Line data Source code
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 : #include <linux/task_work.h>
19 :
20 : #include "posix-timers.h"
21 :
22 : static void posix_cpu_timer_rearm(struct k_itimer *timer);
23 :
24 107 : void posix_cputimers_group_init(struct posix_cputimers *pct, u64 cpu_limit)
25 : {
26 107 : posix_cputimers_init(pct);
27 107 : if (cpu_limit != RLIM_INFINITY) {
28 0 : pct->bases[CPUCLOCK_PROF].nextevt = cpu_limit * NSEC_PER_SEC;
29 0 : pct->timers_active = true;
30 : }
31 107 : }
32 :
33 : /*
34 : * Called after updating RLIMIT_CPU to run cpu timer and update
35 : * tsk->signal->posix_cputimers.bases[clock].nextevt expiration cache if
36 : * necessary. Needs siglock protection since other code may update the
37 : * expiration cache as well.
38 : *
39 : * Returns 0 on success, -ESRCH on failure. Can fail if the task is exiting and
40 : * we cannot lock_task_sighand. Cannot fail if task is current.
41 : */
42 0 : int update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
43 : {
44 0 : u64 nsecs = rlim_new * NSEC_PER_SEC;
45 : unsigned long irq_fl;
46 :
47 0 : if (!lock_task_sighand(task, &irq_fl))
48 : return -ESRCH;
49 0 : set_process_cpu_timer(task, CPUCLOCK_PROF, &nsecs, NULL);
50 0 : unlock_task_sighand(task, &irq_fl);
51 0 : return 0;
52 : }
53 :
54 : /*
55 : * Functions for validating access to tasks.
56 : */
57 0 : static struct pid *pid_for_clock(const clockid_t clock, bool gettime)
58 : {
59 0 : const bool thread = !!CPUCLOCK_PERTHREAD(clock);
60 0 : const pid_t upid = CPUCLOCK_PID(clock);
61 : struct pid *pid;
62 :
63 0 : if (CPUCLOCK_WHICH(clock) >= CPUCLOCK_MAX)
64 : return NULL;
65 :
66 : /*
67 : * If the encoded PID is 0, then the timer is targeted at current
68 : * or the process to which current belongs.
69 : */
70 0 : if (upid == 0)
71 0 : return thread ? task_pid(current) : task_tgid(current);
72 :
73 0 : pid = find_vpid(upid);
74 0 : if (!pid)
75 : return NULL;
76 :
77 0 : if (thread) {
78 0 : struct task_struct *tsk = pid_task(pid, PIDTYPE_PID);
79 0 : return (tsk && same_thread_group(tsk, current)) ? pid : NULL;
80 : }
81 :
82 : /*
83 : * For clock_gettime(PROCESS) allow finding the process by
84 : * with the pid of the current task. The code needs the tgid
85 : * of the process so that pid_task(pid, PIDTYPE_TGID) can be
86 : * used to find the process.
87 : */
88 0 : if (gettime && (pid == task_pid(current)))
89 0 : return task_tgid(current);
90 :
91 : /*
92 : * For processes require that pid identifies a process.
93 : */
94 0 : return pid_has_task(pid, PIDTYPE_TGID) ? pid : NULL;
95 : }
96 :
97 : static inline int validate_clock_permissions(const clockid_t clock)
98 : {
99 : int ret;
100 :
101 : rcu_read_lock();
102 0 : ret = pid_for_clock(clock, false) ? 0 : -EINVAL;
103 : rcu_read_unlock();
104 :
105 : return ret;
106 : }
107 :
108 : static inline enum pid_type clock_pid_type(const clockid_t clock)
109 : {
110 0 : return CPUCLOCK_PERTHREAD(clock) ? PIDTYPE_PID : PIDTYPE_TGID;
111 : }
112 :
113 : static inline struct task_struct *cpu_timer_task_rcu(struct k_itimer *timer)
114 : {
115 0 : return pid_task(timer->it.cpu.pid, clock_pid_type(timer->it_clock));
116 : }
117 :
118 : /*
119 : * Update expiry time from increment, and increase overrun count,
120 : * given the current clock sample.
121 : */
122 0 : static u64 bump_cpu_timer(struct k_itimer *timer, u64 now)
123 : {
124 0 : u64 delta, incr, expires = timer->it.cpu.node.expires;
125 : int i;
126 :
127 0 : if (!timer->it_interval)
128 : return expires;
129 :
130 0 : if (now < expires)
131 : return expires;
132 :
133 0 : incr = timer->it_interval;
134 0 : delta = now + incr - expires;
135 :
136 : /* Don't use (incr*2 < delta), incr*2 might overflow. */
137 0 : for (i = 0; incr < delta - incr; i++)
138 0 : incr = incr << 1;
139 :
140 0 : for (; i >= 0; incr >>= 1, i--) {
141 0 : if (delta < incr)
142 0 : continue;
143 :
144 0 : timer->it.cpu.node.expires += incr;
145 0 : timer->it_overrun += 1LL << i;
146 0 : delta -= incr;
147 : }
148 0 : return timer->it.cpu.node.expires;
149 : }
150 :
151 : /* Check whether all cache entries contain U64_MAX, i.e. eternal expiry time */
152 : static inline bool expiry_cache_is_inactive(const struct posix_cputimers *pct)
153 : {
154 26 : return !(~pct->bases[CPUCLOCK_PROF].nextevt |
155 26 : ~pct->bases[CPUCLOCK_VIRT].nextevt |
156 13 : ~pct->bases[CPUCLOCK_SCHED].nextevt);
157 : }
158 :
159 : static int
160 0 : posix_cpu_clock_getres(const clockid_t which_clock, struct timespec64 *tp)
161 : {
162 0 : int error = validate_clock_permissions(which_clock);
163 :
164 0 : if (!error) {
165 0 : tp->tv_sec = 0;
166 0 : tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
167 0 : if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
168 : /*
169 : * If sched_clock is using a cycle counter, we
170 : * don't have any idea of its true resolution
171 : * exported, but it is much more than 1s/HZ.
172 : */
173 0 : tp->tv_nsec = 1;
174 : }
175 : }
176 0 : return error;
177 : }
178 :
179 : static int
180 0 : posix_cpu_clock_set(const clockid_t clock, const struct timespec64 *tp)
181 : {
182 0 : int error = validate_clock_permissions(clock);
183 :
184 : /*
185 : * You can never reset a CPU clock, but we check for other errors
186 : * in the call before failing with EPERM.
187 : */
188 0 : return error ? : -EPERM;
189 : }
190 :
191 : /*
192 : * Sample a per-thread clock for the given task. clkid is validated.
193 : */
194 0 : static u64 cpu_clock_sample(const clockid_t clkid, struct task_struct *p)
195 : {
196 : u64 utime, stime;
197 :
198 0 : if (clkid == CPUCLOCK_SCHED)
199 0 : return task_sched_runtime(p);
200 :
201 0 : task_cputime(p, &utime, &stime);
202 :
203 0 : switch (clkid) {
204 : case CPUCLOCK_PROF:
205 0 : return utime + stime;
206 : case CPUCLOCK_VIRT:
207 : return utime;
208 : default:
209 0 : WARN_ON_ONCE(1);
210 : }
211 : return 0;
212 : }
213 :
214 : static inline void store_samples(u64 *samples, u64 stime, u64 utime, u64 rtime)
215 : {
216 0 : samples[CPUCLOCK_PROF] = stime + utime;
217 0 : samples[CPUCLOCK_VIRT] = utime;
218 0 : samples[CPUCLOCK_SCHED] = rtime;
219 : }
220 :
221 : static void task_sample_cputime(struct task_struct *p, u64 *samples)
222 : {
223 : u64 stime, utime;
224 :
225 0 : task_cputime(p, &utime, &stime);
226 0 : store_samples(samples, stime, utime, p->se.sum_exec_runtime);
227 : }
228 :
229 : static void proc_sample_cputime_atomic(struct task_cputime_atomic *at,
230 : u64 *samples)
231 : {
232 : u64 stime, utime, rtime;
233 :
234 0 : utime = atomic64_read(&at->utime);
235 0 : stime = atomic64_read(&at->stime);
236 0 : rtime = atomic64_read(&at->sum_exec_runtime);
237 0 : store_samples(samples, stime, utime, rtime);
238 : }
239 :
240 : /*
241 : * Set cputime to sum_cputime if sum_cputime > cputime. Use cmpxchg
242 : * to avoid race conditions with concurrent updates to cputime.
