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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Implement CPU time clocks for the POSIX clock interface.
4 */
5
6#include <linux/sched/signal.h>
7#include <linux/sched/cputime.h>
8#include <linux/posix-timers.h>
9#include <linux/errno.h>
10#include <linux/math64.h>
11#include <linux/uaccess.h>
12#include <linux/kernel_stat.h>
13#include <trace/events/timer.h>
14#include <linux/tick.h>
15#include <linux/workqueue.h>
16#include <linux/compat.h>
17#include <linux/sched/deadline.h>
18
19#include "posix-timers.h"
20
21static void posix_cpu_timer_rearm(struct k_itimer *timer);
22
23/*
24 * Called after updating RLIMIT_CPU to run cpu timer and update
25 * tsk->signal->cputime_expires expiration cache if necessary. Needs
26 * siglock protection since other code may update expiration cache as
27 * well.
28 */
29void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
30{
31 u64 nsecs = rlim_new * NSEC_PER_SEC;
32
33 spin_lock_irq(&task->sighand->siglock);
34 set_process_cpu_timer(task, CPUCLOCK_PROF, &nsecs, NULL);
35 spin_unlock_irq(&task->sighand->siglock);
36}
37
38static int check_clock(const clockid_t which_clock)
39{
40 int error = 0;
41 struct task_struct *p;
42 const pid_t pid = CPUCLOCK_PID(which_clock);
43
44 if (CPUCLOCK_WHICH(which_clock) >= CPUCLOCK_MAX)
45 return -EINVAL;
46
47 if (pid == 0)
48 return 0;
49
50 rcu_read_lock();
51 p = find_task_by_vpid(pid);
52 if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
53 same_thread_group(p, current) : has_group_leader_pid(p))) {
54 error = -EINVAL;
55 }
56 rcu_read_unlock();
57
58 return error;
59}
60
61/*
62 * Update expiry time from increment, and increase overrun count,
63 * given the current clock sample.
64 */
65static void bump_cpu_timer(struct k_itimer *timer, u64 now)
66{
67 int i;
68 u64 delta, incr;
69
70 if (timer->it.cpu.incr == 0)
71 return;
72
73 if (now < timer->it.cpu.expires)
74 return;
75
76 incr = timer->it.cpu.incr;
77 delta = now + incr - timer->it.cpu.expires;
78
79 /* Don't use (incr*2 < delta), incr*2 might overflow. */
80 for (i = 0; incr < delta - incr; i++)
81 incr = incr << 1;
82
83 for (; i >= 0; incr >>= 1, i--) {
84 if (delta < incr)
85 continue;
86
87 timer->it.cpu.expires += incr;
88 timer->it_overrun += 1 << i;
89 delta -= incr;
90 }
91}
92
93/**
94 * task_cputime_zero - Check a task_cputime struct for all zero fields.
95 *
96 * @cputime: The struct to compare.
97 *
98 * Checks @cputime to see if all fields are zero. Returns true if all fields
99 * are zero, false if any field is nonzero.
100 */
101static inline int task_cputime_zero(const struct task_cputime *cputime)
102{
103 if (!cputime->utime && !cputime->stime && !cputime->sum_exec_runtime)
104 return 1;
105 return 0;
106}
107
108static inline u64 prof_ticks(struct task_struct *p)
109{
110 u64 utime, stime;
111
112 task_cputime(p, &utime, &stime);
113
114 return utime + stime;
115}
116static inline u64 virt_ticks(struct task_struct *p)
117{
118 u64 utime, stime;
119
120 task_cputime(p, &utime, &stime);
121
122 return utime;
123}
124
125static int
126posix_cpu_clock_getres(const clockid_t which_clock, struct timespec64 *tp)
127{
128 int error = check_clock(which_clock);
129 if (!error) {
130 tp->tv_sec = 0;
131 tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
132 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
133 /*
134 * If sched_clock is using a cycle counter, we
135 * don't have any idea of its true resolution
136 * exported, but it is much more than 1s/HZ.
137 */
138 tp->tv_nsec = 1;
139 }
140 }
141 return error;
142}
143
144static int
145posix_cpu_clock_set(const clockid_t which_clock, const struct timespec64 *tp)
146{
147 /*
148 * You can never reset a CPU clock, but we check for other errors
149 * in the call before failing with EPERM.
150 */
151 int error = check_clock(which_clock);
152 if (error == 0) {
153 error = -EPERM;
154 }
155 return error;
156}
157
158
159/*
160 * Sample a per-thread clock for the given task.
161 */
162static int cpu_clock_sample(const clockid_t which_clock,
163 struct task_struct *p, u64 *sample)
164{
165 switch (CPUCLOCK_WHICH(which_clock)) {
166 default:
167 return -EINVAL;
168 case CPUCLOCK_PROF:
169 *sample = prof_ticks(p);
170 break;
171 case CPUCLOCK_VIRT:
172 *sample = virt_ticks(p);
173 break;
174 case CPUCLOCK_SCHED:
175 *sample = task_sched_runtime(p);
176 break;
177 }
178 return 0;
179}
180
181/*
182 * Set cputime to sum_cputime if sum_cputime > cputime. Use cmpxchg
183 * to avoid race conditions with concurrent updates to cputime.
