1 // SPDX-License-Identifier: GPL-2.0
3 * Implement CPU time clocks for the POSIX clock interface.
6 #include <linux/sched/signal.h>
7 #include <linux/sched/cputime.h>
8 #include <linux/posix-timers.h>
9 #include <linux/errno.h>
10 #include <linux/math64.h>
11 #include <linux/uaccess.h>
12 #include <linux/kernel_stat.h>
13 #include <trace/events/timer.h>
14 #include <linux/tick.h>
15 #include <linux/workqueue.h>
16 #include <linux/compat.h>
17 #include <linux/sched/deadline.h>
18 #include <linux/task_work.h>
20 #include "posix-timers.h"
22 static void posix_cpu_timer_rearm(struct k_itimer *timer);
24 void posix_cputimers_group_init(struct posix_cputimers *pct, u64 cpu_limit)
26 posix_cputimers_init(pct);
27 if (cpu_limit != RLIM_INFINITY) {
28 pct->bases[CPUCLOCK_PROF].nextevt = cpu_limit * NSEC_PER_SEC;
29 pct->timers_active = true;
34 * Called after updating RLIMIT_CPU to run cpu timer and update
35 * tsk->signal->posix_cputimers.bases[clock].nextevt expiration cache if
36 * necessary. Needs siglock protection since other code may update the
37 * expiration cache as well.
39 * Returns 0 on success, -ESRCH on failure. Can fail if the task is exiting and
40 * we cannot lock_task_sighand. Cannot fail if task is current.
42 int update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
44 u64 nsecs = rlim_new * NSEC_PER_SEC;
47 if (!lock_task_sighand(task, &irq_fl))
49 set_process_cpu_timer(task, CPUCLOCK_PROF, &nsecs, NULL);
50 unlock_task_sighand(task, &irq_fl);
55 * Functions for validating access to tasks.
57 static struct pid *pid_for_clock(const clockid_t clock, bool gettime)
59 const bool thread = !!CPUCLOCK_PERTHREAD(clock);
60 const pid_t upid = CPUCLOCK_PID(clock);
63 if (CPUCLOCK_WHICH(clock) >= CPUCLOCK_MAX)
67 * If the encoded PID is 0, then the timer is targeted at current
68 * or the process to which current belongs.
71 return thread ? task_pid(current) : task_tgid(current);
73 pid = find_vpid(upid);
78 struct task_struct *tsk = pid_task(pid, PIDTYPE_PID);
79 return (tsk && same_thread_group(tsk, current)) ? pid : NULL;
83 * For clock_gettime(PROCESS) allow finding the process by
84 * with the pid of the current task. The code needs the tgid
85 * of the process so that pid_task(pid, PIDTYPE_TGID) can be
86 * used to find the process.
88 if (gettime && (pid == task_pid(current)))
89 return task_tgid(current);
92 * For processes require that pid identifies a process.
94 return pid_has_task(pid, PIDTYPE_TGID) ? pid : NULL;
97 static inline int validate_clock_permissions(const clockid_t clock)
102 ret = pid_for_clock(clock, false) ? 0 : -EINVAL;
108 static inline enum pid_type clock_pid_type(const clockid_t clock)
110 return CPUCLOCK_PERTHREAD(clock) ? PIDTYPE_PID : PIDTYPE_TGID;
113 static inline struct task_struct *cpu_timer_task_rcu(struct k_itimer *timer)
115 return pid_task(timer->it.cpu.pid, clock_pid_type(timer->it_clock));
119 * Update expiry time from increment, and increase overrun count,
120 * given the current clock sample.
122 static u64 bump_cpu_timer(struct k_itimer *timer, u64 now)
124 u64 delta, incr, expires = timer->it.cpu.node.expires;
127 if (!timer->it_interval)
133 incr = timer->it_interval;
134 delta = now + incr - expires;
136 /* Don't use (incr*2 < delta), incr*2 might overflow. */
137 for (i = 0; incr < delta - incr; i++)
140 for (; i >= 0; incr >>= 1, i--) {
144 timer->it.cpu.node.expires += incr;
145 timer->it_overrun += 1LL << i;
148 return timer->it.cpu.node.expires;
151 /* Check whether all cache entries contain U64_MAX, i.e. eternal expiry time */
152 static inline bool expiry_cache_is_inactive(const struct posix_cputimers *pct)
154 return !(~pct->bases[CPUCLOCK_PROF].nextevt |
155 ~pct->bases[CPUCLOCK_VIRT].nextevt |
156 ~pct->bases[CPUCLOCK_SCHED].nextevt);
160 posix_cpu_clock_getres(const clockid_t which_clock, struct timespec64 *tp)
162 int error = validate_clock_permissions(which_clock);
166 tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
167 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
169 * If sched_clock is using a cycle counter, we
170 * don't have any idea of its true resolution
171 * exported, but it is much more than 1s/HZ.
180 posix_cpu_clock_set(const clockid_t clock, const struct timespec64 *tp)
182 int error = validate_clock_permissions(clock);
185 * You can never reset a CPU clock, but we check for other errors
186 * in the call before failing with EPERM.
188 return error ? : -EPERM;
192 * Sample a per-thread clock for the given task. clkid is validated.
194 static u64 cpu_clock_sample(const clockid_t clkid, struct task_struct *p)
198 if (clkid == CPUCLOCK_SCHED)
199 return task_sched_runtime(p);
201 task_cputime(p, &utime, &stime);
205 return utime + stime;
214 static inline void store_samples(u64 *samples, u64 stime, u64 utime, u64 rtime)
216 samples[CPUCLOCK_PROF] = stime + utime;
217 samples[CPUCLOCK_VIRT] = utime;
218 samples[CPUCLOCK_SCHED] = rtime;
221 static void task_sample_cputime(struct task_struct *p, u64 *samples)
225 task_cputime(p, &utime, &stime);
226 store_samples(samples, stime, utime, p->se.sum_exec_runtime);
229 static void proc_sample_cputime_atomic(struct task_cputime_atomic *at,
232 u64 stime, utime, rtime;
234 utime = atomic64_read(&at->utime);
235 stime = atomic64_read(&at->stime);
236 rtime = atomic64_read(&at->sum_exec_runtime);
237 store_samples(samples, stime, utime, rtime);
241 * Set cputime to sum_cputime if sum_cputime > cputime. Use cmpxchg
242 * to avoid race conditions with concurrent updates to cputime.
