1 | /* |
2 | * kernel/sched/core.c |
3 | * |
4 | * Core kernel scheduler code and related syscalls |
5 | * |
6 | * Copyright (C) 1991-2002 Linus Torvalds |
7 | */ |
8 | #include "sched.h" |
9 | |
10 | #include <linux/nospec.h> |
11 | |
12 | #include <linux/kcov.h> |
13 | |
14 | #include <asm/switch_to.h> |
15 | #include <asm/tlb.h> |
16 | |
17 | #include "../workqueue_internal.h" |
18 | #include "../smpboot.h" |
19 | |
20 | #include "pelt.h" |
21 | |
22 | #define CREATE_TRACE_POINTS |
23 | #include <trace/events/sched.h> |
24 | |
25 | DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues); |
26 | |
27 | #if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_JUMP_LABEL) |
28 | /* |
29 | * Debugging: various feature bits |
30 | * |
31 | * If SCHED_DEBUG is disabled, each compilation unit has its own copy of |
32 | * sysctl_sched_features, defined in sched.h, to allow constants propagation |
33 | * at compile time and compiler optimization based on features default. |
34 | */ |
35 | #define SCHED_FEAT(name, enabled) \ |
36 | (1UL << __SCHED_FEAT_##name) * enabled | |
37 | const_debug unsigned int sysctl_sched_features = |
38 | #include "features.h" |
39 | 0; |
40 | #undef SCHED_FEAT |
41 | #endif |
42 | |
43 | /* |
44 | * Number of tasks to iterate in a single balance run. |
45 | * Limited because this is done with IRQs disabled. |
46 | */ |
47 | const_debug unsigned int sysctl_sched_nr_migrate = 32; |
48 | |
49 | /* |
50 | * period over which we measure -rt task CPU usage in us. |
51 | * default: 1s |
52 | */ |
53 | unsigned int sysctl_sched_rt_period = 1000000; |
54 | |
55 | __read_mostly int scheduler_running; |
56 | |
57 | /* |
58 | * part of the period that we allow rt tasks to run in us. |
59 | * default: 0.95s |
60 | */ |
61 | int sysctl_sched_rt_runtime = 950000; |
62 | |
63 | /* |
64 | * __task_rq_lock - lock the rq @p resides on. |
65 | */ |
66 | struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf) |
67 | __acquires(rq->lock) |
68 | { |
69 | struct rq *rq; |
70 | |
71 | lockdep_assert_held(&p->pi_lock); |
72 | |
73 | for (;;) { |
74 | rq = task_rq(p); |
75 | raw_spin_lock(&rq->lock); |
76 | if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) { |
77 | rq_pin_lock(rq, rf); |
78 | return rq; |
79 | } |
80 | raw_spin_unlock(&rq->lock); |
81 | |
82 | while (unlikely(task_on_rq_migrating(p))) |
83 | cpu_relax(); |
84 | } |
85 | } |
86 | |
87 | /* |
88 | * task_rq_lock - lock p->pi_lock and lock the rq @p resides on. |
89 | */ |
90 | struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf) |
91 | __acquires(p->pi_lock) |
92 | __acquires(rq->lock) |
93 | { |
94 | struct rq *rq; |
95 | |
96 | for (;;) { |
97 | raw_spin_lock_irqsave(&p->pi_lock, rf->flags); |
98 | rq = task_rq(p); |
99 | raw_spin_lock(&rq->lock); |
100 | /* |
101 | * move_queued_task() task_rq_lock() |
102 | * |
103 | * ACQUIRE (rq->lock) |
104 | * [S] ->on_rq = MIGRATING [L] rq = task_rq() |
105 | * WMB (__set_task_cpu()) ACQUIRE (rq->lock); |
106 | * [S] ->cpu = new_cpu [L] task_rq() |
107 | * [L] ->on_rq |
108 | * RELEASE (rq->lock) |
109 | * |
110 | * If we observe the old CPU in task_rq_lock(), the acquire of |
111 | * the old rq->lock will fully serialize against the stores. |
112 | * |
113 | * If we observe the new CPU in task_rq_lock(), the address |
114 | * dependency headed by '[L] rq = task_rq()' and the acquire |
115 | * will pair with the WMB to ensure we then also see migrating. |
116 | */ |
117 | if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) { |
118 | rq_pin_lock(rq, rf); |
119 | return rq; |
120 | } |
121 | raw_spin_unlock(&rq->lock); |
122 | raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags); |
123 | |
124 | while (unlikely(task_on_rq_migrating(p))) |
125 | cpu_relax(); |
126 | } |
127 | } |
128 | |
129 | /* |
130 | * RQ-clock updating methods: |
131 | */ |
132 | |
133 | static void update_rq_clock_task(struct rq *rq, s64 delta) |
134 | { |
135 | /* |
136 | * In theory, the compile should just see 0 here, and optimize out the call |
137 | * to sched_rt_avg_update. But I don't trust it... |
138 | */ |
139 | s64 __maybe_unused steal = 0, irq_delta = 0; |
140 | |
141 | #ifdef CONFIG_IRQ_TIME_ACCOUNTING |
142 | irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time; |
143 | |
144 | /* |
145 | * Since irq_time is only updated on {soft,}irq_exit, we might run into |
146 | * this case when a previous update_rq_clock() happened inside a |
147 | * {soft,}irq region. |
148 | * |
149 | * When this happens, we stop ->clock_task and only update the |
150 | * prev_irq_time stamp to account for the part that fit, so that a next |
151 | * update will consume the rest. This ensures ->clock_task is |
152 | * monotonic. |
153 | * |
154 | * It does however cause some slight miss-attribution of {soft,}irq |
155 | * time, a more accurate solution would be to update the irq_time using |
156 | * the current rq->clock timestamp, except that would require using |
157 | * atomic ops. |
158 | */ |
159 | if (irq_delta > delta) |
160 | irq_delta = delta; |
161 | |
162 | rq->prev_irq_time += irq_delta; |
163 | delta -= irq_delta; |
164 | #endif |
165 | #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING |
166 | if (static_key_false((¶virt_steal_rq_enabled))) { |
167 | steal = paravirt_steal_clock(cpu_of(rq)); |
168 | steal -= rq->prev_steal_time_rq; |
169 | |
170 | if (unlikely(steal > delta)) |
171 | steal = delta; |
172 | |
173 | rq->prev_steal_time_rq += steal; |
174 | delta -= steal; |
175 | } |
176 | #endif |
177 | |
178 | rq->clock_task += delta; |
179 | |
180 | #ifdef CONFIG_HAVE_SCHED_AVG_IRQ |
181 | if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY)) |
182 | update_irq_load_avg(rq, irq_delta + steal); |
183 | #endif |
184 | update_rq_clock_pelt(rq, delta); |
185 | } |
186 | |
187 | void update_rq_clock(struct rq *rq) |
188 | { |
189 | s64 delta; |
190 | |
191 | lockdep_assert_held(&rq->lock); |
192 | |
193 | if (rq->clock_update_flags & RQCF_ACT_SKIP) |
194 | return; |
195 | |
196 | #ifdef CONFIG_SCHED_DEBUG |
197 | if (sched_feat(WARN_DOUBLE_CLOCK)) |
198 | SCHED_WARN_ON(rq->clock_update_flags & RQCF_UPDATED); |
199 | rq->clock_update_flags |= RQCF_UPDATED; |
200 | #endif |
201 | |
202 | delta = sched_clock_cpu(cpu_of(rq)) - rq->clock; |
203 | if (delta < 0) |
204 | return; |
205 | rq->clock += delta; |
206 | update_rq_clock_task(rq, delta); |
207 | } |
208 | |
209 | |
210 | #ifdef CONFIG_SCHED_HRTICK |
211 | /* |
212 | * Use HR-timers to deliver accurate preemption points. |
213 | */ |
214 | |
215 | static void hrtick_clear(struct rq *rq) |
216 | { |
217 | if (hrtimer_active(&rq->hrtick_timer)) |
218 | hrtimer_cancel(&rq->hrtick_timer); |
219 | } |
220 | |
221 | /* |
222 | * High-resolution timer tick. |
223 | * Runs from hardirq context with interrupts disabled. |
224 | */ |
225 | static enum hrtimer_restart hrtick(struct hrtimer *timer) |
226 | { |
227 | struct rq *rq = container_of(timer, struct rq, hrtick_timer); |
228 | struct rq_flags rf; |
229 | |
230 | WARN_ON_ONCE(cpu_of(rq) != smp_processor_id()); |
231 | |
232 | rq_lock(rq, &rf); |
233 | update_rq_clock(rq); |
234 | rq->curr->sched_class->task_tick(rq, rq->curr, 1); |
235 | rq_unlock(rq, &rf); |
236 | |
237 | return HRTIMER_NORESTART; |
238 | } |
239 | |
240 | #ifdef CONFIG_SMP |
241 | |
242 | static void __hrtick_restart(struct rq *rq) |
243 | { |
244 | struct hrtimer *timer = &rq->hrtick_timer; |
245 | |
246 | hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED); |
247 | } |
248 | |
249 | /* |
250 | * called from hardirq (IPI) context |
251 | */ |
252 | static void __hrtick_start(void *arg) |
253 | { |
254 | struct rq *rq = arg; |
255 | struct rq_flags rf; |
256 | |
257 | rq_lock(rq, &rf); |
258 | __hrtick_restart(rq); |
259 | rq->hrtick_csd_pending = 0; |
260 | rq_unlock(rq, &rf); |
261 | } |
262 | |
263 | /* |
264 | * Called to set the hrtick timer state. |
265 | * |
266 | * called with rq->lock held and irqs disabled |
267 | */ |
268 | void hrtick_start(struct rq *rq, u64 delay) |
269 | { |
270 | struct hrtimer *timer = &rq->hrtick_timer; |
271 | ktime_t time; |
272 | s64 delta; |
273 | |
274 | /* |
275 | * Don't schedule slices shorter than 10000ns, that just |
276 | * doesn't make sense and can cause timer DoS. |
277 | */ |
278 | delta = max_t(s64, delay, 10000LL); |
279 | time = ktime_add_ns(timer->base->get_time(), delta); |
280 | |
281 | hrtimer_set_expires(timer, time); |
282 | |
283 | if (rq == this_rq()) { |
284 | __hrtick_restart(rq); |
285 | } else if (!rq->hrtick_csd_pending) { |
286 | smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd); |
287 | rq->hrtick_csd_pending = 1; |
288 | } |
289 | } |
290 | |
291 | #else |
292 | /* |
293 | * Called to set the hrtick timer state. |
294 | * |
295 | * called with rq->lock held and irqs disabled |
296 | */ |
297 | void hrtick_start(struct rq *rq, u64 delay) |
298 | { |
299 | /* |
300 | * Don't schedule slices shorter than 10000ns, that just |
301 | * doesn't make sense. Rely on vruntime for fairness. |
302 | */ |
303 | delay = max_t(u64, delay, 10000LL); |
304 | hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay), |
305 | HRTIMER_MODE_REL_PINNED); |
306 | } |
307 | #endif /* CONFIG_SMP */ |
308 | |
309 | static void hrtick_rq_init(struct rq *rq) |
310 | { |
311 | #ifdef CONFIG_SMP |
312 | rq->hrtick_csd_pending = 0; |
313 | |
314 | rq->hrtick_csd.flags = 0; |
315 | rq->hrtick_csd.func = __hrtick_start; |
316 | rq->hrtick_csd.info = rq; |
317 | #endif |
318 | |
319 | hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); |
320 | rq->hrtick_timer.function = hrtick; |
321 | } |
322 | #else /* CONFIG_SCHED_HRTICK */ |
323 | static inline void hrtick_clear(struct rq *rq) |
324 | { |
325 | } |
326 | |
327 | static inline void hrtick_rq_init(struct rq *rq) |
328 | { |
329 | } |
330 | #endif /* CONFIG_SCHED_HRTICK */ |
331 | |
332 | /* |
333 | * cmpxchg based fetch_or, macro so it works for different integer types |
334 | */ |
335 | #define fetch_or(ptr, mask) \ |
336 | ({ \ |
337 | typeof(ptr) _ptr = (ptr); \ |
338 | typeof(mask) _mask = (mask); \ |
339 | typeof(*_ptr) _old, _val = *_ptr; \ |
340 | \ |
341 | for (;;) { \ |
342 | _old = cmpxchg(_ptr, _val, _val | _mask); \ |
343 | if (_old == _val) \ |
344 | break; \ |
345 | _val = _old; \ |
346 | } \ |
347 | _old; \ |
348 | }) |
349 | |
350 | #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG) |
351 | /* |
352 | * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG, |
353 | * this avoids any races wrt polling state changes and thereby avoids |
354 | * spurious IPIs. |
355 | */ |
356 | static bool set_nr_and_not_polling(struct task_struct *p) |
357 | { |
358 | struct thread_info *ti = task_thread_info(p); |
359 | return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG); |
360 | } |
361 | |
362 | /* |
363 | * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set. |
364 | * |
365 | * If this returns true, then the idle task promises to call |
366 | * sched_ttwu_pending() and reschedule soon. |
367 | */ |
368 | static bool set_nr_if_polling(struct task_struct *p) |
369 | { |
370 | struct thread_info *ti = task_thread_info(p); |
371 | typeof(ti->flags) old, val = READ_ONCE(ti->flags); |
372 | |
373 | for (;;) { |
374 | if (!(val & _TIF_POLLING_NRFLAG)) |
375 | return false; |
376 | if (val & _TIF_NEED_RESCHED) |
377 | return true; |
378 | old = cmpxchg(&ti->flags, val, val | _TIF_NEED_RESCHED); |
379 | if (old == val) |
380 | break; |
381 | val = old; |
382 | } |
383 | return true; |
384 | } |
385 | |
386 | #else |
387 | static bool set_nr_and_not_polling(struct task_struct *p) |
388 | { |
389 | set_tsk_need_resched(p); |
390 | return true; |
391 | } |
392 | |
393 | #ifdef CONFIG_SMP |
394 | static bool set_nr_if_polling(struct task_struct *p) |
395 | { |
396 | return false; |
397 | } |
398 | #endif |
399 | #endif |
400 | |
401 | static bool __wake_q_add(struct wake_q_head *head, struct task_struct *task) |
402 | { |
403 | struct wake_q_node *node = &task->wake_q; |
404 | |
405 | /* |
406 | * Atomically grab the task, if ->wake_q is !nil already it means |
407 | * its already queued (either by us or someone else) and will get the |
408 | * wakeup due to that. |
409 | * |
410 | * In order to ensure that a pending wakeup will observe our pending |
411 | * state, even in the failed case, an explicit smp_mb() must be used. |
412 | */ |
413 | smp_mb__before_atomic(); |
414 | if (unlikely(cmpxchg_relaxed(&node->next, NULL, WAKE_Q_TAIL))) |
415 | return false; |
416 | |
417 | /* |
418 | * The head is context local, there can be no concurrency. |
419 | */ |
420 | *head->lastp = node; |
421 | head->lastp = &node->next; |
422 | return true; |
423 | } |
424 | |
425 | /** |
426 | * wake_q_add() - queue a wakeup for 'later' waking. |
427 | * @head: the wake_q_head to add @task to |
428 | * @task: the task to queue for 'later' wakeup |
429 | * |
430 | * Queue a task for later wakeup, most likely by the wake_up_q() call in the |
431 | * same context, _HOWEVER_ this is not guaranteed, the wakeup can come |
432 | * instantly. |
433 | * |
434 | * This function must be used as-if it were wake_up_process(); IOW the task |
435 | * must be ready to be woken at this location. |
436 | */ |
437 | void wake_q_add(struct wake_q_head *head, struct task_struct *task) |
438 | { |
439 | if (__wake_q_add(head, task)) |
440 | get_task_struct(task); |
441 | } |
442 | |
443 | /** |
444 | * wake_q_add_safe() - safely queue a wakeup for 'later' waking. |
445 | * @head: the wake_q_head to add @task to |
446 | * @task: the task to queue for 'later' wakeup |
447 | * |
448 | * Queue a task for later wakeup, most likely by the wake_up_q() call in the |
449 | * same context, _HOWEVER_ this is not guaranteed, the wakeup can come |
450 | * instantly. |
451 | * |
452 | * This function must be used as-if it were wake_up_process(); IOW the task |
453 | * must be ready to be woken at this location. |
454 | * |
455 | * This function is essentially a task-safe equivalent to wake_q_add(). Callers |
456 | * that already hold reference to @task can call the 'safe' version and trust |
457 | * wake_q to do the right thing depending whether or not the @task is already |
458 | * queued for wakeup. |
459 | */ |
460 | void wake_q_add_safe(struct wake_q_head *head, struct task_struct *task) |
461 | { |
462 | if (!__wake_q_add(head, task)) |
463 | put_task_struct(task); |
464 | } |
465 | |
466 | void wake_up_q(struct wake_q_head *head) |
467 | { |
468 | struct wake_q_node *node = head->first; |
469 | |
470 | while (node != WAKE_Q_TAIL) { |
471 | struct task_struct *task; |
472 | |
473 | task = container_of(node, struct task_struct, wake_q); |
474 | BUG_ON(!task); |
475 | /* Task can safely be re-inserted now: */ |
476 | node = node->next; |
477 | task->wake_q.next = NULL; |
478 | |
479 | /* |
480 | * wake_up_process() executes a full barrier, which pairs with |
481 | * the queueing in wake_q_add() so as not to miss wakeups. |
482 | */ |
483 | wake_up_process(task); |
484 | put_task_struct(task); |
485 | } |
486 | } |
487 | |
488 | /* |
489 | * resched_curr - mark rq's current task 'to be rescheduled now'. |
490 | * |
491 | * On UP this means the setting of the need_resched flag, on SMP it |
492 | * might also involve a cross-CPU call to trigger the scheduler on |
493 | * the target CPU. |
494 | */ |
495 | void resched_curr(struct rq *rq) |
496 | { |
497 | struct task_struct *curr = rq->curr; |
498 | int cpu; |
499 | |
500 | lockdep_assert_held(&rq->lock); |
501 | |
502 | if (test_tsk_need_resched(curr)) |
503 | return; |
504 | |
505 | cpu = cpu_of(rq); |
506 | |
507 | if (cpu == smp_processor_id()) { |
508 | set_tsk_need_resched(curr); |
509 | set_preempt_need_resched(); |
510 | return; |
511 | } |
512 | |
513 | if (set_nr_and_not_polling(curr)) |
514 | smp_send_reschedule(cpu); |
515 | else |
516 | trace_sched_wake_idle_without_ipi(cpu); |
517 | } |
518 | |
519 | void resched_cpu(int cpu) |
520 | { |
521 | struct rq *rq = cpu_rq(cpu); |
522 | unsigned long flags; |
523 | |
524 | raw_spin_lock_irqsave(&rq->lock, flags); |
525 | if (cpu_online(cpu) || cpu == smp_processor_id()) |
526 | resched_curr(rq); |
527 | raw_spin_unlock_irqrestore(&rq->lock, flags); |
528 | } |
529 | |
530 | #ifdef CONFIG_SMP |
531 | #ifdef CONFIG_NO_HZ_COMMON |
532 | /* |
533 | * In the semi idle case, use the nearest busy CPU for migrating timers |
534 | * from an idle CPU. This is good for power-savings. |
535 | * |
536 | * We don't do similar optimization for completely idle system, as |
537 | * selecting an idle CPU will add more delays to the timers than intended |
538 | * (as that CPU's timer base may not be uptodate wrt jiffies etc). |
539 | */ |
540 | int get_nohz_timer_target(void) |
541 | { |
542 | int i, cpu = smp_processor_id(); |
543 | struct sched_domain *sd; |
544 | |
545 | if (!idle_cpu(cpu) && housekeeping_cpu(cpu, HK_FLAG_TIMER)) |
546 | return cpu; |
547 | |
548 | rcu_read_lock(); |
549 | for_each_domain(cpu, sd) { |
550 | for_each_cpu(i, sched_domain_span(sd)) { |
551 | if (cpu == i) |
552 | continue; |
553 | |
554 | if (!idle_cpu(i) && housekeeping_cpu(i, HK_FLAG_TIMER)) { |
555 | cpu = i; |
556 | goto unlock; |
557 | } |
558 | } |
559 | } |
560 | |
561 | if (!housekeeping_cpu(cpu, HK_FLAG_TIMER)) |
562 | cpu = housekeeping_any_cpu(HK_FLAG_TIMER); |
563 | unlock: |
564 | rcu_read_unlock(); |
565 | return cpu; |
566 | } |
567 | |
568 | /* |
