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 :
24 175 : void posix_cputimers_group_init(struct posix_cputimers *pct, u64 cpu_limit)
25 : {
26 175 : posix_cputimers_init(pct);
27 175 : if (cpu_limit != RLIM_INFINITY) {
28 0 : pct->bases[CPUCLOCK_PROF].nextevt = cpu_limit * NSEC_PER_SEC;
29 0 : pct->timers_active = true;
30 : }
31 175 : }
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 10 : return !(~pct->bases[CPUCLOCK_PROF].nextevt |
155 10 : ~pct->bases[CPUCLOCK_VIRT].nextevt |
156 5 : ~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 0 : u64 curr_cputime = atomic64_read(cputime);
247 :
248 : do {
249 0 : if (sum_cputime <= curr_cputime)
250 : return;
251 0 : } while (!atomic64_try_cmpxchg(cputime, &curr_cputime, sum_cputime));
252 : }
253 :
254 0 : static void update_gt_cputime(struct task_cputime_atomic *cputime_atomic,
255 : struct task_cputime *sum)
256 : {
257 0 : __update_gt_cputime(&cputime_atomic->utime, sum->utime);
258 0 : __update_gt_cputime(&cputime_atomic->stime, sum->stime);
259 0 : __update_gt_cputime(&cputime_atomic->sum_exec_runtime, sum->sum_exec_runtime);
260 0 : }
261 :
262 : /**
263 : * thread_group_sample_cputime - Sample cputime for a given task
264 : * @tsk: Task for which cputime needs to be started
265 : * @samples: Storage for time samples
266 : *
267 : * Called from sys_getitimer() to calculate the expiry time of an active
268 : * timer. That means group cputime accounting is already active. Called
269 : * with task sighand lock held.
270 : *
271 : * Updates @times with an uptodate sample of the thread group cputimes.
272 : */
273 0 : void thread_group_sample_cputime(struct task_struct *tsk, u64 *samples)
274 : {
275 0 : struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
276 0 : struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
277 :
278 0 : WARN_ON_ONCE(!pct->timers_active);
279 :
280 0 : proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
281 0 : }
282 :
283 : /**
284 : * thread_group_start_cputime - Start cputime and return a sample
285 : * @tsk: Task for which cputime needs to be started
286 : * @samples: Storage for time samples
287 : *
288 : * The thread group cputime accounting is avoided when there are no posix
289 : * CPU timers armed. Before starting a timer it's required to check whether
290 : * the time accounting is active. If not, a full update of the atomic
291 : * accounting store needs to be done and the accounting enabled.
292 : *
293 : * Updates @times with an uptodate sample of the thread group cputimes.
294 : */
295 0 : static void thread_group_start_cputime(struct task_struct *tsk, u64 *samples)
296 : {
297 0 : struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
298 0 : struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
299 :
300 0 : lockdep_assert_task_sighand_held(tsk);
301 :
302 : /* Check if cputimer isn't running. This is accessed without locking. */
303 0 : if (!READ_ONCE(pct->timers_active)) {
304 : struct task_cputime sum;
305 :
306 : /*
307 : * The POSIX timer interface allows for absolute time expiry
308 : * values through the TIMER_ABSTIME flag, therefore we have
309 : * to synchronize the timer to the clock every time we start it.
310 : */
311 0 : thread_group_cputime(tsk, &sum);
312 0 : update_gt_cputime(&cputimer->cputime_atomic, &sum);
313 :
314 : /*
315 : * We're setting timers_active without a lock. Ensure this
316 : * only gets written to in one operation. We set it after
317 : * update_gt_cputime() as a small optimization, but
318 : * barriers are not required because update_gt_cputime()
319 : * can handle concurrent updates.
320 : */
321 0 : WRITE_ONCE(pct->timers_active, true);
322 : }
323 0 : proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
324 0 : }
325 :
326 : static void __thread_group_cputime(struct task_struct *tsk, u64 *samples)
327 : {
328 : struct task_cputime ct;
329 :
330 0 : thread_group_cputime(tsk, &ct);
331 0 : store_samples(samples, ct.stime, ct.utime, ct.sum_exec_runtime);
332 : }
333 :
334 : /*
335 : * Sample a process (thread group) clock for the given task clkid. If the
336 : * group's cputime accounting is already enabled, read the atomic
337 : * store. Otherwise a full update is required. clkid is already validated.
338 : */
339 0 : static u64 cpu_clock_sample_group(const clockid_t clkid, struct task_struct *p,
340 : bool start)
341 : {
342 0 : struct thread_group_cputimer *cputimer = &p->signal->cputimer;
343 0 : struct posix_cputimers *pct = &p->signal->posix_cputimers;
344 : u64 samples[CPUCLOCK_MAX];
345 :
346 0 : if (!READ_ONCE(pct->timers_active)) {
347 0 : if (start)
348 0 : thread_group_start_cputime(p, samples);
349 : else
350 : __thread_group_cputime(p, samples);
351 : } else {
352 0 : proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
353 : }
354 :
355 0 : return samples[clkid];
356 : }
357 :
358 0 : static int posix_cpu_clock_get(const clockid_t clock, struct timespec64 *tp)
359 : {
360 0 : const clockid_t clkid = CPUCLOCK_WHICH(clock);
361 : struct task_struct *tsk;
362 : u64 t;
363 :
364 : rcu_read_lock();
365 0 : tsk = pid_task(pid_for_clock(clock, true), clock_pid_type(clock));
366 0 : if (!tsk) {
367 : rcu_read_unlock();
368 0 : return -EINVAL;
369 : }
370 :
371 0 : if (CPUCLOCK_PERTHREAD(clock))
372 0 : t = cpu_clock_sample(clkid, tsk);
373 : else
374 0 : t = cpu_clock_sample_group(clkid, tsk, false);
375 : rcu_read_unlock();
376 :
377 0 : *tp = ns_to_timespec64(t);
378 0 : return 0;
379 : }
380 :
381 : /*
382 : * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
383 : * This is called from sys_timer_create() and do_cpu_nanosleep() with the
384 : * new timer already all-zeros initialized.
385 : */
386 0 : static int posix_cpu_timer_create(struct k_itimer *new_timer)
387 : {
388 : static struct lock_class_key posix_cpu_timers_key;
389 : struct pid *pid;
390 :
391 : rcu_read_lock();
392 0 : pid = pid_for_clock(new_timer->it_clock, false);
393 0 : if (!pid) {
394 : rcu_read_unlock();
395 0 : return -EINVAL;
396 : }
397 :
398 : /*
399 : * If posix timer expiry is handled in task work context then
400 : * timer::it_lock can be taken without disabling interrupts as all
401 : * other locking happens in task context. This requires a separate
402 : * lock class key otherwise regular posix timer expiry would record
403 : * the lock class being taken in interrupt context and generate a
404 : * false positive warning.
