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 
21 static void posix_cpu_timer_rearm(struct k_itimer *timer);
22 
23 void posix_cputimers_group_init(struct posix_cputimers *pct, u64 cpu_limit)
24 {
25 	posix_cputimers_init(pct);
26 	if (cpu_limit != RLIM_INFINITY) {
27 		pct->bases[CPUCLOCK_PROF].nextevt = cpu_limit * NSEC_PER_SEC;
28 		pct->timers_active = true;
29 	}
30 }
31 
32 /*
33  * Called after updating RLIMIT_CPU to run cpu timer and update
34  * tsk->signal->posix_cputimers.bases[clock].nextevt expiration cache if
35  * necessary. Needs siglock protection since other code may update the
36  * expiration cache as well.
37  */
38 void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
39 {
40 	u64 nsecs = rlim_new * NSEC_PER_SEC;
41 
42 	spin_lock_irq(&task->sighand->siglock);
43 	set_process_cpu_timer(task, CPUCLOCK_PROF, &nsecs, NULL);
44 	spin_unlock_irq(&task->sighand->siglock);
45 }
46 
47 /*
48  * Functions for validating access to tasks.
49  */
50 static struct pid *pid_for_clock(const clockid_t clock, bool gettime)
51 {
52 	const bool thread = !!CPUCLOCK_PERTHREAD(clock);
53 	const pid_t upid = CPUCLOCK_PID(clock);
54 	struct pid *pid;
55 
56 	if (CPUCLOCK_WHICH(clock) >= CPUCLOCK_MAX)
57 		return NULL;
58 
59 	/*
60 	 * If the encoded PID is 0, then the timer is targeted at current
61 	 * or the process to which current belongs.
62 	 */
63 	if (upid == 0)
64 		return thread ? task_pid(current) : task_tgid(current);
65 
66 	pid = find_vpid(upid);
67 	if (!pid)
68 		return NULL;
69 
70 	if (thread) {
71 		struct task_struct *tsk = pid_task(pid, PIDTYPE_PID);
72 		return (tsk && same_thread_group(tsk, current)) ? pid : NULL;
73 	}
74 
75 	/*
76 	 * For clock_gettime(PROCESS) allow finding the process by
77 	 * with the pid of the current task.  The code needs the tgid
78 	 * of the process so that pid_task(pid, PIDTYPE_TGID) can be
79 	 * used to find the process.
80 	 */
81 	if (gettime && (pid == task_pid(current)))
82 		return task_tgid(current);
83 
84 	/*
85 	 * For processes require that pid identifies a process.
86 	 */
87 	return pid_has_task(pid, PIDTYPE_TGID) ? pid : NULL;
88 }
89 
90 static inline int validate_clock_permissions(const clockid_t clock)
91 {
92 	int ret;
93 
94 	rcu_read_lock();
95 	ret = pid_for_clock(clock, false) ? 0 : -EINVAL;
96 	rcu_read_unlock();
97 
98 	return ret;
99 }
100 
101 static inline enum pid_type clock_pid_type(const clockid_t clock)
102 {
103 	return CPUCLOCK_PERTHREAD(clock) ? PIDTYPE_PID : PIDTYPE_TGID;
104 }
105 
106 static inline struct task_struct *cpu_timer_task_rcu(struct k_itimer *timer)
107 {
108 	return pid_task(timer->it.cpu.pid, clock_pid_type(timer->it_clock));
109 }
110 
111 /*
112  * Update expiry time from increment, and increase overrun count,
113  * given the current clock sample.
114  */
115 static u64 bump_cpu_timer(struct k_itimer *timer, u64 now)
116 {
117 	u64 delta, incr, expires = timer->it.cpu.node.expires;
118 	int i;
119 
120 	if (!timer->it_interval)
121 		return expires;
122 
123 	if (now < expires)
124 		return expires;
125 
126 	incr = timer->it_interval;
127 	delta = now + incr - expires;
128 
129 	/* Don't use (incr*2 < delta), incr*2 might overflow. */
130 	for (i = 0; incr < delta - incr; i++)
131 		incr = incr << 1;
132 
133 	for (; i >= 0; incr >>= 1, i--) {
134 		if (delta < incr)
135 			continue;
136 
137 		timer->it.cpu.node.expires += incr;
138 		timer->it_overrun += 1LL << i;
139 		delta -= incr;
140 	}
141 	return timer->it.cpu.node.expires;
142 }
143 
144 /* Check whether all cache entries contain U64_MAX, i.e. eternal expiry time */
145 static inline bool expiry_cache_is_inactive(const struct posix_cputimers *pct)
146 {
147 	return !(~pct->bases[CPUCLOCK_PROF].nextevt |
148 		 ~pct->bases[CPUCLOCK_VIRT].nextevt |
149 		 ~pct->bases[CPUCLOCK_SCHED].nextevt);
150 }
151 
152 static int
153 posix_cpu_clock_getres(const clockid_t which_clock, struct timespec64 *tp)
154 {
155 	int error = validate_clock_permissions(which_clock);
156 
157 	if (!error) {
158 		tp->tv_sec = 0;
159 		tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
160 		if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
161 			/*
162 			 * If sched_clock is using a cycle counter, we
163 			 * don't have any idea of its true resolution
164 			 * exported, but it is much more than 1s/HZ.
165 			 */
166 			tp->tv_nsec = 1;
167 		}
168 	}
169 	return error;
170 }
171 
172 static int
173 posix_cpu_clock_set(const clockid_t clock, const struct timespec64 *tp)
174 {
175 	int error = validate_clock_permissions(clock);
176 
177 	/*
178 	 * You can never reset a CPU clock, but we check for other errors
179 	 * in the call before failing with EPERM.
180 	 */
181 	return error ? : -EPERM;
182 }
183 
184 /*
185  * Sample a per-thread clock for the given task. clkid is validated.
186  */
187 static u64 cpu_clock_sample(const clockid_t clkid, struct task_struct *p)
188 {
189 	u64 utime, stime;
190 
191 	if (clkid == CPUCLOCK_SCHED)
192 		return task_sched_runtime(p);
193 
194 	task_cputime(p, &utime, &stime);
195 
196 	switch (clkid) {
197 	case CPUCLOCK_PROF:
198 		return utime + stime;
199 	case CPUCLOCK_VIRT:
200 		return utime;
201 	default:
202 		WARN_ON_ONCE(1);
203 	}
204 	return 0;
205 }
206 
207 static inline void store_samples(u64 *samples, u64 stime, u64 utime, u64 rtime)
208 {
209 	samples[CPUCLOCK_PROF] = stime + utime;
210 	samples[CPUCLOCK_VIRT] = utime;
211 	samples[CPUCLOCK_SCHED] = rtime;
212 }
213 
214 static void task_sample_cputime(struct task_struct *p, u64 *samples)
215 {
216 	u64 stime, utime;
217 
218 	task_cputime(p, &utime, &stime);
219 	store_samples(samples, stime, utime, p->se.sum_exec_runtime);
220 }
221 
222 static void proc_sample_cputime_atomic(struct task_cputime_atomic *at,
223 				       u64 *samples)
224 {
225 	u64 stime, utime, rtime;
226 
227 	utime = atomic64_read(&at->utime);
228 	stime = atomic64_read(&at->stime);
229 	rtime = atomic64_read(&at->sum_exec_runtime);
230 	store_samples(samples, stime, utime, rtime);
231 }
232 
233 /*
234  * Set cputime to sum_cputime if sum_cputime > cputime. Use cmpxchg
235  * to avoid race conditions with concurrent updates to cputime.