243 : */
244 : static inline void __update_gt_cputime(atomic64_t *cputime, u64 sum_cputime)
245 : {
246 : u64 curr_cputime;
247 : retry:
248 0 : curr_cputime = atomic64_read(cputime);
249 0 : if (sum_cputime > curr_cputime) {
250 0 : if (atomic64_cmpxchg(cputime, curr_cputime, sum_cputime) != curr_cputime)
251 : goto retry;
252 : }
253 : }
254 :
255 0 : static void update_gt_cputime(struct task_cputime_atomic *cputime_atomic,
256 : struct task_cputime *sum)
257 : {
258 0 : __update_gt_cputime(&cputime_atomic->utime, sum->utime);
259 0 : __update_gt_cputime(&cputime_atomic->stime, sum->stime);
260 0 : __update_gt_cputime(&cputime_atomic->sum_exec_runtime, sum->sum_exec_runtime);
261 0 : }
262 :
263 : /**
264 : * thread_group_sample_cputime - Sample cputime for a given task
265 : * @tsk: Task for which cputime needs to be started
266 : * @samples: Storage for time samples
267 : *
268 : * Called from sys_getitimer() to calculate the expiry time of an active
269 : * timer. That means group cputime accounting is already active. Called
270 : * with task sighand lock held.
271 : *
272 : * Updates @times with an uptodate sample of the thread group cputimes.
273 : */
274 0 : void thread_group_sample_cputime(struct task_struct *tsk, u64 *samples)
275 : {
276 0 : struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
277 0 : struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
278 :
279 0 : WARN_ON_ONCE(!pct->timers_active);
280 :
281 0 : proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
282 0 : }
283 :
284 : /**
285 : * thread_group_start_cputime - Start cputime and return a sample
286 : * @tsk: Task for which cputime needs to be started
287 : * @samples: Storage for time samples
288 : *
289 : * The thread group cputime accounting is avoided when there are no posix
290 : * CPU timers armed. Before starting a timer it's required to check whether
291 : * the time accounting is active. If not, a full update of the atomic
292 : * accounting store needs to be done and the accounting enabled.
293 : *
294 : * Updates @times with an uptodate sample of the thread group cputimes.
295 : */
296 0 : static void thread_group_start_cputime(struct task_struct *tsk, u64 *samples)
297 : {
298 0 : struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
299 0 : struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
300 :
301 0 : lockdep_assert_task_sighand_held(tsk);
302 :
303 : /* Check if cputimer isn't running. This is accessed without locking. */
304 0 : if (!READ_ONCE(pct->timers_active)) {
305 : struct task_cputime sum;
306 :
307 : /*
308 : * The POSIX timer interface allows for absolute time expiry
309 : * values through the TIMER_ABSTIME flag, therefore we have
310 : * to synchronize the timer to the clock every time we start it.
311 : */
312 0 : thread_group_cputime(tsk, &sum);
313 0 : update_gt_cputime(&cputimer->cputime_atomic, &sum);
314 :
315 : /*
316 : * We're setting timers_active without a lock. Ensure this
317 : * only gets written to in one operation. We set it after
318 : * update_gt_cputime() as a small optimization, but
319 : * barriers are not required because update_gt_cputime()
320 : * can handle concurrent updates.
321 : */
322 0 : WRITE_ONCE(pct->timers_active, true);
323 : }
324 0 : proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
325 0 : }
326 :
327 : static void __thread_group_cputime(struct task_struct *tsk, u64 *samples)
328 : {
329 : struct task_cputime ct;
330 :
331 0 : thread_group_cputime(tsk, &ct);
332 0 : store_samples(samples, ct.stime, ct.utime, ct.sum_exec_runtime);
333 : }
334 :
335 : /*
336 : * Sample a process (thread group) clock for the given task clkid. If the
337 : * group's cputime accounting is already enabled, read the atomic
338 : * store. Otherwise a full update is required. clkid is already validated.
339 : */
340 0 : static u64 cpu_clock_sample_group(const clockid_t clkid, struct task_struct *p,
341 : bool start)
342 : {
343 0 : struct thread_group_cputimer *cputimer = &p->signal->cputimer;
344 0 : struct posix_cputimers *pct = &p->signal->posix_cputimers;
345 : u64 samples[CPUCLOCK_MAX];
346 :
347 0 : if (!READ_ONCE(pct->timers_active)) {
348 0 : if (start)
349 0 : thread_group_start_cputime(p, samples);
350 : else
351 : __thread_group_cputime(p, samples);
352 : } else {
353 0 : proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
354 : }
355 :
356 0 : return samples[clkid];
357 : }
358 :
359 0 : static int posix_cpu_clock_get(const clockid_t clock, struct timespec64 *tp)
360 : {
361 0 : const clockid_t clkid = CPUCLOCK_WHICH(clock);
362 : struct task_struct *tsk;
363 : u64 t;
364 :
365 : rcu_read_lock();
366 0 : tsk = pid_task(pid_for_clock(clock, true), clock_pid_type(clock));
367 0 : if (!tsk) {
368 : rcu_read_unlock();
369 0 : return -EINVAL;
370 : }
371 :
372 0 : if (CPUCLOCK_PERTHREAD(clock))
373 0 : t = cpu_clock_sample(clkid, tsk);
374 : else
375 0 : t = cpu_clock_sample_group(clkid, tsk, false);
376 : rcu_read_unlock();
377 :
378 0 : *tp = ns_to_timespec64(t);
379 0 : return 0;
380 : }
381 :
382 : /*
383 : * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
384 : * This is called from sys_timer_create() and do_cpu_nanosleep() with the
385 : * new timer already all-zeros initialized.
386 : */
387 0 : static int posix_cpu_timer_create(struct k_itimer *new_timer)
388 : {
389 : static struct lock_class_key posix_cpu_timers_key;
390 : struct pid *pid;
391 :
392 : rcu_read_lock();
393 0 : pid = pid_for_clock(new_timer->it_clock, false);
394 0 : if (!pid) {
395 : rcu_read_unlock();
396 0 : return -EINVAL;
397 : }
398 :
399 : /*
400 : * If posix timer expiry is handled in task work context then
401 : * timer::it_lock can be taken without disabling interrupts as all
402 : * other locking happens in task context. This requires a separate
403 : * lock class key otherwise regular posix timer expiry would record
404 : * the lock class being taken in interrupt context and generate a
405 : * false positive warning.
406 : */
407 : if (IS_ENABLED(CONFIG_POSIX_CPU_TIMERS_TASK_WORK))
408 : lockdep_set_class(&new_timer->it_lock, &posix_cpu_timers_key);
409 :
410 0 : new_timer->kclock = &clock_posix_cpu;
411 0 : timerqueue_init(&new_timer->it.cpu.node);
412 0 : new_timer->it.cpu.pid = get_pid(pid);
413 : rcu_read_unlock();
414 0 : return 0;
415 : }
416 :
417 : static struct posix_cputimer_base *timer_base(struct k_itimer *timer,
418 : struct task_struct *tsk)
419 : {
420 0 : int clkidx = CPUCLOCK_WHICH(timer->it_clock);
421 :
422 0 : if (CPUCLOCK_PERTHREAD(timer->it_clock))
423 0 : return tsk->posix_cputimers.bases + clkidx;
424 : else
425 0 : return tsk->signal->posix_cputimers.bases + clkidx;
426 : }
427 :
428 : /*
429 : * Force recalculating the base earliest expiration on the next tick.
