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
13/*
14 * Called after updating RLIMIT_CPU to run cpu timer and update
15 * tsk->signal->cputime_expires expiration cache if necessary. Needs
16 * siglock protection since other code may update expiration cache as
17 * well.
18 */
19void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
20{
21    cputime_t cputime = secs_to_cputime(rlim_new);
22
23    spin_lock_irq(&task->sighand->siglock);
24    set_process_cpu_timer(task, CPUCLOCK_PROF, &cputime, NULL);
25    spin_unlock_irq(&task->sighand->siglock);
26}
27
28static int check_clock(const clockid_t which_clock)
29{
30    int error = 0;
31    struct task_struct *p;
32    const pid_t pid = CPUCLOCK_PID(which_clock);
33
34    if (CPUCLOCK_WHICH(which_clock) >= CPUCLOCK_MAX)
35        return -EINVAL;
36
37    if (pid == 0)
38        return 0;
39
40    read_lock(&tasklist_lock);
41    p = find_task_by_vpid(pid);
42    if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
43           same_thread_group(p, current) : thread_group_leader(p))) {
44        error = -EINVAL;
45    }
46    read_unlock(&tasklist_lock);
47
48    return error;
49}
50
51static inline union cpu_time_count
52timespec_to_sample(const clockid_t which_clock, const struct timespec *tp)
53{
54    union cpu_time_count ret;
55    ret.sched = 0; /* high half always zero when .cpu used */
56    if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
57        ret.sched = (unsigned long long)tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
58    } else {
59        ret.cpu = timespec_to_cputime(tp);
60    }
61    return ret;
62}
63
64static void sample_to_timespec(const clockid_t which_clock,
65                   union cpu_time_count cpu,
66                   struct timespec *tp)
67{
68    if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED)
69        *tp = ns_to_timespec(cpu.sched);
70    else
71        cputime_to_timespec(cpu.cpu, tp);
72}
73
74static inline int cpu_time_before(const clockid_t which_clock,
75                  union cpu_time_count now,
76                  union cpu_time_count then)
77{
78    if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
79        return now.sched < then.sched;
80    } else {
81        return cputime_lt(now.cpu, then.cpu);
82    }
83}
84static inline void cpu_time_add(const clockid_t which_clock,
85                union cpu_time_count *acc,
86                    union cpu_time_count val)
87{
88    if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
89        acc->sched += val.sched;
90    } else {
91        acc->cpu = cputime_add(acc->cpu, val.cpu);
92    }
93}
94static inline union cpu_time_count cpu_time_sub(const clockid_t which_clock,
95                        union cpu_time_count a,
96                        union cpu_time_count b)
97{
98    if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
99        a.sched -= b.sched;
100    } else {
101        a.cpu = cputime_sub(a.cpu, b.cpu);
102    }
103    return a;
104}
105
106/*
107 * Divide and limit the result to res >= 1
108 *
109 * This is necessary to prevent signal delivery starvation, when the result of
110 * the division would be rounded down to 0.
111 */
112static inline cputime_t cputime_div_non_zero(cputime_t time, unsigned long div)
113{
114    cputime_t res = cputime_div(time, div);
115
116    return max_t(cputime_t, res, 1);
117}
118
119/*
120 * Update expiry time from increment, and increase overrun count,
121 * given the current clock sample.
122 */
123static void bump_cpu_timer(struct k_itimer *timer,
124                  union cpu_time_count now)
125{
126    int i;
127
128    if (timer->it.cpu.incr.sched == 0)
129        return;
130
131    if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
132        unsigned long long delta, incr;
133
134        if (now.sched < timer->it.cpu.expires.sched)
135            return;
136        incr = timer->it.cpu.incr.sched;
137        delta = now.sched + incr - timer->it.cpu.expires.sched;
138        /* Don't use (incr*2 < delta), incr*2 might overflow. */
139        for (i = 0; incr < delta - incr; i++)
140            incr = incr << 1;
141        for (; i >= 0; incr >>= 1, i--) {
142            if (delta < incr)
143                continue;
144            timer->it.cpu.expires.sched += incr;
145            timer->it_overrun += 1 << i;
146            delta -= incr;
147        }
148    } else {
149        cputime_t delta, incr;
150
151        if (cputime_lt(now.cpu, timer->it.cpu.expires.cpu))
152            return;
153        incr = timer->it.cpu.incr.cpu;
154        delta = cputime_sub(cputime_add(now.cpu, incr),
155                    timer->it.cpu.expires.cpu);
156        /* Don't use (incr*2 < delta), incr*2 might overflow. */
157        for (i = 0; cputime_lt(incr, cputime_sub(delta, incr)); i++)
158                 incr = cputime_add(incr, incr);
159        for (; i >= 0; incr = cputime_halve(incr), i--) {
160            if (cputime_lt(delta, incr))
161                continue;
162            timer->it.cpu.expires.cpu =
163                cputime_add(timer->it.cpu.expires.cpu, incr);
164            timer->it_overrun += 1 << i;
165            delta = cputime_sub(delta, incr);
166        }
167    }
168}
169
170static inline cputime_t prof_ticks(struct task_struct *p)
171{
172    return cputime_add(p->utime, p->stime);
173}
174static inline cputime_t virt_ticks(struct task_struct *p)
175{
176    return p->utime;
177}
178
179int posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
180{
181    int error = check_clock(which_clock);
182    if (!error) {
183        tp->tv_sec = 0;
184        tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
185        if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
186            /*
187             * If sched_clock is using a cycle counter, we
188             * don't have any idea of its true resolution
189             * exported, but it is much more than 1s/HZ.
190             */
191            tp->tv_nsec = 1;
192        }
193    }
194    return error;
195}
196
197int posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
198{
199    /*
200     * You can never reset a CPU clock, but we check for other errors
201     * in the call before failing with EPERM.
202     */
203    int error = check_clock(which_clock);
204    if (error == 0) {
205        error = -EPERM;
206    }
207    return error;
208}
209
210
211/*
212 * Sample a per-thread clock for the given task.
