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 :
19 : #include "posix-timers.h"
20 :
21 : static void posix_cpu_timer_rearm(struct k_itimer *timer);
22 :
23 1126 : void posix_cputimers_group_init(struct posix_cputimers *pct, u64 cpu_limit)
24 : {
25 1126 : posix_cputimers_init(pct);
26 1126 : if (cpu_limit != RLIM_INFINITY) {
27 0 : pct->bases[CPUCLOCK_PROF].nextevt = cpu_limit * NSEC_PER_SEC;
28 0 : pct->timers_active = true;
29 : }
30 1126 : }
31 :
32 : /*
33 : * Called after updating RLIMIT_CPU to run cpu timer and update
34 : * tsk->signal->posix_cputimers.bases[clock].nextevt expiration cache if
35 : * necessary. Needs siglock protection since other code may update the
36 : * expiration cache as well.
37 : */
38 0 : void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
39 : {
40 0 : u64 nsecs = rlim_new * NSEC_PER_SEC;
41 :
42 0 : spin_lock_irq(&task->sighand->siglock);
43 0 : set_process_cpu_timer(task, CPUCLOCK_PROF, &nsecs, NULL);
44 0 : spin_unlock_irq(&task->sighand->siglock);
45 0 : }
46 :
47 : /*
48 : * Functions for validating access to tasks.
49 : */
50 0 : static struct pid *pid_for_clock(const clockid_t clock, bool gettime)
51 : {
52 0 : const bool thread = !!CPUCLOCK_PERTHREAD(clock);
53 0 : const pid_t upid = CPUCLOCK_PID(clock);
54 0 : struct pid *pid;
55 :
56 0 : if (CPUCLOCK_WHICH(clock) >= CPUCLOCK_MAX)
57 : return NULL;
58 :
59 : /*
60 : * If the encoded PID is 0, then the timer is targeted at current
61 : * or the process to which current belongs.
62 : */
63 0 : if (upid == 0)
64 0 : return thread ? task_pid(current) : task_tgid(current);
65 :
66 0 : pid = find_vpid(upid);
67 0 : if (!pid)
68 : return NULL;
69 :
70 0 : if (thread) {
71 0 : struct task_struct *tsk = pid_task(pid, PIDTYPE_PID);
72 0 : return (tsk && same_thread_group(tsk, current)) ? pid : NULL;
73 : }
74 :
75 : /*
76 : * For clock_gettime(PROCESS) allow finding the process by
77 : * with the pid of the current task. The code needs the tgid
78 : * of the process so that pid_task(pid, PIDTYPE_TGID) can be
79 : * used to find the process.
80 : */
81 0 : if (gettime && (pid == task_pid(current)))
82 0 : return task_tgid(current);
83 :
84 : /*
85 : * For processes require that pid identifies a process.
86 : */
87 0 : return pid_has_task(pid, PIDTYPE_TGID) ? pid : NULL;
88 : }
89 :
90 0 : static inline int validate_clock_permissions(const clockid_t clock)
91 : {
92 0 : int ret;
93 :
94 0 : rcu_read_lock();
95 0 : ret = pid_for_clock(clock, false) ? 0 : -EINVAL;
96 0 : rcu_read_unlock();
97 :
98 0 : return ret;
99 : }
100 :
101 0 : static inline enum pid_type clock_pid_type(const clockid_t clock)
102 : {
103 0 : return CPUCLOCK_PERTHREAD(clock) ? PIDTYPE_PID : PIDTYPE_TGID;
104 : }
105 :
106 0 : static inline struct task_struct *cpu_timer_task_rcu(struct k_itimer *timer)
107 : {
108 0 : return pid_task(timer->it.cpu.pid, clock_pid_type(timer->it_clock));
109 : }
110 :
111 : /*
112 : * Update expiry time from increment, and increase overrun count,
113 : * given the current clock sample.
114 : */
115 0 : static u64 bump_cpu_timer(struct k_itimer *timer, u64 now)
116 : {
117 0 : u64 delta, incr, expires = timer->it.cpu.node.expires;
118 0 : int i;
119 :
120 0 : if (!timer->it_interval)
121 : return expires;
122 :
123 0 : if (now < expires)
124 : return expires;
125 :
126 0 : incr = timer->it_interval;
127 0 : delta = now + incr - expires;
128 :
129 : /* Don't use (incr*2 < delta), incr*2 might overflow. */
130 0 : for (i = 0; incr < delta - incr; i++)
131 0 : incr = incr << 1;
132 :
133 0 : for (; i >= 0; incr >>= 1, i--) {
134 0 : if (delta < incr)
135 0 : continue;
136 :
137 0 : timer->it.cpu.node.expires += incr;
138 0 : timer->it_overrun += 1LL << i;
139 0 : delta -= incr;
140 : }
141 0 : return timer->it.cpu.node.expires;
142 : }
143 :
144 : /* Check whether all cache entries contain U64_MAX, i.e. eternal expiry time */
145 29300 : static inline bool expiry_cache_is_inactive(const struct posix_cputimers *pct)
146 : {
147 29300 : return !(~pct->bases[CPUCLOCK_PROF].nextevt |
148 29300 : ~pct->bases[CPUCLOCK_VIRT].nextevt |
149 29300 : ~pct->bases[CPUCLOCK_SCHED].nextevt);
150 : }
151 :
152 : static int
153 0 : posix_cpu_clock_getres(const clockid_t which_clock, struct timespec64 *tp)
154 : {
155 0 : int error = validate_clock_permissions(which_clock);
156 :
157 0 : if (!error) {
158 0 : tp->tv_sec = 0;
159 0 : tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
160 0 : if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
161 : /*
162 : * If sched_clock is using a cycle counter, we
163 : * don't have any idea of its true resolution
164 : * exported, but it is much more than 1s/HZ.
165 : */
166 0 : tp->tv_nsec = 1;
167 : }
168 : }
169 0 : return error;
170 : }
171 :
172 : static int
173 0 : posix_cpu_clock_set(const clockid_t clock, const struct timespec64 *tp)
174 : {
175 0 : int error = validate_clock_permissions(clock);
176 :
177 : /*
178 : * You can never reset a CPU clock, but we check for other errors
179 : * in the call before failing with EPERM.
180 : */
181 0 : return error ? : -EPERM;
182 : }
183 :
184 : /*
185 : * Sample a per-thread clock for the given task. clkid is validated.
186 : */
187 0 : static u64 cpu_clock_sample(const clockid_t clkid, struct task_struct *p)
188 : {
189 0 : u64 utime, stime;
190 :
191 0 : if (clkid == CPUCLOCK_SCHED)
192 0 : return task_sched_runtime(p);
193 :
194 0 : task_cputime(p, &utime, &stime);
195 :
196 0 : switch (clkid) {
197 0 : case CPUCLOCK_PROF:
198 0 : return utime + stime;
199 : case CPUCLOCK_VIRT:
200 : return utime;
201 : default:
202 0 : WARN_ON_ONCE(1);
203 : }
204 0 : return 0;
205 : }
206 :
207 0 : static inline void store_samples(u64 *samples, u64 stime, u64 utime, u64 rtime)
208 : {
209 0 : samples[CPUCLOCK_PROF] = stime + utime;
210 0 : samples[CPUCLOCK_VIRT] = utime;
211 0 : samples[CPUCLOCK_SCHED] = rtime;
212 : }
213 :
214 0 : static void task_sample_cputime(struct task_struct *p, u64 *samples)
215 : {
216 0 : u64 stime, utime;
217 :
218 0 : task_cputime(p, &utime, &stime);
219 0 : store_samples(samples, stime, utime, p->se.sum_exec_runtime);
220 0 : }
221 :
222 0 : static void proc_sample_cputime_atomic(struct task_cputime_atomic *at,
223 : u64 *samples)
224 : {
225 0 : u64 stime, utime, rtime;
226 :
227 0 : utime = atomic64_read(&at->utime);
228 0 : stime = atomic64_read(&at->stime);
229 0 : rtime = atomic64_read(&at->sum_exec_runtime);
230 0 : store_samples(samples, stime, utime, rtime);
231 0 : }
232 :
233 : /*
234 : * Set cputime to sum_cputime if sum_cputime > cputime. Use cmpxchg
235 : * to avoid race conditions with concurrent updates to cputime.
