2 * Implement CPU time clocks for the POSIX clock interface.
5 #include <linux/sched.h>
6 #include <linux/posix-timers.h>
7 #include <linux/errno.h>
8 #include <linux/math64.h>
9 #include <asm/uaccess.h>
10 #include <linux/kernel_stat.h>
11 #include <trace/events/timer.h>
14 * Called after updating RLIMIT_CPU to run cpu timer and update
15 * tsk->signal->cputime_expires expiration cache if necessary. Needs
16 * siglock protection since other code may update expiration cache as
19 void update_rlimit_cpu(unsigned long rlim_new)
21 cputime_t cputime = secs_to_cputime(rlim_new);
23 spin_lock_irq(¤t->sighand->siglock);
24 set_process_cpu_timer(current, CPUCLOCK_PROF, &cputime, NULL);
25 spin_unlock_irq(¤t->sighand->siglock);
28 static int check_clock(const clockid_t which_clock)
31 struct task_struct *p;
32 const pid_t pid = CPUCLOCK_PID(which_clock);
34 if (CPUCLOCK_WHICH(which_clock) >= CPUCLOCK_MAX)
40 read_lock(&tasklist_lock);
41 p = find_task_by_vpid(pid);
42 if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
43 same_thread_group(p, current) : thread_group_leader(p))) {
46 read_unlock(&tasklist_lock);
51 static inline union cpu_time_count
52 timespec_to_sample(const clockid_t which_clock, const struct timespec *tp)
54 union cpu_time_count ret;
55 ret.sched = 0; /* high half always zero when .cpu used */
56 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
57 ret.sched = (unsigned long long)tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
59 ret.cpu = timespec_to_cputime(tp);
64 static void sample_to_timespec(const clockid_t which_clock,
65 union cpu_time_count cpu,
68 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED)
69 *tp = ns_to_timespec(cpu.sched);
71 cputime_to_timespec(cpu.cpu, tp);
74 static inline int cpu_time_before(const clockid_t which_clock,
75 union cpu_time_count now,
76 union cpu_time_count then)
78 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
79 return now.sched < then.sched;
81 return cputime_lt(now.cpu, then.cpu);
84 static inline void cpu_time_add(const clockid_t which_clock,
85 union cpu_time_count *acc,
86 union cpu_time_count val)
88 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
89 acc->sched += val.sched;
91 acc->cpu = cputime_add(acc->cpu, val.cpu);
94 static inline union cpu_time_count cpu_time_sub(const clockid_t which_clock,
95 union cpu_time_count a,
96 union cpu_time_count b)
98 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
101 a.cpu = cputime_sub(a.cpu, b.cpu);
107 * Divide and limit the result to res >= 1
109 * This is necessary to prevent signal delivery starvation, when the result of
110 * the division would be rounded down to 0.
112 static inline cputime_t cputime_div_non_zero(cputime_t time, unsigned long div)
114 cputime_t res = cputime_div(time, div);
116 return max_t(cputime_t, res, 1);
120 * Update expiry time from increment, and increase overrun count,
121 * given the current clock sample.
123 static void bump_cpu_timer(struct k_itimer *timer,
124 union cpu_time_count now)
128 if (timer->it.cpu.incr.sched == 0)
131 if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
132 unsigned long long delta, incr;
134 if (now.sched < timer->it.cpu.expires.sched)
136 incr = timer->it.cpu.incr.sched;
137 delta = now.sched + incr - timer->it.cpu.expires.sched;
138 /* Don't use (incr*2 < delta), incr*2 might overflow. */
139 for (i = 0; incr < delta - incr; i++)
141 for (; i >= 0; incr >>= 1, i--) {
144 timer->it.cpu.expires.sched += incr;
145 timer->it_overrun += 1 << i;
149 cputime_t delta, incr;
151 if (cputime_lt(now.cpu, timer->it.cpu.expires.cpu))
153 incr = timer->it.cpu.incr.cpu;
154 delta = cputime_sub(cputime_add(now.cpu, incr),
155 timer->it.cpu.expires.cpu);
156 /* Don't use (incr*2 < delta), incr*2 might overflow. */
157 for (i = 0; cputime_lt(incr, cputime_sub(delta, incr)); i++)
158 incr = cputime_add(incr, incr);
159 for (; i >= 0; incr = cputime_halve(incr), i--) {
160 if (cputime_lt(delta, incr))
162 timer->it.cpu.expires.cpu =
163 cputime_add(timer->it.cpu.expires.cpu, incr);
164 timer->it_overrun += 1 << i;
165 delta = cputime_sub(delta, incr);
170 static inline cputime_t prof_ticks(struct task_struct *p)
172 return cputime_add(p->utime, p->stime);
174 static inline cputime_t virt_ticks(struct task_struct *p)
179 int posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
181 int error = check_clock(which_clock);
184 tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
185 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
187 * If sched_clock is using a cycle counter, we
188 * don't have any idea of its true resolution
189 * exported, but it is much more than 1s/HZ.
197 int posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
200 * You can never reset a CPU clock, but we check for other errors
201 * in the call before failing with EPERM.
203 int error = check_clock(which_clock);
212 * Sample a per-thread clock for the given task.
