4 * Core kernel scheduler code and related syscalls
6 * Copyright (C) 1991-2002 Linus Torvalds
8 #include <linux/sched.h>
9 #include <linux/sched/clock.h>
10 #include <uapi/linux/sched/types.h>
11 #include <linux/sched/loadavg.h>
12 #include <linux/sched/hotplug.h>
13 #include <linux/cpuset.h>
14 #include <linux/delayacct.h>
15 #include <linux/init_task.h>
16 #include <linux/context_tracking.h>
17 #include <linux/rcupdate_wait.h>
19 #include <linux/blkdev.h>
20 #include <linux/kprobes.h>
21 #include <linux/mmu_context.h>
22 #include <linux/module.h>
23 #include <linux/nmi.h>
24 #include <linux/prefetch.h>
25 #include <linux/profile.h>
26 #include <linux/security.h>
27 #include <linux/syscalls.h>
29 #include <asm/switch_to.h>
31 #ifdef CONFIG_PARAVIRT
32 #include <asm/paravirt.h>
36 #include "../workqueue_internal.h"
37 #include "../smpboot.h"
39 #define CREATE_TRACE_POINTS
40 #include <trace/events/sched.h>
42 DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
45 * Debugging: various feature bits
48 #define SCHED_FEAT(name, enabled) \
49 (1UL << __SCHED_FEAT_##name) * enabled |
51 const_debug unsigned int sysctl_sched_features =
58 * Number of tasks to iterate in a single balance run.
59 * Limited because this is done with IRQs disabled.
61 const_debug unsigned int sysctl_sched_nr_migrate = 32;
64 * period over which we average the RT time consumption, measured
69 const_debug unsigned int sysctl_sched_time_avg = MSEC_PER_SEC;
72 * period over which we measure -rt task CPU usage in us.
75 unsigned int sysctl_sched_rt_period = 1000000;
77 __read_mostly int scheduler_running;
80 * part of the period that we allow rt tasks to run in us.
83 int sysctl_sched_rt_runtime = 950000;
85 /* CPUs with isolated domains */
86 cpumask_var_t cpu_isolated_map;
89 * __task_rq_lock - lock the rq @p resides on.
91 struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf)
96 lockdep_assert_held(&p->pi_lock);
100 raw_spin_lock(&rq->lock);
101 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
105 raw_spin_unlock(&rq->lock);
107 while (unlikely(task_on_rq_migrating(p)))
113 * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
115 struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
116 __acquires(p->pi_lock)
122 raw_spin_lock_irqsave(&p->pi_lock, rf->flags);
124 raw_spin_lock(&rq->lock);
126 * move_queued_task() task_rq_lock()
129 * [S] ->on_rq = MIGRATING [L] rq = task_rq()
130 * WMB (__set_task_cpu()) ACQUIRE (rq->lock);
131 * [S] ->cpu = new_cpu [L] task_rq()
135 * If we observe the old cpu in task_rq_lock, the acquire of
136 * the old rq->lock will fully serialize against the stores.
138 * If we observe the new CPU in task_rq_lock, the acquire will
139 * pair with the WMB to ensure we must then also see migrating.
141 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
145 raw_spin_unlock(&rq->lock);
146 raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags);
148 while (unlikely(task_on_rq_migrating(p)))
154 * RQ-clock updating methods:
157 static void update_rq_clock_task(struct rq *rq, s64 delta)
160 * In theory, the compile should just see 0 here, and optimize out the call
161 * to sched_rt_avg_update. But I don't trust it...
163 #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
164 s64 steal = 0, irq_delta = 0;
166 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
167 irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
170 * Since irq_time is only updated on {soft,}irq_exit, we might run into
171 * this case when a previous update_rq_clock() happened inside a
174 * When this happens, we stop ->clock_task and only update the
175 * prev_irq_time stamp to account for the part that fit, so that a next
176 * update will consume the rest. This ensures ->clock_task is
179 * It does however cause some slight miss-attribution of {soft,}irq
180 * time, a more accurate solution would be to update the irq_time using
181 * the current rq->clock timestamp, except that would require using
184 if (irq_delta > delta)
187 rq->prev_irq_time += irq_delta;
190 #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
191 if (static_key_false((¶virt_steal_rq_enabled))) {
192 steal = paravirt_steal_clock(cpu_of(rq));
193 steal -= rq->prev_steal_time_rq;
195 if (unlikely(steal > delta))
198 rq->prev_steal_time_rq += steal;
203 rq->clock_task += delta;
205 #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
206 if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY))
207 sched_rt_avg_update(rq, irq_delta + steal);
211 void update_rq_clock(struct rq *rq)
215 lockdep_assert_held(&rq->lock);
217 if (rq->clock_update_flags & RQCF_ACT_SKIP)
220 #ifdef CONFIG_SCHED_DEBUG
221 if (sched_feat(WARN_DOUBLE_CLOCK))
222 SCHED_WARN_ON(rq->clock_update_flags & RQCF_UPDATED);
223 rq->clock_update_flags |= RQCF_UPDATED;
226 delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
230 update_rq_clock_task(rq, delta);
234 #ifdef CONFIG_SCHED_HRTICK
236 * Use HR-timers to deliver accurate preemption points.
239 static void hrtick_clear(struct rq *rq)
241 if (hrtimer_active(&rq->hrtick_timer))
242 hrtimer_cancel(&rq->hrtick_timer);
246 * High-resolution timer tick.
247 * Runs from hardirq context with interrupts disabled.
249 static enum hrtimer_restart hrtick(struct hrtimer *timer)
251 struct rq *rq = container_of(timer, struct rq, hrtick_timer);
254 WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
258 rq->curr->sched_class->task_tick(rq, rq->curr, 1);
261 return HRTIMER_NORESTART;
266 static void __hrtick_restart(struct rq *rq)
268 struct hrtimer *timer = &rq->hrtick_timer;
270 hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED);
274 * called from hardirq (IPI) context
276 static void __hrtick_start(void *arg)
282 __hrtick_restart(rq);
283 rq->hrtick_csd_pending = 0;
288 * Called to set the hrtick timer state.
290 * called with rq->lock held and irqs disabled
292 void hrtick_start(struct rq *rq, u64 delay)
294 struct hrtimer *timer = &rq->hrtick_timer;
299 * Don't schedule slices shorter than 10000ns, that just
300 * doesn't make sense and can cause timer DoS.
302 delta = max_t(s64, delay, 10000LL);
303 time = ktime_add_ns(timer->base->get_time(), delta);
305 hrtimer_set_expires(timer, time);
307 if (rq == this_rq()) {
308 __hrtick_restart(rq);
309 } else if (!rq->hrtick_csd_pending) {
310 smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd);
311 rq->hrtick_csd_pending = 1;
317 * Called to set the hrtick timer state.
319 * called with rq->lock held and irqs disabled
321 void hrtick_start(struct rq *rq, u64 delay)
324 * Don't schedule slices shorter than 10000ns, that just
325 * doesn't make sense. Rely on vruntime for fairness.
327 delay = max_t(u64, delay, 10000LL);
328 hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay),
329 HRTIMER_MODE_REL_PINNED);
331 #endif /* CONFIG_SMP */
333 static void init_rq_hrtick(struct rq *rq)
336 rq->hrtick_csd_pending = 0;
338 rq->hrtick_csd.flags = 0;
339 rq->hrtick_csd.func = __hrtick_start;
340 rq->hrtick_csd.info = rq;
343 hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
344 rq->hrtick_timer.function = hrtick;
346 #else /* CONFIG_SCHED_HRTICK */
347 static inline void hrtick_clear(struct rq *rq)
351 static inline void init_rq_hrtick(struct rq *rq)
354 #endif /* CONFIG_SCHED_HRTICK */
357 * cmpxchg based fetch_or, macro so it works for different integer types
359 #define fetch_or(ptr, mask) \
361 typeof(ptr) _ptr = (ptr); \
362 typeof(mask) _mask = (mask); \
363 typeof(*_ptr) _old, _val = *_ptr; \
366 _old = cmpxchg(_ptr, _val, _val | _mask); \
374 #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
376 * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
377 * this avoids any races wrt polling state changes and thereby avoids
380 static bool set_nr_and_not_polling(struct task_struct *p)
382 struct thread_info *ti = task_thread_info(p);
383 return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG);
387 * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
389 * If this returns true, then the idle task promises to call
390 * sched_ttwu_pending() and reschedule soon.
392 static bool set_nr_if_polling(struct task_struct *p)
394 struct thread_info *ti = task_thread_info(p);
395 typeof(ti->flags) old, val = READ_ONCE(ti->flags);
398 if (!(val & _TIF_POLLING_NRFLAG))
400 if (val & _TIF_NEED_RESCHED)
402 old = cmpxchg(&ti->flags, val, val | _TIF_NEED_RESCHED);
411 static bool set_nr_and_not_polling(struct task_struct *p)
413 set_tsk_need_resched(p);
418 static bool set_nr_if_polling(struct task_struct *p)
425 void wake_q_add(struct wake_q_head *head, struct task_struct *task)
427 struct wake_q_node *node = &task->wake_q;
430 * Atomically grab the task, if ->wake_q is !nil already it means
431 * its already queued (either by us or someone else) and will get the
432 * wakeup due to that.
434 * This cmpxchg() implies a full barrier, which pairs with the write
435 * barrier implied by the wakeup in wake_up_q().
437 if (cmpxchg(&node->next, NULL, WAKE_Q_TAIL))
440 get_task_struct(task);
443 * The head is context local, there can be no concurrency.
446 head->lastp = &node->next;
449 void wake_up_q(struct wake_q_head *head)
451 struct wake_q_node *node = head->first;
453 while (node != WAKE_Q_TAIL) {
454 struct task_struct *task;
456 task = container_of(node, struct task_struct, wake_q);
458 /* Task can safely be re-inserted now: */
460 task->wake_q.next = NULL;
463 * wake_up_process() implies a wmb() to pair with the queueing
464 * in wake_q_add() so as not to miss wakeups.
466 wake_up_process(task);
467 put_task_struct(task);
472 * resched_curr - mark rq's current task 'to be rescheduled now'.
474 * On UP this means the setting of the need_resched flag, on SMP it
475 * might also involve a cross-CPU call to trigger the scheduler on
478 void resched_curr(struct rq *rq)
480 struct task_struct *curr = rq->curr;
483 lockdep_assert_held(&rq->lock);
485 if (test_tsk_need_resched(curr))
490 if (cpu == smp_processor_id()) {
491 set_tsk_need_resched(curr);
492 set_preempt_need_resched();
496 if (set_nr_and_not_polling(curr))
497 smp_send_reschedule(cpu);
499 trace_sched_wake_idle_without_ipi(cpu);
502 void resched_cpu(int cpu)
504 struct rq *rq = cpu_rq(cpu);
507 if (!raw_spin_trylock_irqsave(&rq->lock, flags))
510 raw_spin_unlock_irqrestore(&rq->lock, flags);
514 #ifdef CONFIG_NO_HZ_COMMON
516 * In the semi idle case, use the nearest busy CPU for migrating timers
517 * from an idle CPU. This is good for power-savings.
519 * We don't do similar optimization for completely idle system, as
520 * selecting an idle CPU will add more delays to the timers than intended
521 * (as that CPU's timer base may not be uptodate wrt jiffies etc).
523 int get_nohz_timer_target(void)
525 int i, cpu = smp_processor_id();
526 struct sched_domain *sd;
528 if (!idle_cpu(cpu) && is_housekeeping_cpu(cpu))
532 for_each_domain(cpu, sd) {
533 for_each_cpu(i, sched_domain_span(sd)) {
537 if (!idle_cpu(i) && is_housekeeping_cpu(i)) {
544 if (!is_housekeeping_cpu(cpu))
545 cpu = housekeeping_any_cpu();
552 * When add_timer_on() enqueues a timer into the timer wheel of an
553 * idle CPU then this timer might expire before the next timer event
554 * which is scheduled to wake up that CPU. In case of a completely
555 * idle system the next event might even be infinite time into the
556 * future. wake_up_idle_cpu() ensures that the CPU is woken up and
557 * leaves the inner idle loop so the newly added timer is taken into
558 * account when the CPU goes back to idle and evaluates the timer
559 * wheel for the next timer event.
561 static void wake_up_idle_cpu(int cpu)
563 struct rq *rq = cpu_rq(cpu);
565 if (cpu == smp_processor_id())
568 if (set_nr_and_not_polling(rq->idle))
569 smp_send_reschedule(cpu);
571 trace_sched_wake_idle_without_ipi(cpu);
574 static bool wake_up_full_nohz_cpu(int cpu)
577 * We just need the target to call irq_exit() and re-evaluate
578 * the next tick. The nohz full kick at least implies that.
579 * If needed we can still optimize that later with an
582 if (cpu_is_offline(cpu))
583 return true; /* Don't try to wake offline CPUs. */
584 if (tick_nohz_full_cpu(cpu)) {
585 if (cpu != smp_processor_id() ||
586 tick_nohz_tick_stopped())
587 tick_nohz_full_kick_cpu(cpu);
595 * Wake up the specified CPU. If the CPU is going offline, it is the
596 * caller's responsibility to deal with the lost wakeup, for example,
597 * by hooking into the CPU_DEAD notifier like timers and hrtimers do.
599 void wake_up_nohz_cpu(int cpu)
601 if (!wake_up_full_nohz_cpu(cpu))
602 wake_up_idle_cpu(cpu);
605 static inline bool got_nohz_idle_kick(void)
607 int cpu = smp_processor_id();
609 if (!test_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu)))
612 if (idle_cpu(cpu) && !need_resched())
616 * We can't run Idle Load Balance on this CPU for this time so we
617 * cancel it and clear NOHZ_BALANCE_KICK
619 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu));
623 #else /* CONFIG_NO_HZ_COMMON */
625 static inline bool got_nohz_idle_kick(void)
630 #endif /* CONFIG_NO_HZ_COMMON */
632 #ifdef CONFIG_NO_HZ_FULL
633 bool sched_can_stop_tick(struct rq *rq)
637 /* Deadline tasks, even if single, need the tick */
638 if (rq->dl.dl_nr_running)
642 * If there are more than one RR tasks, we need the tick to effect the
643 * actual RR behaviour.
645 if (rq->rt.rr_nr_running) {
646 if (rq->rt.rr_nr_running == 1)
653 * If there's no RR tasks, but FIFO tasks, we can skip the tick, no
654 * forced preemption between FIFO tasks.
656 fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running;
661 * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left;
662 * if there's more than one we need the tick for involuntary
665 if (rq->nr_running > 1)
670 #endif /* CONFIG_NO_HZ_FULL */
672 void sched_avg_update(struct rq *rq)
674 s64 period = sched_avg_period();
676 while ((s64)(rq_clock(rq) - rq->age_stamp) > period) {
678 * Inline assembly required to prevent the compiler
679 * optimising this loop into a divmod call.
680 * See __iter_div_u64_rem() for another example of this.
682 asm("" : "+rm" (rq->age_stamp));
683 rq->age_stamp += period;
688 #endif /* CONFIG_SMP */
690 #if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
691 (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))
693 * Iterate task_group tree rooted at *from, calling @down when first entering a
694 * node and @up when leaving it for the final time.
696 * Caller must hold rcu_lock or sufficient equivalent.
698 int walk_tg_tree_from(struct task_group *from,
699 tg_visitor down, tg_visitor up, void *data)
701 struct task_group *parent, *child;
707 ret = (*down)(parent, data);
710 list_for_each_entry_rcu(child, &parent->children, siblings) {
717 ret = (*up)(parent, data);
718 if (ret || parent == from)
722 parent = parent->parent;
729 int tg_nop(struct task_group *tg, void *data)
735 static void set_load_weight(struct task_struct *p)
737 int prio = p->static_prio - MAX_RT_PRIO;
738 struct load_weight *load = &p->se.load;
741 * SCHED_IDLE tasks get minimal weight:
743 if (idle_policy(p->policy)) {
744 load->weight = scale_load(WEIGHT_IDLEPRIO);
745 load->inv_weight = WMULT_IDLEPRIO;
749 load->weight = scale_load(sched_prio_to_weight[prio]);
750 load->inv_weight = sched_prio_to_wmult[prio];
753 static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
755 if (!(flags & ENQUEUE_NOCLOCK))
758 if (!(flags & ENQUEUE_RESTORE))
759 sched_info_queued(rq, p);
761 p->sched_class->enqueue_task(rq, p, flags);
764 static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
766 if (!(flags & DEQUEUE_NOCLOCK))
769 if (!(flags & DEQUEUE_SAVE))
770 sched_info_dequeued(rq, p);
772 p->sched_class->dequeue_task(rq, p, flags);
775 void activate_task(struct rq *rq, struct task_struct *p, int flags)
777 if (task_contributes_to_load(p))
778 rq->nr_uninterruptible--;
780 enqueue_task(rq, p, flags);
783 void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
785 if (task_contributes_to_load(p))
786 rq->nr_uninterruptible++;
788 dequeue_task(rq, p, flags);
791 void sched_set_stop_task(int cpu, struct task_struct *stop)
793 struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
794 struct task_struct *old_stop = cpu_rq(cpu)->stop;
798 * Make it appear like a SCHED_FIFO task, its something
799 * userspace knows about and won't get confused about.
801 * Also, it will make PI more or less work without too
802 * much confusion -- but then, stop work should not
803 * rely on PI working anyway.
805 sched_setscheduler_nocheck(stop, SCHED_FIFO, ¶m);
807 stop->sched_class = &stop_sched_class;
810 cpu_rq(cpu)->stop = stop;
814 * Reset it back to a normal scheduling class so that
815 * it can die in pieces.
817 old_stop->sched_class = &rt_sched_class;
822 * __normal_prio - return the priority that is based on the static prio
824 static inline int __normal_prio(struct task_struct *p)
826 return p->static_prio;
830 * Calculate the expected normal priority: i.e. priority
831 * without taking RT-inheritance into account. Might be
832 * boosted by interactivity modifiers. Changes upon fork,
833 * setprio syscalls, and whenever the interactivity
834 * estimator recalculates.
836 static inline int normal_prio(struct task_struct *p)
840 if (task_has_dl_policy(p))
841 prio = MAX_DL_PRIO-1;
842 else if (task_has_rt_policy(p))
843 prio = MAX_RT_PRIO-1 - p->rt_priority;
845 prio = __normal_prio(p);
850 * Calculate the current priority, i.e. the priority
851 * taken into account by the scheduler. This value might
852 * be boosted by RT tasks, or might be boosted by
853 * interactivity modifiers. Will be RT if the task got
854 * RT-boosted. If not then it returns p->normal_prio.
856 static int effective_prio(struct task_struct *p)
858 p->normal_prio = normal_prio(p);
860 * If we are RT tasks or we were boosted to RT priority,
861 * keep the priority unchanged. Otherwise, update priority
862 * to the normal priority:
864 if (!rt_prio(p->prio))
865 return p->normal_prio;
870 * task_curr - is this task currently executing on a CPU?
871 * @p: the task in question.
873 * Return: 1 if the task is currently executing. 0 otherwise.
875 inline int task_curr(const struct task_struct *p)
877 return cpu_curr(task_cpu(p)) == p;
881 * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock,
882 * use the balance_callback list if you want balancing.
884 * this means any call to check_class_changed() must be followed by a call to
885 * balance_callback().
887 static inline void check_class_changed(struct rq *rq, struct task_struct *p,
888 const struct sched_class *prev_class,
891 if (prev_class != p->sched_class) {
892 if (prev_class->switched_from)
893 prev_class->switched_from(rq, p);
895 p->sched_class->switched_to(rq, p);
896 } else if (oldprio != p->prio || dl_task(p))
897 p->sched_class->prio_changed(rq, p, oldprio);
900 void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
902 const struct sched_class *class;
904 if (p->sched_class == rq->curr->sched_class) {
905 rq->curr->sched_class->check_preempt_curr(rq, p, flags);
907 for_each_class(class) {
908 if (class == rq->curr->sched_class)
910 if (class == p->sched_class) {
918 * A queue event has occurred, and we're going to schedule. In
919 * this case, we can save a useless back to back clock update.
921 if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
922 rq_clock_skip_update(rq, true);
927 * This is how migration works:
929 * 1) we invoke migration_cpu_stop() on the target CPU using
931 * 2) stopper starts to run (implicitly forcing the migrated thread
933 * 3) it checks whether the migrated task is still in the wrong runqueue.
934 * 4) if it's in the wrong runqueue then the migration thread removes
935 * it and puts it into the right queue.
936 * 5) stopper completes and stop_one_cpu() returns and the migration
941 * move_queued_task - move a queued task to new rq.
943 * Returns (locked) new rq. Old rq's lock is released.
945 static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf,
946 struct task_struct *p, int new_cpu)
948 lockdep_assert_held(&rq->lock);
950 p->on_rq = TASK_ON_RQ_MIGRATING;
951 dequeue_task(rq, p, DEQUEUE_NOCLOCK);
952 set_task_cpu(p, new_cpu);
955 rq = cpu_rq(new_cpu);
958 BUG_ON(task_cpu(p) != new_cpu);
959 enqueue_task(rq, p, 0);
960 p->on_rq = TASK_ON_RQ_QUEUED;
961 check_preempt_curr(rq, p, 0);
966 struct migration_arg {
967 struct task_struct *task;
972 * Move (not current) task off this CPU, onto the destination CPU. We're doing
973 * this because either it can't run here any more (set_cpus_allowed()
974 * away from this CPU, or CPU going down), or because we're
975 * attempting to rebalance this task on exec (sched_exec).
977 * So we race with normal scheduler movements, but that's OK, as long
978 * as the task is no longer on this CPU.
980 static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf,
981 struct task_struct *p, int dest_cpu)
983 if (unlikely(!cpu_active(dest_cpu)))
986 /* Affinity changed (again). */
987 if (!cpumask_test_cpu(dest_cpu, &p->cpus_allowed))
991 rq = move_queued_task(rq, rf, p, dest_cpu);
997 * migration_cpu_stop - this will be executed by a highprio stopper thread
998 * and performs thread migration by bumping thread off CPU then
999 * 'pushing' onto another runqueue.
1001 static int migration_cpu_stop(void *data)
1003 struct migration_arg *arg = data;
1004 struct task_struct *p = arg->task;
1005 struct rq *rq = this_rq();
1009 * The original target CPU might have gone down and we might
1010 * be on another CPU but it doesn't matter.
1012 local_irq_disable();
1014 * We need to explicitly wake pending tasks before running
1015 * __migrate_task() such that we will not miss enforcing cpus_allowed
1016 * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
1018 sched_ttwu_pending();
1020 raw_spin_lock(&p->pi_lock);
1023 * If task_rq(p) != rq, it cannot be migrated here, because we're
1024 * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
1025 * we're holding p->pi_lock.
1027 if (task_rq(p) == rq) {
1028 if (task_on_rq_queued(p))
1029 rq = __migrate_task(rq, &rf, p, arg->dest_cpu);
1031 p->wake_cpu = arg->dest_cpu;
1034 raw_spin_unlock(&p->pi_lock);
1041 * sched_class::set_cpus_allowed must do the below, but is not required to
1042 * actually call this function.