236  */
237 static inline void __update_gt_cputime(atomic64_t *cputime, u64 sum_cputime)
238 {
239 	u64 curr_cputime;
240 retry:
241 	curr_cputime = atomic64_read(cputime);
242 	if (sum_cputime > curr_cputime) {
243 		if (atomic64_cmpxchg(cputime, curr_cputime, sum_cputime) != curr_cputime)
244 			goto retry;
245 	}
246 }
247 
248 static void update_gt_cputime(struct task_cputime_atomic *cputime_atomic,
249 			      struct task_cputime *sum)
250 {
251 	__update_gt_cputime(&cputime_atomic->utime, sum->utime);
252 	__update_gt_cputime(&cputime_atomic->stime, sum->stime);
253 	__update_gt_cputime(&cputime_atomic->sum_exec_runtime, sum->sum_exec_runtime);
254 }
255 
256 /**
257  * thread_group_sample_cputime - Sample cputime for a given task
258  * @tsk:	Task for which cputime needs to be started
259  * @samples:	Storage for time samples
260  *
261  * Called from sys_getitimer() to calculate the expiry time of an active
262  * timer. That means group cputime accounting is already active. Called
263  * with task sighand lock held.
264  *
265  * Updates @times with an uptodate sample of the thread group cputimes.
266  */
267 void thread_group_sample_cputime(struct task_struct *tsk, u64 *samples)
268 {
269 	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
270 	struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
271 
272 	WARN_ON_ONCE(!pct->timers_active);
273 
274 	proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
275 }
276 
277 /**
278  * thread_group_start_cputime - Start cputime and return a sample
279  * @tsk:	Task for which cputime needs to be started
280  * @samples:	Storage for time samples
281  *
282  * The thread group cputime accounting is avoided when there are no posix
283  * CPU timers armed. Before starting a timer it's required to check whether
284  * the time accounting is active. If not, a full update of the atomic
285  * accounting store needs to be done and the accounting enabled.
286  *
287  * Updates @times with an uptodate sample of the thread group cputimes.
288  */
289 static void thread_group_start_cputime(struct task_struct *tsk, u64 *samples)
290 {
291 	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
292 	struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
293 
294 	/* Check if cputimer isn't running. This is accessed without locking. */
295 	if (!READ_ONCE(pct->timers_active)) {
296 		struct task_cputime sum;
297 
298 		/*
299 		 * The POSIX timer interface allows for absolute time expiry
300 		 * values through the TIMER_ABSTIME flag, therefore we have
301 		 * to synchronize the timer to the clock every time we start it.
302 		 */
303 		thread_group_cputime(tsk, &sum);
304 		update_gt_cputime(&cputimer->cputime_atomic, &sum);
305 
306 		/*
307 		 * We're setting timers_active without a lock. Ensure this
308 		 * only gets written to in one operation. We set it after
309 		 * update_gt_cputime() as a small optimization, but
310 		 * barriers are not required because update_gt_cputime()
311 		 * can handle concurrent updates.
312 		 */
313 		WRITE_ONCE(pct->timers_active, true);
314 	}
315 	proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
316 }
317 
318 static void __thread_group_cputime(struct task_struct *tsk, u64 *samples)
319 {
320 	struct task_cputime ct;
321 
322 	thread_group_cputime(tsk, &ct);
323 	store_samples(samples, ct.stime, ct.utime, ct.sum_exec_runtime);
324 }
325 
326 /*
327  * Sample a process (thread group) clock for the given task clkid. If the
328  * group's cputime accounting is already enabled, read the atomic
329  * store. Otherwise a full update is required.  clkid is already validated.
330  */
331 static u64 cpu_clock_sample_group(const clockid_t clkid, struct task_struct *p,
332 				  bool start)
333 {
334 	struct thread_group_cputimer *cputimer = &p->signal->cputimer;
335 	struct posix_cputimers *pct = &p->signal->posix_cputimers;
336 	u64 samples[CPUCLOCK_MAX];
337 
338 	if (!READ_ONCE(pct->timers_active)) {
339 		if (start)
340 			thread_group_start_cputime(p, samples);
341 		else
342 			__thread_group_cputime(p, samples);
343 	} else {
344 		proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
345 	}
346 
347 	return samples[clkid];
348 }
349 
350 static int posix_cpu_clock_get(const clockid_t clock, struct timespec64 *tp)
351 {
352 	const clockid_t clkid = CPUCLOCK_WHICH(clock);
353 	struct task_struct *tsk;
354 	u64 t;
355 
356 	rcu_read_lock();
357 	tsk = pid_task(pid_for_clock(clock, true), clock_pid_type(clock));
358 	if (!tsk) {
359 		rcu_read_unlock();
360 		return -EINVAL;
361 	}
362 
363 	if (CPUCLOCK_PERTHREAD(clock))
364 		t = cpu_clock_sample(clkid, tsk);
365 	else
366 		t = cpu_clock_sample_group(clkid, tsk, false);
367 	rcu_read_unlock();
368 
369 	*tp = ns_to_timespec64(t);
370 	return 0;
371 }
372 
373 /*
374  * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
375  * This is called from sys_timer_create() and do_cpu_nanosleep() with the
376  * new timer already all-zeros initialized.
377  */
378 static int posix_cpu_timer_create(struct k_itimer *new_timer)
379 {
380 	static struct lock_class_key posix_cpu_timers_key;
381 	struct pid *pid;
382 
383 	rcu_read_lock();
384 	pid = pid_for_clock(new_timer->it_clock, false);
385 	if (!pid) {
386 		rcu_read_unlock();
387 		return -EINVAL;
388 	}
389 
390 	/*
391 	 * If posix timer expiry is handled in task work context then
392 	 * timer::it_lock can be taken without disabling interrupts as all
393 	 * other locking happens in task context. This requires a separate
394 	 * lock class key otherwise regular posix timer expiry would record
395 	 * the lock class being taken in interrupt context and generate a
396 	 * false positive warning.
397 	 */
398 	if (IS_ENABLED(CONFIG_POSIX_CPU_TIMERS_TASK_WORK))
399 		lockdep_set_class(&new_timer->it_lock, &posix_cpu_timers_key);
400 
401 	new_timer->kclock = &clock_posix_cpu;
402 	timerqueue_init(&new_timer->it.cpu.node);
403 	new_timer->it.cpu.pid = get_pid(pid);
404 	rcu_read_unlock();
405 	return 0;
406 }
407 
408 /*
409  * Clean up a CPU-clock timer that is about to be destroyed.
410  * This is called from timer deletion with the timer already locked.
411  * If we return TIMER_RETRY, it's necessary to release the timer's lock
412  * and try again.  (This happens when the timer is in the middle of firing.)