405 : */
406 : if (IS_ENABLED(CONFIG_POSIX_CPU_TIMERS_TASK_WORK))
407 : lockdep_set_class(&new_timer->it_lock, &posix_cpu_timers_key);
408 :
409 0 : new_timer->kclock = &clock_posix_cpu;
410 0 : timerqueue_init(&new_timer->it.cpu.node);
411 0 : new_timer->it.cpu.pid = get_pid(pid);
412 : rcu_read_unlock();
413 0 : return 0;
414 : }
415 :
416 : static struct posix_cputimer_base *timer_base(struct k_itimer *timer,
417 : struct task_struct *tsk)
418 : {
419 0 : int clkidx = CPUCLOCK_WHICH(timer->it_clock);
420 :
421 0 : if (CPUCLOCK_PERTHREAD(timer->it_clock))
422 0 : return tsk->posix_cputimers.bases + clkidx;
423 : else
424 0 : return tsk->signal->posix_cputimers.bases + clkidx;
425 : }
426 :
427 : /*
428 : * Force recalculating the base earliest expiration on the next tick.
429 : * This will also re-evaluate the need to keep around the process wide
430 : * cputime counter and tick dependency and eventually shut these down
431 : * if necessary.
432 : */
433 : static void trigger_base_recalc_expires(struct k_itimer *timer,
434 : struct task_struct *tsk)
435 : {
436 0 : struct posix_cputimer_base *base = timer_base(timer, tsk);
437 :
438 0 : base->nextevt = 0;
439 : }
440 :
441 : /*
442 : * Dequeue the timer and reset the base if it was its earliest expiration.
443 : * It makes sure the next tick recalculates the base next expiration so we
444 : * don't keep the costly process wide cputime counter around for a random
445 : * amount of time, along with the tick dependency.
446 : *
447 : * If another timer gets queued between this and the next tick, its
448 : * expiration will update the base next event if necessary on the next
449 : * tick.
450 : */
451 0 : static void disarm_timer(struct k_itimer *timer, struct task_struct *p)
452 : {
453 0 : struct cpu_timer *ctmr = &timer->it.cpu;
454 : struct posix_cputimer_base *base;
455 :
456 0 : if (!cpu_timer_dequeue(ctmr))
457 : return;
458 :
459 0 : base = timer_base(timer, p);
460 0 : if (cpu_timer_getexpires(ctmr) == base->nextevt)
461 : trigger_base_recalc_expires(timer, p);
462 : }
463 :
464 :
465 : /*
466 : * Clean up a CPU-clock timer that is about to be destroyed.
467 : * This is called from timer deletion with the timer already locked.
468 : * If we return TIMER_RETRY, it's necessary to release the timer's lock
469 : * and try again. (This happens when the timer is in the middle of firing.)
470 : */
471 0 : static int posix_cpu_timer_del(struct k_itimer *timer)
472 : {
473 0 : struct cpu_timer *ctmr = &timer->it.cpu;
474 : struct sighand_struct *sighand;
475 : struct task_struct *p;
476 : unsigned long flags;
477 0 : int ret = 0;
478 :
479 : rcu_read_lock();
480 0 : p = cpu_timer_task_rcu(timer);
481 0 : if (!p)
482 : goto out;
483 :
484 : /*
485 : * Protect against sighand release/switch in exit/exec and process/
486 : * thread timer list entry concurrent read/writes.
487 : */
488 0 : sighand = lock_task_sighand(p, &flags);
489 0 : if (unlikely(sighand == NULL)) {
490 : /*
491 : * This raced with the reaping of the task. The exit cleanup
492 : * should have removed this timer from the timer queue.
493 : */
494 0 : WARN_ON_ONCE(ctmr->head || timerqueue_node_queued(&ctmr->node));
495 : } else {
496 0 : if (timer->it.cpu.firing)
497 : ret = TIMER_RETRY;
498 : else
499 0 : disarm_timer(timer, p);
500 :
501 0 : unlock_task_sighand(p, &flags);
502 : }
503 :
504 : out:
505 : rcu_read_unlock();
506 0 : if (!ret)
507 0 : put_pid(ctmr->pid);
508 :
509 0 : return ret;
510 : }
511 :
512 : static void cleanup_timerqueue(struct timerqueue_head *head)
513 : {
514 : struct timerqueue_node *node;
515 : struct cpu_timer *ctmr;
516 :
517 1920 : while ((node = timerqueue_getnext(head))) {
518 0 : timerqueue_del(head, node);
519 0 : ctmr = container_of(node, struct cpu_timer, node);
520 0 : ctmr->head = NULL;
521 : }
522 : }
523 :
524 : /*
525 : * Clean out CPU timers which are still armed when a thread exits. The
526 : * timers are only removed from the list. No other updates are done. The
527 : * corresponding posix timers are still accessible, but cannot be rearmed.
528 : *
529 : * This must be called with the siglock held.
530 : */
531 320 : static void cleanup_timers(struct posix_cputimers *pct)
532 : {
533 640 : cleanup_timerqueue(&pct->bases[CPUCLOCK_PROF].tqhead);
534 640 : cleanup_timerqueue(&pct->bases[CPUCLOCK_VIRT].tqhead);
535 640 : cleanup_timerqueue(&pct->bases[CPUCLOCK_SCHED].tqhead);
536 320 : }
537 :
538 : /*
539 : * These are both called with the siglock held, when the current thread
540 : * is being reaped. When the final (leader) thread in the group is reaped,
541 : * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
542 : */
543 160 : void posix_cpu_timers_exit(struct task_struct *tsk)
544 : {
545 160 : cleanup_timers(&tsk->posix_cputimers);
546 160 : }
547 160 : void posix_cpu_timers_exit_group(struct task_struct *tsk)
548 : {
549 160 : cleanup_timers(&tsk->signal->posix_cputimers);
550 160 : }
551 :
552 : /*
553 : * Insert the timer on the appropriate list before any timers that
554 : * expire later. This must be called with the sighand lock held.
555 : */
556 0 : static void arm_timer(struct k_itimer *timer, struct task_struct *p)
557 : {
558 0 : struct posix_cputimer_base *base = timer_base(timer, p);
559 0 : struct cpu_timer *ctmr = &timer->it.cpu;
560 0 : u64 newexp = cpu_timer_getexpires(ctmr);
561 :
562 0 : if (!cpu_timer_enqueue(&base->tqhead, ctmr))
563 : return;
564 :
565 : /*
566 : * We are the new earliest-expiring POSIX 1.b timer, hence
567 : * need to update expiration cache. Take into account that
568 : * for process timers we share expiration cache with itimers
569 : * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
570 : */
571 0 : if (newexp < base->nextevt)
572 0 : base->nextevt = newexp;
573 :
574 : if (CPUCLOCK_PERTHREAD(timer->it_clock))
575 : tick_dep_set_task(p, TICK_DEP_BIT_POSIX_TIMER);
576 : else
577 : tick_dep_set_signal(p, TICK_DEP_BIT_POSIX_TIMER);
578 : }
579 :
580 : /*
581 : * The timer is locked, fire it and arrange for its reload.
582 : */
583 0 : static void cpu_timer_fire(struct k_itimer *timer)
584 : {
585 0 : struct cpu_timer *ctmr = &timer->it.cpu;
586 :
587 0 : if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
588 : /*
589 : * User don't want any signal.
590 : */
591 0 : cpu_timer_setexpires(ctmr, 0);
592 0 : } else if (unlikely(timer->sigq == NULL)) {
593 : /*
594 : * This a special case for clock_nanosleep,
595 : * not a normal timer from sys_timer_create.
