 if (p) {
3156                         if (unlikely(p == RETRY_TASK))
3157                                 goto again;
3158                         return p;
3159                 }
3160         }
3161 
3162         BUG(); /* the idle class will always have a runnable task */
3163 }
3164 
3165 /*
3166  * __schedule() is the main scheduler function.
3167  *
3168  * The main means of driving the scheduler and thus entering this function are:
3169  *
3170  *   1. Explicit blocking: mutex, semaphore, waitqueue, etc.
3171  *
3172  *   2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
3173  *      paths. For example, see arch/x86/entry_64.S.
3174  *
3175  *      To drive preemption between tasks, the scheduler sets the flag in timer
3176  *      interrupt handler scheduler_tick().
3177  *
3178  *   3. Wakeups don't really cause entry into schedule(). They add a
3179  *      task to the run-queue and that's it.
3180  *
3181  *      Now, if the new task added to the run-queue preempts the current
3182  *      task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
3183  *      called on the nearest possible occasion:
3184  *
3185  *       - If the kernel is preemptible (CONFIG_PREEMPT=y):
3186  *
3187  *         - in syscall or exception context, at the next outmost
3188  *           preempt_enable(). (this might be as soon as the wake_up()'s
3189  *           spin_unlock()!)
3190  *
3191  *         - in IRQ context, return from interrupt-handler to
3192  *           preemptible context
3193  *
3194  *       - If the kernel is not preemptible (CONFIG_PREEMPT is not set)
3195  *         then at the next:
3196  *
3197  *          - cond_resched() call
3198  *          - explicit schedule() call
3199  *          - return from syscall or exception to user-space
3200  *          - return from interrupt-handler to user-space
3201  *
3202  * WARNING: must be called with preemption disabled!
3203  */
3204 static void __sched notrace __schedule(bool preempt)
3205 {
3206         struct task_struct *prev, *next;
3207         unsigned long *switch_count;
3208         struct rq *rq;
3209         int cpu;
3210 
3211         cpu = smp_processor_id();
3212         rq = cpu_rq(cpu);
3213         prev = rq->curr;
3214 
3215         /*
3216          * do_exit() calls schedule() with preemption disabled as an exception;
3217          * however we must fix that up, otherwise the next task will see an
3218          * inconsistent (higher) preempt count.
3219          *
3220          * It also avoids the below schedule_debug() test from complaining
3221          * about this.
3222          */
3223         if (unlikely(prev->state == TASK_DEAD))
3224                 preempt_enable_no_resched_notrace();
3225 
3226         schedule_debug(prev);
3227 
3228         if (sched_feat(HRTICK))
3229                 hrtick_clear(rq);
3230 
3231         local_irq_disable();
3232         rcu_note_context_switch();
3233 
3234         /*
3235          * Make sure that signal_pending_state()->signal_pending() below
3236          * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
3237          * done by the caller to avoid the race with signal_wake_up().
3238          */
3239         smp_mb__before_spinlock();
3240         raw_spin_lock(&rq->lock);
3241         lockdep_pin_lock(&rq->lock);
3242 
3243         rq->clock_skip_update <<= 1; /* promote REQ to ACT */
3244 
3245         switch_count = &prev->nivcsw;
3246         if (!preempt && prev->state) {
3247                 if (unlikely(signal_pending_state(prev->state, prev))) {
3248                         prev->state = TASK_RUNNING;
3249                 } else {
3250                         deactivate_task(rq, prev, DEQUEUE_SLEEP);
3251                         prev->on_rq = 0;
3252 
3253                         /*
3254                          * If a worker went to sleep, notify and ask workqueue
3255                          * whether it wants to wake up a task to maintain
3256                          * concurrency.
3257                          */
3258                         if (prev->flags & PF_WQ_WORKER) {
3259                                 struct task_struct *to_wakeup;
3260 
3261                                 to_wakeup = wq_worker_sleeping(prev, cpu);
3262                                 if (to_wakeup)
3263                                         try_to_wake_up_local(to_wakeup);
3264                         }
3265                 }
3266                 switch_count = &prev->nvcsw;
3267         }
3268 
3269         if (task_on_rq_queued(prev))
3270                 update_rq_clock(rq);
3271 
3272         next = pick_next_task(rq, prev);
3273         clear_tsk_need_resched(prev);
3274         clear_preempt_need_resched();
3275         rq->clock_skip_update = 0;
3276 
3277         if (likely(prev != next)) {
3278                 rq->nr_switches++;
3279                 rq->curr = next;
3280                 ++*switch_count;
3281 
3282                 trace_sched_switch(preempt, prev, next);
3283                 rq = context_switch(rq, prev, next); /* unlocks the rq */
3284                 cpu = cpu_of(rq);
3285         } else {
3286                 lockdep_unpin_lock(&rq->lock);
3287                 raw_spin_unlock_irq(&rq->lock);
3288         }
3289 
3290         balance_callback(rq);
3291 }
3292 
3293 static inline void sched_submit_work(struct task_struct *tsk)
3294 {
3295         if (!tsk->state || tsk_is_pi_blocked(tsk))
3296                 return;
3297         /*
3298          * If we are going to sleep and we have plugged IO queued,
3299          * make sure to submit it to avoid deadlocks.
3300          */
3301         if (blk_needs_flush_plug(tsk))
3302                 blk_schedule_flush_plug(tsk);
3303 }
3304 
3305 asmlinkage __visible void __sched schedule(void)
3306 {
3307         struct task_struct *tsk = current;
3308 
3309         sched_submit_work(tsk);
3310         do {
3311                 preempt_disable();
3312                 __schedule(false);
3313                 sched_preempt_enable_no_resched();
3314         } while (need_resched());
3315 }
3316 EXPORT_SYMBOL(schedule);
3317 
3318 #ifdef CONFIG_CONTEXT_TRACKING
3319 asmlinkage __visible void __sched schedule_user(void)
3320 {
3321         /*
3322          * If we come here after a random call to set_need_resched(),
3323          * or we have been woken up remotely but the IPI has not yet arrived,
3324          * we haven't yet exited the RCU idle mode. Do it here manually until
3325          * we find a better solution.
3326          *
3327          * NB: There are buggy callers of this function.  Ideally we
3328          * should warn if prev_state != CONTEXT_USER, but that will trigger
3329          * too frequently to make sense yet.
3330          */
3331         enum ctx_state prev_state = exception_enter();
3332         schedule();
3333         exception_exit(prev_state);
3334 }
3335 #endif
3336 
3337 /**
3338  * schedule_preempt_disabled - called with preemption disabled
3339  *
3340  * Returns with preemption disabled. Note: preempt_count must be 1
3341  */
3342 void __sched schedule_preempt_disabled(void)
3343 {
3344         sched_preempt_enable_no_resched();
3345         schedule();
3346         preempt_disable();
3347 }
3348 
3349 static void __sched notrace preempt_schedule_common(void)
3350 {
3351         do {
3352                 preempt_disable_notrace();
3353                 __schedule(true);
3354                 preempt_enable_no_resched_notrace();
3355 
3356                 /*
3357                  * Check again in case we missed a preemption opportunity
3358                  * between schedule and now.
3359                  */
3360         } while (need_resched());
3361 }
3362 
3363 #ifdef CONFIG_PREEMPT
3364 /*
3365  * this is the entry point to schedule() from in-kernel preemption
3366  * off of preempt_enable. Kernel preemptions off return from interrupt
3367  * occur there and call schedule directly.
3368  */
3369 asmlinkage __visible void __sched notrace preempt_schedule(void)
3370 {
3371         /*
3372          * If there is a non-zero preempt_count or interrupts are disabled,
3373          * we do not want to preempt the current task. Just return..
3374          */
3375         if (likely(!preemptible()))
3376                 return;
3377 
3378         preempt_schedule_common();
3379 }
3380 NOKPROBE_SYMBOL(preempt_schedule);
3381 EXPORT_SYMBOL(preempt_schedule);
3382 
3383 /**
3384  * preempt_schedule_notrace - preempt_schedule called by tracing
3385  *
3386  * The tracing infrastructure uses preempt_enable_notrace to prevent
3387  * recursion and tracing preempt enabling caused by the tracing
3388  * infrastructure itself. But as tracing can happen in areas coming
3389  * from userspace or just about to enter userspace, a preempt enable
3390  * can occur before user_exit() is called. This will cause the scheduler
3391  * to be called when the system is still in usermode.
3392  *
3393  * To prevent this, the preempt_enable_notrace will use this function
3394  * instead of preempt_schedule() to exit user context if needed before
3395  * calling the scheduler.
3396  */
3397 asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
3398 {
3399         enum ctx_state prev_ctx;
3400 
3401         if (likely(!preemptible()))
3402                 return;
3403 
3404         do {
3405                 preempt_disable_notrace();
3406                 /*
3407                  * Needs preempt disabled in case user_exit() is traced
3408                  * and the tracer calls preempt_enable_notrace() causing
3409                  * an infinite recursion.
3410                  */
3411                 prev_ctx = exception_enter();
3412                 __schedule(true);
3413                 exception_exit(prev_ctx);
3414 
3415                 preempt_enable_no_resched_notrace();
3416         } while (need_resched());
3417 }
3418 EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
3419 
3420 #endif /* CONFIG_PREEMPT */
3421 
3422 /*
3423  * this is the entry point to schedule() from kernel preemption
3424  * off of irq context.
3425  * Note, that this is called and return with irqs disabled. This will
3426  * protect us against recursive calling from irq.
3427  */
3428 asmlinkage __visible void __sched preempt_schedule_irq(void)
3429 {
3430         enum ctx_state prev_state;
3431 
3432         /* Catch callers which need to be fixed */
3433         BUG_ON(preempt_count() || !irqs_disabled());
3434 
3435         prev_state = exception_enter();
3436 
3437         do {
3438                 preempt_disable();
3439                 local_irq_enable();
3440                 __schedule(true);
3441                 local_irq_disable();
3442                 sched_preempt_enable_no_resched();
3443         } while (need_resched());
3444 
3445         exception_exit(prev_state);
3446 }
3447 
3448 int default_wake_function(wait_queue_t *curr, unsigned mode, int wake_flags,
3449                           void *key)
3450 {
3451         return try_to_wake_up(curr->private, mode, wake_flags);
3452 }
3453 EXPORT_SYMBOL(default_wake_function);
3454 
3455 #ifdef CONFIG_RT_MUTEXES
3456 
3457 /*
3458  * rt_mutex_setprio - set the current priority of a task
3459  * @p: task
3460  * @prio: prio value (kernel-internal form)
3461  *
3462  * This function changes the 'effective' priority of a task. It does
3463  * not touch ->normal_prio like __setscheduler().
3464  *
3465  * Used by the rt_mutex code to implement priority inheritance
3466  * logic. Call site only calls if the priority of the task changed.
3467  */
3468 void rt_mutex_setprio(struct task_struct *p, int prio)
3469 {
3470         int oldprio, queued, running, enqueue_flag = ENQUEUE_RESTORE;
3471         struct rq *rq;
3472         const struct sched_class *prev_class;
3473 
3474         BUG_ON(prio > MAX_PRIO);
3475 
3476         rq = __task_rq_lock(p);
3477 
3478         /*
3479          * Idle task boosting is a nono in general. There is one
3480          * exception, when PREEMPT_RT and NOHZ is active:
3481          *
3482          * The idle task calls get_next_timer_interrupt() and holds
3483          * the timer wheel base->lock on the CPU and another CPU wants
3484          * to access the timer (probably to cancel it). We can safely
3485          * ignore the boosting request, as the idle CPU runs this code
3486          * with interrupts disabled and will complete the lock
3487          * protected section without being interrupted. So there is no
3488          * real need to boost.
3489          */
3490         if (unlikely(p == rq->idle)) {
3491                 WARN_ON(p != rq->curr);
3492                 WARN_ON(p->pi_blocked_on);
3493                 goto out_unlock;
3494         }
3495 
3496         trace_sched_pi_setprio(p, prio);
3497         oldprio = p->prio;
3498         prev_class = p->sched_class;
3499         queued = task_on_rq_queued(p);
3500         running = task_current(rq, p);
3501         if (queued)
3502                 dequeue_task(rq, p, DEQUEUE_SAVE);
3503         if (running)
3504                 put_prev_task(rq, p);
3505 
3506         /*
3507          * Boosting condition are:
3508          * 1. -rt task is running and holds mutex A
3509          *      --> -dl task blocks on mutex A
3510          *
3511          * 2. -dl task is running and holds mutex A
3512          *      --> -dl task blocks on mutex A and could preempt the
3513          *          running task
3514          */
3515         if (dl_prio(prio)) {
3516                 struct task_struct *pi_task = rt_mutex_get_top_task(p);
3517                 if (!dl_prio(p->normal_prio) ||
3518                     (pi_task && dl_entity_preempt(&pi_task->dl, &p->dl))) {
3519                         p->dl.dl_boosted = 1;
3520                         enqueue_flag |= ENQUEUE_REPLENISH;
3521                 } else
3522                         p->dl.dl_boosted = 0;
3523                 p->sched_class = &dl_sched_class;
3524         } else if (rt_prio(prio)) {
3525                 if (dl_prio(oldprio))
3526                         p->dl.dl_boosted = 0;
3527                 if (oldprio < prio)
3528                         enqueue_flag |= ENQUEUE_HEAD;
3529                 p->sched_class = &rt_sched_class;
3530         } else {
3531                 if (dl_prio(oldprio))
3532                         p->dl.dl_boosted = 0;
3533                 if (rt_prio(oldprio))
3534                         p->rt.timeout = 0;
3535                 p->sched_class = &fair_sched_class;
3536         }
3537 
3538         p->prio = prio;
3539 
3540         if (running)
3541                 p->sched_class->set_curr_task(rq);
3542         if (queued)
3543                 enqueue_task(rq, p, enqueue_flag);
3544 
3545         check_class_changed(rq, p, prev_class, oldprio);
3546 out_unlock:
3547         preempt_disable(); /* avoid rq from going away on us */
3548         __task_rq_unlock(rq);
3549 
3550         balance_callback(rq);
3551         preempt_enable();
3552 }
3553 #endif
3554 
3555 void set_user_nice(struct task_struct *p, long nice)
3556 {
3557         int old_prio, delta, queued;
3558         unsigned long flags;
3559         struct rq *rq;
3560 
3561         if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
3562                 return;
3563         /*
3564          * We have to be careful, if called from sys_setpriority(),
3565          * the task might be in the middle of scheduling on another CPU.
3566          */
3567         rq = task_rq_lock(p, &flags);
3568         /*
3569          * The RT priorities are set via sched_setscheduler(), but we still
3570          * allow the 'normal' nice value to be set - but as expected
3571          * it wont have any effect on scheduling until the task is
3572          * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
3573          */
3574         if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
3575                 p->static_prio = NICE_TO_PRIO(nice);
3576                 goto out_unlock;
3577         }
3578         queued = task_on_rq_queued(p);
3579         if (queued)
3580                 dequeue_task(rq, p, DEQUEUE_SAVE);
3581 
3582         p->static_prio = NICE_TO_PRIO(nice);
3583         set_load_weight(p);
3584         old_prio = p->prio;
3585         p->prio = effective_prio(p);
3586         delta = p->prio - old_prio;
3587 
3588         if (queued) {
3589                 enqueue_task(rq, p, ENQUEUE_RESTORE);
3590                 /*
3591                  * If the task increased its priority or is running and
3592                  * lowered its priority, then reschedule its CPU:
3593                  */
3594                 if (delta < 0 || (delta > 0 && task_running(rq, p)))
3595                         resched_curr(rq);
3596         }
3597 out_unlock:
3598         task_rq_unlock(rq, p, &flags);
3599 }
3600 EXPORT_SYMBOL(set_user_nice);
3601 
3602 /*
3603  * can_nice - check if a task can reduce its nice value
3604  * @p: task
3605  * @nice: nice value
3606  */
3607 int can_nice(const struct task_struct *p, const int nice)
3608 {
3609         /* convert nice value [19,-20] to rlimit style value [1,40] */
3610         int nice_rlim = nice_to_rlimit(nice);
3611 
3612         return (nice_rlim <= task_rlimit(p, RLIMIT_NICE) ||
3613                 capable(CAP_SYS_NICE));
3614 }
3615 
3616 #ifdef __ARCH_WANT_SYS_NICE
3617 
3618 /*
3619  * sys_nice - change the priority of the current process.
3620  * @increment: priority increment
3621  *
3622  * sys_setpriority is a more generic, but much slower function that
3623  * does similar things.
3624  */
3625 SYSCALL_DEFINE1(nice, int, increment)
3626 {
3627         long nice, retval;
3628 
3629         /*
3630          * Setpriority might change our priority at the same moment.
3631          * We don't have to worry. Conceptually one call occurs first
3632          * and we have a single winner.
3633          */
3634         increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH);
3635         nice = task_nice(current) + increment;
3636 
3637         nice = clamp_val(nice, MIN_NICE, MAX_NICE);
3638         if (increment < 0 && !can_nice(current, nice))
3639                 return -EPERM;
3640 
3641         retval = security_task_setnice(current, nice);
3642         if (retval)
3643                 return retval;
3644 
3645         set_user_nice(current, nice);
3646         return 0;
3647 }
3648 
3649 #endif
3650 
3651 /**
3652  * task_prio - return the priority value of a given task.
3653  * @p: the task in question.
3654  *
3655  * Return: The priority value as seen by users in /proc.
3656  * RT tasks are offset by -200. Normal tasks are centered
3657  * around 0, value goes from -16 to +15.
3658  */
3659 int task_prio(const struct task_struct *p)
3660 {
3661         return p->prio - MAX_RT_PRIO;
3662 }
3663 
3664 /**
3665  * idle_cpu - is a given cpu idle currently?
3666  * @cpu: the processor in question.
3667  *
3668  * Return: 1 if the CPU is currently idle. 0 otherwise.
3669  */
3670 int idle_cpu(int cpu)
3671 {
3672         struct rq *rq = cpu_rq(cpu);
3673 
3674         if (rq->curr != rq->idle)
3675                 return 0;
3676 
3677         if (rq->nr_running)
3678                 return 0;
3679 
3680 #ifdef CONFIG_SMP
3681         if (!llist_empty(&rq->wake_list))
3682                 return 0;
3683 #endif
3684 
3685         return 1;
3686 }
3687 
3688 /**
3689  * idle_task - return the idle task for a given cpu.
3690  * @cpu: the processor in question.
3691  *
3692  * Return: The idle task for the cpu @cpu.
3693  */
3694 struct task_struct *idle_task(int cpu)
3695 {
3696         return cpu_rq(cpu)->idle;
3697 }
3698 
3699 /**
3700  * find_process_by_pid - find a process with a matching PID value.
3701  * @pid: the pid in question.
3702  *
3703  * The task of @pid, if found. %NULL otherwise.
3704  */
3705 static struct task_struct *find_process_by_pid(pid_t pid)
3706 {
3707         return pid ? find_task_by_vpid(pid) : current;
3708 }
3709 
3710 /*
3711  * This function initializes the sched_dl_entity of a newly becoming
3712  * SCHED_DEADLINE task.
