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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/mm.h>
 30 #include <linux/module.h>
 31 #include <linux/nmi.h>
 32 #include <linux/init.h>
 33 #include <linux/uaccess.h>
 34 #include <linux/highmem.h>
 35 #include <asm/mmu_context.h>
 36 #include <linux/interrupt.h>
 37 #include <linux/capability.h>
 38 #include <linux/completion.h>
 39 #include <linux/kernel_stat.h>
 40 #include <linux/debug_locks.h>
 41 #include <linux/perf_event.h>
 42 #include <linux/security.h>
 43 #include <linux/notifier.h>
 44 #include <linux/profile.h>
 45 #include <linux/freezer.h>
 46 #include <linux/vmalloc.h>
 47 #include <linux/blkdev.h>
 48 #include <linux/delay.h>
 49 #include <linux/pid_namespace.h>
 50 #include <linux/smp.h>
 51 #include <linux/threads.h>
 52 #include <linux/timer.h>
 53 #include <linux/rcupdate.h>
 54 #include <linux/cpu.h>
 55 #include <linux/cpuset.h>
 56 #include <linux/percpu.h>
 57 #include <linux/proc_fs.h>
 58 #include <linux/seq_file.h>
 59 #include <linux/sysctl.h>
 60 #include <linux/syscalls.h>
 61 #include <linux/times.h>
 62 #include <linux/tsacct_kern.h>
 63 #include <linux/kprobes.h>
 64 #include <linux/delayacct.h>
 65 #include <linux/unistd.h>
 66 #include <linux/pagemap.h>
 67 #include <linux/hrtimer.h>
 68 #include <linux/tick.h>
 69 #include <linux/debugfs.h>
 70 #include <linux/ctype.h>
 71 #include <linux/ftrace.h>
 72 #include <linux/slab.h>
 73 #include <linux/init_task.h>
 74 #include <linux/binfmts.h>
 75 #include <linux/context_tracking.h>
 76 #include <linux/compiler.h>
 77 
 78 #include <asm/switch_to.h>
 79 #include <asm/tlb.h>
 80 #include <asm/irq_regs.h>
 81 #include <asm/mutex.h>
 82 #ifdef CONFIG_PARAVIRT
 83 #include <asm/paravirt.h>
 84 #endif
 85 
 86 #include "sched.h"
 87 #include "../workqueue_internal.h"
 88 #include "../smpboot.h"
 89 
 90 #define CREATE_TRACE_POINTS
 91 #include <trace/events/sched.h>
 92 
 93 void start_bandwidth_timer(struct hrtimer *period_timer, ktime_t period)
 94 {
 95         unsigned long delta;
 96         ktime_t soft, hard, now;
 97 
 98         for (;;) {
 99                 if (hrtimer_active(period_timer))
100                         break;
101 
102                 now = hrtimer_cb_get_time(period_timer);
103                 hrtimer_forward(period_timer, now, period);
104 
105                 soft = hrtimer_get_softexpires(period_timer);
106                 hard = hrtimer_get_expires(period_timer);
107                 delta = ktime_to_ns(ktime_sub(hard, soft));
108                 __hrtimer_start_range_ns(period_timer, soft, delta,
109                                          HRTIMER_MODE_ABS_PINNED, 0);
110         }
111 }
112 
113 DEFINE_MUTEX(sched_domains_mutex);
114 DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
115 
116 static void update_rq_clock_task(struct rq *rq, s64 delta);
117 
118 void update_rq_clock(struct rq *rq)
119 {
120         s64 delta;
121 
122         lockdep_assert_held(&rq->lock);
123 
124         if (rq->clock_skip_update & RQCF_ACT_SKIP)
125                 return;
126 
127         delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
128         if (delta < 0)
129                 return;
130         rq->clock += delta;
131         update_rq_clock_task(rq, delta);
132 }
133 
134 /*
135  * Debugging: various feature bits
136  */
137 
138 #define SCHED_FEAT(name, enabled)       \
139         (1UL << __SCHED_FEAT_##name) * enabled |
140 
141 const_debug unsigned int sysctl_sched_features =
142 #include "features.h"
143         0;
144 
145 #undef SCHED_FEAT
146 
147 #ifdef CONFIG_SCHED_DEBUG
148 #define SCHED_FEAT(name, enabled)       \
149         #name ,
150 
151 static const char * const sched_feat_names[] = {
152 #include "features.h"
153 };
154 
155 #undef SCHED_FEAT
156 
157 static int sched_feat_show(struct seq_file *m, void *v)
158 {
159         int i;
160 
161         for (i = 0; i < __SCHED_FEAT_NR; i++) {
162                 if (!(sysctl_sched_features & (1UL << i)))
163                         seq_puts(m, "NO_");
164                 seq_printf(m, "%s ", sched_feat_names[i]);
165         }
166         seq_puts(m, "\n");
167 
168         return 0;
169 }
170 
171 #ifdef HAVE_JUMP_LABEL
172 
173 #define jump_label_key__true  STATIC_KEY_INIT_TRUE
174 #define jump_label_key__false STATIC_KEY_INIT_FALSE
175 
176 #define SCHED_FEAT(name, enabled)       \
177         jump_label_key__##enabled ,
178 
179 struct static_key sched_feat_keys[__SCHED_FEAT_NR] = {
180 #include "features.h"
181 };
182 
183 #undef SCHED_FEAT
184 
185 static void sched_feat_disable(int i)
186 {
187         if (static_key_enabled(&sched_feat_keys[i]))
188                 static_key_slow_dec(&sched_feat_keys[i]);
189 }
190 
191 static void sched_feat_enable(int i)
192 {
193         if (!static_key_enabled(&sched_feat_keys[i]))
194                 static_key_slow_inc(&sched_feat_keys[i]);
195 }
196 #else
197 static void sched_feat_disable(int i) { };
198 static void sched_feat_enable(int i) { };
199 #endif /* HAVE_JUMP_LABEL */
200 
201 static int sched_feat_set(char *cmp)
202 {
203         int i;
204         int neg = 0;
205 
206         if (strncmp(cmp, "NO_", 3) == 0) {
207                 neg = 1;
208                 cmp += 3;
209         }
210 
211         for (i = 0; i < __SCHED_FEAT_NR; i++) {
212                 if (strcmp(cmp, sched_feat_names[i]) == 0) {
213                         if (neg) {
214                                 sysctl_sched_features &= ~(1UL << i);
215                                 sched_feat_disable(i);
216                         } else {
217                                 sysctl_sched_features |= (1UL << i);
218                                 sched_feat_enable(i);
219                         }
220                         break;
221                 }
222         }
223 
224         return i;
225 }
226 
227 static ssize_t
228 sched_feat_write(struct file *filp, const char __user *ubuf,
229                 size_t cnt, loff_t *ppos)
230 {
231         char buf[64];
232         char *cmp;
233         int i;
234         struct inode *inode;
235 
236         if (cnt > 63)
237                 cnt = 63;
238 
239         if (copy_from_user(&buf, ubuf, cnt))
240                 return -EFAULT;
241 
242         buf[cnt] = 0;
243         cmp = strstrip(buf);
244 
245         /* Ensure the static_key remains in a consistent state */
246         inode = file_inode(filp);
247         mutex_lock(&inode->i_mutex);
248         i = sched_feat_set(cmp);
249         mutex_unlock(&inode->i_mutex);
250         if (i == __SCHED_FEAT_NR)
251                 return -EINVAL;
252 
253         *ppos += cnt;
254 
255         return cnt;
256 }
257 
258 static int sched_feat_open(struct inode *inode, struct file *filp)
259 {
260         return single_open(filp, sched_feat_show, NULL);
261 }
262 
263 static const struct file_operations sched_feat_fops = {
264         .open           = sched_feat_open,
265         .write          = sched_feat_write,
266         .read           = seq_read,
267         .llseek         = seq_lseek,
268         .release        = single_release,
269 };
270 
271 static __init int sched_init_debug(void)
272 {
273         debugfs_create_file("sched_features", 0644, NULL, NULL,
274                         &sched_feat_fops);
275 
276         return 0;
277 }
278 late_initcall(sched_init_debug);
279 #endif /* CONFIG_SCHED_DEBUG */
280 
281 /*
282  * Number of tasks to iterate in a single balance run.
283  * Limited because this is done with IRQs disabled.
284  */
285 const_debug unsigned int sysctl_sched_nr_migrate = 32;
286 
287 /*
288  * period over which we average the RT time consumption, measured
289  * in ms.
290  *
291  * default: 1s
292  */
293 const_debug unsigned int sysctl_sched_time_avg = MSEC_PER_SEC;
294 
295 /*
296  * period over which we measure -rt task cpu usage in us.
297  * default: 1s
298  */
299 unsigned int sysctl_sched_rt_period = 1000000;
300 
301 __read_mostly int scheduler_running;
302 
303 /*
304  * part of the period that we allow rt tasks to run in us.
305  * default: 0.95s
306  */
307 int sysctl_sched_rt_runtime = 950000;
308 
309 /* cpus with isolated domains */
310 cpumask_var_t cpu_isolated_map;
311 
312 /*
313  * this_rq_lock - lock this runqueue and disable interrupts.
314  */
315 static struct rq *this_rq_lock(void)
316         __acquires(rq->lock)
317 {
318         struct rq *rq;
319 
320         local_irq_disable();
321         rq = this_rq();
322         raw_spin_lock(&rq->lock);
323 
324         return rq;
325 }
326 
327 #ifdef CONFIG_SCHED_HRTICK
328 /*
329  * Use HR-timers to deliver accurate preemption points.
330  */
331 
332 static void hrtick_clear(struct rq *rq)
333 {
334         if (hrtimer_active(&rq->hrtick_timer))
335                 hrtimer_cancel(&rq->hrtick_timer);
336 }
337 
338 /*
339  * High-resolution timer tick.
340  * Runs from hardirq context with interrupts disabled.
341  */
342 static enum hrtimer_restart hrtick(struct hrtimer *timer)
343 {
344         struct rq *rq = container_of(timer, struct rq, hrtick_timer);
345 
346         WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
347 
348         raw_spin_lock(&rq->lock);
349         update_rq_clock(rq);
350         rq->curr->sched_class->task_tick(rq, rq->curr, 1);
351         raw_spin_unlock(&rq->lock);
352 
353         return HRTIMER_NORESTART;
354 }
355 
356 #ifdef CONFIG_SMP
357 
358 static int __hrtick_restart(struct rq *rq)
359 {
360         struct hrtimer *timer = &rq->hrtick_timer;
361         ktime_t time = hrtimer_get_softexpires(timer);
362 
363         return __hrtimer_start_range_ns(timer, time, 0, HRTIMER_MODE_ABS_PINNED, 0);
364 }
365 
366 /*
367  * called from hardirq (IPI) context
368  */
369 static void __hrtick_start(void *arg)
370 {
371         struct rq *rq = arg;
372 
373         raw_spin_lock(&rq->lock);
374         __hrtick_restart(rq);
375         rq->hrtick_csd_pending = 0;
376         raw_spin_unlock(&rq->lock);
377 }
378 
379 /*
380  * Called to set the hrtick timer state.
381  *
382  * called with rq->lock held and irqs disabled
383  */
384 void hrtick_start(struct rq *rq, u64 delay)
385 {
386         struct hrtimer *timer = &rq->hrtick_timer;
387         ktime_t time;
388         s64 delta;
389 
390         /*
391          * Don't schedule slices shorter than 10000ns, that just
392          * doesn't make sense and can cause timer DoS.
393          */
394         delta = max_t(s64, delay, 10000LL);
395         time = ktime_add_ns(timer->base->get_time(), delta);
396 
397         hrtimer_set_expires(timer, time);
398 
399         if (rq == this_rq()) {
400                 __hrtick_restart(rq);
401         } else if (!rq->hrtick_csd_pending) {
402                 smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd);
403                 rq->hrtick_csd_pending = 1;
404         }
405 }
406 
407 static int
408 hotplug_hrtick(struct notifier_block *nfb, unsigned long action, void *hcpu)
409 {
410         int cpu = (int)(long)hcpu;
411 
412         switch (action) {
413         case CPU_UP_CANCELED:
414         case CPU_UP_CANCELED_FROZEN:
415         case CPU_DOWN_PREPARE:
416         case CPU_DOWN_PREPARE_FROZEN:
417         case CPU_DEAD:
418         case CPU_DEAD_FROZEN:
419                 hrtick_clear(cpu_rq(cpu));
420                 return NOTIFY_OK;
421         }
422 
423         return NOTIFY_DONE;
424 }
425 
426 static __init void init_hrtick(void)
427 {
428         hotcpu_notifier(hotplug_hrtick, 0);
429 }
430 #else
431 /*
432  * Called to set the hrtick timer state.
433  *
434  * called with rq->lock held and irqs disabled
435  */
436 void hrtick_start(struct rq *rq, u64 delay)
437 {
438         /*
439          * Don't schedule slices shorter than 10000ns, that just
440          * doesn't make sense. Rely on vruntime for fairness.
441          */
442         delay = max_t(u64, delay, 10000LL);
443         __hrtimer_start_range_ns(&rq->hrtick_timer, ns_to_ktime(delay), 0,
444                         HRTIMER_MODE_REL_PINNED, 0);
445 }
446 
447 static inline void init_hrtick(void)
448 {
449 }
450 #endif /* CONFIG_SMP */
451 
452 static void init_rq_hrtick(struct rq *rq)
453 {
454 #ifdef CONFIG_SMP
455         rq->hrtick_csd_pending = 0;
456 
457         rq->hrtick_csd.flags = 0;
458         rq->hrtick_csd.func = __hrtick_start;
459         rq->hrtick_csd.info = rq;
460 #endif
461 
462         hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
463         rq->hrtick_timer.function = hrtick;
464 }
465 #else   /* CONFIG_SCHED_HRTICK */
466 static inline void hrtick_clear(struct rq *rq)
467 {
468 }
469 
470 static inline void init_rq_hrtick(struct rq *rq)
471 {
472 }
473 
474 static inline void init_hrtick(void)
475 {
476 }
477 #endif  /* CONFIG_SCHED_HRTICK */
478 
479 /*
480  * cmpxchg based fetch_or, macro so it works for different integer types
481  */
482 #define fetch_or(ptr, val)                                              \
483 ({      typeof(*(ptr)) __old, __val = *(ptr);                           \
484         for (;;) {                                                      \
485                 __old = cmpxchg((ptr), __val, __val | (val));           \
486                 if (__old == __val)                                     \
487                         break;                                          \
488                 __val = __old;                                          \
489         }                                                               \
490         __old;                                                          \
491 })
492 
493 #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
494 /*
495  * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
496  * this avoids any races wrt polling state changes and thereby avoids
497  * spurious IPIs.
498  */
499 static bool set_nr_and_not_polling(struct task_struct *p)
500 {
501         struct thread_info *ti = task_thread_info(p);
502         return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG);
503 }
504 
505 /*
506  * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
507  *
508  * If this returns true, then the idle task promises to call
509  * sched_ttwu_pending() and reschedule soon.
510  */
511 static bool set_nr_if_polling(struct task_struct *p)
512 {
513         struct thread_info *ti = task_thread_info(p);
514         typeof(ti->flags) old, val = ACCESS_ONCE(ti->flags);
515 
516         for (;;) {
517                 if (!(val & _TIF_POLLING_NRFLAG))
518                         return false;
519                 if (val & _TIF_NEED_RESCHED)
520                         return true;
521                 old = cmpxchg(&ti->flags, val, val | _TIF_NEED_RESCHED);
522                 if (old == val)
523                         break;
524                 val = old;
525         }
526         return true;
527 }
528 
529 #else
530 static bool set_nr_and_not_polling(struct task_struct *p)
531 {
532         set_tsk_need_resched(p);
533         return true;
534 }
535 
536 #ifdef CONFIG_SMP
537 static bool set_nr_if_polling(struct task_struct *p)
538 {
539         return false;
540 }
541 #endif
542 #endif
543 
544 /*
545  * resched_curr - mark rq's current task 'to be rescheduled now'.
546  *
547  * On UP this means the setting of the need_resched flag, on SMP it
548  * might also involve a cross-CPU call to trigger the scheduler on
549  * the target CPU.
550  */
551 void resched_curr(struct rq *rq)
552 {
553         struct task_struct *curr = rq->curr;
554         int cpu;
555 
556         lockdep_assert_held(&rq->lock);
557 
558         if (test_tsk_need_resched(curr))
559                 return;
560 
561         cpu = cpu_of(rq);
562 
563         if (cpu == smp_processor_id()) {
564                 set_tsk_need_resched(curr);
565                 set_preempt_need_resched();
566                 return;
567         }
568 
569         if (set_nr_and_not_polling(curr))
570                 smp_send_reschedule(cpu);
571         else
572                 trace_sched_wake_idle_without_ipi(cpu);
573 }
574 
575 void resched_cpu(int cpu)
576 {
577         struct rq *rq = cpu_rq(cpu);
578         unsigned long flags;
579 
580         if (!raw_spin_trylock_irqsave(&rq->lock, flags))
581                 return;
582         resched_curr(rq);
583         raw_spin_unlock_irqrestore(&rq->lock, flags);
584 }
585 
586 #ifdef CONFIG_SMP
587 #ifdef CONFIG_NO_HZ_COMMON
588 /*
589  * In the semi idle case, use the nearest busy cpu for migrating timers
590  * from an idle cpu.  This is good for power-savings.
591  *
592  * We don't do similar optimization for completely idle system, as
593  * selecting an idle cpu will add more delays to the timers than intended
594  * (as that cpu's timer base may not be uptodate wrt jiffies etc).
595  */
596 int get_nohz_timer_target(int pinned)
597 {
598         int cpu = smp_processor_id();
599         int i;
600         struct sched_domain *sd;
601 
602         if (pinned || !get_sysctl_timer_migration() || !idle_cpu(cpu))
603                 return cpu;
604 
605         rcu_read_lock();
606         for_each_domain(cpu, sd) {
607                 for_each_cpu(i, sched_domain_span(sd)) {
608                         if (!idle_cpu(i)) {
609                                 cpu = i;
610                                 goto unlock;
611                         }
612                 }
613         }
614 unlock:
615         rcu_read_unlock();
616         return cpu;
617 }
618 /*
619  * When add_timer_on() enqueues a timer into the timer wheel of an
620  * idle CPU then this timer might expire before the next timer event
621  * which is scheduled to wake up that CPU. In case of a completely
622  * idle system the next event might even be infinite time into the
623  * future. wake_up_idle_cpu() ensures that the CPU is woken up and
624  * leaves the inner idle loop so the newly added timer is taken into
625  * account when the CPU goes back to idle and evaluates the timer
626  * wheel for the next timer event.
627  */
628 static void wake_up_idle_cpu(int cpu)
629 {
630         struct rq *rq = cpu_rq(cpu);
631 
632         if (cpu == smp_processor_id())
633                 return;
634 
635         if (set_nr_and_not_polling(rq->idle))
636                 smp_send_reschedule(cpu);
637         else
638                 trace_sched_wake_idle_without_ipi(cpu);
639 }
640 
641 static bool wake_up_full_nohz_cpu(int cpu)
642 {
643         /*
644          * We just need the target to call irq_exit() and re-evaluate
645          * the next tick. The nohz full kick at least implies that.
646          * If needed we can still optimize that later with an
647          * empty IRQ.
648          */
649         if (tick_nohz_full_cpu(cpu)) {
650                 if (cpu != smp_processor_id() ||
651                     tick_nohz_tick_stopped())
652                         tick_nohz_full_kick_cpu(cpu);
653                 return true;
654         }
655 
656         return false;
657 }
658 
659 void wake_up_nohz_cpu(int cpu)
660 {
661         if (!wake_up_full_nohz_cpu(cpu))
662                 wake_up_idle_cpu(cpu);
663 }
664 
665 static inline bool got_nohz_idle_kick(void)
666 {
667         int cpu = smp_processor_id();
668 
669         if (!test_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu)))
670                 return false;
671 
672         if (idle_cpu(cpu) && !need_resched())
673                 return true;
674 
675         /*
676          * We can't run Idle Load Balance on this CPU for this time so we
677          * cancel it and clear NOHZ_BALANCE_KICK
678          */
679         clear_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu));
680         return false;
681 }
682 
683 #else /* CONFIG_NO_HZ_COMMON */
684 
685 static inline bool got_nohz_idle_kick(void)
686 {
687         return false;
688 }
689 
690 #endif /* CONFIG_NO_HZ_COMMON */
691 
692 #ifdef CONFIG_NO_HZ_FULL
693 bool sched_can_stop_tick(void)
694 {
695         /*
696          * FIFO realtime policy runs the highest priority task. Other runnable
697          * tasks are of a lower priority. The scheduler tick does nothing.
698          */
699         if (current->policy == SCHED_FIFO)
700                 return true;
701 
702         /*
703          * Round-robin realtime tasks time slice with other tasks at the same
704          * realtime priority. Is this task the only one at this priority?
705          */
706         if (current->policy == SCHED_RR) {
707                 struct sched_rt_entity *rt_se = &current->rt;
708 
709                 return rt_se->run_list.prev == rt_se->run_list.next;
710         }
711 
712         /*
713          * More than one running task need preemption.
714          * nr_running update is assumed to be visible
715          * after IPI is sent from wakers.
716          */
717         if (this_rq()->nr_running > 1)
718                 return false;
719 
720         return true;
721 }
722 #endif /* CONFIG_NO_HZ_FULL */
723 
724 void sched_avg_update(struct rq *rq)
725 {
726         s64 period = sched_avg_period();
727 
728         while ((s64)(rq_clock(rq) - rq->age_stamp) > period) {
729                 /*
730                  * Inline assembly required to prevent the compiler
731                  * optimising this loop into a divmod call.
732                  * See __iter_div_u64_rem() for another example of this.
733                  */
734                 asm("" : "+rm" (rq->age_stamp));
735                 rq->age_stamp += period;
736                 rq->rt_avg /= 2;
737         }
738 }
739 
740 #endif /* CONFIG_SMP */
741 
742 #if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
743                         (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))
744 /*
745  * Iterate task_group tree rooted at *from, calling @down when first entering a
746  * node and @up when leaving it for the final time.
747  *
748  * Caller must hold rcu_lock or sufficient equivalent.
749  */
750 int walk_tg_tree_from(struct task_group *from,
751                              tg_visitor down, tg_visitor up, void *data)
752 {
753         struct task_group *parent, *child;
754         int ret;
755 
756         parent = from;
757 
758 down:
759         ret = (*down)(parent, data);
760         if (ret)
761                 goto out;
762         list_for_each_entry_rcu(child, &parent->children, siblings) {
763                 parent = child;
764                 goto down;
765 
766 up:
767                 continue;
768         }
769         ret = (*up)(parent, data);
770         if (ret || parent == from)
771                 goto out;
772 
773         child = parent;
774         parent = parent->parent;
775         if (parent)
776                 goto up;
777 out:
778         return ret;
779 }
780 
781 int tg_nop(struct task_group *tg, void *data)
782 {
783         return 0;
784 }
785 #endif
786 
787 static void set_load_weight(struct task_struct *p)
788 {
789         int prio = p->static_prio - MAX_RT_PRIO;
790         struct load_weight *load = &p->se.load;
791 
792         /*
793          * SCHED_IDLE tasks get minimal weight:
794          */
795         if (p->policy == SCHED_IDLE) {
796                 load->weight = scale_load(WEIGHT_IDLEPRIO);
797                 load->inv_weight = WMULT_IDLEPRIO;
798                 return;
799         }
800 
801         load->weight = scale_load(prio_to_weight[prio]);
802         load->inv_weight = prio_to_wmult[prio];
803 }
804 
805 static void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
806 {
807         update_rq_clock(rq);
808         sched_info_queued(rq, p);
809         p->sched_class->enqueue_task(rq, p, flags);
810 }
811 
812 static void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
813 {
814         update_rq_clock(rq);
815         sched_info_dequeued(rq, p);
816         p->sched_class->dequeue_task(rq, p, flags);
817 }
818 
819 void activate_task(struct rq *rq, struct task_struct *p, int flags)
820 {
821         if (task_contributes_to_load(p))
822                 rq->nr_uninterruptible--;
823 
824         enqueue_task(rq, p, flags);
825 }
826 
827 void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
828 {
829         if (task_contributes_to_load(p))
830                 rq->nr_uninterruptible++;
831 
832         dequeue_task(rq, p, flags);
833 }
834 
835 static void update_rq_clock_task(struct rq *rq, s64 delta)
836 {
837 /*
838  * In theory, the compile should just see 0 here, and optimize out the call
839  * to sched_rt_avg_update. But I don't trust it...
840  */
841 #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
842         s64 steal = 0, irq_delta = 0;
843 #endif
844 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
845         irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
846 
847         /*
848          * Since irq_time is only updated on {soft,}irq_exit, we might run into
849          * this case when a previous update_rq_clock() happened inside a
850          * {soft,}irq region.
851          *
852          * When this happens, we stop ->clock_task and only update the
853          * prev_irq_time stamp to account for the part that fit, so that a next
854          * update will consume the rest. This ensures ->clock_task is
855          * monotonic.
856          *
857          * It does however cause some slight miss-attribution of {soft,}irq
858          * time, a more accurate solution would be to update the irq_time using
859          * the current rq->clock timestamp, except that would require using
860          * atomic ops.
861          */
862         if (irq_delta > delta)
863                 irq_delta = delta;
864 
865         rq->prev_irq_time += irq_delta;
866         delta -= irq_delta;
867 #endif
868 #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
869         if (static_key_false((&paravirt_steal_rq_enabled))) {
870                 steal = paravirt_steal_clock(cpu_of(rq));
871                 steal -= rq->prev_steal_time_rq;
872 
873                 if (unlikely(steal > delta))
874                         steal = delta;
875 
876                 rq->prev_steal_time_rq += steal;
877                 delta -= steal;
878         }
879 #endif
880 
881         rq->clock_task += delta;
882 
883 #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
884         if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY))
885                 sched_rt_avg_update(rq, irq_delta + steal);
886 #endif
887 }
888 
889 void sched_set_stop_task(int cpu, struct task_struct *stop)
890 {
891         struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
892         struct task_struct *old_stop = cpu_rq(cpu)->stop;
893 
894         if (stop) {
895                 /*
896                  * Make it appear like a SCHED_FIFO task, its something
897                  * userspace knows about and won't get confused about.
898                  *
899                  * Also, it will make PI more or less work without too
900                  * much confusion -- but then, stop work should not
901                  * rely on PI working anyway.
902                  */
903                 sched_setscheduler_nocheck(stop, SCHED_FIFO, &param);
904 
905                 stop->sched_class = &stop_sched_class;
906         }
907 
908         cpu_rq(cpu)->stop = stop;
909 
910         if (old_stop) {
911                 /*
912                  * Reset it back to a normal scheduling class so that
913                  * it can die in pieces.
914                  */
915                 old_stop->sched_class = &rt_sched_class;
916         }
917 }
918 
919 /*
920  * __normal_prio - return the priority that is based on the static prio
921  */
922 static inline int __normal_prio(struct task_struct *p)
923 {
924         return p->static_prio;
925 }
926 
927 /*
928  * Calculate the expected normal priority: i.e. priority
929  * without taking RT-inheritance into account. Might be
930  * boosted by interactivity modifiers. Changes upon fork,
931  * setprio syscalls, and whenever the interactivity
932  * estimator recalculates.
933  */
934 static inline int normal_prio(struct task_struct *p)
935 {
936         int prio;
937 
938         if (task_has_dl_policy(p))
939                 prio = MAX_DL_PRIO-1;
940         else if (task_has_rt_policy(p))
941                 prio = MAX_RT_PRIO-1 - p->rt_priority;
942         else
943                 prio = __normal_prio(p);
944         return prio;
945 }
946 
947 /*
948  * Calculate the current priority, i.e. the priority
949  * taken into account by the scheduler. This value might
950  * be boosted by RT tasks, or might be boosted by
951  * interactivity modifiers. Will be RT if the task got
952  * RT-boosted. If not then it returns p->normal_prio.
953  */
954 static int effective_prio(struct task_struct *p)
955 {
956         p->normal_prio = normal_prio(p);
957         /*
958          * If we are RT tasks or we were boosted to RT priority,
959          * keep the priority unchanged. Otherwise, update priority
960          * to the normal priority:
961          */
962         if (!rt_prio(p->prio))
963                 return p->normal_prio;
964         return p->prio;
965 }
966 
967 /**
968  * task_curr - is this task currently executing on a CPU?
969  * @p: the task in question.
970  *
971  * Return: 1 if the task is currently executing. 0 otherwise.
972  */
973 inline int task_curr(const struct task_struct *p)
974 {
975         return cpu_curr(task_cpu(p)) == p;
976 }
977 
978 /*
979  * Can drop rq->lock because from sched_class::switched_from() methods drop it.
980  */
981 static inline void check_class_changed(struct rq *rq, struct task_struct *p,
982                                        const struct sched_class *prev_class,
983                                        int oldprio)
984 {
985         if (prev_class != p->sched_class) {
986                 if (prev_class->switched_from)
987                         prev_class->switched_from(rq, p);
988                 /* Possble rq->lock 'hole'.  */
989                 p->sched_class->switched_to(rq, p);
990         } else if (oldprio != p->prio || dl_task(p))
991                 p->sched_class->prio_changed(rq, p, oldprio);
992 }
993 
994 void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
995 {
996         const struct sched_class *class;
997 
998         if (p->sched_class == rq->curr->sched_class) {
999                 rq->curr->sched_class->check_preempt_curr(rq, p, flags);
1000         } else {
1001                 for_each_class(class) {
1002                         if (class == rq->curr->sched_class)
1003                                 break;
1004                         if (class == p->sched_class) {
1005                                 resched_curr(rq);
1006                                 break;
1007                         }
1008                 }
1009         }
1010 
1011         /*
1012          * A queue event has occurred, and we're going to schedule.  In
1013          * this case, we can save a useless back to back clock update.
1014          */
1015         if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
1016                 rq_clock_skip_update(rq, true);
1017 }
1018 
1019 #ifdef CONFIG_SMP
1020 void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
1021 {
1022 #ifdef CONFIG_SCHED_DEBUG
1023         /*
1024          * We should never call set_task_cpu() on a blocked task,
1025          * ttwu() will sort out the placement.
1026          */
1027         WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
1028                         !p->on_rq);
1029 
1030 #ifdef CONFIG_LOCKDEP
1031         /*
1032          * The caller should hold either p->pi_lock or rq->lock, when changing
1033          * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
1034          *
1035          * sched_move_task() holds both and thus holding either pins the cgroup,
1036          * see task_group().
1037          *
1038          * Furthermore, all task_rq users should acquire both locks, see
1039          * task_rq_lock().
1040          */
1041         WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
1042                                       lockdep_is_held(&task_rq(p)->lock)));
1043 #endif
1044 #endif
1045 
1046         trace_sched_migrate_task(p, new_cpu);
1047 
1048         if (task_cpu(p) != new_cpu) {
1049                 if (p->sched_class->migrate_task_rq)
1050                         p->sched_class->migrate_task_rq(p, new_cpu);
1051                 p->se.nr_migrations++;
1052                 perf_sw_event_sched(PERF_COUNT_SW_CPU_MIGRATIONS, 1, 0);
1053         }
1054 
1055         __set_task_cpu(p, new_cpu);
1056 }
1057 
1058 static void __migrate_swap_task(struct task_struct *p, int cpu)
1059 {
1060         if (task_on_rq_queued(p)) {
1061                 struct rq *src_rq, *dst_rq;
1062 
1063                 src_rq = task_rq(p);
1064                 dst_rq = cpu_rq(cpu);
1065 
1066                 deactivate_task(src_rq, p, 0);
1067                 set_task_cpu(p, cpu);
1068                 activate_task(dst_rq, p, 0);
1069                 check_preempt_curr(dst_rq, p, 0);
1070         } else {
1071                 /*
1072                  * Task isn't running anymore; make it appear like we migrated
1073                  * it before it went to sleep. This means on wakeup we make the
1074                  * previous cpu our targer instead of where it really is.
