Root/kernel/posix-cpu-timers.c

1/*
2 * Implement CPU time clocks for the POSIX clock interface.
3 */
4
5#include <linux/sched.h>
6#include <linux/posix-timers.h>
7#include <linux/errno.h>
8#include <linux/math64.h>
9#include <asm/uaccess.h>
10#include <linux/kernel_stat.h>
11#include <trace/events/timer.h>
12#include <linux/random.h>
13#include <linux/tick.h>
14#include <linux/workqueue.h>
15
16/*
17 * Called after updating RLIMIT_CPU to run cpu timer and update
18 * tsk->signal->cputime_expires expiration cache if necessary. Needs
19 * siglock protection since other code may update expiration cache as
20 * well.
21 */
22void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
23{
24    cputime_t cputime = secs_to_cputime(rlim_new);
25
26    spin_lock_irq(&task->sighand->siglock);
27    set_process_cpu_timer(task, CPUCLOCK_PROF, &cputime, NULL);
28    spin_unlock_irq(&task->sighand->siglock);
29}
30
31static int check_clock(const clockid_t which_clock)
32{
33    int error = 0;
34    struct task_struct *p;
35    const pid_t pid = CPUCLOCK_PID(which_clock);
36
37    if (CPUCLOCK_WHICH(which_clock) >= CPUCLOCK_MAX)
38        return -EINVAL;
39
40    if (pid == 0)
41        return 0;
42
43    rcu_read_lock();
44    p = find_task_by_vpid(pid);
45    if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
46           same_thread_group(p, current) : has_group_leader_pid(p))) {
47        error = -EINVAL;
48    }
49    rcu_read_unlock();
50
51    return error;
52}
53
54static inline unsigned long long
55timespec_to_sample(const clockid_t which_clock, const struct timespec *tp)
56{
57    unsigned long long ret;
58
59    ret = 0; /* high half always zero when .cpu used */
60    if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
61        ret = (unsigned long long)tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
62    } else {
63        ret = cputime_to_expires(timespec_to_cputime(tp));
64    }
65    return ret;
66}
67
68static void sample_to_timespec(const clockid_t which_clock,
69                   unsigned long long expires,
70                   struct timespec *tp)
71{
72    if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED)
73        *tp = ns_to_timespec(expires);
74    else
75        cputime_to_timespec((__force cputime_t)expires, tp);
76}
77
78/*
79 * Update expiry time from increment, and increase overrun count,
80 * given the current clock sample.
81 */
82static void bump_cpu_timer(struct k_itimer *timer,
83               unsigned long long now)
84{
85    int i;
86    unsigned long long delta, incr;
87
88    if (timer->it.cpu.incr == 0)
89        return;
90
91    if (now < timer->it.cpu.expires)
92        return;
93
94    incr = timer->it.cpu.incr;
95    delta = now + incr - timer->it.cpu.expires;
96
97    /* Don't use (incr*2 < delta), incr*2 might overflow. */
98    for (i = 0; incr < delta - incr; i++)
99        incr = incr << 1;
100
101    for (; i >= 0; incr >>= 1, i--) {
102        if (delta < incr)
103            continue;
104
105        timer->it.cpu.expires += incr;
106        timer->it_overrun += 1 << i;
107        delta -= incr;
108    }
109}
110
111/**
112 * task_cputime_zero - Check a task_cputime struct for all zero fields.
113 *
114 * @cputime: The struct to compare.
115 *
116 * Checks @cputime to see if all fields are zero. Returns true if all fields
117 * are zero, false if any field is nonzero.
118 */
119static inline int task_cputime_zero(const struct task_cputime *cputime)
120{
121    if (!cputime->utime && !cputime->stime && !cputime->sum_exec_runtime)
122        return 1;
123    return 0;
124}
125
126static inline unsigned long long prof_ticks(struct task_struct *p)
127{
128    cputime_t utime, stime;
129
130    task_cputime(p, &utime, &stime);
131
132    return cputime_to_expires(utime + stime);
133}
134static inline unsigned long long virt_ticks(struct task_struct *p)
135{
136    cputime_t utime;
137
138    task_cputime(p, &utime, NULL);
139
140    return cputime_to_expires(utime);
141}
142
143static int
144posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
145{
146    int error = check_clock(which_clock);
147    if (!error) {
148        tp->tv_sec = 0;
149        tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
150        if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
151            /*
152             * If sched_clock is using a cycle counter, we
153             * don't have any idea of its true resolution
154             * exported, but it is much more than 1s/HZ.
155             */
156            tp->tv_nsec = 1;
157        }
158    }
159    return error;
160}
161
162static int
163posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
164{
165    /*
166     * You can never reset a CPU clock, but we check for other errors
167     * in the call before failing with EPERM.
168     */
169    int error = check_clock(which_clock);
170    if (error == 0) {
171        error = -EPERM;
172    }
173    return error;
174}
175
176
177/*
178 * Sample a per-thread clock for the given task.
179 */
180static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
181                unsigned long long *sample)
182{
183    switch (CPUCLOCK_WHICH(which_clock)) {
184    default:
185        return -EINVAL;
186    case CPUCLOCK_PROF:
187        *sample = prof_ticks(p);
188        break;
189    case CPUCLOCK_VIRT:
190        *sample = virt_ticks(p);
191        break;
192    case CPUCLOCK_SCHED:
193        *sample = task_sched_runtime(p);
194        break;
195    }
196    return 0;
197}
198
199static void update_gt_cputime(struct task_cputime *a, struct task_cputime *b)
200{
201    if (b->utime > a->utime)
202        a->utime = b->utime;
203
204    if (b->stime > a->stime)
205        a->stime = b->stime;
206
207    if (b->sum_exec_runtime > a->sum_exec_runtime)
208        a->sum_exec_runtime = b->sum_exec_runtime;
209}
210
211void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
212{
213    struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
214    struct task_cputime sum;
215    unsigned long flags;
216
217    if (!cputimer->running) {
218        /*
219         * The POSIX timer interface allows for absolute time expiry
220         * values through the TIMER_ABSTIME flag, therefore we have
221         * to synchronize the timer to the clock every time we start
222         * it.