184 */
185static inline void __update_gt_cputime(atomic64_t *cputime, u64 sum_cputime)
186{
187 u64 curr_cputime;
188retry:
189 curr_cputime = atomic64_read(cputime);
190 if (sum_cputime > curr_cputime) {
191 if (atomic64_cmpxchg(cputime, curr_cputime, sum_cputime) != curr_cputime)
192 goto retry;
193 }
194}
195
196static void update_gt_cputime(struct task_cputime_atomic *cputime_atomic, struct task_cputime *sum)
197{
198 __update_gt_cputime(&cputime_atomic->utime, sum->utime);
199 __update_gt_cputime(&cputime_atomic->stime, sum->stime);
200 __update_gt_cputime(&cputime_atomic->sum_exec_runtime, sum->sum_exec_runtime);
201}
202
203/* Sample task_cputime_atomic values in "atomic_timers", store results in "times". */
204static inline void sample_cputime_atomic(struct task_cputime *times,
205 struct task_cputime_atomic *atomic_times)
206{
207 times->utime = atomic64_read(&atomic_times->utime);
208 times->stime = atomic64_read(&atomic_times->stime);
209 times->sum_exec_runtime = atomic64_read(&atomic_times->sum_exec_runtime);
210}
211
212void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
213{
214 struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
215 struct task_cputime sum;
216
217 /* Check if cputimer isn't running. This is accessed without locking. */
218 if (!READ_ONCE(cputimer->running)) {
219 /*
220 * The POSIX timer interface allows for absolute time expiry
221 * values through the TIMER_ABSTIME flag, therefore we have
222 * to synchronize the timer to the clock every time we start it.
223 */
224 thread_group_cputime(tsk, &sum);
225 update_gt_cputime(&cputimer->cputime_atomic, &sum);
226
227 /*
228 * We're setting cputimer->running without a lock. Ensure
229 * this only gets written to in one operation. We set
230 * running after update_gt_cputime() as a small optimization,
231 * but barriers are not required because update_gt_cputime()
232 * can handle concurrent updates.
233 */
234 WRITE_ONCE(cputimer->running, true);
235 }
236 sample_cputime_atomic(times, &cputimer->cputime_atomic);
237}
238
239/*
240 * Sample a process (thread group) clock for the given group_leader task.
241 * Must be called with task sighand lock held for safe while_each_thread()
242 * traversal.
243 */
244static int cpu_clock_sample_group(const clockid_t which_clock,
245 struct task_struct *p,
246 u64 *sample)
247{
248 struct task_cputime cputime;
249
250 switch (CPUCLOCK_WHICH(which_clock)) {
251 default:
252 return -EINVAL;
253 case CPUCLOCK_PROF:
254 thread_group_cputime(p, &cputime);
255 *sample = cputime.utime + cputime.stime;
256 break;
257 case CPUCLOCK_VIRT:
258 thread_group_cputime(p, &cputime);
259 *sample = cputime.utime;
260 break;
261 case CPUCLOCK_SCHED:
262 thread_group_cputime(p, &cputime);
263 *sample = cputime.sum_exec_runtime;
264 break;
265 }
266 return 0;
267}
268
269static int posix_cpu_clock_get_task(struct task_struct *tsk,
270 const clockid_t which_clock,
271 struct timespec64 *tp)
272{
273 int err = -EINVAL;
274 u64 rtn;
275
276 if (CPUCLOCK_PERTHREAD(which_clock)) {
277 if (same_thread_group(tsk, current))
278 err = cpu_clock_sample(which_clock, tsk, &rtn);
279 } else {
280 if (tsk == current || thread_group_leader(tsk))
281 err = cpu_clock_sample_group(which_clock, tsk, &rtn);
282 }
283
284 if (!err)
285 *tp = ns_to_timespec64(rtn);
286
287 return err;
288}
289
290
291static int posix_cpu_clock_get(const clockid_t which_clock, struct timespec64 *tp)
292{
293 const pid_t pid = CPUCLOCK_PID(which_clock);
294 int err = -EINVAL;
295
296 if (pid == 0) {
297 /*
298 * Special case constant value for our own clocks.
299 * We don't have to do any lookup to find ourselves.
300 */
301 err = posix_cpu_clock_get_task(current, which_clock, tp);
302 } else {
303 /*
304 * Find the given PID, and validate that the caller
305 * should be able to see it.
306 */
307 struct task_struct *p;
308 rcu_read_lock();
309 p = find_task_by_vpid(pid);
310 if (p)
311 err = posix_cpu_clock_get_task(p, which_clock, tp);
312 rcu_read_unlock();
313 }
314
315 return err;
316}
317
318/*
319 * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
320 * This is called from sys_timer_create() and do_cpu_nanosleep() with the
321 * new timer already all-zeros initialized.
322 */
323static int posix_cpu_timer_create(struct k_itimer *new_timer)
324{
325 int ret = 0;
326 const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
327 struct task_struct *p;
328
329 if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
330 return -EINVAL;
331
332 new_timer->kclock = &clock_posix_cpu;
333
334 INIT_LIST_HEAD(&new_timer->it.cpu.entry);
335
336 rcu_read_lock();
337 if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
338 if (pid == 0) {
339 p = current;
340 } else {
341 p = find_task_by_vpid(pid);
342 if (p && !same_thread_group(p, current))
343 p = NULL;
344 }
345 } else {
346 if (pid == 0) {
347 p = current->group_leader;
348 } else {
349 p = find_task_by_vpid(pid);
350 if (p && !has_group_leader_pid(p))
351 p = NULL;
352 }
353 }
354 new_timer->it.cpu.task = p;
355 if (p) {
356 get_task_struct(p);
357 } else {
358 ret = -EINVAL;
359 }
360 rcu_read_unlock();
361
362 return ret;
363}
364
365/*
366 * Clean up a CPU-clock timer that is about to be destroyed.
367 * This is called from timer deletion with the timer already locked.
368 * If we return TIMER_RETRY, it's necessary to release the timer's lock
369 * and try again. (This happens when the timer is in the middle of firing.)
370 */
371static int posix_cpu_timer_del(struct k_itimer *timer)
372{
373 int ret = 0;
374 unsigned long flags;
375 struct sighand_struct *sighand;
376 struct task_struct *p = timer->it.cpu.task;
377
378 WARN_ON_ONCE(p == NULL);
379
380 /*
381 * Protect against sighand release/switch in exit/exec and process/
382 * thread timer list entry concurrent read/writes.