1075                  */
1076                 p->wake_cpu = cpu;
1077         }
1078 }
1079 
1080 struct migration_swap_arg {
1081         struct task_struct *src_task, *dst_task;
1082         int src_cpu, dst_cpu;
1083 };
1084 
1085 static int migrate_swap_stop(void *data)
1086 {
1087         struct migration_swap_arg *arg = data;
1088         struct rq *src_rq, *dst_rq;
1089         int ret = -EAGAIN;
1090 
1091         src_rq = cpu_rq(arg->src_cpu);
1092         dst_rq = cpu_rq(arg->dst_cpu);
1093 
1094         double_raw_lock(&arg->src_task->pi_lock,
1095                         &arg->dst_task->pi_lock);
1096         double_rq_lock(src_rq, dst_rq);
1097         if (task_cpu(arg->dst_task) != arg->dst_cpu)
1098                 goto unlock;
1099 
1100         if (task_cpu(arg->src_task) != arg->src_cpu)
1101                 goto unlock;
1102 
1103         if (!cpumask_test_cpu(arg->dst_cpu, tsk_cpus_allowed(arg->src_task)))
1104                 goto unlock;
1105 
1106         if (!cpumask_test_cpu(arg->src_cpu, tsk_cpus_allowed(arg->dst_task)))
1107                 goto unlock;
1108 
1109         __migrate_swap_task(arg->src_task, arg->dst_cpu);
1110         __migrate_swap_task(arg->dst_task, arg->src_cpu);
1111 
1112         ret = 0;
1113 
1114 unlock:
1115         double_rq_unlock(src_rq, dst_rq);
1116         raw_spin_unlock(&arg->dst_task->pi_lock);
1117         raw_spin_unlock(&arg->src_task->pi_lock);
1118 
1119         return ret;
1120 }
1121 
1122 /*
1123  * Cross migrate two tasks
1124  */
1125 int migrate_swap(struct task_struct *cur, struct task_struct *p)
1126 {
1127         struct migration_swap_arg arg;
1128         int ret = -EINVAL;
1129 
1130         arg = (struct migration_swap_arg){
1131                 .src_task = cur,
1132                 .src_cpu = task_cpu(cur),
1133                 .dst_task = p,
1134                 .dst_cpu = task_cpu(p),
1135         };
1136 
1137         if (arg.src_cpu == arg.dst_cpu)
1138                 goto out;
1139 
1140         /*
1141          * These three tests are all lockless; this is OK since all of them
1142          * will be re-checked with proper locks held further down the line.
1143          */
1144         if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu))
1145                 goto out;
1146 
1147         if (!cpumask_test_cpu(arg.dst_cpu, tsk_cpus_allowed(arg.src_task)))
1148                 goto out;
1149 
1150         if (!cpumask_test_cpu(arg.src_cpu, tsk_cpus_allowed(arg.dst_task)))
1151                 goto out;
1152 
1153         trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu);
1154         ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg);
1155 
1156 out:
1157         return ret;
1158 }
1159 
1160 struct migration_arg {
1161         struct task_struct *task;
1162         int dest_cpu;
1163 };
1164 
1165 static int migration_cpu_stop(void *data);
1166 
1167 /*
1168  * wait_task_inactive - wait for a thread to unschedule.
1169  *
1170  * If @match_state is nonzero, it's the @p->state value just checked and
1171  * not expected to change.  If it changes, i.e. @p might have woken up,
1172  * then return zero.  When we succeed in waiting for @p to be off its CPU,
1173  * we return a positive number (its total switch count).  If a second call
1174  * a short while later returns the same number, the caller can be sure that
1175  * @p has remained unscheduled the whole time.
1176  *
1177  * The caller must ensure that the task *will* unschedule sometime soon,
1178  * else this function might spin for a *long* time. This function can't
1179  * be called with interrupts off, or it may introduce deadlock with
1180  * smp_call_function() if an IPI is sent by the same process we are
1181  * waiting to become inactive.
1182  */
1183 unsigned long wait_task_inactive(struct task_struct *p, long match_state)
1184 {
1185         unsigned long flags;
1186         int running, queued;
1187         unsigned long ncsw;
1188         struct rq *rq;
1189 
1190         for (;;) {
1191                 /*
1192                  * We do the initial early heuristics without holding
1193                  * any task-queue locks at all. We'll only try to get
1194                  * the runqueue lock when things look like they will
1195                  * work out!
1196                  */
1197                 rq = task_rq(p);
1198 
1199                 /*
1200                  * If the task is actively running on another CPU
1201                  * still, just relax and busy-wait without holding
1202                  * any locks.
1203                  *
1204                  * NOTE! Since we don't hold any locks, it's not
1205                  * even sure that "rq" stays as the right runqueue!
1206                  * But we don't care, since "task_running()" will
1207                  * return false if the runqueue has changed and p
1208                  * is actually now running somewhere else!
1209                  */
1210                 while (task_running(rq, p)) {
1211                         if (match_state && unlikely(p->state != match_state))
1212                                 return 0;
1213                         cpu_relax();
1214                 }
1215 
1216                 /*
1217                  * Ok, time to look more closely! We need the rq
1218                  * lock now, to be *sure*. If we're wrong, we'll
1219                  * just go back and repeat.
1220                  */
1221                 rq = task_rq_lock(p, &flags);
1222                 trace_sched_wait_task(p);
1223                 running = task_running(rq, p);
1224                 queued = task_on_rq_queued(p);
1225                 ncsw = 0;
1226                 if (!match_state || p->state == match_state)
1227                         ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
1228                 task_rq_unlock(rq, p, &flags);
1229 
1230                 /*
1231                  * If it changed from the expected state, bail out now.
1232                  */
1233                 if (unlikely(!ncsw))
1234                         break;
1235 
1236                 /*
1237                  * Was it really running after all now that we
1238                  * checked with the proper locks actually held?
1239                  *
1240                  * Oops. Go back and try again..
1241                  */
1242                 if (unlikely(running)) {
1243                         cpu_relax();
1244                         continue;
1245                 }
1246 
1247                 /*
1248                  * It's not enough that it's not actively running,
1249                  * it must be off the runqueue _entirely_, and not
1250                  * preempted!
1251                  *
1252                  * So if it was still runnable (but just not actively
1253                  * running right now), it's preempted, and we should
1254                  * yield - it could be a while.
1255                  */
1256                 if (unlikely(queued)) {
1257                         ktime_t to = ktime_set(0, NSEC_PER_SEC/HZ);
1258 
1259                         set_current_state(TASK_UNINTERRUPTIBLE);
1260                         schedule_hrtimeout(&to, HRTIMER_MODE_REL);
1261                         continue;
1262                 }
1263 
1264                 /*
1265                  * Ahh, all good. It wasn't running, and it wasn't
1266                  * runnable, which means that it will never become
1267                  * running in the future either. We're all done!
1268                  */
1269                 break;
1270         }
1271 
1272         return ncsw;
1273 }
1274 
1275 /***
1276  * kick_process - kick a running thread to enter/exit the kernel
1277  * @p: the to-be-kicked thread
1278  *
1279  * Cause a process which is running on another CPU to enter
1280  * kernel-mode, without any delay. (to get signals handled.)
1281  *
1282  * NOTE: this function doesn't have to take the runqueue lock,
1283  * because all it wants to ensure is that the remote task enters
1284  * the kernel. If the IPI races and the task has been migrated
1285  * to another CPU then no harm is done and the purpose has been
1286  * achieved as well.
1287  */
1288 void kick_process(struct task_struct *p)
1289 {
1290         int cpu;
1291 
1292         preempt_disable();
1293         cpu = task_cpu(p);
1294         if ((cpu != smp_processor_id()) && task_curr(p))
1295                 smp_send_reschedule(cpu);
1296         preempt_enable();
1297 }
1298 EXPORT_SYMBOL_GPL(kick_process);
1299 #endif /* CONFIG_SMP */
1300 
1301 #ifdef CONFIG_SMP
1302 /*
1303  * ->cpus_allowed is protected by both rq->lock and p->pi_lock
1304  */
1305 static int select_fallback_rq(int cpu, struct task_struct *p)
1306 {
1307         int nid = cpu_to_node(cpu);
1308         const struct cpumask *nodemask = NULL;
1309         enum { cpuset, possible, fail } state = cpuset;
1310         int dest_cpu;
1311 
1312         /*
1313          * If the node that the cpu is on has been offlined, cpu_to_node()
1314          * will return -1. There is no cpu on the node, and we should
1315          * select the cpu on the other node.
1316          */
1317         if (nid != -1) {
1318                 nodemask = cpumask_of_node(nid);
1319 
1320                 /* Look for allowed, online CPU in same node. */
1321                 for_each_cpu(dest_cpu, nodemask) {
1322                         if (!cpu_online(dest_cpu))
1323                                 continue;
1324                         if (!cpu_active(dest_cpu))
1325                                 continue;
1326                         if (cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p)))
1327                                 return dest_cpu;
1328                 }
1329         }
1330 
1331         for (;;) {
1332                 /* Any allowed, online CPU? */
1333                 for_each_cpu(dest_cpu, tsk_cpus_allowed(p)) {
1334                         if (!cpu_online(dest_cpu))
1335                                 continue;
1336                         if (!cpu_active(dest_cpu))
1337                                 continue;
1338                         goto out;
1339                 }
1340 
1341                 switch (state) {
1342                 case cpuset:
1343                         /* No more Mr. Nice Guy. */
1344                         cpuset_cpus_allowed_fallback(p);
1345                         state = possible;
1346                         break;
1347 
1348                 case possible:
1349                         do_set_cpus_allowed(p, cpu_possible_mask);
1350                         state = fail;
1351                         break;
1352 
1353                 case fail:
1354                         BUG();
1355                         break;
1356                 }
1357         }
1358 
1359 out:
1360         if (state != cpuset) {
1361                 /*
1362                  * Don't tell them about moving exiting tasks or
1363                  * kernel threads (both mm NULL), since they never
1364                  * leave kernel.
1365                  */
1366                 if (p->mm && printk_ratelimit()) {
1367                         printk_deferred("process %d (%s) no longer affine to cpu%d\n",
1368                                         task_pid_nr(p), p->comm, cpu);
1369                 }
1370         }
1371 
1372         return dest_cpu;
1373 }
1374 
1375 /*
1376  * The caller (fork, wakeup) owns p->pi_lock, ->cpus_allowed is stable.
1377  */
1378 static inline
1379 int select_task_rq(struct task_struct *p, int cpu, int sd_flags, int wake_flags)
1380 {
1381         if (p->nr_cpus_allowed > 1)
1382                 cpu = p->sched_class->select_task_rq(p, cpu, sd_flags, wake_flags);
1383 
1384         /*
1385          * In order not to call set_task_cpu() on a blocking task we need
1386          * to rely on ttwu() to place the task on a valid ->cpus_allowed
1387          * cpu.
1388          *
1389          * Since this is common to all placement strategies, this lives here.
1390          *
1391          * [ this allows ->select_task() to simply return task_cpu(p) and
1392          *   not worry about this generic constraint ]
1393          */
1394         if (unlikely(!cpumask_test_cpu(cpu, tsk_cpus_allowed(p)) ||
1395                      !cpu_online(cpu)))
1396                 cpu = select_fallback_rq(task_cpu(p), p);
1397 
1398         return cpu;
1399 }
1400 
1401 static void update_avg(u64 *avg, u64 sample)
1402 {
1403         s64 diff = sample - *avg;
1404         *avg += diff >> 3;
1405 }
1406 #endif
1407 
1408 static void
1409 ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
1410 {
1411 #ifdef CONFIG_SCHEDSTATS
1412         struct rq *rq = this_rq();
1413 
1414 #ifdef CONFIG_SMP
1415         int this_cpu = smp_processor_id();
1416 
1417         if (cpu == this_cpu) {
1418                 schedstat_inc(rq, ttwu_local);
1419                 schedstat_inc(p, se.statistics.nr_wakeups_local);
1420         } else {
1421                 struct sched_domain *sd;
1422 
1423                 schedstat_inc(p, se.statistics.nr_wakeups_remote);
1424                 rcu_read_lock();
1425                 for_each_domain(this_cpu, sd) {
1426                         if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
1427                                 schedstat_inc(sd, ttwu_wake_remote);
1428                                 break;
1429                         }
1430                 }
1431                 rcu_read_unlock();
1432         }
1433 
1434         if (wake_flags & WF_MIGRATED)
1435                 schedstat_inc(p, se.statistics.nr_wakeups_migrate);
1436 
1437 #endif /* CONFIG_SMP */
1438 
1439         schedstat_inc(rq, ttwu_count);
1440         schedstat_inc(p, se.statistics.nr_wakeups);
1441 
1442         if (wake_flags & WF_SYNC)
1443                 schedstat_inc(p, se.statistics.nr_wakeups_sync);
1444 
1445 #endif /* CONFIG_SCHEDSTATS */
1446 }
1447 
1448 static void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
1449 {
1450         activate_task(rq, p, en_flags);
1451         p->on_rq = TASK_ON_RQ_QUEUED;
1452 
1453         /* if a worker is waking up, notify workqueue */
1454         if (p->flags & PF_WQ_WORKER)
1455                 wq_worker_waking_up(p, cpu_of(rq));
1456 }
1457 
1458 /*
1459  * Mark the task runnable and perform wakeup-preemption.
1460  */
1461 static void
1462 ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
1463 {
1464         check_preempt_curr(rq, p, wake_flags);
1465         trace_sched_wakeup(p, true);
1466 
1467         p->state = TASK_RUNNING;
1468 #ifdef CONFIG_SMP
1469         if (p->sched_class->task_woken)
1470                 p->sched_class->task_woken(rq, p);
1471 
1472         if (rq->idle_stamp) {
1473                 u64 delta = rq_clock(rq) - rq->idle_stamp;
1474                 u64 max = 2*rq->max_idle_balance_cost;
1475 
1476                 update_avg(&rq->avg_idle, delta);
1477 
1478                 if (rq->avg_idle > max)
1479                         rq->avg_idle = max;
1480 
1481                 rq->idle_stamp = 0;
1482         }
1483 #endif
1484 }
1485 
1486 static void
1487 ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags)
1488 {
1489 #ifdef CONFIG_SMP
1490         if (p->sched_contributes_to_load)
1491                 rq->nr_uninterruptible--;
1492 #endif
1493 
1494         ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_WAKING);
1495         ttwu_do_wakeup(rq, p, wake_flags);
1496 }
1497 
1498 /*
1499  * Called in case the task @p isn't fully descheduled from its runqueue,
1500  * in this case we must do a remote wakeup. Its a 'light' wakeup though,
1501  * since all we need to do is flip p->state to TASK_RUNNING, since
1502  * the task is still ->on_rq.
1503  */
1504 static int ttwu_remote(struct task_struct *p, int wake_flags)
1505 {
1506         struct rq *rq;
1507         int ret = 0;
1508 
1509         rq = __task_rq_lock(p);
1510         if (task_on_rq_queued(p)) {
1511                 /* check_preempt_curr() may use rq clock */
1512                 update_rq_clock(rq);
1513                 ttwu_do_wakeup(rq, p, wake_flags);
1514                 ret = 1;
1515         }
1516         __task_rq_unlock(rq);
1517 
1518         return ret;
1519 }
1520 
1521 #ifdef CONFIG_SMP
1522 void sched_ttwu_pending(void)
1523 {
1524         struct rq *rq = this_rq();
1525         struct llist_node *llist = llist_del_all(&rq->wake_list);
1526         struct task_struct *p;
1527         unsigned long flags;
1528 
1529         if (!llist)
1530                 return;
1531 
1532         raw_spin_lock_irqsave(&rq->lock, flags);
1533 
1534         while (llist) {
1535                 p = llist_entry(llist, struct task_struct, wake_entry);
1536                 llist = llist_next(llist);
1537                 ttwu_do_activate(rq, p, 0);
1538         }
1539 
1540         raw_spin_unlock_irqrestore(&rq->lock, flags);
1541 }
1542 
1543 void scheduler_ipi(void)
1544 {
1545         /*
1546          * Fold TIF_NEED_RESCHED into the preempt_count; anybody setting
1547          * TIF_NEED_RESCHED remotely (for the first time) will also send
1548          * this IPI.
1549          */
1550         preempt_fold_need_resched();
1551 
1552         if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick())
1553                 return;
1554 
1555         /*
1556          * Not all reschedule IPI handlers call irq_enter/irq_exit, since
1557          * traditionally all their work was done from the interrupt return
1558          * path. Now that we actually do some work, we need to make sure
1559          * we do call them.
1560          *
1561          * Some archs already do call them, luckily irq_enter/exit nest
1562          * properly.
1563          *
1564          * Arguably we should visit all archs and update all handlers,
1565          * however a fair share of IPIs are still resched only so this would
1566          * somewhat pessimize the simple resched case.
1567          */
1568         irq_enter();
1569         sched_ttwu_pending();
1570 
1571         /*
1572          * Check if someone kicked us for doing the nohz idle load balance.
1573          */
1574         if (unlikely(got_nohz_idle_kick())) {
1575                 this_rq()->idle_balance = 1;
1576                 raise_softirq_irqoff(SCHED_SOFTIRQ);
1577         }
1578         irq_exit();
1579 }
1580 
1581 static void ttwu_queue_remote(struct task_struct *p, int cpu)
1582 {
1583         struct rq *rq = cpu_rq(cpu);
1584 
1585         if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list)) {
1586                 if (!set_nr_if_polling(rq->idle))
1587                         smp_send_reschedule(cpu);
1588                 else
1589                         trace_sched_wake_idle_without_ipi(cpu);
1590         }
1591 }
1592 
1593 void wake_up_if_idle(int cpu)
1594 {
1595         struct rq *rq = cpu_rq(cpu);
1596         unsigned long flags;
1597 
1598         rcu_read_lock();
1599 
1600         if (!is_idle_task(rcu_dereference(rq->curr)))
1601                 goto out;
1602 
1603         if (set_nr_if_polling(rq->idle)) {
1604                 trace_sched_wake_idle_without_ipi(cpu);
1605         } else {
1606                 raw_spin_lock_irqsave(&rq->lock, flags);
1607                 if (is_idle_task(rq->curr))
1608                         smp_send_reschedule(cpu);
1609                 /* Else cpu is not in idle, do nothing here */
1610                 raw_spin_unlock_irqrestore(&rq->lock, flags);
1611         }
1612 
1613 out:
1614         rcu_read_unlock();
1615 }
1616 
1617 bool cpus_share_cache(int this_cpu, int that_cpu)
1618 {
1619         return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
1620 }
1621 #endif /* CONFIG_SMP */
1622 
1623 static void ttwu_queue(struct task_struct *p, int cpu)
1624 {
1625         struct rq *rq = cpu_rq(cpu);
1626 
1627 #if defined(CONFIG_SMP)
1628         if (sched_feat(TTWU_QUEUE) && !cpus_share_cache(smp_processor_id(), cpu)) {
1629                 sched_clock_cpu(cpu); /* sync clocks x-cpu */
1630                 ttwu_queue_remote(p, cpu);
1631                 return;
1632         }
1633 #endif
1634 
1635         raw_spin_lock(&rq->lock);
1636         ttwu_do_activate(rq, p, 0);
1637         raw_spin_unlock(&rq->lock);
1638 }
1639 
1640 /**
1641  * try_to_wake_up - wake up a thread
1642  * @p: the thread to be awakened
1643  * @state: the mask of task states that can be woken
1644  * @wake_flags: wake modifier flags (WF_*)
1645  *
1646  * Put it on the run-queue if it's not already there. The "current"
1647  * thread is always on the run-queue (except when the actual
1648  * re-schedule is in progress), and as such you're allowed to do
1649  * the simpler "current->state = TASK_RUNNING" to mark yourself
1650  * runnable without the overhead of this.
1651  *
1652  * Return: %true if @p was woken up, %false if it was already running.
1653  * or @state didn't match @p's state.
1654  */
1655 static int
1656 try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
1657 {
1658         unsigned long flags;
1659         int cpu, success = 0;
1660 
1661         /*
1662          * If we are going to wake up a thread waiting for CONDITION we
1663          * need to ensure that CONDITION=1 done by the caller can not be
1664          * reordered with p->state check below. This pairs with mb() in
1665          * set_current_state() the waiting thread does.
1666          */
1667         smp_mb__before_spinlock();
1668         raw_spin_lock_irqsave(&p->pi_lock, flags);
1669         if (!(p->state & state))
1670                 goto out;
1671 
1672         success = 1; /* we're going to change ->state */
1673         cpu = task_cpu(p);
1674 
1675         if (p->on_rq && ttwu_remote(p, wake_flags))
1676                 goto stat;
1677 
1678 #ifdef CONFIG_SMP
1679         /*
1680          * If the owning (remote) cpu is still in the middle of schedule() with
1681          * this task as prev, wait until its done referencing the task.
1682          */
1683         while (p->on_cpu)
1684                 cpu_relax();
1685         /*
1686          * Pairs with the smp_wmb() in finish_lock_switch().
1687          */
1688         smp_rmb();
1689 
1690         p->sched_contributes_to_load = !!task_contributes_to_load(p);
1691         p->state = TASK_WAKING;
1692 
1693         if (p->sched_class->task_waking)
1694                 p->sched_class->task_waking(p);
1695 
1696         cpu = select_task_rq(p, p->wake_cpu, SD_BALANCE_WAKE, wake_flags);
1697         if (task_cpu(p) != cpu) {
1698                 wake_flags |= WF_MIGRATED;
1699                 set_task_cpu(p, cpu);
1700         }
1701 #endif /* CONFIG_SMP */
1702 
1703         ttwu_queue(p, cpu);
1704 stat:
1705         ttwu_stat(p, cpu, wake_flags);
1706 out:
1707         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
1708 
1709         return success;
1710 }
1711 
1712 /**
1713  * try_to_wake_up_local - try to wake up a local task with rq lock held
1714  * @p: the thread to be awakened
1715  *
1716  * Put @p on the run-queue if it's not already there. The caller must
1717  * ensure that this_rq() is locked, @p is bound to this_rq() and not
1718  * the current task.
1719  */
1720 static void try_to_wake_up_local(struct task_struct *p)
1721 {
1722         struct rq *rq = task_rq(p);
1723 
1724         if (WARN_ON_ONCE(rq != this_rq()) ||
1725             WARN_ON_ONCE(p == current))
1726                 return;
1727 
1728         lockdep_assert_held(&rq->lock);
1729 
1730         if (!raw_spin_trylock(&p->pi_lock)) {
1731                 raw_spin_unlock(&rq->lock);
1732                 raw_spin_lock(&p->pi_lock);
1733                 raw_spin_lock(&rq->lock);
1734         }
1735 
1736         if (!(p->state & TASK_NORMAL))
1737                 goto out;
1738 
1739         if (!task_on_rq_queued(p))
1740                 ttwu_activate(rq, p, ENQUEUE_WAKEUP);
1741 
1742         ttwu_do_wakeup(rq, p, 0);
1743         ttwu_stat(p, smp_processor_id(), 0);
1744 out:
1745         raw_spin_unlock(&p->pi_lock);
1746 }
1747 
1748 /**
1749  * wake_up_process - Wake up a specific process
1750  * @p: The process to be woken up.
1751  *
1752  * Attempt to wake up the nominated process and move it to the set of runnable
1753  * processes.
1754  *
1755  * Return: 1 if the process was woken up, 0 if it was already running.
1756  *
1757  * It may be assumed that this function implies a write memory barrier before
1758  * changing the task state if and only if any tasks are woken up.
1759  */
1760 int wake_up_process(struct task_struct *p)
1761 {
1762         WARN_ON(task_is_stopped_or_traced(p));
1763         return try_to_wake_up(p, TASK_NORMAL, 0);
1764 }
1765 EXPORT_SYMBOL(wake_up_process);
1766 
1767 int wake_up_state(struct task_struct *p, unsigned int state)
1768 {
1769         return try_to_wake_up(p, state, 0);
1770 }
1771 
1772 /*
1773  * This function clears the sched_dl_entity static params.
1774  */
1775 void __dl_clear_params(struct task_struct *p)
1776 {
1777         struct sched_dl_entity *dl_se = &p->dl;
1778 
1779         dl_se->dl_runtime = 0;
1780         dl_se->dl_deadline = 0;
1781         dl_se->dl_period = 0;
1782         dl_se->flags = 0;
1783         dl_se->dl_bw = 0;
1784 
1785         dl_se->dl_throttled = 0;
1786         dl_se->dl_new = 1;
1787         dl_se->dl_yielded = 0;
1788 }
1789 
1790 /*
1791  * Perform scheduler related setup for a newly forked process p.
1792  * p is forked by current.
1793  *
1794  * __sched_fork() is basic setup used by init_idle() too:
1795  */
1796 static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
1797 {
1798         p->on_rq                        = 0;
1799 
1800         p->se.on_rq                     = 0;
1801         p->se.exec_start                = 0;
1802         p->se.sum_exec_runtime          = 0;
1803         p->se.prev_sum_exec_runtime     = 0;
1804         p->se.nr_migrations             = 0;
1805         p->se.vruntime                  = 0;
1806 #ifdef CONFIG_SMP
1807         p->se.avg.decay_count           = 0;
1808 #endif
1809         INIT_LIST_HEAD(&p->se.group_node);
1810 
1811 #ifdef CONFIG_SCHEDSTATS
1812         memset(&p->se.statistics, 0, sizeof(p->se.statistics));
1813 #endif
1814 
1815         RB_CLEAR_NODE(&p->dl.rb_node);
1816         init_dl_task_timer(&p->dl);
1817         __dl_clear_params(p);
1818 
1819         INIT_LIST_HEAD(&p->rt.run_list);
1820 
1821 #ifdef CONFIG_PREEMPT_NOTIFIERS
1822         INIT_HLIST_HEAD(&p->preempt_notifiers);
1823 #endif
1824 
1825 #ifdef CONFIG_NUMA_BALANCING
1826         if (p->mm && atomic_read(&p->mm->mm_users) == 1) {
1827                 p->mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
1828                 p->mm->numa_scan_seq = 0;
1829         }
1830 
1831         if (clone_flags & CLONE_VM)
1832                 p->numa_preferred_nid = current->numa_preferred_nid;
1833         else
1834                 p->numa_preferred_nid = -1;
1835 
1836         p->node_stamp = 0ULL;
1837         p->numa_scan_seq = p->mm ? p->mm->numa_scan_seq : 0;
1838         p->numa_scan_period = sysctl_numa_balancing_scan_delay;
1839         p->numa_work.next = &p->numa_work;
1840         p->numa_faults = NULL;
1841         p->last_task_numa_placement = 0;
1842         p->last_sum_exec_runtime = 0;
1843 
1844         p->numa_group = NULL;
1845 #endif /* CONFIG_NUMA_BALANCING */
1846 }
1847 
1848 #ifdef CONFIG_NUMA_BALANCING
1849 #ifdef CONFIG_SCHED_DEBUG
1850 void set_numabalancing_state(bool enabled)
1851 {
1852         if (enabled)
1853                 sched_feat_set("NUMA");
1854         else
1855                 sched_feat_set("NO_NUMA");
1856 }
1857 #else
1858 __read_mostly bool numabalancing_enabled;
1859 
1860 void set_numabalancing_state(bool enabled)
1861 {
1862         numabalancing_enabled = enabled;
1863 }
1864 #endif /* CONFIG_SCHED_DEBUG */
1865 
1866 #ifdef CONFIG_PROC_SYSCTL
1867 int sysctl_numa_balancing(struct ctl_table *table, int write,
1868                          void __user *buffer, size_t *lenp, loff_t *ppos)
1869 {
1870         struct ctl_table t;
1871         int err;
1872         int state = numabalancing_enabled;
1873 
1874         if (write && !capable(CAP_SYS_ADMIN))
1875                 return -EPERM;
1876 
1877         t = *table;
1878         t.data = &state;
1879         err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
1880         if (err < 0)
1881                 return err;
1882         if (write)
1883                 set_numabalancing_state(state);
1884         return err;
1885 }
1886 #endif
1887 #endif
1888 
1889 /*
1890  * fork()/clone()-time setup:
1891  */
1892 int sched_fork(unsigned long clone_flags, struct task_struct *p)
1893 {
1894         unsigned long flags;
1895         int cpu = get_cpu();
1896 
1897         __sched_fork(clone_flags, p);
1898         /*
1899          * We mark the process as running here. This guarantees that
1900          * nobody will actually run it, and a signal or other external
1901          * event cannot wake it up and insert it on the runqueue either.
1902          */
1903         p->state = TASK_RUNNING;
1904 
1905         /*
1906          * Make sure we do not leak PI boosting priority to the child.
1907          */
1908         p->prio = current->normal_prio;
1909 
1910         /*
1911          * Revert to default priority/policy on fork if requested.
1912          */
1913         if (unlikely(p->sched_reset_on_fork)) {
1914                 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
1915                         p->policy = SCHED_NORMAL;
1916                         p->static_prio = NICE_TO_PRIO(0);
1917                         p->rt_priority = 0;
1918                 } else if (PRIO_TO_NICE(p->static_prio) < 0)
1919                         p->static_prio = NICE_TO_PRIO(0);
1920 
1921                 p->prio = p->normal_prio = __normal_prio(p);
1922                 set_load_weight(p);
1923 
1924                 /*
1925                  * We don't need the reset flag anymore after the fork. It has
1926                  * fulfilled its duty:
1927                  */
1928                 p->sched_reset_on_fork = 0;
1929         }
1930 
1931         if (dl_prio(p->prio)) {
1932                 put_cpu();
1933                 return -EAGAIN;
1934         } else if (rt_prio(p->prio)) {
1935                 p->sched_class = &rt_sched_class;
1936         } else {
1937                 p->sched_class = &fair_sched_class;
1938         }
1939 
1940         if (p->sched_class->task_fork)
1941                 p->sched_class->task_fork(p);
1942 
1943         /*
1944          * The child is not yet in the pid-hash so no cgroup attach races,
1945          * and the cgroup is pinned to this child due to cgroup_fork()
1946          * is ran before sched_fork().
1947          *
1948          * Silence PROVE_RCU.
1949          */
1950         raw_spin_lock_irqsave(&p->pi_lock, flags);
1951         set_task_cpu(p, cpu);
1952         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
1953 
1954 #if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
1955         if (likely(sched_info_on()))
1956                 memset(&p->sched_info, 0, sizeof(p->sched_info));
1957 #endif
1958 #if defined(CONFIG_SMP)
1959         p->on_cpu = 0;
1960 #endif
1961         init_task_preempt_count(p);
1962 #ifdef CONFIG_SMP
1963         plist_node_init(&p->pushable_tasks, MAX_PRIO);
1964         RB_CLEAR_NODE(&p->pushable_dl_tasks);
1965 #endif
1966 
1967         put_cpu();
1968         return 0;
1969 }
1970 
1971 unsigned long to_ratio(u64 period, u64 runtime)
1972 {
1973         if (runtime == RUNTIME_INF)
1974                 return 1ULL << 20;
1975 
1976         /*
1977          * Doing this here saves a lot of checks in all
1978          * the calling paths, and returning zero seems
1979          * safe for them anyway.
