4 * Kernel scheduler and related syscalls
6 * Copyright (C) 1991-2002 Linus Torvalds
8 * 1996-12-23 Modified by Dave Grothe to fix bugs in semaphores and
9 * make semaphores SMP safe
10 * 1998-11-19 Implemented schedule_timeout() and related stuff
12 * 2002-01-04 New ultra-scalable O(1) scheduler by Ingo Molnar:
13 * hybrid priority-list and round-robin design with
14 * an array-switch method of distributing timeslices
15 * and per-CPU runqueues. Cleanups and useful suggestions
16 * by Davide Libenzi, preemptible kernel bits by Robert Love.
17 * 2003-09-03 Interactivity tuning by Con Kolivas.
18 * 2004-04-02 Scheduler domains code by Nick Piggin
19 * 2007-04-15 Work begun on replacing all interactivity tuning with a
20 * fair scheduling design by Con Kolivas.
21 * 2007-05-05 Load balancing (smp-nice) and other improvements
23 * 2007-05-06 Interactivity improvements to CFS by Mike Galbraith
24 * 2007-07-01 Group scheduling enhancements by Srivatsa Vaddagiri
25 * 2007-11-29 RT balancing improvements by Steven Rostedt, Gregory Haskins,
26 * Thomas Gleixner, Mike Kravetz
29 #include <linux/kasan.h>
31 #include <linux/module.h>
32 #include <linux/nmi.h>
33 #include <linux/init.h>
34 #include <linux/uaccess.h>
35 #include <linux/highmem.h>
36 #include <linux/mmu_context.h>
37 #include <linux/interrupt.h>
38 #include <linux/capability.h>
39 #include <linux/completion.h>
40 #include <linux/kernel_stat.h>
41 #include <linux/debug_locks.h>
42 #include <linux/perf_event.h>
43 #include <linux/security.h>
44 #include <linux/notifier.h>
45 #include <linux/profile.h>
46 #include <linux/freezer.h>
47 #include <linux/vmalloc.h>
48 #include <linux/blkdev.h>
49 #include <linux/delay.h>
50 #include <linux/pid_namespace.h>
51 #include <linux/smp.h>
52 #include <linux/threads.h>
53 #include <linux/timer.h>
54 #include <linux/rcupdate.h>
55 #include <linux/cpu.h>
56 #include <linux/cpuset.h>
57 #include <linux/percpu.h>
58 #include <linux/proc_fs.h>
59 #include <linux/seq_file.h>
60 #include <linux/sysctl.h>
61 #include <linux/syscalls.h>
62 #include <linux/times.h>
63 #include <linux/tsacct_kern.h>
64 #include <linux/kprobes.h>
65 #include <linux/delayacct.h>
66 #include <linux/unistd.h>
67 #include <linux/pagemap.h>
68 #include <linux/hrtimer.h>
69 #include <linux/tick.h>
70 #include <linux/ctype.h>
71 #include <linux/ftrace.h>
72 #include <linux/slab.h>
73 #include <linux/init_task.h>
74 #include <linux/context_tracking.h>
75 #include <linux/compiler.h>
76 #include <linux/frame.h>
77 #include <linux/prefetch.h>
78 #include <linux/mutex.h>
80 #include <asm/switch_to.h>
82 #include <asm/irq_regs.h>
83 #ifdef CONFIG_PARAVIRT
84 #include <asm/paravirt.h>
88 #include "../workqueue_internal.h"
89 #include "../smpboot.h"
91 #define CREATE_TRACE_POINTS
92 #include <trace/events/sched.h>
94 DEFINE_MUTEX(sched_domains_mutex);
95 DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
97 static void update_rq_clock_task(struct rq *rq, s64 delta);
99 void update_rq_clock(struct rq *rq)
103 lockdep_assert_held(&rq->lock);
105 if (rq->clock_skip_update & RQCF_ACT_SKIP)
108 delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
112 update_rq_clock_task(rq, delta);
116 * Debugging: various feature bits
119 #define SCHED_FEAT(name, enabled) \
120 (1UL << __SCHED_FEAT_##name) * enabled |
122 const_debug unsigned int sysctl_sched_features =
123 #include "features.h"
129 * Number of tasks to iterate in a single balance run.
130 * Limited because this is done with IRQs disabled.
132 const_debug unsigned int sysctl_sched_nr_migrate = 32;
135 * period over which we average the RT time consumption, measured
140 const_debug unsigned int sysctl_sched_time_avg = MSEC_PER_SEC;
143 * period over which we measure -rt task cpu usage in us.
146 unsigned int sysctl_sched_rt_period = 1000000;
148 __read_mostly int scheduler_running;
151 * part of the period that we allow rt tasks to run in us.
154 int sysctl_sched_rt_runtime = 950000;
156 /* cpus with isolated domains */
157 cpumask_var_t cpu_isolated_map;
160 * this_rq_lock - lock this runqueue and disable interrupts.
162 static struct rq *this_rq_lock(void)
169 raw_spin_lock(&rq->lock);
175 * __task_rq_lock - lock the rq @p resides on.
177 struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf)
182 lockdep_assert_held(&p->pi_lock);
186 raw_spin_lock(&rq->lock);
187 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
191 raw_spin_unlock(&rq->lock);
193 while (unlikely(task_on_rq_migrating(p)))
199 * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
201 struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
202 __acquires(p->pi_lock)
208 raw_spin_lock_irqsave(&p->pi_lock, rf->flags);
210 raw_spin_lock(&rq->lock);
212 * move_queued_task() task_rq_lock()
215 * [S] ->on_rq = MIGRATING [L] rq = task_rq()
216 * WMB (__set_task_cpu()) ACQUIRE (rq->lock);
217 * [S] ->cpu = new_cpu [L] task_rq()
221 * If we observe the old cpu in task_rq_lock, the acquire of
222 * the old rq->lock will fully serialize against the stores.
224 * If we observe the new cpu in task_rq_lock, the acquire will
225 * pair with the WMB to ensure we must then also see migrating.
227 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
231 raw_spin_unlock(&rq->lock);
232 raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags);
234 while (unlikely(task_on_rq_migrating(p)))
239 #ifdef CONFIG_SCHED_HRTICK
241 * Use HR-timers to deliver accurate preemption points.
244 static void hrtick_clear(struct rq *rq)
246 if (hrtimer_active(&rq->hrtick_timer))
247 hrtimer_cancel(&rq->hrtick_timer);
251 * High-resolution timer tick.
252 * Runs from hardirq context with interrupts disabled.
254 static enum hrtimer_restart hrtick(struct hrtimer *timer)
256 struct rq *rq = container_of(timer, struct rq, hrtick_timer);
258 WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
260 raw_spin_lock(&rq->lock);
262 rq->curr->sched_class->task_tick(rq, rq->curr, 1);
263 raw_spin_unlock(&rq->lock);
265 return HRTIMER_NORESTART;
270 static void __hrtick_restart(struct rq *rq)
272 struct hrtimer *timer = &rq->hrtick_timer;
274 hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED);
278 * called from hardirq (IPI) context
280 static void __hrtick_start(void *arg)
284 raw_spin_lock(&rq->lock);
285 __hrtick_restart(rq);
286 rq->hrtick_csd_pending = 0;
287 raw_spin_unlock(&rq->lock);
291 * Called to set the hrtick timer state.
293 * called with rq->lock held and irqs disabled
295 void hrtick_start(struct rq *rq, u64 delay)
297 struct hrtimer *timer = &rq->hrtick_timer;
302 * Don't schedule slices shorter than 10000ns, that just
303 * doesn't make sense and can cause timer DoS.
305 delta = max_t(s64, delay, 10000LL);
306 time = ktime_add_ns(timer->base->get_time(), delta);
308 hrtimer_set_expires(timer, time);
310 if (rq == this_rq()) {
311 __hrtick_restart(rq);
312 } else if (!rq->hrtick_csd_pending) {
313 smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd);
314 rq->hrtick_csd_pending = 1;
320 * Called to set the hrtick timer state.
322 * called with rq->lock held and irqs disabled
324 void hrtick_start(struct rq *rq, u64 delay)
327 * Don't schedule slices shorter than 10000ns, that just
328 * doesn't make sense. Rely on vruntime for fairness.
330 delay = max_t(u64, delay, 10000LL);
331 hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay),
332 HRTIMER_MODE_REL_PINNED);
334 #endif /* CONFIG_SMP */
336 static void init_rq_hrtick(struct rq *rq)
339 rq->hrtick_csd_pending = 0;
341 rq->hrtick_csd.flags = 0;
342 rq->hrtick_csd.func = __hrtick_start;
343 rq->hrtick_csd.info = rq;
346 hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
347 rq->hrtick_timer.function = hrtick;
349 #else /* CONFIG_SCHED_HRTICK */
350 static inline void hrtick_clear(struct rq *rq)
354 static inline void init_rq_hrtick(struct rq *rq)
357 #endif /* CONFIG_SCHED_HRTICK */
360 * cmpxchg based fetch_or, macro so it works for different integer types
362 #define fetch_or(ptr, mask) \
364 typeof(ptr) _ptr = (ptr); \
365 typeof(mask) _mask = (mask); \
366 typeof(*_ptr) _old, _val = *_ptr; \
369 _old = cmpxchg(_ptr, _val, _val | _mask); \
377 #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
379 * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
380 * this avoids any races wrt polling state changes and thereby avoids
383 static bool set_nr_and_not_polling(struct task_struct *p)
385 struct thread_info *ti = task_thread_info(p);
386 return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG);
390 * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
392 * If this returns true, then the idle task promises to call
393 * sched_ttwu_pending() and reschedule soon.
395 static bool set_nr_if_polling(struct task_struct *p)
397 struct thread_info *ti = task_thread_info(p);
398 typeof(ti->flags) old, val = READ_ONCE(ti->flags);
401 if (!(val & _TIF_POLLING_NRFLAG))
403 if (val & _TIF_NEED_RESCHED)
405 old = cmpxchg(&ti->flags, val, val | _TIF_NEED_RESCHED);
414 static bool set_nr_and_not_polling(struct task_struct *p)
416 set_tsk_need_resched(p);
421 static bool set_nr_if_polling(struct task_struct *p)
428 void wake_q_add(struct wake_q_head *head, struct task_struct *task)
430 struct wake_q_node *node = &task->wake_q;
433 * Atomically grab the task, if ->wake_q is !nil already it means
434 * its already queued (either by us or someone else) and will get the
435 * wakeup due to that.
437 * This cmpxchg() implies a full barrier, which pairs with the write
438 * barrier implied by the wakeup in wake_up_q().
440 if (cmpxchg(&node->next, NULL, WAKE_Q_TAIL))
443 get_task_struct(task);
446 * The head is context local, there can be no concurrency.
449 head->lastp = &node->next;
452 void wake_up_q(struct wake_q_head *head)
454 struct wake_q_node *node = head->first;
456 while (node != WAKE_Q_TAIL) {
457 struct task_struct *task;
459 task = container_of(node, struct task_struct, wake_q);
461 /* task can safely be re-inserted now */
463 task->wake_q.next = NULL;
466 * wake_up_process() implies a wmb() to pair with the queueing
467 * in wake_q_add() so as not to miss wakeups.
469 wake_up_process(task);
470 put_task_struct(task);
475 * resched_curr - mark rq's current task 'to be rescheduled now'.
477 * On UP this means the setting of the need_resched flag, on SMP it
478 * might also involve a cross-CPU call to trigger the scheduler on
481 void resched_curr(struct rq *rq)
483 struct task_struct *curr = rq->curr;
486 lockdep_assert_held(&rq->lock);
488 if (test_tsk_need_resched(curr))
493 if (cpu == smp_processor_id()) {
494 set_tsk_need_resched(curr);
495 set_preempt_need_resched();
499 if (set_nr_and_not_polling(curr))
500 smp_send_reschedule(cpu);
502 trace_sched_wake_idle_without_ipi(cpu);
505 void resched_cpu(int cpu)
507 struct rq *rq = cpu_rq(cpu);
510 if (!raw_spin_trylock_irqsave(&rq->lock, flags))
513 raw_spin_unlock_irqrestore(&rq->lock, flags);
517 #ifdef CONFIG_NO_HZ_COMMON
519 * In the semi idle case, use the nearest busy cpu for migrating timers
520 * from an idle cpu. This is good for power-savings.
522 * We don't do similar optimization for completely idle system, as
523 * selecting an idle cpu will add more delays to the timers than intended
524 * (as that cpu's timer base may not be uptodate wrt jiffies etc).
526 int get_nohz_timer_target(void)
528 int i, cpu = smp_processor_id();
529 struct sched_domain *sd;
531 if (!idle_cpu(cpu) && is_housekeeping_cpu(cpu))
535 for_each_domain(cpu, sd) {
536 for_each_cpu(i, sched_domain_span(sd)) {
540 if (!idle_cpu(i) && is_housekeeping_cpu(i)) {
547 if (!is_housekeeping_cpu(cpu))
548 cpu = housekeeping_any_cpu();
554 * When add_timer_on() enqueues a timer into the timer wheel of an
555 * idle CPU then this timer might expire before the next timer event
556 * which is scheduled to wake up that CPU. In case of a completely
557 * idle system the next event might even be infinite time into the
558 * future. wake_up_idle_cpu() ensures that the CPU is woken up and
559 * leaves the inner idle loop so the newly added timer is taken into
560 * account when the CPU goes back to idle and evaluates the timer
561 * wheel for the next timer event.
563 static void wake_up_idle_cpu(int cpu)
565 struct rq *rq = cpu_rq(cpu);
567 if (cpu == smp_processor_id())
570 if (set_nr_and_not_polling(rq->idle))
571 smp_send_reschedule(cpu);
573 trace_sched_wake_idle_without_ipi(cpu);
576 static bool wake_up_full_nohz_cpu(int cpu)
579 * We just need the target to call irq_exit() and re-evaluate
580 * the next tick. The nohz full kick at least implies that.
581 * If needed we can still optimize that later with an
584 if (cpu_is_offline(cpu))
585 return true; /* Don't try to wake offline CPUs. */
586 if (tick_nohz_full_cpu(cpu)) {
587 if (cpu != smp_processor_id() ||
588 tick_nohz_tick_stopped())
589 tick_nohz_full_kick_cpu(cpu);
597 * Wake up the specified CPU. If the CPU is going offline, it is the
598 * caller's responsibility to deal with the lost wakeup, for example,
599 * by hooking into the CPU_DEAD notifier like timers and hrtimers do.
601 void wake_up_nohz_cpu(int cpu)
603 if (!wake_up_full_nohz_cpu(cpu))
604 wake_up_idle_cpu(cpu);
607 static inline bool got_nohz_idle_kick(void)
609 int cpu = smp_processor_id();
611 if (!test_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu)))
614 if (idle_cpu(cpu) && !need_resched())
618 * We can't run Idle Load Balance on this CPU for this time so we
619 * cancel it and clear NOHZ_BALANCE_KICK
621 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu));
625 #else /* CONFIG_NO_HZ_COMMON */
627 static inline bool got_nohz_idle_kick(void)
632 #endif /* CONFIG_NO_HZ_COMMON */
634 #ifdef CONFIG_NO_HZ_FULL
635 bool sched_can_stop_tick(struct rq *rq)
639 /* Deadline tasks, even if single, need the tick */
640 if (rq->dl.dl_nr_running)
644 * If there are more than one RR tasks, we need the tick to effect the
645 * actual RR behaviour.
647 if (rq->rt.rr_nr_running) {
648 if (rq->rt.rr_nr_running == 1)
655 * If there's no RR tasks, but FIFO tasks, we can skip the tick, no
656 * forced preemption between FIFO tasks.
658 fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running;
663 * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left;
664 * if there's more than one we need the tick for involuntary
667 if (rq->nr_running > 1)
672 #endif /* CONFIG_NO_HZ_FULL */
674 void sched_avg_update(struct rq *rq)
676 s64 period = sched_avg_period();
678 while ((s64)(rq_clock(rq) - rq->age_stamp) > period) {
680 * Inline assembly required to prevent the compiler
681 * optimising this loop into a divmod call.
682 * See __iter_div_u64_rem() for another example of this.
684 asm("" : "+rm" (rq->age_stamp));
685 rq->age_stamp += period;
690 #endif /* CONFIG_SMP */
692 #if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
693 (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))
695 * Iterate task_group tree rooted at *from, calling @down when first entering a
696 * node and @up when leaving it for the final time.
698 * Caller must hold rcu_lock or sufficient equivalent.
700 int walk_tg_tree_from(struct task_group *from,
701 tg_visitor down, tg_visitor up, void *data)
703 struct task_group *parent, *child;
709 ret = (*down)(parent, data);
712 list_for_each_entry_rcu(child, &parent->children, siblings) {
719 ret = (*up)(parent, data);
720 if (ret || parent == from)
724 parent = parent->parent;
731 int tg_nop(struct task_group *tg, void *data)
737 static void set_load_weight(struct task_struct *p)
739 int prio = p->static_prio - MAX_RT_PRIO;
740 struct load_weight *load = &p->se.load;
743 * SCHED_IDLE tasks get minimal weight:
745 if (idle_policy(p->policy)) {
746 load->weight = scale_load(WEIGHT_IDLEPRIO);
747 load->inv_weight = WMULT_IDLEPRIO;
751 load->weight = scale_load(sched_prio_to_weight[prio]);
752 load->inv_weight = sched_prio_to_wmult[prio];
755 static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
758 if (!(flags & ENQUEUE_RESTORE))
759 sched_info_queued(rq, p);
760 p->sched_class->enqueue_task(rq, p, flags);
763 static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
766 if (!(flags & DEQUEUE_SAVE))
767 sched_info_dequeued(rq, p);
768 p->sched_class->dequeue_task(rq, p, flags);
771 void activate_task(struct rq *rq, struct task_struct *p, int flags)
773 if (task_contributes_to_load(p))
774 rq->nr_uninterruptible--;
776 enqueue_task(rq, p, flags);
779 void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
781 if (task_contributes_to_load(p))
782 rq->nr_uninterruptible++;
784 dequeue_task(rq, p, flags);
787 static void update_rq_clock_task(struct rq *rq, s64 delta)
790 * In theory, the compile should just see 0 here, and optimize out the call
791 * to sched_rt_avg_update. But I don't trust it...
793 #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
794 s64 steal = 0, irq_delta = 0;
796 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
797 irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
800 * Since irq_time is only updated on {soft,}irq_exit, we might run into
801 * this case when a previous update_rq_clock() happened inside a
804 * When this happens, we stop ->clock_task and only update the
805 * prev_irq_time stamp to account for the part that fit, so that a next
806 * update will consume the rest. This ensures ->clock_task is
809 * It does however cause some slight miss-attribution of {soft,}irq
810 * time, a more accurate solution would be to update the irq_time using
811 * the current rq->clock timestamp, except that would require using
814 if (irq_delta > delta)
817 rq->prev_irq_time += irq_delta;
820 #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
821 if (static_key_false((¶virt_steal_rq_enabled))) {
822 steal = paravirt_steal_clock(cpu_of(rq));
823 steal -= rq->prev_steal_time_rq;
825 if (unlikely(steal > delta))
828 rq->prev_steal_time_rq += steal;
833 rq->clock_task += delta;
835 #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
836 if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY))
837 sched_rt_avg_update(rq, irq_delta + steal);
841 void sched_set_stop_task(int cpu, struct task_struct *stop)
843 struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
844 struct task_struct *old_stop = cpu_rq(cpu)->stop;
848 * Make it appear like a SCHED_FIFO task, its something
849 * userspace knows about and won't get confused about.
851 * Also, it will make PI more or less work without too
852 * much confusion -- but then, stop work should not
853 * rely on PI working anyway.
855 sched_setscheduler_nocheck(stop, SCHED_FIFO, ¶m);
857 stop->sched_class = &stop_sched_class;
860 cpu_rq(cpu)->stop = stop;
864 * Reset it back to a normal scheduling class so that
865 * it can die in pieces.
867 old_stop->sched_class = &rt_sched_class;
872 * __normal_prio - return the priority that is based on the static prio
874 static inline int __normal_prio(struct task_struct *p)
876 return p->static_prio;
880 * Calculate the expected normal priority: i.e. priority
881 * without taking RT-inheritance into account. Might be
882 * boosted by interactivity modifiers. Changes upon fork,
883 * setprio syscalls, and whenever the interactivity
884 * estimator recalculates.
886 static inline int normal_prio(struct task_struct *p)
890 if (task_has_dl_policy(p))
891 prio = MAX_DL_PRIO-1;
892 else if (task_has_rt_policy(p))
893 prio = MAX_RT_PRIO-1 - p->rt_priority;
895 prio = __normal_prio(p);
900 * Calculate the current priority, i.e. the priority
901 * taken into account by the scheduler. This value might
902 * be boosted by RT tasks, or might be boosted by
903 * interactivity modifiers. Will be RT if the task got
904 * RT-boosted. If not then it returns p->normal_prio.
906 static int effective_prio(struct task_struct *p)
908 p->normal_prio = normal_prio(p);
910 * If we are RT tasks or we were boosted to RT priority,
911 * keep the priority unchanged. Otherwise, update priority
912 * to the normal priority:
914 if (!rt_prio(p->prio))
915 return p->normal_prio;
920 * task_curr - is this task currently executing on a CPU?
921 * @p: the task in question.
923 * Return: 1 if the task is currently executing. 0 otherwise.
925 inline int task_curr(const struct task_struct *p)
927 return cpu_curr(task_cpu(p)) == p;
931 * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock,
932 * use the balance_callback list if you want balancing.
934 * this means any call to check_class_changed() must be followed by a call to
935 * balance_callback().
937 static inline void check_class_changed(struct rq *rq, struct task_struct *p,
938 const struct sched_class *prev_class,
941 if (prev_class != p->sched_class) {
942 if (prev_class->switched_from)
943 prev_class->switched_from(rq, p);
945 p->sched_class->switched_to(rq, p);
946 } else if (oldprio != p->prio || dl_task(p))
947 p->sched_class->prio_changed(rq, p, oldprio);
950 void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
952 const struct sched_class *class;
954 if (p->sched_class == rq->curr->sched_class) {
955 rq->curr->sched_class->check_preempt_curr(rq, p, flags);
957 for_each_class(class) {
958 if (class == rq->curr->sched_class)
960 if (class == p->sched_class) {
968 * A queue event has occurred, and we're going to schedule. In
969 * this case, we can save a useless back to back clock update.
971 if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
972 rq_clock_skip_update(rq, true);
977 * This is how migration works:
979 * 1) we invoke migration_cpu_stop() on the target CPU using
981 * 2) stopper starts to run (implicitly forcing the migrated thread
983 * 3) it checks whether the migrated task is still in the wrong runqueue.
984 * 4) if it's in the wrong runqueue then the migration thread removes
985 * it and puts it into the right queue.
986 * 5) stopper completes and stop_one_cpu() returns and the migration
991 * move_queued_task - move a queued task to new rq.
993 * Returns (locked) new rq. Old rq's lock is released.
995 static struct rq *move_queued_task(struct rq *rq, struct task_struct *p, int new_cpu)
997 lockdep_assert_held(&rq->lock);
999 p->on_rq = TASK_ON_RQ_MIGRATING;
1000 dequeue_task(rq, p, 0);
1001 set_task_cpu(p, new_cpu);
1002 raw_spin_unlock(&rq->lock);
1004 rq = cpu_rq(new_cpu);
1006 raw_spin_lock(&rq->lock);
1007 BUG_ON(task_cpu(p) != new_cpu);
1008 enqueue_task(rq, p, 0);
1009 p->on_rq = TASK_ON_RQ_QUEUED;
1010 check_preempt_curr(rq, p, 0);
1015 struct migration_arg {
1016 struct task_struct *task;
1021 * Move (not current) task off this cpu, onto dest cpu. We're doing
1022 * this because either it can't run here any more (set_cpus_allowed()
1023 * away from this CPU, or CPU going down), or because we're
1024 * attempting to rebalance this task on exec (sched_exec).
1026 * So we race with normal scheduler movements, but that's OK, as long
1027 * as the task is no longer on this CPU.
1029 static struct rq *__migrate_task(struct rq *rq, struct task_struct *p, int dest_cpu)
1031 if (unlikely(!cpu_active(dest_cpu)))
1034 /* Affinity changed (again). */
1035 if (!cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p)))
1038 rq = move_queued_task(rq, p, dest_cpu);
1044 * migration_cpu_stop - this will be executed by a highprio stopper thread
1045 * and performs thread migration by bumping thread off CPU then
1046 * 'pushing' onto another runqueue.
1048 static int migration_cpu_stop(void *data)
1050 struct migration_arg *arg = data;
1051 struct task_struct *p = arg->task;
1052 struct rq *rq = this_rq();
1055 * The original target cpu might have gone down and we might
1056 * be on another cpu but it doesn't matter.
1058 local_irq_disable();
1060 * We need to explicitly wake pending tasks before running
1061 * __migrate_task() such that we will not miss enforcing cpus_allowed
1062 * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
1064 sched_ttwu_pending();
1066 raw_spin_lock(&p->pi_lock);
1067 raw_spin_lock(&rq->lock);
1069 * If task_rq(p) != rq, it cannot be migrated here, because we're
1070 * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
1071 * we're holding p->pi_lock.
1073 if (task_rq(p) == rq) {
1074 if (task_on_rq_queued(p))
1075 rq = __migrate_task(rq, p, arg->dest_cpu);
1077 p->wake_cpu = arg->dest_cpu;
1079 raw_spin_unlock(&rq->lock);
1080 raw_spin_unlock(&p->pi_lock);
1087 * sched_class::set_cpus_allowed must do the below, but is not required to
1088 * actually call this function.
1090 void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask)
1092 cpumask_copy(&p->cpus_allowed, new_mask);
1093 p->nr_cpus_allowed = cpumask_weight(new_mask);
1096 void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
1098 struct rq *rq = task_rq(p);
1099 bool queued, running;
1101 lockdep_assert_held(&p->pi_lock);
1103 queued = task_on_rq_queued(p);
1104 running = task_current(rq, p);
1108 * Because __kthread_bind() calls this on blocked tasks without
1111 lockdep_assert_held(&rq->lock);
1112 dequeue_task(rq, p, DEQUEUE_SAVE);
1115 put_prev_task(rq, p);
1117 p->sched_class->set_cpus_allowed(p, new_mask);
1120 enqueue_task(rq, p, ENQUEUE_RESTORE);
1122 set_curr_task(rq, p);
1126 * Change a given task's CPU affinity. Migrate the thread to a
1127 * proper CPU and schedule it away if the CPU it's executing on
1128 * is removed from the allowed bitmask.
1130 * NOTE: the caller must have a valid reference to the task, the
1131 * task must not exit() & deallocate itself prematurely. The
1132 * call is not atomic; no spinlocks may be held.
1134 static int __set_cpus_allowed_ptr(struct task_struct *p,
1135 const struct cpumask *new_mask, bool check)
1137 const struct cpumask *cpu_valid_mask = cpu_active_mask;
1138 unsigned int dest_cpu;
1143 rq = task_rq_lock(p, &rf);
1145 if (p->flags & PF_KTHREAD) {
1147 * Kernel threads are allowed on online && !active CPUs
1149 cpu_valid_mask = cpu_online_mask;
1153 * Must re-check here, to close a race against __kthread_bind(),
1154 * sched_setaffinity() is not guaranteed to observe the flag.
1156 if (check && (p->flags & PF_NO_SETAFFINITY)) {
1161 if (cpumask_equal(&p->cpus_allowed, new_mask))
1164 if (!cpumask_intersects(new_mask, cpu_valid_mask)) {
1169 do_set_cpus_allowed(p, new_mask);
1171 if (p->flags & PF_KTHREAD) {
1173 * For kernel threads that do indeed end up on online &&
1174 * !active we want to ensure they are strict per-cpu threads.
1176 WARN_ON(cpumask_intersects(new_mask, cpu_online_mask) &&
1177 !cpumask_intersects(new_mask, cpu_active_mask) &&
1178 p->nr_cpus_allowed != 1);
1181 /* Can the task run on the task's current CPU? If so, we're done */
1182 if (cpumask_test_cpu(task_cpu(p), new_mask))
1185 dest_cpu = cpumask_any_and(cpu_valid_mask, new_mask);
1186 if (task_running(rq, p) || p->state == TASK_WAKING) {
1187 struct migration_arg arg = { p, dest_cpu };
1188 /* Need help from migration thread: drop lock and wait. */
1189 task_rq_unlock(rq, p, &rf);
1190 stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
1191 tlb_migrate_finish(p->mm);
1193 } else if (task_on_rq_queued(p)) {
1195 * OK, since we're going to drop the lock immediately
1196 * afterwards anyway.
