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)
246 u64 curr_cputime = atomic64_read(cputime);
249 if (sum_cputime <= curr_cputime)
251 } while (!atomic64_try_cmpxchg(cputime, &curr_cputime, sum_cputime));
254 static void update_gt_cputime(struct task_cputime_atomic *cputime_atomic,
255 struct task_cputime *sum)
257 __update_gt_cputime(&cputime_atomic->utime, sum->utime);
258 __update_gt_cputime(&cputime_atomic->stime, sum->stime);
259 __update_gt_cputime(&cputime_atomic->sum_exec_runtime, sum->sum_exec_runtime);
263 * thread_group_sample_cputime - Sample cputime for a given task
264 * @tsk: Task for which cputime needs to be started
265 * @samples: Storage for time samples
267 * Called from sys_getitimer() to calculate the expiry time of an active
268 * timer. That means group cputime accounting is already active. Called
269 * with task sighand lock held.
271 * Updates @times with an uptodate sample of the thread group cputimes.
273 void thread_group_sample_cputime(struct task_struct *tsk, u64 *samples)
275 struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
276 struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
278 WARN_ON_ONCE(!pct->timers_active);
280 proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
284 * thread_group_start_cputime - Start cputime and return a sample
285 * @tsk: Task for which cputime needs to be started
286 * @samples: Storage for time samples
288 * The thread group cputime accounting is avoided when there are no posix
289 * CPU timers armed. Before starting a timer it's required to check whether
290 * the time accounting is active. If not, a full update of the atomic
291 * accounting store needs to be done and the accounting enabled.
293 * Updates @times with an uptodate sample of the thread group cputimes.
295 static void thread_group_start_cputime(struct task_struct *tsk, u64 *samples)
297 struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
298 struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
300 lockdep_assert_task_sighand_held(tsk);
302 /* Check if cputimer isn't running. This is accessed without locking. */
303 if (!READ_ONCE(pct->timers_active)) {
304 struct task_cputime sum;
307 * The POSIX timer interface allows for absolute time expiry
308 * values through the TIMER_ABSTIME flag, therefore we have
309 * to synchronize the timer to the clock every time we start it.
311 thread_group_cputime(tsk, &sum);
312 update_gt_cputime(&cputimer->cputime_atomic, &sum);
315 * We're setting timers_active without a lock. Ensure this
316 * only gets written to in one operation. We set it after
317 * update_gt_cputime() as a small optimization, but
318 * barriers are not required because update_gt_cputime()
319 * can handle concurrent updates.
321 WRITE_ONCE(pct->timers_active, true);
323 proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
326 static void __thread_group_cputime(struct task_struct *tsk, u64 *samples)
328 struct task_cputime ct;
330 thread_group_cputime(tsk, &ct);
331 store_samples(samples, ct.stime, ct.utime, ct.sum_exec_runtime);
335 * Sample a process (thread group) clock for the given task clkid. If the
336 * group's cputime accounting is already enabled, read the atomic
337 * store. Otherwise a full update is required. clkid is already validated.
339 static u64 cpu_clock_sample_group(const clockid_t clkid, struct task_struct *p,
342 struct thread_group_cputimer *cputimer = &p->signal->cputimer;
343 struct posix_cputimers *pct = &p->signal->posix_cputimers;
344 u64 samples[CPUCLOCK_MAX];
346 if (!READ_ONCE(pct->timers_active)) {
348 thread_group_start_cputime(p, samples);
350 __thread_group_cputime(p, samples);
352 proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
355 return samples[clkid];
358 static int posix_cpu_clock_get(const clockid_t clock, struct timespec64 *tp)
360 const clockid_t clkid = CPUCLOCK_WHICH(clock);
361 struct task_struct *tsk;
365 tsk = pid_task(pid_for_clock(clock, true), clock_pid_type(clock));
371 if (CPUCLOCK_PERTHREAD(clock))
372 t = cpu_clock_sample(clkid, tsk);
374 t = cpu_clock_sample_group(clkid, tsk, false);
377 *tp = ns_to_timespec64(t);
382 * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
383 * This is called from sys_timer_create() and do_cpu_nanosleep() with the
384 * new timer already all-zeros initialized.
386 static int posix_cpu_timer_create(struct k_itimer *new_timer)
388 static struct lock_class_key posix_cpu_timers_key;
392 pid = pid_for_clock(new_timer->it_clock, false);
399 * If posix timer expiry is handled in task work context then
400 * timer::it_lock can be taken without disabling interrupts as all
401 * other locking happens in task context. This requires a separate
402 * lock class key otherwise regular posix timer expiry would record
403 * the lock class being taken in interrupt context and generate a
404 * false positive warning.
