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>
12 #include <linux/random.h>
13 #include <linux/tick.h>
14 #include <linux/workqueue.h>
17 * Called after updating RLIMIT_CPU to run cpu timer and update
18 * tsk->signal->cputime_expires expiration cache if necessary. Needs
19 * siglock protection since other code may update expiration cache as
22 void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
24 cputime_t cputime = secs_to_cputime(rlim_new);
26 spin_lock_irq(&task->sighand->siglock);
27 set_process_cpu_timer(task, CPUCLOCK_PROF, &cputime, NULL);
28 spin_unlock_irq(&task->sighand->siglock);
31 static int check_clock(const clockid_t which_clock)
34 struct task_struct *p;
35 const pid_t pid = CPUCLOCK_PID(which_clock);
37 if (CPUCLOCK_WHICH(which_clock) >= CPUCLOCK_MAX)
44 p = find_task_by_vpid(pid);
45 if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
46 same_thread_group(p, current) : has_group_leader_pid(p))) {
54 static inline unsigned long long
55 timespec_to_sample(const clockid_t which_clock, const struct timespec *tp)
57 unsigned long long ret;
59 ret = 0; /* high half always zero when .cpu used */
60 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
61 ret = (unsigned long long)tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
63 ret = cputime_to_expires(timespec_to_cputime(tp));
68 static void sample_to_timespec(const clockid_t which_clock,
69 unsigned long long expires,
72 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED)
73 *tp = ns_to_timespec(expires);
75 cputime_to_timespec((__force cputime_t)expires, tp);
79 * Update expiry time from increment, and increase overrun count,
80 * given the current clock sample.
82 static void bump_cpu_timer(struct k_itimer *timer,
83 unsigned long long now)
86 unsigned long long delta, incr;
88 if (timer->it.cpu.incr == 0)
91 if (now < timer->it.cpu.expires)
94 incr = timer->it.cpu.incr;
95 delta = now + incr - timer->it.cpu.expires;
97 /* Don't use (incr*2 < delta), incr*2 might overflow. */
98 for (i = 0; incr < delta - incr; i++)
101 for (; i >= 0; incr >>= 1, i--) {
105 timer->it.cpu.expires += incr;
106 timer->it_overrun += 1 << i;
112 * task_cputime_zero - Check a task_cputime struct for all zero fields.
114 * @cputime: The struct to compare.
116 * Checks @cputime to see if all fields are zero. Returns true if all fields
117 * are zero, false if any field is nonzero.
119 static inline int task_cputime_zero(const struct task_cputime *cputime)
121 if (!cputime->utime && !cputime->stime && !cputime->sum_exec_runtime)
126 static inline unsigned long long prof_ticks(struct task_struct *p)
128 cputime_t utime, stime;
130 task_cputime(p, &utime, &stime);
132 return cputime_to_expires(utime + stime);
134 static inline unsigned long long virt_ticks(struct task_struct *p)
138 task_cputime(p, &utime, NULL);
140 return cputime_to_expires(utime);
144 posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
146 int error = check_clock(which_clock);
149 tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
150 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
152 * If sched_clock is using a cycle counter, we
153 * don't have any idea of its true resolution
154 * exported, but it is much more than 1s/HZ.
163 posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
166 * You can never reset a CPU clock, but we check for other errors
167 * in the call before failing with EPERM.
169 int error = check_clock(which_clock);
178 * Sample a per-thread clock for the given task.
180 static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
181 unsigned long long *sample)
183 switch (CPUCLOCK_WHICH(which_clock)) {
187 *sample = prof_ticks(p);
190 *sample = virt_ticks(p);
193 *sample = task_sched_runtime(p);
199 static void update_gt_cputime(struct task_cputime *a, struct task_cputime *b)
201 if (b->utime > a->utime)
204 if (b->stime > a->stime)
207 if (b->sum_exec_runtime > a->sum_exec_runtime)
208 a->sum_exec_runtime = b->sum_exec_runtime;
211 void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
213 struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
214 struct task_cputime sum;
217 if (!cputimer->running) {
219 * The POSIX timer interface allows for absolute time expiry
220 * values through the TIMER_ABSTIME flag, therefore we have
221 * to synchronize the timer to the clock every time we start
224 thread_group_cputime(tsk, &sum);
225 raw_spin_lock_irqsave(&cputimer->lock, flags);
226 cputimer->running = 1;
227 update_gt_cputime(&cputimer->cputime, &sum);
229 raw_spin_lock_irqsave(&cputimer->lock, flags);
230 *times = cputimer->cputime;
231 raw_spin_unlock_irqrestore(&cputimer->lock, flags);
235 * Sample a process (thread group) clock for the given group_leader task.