1044 void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask)
1046 cpumask_copy(&p->cpus_allowed, new_mask);
1047 p->nr_cpus_allowed = cpumask_weight(new_mask);
1050 void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
1052 struct rq *rq = task_rq(p);
1053 bool queued, running;
1055 lockdep_assert_held(&p->pi_lock);
1057 queued = task_on_rq_queued(p);
1058 running = task_current(rq, p);
1062 * Because __kthread_bind() calls this on blocked tasks without
1065 lockdep_assert_held(&rq->lock);
1066 dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
1069 put_prev_task(rq, p);
1071 p->sched_class->set_cpus_allowed(p, new_mask);
1074 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
1076 set_curr_task(rq, p);
1080 * Change a given task's CPU affinity. Migrate the thread to a
1081 * proper CPU and schedule it away if the CPU it's executing on
1082 * is removed from the allowed bitmask.
1084 * NOTE: the caller must have a valid reference to the task, the
1085 * task must not exit() & deallocate itself prematurely. The
1086 * call is not atomic; no spinlocks may be held.
1088 static int __set_cpus_allowed_ptr(struct task_struct *p,
1089 const struct cpumask *new_mask, bool check)
1091 const struct cpumask *cpu_valid_mask = cpu_active_mask;
1092 unsigned int dest_cpu;
1097 rq = task_rq_lock(p, &rf);
1098 update_rq_clock(rq);
1100 if (p->flags & PF_KTHREAD) {
1102 * Kernel threads are allowed on online && !active CPUs
1104 cpu_valid_mask = cpu_online_mask;
1108 * Must re-check here, to close a race against __kthread_bind(),
1109 * sched_setaffinity() is not guaranteed to observe the flag.
1111 if (check && (p->flags & PF_NO_SETAFFINITY)) {
1116 if (cpumask_equal(&p->cpus_allowed, new_mask))
1119 if (!cpumask_intersects(new_mask, cpu_valid_mask)) {
1124 do_set_cpus_allowed(p, new_mask);
1126 if (p->flags & PF_KTHREAD) {
1128 * For kernel threads that do indeed end up on online &&
1129 * !active we want to ensure they are strict per-CPU threads.
1131 WARN_ON(cpumask_intersects(new_mask, cpu_online_mask) &&
1132 !cpumask_intersects(new_mask, cpu_active_mask) &&
1133 p->nr_cpus_allowed != 1);
1136 /* Can the task run on the task's current CPU? If so, we're done */
1137 if (cpumask_test_cpu(task_cpu(p), new_mask))
1140 dest_cpu = cpumask_any_and(cpu_valid_mask, new_mask);
1141 if (task_running(rq, p) || p->state == TASK_WAKING) {
1142 struct migration_arg arg = { p, dest_cpu };
1143 /* Need help from migration thread: drop lock and wait. */
1144 task_rq_unlock(rq, p, &rf);
1145 stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
1146 tlb_migrate_finish(p->mm);
1148 } else if (task_on_rq_queued(p)) {
1150 * OK, since we're going to drop the lock immediately
1151 * afterwards anyway.
1153 rq = move_queued_task(rq, &rf, p, dest_cpu);
1156 task_rq_unlock(rq, p, &rf);
1161 int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
1163 return __set_cpus_allowed_ptr(p, new_mask, false);
1165 EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
1167 void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
1169 #ifdef CONFIG_SCHED_DEBUG
1171 * We should never call set_task_cpu() on a blocked task,
1172 * ttwu() will sort out the placement.
1174 WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
1178 * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
1179 * because schedstat_wait_{start,end} rebase migrating task's wait_start
1180 * time relying on p->on_rq.
1182 WARN_ON_ONCE(p->state == TASK_RUNNING &&
1183 p->sched_class == &fair_sched_class &&
1184 (p->on_rq && !task_on_rq_migrating(p)));
1186 #ifdef CONFIG_LOCKDEP
1188 * The caller should hold either p->pi_lock or rq->lock, when changing
1189 * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
1191 * sched_move_task() holds both and thus holding either pins the cgroup,
1194 * Furthermore, all task_rq users should acquire both locks, see
1197 WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
1198 lockdep_is_held(&task_rq(p)->lock)));
1202 trace_sched_migrate_task(p, new_cpu);
1204 if (task_cpu(p) != new_cpu) {
1205 if (p->sched_class->migrate_task_rq)
1206 p->sched_class->migrate_task_rq(p);
1207 p->se.nr_migrations++;
1208 perf_event_task_migrate(p);
1211 __set_task_cpu(p, new_cpu);
1214 static void __migrate_swap_task(struct task_struct *p, int cpu)
1216 if (task_on_rq_queued(p)) {
1217 struct rq *src_rq, *dst_rq;
1218 struct rq_flags srf, drf;
1220 src_rq = task_rq(p);
1221 dst_rq = cpu_rq(cpu);
1223 rq_pin_lock(src_rq, &srf);
1224 rq_pin_lock(dst_rq, &drf);
1226 p->on_rq = TASK_ON_RQ_MIGRATING;
1227 deactivate_task(src_rq, p, 0);
1228 set_task_cpu(p, cpu);
1229 activate_task(dst_rq, p, 0);
1230 p->on_rq = TASK_ON_RQ_QUEUED;
1231 check_preempt_curr(dst_rq, p, 0);
1233 rq_unpin_lock(dst_rq, &drf);
1234 rq_unpin_lock(src_rq, &srf);
1238 * Task isn't running anymore; make it appear like we migrated
1239 * it before it went to sleep. This means on wakeup we make the
1240 * previous CPU our target instead of where it really is.
1246 struct migration_swap_arg {
1247 struct task_struct *src_task, *dst_task;
1248 int src_cpu, dst_cpu;
1251 static int migrate_swap_stop(void *data)
1253 struct migration_swap_arg *arg = data;
1254 struct rq *src_rq, *dst_rq;
1257 if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu))
1260 src_rq = cpu_rq(arg->src_cpu);
1261 dst_rq = cpu_rq(arg->dst_cpu);
1263 double_raw_lock(&arg->src_task->pi_lock,
1264 &arg->dst_task->pi_lock);
1265 double_rq_lock(src_rq, dst_rq);
1267 if (task_cpu(arg->dst_task) != arg->dst_cpu)
1270 if (task_cpu(arg->src_task) != arg->src_cpu)
1273 if (!cpumask_test_cpu(arg->dst_cpu, &arg->src_task->cpus_allowed))
1276 if (!cpumask_test_cpu(arg->src_cpu, &arg->dst_task->cpus_allowed))
1279 __migrate_swap_task(arg->src_task, arg->dst_cpu);
1280 __migrate_swap_task(arg->dst_task, arg->src_cpu);
1285 double_rq_unlock(src_rq, dst_rq);
1286 raw_spin_unlock(&arg->dst_task->pi_lock);
1287 raw_spin_unlock(&arg->src_task->pi_lock);
1293 * Cross migrate two tasks
1295 int migrate_swap(struct task_struct *cur, struct task_struct *p)
1297 struct migration_swap_arg arg;
1300 arg = (struct migration_swap_arg){
1302 .src_cpu = task_cpu(cur),
1304 .dst_cpu = task_cpu(p),
1307 if (arg.src_cpu == arg.dst_cpu)
1311 * These three tests are all lockless; this is OK since all of them
1312 * will be re-checked with proper locks held further down the line.
1314 if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu))
1317 if (!cpumask_test_cpu(arg.dst_cpu, &arg.src_task->cpus_allowed))
1320 if (!cpumask_test_cpu(arg.src_cpu, &arg.dst_task->cpus_allowed))
1323 trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu);
1324 ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg);
1331 * wait_task_inactive - wait for a thread to unschedule.
1333 * If @match_state is nonzero, it's the @p->state value just checked and
1334 * not expected to change. If it changes, i.e. @p might have woken up,
1335 * then return zero. When we succeed in waiting for @p to be off its CPU,
1336 * we return a positive number (its total switch count). If a second call
1337 * a short while later returns the same number, the caller can be sure that
1338 * @p has remained unscheduled the whole time.
1340 * The caller must ensure that the task *will* unschedule sometime soon,
1341 * else this function might spin for a *long* time. This function can't
1342 * be called with interrupts off, or it may introduce deadlock with
1343 * smp_call_function() if an IPI is sent by the same process we are
1344 * waiting to become inactive.
1346 unsigned long wait_task_inactive(struct task_struct *p, long match_state)
1348 int running, queued;
1355 * We do the initial early heuristics without holding
1356 * any task-queue locks at all. We'll only try to get
1357 * the runqueue lock when things look like they will
1363 * If the task is actively running on another CPU
1364 * still, just relax and busy-wait without holding
1367 * NOTE! Since we don't hold any locks, it's not
1368 * even sure that "rq" stays as the right runqueue!
1369 * But we don't care, since "task_running()" will
1370 * return false if the runqueue has changed and p
1371 * is actually now running somewhere else!
1373 while (task_running(rq, p)) {
1374 if (match_state && unlikely(p->state != match_state))
1380 * Ok, time to look more closely! We need the rq
1381 * lock now, to be *sure*. If we're wrong, we'll
1382 * just go back and repeat.
1384 rq = task_rq_lock(p, &rf);
1385 trace_sched_wait_task(p);
1386 running = task_running(rq, p);
1387 queued = task_on_rq_queued(p);
1389 if (!match_state || p->state == match_state)
1390 ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
1391 task_rq_unlock(rq, p, &rf);
1394 * If it changed from the expected state, bail out now.
1396 if (unlikely(!ncsw))
1400 * Was it really running after all now that we
1401 * checked with the proper locks actually held?
1403 * Oops. Go back and try again..
1405 if (unlikely(running)) {
1411 * It's not enough that it's not actively running,
1412 * it must be off the runqueue _entirely_, and not
1415 * So if it was still runnable (but just not actively
1416 * running right now), it's preempted, and we should
1417 * yield - it could be a while.
1419 if (unlikely(queued)) {
1420 ktime_t to = NSEC_PER_SEC / HZ;
1422 set_current_state(TASK_UNINTERRUPTIBLE);
1423 schedule_hrtimeout(&to, HRTIMER_MODE_REL);
1428 * Ahh, all good. It wasn't running, and it wasn't
1429 * runnable, which means that it will never become
1430 * running in the future either. We're all done!
1439 * kick_process - kick a running thread to enter/exit the kernel
1440 * @p: the to-be-kicked thread
1442 * Cause a process which is running on another CPU to enter
1443 * kernel-mode, without any delay. (to get signals handled.)
1445 * NOTE: this function doesn't have to take the runqueue lock,
1446 * because all it wants to ensure is that the remote task enters
1447 * the kernel. If the IPI races and the task has been migrated
1448 * to another CPU then no harm is done and the purpose has been
1451 void kick_process(struct task_struct *p)
1457 if ((cpu != smp_processor_id()) && task_curr(p))
1458 smp_send_reschedule(cpu);
1461 EXPORT_SYMBOL_GPL(kick_process);
1464 * ->cpus_allowed is protected by both rq->lock and p->pi_lock
1466 * A few notes on cpu_active vs cpu_online:
1468 * - cpu_active must be a subset of cpu_online
1470 * - on cpu-up we allow per-cpu kthreads on the online && !active cpu,
1471 * see __set_cpus_allowed_ptr(). At this point the newly online
1472 * CPU isn't yet part of the sched domains, and balancing will not
1475 * - on CPU-down we clear cpu_active() to mask the sched domains and
1476 * avoid the load balancer to place new tasks on the to be removed
1477 * CPU. Existing tasks will remain running there and will be taken
1480 * This means that fallback selection must not select !active CPUs.
1481 * And can assume that any active CPU must be online. Conversely
1482 * select_task_rq() below may allow selection of !active CPUs in order
1483 * to satisfy the above rules.
1485 static int select_fallback_rq(int cpu, struct task_struct *p)
1487 int nid = cpu_to_node(cpu);
1488 const struct cpumask *nodemask = NULL;
1489 enum { cpuset, possible, fail } state = cpuset;
1493 * If the node that the CPU is on has been offlined, cpu_to_node()
1494 * will return -1. There is no CPU on the node, and we should
1495 * select the CPU on the other node.
1498 nodemask = cpumask_of_node(nid);
1500 /* Look for allowed, online CPU in same node. */
1501 for_each_cpu(dest_cpu, nodemask) {
1502 if (!cpu_active(dest_cpu))
1504 if (cpumask_test_cpu(dest_cpu, &p->cpus_allowed))
1510 /* Any allowed, online CPU? */
1511 for_each_cpu(dest_cpu, &p->cpus_allowed) {
1512 if (!(p->flags & PF_KTHREAD) && !cpu_active(dest_cpu))
1514 if (!cpu_online(dest_cpu))
1519 /* No more Mr. Nice Guy. */
1522 if (IS_ENABLED(CONFIG_CPUSETS)) {
1523 cpuset_cpus_allowed_fallback(p);
1529 do_set_cpus_allowed(p, cpu_possible_mask);
1540 if (state != cpuset) {
1542 * Don't tell them about moving exiting tasks or
1543 * kernel threads (both mm NULL), since they never
1546 if (p->mm && printk_ratelimit()) {
1547 printk_deferred("process %d (%s) no longer affine to cpu%d\n",
1548 task_pid_nr(p), p->comm, cpu);
1556 * The caller (fork, wakeup) owns p->pi_lock, ->cpus_allowed is stable.
1559 int select_task_rq(struct task_struct *p, int cpu, int sd_flags, int wake_flags)
1561 lockdep_assert_held(&p->pi_lock);
1563 if (p->nr_cpus_allowed > 1)
1564 cpu = p->sched_class->select_task_rq(p, cpu, sd_flags, wake_flags);
1566 cpu = cpumask_any(&p->cpus_allowed);
1569 * In order not to call set_task_cpu() on a blocking task we need
1570 * to rely on ttwu() to place the task on a valid ->cpus_allowed
1573 * Since this is common to all placement strategies, this lives here.
1575 * [ this allows ->select_task() to simply return task_cpu(p) and
1576 * not worry about this generic constraint ]
1578 if (unlikely(!cpumask_test_cpu(cpu, &p->cpus_allowed) ||
1580 cpu = select_fallback_rq(task_cpu(p), p);
1585 static void update_avg(u64 *avg, u64 sample)
1587 s64 diff = sample - *avg;
1593 static inline int __set_cpus_allowed_ptr(struct task_struct *p,
1594 const struct cpumask *new_mask, bool check)
1596 return set_cpus_allowed_ptr(p, new_mask);
1599 #endif /* CONFIG_SMP */
1602 ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
1606 if (!schedstat_enabled())
1612 if (cpu == rq->cpu) {
1613 schedstat_inc(rq->ttwu_local);
1614 schedstat_inc(p->se.statistics.nr_wakeups_local);
1616 struct sched_domain *sd;
1618 schedstat_inc(p->se.statistics.nr_wakeups_remote);
1620 for_each_domain(rq->cpu, sd) {
1621 if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
1622 schedstat_inc(sd->ttwu_wake_remote);
1629 if (wake_flags & WF_MIGRATED)
1630 schedstat_inc(p->se.statistics.nr_wakeups_migrate);
1631 #endif /* CONFIG_SMP */
1633 schedstat_inc(rq->ttwu_count);
1634 schedstat_inc(p->se.statistics.nr_wakeups);
1636 if (wake_flags & WF_SYNC)
1637 schedstat_inc(p->se.statistics.nr_wakeups_sync);
1640 static inline void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
1642 activate_task(rq, p, en_flags);
1643 p->on_rq = TASK_ON_RQ_QUEUED;
1645 /* If a worker is waking up, notify the workqueue: */
1646 if (p->flags & PF_WQ_WORKER)
1647 wq_worker_waking_up(p, cpu_of(rq));
1651 * Mark the task runnable and perform wakeup-preemption.
1653 static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags,
1654 struct rq_flags *rf)
1656 check_preempt_curr(rq, p, wake_flags);
1657 p->state = TASK_RUNNING;
1658 trace_sched_wakeup(p);
1661 if (p->sched_class->task_woken) {
1663 * Our task @p is fully woken up and running; so its safe to
1664 * drop the rq->lock, hereafter rq is only used for statistics.
1666 rq_unpin_lock(rq, rf);
1667 p->sched_class->task_woken(rq, p);
1668 rq_repin_lock(rq, rf);
1671 if (rq->idle_stamp) {
1672 u64 delta = rq_clock(rq) - rq->idle_stamp;
1673 u64 max = 2*rq->max_idle_balance_cost;
1675 update_avg(&rq->avg_idle, delta);
1677 if (rq->avg_idle > max)
1686 ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
1687 struct rq_flags *rf)
1689 int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK;
1691 lockdep_assert_held(&rq->lock);
1694 if (p->sched_contributes_to_load)
1695 rq->nr_uninterruptible--;
1697 if (wake_flags & WF_MIGRATED)
1698 en_flags |= ENQUEUE_MIGRATED;
1701 ttwu_activate(rq, p, en_flags);
1702 ttwu_do_wakeup(rq, p, wake_flags, rf);
1706 * Called in case the task @p isn't fully descheduled from its runqueue,
1707 * in this case we must do a remote wakeup. Its a 'light' wakeup though,
1708 * since all we need to do is flip p->state to TASK_RUNNING, since
1709 * the task is still ->on_rq.
1711 static int ttwu_remote(struct task_struct *p, int wake_flags)
1717 rq = __task_rq_lock(p, &rf);
1718 if (task_on_rq_queued(p)) {
1719 /* check_preempt_curr() may use rq clock */
1720 update_rq_clock(rq);
1721 ttwu_do_wakeup(rq, p, wake_flags, &rf);
1724 __task_rq_unlock(rq, &rf);
1730 void sched_ttwu_pending(void)
1732 struct rq *rq = this_rq();
1733 struct llist_node *llist = llist_del_all(&rq->wake_list);
1734 struct task_struct *p;
1740 rq_lock_irqsave(rq, &rf);
1741 update_rq_clock(rq);
1746 p = llist_entry(llist, struct task_struct, wake_entry);
1747 llist = llist_next(llist);
1749 if (p->sched_remote_wakeup)
1750 wake_flags = WF_MIGRATED;
1752 ttwu_do_activate(rq, p, wake_flags, &rf);
1755 rq_unlock_irqrestore(rq, &rf);
1758 void scheduler_ipi(void)
1761 * Fold TIF_NEED_RESCHED into the preempt_count; anybody setting
1762 * TIF_NEED_RESCHED remotely (for the first time) will also send
1765 preempt_fold_need_resched();
1767 if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick())
1771 * Not all reschedule IPI handlers call irq_enter/irq_exit, since
1772 * traditionally all their work was done from the interrupt return
1773 * path. Now that we actually do some work, we need to make sure
1776 * Some archs already do call them, luckily irq_enter/exit nest
1779 * Arguably we should visit all archs and update all handlers,
1780 * however a fair share of IPIs are still resched only so this would
1781 * somewhat pessimize the simple resched case.
1784 sched_ttwu_pending();
1787 * Check if someone kicked us for doing the nohz idle load balance.
1789 if (unlikely(got_nohz_idle_kick())) {
1790 this_rq()->idle_balance = 1;
1791 raise_softirq_irqoff(SCHED_SOFTIRQ);
1796 static void ttwu_queue_remote(struct task_struct *p, int cpu, int wake_flags)
1798 struct rq *rq = cpu_rq(cpu);
1800 p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED);
1802 if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list)) {
1803 if (!set_nr_if_polling(rq->idle))
1804 smp_send_reschedule(cpu);
1806 trace_sched_wake_idle_without_ipi(cpu);
1810 void wake_up_if_idle(int cpu)
1812 struct rq *rq = cpu_rq(cpu);
1817 if (!is_idle_task(rcu_dereference(rq->curr)))
1820 if (set_nr_if_polling(rq->idle)) {
1821 trace_sched_wake_idle_without_ipi(cpu);
1823 rq_lock_irqsave(rq, &rf);
1824 if (is_idle_task(rq->curr))
1825 smp_send_reschedule(cpu);
1826 /* Else CPU is not idle, do nothing here: */
1827 rq_unlock_irqrestore(rq, &rf);
1834 bool cpus_share_cache(int this_cpu, int that_cpu)
1836 return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
1838 #endif /* CONFIG_SMP */
1840 static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags)
1842 struct rq *rq = cpu_rq(cpu);
1845 #if defined(CONFIG_SMP)
1846 if (sched_feat(TTWU_QUEUE) && !cpus_share_cache(smp_processor_id(), cpu)) {
1847 sched_clock_cpu(cpu); /* Sync clocks across CPUs */
1848 ttwu_queue_remote(p, cpu, wake_flags);
1854 update_rq_clock(rq);
1855 ttwu_do_activate(rq, p, wake_flags, &rf);
1860 * Notes on Program-Order guarantees on SMP systems.
1864 * The basic program-order guarantee on SMP systems is that when a task [t]
1865 * migrates, all its activity on its old CPU [c0] happens-before any subsequent
1866 * execution on its new CPU [c1].
1868 * For migration (of runnable tasks) this is provided by the following means:
1870 * A) UNLOCK of the rq(c0)->lock scheduling out task t
1871 * B) migration for t is required to synchronize *both* rq(c0)->lock and
1872 * rq(c1)->lock (if not at the same time, then in that order).
1873 * C) LOCK of the rq(c1)->lock scheduling in task
1875 * Transitivity guarantees that B happens after A and C after B.
1876 * Note: we only require RCpc transitivity.
1877 * Note: the CPU doing B need not be c0 or c1
1886 * UNLOCK rq(0)->lock
1888 * LOCK rq(0)->lock // orders against CPU0
1890 * UNLOCK rq(0)->lock
1894 * UNLOCK rq(1)->lock
1896 * LOCK rq(1)->lock // orders against CPU2
1899 * UNLOCK rq(1)->lock
1902 * BLOCKING -- aka. SLEEP + WAKEUP
1904 * For blocking we (obviously) need to provide the same guarantee as for
1905 * migration. However the means are completely different as there is no lock
1906 * chain to provide order. Instead we do:
1908 * 1) smp_store_release(X->on_cpu, 0)
1909 * 2) smp_cond_load_acquire(!X->on_cpu)
1913 * CPU0 (schedule) CPU1 (try_to_wake_up) CPU2 (schedule)
1915 * LOCK rq(0)->lock LOCK X->pi_lock
1918 * smp_store_release(X->on_cpu, 0);
1920 * smp_cond_load_acquire(&X->on_cpu, !VAL);
1926 * X->state = RUNNING
1927 * UNLOCK rq(2)->lock
1929 * LOCK rq(2)->lock // orders against CPU1
1932 * UNLOCK rq(2)->lock
1935 * UNLOCK rq(0)->lock
1938 * However; for wakeups there is a second guarantee we must provide, namely we
1939 * must observe the state that lead to our wakeup. That is, not only must our
1940 * task observe its own prior state, it must also observe the stores prior to
1943 * This means that any means of doing remote wakeups must order the CPU doing
1944 * the wakeup against the CPU the task is going to end up running on. This,
1945 * however, is already required for the regular Program-Order guarantee above,
1946 * since the waking CPU is the one issueing the ACQUIRE (smp_cond_load_acquire).