236 : */
237 0 : static inline void __update_gt_cputime(atomic64_t *cputime, u64 sum_cputime)
238 : {
239 0 : u64 curr_cputime;
240 0 : retry:
241 0 : curr_cputime = atomic64_read(cputime);
242 0 : if (sum_cputime > curr_cputime) {
243 0 : if (atomic64_cmpxchg(cputime, curr_cputime, sum_cputime) != curr_cputime)
244 0 : goto retry;
245 : }
246 0 : }
247 :
248 0 : static void update_gt_cputime(struct task_cputime_atomic *cputime_atomic,
249 : struct task_cputime *sum)
250 : {
251 0 : __update_gt_cputime(&cputime_atomic->utime, sum->utime);
252 0 : __update_gt_cputime(&cputime_atomic->stime, sum->stime);
253 0 : __update_gt_cputime(&cputime_atomic->sum_exec_runtime, sum->sum_exec_runtime);
254 0 : }
255 :
256 : /**
257 : * thread_group_sample_cputime - Sample cputime for a given task
258 : * @tsk: Task for which cputime needs to be started
259 : * @samples: Storage for time samples
260 : *
261 : * Called from sys_getitimer() to calculate the expiry time of an active
262 : * timer. That means group cputime accounting is already active. Called
263 : * with task sighand lock held.
264 : *
265 : * Updates @times with an uptodate sample of the thread group cputimes.
266 : */
267 0 : void thread_group_sample_cputime(struct task_struct *tsk, u64 *samples)
268 : {
269 0 : struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
270 0 : struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
271 :
272 0 : WARN_ON_ONCE(!pct->timers_active);
273 :
274 0 : proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
275 0 : }
276 :
277 : /**
278 : * thread_group_start_cputime - Start cputime and return a sample
279 : * @tsk: Task for which cputime needs to be started
280 : * @samples: Storage for time samples
281 : *
282 : * The thread group cputime accouting is avoided when there are no posix
283 : * CPU timers armed. Before starting a timer it's required to check whether
284 : * the time accounting is active. If not, a full update of the atomic
285 : * accounting store needs to be done and the accounting enabled.
286 : *
287 : * Updates @times with an uptodate sample of the thread group cputimes.
288 : */
289 0 : static void thread_group_start_cputime(struct task_struct *tsk, u64 *samples)
290 : {
291 0 : struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
292 0 : struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
293 :
294 : /* Check if cputimer isn't running. This is accessed without locking. */
295 0 : if (!READ_ONCE(pct->timers_active)) {
296 0 : struct task_cputime sum;
297 :
298 : /*
299 : * The POSIX timer interface allows for absolute time expiry
300 : * values through the TIMER_ABSTIME flag, therefore we have
301 : * to synchronize the timer to the clock every time we start it.
302 : */
303 0 : thread_group_cputime(tsk, &sum);
304 0 : update_gt_cputime(&cputimer->cputime_atomic, &sum);
305 :
306 : /*
307 : * We're setting timers_active without a lock. Ensure this
308 : * only gets written to in one operation. We set it after
309 : * update_gt_cputime() as a small optimization, but
310 : * barriers are not required because update_gt_cputime()
311 : * can handle concurrent updates.
312 : */
313 0 : WRITE_ONCE(pct->timers_active, true);
314 : }
315 0 : proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
316 0 : }
317 :
318 0 : static void __thread_group_cputime(struct task_struct *tsk, u64 *samples)
319 : {
320 0 : struct task_cputime ct;
321 :
322 0 : thread_group_cputime(tsk, &ct);
323 0 : store_samples(samples, ct.stime, ct.utime, ct.sum_exec_runtime);
324 0 : }
325 :
326 : /*
327 : * Sample a process (thread group) clock for the given task clkid. If the
328 : * group's cputime accounting is already enabled, read the atomic
329 : * store. Otherwise a full update is required. clkid is already validated.
330 : */
331 0 : static u64 cpu_clock_sample_group(const clockid_t clkid, struct task_struct *p,
332 : bool start)
333 : {
334 0 : struct thread_group_cputimer *cputimer = &p->signal->cputimer;
335 0 : struct posix_cputimers *pct = &p->signal->posix_cputimers;
336 0 : u64 samples[CPUCLOCK_MAX];
337 :
338 0 : if (!READ_ONCE(pct->timers_active)) {
339 0 : if (start)
340 0 : thread_group_start_cputime(p, samples);
341 : else
342 0 : __thread_group_cputime(p, samples);
343 : } else {
344 0 : proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
345 : }
346 :
347 0 : return samples[clkid];
348 : }
349 :
350 0 : static int posix_cpu_clock_get(const clockid_t clock, struct timespec64 *tp)
351 : {
352 0 : const clockid_t clkid = CPUCLOCK_WHICH(clock);
353 0 : struct task_struct *tsk;
354 0 : u64 t;
355 :
356 0 : rcu_read_lock();
357 0 : tsk = pid_task(pid_for_clock(clock, true), clock_pid_type(clock));
358 0 : if (!tsk) {
359 0 : rcu_read_unlock();
360 0 : return -EINVAL;
361 : }
362 :
363 0 : if (CPUCLOCK_PERTHREAD(clock))
364 0 : t = cpu_clock_sample(clkid, tsk);
365 : else
366 0 : t = cpu_clock_sample_group(clkid, tsk, false);
367 0 : rcu_read_unlock();
368 :
369 0 : *tp = ns_to_timespec64(t);
370 0 : return 0;
371 : }
372 :
373 : /*
374 : * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
375 : * This is called from sys_timer_create() and do_cpu_nanosleep() with the
376 : * new timer already all-zeros initialized.
377 : */
378 0 : static int posix_cpu_timer_create(struct k_itimer *new_timer)
379 : {
380 0 : static struct lock_class_key posix_cpu_timers_key;
381 0 : struct pid *pid;
382 :
383 0 : rcu_read_lock();
384 0 : pid = pid_for_clock(new_timer->it_clock, false);
385 0 : if (!pid) {
386 0 : rcu_read_unlock();
387 0 : return -EINVAL;
388 : }
389 :
390 : /*
391 : * If posix timer expiry is handled in task work context then
392 : * timer::it_lock can be taken without disabling interrupts as all
393 : * other locking happens in task context. This requires a seperate
394 : * lock class key otherwise regular posix timer expiry would record
395 : * the lock class being taken in interrupt context and generate a
396 : * false positive warning.
397 : */
398 0 : if (IS_ENABLED(CONFIG_POSIX_CPU_TIMERS_TASK_WORK))
399 0 : lockdep_set_class(&new_timer->it_lock, &posix_cpu_timers_key);
400 :
401 0 : new_timer->kclock = &clock_posix_cpu;
402 0 : timerqueue_init(&new_timer->it.cpu.node);
403 0 : new_timer->it.cpu.pid = get_pid(pid);
404 0 : rcu_read_unlock();
405 0 : return 0;
406 : }
407 :
408 : /*
409 : * Clean up a CPU-clock timer that is about to be destroyed.