236 * Must be called with tasklist_lock held for reading.
238 static int cpu_clock_sample_group(const clockid_t which_clock,
239 struct task_struct *p,
240 unsigned long long *sample)
242 struct task_cputime cputime;
244 switch (CPUCLOCK_WHICH(which_clock)) {
248 thread_group_cputime(p, &cputime);
249 *sample = cputime_to_expires(cputime.utime + cputime.stime);
252 thread_group_cputime(p, &cputime);
253 *sample = cputime_to_expires(cputime.utime);
256 thread_group_cputime(p, &cputime);
257 *sample = cputime.sum_exec_runtime;
264 static int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
266 const pid_t pid = CPUCLOCK_PID(which_clock);
268 unsigned long long rtn;
272 * Special case constant value for our own clocks.
273 * We don't have to do any lookup to find ourselves.
275 if (CPUCLOCK_PERTHREAD(which_clock)) {
277 * Sampling just ourselves we can do with no locking.
279 error = cpu_clock_sample(which_clock,
282 read_lock(&tasklist_lock);
283 error = cpu_clock_sample_group(which_clock,
285 read_unlock(&tasklist_lock);
289 * Find the given PID, and validate that the caller
290 * should be able to see it.
292 struct task_struct *p;
294 p = find_task_by_vpid(pid);
296 if (CPUCLOCK_PERTHREAD(which_clock)) {
297 if (same_thread_group(p, current)) {
298 error = cpu_clock_sample(which_clock,
302 read_lock(&tasklist_lock);
303 if (thread_group_leader(p) && p->sighand) {
305 cpu_clock_sample_group(which_clock,
308 read_unlock(&tasklist_lock);
316 sample_to_timespec(which_clock, rtn, tp);
322 * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
323 * This is called from sys_timer_create() and do_cpu_nanosleep() with the
324 * new timer already all-zeros initialized.
326 static int posix_cpu_timer_create(struct k_itimer *new_timer)
329 const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
330 struct task_struct *p;
332 if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
335 INIT_LIST_HEAD(&new_timer->it.cpu.entry);
338 if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
342 p = find_task_by_vpid(pid);
343 if (p && !same_thread_group(p, current))
348 p = current->group_leader;
350 p = find_task_by_vpid(pid);
351 if (p && !has_group_leader_pid(p))
355 new_timer->it.cpu.task = p;
367 * Clean up a CPU-clock timer that is about to be destroyed.
368 * This is called from timer deletion with the timer already locked.
369 * If we return TIMER_RETRY, it's necessary to release the timer's lock
370 * and try again. (This happens when the timer is in the middle of firing.)
372 static int posix_cpu_timer_del(struct k_itimer *timer)
374 struct task_struct *p = timer->it.cpu.task;
377 if (likely(p != NULL)) {
378 read_lock(&tasklist_lock);
379 if (unlikely(p->sighand == NULL)) {
381 * We raced with the reaping of the task.
382 * The deletion should have cleared us off the list.
384 BUG_ON(!list_empty(&timer->it.cpu.entry));
386 spin_lock(&p->sighand->siglock);
387 if (timer->it.cpu.firing)
390 list_del(&timer->it.cpu.entry);
391 spin_unlock(&p->sighand->siglock);
393 read_unlock(&tasklist_lock);
402 static void cleanup_timers_list(struct list_head *head,
403 unsigned long long curr)
405 struct cpu_timer_list *timer, *next;
407 list_for_each_entry_safe(timer, next, head, entry)
408 list_del_init(&timer->entry);
412 * Clean out CPU timers still ticking when a thread exited. The task
413 * pointer is cleared, and the expiry time is replaced with the residual
414 * time for later timer_gettime calls to return.
415 * This must be called with the siglock held.
417 static void cleanup_timers(struct list_head *head,
418 cputime_t utime, cputime_t stime,
419 unsigned long long sum_exec_runtime)
422 cputime_t ptime = utime + stime;
424 cleanup_timers_list(head, cputime_to_expires(ptime));
425 cleanup_timers_list(++head, cputime_to_expires(utime));
426 cleanup_timers_list(++head, sum_exec_runtime);
430 * These are both called with the siglock held, when the current thread
431 * is being reaped. When the final (leader) thread in the group is reaped,
432 * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
434 void posix_cpu_timers_exit(struct task_struct *tsk)
436 cputime_t utime, stime;
438 add_device_randomness((const void*) &tsk->se.sum_exec_runtime,
439 sizeof(unsigned long long));
440 task_cputime(tsk, &utime, &stime);
441 cleanup_timers(tsk->cpu_timers,
442 utime, stime, tsk->se.sum_exec_runtime);
445 void posix_cpu_timers_exit_group(struct task_struct *tsk)
447 struct signal_struct *const sig = tsk->signal;
448 cputime_t utime, stime;
450 task_cputime(tsk, &utime, &stime);
451 cleanup_timers(tsk->signal->cpu_timers,
452 utime + sig->utime, stime + sig->stime,
453 tsk->se.sum_exec_runtime + sig->sum_sched_runtime);
456 static inline int expires_gt(cputime_t expires, cputime_t new_exp)
458 return expires == 0 || expires > new_exp;
462 * Insert the timer on the appropriate list before any timers that
463 * expire later. This must be called with the tasklist_lock held
464 * for reading, interrupts disabled and p->sighand->siglock taken.