223         */
224        thread_group_cputime(tsk, &sum);
225        raw_spin_lock_irqsave(&cputimer->lock, flags);
226        cputimer->running = 1;
227        update_gt_cputime(&cputimer->cputime, &sum);
228    } else
229        raw_spin_lock_irqsave(&cputimer->lock, flags);
230    *times = cputimer->cputime;
231    raw_spin_unlock_irqrestore(&cputimer->lock, flags);
232}
233
234/*
235 * Sample a process (thread group) clock for the given group_leader task.
236 * Must be called with task sighand lock held for safe while_each_thread()
237 * traversal.
238 */
239static int cpu_clock_sample_group(const clockid_t which_clock,
240                  struct task_struct *p,
241                  unsigned long long *sample)
242{
243    struct task_cputime cputime;
244
245    switch (CPUCLOCK_WHICH(which_clock)) {
246    default:
247        return -EINVAL;
248    case CPUCLOCK_PROF:
249        thread_group_cputime(p, &cputime);
250        *sample = cputime_to_expires(cputime.utime + cputime.stime);
251        break;
252    case CPUCLOCK_VIRT:
253        thread_group_cputime(p, &cputime);
254        *sample = cputime_to_expires(cputime.utime);
255        break;
256    case CPUCLOCK_SCHED:
257        thread_group_cputime(p, &cputime);
258        *sample = cputime.sum_exec_runtime;
259        break;
260    }
261    return 0;
262}
263
264static int posix_cpu_clock_get_task(struct task_struct *tsk,
265                    const clockid_t which_clock,
266                    struct timespec *tp)
267{
268    int err = -EINVAL;
269    unsigned long long rtn;
270
271    if (CPUCLOCK_PERTHREAD(which_clock)) {
272        if (same_thread_group(tsk, current))
273            err = cpu_clock_sample(which_clock, tsk, &rtn);
274    } else {
275        unsigned long flags;
276        struct sighand_struct *sighand;
277
278        /*
279         * while_each_thread() is not yet entirely RCU safe,
280         * keep locking the group while sampling process
281         * clock for now.
282         */
283        sighand = lock_task_sighand(tsk, &flags);
284        if (!sighand)
285            return err;
286
287        if (tsk == current || thread_group_leader(tsk))
288            err = cpu_clock_sample_group(which_clock, tsk, &rtn);
289
290        unlock_task_sighand(tsk, &flags);
291    }
292
293    if (!err)
294        sample_to_timespec(which_clock, rtn, tp);
295
296    return err;
297}
298
299
300static int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
301{
302    const pid_t pid = CPUCLOCK_PID(which_clock);
303    int err = -EINVAL;
304
305    if (pid == 0) {
306        /*
307         * Special case constant value for our own clocks.
308         * We don't have to do any lookup to find ourselves.
309         */
310        err = posix_cpu_clock_get_task(current, which_clock, tp);
311    } else {
312        /*
313         * Find the given PID, and validate that the caller
314         * should be able to see it.
315         */
316        struct task_struct *p;
317        rcu_read_lock();
318        p = find_task_by_vpid(pid);
319        if (p)
320            err = posix_cpu_clock_get_task(p, which_clock, tp);
321        rcu_read_unlock();
322    }
323
324    return err;
325}
326
327
328/*
329 * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
330 * This is called from sys_timer_create() and do_cpu_nanosleep() with the
331 * new timer already all-zeros initialized.
332 */
333static int posix_cpu_timer_create(struct k_itimer *new_timer)
334{
335    int ret = 0;
336    const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
337    struct task_struct *p;
338
339    if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
340        return -EINVAL;
341
342    INIT_LIST_HEAD(&new_timer->it.cpu.entry);
343
344    rcu_read_lock();
345    if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
346        if (pid == 0) {
347            p = current;
348        } else {
349            p = find_task_by_vpid(pid);
350            if (p && !same_thread_group(p, current))
351                p = NULL;
352        }
353    } else {
354        if (pid == 0) {
355            p = current->group_leader;
356        } else {
357            p = find_task_by_vpid(pid);
358            if (p && !has_group_leader_pid(p))
359                p = NULL;
360        }
361    }
362    new_timer->it.cpu.task = p;
363    if (p) {
364        get_task_struct(p);
365    } else {
366        ret = -EINVAL;
367    }
368    rcu_read_unlock();
369
370    return ret;
371}
372
373/*
374 * Clean up a CPU-clock timer that is about to be destroyed.
375 * This is called from timer deletion with the timer already locked.
376 * If we return TIMER_RETRY, it's necessary to release the timer's lock
377 * and try again. (This happens when the timer is in the middle of firing.)
378 */
379static int posix_cpu_timer_del(struct k_itimer *timer)
380{
381    int ret = 0;
382    unsigned long flags;
383    struct sighand_struct *sighand;
384    struct task_struct *p = timer->it.cpu.task;
385
386    WARN_ON_ONCE(p == NULL);
387
388    /*
389     * Protect against sighand release/switch in exit/exec and process/
390     * thread timer list entry concurrent read/writes.
391     */
392    sighand = lock_task_sighand(p, &flags);
393    if (unlikely(sighand == NULL)) {
394        /*
395         * We raced with the reaping of the task.
396         * The deletion should have cleared us off the list.