1951 * try_to_wake_up - wake up a thread
1952 * @p: the thread to be awakened
1953 * @state: the mask of task states that can be woken
1954 * @wake_flags: wake modifier flags (WF_*)
1956 * If (@state & @p->state) @p->state = TASK_RUNNING.
1958 * If the task was not queued/runnable, also place it back on a runqueue.
1960 * Atomic against schedule() which would dequeue a task, also see
1961 * set_current_state().
1963 * Return: %true if @p->state changes (an actual wakeup was done),
1967 try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
1969 unsigned long flags;
1970 int cpu, success = 0;
1973 * If we are going to wake up a thread waiting for CONDITION we
1974 * need to ensure that CONDITION=1 done by the caller can not be
1975 * reordered with p->state check below. This pairs with mb() in
1976 * set_current_state() the waiting thread does.
1978 smp_mb__before_spinlock();
1979 raw_spin_lock_irqsave(&p->pi_lock, flags);
1980 if (!(p->state & state))
1983 trace_sched_waking(p);
1985 /* We're going to change ->state: */
1990 * Ensure we load p->on_rq _after_ p->state, otherwise it would
1991 * be possible to, falsely, observe p->on_rq == 0 and get stuck
1992 * in smp_cond_load_acquire() below.
1994 * sched_ttwu_pending() try_to_wake_up()
1995 * [S] p->on_rq = 1; [L] P->state
1996 * UNLOCK rq->lock -----.
2000 * LOCK rq->lock -----'
2004 * [S] p->state = UNINTERRUPTIBLE [L] p->on_rq
2006 * Pairs with the UNLOCK+LOCK on rq->lock from the
2007 * last wakeup of our task and the schedule that got our task
2011 if (p->on_rq && ttwu_remote(p, wake_flags))
2016 * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
2017 * possible to, falsely, observe p->on_cpu == 0.
2019 * One must be running (->on_cpu == 1) in order to remove oneself
2020 * from the runqueue.
2022 * [S] ->on_cpu = 1; [L] ->on_rq
2026 * [S] ->on_rq = 0; [L] ->on_cpu
2028 * Pairs with the full barrier implied in the UNLOCK+LOCK on rq->lock
2029 * from the consecutive calls to schedule(); the first switching to our
2030 * task, the second putting it to sleep.
2035 * If the owning (remote) CPU is still in the middle of schedule() with
2036 * this task as prev, wait until its done referencing the task.
2038 * Pairs with the smp_store_release() in finish_lock_switch().
2040 * This ensures that tasks getting woken will be fully ordered against
2041 * their previous state and preserve Program Order.
2043 smp_cond_load_acquire(&p->on_cpu, !VAL);
2045 p->sched_contributes_to_load = !!task_contributes_to_load(p);
2046 p->state = TASK_WAKING;
2049 delayacct_blkio_end();
2050 atomic_dec(&task_rq(p)->nr_iowait);
2053 cpu = select_task_rq(p, p->wake_cpu, SD_BALANCE_WAKE, wake_flags);
2054 if (task_cpu(p) != cpu) {
2055 wake_flags |= WF_MIGRATED;
2056 set_task_cpu(p, cpu);
2059 #else /* CONFIG_SMP */
2062 delayacct_blkio_end();
2063 atomic_dec(&task_rq(p)->nr_iowait);
2066 #endif /* CONFIG_SMP */
2068 ttwu_queue(p, cpu, wake_flags);
2070 ttwu_stat(p, cpu, wake_flags);
2072 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2078 * try_to_wake_up_local - try to wake up a local task with rq lock held
2079 * @p: the thread to be awakened
2080 * @cookie: context's cookie for pinning
2082 * Put @p on the run-queue if it's not already there. The caller must
2083 * ensure that this_rq() is locked, @p is bound to this_rq() and not
2086 static void try_to_wake_up_local(struct task_struct *p, struct rq_flags *rf)
2088 struct rq *rq = task_rq(p);
2090 if (WARN_ON_ONCE(rq != this_rq()) ||
2091 WARN_ON_ONCE(p == current))
2094 lockdep_assert_held(&rq->lock);
2096 if (!raw_spin_trylock(&p->pi_lock)) {
2098 * This is OK, because current is on_cpu, which avoids it being
2099 * picked for load-balance and preemption/IRQs are still
2100 * disabled avoiding further scheduler activity on it and we've
2101 * not yet picked a replacement task.
2104 raw_spin_lock(&p->pi_lock);
2108 if (!(p->state & TASK_NORMAL))
2111 trace_sched_waking(p);
2113 if (!task_on_rq_queued(p)) {
2115 delayacct_blkio_end();
2116 atomic_dec(&rq->nr_iowait);
2118 ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK);
2121 ttwu_do_wakeup(rq, p, 0, rf);
2122 ttwu_stat(p, smp_processor_id(), 0);
2124 raw_spin_unlock(&p->pi_lock);
2128 * wake_up_process - Wake up a specific process
2129 * @p: The process to be woken up.
2131 * Attempt to wake up the nominated process and move it to the set of runnable
2134 * Return: 1 if the process was woken up, 0 if it was already running.
2136 * It may be assumed that this function implies a write memory barrier before
2137 * changing the task state if and only if any tasks are woken up.
2139 int wake_up_process(struct task_struct *p)
2141 return try_to_wake_up(p, TASK_NORMAL, 0);
2143 EXPORT_SYMBOL(wake_up_process);
2145 int wake_up_state(struct task_struct *p, unsigned int state)
2147 return try_to_wake_up(p, state, 0);
2151 * This function clears the sched_dl_entity static params.
2153 void __dl_clear_params(struct task_struct *p)
2155 struct sched_dl_entity *dl_se = &p->dl;
2157 dl_se->dl_runtime = 0;
2158 dl_se->dl_deadline = 0;
2159 dl_se->dl_period = 0;
2163 dl_se->dl_throttled = 0;
2164 dl_se->dl_yielded = 0;
2168 * Perform scheduler related setup for a newly forked process p.
2169 * p is forked by current.
2171 * __sched_fork() is basic setup used by init_idle() too:
2173 static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
2178 p->se.exec_start = 0;
2179 p->se.sum_exec_runtime = 0;
2180 p->se.prev_sum_exec_runtime = 0;
2181 p->se.nr_migrations = 0;
2183 INIT_LIST_HEAD(&p->se.group_node);
2185 #ifdef CONFIG_FAIR_GROUP_SCHED
2186 p->se.cfs_rq = NULL;
2189 #ifdef CONFIG_SCHEDSTATS
2190 /* Even if schedstat is disabled, there should not be garbage */
2191 memset(&p->se.statistics, 0, sizeof(p->se.statistics));
2194 RB_CLEAR_NODE(&p->dl.rb_node);
2195 init_dl_task_timer(&p->dl);
2196 __dl_clear_params(p);
2198 INIT_LIST_HEAD(&p->rt.run_list);
2200 p->rt.time_slice = sched_rr_timeslice;
2204 #ifdef CONFIG_PREEMPT_NOTIFIERS
2205 INIT_HLIST_HEAD(&p->preempt_notifiers);
2208 #ifdef CONFIG_NUMA_BALANCING
2209 if (p->mm && atomic_read(&p->mm->mm_users) == 1) {
2210 p->mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2211 p->mm->numa_scan_seq = 0;
2214 if (clone_flags & CLONE_VM)
2215 p->numa_preferred_nid = current->numa_preferred_nid;
2217 p->numa_preferred_nid = -1;
2219 p->node_stamp = 0ULL;
2220 p->numa_scan_seq = p->mm ? p->mm->numa_scan_seq : 0;
2221 p->numa_scan_period = sysctl_numa_balancing_scan_delay;
2222 p->numa_work.next = &p->numa_work;
2223 p->numa_faults = NULL;
2224 p->last_task_numa_placement = 0;
2225 p->last_sum_exec_runtime = 0;
2227 p->numa_group = NULL;
2228 #endif /* CONFIG_NUMA_BALANCING */
2231 DEFINE_STATIC_KEY_FALSE(sched_numa_balancing);
2233 #ifdef CONFIG_NUMA_BALANCING
2235 void set_numabalancing_state(bool enabled)
2238 static_branch_enable(&sched_numa_balancing);
2240 static_branch_disable(&sched_numa_balancing);
2243 #ifdef CONFIG_PROC_SYSCTL
2244 int sysctl_numa_balancing(struct ctl_table *table, int write,
2245 void __user *buffer, size_t *lenp, loff_t *ppos)
2249 int state = static_branch_likely(&sched_numa_balancing);
2251 if (write && !capable(CAP_SYS_ADMIN))
2256 err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2260 set_numabalancing_state(state);
2266 #ifdef CONFIG_SCHEDSTATS
2268 DEFINE_STATIC_KEY_FALSE(sched_schedstats);
2269 static bool __initdata __sched_schedstats = false;
2271 static void set_schedstats(bool enabled)
2274 static_branch_enable(&sched_schedstats);
2276 static_branch_disable(&sched_schedstats);
2279 void force_schedstat_enabled(void)
2281 if (!schedstat_enabled()) {
2282 pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n");
2283 static_branch_enable(&sched_schedstats);
2287 static int __init setup_schedstats(char *str)
2294 * This code is called before jump labels have been set up, so we can't
2295 * change the static branch directly just yet. Instead set a temporary
2296 * variable so init_schedstats() can do it later.
2298 if (!strcmp(str, "enable")) {
2299 __sched_schedstats = true;
2301 } else if (!strcmp(str, "disable")) {
2302 __sched_schedstats = false;
2307 pr_warn("Unable to parse schedstats=\n");
2311 __setup("schedstats=", setup_schedstats);
2313 static void __init init_schedstats(void)
2315 set_schedstats(__sched_schedstats);
2318 #ifdef CONFIG_PROC_SYSCTL
2319 int sysctl_schedstats(struct ctl_table *table, int write,
2320 void __user *buffer, size_t *lenp, loff_t *ppos)
2324 int state = static_branch_likely(&sched_schedstats);
2326 if (write && !capable(CAP_SYS_ADMIN))
2331 err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2335 set_schedstats(state);
2338 #endif /* CONFIG_PROC_SYSCTL */
2339 #else /* !CONFIG_SCHEDSTATS */
2340 static inline void init_schedstats(void) {}
2341 #endif /* CONFIG_SCHEDSTATS */
2344 * fork()/clone()-time setup:
2346 int sched_fork(unsigned long clone_flags, struct task_struct *p)
2348 unsigned long flags;
2349 int cpu = get_cpu();
2351 __sched_fork(clone_flags, p);
2353 * We mark the process as NEW here. This guarantees that
2354 * nobody will actually run it, and a signal or other external
2355 * event cannot wake it up and insert it on the runqueue either.
2357 p->state = TASK_NEW;
2360 * Make sure we do not leak PI boosting priority to the child.
2362 p->prio = current->normal_prio;
2365 * Revert to default priority/policy on fork if requested.
2367 if (unlikely(p->sched_reset_on_fork)) {
2368 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
2369 p->policy = SCHED_NORMAL;
2370 p->static_prio = NICE_TO_PRIO(0);
2372 } else if (PRIO_TO_NICE(p->static_prio) < 0)
2373 p->static_prio = NICE_TO_PRIO(0);
2375 p->prio = p->normal_prio = __normal_prio(p);
2379 * We don't need the reset flag anymore after the fork. It has
2380 * fulfilled its duty:
2382 p->sched_reset_on_fork = 0;
2385 if (dl_prio(p->prio)) {
2388 } else if (rt_prio(p->prio)) {
2389 p->sched_class = &rt_sched_class;
2391 p->sched_class = &fair_sched_class;
2394 init_entity_runnable_average(&p->se);
2397 * The child is not yet in the pid-hash so no cgroup attach races,
2398 * and the cgroup is pinned to this child due to cgroup_fork()
2399 * is ran before sched_fork().
2401 * Silence PROVE_RCU.
2403 raw_spin_lock_irqsave(&p->pi_lock, flags);
2405 * We're setting the CPU for the first time, we don't migrate,
2406 * so use __set_task_cpu().
2408 __set_task_cpu(p, cpu);
2409 if (p->sched_class->task_fork)
2410 p->sched_class->task_fork(p);
2411 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2413 #ifdef CONFIG_SCHED_INFO
2414 if (likely(sched_info_on()))
2415 memset(&p->sched_info, 0, sizeof(p->sched_info));
2417 #if defined(CONFIG_SMP)
2420 init_task_preempt_count(p);
2422 plist_node_init(&p->pushable_tasks, MAX_PRIO);
2423 RB_CLEAR_NODE(&p->pushable_dl_tasks);
2430 unsigned long to_ratio(u64 period, u64 runtime)
2432 if (runtime == RUNTIME_INF)
2436 * Doing this here saves a lot of checks in all
2437 * the calling paths, and returning zero seems
2438 * safe for them anyway.
2443 return div64_u64(runtime << 20, period);
2447 inline struct dl_bw *dl_bw_of(int i)
2449 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
2450 "sched RCU must be held");
2451 return &cpu_rq(i)->rd->dl_bw;
2454 static inline int dl_bw_cpus(int i)
2456 struct root_domain *rd = cpu_rq(i)->rd;
2459 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
2460 "sched RCU must be held");
2461 for_each_cpu_and(i, rd->span, cpu_active_mask)
2467 inline struct dl_bw *dl_bw_of(int i)
2469 return &cpu_rq(i)->dl.dl_bw;
2472 static inline int dl_bw_cpus(int i)
2479 * We must be sure that accepting a new task (or allowing changing the
2480 * parameters of an existing one) is consistent with the bandwidth
2481 * constraints. If yes, this function also accordingly updates the currently
2482 * allocated bandwidth to reflect the new situation.
2484 * This function is called while holding p's rq->lock.
2486 * XXX we should delay bw change until the task's 0-lag point, see
2489 static int dl_overflow(struct task_struct *p, int policy,
2490 const struct sched_attr *attr)
2493 struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
2494 u64 period = attr->sched_period ?: attr->sched_deadline;
2495 u64 runtime = attr->sched_runtime;
2496 u64 new_bw = dl_policy(policy) ? to_ratio(period, runtime) : 0;
2499 /* !deadline task may carry old deadline bandwidth */
2500 if (new_bw == p->dl.dl_bw && task_has_dl_policy(p))
2504 * Either if a task, enters, leave, or stays -deadline but changes
2505 * its parameters, we may need to update accordingly the total
2506 * allocated bandwidth of the container.
2508 raw_spin_lock(&dl_b->lock);
2509 cpus = dl_bw_cpus(task_cpu(p));
2510 if (dl_policy(policy) && !task_has_dl_policy(p) &&
2511 !__dl_overflow(dl_b, cpus, 0, new_bw)) {
2512 __dl_add(dl_b, new_bw);
2514 } else if (dl_policy(policy) && task_has_dl_policy(p) &&
2515 !__dl_overflow(dl_b, cpus, p->dl.dl_bw, new_bw)) {
2516 __dl_clear(dl_b, p->dl.dl_bw);
2517 __dl_add(dl_b, new_bw);
2519 } else if (!dl_policy(policy) && task_has_dl_policy(p)) {
2520 __dl_clear(dl_b, p->dl.dl_bw);
2523 raw_spin_unlock(&dl_b->lock);
2528 extern void init_dl_bw(struct dl_bw *dl_b);
2531 * wake_up_new_task - wake up a newly created task for the first time.
2533 * This function will do some initial scheduler statistics housekeeping
2534 * that must be done for every newly created context, then puts the task
2535 * on the runqueue and wakes it.
2537 void wake_up_new_task(struct task_struct *p)
2542 raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
2543 p->state = TASK_RUNNING;
2546 * Fork balancing, do it here and not earlier because:
2547 * - cpus_allowed can change in the fork path
2548 * - any previously selected CPU might disappear through hotplug
2550 * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq,
2551 * as we're not fully set-up yet.
2553 __set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0));
2555 rq = __task_rq_lock(p, &rf);
2556 update_rq_clock(rq);
2557 post_init_entity_util_avg(&p->se);
2559 activate_task(rq, p, ENQUEUE_NOCLOCK);
2560 p->on_rq = TASK_ON_RQ_QUEUED;
2561 trace_sched_wakeup_new(p);
2562 check_preempt_curr(rq, p, WF_FORK);
2564 if (p->sched_class->task_woken) {
2566 * Nothing relies on rq->lock after this, so its fine to
2569 rq_unpin_lock(rq, &rf);
2570 p->sched_class->task_woken(rq, p);
2571 rq_repin_lock(rq, &rf);
2574 task_rq_unlock(rq, p, &rf);
2577 #ifdef CONFIG_PREEMPT_NOTIFIERS
2579 static struct static_key preempt_notifier_key = STATIC_KEY_INIT_FALSE;
2581 void preempt_notifier_inc(void)
2583 static_key_slow_inc(&preempt_notifier_key);
2585 EXPORT_SYMBOL_GPL(preempt_notifier_inc);
2587 void preempt_notifier_dec(void)
2589 static_key_slow_dec(&preempt_notifier_key);
2591 EXPORT_SYMBOL_GPL(preempt_notifier_dec);
2594 * preempt_notifier_register - tell me when current is being preempted & rescheduled
2595 * @notifier: notifier struct to register
2597 void preempt_notifier_register(struct preempt_notifier *notifier)
2599 if (!static_key_false(&preempt_notifier_key))
2600 WARN(1, "registering preempt_notifier while notifiers disabled\n");
2602 hlist_add_head(¬ifier->link, ¤t->preempt_notifiers);
2604 EXPORT_SYMBOL_GPL(preempt_notifier_register);
2607 * preempt_notifier_unregister - no longer interested in preemption notifications
2608 * @notifier: notifier struct to unregister
2610 * This is *not* safe to call from within a preemption notifier.
2612 void preempt_notifier_unregister(struct preempt_notifier *notifier)
2614 hlist_del(¬ifier->link);
2616 EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
2618 static void __fire_sched_in_preempt_notifiers(struct task_struct *curr)
2620 struct preempt_notifier *notifier;
2622 hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
2623 notifier->ops->sched_in(notifier, raw_smp_processor_id());
2626 static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
2628 if (static_key_false(&preempt_notifier_key))
2629 __fire_sched_in_preempt_notifiers(curr);
2633 __fire_sched_out_preempt_notifiers(struct task_struct *curr,
2634 struct task_struct *next)
2636 struct preempt_notifier *notifier;
2638 hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
2639 notifier->ops->sched_out(notifier, next);
2642 static __always_inline void
2643 fire_sched_out_preempt_notifiers(struct task_struct *curr,
2644 struct task_struct *next)
2646 if (static_key_false(&preempt_notifier_key))
2647 __fire_sched_out_preempt_notifiers(curr, next);
2650 #else /* !CONFIG_PREEMPT_NOTIFIERS */
2652 static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
2657 fire_sched_out_preempt_notifiers(struct task_struct *curr,
2658 struct task_struct *next)
2662 #endif /* CONFIG_PREEMPT_NOTIFIERS */
2665 * prepare_task_switch - prepare to switch tasks
2666 * @rq: the runqueue preparing to switch
2667 * @prev: the current task that is being switched out
2668 * @next: the task we are going to switch to.
2670 * This is called with the rq lock held and interrupts off. It must
2671 * be paired with a subsequent finish_task_switch after the context
2674 * prepare_task_switch sets up locking and calls architecture specific
2678 prepare_task_switch(struct rq *rq, struct task_struct *prev,
2679 struct task_struct *next)
2681 sched_info_switch(rq, prev, next);
2682 perf_event_task_sched_out(prev, next);
2683 fire_sched_out_preempt_notifiers(prev, next);
2684 prepare_lock_switch(rq, next);
2685 prepare_arch_switch(next);
2689 * finish_task_switch - clean up after a task-switch
2690 * @prev: the thread we just switched away from.
2692 * finish_task_switch must be called after the context switch, paired
2693 * with a prepare_task_switch call before the context switch.
2694 * finish_task_switch will reconcile locking set up by prepare_task_switch,
2695 * and do any other architecture-specific cleanup actions.
2697 * Note that we may have delayed dropping an mm in context_switch(). If
2698 * so, we finish that here outside of the runqueue lock. (Doing it
2699 * with the lock held can cause deadlocks; see schedule() for
2702 * The context switch have flipped the stack from under us and restored the
2703 * local variables which were saved when this task called schedule() in the
2704 * past. prev == current is still correct but we need to recalculate this_rq
2705 * because prev may have moved to another CPU.
2707 static struct rq *finish_task_switch(struct task_struct *prev)
2708 __releases(rq->lock)
2710 struct rq *rq = this_rq();
2711 struct mm_struct *mm = rq->prev_mm;
2715 * The previous task will have left us with a preempt_count of 2
2716 * because it left us after:
2719 * preempt_disable(); // 1
2721 * raw_spin_lock_irq(&rq->lock) // 2
2723 * Also, see FORK_PREEMPT_COUNT.
2725 if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET,
2726 "corrupted preempt_count: %s/%d/0x%x\n",
2727 current->comm, current->pid, preempt_count()))
2728 preempt_count_set(FORK_PREEMPT_COUNT);
2733 * A task struct has one reference for the use as "current".
2734 * If a task dies, then it sets TASK_DEAD in tsk->state and calls
2735 * schedule one last time. The schedule call will never return, and
2736 * the scheduled task must drop that reference.
2738 * We must observe prev->state before clearing prev->on_cpu (in
2739 * finish_lock_switch), otherwise a concurrent wakeup can get prev
2740 * running on another CPU and we could rave with its RUNNING -> DEAD
2741 * transition, resulting in a double drop.
2743 prev_state = prev->state;
2744 vtime_task_switch(prev);
2745 perf_event_task_sched_in(prev, current);
2746 finish_lock_switch(rq, prev);
2747 finish_arch_post_lock_switch();
2749 fire_sched_in_preempt_notifiers(current);
2752 if (unlikely(prev_state == TASK_DEAD)) {
2753 if (prev->sched_class->task_dead)
2754 prev->sched_class->task_dead(prev);
2757 * Remove function-return probe instances associated with this
2758 * task and put them back on the free list.
2760 kprobe_flush_task(prev);
2762 /* Task is done with its stack. */
2763 put_task_stack(prev);
2765 put_task_struct(prev);
2768 tick_nohz_task_switch();
2774 /* rq->lock is NOT held, but preemption is disabled */
2775 static void __balance_callback(struct rq *rq)
2777 struct callback_head *head, *next;
2778 void (*func)(struct rq *rq);
2779 unsigned long flags;
2781 raw_spin_lock_irqsave(&rq->lock, flags);
2782 head = rq->balance_callback;
2783 rq->balance_callback = NULL;
2785 func = (void (*)(struct rq *))head->func;
2792 raw_spin_unlock_irqrestore(&rq->lock, flags);
2795 static inline void balance_callback(struct rq *rq)
2797 if (unlikely(rq->balance_callback))
2798 __balance_callback(rq);
2803 static inline void balance_callback(struct rq *rq)
2810 * schedule_tail - first thing a freshly forked thread must call.