413  */
414 static int posix_cpu_timer_del(struct k_itimer *timer)
415 {
416 	struct cpu_timer *ctmr = &timer->it.cpu;
417 	struct sighand_struct *sighand;
418 	struct task_struct *p;
419 	unsigned long flags;
420 	int ret = 0;
421 
422 	rcu_read_lock();
423 	p = cpu_timer_task_rcu(timer);
424 	if (!p)
425 		goto out;
426 
427 	/*
428 	 * Protect against sighand release/switch in exit/exec and process/
429 	 * thread timer list entry concurrent read/writes.
430 	 */
431 	sighand = lock_task_sighand(p, &flags);
432 	if (unlikely(sighand == NULL)) {
433 		/*
434 		 * This raced with the reaping of the task. The exit cleanup
435 		 * should have removed this timer from the timer queue.
436 		 */
437 		WARN_ON_ONCE(ctmr->head || timerqueue_node_queued(&ctmr->node));
438 	} else {
439 		if (timer->it.cpu.firing)
440 			ret = TIMER_RETRY;
441 		else
442 			cpu_timer_dequeue(ctmr);
443 
444 		unlock_task_sighand(p, &flags);
445 	}
446 
447 out:
448 	rcu_read_unlock();
449 	if (!ret)
450 		put_pid(ctmr->pid);
451 
452 	return ret;
453 }
454 
455 static void cleanup_timerqueue(struct timerqueue_head *head)
456 {
457 	struct timerqueue_node *node;
458 	struct cpu_timer *ctmr;
459 
460 	while ((node = timerqueue_getnext(head))) {
461 		timerqueue_del(head, node);
462 		ctmr = container_of(node, struct cpu_timer, node);
463 		ctmr->head = NULL;
464 	}
465 }
466 
467 /*
468  * Clean out CPU timers which are still armed when a thread exits. The
469  * timers are only removed from the list. No other updates are done. The
470  * corresponding posix timers are still accessible, but cannot be rearmed.
471  *
472  * This must be called with the siglock held.
473  */
474 static void cleanup_timers(struct posix_cputimers *pct)
475 {
476 	cleanup_timerqueue(&pct->bases[CPUCLOCK_PROF].tqhead);
477 	cleanup_timerqueue(&pct->bases[CPUCLOCK_VIRT].tqhead);
478 	cleanup_timerqueue(&pct->bases[CPUCLOCK_SCHED].tqhead);
479 }
480 
481 /*
482  * These are both called with the siglock held, when the current thread
483  * is being reaped.  When the final (leader) thread in the group is reaped,
484  * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
485  */
486 void posix_cpu_timers_exit(struct task_struct *tsk)
487 {
488 	cleanup_timers(&tsk->posix_cputimers);
489 }
490 void posix_cpu_timers_exit_group(struct task_struct *tsk)
491 {
492 	cleanup_timers(&tsk->signal->posix_cputimers);
493 }
494 
495 /*
496  * Insert the timer on the appropriate list before any timers that
497  * expire later.  This must be called with the sighand lock held.
498  */
499 static void arm_timer(struct k_itimer *timer, struct task_struct *p)
500 {
501 	int clkidx = CPUCLOCK_WHICH(timer->it_clock);
502 	struct cpu_timer *ctmr = &timer->it.cpu;
503 	u64 newexp = cpu_timer_getexpires(ctmr);
504 	struct posix_cputimer_base *base;
505 
506 	if (CPUCLOCK_PERTHREAD(timer->it_clock))
507 		base = p->posix_cputimers.bases + clkidx;
508 	else
509 		base = p->signal->posix_cputimers.bases + clkidx;
510 
511 	if (!cpu_timer_enqueue(&base->tqhead, ctmr))
512 		return;
513 
514 	/*
515 	 * We are the new earliest-expiring POSIX 1.b timer, hence
516 	 * need to update expiration cache. Take into account that
517 	 * for process timers we share expiration cache with itimers
518 	 * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
519 	 */
520 	if (newexp < base->nextevt)
521 		base->nextevt = newexp;
522 
523 	if (CPUCLOCK_PERTHREAD(timer->it_clock))
524 		tick_dep_set_task(p, TICK_DEP_BIT_POSIX_TIMER);
525 	else
526 		tick_dep_set_signal(p->signal, TICK_DEP_BIT_POSIX_TIMER);
527 }
528 
529 /*
530  * The timer is locked, fire it and arrange for its reload.
531  */
532 static void cpu_timer_fire(struct k_itimer *timer)
533 {
534 	struct cpu_timer *ctmr = &timer->it.cpu;
535 
536 	if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
537 		/*
538 		 * User don't want any signal.
539 		 */
540 		cpu_timer_setexpires(ctmr, 0);
541 	} else if (unlikely(timer->sigq == NULL)) {
542 		/*
543 		 * This a special case for clock_nanosleep,
544 		 * not a normal timer from sys_timer_create.
545 		 */
546 		wake_up_process(timer->it_process);
547 		cpu_timer_setexpires(ctmr, 0);
548 	} else if (!timer->it_interval) {
549 		/*
550 		 * One-shot timer.  Clear it as soon as it's fired.
551 		 */
552 		posix_timer_event(timer, 0);
553 		cpu_timer_setexpires(ctmr, 0);
554 	} else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
555 		/*
556 		 * The signal did not get queued because the signal
557 		 * was ignored, so we won't get any callback to
558 		 * reload the timer.  But we need to keep it
559 		 * ticking in case the signal is deliverable next time.
560 		 */
561 		posix_cpu_timer_rearm(timer);
562 		++timer->it_requeue_pending;
563 	}
564 }
565 
566 /*
567  * Guts of sys_timer_settime for CPU timers.
568  * This is called with the timer locked and interrupts disabled.
569  * If we return TIMER_RETRY, it's necessary to release the timer's lock
570  * and try again.  (This happens when the timer is in the middle of firing.)
571  */
572 static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
573 			       struct itimerspec64 *new, struct itimerspec64 *old)
574 {
575 	clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
576 	u64 old_expires, new_expires, old_incr, val;
577 	struct cpu_timer *ctmr = &timer->it.cpu;
578 	struct sighand_struct *sighand;
579 	struct task_struct *p;
580 	unsigned long flags;
581 	int ret = 0;
582 
583 	rcu_read_lock();
584 	p = cpu_timer_task_rcu(timer);
585 	if (!p) {
586 		/*
587 		 * If p has just been reaped, we can no
588 		 * longer get any information about it at all.
589 		 */
590 		rcu_read_unlock();
591 		return -ESRCH;
592 	}
593 
594 	/*
595 	 * Use the to_ktime conversion because that clamps the maximum
596 	 * value to KTIME_MAX and avoid multiplication overflows.
597 	 */
598 	new_expires = ktime_to_ns(timespec64_to_ktime(new->it_value));
599 
600 	/*
601 	 * Protect against sighand release/switch in exit/exec and p->cpu_timers
602 	 * and p->signal->cpu_timers read/write in arm_timer()
603 	 */
604 	sighand = lock_task_sighand(p, &flags);
605 	/*
606 	 * If p has just been reaped, we can no
607 	 * longer get any information about it at all.