397         */
398        WARN_ON_ONCE(!list_empty(&timer->it.cpu.entry));
399    } else {
400        if (timer->it.cpu.firing)
401            ret = TIMER_RETRY;
402        else
403            list_del(&timer->it.cpu.entry);
404
405        unlock_task_sighand(p, &flags);
406    }
407
408    if (!ret)
409        put_task_struct(p);
410
411    return ret;
412}
413
414static void cleanup_timers_list(struct list_head *head)
415{
416    struct cpu_timer_list *timer, *next;
417
418    list_for_each_entry_safe(timer, next, head, entry)
419        list_del_init(&timer->entry);
420}
421
422/*
423 * Clean out CPU timers still ticking when a thread exited. The task
424 * pointer is cleared, and the expiry time is replaced with the residual
425 * time for later timer_gettime calls to return.
426 * This must be called with the siglock held.
427 */
428static void cleanup_timers(struct list_head *head)
429{
430    cleanup_timers_list(head);
431    cleanup_timers_list(++head);
432    cleanup_timers_list(++head);
433}
434
435/*
436 * These are both called with the siglock held, when the current thread
437 * is being reaped. When the final (leader) thread in the group is reaped,
438 * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
439 */
440void posix_cpu_timers_exit(struct task_struct *tsk)
441{
442    add_device_randomness((const void*) &tsk->se.sum_exec_runtime,
443                        sizeof(unsigned long long));
444    cleanup_timers(tsk->cpu_timers);
445
446}
447void posix_cpu_timers_exit_group(struct task_struct *tsk)
448{
449    cleanup_timers(tsk->signal->cpu_timers);
450}
451
452static inline int expires_gt(cputime_t expires, cputime_t new_exp)
453{
454    return expires == 0 || expires > new_exp;
455}
456
457/*
458 * Insert the timer on the appropriate list before any timers that
459 * expire later. This must be called with the sighand lock held.
460 */
461static void arm_timer(struct k_itimer *timer)
462{
463    struct task_struct *p = timer->it.cpu.task;
464    struct list_head *head, *listpos;
465    struct task_cputime *cputime_expires;
466    struct cpu_timer_list *const nt = &timer->it.cpu;
467    struct cpu_timer_list *next;
468
469    if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
470        head = p->cpu_timers;
471        cputime_expires = &p->cputime_expires;
472    } else {
473        head = p->signal->cpu_timers;
474        cputime_expires = &p->signal->cputime_expires;
475    }
476    head += CPUCLOCK_WHICH(timer->it_clock);
477
478    listpos = head;
479    list_for_each_entry(next, head, entry) {
480        if (nt->expires < next->expires)
481            break;
482        listpos = &next->entry;
483    }
484    list_add(&nt->entry, listpos);
485
486    if (listpos == head) {
487        unsigned long long exp = nt->expires;
488
489        /*
490         * We are the new earliest-expiring POSIX 1.b timer, hence
491         * need to update expiration cache. Take into account that
492         * for process timers we share expiration cache with itimers
493         * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
494         */
495
496        switch (CPUCLOCK_WHICH(timer->it_clock)) {
497        case CPUCLOCK_PROF:
498            if (expires_gt(cputime_expires->prof_exp, expires_to_cputime(exp)))
499                cputime_expires->prof_exp = expires_to_cputime(exp);
500            break;
501        case CPUCLOCK_VIRT:
502            if (expires_gt(cputime_expires->virt_exp, expires_to_cputime(exp)))
503                cputime_expires->virt_exp = expires_to_cputime(exp);
504            break;
505        case CPUCLOCK_SCHED:
506            if (cputime_expires->sched_exp == 0 ||
507                cputime_expires->sched_exp > exp)
508                cputime_expires->sched_exp = exp;
509            break;
510        }
511    }
512}
513
514/*
515 * The timer is locked, fire it and arrange for its reload.
516 */
517static void cpu_timer_fire(struct k_itimer *timer)
518{
519    if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
520        /*
521         * User don't want any signal.
522         */
523        timer->it.cpu.expires = 0;
524    } else if (unlikely(timer->sigq == NULL)) {
525        /*
526         * This a special case for clock_nanosleep,
527         * not a normal timer from sys_timer_create.
528         */
529        wake_up_process(timer->it_process);
530        timer->it.cpu.expires = 0;
531    } else if (timer->it.cpu.incr == 0) {
532        /*
533         * One-shot timer. Clear it as soon as it's fired.
534         */
535        posix_timer_event(timer, 0);
536        timer->it.cpu.expires = 0;
537    } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
538        /*
539         * The signal did not get queued because the signal
540         * was ignored, so we won't get any callback to
541         * reload the timer. But we need to keep it
542         * ticking in case the signal is deliverable next time.
543         */
544        posix_cpu_timer_schedule(timer);
545    }
546}
547
548/*
549 * Sample a process (thread group) timer for the given group_leader task.
550 * Must be called with task sighand lock held for safe while_each_thread()
551 * traversal.
552 */
553static int cpu_timer_sample_group(const clockid_t which_clock,
554                  struct task_struct *p,
555                  unsigned long long *sample)
556{
557    struct task_cputime cputime;
558
559    thread_group_cputimer(p, &cputime);
560    switch (CPUCLOCK_WHICH(which_clock)) {
561    default:
562        return -EINVAL;
563    case CPUCLOCK_PROF:
564        *sample = cputime_to_expires(cputime.utime + cputime.stime);
565        break;
566    case CPUCLOCK_VIRT:
567        *sample = cputime_to_expires(cputime.utime);
568        break;
569    case CPUCLOCK_SCHED:
570        *sample = cputime.sum_exec_runtime + task_delta_exec(p);
571        break;
572    }
573    return 0;
574}
575
576#ifdef CONFIG_NO_HZ_FULL
577static void nohz_kick_work_fn(struct work_struct *work)
578{
579    tick_nohz_full_kick_all();
580}
581
582static DECLARE_WORK(nohz_kick_work, nohz_kick_work_fn);
583
584/*
585 * We need the IPIs to be sent from sane process context.
586 * The posix cpu timers are always set with irqs disabled.
