Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * timeout.c
4 : * Routines to multiplex SIGALRM interrupts for multiple timeout reasons.
5 : *
6 : * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
7 : * Portions Copyright (c) 1994, Regents of the University of California
8 : *
9 : *
10 : * IDENTIFICATION
11 : * src/backend/utils/misc/timeout.c
12 : *
13 : *-------------------------------------------------------------------------
14 : */
15 : #include "postgres.h"
16 :
17 : #include <sys/time.h>
18 :
19 : #include "miscadmin.h"
20 : #include "storage/proc.h"
21 : #include "utils/timeout.h"
22 : #include "utils/timestamp.h"
23 :
24 :
25 : /* Data about any one timeout reason */
26 : typedef struct timeout_params
27 : {
28 : TimeoutId index; /* identifier of timeout reason */
29 :
30 : /* volatile because these may be changed from the signal handler */
31 : volatile bool active; /* true if timeout is in active_timeouts[] */
32 : volatile bool indicator; /* true if timeout has occurred */
33 :
34 : /* callback function for timeout, or NULL if timeout not registered */
35 : timeout_handler_proc timeout_handler;
36 :
37 : TimestampTz start_time; /* time that timeout was last activated */
38 : TimestampTz fin_time; /* time it is, or was last, due to fire */
39 : int interval_in_ms; /* time between firings, or 0 if just once */
40 : } timeout_params;
41 :
42 : /*
43 : * List of possible timeout reasons in the order of enum TimeoutId.
44 : */
45 : static timeout_params all_timeouts[MAX_TIMEOUTS];
46 : static bool all_timeouts_initialized = false;
47 :
48 : /*
49 : * List of active timeouts ordered by their fin_time and priority.
50 : * This list is subject to change by the interrupt handler, so it's volatile.
51 : */
52 : static volatile int num_active_timeouts = 0;
53 : static timeout_params *volatile active_timeouts[MAX_TIMEOUTS];
54 :
55 : /*
56 : * Flag controlling whether the signal handler is allowed to do anything.
57 : * This is useful to avoid race conditions with the handler. Note in
58 : * particular that this lets us make changes in the data structures without
59 : * tediously disabling and re-enabling the timer signal. Most of the time,
60 : * no interrupt would happen anyway during such critical sections, but if
61 : * one does, this rule ensures it's safe. Leaving the signal enabled across
62 : * multiple operations can greatly reduce the number of kernel calls we make,
63 : * too. See comments in schedule_alarm() about that.
64 : *
65 : * We leave this "false" when we're not expecting interrupts, just in case.
66 : */
67 : static volatile sig_atomic_t alarm_enabled = false;
68 :
69 : #define disable_alarm() (alarm_enabled = false)
70 : #define enable_alarm() (alarm_enabled = true)
71 :
72 : /*
73 : * State recording if and when we next expect the interrupt to fire.
74 : * (signal_due_at is valid only when signal_pending is true.)
75 : * Note that the signal handler will unconditionally reset signal_pending to
76 : * false, so that can change asynchronously even when alarm_enabled is false.
77 : */
78 : static volatile sig_atomic_t signal_pending = false;
79 : static volatile TimestampTz signal_due_at = 0;
80 :
81 :
82 : /*****************************************************************************
83 : * Internal helper functions
84 : *
85 : * For all of these, it is caller's responsibility to protect them from
86 : * interruption by the signal handler. Generally, call disable_alarm()
87 : * first to prevent interruption, then update state, and last call
88 : * schedule_alarm(), which will re-enable the signal handler if needed.
89 : *****************************************************************************/
90 :
91 : /*
92 : * Find the index of a given timeout reason in the active array.
93 : * If it's not there, return -1.