430 : * This will also re-evaluate the need to keep around the process wide
431 : * cputime counter and tick dependency and eventually shut these down
432 : * if necessary.
433 : */
434 : static void trigger_base_recalc_expires(struct k_itimer *timer,
435 : struct task_struct *tsk)
436 : {
437 0 : struct posix_cputimer_base *base = timer_base(timer, tsk);
438 :
439 0 : base->nextevt = 0;
440 : }
441 :
442 : /*
443 : * Dequeue the timer and reset the base if it was its earliest expiration.
444 : * It makes sure the next tick recalculates the base next expiration so we
445 : * don't keep the costly process wide cputime counter around for a random
446 : * amount of time, along with the tick dependency.
447 : *
448 : * If another timer gets queued between this and the next tick, its
449 : * expiration will update the base next event if necessary on the next
450 : * tick.
451 : */
452 0 : static void disarm_timer(struct k_itimer *timer, struct task_struct *p)
453 : {
454 0 : struct cpu_timer *ctmr = &timer->it.cpu;
455 : struct posix_cputimer_base *base;
456 :
457 0 : if (!cpu_timer_dequeue(ctmr))
458 : return;
459 :
460 0 : base = timer_base(timer, p);
461 0 : if (cpu_timer_getexpires(ctmr) == base->nextevt)
462 : trigger_base_recalc_expires(timer, p);
463 : }
464 :
465 :
466 : /*
467 : * Clean up a CPU-clock timer that is about to be destroyed.
468 : * This is called from timer deletion with the timer already locked.
469 : * If we return TIMER_RETRY, it's necessary to release the timer's lock
470 : * and try again. (This happens when the timer is in the middle of firing.)
471 : */
472 0 : static int posix_cpu_timer_del(struct k_itimer *timer)
473 : {
474 0 : struct cpu_timer *ctmr = &timer->it.cpu;
475 : struct sighand_struct *sighand;
476 : struct task_struct *p;
477 : unsigned long flags;
478 0 : int ret = 0;
479 :
480 : rcu_read_lock();
481 0 : p = cpu_timer_task_rcu(timer);
482 0 : if (!p)
483 : goto out;
484 :
485 : /*
486 : * Protect against sighand release/switch in exit/exec and process/
487 : * thread timer list entry concurrent read/writes.
488 : */
489 0 : sighand = lock_task_sighand(p, &flags);
490 0 : if (unlikely(sighand == NULL)) {
491 : /*
492 : * This raced with the reaping of the task. The exit cleanup
493 : * should have removed this timer from the timer queue.
494 : */
495 0 : WARN_ON_ONCE(ctmr->head || timerqueue_node_queued(&ctmr->node));
496 : } else {
497 0 : if (timer->it.cpu.firing)
498 : ret = TIMER_RETRY;
499 : else
500 0 : disarm_timer(timer, p);
501 :
502 0 : unlock_task_sighand(p, &flags);
503 : }
504 :
505 : out:
506 : rcu_read_unlock();
507 0 : if (!ret)
508 0 : put_pid(ctmr->pid);
509 :
510 0 : return ret;
511 : }
512 :
513 : static void cleanup_timerqueue(struct timerqueue_head *head)
514 : {
515 : struct timerqueue_node *node;
516 : struct cpu_timer *ctmr;
517 :
518 1116 : while ((node = timerqueue_getnext(head))) {
519 0 : timerqueue_del(head, node);
520 0 : ctmr = container_of(node, struct cpu_timer, node);
521 0 : ctmr->head = NULL;
522 : }
523 : }
524 :
525 : /*
526 : * Clean out CPU timers which are still armed when a thread exits. The
527 : * timers are only removed from the list. No other updates are done. The
528 : * corresponding posix timers are still accessible, but cannot be rearmed.
529 : *
530 : * This must be called with the siglock held.
531 : */
532 186 : static void cleanup_timers(struct posix_cputimers *pct)
533 : {
534 372 : cleanup_timerqueue(&pct->bases[CPUCLOCK_PROF].tqhead);
535 372 : cleanup_timerqueue(&pct->bases[CPUCLOCK_VIRT].tqhead);
536 372 : cleanup_timerqueue(&pct->bases[CPUCLOCK_SCHED].tqhead);
537 186 : }
538 :
539 : /*
540 : * These are both called with the siglock held, when the current thread
541 : * is being reaped. When the final (leader) thread in the group is reaped,
542 : * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
543 : */
544 93 : void posix_cpu_timers_exit(struct task_struct *tsk)
545 : {
546 93 : cleanup_timers(&tsk->posix_cputimers);
547 93 : }
548 93 : void posix_cpu_timers_exit_group(struct task_struct *tsk)
549 : {
550 93 : cleanup_timers(&tsk->signal->posix_cputimers);
551 93 : }
552 :
553 : /*
554 : * Insert the timer on the appropriate list before any timers that
555 : * expire later. This must be called with the sighand lock held.
556 : */
557 0 : static void arm_timer(struct k_itimer *timer, struct task_struct *p)
558 : {
559 0 : struct posix_cputimer_base *base = timer_base(timer, p);
560 0 : struct cpu_timer *ctmr = &timer->it.cpu;
561 0 : u64 newexp = cpu_timer_getexpires(ctmr);
562 :
563 0 : if (!cpu_timer_enqueue(&base->tqhead, ctmr))
564 : return;
565 :
566 : /*
567 : * We are the new earliest-expiring POSIX 1.b timer, hence
568 : * need to update expiration cache. Take into account that
569 : * for process timers we share expiration cache with itimers
570 : * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
571 : */
572 0 : if (newexp < base->nextevt)
573 0 : base->nextevt = newexp;
574 :
575 : if (CPUCLOCK_PERTHREAD(timer->it_clock))
576 : tick_dep_set_task(p, TICK_DEP_BIT_POSIX_TIMER);
577 : else
578 : tick_dep_set_signal(p, TICK_DEP_BIT_POSIX_TIMER);
579 : }
580 :
581 : /*
582 : * The timer is locked, fire it and arrange for its reload.
583 : */
584 0 : static void cpu_timer_fire(struct k_itimer *timer)
585 : {
586 0 : struct cpu_timer *ctmr = &timer->it.cpu;
587 :
588 0 : if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
589 : /*
590 : * User don't want any signal.
591 : */
592 0 : cpu_timer_setexpires(ctmr, 0);
593 0 : } else if (unlikely(timer->sigq == NULL)) {
594 : /*
595 : * This a special case for clock_nanosleep,
596 : * not a normal timer from sys_timer_create.
597 : */
598 0 : wake_up_process(timer->it_process);
599 0 : cpu_timer_setexpires(ctmr, 0);
600 0 : } else if (!timer->it_interval) {
601 : /*
602 : * One-shot timer. Clear it as soon as it's fired.
603 : */
604 0 : posix_timer_event(timer, 0);
605 0 : cpu_timer_setexpires(ctmr, 0);
606 0 : } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
607 : /*
608 : * The signal did not get queued because the signal
609 : * was ignored, so we won't get any callback to
610 : * reload the timer. But we need to keep it
611 : * ticking in case the signal is deliverable next time.
612 : */
613 0 : posix_cpu_timer_rearm(timer);
614 0 : ++timer->it_requeue_pending;
615 : }
616 0 : }
617 :
618 : /*
619 : * Guts of sys_timer_settime for CPU timers.
620 : * This is called with the timer locked and interrupts disabled.
621 : * If we return TIMER_RETRY, it's necessary to release the timer's lock
622 : * and try again. (This happens when the timer is in the middle of firing.)