1980          */
1981         if (period == 0)
1982                 return 0;
1983 
1984         return div64_u64(runtime << 20, period);
1985 }
1986 
1987 #ifdef CONFIG_SMP
1988 inline struct dl_bw *dl_bw_of(int i)
1989 {
1990         rcu_lockdep_assert(rcu_read_lock_sched_held(),
1991                            "sched RCU must be held");
1992         return &cpu_rq(i)->rd->dl_bw;
1993 }
1994 
1995 static inline int dl_bw_cpus(int i)
1996 {
1997         struct root_domain *rd = cpu_rq(i)->rd;
1998         int cpus = 0;
1999 
2000         rcu_lockdep_assert(rcu_read_lock_sched_held(),
2001                            "sched RCU must be held");
2002         for_each_cpu_and(i, rd->span, cpu_active_mask)
2003                 cpus++;
2004 
2005         return cpus;
2006 }
2007 #else
2008 inline struct dl_bw *dl_bw_of(int i)
2009 {
2010         return &cpu_rq(i)->dl.dl_bw;
2011 }
2012 
2013 static inline int dl_bw_cpus(int i)
2014 {
2015         return 1;
2016 }
2017 #endif
2018 
2019 /*
2020  * We must be sure that accepting a new task (or allowing changing the
2021  * parameters of an existing one) is consistent with the bandwidth
2022  * constraints. If yes, this function also accordingly updates the currently
2023  * allocated bandwidth to reflect the new situation.
2024  *
2025  * This function is called while holding p's rq->lock.
2026  *
2027  * XXX we should delay bw change until the task's 0-lag point, see
2028  * __setparam_dl().
2029  */
2030 static int dl_overflow(struct task_struct *p, int policy,
2031                        const struct sched_attr *attr)
2032 {
2033 
2034         struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
2035         u64 period = attr->sched_period ?: attr->sched_deadline;
2036         u64 runtime = attr->sched_runtime;
2037         u64 new_bw = dl_policy(policy) ? to_ratio(period, runtime) : 0;
2038         int cpus, err = -1;
2039 
2040         if (new_bw == p->dl.dl_bw)
2041                 return 0;
2042 
2043         /*
2044          * Either if a task, enters, leave, or stays -deadline but changes
2045          * its parameters, we may need to update accordingly the total
2046          * allocated bandwidth of the container.
2047          */
2048         raw_spin_lock(&dl_b->lock);
2049         cpus = dl_bw_cpus(task_cpu(p));
2050         if (dl_policy(policy) && !task_has_dl_policy(p) &&
2051             !__dl_overflow(dl_b, cpus, 0, new_bw)) {
2052                 __dl_add(dl_b, new_bw);
2053                 err = 0;
2054         } else if (dl_policy(policy) && task_has_dl_policy(p) &&
2055                    !__dl_overflow(dl_b, cpus, p->dl.dl_bw, new_bw)) {
2056                 __dl_clear(dl_b, p->dl.dl_bw);
2057                 __dl_add(dl_b, new_bw);
2058                 err = 0;
2059         } else if (!dl_policy(policy) && task_has_dl_policy(p)) {
2060                 __dl_clear(dl_b, p->dl.dl_bw);
2061                 err = 0;
2062         }
2063         raw_spin_unlock(&dl_b->lock);
2064 
2065         return err;
2066 }
2067 
2068 extern void init_dl_bw(struct dl_bw *dl_b);
2069 
2070 /*
2071  * wake_up_new_task - wake up a newly created task for the first time.
2072  *
2073  * This function will do some initial scheduler statistics housekeeping
2074  * that must be done for every newly created context, then puts the task
2075  * on the runqueue and wakes it.
2076  */
2077 void wake_up_new_task(struct task_struct *p)
2078 {
2079         unsigned long flags;
2080         struct rq *rq;
2081 
2082         raw_spin_lock_irqsave(&p->pi_lock, flags);
2083 #ifdef CONFIG_SMP
2084         /*
2085          * Fork balancing, do it here and not earlier because:
2086          *  - cpus_allowed can change in the fork path
2087          *  - any previously selected cpu might disappear through hotplug
2088          */
2089         set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0));
2090 #endif
2091 
2092         /* Initialize new task's runnable average */
2093         init_task_runnable_average(p);
2094         rq = __task_rq_lock(p);
2095         activate_task(rq, p, 0);
2096         p->on_rq = TASK_ON_RQ_QUEUED;
2097         trace_sched_wakeup_new(p, true);
2098         check_preempt_curr(rq, p, WF_FORK);
2099 #ifdef CONFIG_SMP
2100         if (p->sched_class->task_woken)
2101                 p->sched_class->task_woken(rq, p);
2102 #endif
2103         task_rq_unlock(rq, p, &flags);
2104 }
2105 
2106 #ifdef CONFIG_PREEMPT_NOTIFIERS
2107 
2108 /**
2109  * preempt_notifier_register - tell me when current is being preempted & rescheduled
2110  * @notifier: notifier struct to register
2111  */
2112 void preempt_notifier_register(struct preempt_notifier *notifier)
2113 {
2114         hlist_add_head(&notifier->link, &current->preempt_notifiers);
2115 }
2116 EXPORT_SYMBOL_GPL(preempt_notifier_register);
2117 
2118 /**
2119  * preempt_notifier_unregister - no longer interested in preemption notifications
2120  * @notifier: notifier struct to unregister
2121  *
2122  * This is safe to call from within a preemption notifier.
2123  */
2124 void preempt_notifier_unregister(struct preempt_notifier *notifier)
2125 {
2126         hlist_del(&notifier->link);
2127 }
2128 EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
2129 
2130 static void fire_sched_in_preempt_notifiers(struct task_struct *curr)
2131 {
2132         struct preempt_notifier *notifier;
2133 
2134         hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
2135                 notifier->ops->sched_in(notifier, raw_smp_processor_id());
2136 }
2137 
2138 static void
2139 fire_sched_out_preempt_notifiers(struct task_struct *curr,
2140                                  struct task_struct *next)
2141 {
2142         struct preempt_notifier *notifier;
2143 
2144         hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
2145                 notifier->ops->sched_out(notifier, next);
2146 }
2147 
2148 #else /* !CONFIG_PREEMPT_NOTIFIERS */
2149 
2150 static void fire_sched_in_preempt_notifiers(struct task_struct *curr)
2151 {
2152 }
2153 
2154 static void
2155 fire_sched_out_preempt_notifiers(struct task_struct *curr,
2156                                  struct task_struct *next)
2157 {
2158 }
2159 
2160 #endif /* CONFIG_PREEMPT_NOTIFIERS */
2161 
2162 /**
2163  * prepare_task_switch - prepare to switch tasks
2164  * @rq: the runqueue preparing to switch
2165  * @prev: the current task that is being switched out
2166  * @next: the task we are going to switch to.
2167  *
2168  * This is called with the rq lock held and interrupts off. It must
2169  * be paired with a subsequent finish_task_switch after the context
2170  * switch.
2171  *
2172  * prepare_task_switch sets up locking and calls architecture specific
2173  * hooks.
2174  */
2175 static inline void
2176 prepare_task_switch(struct rq *rq, struct task_struct *prev,
2177                     struct task_struct *next)
2178 {
2179         trace_sched_switch(prev, next);
2180         sched_info_switch(rq, prev, next);
2181         perf_event_task_sched_out(prev, next);
2182         fire_sched_out_preempt_notifiers(prev, next);
2183         prepare_lock_switch(rq, next);
2184         prepare_arch_switch(next);
2185 }
2186 
2187 /**
2188  * finish_task_switch - clean up after a task-switch
2189  * @prev: the thread we just switched away from.
2190  *
2191  * finish_task_switch must be called after the context switch, paired
2192  * with a prepare_task_switch call before the context switch.
2193  * finish_task_switch will reconcile locking set up by prepare_task_switch,
2194  * and do any other architecture-specific cleanup actions.
2195  *
2196  * Note that we may have delayed dropping an mm in context_switch(). If
2197  * so, we finish that here outside of the runqueue lock. (Doing it
2198  * with the lock held can cause deadlocks; see schedule() for
2199  * details.)
2200  *
2201  * The context switch have flipped the stack from under us and restored the
2202  * local variables which were saved when this task called schedule() in the
2203  * past. prev == current is still correct but we need to recalculate this_rq
2204  * because prev may have moved to another CPU.
2205  */
2206 static struct rq *finish_task_switch(struct task_struct *prev)
2207         __releases(rq->lock)
2208 {
2209         struct rq *rq = this_rq();
2210         struct mm_struct *mm = rq->prev_mm;
2211         long prev_state;
2212 
2213         rq->prev_mm = NULL;
2214 
2215         /*
2216          * A task struct has one reference for the use as "current".
2217          * If a task dies, then it sets TASK_DEAD in tsk->state and calls
2218          * schedule one last time. The schedule call will never return, and
2219          * the scheduled task must drop that reference.
2220          * The test for TASK_DEAD must occur while the runqueue locks are
2221          * still held, otherwise prev could be scheduled on another cpu, die
2222          * there before we look at prev->state, and then the reference would
2223          * be dropped twice.
2224          *              Manfred Spraul <manfred@colorfullife.com>
2225          */
2226         prev_state = prev->state;
2227         vtime_task_switch(prev);
2228         finish_arch_switch(prev);
2229         perf_event_task_sched_in(prev, current);
2230         finish_lock_switch(rq, prev);
2231         finish_arch_post_lock_switch();
2232 
2233         fire_sched_in_preempt_notifiers(current);
2234         if (mm)
2235                 mmdrop(mm);
2236         if (unlikely(prev_state == TASK_DEAD)) {
2237                 if (prev->sched_class->task_dead)
2238                         prev->sched_class->task_dead(prev);
2239 
2240                 /*
2241                  * Remove function-return probe instances associated with this
2242                  * task and put them back on the free list.
2243                  */
2244                 kprobe_flush_task(prev);
2245                 put_task_struct(prev);
2246         }
2247 
2248         tick_nohz_task_switch(current);
2249         return rq;
2250 }
2251 
2252 #ifdef CONFIG_SMP
2253 
2254 /* rq->lock is NOT held, but preemption is disabled */
2255 static inline void post_schedule(struct rq *rq)
2256 {
2257         if (rq->post_schedule) {
2258                 unsigned long flags;
2259 
2260                 raw_spin_lock_irqsave(&rq->lock, flags);
2261                 if (rq->curr->sched_class->post_schedule)
2262                         rq->curr->sched_class->post_schedule(rq);
2263                 raw_spin_unlock_irqrestore(&rq->lock, flags);
2264 
2265                 rq->post_schedule = 0;
2266         }
2267 }
2268 
2269 #else
2270 
2271 static inline void post_schedule(struct rq *rq)
2272 {
2273 }
2274 
2275 #endif
2276 
2277 /**
2278  * schedule_tail - first thing a freshly forked thread must call.
2279  * @prev: the thread we just switched away from.
2280  */
2281 asmlinkage __visible void schedule_tail(struct task_struct *prev)
2282         __releases(rq->lock)
2283 {
2284         struct rq *rq;
2285 
2286         /* finish_task_switch() drops rq->lock and enables preemtion */
2287         preempt_disable();
2288         rq = finish_task_switch(prev);
2289         post_schedule(rq);
2290         preempt_enable();
2291 
2292         if (current->set_child_tid)
2293                 put_user(task_pid_vnr(current), current->set_child_tid);
2294 }
2295 
2296 /*
2297  * context_switch - switch to the new MM and the new thread's register state.
2298  */
2299 static inline struct rq *
2300 context_switch(struct rq *rq, struct task_struct *prev,
2301                struct task_struct *next)
2302 {
2303         struct mm_struct *mm, *oldmm;
2304 
2305         prepare_task_switch(rq, prev, next);
2306 
2307         mm = next->mm;
2308         oldmm = prev->active_mm;
2309         /*
2310          * For paravirt, this is coupled with an exit in switch_to to
2311          * combine the page table reload and the switch backend into
2312          * one hypercall.
2313          */
2314         arch_start_context_switch(prev);
2315 
2316         if (!mm) {
2317                 next->active_mm = oldmm;
2318                 atomic_inc(&oldmm->mm_count);
2319                 enter_lazy_tlb(oldmm, next);
2320         } else
2321                 switch_mm(oldmm, mm, next);
2322 
2323         if (!prev->mm) {
2324                 prev->active_mm = NULL;
2325                 rq->prev_mm = oldmm;
2326         }
2327         /*
2328          * Since the runqueue lock will be released by the next
2329          * task (which is an invalid locking op but in the case
2330          * of the scheduler it's an obvious special-case), so we
2331          * do an early lockdep release here:
2332          */
2333         spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
2334 
2335         context_tracking_task_switch(prev, next);
2336         /* Here we just switch the register state and the stack. */
2337         switch_to(prev, next, prev);
2338         barrier();
2339 
2340         return finish_task_switch(prev);
2341 }
2342 
2343 /*
2344  * nr_running and nr_context_switches:
2345  *
2346  * externally visible scheduler statistics: current number of runnable
2347  * threads, total number of context switches performed since bootup.
2348  */
2349 unsigned long nr_running(void)
2350 {
2351         unsigned long i, sum = 0;
2352 
2353         for_each_online_cpu(i)
2354                 sum += cpu_rq(i)->nr_running;
2355 
2356         return sum;
2357 }
2358 
2359 /*
2360  * Check if only the current task is running on the cpu.
2361  */
2362 bool single_task_running(void)
2363 {
2364         if (cpu_rq(smp_processor_id())->nr_running == 1)
2365                 return true;
2366         else
2367                 return false;
2368 }
2369 EXPORT_SYMBOL(single_task_running);
2370 
2371 unsigned long long nr_context_switches(void)
2372 {
2373         int i;
2374         unsigned long long sum = 0;
2375 
2376         for_each_possible_cpu(i)
2377                 sum += cpu_rq(i)->nr_switches;
2378 
2379         return sum;
2380 }
2381 
2382 unsigned long nr_iowait(void)
2383 {
2384         unsigned long i, sum = 0;
2385 
2386         for_each_possible_cpu(i)
2387                 sum += atomic_read(&cpu_rq(i)->nr_iowait);
2388 
2389         return sum;
2390 }
2391 
2392 unsigned long nr_iowait_cpu(int cpu)
2393 {
2394         struct rq *this = cpu_rq(cpu);
2395         return atomic_read(&this->nr_iowait);
2396 }
2397 
2398 void get_iowait_load(unsigned long *nr_waiters, unsigned long *load)
2399 {
2400         struct rq *this = this_rq();
2401         *nr_waiters = atomic_read(&this->nr_iowait);
2402         *load = this->cpu_load[0];
2403 }
2404 
2405 #ifdef CONFIG_SMP
2406 
2407 /*
2408  * sched_exec - execve() is a valuable balancing opportunity, because at
2409  * this point the task has the smallest effective memory and cache footprint.
2410  */
2411 void sched_exec(void)
2412 {
2413         struct task_struct *p = current;
2414         unsigned long flags;
2415         int dest_cpu;
2416 
2417         raw_spin_lock_irqsave(&p->pi_lock, flags);
2418         dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), SD_BALANCE_EXEC, 0);
2419         if (dest_cpu == smp_processor_id())
2420                 goto unlock;
2421 
2422         if (likely(cpu_active(dest_cpu))) {
2423                 struct migration_arg arg = { p, dest_cpu };
2424 
2425                 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2426                 stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
2427                 return;
2428         }
2429 unlock:
2430         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2431 }
2432 
2433 #endif
2434 
2435 DEFINE_PER_CPU(struct kernel_stat, kstat);
2436 DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat);
2437 
2438 EXPORT_PER_CPU_SYMBOL(kstat);
2439 EXPORT_PER_CPU_SYMBOL(kernel_cpustat);
2440 
2441 /*
2442  * Return accounted runtime for the task.
2443  * In case the task is currently running, return the runtime plus current's
2444  * pending runtime that have not been accounted yet.
2445  */
2446 unsigned long long task_sched_runtime(struct task_struct *p)
2447 {
2448         unsigned long flags;
2449         struct rq *rq;
2450         u64 ns;
2451 
2452 #if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
2453         /*
2454          * 64-bit doesn't need locks to atomically read a 64bit value.
2455          * So we have a optimization chance when the task's delta_exec is 0.
2456          * Reading ->on_cpu is racy, but this is ok.
2457          *
2458          * If we race with it leaving cpu, we'll take a lock. So we're correct.
2459          * If we race with it entering cpu, unaccounted time is 0. This is
2460          * indistinguishable from the read occurring a few cycles earlier.
2461          * If we see ->on_cpu without ->on_rq, the task is leaving, and has
2462          * been accounted, so we're correct here as well.
2463          */
2464         if (!p->on_cpu || !task_on_rq_queued(p))
2465                 return p->se.sum_exec_runtime;
2466 #endif
2467 
2468         rq = task_rq_lock(p, &flags);
2469         /*
2470          * Must be ->curr _and_ ->on_rq.  If dequeued, we would
2471          * project cycles that may never be accounted to this
2472          * thread, breaking clock_gettime().
2473          */
2474         if (task_current(rq, p) && task_on_rq_queued(p)) {
2475                 update_rq_clock(rq);
2476                 p->sched_class->update_curr(rq);
2477         }
2478         ns = p->se.sum_exec_runtime;
2479         task_rq_unlock(rq, p, &flags);
2480 
2481         return ns;
2482 }
2483 
2484 /*
2485  * This function gets called by the timer code, with HZ frequency.
2486  * We call it with interrupts disabled.
2487  */
2488 void scheduler_tick(void)
2489 {
2490         int cpu = smp_processor_id();
2491         struct rq *rq = cpu_rq(cpu);
2492         struct task_struct *curr = rq->curr;
2493 
2494         sched_clock_tick();
2495 
2496         raw_spin_lock(&rq->lock);
2497         update_rq_clock(rq);
2498         curr->sched_class->task_tick(rq, curr, 0);
2499         update_cpu_load_active(rq);
2500         raw_spin_unlock(&rq->lock);
2501 
2502         perf_event_task_tick();
2503 
2504 #ifdef CONFIG_SMP
2505         rq->idle_balance = idle_cpu(cpu);
2506         trigger_load_balance(rq);
2507 #endif
2508         rq_last_tick_reset(rq);
2509 }
2510 
2511 #ifdef CONFIG_NO_HZ_FULL
2512 /**
2513  * scheduler_tick_max_deferment
2514  *
2515  * Keep at least one tick per second when a single
2516  * active task is running because the scheduler doesn't
2517  * yet completely support full dynticks environment.
2518  *
2519  * This makes sure that uptime, CFS vruntime, load
2520  * balancing, etc... continue to move forward, even
2521  * with a very low granularity.
2522  *
2523  * Return: Maximum deferment in nanoseconds.
2524  */
2525 u64 scheduler_tick_max_deferment(void)
2526 {
2527         struct rq *rq = this_rq();
2528         unsigned long next, now = ACCESS_ONCE(jiffies);
2529 
2530         next = rq->last_sched_tick + HZ;
2531 
2532         if (time_before_eq(next, now))
2533                 return 0;
2534 
2535         return jiffies_to_nsecs(next - now);
2536 }
2537 #endif
2538 
2539 notrace unsigned long get_parent_ip(unsigned long addr)
2540 {
2541         if (in_lock_functions(addr)) {
2542                 addr = CALLER_ADDR2;
2543                 if (in_lock_functions(addr))
2544                         addr = CALLER_ADDR3;
2545         }
2546         return addr;
2547 }
2548 
2549 #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
2550                                 defined(CONFIG_PREEMPT_TRACER))
2551 
2552 void preempt_count_add(int val)
2553 {
2554 #ifdef CONFIG_DEBUG_PREEMPT
2555         /*
2556          * Underflow?
2557          */
2558         if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
2559                 return;
2560 #endif
2561         __preempt_count_add(val);
2562 #ifdef CONFIG_DEBUG_PREEMPT
2563         /*
2564          * Spinlock count overflowing soon?
2565          */
2566         DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
2567                                 PREEMPT_MASK - 10);
2568 #endif
2569         if (preempt_count() == val) {
2570                 unsigned long ip = get_parent_ip(CALLER_ADDR1);
2571 #ifdef CONFIG_DEBUG_PREEMPT
2572                 current->preempt_disable_ip = ip;
2573 #endif
2574                 trace_preempt_off(CALLER_ADDR0, ip);
2575         }
2576 }
2577 EXPORT_SYMBOL(preempt_count_add);
2578 NOKPROBE_SYMBOL(preempt_count_add);
2579 
2580 void preempt_count_sub(int val)
2581 {
2582 #ifdef CONFIG_DEBUG_PREEMPT
2583         /*
2584          * Underflow?
2585          */
2586         if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
2587                 return;
2588         /*
2589          * Is the spinlock portion underflowing?
2590          */
2591         if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
2592                         !(preempt_count() & PREEMPT_MASK)))
2593                 return;
2594 #endif
2595 
2596         if (preempt_count() == val)
2597                 trace_preempt_on(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
2598         __preempt_count_sub(val);
2599 }
2600 EXPORT_SYMBOL(preempt_count_sub);
2601 NOKPROBE_SYMBOL(preempt_count_sub);
2602 
2603 #endif
2604 
2605 /*
2606  * Print scheduling while atomic bug:
2607  */
2608 static noinline void __schedule_bug(struct task_struct *prev)
2609 {
2610         if (oops_in_progress)
2611                 return;
2612 
2613         printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
2614                 prev->comm, prev->pid, preempt_count());
2615 
2616         debug_show_held_locks(prev);
2617         print_modules();
2618         if (irqs_disabled())
2619                 print_irqtrace_events(prev);
2620 #ifdef CONFIG_DEBUG_PREEMPT
2621         if (in_atomic_preempt_off()) {
2622                 pr_err("Preemption disabled at:");
2623                 print_ip_sym(current->preempt_disable_ip);
2624                 pr_cont("\n");
2625         }
2626 #endif
2627         dump_stack();
2628         add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
2629 }
2630 
2631 /*
2632  * Various schedule()-time debugging checks and statistics:
2633  */
2634 static inline void schedule_debug(struct task_struct *prev)
2635 {
2636 #ifdef CONFIG_SCHED_STACK_END_CHECK
2637         BUG_ON(unlikely(task_stack_end_corrupted(prev)));
2638 #endif
2639         /*
2640          * Test if we are atomic. Since do_exit() needs to call into
2641          * schedule() atomically, we ignore that path. Otherwise whine
2642          * if we are scheduling when we should not.
2643          */
2644         if (unlikely(in_atomic_preempt_off() && prev->state != TASK_DEAD))
2645                 __schedule_bug(prev);
2646         rcu_sleep_check();
2647 
2648         profile_hit(SCHED_PROFILING, __builtin_return_address(0));
2649 
2650         schedstat_inc(this_rq(), sched_count);
2651 }
2652 
2653 /*
2654  * Pick up the highest-prio task:
2655  */
2656 static inline struct task_struct *
2657 pick_next_task(struct rq *rq, struct task_struct *prev)
2658 {
2659         const struct sched_class *class = &fair_sched_class;
2660         struct task_struct *p;
2661 
2662         /*
2663          * Optimization: we know that if all tasks are in
2664          * the fair class we can call that function directly:
2665          */
2666         if (likely(prev->sched_class == class &&
2667                    rq->nr_running == rq->cfs.h_nr_running)) {
2668                 p = fair_sched_class.pick_next_task(rq, prev);
2669                 if (unlikely(p == RETRY_TASK))
2670                         goto again;
2671 
2672                 /* assumes fair_sched_class->next == idle_sched_class */
2673                 if (unlikely(!p))
2674                         p = idle_sched_class.pick_next_task(rq, prev);
2675 
2676                 return p;
2677         }
2678 
2679 again:
2680         for_each_class(class) {
2681                 p = class->pick_next_task(rq, prev);
2682                 if (p) {
2683                         if (unlikely(p == RETRY_TASK))
2684                                 goto again;
2685                         return p;
2686                 }
2687         }
2688 
2689         BUG(); /* the idle class will always have a runnable task */
2690 }
2691 
2692 /*
2693  * __schedule() is the main scheduler function.
2694  *
2695  * The main means of driving the scheduler and thus entering this function are:
2696  *
2697  *   1. Explicit blocking: mutex, semaphore, waitqueue, etc.
2698  *
2699  *   2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
2700  *      paths. For example, see arch/x86/entry_64.S.
2701  *
2702  *      To drive preemption between tasks, the scheduler sets the flag in timer
2703  *      interrupt handler scheduler_tick().
2704  *
2705  *   3. Wakeups don't really cause entry into schedule(). They add a
2706  *      task to the run-queue and that's it.
2707  *
2708  *      Now, if the new task added to the run-queue preempts the current
2709  *      task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
2710  *      called on the nearest possible occasion:
2711  *
2712  *       - If the kernel is preemptible (CONFIG_PREEMPT=y):
2713  *
2714  *         - in syscall or exception context, at the next outmost
2715  *           preempt_enable(). (this might be as soon as the wake_up()'s
2716  *           spin_unlock()!)
2717  *
2718  *         - in IRQ context, return from interrupt-handler to
2719  *           preemptible context
2720  *
2721  *       - If the kernel is not preemptible (CONFIG_PREEMPT is not set)
2722  *         then at the next:
2723  *
2724  *          - cond_resched() call
2725  *          - explicit schedule() call
2726  *          - return from syscall or exception to user-space
2727  *          - return from interrupt-handler to user-space
2728  *
2729  * WARNING: all callers must re-check need_resched() afterward and reschedule
2730  * accordingly in case an event triggered the need for rescheduling (such as
2731  * an interrupt waking up a task) while preemption was disabled in __schedule().
2732  */
2733 static void __sched __schedule(void)
2734 {
2735         struct task_struct *prev, *next;
2736         unsigned long *switch_count;
2737         struct rq *rq;
2738         int cpu;
2739 
2740         preempt_disable();
2741         cpu = smp_processor_id();
2742         rq = cpu_rq(cpu);
2743         rcu_note_context_switch();
2744         prev = rq->curr;
2745 
2746         schedule_debug(prev);
2747 
2748         if (sched_feat(HRTICK))
2749                 hrtick_clear(rq);
2750 
2751         /*
2752          * Make sure that signal_pending_state()->signal_pending() below
2753          * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
2754          * done by the caller to avoid the race with signal_wake_up().
2755          */
2756         smp_mb__before_spinlock();
2757         raw_spin_lock_irq(&rq->lock);
2758 
2759         rq->clock_skip_update <<= 1; /* promote REQ to ACT */
2760 
2761         switch_count = &prev->nivcsw;
2762         if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
2763                 if (unlikely(signal_pending_state(prev->state, prev))) {
2764                         prev->state = TASK_RUNNING;
2765                 } else {
2766                         deactivate_task(rq, prev, DEQUEUE_SLEEP);
2767                         prev->on_rq = 0;
2768 
2769                         /*
2770                          * If a worker went to sleep, notify and ask workqueue
2771                          * whether it wants to wake up a task to maintain
2772                          * concurrency.
2773                          */
2774                         if (prev->flags & PF_WQ_WORKER) {
2775                                 struct task_struct *to_wakeup;
2776 
2777                                 to_wakeup = wq_worker_sleeping(prev, cpu);
2778                                 if (to_wakeup)
2779                                         try_to_wake_up_local(to_wakeup);
2780                         }
2781                 }
2782                 switch_count = &prev->nvcsw;
2783         }
2784 
2785         if (task_on_rq_queued(prev))
2786                 update_rq_clock(rq);
2787 
2788         next = pick_next_task(rq, prev);
2789         clear_tsk_need_resched(prev);
2790         clear_preempt_need_resched();
2791         rq->clock_skip_update = 0;
2792 
2793         if (likely(prev != next)) {
2794                 rq->nr_switches++;
2795                 rq->curr = next;
2796                 ++*switch_count;
2797 
2798                 rq = context_switch(rq, prev, next); /* unlocks the rq */
2799                 cpu = cpu_of(rq);
2800         } else
2801                 raw_spin_unlock_irq(&rq->lock);
2802 
2803         post_schedule(rq);
2804 
2805         sched_preempt_enable_no_resched();
2806 }
2807 
2808 static inline void sched_submit_work(struct task_struct *tsk)
2809 {
2810         if (!tsk->state || tsk_is_pi_blocked(tsk))
2811                 return;
2812         /*
2813          * If we are going to sleep and we have plugged IO queued,
2814          * make sure to submit it to avoid deadlocks.
2815          */
2816         if (blk_needs_flush_plug(tsk))
2817                 blk_schedule_flush_plug(tsk);
2818 }
2819 
2820 asmlinkage __visible void __sched schedule(void)
2821 {
2822         struct task_struct *tsk = current;
2823 
2824         sched_submit_work(tsk);
2825         do {
2826                 __schedule();
2827         } while (need_resched());
2828 }
2829 EXPORT_SYMBOL(schedule);
2830 
2831 #ifdef CONFIG_CONTEXT_TRACKING
2832 asmlinkage __visible void __sched schedule_user(void)
2833 {
2834         /*
2835          * If we come here after a random call to set_need_resched(),
2836          * or we have been woken up remotely but the IPI has not yet arrived,
2837          * we haven't yet exited the RCU idle mode. Do it here manually until
2838          * we find a better solution.
2839          *
2840          * NB: There are buggy callers of this function.  Ideally we
2841          * should warn if prev_state != CONTEXT_USER, but that will trigger
2842          * too frequently to make sense yet.
2843          */
2844         enum ctx_state prev_state = exception_enter();
2845         schedule();
2846         exception_exit(prev_state);
2847 }
2848 #endif
2849 
2850 /**
2851  * schedule_preempt_disabled - called with preemption disabled
2852  *
2853  * Returns with preemption disabled. Note: preempt_count must be 1
2854  */
2855 void __sched schedule_preempt_disabled(void)
2856 {
2857         sched_preempt_enable_no_resched();
2858         schedule();
2859         preempt_disable();
2860 }
2861 
2862 static void __sched notrace preempt_schedule_common(void)
2863 {
2864         do {
2865                 __preempt_count_add(PREEMPT_ACTIVE);
2866                 __schedule();
2867                 __preempt_count_sub(PREEMPT_ACTIVE);
2868 
2869                 /*
2870                  * Check again in case we missed a preemption opportunity
2871                  * between schedule and now.
2872                  */
2873                 barrier();
2874         } while (need_resched());
2875 }
2876 
2877 #ifdef CONFIG_PREEMPT
2878 /*
2879  * this is the entry point to schedule() from in-kernel preemption
2880  * off of preempt_enable. Kernel preemptions off return from interrupt
2881  * occur there and call schedule directly.
2882  */
2883 asmlinkage __visible void __sched notrace preempt_schedule(void)
2884 {
2885         /*
2886          * If there is a non-zero preempt_count or interrupts are disabled,
2887          * we do not want to preempt the current task. Just return..
2888          */
2889         if (likely(!preemptible()))
2890                 return;
2891 
2892         preempt_schedule_common();
2893 }
2894 NOKPROBE_SYMBOL(preempt_schedule);
2895 EXPORT_SYMBOL(preempt_schedule);
2896 
2897 #ifdef CONFIG_CONTEXT_TRACKING
2898 /**
2899  * preempt_schedule_context - preempt_schedule called by tracing
2900  *
2901  * The tracing infrastructure uses preempt_enable_notrace to prevent
2902  * recursion and tracing preempt enabling caused by the tracing
2903  * infrastructure itself. But as tracing can happen in areas coming
2904  * from userspace or just about to enter userspace, a preempt enable
2905  * can occur before user_exit() is called. This will cause the scheduler
2906  * to be called when the system is still in usermode.
2907  *
2908  * To prevent this, the preempt_enable_notrace will use this function
2909  * instead of preempt_schedule() to exit user context if needed before
2910  * calling the scheduler.
2911  */
2912 asmlinkage __visible void __sched notrace preempt_schedule_context(void)
2913 {
2914         enum ctx_state prev_ctx;
2915 
2916         if (likely(!preemptible()))
2917                 return;
2918 
2919         do {
2920                 __preempt_count_add(PREEMPT_ACTIVE);
2921                 /*
2922                  * Needs preempt disabled in case user_exit() is traced
2923                  * and the tracer calls preempt_enable_notrace() causing
2924                  * an infinite recursion.
2925                  */
2926                 prev_ctx = exception_enter();
2927                 __schedule();
2928                 exception_exit(prev_ctx);
2929 
2930                 __preempt_count_sub(PREEMPT_ACTIVE);
2931                 barrier();
2932         } while (need_resched());
2933 }
2934 EXPORT_SYMBOL_GPL(preempt_schedule_context);
2935 #endif /* CONFIG_CONTEXT_TRACKING */
2936 
2937 #endif /* CONFIG_PREEMPT */
2938 
2939 /*
2940  * this is the entry point to schedule() from kernel preemption
2941  * off of irq context.