608 	 */
609 	if (unlikely(sighand == NULL)) {
610 		rcu_read_unlock();
611 		return -ESRCH;
612 	}
613 
614 	/*
615 	 * Disarm any old timer after extracting its expiry time.
616 	 */
617 	old_incr = timer->it_interval;
618 	old_expires = cpu_timer_getexpires(ctmr);
619 
620 	if (unlikely(timer->it.cpu.firing)) {
621 		timer->it.cpu.firing = -1;
622 		ret = TIMER_RETRY;
623 	} else {
624 		cpu_timer_dequeue(ctmr);
625 	}
626 
627 	/*
628 	 * We need to sample the current value to convert the new
629 	 * value from to relative and absolute, and to convert the
630 	 * old value from absolute to relative.  To set a process
631 	 * timer, we need a sample to balance the thread expiry
632 	 * times (in arm_timer).  With an absolute time, we must
633 	 * check if it's already passed.  In short, we need a sample.
634 	 */
635 	if (CPUCLOCK_PERTHREAD(timer->it_clock))
636 		val = cpu_clock_sample(clkid, p);
637 	else
638 		val = cpu_clock_sample_group(clkid, p, true);
639 
640 	if (old) {
641 		if (old_expires == 0) {
642 			old->it_value.tv_sec = 0;
643 			old->it_value.tv_nsec = 0;
644 		} else {
645 			/*
646 			 * Update the timer in case it has overrun already.
647 			 * If it has, we'll report it as having overrun and
648 			 * with the next reloaded timer already ticking,
649 			 * though we are swallowing that pending
650 			 * notification here to install the new setting.
651 			 */
652 			u64 exp = bump_cpu_timer(timer, val);
653 
654 			if (val < exp) {
655 				old_expires = exp - val;
656 				old->it_value = ns_to_timespec64(old_expires);
657 			} else {
658 				old->it_value.tv_nsec = 1;
659 				old->it_value.tv_sec = 0;
660 			}
661 		}
662 	}
663 
664 	if (unlikely(ret)) {
665 		/*
666 		 * We are colliding with the timer actually firing.
667 		 * Punt after filling in the timer's old value, and
668 		 * disable this firing since we are already reporting
669 		 * it as an overrun (thanks to bump_cpu_timer above).
670 		 */
671 		unlock_task_sighand(p, &flags);
672 		goto out;
673 	}
674 
675 	if (new_expires != 0 && !(timer_flags & TIMER_ABSTIME)) {
676 		new_expires += val;
677 	}
678 
679 	/*
680 	 * Install the new expiry time (or zero).
681 	 * For a timer with no notification action, we don't actually
682 	 * arm the timer (we'll just fake it for timer_gettime).
683 	 */
684 	cpu_timer_setexpires(ctmr, new_expires);
685 	if (new_expires != 0 && val < new_expires) {
686 		arm_timer(timer, p);
687 	}
688 
689 	unlock_task_sighand(p, &flags);
690 	/*
691 	 * Install the new reload setting, and
692 	 * set up the signal and overrun bookkeeping.
693 	 */
694 	timer->it_interval = timespec64_to_ktime(new->it_interval);
695 
696 	/*
697 	 * This acts as a modification timestamp for the timer,
698 	 * so any automatic reload attempt will punt on seeing
699 	 * that we have reset the timer manually.
700 	 */
701 	timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
702 		~REQUEUE_PENDING;
703 	timer->it_overrun_last = 0;
704 	timer->it_overrun = -1;
705 
706 	if (new_expires != 0 && !(val < new_expires)) {
707 		/*
708 		 * The designated time already passed, so we notify
709 		 * immediately, even if the thread never runs to
710 		 * accumulate more time on this clock.
711 		 */
712 		cpu_timer_fire(timer);
713 	}
714 
715 	ret = 0;
716  out:
717 	rcu_read_unlock();
718 	if (old)
719 		old->it_interval = ns_to_timespec64(old_incr);
720 
721 	return ret;
722 }
723 
724 static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp)
725 {
726 	clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
727 	struct cpu_timer *ctmr = &timer->it.cpu;
728 	u64 now, expires = cpu_timer_getexpires(ctmr);
729 	struct task_struct *p;
730 
731 	rcu_read_lock();
732 	p = cpu_timer_task_rcu(timer);
733 	if (!p)
734 		goto out;
735 
736 	/*
737 	 * Easy part: convert the reload time.
738 	 */
739 	itp->it_interval = ktime_to_timespec64(timer->it_interval);
740 
741 	if (!expires)
742 		goto out;
743 
744 	/*
745 	 * Sample the clock to take the difference with the expiry time.
746 	 */
747 	if (CPUCLOCK_PERTHREAD(timer->it_clock))
748 		now = cpu_clock_sample(clkid, p);
749 	else
750 		now = cpu_clock_sample_group(clkid, p, false);
751 
752 	if (now < expires) {
753 		itp->it_value = ns_to_timespec64(expires - now);
754 	} else {
755 		/*
756 		 * The timer should have expired already, but the firing
757 		 * hasn't taken place yet.  Say it's just about to expire.
758 		 */
759 		itp->it_value.tv_nsec = 1;
760 		itp->it_value.tv_sec = 0;
761 	}
762 out:
763 	rcu_read_unlock();
764 }
765 
766 #define MAX_COLLECTED	20
767 
768 static u64 collect_timerqueue(struct timerqueue_head *head,
769 			      struct list_head *firing, u64 now)
770 {
771 	struct timerqueue_node *next;
772 	int i = 0;
773 
774 	while ((next = timerqueue_getnext(head))) {
775 		struct cpu_timer *ctmr;
776 		u64 expires;
777 
778 		ctmr = container_of(next, struct cpu_timer, node);
779 		expires = cpu_timer_getexpires(ctmr);
780 		/* Limit the number of timers to expire at once */
781 		if (++i == MAX_COLLECTED || now < expires)
782 			return expires;
783 
784 		ctmr->firing = 1;
785 		cpu_timer_dequeue(ctmr);
786 		list_add_tail(&ctmr->elist, firing);
787 	}
788 
789 	return U64_MAX;
790 }
791 
792 static void collect_posix_cputimers(struct posix_cputimers *pct, u64 *samples,
793 				    struct list_head *firing)
794 {
795 	struct posix_cputimer_base *base = pct->bases;
796 	int i;
797 
798 	for (i = 0; i < CPUCLOCK_MAX; i++, base++) {
799 		base->nextevt = collect_timerqueue(&base->tqhead, firing,
800 						    samples[i]);
801 	}
802 }
803 
804 static inline void check_dl_overrun(struct task_struct *tsk)
805 {
806 	if (tsk->dl.dl_overrun) {
807 		tsk->dl.dl_overrun = 0;
808 		__group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
809 	}
810 }
811 
812 static bool check_rlimit(u64 time, u64 limit, int signo, bool rt, bool hard)
813 {
814 	if (time < limit)
815 		return false;
816 
817 	if (print_fatal_signals) {
818 		pr_info("%s Watchdog Timeout (%s): %s[%d]\n",
819 			rt ? "RT" : "CPU", hard ? "hard" : "soft",
820 			current->comm, task_pid_nr(current));
821 	}
822 	__group_send_sig_info(signo, SEND_SIG_PRIV, current);
823 	return true;
824 }
825 
826 /*
827  * Check for any per-thread CPU timers that have fired and move them off
828  * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
829  * tsk->it_*_expires values to reflect the remaining thread CPU timers.