2811 * @prev: the thread we just switched away from.
2813 asmlinkage __visible void schedule_tail(struct task_struct *prev)
2814 __releases(rq->lock)
2819 * New tasks start with FORK_PREEMPT_COUNT, see there and
2820 * finish_task_switch() for details.
2822 * finish_task_switch() will drop rq->lock() and lower preempt_count
2823 * and the preempt_enable() will end up enabling preemption (on
2824 * PREEMPT_COUNT kernels).
2827 rq = finish_task_switch(prev);
2828 balance_callback(rq);
2831 if (current->set_child_tid)
2832 put_user(task_pid_vnr(current), current->set_child_tid);
2836 * context_switch - switch to the new MM and the new thread's register state.
2838 static __always_inline struct rq *
2839 context_switch(struct rq *rq, struct task_struct *prev,
2840 struct task_struct *next, struct rq_flags *rf)
2842 struct mm_struct *mm, *oldmm;
2844 prepare_task_switch(rq, prev, next);
2847 oldmm = prev->active_mm;
2849 * For paravirt, this is coupled with an exit in switch_to to
2850 * combine the page table reload and the switch backend into
2853 arch_start_context_switch(prev);
2856 next->active_mm = oldmm;
2858 enter_lazy_tlb(oldmm, next);
2860 switch_mm_irqs_off(oldmm, mm, next);
2863 prev->active_mm = NULL;
2864 rq->prev_mm = oldmm;
2867 rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);
2870 * Since the runqueue lock will be released by the next
2871 * task (which is an invalid locking op but in the case
2872 * of the scheduler it's an obvious special-case), so we
2873 * do an early lockdep release here:
2875 rq_unpin_lock(rq, rf);
2876 spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
2878 /* Here we just switch the register state and the stack. */
2879 switch_to(prev, next, prev);
2882 return finish_task_switch(prev);
2886 * nr_running and nr_context_switches:
2888 * externally visible scheduler statistics: current number of runnable
2889 * threads, total number of context switches performed since bootup.
2891 unsigned long nr_running(void)
2893 unsigned long i, sum = 0;
2895 for_each_online_cpu(i)
2896 sum += cpu_rq(i)->nr_running;
2902 * Check if only the current task is running on the CPU.
2904 * Caution: this function does not check that the caller has disabled
2905 * preemption, thus the result might have a time-of-check-to-time-of-use
2906 * race. The caller is responsible to use it correctly, for example:
2908 * - from a non-preemptable section (of course)
2910 * - from a thread that is bound to a single CPU
2912 * - in a loop with very short iterations (e.g. a polling loop)
2914 bool single_task_running(void)
2916 return raw_rq()->nr_running == 1;
2918 EXPORT_SYMBOL(single_task_running);
2920 unsigned long long nr_context_switches(void)
2923 unsigned long long sum = 0;
2925 for_each_possible_cpu(i)
2926 sum += cpu_rq(i)->nr_switches;
2932 * IO-wait accounting, and how its mostly bollocks (on SMP).
2934 * The idea behind IO-wait account is to account the idle time that we could
2935 * have spend running if it were not for IO. That is, if we were to improve the
2936 * storage performance, we'd have a proportional reduction in IO-wait time.
2938 * This all works nicely on UP, where, when a task blocks on IO, we account
2939 * idle time as IO-wait, because if the storage were faster, it could've been
2940 * running and we'd not be idle.
2942 * This has been extended to SMP, by doing the same for each CPU. This however
2945 * Imagine for instance the case where two tasks block on one CPU, only the one
2946 * CPU will have IO-wait accounted, while the other has regular idle. Even
2947 * though, if the storage were faster, both could've ran at the same time,
2948 * utilising both CPUs.
2950 * This means, that when looking globally, the current IO-wait accounting on
2951 * SMP is a lower bound, by reason of under accounting.
2953 * Worse, since the numbers are provided per CPU, they are sometimes
2954 * interpreted per CPU, and that is nonsensical. A blocked task isn't strictly
2955 * associated with any one particular CPU, it can wake to another CPU than it
2956 * blocked on. This means the per CPU IO-wait number is meaningless.
2958 * Task CPU affinities can make all that even more 'interesting'.
2961 unsigned long nr_iowait(void)
2963 unsigned long i, sum = 0;
2965 for_each_possible_cpu(i)
2966 sum += atomic_read(&cpu_rq(i)->nr_iowait);
2972 * Consumers of these two interfaces, like for example the cpufreq menu
2973 * governor are using nonsensical data. Boosting frequency for a CPU that has
2974 * IO-wait which might not even end up running the task when it does become
2978 unsigned long nr_iowait_cpu(int cpu)
2980 struct rq *this = cpu_rq(cpu);
2981 return atomic_read(&this->nr_iowait);
2984 void get_iowait_load(unsigned long *nr_waiters, unsigned long *load)
2986 struct rq *rq = this_rq();
2987 *nr_waiters = atomic_read(&rq->nr_iowait);
2988 *load = rq->load.weight;
2994 * sched_exec - execve() is a valuable balancing opportunity, because at
2995 * this point the task has the smallest effective memory and cache footprint.
2997 void sched_exec(void)
2999 struct task_struct *p = current;
3000 unsigned long flags;
3003 raw_spin_lock_irqsave(&p->pi_lock, flags);
3004 dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), SD_BALANCE_EXEC, 0);
3005 if (dest_cpu == smp_processor_id())
3008 if (likely(cpu_active(dest_cpu))) {
3009 struct migration_arg arg = { p, dest_cpu };
3011 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
3012 stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
3016 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
3021 DEFINE_PER_CPU(struct kernel_stat, kstat);
3022 DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat);
3024 EXPORT_PER_CPU_SYMBOL(kstat);
3025 EXPORT_PER_CPU_SYMBOL(kernel_cpustat);
3028 * The function fair_sched_class.update_curr accesses the struct curr
3029 * and its field curr->exec_start; when called from task_sched_runtime(),
3030 * we observe a high rate of cache misses in practice.
3031 * Prefetching this data results in improved performance.
3033 static inline void prefetch_curr_exec_start(struct task_struct *p)
3035 #ifdef CONFIG_FAIR_GROUP_SCHED
3036 struct sched_entity *curr = (&p->se)->cfs_rq->curr;
3038 struct sched_entity *curr = (&task_rq(p)->cfs)->curr;
3041 prefetch(&curr->exec_start);
3045 * Return accounted runtime for the task.
3046 * In case the task is currently running, return the runtime plus current's
3047 * pending runtime that have not been accounted yet.
3049 unsigned long long task_sched_runtime(struct task_struct *p)
3055 #if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
3057 * 64-bit doesn't need locks to atomically read a 64bit value.
3058 * So we have a optimization chance when the task's delta_exec is 0.
3059 * Reading ->on_cpu is racy, but this is ok.
3061 * If we race with it leaving CPU, we'll take a lock. So we're correct.
3062 * If we race with it entering CPU, unaccounted time is 0. This is
3063 * indistinguishable from the read occurring a few cycles earlier.
3064 * If we see ->on_cpu without ->on_rq, the task is leaving, and has
3065 * been accounted, so we're correct here as well.
3067 if (!p->on_cpu || !task_on_rq_queued(p))
3068 return p->se.sum_exec_runtime;
3071 rq = task_rq_lock(p, &rf);
3073 * Must be ->curr _and_ ->on_rq. If dequeued, we would
3074 * project cycles that may never be accounted to this
3075 * thread, breaking clock_gettime().
3077 if (task_current(rq, p) && task_on_rq_queued(p)) {
3078 prefetch_curr_exec_start(p);
3079 update_rq_clock(rq);
3080 p->sched_class->update_curr(rq);
3082 ns = p->se.sum_exec_runtime;
3083 task_rq_unlock(rq, p, &rf);
3089 * This function gets called by the timer code, with HZ frequency.
3090 * We call it with interrupts disabled.
3092 void scheduler_tick(void)
3094 int cpu = smp_processor_id();
3095 struct rq *rq = cpu_rq(cpu);
3096 struct task_struct *curr = rq->curr;
3103 update_rq_clock(rq);
3104 curr->sched_class->task_tick(rq, curr, 0);
3105 cpu_load_update_active(rq);
3106 calc_global_load_tick(rq);
3110 perf_event_task_tick();
3113 rq->idle_balance = idle_cpu(cpu);
3114 trigger_load_balance(rq);
3116 rq_last_tick_reset(rq);
3119 #ifdef CONFIG_NO_HZ_FULL
3121 * scheduler_tick_max_deferment
3123 * Keep at least one tick per second when a single
3124 * active task is running because the scheduler doesn't
3125 * yet completely support full dynticks environment.
3127 * This makes sure that uptime, CFS vruntime, load
3128 * balancing, etc... continue to move forward, even
3129 * with a very low granularity.
3131 * Return: Maximum deferment in nanoseconds.
3133 u64 scheduler_tick_max_deferment(void)
3135 struct rq *rq = this_rq();
3136 unsigned long next, now = READ_ONCE(jiffies);
3138 next = rq->last_sched_tick + HZ;
3140 if (time_before_eq(next, now))
3143 return jiffies_to_nsecs(next - now);
3147 #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
3148 defined(CONFIG_PREEMPT_TRACER))
3150 * If the value passed in is equal to the current preempt count
3151 * then we just disabled preemption. Start timing the latency.
3153 static inline void preempt_latency_start(int val)
3155 if (preempt_count() == val) {
3156 unsigned long ip = get_lock_parent_ip();
3157 #ifdef CONFIG_DEBUG_PREEMPT
3158 current->preempt_disable_ip = ip;
3160 trace_preempt_off(CALLER_ADDR0, ip);
3164 void preempt_count_add(int val)
3166 #ifdef CONFIG_DEBUG_PREEMPT
3170 if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
3173 __preempt_count_add(val);
3174 #ifdef CONFIG_DEBUG_PREEMPT
3176 * Spinlock count overflowing soon?
3178 DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
3181 preempt_latency_start(val);
3183 EXPORT_SYMBOL(preempt_count_add);
3184 NOKPROBE_SYMBOL(preempt_count_add);
3187 * If the value passed in equals to the current preempt count
3188 * then we just enabled preemption. Stop timing the latency.
3190 static inline void preempt_latency_stop(int val)
3192 if (preempt_count() == val)
3193 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
3196 void preempt_count_sub(int val)
3198 #ifdef CONFIG_DEBUG_PREEMPT
3202 if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
3205 * Is the spinlock portion underflowing?
3207 if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
3208 !(preempt_count() & PREEMPT_MASK)))
3212 preempt_latency_stop(val);
3213 __preempt_count_sub(val);
3215 EXPORT_SYMBOL(preempt_count_sub);
3216 NOKPROBE_SYMBOL(preempt_count_sub);
3219 static inline void preempt_latency_start(int val) { }
3220 static inline void preempt_latency_stop(int val) { }
3223 static inline unsigned long get_preempt_disable_ip(struct task_struct *p)
3225 #ifdef CONFIG_DEBUG_PREEMPT
3226 return p->preempt_disable_ip;
3233 * Print scheduling while atomic bug:
3235 static noinline void __schedule_bug(struct task_struct *prev)
3237 /* Save this before calling printk(), since that will clobber it */
3238 unsigned long preempt_disable_ip = get_preempt_disable_ip(current);
3240 if (oops_in_progress)
3243 printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
3244 prev->comm, prev->pid, preempt_count());
3246 debug_show_held_locks(prev);
3248 if (irqs_disabled())
3249 print_irqtrace_events(prev);
3250 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
3251 && in_atomic_preempt_off()) {
3252 pr_err("Preemption disabled at:");
3253 print_ip_sym(preempt_disable_ip);
3257 panic("scheduling while atomic\n");
3260 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
3264 * Various schedule()-time debugging checks and statistics:
3266 static inline void schedule_debug(struct task_struct *prev)
3268 #ifdef CONFIG_SCHED_STACK_END_CHECK
3269 if (task_stack_end_corrupted(prev))
3270 panic("corrupted stack end detected inside scheduler\n");
3273 if (unlikely(in_atomic_preempt_off())) {
3274 __schedule_bug(prev);
3275 preempt_count_set(PREEMPT_DISABLED);
3279 profile_hit(SCHED_PROFILING, __builtin_return_address(0));
3281 schedstat_inc(this_rq()->sched_count);
3285 * Pick up the highest-prio task:
3287 static inline struct task_struct *
3288 pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
3290 const struct sched_class *class;
3291 struct task_struct *p;
3294 * Optimization: we know that if all tasks are in the fair class we can
3295 * call that function directly, but only if the @prev task wasn't of a
3296 * higher scheduling class, because otherwise those loose the
3297 * opportunity to pull in more work from other CPUs.
3299 if (likely((prev->sched_class == &idle_sched_class ||
3300 prev->sched_class == &fair_sched_class) &&
3301 rq->nr_running == rq->cfs.h_nr_running)) {
3303 p = fair_sched_class.pick_next_task(rq, prev, rf);
3304 if (unlikely(p == RETRY_TASK))
3307 /* Assumes fair_sched_class->next == idle_sched_class */
3309 p = idle_sched_class.pick_next_task(rq, prev, rf);
3315 for_each_class(class) {
3316 p = class->pick_next_task(rq, prev, rf);
3318 if (unlikely(p == RETRY_TASK))
3324 /* The idle class should always have a runnable task: */
3329 * __schedule() is the main scheduler function.
3331 * The main means of driving the scheduler and thus entering this function are:
3333 * 1. Explicit blocking: mutex, semaphore, waitqueue, etc.
3335 * 2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
3336 * paths. For example, see arch/x86/entry_64.S.
3338 * To drive preemption between tasks, the scheduler sets the flag in timer
3339 * interrupt handler scheduler_tick().
3341 * 3. Wakeups don't really cause entry into schedule(). They add a
3342 * task to the run-queue and that's it.
3344 * Now, if the new task added to the run-queue preempts the current
3345 * task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
3346 * called on the nearest possible occasion:
3348 * - If the kernel is preemptible (CONFIG_PREEMPT=y):
3350 * - in syscall or exception context, at the next outmost
3351 * preempt_enable(). (this might be as soon as the wake_up()'s
3354 * - in IRQ context, return from interrupt-handler to
3355 * preemptible context
3357 * - If the kernel is not preemptible (CONFIG_PREEMPT is not set)
3360 * - cond_resched() call
3361 * - explicit schedule() call
3362 * - return from syscall or exception to user-space
3363 * - return from interrupt-handler to user-space
3365 * WARNING: must be called with preemption disabled!
3367 static void __sched notrace __schedule(bool preempt)
3369 struct task_struct *prev, *next;
3370 unsigned long *switch_count;
3375 cpu = smp_processor_id();
3379 schedule_debug(prev);
3381 if (sched_feat(HRTICK))
3384 local_irq_disable();
3385 rcu_note_context_switch(preempt);
3388 * Make sure that signal_pending_state()->signal_pending() below
3389 * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
3390 * done by the caller to avoid the race with signal_wake_up().
3392 smp_mb__before_spinlock();
3395 /* Promote REQ to ACT */
3396 rq->clock_update_flags <<= 1;
3397 update_rq_clock(rq);
3399 switch_count = &prev->nivcsw;
3400 if (!preempt && prev->state) {
3401 if (unlikely(signal_pending_state(prev->state, prev))) {
3402 prev->state = TASK_RUNNING;
3404 deactivate_task(rq, prev, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK);
3407 if (prev->in_iowait) {
3408 atomic_inc(&rq->nr_iowait);
3409 delayacct_blkio_start();
3413 * If a worker went to sleep, notify and ask workqueue
3414 * whether it wants to wake up a task to maintain
3417 if (prev->flags & PF_WQ_WORKER) {
3418 struct task_struct *to_wakeup;
3420 to_wakeup = wq_worker_sleeping(prev);
3422 try_to_wake_up_local(to_wakeup, &rf);
3425 switch_count = &prev->nvcsw;
3428 next = pick_next_task(rq, prev, &rf);
3429 clear_tsk_need_resched(prev);
3430 clear_preempt_need_resched();
3432 if (likely(prev != next)) {
3437 trace_sched_switch(preempt, prev, next);
3439 /* Also unlocks the rq: */
3440 rq = context_switch(rq, prev, next, &rf);
3442 rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);
3443 rq_unlock_irq(rq, &rf);
3446 balance_callback(rq);
3449 void __noreturn do_task_dead(void)
3452 * The setting of TASK_RUNNING by try_to_wake_up() may be delayed
3453 * when the following two conditions become true.
3454 * - There is race condition of mmap_sem (It is acquired by
3456 * - SMI occurs before setting TASK_RUNINNG.
3457 * (or hypervisor of virtual machine switches to other guest)
3458 * As a result, we may become TASK_RUNNING after becoming TASK_DEAD
3460 * To avoid it, we have to wait for releasing tsk->pi_lock which
3461 * is held by try_to_wake_up()
3464 raw_spin_unlock_wait(¤t->pi_lock);
3466 /* Causes final put_task_struct in finish_task_switch(): */
3467 __set_current_state(TASK_DEAD);
3469 /* Tell freezer to ignore us: */
3470 current->flags |= PF_NOFREEZE;
3475 /* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */
3480 static inline void sched_submit_work(struct task_struct *tsk)
3482 if (!tsk->state || tsk_is_pi_blocked(tsk))
3485 * If we are going to sleep and we have plugged IO queued,
3486 * make sure to submit it to avoid deadlocks.
3488 if (blk_needs_flush_plug(tsk))
3489 blk_schedule_flush_plug(tsk);
3492 asmlinkage __visible void __sched schedule(void)
3494 struct task_struct *tsk = current;
3496 sched_submit_work(tsk);
3500 sched_preempt_enable_no_resched();
3501 } while (need_resched());
3503 EXPORT_SYMBOL(schedule);
3506 * synchronize_rcu_tasks() makes sure that no task is stuck in preempted
3507 * state (have scheduled out non-voluntarily) by making sure that all
3508 * tasks have either left the run queue or have gone into user space.
3509 * As idle tasks do not do either, they must not ever be preempted
3510 * (schedule out non-voluntarily).
3512 * schedule_idle() is similar to schedule_preempt_disable() except that it
3513 * never enables preemption because it does not call sched_submit_work().
3515 void __sched schedule_idle(void)
3518 * As this skips calling sched_submit_work(), which the idle task does
3519 * regardless because that function is a nop when the task is in a
3520 * TASK_RUNNING state, make sure this isn't used someplace that the
3521 * current task can be in any other state. Note, idle is always in the
3522 * TASK_RUNNING state.
3524 WARN_ON_ONCE(current->state);
3527 } while (need_resched());
3530 #ifdef CONFIG_CONTEXT_TRACKING
3531 asmlinkage __visible void __sched schedule_user(void)
3534 * If we come here after a random call to set_need_resched(),
3535 * or we have been woken up remotely but the IPI has not yet arrived,
3536 * we haven't yet exited the RCU idle mode. Do it here manually until
3537 * we find a better solution.
3539 * NB: There are buggy callers of this function. Ideally we
3540 * should warn if prev_state != CONTEXT_USER, but that will trigger
3541 * too frequently to make sense yet.
3543 enum ctx_state prev_state = exception_enter();
3545 exception_exit(prev_state);
3550 * schedule_preempt_disabled - called with preemption disabled
3552 * Returns with preemption disabled. Note: preempt_count must be 1
3554 void __sched schedule_preempt_disabled(void)
3556 sched_preempt_enable_no_resched();
3561 static void __sched notrace preempt_schedule_common(void)
3565 * Because the function tracer can trace preempt_count_sub()
3566 * and it also uses preempt_enable/disable_notrace(), if
3567 * NEED_RESCHED is set, the preempt_enable_notrace() called
3568 * by the function tracer will call this function again and
3569 * cause infinite recursion.
3571 * Preemption must be disabled here before the function
3572 * tracer can trace. Break up preempt_disable() into two
3573 * calls. One to disable preemption without fear of being
3574 * traced. The other to still record the preemption latency,
3575 * which can also be traced by the function tracer.
3577 preempt_disable_notrace();
3578 preempt_latency_start(1);
3580 preempt_latency_stop(1);
3581 preempt_enable_no_resched_notrace();
3584 * Check again in case we missed a preemption opportunity
3585 * between schedule and now.
3587 } while (need_resched());
3590 #ifdef CONFIG_PREEMPT
3592 * this is the entry point to schedule() from in-kernel preemption
3593 * off of preempt_enable. Kernel preemptions off return from interrupt
3594 * occur there and call schedule directly.
3596 asmlinkage __visible void __sched notrace preempt_schedule(void)
3599 * If there is a non-zero preempt_count or interrupts are disabled,
3600 * we do not want to preempt the current task. Just return..
3602 if (likely(!preemptible()))
3605 preempt_schedule_common();
3607 NOKPROBE_SYMBOL(preempt_schedule);
3608 EXPORT_SYMBOL(preempt_schedule);
3611 * preempt_schedule_notrace - preempt_schedule called by tracing
3613 * The tracing infrastructure uses preempt_enable_notrace to prevent
3614 * recursion and tracing preempt enabling caused by the tracing
3615 * infrastructure itself. But as tracing can happen in areas coming
3616 * from userspace or just about to enter userspace, a preempt enable
3617 * can occur before user_exit() is called. This will cause the scheduler
3618 * to be called when the system is still in usermode.
3620 * To prevent this, the preempt_enable_notrace will use this function
3621 * instead of preempt_schedule() to exit user context if needed before
3622 * calling the scheduler.
3624 asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
3626 enum ctx_state prev_ctx;
3628 if (likely(!preemptible()))
3633 * Because the function tracer can trace preempt_count_sub()
3634 * and it also uses preempt_enable/disable_notrace(), if
3635 * NEED_RESCHED is set, the preempt_enable_notrace() called
3636 * by the function tracer will call this function again and
3637 * cause infinite recursion.
3639 * Preemption must be disabled here before the function
3640 * tracer can trace. Break up preempt_disable() into two
3641 * calls. One to disable preemption without fear of being
3642 * traced. The other to still record the preemption latency,
3643 * which can also be traced by the function tracer.
3645 preempt_disable_notrace();
3646 preempt_latency_start(1);
3648 * Needs preempt disabled in case user_exit() is traced
3649 * and the tracer calls preempt_enable_notrace() causing
3650 * an infinite recursion.
3652 prev_ctx = exception_enter();
3654 exception_exit(prev_ctx);
3656 preempt_latency_stop(1);
3657 preempt_enable_no_resched_notrace();
3658 } while (need_resched());
3660 EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
3662 #endif /* CONFIG_PREEMPT */
3665 * this is the entry point to schedule() from kernel preemption
3666 * off of irq context.
3667 * Note, that this is called and return with irqs disabled. This will
3668 * protect us against recursive calling from irq.