587 */
588static void posix_cpu_timer_kick_nohz(void)
589{
590    if (context_tracking_is_enabled())
591        schedule_work(&nohz_kick_work);
592}
593
594bool posix_cpu_timers_can_stop_tick(struct task_struct *tsk)
595{
596    if (!task_cputime_zero(&tsk->cputime_expires))
597        return false;
598
599    if (tsk->signal->cputimer.running)
600        return false;
601
602    return true;
603}
604#else
605static inline void posix_cpu_timer_kick_nohz(void) { }
606#endif
607
608/*
609 * Guts of sys_timer_settime for CPU timers.
610 * This is called with the timer locked and interrupts disabled.
611 * If we return TIMER_RETRY, it's necessary to release the timer's lock
612 * and try again. (This happens when the timer is in the middle of firing.)
613 */
614static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
615                   struct itimerspec *new, struct itimerspec *old)
616{
617    unsigned long flags;
618    struct sighand_struct *sighand;
619    struct task_struct *p = timer->it.cpu.task;
620    unsigned long long old_expires, new_expires, old_incr, val;
621    int ret;
622
623    WARN_ON_ONCE(p == NULL);
624
625    new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
626
627    /*
628     * Protect against sighand release/switch in exit/exec and p->cpu_timers
629     * and p->signal->cpu_timers read/write in arm_timer()
630     */
631    sighand = lock_task_sighand(p, &flags);
632    /*
633     * If p has just been reaped, we can no
634     * longer get any information about it at all.
635     */
636    if (unlikely(sighand == NULL)) {
637        return -ESRCH;
638    }
639
640    /*
641     * Disarm any old timer after extracting its expiry time.
642     */
643    WARN_ON_ONCE(!irqs_disabled());
644
645    ret = 0;
646    old_incr = timer->it.cpu.incr;
647    old_expires = timer->it.cpu.expires;
648    if (unlikely(timer->it.cpu.firing)) {
649        timer->it.cpu.firing = -1;
650        ret = TIMER_RETRY;
651    } else
652        list_del_init(&timer->it.cpu.entry);
653
654    /*
655     * We need to sample the current value to convert the new
656     * value from to relative and absolute, and to convert the
657     * old value from absolute to relative. To set a process
658     * timer, we need a sample to balance the thread expiry
659     * times (in arm_timer). With an absolute time, we must
660     * check if it's already passed. In short, we need a sample.
661     */
662    if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
663        cpu_clock_sample(timer->it_clock, p, &val);
664    } else {
665        cpu_timer_sample_group(timer->it_clock, p, &val);
666    }
667
668    if (old) {
669        if (old_expires == 0) {
670            old->it_value.tv_sec = 0;
671            old->it_value.tv_nsec = 0;
672        } else {
673            /*
674             * Update the timer in case it has
675             * overrun already. If it has,
676             * we'll report it as having overrun
677             * and with the next reloaded timer
678             * already ticking, though we are
679             * swallowing that pending
680             * notification here to install the
681             * new setting.
682             */
683            bump_cpu_timer(timer, val);
684            if (val < timer->it.cpu.expires) {
685                old_expires = timer->it.cpu.expires - val;
686                sample_to_timespec(timer->it_clock,
687                           old_expires,
688                           &old->it_value);
689            } else {
690                old->it_value.tv_nsec = 1;
691                old->it_value.tv_sec = 0;
692            }
693        }
694    }
695
696    if (unlikely(ret)) {
697        /*
698         * We are colliding with the timer actually firing.
699         * Punt after filling in the timer's old value, and
700         * disable this firing since we are already reporting
701         * it as an overrun (thanks to bump_cpu_timer above).
702         */
703        unlock_task_sighand(p, &flags);
704        goto out;
705    }
706
707    if (new_expires != 0 && !(timer_flags & TIMER_ABSTIME)) {
708        new_expires += val;
709    }
710
711    /*
712     * Install the new expiry time (or zero).
713     * For a timer with no notification action, we don't actually
714     * arm the timer (we'll just fake it for timer_gettime).
715     */
716    timer->it.cpu.expires = new_expires;
717    if (new_expires != 0 && val < new_expires) {
718        arm_timer(timer);
719    }
720
721    unlock_task_sighand(p, &flags);
722    /*
723     * Install the new reload setting, and
724     * set up the signal and overrun bookkeeping.
725     */
726    timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
727                        &new->it_interval);
728
729    /*
730     * This acts as a modification timestamp for the timer,
731     * so any automatic reload attempt will punt on seeing
732     * that we have reset the timer manually.
733     */
734    timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
735        ~REQUEUE_PENDING;
736    timer->it_overrun_last = 0;
737    timer->it_overrun = -1;
738
739    if (new_expires != 0 && !(val < new_expires)) {
740        /*
741         * The designated time already passed, so we notify
742         * immediately, even if the thread never runs to
743         * accumulate more time on this clock.
744         */
745        cpu_timer_fire(timer);
746    }
747
748    ret = 0;
749 out:
750    if (old) {
751        sample_to_timespec(timer->it_clock,
752                   old_incr, &old->it_interval);
753    }
754    if (!ret)
755        posix_cpu_timer_kick_nohz();
756    return ret;
757}
758
759static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
760{
761    unsigned long long now;
762    struct task_struct *p = timer->it.cpu.task;
763
764    WARN_ON_ONCE(p == NULL);
765
766    /*
767     * Easy part: convert the reload time.
768     */
769    sample_to_timespec(timer->it_clock,
770               timer->it.cpu.incr, &itp->it_interval);
771
772    if (timer->it.cpu.expires == 0) { /* Timer not armed at all. */
773        itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
774        return;
775    }
776
777    /*
778     * Sample the clock to take the difference with the expiry time.