213 */
214static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
215                union cpu_time_count *cpu)
216{
217    switch (CPUCLOCK_WHICH(which_clock)) {
218    default:
219        return -EINVAL;
220    case CPUCLOCK_PROF:
221        cpu->cpu = prof_ticks(p);
222        break;
223    case CPUCLOCK_VIRT:
224        cpu->cpu = virt_ticks(p);
225        break;
226    case CPUCLOCK_SCHED:
227        cpu->sched = task_sched_runtime(p);
228        break;
229    }
230    return 0;
231}
232
233void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
234{
235    struct signal_struct *sig = tsk->signal;
236    struct task_struct *t;
237
238    times->utime = sig->utime;
239    times->stime = sig->stime;
240    times->sum_exec_runtime = sig->sum_sched_runtime;
241
242    rcu_read_lock();
243    /* make sure we can trust tsk->thread_group list */
244    if (!likely(pid_alive(tsk)))
245        goto out;
246
247    t = tsk;
248    do {
249        times->utime = cputime_add(times->utime, t->utime);
250        times->stime = cputime_add(times->stime, t->stime);
251        times->sum_exec_runtime += t->se.sum_exec_runtime;
252    } while_each_thread(tsk, t);
253out:
254    rcu_read_unlock();
255}
256
257static void update_gt_cputime(struct task_cputime *a, struct task_cputime *b)
258{
259    if (cputime_gt(b->utime, a->utime))
260        a->utime = b->utime;
261
262    if (cputime_gt(b->stime, a->stime))
263        a->stime = b->stime;
264
265    if (b->sum_exec_runtime > a->sum_exec_runtime)
266        a->sum_exec_runtime = b->sum_exec_runtime;
267}
268
269void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
270{
271    struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
272    struct task_cputime sum;
273    unsigned long flags;
274
275    spin_lock_irqsave(&cputimer->lock, flags);
276    if (!cputimer->running) {
277        cputimer->running = 1;
278        /*
279         * The POSIX timer interface allows for absolute time expiry
280         * values through the TIMER_ABSTIME flag, therefore we have
281         * to synchronize the timer to the clock every time we start
282         * it.
283         */
284        thread_group_cputime(tsk, &sum);
285        update_gt_cputime(&cputimer->cputime, &sum);
286    }
287    *times = cputimer->cputime;
288    spin_unlock_irqrestore(&cputimer->lock, flags);
289}
290
291/*
292 * Sample a process (thread group) clock for the given group_leader task.
293 * Must be called with tasklist_lock held for reading.
294 */
295static int cpu_clock_sample_group(const clockid_t which_clock,
296                  struct task_struct *p,
297                  union cpu_time_count *cpu)
298{
299    struct task_cputime cputime;
300
301    switch (CPUCLOCK_WHICH(which_clock)) {
302    default:
303        return -EINVAL;
304    case CPUCLOCK_PROF:
305        thread_group_cputime(p, &cputime);
306        cpu->cpu = cputime_add(cputime.utime, cputime.stime);
307        break;
308    case CPUCLOCK_VIRT:
309        thread_group_cputime(p, &cputime);
310        cpu->cpu = cputime.utime;
311        break;
312    case CPUCLOCK_SCHED:
313        cpu->sched = thread_group_sched_runtime(p);
314        break;
315    }
316    return 0;
317}
318
319
320int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
321{
322    const pid_t pid = CPUCLOCK_PID(which_clock);
323    int error = -EINVAL;
324    union cpu_time_count rtn;
325
326    if (pid == 0) {
327        /*
328         * Special case constant value for our own clocks.
329         * We don't have to do any lookup to find ourselves.
330         */
331        if (CPUCLOCK_PERTHREAD(which_clock)) {
332            /*
333             * Sampling just ourselves we can do with no locking.
334             */
335            error = cpu_clock_sample(which_clock,
336                         current, &rtn);
337        } else {
338            read_lock(&tasklist_lock);
339            error = cpu_clock_sample_group(which_clock,
340                               current, &rtn);
341            read_unlock(&tasklist_lock);
342        }
343    } else {
344        /*
345         * Find the given PID, and validate that the caller
346         * should be able to see it.
347         */
348        struct task_struct *p;
349        rcu_read_lock();
350        p = find_task_by_vpid(pid);
351        if (p) {
352            if (CPUCLOCK_PERTHREAD(which_clock)) {
353                if (same_thread_group(p, current)) {
354                    error = cpu_clock_sample(which_clock,
355                                 p, &rtn);
356                }
357            } else {
358                read_lock(&tasklist_lock);
359                if (thread_group_leader(p) && p->sighand) {
360                    error =
361                        cpu_clock_sample_group(which_clock,
362                                       p, &rtn);
363                }
364                read_unlock(&tasklist_lock);
365            }
366        }
367        rcu_read_unlock();
368    }
369
370    if (error)
371        return error;
372    sample_to_timespec(which_clock, rtn, tp);
373    return 0;
374}
375
376
377/*
378 * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
379 * This is called from sys_timer_create() and do_cpu_nanosleep() with the
380 * new timer already all-zeros initialized.
381 */
382int posix_cpu_timer_create(struct k_itimer *new_timer)
383{
384    int ret = 0;
385    const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
386    struct task_struct *p;
387
388    if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
389        return -EINVAL;
390
391    INIT_LIST_HEAD(&new_timer->it.cpu.entry);
392
393    read_lock(&tasklist_lock);
394    if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
395        if (pid == 0) {
396            p = current;
397        } else {
398            p = find_task_by_vpid(pid);
399            if (p && !same_thread_group(p, current))
400                p = NULL;
401        }
402    } else {
403        if (pid == 0) {
404            p = current->group_leader;
405        } else {
406            p = find_task_by_vpid(pid);
407            if (p && !thread_group_leader(p))
408                p = NULL;
409        }
410    }
411    new_timer->it.cpu.task = p;
412    if (p) {
413        get_task_struct(p);
414    } else {
415        ret = -EINVAL;
416    }
417    read_unlock(&tasklist_lock);
418
419    return ret;
420}
421
422/*
423 * Clean up a CPU-clock timer that is about to be destroyed.
424 * This is called from timer deletion with the timer already locked.
425 * If we return TIMER_RETRY, it's necessary to release the timer's lock
426 * and try again. (This happens when the timer is in the middle of firing.)
427 */
428int posix_cpu_timer_del(struct k_itimer *timer)
429{
430    struct task_struct *p = timer->it.cpu.task;
431    int ret = 0;
432
433    if (likely(p != NULL)) {
434        read_lock(&tasklist_lock);
435        if (unlikely(p->sighand == NULL)) {
436            /*
437             * We raced with the reaping of the task.
438             * The deletion should have cleared us off the list.
