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(struct task_struct *task, unsigned long rlim_new)
21 cputime_t cputime = secs_to_cputime(rlim_new);
23 spin_lock_irq(&task->sighand->siglock);
24 set_process_cpu_timer(task, CPUCLOCK_PROF, &cputime, NULL);
25 spin_unlock_irq(&task->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)
41 p = find_task_by_vpid(pid);
42 if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
43 same_thread_group(p, current) : has_group_leader_pid(p))) {
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)
180 posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
182 int error = check_clock(which_clock);
185 tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
186 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
188 * If sched_clock is using a cycle counter, we
189 * don't have any idea of its true resolution
190 * exported, but it is much more than 1s/HZ.
199 posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
202 * You can never reset a CPU clock, but we check for other errors
203 * in the call before failing with EPERM.
205 int error = check_clock(which_clock);
214 * Sample a per-thread clock for the given task.
216 static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
217 union cpu_time_count *cpu)
219 switch (CPUCLOCK_WHICH(which_clock)) {
223 cpu->cpu = prof_ticks(p);
226 cpu->cpu = virt_ticks(p);
229 cpu->sched = task_sched_runtime(p);
235 void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
237 struct signal_struct *sig = tsk->signal;
238 struct task_struct *t;
240 times->utime = sig->utime;
241 times->stime = sig->stime;
242 times->sum_exec_runtime = sig->sum_sched_runtime;
245 /* make sure we can trust tsk->thread_group list */
246 if (!likely(pid_alive(tsk)))
251 times->utime = cputime_add(times->utime, t->utime);
252 times->stime = cputime_add(times->stime, t->stime);
253 times->sum_exec_runtime += t->se.sum_exec_runtime;
254 } while_each_thread(tsk, t);
259 static void update_gt_cputime(struct task_cputime *a, struct task_cputime *b)
261 if (cputime_gt(b->utime, a->utime))
264 if (cputime_gt(b->stime, a->stime))
267 if (b->sum_exec_runtime > a->sum_exec_runtime)
268 a->sum_exec_runtime = b->sum_exec_runtime;
271 void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
273 struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
274 struct task_cputime sum;
277 spin_lock_irqsave(&cputimer->lock, flags);
278 if (!cputimer->running) {
279 cputimer->running = 1;
281 * The POSIX timer interface allows for absolute time expiry
282 * values through the TIMER_ABSTIME flag, therefore we have
283 * to synchronize the timer to the clock every time we start
286 thread_group_cputime(tsk, &sum);
287 update_gt_cputime(&cputimer->cputime, &sum);
289 *times = cputimer->cputime;
290 spin_unlock_irqrestore(&cputimer->lock, flags);
294 * Sample a process (thread group) clock for the given group_leader task.
295 * Must be called with tasklist_lock held for reading.
297 static int cpu_clock_sample_group(const clockid_t which_clock,
298 struct task_struct *p,
299 union cpu_time_count *cpu)
301 struct task_cputime cputime;
303 switch (CPUCLOCK_WHICH(which_clock)) {
307 thread_group_cputime(p, &cputime);
308 cpu->cpu = cputime_add(cputime.utime, cputime.stime);
311 thread_group_cputime(p, &cputime);
312 cpu->cpu = cputime.utime;
315 cpu->sched = thread_group_sched_runtime(p);
322 static int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
324 const pid_t pid = CPUCLOCK_PID(which_clock);
326 union cpu_time_count rtn;
330 * Special case constant value for our own clocks.
331 * We don't have to do any lookup to find ourselves.
333 if (CPUCLOCK_PERTHREAD(which_clock)) {
335 * Sampling just ourselves we can do with no locking.
337 error = cpu_clock_sample(which_clock,
340 read_lock(&tasklist_lock);
341 error = cpu_clock_sample_group(which_clock,
343 read_unlock(&tasklist_lock);
347 * Find the given PID, and validate that the caller
348 * should be able to see it.
350 struct task_struct *p;
352 p = find_task_by_vpid(pid);
354 if (CPUCLOCK_PERTHREAD(which_clock)) {
355 if (same_thread_group(p, current)) {
356 error = cpu_clock_sample(which_clock,
360 read_lock(&tasklist_lock);
361 if (thread_group_leader(p) && p->sighand) {
363 cpu_clock_sample_group(which_clock,
366 read_unlock(&tasklist_lock);
374 sample_to_timespec(which_clock, rtn, tp);
380 * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
381 * This is called from sys_timer_create() and do_cpu_nanosleep() with the
382 * new timer already all-zeros initialized.