214 static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
215 union cpu_time_count *cpu)
217 switch (CPUCLOCK_WHICH(which_clock)) {
221 cpu->cpu = prof_ticks(p);
224 cpu->cpu = virt_ticks(p);
227 cpu->sched = task_sched_runtime(p);
233 void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
235 struct sighand_struct *sighand;
236 struct signal_struct *sig;
237 struct task_struct *t;
239 *times = INIT_CPUTIME;
242 sighand = rcu_dereference(tsk->sighand);
250 times->utime = cputime_add(times->utime, t->utime);
251 times->stime = cputime_add(times->stime, t->stime);
252 times->sum_exec_runtime += t->se.sum_exec_runtime;
257 times->utime = cputime_add(times->utime, sig->utime);
258 times->stime = cputime_add(times->stime, sig->stime);
259 times->sum_exec_runtime += sig->sum_sched_runtime;
264 static void update_gt_cputime(struct task_cputime *a, struct task_cputime *b)
266 if (cputime_gt(b->utime, a->utime))
269 if (cputime_gt(b->stime, a->stime))
272 if (b->sum_exec_runtime > a->sum_exec_runtime)
273 a->sum_exec_runtime = b->sum_exec_runtime;
276 void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
278 struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
279 struct task_cputime sum;
282 spin_lock_irqsave(&cputimer->lock, flags);
283 if (!cputimer->running) {
284 cputimer->running = 1;
286 * The POSIX timer interface allows for absolute time expiry
287 * values through the TIMER_ABSTIME flag, therefore we have
288 * to synchronize the timer to the clock every time we start
291 thread_group_cputime(tsk, &sum);
292 update_gt_cputime(&cputimer->cputime, &sum);
294 *times = cputimer->cputime;
295 spin_unlock_irqrestore(&cputimer->lock, flags);
299 * Sample a process (thread group) clock for the given group_leader task.
300 * Must be called with tasklist_lock held for reading.
302 static int cpu_clock_sample_group(const clockid_t which_clock,
303 struct task_struct *p,
304 union cpu_time_count *cpu)
306 struct task_cputime cputime;
308 switch (CPUCLOCK_WHICH(which_clock)) {
312 thread_group_cputime(p, &cputime);
313 cpu->cpu = cputime_add(cputime.utime, cputime.stime);
316 thread_group_cputime(p, &cputime);
317 cpu->cpu = cputime.utime;
320 cpu->sched = thread_group_sched_runtime(p);
327 int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
329 const pid_t pid = CPUCLOCK_PID(which_clock);
331 union cpu_time_count rtn;
335 * Special case constant value for our own clocks.
336 * We don't have to do any lookup to find ourselves.
338 if (CPUCLOCK_PERTHREAD(which_clock)) {
340 * Sampling just ourselves we can do with no locking.
342 error = cpu_clock_sample(which_clock,
345 read_lock(&tasklist_lock);
346 error = cpu_clock_sample_group(which_clock,
348 read_unlock(&tasklist_lock);
352 * Find the given PID, and validate that the caller
353 * should be able to see it.
355 struct task_struct *p;
357 p = find_task_by_vpid(pid);
359 if (CPUCLOCK_PERTHREAD(which_clock)) {
360 if (same_thread_group(p, current)) {
361 error = cpu_clock_sample(which_clock,
365 read_lock(&tasklist_lock);
366 if (thread_group_leader(p) && p->signal) {
368 cpu_clock_sample_group(which_clock,
371 read_unlock(&tasklist_lock);
379 sample_to_timespec(which_clock, rtn, tp);
385 * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
386 * This is called from sys_timer_create() and do_cpu_nanosleep() with the
387 * new timer already all-zeros initialized.
389 int posix_cpu_timer_create(struct k_itimer *new_timer)
392 const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
393 struct task_struct *p;
395 if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
398 INIT_LIST_HEAD(&new_timer->it.cpu.entry);
400 read_lock(&tasklist_lock);
401 if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
405 p = find_task_by_vpid(pid);
406 if (p && !same_thread_group(p, current))
411 p = current->group_leader;
413 p = find_task_by_vpid(pid);
414 if (p && !thread_group_leader(p))
418 new_timer->it.cpu.task = p;
424 read_unlock(&tasklist_lock);
430 * Clean up a CPU-clock timer that is about to be destroyed.
431 * This is called from timer deletion with the timer already locked.
432 * If we return TIMER_RETRY, it's necessary to release the timer's lock
433 * and try again. (This happens when the timer is in the middle of firing.)
435 int posix_cpu_timer_del(struct k_itimer *timer)
437 struct task_struct *p = timer->it.cpu.task;
440 if (likely(p != NULL)) {
441 read_lock(&tasklist_lock);
442 if (unlikely(p->signal == NULL)) {
444 * We raced with the reaping of the task.
445 * The deletion should have cleared us off the list.
447 BUG_ON(!list_empty(&timer->it.cpu.entry));
449 spin_lock(&p->sighand->siglock);
450 if (timer->it.cpu.firing)
453 list_del(&timer->it.cpu.entry);
454 spin_unlock(&p->sighand->siglock);
456 read_unlock(&tasklist_lock);
466 * Clean out CPU timers still ticking when a thread exited. The task
467 * pointer is cleared, and the expiry time is replaced with the residual
468 * time for later timer_gettime calls to return.
469 * This must be called with the siglock held.