596 : */
597 0 : wake_up_process(timer->it_process);
598 0 : cpu_timer_setexpires(ctmr, 0);
599 0 : } else if (!timer->it_interval) {
600 : /*
601 : * One-shot timer. Clear it as soon as it's fired.
602 : */
603 0 : posix_timer_event(timer, 0);
604 0 : cpu_timer_setexpires(ctmr, 0);
605 0 : } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
606 : /*
607 : * The signal did not get queued because the signal
608 : * was ignored, so we won't get any callback to
609 : * reload the timer. But we need to keep it
610 : * ticking in case the signal is deliverable next time.
611 : */
612 0 : posix_cpu_timer_rearm(timer);
613 0 : ++timer->it_requeue_pending;
614 : }
615 0 : }
616 :
617 : /*
618 : * Guts of sys_timer_settime for CPU timers.
619 : * This is called with the timer locked and interrupts disabled.
620 : * If we return TIMER_RETRY, it's necessary to release the timer's lock
621 : * and try again. (This happens when the timer is in the middle of firing.)
622 : */
623 0 : static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
624 : struct itimerspec64 *new, struct itimerspec64 *old)
625 : {
626 0 : clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
627 : u64 old_expires, new_expires, old_incr, val;
628 0 : struct cpu_timer *ctmr = &timer->it.cpu;
629 : struct sighand_struct *sighand;
630 : struct task_struct *p;
631 : unsigned long flags;
632 0 : int ret = 0;
633 :
634 : rcu_read_lock();
635 0 : p = cpu_timer_task_rcu(timer);
636 0 : if (!p) {
637 : /*
638 : * If p has just been reaped, we can no
639 : * longer get any information about it at all.
640 : */
641 : rcu_read_unlock();
642 0 : return -ESRCH;
643 : }
644 :
645 : /*
646 : * Use the to_ktime conversion because that clamps the maximum
647 : * value to KTIME_MAX and avoid multiplication overflows.
648 : */
649 0 : new_expires = ktime_to_ns(timespec64_to_ktime(new->it_value));
650 :
651 : /*
652 : * Protect against sighand release/switch in exit/exec and p->cpu_timers
653 : * and p->signal->cpu_timers read/write in arm_timer()
654 : */
655 0 : sighand = lock_task_sighand(p, &flags);
656 : /*
657 : * If p has just been reaped, we can no
658 : * longer get any information about it at all.
659 : */
660 0 : if (unlikely(sighand == NULL)) {
661 : rcu_read_unlock();
662 0 : return -ESRCH;
663 : }
664 :
665 : /*
666 : * Disarm any old timer after extracting its expiry time.
667 : */
668 0 : old_incr = timer->it_interval;
669 0 : old_expires = cpu_timer_getexpires(ctmr);
670 :
671 0 : if (unlikely(timer->it.cpu.firing)) {
672 0 : timer->it.cpu.firing = -1;
673 0 : ret = TIMER_RETRY;
674 : } else {
675 : cpu_timer_dequeue(ctmr);
676 : }
677 :
678 : /*
679 : * We need to sample the current value to convert the new
680 : * value from to relative and absolute, and to convert the
681 : * old value from absolute to relative. To set a process
682 : * timer, we need a sample to balance the thread expiry
683 : * times (in arm_timer). With an absolute time, we must
684 : * check if it's already passed. In short, we need a sample.
685 : */
686 0 : if (CPUCLOCK_PERTHREAD(timer->it_clock))
687 0 : val = cpu_clock_sample(clkid, p);
688 : else
689 0 : val = cpu_clock_sample_group(clkid, p, true);
690 :
691 0 : if (old) {
692 0 : if (old_expires == 0) {
693 0 : old->it_value.tv_sec = 0;
694 0 : old->it_value.tv_nsec = 0;
695 : } else {
696 : /*
697 : * Update the timer in case it has overrun already.
698 : * If it has, we'll report it as having overrun and
699 : * with the next reloaded timer already ticking,
700 : * though we are swallowing that pending
701 : * notification here to install the new setting.
702 : */
703 0 : u64 exp = bump_cpu_timer(timer, val);
704 :
705 0 : if (val < exp) {
706 0 : old_expires = exp - val;
707 0 : old->it_value = ns_to_timespec64(old_expires);
708 : } else {
709 0 : old->it_value.tv_nsec = 1;
710 0 : old->it_value.tv_sec = 0;
711 : }
712 : }
713 : }
714 :
715 0 : if (unlikely(ret)) {
716 : /*
717 : * We are colliding with the timer actually firing.
718 : * Punt after filling in the timer's old value, and
719 : * disable this firing since we are already reporting
720 : * it as an overrun (thanks to bump_cpu_timer above).
721 : */
722 0 : unlock_task_sighand(p, &flags);
723 : goto out;
724 : }
725 :
726 0 : if (new_expires != 0 && !(timer_flags & TIMER_ABSTIME)) {
727 0 : new_expires += val;
728 : }
729 :
730 : /*
731 : * Install the new expiry time (or zero).
732 : * For a timer with no notification action, we don't actually
733 : * arm the timer (we'll just fake it for timer_gettime).
734 : */
735 0 : cpu_timer_setexpires(ctmr, new_expires);
736 0 : if (new_expires != 0 && val < new_expires) {
737 0 : arm_timer(timer, p);
738 : }
739 :
740 0 : unlock_task_sighand(p, &flags);
741 : /*
742 : * Install the new reload setting, and
743 : * set up the signal and overrun bookkeeping.
744 : */
745 0 : timer->it_interval = timespec64_to_ktime(new->it_interval);
746 :
747 : /*
748 : * This acts as a modification timestamp for the timer,
749 : * so any automatic reload attempt will punt on seeing
750 : * that we have reset the timer manually.
751 : */
752 0 : timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
753 : ~REQUEUE_PENDING;
754 0 : timer->it_overrun_last = 0;
755 0 : timer->it_overrun = -1;
756 :
757 0 : if (val >= new_expires) {
758 0 : if (new_expires != 0) {
759 : /*
760 : * The designated time already passed, so we notify
761 : * immediately, even if the thread never runs to
762 : * accumulate more time on this clock.
763 : */
764 0 : cpu_timer_fire(timer);
765 : }
766 :
767 : /*
768 : * Make sure we don't keep around the process wide cputime
769 : * counter or the tick dependency if they are not necessary.
770 : */
771 0 : sighand = lock_task_sighand(p, &flags);
772 0 : if (!sighand)
773 : goto out;
774 :
775 0 : if (!cpu_timer_queued(ctmr))
776 : trigger_base_recalc_expires(timer, p);
777 :
778 0 : unlock_task_sighand(p, &flags);
779 : }
780 : out:
781 : rcu_read_unlock();
782 0 : if (old)
783 0 : old->it_interval = ns_to_timespec64(old_incr);
784 :
785 : return ret;
786 : }
787 :
788 0 : static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp)
789 : {
790 0 : clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
791 0 : struct cpu_timer *ctmr = &timer->it.cpu;
792 0 : u64 now, expires = cpu_timer_getexpires(ctmr);
793 : struct task_struct *p;
794 :
795 : rcu_read_lock();
796 0 : p = cpu_timer_task_rcu(timer);
797 0 : if (!p)
798 : goto out;
799 :
800 : /*
801 : * Easy part: convert the reload time.