439             */
440            BUG_ON(!list_empty(&timer->it.cpu.entry));
441        } else {
442            spin_lock(&p->sighand->siglock);
443            if (timer->it.cpu.firing)
444                ret = TIMER_RETRY;
445            else
446                list_del(&timer->it.cpu.entry);
447            spin_unlock(&p->sighand->siglock);
448        }
449        read_unlock(&tasklist_lock);
450
451        if (!ret)
452            put_task_struct(p);
453    }
454
455    return ret;
456}
457
458/*
459 * Clean out CPU timers still ticking when a thread exited. The task
460 * pointer is cleared, and the expiry time is replaced with the residual
461 * time for later timer_gettime calls to return.
462 * This must be called with the siglock held.
463 */
464static void cleanup_timers(struct list_head *head,
465               cputime_t utime, cputime_t stime,
466               unsigned long long sum_exec_runtime)
467{
468    struct cpu_timer_list *timer, *next;
469    cputime_t ptime = cputime_add(utime, stime);
470
471    list_for_each_entry_safe(timer, next, head, entry) {
472        list_del_init(&timer->entry);
473        if (cputime_lt(timer->expires.cpu, ptime)) {
474            timer->expires.cpu = cputime_zero;
475        } else {
476            timer->expires.cpu = cputime_sub(timer->expires.cpu,
477                             ptime);
478        }
479    }
480
481    ++head;
482    list_for_each_entry_safe(timer, next, head, entry) {
483        list_del_init(&timer->entry);
484        if (cputime_lt(timer->expires.cpu, utime)) {
485            timer->expires.cpu = cputime_zero;
486        } else {
487            timer->expires.cpu = cputime_sub(timer->expires.cpu,
488                             utime);
489        }
490    }
491
492    ++head;
493    list_for_each_entry_safe(timer, next, head, entry) {
494        list_del_init(&timer->entry);
495        if (timer->expires.sched < sum_exec_runtime) {
496            timer->expires.sched = 0;
497        } else {
498            timer->expires.sched -= sum_exec_runtime;
499        }
500    }
501}
502
503/*
504 * These are both called with the siglock held, when the current thread
505 * is being reaped. When the final (leader) thread in the group is reaped,
506 * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
507 */
508void posix_cpu_timers_exit(struct task_struct *tsk)
509{
510    cleanup_timers(tsk->cpu_timers,
511               tsk->utime, tsk->stime, tsk->se.sum_exec_runtime);
512
513}
514void posix_cpu_timers_exit_group(struct task_struct *tsk)
515{
516    struct signal_struct *const sig = tsk->signal;
517
518    cleanup_timers(tsk->signal->cpu_timers,
519               cputime_add(tsk->utime, sig->utime),
520               cputime_add(tsk->stime, sig->stime),
521               tsk->se.sum_exec_runtime + sig->sum_sched_runtime);
522}
523
524static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
525{
526    /*
527     * That's all for this thread or process.
528     * We leave our residual in expires to be reported.
529     */
530    put_task_struct(timer->it.cpu.task);
531    timer->it.cpu.task = NULL;
532    timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
533                         timer->it.cpu.expires,
534                         now);
535}
536
537static inline int expires_gt(cputime_t expires, cputime_t new_exp)
538{
539    return cputime_eq(expires, cputime_zero) ||
540           cputime_gt(expires, new_exp);
541}
542
543/*
544 * Insert the timer on the appropriate list before any timers that
545 * expire later. This must be called with the tasklist_lock held
546 * for reading, interrupts disabled and p->sighand->siglock taken.
547 */
548static void arm_timer(struct k_itimer *timer)
549{
550    struct task_struct *p = timer->it.cpu.task;
551    struct list_head *head, *listpos;
552    struct task_cputime *cputime_expires;
553    struct cpu_timer_list *const nt = &timer->it.cpu;
554    struct cpu_timer_list *next;
555
556    if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
557        head = p->cpu_timers;
558        cputime_expires = &p->cputime_expires;
559    } else {
560        head = p->signal->cpu_timers;
561        cputime_expires = &p->signal->cputime_expires;
562    }
563    head += CPUCLOCK_WHICH(timer->it_clock);
564
565    listpos = head;
566    list_for_each_entry(next, head, entry) {
567        if (cpu_time_before(timer->it_clock, nt->expires, next->expires))
568            break;
569        listpos = &next->entry;
570    }
571    list_add(&nt->entry, listpos);
572
573    if (listpos == head) {
574        union cpu_time_count *exp = &nt->expires;
575
576        /*
577         * We are the new earliest-expiring POSIX 1.b timer, hence
578         * need to update expiration cache. Take into account that
579         * for process timers we share expiration cache with itimers
580         * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
581         */
582
583        switch (CPUCLOCK_WHICH(timer->it_clock)) {
584        case CPUCLOCK_PROF:
585            if (expires_gt(cputime_expires->prof_exp, exp->cpu))
586                cputime_expires->prof_exp = exp->cpu;
587            break;
588        case CPUCLOCK_VIRT:
589            if (expires_gt(cputime_expires->virt_exp, exp->cpu))
590                cputime_expires->virt_exp = exp->cpu;
591            break;
592        case CPUCLOCK_SCHED:
593            if (cputime_expires->sched_exp == 0 ||
594                cputime_expires->sched_exp > exp->sched)
595                cputime_expires->sched_exp = exp->sched;
596            break;
597        }
598    }
599}
600
601/*
602 * The timer is locked, fire it and arrange for its reload.
603 */
604static void cpu_timer_fire(struct k_itimer *timer)
605{
606    if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
607        /*
608         * User don't want any signal.
609         */
610        timer->it.cpu.expires.sched = 0;
611    } else if (unlikely(timer->sigq == NULL)) {
612        /*
613         * This a special case for clock_nanosleep,
614         * not a normal timer from sys_timer_create.
615         */
616        wake_up_process(timer->it_process);
617        timer->it.cpu.expires.sched = 0;
618    } else if (timer->it.cpu.incr.sched == 0) {
619        /*
620         * One-shot timer. Clear it as soon as it's fired.
621         */
622        posix_timer_event(timer, 0);
623        timer->it.cpu.expires.sched = 0;
624    } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
625        /*
626         * The signal did not get queued because the signal
627         * was ignored, so we won't get any callback to
628         * reload the timer. But we need to keep it
629         * ticking in case the signal is deliverable next time.
630         */
631        posix_cpu_timer_schedule(timer);
632    }
633}
634
635/*
636 * Sample a process (thread group) timer for the given group_leader task.
637 * Must be called with tasklist_lock held for reading.