94 : */
95 : static int
96 41124 : find_active_timeout(TimeoutId id)
97 : {
98 : int i;
99 :
100 41432 : for (i = 0; i < num_active_timeouts; i++)
101 : {
102 41432 : if (active_timeouts[i]->index == id)
103 41124 : return i;
104 : }
105 :
106 0 : return -1;
107 : }
108 :
109 : /*
110 : * Insert specified timeout reason into the list of active timeouts
111 : * at the given index.
112 : */
113 : static void
114 94068 : insert_timeout(TimeoutId id, int index)
115 : {
116 : int i;
117 :
118 94068 : if (index < 0 || index > num_active_timeouts)
119 0 : elog(FATAL, "timeout index %d out of range 0..%d", index,
120 : num_active_timeouts);
121 :
122 : Assert(!all_timeouts[id].active);
123 94068 : all_timeouts[id].active = true;
124 :
125 95888 : for (i = num_active_timeouts - 1; i >= index; i--)
126 1820 : active_timeouts[i + 1] = active_timeouts[i];
127 :
128 94068 : active_timeouts[index] = &all_timeouts[id];
129 :
130 94068 : num_active_timeouts++;
131 94068 : }
132 :
133 : /*
134 : * Remove the index'th element from the timeout list.
135 : */
136 : static void
137 41238 : remove_timeout_index(int index)
138 : {
139 : int i;
140 :
141 41238 : if (index < 0 || index >= num_active_timeouts)
142 0 : elog(FATAL, "timeout index %d out of range 0..%d", index,
143 : num_active_timeouts - 1);
144 :
145 : Assert(active_timeouts[index]->active);
146 41238 : active_timeouts[index]->active = false;
147 :
148 43328 : for (i = index + 1; i < num_active_timeouts; i++)
149 2090 : active_timeouts[i - 1] = active_timeouts[i];
150 :
151 41238 : num_active_timeouts--;
152 41238 : }
153 :
154 : /*
155 : * Enable the specified timeout reason
156 : */
157 : static void
158 94068 : enable_timeout(TimeoutId id, TimestampTz now, TimestampTz fin_time,
159 : int interval_in_ms)
160 : {
161 : int i;
162 :
163 : /* Assert request is sane */
164 : Assert(all_timeouts_initialized);
165 : Assert(all_timeouts[id].timeout_handler != NULL);
166 :
167 : /*
168 : * If this timeout was already active, momentarily disable it. We
169 : * interpret the call as a directive to reschedule the timeout.
170 : */
171 94068 : if (all_timeouts[id].active)
172 0 : remove_timeout_index(find_active_timeout(id));
173 :
174 : /*
175 : * Find out the index where to insert the new timeout. We sort by
176 : * fin_time, and for equal fin_time by priority.
177 : */
178 94666 : for (i = 0; i < num_active_timeouts; i++)
179 : {
180 2398 : timeout_params *old_timeout = active_timeouts[i];
181 :
182 2398 : if (fin_time < old_timeout->fin_time)
183 1800 : break;
184 598 : if (fin_time == old_timeout->fin_time && id < old_timeout->index)
185 0 : break;
186 : }
187 :
188 : /*
189 : * Mark the timeout active, and insert it into the active list.
190 : */
191 94068 : all_timeouts[id].indicator = false;
192 94068 : all_timeouts[id].start_time = now;
193 94068 : all_timeouts[id].fin_time = fin_time;
194 94068 : all_timeouts[id].interval_in_ms = interval_in_ms;
195 :
196 94068 : insert_timeout(id, i);
197 94068 : }
198 :
199 : /*
200 : * Schedule alarm for the next active timeout, if any
201 : *
202 : * We assume the caller has obtained the current time, or a close-enough
203 : * approximation. (It's okay if a tick or two has passed since "now", or
204 : * if a little more time elapses before we reach the kernel call; that will
205 : * cause us to ask for an interrupt a tick or two later than the nearest
206 : * timeout, which is no big deal. Passing a "now" value that's in the future
207 : * would be bad though.)