830  */
831 static void check_thread_timers(struct task_struct *tsk,
832 				struct list_head *firing)
833 {
834 	struct posix_cputimers *pct = &tsk->posix_cputimers;
835 	u64 samples[CPUCLOCK_MAX];
836 	unsigned long soft;
837 
838 	if (dl_task(tsk))
839 		check_dl_overrun(tsk);
840 
841 	if (expiry_cache_is_inactive(pct))
842 		return;
843 
844 	task_sample_cputime(tsk, samples);
845 	collect_posix_cputimers(pct, samples, firing);
846 
847 	/*
848 	 * Check for the special case thread timers.
849 	 */
850 	soft = task_rlimit(tsk, RLIMIT_RTTIME);
851 	if (soft != RLIM_INFINITY) {
852 		/* Task RT timeout is accounted in jiffies. RTTIME is usec */
853 		unsigned long rttime = tsk->rt.timeout * (USEC_PER_SEC / HZ);
854 		unsigned long hard = task_rlimit_max(tsk, RLIMIT_RTTIME);
855 
856 		/* At the hard limit, send SIGKILL. No further action. */
857 		if (hard != RLIM_INFINITY &&
858 		    check_rlimit(rttime, hard, SIGKILL, true, true))
859 			return;
860 
861 		/* At the soft limit, send a SIGXCPU every second */
862 		if (check_rlimit(rttime, soft, SIGXCPU, true, false)) {
863 			soft += USEC_PER_SEC;
864 			tsk->signal->rlim[RLIMIT_RTTIME].rlim_cur = soft;
865 		}
866 	}
867 
868 	if (expiry_cache_is_inactive(pct))
869 		tick_dep_clear_task(tsk, TICK_DEP_BIT_POSIX_TIMER);
870 }
871 
872 static inline void stop_process_timers(struct signal_struct *sig)
873 {
874 	struct posix_cputimers *pct = &sig->posix_cputimers;
875 
876 	/* Turn off the active flag. This is done without locking. */
877 	WRITE_ONCE(pct->timers_active, false);
878 	tick_dep_clear_signal(sig, TICK_DEP_BIT_POSIX_TIMER);
879 }
880 
881 static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
882 			     u64 *expires, u64 cur_time, int signo)
883 {
884 	if (!it->expires)
885 		return;
886 
887 	if (cur_time >= it->expires) {
888 		if (it->incr)
889 			it->expires += it->incr;
890 		else
891 			it->expires = 0;
892 
893 		trace_itimer_expire(signo == SIGPROF ?
894 				    ITIMER_PROF : ITIMER_VIRTUAL,
895 				    task_tgid(tsk), cur_time);
896 		__group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
897 	}
898 
899 	if (it->expires && it->expires < *expires)
900 		*expires = it->expires;
901 }
902 
903 /*
904  * Check for any per-thread CPU timers that have fired and move them
905  * off the tsk->*_timers list onto the firing list.  Per-thread timers
906  * have already been taken off.
907  */
908 static void check_process_timers(struct task_struct *tsk,
909 				 struct list_head *firing)
910 {
911 	struct signal_struct *const sig = tsk->signal;
912 	struct posix_cputimers *pct = &sig->posix_cputimers;
913 	u64 samples[CPUCLOCK_MAX];
914 	unsigned long soft;
915 
916 	/*
917 	 * If there are no active process wide timers (POSIX 1.b, itimers,
918 	 * RLIMIT_CPU) nothing to check. Also skip the process wide timer
919 	 * processing when there is already another task handling them.
920 	 */
921 	if (!READ_ONCE(pct->timers_active) || pct->expiry_active)
922 		return;
923 
924 	/*
925 	 * Signify that a thread is checking for process timers.
926 	 * Write access to this field is protected by the sighand lock.
927 	 */
928 	pct->expiry_active = true;
929 
930 	/*
931 	 * Collect the current process totals. Group accounting is active
932 	 * so the sample can be taken directly.
933 	 */
934 	proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic, samples);
935 	collect_posix_cputimers(pct, samples, firing);
936 
937 	/*
938 	 * Check for the special case process timers.
939 	 */
940 	check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF],
941 			 &pct->bases[CPUCLOCK_PROF].nextevt,
942 			 samples[CPUCLOCK_PROF], SIGPROF);
943 	check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT],
944 			 &pct->bases[CPUCLOCK_VIRT].nextevt,
945 			 samples[CPUCLOCK_VIRT], SIGVTALRM);
946 
947 	soft = task_rlimit(tsk, RLIMIT_CPU);
948 	if (soft != RLIM_INFINITY) {
949 		/* RLIMIT_CPU is in seconds. Samples are nanoseconds */
950 		unsigned long hard = task_rlimit_max(tsk, RLIMIT_CPU);
951 		u64 ptime = samples[CPUCLOCK_PROF];
952 		u64 softns = (u64)soft * NSEC_PER_SEC;
953 		u64 hardns = (u64)hard * NSEC_PER_SEC;
954 
955 		/* At the hard limit, send SIGKILL. No further action. */
956 		if (hard != RLIM_INFINITY &&
957 		    check_rlimit(ptime, hardns, SIGKILL, false, true))
958 			return;
959 
960 		/* At the soft limit, send a SIGXCPU every second */
961 		if (check_rlimit(ptime, softns, SIGXCPU, false, false)) {
962 			sig->rlim[RLIMIT_CPU].rlim_cur = soft + 1;
963 			softns += NSEC_PER_SEC;
964 		}
965 
966 		/* Update the expiry cache */
967 		if (softns < pct->bases[CPUCLOCK_PROF].nextevt)
968 			pct->bases[CPUCLOCK_PROF].nextevt = softns;
969 	}
970 
971 	if (expiry_cache_is_inactive(pct))
972 		stop_process_timers(sig);
973 
974 	pct->expiry_active = false;
975 }
976 
977 /*
978  * This is called from the signal code (via posixtimer_rearm)
979  * when the last timer signal was delivered and we have to reload the timer.
980  */
981 static void posix_cpu_timer_rearm(struct k_itimer *timer)
982 {
983 	clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
984 	struct task_struct *p;
985 	struct sighand_struct *sighand;
986 	unsigned long flags;
987 	u64 now;
988 
989 	rcu_read_lock();
990 	p = cpu_timer_task_rcu(timer);
991 	if (!p)
992 		goto out;
993 
994 	/*
995 	 * Fetch the current sample and update the timer's expiry time.