3713  *
3714  * Only the static values are considered here, the actual runtime and the
3715  * absolute deadline will be properly calculated when the task is enqueued
3716  * for the first time with its new policy.
3717  */
3718 static void
3719 __setparam_dl(struct task_struct *p, const struct sched_attr *attr)
3720 {
3721         struct sched_dl_entity *dl_se = &p->dl;
3722 
3723         dl_se->dl_runtime = attr->sched_runtime;
3724         dl_se->dl_deadline = attr->sched_deadline;
3725         dl_se->dl_period = attr->sched_period ?: dl_se->dl_deadline;
3726         dl_se->flags = attr->sched_flags;
3727         dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime);
3728 
3729         /*
3730          * Changing the parameters of a task is 'tricky' and we're not doing
3731          * the correct thing -- also see task_dead_dl() and switched_from_dl().
3732          *
3733          * What we SHOULD do is delay the bandwidth release until the 0-lag
3734          * point. This would include retaining the task_struct until that time
3735          * and change dl_overflow() to not immediately decrement the current
3736          * amount.
3737          *
3738          * Instead we retain the current runtime/deadline and let the new
3739          * parameters take effect after the current reservation period lapses.
3740          * This is safe (albeit pessimistic) because the 0-lag point is always
3741          * before the current scheduling deadline.
3742          *
3743          * We can still have temporary overloads because we do not delay the
3744          * change in bandwidth until that time; so admission control is
3745          * not on the safe side. It does however guarantee tasks will never
3746          * consume more than promised.
3747          */
3748 }
3749 
3750 /*
3751  * sched_setparam() passes in -1 for its policy, to let the functions
3752  * it calls know not to change it.
3753  */
3754 #define SETPARAM_POLICY -1
3755 
3756 static void __setscheduler_params(struct task_struct *p,
3757                 const struct sched_attr *attr)
3758 {
3759         int policy = attr->sched_policy;
3760 
3761         if (policy == SETPARAM_POLICY)
3762                 policy = p->policy;
3763 
3764         p->policy = policy;
3765 
3766         if (dl_policy(policy))
3767                 __setparam_dl(p, attr);
3768         else if (fair_policy(policy))
3769                 p->static_prio = NICE_TO_PRIO(attr->sched_nice);
3770 
3771         /*
3772          * __sched_setscheduler() ensures attr->sched_priority == 0 when
3773          * !rt_policy. Always setting this ensures that things like
3774          * getparam()/getattr() don't report silly values for !rt tasks.
3775          */
3776         p->rt_priority = attr->sched_priority;
3777         p->normal_prio = normal_prio(p);
3778         set_load_weight(p);
3779 }
3780 
3781 /* Actually do priority change: must hold pi & rq lock. */
3782 static void __setscheduler(struct rq *rq, struct task_struct *p,
3783                            const struct sched_attr *attr, bool keep_boost)
3784 {
3785         __setscheduler_params(p, attr);
3786 
3787         /*
3788          * Keep a potential priority boosting if called from
3789          * sched_setscheduler().
3790          */
3791         if (keep_boost)
3792                 p->prio = rt_mutex_get_effective_prio(p, normal_prio(p));
3793         else
3794                 p->prio = normal_prio(p);
3795 
3796         if (dl_prio(p->prio))
3797                 p->sched_class = &dl_sched_class;
3798         else if (rt_prio(p->prio))
3799                 p->sched_class = &rt_sched_class;
3800         else
3801                 p->sched_class = &fair_sched_class;
3802 }
3803 
3804 static void
3805 __getparam_dl(struct task_struct *p, struct sched_attr *attr)
3806 {
3807         struct sched_dl_entity *dl_se = &p->dl;
3808 
3809         attr->sched_priority = p->rt_priority;
3810         attr->sched_runtime = dl_se->dl_runtime;
3811         attr->sched_deadline = dl_se->dl_deadline;
3812         attr->sched_period = dl_se->dl_period;
3813         attr->sched_flags = dl_se->flags;
3814 }
3815 
3816 /*
3817  * This function validates the new parameters of a -deadline task.
3818  * We ask for the deadline not being zero, and greater or equal
3819  * than the runtime, as well as the period of being zero or
3820  * greater than deadline. Furthermore, we have to be sure that
3821  * user parameters are above the internal resolution of 1us (we
3822  * check sched_runtime only since it is always the smaller one) and
3823  * below 2^63 ns (we have to check both sched_deadline and
3824  * sched_period, as the latter can be zero).
3825  */
3826 static bool
3827 __checkparam_dl(const struct sched_attr *attr)
3828 {
3829         /* deadline != 0 */
3830         if (attr->sched_deadline == 0)
3831                 return false;
3832 
3833         /*
3834          * Since we truncate DL_SCALE bits, make sure we're at least
3835          * that big.
3836          */
3837         if (attr->sched_runtime < (1ULL << DL_SCALE))
3838                 return false;
3839 
3840         /*
3841          * Since we use the MSB for wrap-around and sign issues, make
3842          * sure it's not set (mind that period can be equal to zero).
3843          */
3844         if (attr->sched_deadline & (1ULL << 63) ||
3845             attr->sched_period & (1ULL << 63))
3846                 return false;
3847 
3848         /* runtime <= deadline <= period (if period != 0) */
3849         if ((attr->sched_period != 0 &&
3850              attr->sched_period < attr->sched_deadline) ||
3851             attr->sched_deadline < attr->sched_runtime)
3852                 return false;
3853 
3854         return true;
3855 }
3856 
3857 /*
3858  * check the target process has a UID that matches the current process's
3859  */
3860 static bool check_same_owner(struct task_struct *p)
3861 {
3862         const struct cred *cred = current_cred(), *pcred;
3863         bool match;
3864 
3865         rcu_read_lock();
3866         pcred = __task_cred(p);
3867         match = (uid_eq(cred->euid, pcred->euid) ||
3868                  uid_eq(cred->euid, pcred->uid));
3869         rcu_read_unlock();
3870         return match;
3871 }
3872 
3873 static bool dl_param_changed(struct task_struct *p,
3874                 const struct sched_attr *attr)
3875 {
3876         struct sched_dl_entity *dl_se = &p->dl;
3877 
3878         if (dl_se->dl_runtime != attr->sched_runtime ||
3879                 dl_se->dl_deadline != attr->sched_deadline ||
3880                 dl_se->dl_period != attr->sched_period ||
3881                 dl_se->flags != attr->sched_flags)
3882                 return true;
3883 
3884         return false;
3885 }
3886 
3887 static int __sched_setscheduler(struct task_struct *p,
3888                                 const struct sched_attr *attr,
3889                                 bool user, bool pi)
3890 {
3891         int newprio = dl_policy(attr->sched_policy) ? MAX_DL_PRIO - 1 :
3892                       MAX_RT_PRIO - 1 - attr->sched_priority;
3893         int retval, oldprio, oldpolicy = -1, queued, running;
3894         int new_effective_prio, policy = attr->sched_policy;
3895         unsigned long flags;
3896         const struct sched_class *prev_class;
3897         struct rq *rq;
3898         int reset_on_fork;
3899 
3900         /* may grab non-irq protected spin_locks */
3901         BUG_ON(in_interrupt());
3902 recheck:
3903         /* double check policy once rq lock held */
3904         if (policy < 0) {
3905                 reset_on_fork = p->sched_reset_on_fork;
3906                 policy = oldpolicy = p->policy;
3907         } else {
3908                 reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK);
3909 
3910                 if (!valid_policy(policy))
3911                         return -EINVAL;
3912         }
3913 
3914         if (attr->sched_flags & ~(SCHED_FLAG_RESET_ON_FORK))
3915                 return -EINVAL;
3916 
3917         /*
3918          * Valid priorities for SCHED_FIFO and SCHED_RR are
3919          * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
3920          * SCHED_BATCH and SCHED_IDLE is 0.
3921          */
3922         if ((p->mm && attr->sched_priority > MAX_USER_RT_PRIO-1) ||
3923             (!p->mm && attr->sched_priority > MAX_RT_PRIO-1))
3924                 return -EINVAL;
3925         if ((dl_policy(policy) && !__checkparam_dl(attr)) ||
3926             (rt_policy(policy) != (attr->sched_priority != 0)))
3927                 return -EINVAL;
3928 
3929         /*
3930          * Allow unprivileged RT tasks to decrease priority:
3931          */
3932         if (user && !capable(CAP_SYS_NICE)) {
3933                 if (fair_policy(policy)) {
3934                         if (attr->sched_nice < task_nice(p) &&
3935                             !can_nice(p, attr->sched_nice))
3936                                 return -EPERM;
3937                 }
3938 
3939                 if (rt_policy(policy)) {
3940                         unsigned long rlim_rtprio =
3941                                         task_rlimit(p, RLIMIT_RTPRIO);
3942 
3943                         /* can't set/change the rt policy */
3944                         if (policy != p->policy && !rlim_rtprio)
3945                                 return -EPERM;
3946 
3947                         /* can't increase priority */
3948                         if (attr->sched_priority > p->rt_priority &&
3949                             attr->sched_priority > rlim_rtprio)
3950                                 return -EPERM;
3951                 }
3952 
3953                  /*
3954                   * Can't set/change SCHED_DEADLINE policy at all for now
3955                   * (safest behavior); in the future we would like to allow
3956                   * unprivileged DL tasks to increase their relative deadline
3957                   * or reduce their runtime (both ways reducing utilization)
3958                   */
3959                 if (dl_policy(policy))
3960                         return -EPERM;
3961 
3962                 /*
3963                  * Treat SCHED_IDLE as nice 20. Only allow a switch to
3964                  * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
3965                  */
3966                 if (idle_policy(p->policy) && !idle_policy(policy)) {
3967                         if (!can_nice(p, task_nice(p)))
3968                                 return -EPERM;
3969                 }
3970 
3971                 /* can't change other user's priorities */
3972                 if (!check_same_owner(p))
3973                         return -EPERM;
3974 
3975                 /* Normal users shall not reset the sched_reset_on_fork flag */
3976                 if (p->sched_reset_on_fork && !reset_on_fork)
3977                         return -EPERM;
3978         }
3979 
3980         if (user) {
3981                 retval = security_task_setscheduler(p);
3982                 if (retval)
3983                         return retval;
3984         }
3985 
3986         /*
3987          * make sure no PI-waiters arrive (or leave) while we are
3988          * changing the priority of the task:
3989          *
3990          * To be able to change p->policy safely, the appropriate
3991          * runqueue lock must be held.
3992          */
3993         rq = task_rq_lock(p, &flags);
3994 
3995         /*
3996          * Changing the policy of the stop threads its a very bad idea
3997          */
3998         if (p == rq->stop) {
3999                 task_rq_unlock(rq, p, &flags);
4000                 return -EINVAL;
4001         }
4002 
4003         /*
4004          * If not changing anything there's no need to proceed further,
4005          * but store a possible modification of reset_on_fork.
4006          */
4007         if (unlikely(policy == p->policy)) {
4008                 if (fair_policy(policy) && attr->sched_nice != task_nice(p))
4009                         goto change;
4010                 if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
4011                         goto change;
4012                 if (dl_policy(policy) && dl_param_changed(p, attr))
4013                         goto change;
4014 
4015                 p->sched_reset_on_fork = reset_on_fork;
4016                 task_rq_unlock(rq, p, &flags);
4017                 return 0;
4018         }
4019 change:
4020 
4021         if (user) {
4022 #ifdef CONFIG_RT_GROUP_SCHED
4023                 /*
4024                  * Do not allow realtime tasks into groups that have no runtime
4025                  * assigned.
4026                  */
4027                 if (rt_bandwidth_enabled() && rt_policy(policy) &&
4028                                 task_group(p)->rt_bandwidth.rt_runtime == 0 &&
4029                                 !task_group_is_autogroup(task_group(p))) {
4030                         task_rq_unlock(rq, p, &flags);
4031                         return -EPERM;
4032                 }
4033 #endif
4034 #ifdef CONFIG_SMP
4035                 if (dl_bandwidth_enabled() && dl_policy(policy)) {
4036                         cpumask_t *span = rq->rd->span;
4037 
4038                         /*
4039                          * Don't allow tasks with an affinity mask smaller than
4040                          * the entire root_domain to become SCHED_DEADLINE. We
4041                          * will also fail if there's no bandwidth available.
4042                          */
4043                         if (!cpumask_subset(span, &p->cpus_allowed) ||
4044                             rq->rd->dl_bw.bw == 0) {
4045                                 task_rq_unlock(rq, p, &flags);
4046                                 return -EPERM;
4047                         }
4048                 }
4049 #endif
4050         }
4051 
4052         /* recheck policy now with rq lock held */
4053         if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
4054                 policy = oldpolicy = -1;
4055                 task_rq_unlock(rq, p, &flags);
4056                 goto recheck;
4057         }
4058 
4059         /*
4060          * If setscheduling to SCHED_DEADLINE (or changing the parameters
4061          * of a SCHED_DEADLINE task) we need to check if enough bandwidth
4062          * is available.
4063          */
4064         if ((dl_policy(policy) || dl_task(p)) && dl_overflow(p, policy, attr)) {
4065                 task_rq_unlock(rq, p, &flags);
4066                 return -EBUSY;
4067         }
4068 
4069         p->sched_reset_on_fork = reset_on_fork;
4070         oldprio = p->prio;
4071 
4072         if (pi) {
4073                 /*
4074                  * Take priority boosted tasks into account. If the new
4075                  * effective priority is unchanged, we just store the new
4076                  * normal parameters and do not touch the scheduler class and
4077                  * the runqueue. This will be done when the task deboost
4078                  * itself.
4079                  */
4080                 new_effective_prio = rt_mutex_get_effective_prio(p, newprio);
4081                 if (new_effective_prio == oldprio) {
4082                         __setscheduler_params(p, attr);
4083                         task_rq_unlock(rq, p, &flags);
4084                         return 0;
4085                 }
4086         }
4087 
4088         queued = task_on_rq_queued(p);
4089         running = task_current(rq, p);
4090         if (queued)
4091                 dequeue_task(rq, p, DEQUEUE_SAVE);
4092         if (running)
4093                 put_prev_task(rq, p);
4094 
4095         prev_class = p->sched_class;
4096         __setscheduler(rq, p, attr, pi);
4097 
4098         if (running)
4099                 p->sched_class->set_curr_task(rq);
4100         if (queued) {
4101                 int enqueue_flags = ENQUEUE_RESTORE;
4102                 /*
4103                  * We enqueue to tail when the priority of a task is
4104                  * increased (user space view).
4105                  */
4106                 if (oldprio <= p->prio)
4107                         enqueue_flags |= ENQUEUE_HEAD;
4108 
4109                 enqueue_task(rq, p, enqueue_flags);
4110         }
4111 
4112         check_class_changed(rq, p, prev_class, oldprio);
4113         preempt_disable(); /* avoid rq from going away on us */
4114         task_rq_unlock(rq, p, &flags);
4115 
4116         if (pi)
4117                 rt_mutex_adjust_pi(p);
4118 
4119         /*
4120          * Run balance callbacks after we've adjusted the PI chain.
4121          */
4122         balance_callback(rq);
4123         preempt_enable();
4124 
4125         return 0;
4126 }
4127 
4128 static int _sched_setscheduler(struct task_struct *p, int policy,
4129                                const struct sched_param *param, bool check)
4130 {
4131         struct sched_attr attr = {
4132                 .sched_policy   = policy,
4133                 .sched_priority = param->sched_priority,
4134                 .sched_nice     = PRIO_TO_NICE(p->static_prio),
4135         };
4136 
4137         /* Fixup the legacy SCHED_RESET_ON_FORK hack. */
4138         if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) {
4139                 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
4140                 policy &= ~SCHED_RESET_ON_FORK;
4141                 attr.sched_policy = policy;
4142         }
4143 
4144         return __sched_setscheduler(p, &attr, check, true);
4145 }
4146 /**
4147  * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
4148  * @p: the task in question.
4149  * @policy: new policy.
4150  * @param: structure containing the new RT priority.
4151  *
4152  * Return: 0 on success. An error code otherwise.
4153  *
4154  * NOTE that the task may be already dead.
4155  */
4156 int sched_setscheduler(struct task_struct *p, int policy,
4157                        const struct sched_param *param)
4158 {
4159         return _sched_setscheduler(p, policy, param, true);
4160 }
4161 EXPORT_SYMBOL_GPL(sched_setscheduler);
4162 
4163 int sched_setattr(struct task_struct *p, const struct sched_attr *attr)
4164 {
4165         return __sched_setscheduler(p, attr, true, true);
4166 }
4167 EXPORT_SYMBOL_GPL(sched_setattr);
4168 
4169 /**
4170  * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
4171  * @p: the task in question.
4172  * @policy: new policy.
4173  * @param: structure containing the new RT priority.
4174  *
4175  * Just like sched_setscheduler, only don't bother checking if the
4176  * current context has permission.  For example, this is needed in
4177  * stop_machine(): we create temporary high priority worker threads,
4178  * but our caller might not have that capability.
4179  *
4180  * Return: 0 on success. An error code otherwise.
4181  */
4182 int sched_setscheduler_nocheck(struct task_struct *p, int policy,
4183                                const struct sched_param *param)
4184 {
4185         return _sched_setscheduler(p, policy, param, false);
4186 }
4187 EXPORT_SYMBOL_GPL(sched_setscheduler_nocheck);
4188 
4189 static int
4190 do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
4191 {
4192         struct sched_param lparam;
4193         struct task_struct *p;
4194         int retval;
4195 
4196         if (!param || pid < 0)
4197                 return -EINVAL;
4198         if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
4199                 return -EFAULT;
4200 
4201         rcu_read_lock();
4202         retval = -ESRCH;
4203         p = find_process_by_pid(pid);
4204         if (p != NULL)
4205                 retval = sched_setscheduler(p, policy, &lparam);
4206         rcu_read_unlock();
4207 
4208         return retval;
4209 }
4210 
4211 /*
4212  * Mimics kernel/events/core.c perf_copy_attr().
4213  */
4214 static int sched_copy_attr(struct sched_attr __user *uattr,
4215                            struct sched_attr *attr)
4216 {
4217         u32 size;
4218         int ret;
4219 
4220         if (!access_ok(VERIFY_WRITE, uattr, SCHED_ATTR_SIZE_VER0))
4221                 return -EFAULT;
4222 
4223         /*
4224          * zero the full structure, so that a short copy will be nice.
4225          */
4226         memset(attr, 0, sizeof(*attr));
4227 
4228         ret = get_user(size, &uattr->size);
4229         if (ret)
4230                 return ret;
4231 
4232         if (size > PAGE_SIZE)   /* silly large */
4233                 goto err_size;
4234 
4235         if (!size)              /* abi compat */
4236                 size = SCHED_ATTR_SIZE_VER0;
4237 
4238         if (size < SCHED_ATTR_SIZE_VER0)
4239                 goto err_size;
4240 
4241         /*
4242          * If we're handed a bigger struct than we know of,
4243          * ensure all the unknown bits are 0 - i.e. new
4244          * user-space does not rely on any kernel feature
4245          * extensions we dont know about yet.