410 : * This is called from timer deletion with the timer already locked.
411 : * If we return TIMER_RETRY, it's necessary to release the timer's lock
412 : * and try again. (This happens when the timer is in the middle of firing.)
413 : */
414 0 : static int posix_cpu_timer_del(struct k_itimer *timer)
415 : {
416 0 : struct cpu_timer *ctmr = &timer->it.cpu;
417 0 : struct sighand_struct *sighand;
418 0 : struct task_struct *p;
419 0 : unsigned long flags;
420 0 : int ret = 0;
421 :
422 0 : rcu_read_lock();
423 0 : p = cpu_timer_task_rcu(timer);
424 0 : if (!p)
425 0 : goto out;
426 :
427 : /*
428 : * Protect against sighand release/switch in exit/exec and process/
429 : * thread timer list entry concurrent read/writes.
430 : */
431 0 : sighand = lock_task_sighand(p, &flags);
432 0 : if (unlikely(sighand == NULL)) {
433 : /*
434 : * This raced with the reaping of the task. The exit cleanup
435 : * should have removed this timer from the timer queue.
436 : */
437 0 : WARN_ON_ONCE(ctmr->head || timerqueue_node_queued(&ctmr->node));
438 : } else {
439 0 : if (timer->it.cpu.firing)
440 : ret = TIMER_RETRY;
441 : else
442 0 : cpu_timer_dequeue(ctmr);
443 :
444 0 : unlock_task_sighand(p, &flags);
445 : }
446 :
447 0 : out:
448 0 : rcu_read_unlock();
449 0 : if (!ret)
450 0 : put_pid(ctmr->pid);
451 :
452 0 : return ret;
453 : }
454 :
455 6312 : static void cleanup_timerqueue(struct timerqueue_head *head)
456 : {
457 6312 : struct timerqueue_node *node;
458 6312 : struct cpu_timer *ctmr;
459 :
460 6312 : while ((node = timerqueue_getnext(head))) {
461 0 : timerqueue_del(head, node);
462 0 : ctmr = container_of(node, struct cpu_timer, node);
463 0 : ctmr->head = NULL;
464 : }
465 6312 : }
466 :
467 : /*
468 : * Clean out CPU timers which are still armed when a thread exits. The
469 : * timers are only removed from the list. No other updates are done. The
470 : * corresponding posix timers are still accessible, but cannot be rearmed.
471 : *
472 : * This must be called with the siglock held.
473 : */
474 2104 : static void cleanup_timers(struct posix_cputimers *pct)
475 : {
476 2104 : cleanup_timerqueue(&pct->bases[CPUCLOCK_PROF].tqhead);
477 2104 : cleanup_timerqueue(&pct->bases[CPUCLOCK_VIRT].tqhead);
478 2104 : cleanup_timerqueue(&pct->bases[CPUCLOCK_SCHED].tqhead);
479 2104 : }
480 :
481 : /*
482 : * These are both called with the siglock held, when the current thread
483 : * is being reaped. When the final (leader) thread in the group is reaped,
484 : * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
485 : */
486 1053 : void posix_cpu_timers_exit(struct task_struct *tsk)
487 : {
488 1053 : cleanup_timers(&tsk->posix_cputimers);
489 1053 : }
490 1051 : void posix_cpu_timers_exit_group(struct task_struct *tsk)
491 : {
492 1051 : cleanup_timers(&tsk->signal->posix_cputimers);
493 1051 : }
494 :
495 : /*
496 : * Insert the timer on the appropriate list before any timers that
497 : * expire later. This must be called with the sighand lock held.
498 : */
499 0 : static void arm_timer(struct k_itimer *timer, struct task_struct *p)
500 : {
501 0 : int clkidx = CPUCLOCK_WHICH(timer->it_clock);
502 0 : struct cpu_timer *ctmr = &timer->it.cpu;
503 0 : u64 newexp = cpu_timer_getexpires(ctmr);
504 0 : struct posix_cputimer_base *base;
505 :
506 0 : if (CPUCLOCK_PERTHREAD(timer->it_clock))
507 0 : base = p->posix_cputimers.bases + clkidx;
508 : else
509 0 : base = p->signal->posix_cputimers.bases + clkidx;
510 :
511 0 : if (!cpu_timer_enqueue(&base->tqhead, ctmr))
512 : return;
513 :
514 : /*
515 : * We are the new earliest-expiring POSIX 1.b timer, hence
516 : * need to update expiration cache. Take into account that
517 : * for process timers we share expiration cache with itimers
518 : * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
519 : */
520 0 : if (newexp < base->nextevt)
521 0 : base->nextevt = newexp;
522 :
523 0 : if (CPUCLOCK_PERTHREAD(timer->it_clock))
524 0 : tick_dep_set_task(p, TICK_DEP_BIT_POSIX_TIMER);
525 : else
526 0 : tick_dep_set_signal(p->signal, TICK_DEP_BIT_POSIX_TIMER);
527 : }
528 :
529 : /*
530 : * The timer is locked, fire it and arrange for its reload.
531 : */
532 0 : static void cpu_timer_fire(struct k_itimer *timer)
533 : {
534 0 : struct cpu_timer *ctmr = &timer->it.cpu;
535 :
536 0 : if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
537 : /*
538 : * User don't want any signal.
539 : */
540 0 : cpu_timer_setexpires(ctmr, 0);
541 0 : } else if (unlikely(timer->sigq == NULL)) {
542 : /*
543 : * This a special case for clock_nanosleep,
544 : * not a normal timer from sys_timer_create.
545 : */
546 0 : wake_up_process(timer->it_process);
547 0 : cpu_timer_setexpires(ctmr, 0);
548 0 : } else if (!timer->it_interval) {
549 : /*
550 : * One-shot timer. Clear it as soon as it's fired.
551 : */
552 0 : posix_timer_event(timer, 0);
553 0 : cpu_timer_setexpires(ctmr, 0);
554 0 : } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
555 : /*
556 : * The signal did not get queued because the signal
557 : * was ignored, so we won't get any callback to
558 : * reload the timer. But we need to keep it
559 : * ticking in case the signal is deliverable next time.
560 : */
561 0 : posix_cpu_timer_rearm(timer);
562 0 : ++timer->it_requeue_pending;
563 : }
564 0 : }
565 :
566 : /*
567 : * Guts of sys_timer_settime for CPU timers.
568 : * This is called with the timer locked and interrupts disabled.
569 : * If we return TIMER_RETRY, it's necessary to release the timer's lock
570 : * and try again. (This happens when the timer is in the middle of firing.)
571 : */
572 0 : static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
573 : struct itimerspec64 *new, struct itimerspec64 *old)
574 : {
575 0 : clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
576 0 : u64 old_expires, new_expires, old_incr, val;
577 0 : struct cpu_timer *ctmr = &timer->it.cpu;
578 0 : struct sighand_struct *sighand;
579 0 : struct task_struct *p;
580 0 : unsigned long flags;
581 0 : int ret = 0;
582 :
583 0 : rcu_read_lock();
584 0 : p = cpu_timer_task_rcu(timer);
585 0 : if (!p) {
586 : /*
587 : * If p has just been reaped, we can no
588 : * longer get any information about it at all.
589 : */
590 0 : rcu_read_unlock();
591 0 : return -ESRCH;
592 : }
593 :
594 : /*
595 : * Use the to_ktime conversion because that clamps the maximum
596 : * value to KTIME_MAX and avoid multiplication overflows.