244 static inline void __update_gt_cputime(atomic64_t *cputime, u64 sum_cputime)
248 curr_cputime = atomic64_read(cputime);
249 if (sum_cputime > curr_cputime) {
250 if (atomic64_cmpxchg(cputime, curr_cputime, sum_cputime) != curr_cputime)
255 static void update_gt_cputime(struct task_cputime_atomic *cputime_atomic,
256 struct task_cputime *sum)
258 __update_gt_cputime(&cputime_atomic->utime, sum->utime);
259 __update_gt_cputime(&cputime_atomic->stime, sum->stime);
260 __update_gt_cputime(&cputime_atomic->sum_exec_runtime, sum->sum_exec_runtime);
264 * thread_group_sample_cputime - Sample cputime for a given task
265 * @tsk: Task for which cputime needs to be started
266 * @samples: Storage for time samples
268 * Called from sys_getitimer() to calculate the expiry time of an active
269 * timer. That means group cputime accounting is already active. Called
270 * with task sighand lock held.
272 * Updates @times with an uptodate sample of the thread group cputimes.
274 void thread_group_sample_cputime(struct task_struct *tsk, u64 *samples)
276 struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
277 struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
279 WARN_ON_ONCE(!pct->timers_active);
281 proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
285 * thread_group_start_cputime - Start cputime and return a sample
286 * @tsk: Task for which cputime needs to be started
287 * @samples: Storage for time samples
289 * The thread group cputime accounting is avoided when there are no posix
290 * CPU timers armed. Before starting a timer it's required to check whether
291 * the time accounting is active. If not, a full update of the atomic
292 * accounting store needs to be done and the accounting enabled.
294 * Updates @times with an uptodate sample of the thread group cputimes.
296 static void thread_group_start_cputime(struct task_struct *tsk, u64 *samples)
298 struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
299 struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
301 lockdep_assert_task_sighand_held(tsk);
303 /* Check if cputimer isn't running. This is accessed without locking. */
304 if (!READ_ONCE(pct->timers_active)) {
305 struct task_cputime sum;
308 * The POSIX timer interface allows for absolute time expiry
309 * values through the TIMER_ABSTIME flag, therefore we have
310 * to synchronize the timer to the clock every time we start it.
312 thread_group_cputime(tsk, &sum);
313 update_gt_cputime(&cputimer->cputime_atomic, &sum);
316 * We're setting timers_active without a lock. Ensure this
317 * only gets written to in one operation. We set it after
318 * update_gt_cputime() as a small optimization, but
319 * barriers are not required because update_gt_cputime()
320 * can handle concurrent updates.
322 WRITE_ONCE(pct->timers_active, true);
324 proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
327 static void __thread_group_cputime(struct task_struct *tsk, u64 *samples)
329 struct task_cputime ct;
331 thread_group_cputime(tsk, &ct);
332 store_samples(samples, ct.stime, ct.utime, ct.sum_exec_runtime);
336 * Sample a process (thread group) clock for the given task clkid. If the
337 * group's cputime accounting is already enabled, read the atomic
338 * store. Otherwise a full update is required. clkid is already validated.
340 static u64 cpu_clock_sample_group(const clockid_t clkid, struct task_struct *p,
343 struct thread_group_cputimer *cputimer = &p->signal->cputimer;
344 struct posix_cputimers *pct = &p->signal->posix_cputimers;
345 u64 samples[CPUCLOCK_MAX];
347 if (!READ_ONCE(pct->timers_active)) {
349 thread_group_start_cputime(p, samples);
351 __thread_group_cputime(p, samples);
353 proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
356 return samples[clkid];
359 static int posix_cpu_clock_get(const clockid_t clock, struct timespec64 *tp)
361 const clockid_t clkid = CPUCLOCK_WHICH(clock);
362 struct task_struct *tsk;
366 tsk = pid_task(pid_for_clock(clock, true), clock_pid_type(clock));
372 if (CPUCLOCK_PERTHREAD(clock))
373 t = cpu_clock_sample(clkid, tsk);
375 t = cpu_clock_sample_group(clkid, tsk, false);
378 *tp = ns_to_timespec64(t);
383 * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
384 * This is called from sys_timer_create() and do_cpu_nanosleep() with the
385 * new timer already all-zeros initialized.
387 static int posix_cpu_timer_create(struct k_itimer *new_timer)
389 static struct lock_class_key posix_cpu_timers_key;
393 pid = pid_for_clock(new_timer->it_clock, false);
400 * If posix timer expiry is handled in task work context then
401 * timer::it_lock can be taken without disabling interrupts as all
402 * other locking happens in task context. This requires a separate
403 * lock class key otherwise regular posix timer expiry would record
404 * the lock class being taken in interrupt context and generate a
405 * false positive warning.
407 if (IS_ENABLED(CONFIG_POSIX_CPU_TIMERS_TASK_WORK))
408 lockdep_set_class(&new_timer->it_lock, &posix_cpu_timers_key);
410 new_timer->kclock = &clock_posix_cpu;
411 timerqueue_init(&new_timer->it.cpu.node);
412 new_timer->it.cpu.pid = get_pid(pid);
417 static struct posix_cputimer_base *timer_base(struct k_itimer *timer,
418 struct task_struct *tsk)
420 int clkidx = CPUCLOCK_WHICH(timer->it_clock);
422 if (CPUCLOCK_PERTHREAD(timer->it_clock))
423 return tsk->posix_cputimers.bases + clkidx;
425 return tsk->signal->posix_cputimers.bases + clkidx;
429 * Force recalculating the base earliest expiration on the next tick.