208 : */
209 : static void
210 108058 : schedule_alarm(TimestampTz now)
211 : {
212 108058 : if (num_active_timeouts > 0)
213 : {
214 : struct itimerval timeval;
215 : TimestampTz nearest_timeout;
216 : long secs;
217 : int usecs;
218 :
219 540090 : MemSet(&timeval, 0, sizeof(struct itimerval));
220 :
221 : /*
222 : * If we think there's a signal pending, but current time is more than
223 : * 10ms past when the signal was due, then assume that the timeout
224 : * request got lost somehow; clear signal_pending so that we'll reset
225 : * the interrupt request below. (10ms corresponds to the worst-case
226 : * timeout granularity on modern systems.) It won't hurt us if the
227 : * interrupt does manage to fire between now and when we reach the
228 : * setitimer() call.
229 : */
230 108018 : if (signal_pending && now > signal_due_at + 10 * 1000)
231 0 : signal_pending = false;
232 :
233 : /*
234 : * Get the time remaining till the nearest pending timeout. If it is
235 : * negative, assume that we somehow missed an interrupt, and clear
236 : * signal_pending. This gives us another chance to recover if the
237 : * kernel drops a timeout request for some reason.
238 : */
239 108018 : nearest_timeout = active_timeouts[0]->fin_time;
240 108018 : if (now > nearest_timeout)
241 : {
242 0 : signal_pending = false;
243 : /* force an interrupt as soon as possible */
244 0 : secs = 0;
245 0 : usecs = 1;
246 : }
247 : else
248 : {
249 108018 : TimestampDifference(now, nearest_timeout,
250 : &secs, &usecs);
251 :
252 : /*
253 : * It's possible that the difference is less than a microsecond;
254 : * ensure we don't cancel, rather than set, the interrupt.
255 : */
256 108018 : if (secs == 0 && usecs == 0)
257 0 : usecs = 1;
258 : }
259 :
260 108018 : timeval.it_value.tv_sec = secs;
261 108018 : timeval.it_value.tv_usec = usecs;
262 :
263 : /*
264 : * We must enable the signal handler before calling setitimer(); if we
265 : * did it in the other order, we'd have a race condition wherein the
266 : * interrupt could occur before we can set alarm_enabled, so that the
267 : * signal handler would fail to do anything.
268 : *
269 : * Because we didn't bother to disable the timer in disable_alarm(),
270 : * it's possible that a previously-set interrupt will fire between
271 : * enable_alarm() and setitimer(). This is safe, however. There are
272 : * two possible outcomes:
273 : *
274 : * 1. The signal handler finds nothing to do (because the nearest
275 : * timeout event is still in the future). It will re-set the timer
276 : * and return. Then we'll overwrite the timer value with a new one.
277 : * This will mean that the timer fires a little later than we
278 : * intended, but only by the amount of time it takes for the signal
279 : * handler to do nothing useful, which shouldn't be much.
280 : *
281 : * 2. The signal handler executes and removes one or more timeout
282 : * events. When it returns, either the queue is now empty or the
283 : * frontmost event is later than the one we looked at above. So we'll
284 : * overwrite the timer value with one that is too soon (plus or minus
285 : * the signal handler's execution time), causing a useless interrupt
286 : * to occur. But the handler will then re-set the timer and
287 : * everything will still work as expected.
288 : *
289 : * Since these cases are of very low probability (the window here
290 : * being quite narrow), it's not worth adding cycles to the mainline
291 : * code to prevent occasional wasted interrupts.
292 : */
293 108018 : enable_alarm();
294 :
295 : /*
296 : * If there is already an interrupt pending that's at or before the
297 : * needed time, we need not do anything more. The signal handler will
298 : * do the right thing in the first case, and re-schedule the interrupt
299 : * for later in the second case. It might seem that the extra
300 : * interrupt is wasted work, but it's not terribly much work, and this
301 : * method has very significant advantages in the common use-case where
302 : * we repeatedly set a timeout that we don't expect to reach and then
303 : * cancel it. Instead of invoking setitimer() every time the timeout
304 : * is set or canceled, we perform one interrupt and a re-scheduling
305 : * setitimer() call at intervals roughly equal to the timeout delay.