569 | * When add_timer_on() enqueues a timer into the timer wheel of an |
570 | * idle CPU then this timer might expire before the next timer event |
571 | * which is scheduled to wake up that CPU. In case of a completely |
572 | * idle system the next event might even be infinite time into the |
573 | * future. wake_up_idle_cpu() ensures that the CPU is woken up and |
574 | * leaves the inner idle loop so the newly added timer is taken into |
575 | * account when the CPU goes back to idle and evaluates the timer |
576 | * wheel for the next timer event. |
577 | */ |
578 | static void wake_up_idle_cpu(int cpu) |
579 | { |
580 | struct rq *rq = cpu_rq(cpu); |
581 | |
582 | if (cpu == smp_processor_id()) |
583 | return; |
584 | |
585 | if (set_nr_and_not_polling(rq->idle)) |
586 | smp_send_reschedule(cpu); |
587 | else |
588 | trace_sched_wake_idle_without_ipi(cpu); |
589 | } |
590 | |
591 | static bool wake_up_full_nohz_cpu(int cpu) |
592 | { |
593 | /* |
594 | * We just need the target to call irq_exit() and re-evaluate |
595 | * the next tick. The nohz full kick at least implies that. |
596 | * If needed we can still optimize that later with an |
597 | * empty IRQ. |
598 | */ |
599 | if (cpu_is_offline(cpu)) |
600 | return true; /* Don't try to wake offline CPUs. */ |
601 | if (tick_nohz_full_cpu(cpu)) { |
602 | if (cpu != smp_processor_id() || |
603 | tick_nohz_tick_stopped()) |
604 | tick_nohz_full_kick_cpu(cpu); |
605 | return true; |
606 | } |
607 | |
608 | return false; |
609 | } |
610 | |
611 | /* |
612 | * Wake up the specified CPU. If the CPU is going offline, it is the |
613 | * caller's responsibility to deal with the lost wakeup, for example, |
614 | * by hooking into the CPU_DEAD notifier like timers and hrtimers do. |
615 | */ |
616 | void wake_up_nohz_cpu(int cpu) |
617 | { |
618 | if (!wake_up_full_nohz_cpu(cpu)) |
619 | wake_up_idle_cpu(cpu); |
620 | } |
621 | |
622 | static inline bool got_nohz_idle_kick(void) |
623 | { |
624 | int cpu = smp_processor_id(); |
625 | |
626 | if (!(atomic_read(nohz_flags(cpu)) & NOHZ_KICK_MASK)) |
627 | return false; |
628 | |
629 | if (idle_cpu(cpu) && !need_resched()) |
630 | return true; |
631 | |
632 | /* |
633 | * We can't run Idle Load Balance on this CPU for this time so we |
634 | * cancel it and clear NOHZ_BALANCE_KICK |
635 | */ |
636 | atomic_andnot(NOHZ_KICK_MASK, nohz_flags(cpu)); |
637 | return false; |
638 | } |
639 | |
640 | #else /* CONFIG_NO_HZ_COMMON */ |
641 | |
642 | static inline bool got_nohz_idle_kick(void) |
643 | { |
644 | return false; |
645 | } |
646 | |
647 | #endif /* CONFIG_NO_HZ_COMMON */ |
648 | |
649 | #ifdef CONFIG_NO_HZ_FULL |
650 | bool sched_can_stop_tick(struct rq *rq) |
651 | { |
652 | int fifo_nr_running; |
653 | |
654 | /* Deadline tasks, even if single, need the tick */ |
655 | if (rq->dl.dl_nr_running) |
656 | return false; |
657 | |
658 | /* |
659 | * If there are more than one RR tasks, we need the tick to effect the |
660 | * actual RR behaviour. |
661 | */ |
662 | if (rq->rt.rr_nr_running) { |
663 | if (rq->rt.rr_nr_running == 1) |
664 | return true; |
665 | else |
666 | return false; |
667 | } |
668 | |
669 | /* |
670 | * If there's no RR tasks, but FIFO tasks, we can skip the tick, no |
671 | * forced preemption between FIFO tasks. |
672 | */ |
673 | fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running; |
674 | if (fifo_nr_running) |
675 | return true; |
676 | |
677 | /* |
678 | * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left; |
679 | * if there's more than one we need the tick for involuntary |
680 | * preemption. |
681 | */ |
682 | if (rq->nr_running > 1) |
683 | return false; |
684 | |
685 | return true; |
686 | } |
687 | #endif /* CONFIG_NO_HZ_FULL */ |
688 | #endif /* CONFIG_SMP */ |
689 | |
690 | #if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \ |
691 | (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH))) |
692 | /* |
693 | * Iterate task_group tree rooted at *from, calling @down when first entering a |
694 | * node and @up when leaving it for the final time. |
695 | * |
696 | * Caller must hold rcu_lock or sufficient equivalent. |
697 | */ |
698 | int walk_tg_tree_from(struct task_group *from, |
699 | tg_visitor down, tg_visitor up, void *data) |
700 | { |
701 | struct task_group *parent, *child; |
702 | int ret; |
703 | |
704 | parent = from; |
705 | |
706 | down: |
707 | ret = (*down)(parent, data); |
708 | if (ret) |
709 | goto out; |
710 | list_for_each_entry_rcu(child, &parent->children, siblings) { |
711 | parent = child; |
712 | goto down; |
713 | |
714 | up: |
715 | continue; |
716 | } |
717 | ret = (*up)(parent, data); |
718 | if (ret || parent == from) |
719 | goto out; |
720 | |
721 | child = parent; |
722 | parent = parent->parent; |
723 | if (parent) |
724 | goto up; |
725 | out: |
726 | return ret; |
727 | } |
728 | |
729 | int tg_nop(struct task_group *tg, void *data) |
730 | { |
731 | return 0; |
732 | } |
733 | #endif |
734 | |
735 | static void set_load_weight(struct task_struct *p, bool update_load) |
736 | { |
737 | int prio = p->static_prio - MAX_RT_PRIO; |
738 | struct load_weight *load = &p->se.load; |
739 | |
740 | /* |
741 | * SCHED_IDLE tasks get minimal weight: |
742 | */ |
743 | if (task_has_idle_policy(p)) { |
744 | load->weight = scale_load(WEIGHT_IDLEPRIO); |
745 | load->inv_weight = WMULT_IDLEPRIO; |
746 | p->se.runnable_weight = load->weight; |
747 | return; |
748 | } |
749 | |
750 | /* |
751 | * SCHED_OTHER tasks have to update their load when changing their |
752 | * weight |
753 | */ |
754 | if (update_load && p->sched_class == &fair_sched_class) { |
755 | reweight_task(p, prio); |
756 | } else { |
757 | load->weight = scale_load(sched_prio_to_weight[prio]); |
758 | load->inv_weight = sched_prio_to_wmult[prio]; |
759 | p->se.runnable_weight = load->weight; |
760 | } |
761 | } |
762 | |
763 | static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags) |
764 | { |
765 | if (!(flags & ENQUEUE_NOCLOCK)) |
766 | update_rq_clock(rq); |
767 | |
768 | if (!(flags & ENQUEUE_RESTORE)) { |
769 | sched_info_queued(rq, p); |
770 | psi_enqueue(p, flags & ENQUEUE_WAKEUP); |
771 | } |
772 | |
773 | p->sched_class->enqueue_task(rq, p, flags); |
774 | } |
775 | |
776 | static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags) |
777 | { |
778 | if (!(flags & DEQUEUE_NOCLOCK)) |
779 | update_rq_clock(rq); |
780 | |
781 | if (!(flags & DEQUEUE_SAVE)) { |
782 | sched_info_dequeued(rq, p); |
783 | psi_dequeue(p, flags & DEQUEUE_SLEEP); |
784 | } |
785 | |
786 | p->sched_class->dequeue_task(rq, p, flags); |
787 | } |
788 | |
789 | void activate_task(struct rq *rq, struct task_struct *p, int flags) |
790 | { |
791 | if (task_contributes_to_load(p)) |
792 | rq->nr_uninterruptible--; |
793 | |
794 | enqueue_task(rq, p, flags); |
795 | } |
796 | |
797 | void deactivate_task(struct rq *rq, struct task_struct *p, int flags) |
798 | { |
799 | if (task_contributes_to_load(p)) |
800 | rq->nr_uninterruptible++; |
801 | |
802 | dequeue_task(rq, p, flags); |
803 | } |
804 | |
805 | /* |
806 | * __normal_prio - return the priority that is based on the static prio |
807 | */ |
808 | static inline int __normal_prio(struct task_struct *p) |
809 | { |
810 | return p->static_prio; |
811 | } |
812 | |
813 | /* |
814 | * Calculate the expected normal priority: i.e. priority |
815 | * without taking RT-inheritance into account. Might be |
816 | * boosted by interactivity modifiers. Changes upon fork, |
817 | * setprio syscalls, and whenever the interactivity |
818 | * estimator recalculates. |
819 | */ |
820 | static inline int normal_prio(struct task_struct *p) |
821 | { |
822 | int prio; |
823 | |
824 | if (task_has_dl_policy(p)) |
825 | prio = MAX_DL_PRIO-1; |
826 | else if (task_has_rt_policy(p)) |
827 | prio = MAX_RT_PRIO-1 - p->rt_priority; |
828 | else |
829 | prio = __normal_prio(p); |
830 | return prio; |
831 | } |
832 | |
833 | /* |
834 | * Calculate the current priority, i.e. the priority |
835 | * taken into account by the scheduler. This value might |
836 | * be boosted by RT tasks, or might be boosted by |
837 | * interactivity modifiers. Will be RT if the task got |
838 | * RT-boosted. If not then it returns p->normal_prio. |
839 | */ |
840 | static int effective_prio(struct task_struct *p) |
841 | { |
842 | p->normal_prio = normal_prio(p); |
843 | /* |
844 | * If we are RT tasks or we were boosted to RT priority, |
845 | * keep the priority unchanged. Otherwise, update priority |
846 | * to the normal priority: |
847 | */ |
848 | if (!rt_prio(p->prio)) |
849 | return p->normal_prio; |
850 | return p->prio; |
851 | } |
852 | |
853 | /** |
854 | * task_curr - is this task currently executing on a CPU? |
855 | * @p: the task in question. |
856 | * |
857 | * Return: 1 if the task is currently executing. 0 otherwise. |
858 | */ |
859 | inline int task_curr(const struct task_struct *p) |
860 | { |
861 | return cpu_curr(task_cpu(p)) == p; |
862 | } |
863 | |
864 | /* |
865 | * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock, |
866 | * use the balance_callback list if you want balancing. |
867 | * |
868 | * this means any call to check_class_changed() must be followed by a call to |
869 | * balance_callback(). |
870 | */ |
871 | static inline void check_class_changed(struct rq *rq, struct task_struct *p, |
872 | const struct sched_class *prev_class, |
873 | int oldprio) |
874 | { |
875 | if (prev_class != p->sched_class) { |
876 | if (prev_class->switched_from) |
877 | prev_class->switched_from(rq, p); |
878 | |
879 | p->sched_class->switched_to(rq, p); |
880 | } else if (oldprio != p->prio || dl_task(p)) |
881 | p->sched_class->prio_changed(rq, p, oldprio); |
882 | } |
883 | |
884 | void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags) |
885 | { |
886 | const struct sched_class *class; |
887 | |
888 | if (p->sched_class == rq->curr->sched_class) { |
889 | rq->curr->sched_class->check_preempt_curr(rq, p, flags); |
890 | } else { |
891 | for_each_class(class) { |
892 | if (class == rq->curr->sched_class) |
893 | break; |
894 | if (class == p->sched_class) { |
895 | resched_curr(rq); |
896 | break; |
897 | } |
898 | } |
899 | } |
900 | |
901 | /* |
902 | * A queue event has occurred, and we're going to schedule. In |
903 | * this case, we can save a useless back to back clock update. |
904 | */ |
905 | if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr)) |
906 | rq_clock_skip_update(rq); |
907 | } |
908 | |
909 | #ifdef CONFIG_SMP |
910 | |
911 | static inline bool is_per_cpu_kthread(struct task_struct *p) |
912 | { |
913 | if (!(p->flags & PF_KTHREAD)) |
914 | return false; |
915 | |
916 | if (p->nr_cpus_allowed != 1) |
917 | return false; |
918 | |
919 | return true; |
920 | } |
921 | |
922 | /* |
923 | * Per-CPU kthreads are allowed to run on !actie && online CPUs, see |
924 | * __set_cpus_allowed_ptr() and select_fallback_rq(). |
925 | */ |
926 | static inline bool is_cpu_allowed(struct task_struct *p, int cpu) |
927 | { |
928 | if (!cpumask_test_cpu(cpu, &p->cpus_allowed)) |
929 | return false; |
930 | |
931 | if (is_per_cpu_kthread(p)) |
932 | return cpu_online(cpu); |
933 | |
934 | return cpu_active(cpu); |
935 | } |
936 | |
937 | /* |
938 | * This is how migration works: |
939 | * |
940 | * 1) we invoke migration_cpu_stop() on the target CPU using |
941 | * stop_one_cpu(). |
942 | * 2) stopper starts to run (implicitly forcing the migrated thread |
943 | * off the CPU) |
944 | * 3) it checks whether the migrated task is still in the wrong runqueue. |
945 | * 4) if it's in the wrong runqueue then the migration thread removes |
946 | * it and puts it into the right queue. |
947 | * 5) stopper completes and stop_one_cpu() returns and the migration |
948 | * is done. |
949 | */ |
950 | |
951 | /* |
952 | * move_queued_task - move a queued task to new rq. |
953 | * |
954 | * Returns (locked) new rq. Old rq's lock is released. |
955 | */ |
956 | static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf, |
957 | struct task_struct *p, int new_cpu) |
958 | { |
959 | lockdep_assert_held(&rq->lock); |
960 | |
961 | WRITE_ONCE(p->on_rq, TASK_ON_RQ_MIGRATING); |
962 | dequeue_task(rq, p, DEQUEUE_NOCLOCK); |
963 | set_task_cpu(p, new_cpu); |
964 | rq_unlock(rq, rf); |
965 | |
966 | rq = cpu_rq(new_cpu); |
967 | |
968 | rq_lock(rq, rf); |
969 | BUG_ON(task_cpu(p) != new_cpu); |
970 | enqueue_task(rq, p, 0); |
971 | p->on_rq = TASK_ON_RQ_QUEUED; |
972 | check_preempt_curr(rq, p, 0); |
973 | |
974 | return rq; |
975 | } |
976 | |
977 | struct migration_arg { |
978 | struct task_struct *task; |
979 | int dest_cpu; |
980 | }; |
981 | |
982 | /* |
983 | * Move (not current) task off this CPU, onto the destination CPU. We're doing |
984 | * this because either it can't run here any more (set_cpus_allowed() |
985 | * away from this CPU, or CPU going down), or because we're |
986 | * attempting to rebalance this task on exec (sched_exec). |
987 | * |
988 | * So we race with normal scheduler movements, but that's OK, as long |
989 | * as the task is no longer on this CPU. |
990 | */ |
991 | static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf, |
992 | struct task_struct *p, int dest_cpu) |
993 | { |
994 | /* Affinity changed (again). */ |
995 | if (!is_cpu_allowed(p, dest_cpu)) |
996 | return rq; |
997 | |
998 | update_rq_clock(rq); |
999 | rq = move_queued_task(rq, rf, p, dest_cpu); |
1000 | |
1001 | return rq; |
1002 | } |
1003 | |
1004 | /* |
1005 | * migration_cpu_stop - this will be executed by a highprio stopper thread |
1006 | * and performs thread migration by bumping thread off CPU then |
1007 | * 'pushing' onto another runqueue. |
1008 | */ |
1009 | static int migration_cpu_stop(void *data) |
1010 | { |
1011 | struct migration_arg *arg = data; |
1012 | struct task_struct *p = arg->task; |
1013 | struct rq *rq = this_rq(); |
1014 | struct rq_flags rf; |
1015 | |
1016 | /* |
1017 | * The original target CPU might have gone down and we might |
1018 | * be on another CPU but it doesn't matter. |
1019 | */ |
1020 | local_irq_disable(); |
1021 | /* |
1022 | * We need to explicitly wake pending tasks before running |
1023 | * __migrate_task() such that we will not miss enforcing cpus_allowed |
1024 | * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test. |
1025 | */ |
1026 | sched_ttwu_pending(); |
1027 | |
1028 | raw_spin_lock(&p->pi_lock); |
1029 | rq_lock(rq, &rf); |
1030 | /* |
1031 | * If task_rq(p) != rq, it cannot be migrated here, because we're |
1032 | * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because |
1033 | * we're holding p->pi_lock. |
1034 | */ |
1035 | if (task_rq(p) == rq) { |
1036 | if (task_on_rq_queued(p)) |
1037 | rq = __migrate_task(rq, &rf, p, arg->dest_cpu); |
1038 | else |
1039 | p->wake_cpu = arg->dest_cpu; |
1040 | } |
1041 | rq_unlock(rq, &rf); |
1042 | raw_spin_unlock(&p->pi_lock); |
1043 | |
1044 | local_irq_enable(); |
1045 | return 0; |
1046 | } |
1047 | |
1048 | /* |
1049 | * sched_class::set_cpus_allowed must do the below, but is not required to |
1050 | * actually call this function. |
1051 | */ |
1052 | void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask) |
1053 | { |
1054 | cpumask_copy(&p->cpus_allowed, new_mask); |
1055 | p->nr_cpus_allowed = cpumask_weight(new_mask); |
1056 | } |
1057 | |
1058 | void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask) |
1059 | { |
1060 | struct rq *rq = task_rq(p); |
1061 | bool queued, running; |
1062 | |
1063 | lockdep_assert_held(&p->pi_lock); |
1064 | |
1065 | queued = task_on_rq_queued(p); |
1066 | running = task_current(rq, p); |
1067 | |
1068 | if (queued) { |
1069 | /* |
1070 | * Because __kthread_bind() calls this on blocked tasks without |
1071 | * holding rq->lock. |
1072 | */ |
1073 | lockdep_assert_held(&rq->lock); |
1074 | dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK); |
1075 | } |
1076 | if (running) |
1077 | put_prev_task(rq, p); |
1078 | |
1079 | p->sched_class->set_cpus_allowed(p, new_mask); |
1080 | |
1081 | if (queued) |
1082 | enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK); |
1083 | if (running) |
1084 | set_curr_task(rq, p); |
1085 | } |
1086 | |
1087 | /* |
1088 | * Change a given task's CPU affinity. Migrate the thread to a |
1089 | * proper CPU and schedule it away if the CPU it's executing on |
1090 | * is removed from the allowed bitmask. |
1091 | * |
1092 | * NOTE: the caller must have a valid reference to the task, the |
1093 | * task must not exit() & deallocate itself prematurely. The |
1094 | * call is not atomic; no spinlocks may be held. |
1095 | */ |
1096 | static int __set_cpus_allowed_ptr(struct task_struct *p, |
1097 | const struct cpumask *new_mask, bool check) |
1098 | { |
1099 | const struct cpumask *cpu_valid_mask = cpu_active_mask; |
1100 | unsigned int dest_cpu; |
1101 | struct rq_flags rf; |
1102 | struct rq *rq; |
1103 | int ret = 0; |
1104 | |
1105 | rq = task_rq_lock(p, &rf); |
1106 | update_rq_clock(rq); |
1107 | |
1108 | if (p->flags & PF_KTHREAD) { |
1109 | /* |
1110 | * Kernel threads are allowed on online && !active CPUs |
1111 | */ |
1112 | cpu_valid_mask = cpu_online_mask; |
1113 | } |
1114 | |
1115 | /* |
1116 | * Must re-check here, to close a race against __kthread_bind(), |
1117 | * sched_setaffinity() is not guaranteed to observe the flag. |
1118 | */ |
1119 | if (check && (p->flags & PF_NO_SETAFFINITY)) { |
1120 | ret = -EINVAL; |