802 : */
803 0 : itp->it_interval = ktime_to_timespec64(timer->it_interval);
804 :
805 0 : if (!expires)
806 : goto out;
807 :
808 : /*
809 : * Sample the clock to take the difference with the expiry time.
810 : */
811 0 : if (CPUCLOCK_PERTHREAD(timer->it_clock))
812 0 : now = cpu_clock_sample(clkid, p);
813 : else
814 0 : now = cpu_clock_sample_group(clkid, p, false);
815 :
816 0 : if (now < expires) {
817 0 : itp->it_value = ns_to_timespec64(expires - now);
818 : } else {
819 : /*
820 : * The timer should have expired already, but the firing
821 : * hasn't taken place yet. Say it's just about to expire.
822 : */
823 0 : itp->it_value.tv_nsec = 1;
824 0 : itp->it_value.tv_sec = 0;
825 : }
826 : out:
827 : rcu_read_unlock();
828 0 : }
829 :
830 : #define MAX_COLLECTED 20
831 :
832 0 : static u64 collect_timerqueue(struct timerqueue_head *head,
833 : struct list_head *firing, u64 now)
834 : {
835 : struct timerqueue_node *next;
836 0 : int i = 0;
837 :
838 0 : while ((next = timerqueue_getnext(head))) {
839 : struct cpu_timer *ctmr;
840 : u64 expires;
841 :
842 0 : ctmr = container_of(next, struct cpu_timer, node);
843 0 : expires = cpu_timer_getexpires(ctmr);
844 : /* Limit the number of timers to expire at once */
845 0 : if (++i == MAX_COLLECTED || now < expires)
846 : return expires;
847 :
848 0 : ctmr->firing = 1;
849 : /* See posix_cpu_timer_wait_running() */
850 0 : rcu_assign_pointer(ctmr->handling, current);
851 0 : cpu_timer_dequeue(ctmr);
852 0 : list_add_tail(&ctmr->elist, firing);
853 : }
854 :
855 : return U64_MAX;
856 : }
857 :
858 0 : static void collect_posix_cputimers(struct posix_cputimers *pct, u64 *samples,
859 : struct list_head *firing)
860 : {
861 0 : struct posix_cputimer_base *base = pct->bases;
862 : int i;
863 :
864 0 : for (i = 0; i < CPUCLOCK_MAX; i++, base++) {
865 0 : base->nextevt = collect_timerqueue(&base->tqhead, firing,
866 0 : samples[i]);
867 : }
868 0 : }
869 :
870 : static inline void check_dl_overrun(struct task_struct *tsk)
871 : {
872 0 : if (tsk->dl.dl_overrun) {
873 0 : tsk->dl.dl_overrun = 0;
874 0 : send_signal_locked(SIGXCPU, SEND_SIG_PRIV, tsk, PIDTYPE_TGID);
875 : }
876 : }
877 :
878 0 : static bool check_rlimit(u64 time, u64 limit, int signo, bool rt, bool hard)
879 : {
880 0 : if (time < limit)
881 : return false;
882 :
883 0 : if (print_fatal_signals) {
884 0 : pr_info("%s Watchdog Timeout (%s): %s[%d]\n",
885 : rt ? "RT" : "CPU", hard ? "hard" : "soft",
886 : current->comm, task_pid_nr(current));
887 : }
888 0 : send_signal_locked(signo, SEND_SIG_PRIV, current, PIDTYPE_TGID);
889 0 : return true;
890 : }
891 :
892 : /*
893 : * Check for any per-thread CPU timers that have fired and move them off
894 : * the tsk->cpu_timers[N] list onto the firing list. Here we update the
895 : * tsk->it_*_expires values to reflect the remaining thread CPU timers.
896 : */
897 0 : static void check_thread_timers(struct task_struct *tsk,
898 : struct list_head *firing)
899 : {
900 0 : struct posix_cputimers *pct = &tsk->posix_cputimers;
901 : u64 samples[CPUCLOCK_MAX];
902 : unsigned long soft;
903 :
904 0 : if (dl_task(tsk))
905 : check_dl_overrun(tsk);
906 :
907 0 : if (expiry_cache_is_inactive(pct))
908 0 : return;
909 :
910 0 : task_sample_cputime(tsk, samples);
911 0 : collect_posix_cputimers(pct, samples, firing);
912 :
913 : /*
914 : * Check for the special case thread timers.
915 : */
916 0 : soft = task_rlimit(tsk, RLIMIT_RTTIME);
917 0 : if (soft != RLIM_INFINITY) {
918 : /* Task RT timeout is accounted in jiffies. RTTIME is usec */
919 0 : unsigned long rttime = tsk->rt.timeout * (USEC_PER_SEC / HZ);
920 0 : unsigned long hard = task_rlimit_max(tsk, RLIMIT_RTTIME);
921 :
922 : /* At the hard limit, send SIGKILL. No further action. */
923 0 : if (hard != RLIM_INFINITY &&
924 0 : check_rlimit(rttime, hard, SIGKILL, true, true))
925 : return;
926 :
927 : /* At the soft limit, send a SIGXCPU every second */
928 0 : if (check_rlimit(rttime, soft, SIGXCPU, true, false)) {
929 0 : soft += USEC_PER_SEC;
930 0 : tsk->signal->rlim[RLIMIT_RTTIME].rlim_cur = soft;
931 : }
932 : }
933 :
934 0 : if (expiry_cache_is_inactive(pct))
935 : tick_dep_clear_task(tsk, TICK_DEP_BIT_POSIX_TIMER);
936 : }
937 :
938 : static inline void stop_process_timers(struct signal_struct *sig)
939 : {
940 0 : struct posix_cputimers *pct = &sig->posix_cputimers;
941 :
942 : /* Turn off the active flag. This is done without locking. */
943 0 : WRITE_ONCE(pct->timers_active, false);
944 0 : tick_dep_clear_signal(sig, TICK_DEP_BIT_POSIX_TIMER);
945 : }
946 :
947 0 : static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
948 : u64 *expires, u64 cur_time, int signo)
949 : {
950 0 : if (!it->expires)
951 : return;
952 :
953 0 : if (cur_time >= it->expires) {
954 0 : if (it->incr)
955 0 : it->expires += it->incr;
956 : else
957 0 : it->expires = 0;
958 :
959 0 : trace_itimer_expire(signo == SIGPROF ?
960 : ITIMER_PROF : ITIMER_VIRTUAL,
961 : task_tgid(tsk), cur_time);
962 0 : send_signal_locked(signo, SEND_SIG_PRIV, tsk, PIDTYPE_TGID);
963 : }
964 :
965 0 : if (it->expires && it->expires < *expires)
966 0 : *expires = it->expires;
967 : }
968 :
969 : /*
970 : * Check for any per-thread CPU timers that have fired and move them
971 : * off the tsk->*_timers list onto the firing list. Per-thread timers
972 : * have already been taken off.