466 static void arm_timer(struct k_itimer *timer)
468 struct task_struct *p = timer->it.cpu.task;
469 struct list_head *head, *listpos;
470 struct task_cputime *cputime_expires;
471 struct cpu_timer_list *const nt = &timer->it.cpu;
472 struct cpu_timer_list *next;
474 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
475 head = p->cpu_timers;
476 cputime_expires = &p->cputime_expires;
478 head = p->signal->cpu_timers;
479 cputime_expires = &p->signal->cputime_expires;
481 head += CPUCLOCK_WHICH(timer->it_clock);
484 list_for_each_entry(next, head, entry) {
485 if (nt->expires < next->expires)
487 listpos = &next->entry;
489 list_add(&nt->entry, listpos);
491 if (listpos == head) {
492 unsigned long long exp = nt->expires;
495 * We are the new earliest-expiring POSIX 1.b timer, hence
496 * need to update expiration cache. Take into account that
497 * for process timers we share expiration cache with itimers
498 * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
501 switch (CPUCLOCK_WHICH(timer->it_clock)) {
503 if (expires_gt(cputime_expires->prof_exp, expires_to_cputime(exp)))
504 cputime_expires->prof_exp = expires_to_cputime(exp);
507 if (expires_gt(cputime_expires->virt_exp, expires_to_cputime(exp)))
508 cputime_expires->virt_exp = expires_to_cputime(exp);
511 if (cputime_expires->sched_exp == 0 ||
512 cputime_expires->sched_exp > exp)
513 cputime_expires->sched_exp = exp;
520 * The timer is locked, fire it and arrange for its reload.
522 static void cpu_timer_fire(struct k_itimer *timer)
524 if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
526 * User don't want any signal.
528 timer->it.cpu.expires = 0;
529 } else if (unlikely(timer->sigq == NULL)) {
531 * This a special case for clock_nanosleep,
532 * not a normal timer from sys_timer_create.
534 wake_up_process(timer->it_process);
535 timer->it.cpu.expires = 0;
536 } else if (timer->it.cpu.incr == 0) {
538 * One-shot timer. Clear it as soon as it's fired.
540 posix_timer_event(timer, 0);
541 timer->it.cpu.expires = 0;
542 } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
544 * The signal did not get queued because the signal
545 * was ignored, so we won't get any callback to
546 * reload the timer. But we need to keep it
547 * ticking in case the signal is deliverable next time.
549 posix_cpu_timer_schedule(timer);
554 * Sample a process (thread group) timer for the given group_leader task.
555 * Must be called with tasklist_lock held for reading.
557 static int cpu_timer_sample_group(const clockid_t which_clock,
558 struct task_struct *p,
559 unsigned long long *sample)
561 struct task_cputime cputime;
563 thread_group_cputimer(p, &cputime);
564 switch (CPUCLOCK_WHICH(which_clock)) {
568 *sample = cputime_to_expires(cputime.utime + cputime.stime);
571 *sample = cputime_to_expires(cputime.utime);
574 *sample = cputime.sum_exec_runtime + task_delta_exec(p);
580 #ifdef CONFIG_NO_HZ_FULL
581 static void nohz_kick_work_fn(struct work_struct *work)
583 tick_nohz_full_kick_all();
586 static DECLARE_WORK(nohz_kick_work, nohz_kick_work_fn);
589 * We need the IPIs to be sent from sane process context.
590 * The posix cpu timers are always set with irqs disabled.
592 static void posix_cpu_timer_kick_nohz(void)
594 if (context_tracking_is_enabled())
595 schedule_work(&nohz_kick_work);
598 bool posix_cpu_timers_can_stop_tick(struct task_struct *tsk)
600 if (!task_cputime_zero(&tsk->cputime_expires))
603 if (tsk->signal->cputimer.running)
609 static inline void posix_cpu_timer_kick_nohz(void) { }
613 * Guts of sys_timer_settime for CPU timers.
614 * This is called with the timer locked and interrupts disabled.
615 * If we return TIMER_RETRY, it's necessary to release the timer's lock
616 * and try again. (This happens when the timer is in the middle of firing.)