638 */
639static int cpu_timer_sample_group(const clockid_t which_clock,
640                  struct task_struct *p,
641                  union cpu_time_count *cpu)
642{
643    struct task_cputime cputime;
644
645    thread_group_cputimer(p, &cputime);
646    switch (CPUCLOCK_WHICH(which_clock)) {
647    default:
648        return -EINVAL;
649    case CPUCLOCK_PROF:
650        cpu->cpu = cputime_add(cputime.utime, cputime.stime);
651        break;
652    case CPUCLOCK_VIRT:
653        cpu->cpu = cputime.utime;
654        break;
655    case CPUCLOCK_SCHED:
656        cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
657        break;
658    }
659    return 0;
660}
661
662/*
663 * Guts of sys_timer_settime for CPU timers.
664 * This is called with the timer locked and interrupts disabled.
665 * If we return TIMER_RETRY, it's necessary to release the timer's lock
666 * and try again. (This happens when the timer is in the middle of firing.)
667 */
668int posix_cpu_timer_set(struct k_itimer *timer, int flags,
669            struct itimerspec *new, struct itimerspec *old)
670{
671    struct task_struct *p = timer->it.cpu.task;
672    union cpu_time_count old_expires, new_expires, old_incr, val;
673    int ret;
674
675    if (unlikely(p == NULL)) {
676        /*
677         * Timer refers to a dead task's clock.
678         */
679        return -ESRCH;
680    }
681
682    new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
683
684    read_lock(&tasklist_lock);
685    /*
686     * We need the tasklist_lock to protect against reaping that
687     * clears p->sighand. If p has just been reaped, we can no
688     * longer get any information about it at all.
689     */
690    if (unlikely(p->sighand == NULL)) {
691        read_unlock(&tasklist_lock);
692        put_task_struct(p);
693        timer->it.cpu.task = NULL;
694        return -ESRCH;
695    }
696
697    /*
698     * Disarm any old timer after extracting its expiry time.
699     */
700    BUG_ON(!irqs_disabled());
701
702    ret = 0;
703    old_incr = timer->it.cpu.incr;
704    spin_lock(&p->sighand->siglock);
705    old_expires = timer->it.cpu.expires;
706    if (unlikely(timer->it.cpu.firing)) {
707        timer->it.cpu.firing = -1;
708        ret = TIMER_RETRY;
709    } else
710        list_del_init(&timer->it.cpu.entry);
711
712    /*
713     * We need to sample the current value to convert the new
714     * value from to relative and absolute, and to convert the
715     * old value from absolute to relative. To set a process
716     * timer, we need a sample to balance the thread expiry
717     * times (in arm_timer). With an absolute time, we must
718     * check if it's already passed. In short, we need a sample.
719     */
720    if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
721        cpu_clock_sample(timer->it_clock, p, &val);
722    } else {
723        cpu_timer_sample_group(timer->it_clock, p, &val);
724    }
725
726    if (old) {
727        if (old_expires.sched == 0) {
728            old->it_value.tv_sec = 0;
729            old->it_value.tv_nsec = 0;
730        } else {
731            /*
732             * Update the timer in case it has
733             * overrun already. If it has,
734             * we'll report it as having overrun
735             * and with the next reloaded timer
736             * already ticking, though we are
737             * swallowing that pending
738             * notification here to install the
739             * new setting.
740             */
741            bump_cpu_timer(timer, val);
742            if (cpu_time_before(timer->it_clock, val,
743                        timer->it.cpu.expires)) {
744                old_expires = cpu_time_sub(
745                    timer->it_clock,
746                    timer->it.cpu.expires, val);
747                sample_to_timespec(timer->it_clock,
748                           old_expires,
749                           &old->it_value);
750            } else {
751                old->it_value.tv_nsec = 1;
752                old->it_value.tv_sec = 0;
753            }
754        }
755    }
756
757    if (unlikely(ret)) {
758        /*
759         * We are colliding with the timer actually firing.
760         * Punt after filling in the timer's old value, and
761         * disable this firing since we are already reporting
762         * it as an overrun (thanks to bump_cpu_timer above).
763         */
764        spin_unlock(&p->sighand->siglock);
765        read_unlock(&tasklist_lock);
766        goto out;
767    }
768
769    if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
770        cpu_time_add(timer->it_clock, &new_expires, val);
771    }
772
773    /*
774     * Install the new expiry time (or zero).
775     * For a timer with no notification action, we don't actually
776     * arm the timer (we'll just fake it for timer_gettime).
777     */
778    timer->it.cpu.expires = new_expires;
779    if (new_expires.sched != 0 &&
780        cpu_time_before(timer->it_clock, val, new_expires)) {
781        arm_timer(timer);
782    }
783
784    spin_unlock(&p->sighand->siglock);
785    read_unlock(&tasklist_lock);
786
787    /*
788     * Install the new reload setting, and
789     * set up the signal and overrun bookkeeping.
790     */
791    timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
792                        &new->it_interval);
793
794    /*
795     * This acts as a modification timestamp for the timer,
796     * so any automatic reload attempt will punt on seeing
797     * that we have reset the timer manually.
798     */
799    timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
800        ~REQUEUE_PENDING;
801    timer->it_overrun_last = 0;
802    timer->it_overrun = -1;
803
804    if (new_expires.sched != 0 &&
805        !cpu_time_before(timer->it_clock, val, new_expires)) {
806        /*
807         * The designated time already passed, so we notify
808         * immediately, even if the thread never runs to
809         * accumulate more time on this clock.
810         */
811        cpu_timer_fire(timer);
812    }
813
814    ret = 0;
815 out:
816    if (old) {
817        sample_to_timespec(timer->it_clock,
818                   old_incr, &old->it_interval);
819    }
820    return ret;
821}
822
823void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
824{
825    union cpu_time_count now;
826    struct task_struct *p = timer->it.cpu.task;
827    int clear_dead;
828
829    /*
830     * Easy part: convert the reload time.
831     */
832    sample_to_timespec(timer->it_clock,
833               timer->it.cpu.incr, &itp->it_interval);
834
835    if (timer->it.cpu.expires.sched == 0) { /* Timer not armed at all. */
836        itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
837        return;
838    }
839
840    if (unlikely(p == NULL)) {
841        /*
842         * This task already died and the timer will never fire.
843         * In this case, expires is actually the dead value.
844         */
845    dead:
846        sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
847                   &itp->it_value);
848        return;
849    }
850
851    /*
852     * Sample the clock to take the difference with the expiry time.
853     */
854    if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
855        cpu_clock_sample(timer->it_clock, p, &now);
856        clear_dead = p->exit_state;
857    } else {
858        read_lock(&tasklist_lock);
859        if (unlikely(p->sighand == NULL)) {
860            /*
861             * The process has been reaped.