383 */
384 sighand = lock_task_sighand(p, &flags);
385 if (unlikely(sighand == NULL)) {
386 /*
387 * We raced with the reaping of the task.
388 * The deletion should have cleared us off the list.
389 */
390 WARN_ON_ONCE(!list_empty(&timer->it.cpu.entry));
391 } else {
392 if (timer->it.cpu.firing)
393 ret = TIMER_RETRY;
394 else
395 list_del(&timer->it.cpu.entry);
396
397 unlock_task_sighand(p, &flags);
398 }
399
400 if (!ret)
401 put_task_struct(p);
402
403 return ret;
404}
405
406static void cleanup_timers_list(struct list_head *head)
407{
408 struct cpu_timer_list *timer, *next;
409
410 list_for_each_entry_safe(timer, next, head, entry)
411 list_del_init(&timer->entry);
412}
413
414/*
415 * Clean out CPU timers still ticking when a thread exited. The task
416 * pointer is cleared, and the expiry time is replaced with the residual
417 * time for later timer_gettime calls to return.
418 * This must be called with the siglock held.
419 */
420static void cleanup_timers(struct list_head *head)
421{
422 cleanup_timers_list(head);
423 cleanup_timers_list(++head);
424 cleanup_timers_list(++head);
425}
426
427/*
428 * These are both called with the siglock held, when the current thread
429 * is being reaped. When the final (leader) thread in the group is reaped,
430 * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
431 */
432void posix_cpu_timers_exit(struct task_struct *tsk)
433{
434 cleanup_timers(tsk->cpu_timers);
435}
436void posix_cpu_timers_exit_group(struct task_struct *tsk)
437{
438 cleanup_timers(tsk->signal->cpu_timers);
439}
440
441static inline int expires_gt(u64 expires, u64 new_exp)
442{
443 return expires == 0 || expires > new_exp;
444}
445
446/*
447 * Insert the timer on the appropriate list before any timers that
448 * expire later. This must be called with the sighand lock held.
449 */
450static void arm_timer(struct k_itimer *timer)
451{
452 struct task_struct *p = timer->it.cpu.task;
453 struct list_head *head, *listpos;
454 struct task_cputime *cputime_expires;
455 struct cpu_timer_list *const nt = &timer->it.cpu;
456 struct cpu_timer_list *next;
457
458 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
459 head = p->cpu_timers;
460 cputime_expires = &p->cputime_expires;
461 } else {
462 head = p->signal->cpu_timers;
463 cputime_expires = &p->signal->cputime_expires;
464 }
465 head += CPUCLOCK_WHICH(timer->it_clock);
466
467 listpos = head;
468 list_for_each_entry(next, head, entry) {
469 if (nt->expires < next->expires)
470 break;
471 listpos = &next->entry;
472 }
473 list_add(&nt->entry, listpos);
474
475 if (listpos == head) {
476 u64 exp = nt->expires;
477
478 /*
479 * We are the new earliest-expiring POSIX 1.b timer, hence
480 * need to update expiration cache. Take into account that
481 * for process timers we share expiration cache with itimers
482 * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
483 */
484
485 switch (CPUCLOCK_WHICH(timer->it_clock)) {
486 case CPUCLOCK_PROF:
487 if (expires_gt(cputime_expires->prof_exp, exp))
488 cputime_expires->prof_exp = exp;
489 break;
490 case CPUCLOCK_VIRT:
491 if (expires_gt(cputime_expires->virt_exp, exp))
492 cputime_expires->virt_exp = exp;
493 break;
494 case CPUCLOCK_SCHED:
495 if (expires_gt(cputime_expires->sched_exp, exp))
496 cputime_expires->sched_exp = exp;
497 break;
498 }
499 if (CPUCLOCK_PERTHREAD(timer->it_clock))
500 tick_dep_set_task(p, TICK_DEP_BIT_POSIX_TIMER);
501 else
502 tick_dep_set_signal(p->signal, TICK_DEP_BIT_POSIX_TIMER);
503 }
504}
505
506/*
507 * The timer is locked, fire it and arrange for its reload.
508 */
509static void cpu_timer_fire(struct k_itimer *timer)
510{
511 if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
512 /*
513 * User don't want any signal.
514 */
515 timer->it.cpu.expires = 0;
516 } else if (unlikely(timer->sigq == NULL)) {
517 /*
518 * This a special case for clock_nanosleep,
519 * not a normal timer from sys_timer_create.
520 */
521 wake_up_process(timer->it_process);
522 timer->it.cpu.expires = 0;
523 } else if (timer->it.cpu.incr == 0) {
524 /*
525 * One-shot timer. Clear it as soon as it's fired.
526 */
527 posix_timer_event(timer, 0);
528 timer->it.cpu.expires = 0;
529 } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
530 /*
531 * The signal did not get queued because the signal
532 * was ignored, so we won't get any callback to
533 * reload the timer. But we need to keep it
534 * ticking in case the signal is deliverable next time.
535 */
536 posix_cpu_timer_rearm(timer);
537 ++timer->it_requeue_pending;
538 }
539}
540
541/*
542 * Sample a process (thread group) timer for the given group_leader task.
543 * Must be called with task sighand lock held for safe while_each_thread()
544 * traversal.
545 */
546static int cpu_timer_sample_group(const clockid_t which_clock,
547 struct task_struct *p, u64 *sample)
548{
549 struct task_cputime cputime;
550
551 thread_group_cputimer(p, &cputime);
552 switch (CPUCLOCK_WHICH(which_clock)) {
553 default:
554 return -EINVAL;
555 case CPUCLOCK_PROF:
556 *sample = cputime.utime + cputime.stime;
557 break;
558 case CPUCLOCK_VIRT:
559 *sample = cputime.utime;
560 break;
561 case CPUCLOCK_SCHED:
562 *sample = cputime.sum_exec_runtime;
563 break;
564 }
565 return 0;
566}
567
568/*
569 * Guts of sys_timer_settime for CPU timers.