406 if (IS_ENABLED(CONFIG_POSIX_CPU_TIMERS_TASK_WORK))
407 lockdep_set_class(&new_timer->it_lock, &posix_cpu_timers_key);
409 new_timer->kclock = &clock_posix_cpu;
410 timerqueue_init(&new_timer->it.cpu.node);
411 new_timer->it.cpu.pid = get_pid(pid);
416 static struct posix_cputimer_base *timer_base(struct k_itimer *timer,
417 struct task_struct *tsk)
419 int clkidx = CPUCLOCK_WHICH(timer->it_clock);
421 if (CPUCLOCK_PERTHREAD(timer->it_clock))
422 return tsk->posix_cputimers.bases + clkidx;
424 return tsk->signal->posix_cputimers.bases + clkidx;
428 * Force recalculating the base earliest expiration on the next tick.
429 * This will also re-evaluate the need to keep around the process wide
430 * cputime counter and tick dependency and eventually shut these down
433 static void trigger_base_recalc_expires(struct k_itimer *timer,
434 struct task_struct *tsk)
436 struct posix_cputimer_base *base = timer_base(timer, tsk);
442 * Dequeue the timer and reset the base if it was its earliest expiration.
443 * It makes sure the next tick recalculates the base next expiration so we
444 * don't keep the costly process wide cputime counter around for a random
445 * amount of time, along with the tick dependency.
447 * If another timer gets queued between this and the next tick, its
448 * expiration will update the base next event if necessary on the next
451 static void disarm_timer(struct k_itimer *timer, struct task_struct *p)
453 struct cpu_timer *ctmr = &timer->it.cpu;
454 struct posix_cputimer_base *base;
456 if (!cpu_timer_dequeue(ctmr))
459 base = timer_base(timer, p);
460 if (cpu_timer_getexpires(ctmr) == base->nextevt)
461 trigger_base_recalc_expires(timer, p);
466 * Clean up a CPU-clock timer that is about to be destroyed.
467 * This is called from timer deletion with the timer already locked.
468 * If we return TIMER_RETRY, it's necessary to release the timer's lock
469 * and try again. (This happens when the timer is in the middle of firing.)
471 static int posix_cpu_timer_del(struct k_itimer *timer)
473 struct cpu_timer *ctmr = &timer->it.cpu;
474 struct sighand_struct *sighand;
475 struct task_struct *p;
480 p = cpu_timer_task_rcu(timer);
485 * Protect against sighand release/switch in exit/exec and process/
486 * thread timer list entry concurrent read/writes.
488 sighand = lock_task_sighand(p, &flags);
489 if (unlikely(sighand == NULL)) {
491 * This raced with the reaping of the task. The exit cleanup
492 * should have removed this timer from the timer queue.
494 WARN_ON_ONCE(ctmr->head || timerqueue_node_queued(&ctmr->node));
496 if (timer->it.cpu.firing)
499 disarm_timer(timer, p);
501 unlock_task_sighand(p, &flags);
512 static void cleanup_timerqueue(struct timerqueue_head *head)
514 struct timerqueue_node *node;
515 struct cpu_timer *ctmr;
517 while ((node = timerqueue_getnext(head))) {
518 timerqueue_del(head, node);
519 ctmr = container_of(node, struct cpu_timer, node);
525 * Clean out CPU timers which are still armed when a thread exits. The
526 * timers are only removed from the list. No other updates are done. The
527 * corresponding posix timers are still accessible, but cannot be rearmed.
529 * This must be called with the siglock held.
531 static void cleanup_timers(struct posix_cputimers *pct)
533 cleanup_timerqueue(&pct->bases[CPUCLOCK_PROF].tqhead);
534 cleanup_timerqueue(&pct->bases[CPUCLOCK_VIRT].tqhead);
535 cleanup_timerqueue(&pct->bases[CPUCLOCK_SCHED].tqhead);
539 * These are both called with the siglock held, when the current thread
540 * is being reaped. When the final (leader) thread in the group is reaped,
541 * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
543 void posix_cpu_timers_exit(struct task_struct *tsk)
545 cleanup_timers(&tsk->posix_cputimers);
547 void posix_cpu_timers_exit_group(struct task_struct *tsk)
549 cleanup_timers(&tsk->signal->posix_cputimers);
553 * Insert the timer on the appropriate list before any timers that
554 * expire later. This must be called with the sighand lock held.
556 static void arm_timer(struct k_itimer *timer, struct task_struct *p)
558 struct posix_cputimer_base *base = timer_base(timer, p);
559 struct cpu_timer *ctmr = &timer->it.cpu;
560 u64 newexp = cpu_timer_getexpires(ctmr);
562 if (!cpu_timer_enqueue(&base->tqhead, ctmr))
566 * We are the new earliest-expiring POSIX 1.b timer, hence
567 * need to update expiration cache. Take into account that
568 * for process timers we share expiration cache with itimers
569 * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
571 if (newexp < base->nextevt)
572 base->nextevt = newexp;
574 if (CPUCLOCK_PERTHREAD(timer->it_clock))
575 tick_dep_set_task(p, TICK_DEP_BIT_POSIX_TIMER);
577 tick_dep_set_signal(p, TICK_DEP_BIT_POSIX_TIMER);
581 * The timer is locked, fire it and arrange for its reload.
583 static void cpu_timer_fire(struct k_itimer *timer)
585 struct cpu_timer *ctmr = &timer->it.cpu;
587 if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
589 * User don't want any signal.