973 : */
974 0 : static void check_process_timers(struct task_struct *tsk,
975 : struct list_head *firing)
976 : {
977 0 : struct signal_struct *const sig = tsk->signal;
978 0 : struct posix_cputimers *pct = &sig->posix_cputimers;
979 : u64 samples[CPUCLOCK_MAX];
980 : unsigned long soft;
981 :
982 : /*
983 : * If there are no active process wide timers (POSIX 1.b, itimers,
984 : * RLIMIT_CPU) nothing to check. Also skip the process wide timer
985 : * processing when there is already another task handling them.
986 : */
987 0 : if (!READ_ONCE(pct->timers_active) || pct->expiry_active)
988 0 : return;
989 :
990 : /*
991 : * Signify that a thread is checking for process timers.
992 : * Write access to this field is protected by the sighand lock.
993 : */
994 0 : pct->expiry_active = true;
995 :
996 : /*
997 : * Collect the current process totals. Group accounting is active
998 : * so the sample can be taken directly.
999 : */
1000 0 : proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic, samples);
1001 0 : collect_posix_cputimers(pct, samples, firing);
1002 :
1003 : /*
1004 : * Check for the special case process timers.
1005 : */
1006 0 : check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF],
1007 : &pct->bases[CPUCLOCK_PROF].nextevt,
1008 : samples[CPUCLOCK_PROF], SIGPROF);
1009 0 : check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT],
1010 : &pct->bases[CPUCLOCK_VIRT].nextevt,
1011 : samples[CPUCLOCK_VIRT], SIGVTALRM);
1012 :
1013 0 : soft = task_rlimit(tsk, RLIMIT_CPU);
1014 0 : if (soft != RLIM_INFINITY) {
1015 : /* RLIMIT_CPU is in seconds. Samples are nanoseconds */
1016 0 : unsigned long hard = task_rlimit_max(tsk, RLIMIT_CPU);
1017 0 : u64 ptime = samples[CPUCLOCK_PROF];
1018 0 : u64 softns = (u64)soft * NSEC_PER_SEC;
1019 0 : u64 hardns = (u64)hard * NSEC_PER_SEC;
1020 :
1021 : /* At the hard limit, send SIGKILL. No further action. */
1022 0 : if (hard != RLIM_INFINITY &&
1023 0 : check_rlimit(ptime, hardns, SIGKILL, false, true))
1024 : return;
1025 :
1026 : /* At the soft limit, send a SIGXCPU every second */
1027 0 : if (check_rlimit(ptime, softns, SIGXCPU, false, false)) {
1028 0 : sig->rlim[RLIMIT_CPU].rlim_cur = soft + 1;
1029 0 : softns += NSEC_PER_SEC;
1030 : }
1031 :
1032 : /* Update the expiry cache */
1033 0 : if (softns < pct->bases[CPUCLOCK_PROF].nextevt)
1034 0 : pct->bases[CPUCLOCK_PROF].nextevt = softns;
1035 : }
1036 :
1037 0 : if (expiry_cache_is_inactive(pct))
1038 : stop_process_timers(sig);
1039 :
1040 0 : pct->expiry_active = false;
1041 : }
1042 :
1043 : /*
1044 : * This is called from the signal code (via posixtimer_rearm)
1045 : * when the last timer signal was delivered and we have to reload the timer.
1046 : */
1047 0 : static void posix_cpu_timer_rearm(struct k_itimer *timer)
1048 : {
1049 0 : clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
1050 : struct task_struct *p;
1051 : struct sighand_struct *sighand;
1052 : unsigned long flags;
1053 : u64 now;
1054 :
1055 : rcu_read_lock();
1056 0 : p = cpu_timer_task_rcu(timer);
1057 0 : if (!p)
1058 : goto out;
1059 :
1060 : /* Protect timer list r/w in arm_timer() */
1061 0 : sighand = lock_task_sighand(p, &flags);
1062 0 : if (unlikely(sighand == NULL))
1063 : goto out;
1064 :
1065 : /*
1066 : * Fetch the current sample and update the timer's expiry time.
1067 : */
1068 0 : if (CPUCLOCK_PERTHREAD(timer->it_clock))
1069 0 : now = cpu_clock_sample(clkid, p);
1070 : else
1071 0 : now = cpu_clock_sample_group(clkid, p, true);
1072 :
1073 0 : bump_cpu_timer(timer, now);
1074 :
1075 : /*
1076 : * Now re-arm for the new expiry time.
1077 : */
1078 0 : arm_timer(timer, p);
1079 0 : unlock_task_sighand(p, &flags);
1080 : out:
1081 : rcu_read_unlock();
1082 0 : }
1083 :
1084 : /**
1085 : * task_cputimers_expired - Check whether posix CPU timers are expired
1086 : *
1087 : * @samples: Array of current samples for the CPUCLOCK clocks
1088 : * @pct: Pointer to a posix_cputimers container
1089 : *
1090 : * Returns true if any member of @samples is greater than the corresponding
1091 : * member of @pct->bases[CLK].nextevt. False otherwise
1092 : */
1093 : static inline bool
1094 : task_cputimers_expired(const u64 *samples, struct posix_cputimers *pct)
1095 : {
1096 : int i;
1097 :
1098 0 : for (i = 0; i < CPUCLOCK_MAX; i++) {
1099 0 : if (samples[i] >= pct->bases[i].nextevt)
1100 : return true;
1101 : }
1102 : return false;
1103 : }
1104 :
1105 : /**
1106 : * fastpath_timer_check - POSIX CPU timers fast path.
1107 : *
1108 : * @tsk: The task (thread) being checked.
1109 : *
1110 : * Check the task and thread group timers. If both are zero (there are no
1111 : * timers set) return false. Otherwise snapshot the task and thread group
1112 : * timers and compare them with the corresponding expiration times. Return
1113 : * true if a timer has expired, else return false.
1114 : */
1115 5 : static inline bool fastpath_timer_check(struct task_struct *tsk)
1116 : {
1117 5 : struct posix_cputimers *pct = &tsk->posix_cputimers;
1118 : struct signal_struct *sig;
1119 :
1120 5 : if (!expiry_cache_is_inactive(pct)) {
1121 : u64 samples[CPUCLOCK_MAX];
1122 :
1123 : task_sample_cputime(tsk, samples);
1124 0 : if (task_cputimers_expired(samples, pct))
1125 0 : return true;
1126 : }
1127 :
1128 5 : sig = tsk->signal;
1129 5 : pct = &sig->posix_cputimers;
1130 : /*
1131 : * Check if thread group timers expired when timers are active and
1132 : * no other thread in the group is already handling expiry for
1133 : * thread group cputimers. These fields are read without the
1134 : * sighand lock. However, this is fine because this is meant to be
1135 : * a fastpath heuristic to determine whether we should try to
1136 : * acquire the sighand lock to handle timer expiry.
1137 : *
1138 : * In the worst case scenario, if concurrently timers_active is set
1139 : * or expiry_active is cleared, but the current thread doesn't see
1140 : * the change yet, the timer checks are delayed until the next
1141 : * thread in the group gets a scheduler interrupt to handle the
1142 : * timer. This isn't an issue in practice because these types of
1143 : * delays with signals actually getting sent are expected.