430 * This will also re-evaluate the need to keep around the process wide
431 * cputime counter and tick dependency and eventually shut these down
434 static void trigger_base_recalc_expires(struct k_itimer *timer,
435 struct task_struct *tsk)
437 struct posix_cputimer_base *base = timer_base(timer, tsk);
443 * Dequeue the timer and reset the base if it was its earliest expiration.
444 * It makes sure the next tick recalculates the base next expiration so we
445 * don't keep the costly process wide cputime counter around for a random
446 * amount of time, along with the tick dependency.
448 * If another timer gets queued between this and the next tick, its
449 * expiration will update the base next event if necessary on the next
452 static void disarm_timer(struct k_itimer *timer, struct task_struct *p)
454 struct cpu_timer *ctmr = &timer->it.cpu;
455 struct posix_cputimer_base *base;
457 if (!cpu_timer_dequeue(ctmr))
460 base = timer_base(timer, p);
461 if (cpu_timer_getexpires(ctmr) == base->nextevt)
462 trigger_base_recalc_expires(timer, p);
467 * Clean up a CPU-clock timer that is about to be destroyed.
468 * This is called from timer deletion with the timer already locked.
469 * If we return TIMER_RETRY, it's necessary to release the timer's lock
470 * and try again. (This happens when the timer is in the middle of firing.)
472 static int posix_cpu_timer_del(struct k_itimer *timer)
474 struct cpu_timer *ctmr = &timer->it.cpu;
475 struct sighand_struct *sighand;
476 struct task_struct *p;
481 p = cpu_timer_task_rcu(timer);
486 * Protect against sighand release/switch in exit/exec and process/
487 * thread timer list entry concurrent read/writes.
489 sighand = lock_task_sighand(p, &flags);
490 if (unlikely(sighand == NULL)) {
492 * This raced with the reaping of the task. The exit cleanup
493 * should have removed this timer from the timer queue.
495 WARN_ON_ONCE(ctmr->head || timerqueue_node_queued(&ctmr->node));
497 if (timer->it.cpu.firing)
500 disarm_timer(timer, p);
502 unlock_task_sighand(p, &flags);
513 static void cleanup_timerqueue(struct timerqueue_head *head)
515 struct timerqueue_node *node;
516 struct cpu_timer *ctmr;
518 while ((node = timerqueue_getnext(head))) {
519 timerqueue_del(head, node);
520 ctmr = container_of(node, struct cpu_timer, node);
526 * Clean out CPU timers which are still armed when a thread exits. The
527 * timers are only removed from the list. No other updates are done. The
528 * corresponding posix timers are still accessible, but cannot be rearmed.
530 * This must be called with the siglock held.
532 static void cleanup_timers(struct posix_cputimers *pct)
534 cleanup_timerqueue(&pct->bases[CPUCLOCK_PROF].tqhead);
535 cleanup_timerqueue(&pct->bases[CPUCLOCK_VIRT].tqhead);
536 cleanup_timerqueue(&pct->bases[CPUCLOCK_SCHED].tqhead);
540 * These are both called with the siglock held, when the current thread
541 * is being reaped. When the final (leader) thread in the group is reaped,
542 * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
544 void posix_cpu_timers_exit(struct task_struct *tsk)
546 cleanup_timers(&tsk->posix_cputimers);
548 void posix_cpu_timers_exit_group(struct task_struct *tsk)
550 cleanup_timers(&tsk->signal->posix_cputimers);
554 * Insert the timer on the appropriate list before any timers that
555 * expire later. This must be called with the sighand lock held.
557 static void arm_timer(struct k_itimer *timer, struct task_struct *p)
559 struct posix_cputimer_base *base = timer_base(timer, p);
560 struct cpu_timer *ctmr = &timer->it.cpu;
561 u64 newexp = cpu_timer_getexpires(ctmr);
563 if (!cpu_timer_enqueue(&base->tqhead, ctmr))
567 * We are the new earliest-expiring POSIX 1.b timer, hence
568 * need to update expiration cache. Take into account that
569 * for process timers we share expiration cache with itimers
570 * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
572 if (newexp < base->nextevt)
573 base->nextevt = newexp;
575 if (CPUCLOCK_PERTHREAD(timer->it_clock))
576 tick_dep_set_task(p, TICK_DEP_BIT_POSIX_TIMER);
578 tick_dep_set_signal(p, TICK_DEP_BIT_POSIX_TIMER);
582 * The timer is locked, fire it and arrange for its reload.
584 static void cpu_timer_fire(struct k_itimer *timer)
586 struct cpu_timer *ctmr = &timer->it.cpu;
588 if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
590 * User don't want any signal.
592 cpu_timer_setexpires(ctmr, 0);
593 } else if (unlikely(timer->sigq == NULL)) {
595 * This a special case for clock_nanosleep,
596 * not a normal timer from sys_timer_create.
598 wake_up_process(timer->it_process);
599 cpu_timer_setexpires(ctmr, 0);
600 } else if (!timer->it_interval) {
602 * One-shot timer. Clear it as soon as it's fired.
604 posix_timer_event(timer, 0);
605 cpu_timer_setexpires(ctmr, 0);
606 } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
608 * The signal did not get queued because the signal
609 * was ignored, so we won't get any callback to
610 * reload the timer. But we need to keep it
611 * ticking in case the signal is deliverable next time.
613 posix_cpu_timer_rearm(timer);
614 ++timer->it_requeue_pending;
619 * Guts of sys_timer_settime for CPU timers.
620 * This is called with the timer locked and interrupts disabled.
621 * If we return TIMER_RETRY, it's necessary to release the timer's lock
622 * and try again. (This happens when the timer is in the middle of firing.)