384 static int posix_cpu_timer_create(struct k_itimer *new_timer)
387 const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
388 struct task_struct *p;
390 if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
393 INIT_LIST_HEAD(&new_timer->it.cpu.entry);
396 if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
400 p = find_task_by_vpid(pid);
401 if (p && !same_thread_group(p, current))
406 p = current->group_leader;
408 p = find_task_by_vpid(pid);
409 if (p && !has_group_leader_pid(p))
413 new_timer->it.cpu.task = p;
425 * Clean up a CPU-clock timer that is about to be destroyed.
426 * This is called from timer deletion with the timer already locked.
427 * If we return TIMER_RETRY, it's necessary to release the timer's lock
428 * and try again. (This happens when the timer is in the middle of firing.)
430 static int posix_cpu_timer_del(struct k_itimer *timer)
432 struct task_struct *p = timer->it.cpu.task;
435 if (likely(p != NULL)) {
436 read_lock(&tasklist_lock);
437 if (unlikely(p->sighand == NULL)) {
439 * We raced with the reaping of the task.
440 * The deletion should have cleared us off the list.
442 BUG_ON(!list_empty(&timer->it.cpu.entry));
444 spin_lock(&p->sighand->siglock);
445 if (timer->it.cpu.firing)
448 list_del(&timer->it.cpu.entry);
449 spin_unlock(&p->sighand->siglock);
451 read_unlock(&tasklist_lock);
461 * Clean out CPU timers still ticking when a thread exited. The task
462 * pointer is cleared, and the expiry time is replaced with the residual
463 * time for later timer_gettime calls to return.
464 * This must be called with the siglock held.
466 static void cleanup_timers(struct list_head *head,
467 cputime_t utime, cputime_t stime,
468 unsigned long long sum_exec_runtime)
470 struct cpu_timer_list *timer, *next;
471 cputime_t ptime = cputime_add(utime, stime);
473 list_for_each_entry_safe(timer, next, head, entry) {
474 list_del_init(&timer->entry);
475 if (cputime_lt(timer->expires.cpu, ptime)) {
476 timer->expires.cpu = cputime_zero;
478 timer->expires.cpu = cputime_sub(timer->expires.cpu,
484 list_for_each_entry_safe(timer, next, head, entry) {
485 list_del_init(&timer->entry);
486 if (cputime_lt(timer->expires.cpu, utime)) {
487 timer->expires.cpu = cputime_zero;
489 timer->expires.cpu = cputime_sub(timer->expires.cpu,
495 list_for_each_entry_safe(timer, next, head, entry) {
496 list_del_init(&timer->entry);
497 if (timer->expires.sched < sum_exec_runtime) {
498 timer->expires.sched = 0;
500 timer->expires.sched -= sum_exec_runtime;
506 * These are both called with the siglock held, when the current thread
507 * is being reaped. When the final (leader) thread in the group is reaped,
508 * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
510 void posix_cpu_timers_exit(struct task_struct *tsk)
512 cleanup_timers(tsk->cpu_timers,
513 tsk->utime, tsk->stime, tsk->se.sum_exec_runtime);
516 void posix_cpu_timers_exit_group(struct task_struct *tsk)
518 struct signal_struct *const sig = tsk->signal;
520 cleanup_timers(tsk->signal->cpu_timers,
521 cputime_add(tsk->utime, sig->utime),
522 cputime_add(tsk->stime, sig->stime),
523 tsk->se.sum_exec_runtime + sig->sum_sched_runtime);
526 static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
529 * That's all for this thread or process.
530 * We leave our residual in expires to be reported.
532 put_task_struct(timer->it.cpu.task);
533 timer->it.cpu.task = NULL;
534 timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
535 timer->it.cpu.expires,
539 static inline int expires_gt(cputime_t expires, cputime_t new_exp)
541 return cputime_eq(expires, cputime_zero) ||
542 cputime_gt(expires, new_exp);
546 * Insert the timer on the appropriate list before any timers that
547 * expire later. This must be called with the tasklist_lock held
548 * for reading, interrupts disabled and p->sighand->siglock taken.