996 	 */
997 	if (CPUCLOCK_PERTHREAD(timer->it_clock))
998 		now = cpu_clock_sample(clkid, p);
999 	else
1000 		now = cpu_clock_sample_group(clkid, p, true);
1001 
1002 	bump_cpu_timer(timer, now);
1003 
1004 	/* Protect timer list r/w in arm_timer() */
1005 	sighand = lock_task_sighand(p, &flags);
1006 	if (unlikely(sighand == NULL))
1007 		goto out;
1008 
1009 	/*
1010 	 * Now re-arm for the new expiry time.
1011 	 */
1012 	arm_timer(timer, p);
1013 	unlock_task_sighand(p, &flags);
1014 out:
1015 	rcu_read_unlock();
1016 }
1017 
1018 /**
1019  * task_cputimers_expired - Check whether posix CPU timers are expired
1020  *
1021  * @samples:	Array of current samples for the CPUCLOCK clocks
1022  * @pct:	Pointer to a posix_cputimers container
1023  *
1024  * Returns true if any member of @samples is greater than the corresponding
1025  * member of @pct->bases[CLK].nextevt. False otherwise
1026  */
1027 static inline bool
1028 task_cputimers_expired(const u64 *samples, struct posix_cputimers *pct)
1029 {
1030 	int i;
1031 
1032 	for (i = 0; i < CPUCLOCK_MAX; i++) {
1033 		if (samples[i] >= pct->bases[i].nextevt)
1034 			return true;
1035 	}
1036 	return false;
1037 }
1038 
1039 /**
1040  * fastpath_timer_check - POSIX CPU timers fast path.
1041  *
1042  * @tsk:	The task (thread) being checked.
1043  *
1044  * Check the task and thread group timers.  If both are zero (there are no
1045  * timers set) return false.  Otherwise snapshot the task and thread group
1046  * timers and compare them with the corresponding expiration times.  Return
1047  * true if a timer has expired, else return false.
1048  */
1049 static inline bool fastpath_timer_check(struct task_struct *tsk)
1050 {
1051 	struct posix_cputimers *pct = &tsk->posix_cputimers;
1052 	struct signal_struct *sig;
1053 
1054 	if (!expiry_cache_is_inactive(pct)) {
1055 		u64 samples[CPUCLOCK_MAX];
1056 
1057 		task_sample_cputime(tsk, samples);
1058 		if (task_cputimers_expired(samples, pct))
1059 			return true;
1060 	}
1061 
1062 	sig = tsk->signal;
1063 	pct = &sig->posix_cputimers;
1064 	/*
1065 	 * Check if thread group timers expired when timers are active and
1066 	 * no other thread in the group is already handling expiry for
1067 	 * thread group cputimers. These fields are read without the
1068 	 * sighand lock. However, this is fine because this is meant to be
1069 	 * a fastpath heuristic to determine whether we should try to
1070 	 * acquire the sighand lock to handle timer expiry.
1071 	 *
1072 	 * In the worst case scenario, if concurrently timers_active is set
1073 	 * or expiry_active is cleared, but the current thread doesn't see
1074 	 * the change yet, the timer checks are delayed until the next
1075 	 * thread in the group gets a scheduler interrupt to handle the
1076 	 * timer. This isn't an issue in practice because these types of
1077 	 * delays with signals actually getting sent are expected.
1078 	 */
1079 	if (READ_ONCE(pct->timers_active) && !READ_ONCE(pct->expiry_active)) {
1080 		u64 samples[CPUCLOCK_MAX];
1081 
1082 		proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic,
1083 					   samples);
1084 
1085 		if (task_cputimers_expired(samples, pct))
1086 			return true;
1087 	}
1088 
1089 	if (dl_task(tsk) && tsk->dl.dl_overrun)
1090 		return true;
1091 
1092 	return false;
1093 }
1094 
1095 static void handle_posix_cpu_timers(struct task_struct *tsk);
1096 
1097 #ifdef CONFIG_POSIX_CPU_TIMERS_TASK_WORK
1098 static void posix_cpu_timers_work(struct callback_head *work)
1099 {
1100 	handle_posix_cpu_timers(current);
1101 }
1102 
1103 /*
1104  * Initialize posix CPU timers task work in init task. Out of line to
1105  * keep the callback static and to avoid header recursion hell.
1106  */
1107 void __init posix_cputimers_init_work(void)
1108 {
1109 	init_task_work(&current->posix_cputimers_work.work,
1110 		       posix_cpu_timers_work);
1111 }
1112 
1113 /*
1114  * Note: All operations on tsk->posix_cputimer_work.scheduled happen either
1115  * in hard interrupt context or in task context with interrupts
1116  * disabled. Aside of that the writer/reader interaction is always in the
1117  * context of the current task, which means they are strict per CPU.
1118  */
1119 static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
1120 {
1121 	return tsk->posix_cputimers_work.scheduled;
1122 }
1123 
1124 static inline void __run_posix_cpu_timers(struct task_struct *tsk)
1125 {
1126 	if (WARN_ON_ONCE(tsk->posix_cputimers_work.scheduled))
1127 		return;
1128 
1129 	/* Schedule task work to actually expire the timers */
1130 	tsk->posix_cputimers_work.scheduled = true;
1131 	task_work_add(tsk, &tsk->posix_cputimers_work.work, TWA_RESUME);
1132 }
1133 
1134 static inline bool posix_cpu_timers_enable_work(struct task_struct *tsk,
1135 						unsigned long start)
1136 {
1137 	bool ret = true;
1138 
1139 	/*
1140 	 * On !RT kernels interrupts are disabled while collecting expired
1141 	 * timers, so no tick can happen and the fast path check can be
1142 	 * reenabled without further checks.
1143 	 */
1144 	if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
1145 		tsk->posix_cputimers_work.scheduled = false;
1146 		return true;
1147 	}
1148 
1149 	/*
1150 	 * On RT enabled kernels ticks can happen while the expired timers
1151 	 * are collected under sighand lock. But any tick which observes
1152 	 * the CPUTIMERS_WORK_SCHEDULED bit set, does not run the fastpath
1153 	 * checks. So reenabling the tick work has do be done carefully:
1154 	 *
1155 	 * Disable interrupts and run the fast path check if jiffies have
1156 	 * advanced since the collecting of expired timers started. If
1157 	 * jiffies have not advanced or the fast path check did not find
1158 	 * newly expired timers, reenable the fast path check in the timer
1159 	 * interrupt. If there are newly expired timers, return false and
1160 	 * let the collection loop repeat.
1161 	 */
1162 	local_irq_disable();
1163 	if (start != jiffies && fastpath_timer_check(tsk))
1164 		ret = false;
1165 	else
1166 		tsk->posix_cputimers_work.scheduled = false;
1167 	local_irq_enable();
1168 
1169 	return ret;
1170 }
1171 #else /* CONFIG_POSIX_CPU_TIMERS_TASK_WORK */
1172 static inline void __run_posix_cpu_timers(struct task_struct *tsk)
1173 {
1174 	lockdep_posixtimer_enter();
1175 	handle_posix_cpu_timers(tsk);
1176 	lockdep_posixtimer_exit();
1177 }
1178 
1179 static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
1180 {
1181 	return false;
1182 }
1183 
1184 static inline bool posix_cpu_timers_enable_work(struct task_struct *tsk,
1185 						unsigned long start)
1186 {
1187 	return true;
1188 }
1189 #endif /* CONFIG_POSIX_CPU_TIMERS_TASK_WORK */
1190 
1191 static void handle_posix_cpu_timers(struct task_struct *tsk)
1192 {
1193 	struct k_itimer *timer, *next;
1194 	unsigned long flags, start;
1195 	LIST_HEAD(firing);
1196 
1197 	if (!lock_task_sighand(tsk, &flags))
1198 		return;
1199 
1200 	do {
1201 		/*
1202 		 * On RT locking sighand lock does not disable interrupts,
1203 		 * so this needs to be careful vs. ticks. Store the current
1204 		 * jiffies value.