624 static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
625 struct itimerspec64 *new, struct itimerspec64 *old)
627 clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
628 u64 old_expires, new_expires, old_incr, val;
629 struct cpu_timer *ctmr = &timer->it.cpu;
630 struct sighand_struct *sighand;
631 struct task_struct *p;
636 p = cpu_timer_task_rcu(timer);
639 * If p has just been reaped, we can no
640 * longer get any information about it at all.
647 * Use the to_ktime conversion because that clamps the maximum
648 * value to KTIME_MAX and avoid multiplication overflows.
650 new_expires = ktime_to_ns(timespec64_to_ktime(new->it_value));
653 * Protect against sighand release/switch in exit/exec and p->cpu_timers
654 * and p->signal->cpu_timers read/write in arm_timer()
656 sighand = lock_task_sighand(p, &flags);
658 * If p has just been reaped, we can no
659 * longer get any information about it at all.
661 if (unlikely(sighand == NULL)) {
667 * Disarm any old timer after extracting its expiry time.
669 old_incr = timer->it_interval;
670 old_expires = cpu_timer_getexpires(ctmr);
672 if (unlikely(timer->it.cpu.firing)) {
673 timer->it.cpu.firing = -1;
676 cpu_timer_dequeue(ctmr);
680 * We need to sample the current value to convert the new
681 * value from to relative and absolute, and to convert the
682 * old value from absolute to relative. To set a process
683 * timer, we need a sample to balance the thread expiry
684 * times (in arm_timer). With an absolute time, we must
685 * check if it's already passed. In short, we need a sample.
687 if (CPUCLOCK_PERTHREAD(timer->it_clock))
688 val = cpu_clock_sample(clkid, p);
690 val = cpu_clock_sample_group(clkid, p, true);
693 if (old_expires == 0) {
694 old->it_value.tv_sec = 0;
695 old->it_value.tv_nsec = 0;
698 * Update the timer in case it has overrun already.
699 * If it has, we'll report it as having overrun and
700 * with the next reloaded timer already ticking,
701 * though we are swallowing that pending
702 * notification here to install the new setting.
704 u64 exp = bump_cpu_timer(timer, val);
707 old_expires = exp - val;
708 old->it_value = ns_to_timespec64(old_expires);
710 old->it_value.tv_nsec = 1;
711 old->it_value.tv_sec = 0;
718 * We are colliding with the timer actually firing.
719 * Punt after filling in the timer's old value, and
720 * disable this firing since we are already reporting
721 * it as an overrun (thanks to bump_cpu_timer above).
723 unlock_task_sighand(p, &flags);
727 if (new_expires != 0 && !(timer_flags & TIMER_ABSTIME)) {
732 * Install the new expiry time (or zero).
733 * For a timer with no notification action, we don't actually
734 * arm the timer (we'll just fake it for timer_gettime).
736 cpu_timer_setexpires(ctmr, new_expires);
737 if (new_expires != 0 && val < new_expires) {
741 unlock_task_sighand(p, &flags);
743 * Install the new reload setting, and
744 * set up the signal and overrun bookkeeping.
746 timer->it_interval = timespec64_to_ktime(new->it_interval);
749 * This acts as a modification timestamp for the timer,
750 * so any automatic reload attempt will punt on seeing
751 * that we have reset the timer manually.
753 timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
755 timer->it_overrun_last = 0;
756 timer->it_overrun = -1;
758 if (val >= new_expires) {
759 if (new_expires != 0) {
761 * The designated time already passed, so we notify
762 * immediately, even if the thread never runs to
763 * accumulate more time on this clock.
765 cpu_timer_fire(timer);
769 * Make sure we don't keep around the process wide cputime
770 * counter or the tick dependency if they are not necessary.
772 sighand = lock_task_sighand(p, &flags);
776 if (!cpu_timer_queued(ctmr))
777 trigger_base_recalc_expires(timer, p);
779 unlock_task_sighand(p, &flags);
784 old->it_interval = ns_to_timespec64(old_incr);
789 static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp)
791 clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
792 struct cpu_timer *ctmr = &timer->it.cpu;
793 u64 now, expires = cpu_timer_getexpires(ctmr);
794 struct task_struct *p;
797 p = cpu_timer_task_rcu(timer);
802 * Easy part: convert the reload time.
804 itp->it_interval = ktime_to_timespec64(timer->it_interval);
810 * Sample the clock to take the difference with the expiry time.
812 if (CPUCLOCK_PERTHREAD(timer->it_clock))
813 now = cpu_clock_sample(clkid, p);
815 now = cpu_clock_sample_group(clkid, p, false);
818 itp->it_value = ns_to_timespec64(expires - now);
821 * The timer should have expired already, but the firing
822 * hasn't taken place yet. Say it's just about to expire.
824 itp->it_value.tv_nsec = 1;
825 itp->it_value.tv_sec = 0;
831 #define MAX_COLLECTED 20
833 static u64 collect_timerqueue(struct timerqueue_head *head,
834 struct list_head *firing, u64 now)
836 struct timerqueue_node *next;
839 while ((next = timerqueue_getnext(head))) {
840 struct cpu_timer *ctmr;
843 ctmr = container_of(next, struct cpu_timer, node);
844 expires = cpu_timer_getexpires(ctmr);
845 /* Limit the number of timers to expire at once */
846 if (++i == MAX_COLLECTED || now < expires)
850 cpu_timer_dequeue(ctmr);
851 list_add_tail(&ctmr->elist, firing);
857 static void collect_posix_cputimers(struct posix_cputimers *pct, u64 *samples,
858 struct list_head *firing)
860 struct posix_cputimer_base *base = pct->bases;
863 for (i = 0; i < CPUCLOCK_MAX; i++, base++) {
864 base->nextevt = collect_timerqueue(&base->tqhead, firing,
869 static inline void check_dl_overrun(struct task_struct *tsk)
871 if (tsk->dl.dl_overrun) {
872 tsk->dl.dl_overrun = 0;
873 send_signal_locked(SIGXCPU, SEND_SIG_PRIV, tsk, PIDTYPE_TGID);
877 static bool check_rlimit(u64 time, u64 limit, int signo, bool rt, bool hard)
882 if (print_fatal_signals) {
883 pr_info("%s Watchdog Timeout (%s): %s[%d]\n",
884 rt ? "RT" : "CPU", hard ? "hard" : "soft",
885 current->comm, task_pid_nr(current));
887 send_signal_locked(signo, SEND_SIG_PRIV, current, PIDTYPE_TGID);
892 * Check for any per-thread CPU timers that have fired and move them off
893 * the tsk->cpu_timers[N] list onto the firing list. Here we update the
894 * tsk->it_*_expires values to reflect the remaining thread CPU timers.