591 cpu_timer_setexpires(ctmr, 0);
592 } else if (unlikely(timer->sigq == NULL)) {
594 * This a special case for clock_nanosleep,
595 * not a normal timer from sys_timer_create.
597 wake_up_process(timer->it_process);
598 cpu_timer_setexpires(ctmr, 0);
599 } else if (!timer->it_interval) {
601 * One-shot timer. Clear it as soon as it's fired.
603 posix_timer_event(timer, 0);
604 cpu_timer_setexpires(ctmr, 0);
605 } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
607 * The signal did not get queued because the signal
608 * was ignored, so we won't get any callback to
609 * reload the timer. But we need to keep it
610 * ticking in case the signal is deliverable next time.
612 posix_cpu_timer_rearm(timer);
613 ++timer->it_requeue_pending;
618 * Guts of sys_timer_settime for CPU timers.
619 * This is called with the timer locked and interrupts disabled.
620 * If we return TIMER_RETRY, it's necessary to release the timer's lock
621 * and try again. (This happens when the timer is in the middle of firing.)
623 static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
624 struct itimerspec64 *new, struct itimerspec64 *old)
626 clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
627 u64 old_expires, new_expires, old_incr, val;
628 struct cpu_timer *ctmr = &timer->it.cpu;
629 struct sighand_struct *sighand;
630 struct task_struct *p;
635 p = cpu_timer_task_rcu(timer);
638 * If p has just been reaped, we can no
639 * longer get any information about it at all.
646 * Use the to_ktime conversion because that clamps the maximum
647 * value to KTIME_MAX and avoid multiplication overflows.
649 new_expires = ktime_to_ns(timespec64_to_ktime(new->it_value));
652 * Protect against sighand release/switch in exit/exec and p->cpu_timers
653 * and p->signal->cpu_timers read/write in arm_timer()
655 sighand = lock_task_sighand(p, &flags);
657 * If p has just been reaped, we can no
658 * longer get any information about it at all.
660 if (unlikely(sighand == NULL)) {
666 * Disarm any old timer after extracting its expiry time.
668 old_incr = timer->it_interval;
669 old_expires = cpu_timer_getexpires(ctmr);
671 if (unlikely(timer->it.cpu.firing)) {
672 timer->it.cpu.firing = -1;
675 cpu_timer_dequeue(ctmr);
679 * We need to sample the current value to convert the new
680 * value from to relative and absolute, and to convert the
681 * old value from absolute to relative. To set a process
682 * timer, we need a sample to balance the thread expiry
683 * times (in arm_timer). With an absolute time, we must
684 * check if it's already passed. In short, we need a sample.
686 if (CPUCLOCK_PERTHREAD(timer->it_clock))
687 val = cpu_clock_sample(clkid, p);
689 val = cpu_clock_sample_group(clkid, p, true);
692 if (old_expires == 0) {
693 old->it_value.tv_sec = 0;
694 old->it_value.tv_nsec = 0;
697 * Update the timer in case it has overrun already.
698 * If it has, we'll report it as having overrun and
699 * with the next reloaded timer already ticking,
700 * though we are swallowing that pending
701 * notification here to install the new setting.
703 u64 exp = bump_cpu_timer(timer, val);
706 old_expires = exp - val;
707 old->it_value = ns_to_timespec64(old_expires);
709 old->it_value.tv_nsec = 1;
710 old->it_value.tv_sec = 0;
717 * We are colliding with the timer actually firing.
718 * Punt after filling in the timer's old value, and
719 * disable this firing since we are already reporting
720 * it as an overrun (thanks to bump_cpu_timer above).
722 unlock_task_sighand(p, &flags);
726 if (new_expires != 0 && !(timer_flags & TIMER_ABSTIME)) {
731 * Install the new expiry time (or zero).
732 * For a timer with no notification action, we don't actually
733 * arm the timer (we'll just fake it for timer_gettime).
735 cpu_timer_setexpires(ctmr, new_expires);
736 if (new_expires != 0 && val < new_expires) {
740 unlock_task_sighand(p, &flags);
742 * Install the new reload setting, and
743 * set up the signal and overrun bookkeeping.
745 timer->it_interval = timespec64_to_ktime(new->it_interval);
748 * This acts as a modification timestamp for the timer,
749 * so any automatic reload attempt will punt on seeing
750 * that we have reset the timer manually.
752 timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
754 timer->it_overrun_last = 0;
755 timer->it_overrun = -1;
757 if (val >= new_expires) {
758 if (new_expires != 0) {
760 * The designated time already passed, so we notify
761 * immediately, even if the thread never runs to
762 * accumulate more time on this clock.
764 cpu_timer_fire(timer);
768 * Make sure we don't keep around the process wide cputime
769 * counter or the tick dependency if they are not necessary.
771 sighand = lock_task_sighand(p, &flags);
775 if (!cpu_timer_queued(ctmr))
776 trigger_base_recalc_expires(timer, p);
778 unlock_task_sighand(p, &flags);
783 old->it_interval = ns_to_timespec64(old_incr);
788 static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp)
790 clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
791 struct cpu_timer *ctmr = &timer->it.cpu;
792 u64 now, expires = cpu_timer_getexpires(ctmr);
793 struct task_struct *p;
796 p = cpu_timer_task_rcu(timer);
801 * Easy part: convert the reload time.