1121 | goto out; |
1122 | } |
1123 | |
1124 | if (cpumask_equal(&p->cpus_allowed, new_mask)) |
1125 | goto out; |
1126 | |
1127 | if (!cpumask_intersects(new_mask, cpu_valid_mask)) { |
1128 | ret = -EINVAL; |
1129 | goto out; |
1130 | } |
1131 | |
1132 | do_set_cpus_allowed(p, new_mask); |
1133 | |
1134 | if (p->flags & PF_KTHREAD) { |
1135 | /* |
1136 | * For kernel threads that do indeed end up on online && |
1137 | * !active we want to ensure they are strict per-CPU threads. |
1138 | */ |
1139 | WARN_ON(cpumask_intersects(new_mask, cpu_online_mask) && |
1140 | !cpumask_intersects(new_mask, cpu_active_mask) && |
1141 | p->nr_cpus_allowed != 1); |
1142 | } |
1143 | |
1144 | /* Can the task run on the task's current CPU? If so, we're done */ |
1145 | if (cpumask_test_cpu(task_cpu(p), new_mask)) |
1146 | goto out; |
1147 | |
1148 | dest_cpu = cpumask_any_and(cpu_valid_mask, new_mask); |
1149 | if (task_running(rq, p) || p->state == TASK_WAKING) { |
1150 | struct migration_arg arg = { p, dest_cpu }; |
1151 | /* Need help from migration thread: drop lock and wait. */ |
1152 | task_rq_unlock(rq, p, &rf); |
1153 | stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg); |
1154 | tlb_migrate_finish(p->mm); |
1155 | return 0; |
1156 | } else if (task_on_rq_queued(p)) { |
1157 | /* |
1158 | * OK, since we're going to drop the lock immediately |
1159 | * afterwards anyway. |
1160 | */ |
1161 | rq = move_queued_task(rq, &rf, p, dest_cpu); |
1162 | } |
1163 | out: |
1164 | task_rq_unlock(rq, p, &rf); |
1165 | |
1166 | return ret; |
1167 | } |
1168 | |
1169 | int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask) |
1170 | { |
1171 | return __set_cpus_allowed_ptr(p, new_mask, false); |
1172 | } |
1173 | EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr); |
1174 | |
1175 | void set_task_cpu(struct task_struct *p, unsigned int new_cpu) |
1176 | { |
1177 | #ifdef CONFIG_SCHED_DEBUG |
1178 | /* |
1179 | * We should never call set_task_cpu() on a blocked task, |
1180 | * ttwu() will sort out the placement. |
1181 | */ |
1182 | WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING && |
1183 | !p->on_rq); |
1184 | |
1185 | /* |
1186 | * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING, |
1187 | * because schedstat_wait_{start,end} rebase migrating task's wait_start |
1188 | * time relying on p->on_rq. |
1189 | */ |
1190 | WARN_ON_ONCE(p->state == TASK_RUNNING && |
1191 | p->sched_class == &fair_sched_class && |
1192 | (p->on_rq && !task_on_rq_migrating(p))); |
1193 | |
1194 | #ifdef CONFIG_LOCKDEP |
1195 | /* |
1196 | * The caller should hold either p->pi_lock or rq->lock, when changing |
1197 | * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks. |
1198 | * |
1199 | * sched_move_task() holds both and thus holding either pins the cgroup, |
1200 | * see task_group(). |
1201 | * |
1202 | * Furthermore, all task_rq users should acquire both locks, see |
1203 | * task_rq_lock(). |
1204 | */ |
1205 | WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) || |
1206 | lockdep_is_held(&task_rq(p)->lock))); |
1207 | #endif |
1208 | /* |
1209 | * Clearly, migrating tasks to offline CPUs is a fairly daft thing. |
1210 | */ |
1211 | WARN_ON_ONCE(!cpu_online(new_cpu)); |
1212 | #endif |
1213 | |
1214 | trace_sched_migrate_task(p, new_cpu); |
1215 | |
1216 | if (task_cpu(p) != new_cpu) { |
1217 | if (p->sched_class->migrate_task_rq) |
1218 | p->sched_class->migrate_task_rq(p, new_cpu); |
1219 | p->se.nr_migrations++; |
1220 | rseq_migrate(p); |
1221 | perf_event_task_migrate(p); |
1222 | } |
1223 | |
1224 | __set_task_cpu(p, new_cpu); |
1225 | } |
1226 | |
1227 | #ifdef CONFIG_NUMA_BALANCING |
1228 | static void __migrate_swap_task(struct task_struct *p, int cpu) |
1229 | { |
1230 | if (task_on_rq_queued(p)) { |
1231 | struct rq *src_rq, *dst_rq; |
1232 | struct rq_flags srf, drf; |
1233 | |
1234 | src_rq = task_rq(p); |
1235 | dst_rq = cpu_rq(cpu); |
1236 | |
1237 | rq_pin_lock(src_rq, &srf); |
1238 | rq_pin_lock(dst_rq, &drf); |
1239 | |
1240 | p->on_rq = TASK_ON_RQ_MIGRATING; |
1241 | deactivate_task(src_rq, p, 0); |
1242 | set_task_cpu(p, cpu); |
1243 | activate_task(dst_rq, p, 0); |
1244 | p->on_rq = TASK_ON_RQ_QUEUED; |
1245 | check_preempt_curr(dst_rq, p, 0); |
1246 | |
1247 | rq_unpin_lock(dst_rq, &drf); |
1248 | rq_unpin_lock(src_rq, &srf); |
1249 | |
1250 | } else { |
1251 | /* |
1252 | * Task isn't running anymore; make it appear like we migrated |
1253 | * it before it went to sleep. This means on wakeup we make the |
1254 | * previous CPU our target instead of where it really is. |
1255 | */ |
1256 | p->wake_cpu = cpu; |
1257 | } |
1258 | } |
1259 | |
1260 | struct migration_swap_arg { |
1261 | struct task_struct *src_task, *dst_task; |
1262 | int src_cpu, dst_cpu; |
1263 | }; |
1264 | |
1265 | static int migrate_swap_stop(void *data) |
1266 | { |
1267 | struct migration_swap_arg *arg = data; |
1268 | struct rq *src_rq, *dst_rq; |
1269 | int ret = -EAGAIN; |
1270 | |
1271 | if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu)) |
1272 | return -EAGAIN; |
1273 | |
1274 | src_rq = cpu_rq(arg->src_cpu); |
1275 | dst_rq = cpu_rq(arg->dst_cpu); |
1276 | |
1277 | double_raw_lock(&arg->src_task->pi_lock, |
1278 | &arg->dst_task->pi_lock); |
1279 | double_rq_lock(src_rq, dst_rq); |
1280 | |
1281 | if (task_cpu(arg->dst_task) != arg->dst_cpu) |
1282 | goto unlock; |
1283 | |
1284 | if (task_cpu(arg->src_task) != arg->src_cpu) |
1285 | goto unlock; |
1286 | |
1287 | if (!cpumask_test_cpu(arg->dst_cpu, &arg->src_task->cpus_allowed)) |
1288 | goto unlock; |
1289 | |
1290 | if (!cpumask_test_cpu(arg->src_cpu, &arg->dst_task->cpus_allowed)) |
1291 | goto unlock; |
1292 | |
1293 | __migrate_swap_task(arg->src_task, arg->dst_cpu); |
1294 | __migrate_swap_task(arg->dst_task, arg->src_cpu); |
1295 | |
1296 | ret = 0; |
1297 | |
1298 | unlock: |
1299 | double_rq_unlock(src_rq, dst_rq); |
1300 | raw_spin_unlock(&arg->dst_task->pi_lock); |
1301 | raw_spin_unlock(&arg->src_task->pi_lock); |
1302 | |
1303 | return ret; |
1304 | } |
1305 | |
1306 | /* |
1307 | * Cross migrate two tasks |
1308 | */ |
1309 | int migrate_swap(struct task_struct *cur, struct task_struct *p, |
1310 | int target_cpu, int curr_cpu) |
1311 | { |
1312 | struct migration_swap_arg arg; |
1313 | int ret = -EINVAL; |
1314 | |
1315 | arg = (struct migration_swap_arg){ |
1316 | .src_task = cur, |
1317 | .src_cpu = curr_cpu, |
1318 | .dst_task = p, |
1319 | .dst_cpu = target_cpu, |
1320 | }; |
1321 | |
1322 | if (arg.src_cpu == arg.dst_cpu) |
1323 | goto out; |
1324 | |
1325 | /* |
1326 | * These three tests are all lockless; this is OK since all of them |
1327 | * will be re-checked with proper locks held further down the line. |
1328 | */ |
1329 | if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu)) |
1330 | goto out; |
1331 | |
1332 | if (!cpumask_test_cpu(arg.dst_cpu, &arg.src_task->cpus_allowed)) |
1333 | goto out; |
1334 | |
1335 | if (!cpumask_test_cpu(arg.src_cpu, &arg.dst_task->cpus_allowed)) |
1336 | goto out; |
1337 | |
1338 | trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu); |
1339 | ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg); |
1340 | |
1341 | out: |
1342 | return ret; |
1343 | } |
1344 | #endif /* CONFIG_NUMA_BALANCING */ |
1345 | |
1346 | /* |
1347 | * wait_task_inactive - wait for a thread to unschedule. |
1348 | * |
1349 | * If @match_state is nonzero, it's the @p->state value just checked and |
1350 | * not expected to change. If it changes, i.e. @p might have woken up, |
1351 | * then return zero. When we succeed in waiting for @p to be off its CPU, |
1352 | * we return a positive number (its total switch count). If a second call |
1353 | * a short while later returns the same number, the caller can be sure that |
1354 | * @p has remained unscheduled the whole time. |
1355 | * |
1356 | * The caller must ensure that the task *will* unschedule sometime soon, |
1357 | * else this function might spin for a *long* time. This function can't |
1358 | * be called with interrupts off, or it may introduce deadlock with |
1359 | * smp_call_function() if an IPI is sent by the same process we are |
1360 | * waiting to become inactive. |
1361 | */ |
1362 | unsigned long wait_task_inactive(struct task_struct *p, long match_state) |
1363 | { |
1364 | int running, queued; |
1365 | struct rq_flags rf; |
1366 | unsigned long ncsw; |
1367 | struct rq *rq; |
1368 | |
1369 | for (;;) { |
1370 | /* |
1371 | * We do the initial early heuristics without holding |
1372 | * any task-queue locks at all. We'll only try to get |
1373 | * the runqueue lock when things look like they will |
1374 | * work out! |
1375 | */ |
1376 | rq = task_rq(p); |
1377 | |
1378 | /* |
1379 | * If the task is actively running on another CPU |
1380 | * still, just relax and busy-wait without holding |
1381 | * any locks. |
1382 | * |
1383 | * NOTE! Since we don't hold any locks, it's not |
1384 | * even sure that "rq" stays as the right runqueue! |
1385 | * But we don't care, since "task_running()" will |
1386 | * return false if the runqueue has changed and p |
1387 | * is actually now running somewhere else! |
1388 | */ |
1389 | while (task_running(rq, p)) { |
1390 | if (match_state && unlikely(p->state != match_state)) |
1391 | return 0; |
1392 | cpu_relax(); |
1393 | } |
1394 | |
1395 | /* |
1396 | * Ok, time to look more closely! We need the rq |
1397 | * lock now, to be *sure*. If we're wrong, we'll |
1398 | * just go back and repeat. |
1399 | */ |
1400 | rq = task_rq_lock(p, &rf); |
1401 | trace_sched_wait_task(p); |
1402 | running = task_running(rq, p); |
1403 | queued = task_on_rq_queued(p); |
1404 | ncsw = 0; |
1405 | if (!match_state || p->state == match_state) |
1406 | ncsw = p->nvcsw | LONG_MIN; /* sets MSB */ |
1407 | task_rq_unlock(rq, p, &rf); |
1408 | |
1409 | /* |
1410 | * If it changed from the expected state, bail out now. |
1411 | */ |
1412 | if (unlikely(!ncsw)) |
1413 | break; |
1414 | |
1415 | /* |
1416 | * Was it really running after all now that we |
1417 | * checked with the proper locks actually held? |
1418 | * |
1419 | * Oops. Go back and try again.. |
1420 | */ |
1421 | if (unlikely(running)) { |
1422 | cpu_relax(); |
1423 | continue; |
1424 | } |
1425 | |
1426 | /* |
1427 | * It's not enough that it's not actively running, |
1428 | * it must be off the runqueue _entirely_, and not |
1429 | * preempted! |
1430 | * |
1431 | * So if it was still runnable (but just not actively |
1432 | * running right now), it's preempted, and we should |
1433 | * yield - it could be a while. |
1434 | */ |
1435 | if (unlikely(queued)) { |
1436 | ktime_t to = NSEC_PER_SEC / HZ; |
1437 | |
1438 | set_current_state(TASK_UNINTERRUPTIBLE); |
1439 | schedule_hrtimeout(&to, HRTIMER_MODE_REL); |
1440 | continue; |
1441 | } |
1442 | |
1443 | /* |
1444 | * Ahh, all good. It wasn't running, and it wasn't |
1445 | * runnable, which means that it will never become |
1446 | * running in the future either. We're all done! |
1447 | */ |
1448 | break; |
1449 | } |
1450 | |
1451 | return ncsw; |
1452 | } |
1453 | |
1454 | /*** |
1455 | * kick_process - kick a running thread to enter/exit the kernel |
1456 | * @p: the to-be-kicked thread |
1457 | * |
1458 | * Cause a process which is running on another CPU to enter |
1459 | * kernel-mode, without any delay. (to get signals handled.) |
1460 | * |
1461 | * NOTE: this function doesn't have to take the runqueue lock, |
1462 | * because all it wants to ensure is that the remote task enters |
1463 | * the kernel. If the IPI races and the task has been migrated |
1464 | * to another CPU then no harm is done and the purpose has been |
1465 | * achieved as well. |
1466 | */ |
1467 | void kick_process(struct task_struct *p) |
1468 | { |
1469 | int cpu; |
1470 | |
1471 | preempt_disable(); |
1472 | cpu = task_cpu(p); |
1473 | if ((cpu != smp_processor_id()) && task_curr(p)) |
1474 | smp_send_reschedule(cpu); |
1475 | preempt_enable(); |
1476 | } |
1477 | EXPORT_SYMBOL_GPL(kick_process); |
1478 | |
1479 | /* |
1480 | * ->cpus_allowed is protected by both rq->lock and p->pi_lock |
1481 | * |
1482 | * A few notes on cpu_active vs cpu_online: |
1483 | * |
1484 | * - cpu_active must be a subset of cpu_online |
1485 | * |
1486 | * - on CPU-up we allow per-CPU kthreads on the online && !active CPU, |
1487 | * see __set_cpus_allowed_ptr(). At this point the newly online |
1488 | * CPU isn't yet part of the sched domains, and balancing will not |
1489 | * see it. |
1490 | * |
1491 | * - on CPU-down we clear cpu_active() to mask the sched domains and |
1492 | * avoid the load balancer to place new tasks on the to be removed |
1493 | * CPU. Existing tasks will remain running there and will be taken |
1494 | * off. |
1495 | * |
1496 | * This means that fallback selection must not select !active CPUs. |
1497 | * And can assume that any active CPU must be online. Conversely |
1498 | * select_task_rq() below may allow selection of !active CPUs in order |
1499 | * to satisfy the above rules. |
1500 | */ |
1501 | static int select_fallback_rq(int cpu, struct task_struct *p) |
1502 | { |
1503 | int nid = cpu_to_node(cpu); |
1504 | const struct cpumask *nodemask = NULL; |
1505 | enum { cpuset, possible, fail } state = cpuset; |
1506 | int dest_cpu; |
1507 | |
1508 | /* |
1509 | * If the node that the CPU is on has been offlined, cpu_to_node() |
1510 | * will return -1. There is no CPU on the node, and we should |
1511 | * select the CPU on the other node. |
1512 | */ |
1513 | if (nid != -1) { |
1514 | nodemask = cpumask_of_node(nid); |
1515 | |
1516 | /* Look for allowed, online CPU in same node. */ |
1517 | for_each_cpu(dest_cpu, nodemask) { |
1518 | if (!cpu_active(dest_cpu)) |
1519 | continue; |
1520 | if (cpumask_test_cpu(dest_cpu, &p->cpus_allowed)) |
1521 | return dest_cpu; |
1522 | } |
1523 | } |
1524 | |
1525 | for (;;) { |
1526 | /* Any allowed, online CPU? */ |
1527 | for_each_cpu(dest_cpu, &p->cpus_allowed) { |
1528 | if (!is_cpu_allowed(p, dest_cpu)) |
1529 | continue; |
1530 | |
1531 | goto out; |
1532 | } |
1533 | |
1534 | /* No more Mr. Nice Guy. */ |
1535 | switch (state) { |
1536 | case cpuset: |
1537 | if (IS_ENABLED(CONFIG_CPUSETS)) { |
1538 | cpuset_cpus_allowed_fallback(p); |
1539 | state = possible; |
1540 | break; |
1541 | } |
1542 | /* Fall-through */ |
1543 | case possible: |
1544 | do_set_cpus_allowed(p, cpu_possible_mask); |
1545 | state = fail; |
1546 | break; |
1547 | |
1548 | case fail: |
1549 | BUG(); |
1550 | break; |
1551 | } |
1552 | } |
1553 | |
1554 | out: |
1555 | if (state != cpuset) { |
1556 | /* |
1557 | * Don't tell them about moving exiting tasks or |
1558 | * kernel threads (both mm NULL), since they never |
1559 | * leave kernel. |
1560 | */ |
1561 | if (p->mm && printk_ratelimit()) { |
1562 | printk_deferred("process %d (%s) no longer affine to cpu%d\n" , |
1563 | task_pid_nr(p), p->comm, cpu); |
1564 | } |
1565 | } |
1566 | |
1567 | return dest_cpu; |
1568 | } |
1569 | |
1570 | /* |
1571 | * The caller (fork, wakeup) owns p->pi_lock, ->cpus_allowed is stable. |
1572 | */ |
1573 | static inline |
1574 | int select_task_rq(struct task_struct *p, int cpu, int sd_flags, int wake_flags) |
1575 | { |
1576 | lockdep_assert_held(&p->pi_lock); |
1577 | |
1578 | if (p->nr_cpus_allowed > 1) |
1579 | cpu = p->sched_class->select_task_rq(p, cpu, sd_flags, wake_flags); |
1580 | else |
1581 | cpu = cpumask_any(&p->cpus_allowed); |
1582 | |
1583 | /* |
1584 | * In order not to call set_task_cpu() on a blocking task we need |
1585 | * to rely on ttwu() to place the task on a valid ->cpus_allowed |
1586 | * CPU. |
1587 | * |
1588 | * Since this is common to all placement strategies, this lives here. |
1589 | * |
1590 | * [ this allows ->select_task() to simply return task_cpu(p) and |
1591 | * not worry about this generic constraint ] |
1592 | */ |
1593 | if (unlikely(!is_cpu_allowed(p, cpu))) |
1594 | cpu = select_fallback_rq(task_cpu(p), p); |
1595 | |
1596 | return cpu; |
1597 | } |
1598 | |
1599 | static void update_avg(u64 *avg, u64 sample) |
1600 | { |
1601 | s64 diff = sample - *avg; |
1602 | *avg += diff >> 3; |
1603 | } |
1604 | |
1605 | void sched_set_stop_task(int cpu, struct task_struct *stop) |
1606 | { |
1607 | struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 }; |
1608 | struct task_struct *old_stop = cpu_rq(cpu)->stop; |
1609 | |
1610 | if (stop) { |
1611 | /* |
1612 | * Make it appear like a SCHED_FIFO task, its something |
1613 | * userspace knows about and won't get confused about. |
1614 | * |
1615 | * Also, it will make PI more or less work without too |
1616 | * much confusion -- but then, stop work should not |
1617 | * rely on PI working anyway. |
1618 | */ |
1619 | sched_setscheduler_nocheck(stop, SCHED_FIFO, ¶m); |
1620 | |
1621 | stop->sched_class = &stop_sched_class; |
1622 | } |
1623 | |
1624 | cpu_rq(cpu)->stop = stop; |
1625 | |
1626 | if (old_stop) { |
1627 | /* |
1628 | * Reset it back to a normal scheduling class so that |
1629 | * it can die in pieces. |
1630 | */ |
1631 | old_stop->sched_class = &rt_sched_class; |
1632 | } |
1633 | } |
1634 | |
1635 | #else |
1636 | |
1637 | static inline int __set_cpus_allowed_ptr(struct task_struct *p, |
1638 | const struct cpumask *new_mask, bool check) |
1639 | { |
1640 | return set_cpus_allowed_ptr(p, new_mask); |
1641 | } |
1642 | |
1643 | #endif /* CONFIG_SMP */ |
1644 | |
1645 | static void |