550 static void arm_timer(struct k_itimer *timer)
552 struct task_struct *p = timer->it.cpu.task;
553 struct list_head *head, *listpos;
554 struct task_cputime *cputime_expires;
555 struct cpu_timer_list *const nt = &timer->it.cpu;
556 struct cpu_timer_list *next;
558 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
559 head = p->cpu_timers;
560 cputime_expires = &p->cputime_expires;
562 head = p->signal->cpu_timers;
563 cputime_expires = &p->signal->cputime_expires;
565 head += CPUCLOCK_WHICH(timer->it_clock);
568 list_for_each_entry(next, head, entry) {
569 if (cpu_time_before(timer->it_clock, nt->expires, next->expires))
571 listpos = &next->entry;
573 list_add(&nt->entry, listpos);
575 if (listpos == head) {
576 union cpu_time_count *exp = &nt->expires;
579 * We are the new earliest-expiring POSIX 1.b timer, hence
580 * need to update expiration cache. Take into account that
581 * for process timers we share expiration cache with itimers
582 * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
585 switch (CPUCLOCK_WHICH(timer->it_clock)) {
587 if (expires_gt(cputime_expires->prof_exp, exp->cpu))
588 cputime_expires->prof_exp = exp->cpu;
591 if (expires_gt(cputime_expires->virt_exp, exp->cpu))
592 cputime_expires->virt_exp = exp->cpu;
595 if (cputime_expires->sched_exp == 0 ||
596 cputime_expires->sched_exp > exp->sched)
597 cputime_expires->sched_exp = exp->sched;
604 * The timer is locked, fire it and arrange for its reload.
606 static void cpu_timer_fire(struct k_itimer *timer)
608 if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
610 * User don't want any signal.
612 timer->it.cpu.expires.sched = 0;
613 } else if (unlikely(timer->sigq == NULL)) {
615 * This a special case for clock_nanosleep,
616 * not a normal timer from sys_timer_create.
618 wake_up_process(timer->it_process);
619 timer->it.cpu.expires.sched = 0;
620 } else if (timer->it.cpu.incr.sched == 0) {
622 * One-shot timer. Clear it as soon as it's fired.
624 posix_timer_event(timer, 0);
625 timer->it.cpu.expires.sched = 0;
626 } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
628 * The signal did not get queued because the signal
629 * was ignored, so we won't get any callback to
630 * reload the timer. But we need to keep it
631 * ticking in case the signal is deliverable next time.
633 posix_cpu_timer_schedule(timer);
638 * Sample a process (thread group) timer for the given group_leader task.
639 * Must be called with tasklist_lock held for reading.
641 static int cpu_timer_sample_group(const clockid_t which_clock,
642 struct task_struct *p,
643 union cpu_time_count *cpu)
645 struct task_cputime cputime;
647 thread_group_cputimer(p, &cputime);
648 switch (CPUCLOCK_WHICH(which_clock)) {
652 cpu->cpu = cputime_add(cputime.utime, cputime.stime);
655 cpu->cpu = cputime.utime;
658 cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
665 * Guts of sys_timer_settime for CPU timers.
666 * This is called with the timer locked and interrupts disabled.
667 * If we return TIMER_RETRY, it's necessary to release the timer's lock
668 * and try again. (This happens when the timer is in the middle of firing.)
670 static int posix_cpu_timer_set(struct k_itimer *timer, int flags,
671 struct itimerspec *new, struct itimerspec *old)
673 struct task_struct *p = timer->it.cpu.task;
674 union cpu_time_count old_expires, new_expires, old_incr, val;
677 if (unlikely(p == NULL)) {
679 * Timer refers to a dead task's clock.
684 new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
686 read_lock(&tasklist_lock);
688 * We need the tasklist_lock to protect against reaping that
689 * clears p->sighand. If p has just been reaped, we can no
690 * longer get any information about it at all.
692 if (unlikely(p->sighand == NULL)) {
693 read_unlock(&tasklist_lock);
695 timer->it.cpu.task = NULL;
700 * Disarm any old timer after extracting its expiry time.
702 BUG_ON(!irqs_disabled());
705 old_incr = timer->it.cpu.incr;
706 spin_lock(&p->sighand->siglock);
707 old_expires = timer->it.cpu.expires;
708 if (unlikely(timer->it.cpu.firing)) {
709 timer->it.cpu.firing = -1;
712 list_del_init(&timer->it.cpu.entry);
715 * We need to sample the current value to convert the new
716 * value from to relative and absolute, and to convert the
717 * old value from absolute to relative. To set a process
718 * timer, we need a sample to balance the thread expiry
719 * times (in arm_timer). With an absolute time, we must
720 * check if it's already passed. In short, we need a sample.
722 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
723 cpu_clock_sample(timer->it_clock, p, &val);
725 cpu_timer_sample_group(timer->it_clock, p, &val);
729 if (old_expires.sched == 0) {
730 old->it_value.tv_sec = 0;
731 old->it_value.tv_nsec = 0;
734 * Update the timer in case it has
735 * overrun already. If it has,
736 * we'll report it as having overrun
737 * and with the next reloaded timer
738 * already ticking, though we are
739 * swallowing that pending
740 * notification here to install the
743 bump_cpu_timer(timer, val);
744 if (cpu_time_before(timer->it_clock, val,
745 timer->it.cpu.expires)) {
746 old_expires = cpu_time_sub(
748 timer->it.cpu.expires, val);
749 sample_to_timespec(timer->it_clock,
753 old->it_value.tv_nsec = 1;
754 old->it_value.tv_sec = 0;
761 * We are colliding with the timer actually firing.