4246          */
4247         if (size > sizeof(*attr)) {
4248                 unsigned char __user *addr;
4249                 unsigned char __user *end;
4250                 unsigned char val;
4251 
4252                 addr = (void __user *)uattr + sizeof(*attr);
4253                 end  = (void __user *)uattr + size;
4254 
4255                 for (; addr < end; addr++) {
4256                         ret = get_user(val, addr);
4257                         if (ret)
4258                                 return ret;
4259                         if (val)
4260                                 goto err_size;
4261                 }
4262                 size = sizeof(*attr);
4263         }
4264 
4265         ret = copy_from_user(attr, uattr, size);
4266         if (ret)
4267                 return -EFAULT;
4268 
4269         /*
4270          * XXX: do we want to be lenient like existing syscalls; or do we want
4271          * to be strict and return an error on out-of-bounds values?
4272          */
4273         attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE);
4274 
4275         return 0;
4276 
4277 err_size:
4278         put_user(sizeof(*attr), &uattr->size);
4279         return -E2BIG;
4280 }
4281 
4282 /**
4283  * sys_sched_setscheduler - set/change the scheduler policy and RT priority
4284  * @pid: the pid in question.
4285  * @policy: new policy.
4286  * @param: structure containing the new RT priority.
4287  *
4288  * Return: 0 on success. An error code otherwise.
4289  */
4290 SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy,
4291                 struct sched_param __user *, param)
4292 {
4293         /* negative values for policy are not valid */
4294         if (policy < 0)
4295                 return -EINVAL;
4296 
4297         return do_sched_setscheduler(pid, policy, param);
4298 }
4299 
4300 /**
4301  * sys_sched_setparam - set/change the RT priority of a thread
4302  * @pid: the pid in question.
4303  * @param: structure containing the new RT priority.
4304  *
4305  * Return: 0 on success. An error code otherwise.
4306  */
4307 SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
4308 {
4309         return do_sched_setscheduler(pid, SETPARAM_POLICY, param);
4310 }
4311 
4312 /**
4313  * sys_sched_setattr - same as above, but with extended sched_attr
4314  * @pid: the pid in question.
4315  * @uattr: structure containing the extended parameters.
4316  * @flags: for future extension.
4317  */
4318 SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
4319                                unsigned int, flags)
4320 {
4321         struct sched_attr attr;
4322         struct task_struct *p;
4323         int retval;
4324 
4325         if (!uattr || pid < 0 || flags)
4326                 return -EINVAL;
4327 
4328         retval = sched_copy_attr(uattr, &attr);
4329         if (retval)
4330                 return retval;
4331 
4332         if ((int)attr.sched_policy < 0)
4333                 return -EINVAL;
4334 
4335         rcu_read_lock();
4336         retval = -ESRCH;
4337         p = find_process_by_pid(pid);
4338         if (p != NULL)
4339                 retval = sched_setattr(p, &attr);
4340         rcu_read_unlock();
4341 
4342         return retval;
4343 }
4344 
4345 /**
4346  * sys_sched_getscheduler - get the policy (scheduling class) of a thread
4347  * @pid: the pid in question.
4348  *
4349  * Return: On success, the policy of the thread. Otherwise, a negative error
4350  * code.
4351  */
4352 SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
4353 {
4354         struct task_struct *p;
4355         int retval;
4356 
4357         if (pid < 0)
4358                 return -EINVAL;
4359 
4360         retval = -ESRCH;
4361         rcu_read_lock();
4362         p = find_process_by_pid(pid);
4363         if (p) {
4364                 retval = security_task_getscheduler(p);
4365                 if (!retval)
4366                         retval = p->policy
4367                                 | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0);
4368         }
4369         rcu_read_unlock();
4370         return retval;
4371 }
4372 
4373 /**
4374  * sys_sched_getparam - get the RT priority of a thread
4375  * @pid: the pid in question.
4376  * @param: structure containing the RT priority.
4377  *
4378  * Return: On success, 0 and the RT priority is in @param. Otherwise, an error
4379  * code.
4380  */
4381 SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
4382 {
4383         struct sched_param lp = { .sched_priority = 0 };
4384         struct task_struct *p;
4385         int retval;
4386 
4387         if (!param || pid < 0)
4388                 return -EINVAL;
4389 
4390         rcu_read_lock();
4391         p = find_process_by_pid(pid);
4392         retval = -ESRCH;
4393         if (!p)
4394                 goto out_unlock;
4395 
4396         retval = security_task_getscheduler(p);
4397         if (retval)
4398                 goto out_unlock;
4399 
4400         if (task_has_rt_policy(p))
4401                 lp.sched_priority = p->rt_priority;
4402         rcu_read_unlock();
4403 
4404         /*
4405          * This one might sleep, we cannot do it with a spinlock held ...
4406          */
4407         retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
4408 
4409         return retval;
4410 
4411 out_unlock:
4412         rcu_read_unlock();
4413         return retval;
4414 }
4415 
4416 static int sched_read_attr(struct sched_attr __user *uattr,
4417                            struct sched_attr *attr,
4418                            unsigned int usize)
4419 {
4420         int ret;
4421 
4422         if (!access_ok(VERIFY_WRITE, uattr, usize))
4423                 return -EFAULT;
4424 
4425         /*
4426          * If we're handed a smaller struct than we know of,
4427          * ensure all the unknown bits are 0 - i.e. old
4428          * user-space does not get uncomplete information.
4429          */
4430         if (usize < sizeof(*attr)) {
4431                 unsigned char *addr;
4432                 unsigned char *end;
4433 
4434                 addr = (void *)attr + usize;
4435                 end  = (void *)attr + sizeof(*attr);
4436 
4437                 for (; addr < end; addr++) {
4438                         if (*addr)
4439                                 return -EFBIG;
4440                 }
4441 
4442                 attr->size = usize;
4443         }
4444 
4445         ret = copy_to_user(uattr, attr, attr->size);
4446         if (ret)
4447                 return -EFAULT;
4448 
4449         return 0;
4450 }
4451 
4452 /**
4453  * sys_sched_getattr - similar to sched_getparam, but with sched_attr
4454  * @pid: the pid in question.
4455  * @uattr: structure containing the extended parameters.
4456  * @size: sizeof(attr) for fwd/bwd comp.
4457  * @flags: for future extension.
4458  */
4459 SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
4460                 unsigned int, size, unsigned int, flags)
4461 {
4462         struct sched_attr attr = {
4463                 .size = sizeof(struct sched_attr),
4464         };
4465         struct task_struct *p;
4466         int retval;
4467 
4468         if (!uattr || pid < 0 || size > PAGE_SIZE ||
4469             size < SCHED_ATTR_SIZE_VER0 || flags)
4470                 return -EINVAL;
4471 
4472         rcu_read_lock();
4473         p = find_process_by_pid(pid);
4474         retval = -ESRCH;
4475         if (!p)
4476                 goto out_unlock;
4477 
4478         retval = security_task_getscheduler(p);
4479         if (retval)
4480                 goto out_unlock;
4481 
4482         attr.sched_policy = p->policy;
4483         if (p->sched_reset_on_fork)
4484                 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
4485         if (task_has_dl_policy(p))
4486                 __getparam_dl(p, &attr);
4487         else if (task_has_rt_policy(p))
4488                 attr.sched_priority = p->rt_priority;
4489         else
4490                 attr.sched_nice = task_nice(p);
4491 
4492         rcu_read_unlock();
4493 
4494         retval = sched_read_attr(uattr, &attr, size);
4495         return retval;
4496 
4497 out_unlock:
4498         rcu_read_unlock();
4499         return retval;
4500 }
4501 
4502 long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
4503 {
4504         cpumask_var_t cpus_allowed, new_mask;
4505         struct task_struct *p;
4506         int retval;
4507 
4508         rcu_read_lock();
4509 
4510         p = find_process_by_pid(pid);
4511         if (!p) {
4512                 rcu_read_unlock();
4513                 return -ESRCH;
4514         }
4515 
4516         /* Prevent p going away */
4517         get_task_struct(p);
4518         rcu_read_unlock();
4519 
4520         if (p->flags & PF_NO_SETAFFINITY) {
4521                 retval = -EINVAL;
4522                 goto out_put_task;
4523         }
4524         if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
4525                 retval = -ENOMEM;
4526                 goto out_put_task;
4527         }
4528         if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
4529                 retval = -ENOMEM;
4530                 goto out_free_cpus_allowed;
4531         }
4532         retval = -EPERM;
4533         if (!check_same_owner(p)) {
4534                 rcu_read_lock();
4535                 if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
4536                         rcu_read_unlock();
4537                         goto out_free_new_mask;
4538                 }
4539                 rcu_read_unlock();
4540         }
4541 
4542         retval = security_task_setscheduler(p);
4543         if (retval)
4544                 goto out_free_new_mask;
4545 
4546 
4547         cpuset_cpus_allowed(p, cpus_allowed);
4548         cpumask_and(new_mask, in_mask, cpus_allowed);
4549 
4550         /*
4551          * Since bandwidth control happens on root_domain basis,
4552          * if admission test is enabled, we only admit -deadline
4553          * tasks allowed to run on all the CPUs in the task's
4554          * root_domain.
4555          */
4556 #ifdef CONFIG_SMP
4557         if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {
4558                 rcu_read_lock();
4559                 if (!cpumask_subset(task_rq(p)->rd->span, new_mask)) {
4560                         retval = -EBUSY;
4561                         rcu_read_unlock();
4562                         goto out_free_new_mask;
4563                 }
4564                 rcu_read_unlock();
4565         }
4566 #endif
4567 again:
4568         retval = __set_cpus_allowed_ptr(p, new_mask, true);
4569 
4570         if (!retval) {
4571                 cpuset_cpus_allowed(p, cpus_allowed);
4572                 if (!cpumask_subset(new_mask, cpus_allowed)) {
4573                         /*
4574                          * We must have raced with a concurrent cpuset
4575                          * update. Just reset the cpus_allowed to the
4576                          * cpuset's cpus_allowed
4577                          */
4578                         cpumask_copy(new_mask, cpus_allowed);
4579                         goto again;
4580                 }
4581         }
4582 out_free_new_mask:
4583         free_cpumask_var(new_mask);
4584 out_free_cpus_allowed:
4585         free_cpumask_var(cpus_allowed);
4586 out_put_task:
4587         put_task_struct(p);
4588         return retval;
4589 }
4590 
4591 static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
4592                              struct cpumask *new_mask)
4593 {
4594         if (len < cpumask_size())
4595                 cpumask_clear(new_mask);
4596         else if (len > cpumask_size())
4597                 len = cpumask_size();
4598 
4599         return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
4600 }
4601 
4602 /**
4603  * sys_sched_setaffinity - set the cpu affinity of a process
4604  * @pid: pid of the process
4605  * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4606  * @user_mask_ptr: user-space pointer to the new cpu mask
4607  *
4608  * Return: 0 on success. An error code otherwise.
4609  */
4610 SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
4611                 unsigned long __user *, user_mask_ptr)
4612 {
4613         cpumask_var_t new_mask;
4614         int retval;
4615 
4616         if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
4617                 return -ENOMEM;
4618 
4619         retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
4620         if (retval == 0)
4621                 retval = sched_setaffinity(pid, new_mask);
4622         free_cpumask_var(new_mask);
4623         return retval;
4624 }
4625 
4626 long sched_getaffinity(pid_t pid, struct cpumask *mask)
4627 {
4628         struct task_struct *p;
4629         unsigned long flags;
4630         int retval;
4631 
4632         rcu_read_lock();
4633 
4634         retval = -ESRCH;
4635         p = find_process_by_pid(pid);
4636         if (!p)
4637                 goto out_unlock;
4638 
4639         retval = security_task_getscheduler(p);
4640         if (retval)
4641                 goto out_unlock;
4642 
4643         raw_spin_lock_irqsave(&p->pi_lock, flags);
4644         cpumask_and(mask, &p->cpus_allowed, cpu_active_mask);
4645         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
4646 
4647 out_unlock:
4648         rcu_read_unlock();
4649 
4650         return retval;
4651 }
4652 
4653 /**
4654  * sys_sched_getaffinity - get the cpu affinity of a process
4655  * @pid: pid of the process
4656  * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4657  * @user_mask_ptr: user-space pointer to hold the current cpu mask
4658  *
4659  * Return: 0 on success. An error code otherwise.
4660  */
4661 SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
4662                 unsigned long __user *, user_mask_ptr)
4663 {
4664         int ret;
4665         cpumask_var_t mask;
4666 
4667         if ((len * BITS_PER_BYTE) < nr_cpu_ids)
4668                 return -EINVAL;
4669         if (len & (sizeof(unsigned long)-1))
4670                 return -EINVAL;
4671 
4672         if (!alloc_cpumask_var(&mask, GFP_KERNEL))
4673                 return -ENOMEM;
4674 
4675         ret = sched_getaffinity(pid, mask);
4676         if (ret == 0) {
4677                 size_t retlen = min_t(size_t, len, cpumask_size());
4678 
4679                 if (copy_to_user(user_mask_ptr, mask, retlen))
4680                         ret = -EFAULT;
4681                 else
4682                         ret = retlen;
4683         }
4684         free_cpumask_var(mask);
4685 
4686         return ret;
4687 }
4688 
4689 /**
4690  * sys_sched_yield - yield the current processor to other threads.
4691  *
4692  * This function yields the current CPU to other tasks. If there are no
4693  * other threads running on this CPU then this function will return.
4694  *
4695  * Return: 0.
4696  */
4697 SYSCALL_DEFINE0(sched_yield)
4698 {
4699         struct rq *rq = this_rq_lock();
4700 
4701         schedstat_inc(rq, yld_count);
4702         current->sched_class->yield_task(rq);
4703 
4704         /*
4705          * Since we are going to call schedule() anyway, there's
4706          * no need to preempt or enable interrupts:
4707          */
4708         __release(rq->lock);
4709         spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
4710         do_raw_spin_unlock(&rq->lock);
4711         sched_preempt_enable_no_resched();
4712 
4713         schedule();
4714 
4715         return 0;
4716 }
4717 
4718 int __sched _cond_resched(void)
4719 {
4720         if (should_resched(0)) {
4721                 preempt_schedule_common();
4722                 return 1;
4723         }
4724         return 0;
4725 }
4726 EXPORT_SYMBOL(_cond_resched);
4727 
4728 /*
4729  * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
4730  * call schedule, and on return reacquire the lock.
4731  *
4732  * This works OK both with and without CONFIG_PREEMPT. We do strange low-level
4733  * operations here to prevent schedule() from being called twice (once via
4734  * spin_unlock(), once by hand).
4735  */
4736 int __cond_resched_lock(spinlock_t *lock)
4737 {
4738         int resched = should_resched(PREEMPT_LOCK_OFFSET);
4739         int ret = 0;
4740 
4741         lockdep_assert_held(lock);
4742 
4743         if (spin_needbreak(lock) || resched) {
4744                 spin_unlock(lock);
4745                 if (resched)
4746                         preempt_schedule_common();
4747                 else
4748                         cpu_relax();
4749                 ret = 1;
4750                 spin_lock(lock);
4751         }
4752         return ret;
4753 }
4754 EXPORT_SYMBOL(__cond_resched_lock);
4755 
4756 int __sched __cond_resched_softirq(void)
4757 {
4758         BUG_ON(!in_softirq());
4759 
4760         if (should_resched(SOFTIRQ_DISABLE_OFFSET)) {
4761                 local_bh_enable();
4762                 preempt_schedule_common();
4763                 local_bh_disable();
4764                 return 1;
4765         }
4766         return 0;
4767 }
4768 EXPORT_SYMBOL(__cond_resched_softirq);
4769 
4770 /**
4771  * yield - yield the current processor to other threads.
4772  *
4773  * Do not ever use this function, there's a 99% chance you're doing it wrong.
4774  *
4775  * The scheduler is at all times free to pick the calling task as the most
4776  * eligible task to run, if removing the yield() call from your code breaks
4777  * it, its already broken.
4778  *
4779  * Typical broken usage is:
4780  *
4781  * while (!event)
4782  *      yield();
4783  *
4784  * where one assumes that yield() will let 'the other' process run that will
4785  * make event true. If the current task is a SCHED_FIFO task that will never
4786  * happen. Never use yield() as a progress guarantee!!
4787  *
4788  * If you want to use yield() to wait for something, use wait_event().
4789  * If you want to use yield() to be 'nice' for others, use cond_resched().
4790  * If you still want to use yield(), do not!
4791  */
4792 void __sched yield(void)
4793 {
4794         set_current_state(TASK_RUNNING);
4795         sys_sched_yield();
4796 }
4797 EXPORT_SYMBOL(yield);
4798 
4799 /**
4800  * yield_to - yield the current processor to another thread in
4801  * your thread group, or accelerate that thread toward the
4802  * processor it's on.
4803  * @p: target task
4804  * @preempt: whether task preemption is allowed or not
4805  *
4806  * It's the caller's job to ensure that the target task struct
4807  * can't go away on us before we can do any checks.
4808  *
4809  * Return:
4810  *      true (>0) if we indeed boosted the target task.
4811  *      false (0) if we failed to boost the target.
4812  *      -ESRCH if there's no task to yield to.
4813  */
4814 int __sched yield_to(struct task_struct *p, bool preempt)
4815 {
4816         struct task_struct *curr = current;
4817         struct rq *rq, *p_rq;
4818         unsigned long flags;
4819         int yielded = 0;
4820 
4821         local_irq_save(flags);
4822         rq = this_rq();
4823 
4824 again:
4825         p_rq = task_rq(p);
4826         /*
4827          * If we're the only runnable task on the rq and target rq also
4828          * has only one task, there's absolutely no point in yielding.
4829          */
4830         if (rq->nr_running == 1 && p_rq->nr_running == 1) {
4831                 yielded = -ESRCH;
4832                 goto out_irq;
4833         }
4834 
4835         double_rq_lock(rq, p_rq);
4836         if (task_rq(p) != p_rq) {
4837                 double_rq_unlock(rq, p_rq);
4838                 goto again;
4839         }
4840 
4841         if (!curr->sched_class->yield_to_task)
4842                 goto out_unlock;
4843 
4844         if (curr->sched_class != p->sched_class)
4845                 goto out_unlock;
4846 
4847         if (task_running(p_rq, p) || p->state)
4848                 goto out_unlock;
4849 
4850         yielded = curr->sched_class->yield_to_task(rq, p, preempt);
4851         if (yielded) {
4852                 schedstat_inc(rq, yld_count);
4853                 /*
4854                  * Make p's CPU reschedule; pick_next_entity takes care of
4855                  * fairness.