803 itp->it_interval = ktime_to_timespec64(timer->it_interval);
809 * Sample the clock to take the difference with the expiry time.
811 if (CPUCLOCK_PERTHREAD(timer->it_clock))
812 now = cpu_clock_sample(clkid, p);
814 now = cpu_clock_sample_group(clkid, p, false);
817 itp->it_value = ns_to_timespec64(expires - now);
820 * The timer should have expired already, but the firing
821 * hasn't taken place yet. Say it's just about to expire.
823 itp->it_value.tv_nsec = 1;
824 itp->it_value.tv_sec = 0;
830 #define MAX_COLLECTED 20
832 static u64 collect_timerqueue(struct timerqueue_head *head,
833 struct list_head *firing, u64 now)
835 struct timerqueue_node *next;
838 while ((next = timerqueue_getnext(head))) {
839 struct cpu_timer *ctmr;
842 ctmr = container_of(next, struct cpu_timer, node);
843 expires = cpu_timer_getexpires(ctmr);
844 /* Limit the number of timers to expire at once */
845 if (++i == MAX_COLLECTED || now < expires)
849 cpu_timer_dequeue(ctmr);
850 list_add_tail(&ctmr->elist, firing);
856 static void collect_posix_cputimers(struct posix_cputimers *pct, u64 *samples,
857 struct list_head *firing)
859 struct posix_cputimer_base *base = pct->bases;
862 for (i = 0; i < CPUCLOCK_MAX; i++, base++) {
863 base->nextevt = collect_timerqueue(&base->tqhead, firing,
868 static inline void check_dl_overrun(struct task_struct *tsk)
870 if (tsk->dl.dl_overrun) {
871 tsk->dl.dl_overrun = 0;
872 send_signal_locked(SIGXCPU, SEND_SIG_PRIV, tsk, PIDTYPE_TGID);
876 static bool check_rlimit(u64 time, u64 limit, int signo, bool rt, bool hard)
881 if (print_fatal_signals) {
882 pr_info("%s Watchdog Timeout (%s): %s[%d]\n",
883 rt ? "RT" : "CPU", hard ? "hard" : "soft",
884 current->comm, task_pid_nr(current));
886 send_signal_locked(signo, SEND_SIG_PRIV, current, PIDTYPE_TGID);
891 * Check for any per-thread CPU timers that have fired and move them off
892 * the tsk->cpu_timers[N] list onto the firing list. Here we update the
893 * tsk->it_*_expires values to reflect the remaining thread CPU timers.
895 static void check_thread_timers(struct task_struct *tsk,
896 struct list_head *firing)
898 struct posix_cputimers *pct = &tsk->posix_cputimers;
899 u64 samples[CPUCLOCK_MAX];
903 check_dl_overrun(tsk);
905 if (expiry_cache_is_inactive(pct))
908 task_sample_cputime(tsk, samples);
909 collect_posix_cputimers(pct, samples, firing);
912 * Check for the special case thread timers.
914 soft = task_rlimit(tsk, RLIMIT_RTTIME);
915 if (soft != RLIM_INFINITY) {
916 /* Task RT timeout is accounted in jiffies. RTTIME is usec */
917 unsigned long rttime = tsk->rt.timeout * (USEC_PER_SEC / HZ);
918 unsigned long hard = task_rlimit_max(tsk, RLIMIT_RTTIME);
920 /* At the hard limit, send SIGKILL. No further action. */
921 if (hard != RLIM_INFINITY &&
922 check_rlimit(rttime, hard, SIGKILL, true, true))
925 /* At the soft limit, send a SIGXCPU every second */
926 if (check_rlimit(rttime, soft, SIGXCPU, true, false)) {
927 soft += USEC_PER_SEC;
928 tsk->signal->rlim[RLIMIT_RTTIME].rlim_cur = soft;
932 if (expiry_cache_is_inactive(pct))
933 tick_dep_clear_task(tsk, TICK_DEP_BIT_POSIX_TIMER);
936 static inline void stop_process_timers(struct signal_struct *sig)
938 struct posix_cputimers *pct = &sig->posix_cputimers;
940 /* Turn off the active flag. This is done without locking. */
941 WRITE_ONCE(pct->timers_active, false);
942 tick_dep_clear_signal(sig, TICK_DEP_BIT_POSIX_TIMER);
945 static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
946 u64 *expires, u64 cur_time, int signo)
951 if (cur_time >= it->expires) {
953 it->expires += it->incr;
957 trace_itimer_expire(signo == SIGPROF ?
958 ITIMER_PROF : ITIMER_VIRTUAL,
959 task_tgid(tsk), cur_time);
960 send_signal_locked(signo, SEND_SIG_PRIV, tsk, PIDTYPE_TGID);
963 if (it->expires && it->expires < *expires)
964 *expires = it->expires;
968 * Check for any per-thread CPU timers that have fired and move them
969 * off the tsk->*_timers list onto the firing list. Per-thread timers
970 * have already been taken off.