762 * Punt after filling in the timer's old value, and
763 * disable this firing since we are already reporting
764 * it as an overrun (thanks to bump_cpu_timer above).
766 spin_unlock(&p->sighand->siglock);
767 read_unlock(&tasklist_lock);
771 if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
772 cpu_time_add(timer->it_clock, &new_expires, val);
776 * Install the new expiry time (or zero).
777 * For a timer with no notification action, we don't actually
778 * arm the timer (we'll just fake it for timer_gettime).
780 timer->it.cpu.expires = new_expires;
781 if (new_expires.sched != 0 &&
782 cpu_time_before(timer->it_clock, val, new_expires)) {
786 spin_unlock(&p->sighand->siglock);
787 read_unlock(&tasklist_lock);
790 * Install the new reload setting, and
791 * set up the signal and overrun bookkeeping.
793 timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
797 * This acts as a modification timestamp for the timer,
798 * so any automatic reload attempt will punt on seeing
799 * that we have reset the timer manually.
801 timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
803 timer->it_overrun_last = 0;
804 timer->it_overrun = -1;
806 if (new_expires.sched != 0 &&
807 !cpu_time_before(timer->it_clock, val, new_expires)) {
809 * The designated time already passed, so we notify
810 * immediately, even if the thread never runs to
811 * accumulate more time on this clock.
813 cpu_timer_fire(timer);
819 sample_to_timespec(timer->it_clock,
820 old_incr, &old->it_interval);
825 static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
827 union cpu_time_count now;
828 struct task_struct *p = timer->it.cpu.task;
832 * Easy part: convert the reload time.
834 sample_to_timespec(timer->it_clock,
835 timer->it.cpu.incr, &itp->it_interval);
837 if (timer->it.cpu.expires.sched == 0) { /* Timer not armed at all. */
838 itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
842 if (unlikely(p == NULL)) {
844 * This task already died and the timer will never fire.
845 * In this case, expires is actually the dead value.
848 sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
854 * Sample the clock to take the difference with the expiry time.
856 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
857 cpu_clock_sample(timer->it_clock, p, &now);
858 clear_dead = p->exit_state;
860 read_lock(&tasklist_lock);
861 if (unlikely(p->sighand == NULL)) {
863 * The process has been reaped.
864 * We can't even collect a sample any more.
865 * Call the timer disarmed, nothing else to do.
868 timer->it.cpu.task = NULL;
869 timer->it.cpu.expires.sched = 0;
870 read_unlock(&tasklist_lock);
873 cpu_timer_sample_group(timer->it_clock, p, &now);
874 clear_dead = (unlikely(p->exit_state) &&
875 thread_group_empty(p));
877 read_unlock(&tasklist_lock);
880 if (unlikely(clear_dead)) {
882 * We've noticed that the thread is dead, but
883 * not yet reaped. Take this opportunity to
886 clear_dead_task(timer, now);
890 if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
891 sample_to_timespec(timer->it_clock,
892 cpu_time_sub(timer->it_clock,
893 timer->it.cpu.expires, now),
897 * The timer should have expired already, but the firing
898 * hasn't taken place yet. Say it's just about to expire.
900 itp->it_value.tv_nsec = 1;
901 itp->it_value.tv_sec = 0;
906 * Check for any per-thread CPU timers that have fired and move them off
907 * the tsk->cpu_timers[N] list onto the firing list. Here we update the
908 * tsk->it_*_expires values to reflect the remaining thread CPU timers.
910 static void check_thread_timers(struct task_struct *tsk,
911 struct list_head *firing)
914 struct list_head *timers = tsk->cpu_timers;
915 struct signal_struct *const sig = tsk->signal;
919 tsk->cputime_expires.prof_exp = cputime_zero;
920 while (!list_empty(timers)) {
921 struct cpu_timer_list *t = list_first_entry(timers,
922 struct cpu_timer_list,
924 if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
925 tsk->cputime_expires.prof_exp = t->expires.cpu;
929 list_move_tail(&t->entry, firing);
934 tsk->cputime_expires.virt_exp = cputime_zero;
935 while (!list_empty(timers)) {
936 struct cpu_timer_list *t = list_first_entry(timers,
937 struct cpu_timer_list,
939 if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
940 tsk->cputime_expires.virt_exp = t->expires.cpu;
944 list_move_tail(&t->entry, firing);
949 tsk->cputime_expires.sched_exp = 0;
950 while (!list_empty(timers)) {
951 struct cpu_timer_list *t = list_first_entry(timers,
952 struct cpu_timer_list,
954 if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
955 tsk->cputime_expires.sched_exp = t->expires.sched;
959 list_move_tail(&t->entry, firing);
963 * Check for the special case thread timers.