779     */
780    if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
781        cpu_clock_sample(timer->it_clock, p, &now);
782    } else {
783        struct sighand_struct *sighand;
784        unsigned long flags;
785
786        /*
787         * Protect against sighand release/switch in exit/exec and
788         * also make timer sampling safe if it ends up calling
789         * thread_group_cputime().
790         */
791        sighand = lock_task_sighand(p, &flags);
792        if (unlikely(sighand == NULL)) {
793            /*
794             * The process has been reaped.
795             * We can't even collect a sample any more.
796             * Call the timer disarmed, nothing else to do.
797             */
798            timer->it.cpu.expires = 0;
799            sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
800                       &itp->it_value);
801        } else {
802            cpu_timer_sample_group(timer->it_clock, p, &now);
803            unlock_task_sighand(p, &flags);
804        }
805    }
806
807    if (now < timer->it.cpu.expires) {
808        sample_to_timespec(timer->it_clock,
809                   timer->it.cpu.expires - now,
810                   &itp->it_value);
811    } else {
812        /*
813         * The timer should have expired already, but the firing
814         * hasn't taken place yet. Say it's just about to expire.
815         */
816        itp->it_value.tv_nsec = 1;
817        itp->it_value.tv_sec = 0;
818    }
819}
820
821static unsigned long long
822check_timers_list(struct list_head *timers,
823          struct list_head *firing,
824          unsigned long long curr)
825{
826    int maxfire = 20;
827
828    while (!list_empty(timers)) {
829        struct cpu_timer_list *t;
830
831        t = list_first_entry(timers, struct cpu_timer_list, entry);
832
833        if (!--maxfire || curr < t->expires)
834            return t->expires;
835
836        t->firing = 1;
837        list_move_tail(&t->entry, firing);
838    }
839
840    return 0;
841}
842
843/*
844 * Check for any per-thread CPU timers that have fired and move them off
845 * the tsk->cpu_timers[N] list onto the firing list. Here we update the
846 * tsk->it_*_expires values to reflect the remaining thread CPU timers.
847 */
848static void check_thread_timers(struct task_struct *tsk,
849                struct list_head *firing)
850{
851    struct list_head *timers = tsk->cpu_timers;
852    struct signal_struct *const sig = tsk->signal;
853    struct task_cputime *tsk_expires = &tsk->cputime_expires;
854    unsigned long long expires;
855    unsigned long soft;
856
857    expires = check_timers_list(timers, firing, prof_ticks(tsk));
858    tsk_expires->prof_exp = expires_to_cputime(expires);
859
860    expires = check_timers_list(++timers, firing, virt_ticks(tsk));
861    tsk_expires->virt_exp = expires_to_cputime(expires);
862
863    tsk_expires->sched_exp = check_timers_list(++timers, firing,
864                           tsk->se.sum_exec_runtime);
865
866    /*
867     * Check for the special case thread timers.
868     */
869    soft = ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
870    if (soft != RLIM_INFINITY) {
871        unsigned long hard =
872            ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);
873
874        if (hard != RLIM_INFINITY &&
875            tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
876            /*
877             * At the hard limit, we just die.
878             * No need to calculate anything else now.
879             */
880            __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
881            return;
882        }
883        if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {
884            /*
885             * At the soft limit, send a SIGXCPU every second.
886             */
887            if (soft < hard) {
888                soft += USEC_PER_SEC;
889                sig->rlim[RLIMIT_RTTIME].rlim_cur = soft;
890            }
891            printk(KERN_INFO
892                "RT Watchdog Timeout: %s[%d]\n",
893                tsk->comm, task_pid_nr(tsk));
894            __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
895        }
896    }
897}
898
899static void stop_process_timers(struct signal_struct *sig)
900{
901    struct thread_group_cputimer *cputimer = &sig->cputimer;
902    unsigned long flags;
903
904    raw_spin_lock_irqsave(&cputimer->lock, flags);
905    cputimer->running = 0;
906    raw_spin_unlock_irqrestore(&cputimer->lock, flags);
907}
908
909static u32 onecputick;
910
911static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
912                 unsigned long long *expires,
913                 unsigned long long cur_time, int signo)
914{
915    if (!it->expires)
916        return;
917
918    if (cur_time >= it->expires) {
919        if (it->incr) {
920            it->expires += it->incr;
921            it->error += it->incr_error;
922            if (it->error >= onecputick) {
923                it->expires -= cputime_one_jiffy;
924                it->error -= onecputick;
925            }
926        } else {
927            it->expires = 0;
928        }
929
930        trace_itimer_expire(signo == SIGPROF ?
931                    ITIMER_PROF : ITIMER_VIRTUAL,
932                    tsk->signal->leader_pid, cur_time);
933        __group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
934    }
935
936    if (it->expires && (!*expires || it->expires < *expires)) {
937        *expires = it->expires;
938    }
939}
940
941/*
942 * Check for any per-thread CPU timers that have fired and move them
943 * off the tsk->*_timers list onto the firing list. Per-thread timers
944 * have already been taken off.
945 */
946static void check_process_timers(struct task_struct *tsk,
947                 struct list_head *firing)
948{
949    struct signal_struct *const sig = tsk->signal;
950    unsigned long long utime, ptime, virt_expires, prof_expires;
951    unsigned long long sum_sched_runtime, sched_expires;
952    struct list_head *timers = sig->cpu_timers;
953    struct task_cputime cputime;
954    unsigned long soft;
955
956    /*
957     * Collect the current process totals.
958     */
959    thread_group_cputimer(tsk, &cputime);
960    utime = cputime_to_expires(cputime.utime);
961    ptime = utime + cputime_to_expires(cputime.stime);
962    sum_sched_runtime = cputime.sum_exec_runtime;
963
964    prof_expires = check_timers_list(timers, firing, ptime);
965    virt_expires = check_timers_list(++timers, firing, utime);
966    sched_expires = check_timers_list(++timers, firing, sum_sched_runtime);
967
968    /*
969     * Check for the special case process timers.