623 : */
624 0 : static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
625 : struct itimerspec64 *new, struct itimerspec64 *old)
626 : {
627 0 : clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
628 : u64 old_expires, new_expires, old_incr, val;
629 0 : struct cpu_timer *ctmr = &timer->it.cpu;
630 : struct sighand_struct *sighand;
631 : struct task_struct *p;
632 : unsigned long flags;
633 0 : int ret = 0;
634 :
635 : rcu_read_lock();
636 0 : p = cpu_timer_task_rcu(timer);
637 0 : if (!p) {
638 : /*
639 : * If p has just been reaped, we can no
640 : * longer get any information about it at all.
641 : */
642 : rcu_read_unlock();
643 0 : return -ESRCH;
644 : }
645 :
646 : /*
647 : * Use the to_ktime conversion because that clamps the maximum
648 : * value to KTIME_MAX and avoid multiplication overflows.
649 : */
650 0 : new_expires = ktime_to_ns(timespec64_to_ktime(new->it_value));
651 :
652 : /*
653 : * Protect against sighand release/switch in exit/exec and p->cpu_timers
654 : * and p->signal->cpu_timers read/write in arm_timer()
655 : */
656 0 : sighand = lock_task_sighand(p, &flags);
657 : /*
658 : * If p has just been reaped, we can no
659 : * longer get any information about it at all.
660 : */
661 0 : if (unlikely(sighand == NULL)) {
662 : rcu_read_unlock();
663 0 : return -ESRCH;
664 : }
665 :
666 : /*
667 : * Disarm any old timer after extracting its expiry time.
668 : */
669 0 : old_incr = timer->it_interval;
670 0 : old_expires = cpu_timer_getexpires(ctmr);
671 :
672 0 : if (unlikely(timer->it.cpu.firing)) {
673 0 : timer->it.cpu.firing = -1;
674 0 : ret = TIMER_RETRY;
675 : } else {
676 : cpu_timer_dequeue(ctmr);
677 : }
678 :
679 : /*
680 : * We need to sample the current value to convert the new
681 : * value from to relative and absolute, and to convert the
682 : * old value from absolute to relative. To set a process
683 : * timer, we need a sample to balance the thread expiry
684 : * times (in arm_timer). With an absolute time, we must
685 : * check if it's already passed. In short, we need a sample.
686 : */
687 0 : if (CPUCLOCK_PERTHREAD(timer->it_clock))
688 0 : val = cpu_clock_sample(clkid, p);
689 : else
690 0 : val = cpu_clock_sample_group(clkid, p, true);
691 :
692 0 : if (old) {
693 0 : if (old_expires == 0) {
694 0 : old->it_value.tv_sec = 0;
695 0 : old->it_value.tv_nsec = 0;
696 : } else {
697 : /*
698 : * Update the timer in case it has overrun already.
699 : * If it has, we'll report it as having overrun and
700 : * with the next reloaded timer already ticking,
701 : * though we are swallowing that pending
702 : * notification here to install the new setting.
703 : */
704 0 : u64 exp = bump_cpu_timer(timer, val);
705 :
706 0 : if (val < exp) {
707 0 : old_expires = exp - val;
708 0 : old->it_value = ns_to_timespec64(old_expires);
709 : } else {
710 0 : old->it_value.tv_nsec = 1;
711 0 : old->it_value.tv_sec = 0;
712 : }
713 : }
714 : }
715 :
716 0 : if (unlikely(ret)) {
717 : /*
718 : * We are colliding with the timer actually firing.
719 : * Punt after filling in the timer's old value, and
720 : * disable this firing since we are already reporting
721 : * it as an overrun (thanks to bump_cpu_timer above).
722 : */
723 0 : unlock_task_sighand(p, &flags);
724 : goto out;
725 : }
726 :
727 0 : if (new_expires != 0 && !(timer_flags & TIMER_ABSTIME)) {
728 0 : new_expires += val;
729 : }
730 :
731 : /*
732 : * Install the new expiry time (or zero).
733 : * For a timer with no notification action, we don't actually
734 : * arm the timer (we'll just fake it for timer_gettime).
735 : */
736 0 : cpu_timer_setexpires(ctmr, new_expires);
737 0 : if (new_expires != 0 && val < new_expires) {
738 0 : arm_timer(timer, p);
739 : }
740 :
741 0 : unlock_task_sighand(p, &flags);
742 : /*
743 : * Install the new reload setting, and
744 : * set up the signal and overrun bookkeeping.
745 : */
746 0 : timer->it_interval = timespec64_to_ktime(new->it_interval);
747 :
748 : /*
749 : * This acts as a modification timestamp for the timer,
750 : * so any automatic reload attempt will punt on seeing
751 : * that we have reset the timer manually.
752 : */
753 0 : timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
754 : ~REQUEUE_PENDING;
755 0 : timer->it_overrun_last = 0;
756 0 : timer->it_overrun = -1;
757 :
758 0 : if (val >= new_expires) {
759 0 : if (new_expires != 0) {
760 : /*
761 : * The designated time already passed, so we notify
762 : * immediately, even if the thread never runs to
763 : * accumulate more time on this clock.
764 : */
765 0 : cpu_timer_fire(timer);
766 : }
767 :
768 : /*
769 : * Make sure we don't keep around the process wide cputime
770 : * counter or the tick dependency if they are not necessary.
771 : */
772 0 : sighand = lock_task_sighand(p, &flags);
773 0 : if (!sighand)
774 : goto out;
775 :
776 0 : if (!cpu_timer_queued(ctmr))
777 : trigger_base_recalc_expires(timer, p);
778 :
779 0 : unlock_task_sighand(p, &flags);
780 : }
781 : out:
782 : rcu_read_unlock();
783 0 : if (old)
784 0 : old->it_interval = ns_to_timespec64(old_incr);
785 :
786 : return ret;
787 : }
788 :
789 0 : static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp)
790 : {
791 0 : clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
792 0 : struct cpu_timer *ctmr = &timer->it.cpu;
793 0 : u64 now, expires = cpu_timer_getexpires(ctmr);
794 : struct task_struct *p;
795 :
796 : rcu_read_lock();
797 0 : p = cpu_timer_task_rcu(timer);
798 0 : if (!p)
799 : goto out;
800 :
801 : /*
802 : * Easy part: convert the reload time.
803 : */
804 0 : itp->it_interval = ktime_to_timespec64(timer->it_interval);
805 :
806 0 : if (!expires)
807 : goto out;
808 :
809 : /*
810 : * Sample the clock to take the difference with the expiry time.
811 : */
812 0 : if (CPUCLOCK_PERTHREAD(timer->it_clock))
813 0 : now = cpu_clock_sample(clkid, p);
814 : else
815 0 : now = cpu_clock_sample_group(clkid, p, false);
816 :
817 0 : if (now < expires) {
818 0 : itp->it_value = ns_to_timespec64(expires - now);
819 : } else {
820 : /*
821 : * The timer should have expired already, but the firing
822 : * hasn't taken place yet. Say it's just about to expire.