972 static void check_process_timers(struct task_struct *tsk,
973 struct list_head *firing)
975 struct signal_struct *const sig = tsk->signal;
976 struct posix_cputimers *pct = &sig->posix_cputimers;
977 u64 samples[CPUCLOCK_MAX];
981 * If there are no active process wide timers (POSIX 1.b, itimers,
982 * RLIMIT_CPU) nothing to check. Also skip the process wide timer
983 * processing when there is already another task handling them.
985 if (!READ_ONCE(pct->timers_active) || pct->expiry_active)
989 * Signify that a thread is checking for process timers.
990 * Write access to this field is protected by the sighand lock.
992 pct->expiry_active = true;
995 * Collect the current process totals. Group accounting is active
996 * so the sample can be taken directly.
998 proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic, samples);
999 collect_posix_cputimers(pct, samples, firing);
1002 * Check for the special case process timers.
1004 check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF],
1005 &pct->bases[CPUCLOCK_PROF].nextevt,
1006 samples[CPUCLOCK_PROF], SIGPROF);
1007 check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT],
1008 &pct->bases[CPUCLOCK_VIRT].nextevt,
1009 samples[CPUCLOCK_VIRT], SIGVTALRM);
1011 soft = task_rlimit(tsk, RLIMIT_CPU);
1012 if (soft != RLIM_INFINITY) {
1013 /* RLIMIT_CPU is in seconds. Samples are nanoseconds */
1014 unsigned long hard = task_rlimit_max(tsk, RLIMIT_CPU);
1015 u64 ptime = samples[CPUCLOCK_PROF];
1016 u64 softns = (u64)soft * NSEC_PER_SEC;
1017 u64 hardns = (u64)hard * NSEC_PER_SEC;
1019 /* At the hard limit, send SIGKILL. No further action. */
1020 if (hard != RLIM_INFINITY &&
1021 check_rlimit(ptime, hardns, SIGKILL, false, true))
1024 /* At the soft limit, send a SIGXCPU every second */
1025 if (check_rlimit(ptime, softns, SIGXCPU, false, false)) {
1026 sig->rlim[RLIMIT_CPU].rlim_cur = soft + 1;
1027 softns += NSEC_PER_SEC;
1030 /* Update the expiry cache */
1031 if (softns < pct->bases[CPUCLOCK_PROF].nextevt)
1032 pct->bases[CPUCLOCK_PROF].nextevt = softns;
1035 if (expiry_cache_is_inactive(pct))
1036 stop_process_timers(sig);
1038 pct->expiry_active = false;
1042 * This is called from the signal code (via posixtimer_rearm)
1043 * when the last timer signal was delivered and we have to reload the timer.
1045 static void posix_cpu_timer_rearm(struct k_itimer *timer)
1047 clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
1048 struct task_struct *p;
1049 struct sighand_struct *sighand;
1050 unsigned long flags;
1054 p = cpu_timer_task_rcu(timer);
1058 /* Protect timer list r/w in arm_timer() */
1059 sighand = lock_task_sighand(p, &flags);
1060 if (unlikely(sighand == NULL))
1064 * Fetch the current sample and update the timer's expiry time.
1066 if (CPUCLOCK_PERTHREAD(timer->it_clock))
1067 now = cpu_clock_sample(clkid, p);
1069 now = cpu_clock_sample_group(clkid, p, true);
1071 bump_cpu_timer(timer, now);
1074 * Now re-arm for the new expiry time.
1076 arm_timer(timer, p);
1077 unlock_task_sighand(p, &flags);
1083 * task_cputimers_expired - Check whether posix CPU timers are expired
1085 * @samples: Array of current samples for the CPUCLOCK clocks
1086 * @pct: Pointer to a posix_cputimers container
1088 * Returns true if any member of @samples is greater than the corresponding
1089 * member of @pct->bases[CLK].nextevt. False otherwise
1092 task_cputimers_expired(const u64 *samples, struct posix_cputimers *pct)
1096 for (i = 0; i < CPUCLOCK_MAX; i++) {
1097 if (samples[i] >= pct->bases[i].nextevt)
1104 * fastpath_timer_check - POSIX CPU timers fast path.
1106 * @tsk: The task (thread) being checked.
1108 * Check the task and thread group timers. If both are zero (there are no
1109 * timers set) return false. Otherwise snapshot the task and thread group
1110 * timers and compare them with the corresponding expiration times. Return
1111 * true if a timer has expired, else return false.
1113 static inline bool fastpath_timer_check(struct task_struct *tsk)
1115 struct posix_cputimers *pct = &tsk->posix_cputimers;
1116 struct signal_struct *sig;
1118 if (!expiry_cache_is_inactive(pct)) {
1119 u64 samples[CPUCLOCK_MAX];
1121 task_sample_cputime(tsk, samples);
1122 if (task_cputimers_expired(samples, pct))
1127 pct = &sig->posix_cputimers;
1129 * Check if thread group timers expired when timers are active and
1130 * no other thread in the group is already handling expiry for
1131 * thread group cputimers. These fields are read without the
1132 * sighand lock. However, this is fine because this is meant to be
1133 * a fastpath heuristic to determine whether we should try to
1134 * acquire the sighand lock to handle timer expiry.