471 static void cleanup_timers(struct list_head *head,
472 cputime_t utime, cputime_t stime,
473 unsigned long long sum_exec_runtime)
475 struct cpu_timer_list *timer, *next;
476 cputime_t ptime = cputime_add(utime, stime);
478 list_for_each_entry_safe(timer, next, head, entry) {
479 list_del_init(&timer->entry);
480 if (cputime_lt(timer->expires.cpu, ptime)) {
481 timer->expires.cpu = cputime_zero;
483 timer->expires.cpu = cputime_sub(timer->expires.cpu,
489 list_for_each_entry_safe(timer, next, head, entry) {
490 list_del_init(&timer->entry);
491 if (cputime_lt(timer->expires.cpu, utime)) {
492 timer->expires.cpu = cputime_zero;
494 timer->expires.cpu = cputime_sub(timer->expires.cpu,
500 list_for_each_entry_safe(timer, next, head, entry) {
501 list_del_init(&timer->entry);
502 if (timer->expires.sched < sum_exec_runtime) {
503 timer->expires.sched = 0;
505 timer->expires.sched -= sum_exec_runtime;
511 * These are both called with the siglock held, when the current thread
512 * is being reaped. When the final (leader) thread in the group is reaped,
513 * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
515 void posix_cpu_timers_exit(struct task_struct *tsk)
517 cleanup_timers(tsk->cpu_timers,
518 tsk->utime, tsk->stime, tsk->se.sum_exec_runtime);
521 void posix_cpu_timers_exit_group(struct task_struct *tsk)
523 struct signal_struct *const sig = tsk->signal;
525 cleanup_timers(tsk->signal->cpu_timers,
526 cputime_add(tsk->utime, sig->utime),
527 cputime_add(tsk->stime, sig->stime),
528 tsk->se.sum_exec_runtime + sig->sum_sched_runtime);
531 static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
534 * That's all for this thread or process.
535 * We leave our residual in expires to be reported.
537 put_task_struct(timer->it.cpu.task);
538 timer->it.cpu.task = NULL;
539 timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
540 timer->it.cpu.expires,
544 static inline int expires_gt(cputime_t expires, cputime_t new_exp)
546 return cputime_eq(expires, cputime_zero) ||
547 cputime_gt(expires, new_exp);
550 static inline int expires_le(cputime_t expires, cputime_t new_exp)
552 return !cputime_eq(expires, cputime_zero) &&
553 cputime_le(expires, new_exp);
556 * Insert the timer on the appropriate list before any timers that
557 * expire later. This must be called with the tasklist_lock held
558 * for reading, and interrupts disabled.
560 static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
562 struct task_struct *p = timer->it.cpu.task;
563 struct list_head *head, *listpos;
564 struct cpu_timer_list *const nt = &timer->it.cpu;
565 struct cpu_timer_list *next;
567 head = (CPUCLOCK_PERTHREAD(timer->it_clock) ?
568 p->cpu_timers : p->signal->cpu_timers);
569 head += CPUCLOCK_WHICH(timer->it_clock);
571 BUG_ON(!irqs_disabled());
572 spin_lock(&p->sighand->siglock);
575 if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
576 list_for_each_entry(next, head, entry) {
577 if (next->expires.sched > nt->expires.sched)
579 listpos = &next->entry;
582 list_for_each_entry(next, head, entry) {
583 if (cputime_gt(next->expires.cpu, nt->expires.cpu))
585 listpos = &next->entry;
588 list_add(&nt->entry, listpos);
590 if (listpos == head) {
592 * We are the new earliest-expiring timer.
593 * If we are a thread timer, there can always
594 * be a process timer telling us to stop earlier.
597 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
598 union cpu_time_count *exp = &nt->expires;
600 switch (CPUCLOCK_WHICH(timer->it_clock)) {
604 if (expires_gt(p->cputime_expires.prof_exp,
606 p->cputime_expires.prof_exp = exp->cpu;
609 if (expires_gt(p->cputime_expires.virt_exp,
611 p->cputime_expires.virt_exp = exp->cpu;
614 if (p->cputime_expires.sched_exp == 0 ||
615 p->cputime_expires.sched_exp > exp->sched)
616 p->cputime_expires.sched_exp =
621 struct signal_struct *const sig = p->signal;
622 union cpu_time_count *exp = &timer->it.cpu.expires;
625 * For a process timer, set the cached expiration time.
627 switch (CPUCLOCK_WHICH(timer->it_clock)) {
631 if (expires_gt(sig->cputime_expires.virt_exp, exp->cpu))
632 sig->cputime_expires.virt_exp = exp->cpu;
634 if (expires_gt(sig->cputime_expires.prof_exp, exp->cpu))
635 sig->cputime_expires.prof_exp = exp->cpu;
638 sig->cputime_expires.sched_exp = exp->sched;
644 spin_unlock(&p->sighand->siglock);
648 * The timer is locked, fire it and arrange for its reload.
650 static void cpu_timer_fire(struct k_itimer *timer)
652 if (unlikely(timer->sigq == NULL)) {
654 * This a special case for clock_nanosleep,
655 * not a normal timer from sys_timer_create.
657 wake_up_process(timer->it_process);
658 timer->it.cpu.expires.sched = 0;
659 } else if (timer->it.cpu.incr.sched == 0) {
661 * One-shot timer. Clear it as soon as it's fired.
663 posix_timer_event(timer, 0);
664 timer->it.cpu.expires.sched = 0;
665 } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
667 * The signal did not get queued because the signal
668 * was ignored, so we won't get any callback to
669 * reload the timer. But we need to keep it
670 * ticking in case the signal is deliverable next time.
672 posix_cpu_timer_schedule(timer);
677 * Sample a process (thread group) timer for the given group_leader task.
678 * Must be called with tasklist_lock held for reading.