570 * This is called with the timer locked and interrupts disabled.
571 * If we return TIMER_RETRY, it's necessary to release the timer's lock
572 * and try again. (This happens when the timer is in the middle of firing.)
573 */
574static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
575 struct itimerspec64 *new, struct itimerspec64 *old)
576{
577 unsigned long flags;
578 struct sighand_struct *sighand;
579 struct task_struct *p = timer->it.cpu.task;
580 u64 old_expires, new_expires, old_incr, val;
581 int ret;
582
583 WARN_ON_ONCE(p == NULL);
584
585 /*
586 * Use the to_ktime conversion because that clamps the maximum
587 * value to KTIME_MAX and avoid multiplication overflows.
588 */
589 new_expires = ktime_to_ns(timespec64_to_ktime(new->it_value));
590
591 /*
592 * Protect against sighand release/switch in exit/exec and p->cpu_timers
593 * and p->signal->cpu_timers read/write in arm_timer()
594 */
595 sighand = lock_task_sighand(p, &flags);
596 /*
597 * If p has just been reaped, we can no
598 * longer get any information about it at all.
599 */
600 if (unlikely(sighand == NULL)) {
601 return -ESRCH;
602 }
603
604 /*
605 * Disarm any old timer after extracting its expiry time.
606 */
607 lockdep_assert_irqs_disabled();
608
609 ret = 0;
610 old_incr = timer->it.cpu.incr;
611 old_expires = timer->it.cpu.expires;
612 if (unlikely(timer->it.cpu.firing)) {
613 timer->it.cpu.firing = -1;
614 ret = TIMER_RETRY;
615 } else
616 list_del_init(&timer->it.cpu.entry);
617
618 /*
619 * We need to sample the current value to convert the new
620 * value from to relative and absolute, and to convert the
621 * old value from absolute to relative. To set a process
622 * timer, we need a sample to balance the thread expiry
623 * times (in arm_timer). With an absolute time, we must
624 * check if it's already passed. In short, we need a sample.
625 */
626 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
627 cpu_clock_sample(timer->it_clock, p, &val);
628 } else {
629 cpu_timer_sample_group(timer->it_clock, p, &val);
630 }
631
632 if (old) {
633 if (old_expires == 0) {
634 old->it_value.tv_sec = 0;
635 old->it_value.tv_nsec = 0;
636 } else {
637 /*
638 * Update the timer in case it has
639 * overrun already. If it has,
640 * we'll report it as having overrun
641 * and with the next reloaded timer
642 * already ticking, though we are
643 * swallowing that pending
644 * notification here to install the
645 * new setting.
646 */
647 bump_cpu_timer(timer, val);
648 if (val < timer->it.cpu.expires) {
649 old_expires = timer->it.cpu.expires - val;
650 old->it_value = ns_to_timespec64(old_expires);
651 } else {
652 old->it_value.tv_nsec = 1;
653 old->it_value.tv_sec = 0;
654 }
655 }
656 }
657
658 if (unlikely(ret)) {
659 /*
660 * We are colliding with the timer actually firing.
661 * Punt after filling in the timer's old value, and
662 * disable this firing since we are already reporting
663 * it as an overrun (thanks to bump_cpu_timer above).
664 */
665 unlock_task_sighand(p, &flags);
666 goto out;
667 }
668
669 if (new_expires != 0 && !(timer_flags & TIMER_ABSTIME)) {
670 new_expires += val;
671 }
672
673 /*
674 * Install the new expiry time (or zero).
675 * For a timer with no notification action, we don't actually
676 * arm the timer (we'll just fake it for timer_gettime).
677 */
678 timer->it.cpu.expires = new_expires;
679 if (new_expires != 0 && val < new_expires) {
680 arm_timer(timer);
681 }
682
683 unlock_task_sighand(p, &flags);
684 /*
685 * Install the new reload setting, and
686 * set up the signal and overrun bookkeeping.
687 */
688 timer->it.cpu.incr = timespec64_to_ns(&new->it_interval);
689
690 /*
691 * This acts as a modification timestamp for the timer,
692 * so any automatic reload attempt will punt on seeing
693 * that we have reset the timer manually.
694 */
695 timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
696 ~REQUEUE_PENDING;
697 timer->it_overrun_last = 0;
698 timer->it_overrun = -1;
699
700 if (new_expires != 0 && !(val < new_expires)) {
701 /*
702 * The designated time already passed, so we notify
703 * immediately, even if the thread never runs to
704 * accumulate more time on this clock.
705 */
706 cpu_timer_fire(timer);
707 }
708
709 ret = 0;
710 out:
711 if (old)
712 old->it_interval = ns_to_timespec64(old_incr);
713
714 return ret;
715}
716
717static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp)
718{
719 u64 now;
720 struct task_struct *p = timer->it.cpu.task;
721
722 WARN_ON_ONCE(p == NULL);
723
724 /*
725 * Easy part: convert the reload time.
726 */
727 itp->it_interval = ns_to_timespec64(timer->it.cpu.incr);
728
729 if (!timer->it.cpu.expires)
730 return;
731
732 /*
733 * Sample the clock to take the difference with the expiry time.
734 */
735 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
736 cpu_clock_sample(timer->it_clock, p, &now);
737 } else {
738 struct sighand_struct *sighand;
739 unsigned long flags;
740
741 /*
742 * Protect against sighand release/switch in exit/exec and
743 * also make timer sampling safe if it ends up calling
744 * thread_group_cputime().
745 */
746 sighand = lock_task_sighand(p, &flags);
747 if (unlikely(sighand == NULL)) {
748 /*
749 * The process has been reaped.
750 * We can't even collect a sample any more.
751 * Call the timer disarmed, nothing else to do.