2942  * Note, that this is called and return with irqs disabled. This will
2943  * protect us against recursive calling from irq.
2944  */
2945 asmlinkage __visible void __sched preempt_schedule_irq(void)
2946 {
2947         enum ctx_state prev_state;
2948 
2949         /* Catch callers which need to be fixed */
2950         BUG_ON(preempt_count() || !irqs_disabled());
2951 
2952         prev_state = exception_enter();
2953 
2954         do {
2955                 __preempt_count_add(PREEMPT_ACTIVE);
2956                 local_irq_enable();
2957                 __schedule();
2958                 local_irq_disable();
2959                 __preempt_count_sub(PREEMPT_ACTIVE);
2960 
2961                 /*
2962                  * Check again in case we missed a preemption opportunity
2963                  * between schedule and now.
2964                  */
2965                 barrier();
2966         } while (need_resched());
2967 
2968         exception_exit(prev_state);
2969 }
2970 
2971 int default_wake_function(wait_queue_t *curr, unsigned mode, int wake_flags,
2972                           void *key)
2973 {
2974         return try_to_wake_up(curr->private, mode, wake_flags);
2975 }
2976 EXPORT_SYMBOL(default_wake_function);
2977 
2978 #ifdef CONFIG_RT_MUTEXES
2979 
2980 /*
2981  * rt_mutex_setprio - set the current priority of a task
2982  * @p: task
2983  * @prio: prio value (kernel-internal form)
2984  *
2985  * This function changes the 'effective' priority of a task. It does
2986  * not touch ->normal_prio like __setscheduler().
2987  *
2988  * Used by the rt_mutex code to implement priority inheritance
2989  * logic. Call site only calls if the priority of the task changed.
2990  */
2991 void rt_mutex_setprio(struct task_struct *p, int prio)
2992 {
2993         int oldprio, queued, running, enqueue_flag = 0;
2994         struct rq *rq;
2995         const struct sched_class *prev_class;
2996 
2997         BUG_ON(prio > MAX_PRIO);
2998 
2999         rq = __task_rq_lock(p);
3000 
3001         /*
3002          * Idle task boosting is a nono in general. There is one
3003          * exception, when PREEMPT_RT and NOHZ is active:
3004          *
3005          * The idle task calls get_next_timer_interrupt() and holds
3006          * the timer wheel base->lock on the CPU and another CPU wants
3007          * to access the timer (probably to cancel it). We can safely
3008          * ignore the boosting request, as the idle CPU runs this code
3009          * with interrupts disabled and will complete the lock
3010          * protected section without being interrupted. So there is no
3011          * real need to boost.
3012          */
3013         if (unlikely(p == rq->idle)) {
3014                 WARN_ON(p != rq->curr);
3015                 WARN_ON(p->pi_blocked_on);
3016                 goto out_unlock;
3017         }
3018 
3019         trace_sched_pi_setprio(p, prio);
3020         oldprio = p->prio;
3021         prev_class = p->sched_class;
3022         queued = task_on_rq_queued(p);
3023         running = task_current(rq, p);
3024         if (queued)
3025                 dequeue_task(rq, p, 0);
3026         if (running)
3027                 put_prev_task(rq, p);
3028 
3029         /*
3030          * Boosting condition are:
3031          * 1. -rt task is running and holds mutex A
3032          *      --> -dl task blocks on mutex A
3033          *
3034          * 2. -dl task is running and holds mutex A
3035          *      --> -dl task blocks on mutex A and could preempt the
3036          *          running task
3037          */
3038         if (dl_prio(prio)) {
3039                 struct task_struct *pi_task = rt_mutex_get_top_task(p);
3040                 if (!dl_prio(p->normal_prio) ||
3041                     (pi_task && dl_entity_preempt(&pi_task->dl, &p->dl))) {
3042                         p->dl.dl_boosted = 1;
3043                         p->dl.dl_throttled = 0;
3044                         enqueue_flag = ENQUEUE_REPLENISH;
3045                 } else
3046                         p->dl.dl_boosted = 0;
3047                 p->sched_class = &dl_sched_class;
3048         } else if (rt_prio(prio)) {
3049                 if (dl_prio(oldprio))
3050                         p->dl.dl_boosted = 0;
3051                 if (oldprio < prio)
3052                         enqueue_flag = ENQUEUE_HEAD;
3053                 p->sched_class = &rt_sched_class;
3054         } else {
3055                 if (dl_prio(oldprio))
3056                         p->dl.dl_boosted = 0;
3057                 if (rt_prio(oldprio))
3058                         p->rt.timeout = 0;
3059                 p->sched_class = &fair_sched_class;
3060         }
3061 
3062         p->prio = prio;
3063 
3064         if (running)
3065                 p->sched_class->set_curr_task(rq);
3066         if (queued)
3067                 enqueue_task(rq, p, enqueue_flag);
3068 
3069         check_class_changed(rq, p, prev_class, oldprio);
3070 out_unlock:
3071         __task_rq_unlock(rq);
3072 }
3073 #endif
3074 
3075 void set_user_nice(struct task_struct *p, long nice)
3076 {
3077         int old_prio, delta, queued;
3078         unsigned long flags;
3079         struct rq *rq;
3080 
3081         if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
3082                 return;
3083         /*
3084          * We have to be careful, if called from sys_setpriority(),
3085          * the task might be in the middle of scheduling on another CPU.
3086          */
3087         rq = task_rq_lock(p, &flags);
3088         /*
3089          * The RT priorities are set via sched_setscheduler(), but we still
3090          * allow the 'normal' nice value to be set - but as expected
3091          * it wont have any effect on scheduling until the task is
3092          * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
3093          */
3094         if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
3095                 p->static_prio = NICE_TO_PRIO(nice);
3096                 goto out_unlock;
3097         }
3098         queued = task_on_rq_queued(p);
3099         if (queued)
3100                 dequeue_task(rq, p, 0);
3101 
3102         p->static_prio = NICE_TO_PRIO(nice);
3103         set_load_weight(p);
3104         old_prio = p->prio;
3105         p->prio = effective_prio(p);
3106         delta = p->prio - old_prio;
3107 
3108         if (queued) {
3109                 enqueue_task(rq, p, 0);
3110                 /*
3111                  * If the task increased its priority or is running and
3112                  * lowered its priority, then reschedule its CPU:
3113                  */
3114                 if (delta < 0 || (delta > 0 && task_running(rq, p)))
3115                         resched_curr(rq);
3116         }
3117 out_unlock:
3118         task_rq_unlock(rq, p, &flags);
3119 }
3120 EXPORT_SYMBOL(set_user_nice);
3121 
3122 /*
3123  * can_nice - check if a task can reduce its nice value
3124  * @p: task
3125  * @nice: nice value
3126  */
3127 int can_nice(const struct task_struct *p, const int nice)
3128 {
3129         /* convert nice value [19,-20] to rlimit style value [1,40] */
3130         int nice_rlim = nice_to_rlimit(nice);
3131 
3132         return (nice_rlim <= task_rlimit(p, RLIMIT_NICE) ||
3133                 capable(CAP_SYS_NICE));
3134 }
3135 
3136 #ifdef __ARCH_WANT_SYS_NICE
3137 
3138 /*
3139  * sys_nice - change the priority of the current process.
3140  * @increment: priority increment
3141  *
3142  * sys_setpriority is a more generic, but much slower function that
3143  * does similar things.
3144  */
3145 SYSCALL_DEFINE1(nice, int, increment)
3146 {
3147         long nice, retval;
3148 
3149         /*
3150          * Setpriority might change our priority at the same moment.
3151          * We don't have to worry. Conceptually one call occurs first
3152          * and we have a single winner.
3153          */
3154         increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH);
3155         nice = task_nice(current) + increment;
3156 
3157         nice = clamp_val(nice, MIN_NICE, MAX_NICE);
3158         if (increment < 0 && !can_nice(current, nice))
3159                 return -EPERM;
3160 
3161         retval = security_task_setnice(current, nice);
3162         if (retval)
3163                 return retval;
3164 
3165         set_user_nice(current, nice);
3166         return 0;
3167 }
3168 
3169 #endif
3170 
3171 /**
3172  * task_prio - return the priority value of a given task.
3173  * @p: the task in question.
3174  *
3175  * Return: The priority value as seen by users in /proc.
3176  * RT tasks are offset by -200. Normal tasks are centered
3177  * around 0, value goes from -16 to +15.
3178  */
3179 int task_prio(const struct task_struct *p)
3180 {
3181         return p->prio - MAX_RT_PRIO;
3182 }
3183 
3184 /**
3185  * idle_cpu - is a given cpu idle currently?
3186  * @cpu: the processor in question.
3187  *
3188  * Return: 1 if the CPU is currently idle. 0 otherwise.
3189  */
3190 int idle_cpu(int cpu)
3191 {
3192         struct rq *rq = cpu_rq(cpu);
3193 
3194         if (rq->curr != rq->idle)
3195                 return 0;
3196 
3197         if (rq->nr_running)
3198                 return 0;
3199 
3200 #ifdef CONFIG_SMP
3201         if (!llist_empty(&rq->wake_list))
3202                 return 0;
3203 #endif
3204 
3205         return 1;
3206 }
3207 
3208 /**
3209  * idle_task - return the idle task for a given cpu.
3210  * @cpu: the processor in question.
3211  *
3212  * Return: The idle task for the cpu @cpu.
3213  */
3214 struct task_struct *idle_task(int cpu)
3215 {
3216         return cpu_rq(cpu)->idle;
3217 }
3218 
3219 /**
3220  * find_process_by_pid - find a process with a matching PID value.
3221  * @pid: the pid in question.
3222  *
3223  * The task of @pid, if found. %NULL otherwise.
3224  */
3225 static struct task_struct *find_process_by_pid(pid_t pid)
3226 {
3227         return pid ? find_task_by_vpid(pid) : current;
3228 }
3229 
3230 /*
3231  * This function initializes the sched_dl_entity of a newly becoming
3232  * SCHED_DEADLINE task.
3233  *
3234  * Only the static values are considered here, the actual runtime and the
3235  * absolute deadline will be properly calculated when the task is enqueued
3236  * for the first time with its new policy.
3237  */
3238 static void
3239 __setparam_dl(struct task_struct *p, const struct sched_attr *attr)
3240 {
3241         struct sched_dl_entity *dl_se = &p->dl;
3242 
3243         dl_se->dl_runtime = attr->sched_runtime;
3244         dl_se->dl_deadline = attr->sched_deadline;
3245         dl_se->dl_period = attr->sched_period ?: dl_se->dl_deadline;
3246         dl_se->flags = attr->sched_flags;
3247         dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime);
3248 
3249         /*
3250          * Changing the parameters of a task is 'tricky' and we're not doing
3251          * the correct thing -- also see task_dead_dl() and switched_from_dl().
3252          *
3253          * What we SHOULD do is delay the bandwidth release until the 0-lag
3254          * point. This would include retaining the task_struct until that time
3255          * and change dl_overflow() to not immediately decrement the current
3256          * amount.
3257          *
3258          * Instead we retain the current runtime/deadline and let the new
3259          * parameters take effect after the current reservation period lapses.
3260          * This is safe (albeit pessimistic) because the 0-lag point is always
3261          * before the current scheduling deadline.
3262          *
3263          * We can still have temporary overloads because we do not delay the
3264          * change in bandwidth until that time; so admission control is
3265          * not on the safe side. It does however guarantee tasks will never
3266          * consume more than promised.
3267          */
3268 }
3269 
3270 /*
3271  * sched_setparam() passes in -1 for its policy, to let the functions
3272  * it calls know not to change it.
3273  */
3274 #define SETPARAM_POLICY -1
3275 
3276 static void __setscheduler_params(struct task_struct *p,
3277                 const struct sched_attr *attr)
3278 {
3279         int policy = attr->sched_policy;
3280 
3281         if (policy == SETPARAM_POLICY)
3282                 policy = p->policy;
3283 
3284         p->policy = policy;
3285 
3286         if (dl_policy(policy))
3287                 __setparam_dl(p, attr);
3288         else if (fair_policy(policy))
3289                 p->static_prio = NICE_TO_PRIO(attr->sched_nice);
3290 
3291         /*
3292          * __sched_setscheduler() ensures attr->sched_priority == 0 when
3293          * !rt_policy. Always setting this ensures that things like
3294          * getparam()/getattr() don't report silly values for !rt tasks.
3295          */
3296         p->rt_priority = attr->sched_priority;
3297         p->normal_prio = normal_prio(p);
3298         set_load_weight(p);
3299 }
3300 
3301 /* Actually do priority change: must hold pi & rq lock. */
3302 static void __setscheduler(struct rq *rq, struct task_struct *p,
3303                            const struct sched_attr *attr, bool keep_boost)
3304 {
3305         __setscheduler_params(p, attr);
3306 
3307         /*
3308          * Keep a potential priority boosting if called from
3309          * sched_setscheduler().
3310          */
3311         if (keep_boost)
3312                 p->prio = rt_mutex_get_effective_prio(p, normal_prio(p));
3313         else
3314                 p->prio = normal_prio(p);
3315 
3316         if (dl_prio(p->prio))
3317                 p->sched_class = &dl_sched_class;
3318         else if (rt_prio(p->prio))
3319                 p->sched_class = &rt_sched_class;
3320         else
3321                 p->sched_class = &fair_sched_class;
3322 }
3323 
3324 static void
3325 __getparam_dl(struct task_struct *p, struct sched_attr *attr)
3326 {
3327         struct sched_dl_entity *dl_se = &p->dl;
3328 
3329         attr->sched_priority = p->rt_priority;
3330         attr->sched_runtime = dl_se->dl_runtime;
3331         attr->sched_deadline = dl_se->dl_deadline;
3332         attr->sched_period = dl_se->dl_period;
3333         attr->sched_flags = dl_se->flags;
3334 }
3335 
3336 /*
3337  * This function validates the new parameters of a -deadline task.
3338  * We ask for the deadline not being zero, and greater or equal
3339  * than the runtime, as well as the period of being zero or
3340  * greater than deadline. Furthermore, we have to be sure that
3341  * user parameters are above the internal resolution of 1us (we
3342  * check sched_runtime only since it is always the smaller one) and
3343  * below 2^63 ns (we have to check both sched_deadline and
3344  * sched_period, as the latter can be zero).
3345  */
3346 static bool
3347 __checkparam_dl(const struct sched_attr *attr)
3348 {
3349         /* deadline != 0 */
3350         if (attr->sched_deadline == 0)
3351                 return false;
3352 
3353         /*
3354          * Since we truncate DL_SCALE bits, make sure we're at least
3355          * that big.
3356          */
3357         if (attr->sched_runtime < (1ULL << DL_SCALE))
3358                 return false;
3359 
3360         /*
3361          * Since we use the MSB for wrap-around and sign issues, make
3362          * sure it's not set (mind that period can be equal to zero).
3363          */
3364         if (attr->sched_deadline & (1ULL << 63) ||
3365             attr->sched_period & (1ULL << 63))
3366                 return false;
3367 
3368         /* runtime <= deadline <= period (if period != 0) */
3369         if ((attr->sched_period != 0 &&
3370              attr->sched_period < attr->sched_deadline) ||
3371             attr->sched_deadline < attr->sched_runtime)
3372                 return false;
3373 
3374         return true;
3375 }
3376 
3377 /*
3378  * check the target process has a UID that matches the current process's
3379  */
3380 static bool check_same_owner(struct task_struct *p)
3381 {
3382         const struct cred *cred = current_cred(), *pcred;
3383         bool match;
3384 
3385         rcu_read_lock();
3386         pcred = __task_cred(p);
3387         match = (uid_eq(cred->euid, pcred->euid) ||
3388                  uid_eq(cred->euid, pcred->uid));
3389         rcu_read_unlock();
3390         return match;
3391 }
3392 
3393 static bool dl_param_changed(struct task_struct *p,
3394                 const struct sched_attr *attr)
3395 {
3396         struct sched_dl_entity *dl_se = &p->dl;
3397 
3398         if (dl_se->dl_runtime != attr->sched_runtime ||
3399                 dl_se->dl_deadline != attr->sched_deadline ||
3400                 dl_se->dl_period != attr->sched_period ||
3401                 dl_se->flags != attr->sched_flags)
3402                 return true;
3403 
3404         return false;
3405 }
3406 
3407 static int __sched_setscheduler(struct task_struct *p,
3408                                 const struct sched_attr *attr,
3409                                 bool user)
3410 {
3411         int newprio = dl_policy(attr->sched_policy) ? MAX_DL_PRIO - 1 :
3412                       MAX_RT_PRIO - 1 - attr->sched_priority;
3413         int retval, oldprio, oldpolicy = -1, queued, running;
3414         int new_effective_prio, policy = attr->sched_policy;
3415         unsigned long flags;
3416         const struct sched_class *prev_class;
3417         struct rq *rq;
3418         int reset_on_fork;
3419 
3420         /* may grab non-irq protected spin_locks */
3421         BUG_ON(in_interrupt());
3422 recheck:
3423         /* double check policy once rq lock held */
3424         if (policy < 0) {
3425                 reset_on_fork = p->sched_reset_on_fork;
3426                 policy = oldpolicy = p->policy;
3427         } else {
3428                 reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK);
3429 
3430                 if (policy != SCHED_DEADLINE &&
3431                                 policy != SCHED_FIFO && policy != SCHED_RR &&
3432                                 policy != SCHED_NORMAL && policy != SCHED_BATCH &&
3433                                 policy != SCHED_IDLE)
3434                         return -EINVAL;
3435         }
3436 
3437         if (attr->sched_flags & ~(SCHED_FLAG_RESET_ON_FORK))
3438                 return -EINVAL;
3439 
3440         /*
3441          * Valid priorities for SCHED_FIFO and SCHED_RR are
3442          * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
3443          * SCHED_BATCH and SCHED_IDLE is 0.
3444          */
3445         if ((p->mm && attr->sched_priority > MAX_USER_RT_PRIO-1) ||
3446             (!p->mm && attr->sched_priority > MAX_RT_PRIO-1))
3447                 return -EINVAL;
3448         if ((dl_policy(policy) && !__checkparam_dl(attr)) ||
3449             (rt_policy(policy) != (attr->sched_priority != 0)))
3450                 return -EINVAL;
3451 
3452         /*
3453          * Allow unprivileged RT tasks to decrease priority:
3454          */
3455         if (user && !capable(CAP_SYS_NICE)) {
3456                 if (fair_policy(policy)) {
3457                         if (attr->sched_nice < task_nice(p) &&
3458                             !can_nice(p, attr->sched_nice))
3459                                 return -EPERM;
3460                 }
3461 
3462                 if (rt_policy(policy)) {
3463                         unsigned long rlim_rtprio =
3464                                         task_rlimit(p, RLIMIT_RTPRIO);
3465 
3466                         /* can't set/change the rt policy */
3467                         if (policy != p->policy && !rlim_rtprio)
3468                                 return -EPERM;
3469 
3470                         /* can't increase priority */
3471                         if (attr->sched_priority > p->rt_priority &&
3472                             attr->sched_priority > rlim_rtprio)
3473                                 return -EPERM;
3474                 }
3475 
3476                  /*
3477                   * Can't set/change SCHED_DEADLINE policy at all for now
3478                   * (safest behavior); in the future we would like to allow
3479                   * unprivileged DL tasks to increase their relative deadline
3480                   * or reduce their runtime (both ways reducing utilization)
3481                   */
3482                 if (dl_policy(policy))
3483                         return -EPERM;
3484 
3485                 /*
3486                  * Treat SCHED_IDLE as nice 20. Only allow a switch to
3487                  * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
3488                  */
3489                 if (p->policy == SCHED_IDLE && policy != SCHED_IDLE) {
3490                         if (!can_nice(p, task_nice(p)))
3491                                 return -EPERM;
3492                 }
3493 
3494                 /* can't change other user's priorities */
3495                 if (!check_same_owner(p))
3496                         return -EPERM;
3497 
3498                 /* Normal users shall not reset the sched_reset_on_fork flag */
3499                 if (p->sched_reset_on_fork && !reset_on_fork)
3500                         return -EPERM;
3501         }
3502 
3503         if (user) {
3504                 retval = security_task_setscheduler(p);
3505                 if (retval)
3506                         return retval;
3507         }
3508 
3509         /*
3510          * make sure no PI-waiters arrive (or leave) while we are
3511          * changing the priority of the task:
3512          *
3513          * To be able to change p->policy safely, the appropriate
3514          * runqueue lock must be held.
3515          */
3516         rq = task_rq_lock(p, &flags);
3517 
3518         /*
3519          * Changing the policy of the stop threads its a very bad idea
3520          */
3521         if (p == rq->stop) {
3522                 task_rq_unlock(rq, p, &flags);
3523                 return -EINVAL;
3524         }
3525 
3526         /*
3527          * If not changing anything there's no need to proceed further,
3528          * but store a possible modification of reset_on_fork.
3529          */
3530         if (unlikely(policy == p->policy)) {
3531                 if (fair_policy(policy) && attr->sched_nice != task_nice(p))
3532                         goto change;
3533                 if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
3534                         goto change;
3535                 if (dl_policy(policy) && dl_param_changed(p, attr))
3536                         goto change;
3537 
3538                 p->sched_reset_on_fork = reset_on_fork;
3539                 task_rq_unlock(rq, p, &flags);
3540                 return 0;
3541         }
3542 change:
3543 
3544         if (user) {
3545 #ifdef CONFIG_RT_GROUP_SCHED
3546                 /*
3547                  * Do not allow realtime tasks into groups that have no runtime
3548                  * assigned.
3549                  */
3550                 if (rt_bandwidth_enabled() && rt_policy(policy) &&
3551                                 task_group(p)->rt_bandwidth.rt_runtime == 0 &&
3552                                 !task_group_is_autogroup(task_group(p))) {
3553                         task_rq_unlock(rq, p, &flags);
3554                         return -EPERM;
3555                 }
3556 #endif
3557 #ifdef CONFIG_SMP
3558                 if (dl_bandwidth_enabled() && dl_policy(policy)) {
3559                         cpumask_t *span = rq->rd->span;
3560 
3561                         /*
3562                          * Don't allow tasks with an affinity mask smaller than
3563                          * the entire root_domain to become SCHED_DEADLINE. We
3564                          * will also fail if there's no bandwidth available.
3565                          */
3566                         if (!cpumask_subset(span, &p->cpus_allowed) ||
3567                             rq->rd->dl_bw.bw == 0) {
3568                                 task_rq_unlock(rq, p, &flags);
3569                                 return -EPERM;
3570                         }
3571                 }
3572 #endif
3573         }
3574 
3575         /* recheck policy now with rq lock held */
3576         if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
3577                 policy = oldpolicy = -1;
3578                 task_rq_unlock(rq, p, &flags);
3579                 goto recheck;
3580         }
3581 
3582         /*
3583          * If setscheduling to SCHED_DEADLINE (or changing the parameters
3584          * of a SCHED_DEADLINE task) we need to check if enough bandwidth
3585          * is available.
3586          */
3587         if ((dl_policy(policy) || dl_task(p)) && dl_overflow(p, policy, attr)) {
3588                 task_rq_unlock(rq, p, &flags);
3589                 return -EBUSY;
3590         }
3591 
3592         p->sched_reset_on_fork = reset_on_fork;
3593         oldprio = p->prio;
3594 
3595         /*
3596          * Take priority boosted tasks into account. If the new
3597          * effective priority is unchanged, we just store the new
3598          * normal parameters and do not touch the scheduler class and
3599          * the runqueue. This will be done when the task deboost
3600          * itself.
3601          */
3602         new_effective_prio = rt_mutex_get_effective_prio(p, newprio);
3603         if (new_effective_prio == oldprio) {
3604                 __setscheduler_params(p, attr);
3605                 task_rq_unlock(rq, p, &flags);
3606                 return 0;
3607         }
3608 
3609         queued = task_on_rq_queued(p);
3610         running = task_current(rq, p);
3611         if (queued)
3612                 dequeue_task(rq, p, 0);
3613         if (running)
3614                 put_prev_task(rq, p);
3615 
3616         prev_class = p->sched_class;
3617         __setscheduler(rq, p, attr, true);
3618 
3619         if (running)
3620                 p->sched_class->set_curr_task(rq);
3621         if (queued) {
3622                 /*
3623                  * We enqueue to tail when the priority of a task is
3624                  * increased (user space view).
3625                  */
3626                 enqueue_task(rq, p, oldprio <= p->prio ? ENQUEUE_HEAD : 0);
3627         }
3628 
3629         check_class_changed(rq, p, prev_class, oldprio);
3630         task_rq_unlock(rq, p, &flags);
3631 
3632         rt_mutex_adjust_pi(p);
3633 
3634         return 0;
3635 }
3636 
3637 static int _sched_setscheduler(struct task_struct *p, int policy,
3638                                const struct sched_param *param, bool check)
3639 {
3640         struct sched_attr attr = {
3641                 .sched_policy   = policy,
3642                 .sched_priority = param->sched_priority,
3643                 .sched_nice     = PRIO_TO_NICE(p->static_prio),
3644         };
3645 
3646         /* Fixup the legacy SCHED_RESET_ON_FORK hack. */
3647         if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) {
3648                 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
3649                 policy &= ~SCHED_RESET_ON_FORK;
3650                 attr.sched_policy = policy;
3651         }
3652 
3653         return __sched_setscheduler(p, &attr, check);
3654 }
3655 /**
3656  * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
3657  * @p: the task in question.
3658  * @policy: new policy.
3659  * @param: structure containing the new RT priority.
3660  *
3661  * Return: 0 on success. An error code otherwise.
3662  *
3663  * NOTE that the task may be already dead.
3664  */
3665 int sched_setscheduler(struct task_struct *p, int policy,
3666                        const struct sched_param *param)
3667 {
3668         return _sched_setscheduler(p, policy, param, true);
3669 }
3670 EXPORT_SYMBOL_GPL(sched_setscheduler);
3671 
3672 int sched_setattr(struct task_struct *p, const struct sched_attr *attr)
3673 {
3674         return __sched_setscheduler(p, attr, true);
3675 }
3676 EXPORT_SYMBOL_GPL(sched_setattr);
3677 
3678 /**
3679  * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
3680  * @p: the task in question.
3681  * @policy: new policy.
3682  * @param: structure containing the new RT priority.
3683  *
3684  * Just like sched_setscheduler, only don't bother checking if the
3685  * current context has permission.  For example, this is needed in
3686  * stop_machine(): we create temporary high priority worker threads,
3687  * but our caller might not have that capability.
3688  *
3689  * Return: 0 on success. An error code otherwise.
3690  */
3691 int sched_setscheduler_nocheck(struct task_struct *p, int policy,
3692                                const struct sched_param *param)
3693 {
3694         return _sched_setscheduler(p, policy, param, false);
3695 }
3696 
3697 static int
3698 do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
3699 {
3700         struct sched_param lparam;
3701         struct task_struct *p;
3702         int retval;
3703 
3704         if (!param || pid < 0)
3705                 return -EINVAL;
3706         if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
3707                 return -EFAULT;
3708 
3709         rcu_read_lock();
3710         retval = -ESRCH;
3711         p = find_process_by_pid(pid);
3712         if (p != NULL)
3713                 retval = sched_setscheduler(p, policy, &lparam);
3714         rcu_read_unlock();
3715 
3716         return retval;
3717 }
3718 
3719 /*
3720  * Mimics kernel/events/core.c perf_copy_attr().
3721  */
3722 static int sched_copy_attr(struct sched_attr __user *uattr,
3723                            struct sched_attr *attr)
3724 {
3725         u32 size;
3726         int ret;
3727 
3728         if (!access_ok(VERIFY_WRITE, uattr, SCHED_ATTR_SIZE_VER0))
3729                 return -EFAULT;
3730 
3731         /*
3732          * zero the full structure, so that a short copy will be nice.
3733          */
3734         memset(attr, 0, sizeof(*attr));
3735 
3736         ret = get_user(size, &uattr->size);
3737         if (ret)
3738                 return ret;
3739 
3740         if (size > PAGE_SIZE)   /* silly large */
3741                 goto err_size;
3742 
3743         if (!size)              /* abi compat */
3744                 size = SCHED_ATTR_SIZE_VER0;
3745 
3746         if (size < SCHED_ATTR_SIZE_VER0)
3747                 goto err_size;
3748 
3749         /*
3750          * If we're handed a bigger struct than we know of,
3751          * ensure all the unknown bits are 0 - i.e. new
3752          * user-space does not rely on any kernel feature
3753          * extensions we dont know about yet.
3754          */
3755         if (size > sizeof(*attr)) {
3756                 unsigned char __user *addr;
3757                 unsigned char __user *end;
3758                 unsigned char val;
3759 
3760                 addr = (void __user *)uattr + sizeof(*attr);
3761                 end  = (void __user *)uattr + size;
3762 
3763                 for (; addr < end; addr++) {
3764                         ret = get_user(val, addr);
3765                         if (ret)
3766                                 return ret;
3767                         if (val)
3768                                 goto err_size;
3769                 }
3770                 size = sizeof(*attr);
3771         }
3772 
3773         ret = copy_from_user(attr, uattr, size);
3774         if (ret)
3775                 return -EFAULT;
3776 
3777         /*
3778          * XXX: do we want to be lenient like existing syscalls; or do we want
3779          * to be strict and return an error on out-of-bounds values?
3780          */
3781         attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE);
3782 
3783         return 0;
3784 
3785 err_size:
3786         put_user(sizeof(*attr), &uattr->size);
3787         return -E2BIG;
3788 }
3789 
3790 /**
3791  * sys_sched_setscheduler - set/change the scheduler policy and RT priority
3792  * @pid: the pid in question.
3793  * @policy: new policy.
3794  * @param: structure containing the new RT priority.
3795  *
3796  * Return: 0 on success. An error code otherwise.
3797  */
3798 SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy,
3799                 struct sched_param __user *, param)
3800 {
3801         /* negative values for policy are not valid */
3802         if (policy < 0)
3803                 return -EINVAL;
3804 
3805         return do_sched_setscheduler(pid, policy, param);
3806 }
3807 
3808 /**
3809  * sys_sched_setparam - set/change the RT priority of a thread
3810  * @pid: the pid in question.
3811  * @param: structure containing the new RT priority.
3812  *
3813  * Return: 0 on success. An error code otherwise.
3814  */
3815 SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
3816 {
3817         return do_sched_setscheduler(pid, SETPARAM_POLICY, param);
3818 }
3819 
3820 /**
3821  * sys_sched_setattr - same as above, but with extended sched_attr
3822  * @pid: the pid in question.
3823  * @uattr: structure containing the extended parameters.
3824  * @flags: for future extension.
3825  */
3826 SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
3827                                unsigned int, flags)
3828 {
3829         struct sched_attr attr;
3830         struct task_struct *p;
3831         int retval;
3832 
3833         if (!uattr || pid < 0 || flags)
3834                 return -EINVAL;
3835 
3836         retval = sched_copy_attr(uattr, &attr);
3837         if (retval)
3838                 return retval;
3839 
3840         if ((int)attr.sched_policy < 0)
3841                 return -EINVAL;
3842 
3843         rcu_read_lock();
3844         retval = -ESRCH;
3845         p = find_process_by_pid(pid);
3846         if (p != NULL)
3847                 retval = sched_setattr(p, &attr);
3848         rcu_read_unlock();
3849 
3850         return retval;
3851 }
3852 
3853 /**
3854  * sys_sched_getscheduler - get the policy (scheduling class) of a thread
3855  * @pid: the pid in question.
3856  *
3857  * Return: On success, the policy of the thread. Otherwise, a negative error
3858  * code.