823 : */
824 0 : itp->it_value.tv_nsec = 1;
825 0 : itp->it_value.tv_sec = 0;
826 : }
827 : out:
828 : rcu_read_unlock();
829 0 : }
830 :
831 : #define MAX_COLLECTED 20
832 :
833 0 : static u64 collect_timerqueue(struct timerqueue_head *head,
834 : struct list_head *firing, u64 now)
835 : {
836 : struct timerqueue_node *next;
837 0 : int i = 0;
838 :
839 0 : while ((next = timerqueue_getnext(head))) {
840 : struct cpu_timer *ctmr;
841 : u64 expires;
842 :
843 0 : ctmr = container_of(next, struct cpu_timer, node);
844 0 : expires = cpu_timer_getexpires(ctmr);
845 : /* Limit the number of timers to expire at once */
846 0 : if (++i == MAX_COLLECTED || now < expires)
847 : return expires;
848 :
849 0 : ctmr->firing = 1;
850 0 : cpu_timer_dequeue(ctmr);
851 0 : list_add_tail(&ctmr->elist, firing);
852 : }
853 :
854 : return U64_MAX;
855 : }
856 :
857 0 : static void collect_posix_cputimers(struct posix_cputimers *pct, u64 *samples,
858 : struct list_head *firing)
859 : {
860 0 : struct posix_cputimer_base *base = pct->bases;
861 : int i;
862 :
863 0 : for (i = 0; i < CPUCLOCK_MAX; i++, base++) {
864 0 : base->nextevt = collect_timerqueue(&base->tqhead, firing,
865 0 : samples[i]);
866 : }
867 0 : }
868 :
869 : static inline void check_dl_overrun(struct task_struct *tsk)
870 : {
871 0 : if (tsk->dl.dl_overrun) {
872 0 : tsk->dl.dl_overrun = 0;
873 0 : __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
874 : }
875 : }
876 :
877 0 : static bool check_rlimit(u64 time, u64 limit, int signo, bool rt, bool hard)
878 : {
879 0 : if (time < limit)
880 : return false;
881 :
882 0 : if (print_fatal_signals) {
883 0 : pr_info("%s Watchdog Timeout (%s): %s[%d]\n",
884 : rt ? "RT" : "CPU", hard ? "hard" : "soft",
885 : current->comm, task_pid_nr(current));
886 : }
887 0 : __group_send_sig_info(signo, SEND_SIG_PRIV, current);
888 0 : return true;
889 : }
890 :
891 : /*
892 : * Check for any per-thread CPU timers that have fired and move them off
893 : * the tsk->cpu_timers[N] list onto the firing list. Here we update the
894 : * tsk->it_*_expires values to reflect the remaining thread CPU timers.
895 : */
896 0 : static void check_thread_timers(struct task_struct *tsk,
897 : struct list_head *firing)
898 : {
899 0 : struct posix_cputimers *pct = &tsk->posix_cputimers;
900 : u64 samples[CPUCLOCK_MAX];
901 : unsigned long soft;
902 :
903 0 : if (dl_task(tsk))
904 : check_dl_overrun(tsk);
905 :
906 0 : if (expiry_cache_is_inactive(pct))
907 0 : return;
908 :
909 0 : task_sample_cputime(tsk, samples);
910 0 : collect_posix_cputimers(pct, samples, firing);
911 :
912 : /*
913 : * Check for the special case thread timers.
914 : */
915 0 : soft = task_rlimit(tsk, RLIMIT_RTTIME);
916 0 : if (soft != RLIM_INFINITY) {
917 : /* Task RT timeout is accounted in jiffies. RTTIME is usec */
918 0 : unsigned long rttime = tsk->rt.timeout * (USEC_PER_SEC / HZ);
919 0 : unsigned long hard = task_rlimit_max(tsk, RLIMIT_RTTIME);
920 :
921 : /* At the hard limit, send SIGKILL. No further action. */
922 0 : if (hard != RLIM_INFINITY &&
923 0 : check_rlimit(rttime, hard, SIGKILL, true, true))
924 : return;
925 :
926 : /* At the soft limit, send a SIGXCPU every second */
927 0 : if (check_rlimit(rttime, soft, SIGXCPU, true, false)) {
928 0 : soft += USEC_PER_SEC;
929 0 : tsk->signal->rlim[RLIMIT_RTTIME].rlim_cur = soft;
930 : }
931 : }
932 :
933 0 : if (expiry_cache_is_inactive(pct))
934 : tick_dep_clear_task(tsk, TICK_DEP_BIT_POSIX_TIMER);
935 : }
936 :
937 : static inline void stop_process_timers(struct signal_struct *sig)
938 : {
939 0 : struct posix_cputimers *pct = &sig->posix_cputimers;
940 :
941 : /* Turn off the active flag. This is done without locking. */
942 0 : WRITE_ONCE(pct->timers_active, false);
943 0 : tick_dep_clear_signal(sig, TICK_DEP_BIT_POSIX_TIMER);
944 : }
945 :
946 0 : static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
947 : u64 *expires, u64 cur_time, int signo)
948 : {
949 0 : if (!it->expires)
950 : return;
951 :
952 0 : if (cur_time >= it->expires) {
953 0 : if (it->incr)
954 0 : it->expires += it->incr;
955 : else
956 0 : it->expires = 0;
957 :
958 0 : trace_itimer_expire(signo == SIGPROF ?
959 : ITIMER_PROF : ITIMER_VIRTUAL,
960 : task_tgid(tsk), cur_time);
961 0 : __group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
962 : }
963 :
964 0 : if (it->expires && it->expires < *expires)
965 0 : *expires = it->expires;
966 : }
967 :
968 : /*
969 : * Check for any per-thread CPU timers that have fired and move them
970 : * off the tsk->*_timers list onto the firing list. Per-thread timers
971 : * have already been taken off.
972 : */
973 0 : static void check_process_timers(struct task_struct *tsk,
974 : struct list_head *firing)
975 : {
976 0 : struct signal_struct *const sig = tsk->signal;
977 0 : struct posix_cputimers *pct = &sig->posix_cputimers;
978 : u64 samples[CPUCLOCK_MAX];
979 : unsigned long soft;
980 :
981 : /*
982 : * If there are no active process wide timers (POSIX 1.b, itimers,
983 : * RLIMIT_CPU) nothing to check. Also skip the process wide timer
984 : * processing when there is already another task handling them.
985 : */
986 0 : if (!READ_ONCE(pct->timers_active) || pct->expiry_active)
987 0 : return;
988 :
989 : /*
990 : * Signify that a thread is checking for process timers.
991 : * Write access to this field is protected by the sighand lock.
992 : */
993 0 : pct->expiry_active = true;
994 :
995 : /*
996 : * Collect the current process totals. Group accounting is active
997 : * so the sample can be taken directly.
998 : */
999 0 : proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic, samples);
1000 0 : collect_posix_cputimers(pct, samples, firing);
1001 :
1002 : /*
1003 : * Check for the special case process timers.
1004 : */
1005 0 : check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF],
1006 : &pct->bases[CPUCLOCK_PROF].nextevt,
1007 : samples[CPUCLOCK_PROF], SIGPROF);
1008 0 : check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT],
1009 : &pct->bases[CPUCLOCK_VIRT].nextevt,
1010 : samples[CPUCLOCK_VIRT], SIGVTALRM);
1011 :
1012 0 : soft = task_rlimit(tsk, RLIMIT_CPU);
1013 0 : if (soft != RLIM_INFINITY) {
1014 : /* RLIMIT_CPU is in seconds. Samples are nanoseconds */
1015 0 : unsigned long hard = task_rlimit_max(tsk, RLIMIT_CPU);
1016 0 : u64 ptime = samples[CPUCLOCK_PROF];
1017 0 : u64 softns = (u64)soft * NSEC_PER_SEC;
1018 0 : u64 hardns = (u64)hard * NSEC_PER_SEC;
1019 :
1020 : /* At the hard limit, send SIGKILL. No further action. */
1021 0 : if (hard != RLIM_INFINITY &&
1022 0 : check_rlimit(ptime, hardns, SIGKILL, false, true))
1023 : return;
1024 :
1025 : /* At the soft limit, send a SIGXCPU every second */
1026 0 : if (check_rlimit(ptime, softns, SIGXCPU, false, false)) {
1027 0 : sig->rlim[RLIMIT_CPU].rlim_cur = soft + 1;
1028 0 : softns += NSEC_PER_SEC;
1029 : }
1030 :
1031 : /* Update the expiry cache */
1032 0 : if (softns < pct->bases[CPUCLOCK_PROF].nextevt)
1033 0 : pct->bases[CPUCLOCK_PROF].nextevt = softns;
1034 : }
1035 :
1036 0 : if (expiry_cache_is_inactive(pct))
1037 : stop_process_timers(sig);
1038 :
1039 0 : pct->expiry_active = false;
1040 : }
1041 :
1042 : /*
1043 : * This is called from the signal code (via posixtimer_rearm)
1044 : * when the last timer signal was delivered and we have to reload the timer.