896 static void check_thread_timers(struct task_struct *tsk,
897 struct list_head *firing)
899 struct posix_cputimers *pct = &tsk->posix_cputimers;
900 u64 samples[CPUCLOCK_MAX];
904 check_dl_overrun(tsk);
906 if (expiry_cache_is_inactive(pct))
909 task_sample_cputime(tsk, samples);
910 collect_posix_cputimers(pct, samples, firing);
913 * Check for the special case thread timers.
915 soft = task_rlimit(tsk, RLIMIT_RTTIME);
916 if (soft != RLIM_INFINITY) {
917 /* Task RT timeout is accounted in jiffies. RTTIME is usec */
918 unsigned long rttime = tsk->rt.timeout * (USEC_PER_SEC / HZ);
919 unsigned long hard = task_rlimit_max(tsk, RLIMIT_RTTIME);
921 /* At the hard limit, send SIGKILL. No further action. */
922 if (hard != RLIM_INFINITY &&
923 check_rlimit(rttime, hard, SIGKILL, true, true))
926 /* At the soft limit, send a SIGXCPU every second */
927 if (check_rlimit(rttime, soft, SIGXCPU, true, false)) {
928 soft += USEC_PER_SEC;
929 tsk->signal->rlim[RLIMIT_RTTIME].rlim_cur = soft;
933 if (expiry_cache_is_inactive(pct))
934 tick_dep_clear_task(tsk, TICK_DEP_BIT_POSIX_TIMER);
937 static inline void stop_process_timers(struct signal_struct *sig)
939 struct posix_cputimers *pct = &sig->posix_cputimers;
941 /* Turn off the active flag. This is done without locking. */
942 WRITE_ONCE(pct->timers_active, false);
943 tick_dep_clear_signal(sig, TICK_DEP_BIT_POSIX_TIMER);
946 static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
947 u64 *expires, u64 cur_time, int signo)
952 if (cur_time >= it->expires) {
954 it->expires += it->incr;
958 trace_itimer_expire(signo == SIGPROF ?
959 ITIMER_PROF : ITIMER_VIRTUAL,
960 task_tgid(tsk), cur_time);
961 send_signal_locked(signo, SEND_SIG_PRIV, tsk, PIDTYPE_TGID);
964 if (it->expires && it->expires < *expires)
965 *expires = it->expires;
969 * Check for any per-thread CPU timers that have fired and move them
970 * off the tsk->*_timers list onto the firing list. Per-thread timers
971 * have already been taken off.
973 static void check_process_timers(struct task_struct *tsk,
974 struct list_head *firing)
976 struct signal_struct *const sig = tsk->signal;
977 struct posix_cputimers *pct = &sig->posix_cputimers;
978 u64 samples[CPUCLOCK_MAX];
982 * If there are no active process wide timers (POSIX 1.b, itimers,
983 * RLIMIT_CPU) nothing to check. Also skip the process wide timer
984 * processing when there is already another task handling them.
986 if (!READ_ONCE(pct->timers_active) || pct->expiry_active)
990 * Signify that a thread is checking for process timers.
991 * Write access to this field is protected by the sighand lock.
993 pct->expiry_active = true;
996 * Collect the current process totals. Group accounting is active
997 * so the sample can be taken directly.
999 proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic, samples);
1000 collect_posix_cputimers(pct, samples, firing);
1003 * Check for the special case process timers.
1005 check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF],
1006 &pct->bases[CPUCLOCK_PROF].nextevt,
1007 samples[CPUCLOCK_PROF], SIGPROF);
1008 check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT],
1009 &pct->bases[CPUCLOCK_VIRT].nextevt,
1010 samples[CPUCLOCK_VIRT], SIGVTALRM);
1012 soft = task_rlimit(tsk, RLIMIT_CPU);
1013 if (soft != RLIM_INFINITY) {
1014 /* RLIMIT_CPU is in seconds. Samples are nanoseconds */
1015 unsigned long hard = task_rlimit_max(tsk, RLIMIT_CPU);
1016 u64 ptime = samples[CPUCLOCK_PROF];
1017 u64 softns = (u64)soft * NSEC_PER_SEC;
1018 u64 hardns = (u64)hard * NSEC_PER_SEC;
1020 /* At the hard limit, send SIGKILL. No further action. */
1021 if (hard != RLIM_INFINITY &&
1022 check_rlimit(ptime, hardns, SIGKILL, false, true))
1025 /* At the soft limit, send a SIGXCPU every second */
1026 if (check_rlimit(ptime, softns, SIGXCPU, false, false)) {
1027 sig->rlim[RLIMIT_CPU].rlim_cur = soft + 1;
1028 softns += NSEC_PER_SEC;
1031 /* Update the expiry cache */
1032 if (softns < pct->bases[CPUCLOCK_PROF].nextevt)
1033 pct->bases[CPUCLOCK_PROF].nextevt = softns;
1036 if (expiry_cache_is_inactive(pct))
1037 stop_process_timers(sig);
1039 pct->expiry_active = false;
1043 * This is called from the signal code (via posixtimer_rearm)
1044 * when the last timer signal was delivered and we have to reload the timer.