1198 rq_unpin_lock(rq, &rf);
1199 rq = move_queued_task(rq, p, dest_cpu);
1200 rq_repin_lock(rq, &rf);
1203 task_rq_unlock(rq, p, &rf);
1208 int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
1210 return __set_cpus_allowed_ptr(p, new_mask, false);
1212 EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
1214 void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
1216 #ifdef CONFIG_SCHED_DEBUG
1218 * We should never call set_task_cpu() on a blocked task,
1219 * ttwu() will sort out the placement.
1221 WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
1225 * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
1226 * because schedstat_wait_{start,end} rebase migrating task's wait_start
1227 * time relying on p->on_rq.
1229 WARN_ON_ONCE(p->state == TASK_RUNNING &&
1230 p->sched_class == &fair_sched_class &&
1231 (p->on_rq && !task_on_rq_migrating(p)));
1233 #ifdef CONFIG_LOCKDEP
1235 * The caller should hold either p->pi_lock or rq->lock, when changing
1236 * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
1238 * sched_move_task() holds both and thus holding either pins the cgroup,
1241 * Furthermore, all task_rq users should acquire both locks, see
1244 WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
1245 lockdep_is_held(&task_rq(p)->lock)));
1249 trace_sched_migrate_task(p, new_cpu);
1251 if (task_cpu(p) != new_cpu) {
1252 if (p->sched_class->migrate_task_rq)
1253 p->sched_class->migrate_task_rq(p);
1254 p->se.nr_migrations++;
1255 perf_event_task_migrate(p);
1258 __set_task_cpu(p, new_cpu);
1261 static void __migrate_swap_task(struct task_struct *p, int cpu)
1263 if (task_on_rq_queued(p)) {
1264 struct rq *src_rq, *dst_rq;
1266 src_rq = task_rq(p);
1267 dst_rq = cpu_rq(cpu);
1269 p->on_rq = TASK_ON_RQ_MIGRATING;
1270 deactivate_task(src_rq, p, 0);
1271 set_task_cpu(p, cpu);
1272 activate_task(dst_rq, p, 0);
1273 p->on_rq = TASK_ON_RQ_QUEUED;
1274 check_preempt_curr(dst_rq, p, 0);
1277 * Task isn't running anymore; make it appear like we migrated
1278 * it before it went to sleep. This means on wakeup we make the
1279 * previous cpu our target instead of where it really is.
1285 struct migration_swap_arg {
1286 struct task_struct *src_task, *dst_task;
1287 int src_cpu, dst_cpu;
1290 static int migrate_swap_stop(void *data)
1292 struct migration_swap_arg *arg = data;
1293 struct rq *src_rq, *dst_rq;
1296 if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu))
1299 src_rq = cpu_rq(arg->src_cpu);
1300 dst_rq = cpu_rq(arg->dst_cpu);
1302 double_raw_lock(&arg->src_task->pi_lock,
1303 &arg->dst_task->pi_lock);
1304 double_rq_lock(src_rq, dst_rq);
1306 if (task_cpu(arg->dst_task) != arg->dst_cpu)
1309 if (task_cpu(arg->src_task) != arg->src_cpu)
1312 if (!cpumask_test_cpu(arg->dst_cpu, tsk_cpus_allowed(arg->src_task)))
1315 if (!cpumask_test_cpu(arg->src_cpu, tsk_cpus_allowed(arg->dst_task)))
1318 __migrate_swap_task(arg->src_task, arg->dst_cpu);
1319 __migrate_swap_task(arg->dst_task, arg->src_cpu);
1324 double_rq_unlock(src_rq, dst_rq);
1325 raw_spin_unlock(&arg->dst_task->pi_lock);
1326 raw_spin_unlock(&arg->src_task->pi_lock);
1332 * Cross migrate two tasks
1334 int migrate_swap(struct task_struct *cur, struct task_struct *p)
1336 struct migration_swap_arg arg;
1339 arg = (struct migration_swap_arg){
1341 .src_cpu = task_cpu(cur),
1343 .dst_cpu = task_cpu(p),
1346 if (arg.src_cpu == arg.dst_cpu)
1350 * These three tests are all lockless; this is OK since all of them
1351 * will be re-checked with proper locks held further down the line.
1353 if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu))
1356 if (!cpumask_test_cpu(arg.dst_cpu, tsk_cpus_allowed(arg.src_task)))
1359 if (!cpumask_test_cpu(arg.src_cpu, tsk_cpus_allowed(arg.dst_task)))
1362 trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu);
1363 ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg);
1370 * wait_task_inactive - wait for a thread to unschedule.
1372 * If @match_state is nonzero, it's the @p->state value just checked and
1373 * not expected to change. If it changes, i.e. @p might have woken up,
1374 * then return zero. When we succeed in waiting for @p to be off its CPU,
1375 * we return a positive number (its total switch count). If a second call
1376 * a short while later returns the same number, the caller can be sure that
1377 * @p has remained unscheduled the whole time.
1379 * The caller must ensure that the task *will* unschedule sometime soon,
1380 * else this function might spin for a *long* time. This function can't
1381 * be called with interrupts off, or it may introduce deadlock with
1382 * smp_call_function() if an IPI is sent by the same process we are
1383 * waiting to become inactive.
1385 unsigned long wait_task_inactive(struct task_struct *p, long match_state)
1387 int running, queued;
1394 * We do the initial early heuristics without holding
1395 * any task-queue locks at all. We'll only try to get
1396 * the runqueue lock when things look like they will
1402 * If the task is actively running on another CPU
1403 * still, just relax and busy-wait without holding
1406 * NOTE! Since we don't hold any locks, it's not
1407 * even sure that "rq" stays as the right runqueue!
1408 * But we don't care, since "task_running()" will
1409 * return false if the runqueue has changed and p
1410 * is actually now running somewhere else!
1412 while (task_running(rq, p)) {
1413 if (match_state && unlikely(p->state != match_state))
1419 * Ok, time to look more closely! We need the rq
1420 * lock now, to be *sure*. If we're wrong, we'll
1421 * just go back and repeat.
1423 rq = task_rq_lock(p, &rf);
1424 trace_sched_wait_task(p);
1425 running = task_running(rq, p);
1426 queued = task_on_rq_queued(p);
1428 if (!match_state || p->state == match_state)
1429 ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
1430 task_rq_unlock(rq, p, &rf);
1433 * If it changed from the expected state, bail out now.
1435 if (unlikely(!ncsw))
1439 * Was it really running after all now that we
1440 * checked with the proper locks actually held?
1442 * Oops. Go back and try again..
1444 if (unlikely(running)) {
1450 * It's not enough that it's not actively running,
1451 * it must be off the runqueue _entirely_, and not
1454 * So if it was still runnable (but just not actively
1455 * running right now), it's preempted, and we should
1456 * yield - it could be a while.
1458 if (unlikely(queued)) {
1459 ktime_t to = NSEC_PER_SEC / HZ;
1461 set_current_state(TASK_UNINTERRUPTIBLE);
1462 schedule_hrtimeout(&to, HRTIMER_MODE_REL);
1467 * Ahh, all good. It wasn't running, and it wasn't
1468 * runnable, which means that it will never become
1469 * running in the future either. We're all done!
1478 * kick_process - kick a running thread to enter/exit the kernel
1479 * @p: the to-be-kicked thread
1481 * Cause a process which is running on another CPU to enter
1482 * kernel-mode, without any delay. (to get signals handled.)
1484 * NOTE: this function doesn't have to take the runqueue lock,
1485 * because all it wants to ensure is that the remote task enters
1486 * the kernel. If the IPI races and the task has been migrated
1487 * to another CPU then no harm is done and the purpose has been
1490 void kick_process(struct task_struct *p)
1496 if ((cpu != smp_processor_id()) && task_curr(p))
1497 smp_send_reschedule(cpu);
1500 EXPORT_SYMBOL_GPL(kick_process);
1503 * ->cpus_allowed is protected by both rq->lock and p->pi_lock
1505 * A few notes on cpu_active vs cpu_online:
1507 * - cpu_active must be a subset of cpu_online
1509 * - on cpu-up we allow per-cpu kthreads on the online && !active cpu,
1510 * see __set_cpus_allowed_ptr(). At this point the newly online
1511 * cpu isn't yet part of the sched domains, and balancing will not
1514 * - on cpu-down we clear cpu_active() to mask the sched domains and
1515 * avoid the load balancer to place new tasks on the to be removed
1516 * cpu. Existing tasks will remain running there and will be taken
1519 * This means that fallback selection must not select !active CPUs.
1520 * And can assume that any active CPU must be online. Conversely
1521 * select_task_rq() below may allow selection of !active CPUs in order
1522 * to satisfy the above rules.
1524 static int select_fallback_rq(int cpu, struct task_struct *p)
1526 int nid = cpu_to_node(cpu);
1527 const struct cpumask *nodemask = NULL;
1528 enum { cpuset, possible, fail } state = cpuset;
1532 * If the node that the cpu is on has been offlined, cpu_to_node()
1533 * will return -1. There is no cpu on the node, and we should
1534 * select the cpu on the other node.
1537 nodemask = cpumask_of_node(nid);
1539 /* Look for allowed, online CPU in same node. */
1540 for_each_cpu(dest_cpu, nodemask) {
1541 if (!cpu_active(dest_cpu))
1543 if (cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p)))
1549 /* Any allowed, online CPU? */
1550 for_each_cpu(dest_cpu, tsk_cpus_allowed(p)) {
1551 if (!(p->flags & PF_KTHREAD) && !cpu_active(dest_cpu))
1553 if (!cpu_online(dest_cpu))
1558 /* No more Mr. Nice Guy. */
1561 if (IS_ENABLED(CONFIG_CPUSETS)) {
1562 cpuset_cpus_allowed_fallback(p);
1568 do_set_cpus_allowed(p, cpu_possible_mask);
1579 if (state != cpuset) {
1581 * Don't tell them about moving exiting tasks or
1582 * kernel threads (both mm NULL), since they never
1585 if (p->mm && printk_ratelimit()) {
1586 printk_deferred("process %d (%s) no longer affine to cpu%d\n",
1587 task_pid_nr(p), p->comm, cpu);
1595 * The caller (fork, wakeup) owns p->pi_lock, ->cpus_allowed is stable.
1598 int select_task_rq(struct task_struct *p, int cpu, int sd_flags, int wake_flags)
1600 lockdep_assert_held(&p->pi_lock);
1602 if (tsk_nr_cpus_allowed(p) > 1)
1603 cpu = p->sched_class->select_task_rq(p, cpu, sd_flags, wake_flags);
1605 cpu = cpumask_any(tsk_cpus_allowed(p));
1608 * In order not to call set_task_cpu() on a blocking task we need
1609 * to rely on ttwu() to place the task on a valid ->cpus_allowed
1612 * Since this is common to all placement strategies, this lives here.
1614 * [ this allows ->select_task() to simply return task_cpu(p) and
1615 * not worry about this generic constraint ]
1617 if (unlikely(!cpumask_test_cpu(cpu, tsk_cpus_allowed(p)) ||
1619 cpu = select_fallback_rq(task_cpu(p), p);
1624 static void update_avg(u64 *avg, u64 sample)
1626 s64 diff = sample - *avg;
1632 static inline int __set_cpus_allowed_ptr(struct task_struct *p,
1633 const struct cpumask *new_mask, bool check)
1635 return set_cpus_allowed_ptr(p, new_mask);
1638 #endif /* CONFIG_SMP */
1641 ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
1645 if (!schedstat_enabled())
1651 if (cpu == rq->cpu) {
1652 schedstat_inc(rq->ttwu_local);
1653 schedstat_inc(p->se.statistics.nr_wakeups_local);
1655 struct sched_domain *sd;
1657 schedstat_inc(p->se.statistics.nr_wakeups_remote);
1659 for_each_domain(rq->cpu, sd) {
1660 if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
1661 schedstat_inc(sd->ttwu_wake_remote);
1668 if (wake_flags & WF_MIGRATED)
1669 schedstat_inc(p->se.statistics.nr_wakeups_migrate);
1670 #endif /* CONFIG_SMP */
1672 schedstat_inc(rq->ttwu_count);
1673 schedstat_inc(p->se.statistics.nr_wakeups);
1675 if (wake_flags & WF_SYNC)
1676 schedstat_inc(p->se.statistics.nr_wakeups_sync);
1679 static inline void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
1681 activate_task(rq, p, en_flags);
1682 p->on_rq = TASK_ON_RQ_QUEUED;
1684 /* if a worker is waking up, notify workqueue */
1685 if (p->flags & PF_WQ_WORKER)
1686 wq_worker_waking_up(p, cpu_of(rq));
1690 * Mark the task runnable and perform wakeup-preemption.
1692 static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags,
1693 struct rq_flags *rf)
1695 check_preempt_curr(rq, p, wake_flags);
1696 p->state = TASK_RUNNING;
1697 trace_sched_wakeup(p);
1700 if (p->sched_class->task_woken) {
1702 * Our task @p is fully woken up and running; so its safe to
1703 * drop the rq->lock, hereafter rq is only used for statistics.
1705 rq_unpin_lock(rq, rf);
1706 p->sched_class->task_woken(rq, p);
1707 rq_repin_lock(rq, rf);
1710 if (rq->idle_stamp) {
1711 u64 delta = rq_clock(rq) - rq->idle_stamp;
1712 u64 max = 2*rq->max_idle_balance_cost;
1714 update_avg(&rq->avg_idle, delta);
1716 if (rq->avg_idle > max)
1725 ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
1726 struct rq_flags *rf)
1728 int en_flags = ENQUEUE_WAKEUP;
1730 lockdep_assert_held(&rq->lock);
1733 if (p->sched_contributes_to_load)
1734 rq->nr_uninterruptible--;
1736 if (wake_flags & WF_MIGRATED)
1737 en_flags |= ENQUEUE_MIGRATED;
1740 ttwu_activate(rq, p, en_flags);
1741 ttwu_do_wakeup(rq, p, wake_flags, rf);
1745 * Called in case the task @p isn't fully descheduled from its runqueue,
1746 * in this case we must do a remote wakeup. Its a 'light' wakeup though,
1747 * since all we need to do is flip p->state to TASK_RUNNING, since
1748 * the task is still ->on_rq.
1750 static int ttwu_remote(struct task_struct *p, int wake_flags)
1756 rq = __task_rq_lock(p, &rf);
1757 if (task_on_rq_queued(p)) {
1758 /* check_preempt_curr() may use rq clock */
1759 update_rq_clock(rq);
1760 ttwu_do_wakeup(rq, p, wake_flags, &rf);
1763 __task_rq_unlock(rq, &rf);
1769 void sched_ttwu_pending(void)
1771 struct rq *rq = this_rq();
1772 struct llist_node *llist = llist_del_all(&rq->wake_list);
1773 struct task_struct *p;
1774 unsigned long flags;
1780 raw_spin_lock_irqsave(&rq->lock, flags);
1781 rq_pin_lock(rq, &rf);
1786 p = llist_entry(llist, struct task_struct, wake_entry);
1787 llist = llist_next(llist);
1789 if (p->sched_remote_wakeup)
1790 wake_flags = WF_MIGRATED;
1792 ttwu_do_activate(rq, p, wake_flags, &rf);
1795 rq_unpin_lock(rq, &rf);
1796 raw_spin_unlock_irqrestore(&rq->lock, flags);
1799 void scheduler_ipi(void)
1802 * Fold TIF_NEED_RESCHED into the preempt_count; anybody setting
1803 * TIF_NEED_RESCHED remotely (for the first time) will also send
1806 preempt_fold_need_resched();
1808 if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick())
1812 * Not all reschedule IPI handlers call irq_enter/irq_exit, since
1813 * traditionally all their work was done from the interrupt return
1814 * path. Now that we actually do some work, we need to make sure
1817 * Some archs already do call them, luckily irq_enter/exit nest
1820 * Arguably we should visit all archs and update all handlers,
1821 * however a fair share of IPIs are still resched only so this would
1822 * somewhat pessimize the simple resched case.
1825 sched_ttwu_pending();
1828 * Check if someone kicked us for doing the nohz idle load balance.
1830 if (unlikely(got_nohz_idle_kick())) {
1831 this_rq()->idle_balance = 1;
1832 raise_softirq_irqoff(SCHED_SOFTIRQ);
1837 static void ttwu_queue_remote(struct task_struct *p, int cpu, int wake_flags)
1839 struct rq *rq = cpu_rq(cpu);
1841 p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED);
1843 if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list)) {
1844 if (!set_nr_if_polling(rq->idle))
1845 smp_send_reschedule(cpu);
1847 trace_sched_wake_idle_without_ipi(cpu);
1851 void wake_up_if_idle(int cpu)
1853 struct rq *rq = cpu_rq(cpu);
1854 unsigned long flags;
1858 if (!is_idle_task(rcu_dereference(rq->curr)))
1861 if (set_nr_if_polling(rq->idle)) {
1862 trace_sched_wake_idle_without_ipi(cpu);
1864 raw_spin_lock_irqsave(&rq->lock, flags);
1865 if (is_idle_task(rq->curr))
1866 smp_send_reschedule(cpu);
1867 /* Else cpu is not in idle, do nothing here */
1868 raw_spin_unlock_irqrestore(&rq->lock, flags);
1875 bool cpus_share_cache(int this_cpu, int that_cpu)
1877 return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
1879 #endif /* CONFIG_SMP */
1881 static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags)
1883 struct rq *rq = cpu_rq(cpu);
1886 #if defined(CONFIG_SMP)
1887 if (sched_feat(TTWU_QUEUE) && !cpus_share_cache(smp_processor_id(), cpu)) {
1888 sched_clock_cpu(cpu); /* sync clocks x-cpu */
1889 ttwu_queue_remote(p, cpu, wake_flags);
1894 raw_spin_lock(&rq->lock);
1895 rq_pin_lock(rq, &rf);
1896 ttwu_do_activate(rq, p, wake_flags, &rf);
1897 rq_unpin_lock(rq, &rf);
1898 raw_spin_unlock(&rq->lock);
1902 * Notes on Program-Order guarantees on SMP systems.
1906 * The basic program-order guarantee on SMP systems is that when a task [t]
1907 * migrates, all its activity on its old cpu [c0] happens-before any subsequent
1908 * execution on its new cpu [c1].
1910 * For migration (of runnable tasks) this is provided by the following means:
1912 * A) UNLOCK of the rq(c0)->lock scheduling out task t
1913 * B) migration for t is required to synchronize *both* rq(c0)->lock and
1914 * rq(c1)->lock (if not at the same time, then in that order).
1915 * C) LOCK of the rq(c1)->lock scheduling in task
1917 * Transitivity guarantees that B happens after A and C after B.
1918 * Note: we only require RCpc transitivity.
1919 * Note: the cpu doing B need not be c0 or c1
1928 * UNLOCK rq(0)->lock
1930 * LOCK rq(0)->lock // orders against CPU0
1932 * UNLOCK rq(0)->lock
1936 * UNLOCK rq(1)->lock
1938 * LOCK rq(1)->lock // orders against CPU2
1941 * UNLOCK rq(1)->lock
1944 * BLOCKING -- aka. SLEEP + WAKEUP
1946 * For blocking we (obviously) need to provide the same guarantee as for
1947 * migration. However the means are completely different as there is no lock
1948 * chain to provide order. Instead we do:
1950 * 1) smp_store_release(X->on_cpu, 0)
1951 * 2) smp_cond_load_acquire(!X->on_cpu)
1955 * CPU0 (schedule) CPU1 (try_to_wake_up) CPU2 (schedule)
1957 * LOCK rq(0)->lock LOCK X->pi_lock
1960 * smp_store_release(X->on_cpu, 0);
1962 * smp_cond_load_acquire(&X->on_cpu, !VAL);
1968 * X->state = RUNNING
1969 * UNLOCK rq(2)->lock
1971 * LOCK rq(2)->lock // orders against CPU1
1974 * UNLOCK rq(2)->lock
1977 * UNLOCK rq(0)->lock
1980 * However; for wakeups there is a second guarantee we must provide, namely we
1981 * must observe the state that lead to our wakeup. That is, not only must our
1982 * task observe its own prior state, it must also observe the stores prior to
1985 * This means that any means of doing remote wakeups must order the CPU doing
1986 * the wakeup against the CPU the task is going to end up running on. This,
1987 * however, is already required for the regular Program-Order guarantee above,
1988 * since the waking CPU is the one issueing the ACQUIRE (smp_cond_load_acquire).
1993 * try_to_wake_up - wake up a thread
1994 * @p: the thread to be awakened
1995 * @state: the mask of task states that can be woken
1996 * @wake_flags: wake modifier flags (WF_*)
1998 * If (@state & @p->state) @p->state = TASK_RUNNING.
2000 * If the task was not queued/runnable, also place it back on a runqueue.
2002 * Atomic against schedule() which would dequeue a task, also see
2003 * set_current_state().
2005 * Return: %true if @p->state changes (an actual wakeup was done),
2009 try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
2011 unsigned long flags;
2012 int cpu, success = 0;
2015 * If we are going to wake up a thread waiting for CONDITION we
2016 * need to ensure that CONDITION=1 done by the caller can not be
2017 * reordered with p->state check below. This pairs with mb() in
2018 * set_current_state() the waiting thread does.
2020 smp_mb__before_spinlock();
2021 raw_spin_lock_irqsave(&p->pi_lock, flags);
2022 if (!(p->state & state))
2025 trace_sched_waking(p);
2027 success = 1; /* we're going to change ->state */
2031 * Ensure we load p->on_rq _after_ p->state, otherwise it would
2032 * be possible to, falsely, observe p->on_rq == 0 and get stuck
2033 * in smp_cond_load_acquire() below.
2035 * sched_ttwu_pending() try_to_wake_up()
2036 * [S] p->on_rq = 1; [L] P->state
2037 * UNLOCK rq->lock -----.
2041 * LOCK rq->lock -----'
2045 * [S] p->state = UNINTERRUPTIBLE [L] p->on_rq
2047 * Pairs with the UNLOCK+LOCK on rq->lock from the
2048 * last wakeup of our task and the schedule that got our task
2052 if (p->on_rq && ttwu_remote(p, wake_flags))
2057 * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
2058 * possible to, falsely, observe p->on_cpu == 0.
2060 * One must be running (->on_cpu == 1) in order to remove oneself
2061 * from the runqueue.
2063 * [S] ->on_cpu = 1; [L] ->on_rq
2067 * [S] ->on_rq = 0; [L] ->on_cpu
2069 * Pairs with the full barrier implied in the UNLOCK+LOCK on rq->lock
2070 * from the consecutive calls to schedule(); the first switching to our
2071 * task, the second putting it to sleep.
2076 * If the owning (remote) cpu is still in the middle of schedule() with
2077 * this task as prev, wait until its done referencing the task.
2079 * Pairs with the smp_store_release() in finish_lock_switch().
2081 * This ensures that tasks getting woken will be fully ordered against
2082 * their previous state and preserve Program Order.
2084 smp_cond_load_acquire(&p->on_cpu, !VAL);
2086 p->sched_contributes_to_load = !!task_contributes_to_load(p);
2087 p->state = TASK_WAKING;
2089 cpu = select_task_rq(p, p->wake_cpu, SD_BALANCE_WAKE, wake_flags);
2090 if (task_cpu(p) != cpu) {
2091 wake_flags |= WF_MIGRATED;
2092 set_task_cpu(p, cpu);
2094 #endif /* CONFIG_SMP */
2096 ttwu_queue(p, cpu, wake_flags);
2098 ttwu_stat(p, cpu, wake_flags);
2100 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2106 * try_to_wake_up_local - try to wake up a local task with rq lock held
2107 * @p: the thread to be awakened
2108 * @cookie: context's cookie for pinning
2110 * Put @p on the run-queue if it's not already there. The caller must
2111 * ensure that this_rq() is locked, @p is bound to this_rq() and not
2114 static void try_to_wake_up_local(struct task_struct *p, struct rq_flags *rf)
2116 struct rq *rq = task_rq(p);
2118 if (WARN_ON_ONCE(rq != this_rq()) ||
2119 WARN_ON_ONCE(p == current))
2122 lockdep_assert_held(&rq->lock);
2124 if (!raw_spin_trylock(&p->pi_lock)) {
2126 * This is OK, because current is on_cpu, which avoids it being
2127 * picked for load-balance and preemption/IRQs are still
2128 * disabled avoiding further scheduler activity on it and we've
2129 * not yet picked a replacement task.
2131 rq_unpin_lock(rq, rf);
2132 raw_spin_unlock(&rq->lock);
2133 raw_spin_lock(&p->pi_lock);
2134 raw_spin_lock(&rq->lock);
2135 rq_repin_lock(rq, rf);
2138 if (!(p->state & TASK_NORMAL))
2141 trace_sched_waking(p);
2143 if (!task_on_rq_queued(p))
2144 ttwu_activate(rq, p, ENQUEUE_WAKEUP);
2146 ttwu_do_wakeup(rq, p, 0, rf);
2147 ttwu_stat(p, smp_processor_id(), 0);
2149 raw_spin_unlock(&p->pi_lock);
2153 * wake_up_process - Wake up a specific process
2154 * @p: The process to be woken up.
2156 * Attempt to wake up the nominated process and move it to the set of runnable
2159 * Return: 1 if the process was woken up, 0 if it was already running.
2161 * It may be assumed that this function implies a write memory barrier before
2162 * changing the task state if and only if any tasks are woken up.
2164 int wake_up_process(struct task_struct *p)
2166 return try_to_wake_up(p, TASK_NORMAL, 0);
2168 EXPORT_SYMBOL(wake_up_process);
2170 int wake_up_state(struct task_struct *p, unsigned int state)
2172 return try_to_wake_up(p, state, 0);
2176 * This function clears the sched_dl_entity static params.
2178 void __dl_clear_params(struct task_struct *p)
2180 struct sched_dl_entity *dl_se = &p->dl;
2182 dl_se->dl_runtime = 0;
2183 dl_se->dl_deadline = 0;
2184 dl_se->dl_period = 0;
2188 dl_se->dl_throttled = 0;
2189 dl_se->dl_yielded = 0;
2193 * Perform scheduler related setup for a newly forked process p.
2194 * p is forked by current.
2196 * __sched_fork() is basic setup used by init_idle() too:
2198 static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
2203 p->se.exec_start = 0;
2204 p->se.sum_exec_runtime = 0;
2205 p->se.prev_sum_exec_runtime = 0;
2206 p->se.nr_migrations = 0;
2208 INIT_LIST_HEAD(&p->se.group_node);
2210 #ifdef CONFIG_FAIR_GROUP_SCHED
2211 p->se.cfs_rq = NULL;
2214 #ifdef CONFIG_SCHEDSTATS
2215 /* Even if schedstat is disabled, there should not be garbage */
2216 memset(&p->se.statistics, 0, sizeof(p->se.statistics));
2219 RB_CLEAR_NODE(&p->dl.rb_node);
2220 init_dl_task_timer(&p->dl);
2221 __dl_clear_params(p);
2223 INIT_LIST_HEAD(&p->rt.run_list);
2225 p->rt.time_slice = sched_rr_timeslice;
2229 #ifdef CONFIG_PREEMPT_NOTIFIERS
2230 INIT_HLIST_HEAD(&p->preempt_notifiers);
2233 #ifdef CONFIG_NUMA_BALANCING
2234 if (p->mm && atomic_read(&p->mm->mm_users) == 1) {
2235 p->mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2236 p->mm->numa_scan_seq = 0;
2239 if (clone_flags & CLONE_VM)
2240 p->numa_preferred_nid = current->numa_preferred_nid;
2242 p->numa_preferred_nid = -1;
2244 p->node_stamp = 0ULL;
2245 p->numa_scan_seq = p->mm ? p->mm->numa_scan_seq : 0;
2246 p->numa_scan_period = sysctl_numa_balancing_scan_delay;
2247 p->numa_work.next = &p->numa_work;
2248 p->numa_faults = NULL;
2249 p->last_task_numa_placement = 0;
2250 p->last_sum_exec_runtime = 0;
2252 p->numa_group = NULL;
2253 #endif /* CONFIG_NUMA_BALANCING */
2256 DEFINE_STATIC_KEY_FALSE(sched_numa_balancing);
2258 #ifdef CONFIG_NUMA_BALANCING
2260 void set_numabalancing_state(bool enabled)
2263 static_branch_enable(&sched_numa_balancing);
2265 static_branch_disable(&sched_numa_balancing);
2268 #ifdef CONFIG_PROC_SYSCTL
2269 int sysctl_numa_balancing(struct ctl_table *table, int write,
2270 void __user *buffer, size_t *lenp, loff_t *ppos)
2274 int state = static_branch_likely(&sched_numa_balancing);
2276 if (write && !capable(CAP_SYS_ADMIN))
2281 err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2285 set_numabalancing_state(state);
2291 #ifdef CONFIG_SCHEDSTATS
2293 DEFINE_STATIC_KEY_FALSE(sched_schedstats);
2294 static bool __initdata __sched_schedstats = false;
2296 static void set_schedstats(bool enabled)
2299 static_branch_enable(&sched_schedstats);
2301 static_branch_disable(&sched_schedstats);
2304 void force_schedstat_enabled(void)
2306 if (!schedstat_enabled()) {
2307 pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n");
2308 static_branch_enable(&sched_schedstats);
2312 static int __init setup_schedstats(char *str)
2319 * This code is called before jump labels have been set up, so we can't
2320 * change the static branch directly just yet. Instead set a temporary
2321 * variable so init_schedstats() can do it later.