1045 : */
1046 0 : static void posix_cpu_timer_rearm(struct k_itimer *timer)
1047 : {
1048 0 : clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
1049 : struct task_struct *p;
1050 : struct sighand_struct *sighand;
1051 : unsigned long flags;
1052 : u64 now;
1053 :
1054 : rcu_read_lock();
1055 0 : p = cpu_timer_task_rcu(timer);
1056 0 : if (!p)
1057 : goto out;
1058 :
1059 : /* Protect timer list r/w in arm_timer() */
1060 0 : sighand = lock_task_sighand(p, &flags);
1061 0 : if (unlikely(sighand == NULL))
1062 : goto out;
1063 :
1064 : /*
1065 : * Fetch the current sample and update the timer's expiry time.
1066 : */
1067 0 : if (CPUCLOCK_PERTHREAD(timer->it_clock))
1068 0 : now = cpu_clock_sample(clkid, p);
1069 : else
1070 0 : now = cpu_clock_sample_group(clkid, p, true);
1071 :
1072 0 : bump_cpu_timer(timer, now);
1073 :
1074 : /*
1075 : * Now re-arm for the new expiry time.
1076 : */
1077 0 : arm_timer(timer, p);
1078 0 : unlock_task_sighand(p, &flags);
1079 : out:
1080 : rcu_read_unlock();
1081 0 : }
1082 :
1083 : /**
1084 : * task_cputimers_expired - Check whether posix CPU timers are expired
1085 : *
1086 : * @samples: Array of current samples for the CPUCLOCK clocks
1087 : * @pct: Pointer to a posix_cputimers container
1088 : *
1089 : * Returns true if any member of @samples is greater than the corresponding
1090 : * member of @pct->bases[CLK].nextevt. False otherwise
1091 : */
1092 : static inline bool
1093 : task_cputimers_expired(const u64 *samples, struct posix_cputimers *pct)
1094 : {
1095 : int i;
1096 :
1097 0 : for (i = 0; i < CPUCLOCK_MAX; i++) {
1098 0 : if (samples[i] >= pct->bases[i].nextevt)
1099 : return true;
1100 : }
1101 : return false;
1102 : }
1103 :
1104 : /**
1105 : * fastpath_timer_check - POSIX CPU timers fast path.
1106 : *
1107 : * @tsk: The task (thread) being checked.
1108 : *
1109 : * Check the task and thread group timers. If both are zero (there are no
1110 : * timers set) return false. Otherwise snapshot the task and thread group
1111 : * timers and compare them with the corresponding expiration times. Return
1112 : * true if a timer has expired, else return false.
1113 : */
1114 13 : static inline bool fastpath_timer_check(struct task_struct *tsk)
1115 : {
1116 13 : struct posix_cputimers *pct = &tsk->posix_cputimers;
1117 : struct signal_struct *sig;
1118 :
1119 13 : if (!expiry_cache_is_inactive(pct)) {
1120 : u64 samples[CPUCLOCK_MAX];
1121 :
1122 : task_sample_cputime(tsk, samples);
1123 0 : if (task_cputimers_expired(samples, pct))
1124 0 : return true;
1125 : }
1126 :
1127 13 : sig = tsk->signal;
1128 13 : pct = &sig->posix_cputimers;
1129 : /*
1130 : * Check if thread group timers expired when timers are active and
1131 : * no other thread in the group is already handling expiry for
1132 : * thread group cputimers. These fields are read without the
1133 : * sighand lock. However, this is fine because this is meant to be
1134 : * a fastpath heuristic to determine whether we should try to
1135 : * acquire the sighand lock to handle timer expiry.
1136 : *
1137 : * In the worst case scenario, if concurrently timers_active is set
1138 : * or expiry_active is cleared, but the current thread doesn't see
1139 : * the change yet, the timer checks are delayed until the next
1140 : * thread in the group gets a scheduler interrupt to handle the
1141 : * timer. This isn't an issue in practice because these types of
1142 : * delays with signals actually getting sent are expected.
1143 : */
1144 13 : if (READ_ONCE(pct->timers_active) && !READ_ONCE(pct->expiry_active)) {
1145 : u64 samples[CPUCLOCK_MAX];
1146 :
1147 0 : proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic,
1148 : samples);
1149 :
1150 0 : if (task_cputimers_expired(samples, pct))
1151 0 : return true;
1152 : }
1153 :
1154 26 : if (dl_task(tsk) && tsk->dl.dl_overrun)
1155 : return true;
1156 :
1157 13 : return false;
1158 : }
1159 :
1160 : static void handle_posix_cpu_timers(struct task_struct *tsk);
1161 :
1162 : #ifdef CONFIG_POSIX_CPU_TIMERS_TASK_WORK
1163 : static void posix_cpu_timers_work(struct callback_head *work)
1164 : {
1165 : handle_posix_cpu_timers(current);
1166 : }
1167 :
1168 : /*
1169 : * Clear existing posix CPU timers task work.
1170 : */
1171 : void clear_posix_cputimers_work(struct task_struct *p)
1172 : {
1173 : /*
1174 : * A copied work entry from the old task is not meaningful, clear it.
1175 : * N.B. init_task_work will not do this.
1176 : */
1177 : memset(&p->posix_cputimers_work.work, 0,
1178 : sizeof(p->posix_cputimers_work.work));
1179 : init_task_work(&p->posix_cputimers_work.work,
1180 : posix_cpu_timers_work);
1181 : p->posix_cputimers_work.scheduled = false;
1182 : }
1183 :
1184 : /*
1185 : * Initialize posix CPU timers task work in init task. Out of line to
1186 : * keep the callback static and to avoid header recursion hell.
1187 : */
1188 : void __init posix_cputimers_init_work(void)
1189 : {
1190 : clear_posix_cputimers_work(current);
1191 : }
1192 :
1193 : /*
1194 : * Note: All operations on tsk->posix_cputimer_work.scheduled happen either
1195 : * in hard interrupt context or in task context with interrupts
1196 : * disabled. Aside of that the writer/reader interaction is always in the
1197 : * context of the current task, which means they are strict per CPU.
1198 : */
1199 : static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
1200 : {
1201 : return tsk->posix_cputimers_work.scheduled;
1202 : }
1203 :
1204 : static inline void __run_posix_cpu_timers(struct task_struct *tsk)
1205 : {
1206 : if (WARN_ON_ONCE(tsk->posix_cputimers_work.scheduled))
1207 : return;
1208 :
1209 : /* Schedule task work to actually expire the timers */
1210 : tsk->posix_cputimers_work.scheduled = true;
1211 : task_work_add(tsk, &tsk->posix_cputimers_work.work, TWA_RESUME);
1212 : }
1213 :
1214 : static inline bool posix_cpu_timers_enable_work(struct task_struct *tsk,
1215 : unsigned long start)
1216 : {
1217 : bool ret = true;
1218 :
1219 : /*
1220 : * On !RT kernels interrupts are disabled while collecting expired
1221 : * timers, so no tick can happen and the fast path check can be
1222 : * reenabled without further checks.
1223 : */
1224 : if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
1225 : tsk->posix_cputimers_work.scheduled = false;
1226 : return true;
1227 : }
1228 :
1229 : /*
1230 : * On RT enabled kernels ticks can happen while the expired timers
1231 : * are collected under sighand lock. But any tick which observes
1232 : * the CPUTIMERS_WORK_SCHEDULED bit set, does not run the fastpath
1233 : * checks. So reenabling the tick work has do be done carefully:
1234 : *
1235 : * Disable interrupts and run the fast path check if jiffies have
1236 : * advanced since the collecting of expired timers started. If
1237 : * jiffies have not advanced or the fast path check did not find
1238 : * newly expired timers, reenable the fast path check in the timer
1239 : * interrupt. If there are newly expired timers, return false and
1240 : * let the collection loop repeat.