4856                  */
4857                 if (preempt && rq != p_rq)
4858                         resched_curr(p_rq);
4859         }
4860 
4861 out_unlock:
4862         double_rq_unlock(rq, p_rq);
4863 out_irq:
4864         local_irq_restore(flags);
4865 
4866         if (yielded > 0)
4867                 schedule();
4868 
4869         return yielded;
4870 }
4871 EXPORT_SYMBOL_GPL(yield_to);
4872 
4873 /*
4874  * This task is about to go to sleep on IO. Increment rq->nr_iowait so
4875  * that process accounting knows that this is a task in IO wait state.
4876  */
4877 long __sched io_schedule_timeout(long timeout)
4878 {
4879         int old_iowait = current->in_iowait;
4880         struct rq *rq;
4881         long ret;
4882 
4883         current->in_iowait = 1;
4884         blk_schedule_flush_plug(current);
4885 
4886         delayacct_blkio_start();
4887         rq = raw_rq();
4888         atomic_inc(&rq->nr_iowait);
4889         ret = schedule_timeout(timeout);
4890         current->in_iowait = old_iowait;
4891         atomic_dec(&rq->nr_iowait);
4892         delayacct_blkio_end();
4893 
4894         return ret;
4895 }
4896 EXPORT_SYMBOL(io_schedule_timeout);
4897 
4898 /**
4899  * sys_sched_get_priority_max - return maximum RT priority.
4900  * @policy: scheduling class.
4901  *
4902  * Return: On success, this syscall returns the maximum
4903  * rt_priority that can be used by a given scheduling class.
4904  * On failure, a negative error code is returned.
4905  */
4906 SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
4907 {
4908         int ret = -EINVAL;
4909 
4910         switch (policy) {
4911         case SCHED_FIFO:
4912         case SCHED_RR:
4913                 ret = MAX_USER_RT_PRIO-1;
4914                 break;
4915         case SCHED_DEADLINE:
4916         case SCHED_NORMAL:
4917         case SCHED_BATCH:
4918         case SCHED_IDLE:
4919                 ret = 0;
4920                 break;
4921         }
4922         return ret;
4923 }
4924 
4925 /**
4926  * sys_sched_get_priority_min - return minimum RT priority.
4927  * @policy: scheduling class.
4928  *
4929  * Return: On success, this syscall returns the minimum
4930  * rt_priority that can be used by a given scheduling class.
4931  * On failure, a negative error code is returned.
4932  */
4933 SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
4934 {
4935         int ret = -EINVAL;
4936 
4937         switch (policy) {
4938         case SCHED_FIFO:
4939         case SCHED_RR:
4940                 ret = 1;
4941                 break;
4942         case SCHED_DEADLINE:
4943         case SCHED_NORMAL:
4944         case SCHED_BATCH:
4945         case SCHED_IDLE:
4946                 ret = 0;
4947         }
4948         return ret;
4949 }
4950 
4951 /**
4952  * sys_sched_rr_get_interval - return the default timeslice of a process.
4953  * @pid: pid of the process.
4954  * @interval: userspace pointer to the timeslice value.
4955  *
4956  * this syscall writes the default timeslice value of a given process
4957  * into the user-space timespec buffer. A value of '' means infinity.
4958  *
4959  * Return: On success, 0 and the timeslice is in @interval. Otherwise,
4960  * an error code.
4961  */
4962 SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
4963                 struct timespec __user *, interval)
4964 {
4965         struct task_struct *p;
4966         unsigned int time_slice;
4967         unsigned long flags;
4968         struct rq *rq;
4969         int retval;
4970         struct timespec t;
4971 
4972         if (pid < 0)
4973                 return -EINVAL;
4974 
4975         retval = -ESRCH;
4976         rcu_read_lock();
4977         p = find_process_by_pid(pid);
4978         if (!p)
4979                 goto out_unlock;
4980 
4981         retval = security_task_getscheduler(p);
4982         if (retval)
4983                 goto out_unlock;
4984 
4985         rq = task_rq_lock(p, &flags);
4986         time_slice = 0;
4987         if (p->sched_class->get_rr_interval)
4988                 time_slice = p->sched_class->get_rr_interval(rq, p);
4989         task_rq_unlock(rq, p, &flags);
4990 
4991         rcu_read_unlock();
4992         jiffies_to_timespec(time_slice, &t);
4993         retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
4994         return retval;
4995 
4996 out_unlock:
4997         rcu_read_unlock();
4998         return retval;
4999 }
5000 
5001 static const char stat_nam[] = TASK_STATE_TO_CHAR_STR;
5002 
5003 void sched_show_task(struct task_struct *p)
5004 {
5005         unsigned long free = 0;
5006         int ppid;
5007         unsigned long state = p->state;
5008 
5009         if (state)
5010                 state = __ffs(state) + 1;
5011         printk(KERN_INFO "%-15.15s %c", p->comm,
5012                 state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?');
5013 #if BITS_PER_LONG == 32
5014         if (state == TASK_RUNNING)
5015                 printk(KERN_CONT " running  ");
5016         else
5017                 printk(KERN_CONT " %08lx ", thread_saved_pc(p));
5018 #else
5019         if (state == TASK_RUNNING)
5020                 printk(KERN_CONT "  running task    ");
5021         else
5022                 printk(KERN_CONT " %016lx ", thread_saved_pc(p));
5023 #endif
5024 #ifdef CONFIG_DEBUG_STACK_USAGE
5025         free = stack_not_used(p);
5026 #endif
5027         ppid = 0;
5028         rcu_read_lock();
5029         if (pid_alive(p))
5030                 ppid = task_pid_nr(rcu_dereference(p->real_parent));
5031         rcu_read_unlock();
5032         printk(KERN_CONT "%5lu %5d %6d 0x%08lx\n", free,
5033                 task_pid_nr(p), ppid,
5034                 (unsigned long)task_thread_info(p)->flags);
5035 
5036         print_worker_info(KERN_INFO, p);
5037         show_stack(p, NULL);
5038 }
5039 
5040 void show_state_filter(unsigned long state_filter)
5041 {
5042         struct task_struct *g, *p;
5043 
5044 #if BITS_PER_LONG == 32
5045         printk(KERN_INFO
5046                 "  task                PC stack   pid father\n");
5047 #else
5048         printk(KERN_INFO
5049                 "  task                        PC stack   pid father\n");
5050 #endif
5051         rcu_read_lock();
5052         for_each_process_thread(g, p) {
5053                 /*
5054                  * reset the NMI-timeout, listing all files on a slow
5055                  * console might take a lot of time:
5056                  */
5057                 touch_nmi_watchdog();
5058                 if (!state_filter || (p->state & state_filter))
5059                         sched_show_task(p);
5060         }
5061 
5062         touch_all_softlockup_watchdogs();
5063 
5064 #ifdef CONFIG_SCHED_DEBUG
5065         sysrq_sched_debug_show();
5066 #endif
5067         rcu_read_unlock();
5068         /*
5069          * Only show locks if all tasks are dumped:
5070          */
5071         if (!state_filter)
5072                 debug_show_all_locks();
5073 }
5074 
5075 void init_idle_bootup_task(struct task_struct *idle)
5076 {
5077         idle->sched_class = &idle_sched_class;
5078 }
5079 
5080 /**
5081  * init_idle - set up an idle thread for a given CPU
5082  * @idle: task in question
5083  * @cpu: cpu the idle task belongs to
5084  *
5085  * NOTE: this function does not set the idle thread's NEED_RESCHED
5086  * flag, to make booting more robust.
5087  */
5088 void init_idle(struct task_struct *idle, int cpu)
5089 {
5090         struct rq *rq = cpu_rq(cpu);
5091         unsigned long flags;
5092 
5093         raw_spin_lock_irqsave(&idle->pi_lock, flags);
5094         raw_spin_lock(&rq->lock);
5095 
5096         __sched_fork(0, idle);
5097         idle->state = TASK_RUNNING;
5098         idle->se.exec_start = sched_clock();
5099 
5100         kasan_unpoison_task_stack(idle);
5101 
5102 #ifdef CONFIG_SMP
5103         /*
5104          * Its possible that init_idle() gets called multiple times on a task,
5105          * in that case do_set_cpus_allowed() will not do the right thing.
5106          *
5107          * And since this is boot we can forgo the serialization.
5108          */
5109         set_cpus_allowed_common(idle, cpumask_of(cpu));
5110 #endif
5111         /*
5112          * We're having a chicken and egg problem, even though we are
5113          * holding rq->lock, the cpu isn't yet set to this cpu so the
5114          * lockdep check in task_group() will fail.
5115          *
5116          * Similar case to sched_fork(). / Alternatively we could
5117          * use task_rq_lock() here and obtain the other rq->lock.
5118          *
5119          * Silence PROVE_RCU
5120          */
5121         rcu_read_lock();
5122         __set_task_cpu(idle, cpu);
5123         rcu_read_unlock();
5124 
5125         rq->curr = rq->idle = idle;
5126         idle->on_rq = TASK_ON_RQ_QUEUED;
5127 #ifdef CONFIG_SMP
5128         idle->on_cpu = 1;
5129 #endif
5130         raw_spin_unlock(&rq->lock);
5131         raw_spin_unlock_irqrestore(&idle->pi_lock, flags);
5132 
5133         /* Set the preempt count _outside_ the spinlocks! */
5134         init_idle_preempt_count(idle, cpu);
5135 
5136         /*
5137          * The idle tasks have their own, simple scheduling class:
5138          */
5139         idle->sched_class = &idle_sched_class;
5140         ftrace_graph_init_idle_task(idle, cpu);
5141         vtime_init_idle(idle, cpu);
5142 #ifdef CONFIG_SMP
5143         sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu);
5144 #endif
5145 }
5146 
5147 int cpuset_cpumask_can_shrink(const struct cpumask *cur,
5148                               const struct cpumask *trial)
5149 {
5150         int ret = 1, trial_cpus;
5151         struct dl_bw *cur_dl_b;
5152         unsigned long flags;
5153 
5154         if (!cpumask_weight(cur))
5155                 return ret;
5156 
5157         rcu_read_lock_sched();
5158         cur_dl_b = dl_bw_of(cpumask_any(cur));
5159         trial_cpus = cpumask_weight(trial);
5160 
5161         raw_spin_lock_irqsave(&cur_dl_b->lock, flags);
5162         if (cur_dl_b->bw != -1 &&
5163             cur_dl_b->bw * trial_cpus < cur_dl_b->total_bw)
5164                 ret = 0;
5165         raw_spin_unlock_irqrestore(&cur_dl_b->lock, flags);
5166         rcu_read_unlock_sched();
5167 
5168         return ret;
5169 }
5170 
5171 int task_can_attach(struct task_struct *p,
5172                     const struct cpumask *cs_cpus_allowed)
5173 {
5174         int ret = 0;
5175 
5176         /*
5177          * Kthreads which disallow setaffinity shouldn't be moved
5178          * to a new cpuset; we don't want to change their cpu
5179          * affinity and isolating such threads by their set of
5180          * allowed nodes is unnecessary.  Thus, cpusets are not
5181          * applicable for such threads.  This prevents checking for
5182          * success of set_cpus_allowed_ptr() on all attached tasks
5183          * before cpus_allowed may be changed.
5184          */
5185         if (p->flags & PF_NO_SETAFFINITY) {
5186                 ret = -EINVAL;
5187                 goto out;
5188         }
5189 
5190 #ifdef CONFIG_SMP
5191         if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span,
5192                                               cs_cpus_allowed)) {
5193                 unsigned int dest_cpu = cpumask_any_and(cpu_active_mask,
5194                                                         cs_cpus_allowed);
5195                 struct dl_bw *dl_b;
5196                 bool overflow;
5197                 int cpus;
5198                 unsigned long flags;
5199 
5200                 rcu_read_lock_sched();
5201                 dl_b = dl_bw_of(dest_cpu);
5202                 raw_spin_lock_irqsave(&dl_b->lock, flags);
5203                 cpus = dl_bw_cpus(dest_cpu);
5204                 overflow = __dl_overflow(dl_b, cpus, 0, p->dl.dl_bw);
5205                 if (overflow)
5206                         ret = -EBUSY;
5207                 else {
5208                         /*
5209                          * We reserve space for this task in the destination
5210                          * root_domain, as we can't fail after this point.
5211                          * We will free resources in the source root_domain
5212                          * later on (see set_cpus_allowed_dl()).
5213                          */
5214                         __dl_add(dl_b, p->dl.dl_bw);
5215                 }
5216                 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
5217                 rcu_read_unlock_sched();
5218 
5219         }
5220 #endif
5221 out:
5222         return ret;
5223 }
5224 
5225 #ifdef CONFIG_SMP
5226 
5227 #ifdef CONFIG_NUMA_BALANCING
5228 /* Migrate current task p to target_cpu */
5229 int migrate_task_to(struct task_struct *p, int target_cpu)
5230 {
5231         struct migration_arg arg = { p, target_cpu };
5232         int curr_cpu = task_cpu(p);
5233 
5234         if (curr_cpu == target_cpu)
5235                 return 0;
5236 
5237         if (!cpumask_test_cpu(target_cpu, tsk_cpus_allowed(p)))
5238                 return -EINVAL;
5239 
5240         /* TODO: This is not properly updating schedstats */
5241 
5242         trace_sched_move_numa(p, curr_cpu, target_cpu);
5243         return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);
5244 }
5245 
5246 /*
5247  * Requeue a task on a given node and accurately track the number of NUMA
5248  * tasks on the runqueues
5249  */
5250 void sched_setnuma(struct task_struct *p, int nid)
5251 {
5252         struct rq *rq;
5253         unsigned long flags;
5254         bool queued, running;
5255 
5256         rq = task_rq_lock(p, &flags);
5257         queued = task_on_rq_queued(p);
5258         running = task_current(rq, p);
5259 
5260         if (queued)
5261                 dequeue_task(rq, p, DEQUEUE_SAVE);
5262         if (running)
5263                 put_prev_task(rq, p);
5264 
5265         p->numa_preferred_nid = nid;
5266 
5267         if (running)
5268                 p->sched_class->set_curr_task(rq);
5269         if (queued)
5270                 enqueue_task(rq, p, ENQUEUE_RESTORE);
5271         task_rq_unlock(rq, p, &flags);
5272 }
5273 #endif /* CONFIG_NUMA_BALANCING */
5274 
5275 #ifdef CONFIG_HOTPLUG_CPU
5276 /*
5277  * Ensures that the idle task is using init_mm right before its cpu goes
5278  * offline.
5279  */
5280 void idle_task_exit(void)
5281 {
5282         struct mm_struct *mm = current->active_mm;
5283 
5284         BUG_ON(cpu_online(smp_processor_id()));
5285 
5286         if (mm != &init_mm) {
5287                 switch_mm(mm, &init_mm, current);
5288                 finish_arch_post_lock_switch();
5289         }
5290         mmdrop(mm);
5291 }
5292 
5293 /*
5294  * Since this CPU is going 'away' for a while, fold any nr_active delta
5295  * we might have. Assumes we're called after migrate_tasks() so that the
5296  * nr_active count is stable.
5297  *
5298  * Also see the comment "Global load-average calculations".
5299  */
5300 static void calc_load_migrate(struct rq *rq)
5301 {
5302         long delta = calc_load_fold_active(rq);
5303         if (delta)
5304                 atomic_long_add(delta, &calc_load_tasks);
5305 }
5306 
5307 static void put_prev_task_fake(struct rq *rq, struct task_struct *prev)
5308 {
5309 }
5310 
5311 static const struct sched_class fake_sched_class = {
5312         .put_prev_task = put_prev_task_fake,
5313 };
5314 
5315 static struct task_struct fake_task = {
5316         /*
5317          * Avoid pull_{rt,dl}_task()
5318          */
5319         .prio = MAX_PRIO + 1,
5320         .sched_class = &fake_sched_class,
5321 };
5322 
5323 /*
5324  * Migrate all tasks from the rq, sleeping tasks will be migrated by
5325  * try_to_wake_up()->select_task_rq().
5326  *
5327  * Called with rq->lock held even though we'er in stop_machine() and
5328  * there's no concurrency possible, we hold the required locks anyway
5329  * because of lock validation efforts.
5330  */
5331 static void migrate_tasks(struct rq *dead_rq)
5332 {
5333         struct rq *rq = dead_rq;
5334         struct task_struct *next, *stop = rq->stop;
5335         int dest_cpu;
5336 
5337         /*
5338          * Fudge the rq selection such that the below task selection loop
5339          * doesn't get stuck on the currently eligible stop task.
5340          *
5341          * We're currently inside stop_machine() and the rq is either stuck
5342          * in the stop_machine_cpu_stop() loop, or we're executing this code,
5343          * either way we should never end up calling schedule() until we're
5344          * done here.
5345          */
5346         rq->stop = NULL;
5347 
5348         /*
5349          * put_prev_task() and pick_next_task() sched
5350          * class method both need to have an up-to-date
5351          * value of rq->clock[_task]
5352          */
5353         update_rq_clock(rq);
5354 
5355         for (;;) {
5356                 /*
5357                  * There's this thread running, bail when that's the only
5358                  * remaining thread.
5359                  */
5360                 if (rq->nr_running == 1)
5361                         break;
5362 
5363                 /*
5364                  * pick_next_task assumes pinned rq->lock.
5365                  */
5366                 lockdep_pin_lock(&rq->lock);
5367                 next = pick_next_task(rq, &fake_task);
5368                 BUG_ON(!next);
5369                 next->sched_class->put_prev_task(rq, next);
5370 
5371                 /*
5372                  * Rules for changing task_struct::cpus_allowed are holding
5373                  * both pi_lock and rq->lock, such that holding either
5374                  * stabilizes the mask.
5375                  *
5376                  * Drop rq->lock is not quite as disastrous as it usually is
5377                  * because !cpu_active at this point, which means load-balance
5378                  * will not interfere. Also, stop-machine.
5379                  */
5380                 lockdep_unpin_lock(&rq->lock);
5381                 raw_spin_unlock(&rq->lock);
5382                 raw_spin_lock(&next->pi_lock);
5383                 raw_spin_lock(&rq->lock);
5384 
5385                 /*
5386                  * Since we're inside stop-machine, _nothing_ should have
5387                  * changed the task, WARN if weird stuff happened, because in
5388                  * that case the above rq->lock drop is a fail too.