965 soft = ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
966 if (soft != RLIM_INFINITY) {
968 ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);
970 if (hard != RLIM_INFINITY &&
971 tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
973 * At the hard limit, we just die.
974 * No need to calculate anything else now.
976 __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
979 if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {
981 * At the soft limit, send a SIGXCPU every second.
984 soft += USEC_PER_SEC;
985 sig->rlim[RLIMIT_RTTIME].rlim_cur = soft;
988 "RT Watchdog Timeout: %s[%d]\n",
989 tsk->comm, task_pid_nr(tsk));
990 __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
995 static void stop_process_timers(struct signal_struct *sig)
997 struct thread_group_cputimer *cputimer = &sig->cputimer;
1000 spin_lock_irqsave(&cputimer->lock, flags);
1001 cputimer->running = 0;
1002 spin_unlock_irqrestore(&cputimer->lock, flags);
1005 static u32 onecputick;
1007 static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
1008 cputime_t *expires, cputime_t cur_time, int signo)
1010 if (cputime_eq(it->expires, cputime_zero))
1013 if (cputime_ge(cur_time, it->expires)) {
1014 if (!cputime_eq(it->incr, cputime_zero)) {
1015 it->expires = cputime_add(it->expires, it->incr);
1016 it->error += it->incr_error;
1017 if (it->error >= onecputick) {
1018 it->expires = cputime_sub(it->expires,
1020 it->error -= onecputick;
1023 it->expires = cputime_zero;
1026 trace_itimer_expire(signo == SIGPROF ?
1027 ITIMER_PROF : ITIMER_VIRTUAL,
1028 tsk->signal->leader_pid, cur_time);
1029 __group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
1032 if (!cputime_eq(it->expires, cputime_zero) &&
1033 (cputime_eq(*expires, cputime_zero) ||
1034 cputime_lt(it->expires, *expires))) {
1035 *expires = it->expires;
1040 * task_cputime_zero - Check a task_cputime struct for all zero fields.
1042 * @cputime: The struct to compare.
1044 * Checks @cputime to see if all fields are zero. Returns true if all fields
1045 * are zero, false if any field is nonzero.
1047 static inline int task_cputime_zero(const struct task_cputime *cputime)
1049 if (cputime_eq(cputime->utime, cputime_zero) &&
1050 cputime_eq(cputime->stime, cputime_zero) &&
1051 cputime->sum_exec_runtime == 0)
1057 * Check for any per-thread CPU timers that have fired and move them
1058 * off the tsk->*_timers list onto the firing list. Per-thread timers
1059 * have already been taken off.
1061 static void check_process_timers(struct task_struct *tsk,
1062 struct list_head *firing)
1065 struct signal_struct *const sig = tsk->signal;
1066 cputime_t utime, ptime, virt_expires, prof_expires;
1067 unsigned long long sum_sched_runtime, sched_expires;
1068 struct list_head *timers = sig->cpu_timers;
1069 struct task_cputime cputime;
1073 * Collect the current process totals.
1075 thread_group_cputimer(tsk, &cputime);
1076 utime = cputime.utime;
1077 ptime = cputime_add(utime, cputime.stime);
1078 sum_sched_runtime = cputime.sum_exec_runtime;
1080 prof_expires = cputime_zero;
1081 while (!list_empty(timers)) {
1082 struct cpu_timer_list *tl = list_first_entry(timers,
1083 struct cpu_timer_list,
1085 if (!--maxfire || cputime_lt(ptime, tl->expires.cpu)) {
1086 prof_expires = tl->expires.cpu;
1090 list_move_tail(&tl->entry, firing);
1095 virt_expires = cputime_zero;
1096 while (!list_empty(timers)) {
1097 struct cpu_timer_list *tl = list_first_entry(timers,
1098 struct cpu_timer_list,
1100 if (!--maxfire || cputime_lt(utime, tl->expires.cpu)) {
1101 virt_expires = tl->expires.cpu;
1105 list_move_tail(&tl->entry, firing);
1111 while (!list_empty(timers)) {
1112 struct cpu_timer_list *tl = list_first_entry(timers,
1113 struct cpu_timer_list,
1115 if (!--maxfire || sum_sched_runtime < tl->expires.sched) {
1116 sched_expires = tl->expires.sched;
1120 list_move_tail(&tl->entry, firing);
1124 * Check for the special case process timers.