752 */
753 timer->it.cpu.expires = 0;
754 return;
755 } else {
756 cpu_timer_sample_group(timer->it_clock, p, &now);
757 unlock_task_sighand(p, &flags);
758 }
759 }
760
761 if (now < timer->it.cpu.expires) {
762 itp->it_value = ns_to_timespec64(timer->it.cpu.expires - now);
763 } else {
764 /*
765 * The timer should have expired already, but the firing
766 * hasn't taken place yet. Say it's just about to expire.
767 */
768 itp->it_value.tv_nsec = 1;
769 itp->it_value.tv_sec = 0;
770 }
771}
772
773static unsigned long long
774check_timers_list(struct list_head *timers,
775 struct list_head *firing,
776 unsigned long long curr)
777{
778 int maxfire = 20;
779
780 while (!list_empty(timers)) {
781 struct cpu_timer_list *t;
782
783 t = list_first_entry(timers, struct cpu_timer_list, entry);
784
785 if (!--maxfire || curr < t->expires)
786 return t->expires;
787
788 t->firing = 1;
789 list_move_tail(&t->entry, firing);
790 }
791
792 return 0;
793}
794
795static inline void check_dl_overrun(struct task_struct *tsk)
796{
797 if (tsk->dl.dl_overrun) {
798 tsk->dl.dl_overrun = 0;
799 __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
800 }
801}
802
803/*
804 * Check for any per-thread CPU timers that have fired and move them off
805 * the tsk->cpu_timers[N] list onto the firing list. Here we update the
806 * tsk->it_*_expires values to reflect the remaining thread CPU timers.
807 */
808static void check_thread_timers(struct task_struct *tsk,
809 struct list_head *firing)
810{
811 struct list_head *timers = tsk->cpu_timers;
812 struct task_cputime *tsk_expires = &tsk->cputime_expires;
813 u64 expires;
814 unsigned long soft;
815
816 if (dl_task(tsk))
817 check_dl_overrun(tsk);
818
819 /*
820 * If cputime_expires is zero, then there are no active
821 * per thread CPU timers.
822 */
823 if (task_cputime_zero(&tsk->cputime_expires))
824 return;
825
826 expires = check_timers_list(timers, firing, prof_ticks(tsk));
827 tsk_expires->prof_exp = expires;
828
829 expires = check_timers_list(++timers, firing, virt_ticks(tsk));
830 tsk_expires->virt_exp = expires;
831
832 tsk_expires->sched_exp = check_timers_list(++timers, firing,
833 tsk->se.sum_exec_runtime);
834
835 /*
836 * Check for the special case thread timers.
837 */
838 soft = task_rlimit(tsk, RLIMIT_RTTIME);
839 if (soft != RLIM_INFINITY) {
840 unsigned long hard = task_rlimit_max(tsk, RLIMIT_RTTIME);
841
842 if (hard != RLIM_INFINITY &&
843 tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
844 /*
845 * At the hard limit, we just die.
846 * No need to calculate anything else now.
847 */
848 if (print_fatal_signals) {
849 pr_info("CPU Watchdog Timeout (hard): %s[%d]\n",
850 tsk->comm, task_pid_nr(tsk));
851 }
852 __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
853 return;
854 }
855 if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {
856 /*
857 * At the soft limit, send a SIGXCPU every second.
858 */
859 if (soft < hard) {
860 soft += USEC_PER_SEC;
861 tsk->signal->rlim[RLIMIT_RTTIME].rlim_cur =
862 soft;
863 }
864 if (print_fatal_signals) {
865 pr_info("RT Watchdog Timeout (soft): %s[%d]\n",
866 tsk->comm, task_pid_nr(tsk));
867 }
868 __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
869 }
870 }
871 if (task_cputime_zero(tsk_expires))
872 tick_dep_clear_task(tsk, TICK_DEP_BIT_POSIX_TIMER);
873}
874
875static inline void stop_process_timers(struct signal_struct *sig)
876{
877 struct thread_group_cputimer *cputimer = &sig->cputimer;
878
879 /* Turn off cputimer->running. This is done without locking. */
880 WRITE_ONCE(cputimer->running, false);
881 tick_dep_clear_signal(sig, TICK_DEP_BIT_POSIX_TIMER);
882}
883
884static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
885 u64 *expires, u64 cur_time, int signo)
886{
887 if (!it->expires)
888 return;
889
890 if (cur_time >= it->expires) {
891 if (it->incr)
892 it->expires += it->incr;
893 else
894 it->expires = 0;
895
896 trace_itimer_expire(signo == SIGPROF ?
897 ITIMER_PROF : ITIMER_VIRTUAL,
898 tsk->signal->leader_pid, cur_time);
899 __group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
900 }
901
902 if (it->expires && (!*expires || it->expires < *expires))
903 *expires = it->expires;
904}
905
906/*
907 * Check for any per-thread CPU timers that have fired and move them
908 * off the tsk->*_timers list onto the firing list. Per-thread timers
909 * have already been taken off.
910 */
911static void check_process_timers(struct task_struct *tsk,
912 struct list_head *firing)
913{
914 struct signal_struct *const sig = tsk->signal;
915 u64 utime, ptime, virt_expires, prof_expires;
916 u64 sum_sched_runtime, sched_expires;
917 struct list_head *timers = sig->cpu_timers;
918 struct task_cputime cputime;
919 unsigned long soft;
920
921 if (dl_task(tsk))
922 check_dl_overrun(tsk);
923
924 /*
925 * If cputimer is not running, then there are no active
926 * process wide timers (POSIX 1.b, itimers, RLIMIT_CPU).
927 */
928 if (!READ_ONCE(tsk->signal->cputimer.running))
929 return;
930
931 /*
932 * Signify that a thread is checking for process timers.
933 * Write access to this field is protected by the sighand lock.
934 */
935 sig->cputimer.checking_timer = true;
936
937 /*
938 * Collect the current process totals.