1646 | ttwu_stat(struct task_struct *p, int cpu, int wake_flags) |
1647 | { |
1648 | struct rq *rq; |
1649 | |
1650 | if (!schedstat_enabled()) |
1651 | return; |
1652 | |
1653 | rq = this_rq(); |
1654 | |
1655 | #ifdef CONFIG_SMP |
1656 | if (cpu == rq->cpu) { |
1657 | __schedstat_inc(rq->ttwu_local); |
1658 | __schedstat_inc(p->se.statistics.nr_wakeups_local); |
1659 | } else { |
1660 | struct sched_domain *sd; |
1661 | |
1662 | __schedstat_inc(p->se.statistics.nr_wakeups_remote); |
1663 | rcu_read_lock(); |
1664 | for_each_domain(rq->cpu, sd) { |
1665 | if (cpumask_test_cpu(cpu, sched_domain_span(sd))) { |
1666 | __schedstat_inc(sd->ttwu_wake_remote); |
1667 | break; |
1668 | } |
1669 | } |
1670 | rcu_read_unlock(); |
1671 | } |
1672 | |
1673 | if (wake_flags & WF_MIGRATED) |
1674 | __schedstat_inc(p->se.statistics.nr_wakeups_migrate); |
1675 | #endif /* CONFIG_SMP */ |
1676 | |
1677 | __schedstat_inc(rq->ttwu_count); |
1678 | __schedstat_inc(p->se.statistics.nr_wakeups); |
1679 | |
1680 | if (wake_flags & WF_SYNC) |
1681 | __schedstat_inc(p->se.statistics.nr_wakeups_sync); |
1682 | } |
1683 | |
1684 | static inline void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags) |
1685 | { |
1686 | activate_task(rq, p, en_flags); |
1687 | p->on_rq = TASK_ON_RQ_QUEUED; |
1688 | |
1689 | /* If a worker is waking up, notify the workqueue: */ |
1690 | if (p->flags & PF_WQ_WORKER) |
1691 | wq_worker_waking_up(p, cpu_of(rq)); |
1692 | } |
1693 | |
1694 | /* |
1695 | * Mark the task runnable and perform wakeup-preemption. |
1696 | */ |
1697 | static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags, |
1698 | struct rq_flags *rf) |
1699 | { |
1700 | check_preempt_curr(rq, p, wake_flags); |
1701 | p->state = TASK_RUNNING; |
1702 | trace_sched_wakeup(p); |
1703 | |
1704 | #ifdef CONFIG_SMP |
1705 | if (p->sched_class->task_woken) { |
1706 | /* |
1707 | * Our task @p is fully woken up and running; so its safe to |
1708 | * drop the rq->lock, hereafter rq is only used for statistics. |
1709 | */ |
1710 | rq_unpin_lock(rq, rf); |
1711 | p->sched_class->task_woken(rq, p); |
1712 | rq_repin_lock(rq, rf); |
1713 | } |
1714 | |
1715 | if (rq->idle_stamp) { |
1716 | u64 delta = rq_clock(rq) - rq->idle_stamp; |
1717 | u64 max = 2*rq->max_idle_balance_cost; |
1718 | |
1719 | update_avg(&rq->avg_idle, delta); |
1720 | |
1721 | if (rq->avg_idle > max) |
1722 | rq->avg_idle = max; |
1723 | |
1724 | rq->idle_stamp = 0; |
1725 | } |
1726 | #endif |
1727 | } |
1728 | |
1729 | static void |
1730 | ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags, |
1731 | struct rq_flags *rf) |
1732 | { |
1733 | int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK; |
1734 | |
1735 | lockdep_assert_held(&rq->lock); |
1736 | |
1737 | #ifdef CONFIG_SMP |
1738 | if (p->sched_contributes_to_load) |
1739 | rq->nr_uninterruptible--; |
1740 | |
1741 | if (wake_flags & WF_MIGRATED) |
1742 | en_flags |= ENQUEUE_MIGRATED; |
1743 | #endif |
1744 | |
1745 | ttwu_activate(rq, p, en_flags); |
1746 | ttwu_do_wakeup(rq, p, wake_flags, rf); |
1747 | } |
1748 | |
1749 | /* |
1750 | * Called in case the task @p isn't fully descheduled from its runqueue, |
1751 | * in this case we must do a remote wakeup. Its a 'light' wakeup though, |
1752 | * since all we need to do is flip p->state to TASK_RUNNING, since |
1753 | * the task is still ->on_rq. |
1754 | */ |
1755 | static int ttwu_remote(struct task_struct *p, int wake_flags) |
1756 | { |
1757 | struct rq_flags rf; |
1758 | struct rq *rq; |
1759 | int ret = 0; |
1760 | |
1761 | rq = __task_rq_lock(p, &rf); |
1762 | if (task_on_rq_queued(p)) { |
1763 | /* check_preempt_curr() may use rq clock */ |
1764 | update_rq_clock(rq); |
1765 | ttwu_do_wakeup(rq, p, wake_flags, &rf); |
1766 | ret = 1; |
1767 | } |
1768 | __task_rq_unlock(rq, &rf); |
1769 | |
1770 | return ret; |
1771 | } |
1772 | |
1773 | #ifdef CONFIG_SMP |
1774 | void sched_ttwu_pending(void) |
1775 | { |
1776 | struct rq *rq = this_rq(); |
1777 | struct llist_node *llist = llist_del_all(&rq->wake_list); |
1778 | struct task_struct *p, *t; |
1779 | struct rq_flags rf; |
1780 | |
1781 | if (!llist) |
1782 | return; |
1783 | |
1784 | rq_lock_irqsave(rq, &rf); |
1785 | update_rq_clock(rq); |
1786 | |
1787 | llist_for_each_entry_safe(p, t, llist, wake_entry) |
1788 | ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf); |
1789 | |
1790 | rq_unlock_irqrestore(rq, &rf); |
1791 | } |
1792 | |
1793 | void scheduler_ipi(void) |
1794 | { |
1795 | /* |
1796 | * Fold TIF_NEED_RESCHED into the preempt_count; anybody setting |
1797 | * TIF_NEED_RESCHED remotely (for the first time) will also send |
1798 | * this IPI. |
1799 | */ |
1800 | preempt_fold_need_resched(); |
1801 | |
1802 | if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick()) |
1803 | return; |
1804 | |
1805 | /* |
1806 | * Not all reschedule IPI handlers call irq_enter/irq_exit, since |
1807 | * traditionally all their work was done from the interrupt return |
1808 | * path. Now that we actually do some work, we need to make sure |
1809 | * we do call them. |
1810 | * |
1811 | * Some archs already do call them, luckily irq_enter/exit nest |
1812 | * properly. |
1813 | * |
1814 | * Arguably we should visit all archs and update all handlers, |
1815 | * however a fair share of IPIs are still resched only so this would |
1816 | * somewhat pessimize the simple resched case. |
1817 | */ |
1818 | irq_enter(); |
1819 | sched_ttwu_pending(); |
1820 | |
1821 | /* |
1822 | * Check if someone kicked us for doing the nohz idle load balance. |
1823 | */ |
1824 | if (unlikely(got_nohz_idle_kick())) { |
1825 | this_rq()->idle_balance = 1; |
1826 | raise_softirq_irqoff(SCHED_SOFTIRQ); |
1827 | } |
1828 | irq_exit(); |
1829 | } |
1830 | |
1831 | static void ttwu_queue_remote(struct task_struct *p, int cpu, int wake_flags) |
1832 | { |
1833 | struct rq *rq = cpu_rq(cpu); |
1834 | |
1835 | p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED); |
1836 | |
1837 | if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list)) { |
1838 | if (!set_nr_if_polling(rq->idle)) |
1839 | smp_send_reschedule(cpu); |
1840 | else |
1841 | trace_sched_wake_idle_without_ipi(cpu); |
1842 | } |
1843 | } |
1844 | |
1845 | void wake_up_if_idle(int cpu) |
1846 | { |
1847 | struct rq *rq = cpu_rq(cpu); |
1848 | struct rq_flags rf; |
1849 | |
1850 | rcu_read_lock(); |
1851 | |
1852 | if (!is_idle_task(rcu_dereference(rq->curr))) |
1853 | goto out; |
1854 | |
1855 | if (set_nr_if_polling(rq->idle)) { |
1856 | trace_sched_wake_idle_without_ipi(cpu); |
1857 | } else { |
1858 | rq_lock_irqsave(rq, &rf); |
1859 | if (is_idle_task(rq->curr)) |
1860 | smp_send_reschedule(cpu); |
1861 | /* Else CPU is not idle, do nothing here: */ |
1862 | rq_unlock_irqrestore(rq, &rf); |
1863 | } |
1864 | |
1865 | out: |
1866 | rcu_read_unlock(); |
1867 | } |
1868 | |
1869 | bool cpus_share_cache(int this_cpu, int that_cpu) |
1870 | { |
1871 | return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu); |
1872 | } |
1873 | #endif /* CONFIG_SMP */ |
1874 | |
1875 | static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags) |
1876 | { |
1877 | struct rq *rq = cpu_rq(cpu); |
1878 | struct rq_flags rf; |
1879 | |
1880 | #if defined(CONFIG_SMP) |
1881 | if (sched_feat(TTWU_QUEUE) && !cpus_share_cache(smp_processor_id(), cpu)) { |
1882 | sched_clock_cpu(cpu); /* Sync clocks across CPUs */ |
1883 | ttwu_queue_remote(p, cpu, wake_flags); |
1884 | return; |
1885 | } |
1886 | #endif |
1887 | |
1888 | rq_lock(rq, &rf); |
1889 | update_rq_clock(rq); |
1890 | ttwu_do_activate(rq, p, wake_flags, &rf); |
1891 | rq_unlock(rq, &rf); |
1892 | } |
1893 | |
1894 | /* |
1895 | * Notes on Program-Order guarantees on SMP systems. |
1896 | * |
1897 | * MIGRATION |
1898 | * |
1899 | * The basic program-order guarantee on SMP systems is that when a task [t] |
1900 | * migrates, all its activity on its old CPU [c0] happens-before any subsequent |
1901 | * execution on its new CPU [c1]. |
1902 | * |
1903 | * For migration (of runnable tasks) this is provided by the following means: |
1904 | * |
1905 | * A) UNLOCK of the rq(c0)->lock scheduling out task t |
1906 | * B) migration for t is required to synchronize *both* rq(c0)->lock and |
1907 | * rq(c1)->lock (if not at the same time, then in that order). |
1908 | * C) LOCK of the rq(c1)->lock scheduling in task |
1909 | * |
1910 | * Release/acquire chaining guarantees that B happens after A and C after B. |
1911 | * Note: the CPU doing B need not be c0 or c1 |
1912 | * |
1913 | * Example: |
1914 | * |
1915 | * CPU0 CPU1 CPU2 |
1916 | * |
1917 | * LOCK rq(0)->lock |
1918 | * sched-out X |
1919 | * sched-in Y |
1920 | * UNLOCK rq(0)->lock |
1921 | * |
1922 | * LOCK rq(0)->lock // orders against CPU0 |
1923 | * dequeue X |
1924 | * UNLOCK rq(0)->lock |
1925 | * |
1926 | * LOCK rq(1)->lock |
1927 | * enqueue X |
1928 | * UNLOCK rq(1)->lock |
1929 | * |
1930 | * LOCK rq(1)->lock // orders against CPU2 |
1931 | * sched-out Z |
1932 | * sched-in X |
1933 | * UNLOCK rq(1)->lock |
1934 | * |
1935 | * |
1936 | * BLOCKING -- aka. SLEEP + WAKEUP |
1937 | * |
1938 | * For blocking we (obviously) need to provide the same guarantee as for |
1939 | * migration. However the means are completely different as there is no lock |
1940 | * chain to provide order. Instead we do: |
1941 | * |
1942 | * 1) smp_store_release(X->on_cpu, 0) |
1943 | * 2) smp_cond_load_acquire(!X->on_cpu) |
1944 | * |
1945 | * Example: |
1946 | * |
1947 | * CPU0 (schedule) CPU1 (try_to_wake_up) CPU2 (schedule) |
1948 | * |
1949 | * LOCK rq(0)->lock LOCK X->pi_lock |
1950 | * dequeue X |
1951 | * sched-out X |
1952 | * smp_store_release(X->on_cpu, 0); |
1953 | * |
1954 | * smp_cond_load_acquire(&X->on_cpu, !VAL); |
1955 | * X->state = WAKING |
1956 | * set_task_cpu(X,2) |
1957 | * |
1958 | * LOCK rq(2)->lock |
1959 | * enqueue X |
1960 | * X->state = RUNNING |
1961 | * UNLOCK rq(2)->lock |
1962 | * |
1963 | * LOCK rq(2)->lock // orders against CPU1 |
1964 | * sched-out Z |
1965 | * sched-in X |
1966 | * UNLOCK rq(2)->lock |
1967 | * |
1968 | * UNLOCK X->pi_lock |
1969 | * UNLOCK rq(0)->lock |
1970 | * |
1971 | * |
1972 | * However, for wakeups there is a second guarantee we must provide, namely we |
1973 | * must ensure that CONDITION=1 done by the caller can not be reordered with |
1974 | * accesses to the task state; see try_to_wake_up() and set_current_state(). |
1975 | */ |
1976 | |
1977 | /** |
1978 | * try_to_wake_up - wake up a thread |
1979 | * @p: the thread to be awakened |
1980 | * @state: the mask of task states that can be woken |
1981 | * @wake_flags: wake modifier flags (WF_*) |
1982 | * |
1983 | * If (@state & @p->state) @p->state = TASK_RUNNING. |
1984 | * |
1985 | * If the task was not queued/runnable, also place it back on a runqueue. |
1986 | * |
1987 | * Atomic against schedule() which would dequeue a task, also see |
1988 | * set_current_state(). |
1989 | * |
1990 | * This function executes a full memory barrier before accessing the task |
1991 | * state; see set_current_state(). |
1992 | * |
1993 | * Return: %true if @p->state changes (an actual wakeup was done), |
1994 | * %false otherwise. |
1995 | */ |
1996 | static int |
1997 | try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) |
1998 | { |
1999 | unsigned long flags; |
2000 | int cpu, success = 0; |
2001 | |
2002 | /* |
2003 | * If we are going to wake up a thread waiting for CONDITION we |
2004 | * need to ensure that CONDITION=1 done by the caller can not be |
2005 | * reordered with p->state check below. This pairs with mb() in |
2006 | * set_current_state() the waiting thread does. |
2007 | */ |
2008 | raw_spin_lock_irqsave(&p->pi_lock, flags); |
2009 | smp_mb__after_spinlock(); |
2010 | if (!(p->state & state)) |
2011 | goto out; |
2012 | |
2013 | trace_sched_waking(p); |
2014 | |
2015 | /* We're going to change ->state: */ |
2016 | success = 1; |
2017 | cpu = task_cpu(p); |
2018 | |
2019 | /* |
2020 | * Ensure we load p->on_rq _after_ p->state, otherwise it would |
2021 | * be possible to, falsely, observe p->on_rq == 0 and get stuck |
2022 | * in smp_cond_load_acquire() below. |
2023 | * |
2024 | * sched_ttwu_pending() try_to_wake_up() |
2025 | * STORE p->on_rq = 1 LOAD p->state |
2026 | * UNLOCK rq->lock |
2027 | * |
2028 | * __schedule() (switch to task 'p') |
2029 | * LOCK rq->lock smp_rmb(); |
2030 | * smp_mb__after_spinlock(); |
2031 | * UNLOCK rq->lock |
2032 | * |
2033 | * [task p] |
2034 | * STORE p->state = UNINTERRUPTIBLE LOAD p->on_rq |
2035 | * |
2036 | * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in |
2037 | * __schedule(). See the comment for smp_mb__after_spinlock(). |
2038 | */ |
2039 | smp_rmb(); |
2040 | if (p->on_rq && ttwu_remote(p, wake_flags)) |
2041 | goto stat; |
2042 | |
2043 | #ifdef CONFIG_SMP |
2044 | /* |
2045 | * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be |
2046 | * possible to, falsely, observe p->on_cpu == 0. |
2047 | * |
2048 | * One must be running (->on_cpu == 1) in order to remove oneself |
2049 | * from the runqueue. |
2050 | * |
2051 | * __schedule() (switch to task 'p') try_to_wake_up() |
2052 | * STORE p->on_cpu = 1 LOAD p->on_rq |
2053 | * UNLOCK rq->lock |
2054 | * |
2055 | * __schedule() (put 'p' to sleep) |
2056 | * LOCK rq->lock smp_rmb(); |
2057 | * smp_mb__after_spinlock(); |
2058 | * STORE p->on_rq = 0 LOAD p->on_cpu |
2059 | * |
2060 | * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in |
2061 | * __schedule(). See the comment for smp_mb__after_spinlock(). |
2062 | */ |
2063 | smp_rmb(); |
2064 | |
2065 | /* |
2066 | * If the owning (remote) CPU is still in the middle of schedule() with |
2067 | * this task as prev, wait until its done referencing the task. |
2068 | * |
2069 | * Pairs with the smp_store_release() in finish_task(). |
2070 | * |
2071 | * This ensures that tasks getting woken will be fully ordered against |
2072 | * their previous state and preserve Program Order. |
2073 | */ |
2074 | smp_cond_load_acquire(&p->on_cpu, !VAL); |
2075 | |
2076 | p->sched_contributes_to_load = !!task_contributes_to_load(p); |
2077 | p->state = TASK_WAKING; |
2078 | |
2079 | if (p->in_iowait) { |
2080 | delayacct_blkio_end(p); |
2081 | atomic_dec(&task_rq(p)->nr_iowait); |
2082 | } |
2083 | |
2084 | cpu = select_task_rq(p, p->wake_cpu, SD_BALANCE_WAKE, wake_flags); |
2085 | if (task_cpu(p) != cpu) { |
2086 | wake_flags |= WF_MIGRATED; |
2087 | psi_ttwu_dequeue(p); |
2088 | set_task_cpu(p, cpu); |
2089 | } |
2090 | |
2091 | #else /* CONFIG_SMP */ |
2092 | |
2093 | if (p->in_iowait) { |
2094 | delayacct_blkio_end(p); |
2095 | atomic_dec(&task_rq(p)->nr_iowait); |
2096 | } |
2097 | |
2098 | #endif /* CONFIG_SMP */ |
2099 | |
2100 | ttwu_queue(p, cpu, wake_flags); |
2101 | stat: |
2102 | ttwu_stat(p, cpu, wake_flags); |
2103 | out: |
2104 | raw_spin_unlock_irqrestore(&p->pi_lock, flags); |
2105 | |
2106 | return success; |
2107 | } |
2108 | |
2109 | /** |
2110 | * try_to_wake_up_local - try to wake up a local task with rq lock held |
2111 | * @p: the thread to be awakened |
2112 | * @rf: request-queue flags for pinning |
2113 | * |
2114 | * Put @p on the run-queue if it's not already there. The caller must |
2115 | * ensure that this_rq() is locked, @p is bound to this_rq() and not |
2116 | * the current task. |
2117 | */ |
2118 | static void try_to_wake_up_local(struct task_struct *p, struct rq_flags *rf) |
2119 | { |
2120 | struct rq *rq = task_rq(p); |
2121 | |
2122 | if (WARN_ON_ONCE(rq != this_rq()) || |
2123 | WARN_ON_ONCE(p == current)) |
2124 | return; |
2125 | |
2126 | lockdep_assert_held(&rq->lock); |
2127 | |
2128 | if (!raw_spin_trylock(&p->pi_lock)) { |
2129 | /* |
2130 | * This is OK, because current is on_cpu, which avoids it being |
2131 | * picked for load-balance and preemption/IRQs are still |
2132 | * disabled avoiding further scheduler activity on it and we've |
2133 | * not yet picked a replacement task. |
2134 | */ |
2135 | rq_unlock(rq, rf); |
2136 | raw_spin_lock(&p->pi_lock); |
2137 | rq_relock(rq, rf); |
2138 | } |
2139 | |
2140 | if (!(p->state & TASK_NORMAL)) |
2141 | goto out; |
2142 | |
2143 | trace_sched_waking(p); |
2144 | |
2145 | if (!task_on_rq_queued(p)) { |
2146 | if (p->in_iowait) { |
2147 | delayacct_blkio_end(p); |
2148 | atomic_dec(&rq->nr_iowait); |
2149 | } |
2150 | ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK); |
2151 | } |
2152 | |
2153 | ttwu_do_wakeup(rq, p, 0, rf); |
2154 | ttwu_stat(p, smp_processor_id(), 0); |
2155 | out: |
2156 | raw_spin_unlock(&p->pi_lock); |
2157 | } |
2158 | |
2159 | /** |
2160 | * wake_up_process - Wake up a specific process |
2161 | * @p: The process to be woken up. |
2162 | * |
2163 | * Attempt to wake up the nominated process and move it to the set of runnable |
2164 | * processes. |
2165 | * |
2166 | * Return: 1 if the process was woken up, 0 if it was already running. |
2167 | * |
2168 | * This function executes a full memory barrier before accessing the task state. |
2169 | */ |
2170 | int wake_up_process(struct task_struct *p) |
2171 | { |
2172 | return try_to_wake_up(p, TASK_NORMAL, 0); |
2173 | } |
2174 | EXPORT_SYMBOL(wake_up_process); |
2175 | |
2176 | int wake_up_state(struct task_struct *p, unsigned int state) |
2177 | { |
2178 | return try_to_wake_up(p, state, 0); |
2179 | } |
2180 | |
2181 | /* |
2182 | * Perform scheduler related setup for a newly forked process p. |