1046 static void posix_cpu_timer_rearm(struct k_itimer *timer)
1048 clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
1049 struct task_struct *p;
1050 struct sighand_struct *sighand;
1051 unsigned long flags;
1055 p = cpu_timer_task_rcu(timer);
1059 /* Protect timer list r/w in arm_timer() */
1060 sighand = lock_task_sighand(p, &flags);
1061 if (unlikely(sighand == NULL))
1065 * Fetch the current sample and update the timer's expiry time.
1067 if (CPUCLOCK_PERTHREAD(timer->it_clock))
1068 now = cpu_clock_sample(clkid, p);
1070 now = cpu_clock_sample_group(clkid, p, true);
1072 bump_cpu_timer(timer, now);
1075 * Now re-arm for the new expiry time.
1077 arm_timer(timer, p);
1078 unlock_task_sighand(p, &flags);
1084 * task_cputimers_expired - Check whether posix CPU timers are expired
1086 * @samples: Array of current samples for the CPUCLOCK clocks
1087 * @pct: Pointer to a posix_cputimers container
1089 * Returns true if any member of @samples is greater than the corresponding
1090 * member of @pct->bases[CLK].nextevt. False otherwise
1093 task_cputimers_expired(const u64 *samples, struct posix_cputimers *pct)
1097 for (i = 0; i < CPUCLOCK_MAX; i++) {
1098 if (samples[i] >= pct->bases[i].nextevt)
1105 * fastpath_timer_check - POSIX CPU timers fast path.
1107 * @tsk: The task (thread) being checked.
1109 * Check the task and thread group timers. If both are zero (there are no
1110 * timers set) return false. Otherwise snapshot the task and thread group
1111 * timers and compare them with the corresponding expiration times. Return
1112 * true if a timer has expired, else return false.
1114 static inline bool fastpath_timer_check(struct task_struct *tsk)
1116 struct posix_cputimers *pct = &tsk->posix_cputimers;
1117 struct signal_struct *sig;
1119 if (!expiry_cache_is_inactive(pct)) {
1120 u64 samples[CPUCLOCK_MAX];
1122 task_sample_cputime(tsk, samples);
1123 if (task_cputimers_expired(samples, pct))
1128 pct = &sig->posix_cputimers;
1130 * Check if thread group timers expired when timers are active and
1131 * no other thread in the group is already handling expiry for
1132 * thread group cputimers. These fields are read without the
1133 * sighand lock. However, this is fine because this is meant to be
1134 * a fastpath heuristic to determine whether we should try to
1135 * acquire the sighand lock to handle timer expiry.
1137 * In the worst case scenario, if concurrently timers_active is set
1138 * or expiry_active is cleared, but the current thread doesn't see
1139 * the change yet, the timer checks are delayed until the next
1140 * thread in the group gets a scheduler interrupt to handle the
1141 * timer. This isn't an issue in practice because these types of
1142 * delays with signals actually getting sent are expected.
1144 if (READ_ONCE(pct->timers_active) && !READ_ONCE(pct->expiry_active)) {
1145 u64 samples[CPUCLOCK_MAX];
1147 proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic,
1150 if (task_cputimers_expired(samples, pct))
1154 if (dl_task(tsk) && tsk->dl.dl_overrun)
1160 static void handle_posix_cpu_timers(struct task_struct *tsk);
1162 #ifdef CONFIG_POSIX_CPU_TIMERS_TASK_WORK
1163 static void posix_cpu_timers_work(struct callback_head *work)
1165 handle_posix_cpu_timers(current);
1169 * Clear existing posix CPU timers task work.
1171 void clear_posix_cputimers_work(struct task_struct *p)
1174 * A copied work entry from the old task is not meaningful, clear it.
1175 * N.B. init_task_work will not do this.
1177 memset(&p->posix_cputimers_work.work, 0,
1178 sizeof(p->posix_cputimers_work.work));
1179 init_task_work(&p->posix_cputimers_work.work,
1180 posix_cpu_timers_work);
1181 p->posix_cputimers_work.scheduled = false;
1185 * Initialize posix CPU timers task work in init task. Out of line to
1186 * keep the callback static and to avoid header recursion hell.
1188 void __init posix_cputimers_init_work(void)
1190 clear_posix_cputimers_work(current);
1194 * Note: All operations on tsk->posix_cputimer_work.scheduled happen either
1195 * in hard interrupt context or in task context with interrupts
1196 * disabled. Aside of that the writer/reader interaction is always in the
1197 * context of the current task, which means they are strict per CPU.
1199 static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
1201 return tsk->posix_cputimers_work.scheduled;
1204 static inline void __run_posix_cpu_timers(struct task_struct *tsk)
1206 if (WARN_ON_ONCE(tsk->posix_cputimers_work.scheduled))
1209 /* Schedule task work to actually expire the timers */
1210 tsk->posix_cputimers_work.scheduled = true;
1211 task_work_add(tsk, &tsk->posix_cputimers_work.work, TWA_RESUME);
1214 static inline bool posix_cpu_timers_enable_work(struct task_struct *tsk,
1215 unsigned long start)
1220 * On !RT kernels interrupts are disabled while collecting expired
1221 * timers, so no tick can happen and the fast path check can be
1222 * reenabled without further checks.
1224 if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
1225 tsk->posix_cputimers_work.scheduled = false;
1230 * On RT enabled kernels ticks can happen while the expired timers
1231 * are collected under sighand lock. But any tick which observes
1232 * the CPUTIMERS_WORK_SCHEDULED bit set, does not run the fastpath
1233 * checks. So reenabling the tick work has do be done carefully:
1235 * Disable interrupts and run the fast path check if jiffies have
1236 * advanced since the collecting of expired timers started. If
1237 * jiffies have not advanced or the fast path check did not find
1238 * newly expired timers, reenable the fast path check in the timer
1239 * interrupt. If there are newly expired timers, return false and
1240 * let the collection loop repeat.
