Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * procsignal.c
4 : * Routines for interprocess signaling
5 : *
6 : *
7 : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
8 : * Portions Copyright (c) 1994, Regents of the University of California
9 : *
10 : * IDENTIFICATION
11 : * src/backend/storage/ipc/procsignal.c
12 : *
13 : *-------------------------------------------------------------------------
14 : */
15 : #include "postgres.h"
16 :
17 : #include <signal.h>
18 : #include <unistd.h>
19 :
20 : #include "access/parallel.h"
21 : #include "commands/async.h"
22 : #include "miscadmin.h"
23 : #include "pgstat.h"
24 : #include "port/pg_bitutils.h"
25 : #include "replication/logicalctl.h"
26 : #include "replication/logicalworker.h"
27 : #include "replication/walsender.h"
28 : #include "storage/condition_variable.h"
29 : #include "storage/ipc.h"
30 : #include "storage/latch.h"
31 : #include "storage/proc.h"
32 : #include "storage/shmem.h"
33 : #include "storage/sinval.h"
34 : #include "storage/smgr.h"
35 : #include "tcop/tcopprot.h"
36 : #include "utils/memutils.h"
37 : #include "utils/wait_event.h"
38 :
39 : /*
40 : * The SIGUSR1 signal is multiplexed to support signaling multiple event
41 : * types. The specific reason is communicated via flags in shared memory.
42 : * We keep a boolean flag for each possible "reason", so that different
43 : * reasons can be signaled to a process concurrently. (However, if the same
44 : * reason is signaled more than once nearly simultaneously, the process may
45 : * observe it only once.)
46 : *
47 : * Each process that wants to receive signals registers its process ID
48 : * in the ProcSignalSlots array. The array is indexed by ProcNumber to make
49 : * slot allocation simple, and to avoid having to search the array when you
50 : * know the ProcNumber of the process you're signaling. (We do support
51 : * signaling without ProcNumber, but it's a bit less efficient.)
52 : *
53 : * The fields in each slot are protected by a spinlock, pss_mutex. pss_pid can
54 : * also be read without holding the spinlock, as a quick preliminary check
55 : * when searching for a particular PID in the array.
56 : *
57 : * pss_signalFlags are intended to be set in cases where we don't need to
58 : * keep track of whether or not the target process has handled the signal,
59 : * but sometimes we need confirmation, as when making a global state change
60 : * that cannot be considered complete until all backends have taken notice
61 : * of it. For such use cases, we set a bit in pss_barrierCheckMask and then
62 : * increment the current "barrier generation"; when the new barrier generation
63 : * (or greater) appears in the pss_barrierGeneration flag of every process,
64 : * we know that the message has been received everywhere.
65 : */
66 : typedef struct
67 : {
68 : pg_atomic_uint32 pss_pid;
69 : int pss_cancel_key_len; /* 0 means no cancellation is possible */
70 : uint8 pss_cancel_key[MAX_CANCEL_KEY_LENGTH];
71 : volatile sig_atomic_t pss_signalFlags[NUM_PROCSIGNALS];
72 : slock_t pss_mutex; /* protects the above fields */
73 :
74 : /* Barrier-related fields (not protected by pss_mutex) */
75 : pg_atomic_uint64 pss_barrierGeneration;
76 : pg_atomic_uint32 pss_barrierCheckMask;
77 : ConditionVariable pss_barrierCV;
78 : } ProcSignalSlot;
79 :
80 : /*
81 : * Information that is global to the entire ProcSignal system can be stored
82 : * here.
83 : *
84 : * psh_barrierGeneration is the highest barrier generation in existence.
85 : */
86 : struct ProcSignalHeader
87 : {
88 : pg_atomic_uint64 psh_barrierGeneration;
89 : ProcSignalSlot psh_slot[FLEXIBLE_ARRAY_MEMBER];
90 : };
91 :
92 : /*
93 : * We reserve a slot for each possible ProcNumber, plus one for each
94 : * possible auxiliary process type. (This scheme assumes there is not
95 : * more than one of any auxiliary process type at a time, except for
96 : * IO workers.)