2323 if (!strcmp(str, "enable")) {
2324 __sched_schedstats = true;
2326 } else if (!strcmp(str, "disable")) {
2327 __sched_schedstats = false;
2332 pr_warn("Unable to parse schedstats=\n");
2336 __setup("schedstats=", setup_schedstats);
2338 static void __init init_schedstats(void)
2340 set_schedstats(__sched_schedstats);
2343 #ifdef CONFIG_PROC_SYSCTL
2344 int sysctl_schedstats(struct ctl_table *table, int write,
2345 void __user *buffer, size_t *lenp, loff_t *ppos)
2349 int state = static_branch_likely(&sched_schedstats);
2351 if (write && !capable(CAP_SYS_ADMIN))
2356 err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2360 set_schedstats(state);
2363 #endif /* CONFIG_PROC_SYSCTL */
2364 #else /* !CONFIG_SCHEDSTATS */
2365 static inline void init_schedstats(void) {}
2366 #endif /* CONFIG_SCHEDSTATS */
2369 * fork()/clone()-time setup:
2371 int sched_fork(unsigned long clone_flags, struct task_struct *p)
2373 unsigned long flags;
2374 int cpu = get_cpu();
2376 __sched_fork(clone_flags, p);
2378 * We mark the process as NEW here. This guarantees that
2379 * nobody will actually run it, and a signal or other external
2380 * event cannot wake it up and insert it on the runqueue either.
2382 p->state = TASK_NEW;
2385 * Make sure we do not leak PI boosting priority to the child.
2387 p->prio = current->normal_prio;
2390 * Revert to default priority/policy on fork if requested.
2392 if (unlikely(p->sched_reset_on_fork)) {
2393 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
2394 p->policy = SCHED_NORMAL;
2395 p->static_prio = NICE_TO_PRIO(0);
2397 } else if (PRIO_TO_NICE(p->static_prio) < 0)
2398 p->static_prio = NICE_TO_PRIO(0);
2400 p->prio = p->normal_prio = __normal_prio(p);
2404 * We don't need the reset flag anymore after the fork. It has
2405 * fulfilled its duty:
2407 p->sched_reset_on_fork = 0;
2410 if (dl_prio(p->prio)) {
2413 } else if (rt_prio(p->prio)) {
2414 p->sched_class = &rt_sched_class;
2416 p->sched_class = &fair_sched_class;
2419 init_entity_runnable_average(&p->se);
2422 * The child is not yet in the pid-hash so no cgroup attach races,
2423 * and the cgroup is pinned to this child due to cgroup_fork()
2424 * is ran before sched_fork().
2426 * Silence PROVE_RCU.
2428 raw_spin_lock_irqsave(&p->pi_lock, flags);
2430 * We're setting the cpu for the first time, we don't migrate,
2431 * so use __set_task_cpu().
2433 __set_task_cpu(p, cpu);
2434 if (p->sched_class->task_fork)
2435 p->sched_class->task_fork(p);
2436 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2438 #ifdef CONFIG_SCHED_INFO
2439 if (likely(sched_info_on()))
2440 memset(&p->sched_info, 0, sizeof(p->sched_info));
2442 #if defined(CONFIG_SMP)
2445 init_task_preempt_count(p);
2447 plist_node_init(&p->pushable_tasks, MAX_PRIO);
2448 RB_CLEAR_NODE(&p->pushable_dl_tasks);
2455 unsigned long to_ratio(u64 period, u64 runtime)
2457 if (runtime == RUNTIME_INF)
2461 * Doing this here saves a lot of checks in all
2462 * the calling paths, and returning zero seems
2463 * safe for them anyway.
2468 return div64_u64(runtime << 20, period);
2472 inline struct dl_bw *dl_bw_of(int i)
2474 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
2475 "sched RCU must be held");
2476 return &cpu_rq(i)->rd->dl_bw;
2479 static inline int dl_bw_cpus(int i)
2481 struct root_domain *rd = cpu_rq(i)->rd;
2484 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
2485 "sched RCU must be held");
2486 for_each_cpu_and(i, rd->span, cpu_active_mask)
2492 inline struct dl_bw *dl_bw_of(int i)
2494 return &cpu_rq(i)->dl.dl_bw;
2497 static inline int dl_bw_cpus(int i)
2504 * We must be sure that accepting a new task (or allowing changing the
2505 * parameters of an existing one) is consistent with the bandwidth
2506 * constraints. If yes, this function also accordingly updates the currently
2507 * allocated bandwidth to reflect the new situation.
2509 * This function is called while holding p's rq->lock.
2511 * XXX we should delay bw change until the task's 0-lag point, see
2514 static int dl_overflow(struct task_struct *p, int policy,
2515 const struct sched_attr *attr)
2518 struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
2519 u64 period = attr->sched_period ?: attr->sched_deadline;
2520 u64 runtime = attr->sched_runtime;
2521 u64 new_bw = dl_policy(policy) ? to_ratio(period, runtime) : 0;
2524 /* !deadline task may carry old deadline bandwidth */
2525 if (new_bw == p->dl.dl_bw && task_has_dl_policy(p))
2529 * Either if a task, enters, leave, or stays -deadline but changes
2530 * its parameters, we may need to update accordingly the total
2531 * allocated bandwidth of the container.
2533 raw_spin_lock(&dl_b->lock);
2534 cpus = dl_bw_cpus(task_cpu(p));
2535 if (dl_policy(policy) && !task_has_dl_policy(p) &&
2536 !__dl_overflow(dl_b, cpus, 0, new_bw)) {
2537 __dl_add(dl_b, new_bw);
2539 } else if (dl_policy(policy) && task_has_dl_policy(p) &&
2540 !__dl_overflow(dl_b, cpus, p->dl.dl_bw, new_bw)) {
2541 __dl_clear(dl_b, p->dl.dl_bw);
2542 __dl_add(dl_b, new_bw);
2544 } else if (!dl_policy(policy) && task_has_dl_policy(p)) {
2545 __dl_clear(dl_b, p->dl.dl_bw);
2548 raw_spin_unlock(&dl_b->lock);
2553 extern void init_dl_bw(struct dl_bw *dl_b);
2556 * wake_up_new_task - wake up a newly created task for the first time.
2558 * This function will do some initial scheduler statistics housekeeping
2559 * that must be done for every newly created context, then puts the task
2560 * on the runqueue and wakes it.
2562 void wake_up_new_task(struct task_struct *p)
2567 raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
2568 p->state = TASK_RUNNING;
2571 * Fork balancing, do it here and not earlier because:
2572 * - cpus_allowed can change in the fork path
2573 * - any previously selected cpu might disappear through hotplug
2575 * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq,
2576 * as we're not fully set-up yet.
2578 __set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0));
2580 rq = __task_rq_lock(p, &rf);
2581 update_rq_clock(rq);
2582 post_init_entity_util_avg(&p->se);
2584 activate_task(rq, p, 0);
2585 p->on_rq = TASK_ON_RQ_QUEUED;
2586 trace_sched_wakeup_new(p);
2587 check_preempt_curr(rq, p, WF_FORK);
2589 if (p->sched_class->task_woken) {
2591 * Nothing relies on rq->lock after this, so its fine to
2594 rq_unpin_lock(rq, &rf);
2595 p->sched_class->task_woken(rq, p);
2596 rq_repin_lock(rq, &rf);
2599 task_rq_unlock(rq, p, &rf);
2602 #ifdef CONFIG_PREEMPT_NOTIFIERS
2604 static struct static_key preempt_notifier_key = STATIC_KEY_INIT_FALSE;
2606 void preempt_notifier_inc(void)
2608 static_key_slow_inc(&preempt_notifier_key);
2610 EXPORT_SYMBOL_GPL(preempt_notifier_inc);
2612 void preempt_notifier_dec(void)
2614 static_key_slow_dec(&preempt_notifier_key);
2616 EXPORT_SYMBOL_GPL(preempt_notifier_dec);
2619 * preempt_notifier_register - tell me when current is being preempted & rescheduled
2620 * @notifier: notifier struct to register
2622 void preempt_notifier_register(struct preempt_notifier *notifier)
2624 if (!static_key_false(&preempt_notifier_key))
2625 WARN(1, "registering preempt_notifier while notifiers disabled\n");
2627 hlist_add_head(¬ifier->link, ¤t->preempt_notifiers);
2629 EXPORT_SYMBOL_GPL(preempt_notifier_register);
2632 * preempt_notifier_unregister - no longer interested in preemption notifications
2633 * @notifier: notifier struct to unregister
2635 * This is *not* safe to call from within a preemption notifier.
2637 void preempt_notifier_unregister(struct preempt_notifier *notifier)
2639 hlist_del(¬ifier->link);
2641 EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
2643 static void __fire_sched_in_preempt_notifiers(struct task_struct *curr)
2645 struct preempt_notifier *notifier;
2647 hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
2648 notifier->ops->sched_in(notifier, raw_smp_processor_id());
2651 static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
2653 if (static_key_false(&preempt_notifier_key))
2654 __fire_sched_in_preempt_notifiers(curr);
2658 __fire_sched_out_preempt_notifiers(struct task_struct *curr,
2659 struct task_struct *next)
2661 struct preempt_notifier *notifier;
2663 hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
2664 notifier->ops->sched_out(notifier, next);
2667 static __always_inline void
2668 fire_sched_out_preempt_notifiers(struct task_struct *curr,
2669 struct task_struct *next)
2671 if (static_key_false(&preempt_notifier_key))
2672 __fire_sched_out_preempt_notifiers(curr, next);
2675 #else /* !CONFIG_PREEMPT_NOTIFIERS */
2677 static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
2682 fire_sched_out_preempt_notifiers(struct task_struct *curr,
2683 struct task_struct *next)
2687 #endif /* CONFIG_PREEMPT_NOTIFIERS */
2690 * prepare_task_switch - prepare to switch tasks
2691 * @rq: the runqueue preparing to switch
2692 * @prev: the current task that is being switched out
2693 * @next: the task we are going to switch to.
2695 * This is called with the rq lock held and interrupts off. It must
2696 * be paired with a subsequent finish_task_switch after the context
2699 * prepare_task_switch sets up locking and calls architecture specific
2703 prepare_task_switch(struct rq *rq, struct task_struct *prev,
2704 struct task_struct *next)
2706 sched_info_switch(rq, prev, next);
2707 perf_event_task_sched_out(prev, next);
2708 fire_sched_out_preempt_notifiers(prev, next);
2709 prepare_lock_switch(rq, next);
2710 prepare_arch_switch(next);
2714 * finish_task_switch - clean up after a task-switch
2715 * @prev: the thread we just switched away from.
2717 * finish_task_switch must be called after the context switch, paired
2718 * with a prepare_task_switch call before the context switch.
2719 * finish_task_switch will reconcile locking set up by prepare_task_switch,
2720 * and do any other architecture-specific cleanup actions.
2722 * Note that we may have delayed dropping an mm in context_switch(). If
2723 * so, we finish that here outside of the runqueue lock. (Doing it
2724 * with the lock held can cause deadlocks; see schedule() for
2727 * The context switch have flipped the stack from under us and restored the
2728 * local variables which were saved when this task called schedule() in the
2729 * past. prev == current is still correct but we need to recalculate this_rq
2730 * because prev may have moved to another CPU.
2732 static struct rq *finish_task_switch(struct task_struct *prev)
2733 __releases(rq->lock)
2735 struct rq *rq = this_rq();
2736 struct mm_struct *mm = rq->prev_mm;
2740 * The previous task will have left us with a preempt_count of 2
2741 * because it left us after:
2744 * preempt_disable(); // 1
2746 * raw_spin_lock_irq(&rq->lock) // 2
2748 * Also, see FORK_PREEMPT_COUNT.
2750 if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET,
2751 "corrupted preempt_count: %s/%d/0x%x\n",
2752 current->comm, current->pid, preempt_count()))
2753 preempt_count_set(FORK_PREEMPT_COUNT);
2758 * A task struct has one reference for the use as "current".
2759 * If a task dies, then it sets TASK_DEAD in tsk->state and calls
2760 * schedule one last time. The schedule call will never return, and
2761 * the scheduled task must drop that reference.
2763 * We must observe prev->state before clearing prev->on_cpu (in
2764 * finish_lock_switch), otherwise a concurrent wakeup can get prev
2765 * running on another CPU and we could rave with its RUNNING -> DEAD
2766 * transition, resulting in a double drop.
2768 prev_state = prev->state;
2769 vtime_task_switch(prev);
2770 perf_event_task_sched_in(prev, current);
2771 finish_lock_switch(rq, prev);
2772 finish_arch_post_lock_switch();
2774 fire_sched_in_preempt_notifiers(current);
2777 if (unlikely(prev_state == TASK_DEAD)) {
2778 if (prev->sched_class->task_dead)
2779 prev->sched_class->task_dead(prev);
2782 * Remove function-return probe instances associated with this
2783 * task and put them back on the free list.
2785 kprobe_flush_task(prev);
2787 /* Task is done with its stack. */
2788 put_task_stack(prev);
2790 put_task_struct(prev);
2793 tick_nohz_task_switch();
2799 /* rq->lock is NOT held, but preemption is disabled */
2800 static void __balance_callback(struct rq *rq)
2802 struct callback_head *head, *next;
2803 void (*func)(struct rq *rq);
2804 unsigned long flags;
2806 raw_spin_lock_irqsave(&rq->lock, flags);
2807 head = rq->balance_callback;
2808 rq->balance_callback = NULL;
2810 func = (void (*)(struct rq *))head->func;
2817 raw_spin_unlock_irqrestore(&rq->lock, flags);
2820 static inline void balance_callback(struct rq *rq)
2822 if (unlikely(rq->balance_callback))
2823 __balance_callback(rq);
2828 static inline void balance_callback(struct rq *rq)
2835 * schedule_tail - first thing a freshly forked thread must call.
2836 * @prev: the thread we just switched away from.
2838 asmlinkage __visible void schedule_tail(struct task_struct *prev)
2839 __releases(rq->lock)
2844 * New tasks start with FORK_PREEMPT_COUNT, see there and
2845 * finish_task_switch() for details.
2847 * finish_task_switch() will drop rq->lock() and lower preempt_count
2848 * and the preempt_enable() will end up enabling preemption (on
2849 * PREEMPT_COUNT kernels).
2852 rq = finish_task_switch(prev);
2853 balance_callback(rq);
2856 if (current->set_child_tid)
2857 put_user(task_pid_vnr(current), current->set_child_tid);
2861 * context_switch - switch to the new MM and the new thread's register state.
2863 static __always_inline struct rq *
2864 context_switch(struct rq *rq, struct task_struct *prev,
2865 struct task_struct *next, struct rq_flags *rf)
2867 struct mm_struct *mm, *oldmm;
2869 prepare_task_switch(rq, prev, next);
2872 oldmm = prev->active_mm;
2874 * For paravirt, this is coupled with an exit in switch_to to
2875 * combine the page table reload and the switch backend into
2878 arch_start_context_switch(prev);
2881 next->active_mm = oldmm;
2882 atomic_inc(&oldmm->mm_count);
2883 enter_lazy_tlb(oldmm, next);
2885 switch_mm_irqs_off(oldmm, mm, next);
2888 prev->active_mm = NULL;
2889 rq->prev_mm = oldmm;
2892 rq->clock_skip_update = 0;
2895 * Since the runqueue lock will be released by the next
2896 * task (which is an invalid locking op but in the case
2897 * of the scheduler it's an obvious special-case), so we
2898 * do an early lockdep release here:
2900 rq_unpin_lock(rq, rf);
2901 spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
2903 /* Here we just switch the register state and the stack. */
2904 switch_to(prev, next, prev);
2907 return finish_task_switch(prev);
2911 * nr_running and nr_context_switches:
2913 * externally visible scheduler statistics: current number of runnable
2914 * threads, total number of context switches performed since bootup.
2916 unsigned long nr_running(void)
2918 unsigned long i, sum = 0;
2920 for_each_online_cpu(i)
2921 sum += cpu_rq(i)->nr_running;
2927 * Check if only the current task is running on the cpu.
2929 * Caution: this function does not check that the caller has disabled
2930 * preemption, thus the result might have a time-of-check-to-time-of-use
2931 * race. The caller is responsible to use it correctly, for example:
2933 * - from a non-preemptable section (of course)
2935 * - from a thread that is bound to a single CPU
2937 * - in a loop with very short iterations (e.g. a polling loop)
2939 bool single_task_running(void)
2941 return raw_rq()->nr_running == 1;
2943 EXPORT_SYMBOL(single_task_running);
2945 unsigned long long nr_context_switches(void)
2948 unsigned long long sum = 0;
2950 for_each_possible_cpu(i)
2951 sum += cpu_rq(i)->nr_switches;
2956 unsigned long nr_iowait(void)
2958 unsigned long i, sum = 0;
2960 for_each_possible_cpu(i)
2961 sum += atomic_read(&cpu_rq(i)->nr_iowait);
2966 unsigned long nr_iowait_cpu(int cpu)
2968 struct rq *this = cpu_rq(cpu);
2969 return atomic_read(&this->nr_iowait);
2972 void get_iowait_load(unsigned long *nr_waiters, unsigned long *load)
2974 struct rq *rq = this_rq();
2975 *nr_waiters = atomic_read(&rq->nr_iowait);
2976 *load = rq->load.weight;
2982 * sched_exec - execve() is a valuable balancing opportunity, because at
2983 * this point the task has the smallest effective memory and cache footprint.
2985 void sched_exec(void)
2987 struct task_struct *p = current;
2988 unsigned long flags;
2991 raw_spin_lock_irqsave(&p->pi_lock, flags);
2992 dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), SD_BALANCE_EXEC, 0);
2993 if (dest_cpu == smp_processor_id())
2996 if (likely(cpu_active(dest_cpu))) {
2997 struct migration_arg arg = { p, dest_cpu };
2999 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
3000 stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
3004 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
3009 DEFINE_PER_CPU(struct kernel_stat, kstat);
3010 DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat);
3012 EXPORT_PER_CPU_SYMBOL(kstat);
3013 EXPORT_PER_CPU_SYMBOL(kernel_cpustat);
3016 * The function fair_sched_class.update_curr accesses the struct curr
3017 * and its field curr->exec_start; when called from task_sched_runtime(),
3018 * we observe a high rate of cache misses in practice.
3019 * Prefetching this data results in improved performance.
3021 static inline void prefetch_curr_exec_start(struct task_struct *p)
3023 #ifdef CONFIG_FAIR_GROUP_SCHED
3024 struct sched_entity *curr = (&p->se)->cfs_rq->curr;
3026 struct sched_entity *curr = (&task_rq(p)->cfs)->curr;
3029 prefetch(&curr->exec_start);
3033 * Return accounted runtime for the task.
3034 * In case the task is currently running, return the runtime plus current's
3035 * pending runtime that have not been accounted yet.
3037 unsigned long long task_sched_runtime(struct task_struct *p)
3043 #if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
3045 * 64-bit doesn't need locks to atomically read a 64bit value.
3046 * So we have a optimization chance when the task's delta_exec is 0.
3047 * Reading ->on_cpu is racy, but this is ok.
3049 * If we race with it leaving cpu, we'll take a lock. So we're correct.
3050 * If we race with it entering cpu, unaccounted time is 0. This is
3051 * indistinguishable from the read occurring a few cycles earlier.
3052 * If we see ->on_cpu without ->on_rq, the task is leaving, and has
3053 * been accounted, so we're correct here as well.
3055 if (!p->on_cpu || !task_on_rq_queued(p))
3056 return p->se.sum_exec_runtime;
3059 rq = task_rq_lock(p, &rf);
3061 * Must be ->curr _and_ ->on_rq. If dequeued, we would
3062 * project cycles that may never be accounted to this
3063 * thread, breaking clock_gettime().
3065 if (task_current(rq, p) && task_on_rq_queued(p)) {
3066 prefetch_curr_exec_start(p);
3067 update_rq_clock(rq);
3068 p->sched_class->update_curr(rq);
3070 ns = p->se.sum_exec_runtime;
3071 task_rq_unlock(rq, p, &rf);
3077 * This function gets called by the timer code, with HZ frequency.
3078 * We call it with interrupts disabled.
3080 void scheduler_tick(void)
3082 int cpu = smp_processor_id();
3083 struct rq *rq = cpu_rq(cpu);
3084 struct task_struct *curr = rq->curr;
3088 raw_spin_lock(&rq->lock);
3089 update_rq_clock(rq);
3090 curr->sched_class->task_tick(rq, curr, 0);
3091 cpu_load_update_active(rq);
3092 calc_global_load_tick(rq);
3093 raw_spin_unlock(&rq->lock);
3095 perf_event_task_tick();
3098 rq->idle_balance = idle_cpu(cpu);
3099 trigger_load_balance(rq);
3101 rq_last_tick_reset(rq);
3104 #ifdef CONFIG_NO_HZ_FULL
3106 * scheduler_tick_max_deferment
3108 * Keep at least one tick per second when a single
3109 * active task is running because the scheduler doesn't
3110 * yet completely support full dynticks environment.
3112 * This makes sure that uptime, CFS vruntime, load
3113 * balancing, etc... continue to move forward, even
3114 * with a very low granularity.
3116 * Return: Maximum deferment in nanoseconds.
3118 u64 scheduler_tick_max_deferment(void)
3120 struct rq *rq = this_rq();
3121 unsigned long next, now = READ_ONCE(jiffies);
3123 next = rq->last_sched_tick + HZ;
3125 if (time_before_eq(next, now))
3128 return jiffies_to_nsecs(next - now);
3132 #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
3133 defined(CONFIG_PREEMPT_TRACER))
3135 * If the value passed in is equal to the current preempt count
3136 * then we just disabled preemption. Start timing the latency.
3138 static inline void preempt_latency_start(int val)
3140 if (preempt_count() == val) {
3141 unsigned long ip = get_lock_parent_ip();
3142 #ifdef CONFIG_DEBUG_PREEMPT
3143 current->preempt_disable_ip = ip;
3145 trace_preempt_off(CALLER_ADDR0, ip);
3149 void preempt_count_add(int val)
3151 #ifdef CONFIG_DEBUG_PREEMPT
3155 if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
3158 __preempt_count_add(val);
3159 #ifdef CONFIG_DEBUG_PREEMPT
3161 * Spinlock count overflowing soon?
3163 DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
3166 preempt_latency_start(val);
3168 EXPORT_SYMBOL(preempt_count_add);
3169 NOKPROBE_SYMBOL(preempt_count_add);
3172 * If the value passed in equals to the current preempt count
3173 * then we just enabled preemption. Stop timing the latency.
3175 static inline void preempt_latency_stop(int val)
3177 if (preempt_count() == val)
3178 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
3181 void preempt_count_sub(int val)
3183 #ifdef CONFIG_DEBUG_PREEMPT
3187 if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
3190 * Is the spinlock portion underflowing?
3192 if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
3193 !(preempt_count() & PREEMPT_MASK)))
3197 preempt_latency_stop(val);
3198 __preempt_count_sub(val);
3200 EXPORT_SYMBOL(preempt_count_sub);
3201 NOKPROBE_SYMBOL(preempt_count_sub);
3204 static inline void preempt_latency_start(int val) { }
3205 static inline void preempt_latency_stop(int val) { }
3209 * Print scheduling while atomic bug:
3211 static noinline void __schedule_bug(struct task_struct *prev)
3213 /* Save this before calling printk(), since that will clobber it */
3214 unsigned long preempt_disable_ip = get_preempt_disable_ip(current);
3216 if (oops_in_progress)
3219 printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
3220 prev->comm, prev->pid, preempt_count());
3222 debug_show_held_locks(prev);
3224 if (irqs_disabled())
3225 print_irqtrace_events(prev);
3226 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
3227 && in_atomic_preempt_off()) {
3228 pr_err("Preemption disabled at:");
3229 print_ip_sym(preempt_disable_ip);
3233 panic("scheduling while atomic\n");
3236 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
3240 * Various schedule()-time debugging checks and statistics:
3242 static inline void schedule_debug(struct task_struct *prev)
3244 #ifdef CONFIG_SCHED_STACK_END_CHECK
3245 if (task_stack_end_corrupted(prev))
3246 panic("corrupted stack end detected inside scheduler\n");
3249 if (unlikely(in_atomic_preempt_off())) {
3250 __schedule_bug(prev);
3251 preempt_count_set(PREEMPT_DISABLED);
3255 profile_hit(SCHED_PROFILING, __builtin_return_address(0));
3257 schedstat_inc(this_rq()->sched_count);
3261 * Pick up the highest-prio task:
3263 static inline struct task_struct *
3264 pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
3266 const struct sched_class *class = &fair_sched_class;
3267 struct task_struct *p;
3270 * Optimization: we know that if all tasks are in
3271 * the fair class we can call that function directly:
3273 if (likely(prev->sched_class == class &&
3274 rq->nr_running == rq->cfs.h_nr_running)) {
3275 p = fair_sched_class.pick_next_task(rq, prev, rf);
3276 if (unlikely(p == RETRY_TASK))
3279 /* assumes fair_sched_class->next == idle_sched_class */
3281 p = idle_sched_class.pick_next_task(rq, prev, rf);
3287 for_each_class(class) {
3288 p = class->pick_next_task(rq, prev, rf);
3290 if (unlikely(p == RETRY_TASK))
3296 BUG(); /* the idle class will always have a runnable task */
3300 * __schedule() is the main scheduler function.
3302 * The main means of driving the scheduler and thus entering this function are:
3304 * 1. Explicit blocking: mutex, semaphore, waitqueue, etc.
3306 * 2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
3307 * paths. For example, see arch/x86/entry_64.S.
3309 * To drive preemption between tasks, the scheduler sets the flag in timer
3310 * interrupt handler scheduler_tick().
3312 * 3. Wakeups don't really cause entry into schedule(). They add a
3313 * task to the run-queue and that's it.
3315 * Now, if the new task added to the run-queue preempts the current
3316 * task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
3317 * called on the nearest possible occasion:
3319 * - If the kernel is preemptible (CONFIG_PREEMPT=y):
3321 * - in syscall or exception context, at the next outmost
3322 * preempt_enable(). (this might be as soon as the wake_up()'s
3325 * - in IRQ context, return from interrupt-handler to
3326 * preemptible context
3328 * - If the kernel is not preemptible (CONFIG_PREEMPT is not set)
3331 * - cond_resched() call
3332 * - explicit schedule() call
3333 * - return from syscall or exception to user-space
3334 * - return from interrupt-handler to user-space
3336 * WARNING: must be called with preemption disabled!
3338 static void __sched notrace __schedule(bool preempt)
3340 struct task_struct *prev, *next;
3341 unsigned long *switch_count;
3346 cpu = smp_processor_id();
3350 schedule_debug(prev);
3352 if (sched_feat(HRTICK))
3355 local_irq_disable();
3356 rcu_note_context_switch();
3359 * Make sure that signal_pending_state()->signal_pending() below
3360 * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
3361 * done by the caller to avoid the race with signal_wake_up().