680 static int cpu_timer_sample_group(const clockid_t which_clock,
681 struct task_struct *p,
682 union cpu_time_count *cpu)
684 struct task_cputime cputime;
686 thread_group_cputimer(p, &cputime);
687 switch (CPUCLOCK_WHICH(which_clock)) {
691 cpu->cpu = cputime_add(cputime.utime, cputime.stime);
694 cpu->cpu = cputime.utime;
697 cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
704 * Guts of sys_timer_settime for CPU timers.
705 * This is called with the timer locked and interrupts disabled.
706 * If we return TIMER_RETRY, it's necessary to release the timer's lock
707 * and try again. (This happens when the timer is in the middle of firing.)
709 int posix_cpu_timer_set(struct k_itimer *timer, int flags,
710 struct itimerspec *new, struct itimerspec *old)
712 struct task_struct *p = timer->it.cpu.task;
713 union cpu_time_count old_expires, new_expires, val;
716 if (unlikely(p == NULL)) {
718 * Timer refers to a dead task's clock.
723 new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
725 read_lock(&tasklist_lock);
727 * We need the tasklist_lock to protect against reaping that
728 * clears p->signal. If p has just been reaped, we can no
729 * longer get any information about it at all.
731 if (unlikely(p->signal == NULL)) {
732 read_unlock(&tasklist_lock);
734 timer->it.cpu.task = NULL;
739 * Disarm any old timer after extracting its expiry time.
741 BUG_ON(!irqs_disabled());
744 spin_lock(&p->sighand->siglock);
745 old_expires = timer->it.cpu.expires;
746 if (unlikely(timer->it.cpu.firing)) {
747 timer->it.cpu.firing = -1;
750 list_del_init(&timer->it.cpu.entry);
751 spin_unlock(&p->sighand->siglock);
754 * We need to sample the current value to convert the new
755 * value from to relative and absolute, and to convert the
756 * old value from absolute to relative. To set a process
757 * timer, we need a sample to balance the thread expiry
758 * times (in arm_timer). With an absolute time, we must
759 * check if it's already passed. In short, we need a sample.
761 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
762 cpu_clock_sample(timer->it_clock, p, &val);
764 cpu_timer_sample_group(timer->it_clock, p, &val);
768 if (old_expires.sched == 0) {
769 old->it_value.tv_sec = 0;
770 old->it_value.tv_nsec = 0;
773 * Update the timer in case it has
774 * overrun already. If it has,
775 * we'll report it as having overrun
776 * and with the next reloaded timer
777 * already ticking, though we are
778 * swallowing that pending
779 * notification here to install the
782 bump_cpu_timer(timer, val);
783 if (cpu_time_before(timer->it_clock, val,
784 timer->it.cpu.expires)) {
785 old_expires = cpu_time_sub(
787 timer->it.cpu.expires, val);
788 sample_to_timespec(timer->it_clock,
792 old->it_value.tv_nsec = 1;
793 old->it_value.tv_sec = 0;
800 * We are colliding with the timer actually firing.
801 * Punt after filling in the timer's old value, and
802 * disable this firing since we are already reporting
803 * it as an overrun (thanks to bump_cpu_timer above).
805 read_unlock(&tasklist_lock);
809 if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
810 cpu_time_add(timer->it_clock, &new_expires, val);
814 * Install the new expiry time (or zero).
815 * For a timer with no notification action, we don't actually
816 * arm the timer (we'll just fake it for timer_gettime).
818 timer->it.cpu.expires = new_expires;
819 if (new_expires.sched != 0 &&
820 (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
821 cpu_time_before(timer->it_clock, val, new_expires)) {
822 arm_timer(timer, val);
825 read_unlock(&tasklist_lock);
828 * Install the new reload setting, and
829 * set up the signal and overrun bookkeeping.
831 timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
835 * This acts as a modification timestamp for the timer,
836 * so any automatic reload attempt will punt on seeing
837 * that we have reset the timer manually.
839 timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
841 timer->it_overrun_last = 0;
842 timer->it_overrun = -1;
844 if (new_expires.sched != 0 &&
845 (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
846 !cpu_time_before(timer->it_clock, val, new_expires)) {
848 * The designated time already passed, so we notify
849 * immediately, even if the thread never runs to
850 * accumulate more time on this clock.
852 cpu_timer_fire(timer);
858 sample_to_timespec(timer->it_clock,
859 timer->it.cpu.incr, &old->it_interval);
864 void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
866 union cpu_time_count now;
867 struct task_struct *p = timer->it.cpu.task;
871 * Easy part: convert the reload time.
873 sample_to_timespec(timer->it_clock,
874 timer->it.cpu.incr, &itp->it_interval);
876 if (timer->it.cpu.expires.sched == 0) { /* Timer not armed at all. */
877 itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
881 if (unlikely(p == NULL)) {
883 * This task already died and the timer will never fire.
884 * In this case, expires is actually the dead value.
887 sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
893 * Sample the clock to take the difference with the expiry time.
895 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
896 cpu_clock_sample(timer->it_clock, p, &now);
897 clear_dead = p->exit_state;
899 read_lock(&tasklist_lock);
900 if (unlikely(p->signal == NULL)) {
902 * The process has been reaped.
903 * We can't even collect a sample any more.
904 * Call the timer disarmed, nothing else to do.