1144 : */
1145 5 : if (READ_ONCE(pct->timers_active) && !READ_ONCE(pct->expiry_active)) {
1146 : u64 samples[CPUCLOCK_MAX];
1147 :
1148 0 : proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic,
1149 : samples);
1150 :
1151 0 : if (task_cputimers_expired(samples, pct))
1152 0 : return true;
1153 : }
1154 :
1155 10 : if (dl_task(tsk) && tsk->dl.dl_overrun)
1156 : return true;
1157 :
1158 5 : return false;
1159 : }
1160 :
1161 : static void handle_posix_cpu_timers(struct task_struct *tsk);
1162 :
1163 : #ifdef CONFIG_POSIX_CPU_TIMERS_TASK_WORK
1164 : static void posix_cpu_timers_work(struct callback_head *work)
1165 : {
1166 : struct posix_cputimers_work *cw = container_of(work, typeof(*cw), work);
1167 :
1168 : mutex_lock(&cw->mutex);
1169 : handle_posix_cpu_timers(current);
1170 : mutex_unlock(&cw->mutex);
1171 : }
1172 :
1173 : /*
1174 : * Invoked from the posix-timer core when a cancel operation failed because
1175 : * the timer is marked firing. The caller holds rcu_read_lock(), which
1176 : * protects the timer and the task which is expiring it from being freed.
1177 : */
1178 : static void posix_cpu_timer_wait_running(struct k_itimer *timr)
1179 : {
1180 : struct task_struct *tsk = rcu_dereference(timr->it.cpu.handling);
1181 :
1182 : /* Has the handling task completed expiry already? */
1183 : if (!tsk)
1184 : return;
1185 :
1186 : /* Ensure that the task cannot go away */
1187 : get_task_struct(tsk);
1188 : /* Now drop the RCU protection so the mutex can be locked */
1189 : rcu_read_unlock();
1190 : /* Wait on the expiry mutex */
1191 : mutex_lock(&tsk->posix_cputimers_work.mutex);
1192 : /* Release it immediately again. */
1193 : mutex_unlock(&tsk->posix_cputimers_work.mutex);
1194 : /* Drop the task reference. */
1195 : put_task_struct(tsk);
1196 : /* Relock RCU so the callsite is balanced */
1197 : rcu_read_lock();
1198 : }
1199 :
1200 : static void posix_cpu_timer_wait_running_nsleep(struct k_itimer *timr)
1201 : {
1202 : /* Ensure that timr->it.cpu.handling task cannot go away */
1203 : rcu_read_lock();
1204 : spin_unlock_irq(&timr->it_lock);
1205 : posix_cpu_timer_wait_running(timr);
1206 : rcu_read_unlock();
1207 : /* @timr is on stack and is valid */
1208 : spin_lock_irq(&timr->it_lock);
1209 : }
1210 :
1211 : /*
1212 : * Clear existing posix CPU timers task work.
1213 : */
1214 : void clear_posix_cputimers_work(struct task_struct *p)
1215 : {
1216 : /*
1217 : * A copied work entry from the old task is not meaningful, clear it.
1218 : * N.B. init_task_work will not do this.
1219 : */
1220 : memset(&p->posix_cputimers_work.work, 0,
1221 : sizeof(p->posix_cputimers_work.work));
1222 : init_task_work(&p->posix_cputimers_work.work,
1223 : posix_cpu_timers_work);
1224 : mutex_init(&p->posix_cputimers_work.mutex);
1225 : p->posix_cputimers_work.scheduled = false;
1226 : }
1227 :
1228 : /*
1229 : * Initialize posix CPU timers task work in init task. Out of line to
1230 : * keep the callback static and to avoid header recursion hell.
1231 : */
1232 : void __init posix_cputimers_init_work(void)
1233 : {
1234 : clear_posix_cputimers_work(current);
1235 : }
1236 :
1237 : /*
1238 : * Note: All operations on tsk->posix_cputimer_work.scheduled happen either
1239 : * in hard interrupt context or in task context with interrupts
1240 : * disabled. Aside of that the writer/reader interaction is always in the
1241 : * context of the current task, which means they are strict per CPU.
1242 : */
1243 : static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
1244 : {
1245 : return tsk->posix_cputimers_work.scheduled;
1246 : }
1247 :
1248 : static inline void __run_posix_cpu_timers(struct task_struct *tsk)
1249 : {
1250 : if (WARN_ON_ONCE(tsk->posix_cputimers_work.scheduled))
1251 : return;
1252 :
1253 : /* Schedule task work to actually expire the timers */
1254 : tsk->posix_cputimers_work.scheduled = true;
1255 : task_work_add(tsk, &tsk->posix_cputimers_work.work, TWA_RESUME);
1256 : }
1257 :
1258 : static inline bool posix_cpu_timers_enable_work(struct task_struct *tsk,
1259 : unsigned long start)
1260 : {
1261 : bool ret = true;
1262 :
1263 : /*
1264 : * On !RT kernels interrupts are disabled while collecting expired
1265 : * timers, so no tick can happen and the fast path check can be
1266 : * reenabled without further checks.
1267 : */
1268 : if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
1269 : tsk->posix_cputimers_work.scheduled = false;
1270 : return true;
1271 : }
1272 :
1273 : /*
1274 : * On RT enabled kernels ticks can happen while the expired timers
1275 : * are collected under sighand lock. But any tick which observes
1276 : * the CPUTIMERS_WORK_SCHEDULED bit set, does not run the fastpath
1277 : * checks. So reenabling the tick work has do be done carefully:
1278 : *
1279 : * Disable interrupts and run the fast path check if jiffies have
1280 : * advanced since the collecting of expired timers started. If
1281 : * jiffies have not advanced or the fast path check did not find
1282 : * newly expired timers, reenable the fast path check in the timer
1283 : * interrupt. If there are newly expired timers, return false and
1284 : * let the collection loop repeat.
1285 : */
1286 : local_irq_disable();
1287 : if (start != jiffies && fastpath_timer_check(tsk))
1288 : ret = false;
1289 : else
1290 : tsk->posix_cputimers_work.scheduled = false;
1291 : local_irq_enable();
1292 :
1293 : return ret;
1294 : }
1295 : #else /* CONFIG_POSIX_CPU_TIMERS_TASK_WORK */
1296 : static inline void __run_posix_cpu_timers(struct task_struct *tsk)
1297 : {
1298 : lockdep_posixtimer_enter();
1299 0 : handle_posix_cpu_timers(tsk);
1300 : lockdep_posixtimer_exit();
1301 : }
1302 :
1303 0 : static void posix_cpu_timer_wait_running(struct k_itimer *timr)
1304 : {
1305 : cpu_relax();
1306 0 : }
1307 :
1308 : static void posix_cpu_timer_wait_running_nsleep(struct k_itimer *timr)
1309 : {
1310 0 : spin_unlock_irq(&timr->it_lock);
1311 : cpu_relax();
1312 0 : spin_lock_irq(&timr->it_lock);
1313 : }
1314 :
1315 : static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
1316 : {
1317 : return false;
1318 : }
1319 :
1320 : static inline bool posix_cpu_timers_enable_work(struct task_struct *tsk,
1321 : unsigned long start)
1322 : {
1323 : return true;
1324 : }
1325 : #endif /* CONFIG_POSIX_CPU_TIMERS_TASK_WORK */
1326 :
1327 0 : static void handle_posix_cpu_timers(struct task_struct *tsk)
1328 : {
1329 : struct k_itimer *timer, *next;
1330 : unsigned long flags, start;
1331 0 : LIST_HEAD(firing);
1332 :
1333 0 : if (!lock_task_sighand(tsk, &flags))
1334 0 : return;
1335 :
1336 : do {
1337 : /*
1338 : * On RT locking sighand lock does not disable interrupts,
1339 : * so this needs to be careful vs. ticks. Store the current
1340 : * jiffies value.