3363 smp_mb__before_spinlock();
3364 raw_spin_lock(&rq->lock);
3365 rq_pin_lock(rq, &rf);
3367 rq->clock_skip_update <<= 1; /* promote REQ to ACT */
3369 switch_count = &prev->nivcsw;
3370 if (!preempt && prev->state) {
3371 if (unlikely(signal_pending_state(prev->state, prev))) {
3372 prev->state = TASK_RUNNING;
3374 deactivate_task(rq, prev, DEQUEUE_SLEEP);
3378 * If a worker went to sleep, notify and ask workqueue
3379 * whether it wants to wake up a task to maintain
3382 if (prev->flags & PF_WQ_WORKER) {
3383 struct task_struct *to_wakeup;
3385 to_wakeup = wq_worker_sleeping(prev);
3387 try_to_wake_up_local(to_wakeup, &rf);
3390 switch_count = &prev->nvcsw;
3393 if (task_on_rq_queued(prev))
3394 update_rq_clock(rq);
3396 next = pick_next_task(rq, prev, &rf);
3397 clear_tsk_need_resched(prev);
3398 clear_preempt_need_resched();
3400 if (likely(prev != next)) {
3405 trace_sched_switch(preempt, prev, next);
3406 rq = context_switch(rq, prev, next, &rf); /* unlocks the rq */
3408 rq->clock_skip_update = 0;
3409 rq_unpin_lock(rq, &rf);
3410 raw_spin_unlock_irq(&rq->lock);
3413 balance_callback(rq);
3416 void __noreturn do_task_dead(void)
3419 * The setting of TASK_RUNNING by try_to_wake_up() may be delayed
3420 * when the following two conditions become true.
3421 * - There is race condition of mmap_sem (It is acquired by
3423 * - SMI occurs before setting TASK_RUNINNG.
3424 * (or hypervisor of virtual machine switches to other guest)
3425 * As a result, we may become TASK_RUNNING after becoming TASK_DEAD
3427 * To avoid it, we have to wait for releasing tsk->pi_lock which
3428 * is held by try_to_wake_up()
3431 raw_spin_unlock_wait(¤t->pi_lock);
3433 /* causes final put_task_struct in finish_task_switch(). */
3434 __set_current_state(TASK_DEAD);
3435 current->flags |= PF_NOFREEZE; /* tell freezer to ignore us */
3438 /* Avoid "noreturn function does return". */
3440 cpu_relax(); /* For when BUG is null */
3443 static inline void sched_submit_work(struct task_struct *tsk)
3445 if (!tsk->state || tsk_is_pi_blocked(tsk))
3448 * If we are going to sleep and we have plugged IO queued,
3449 * make sure to submit it to avoid deadlocks.
3451 if (blk_needs_flush_plug(tsk))
3452 blk_schedule_flush_plug(tsk);
3455 asmlinkage __visible void __sched schedule(void)
3457 struct task_struct *tsk = current;
3459 sched_submit_work(tsk);
3463 sched_preempt_enable_no_resched();
3464 } while (need_resched());
3466 EXPORT_SYMBOL(schedule);
3468 #ifdef CONFIG_CONTEXT_TRACKING
3469 asmlinkage __visible void __sched schedule_user(void)
3472 * If we come here after a random call to set_need_resched(),
3473 * or we have been woken up remotely but the IPI has not yet arrived,
3474 * we haven't yet exited the RCU idle mode. Do it here manually until
3475 * we find a better solution.
3477 * NB: There are buggy callers of this function. Ideally we
3478 * should warn if prev_state != CONTEXT_USER, but that will trigger
3479 * too frequently to make sense yet.
3481 enum ctx_state prev_state = exception_enter();
3483 exception_exit(prev_state);
3488 * schedule_preempt_disabled - called with preemption disabled
3490 * Returns with preemption disabled. Note: preempt_count must be 1
3492 void __sched schedule_preempt_disabled(void)
3494 sched_preempt_enable_no_resched();
3499 static void __sched notrace preempt_schedule_common(void)
3503 * Because the function tracer can trace preempt_count_sub()
3504 * and it also uses preempt_enable/disable_notrace(), if
3505 * NEED_RESCHED is set, the preempt_enable_notrace() called
3506 * by the function tracer will call this function again and
3507 * cause infinite recursion.
3509 * Preemption must be disabled here before the function
3510 * tracer can trace. Break up preempt_disable() into two
3511 * calls. One to disable preemption without fear of being
3512 * traced. The other to still record the preemption latency,
3513 * which can also be traced by the function tracer.
3515 preempt_disable_notrace();
3516 preempt_latency_start(1);
3518 preempt_latency_stop(1);
3519 preempt_enable_no_resched_notrace();
3522 * Check again in case we missed a preemption opportunity
3523 * between schedule and now.
3525 } while (need_resched());
3528 #ifdef CONFIG_PREEMPT
3530 * this is the entry point to schedule() from in-kernel preemption
3531 * off of preempt_enable. Kernel preemptions off return from interrupt
3532 * occur there and call schedule directly.
3534 asmlinkage __visible void __sched notrace preempt_schedule(void)
3537 * If there is a non-zero preempt_count or interrupts are disabled,
3538 * we do not want to preempt the current task. Just return..
3540 if (likely(!preemptible()))
3543 preempt_schedule_common();
3545 NOKPROBE_SYMBOL(preempt_schedule);
3546 EXPORT_SYMBOL(preempt_schedule);
3549 * preempt_schedule_notrace - preempt_schedule called by tracing
3551 * The tracing infrastructure uses preempt_enable_notrace to prevent
3552 * recursion and tracing preempt enabling caused by the tracing
3553 * infrastructure itself. But as tracing can happen in areas coming
3554 * from userspace or just about to enter userspace, a preempt enable
3555 * can occur before user_exit() is called. This will cause the scheduler
3556 * to be called when the system is still in usermode.
3558 * To prevent this, the preempt_enable_notrace will use this function
3559 * instead of preempt_schedule() to exit user context if needed before
3560 * calling the scheduler.
3562 asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
3564 enum ctx_state prev_ctx;
3566 if (likely(!preemptible()))
3571 * Because the function tracer can trace preempt_count_sub()
3572 * and it also uses preempt_enable/disable_notrace(), if
3573 * NEED_RESCHED is set, the preempt_enable_notrace() called
3574 * by the function tracer will call this function again and
3575 * cause infinite recursion.
3577 * Preemption must be disabled here before the function
3578 * tracer can trace. Break up preempt_disable() into two
3579 * calls. One to disable preemption without fear of being
3580 * traced. The other to still record the preemption latency,
3581 * which can also be traced by the function tracer.
3583 preempt_disable_notrace();
3584 preempt_latency_start(1);
3586 * Needs preempt disabled in case user_exit() is traced
3587 * and the tracer calls preempt_enable_notrace() causing
3588 * an infinite recursion.
3590 prev_ctx = exception_enter();
3592 exception_exit(prev_ctx);
3594 preempt_latency_stop(1);
3595 preempt_enable_no_resched_notrace();
3596 } while (need_resched());
3598 EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
3600 #endif /* CONFIG_PREEMPT */
3603 * this is the entry point to schedule() from kernel preemption
3604 * off of irq context.
3605 * Note, that this is called and return with irqs disabled. This will
3606 * protect us against recursive calling from irq.
3608 asmlinkage __visible void __sched preempt_schedule_irq(void)
3610 enum ctx_state prev_state;
3612 /* Catch callers which need to be fixed */
3613 BUG_ON(preempt_count() || !irqs_disabled());
3615 prev_state = exception_enter();
3621 local_irq_disable();
3622 sched_preempt_enable_no_resched();
3623 } while (need_resched());
3625 exception_exit(prev_state);
3628 int default_wake_function(wait_queue_t *curr, unsigned mode, int wake_flags,
3631 return try_to_wake_up(curr->private, mode, wake_flags);
3633 EXPORT_SYMBOL(default_wake_function);
3635 #ifdef CONFIG_RT_MUTEXES
3638 * rt_mutex_setprio - set the current priority of a task
3640 * @prio: prio value (kernel-internal form)
3642 * This function changes the 'effective' priority of a task. It does
3643 * not touch ->normal_prio like __setscheduler().
3645 * Used by the rt_mutex code to implement priority inheritance
3646 * logic. Call site only calls if the priority of the task changed.
3648 void rt_mutex_setprio(struct task_struct *p, int prio)
3650 int oldprio, queued, running, queue_flag = DEQUEUE_SAVE | DEQUEUE_MOVE;
3651 const struct sched_class *prev_class;
3655 BUG_ON(prio > MAX_PRIO);
3657 rq = __task_rq_lock(p, &rf);
3658 update_rq_clock(rq);
3661 * Idle task boosting is a nono in general. There is one
3662 * exception, when PREEMPT_RT and NOHZ is active:
3664 * The idle task calls get_next_timer_interrupt() and holds
3665 * the timer wheel base->lock on the CPU and another CPU wants
3666 * to access the timer (probably to cancel it). We can safely
3667 * ignore the boosting request, as the idle CPU runs this code
3668 * with interrupts disabled and will complete the lock
3669 * protected section without being interrupted. So there is no
3670 * real need to boost.
3672 if (unlikely(p == rq->idle)) {
3673 WARN_ON(p != rq->curr);
3674 WARN_ON(p->pi_blocked_on);
3678 trace_sched_pi_setprio(p, prio);
3681 if (oldprio == prio)
3682 queue_flag &= ~DEQUEUE_MOVE;
3684 prev_class = p->sched_class;
3685 queued = task_on_rq_queued(p);
3686 running = task_current(rq, p);
3688 dequeue_task(rq, p, queue_flag);
3690 put_prev_task(rq, p);
3693 * Boosting condition are:
3694 * 1. -rt task is running and holds mutex A
3695 * --> -dl task blocks on mutex A
3697 * 2. -dl task is running and holds mutex A
3698 * --> -dl task blocks on mutex A and could preempt the
3701 if (dl_prio(prio)) {
3702 struct task_struct *pi_task = rt_mutex_get_top_task(p);
3703 if (!dl_prio(p->normal_prio) ||
3704 (pi_task && dl_entity_preempt(&pi_task->dl, &p->dl))) {
3705 p->dl.dl_boosted = 1;
3706 queue_flag |= ENQUEUE_REPLENISH;
3708 p->dl.dl_boosted = 0;
3709 p->sched_class = &dl_sched_class;
3710 } else if (rt_prio(prio)) {
3711 if (dl_prio(oldprio))
3712 p->dl.dl_boosted = 0;
3714 queue_flag |= ENQUEUE_HEAD;
3715 p->sched_class = &rt_sched_class;
3717 if (dl_prio(oldprio))
3718 p->dl.dl_boosted = 0;
3719 if (rt_prio(oldprio))
3721 p->sched_class = &fair_sched_class;
3727 enqueue_task(rq, p, queue_flag);
3729 set_curr_task(rq, p);
3731 check_class_changed(rq, p, prev_class, oldprio);
3733 preempt_disable(); /* avoid rq from going away on us */
3734 __task_rq_unlock(rq, &rf);
3736 balance_callback(rq);
3741 void set_user_nice(struct task_struct *p, long nice)
3743 bool queued, running;
3744 int old_prio, delta;
3748 if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
3751 * We have to be careful, if called from sys_setpriority(),
3752 * the task might be in the middle of scheduling on another CPU.
3754 rq = task_rq_lock(p, &rf);
3755 update_rq_clock(rq);
3758 * The RT priorities are set via sched_setscheduler(), but we still
3759 * allow the 'normal' nice value to be set - but as expected
3760 * it wont have any effect on scheduling until the task is
3761 * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
3763 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
3764 p->static_prio = NICE_TO_PRIO(nice);
3767 queued = task_on_rq_queued(p);
3768 running = task_current(rq, p);
3770 dequeue_task(rq, p, DEQUEUE_SAVE);
3772 put_prev_task(rq, p);
3774 p->static_prio = NICE_TO_PRIO(nice);
3777 p->prio = effective_prio(p);
3778 delta = p->prio - old_prio;
3781 enqueue_task(rq, p, ENQUEUE_RESTORE);
3783 * If the task increased its priority or is running and
3784 * lowered its priority, then reschedule its CPU:
3786 if (delta < 0 || (delta > 0 && task_running(rq, p)))
3790 set_curr_task(rq, p);
3792 task_rq_unlock(rq, p, &rf);
3794 EXPORT_SYMBOL(set_user_nice);
3797 * can_nice - check if a task can reduce its nice value
3801 int can_nice(const struct task_struct *p, const int nice)
3803 /* convert nice value [19,-20] to rlimit style value [1,40] */
3804 int nice_rlim = nice_to_rlimit(nice);
3806 return (nice_rlim <= task_rlimit(p, RLIMIT_NICE) ||
3807 capable(CAP_SYS_NICE));
3810 #ifdef __ARCH_WANT_SYS_NICE
3813 * sys_nice - change the priority of the current process.
3814 * @increment: priority increment
3816 * sys_setpriority is a more generic, but much slower function that
3817 * does similar things.
3819 SYSCALL_DEFINE1(nice, int, increment)
3824 * Setpriority might change our priority at the same moment.
3825 * We don't have to worry. Conceptually one call occurs first
3826 * and we have a single winner.
3828 increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH);
3829 nice = task_nice(current) + increment;
3831 nice = clamp_val(nice, MIN_NICE, MAX_NICE);
3832 if (increment < 0 && !can_nice(current, nice))
3835 retval = security_task_setnice(current, nice);
3839 set_user_nice(current, nice);
3846 * task_prio - return the priority value of a given task.
3847 * @p: the task in question.
3849 * Return: The priority value as seen by users in /proc.
3850 * RT tasks are offset by -200. Normal tasks are centered
3851 * around 0, value goes from -16 to +15.
3853 int task_prio(const struct task_struct *p)
3855 return p->prio - MAX_RT_PRIO;
3859 * idle_cpu - is a given cpu idle currently?
3860 * @cpu: the processor in question.
3862 * Return: 1 if the CPU is currently idle. 0 otherwise.
3864 int idle_cpu(int cpu)
3866 struct rq *rq = cpu_rq(cpu);
3868 if (rq->curr != rq->idle)
3875 if (!llist_empty(&rq->wake_list))
3883 * idle_task - return the idle task for a given cpu.
3884 * @cpu: the processor in question.
3886 * Return: The idle task for the cpu @cpu.
3888 struct task_struct *idle_task(int cpu)
3890 return cpu_rq(cpu)->idle;
3894 * find_process_by_pid - find a process with a matching PID value.
3895 * @pid: the pid in question.
3897 * The task of @pid, if found. %NULL otherwise.
3899 static struct task_struct *find_process_by_pid(pid_t pid)
3901 return pid ? find_task_by_vpid(pid) : current;
3905 * This function initializes the sched_dl_entity of a newly becoming
3906 * SCHED_DEADLINE task.
3908 * Only the static values are considered here, the actual runtime and the
3909 * absolute deadline will be properly calculated when the task is enqueued
3910 * for the first time with its new policy.
3913 __setparam_dl(struct task_struct *p, const struct sched_attr *attr)
3915 struct sched_dl_entity *dl_se = &p->dl;
3917 dl_se->dl_runtime = attr->sched_runtime;
3918 dl_se->dl_deadline = attr->sched_deadline;
3919 dl_se->dl_period = attr->sched_period ?: dl_se->dl_deadline;
3920 dl_se->flags = attr->sched_flags;
3921 dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime);
3924 * Changing the parameters of a task is 'tricky' and we're not doing
3925 * the correct thing -- also see task_dead_dl() and switched_from_dl().
3927 * What we SHOULD do is delay the bandwidth release until the 0-lag
3928 * point. This would include retaining the task_struct until that time
3929 * and change dl_overflow() to not immediately decrement the current
3932 * Instead we retain the current runtime/deadline and let the new
3933 * parameters take effect after the current reservation period lapses.
3934 * This is safe (albeit pessimistic) because the 0-lag point is always
3935 * before the current scheduling deadline.
3937 * We can still have temporary overloads because we do not delay the
3938 * change in bandwidth until that time; so admission control is
3939 * not on the safe side. It does however guarantee tasks will never
3940 * consume more than promised.
3945 * sched_setparam() passes in -1 for its policy, to let the functions
3946 * it calls know not to change it.
3948 #define SETPARAM_POLICY -1
3950 static void __setscheduler_params(struct task_struct *p,
3951 const struct sched_attr *attr)
3953 int policy = attr->sched_policy;
3955 if (policy == SETPARAM_POLICY)
3960 if (dl_policy(policy))
3961 __setparam_dl(p, attr);
3962 else if (fair_policy(policy))
3963 p->static_prio = NICE_TO_PRIO(attr->sched_nice);
3966 * __sched_setscheduler() ensures attr->sched_priority == 0 when
3967 * !rt_policy. Always setting this ensures that things like
3968 * getparam()/getattr() don't report silly values for !rt tasks.
3970 p->rt_priority = attr->sched_priority;
3971 p->normal_prio = normal_prio(p);
3975 /* Actually do priority change: must hold pi & rq lock. */
3976 static void __setscheduler(struct rq *rq, struct task_struct *p,
3977 const struct sched_attr *attr, bool keep_boost)
3979 __setscheduler_params(p, attr);
3982 * Keep a potential priority boosting if called from
3983 * sched_setscheduler().
3986 p->prio = rt_mutex_get_effective_prio(p, normal_prio(p));
3988 p->prio = normal_prio(p);
3990 if (dl_prio(p->prio))
3991 p->sched_class = &dl_sched_class;
3992 else if (rt_prio(p->prio))
3993 p->sched_class = &rt_sched_class;
3995 p->sched_class = &fair_sched_class;
3999 __getparam_dl(struct task_struct *p, struct sched_attr *attr)
4001 struct sched_dl_entity *dl_se = &p->dl;
4003 attr->sched_priority = p->rt_priority;
4004 attr->sched_runtime = dl_se->dl_runtime;
4005 attr->sched_deadline = dl_se->dl_deadline;
4006 attr->sched_period = dl_se->dl_period;
4007 attr->sched_flags = dl_se->flags;
4011 * This function validates the new parameters of a -deadline task.
4012 * We ask for the deadline not being zero, and greater or equal
4013 * than the runtime, as well as the period of being zero or
4014 * greater than deadline. Furthermore, we have to be sure that
4015 * user parameters are above the internal resolution of 1us (we
4016 * check sched_runtime only since it is always the smaller one) and
4017 * below 2^63 ns (we have to check both sched_deadline and
4018 * sched_period, as the latter can be zero).
4021 __checkparam_dl(const struct sched_attr *attr)
4024 if (attr->sched_deadline == 0)
4028 * Since we truncate DL_SCALE bits, make sure we're at least
4031 if (attr->sched_runtime < (1ULL << DL_SCALE))
4035 * Since we use the MSB for wrap-around and sign issues, make
4036 * sure it's not set (mind that period can be equal to zero).
4038 if (attr->sched_deadline & (1ULL << 63) ||
4039 attr->sched_period & (1ULL << 63))
4042 /* runtime <= deadline <= period (if period != 0) */
4043 if ((attr->sched_period != 0 &&
4044 attr->sched_period < attr->sched_deadline) ||
4045 attr->sched_deadline < attr->sched_runtime)
4052 * check the target process has a UID that matches the current process's
4054 static bool check_same_owner(struct task_struct *p)
4056 const struct cred *cred = current_cred(), *pcred;
4060 pcred = __task_cred(p);
4061 match = (uid_eq(cred->euid, pcred->euid) ||
4062 uid_eq(cred->euid, pcred->uid));
4067 static bool dl_param_changed(struct task_struct *p,
4068 const struct sched_attr *attr)
4070 struct sched_dl_entity *dl_se = &p->dl;
4072 if (dl_se->dl_runtime != attr->sched_runtime ||
4073 dl_se->dl_deadline != attr->sched_deadline ||
4074 dl_se->dl_period != attr->sched_period ||
4075 dl_se->flags != attr->sched_flags)
4081 static int __sched_setscheduler(struct task_struct *p,
4082 const struct sched_attr *attr,
4085 int newprio = dl_policy(attr->sched_policy) ? MAX_DL_PRIO - 1 :
4086 MAX_RT_PRIO - 1 - attr->sched_priority;
4087 int retval, oldprio, oldpolicy = -1, queued, running;
4088 int new_effective_prio, policy = attr->sched_policy;
4089 const struct sched_class *prev_class;
4092 int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE;
4095 /* may grab non-irq protected spin_locks */
4096 BUG_ON(in_interrupt());
4098 /* double check policy once rq lock held */
4100 reset_on_fork = p->sched_reset_on_fork;
4101 policy = oldpolicy = p->policy;
4103 reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK);
4105 if (!valid_policy(policy))
4109 if (attr->sched_flags & ~(SCHED_FLAG_RESET_ON_FORK))
4113 * Valid priorities for SCHED_FIFO and SCHED_RR are
4114 * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
4115 * SCHED_BATCH and SCHED_IDLE is 0.
4117 if ((p->mm && attr->sched_priority > MAX_USER_RT_PRIO-1) ||
4118 (!p->mm && attr->sched_priority > MAX_RT_PRIO-1))
4120 if ((dl_policy(policy) && !__checkparam_dl(attr)) ||
4121 (rt_policy(policy) != (attr->sched_priority != 0)))
4125 * Allow unprivileged RT tasks to decrease priority:
4127 if (user && !capable(CAP_SYS_NICE)) {
4128 if (fair_policy(policy)) {
4129 if (attr->sched_nice < task_nice(p) &&
4130 !can_nice(p, attr->sched_nice))
4134 if (rt_policy(policy)) {
4135 unsigned long rlim_rtprio =
4136 task_rlimit(p, RLIMIT_RTPRIO);
4138 /* can't set/change the rt policy */
4139 if (policy != p->policy && !rlim_rtprio)
4142 /* can't increase priority */
4143 if (attr->sched_priority > p->rt_priority &&
4144 attr->sched_priority > rlim_rtprio)
4149 * Can't set/change SCHED_DEADLINE policy at all for now
4150 * (safest behavior); in the future we would like to allow
4151 * unprivileged DL tasks to increase their relative deadline
4152 * or reduce their runtime (both ways reducing utilization)
4154 if (dl_policy(policy))
4158 * Treat SCHED_IDLE as nice 20. Only allow a switch to
4159 * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
4161 if (idle_policy(p->policy) && !idle_policy(policy)) {
4162 if (!can_nice(p, task_nice(p)))
4166 /* can't change other user's priorities */
4167 if (!check_same_owner(p))
4170 /* Normal users shall not reset the sched_reset_on_fork flag */
4171 if (p->sched_reset_on_fork && !reset_on_fork)
4176 retval = security_task_setscheduler(p);
4182 * make sure no PI-waiters arrive (or leave) while we are
4183 * changing the priority of the task:
4185 * To be able to change p->policy safely, the appropriate
4186 * runqueue lock must be held.
4188 rq = task_rq_lock(p, &rf);
4189 update_rq_clock(rq);
4192 * Changing the policy of the stop threads its a very bad idea
4194 if (p == rq->stop) {
4195 task_rq_unlock(rq, p, &rf);
4200 * If not changing anything there's no need to proceed further,
4201 * but store a possible modification of reset_on_fork.
4203 if (unlikely(policy == p->policy)) {
4204 if (fair_policy(policy) && attr->sched_nice != task_nice(p))
4206 if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
4208 if (dl_policy(policy) && dl_param_changed(p, attr))
4211 p->sched_reset_on_fork = reset_on_fork;
4212 task_rq_unlock(rq, p, &rf);
4218 #ifdef CONFIG_RT_GROUP_SCHED
4220 * Do not allow realtime tasks into groups that have no runtime
4223 if (rt_bandwidth_enabled() && rt_policy(policy) &&
4224 task_group(p)->rt_bandwidth.rt_runtime == 0 &&
4225 !task_group_is_autogroup(task_group(p))) {
4226 task_rq_unlock(rq, p, &rf);
4231 if (dl_bandwidth_enabled() && dl_policy(policy)) {
4232 cpumask_t *span = rq->rd->span;
4235 * Don't allow tasks with an affinity mask smaller than
4236 * the entire root_domain to become SCHED_DEADLINE. We
4237 * will also fail if there's no bandwidth available.
4239 if (!cpumask_subset(span, &p->cpus_allowed) ||
4240 rq->rd->dl_bw.bw == 0) {
4241 task_rq_unlock(rq, p, &rf);
4248 /* recheck policy now with rq lock held */
4249 if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
4250 policy = oldpolicy = -1;
4251 task_rq_unlock(rq, p, &rf);
4256 * If setscheduling to SCHED_DEADLINE (or changing the parameters
4257 * of a SCHED_DEADLINE task) we need to check if enough bandwidth
4260 if ((dl_policy(policy) || dl_task(p)) && dl_overflow(p, policy, attr)) {
4261 task_rq_unlock(rq, p, &rf);
4265 p->sched_reset_on_fork = reset_on_fork;
4270 * Take priority boosted tasks into account. If the new
4271 * effective priority is unchanged, we just store the new
4272 * normal parameters and do not touch the scheduler class and
4273 * the runqueue. This will be done when the task deboost
4276 new_effective_prio = rt_mutex_get_effective_prio(p, newprio);
4277 if (new_effective_prio == oldprio)
4278 queue_flags &= ~DEQUEUE_MOVE;
4281 queued = task_on_rq_queued(p);
4282 running = task_current(rq, p);
4284 dequeue_task(rq, p, queue_flags);
4286 put_prev_task(rq, p);
4288 prev_class = p->sched_class;
4289 __setscheduler(rq, p, attr, pi);
4293 * We enqueue to tail when the priority of a task is
4294 * increased (user space view).
4296 if (oldprio < p->prio)
4297 queue_flags |= ENQUEUE_HEAD;
4299 enqueue_task(rq, p, queue_flags);
4302 set_curr_task(rq, p);
4304 check_class_changed(rq, p, prev_class, oldprio);
4305 preempt_disable(); /* avoid rq from going away on us */
4306 task_rq_unlock(rq, p, &rf);
4309 rt_mutex_adjust_pi(p);
4312 * Run balance callbacks after we've adjusted the PI chain.
4314 balance_callback(rq);
4320 static int _sched_setscheduler(struct task_struct *p, int policy,
4321 const struct sched_param *param, bool check)
4323 struct sched_attr attr = {
4324 .sched_policy = policy,
4325 .sched_priority = param->sched_priority,
4326 .sched_nice = PRIO_TO_NICE(p->static_prio),
4329 /* Fixup the legacy SCHED_RESET_ON_FORK hack. */
4330 if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) {
4331 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
4332 policy &= ~SCHED_RESET_ON_FORK;
4333 attr.sched_policy = policy;
4336 return __sched_setscheduler(p, &attr, check, true);
4339 * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
4340 * @p: the task in question.
4341 * @policy: new policy.
4342 * @param: structure containing the new RT priority.
4344 * Return: 0 on success. An error code otherwise.
4346 * NOTE that the task may be already dead.
4348 int sched_setscheduler(struct task_struct *p, int policy,
4349 const struct sched_param *param)
4351 return _sched_setscheduler(p, policy, param, true);
4353 EXPORT_SYMBOL_GPL(sched_setscheduler);
4355 int sched_setattr(struct task_struct *p, const struct sched_attr *attr)
4357 return __sched_setscheduler(p, attr, true, true);
4359 EXPORT_SYMBOL_GPL(sched_setattr);
4362 * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
4363 * @p: the task in question.
4364 * @policy: new policy.
4365 * @param: structure containing the new RT priority.
4367 * Just like sched_setscheduler, only don't bother checking if the
4368 * current context has permission. For example, this is needed in
4369 * stop_machine(): we create temporary high priority worker threads,
4370 * but our caller might not have that capability.
4372 * Return: 0 on success. An error code otherwise.
4374 int sched_setscheduler_nocheck(struct task_struct *p, int policy,
4375 const struct sched_param *param)
4377 return _sched_setscheduler(p, policy, param, false);
4379 EXPORT_SYMBOL_GPL(sched_setscheduler_nocheck);
4382 do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
4384 struct sched_param lparam;
4385 struct task_struct *p;
4388 if (!param || pid < 0)
4390 if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
4395 p = find_process_by_pid(pid);
4397 retval = sched_setscheduler(p, policy, &lparam);
4404 * Mimics kernel/events/core.c perf_copy_attr().
4406 static int sched_copy_attr(struct sched_attr __user *uattr,
4407 struct sched_attr *attr)
4412 if (!access_ok(VERIFY_WRITE, uattr, SCHED_ATTR_SIZE_VER0))
4416 * zero the full structure, so that a short copy will be nice.
4418 memset(attr, 0, sizeof(*attr));
4420 ret = get_user(size, &uattr->size);
4424 if (size > PAGE_SIZE) /* silly large */
4427 if (!size) /* abi compat */
4428 size = SCHED_ATTR_SIZE_VER0;
4430 if (size < SCHED_ATTR_SIZE_VER0)
4434 * If we're handed a bigger struct than we know of,
4435 * ensure all the unknown bits are 0 - i.e. new
4436 * user-space does not rely on any kernel feature
4437 * extensions we dont know about yet.