5389                  */
5390                 if (WARN_ON(task_rq(next) != rq || !task_on_rq_queued(next))) {
5391                         raw_spin_unlock(&next->pi_lock);
5392                         continue;
5393                 }
5394 
5395                 /* Find suitable destination for @next, with force if needed. */
5396                 dest_cpu = select_fallback_rq(dead_rq->cpu, next);
5397 
5398                 rq = __migrate_task(rq, next, dest_cpu);
5399                 if (rq != dead_rq) {
5400                         raw_spin_unlock(&rq->lock);
5401                         rq = dead_rq;
5402                         raw_spin_lock(&rq->lock);
5403                 }
5404                 raw_spin_unlock(&next->pi_lock);
5405         }
5406 
5407         rq->stop = stop;
5408 }
5409 #endif /* CONFIG_HOTPLUG_CPU */
5410 
5411 #if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_SYSCTL)
5412 
5413 static struct ctl_table sd_ctl_dir[] = {
5414         {
5415                 .procname       = "sched_domain",
5416                 .mode           = 0555,
5417         },
5418         {}
5419 };
5420 
5421 static struct ctl_table sd_ctl_root[] = {
5422         {
5423                 .procname       = "kernel",
5424                 .mode           = 0555,
5425                 .child          = sd_ctl_dir,
5426         },
5427         {}
5428 };
5429 
5430 static struct ctl_table *sd_alloc_ctl_entry(int n)
5431 {
5432         struct ctl_table *entry =
5433                 kcalloc(n, sizeof(struct ctl_table), GFP_KERNEL);
5434 
5435         return entry;
5436 }
5437 
5438 static void sd_free_ctl_entry(struct ctl_table **tablep)
5439 {
5440         struct ctl_table *entry;
5441 
5442         /*
5443          * In the intermediate directories, both the child directory and
5444          * procname are dynamically allocated and could fail but the mode
5445          * will always be set. In the lowest directory the names are
5446          * static strings and all have proc handlers.
5447          */
5448         for (entry = *tablep; entry->mode; entry++) {
5449                 if (entry->child)
5450                         sd_free_ctl_entry(&entry->child);
5451                 if (entry->proc_handler == NULL)
5452                         kfree(entry->procname);
5453         }
5454 
5455         kfree(*tablep);
5456         *tablep = NULL;
5457 }
5458 
5459 static int min_load_idx = 0;
5460 static int max_load_idx = CPU_LOAD_IDX_MAX-1;
5461 
5462 static void
5463 set_table_entry(struct ctl_table *entry,
5464                 const char *procname, void *data, int maxlen,
5465                 umode_t mode, proc_handler *proc_handler,
5466                 bool load_idx)
5467 {
5468         entry->procname = procname;
5469         entry->data = data;
5470         entry->maxlen = maxlen;
5471         entry->mode = mode;
5472         entry->proc_handler = proc_handler;
5473 
5474         if (load_idx) {
5475                 entry->extra1 = &min_load_idx;
5476                 entry->extra2 = &max_load_idx;
5477         }
5478 }
5479 
5480 static struct ctl_table *
5481 sd_alloc_ctl_domain_table(struct sched_domain *sd)
5482 {
5483         struct ctl_table *table = sd_alloc_ctl_entry(14);
5484 
5485         if (table == NULL)
5486                 return NULL;
5487 
5488         set_table_entry(&table[0], "min_interval", &sd->min_interval,
5489                 sizeof(long), 0644, proc_doulongvec_minmax, false);
5490         set_table_entry(&table[1], "max_interval", &sd->max_interval,
5491                 sizeof(long), 0644, proc_doulongvec_minmax, false);
5492         set_table_entry(&table[2], "busy_idx", &sd->busy_idx,
5493                 sizeof(int), 0644, proc_dointvec_minmax, true);
5494         set_table_entry(&table[3], "idle_idx", &sd->idle_idx,
5495                 sizeof(int), 0644, proc_dointvec_minmax, true);
5496         set_table_entry(&table[4], "newidle_idx", &sd->newidle_idx,
5497                 sizeof(int), 0644, proc_dointvec_minmax, true);
5498         set_table_entry(&table[5], "wake_idx", &sd->wake_idx,
5499                 sizeof(int), 0644, proc_dointvec_minmax, true);
5500         set_table_entry(&table[6], "forkexec_idx", &sd->forkexec_idx,
5501                 sizeof(int), 0644, proc_dointvec_minmax, true);
5502         set_table_entry(&table[7], "busy_factor", &sd->busy_factor,
5503                 sizeof(int), 0644, proc_dointvec_minmax, false);
5504         set_table_entry(&table[8], "imbalance_pct", &sd->imbalance_pct,
5505                 sizeof(int), 0644, proc_dointvec_minmax, false);
5506         set_table_entry(&table[9], "cache_nice_tries",
5507                 &sd->cache_nice_tries,
5508                 sizeof(int), 0644, proc_dointvec_minmax, false);
5509         set_table_entry(&table[10], "flags", &sd->flags,
5510                 sizeof(int), 0644, proc_dointvec_minmax, false);
5511         set_table_entry(&table[11], "max_newidle_lb_cost",
5512                 &sd->max_newidle_lb_cost,
5513                 sizeof(long), 0644, proc_doulongvec_minmax, false);
5514         set_table_entry(&table[12], "name", sd->name,
5515                 CORENAME_MAX_SIZE, 0444, proc_dostring, false);
5516         /* &table[13] is terminator */
5517 
5518         return table;
5519 }
5520 
5521 static struct ctl_table *sd_alloc_ctl_cpu_table(int cpu)
5522 {
5523         struct ctl_table *entry, *table;
5524         struct sched_domain *sd;
5525         int domain_num = 0, i;
5526         char buf[32];
5527 
5528         for_each_domain(cpu, sd)
5529                 domain_num++;
5530         entry = table = sd_alloc_ctl_entry(domain_num + 1);
5531         if (table == NULL)
5532                 return NULL;
5533 
5534         i = 0;
5535         for_each_domain(cpu, sd) {
5536                 snprintf(buf, 32, "domain%d", i);
5537                 entry->procname = kstrdup(buf, GFP_KERNEL);
5538                 entry->mode = 0555;
5539                 entry->child = sd_alloc_ctl_domain_table(sd);
5540                 entry++;
5541                 i++;
5542         }
5543         return table;
5544 }
5545 
5546 static struct ctl_table_header *sd_sysctl_header;
5547 static void register_sched_domain_sysctl(void)
5548 {
5549         int i, cpu_num = num_possible_cpus();
5550         struct ctl_table *entry = sd_alloc_ctl_entry(cpu_num + 1);
5551         char buf[32];
5552 
5553         WARN_ON(sd_ctl_dir[0].child);
5554         sd_ctl_dir[0].child = entry;
5555 
5556         if (entry == NULL)
5557                 return;
5558 
5559         for_each_possible_cpu(i) {
5560                 snprintf(buf, 32, "cpu%d", i);
5561                 entry->procname = kstrdup(buf, GFP_KERNEL);
5562                 entry->mode = 0555;
5563                 entry->child = sd_alloc_ctl_cpu_table(i);
5564                 entry++;
5565         }
5566 
5567         WARN_ON(sd_sysctl_header);
5568         sd_sysctl_header = register_sysctl_table(sd_ctl_root);
5569 }
5570 
5571 /* may be called multiple times per register */
5572 static void unregister_sched_domain_sysctl(void)
5573 {
5574         unregister_sysctl_table(sd_sysctl_header);
5575         sd_sysctl_header = NULL;
5576         if (sd_ctl_dir[0].child)
5577                 sd_free_ctl_entry(&sd_ctl_dir[0].child);
5578 }
5579 #else
5580 static void register_sched_domain_sysctl(void)
5581 {
5582 }
5583 static void unregister_sched_domain_sysctl(void)
5584 {
5585 }
5586 #endif /* CONFIG_SCHED_DEBUG && CONFIG_SYSCTL */
5587 
5588 static void set_rq_online(struct rq *rq)
5589 {
5590         if (!rq->online) {
5591                 const struct sched_class *class;
5592 
5593                 cpumask_set_cpu(rq->cpu, rq->rd->online);
5594                 rq->online = 1;
5595 
5596                 for_each_class(class) {
5597                         if (class->rq_online)
5598                                 class->rq_online(rq);
5599                 }
5600         }
5601 }
5602 
5603 static void set_rq_offline(struct rq *rq)
5604 {
5605         if (rq->online) {
5606                 const struct sched_class *class;
5607 
5608                 for_each_class(class) {
5609                         if (class->rq_offline)
5610                                 class->rq_offline(rq);
5611                 }
5612 
5613                 cpumask_clear_cpu(rq->cpu, rq->rd->online);
5614                 rq->online = 0;
5615         }
5616 }
5617 
5618 /*
5619  * migration_call - callback that gets triggered when a CPU is added.
5620  * Here we can start up the necessary migration thread for the new CPU.
5621  */
5622 static int
5623 migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
5624 {
5625         int cpu = (long)hcpu;
5626         unsigned long flags;
5627         struct rq *rq = cpu_rq(cpu);
5628 
5629         switch (action & ~CPU_TASKS_FROZEN) {
5630 
5631         case CPU_UP_PREPARE:
5632                 rq->calc_load_update = calc_load_update;
5633                 break;
5634 
5635         case CPU_ONLINE:
5636                 /* Update our root-domain */
5637                 raw_spin_lock_irqsave(&rq->lock, flags);
5638                 if (rq->rd) {
5639                         BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
5640 
5641                         set_rq_online(rq);
5642                 }
5643                 raw_spin_unlock_irqrestore(&rq->lock, flags);
5644                 break;
5645 
5646 #ifdef CONFIG_HOTPLUG_CPU
5647         case CPU_DYING:
5648                 sched_ttwu_pending();
5649                 /* Update our root-domain */
5650                 raw_spin_lock_irqsave(&rq->lock, flags);
5651                 if (rq->rd) {
5652                         BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
5653                         set_rq_offline(rq);
5654                 }
5655                 migrate_tasks(rq);
5656                 BUG_ON(rq->nr_running != 1); /* the migration thread */
5657                 raw_spin_unlock_irqrestore(&rq->lock, flags);
5658                 break;
5659 
5660         case CPU_DEAD:
5661                 calc_load_migrate(rq);
5662                 break;
5663 #endif
5664         }
5665 
5666         update_max_interval();
5667 
5668         return NOTIFY_OK;
5669 }
5670 
5671 /*
5672  * Register at high priority so that task migration (migrate_all_tasks)
5673  * happens before everything else.  This has to be lower priority than
5674  * the notifier in the perf_event subsystem, though.
5675  */
5676 static struct notifier_block migration_notifier = {
5677         .notifier_call = migration_call,
5678         .priority = CPU_PRI_MIGRATION,
5679 };
5680 
5681 static void set_cpu_rq_start_time(void)
5682 {
5683         int cpu = smp_processor_id();
5684         struct rq *rq = cpu_rq(cpu);
5685         rq->age_stamp = sched_clock_cpu(cpu);
5686 }
5687 
5688 static int sched_cpu_active(struct notifier_block *nfb,
5689                                       unsigned long action, void *hcpu)
5690 {
5691         int cpu = (long)hcpu;
5692 
5693         switch (action & ~CPU_TASKS_FROZEN) {
5694         case CPU_STARTING:
5695                 set_cpu_rq_start_time();
5696                 return NOTIFY_OK;
5697 
5698         case CPU_ONLINE:
5699                 /*
5700                  * At this point a starting CPU has marked itself as online via
5701                  * set_cpu_online(). But it might not yet have marked itself
5702                  * as active, which is essential from here on.
5703                  */
5704                 set_cpu_active(cpu, true);
5705                 stop_machine_unpark(cpu);
5706                 return NOTIFY_OK;
5707 
5708         case CPU_DOWN_FAILED:
5709                 set_cpu_active(cpu, true);
5710                 return NOTIFY_OK;
5711 
5712         default:
5713                 return NOTIFY_DONE;
5714         }
5715 }
5716 
5717 static int sched_cpu_inactive(struct notifier_block *nfb,
5718                                         unsigned long action, void *hcpu)
5719 {
5720         switch (action & ~CPU_TASKS_FROZEN) {
5721         case CPU_DOWN_PREPARE:
5722                 set_cpu_active((long)hcpu, false);
5723                 return NOTIFY_OK;
5724         default:
5725                 return NOTIFY_DONE;
5726         }
5727 }
5728 
5729 static int __init migration_init(void)
5730 {
5731         void *cpu = (void *)(long)smp_processor_id();
5732         int err;
5733 
5734         /* Initialize migration for the boot CPU */
5735         err = migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
5736         BUG_ON(err == NOTIFY_BAD);
5737         migration_call(&migration_notifier, CPU_ONLINE, cpu);
5738         register_cpu_notifier(&migration_notifier);
5739 
5740         /* Register cpu active notifiers */
5741         cpu_notifier(sched_cpu_active, CPU_PRI_SCHED_ACTIVE);
5742         cpu_notifier(sched_cpu_inactive, CPU_PRI_SCHED_INACTIVE);
5743 
5744         return 0;
5745 }
5746 early_initcall(migration_init);
5747 
5748 static cpumask_var_t sched_domains_tmpmask; /* sched_domains_mutex */
5749 
5750 #ifdef CONFIG_SCHED_DEBUG
5751 
5752 static __read_mostly int sched_debug_enabled;
5753 
5754 static int __init sched_debug_setup(char *str)
5755 {
5756         sched_debug_enabled = 1;
5757 
5758         return 0;
5759 }
5760 early_param("sched_debug", sched_debug_setup);
5761 
5762 static inline bool sched_debug(void)
5763 {
5764         return sched_debug_enabled;
5765 }
5766 
5767 static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,
5768                                   struct cpumask *groupmask)
5769 {
5770         struct sched_group *group = sd->groups;
5771 
5772         cpumask_clear(groupmask);
5773 
5774         printk(KERN_DEBUG "%*s domain %d: ", level, "", level);
5775 
5776         if (!(sd->flags & SD_LOAD_BALANCE)) {
5777                 printk("does not load-balance\n");
5778                 if (sd->parent)
5779                         printk(KERN_ERR "ERROR: !SD_LOAD_BALANCE domain"
5780                                         " has parent");
5781                 return -1;
5782         }
5783 
5784         printk(KERN_CONT "span %*pbl level %s\n",
5785                cpumask_pr_args(sched_domain_span(sd)), sd->name);
5786 
5787         if (!cpumask_test_cpu(cpu, sched_domain_span(sd))) {
5788                 printk(KERN_ERR "ERROR: domain->span does not contain "
5789                                 "CPU%d\n", cpu);
5790         }
5791         if (!cpumask_test_cpu(cpu, sched_group_cpus(group))) {
5792                 printk(KERN_ERR "ERROR: domain->groups does not contain"
5793                                 " CPU%d\n", cpu);
5794         }
5795 
5796         printk(KERN_DEBUG "%*s groups:", level + 1, "");
5797         do {
5798                 if (!group) {
5799                         printk("\n");
5800                         printk(KERN_ERR "ERROR: group is NULL\n");
5801                         break;
5802                 }
5803 
5804                 if (!cpumask_weight(sched_group_cpus(group))) {
5805                         printk(KERN_CONT "\n");
5806                         printk(KERN_ERR "ERROR: empty group\n");
5807                         break;
5808                 }
5809 
5810                 if (!(sd->flags & SD_OVERLAP) &&
5811                     cpumask_intersects(groupmask, sched_group_cpus(group))) {
5812                         printk(KERN_CONT "\n");
5813                         printk(KERN_ERR "ERROR: repeated CPUs\n");
5814                         break;
5815                 }
5816 
5817                 cpumask_or(groupmask, groupmask, sched_group_cpus(group));
5818 
5819                 printk(KERN_CONT " %*pbl",
5820                        cpumask_pr_args(sched_group_cpus(group)));
5821                 if (group->sgc->capacity != SCHED_CAPACITY_SCALE) {
5822                         printk(KERN_CONT " (cpu_capacity = %d)",
5823                                 group->sgc->capacity);
5824                 }
5825 
5826                 group = group->next;
5827         } while (group != sd->groups);
5828         printk(KERN_CONT "\n");
5829 
5830         if (!cpumask_equal(sched_domain_span(sd), groupmask))
5831                 printk(KERN_ERR "ERROR: groups don't span domain->span\n");
5832 
5833         if (sd->parent &&
5834             !cpumask_subset(groupmask, sched_domain_span(sd->parent)))
5835                 printk(KERN_ERR "ERROR: parent span is not a superset "
5836                         "of domain->span\n");
5837         return 0;
5838 }
5839 
5840 static void sched_domain_debug(struct sched_domain *sd, int cpu)
5841 {
5842         int level = 0;
5843 
5844         if (!sched_debug_enabled)
5845                 return;
5846 
5847         if (!sd) {
5848                 printk(KERN_DEBUG "CPU%d attaching NULL sched-domain.\n", cpu);
5849                 return;
5850         }
5851 
5852         printk(KERN_DEBUG "CPU%d attaching sched-domain:\n", cpu);
5853 
5854         for (;;) {
5855                 if (sched_domain_debug_one(sd, cpu, level, sched_domains_tmpmask))
5856                         break;
5857                 level++;
5858                 sd = sd->parent;
5859                 if (!sd)
5860                         break;
5861         }
5862 }
5863 #else /* !CONFIG_SCHED_DEBUG */
5864 # define sched_domain_debug(sd, cpu) do { } while (0)
5865 static inline bool sched_debug(void)
5866 {
5867         return false;
5868 }
5869 #endif /* CONFIG_SCHED_DEBUG */
5870 
5871 static int sd_degenerate(struct sched_domain *sd)
5872 {
5873         if (cpumask_weight(sched_domain_span(sd)) == 1)
5874                 return 1;
5875 
5876         /* Following flags need at least 2 groups */
5877         if (sd->flags & (SD_LOAD_BALANCE |
5878                          SD_BALANCE_NEWIDLE |
5879                          SD_BALANCE_FORK |
5880                          SD_BALANCE_EXEC |
5881                          SD_SHARE_CPUCAPACITY |
5882                          SD_SHARE_PKG_RESOURCES |
5883                          SD_SHARE_POWERDOMAIN)) {
5884                 if (sd->groups != sd->groups->next)
5885                         return 0;
5886         }
5887 
5888         /* Following flags don't use groups */
5889         if (sd->flags & (SD_WAKE_AFFINE))
5890                 return 0;
5891 
5892         return 1;
5893 }
5894 
5895 static int
5896 sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
5897 {
5898         unsigned long cflags = sd->flags, pflags = parent->flags;
5899 
5900         if (sd_degenerate(parent))
5901                 return 1;
5902 
5903         if (!cpumask_equal(sched_domain_span(sd), sched_domain_span(parent)))
5904                 return 0;
5905 
5906         /* Flags needing groups don't count if only 1 group in parent */
5907         if (parent->groups == parent->groups->next) {
5908                 pflags &= ~(SD_LOAD_BALANCE |
5909                                 SD_BALANCE_NEWIDLE |
5910                                 SD_BALANCE_FORK |
5911                                 SD_BALANCE_EXEC |
5912                                 SD_SHARE_CPUCAPACITY |
5913                                 SD_SHARE_PKG_RESOURCES |
5914                                 SD_PREFER_SIBLING |
5915                                 SD_SHARE_POWERDOMAIN);
5916                 if (nr_node_ids == 1)
5917                         pflags &= ~SD_SERIALIZE;
5918         }
5919         if (~cflags & pflags)
5920                 return 0;
5921 
5922         return 1;
5923 }
5924 
5925 static void free_rootdomain(struct rcu_head *rcu)
5926 {
5927         struct root_domain *rd = container_of(rcu, struct root_domain, rcu);
5928 
5929         cpupri_cleanup(&rd->cpupri);
5930         cpudl_cleanup(&rd->cpudl);
5931         free_cpumask_var(rd->dlo_mask);
5932         free_cpumask_var(rd->rto_mask);
5933         free_cpumask_var(rd->online);
5934         free_cpumask_var(rd->span);
5935         kfree(rd);
5936 }
5937 
5938 static void rq_attach_root(struct rq *rq, struct root_domain *rd)
5939 {
5940         struct root_domain *old_rd = NULL;
5941         unsigned long flags;
5942 
5943         raw_spin_lock_irqsave(&rq->lock, flags);
5944 
5945         if (rq->rd) {
5946                 old_rd = rq->rd;
5947 
5948                 if (cpumask_test_cpu(rq->cpu, old_rd->online))
5949                         set_rq_offline(rq);
5950 
5951                 cpumask_clear_cpu(rq->cpu, old_rd->span);
5952 
5953                 /*
5954                  * If we dont want to free the old_rd yet then
5955                  * set old_rd to NULL to skip the freeing later
5956                  * in this function:
5957                  */
5958                 if (!atomic_dec_and_test(&old_rd->refcount))
5959                         old_rd = NULL;
5960         }
5961 
5962         atomic_inc(&rd->refcount);
5963         rq->rd = rd;
5964 
5965         cpumask_set_cpu(rq->cpu, rd->span);
5966         if (cpumask_test_cpu(rq->cpu, cpu_active_mask))
5967                 set_rq_online(rq);
5968 
5969         raw_spin_unlock_irqrestore(&rq->lock, flags);
5970 
5971         if (old_rd)
5972                 call_rcu_sched(&old_rd->rcu, free_rootdomain);
5973 }
5974 
5975 static int init_rootdomain(struct root_domain *rd)
5976 {
5977         memset(rd, 0, sizeof(*rd));
5978 
5979         if (!zalloc_cpumask_var(&rd->span, GFP_KERNEL))
5980                 goto out;
5981         if (!zalloc_cpumask_var(&rd->online, GFP_KERNEL))
5982                 goto free_span;
5983         if (!zalloc_cpumask_var(&rd->dlo_mask, GFP_KERNEL))
5984                 goto free_online;
5985         if (!zalloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))
5986                 goto free_dlo_mask;
5987 
5988         init_dl_bw(&rd->dl_bw);
5989         if (cpudl_init(&rd->cpudl) != 0)
5990                 goto free_dlo_mask;
5991 
5992         if (cpupri_init(&rd->cpupri) != 0)
5993                 goto free_rto_mask;
5994         return 0;
5995 
5996 free_rto_mask:
5997         free_cpumask_var(rd->rto_mask);
5998 free_dlo_mask:
5999         free_cpumask_var(rd->dlo_mask);
6000 free_online:
6001         free_cpumask_var(rd->online);
6002 free_span:
6003         free_cpumask_var(rd->span);
6004 out:
6005         return -ENOMEM;
6006 }
6007 
6008 /*
6009  * By default the system creates a single root-domain with all cpus as
6010  * members (mimicking the global state we have today).