862             * We can't even collect a sample any more.
863             * Call the timer disarmed, nothing else to do.
864             */
865            put_task_struct(p);
866            timer->it.cpu.task = NULL;
867            timer->it.cpu.expires.sched = 0;
868            read_unlock(&tasklist_lock);
869            goto dead;
870        } else {
871            cpu_timer_sample_group(timer->it_clock, p, &now);
872            clear_dead = (unlikely(p->exit_state) &&
873                      thread_group_empty(p));
874        }
875        read_unlock(&tasklist_lock);
876    }
877
878    if (unlikely(clear_dead)) {
879        /*
880         * We've noticed that the thread is dead, but
881         * not yet reaped. Take this opportunity to
882         * drop our task ref.
883         */
884        clear_dead_task(timer, now);
885        goto dead;
886    }
887
888    if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
889        sample_to_timespec(timer->it_clock,
890                   cpu_time_sub(timer->it_clock,
891                        timer->it.cpu.expires, now),
892                   &itp->it_value);
893    } else {
894        /*
895         * The timer should have expired already, but the firing
896         * hasn't taken place yet. Say it's just about to expire.
897         */
898        itp->it_value.tv_nsec = 1;
899        itp->it_value.tv_sec = 0;
900    }
901}
902
903/*
904 * Check for any per-thread CPU timers that have fired and move them off
905 * the tsk->cpu_timers[N] list onto the firing list. Here we update the
906 * tsk->it_*_expires values to reflect the remaining thread CPU timers.
907 */
908static void check_thread_timers(struct task_struct *tsk,
909                struct list_head *firing)
910{
911    int maxfire;
912    struct list_head *timers = tsk->cpu_timers;
913    struct signal_struct *const sig = tsk->signal;
914    unsigned long soft;
915
916    maxfire = 20;
917    tsk->cputime_expires.prof_exp = cputime_zero;
918    while (!list_empty(timers)) {
919        struct cpu_timer_list *t = list_first_entry(timers,
920                              struct cpu_timer_list,
921                              entry);
922        if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
923            tsk->cputime_expires.prof_exp = t->expires.cpu;
924            break;
925        }
926        t->firing = 1;
927        list_move_tail(&t->entry, firing);
928    }
929
930    ++timers;
931    maxfire = 20;
932    tsk->cputime_expires.virt_exp = cputime_zero;
933    while (!list_empty(timers)) {
934        struct cpu_timer_list *t = list_first_entry(timers,
935                              struct cpu_timer_list,
936                              entry);
937        if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
938            tsk->cputime_expires.virt_exp = t->expires.cpu;
939            break;
940        }
941        t->firing = 1;
942        list_move_tail(&t->entry, firing);
943    }
944
945    ++timers;
946    maxfire = 20;
947    tsk->cputime_expires.sched_exp = 0;
948    while (!list_empty(timers)) {
949        struct cpu_timer_list *t = list_first_entry(timers,
950                              struct cpu_timer_list,
951                              entry);
952        if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
953            tsk->cputime_expires.sched_exp = t->expires.sched;
954            break;
955        }
956        t->firing = 1;
957        list_move_tail(&t->entry, firing);
958    }
959
960    /*
961     * Check for the special case thread timers.
962     */
963    soft = ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
964    if (soft != RLIM_INFINITY) {
965        unsigned long hard =
966            ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);
967
968        if (hard != RLIM_INFINITY &&
969            tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
970            /*
971             * At the hard limit, we just die.
972             * No need to calculate anything else now.
973             */
974            __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
975            return;
976        }
977        if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {
978            /*
979             * At the soft limit, send a SIGXCPU every second.
980             */
981            if (soft < hard) {
982                soft += USEC_PER_SEC;
983                sig->rlim[RLIMIT_RTTIME].rlim_cur = soft;
984            }
985            printk(KERN_INFO
986                "RT Watchdog Timeout: %s[%d]\n",
987                tsk->comm, task_pid_nr(tsk));
988            __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
989        }
990    }
991}
992
993static void stop_process_timers(struct signal_struct *sig)
994{
995    struct thread_group_cputimer *cputimer = &sig->cputimer;
996    unsigned long flags;
997
998    spin_lock_irqsave(&cputimer->lock, flags);
999    cputimer->running = 0;
1000    spin_unlock_irqrestore(&cputimer->lock, flags);
1001}
1002
1003static u32 onecputick;
1004
1005static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
1006                 cputime_t *expires, cputime_t cur_time, int signo)
1007{
1008    if (cputime_eq(it->expires, cputime_zero))
1009        return;
1010
1011    if (cputime_ge(cur_time, it->expires)) {
1012        if (!cputime_eq(it->incr, cputime_zero)) {
1013            it->expires = cputime_add(it->expires, it->incr);
1014            it->error += it->incr_error;
1015            if (it->error >= onecputick) {
1016                it->expires = cputime_sub(it->expires,
1017                              cputime_one_jiffy);
1018                it->error -= onecputick;
1019            }
1020        } else {
1021            it->expires = cputime_zero;
1022        }
1023
1024        trace_itimer_expire(signo == SIGPROF ?
1025                    ITIMER_PROF : ITIMER_VIRTUAL,
1026                    tsk->signal->leader_pid, cur_time);
1027        __group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
1028    }
1029
1030    if (!cputime_eq(it->expires, cputime_zero) &&
1031        (cputime_eq(*expires, cputime_zero) ||
1032         cputime_lt(it->expires, *expires))) {
1033        *expires = it->expires;
1034    }
1035}
1036
1037/**
1038 * task_cputime_zero - Check a task_cputime struct for all zero fields.
1039 *
1040 * @cputime: The struct to compare.
1041 *
1042 * Checks @cputime to see if all fields are zero. Returns true if all fields
1043 * are zero, false if any field is nonzero.
1044 */
1045static inline int task_cputime_zero(const struct task_cputime *cputime)
1046{
1047    if (cputime_eq(cputime->utime, cputime_zero) &&
1048        cputime_eq(cputime->stime, cputime_zero) &&
1049        cputime->sum_exec_runtime == 0)
1050        return 1;
1051    return 0;
1052}
1053
1054/*
1055 * Check for any per-thread CPU timers that have fired and move them
1056 * off the tsk->*_timers list onto the firing list. Per-thread timers
1057 * have already been taken off.