1136 * In the worst case scenario, if concurrently timers_active is set
1137 * or expiry_active is cleared, but the current thread doesn't see
1138 * the change yet, the timer checks are delayed until the next
1139 * thread in the group gets a scheduler interrupt to handle the
1140 * timer. This isn't an issue in practice because these types of
1141 * delays with signals actually getting sent are expected.
1143 if (READ_ONCE(pct->timers_active) && !READ_ONCE(pct->expiry_active)) {
1144 u64 samples[CPUCLOCK_MAX];
1146 proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic,
1149 if (task_cputimers_expired(samples, pct))
1153 if (dl_task(tsk) && tsk->dl.dl_overrun)
1159 static void handle_posix_cpu_timers(struct task_struct *tsk);
1161 #ifdef CONFIG_POSIX_CPU_TIMERS_TASK_WORK
1162 static void posix_cpu_timers_work(struct callback_head *work)
1164 handle_posix_cpu_timers(current);
1168 * Clear existing posix CPU timers task work.
1170 void clear_posix_cputimers_work(struct task_struct *p)
1173 * A copied work entry from the old task is not meaningful, clear it.
1174 * N.B. init_task_work will not do this.
1176 memset(&p->posix_cputimers_work.work, 0,
1177 sizeof(p->posix_cputimers_work.work));
1178 init_task_work(&p->posix_cputimers_work.work,
1179 posix_cpu_timers_work);
1180 p->posix_cputimers_work.scheduled = false;
1184 * Initialize posix CPU timers task work in init task. Out of line to
1185 * keep the callback static and to avoid header recursion hell.
1187 void __init posix_cputimers_init_work(void)
1189 clear_posix_cputimers_work(current);
1193 * Note: All operations on tsk->posix_cputimer_work.scheduled happen either
1194 * in hard interrupt context or in task context with interrupts
1195 * disabled. Aside of that the writer/reader interaction is always in the
1196 * context of the current task, which means they are strict per CPU.
1198 static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
1200 return tsk->posix_cputimers_work.scheduled;
1203 static inline void __run_posix_cpu_timers(struct task_struct *tsk)
1205 if (WARN_ON_ONCE(tsk->posix_cputimers_work.scheduled))
1208 /* Schedule task work to actually expire the timers */
1209 tsk->posix_cputimers_work.scheduled = true;
1210 task_work_add(tsk, &tsk->posix_cputimers_work.work, TWA_RESUME);
1213 static inline bool posix_cpu_timers_enable_work(struct task_struct *tsk,
1214 unsigned long start)
1219 * On !RT kernels interrupts are disabled while collecting expired
1220 * timers, so no tick can happen and the fast path check can be
1221 * reenabled without further checks.
1223 if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
1224 tsk->posix_cputimers_work.scheduled = false;
1229 * On RT enabled kernels ticks can happen while the expired timers
1230 * are collected under sighand lock. But any tick which observes
1231 * the CPUTIMERS_WORK_SCHEDULED bit set, does not run the fastpath
1232 * checks. So reenabling the tick work has do be done carefully:
1234 * Disable interrupts and run the fast path check if jiffies have
1235 * advanced since the collecting of expired timers started. If
1236 * jiffies have not advanced or the fast path check did not find
1237 * newly expired timers, reenable the fast path check in the timer
1238 * interrupt. If there are newly expired timers, return false and
1239 * let the collection loop repeat.
1241 local_irq_disable();
1242 if (start != jiffies && fastpath_timer_check(tsk))
1245 tsk->posix_cputimers_work.scheduled = false;
1250 #else /* CONFIG_POSIX_CPU_TIMERS_TASK_WORK */
1251 static inline void __run_posix_cpu_timers(struct task_struct *tsk)
1253 lockdep_posixtimer_enter();
1254 handle_posix_cpu_timers(tsk);
1255 lockdep_posixtimer_exit();
1258 static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
1263 static inline bool posix_cpu_timers_enable_work(struct task_struct *tsk,
1264 unsigned long start)
1268 #endif /* CONFIG_POSIX_CPU_TIMERS_TASK_WORK */
1270 static void handle_posix_cpu_timers(struct task_struct *tsk)
1272 struct k_itimer *timer, *next;
1273 unsigned long flags, start;
1276 if (!lock_task_sighand(tsk, &flags))
1281 * On RT locking sighand lock does not disable interrupts,
1282 * so this needs to be careful vs. ticks. Store the current
1285 start = READ_ONCE(jiffies);
1289 * Here we take off tsk->signal->cpu_timers[N] and
1290 * tsk->cpu_timers[N] all the timers that are firing, and
1291 * put them on the firing list.