6011  */
6012 struct root_domain def_root_domain;
6013 
6014 static void init_defrootdomain(void)
6015 {
6016         init_rootdomain(&def_root_domain);
6017 
6018         atomic_set(&def_root_domain.refcount, 1);
6019 }
6020 
6021 static struct root_domain *alloc_rootdomain(void)
6022 {
6023         struct root_domain *rd;
6024 
6025         rd = kmalloc(sizeof(*rd), GFP_KERNEL);
6026         if (!rd)
6027                 return NULL;
6028 
6029         if (init_rootdomain(rd) != 0) {
6030                 kfree(rd);
6031                 return NULL;
6032         }
6033 
6034         return rd;
6035 }
6036 
6037 static void free_sched_groups(struct sched_group *sg, int free_sgc)
6038 {
6039         struct sched_group *tmp, *first;
6040 
6041         if (!sg)
6042                 return;
6043 
6044         first = sg;
6045         do {
6046                 tmp = sg->next;
6047 
6048                 if (free_sgc && atomic_dec_and_test(&sg->sgc->ref))
6049                         kfree(sg->sgc);
6050 
6051                 kfree(sg);
6052                 sg = tmp;
6053         } while (sg != first);
6054 }
6055 
6056 static void free_sched_domain(struct rcu_head *rcu)
6057 {
6058         struct sched_domain *sd = container_of(rcu, struct sched_domain, rcu);
6059 
6060         /*
6061          * If its an overlapping domain it has private groups, iterate and
6062          * nuke them all.
6063          */
6064         if (sd->flags & SD_OVERLAP) {
6065                 free_sched_groups(sd->groups, 1);
6066         } else if (atomic_dec_and_test(&sd->groups->ref)) {
6067                 kfree(sd->groups->sgc);
6068                 kfree(sd->groups);
6069         }
6070         kfree(sd);
6071 }
6072 
6073 static void destroy_sched_domain(struct sched_domain *sd, int cpu)
6074 {
6075         call_rcu(&sd->rcu, free_sched_domain);
6076 }
6077 
6078 static void destroy_sched_domains(struct sched_domain *sd, int cpu)
6079 {
6080         for (; sd; sd = sd->parent)
6081                 destroy_sched_domain(sd, cpu);
6082 }
6083 
6084 /*
6085  * Keep a special pointer to the highest sched_domain that has
6086  * SD_SHARE_PKG_RESOURCE set (Last Level Cache Domain) for this
6087  * allows us to avoid some pointer chasing select_idle_sibling().
6088  *
6089  * Also keep a unique ID per domain (we use the first cpu number in
6090  * the cpumask of the domain), this allows us to quickly tell if
6091  * two cpus are in the same cache domain, see cpus_share_cache().
6092  */
6093 DEFINE_PER_CPU(struct sched_domain *, sd_llc);
6094 DEFINE_PER_CPU(int, sd_llc_size);
6095 DEFINE_PER_CPU(int, sd_llc_id);
6096 DEFINE_PER_CPU(struct sched_domain *, sd_numa);
6097 DEFINE_PER_CPU(struct sched_domain *, sd_busy);
6098 DEFINE_PER_CPU(struct sched_domain *, sd_asym);
6099 
6100 static void update_top_cache_domain(int cpu)
6101 {
6102         struct sched_domain *sd;
6103         struct sched_domain *busy_sd = NULL;
6104         int id = cpu;
6105         int size = 1;
6106 
6107         sd = highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES);
6108         if (sd) {
6109                 id = cpumask_first(sched_domain_span(sd));
6110                 size = cpumask_weight(sched_domain_span(sd));
6111                 busy_sd = sd->parent; /* sd_busy */
6112         }
6113         rcu_assign_pointer(per_cpu(sd_busy, cpu), busy_sd);
6114 
6115         rcu_assign_pointer(per_cpu(sd_llc, cpu), sd);
6116         per_cpu(sd_llc_size, cpu) = size;
6117         per_cpu(sd_llc_id, cpu) = id;
6118 
6119         sd = lowest_flag_domain(cpu, SD_NUMA);
6120         rcu_assign_pointer(per_cpu(sd_numa, cpu), sd);
6121 
6122         sd = highest_flag_domain(cpu, SD_ASYM_PACKING);
6123         rcu_assign_pointer(per_cpu(sd_asym, cpu), sd);
6124 }
6125 
6126 /*
6127  * Attach the domain 'sd' to 'cpu' as its base domain. Callers must
6128  * hold the hotplug lock.
6129  */
6130 static void
6131 cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
6132 {
6133         struct rq *rq = cpu_rq(cpu);
6134         struct sched_domain *tmp;
6135 
6136         /* Remove the sched domains which do not contribute to scheduling. */
6137         for (tmp = sd; tmp; ) {
6138                 struct sched_domain *parent = tmp->parent;
6139                 if (!parent)
6140                         break;
6141 
6142                 if (sd_parent_degenerate(tmp, parent)) {
6143                         tmp->parent = parent->parent;
6144                         if (parent->parent)
6145                                 parent->parent->child = tmp;
6146                         /*
6147                          * Transfer SD_PREFER_SIBLING down in case of a
6148                          * degenerate parent; the spans match for this
6149                          * so the property transfers.
6150                          */
6151                         if (parent->flags & SD_PREFER_SIBLING)
6152                                 tmp->flags |= SD_PREFER_SIBLING;
6153                         destroy_sched_domain(parent, cpu);
6154                 } else
6155                         tmp = tmp->parent;
6156         }
6157 
6158         if (sd && sd_degenerate(sd)) {
6159                 tmp = sd;
6160                 sd = sd->parent;
6161                 destroy_sched_domain(tmp, cpu);
6162                 if (sd)
6163                         sd->child = NULL;
6164         }
6165 
6166         sched_domain_debug(sd, cpu);
6167 
6168         rq_attach_root(rq, rd);
6169         tmp = rq->sd;
6170         rcu_assign_pointer(rq->sd, sd);
6171         destroy_sched_domains(tmp, cpu);
6172 
6173         update_top_cache_domain(cpu);
6174 }
6175 
6176 /* Setup the mask of cpus configured for isolated domains */
6177 static int __init isolated_cpu_setup(char *str)
6178 {
6179         alloc_bootmem_cpumask_var(&cpu_isolated_map);
6180         cpulist_parse(str, cpu_isolated_map);
6181         return 1;
6182 }
6183 
6184 __setup("isolcpus=", isolated_cpu_setup);
6185 
6186 struct s_data {
6187         struct sched_domain ** __percpu sd;
6188         struct root_domain      *rd;
6189 };
6190 
6191 enum s_alloc {
6192         sa_rootdomain,
6193         sa_sd,
6194         sa_sd_storage,
6195         sa_none,
6196 };
6197 
6198 /*
6199  * Build an iteration mask that can exclude certain CPUs from the upwards
6200  * domain traversal.
6201  *
6202  * Asymmetric node setups can result in situations where the domain tree is of
6203  * unequal depth, make sure to skip domains that already cover the entire
6204  * range.
6205  *
6206  * In that case build_sched_domains() will have terminated the iteration early
6207  * and our sibling sd spans will be empty. Domains should always include the
6208  * cpu they're built on, so check that.
6209  *
6210  */
6211 static void build_group_mask(struct sched_domain *sd, struct sched_group *sg)
6212 {
6213         const struct cpumask *span = sched_domain_span(sd);
6214         struct sd_data *sdd = sd->private;
6215         struct sched_domain *sibling;
6216         int i;
6217 
6218         for_each_cpu(i, span) {
6219                 sibling = *per_cpu_ptr(sdd->sd, i);
6220                 if (!cpumask_test_cpu(i, sched_domain_span(sibling)))
6221                         continue;
6222 
6223                 cpumask_set_cpu(i, sched_group_mask(sg));
6224         }
6225 }
6226 
6227 /*
6228  * Return the canonical balance cpu for this group, this is the first cpu
6229  * of this group that's also in the iteration mask.
6230  */
6231 int group_balance_cpu(struct sched_group *sg)
6232 {
6233         return cpumask_first_and(sched_group_cpus(sg), sched_group_mask(sg));
6234 }
6235 
6236 static int
6237 build_overlap_sched_groups(struct sched_domain *sd, int cpu)
6238 {
6239         struct sched_group *first = NULL, *last = NULL, *groups = NULL, *sg;
6240         const struct cpumask *span = sched_domain_span(sd);
6241         struct cpumask *covered = sched_domains_tmpmask;
6242         struct sd_data *sdd = sd->private;
6243         struct sched_domain *sibling;
6244         int i;
6245 
6246         cpumask_clear(covered);
6247 
6248         for_each_cpu(i, span) {
6249                 struct cpumask *sg_span;
6250 
6251                 if (cpumask_test_cpu(i, covered))
6252                         continue;
6253 
6254                 sibling = *per_cpu_ptr(sdd->sd, i);
6255 
6256                 /* See the comment near build_group_mask(). */
6257                 if (!cpumask_test_cpu(i, sched_domain_span(sibling)))
6258                         continue;
6259 
6260                 sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(),
6261                                 GFP_KERNEL, cpu_to_node(cpu));
6262 
6263                 if (!sg)
6264                         goto fail;
6265 
6266                 sg_span = sched_group_cpus(sg);
6267                 if (sibling->child)
6268                         cpumask_copy(sg_span, sched_domain_span(sibling->child));
6269                 else
6270                         cpumask_set_cpu(i, sg_span);
6271 
6272                 cpumask_or(covered, covered, sg_span);
6273 
6274                 sg->sgc = *per_cpu_ptr(sdd->sgc, i);
6275                 if (atomic_inc_return(&sg->sgc->ref) == 1)
6276                         build_group_mask(sd, sg);
6277 
6278                 /*
6279                  * Initialize sgc->capacity such that even if we mess up the
6280                  * domains and no possible iteration will get us here, we won't
6281                  * die on a /0 trap.
6282                  */
6283                 sg->sgc->capacity = SCHED_CAPACITY_SCALE * cpumask_weight(sg_span);
6284 
6285                 /*
6286                  * Make sure the first group of this domain contains the
6287                  * canonical balance cpu. Otherwise the sched_domain iteration
6288                  * breaks. See update_sg_lb_stats().
6289                  */
6290                 if ((!groups && cpumask_test_cpu(cpu, sg_span)) ||
6291                     group_balance_cpu(sg) == cpu)
6292                         groups = sg;
6293 
6294                 if (!first)
6295                         first = sg;
6296                 if (last)
6297                         last->next = sg;
6298                 last = sg;
6299                 last->next = first;
6300         }
6301         sd->groups = groups;
6302 
6303         return 0;
6304 
6305 fail:
6306         free_sched_groups(first, 0);
6307 
6308         return -ENOMEM;
6309 }
6310 
6311 static int get_group(int cpu, struct sd_data *sdd, struct sched_group **sg)
6312 {
6313         struct sched_domain *sd = *per_cpu_ptr(sdd->sd, cpu);
6314         struct sched_domain *child = sd->child;
6315 
6316         if (child)
6317                 cpu = cpumask_first(sched_domain_span(child));
6318 
6319         if (sg) {
6320                 *sg = *per_cpu_ptr(sdd->sg, cpu);
6321                 (*sg)->sgc = *per_cpu_ptr(sdd->sgc, cpu);
6322                 atomic_set(&(*sg)->sgc->ref, 1); /* for claim_allocations */
6323         }
6324 
6325         return cpu;
6326 }
6327 
6328 /*
6329  * build_sched_groups will build a circular linked list of the groups
6330  * covered by the given span, and will set each group's ->cpumask correctly,
6331  * and ->cpu_capacity to 0.
6332  *
6333  * Assumes the sched_domain tree is fully constructed
6334  */
6335 static int
6336 build_sched_groups(struct sched_domain *sd, int cpu)
6337 {
6338         struct sched_group *first = NULL, *last = NULL;
6339         struct sd_data *sdd = sd->private;
6340         const struct cpumask *span = sched_domain_span(sd);
6341         struct cpumask *covered;
6342         int i;
6343 
6344         get_group(cpu, sdd, &sd->groups);
6345         atomic_inc(&sd->groups->ref);
6346 
6347         if (cpu != cpumask_first(span))
6348                 return 0;
6349 
6350         lockdep_assert_held(&sched_domains_mutex);
6351         covered = sched_domains_tmpmask;
6352 
6353         cpumask_clear(covered);
6354 
6355         for_each_cpu(i, span) {
6356                 struct sched_group *sg;
6357                 int group, j;
6358 
6359                 if (cpumask_test_cpu(i, covered))
6360                         continue;
6361 
6362                 group = get_group(i, sdd, &sg);
6363                 cpumask_setall(sched_group_mask(sg));
6364 
6365                 for_each_cpu(j, span) {
6366                         if (get_group(j, sdd, NULL) != group)
6367                                 continue;
6368 
6369                         cpumask_set_cpu(j, covered);
6370                         cpumask_set_cpu(j, sched_group_cpus(sg));
6371                 }
6372 
6373                 if (!first)
6374                         first = sg;
6375                 if (last)
6376                         last->next = sg;
6377                 last = sg;
6378         }
6379         last->next = first;
6380 
6381         return 0;
6382 }
6383 
6384 /*
6385  * Initialize sched groups cpu_capacity.
6386  *
6387  * cpu_capacity indicates the capacity of sched group, which is used while
6388  * distributing the load between different sched groups in a sched domain.
6389  * Typically cpu_capacity for all the groups in a sched domain will be same
6390  * unless there are asymmetries in the topology. If there are asymmetries,
6391  * group having more cpu_capacity will pickup more load compared to the
6392  * group having less cpu_capacity.
6393  */
6394 static void init_sched_groups_capacity(int cpu, struct sched_domain *sd)
6395 {
6396         struct sched_group *sg = sd->groups;
6397 
6398         WARN_ON(!sg);
6399 
6400         do {
6401                 sg->group_weight = cpumask_weight(sched_group_cpus(sg));
6402                 sg = sg->next;
6403         } while (sg != sd->groups);
6404 
6405         if (cpu != group_balance_cpu(sg))
6406                 return;
6407 
6408         update_group_capacity(sd, cpu);
6409         atomic_set(&sg->sgc->nr_busy_cpus, sg->group_weight);
6410 }
6411 
6412 /*
6413  * Initializers for schedule domains
6414  * Non-inlined to reduce accumulated stack pressure in build_sched_domains()
6415  */
6416 
6417 static int default_relax_domain_level = -1;
6418 int sched_domain_level_max;
6419 
6420 static int __init setup_relax_domain_level(char *str)
6421 {
6422         if (kstrtoint(str, 0, &default_relax_domain_level))
6423                 pr_warn("Unable to set relax_domain_level\n");
6424 
6425         return 1;
6426 }
6427 __setup("relax_domain_level=", setup_relax_domain_level);
6428 
6429 static void set_domain_attribute(struct sched_domain *sd,
6430                                  struct sched_domain_attr *attr)
6431 {
6432         int request;
6433 
6434         if (!attr || attr->relax_domain_level < 0) {
6435                 if (default_relax_domain_level < 0)
6436                         return;
6437                 else
6438                         request = default_relax_domain_level;
6439         } else
6440                 request = attr->relax_domain_level;
6441         if (request < sd->level) {
6442                 /* turn off idle balance on this domain */
6443                 sd->flags &= ~(SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
6444         } else {
6445                 /* turn on idle balance on this domain */
6446                 sd->flags |= (SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
6447         }
6448 }
6449 
6450 static void __sdt_free(const struct cpumask *cpu_map);
6451 static int __sdt_alloc(const struct cpumask *cpu_map);
6452 
6453 static void __free_domain_allocs(struct s_data *d, enum s_alloc what,
6454                                  const struct cpumask *cpu_map)
6455 {
6456         switch (what) {
6457         case sa_rootdomain:
6458                 if (!atomic_read(&d->rd->refcount))
6459                         free_rootdomain(&d->rd->rcu); /* fall through */
6460         case sa_sd:
6461                 free_percpu(d->sd); /* fall through */
6462         case sa_sd_storage:
6463                 __sdt_free(cpu_map); /* fall through */
6464         case sa_none:
6465                 break;
6466         }
6467 }
6468 
6469 static enum s_alloc __visit_domain_allocation_hell(struct s_data *d,
6470                                                    const struct cpumask *cpu_map)
6471 {
6472         memset(d, 0, sizeof(*d));
6473 
6474         if (__sdt_alloc(cpu_map))
6475                 return sa_sd_storage;
6476         d->sd = alloc_percpu(struct sched_domain *);
6477         if (!d->sd)
6478                 return sa_sd_storage;
6479         d->rd = alloc_rootdomain();
6480         if (!d->rd)
6481                 return sa_sd;
6482         return sa_rootdomain;
6483 }
6484 
6485 /*
6486  * NULL the sd_data elements we've used to build the sched_domain and
6487  * sched_group structure so that the subsequent __free_domain_allocs()
6488  * will not free the data we're using.