1242 local_irq_disable();
1243 if (start != jiffies && fastpath_timer_check(tsk))
1246 tsk->posix_cputimers_work.scheduled = false;
1251 #else /* CONFIG_POSIX_CPU_TIMERS_TASK_WORK */
1252 static inline void __run_posix_cpu_timers(struct task_struct *tsk)
1254 lockdep_posixtimer_enter();
1255 handle_posix_cpu_timers(tsk);
1256 lockdep_posixtimer_exit();
1259 static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
1264 static inline bool posix_cpu_timers_enable_work(struct task_struct *tsk,
1265 unsigned long start)
1269 #endif /* CONFIG_POSIX_CPU_TIMERS_TASK_WORK */
1271 static void handle_posix_cpu_timers(struct task_struct *tsk)
1273 struct k_itimer *timer, *next;
1274 unsigned long flags, start;
1277 if (!lock_task_sighand(tsk, &flags))
1282 * On RT locking sighand lock does not disable interrupts,
1283 * so this needs to be careful vs. ticks. Store the current
1286 start = READ_ONCE(jiffies);
1290 * Here we take off tsk->signal->cpu_timers[N] and
1291 * tsk->cpu_timers[N] all the timers that are firing, and
1292 * put them on the firing list.
1294 check_thread_timers(tsk, &firing);
1296 check_process_timers(tsk, &firing);
1299 * The above timer checks have updated the expiry cache and
1300 * because nothing can have queued or modified timers after
1301 * sighand lock was taken above it is guaranteed to be
1302 * consistent. So the next timer interrupt fastpath check
1303 * will find valid data.
1305 * If timer expiry runs in the timer interrupt context then
1306 * the loop is not relevant as timers will be directly
1307 * expired in interrupt context. The stub function below
1308 * returns always true which allows the compiler to
1309 * optimize the loop out.
1311 * If timer expiry is deferred to task work context then
1312 * the following rules apply:
1314 * - On !RT kernels no tick can have happened on this CPU
1315 * after sighand lock was acquired because interrupts are
1316 * disabled. So reenabling task work before dropping
1317 * sighand lock and reenabling interrupts is race free.
1319 * - On RT kernels ticks might have happened but the tick
1320 * work ignored posix CPU timer handling because the
1321 * CPUTIMERS_WORK_SCHEDULED bit is set. Reenabling work
1322 * must be done very carefully including a check whether
1323 * ticks have happened since the start of the timer
1324 * expiry checks. posix_cpu_timers_enable_work() takes
1325 * care of that and eventually lets the expiry checks
1328 } while (!posix_cpu_timers_enable_work(tsk, start));
1331 * We must release sighand lock before taking any timer's lock.
1332 * There is a potential race with timer deletion here, as the
1333 * siglock now protects our private firing list. We have set
1334 * the firing flag in each timer, so that a deletion attempt
1335 * that gets the timer lock before we do will give it up and
1336 * spin until we've taken care of that timer below.
1338 unlock_task_sighand(tsk, &flags);
1341 * Now that all the timers on our list have the firing flag,
1342 * no one will touch their list entries but us. We'll take
1343 * each timer's lock before clearing its firing flag, so no
1344 * timer call will interfere.
1346 list_for_each_entry_safe(timer, next, &firing, it.cpu.elist) {
1350 * spin_lock() is sufficient here even independent of the
1351 * expiry context. If expiry happens in hard interrupt
1352 * context it's obvious. For task work context it's safe
1353 * because all other operations on timer::it_lock happen in
1354 * task context (syscall or exit).
1356 spin_lock(&timer->it_lock);
1357 list_del_init(&timer->it.cpu.elist);
1358 cpu_firing = timer->it.cpu.firing;
1359 timer->it.cpu.firing = 0;
1361 * The firing flag is -1 if we collided with a reset
1362 * of the timer, which already reported this
1363 * almost-firing as an overrun. So don't generate an event.
1365 if (likely(cpu_firing >= 0))
1366 cpu_timer_fire(timer);
1367 spin_unlock(&timer->it_lock);
1372 * This is called from the timer interrupt handler. The irq handler has
1373 * already updated our counts. We need to check if any timers fire now.
1374 * Interrupts are disabled.
1376 void run_posix_cpu_timers(void)
1378 struct task_struct *tsk = current;
1380 lockdep_assert_irqs_disabled();
1383 * If the actual expiry is deferred to task work context and the
1384 * work is already scheduled there is no point to do anything here.
1386 if (posix_cpu_timers_work_scheduled(tsk))
1390 * The fast path checks that there are no expired thread or thread
1391 * group timers. If that's so, just return.
1393 if (!fastpath_timer_check(tsk))
1396 __run_posix_cpu_timers(tsk);
1400 * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
1401 * The tsk->sighand->siglock must be held by the caller.
1403 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clkid,
1404 u64 *newval, u64 *oldval)
1408 if (WARN_ON_ONCE(clkid >= CPUCLOCK_SCHED))
1411 nextevt = &tsk->signal->posix_cputimers.bases[clkid].nextevt;
1412 now = cpu_clock_sample_group(clkid, tsk, true);
1416 * We are setting itimer. The *oldval is absolute and we update
1417 * it to be relative, *newval argument is relative and we update
1418 * it to be absolute.
1421 if (*oldval <= now) {
1422 /* Just about to fire. */
1423 *oldval = TICK_NSEC;
1434 * Update expiration cache if this is the earliest timer. CPUCLOCK_PROF
1435 * expiry cache is also used by RLIMIT_CPU!.