2183 | * p is forked by current. |
2184 | * |
2185 | * __sched_fork() is basic setup used by init_idle() too: |
2186 | */ |
2187 | static void __sched_fork(unsigned long clone_flags, struct task_struct *p) |
2188 | { |
2189 | p->on_rq = 0; |
2190 | |
2191 | p->se.on_rq = 0; |
2192 | p->se.exec_start = 0; |
2193 | p->se.sum_exec_runtime = 0; |
2194 | p->se.prev_sum_exec_runtime = 0; |
2195 | p->se.nr_migrations = 0; |
2196 | p->se.vruntime = 0; |
2197 | INIT_LIST_HEAD(&p->se.group_node); |
2198 | |
2199 | #ifdef CONFIG_FAIR_GROUP_SCHED |
2200 | p->se.cfs_rq = NULL; |
2201 | #endif |
2202 | |
2203 | #ifdef CONFIG_SCHEDSTATS |
2204 | /* Even if schedstat is disabled, there should not be garbage */ |
2205 | memset(&p->se.statistics, 0, sizeof(p->se.statistics)); |
2206 | #endif |
2207 | |
2208 | RB_CLEAR_NODE(&p->dl.rb_node); |
2209 | init_dl_task_timer(&p->dl); |
2210 | init_dl_inactive_task_timer(&p->dl); |
2211 | __dl_clear_params(p); |
2212 | |
2213 | INIT_LIST_HEAD(&p->rt.run_list); |
2214 | p->rt.timeout = 0; |
2215 | p->rt.time_slice = sched_rr_timeslice; |
2216 | p->rt.on_rq = 0; |
2217 | p->rt.on_list = 0; |
2218 | |
2219 | #ifdef CONFIG_PREEMPT_NOTIFIERS |
2220 | INIT_HLIST_HEAD(&p->preempt_notifiers); |
2221 | #endif |
2222 | |
2223 | #ifdef CONFIG_COMPACTION |
2224 | p->capture_control = NULL; |
2225 | #endif |
2226 | init_numa_balancing(clone_flags, p); |
2227 | } |
2228 | |
2229 | DEFINE_STATIC_KEY_FALSE(sched_numa_balancing); |
2230 | |
2231 | #ifdef CONFIG_NUMA_BALANCING |
2232 | |
2233 | void set_numabalancing_state(bool enabled) |
2234 | { |
2235 | if (enabled) |
2236 | static_branch_enable(&sched_numa_balancing); |
2237 | else |
2238 | static_branch_disable(&sched_numa_balancing); |
2239 | } |
2240 | |
2241 | #ifdef CONFIG_PROC_SYSCTL |
2242 | int sysctl_numa_balancing(struct ctl_table *table, int write, |
2243 | void __user *buffer, size_t *lenp, loff_t *ppos) |
2244 | { |
2245 | struct ctl_table t; |
2246 | int err; |
2247 | int state = static_branch_likely(&sched_numa_balancing); |
2248 | |
2249 | if (write && !capable(CAP_SYS_ADMIN)) |
2250 | return -EPERM; |
2251 | |
2252 | t = *table; |
2253 | t.data = &state; |
2254 | err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); |
2255 | if (err < 0) |
2256 | return err; |
2257 | if (write) |
2258 | set_numabalancing_state(state); |
2259 | return err; |
2260 | } |
2261 | #endif |
2262 | #endif |
2263 | |
2264 | #ifdef CONFIG_SCHEDSTATS |
2265 | |
2266 | DEFINE_STATIC_KEY_FALSE(sched_schedstats); |
2267 | static bool __initdata __sched_schedstats = false; |
2268 | |
2269 | static void set_schedstats(bool enabled) |
2270 | { |
2271 | if (enabled) |
2272 | static_branch_enable(&sched_schedstats); |
2273 | else |
2274 | static_branch_disable(&sched_schedstats); |
2275 | } |
2276 | |
2277 | void force_schedstat_enabled(void) |
2278 | { |
2279 | if (!schedstat_enabled()) { |
2280 | pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n" ); |
2281 | static_branch_enable(&sched_schedstats); |
2282 | } |
2283 | } |
2284 | |
2285 | static int __init setup_schedstats(char *str) |
2286 | { |
2287 | int ret = 0; |
2288 | if (!str) |
2289 | goto out; |
2290 | |
2291 | /* |
2292 | * This code is called before jump labels have been set up, so we can't |
2293 | * change the static branch directly just yet. Instead set a temporary |
2294 | * variable so init_schedstats() can do it later. |
2295 | */ |
2296 | if (!strcmp(str, "enable" )) { |
2297 | __sched_schedstats = true; |
2298 | ret = 1; |
2299 | } else if (!strcmp(str, "disable" )) { |
2300 | __sched_schedstats = false; |
2301 | ret = 1; |
2302 | } |
2303 | out: |
2304 | if (!ret) |
2305 | pr_warn("Unable to parse schedstats=\n" ); |
2306 | |
2307 | return ret; |
2308 | } |
2309 | __setup("schedstats=" , setup_schedstats); |
2310 | |
2311 | static void __init init_schedstats(void) |
2312 | { |
2313 | set_schedstats(__sched_schedstats); |
2314 | } |
2315 | |
2316 | #ifdef CONFIG_PROC_SYSCTL |
2317 | int sysctl_schedstats(struct ctl_table *table, int write, |
2318 | void __user *buffer, size_t *lenp, loff_t *ppos) |
2319 | { |
2320 | struct ctl_table t; |
2321 | int err; |
2322 | int state = static_branch_likely(&sched_schedstats); |
2323 | |
2324 | if (write && !capable(CAP_SYS_ADMIN)) |
2325 | return -EPERM; |
2326 | |
2327 | t = *table; |
2328 | t.data = &state; |
2329 | err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); |
2330 | if (err < 0) |
2331 | return err; |
2332 | if (write) |
2333 | set_schedstats(state); |
2334 | return err; |
2335 | } |
2336 | #endif /* CONFIG_PROC_SYSCTL */ |
2337 | #else /* !CONFIG_SCHEDSTATS */ |
2338 | static inline void init_schedstats(void) {} |
2339 | #endif /* CONFIG_SCHEDSTATS */ |
2340 | |
2341 | /* |
2342 | * fork()/clone()-time setup: |
2343 | */ |
2344 | int sched_fork(unsigned long clone_flags, struct task_struct *p) |
2345 | { |
2346 | unsigned long flags; |
2347 | |
2348 | __sched_fork(clone_flags, p); |
2349 | /* |
2350 | * We mark the process as NEW here. This guarantees that |
2351 | * nobody will actually run it, and a signal or other external |
2352 | * event cannot wake it up and insert it on the runqueue either. |
2353 | */ |
2354 | p->state = TASK_NEW; |
2355 | |
2356 | /* |
2357 | * Make sure we do not leak PI boosting priority to the child. |
2358 | */ |
2359 | p->prio = current->normal_prio; |
2360 | |
2361 | /* |
2362 | * Revert to default priority/policy on fork if requested. |
2363 | */ |
2364 | if (unlikely(p->sched_reset_on_fork)) { |
2365 | if (task_has_dl_policy(p) || task_has_rt_policy(p)) { |
2366 | p->policy = SCHED_NORMAL; |
2367 | p->static_prio = NICE_TO_PRIO(0); |
2368 | p->rt_priority = 0; |
2369 | } else if (PRIO_TO_NICE(p->static_prio) < 0) |
2370 | p->static_prio = NICE_TO_PRIO(0); |
2371 | |
2372 | p->prio = p->normal_prio = __normal_prio(p); |
2373 | set_load_weight(p, false); |
2374 | |
2375 | /* |
2376 | * We don't need the reset flag anymore after the fork. It has |
2377 | * fulfilled its duty: |
2378 | */ |
2379 | p->sched_reset_on_fork = 0; |
2380 | } |
2381 | |
2382 | if (dl_prio(p->prio)) |
2383 | return -EAGAIN; |
2384 | else if (rt_prio(p->prio)) |
2385 | p->sched_class = &rt_sched_class; |
2386 | else |
2387 | p->sched_class = &fair_sched_class; |
2388 | |
2389 | init_entity_runnable_average(&p->se); |
2390 | |
2391 | /* |
2392 | * The child is not yet in the pid-hash so no cgroup attach races, |
2393 | * and the cgroup is pinned to this child due to cgroup_fork() |
2394 | * is ran before sched_fork(). |
2395 | * |
2396 | * Silence PROVE_RCU. |
2397 | */ |
2398 | raw_spin_lock_irqsave(&p->pi_lock, flags); |
2399 | /* |
2400 | * We're setting the CPU for the first time, we don't migrate, |
2401 | * so use __set_task_cpu(). |
2402 | */ |
2403 | __set_task_cpu(p, smp_processor_id()); |
2404 | if (p->sched_class->task_fork) |
2405 | p->sched_class->task_fork(p); |
2406 | raw_spin_unlock_irqrestore(&p->pi_lock, flags); |
2407 | |
2408 | #ifdef CONFIG_SCHED_INFO |
2409 | if (likely(sched_info_on())) |
2410 | memset(&p->sched_info, 0, sizeof(p->sched_info)); |
2411 | #endif |
2412 | #if defined(CONFIG_SMP) |
2413 | p->on_cpu = 0; |
2414 | #endif |
2415 | init_task_preempt_count(p); |
2416 | #ifdef CONFIG_SMP |
2417 | plist_node_init(&p->pushable_tasks, MAX_PRIO); |
2418 | RB_CLEAR_NODE(&p->pushable_dl_tasks); |
2419 | #endif |
2420 | return 0; |
2421 | } |
2422 | |
2423 | unsigned long to_ratio(u64 period, u64 runtime) |
2424 | { |
2425 | if (runtime == RUNTIME_INF) |
2426 | return BW_UNIT; |
2427 | |
2428 | /* |
2429 | * Doing this here saves a lot of checks in all |
2430 | * the calling paths, and returning zero seems |
2431 | * safe for them anyway. |
2432 | */ |
2433 | if (period == 0) |
2434 | return 0; |
2435 | |
2436 | return div64_u64(runtime << BW_SHIFT, period); |
2437 | } |
2438 | |
2439 | /* |
2440 | * wake_up_new_task - wake up a newly created task for the first time. |
2441 | * |
2442 | * This function will do some initial scheduler statistics housekeeping |
2443 | * that must be done for every newly created context, then puts the task |
2444 | * on the runqueue and wakes it. |
2445 | */ |
2446 | void wake_up_new_task(struct task_struct *p) |
2447 | { |
2448 | struct rq_flags rf; |
2449 | struct rq *rq; |
2450 | |
2451 | raw_spin_lock_irqsave(&p->pi_lock, rf.flags); |
2452 | p->state = TASK_RUNNING; |
2453 | #ifdef CONFIG_SMP |
2454 | /* |
2455 | * Fork balancing, do it here and not earlier because: |
2456 | * - cpus_allowed can change in the fork path |
2457 | * - any previously selected CPU might disappear through hotplug |
2458 | * |
2459 | * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq, |
2460 | * as we're not fully set-up yet. |
2461 | */ |
2462 | p->recent_used_cpu = task_cpu(p); |
2463 | __set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0)); |
2464 | #endif |
2465 | rq = __task_rq_lock(p, &rf); |
2466 | update_rq_clock(rq); |
2467 | post_init_entity_util_avg(p); |
2468 | |
2469 | activate_task(rq, p, ENQUEUE_NOCLOCK); |
2470 | p->on_rq = TASK_ON_RQ_QUEUED; |
2471 | trace_sched_wakeup_new(p); |
2472 | check_preempt_curr(rq, p, WF_FORK); |
2473 | #ifdef CONFIG_SMP |
2474 | if (p->sched_class->task_woken) { |
2475 | /* |
2476 | * Nothing relies on rq->lock after this, so its fine to |
2477 | * drop it. |
2478 | */ |
2479 | rq_unpin_lock(rq, &rf); |
2480 | p->sched_class->task_woken(rq, p); |
2481 | rq_repin_lock(rq, &rf); |
2482 | } |
2483 | #endif |
2484 | task_rq_unlock(rq, p, &rf); |
2485 | } |
2486 | |
2487 | #ifdef CONFIG_PREEMPT_NOTIFIERS |
2488 | |
2489 | static DEFINE_STATIC_KEY_FALSE(preempt_notifier_key); |
2490 | |
2491 | void preempt_notifier_inc(void) |
2492 | { |
2493 | static_branch_inc(&preempt_notifier_key); |
2494 | } |
2495 | EXPORT_SYMBOL_GPL(preempt_notifier_inc); |
2496 | |
2497 | void preempt_notifier_dec(void) |
2498 | { |
2499 | static_branch_dec(&preempt_notifier_key); |
2500 | } |
2501 | EXPORT_SYMBOL_GPL(preempt_notifier_dec); |
2502 | |
2503 | /** |
2504 | * preempt_notifier_register - tell me when current is being preempted & rescheduled |
2505 | * @notifier: notifier struct to register |
2506 | */ |
2507 | void preempt_notifier_register(struct preempt_notifier *notifier) |
2508 | { |
2509 | if (!static_branch_unlikely(&preempt_notifier_key)) |
2510 | WARN(1, "registering preempt_notifier while notifiers disabled\n" ); |
2511 | |
2512 | hlist_add_head(¬ifier->link, ¤t->preempt_notifiers); |
2513 | } |
2514 | EXPORT_SYMBOL_GPL(preempt_notifier_register); |
2515 | |
2516 | /** |
2517 | * preempt_notifier_unregister - no longer interested in preemption notifications |
2518 | * @notifier: notifier struct to unregister |
2519 | * |
2520 | * This is *not* safe to call from within a preemption notifier. |
2521 | */ |
2522 | void preempt_notifier_unregister(struct preempt_notifier *notifier) |
2523 | { |
2524 | hlist_del(¬ifier->link); |
2525 | } |
2526 | EXPORT_SYMBOL_GPL(preempt_notifier_unregister); |
2527 | |
2528 | static void __fire_sched_in_preempt_notifiers(struct task_struct *curr) |
2529 | { |
2530 | struct preempt_notifier *notifier; |
2531 | |
2532 | hlist_for_each_entry(notifier, &curr->preempt_notifiers, link) |
2533 | notifier->ops->sched_in(notifier, raw_smp_processor_id()); |
2534 | } |
2535 | |
2536 | static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr) |
2537 | { |
2538 | if (static_branch_unlikely(&preempt_notifier_key)) |
2539 | __fire_sched_in_preempt_notifiers(curr); |
2540 | } |
2541 | |
2542 | static void |
2543 | __fire_sched_out_preempt_notifiers(struct task_struct *curr, |
2544 | struct task_struct *next) |
2545 | { |
2546 | struct preempt_notifier *notifier; |
2547 | |
2548 | hlist_for_each_entry(notifier, &curr->preempt_notifiers, link) |
2549 | notifier->ops->sched_out(notifier, next); |
2550 | } |
2551 | |
2552 | static __always_inline void |
2553 | fire_sched_out_preempt_notifiers(struct task_struct *curr, |
2554 | struct task_struct *next) |
2555 | { |
2556 | if (static_branch_unlikely(&preempt_notifier_key)) |
2557 | __fire_sched_out_preempt_notifiers(curr, next); |
2558 | } |
2559 | |
2560 | #else /* !CONFIG_PREEMPT_NOTIFIERS */ |
2561 | |
2562 | static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr) |
2563 | { |
2564 | } |
2565 | |
2566 | static inline void |
2567 | fire_sched_out_preempt_notifiers(struct task_struct *curr, |
2568 | struct task_struct *next) |
2569 | { |
2570 | } |
2571 | |
2572 | #endif /* CONFIG_PREEMPT_NOTIFIERS */ |
2573 | |
2574 | static inline void prepare_task(struct task_struct *next) |
2575 | { |
2576 | #ifdef CONFIG_SMP |
2577 | /* |
2578 | * Claim the task as running, we do this before switching to it |
2579 | * such that any running task will have this set. |
2580 | */ |
2581 | next->on_cpu = 1; |
2582 | #endif |
2583 | } |
2584 | |
2585 | static inline void finish_task(struct task_struct *prev) |
2586 | { |
2587 | #ifdef CONFIG_SMP |
2588 | /* |
2589 | * After ->on_cpu is cleared, the task can be moved to a different CPU. |
2590 | * We must ensure this doesn't happen until the switch is completely |
2591 | * finished. |
2592 | * |
2593 | * In particular, the load of prev->state in finish_task_switch() must |
2594 | * happen before this. |
2595 | * |
2596 | * Pairs with the smp_cond_load_acquire() in try_to_wake_up(). |
2597 | */ |
2598 | smp_store_release(&prev->on_cpu, 0); |
2599 | #endif |
2600 | } |
2601 | |
2602 | static inline void |
2603 | prepare_lock_switch(struct rq *rq, struct task_struct *next, struct rq_flags *rf) |
2604 | { |
2605 | /* |
2606 | * Since the runqueue lock will be released by the next |
2607 | * task (which is an invalid locking op but in the case |
2608 | * of the scheduler it's an obvious special-case), so we |
2609 | * do an early lockdep release here: |
2610 | */ |
2611 | rq_unpin_lock(rq, rf); |
2612 | spin_release(&rq->lock.dep_map, 1, _THIS_IP_); |
2613 | #ifdef CONFIG_DEBUG_SPINLOCK |
2614 | /* this is a valid case when another task releases the spinlock */ |
2615 | rq->lock.owner = next; |
2616 | #endif |
2617 | } |
2618 | |
2619 | static inline void finish_lock_switch(struct rq *rq) |
2620 | { |
2621 | /* |
2622 | * If we are tracking spinlock dependencies then we have to |
2623 | * fix up the runqueue lock - which gets 'carried over' from |
2624 | * prev into current: |
2625 | */ |
2626 | spin_acquire(&rq->lock.dep_map, 0, 0, _THIS_IP_); |
2627 | raw_spin_unlock_irq(&rq->lock); |
2628 | } |
2629 | |
2630 | /* |
2631 | * NOP if the arch has not defined these: |
2632 | */ |
2633 | |
2634 | #ifndef prepare_arch_switch |
2635 | # define prepare_arch_switch(next) do { } while (0) |
2636 | #endif |
2637 | |
2638 | #ifndef finish_arch_post_lock_switch |
2639 | # define finish_arch_post_lock_switch() do { } while (0) |
2640 | #endif |
2641 | |
2642 | /** |
2643 | * prepare_task_switch - prepare to switch tasks |
2644 | * @rq: the runqueue preparing to switch |
2645 | * @prev: the current task that is being switched out |
2646 | * @next: the task we are going to switch to. |
2647 | * |
2648 | * This is called with the rq lock held and interrupts off. It must |
2649 | * be paired with a subsequent finish_task_switch after the context |
2650 | * switch. |
2651 | * |
2652 | * prepare_task_switch sets up locking and calls architecture specific |
2653 | * hooks. |
2654 | */ |
2655 | static inline void |
2656 | prepare_task_switch(struct rq *rq, struct task_struct *prev, |
2657 | struct task_struct *next) |
2658 | { |
2659 | kcov_prepare_switch(prev); |
2660 | sched_info_switch(rq, prev, next); |
2661 | perf_event_task_sched_out(prev, next); |
2662 | rseq_preempt(prev); |
2663 | fire_sched_out_preempt_notifiers(prev, next); |
2664 | prepare_task(next); |
2665 | prepare_arch_switch(next); |
2666 | } |
2667 | |
2668 | /** |
2669 | * finish_task_switch - clean up after a task-switch |
2670 | * @prev: the thread we just switched away from. |
2671 | * |
2672 | * finish_task_switch must be called after the context switch, paired |
2673 | * with a prepare_task_switch call before the context switch. |
2674 | * finish_task_switch will reconcile locking set up by prepare_task_switch, |
2675 | * and do any other architecture-specific cleanup actions. |
2676 | * |
2677 | * Note that we may have delayed dropping an mm in context_switch(). If |
2678 | * so, we finish that here outside of the runqueue lock. (Doing it |
2679 | * with the lock held can cause deadlocks; see schedule() for |
2680 | * details.) |
2681 | * |
2682 | * The context switch have flipped the stack from under us and restored the |
2683 | * local variables which were saved when this task called schedule() in the |
2684 | * past. prev == current is still correct but we need to recalculate this_rq |
2685 | * because prev may have moved to another CPU. |
2686 | */ |
2687 | static struct rq *finish_task_switch(struct task_struct *prev) |
2688 | __releases(rq->lock) |
2689 | { |
2690 | struct rq *rq = this_rq(); |
2691 | struct mm_struct *mm = rq->prev_mm; |
2692 | long prev_state; |
2693 | |
2694 | /* |
2695 | * The previous task will have left us with a preempt_count of 2 |
2696 | * because it left us after: |
2697 | * |
2698 | * schedule() |
2699 | * preempt_disable(); // 1 |
2700 | * __schedule() |
2701 | * raw_spin_lock_irq(&rq->lock) // 2 |
2702 | * |
2703 | * Also, see FORK_PREEMPT_COUNT. |
2704 | */ |
2705 | if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET, |