6489  */
6490 static void claim_allocations(int cpu, struct sched_domain *sd)
6491 {
6492         struct sd_data *sdd = sd->private;
6493 
6494         WARN_ON_ONCE(*per_cpu_ptr(sdd->sd, cpu) != sd);
6495         *per_cpu_ptr(sdd->sd, cpu) = NULL;
6496 
6497         if (atomic_read(&(*per_cpu_ptr(sdd->sg, cpu))->ref))
6498                 *per_cpu_ptr(sdd->sg, cpu) = NULL;
6499 
6500         if (atomic_read(&(*per_cpu_ptr(sdd->sgc, cpu))->ref))
6501                 *per_cpu_ptr(sdd->sgc, cpu) = NULL;
6502 }
6503 
6504 #ifdef CONFIG_NUMA
6505 static int sched_domains_numa_levels;
6506 enum numa_topology_type sched_numa_topology_type;
6507 static int *sched_domains_numa_distance;
6508 int sched_max_numa_distance;
6509 static struct cpumask ***sched_domains_numa_masks;
6510 static int sched_domains_curr_level;
6511 #endif
6512 
6513 /*
6514  * SD_flags allowed in topology descriptions.
6515  *
6516  * SD_SHARE_CPUCAPACITY      - describes SMT topologies
6517  * SD_SHARE_PKG_RESOURCES - describes shared caches
6518  * SD_NUMA                - describes NUMA topologies
6519  * SD_SHARE_POWERDOMAIN   - describes shared power domain
6520  *
6521  * Odd one out:
6522  * SD_ASYM_PACKING        - describes SMT quirks
6523  */
6524 #define TOPOLOGY_SD_FLAGS               \
6525         (SD_SHARE_CPUCAPACITY |         \
6526          SD_SHARE_PKG_RESOURCES |       \
6527          SD_NUMA |                      \
6528          SD_ASYM_PACKING |              \
6529          SD_SHARE_POWERDOMAIN)
6530 
6531 static struct sched_domain *
6532 sd_init(struct sched_domain_topology_level *tl, int cpu)
6533 {
6534         struct sched_domain *sd = *per_cpu_ptr(tl->data.sd, cpu);
6535         int sd_weight, sd_flags = 0;
6536 
6537 #ifdef CONFIG_NUMA
6538         /*
6539          * Ugly hack to pass state to sd_numa_mask()...
6540          */
6541         sched_domains_curr_level = tl->numa_level;
6542 #endif
6543 
6544         sd_weight = cpumask_weight(tl->mask(cpu));
6545 
6546         if (tl->sd_flags)
6547                 sd_flags = (*tl->sd_flags)();
6548         if (WARN_ONCE(sd_flags & ~TOPOLOGY_SD_FLAGS,
6549                         "wrong sd_flags in topology description\n"))
6550                 sd_flags &= ~TOPOLOGY_SD_FLAGS;
6551 
6552         *sd = (struct sched_domain){
6553                 .min_interval           = sd_weight,
6554                 .max_interval           = 2*sd_weight,
6555                 .busy_factor            = 32,
6556                 .imbalance_pct          = 125,
6557 
6558                 .cache_nice_tries       = 0,
6559                 .busy_idx               = 0,
6560                 .idle_idx               = 0,
6561                 .newidle_idx            = 0,
6562                 .wake_idx               = 0,
6563                 .forkexec_idx           = 0,
6564 
6565                 .flags                  = 1*SD_LOAD_BALANCE
6566                                         | 1*SD_BALANCE_NEWIDLE
6567                                         | 1*SD_BALANCE_EXEC
6568                                         | 1*SD_BALANCE_FORK
6569                                         | 0*SD_BALANCE_WAKE
6570                                         | 1*SD_WAKE_AFFINE
6571                                         | 0*SD_SHARE_CPUCAPACITY
6572                                         | 0*SD_SHARE_PKG_RESOURCES
6573                                         | 0*SD_SERIALIZE
6574                                         | 0*SD_PREFER_SIBLING
6575                                         | 0*SD_NUMA
6576                                         | sd_flags
6577                                         ,
6578 
6579                 .last_balance           = jiffies,
6580                 .balance_interval       = sd_weight,
6581                 .smt_gain               = 0,
6582                 .max_newidle_lb_cost    = 0,
6583                 .next_decay_max_lb_cost = jiffies,
6584 #ifdef CONFIG_SCHED_DEBUG
6585                 .name                   = tl->name,
6586 #endif
6587         };
6588 
6589         /*
6590          * Convert topological properties into behaviour.
6591          */
6592 
6593         if (sd->flags & SD_SHARE_CPUCAPACITY) {
6594                 sd->flags |= SD_PREFER_SIBLING;
6595                 sd->imbalance_pct = 110;
6596                 sd->smt_gain = 1178; /* ~15% */
6597 
6598         } else if (sd->flags & SD_SHARE_PKG_RESOURCES) {
6599                 sd->imbalance_pct = 117;
6600                 sd->cache_nice_tries = 1;
6601                 sd->busy_idx = 2;
6602 
6603 #ifdef CONFIG_NUMA
6604         } else if (sd->flags & SD_NUMA) {
6605                 sd->cache_nice_tries = 2;
6606                 sd->busy_idx = 3;
6607                 sd->idle_idx = 2;
6608 
6609                 sd->flags |= SD_SERIALIZE;
6610                 if (sched_domains_numa_distance[tl->numa_level] > RECLAIM_DISTANCE) {
6611                         sd->flags &= ~(SD_BALANCE_EXEC |
6612                                        SD_BALANCE_FORK |
6613                                        SD_WAKE_AFFINE);
6614                 }
6615 
6616 #endif
6617         } else {
6618                 sd->flags |= SD_PREFER_SIBLING;
6619                 sd->cache_nice_tries = 1;
6620                 sd->busy_idx = 2;
6621                 sd->idle_idx = 1;
6622         }
6623 
6624         sd->private = &tl->data;
6625 
6626         return sd;
6627 }
6628 
6629 /*
6630  * Topology list, bottom-up.
6631  */
6632 static struct sched_domain_topology_level default_topology[] = {
6633 #ifdef CONFIG_SCHED_SMT
6634         { cpu_smt_mask, cpu_smt_flags, SD_INIT_NAME(SMT) },
6635 #endif
6636 #ifdef CONFIG_SCHED_MC
6637         { cpu_coregroup_mask, cpu_core_flags, SD_INIT_NAME(MC) },
6638 #endif
6639         { cpu_cpu_mask, SD_INIT_NAME(DIE) },
6640         { NULL, },
6641 };
6642 
6643 static struct sched_domain_topology_level *sched_domain_topology =
6644         default_topology;
6645 
6646 #define for_each_sd_topology(tl)                        \
6647         for (tl = sched_domain_topology; tl->mask; tl++)
6648 
6649 void set_sched_topology(struct sched_domain_topology_level *tl)
6650 {
6651         sched_domain_topology = tl;
6652 }
6653 
6654 #ifdef CONFIG_NUMA
6655 
6656 static const struct cpumask *sd_numa_mask(int cpu)
6657 {
6658         return sched_domains_numa_masks[sched_domains_curr_level][cpu_to_node(cpu)];
6659 }
6660 
6661 static void sched_numa_warn(const char *str)
6662 {
6663         static int done = false;
6664         int i,j;
6665 
6666         if (done)
6667                 return;
6668 
6669         done = true;
6670 
6671         printk(KERN_WARNING "ERROR: %s\n\n", str);
6672 
6673         for (i = 0; i < nr_node_ids; i++) {
6674                 printk(KERN_WARNING "  ");
6675                 for (j = 0; j < nr_node_ids; j++)
6676                         printk(KERN_CONT "%02d ", node_distance(i,j));
6677                 printk(KERN_CONT "\n");
6678         }
6679         printk(KERN_WARNING "\n");
6680 }
6681 
6682 bool find_numa_distance(int distance)
6683 {
6684         int i;
6685 
6686         if (distance == node_distance(0, 0))
6687                 return true;
6688 
6689         for (i = 0; i < sched_domains_numa_levels; i++) {
6690                 if (sched_domains_numa_distance[i] == distance)
6691                         return true;
6692         }
6693 
6694         return false;
6695 }
6696 
6697 /*
6698  * A system can have three types of NUMA topology:
6699  * NUMA_DIRECT: all nodes are directly connected, or not a NUMA system
6700  * NUMA_GLUELESS_MESH: some nodes reachable through intermediary nodes
6701  * NUMA_BACKPLANE: nodes can reach other nodes through a backplane
6702  *
6703  * The difference between a glueless mesh topology and a backplane
6704  * topology lies in whether communication between not directly
6705  * connected nodes goes through intermediary nodes (where programs
6706  * could run), or through backplane controllers. This affects
6707  * placement of programs.
6708  *
6709  * The type of topology can be discerned with the following tests:
6710  * - If the maximum distance between any nodes is 1 hop, the system
6711  *   is directly connected.
6712  * - If for two nodes A and B, located N > 1 hops away from each other,
6713  *   there is an intermediary node C, which is < N hops away from both
6714  *   nodes A and B, the system is a glueless mesh.
6715  */
6716 static void init_numa_topology_type(void)
6717 {
6718         int a, b, c, n;
6719 
6720         n = sched_max_numa_distance;
6721 
6722         if (sched_domains_numa_levels <= 1) {
6723                 sched_numa_topology_type = NUMA_DIRECT;
6724                 return;
6725         }
6726 
6727         for_each_online_node(a) {
6728                 for_each_online_node(b) {
6729                         /* Find two nodes furthest removed from each other. */
6730                         if (node_distance(a, b) < n)
6731                                 continue;
6732 
6733                         /* Is there an intermediary node between a and b? */
6734                         for_each_online_node(c) {
6735                                 if (node_distance(a, c) < n &&
6736                                     node_distance(b, c) < n) {
6737                                         sched_numa_topology_type =
6738                                                         NUMA_GLUELESS_MESH;
6739                                         return;
6740                                 }
6741                         }
6742 
6743                         sched_numa_topology_type = NUMA_BACKPLANE;
6744                         return;
6745                 }
6746         }
6747 }
6748 
6749 static void sched_init_numa(void)
6750 {
6751         int next_distance, curr_distance = node_distance(0, 0);
6752         struct sched_domain_topology_level *tl;
6753         int level = 0;
6754         int i, j, k;
6755 
6756         sched_domains_numa_distance = kzalloc(sizeof(int) * nr_node_ids, GFP_KERNEL);
6757         if (!sched_domains_numa_distance)
6758                 return;
6759 
6760         /*
6761          * O(nr_nodes^2) deduplicating selection sort -- in order to find the
6762          * unique distances in the node_distance() table.
6763          *
6764          * Assumes node_distance(0,j) includes all distances in
6765          * node_distance(i,j) in order to avoid cubic time.
6766          */
6767         next_distance = curr_distance;
6768         for (i = 0; i < nr_node_ids; i++) {
6769                 for (j = 0; j < nr_node_ids; j++) {
6770                         for (k = 0; k < nr_node_ids; k++) {
6771                                 int distance = node_distance(i, k);
6772 
6773                                 if (distance > curr_distance &&
6774                                     (distance < next_distance ||
6775                                      next_distance == curr_distance))
6776                                         next_distance = distance;
6777 
6778                                 /*
6779                                  * While not a strong assumption it would be nice to know
6780                                  * about cases where if node A is connected to B, B is not
6781                                  * equally connected to A.
6782                                  */
6783                                 if (sched_debug() && node_distance(k, i) != distance)
6784                                         sched_numa_warn("Node-distance not symmetric");
6785 
6786                                 if (sched_debug() && i && !find_numa_distance(distance))
6787                                         sched_numa_warn("Node-0 not representative");
6788                         }
6789                         if (next_distance != curr_distance) {
6790                                 sched_domains_numa_distance[level++] = next_distance;
6791                                 sched_domains_numa_levels = level;
6792                                 curr_distance = next_distance;
6793                         } else break;
6794                 }
6795 
6796                 /*
6797                  * In case of sched_debug() we verify the above assumption.
6798                  */
6799                 if (!sched_debug())
6800                         break;
6801         }
6802 
6803         if (!level)
6804                 return;
6805 
6806         /*
6807          * 'level' contains the number of unique distances, excluding the
6808          * identity distance node_distance(i,i).
6809          *
6810          * The sched_domains_numa_distance[] array includes the actual distance
6811          * numbers.
6812          */
6813 
6814         /*
6815          * Here, we should temporarily reset sched_domains_numa_levels to 0.
6816          * If it fails to allocate memory for array sched_domains_numa_masks[][],
6817          * the array will contain less then 'level' members. This could be
6818          * dangerous when we use it to iterate array sched_domains_numa_masks[][]
6819          * in other functions.
6820          *
6821          * We reset it to 'level' at the end of this function.
6822          */
6823         sched_domains_numa_levels = 0;
6824 
6825         sched_domains_numa_masks = kzalloc(sizeof(void *) * level, GFP_KERNEL);
6826         if (!sched_domains_numa_masks)
6827                 return;
6828 
6829         /*
6830          * Now for each level, construct a mask per node which contains all
6831          * cpus of nodes that are that many hops away from us.
6832          */
6833         for (i = 0; i < level; i++) {
6834                 sched_domains_numa_masks[i] =
6835                         kzalloc(nr_node_ids * sizeof(void *), GFP_KERNEL);
6836                 if (!sched_domains_numa_masks[i])
6837                         return;
6838 
6839                 for (j = 0; j < nr_node_ids; j++) {
6840                         struct cpumask *mask = kzalloc(cpumask_size(), GFP_KERNEL);
6841                         if (!mask)
6842                                 return;
6843 
6844                         sched_domains_numa_masks[i][j] = mask;
6845 
6846                         for_each_node(k) {
6847                                 if (node_distance(j, k) > sched_domains_numa_distance[i])
6848                                         continue;
6849 
6850                                 cpumask_or(mask, mask, cpumask_of_node(k));
6851                         }
6852                 }
6853         }
6854 
6855         /* Compute default topology size */
6856         for (i = 0; sched_domain_topology[i].mask; i++);
6857 
6858         tl = kzalloc((i + level + 1) *
6859                         sizeof(struct sched_domain_topology_level), GFP_KERNEL);
6860         if (!tl)
6861                 return;
6862 
6863         /*
6864          * Copy the default topology bits..
6865          */
6866         for (i = 0; sched_domain_topology[i].mask; i++)
6867                 tl[i] = sched_domain_topology[i];
6868 
6869         /*
6870          * .. and append 'j' levels of NUMA goodness.
6871          */
6872         for (j = 0; j < level; i++, j++) {
6873                 tl[i] = (struct sched_domain_topology_level){
6874                         .mask = sd_numa_mask,
6875                         .sd_flags = cpu_numa_flags,
6876                         .flags = SDTL_OVERLAP,
6877                         .numa_level = j,
6878                         SD_INIT_NAME(NUMA)
6879                 };
6880         }
6881 
6882         sched_domain_topology = tl;
6883 
6884         sched_domains_numa_levels = level;
6885         sched_max_numa_distance = sched_domains_numa_distance[level - 1];
6886 
6887         init_numa_topology_type();
6888 }
6889 
6890 static void sched_domains_numa_masks_set(int cpu)
6891 {
6892         int i, j;
6893         int node = cpu_to_node(cpu);
6894 
6895         for (i = 0; i < sched_domains_numa_levels; i++) {
6896                 for (j = 0; j < nr_node_ids; j++) {
6897                         if (node_distance(j, node) <= sched_domains_numa_distance[i])
6898                                 cpumask_set_cpu(cpu, sched_domains_numa_masks[i][j]);
6899                 }
6900         }
6901 }
6902 
6903 static void sched_domains_numa_masks_clear(int cpu)
6904 {
6905         int i, j;
6906         for (i = 0; i < sched_domains_numa_levels; i++) {
6907                 for (j = 0; j < nr_node_ids; j++)
6908                         cpumask_clear_cpu(cpu, sched_domains_numa_masks[i][j]);
6909         }
6910 }
6911 
6912 /*
6913  * Update sched_domains_numa_masks[level][node] array when new cpus
6914  * are onlined.