3859  */
3860 SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
3861 {
3862         struct task_struct *p;
3863         int retval;
3864 
3865         if (pid < 0)
3866                 return -EINVAL;
3867 
3868         retval = -ESRCH;
3869         rcu_read_lock();
3870         p = find_process_by_pid(pid);
3871         if (p) {
3872                 retval = security_task_getscheduler(p);
3873                 if (!retval)
3874                         retval = p->policy
3875                                 | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0);
3876         }
3877         rcu_read_unlock();
3878         return retval;
3879 }
3880 
3881 /**
3882  * sys_sched_getparam - get the RT priority of a thread
3883  * @pid: the pid in question.
3884  * @param: structure containing the RT priority.
3885  *
3886  * Return: On success, 0 and the RT priority is in @param. Otherwise, an error
3887  * code.
3888  */
3889 SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
3890 {
3891         struct sched_param lp = { .sched_priority = 0 };
3892         struct task_struct *p;
3893         int retval;
3894 
3895         if (!param || pid < 0)
3896                 return -EINVAL;
3897 
3898         rcu_read_lock();
3899         p = find_process_by_pid(pid);
3900         retval = -ESRCH;
3901         if (!p)
3902                 goto out_unlock;
3903 
3904         retval = security_task_getscheduler(p);
3905         if (retval)
3906                 goto out_unlock;
3907 
3908         if (task_has_rt_policy(p))
3909                 lp.sched_priority = p->rt_priority;
3910         rcu_read_unlock();
3911 
3912         /*
3913          * This one might sleep, we cannot do it with a spinlock held ...
3914          */
3915         retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
3916 
3917         return retval;
3918 
3919 out_unlock:
3920         rcu_read_unlock();
3921         return retval;
3922 }
3923 
3924 static int sched_read_attr(struct sched_attr __user *uattr,
3925                            struct sched_attr *attr,
3926                            unsigned int usize)
3927 {
3928         int ret;
3929 
3930         if (!access_ok(VERIFY_WRITE, uattr, usize))
3931                 return -EFAULT;
3932 
3933         /*
3934          * If we're handed a smaller struct than we know of,
3935          * ensure all the unknown bits are 0 - i.e. old
3936          * user-space does not get uncomplete information.
3937          */
3938         if (usize < sizeof(*attr)) {
3939                 unsigned char *addr;
3940                 unsigned char *end;
3941 
3942                 addr = (void *)attr + usize;
3943                 end  = (void *)attr + sizeof(*attr);
3944 
3945                 for (; addr < end; addr++) {
3946                         if (*addr)
3947                                 return -EFBIG;
3948                 }
3949 
3950                 attr->size = usize;
3951         }
3952 
3953         ret = copy_to_user(uattr, attr, attr->size);
3954         if (ret)
3955                 return -EFAULT;
3956 
3957         return 0;
3958 }
3959 
3960 /**
3961  * sys_sched_getattr - similar to sched_getparam, but with sched_attr
3962  * @pid: the pid in question.
3963  * @uattr: structure containing the extended parameters.
3964  * @size: sizeof(attr) for fwd/bwd comp.
3965  * @flags: for future extension.
3966  */
3967 SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
3968                 unsigned int, size, unsigned int, flags)
3969 {
3970         struct sched_attr attr = {
3971                 .size = sizeof(struct sched_attr),
3972         };
3973         struct task_struct *p;
3974         int retval;
3975 
3976         if (!uattr || pid < 0 || size > PAGE_SIZE ||
3977             size < SCHED_ATTR_SIZE_VER0 || flags)
3978                 return -EINVAL;
3979 
3980         rcu_read_lock();
3981         p = find_process_by_pid(pid);
3982         retval = -ESRCH;
3983         if (!p)
3984                 goto out_unlock;
3985 
3986         retval = security_task_getscheduler(p);
3987         if (retval)
3988                 goto out_unlock;
3989 
3990         attr.sched_policy = p->policy;
3991         if (p->sched_reset_on_fork)
3992                 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
3993         if (task_has_dl_policy(p))
3994                 __getparam_dl(p, &attr);
3995         else if (task_has_rt_policy(p))
3996                 attr.sched_priority = p->rt_priority;
3997         else
3998                 attr.sched_nice = task_nice(p);
3999 
4000         rcu_read_unlock();
4001 
4002         retval = sched_read_attr(uattr, &attr, size);
4003         return retval;
4004 
4005 out_unlock:
4006         rcu_read_unlock();
4007         return retval;
4008 }
4009 
4010 long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
4011 {
4012         cpumask_var_t cpus_allowed, new_mask;
4013         struct task_struct *p;
4014         int retval;
4015 
4016         rcu_read_lock();
4017 
4018         p = find_process_by_pid(pid);
4019         if (!p) {
4020                 rcu_read_unlock();
4021                 return -ESRCH;
4022         }
4023 
4024         /* Prevent p going away */
4025         get_task_struct(p);
4026         rcu_read_unlock();
4027 
4028         if (p->flags & PF_NO_SETAFFINITY) {
4029                 retval = -EINVAL;
4030                 goto out_put_task;
4031         }
4032         if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
4033                 retval = -ENOMEM;
4034                 goto out_put_task;
4035         }
4036         if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
4037                 retval = -ENOMEM;
4038                 goto out_free_cpus_allowed;
4039         }
4040         retval = -EPERM;
4041         if (!check_same_owner(p)) {
4042                 rcu_read_lock();
4043                 if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
4044                         rcu_read_unlock();
4045                         goto out_free_new_mask;
4046                 }
4047                 rcu_read_unlock();
4048         }
4049 
4050         retval = security_task_setscheduler(p);
4051         if (retval)
4052                 goto out_free_new_mask;
4053 
4054 
4055         cpuset_cpus_allowed(p, cpus_allowed);
4056         cpumask_and(new_mask, in_mask, cpus_allowed);
4057 
4058         /*
4059          * Since bandwidth control happens on root_domain basis,
4060          * if admission test is enabled, we only admit -deadline
4061          * tasks allowed to run on all the CPUs in the task's
4062          * root_domain.
4063          */
4064 #ifdef CONFIG_SMP
4065         if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {
4066                 rcu_read_lock();
4067                 if (!cpumask_subset(task_rq(p)->rd->span, new_mask)) {
4068                         retval = -EBUSY;
4069                         rcu_read_unlock();
4070                         goto out_free_new_mask;
4071                 }
4072                 rcu_read_unlock();
4073         }
4074 #endif
4075 again:
4076         retval = set_cpus_allowed_ptr(p, new_mask);
4077 
4078         if (!retval) {
4079                 cpuset_cpus_allowed(p, cpus_allowed);
4080                 if (!cpumask_subset(new_mask, cpus_allowed)) {
4081                         /*
4082                          * We must have raced with a concurrent cpuset
4083                          * update. Just reset the cpus_allowed to the
4084                          * cpuset's cpus_allowed
4085                          */
4086                         cpumask_copy(new_mask, cpus_allowed);
4087                         goto again;
4088                 }
4089         }
4090 out_free_new_mask:
4091         free_cpumask_var(new_mask);
4092 out_free_cpus_allowed:
4093         free_cpumask_var(cpus_allowed);
4094 out_put_task:
4095         put_task_struct(p);
4096         return retval;
4097 }
4098 
4099 static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
4100                              struct cpumask *new_mask)
4101 {
4102         if (len < cpumask_size())
4103                 cpumask_clear(new_mask);
4104         else if (len > cpumask_size())
4105                 len = cpumask_size();
4106 
4107         return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
4108 }
4109 
4110 /**
4111  * sys_sched_setaffinity - set the cpu affinity of a process
4112  * @pid: pid of the process
4113  * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4114  * @user_mask_ptr: user-space pointer to the new cpu mask
4115  *
4116  * Return: 0 on success. An error code otherwise.
4117  */
4118 SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
4119                 unsigned long __user *, user_mask_ptr)
4120 {
4121         cpumask_var_t new_mask;
4122         int retval;
4123 
4124         if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
4125                 return -ENOMEM;
4126 
4127         retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
4128         if (retval == 0)
4129                 retval = sched_setaffinity(pid, new_mask);
4130         free_cpumask_var(new_mask);
4131         return retval;
4132 }
4133 
4134 long sched_getaffinity(pid_t pid, struct cpumask *mask)
4135 {
4136         struct task_struct *p;
4137         unsigned long flags;
4138         int retval;
4139 
4140         rcu_read_lock();
4141 
4142         retval = -ESRCH;
4143         p = find_process_by_pid(pid);
4144         if (!p)
4145                 goto out_unlock;
4146 
4147         retval = security_task_getscheduler(p);
4148         if (retval)
4149                 goto out_unlock;
4150 
4151         raw_spin_lock_irqsave(&p->pi_lock, flags);
4152         cpumask_and(mask, &p->cpus_allowed, cpu_active_mask);
4153         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
4154 
4155 out_unlock:
4156         rcu_read_unlock();
4157 
4158         return retval;
4159 }
4160 
4161 /**
4162  * sys_sched_getaffinity - get the cpu affinity of a process
4163  * @pid: pid of the process
4164  * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4165  * @user_mask_ptr: user-space pointer to hold the current cpu mask
4166  *
4167  * Return: 0 on success. An error code otherwise.
4168  */
4169 SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
4170                 unsigned long __user *, user_mask_ptr)
4171 {
4172         int ret;
4173         cpumask_var_t mask;
4174 
4175         if ((len * BITS_PER_BYTE) < nr_cpu_ids)
4176                 return -EINVAL;
4177         if (len & (sizeof(unsigned long)-1))
4178                 return -EINVAL;
4179 
4180         if (!alloc_cpumask_var(&mask, GFP_KERNEL))
4181                 return -ENOMEM;
4182 
4183         ret = sched_getaffinity(pid, mask);
4184         if (ret == 0) {
4185                 size_t retlen = min_t(size_t, len, cpumask_size());
4186 
4187                 if (copy_to_user(user_mask_ptr, mask, retlen))
4188                         ret = -EFAULT;
4189                 else
4190                         ret = retlen;
4191         }
4192         free_cpumask_var(mask);
4193 
4194         return ret;
4195 }
4196 
4197 /**
4198  * sys_sched_yield - yield the current processor to other threads.
4199  *
4200  * This function yields the current CPU to other tasks. If there are no
4201  * other threads running on this CPU then this function will return.
4202  *
4203  * Return: 0.
4204  */
4205 SYSCALL_DEFINE0(sched_yield)
4206 {
4207         struct rq *rq = this_rq_lock();
4208 
4209         schedstat_inc(rq, yld_count);
4210         current->sched_class->yield_task(rq);
4211 
4212         /*
4213          * Since we are going to call schedule() anyway, there's
4214          * no need to preempt or enable interrupts:
4215          */
4216         __release(rq->lock);
4217         spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
4218         do_raw_spin_unlock(&rq->lock);
4219         sched_preempt_enable_no_resched();
4220 
4221         schedule();
4222 
4223         return 0;
4224 }
4225 
4226 int __sched _cond_resched(void)
4227 {
4228         if (should_resched()) {
4229                 preempt_schedule_common();
4230                 return 1;
4231         }
4232         return 0;
4233 }
4234 EXPORT_SYMBOL(_cond_resched);
4235 
4236 /*
4237  * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
4238  * call schedule, and on return reacquire the lock.
4239  *
4240  * This works OK both with and without CONFIG_PREEMPT. We do strange low-level
4241  * operations here to prevent schedule() from being called twice (once via
4242  * spin_unlock(), once by hand).
4243  */
4244 int __cond_resched_lock(spinlock_t *lock)
4245 {
4246         int resched = should_resched();
4247         int ret = 0;
4248 
4249         lockdep_assert_held(lock);
4250 
4251         if (spin_needbreak(lock) || resched) {
4252                 spin_unlock(lock);
4253                 if (resched)
4254                         preempt_schedule_common();
4255                 else
4256                         cpu_relax();
4257                 ret = 1;
4258                 spin_lock(lock);
4259         }
4260         return ret;
4261 }
4262 EXPORT_SYMBOL(__cond_resched_lock);
4263 
4264 int __sched __cond_resched_softirq(void)
4265 {
4266         BUG_ON(!in_softirq());
4267 
4268         if (should_resched()) {
4269                 local_bh_enable();
4270                 preempt_schedule_common();
4271                 local_bh_disable();
4272                 return 1;
4273         }
4274         return 0;
4275 }
4276 EXPORT_SYMBOL(__cond_resched_softirq);
4277 
4278 /**
4279  * yield - yield the current processor to other threads.
4280  *
4281  * Do not ever use this function, there's a 99% chance you're doing it wrong.
4282  *
4283  * The scheduler is at all times free to pick the calling task as the most
4284  * eligible task to run, if removing the yield() call from your code breaks
4285  * it, its already broken.
4286  *
4287  * Typical broken usage is:
4288  *
4289  * while (!event)
4290  *      yield();
4291  *
4292  * where one assumes that yield() will let 'the other' process run that will
4293  * make event true. If the current task is a SCHED_FIFO task that will never
4294  * happen. Never use yield() as a progress guarantee!!
4295  *
4296  * If you want to use yield() to wait for something, use wait_event().
4297  * If you want to use yield() to be 'nice' for others, use cond_resched().
4298  * If you still want to use yield(), do not!
4299  */
4300 void __sched yield(void)
4301 {
4302         set_current_state(TASK_RUNNING);
4303         sys_sched_yield();
4304 }
4305 EXPORT_SYMBOL(yield);
4306 
4307 /**
4308  * yield_to - yield the current processor to another thread in
4309  * your thread group, or accelerate that thread toward the
4310  * processor it's on.
4311  * @p: target task
4312  * @preempt: whether task preemption is allowed or not
4313  *
4314  * It's the caller's job to ensure that the target task struct
4315  * can't go away on us before we can do any checks.
4316  *
4317  * Return:
4318  *      true (>0) if we indeed boosted the target task.
4319  *      false (0) if we failed to boost the target.
4320  *      -ESRCH if there's no task to yield to.
4321  */
4322 int __sched yield_to(struct task_struct *p, bool preempt)
4323 {
4324         struct task_struct *curr = current;
4325         struct rq *rq, *p_rq;
4326         unsigned long flags;
4327         int yielded = 0;
4328 
4329         local_irq_save(flags);
4330         rq = this_rq();
4331 
4332 again:
4333         p_rq = task_rq(p);
4334         /*
4335          * If we're the only runnable task on the rq and target rq also
4336          * has only one task, there's absolutely no point in yielding.
4337          */
4338         if (rq->nr_running == 1 && p_rq->nr_running == 1) {
4339                 yielded = -ESRCH;
4340                 goto out_irq;
4341         }
4342 
4343         double_rq_lock(rq, p_rq);
4344         if (task_rq(p) != p_rq) {
4345                 double_rq_unlock(rq, p_rq);
4346                 goto again;
4347         }
4348 
4349         if (!curr->sched_class->yield_to_task)
4350                 goto out_unlock;
4351 
4352         if (curr->sched_class != p->sched_class)
4353                 goto out_unlock;
4354 
4355         if (task_running(p_rq, p) || p->state)
4356                 goto out_unlock;
4357 
4358         yielded = curr->sched_class->yield_to_task(rq, p, preempt);
4359         if (yielded) {
4360                 schedstat_inc(rq, yld_count);
4361                 /*
4362                  * Make p's CPU reschedule; pick_next_entity takes care of
4363                  * fairness.
4364                  */
4365                 if (preempt && rq != p_rq)
4366                         resched_curr(p_rq);
4367         }
4368 
4369 out_unlock:
4370         double_rq_unlock(rq, p_rq);
4371 out_irq:
4372         local_irq_restore(flags);
4373 
4374         if (yielded > 0)
4375                 schedule();
4376 
4377         return yielded;
4378 }
4379 EXPORT_SYMBOL_GPL(yield_to);
4380 
4381 /*
4382  * This task is about to go to sleep on IO. Increment rq->nr_iowait so
4383  * that process accounting knows that this is a task in IO wait state.
4384  */
4385 long __sched io_schedule_timeout(long timeout)
4386 {
4387         int old_iowait = current->in_iowait;
4388         struct rq *rq;
4389         long ret;
4390 
4391         current->in_iowait = 1;
4392         blk_schedule_flush_plug(current);
4393 
4394         delayacct_blkio_start();
4395         rq = raw_rq();
4396         atomic_inc(&rq->nr_iowait);
4397         ret = schedule_timeout(timeout);
4398         current->in_iowait = old_iowait;
4399         atomic_dec(&rq->nr_iowait);
4400         delayacct_blkio_end();
4401 
4402         return ret;
4403 }
4404 EXPORT_SYMBOL(io_schedule_timeout);
4405 
4406 /**
4407  * sys_sched_get_priority_max - return maximum RT priority.
4408  * @policy: scheduling class.
4409  *
4410  * Return: On success, this syscall returns the maximum
4411  * rt_priority that can be used by a given scheduling class.
4412  * On failure, a negative error code is returned.
4413  */
4414 SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
4415 {
4416         int ret = -EINVAL;
4417 
4418         switch (policy) {
4419         case SCHED_FIFO:
4420         case SCHED_RR:
4421                 ret = MAX_USER_RT_PRIO-1;
4422                 break;
4423         case SCHED_DEADLINE:
4424         case SCHED_NORMAL:
4425         case SCHED_BATCH:
4426         case SCHED_IDLE:
4427                 ret = 0;
4428                 break;
4429         }
4430         return ret;
4431 }
4432 
4433 /**
4434  * sys_sched_get_priority_min - return minimum RT priority.
4435  * @policy: scheduling class.
4436  *
4437  * Return: On success, this syscall returns the minimum
4438  * rt_priority that can be used by a given scheduling class.
4439  * On failure, a negative error code is returned.
4440  */
4441 SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
4442 {
4443         int ret = -EINVAL;
4444 
4445         switch (policy) {
4446         case SCHED_FIFO:
4447         case SCHED_RR:
4448                 ret = 1;
4449                 break;
4450         case SCHED_DEADLINE:
4451         case SCHED_NORMAL:
4452         case SCHED_BATCH:
4453         case SCHED_IDLE:
4454                 ret = 0;
4455         }
4456         return ret;
4457 }
4458 
4459 /**
4460  * sys_sched_rr_get_interval - return the default timeslice of a process.
4461  * @pid: pid of the process.
4462  * @interval: userspace pointer to the timeslice value.
4463  *
4464  * this syscall writes the default timeslice value of a given process
4465  * into the user-space timespec buffer. A value of '' means infinity.
4466  *
4467  * Return: On success, 0 and the timeslice is in @interval. Otherwise,
4468  * an error code.
4469  */
4470 SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
4471                 struct timespec __user *, interval)
4472 {
4473         struct task_struct *p;
4474         unsigned int time_slice;
4475         unsigned long flags;
4476         struct rq *rq;
4477         int retval;
4478         struct timespec t;
4479 
4480         if (pid < 0)
4481                 return -EINVAL;
4482 
4483         retval = -ESRCH;
4484         rcu_read_lock();
4485         p = find_process_by_pid(pid);
4486         if (!p)
4487                 goto out_unlock;
4488 
4489         retval = security_task_getscheduler(p);
4490         if (retval)
4491                 goto out_unlock;
4492 
4493         rq = task_rq_lock(p, &flags);
4494         time_slice = 0;
4495         if (p->sched_class->get_rr_interval)
4496                 time_slice = p->sched_class->get_rr_interval(rq, p);
4497         task_rq_unlock(rq, p, &flags);
4498 
4499         rcu_read_unlock();
4500         jiffies_to_timespec(time_slice, &t);
4501         retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
4502         return retval;
4503 
4504 out_unlock:
4505         rcu_read_unlock();
4506         return retval;
4507 }
4508 
4509 static const char stat_nam[] = TASK_STATE_TO_CHAR_STR;
4510 
4511 void sched_show_task(struct task_struct *p)
4512 {
4513         unsigned long free = 0;
4514         int ppid;
4515         unsigned long state = p->state;
4516 
4517         if (state)
4518                 state = __ffs(state) + 1;
4519         printk(KERN_INFO "%-15.15s %c", p->comm,
4520                 state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?');
4521 #if BITS_PER_LONG == 32
4522         if (state == TASK_RUNNING)
4523                 printk(KERN_CONT " running  ");
4524         else
4525                 printk(KERN_CONT " %08lx ", thread_saved_pc(p));
4526 #else
4527         if (state == TASK_RUNNING)
4528                 printk(KERN_CONT "  running task    ");
4529         else
4530                 printk(KERN_CONT " %016lx ", thread_saved_pc(p));
4531 #endif
4532 #ifdef CONFIG_DEBUG_STACK_USAGE
4533         free = stack_not_used(p);
4534 #endif
4535         ppid = 0;
4536         rcu_read_lock();
4537         if (pid_alive(p))
4538                 ppid = task_pid_nr(rcu_dereference(p->real_parent));
4539         rcu_read_unlock();
4540         printk(KERN_CONT "%5lu %5d %6d 0x%08lx\n", free,
4541                 task_pid_nr(p), ppid,
4542                 (unsigned long)task_thread_info(p)->flags);
4543 
4544         print_worker_info(KERN_INFO, p);
4545         show_stack(p, NULL);
4546 }
4547 
4548 void show_state_filter(unsigned long state_filter)
4549 {
4550         struct task_struct *g, *p;
4551 
4552 #if BITS_PER_LONG == 32
4553         printk(KERN_INFO
4554                 "  task                PC stack   pid father\n");
4555 #else
4556         printk(KERN_INFO
4557                 "  task                        PC stack   pid father\n");
4558 #endif
4559         rcu_read_lock();
4560         for_each_process_thread(g, p) {
4561                 /*
4562                  * reset the NMI-timeout, listing all files on a slow
4563                  * console might take a lot of time:
4564                  */
4565                 touch_nmi_watchdog();
4566                 if (!state_filter || (p->state & state_filter))
4567                         sched_show_task(p);
4568         }
4569 
4570         touch_all_softlockup_watchdogs();
4571 
4572 #ifdef CONFIG_SCHED_DEBUG
4573         sysrq_sched_debug_show();
4574 #endif
4575         rcu_read_unlock();
4576         /*
4577          * Only show locks if all tasks are dumped:
4578          */
4579         if (!state_filter)
4580                 debug_show_all_locks();
4581 }
4582 
4583 void init_idle_bootup_task(struct task_struct *idle)
4584 {
4585         idle->sched_class = &idle_sched_class;
4586 }
4587 
4588 /**
4589  * init_idle - set up an idle thread for a given CPU
4590  * @idle: task in question
4591  * @cpu: cpu the idle task belongs to
4592  *
4593  * NOTE: this function does not set the idle thread's NEED_RESCHED
4594  * flag, to make booting more robust.
4595  */
4596 void init_idle(struct task_struct *idle, int cpu)
4597 {
4598         struct rq *rq = cpu_rq(cpu);
4599         unsigned long flags;
4600 
4601         raw_spin_lock_irqsave(&rq->lock, flags);
4602 
4603         __sched_fork(0, idle);
4604         idle->state = TASK_RUNNING;
4605         idle->se.exec_start = sched_clock();
4606 
4607         do_set_cpus_allowed(idle, cpumask_of(cpu));
4608         /*
4609          * We're having a chicken and egg problem, even though we are
4610          * holding rq->lock, the cpu isn't yet set to this cpu so the
4611          * lockdep check in task_group() will fail.
4612          *
4613          * Similar case to sched_fork(). / Alternatively we could
4614          * use task_rq_lock() here and obtain the other rq->lock.
4615          *
4616          * Silence PROVE_RCU
4617          */
4618         rcu_read_lock();
4619         __set_task_cpu(idle, cpu);
4620         rcu_read_unlock();
4621 
4622         rq->curr = rq->idle = idle;
4623         idle->on_rq = TASK_ON_RQ_QUEUED;
4624 #if defined(CONFIG_SMP)
4625         idle->on_cpu = 1;
4626 #endif
4627         raw_spin_unlock_irqrestore(&rq->lock, flags);
4628 
4629         /* Set the preempt count _outside_ the spinlocks! */
4630         init_idle_preempt_count(idle, cpu);
4631 
4632         /*
4633          * The idle tasks have their own, simple scheduling class:
4634          */
4635         idle->sched_class = &idle_sched_class;
4636         ftrace_graph_init_idle_task(idle, cpu);
4637         vtime_init_idle(idle, cpu);
4638 #if defined(CONFIG_SMP)
4639         sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu);
4640 #endif
4641 }
4642 
4643 int cpuset_cpumask_can_shrink(const struct cpumask *cur,
4644                               const struct cpumask *trial)
4645 {
4646         int ret = 1, trial_cpus;
4647         struct dl_bw *cur_dl_b;
4648         unsigned long flags;
4649 
4650         if (!cpumask_weight(cur))
4651                 return ret;
4652 
4653         rcu_read_lock_sched();
4654         cur_dl_b = dl_bw_of(cpumask_any(cur));
4655         trial_cpus = cpumask_weight(trial);
4656 
4657         raw_spin_lock_irqsave(&cur_dl_b->lock, flags);
4658         if (cur_dl_b->bw != -1 &&
4659             cur_dl_b->bw * trial_cpus < cur_dl_b->total_bw)
4660                 ret = 0;
4661         raw_spin_unlock_irqrestore(&cur_dl_b->lock, flags);
4662         rcu_read_unlock_sched();
4663 
4664         return ret;
4665 }
4666 
4667 int task_can_attach(struct task_struct *p,
4668                     const struct cpumask *cs_cpus_allowed)
4669 {
4670         int ret = 0;
4671 
4672         /*
4673          * Kthreads which disallow setaffinity shouldn't be moved
4674          * to a new cpuset; we don't want to change their cpu
4675          * affinity and isolating such threads by their set of
4676          * allowed nodes is unnecessary.  Thus, cpusets are not
4677          * applicable for such threads.  This prevents checking for
4678          * success of set_cpus_allowed_ptr() on all attached tasks
4679          * before cpus_allowed may be changed.
4680          */
4681         if (p->flags & PF_NO_SETAFFINITY) {
4682                 ret = -EINVAL;
4683                 goto out;
4684         }
4685 
4686 #ifdef CONFIG_SMP
4687         if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span,
4688                                               cs_cpus_allowed)) {
4689                 unsigned int dest_cpu = cpumask_any_and(cpu_active_mask,
4690                                                         cs_cpus_allowed);
4691                 struct dl_bw *dl_b;
4692                 bool overflow;
4693                 int cpus;
4694                 unsigned long flags;
4695 
4696                 rcu_read_lock_sched();
4697                 dl_b = dl_bw_of(dest_cpu);
4698                 raw_spin_lock_irqsave(&dl_b->lock, flags);
4699                 cpus = dl_bw_cpus(dest_cpu);
4700                 overflow = __dl_overflow(dl_b, cpus, 0, p->dl.dl_bw);
4701                 if (overflow)
4702                         ret = -EBUSY;
4703                 else {
4704                         /*
4705                          * We reserve space for this task in the destination
4706                          * root_domain, as we can't fail after this point.
4707                          * We will free resources in the source root_domain
4708                          * later on (see set_cpus_allowed_dl()).
4709                          */
4710                         __dl_add(dl_b, p->dl.dl_bw);
4711                 }
4712                 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
4713                 rcu_read_unlock_sched();
4714 
4715         }
4716 #endif
4717 out:
4718         return ret;
4719 }
4720 
4721 #ifdef CONFIG_SMP
4722 /*
4723  * move_queued_task - move a queued task to new rq.
4724  *
4725  * Returns (locked) new rq. Old rq's lock is released.
4726  */
4727 static struct rq *move_queued_task(struct task_struct *p, int new_cpu)
4728 {
4729         struct rq *rq = task_rq(p);
4730 
4731         lockdep_assert_held(&rq->lock);
4732 
4733         dequeue_task(rq, p, 0);
4734         p->on_rq = TASK_ON_RQ_MIGRATING;
4735         set_task_cpu(p, new_cpu);
4736         raw_spin_unlock(&rq->lock);
4737 
4738         rq = cpu_rq(new_cpu);
4739 
4740         raw_spin_lock(&rq->lock);
4741         BUG_ON(task_cpu(p) != new_cpu);
4742         p->on_rq = TASK_ON_RQ_QUEUED;
4743         enqueue_task(rq, p, 0);
4744         check_preempt_curr(rq, p, 0);
4745 
4746         return rq;
4747 }
4748 
4749 void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
4750 {
4751         if (p->sched_class->set_cpus_allowed)
4752                 p->sched_class->set_cpus_allowed(p, new_mask);
4753 
4754         cpumask_copy(&p->cpus_allowed, new_mask);
4755         p->nr_cpus_allowed = cpumask_weight(new_mask);
4756 }
4757 
4758 /*
4759  * This is how migration works:
4760  *
4761  * 1) we invoke migration_cpu_stop() on the target CPU using
4762  *    stop_one_cpu().
4763  * 2) stopper starts to run (implicitly forcing the migrated thread
4764  *    off the CPU)
4765  * 3) it checks whether the migrated task is still in the wrong runqueue.
4766  * 4) if it's in the wrong runqueue then the migration thread removes
4767  *    it and puts it into the right queue.
4768  * 5) stopper completes and stop_one_cpu() returns and the migration
4769  *    is done.
4770  */
4771 
4772 /*
4773  * Change a given task's CPU affinity. Migrate the thread to a
4774  * proper CPU and schedule it away if the CPU it's executing on
4775  * is removed from the allowed bitmask.
4776  *
4777  * NOTE: the caller must have a valid reference to the task, the
4778  * task must not exit() & deallocate itself prematurely. The
4779  * call is not atomic; no spinlocks may be held.
4780  */
4781 int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
4782 {
4783         unsigned long flags;
4784         struct rq *rq;
4785         unsigned int dest_cpu;
4786         int ret = 0;
4787 
4788         rq = task_rq_lock(p, &flags);
4789 
4790         if (cpumask_equal(&p->cpus_allowed, new_mask))
4791                 goto out;
4792 
4793         if (!cpumask_intersects(new_mask, cpu_active_mask)) {
4794                 ret = -EINVAL;
4795                 goto out;
4796         }
4797 
4798         do_set_cpus_allowed(p, new_mask);
4799 
4800         /* Can the task run on the task's current CPU? If so, we're done */
4801         if (cpumask_test_cpu(task_cpu(p), new_mask))
4802                 goto out;
4803 
4804         dest_cpu = cpumask_any_and(cpu_active_mask, new_mask);
4805         if (task_running(rq, p) || p->state == TASK_WAKING) {
4806                 struct migration_arg arg = { p, dest_cpu };
4807                 /* Need help from migration thread: drop lock and wait. */
4808                 task_rq_unlock(rq, p, &flags);
4809                 stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
4810                 tlb_migrate_finish(p->mm);
4811                 return 0;
4812         } else if (task_on_rq_queued(p))
4813                 rq = move_queued_task(p, dest_cpu);
4814 out:
4815         task_rq_unlock(rq, p, &flags);
4816 
4817         return ret;
4818 }
4819 EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
4820 
4821 /*
4822  * Move (not current) task off this cpu, onto dest cpu. We're doing
4823  * this because either it can't run here any more (set_cpus_allowed()
4824  * away from this CPU, or CPU going down), or because we're
4825  * attempting to rebalance this task on exec (sched_exec).
4826  *
4827  * So we race with normal scheduler movements, but that's OK, as long
4828  * as the task is no longer on this CPU.
4829  *
4830  * Returns non-zero if task was successfully migrated.
4831  */
4832 static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
4833 {
4834         struct rq *rq;
4835         int ret = 0;
4836 
4837         if (unlikely(!cpu_active(dest_cpu)))
4838                 return ret;
4839 
4840         rq = cpu_rq(src_cpu);
4841 
4842         raw_spin_lock(&p->pi_lock);
4843         raw_spin_lock(&rq->lock);
4844         /* Already moved. */
4845         if (task_cpu(p) != src_cpu)
4846                 goto done;
4847 
4848         /* Affinity changed (again). */
4849         if (!cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p)))
4850                 goto fail;
4851 
4852         /*
4853          * If we're not on a rq, the next wake-up will ensure we're
4854          * placed properly.