306 : * For example, with statement_timeout = 1s and a throughput of
307 : * thousands of queries per second, this method requires an interrupt
308 : * and setitimer() call roughly once a second, rather than thousands
309 : * of setitimer() calls per second.
310 : *
311 : * Because of the possible passage of time between when we obtained
312 : * "now" and when we reach setitimer(), the kernel's opinion of when
313 : * to trigger the interrupt is likely to be a bit later than
314 : * signal_due_at. That's fine, for the same reasons described above.
315 : */
316 108018 : if (signal_pending && nearest_timeout >= signal_due_at)
317 71038 : return;
318 :
319 : /*
320 : * As with calling enable_alarm(), we must set signal_pending *before*
321 : * calling setitimer(); if we did it after, the signal handler could
322 : * trigger before we set it, leaving us with a false opinion that a
323 : * signal is still coming.
324 : *
325 : * Other race conditions involved with setting/checking signal_pending
326 : * are okay, for the reasons described above. One additional point is
327 : * that the signal handler could fire after we set signal_due_at, but
328 : * still before the setitimer() call. Then the handler could
329 : * overwrite signal_due_at with a value it computes, which will be the
330 : * same as or perhaps later than what we just computed. After we
331 : * perform setitimer(), the net effect would be that signal_due_at
332 : * gives a time later than when the interrupt will really happen;
333 : * which is a safe situation.
334 : */
335 36980 : signal_due_at = nearest_timeout;
336 36980 : signal_pending = true;
337 :
338 : /* Set the alarm timer */
339 36980 : if (setitimer(ITIMER_REAL, &timeval, NULL) != 0)
340 : {
341 : /*
342 : * Clearing signal_pending here is a bit pro forma, but not
343 : * entirely so, since something in the FATAL exit path could try
344 : * to use timeout facilities.
345 : */
346 0 : signal_pending = false;
347 0 : elog(FATAL, "could not enable SIGALRM timer: %m");
348 : }
349 : }
350 : }
351 :
352 :
353 : /*****************************************************************************
354 : * Signal handler
355 : *****************************************************************************/
356 :
357 : /*
358 : * Signal handler for SIGALRM
359 : *
360 : * Process any active timeout reasons and then reschedule the interrupt
361 : * as needed.
362 : */
363 : static void
364 234 : handle_sig_alarm(SIGNAL_ARGS)
365 : {
366 234 : int save_errno = errno;
367 :
368 : /*
369 : * Bump the holdoff counter, to make sure nothing we call will process
370 : * interrupts directly. No timeout handler should do that, but these
371 : * failures are hard to debug, so better be sure.
372 : */
373 234 : HOLD_INTERRUPTS();
374 :
375 : /*
376 : * SIGALRM is always cause for waking anything waiting on the process
377 : * latch.
378 : */
379 234 : SetLatch(MyLatch);
380 :
381 : /*
382 : * Always reset signal_pending, even if !alarm_enabled, since indeed no
383 : * signal is now pending.
384 : */
385 234 : signal_pending = false;
386 :
387 : /*
388 : * Fire any pending timeouts, but only if we're enabled to do so.
389 : */
390 234 : if (alarm_enabled)
391 : {
392 : /*
393 : * Disable alarms, just in case this platform allows signal handlers
394 : * to interrupt themselves. schedule_alarm() will re-enable if
395 : * appropriate.