4439 if (size > sizeof(*attr)) {
4440 unsigned char __user *addr;
4441 unsigned char __user *end;
4444 addr = (void __user *)uattr + sizeof(*attr);
4445 end = (void __user *)uattr + size;
4447 for (; addr < end; addr++) {
4448 ret = get_user(val, addr);
4454 size = sizeof(*attr);
4457 ret = copy_from_user(attr, uattr, size);
4462 * XXX: do we want to be lenient like existing syscalls; or do we want
4463 * to be strict and return an error on out-of-bounds values?
4465 attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE);
4470 put_user(sizeof(*attr), &uattr->size);
4475 * sys_sched_setscheduler - set/change the scheduler policy and RT priority
4476 * @pid: the pid in question.
4477 * @policy: new policy.
4478 * @param: structure containing the new RT priority.
4480 * Return: 0 on success. An error code otherwise.
4482 SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy,
4483 struct sched_param __user *, param)
4485 /* negative values for policy are not valid */
4489 return do_sched_setscheduler(pid, policy, param);
4493 * sys_sched_setparam - set/change the RT priority of a thread
4494 * @pid: the pid in question.
4495 * @param: structure containing the new RT priority.
4497 * Return: 0 on success. An error code otherwise.
4499 SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
4501 return do_sched_setscheduler(pid, SETPARAM_POLICY, param);
4505 * sys_sched_setattr - same as above, but with extended sched_attr
4506 * @pid: the pid in question.
4507 * @uattr: structure containing the extended parameters.
4508 * @flags: for future extension.
4510 SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
4511 unsigned int, flags)
4513 struct sched_attr attr;
4514 struct task_struct *p;
4517 if (!uattr || pid < 0 || flags)
4520 retval = sched_copy_attr(uattr, &attr);
4524 if ((int)attr.sched_policy < 0)
4529 p = find_process_by_pid(pid);
4531 retval = sched_setattr(p, &attr);
4538 * sys_sched_getscheduler - get the policy (scheduling class) of a thread
4539 * @pid: the pid in question.
4541 * Return: On success, the policy of the thread. Otherwise, a negative error
4544 SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
4546 struct task_struct *p;
4554 p = find_process_by_pid(pid);
4556 retval = security_task_getscheduler(p);
4559 | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0);
4566 * sys_sched_getparam - get the RT priority of a thread
4567 * @pid: the pid in question.
4568 * @param: structure containing the RT priority.
4570 * Return: On success, 0 and the RT priority is in @param. Otherwise, an error
4573 SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
4575 struct sched_param lp = { .sched_priority = 0 };
4576 struct task_struct *p;
4579 if (!param || pid < 0)
4583 p = find_process_by_pid(pid);
4588 retval = security_task_getscheduler(p);
4592 if (task_has_rt_policy(p))
4593 lp.sched_priority = p->rt_priority;
4597 * This one might sleep, we cannot do it with a spinlock held ...
4599 retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
4608 static int sched_read_attr(struct sched_attr __user *uattr,
4609 struct sched_attr *attr,
4614 if (!access_ok(VERIFY_WRITE, uattr, usize))
4618 * If we're handed a smaller struct than we know of,
4619 * ensure all the unknown bits are 0 - i.e. old
4620 * user-space does not get uncomplete information.
4622 if (usize < sizeof(*attr)) {
4623 unsigned char *addr;
4626 addr = (void *)attr + usize;
4627 end = (void *)attr + sizeof(*attr);
4629 for (; addr < end; addr++) {
4637 ret = copy_to_user(uattr, attr, attr->size);
4645 * sys_sched_getattr - similar to sched_getparam, but with sched_attr
4646 * @pid: the pid in question.
4647 * @uattr: structure containing the extended parameters.
4648 * @size: sizeof(attr) for fwd/bwd comp.
4649 * @flags: for future extension.
4651 SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
4652 unsigned int, size, unsigned int, flags)
4654 struct sched_attr attr = {
4655 .size = sizeof(struct sched_attr),
4657 struct task_struct *p;
4660 if (!uattr || pid < 0 || size > PAGE_SIZE ||
4661 size < SCHED_ATTR_SIZE_VER0 || flags)
4665 p = find_process_by_pid(pid);
4670 retval = security_task_getscheduler(p);
4674 attr.sched_policy = p->policy;
4675 if (p->sched_reset_on_fork)
4676 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
4677 if (task_has_dl_policy(p))
4678 __getparam_dl(p, &attr);
4679 else if (task_has_rt_policy(p))
4680 attr.sched_priority = p->rt_priority;
4682 attr.sched_nice = task_nice(p);
4686 retval = sched_read_attr(uattr, &attr, size);
4694 long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
4696 cpumask_var_t cpus_allowed, new_mask;
4697 struct task_struct *p;
4702 p = find_process_by_pid(pid);
4708 /* Prevent p going away */
4712 if (p->flags & PF_NO_SETAFFINITY) {
4716 if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
4720 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
4722 goto out_free_cpus_allowed;
4725 if (!check_same_owner(p)) {
4727 if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
4729 goto out_free_new_mask;
4734 retval = security_task_setscheduler(p);
4736 goto out_free_new_mask;
4739 cpuset_cpus_allowed(p, cpus_allowed);
4740 cpumask_and(new_mask, in_mask, cpus_allowed);
4743 * Since bandwidth control happens on root_domain basis,
4744 * if admission test is enabled, we only admit -deadline
4745 * tasks allowed to run on all the CPUs in the task's
4749 if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {
4751 if (!cpumask_subset(task_rq(p)->rd->span, new_mask)) {
4754 goto out_free_new_mask;
4760 retval = __set_cpus_allowed_ptr(p, new_mask, true);
4763 cpuset_cpus_allowed(p, cpus_allowed);
4764 if (!cpumask_subset(new_mask, cpus_allowed)) {
4766 * We must have raced with a concurrent cpuset
4767 * update. Just reset the cpus_allowed to the
4768 * cpuset's cpus_allowed
4770 cpumask_copy(new_mask, cpus_allowed);
4775 free_cpumask_var(new_mask);
4776 out_free_cpus_allowed:
4777 free_cpumask_var(cpus_allowed);
4783 static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
4784 struct cpumask *new_mask)
4786 if (len < cpumask_size())
4787 cpumask_clear(new_mask);
4788 else if (len > cpumask_size())
4789 len = cpumask_size();
4791 return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
4795 * sys_sched_setaffinity - set the cpu affinity of a process
4796 * @pid: pid of the process
4797 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4798 * @user_mask_ptr: user-space pointer to the new cpu mask
4800 * Return: 0 on success. An error code otherwise.
4802 SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
4803 unsigned long __user *, user_mask_ptr)
4805 cpumask_var_t new_mask;
4808 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
4811 retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
4813 retval = sched_setaffinity(pid, new_mask);
4814 free_cpumask_var(new_mask);
4818 long sched_getaffinity(pid_t pid, struct cpumask *mask)
4820 struct task_struct *p;
4821 unsigned long flags;
4827 p = find_process_by_pid(pid);
4831 retval = security_task_getscheduler(p);
4835 raw_spin_lock_irqsave(&p->pi_lock, flags);
4836 cpumask_and(mask, &p->cpus_allowed, cpu_active_mask);
4837 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
4846 * sys_sched_getaffinity - get the cpu affinity of a process
4847 * @pid: pid of the process
4848 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4849 * @user_mask_ptr: user-space pointer to hold the current cpu mask
4851 * Return: size of CPU mask copied to user_mask_ptr on success. An
4852 * error code otherwise.
4854 SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
4855 unsigned long __user *, user_mask_ptr)
4860 if ((len * BITS_PER_BYTE) < nr_cpu_ids)
4862 if (len & (sizeof(unsigned long)-1))
4865 if (!alloc_cpumask_var(&mask, GFP_KERNEL))
4868 ret = sched_getaffinity(pid, mask);
4870 size_t retlen = min_t(size_t, len, cpumask_size());
4872 if (copy_to_user(user_mask_ptr, mask, retlen))
4877 free_cpumask_var(mask);
4883 * sys_sched_yield - yield the current processor to other threads.
4885 * This function yields the current CPU to other tasks. If there are no
4886 * other threads running on this CPU then this function will return.
4890 SYSCALL_DEFINE0(sched_yield)
4892 struct rq *rq = this_rq_lock();
4894 schedstat_inc(rq->yld_count);
4895 current->sched_class->yield_task(rq);
4898 * Since we are going to call schedule() anyway, there's
4899 * no need to preempt or enable interrupts:
4901 __release(rq->lock);
4902 spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
4903 do_raw_spin_unlock(&rq->lock);
4904 sched_preempt_enable_no_resched();
4911 #ifndef CONFIG_PREEMPT
4912 int __sched _cond_resched(void)
4914 if (should_resched(0)) {
4915 preempt_schedule_common();
4920 EXPORT_SYMBOL(_cond_resched);
4924 * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
4925 * call schedule, and on return reacquire the lock.
4927 * This works OK both with and without CONFIG_PREEMPT. We do strange low-level
4928 * operations here to prevent schedule() from being called twice (once via
4929 * spin_unlock(), once by hand).
4931 int __cond_resched_lock(spinlock_t *lock)
4933 int resched = should_resched(PREEMPT_LOCK_OFFSET);
4936 lockdep_assert_held(lock);
4938 if (spin_needbreak(lock) || resched) {
4941 preempt_schedule_common();
4949 EXPORT_SYMBOL(__cond_resched_lock);
4951 int __sched __cond_resched_softirq(void)
4953 BUG_ON(!in_softirq());
4955 if (should_resched(SOFTIRQ_DISABLE_OFFSET)) {
4957 preempt_schedule_common();
4963 EXPORT_SYMBOL(__cond_resched_softirq);
4966 * yield - yield the current processor to other threads.
4968 * Do not ever use this function, there's a 99% chance you're doing it wrong.
4970 * The scheduler is at all times free to pick the calling task as the most
4971 * eligible task to run, if removing the yield() call from your code breaks
4972 * it, its already broken.
4974 * Typical broken usage is:
4979 * where one assumes that yield() will let 'the other' process run that will
4980 * make event true. If the current task is a SCHED_FIFO task that will never
4981 * happen. Never use yield() as a progress guarantee!!
4983 * If you want to use yield() to wait for something, use wait_event().
4984 * If you want to use yield() to be 'nice' for others, use cond_resched().
4985 * If you still want to use yield(), do not!
4987 void __sched yield(void)
4989 set_current_state(TASK_RUNNING);
4992 EXPORT_SYMBOL(yield);
4995 * yield_to - yield the current processor to another thread in
4996 * your thread group, or accelerate that thread toward the
4997 * processor it's on.
4999 * @preempt: whether task preemption is allowed or not
5001 * It's the caller's job to ensure that the target task struct
5002 * can't go away on us before we can do any checks.
5005 * true (>0) if we indeed boosted the target task.
5006 * false (0) if we failed to boost the target.
5007 * -ESRCH if there's no task to yield to.
5009 int __sched yield_to(struct task_struct *p, bool preempt)
5011 struct task_struct *curr = current;
5012 struct rq *rq, *p_rq;
5013 unsigned long flags;
5016 local_irq_save(flags);
5022 * If we're the only runnable task on the rq and target rq also
5023 * has only one task, there's absolutely no point in yielding.
5025 if (rq->nr_running == 1 && p_rq->nr_running == 1) {
5030 double_rq_lock(rq, p_rq);
5031 if (task_rq(p) != p_rq) {
5032 double_rq_unlock(rq, p_rq);
5036 if (!curr->sched_class->yield_to_task)
5039 if (curr->sched_class != p->sched_class)
5042 if (task_running(p_rq, p) || p->state)
5045 yielded = curr->sched_class->yield_to_task(rq, p, preempt);
5047 schedstat_inc(rq->yld_count);
5049 * Make p's CPU reschedule; pick_next_entity takes care of
5052 if (preempt && rq != p_rq)
5057 double_rq_unlock(rq, p_rq);
5059 local_irq_restore(flags);
5066 EXPORT_SYMBOL_GPL(yield_to);
5069 * This task is about to go to sleep on IO. Increment rq->nr_iowait so
5070 * that process accounting knows that this is a task in IO wait state.
5072 long __sched io_schedule_timeout(long timeout)
5074 int old_iowait = current->in_iowait;
5078 current->in_iowait = 1;
5079 blk_schedule_flush_plug(current);
5081 delayacct_blkio_start();
5083 atomic_inc(&rq->nr_iowait);
5084 ret = schedule_timeout(timeout);
5085 current->in_iowait = old_iowait;
5086 atomic_dec(&rq->nr_iowait);
5087 delayacct_blkio_end();
5091 EXPORT_SYMBOL(io_schedule_timeout);
5094 * sys_sched_get_priority_max - return maximum RT priority.
5095 * @policy: scheduling class.
5097 * Return: On success, this syscall returns the maximum
5098 * rt_priority that can be used by a given scheduling class.
5099 * On failure, a negative error code is returned.
5101 SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
5108 ret = MAX_USER_RT_PRIO-1;
5110 case SCHED_DEADLINE:
5121 * sys_sched_get_priority_min - return minimum RT priority.
5122 * @policy: scheduling class.
5124 * Return: On success, this syscall returns the minimum
5125 * rt_priority that can be used by a given scheduling class.
5126 * On failure, a negative error code is returned.
5128 SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
5137 case SCHED_DEADLINE:
5147 * sys_sched_rr_get_interval - return the default timeslice of a process.
5148 * @pid: pid of the process.
5149 * @interval: userspace pointer to the timeslice value.
5151 * this syscall writes the default timeslice value of a given process
5152 * into the user-space timespec buffer. A value of '0' means infinity.
5154 * Return: On success, 0 and the timeslice is in @interval. Otherwise,
5157 SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
5158 struct timespec __user *, interval)
5160 struct task_struct *p;
5161 unsigned int time_slice;
5172 p = find_process_by_pid(pid);
5176 retval = security_task_getscheduler(p);
5180 rq = task_rq_lock(p, &rf);
5182 if (p->sched_class->get_rr_interval)
5183 time_slice = p->sched_class->get_rr_interval(rq, p);
5184 task_rq_unlock(rq, p, &rf);
5187 jiffies_to_timespec(time_slice, &t);
5188 retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
5196 static const char stat_nam[] = TASK_STATE_TO_CHAR_STR;
5198 void sched_show_task(struct task_struct *p)
5200 unsigned long free = 0;
5202 unsigned long state = p->state;
5204 if (!try_get_task_stack(p))
5207 state = __ffs(state) + 1;
5208 printk(KERN_INFO "%-15.15s %c", p->comm,
5209 state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?');
5210 if (state == TASK_RUNNING)
5211 printk(KERN_CONT " running task ");
5212 #ifdef CONFIG_DEBUG_STACK_USAGE
5213 free = stack_not_used(p);
5218 ppid = task_pid_nr(rcu_dereference(p->real_parent));
5220 printk(KERN_CONT "%5lu %5d %6d 0x%08lx\n", free,
5221 task_pid_nr(p), ppid,
5222 (unsigned long)task_thread_info(p)->flags);
5224 print_worker_info(KERN_INFO, p);
5225 show_stack(p, NULL);
5229 void show_state_filter(unsigned long state_filter)
5231 struct task_struct *g, *p;
5233 #if BITS_PER_LONG == 32
5235 " task PC stack pid father\n");
5238 " task PC stack pid father\n");
5241 for_each_process_thread(g, p) {
5243 * reset the NMI-timeout, listing all files on a slow
5244 * console might take a lot of time:
5245 * Also, reset softlockup watchdogs on all CPUs, because
5246 * another CPU might be blocked waiting for us to process
5249 touch_nmi_watchdog();
5250 touch_all_softlockup_watchdogs();
5251 if (!state_filter || (p->state & state_filter))
5255 #ifdef CONFIG_SCHED_DEBUG
5257 sysrq_sched_debug_show();
5261 * Only show locks if all tasks are dumped:
5264 debug_show_all_locks();
5267 void init_idle_bootup_task(struct task_struct *idle)
5269 idle->sched_class = &idle_sched_class;
5273 * init_idle - set up an idle thread for a given CPU
5274 * @idle: task in question
5275 * @cpu: cpu the idle task belongs to
5277 * NOTE: this function does not set the idle thread's NEED_RESCHED
5278 * flag, to make booting more robust.
5280 void init_idle(struct task_struct *idle, int cpu)
5282 struct rq *rq = cpu_rq(cpu);
5283 unsigned long flags;
5285 raw_spin_lock_irqsave(&idle->pi_lock, flags);
5286 raw_spin_lock(&rq->lock);
5288 __sched_fork(0, idle);
5289 idle->state = TASK_RUNNING;
5290 idle->se.exec_start = sched_clock();
5291 idle->flags |= PF_IDLE;
5293 kasan_unpoison_task_stack(idle);
5297 * Its possible that init_idle() gets called multiple times on a task,
5298 * in that case do_set_cpus_allowed() will not do the right thing.
5300 * And since this is boot we can forgo the serialization.
5302 set_cpus_allowed_common(idle, cpumask_of(cpu));
5305 * We're having a chicken and egg problem, even though we are
5306 * holding rq->lock, the cpu isn't yet set to this cpu so the
5307 * lockdep check in task_group() will fail.
5309 * Similar case to sched_fork(). / Alternatively we could
5310 * use task_rq_lock() here and obtain the other rq->lock.
5315 __set_task_cpu(idle, cpu);
5318 rq->curr = rq->idle = idle;
5319 idle->on_rq = TASK_ON_RQ_QUEUED;
5323 raw_spin_unlock(&rq->lock);
5324 raw_spin_unlock_irqrestore(&idle->pi_lock, flags);
5326 /* Set the preempt count _outside_ the spinlocks! */
5327 init_idle_preempt_count(idle, cpu);
5330 * The idle tasks have their own, simple scheduling class:
5332 idle->sched_class = &idle_sched_class;
5333 ftrace_graph_init_idle_task(idle, cpu);
5334 vtime_init_idle(idle, cpu);
5336 sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu);
5340 int cpuset_cpumask_can_shrink(const struct cpumask *cur,
5341 const struct cpumask *trial)
5343 int ret = 1, trial_cpus;
5344 struct dl_bw *cur_dl_b;
5345 unsigned long flags;
5347 if (!cpumask_weight(cur))
5350 rcu_read_lock_sched();
5351 cur_dl_b = dl_bw_of(cpumask_any(cur));
5352 trial_cpus = cpumask_weight(trial);
5354 raw_spin_lock_irqsave(&cur_dl_b->lock, flags);
5355 if (cur_dl_b->bw != -1 &&
5356 cur_dl_b->bw * trial_cpus < cur_dl_b->total_bw)
5358 raw_spin_unlock_irqrestore(&cur_dl_b->lock, flags);
5359 rcu_read_unlock_sched();
5364 int task_can_attach(struct task_struct *p,
5365 const struct cpumask *cs_cpus_allowed)
5370 * Kthreads which disallow setaffinity shouldn't be moved
5371 * to a new cpuset; we don't want to change their cpu
5372 * affinity and isolating such threads by their set of
5373 * allowed nodes is unnecessary. Thus, cpusets are not
5374 * applicable for such threads. This prevents checking for
5375 * success of set_cpus_allowed_ptr() on all attached tasks
5376 * before cpus_allowed may be changed.
5378 if (p->flags & PF_NO_SETAFFINITY) {
5384 if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span,
5386 unsigned int dest_cpu = cpumask_any_and(cpu_active_mask,
5391 unsigned long flags;
5393 rcu_read_lock_sched();
5394 dl_b = dl_bw_of(dest_cpu);
5395 raw_spin_lock_irqsave(&dl_b->lock, flags);
5396 cpus = dl_bw_cpus(dest_cpu);
5397 overflow = __dl_overflow(dl_b, cpus, 0, p->dl.dl_bw);
5402 * We reserve space for this task in the destination
5403 * root_domain, as we can't fail after this point.
5404 * We will free resources in the source root_domain
5405 * later on (see set_cpus_allowed_dl()).
5407 __dl_add(dl_b, p->dl.dl_bw);
5409 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
5410 rcu_read_unlock_sched();
5420 static bool sched_smp_initialized __read_mostly;
5422 #ifdef CONFIG_NUMA_BALANCING
5423 /* Migrate current task p to target_cpu */
5424 int migrate_task_to(struct task_struct *p, int target_cpu)
5426 struct migration_arg arg = { p, target_cpu };
5427 int curr_cpu = task_cpu(p);
5429 if (curr_cpu == target_cpu)
5432 if (!cpumask_test_cpu(target_cpu, tsk_cpus_allowed(p)))
5435 /* TODO: This is not properly updating schedstats */
5437 trace_sched_move_numa(p, curr_cpu, target_cpu);
5438 return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);
5442 * Requeue a task on a given node and accurately track the number of NUMA
5443 * tasks on the runqueues
5445 void sched_setnuma(struct task_struct *p, int nid)
5447 bool queued, running;
5451 rq = task_rq_lock(p, &rf);
5452 queued = task_on_rq_queued(p);
5453 running = task_current(rq, p);
5456 dequeue_task(rq, p, DEQUEUE_SAVE);
5458 put_prev_task(rq, p);
5460 p->numa_preferred_nid = nid;
5463 enqueue_task(rq, p, ENQUEUE_RESTORE);
5465 set_curr_task(rq, p);
5466 task_rq_unlock(rq, p, &rf);
5468 #endif /* CONFIG_NUMA_BALANCING */
5470 #ifdef CONFIG_HOTPLUG_CPU
5472 * Ensures that the idle task is using init_mm right before its cpu goes
5475 void idle_task_exit(void)
5477 struct mm_struct *mm = current->active_mm;
5479 BUG_ON(cpu_online(smp_processor_id()));
5481 if (mm != &init_mm) {
5482 switch_mm_irqs_off(mm, &init_mm, current);
5483 finish_arch_post_lock_switch();
5489 * Since this CPU is going 'away' for a while, fold any nr_active delta
5490 * we might have. Assumes we're called after migrate_tasks() so that the
5491 * nr_active count is stable. We need to take the teardown thread which
5492 * is calling this into account, so we hand in adjust = 1 to the load
5495 * Also see the comment "Global load-average calculations".
5497 static void calc_load_migrate(struct rq *rq)
5499 long delta = calc_load_fold_active(rq, 1);
5501 atomic_long_add(delta, &calc_load_tasks);
5504 static void put_prev_task_fake(struct rq *rq, struct task_struct *prev)
5508 static const struct sched_class fake_sched_class = {
5509 .put_prev_task = put_prev_task_fake,
5512 static struct task_struct fake_task = {
5514 * Avoid pull_{rt,dl}_task()
5516 .prio = MAX_PRIO + 1,
5517 .sched_class = &fake_sched_class,
5521 * Migrate all tasks from the rq, sleeping tasks will be migrated by
5522 * try_to_wake_up()->select_task_rq().
5524 * Called with rq->lock held even though we'er in stop_machine() and
5525 * there's no concurrency possible, we hold the required locks anyway
5526 * because of lock validation efforts.
5528 static void migrate_tasks(struct rq *dead_rq)
5530 struct rq *rq = dead_rq;
5531 struct task_struct *next, *stop = rq->stop;
5536 * Fudge the rq selection such that the below task selection loop
5537 * doesn't get stuck on the currently eligible stop task.
5539 * We're currently inside stop_machine() and the rq is either stuck
5540 * in the stop_machine_cpu_stop() loop, or we're executing this code,
5541 * either way we should never end up calling schedule() until we're
5547 * put_prev_task() and pick_next_task() sched
5548 * class method both need to have an up-to-date
5549 * value of rq->clock[_task]
5551 update_rq_clock(rq);
5555 * There's this thread running, bail when that's the only
5558 if (rq->nr_running == 1)
5562 * pick_next_task assumes pinned rq->lock.
5564 rq_pin_lock(rq, &rf);
5565 next = pick_next_task(rq, &fake_task, &rf);
5567 next->sched_class->put_prev_task(rq, next);
5570 * Rules for changing task_struct::cpus_allowed are holding
5571 * both pi_lock and rq->lock, such that holding either
5572 * stabilizes the mask.
5574 * Drop rq->lock is not quite as disastrous as it usually is
5575 * because !cpu_active at this point, which means load-balance
5576 * will not interfere. Also, stop-machine.
5578 rq_unpin_lock(rq, &rf);
5579 raw_spin_unlock(&rq->lock);
5580 raw_spin_lock(&next->pi_lock);
5581 raw_spin_lock(&rq->lock);
5584 * Since we're inside stop-machine, _nothing_ should have
5585 * changed the task, WARN if weird stuff happened, because in
5586 * that case the above rq->lock drop is a fail too.
5588 if (WARN_ON(task_rq(next) != rq || !task_on_rq_queued(next))) {
5589 raw_spin_unlock(&next->pi_lock);
5593 /* Find suitable destination for @next, with force if needed. */
5594 dest_cpu = select_fallback_rq(dead_rq->cpu, next);
5596 rq = __migrate_task(rq, next, dest_cpu);
5597 if (rq != dead_rq) {
5598 raw_spin_unlock(&rq->lock);
5600 raw_spin_lock(&rq->lock);
5602 raw_spin_unlock(&next->pi_lock);
5607 #endif /* CONFIG_HOTPLUG_CPU */
5609 static void set_rq_online(struct rq *rq)
5612 const struct sched_class *class;
5614 cpumask_set_cpu(rq->cpu, rq->rd->online);
5617 for_each_class(class) {
5618 if (class->rq_online)
5619 class->rq_online(rq);
5624 static void set_rq_offline(struct rq *rq)
5627 const struct sched_class *class;
5629 for_each_class(class) {
5630 if (class->rq_offline)
5631 class->rq_offline(rq);
5634 cpumask_clear_cpu(rq->cpu, rq->rd->online);
5639 static void set_cpu_rq_start_time(unsigned int cpu)
5641 struct rq *rq = cpu_rq(cpu);
5643 rq->age_stamp = sched_clock_cpu(cpu);
5646 static cpumask_var_t sched_domains_tmpmask; /* sched_domains_mutex */
5648 #ifdef CONFIG_SCHED_DEBUG
5650 static __read_mostly int sched_debug_enabled;
5652 static int __init sched_debug_setup(char *str)
5654 sched_debug_enabled = 1;
5658 early_param("sched_debug", sched_debug_setup);
5660 static inline bool sched_debug(void)
5662 return sched_debug_enabled;
5665 static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,
5666 struct cpumask *groupmask)
5668 struct sched_group *group = sd->groups;
5670 cpumask_clear(groupmask);
5672 printk(KERN_DEBUG "%*s domain %d: ", level, "", level);
5674 if (!(sd->flags & SD_LOAD_BALANCE)) {
5675 printk("does not load-balance\n");
5677 printk(KERN_ERR "ERROR: !SD_LOAD_BALANCE domain"
5682 printk(KERN_CONT "span %*pbl level %s\n",
5683 cpumask_pr_args(sched_domain_span(sd)), sd->name);
5685 if (!cpumask_test_cpu(cpu, sched_domain_span(sd))) {
5686 printk(KERN_ERR "ERROR: domain->span does not contain "
5689 if (!cpumask_test_cpu(cpu, sched_group_cpus(group))) {
5690 printk(KERN_ERR "ERROR: domain->groups does not contain"
5694 printk(KERN_DEBUG "%*s groups:", level + 1, "");
5698 printk(KERN_ERR "ERROR: group is NULL\n");
5702 if (!cpumask_weight(sched_group_cpus(group))) {
5703 printk(KERN_CONT "\n");
5704 printk(KERN_ERR "ERROR: empty group\n");
5708 if (!(sd->flags & SD_OVERLAP) &&
5709 cpumask_intersects(groupmask, sched_group_cpus(group))) {
5710 printk(KERN_CONT "\n");
5711 printk(KERN_ERR "ERROR: repeated CPUs\n");
5715 cpumask_or(groupmask, groupmask, sched_group_cpus(group));
5717 printk(KERN_CONT " %*pbl",
5718 cpumask_pr_args(sched_group_cpus(group)));
5719 if (group->sgc->capacity != SCHED_CAPACITY_SCALE) {
5720 printk(KERN_CONT " (cpu_capacity = %lu)",
5721 group->sgc->capacity);
5724 group = group->next;
5725 } while (group != sd->groups);
5726 printk(KERN_CONT "\n");
5728 if (!cpumask_equal(sched_domain_span(sd), groupmask))
5729 printk(KERN_ERR "ERROR: groups don't span domain->span\n");
5732 !cpumask_subset(groupmask, sched_domain_span(sd->parent)))
5733 printk(KERN_ERR "ERROR: parent span is not a superset "
5734 "of domain->span\n");
5738 static void sched_domain_debug(struct sched_domain *sd, int cpu)
5742 if (!sched_debug_enabled)
5746 printk(KERN_DEBUG "CPU%d attaching NULL sched-domain.\n", cpu);
5750 printk(KERN_DEBUG "CPU%d attaching sched-domain:\n", cpu);
5753 if (sched_domain_debug_one(sd, cpu, level, sched_domains_tmpmask))
5761 #else /* !CONFIG_SCHED_DEBUG */
5763 # define sched_debug_enabled 0
5764 # define sched_domain_debug(sd, cpu) do { } while (0)
5765 static inline bool sched_debug(void)
5769 #endif /* CONFIG_SCHED_DEBUG */
5771 static int sd_degenerate(struct sched_domain *sd)
5773 if (cpumask_weight(sched_domain_span(sd)) == 1)
5776 /* Following flags need at least 2 groups */
5777 if (sd->flags & (SD_LOAD_BALANCE |
5778 SD_BALANCE_NEWIDLE |
5781 SD_SHARE_CPUCAPACITY |
5782 SD_ASYM_CPUCAPACITY |
5783 SD_SHARE_PKG_RESOURCES |
5784 SD_SHARE_POWERDOMAIN)) {
5785 if (sd->groups != sd->groups->next)
5789 /* Following flags don't use groups */
5790 if (sd->flags & (SD_WAKE_AFFINE))
5797 sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
5799 unsigned long cflags = sd->flags, pflags = parent->flags;
5801 if (sd_degenerate(parent))
5804 if (!cpumask_equal(sched_domain_span(sd), sched_domain_span(parent)))
5807 /* Flags needing groups don't count if only 1 group in parent */
5808 if (parent->groups == parent->groups->next) {
5809 pflags &= ~(SD_LOAD_BALANCE |
5810 SD_BALANCE_NEWIDLE |
5813 SD_ASYM_CPUCAPACITY |
5814 SD_SHARE_CPUCAPACITY |
5815 SD_SHARE_PKG_RESOURCES |
5817 SD_SHARE_POWERDOMAIN);
5818 if (nr_node_ids == 1)
5819 pflags &= ~SD_SERIALIZE;
5821 if (~cflags & pflags)
5827 static void free_rootdomain(struct rcu_head *rcu)
5829 struct root_domain *rd = container_of(rcu, struct root_domain, rcu);
5831 cpupri_cleanup(&rd->cpupri);
5832 cpudl_cleanup(&rd->cpudl);
5833 free_cpumask_var(rd->dlo_mask);
5834 free_cpumask_var(rd->rto_mask);
5835 free_cpumask_var(rd->online);
5836 free_cpumask_var(rd->span);
5840 static void rq_attach_root(struct rq *rq, struct root_domain *rd)
5842 struct root_domain *old_rd = NULL;
5843 unsigned long flags;
5845 raw_spin_lock_irqsave(&rq->lock, flags);
5850 if (cpumask_test_cpu(rq->cpu, old_rd->online))
5853 cpumask_clear_cpu(rq->cpu, old_rd->span);
5856 * If we dont want to free the old_rd yet then
5857 * set old_rd to NULL to skip the freeing later
5860 if (!atomic_dec_and_test(&old_rd->refcount))
5864 atomic_inc(&rd->refcount);
5867 cpumask_set_cpu(rq->cpu, rd->span);
5868 if (cpumask_test_cpu(rq->cpu, cpu_active_mask))
5871 raw_spin_unlock_irqrestore(&rq->lock, flags);
5874 call_rcu_sched(&old_rd->rcu, free_rootdomain);
5877 static int init_rootdomain(struct root_domain *rd)
5879 memset(rd, 0, sizeof(*rd));
5881 if (!zalloc_cpumask_var(&rd->span, GFP_KERNEL))
5883 if (!zalloc_cpumask_var(&rd->online, GFP_KERNEL))
5885 if (!zalloc_cpumask_var(&rd->dlo_mask, GFP_KERNEL))
5887 if (!zalloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))
5890 init_dl_bw(&rd->dl_bw);
5891 if (cpudl_init(&rd->cpudl) != 0)
5894 if (cpupri_init(&rd->cpupri) != 0)
5899 free_cpumask_var(rd->rto_mask);
5901 free_cpumask_var(rd->dlo_mask);
5903 free_cpumask_var(rd->online);
5905 free_cpumask_var(rd->span);
5911 * By default the system creates a single root-domain with all cpus as
5912 * members (mimicking the global state we have today).