1293 check_thread_timers(tsk, &firing);
1295 check_process_timers(tsk, &firing);
1298 * The above timer checks have updated the expiry cache and
1299 * because nothing can have queued or modified timers after
1300 * sighand lock was taken above it is guaranteed to be
1301 * consistent. So the next timer interrupt fastpath check
1302 * will find valid data.
1304 * If timer expiry runs in the timer interrupt context then
1305 * the loop is not relevant as timers will be directly
1306 * expired in interrupt context. The stub function below
1307 * returns always true which allows the compiler to
1308 * optimize the loop out.
1310 * If timer expiry is deferred to task work context then
1311 * the following rules apply:
1313 * - On !RT kernels no tick can have happened on this CPU
1314 * after sighand lock was acquired because interrupts are
1315 * disabled. So reenabling task work before dropping
1316 * sighand lock and reenabling interrupts is race free.
1318 * - On RT kernels ticks might have happened but the tick
1319 * work ignored posix CPU timer handling because the
1320 * CPUTIMERS_WORK_SCHEDULED bit is set. Reenabling work
1321 * must be done very carefully including a check whether
1322 * ticks have happened since the start of the timer
1323 * expiry checks. posix_cpu_timers_enable_work() takes
1324 * care of that and eventually lets the expiry checks
1327 } while (!posix_cpu_timers_enable_work(tsk, start));
1330 * We must release sighand lock before taking any timer's lock.
1331 * There is a potential race with timer deletion here, as the
1332 * siglock now protects our private firing list. We have set
1333 * the firing flag in each timer, so that a deletion attempt
1334 * that gets the timer lock before we do will give it up and
1335 * spin until we've taken care of that timer below.
1337 unlock_task_sighand(tsk, &flags);
1340 * Now that all the timers on our list have the firing flag,
1341 * no one will touch their list entries but us. We'll take
1342 * each timer's lock before clearing its firing flag, so no
1343 * timer call will interfere.
1345 list_for_each_entry_safe(timer, next, &firing, it.cpu.elist) {
1349 * spin_lock() is sufficient here even independent of the
1350 * expiry context. If expiry happens in hard interrupt
1351 * context it's obvious. For task work context it's safe
1352 * because all other operations on timer::it_lock happen in
1353 * task context (syscall or exit).
1355 spin_lock(&timer->it_lock);
1356 list_del_init(&timer->it.cpu.elist);
1357 cpu_firing = timer->it.cpu.firing;
1358 timer->it.cpu.firing = 0;
1360 * The firing flag is -1 if we collided with a reset
1361 * of the timer, which already reported this
1362 * almost-firing as an overrun. So don't generate an event.
1364 if (likely(cpu_firing >= 0))
1365 cpu_timer_fire(timer);
1366 spin_unlock(&timer->it_lock);
1371 * This is called from the timer interrupt handler. The irq handler has
1372 * already updated our counts. We need to check if any timers fire now.
1373 * Interrupts are disabled.
1375 void run_posix_cpu_timers(void)
1377 struct task_struct *tsk = current;
1379 lockdep_assert_irqs_disabled();
1382 * If the actual expiry is deferred to task work context and the
1383 * work is already scheduled there is no point to do anything here.
1385 if (posix_cpu_timers_work_scheduled(tsk))
1389 * The fast path checks that there are no expired thread or thread
1390 * group timers. If that's so, just return.
1392 if (!fastpath_timer_check(tsk))
1395 __run_posix_cpu_timers(tsk);
1399 * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
1400 * The tsk->sighand->siglock must be held by the caller.
1402 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clkid,
1403 u64 *newval, u64 *oldval)
1407 if (WARN_ON_ONCE(clkid >= CPUCLOCK_SCHED))
1410 nextevt = &tsk->signal->posix_cputimers.bases[clkid].nextevt;
1411 now = cpu_clock_sample_group(clkid, tsk, true);
1415 * We are setting itimer. The *oldval is absolute and we update
1416 * it to be relative, *newval argument is relative and we update
1417 * it to be absolute.
1420 if (*oldval <= now) {
1421 /* Just about to fire. */
1422 *oldval = TICK_NSEC;
1433 * Update expiration cache if this is the earliest timer. CPUCLOCK_PROF
1434 * expiry cache is also used by RLIMIT_CPU!.
1436 if (*newval < *nextevt)
1439 tick_dep_set_signal(tsk, TICK_DEP_BIT_POSIX_TIMER);
1442 static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1443 const struct timespec64 *rqtp)
1445 struct itimerspec64 it;
1446 struct k_itimer timer;
1451 * Set up a temporary timer and then wait for it to go off.
1453 memset(&timer, 0, sizeof timer);
1454 spin_lock_init(&timer.it_lock);
1455 timer.it_clock = which_clock;
1456 timer.it_overrun = -1;
1457 error = posix_cpu_timer_create(&timer);
1458 timer.it_process = current;
1461 static struct itimerspec64 zero_it;
1462 struct restart_block *restart;
1464 memset(&it, 0, sizeof(it));
1465 it.it_value = *rqtp;
1467 spin_lock_irq(&timer.it_lock);
1468 error = posix_cpu_timer_set(&timer, flags, &it, NULL);
1470 spin_unlock_irq(&timer.it_lock);
1474 while (!signal_pending(current)) {
1475 if (!cpu_timer_getexpires(&timer.it.cpu)) {
1477 * Our timer fired and was reset, below
1478 * deletion can not fail.