1058 */
1059static void check_process_timers(struct task_struct *tsk,
1060                 struct list_head *firing)
1061{
1062    int maxfire;
1063    struct signal_struct *const sig = tsk->signal;
1064    cputime_t utime, ptime, virt_expires, prof_expires;
1065    unsigned long long sum_sched_runtime, sched_expires;
1066    struct list_head *timers = sig->cpu_timers;
1067    struct task_cputime cputime;
1068    unsigned long soft;
1069
1070    /*
1071     * Collect the current process totals.
1072     */
1073    thread_group_cputimer(tsk, &cputime);
1074    utime = cputime.utime;
1075    ptime = cputime_add(utime, cputime.stime);
1076    sum_sched_runtime = cputime.sum_exec_runtime;
1077    maxfire = 20;
1078    prof_expires = cputime_zero;
1079    while (!list_empty(timers)) {
1080        struct cpu_timer_list *tl = list_first_entry(timers,
1081                              struct cpu_timer_list,
1082                              entry);
1083        if (!--maxfire || cputime_lt(ptime, tl->expires.cpu)) {
1084            prof_expires = tl->expires.cpu;
1085            break;
1086        }
1087        tl->firing = 1;
1088        list_move_tail(&tl->entry, firing);
1089    }
1090
1091    ++timers;
1092    maxfire = 20;
1093    virt_expires = cputime_zero;
1094    while (!list_empty(timers)) {
1095        struct cpu_timer_list *tl = list_first_entry(timers,
1096                              struct cpu_timer_list,
1097                              entry);
1098        if (!--maxfire || cputime_lt(utime, tl->expires.cpu)) {
1099            virt_expires = tl->expires.cpu;
1100            break;
1101        }
1102        tl->firing = 1;
1103        list_move_tail(&tl->entry, firing);
1104    }
1105
1106    ++timers;
1107    maxfire = 20;
1108    sched_expires = 0;
1109    while (!list_empty(timers)) {
1110        struct cpu_timer_list *tl = list_first_entry(timers,
1111                              struct cpu_timer_list,
1112                              entry);
1113        if (!--maxfire || sum_sched_runtime < tl->expires.sched) {
1114            sched_expires = tl->expires.sched;
1115            break;
1116        }
1117        tl->firing = 1;
1118        list_move_tail(&tl->entry, firing);
1119    }
1120
1121    /*
1122     * Check for the special case process timers.
1123     */
1124    check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime,
1125             SIGPROF);
1126    check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
1127             SIGVTALRM);
1128    soft = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1129    if (soft != RLIM_INFINITY) {
1130        unsigned long psecs = cputime_to_secs(ptime);
1131        unsigned long hard =
1132            ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
1133        cputime_t x;
1134        if (psecs >= hard) {
1135            /*
1136             * At the hard limit, we just die.
1137             * No need to calculate anything else now.
1138             */
1139            __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1140            return;
1141        }
1142        if (psecs >= soft) {
1143            /*
1144             * At the soft limit, send a SIGXCPU every second.
1145             */
1146            __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1147            if (soft < hard) {
1148                soft++;
1149                sig->rlim[RLIMIT_CPU].rlim_cur = soft;
1150            }
1151        }
1152        x = secs_to_cputime(soft);
1153        if (cputime_eq(prof_expires, cputime_zero) ||
1154            cputime_lt(x, prof_expires)) {
1155            prof_expires = x;
1156        }
1157    }
1158
1159    sig->cputime_expires.prof_exp = prof_expires;
1160    sig->cputime_expires.virt_exp = virt_expires;
1161    sig->cputime_expires.sched_exp = sched_expires;
1162    if (task_cputime_zero(&sig->cputime_expires))
1163        stop_process_timers(sig);
1164}
1165
1166/*
1167 * This is called from the signal code (via do_schedule_next_timer)
1168 * when the last timer signal was delivered and we have to reload the timer.
1169 */
1170void posix_cpu_timer_schedule(struct k_itimer *timer)
1171{
1172    struct task_struct *p = timer->it.cpu.task;
1173    union cpu_time_count now;
1174
1175    if (unlikely(p == NULL))
1176        /*
1177         * The task was cleaned up already, no future firings.
1178         */
1179        goto out;
1180
1181    /*
1182     * Fetch the current sample and update the timer's expiry time.
1183     */
1184    if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1185        cpu_clock_sample(timer->it_clock, p, &now);
1186        bump_cpu_timer(timer, now);
1187        if (unlikely(p->exit_state)) {
1188            clear_dead_task(timer, now);
1189            goto out;
1190        }
1191        read_lock(&tasklist_lock); /* arm_timer needs it. */
1192        spin_lock(&p->sighand->siglock);
1193    } else {
1194        read_lock(&tasklist_lock);
1195        if (unlikely(p->sighand == NULL)) {
1196            /*
1197             * The process has been reaped.
1198             * We can't even collect a sample any more.
1199             */
1200            put_task_struct(p);
1201            timer->it.cpu.task = p = NULL;
1202            timer->it.cpu.expires.sched = 0;
1203            goto out_unlock;
1204        } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1205            /*
1206             * We've noticed that the thread is dead, but
1207             * not yet reaped. Take this opportunity to
1208             * drop our task ref.
1209             */
1210            clear_dead_task(timer, now);
1211            goto out_unlock;
1212        }
1213        spin_lock(&p->sighand->siglock);
1214        cpu_timer_sample_group(timer->it_clock, p, &now);
1215        bump_cpu_timer(timer, now);
1216        /* Leave the tasklist_lock locked for the call below. */
1217    }
1218
1219    /*
1220     * Now re-arm for the new expiry time.
1221     */
1222    BUG_ON(!irqs_disabled());
1223    arm_timer(timer);
1224    spin_unlock(&p->sighand->siglock);
1225
1226out_unlock:
1227    read_unlock(&tasklist_lock);
1228
1229out:
1230    timer->it_overrun_last = timer->it_overrun;
1231    timer->it_overrun = -1;
1232    ++timer->it_requeue_pending;
1233}
1234
1235/**
1236 * task_cputime_expired - Compare two task_cputime entities.
1237 *
1238 * @sample: The task_cputime structure to be checked for expiration.
1239 * @expires: Expiration times, against which @sample will be checked.
1240 *
1241 * Checks @sample against @expires to see if any field of @sample has expired.
1242 * Returns true if any field of the former is greater than the corresponding
1243 * field of the latter if the latter field is set. Otherwise returns false.