3670 asmlinkage __visible void __sched preempt_schedule_irq(void)
3672 enum ctx_state prev_state;
3674 /* Catch callers which need to be fixed */
3675 BUG_ON(preempt_count() || !irqs_disabled());
3677 prev_state = exception_enter();
3683 local_irq_disable();
3684 sched_preempt_enable_no_resched();
3685 } while (need_resched());
3687 exception_exit(prev_state);
3690 int default_wake_function(wait_queue_t *curr, unsigned mode, int wake_flags,
3693 return try_to_wake_up(curr->private, mode, wake_flags);
3695 EXPORT_SYMBOL(default_wake_function);
3697 #ifdef CONFIG_RT_MUTEXES
3699 static inline int __rt_effective_prio(struct task_struct *pi_task, int prio)
3702 prio = min(prio, pi_task->prio);
3707 static inline int rt_effective_prio(struct task_struct *p, int prio)
3709 struct task_struct *pi_task = rt_mutex_get_top_task(p);
3711 return __rt_effective_prio(pi_task, prio);
3715 * rt_mutex_setprio - set the current priority of a task
3717 * @pi_task: donor task
3719 * This function changes the 'effective' priority of a task. It does
3720 * not touch ->normal_prio like __setscheduler().
3722 * Used by the rt_mutex code to implement priority inheritance
3723 * logic. Call site only calls if the priority of the task changed.
3725 void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task)
3727 int prio, oldprio, queued, running, queue_flag =
3728 DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
3729 const struct sched_class *prev_class;
3733 /* XXX used to be waiter->prio, not waiter->task->prio */
3734 prio = __rt_effective_prio(pi_task, p->normal_prio);
3737 * If nothing changed; bail early.
3739 if (p->pi_top_task == pi_task && prio == p->prio && !dl_prio(prio))
3742 rq = __task_rq_lock(p, &rf);
3743 update_rq_clock(rq);
3745 * Set under pi_lock && rq->lock, such that the value can be used under
3748 * Note that there is loads of tricky to make this pointer cache work
3749 * right. rt_mutex_slowunlock()+rt_mutex_postunlock() work together to
3750 * ensure a task is de-boosted (pi_task is set to NULL) before the
3751 * task is allowed to run again (and can exit). This ensures the pointer
3752 * points to a blocked task -- which guaratees the task is present.
3754 p->pi_top_task = pi_task;
3757 * For FIFO/RR we only need to set prio, if that matches we're done.
3759 if (prio == p->prio && !dl_prio(prio))
3763 * Idle task boosting is a nono in general. There is one
3764 * exception, when PREEMPT_RT and NOHZ is active:
3766 * The idle task calls get_next_timer_interrupt() and holds
3767 * the timer wheel base->lock on the CPU and another CPU wants
3768 * to access the timer (probably to cancel it). We can safely
3769 * ignore the boosting request, as the idle CPU runs this code
3770 * with interrupts disabled and will complete the lock
3771 * protected section without being interrupted. So there is no
3772 * real need to boost.
3774 if (unlikely(p == rq->idle)) {
3775 WARN_ON(p != rq->curr);
3776 WARN_ON(p->pi_blocked_on);
3780 trace_sched_pi_setprio(p, pi_task);
3783 if (oldprio == prio)
3784 queue_flag &= ~DEQUEUE_MOVE;
3786 prev_class = p->sched_class;
3787 queued = task_on_rq_queued(p);
3788 running = task_current(rq, p);
3790 dequeue_task(rq, p, queue_flag);
3792 put_prev_task(rq, p);
3795 * Boosting condition are:
3796 * 1. -rt task is running and holds mutex A
3797 * --> -dl task blocks on mutex A
3799 * 2. -dl task is running and holds mutex A
3800 * --> -dl task blocks on mutex A and could preempt the
3803 if (dl_prio(prio)) {
3804 if (!dl_prio(p->normal_prio) ||
3805 (pi_task && dl_entity_preempt(&pi_task->dl, &p->dl))) {
3806 p->dl.dl_boosted = 1;
3807 queue_flag |= ENQUEUE_REPLENISH;
3809 p->dl.dl_boosted = 0;
3810 p->sched_class = &dl_sched_class;
3811 } else if (rt_prio(prio)) {
3812 if (dl_prio(oldprio))
3813 p->dl.dl_boosted = 0;
3815 queue_flag |= ENQUEUE_HEAD;
3816 p->sched_class = &rt_sched_class;
3818 if (dl_prio(oldprio))
3819 p->dl.dl_boosted = 0;
3820 if (rt_prio(oldprio))
3822 p->sched_class = &fair_sched_class;
3828 enqueue_task(rq, p, queue_flag);
3830 set_curr_task(rq, p);
3832 check_class_changed(rq, p, prev_class, oldprio);
3834 /* Avoid rq from going away on us: */
3836 __task_rq_unlock(rq, &rf);
3838 balance_callback(rq);
3842 static inline int rt_effective_prio(struct task_struct *p, int prio)
3848 void set_user_nice(struct task_struct *p, long nice)
3850 bool queued, running;
3851 int old_prio, delta;
3855 if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
3858 * We have to be careful, if called from sys_setpriority(),
3859 * the task might be in the middle of scheduling on another CPU.
3861 rq = task_rq_lock(p, &rf);
3862 update_rq_clock(rq);
3865 * The RT priorities are set via sched_setscheduler(), but we still
3866 * allow the 'normal' nice value to be set - but as expected
3867 * it wont have any effect on scheduling until the task is
3868 * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
3870 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
3871 p->static_prio = NICE_TO_PRIO(nice);
3874 queued = task_on_rq_queued(p);
3875 running = task_current(rq, p);
3877 dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
3879 put_prev_task(rq, p);
3881 p->static_prio = NICE_TO_PRIO(nice);
3884 p->prio = effective_prio(p);
3885 delta = p->prio - old_prio;
3888 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
3890 * If the task increased its priority or is running and
3891 * lowered its priority, then reschedule its CPU:
3893 if (delta < 0 || (delta > 0 && task_running(rq, p)))
3897 set_curr_task(rq, p);
3899 task_rq_unlock(rq, p, &rf);
3901 EXPORT_SYMBOL(set_user_nice);
3904 * can_nice - check if a task can reduce its nice value
3908 int can_nice(const struct task_struct *p, const int nice)
3910 /* Convert nice value [19,-20] to rlimit style value [1,40]: */
3911 int nice_rlim = nice_to_rlimit(nice);
3913 return (nice_rlim <= task_rlimit(p, RLIMIT_NICE) ||
3914 capable(CAP_SYS_NICE));
3917 #ifdef __ARCH_WANT_SYS_NICE
3920 * sys_nice - change the priority of the current process.
3921 * @increment: priority increment
3923 * sys_setpriority is a more generic, but much slower function that
3924 * does similar things.
3926 SYSCALL_DEFINE1(nice, int, increment)
3931 * Setpriority might change our priority at the same moment.
3932 * We don't have to worry. Conceptually one call occurs first
3933 * and we have a single winner.
3935 increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH);
3936 nice = task_nice(current) + increment;
3938 nice = clamp_val(nice, MIN_NICE, MAX_NICE);
3939 if (increment < 0 && !can_nice(current, nice))
3942 retval = security_task_setnice(current, nice);
3946 set_user_nice(current, nice);
3953 * task_prio - return the priority value of a given task.
3954 * @p: the task in question.
3956 * Return: The priority value as seen by users in /proc.
3957 * RT tasks are offset by -200. Normal tasks are centered
3958 * around 0, value goes from -16 to +15.
3960 int task_prio(const struct task_struct *p)
3962 return p->prio - MAX_RT_PRIO;
3966 * idle_cpu - is a given CPU idle currently?
3967 * @cpu: the processor in question.
3969 * Return: 1 if the CPU is currently idle. 0 otherwise.
3971 int idle_cpu(int cpu)
3973 struct rq *rq = cpu_rq(cpu);
3975 if (rq->curr != rq->idle)
3982 if (!llist_empty(&rq->wake_list))
3990 * idle_task - return the idle task for a given CPU.
3991 * @cpu: the processor in question.
3993 * Return: The idle task for the CPU @cpu.
3995 struct task_struct *idle_task(int cpu)
3997 return cpu_rq(cpu)->idle;
4001 * find_process_by_pid - find a process with a matching PID value.
4002 * @pid: the pid in question.
4004 * The task of @pid, if found. %NULL otherwise.
4006 static struct task_struct *find_process_by_pid(pid_t pid)
4008 return pid ? find_task_by_vpid(pid) : current;
4012 * This function initializes the sched_dl_entity of a newly becoming
4013 * SCHED_DEADLINE task.
4015 * Only the static values are considered here, the actual runtime and the
4016 * absolute deadline will be properly calculated when the task is enqueued
4017 * for the first time with its new policy.
4020 __setparam_dl(struct task_struct *p, const struct sched_attr *attr)
4022 struct sched_dl_entity *dl_se = &p->dl;
4024 dl_se->dl_runtime = attr->sched_runtime;
4025 dl_se->dl_deadline = attr->sched_deadline;
4026 dl_se->dl_period = attr->sched_period ?: dl_se->dl_deadline;
4027 dl_se->flags = attr->sched_flags;
4028 dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime);
4031 * Changing the parameters of a task is 'tricky' and we're not doing
4032 * the correct thing -- also see task_dead_dl() and switched_from_dl().
4034 * What we SHOULD do is delay the bandwidth release until the 0-lag
4035 * point. This would include retaining the task_struct until that time
4036 * and change dl_overflow() to not immediately decrement the current
4039 * Instead we retain the current runtime/deadline and let the new
4040 * parameters take effect after the current reservation period lapses.
4041 * This is safe (albeit pessimistic) because the 0-lag point is always
4042 * before the current scheduling deadline.
4044 * We can still have temporary overloads because we do not delay the
4045 * change in bandwidth until that time; so admission control is
4046 * not on the safe side. It does however guarantee tasks will never
4047 * consume more than promised.
4052 * sched_setparam() passes in -1 for its policy, to let the functions
4053 * it calls know not to change it.
4055 #define SETPARAM_POLICY -1
4057 static void __setscheduler_params(struct task_struct *p,
4058 const struct sched_attr *attr)
4060 int policy = attr->sched_policy;
4062 if (policy == SETPARAM_POLICY)
4067 if (dl_policy(policy))
4068 __setparam_dl(p, attr);
4069 else if (fair_policy(policy))
4070 p->static_prio = NICE_TO_PRIO(attr->sched_nice);
4073 * __sched_setscheduler() ensures attr->sched_priority == 0 when
4074 * !rt_policy. Always setting this ensures that things like
4075 * getparam()/getattr() don't report silly values for !rt tasks.
4077 p->rt_priority = attr->sched_priority;
4078 p->normal_prio = normal_prio(p);
4082 /* Actually do priority change: must hold pi & rq lock. */
4083 static void __setscheduler(struct rq *rq, struct task_struct *p,
4084 const struct sched_attr *attr, bool keep_boost)
4086 __setscheduler_params(p, attr);
4089 * Keep a potential priority boosting if called from
4090 * sched_setscheduler().
4092 p->prio = normal_prio(p);
4094 p->prio = rt_effective_prio(p, p->prio);
4096 if (dl_prio(p->prio))
4097 p->sched_class = &dl_sched_class;
4098 else if (rt_prio(p->prio))
4099 p->sched_class = &rt_sched_class;
4101 p->sched_class = &fair_sched_class;
4105 __getparam_dl(struct task_struct *p, struct sched_attr *attr)
4107 struct sched_dl_entity *dl_se = &p->dl;
4109 attr->sched_priority = p->rt_priority;
4110 attr->sched_runtime = dl_se->dl_runtime;
4111 attr->sched_deadline = dl_se->dl_deadline;
4112 attr->sched_period = dl_se->dl_period;
4113 attr->sched_flags = dl_se->flags;
4117 * This function validates the new parameters of a -deadline task.
4118 * We ask for the deadline not being zero, and greater or equal
4119 * than the runtime, as well as the period of being zero or
4120 * greater than deadline. Furthermore, we have to be sure that
4121 * user parameters are above the internal resolution of 1us (we
4122 * check sched_runtime only since it is always the smaller one) and
4123 * below 2^63 ns (we have to check both sched_deadline and
4124 * sched_period, as the latter can be zero).
4127 __checkparam_dl(const struct sched_attr *attr)
4130 if (attr->sched_deadline == 0)
4134 * Since we truncate DL_SCALE bits, make sure we're at least
4137 if (attr->sched_runtime < (1ULL << DL_SCALE))
4141 * Since we use the MSB for wrap-around and sign issues, make
4142 * sure it's not set (mind that period can be equal to zero).
4144 if (attr->sched_deadline & (1ULL << 63) ||
4145 attr->sched_period & (1ULL << 63))
4148 /* runtime <= deadline <= period (if period != 0) */
4149 if ((attr->sched_period != 0 &&
4150 attr->sched_period < attr->sched_deadline) ||
4151 attr->sched_deadline < attr->sched_runtime)
4158 * Check the target process has a UID that matches the current process's:
4160 static bool check_same_owner(struct task_struct *p)
4162 const struct cred *cred = current_cred(), *pcred;
4166 pcred = __task_cred(p);
4167 match = (uid_eq(cred->euid, pcred->euid) ||
4168 uid_eq(cred->euid, pcred->uid));
4173 static bool dl_param_changed(struct task_struct *p, const struct sched_attr *attr)
4175 struct sched_dl_entity *dl_se = &p->dl;
4177 if (dl_se->dl_runtime != attr->sched_runtime ||
4178 dl_se->dl_deadline != attr->sched_deadline ||
4179 dl_se->dl_period != attr->sched_period ||
4180 dl_se->flags != attr->sched_flags)
4186 static int __sched_setscheduler(struct task_struct *p,
4187 const struct sched_attr *attr,
4190 int newprio = dl_policy(attr->sched_policy) ? MAX_DL_PRIO - 1 :
4191 MAX_RT_PRIO - 1 - attr->sched_priority;
4192 int retval, oldprio, oldpolicy = -1, queued, running;
4193 int new_effective_prio, policy = attr->sched_policy;
4194 const struct sched_class *prev_class;
4197 int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
4200 /* May grab non-irq protected spin_locks: */
4201 BUG_ON(in_interrupt());
4203 /* Double check policy once rq lock held: */
4205 reset_on_fork = p->sched_reset_on_fork;
4206 policy = oldpolicy = p->policy;
4208 reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK);
4210 if (!valid_policy(policy))
4214 if (attr->sched_flags & ~(SCHED_FLAG_RESET_ON_FORK))
4218 * Valid priorities for SCHED_FIFO and SCHED_RR are
4219 * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
4220 * SCHED_BATCH and SCHED_IDLE is 0.
4222 if ((p->mm && attr->sched_priority > MAX_USER_RT_PRIO-1) ||
4223 (!p->mm && attr->sched_priority > MAX_RT_PRIO-1))
4225 if ((dl_policy(policy) && !__checkparam_dl(attr)) ||
4226 (rt_policy(policy) != (attr->sched_priority != 0)))
4230 * Allow unprivileged RT tasks to decrease priority:
4232 if (user && !capable(CAP_SYS_NICE)) {
4233 if (fair_policy(policy)) {
4234 if (attr->sched_nice < task_nice(p) &&
4235 !can_nice(p, attr->sched_nice))
4239 if (rt_policy(policy)) {
4240 unsigned long rlim_rtprio =
4241 task_rlimit(p, RLIMIT_RTPRIO);
4243 /* Can't set/change the rt policy: */
4244 if (policy != p->policy && !rlim_rtprio)
4247 /* Can't increase priority: */
4248 if (attr->sched_priority > p->rt_priority &&
4249 attr->sched_priority > rlim_rtprio)
4254 * Can't set/change SCHED_DEADLINE policy at all for now
4255 * (safest behavior); in the future we would like to allow
4256 * unprivileged DL tasks to increase their relative deadline
4257 * or reduce their runtime (both ways reducing utilization)
4259 if (dl_policy(policy))
4263 * Treat SCHED_IDLE as nice 20. Only allow a switch to
4264 * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
4266 if (idle_policy(p->policy) && !idle_policy(policy)) {
4267 if (!can_nice(p, task_nice(p)))
4271 /* Can't change other user's priorities: */
4272 if (!check_same_owner(p))
4275 /* Normal users shall not reset the sched_reset_on_fork flag: */
4276 if (p->sched_reset_on_fork && !reset_on_fork)
4281 retval = security_task_setscheduler(p);
4287 * Make sure no PI-waiters arrive (or leave) while we are
4288 * changing the priority of the task:
4290 * To be able to change p->policy safely, the appropriate
4291 * runqueue lock must be held.
4293 rq = task_rq_lock(p, &rf);
4294 update_rq_clock(rq);
4297 * Changing the policy of the stop threads its a very bad idea:
4299 if (p == rq->stop) {
4300 task_rq_unlock(rq, p, &rf);
4305 * If not changing anything there's no need to proceed further,
4306 * but store a possible modification of reset_on_fork.
4308 if (unlikely(policy == p->policy)) {
4309 if (fair_policy(policy) && attr->sched_nice != task_nice(p))
4311 if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
4313 if (dl_policy(policy) && dl_param_changed(p, attr))
4316 p->sched_reset_on_fork = reset_on_fork;
4317 task_rq_unlock(rq, p, &rf);
4323 #ifdef CONFIG_RT_GROUP_SCHED
4325 * Do not allow realtime tasks into groups that have no runtime
4328 if (rt_bandwidth_enabled() && rt_policy(policy) &&
4329 task_group(p)->rt_bandwidth.rt_runtime == 0 &&
4330 !task_group_is_autogroup(task_group(p))) {
4331 task_rq_unlock(rq, p, &rf);
4336 if (dl_bandwidth_enabled() && dl_policy(policy)) {
4337 cpumask_t *span = rq->rd->span;
4340 * Don't allow tasks with an affinity mask smaller than
4341 * the entire root_domain to become SCHED_DEADLINE. We
4342 * will also fail if there's no bandwidth available.
4344 if (!cpumask_subset(span, &p->cpus_allowed) ||
4345 rq->rd->dl_bw.bw == 0) {
4346 task_rq_unlock(rq, p, &rf);
4353 /* Re-check policy now with rq lock held: */
4354 if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
4355 policy = oldpolicy = -1;
4356 task_rq_unlock(rq, p, &rf);
4361 * If setscheduling to SCHED_DEADLINE (or changing the parameters
4362 * of a SCHED_DEADLINE task) we need to check if enough bandwidth
4365 if ((dl_policy(policy) || dl_task(p)) && dl_overflow(p, policy, attr)) {
4366 task_rq_unlock(rq, p, &rf);
4370 p->sched_reset_on_fork = reset_on_fork;
4375 * Take priority boosted tasks into account. If the new
4376 * effective priority is unchanged, we just store the new
4377 * normal parameters and do not touch the scheduler class and
4378 * the runqueue. This will be done when the task deboost
4381 new_effective_prio = rt_effective_prio(p, newprio);
4382 if (new_effective_prio == oldprio)
4383 queue_flags &= ~DEQUEUE_MOVE;
4386 queued = task_on_rq_queued(p);
4387 running = task_current(rq, p);
4389 dequeue_task(rq, p, queue_flags);
4391 put_prev_task(rq, p);
4393 prev_class = p->sched_class;
4394 __setscheduler(rq, p, attr, pi);
4398 * We enqueue to tail when the priority of a task is
4399 * increased (user space view).
4401 if (oldprio < p->prio)
4402 queue_flags |= ENQUEUE_HEAD;
4404 enqueue_task(rq, p, queue_flags);
4407 set_curr_task(rq, p);
4409 check_class_changed(rq, p, prev_class, oldprio);
4411 /* Avoid rq from going away on us: */
4413 task_rq_unlock(rq, p, &rf);
4416 rt_mutex_adjust_pi(p);
4418 /* Run balance callbacks after we've adjusted the PI chain: */
4419 balance_callback(rq);
4425 static int _sched_setscheduler(struct task_struct *p, int policy,
4426 const struct sched_param *param, bool check)
4428 struct sched_attr attr = {
4429 .sched_policy = policy,
4430 .sched_priority = param->sched_priority,
4431 .sched_nice = PRIO_TO_NICE(p->static_prio),
4434 /* Fixup the legacy SCHED_RESET_ON_FORK hack. */
4435 if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) {
4436 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
4437 policy &= ~SCHED_RESET_ON_FORK;
4438 attr.sched_policy = policy;
4441 return __sched_setscheduler(p, &attr, check, true);
4444 * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
4445 * @p: the task in question.
4446 * @policy: new policy.
4447 * @param: structure containing the new RT priority.
4449 * Return: 0 on success. An error code otherwise.
4451 * NOTE that the task may be already dead.
4453 int sched_setscheduler(struct task_struct *p, int policy,
4454 const struct sched_param *param)
4456 return _sched_setscheduler(p, policy, param, true);
4458 EXPORT_SYMBOL_GPL(sched_setscheduler);
4460 int sched_setattr(struct task_struct *p, const struct sched_attr *attr)
4462 return __sched_setscheduler(p, attr, true, true);
4464 EXPORT_SYMBOL_GPL(sched_setattr);
4467 * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
4468 * @p: the task in question.
4469 * @policy: new policy.
4470 * @param: structure containing the new RT priority.
4472 * Just like sched_setscheduler, only don't bother checking if the
4473 * current context has permission. For example, this is needed in
4474 * stop_machine(): we create temporary high priority worker threads,
4475 * but our caller might not have that capability.
4477 * Return: 0 on success. An error code otherwise.
4479 int sched_setscheduler_nocheck(struct task_struct *p, int policy,
4480 const struct sched_param *param)
4482 return _sched_setscheduler(p, policy, param, false);
4484 EXPORT_SYMBOL_GPL(sched_setscheduler_nocheck);
4487 do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
4489 struct sched_param lparam;
4490 struct task_struct *p;
4493 if (!param || pid < 0)
4495 if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
4500 p = find_process_by_pid(pid);
4502 retval = sched_setscheduler(p, policy, &lparam);
4509 * Mimics kernel/events/core.c perf_copy_attr().
4511 static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *attr)
4516 if (!access_ok(VERIFY_WRITE, uattr, SCHED_ATTR_SIZE_VER0))
4519 /* Zero the full structure, so that a short copy will be nice: */
4520 memset(attr, 0, sizeof(*attr));
4522 ret = get_user(size, &uattr->size);
4526 /* Bail out on silly large: */
4527 if (size > PAGE_SIZE)
4530 /* ABI compatibility quirk: */
4532 size = SCHED_ATTR_SIZE_VER0;
4534 if (size < SCHED_ATTR_SIZE_VER0)
4538 * If we're handed a bigger struct than we know of,
4539 * ensure all the unknown bits are 0 - i.e. new
4540 * user-space does not rely on any kernel feature
4541 * extensions we dont know about yet.
4543 if (size > sizeof(*attr)) {
4544 unsigned char __user *addr;
4545 unsigned char __user *end;
4548 addr = (void __user *)uattr + sizeof(*attr);
4549 end = (void __user *)uattr + size;
4551 for (; addr < end; addr++) {
4552 ret = get_user(val, addr);
4558 size = sizeof(*attr);
4561 ret = copy_from_user(attr, uattr, size);
4566 * XXX: Do we want to be lenient like existing syscalls; or do we want
4567 * to be strict and return an error on out-of-bounds values?