597 : */
598 0 : new_expires = ktime_to_ns(timespec64_to_ktime(new->it_value));
599 :
600 : /*
601 : * Protect against sighand release/switch in exit/exec and p->cpu_timers
602 : * and p->signal->cpu_timers read/write in arm_timer()
603 : */
604 0 : sighand = lock_task_sighand(p, &flags);
605 : /*
606 : * If p has just been reaped, we can no
607 : * longer get any information about it at all.
608 : */
609 0 : if (unlikely(sighand == NULL)) {
610 0 : rcu_read_unlock();
611 0 : return -ESRCH;
612 : }
613 :
614 : /*
615 : * Disarm any old timer after extracting its expiry time.
616 : */
617 0 : old_incr = timer->it_interval;
618 0 : old_expires = cpu_timer_getexpires(ctmr);
619 :
620 0 : if (unlikely(timer->it.cpu.firing)) {
621 0 : timer->it.cpu.firing = -1;
622 0 : ret = TIMER_RETRY;
623 : } else {
624 0 : cpu_timer_dequeue(ctmr);
625 : }
626 :
627 : /*
628 : * We need to sample the current value to convert the new
629 : * value from to relative and absolute, and to convert the
630 : * old value from absolute to relative. To set a process
631 : * timer, we need a sample to balance the thread expiry
632 : * times (in arm_timer). With an absolute time, we must
633 : * check if it's already passed. In short, we need a sample.
634 : */
635 0 : if (CPUCLOCK_PERTHREAD(timer->it_clock))
636 0 : val = cpu_clock_sample(clkid, p);
637 : else
638 0 : val = cpu_clock_sample_group(clkid, p, true);
639 :
640 0 : if (old) {
641 0 : if (old_expires == 0) {
642 0 : old->it_value.tv_sec = 0;
643 0 : old->it_value.tv_nsec = 0;
644 : } else {
645 : /*
646 : * Update the timer in case it has overrun already.
647 : * If it has, we'll report it as having overrun and
648 : * with the next reloaded timer already ticking,
649 : * though we are swallowing that pending
650 : * notification here to install the new setting.
651 : */
652 0 : u64 exp = bump_cpu_timer(timer, val);
653 :
654 0 : if (val < exp) {
655 0 : old_expires = exp - val;
656 0 : old->it_value = ns_to_timespec64(old_expires);
657 : } else {
658 0 : old->it_value.tv_nsec = 1;
659 0 : old->it_value.tv_sec = 0;
660 : }
661 : }
662 : }
663 :
664 0 : if (unlikely(ret)) {
665 : /*
666 : * We are colliding with the timer actually firing.
667 : * Punt after filling in the timer's old value, and
668 : * disable this firing since we are already reporting
669 : * it as an overrun (thanks to bump_cpu_timer above).
670 : */
671 0 : unlock_task_sighand(p, &flags);
672 0 : goto out;
673 : }
674 :
675 0 : if (new_expires != 0 && !(timer_flags & TIMER_ABSTIME)) {
676 0 : new_expires += val;
677 : }
678 :
679 : /*
680 : * Install the new expiry time (or zero).
681 : * For a timer with no notification action, we don't actually
682 : * arm the timer (we'll just fake it for timer_gettime).
683 : */
684 0 : cpu_timer_setexpires(ctmr, new_expires);
685 0 : if (new_expires != 0 && val < new_expires) {
686 0 : arm_timer(timer, p);
687 : }
688 :
689 0 : unlock_task_sighand(p, &flags);
690 : /*
691 : * Install the new reload setting, and
692 : * set up the signal and overrun bookkeeping.
693 : */
694 0 : timer->it_interval = timespec64_to_ktime(new->it_interval);
695 :
696 : /*
697 : * This acts as a modification timestamp for the timer,
698 : * so any automatic reload attempt will punt on seeing
699 : * that we have reset the timer manually.
700 : */
701 0 : timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
702 : ~REQUEUE_PENDING;
703 0 : timer->it_overrun_last = 0;
704 0 : timer->it_overrun = -1;
705 :
706 0 : if (new_expires != 0 && !(val < new_expires)) {
707 : /*
708 : * The designated time already passed, so we notify
709 : * immediately, even if the thread never runs to
710 : * accumulate more time on this clock.
711 : */
712 0 : cpu_timer_fire(timer);
713 : }
714 :
715 : ret = 0;
716 0 : out:
717 0 : rcu_read_unlock();
718 0 : if (old)
719 0 : old->it_interval = ns_to_timespec64(old_incr);
720 :
721 : return ret;
722 : }
723 :
724 0 : static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp)
725 : {
726 0 : clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
727 0 : struct cpu_timer *ctmr = &timer->it.cpu;
728 0 : u64 now, expires = cpu_timer_getexpires(ctmr);
729 0 : struct task_struct *p;
730 :
731 0 : rcu_read_lock();
732 0 : p = cpu_timer_task_rcu(timer);
733 0 : if (!p)
734 0 : goto out;
735 :
736 : /*
737 : * Easy part: convert the reload time.
738 : */
739 0 : itp->it_interval = ktime_to_timespec64(timer->it_interval);
740 :
741 0 : if (!expires)
742 0 : goto out;
743 :
744 : /*
745 : * Sample the clock to take the difference with the expiry time.
746 : */
747 0 : if (CPUCLOCK_PERTHREAD(timer->it_clock))
748 0 : now = cpu_clock_sample(clkid, p);
749 : else
750 0 : now = cpu_clock_sample_group(clkid, p, false);
751 :
752 0 : if (now < expires) {
753 0 : itp->it_value = ns_to_timespec64(expires - now);
754 : } else {
755 : /*
756 : * The timer should have expired already, but the firing
757 : * hasn't taken place yet. Say it's just about to expire.
758 : */
759 0 : itp->it_value.tv_nsec = 1;
760 0 : itp->it_value.tv_sec = 0;
761 : }
762 0 : out:
763 0 : rcu_read_unlock();
764 0 : }
765 :
766 : #define MAX_COLLECTED 20
767 :
768 0 : static u64 collect_timerqueue(struct timerqueue_head *head,
769 : struct list_head *firing, u64 now)
770 : {
771 0 : struct timerqueue_node *next;
772 0 : int i = 0;
773 :
774 0 : while ((next = timerqueue_getnext(head))) {
775 0 : struct cpu_timer *ctmr;
776 0 : u64 expires;
777 :
778 0 : ctmr = container_of(next, struct cpu_timer, node);
779 0 : expires = cpu_timer_getexpires(ctmr);
780 : /* Limit the number of timers to expire at once */
781 0 : if (++i == MAX_COLLECTED || now < expires)
782 0 : return expires;
783 :
784 0 : ctmr->firing = 1;
785 0 : cpu_timer_dequeue(ctmr);
786 0 : list_add_tail(&ctmr->elist, firing);
787 : }
788 :
789 : return U64_MAX;
790 : }
791 :
792 0 : static void collect_posix_cputimers(struct posix_cputimers *pct, u64 *samples,
793 : struct list_head *firing)
794 : {
795 0 : struct posix_cputimer_base *base = pct->bases;
796 0 : int i;
797 :
798 0 : for (i = 0; i < CPUCLOCK_MAX; i++, base++) {
799 0 : base->nextevt = collect_timerqueue(&base->tqhead, firing,
800 0 : samples[i]);
801 : }
802 0 : }
803 :
804 0 : static inline void check_dl_overrun(struct task_struct *tsk)
805 : {
806 0 : if (tsk->dl.dl_overrun) {
807 0 : tsk->dl.dl_overrun = 0;
808 0 : __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
809 : }
810 0 : }
811 :
812 0 : static bool check_rlimit(u64 time, u64 limit, int signo, bool rt, bool hard)
813 : {
814 0 : if (time < limit)
815 : return false;
816 :
817 0 : if (print_fatal_signals) {
818 0 : pr_info("%s Watchdog Timeout (%s): %s[%d]\n",
819 : rt ? "RT" : "CPU", hard ? "hard" : "soft",
820 : current->comm, task_pid_nr(current));
821 : }
822 0 : __group_send_sig_info(signo, SEND_SIG_PRIV, current);
823 0 : return true;
824 : }
825 :
826 : /*
827 : * Check for any per-thread CPU timers that have fired and move them off
828 : * the tsk->cpu_timers[N] list onto the firing list. Here we update the
829 : * tsk->it_*_expires values to reflect the remaining thread CPU timers.