618 static int posix_cpu_timer_set(struct k_itimer *timer, int flags,
619 struct itimerspec *new, struct itimerspec *old)
621 struct task_struct *p = timer->it.cpu.task;
622 unsigned long long old_expires, new_expires, old_incr, val;
625 if (unlikely(p == NULL)) {
627 * Timer refers to a dead task's clock.
632 new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
634 read_lock(&tasklist_lock);
636 * We need the tasklist_lock to protect against reaping that
637 * clears p->sighand. If p has just been reaped, we can no
638 * longer get any information about it at all.
640 if (unlikely(p->sighand == NULL)) {
641 read_unlock(&tasklist_lock);
643 timer->it.cpu.task = NULL;
648 * Disarm any old timer after extracting its expiry time.
650 BUG_ON(!irqs_disabled());
653 old_incr = timer->it.cpu.incr;
654 spin_lock(&p->sighand->siglock);
655 old_expires = timer->it.cpu.expires;
656 if (unlikely(timer->it.cpu.firing)) {
657 timer->it.cpu.firing = -1;
660 list_del_init(&timer->it.cpu.entry);
663 * We need to sample the current value to convert the new
664 * value from to relative and absolute, and to convert the
665 * old value from absolute to relative. To set a process
666 * timer, we need a sample to balance the thread expiry
667 * times (in arm_timer). With an absolute time, we must
668 * check if it's already passed. In short, we need a sample.
670 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
671 cpu_clock_sample(timer->it_clock, p, &val);
673 cpu_timer_sample_group(timer->it_clock, p, &val);
677 if (old_expires == 0) {
678 old->it_value.tv_sec = 0;
679 old->it_value.tv_nsec = 0;
682 * Update the timer in case it has
683 * overrun already. If it has,
684 * we'll report it as having overrun
685 * and with the next reloaded timer
686 * already ticking, though we are
687 * swallowing that pending
688 * notification here to install the
691 bump_cpu_timer(timer, val);
692 if (val < timer->it.cpu.expires) {
693 old_expires = timer->it.cpu.expires - val;
694 sample_to_timespec(timer->it_clock,
698 old->it_value.tv_nsec = 1;
699 old->it_value.tv_sec = 0;
706 * We are colliding with the timer actually firing.
707 * Punt after filling in the timer's old value, and
708 * disable this firing since we are already reporting
709 * it as an overrun (thanks to bump_cpu_timer above).
711 spin_unlock(&p->sighand->siglock);
712 read_unlock(&tasklist_lock);
716 if (new_expires != 0 && !(flags & TIMER_ABSTIME)) {
721 * Install the new expiry time (or zero).
722 * For a timer with no notification action, we don't actually
723 * arm the timer (we'll just fake it for timer_gettime).
725 timer->it.cpu.expires = new_expires;
726 if (new_expires != 0 && val < new_expires) {
730 spin_unlock(&p->sighand->siglock);
731 read_unlock(&tasklist_lock);
734 * Install the new reload setting, and
735 * set up the signal and overrun bookkeeping.
737 timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
741 * This acts as a modification timestamp for the timer,
742 * so any automatic reload attempt will punt on seeing
743 * that we have reset the timer manually.
745 timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
747 timer->it_overrun_last = 0;
748 timer->it_overrun = -1;
750 if (new_expires != 0 && !(val < new_expires)) {
752 * The designated time already passed, so we notify
753 * immediately, even if the thread never runs to
754 * accumulate more time on this clock.
756 cpu_timer_fire(timer);
762 sample_to_timespec(timer->it_clock,
763 old_incr, &old->it_interval);
766 posix_cpu_timer_kick_nohz();
770 static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
772 unsigned long long now;
773 struct task_struct *p = timer->it.cpu.task;
776 * Easy part: convert the reload time.
778 sample_to_timespec(timer->it_clock,
779 timer->it.cpu.incr, &itp->it_interval);
781 if (timer->it.cpu.expires == 0) { /* Timer not armed at all. */
782 itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
786 if (unlikely(p == NULL)) {
787 WARN_ON_ONCE(CPUCLOCK_PERTHREAD(timer->it_clock));
789 * This task already died and the timer will never fire.
790 * In this case, expires is actually the dead value.
793 sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
799 * Sample the clock to take the difference with the expiry time.
801 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
802 cpu_clock_sample(timer->it_clock, p, &now);
804 read_lock(&tasklist_lock);
805 if (unlikely(p->sighand == NULL)) {
807 * The process has been reaped.
808 * We can't even collect a sample any more.
809 * Call the timer disarmed, nothing else to do.