1126 check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime,
1128 check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
1130 soft = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1131 if (soft != RLIM_INFINITY) {
1132 unsigned long psecs = cputime_to_secs(ptime);
1133 unsigned long hard =
1134 ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
1136 if (psecs >= hard) {
1138 * At the hard limit, we just die.
1139 * No need to calculate anything else now.
1141 __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1144 if (psecs >= soft) {
1146 * At the soft limit, send a SIGXCPU every second.
1148 __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1151 sig->rlim[RLIMIT_CPU].rlim_cur = soft;
1154 x = secs_to_cputime(soft);
1155 if (cputime_eq(prof_expires, cputime_zero) ||
1156 cputime_lt(x, prof_expires)) {
1161 sig->cputime_expires.prof_exp = prof_expires;
1162 sig->cputime_expires.virt_exp = virt_expires;
1163 sig->cputime_expires.sched_exp = sched_expires;
1164 if (task_cputime_zero(&sig->cputime_expires))
1165 stop_process_timers(sig);
1169 * This is called from the signal code (via do_schedule_next_timer)
1170 * when the last timer signal was delivered and we have to reload the timer.
1172 void posix_cpu_timer_schedule(struct k_itimer *timer)
1174 struct task_struct *p = timer->it.cpu.task;
1175 union cpu_time_count now;
1177 if (unlikely(p == NULL))
1179 * The task was cleaned up already, no future firings.
1184 * Fetch the current sample and update the timer's expiry time.
1186 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1187 cpu_clock_sample(timer->it_clock, p, &now);
1188 bump_cpu_timer(timer, now);
1189 if (unlikely(p->exit_state)) {
1190 clear_dead_task(timer, now);
1193 read_lock(&tasklist_lock); /* arm_timer needs it. */
1194 spin_lock(&p->sighand->siglock);
1196 read_lock(&tasklist_lock);
1197 if (unlikely(p->sighand == NULL)) {
1199 * The process has been reaped.
1200 * We can't even collect a sample any more.
1203 timer->it.cpu.task = p = NULL;
1204 timer->it.cpu.expires.sched = 0;
1206 } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1208 * We've noticed that the thread is dead, but
1209 * not yet reaped. Take this opportunity to
1210 * drop our task ref.
1212 clear_dead_task(timer, now);
1215 spin_lock(&p->sighand->siglock);
1216 cpu_timer_sample_group(timer->it_clock, p, &now);
1217 bump_cpu_timer(timer, now);
1218 /* Leave the tasklist_lock locked for the call below. */
1222 * Now re-arm for the new expiry time.
1224 BUG_ON(!irqs_disabled());
1226 spin_unlock(&p->sighand->siglock);
1229 read_unlock(&tasklist_lock);
1232 timer->it_overrun_last = timer->it_overrun;
1233 timer->it_overrun = -1;
1234 ++timer->it_requeue_pending;
1238 * task_cputime_expired - Compare two task_cputime entities.
1240 * @sample: The task_cputime structure to be checked for expiration.
1241 * @expires: Expiration times, against which @sample will be checked.
1243 * Checks @sample against @expires to see if any field of @sample has expired.
1244 * Returns true if any field of the former is greater than the corresponding
1245 * field of the latter if the latter field is set. Otherwise returns false.
1247 static inline int task_cputime_expired(const struct task_cputime *sample,
1248 const struct task_cputime *expires)
1250 if (!cputime_eq(expires->utime, cputime_zero) &&
1251 cputime_ge(sample->utime, expires->utime))
1253 if (!cputime_eq(expires->stime, cputime_zero) &&
1254 cputime_ge(cputime_add(sample->utime, sample->stime),
1257 if (expires->sum_exec_runtime != 0 &&
1258 sample->sum_exec_runtime >= expires->sum_exec_runtime)
1264 * fastpath_timer_check - POSIX CPU timers fast path.
1266 * @tsk: The task (thread) being checked.
1268 * Check the task and thread group timers. If both are zero (there are no
1269 * timers set) return false. Otherwise snapshot the task and thread group
1270 * timers and compare them with the corresponding expiration times. Return
1271 * true if a timer has expired, else return false.
1273 static inline int fastpath_timer_check(struct task_struct *tsk)
1275 struct signal_struct *sig;
1277 if (!task_cputime_zero(&tsk->cputime_expires)) {
1278 struct task_cputime task_sample = {
1279 .utime = tsk->utime,
1280 .stime = tsk->stime,
1281 .sum_exec_runtime = tsk->se.sum_exec_runtime
1284 if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
1289 if (sig->cputimer.running) {
1290 struct task_cputime group_sample;
1292 spin_lock(&sig->cputimer.lock);
1293 group_sample = sig->cputimer.cputime;
1294 spin_unlock(&sig->cputimer.lock);
1296 if (task_cputime_expired(&group_sample, &sig->cputime_expires))
1304 * This is called from the timer interrupt handler. The irq handler has
1305 * already updated our counts. We need to check if any timers fire now.