1341 : */
1342 0 : start = READ_ONCE(jiffies);
1343 0 : barrier();
1344 :
1345 : /*
1346 : * Here we take off tsk->signal->cpu_timers[N] and
1347 : * tsk->cpu_timers[N] all the timers that are firing, and
1348 : * put them on the firing list.
1349 : */
1350 0 : check_thread_timers(tsk, &firing);
1351 :
1352 0 : check_process_timers(tsk, &firing);
1353 :
1354 : /*
1355 : * The above timer checks have updated the expiry cache and
1356 : * because nothing can have queued or modified timers after
1357 : * sighand lock was taken above it is guaranteed to be
1358 : * consistent. So the next timer interrupt fastpath check
1359 : * will find valid data.
1360 : *
1361 : * If timer expiry runs in the timer interrupt context then
1362 : * the loop is not relevant as timers will be directly
1363 : * expired in interrupt context. The stub function below
1364 : * returns always true which allows the compiler to
1365 : * optimize the loop out.
1366 : *
1367 : * If timer expiry is deferred to task work context then
1368 : * the following rules apply:
1369 : *
1370 : * - On !RT kernels no tick can have happened on this CPU
1371 : * after sighand lock was acquired because interrupts are
1372 : * disabled. So reenabling task work before dropping
1373 : * sighand lock and reenabling interrupts is race free.
1374 : *
1375 : * - On RT kernels ticks might have happened but the tick
1376 : * work ignored posix CPU timer handling because the
1377 : * CPUTIMERS_WORK_SCHEDULED bit is set. Reenabling work
1378 : * must be done very carefully including a check whether
1379 : * ticks have happened since the start of the timer
1380 : * expiry checks. posix_cpu_timers_enable_work() takes
1381 : * care of that and eventually lets the expiry checks
1382 : * run again.
1383 : */
1384 0 : } while (!posix_cpu_timers_enable_work(tsk, start));
1385 :
1386 : /*
1387 : * We must release sighand lock before taking any timer's lock.
1388 : * There is a potential race with timer deletion here, as the
1389 : * siglock now protects our private firing list. We have set
1390 : * the firing flag in each timer, so that a deletion attempt
1391 : * that gets the timer lock before we do will give it up and
1392 : * spin until we've taken care of that timer below.
1393 : */
1394 0 : unlock_task_sighand(tsk, &flags);
1395 :
1396 : /*
1397 : * Now that all the timers on our list have the firing flag,
1398 : * no one will touch their list entries but us. We'll take
1399 : * each timer's lock before clearing its firing flag, so no
1400 : * timer call will interfere.
1401 : */
1402 0 : list_for_each_entry_safe(timer, next, &firing, it.cpu.elist) {
1403 : int cpu_firing;
1404 :
1405 : /*
1406 : * spin_lock() is sufficient here even independent of the
1407 : * expiry context. If expiry happens in hard interrupt
1408 : * context it's obvious. For task work context it's safe
1409 : * because all other operations on timer::it_lock happen in
1410 : * task context (syscall or exit).
1411 : */
1412 0 : spin_lock(&timer->it_lock);
1413 0 : list_del_init(&timer->it.cpu.elist);
1414 0 : cpu_firing = timer->it.cpu.firing;
1415 0 : timer->it.cpu.firing = 0;
1416 : /*
1417 : * The firing flag is -1 if we collided with a reset
1418 : * of the timer, which already reported this
1419 : * almost-firing as an overrun. So don't generate an event.
1420 : */
1421 0 : if (likely(cpu_firing >= 0))
1422 0 : cpu_timer_fire(timer);
1423 : /* See posix_cpu_timer_wait_running() */
1424 0 : rcu_assign_pointer(timer->it.cpu.handling, NULL);
1425 0 : spin_unlock(&timer->it_lock);
1426 : }
1427 : }
1428 :
1429 : /*
1430 : * This is called from the timer interrupt handler. The irq handler has
1431 : * already updated our counts. We need to check if any timers fire now.
1432 : * Interrupts are disabled.
1433 : */
1434 5 : void run_posix_cpu_timers(void)
1435 : {
1436 5 : struct task_struct *tsk = current;
1437 :
1438 : lockdep_assert_irqs_disabled();
1439 :
1440 : /*
1441 : * If the actual expiry is deferred to task work context and the
1442 : * work is already scheduled there is no point to do anything here.
1443 : */
1444 5 : if (posix_cpu_timers_work_scheduled(tsk))
1445 : return;
1446 :
1447 : /*
1448 : * The fast path checks that there are no expired thread or thread
1449 : * group timers. If that's so, just return.
1450 : */
1451 5 : if (!fastpath_timer_check(tsk))
1452 : return;
1453 :
1454 : __run_posix_cpu_timers(tsk);
1455 : }
1456 :
1457 : /*
1458 : * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
1459 : * The tsk->sighand->siglock must be held by the caller.
1460 : */
1461 0 : void set_process_cpu_timer(struct task_struct *tsk, unsigned int clkid,
1462 : u64 *newval, u64 *oldval)
1463 : {
1464 : u64 now, *nextevt;
1465 :
1466 0 : if (WARN_ON_ONCE(clkid >= CPUCLOCK_SCHED))
1467 : return;
1468 :
1469 0 : nextevt = &tsk->signal->posix_cputimers.bases[clkid].nextevt;
1470 0 : now = cpu_clock_sample_group(clkid, tsk, true);
1471 :
1472 0 : if (oldval) {
1473 : /*
1474 : * We are setting itimer. The *oldval is absolute and we update
1475 : * it to be relative, *newval argument is relative and we update
1476 : * it to be absolute.
1477 : */
1478 0 : if (*oldval) {
1479 0 : if (*oldval <= now) {
1480 : /* Just about to fire. */
1481 0 : *oldval = TICK_NSEC;
1482 : } else {
1483 0 : *oldval -= now;
1484 : }
1485 : }
1486 :
1487 0 : if (*newval)
1488 0 : *newval += now;
1489 : }
1490 :
1491 : /*
1492 : * Update expiration cache if this is the earliest timer. CPUCLOCK_PROF
1493 : * expiry cache is also used by RLIMIT_CPU!.
1494 : */
1495 0 : if (*newval < *nextevt)
1496 0 : *nextevt = *newval;
1497 :
1498 : tick_dep_set_signal(tsk, TICK_DEP_BIT_POSIX_TIMER);
1499 : }
1500 :
1501 0 : static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1502 : const struct timespec64 *rqtp)
1503 : {
1504 : struct itimerspec64 it;
1505 : struct k_itimer timer;
1506 : u64 expires;
1507 : int error;
1508 :
1509 : /*
1510 : * Set up a temporary timer and then wait for it to go off.