1205 		 */
1206 		start = READ_ONCE(jiffies);
1207 		barrier();
1208 
1209 		/*
1210 		 * Here we take off tsk->signal->cpu_timers[N] and
1211 		 * tsk->cpu_timers[N] all the timers that are firing, and
1212 		 * put them on the firing list.
1213 		 */
1214 		check_thread_timers(tsk, &firing);
1215 
1216 		check_process_timers(tsk, &firing);
1217 
1218 		/*
1219 		 * The above timer checks have updated the expiry cache and
1220 		 * because nothing can have queued or modified timers after
1221 		 * sighand lock was taken above it is guaranteed to be
1222 		 * consistent. So the next timer interrupt fastpath check
1223 		 * will find valid data.
1224 		 *
1225 		 * If timer expiry runs in the timer interrupt context then
1226 		 * the loop is not relevant as timers will be directly
1227 		 * expired in interrupt context. The stub function below
1228 		 * returns always true which allows the compiler to
1229 		 * optimize the loop out.
1230 		 *
1231 		 * If timer expiry is deferred to task work context then
1232 		 * the following rules apply:
1233 		 *
1234 		 * - On !RT kernels no tick can have happened on this CPU
1235 		 *   after sighand lock was acquired because interrupts are
1236 		 *   disabled. So reenabling task work before dropping
1237 		 *   sighand lock and reenabling interrupts is race free.
1238 		 *
1239 		 * - On RT kernels ticks might have happened but the tick
1240 		 *   work ignored posix CPU timer handling because the
1241 		 *   CPUTIMERS_WORK_SCHEDULED bit is set. Reenabling work
1242 		 *   must be done very carefully including a check whether
1243 		 *   ticks have happened since the start of the timer
1244 		 *   expiry checks. posix_cpu_timers_enable_work() takes
1245 		 *   care of that and eventually lets the expiry checks
1246 		 *   run again.
1247 		 */
1248 	} while (!posix_cpu_timers_enable_work(tsk, start));
1249 
1250 	/*
1251 	 * We must release sighand lock before taking any timer's lock.
1252 	 * There is a potential race with timer deletion here, as the
1253 	 * siglock now protects our private firing list.  We have set
1254 	 * the firing flag in each timer, so that a deletion attempt
1255 	 * that gets the timer lock before we do will give it up and
1256 	 * spin until we've taken care of that timer below.
1257 	 */
1258 	unlock_task_sighand(tsk, &flags);
1259 
1260 	/*
1261 	 * Now that all the timers on our list have the firing flag,
1262 	 * no one will touch their list entries but us.  We'll take
1263 	 * each timer's lock before clearing its firing flag, so no
1264 	 * timer call will interfere.
1265 	 */
1266 	list_for_each_entry_safe(timer, next, &firing, it.cpu.elist) {
1267 		int cpu_firing;
1268 
1269 		/*
1270 		 * spin_lock() is sufficient here even independent of the
1271 		 * expiry context. If expiry happens in hard interrupt
1272 		 * context it's obvious. For task work context it's safe
1273 		 * because all other operations on timer::it_lock happen in
1274 		 * task context (syscall or exit).
1275 		 */
1276 		spin_lock(&timer->it_lock);
1277 		list_del_init(&timer->it.cpu.elist);
1278 		cpu_firing = timer->it.cpu.firing;
1279 		timer->it.cpu.firing = 0;
1280 		/*
1281 		 * The firing flag is -1 if we collided with a reset
1282 		 * of the timer, which already reported this
1283 		 * almost-firing as an overrun.  So don't generate an event.
1284 		 */
1285 		if (likely(cpu_firing >= 0))
1286 			cpu_timer_fire(timer);
1287 		spin_unlock(&timer->it_lock);
1288 	}
1289 }
1290 
1291 /*
1292  * This is called from the timer interrupt handler.  The irq handler has
1293  * already updated our counts.  We need to check if any timers fire now.
1294  * Interrupts are disabled.
1295  */
1296 void run_posix_cpu_timers(void)
1297 {
1298 	struct task_struct *tsk = current;
1299 
1300 	lockdep_assert_irqs_disabled();
1301 
1302 	/*
1303 	 * If the actual expiry is deferred to task work context and the
1304 	 * work is already scheduled there is no point to do anything here.
1305 	 */
1306 	if (posix_cpu_timers_work_scheduled(tsk))
1307 		return;
1308 
1309 	/*
1310 	 * The fast path checks that there are no expired thread or thread
1311 	 * group timers.  If that's so, just return.
1312 	 */
1313 	if (!fastpath_timer_check(tsk))
1314 		return;
1315 
1316 	__run_posix_cpu_timers(tsk);
1317 }
1318 
1319 /*
1320  * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
1321  * The tsk->sighand->siglock must be held by the caller.
1322  */
1323 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clkid,
1324 			   u64 *newval, u64 *oldval)
1325 {
1326 	u64 now, *nextevt;
1327 
1328 	if (WARN_ON_ONCE(clkid >= CPUCLOCK_SCHED))
1329 		return;
1330 
1331 	nextevt = &tsk->signal->posix_cputimers.bases[clkid].nextevt;
1332 	now = cpu_clock_sample_group(clkid, tsk, true);
1333 
1334 	if (oldval) {
1335 		/*
1336 		 * We are setting itimer. The *oldval is absolute and we update
1337 		 * it to be relative, *newval argument is relative and we update
1338 		 * it to be absolute.
1339 		 */
1340 		if (*oldval) {
1341 			if (*oldval <= now) {
1342 				/* Just about to fire. */
1343 				*oldval = TICK_NSEC;
1344 			} else {
1345 				*oldval -= now;
1346 			}
1347 		}
1348 
1349 		if (!*newval)
1350 			return;
1351 		*newval += now;
1352 	}
1353 
1354 	/*
1355 	 * Update expiration cache if this is the earliest timer. CPUCLOCK_PROF
1356 	 * expiry cache is also used by RLIMIT_CPU!.
1357 	 */
1358 	if (*newval < *nextevt)
1359 		*nextevt = *newval;
1360 
1361 	tick_dep_set_signal(tsk->signal, TICK_DEP_BIT_POSIX_TIMER);
1362 }
1363 
1364 static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1365 			    const struct timespec64 *rqtp)
1366 {
1367 	struct itimerspec64 it;
1368 	struct k_itimer timer;
1369 	u64 expires;
1370 	int error;
1371 
1372 	/*
1373 	 * Set up a temporary timer and then wait for it to go off.