396 : */
397 184 : disable_alarm();
398 :
399 184 : if (num_active_timeouts > 0)
400 : {
401 184 : TimestampTz now = GetCurrentTimestamp();
402 :
403 : /* While the first pending timeout has been reached ... */
404 298 : while (num_active_timeouts > 0 &&
405 258 : now >= active_timeouts[0]->fin_time)
406 : {
407 114 : timeout_params *this_timeout = active_timeouts[0];
408 :
409 : /* Remove it from the active list */
410 114 : remove_timeout_index(0);
411 :
412 : /* Mark it as fired */
413 114 : this_timeout->indicator = true;
414 :
415 : /* And call its handler function */
416 114 : this_timeout->timeout_handler();
417 :
418 : /* If it should fire repeatedly, re-enable it. */
419 114 : if (this_timeout->interval_in_ms > 0)
420 : {
421 : TimestampTz new_fin_time;
422 :
423 : /*
424 : * To guard against drift, schedule the next instance of
425 : * the timeout based on the intended firing time rather
426 : * than the actual firing time. But if the timeout was so
427 : * late that we missed an entire cycle, fall back to
428 : * scheduling based on the actual firing time.
429 : */
430 12 : new_fin_time =
431 12 : TimestampTzPlusMilliseconds(this_timeout->fin_time,
432 : this_timeout->interval_in_ms);
433 12 : if (new_fin_time < now)
434 0 : new_fin_time =
435 0 : TimestampTzPlusMilliseconds(now,
436 : this_timeout->interval_in_ms);
437 12 : enable_timeout(this_timeout->index, now, new_fin_time,
438 : this_timeout->interval_in_ms);
439 : }
440 :
441 : /*
442 : * The handler might not take negligible time (CheckDeadLock
443 : * for instance isn't too cheap), so let's update our idea of
444 : * "now" after each one.
445 : */
446 114 : now = GetCurrentTimestamp();
447 : }
448 :
449 : /* Done firing timeouts, so reschedule next interrupt if any */
450 184 : schedule_alarm(now);
451 : }
452 : }
453 :
454 234 : RESUME_INTERRUPTS();
455 :
456 234 : errno = save_errno;
457 234 : }
458 :
459 :
460 : /*****************************************************************************
461 : * Public API
462 : *****************************************************************************/
463 :
464 : /*
465 : * Initialize timeout module.
466 : *
467 : * This must be called in every process that wants to use timeouts.
468 : *
469 : * If the process was forked from another one that was also using this
470 : * module, be sure to call this before re-enabling signals; else handlers
471 : * meant to run in the parent process might get invoked in this one.
472 : */
473 : void
474 43048 : InitializeTimeouts(void)
475 : {
476 : int i;
477 :
478 : /* Initialize, or re-initialize, all local state */
479 43048 : disable_alarm();
480 :
481 43048 : num_active_timeouts = 0;
482 :
483 990104 : for (i = 0; i < MAX_TIMEOUTS; i++)
484 : {
485 947056 : all_timeouts[i].index = i;
486 947056 : all_timeouts[i].active = false;
487 947056 : all_timeouts[i].indicator = false;
488 947056 : all_timeouts[i].timeout_handler = NULL;
489 947056 : all_timeouts[i].start_time = 0;
490 947056 : all_timeouts[i].fin_time = 0;
491 947056 : all_timeouts[i].interval_in_ms = 0;
492 : }
493 :
494 43048 : all_timeouts_initialized = true;
495 :
496 : /* Now establish the signal handler */
497 43048 : pqsignal(SIGALRM, handle_sig_alarm);
498 43048 : }
499 :
500 : /*
501 : * Register a timeout reason
502 : *
503 : * For predefined timeouts, this just registers the callback function.
504 : *
505 : * For user-defined timeouts, pass id == USER_TIMEOUT; we then allocate and
506 : * return a timeout ID.