939 */
940 thread_group_cputimer(tsk, &cputime);
941 utime = cputime.utime;
942 ptime = utime + cputime.stime;
943 sum_sched_runtime = cputime.sum_exec_runtime;
944
945 prof_expires = check_timers_list(timers, firing, ptime);
946 virt_expires = check_timers_list(++timers, firing, utime);
947 sched_expires = check_timers_list(++timers, firing, sum_sched_runtime);
948
949 /*
950 * Check for the special case process timers.
951 */
952 check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime,
953 SIGPROF);
954 check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
955 SIGVTALRM);
956 soft = task_rlimit(tsk, RLIMIT_CPU);
957 if (soft != RLIM_INFINITY) {
958 unsigned long psecs = div_u64(ptime, NSEC_PER_SEC);
959 unsigned long hard = task_rlimit_max(tsk, RLIMIT_CPU);
960 u64 x;
961 if (psecs >= hard) {
962 /*
963 * At the hard limit, we just die.
964 * No need to calculate anything else now.
965 */
966 if (print_fatal_signals) {
967 pr_info("RT Watchdog Timeout (hard): %s[%d]\n",
968 tsk->comm, task_pid_nr(tsk));
969 }
970 __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
971 return;
972 }
973 if (psecs >= soft) {
974 /*
975 * At the soft limit, send a SIGXCPU every second.
976 */
977 if (print_fatal_signals) {
978 pr_info("CPU Watchdog Timeout (soft): %s[%d]\n",
979 tsk->comm, task_pid_nr(tsk));
980 }
981 __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
982 if (soft < hard) {
983 soft++;
984 sig->rlim[RLIMIT_CPU].rlim_cur = soft;
985 }
986 }
987 x = soft * NSEC_PER_SEC;
988 if (!prof_expires || x < prof_expires)
989 prof_expires = x;
990 }
991
992 sig->cputime_expires.prof_exp = prof_expires;
993 sig->cputime_expires.virt_exp = virt_expires;
994 sig->cputime_expires.sched_exp = sched_expires;
995 if (task_cputime_zero(&sig->cputime_expires))
996 stop_process_timers(sig);
997
998 sig->cputimer.checking_timer = false;
999}
1000
1001/*
1002 * This is called from the signal code (via posixtimer_rearm)
1003 * when the last timer signal was delivered and we have to reload the timer.
1004 */
1005static void posix_cpu_timer_rearm(struct k_itimer *timer)
1006{
1007 struct sighand_struct *sighand;
1008 unsigned long flags;
1009 struct task_struct *p = timer->it.cpu.task;
1010 u64 now;
1011
1012 WARN_ON_ONCE(p == NULL);
1013
1014 /*
1015 * Fetch the current sample and update the timer's expiry time.
1016 */
1017 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1018 cpu_clock_sample(timer->it_clock, p, &now);
1019 bump_cpu_timer(timer, now);
1020 if (unlikely(p->exit_state))
1021 return;
1022
1023 /* Protect timer list r/w in arm_timer() */
1024 sighand = lock_task_sighand(p, &flags);
1025 if (!sighand)
1026 return;
1027 } else {
1028 /*
1029 * Protect arm_timer() and timer sampling in case of call to
1030 * thread_group_cputime().
1031 */
1032 sighand = lock_task_sighand(p, &flags);
1033 if (unlikely(sighand == NULL)) {
1034 /*
1035 * The process has been reaped.
1036 * We can't even collect a sample any more.
1037 */
1038 timer->it.cpu.expires = 0;
1039 return;
1040 } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1041 /* If the process is dying, no need to rearm */
1042 goto unlock;
1043 }
1044 cpu_timer_sample_group(timer->it_clock, p, &now);
1045 bump_cpu_timer(timer, now);
1046 /* Leave the sighand locked for the call below. */
1047 }
1048
1049 /*
1050 * Now re-arm for the new expiry time.
1051 */
1052 lockdep_assert_irqs_disabled();
1053 arm_timer(timer);
1054unlock:
1055 unlock_task_sighand(p, &flags);
1056}
1057
1058/**
1059 * task_cputime_expired - Compare two task_cputime entities.
1060 *
1061 * @sample: The task_cputime structure to be checked for expiration.
1062 * @expires: Expiration times, against which @sample will be checked.
1063 *
1064 * Checks @sample against @expires to see if any field of @sample has expired.
1065 * Returns true if any field of the former is greater than the corresponding
1066 * field of the latter if the latter field is set. Otherwise returns false.
1067 */
1068static inline int task_cputime_expired(const struct task_cputime *sample,
1069 const struct task_cputime *expires)
1070{
1071 if (expires->utime && sample->utime >= expires->utime)
1072 return 1;
1073 if (expires->stime && sample->utime + sample->stime >= expires->stime)
1074 return 1;
1075 if (expires->sum_exec_runtime != 0 &&
1076 sample->sum_exec_runtime >= expires->sum_exec_runtime)
1077 return 1;
1078 return 0;
1079}
1080
1081/**
1082 * fastpath_timer_check - POSIX CPU timers fast path.
1083 *
1084 * @tsk: The task (thread) being checked.
1085 *
1086 * Check the task and thread group timers. If both are zero (there are no
1087 * timers set) return false. Otherwise snapshot the task and thread group
1088 * timers and compare them with the corresponding expiration times. Return
1089 * true if a timer has expired, else return false.
1090 */
1091static inline int fastpath_timer_check(struct task_struct *tsk)
1092{
1093 struct signal_struct *sig;
1094
1095 if (!task_cputime_zero(&tsk->cputime_expires)) {
1096 struct task_cputime task_sample;
1097
1098 task_cputime(tsk, &task_sample.utime, &task_sample.stime);
1099 task_sample.sum_exec_runtime = tsk->se.sum_exec_runtime;
1100 if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
1101 return 1;
1102 }
1103
1104 sig = tsk->signal;
1105 /*
1106 * Check if thread group timers expired when the cputimer is
1107 * running and no other thread in the group is already checking
1108 * for thread group cputimers. These fields are read without the
1109 * sighand lock. However, this is fine because this is meant to
1110 * be a fastpath heuristic to determine whether we should try to
1111 * acquire the sighand lock to check/handle timers.