907 timer->it.cpu.task = NULL;
908 timer->it.cpu.expires.sched = 0;
909 read_unlock(&tasklist_lock);
912 cpu_timer_sample_group(timer->it_clock, p, &now);
913 clear_dead = (unlikely(p->exit_state) &&
914 thread_group_empty(p));
916 read_unlock(&tasklist_lock);
919 if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
920 if (timer->it.cpu.incr.sched == 0 &&
921 cpu_time_before(timer->it_clock,
922 timer->it.cpu.expires, now)) {
924 * Do-nothing timer expired and has no reload,
925 * so it's as if it was never set.
927 timer->it.cpu.expires.sched = 0;
928 itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
932 * Account for any expirations and reloads that should
935 bump_cpu_timer(timer, now);
938 if (unlikely(clear_dead)) {
940 * We've noticed that the thread is dead, but
941 * not yet reaped. Take this opportunity to
944 clear_dead_task(timer, now);
948 if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
949 sample_to_timespec(timer->it_clock,
950 cpu_time_sub(timer->it_clock,
951 timer->it.cpu.expires, now),
955 * The timer should have expired already, but the firing
956 * hasn't taken place yet. Say it's just about to expire.
958 itp->it_value.tv_nsec = 1;
959 itp->it_value.tv_sec = 0;
964 * Check for any per-thread CPU timers that have fired and move them off
965 * the tsk->cpu_timers[N] list onto the firing list. Here we update the
966 * tsk->it_*_expires values to reflect the remaining thread CPU timers.
968 static void check_thread_timers(struct task_struct *tsk,
969 struct list_head *firing)
972 struct list_head *timers = tsk->cpu_timers;
973 struct signal_struct *const sig = tsk->signal;
977 tsk->cputime_expires.prof_exp = cputime_zero;
978 while (!list_empty(timers)) {
979 struct cpu_timer_list *t = list_first_entry(timers,
980 struct cpu_timer_list,
982 if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
983 tsk->cputime_expires.prof_exp = t->expires.cpu;
987 list_move_tail(&t->entry, firing);
992 tsk->cputime_expires.virt_exp = cputime_zero;
993 while (!list_empty(timers)) {
994 struct cpu_timer_list *t = list_first_entry(timers,
995 struct cpu_timer_list,
997 if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
998 tsk->cputime_expires.virt_exp = t->expires.cpu;
1002 list_move_tail(&t->entry, firing);
1007 tsk->cputime_expires.sched_exp = 0;
1008 while (!list_empty(timers)) {
1009 struct cpu_timer_list *t = list_first_entry(timers,
1010 struct cpu_timer_list,
1012 if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
1013 tsk->cputime_expires.sched_exp = t->expires.sched;
1017 list_move_tail(&t->entry, firing);
1021 * Check for the special case thread timers.
1023 soft = ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
1024 if (soft != RLIM_INFINITY) {
1025 unsigned long hard =
1026 ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);
1028 if (hard != RLIM_INFINITY &&
1029 tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
1031 * At the hard limit, we just die.
1032 * No need to calculate anything else now.
1034 __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1037 if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {
1039 * At the soft limit, send a SIGXCPU every second.
1042 soft += USEC_PER_SEC;
1043 sig->rlim[RLIMIT_RTTIME].rlim_cur = soft;
1046 "RT Watchdog Timeout: %s[%d]\n",
1047 tsk->comm, task_pid_nr(tsk));
1048 __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1053 static void stop_process_timers(struct task_struct *tsk)
1055 struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
1056 unsigned long flags;
1058 if (!cputimer->running)
1061 spin_lock_irqsave(&cputimer->lock, flags);
1062 cputimer->running = 0;
1063 spin_unlock_irqrestore(&cputimer->lock, flags);
1066 static u32 onecputick;
1068 static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
1069 cputime_t *expires, cputime_t cur_time, int signo)
1071 if (cputime_eq(it->expires, cputime_zero))
1074 if (cputime_ge(cur_time, it->expires)) {
1075 if (!cputime_eq(it->incr, cputime_zero)) {
1076 it->expires = cputime_add(it->expires, it->incr);
1077 it->error += it->incr_error;
1078 if (it->error >= onecputick) {
1079 it->expires = cputime_sub(it->expires,
1081 it->error -= onecputick;
1084 it->expires = cputime_zero;
1087 trace_itimer_expire(signo == SIGPROF ?
1088 ITIMER_PROF : ITIMER_VIRTUAL,
1089 tsk->signal->leader_pid, cur_time);
1090 __group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
1093 if (!cputime_eq(it->expires, cputime_zero) &&
1094 (cputime_eq(*expires, cputime_zero) ||
1095 cputime_lt(it->expires, *expires))) {
1096 *expires = it->expires;
1101 * Check for any per-thread CPU timers that have fired and move them
1102 * off the tsk->*_timers list onto the firing list. Per-thread timers
1103 * have already been taken off.
1105 static void check_process_timers(struct task_struct *tsk,
1106 struct list_head *firing)
1109 struct signal_struct *const sig = tsk->signal;
1110 cputime_t utime, ptime, virt_expires, prof_expires;
1111 unsigned long long sum_sched_runtime, sched_expires;
1112 struct list_head *timers = sig->cpu_timers;
1113 struct task_cputime cputime;
1117 * Don't sample the current process CPU clocks if there are no timers.
1119 if (list_empty(&timers[CPUCLOCK_PROF]) &&
1120 cputime_eq(sig->it[CPUCLOCK_PROF].expires, cputime_zero) &&
1121 sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY &&
1122 list_empty(&timers[CPUCLOCK_VIRT]) &&
1123 cputime_eq(sig->it[CPUCLOCK_VIRT].expires, cputime_zero) &&
1124 list_empty(&timers[CPUCLOCK_SCHED])) {
1125 stop_process_timers(tsk);
1130 * Collect the current process totals.