5914 struct root_domain def_root_domain;
5916 static void init_defrootdomain(void)
5918 init_rootdomain(&def_root_domain);
5920 atomic_set(&def_root_domain.refcount, 1);
5923 static struct root_domain *alloc_rootdomain(void)
5925 struct root_domain *rd;
5927 rd = kmalloc(sizeof(*rd), GFP_KERNEL);
5931 if (init_rootdomain(rd) != 0) {
5939 static void free_sched_groups(struct sched_group *sg, int free_sgc)
5941 struct sched_group *tmp, *first;
5950 if (free_sgc && atomic_dec_and_test(&sg->sgc->ref))
5955 } while (sg != first);
5958 static void destroy_sched_domain(struct sched_domain *sd)
5961 * If its an overlapping domain it has private groups, iterate and
5964 if (sd->flags & SD_OVERLAP) {
5965 free_sched_groups(sd->groups, 1);
5966 } else if (atomic_dec_and_test(&sd->groups->ref)) {
5967 kfree(sd->groups->sgc);
5970 if (sd->shared && atomic_dec_and_test(&sd->shared->ref))
5975 static void destroy_sched_domains_rcu(struct rcu_head *rcu)
5977 struct sched_domain *sd = container_of(rcu, struct sched_domain, rcu);
5980 struct sched_domain *parent = sd->parent;
5981 destroy_sched_domain(sd);
5986 static void destroy_sched_domains(struct sched_domain *sd)
5989 call_rcu(&sd->rcu, destroy_sched_domains_rcu);
5993 * Keep a special pointer to the highest sched_domain that has
5994 * SD_SHARE_PKG_RESOURCE set (Last Level Cache Domain) for this
5995 * allows us to avoid some pointer chasing select_idle_sibling().
5997 * Also keep a unique ID per domain (we use the first cpu number in
5998 * the cpumask of the domain), this allows us to quickly tell if
5999 * two cpus are in the same cache domain, see cpus_share_cache().
6001 DEFINE_PER_CPU(struct sched_domain *, sd_llc);
6002 DEFINE_PER_CPU(int, sd_llc_size);
6003 DEFINE_PER_CPU(int, sd_llc_id);
6004 DEFINE_PER_CPU(struct sched_domain_shared *, sd_llc_shared);
6005 DEFINE_PER_CPU(struct sched_domain *, sd_numa);
6006 DEFINE_PER_CPU(struct sched_domain *, sd_asym);
6008 static void update_top_cache_domain(int cpu)
6010 struct sched_domain_shared *sds = NULL;
6011 struct sched_domain *sd;
6015 sd = highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES);
6017 id = cpumask_first(sched_domain_span(sd));
6018 size = cpumask_weight(sched_domain_span(sd));
6022 rcu_assign_pointer(per_cpu(sd_llc, cpu), sd);
6023 per_cpu(sd_llc_size, cpu) = size;
6024 per_cpu(sd_llc_id, cpu) = id;
6025 rcu_assign_pointer(per_cpu(sd_llc_shared, cpu), sds);
6027 sd = lowest_flag_domain(cpu, SD_NUMA);
6028 rcu_assign_pointer(per_cpu(sd_numa, cpu), sd);
6030 sd = highest_flag_domain(cpu, SD_ASYM_PACKING);
6031 rcu_assign_pointer(per_cpu(sd_asym, cpu), sd);
6035 * Attach the domain 'sd' to 'cpu' as its base domain. Callers must
6036 * hold the hotplug lock.
6039 cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
6041 struct rq *rq = cpu_rq(cpu);
6042 struct sched_domain *tmp;
6044 /* Remove the sched domains which do not contribute to scheduling. */
6045 for (tmp = sd; tmp; ) {
6046 struct sched_domain *parent = tmp->parent;
6050 if (sd_parent_degenerate(tmp, parent)) {
6051 tmp->parent = parent->parent;
6053 parent->parent->child = tmp;
6055 * Transfer SD_PREFER_SIBLING down in case of a
6056 * degenerate parent; the spans match for this
6057 * so the property transfers.
6059 if (parent->flags & SD_PREFER_SIBLING)
6060 tmp->flags |= SD_PREFER_SIBLING;
6061 destroy_sched_domain(parent);
6066 if (sd && sd_degenerate(sd)) {
6069 destroy_sched_domain(tmp);
6074 sched_domain_debug(sd, cpu);
6076 rq_attach_root(rq, rd);
6078 rcu_assign_pointer(rq->sd, sd);
6079 destroy_sched_domains(tmp);
6081 update_top_cache_domain(cpu);
6084 /* Setup the mask of cpus configured for isolated domains */
6085 static int __init isolated_cpu_setup(char *str)
6089 alloc_bootmem_cpumask_var(&cpu_isolated_map);
6090 ret = cpulist_parse(str, cpu_isolated_map);
6092 pr_err("sched: Error, all isolcpus= values must be between 0 and %d\n", nr_cpu_ids);
6097 __setup("isolcpus=", isolated_cpu_setup);
6100 struct sched_domain ** __percpu sd;
6101 struct root_domain *rd;
6112 * Build an iteration mask that can exclude certain CPUs from the upwards
6115 * Asymmetric node setups can result in situations where the domain tree is of
6116 * unequal depth, make sure to skip domains that already cover the entire
6119 * In that case build_sched_domains() will have terminated the iteration early
6120 * and our sibling sd spans will be empty. Domains should always include the
6121 * cpu they're built on, so check that.
6124 static void build_group_mask(struct sched_domain *sd, struct sched_group *sg)
6126 const struct cpumask *span = sched_domain_span(sd);
6127 struct sd_data *sdd = sd->private;
6128 struct sched_domain *sibling;
6131 for_each_cpu(i, span) {
6132 sibling = *per_cpu_ptr(sdd->sd, i);
6133 if (!cpumask_test_cpu(i, sched_domain_span(sibling)))
6136 cpumask_set_cpu(i, sched_group_mask(sg));
6141 * Return the canonical balance cpu for this group, this is the first cpu
6142 * of this group that's also in the iteration mask.
6144 int group_balance_cpu(struct sched_group *sg)
6146 return cpumask_first_and(sched_group_cpus(sg), sched_group_mask(sg));
6150 build_overlap_sched_groups(struct sched_domain *sd, int cpu)
6152 struct sched_group *first = NULL, *last = NULL, *groups = NULL, *sg;
6153 const struct cpumask *span = sched_domain_span(sd);
6154 struct cpumask *covered = sched_domains_tmpmask;
6155 struct sd_data *sdd = sd->private;
6156 struct sched_domain *sibling;
6159 cpumask_clear(covered);
6161 for_each_cpu(i, span) {
6162 struct cpumask *sg_span;
6164 if (cpumask_test_cpu(i, covered))
6167 sibling = *per_cpu_ptr(sdd->sd, i);
6169 /* See the comment near build_group_mask(). */
6170 if (!cpumask_test_cpu(i, sched_domain_span(sibling)))
6173 sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(),
6174 GFP_KERNEL, cpu_to_node(cpu));
6179 sg_span = sched_group_cpus(sg);
6181 cpumask_copy(sg_span, sched_domain_span(sibling->child));
6183 cpumask_set_cpu(i, sg_span);
6185 cpumask_or(covered, covered, sg_span);
6187 sg->sgc = *per_cpu_ptr(sdd->sgc, i);
6188 if (atomic_inc_return(&sg->sgc->ref) == 1)
6189 build_group_mask(sd, sg);
6192 * Initialize sgc->capacity such that even if we mess up the
6193 * domains and no possible iteration will get us here, we won't
6196 sg->sgc->capacity = SCHED_CAPACITY_SCALE * cpumask_weight(sg_span);
6197 sg->sgc->min_capacity = SCHED_CAPACITY_SCALE;
6200 * Make sure the first group of this domain contains the
6201 * canonical balance cpu. Otherwise the sched_domain iteration
6202 * breaks. See update_sg_lb_stats().
6204 if ((!groups && cpumask_test_cpu(cpu, sg_span)) ||
6205 group_balance_cpu(sg) == cpu)
6215 sd->groups = groups;
6220 free_sched_groups(first, 0);
6225 static int get_group(int cpu, struct sd_data *sdd, struct sched_group **sg)
6227 struct sched_domain *sd = *per_cpu_ptr(sdd->sd, cpu);
6228 struct sched_domain *child = sd->child;
6231 cpu = cpumask_first(sched_domain_span(child));
6234 *sg = *per_cpu_ptr(sdd->sg, cpu);
6235 (*sg)->sgc = *per_cpu_ptr(sdd->sgc, cpu);
6236 atomic_set(&(*sg)->sgc->ref, 1); /* for claim_allocations */
6243 * build_sched_groups will build a circular linked list of the groups
6244 * covered by the given span, and will set each group's ->cpumask correctly,
6245 * and ->cpu_capacity to 0.
6247 * Assumes the sched_domain tree is fully constructed
6250 build_sched_groups(struct sched_domain *sd, int cpu)
6252 struct sched_group *first = NULL, *last = NULL;
6253 struct sd_data *sdd = sd->private;
6254 const struct cpumask *span = sched_domain_span(sd);
6255 struct cpumask *covered;
6258 get_group(cpu, sdd, &sd->groups);
6259 atomic_inc(&sd->groups->ref);
6261 if (cpu != cpumask_first(span))
6264 lockdep_assert_held(&sched_domains_mutex);
6265 covered = sched_domains_tmpmask;
6267 cpumask_clear(covered);
6269 for_each_cpu(i, span) {
6270 struct sched_group *sg;
6273 if (cpumask_test_cpu(i, covered))
6276 group = get_group(i, sdd, &sg);
6277 cpumask_setall(sched_group_mask(sg));
6279 for_each_cpu(j, span) {
6280 if (get_group(j, sdd, NULL) != group)
6283 cpumask_set_cpu(j, covered);
6284 cpumask_set_cpu(j, sched_group_cpus(sg));
6299 * Initialize sched groups cpu_capacity.
6301 * cpu_capacity indicates the capacity of sched group, which is used while
6302 * distributing the load between different sched groups in a sched domain.
6303 * Typically cpu_capacity for all the groups in a sched domain will be same
6304 * unless there are asymmetries in the topology. If there are asymmetries,
6305 * group having more cpu_capacity will pickup more load compared to the
6306 * group having less cpu_capacity.
6308 static void init_sched_groups_capacity(int cpu, struct sched_domain *sd)
6310 struct sched_group *sg = sd->groups;
6315 int cpu, max_cpu = -1;
6317 sg->group_weight = cpumask_weight(sched_group_cpus(sg));
6319 if (!(sd->flags & SD_ASYM_PACKING))
6322 for_each_cpu(cpu, sched_group_cpus(sg)) {
6325 else if (sched_asym_prefer(cpu, max_cpu))
6328 sg->asym_prefer_cpu = max_cpu;
6332 } while (sg != sd->groups);
6334 if (cpu != group_balance_cpu(sg))
6337 update_group_capacity(sd, cpu);
6341 * Initializers for schedule domains
6342 * Non-inlined to reduce accumulated stack pressure in build_sched_domains()
6345 static int default_relax_domain_level = -1;
6346 int sched_domain_level_max;
6348 static int __init setup_relax_domain_level(char *str)
6350 if (kstrtoint(str, 0, &default_relax_domain_level))
6351 pr_warn("Unable to set relax_domain_level\n");
6355 __setup("relax_domain_level=", setup_relax_domain_level);
6357 static void set_domain_attribute(struct sched_domain *sd,
6358 struct sched_domain_attr *attr)
6362 if (!attr || attr->relax_domain_level < 0) {
6363 if (default_relax_domain_level < 0)
6366 request = default_relax_domain_level;
6368 request = attr->relax_domain_level;
6369 if (request < sd->level) {
6370 /* turn off idle balance on this domain */
6371 sd->flags &= ~(SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
6373 /* turn on idle balance on this domain */
6374 sd->flags |= (SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
6378 static void __sdt_free(const struct cpumask *cpu_map);
6379 static int __sdt_alloc(const struct cpumask *cpu_map);
6381 static void __free_domain_allocs(struct s_data *d, enum s_alloc what,
6382 const struct cpumask *cpu_map)
6386 if (!atomic_read(&d->rd->refcount))
6387 free_rootdomain(&d->rd->rcu); /* fall through */
6389 free_percpu(d->sd); /* fall through */
6391 __sdt_free(cpu_map); /* fall through */
6397 static enum s_alloc __visit_domain_allocation_hell(struct s_data *d,
6398 const struct cpumask *cpu_map)
6400 memset(d, 0, sizeof(*d));
6402 if (__sdt_alloc(cpu_map))
6403 return sa_sd_storage;
6404 d->sd = alloc_percpu(struct sched_domain *);
6406 return sa_sd_storage;
6407 d->rd = alloc_rootdomain();
6410 return sa_rootdomain;
6414 * NULL the sd_data elements we've used to build the sched_domain and
6415 * sched_group structure so that the subsequent __free_domain_allocs()
6416 * will not free the data we're using.
6418 static void claim_allocations(int cpu, struct sched_domain *sd)
6420 struct sd_data *sdd = sd->private;
6422 WARN_ON_ONCE(*per_cpu_ptr(sdd->sd, cpu) != sd);
6423 *per_cpu_ptr(sdd->sd, cpu) = NULL;
6425 if (atomic_read(&(*per_cpu_ptr(sdd->sds, cpu))->ref))
6426 *per_cpu_ptr(sdd->sds, cpu) = NULL;
6428 if (atomic_read(&(*per_cpu_ptr(sdd->sg, cpu))->ref))
6429 *per_cpu_ptr(sdd->sg, cpu) = NULL;
6431 if (atomic_read(&(*per_cpu_ptr(sdd->sgc, cpu))->ref))
6432 *per_cpu_ptr(sdd->sgc, cpu) = NULL;
6436 static int sched_domains_numa_levels;
6437 enum numa_topology_type sched_numa_topology_type;
6438 static int *sched_domains_numa_distance;
6439 int sched_max_numa_distance;
6440 static struct cpumask ***sched_domains_numa_masks;
6441 static int sched_domains_curr_level;
6445 * SD_flags allowed in topology descriptions.
6447 * These flags are purely descriptive of the topology and do not prescribe
6448 * behaviour. Behaviour is artificial and mapped in the below sd_init()
6451 * SD_SHARE_CPUCAPACITY - describes SMT topologies
6452 * SD_SHARE_PKG_RESOURCES - describes shared caches
6453 * SD_NUMA - describes NUMA topologies
6454 * SD_SHARE_POWERDOMAIN - describes shared power domain
6455 * SD_ASYM_CPUCAPACITY - describes mixed capacity topologies
6457 * Odd one out, which beside describing the topology has a quirk also
6458 * prescribes the desired behaviour that goes along with it:
6460 * SD_ASYM_PACKING - describes SMT quirks
6462 #define TOPOLOGY_SD_FLAGS \
6463 (SD_SHARE_CPUCAPACITY | \
6464 SD_SHARE_PKG_RESOURCES | \
6467 SD_ASYM_CPUCAPACITY | \
6468 SD_SHARE_POWERDOMAIN)
6470 static struct sched_domain *
6471 sd_init(struct sched_domain_topology_level *tl,
6472 const struct cpumask *cpu_map,
6473 struct sched_domain *child, int cpu)
6475 struct sd_data *sdd = &tl->data;
6476 struct sched_domain *sd = *per_cpu_ptr(sdd->sd, cpu);
6477 int sd_id, sd_weight, sd_flags = 0;
6481 * Ugly hack to pass state to sd_numa_mask()...
6483 sched_domains_curr_level = tl->numa_level;
6486 sd_weight = cpumask_weight(tl->mask(cpu));
6489 sd_flags = (*tl->sd_flags)();
6490 if (WARN_ONCE(sd_flags & ~TOPOLOGY_SD_FLAGS,
6491 "wrong sd_flags in topology description\n"))
6492 sd_flags &= ~TOPOLOGY_SD_FLAGS;
6494 *sd = (struct sched_domain){
6495 .min_interval = sd_weight,
6496 .max_interval = 2*sd_weight,
6498 .imbalance_pct = 125,
6500 .cache_nice_tries = 0,
6507 .flags = 1*SD_LOAD_BALANCE
6508 | 1*SD_BALANCE_NEWIDLE
6513 | 0*SD_SHARE_CPUCAPACITY
6514 | 0*SD_SHARE_PKG_RESOURCES
6516 | 0*SD_PREFER_SIBLING
6521 .last_balance = jiffies,
6522 .balance_interval = sd_weight,
6524 .max_newidle_lb_cost = 0,
6525 .next_decay_max_lb_cost = jiffies,
6527 #ifdef CONFIG_SCHED_DEBUG
6532 cpumask_and(sched_domain_span(sd), cpu_map, tl->mask(cpu));
6533 sd_id = cpumask_first(sched_domain_span(sd));
6536 * Convert topological properties into behaviour.
6539 if (sd->flags & SD_ASYM_CPUCAPACITY) {
6540 struct sched_domain *t = sd;
6542 for_each_lower_domain(t)
6543 t->flags |= SD_BALANCE_WAKE;
6546 if (sd->flags & SD_SHARE_CPUCAPACITY) {
6547 sd->flags |= SD_PREFER_SIBLING;
6548 sd->imbalance_pct = 110;
6549 sd->smt_gain = 1178; /* ~15% */
6551 } else if (sd->flags & SD_SHARE_PKG_RESOURCES) {
6552 sd->imbalance_pct = 117;
6553 sd->cache_nice_tries = 1;
6557 } else if (sd->flags & SD_NUMA) {
6558 sd->cache_nice_tries = 2;
6562 sd->flags |= SD_SERIALIZE;
6563 if (sched_domains_numa_distance[tl->numa_level] > RECLAIM_DISTANCE) {
6564 sd->flags &= ~(SD_BALANCE_EXEC |
6571 sd->flags |= SD_PREFER_SIBLING;
6572 sd->cache_nice_tries = 1;
6578 * For all levels sharing cache; connect a sched_domain_shared
6581 if (sd->flags & SD_SHARE_PKG_RESOURCES) {
6582 sd->shared = *per_cpu_ptr(sdd->sds, sd_id);
6583 atomic_inc(&sd->shared->ref);
6584 atomic_set(&sd->shared->nr_busy_cpus, sd_weight);
6593 * Topology list, bottom-up.
6595 static struct sched_domain_topology_level default_topology[] = {
6596 #ifdef CONFIG_SCHED_SMT
6597 { cpu_smt_mask, cpu_smt_flags, SD_INIT_NAME(SMT) },
6599 #ifdef CONFIG_SCHED_MC
6600 { cpu_coregroup_mask, cpu_core_flags, SD_INIT_NAME(MC) },
6602 { cpu_cpu_mask, SD_INIT_NAME(DIE) },
6606 static struct sched_domain_topology_level *sched_domain_topology =
6609 #define for_each_sd_topology(tl) \
6610 for (tl = sched_domain_topology; tl->mask; tl++)
6612 void set_sched_topology(struct sched_domain_topology_level *tl)
6614 if (WARN_ON_ONCE(sched_smp_initialized))
6617 sched_domain_topology = tl;
6622 static const struct cpumask *sd_numa_mask(int cpu)
6624 return sched_domains_numa_masks[sched_domains_curr_level][cpu_to_node(cpu)];
6627 static void sched_numa_warn(const char *str)
6629 static int done = false;
6637 printk(KERN_WARNING "ERROR: %s\n\n", str);
6639 for (i = 0; i < nr_node_ids; i++) {
6640 printk(KERN_WARNING " ");
6641 for (j = 0; j < nr_node_ids; j++)
6642 printk(KERN_CONT "%02d ", node_distance(i,j));
6643 printk(KERN_CONT "\n");
6645 printk(KERN_WARNING "\n");
6648 bool find_numa_distance(int distance)
6652 if (distance == node_distance(0, 0))
6655 for (i = 0; i < sched_domains_numa_levels; i++) {
6656 if (sched_domains_numa_distance[i] == distance)
6664 * A system can have three types of NUMA topology:
6665 * NUMA_DIRECT: all nodes are directly connected, or not a NUMA system
6666 * NUMA_GLUELESS_MESH: some nodes reachable through intermediary nodes
6667 * NUMA_BACKPLANE: nodes can reach other nodes through a backplane
6669 * The difference between a glueless mesh topology and a backplane
6670 * topology lies in whether communication between not directly
6671 * connected nodes goes through intermediary nodes (where programs
6672 * could run), or through backplane controllers. This affects
6673 * placement of programs.
6675 * The type of topology can be discerned with the following tests:
6676 * - If the maximum distance between any nodes is 1 hop, the system
6677 * is directly connected.
6678 * - If for two nodes A and B, located N > 1 hops away from each other,
6679 * there is an intermediary node C, which is < N hops away from both
6680 * nodes A and B, the system is a glueless mesh.
6682 static void init_numa_topology_type(void)
6686 n = sched_max_numa_distance;
6688 if (sched_domains_numa_levels <= 1) {
6689 sched_numa_topology_type = NUMA_DIRECT;
6693 for_each_online_node(a) {
6694 for_each_online_node(b) {
6695 /* Find two nodes furthest removed from each other. */
6696 if (node_distance(a, b) < n)
6699 /* Is there an intermediary node between a and b? */
6700 for_each_online_node(c) {
6701 if (node_distance(a, c) < n &&
6702 node_distance(b, c) < n) {
6703 sched_numa_topology_type =
6709 sched_numa_topology_type = NUMA_BACKPLANE;
6715 static void sched_init_numa(void)
6717 int next_distance, curr_distance = node_distance(0, 0);
6718 struct sched_domain_topology_level *tl;
6722 sched_domains_numa_distance = kzalloc(sizeof(int) * nr_node_ids, GFP_KERNEL);
6723 if (!sched_domains_numa_distance)
6727 * O(nr_nodes^2) deduplicating selection sort -- in order to find the
6728 * unique distances in the node_distance() table.
6730 * Assumes node_distance(0,j) includes all distances in
6731 * node_distance(i,j) in order to avoid cubic time.
6733 next_distance = curr_distance;
6734 for (i = 0; i < nr_node_ids; i++) {
6735 for (j = 0; j < nr_node_ids; j++) {
6736 for (k = 0; k < nr_node_ids; k++) {
6737 int distance = node_distance(i, k);
6739 if (distance > curr_distance &&
6740 (distance < next_distance ||
6741 next_distance == curr_distance))
6742 next_distance = distance;
6745 * While not a strong assumption it would be nice to know
6746 * about cases where if node A is connected to B, B is not
6747 * equally connected to A.
6749 if (sched_debug() && node_distance(k, i) != distance)
6750 sched_numa_warn("Node-distance not symmetric");
6752 if (sched_debug() && i && !find_numa_distance(distance))
6753 sched_numa_warn("Node-0 not representative");
6755 if (next_distance != curr_distance) {
6756 sched_domains_numa_distance[level++] = next_distance;
6757 sched_domains_numa_levels = level;
6758 curr_distance = next_distance;
6763 * In case of sched_debug() we verify the above assumption.
6773 * 'level' contains the number of unique distances, excluding the
6774 * identity distance node_distance(i,i).
6776 * The sched_domains_numa_distance[] array includes the actual distance
6781 * Here, we should temporarily reset sched_domains_numa_levels to 0.
6782 * If it fails to allocate memory for array sched_domains_numa_masks[][],
6783 * the array will contain less then 'level' members. This could be
6784 * dangerous when we use it to iterate array sched_domains_numa_masks[][]
6785 * in other functions.
6787 * We reset it to 'level' at the end of this function.
6789 sched_domains_numa_levels = 0;
6791 sched_domains_numa_masks = kzalloc(sizeof(void *) * level, GFP_KERNEL);
6792 if (!sched_domains_numa_masks)
6796 * Now for each level, construct a mask per node which contains all
6797 * cpus of nodes that are that many hops away from us.
6799 for (i = 0; i < level; i++) {
6800 sched_domains_numa_masks[i] =
6801 kzalloc(nr_node_ids * sizeof(void *), GFP_KERNEL);
6802 if (!sched_domains_numa_masks[i])
6805 for (j = 0; j < nr_node_ids; j++) {
6806 struct cpumask *mask = kzalloc(cpumask_size(), GFP_KERNEL);
6810 sched_domains_numa_masks[i][j] = mask;
6813 if (node_distance(j, k) > sched_domains_numa_distance[i])
6816 cpumask_or(mask, mask, cpumask_of_node(k));
6821 /* Compute default topology size */
6822 for (i = 0; sched_domain_topology[i].mask; i++);
6824 tl = kzalloc((i + level + 1) *
6825 sizeof(struct sched_domain_topology_level), GFP_KERNEL);
6830 * Copy the default topology bits..