1112 *
1113 * In the worst case scenario, if 'running' or 'checking_timer' gets
1114 * set but the current thread doesn't see the change yet, we'll wait
1115 * until the next thread in the group gets a scheduler interrupt to
1116 * handle the timer. This isn't an issue in practice because these
1117 * types of delays with signals actually getting sent are expected.
1118 */
1119 if (READ_ONCE(sig->cputimer.running) &&
1120 !READ_ONCE(sig->cputimer.checking_timer)) {
1121 struct task_cputime group_sample;
1122
1123 sample_cputime_atomic(&group_sample, &sig->cputimer.cputime_atomic);
1124
1125 if (task_cputime_expired(&group_sample, &sig->cputime_expires))
1126 return 1;
1127 }
1128
1129 if (dl_task(tsk) && tsk->dl.dl_overrun)
1130 return 1;
1131
1132 return 0;
1133}
1134
1135/*
1136 * This is called from the timer interrupt handler. The irq handler has
1137 * already updated our counts. We need to check if any timers fire now.
1138 * Interrupts are disabled.
1139 */
1140void run_posix_cpu_timers(struct task_struct *tsk)
1141{
1142 LIST_HEAD(firing);
1143 struct k_itimer *timer, *next;
1144 unsigned long flags;
1145
1146 lockdep_assert_irqs_disabled();
1147
1148 /*
1149 * The fast path checks that there are no expired thread or thread
1150 * group timers. If that's so, just return.
1151 */
1152 if (!fastpath_timer_check(tsk))
1153 return;
1154
1155 if (!lock_task_sighand(tsk, &flags))
1156 return;
1157 /*
1158 * Here we take off tsk->signal->cpu_timers[N] and
1159 * tsk->cpu_timers[N] all the timers that are firing, and
1160 * put them on the firing list.
1161 */
1162 check_thread_timers(tsk, &firing);
1163
1164 check_process_timers(tsk, &firing);
1165
1166 /*
1167 * We must release these locks before taking any timer's lock.
1168 * There is a potential race with timer deletion here, as the
1169 * siglock now protects our private firing list. We have set
1170 * the firing flag in each timer, so that a deletion attempt
1171 * that gets the timer lock before we do will give it up and
1172 * spin until we've taken care of that timer below.
1173 */
1174 unlock_task_sighand(tsk, &flags);
1175
1176 /*
1177 * Now that all the timers on our list have the firing flag,
1178 * no one will touch their list entries but us. We'll take
1179 * each timer's lock before clearing its firing flag, so no
1180 * timer call will interfere.
1181 */
1182 list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1183 int cpu_firing;
1184
1185 spin_lock(&timer->it_lock);
1186 list_del_init(&timer->it.cpu.entry);
1187 cpu_firing = timer->it.cpu.firing;
1188 timer->it.cpu.firing = 0;
1189 /*
1190 * The firing flag is -1 if we collided with a reset
1191 * of the timer, which already reported this
1192 * almost-firing as an overrun. So don't generate an event.
1193 */
1194 if (likely(cpu_firing >= 0))
1195 cpu_timer_fire(timer);
1196 spin_unlock(&timer->it_lock);
1197 }
1198}
1199
1200/*
1201 * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
1202 * The tsk->sighand->siglock must be held by the caller.
1203 */
1204void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1205 u64 *newval, u64 *oldval)
1206{
1207 u64 now;
1208 int ret;
1209
1210 WARN_ON_ONCE(clock_idx == CPUCLOCK_SCHED);
1211 ret = cpu_timer_sample_group(clock_idx, tsk, &now);
1212
1213 if (oldval && ret != -EINVAL) {
1214 /*
1215 * We are setting itimer. The *oldval is absolute and we update
1216 * it to be relative, *newval argument is relative and we update
1217 * it to be absolute.
1218 */
1219 if (*oldval) {
1220 if (*oldval <= now) {
1221 /* Just about to fire. */
1222 *oldval = TICK_NSEC;
1223 } else {
1224 *oldval -= now;
1225 }
1226 }
1227
1228 if (!*newval)
1229 return;
1230 *newval += now;
1231 }
1232
1233 /*
1234 * Update expiration cache if we are the earliest timer, or eventually
1235 * RLIMIT_CPU limit is earlier than prof_exp cpu timer expire.
1236 */
1237 switch (clock_idx) {
1238 case CPUCLOCK_PROF:
1239 if (expires_gt(tsk->signal->cputime_expires.prof_exp, *newval))
1240 tsk->signal->cputime_expires.prof_exp = *newval;
1241 break;
1242 case CPUCLOCK_VIRT:
1243 if (expires_gt(tsk->signal->cputime_expires.virt_exp, *newval))
1244 tsk->signal->cputime_expires.virt_exp = *newval;
1245 break;
1246 }
1247
1248 tick_dep_set_signal(tsk->signal, TICK_DEP_BIT_POSIX_TIMER);
1249}
1250
1251static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1252 const struct timespec64 *rqtp)
1253{
1254 struct itimerspec64 it;
1255 struct k_itimer timer;
1256 u64 expires;
1257 int error;
1258
1259 /*
1260 * Set up a temporary timer and then wait for it to go off.
1261 */
1262 memset(&timer, 0, sizeof timer);
1263 spin_lock_init(&timer.it_lock);
1264 timer.it_clock = which_clock;
1265 timer.it_overrun = -1;
1266 error = posix_cpu_timer_create(&timer);
1267 timer.it_process = current;
1268 if (!error) {
1269 static struct itimerspec64 zero_it;
1270 struct restart_block *restart;
1271
1272 memset(&it, 0, sizeof(it));
1273 it.it_value = *rqtp;
1274
1275 spin_lock_irq(&timer.it_lock);
1276 error = posix_cpu_timer_set(&timer, flags, &it, NULL);
1277 if (error) {
1278 spin_unlock_irq(&timer.it_lock);
1279 return error;
1280 }
1281
1282 while (!signal_pending(current)) {
1283 if (timer.it.cpu.expires == 0) {
1284 /*
1285 * Our timer fired and was reset, below
1286 * deletion can not fail.