1132 thread_group_cputimer(tsk, &cputime);
1133 utime = cputime.utime;
1134 ptime = cputime_add(utime, cputime.stime);
1135 sum_sched_runtime = cputime.sum_exec_runtime;
1137 prof_expires = cputime_zero;
1138 while (!list_empty(timers)) {
1139 struct cpu_timer_list *tl = list_first_entry(timers,
1140 struct cpu_timer_list,
1142 if (!--maxfire || cputime_lt(ptime, tl->expires.cpu)) {
1143 prof_expires = tl->expires.cpu;
1147 list_move_tail(&tl->entry, firing);
1152 virt_expires = cputime_zero;
1153 while (!list_empty(timers)) {
1154 struct cpu_timer_list *tl = list_first_entry(timers,
1155 struct cpu_timer_list,
1157 if (!--maxfire || cputime_lt(utime, tl->expires.cpu)) {
1158 virt_expires = tl->expires.cpu;
1162 list_move_tail(&tl->entry, firing);
1168 while (!list_empty(timers)) {
1169 struct cpu_timer_list *tl = list_first_entry(timers,
1170 struct cpu_timer_list,
1172 if (!--maxfire || sum_sched_runtime < tl->expires.sched) {
1173 sched_expires = tl->expires.sched;
1177 list_move_tail(&tl->entry, firing);
1181 * Check for the special case process timers.
1183 check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime,
1185 check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
1187 soft = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1188 if (soft != RLIM_INFINITY) {
1189 unsigned long psecs = cputime_to_secs(ptime);
1190 unsigned long hard =
1191 ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
1193 if (psecs >= hard) {
1195 * At the hard limit, we just die.
1196 * No need to calculate anything else now.
1198 __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1201 if (psecs >= soft) {
1203 * At the soft limit, send a SIGXCPU every second.
1205 __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1208 sig->rlim[RLIMIT_CPU].rlim_cur = soft;
1211 x = secs_to_cputime(soft);
1212 if (cputime_eq(prof_expires, cputime_zero) ||
1213 cputime_lt(x, prof_expires)) {
1218 if (!cputime_eq(prof_expires, cputime_zero) &&
1219 (cputime_eq(sig->cputime_expires.prof_exp, cputime_zero) ||
1220 cputime_gt(sig->cputime_expires.prof_exp, prof_expires)))
1221 sig->cputime_expires.prof_exp = prof_expires;
1222 if (!cputime_eq(virt_expires, cputime_zero) &&
1223 (cputime_eq(sig->cputime_expires.virt_exp, cputime_zero) ||
1224 cputime_gt(sig->cputime_expires.virt_exp, virt_expires)))
1225 sig->cputime_expires.virt_exp = virt_expires;
1226 if (sched_expires != 0 &&
1227 (sig->cputime_expires.sched_exp == 0 ||
1228 sig->cputime_expires.sched_exp > sched_expires))
1229 sig->cputime_expires.sched_exp = sched_expires;
1233 * This is called from the signal code (via do_schedule_next_timer)
1234 * when the last timer signal was delivered and we have to reload the timer.
1236 void posix_cpu_timer_schedule(struct k_itimer *timer)
1238 struct task_struct *p = timer->it.cpu.task;
1239 union cpu_time_count now;
1241 if (unlikely(p == NULL))
1243 * The task was cleaned up already, no future firings.
1248 * Fetch the current sample and update the timer's expiry time.
1250 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1251 cpu_clock_sample(timer->it_clock, p, &now);
1252 bump_cpu_timer(timer, now);
1253 if (unlikely(p->exit_state)) {
1254 clear_dead_task(timer, now);
1257 read_lock(&tasklist_lock); /* arm_timer needs it. */
1259 read_lock(&tasklist_lock);
1260 if (unlikely(p->signal == NULL)) {
1262 * The process has been reaped.
1263 * We can't even collect a sample any more.
1266 timer->it.cpu.task = p = NULL;
1267 timer->it.cpu.expires.sched = 0;
1269 } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1271 * We've noticed that the thread is dead, but
1272 * not yet reaped. Take this opportunity to
1273 * drop our task ref.
1275 clear_dead_task(timer, now);
1278 cpu_timer_sample_group(timer->it_clock, p, &now);
1279 bump_cpu_timer(timer, now);
1280 /* Leave the tasklist_lock locked for the call below. */
1284 * Now re-arm for the new expiry time.
1286 arm_timer(timer, now);
1289 read_unlock(&tasklist_lock);
1292 timer->it_overrun_last = timer->it_overrun;
1293 timer->it_overrun = -1;
1294 ++timer->it_requeue_pending;
1298 * task_cputime_zero - Check a task_cputime struct for all zero fields.
1300 * @cputime: The struct to compare.
1302 * Checks @cputime to see if all fields are zero. Returns true if all fields
1303 * are zero, false if any field is nonzero.
1305 static inline int task_cputime_zero(const struct task_cputime *cputime)
1307 if (cputime_eq(cputime->utime, cputime_zero) &&
1308 cputime_eq(cputime->stime, cputime_zero) &&
1309 cputime->sum_exec_runtime == 0)
1315 * task_cputime_expired - Compare two task_cputime entities.
1317 * @sample: The task_cputime structure to be checked for expiration.
1318 * @expires: Expiration times, against which @sample will be checked.