507 : */
508 : TimeoutId
509 187774 : RegisterTimeout(TimeoutId id, timeout_handler_proc handler)
510 : {
511 : Assert(all_timeouts_initialized);
512 :
513 : /* There's no need to disable the signal handler here. */
514 :
515 187774 : if (id >= USER_TIMEOUT)
516 : {
517 : /* Allocate a user-defined timeout reason */
518 0 : for (id = USER_TIMEOUT; id < MAX_TIMEOUTS; id++)
519 0 : if (all_timeouts[id].timeout_handler == NULL)
520 0 : break;
521 0 : if (id >= MAX_TIMEOUTS)
522 0 : ereport(FATAL,
523 : (errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
524 : errmsg("cannot add more timeout reasons")));
525 : }
526 :
527 : Assert(all_timeouts[id].timeout_handler == NULL);
528 :
529 187774 : all_timeouts[id].timeout_handler = handler;
530 :
531 187774 : return id;
532 : }
533 :
534 : /*
535 : * Reschedule any pending SIGALRM interrupt.
536 : *
537 : * This can be used during error recovery in case query cancel resulted in loss
538 : * of a SIGALRM event (due to longjmp'ing out of handle_sig_alarm before it
539 : * could do anything). But note it's not necessary if any of the public
540 : * enable_ or disable_timeout functions are called in the same area, since
541 : * those all do schedule_alarm() internally if needed.
542 : */
543 : void
544 49268 : reschedule_timeouts(void)
545 : {
546 : /* For flexibility, allow this to be called before we're initialized. */
547 49268 : if (!all_timeouts_initialized)
548 0 : return;
549 :
550 : /* Disable timeout interrupts for safety. */
551 49268 : disable_alarm();
552 :
553 : /* Reschedule the interrupt, if any timeouts remain active. */
554 49268 : if (num_active_timeouts > 0)
555 12328 : schedule_alarm(GetCurrentTimestamp());
556 : }
557 :
558 : /*
559 : * Enable the specified timeout to fire after the specified delay.
560 : *
561 : * Delay is given in milliseconds.
562 : */
563 : void
564 92726 : enable_timeout_after(TimeoutId id, int delay_ms)
565 : {
566 : TimestampTz now;
567 : TimestampTz fin_time;
568 :
569 : /* Disable timeout interrupts for safety. */
570 92726 : disable_alarm();
571 :
572 : /* Queue the timeout at the appropriate time. */
573 92726 : now = GetCurrentTimestamp();
574 92726 : fin_time = TimestampTzPlusMilliseconds(now, delay_ms);
575 92726 : enable_timeout(id, now, fin_time, 0);
576 :
577 : /* Set the timer interrupt. */
578 92726 : schedule_alarm(now);
579 92726 : }
580 :
581 : /*
582 : * Enable the specified timeout to fire periodically, with the specified
583 : * delay as the time between firings.
584 : *
585 : * Delay is given in milliseconds.
586 : */
587 : void
588 722 : enable_timeout_every(TimeoutId id, TimestampTz fin_time, int delay_ms)
589 : {
590 : TimestampTz now;
591 :
592 : /* Disable timeout interrupts for safety. */
593 722 : disable_alarm();
594 :
595 : /* Queue the timeout at the appropriate time. */
596 722 : now = GetCurrentTimestamp();
597 722 : enable_timeout(id, now, fin_time, delay_ms);
598 :
599 : /* Set the timer interrupt. */
600 722 : schedule_alarm(now);
601 722 : }
602 :
603 : /*
604 : * Enable the specified timeout to fire at the specified time.
605 : *
606 : * This is provided to support cases where there's a reason to calculate
607 : * the timeout by reference to some point other than "now". If there isn't,
608 : * use enable_timeout_after(), to avoid calling GetCurrentTimestamp() twice.