812 timer->it.cpu.task = NULL;
813 timer->it.cpu.expires = 0;
814 read_unlock(&tasklist_lock);
817 cpu_timer_sample_group(timer->it_clock, p, &now);
819 read_unlock(&tasklist_lock);
822 if (now < timer->it.cpu.expires) {
823 sample_to_timespec(timer->it_clock,
824 timer->it.cpu.expires - now,
828 * The timer should have expired already, but the firing
829 * hasn't taken place yet. Say it's just about to expire.
831 itp->it_value.tv_nsec = 1;
832 itp->it_value.tv_sec = 0;
836 static unsigned long long
837 check_timers_list(struct list_head *timers,
838 struct list_head *firing,
839 unsigned long long curr)
843 while (!list_empty(timers)) {
844 struct cpu_timer_list *t;
846 t = list_first_entry(timers, struct cpu_timer_list, entry);
848 if (!--maxfire || curr < t->expires)
852 list_move_tail(&t->entry, firing);
859 * Check for any per-thread CPU timers that have fired and move them off
860 * the tsk->cpu_timers[N] list onto the firing list. Here we update the
861 * tsk->it_*_expires values to reflect the remaining thread CPU timers.
863 static void check_thread_timers(struct task_struct *tsk,
864 struct list_head *firing)
866 struct list_head *timers = tsk->cpu_timers;
867 struct signal_struct *const sig = tsk->signal;
868 struct task_cputime *tsk_expires = &tsk->cputime_expires;
869 unsigned long long expires;
872 expires = check_timers_list(timers, firing, prof_ticks(tsk));
873 tsk_expires->prof_exp = expires_to_cputime(expires);
875 expires = check_timers_list(++timers, firing, virt_ticks(tsk));
876 tsk_expires->virt_exp = expires_to_cputime(expires);
878 tsk_expires->sched_exp = check_timers_list(++timers, firing,
879 tsk->se.sum_exec_runtime);
882 * Check for the special case thread timers.
884 soft = ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
885 if (soft != RLIM_INFINITY) {
887 ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);
889 if (hard != RLIM_INFINITY &&
890 tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
892 * At the hard limit, we just die.
893 * No need to calculate anything else now.
895 __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
898 if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {
900 * At the soft limit, send a SIGXCPU every second.
903 soft += USEC_PER_SEC;
904 sig->rlim[RLIMIT_RTTIME].rlim_cur = soft;
907 "RT Watchdog Timeout: %s[%d]\n",
908 tsk->comm, task_pid_nr(tsk));
909 __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
914 static void stop_process_timers(struct signal_struct *sig)
916 struct thread_group_cputimer *cputimer = &sig->cputimer;
919 raw_spin_lock_irqsave(&cputimer->lock, flags);
920 cputimer->running = 0;
921 raw_spin_unlock_irqrestore(&cputimer->lock, flags);
924 static u32 onecputick;
926 static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
927 unsigned long long *expires,
928 unsigned long long cur_time, int signo)
933 if (cur_time >= it->expires) {
935 it->expires += it->incr;
936 it->error += it->incr_error;
937 if (it->error >= onecputick) {
938 it->expires -= cputime_one_jiffy;
939 it->error -= onecputick;
945 trace_itimer_expire(signo == SIGPROF ?
946 ITIMER_PROF : ITIMER_VIRTUAL,
947 tsk->signal->leader_pid, cur_time);
948 __group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
951 if (it->expires && (!*expires || it->expires < *expires)) {
952 *expires = it->expires;
957 * Check for any per-thread CPU timers that have fired and move them
958 * off the tsk->*_timers list onto the firing list. Per-thread timers
959 * have already been taken off.
961 static void check_process_timers(struct task_struct *tsk,
962 struct list_head *firing)
964 struct signal_struct *const sig = tsk->signal;
965 unsigned long long utime, ptime, virt_expires, prof_expires;
966 unsigned long long sum_sched_runtime, sched_expires;
967 struct list_head *timers = sig->cpu_timers;
968 struct task_cputime cputime;
972 * Collect the current process totals.
974 thread_group_cputimer(tsk, &cputime);
975 utime = cputime_to_expires(cputime.utime);
976 ptime = utime + cputime_to_expires(cputime.stime);
977 sum_sched_runtime = cputime.sum_exec_runtime;
979 prof_expires = check_timers_list(timers, firing, ptime);
980 virt_expires = check_timers_list(++timers, firing, utime);
981 sched_expires = check_timers_list(++timers, firing, sum_sched_runtime);
984 * Check for the special case process timers.
986 check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime,
988 check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
990 soft = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
991 if (soft != RLIM_INFINITY) {
992 unsigned long psecs = cputime_to_secs(ptime);
994 ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
998 * At the hard limit, we just die.