970     */
971    check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime,
972             SIGPROF);
973    check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
974             SIGVTALRM);
975    soft = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
976    if (soft != RLIM_INFINITY) {
977        unsigned long psecs = cputime_to_secs(ptime);
978        unsigned long hard =
979            ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
980        cputime_t x;
981        if (psecs >= hard) {
982            /*
983             * At the hard limit, we just die.
984             * No need to calculate anything else now.
985             */
986            __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
987            return;
988        }
989        if (psecs >= soft) {
990            /*
991             * At the soft limit, send a SIGXCPU every second.
992             */
993            __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
994            if (soft < hard) {
995                soft++;
996                sig->rlim[RLIMIT_CPU].rlim_cur = soft;
997            }
998        }
999        x = secs_to_cputime(soft);
1000        if (!prof_expires || x < prof_expires) {
1001            prof_expires = x;
1002        }
1003    }
1004
1005    sig->cputime_expires.prof_exp = expires_to_cputime(prof_expires);
1006    sig->cputime_expires.virt_exp = expires_to_cputime(virt_expires);
1007    sig->cputime_expires.sched_exp = sched_expires;
1008    if (task_cputime_zero(&sig->cputime_expires))
1009        stop_process_timers(sig);
1010}
1011
1012/*
1013 * This is called from the signal code (via do_schedule_next_timer)
1014 * when the last timer signal was delivered and we have to reload the timer.
1015 */
1016void posix_cpu_timer_schedule(struct k_itimer *timer)
1017{
1018    struct sighand_struct *sighand;
1019    unsigned long flags;
1020    struct task_struct *p = timer->it.cpu.task;
1021    unsigned long long now;
1022
1023    WARN_ON_ONCE(p == NULL);
1024
1025    /*
1026     * Fetch the current sample and update the timer's expiry time.
1027     */
1028    if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1029        cpu_clock_sample(timer->it_clock, p, &now);
1030        bump_cpu_timer(timer, now);
1031        if (unlikely(p->exit_state))
1032            goto out;
1033
1034        /* Protect timer list r/w in arm_timer() */
1035        sighand = lock_task_sighand(p, &flags);
1036        if (!sighand)
1037            goto out;
1038    } else {
1039        /*
1040         * Protect arm_timer() and timer sampling in case of call to
1041         * thread_group_cputime().
1042         */
1043        sighand = lock_task_sighand(p, &flags);
1044        if (unlikely(sighand == NULL)) {
1045            /*
1046             * The process has been reaped.
1047             * We can't even collect a sample any more.
1048             */
1049            timer->it.cpu.expires = 0;
1050            goto out;
1051        } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1052            unlock_task_sighand(p, &flags);
1053            /* Optimizations: if the process is dying, no need to rearm */
1054            goto out;
1055        }
1056        cpu_timer_sample_group(timer->it_clock, p, &now);
1057        bump_cpu_timer(timer, now);
1058        /* Leave the sighand locked for the call below. */
1059    }
1060
1061    /*
1062     * Now re-arm for the new expiry time.
1063     */
1064    WARN_ON_ONCE(!irqs_disabled());
1065    arm_timer(timer);
1066    unlock_task_sighand(p, &flags);
1067
1068    /* Kick full dynticks CPUs in case they need to tick on the new timer */
1069    posix_cpu_timer_kick_nohz();
1070out:
1071    timer->it_overrun_last = timer->it_overrun;
1072    timer->it_overrun = -1;
1073    ++timer->it_requeue_pending;
1074}
1075
1076/**
1077 * task_cputime_expired - Compare two task_cputime entities.
1078 *
1079 * @sample: The task_cputime structure to be checked for expiration.
1080 * @expires: Expiration times, against which @sample will be checked.
1081 *
1082 * Checks @sample against @expires to see if any field of @sample has expired.
1083 * Returns true if any field of the former is greater than the corresponding
1084 * field of the latter if the latter field is set. Otherwise returns false.
1085 */
1086static inline int task_cputime_expired(const struct task_cputime *sample,
1087                    const struct task_cputime *expires)
1088{
1089    if (expires->utime && sample->utime >= expires->utime)
1090        return 1;
1091    if (expires->stime && sample->utime + sample->stime >= expires->stime)
1092        return 1;
1093    if (expires->sum_exec_runtime != 0 &&
1094        sample->sum_exec_runtime >= expires->sum_exec_runtime)
1095        return 1;
1096    return 0;
1097}
1098
1099/**
1100 * fastpath_timer_check - POSIX CPU timers fast path.
1101 *
1102 * @tsk: The task (thread) being checked.
1103 *
1104 * Check the task and thread group timers. If both are zero (there are no
1105 * timers set) return false. Otherwise snapshot the task and thread group
1106 * timers and compare them with the corresponding expiration times. Return
1107 * true if a timer has expired, else return false.
1108 */
1109static inline int fastpath_timer_check(struct task_struct *tsk)
1110{
1111    struct signal_struct *sig;
1112    cputime_t utime, stime;
1113
1114    task_cputime(tsk, &utime, &stime);
1115
1116    if (!task_cputime_zero(&tsk->cputime_expires)) {
1117        struct task_cputime task_sample = {
1118            .utime = utime,
1119            .stime = stime,
1120            .sum_exec_runtime = tsk->se.sum_exec_runtime
1121        };
1122
1123        if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
1124            return 1;
1125    }
1126
1127    sig = tsk->signal;
1128    if (sig->cputimer.running) {
1129        struct task_cputime group_sample;
1130
1131        raw_spin_lock(&sig->cputimer.lock);
1132        group_sample = sig->cputimer.cputime;
1133        raw_spin_unlock(&sig->cputimer.lock);
1134
1135        if (task_cputime_expired(&group_sample, &sig->cputime_expires))
1136            return 1;
1137    }
1138
1139    return 0;
1140}
1141
1142/*
1143 * This is called from the timer interrupt handler. The irq handler has
1144 * already updated our counts. We need to check if any timers fire now.