4855          */
4856         if (task_on_rq_queued(p))
4857                 rq = move_queued_task(p, dest_cpu);
4858 done:
4859         ret = 1;
4860 fail:
4861         raw_spin_unlock(&rq->lock);
4862         raw_spin_unlock(&p->pi_lock);
4863         return ret;
4864 }
4865 
4866 #ifdef CONFIG_NUMA_BALANCING
4867 /* Migrate current task p to target_cpu */
4868 int migrate_task_to(struct task_struct *p, int target_cpu)
4869 {
4870         struct migration_arg arg = { p, target_cpu };
4871         int curr_cpu = task_cpu(p);
4872 
4873         if (curr_cpu == target_cpu)
4874                 return 0;
4875 
4876         if (!cpumask_test_cpu(target_cpu, tsk_cpus_allowed(p)))
4877                 return -EINVAL;
4878 
4879         /* TODO: This is not properly updating schedstats */
4880 
4881         trace_sched_move_numa(p, curr_cpu, target_cpu);
4882         return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);
4883 }
4884 
4885 /*
4886  * Requeue a task on a given node and accurately track the number of NUMA
4887  * tasks on the runqueues
4888  */
4889 void sched_setnuma(struct task_struct *p, int nid)
4890 {
4891         struct rq *rq;
4892         unsigned long flags;
4893         bool queued, running;
4894 
4895         rq = task_rq_lock(p, &flags);
4896         queued = task_on_rq_queued(p);
4897         running = task_current(rq, p);
4898 
4899         if (queued)
4900                 dequeue_task(rq, p, 0);
4901         if (running)
4902                 put_prev_task(rq, p);
4903 
4904         p->numa_preferred_nid = nid;
4905 
4906         if (running)
4907                 p->sched_class->set_curr_task(rq);
4908         if (queued)
4909                 enqueue_task(rq, p, 0);
4910         task_rq_unlock(rq, p, &flags);
4911 }
4912 #endif
4913 
4914 /*
4915  * migration_cpu_stop - this will be executed by a highprio stopper thread
4916  * and performs thread migration by bumping thread off CPU then
4917  * 'pushing' onto another runqueue.
4918  */
4919 static int migration_cpu_stop(void *data)
4920 {
4921         struct migration_arg *arg = data;
4922 
4923         /*
4924          * The original target cpu might have gone down and we might
4925          * be on another cpu but it doesn't matter.
4926          */
4927         local_irq_disable();
4928         /*
4929          * We need to explicitly wake pending tasks before running
4930          * __migrate_task() such that we will not miss enforcing cpus_allowed
4931          * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
4932          */
4933         sched_ttwu_pending();
4934         __migrate_task(arg->task, raw_smp_processor_id(), arg->dest_cpu);
4935         local_irq_enable();
4936         return 0;
4937 }
4938 
4939 #ifdef CONFIG_HOTPLUG_CPU
4940 
4941 /*
4942  * Ensures that the idle task is using init_mm right before its cpu goes
4943  * offline.
4944  */
4945 void idle_task_exit(void)
4946 {
4947         struct mm_struct *mm = current->active_mm;
4948 
4949         BUG_ON(cpu_online(smp_processor_id()));
4950 
4951         if (mm != &init_mm) {
4952                 switch_mm(mm, &init_mm, current);
4953                 finish_arch_post_lock_switch();
4954         }
4955         mmdrop(mm);
4956 }
4957 
4958 /*
4959  * Since this CPU is going 'away' for a while, fold any nr_active delta
4960  * we might have. Assumes we're called after migrate_tasks() so that the
4961  * nr_active count is stable.
4962  *
4963  * Also see the comment "Global load-average calculations".
4964  */
4965 static void calc_load_migrate(struct rq *rq)
4966 {
4967         long delta = calc_load_fold_active(rq);
4968         if (delta)
4969                 atomic_long_add(delta, &calc_load_tasks);
4970 }
4971 
4972 static void put_prev_task_fake(struct rq *rq, struct task_struct *prev)
4973 {
4974 }
4975 
4976 static const struct sched_class fake_sched_class = {
4977         .put_prev_task = put_prev_task_fake,
4978 };
4979 
4980 static struct task_struct fake_task = {
4981         /*
4982          * Avoid pull_{rt,dl}_task()
4983          */
4984         .prio = MAX_PRIO + 1,
4985         .sched_class = &fake_sched_class,
4986 };
4987 
4988 /*
4989  * Migrate all tasks from the rq, sleeping tasks will be migrated by
4990  * try_to_wake_up()->select_task_rq().
4991  *
4992  * Called with rq->lock held even though we'er in stop_machine() and
4993  * there's no concurrency possible, we hold the required locks anyway
4994  * because of lock validation efforts.
4995  */
4996 static void migrate_tasks(unsigned int dead_cpu)
4997 {
4998         struct rq *rq = cpu_rq(dead_cpu);
4999         struct task_struct *next, *stop = rq->stop;
5000         int dest_cpu;
5001 
5002         /*
5003          * Fudge the rq selection such that the below task selection loop
5004          * doesn't get stuck on the currently eligible stop task.
5005          *
5006          * We're currently inside stop_machine() and the rq is either stuck
5007          * in the stop_machine_cpu_stop() loop, or we're executing this code,
5008          * either way we should never end up calling schedule() until we're
5009          * done here.
5010          */
5011         rq->stop = NULL;
5012 
5013         /*
5014          * put_prev_task() and pick_next_task() sched
5015          * class method both need to have an up-to-date
5016          * value of rq->clock[_task]
5017          */
5018         update_rq_clock(rq);
5019 
5020         for ( ; ; ) {
5021                 /*
5022                  * There's this thread running, bail when that's the only
5023                  * remaining thread.
5024                  */
5025                 if (rq->nr_running == 1)
5026                         break;
5027 
5028                 next = pick_next_task(rq, &fake_task);
5029                 BUG_ON(!next);
5030                 next->sched_class->put_prev_task(rq, next);
5031 
5032                 /* Find suitable destination for @next, with force if needed. */
5033                 dest_cpu = select_fallback_rq(dead_cpu, next);
5034                 raw_spin_unlock(&rq->lock);
5035 
5036                 __migrate_task(next, dead_cpu, dest_cpu);
5037 
5038                 raw_spin_lock(&rq->lock);
5039         }
5040 
5041         rq->stop = stop;
5042 }
5043 
5044 #endif /* CONFIG_HOTPLUG_CPU */
5045 
5046 #if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_SYSCTL)
5047 
5048 static struct ctl_table sd_ctl_dir[] = {
5049         {
5050                 .procname       = "sched_domain",
5051                 .mode           = 0555,
5052         },
5053         {}
5054 };
5055 
5056 static struct ctl_table sd_ctl_root[] = {
5057         {
5058                 .procname       = "kernel",
5059                 .mode           = 0555,
5060                 .child          = sd_ctl_dir,
5061         },
5062         {}
5063 };
5064 
5065 static struct ctl_table *sd_alloc_ctl_entry(int n)
5066 {
5067         struct ctl_table *entry =
5068                 kcalloc(n, sizeof(struct ctl_table), GFP_KERNEL);
5069 
5070         return entry;
5071 }
5072 
5073 static void sd_free_ctl_entry(struct ctl_table **tablep)
5074 {
5075         struct ctl_table *entry;
5076 
5077         /*
5078          * In the intermediate directories, both the child directory and
5079          * procname are dynamically allocated and could fail but the mode
5080          * will always be set. In the lowest directory the names are
5081          * static strings and all have proc handlers.
5082          */
5083         for (entry = *tablep; entry->mode; entry++) {
5084                 if (entry->child)
5085                         sd_free_ctl_entry(&entry->child);
5086                 if (entry->proc_handler == NULL)
5087                         kfree(entry->procname);
5088         }
5089 
5090         kfree(*tablep);
5091         *tablep = NULL;
5092 }
5093 
5094 static int min_load_idx = 0;
5095 static int max_load_idx = CPU_LOAD_IDX_MAX-1;
5096 
5097 static void
5098 set_table_entry(struct ctl_table *entry,
5099                 const char *procname, void *data, int maxlen,
5100                 umode_t mode, proc_handler *proc_handler,
5101                 bool load_idx)
5102 {
5103         entry->procname = procname;
5104         entry->data = data;
5105         entry->maxlen = maxlen;
5106         entry->mode = mode;
5107         entry->proc_handler = proc_handler;
5108 
5109         if (load_idx) {
5110                 entry->extra1 = &min_load_idx;
5111                 entry->extra2 = &max_load_idx;
5112         }
5113 }
5114 
5115 static struct ctl_table *
5116 sd_alloc_ctl_domain_table(struct sched_domain *sd)
5117 {
5118         struct ctl_table *table = sd_alloc_ctl_entry(14);
5119 
5120         if (table == NULL)
5121                 return NULL;
5122 
5123         set_table_entry(&table[0], "min_interval", &sd->min_interval,
5124                 sizeof(long), 0644, proc_doulongvec_minmax, false);
5125         set_table_entry(&table[1], "max_interval", &sd->max_interval,
5126                 sizeof(long), 0644, proc_doulongvec_minmax, false);
5127         set_table_entry(&table[2], "busy_idx", &sd->busy_idx,
5128                 sizeof(int), 0644, proc_dointvec_minmax, true);
5129         set_table_entry(&table[3], "idle_idx", &sd->idle_idx,
5130                 sizeof(int), 0644, proc_dointvec_minmax, true);
5131         set_table_entry(&table[4], "newidle_idx", &sd->newidle_idx,
5132                 sizeof(int), 0644, proc_dointvec_minmax, true);
5133         set_table_entry(&table[5], "wake_idx", &sd->wake_idx,
5134                 sizeof(int), 0644, proc_dointvec_minmax, true);
5135         set_table_entry(&table[6], "forkexec_idx", &sd->forkexec_idx,
5136                 sizeof(int), 0644, proc_dointvec_minmax, true);
5137         set_table_entry(&table[7], "busy_factor", &sd->busy_factor,
5138                 sizeof(int), 0644, proc_dointvec_minmax, false);
5139         set_table_entry(&table[8], "imbalance_pct", &sd->imbalance_pct,
5140                 sizeof(int), 0644, proc_dointvec_minmax, false);
5141         set_table_entry(&table[9], "cache_nice_tries",
5142                 &sd->cache_nice_tries,
5143                 sizeof(int), 0644, proc_dointvec_minmax, false);
5144         set_table_entry(&table[10], "flags", &sd->flags,
5145                 sizeof(int), 0644, proc_dointvec_minmax, false);
5146         set_table_entry(&table[11], "max_newidle_lb_cost",
5147                 &sd->max_newidle_lb_cost,
5148                 sizeof(long), 0644, proc_doulongvec_minmax, false);
5149         set_table_entry(&table[12], "name", sd->name,
5150                 CORENAME_MAX_SIZE, 0444, proc_dostring, false);
5151         /* &table[13] is terminator */
5152 
5153         return table;
5154 }
5155 
5156 static struct ctl_table *sd_alloc_ctl_cpu_table(int cpu)
5157 {
5158         struct ctl_table *entry, *table;
5159         struct sched_domain *sd;
5160         int domain_num = 0, i;
5161         char buf[32];
5162 
5163         for_each_domain(cpu, sd)
5164                 domain_num++;
5165         entry = table = sd_alloc_ctl_entry(domain_num + 1);
5166         if (table == NULL)
5167                 return NULL;
5168 
5169         i = 0;
5170         for_each_domain(cpu, sd) {
5171                 snprintf(buf, 32, "domain%d", i);
5172                 entry->procname = kstrdup(buf, GFP_KERNEL);
5173                 entry->mode = 0555;
5174                 entry->child = sd_alloc_ctl_domain_table(sd);
5175                 entry++;
5176                 i++;
5177         }
5178         return table;
5179 }
5180 
5181 static struct ctl_table_header *sd_sysctl_header;
5182 static void register_sched_domain_sysctl(void)
5183 {
5184         int i, cpu_num = num_possible_cpus();
5185         struct ctl_table *entry = sd_alloc_ctl_entry(cpu_num + 1);
5186         char buf[32];
5187 
5188         WARN_ON(sd_ctl_dir[0].child);
5189         sd_ctl_dir[0].child = entry;
5190 
5191         if (entry == NULL)
5192                 return;
5193 
5194         for_each_possible_cpu(i) {
5195                 snprintf(buf, 32, "cpu%d", i);
5196                 entry->procname = kstrdup(buf, GFP_KERNEL);
5197                 entry->mode = 0555;
5198                 entry->child = sd_alloc_ctl_cpu_table(i);
5199                 entry++;
5200         }
5201 
5202         WARN_ON(sd_sysctl_header);
5203         sd_sysctl_header = register_sysctl_table(sd_ctl_root);
5204 }
5205 
5206 /* may be called multiple times per register */
5207 static void unregister_sched_domain_sysctl(void)
5208 {
5209         if (sd_sysctl_header)
5210                 unregister_sysctl_table(sd_sysctl_header);
5211         sd_sysctl_header = NULL;
5212         if (sd_ctl_dir[0].child)
5213                 sd_free_ctl_entry(&sd_ctl_dir[0].child);
5214 }
5215 #else
5216 static void register_sched_domain_sysctl(void)
5217 {
5218 }
5219 static void unregister_sched_domain_sysctl(void)
5220 {
5221 }
5222 #endif
5223 
5224 static void set_rq_online(struct rq *rq)
5225 {
5226         if (!rq->online) {
5227                 const struct sched_class *class;
5228 
5229                 cpumask_set_cpu(rq->cpu, rq->rd->online);
5230                 rq->online = 1;
5231 
5232                 for_each_class(class) {
5233                         if (class->rq_online)
5234                                 class->rq_online(rq);
5235                 }
5236         }
5237 }
5238 
5239 static void set_rq_offline(struct rq *rq)
5240 {
5241         if (rq->online) {
5242                 const struct sched_class *class;
5243 
5244                 for_each_class(class) {
5245                         if (class->rq_offline)
5246                                 class->rq_offline(rq);
5247                 }
5248 
5249                 cpumask_clear_cpu(rq->cpu, rq->rd->online);
5250                 rq->online = 0;
5251         }
5252 }
5253 
5254 /*
5255  * migration_call - callback that gets triggered when a CPU is added.
5256  * Here we can start up the necessary migration thread for the new CPU.
5257  */
5258 static int
5259 migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
5260 {
5261         int cpu = (long)hcpu;
5262         unsigned long flags;
5263         struct rq *rq = cpu_rq(cpu);
5264 
5265         switch (action & ~CPU_TASKS_FROZEN) {
5266 
5267         case CPU_UP_PREPARE:
5268                 rq->calc_load_update = calc_load_update;
5269                 break;
5270 
5271         case CPU_ONLINE:
5272                 /* Update our root-domain */
5273                 raw_spin_lock_irqsave(&rq->lock, flags);
5274                 if (rq->rd) {
5275                         BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
5276 
5277                         set_rq_online(rq);
5278                 }
5279                 raw_spin_unlock_irqrestore(&rq->lock, flags);
5280                 break;
5281 
5282 #ifdef CONFIG_HOTPLUG_CPU
5283         case CPU_DYING:
5284                 sched_ttwu_pending();
5285                 /* Update our root-domain */
5286                 raw_spin_lock_irqsave(&rq->lock, flags);
5287                 if (rq->rd) {
5288                         BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
5289                         set_rq_offline(rq);
5290                 }
5291                 migrate_tasks(cpu);
5292                 BUG_ON(rq->nr_running != 1); /* the migration thread */
5293                 raw_spin_unlock_irqrestore(&rq->lock, flags);
5294                 break;
5295 
5296         case CPU_DEAD:
5297                 calc_load_migrate(rq);
5298                 break;
5299 #endif
5300         }
5301 
5302         update_max_interval();
5303 
5304         return NOTIFY_OK;
5305 }
5306 
5307 /*
5308  * Register at high priority so that task migration (migrate_all_tasks)
5309  * happens before everything else.  This has to be lower priority than
5310  * the notifier in the perf_event subsystem, though.
5311  */
5312 static struct notifier_block migration_notifier = {
5313         .notifier_call = migration_call,
5314         .priority = CPU_PRI_MIGRATION,
5315 };
5316 
5317 static void __cpuinit set_cpu_rq_start_time(void)
5318 {
5319         int cpu = smp_processor_id();
5320         struct rq *rq = cpu_rq(cpu);
5321         rq->age_stamp = sched_clock_cpu(cpu);
5322 }
5323 
5324 static int sched_cpu_active(struct notifier_block *nfb,
5325                                       unsigned long action, void *hcpu)
5326 {
5327         switch (action & ~CPU_TASKS_FROZEN) {
5328         case CPU_STARTING:
5329                 set_cpu_rq_start_time();
5330                 return NOTIFY_OK;
5331         case CPU_DOWN_FAILED:
5332                 set_cpu_active((long)hcpu, true);
5333                 return NOTIFY_OK;
5334         default:
5335                 return NOTIFY_DONE;
5336         }
5337 }
5338 
5339 static int sched_cpu_inactive(struct notifier_block *nfb,
5340                                         unsigned long action, void *hcpu)
5341 {
5342         switch (action & ~CPU_TASKS_FROZEN) {
5343         case CPU_DOWN_PREPARE:
5344                 set_cpu_active((long)hcpu, false);
5345                 return NOTIFY_OK;
5346         default:
5347                 return NOTIFY_DONE;
5348         }
5349 }
5350 
5351 static int __init migration_init(void)
5352 {
5353         void *cpu = (void *)(long)smp_processor_id();
5354         int err;
5355 
5356         /* Initialize migration for the boot CPU */
5357         err = migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
5358         BUG_ON(err == NOTIFY_BAD);
5359         migration_call(&migration_notifier, CPU_ONLINE, cpu);
5360         register_cpu_notifier(&migration_notifier);
5361 
5362         /* Register cpu active notifiers */
5363         cpu_notifier(sched_cpu_active, CPU_PRI_SCHED_ACTIVE);
5364         cpu_notifier(sched_cpu_inactive, CPU_PRI_SCHED_INACTIVE);
5365 
5366         return 0;
5367 }
5368 early_initcall(migration_init);
5369 #endif
5370 
5371 #ifdef CONFIG_SMP
5372 
5373 static cpumask_var_t sched_domains_tmpmask; /* sched_domains_mutex */
5374 
5375 #ifdef CONFIG_SCHED_DEBUG
5376 
5377 static __read_mostly int sched_debug_enabled;
5378 
5379 static int __init sched_debug_setup(char *str)
5380 {
5381         sched_debug_enabled = 1;
5382 
5383         return 0;
5384 }
5385 early_param("sched_debug", sched_debug_setup);
5386 
5387 static inline bool sched_debug(void)
5388 {
5389         return sched_debug_enabled;
5390 }
5391 
5392 static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,
5393                                   struct cpumask *groupmask)
5394 {
5395         struct sched_group *group = sd->groups;
5396 
5397         cpumask_clear(groupmask);
5398 
5399         printk(KERN_DEBUG "%*s domain %d: ", level, "", level);
5400 
5401         if (!(sd->flags & SD_LOAD_BALANCE)) {
5402                 printk("does not load-balance\n");
5403                 if (sd->parent)
5404                         printk(KERN_ERR "ERROR: !SD_LOAD_BALANCE domain"
5405                                         " has parent");
5406                 return -1;
5407         }
5408 
5409         printk(KERN_CONT "span %*pbl level %s\n",
5410                cpumask_pr_args(sched_domain_span(sd)), sd->name);
5411 
5412         if (!cpumask_test_cpu(cpu, sched_domain_span(sd))) {
5413                 printk(KERN_ERR "ERROR: domain->span does not contain "
5414                                 "CPU%d\n", cpu);
5415         }
5416         if (!cpumask_test_cpu(cpu, sched_group_cpus(group))) {
5417                 printk(KERN_ERR "ERROR: domain->groups does not contain"
5418                                 " CPU%d\n", cpu);
5419         }
5420 
5421         printk(KERN_DEBUG "%*s groups:", level + 1, "");
5422         do {
5423                 if (!group) {
5424                         printk("\n");
5425                         printk(KERN_ERR "ERROR: group is NULL\n");
5426                         break;
5427                 }
5428 
5429                 if (!cpumask_weight(sched_group_cpus(group))) {
5430                         printk(KERN_CONT "\n");
5431                         printk(KERN_ERR "ERROR: empty group\n");
5432                         break;
5433                 }
5434 
5435                 if (!(sd->flags & SD_OVERLAP) &&
5436                     cpumask_intersects(groupmask, sched_group_cpus(group))) {
5437                         printk(KERN_CONT "\n");
5438                         printk(KERN_ERR "ERROR: repeated CPUs\n");
5439                         break;
5440                 }
5441 
5442                 cpumask_or(groupmask, groupmask, sched_group_cpus(group));
5443 
5444                 printk(KERN_CONT " %*pbl",
5445                        cpumask_pr_args(sched_group_cpus(group)));
5446                 if (group->sgc->capacity != SCHED_CAPACITY_SCALE) {
5447                         printk(KERN_CONT " (cpu_capacity = %d)",
5448                                 group->sgc->capacity);
5449                 }
5450 
5451                 group = group->next;
5452         } while (group != sd->groups);
5453         printk(KERN_CONT "\n");
5454 
5455         if (!cpumask_equal(sched_domain_span(sd), groupmask))
5456                 printk(KERN_ERR "ERROR: groups don't span domain->span\n");
5457 
5458         if (sd->parent &&
5459             !cpumask_subset(groupmask, sched_domain_span(sd->parent)))
5460                 printk(KERN_ERR "ERROR: parent span is not a superset "
5461                         "of domain->span\n");
5462         return 0;
5463 }
5464 
5465 static void sched_domain_debug(struct sched_domain *sd, int cpu)
5466 {
5467         int level = 0;
5468 
5469         if (!sched_debug_enabled)
5470                 return;
5471 
5472         if (!sd) {
5473                 printk(KERN_DEBUG "CPU%d attaching NULL sched-domain.\n", cpu);
5474                 return;
5475         }
5476 
5477         printk(KERN_DEBUG "CPU%d attaching sched-domain:\n", cpu);
5478 
5479         for (;;) {
5480                 if (sched_domain_debug_one(sd, cpu, level, sched_domains_tmpmask))
5481                         break;
5482                 level++;
5483                 sd = sd->parent;
5484                 if (!sd)
5485                         break;
5486         }
5487 }
5488 #else /* !CONFIG_SCHED_DEBUG */
5489 # define sched_domain_debug(sd, cpu) do { } while (0)
5490 static inline bool sched_debug(void)
5491 {
5492         return false;
5493 }
5494 #endif /* CONFIG_SCHED_DEBUG */
5495 
5496 static int sd_degenerate(struct sched_domain *sd)
5497 {
5498         if (cpumask_weight(sched_domain_span(sd)) == 1)
5499                 return 1;
5500 
5501         /* Following flags need at least 2 groups */
5502         if (sd->flags & (SD_LOAD_BALANCE |
5503                          SD_BALANCE_NEWIDLE |
5504                          SD_BALANCE_FORK |
5505                          SD_BALANCE_EXEC |
5506                          SD_SHARE_CPUCAPACITY |
5507                          SD_SHARE_PKG_RESOURCES |
5508                          SD_SHARE_POWERDOMAIN)) {
5509                 if (sd->groups != sd->groups->next)
5510                         return 0;
5511         }
5512 
5513         /* Following flags don't use groups */
5514         if (sd->flags & (SD_WAKE_AFFINE))
5515                 return 0;
5516 
5517         return 1;
5518 }
5519 
5520 static int
5521 sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
5522 {
5523         unsigned long cflags = sd->flags, pflags = parent->flags;
5524 
5525         if (sd_degenerate(parent))
5526                 return 1;
5527 
5528         if (!cpumask_equal(sched_domain_span(sd), sched_domain_span(parent)))
5529                 return 0;
5530 
5531         /* Flags needing groups don't count if only 1 group in parent */
5532         if (parent->groups == parent->groups->next) {
5533                 pflags &= ~(SD_LOAD_BALANCE |
5534                                 SD_BALANCE_NEWIDLE |
5535                                 SD_BALANCE_FORK |
5536                                 SD_BALANCE_EXEC |
5537                                 SD_SHARE_CPUCAPACITY |
5538                                 SD_SHARE_PKG_RESOURCES |
5539                                 SD_PREFER_SIBLING |
5540                                 SD_SHARE_POWERDOMAIN);
5541                 if (nr_node_ids == 1)
5542                         pflags &= ~SD_SERIALIZE;
5543         }
5544         if (~cflags & pflags)
5545                 return 0;
5546 
5547         return 1;
5548 }
5549 
5550 static void free_rootdomain(struct rcu_head *rcu)
5551 {
5552         struct root_domain *rd = container_of(rcu, struct root_domain, rcu);
5553 
5554         cpupri_cleanup(&rd->cpupri);
5555         cpudl_cleanup(&rd->cpudl);
5556         free_cpumask_var(rd->dlo_mask);
5557         free_cpumask_var(rd->rto_mask);
5558         free_cpumask_var(rd->online);
5559         free_cpumask_var(rd->span);
5560         kfree(rd);
5561 }
5562 
5563 static void rq_attach_root(struct rq *rq, struct root_domain *rd)
5564 {
5565         struct root_domain *old_rd = NULL;
5566         unsigned long flags;
5567 
5568         raw_spin_lock_irqsave(&rq->lock, flags);
5569 
5570         if (rq->rd) {
5571                 old_rd = rq->rd;
5572 
5573                 if (cpumask_test_cpu(rq->cpu, old_rd->online))
5574                         set_rq_offline(rq);
5575 
5576                 cpumask_clear_cpu(rq->cpu, old_rd->span);
5577 
5578                 /*
5579                  * If we dont want to free the old_rd yet then
5580                  * set old_rd to NULL to skip the freeing later
5581                  * in this function:
5582                  */
5583                 if (!atomic_dec_and_test(&old_rd->refcount))
5584                         old_rd = NULL;
5585         }
5586 
5587         atomic_inc(&rd->refcount);
5588         rq->rd = rd;
5589 
5590         cpumask_set_cpu(rq->cpu, rd->span);
5591         if (cpumask_test_cpu(rq->cpu, cpu_active_mask))
5592                 set_rq_online(rq);
5593 
5594         raw_spin_unlock_irqrestore(&rq->lock, flags);
5595 
5596         if (old_rd)
5597                 call_rcu_sched(&old_rd->rcu, free_rootdomain);
5598 }
5599 
5600 static int init_rootdomain(struct root_domain *rd)
5601 {
5602         memset(rd, 0, sizeof(*rd));
5603 
5604         if (!alloc_cpumask_var(&rd->span, GFP_KERNEL))
5605                 goto out;
5606         if (!alloc_cpumask_var(&rd->online, GFP_KERNEL))
5607                 goto free_span;
5608         if (!alloc_cpumask_var(&rd->dlo_mask, GFP_KERNEL))
5609                 goto free_online;
5610         if (!alloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))
5611                 goto free_dlo_mask;
5612 
5613         init_dl_bw(&rd->dl_bw);
5614         if (cpudl_init(&rd->cpudl) != 0)
5615                 goto free_dlo_mask;
5616 
5617         if (cpupri_init(&rd->cpupri) != 0)
5618                 goto free_rto_mask;
5619         return 0;
5620 
5621 free_rto_mask:
5622         free_cpumask_var(rd->rto_mask);
5623 free_dlo_mask:
5624         free_cpumask_var(rd->dlo_mask);
5625 free_online:
5626         free_cpumask_var(rd->online);
5627 free_span:
5628         free_cpumask_var(rd->span);
5629 out:
5630         return -ENOMEM;
5631 }
5632 
5633 /*
5634  * By default the system creates a single root-domain with all cpus as
5635  * members (mimicking the global state we have today).
5636  */
5637 struct root_domain def_root_domain;
5638 
5639 static void init_defrootdomain(void)
5640 {
5641         init_rootdomain(&def_root_domain);
5642 
5643         atomic_set(&def_root_domain.refcount, 1);
5644 }
5645 
5646 static struct root_domain *alloc_rootdomain(void)
5647 {
5648         struct root_domain *rd;
5649 
5650         rd = kmalloc(sizeof(*rd), GFP_KERNEL);
5651         if (!rd)
5652                 return NULL;
5653 
5654         if (init_rootdomain(rd) != 0) {
5655                 kfree(rd);
5656                 return NULL;
5657         }
5658 
5659         return rd;
5660 }
5661 
5662 static void free_sched_groups(struct sched_group *sg, int free_sgc)
5663 {
5664         struct sched_group *tmp, *first;
5665 
5666         if (!sg)
5667                 return;
5668 
5669         first = sg;
5670         do {
5671                 tmp = sg->next;
5672 
5673                 if (free_sgc && atomic_dec_and_test(&sg->sgc->ref))
5674                         kfree(sg->sgc);
5675 
5676                 kfree(sg);
5677                 sg = tmp;
5678         } while (sg != first);
5679 }
5680 
5681 static void free_sched_domain(struct rcu_head *rcu)
5682 {
5683         struct sched_domain *sd = container_of(rcu, struct sched_domain, rcu);
5684 
5685         /*
5686          * If its an overlapping domain it has private groups, iterate and
5687          * nuke them all.
5688          */
5689         if (sd->flags & SD_OVERLAP) {
5690                 free_sched_groups(sd->groups, 1);
5691         } else if (atomic_dec_and_test(&sd->groups->ref)) {
5692                 kfree(sd->groups->sgc);
5693                 kfree(sd->groups);
5694         }
5695         kfree(sd);
5696 }
5697 
5698 static void destroy_sched_domain(struct sched_domain *sd, int cpu)
5699 {
5700         call_rcu(&sd->rcu, free_sched_domain);
5701 }
5702 
5703 static void destroy_sched_domains(struct sched_domain *sd, int cpu)
5704 {
5705         for (; sd; sd = sd->parent)
5706                 destroy_sched_domain(sd, cpu);
5707 }
5708 
5709 /*
5710  * Keep a special pointer to the highest sched_domain that has
5711  * SD_SHARE_PKG_RESOURCE set (Last Level Cache Domain) for this
5712  * allows us to avoid some pointer chasing select_idle_sibling().
5713  *
5714  * Also keep a unique ID per domain (we use the first cpu number in
5715  * the cpumask of the domain), this allows us to quickly tell if
5716  * two cpus are in the same cache domain, see cpus_share_cache().
5717  */
5718 DEFINE_PER_CPU(struct sched_domain *, sd_llc);
5719 DEFINE_PER_CPU(int, sd_llc_size);
5720 DEFINE_PER_CPU(int, sd_llc_id);
5721 DEFINE_PER_CPU(struct sched_domain *, sd_numa);
5722 DEFINE_PER_CPU(struct sched_domain *, sd_busy);
5723 DEFINE_PER_CPU(struct sched_domain *, sd_asym);
5724 
5725 static void update_top_cache_domain(int cpu)
5726 {
5727         struct sched_domain *sd;
5728         struct sched_domain *busy_sd = NULL;
5729         int id = cpu;
5730         int size = 1;
5731 
5732         sd = highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES);
5733         if (sd) {
5734                 id = cpumask_first(sched_domain_span(sd));
5735                 size = cpumask_weight(sched_domain_span(sd));
5736                 busy_sd = sd->parent; /* sd_busy */
5737         }
5738         rcu_assign_pointer(per_cpu(sd_busy, cpu), busy_sd);
5739 
5740         rcu_assign_pointer(per_cpu(sd_llc, cpu), sd);
5741         per_cpu(sd_llc_size, cpu) = size;
5742         per_cpu(sd_llc_id, cpu) = id;
5743 
5744         sd = lowest_flag_domain(cpu, SD_NUMA);
5745         rcu_assign_pointer(per_cpu(sd_numa, cpu), sd);
5746 
5747         sd = highest_flag_domain(cpu, SD_ASYM_PACKING);
5748         rcu_assign_pointer(per_cpu(sd_asym, cpu), sd);
5749 }
5750 
5751 /*
5752  * Attach the domain 'sd' to 'cpu' as its base domain. Callers must
5753  * hold the hotplug lock.