999 * No need to calculate anything else now.
1001 __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1004 if (psecs >= soft) {
1006 * At the soft limit, send a SIGXCPU every second.
1008 __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1011 sig->rlim[RLIMIT_CPU].rlim_cur = soft;
1014 x = secs_to_cputime(soft);
1015 if (!prof_expires || x < prof_expires) {
1020 sig->cputime_expires.prof_exp = expires_to_cputime(prof_expires);
1021 sig->cputime_expires.virt_exp = expires_to_cputime(virt_expires);
1022 sig->cputime_expires.sched_exp = sched_expires;
1023 if (task_cputime_zero(&sig->cputime_expires))
1024 stop_process_timers(sig);
1028 * This is called from the signal code (via do_schedule_next_timer)
1029 * when the last timer signal was delivered and we have to reload the timer.
1031 void posix_cpu_timer_schedule(struct k_itimer *timer)
1033 struct task_struct *p = timer->it.cpu.task;
1034 unsigned long long now;
1036 if (unlikely(p == NULL)) {
1037 WARN_ON_ONCE(CPUCLOCK_PERTHREAD(timer->it_clock));
1039 * The task was cleaned up already, no future firings.
1045 * Fetch the current sample and update the timer's expiry time.
1047 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1048 cpu_clock_sample(timer->it_clock, p, &now);
1049 bump_cpu_timer(timer, now);
1050 if (unlikely(p->exit_state))
1053 read_lock(&tasklist_lock); /* arm_timer needs it. */
1054 spin_lock(&p->sighand->siglock);
1056 read_lock(&tasklist_lock);
1057 if (unlikely(p->sighand == NULL)) {
1059 * The process has been reaped.
1060 * We can't even collect a sample any more.
1063 timer->it.cpu.task = p = NULL;
1064 timer->it.cpu.expires = 0;
1065 read_unlock(&tasklist_lock);
1067 } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1068 read_unlock(&tasklist_lock);
1069 /* Optimizations: if the process is dying, no need to rearm */
1072 spin_lock(&p->sighand->siglock);
1073 cpu_timer_sample_group(timer->it_clock, p, &now);
1074 bump_cpu_timer(timer, now);
1075 /* Leave the tasklist_lock locked for the call below. */
1079 * Now re-arm for the new expiry time.
1081 BUG_ON(!irqs_disabled());
1083 spin_unlock(&p->sighand->siglock);
1084 read_unlock(&tasklist_lock);
1086 /* Kick full dynticks CPUs in case they need to tick on the new timer */
1087 posix_cpu_timer_kick_nohz();
1090 timer->it_overrun_last = timer->it_overrun;
1091 timer->it_overrun = -1;
1092 ++timer->it_requeue_pending;
1096 * task_cputime_expired - Compare two task_cputime entities.
1098 * @sample: The task_cputime structure to be checked for expiration.
1099 * @expires: Expiration times, against which @sample will be checked.
1101 * Checks @sample against @expires to see if any field of @sample has expired.
1102 * Returns true if any field of the former is greater than the corresponding
1103 * field of the latter if the latter field is set. Otherwise returns false.
1105 static inline int task_cputime_expired(const struct task_cputime *sample,
1106 const struct task_cputime *expires)
1108 if (expires->utime && sample->utime >= expires->utime)
1110 if (expires->stime && sample->utime + sample->stime >= expires->stime)
1112 if (expires->sum_exec_runtime != 0 &&
1113 sample->sum_exec_runtime >= expires->sum_exec_runtime)
1119 * fastpath_timer_check - POSIX CPU timers fast path.
1121 * @tsk: The task (thread) being checked.
1123 * Check the task and thread group timers. If both are zero (there are no
1124 * timers set) return false. Otherwise snapshot the task and thread group
1125 * timers and compare them with the corresponding expiration times. Return
1126 * true if a timer has expired, else return false.
1128 static inline int fastpath_timer_check(struct task_struct *tsk)
1130 struct signal_struct *sig;
1131 cputime_t utime, stime;
1133 task_cputime(tsk, &utime, &stime);
1135 if (!task_cputime_zero(&tsk->cputime_expires)) {
1136 struct task_cputime task_sample = {
1139 .sum_exec_runtime = tsk->se.sum_exec_runtime
1142 if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
1147 if (sig->cputimer.running) {
1148 struct task_cputime group_sample;
1150 raw_spin_lock(&sig->cputimer.lock);
1151 group_sample = sig->cputimer.cputime;
1152 raw_spin_unlock(&sig->cputimer.lock);
1154 if (task_cputime_expired(&group_sample, &sig->cputime_expires))
1162 * This is called from the timer interrupt handler. The irq handler has
1163 * already updated our counts. We need to check if any timers fire now.