1145 * Interrupts are disabled.
1146 */
1147void run_posix_cpu_timers(struct task_struct *tsk)
1148{
1149    LIST_HEAD(firing);
1150    struct k_itimer *timer, *next;
1151    unsigned long flags;
1152
1153    WARN_ON_ONCE(!irqs_disabled());
1154
1155    /*
1156     * The fast path checks that there are no expired thread or thread
1157     * group timers. If that's so, just return.
1158     */
1159    if (!fastpath_timer_check(tsk))
1160        return;
1161
1162    if (!lock_task_sighand(tsk, &flags))
1163        return;
1164    /*
1165     * Here we take off tsk->signal->cpu_timers[N] and
1166     * tsk->cpu_timers[N] all the timers that are firing, and
1167     * put them on the firing list.
1168     */
1169    check_thread_timers(tsk, &firing);
1170    /*
1171     * If there are any active process wide timers (POSIX 1.b, itimers,
1172     * RLIMIT_CPU) cputimer must be running.
1173     */
1174    if (tsk->signal->cputimer.running)
1175        check_process_timers(tsk, &firing);
1176
1177    /*
1178     * We must release these locks before taking any timer's lock.
1179     * There is a potential race with timer deletion here, as the
1180     * siglock now protects our private firing list. We have set
1181     * the firing flag in each timer, so that a deletion attempt
1182     * that gets the timer lock before we do will give it up and
1183     * spin until we've taken care of that timer below.
1184     */
1185    unlock_task_sighand(tsk, &flags);
1186
1187    /*
1188     * Now that all the timers on our list have the firing flag,
1189     * no one will touch their list entries but us. We'll take
1190     * each timer's lock before clearing its firing flag, so no
1191     * timer call will interfere.
1192     */
1193    list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1194        int cpu_firing;
1195
1196        spin_lock(&timer->it_lock);
1197        list_del_init(&timer->it.cpu.entry);
1198        cpu_firing = timer->it.cpu.firing;
1199        timer->it.cpu.firing = 0;
1200        /*
1201         * The firing flag is -1 if we collided with a reset
1202         * of the timer, which already reported this
1203         * almost-firing as an overrun. So don't generate an event.
1204         */
1205        if (likely(cpu_firing >= 0))
1206            cpu_timer_fire(timer);
1207        spin_unlock(&timer->it_lock);
1208    }
1209}
1210
1211/*
1212 * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
1213 * The tsk->sighand->siglock must be held by the caller.
1214 */
1215void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1216               cputime_t *newval, cputime_t *oldval)
1217{
1218    unsigned long long now;
1219
1220    WARN_ON_ONCE(clock_idx == CPUCLOCK_SCHED);
1221    cpu_timer_sample_group(clock_idx, tsk, &now);
1222
1223    if (oldval) {
1224        /*
1225         * We are setting itimer. The *oldval is absolute and we update
1226         * it to be relative, *newval argument is relative and we update
1227         * it to be absolute.
1228         */
1229        if (*oldval) {
1230            if (*oldval <= now) {
1231                /* Just about to fire. */
1232                *oldval = cputime_one_jiffy;
1233            } else {
1234                *oldval -= now;
1235            }
1236        }
1237
1238        if (!*newval)
1239            goto out;
1240        *newval += now;
1241    }
1242
1243    /*
1244     * Update expiration cache if we are the earliest timer, or eventually
1245     * RLIMIT_CPU limit is earlier than prof_exp cpu timer expire.
1246     */
1247    switch (clock_idx) {
1248    case CPUCLOCK_PROF:
1249        if (expires_gt(tsk->signal->cputime_expires.prof_exp, *newval))
1250            tsk->signal->cputime_expires.prof_exp = *newval;
1251        break;
1252    case CPUCLOCK_VIRT:
1253        if (expires_gt(tsk->signal->cputime_expires.virt_exp, *newval))
1254            tsk->signal->cputime_expires.virt_exp = *newval;
1255        break;
1256    }
1257out:
1258    posix_cpu_timer_kick_nohz();
1259}
1260
1261static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1262                struct timespec *rqtp, struct itimerspec *it)
1263{
1264    struct k_itimer timer;
1265    int error;
1266
1267    /*
1268     * Set up a temporary timer and then wait for it to go off.
1269     */
1270    memset(&timer, 0, sizeof timer);
1271    spin_lock_init(&timer.it_lock);
1272    timer.it_clock = which_clock;
1273    timer.it_overrun = -1;
1274    error = posix_cpu_timer_create(&timer);
1275    timer.it_process = current;
1276    if (!error) {
1277        static struct itimerspec zero_it;
1278
1279        memset(it, 0, sizeof *it);
1280        it->it_value = *rqtp;
1281
1282        spin_lock_irq(&timer.it_lock);
1283        error = posix_cpu_timer_set(&timer, flags, it, NULL);
1284        if (error) {
1285            spin_unlock_irq(&timer.it_lock);
1286            return error;
1287        }
1288
1289        while (!signal_pending(current)) {
1290            if (timer.it.cpu.expires == 0) {
1291                /*
1292                 * Our timer fired and was reset, below
1293                 * deletion can not fail.
1294                 */
1295                posix_cpu_timer_del(&timer);
1296                spin_unlock_irq(&timer.it_lock);
1297                return 0;
1298            }
1299
1300            /*
1301             * Block until cpu_timer_fire (or a signal) wakes us.
1302             */
1303            __set_current_state(TASK_INTERRUPTIBLE);
1304            spin_unlock_irq(&timer.it_lock);
1305            schedule();
1306            spin_lock_irq(&timer.it_lock);
1307        }
1308
1309        /*
1310         * We were interrupted by a signal.