830 : */
831 0 : static void check_thread_timers(struct task_struct *tsk,
832 : struct list_head *firing)
833 : {
834 0 : struct posix_cputimers *pct = &tsk->posix_cputimers;
835 0 : u64 samples[CPUCLOCK_MAX];
836 0 : unsigned long soft;
837 :
838 0 : if (dl_task(tsk))
839 0 : check_dl_overrun(tsk);
840 :
841 0 : if (expiry_cache_is_inactive(pct))
842 0 : return;
843 :
844 0 : task_sample_cputime(tsk, samples);
845 0 : collect_posix_cputimers(pct, samples, firing);
846 :
847 : /*
848 : * Check for the special case thread timers.
849 : */
850 0 : soft = task_rlimit(tsk, RLIMIT_RTTIME);
851 0 : if (soft != RLIM_INFINITY) {
852 : /* Task RT timeout is accounted in jiffies. RTTIME is usec */
853 0 : unsigned long rttime = tsk->rt.timeout * (USEC_PER_SEC / HZ);
854 0 : unsigned long hard = task_rlimit_max(tsk, RLIMIT_RTTIME);
855 :
856 : /* At the hard limit, send SIGKILL. No further action. */
857 0 : if (hard != RLIM_INFINITY &&
858 0 : check_rlimit(rttime, hard, SIGKILL, true, true))
859 : return;
860 :
861 : /* At the soft limit, send a SIGXCPU every second */
862 0 : if (check_rlimit(rttime, soft, SIGXCPU, true, false)) {
863 0 : soft += USEC_PER_SEC;
864 0 : tsk->signal->rlim[RLIMIT_RTTIME].rlim_cur = soft;
865 : }
866 : }
867 :
868 0 : if (expiry_cache_is_inactive(pct))
869 0 : tick_dep_clear_task(tsk, TICK_DEP_BIT_POSIX_TIMER);
870 : }
871 :
872 0 : static inline void stop_process_timers(struct signal_struct *sig)
873 : {
874 0 : struct posix_cputimers *pct = &sig->posix_cputimers;
875 :
876 : /* Turn off the active flag. This is done without locking. */
877 0 : WRITE_ONCE(pct->timers_active, false);
878 0 : tick_dep_clear_signal(sig, TICK_DEP_BIT_POSIX_TIMER);
879 0 : }
880 :
881 0 : static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
882 : u64 *expires, u64 cur_time, int signo)
883 : {
884 0 : if (!it->expires)
885 : return;
886 :
887 0 : if (cur_time >= it->expires) {
888 0 : if (it->incr)
889 0 : it->expires += it->incr;
890 : else
891 0 : it->expires = 0;
892 :
893 0 : trace_itimer_expire(signo == SIGPROF ?
894 : ITIMER_PROF : ITIMER_VIRTUAL,
895 : task_tgid(tsk), cur_time);
896 0 : __group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
897 : }
898 :
899 0 : if (it->expires && it->expires < *expires)
900 0 : *expires = it->expires;
901 : }
902 :
903 : /*
904 : * Check for any per-thread CPU timers that have fired and move them
905 : * off the tsk->*_timers list onto the firing list. Per-thread timers
906 : * have already been taken off.
907 : */
908 0 : static void check_process_timers(struct task_struct *tsk,
909 : struct list_head *firing)
910 : {
911 0 : struct signal_struct *const sig = tsk->signal;
912 0 : struct posix_cputimers *pct = &sig->posix_cputimers;
913 0 : u64 samples[CPUCLOCK_MAX];
914 0 : unsigned long soft;
915 :
916 : /*
917 : * If there are no active process wide timers (POSIX 1.b, itimers,
918 : * RLIMIT_CPU) nothing to check. Also skip the process wide timer
919 : * processing when there is already another task handling them.
920 : */
921 0 : if (!READ_ONCE(pct->timers_active) || pct->expiry_active)
922 0 : return;
923 :
924 : /*
925 : * Signify that a thread is checking for process timers.
926 : * Write access to this field is protected by the sighand lock.
927 : */
928 0 : pct->expiry_active = true;
929 :
930 : /*
931 : * Collect the current process totals. Group accounting is active
932 : * so the sample can be taken directly.
933 : */
934 0 : proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic, samples);
935 0 : collect_posix_cputimers(pct, samples, firing);
936 :
937 : /*
938 : * Check for the special case process timers.
939 : */
940 0 : check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF],
941 : &pct->bases[CPUCLOCK_PROF].nextevt,
942 : samples[CPUCLOCK_PROF], SIGPROF);
943 0 : check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT],
944 : &pct->bases[CPUCLOCK_VIRT].nextevt,
945 : samples[CPUCLOCK_VIRT], SIGVTALRM);
946 :
947 0 : soft = task_rlimit(tsk, RLIMIT_CPU);
948 0 : if (soft != RLIM_INFINITY) {
949 : /* RLIMIT_CPU is in seconds. Samples are nanoseconds */
950 0 : unsigned long hard = task_rlimit_max(tsk, RLIMIT_CPU);
951 0 : u64 ptime = samples[CPUCLOCK_PROF];
952 0 : u64 softns = (u64)soft * NSEC_PER_SEC;
953 0 : u64 hardns = (u64)hard * NSEC_PER_SEC;
954 :
955 : /* At the hard limit, send SIGKILL. No further action. */
956 0 : if (hard != RLIM_INFINITY &&
957 0 : check_rlimit(ptime, hardns, SIGKILL, false, true))
958 : return;
959 :
960 : /* At the soft limit, send a SIGXCPU every second */
961 0 : if (check_rlimit(ptime, softns, SIGXCPU, false, false)) {
962 0 : sig->rlim[RLIMIT_CPU].rlim_cur = soft + 1;
963 0 : softns += NSEC_PER_SEC;
964 : }
965 :
966 : /* Update the expiry cache */
967 0 : if (softns < pct->bases[CPUCLOCK_PROF].nextevt)
968 0 : pct->bases[CPUCLOCK_PROF].nextevt = softns;
969 : }
970 :
971 0 : if (expiry_cache_is_inactive(pct))
972 0 : stop_process_timers(sig);
973 :
974 0 : pct->expiry_active = false;
975 : }
976 :
977 : /*
978 : * This is called from the signal code (via posixtimer_rearm)
979 : * when the last timer signal was delivered and we have to reload the timer.
980 : */
981 0 : static void posix_cpu_timer_rearm(struct k_itimer *timer)
982 : {
983 0 : clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
984 0 : struct task_struct *p;
985 0 : struct sighand_struct *sighand;
986 0 : unsigned long flags;
987 0 : u64 now;
988 :
989 0 : rcu_read_lock();
990 0 : p = cpu_timer_task_rcu(timer);
991 0 : if (!p)
992 0 : goto out;
993 :
994 : /*
995 : * Fetch the current sample and update the timer's expiry time.