6832 for (i = 0; sched_domain_topology[i].mask; i++)
6833 tl[i] = sched_domain_topology[i];
6836 * .. and append 'j' levels of NUMA goodness.
6838 for (j = 0; j < level; i++, j++) {
6839 tl[i] = (struct sched_domain_topology_level){
6840 .mask = sd_numa_mask,
6841 .sd_flags = cpu_numa_flags,
6842 .flags = SDTL_OVERLAP,
6848 sched_domain_topology = tl;
6850 sched_domains_numa_levels = level;
6851 sched_max_numa_distance = sched_domains_numa_distance[level - 1];
6853 init_numa_topology_type();
6856 static void sched_domains_numa_masks_set(unsigned int cpu)
6858 int node = cpu_to_node(cpu);
6861 for (i = 0; i < sched_domains_numa_levels; i++) {
6862 for (j = 0; j < nr_node_ids; j++) {
6863 if (node_distance(j, node) <= sched_domains_numa_distance[i])
6864 cpumask_set_cpu(cpu, sched_domains_numa_masks[i][j]);
6869 static void sched_domains_numa_masks_clear(unsigned int cpu)
6873 for (i = 0; i < sched_domains_numa_levels; i++) {
6874 for (j = 0; j < nr_node_ids; j++)
6875 cpumask_clear_cpu(cpu, sched_domains_numa_masks[i][j]);
6880 static inline void sched_init_numa(void) { }
6881 static void sched_domains_numa_masks_set(unsigned int cpu) { }
6882 static void sched_domains_numa_masks_clear(unsigned int cpu) { }
6883 #endif /* CONFIG_NUMA */
6885 static int __sdt_alloc(const struct cpumask *cpu_map)
6887 struct sched_domain_topology_level *tl;
6890 for_each_sd_topology(tl) {
6891 struct sd_data *sdd = &tl->data;
6893 sdd->sd = alloc_percpu(struct sched_domain *);
6897 sdd->sds = alloc_percpu(struct sched_domain_shared *);
6901 sdd->sg = alloc_percpu(struct sched_group *);
6905 sdd->sgc = alloc_percpu(struct sched_group_capacity *);
6909 for_each_cpu(j, cpu_map) {
6910 struct sched_domain *sd;
6911 struct sched_domain_shared *sds;
6912 struct sched_group *sg;
6913 struct sched_group_capacity *sgc;
6915 sd = kzalloc_node(sizeof(struct sched_domain) + cpumask_size(),
6916 GFP_KERNEL, cpu_to_node(j));
6920 *per_cpu_ptr(sdd->sd, j) = sd;
6922 sds = kzalloc_node(sizeof(struct sched_domain_shared),
6923 GFP_KERNEL, cpu_to_node(j));
6927 *per_cpu_ptr(sdd->sds, j) = sds;
6929 sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(),
6930 GFP_KERNEL, cpu_to_node(j));
6936 *per_cpu_ptr(sdd->sg, j) = sg;
6938 sgc = kzalloc_node(sizeof(struct sched_group_capacity) + cpumask_size(),
6939 GFP_KERNEL, cpu_to_node(j));
6943 *per_cpu_ptr(sdd->sgc, j) = sgc;
6950 static void __sdt_free(const struct cpumask *cpu_map)
6952 struct sched_domain_topology_level *tl;
6955 for_each_sd_topology(tl) {
6956 struct sd_data *sdd = &tl->data;
6958 for_each_cpu(j, cpu_map) {
6959 struct sched_domain *sd;
6962 sd = *per_cpu_ptr(sdd->sd, j);
6963 if (sd && (sd->flags & SD_OVERLAP))
6964 free_sched_groups(sd->groups, 0);
6965 kfree(*per_cpu_ptr(sdd->sd, j));
6969 kfree(*per_cpu_ptr(sdd->sds, j));
6971 kfree(*per_cpu_ptr(sdd->sg, j));
6973 kfree(*per_cpu_ptr(sdd->sgc, j));
6975 free_percpu(sdd->sd);
6977 free_percpu(sdd->sds);
6979 free_percpu(sdd->sg);
6981 free_percpu(sdd->sgc);
6986 struct sched_domain *build_sched_domain(struct sched_domain_topology_level *tl,
6987 const struct cpumask *cpu_map, struct sched_domain_attr *attr,
6988 struct sched_domain *child, int cpu)
6990 struct sched_domain *sd = sd_init(tl, cpu_map, child, cpu);
6993 sd->level = child->level + 1;
6994 sched_domain_level_max = max(sched_domain_level_max, sd->level);
6997 if (!cpumask_subset(sched_domain_span(child),
6998 sched_domain_span(sd))) {
6999 pr_err("BUG: arch topology borken\n");
7000 #ifdef CONFIG_SCHED_DEBUG
7001 pr_err(" the %s domain not a subset of the %s domain\n",
7002 child->name, sd->name);
7004 /* Fixup, ensure @sd has at least @child cpus. */
7005 cpumask_or(sched_domain_span(sd),
7006 sched_domain_span(sd),
7007 sched_domain_span(child));
7011 set_domain_attribute(sd, attr);
7017 * Build sched domains for a given set of cpus and attach the sched domains
7018 * to the individual cpus
7020 static int build_sched_domains(const struct cpumask *cpu_map,
7021 struct sched_domain_attr *attr)
7023 enum s_alloc alloc_state;
7024 struct sched_domain *sd;
7026 struct rq *rq = NULL;
7027 int i, ret = -ENOMEM;
7029 alloc_state = __visit_domain_allocation_hell(&d, cpu_map);
7030 if (alloc_state != sa_rootdomain)
7033 /* Set up domains for cpus specified by the cpu_map. */
7034 for_each_cpu(i, cpu_map) {
7035 struct sched_domain_topology_level *tl;
7038 for_each_sd_topology(tl) {
7039 sd = build_sched_domain(tl, cpu_map, attr, sd, i);
7040 if (tl == sched_domain_topology)
7041 *per_cpu_ptr(d.sd, i) = sd;
7042 if (tl->flags & SDTL_OVERLAP || sched_feat(FORCE_SD_OVERLAP))
7043 sd->flags |= SD_OVERLAP;
7044 if (cpumask_equal(cpu_map, sched_domain_span(sd)))
7049 /* Build the groups for the domains */
7050 for_each_cpu(i, cpu_map) {
7051 for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
7052 sd->span_weight = cpumask_weight(sched_domain_span(sd));
7053 if (sd->flags & SD_OVERLAP) {
7054 if (build_overlap_sched_groups(sd, i))
7057 if (build_sched_groups(sd, i))
7063 /* Calculate CPU capacity for physical packages and nodes */
7064 for (i = nr_cpumask_bits-1; i >= 0; i--) {
7065 if (!cpumask_test_cpu(i, cpu_map))
7068 for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
7069 claim_allocations(i, sd);
7070 init_sched_groups_capacity(i, sd);
7074 /* Attach the domains */
7076 for_each_cpu(i, cpu_map) {
7078 sd = *per_cpu_ptr(d.sd, i);
7080 /* Use READ_ONCE()/WRITE_ONCE() to avoid load/store tearing: */
7081 if (rq->cpu_capacity_orig > READ_ONCE(d.rd->max_cpu_capacity))
7082 WRITE_ONCE(d.rd->max_cpu_capacity, rq->cpu_capacity_orig);
7084 cpu_attach_domain(sd, d.rd, i);
7088 if (rq && sched_debug_enabled) {
7089 pr_info("span: %*pbl (max cpu_capacity = %lu)\n",
7090 cpumask_pr_args(cpu_map), rq->rd->max_cpu_capacity);
7095 __free_domain_allocs(&d, alloc_state, cpu_map);
7099 static cpumask_var_t *doms_cur; /* current sched domains */
7100 static int ndoms_cur; /* number of sched domains in 'doms_cur' */
7101 static struct sched_domain_attr *dattr_cur;
7102 /* attribues of custom domains in 'doms_cur' */
7105 * Special case: If a kmalloc of a doms_cur partition (array of
7106 * cpumask) fails, then fallback to a single sched domain,
7107 * as determined by the single cpumask fallback_doms.
7109 static cpumask_var_t fallback_doms;
7112 * arch_update_cpu_topology lets virtualized architectures update the
7113 * cpu core maps. It is supposed to return 1 if the topology changed
7114 * or 0 if it stayed the same.
7116 int __weak arch_update_cpu_topology(void)
7121 cpumask_var_t *alloc_sched_domains(unsigned int ndoms)
7124 cpumask_var_t *doms;
7126 doms = kmalloc(sizeof(*doms) * ndoms, GFP_KERNEL);
7129 for (i = 0; i < ndoms; i++) {
7130 if (!alloc_cpumask_var(&doms[i], GFP_KERNEL)) {
7131 free_sched_domains(doms, i);
7138 void free_sched_domains(cpumask_var_t doms[], unsigned int ndoms)
7141 for (i = 0; i < ndoms; i++)
7142 free_cpumask_var(doms[i]);
7147 * Set up scheduler domains and groups. Callers must hold the hotplug lock.
7148 * For now this just excludes isolated cpus, but could be used to
7149 * exclude other special cases in the future.
7151 static int init_sched_domains(const struct cpumask *cpu_map)
7155 arch_update_cpu_topology();
7157 doms_cur = alloc_sched_domains(ndoms_cur);
7159 doms_cur = &fallback_doms;
7160 cpumask_andnot(doms_cur[0], cpu_map, cpu_isolated_map);
7161 err = build_sched_domains(doms_cur[0], NULL);
7162 register_sched_domain_sysctl();
7168 * Detach sched domains from a group of cpus specified in cpu_map
7169 * These cpus will now be attached to the NULL domain
7171 static void detach_destroy_domains(const struct cpumask *cpu_map)
7176 for_each_cpu(i, cpu_map)
7177 cpu_attach_domain(NULL, &def_root_domain, i);
7181 /* handle null as "default" */
7182 static int dattrs_equal(struct sched_domain_attr *cur, int idx_cur,
7183 struct sched_domain_attr *new, int idx_new)
7185 struct sched_domain_attr tmp;
7192 return !memcmp(cur ? (cur + idx_cur) : &tmp,
7193 new ? (new + idx_new) : &tmp,
7194 sizeof(struct sched_domain_attr));
7198 * Partition sched domains as specified by the 'ndoms_new'
7199 * cpumasks in the array doms_new[] of cpumasks. This compares
7200 * doms_new[] to the current sched domain partitioning, doms_cur[].
7201 * It destroys each deleted domain and builds each new domain.
7203 * 'doms_new' is an array of cpumask_var_t's of length 'ndoms_new'.
7204 * The masks don't intersect (don't overlap.) We should setup one
7205 * sched domain for each mask. CPUs not in any of the cpumasks will
7206 * not be load balanced. If the same cpumask appears both in the
7207 * current 'doms_cur' domains and in the new 'doms_new', we can leave
7210 * The passed in 'doms_new' should be allocated using
7211 * alloc_sched_domains. This routine takes ownership of it and will
7212 * free_sched_domains it when done with it. If the caller failed the
7213 * alloc call, then it can pass in doms_new == NULL && ndoms_new == 1,
7214 * and partition_sched_domains() will fallback to the single partition
7215 * 'fallback_doms', it also forces the domains to be rebuilt.
7217 * If doms_new == NULL it will be replaced with cpu_online_mask.
7218 * ndoms_new == 0 is a special case for destroying existing domains,
7219 * and it will not create the default domain.
7221 * Call with hotplug lock held
7223 void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
7224 struct sched_domain_attr *dattr_new)
7229 mutex_lock(&sched_domains_mutex);
7231 /* always unregister in case we don't destroy any domains */
7232 unregister_sched_domain_sysctl();
7234 /* Let architecture update cpu core mappings. */
7235 new_topology = arch_update_cpu_topology();
7237 n = doms_new ? ndoms_new : 0;
7239 /* Destroy deleted domains */
7240 for (i = 0; i < ndoms_cur; i++) {
7241 for (j = 0; j < n && !new_topology; j++) {
7242 if (cpumask_equal(doms_cur[i], doms_new[j])
7243 && dattrs_equal(dattr_cur, i, dattr_new, j))
7246 /* no match - a current sched domain not in new doms_new[] */
7247 detach_destroy_domains(doms_cur[i]);
7253 if (doms_new == NULL) {
7255 doms_new = &fallback_doms;
7256 cpumask_andnot(doms_new[0], cpu_active_mask, cpu_isolated_map);
7257 WARN_ON_ONCE(dattr_new);
7260 /* Build new domains */
7261 for (i = 0; i < ndoms_new; i++) {
7262 for (j = 0; j < n && !new_topology; j++) {
7263 if (cpumask_equal(doms_new[i], doms_cur[j])
7264 && dattrs_equal(dattr_new, i, dattr_cur, j))
7267 /* no match - add a new doms_new */
7268 build_sched_domains(doms_new[i], dattr_new ? dattr_new + i : NULL);
7273 /* Remember the new sched domains */
7274 if (doms_cur != &fallback_doms)
7275 free_sched_domains(doms_cur, ndoms_cur);
7276 kfree(dattr_cur); /* kfree(NULL) is safe */
7277 doms_cur = doms_new;
7278 dattr_cur = dattr_new;
7279 ndoms_cur = ndoms_new;
7281 register_sched_domain_sysctl();
7283 mutex_unlock(&sched_domains_mutex);
7286 static int num_cpus_frozen; /* used to mark begin/end of suspend/resume */
7289 * Update cpusets according to cpu_active mask. If cpusets are
7290 * disabled, cpuset_update_active_cpus() becomes a simple wrapper
7291 * around partition_sched_domains().
7293 * If we come here as part of a suspend/resume, don't touch cpusets because we
7294 * want to restore it back to its original state upon resume anyway.
7296 static void cpuset_cpu_active(void)
7298 if (cpuhp_tasks_frozen) {
7300 * num_cpus_frozen tracks how many CPUs are involved in suspend
7301 * resume sequence. As long as this is not the last online
7302 * operation in the resume sequence, just build a single sched
7303 * domain, ignoring cpusets.
7306 if (likely(num_cpus_frozen)) {
7307 partition_sched_domains(1, NULL, NULL);
7311 * This is the last CPU online operation. So fall through and
7312 * restore the original sched domains by considering the
7313 * cpuset configurations.
7316 cpuset_update_active_cpus(true);
7319 static int cpuset_cpu_inactive(unsigned int cpu)
7321 unsigned long flags;
7326 if (!cpuhp_tasks_frozen) {
7327 rcu_read_lock_sched();
7328 dl_b = dl_bw_of(cpu);
7330 raw_spin_lock_irqsave(&dl_b->lock, flags);
7331 cpus = dl_bw_cpus(cpu);
7332 overflow = __dl_overflow(dl_b, cpus, 0, 0);
7333 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
7335 rcu_read_unlock_sched();
7339 cpuset_update_active_cpus(false);
7342 partition_sched_domains(1, NULL, NULL);
7347 int sched_cpu_activate(unsigned int cpu)
7349 struct rq *rq = cpu_rq(cpu);
7350 unsigned long flags;
7352 set_cpu_active(cpu, true);
7354 if (sched_smp_initialized) {
7355 sched_domains_numa_masks_set(cpu);
7356 cpuset_cpu_active();
7360 * Put the rq online, if not already. This happens:
7362 * 1) In the early boot process, because we build the real domains
7363 * after all cpus have been brought up.
7365 * 2) At runtime, if cpuset_cpu_active() fails to rebuild the
7368 raw_spin_lock_irqsave(&rq->lock, flags);
7370 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
7373 raw_spin_unlock_irqrestore(&rq->lock, flags);
7375 update_max_interval();
7380 int sched_cpu_deactivate(unsigned int cpu)
7384 set_cpu_active(cpu, false);
7386 * We've cleared cpu_active_mask, wait for all preempt-disabled and RCU
7387 * users of this state to go away such that all new such users will
7390 * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
7391 * not imply sync_sched(), so wait for both.
7393 * Do sync before park smpboot threads to take care the rcu boost case.
7395 if (IS_ENABLED(CONFIG_PREEMPT))
7396 synchronize_rcu_mult(call_rcu, call_rcu_sched);
7400 if (!sched_smp_initialized)
7403 ret = cpuset_cpu_inactive(cpu);
7405 set_cpu_active(cpu, true);
7408 sched_domains_numa_masks_clear(cpu);
7412 static void sched_rq_cpu_starting(unsigned int cpu)
7414 struct rq *rq = cpu_rq(cpu);
7416 rq->calc_load_update = calc_load_update;
7417 update_max_interval();
7420 int sched_cpu_starting(unsigned int cpu)
7422 set_cpu_rq_start_time(cpu);
7423 sched_rq_cpu_starting(cpu);
7427 #ifdef CONFIG_HOTPLUG_CPU
7428 int sched_cpu_dying(unsigned int cpu)
7430 struct rq *rq = cpu_rq(cpu);
7431 unsigned long flags;
7433 /* Handle pending wakeups and then migrate everything off */
7434 sched_ttwu_pending();
7435 raw_spin_lock_irqsave(&rq->lock, flags);
7437 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
7441 BUG_ON(rq->nr_running != 1);
7442 raw_spin_unlock_irqrestore(&rq->lock, flags);
7443 calc_load_migrate(rq);
7444 update_max_interval();
7445 nohz_balance_exit_idle(cpu);
7451 #ifdef CONFIG_SCHED_SMT
7452 DEFINE_STATIC_KEY_FALSE(sched_smt_present);
7454 static void sched_init_smt(void)
7457 * We've enumerated all CPUs and will assume that if any CPU
7458 * has SMT siblings, CPU0 will too.
7460 if (cpumask_weight(cpu_smt_mask(0)) > 1)
7461 static_branch_enable(&sched_smt_present);
7464 static inline void sched_init_smt(void) { }
7467 void __init sched_init_smp(void)
7469 cpumask_var_t non_isolated_cpus;
7471 alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL);
7472 alloc_cpumask_var(&fallback_doms, GFP_KERNEL);
7477 * There's no userspace yet to cause hotplug operations; hence all the
7478 * cpu masks are stable and all blatant races in the below code cannot
7481 mutex_lock(&sched_domains_mutex);
7482 init_sched_domains(cpu_active_mask);
7483 cpumask_andnot(non_isolated_cpus, cpu_possible_mask, cpu_isolated_map);
7484 if (cpumask_empty(non_isolated_cpus))
7485 cpumask_set_cpu(smp_processor_id(), non_isolated_cpus);
7486 mutex_unlock(&sched_domains_mutex);
7488 /* Move init over to a non-isolated CPU */
7489 if (set_cpus_allowed_ptr(current, non_isolated_cpus) < 0)
7491 sched_init_granularity();
7492 free_cpumask_var(non_isolated_cpus);
7494 init_sched_rt_class();
7495 init_sched_dl_class();
7499 sched_smp_initialized = true;
7502 static int __init migration_init(void)
7504 sched_rq_cpu_starting(smp_processor_id());
7507 early_initcall(migration_init);
7510 void __init sched_init_smp(void)
7512 sched_init_granularity();
7514 #endif /* CONFIG_SMP */
7516 int in_sched_functions(unsigned long addr)
7518 return in_lock_functions(addr) ||
7519 (addr >= (unsigned long)__sched_text_start
7520 && addr < (unsigned long)__sched_text_end);
7523 #ifdef CONFIG_CGROUP_SCHED
7525 * Default task group.
7526 * Every task in system belongs to this group at bootup.
7528 struct task_group root_task_group;
7529 LIST_HEAD(task_groups);
7531 /* Cacheline aligned slab cache for task_group */
7532 static struct kmem_cache *task_group_cache __read_mostly;
7535 DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
7536 DECLARE_PER_CPU(cpumask_var_t, select_idle_mask);
7538 #define WAIT_TABLE_BITS 8
7539 #define WAIT_TABLE_SIZE (1 << WAIT_TABLE_BITS)
7540 static wait_queue_head_t bit_wait_table[WAIT_TABLE_SIZE] __cacheline_aligned;
7542 wait_queue_head_t *bit_waitqueue(void *word, int bit)
7544 const int shift = BITS_PER_LONG == 32 ? 5 : 6;
7545 unsigned long val = (unsigned long)word << shift | bit;
7547 return bit_wait_table + hash_long(val, WAIT_TABLE_BITS);
7549 EXPORT_SYMBOL(bit_waitqueue);
7551 void __init sched_init(void)
7554 unsigned long alloc_size = 0, ptr;
7556 for (i = 0; i < WAIT_TABLE_SIZE; i++)
7557 init_waitqueue_head(bit_wait_table + i);
7559 #ifdef CONFIG_FAIR_GROUP_SCHED
7560 alloc_size += 2 * nr_cpu_ids * sizeof(void **);
7562 #ifdef CONFIG_RT_GROUP_SCHED
7563 alloc_size += 2 * nr_cpu_ids * sizeof(void **);
7566 ptr = (unsigned long)kzalloc(alloc_size, GFP_NOWAIT);
7568 #ifdef CONFIG_FAIR_GROUP_SCHED
7569 root_task_group.se = (struct sched_entity **)ptr;
7570 ptr += nr_cpu_ids * sizeof(void **);
7572 root_task_group.cfs_rq = (struct cfs_rq **)ptr;
7573 ptr += nr_cpu_ids * sizeof(void **);
7575 #endif /* CONFIG_FAIR_GROUP_SCHED */
7576 #ifdef CONFIG_RT_GROUP_SCHED
7577 root_task_group.rt_se = (struct sched_rt_entity **)ptr;
7578 ptr += nr_cpu_ids * sizeof(void **);
7580 root_task_group.rt_rq = (struct rt_rq **)ptr;
7581 ptr += nr_cpu_ids * sizeof(void **);
7583 #endif /* CONFIG_RT_GROUP_SCHED */
7585 #ifdef CONFIG_CPUMASK_OFFSTACK
7586 for_each_possible_cpu(i) {
7587 per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
7588 cpumask_size(), GFP_KERNEL, cpu_to_node(i));
7589 per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node(
7590 cpumask_size(), GFP_KERNEL, cpu_to_node(i));
7592 #endif /* CONFIG_CPUMASK_OFFSTACK */
7594 init_rt_bandwidth(&def_rt_bandwidth,
7595 global_rt_period(), global_rt_runtime());
7596 init_dl_bandwidth(&def_dl_bandwidth,
7597 global_rt_period(), global_rt_runtime());
7600 init_defrootdomain();
7603 #ifdef CONFIG_RT_GROUP_SCHED
7604 init_rt_bandwidth(&root_task_group.rt_bandwidth,
7605 global_rt_period(), global_rt_runtime());
7606 #endif /* CONFIG_RT_GROUP_SCHED */
7608 #ifdef CONFIG_CGROUP_SCHED
7609 task_group_cache = KMEM_CACHE(task_group, 0);
7611 list_add(&root_task_group.list, &task_groups);
7612 INIT_LIST_HEAD(&root_task_group.children);
7613 INIT_LIST_HEAD(&root_task_group.siblings);
7614 autogroup_init(&init_task);
7615 #endif /* CONFIG_CGROUP_SCHED */
7617 for_each_possible_cpu(i) {
7621 raw_spin_lock_init(&rq->lock);
7623 rq->calc_load_active = 0;
7624 rq->calc_load_update = jiffies + LOAD_FREQ;
7625 init_cfs_rq(&rq->cfs);
7626 init_rt_rq(&rq->rt);
7627 init_dl_rq(&rq->dl);
7628 #ifdef CONFIG_FAIR_GROUP_SCHED
7629 root_task_group.shares = ROOT_TASK_GROUP_LOAD;
7630 INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
7631 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
7633 * How much cpu bandwidth does root_task_group get?
7635 * In case of task-groups formed thr' the cgroup filesystem, it
7636 * gets 100% of the cpu resources in the system. This overall
7637 * system cpu resource is divided among the tasks of
7638 * root_task_group and its child task-groups in a fair manner,
7639 * based on each entity's (task or task-group's) weight
7640 * (se->load.weight).
7642 * In other words, if root_task_group has 10 tasks of weight
7643 * 1024) and two child groups A0 and A1 (of weight 1024 each),
7644 * then A0's share of the cpu resource is:
7646 * A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
7648 * We achieve this by letting root_task_group's tasks sit
7649 * directly in rq->cfs (i.e root_task_group->se[] = NULL).
7651 init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
7652 init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
7653 #endif /* CONFIG_FAIR_GROUP_SCHED */
7655 rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;
7656 #ifdef CONFIG_RT_GROUP_SCHED
7657 init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL);
7660 for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
7661 rq->cpu_load[j] = 0;
7666 rq->cpu_capacity = rq->cpu_capacity_orig = SCHED_CAPACITY_SCALE;
7667 rq->balance_callback = NULL;
7668 rq->active_balance = 0;
7669 rq->next_balance = jiffies;
7674 rq->avg_idle = 2*sysctl_sched_migration_cost;
7675 rq->max_idle_balance_cost = sysctl_sched_migration_cost;
7677 INIT_LIST_HEAD(&rq->cfs_tasks);
7679 rq_attach_root(rq, &def_root_domain);
7680 #ifdef CONFIG_NO_HZ_COMMON
7681 rq->last_load_update_tick = jiffies;
7684 #ifdef CONFIG_NO_HZ_FULL
7685 rq->last_sched_tick = 0;
7687 #endif /* CONFIG_SMP */
7689 atomic_set(&rq->nr_iowait, 0);
7692 set_load_weight(&init_task);
7695 * The boot idle thread does lazy MMU switching as well:
7697 atomic_inc(&init_mm.mm_count);
7698 enter_lazy_tlb(&init_mm, current);
7701 * Make us the idle thread. Technically, schedule() should not be
7702 * called from this thread, however somewhere below it might be,
7703 * but because we are the idle thread, we just pick up running again
7704 * when this runqueue becomes "idle".
7706 init_idle(current, smp_processor_id());
7708 calc_load_update = jiffies + LOAD_FREQ;
7711 zalloc_cpumask_var(&sched_domains_tmpmask, GFP_NOWAIT);
7712 /* May be allocated at isolcpus cmdline parse time */
7713 if (cpu_isolated_map == NULL)
7714 zalloc_cpumask_var(&cpu_isolated_map, GFP_NOWAIT);
7715 idle_thread_set_boot_cpu();
7716 set_cpu_rq_start_time(smp_processor_id());
7718 init_sched_fair_class();
7722 scheduler_running = 1;
7725 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
7726 static inline int preempt_count_equals(int preempt_offset)
7728 int nested = preempt_count() + rcu_preempt_depth();
7730 return (nested == preempt_offset);
7733 void __might_sleep(const char *file, int line, int preempt_offset)
7736 * Blocking primitives will set (and therefore destroy) current->state,
7737 * since we will exit with TASK_RUNNING make sure we enter with it,
7738 * otherwise we will destroy state.
7740 WARN_ONCE(current->state != TASK_RUNNING && current->task_state_change,
7741 "do not call blocking ops when !TASK_RUNNING; "
7742 "state=%lx set at [<%p>] %pS\n",
7744 (void *)current->task_state_change,
7745 (void *)current->task_state_change);
7747 ___might_sleep(file, line, preempt_offset);
7749 EXPORT_SYMBOL(__might_sleep);
7751 void ___might_sleep(const char *file, int line, int preempt_offset)
7753 static unsigned long prev_jiffy; /* ratelimiting */
7754 unsigned long preempt_disable_ip;
7756 rcu_sleep_check(); /* WARN_ON_ONCE() by default, no rate limit reqd. */
7757 if ((preempt_count_equals(preempt_offset) && !irqs_disabled() &&
7758 !is_idle_task(current)) ||
7759 system_state != SYSTEM_RUNNING || oops_in_progress)
7761 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
7763 prev_jiffy = jiffies;
7765 /* Save this before calling printk(), since that will clobber it */
7766 preempt_disable_ip = get_preempt_disable_ip(current);
7769 "BUG: sleeping function called from invalid context at %s:%d\n",
7772 "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
7773 in_atomic(), irqs_disabled(),
7774 current->pid, current->comm);
7776 if (task_stack_end_corrupted(current))
7777 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
7779 debug_show_held_locks(current);
7780 if (irqs_disabled())
7781 print_irqtrace_events(current);
7782 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
7783 && !preempt_count_equals(preempt_offset)) {
7784 pr_err("Preemption disabled at:");
7785 print_ip_sym(preempt_disable_ip);
7789 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
7791 EXPORT_SYMBOL(___might_sleep);
7794 #ifdef CONFIG_MAGIC_SYSRQ
7795 void normalize_rt_tasks(void)
7797 struct task_struct *g, *p;
7798 struct sched_attr attr = {
7799 .sched_policy = SCHED_NORMAL,
7802 read_lock(&tasklist_lock);
7803 for_each_process_thread(g, p) {
7805 * Only normalize user tasks:
7807 if (p->flags & PF_KTHREAD)
7810 p->se.exec_start = 0;
7811 schedstat_set(p->se.statistics.wait_start, 0);
7812 schedstat_set(p->se.statistics.sleep_start, 0);
7813 schedstat_set(p->se.statistics.block_start, 0);
7815 if (!dl_task(p) && !rt_task(p)) {
7817 * Renice negative nice level userspace
7820 if (task_nice(p) < 0)
7821 set_user_nice(p, 0);
7825 __sched_setscheduler(p, &attr, false, false);
7827 read_unlock(&tasklist_lock);
7830 #endif /* CONFIG_MAGIC_SYSRQ */
7832 #if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB)
7834 * These functions are only useful for the IA64 MCA handling, or kdb.