1164 * Interrupts are disabled.
1166 void run_posix_cpu_timers(struct task_struct *tsk)
1169 struct k_itimer *timer, *next;
1170 unsigned long flags;
1172 BUG_ON(!irqs_disabled());
1175 * The fast path checks that there are no expired thread or thread
1176 * group timers. If that's so, just return.
1178 if (!fastpath_timer_check(tsk))
1181 if (!lock_task_sighand(tsk, &flags))
1184 * Here we take off tsk->signal->cpu_timers[N] and
1185 * tsk->cpu_timers[N] all the timers that are firing, and
1186 * put them on the firing list.
1188 check_thread_timers(tsk, &firing);
1190 * If there are any active process wide timers (POSIX 1.b, itimers,
1191 * RLIMIT_CPU) cputimer must be running.
1193 if (tsk->signal->cputimer.running)
1194 check_process_timers(tsk, &firing);
1197 * We must release these locks before taking any timer's lock.
1198 * There is a potential race with timer deletion here, as the
1199 * siglock now protects our private firing list. We have set
1200 * the firing flag in each timer, so that a deletion attempt
1201 * that gets the timer lock before we do will give it up and
1202 * spin until we've taken care of that timer below.
1204 unlock_task_sighand(tsk, &flags);
1207 * Now that all the timers on our list have the firing flag,
1208 * no one will touch their list entries but us. We'll take
1209 * each timer's lock before clearing its firing flag, so no
1210 * timer call will interfere.
1212 list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1215 spin_lock(&timer->it_lock);
1216 list_del_init(&timer->it.cpu.entry);
1217 cpu_firing = timer->it.cpu.firing;
1218 timer->it.cpu.firing = 0;
1220 * The firing flag is -1 if we collided with a reset
1221 * of the timer, which already reported this
1222 * almost-firing as an overrun. So don't generate an event.
1224 if (likely(cpu_firing >= 0))
1225 cpu_timer_fire(timer);
1226 spin_unlock(&timer->it_lock);
1231 * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
1232 * The tsk->sighand->siglock must be held by the caller.
1234 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1235 cputime_t *newval, cputime_t *oldval)
1237 unsigned long long now;
1239 BUG_ON(clock_idx == CPUCLOCK_SCHED);
1240 cpu_timer_sample_group(clock_idx, tsk, &now);
1244 * We are setting itimer. The *oldval is absolute and we update
1245 * it to be relative, *newval argument is relative and we update
1246 * it to be absolute.
1249 if (*oldval <= now) {
1250 /* Just about to fire. */
1251 *oldval = cputime_one_jiffy;
1263 * Update expiration cache if we are the earliest timer, or eventually
1264 * RLIMIT_CPU limit is earlier than prof_exp cpu timer expire.
1266 switch (clock_idx) {
1268 if (expires_gt(tsk->signal->cputime_expires.prof_exp, *newval))
1269 tsk->signal->cputime_expires.prof_exp = *newval;
1272 if (expires_gt(tsk->signal->cputime_expires.virt_exp, *newval))
1273 tsk->signal->cputime_expires.virt_exp = *newval;
1277 posix_cpu_timer_kick_nohz();
1280 static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1281 struct timespec *rqtp, struct itimerspec *it)
1283 struct k_itimer timer;
1287 * Set up a temporary timer and then wait for it to go off.
1289 memset(&timer, 0, sizeof timer);
1290 spin_lock_init(&timer.it_lock);
1291 timer.it_clock = which_clock;
1292 timer.it_overrun = -1;
1293 error = posix_cpu_timer_create(&timer);
1294 timer.it_process = current;
1296 static struct itimerspec zero_it;
1298 memset(it, 0, sizeof *it);
1299 it->it_value = *rqtp;
1301 spin_lock_irq(&timer.it_lock);
1302 error = posix_cpu_timer_set(&timer, flags, it, NULL);
1304 spin_unlock_irq(&timer.it_lock);
1308 while (!signal_pending(current)) {
1309 if (timer.it.cpu.expires == 0) {
1311 * Our timer fired and was reset, below
1312 * deletion can not fail.
1314 posix_cpu_timer_del(&timer);
1315 spin_unlock_irq(&timer.it_lock);
1320 * Block until cpu_timer_fire (or a signal) wakes us.
1322 __set_current_state(TASK_INTERRUPTIBLE);
1323 spin_unlock_irq(&timer.it_lock);
1325 spin_lock_irq(&timer.it_lock);
1329 * We were interrupted by a signal.
1331 sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
1332 error = posix_cpu_timer_set(&timer, 0, &zero_it, it);
1335 * Timer is now unarmed, deletion can not fail.