1244 */
1245static inline int task_cputime_expired(const struct task_cputime *sample,
1246                    const struct task_cputime *expires)
1247{
1248    if (!cputime_eq(expires->utime, cputime_zero) &&
1249        cputime_ge(sample->utime, expires->utime))
1250        return 1;
1251    if (!cputime_eq(expires->stime, cputime_zero) &&
1252        cputime_ge(cputime_add(sample->utime, sample->stime),
1253               expires->stime))
1254        return 1;
1255    if (expires->sum_exec_runtime != 0 &&
1256        sample->sum_exec_runtime >= expires->sum_exec_runtime)
1257        return 1;
1258    return 0;
1259}
1260
1261/**
1262 * fastpath_timer_check - POSIX CPU timers fast path.
1263 *
1264 * @tsk: The task (thread) being checked.
1265 *
1266 * Check the task and thread group timers. If both are zero (there are no
1267 * timers set) return false. Otherwise snapshot the task and thread group
1268 * timers and compare them with the corresponding expiration times. Return
1269 * true if a timer has expired, else return false.
1270 */
1271static inline int fastpath_timer_check(struct task_struct *tsk)
1272{
1273    struct signal_struct *sig;
1274
1275    if (!task_cputime_zero(&tsk->cputime_expires)) {
1276        struct task_cputime task_sample = {
1277            .utime = tsk->utime,
1278            .stime = tsk->stime,
1279            .sum_exec_runtime = tsk->se.sum_exec_runtime
1280        };
1281
1282        if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
1283            return 1;
1284    }
1285
1286    sig = tsk->signal;
1287    if (sig->cputimer.running) {
1288        struct task_cputime group_sample;
1289
1290        spin_lock(&sig->cputimer.lock);
1291        group_sample = sig->cputimer.cputime;
1292        spin_unlock(&sig->cputimer.lock);
1293
1294        if (task_cputime_expired(&group_sample, &sig->cputime_expires))
1295            return 1;
1296    }
1297
1298    return 0;
1299}
1300
1301/*
1302 * This is called from the timer interrupt handler. The irq handler has
1303 * already updated our counts. We need to check if any timers fire now.
1304 * Interrupts are disabled.
1305 */
1306void run_posix_cpu_timers(struct task_struct *tsk)
1307{
1308    LIST_HEAD(firing);
1309    struct k_itimer *timer, *next;
1310    unsigned long flags;
1311
1312    BUG_ON(!irqs_disabled());
1313
1314    /*
1315     * The fast path checks that there are no expired thread or thread
1316     * group timers. If that's so, just return.
1317     */
1318    if (!fastpath_timer_check(tsk))
1319        return;
1320
1321    if (!lock_task_sighand(tsk, &flags))
1322        return;
1323    /*
1324     * Here we take off tsk->signal->cpu_timers[N] and
1325     * tsk->cpu_timers[N] all the timers that are firing, and
1326     * put them on the firing list.
1327     */
1328    check_thread_timers(tsk, &firing);
1329    /*
1330     * If there are any active process wide timers (POSIX 1.b, itimers,
1331     * RLIMIT_CPU) cputimer must be running.
1332     */
1333    if (tsk->signal->cputimer.running)
1334        check_process_timers(tsk, &firing);
1335
1336    /*
1337     * We must release these locks before taking any timer's lock.
1338     * There is a potential race with timer deletion here, as the
1339     * siglock now protects our private firing list. We have set
1340     * the firing flag in each timer, so that a deletion attempt
1341     * that gets the timer lock before we do will give it up and
1342     * spin until we've taken care of that timer below.
1343     */
1344    unlock_task_sighand(tsk, &flags);
1345
1346    /*
1347     * Now that all the timers on our list have the firing flag,
1348     * noone will touch their list entries but us. We'll take
1349     * each timer's lock before clearing its firing flag, so no
1350     * timer call will interfere.
1351     */
1352    list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1353        int cpu_firing;
1354
1355        spin_lock(&timer->it_lock);
1356        list_del_init(&timer->it.cpu.entry);
1357        cpu_firing = timer->it.cpu.firing;
1358        timer->it.cpu.firing = 0;
1359        /*
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.
1363         */
1364        if (likely(cpu_firing >= 0))
1365            cpu_timer_fire(timer);
1366        spin_unlock(&timer->it_lock);
1367    }
1368}
1369
1370/*
1371 * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
1372 * The tsk->sighand->siglock must be held by the caller.
1373 */
1374void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1375               cputime_t *newval, cputime_t *oldval)
1376{
1377    union cpu_time_count now;
1378
1379    BUG_ON(clock_idx == CPUCLOCK_SCHED);
1380    cpu_timer_sample_group(clock_idx, tsk, &now);
1381
1382    if (oldval) {
1383        /*
1384         * We are setting itimer. The *oldval is absolute and we update
1385         * it to be relative, *newval argument is relative and we update
1386         * it to be absolute.
1387         */
1388        if (!cputime_eq(*oldval, cputime_zero)) {
1389            if (cputime_le(*oldval, now.cpu)) {
1390                /* Just about to fire. */
1391                *oldval = cputime_one_jiffy;
1392            } else {
1393                *oldval = cputime_sub(*oldval, now.cpu);
1394            }
1395        }
1396
1397        if (cputime_eq(*newval, cputime_zero))
1398            return;
1399        *newval = cputime_add(*newval, now.cpu);
1400    }
1401
1402    /*
1403     * Update expiration cache if we are the earliest timer, or eventually
1404     * RLIMIT_CPU limit is earlier than prof_exp cpu timer expire.
1405     */
1406    switch (clock_idx) {
1407    case CPUCLOCK_PROF:
1408        if (expires_gt(tsk->signal->cputime_expires.prof_exp, *newval))
1409            tsk->signal->cputime_expires.prof_exp = *newval;
1410        break;
1411    case CPUCLOCK_VIRT:
1412        if (expires_gt(tsk->signal->cputime_expires.virt_exp, *newval))
1413            tsk->signal->cputime_expires.virt_exp = *newval;
1414        break;
1415    }
1416}
1417
1418static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1419                struct timespec *rqtp, struct itimerspec *it)
1420{
1421    struct k_itimer timer;
1422    int error;
1423
1424    /*
1425     * Set up a temporary timer and then wait for it to go off.