5754  */
5755 static void
5756 cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
5757 {
5758         struct rq *rq = cpu_rq(cpu);
5759         struct sched_domain *tmp;
5760 
5761         /* Remove the sched domains which do not contribute to scheduling. */
5762         for (tmp = sd; tmp; ) {
5763                 struct sched_domain *parent = tmp->parent;
5764                 if (!parent)
5765                         break;
5766 
5767                 if (sd_parent_degenerate(tmp, parent)) {
5768                         tmp->parent = parent->parent;
5769                         if (parent->parent)
5770                                 parent->parent->child = tmp;
5771                         /*
5772                          * Transfer SD_PREFER_SIBLING down in case of a
5773                          * degenerate parent; the spans match for this
5774                          * so the property transfers.
5775                          */
5776                         if (parent->flags & SD_PREFER_SIBLING)
5777                                 tmp->flags |= SD_PREFER_SIBLING;
5778                         destroy_sched_domain(parent, cpu);
5779                 } else
5780                         tmp = tmp->parent;
5781         }
5782 
5783         if (sd && sd_degenerate(sd)) {
5784                 tmp = sd;
5785                 sd = sd->parent;
5786                 destroy_sched_domain(tmp, cpu);
5787                 if (sd)
5788                         sd->child = NULL;
5789         }
5790 
5791         sched_domain_debug(sd, cpu);
5792 
5793         rq_attach_root(rq, rd);
5794         tmp = rq->sd;
5795         rcu_assign_pointer(rq->sd, sd);
5796         destroy_sched_domains(tmp, cpu);
5797 
5798         update_top_cache_domain(cpu);
5799 }
5800 
5801 /* Setup the mask of cpus configured for isolated domains */
5802 static int __init isolated_cpu_setup(char *str)
5803 {
5804         alloc_bootmem_cpumask_var(&cpu_isolated_map);
5805         cpulist_parse(str, cpu_isolated_map);
5806         return 1;
5807 }
5808 
5809 __setup("isolcpus=", isolated_cpu_setup);
5810 
5811 struct s_data {
5812         struct sched_domain ** __percpu sd;
5813         struct root_domain      *rd;
5814 };
5815 
5816 enum s_alloc {
5817         sa_rootdomain,
5818         sa_sd,
5819         sa_sd_storage,
5820         sa_none,
5821 };
5822 
5823 /*
5824  * Build an iteration mask that can exclude certain CPUs from the upwards
5825  * domain traversal.
5826  *
5827  * Asymmetric node setups can result in situations where the domain tree is of
5828  * unequal depth, make sure to skip domains that already cover the entire
5829  * range.
5830  *
5831  * In that case build_sched_domains() will have terminated the iteration early
5832  * and our sibling sd spans will be empty. Domains should always include the
5833  * cpu they're built on, so check that.
5834  *
5835  */
5836 static void build_group_mask(struct sched_domain *sd, struct sched_group *sg)
5837 {
5838         const struct cpumask *span = sched_domain_span(sd);
5839         struct sd_data *sdd = sd->private;
5840         struct sched_domain *sibling;
5841         int i;
5842 
5843         for_each_cpu(i, span) {
5844                 sibling = *per_cpu_ptr(sdd->sd, i);
5845                 if (!cpumask_test_cpu(i, sched_domain_span(sibling)))
5846                         continue;
5847 
5848                 cpumask_set_cpu(i, sched_group_mask(sg));
5849         }
5850 }
5851 
5852 /*
5853  * Return the canonical balance cpu for this group, this is the first cpu
5854  * of this group that's also in the iteration mask.
5855  */
5856 int group_balance_cpu(struct sched_group *sg)
5857 {
5858         return cpumask_first_and(sched_group_cpus(sg), sched_group_mask(sg));
5859 }
5860 
5861 static int
5862 build_overlap_sched_groups(struct sched_domain *sd, int cpu)
5863 {
5864         struct sched_group *first = NULL, *last = NULL, *groups = NULL, *sg;
5865         const struct cpumask *span = sched_domain_span(sd);
5866         struct cpumask *covered = sched_domains_tmpmask;
5867         struct sd_data *sdd = sd->private;
5868         struct sched_domain *sibling;
5869         int i;
5870 
5871         cpumask_clear(covered);
5872 
5873         for_each_cpu(i, span) {
5874                 struct cpumask *sg_span;
5875 
5876                 if (cpumask_test_cpu(i, covered))
5877                         continue;
5878 
5879                 sibling = *per_cpu_ptr(sdd->sd, i);
5880 
5881                 /* See the comment near build_group_mask(). */
5882                 if (!cpumask_test_cpu(i, sched_domain_span(sibling)))
5883                         continue;
5884 
5885                 sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(),
5886                                 GFP_KERNEL, cpu_to_node(cpu));
5887 
5888                 if (!sg)
5889                         goto fail;
5890 
5891                 sg_span = sched_group_cpus(sg);
5892                 if (sibling->child)
5893                         cpumask_copy(sg_span, sched_domain_span(sibling->child));
5894                 else
5895                         cpumask_set_cpu(i, sg_span);
5896 
5897                 cpumask_or(covered, covered, sg_span);
5898 
5899                 sg->sgc = *per_cpu_ptr(sdd->sgc, i);
5900                 if (atomic_inc_return(&sg->sgc->ref) == 1)
5901                         build_group_mask(sd, sg);
5902 
5903                 /*
5904                  * Initialize sgc->capacity such that even if we mess up the
5905                  * domains and no possible iteration will get us here, we won't
5906                  * die on a /0 trap.
5907                  */
5908                 sg->sgc->capacity = SCHED_CAPACITY_SCALE * cpumask_weight(sg_span);
5909 
5910                 /*
5911                  * Make sure the first group of this domain contains the
5912                  * canonical balance cpu. Otherwise the sched_domain iteration
5913                  * breaks. See update_sg_lb_stats().
5914                  */
5915                 if ((!groups && cpumask_test_cpu(cpu, sg_span)) ||
5916                     group_balance_cpu(sg) == cpu)
5917                         groups = sg;
5918 
5919                 if (!first)
5920                         first = sg;
5921                 if (last)
5922                         last->next = sg;
5923                 last = sg;
5924                 last->next = first;
5925         }
5926         sd->groups = groups;
5927 
5928         return 0;
5929 
5930 fail:
5931         free_sched_groups(first, 0);
5932 
5933         return -ENOMEM;
5934 }
5935 
5936 static int get_group(int cpu, struct sd_data *sdd, struct sched_group **sg)
5937 {
5938         struct sched_domain *sd = *per_cpu_ptr(sdd->sd, cpu);
5939         struct sched_domain *child = sd->child;
5940 
5941         if (child)
5942                 cpu = cpumask_first(sched_domain_span(child));
5943 
5944         if (sg) {
5945                 *sg = *per_cpu_ptr(sdd->sg, cpu);
5946                 (*sg)->sgc = *per_cpu_ptr(sdd->sgc, cpu);
5947                 atomic_set(&(*sg)->sgc->ref, 1); /* for claim_allocations */
5948         }
5949 
5950         return cpu;
5951 }
5952 
5953 /*
5954  * build_sched_groups will build a circular linked list of the groups
5955  * covered by the given span, and will set each group's ->cpumask correctly,
5956  * and ->cpu_capacity to 0.
5957  *
5958  * Assumes the sched_domain tree is fully constructed
5959  */
5960 static int
5961 build_sched_groups(struct sched_domain *sd, int cpu)
5962 {
5963         struct sched_group *first = NULL, *last = NULL;
5964         struct sd_data *sdd = sd->private;
5965         const struct cpumask *span = sched_domain_span(sd);
5966         struct cpumask *covered;
5967         int i;
5968 
5969         get_group(cpu, sdd, &sd->groups);
5970         atomic_inc(&sd->groups->ref);
5971 
5972         if (cpu != cpumask_first(span))
5973                 return 0;
5974 
5975         lockdep_assert_held(&sched_domains_mutex);
5976         covered = sched_domains_tmpmask;
5977 
5978         cpumask_clear(covered);
5979 
5980         for_each_cpu(i, span) {
5981                 struct sched_group *sg;
5982                 int group, j;
5983 
5984                 if (cpumask_test_cpu(i, covered))
5985                         continue;
5986 
5987                 group = get_group(i, sdd, &sg);
5988                 cpumask_setall(sched_group_mask(sg));
5989 
5990                 for_each_cpu(j, span) {
5991                         if (get_group(j, sdd, NULL) != group)
5992                                 continue;
5993 
5994                         cpumask_set_cpu(j, covered);
5995                         cpumask_set_cpu(j, sched_group_cpus(sg));
5996                 }
5997 
5998                 if (!first)
5999                         first = sg;
6000                 if (last)
6001                         last->next = sg;
6002                 last = sg;
6003         }
6004         last->next = first;
6005 
6006         return 0;
6007 }
6008 
6009 /*
6010  * Initialize sched groups cpu_capacity.
6011  *
6012  * cpu_capacity indicates the capacity of sched group, which is used while
6013  * distributing the load between different sched groups in a sched domain.
6014  * Typically cpu_capacity for all the groups in a sched domain will be same
6015  * unless there are asymmetries in the topology. If there are asymmetries,
6016  * group having more cpu_capacity will pickup more load compared to the
6017  * group having less cpu_capacity.
6018  */
6019 static void init_sched_groups_capacity(int cpu, struct sched_domain *sd)
6020 {
6021         struct sched_group *sg = sd->groups;
6022 
6023         WARN_ON(!sg);
6024 
6025         do {
6026                 sg->group_weight = cpumask_weight(sched_group_cpus(sg));
6027                 sg = sg->next;
6028         } while (sg != sd->groups);
6029 
6030         if (cpu != group_balance_cpu(sg))
6031                 return;
6032 
6033         update_group_capacity(sd, cpu);
6034         atomic_set(&sg->sgc->nr_busy_cpus, sg->group_weight);
6035 }
6036 
6037 /*
6038  * Initializers for schedule domains
6039  * Non-inlined to reduce accumulated stack pressure in build_sched_domains()
6040  */
6041 
6042 static int default_relax_domain_level = -1;
6043 int sched_domain_level_max;
6044 
6045 static int __init setup_relax_domain_level(char *str)
6046 {
6047         if (kstrtoint(str, 0, &default_relax_domain_level))
6048                 pr_warn("Unable to set relax_domain_level\n");
6049 
6050         return 1;
6051 }
6052 __setup("relax_domain_level=", setup_relax_domain_level);
6053 
6054 static void set_domain_attribute(struct sched_domain *sd,
6055                                  struct sched_domain_attr *attr)
6056 {
6057         int request;
6058 
6059         if (!attr || attr->relax_domain_level < 0) {
6060                 if (default_relax_domain_level < 0)
6061                         return;
6062                 else
6063                         request = default_relax_domain_level;
6064         } else
6065                 request = attr->relax_domain_level;
6066         if (request < sd->level) {
6067                 /* turn off idle balance on this domain */
6068                 sd->flags &= ~(SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
6069         } else {
6070                 /* turn on idle balance on this domain */
6071                 sd->flags |= (SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
6072         }
6073 }
6074 
6075 static void __sdt_free(const struct cpumask *cpu_map);
6076 static int __sdt_alloc(const struct cpumask *cpu_map);
6077 
6078 static void __free_domain_allocs(struct s_data *d, enum s_alloc what,
6079                                  const struct cpumask *cpu_map)
6080 {
6081         switch (what) {
6082         case sa_rootdomain:
6083                 if (!atomic_read(&d->rd->refcount))
6084                         free_rootdomain(&d->rd->rcu); /* fall through */
6085         case sa_sd:
6086                 free_percpu(d->sd); /* fall through */
6087         case sa_sd_storage:
6088                 __sdt_free(cpu_map); /* fall through */
6089         case sa_none:
6090                 break;
6091         }
6092 }
6093 
6094 static enum s_alloc __visit_domain_allocation_hell(struct s_data *d,
6095                                                    const struct cpumask *cpu_map)
6096 {
6097         memset(d, 0, sizeof(*d));
6098 
6099         if (__sdt_alloc(cpu_map))
6100                 return sa_sd_storage;
6101         d->sd = alloc_percpu(struct sched_domain *);
6102         if (!d->sd)
6103                 return sa_sd_storage;
6104         d->rd = alloc_rootdomain();
6105         if (!d->rd)
6106                 return sa_sd;
6107         return sa_rootdomain;
6108 }
6109 
6110 /*
6111  * NULL the sd_data elements we've used to build the sched_domain and
6112  * sched_group structure so that the subsequent __free_domain_allocs()
6113  * will not free the data we're using.
6114  */
6115 static void claim_allocations(int cpu, struct sched_domain *sd)
6116 {
6117         struct sd_data *sdd = sd->private;
6118 
6119         WARN_ON_ONCE(*per_cpu_ptr(sdd->sd, cpu) != sd);
6120         *per_cpu_ptr(sdd->sd, cpu) = NULL;
6121 
6122         if (atomic_read(&(*per_cpu_ptr(sdd->sg, cpu))->ref))
6123                 *per_cpu_ptr(sdd->sg, cpu) = NULL;
6124 
6125         if (atomic_read(&(*per_cpu_ptr(sdd->sgc, cpu))->ref))
6126                 *per_cpu_ptr(sdd->sgc, cpu) = NULL;
6127 }
6128 
6129 #ifdef CONFIG_NUMA
6130 static int sched_domains_numa_levels;
6131 enum numa_topology_type sched_numa_topology_type;
6132 static int *sched_domains_numa_distance;
6133 int sched_max_numa_distance;
6134 static struct cpumask ***sched_domains_numa_masks;
6135 static int sched_domains_curr_level;
6136 #endif
6137 
6138 /*
6139  * SD_flags allowed in topology descriptions.
6140  *
6141  * SD_SHARE_CPUCAPACITY      - describes SMT topologies
6142  * SD_SHARE_PKG_RESOURCES - describes shared caches
6143  * SD_NUMA                - describes NUMA topologies
6144  * SD_SHARE_POWERDOMAIN   - describes shared power domain
6145  *
6146  * Odd one out:
6147  * SD_ASYM_PACKING        - describes SMT quirks
6148  */
6149 #define TOPOLOGY_SD_FLAGS               \
6150         (SD_SHARE_CPUCAPACITY |         \
6151          SD_SHARE_PKG_RESOURCES |       \
6152          SD_NUMA |                      \
6153          SD_ASYM_PACKING |              \
6154          SD_SHARE_POWERDOMAIN)
6155 
6156 static struct sched_domain *
6157 sd_init(struct sched_domain_topology_level *tl, int cpu)
6158 {
6159         struct sched_domain *sd = *per_cpu_ptr(tl->data.sd, cpu);
6160         int sd_weight, sd_flags = 0;
6161 
6162 #ifdef CONFIG_NUMA
6163         /*
6164          * Ugly hack to pass state to sd_numa_mask()...
6165          */
6166         sched_domains_curr_level = tl->numa_level;
6167 #endif
6168 
6169         sd_weight = cpumask_weight(tl->mask(cpu));
6170 
6171         if (tl->sd_flags)
6172                 sd_flags = (*tl->sd_flags)();
6173         if (WARN_ONCE(sd_flags & ~TOPOLOGY_SD_FLAGS,
6174                         "wrong sd_flags in topology description\n"))
6175                 sd_flags &= ~TOPOLOGY_SD_FLAGS;
6176 
6177         *sd = (struct sched_domain){
6178                 .min_interval           = sd_weight,
6179                 .max_interval           = 2*sd_weight,
6180                 .busy_factor            = 32,
6181                 .imbalance_pct          = 125,
6182 
6183                 .cache_nice_tries       = 0,
6184                 .busy_idx               = 0,
6185                 .idle_idx               = 0,
6186                 .newidle_idx            = 0,
6187                 .wake_idx               = 0,
6188                 .forkexec_idx           = 0,
6189 
6190                 .flags                  = 1*SD_LOAD_BALANCE
6191                                         | 1*SD_BALANCE_NEWIDLE
6192                                         | 1*SD_BALANCE_EXEC
6193                                         | 1*SD_BALANCE_FORK
6194                                         | 0*SD_BALANCE_WAKE
6195                                         | 1*SD_WAKE_AFFINE
6196                                         | 0*SD_SHARE_CPUCAPACITY
6197                                         | 0*SD_SHARE_PKG_RESOURCES
6198                                         | 0*SD_SERIALIZE
6199                                         | 0*SD_PREFER_SIBLING
6200                                         | 0*SD_NUMA
6201                                         | sd_flags
6202                                         ,
6203 
6204                 .last_balance           = jiffies,
6205                 .balance_interval       = sd_weight,
6206                 .smt_gain               = 0,
6207                 .max_newidle_lb_cost    = 0,
6208                 .next_decay_max_lb_cost = jiffies,
6209 #ifdef CONFIG_SCHED_DEBUG
6210                 .name                   = tl->name,
6211 #endif
6212         };
6213 
6214         /*
6215          * Convert topological properties into behaviour.
6216          */
6217 
6218         if (sd->flags & SD_SHARE_CPUCAPACITY) {
6219                 sd->flags |= SD_PREFER_SIBLING;
6220                 sd->imbalance_pct = 110;
6221                 sd->smt_gain = 1178; /* ~15% */
6222 
6223         } else if (sd->flags & SD_SHARE_PKG_RESOURCES) {
6224                 sd->imbalance_pct = 117;
6225                 sd->cache_nice_tries = 1;
6226                 sd->busy_idx = 2;
6227 
6228 #ifdef CONFIG_NUMA
6229         } else if (sd->flags & SD_NUMA) {
6230                 sd->cache_nice_tries = 2;
6231                 sd->busy_idx = 3;
6232                 sd->idle_idx = 2;
6233 
6234                 sd->flags |= SD_SERIALIZE;
6235                 if (sched_domains_numa_distance[tl->numa_level] > RECLAIM_DISTANCE) {
6236                         sd->flags &= ~(SD_BALANCE_EXEC |
6237                                        SD_BALANCE_FORK |
6238                                        SD_WAKE_AFFINE);
6239                 }
6240 
6241 #endif
6242         } else {
6243                 sd->flags |= SD_PREFER_SIBLING;
6244                 sd->cache_nice_tries = 1;
6245                 sd->busy_idx = 2;
6246                 sd->idle_idx = 1;
6247         }
6248 
6249         sd->private = &tl->data;
6250 
6251         return sd;
6252 }
6253 
6254 /*
6255  * Topology list, bottom-up.
6256  */
6257 static struct sched_domain_topology_level default_topology[] = {
6258 #ifdef CONFIG_SCHED_SMT
6259         { cpu_smt_mask, cpu_smt_flags, SD_INIT_NAME(SMT) },
6260 #endif
6261 #ifdef CONFIG_SCHED_MC
6262         { cpu_coregroup_mask, cpu_core_flags, SD_INIT_NAME(MC) },
6263 #endif
6264         { cpu_cpu_mask, SD_INIT_NAME(DIE) },
6265         { NULL, },
6266 };
6267 
6268 struct sched_domain_topology_level *sched_domain_topology = default_topology;
6269 
6270 #define for_each_sd_topology(tl)                        \
6271         for (tl = sched_domain_topology; tl->mask; tl++)
6272 
6273 void set_sched_topology(struct sched_domain_topology_level *tl)
6274 {
6275         sched_domain_topology = tl;
6276 }
6277 
6278 #ifdef CONFIG_NUMA
6279 
6280 static const struct cpumask *sd_numa_mask(int cpu)
6281 {
6282         return sched_domains_numa_masks[sched_domains_curr_level][cpu_to_node(cpu)];
6283 }
6284 
6285 static void sched_numa_warn(const char *str)
6286 {
6287         static int done = false;
6288         int i,j;
6289 
6290         if (done)
6291                 return;
6292 
6293         done = true;
6294 
6295         printk(KERN_WARNING "ERROR: %s\n\n", str);
6296 
6297         for (i = 0; i < nr_node_ids; i++) {
6298                 printk(KERN_WARNING "  ");
6299                 for (j = 0; j < nr_node_ids; j++)
6300                         printk(KERN_CONT "%02d ", node_distance(i,j));
6301                 printk(KERN_CONT "\n");
6302         }
6303         printk(KERN_WARNING "\n");
6304 }
6305 
6306 bool find_numa_distance(int distance)
6307 {
6308         int i;
6309 
6310         if (distance == node_distance(0, 0))
6311                 return true;
6312 
6313         for (i = 0; i < sched_domains_numa_levels; i++) {
6314                 if (sched_domains_numa_distance[i] == distance)
6315                         return true;
6316         }
6317 
6318         return false;
6319 }
6320 
6321 /*
6322  * A system can have three types of NUMA topology:
6323  * NUMA_DIRECT: all nodes are directly connected, or not a NUMA system
6324  * NUMA_GLUELESS_MESH: some nodes reachable through intermediary nodes
6325  * NUMA_BACKPLANE: nodes can reach other nodes through a backplane
6326  *
6327  * The difference between a glueless mesh topology and a backplane
6328  * topology lies in whether communication between not directly
6329  * connected nodes goes through intermediary nodes (where programs
6330  * could run), or through backplane controllers. This affects
6331  * placement of programs.
6332  *
6333  * The type of topology can be discerned with the following tests:
6334  * - If the maximum distance between any nodes is 1 hop, the system
6335  *   is directly connected.
6336  * - If for two nodes A and B, located N > 1 hops away from each other,
6337  *   there is an intermediary node C, which is < N hops away from both
6338  *   nodes A and B, the system is a glueless mesh.
6339  */
6340 static void init_numa_topology_type(void)
6341 {
6342         int a, b, c, n;
6343 
6344         n = sched_max_numa_distance;
6345 
6346         if (n <= 1)
6347                 sched_numa_topology_type = NUMA_DIRECT;
6348 
6349         for_each_online_node(a) {
6350                 for_each_online_node(b) {
6351                         /* Find two nodes furthest removed from each other. */
6352                         if (node_distance(a, b) < n)
6353                                 continue;
6354 
6355                         /* Is there an intermediary node between a and b? */
6356                         for_each_online_node(c) {
6357                                 if (node_distance(a, c) < n &&
6358                                     node_distance(b, c) < n) {
6359                                         sched_numa_topology_type =
6360                                                         NUMA_GLUELESS_MESH;
6361                                         return;
6362                                 }
6363                         }
6364 
6365                         sched_numa_topology_type = NUMA_BACKPLANE;
6366                         return;
6367                 }
6368         }
6369 }
6370 
6371 static void sched_init_numa(void)
6372 {
6373         int next_distance, curr_distance = node_distance(0, 0);
6374         struct sched_domain_topology_level *tl;
6375         int level = 0;
6376         int i, j, k;
6377 
6378         sched_domains_numa_distance = kzalloc(sizeof(int) * nr_node_ids, GFP_KERNEL);
6379         if (!sched_domains_numa_distance)
6380                 return;
6381 
6382         /*
6383          * O(nr_nodes^2) deduplicating selection sort -- in order to find the
6384          * unique distances in the node_distance() table.
6385          *
6386          * Assumes node_distance(0,j) includes all distances in
6387          * node_distance(i,j) in order to avoid cubic time.
6388          */
6389         next_distance = curr_distance;
6390         for (i = 0; i < nr_node_ids; i++) {
6391                 for (j = 0; j < nr_node_ids; j++) {
6392                         for (k = 0; k < nr_node_ids; k++) {
6393                                 int distance = node_distance(i, k);
6394 
6395                                 if (distance > curr_distance &&
6396                                     (distance < next_distance ||
6397                                      next_distance == curr_distance))
6398                                         next_distance = distance;
6399 
6400                                 /*
6401                                  * While not a strong assumption it would be nice to know
6402                                  * about cases where if node A is connected to B, B is not
6403                                  * equally connected to A.
6404                                  */
6405                                 if (sched_debug() && node_distance(k, i) != distance)
6406                                         sched_numa_warn("Node-distance not symmetric");
6407 
6408                                 if (sched_debug() && i && !find_numa_distance(distance))
6409                                         sched_numa_warn("Node-0 not representative");
6410                         }
6411                         if (next_distance != curr_distance) {
6412                                 sched_domains_numa_distance[level++] = next_distance;
6413                                 sched_domains_numa_levels = level;
6414                                 curr_distance = next_distance;
6415                         } else break;
6416                 }
6417 
6418                 /*
6419                  * In case of sched_debug() we verify the above assumption.
6420                  */
6421                 if (!sched_debug())
6422                         break;
6423         }
6424 
6425         if (!level)
6426                 return;
6427 
6428         /*
6429          * 'level' contains the number of unique distances, excluding the
6430          * identity distance node_distance(i,i).
6431          *
6432          * The sched_domains_numa_distance[] array includes the actual distance
6433          * numbers.
6434          */
6435 
6436         /*
6437          * Here, we should temporarily reset sched_domains_numa_levels to 0.
6438          * If it fails to allocate memory for array sched_domains_numa_masks[][],
6439          * the array will contain less then 'level' members. This could be
6440          * dangerous when we use it to iterate array sched_domains_numa_masks[][]
6441          * in other functions.
6442          *
6443          * We reset it to 'level' at the end of this function.
6444          */
6445         sched_domains_numa_levels = 0;
6446 
6447         sched_domains_numa_masks = kzalloc(sizeof(void *) * level, GFP_KERNEL);
6448         if (!sched_domains_numa_masks)
6449                 return;
6450 
6451         /*
6452          * Now for each level, construct a mask per node which contains all
6453          * cpus of nodes that are that many hops away from us.
6454          */
6455         for (i = 0; i < level; i++) {
6456                 sched_domains_numa_masks[i] =
6457                         kzalloc(nr_node_ids * sizeof(void *), GFP_KERNEL);
6458                 if (!sched_domains_numa_masks[i])
6459                         return;
6460 
6461                 for (j = 0; j < nr_node_ids; j++) {
6462                         struct cpumask *mask = kzalloc(cpumask_size(), GFP_KERNEL);
6463                         if (!mask)
6464                                 return;
6465 
6466                         sched_domains_numa_masks[i][j] = mask;
6467 
6468                         for (k = 0; k < nr_node_ids; k++) {
6469                                 if (node_distance(j, k) > sched_domains_numa_distance[i])
6470                                         continue;
6471 
6472                                 cpumask_or(mask, mask, cpumask_of_node(k));
6473                         }
6474                 }
6475         }
6476 
6477         /* Compute default topology size */
6478         for (i = 0; sched_domain_topology[i].mask; i++);
6479 
6480         tl = kzalloc((i + level + 1) *
6481                         sizeof(struct sched_domain_topology_level), GFP_KERNEL);
6482         if (!tl)
6483                 return;
6484 
6485         /*
6486          * Copy the default topology bits..
6487          */
6488         for (i = 0; sched_domain_topology[i].mask; i++)
6489                 tl[i] = sched_domain_topology[i];
6490 
6491         /*
6492          * .. and append 'j' levels of NUMA goodness.
6493          */
6494         for (j = 0; j < level; i++, j++) {
6495                 tl[i] = (struct sched_domain_topology_level){
6496                         .mask = sd_numa_mask,
6497                         .sd_flags = cpu_numa_flags,
6498                         .flags = SDTL_OVERLAP,
6499                         .numa_level = j,
6500                         SD_INIT_NAME(NUMA)
6501                 };
6502         }
6503 
6504         sched_domain_topology = tl;
6505 
6506         sched_domains_numa_levels = level;
6507         sched_max_numa_distance = sched_domains_numa_distance[level - 1];
6508 
6509         init_numa_topology_type();
6510 }
6511 
6512 static void sched_domains_numa_masks_set(int cpu)
6513 {
6514         int i, j;
6515         int node = cpu_to_node(cpu);
6516 
6517         for (i = 0; i < sched_domains_numa_levels; i++) {
6518                 for (j = 0; j < nr_node_ids; j++) {
6519                         if (node_distance(j, node) <= sched_domains_numa_distance[i])
6520                                 cpumask_set_cpu(cpu, sched_domains_numa_masks[i][j]);
6521                 }
6522         }
6523 }
6524 
6525 static void sched_domains_numa_masks_clear(int cpu)
6526 {
6527         int i, j;
6528         for (i = 0; i < sched_domains_numa_levels; i++) {
6529                 for (j = 0; j < nr_node_ids; j++)
6530                         cpumask_clear_cpu(cpu, sched_domains_numa_masks[i][j]);
6531         }
6532 }
6533 
6534 /*
6535  * Update sched_domains_numa_masks[level][node] array when new cpus
6536  * are onlined.