6915  */
6916 static int sched_domains_numa_masks_update(struct notifier_block *nfb,
6917                                            unsigned long action,
6918                                            void *hcpu)
6919 {
6920         int cpu = (long)hcpu;
6921 
6922         switch (action & ~CPU_TASKS_FROZEN) {
6923         case CPU_ONLINE:
6924                 sched_domains_numa_masks_set(cpu);
6925                 break;
6926 
6927         case CPU_DEAD:
6928                 sched_domains_numa_masks_clear(cpu);
6929                 break;
6930 
6931         default:
6932                 return NOTIFY_DONE;
6933         }
6934 
6935         return NOTIFY_OK;
6936 }
6937 #else
6938 static inline void sched_init_numa(void)
6939 {
6940 }
6941 
6942 static int sched_domains_numa_masks_update(struct notifier_block *nfb,
6943                                            unsigned long action,
6944                                            void *hcpu)
6945 {
6946         return 0;
6947 }
6948 #endif /* CONFIG_NUMA */
6949 
6950 static int __sdt_alloc(const struct cpumask *cpu_map)
6951 {
6952         struct sched_domain_topology_level *tl;
6953         int j;
6954 
6955         for_each_sd_topology(tl) {
6956                 struct sd_data *sdd = &tl->data;
6957 
6958                 sdd->sd = alloc_percpu(struct sched_domain *);
6959                 if (!sdd->sd)
6960                         return -ENOMEM;
6961 
6962                 sdd->sg = alloc_percpu(struct sched_group *);
6963                 if (!sdd->sg)
6964                         return -ENOMEM;
6965 
6966                 sdd->sgc = alloc_percpu(struct sched_group_capacity *);
6967                 if (!sdd->sgc)
6968                         return -ENOMEM;
6969 
6970                 for_each_cpu(j, cpu_map) {
6971                         struct sched_domain *sd;
6972                         struct sched_group *sg;
6973                         struct sched_group_capacity *sgc;
6974 
6975                         sd = kzalloc_node(sizeof(struct sched_domain) + cpumask_size(),
6976                                         GFP_KERNEL, cpu_to_node(j));
6977                         if (!sd)
6978                                 return -ENOMEM;
6979 
6980                         *per_cpu_ptr(sdd->sd, j) = sd;
6981 
6982                         sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(),
6983                                         GFP_KERNEL, cpu_to_node(j));
6984                         if (!sg)
6985                                 return -ENOMEM;
6986 
6987                         sg->next = sg;
6988 
6989                         *per_cpu_ptr(sdd->sg, j) = sg;
6990 
6991                         sgc = kzalloc_node(sizeof(struct sched_group_capacity) + cpumask_size(),
6992                                         GFP_KERNEL, cpu_to_node(j));
6993                         if (!sgc)
6994                                 return -ENOMEM;
6995 
6996                         *per_cpu_ptr(sdd->sgc, j) = sgc;
6997                 }
6998         }
6999 
7000         return 0;
7001 }
7002 
7003 static void __sdt_free(const struct cpumask *cpu_map)
7004 {
7005         struct sched_domain_topology_level *tl;
7006         int j;
7007 
7008         for_each_sd_topology(tl) {
7009                 struct sd_data *sdd = &tl->data;
7010 
7011                 for_each_cpu(j, cpu_map) {
7012                         struct sched_domain *sd;
7013 
7014                         if (sdd->sd) {
7015                                 sd = *per_cpu_ptr(sdd->sd, j);
7016                                 if (sd && (sd->flags & SD_OVERLAP))
7017                                         free_sched_groups(sd->groups, 0);
7018                                 kfree(*per_cpu_ptr(sdd->sd, j));
7019                         }
7020 
7021                         if (sdd->sg)
7022                                 kfree(*per_cpu_ptr(sdd->sg, j));
7023                         if (sdd->sgc)
7024                                 kfree(*per_cpu_ptr(sdd->sgc, j));
7025                 }
7026                 free_percpu(sdd->sd);
7027                 sdd->sd = NULL;
7028                 free_percpu(sdd->sg);
7029                 sdd->sg = NULL;
7030                 free_percpu(sdd->sgc);
7031                 sdd->sgc = NULL;
7032         }
7033 }
7034 
7035 struct sched_domain *build_sched_domain(struct sched_domain_topology_level *tl,
7036                 const struct cpumask *cpu_map, struct sched_domain_attr *attr,
7037                 struct sched_domain *child, int cpu)
7038 {
7039         struct sched_domain *sd = sd_init(tl, cpu);
7040         if (!sd)
7041                 return child;
7042 
7043         cpumask_and(sched_domain_span(sd), cpu_map, tl->mask(cpu));
7044         if (child) {
7045                 sd->level = child->level + 1;
7046                 sched_domain_level_max = max(sched_domain_level_max, sd->level);
7047                 child->parent = sd;
7048                 sd->child = child;
7049 
7050                 if (!cpumask_subset(sched_domain_span(child),
7051                                     sched_domain_span(sd))) {
7052                         pr_err("BUG: arch topology borken\n");
7053 #ifdef CONFIG_SCHED_DEBUG
7054                         pr_err("     the %s domain not a subset of the %s domain\n",
7055                                         child->name, sd->name);
7056 #endif
7057                         /* Fixup, ensure @sd has at least @child cpus. */
7058                         cpumask_or(sched_domain_span(sd),
7059                                    sched_domain_span(sd),
7060                                    sched_domain_span(child));
7061                 }
7062 
7063         }
7064         set_domain_attribute(sd, attr);
7065 
7066         return sd;
7067 }
7068 
7069 /*
7070  * Build sched domains for a given set of cpus and attach the sched domains
7071  * to the individual cpus
7072  */
7073 static int build_sched_domains(const struct cpumask *cpu_map,
7074                                struct sched_domain_attr *attr)
7075 {
7076         enum s_alloc alloc_state;
7077         struct sched_domain *sd;
7078         struct s_data d;
7079         int i, ret = -ENOMEM;
7080 
7081         alloc_state = __visit_domain_allocation_hell(&d, cpu_map);
7082         if (alloc_state != sa_rootdomain)
7083                 goto error;
7084 
7085         /* Set up domains for cpus specified by the cpu_map. */
7086         for_each_cpu(i, cpu_map) {
7087                 struct sched_domain_topology_level *tl;
7088 
7089                 sd = NULL;
7090                 for_each_sd_topology(tl) {
7091                         sd = build_sched_domain(tl, cpu_map, attr, sd, i);
7092                         if (tl == sched_domain_topology)
7093                                 *per_cpu_ptr(d.sd, i) = sd;
7094                         if (tl->flags & SDTL_OVERLAP || sched_feat(FORCE_SD_OVERLAP))
7095                                 sd->flags |= SD_OVERLAP;
7096                         if (cpumask_equal(cpu_map, sched_domain_span(sd)))
7097                                 break;
7098                 }
7099         }
7100 
7101         /* Build the groups for the domains */
7102         for_each_cpu(i, cpu_map) {
7103                 for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
7104                         sd->span_weight = cpumask_weight(sched_domain_span(sd));
7105                         if (sd->flags & SD_OVERLAP) {
7106                                 if (build_overlap_sched_groups(sd, i))
7107                                         goto error;
7108                         } else {
7109                                 if (build_sched_groups(sd, i))
7110                                         goto error;
7111                         }
7112                 }
7113         }
7114 
7115         /* Calculate CPU capacity for physical packages and nodes */
7116         for (i = nr_cpumask_bits-1; i >= 0; i--) {
7117                 if (!cpumask_test_cpu(i, cpu_map))
7118                         continue;
7119 
7120                 for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
7121                         claim_allocations(i, sd);
7122                         init_sched_groups_capacity(i, sd);
7123                 }
7124         }
7125 
7126         /* Attach the domains */
7127         rcu_read_lock();
7128         for_each_cpu(i, cpu_map) {
7129                 sd = *per_cpu_ptr(d.sd, i);
7130                 cpu_attach_domain(sd, d.rd, i);
7131         }
7132         rcu_read_unlock();
7133 
7134         ret = 0;
7135 error:
7136         __free_domain_allocs(&d, alloc_state, cpu_map);
7137         return ret;
7138 }
7139 
7140 static cpumask_var_t *doms_cur; /* current sched domains */
7141 static int ndoms_cur;           /* number of sched domains in 'doms_cur' */
7142 static struct sched_domain_attr *dattr_cur;
7143                                 /* attribues of custom domains in 'doms_cur' */
7144 
7145 /*
7146  * Special case: If a kmalloc of a doms_cur partition (array of
7147  * cpumask) fails, then fallback to a single sched domain,
7148  * as determined by the single cpumask fallback_doms.
7149  */
7150 static cpumask_var_t fallback_doms;
7151 
7152 /*
7153  * arch_update_cpu_topology lets virtualized architectures update the
7154  * cpu core maps. It is supposed to return 1 if the topology changed
7155  * or 0 if it stayed the same.
7156  */
7157 int __weak arch_update_cpu_topology(void)
7158 {
7159         return 0;
7160 }
7161 
7162 cpumask_var_t *alloc_sched_domains(unsigned int ndoms)
7163 {
7164         int i;
7165         cpumask_var_t *doms;
7166 
7167         doms = kmalloc(sizeof(*doms) * ndoms, GFP_KERNEL);
7168         if (!doms)
7169                 return NULL;
7170         for (i = 0; i < ndoms; i++) {
7171                 if (!alloc_cpumask_var(&doms[i], GFP_KERNEL)) {
7172                         free_sched_domains(doms, i);
7173                         return NULL;
7174                 }
7175         }
7176         return doms;
7177 }
7178 
7179 void free_sched_domains(cpumask_var_t doms[], unsigned int ndoms)
7180 {
7181         unsigned int i;
7182         for (i = 0; i < ndoms; i++)
7183                 free_cpumask_var(doms[i]);
7184         kfree(doms);
7185 }
7186 
7187 /*
7188  * Set up scheduler domains and groups. Callers must hold the hotplug lock.
7189  * For now this just excludes isolated cpus, but could be used to
7190  * exclude other special cases in the future.
7191  */
7192 static int init_sched_domains(const struct cpumask *cpu_map)
7193 {
7194         int err;
7195 
7196         arch_update_cpu_topology();
7197         ndoms_cur = 1;
7198         doms_cur = alloc_sched_domains(ndoms_cur);
7199         if (!doms_cur)
7200                 doms_cur = &fallback_doms;
7201         cpumask_andnot(doms_cur[0], cpu_map, cpu_isolated_map);
7202         err = build_sched_domains(doms_cur[0], NULL);
7203         register_sched_domain_sysctl();
7204 
7205         return err;
7206 }
7207 
7208 /*
7209  * Detach sched domains from a group of cpus specified in cpu_map
7210  * These cpus will now be attached to the NULL domain
7211  */
7212 static void detach_destroy_domains(const struct cpumask *cpu_map)
7213 {
7214         int i;
7215 
7216         rcu_read_lock();
7217         for_each_cpu(i, cpu_map)
7218                 cpu_attach_domain(NULL, &def_root_domain, i);
7219         rcu_read_unlock();
7220 }
7221 
7222 /* handle null as "default" */
7223 static int dattrs_equal(struct sched_domain_attr *cur, int idx_cur,
7224                         struct sched_domain_attr *new, int idx_new)
7225 {
7226         struct sched_domain_attr tmp;
7227 
7228         /* fast path */
7229         if (!new && !cur)
7230                 return 1;
7231 
7232         tmp = SD_ATTR_INIT;
7233         return !memcmp(cur ? (cur + idx_cur) : &tmp,
7234                         new ? (new + idx_new) : &tmp,
7235                         sizeof(struct sched_domain_attr));
7236 }
7237 
7238 /*
7239  * Partition sched domains as specified by the 'ndoms_new'
7240  * cpumasks in the array doms_new[] of cpumasks. This compares
7241  * doms_new[] to the current sched domain partitioning, doms_cur[].
7242  * It destroys each deleted domain and builds each new domain.
7243  *
7244  * 'doms_new' is an array of cpumask_var_t's of length 'ndoms_new'.
7245  * The masks don't intersect (don't overlap.) We should setup one
7246  * sched domain for each mask. CPUs not in any of the cpumasks will
7247  * not be load balanced. If the same cpumask appears both in the
7248  * current 'doms_cur' domains and in the new 'doms_new', we can leave
7249  * it as it is.
7250  *
7251  * The passed in 'doms_new' should be allocated using
7252  * alloc_sched_domains.  This routine takes ownership of it and will
7253  * free_sched_domains it when done with it. If the caller failed the
7254  * alloc call, then it can pass in doms_new == NULL && ndoms_new == 1,
7255  * and partition_sched_domains() will fallback to the single partition
7256  * 'fallback_doms', it also forces the domains to be rebuilt.
7257  *
7258  * If doms_new == NULL it will be replaced with cpu_online_mask.
7259  * ndoms_new == 0 is a special case for destroying existing domains,
7260  * and it will not create the default domain.
7261  *
7262  * Call with hotplug lock held
7263  */
7264 void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
7265                              struct sched_domain_attr *dattr_new)
7266 {
7267         int i, j, n;
7268         int new_topology;
7269 
7270         mutex_lock(&sched_domains_mutex);
7271 
7272         /* always unregister in case we don't destroy any domains */
7273         unregister_sched_domain_sysctl();
7274 
7275         /* Let architecture update cpu core mappings. */
7276         new_topology = arch_update_cpu_topology();
7277 
7278         n = doms_new ? ndoms_new : 0;
7279 
7280         /* Destroy deleted domains */
7281         for (i = 0; i < ndoms_cur; i++) {
7282                 for (j = 0; j < n && !new_topology; j++) {
7283                         if (cpumask_equal(doms_cur[i], doms_new[j])
7284                             && dattrs_equal(dattr_cur, i, dattr_new, j))
7285                                 goto match1;
7286                 }
7287                 /* no match - a current sched domain not in new doms_new[] */
7288                 detach_destroy_domains(doms_cur[i]);
7289 match1:
7290                 ;
7291         }
7292 
7293         n = ndoms_cur;
7294         if (doms_new == NULL) {
7295                 n = 0;
7296                 doms_new = &fallback_doms;
7297                 cpumask_andnot(doms_new[0], cpu_active_mask, cpu_isolated_map);
7298                 WARN_ON_ONCE(dattr_new);
7299         }
7300 
7301         /* Build new domains */
7302         for (i = 0; i < ndoms_new; i++) {
7303                 for (j = 0; j < n && !new_topology; j++) {
7304                         if (cpumask_equal(doms_new[i], doms_cur[j])
7305                             && dattrs_equal(dattr_new, i, dattr_cur, j))
7306                                 goto match2;
7307                 }
7308                 /* no match - add a new doms_new */
7309                 build_sched_domains(doms_new[i], dattr_new ? dattr_new + i : NULL);
7310 match2:
7311                 ;
7312         }
7313 
7314         /* Remember the new sched domains */
7315         if (doms_cur != &fallback_doms)
7316                 free_sched_domains(doms_cur, ndoms_cur);
7317         kfree(dattr_cur);       /* kfree(NULL) is safe */
7318         doms_cur = doms_new;
7319         dattr_cur = dattr_new;
7320         ndoms_cur = ndoms_new;
7321 
7322         register_sched_domain_sysctl();
7323 
7324         mutex_unlock(&sched_domains_mutex);
7325 }
7326 
7327 static int num_cpus_frozen;     /* used to mark begin/end of suspend/resume */
7328 
7329 /*
7330  * Update cpusets according to cpu_active mask.  If cpusets are
7331  * disabled, cpuset_update_active_cpus() becomes a simple wrapper
7332  * around partition_sched_domains().
7333  *
7334  * If we come here as part of a suspend/resume, don't touch cpusets because we
7335  * want to restore it back to its original state upon resume anyway.
7336  */
7337 static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action,
7338                              void *hcpu)
7339 {
7340         switch (action) {
7341         case CPU_ONLINE_FROZEN:
7342         case CPU_DOWN_FAILED_FROZEN:
7343 
7344                 /*
7345                  * num_cpus_frozen tracks how many CPUs are involved in suspend
7346                  * resume sequence. As long as this is not the last online
7347                  * operation in the resume sequence, just build a single sched
7348                  * domain, ignoring cpusets.
7349                  */
7350                 num_cpus_frozen--;
7351                 if (likely(num_cpus_frozen)) {
7352                         partition_sched_domains(1, NULL, NULL);
7353                         break;
7354                 }
7355 
7356                 /*
7357                  * This is the last CPU online operation. So fall through and
7358                  * restore the original sched domains by considering the
7359                  * cpuset configurations.
7360                  */
7361 
7362         case CPU_ONLINE:
7363                 cpuset_update_active_cpus(true);
7364                 break;
7365         default:
7366                 return NOTIFY_DONE;
7367         }
7368         return NOTIFY_OK;
7369 }
7370 
7371 static int cpuset_cpu_inactive(struct notifier_block *nfb, unsigned long action,
7372                                void *hcpu)
7373 {
7374         unsigned long flags;
7375         long cpu = (long)hcpu;
7376         struct dl_bw *dl_b;
7377         bool overflow;
7378         int cpus;
7379 
7380         switch (action) {
7381         case CPU_DOWN_PREPARE:
7382                 rcu_read_lock_sched();
7383                 dl_b = dl_bw_of(cpu);
7384 
7385                 raw_spin_lock_irqsave(&dl_b->lock, flags);
7386                 cpus = dl_bw_cpus(cpu);
7387                 overflow = __dl_overflow(dl_b, cpus, 0, 0);
7388                 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
7389 
7390                 rcu_read_unlock_sched();
7391 
7392                 if (overflow)
7393                         return notifier_from_errno(-EBUSY);
7394                 cpuset_update_active_cpus(false);
7395                 break;
7396         case CPU_DOWN_PREPARE_FROZEN:
7397                 num_cpus_frozen++;
7398                 partition_sched_domains(1, NULL, NULL);
7399                 break;
7400         default:
7401                 return NOTIFY_DONE;
7402         }
7403         return NOTIFY_OK;
7404 }
7405 
7406 void __init sched_init_smp(void)
7407 {
7408         cpumask_var_t non_isolated_cpus;
7409 
7410         alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL);
7411         alloc_cpumask_var(&fallback_doms, GFP_KERNEL);
7412 
7413         sched_init_numa();
7414 
7415         /*
7416          * There's no userspace yet to cause hotplug operations; hence all the
7417          * cpu masks are stable and all blatant races in the below code cannot
7418          * happen.
7419          */
7420         mutex_lock(&sched_domains_mutex);
7421         init_sched_domains(cpu_active_mask);
7422         cpumask_andnot(non_isolated_cpus, cpu_possible_mask, cpu_isolated_map);
7423         if (cpumask_empty(non_isolated_cpus))
7424                 cpumask_set_cpu(smp_processor_id(), non_isolated_cpus);
7425         mutex_unlock(&sched_domains_mutex);
7426 
7427         hotcpu_notifier(sched_domains_numa_masks_update, CPU_PRI_SCHED_ACTIVE);
7428         hotcpu_notifier(cpuset_cpu_active, CPU_PRI_CPUSET_ACTIVE);
7429         hotcpu_notifier(cpuset_cpu_inactive, CPU_PRI_CPUSET_INACTIVE);
7430 
7431         init_hrtick();
7432 
7433         /* Move init over to a non-isolated CPU */
7434         if (set_cpus_allowed_ptr(current, non_isolated_cpus) < 0)
7435                 BUG();
7436         sched_init_granularity();
7437         free_cpumask_var(non_isolated_cpus);
7438 
7439         init_sched_rt_class();
7440         init_sched_dl_class();
7441 }
7442 #else
7443 void __init sched_init_smp(void)
7444 {
7445         sched_init_granularity();
7446 }
7447 #endif /* CONFIG_SMP */
7448 
7449 int in_sched_functions(unsigned long addr)
7450 {
7451         return in_lock_functions(addr) ||
7452                 (addr >= (unsigned long)__sched_text_start
7453                 && addr < (unsigned long)__sched_text_end);
7454 }
7455 
7456 #ifdef CONFIG_CGROUP_SCHED
7457 /*
7458  * Default task group.
7459  * Every task in system belongs to this group at bootup.
7460  */
7461 struct task_group root_task_group;
7462 LIST_HEAD(task_groups);
7463 
7464 /* Cacheline aligned slab cache for task_group */
7465 static struct kmem_cache *task_group_cache __read_mostly;
7466 #endif
7467 
7468 DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
7469 
7470 void __init sched_init(void)
7471 {
7472         int i, j;
7473         unsigned long alloc_size = 0, ptr;
7474 
7475 #ifdef CONFIG_FAIR_GROUP_SCHED
7476         alloc_size += 2 * nr_cpu_ids * sizeof(void **);
7477 #endif
7478 #ifdef CONFIG_RT_GROUP_SCHED
7479         alloc_size += 2 * nr_cpu_ids * sizeof(void **);
7480 #endif
7481         if (alloc_size) {
7482                 ptr = (unsigned long)kzalloc(alloc_size, GFP_NOWAIT);
7483 
7484 #ifdef CONFIG_FAIR_GROUP_SCHED
7485                 root_task_group