4569 attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE);
4574 put_user(sizeof(*attr), &uattr->size);
4579 * sys_sched_setscheduler - set/change the scheduler policy and RT priority
4580 * @pid: the pid in question.
4581 * @policy: new policy.
4582 * @param: structure containing the new RT priority.
4584 * Return: 0 on success. An error code otherwise.
4586 SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy, struct sched_param __user *, param)
4591 return do_sched_setscheduler(pid, policy, param);
4595 * sys_sched_setparam - set/change the RT priority of a thread
4596 * @pid: the pid in question.
4597 * @param: structure containing the new RT priority.
4599 * Return: 0 on success. An error code otherwise.
4601 SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
4603 return do_sched_setscheduler(pid, SETPARAM_POLICY, param);
4607 * sys_sched_setattr - same as above, but with extended sched_attr
4608 * @pid: the pid in question.
4609 * @uattr: structure containing the extended parameters.
4610 * @flags: for future extension.
4612 SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
4613 unsigned int, flags)
4615 struct sched_attr attr;
4616 struct task_struct *p;
4619 if (!uattr || pid < 0 || flags)
4622 retval = sched_copy_attr(uattr, &attr);
4626 if ((int)attr.sched_policy < 0)
4631 p = find_process_by_pid(pid);
4633 retval = sched_setattr(p, &attr);
4640 * sys_sched_getscheduler - get the policy (scheduling class) of a thread
4641 * @pid: the pid in question.
4643 * Return: On success, the policy of the thread. Otherwise, a negative error
4646 SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
4648 struct task_struct *p;
4656 p = find_process_by_pid(pid);
4658 retval = security_task_getscheduler(p);
4661 | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0);
4668 * sys_sched_getparam - get the RT priority of a thread
4669 * @pid: the pid in question.
4670 * @param: structure containing the RT priority.
4672 * Return: On success, 0 and the RT priority is in @param. Otherwise, an error
4675 SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
4677 struct sched_param lp = { .sched_priority = 0 };
4678 struct task_struct *p;
4681 if (!param || pid < 0)
4685 p = find_process_by_pid(pid);
4690 retval = security_task_getscheduler(p);
4694 if (task_has_rt_policy(p))
4695 lp.sched_priority = p->rt_priority;
4699 * This one might sleep, we cannot do it with a spinlock held ...
4701 retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
4710 static int sched_read_attr(struct sched_attr __user *uattr,
4711 struct sched_attr *attr,
4716 if (!access_ok(VERIFY_WRITE, uattr, usize))
4720 * If we're handed a smaller struct than we know of,
4721 * ensure all the unknown bits are 0 - i.e. old
4722 * user-space does not get uncomplete information.
4724 if (usize < sizeof(*attr)) {
4725 unsigned char *addr;
4728 addr = (void *)attr + usize;
4729 end = (void *)attr + sizeof(*attr);
4731 for (; addr < end; addr++) {
4739 ret = copy_to_user(uattr, attr, attr->size);
4747 * sys_sched_getattr - similar to sched_getparam, but with sched_attr
4748 * @pid: the pid in question.
4749 * @uattr: structure containing the extended parameters.
4750 * @size: sizeof(attr) for fwd/bwd comp.
4751 * @flags: for future extension.
4753 SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
4754 unsigned int, size, unsigned int, flags)
4756 struct sched_attr attr = {
4757 .size = sizeof(struct sched_attr),
4759 struct task_struct *p;
4762 if (!uattr || pid < 0 || size > PAGE_SIZE ||
4763 size < SCHED_ATTR_SIZE_VER0 || flags)
4767 p = find_process_by_pid(pid);
4772 retval = security_task_getscheduler(p);
4776 attr.sched_policy = p->policy;
4777 if (p->sched_reset_on_fork)
4778 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
4779 if (task_has_dl_policy(p))
4780 __getparam_dl(p, &attr);
4781 else if (task_has_rt_policy(p))
4782 attr.sched_priority = p->rt_priority;
4784 attr.sched_nice = task_nice(p);
4788 retval = sched_read_attr(uattr, &attr, size);
4796 long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
4798 cpumask_var_t cpus_allowed, new_mask;
4799 struct task_struct *p;
4804 p = find_process_by_pid(pid);
4810 /* Prevent p going away */
4814 if (p->flags & PF_NO_SETAFFINITY) {
4818 if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
4822 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
4824 goto out_free_cpus_allowed;
4827 if (!check_same_owner(p)) {
4829 if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
4831 goto out_free_new_mask;
4836 retval = security_task_setscheduler(p);
4838 goto out_free_new_mask;
4841 cpuset_cpus_allowed(p, cpus_allowed);
4842 cpumask_and(new_mask, in_mask, cpus_allowed);
4845 * Since bandwidth control happens on root_domain basis,
4846 * if admission test is enabled, we only admit -deadline
4847 * tasks allowed to run on all the CPUs in the task's
4851 if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {
4853 if (!cpumask_subset(task_rq(p)->rd->span, new_mask)) {
4856 goto out_free_new_mask;
4862 retval = __set_cpus_allowed_ptr(p, new_mask, true);
4865 cpuset_cpus_allowed(p, cpus_allowed);
4866 if (!cpumask_subset(new_mask, cpus_allowed)) {
4868 * We must have raced with a concurrent cpuset
4869 * update. Just reset the cpus_allowed to the
4870 * cpuset's cpus_allowed
4872 cpumask_copy(new_mask, cpus_allowed);
4877 free_cpumask_var(new_mask);
4878 out_free_cpus_allowed:
4879 free_cpumask_var(cpus_allowed);
4885 static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
4886 struct cpumask *new_mask)
4888 if (len < cpumask_size())
4889 cpumask_clear(new_mask);
4890 else if (len > cpumask_size())
4891 len = cpumask_size();
4893 return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
4897 * sys_sched_setaffinity - set the CPU affinity of a process
4898 * @pid: pid of the process
4899 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4900 * @user_mask_ptr: user-space pointer to the new CPU mask
4902 * Return: 0 on success. An error code otherwise.
4904 SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
4905 unsigned long __user *, user_mask_ptr)
4907 cpumask_var_t new_mask;
4910 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
4913 retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
4915 retval = sched_setaffinity(pid, new_mask);
4916 free_cpumask_var(new_mask);
4920 long sched_getaffinity(pid_t pid, struct cpumask *mask)
4922 struct task_struct *p;
4923 unsigned long flags;
4929 p = find_process_by_pid(pid);
4933 retval = security_task_getscheduler(p);
4937 raw_spin_lock_irqsave(&p->pi_lock, flags);
4938 cpumask_and(mask, &p->cpus_allowed, cpu_active_mask);
4939 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
4948 * sys_sched_getaffinity - get the CPU affinity of a process
4949 * @pid: pid of the process
4950 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4951 * @user_mask_ptr: user-space pointer to hold the current CPU mask
4953 * Return: size of CPU mask copied to user_mask_ptr on success. An
4954 * error code otherwise.
4956 SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
4957 unsigned long __user *, user_mask_ptr)
4962 if ((len * BITS_PER_BYTE) < nr_cpu_ids)
4964 if (len & (sizeof(unsigned long)-1))
4967 if (!alloc_cpumask_var(&mask, GFP_KERNEL))
4970 ret = sched_getaffinity(pid, mask);
4972 size_t retlen = min_t(size_t, len, cpumask_size());
4974 if (copy_to_user(user_mask_ptr, mask, retlen))
4979 free_cpumask_var(mask);
4985 * sys_sched_yield - yield the current processor to other threads.
4987 * This function yields the current CPU to other tasks. If there are no
4988 * other threads running on this CPU then this function will return.
4992 SYSCALL_DEFINE0(sched_yield)
4997 local_irq_disable();
5001 schedstat_inc(rq->yld_count);
5002 current->sched_class->yield_task(rq);
5005 * Since we are going to call schedule() anyway, there's
5006 * no need to preempt or enable interrupts:
5010 sched_preempt_enable_no_resched();
5017 #ifndef CONFIG_PREEMPT
5018 int __sched _cond_resched(void)
5020 if (should_resched(0)) {
5021 preempt_schedule_common();
5026 EXPORT_SYMBOL(_cond_resched);
5030 * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
5031 * call schedule, and on return reacquire the lock.
5033 * This works OK both with and without CONFIG_PREEMPT. We do strange low-level
5034 * operations here to prevent schedule() from being called twice (once via
5035 * spin_unlock(), once by hand).
5037 int __cond_resched_lock(spinlock_t *lock)
5039 int resched = should_resched(PREEMPT_LOCK_OFFSET);
5042 lockdep_assert_held(lock);
5044 if (spin_needbreak(lock) || resched) {
5047 preempt_schedule_common();
5055 EXPORT_SYMBOL(__cond_resched_lock);
5057 int __sched __cond_resched_softirq(void)
5059 BUG_ON(!in_softirq());
5061 if (should_resched(SOFTIRQ_DISABLE_OFFSET)) {
5063 preempt_schedule_common();
5069 EXPORT_SYMBOL(__cond_resched_softirq);
5072 * yield - yield the current processor to other threads.
5074 * Do not ever use this function, there's a 99% chance you're doing it wrong.
5076 * The scheduler is at all times free to pick the calling task as the most
5077 * eligible task to run, if removing the yield() call from your code breaks
5078 * it, its already broken.
5080 * Typical broken usage is:
5085 * where one assumes that yield() will let 'the other' process run that will
5086 * make event true. If the current task is a SCHED_FIFO task that will never
5087 * happen. Never use yield() as a progress guarantee!!
5089 * If you want to use yield() to wait for something, use wait_event().
5090 * If you want to use yield() to be 'nice' for others, use cond_resched().
5091 * If you still want to use yield(), do not!
5093 void __sched yield(void)
5095 set_current_state(TASK_RUNNING);
5098 EXPORT_SYMBOL(yield);
5101 * yield_to - yield the current processor to another thread in
5102 * your thread group, or accelerate that thread toward the
5103 * processor it's on.
5105 * @preempt: whether task preemption is allowed or not
5107 * It's the caller's job to ensure that the target task struct
5108 * can't go away on us before we can do any checks.
5111 * true (>0) if we indeed boosted the target task.
5112 * false (0) if we failed to boost the target.
5113 * -ESRCH if there's no task to yield to.
5115 int __sched yield_to(struct task_struct *p, bool preempt)
5117 struct task_struct *curr = current;
5118 struct rq *rq, *p_rq;
5119 unsigned long flags;
5122 local_irq_save(flags);
5128 * If we're the only runnable task on the rq and target rq also
5129 * has only one task, there's absolutely no point in yielding.
5131 if (rq->nr_running == 1 && p_rq->nr_running == 1) {
5136 double_rq_lock(rq, p_rq);
5137 if (task_rq(p) != p_rq) {
5138 double_rq_unlock(rq, p_rq);
5142 if (!curr->sched_class->yield_to_task)
5145 if (curr->sched_class != p->sched_class)
5148 if (task_running(p_rq, p) || p->state)
5151 yielded = curr->sched_class->yield_to_task(rq, p, preempt);
5153 schedstat_inc(rq->yld_count);
5155 * Make p's CPU reschedule; pick_next_entity takes care of
5158 if (preempt && rq != p_rq)
5163 double_rq_unlock(rq, p_rq);
5165 local_irq_restore(flags);
5172 EXPORT_SYMBOL_GPL(yield_to);
5174 int io_schedule_prepare(void)
5176 int old_iowait = current->in_iowait;
5178 current->in_iowait = 1;
5179 blk_schedule_flush_plug(current);
5184 void io_schedule_finish(int token)
5186 current->in_iowait = token;
5190 * This task is about to go to sleep on IO. Increment rq->nr_iowait so
5191 * that process accounting knows that this is a task in IO wait state.
5193 long __sched io_schedule_timeout(long timeout)
5198 token = io_schedule_prepare();
5199 ret = schedule_timeout(timeout);
5200 io_schedule_finish(token);
5204 EXPORT_SYMBOL(io_schedule_timeout);
5206 void io_schedule(void)
5210 token = io_schedule_prepare();
5212 io_schedule_finish(token);
5214 EXPORT_SYMBOL(io_schedule);
5217 * sys_sched_get_priority_max - return maximum RT priority.
5218 * @policy: scheduling class.
5220 * Return: On success, this syscall returns the maximum
5221 * rt_priority that can be used by a given scheduling class.
5222 * On failure, a negative error code is returned.
5224 SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
5231 ret = MAX_USER_RT_PRIO-1;
5233 case SCHED_DEADLINE:
5244 * sys_sched_get_priority_min - return minimum RT priority.
5245 * @policy: scheduling class.
5247 * Return: On success, this syscall returns the minimum
5248 * rt_priority that can be used by a given scheduling class.
5249 * On failure, a negative error code is returned.
5251 SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
5260 case SCHED_DEADLINE:
5270 * sys_sched_rr_get_interval - return the default timeslice of a process.
5271 * @pid: pid of the process.
5272 * @interval: userspace pointer to the timeslice value.
5274 * this syscall writes the default timeslice value of a given process
5275 * into the user-space timespec buffer. A value of '0' means infinity.
5277 * Return: On success, 0 and the timeslice is in @interval. Otherwise,
5280 SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
5281 struct timespec __user *, interval)
5283 struct task_struct *p;
5284 unsigned int time_slice;
5295 p = find_process_by_pid(pid);
5299 retval = security_task_getscheduler(p);
5303 rq = task_rq_lock(p, &rf);
5305 if (p->sched_class->get_rr_interval)
5306 time_slice = p->sched_class->get_rr_interval(rq, p);
5307 task_rq_unlock(rq, p, &rf);
5310 jiffies_to_timespec(time_slice, &t);
5311 retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
5319 static const char stat_nam[] = TASK_STATE_TO_CHAR_STR;
5321 void sched_show_task(struct task_struct *p)
5323 unsigned long free = 0;
5325 unsigned long state = p->state;
5327 /* Make sure the string lines up properly with the number of task states: */
5328 BUILD_BUG_ON(sizeof(TASK_STATE_TO_CHAR_STR)-1 != ilog2(TASK_STATE_MAX)+1);
5330 if (!try_get_task_stack(p))
5333 state = __ffs(state) + 1;
5334 printk(KERN_INFO "%-15.15s %c", p->comm,
5335 state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?');
5336 if (state == TASK_RUNNING)
5337 printk(KERN_CONT " running task ");
5338 #ifdef CONFIG_DEBUG_STACK_USAGE
5339 free = stack_not_used(p);
5344 ppid = task_pid_nr(rcu_dereference(p->real_parent));
5346 printk(KERN_CONT "%5lu %5d %6d 0x%08lx\n", free,
5347 task_pid_nr(p), ppid,
5348 (unsigned long)task_thread_info(p)->flags);
5350 print_worker_info(KERN_INFO, p);
5351 show_stack(p, NULL);
5355 void show_state_filter(unsigned long state_filter)
5357 struct task_struct *g, *p;
5359 #if BITS_PER_LONG == 32
5361 " task PC stack pid father\n");
5364 " task PC stack pid father\n");
5367 for_each_process_thread(g, p) {
5369 * reset the NMI-timeout, listing all files on a slow
5370 * console might take a lot of time:
5371 * Also, reset softlockup watchdogs on all CPUs, because
5372 * another CPU might be blocked waiting for us to process
5375 touch_nmi_watchdog();
5376 touch_all_softlockup_watchdogs();
5377 if (!state_filter || (p->state & state_filter))
5381 #ifdef CONFIG_SCHED_DEBUG
5383 sysrq_sched_debug_show();
5387 * Only show locks if all tasks are dumped:
5390 debug_show_all_locks();
5393 void init_idle_bootup_task(struct task_struct *idle)
5395 idle->sched_class = &idle_sched_class;
5399 * init_idle - set up an idle thread for a given CPU
5400 * @idle: task in question
5401 * @cpu: CPU the idle task belongs to
5403 * NOTE: this function does not set the idle thread's NEED_RESCHED
5404 * flag, to make booting more robust.
5406 void init_idle(struct task_struct *idle, int cpu)
5408 struct rq *rq = cpu_rq(cpu);
5409 unsigned long flags;
5411 raw_spin_lock_irqsave(&idle->pi_lock, flags);
5412 raw_spin_lock(&rq->lock);
5414 __sched_fork(0, idle);
5415 idle->state = TASK_RUNNING;
5416 idle->se.exec_start = sched_clock();
5417 idle->flags |= PF_IDLE;
5419 kasan_unpoison_task_stack(idle);
5423 * Its possible that init_idle() gets called multiple times on a task,
5424 * in that case do_set_cpus_allowed() will not do the right thing.
5426 * And since this is boot we can forgo the serialization.
5428 set_cpus_allowed_common(idle, cpumask_of(cpu));
5431 * We're having a chicken and egg problem, even though we are
5432 * holding rq->lock, the CPU isn't yet set to this CPU so the
5433 * lockdep check in task_group() will fail.
5435 * Similar case to sched_fork(). / Alternatively we could
5436 * use task_rq_lock() here and obtain the other rq->lock.
5441 __set_task_cpu(idle, cpu);
5444 rq->curr = rq->idle = idle;
5445 idle->on_rq = TASK_ON_RQ_QUEUED;
5449 raw_spin_unlock(&rq->lock);
5450 raw_spin_unlock_irqrestore(&idle->pi_lock, flags);
5452 /* Set the preempt count _outside_ the spinlocks! */
5453 init_idle_preempt_count(idle, cpu);
5456 * The idle tasks have their own, simple scheduling class:
5458 idle->sched_class = &idle_sched_class;
5459 ftrace_graph_init_idle_task(idle, cpu);
5460 vtime_init_idle(idle, cpu);
5462 sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu);
5466 int cpuset_cpumask_can_shrink(const struct cpumask *cur,
5467 const struct cpumask *trial)
5469 int ret = 1, trial_cpus;
5470 struct dl_bw *cur_dl_b;
5471 unsigned long flags;
5473 if (!cpumask_weight(cur))
5476 rcu_read_lock_sched();
5477 cur_dl_b = dl_bw_of(cpumask_any(cur));
5478 trial_cpus = cpumask_weight(trial);
5480 raw_spin_lock_irqsave(&cur_dl_b->lock, flags);
5481 if (cur_dl_b->bw != -1 &&
5482 cur_dl_b->bw * trial_cpus < cur_dl_b->total_bw)
5484 raw_spin_unlock_irqrestore(&cur_dl_b->lock, flags);
5485 rcu_read_unlock_sched();
5490 int task_can_attach(struct task_struct *p,
5491 const struct cpumask *cs_cpus_allowed)
5496 * Kthreads which disallow setaffinity shouldn't be moved
5497 * to a new cpuset; we don't want to change their CPU
5498 * affinity and isolating such threads by their set of
5499 * allowed nodes is unnecessary. Thus, cpusets are not
5500 * applicable for such threads. This prevents checking for
5501 * success of set_cpus_allowed_ptr() on all attached tasks
5502 * before cpus_allowed may be changed.
5504 if (p->flags & PF_NO_SETAFFINITY) {
5510 if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span,
5512 unsigned int dest_cpu = cpumask_any_and(cpu_active_mask,
5517 unsigned long flags;
5519 rcu_read_lock_sched();
5520 dl_b = dl_bw_of(dest_cpu);
5521 raw_spin_lock_irqsave(&dl_b->lock, flags);
5522 cpus = dl_bw_cpus(dest_cpu);
5523 overflow = __dl_overflow(dl_b, cpus, 0, p->dl.dl_bw);
5528 * We reserve space for this task in the destination
5529 * root_domain, as we can't fail after this point.
5530 * We will free resources in the source root_domain
5531 * later on (see set_cpus_allowed_dl()).
5533 __dl_add(dl_b, p->dl.dl_bw);
5535 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
5536 rcu_read_unlock_sched();
5546 bool sched_smp_initialized __read_mostly;
5548 #ifdef CONFIG_NUMA_BALANCING
5549 /* Migrate current task p to target_cpu */
5550 int migrate_task_to(struct task_struct *p, int target_cpu)
5552 struct migration_arg arg = { p, target_cpu };
5553 int curr_cpu = task_cpu(p);
5555 if (curr_cpu == target_cpu)
5558 if (!cpumask_test_cpu(target_cpu, &p->cpus_allowed))
5561 /* TODO: This is not properly updating schedstats */
5563 trace_sched_move_numa(p, curr_cpu, target_cpu);
5564 return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);
5568 * Requeue a task on a given node and accurately track the number of NUMA
5569 * tasks on the runqueues
5571 void sched_setnuma(struct task_struct *p, int nid)
5573 bool queued, running;
5577 rq = task_rq_lock(p, &rf);
5578 queued = task_on_rq_queued(p);
5579 running = task_current(rq, p);
5582 dequeue_task(rq, p, DEQUEUE_SAVE);
5584 put_prev_task(rq, p);
5586 p->numa_preferred_nid = nid;
5589 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
5591 set_curr_task(rq, p);
5592 task_rq_unlock(rq, p, &rf);
5594 #endif /* CONFIG_NUMA_BALANCING */
5596 #ifdef CONFIG_HOTPLUG_CPU
5598 * Ensure that the idle task is using init_mm right before its CPU goes
5601 void idle_task_exit(void)
5603 struct mm_struct *mm = current->active_mm;
5605 BUG_ON(cpu_online(smp_processor_id()));
5607 if (mm != &init_mm) {
5608 switch_mm_irqs_off(mm, &init_mm, current);
5609 finish_arch_post_lock_switch();
5615 * Since this CPU is going 'away' for a while, fold any nr_active delta
5616 * we might have. Assumes we're called after migrate_tasks() so that the
5617 * nr_active count is stable. We need to take the teardown thread which
5618 * is calling this into account, so we hand in adjust = 1 to the load
5621 * Also see the comment "Global load-average calculations".
5623 static void calc_load_migrate(struct rq *rq)
5625 long delta = calc_load_fold_active(rq, 1);
5627 atomic_long_add(delta, &calc_load_tasks);
5630 static void put_prev_task_fake(struct rq *rq, struct task_struct *prev)
5634 static const struct sched_class fake_sched_class = {
5635 .put_prev_task = put_prev_task_fake,
5638 static struct task_struct fake_task = {
5640 * Avoid pull_{rt,dl}_task()
5642 .prio = MAX_PRIO + 1,
5643 .sched_class = &fake_sched_class,
5647 * Migrate all tasks from the rq, sleeping tasks will be migrated by
5648 * try_to_wake_up()->select_task_rq().
5650 * Called with rq->lock held even though we'er in stop_machine() and
5651 * there's no concurrency possible, we hold the required locks anyway
5652 * because of lock validation efforts.
5654 static void migrate_tasks(struct rq *dead_rq, struct rq_flags *rf)
5656 struct rq *rq = dead_rq;
5657 struct task_struct *next, *stop = rq->stop;
5658 struct rq_flags orf = *rf;
5662 * Fudge the rq selection such that the below task selection loop
5663 * doesn't get stuck on the currently eligible stop task.