2706 | "corrupted preempt_count: %s/%d/0x%x\n" , |
2707 | current->comm, current->pid, preempt_count())) |
2708 | preempt_count_set(FORK_PREEMPT_COUNT); |
2709 | |
2710 | rq->prev_mm = NULL; |
2711 | |
2712 | /* |
2713 | * A task struct has one reference for the use as "current". |
2714 | * If a task dies, then it sets TASK_DEAD in tsk->state and calls |
2715 | * schedule one last time. The schedule call will never return, and |
2716 | * the scheduled task must drop that reference. |
2717 | * |
2718 | * We must observe prev->state before clearing prev->on_cpu (in |
2719 | * finish_task), otherwise a concurrent wakeup can get prev |
2720 | * running on another CPU and we could rave with its RUNNING -> DEAD |
2721 | * transition, resulting in a double drop. |
2722 | */ |
2723 | prev_state = prev->state; |
2724 | vtime_task_switch(prev); |
2725 | perf_event_task_sched_in(prev, current); |
2726 | finish_task(prev); |
2727 | finish_lock_switch(rq); |
2728 | finish_arch_post_lock_switch(); |
2729 | kcov_finish_switch(current); |
2730 | |
2731 | fire_sched_in_preempt_notifiers(current); |
2732 | /* |
2733 | * When switching through a kernel thread, the loop in |
2734 | * membarrier_{private,global}_expedited() may have observed that |
2735 | * kernel thread and not issued an IPI. It is therefore possible to |
2736 | * schedule between user->kernel->user threads without passing though |
2737 | * switch_mm(). Membarrier requires a barrier after storing to |
2738 | * rq->curr, before returning to userspace, so provide them here: |
2739 | * |
2740 | * - a full memory barrier for {PRIVATE,GLOBAL}_EXPEDITED, implicitly |
2741 | * provided by mmdrop(), |
2742 | * - a sync_core for SYNC_CORE. |
2743 | */ |
2744 | if (mm) { |
2745 | membarrier_mm_sync_core_before_usermode(mm); |
2746 | mmdrop(mm); |
2747 | } |
2748 | if (unlikely(prev_state == TASK_DEAD)) { |
2749 | if (prev->sched_class->task_dead) |
2750 | prev->sched_class->task_dead(prev); |
2751 | |
2752 | /* |
2753 | * Remove function-return probe instances associated with this |
2754 | * task and put them back on the free list. |
2755 | */ |
2756 | kprobe_flush_task(prev); |
2757 | |
2758 | /* Task is done with its stack. */ |
2759 | put_task_stack(prev); |
2760 | |
2761 | put_task_struct(prev); |
2762 | } |
2763 | |
2764 | tick_nohz_task_switch(); |
2765 | return rq; |
2766 | } |
2767 | |
2768 | #ifdef CONFIG_SMP |
2769 | |
2770 | /* rq->lock is NOT held, but preemption is disabled */ |
2771 | static void __balance_callback(struct rq *rq) |
2772 | { |
2773 | struct callback_head *head, *next; |
2774 | void (*func)(struct rq *rq); |
2775 | unsigned long flags; |
2776 | |
2777 | raw_spin_lock_irqsave(&rq->lock, flags); |
2778 | head = rq->balance_callback; |
2779 | rq->balance_callback = NULL; |
2780 | while (head) { |
2781 | func = (void (*)(struct rq *))head->func; |
2782 | next = head->next; |
2783 | head->next = NULL; |
2784 | head = next; |
2785 | |
2786 | func(rq); |
2787 | } |
2788 | raw_spin_unlock_irqrestore(&rq->lock, flags); |
2789 | } |
2790 | |
2791 | static inline void balance_callback(struct rq *rq) |
2792 | { |
2793 | if (unlikely(rq->balance_callback)) |
2794 | __balance_callback(rq); |
2795 | } |
2796 | |
2797 | #else |
2798 | |
2799 | static inline void balance_callback(struct rq *rq) |
2800 | { |
2801 | } |
2802 | |
2803 | #endif |
2804 | |
2805 | /** |
2806 | * schedule_tail - first thing a freshly forked thread must call. |
2807 | * @prev: the thread we just switched away from. |
2808 | */ |
2809 | asmlinkage __visible void schedule_tail(struct task_struct *prev) |
2810 | __releases(rq->lock) |
2811 | { |
2812 | struct rq *rq; |
2813 | |
2814 | /* |
2815 | * New tasks start with FORK_PREEMPT_COUNT, see there and |
2816 | * finish_task_switch() for details. |
2817 | * |
2818 | * finish_task_switch() will drop rq->lock() and lower preempt_count |
2819 | * and the preempt_enable() will end up enabling preemption (on |
2820 | * PREEMPT_COUNT kernels). |
2821 | */ |
2822 | |
2823 | rq = finish_task_switch(prev); |
2824 | balance_callback(rq); |
2825 | preempt_enable(); |
2826 | |
2827 | if (current->set_child_tid) |
2828 | put_user(task_pid_vnr(current), current->set_child_tid); |
2829 | |
2830 | calculate_sigpending(); |
2831 | } |
2832 | |
2833 | /* |
2834 | * context_switch - switch to the new MM and the new thread's register state. |
2835 | */ |
2836 | static __always_inline struct rq * |
2837 | context_switch(struct rq *rq, struct task_struct *prev, |
2838 | struct task_struct *next, struct rq_flags *rf) |
2839 | { |
2840 | struct mm_struct *mm, *oldmm; |
2841 | |
2842 | prepare_task_switch(rq, prev, next); |
2843 | |
2844 | mm = next->mm; |
2845 | oldmm = prev->active_mm; |
2846 | /* |
2847 | * For paravirt, this is coupled with an exit in switch_to to |
2848 | * combine the page table reload and the switch backend into |
2849 | * one hypercall. |
2850 | */ |
2851 | arch_start_context_switch(prev); |
2852 | |
2853 | /* |
2854 | * If mm is non-NULL, we pass through switch_mm(). If mm is |
2855 | * NULL, we will pass through mmdrop() in finish_task_switch(). |
2856 | * Both of these contain the full memory barrier required by |
2857 | * membarrier after storing to rq->curr, before returning to |
2858 | * user-space. |
2859 | */ |
2860 | if (!mm) { |
2861 | next->active_mm = oldmm; |
2862 | mmgrab(oldmm); |
2863 | enter_lazy_tlb(oldmm, next); |
2864 | } else |
2865 | switch_mm_irqs_off(oldmm, mm, next); |
2866 | |
2867 | if (!prev->mm) { |
2868 | prev->active_mm = NULL; |
2869 | rq->prev_mm = oldmm; |
2870 | } |
2871 | |
2872 | rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP); |
2873 | |
2874 | prepare_lock_switch(rq, next, rf); |
2875 | |
2876 | /* Here we just switch the register state and the stack. */ |
2877 | switch_to(prev, next, prev); |
2878 | barrier(); |
2879 | |
2880 | return finish_task_switch(prev); |
2881 | } |
2882 | |
2883 | /* |
2884 | * nr_running and nr_context_switches: |
2885 | * |
2886 | * externally visible scheduler statistics: current number of runnable |
2887 | * threads, total number of context switches performed since bootup. |
2888 | */ |
2889 | unsigned long nr_running(void) |
2890 | { |
2891 | unsigned long i, sum = 0; |
2892 | |
2893 | for_each_online_cpu(i) |
2894 | sum += cpu_rq(i)->nr_running; |
2895 | |
2896 | return sum; |
2897 | } |
2898 | |
2899 | /* |
2900 | * Check if only the current task is running on the CPU. |
2901 | * |
2902 | * Caution: this function does not check that the caller has disabled |
2903 | * preemption, thus the result might have a time-of-check-to-time-of-use |
2904 | * race. The caller is responsible to use it correctly, for example: |
2905 | * |
2906 | * - from a non-preemptible section (of course) |
2907 | * |
2908 | * - from a thread that is bound to a single CPU |
2909 | * |
2910 | * - in a loop with very short iterations (e.g. a polling loop) |
2911 | */ |
2912 | bool single_task_running(void) |
2913 | { |
2914 | return raw_rq()->nr_running == 1; |
2915 | } |
2916 | EXPORT_SYMBOL(single_task_running); |
2917 | |
2918 | unsigned long long nr_context_switches(void) |
2919 | { |
2920 | int i; |
2921 | unsigned long long sum = 0; |
2922 | |
2923 | for_each_possible_cpu(i) |
2924 | sum += cpu_rq(i)->nr_switches; |
2925 | |
2926 | return sum; |
2927 | } |
2928 | |
2929 | /* |
2930 | * Consumers of these two interfaces, like for example the cpuidle menu |
2931 | * governor, are using nonsensical data. Preferring shallow idle state selection |
2932 | * for a CPU that has IO-wait which might not even end up running the task when |
2933 | * it does become runnable. |
2934 | */ |
2935 | |
2936 | unsigned long nr_iowait_cpu(int cpu) |
2937 | { |
2938 | return atomic_read(&cpu_rq(cpu)->nr_iowait); |
2939 | } |
2940 | |
2941 | /* |
2942 | * IO-wait accounting, and how its mostly bollocks (on SMP). |
2943 | * |
2944 | * The idea behind IO-wait account is to account the idle time that we could |
2945 | * have spend running if it were not for IO. That is, if we were to improve the |
2946 | * storage performance, we'd have a proportional reduction in IO-wait time. |
2947 | * |
2948 | * This all works nicely on UP, where, when a task blocks on IO, we account |
2949 | * idle time as IO-wait, because if the storage were faster, it could've been |
2950 | * running and we'd not be idle. |
2951 | * |
2952 | * This has been extended to SMP, by doing the same for each CPU. This however |
2953 | * is broken. |
2954 | * |
2955 | * Imagine for instance the case where two tasks block on one CPU, only the one |
2956 | * CPU will have IO-wait accounted, while the other has regular idle. Even |
2957 | * though, if the storage were faster, both could've ran at the same time, |
2958 | * utilising both CPUs. |
2959 | * |
2960 | * This means, that when looking globally, the current IO-wait accounting on |
2961 | * SMP is a lower bound, by reason of under accounting. |
2962 | * |
2963 | * Worse, since the numbers are provided per CPU, they are sometimes |
2964 | * interpreted per CPU, and that is nonsensical. A blocked task isn't strictly |
2965 | * associated with any one particular CPU, it can wake to another CPU than it |
2966 | * blocked on. This means the per CPU IO-wait number is meaningless. |
2967 | * |
2968 | * Task CPU affinities can make all that even more 'interesting'. |
2969 | */ |
2970 | |
2971 | unsigned long nr_iowait(void) |
2972 | { |
2973 | unsigned long i, sum = 0; |
2974 | |
2975 | for_each_possible_cpu(i) |
2976 | sum += nr_iowait_cpu(i); |
2977 | |
2978 | return sum; |
2979 | } |
2980 | |
2981 | #ifdef CONFIG_SMP |
2982 | |
2983 | /* |
2984 | * sched_exec - execve() is a valuable balancing opportunity, because at |
2985 | * this point the task has the smallest effective memory and cache footprint. |
2986 | */ |
2987 | void sched_exec(void) |
2988 | { |
2989 | struct task_struct *p = current; |
2990 | unsigned long flags; |
2991 | int dest_cpu; |
2992 | |
2993 | raw_spin_lock_irqsave(&p->pi_lock, flags); |
2994 | dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), SD_BALANCE_EXEC, 0); |
2995 | if (dest_cpu == smp_processor_id()) |
2996 | goto unlock; |
2997 | |
2998 | if (likely(cpu_active(dest_cpu))) { |
2999 | struct migration_arg arg = { p, dest_cpu }; |
3000 | |
3001 | raw_spin_unlock_irqrestore(&p->pi_lock, flags); |
3002 | stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg); |
3003 | return; |
3004 | } |
3005 | unlock: |
3006 | raw_spin_unlock_irqrestore(&p->pi_lock, flags); |
3007 | } |
3008 | |
3009 | #endif |
3010 | |
3011 | DEFINE_PER_CPU(struct kernel_stat, kstat); |
3012 | DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat); |
3013 | |
3014 | EXPORT_PER_CPU_SYMBOL(kstat); |
3015 | EXPORT_PER_CPU_SYMBOL(kernel_cpustat); |
3016 | |
3017 | /* |
3018 | * The function fair_sched_class.update_curr accesses the struct curr |
3019 | * and its field curr->exec_start; when called from task_sched_runtime(), |
3020 | * we observe a high rate of cache misses in practice. |
3021 | * Prefetching this data results in improved performance. |
3022 | */ |
3023 | static inline void prefetch_curr_exec_start(struct task_struct *p) |
3024 | { |
3025 | #ifdef CONFIG_FAIR_GROUP_SCHED |
3026 | struct sched_entity *curr = (&p->se)->cfs_rq->curr; |
3027 | #else |
3028 | struct sched_entity *curr = (&task_rq(p)->cfs)->curr; |
3029 | #endif |
3030 | prefetch(curr); |
3031 | prefetch(&curr->exec_start); |
3032 | } |
3033 | |
3034 | /* |
3035 | * Return accounted runtime for the task. |
3036 | * In case the task is currently running, return the runtime plus current's |
3037 | * pending runtime that have not been accounted yet. |
3038 | */ |
3039 | unsigned long long task_sched_runtime(struct task_struct *p) |
3040 | { |
3041 | struct rq_flags rf; |
3042 | struct rq *rq; |
3043 | u64 ns; |
3044 | |
3045 | #if defined(CONFIG_64BIT) && defined(CONFIG_SMP) |
3046 | /* |
3047 | * 64-bit doesn't need locks to atomically read a 64-bit value. |
3048 | * So we have a optimization chance when the task's delta_exec is 0. |
3049 | * Reading ->on_cpu is racy, but this is ok. |
3050 | * |
3051 | * If we race with it leaving CPU, we'll take a lock. So we're correct. |
3052 | * If we race with it entering CPU, unaccounted time is 0. This is |
3053 | * indistinguishable from the read occurring a few cycles earlier. |
3054 | * If we see ->on_cpu without ->on_rq, the task is leaving, and has |
3055 | * been accounted, so we're correct here as well. |
3056 | */ |
3057 | if (!p->on_cpu || !task_on_rq_queued(p)) |
3058 | return p->se.sum_exec_runtime; |
3059 | #endif |
3060 | |
3061 | rq = task_rq_lock(p, &rf); |
3062 | /* |
3063 | * Must be ->curr _and_ ->on_rq. If dequeued, we would |
3064 | * project cycles that may never be accounted to this |
3065 | * thread, breaking clock_gettime(). |
3066 | */ |
3067 | if (task_current(rq, p) && task_on_rq_queued(p)) { |
3068 | prefetch_curr_exec_start(p); |
3069 | update_rq_clock(rq); |
3070 | p->sched_class->update_curr(rq); |
3071 | } |
3072 | ns = p->se.sum_exec_runtime; |
3073 | task_rq_unlock(rq, p, &rf); |
3074 | |
3075 | return ns; |
3076 | } |
3077 | |
3078 | /* |
3079 | * This function gets called by the timer code, with HZ frequency. |
3080 | * We call it with interrupts disabled. |
3081 | */ |
3082 | void scheduler_tick(void) |
3083 | { |
3084 | int cpu = smp_processor_id(); |
3085 | struct rq *rq = cpu_rq(cpu); |
3086 | struct task_struct *curr = rq->curr; |
3087 | struct rq_flags rf; |
3088 | |
3089 | sched_clock_tick(); |
3090 | |
3091 | rq_lock(rq, &rf); |
3092 | |
3093 | update_rq_clock(rq); |
3094 | curr->sched_class->task_tick(rq, curr, 0); |
3095 | cpu_load_update_active(rq); |
3096 | calc_global_load_tick(rq); |
3097 | psi_task_tick(rq); |
3098 | |
3099 | rq_unlock(rq, &rf); |
3100 | |
3101 | perf_event_task_tick(); |
3102 | |
3103 | #ifdef CONFIG_SMP |
3104 | rq->idle_balance = idle_cpu(cpu); |
3105 | trigger_load_balance(rq); |
3106 | #endif |
3107 | } |
3108 | |
3109 | #ifdef CONFIG_NO_HZ_FULL |
3110 | |
3111 | struct tick_work { |
3112 | int cpu; |
3113 | struct delayed_work work; |
3114 | }; |
3115 | |
3116 | static struct tick_work __percpu *tick_work_cpu; |
3117 | |
3118 | static void sched_tick_remote(struct work_struct *work) |
3119 | { |
3120 | struct delayed_work *dwork = to_delayed_work(work); |
3121 | struct tick_work *twork = container_of(dwork, struct tick_work, work); |
3122 | int cpu = twork->cpu; |
3123 | struct rq *rq = cpu_rq(cpu); |
3124 | struct task_struct *curr; |
3125 | struct rq_flags rf; |
3126 | u64 delta; |
3127 | |
3128 | /* |
3129 | * Handle the tick only if it appears the remote CPU is running in full |
3130 | * dynticks mode. The check is racy by nature, but missing a tick or |
3131 | * having one too much is no big deal because the scheduler tick updates |
3132 | * statistics and checks timeslices in a time-independent way, regardless |
3133 | * of when exactly it is running. |
3134 | */ |
3135 | if (idle_cpu(cpu) || !tick_nohz_tick_stopped_cpu(cpu)) |
3136 | goto out_requeue; |
3137 | |
3138 | rq_lock_irq(rq, &rf); |
3139 | curr = rq->curr; |
3140 | if (is_idle_task(curr)) |
3141 | goto out_unlock; |
3142 | |
3143 | update_rq_clock(rq); |
3144 | delta = rq_clock_task(rq) - curr->se.exec_start; |
3145 | |
3146 | /* |
3147 | * Make sure the next tick runs within a reasonable |
3148 | * amount of time. |
3149 | */ |
3150 | WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3); |
3151 | curr->sched_class->task_tick(rq, curr, 0); |
3152 | |
3153 | out_unlock: |
3154 | rq_unlock_irq(rq, &rf); |
3155 | |
3156 | out_requeue: |
3157 | /* |
3158 | * Run the remote tick once per second (1Hz). This arbitrary |
3159 | * frequency is large enough to avoid overload but short enough |
3160 | * to keep scheduler internal stats reasonably up to date. |
3161 | */ |
3162 | queue_delayed_work(system_unbound_wq, dwork, HZ); |
3163 | } |
3164 | |
3165 | static void sched_tick_start(int cpu) |
3166 | { |
3167 | struct tick_work *twork; |
3168 | |
3169 | if (housekeeping_cpu(cpu, HK_FLAG_TICK)) |
3170 | return; |
3171 | |
3172 | WARN_ON_ONCE(!tick_work_cpu); |
3173 | |
3174 | twork = per_cpu_ptr(tick_work_cpu, cpu); |
3175 | twork->cpu = cpu; |
3176 | INIT_DELAYED_WORK(&twork->work, sched_tick_remote); |
3177 | queue_delayed_work(system_unbound_wq, &twork->work, HZ); |
3178 | } |
3179 | |
3180 | #ifdef CONFIG_HOTPLUG_CPU |
3181 | static void sched_tick_stop(int cpu) |
3182 | { |
3183 | struct tick_work *twork; |
3184 | |
3185 | if (housekeeping_cpu(cpu, HK_FLAG_TICK)) |
3186 | return; |
3187 | |
3188 | WARN_ON_ONCE(!tick_work_cpu); |
3189 | |
3190 | twork = per_cpu_ptr(tick_work_cpu, cpu); |
3191 | cancel_delayed_work_sync(&twork->work); |
3192 | } |
3193 | #endif /* CONFIG_HOTPLUG_CPU */ |
3194 | |
3195 | int __init sched_tick_offload_init(void) |
3196 | { |
3197 | tick_work_cpu = alloc_percpu(struct tick_work); |
3198 | BUG_ON(!tick_work_cpu); |
3199 | |
3200 | return 0; |
3201 | } |
3202 | |
3203 | #else /* !CONFIG_NO_HZ_FULL */ |
3204 | static inline void sched_tick_start(int cpu) { } |
3205 | static inline void sched_tick_stop(int cpu) { } |
3206 | #endif |
3207 | |
3208 | #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \ |
3209 | defined(CONFIG_TRACE_PREEMPT_TOGGLE)) |
3210 | /* |
3211 | * If the value passed in is equal to the current preempt count |
3212 | * then we just disabled preemption. Start timing the latency. |