609 : */
610 : void
611 0 : enable_timeout_at(TimeoutId id, TimestampTz fin_time)
612 : {
613 : TimestampTz now;
614 :
615 : /* Disable timeout interrupts for safety. */
616 0 : disable_alarm();
617 :
618 : /* Queue the timeout at the appropriate time. */
619 0 : now = GetCurrentTimestamp();
620 0 : enable_timeout(id, now, fin_time, 0);
621 :
622 : /* Set the timer interrupt. */
623 0 : schedule_alarm(now);
624 0 : }
625 :
626 : /*
627 : * Enable multiple timeouts at once.
628 : *
629 : * This works like calling enable_timeout_after() and/or enable_timeout_at()
630 : * multiple times. Use this to reduce the number of GetCurrentTimestamp()
631 : * and setitimer() calls needed to establish multiple timeouts.
632 : */
633 : void
634 304 : enable_timeouts(const EnableTimeoutParams *timeouts, int count)
635 : {
636 : TimestampTz now;
637 : int i;
638 :
639 : /* Disable timeout interrupts for safety. */
640 304 : disable_alarm();
641 :
642 : /* Queue the timeout(s) at the appropriate times. */
643 304 : now = GetCurrentTimestamp();
644 :
645 912 : for (i = 0; i < count; i++)
646 : {
647 608 : TimeoutId id = timeouts[i].id;
648 : TimestampTz fin_time;
649 :
650 608 : switch (timeouts[i].type)
651 : {
652 582 : case TMPARAM_AFTER:
653 582 : fin_time = TimestampTzPlusMilliseconds(now,
654 : timeouts[i].delay_ms);
655 582 : enable_timeout(id, now, fin_time, 0);
656 582 : break;
657 :
658 26 : case TMPARAM_AT:
659 26 : enable_timeout(id, now, timeouts[i].fin_time, 0);
660 26 : break;
661 :
662 0 : case TMPARAM_EVERY:
663 0 : fin_time = TimestampTzPlusMilliseconds(now,
664 : timeouts[i].delay_ms);
665 0 : enable_timeout(id, now, fin_time, timeouts[i].delay_ms);
666 0 : break;
667 :
668 0 : default:
669 0 : elog(ERROR, "unrecognized timeout type %d",
670 : (int) timeouts[i].type);
671 : break;
672 : }
673 : }
674 :
675 : /* Set the timer interrupt. */
676 304 : schedule_alarm(now);
677 304 : }
678 :
679 : /*
680 : * Cancel the specified timeout.
681 : *
682 : * The timeout's I've-been-fired indicator is reset,
683 : * unless keep_indicator is true.
684 : *
685 : * When a timeout is canceled, any other active timeout remains in force.
686 : * It's not an error to disable a timeout that is not enabled.
687 : */
688 : void
689 41002 : disable_timeout(TimeoutId id, bool keep_indicator)
690 : {
691 : /* Assert request is sane */
692 : Assert(all_timeouts_initialized);
693 : Assert(all_timeouts[id].timeout_handler != NULL);
694 :
695 : /* Disable timeout interrupts for safety. */
696 41002 : disable_alarm();
697 :
698 : /* Find the timeout and remove it from the active list. */
699 41002 : if (all_timeouts[id].active)
700 40514 : remove_timeout_index(find_active_timeout(id));
701 :
702 : /* Mark it inactive, whether it was active or not. */
703 41002 : if (!keep_indicator)
704 41002 : all_timeouts[id].indicator = false;
705 :
706 : /* Reschedule the interrupt, if any timeouts remain active. */
707 41002 : if (num_active_timeouts > 0)
708 1464 : schedule_alarm(GetCurrentTimestamp());
709 41002 : }
710 :
711 : /*
712 : * Cancel multiple timeouts at once.
713 : *
714 : * The timeouts' I've-been-fired indicators are reset,
715 : * unless timeouts[i].keep_indicator is true.
716 : *
717 : * This works like calling disable_timeout() multiple times.
718 : * Use this to reduce the number of GetCurrentTimestamp()
719 : * and setitimer() calls needed to cancel multiple timeouts.