1320 * Checks @sample against @expires to see if any field of @sample has expired.
1321 * Returns true if any field of the former is greater than the corresponding
1322 * field of the latter if the latter field is set. Otherwise returns false.
1324 static inline int task_cputime_expired(const struct task_cputime *sample,
1325 const struct task_cputime *expires)
1327 if (!cputime_eq(expires->utime, cputime_zero) &&
1328 cputime_ge(sample->utime, expires->utime))
1330 if (!cputime_eq(expires->stime, cputime_zero) &&
1331 cputime_ge(cputime_add(sample->utime, sample->stime),
1334 if (expires->sum_exec_runtime != 0 &&
1335 sample->sum_exec_runtime >= expires->sum_exec_runtime)
1341 * fastpath_timer_check - POSIX CPU timers fast path.
1343 * @tsk: The task (thread) being checked.
1345 * Check the task and thread group timers. If both are zero (there are no
1346 * timers set) return false. Otherwise snapshot the task and thread group
1347 * timers and compare them with the corresponding expiration times. Return
1348 * true if a timer has expired, else return false.
1350 static inline int fastpath_timer_check(struct task_struct *tsk)
1352 struct signal_struct *sig;
1354 /* tsk == current, ensure it is safe to use ->signal/sighand */
1355 if (unlikely(tsk->exit_state))
1358 if (!task_cputime_zero(&tsk->cputime_expires)) {
1359 struct task_cputime task_sample = {
1360 .utime = tsk->utime,
1361 .stime = tsk->stime,
1362 .sum_exec_runtime = tsk->se.sum_exec_runtime
1365 if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
1370 if (!task_cputime_zero(&sig->cputime_expires)) {
1371 struct task_cputime group_sample;
1373 thread_group_cputimer(tsk, &group_sample);
1374 if (task_cputime_expired(&group_sample, &sig->cputime_expires))
1382 * This is called from the timer interrupt handler. The irq handler has
1383 * already updated our counts. We need to check if any timers fire now.
1384 * Interrupts are disabled.
1386 void run_posix_cpu_timers(struct task_struct *tsk)
1389 struct k_itimer *timer, *next;
1391 BUG_ON(!irqs_disabled());
1394 * The fast path checks that there are no expired thread or thread
1395 * group timers. If that's so, just return.
1397 if (!fastpath_timer_check(tsk))
1400 spin_lock(&tsk->sighand->siglock);
1402 * Here we take off tsk->signal->cpu_timers[N] and
1403 * tsk->cpu_timers[N] all the timers that are firing, and
1404 * put them on the firing list.
1406 check_thread_timers(tsk, &firing);
1407 check_process_timers(tsk, &firing);
1410 * We must release these locks before taking any timer's lock.
1411 * There is a potential race with timer deletion here, as the
1412 * siglock now protects our private firing list. We have set
1413 * the firing flag in each timer, so that a deletion attempt
1414 * that gets the timer lock before we do will give it up and
1415 * spin until we've taken care of that timer below.
1417 spin_unlock(&tsk->sighand->siglock);
1420 * Now that all the timers on our list have the firing flag,
1421 * noone will touch their list entries but us. We'll take
1422 * each timer's lock before clearing its firing flag, so no
1423 * timer call will interfere.
1425 list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1428 spin_lock(&timer->it_lock);
1429 list_del_init(&timer->it.cpu.entry);
1430 cpu_firing = timer->it.cpu.firing;
1431 timer->it.cpu.firing = 0;
1433 * The firing flag is -1 if we collided with a reset
1434 * of the timer, which already reported this
1435 * almost-firing as an overrun. So don't generate an event.
1437 if (likely(cpu_firing >= 0))
1438 cpu_timer_fire(timer);
1439 spin_unlock(&timer->it_lock);
1444 * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
1445 * The tsk->sighand->siglock must be held by the caller.
1447 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1448 cputime_t *newval, cputime_t *oldval)
1450 union cpu_time_count now;
1452 BUG_ON(clock_idx == CPUCLOCK_SCHED);
1453 cpu_timer_sample_group(clock_idx, tsk, &now);
1457 * We are setting itimer. The *oldval is absolute and we update
1458 * it to be relative, *newval argument is relative and we update
1459 * it to be absolute.
1461 if (!cputime_eq(*oldval, cputime_zero)) {
1462 if (cputime_le(*oldval, now.cpu)) {
1463 /* Just about to fire. */
1464 *oldval = cputime_one_jiffy;
1466 *oldval = cputime_sub(*oldval, now.cpu);
1470 if (cputime_eq(*newval, cputime_zero))
1472 *newval = cputime_add(*newval, now.cpu);
1476 * Update expiration cache if we are the earliest timer, or eventually
1477 * RLIMIT_CPU limit is earlier than prof_exp cpu timer expire.
1479 switch (clock_idx) {
1481 if (expires_gt(tsk->signal->cputime_expires.prof_exp, *newval))
1482 tsk->signal->cputime_expires.prof_exp = *newval;
1485 if (expires_gt(tsk->signal->cputime_expires.virt_exp, *newval))
1486 tsk->signal->cputime_expires.virt_exp = *newval;
1491 static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1492 struct timespec *rqtp, struct itimerspec *it)
1494 struct k_itimer timer;
1498 * Set up a temporary timer and then wait for it to go off.