5665 * We're currently inside stop_machine() and the rq is either stuck
5666 * in the stop_machine_cpu_stop() loop, or we're executing this code,
5667 * either way we should never end up calling schedule() until we're
5673 * put_prev_task() and pick_next_task() sched
5674 * class method both need to have an up-to-date
5675 * value of rq->clock[_task]
5677 update_rq_clock(rq);
5681 * There's this thread running, bail when that's the only
5684 if (rq->nr_running == 1)
5688 * pick_next_task() assumes pinned rq->lock:
5690 next = pick_next_task(rq, &fake_task, rf);
5692 next->sched_class->put_prev_task(rq, next);
5695 * Rules for changing task_struct::cpus_allowed are holding
5696 * both pi_lock and rq->lock, such that holding either
5697 * stabilizes the mask.
5699 * Drop rq->lock is not quite as disastrous as it usually is
5700 * because !cpu_active at this point, which means load-balance
5701 * will not interfere. Also, stop-machine.
5704 raw_spin_lock(&next->pi_lock);
5708 * Since we're inside stop-machine, _nothing_ should have
5709 * changed the task, WARN if weird stuff happened, because in
5710 * that case the above rq->lock drop is a fail too.
5712 if (WARN_ON(task_rq(next) != rq || !task_on_rq_queued(next))) {
5713 raw_spin_unlock(&next->pi_lock);
5717 /* Find suitable destination for @next, with force if needed. */
5718 dest_cpu = select_fallback_rq(dead_rq->cpu, next);
5719 rq = __migrate_task(rq, rf, next, dest_cpu);
5720 if (rq != dead_rq) {
5726 raw_spin_unlock(&next->pi_lock);
5731 #endif /* CONFIG_HOTPLUG_CPU */
5733 void set_rq_online(struct rq *rq)
5736 const struct sched_class *class;
5738 cpumask_set_cpu(rq->cpu, rq->rd->online);
5741 for_each_class(class) {
5742 if (class->rq_online)
5743 class->rq_online(rq);
5748 void set_rq_offline(struct rq *rq)
5751 const struct sched_class *class;
5753 for_each_class(class) {
5754 if (class->rq_offline)
5755 class->rq_offline(rq);
5758 cpumask_clear_cpu(rq->cpu, rq->rd->online);
5763 static void set_cpu_rq_start_time(unsigned int cpu)
5765 struct rq *rq = cpu_rq(cpu);
5767 rq->age_stamp = sched_clock_cpu(cpu);
5771 * used to mark begin/end of suspend/resume:
5773 static int num_cpus_frozen;
5776 * Update cpusets according to cpu_active mask. If cpusets are
5777 * disabled, cpuset_update_active_cpus() becomes a simple wrapper
5778 * around partition_sched_domains().
5780 * If we come here as part of a suspend/resume, don't touch cpusets because we
5781 * want to restore it back to its original state upon resume anyway.
5783 static void cpuset_cpu_active(void)
5785 if (cpuhp_tasks_frozen) {
5787 * num_cpus_frozen tracks how many CPUs are involved in suspend
5788 * resume sequence. As long as this is not the last online
5789 * operation in the resume sequence, just build a single sched
5790 * domain, ignoring cpusets.
5793 if (likely(num_cpus_frozen)) {
5794 partition_sched_domains(1, NULL, NULL);
5798 * This is the last CPU online operation. So fall through and
5799 * restore the original sched domains by considering the
5800 * cpuset configurations.
5803 cpuset_update_active_cpus();
5806 static int cpuset_cpu_inactive(unsigned int cpu)
5808 unsigned long flags;
5813 if (!cpuhp_tasks_frozen) {
5814 rcu_read_lock_sched();
5815 dl_b = dl_bw_of(cpu);
5817 raw_spin_lock_irqsave(&dl_b->lock, flags);
5818 cpus = dl_bw_cpus(cpu);
5819 overflow = __dl_overflow(dl_b, cpus, 0, 0);
5820 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
5822 rcu_read_unlock_sched();
5826 cpuset_update_active_cpus();
5829 partition_sched_domains(1, NULL, NULL);
5834 int sched_cpu_activate(unsigned int cpu)
5836 struct rq *rq = cpu_rq(cpu);
5839 set_cpu_active(cpu, true);
5841 if (sched_smp_initialized) {
5842 sched_domains_numa_masks_set(cpu);
5843 cpuset_cpu_active();
5847 * Put the rq online, if not already. This happens:
5849 * 1) In the early boot process, because we build the real domains
5850 * after all CPUs have been brought up.
5852 * 2) At runtime, if cpuset_cpu_active() fails to rebuild the
5855 rq_lock_irqsave(rq, &rf);
5857 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
5860 rq_unlock_irqrestore(rq, &rf);
5862 update_max_interval();
5867 int sched_cpu_deactivate(unsigned int cpu)
5871 set_cpu_active(cpu, false);
5873 * We've cleared cpu_active_mask, wait for all preempt-disabled and RCU
5874 * users of this state to go away such that all new such users will
5877 * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
5878 * not imply sync_sched(), so wait for both.
5880 * Do sync before park smpboot threads to take care the rcu boost case.
5882 if (IS_ENABLED(CONFIG_PREEMPT))
5883 synchronize_rcu_mult(call_rcu, call_rcu_sched);
5887 if (!sched_smp_initialized)
5890 ret = cpuset_cpu_inactive(cpu);
5892 set_cpu_active(cpu, true);
5895 sched_domains_numa_masks_clear(cpu);
5899 static void sched_rq_cpu_starting(unsigned int cpu)
5901 struct rq *rq = cpu_rq(cpu);
5903 rq->calc_load_update = calc_load_update;
5904 update_max_interval();
5907 int sched_cpu_starting(unsigned int cpu)
5909 set_cpu_rq_start_time(cpu);
5910 sched_rq_cpu_starting(cpu);
5914 #ifdef CONFIG_HOTPLUG_CPU
5915 int sched_cpu_dying(unsigned int cpu)
5917 struct rq *rq = cpu_rq(cpu);
5920 /* Handle pending wakeups and then migrate everything off */
5921 sched_ttwu_pending();
5923 rq_lock_irqsave(rq, &rf);
5925 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
5928 migrate_tasks(rq, &rf);
5929 BUG_ON(rq->nr_running != 1);
5930 rq_unlock_irqrestore(rq, &rf);
5932 calc_load_migrate(rq);
5933 update_max_interval();
5934 nohz_balance_exit_idle(cpu);
5940 #ifdef CONFIG_SCHED_SMT
5941 DEFINE_STATIC_KEY_FALSE(sched_smt_present);
5943 static void sched_init_smt(void)
5946 * We've enumerated all CPUs and will assume that if any CPU
5947 * has SMT siblings, CPU0 will too.
5949 if (cpumask_weight(cpu_smt_mask(0)) > 1)
5950 static_branch_enable(&sched_smt_present);
5953 static inline void sched_init_smt(void) { }
5956 void __init sched_init_smp(void)
5958 cpumask_var_t non_isolated_cpus;
5960 alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL);
5961 alloc_cpumask_var(&fallback_doms, GFP_KERNEL);
5966 * There's no userspace yet to cause hotplug operations; hence all the
5967 * CPU masks are stable and all blatant races in the below code cannot
5970 mutex_lock(&sched_domains_mutex);
5971 init_sched_domains(cpu_active_mask);
5972 cpumask_andnot(non_isolated_cpus, cpu_possible_mask, cpu_isolated_map);
5973 if (cpumask_empty(non_isolated_cpus))
5974 cpumask_set_cpu(smp_processor_id(), non_isolated_cpus);
5975 mutex_unlock(&sched_domains_mutex);
5977 /* Move init over to a non-isolated CPU */
5978 if (set_cpus_allowed_ptr(current, non_isolated_cpus) < 0)
5980 sched_init_granularity();
5981 free_cpumask_var(non_isolated_cpus);
5983 init_sched_rt_class();
5984 init_sched_dl_class();
5987 sched_clock_init_late();
5989 sched_smp_initialized = true;
5992 static int __init migration_init(void)
5994 sched_rq_cpu_starting(smp_processor_id());
5997 early_initcall(migration_init);
6000 void __init sched_init_smp(void)
6002 sched_init_granularity();
6003 sched_clock_init_late();
6005 #endif /* CONFIG_SMP */
6007 int in_sched_functions(unsigned long addr)
6009 return in_lock_functions(addr) ||
6010 (addr >= (unsigned long)__sched_text_start
6011 && addr < (unsigned long)__sched_text_end);
6014 #ifdef CONFIG_CGROUP_SCHED
6016 * Default task group.
6017 * Every task in system belongs to this group at bootup.
6019 struct task_group root_task_group;
6020 LIST_HEAD(task_groups);
6022 /* Cacheline aligned slab cache for task_group */
6023 static struct kmem_cache *task_group_cache __read_mostly;
6026 DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
6027 DECLARE_PER_CPU(cpumask_var_t, select_idle_mask);
6029 #define WAIT_TABLE_BITS 8
6030 #define WAIT_TABLE_SIZE (1 << WAIT_TABLE_BITS)
6031 static wait_queue_head_t bit_wait_table[WAIT_TABLE_SIZE] __cacheline_aligned;
6033 wait_queue_head_t *bit_waitqueue(void *word, int bit)
6035 const int shift = BITS_PER_LONG == 32 ? 5 : 6;
6036 unsigned long val = (unsigned long)word << shift | bit;
6038 return bit_wait_table + hash_long(val, WAIT_TABLE_BITS);
6040 EXPORT_SYMBOL(bit_waitqueue);
6042 void __init sched_init(void)
6045 unsigned long alloc_size = 0, ptr;
6049 for (i = 0; i < WAIT_TABLE_SIZE; i++)
6050 init_waitqueue_head(bit_wait_table + i);
6052 #ifdef CONFIG_FAIR_GROUP_SCHED
6053 alloc_size += 2 * nr_cpu_ids * sizeof(void **);
6055 #ifdef CONFIG_RT_GROUP_SCHED
6056 alloc_size += 2 * nr_cpu_ids * sizeof(void **);
6059 ptr = (unsigned long)kzalloc(alloc_size, GFP_NOWAIT);
6061 #ifdef CONFIG_FAIR_GROUP_SCHED
6062 root_task_group.se = (struct sched_entity **)ptr;
6063 ptr += nr_cpu_ids * sizeof(void **);
6065 root_task_group.cfs_rq = (struct cfs_rq **)ptr;
6066 ptr += nr_cpu_ids * sizeof(void **);
6068 #endif /* CONFIG_FAIR_GROUP_SCHED */
6069 #ifdef CONFIG_RT_GROUP_SCHED
6070 root_task_group.rt_se = (struct sched_rt_entity **)ptr;
6071 ptr += nr_cpu_ids * sizeof(void **);
6073 root_task_group.rt_rq = (struct rt_rq **)ptr;
6074 ptr += nr_cpu_ids * sizeof(void **);
6076 #endif /* CONFIG_RT_GROUP_SCHED */
6078 #ifdef CONFIG_CPUMASK_OFFSTACK
6079 for_each_possible_cpu(i) {
6080 per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
6081 cpumask_size(), GFP_KERNEL, cpu_to_node(i));
6082 per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node(
6083 cpumask_size(), GFP_KERNEL, cpu_to_node(i));
6085 #endif /* CONFIG_CPUMASK_OFFSTACK */
6087 init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime());
6088 init_dl_bandwidth(&def_dl_bandwidth, global_rt_period(), global_rt_runtime());
6091 init_defrootdomain();
6094 #ifdef CONFIG_RT_GROUP_SCHED
6095 init_rt_bandwidth(&root_task_group.rt_bandwidth,
6096 global_rt_period(), global_rt_runtime());
6097 #endif /* CONFIG_RT_GROUP_SCHED */
6099 #ifdef CONFIG_CGROUP_SCHED
6100 task_group_cache = KMEM_CACHE(task_group, 0);
6102 list_add(&root_task_group.list, &task_groups);
6103 INIT_LIST_HEAD(&root_task_group.children);
6104 INIT_LIST_HEAD(&root_task_group.siblings);
6105 autogroup_init(&init_task);
6106 #endif /* CONFIG_CGROUP_SCHED */
6108 for_each_possible_cpu(i) {
6112 raw_spin_lock_init(&rq->lock);
6114 rq->calc_load_active = 0;
6115 rq->calc_load_update = jiffies + LOAD_FREQ;
6116 init_cfs_rq(&rq->cfs);
6117 init_rt_rq(&rq->rt);
6118 init_dl_rq(&rq->dl);
6119 #ifdef CONFIG_FAIR_GROUP_SCHED
6120 root_task_group.shares = ROOT_TASK_GROUP_LOAD;
6121 INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
6122 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
6124 * How much CPU bandwidth does root_task_group get?
6126 * In case of task-groups formed thr' the cgroup filesystem, it
6127 * gets 100% of the CPU resources in the system. This overall
6128 * system CPU resource is divided among the tasks of
6129 * root_task_group and its child task-groups in a fair manner,
6130 * based on each entity's (task or task-group's) weight
6131 * (se->load.weight).
6133 * In other words, if root_task_group has 10 tasks of weight
6134 * 1024) and two child groups A0 and A1 (of weight 1024 each),
6135 * then A0's share of the CPU resource is:
6137 * A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
6139 * We achieve this by letting root_task_group's tasks sit
6140 * directly in rq->cfs (i.e root_task_group->se[] = NULL).
6142 init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
6143 init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
6144 #endif /* CONFIG_FAIR_GROUP_SCHED */
6146 rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;
6147 #ifdef CONFIG_RT_GROUP_SCHED
6148 init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL);
6151 for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
6152 rq->cpu_load[j] = 0;
6157 rq->cpu_capacity = rq->cpu_capacity_orig = SCHED_CAPACITY_SCALE;
6158 rq->balance_callback = NULL;
6159 rq->active_balance = 0;
6160 rq->next_balance = jiffies;
6165 rq->avg_idle = 2*sysctl_sched_migration_cost;
6166 rq->max_idle_balance_cost = sysctl_sched_migration_cost;
6168 INIT_LIST_HEAD(&rq->cfs_tasks);
6170 rq_attach_root(rq, &def_root_domain);
6171 #ifdef CONFIG_NO_HZ_COMMON
6172 rq->last_load_update_tick = jiffies;
6175 #ifdef CONFIG_NO_HZ_FULL
6176 rq->last_sched_tick = 0;
6178 #endif /* CONFIG_SMP */
6180 atomic_set(&rq->nr_iowait, 0);
6183 set_load_weight(&init_task);
6186 * The boot idle thread does lazy MMU switching as well:
6189 enter_lazy_tlb(&init_mm, current);
6192 * Make us the idle thread. Technically, schedule() should not be
6193 * called from this thread, however somewhere below it might be,
6194 * but because we are the idle thread, we just pick up running again
6195 * when this runqueue becomes "idle".
6197 init_idle(current, smp_processor_id());
6199 calc_load_update = jiffies + LOAD_FREQ;
6202 zalloc_cpumask_var(&sched_domains_tmpmask, GFP_NOWAIT);
6203 /* May be allocated at isolcpus cmdline parse time */
6204 if (cpu_isolated_map == NULL)
6205 zalloc_cpumask_var(&cpu_isolated_map, GFP_NOWAIT);
6206 idle_thread_set_boot_cpu();
6207 set_cpu_rq_start_time(smp_processor_id());
6209 init_sched_fair_class();
6213 scheduler_running = 1;
6216 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
6217 static inline int preempt_count_equals(int preempt_offset)
6219 int nested = preempt_count() + rcu_preempt_depth();
6221 return (nested == preempt_offset);
6224 void __might_sleep(const char *file, int line, int preempt_offset)
6227 * Blocking primitives will set (and therefore destroy) current->state,
6228 * since we will exit with TASK_RUNNING make sure we enter with it,
6229 * otherwise we will destroy state.
6231 WARN_ONCE(current->state != TASK_RUNNING && current->task_state_change,
6232 "do not call blocking ops when !TASK_RUNNING; "
6233 "state=%lx set at [<%p>] %pS\n",
6235 (void *)current->task_state_change,
6236 (void *)current->task_state_change);
6238 ___might_sleep(file, line, preempt_offset);
6240 EXPORT_SYMBOL(__might_sleep);
6242 void ___might_sleep(const char *file, int line, int preempt_offset)
6244 /* Ratelimiting timestamp: */
6245 static unsigned long prev_jiffy;
6247 unsigned long preempt_disable_ip;
6249 /* WARN_ON_ONCE() by default, no rate limit required: */
6252 if ((preempt_count_equals(preempt_offset) && !irqs_disabled() &&
6253 !is_idle_task(current)) ||
6254 system_state != SYSTEM_RUNNING || oops_in_progress)
6256 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
6258 prev_jiffy = jiffies;
6260 /* Save this before calling printk(), since that will clobber it: */
6261 preempt_disable_ip = get_preempt_disable_ip(current);
6264 "BUG: sleeping function called from invalid context at %s:%d\n",
6267 "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
6268 in_atomic(), irqs_disabled(),
6269 current->pid, current->comm);
6271 if (task_stack_end_corrupted(current))
6272 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
6274 debug_show_held_locks(current);
6275 if (irqs_disabled())
6276 print_irqtrace_events(current);
6277 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
6278 && !preempt_count_equals(preempt_offset)) {
6279 pr_err("Preemption disabled at:");
6280 print_ip_sym(preempt_disable_ip);
6284 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
6286 EXPORT_SYMBOL(___might_sleep);
6289 #ifdef CONFIG_MAGIC_SYSRQ
6290 void normalize_rt_tasks(void)
6292 struct task_struct *g, *p;
6293 struct sched_attr attr = {
6294 .sched_policy = SCHED_NORMAL,
6297 read_lock(&tasklist_lock);
6298 for_each_process_thread(g, p) {
6300 * Only normalize user tasks:
6302 if (p->flags & PF_KTHREAD)
6305 p->se.exec_start = 0;
6306 schedstat_set(p->se.statistics.wait_start, 0);
6307 schedstat_set(p->se.statistics.sleep_start, 0);
6308 schedstat_set(p->se.statistics.block_start, 0);
6310 if (!dl_task(p) && !rt_task(p)) {
6312 * Renice negative nice level userspace
6315 if (task_nice(p) < 0)
6316 set_user_nice(p, 0);
6320 __sched_setscheduler(p, &attr, false, false);
6322 read_unlock(&tasklist_lock);
6325 #endif /* CONFIG_MAGIC_SYSRQ */
6327 #if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB)
6329 * These functions are only useful for the IA64 MCA handling, or kdb.
6331 * They can only be called when the whole system has been
6332 * stopped - every CPU needs to be quiescent, and no scheduling
6333 * activity can take place. Using them for anything else would
6334 * be a serious bug, and as a result, they aren't even visible
6335 * under any other configuration.
6339 * curr_task - return the current task for a given CPU.
6340 * @cpu: the processor in question.
6342 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
6344 * Return: The current task for @cpu.
6346 struct task_struct *curr_task(int cpu)
6348 return cpu_curr(cpu);
6351 #endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */
6355 * set_curr_task - set the current task for a given CPU.
6356 * @cpu: the processor in question.
6357 * @p: the task pointer to set.
6359 * Description: This function must only be used when non-maskable interrupts
6360 * are serviced on a separate stack. It allows the architecture to switch the
6361 * notion of the current task on a CPU in a non-blocking manner. This function
6362 * must be called with all CPU's synchronized, and interrupts disabled, the
6363 * and caller must save the original value of the current task (see
6364 * curr_task() above) and restore that value before reenabling interrupts and
6365 * re-starting the system.
6367 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
6369 void ia64_set_curr_task(int cpu, struct task_struct *p)
6376 #ifdef CONFIG_CGROUP_SCHED
6377 /* task_group_lock serializes the addition/removal of task groups */
6378 static DEFINE_SPINLOCK(task_group_lock);
6380 static void sched_free_group(struct task_group *tg)
6382 free_fair_sched_group(tg);
6383 free_rt_sched_group(tg);
6385 kmem_cache_free(task_group_cache, tg);
6388 /* allocate runqueue etc for a new task group */
6389 struct task_group *sched_create_group(struct task_group *parent)
6391 struct task_group *tg;
6393 tg = kmem_cache_alloc(task_group_cache, GFP_KERNEL | __GFP_ZERO);
6395 return ERR_PTR(-ENOMEM);
6397 if (!alloc_fair_sched_group(tg, parent))
6400 if (!alloc_rt_sched_group(tg, parent))
6406 sched_free_group(tg);
6407 return ERR_PTR(-ENOMEM);
6410 void sched_online_group(struct task_group *tg, struct task_group *parent)
6412 unsigned long flags;
6414 spin_lock_irqsave(&task_group_lock, flags);
6415 list_add_rcu(&tg->list, &task_groups);
6417 /* Root should already exist: */
6420 tg->parent = parent;
6421 INIT_LIST_HEAD(&tg->children);
6422 list_add_rcu(&tg->siblings, &parent->children);
6423 spin_unlock_irqrestore(&task_group_lock, flags);
6425 online_fair_sched_group(tg);
6428 /* rcu callback to free various structures associated with a task group */
6429 static void sched_free_group_rcu(struct rcu_head *rhp)
6431 /* Now it should be safe to free those cfs_rqs: */
6432 sched_free_group(container_of(rhp, struct task_group, rcu));
6435 void sched_destroy_group(struct task_group *tg)
6437 /* Wait for possible concurrent references to cfs_rqs complete: */
6438 call_rcu(&tg->rcu, sched_free_group_rcu);
6441 void sched_offline_group(struct task_group *tg)
6443 unsigned long flags;
6445 /* End participation in shares distribution: */
6446 unregister_fair_sched_group(tg);
6448 spin_lock_irqsave(&task_group_lock, flags);
6449 list_del_rcu(&tg->list);
6450 list_del_rcu(&tg->siblings);
6451 spin_unlock_irqrestore(&task_group_lock, flags);
6454 static void sched_change_group(struct task_struct *tsk, int type)
6456 struct task_group *tg;
6459 * All callers are synchronized by task_rq_lock(); we do not use RCU
6460 * which is pointless here. Thus, we pass "true" to task_css_check()
6461 * to prevent lockdep warnings.
6463 tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
6464 struct task_group, css);
6465 tg = autogroup_task_group(tsk, tg);
6466 tsk->sched_task_group = tg;
6468 #ifdef CONFIG_FAIR_GROUP_SCHED
6469 if (tsk->sched_class->task_change_group)
6470 tsk->sched_class->task_change_group(tsk, type);
6473 set_task_rq(tsk, task_cpu(tsk));
6477 * Change task's runqueue when it moves between groups.
6479 * The caller of this function should have put the task in its new group by
6480 * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect
6483 void sched_move_task(struct task_struct *tsk)
6485 int queued, running, queue_flags =
6486 DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
6490 rq = task_rq_lock(tsk, &rf);
6491 update_rq_clock(rq);
6493 running = task_current(rq, tsk);
6494 queued = task_on_rq_queued(tsk);
6497 dequeue_task(rq, tsk, queue_flags);
6499 put_prev_task(rq, tsk);
6501 sched_change_group(tsk, TASK_MOVE_GROUP);
6504 enqueue_task(rq, tsk, queue_flags);
6506 set_curr_task(rq, tsk);
6508 task_rq_unlock(rq, tsk, &rf);
6510 #endif /* CONFIG_CGROUP_SCHED */
6512 #ifdef CONFIG_RT_GROUP_SCHED
6514 * Ensure that the real time constraints are schedulable.