1241 : */
1242 : local_irq_disable();
1243 : if (start != jiffies && fastpath_timer_check(tsk))
1244 : ret = false;
1245 : else
1246 : tsk->posix_cputimers_work.scheduled = false;
1247 : local_irq_enable();
1248 :
1249 : return ret;
1250 : }
1251 : #else /* CONFIG_POSIX_CPU_TIMERS_TASK_WORK */
1252 : static inline void __run_posix_cpu_timers(struct task_struct *tsk)
1253 : {
1254 : lockdep_posixtimer_enter();
1255 0 : handle_posix_cpu_timers(tsk);
1256 : lockdep_posixtimer_exit();
1257 : }
1258 :
1259 : static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
1260 : {
1261 : return false;
1262 : }
1263 :
1264 : static inline bool posix_cpu_timers_enable_work(struct task_struct *tsk,
1265 : unsigned long start)
1266 : {
1267 : return true;
1268 : }
1269 : #endif /* CONFIG_POSIX_CPU_TIMERS_TASK_WORK */
1270 :
1271 0 : static void handle_posix_cpu_timers(struct task_struct *tsk)
1272 : {
1273 : struct k_itimer *timer, *next;
1274 : unsigned long flags, start;
1275 0 : LIST_HEAD(firing);
1276 :
1277 0 : if (!lock_task_sighand(tsk, &flags))
1278 0 : return;
1279 :
1280 : do {
1281 : /*
1282 : * On RT locking sighand lock does not disable interrupts,
1283 : * so this needs to be careful vs. ticks. Store the current
1284 : * jiffies value.
1285 : */
1286 0 : start = READ_ONCE(jiffies);
1287 0 : barrier();
1288 :
1289 : /*
1290 : * Here we take off tsk->signal->cpu_timers[N] and
1291 : * tsk->cpu_timers[N] all the timers that are firing, and
1292 : * put them on the firing list.
1293 : */
1294 0 : check_thread_timers(tsk, &firing);
1295 :
1296 0 : check_process_timers(tsk, &firing);
1297 :
1298 : /*
1299 : * The above timer checks have updated the expiry cache and
1300 : * because nothing can have queued or modified timers after
1301 : * sighand lock was taken above it is guaranteed to be
1302 : * consistent. So the next timer interrupt fastpath check
1303 : * will find valid data.
1304 : *
1305 : * If timer expiry runs in the timer interrupt context then
1306 : * the loop is not relevant as timers will be directly
1307 : * expired in interrupt context. The stub function below
1308 : * returns always true which allows the compiler to
1309 : * optimize the loop out.
1310 : *
1311 : * If timer expiry is deferred to task work context then
1312 : * the following rules apply:
1313 : *
1314 : * - On !RT kernels no tick can have happened on this CPU
1315 : * after sighand lock was acquired because interrupts are
1316 : * disabled. So reenabling task work before dropping
1317 : * sighand lock and reenabling interrupts is race free.
1318 : *
1319 : * - On RT kernels ticks might have happened but the tick
1320 : * work ignored posix CPU timer handling because the
1321 : * CPUTIMERS_WORK_SCHEDULED bit is set. Reenabling work
1322 : * must be done very carefully including a check whether
1323 : * ticks have happened since the start of the timer
1324 : * expiry checks. posix_cpu_timers_enable_work() takes
1325 : * care of that and eventually lets the expiry checks
1326 : * run again.
1327 : */
1328 0 : } while (!posix_cpu_timers_enable_work(tsk, start));
1329 :
1330 : /*
1331 : * We must release sighand lock before taking any timer's lock.
1332 : * There is a potential race with timer deletion here, as the
1333 : * siglock now protects our private firing list. We have set
1334 : * the firing flag in each timer, so that a deletion attempt
1335 : * that gets the timer lock before we do will give it up and
1336 : * spin until we've taken care of that timer below.
1337 : */
1338 0 : unlock_task_sighand(tsk, &flags);
1339 :
1340 : /*
1341 : * Now that all the timers on our list have the firing flag,
1342 : * no one will touch their list entries but us. We'll take
1343 : * each timer's lock before clearing its firing flag, so no
1344 : * timer call will interfere.
1345 : */
1346 0 : list_for_each_entry_safe(timer, next, &firing, it.cpu.elist) {
1347 : int cpu_firing;
1348 :
1349 : /*
1350 : * spin_lock() is sufficient here even independent of the
1351 : * expiry context. If expiry happens in hard interrupt
1352 : * context it's obvious. For task work context it's safe
1353 : * because all other operations on timer::it_lock happen in
1354 : * task context (syscall or exit).
1355 : */
1356 0 : spin_lock(&timer->it_lock);
1357 0 : list_del_init(&timer->it.cpu.elist);
1358 0 : cpu_firing = timer->it.cpu.firing;
1359 0 : timer->it.cpu.firing = 0;
1360 : /*
1361 : * The firing flag is -1 if we collided with a reset
1362 : * of the timer, which already reported this
1363 : * almost-firing as an overrun. So don't generate an event.
1364 : */
1365 0 : if (likely(cpu_firing >= 0))
1366 0 : cpu_timer_fire(timer);
1367 0 : spin_unlock(&timer->it_lock);
1368 : }
1369 : }
1370 :
1371 : /*
1372 : * This is called from the timer interrupt handler. The irq handler has
1373 : * already updated our counts. We need to check if any timers fire now.
1374 : * Interrupts are disabled.
1375 : */
1376 13 : void run_posix_cpu_timers(void)
1377 : {
1378 13 : struct task_struct *tsk = current;
1379 :
1380 : lockdep_assert_irqs_disabled();
1381 :
1382 : /*
1383 : * If the actual expiry is deferred to task work context and the
1384 : * work is already scheduled there is no point to do anything here.
1385 : */
1386 13 : if (posix_cpu_timers_work_scheduled(tsk))
1387 : return;
1388 :
1389 : /*
1390 : * The fast path checks that there are no expired thread or thread
1391 : * group timers. If that's so, just return.
1392 : */
1393 13 : if (!fastpath_timer_check(tsk))
1394 : return;
1395 :
1396 : __run_posix_cpu_timers(tsk);
1397 : }
1398 :
1399 : /*
1400 : * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
1401 : * The tsk->sighand->siglock must be held by the caller.
1402 : */
1403 0 : void set_process_cpu_timer(struct task_struct *tsk, unsigned int clkid,
1404 : u64 *newval, u64 *oldval)
1405 : {
1406 : u64 now, *nextevt;
1407 :
1408 0 : if (WARN_ON_ONCE(clkid >= CPUCLOCK_SCHED))
1409 : return;
1410 :
1411 0 : nextevt = &tsk->signal->posix_cputimers.bases[clkid].nextevt;
1412 0 : now = cpu_clock_sample_group(clkid, tsk, true);
1413 :
1414 0 : if (oldval) {
1415 : /*
1416 : * We are setting itimer. The *oldval is absolute and we update
1417 : * it to be relative, *newval argument is relative and we update
1418 : * it to be absolute.
1419 : */
1420 0 : if (*oldval) {
1421 0 : if (*oldval <= now) {
1422 : /* Just about to fire. */
1423 0 : *oldval = TICK_NSEC;
1424 : } else {
1425 0 : *oldval -= now;
1426 : }
1427 : }
1428 :
1429 0 : if (*newval)
1430 0 : *newval += now;
1431 : }
1432 :
1433 : /*
1434 : * Update expiration cache if this is the earliest timer. CPUCLOCK_PROF
1435 : * expiry cache is also used by RLIMIT_CPU!.