1500 memset(&timer, 0, sizeof timer);
1501 spin_lock_init(&timer.it_lock);
1502 timer.it_clock = which_clock;
1503 timer.it_overrun = -1;
1504 error = posix_cpu_timer_create(&timer);
1505 timer.it_process = current;
1507 static struct itimerspec zero_it;
1509 memset(it, 0, sizeof *it);
1510 it->it_value = *rqtp;
1512 spin_lock_irq(&timer.it_lock);
1513 error = posix_cpu_timer_set(&timer, flags, it, NULL);
1515 spin_unlock_irq(&timer.it_lock);
1519 while (!signal_pending(current)) {
1520 if (timer.it.cpu.expires.sched == 0) {
1522 * Our timer fired and was reset.
1524 spin_unlock_irq(&timer.it_lock);
1529 * Block until cpu_timer_fire (or a signal) wakes us.
1531 __set_current_state(TASK_INTERRUPTIBLE);
1532 spin_unlock_irq(&timer.it_lock);
1534 spin_lock_irq(&timer.it_lock);
1538 * We were interrupted by a signal.
1540 sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
1541 posix_cpu_timer_set(&timer, 0, &zero_it, it);
1542 spin_unlock_irq(&timer.it_lock);
1544 if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
1546 * It actually did fire already.
1551 error = -ERESTART_RESTARTBLOCK;
1557 int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1558 struct timespec *rqtp, struct timespec __user *rmtp)
1560 struct restart_block *restart_block =
1561 ¤t_thread_info()->restart_block;
1562 struct itimerspec it;
1566 * Diagnose required errors first.
1568 if (CPUCLOCK_PERTHREAD(which_clock) &&
1569 (CPUCLOCK_PID(which_clock) == 0 ||
1570 CPUCLOCK_PID(which_clock) == current->pid))
1573 error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);
1575 if (error == -ERESTART_RESTARTBLOCK) {
1577 if (flags & TIMER_ABSTIME)
1578 return -ERESTARTNOHAND;
1580 * Report back to the user the time still remaining.
1582 if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1585 restart_block->fn = posix_cpu_nsleep_restart;
1586 restart_block->arg0 = which_clock;
1587 restart_block->arg1 = (unsigned long) rmtp;
1588 restart_block->arg2 = rqtp->tv_sec;
1589 restart_block->arg3 = rqtp->tv_nsec;
1594 long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1596 clockid_t which_clock = restart_block->arg0;
1597 struct timespec __user *rmtp;
1599 struct itimerspec it;
1602 rmtp = (struct timespec __user *) restart_block->arg1;
1603 t.tv_sec = restart_block->arg2;
1604 t.tv_nsec = restart_block->arg3;
1606 restart_block->fn = do_no_restart_syscall;
1607 error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);
1609 if (error == -ERESTART_RESTARTBLOCK) {
1611 * Report back to the user the time still remaining.
1613 if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1616 restart_block->fn = posix_cpu_nsleep_restart;
1617 restart_block->arg0 = which_clock;
1618 restart_block->arg1 = (unsigned long) rmtp;
1619 restart_block->arg2 = t.tv_sec;
1620 restart_block->arg3 = t.tv_nsec;
1627 #define PROCESS_CLOCK MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
1628 #define THREAD_CLOCK MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
1630 static int process_cpu_clock_getres(const clockid_t which_clock,
1631 struct timespec *tp)
1633 return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1635 static int process_cpu_clock_get(const clockid_t which_clock,
1636 struct timespec *tp)
1638 return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1640 static int process_cpu_timer_create(struct k_itimer *timer)
1642 timer->it_clock = PROCESS_CLOCK;
1643 return posix_cpu_timer_create(timer);
1645 static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1646 struct timespec *rqtp,
1647 struct timespec __user *rmtp)
1649 return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
1651 static long process_cpu_nsleep_restart(struct restart_block *restart_block)
1655 static int thread_cpu_clock_getres(const clockid_t which_clock,
1656 struct timespec *tp)
1658 return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1660 static int thread_cpu_clock_get(const clockid_t which_clock,
1661 struct timespec *tp)
1663 return posix_cpu_clock_get(THREAD_CLOCK, tp);
1665 static int thread_cpu_timer_create(struct k_itimer *timer)
1667 timer->it_clock = THREAD_CLOCK;
1668 return posix_cpu_timer_create(timer);
1670 static int thread_cpu_nsleep(const clockid_t which_clock, int flags,
1671 struct timespec *rqtp, struct timespec __user *rmtp)
1675 static long thread_cpu_nsleep_restart(struct restart_block *restart_block)
1680 static __init int init_posix_cpu_timers(void)
1682 struct k_clock process = {
1683 .clock_getres = process_cpu_clock_getres,
1684 .clock_get = process_cpu_clock_get,
1685 .clock_set = do_posix_clock_nosettime,
1686 .timer_create = process_cpu_timer_create,
1687 .nsleep = process_cpu_nsleep,
1688 .nsleep_restart = process_cpu_nsleep_restart,
1690 struct k_clock thread = {
1691 .clock_getres = thread_cpu_clock_getres,
1692 .clock_get = thread_cpu_clock_get,
1693 .clock_set = do_posix_clock_nosettime,
1694 .timer_create = thread_cpu_timer_create,
1695 .nsleep = thread_cpu_nsleep,
1696 .nsleep_restart = thread_cpu_nsleep_restart,
1700 register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
1701 register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
1703 cputime_to_timespec(cputime_one_jiffy, &ts);
1704 onecputick = ts.tv_nsec;
1705 WARN_ON(ts.tv_sec != 0);
1709 __initcall(init_posix_cpu_timers);