1480 posix_cpu_timer_del(&timer);
1481 spin_unlock_irq(&timer.it_lock);
1486 * Block until cpu_timer_fire (or a signal) wakes us.
1488 __set_current_state(TASK_INTERRUPTIBLE);
1489 spin_unlock_irq(&timer.it_lock);
1491 spin_lock_irq(&timer.it_lock);
1495 * We were interrupted by a signal.
1497 expires = cpu_timer_getexpires(&timer.it.cpu);
1498 error = posix_cpu_timer_set(&timer, 0, &zero_it, &it);
1501 * Timer is now unarmed, deletion can not fail.
1503 posix_cpu_timer_del(&timer);
1505 spin_unlock_irq(&timer.it_lock);
1507 while (error == TIMER_RETRY) {
1509 * We need to handle case when timer was or is in the
1510 * middle of firing. In other cases we already freed
1513 spin_lock_irq(&timer.it_lock);
1514 error = posix_cpu_timer_del(&timer);
1515 spin_unlock_irq(&timer.it_lock);
1518 if ((it.it_value.tv_sec | it.it_value.tv_nsec) == 0) {
1520 * It actually did fire already.
1525 error = -ERESTART_RESTARTBLOCK;
1527 * Report back to the user the time still remaining.
1529 restart = ¤t->restart_block;
1530 restart->nanosleep.expires = expires;
1531 if (restart->nanosleep.type != TT_NONE)
1532 error = nanosleep_copyout(restart, &it.it_value);
1538 static long posix_cpu_nsleep_restart(struct restart_block *restart_block);
1540 static int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1541 const struct timespec64 *rqtp)
1543 struct restart_block *restart_block = ¤t->restart_block;
1547 * Diagnose required errors first.
1549 if (CPUCLOCK_PERTHREAD(which_clock) &&
1550 (CPUCLOCK_PID(which_clock) == 0 ||
1551 CPUCLOCK_PID(which_clock) == task_pid_vnr(current)))
1554 error = do_cpu_nanosleep(which_clock, flags, rqtp);
1556 if (error == -ERESTART_RESTARTBLOCK) {
1558 if (flags & TIMER_ABSTIME)
1559 return -ERESTARTNOHAND;
1561 restart_block->nanosleep.clockid = which_clock;
1562 set_restart_fn(restart_block, posix_cpu_nsleep_restart);
1567 static long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1569 clockid_t which_clock = restart_block->nanosleep.clockid;
1570 struct timespec64 t;
1572 t = ns_to_timespec64(restart_block->nanosleep.expires);
1574 return do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t);
1577 #define PROCESS_CLOCK make_process_cpuclock(0, CPUCLOCK_SCHED)
1578 #define THREAD_CLOCK make_thread_cpuclock(0, CPUCLOCK_SCHED)
1580 static int process_cpu_clock_getres(const clockid_t which_clock,
1581 struct timespec64 *tp)
1583 return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1585 static int process_cpu_clock_get(const clockid_t which_clock,
1586 struct timespec64 *tp)
1588 return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1590 static int process_cpu_timer_create(struct k_itimer *timer)
1592 timer->it_clock = PROCESS_CLOCK;
1593 return posix_cpu_timer_create(timer);
1595 static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1596 const struct timespec64 *rqtp)
1598 return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp);
1600 static int thread_cpu_clock_getres(const clockid_t which_clock,
1601 struct timespec64 *tp)
1603 return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1605 static int thread_cpu_clock_get(const clockid_t which_clock,
1606 struct timespec64 *tp)
1608 return posix_cpu_clock_get(THREAD_CLOCK, tp);
1610 static int thread_cpu_timer_create(struct k_itimer *timer)
1612 timer->it_clock = THREAD_CLOCK;
1613 return posix_cpu_timer_create(timer);
1616 const struct k_clock clock_posix_cpu = {
1617 .clock_getres = posix_cpu_clock_getres,
1618 .clock_set = posix_cpu_clock_set,
1619 .clock_get_timespec = posix_cpu_clock_get,
1620 .timer_create = posix_cpu_timer_create,
1621 .nsleep = posix_cpu_nsleep,
1622 .timer_set = posix_cpu_timer_set,
1623 .timer_del = posix_cpu_timer_del,
1624 .timer_get = posix_cpu_timer_get,
1625 .timer_rearm = posix_cpu_timer_rearm,
1628 const struct k_clock clock_process = {
1629 .clock_getres = process_cpu_clock_getres,
1630 .clock_get_timespec = process_cpu_clock_get,
1631 .timer_create = process_cpu_timer_create,
1632 .nsleep = process_cpu_nsleep,
1635 const struct k_clock clock_thread = {
1636 .clock_getres = thread_cpu_clock_getres,
1637 .clock_get_timespec = thread_cpu_clock_get,
1638 .timer_create = thread_cpu_timer_create,