1436 : */
1437 0 : if (*newval < *nextevt)
1438 0 : *nextevt = *newval;
1439 :
1440 : tick_dep_set_signal(tsk, TICK_DEP_BIT_POSIX_TIMER);
1441 : }
1442 :
1443 0 : static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1444 : const struct timespec64 *rqtp)
1445 : {
1446 : struct itimerspec64 it;
1447 : struct k_itimer timer;
1448 : u64 expires;
1449 : int error;
1450 :
1451 : /*
1452 : * Set up a temporary timer and then wait for it to go off.
1453 : */
1454 0 : memset(&timer, 0, sizeof timer);
1455 0 : spin_lock_init(&timer.it_lock);
1456 0 : timer.it_clock = which_clock;
1457 0 : timer.it_overrun = -1;
1458 0 : error = posix_cpu_timer_create(&timer);
1459 0 : timer.it_process = current;
1460 :
1461 0 : if (!error) {
1462 : static struct itimerspec64 zero_it;
1463 : struct restart_block *restart;
1464 :
1465 0 : memset(&it, 0, sizeof(it));
1466 0 : it.it_value = *rqtp;
1467 :
1468 0 : spin_lock_irq(&timer.it_lock);
1469 0 : error = posix_cpu_timer_set(&timer, flags, &it, NULL);
1470 0 : if (error) {
1471 0 : spin_unlock_irq(&timer.it_lock);
1472 0 : return error;
1473 : }
1474 :
1475 0 : while (!signal_pending(current)) {
1476 0 : if (!cpu_timer_getexpires(&timer.it.cpu)) {
1477 : /*
1478 : * Our timer fired and was reset, below
1479 : * deletion can not fail.
1480 : */
1481 0 : posix_cpu_timer_del(&timer);
1482 0 : spin_unlock_irq(&timer.it_lock);
1483 0 : return 0;
1484 : }
1485 :
1486 : /*
1487 : * Block until cpu_timer_fire (or a signal) wakes us.
1488 : */
1489 0 : __set_current_state(TASK_INTERRUPTIBLE);
1490 0 : spin_unlock_irq(&timer.it_lock);
1491 0 : schedule();
1492 : spin_lock_irq(&timer.it_lock);
1493 : }
1494 :
1495 : /*
1496 : * We were interrupted by a signal.
1497 : */
1498 0 : expires = cpu_timer_getexpires(&timer.it.cpu);
1499 0 : error = posix_cpu_timer_set(&timer, 0, &zero_it, &it);
1500 0 : if (!error) {
1501 : /*
1502 : * Timer is now unarmed, deletion can not fail.
1503 : */
1504 0 : posix_cpu_timer_del(&timer);
1505 : }
1506 : spin_unlock_irq(&timer.it_lock);
1507 :
1508 0 : while (error == TIMER_RETRY) {
1509 : /*
1510 : * We need to handle case when timer was or is in the
1511 : * middle of firing. In other cases we already freed
1512 : * resources.
1513 : */
1514 0 : spin_lock_irq(&timer.it_lock);
1515 0 : error = posix_cpu_timer_del(&timer);
1516 : spin_unlock_irq(&timer.it_lock);
1517 : }
1518 :
1519 0 : if ((it.it_value.tv_sec | it.it_value.tv_nsec) == 0) {
1520 : /*
1521 : * It actually did fire already.
1522 : */
1523 : return 0;
1524 : }
1525 :
1526 0 : error = -ERESTART_RESTARTBLOCK;
1527 : /*
1528 : * Report back to the user the time still remaining.
1529 : */
1530 0 : restart = ¤t->restart_block;
1531 0 : restart->nanosleep.expires = expires;
1532 0 : if (restart->nanosleep.type != TT_NONE)
1533 0 : error = nanosleep_copyout(restart, &it.it_value);
1534 : }
1535 :
1536 : return error;
1537 : }
1538 :
1539 : static long posix_cpu_nsleep_restart(struct restart_block *restart_block);
1540 :
1541 0 : static int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1542 : const struct timespec64 *rqtp)
1543 : {
1544 0 : struct restart_block *restart_block = ¤t->restart_block;
1545 : int error;
1546 :
1547 : /*
1548 : * Diagnose required errors first.
1549 : */
1550 0 : if (CPUCLOCK_PERTHREAD(which_clock) &&
1551 0 : (CPUCLOCK_PID(which_clock) == 0 ||
1552 0 : CPUCLOCK_PID(which_clock) == task_pid_vnr(current)))
1553 : return -EINVAL;
1554 :
1555 0 : error = do_cpu_nanosleep(which_clock, flags, rqtp);
1556 :
1557 0 : if (error == -ERESTART_RESTARTBLOCK) {
1558 :
1559 0 : if (flags & TIMER_ABSTIME)
1560 : return -ERESTARTNOHAND;
1561 :
1562 0 : restart_block->nanosleep.clockid = which_clock;
1563 0 : set_restart_fn(restart_block, posix_cpu_nsleep_restart);
1564 : }
1565 : return error;
1566 : }
1567 :
1568 0 : static long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1569 : {
1570 0 : clockid_t which_clock = restart_block->nanosleep.clockid;
1571 : struct timespec64 t;
1572 :
1573 0 : t = ns_to_timespec64(restart_block->nanosleep.expires);
1574 :
1575 0 : return do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t);
1576 : }
1577 :
1578 : #define PROCESS_CLOCK make_process_cpuclock(0, CPUCLOCK_SCHED)
1579 : #define THREAD_CLOCK make_thread_cpuclock(0, CPUCLOCK_SCHED)
1580 :
1581 0 : static int process_cpu_clock_getres(const clockid_t which_clock,
1582 : struct timespec64 *tp)
1583 : {
1584 0 : return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1585 : }
1586 0 : static int process_cpu_clock_get(const clockid_t which_clock,
1587 : struct timespec64 *tp)
1588 : {
1589 0 : return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1590 : }
1591 0 : static int process_cpu_timer_create(struct k_itimer *timer)
1592 : {
1593 0 : timer->it_clock = PROCESS_CLOCK;
1594 0 : return posix_cpu_timer_create(timer);
1595 : }
1596 0 : static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1597 : const struct timespec64 *rqtp)
1598 : {
1599 0 : return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp);
1600 : }
1601 0 : static int thread_cpu_clock_getres(const clockid_t which_clock,
1602 : struct timespec64 *tp)
1603 : {
1604 0 : return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1605 : }
1606 0 : static int thread_cpu_clock_get(const clockid_t which_clock,
1607 : struct timespec64 *tp)
1608 : {
1609 0 : return posix_cpu_clock_get(THREAD_CLOCK, tp);
1610 : }
1611 0 : static int thread_cpu_timer_create(struct k_itimer *timer)
1612 : {
1613 0 : timer->it_clock = THREAD_CLOCK;
1614 0 : return posix_cpu_timer_create(timer);
1615 : }
1616 :
1617 : const struct k_clock clock_posix_cpu = {
1618 : .clock_getres = posix_cpu_clock_getres,
1619 : .clock_set = posix_cpu_clock_set,
1620 : .clock_get_timespec = posix_cpu_clock_get,
1621 : .timer_create = posix_cpu_timer_create,
1622 : .nsleep = posix_cpu_nsleep,
1623 : .timer_set = posix_cpu_timer_set,
1624 : .timer_del = posix_cpu_timer_del,
1625 : .timer_get = posix_cpu_timer_get,
1626 : .timer_rearm = posix_cpu_timer_rearm,
1627 : };
1628 :
1629 : const struct k_clock clock_process = {
1630 : .clock_getres = process_cpu_clock_getres,
1631 : .clock_get_timespec = process_cpu_clock_get,
1632 : .timer_create = process_cpu_timer_create,
1633 : .nsleep = process_cpu_nsleep,
1634 : };
1635 :
1636 : const struct k_clock clock_thread = {
1637 : .clock_getres = thread_cpu_clock_getres,
1638 : .clock_get_timespec = thread_cpu_clock_get,
1639 : .timer_create = thread_cpu_timer_create,
1640 : };
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