1511 : */
1512 0 : memset(&timer, 0, sizeof timer);
1513 0 : spin_lock_init(&timer.it_lock);
1514 0 : timer.it_clock = which_clock;
1515 0 : timer.it_overrun = -1;
1516 0 : error = posix_cpu_timer_create(&timer);
1517 0 : timer.it_process = current;
1518 :
1519 0 : if (!error) {
1520 : static struct itimerspec64 zero_it;
1521 : struct restart_block *restart;
1522 :
1523 0 : memset(&it, 0, sizeof(it));
1524 0 : it.it_value = *rqtp;
1525 :
1526 0 : spin_lock_irq(&timer.it_lock);
1527 0 : error = posix_cpu_timer_set(&timer, flags, &it, NULL);
1528 0 : if (error) {
1529 0 : spin_unlock_irq(&timer.it_lock);
1530 0 : return error;
1531 : }
1532 :
1533 0 : while (!signal_pending(current)) {
1534 0 : if (!cpu_timer_getexpires(&timer.it.cpu)) {
1535 : /*
1536 : * Our timer fired and was reset, below
1537 : * deletion can not fail.
1538 : */
1539 0 : posix_cpu_timer_del(&timer);
1540 0 : spin_unlock_irq(&timer.it_lock);
1541 0 : return 0;
1542 : }
1543 :
1544 : /*
1545 : * Block until cpu_timer_fire (or a signal) wakes us.
1546 : */
1547 0 : __set_current_state(TASK_INTERRUPTIBLE);
1548 0 : spin_unlock_irq(&timer.it_lock);
1549 0 : schedule();
1550 : spin_lock_irq(&timer.it_lock);
1551 : }
1552 :
1553 : /*
1554 : * We were interrupted by a signal.
1555 : */
1556 0 : expires = cpu_timer_getexpires(&timer.it.cpu);
1557 0 : error = posix_cpu_timer_set(&timer, 0, &zero_it, &it);
1558 0 : if (!error) {
1559 : /* Timer is now unarmed, deletion can not fail. */
1560 0 : posix_cpu_timer_del(&timer);
1561 : } else {
1562 0 : while (error == TIMER_RETRY) {
1563 0 : posix_cpu_timer_wait_running_nsleep(&timer);
1564 0 : error = posix_cpu_timer_del(&timer);
1565 : }
1566 : }
1567 :
1568 0 : spin_unlock_irq(&timer.it_lock);
1569 :
1570 0 : if ((it.it_value.tv_sec | it.it_value.tv_nsec) == 0) {
1571 : /*
1572 : * It actually did fire already.
1573 : */
1574 : return 0;
1575 : }
1576 :
1577 0 : error = -ERESTART_RESTARTBLOCK;
1578 : /*
1579 : * Report back to the user the time still remaining.
1580 : */
1581 0 : restart = ¤t->restart_block;
1582 0 : restart->nanosleep.expires = expires;
1583 0 : if (restart->nanosleep.type != TT_NONE)
1584 0 : error = nanosleep_copyout(restart, &it.it_value);
1585 : }
1586 :
1587 : return error;
1588 : }
1589 :
1590 : static long posix_cpu_nsleep_restart(struct restart_block *restart_block);
1591 :
1592 0 : static int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1593 : const struct timespec64 *rqtp)
1594 : {
1595 0 : struct restart_block *restart_block = ¤t->restart_block;
1596 : int error;
1597 :
1598 : /*
1599 : * Diagnose required errors first.
1600 : */
1601 0 : if (CPUCLOCK_PERTHREAD(which_clock) &&
1602 0 : (CPUCLOCK_PID(which_clock) == 0 ||
1603 0 : CPUCLOCK_PID(which_clock) == task_pid_vnr(current)))
1604 : return -EINVAL;
1605 :
1606 0 : error = do_cpu_nanosleep(which_clock, flags, rqtp);
1607 :
1608 0 : if (error == -ERESTART_RESTARTBLOCK) {
1609 :
1610 0 : if (flags & TIMER_ABSTIME)
1611 : return -ERESTARTNOHAND;
1612 :
1613 0 : restart_block->nanosleep.clockid = which_clock;
1614 0 : set_restart_fn(restart_block, posix_cpu_nsleep_restart);
1615 : }
1616 : return error;
1617 : }
1618 :
1619 0 : static long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1620 : {
1621 0 : clockid_t which_clock = restart_block->nanosleep.clockid;
1622 : struct timespec64 t;
1623 :
1624 0 : t = ns_to_timespec64(restart_block->nanosleep.expires);
1625 :
1626 0 : return do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t);
1627 : }
1628 :
1629 : #define PROCESS_CLOCK make_process_cpuclock(0, CPUCLOCK_SCHED)
1630 : #define THREAD_CLOCK make_thread_cpuclock(0, CPUCLOCK_SCHED)
1631 :
1632 0 : static int process_cpu_clock_getres(const clockid_t which_clock,
1633 : struct timespec64 *tp)
1634 : {
1635 0 : return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1636 : }
1637 0 : static int process_cpu_clock_get(const clockid_t which_clock,
1638 : struct timespec64 *tp)
1639 : {
1640 0 : return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1641 : }
1642 0 : static int process_cpu_timer_create(struct k_itimer *timer)
1643 : {
1644 0 : timer->it_clock = PROCESS_CLOCK;
1645 0 : return posix_cpu_timer_create(timer);
1646 : }
1647 0 : static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1648 : const struct timespec64 *rqtp)
1649 : {
1650 0 : return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp);
1651 : }
1652 0 : static int thread_cpu_clock_getres(const clockid_t which_clock,
1653 : struct timespec64 *tp)
1654 : {
1655 0 : return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1656 : }
1657 0 : static int thread_cpu_clock_get(const clockid_t which_clock,
1658 : struct timespec64 *tp)
1659 : {
1660 0 : return posix_cpu_clock_get(THREAD_CLOCK, tp);
1661 : }
1662 0 : static int thread_cpu_timer_create(struct k_itimer *timer)
1663 : {
1664 0 : timer->it_clock = THREAD_CLOCK;
1665 0 : return posix_cpu_timer_create(timer);
1666 : }
1667 :
1668 : const struct k_clock clock_posix_cpu = {
1669 : .clock_getres = posix_cpu_clock_getres,
1670 : .clock_set = posix_cpu_clock_set,
1671 : .clock_get_timespec = posix_cpu_clock_get,
1672 : .timer_create = posix_cpu_timer_create,
1673 : .nsleep = posix_cpu_nsleep,
1674 : .timer_set = posix_cpu_timer_set,
1675 : .timer_del = posix_cpu_timer_del,
1676 : .timer_get = posix_cpu_timer_get,
1677 : .timer_rearm = posix_cpu_timer_rearm,
1678 : .timer_wait_running = posix_cpu_timer_wait_running,
1679 : };
1680 :
1681 : const struct k_clock clock_process = {
1682 : .clock_getres = process_cpu_clock_getres,
1683 : .clock_get_timespec = process_cpu_clock_get,
1684 : .timer_create = process_cpu_timer_create,
1685 : .nsleep = process_cpu_nsleep,
1686 : };
1687 :
1688 : const struct k_clock clock_thread = {
1689 : .clock_getres = thread_cpu_clock_getres,
1690 : .clock_get_timespec = thread_cpu_clock_get,
1691 : .timer_create = thread_cpu_timer_create,
1692 : };
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