1311         */
1312        sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
1313        error = posix_cpu_timer_set(&timer, 0, &zero_it, it);
1314        if (!error) {
1315            /*
1316             * Timer is now unarmed, deletion can not fail.
1317             */
1318            posix_cpu_timer_del(&timer);
1319        }
1320        spin_unlock_irq(&timer.it_lock);
1321
1322        while (error == TIMER_RETRY) {
1323            /*
1324             * We need to handle case when timer was or is in the
1325             * middle of firing. In other cases we already freed
1326             * resources.
1327             */
1328            spin_lock_irq(&timer.it_lock);
1329            error = posix_cpu_timer_del(&timer);
1330            spin_unlock_irq(&timer.it_lock);
1331        }
1332
1333        if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
1334            /*
1335             * It actually did fire already.
1336             */
1337            return 0;
1338        }
1339
1340        error = -ERESTART_RESTARTBLOCK;
1341    }
1342
1343    return error;
1344}
1345
1346static long posix_cpu_nsleep_restart(struct restart_block *restart_block);
1347
1348static int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1349                struct timespec *rqtp, struct timespec __user *rmtp)
1350{
1351    struct restart_block *restart_block =
1352        &current_thread_info()->restart_block;
1353    struct itimerspec it;
1354    int error;
1355
1356    /*
1357     * Diagnose required errors first.
1358     */
1359    if (CPUCLOCK_PERTHREAD(which_clock) &&
1360        (CPUCLOCK_PID(which_clock) == 0 ||
1361         CPUCLOCK_PID(which_clock) == current->pid))
1362        return -EINVAL;
1363
1364    error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);
1365
1366    if (error == -ERESTART_RESTARTBLOCK) {
1367
1368        if (flags & TIMER_ABSTIME)
1369            return -ERESTARTNOHAND;
1370        /*
1371         * Report back to the user the time still remaining.
1372         */
1373        if (rmtp && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1374            return -EFAULT;
1375
1376        restart_block->fn = posix_cpu_nsleep_restart;
1377        restart_block->nanosleep.clockid = which_clock;
1378        restart_block->nanosleep.rmtp = rmtp;
1379        restart_block->nanosleep.expires = timespec_to_ns(rqtp);
1380    }
1381    return error;
1382}
1383
1384static long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1385{
1386    clockid_t which_clock = restart_block->nanosleep.clockid;
1387    struct timespec t;
1388    struct itimerspec it;
1389    int error;
1390
1391    t = ns_to_timespec(restart_block->nanosleep.expires);
1392
1393    error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);
1394
1395    if (error == -ERESTART_RESTARTBLOCK) {
1396        struct timespec __user *rmtp = restart_block->nanosleep.rmtp;
1397        /*
1398         * Report back to the user the time still remaining.
1399         */
1400        if (rmtp && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1401            return -EFAULT;
1402
1403        restart_block->nanosleep.expires = timespec_to_ns(&t);
1404    }
1405    return error;
1406
1407}
1408
1409#define PROCESS_CLOCK MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
1410#define THREAD_CLOCK MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
1411
1412static int process_cpu_clock_getres(const clockid_t which_clock,
1413                    struct timespec *tp)
1414{
1415    return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1416}
1417static int process_cpu_clock_get(const clockid_t which_clock,
1418                 struct timespec *tp)
1419{
1420    return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1421}
1422static int process_cpu_timer_create(struct k_itimer *timer)
1423{
1424    timer->it_clock = PROCESS_CLOCK;
1425    return posix_cpu_timer_create(timer);
1426}
1427static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1428                  struct timespec *rqtp,
1429                  struct timespec __user *rmtp)
1430{
1431    return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
1432}
1433static long process_cpu_nsleep_restart(struct restart_block *restart_block)
1434{
1435    return -EINVAL;
1436}
1437static int thread_cpu_clock_getres(const clockid_t which_clock,
1438                   struct timespec *tp)
1439{
1440    return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1441}
1442static int thread_cpu_clock_get(const clockid_t which_clock,
1443                struct timespec *tp)
1444{
1445    return posix_cpu_clock_get(THREAD_CLOCK, tp);
1446}
1447static int thread_cpu_timer_create(struct k_itimer *timer)
1448{
1449    timer->it_clock = THREAD_CLOCK;
1450    return posix_cpu_timer_create(timer);
1451}
1452
1453struct k_clock clock_posix_cpu = {
1454    .clock_getres = posix_cpu_clock_getres,
1455    .clock_set = posix_cpu_clock_set,
1456    .clock_get = posix_cpu_clock_get,
1457    .timer_create = posix_cpu_timer_create,
1458    .nsleep = posix_cpu_nsleep,
1459    .nsleep_restart = posix_cpu_nsleep_restart,
1460    .timer_set = posix_cpu_timer_set,
1461    .timer_del = posix_cpu_timer_del,
1462    .timer_get = posix_cpu_timer_get,
1463};
1464
1465static __init int init_posix_cpu_timers(void)
1466{
1467    struct k_clock process = {
1468        .clock_getres = process_cpu_clock_getres,
1469        .clock_get = process_cpu_clock_get,
1470        .timer_create = process_cpu_timer_create,
1471        .nsleep = process_cpu_nsleep,
1472        .nsleep_restart = process_cpu_nsleep_restart,
1473    };
1474    struct k_clock thread = {
1475        .clock_getres = thread_cpu_clock_getres,
1476        .clock_get = thread_cpu_clock_get,
1477        .timer_create = thread_cpu_timer_create,
1478    };
1479    struct timespec ts;
1480
1481    posix_timers_register_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
1482    posix_timers_register_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
1483
1484    cputime_to_timespec(cputime_one_jiffy, &ts);
1485    onecputick = ts.tv_nsec;
1486    WARN_ON(ts.tv_sec != 0);
1487
1488    return 0;
1489}
1490__initcall(init_posix_cpu_timers);
1491

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