1426     */
1427    memset(&timer, 0, sizeof timer);
1428    spin_lock_init(&timer.it_lock);
1429    timer.it_clock = which_clock;
1430    timer.it_overrun = -1;
1431    error = posix_cpu_timer_create(&timer);
1432    timer.it_process = current;
1433    if (!error) {
1434        static struct itimerspec zero_it;
1435
1436        memset(it, 0, sizeof *it);
1437        it->it_value = *rqtp;
1438
1439        spin_lock_irq(&timer.it_lock);
1440        error = posix_cpu_timer_set(&timer, flags, it, NULL);
1441        if (error) {
1442            spin_unlock_irq(&timer.it_lock);
1443            return error;
1444        }
1445
1446        while (!signal_pending(current)) {
1447            if (timer.it.cpu.expires.sched == 0) {
1448                /*
1449                 * Our timer fired and was reset.
1450                 */
1451                spin_unlock_irq(&timer.it_lock);
1452                return 0;
1453            }
1454
1455            /*
1456             * Block until cpu_timer_fire (or a signal) wakes us.
1457             */
1458            __set_current_state(TASK_INTERRUPTIBLE);
1459            spin_unlock_irq(&timer.it_lock);
1460            schedule();
1461            spin_lock_irq(&timer.it_lock);
1462        }
1463
1464        /*
1465         * We were interrupted by a signal.
1466         */
1467        sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
1468        posix_cpu_timer_set(&timer, 0, &zero_it, it);
1469        spin_unlock_irq(&timer.it_lock);
1470
1471        if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
1472            /*
1473             * It actually did fire already.
1474             */
1475            return 0;
1476        }
1477
1478        error = -ERESTART_RESTARTBLOCK;
1479    }
1480
1481    return error;
1482}
1483
1484int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1485             struct timespec *rqtp, struct timespec __user *rmtp)
1486{
1487    struct restart_block *restart_block =
1488        &current_thread_info()->restart_block;
1489    struct itimerspec it;
1490    int error;
1491
1492    /*
1493     * Diagnose required errors first.
1494     */
1495    if (CPUCLOCK_PERTHREAD(which_clock) &&
1496        (CPUCLOCK_PID(which_clock) == 0 ||
1497         CPUCLOCK_PID(which_clock) == current->pid))
1498        return -EINVAL;
1499
1500    error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);
1501
1502    if (error == -ERESTART_RESTARTBLOCK) {
1503
1504               if (flags & TIMER_ABSTIME)
1505            return -ERESTARTNOHAND;
1506        /*
1507          * Report back to the user the time still remaining.
1508          */
1509        if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1510            return -EFAULT;
1511
1512        restart_block->fn = posix_cpu_nsleep_restart;
1513        restart_block->arg0 = which_clock;
1514        restart_block->arg1 = (unsigned long) rmtp;
1515        restart_block->arg2 = rqtp->tv_sec;
1516        restart_block->arg3 = rqtp->tv_nsec;
1517    }
1518    return error;
1519}
1520
1521long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1522{
1523    clockid_t which_clock = restart_block->arg0;
1524    struct timespec __user *rmtp;
1525    struct timespec t;
1526    struct itimerspec it;
1527    int error;
1528
1529    rmtp = (struct timespec __user *) restart_block->arg1;
1530    t.tv_sec = restart_block->arg2;
1531    t.tv_nsec = restart_block->arg3;
1532
1533    restart_block->fn = do_no_restart_syscall;
1534    error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);
1535
1536    if (error == -ERESTART_RESTARTBLOCK) {
1537        /*
1538          * Report back to the user the time still remaining.
1539          */
1540        if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1541            return -EFAULT;
1542
1543        restart_block->fn = posix_cpu_nsleep_restart;
1544        restart_block->arg0 = which_clock;
1545        restart_block->arg1 = (unsigned long) rmtp;
1546        restart_block->arg2 = t.tv_sec;
1547        restart_block->arg3 = t.tv_nsec;
1548    }
1549    return error;
1550
1551}
1552
1553
1554#define PROCESS_CLOCK MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
1555#define THREAD_CLOCK MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
1556
1557static int process_cpu_clock_getres(const clockid_t which_clock,
1558                    struct timespec *tp)
1559{
1560    return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1561}
1562static int process_cpu_clock_get(const clockid_t which_clock,
1563                 struct timespec *tp)
1564{
1565    return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1566}
1567static int process_cpu_timer_create(struct k_itimer *timer)
1568{
1569    timer->it_clock = PROCESS_CLOCK;
1570    return posix_cpu_timer_create(timer);
1571}
1572static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1573                  struct timespec *rqtp,
1574                  struct timespec __user *rmtp)
1575{
1576    return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
1577}
1578static long process_cpu_nsleep_restart(struct restart_block *restart_block)
1579{
1580    return -EINVAL;
1581}
1582static int thread_cpu_clock_getres(const clockid_t which_clock,
1583                   struct timespec *tp)
1584{
1585    return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1586}
1587static int thread_cpu_clock_get(const clockid_t which_clock,
1588                struct timespec *tp)
1589{
1590    return posix_cpu_clock_get(THREAD_CLOCK, tp);
1591}
1592static int thread_cpu_timer_create(struct k_itimer *timer)
1593{
1594    timer->it_clock = THREAD_CLOCK;
1595    return posix_cpu_timer_create(timer);
1596}
1597static int thread_cpu_nsleep(const clockid_t which_clock, int flags,
1598                  struct timespec *rqtp, struct timespec __user *rmtp)
1599{
1600    return -EINVAL;
1601}
1602static long thread_cpu_nsleep_restart(struct restart_block *restart_block)
1603{
1604    return -EINVAL;
1605}
1606
1607static __init int init_posix_cpu_timers(void)
1608{
1609    struct k_clock process = {
1610        .clock_getres = process_cpu_clock_getres,
1611        .clock_get = process_cpu_clock_get,
1612        .clock_set = do_posix_clock_nosettime,
1613        .timer_create = process_cpu_timer_create,
1614        .nsleep = process_cpu_nsleep,
1615        .nsleep_restart = process_cpu_nsleep_restart,
1616    };
1617    struct k_clock thread = {
1618        .clock_getres = thread_cpu_clock_getres,
1619        .clock_get = thread_cpu_clock_get,
1620        .clock_set = do_posix_clock_nosettime,
1621        .timer_create = thread_cpu_timer_create,
1622        .nsleep = thread_cpu_nsleep,
1623        .nsleep_restart = thread_cpu_nsleep_restart,
1624    };
1625    struct timespec ts;
1626
1627    register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
1628    register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
1629
1630    cputime_to_timespec(cputime_one_jiffy, &ts);
1631    onecputick = ts.tv_nsec;
1632    WARN_ON(ts.tv_sec != 0);
1633
1634    return 0;
1635}
1636__initcall(init_posix_cpu_timers);
1637

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