1306 * Interrupts are disabled.
1308 void run_posix_cpu_timers(struct task_struct *tsk)
1311 struct k_itimer *timer, *next;
1312 unsigned long flags;
1314 BUG_ON(!irqs_disabled());
1317 * The fast path checks that there are no expired thread or thread
1318 * group timers. If that's so, just return.
1320 if (!fastpath_timer_check(tsk))
1323 if (!lock_task_sighand(tsk, &flags))
1326 * Here we take off tsk->signal->cpu_timers[N] and
1327 * tsk->cpu_timers[N] all the timers that are firing, and
1328 * put them on the firing list.
1330 check_thread_timers(tsk, &firing);
1332 * If there are any active process wide timers (POSIX 1.b, itimers,
1333 * RLIMIT_CPU) cputimer must be running.
1335 if (tsk->signal->cputimer.running)
1336 check_process_timers(tsk, &firing);
1339 * We must release these locks before taking any timer's lock.
1340 * There is a potential race with timer deletion here, as the
1341 * siglock now protects our private firing list. We have set
1342 * the firing flag in each timer, so that a deletion attempt
1343 * that gets the timer lock before we do will give it up and
1344 * spin until we've taken care of that timer below.
1346 unlock_task_sighand(tsk, &flags);
1349 * Now that all the timers on our list have the firing flag,
1350 * no one will touch their list entries but us. We'll take
1351 * each timer's lock before clearing its firing flag, so no
1352 * timer call will interfere.
1354 list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1357 spin_lock(&timer->it_lock);
1358 list_del_init(&timer->it.cpu.entry);
1359 cpu_firing = timer->it.cpu.firing;
1360 timer->it.cpu.firing = 0;
1362 * The firing flag is -1 if we collided with a reset
1363 * of the timer, which already reported this
1364 * almost-firing as an overrun. So don't generate an event.
1366 if (likely(cpu_firing >= 0))
1367 cpu_timer_fire(timer);
1368 spin_unlock(&timer->it_lock);
1373 * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
1374 * The tsk->sighand->siglock must be held by the caller.
1376 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1377 cputime_t *newval, cputime_t *oldval)
1379 union cpu_time_count now;
1381 BUG_ON(clock_idx == CPUCLOCK_SCHED);
1382 cpu_timer_sample_group(clock_idx, tsk, &now);
1386 * We are setting itimer. The *oldval is absolute and we update
1387 * it to be relative, *newval argument is relative and we update
1388 * it to be absolute.
1390 if (!cputime_eq(*oldval, cputime_zero)) {
1391 if (cputime_le(*oldval, now.cpu)) {
1392 /* Just about to fire. */
1393 *oldval = cputime_one_jiffy;
1395 *oldval = cputime_sub(*oldval, now.cpu);
1399 if (cputime_eq(*newval, cputime_zero))
1401 *newval = cputime_add(*newval, now.cpu);
1405 * Update expiration cache if we are the earliest timer, or eventually
1406 * RLIMIT_CPU limit is earlier than prof_exp cpu timer expire.
1408 switch (clock_idx) {
1410 if (expires_gt(tsk->signal->cputime_expires.prof_exp, *newval))
1411 tsk->signal->cputime_expires.prof_exp = *newval;
1414 if (expires_gt(tsk->signal->cputime_expires.virt_exp, *newval))
1415 tsk->signal->cputime_expires.virt_exp = *newval;
1420 static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1421 struct timespec *rqtp, struct itimerspec *it)
1423 struct k_itimer timer;
1427 * Set up a temporary timer and then wait for it to go off.
1429 memset(&timer, 0, sizeof timer);
1430 spin_lock_init(&timer.it_lock);
1431 timer.it_clock = which_clock;
1432 timer.it_overrun = -1;
1433 error = posix_cpu_timer_create(&timer);
1434 timer.it_process = current;
1436 static struct itimerspec zero_it;
1438 memset(it, 0, sizeof *it);
1439 it->it_value = *rqtp;
1441 spin_lock_irq(&timer.it_lock);
1442 error = posix_cpu_timer_set(&timer, flags, it, NULL);
1444 spin_unlock_irq(&timer.it_lock);
1448 while (!signal_pending(current)) {
1449 if (timer.it.cpu.expires.sched == 0) {
1451 * Our timer fired and was reset.
1453 spin_unlock_irq(&timer.it_lock);
1458 * Block until cpu_timer_fire (or a signal) wakes us.