996 : */
997 0 : if (CPUCLOCK_PERTHREAD(timer->it_clock))
998 0 : now = cpu_clock_sample(clkid, p);
999 : else
1000 0 : now = cpu_clock_sample_group(clkid, p, true);
1001 :
1002 0 : bump_cpu_timer(timer, now);
1003 :
1004 : /* Protect timer list r/w in arm_timer() */
1005 0 : sighand = lock_task_sighand(p, &flags);
1006 0 : if (unlikely(sighand == NULL))
1007 0 : goto out;
1008 :
1009 : /*
1010 : * Now re-arm for the new expiry time.
1011 : */
1012 0 : arm_timer(timer, p);
1013 0 : unlock_task_sighand(p, &flags);
1014 0 : out:
1015 0 : rcu_read_unlock();
1016 0 : }
1017 :
1018 : /**
1019 : * task_cputimers_expired - Check whether posix CPU timers are expired
1020 : *
1021 : * @samples: Array of current samples for the CPUCLOCK clocks
1022 : * @pct: Pointer to a posix_cputimers container
1023 : *
1024 : * Returns true if any member of @samples is greater than the corresponding
1025 : * member of @pct->bases[CLK].nextevt. False otherwise
1026 : */
1027 : static inline bool
1028 0 : task_cputimers_expired(const u64 *samples, struct posix_cputimers *pct)
1029 : {
1030 0 : int i;
1031 :
1032 0 : for (i = 0; i < CPUCLOCK_MAX; i++) {
1033 0 : if (samples[i] >= pct->bases[i].nextevt)
1034 : return true;
1035 : }
1036 : return false;
1037 : }
1038 :
1039 : /**
1040 : * fastpath_timer_check - POSIX CPU timers fast path.
1041 : *
1042 : * @tsk: The task (thread) being checked.
1043 : *
1044 : * Check the task and thread group timers. If both are zero (there are no
1045 : * timers set) return false. Otherwise snapshot the task and thread group
1046 : * timers and compare them with the corresponding expiration times. Return
1047 : * true if a timer has expired, else return false.
1048 : */
1049 29300 : static inline bool fastpath_timer_check(struct task_struct *tsk)
1050 : {
1051 29300 : struct posix_cputimers *pct = &tsk->posix_cputimers;
1052 29300 : struct signal_struct *sig;
1053 :
1054 29300 : if (!expiry_cache_is_inactive(pct)) {
1055 0 : u64 samples[CPUCLOCK_MAX];
1056 :
1057 0 : task_sample_cputime(tsk, samples);
1058 0 : if (task_cputimers_expired(samples, pct))
1059 0 : return true;
1060 : }
1061 :
1062 29300 : sig = tsk->signal;
1063 29300 : pct = &sig->posix_cputimers;
1064 : /*
1065 : * Check if thread group timers expired when timers are active and
1066 : * no other thread in the group is already handling expiry for
1067 : * thread group cputimers. These fields are read without the
1068 : * sighand lock. However, this is fine because this is meant to be
1069 : * a fastpath heuristic to determine whether we should try to
1070 : * acquire the sighand lock to handle timer expiry.
1071 : *
1072 : * In the worst case scenario, if concurrently timers_active is set
1073 : * or expiry_active is cleared, but the current thread doesn't see
1074 : * the change yet, the timer checks are delayed until the next
1075 : * thread in the group gets a scheduler interrupt to handle the
1076 : * timer. This isn't an issue in practice because these types of
1077 : * delays with signals actually getting sent are expected.
1078 : */
1079 29300 : if (READ_ONCE(pct->timers_active) && !READ_ONCE(pct->expiry_active)) {
1080 0 : u64 samples[CPUCLOCK_MAX];
1081 :
1082 0 : proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic,
1083 : samples);
1084 :
1085 0 : if (task_cputimers_expired(samples, pct))
1086 0 : return true;
1087 : }
1088 :
1089 29300 : if (dl_task(tsk) && tsk->dl.dl_overrun)
1090 0 : return true;
1091 :
1092 : return false;
1093 : }
1094 :
1095 : static void handle_posix_cpu_timers(struct task_struct *tsk);
1096 :
1097 : #ifdef CONFIG_POSIX_CPU_TIMERS_TASK_WORK
1098 0 : static void posix_cpu_timers_work(struct callback_head *work)
1099 : {
1100 0 : handle_posix_cpu_timers(current);
1101 0 : }
1102 :
1103 : /*
1104 : * Initialize posix CPU timers task work in init task. Out of line to
1105 : * keep the callback static and to avoid header recursion hell.
1106 : */
1107 1 : void __init posix_cputimers_init_work(void)
1108 : {
1109 1 : init_task_work(¤t->posix_cputimers_work.work,
1110 : posix_cpu_timers_work);
1111 1 : }
1112 :
1113 : /*
1114 : * Note: All operations on tsk->posix_cputimer_work.scheduled happen either
1115 : * in hard interrupt context or in task context with interrupts
1116 : * disabled. Aside of that the writer/reader interaction is always in the
1117 : * context of the current task, which means they are strict per CPU.
1118 : */
1119 29168 : static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
1120 : {
1121 29168 : return tsk->posix_cputimers_work.scheduled;
1122 : }
1123 :
1124 0 : static inline void __run_posix_cpu_timers(struct task_struct *tsk)
1125 : {
1126 0 : if (WARN_ON_ONCE(tsk->posix_cputimers_work.scheduled))
1127 : return;
1128 :
1129 : /* Schedule task work to actually expire the timers */
1130 0 : tsk->posix_cputimers_work.scheduled = true;
1131 0 : task_work_add(tsk, &tsk->posix_cputimers_work.work, TWA_RESUME);
1132 : }
1133 :
1134 0 : static inline bool posix_cpu_timers_enable_work(struct task_struct *tsk,
1135 : unsigned long start)
1136 : {
1137 0 : bool ret = true;
1138 :
1139 : /*
1140 : * On !RT kernels interrupts are disabled while collecting expired
1141 : * timers, so no tick can happen and the fast path check can be
1142 : * reenabled without further checks.
1143 : */
1144 0 : if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
1145 0 : tsk->posix_cputimers_work.scheduled = false;
1146 0 : return true;
1147 : }
1148 :
1149 : /*
1150 : * On RT enabled kernels ticks can happen while the expired timers
1151 : * are collected under sighand lock. But any tick which observes
1152 : * the CPUTIMERS_WORK_SCHEDULED bit set, does not run the fastpath
1153 : * checks. So reenabling the tick work has do be done carefully:
1154 : *
1155 : * Disable interrupts and run the fast path check if jiffies have
1156 : * advanced since the collecting of expired timers started. If
1157 : * jiffies have not advanced or the fast path check did not find
1158 : * newly expired timers, reenable the fast path check in the timer
1159 : * interrupt. If there are newly expired timers, return false and
1160 : * let the collection loop repeat.