1374 	 */
1375 	memset(&timer, 0, sizeof timer);
1376 	spin_lock_init(&timer.it_lock);
1377 	timer.it_clock = which_clock;
1378 	timer.it_overrun = -1;
1379 	error = posix_cpu_timer_create(&timer);
1380 	timer.it_process = current;
1381 
1382 	if (!error) {
1383 		static struct itimerspec64 zero_it;
1384 		struct restart_block *restart;
1385 
1386 		memset(&it, 0, sizeof(it));
1387 		it.it_value = *rqtp;
1388 
1389 		spin_lock_irq(&timer.it_lock);
1390 		error = posix_cpu_timer_set(&timer, flags, &it, NULL);
1391 		if (error) {
1392 			spin_unlock_irq(&timer.it_lock);
1393 			return error;
1394 		}
1395 
1396 		while (!signal_pending(current)) {
1397 			if (!cpu_timer_getexpires(&timer.it.cpu)) {
1398 				/*
1399 				 * Our timer fired and was reset, below
1400 				 * deletion can not fail.
1401 				 */
1402 				posix_cpu_timer_del(&timer);
1403 				spin_unlock_irq(&timer.it_lock);
1404 				return 0;
1405 			}
1406 
1407 			/*
1408 			 * Block until cpu_timer_fire (or a signal) wakes us.
1409 			 */
1410 			__set_current_state(TASK_INTERRUPTIBLE);
1411 			spin_unlock_irq(&timer.it_lock);
1412 			schedule();
1413 			spin_lock_irq(&timer.it_lock);
1414 		}
1415 
1416 		/*
1417 		 * We were interrupted by a signal.
1418 		 */
1419 		expires = cpu_timer_getexpires(&timer.it.cpu);
1420 		error = posix_cpu_timer_set(&timer, 0, &zero_it, &it);
1421 		if (!error) {
1422 			/*
1423 			 * Timer is now unarmed, deletion can not fail.
1424 			 */
1425 			posix_cpu_timer_del(&timer);
1426 		}
1427 		spin_unlock_irq(&timer.it_lock);
1428 
1429 		while (error == TIMER_RETRY) {
1430 			/*
1431 			 * We need to handle case when timer was or is in the
1432 			 * middle of firing. In other cases we already freed
1433 			 * resources.
1434 			 */
1435 			spin_lock_irq(&timer.it_lock);
1436 			error = posix_cpu_timer_del(&timer);
1437 			spin_unlock_irq(&timer.it_lock);
1438 		}
1439 
1440 		if ((it.it_value.tv_sec | it.it_value.tv_nsec) == 0) {
1441 			/*
1442 			 * It actually did fire already.
1443 			 */
1444 			return 0;
1445 		}
1446 
1447 		error = -ERESTART_RESTARTBLOCK;
1448 		/*
1449 		 * Report back to the user the time still remaining.
1450 		 */
1451 		restart = &current->restart_block;
1452 		restart->nanosleep.expires = expires;
1453 		if (restart->nanosleep.type != TT_NONE)
1454 			error = nanosleep_copyout(restart, &it.it_value);
1455 	}
1456 
1457 	return error;
1458 }
1459 
1460 static long posix_cpu_nsleep_restart(struct restart_block *restart_block);
1461 
1462 static int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1463 			    const struct timespec64 *rqtp)
1464 {
1465 	struct restart_block *restart_block = &current->restart_block;
1466 	int error;
1467 
1468 	/*
1469 	 * Diagnose required errors first.
1470 	 */
1471 	if (CPUCLOCK_PERTHREAD(which_clock) &&
1472 	    (CPUCLOCK_PID(which_clock) == 0 ||
1473 	     CPUCLOCK_PID(which_clock) == task_pid_vnr(current)))
1474 		return -EINVAL;
1475 
1476 	error = do_cpu_nanosleep(which_clock, flags, rqtp);
1477 
1478 	if (error == -ERESTART_RESTARTBLOCK) {
1479 
1480 		if (flags & TIMER_ABSTIME)
1481 			return -ERESTARTNOHAND;
1482 
1483 		restart_block->nanosleep.clockid = which_clock;
1484 		set_restart_fn(restart_block, posix_cpu_nsleep_restart);
1485 	}
1486 	return error;
1487 }
1488 
1489 static long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1490 {
1491 	clockid_t which_clock = restart_block->nanosleep.clockid;
1492 	struct timespec64 t;
1493 
1494 	t = ns_to_timespec64(restart_block->nanosleep.expires);
1495 
1496 	return do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t);
1497 }
1498 
1499 #define PROCESS_CLOCK	make_process_cpuclock(0, CPUCLOCK_SCHED)
1500 #define THREAD_CLOCK	make_thread_cpuclock(0, CPUCLOCK_SCHED)
1501 
1502 static int process_cpu_clock_getres(const clockid_t which_clock,
1503 				    struct timespec64 *tp)
1504 {
1505 	return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1506 }
1507 static int process_cpu_clock_get(const clockid_t which_clock,
1508 				 struct timespec64 *tp)
1509 {
1510 	return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1511 }
1512 static int process_cpu_timer_create(struct k_itimer *timer)
1513 {
1514 	timer->it_clock = PROCESS_CLOCK;
1515 	return posix_cpu_timer_create(timer);
1516 }
1517 static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1518 			      const struct timespec64 *rqtp)
1519 {
1520 	return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp);
1521 }
1522 static int thread_cpu_clock_getres(const clockid_t which_clock,
1523 				   struct timespec64 *tp)
1524 {
1525 	return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1526 }
1527 static int thread_cpu_clock_get(const clockid_t which_clock,
1528 				struct timespec64 *tp)
1529 {
1530 	return posix_cpu_clock_get(THREAD_CLOCK, tp);
1531 }
1532 static int thread_cpu_timer_create(struct k_itimer *timer)
1533 {
1534 	timer->it_clock = THREAD_CLOCK;
1535 	return posix_cpu_timer_create(timer);
1536 }
1537 
1538 const struct k_clock clock_posix_cpu = {
1539 	.clock_getres		= posix_cpu_clock_getres,
1540 	.clock_set		= posix_cpu_clock_set,
1541 	.clock_get_timespec	= posix_cpu_clock_get,
1542 	.timer_create		= posix_cpu_timer_create,
1543 	.nsleep			= posix_cpu_nsleep,
1544 	.timer_set		= posix_cpu_timer_set,
1545 	.timer_del		= posix_cpu_timer_del,
1546 	.timer_get		= posix_cpu_timer_get,
1547 	.timer_rearm		= posix_cpu_timer_rearm,
1548 };
1549 
1550 const struct k_clock clock_process = {
1551 	.clock_getres		= process_cpu_clock_getres,
1552 	.clock_get_timespec	= process_cpu_clock_get,
1553 	.timer_create		= process_cpu_timer_create,
1554 	.nsleep			= process_cpu_nsleep,
1555 };
1556 
1557 const struct k_clock clock_thread = {
1558 	.clock_getres		= thread_cpu_clock_getres,
1559 	.clock_get_timespec	= thread_cpu_clock_get,
1560 	.timer_create		= thread_cpu_timer_create,
1561 };
1562