720 : */
721 : void
722 346 : disable_timeouts(const DisableTimeoutParams *timeouts, int count)
723 : {
724 : int i;
725 :
726 : Assert(all_timeouts_initialized);
727 :
728 : /* Disable timeout interrupts for safety. */
729 346 : disable_alarm();
730 :
731 : /* Cancel the timeout(s). */
732 1038 : for (i = 0; i < count; i++)
733 : {
734 692 : TimeoutId id = timeouts[i].id;
735 :
736 : Assert(all_timeouts[id].timeout_handler != NULL);
737 :
738 692 : if (all_timeouts[id].active)
739 610 : remove_timeout_index(find_active_timeout(id));
740 :
741 692 : if (!timeouts[i].keep_indicator)
742 346 : all_timeouts[id].indicator = false;
743 : }
744 :
745 : /* Reschedule the interrupt, if any timeouts remain active. */
746 346 : if (num_active_timeouts > 0)
747 330 : schedule_alarm(GetCurrentTimestamp());
748 346 : }
749 :
750 : /*
751 : * Disable the signal handler, remove all timeouts from the active list,
752 : * and optionally reset their timeout indicators.
753 : */
754 : void
755 35412 : disable_all_timeouts(bool keep_indicators)
756 : {
757 : int i;
758 :
759 35412 : disable_alarm();
760 :
761 : /*
762 : * We used to disable the timer interrupt here, but in common usage
763 : * patterns it's cheaper to leave it enabled; that may save us from having
764 : * to enable it again shortly. See comments in schedule_alarm().
765 : */
766 :
767 35412 : num_active_timeouts = 0;
768 :
769 814476 : for (i = 0; i < MAX_TIMEOUTS; i++)
770 : {
771 779064 : all_timeouts[i].active = false;
772 779064 : if (!keep_indicators)
773 779064 : all_timeouts[i].indicator = false;
774 : }
775 35412 : }
776 :
777 : /*
778 : * Return true if the timeout is active (enabled and not yet fired)
779 : *
780 : * This is, of course, subject to race conditions, as the timeout could fire
781 : * immediately after we look.
782 : */
783 : bool
784 4572074 : get_timeout_active(TimeoutId id)
785 : {
786 4572074 : return all_timeouts[id].active;
787 : }
788 :
789 : /*
790 : * Return the timeout's I've-been-fired indicator
791 : *
792 : * If reset_indicator is true, reset the indicator when returning true.
793 : * To avoid missing timeouts due to race conditions, we are careful not to
794 : * reset the indicator when returning false.
795 : */
796 : bool
797 188 : get_timeout_indicator(TimeoutId id, bool reset_indicator)
798 : {
799 188 : if (all_timeouts[id].indicator)
800 : {
801 18 : if (reset_indicator)
802 18 : all_timeouts[id].indicator = false;
803 18 : return true;
804 : }
805 170 : return false;
806 : }
807 :
808 : /*
809 : * Return the time when the timeout was most recently activated
810 : *
811 : * Note: will return 0 if timeout has never been activated in this process.
812 : * However, we do *not* reset the start_time when a timeout occurs, so as
813 : * not to create a race condition if SIGALRM fires just as some code is
814 : * about to fetch the value.
815 : */
816 : TimestampTz
817 2026 : get_timeout_start_time(TimeoutId id)
818 : {
819 2026 : return all_timeouts[id].start_time;
820 : }
821 :
822 : /*
823 : * Return the time when the timeout is, or most recently was, due to fire
824 : *
825 : * Note: will return 0 if timeout has never been activated in this process.
826 : * However, we do *not* reset the fin_time when a timeout occurs, so as
827 : * not to create a race condition if SIGALRM fires just as some code is
828 : * about to fetch the value.
829 : */
830 : TimestampTz
831 0 : get_timeout_finish_time(TimeoutId id)
832 : {
833 0 : return all_timeouts[id].fin_time;
834 : }
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