1337 posix_cpu_timer_del(&timer);
1339 spin_unlock_irq(&timer.it_lock);
1341 while (error == TIMER_RETRY) {
1343 * We need to handle case when timer was or is in the
1344 * middle of firing. In other cases we already freed
1347 spin_lock_irq(&timer.it_lock);
1348 error = posix_cpu_timer_del(&timer);
1349 spin_unlock_irq(&timer.it_lock);
1352 if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
1354 * It actually did fire already.
1359 error = -ERESTART_RESTARTBLOCK;
1365 static long posix_cpu_nsleep_restart(struct restart_block *restart_block);
1367 static int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1368 struct timespec *rqtp, struct timespec __user *rmtp)
1370 struct restart_block *restart_block =
1371 ¤t_thread_info()->restart_block;
1372 struct itimerspec it;
1376 * Diagnose required errors first.
1378 if (CPUCLOCK_PERTHREAD(which_clock) &&
1379 (CPUCLOCK_PID(which_clock) == 0 ||
1380 CPUCLOCK_PID(which_clock) == current->pid))
1383 error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);
1385 if (error == -ERESTART_RESTARTBLOCK) {
1387 if (flags & TIMER_ABSTIME)
1388 return -ERESTARTNOHAND;
1390 * Report back to the user the time still remaining.
1392 if (rmtp && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1395 restart_block->fn = posix_cpu_nsleep_restart;
1396 restart_block->nanosleep.clockid = which_clock;
1397 restart_block->nanosleep.rmtp = rmtp;
1398 restart_block->nanosleep.expires = timespec_to_ns(rqtp);
1403 static long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1405 clockid_t which_clock = restart_block->nanosleep.clockid;
1407 struct itimerspec it;
1410 t = ns_to_timespec(restart_block->nanosleep.expires);
1412 error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);
1414 if (error == -ERESTART_RESTARTBLOCK) {
1415 struct timespec __user *rmtp = restart_block->nanosleep.rmtp;
1417 * Report back to the user the time still remaining.
1419 if (rmtp && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1422 restart_block->nanosleep.expires = timespec_to_ns(&t);
1428 #define PROCESS_CLOCK MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
1429 #define THREAD_CLOCK MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
1431 static int process_cpu_clock_getres(const clockid_t which_clock,
1432 struct timespec *tp)
1434 return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1436 static int process_cpu_clock_get(const clockid_t which_clock,
1437 struct timespec *tp)
1439 return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1441 static int process_cpu_timer_create(struct k_itimer *timer)
1443 timer->it_clock = PROCESS_CLOCK;
1444 return posix_cpu_timer_create(timer);
1446 static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1447 struct timespec *rqtp,
1448 struct timespec __user *rmtp)
1450 return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
1452 static long process_cpu_nsleep_restart(struct restart_block *restart_block)
1456 static int thread_cpu_clock_getres(const clockid_t which_clock,
1457 struct timespec *tp)
1459 return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1461 static int thread_cpu_clock_get(const clockid_t which_clock,
1462 struct timespec *tp)
1464 return posix_cpu_clock_get(THREAD_CLOCK, tp);
1466 static int thread_cpu_timer_create(struct k_itimer *timer)
1468 timer->it_clock = THREAD_CLOCK;
1469 return posix_cpu_timer_create(timer);
1472 struct k_clock clock_posix_cpu = {
1473 .clock_getres = posix_cpu_clock_getres,
1474 .clock_set = posix_cpu_clock_set,
1475 .clock_get = posix_cpu_clock_get,
1476 .timer_create = posix_cpu_timer_create,
1477 .nsleep = posix_cpu_nsleep,
1478 .nsleep_restart = posix_cpu_nsleep_restart,
1479 .timer_set = posix_cpu_timer_set,
1480 .timer_del = posix_cpu_timer_del,
1481 .timer_get = posix_cpu_timer_get,
1484 static __init int init_posix_cpu_timers(void)
1486 struct k_clock process = {
1487 .clock_getres = process_cpu_clock_getres,
1488 .clock_get = process_cpu_clock_get,
1489 .timer_create = process_cpu_timer_create,
1490 .nsleep = process_cpu_nsleep,
1491 .nsleep_restart = process_cpu_nsleep_restart,
1493 struct k_clock thread = {
1494 .clock_getres = thread_cpu_clock_getres,
1495 .clock_get = thread_cpu_clock_get,
1496 .timer_create = thread_cpu_timer_create,
1500 posix_timers_register_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
1501 posix_timers_register_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
1503 cputime_to_timespec(cputime_one_jiffy, &ts);
1504 onecputick = ts.tv_nsec;
1505 WARN_ON(ts.tv_sec != 0);
1509 __initcall(init_posix_cpu_timers);