7836 * They can only be called when the whole system has been
7837 * stopped - every CPU needs to be quiescent, and no scheduling
7838 * activity can take place. Using them for anything else would
7839 * be a serious bug, and as a result, they aren't even visible
7840 * under any other configuration.
7844 * curr_task - return the current task for a given cpu.
7845 * @cpu: the processor in question.
7847 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
7849 * Return: The current task for @cpu.
7851 struct task_struct *curr_task(int cpu)
7853 return cpu_curr(cpu);
7856 #endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */
7860 * set_curr_task - set the current task for a given cpu.
7861 * @cpu: the processor in question.
7862 * @p: the task pointer to set.
7864 * Description: This function must only be used when non-maskable interrupts
7865 * are serviced on a separate stack. It allows the architecture to switch the
7866 * notion of the current task on a cpu in a non-blocking manner. This function
7867 * must be called with all CPU's synchronized, and interrupts disabled, the
7868 * and caller must save the original value of the current task (see
7869 * curr_task() above) and restore that value before reenabling interrupts and
7870 * re-starting the system.
7872 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
7874 void ia64_set_curr_task(int cpu, struct task_struct *p)
7881 #ifdef CONFIG_CGROUP_SCHED
7882 /* task_group_lock serializes the addition/removal of task groups */
7883 static DEFINE_SPINLOCK(task_group_lock);
7885 static void sched_free_group(struct task_group *tg)
7887 free_fair_sched_group(tg);
7888 free_rt_sched_group(tg);
7890 kmem_cache_free(task_group_cache, tg);
7893 /* allocate runqueue etc for a new task group */
7894 struct task_group *sched_create_group(struct task_group *parent)
7896 struct task_group *tg;
7898 tg = kmem_cache_alloc(task_group_cache, GFP_KERNEL | __GFP_ZERO);
7900 return ERR_PTR(-ENOMEM);
7902 if (!alloc_fair_sched_group(tg, parent))
7905 if (!alloc_rt_sched_group(tg, parent))
7911 sched_free_group(tg);
7912 return ERR_PTR(-ENOMEM);
7915 void sched_online_group(struct task_group *tg, struct task_group *parent)
7917 unsigned long flags;
7919 spin_lock_irqsave(&task_group_lock, flags);
7920 list_add_rcu(&tg->list, &task_groups);
7922 WARN_ON(!parent); /* root should already exist */
7924 tg->parent = parent;
7925 INIT_LIST_HEAD(&tg->children);
7926 list_add_rcu(&tg->siblings, &parent->children);
7927 spin_unlock_irqrestore(&task_group_lock, flags);
7929 online_fair_sched_group(tg);
7932 /* rcu callback to free various structures associated with a task group */
7933 static void sched_free_group_rcu(struct rcu_head *rhp)
7935 /* now it should be safe to free those cfs_rqs */
7936 sched_free_group(container_of(rhp, struct task_group, rcu));
7939 void sched_destroy_group(struct task_group *tg)
7941 /* wait for possible concurrent references to cfs_rqs complete */
7942 call_rcu(&tg->rcu, sched_free_group_rcu);
7945 void sched_offline_group(struct task_group *tg)
7947 unsigned long flags;
7949 /* end participation in shares distribution */
7950 unregister_fair_sched_group(tg);
7952 spin_lock_irqsave(&task_group_lock, flags);
7953 list_del_rcu(&tg->list);
7954 list_del_rcu(&tg->siblings);
7955 spin_unlock_irqrestore(&task_group_lock, flags);
7958 static void sched_change_group(struct task_struct *tsk, int type)
7960 struct task_group *tg;
7963 * All callers are synchronized by task_rq_lock(); we do not use RCU
7964 * which is pointless here. Thus, we pass "true" to task_css_check()
7965 * to prevent lockdep warnings.
7967 tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
7968 struct task_group, css);
7969 tg = autogroup_task_group(tsk, tg);
7970 tsk->sched_task_group = tg;
7972 #ifdef CONFIG_FAIR_GROUP_SCHED
7973 if (tsk->sched_class->task_change_group)
7974 tsk->sched_class->task_change_group(tsk, type);
7977 set_task_rq(tsk, task_cpu(tsk));
7981 * Change task's runqueue when it moves between groups.
7983 * The caller of this function should have put the task in its new group by
7984 * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect
7987 void sched_move_task(struct task_struct *tsk)
7989 int queued, running;
7993 rq = task_rq_lock(tsk, &rf);
7995 running = task_current(rq, tsk);
7996 queued = task_on_rq_queued(tsk);
7999 dequeue_task(rq, tsk, DEQUEUE_SAVE | DEQUEUE_MOVE);
8000 if (unlikely(running))
8001 put_prev_task(rq, tsk);
8003 sched_change_group(tsk, TASK_MOVE_GROUP);
8006 enqueue_task(rq, tsk, ENQUEUE_RESTORE | ENQUEUE_MOVE);
8007 if (unlikely(running))
8008 set_curr_task(rq, tsk);
8010 task_rq_unlock(rq, tsk, &rf);
8012 #endif /* CONFIG_CGROUP_SCHED */
8014 #ifdef CONFIG_RT_GROUP_SCHED
8016 * Ensure that the real time constraints are schedulable.
8018 static DEFINE_MUTEX(rt_constraints_mutex);
8020 /* Must be called with tasklist_lock held */
8021 static inline int tg_has_rt_tasks(struct task_group *tg)
8023 struct task_struct *g, *p;
8026 * Autogroups do not have RT tasks; see autogroup_create().
8028 if (task_group_is_autogroup(tg))
8031 for_each_process_thread(g, p) {
8032 if (rt_task(p) && task_group(p) == tg)
8039 struct rt_schedulable_data {
8040 struct task_group *tg;
8045 static int tg_rt_schedulable(struct task_group *tg, void *data)
8047 struct rt_schedulable_data *d = data;
8048 struct task_group *child;
8049 unsigned long total, sum = 0;
8050 u64 period, runtime;
8052 period = ktime_to_ns(tg->rt_bandwidth.rt_period);
8053 runtime = tg->rt_bandwidth.rt_runtime;
8056 period = d->rt_period;
8057 runtime = d->rt_runtime;
8061 * Cannot have more runtime than the period.
8063 if (runtime > period && runtime != RUNTIME_INF)
8067 * Ensure we don't starve existing RT tasks.
8069 if (rt_bandwidth_enabled() && !runtime && tg_has_rt_tasks(tg))
8072 total = to_ratio(period, runtime);
8075 * Nobody can have more than the global setting allows.
8077 if (total > to_ratio(global_rt_period(), global_rt_runtime()))
8081 * The sum of our children's runtime should not exceed our own.
8083 list_for_each_entry_rcu(child, &tg->children, siblings) {
8084 period = ktime_to_ns(child->rt_bandwidth.rt_period);
8085 runtime = child->rt_bandwidth.rt_runtime;
8087 if (child == d->tg) {
8088 period = d->rt_period;
8089 runtime = d->rt_runtime;
8092 sum += to_ratio(period, runtime);
8101 static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime)
8105 struct rt_schedulable_data data = {
8107 .rt_period = period,
8108 .rt_runtime = runtime,
8112 ret = walk_tg_tree(tg_rt_schedulable, tg_nop, &data);
8118 static int tg_set_rt_bandwidth(struct task_group *tg,
8119 u64 rt_period, u64 rt_runtime)
8124 * Disallowing the root group RT runtime is BAD, it would disallow the
8125 * kernel creating (and or operating) RT threads.
8127 if (tg == &root_task_group && rt_runtime == 0)
8130 /* No period doesn't make any sense. */
8134 mutex_lock(&rt_constraints_mutex);
8135 read_lock(&tasklist_lock);
8136 err = __rt_schedulable(tg, rt_period, rt_runtime);
8140 raw_spin_lock_irq(&tg->rt_bandwidth.rt_runtime_lock);
8141 tg->rt_bandwidth.rt_period = ns_to_ktime(rt_period);
8142 tg->rt_bandwidth.rt_runtime = rt_runtime;
8144 for_each_possible_cpu(i) {
8145 struct rt_rq *rt_rq = tg->rt_rq[i];
8147 raw_spin_lock(&rt_rq->rt_runtime_lock);
8148 rt_rq->rt_runtime = rt_runtime;
8149 raw_spin_unlock(&rt_rq->rt_runtime_lock);
8151 raw_spin_unlock_irq(&tg->rt_bandwidth.rt_runtime_lock);
8153 read_unlock(&tasklist_lock);
8154 mutex_unlock(&rt_constraints_mutex);
8159 static int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us)
8161 u64 rt_runtime, rt_period;
8163 rt_period = ktime_to_ns(tg->rt_bandwidth.rt_period);
8164 rt_runtime = (u64)rt_runtime_us * NSEC_PER_USEC;
8165 if (rt_runtime_us < 0)
8166 rt_runtime = RUNTIME_INF;
8168 return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
8171 static long sched_group_rt_runtime(struct task_group *tg)
8175 if (tg->rt_bandwidth.rt_runtime == RUNTIME_INF)
8178 rt_runtime_us = tg->rt_bandwidth.rt_runtime;
8179 do_div(rt_runtime_us, NSEC_PER_USEC);
8180 return rt_runtime_us;
8183 static int sched_group_set_rt_period(struct task_group *tg, u64 rt_period_us)
8185 u64 rt_runtime, rt_period;
8187 rt_period = rt_period_us * NSEC_PER_USEC;
8188 rt_runtime = tg->rt_bandwidth.rt_runtime;
8190 return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
8193 static long sched_group_rt_period(struct task_group *tg)
8197 rt_period_us = ktime_to_ns(tg->rt_bandwidth.rt_period);
8198 do_div(rt_period_us, NSEC_PER_USEC);
8199 return rt_period_us;
8201 #endif /* CONFIG_RT_GROUP_SCHED */
8203 #ifdef CONFIG_RT_GROUP_SCHED
8204 static int sched_rt_global_constraints(void)
8208 mutex_lock(&rt_constraints_mutex);
8209 read_lock(&tasklist_lock);
8210 ret = __rt_schedulable(NULL, 0, 0);
8211 read_unlock(&tasklist_lock);
8212 mutex_unlock(&rt_constraints_mutex);
8217 static int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk)
8219 /* Don't accept realtime tasks when there is no way for them to run */
8220 if (rt_task(tsk) && tg->rt_bandwidth.rt_runtime == 0)
8226 #else /* !CONFIG_RT_GROUP_SCHED */
8227 static int sched_rt_global_constraints(void)
8229 unsigned long flags;
8232 raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
8233 for_each_possible_cpu(i) {
8234 struct rt_rq *rt_rq = &cpu_rq(i)->rt;
8236 raw_spin_lock(&rt_rq->rt_runtime_lock);
8237 rt_rq->rt_runtime = global_rt_runtime();
8238 raw_spin_unlock(&rt_rq->rt_runtime_lock);
8240 raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
8244 #endif /* CONFIG_RT_GROUP_SCHED */
8246 static int sched_dl_global_validate(void)
8248 u64 runtime = global_rt_runtime();
8249 u64 period = global_rt_period();
8250 u64 new_bw = to_ratio(period, runtime);
8253 unsigned long flags;
8256 * Here we want to check the bandwidth not being set to some
8257 * value smaller than the currently allocated bandwidth in
8258 * any of the root_domains.
8260 * FIXME: Cycling on all the CPUs is overdoing, but simpler than
8261 * cycling on root_domains... Discussion on different/better
8262 * solutions is welcome!
8264 for_each_possible_cpu(cpu) {
8265 rcu_read_lock_sched();
8266 dl_b = dl_bw_of(cpu);
8268 raw_spin_lock_irqsave(&dl_b->lock, flags);
8269 if (new_bw < dl_b->total_bw)
8271 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
8273 rcu_read_unlock_sched();
8282 static void sched_dl_do_global(void)
8287 unsigned long flags;
8289 def_dl_bandwidth.dl_period = global_rt_period();
8290 def_dl_bandwidth.dl_runtime = global_rt_runtime();
8292 if (global_rt_runtime() != RUNTIME_INF)
8293 new_bw = to_ratio(global_rt_period(), global_rt_runtime());
8296 * FIXME: As above...
8298 for_each_possible_cpu(cpu) {
8299 rcu_read_lock_sched();
8300 dl_b = dl_bw_of(cpu);
8302 raw_spin_lock_irqsave(&dl_b->lock, flags);
8304 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
8306 rcu_read_unlock_sched();
8310 static int sched_rt_global_validate(void)
8312 if (sysctl_sched_rt_period <= 0)
8315 if ((sysctl_sched_rt_runtime != RUNTIME_INF) &&
8316 (sysctl_sched_rt_runtime > sysctl_sched_rt_period))
8322 static void sched_rt_do_global(void)
8324 def_rt_bandwidth.rt_runtime = global_rt_runtime();
8325 def_rt_bandwidth.rt_period = ns_to_ktime(global_rt_period());
8328 int sched_rt_handler(struct ctl_table *table, int write,
8329 void __user *buffer, size_t *lenp,
8332 int old_period, old_runtime;
8333 static DEFINE_MUTEX(mutex);
8337 old_period = sysctl_sched_rt_period;
8338 old_runtime = sysctl_sched_rt_runtime;
8340 ret = proc_dointvec(table, write, buffer, lenp, ppos);
8342 if (!ret && write) {
8343 ret = sched_rt_global_validate();
8347 ret = sched_dl_global_validate();
8351 ret = sched_rt_global_constraints();
8355 sched_rt_do_global();
8356 sched_dl_do_global();
8360 sysctl_sched_rt_period = old_period;
8361 sysctl_sched_rt_runtime = old_runtime;
8363 mutex_unlock(&mutex);
8368 int sched_rr_handler(struct ctl_table *table, int write,
8369 void __user *buffer, size_t *lenp,
8373 static DEFINE_MUTEX(mutex);
8376 ret = proc_dointvec(table, write, buffer, lenp, ppos);
8377 /* make sure that internally we keep jiffies */
8378 /* also, writing zero resets timeslice to default */
8379 if (!ret && write) {
8380 sched_rr_timeslice = sched_rr_timeslice <= 0 ?
8381 RR_TIMESLICE : msecs_to_jiffies(sched_rr_timeslice);
8383 mutex_unlock(&mutex);
8387 #ifdef CONFIG_CGROUP_SCHED
8389 static inline struct task_group *css_tg(struct cgroup_subsys_state *css)
8391 return css ? container_of(css, struct task_group, css) : NULL;
8394 static struct cgroup_subsys_state *
8395 cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
8397 struct task_group *parent = css_tg(parent_css);
8398 struct task_group *tg;
8401 /* This is early initialization for the top cgroup */
8402 return &root_task_group.css;
8405 tg = sched_create_group(parent);
8407 return ERR_PTR(-ENOMEM);
8409 sched_online_group(tg, parent);
8414 static void cpu_cgroup_css_released(struct cgroup_subsys_state *css)
8416 struct task_group *tg = css_tg(css);
8418 sched_offline_group(tg);
8421 static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
8423 struct task_group *tg = css_tg(css);
8426 * Relies on the RCU grace period between css_released() and this.
8428 sched_free_group(tg);
8432 * This is called before wake_up_new_task(), therefore we really only
8433 * have to set its group bits, all the other stuff does not apply.
8435 static void cpu_cgroup_fork(struct task_struct *task)
8440 rq = task_rq_lock(task, &rf);
8442 update_rq_clock(rq);
8443 sched_change_group(task, TASK_SET_GROUP);
8445 task_rq_unlock(rq, task, &rf);
8448 static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
8450 struct task_struct *task;
8451 struct cgroup_subsys_state *css;
8454 cgroup_taskset_for_each(task, css, tset) {
8455 #ifdef CONFIG_RT_GROUP_SCHED
8456 if (!sched_rt_can_attach(css_tg(css), task))
8459 /* We don't support RT-tasks being in separate groups */
8460 if (task->sched_class != &fair_sched_class)
8464 * Serialize against wake_up_new_task() such that if its
8465 * running, we're sure to observe its full state.
8467 raw_spin_lock_irq(&task->pi_lock);
8469 * Avoid calling sched_move_task() before wake_up_new_task()
8470 * has happened. This would lead to problems with PELT, due to
8471 * move wanting to detach+attach while we're not attached yet.
8473 if (task->state == TASK_NEW)
8475 raw_spin_unlock_irq(&task->pi_lock);
8483 static void cpu_cgroup_attach(struct cgroup_taskset *tset)
8485 struct task_struct *task;
8486 struct cgroup_subsys_state *css;
8488 cgroup_taskset_for_each(task, css, tset)
8489 sched_move_task(task);
8492 #ifdef CONFIG_FAIR_GROUP_SCHED
8493 static int cpu_shares_write_u64(struct cgroup_subsys_state *css,
8494 struct cftype *cftype, u64 shareval)
8496 return sched_group_set_shares(css_tg(css), scale_load(shareval));
8499 static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css,
8502 struct task_group *tg = css_tg(css);
8504 return (u64) scale_load_down(tg->shares);
8507 #ifdef CONFIG_CFS_BANDWIDTH
8508 static DEFINE_MUTEX(cfs_constraints_mutex);
8510 const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */
8511 const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */
8513 static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
8515 static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
8517 int i, ret = 0, runtime_enabled, runtime_was_enabled;
8518 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
8520 if (tg == &root_task_group)
8524 * Ensure we have at some amount of bandwidth every period. This is
8525 * to prevent reaching a state of large arrears when throttled via
8526 * entity_tick() resulting in prolonged exit starvation.
8528 if (quota < min_cfs_quota_period || period < min_cfs_quota_period)
8532 * Likewise, bound things on the otherside by preventing insane quota
8533 * periods. This also allows us to normalize in computing quota
8536 if (period > max_cfs_quota_period)
8540 * Prevent race between setting of cfs_rq->runtime_enabled and
8541 * unthrottle_offline_cfs_rqs().
8544 mutex_lock(&cfs_constraints_mutex);
8545 ret = __cfs_schedulable(tg, period, quota);
8549 runtime_enabled = quota != RUNTIME_INF;
8550 runtime_was_enabled = cfs_b->quota != RUNTIME_INF;
8552 * If we need to toggle cfs_bandwidth_used, off->on must occur
8553 * before making related changes, and on->off must occur afterwards
8555 if (runtime_enabled && !runtime_was_enabled)
8556 cfs_bandwidth_usage_inc();
8557 raw_spin_lock_irq(&cfs_b->lock);
8558 cfs_b->period = ns_to_ktime(period);
8559 cfs_b->quota = quota;
8561 __refill_cfs_bandwidth_runtime(cfs_b);
8562 /* restart the period timer (if active) to handle new period expiry */
8563 if (runtime_enabled)
8564 start_cfs_bandwidth(cfs_b);
8565 raw_spin_unlock_irq(&cfs_b->lock);
8567 for_each_online_cpu(i) {
8568 struct cfs_rq *cfs_rq = tg->cfs_rq[i];
8569 struct rq *rq = cfs_rq->rq;
8571 raw_spin_lock_irq(&rq->lock);
8572 cfs_rq->runtime_enabled = runtime_enabled;
8573 cfs_rq->runtime_remaining = 0;
8575 if (cfs_rq->throttled)
8576 unthrottle_cfs_rq(cfs_rq);
8577 raw_spin_unlock_irq(&rq->lock);
8579 if (runtime_was_enabled && !runtime_enabled)
8580 cfs_bandwidth_usage_dec();
8582 mutex_unlock(&cfs_constraints_mutex);
8588 int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)
8592 period = ktime_to_ns(tg->cfs_bandwidth.period);
8593 if (cfs_quota_us < 0)
8594 quota = RUNTIME_INF;
8596 quota = (u64)cfs_quota_us * NSEC_PER_USEC;
8598 return tg_set_cfs_bandwidth(tg, period, quota);
8601 long tg_get_cfs_quota(struct task_group *tg)
8605 if (tg->cfs_bandwidth.quota == RUNTIME_INF)
8608 quota_us = tg->cfs_bandwidth.quota;
8609 do_div(quota_us, NSEC_PER_USEC);
8614 int tg_set_cfs_period(struct task_group *tg, long cfs_period_us)
8618 period = (u64)cfs_period_us * NSEC_PER_USEC;
8619 quota = tg->cfs_bandwidth.quota;
8621 return tg_set_cfs_bandwidth(tg, period, quota);
8624 long tg_get_cfs_period(struct task_group *tg)
8628 cfs_period_us = ktime_to_ns(tg->cfs_bandwidth.period);
8629 do_div(cfs_period_us, NSEC_PER_USEC);
8631 return cfs_period_us;
8634 static s64 cpu_cfs_quota_read_s64(struct cgroup_subsys_state *css,
8637 return tg_get_cfs_quota(css_tg(css));
8640 static int cpu_cfs_quota_write_s64(struct cgroup_subsys_state *css,
8641 struct cftype *cftype, s64 cfs_quota_us)
8643 return tg_set_cfs_quota(css_tg(css), cfs_quota_us);
8646 static u64 cpu_cfs_period_read_u64(struct cgroup_subsys_state *css,
8649 return tg_get_cfs_period(css_tg(css));
8652 static int cpu_cfs_period_write_u64(struct cgroup_subsys_state *css,
8653 struct cftype *cftype, u64 cfs_period_us)
8655 return tg_set_cfs_period(css_tg(css), cfs_period_us);
8658 struct cfs_schedulable_data {
8659 struct task_group *tg;
8664 * normalize group quota/period to be quota/max_period
8665 * note: units are usecs
8667 static u64 normalize_cfs_quota(struct task_group *tg,
8668 struct cfs_schedulable_data *d)
8676 period = tg_get_cfs_period(tg);
8677 quota = tg_get_cfs_quota(tg);
8680 /* note: these should typically be equivalent */
8681 if (quota == RUNTIME_INF || quota == -1)
8684 return to_ratio(period, quota);
8687 static int tg_cfs_schedulable_down(struct task_group *tg, void *data)
8689 struct cfs_schedulable_data *d = data;
8690 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
8691 s64 quota = 0, parent_quota = -1;
8694 quota = RUNTIME_INF;
8696 struct cfs_bandwidth *parent_b = &tg->parent->cfs_bandwidth;
8698 quota = normalize_cfs_quota(tg, d);
8699 parent_quota = parent_b->hierarchical_quota;
8702 * ensure max(child_quota) <= parent_quota, inherit when no
8705 if (quota == RUNTIME_INF)
8706 quota = parent_quota;
8707 else if (parent_quota != RUNTIME_INF && quota > parent_quota)
8710 cfs_b->hierarchical_quota = quota;
8715 static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota)
8718 struct cfs_schedulable_data data = {
8724 if (quota != RUNTIME_INF) {
8725 do_div(data.period, NSEC_PER_USEC);
8726 do_div(data.quota, NSEC_PER_USEC);
8730 ret = walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data);
8736 static int cpu_stats_show(struct seq_file *sf, void *v)
8738 struct task_group *tg = css_tg(seq_css(sf));
8739 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
8741 seq_printf(sf, "nr_periods %d\n", cfs_b->nr_periods);
8742 seq_printf(sf, "nr_throttled %d\n", cfs_b->nr_throttled);
8743 seq_printf(sf, "throttled_time %llu\n", cfs_b->throttled_time);
8747 #endif /* CONFIG_CFS_BANDWIDTH */
8748 #endif /* CONFIG_FAIR_GROUP_SCHED */
8750 #ifdef CONFIG_RT_GROUP_SCHED
8751 static int cpu_rt_runtime_write(struct cgroup_subsys_state *css,
8752 struct cftype *cft, s64 val)
8754 return sched_group_set_rt_runtime(css_tg(css), val);
8757 static s64 cpu_rt_runtime_read(struct cgroup_subsys_state *css,
8760 return sched_group_rt_runtime(css_tg(css));
8763 static int cpu_rt_period_write_uint(struct cgroup_subsys_state *css,
8764 struct cftype *cftype, u64 rt_period_us)
8766 return sched_group_set_rt_period(css_tg(css), rt_period_us);
8769 static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css,
8772 return sched_group_rt_period(css_tg(css));
8774 #endif /* CONFIG_RT_GROUP_SCHED */
8776 static struct cftype cpu_files[] = {
8777 #ifdef CONFIG_FAIR_GROUP_SCHED
8780 .read_u64 = cpu_shares_read_u64,
8781 .write_u64 = cpu_shares_write_u64,
8784 #ifdef CONFIG_CFS_BANDWIDTH
8786 .name = "cfs_quota_us",
8787 .read_s64 = cpu_cfs_quota_read_s64,
8788 .write_s64 = cpu_cfs_quota_write_s64,
8791 .name = "cfs_period_us",
8792 .read_u64 = cpu_cfs_period_read_u64,
8793 .write_u64 = cpu_cfs_period_write_u64,
8797 .seq_show = cpu_stats_show,
8800 #ifdef CONFIG_RT_GROUP_SCHED
8802 .name = "rt_runtime_us",
8803 .read_s64 = cpu_rt_runtime_read,
8804 .write_s64 = cpu_rt_runtime_write,
8807 .name = "rt_period_us",
8808 .read_u64 = cpu_rt_period_read_uint,
8809 .write_u64 = cpu_rt_period_write_uint,
8815 struct cgroup_subsys cpu_cgrp_subsys = {
8816 .css_alloc = cpu_cgroup_css_alloc,
8817 .css_released = cpu_cgroup_css_released,
8818 .css_free = cpu_cgroup_css_free,
8819 .fork = cpu_cgroup_fork,
8820 .can_attach = cpu_cgroup_can_attach,
8821 .attach = cpu_cgroup_attach,
8822 .legacy_cftypes = cpu_files,
8826 #endif /* CONFIG_CGROUP_SCHED */
8828 void dump_cpu_task(int cpu)
8830 pr_info("Task dump for CPU %d:\n", cpu);
8831 sched_show_task(cpu_curr(cpu));
8835 * Nice levels are multiplicative, with a gentle 10% change for every
8836 * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
8837 * nice 1, it will get ~10% less CPU time than another CPU-bound task
8838 * that remained on nice 0.
8840 * The "10% effect" is relative and cumulative: from _any_ nice level,
8841 * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
8842 * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
8843 * If a task goes up by ~10% and another task goes down by ~10% then
8844 * the relative distance between them is ~25%.)
8846 const int sched_prio_to_weight[40] = {
8847 /* -20 */ 88761, 71755, 56483, 46273, 36291,
8848 /* -15 */ 29154, 23254, 18705, 14949, 11916,
8849 /* -10 */ 9548, 7620, 6100, 4904, 3906,
8850 /* -5 */ 3121, 2501, 1991, 1586, 1277,
8851 /* 0 */ 1024, 820, 655, 526, 423,
8852 /* 5 */ 335, 272, 215, 172, 137,
8853 /* 10 */ 110, 87, 70, 56, 45,
8854 /* 15 */ 36, 29, 23, 18, 15,
8858 * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated.
8860 * In cases where the weight does not change often, we can use the
8861 * precalculated inverse to speed up arithmetics by turning divisions
8862 * into multiplications:
8864 const u32 sched_prio_to_wmult[40] = {
8865 /* -20 */ 48388, 59856, 76040, 92818, 118348,
8866 /* -15 */ 147320, 184698, 229616, 287308, 360437,
8867 /* -10 */ 449829, 563644, 704093, 875809, 1099582,
8868 /* -5 */ 1376151, 1717300, 2157191, 2708050, 3363326,
8869 /* 0 */ 4194304, 5237765, 6557202, 8165337, 10153587,
8870 /* 5 */ 12820798, 15790321, 19976592, 24970740, 31350126,
8871 /* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717,
8872 /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153,