1437 if (*newval < *nextevt)
1440 tick_dep_set_signal(tsk, TICK_DEP_BIT_POSIX_TIMER);
1443 static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1444 const struct timespec64 *rqtp)
1446 struct itimerspec64 it;
1447 struct k_itimer timer;
1452 * Set up a temporary timer and then wait for it to go off.
1454 memset(&timer, 0, sizeof timer);
1455 spin_lock_init(&timer.it_lock);
1456 timer.it_clock = which_clock;
1457 timer.it_overrun = -1;
1458 error = posix_cpu_timer_create(&timer);
1459 timer.it_process = current;
1462 static struct itimerspec64 zero_it;
1463 struct restart_block *restart;
1465 memset(&it, 0, sizeof(it));
1466 it.it_value = *rqtp;
1468 spin_lock_irq(&timer.it_lock);
1469 error = posix_cpu_timer_set(&timer, flags, &it, NULL);
1471 spin_unlock_irq(&timer.it_lock);
1475 while (!signal_pending(current)) {
1476 if (!cpu_timer_getexpires(&timer.it.cpu)) {
1478 * Our timer fired and was reset, below
1479 * deletion can not fail.
1481 posix_cpu_timer_del(&timer);
1482 spin_unlock_irq(&timer.it_lock);
1487 * Block until cpu_timer_fire (or a signal) wakes us.
1489 __set_current_state(TASK_INTERRUPTIBLE);
1490 spin_unlock_irq(&timer.it_lock);
1492 spin_lock_irq(&timer.it_lock);
1496 * We were interrupted by a signal.
1498 expires = cpu_timer_getexpires(&timer.it.cpu);
1499 error = posix_cpu_timer_set(&timer, 0, &zero_it, &it);
1502 * Timer is now unarmed, deletion can not fail.
1504 posix_cpu_timer_del(&timer);
1506 spin_unlock_irq(&timer.it_lock);
1508 while (error == TIMER_RETRY) {
1510 * We need to handle case when timer was or is in the
1511 * middle of firing. In other cases we already freed
1514 spin_lock_irq(&timer.it_lock);
1515 error = posix_cpu_timer_del(&timer);
1516 spin_unlock_irq(&timer.it_lock);
1519 if ((it.it_value.tv_sec | it.it_value.tv_nsec) == 0) {
1521 * It actually did fire already.
1526 error = -ERESTART_RESTARTBLOCK;
1528 * Report back to the user the time still remaining.
1530 restart = ¤t->restart_block;
1531 restart->nanosleep.expires = expires;
1532 if (restart->nanosleep.type != TT_NONE)
1533 error = nanosleep_copyout(restart, &it.it_value);
1539 static long posix_cpu_nsleep_restart(struct restart_block *restart_block);
1541 static int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1542 const struct timespec64 *rqtp)
1544 struct restart_block *restart_block = ¤t->restart_block;
1548 * Diagnose required errors first.
1550 if (CPUCLOCK_PERTHREAD(which_clock) &&
1551 (CPUCLOCK_PID(which_clock) == 0 ||
1552 CPUCLOCK_PID(which_clock) == task_pid_vnr(current)))
1555 error = do_cpu_nanosleep(which_clock, flags, rqtp);
1557 if (error == -ERESTART_RESTARTBLOCK) {
1559 if (flags & TIMER_ABSTIME)
1560 return -ERESTARTNOHAND;
1562 restart_block->nanosleep.clockid = which_clock;
1563 set_restart_fn(restart_block, posix_cpu_nsleep_restart);
1568 static long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1570 clockid_t which_clock = restart_block->nanosleep.clockid;
1571 struct timespec64 t;
1573 t = ns_to_timespec64(restart_block->nanosleep.expires);
1575 return do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t);
1578 #define PROCESS_CLOCK make_process_cpuclock(0, CPUCLOCK_SCHED)
1579 #define THREAD_CLOCK make_thread_cpuclock(0, CPUCLOCK_SCHED)
1581 static int process_cpu_clock_getres(const clockid_t which_clock,
1582 struct timespec64 *tp)
1584 return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1586 static int process_cpu_clock_get(const clockid_t which_clock,
1587 struct timespec64 *tp)
1589 return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1591 static int process_cpu_timer_create(struct k_itimer *timer)
1593 timer->it_clock = PROCESS_CLOCK;
1594 return posix_cpu_timer_create(timer);
1596 static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1597 const struct timespec64 *rqtp)
1599 return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp);
1601 static int thread_cpu_clock_getres(const clockid_t which_clock,
1602 struct timespec64 *tp)
1604 return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1606 static int thread_cpu_clock_get(const clockid_t which_clock,
1607 struct timespec64 *tp)
1609 return posix_cpu_clock_get(THREAD_CLOCK, tp);
1611 static int thread_cpu_timer_create(struct k_itimer *timer)
1613 timer->it_clock = THREAD_CLOCK;
1614 return posix_cpu_timer_create(timer);
1617 const struct k_clock clock_posix_cpu = {
1618 .clock_getres = posix_cpu_clock_getres,
1619 .clock_set = posix_cpu_clock_set,
1620 .clock_get_timespec = posix_cpu_clock_get,
1621 .timer_create = posix_cpu_timer_create,
1622 .nsleep = posix_cpu_nsleep,
1623 .timer_set = posix_cpu_timer_set,
1624 .timer_del = posix_cpu_timer_del,
1625 .timer_get = posix_cpu_timer_get,
1626 .timer_rearm = posix_cpu_timer_rearm,
1629 const struct k_clock clock_process = {
1630 .clock_getres = process_cpu_clock_getres,
1631 .clock_get_timespec = process_cpu_clock_get,
1632 .timer_create = process_cpu_timer_create,
1633 .nsleep = process_cpu_nsleep,
1636 const struct k_clock clock_thread = {
1637 .clock_getres = thread_cpu_clock_getres,
1638 .clock_get_timespec = thread_cpu_clock_get,
1639 .timer_create = thread_cpu_timer_create,