3213 | */ |
3214 | static inline void preempt_latency_start(int val) |
3215 | { |
3216 | if (preempt_count() == val) { |
3217 | unsigned long ip = get_lock_parent_ip(); |
3218 | #ifdef CONFIG_DEBUG_PREEMPT |
3219 | current->preempt_disable_ip = ip; |
3220 | #endif |
3221 | trace_preempt_off(CALLER_ADDR0, ip); |
3222 | } |
3223 | } |
3224 | |
3225 | void preempt_count_add(int val) |
3226 | { |
3227 | #ifdef CONFIG_DEBUG_PREEMPT |
3228 | /* |
3229 | * Underflow? |
3230 | */ |
3231 | if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0))) |
3232 | return; |
3233 | #endif |
3234 | __preempt_count_add(val); |
3235 | #ifdef CONFIG_DEBUG_PREEMPT |
3236 | /* |
3237 | * Spinlock count overflowing soon? |
3238 | */ |
3239 | DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >= |
3240 | PREEMPT_MASK - 10); |
3241 | #endif |
3242 | preempt_latency_start(val); |
3243 | } |
3244 | EXPORT_SYMBOL(preempt_count_add); |
3245 | NOKPROBE_SYMBOL(preempt_count_add); |
3246 | |
3247 | /* |
3248 | * If the value passed in equals to the current preempt count |
3249 | * then we just enabled preemption. Stop timing the latency. |
3250 | */ |
3251 | static inline void preempt_latency_stop(int val) |
3252 | { |
3253 | if (preempt_count() == val) |
3254 | trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip()); |
3255 | } |
3256 | |
3257 | void preempt_count_sub(int val) |
3258 | { |
3259 | #ifdef CONFIG_DEBUG_PREEMPT |
3260 | /* |
3261 | * Underflow? |
3262 | */ |
3263 | if (DEBUG_LOCKS_WARN_ON(val > preempt_count())) |
3264 | return; |
3265 | /* |
3266 | * Is the spinlock portion underflowing? |
3267 | */ |
3268 | if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) && |
3269 | !(preempt_count() & PREEMPT_MASK))) |
3270 | return; |
3271 | #endif |
3272 | |
3273 | preempt_latency_stop(val); |
3274 | __preempt_count_sub(val); |
3275 | } |
3276 | EXPORT_SYMBOL(preempt_count_sub); |
3277 | NOKPROBE_SYMBOL(preempt_count_sub); |
3278 | |
3279 | #else |
3280 | static inline void preempt_latency_start(int val) { } |
3281 | static inline void preempt_latency_stop(int val) { } |
3282 | #endif |
3283 | |
3284 | static inline unsigned long get_preempt_disable_ip(struct task_struct *p) |
3285 | { |
3286 | #ifdef CONFIG_DEBUG_PREEMPT |
3287 | return p->preempt_disable_ip; |
3288 | #else |
3289 | return 0; |
3290 | #endif |
3291 | } |
3292 | |
3293 | /* |
3294 | * Print scheduling while atomic bug: |
3295 | */ |
3296 | static noinline void __schedule_bug(struct task_struct *prev) |
3297 | { |
3298 | /* Save this before calling printk(), since that will clobber it */ |
3299 | unsigned long preempt_disable_ip = get_preempt_disable_ip(current); |
3300 | |
3301 | if (oops_in_progress) |
3302 | return; |
3303 | |
3304 | printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n" , |
3305 | prev->comm, prev->pid, preempt_count()); |
3306 | |
3307 | debug_show_held_locks(prev); |
3308 | print_modules(); |
3309 | if (irqs_disabled()) |
3310 | print_irqtrace_events(prev); |
3311 | if (IS_ENABLED(CONFIG_DEBUG_PREEMPT) |
3312 | && in_atomic_preempt_off()) { |
3313 | pr_err("Preemption disabled at:" ); |
3314 | print_ip_sym(preempt_disable_ip); |
3315 | pr_cont("\n" ); |
3316 | } |
3317 | if (panic_on_warn) |
3318 | panic("scheduling while atomic\n" ); |
3319 | |
3320 | dump_stack(); |
3321 | add_taint(TAINT_WARN, LOCKDEP_STILL_OK); |
3322 | } |
3323 | |
3324 | /* |
3325 | * Various schedule()-time debugging checks and statistics: |
3326 | */ |
3327 | static inline void schedule_debug(struct task_struct *prev) |
3328 | { |
3329 | #ifdef CONFIG_SCHED_STACK_END_CHECK |
3330 | if (task_stack_end_corrupted(prev)) |
3331 | panic("corrupted stack end detected inside scheduler\n" ); |
3332 | #endif |
3333 | |
3334 | if (unlikely(in_atomic_preempt_off())) { |
3335 | __schedule_bug(prev); |
3336 | preempt_count_set(PREEMPT_DISABLED); |
3337 | } |
3338 | rcu_sleep_check(); |
3339 | |
3340 | profile_hit(SCHED_PROFILING, __builtin_return_address(0)); |
3341 | |
3342 | schedstat_inc(this_rq()->sched_count); |
3343 | } |
3344 | |
3345 | /* |
3346 | * Pick up the highest-prio task: |
3347 | */ |
3348 | static inline struct task_struct * |
3349 | pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) |
3350 | { |
3351 | const struct sched_class *class; |
3352 | struct task_struct *p; |
3353 | |
3354 | /* |
3355 | * Optimization: we know that if all tasks are in the fair class we can |
3356 | * call that function directly, but only if the @prev task wasn't of a |
3357 | * higher scheduling class, because otherwise those loose the |
3358 | * opportunity to pull in more work from other CPUs. |
3359 | */ |
3360 | if (likely((prev->sched_class == &idle_sched_class || |
3361 | prev->sched_class == &fair_sched_class) && |
3362 | rq->nr_running == rq->cfs.h_nr_running)) { |
3363 | |
3364 | p = fair_sched_class.pick_next_task(rq, prev, rf); |
3365 | if (unlikely(p == RETRY_TASK)) |
3366 | goto again; |
3367 | |
3368 | /* Assumes fair_sched_class->next == idle_sched_class */ |
3369 | if (unlikely(!p)) |
3370 | p = idle_sched_class.pick_next_task(rq, prev, rf); |
3371 | |
3372 | return p; |
3373 | } |
3374 | |
3375 | again: |
3376 | for_each_class(class) { |
3377 | p = class->pick_next_task(rq, prev, rf); |
3378 | if (p) { |
3379 | if (unlikely(p == RETRY_TASK)) |
3380 | goto again; |
3381 | return p; |
3382 | } |
3383 | } |
3384 | |
3385 | /* The idle class should always have a runnable task: */ |
3386 | BUG(); |
3387 | } |
3388 | |
3389 | /* |
3390 | * __schedule() is the main scheduler function. |
3391 | * |
3392 | * The main means of driving the scheduler and thus entering this function are: |
3393 | * |
3394 | * 1. Explicit blocking: mutex, semaphore, waitqueue, etc. |
3395 | * |
3396 | * 2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return |
3397 | * paths. For example, see arch/x86/entry_64.S. |
3398 | * |
3399 | * To drive preemption between tasks, the scheduler sets the flag in timer |
3400 | * interrupt handler scheduler_tick(). |
3401 | * |
3402 | * 3. Wakeups don't really cause entry into schedule(). They add a |
3403 | * task to the run-queue and that's it. |
3404 | * |
3405 | * Now, if the new task added to the run-queue preempts the current |
3406 | * task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets |
3407 | * called on the nearest possible occasion: |
3408 | * |
3409 | * - If the kernel is preemptible (CONFIG_PREEMPT=y): |
3410 | * |
3411 | * - in syscall or exception context, at the next outmost |
3412 | * preempt_enable(). (this might be as soon as the wake_up()'s |
3413 | * spin_unlock()!) |
3414 | * |
3415 | * - in IRQ context, return from interrupt-handler to |
3416 | * preemptible context |
3417 | * |
3418 | * - If the kernel is not preemptible (CONFIG_PREEMPT is not set) |
3419 | * then at the next: |
3420 | * |
3421 | * - cond_resched() call |
3422 | * - explicit schedule() call |
3423 | * - return from syscall or exception to user-space |
3424 | * - return from interrupt-handler to user-space |
3425 | * |
3426 | * WARNING: must be called with preemption disabled! |
3427 | */ |
3428 | static void __sched notrace __schedule(bool preempt) |
3429 | { |
3430 | struct task_struct *prev, *next; |
3431 | unsigned long *switch_count; |
3432 | struct rq_flags rf; |
3433 | struct rq *rq; |
3434 | int cpu; |
3435 | |
3436 | cpu = smp_processor_id(); |
3437 | rq = cpu_rq(cpu); |
3438 | prev = rq->curr; |
3439 | |
3440 | schedule_debug(prev); |
3441 | |
3442 | if (sched_feat(HRTICK)) |
3443 | hrtick_clear(rq); |
3444 | |
3445 | local_irq_disable(); |
3446 | rcu_note_context_switch(preempt); |
3447 | |
3448 | /* |
3449 | * Make sure that signal_pending_state()->signal_pending() below |
3450 | * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE) |
3451 | * done by the caller to avoid the race with signal_wake_up(). |
3452 | * |
3453 | * The membarrier system call requires a full memory barrier |
3454 | * after coming from user-space, before storing to rq->curr. |
3455 | */ |
3456 | rq_lock(rq, &rf); |
3457 | smp_mb__after_spinlock(); |
3458 | |
3459 | /* Promote REQ to ACT */ |
3460 | rq->clock_update_flags <<= 1; |
3461 | update_rq_clock(rq); |
3462 | |
3463 | switch_count = &prev->nivcsw; |
3464 | if (!preempt && prev->state) { |
3465 | if (signal_pending_state(prev->state, prev)) { |
3466 | prev->state = TASK_RUNNING; |
3467 | } else { |
3468 | deactivate_task(rq, prev, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK); |
3469 | prev->on_rq = 0; |
3470 | |
3471 | if (prev->in_iowait) { |
3472 | atomic_inc(&rq->nr_iowait); |
3473 | delayacct_blkio_start(); |
3474 | } |
3475 | |
3476 | /* |
3477 | * If a worker went to sleep, notify and ask workqueue |
3478 | * whether it wants to wake up a task to maintain |
3479 | * concurrency. |
3480 | */ |
3481 | if (prev->flags & PF_WQ_WORKER) { |
3482 | struct task_struct *to_wakeup; |
3483 | |
3484 | to_wakeup = wq_worker_sleeping(prev); |
3485 | if (to_wakeup) |
3486 | try_to_wake_up_local(to_wakeup, &rf); |
3487 | } |
3488 | } |
3489 | switch_count = &prev->nvcsw; |
3490 | } |
3491 | |
3492 | next = pick_next_task(rq, prev, &rf); |
3493 | clear_tsk_need_resched(prev); |
3494 | clear_preempt_need_resched(); |
3495 | |
3496 | if (likely(prev != next)) { |
3497 | rq->nr_switches++; |
3498 | rq->curr = next; |
3499 | /* |
3500 | * The membarrier system call requires each architecture |
3501 | * to have a full memory barrier after updating |
3502 | * rq->curr, before returning to user-space. |
3503 | * |
3504 | * Here are the schemes providing that barrier on the |
3505 | * various architectures: |
3506 | * - mm ? switch_mm() : mmdrop() for x86, s390, sparc, PowerPC. |
3507 | * switch_mm() rely on membarrier_arch_switch_mm() on PowerPC. |
3508 | * - finish_lock_switch() for weakly-ordered |
3509 | * architectures where spin_unlock is a full barrier, |
3510 | * - switch_to() for arm64 (weakly-ordered, spin_unlock |
3511 | * is a RELEASE barrier), |
3512 | */ |
3513 | ++*switch_count; |
3514 | |
3515 | trace_sched_switch(preempt, prev, next); |
3516 | |
3517 | /* Also unlocks the rq: */ |
3518 | rq = context_switch(rq, prev, next, &rf); |
3519 | } else { |
3520 | rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP); |
3521 | rq_unlock_irq(rq, &rf); |
3522 | } |
3523 | |
3524 | balance_callback(rq); |
3525 | } |
3526 | |
3527 | void __noreturn do_task_dead(void) |
3528 | { |
3529 | /* Causes final put_task_struct in finish_task_switch(): */ |
3530 | set_special_state(TASK_DEAD); |
3531 | |
3532 | /* Tell freezer to ignore us: */ |
3533 | current->flags |= PF_NOFREEZE; |
3534 | |
3535 | __schedule(false); |
3536 | BUG(); |
3537 | |
3538 | /* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */ |
3539 | for (;;) |
3540 | cpu_relax(); |
3541 | } |
3542 | |
3543 | static inline void sched_submit_work(struct task_struct *tsk) |
3544 | { |
3545 | if (!tsk->state || tsk_is_pi_blocked(tsk)) |
3546 | return; |
3547 | /* |
3548 | * If we are going to sleep and we have plugged IO queued, |
3549 | * make sure to submit it to avoid deadlocks. |
3550 | */ |
3551 | if (blk_needs_flush_plug(tsk)) |
3552 | blk_schedule_flush_plug(tsk); |
3553 | } |
3554 | |
3555 | asmlinkage __visible void __sched schedule(void) |
3556 | { |
3557 | struct task_struct *tsk = current; |
3558 | |
3559 | sched_submit_work(tsk); |
3560 | do { |
3561 | preempt_disable(); |
3562 | __schedule(false); |
3563 | sched_preempt_enable_no_resched(); |
3564 | } while (need_resched()); |
3565 | } |
3566 | EXPORT_SYMBOL(schedule); |
3567 | |
3568 | /* |
3569 | * synchronize_rcu_tasks() makes sure that no task is stuck in preempted |
3570 | * state (have scheduled out non-voluntarily) by making sure that all |
3571 | * tasks have either left the run queue or have gone into user space. |
3572 | * As idle tasks do not do either, they must not ever be preempted |
3573 | * (schedule out non-voluntarily). |
3574 | * |
3575 | * schedule_idle() is similar to schedule_preempt_disable() except that it |
3576 | * never enables preemption because it does not call sched_submit_work(). |
3577 | */ |
3578 | void __sched schedule_idle(void) |
3579 | { |
3580 | /* |
3581 | * As this skips calling sched_submit_work(), which the idle task does |
3582 | * regardless because that function is a nop when the task is in a |
3583 | * TASK_RUNNING state, make sure this isn't used someplace that the |
3584 | * current task can be in any other state. Note, idle is always in the |
3585 | * TASK_RUNNING state. |
3586 | */ |
3587 | WARN_ON_ONCE(current->state); |
3588 | do { |
3589 | __schedule(false); |
3590 | } while (need_resched()); |
3591 | } |
3592 | |
3593 | #ifdef CONFIG_CONTEXT_TRACKING |
3594 | asmlinkage __visible void __sched schedule_user(void) |
3595 | { |
3596 | /* |
3597 | * If we come here after a random call to set_need_resched(), |
3598 | * or we have been woken up remotely but the IPI has not yet arrived, |
3599 | * we haven't yet exited the RCU idle mode. Do it here manually until |
3600 | * we find a better solution. |
3601 | * |
3602 | * NB: There are buggy callers of this function. Ideally we |
3603 | * should warn if prev_state != CONTEXT_USER, but that will trigger |
3604 | * too frequently to make sense yet. |
3605 | */ |
3606 | enum ctx_state prev_state = exception_enter(); |
3607 | schedule(); |
3608 | exception_exit(prev_state); |
3609 | } |
3610 | #endif |
3611 | |
3612 | /** |
3613 | * schedule_preempt_disabled - called with preemption disabled |
3614 | * |
3615 | * Returns with preemption disabled. Note: preempt_count must be 1 |
3616 | */ |
3617 | void __sched schedule_preempt_disabled(void) |
3618 | { |
3619 | sched_preempt_enable_no_resched(); |
3620 | schedule(); |
3621 | preempt_disable(); |
3622 | } |
3623 | |
3624 | static void __sched notrace preempt_schedule_common(void) |
3625 | { |
3626 | do { |
3627 | /* |
3628 | * Because the function tracer can trace preempt_count_sub() |
3629 | * and it also uses preempt_enable/disable_notrace(), if |
3630 | * NEED_RESCHED is set, the preempt_enable_notrace() called |
3631 | * by the function tracer will call this function again and |
3632 | * cause infinite recursion. |
3633 | * |
3634 | * Preemption must be disabled here before the function |
3635 | * tracer can trace. Break up preempt_disable() into two |
3636 | * calls. One to disable preemption without fear of being |
3637 | * traced. The other to still record the preemption latency, |
3638 | * which can also be traced by the function tracer. |
3639 | */ |
3640 | preempt_disable_notrace(); |
3641 | preempt_latency_start(1); |
3642 | __schedule(true); |
3643 | preempt_latency_stop(1); |
3644 | preempt_enable_no_resched_notrace(); |
3645 | |
3646 | /* |
3647 | * Check again in case we missed a preemption opportunity |
3648 | * between schedule and now. |
3649 | */ |
3650 | } while (need_resched()); |
3651 | } |
3652 | |
3653 | #ifdef CONFIG_PREEMPT |
3654 | /* |
3655 | * this is the entry point to schedule() from in-kernel preemption |
3656 | * off of preempt_enable. Kernel preemptions off return from interrupt |
3657 | * occur there and call schedule directly. |
3658 | */ |
3659 | asmlinkage __visible void __sched notrace preempt_schedule(void) |
3660 | { |
3661 | /* |
3662 | * If there is a non-zero preempt_count or interrupts are disabled, |
3663 | * we do not want to preempt the current task. Just return.. |
3664 | */ |
3665 | if (likely(!preemptible())) |
3666 | return; |
3667 | |
3668 | preempt_schedule_common(); |
3669 | } |
3670 | NOKPROBE_SYMBOL(preempt_schedule); |
3671 | EXPORT_SYMBOL(preempt_schedule); |
3672 | |
3673 | /** |
3674 | * preempt_schedule_notrace - preempt_schedule called by tracing |
3675 | * |
3676 | * The tracing infrastructure uses preempt_enable_notrace to prevent |
3677 | * recursion and tracing preempt enabling caused by the tracing |
3678 | * infrastructure itself. But as tracing can happen in areas coming |
3679 | * from userspace or just about to enter userspace, a preempt enable |
3680 | * can occur before user_exit() is called. This will cause the scheduler |
3681 | * to be called when the system is still in usermode. |
3682 | * |
3683 | * To prevent this, the preempt_enable_notrace will use this function |
3684 | * instead of preempt_schedule() to exit user context if needed before |
3685 | * calling the scheduler. |
3686 | */ |
3687 | asmlinkage __visible void __sched notrace preempt_schedule_notrace(void) |
3688 | { |
3689 | enum ctx_state prev_ctx; |
3690 | |
3691 | if (likely(!preemptible())) |
3692 | return; |
3693 | |
3694 | do { |
3695 | /* |
3696 | * Because the function tracer can trace preempt_count_sub() |
3697 | * and it also uses preempt_enable/disable_notrace(), if |
3698 | * NEED_RESCHED is set, the preempt_enable_notrace() called |
3699 | * by the function tracer will call this function again and |
3700 | * cause infinite recursion. |
3701 | * |
3702 | * Preemption must be disabled here before the function |
3703 | * tracer can trace. Break up preempt_disable() into two |
3704 | * calls. One to disable preemption without fear of being |
3705 | * traced. The other to still record the preemption latency, |
3706 | * which can also be traced by the function tracer. |
3707 | */ |
3708 | preempt_disable_notrace(); |
3709 | preempt_latency_start(1); |
3710 | /* |
3711 | * Needs preempt disabled in case user_exit() is traced |