1161 : */
1162 : local_irq_disable();
1163 : if (start != jiffies && fastpath_timer_check(tsk))
1164 : ret = false;
1165 : else
1166 : tsk->posix_cputimers_work.scheduled = false;
1167 : local_irq_enable();
1168 :
1169 : return ret;
1170 : }
1171 : #else /* CONFIG_POSIX_CPU_TIMERS_TASK_WORK */
1172 : static inline void __run_posix_cpu_timers(struct task_struct *tsk)
1173 : {
1174 : lockdep_posixtimer_enter();
1175 : handle_posix_cpu_timers(tsk);
1176 : lockdep_posixtimer_exit();
1177 : }
1178 :
1179 : static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
1180 : {
1181 : return false;
1182 : }
1183 :
1184 : static inline bool posix_cpu_timers_enable_work(struct task_struct *tsk,
1185 : unsigned long start)
1186 : {
1187 : return true;
1188 : }
1189 : #endif /* CONFIG_POSIX_CPU_TIMERS_TASK_WORK */
1190 :
1191 0 : static void handle_posix_cpu_timers(struct task_struct *tsk)
1192 : {
1193 0 : struct k_itimer *timer, *next;
1194 0 : unsigned long flags, start;
1195 0 : LIST_HEAD(firing);
1196 :
1197 0 : if (!lock_task_sighand(tsk, &flags))
1198 0 : return;
1199 :
1200 0 : do {
1201 : /*
1202 : * On RT locking sighand lock does not disable interrupts,
1203 : * so this needs to be careful vs. ticks. Store the current
1204 : * jiffies value.
1205 : */
1206 0 : start = READ_ONCE(jiffies);
1207 0 : barrier();
1208 :
1209 : /*
1210 : * Here we take off tsk->signal->cpu_timers[N] and
1211 : * tsk->cpu_timers[N] all the timers that are firing, and
1212 : * put them on the firing list.
1213 : */
1214 0 : check_thread_timers(tsk, &firing);
1215 :
1216 0 : check_process_timers(tsk, &firing);
1217 :
1218 : /*
1219 : * The above timer checks have updated the exipry cache and
1220 : * because nothing can have queued or modified timers after
1221 : * sighand lock was taken above it is guaranteed to be
1222 : * consistent. So the next timer interrupt fastpath check
1223 : * will find valid data.
1224 : *
1225 : * If timer expiry runs in the timer interrupt context then
1226 : * the loop is not relevant as timers will be directly
1227 : * expired in interrupt context. The stub function below
1228 : * returns always true which allows the compiler to
1229 : * optimize the loop out.
1230 : *
1231 : * If timer expiry is deferred to task work context then
1232 : * the following rules apply:
1233 : *
1234 : * - On !RT kernels no tick can have happened on this CPU
1235 : * after sighand lock was acquired because interrupts are
1236 : * disabled. So reenabling task work before dropping
1237 : * sighand lock and reenabling interrupts is race free.
1238 : *
1239 : * - On RT kernels ticks might have happened but the tick
1240 : * work ignored posix CPU timer handling because the
1241 : * CPUTIMERS_WORK_SCHEDULED bit is set. Reenabling work
1242 : * must be done very carefully including a check whether
1243 : * ticks have happened since the start of the timer
1244 : * expiry checks. posix_cpu_timers_enable_work() takes
1245 : * care of that and eventually lets the expiry checks
1246 : * run again.
1247 : */
1248 0 : } while (!posix_cpu_timers_enable_work(tsk, start));
1249 :
1250 : /*
1251 : * We must release sighand lock before taking any timer's lock.
1252 : * There is a potential race with timer deletion here, as the
1253 : * siglock now protects our private firing list. We have set
1254 : * the firing flag in each timer, so that a deletion attempt
1255 : * that gets the timer lock before we do will give it up and
1256 : * spin until we've taken care of that timer below.
1257 : */
1258 0 : unlock_task_sighand(tsk, &flags);
1259 :
1260 : /*
1261 : * Now that all the timers on our list have the firing flag,
1262 : * no one will touch their list entries but us. We'll take
1263 : * each timer's lock before clearing its firing flag, so no
1264 : * timer call will interfere.
1265 : */
1266 0 : list_for_each_entry_safe(timer, next, &firing, it.cpu.elist) {
1267 0 : int cpu_firing;
1268 :
1269 : /*
1270 : * spin_lock() is sufficient here even independent of the
1271 : * expiry context. If expiry happens in hard interrupt
1272 : * context it's obvious. For task work context it's safe
1273 : * because all other operations on timer::it_lock happen in
1274 : * task context (syscall or exit).
1275 : */
1276 0 : spin_lock(&timer->it_lock);
1277 0 : list_del_init(&timer->it.cpu.elist);
1278 0 : cpu_firing = timer->it.cpu.firing;
1279 0 : timer->it.cpu.firing = 0;
1280 : /*
1281 : * The firing flag is -1 if we collided with a reset
1282 : * of the timer, which already reported this
1283 : * almost-firing as an overrun. So don't generate an event.
1284 : */
1285 0 : if (likely(cpu_firing >= 0))
1286 0 : cpu_timer_fire(timer);
1287 0 : spin_unlock(&timer->it_lock);
1288 : }
1289 : }
1290 :
1291 : /*
1292 : * This is called from the timer interrupt handler. The irq handler has
1293 : * already updated our counts. We need to check if any timers fire now.
1294 : * Interrupts are disabled.
1295 : */
1296 28925 : void run_posix_cpu_timers(void)
1297 : {
1298 28925 : struct task_struct *tsk = current;
1299 :
1300 57924 : lockdep_assert_irqs_disabled();
1301 :
1302 : /*
1303 : * If the actual expiry is deferred to task work context and the
1304 : * work is already scheduled there is no point to do anything here.
1305 : */
1306 29168 : if (posix_cpu_timers_work_scheduled(tsk))
1307 : return;
1308 :
1309 : /*
1310 : * The fast path checks that there are no expired thread or thread
1311 : * group timers. If that's so, just return.
1312 : */
1313 29366 : if (!fastpath_timer_check(tsk))
1314 : return;
1315 :
1316 0 : __run_posix_cpu_timers(tsk);
1317 : }
1318 :
1319 : /*
1320 : * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
1321 : * The tsk->sighand->siglock must be held by the caller.
1322 : */
1323 0 : void set_process_cpu_timer(struct task_struct *tsk, unsigned int clkid,
1324 : u64 *newval, u64 *oldval)
1325 : {
1326 0 : u64 now, *nextevt;
1327 :
1328 0 : if (WARN_ON_ONCE(clkid >= CPUCLOCK_SCHED))
1329 : return;
1330 :
1331 0 : nextevt = &tsk->signal->posix_cputimers.bases[clkid].nextevt;
1332 0 : now = cpu_clock_sample_group(clkid, tsk, true);
1333 :
1334 0 : if (oldval) {
1335 : /*
1336 : * We are setting itimer. The *oldval is absolute and we update
1337 : * it to be relative, *newval argument is relative and we update
1338 : * it to be absolute.
1339 : */
1340 0 : if (*oldval) {
1341 0 : if (*oldval <= now) {
1342 : /* Just about to fire. */
1343 0 : *oldval = TICK_NSEC;
1344 : } else {
1345 0 : *oldval -= now;
1346 : }
1347 : }
1348 :
1349 0 : if (!*newval)
1350 : return;
1351 0 : *newval += now;
1352 : }
1353 :
1354 : /*
1355 : * Update expiration cache if this is the earliest timer. CPUCLOCK_PROF
1356 : * expiry cache is also used by RLIMIT_CPU!.
1357 : */
1358 0 : if (*newval < *nextevt)
1359 0 : *nextevt = *newval;
1360 :
1361 0 : tick_dep_set_signal(tsk->signal, TICK_DEP_BIT_POSIX_TIMER);
1362 : }
1363 :
1364 0 : static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1365 : const struct timespec64 *rqtp)
1366 : {
1367 0 : struct itimerspec64 it;
1368 0 : struct k_itimer timer;
1369 0 : u64 expires;
1370 0 : int error;
1371 :
1372 : /*
1373 : * Set up a temporary timer and then wait for it to go off.