1287 */
1288 posix_cpu_timer_del(&timer);
1289 spin_unlock_irq(&timer.it_lock);
1290 return 0;
1291 }
1292
1293 /*
1294 * Block until cpu_timer_fire (or a signal) wakes us.
1295 */
1296 __set_current_state(TASK_INTERRUPTIBLE);
1297 spin_unlock_irq(&timer.it_lock);
1298 schedule();
1299 spin_lock_irq(&timer.it_lock);
1300 }
1301
1302 /*
1303 * We were interrupted by a signal.
1304 */
1305 expires = timer.it.cpu.expires;
1306 error = posix_cpu_timer_set(&timer, 0, &zero_it, &it);
1307 if (!error) {
1308 /*
1309 * Timer is now unarmed, deletion can not fail.
1310 */
1311 posix_cpu_timer_del(&timer);
1312 }
1313 spin_unlock_irq(&timer.it_lock);
1314
1315 while (error == TIMER_RETRY) {
1316 /*
1317 * We need to handle case when timer was or is in the
1318 * middle of firing. In other cases we already freed
1319 * resources.
1320 */
1321 spin_lock_irq(&timer.it_lock);
1322 error = posix_cpu_timer_del(&timer);
1323 spin_unlock_irq(&timer.it_lock);
1324 }
1325
1326 if ((it.it_value.tv_sec | it.it_value.tv_nsec) == 0) {
1327 /*
1328 * It actually did fire already.
1329 */
1330 return 0;
1331 }
1332
1333 error = -ERESTART_RESTARTBLOCK;
1334 /*
1335 * Report back to the user the time still remaining.
1336 */
1337 restart = ¤t->restart_block;
1338 restart->nanosleep.expires = expires;
1339 if (restart->nanosleep.type != TT_NONE)
1340 error = nanosleep_copyout(restart, &it.it_value);
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 const struct timespec64 *rqtp)
1350{
1351 struct restart_block *restart_block = ¤t->restart_block;
1352 int error;
1353
1354 /*
1355 * Diagnose required errors first.
1356 */
1357 if (CPUCLOCK_PERTHREAD(which_clock) &&
1358 (CPUCLOCK_PID(which_clock) == 0 ||
1359 CPUCLOCK_PID(which_clock) == task_pid_vnr(current)))
1360 return -EINVAL;
1361
1362 error = do_cpu_nanosleep(which_clock, flags, rqtp);
1363
1364 if (error == -ERESTART_RESTARTBLOCK) {
1365
1366 if (flags & TIMER_ABSTIME)
1367 return -ERESTARTNOHAND;
1368
1369 restart_block->fn = posix_cpu_nsleep_restart;
1370 restart_block->nanosleep.clockid = which_clock;
1371 }
1372 return error;
1373}
1374
1375static long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1376{
1377 clockid_t which_clock = restart_block->nanosleep.clockid;
1378 struct timespec64 t;
1379
1380 t = ns_to_timespec64(restart_block->nanosleep.expires);
1381
1382 return do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t);
1383}
1384
1385#define PROCESS_CLOCK make_process_cpuclock(0, CPUCLOCK_SCHED)
1386#define THREAD_CLOCK make_thread_cpuclock(0, CPUCLOCK_SCHED)
1387
1388static int process_cpu_clock_getres(const clockid_t which_clock,
1389 struct timespec64 *tp)
1390{
1391 return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1392}
1393static int process_cpu_clock_get(const clockid_t which_clock,
1394 struct timespec64 *tp)
1395{
1396 return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1397}
1398static int process_cpu_timer_create(struct k_itimer *timer)
1399{
1400 timer->it_clock = PROCESS_CLOCK;
1401 return posix_cpu_timer_create(timer);
1402}
1403static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1404 const struct timespec64 *rqtp)
1405{
1406 return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp);
1407}
1408static int thread_cpu_clock_getres(const clockid_t which_clock,
1409 struct timespec64 *tp)
1410{
1411 return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1412}
1413static int thread_cpu_clock_get(const clockid_t which_clock,
1414 struct timespec64 *tp)
1415{
1416 return posix_cpu_clock_get(THREAD_CLOCK, tp);
1417}
1418static int thread_cpu_timer_create(struct k_itimer *timer)
1419{
1420 timer->it_clock = THREAD_CLOCK;
1421 return posix_cpu_timer_create(timer);
1422}
1423
1424const struct k_clock clock_posix_cpu = {
1425 .clock_getres = posix_cpu_clock_getres,
1426 .clock_set = posix_cpu_clock_set,
1427 .clock_get = posix_cpu_clock_get,
1428 .timer_create = posix_cpu_timer_create,
1429 .nsleep = posix_cpu_nsleep,
1430 .timer_set = posix_cpu_timer_set,
1431 .timer_del = posix_cpu_timer_del,
1432 .timer_get = posix_cpu_timer_get,
1433 .timer_rearm = posix_cpu_timer_rearm,
1434};
1435
1436const struct k_clock clock_process = {
1437 .clock_getres = process_cpu_clock_getres,
1438 .clock_get = process_cpu_clock_get,
1439 .timer_create = process_cpu_timer_create,
1440 .nsleep = process_cpu_nsleep,
1441};
1442
1443const struct k_clock clock_thread = {
1444 .clock_getres = thread_cpu_clock_getres,
1445 .clock_get = thread_cpu_clock_get,
1446 .timer_create = thread_cpu_timer_create,
1447};