3712 | * and the tracer calls preempt_enable_notrace() causing |
3713 | * an infinite recursion. |
3714 | */ |
3715 | prev_ctx = exception_enter(); |
3716 | __schedule(true); |
3717 | exception_exit(prev_ctx); |
3718 | |
3719 | preempt_latency_stop(1); |
3720 | preempt_enable_no_resched_notrace(); |
3721 | } while (need_resched()); |
3722 | } |
3723 | EXPORT_SYMBOL_GPL(preempt_schedule_notrace); |
3724 | |
3725 | #endif /* CONFIG_PREEMPT */ |
3726 | |
3727 | /* |
3728 | * this is the entry point to schedule() from kernel preemption |
3729 | * off of irq context. |
3730 | * Note, that this is called and return with irqs disabled. This will |
3731 | * protect us against recursive calling from irq. |
3732 | */ |
3733 | asmlinkage __visible void __sched preempt_schedule_irq(void) |
3734 | { |
3735 | enum ctx_state prev_state; |
3736 | |
3737 | /* Catch callers which need to be fixed */ |
3738 | BUG_ON(preempt_count() || !irqs_disabled()); |
3739 | |
3740 | prev_state = exception_enter(); |
3741 | |
3742 | do { |
3743 | preempt_disable(); |
3744 | local_irq_enable(); |
3745 | __schedule(true); |
3746 | local_irq_disable(); |
3747 | sched_preempt_enable_no_resched(); |
3748 | } while (need_resched()); |
3749 | |
3750 | exception_exit(prev_state); |
3751 | } |
3752 | |
3753 | int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags, |
3754 | void *key) |
3755 | { |
3756 | return try_to_wake_up(curr->private, mode, wake_flags); |
3757 | } |
3758 | EXPORT_SYMBOL(default_wake_function); |
3759 | |
3760 | #ifdef CONFIG_RT_MUTEXES |
3761 | |
3762 | static inline int __rt_effective_prio(struct task_struct *pi_task, int prio) |
3763 | { |
3764 | if (pi_task) |
3765 | prio = min(prio, pi_task->prio); |
3766 | |
3767 | return prio; |
3768 | } |
3769 | |
3770 | static inline int rt_effective_prio(struct task_struct *p, int prio) |
3771 | { |
3772 | struct task_struct *pi_task = rt_mutex_get_top_task(p); |
3773 | |
3774 | return __rt_effective_prio(pi_task, prio); |
3775 | } |
3776 | |
3777 | /* |
3778 | * rt_mutex_setprio - set the current priority of a task |
3779 | * @p: task to boost |
3780 | * @pi_task: donor task |
3781 | * |
3782 | * This function changes the 'effective' priority of a task. It does |
3783 | * not touch ->normal_prio like __setscheduler(). |
3784 | * |
3785 | * Used by the rt_mutex code to implement priority inheritance |
3786 | * logic. Call site only calls if the priority of the task changed. |
3787 | */ |
3788 | void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task) |
3789 | { |
3790 | int prio, oldprio, queued, running, queue_flag = |
3791 | DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK; |
3792 | const struct sched_class *prev_class; |
3793 | struct rq_flags rf; |
3794 | struct rq *rq; |
3795 | |
3796 | /* XXX used to be waiter->prio, not waiter->task->prio */ |
3797 | prio = __rt_effective_prio(pi_task, p->normal_prio); |
3798 | |
3799 | /* |
3800 | * If nothing changed; bail early. |
3801 | */ |
3802 | if (p->pi_top_task == pi_task && prio == p->prio && !dl_prio(prio)) |
3803 | return; |
3804 | |
3805 | rq = __task_rq_lock(p, &rf); |
3806 | update_rq_clock(rq); |
3807 | /* |
3808 | * Set under pi_lock && rq->lock, such that the value can be used under |
3809 | * either lock. |
3810 | * |
3811 | * Note that there is loads of tricky to make this pointer cache work |
3812 | * right. rt_mutex_slowunlock()+rt_mutex_postunlock() work together to |
3813 | * ensure a task is de-boosted (pi_task is set to NULL) before the |
3814 | * task is allowed to run again (and can exit). This ensures the pointer |
3815 | * points to a blocked task -- which guaratees the task is present. |
3816 | */ |
3817 | p->pi_top_task = pi_task; |
3818 | |
3819 | /* |
3820 | * For FIFO/RR we only need to set prio, if that matches we're done. |
3821 | */ |
3822 | if (prio == p->prio && !dl_prio(prio)) |
3823 | goto out_unlock; |
3824 | |
3825 | /* |
3826 | * Idle task boosting is a nono in general. There is one |
3827 | * exception, when PREEMPT_RT and NOHZ is active: |
3828 | * |
3829 | * The idle task calls get_next_timer_interrupt() and holds |
3830 | * the timer wheel base->lock on the CPU and another CPU wants |
3831 | * to access the timer (probably to cancel it). We can safely |
3832 | * ignore the boosting request, as the idle CPU runs this code |
3833 | * with interrupts disabled and will complete the lock |
3834 | * protected section without being interrupted. So there is no |
3835 | * real need to boost. |
3836 | */ |
3837 | if (unlikely(p == rq->idle)) { |
3838 | WARN_ON(p != rq->curr); |
3839 | WARN_ON(p->pi_blocked_on); |
3840 | goto out_unlock; |
3841 | } |
3842 | |
3843 | trace_sched_pi_setprio(p, pi_task); |
3844 | oldprio = p->prio; |
3845 | |
3846 | if (oldprio == prio) |
3847 | queue_flag &= ~DEQUEUE_MOVE; |
3848 | |
3849 | prev_class = p->sched_class; |
3850 | queued = task_on_rq_queued(p); |
3851 | running = task_current(rq, p); |
3852 | if (queued) |
3853 | dequeue_task(rq, p, queue_flag); |
3854 | if (running) |
3855 | put_prev_task(rq, p); |
3856 | |
3857 | /* |
3858 | * Boosting condition are: |
3859 | * 1. -rt task is running and holds mutex A |
3860 | * --> -dl task blocks on mutex A |
3861 | * |
3862 | * 2. -dl task is running and holds mutex A |
3863 | * --> -dl task blocks on mutex A and could preempt the |
3864 | * running task |
3865 | */ |
3866 | if (dl_prio(prio)) { |
3867 | if (!dl_prio(p->normal_prio) || |
3868 | (pi_task && dl_entity_preempt(&pi_task->dl, &p->dl))) { |
3869 | p->dl.dl_boosted = 1; |
3870 | queue_flag |= ENQUEUE_REPLENISH; |
3871 | } else |
3872 | p->dl.dl_boosted = 0; |
3873 | p->sched_class = &dl_sched_class; |
3874 | } else if (rt_prio(prio)) { |
3875 | if (dl_prio(oldprio)) |
3876 | p->dl.dl_boosted = 0; |
3877 | if (oldprio < prio) |
3878 | queue_flag |= ENQUEUE_HEAD; |
3879 | p->sched_class = &rt_sched_class; |
3880 | } else { |
3881 | if (dl_prio(oldprio)) |
3882 | p->dl.dl_boosted = 0; |
3883 | if (rt_prio(oldprio)) |
3884 | p->rt.timeout = 0; |
3885 | p->sched_class = &fair_sched_class; |
3886 | } |
3887 | |
3888 | p->prio = prio; |
3889 | |
3890 | if (queued) |
3891 | enqueue_task(rq, p, queue_flag); |
3892 | if (running) |
3893 | set_curr_task(rq, p); |
3894 | |
3895 | check_class_changed(rq, p, prev_class, oldprio); |
3896 | out_unlock: |
3897 | /* Avoid rq from going away on us: */ |
3898 | preempt_disable(); |
3899 | __task_rq_unlock(rq, &rf); |
3900 | |
3901 | balance_callback(rq); |
3902 | preempt_enable(); |
3903 | } |
3904 | #else |
3905 | static inline int rt_effective_prio(struct task_struct *p, int prio) |
3906 | { |
3907 | return prio; |
3908 | } |
3909 | #endif |
3910 | |
3911 | void set_user_nice(struct task_struct *p, long nice) |
3912 | { |
3913 | bool queued, running; |
3914 | int old_prio, delta; |
3915 | struct rq_flags rf; |
3916 | struct rq *rq; |
3917 | |
3918 | if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE) |
3919 | return; |
3920 | /* |
3921 | * We have to be careful, if called from sys_setpriority(), |
3922 | * the task might be in the middle of scheduling on another CPU. |
3923 | */ |
3924 | rq = task_rq_lock(p, &rf); |
3925 | update_rq_clock(rq); |
3926 | |
3927 | /* |
3928 | * The RT priorities are set via sched_setscheduler(), but we still |
3929 | * allow the 'normal' nice value to be set - but as expected |
3930 | * it wont have any effect on scheduling until the task is |
3931 | * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR: |
3932 | */ |
3933 | if (task_has_dl_policy(p) || task_has_rt_policy(p)) { |
3934 | p->static_prio = NICE_TO_PRIO(nice); |
3935 | goto out_unlock; |
3936 | } |
3937 | queued = task_on_rq_queued(p); |
3938 | running = task_current(rq, p); |
3939 | if (queued) |
3940 | dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK); |
3941 | if (running) |
3942 | put_prev_task(rq, p); |
3943 | |
3944 | p->static_prio = NICE_TO_PRIO(nice); |
3945 | set_load_weight(p, true); |
3946 | old_prio = p->prio; |
3947 | p->prio = effective_prio(p); |
3948 | delta = p->prio - old_prio; |
3949 | |
3950 | if (queued) { |
3951 | enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK); |
3952 | /* |
3953 | * If the task increased its priority or is running and |
3954 | * lowered its priority, then reschedule its CPU: |
3955 | */ |
3956 | if (delta < 0 || (delta > 0 && task_running(rq, p))) |
3957 | resched_curr(rq); |
3958 | } |
3959 | if (running) |
3960 | set_curr_task(rq, p); |
3961 | out_unlock: |
3962 | task_rq_unlock(rq, p, &rf); |
3963 | } |
3964 | EXPORT_SYMBOL(set_user_nice); |
3965 | |
3966 | /* |
3967 | * can_nice - check if a task can reduce its nice value |
3968 | * @p: task |
3969 | * @nice: nice value |
3970 | */ |
3971 | int can_nice(const struct task_struct *p, const int nice) |
3972 | { |
3973 | /* Convert nice value [19,-20] to rlimit style value [1,40]: */ |
3974 | int nice_rlim = nice_to_rlimit(nice); |
3975 | |
3976 | return (nice_rlim <= task_rlimit(p, RLIMIT_NICE) || |
3977 | capable(CAP_SYS_NICE)); |
3978 | } |
3979 | |
3980 | #ifdef __ARCH_WANT_SYS_NICE |
3981 | |
3982 | /* |
3983 | * sys_nice - change the priority of the current process. |
3984 | * @increment: priority increment |
3985 | * |
3986 | * sys_setpriority is a more generic, but much slower function that |
3987 | * does similar things. |
3988 | */ |
3989 | SYSCALL_DEFINE1(nice, int, increment) |
3990 | { |
3991 | long nice, retval; |
3992 | |
3993 | /* |
3994 | * Setpriority might change our priority at the same moment. |
3995 | * We don't have to worry. Conceptually one call occurs first |
3996 | * and we have a single winner. |
3997 | */ |
3998 | increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH); |
3999 | nice = task_nice(current) + increment; |
4000 | |
4001 | nice = clamp_val(nice, MIN_NICE, MAX_NICE); |
4002 | if (increment < 0 && !can_nice(current, nice)) |
4003 | return -EPERM; |
4004 | |
4005 | retval = security_task_setnice(current, nice); |
4006 | if (retval) |
4007 | return retval; |
4008 | |
4009 | set_user_nice(current, nice); |
4010 | return 0; |
4011 | } |
4012 | |
4013 | #endif |
4014 | |
4015 | /** |
4016 | * task_prio - return the priority value of a given task. |
4017 | * @p: the task in question. |
4018 | * |
4019 | * Return: The priority value as seen by users in /proc. |
4020 | * RT tasks are offset by -200. Normal tasks are centered |
4021 | * around 0, value goes from -16 to +15. |
4022 | */ |
4023 | int task_prio(const struct task_struct *p) |
4024 | { |
4025 | return p->prio - MAX_RT_PRIO; |
4026 | } |
4027 | |
4028 | /** |
4029 | * idle_cpu - is a given CPU idle currently? |
4030 | * @cpu: the processor in question. |
4031 | * |
4032 | * Return: 1 if the CPU is currently idle. 0 otherwise. |
4033 | */ |
4034 | int idle_cpu(int cpu) |
4035 | { |
4036 | struct rq *rq = cpu_rq(cpu); |
4037 | |
4038 | if (rq->curr != rq->idle) |
4039 | return 0; |
4040 | |
4041 | if (rq->nr_running) |
4042 | return 0; |
4043 | |
4044 | #ifdef CONFIG_SMP |
4045 | if (!llist_empty(&rq->wake_list)) |
4046 | return 0; |
4047 | #endif |
4048 | |
4049 | return 1; |
4050 | } |
4051 | |
4052 | /** |
4053 | * available_idle_cpu - is a given CPU idle for enqueuing work. |
4054 | * @cpu: the CPU in question. |
4055 | * |
4056 | * Return: 1 if the CPU is currently idle. 0 otherwise. |
4057 | */ |
4058 | int available_idle_cpu(int cpu) |
4059 | { |
4060 | if (!idle_cpu(cpu)) |
4061 | return 0; |
4062 | |
4063 | if (vcpu_is_preempted(cpu)) |
4064 | return 0; |
4065 | |
4066 | return 1; |
4067 | } |
4068 | |
4069 | /** |
4070 | * idle_task - return the idle task for a given CPU. |
4071 | * @cpu: the processor in question. |
4072 | * |
4073 | * Return: The idle task for the CPU @cpu. |
4074 | */ |
4075 | struct task_struct *idle_task(int cpu) |
4076 | { |
4077 | return cpu_rq(cpu)->idle; |
4078 | } |
4079 | |
4080 | /** |
4081 | * find_process_by_pid - find a process with a matching PID value. |
4082 | * @pid: the pid in question. |
4083 | * |
4084 | * The task of @pid, if found. %NULL otherwise. |
4085 | */ |
4086 | static struct task_struct *find_process_by_pid(pid_t pid) |
4087 | { |
4088 | return pid ? find_task_by_vpid(pid) : current; |
4089 | } |
4090 | |
4091 | /* |
4092 | * sched_setparam() passes in -1 for its policy, to let the functions |
4093 | * it calls know not to change it. |
4094 | */ |
4095 | #define SETPARAM_POLICY -1 |
4096 | |
4097 | static void __setscheduler_params(struct task_struct *p, |
4098 | const struct sched_attr *attr) |
4099 | { |
4100 | int policy = attr->sched_policy; |
4101 | |
4102 | if (policy == SETPARAM_POLICY) |
4103 | policy = p->policy; |
4104 | |
4105 | p->policy = policy; |
4106 | |
4107 | if (dl_policy(policy)) |
4108 | __setparam_dl(p, attr); |
4109 | else if (fair_policy(policy)) |
4110 | p->static_prio = NICE_TO_PRIO(attr->sched_nice); |
4111 | |
4112 | /* |
4113 | * __sched_setscheduler() ensures attr->sched_priority == 0 when |
4114 | * !rt_policy. Always setting this ensures that things like |
4115 | * getparam()/getattr() don't report silly values for !rt tasks. |
4116 | */ |
4117 | p->rt_priority = attr->sched_priority; |
4118 | p->normal_prio = normal_prio(p); |
4119 | set_load_weight(p, true); |
4120 | } |
4121 | |
4122 | /* Actually do priority change: must hold pi & rq lock. */ |
4123 | static void __setscheduler(struct rq *rq, struct task_struct *p, |
4124 | const struct sched_attr *attr, bool keep_boost) |
4125 | { |
4126 | __setscheduler_params(p, attr); |
4127 | |
4128 | /* |
4129 | * Keep a potential priority boosting if called from |
4130 | * sched_setscheduler(). |
4131 | */ |
4132 | p->prio = normal_prio(p); |
4133 | if (keep_boost) |
4134 | p->prio = rt_effective_prio(p, p->prio); |
4135 | |
4136 | if (dl_prio(p->prio)) |
4137 | p->sched_class = &dl_sched_class; |
4138 | else if (rt_prio(p->prio)) |
4139 | p->sched_class = &rt_sched_class; |
4140 | else |
4141 | p->sched_class = &fair_sched_class; |
4142 | } |
4143 | |
4144 | /* |
4145 | * Check the target process has a UID that matches the current process's: |
4146 | */ |
4147 | static bool check_same_owner(struct task_struct *p) |
4148 | { |
4149 | const struct cred *cred = current_cred(), *pcred; |
4150 | bool match; |
4151 | |
4152 | rcu_read_lock(); |
4153 | pcred = __task_cred(p); |
4154 | match = (uid_eq(cred->euid, pcred->euid) || |
4155 | uid_eq(cred->euid, pcred->uid)); |
4156 | rcu_read_unlock(); |
4157 | return match; |
4158 | } |
4159 | |
4160 | static int __sched_setscheduler(struct task_struct *p, |
4161 | const struct sched_attr *attr, |
4162 | bool user, bool pi) |
4163 | { |
4164 | int newprio = dl_policy(attr->sched_policy) ? MAX_DL_PRIO - 1 : |
4165 | MAX_RT_PRIO - 1 - attr->sched_priority; |
4166 | int retval, oldprio, oldpolicy = -1, queued, running; |
4167 | int new_effective_prio, policy = attr->sched_policy; |
4168 | const struct sched_class *prev_class; |
4169 | struct rq_flags rf; |
4170 | int reset_on_fork; |
4171 | int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK; |
4172 | struct rq *rq; |
4173 | |
4174 | /* The pi code expects interrupts enabled */ |
4175 | BUG_ON(pi && in_interrupt()); |
4176 | recheck: |
4177 | /* Double check policy once rq lock held: */ |
4178 | if (policy < 0) { |
4179 | reset_on_fork = p->sched_reset_on_fork; |
4180 | policy = oldpolicy = p->policy; |
4181 | } else { |
4182 | reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK); |
4183 | |
4184 | if (!valid_policy(policy)) |
4185 | return -EINVAL; |
4186 | } |
4187 | |
4188 | if (attr->sched_flags & ~(SCHED_FLAG_ALL | SCHED_FLAG_SUGOV)) |
4189 | return -EINVAL; |
4190 | |
4191 | /* |
4192 | * Valid priorities for SCHED_FIFO and SCHED_RR are |
4193 | * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL, |
4194 | * SCHED_BATCH and SCHED_IDLE is 0. |
4195 | */ |
4196 | if ((p->mm && attr->sched_priority > MAX_USER_RT_PRIO-1) || |
4197 | (!p->mm && attr->sched_priority > MAX_RT_PRIO-1)) |
4198 | return -EINVAL; |
4199 | if ((dl_policy(policy) && !__checkparam_dl(attr)) || |
4200 | (rt_policy(policy) != (attr->sched_priority != 0))) |
4201 | return -EINVAL; |
4202 | |
4203 | /* |
4204 | * Allow unprivileged RT tasks to decrease priority: |
4205 | */ |
4206 | if (user && !capable(CAP_SYS_NICE)) { |
4207 | if (fair_policy(policy)) { |
4208 | if (attr->sched_nice < task_nice(p) && |
4209 | !can_nice(p, attr->sched_nice)) |
4210 | return -EPERM; |
4211 | } |
4212 | |
4213 | if (rt_policy(policy)) { |
4214 | unsigned long rlim_rtprio = |
4215 | task_rlimit(p, RLIMIT_RTPRIO); |
4216 | |
4217 | /* Can't set/change the rt policy: */ |
4218 | if (policy != p->policy && !rlim_rtprio) |
4219 | return -EPERM; |
4220 | |
4221 | /* Can't increase priority: */ |
4222 | if (attr->sched_priority > p->rt_priority && |
4223 | attr->sched_priority > rlim_rtprio) |
4224 | return -EPERM; |
4225 | } |
4226 | |
4227 | /* |
4228 | * Can't set/change SCHED_DEADLINE policy at all for now |
4229 | * (safest behavior); in the future we would like to allow |
4230 | * unprivileged DL tasks to increase their relative deadline |
4231 | * or reduce their runtime (both ways reducing utilization) |
4232 | */ |
4233 | if (dl_policy(policy)) |
4234 | return -EPERM; |
4235 | |
4236 | /* |
4237 | * Treat SCHED_IDLE as nice 20. Only allow a switch to |
4238 | * SCHED_NORMAL if the RLIMIT_NICE would normally permit it. |
4239 | */ |
4240 | if ( |
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