1374 : */
1375 0 : memset(&timer, 0, sizeof timer);
1376 0 : spin_lock_init(&timer.it_lock);
1377 0 : timer.it_clock = which_clock;
1378 0 : timer.it_overrun = -1;
1379 0 : error = posix_cpu_timer_create(&timer);
1380 0 : timer.it_process = current;
1381 :
1382 0 : if (!error) {
1383 0 : static struct itimerspec64 zero_it;
1384 0 : struct restart_block *restart;
1385 :
1386 0 : memset(&it, 0, sizeof(it));
1387 0 : it.it_value = *rqtp;
1388 :
1389 0 : spin_lock_irq(&timer.it_lock);
1390 0 : error = posix_cpu_timer_set(&timer, flags, &it, NULL);
1391 0 : if (error) {
1392 0 : spin_unlock_irq(&timer.it_lock);
1393 0 : return error;
1394 : }
1395 :
1396 0 : while (!signal_pending(current)) {
1397 0 : if (!cpu_timer_getexpires(&timer.it.cpu)) {
1398 : /*
1399 : * Our timer fired and was reset, below
1400 : * deletion can not fail.
1401 : */
1402 0 : posix_cpu_timer_del(&timer);
1403 0 : spin_unlock_irq(&timer.it_lock);
1404 0 : return 0;
1405 : }
1406 :
1407 : /*
1408 : * Block until cpu_timer_fire (or a signal) wakes us.
1409 : */
1410 0 : __set_current_state(TASK_INTERRUPTIBLE);
1411 0 : spin_unlock_irq(&timer.it_lock);
1412 0 : schedule();
1413 0 : spin_lock_irq(&timer.it_lock);
1414 : }
1415 :
1416 : /*
1417 : * We were interrupted by a signal.
1418 : */
1419 0 : expires = cpu_timer_getexpires(&timer.it.cpu);
1420 0 : error = posix_cpu_timer_set(&timer, 0, &zero_it, &it);
1421 0 : if (!error) {
1422 : /*
1423 : * Timer is now unarmed, deletion can not fail.
1424 : */
1425 0 : posix_cpu_timer_del(&timer);
1426 : }
1427 0 : spin_unlock_irq(&timer.it_lock);
1428 :
1429 0 : while (error == TIMER_RETRY) {
1430 : /*
1431 : * We need to handle case when timer was or is in the
1432 : * middle of firing. In other cases we already freed
1433 : * resources.
1434 : */
1435 0 : spin_lock_irq(&timer.it_lock);
1436 0 : error = posix_cpu_timer_del(&timer);
1437 0 : spin_unlock_irq(&timer.it_lock);
1438 : }
1439 :
1440 0 : if ((it.it_value.tv_sec | it.it_value.tv_nsec) == 0) {
1441 : /*
1442 : * It actually did fire already.
1443 : */
1444 : return 0;
1445 : }
1446 :
1447 0 : error = -ERESTART_RESTARTBLOCK;
1448 : /*
1449 : * Report back to the user the time still remaining.
1450 : */
1451 0 : restart = ¤t->restart_block;
1452 0 : restart->nanosleep.expires = expires;
1453 0 : if (restart->nanosleep.type != TT_NONE)
1454 0 : error = nanosleep_copyout(restart, &it.it_value);
1455 : }
1456 :
1457 : return error;
1458 : }
1459 :
1460 : static long posix_cpu_nsleep_restart(struct restart_block *restart_block);
1461 :
1462 0 : static int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1463 : const struct timespec64 *rqtp)
1464 : {
1465 0 : struct restart_block *restart_block = ¤t->restart_block;
1466 0 : int error;
1467 :
1468 : /*
1469 : * Diagnose required errors first.
1470 : */
1471 0 : if (CPUCLOCK_PERTHREAD(which_clock) &&
1472 0 : (CPUCLOCK_PID(which_clock) == 0 ||
1473 0 : CPUCLOCK_PID(which_clock) == task_pid_vnr(current)))
1474 0 : return -EINVAL;
1475 :
1476 0 : error = do_cpu_nanosleep(which_clock, flags, rqtp);
1477 :
1478 0 : if (error == -ERESTART_RESTARTBLOCK) {
1479 :
1480 0 : if (flags & TIMER_ABSTIME)
1481 : return -ERESTARTNOHAND;
1482 :
1483 0 : restart_block->fn = posix_cpu_nsleep_restart;
1484 0 : restart_block->nanosleep.clockid = which_clock;
1485 : }
1486 : return error;
1487 : }
1488 :
1489 0 : static long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1490 : {
1491 0 : clockid_t which_clock = restart_block->nanosleep.clockid;
1492 0 : struct timespec64 t;
1493 :
1494 0 : t = ns_to_timespec64(restart_block->nanosleep.expires);
1495 :
1496 0 : return do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t);
1497 : }
1498 :
1499 : #define PROCESS_CLOCK make_process_cpuclock(0, CPUCLOCK_SCHED)
1500 : #define THREAD_CLOCK make_thread_cpuclock(0, CPUCLOCK_SCHED)
1501 :
1502 0 : static int process_cpu_clock_getres(const clockid_t which_clock,
1503 : struct timespec64 *tp)
1504 : {
1505 0 : return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1506 : }
1507 0 : static int process_cpu_clock_get(const clockid_t which_clock,
1508 : struct timespec64 *tp)
1509 : {
1510 0 : return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1511 : }
1512 0 : static int process_cpu_timer_create(struct k_itimer *timer)
1513 : {
1514 0 : timer->it_clock = PROCESS_CLOCK;
1515 0 : return posix_cpu_timer_create(timer);
1516 : }
1517 0 : static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1518 : const struct timespec64 *rqtp)
1519 : {
1520 0 : return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp);
1521 : }
1522 0 : static int thread_cpu_clock_getres(const clockid_t which_clock,
1523 : struct timespec64 *tp)
1524 : {
1525 0 : return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1526 : }
1527 0 : static int thread_cpu_clock_get(const clockid_t which_clock,
1528 : struct timespec64 *tp)
1529 : {
1530 0 : return posix_cpu_clock_get(THREAD_CLOCK, tp);
1531 : }
1532 0 : static int thread_cpu_timer_create(struct k_itimer *timer)
1533 : {
1534 0 : timer->it_clock = THREAD_CLOCK;
1535 0 : return posix_cpu_timer_create(timer);
1536 : }
1537 :
1538 : const struct k_clock clock_posix_cpu = {
1539 : .clock_getres = posix_cpu_clock_getres,
1540 : .clock_set = posix_cpu_clock_set,
1541 : .clock_get_timespec = posix_cpu_clock_get,
1542 : .timer_create = posix_cpu_timer_create,
1543 : .nsleep = posix_cpu_nsleep,
1544 : .timer_set = posix_cpu_timer_set,
1545 : .timer_del = posix_cpu_timer_del,
1546 : .timer_get = posix_cpu_timer_get,
1547 : .timer_rearm = posix_cpu_timer_rearm,
1548 : };
1549 :
1550 : const struct k_clock clock_process = {
1551 : .clock_getres = process_cpu_clock_getres,
1552 : .clock_get_timespec = process_cpu_clock_get,
1553 : .timer_create = process_cpu_timer_create,
1554 : .nsleep = process_cpu_nsleep,
1555 : };
1556 :
1557 : const struct k_clock clock_thread = {
1558 : .clock_getres = thread_cpu_clock_getres,
1559 : .clock_get_timespec = thread_cpu_clock_get,
1560 : .timer_create = thread_cpu_timer_create,
1561 : };
|