6516 static DEFINE_MUTEX(rt_constraints_mutex);
6518 /* Must be called with tasklist_lock held */
6519 static inline int tg_has_rt_tasks(struct task_group *tg)
6521 struct task_struct *g, *p;
6524 * Autogroups do not have RT tasks; see autogroup_create().
6526 if (task_group_is_autogroup(tg))
6529 for_each_process_thread(g, p) {
6530 if (rt_task(p) && task_group(p) == tg)
6537 struct rt_schedulable_data {
6538 struct task_group *tg;
6543 static int tg_rt_schedulable(struct task_group *tg, void *data)
6545 struct rt_schedulable_data *d = data;
6546 struct task_group *child;
6547 unsigned long total, sum = 0;
6548 u64 period, runtime;
6550 period = ktime_to_ns(tg->rt_bandwidth.rt_period);
6551 runtime = tg->rt_bandwidth.rt_runtime;
6554 period = d->rt_period;
6555 runtime = d->rt_runtime;
6559 * Cannot have more runtime than the period.
6561 if (runtime > period && runtime != RUNTIME_INF)
6565 * Ensure we don't starve existing RT tasks.
6567 if (rt_bandwidth_enabled() && !runtime && tg_has_rt_tasks(tg))
6570 total = to_ratio(period, runtime);
6573 * Nobody can have more than the global setting allows.
6575 if (total > to_ratio(global_rt_period(), global_rt_runtime()))
6579 * The sum of our children's runtime should not exceed our own.
6581 list_for_each_entry_rcu(child, &tg->children, siblings) {
6582 period = ktime_to_ns(child->rt_bandwidth.rt_period);
6583 runtime = child->rt_bandwidth.rt_runtime;
6585 if (child == d->tg) {
6586 period = d->rt_period;
6587 runtime = d->rt_runtime;
6590 sum += to_ratio(period, runtime);
6599 static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime)
6603 struct rt_schedulable_data data = {
6605 .rt_period = period,
6606 .rt_runtime = runtime,
6610 ret = walk_tg_tree(tg_rt_schedulable, tg_nop, &data);
6616 static int tg_set_rt_bandwidth(struct task_group *tg,
6617 u64 rt_period, u64 rt_runtime)
6622 * Disallowing the root group RT runtime is BAD, it would disallow the
6623 * kernel creating (and or operating) RT threads.
6625 if (tg == &root_task_group && rt_runtime == 0)
6628 /* No period doesn't make any sense. */
6632 mutex_lock(&rt_constraints_mutex);
6633 read_lock(&tasklist_lock);
6634 err = __rt_schedulable(tg, rt_period, rt_runtime);
6638 raw_spin_lock_irq(&tg->rt_bandwidth.rt_runtime_lock);
6639 tg->rt_bandwidth.rt_period = ns_to_ktime(rt_period);
6640 tg->rt_bandwidth.rt_runtime = rt_runtime;
6642 for_each_possible_cpu(i) {
6643 struct rt_rq *rt_rq = tg->rt_rq[i];
6645 raw_spin_lock(&rt_rq->rt_runtime_lock);
6646 rt_rq->rt_runtime = rt_runtime;
6647 raw_spin_unlock(&rt_rq->rt_runtime_lock);
6649 raw_spin_unlock_irq(&tg->rt_bandwidth.rt_runtime_lock);
6651 read_unlock(&tasklist_lock);
6652 mutex_unlock(&rt_constraints_mutex);
6657 static int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us)
6659 u64 rt_runtime, rt_period;
6661 rt_period = ktime_to_ns(tg->rt_bandwidth.rt_period);
6662 rt_runtime = (u64)rt_runtime_us * NSEC_PER_USEC;
6663 if (rt_runtime_us < 0)
6664 rt_runtime = RUNTIME_INF;
6666 return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
6669 static long sched_group_rt_runtime(struct task_group *tg)
6673 if (tg->rt_bandwidth.rt_runtime == RUNTIME_INF)
6676 rt_runtime_us = tg->rt_bandwidth.rt_runtime;
6677 do_div(rt_runtime_us, NSEC_PER_USEC);
6678 return rt_runtime_us;
6681 static int sched_group_set_rt_period(struct task_group *tg, u64 rt_period_us)
6683 u64 rt_runtime, rt_period;
6685 rt_period = rt_period_us * NSEC_PER_USEC;
6686 rt_runtime = tg->rt_bandwidth.rt_runtime;
6688 return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
6691 static long sched_group_rt_period(struct task_group *tg)
6695 rt_period_us = ktime_to_ns(tg->rt_bandwidth.rt_period);
6696 do_div(rt_period_us, NSEC_PER_USEC);
6697 return rt_period_us;
6699 #endif /* CONFIG_RT_GROUP_SCHED */
6701 #ifdef CONFIG_RT_GROUP_SCHED
6702 static int sched_rt_global_constraints(void)
6706 mutex_lock(&rt_constraints_mutex);
6707 read_lock(&tasklist_lock);
6708 ret = __rt_schedulable(NULL, 0, 0);
6709 read_unlock(&tasklist_lock);
6710 mutex_unlock(&rt_constraints_mutex);
6715 static int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk)
6717 /* Don't accept realtime tasks when there is no way for them to run */
6718 if (rt_task(tsk) && tg->rt_bandwidth.rt_runtime == 0)
6724 #else /* !CONFIG_RT_GROUP_SCHED */
6725 static int sched_rt_global_constraints(void)
6727 unsigned long flags;
6730 raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
6731 for_each_possible_cpu(i) {
6732 struct rt_rq *rt_rq = &cpu_rq(i)->rt;
6734 raw_spin_lock(&rt_rq->rt_runtime_lock);
6735 rt_rq->rt_runtime = global_rt_runtime();
6736 raw_spin_unlock(&rt_rq->rt_runtime_lock);
6738 raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
6742 #endif /* CONFIG_RT_GROUP_SCHED */
6744 static int sched_dl_global_validate(void)
6746 u64 runtime = global_rt_runtime();
6747 u64 period = global_rt_period();
6748 u64 new_bw = to_ratio(period, runtime);
6751 unsigned long flags;
6754 * Here we want to check the bandwidth not being set to some
6755 * value smaller than the currently allocated bandwidth in
6756 * any of the root_domains.
6758 * FIXME: Cycling on all the CPUs is overdoing, but simpler than
6759 * cycling on root_domains... Discussion on different/better
6760 * solutions is welcome!
6762 for_each_possible_cpu(cpu) {
6763 rcu_read_lock_sched();
6764 dl_b = dl_bw_of(cpu);
6766 raw_spin_lock_irqsave(&dl_b->lock, flags);
6767 if (new_bw < dl_b->total_bw)
6769 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
6771 rcu_read_unlock_sched();
6780 static void sched_dl_do_global(void)
6785 unsigned long flags;
6787 def_dl_bandwidth.dl_period = global_rt_period();
6788 def_dl_bandwidth.dl_runtime = global_rt_runtime();
6790 if (global_rt_runtime() != RUNTIME_INF)
6791 new_bw = to_ratio(global_rt_period(), global_rt_runtime());
6794 * FIXME: As above...
6796 for_each_possible_cpu(cpu) {
6797 rcu_read_lock_sched();
6798 dl_b = dl_bw_of(cpu);
6800 raw_spin_lock_irqsave(&dl_b->lock, flags);
6802 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
6804 rcu_read_unlock_sched();
6808 static int sched_rt_global_validate(void)
6810 if (sysctl_sched_rt_period <= 0)
6813 if ((sysctl_sched_rt_runtime != RUNTIME_INF) &&
6814 (sysctl_sched_rt_runtime > sysctl_sched_rt_period))
6820 static void sched_rt_do_global(void)
6822 def_rt_bandwidth.rt_runtime = global_rt_runtime();
6823 def_rt_bandwidth.rt_period = ns_to_ktime(global_rt_period());
6826 int sched_rt_handler(struct ctl_table *table, int write,
6827 void __user *buffer, size_t *lenp,
6830 int old_period, old_runtime;
6831 static DEFINE_MUTEX(mutex);
6835 old_period = sysctl_sched_rt_period;
6836 old_runtime = sysctl_sched_rt_runtime;
6838 ret = proc_dointvec(table, write, buffer, lenp, ppos);
6840 if (!ret && write) {
6841 ret = sched_rt_global_validate();
6845 ret = sched_dl_global_validate();
6849 ret = sched_rt_global_constraints();
6853 sched_rt_do_global();
6854 sched_dl_do_global();
6858 sysctl_sched_rt_period = old_period;
6859 sysctl_sched_rt_runtime = old_runtime;
6861 mutex_unlock(&mutex);
6866 int sched_rr_handler(struct ctl_table *table, int write,
6867 void __user *buffer, size_t *lenp,
6871 static DEFINE_MUTEX(mutex);
6874 ret = proc_dointvec(table, write, buffer, lenp, ppos);
6876 * Make sure that internally we keep jiffies.
6877 * Also, writing zero resets the timeslice to default:
6879 if (!ret && write) {
6880 sched_rr_timeslice =
6881 sysctl_sched_rr_timeslice <= 0 ? RR_TIMESLICE :
6882 msecs_to_jiffies(sysctl_sched_rr_timeslice);
6884 mutex_unlock(&mutex);
6888 #ifdef CONFIG_CGROUP_SCHED
6890 static inline struct task_group *css_tg(struct cgroup_subsys_state *css)
6892 return css ? container_of(css, struct task_group, css) : NULL;
6895 static struct cgroup_subsys_state *
6896 cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
6898 struct task_group *parent = css_tg(parent_css);
6899 struct task_group *tg;
6902 /* This is early initialization for the top cgroup */
6903 return &root_task_group.css;
6906 tg = sched_create_group(parent);
6908 return ERR_PTR(-ENOMEM);
6913 /* Expose task group only after completing cgroup initialization */
6914 static int cpu_cgroup_css_online(struct cgroup_subsys_state *css)
6916 struct task_group *tg = css_tg(css);
6917 struct task_group *parent = css_tg(css->parent);
6920 sched_online_group(tg, parent);
6924 static void cpu_cgroup_css_released(struct cgroup_subsys_state *css)
6926 struct task_group *tg = css_tg(css);
6928 sched_offline_group(tg);
6931 static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
6933 struct task_group *tg = css_tg(css);
6936 * Relies on the RCU grace period between css_released() and this.
6938 sched_free_group(tg);
6942 * This is called before wake_up_new_task(), therefore we really only
6943 * have to set its group bits, all the other stuff does not apply.
6945 static void cpu_cgroup_fork(struct task_struct *task)
6950 rq = task_rq_lock(task, &rf);
6952 update_rq_clock(rq);
6953 sched_change_group(task, TASK_SET_GROUP);
6955 task_rq_unlock(rq, task, &rf);
6958 static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
6960 struct task_struct *task;
6961 struct cgroup_subsys_state *css;
6964 cgroup_taskset_for_each(task, css, tset) {
6965 #ifdef CONFIG_RT_GROUP_SCHED
6966 if (!sched_rt_can_attach(css_tg(css), task))
6969 /* We don't support RT-tasks being in separate groups */
6970 if (task->sched_class != &fair_sched_class)
6974 * Serialize against wake_up_new_task() such that if its
6975 * running, we're sure to observe its full state.
6977 raw_spin_lock_irq(&task->pi_lock);
6979 * Avoid calling sched_move_task() before wake_up_new_task()
6980 * has happened. This would lead to problems with PELT, due to
6981 * move wanting to detach+attach while we're not attached yet.
6983 if (task->state == TASK_NEW)
6985 raw_spin_unlock_irq(&task->pi_lock);
6993 static void cpu_cgroup_attach(struct cgroup_taskset *tset)
6995 struct task_struct *task;
6996 struct cgroup_subsys_state *css;
6998 cgroup_taskset_for_each(task, css, tset)
6999 sched_move_task(task);
7002 #ifdef CONFIG_FAIR_GROUP_SCHED
7003 static int cpu_shares_write_u64(struct cgroup_subsys_state *css,
7004 struct cftype *cftype, u64 shareval)
7006 return sched_group_set_shares(css_tg(css), scale_load(shareval));
7009 static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css,
7012 struct task_group *tg = css_tg(css);
7014 return (u64) scale_load_down(tg->shares);
7017 #ifdef CONFIG_CFS_BANDWIDTH
7018 static DEFINE_MUTEX(cfs_constraints_mutex);
7020 const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */
7021 const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */
7023 static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
7025 static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
7027 int i, ret = 0, runtime_enabled, runtime_was_enabled;
7028 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
7030 if (tg == &root_task_group)
7034 * Ensure we have at some amount of bandwidth every period. This is
7035 * to prevent reaching a state of large arrears when throttled via
7036 * entity_tick() resulting in prolonged exit starvation.
7038 if (quota < min_cfs_quota_period || period < min_cfs_quota_period)
7042 * Likewise, bound things on the otherside by preventing insane quota
7043 * periods. This also allows us to normalize in computing quota
7046 if (period > max_cfs_quota_period)
7050 * Prevent race between setting of cfs_rq->runtime_enabled and
7051 * unthrottle_offline_cfs_rqs().
7054 mutex_lock(&cfs_constraints_mutex);
7055 ret = __cfs_schedulable(tg, period, quota);
7059 runtime_enabled = quota != RUNTIME_INF;
7060 runtime_was_enabled = cfs_b->quota != RUNTIME_INF;
7062 * If we need to toggle cfs_bandwidth_used, off->on must occur
7063 * before making related changes, and on->off must occur afterwards
7065 if (runtime_enabled && !runtime_was_enabled)
7066 cfs_bandwidth_usage_inc();
7067 raw_spin_lock_irq(&cfs_b->lock);
7068 cfs_b->period = ns_to_ktime(period);
7069 cfs_b->quota = quota;
7071 __refill_cfs_bandwidth_runtime(cfs_b);
7073 /* Restart the period timer (if active) to handle new period expiry: */
7074 if (runtime_enabled)
7075 start_cfs_bandwidth(cfs_b);
7077 raw_spin_unlock_irq(&cfs_b->lock);
7079 for_each_online_cpu(i) {
7080 struct cfs_rq *cfs_rq = tg->cfs_rq[i];
7081 struct rq *rq = cfs_rq->rq;
7084 rq_lock_irq(rq, &rf);
7085 cfs_rq->runtime_enabled = runtime_enabled;
7086 cfs_rq->runtime_remaining = 0;
7088 if (cfs_rq->throttled)
7089 unthrottle_cfs_rq(cfs_rq);
7090 rq_unlock_irq(rq, &rf);
7092 if (runtime_was_enabled && !runtime_enabled)
7093 cfs_bandwidth_usage_dec();
7095 mutex_unlock(&cfs_constraints_mutex);
7101 int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)
7105 period = ktime_to_ns(tg->cfs_bandwidth.period);
7106 if (cfs_quota_us < 0)
7107 quota = RUNTIME_INF;
7109 quota = (u64)cfs_quota_us * NSEC_PER_USEC;
7111 return tg_set_cfs_bandwidth(tg, period, quota);
7114 long tg_get_cfs_quota(struct task_group *tg)
7118 if (tg->cfs_bandwidth.quota == RUNTIME_INF)
7121 quota_us = tg->cfs_bandwidth.quota;
7122 do_div(quota_us, NSEC_PER_USEC);
7127 int tg_set_cfs_period(struct task_group *tg, long cfs_period_us)
7131 period = (u64)cfs_period_us * NSEC_PER_USEC;
7132 quota = tg->cfs_bandwidth.quota;
7134 return tg_set_cfs_bandwidth(tg, period, quota);
7137 long tg_get_cfs_period(struct task_group *tg)
7141 cfs_period_us = ktime_to_ns(tg->cfs_bandwidth.period);
7142 do_div(cfs_period_us, NSEC_PER_USEC);
7144 return cfs_period_us;
7147 static s64 cpu_cfs_quota_read_s64(struct cgroup_subsys_state *css,
7150 return tg_get_cfs_quota(css_tg(css));
7153 static int cpu_cfs_quota_write_s64(struct cgroup_subsys_state *css,
7154 struct cftype *cftype, s64 cfs_quota_us)
7156 return tg_set_cfs_quota(css_tg(css), cfs_quota_us);
7159 static u64 cpu_cfs_period_read_u64(struct cgroup_subsys_state *css,
7162 return tg_get_cfs_period(css_tg(css));
7165 static int cpu_cfs_period_write_u64(struct cgroup_subsys_state *css,
7166 struct cftype *cftype, u64 cfs_period_us)
7168 return tg_set_cfs_period(css_tg(css), cfs_period_us);
7171 struct cfs_schedulable_data {
7172 struct task_group *tg;
7177 * normalize group quota/period to be quota/max_period
7178 * note: units are usecs
7180 static u64 normalize_cfs_quota(struct task_group *tg,
7181 struct cfs_schedulable_data *d)
7189 period = tg_get_cfs_period(tg);
7190 quota = tg_get_cfs_quota(tg);
7193 /* note: these should typically be equivalent */
7194 if (quota == RUNTIME_INF || quota == -1)
7197 return to_ratio(period, quota);
7200 static int tg_cfs_schedulable_down(struct task_group *tg, void *data)
7202 struct cfs_schedulable_data *d = data;
7203 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
7204 s64 quota = 0, parent_quota = -1;
7207 quota = RUNTIME_INF;
7209 struct cfs_bandwidth *parent_b = &tg->parent->cfs_bandwidth;
7211 quota = normalize_cfs_quota(tg, d);
7212 parent_quota = parent_b->hierarchical_quota;
7215 * Ensure max(child_quota) <= parent_quota, inherit when no
7218 if (quota == RUNTIME_INF)
7219 quota = parent_quota;
7220 else if (parent_quota != RUNTIME_INF && quota > parent_quota)
7223 cfs_b->hierarchical_quota = quota;
7228 static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota)
7231 struct cfs_schedulable_data data = {
7237 if (quota != RUNTIME_INF) {
7238 do_div(data.period, NSEC_PER_USEC);
7239 do_div(data.quota, NSEC_PER_USEC);
7243 ret = walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data);
7249 static int cpu_stats_show(struct seq_file *sf, void *v)
7251 struct task_group *tg = css_tg(seq_css(sf));
7252 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
7254 seq_printf(sf, "nr_periods %d\n", cfs_b->nr_periods);
7255 seq_printf(sf, "nr_throttled %d\n", cfs_b->nr_throttled);
7256 seq_printf(sf, "throttled_time %llu\n", cfs_b->throttled_time);
7260 #endif /* CONFIG_CFS_BANDWIDTH */
7261 #endif /* CONFIG_FAIR_GROUP_SCHED */
7263 #ifdef CONFIG_RT_GROUP_SCHED
7264 static int cpu_rt_runtime_write(struct cgroup_subsys_state *css,
7265 struct cftype *cft, s64 val)
7267 return sched_group_set_rt_runtime(css_tg(css), val);
7270 static s64 cpu_rt_runtime_read(struct cgroup_subsys_state *css,
7273 return sched_group_rt_runtime(css_tg(css));
7276 static int cpu_rt_period_write_uint(struct cgroup_subsys_state *css,
7277 struct cftype *cftype, u64 rt_period_us)
7279 return sched_group_set_rt_period(css_tg(css), rt_period_us);
7282 static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css,
7285 return sched_group_rt_period(css_tg(css));
7287 #endif /* CONFIG_RT_GROUP_SCHED */
7289 static struct cftype cpu_files[] = {
7290 #ifdef CONFIG_FAIR_GROUP_SCHED
7293 .read_u64 = cpu_shares_read_u64,
7294 .write_u64 = cpu_shares_write_u64,
7297 #ifdef CONFIG_CFS_BANDWIDTH
7299 .name = "cfs_quota_us",
7300 .read_s64 = cpu_cfs_quota_read_s64,
7301 .write_s64 = cpu_cfs_quota_write_s64,
7304 .name = "cfs_period_us",
7305 .read_u64 = cpu_cfs_period_read_u64,
7306 .write_u64 = cpu_cfs_period_write_u64,
7310 .seq_show = cpu_stats_show,
7313 #ifdef CONFIG_RT_GROUP_SCHED
7315 .name = "rt_runtime_us",
7316 .read_s64 = cpu_rt_runtime_read,
7317 .write_s64 = cpu_rt_runtime_write,
7320 .name = "rt_period_us",
7321 .read_u64 = cpu_rt_period_read_uint,
7322 .write_u64 = cpu_rt_period_write_uint,
7328 struct cgroup_subsys cpu_cgrp_subsys = {
7329 .css_alloc = cpu_cgroup_css_alloc,
7330 .css_online = cpu_cgroup_css_online,
7331 .css_released = cpu_cgroup_css_released,
7332 .css_free = cpu_cgroup_css_free,
7333 .fork = cpu_cgroup_fork,
7334 .can_attach = cpu_cgroup_can_attach,
7335 .attach = cpu_cgroup_attach,
7336 .legacy_cftypes = cpu_files,
7340 #endif /* CONFIG_CGROUP_SCHED */
7342 void dump_cpu_task(int cpu)
7344 pr_info("Task dump for CPU %d:\n", cpu);
7345 sched_show_task(cpu_curr(cpu));
7349 * Nice levels are multiplicative, with a gentle 10% change for every
7350 * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
7351 * nice 1, it will get ~10% less CPU time than another CPU-bound task
7352 * that remained on nice 0.
7354 * The "10% effect" is relative and cumulative: from _any_ nice level,
7355 * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
7356 * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
7357 * If a task goes up by ~10% and another task goes down by ~10% then
7358 * the relative distance between them is ~25%.)
7360 const int sched_prio_to_weight[40] = {
7361 /* -20 */ 88761, 71755, 56483, 46273, 36291,
7362 /* -15 */ 29154, 23254, 18705, 14949, 11916,
7363 /* -10 */ 9548, 7620, 6100, 4904, 3906,
7364 /* -5 */ 3121, 2501, 1991, 1586, 1277,
7365 /* 0 */ 1024, 820, 655, 526, 423,
7366 /* 5 */ 335, 272, 215, 172, 137,
7367 /* 10 */ 110, 87, 70, 56, 45,
7368 /* 15 */ 36, 29, 23, 18, 15,
7372 * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated.
7374 * In cases where the weight does not change often, we can use the
7375 * precalculated inverse to speed up arithmetics by turning divisions
7376 * into multiplications:
7378 const u32 sched_prio_to_wmult[40] = {
7379 /* -20 */ 48388, 59856, 76040, 92818, 118348,
7380 /* -15 */ 147320, 184698, 229616, 287308, 360437,
7381 /* -10 */ 449829, 563644, 704093, 875809, 1099582,
7382 /* -5 */ 1376151, 1717300, 2157191, 2708050, 3363326,
7383 /* 0 */ 4194304, 5237765, 6557202, 8165337, 10153587,
7384 /* 5 */ 12820798, 15790321, 19976592, 24970740, 31350126,
7385 /* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717,
7386 /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153,