6537  */
6538 static int sched_domains_numa_masks_update(struct notifier_block *nfb,
6539                                            unsigned long action,
6540                                            void *hcpu)
6541 {
6542         int cpu = (long)hcpu;
6543 
6544         switch (action & ~CPU_TASKS_FROZEN) {
6545         case CPU_ONLINE:
6546                 sched_domains_numa_masks_set(cpu);
6547                 break;
6548 
6549         case CPU_DEAD:
6550                 sched_domains_numa_masks_clear(cpu);
6551                 break;
6552 
6553         default:
6554                 return NOTIFY_DONE;
6555         }
6556 
6557         return NOTIFY_OK;
6558 }
6559 #else
6560 static inline void sched_init_numa(void)
6561 {
6562 }
6563 
6564 static int sched_domains_numa_masks_update(struct notifier_block *nfb,
6565                                            unsigned long action,
6566                                            void *hcpu)
6567 {
6568         return 0;
6569 }
6570 #endif /* CONFIG_NUMA */
6571 
6572 static int __sdt_alloc(const struct cpumask *cpu_map)
6573 {
6574         struct sched_domain_topology_level *tl;
6575         int j;
6576 
6577         for_each_sd_topology(tl) {
6578                 struct sd_data *sdd = &tl->data;
6579 
6580                 sdd->sd = alloc_percpu(struct sched_domain *);
6581                 if (!sdd->sd)
6582                         return -ENOMEM;
6583 
6584                 sdd->sg = alloc_percpu(struct sched_group *);
6585                 if (!sdd->sg)
6586                         return -ENOMEM;
6587 
6588                 sdd->sgc = alloc_percpu(struct sched_group_capacity *);
6589                 if (!sdd->sgc)
6590                         return -ENOMEM;
6591 
6592                 for_each_cpu(j, cpu_map) {
6593                         struct sched_domain *sd;
6594                         struct sched_group *sg;
6595                         struct sched_group_capacity *sgc;
6596 
6597                         sd = kzalloc_node(sizeof(struct sched_domain) + cpumask_size(),
6598                                         GFP_KERNEL, cpu_to_node(j));
6599                         if (!sd)
6600                                 return -ENOMEM;
6601 
6602                         *per_cpu_ptr(sdd->sd, j) = sd;
6603 
6604                         sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(),
6605                                         GFP_KERNEL, cpu_to_node(j));
6606                         if (!sg)
6607                                 return -ENOMEM;
6608 
6609                         sg->next = sg;
6610 
6611                         *per_cpu_ptr(sdd->sg, j) = sg;
6612 
6613                         sgc = kzalloc_node(sizeof(struct sched_group_capacity) + cpumask_size(),
6614                                         GFP_KERNEL, cpu_to_node(j));
6615                         if (!sgc)
6616                                 return -ENOMEM;
6617 
6618                         *per_cpu_ptr(sdd->sgc, j) = sgc;
6619                 }
6620         }
6621 
6622         return 0;
6623 }
6624 
6625 static void __sdt_free(const struct cpumask *cpu_map)
6626 {
6627         struct sched_domain_topology_level *tl;
6628         int j;
6629 
6630         for_each_sd_topology(tl) {
6631                 struct sd_data *sdd = &tl->data;
6632 
6633                 for_each_cpu(j, cpu_map) {
6634                         struct sched_domain *sd;
6635 
6636                         if (sdd->sd) {
6637                                 sd = *per_cpu_ptr(sdd->sd, j);
6638                                 if (sd && (sd->flags & SD_OVERLAP))
6639                                         free_sched_groups(sd->groups, 0);
6640                                 kfree(*per_cpu_ptr(sdd->sd, j));
6641                         }
6642 
6643                         if (sdd->sg)
6644                                 kfree(*per_cpu_ptr(sdd->sg, j));
6645                         if (sdd->sgc)
6646                                 kfree(*per_cpu_ptr(sdd->sgc, j));
6647                 }
6648                 free_percpu(sdd->sd);
6649                 sdd->sd = NULL;
6650                 free_percpu(sdd->sg);
6651                 sdd->sg = NULL;
6652                 free_percpu(sdd->sgc);
6653                 sdd->sgc = NULL;
6654         }
6655 }
6656 
6657 struct sched_domain *build_sched_domain(struct sched_domain_topology_level *tl,
6658                 const struct cpumask *cpu_map, struct sched_domain_attr *attr,
6659                 struct sched_domain *child, int cpu)
6660 {
6661         struct sched_domain *sd = sd_init(tl, cpu);
6662         if (!sd)
6663                 return child;
6664 
6665         cpumask_and(sched_domain_span(sd), cpu_map, tl->mask(cpu));
6666         if (child) {
6667                 sd->level = child->level + 1;
6668                 sched_domain_level_max = max(sched_domain_level_max, sd->level);
6669                 child->parent = sd;
6670                 sd->child = child;
6671 
6672                 if (!cpumask_subset(sched_domain_span(child),
6673                                     sched_domain_span(sd))) {
6674                         pr_err("BUG: arch topology borken\n");
6675 #ifdef CONFIG_SCHED_DEBUG
6676                         pr_err("     the %s domain not a subset of the %s domain\n",
6677                                         child->name, sd->name);
6678 #endif
6679                         /* Fixup, ensure @sd has at least @child cpus. */
6680                         cpumask_or(sched_domain_span(sd),
6681                                    sched_domain_span(sd),
6682                                    sched_domain_span(child));
6683                 }
6684 
6685         }
6686         set_domain_attribute(sd, attr);
6687 
6688         return sd;
6689 }
6690 
6691 /*
6692  * Build sched domains for a given set of cpus and attach the sched domains
6693  * to the individual cpus
6694  */
6695 static int build_sched_domains(const struct cpumask *cpu_map,
6696                                struct sched_domain_attr *attr)
6697 {
6698         enum s_alloc alloc_state;
6699         struct sched_domain *sd;
6700         struct s_data d;
6701         int i, ret = -ENOMEM;
6702 
6703         alloc_state = __visit_domain_allocation_hell(&d, cpu_map);
6704         if (alloc_state != sa_rootdomain)
6705                 goto error;
6706 
6707         /* Set up domains for cpus specified by the cpu_map. */
6708         for_each_cpu(i, cpu_map) {
6709                 struct sched_domain_topology_level *tl;
6710 
6711                 sd = NULL;
6712                 for_each_sd_topology(tl) {
6713                         sd = build_sched_domain(tl, cpu_map, attr, sd, i);
6714                         if (tl == sched_domain_topology)
6715                                 *per_cpu_ptr(d.sd, i) = sd;
6716                         if (tl->flags & SDTL_OVERLAP || sched_feat(FORCE_SD_OVERLAP))
6717                                 sd->flags |= SD_OVERLAP;
6718                         if (cpumask_equal(cpu_map, sched_domain_span(sd)))
6719                                 break;
6720                 }
6721         }
6722 
6723         /* Build the groups for the domains */
6724         for_each_cpu(i, cpu_map) {
6725                 for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
6726                         sd->span_weight = cpumask_weight(sched_domain_span(sd));
6727                         if (sd->flags & SD_OVERLAP) {
6728                                 if (build_overlap_sched_groups(sd, i))
6729                                         goto error;
6730                         } else {
6731                                 if (build_sched_groups(sd, i))
6732                                         goto error;
6733                         }
6734                 }
6735         }
6736 
6737         /* Calculate CPU capacity for physical packages and nodes */
6738         for (i = nr_cpumask_bits-1; i >= 0; i--) {
6739                 if (!cpumask_test_cpu(i, cpu_map))
6740                         continue;
6741 
6742                 for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
6743                         claim_allocations(i, sd);
6744                         init_sched_groups_capacity(i, sd);
6745                 }
6746         }
6747 
6748         /* Attach the domains */
6749         rcu_read_lock();
6750         for_each_cpu(i, cpu_map) {
6751                 sd = *per_cpu_ptr(d.sd, i);
6752                 cpu_attach_domain(sd, d.rd, i);
6753         }
6754         rcu_read_unlock();
6755 
6756         ret = 0;
6757 error:
6758         __free_domain_allocs(&d, alloc_state, cpu_map);
6759         return ret;
6760 }
6761 
6762 static cpumask_var_t *doms_cur; /* current sched domains */
6763 static int ndoms_cur;           /* number of sched domains in 'doms_cur' */
6764 static struct sched_domain_attr *dattr_cur;
6765                                 /* attribues of custom domains in 'doms_cur' */
6766 
6767 /*
6768  * Special case: If a kmalloc of a doms_cur partition (array of
6769  * cpumask) fails, then fallback to a single sched domain,
6770  * as determined by the single cpumask fallback_doms.
6771  */
6772 static cpumask_var_t fallback_doms;
6773 
6774 /*
6775  * arch_update_cpu_topology lets virtualized architectures update the
6776  * cpu core maps. It is supposed to return 1 if the topology changed
6777  * or 0 if it stayed the same.
6778  */
6779 int __weak arch_update_cpu_topology(void)
6780 {
6781         return 0;
6782 }
6783 
6784 cpumask_var_t *alloc_sched_domains(unsigned int ndoms)
6785 {
6786         int i;
6787         cpumask_var_t *doms;
6788 
6789         doms = kmalloc(sizeof(*doms) * ndoms, GFP_KERNEL);
6790         if (!doms)
6791                 return NULL;
6792         for (i = 0; i < ndoms; i++) {
6793                 if (!alloc_cpumask_var(&doms[i], GFP_KERNEL)) {
6794                         free_sched_domains(doms, i);
6795                         return NULL;
6796                 }
6797         }
6798         return doms;
6799 }
6800 
6801 void free_sched_domains(cpumask_var_t doms[], unsigned int ndoms)
6802 {
6803         unsigned int i;
6804         for (i = 0; i < ndoms; i++)
6805                 free_cpumask_var(doms[i]);
6806         kfree(doms);
6807 }
6808 
6809 /*
6810  * Set up scheduler domains and groups. Callers must hold the hotplug lock.
6811  * For now this just excludes isolated cpus, but could be used to
6812  * exclude other special cases in the future.
6813  */
6814 static int init_sched_domains(const struct cpumask *cpu_map)
6815 {
6816         int err;
6817 
6818         arch_update_cpu_topology();
6819         ndoms_cur = 1;
6820         doms_cur = alloc_sched_domains(ndoms_cur);
6821         if (!doms_cur)
6822                 doms_cur = &fallback_doms;
6823         cpumask_andnot(doms_cur[0], cpu_map, cpu_isolated_map);
6824         err = build_sched_domains(doms_cur[0], NULL);
6825         register_sched_domain_sysctl();
6826 
6827         return err;
6828 }
6829 
6830 /*
6831  * Detach sched domains from a group of cpus specified in cpu_map
6832  * These cpus will now be attached to the NULL domain
6833  */
6834 static void detach_destroy_domains(const struct cpumask *cpu_map)
6835 {
6836         int i;
6837 
6838         rcu_read_lock();
6839         for_each_cpu(i, cpu_map)
6840                 cpu_attach_domain(NULL, &def_root_domain, i);
6841         rcu_read_unlock();
6842 }
6843 
6844 /* handle null as "default" */
6845 static int dattrs_equal(struct sched_domain_attr *cur, int idx_cur,
6846                         struct sched_domain_attr *new, int idx_new)
6847 {
6848         struct sched_domain_attr tmp;
6849 
6850         /* fast path */
6851         if (!new && !cur)
6852                 return 1;
6853 
6854         tmp = SD_ATTR_INIT;
6855         return !memcmp(cur ? (cur + idx_cur) : &tmp,
6856                         new ? (new + idx_new) : &tmp,
6857                         sizeof(struct sched_domain_attr));
6858 }
6859 
6860 /*
6861  * Partition sched domains as specified by the 'ndoms_new'
6862  * cpumasks in the array doms_new[] of cpumasks. This compares
6863  * doms_new[] to the current sched domain partitioning, doms_cur[].
6864  * It destroys each deleted domain and builds each new domain.
6865  *
6866  * 'doms_new' is an array of cpumask_var_t's of length 'ndoms_new'.
6867  * The masks don't intersect (don't overlap.) We should setup one
6868  * sched domain for each mask. CPUs not in any of the cpumasks will
6869  * not be load balanced. If the same cpumask appears both in the
6870  * current 'doms_cur' domains and in the new 'doms_new', we can leave
6871  * it as it is.
6872  *
6873  * The passed in 'doms_new' should be allocated using
6874  * alloc_sched_domains.  This routine takes ownership of it and will
6875  * free_sched_domains it when done with it. If the caller failed the
6876  * alloc call, then it can pass in doms_new == NULL && ndoms_new == 1,
6877  * and partition_sched_domains() will fallback to the single partition
6878  * 'fallback_doms', it also forces the domains to be rebuilt.
6879  *
6880  * If doms_new == NULL it will be replaced with cpu_online_mask.
6881  * ndoms_new == 0 is a special case for destroying existing domains,
6882  * and it will not create the default domain.
6883  *
6884  * Call with hotplug lock held
6885  */
6886 void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
6887                              struct sched_domain_attr *dattr_new)
6888 {
6889         int i, j, n;
6890         int new_topology;
6891 
6892         mutex_lock(&sched_domains_mutex);
6893 
6894         /* always unregister in case we don't destroy any domains */
6895         unregister_sched_domain_sysctl();
6896 
6897         /* Let architecture update cpu core mappings. */
6898         new_topology = arch_update_cpu_topology();
6899 
6900         n = doms_new ? ndoms_new : 0;
6901 
6902         /* Destroy deleted domains */
6903         for (i = 0; i < ndoms_cur; i++) {
6904                 for (j = 0; j < n && !new_topology; j++) {
6905                         if (cpumask_equal(doms_cur[i], doms_new[j])
6906                             && dattrs_equal(dattr_cur, i, dattr_new, j))
6907                                 goto match1;
6908                 }
6909                 /* no match - a current sched domain not in new doms_new[] */
6910                 detach_destroy_domains(doms_cur[i]);
6911 match1:
6912                 ;
6913         }
6914 
6915         n = ndoms_cur;
6916         if (doms_new == NULL) {
6917                 n = 0;
6918                 doms_new = &fallback_doms;
6919                 cpumask_andnot(doms_new[0], cpu_active_mask, cpu_isolated_map);
6920                 WARN_ON_ONCE(dattr_new);
6921         }
6922 
6923         /* Build new domains */
6924         for (i = 0; i < ndoms_new; i++) {
6925                 for (j = 0; j < n && !new_topology; j++) {
6926                         if (cpumask_equal(doms_new[i], doms_cur[j])
6927                             && dattrs_equal(dattr_new, i, dattr_cur, j))
6928                                 goto match2;
6929                 }
6930                 /* no match - add a new doms_new */
6931                 build_sched_domains(doms_new[i], dattr_new ? dattr_new + i : NULL);
6932 match2:
6933                 ;
6934         }
6935 
6936         /* Remember the new sched domains */
6937         if (doms_cur != &fallback_doms)
6938                 free_sched_domains(doms_cur, ndoms_cur);
6939         kfree(dattr_cur);       /* kfree(NULL) is safe */
6940         doms_cur = doms_new;
6941         dattr_cur = dattr_new;
6942         ndoms_cur = ndoms_new;
6943 
6944         register_sched_domain_sysctl();
6945 
6946         mutex_unlock(&sched_domains_mutex);
6947 }
6948 
6949 static int num_cpus_frozen;     /* used to mark begin/end of suspend/resume */
6950 
6951 /*
6952  * Update cpusets according to cpu_active mask.  If cpusets are
6953  * disabled, cpuset_update_active_cpus() becomes a simple wrapper
6954  * around partition_sched_domains().
6955  *
6956  * If we come here as part of a suspend/resume, don't touch cpusets because we
6957  * want to restore it back to its original state upon resume anyway.
6958  */
6959 static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action,
6960                              void *hcpu)
6961 {
6962         switch (action) {
6963         case CPU_ONLINE_FROZEN:
6964         case CPU_DOWN_FAILED_FROZEN:
6965 
6966                 /*
6967                  * num_cpus_frozen tracks how many CPUs are involved in suspend
6968                  * resume sequence. As long as this is not the last online
6969                  * operation in the resume sequence, just build a single sched
6970                  * domain, ignoring cpusets.
6971                  */
6972                 num_cpus_frozen--;
6973                 if (likely(num_cpus_frozen)) {
6974                         partition_sched_domains(1, NULL, NULL);
6975                         break;
6976                 }
6977 
6978                 /*
6979                  * This is the last CPU online operation. So fall through and
6980                  * restore the original sched domains by considering the
6981                  * cpuset configurations.
6982                  */
6983 
6984         case CPU_ONLINE:
6985                 cpuset_update_active_cpus(true);
6986                 break;
6987         default:
6988                 return NOTIFY_DONE;
6989         }
6990         return NOTIFY_OK;
6991 }
6992 
6993 static int cpuset_cpu_inactive(struct notifier_block *nfb, unsigned long action,
6994                                void *hcpu)
6995 {
6996         unsigned long flags;
6997         long cpu = (long)hcpu;
6998         struct dl_bw *dl_b;
6999         bool overflow;
7000         int cpus;
7001 
7002         switch (action) {
7003         case CPU_DOWN_PREPARE:
7004                 rcu_read_lock_sched();
7005                 dl_b = dl_bw_of(cpu);
7006 
7007                 raw_spin_lock_irqsave(&dl_b->lock, flags);
7008                 cpus = dl_bw_cpus(cpu);
7009                 overflow = __dl_overflow(dl_b, cpus, 0, 0);
7010                 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
7011 
7012                 rcu_read_unlock_sched();
7013 
7014                 if (overflow)
7015                         return notifier_from_errno(-EBUSY);
7016                 cpuset_update_active_cpus(false);
7017                 break;
7018         case CPU_DOWN_PREPARE_FROZEN:
7019                 num_cpus_frozen++;
7020                 partition_sched_domains(1, NULL, NULL);
7021                 break;
7022         default:
7023                 return NOTIFY_DONE;
7024         }
7025         return NOTIFY_OK;
7026 }
7027 
7028 void __init sched_init_smp(void)
7029 {
7030         cpumask_var_t non_isolated_cpus;
7031 
7032         alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL);
7033         alloc_cpumask_var(&fallback_doms, GFP_KERNEL);
7034 
7035         sched_init_numa();
7036 
7037         /*
7038          * There's no userspace yet to cause hotplug operations; hence all the
7039          * cpu masks are stable and all blatant races in the below code cannot
7040          * happen.
7041          */
7042         mutex_lock(&sched_domains_mutex);
7043         init_sched_domains(cpu_active_mask);
7044         cpumask_andnot(non_isolated_cpus, cpu_possible_mask, cpu_isolated_map);
7045         if (cpumask_empty(non_isolated_cpus))
7046                 cpumask_set_cpu(smp_processor_id(), non_isolated_cpus);
7047         mutex_unlock(&sched_domains_mutex);
7048 
7049         hotcpu_notifier(sched_domains_numa_masks_update, CPU_PRI_SCHED_ACTIVE);
7050         hotcpu_notifier(cpuset_cpu_active, CPU_PRI_CPUSET_ACTIVE);
7051         hotcpu_notifier(cpuset_cpu_inactive, CPU_PRI_CPUSET_INACTIVE);
7052 
7053         init_hrtick();
7054 
7055         /* Move init over to a non-isolated CPU */
7056         if (set_cpus_allowed_ptr(current, non_isolated_cpus) < 0)
7057                 BUG();
7058         sched_init_granularity();
7059         free_cpumask_var(non_isolated_cpus);
7060 
7061         init_sched_rt_class();
7062         init_sched_dl_class();
7063 }
7064 #else
7065 void __init sched_init_smp(void)
7066 {
7067         sched_init_granularity();
7068 }
7069 #endif /* CONFIG_SMP */
7070 
7071 const_debug unsigned int sysctl_timer_migration = 1;
7072 
7073 int in_sched_functions(unsigned long addr)
7074 {
7075         return in_lock_functions(addr) ||
7076                 (addr >= (unsigned long)__sched_text_start
7077                 && addr < (unsigned long)__sched_text_end);
7078 }
7079 
7080 #ifdef CONFIG_CGROUP_SCHED
7081 /*
7082  * Default task group.
7083  * Every task in system belongs to this group at bootup.
7084  */
7085 struct task_group root_task_group;
7086 LIST_HEAD(task_groups);
7087 #endif
7088 
7089 DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
7090 
7091 void __init sched_init(void)
7092 {
7093         int i, j;
7094         unsigned long alloc_size = 0, ptr;
7095 
7096 #ifdef CONFIG_FAIR_GROUP_SCHED
7097         alloc_size += 2 * nr_cpu_ids * sizeof(void **);
7098 #endif
7099 #ifdef CONFIG_RT_GROUP_SCHED
7100         alloc_size += 2 * nr_cpu_ids * sizeof(void **);
7101 #endif
7102         if (alloc_size) {
7103                 ptr = (unsigned long)kzalloc(alloc_size, GFP_NOWAIT);
7104 
7105 #ifdef CONFIG_FAIR_GROUP_SCHED
7106                 root_task_group.se = (struct sched_entity **)ptr;
7107                 ptr += nr_cpu_ids * sizeof(void **);
7108 
7109                 root_task_group.cfs_rq = (struct cfs_rq **)ptr;
7110                 ptr += nr_cpu_ids * sizeof(void **);
7111 
7112 #endif /* CONFIG_FAIR_GROUP_SCHED */
7113 #ifdef CONFIG_RT_GROUP_SCHED
7114                 root_task_group.rt_se = (struct sched_rt_entity **)ptr;
7115                 ptr += nr_cpu_ids * sizeof(void **);
7116 
7117                 root_task_group.rt_rq = (struct rt_rq **)ptr;
7118                 ptr += nr_cpu_ids * sizeof(void **);
7119 
7120 #endif /* CONFIG_RT_GROUP_SCHED */
7121         }
7122 #ifdef CONFIG_CPUMASK_OFFSTACK
7123         for_each_possible_cpu(i) {
7124                 per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
7125                         cpumask_size(), GFP_KERNEL, cpu_to_node(i));
7126         }
7127 #endif /* CONFIG_CPUMASK_OFFSTACK */
7128 
7129         init_rt_bandwidth(&def_rt_bandwidth,
7130                         global_rt_period(), global_rt_runtime());
7131         init_dl_bandwidth(&def_dl_bandwidth,
7132                         global_rt_period(), global_rt_runtime());
7133 
7134 #ifdef CONFIG_SMP
7135         init_defrootdomain();
7136 #endif
7137 
7138 #ifdef CONFIG_RT_GROUP_SCHED
7139         init_rt_bandwidth(&root_task_group.rt_bandwidth,
7140                         global_rt_period(), global_rt_runtime());
7141 #endif /* CONFIG_RT_GROUP_SCHED */
7142 
7143 #ifdef CONFIG_CGROUP_SCHED
7144         list_add(&root_task_group.list, &task_groups);
7145         INIT_LIST_HEAD(&root_task_group.children);
7146         INIT_LIST_HEAD(&root_task_group.siblings);
7147         autogroup_init(&init_task);
7148 
7149 #endif /* CONFIG_CGROUP_SCHED */
7150 
7151         for_each_possible_cpu(i) {
7152                 struct rq *rq;
7153 
7154                 rq = cpu_rq(i);
7155                 raw_spin_lock_init(&rq->lock);
7156                 rq->nr_running = 0;
7157                 rq->calc_load_active = 0;
7158                 rq->calc_load_update = jiffies + LOAD_FREQ;
7159                 init_cfs_rq(&rq->cfs);
7160                 init_rt_rq(&rq->rt);
7161                 init_dl_rq(&rq->dl);
7162 #ifdef CONFIG_FAIR_GROUP_SCHED
7163                 root_task_group.shares = ROOT_TASK_GROUP_LOAD;
7164                 INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
7165                 /*
7166                  * How much cpu bandwidth does root_task_group get?
7167                  *
7168                  * In case of task-groups formed thr' the cgroup filesystem, it
7169                  * gets 100% of the cpu resources in the system. This overall
7170                  * system cpu resource is divided among the tasks of
7171                  * root_task_group and its child task-groups in a fair manner,
7172                  * based on each entity's (task or task-group's) weight
7173                  * (se->load.weight).
7174                  *
7175                  * In other words, if root_task_group has 10 tasks of weight
7176                  * 1024) and two child groups A0 and A1 (of weight 1024 each),
7177                  * then A0's share of the cpu resource is:
7178                  *
7179                  *      A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
7180                  *
7181                  * We achieve this by letting root_task_group's tasks sit
7182                  * directly in rq->cfs (i.e root_task_group->se[] = NULL).
7183                  */
7184                 init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
7185                 init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
7186 #endif /* CONFIG_FAIR_GROUP_SCHED */
7187 
7188                 rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;
7189 #ifdef CONFIG_RT_GROUP_SCHED
7190                 init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL);
7191 #endif
7192 
7193                 for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
7194                         rq->cpu_load[j] = 0;
7195 
7196                 rq->last_load_update_tick = jiffies;
7197 
7198 #ifdef CONFIG_SMP
7199                 rq->sd = NULL;
7200                 rq->rd = NULL;
7201                 rq->cpu_capacity = rq->cpu_capacity_orig = SCHED_CAPACITY_SCALE;
7202                 rq->post_schedule = 0;
7203                 rq->active_balance = 0;
7204                 rq->next_balance = jiffies;
7205                 rq->push_cpu = 0;
7206                 rq->cpu = i;
7207                 rq->online = 0;
7208                 rq->idle_stamp = 0;
7209                 rq->avg_idle = 2*sysctl_sched_migration_cost;
7210                 rq->max_idle_balance_cost = sysctl_sched_migration_cost;
7211 
7212                 INIT_LIST_HEAD(&rq->cfs_tasks);
7213 
7214                 rq_attach_root(rq, &def_root_domain);
7215 #ifdef CONFIG_NO_HZ_COMMON
7216                 rq->nohz_flags = 0;
7217 #endif
7218 #ifdef CONFIG_NO_HZ_FULL
7219                 rq->last_sched_tick = 0;
7220 #endif
7221 #endif
7222                 init_rq_hrtick(rq);
7223                 atomic_set(&rq->nr_iowait, 0);
7224         }
7225 
7226         set_load_weight(&init_task);
7227 
7228 #ifdef CONFIG_PREEMPT_NOTIFIERS
7229         INIT_HLIST_HEAD(&init_task.preempt_notifiers);
7230 #endif
7231 
7232         /*
7233          * The boot idle thread does lazy MMU switching as well:
7234          */
7235         atomic_inc(&init_mm.mm_count);
7236         enter_lazy_tlb(&init_mm, current);
7237 
7238         /*
7239          * During early bootup we pretend to be a normal task:
7240          */
7241         current->sched_class = &fair_sched_class;
7242 
7243         /*
7244          * Make us the idle thread. Technically, schedule() should not be
7245          * called from this thread, however somewhere below it might be,
7246          * but because we are the idle thread, we just pick up running again
7247          * when this runqueue becomes "idle".
7248          */
7249         init_idle(current, smp_processor_id());
7250 
7251         calc_load_update = jiffies + LOAD_FREQ;
7252 
7253 #ifdef CONFIG_SMP
7254         zalloc_cpumask_var(&sched_domains_tmpmask, GFP_NOWAIT);
7255         /* May be allocated at isolcpus cmdline parse time */
7256         if (cpu_isolated_map == NULL)
7257                 zalloc_cpumask_var(&cpu_isolated_map, GFP_NOWAIT);
7258         idle_thread_set_boot_cpu();
7259         set_cpu_rq_start_time();
7260 #endif
7261         init_sched_fair_class();
7262 
7263         scheduler_running = 1;
7264 }
7265 
7266 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
7267 static inline int preempt_count_equals(int preempt_offset)
7268 {
7269         int nested = (preempt_count() & ~PREEMPT_ACTIVE) + rcu_preempt_depth();
7270 
7271         return (nested == preempt_offset);
7272 }
7273 
7274 void __might_sleep(const char *file, int line, int preempt_offset)
7275 {
7276         /*
7277          * Blocking primitives will set (and therefore destroy) current->state,
7278          * since we will exit with TASK_RUNNING make sure we enter with it,
7279          * otherwise we will destroy state.
7280          */
7281         WARN_ONCE(current->state != TASK_RUNNING && current->task_state_change,
7282                         "do not call blocking ops when !TASK_RUNNING; "
7283                         "state=%lx set at [<%p>] %pS\n",
7284                         current->state,
7285                         (void *)current->task_state_change,
7286                         (void *)current->task_state_change);
7287 
7288         ___might_sleep(file, line, preempt_offset);
7289 }
7290 EXPORT_SYMBOL(__might_sleep);
7291 
7292 void ___might_sleep(const char *file, int line, int preempt_offset)
7293 {
7294         static unsigned long prev_jiffy;        /* ratelimiting */
7295 
7296         rcu_sleep_check(); /* WARN_ON_ONCE() by default, no rate limit reqd. */
7297         if ((preempt_count_equals(preempt_offset) && !irqs_disabled() &&
7298              !is_idle_task(current)) ||
7299             system_state != SYSTEM_RUNNING || oops_in_progress)
7300                 return;
7301         if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
7302                 return;
7303         prev_jiffy = jiffies;
7304 
7305         printk(KERN_ERR
7306                 "BUG: sleeping function called from invalid context at %s:%d\n",
7307                         file, line);
7308         printk(KERN_ERR
7309                 "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
7310                         in_atomic(), irqs_disabled(),
7311                         current->pid, current->comm);
7312 
7313         if (task_stack_end_corrupted(current))
7314                 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
7315 
7316         debug_show_held_locks(current);
7317         if (irqs_disabled())
7318                 print_irqtrace_events(current);
7319 #ifdef CONFIG_DEBUG_PREEMPT
7320         if (!preempt_count_equals(preempt_offset)) {
7321                 pr_err("Preemption disabled at:");
7322                 print_ip_sym(current->preempt_disable_ip);
7323                 pr_cont("\n");
7324         }
7325 #endif
7326         dump_stack();
7327 }
7328 EXPORT_SYMBOL(___might_sleep);
7329 #endif
7330 
7331 #ifdef CONFIG_MAGIC_SYSRQ
7332 static void normalize_task(struct rq *rq, struct task_struct *p)
7333 {
7334         const struct sched_class *prev_class = p->sched_class;
7335         struct sched_attr attr = {
7336                 .sched_policy = SCHED_NORMAL,
7337         };
7338         int old_prio = p->prio;
7339         int queued;
7340 
7341         queued = task_on_rq_queued(p);
7342         if (queued)
7343                 dequeue_task(rq, p, 0);
7344         __setscheduler(rq, p, &attr, false);
7345         if (queued) {
7346                 enqueue_task(rq, p, 0);
7347                 resched_curr(rq);
7348         }
7349 
7350         check_class_changed(rq, p, prev_class, old_prio);
7351 }
7352 
7353 void normalize_rt_tasks(void)
7354 {
7355         struct task_struct *g, *p;
7356         unsigned long flags;
7357         struct rq *rq;
7358 
7359         read_lock(&tasklist_lock);
7360         for_each_process_thread(g, p) {
7361                 /*
7362                  * Only normalize user tasks:
7363                  */
7364                 if (p->flags & PF_KTHREAD)
7365                         continue;
7366 
7367                 p->se.exec_start                = 0;
7368 #ifdef CONFIG_SCHEDSTATS
7369                 p->se.statistics.wait_start     = 0;
7370                 p->se.statistics.sleep_start    = 0;
7371                 p->se.statistics.block_start    = 0;
7372 #endif
7373 
7374                 if (!dl_task(p) && !rt_task(p)) {
7375                         /*
7376                          * Renice negative nice level userspace
7377                          * tasks back to 0:
7378                          */
7379                         if (task_nice(p) < 0)
7380                                 set_user_nice(p, 0);
7381                         continue;
7382                 }
7383 
7384                 rq = task_rq_lock(p, &flags);
7385                 normalize_task(rq, p);
7386                 task_rq_unlock(rq, p, &flags);
7387         }
7388         read_unlock(&tasklist_lock);
7389 }
7390 
7391 #endif /* CONFIG_MAGIC_SYSRQ */
7392 
7393 #if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB)
7394 /*
7395  * These functions are only useful for the IA64 MCA handling, or kdb.
7396  *
7397  * They can only be called when the whole system has been
7398  * stopped - every CPU needs to be quiescent, and no scheduling
7399  * activity can take place. Using them for anything else would
7400  * be a serious bug, and as a result, they aren't even visible
7401  * under any other configuration.
7402  */
7403 
7404 /**
7405  * curr_task - return the current task for a given cpu.
7406  * @cpu: the processor in question.
7407  *
7408  * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
7409  *
7410  * Return: The current task for @cpu.
7411  */
7412 struct task_struct *curr_task(int cpu)
7413 {
7414         return cpu_curr(cpu);
7415 }
7416 
7417 #endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */
7418 
7419 #ifdef CONFIG_IA64
7420 /**
7421  * set_curr_task - set the current task for a given cpu.
7422  * @cpu: the processor in question.
7423  * @p: the task pointer to set.
7424  *
7425  * Description: This function must only be used when non-maskable interrupts
7426  * are serviced on a separate stack. It allows the architecture to switch the
7427  * notion of the current task on a cpu in a non-blocking manner. This function
7428  * must be called with all CPU's synchronized, and interrupts disabled, the
7429  * and caller must save the original value of the current task (see
7430  * curr_task() above) and restore that value before reenabling interrupts and
7431  * re-starting the system.
7432  *
7433  * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
7434  */
7435 void set_curr_task(int cpu, struct task_struct *p)
7436 {
7437         cpu_curr(cpu) = p;
7438 }
7439 
7440 #endif
7441 
7442 #ifdef CONFIG_CGROUP_SCHED
7443 /* task_group_lock serializes the addition/removal of task groups */
7444 static DEFINE_SPINLOCK(task_group_lock);
7445 
7446 static void free_sched_group(struct task_group *tg)
7447 {
7448         free_fair_sched_group(tg);
7449         free_rt_sched_group(tg);
7450         autogroup_free(tg);
7451         kfree(tg);
7452 }
7453 
7454 /* allocate runqueue etc for a new task group */
7455 struct task_group *sched_create_group(struct task_group *parent)
7456 {
7457         struct task_group *tg;
7458 
7459         tg = kzalloc(sizeof(*tg), GFP_KERNEL);
7460         if (!tg)
7461                 return ERR_PTR(-ENOMEM);
7462 
7463         if (!alloc_fair_sched_group(tg, parent))
7464                 goto err;
7465 
7466         if (!alloc_rt_sched_group(tg, parent))
7467                 goto err;
7468 
7469         return tg;
7470 
7471 err:
7472         free_sched_group(tg);
7473         return ERR_PTR(-ENOMEM);
7474 }
7475 
7476 void sched_online_group(struct task_group *tg, struct task_group *parent)
7477 {
7478         unsigned long flags;
7479 
7480         spin_lock_irqsave(&task_group_lock, flags);
7481         list_add_rcu(&tg->list, &task_groups);
7482 
7483         WARN_ON(!parent); /* root should already exist */
7484 
7485         tg->parent = parent;
7486         INIT_LIST_HEAD(&tg->children);
7487         list_add_rcu(&tg->siblings, &parent->children);
748