1460 __set_current_state(TASK_INTERRUPTIBLE);
1461 spin_unlock_irq(&timer.it_lock);
1463 spin_lock_irq(&timer.it_lock);
1467 * We were interrupted by a signal.
1469 sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
1470 posix_cpu_timer_set(&timer, 0, &zero_it, it);
1471 spin_unlock_irq(&timer.it_lock);
1473 if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
1475 * It actually did fire already.
1480 error = -ERESTART_RESTARTBLOCK;
1486 static long posix_cpu_nsleep_restart(struct restart_block *restart_block);
1488 static int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1489 struct timespec *rqtp, struct timespec __user *rmtp)
1491 struct restart_block *restart_block =
1492 ¤t_thread_info()->restart_block;
1493 struct itimerspec it;
1497 * Diagnose required errors first.
1499 if (CPUCLOCK_PERTHREAD(which_clock) &&
1500 (CPUCLOCK_PID(which_clock) == 0 ||
1501 CPUCLOCK_PID(which_clock) == current->pid))
1504 error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);
1506 if (error == -ERESTART_RESTARTBLOCK) {
1508 if (flags & TIMER_ABSTIME)
1509 return -ERESTARTNOHAND;
1511 * Report back to the user the time still remaining.
1513 if (rmtp && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1516 restart_block->fn = posix_cpu_nsleep_restart;
1517 restart_block->nanosleep.clockid = which_clock;
1518 restart_block->nanosleep.rmtp = rmtp;
1519 restart_block->nanosleep.expires = timespec_to_ns(rqtp);
1524 static long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1526 clockid_t which_clock = restart_block->nanosleep.clockid;
1528 struct itimerspec it;
1531 t = ns_to_timespec(restart_block->nanosleep.expires);
1533 error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);
1535 if (error == -ERESTART_RESTARTBLOCK) {
1536 struct timespec __user *rmtp = restart_block->nanosleep.rmtp;
1538 * Report back to the user the time still remaining.
1540 if (rmtp && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1543 restart_block->nanosleep.expires = timespec_to_ns(&t);
1549 #define PROCESS_CLOCK MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
1550 #define THREAD_CLOCK MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
1552 static int process_cpu_clock_getres(const clockid_t which_clock,
1553 struct timespec *tp)
1555 return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1557 static int process_cpu_clock_get(const clockid_t which_clock,
1558 struct timespec *tp)
1560 return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1562 static int process_cpu_timer_create(struct k_itimer *timer)
1564 timer->it_clock = PROCESS_CLOCK;
1565 return posix_cpu_timer_create(timer);
1567 static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1568 struct timespec *rqtp,
1569 struct timespec __user *rmtp)
1571 return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
1573 static long process_cpu_nsleep_restart(struct restart_block *restart_block)
1577 static int thread_cpu_clock_getres(const clockid_t which_clock,
1578 struct timespec *tp)
1580 return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1582 static int thread_cpu_clock_get(const clockid_t which_clock,
1583 struct timespec *tp)
1585 return posix_cpu_clock_get(THREAD_CLOCK, tp);
1587 static int thread_cpu_timer_create(struct k_itimer *timer)
1589 timer->it_clock = THREAD_CLOCK;
1590 return posix_cpu_timer_create(timer);
1593 struct k_clock clock_posix_cpu = {
1594 .clock_getres = posix_cpu_clock_getres,
1595 .clock_set = posix_cpu_clock_set,
1596 .clock_get = posix_cpu_clock_get,
1597 .timer_create = posix_cpu_timer_create,
1598 .nsleep = posix_cpu_nsleep,
1599 .nsleep_restart = posix_cpu_nsleep_restart,
1600 .timer_set = posix_cpu_timer_set,
1601 .timer_del = posix_cpu_timer_del,
1602 .timer_get = posix_cpu_timer_get,
1605 static __init int init_posix_cpu_timers(void)
1607 struct k_clock process = {
1608 .clock_getres = process_cpu_clock_getres,
1609 .clock_get = process_cpu_clock_get,
1610 .timer_create = process_cpu_timer_create,
1611 .nsleep = process_cpu_nsleep,
1612 .nsleep_restart = process_cpu_nsleep_restart,
1614 struct k_clock thread = {
1615 .clock_getres = thread_cpu_clock_getres,
1616 .clock_get = thread_cpu_clock_get,
1617 .timer_create = thread_cpu_timer_create,
1621 posix_timers_register_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
1622 posix_timers_register_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
1624 cputime_to_timespec(cputime_one_jiffy, &ts);
1625 onecputick = ts.tv_nsec;
1626 WARN_ON(ts.tv_sec != 0);
1630 __initcall(init_posix_cpu_timers);