97 : */
98 : #define NumProcSignalSlots (MaxBackends + NUM_AUXILIARY_PROCS)
99 :
100 : /* Check whether the relevant type bit is set in the flags. */
101 : #define BARRIER_SHOULD_CHECK(flags, type) \
102 : (((flags) & (((uint32) 1) << (uint32) (type))) != 0)
103 :
104 : /* Clear the relevant type bit from the flags. */
105 : #define BARRIER_CLEAR_BIT(flags, type) \
106 : ((flags) &= ~(((uint32) 1) << (uint32) (type)))
107 :
108 : NON_EXEC_STATIC ProcSignalHeader *ProcSignal = NULL;
109 : static ProcSignalSlot *MyProcSignalSlot = NULL;
110 :
111 : static bool CheckProcSignal(ProcSignalReason reason);
112 : static void CleanupProcSignalState(int status, Datum arg);
113 : static void ResetProcSignalBarrierBits(uint32 flags);
114 :
115 : /*
116 : * ProcSignalShmemSize
117 : * Compute space needed for ProcSignal's shared memory
118 : */
119 : Size
120 3342 : ProcSignalShmemSize(void)
121 : {
122 : Size size;
123 :
124 3342 : size = mul_size(NumProcSignalSlots, sizeof(ProcSignalSlot));
125 3342 : size = add_size(size, offsetof(ProcSignalHeader, psh_slot));
126 3342 : return size;
127 : }
128 :
129 : /*
130 : * ProcSignalShmemInit
131 : * Allocate and initialize ProcSignal's shared memory
132 : */
133 : void
134 1165 : ProcSignalShmemInit(void)
135 : {
136 1165 : Size size = ProcSignalShmemSize();
137 : bool found;
138 :
139 1165 : ProcSignal = (ProcSignalHeader *)
140 1165 : ShmemInitStruct("ProcSignal", size, &found);
141 :
142 : /* If we're first, initialize. */
143 1165 : if (!found)
144 : {
145 : int i;
146 :
147 1165 : pg_atomic_init_u64(&ProcSignal->psh_barrierGeneration, 0);
148 :
149 153019 : for (i = 0; i < NumProcSignalSlots; ++i)
150 : {
151 151854 : ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
152 :
153 151854 : SpinLockInit(&slot->pss_mutex);
154 151854 : pg_atomic_init_u32(&slot->pss_pid, 0);
155 151854 : slot->pss_cancel_key_len = 0;
156 759270 : MemSet(slot->pss_signalFlags, 0, sizeof(slot->pss_signalFlags));
157 151854 : pg_atomic_init_u64(&slot->pss_barrierGeneration, PG_UINT64_MAX);
158 151854 : pg_atomic_init_u32(&slot->pss_barrierCheckMask, 0);
159 151854 : ConditionVariableInit(&slot->pss_barrierCV);
160 : }
161 : }
162 1165 : }
163 :
164 : /*
165 : * ProcSignalInit
166 : * Register the current process in the ProcSignal array
167 : */
168 : void
169 23890 : ProcSignalInit(const uint8 *cancel_key, int cancel_key_len)
170 : {
171 : ProcSignalSlot *slot;
172 : uint64 barrier_generation;
173 : uint32 old_pss_pid;
174 :
175 : Assert(cancel_key_len >= 0 && cancel_key_len <= MAX_CANCEL_KEY_LENGTH);
176 23890 : if (MyProcNumber < 0)
177 0 : elog(ERROR, "MyProcNumber not set");
178 23890 : if (MyProcNumber >= NumProcSignalSlots)
179 0 : elog(ERROR, "unexpected MyProcNumber %d in ProcSignalInit (max %d)", MyProcNumber, NumProcSignalSlots);
180 23890 : slot = &ProcSignal->psh_slot[MyProcNumber];
181 :
182 23890 : SpinLockAcquire(&slot->pss_mutex);
183 :
184 : /* Value used for sanity check below */
185 23890 : old_pss_pid = pg_atomic_read_u32(&slot->pss_pid);
186 :
187 : /* Clear out any leftover signal reasons */
188 119450 : MemSet(slot->pss_signalFlags, 0, NUM_PROCSIGNALS * sizeof(sig_atomic_t));
189 :
190 : /*
191 : * Initialize barrier state. Since we're a brand-new process, there
192 : * shouldn't be any leftover backend-private state that needs to be
193 : * updated. Therefore, we can broadcast the latest barrier generation and
194 : * disregard any previously-set check bits.
195 : *
196 : * NB: This only works if this initialization happens early enough in the
197 : * startup sequence that we haven't yet cached any state that might need
198 : * to be invalidated. That's also why we have a memory barrier here, to be
199 : * sure that any later reads of memory happen strictly after this.
200 : */
201 23890 : pg_atomic_write_u32(&slot->pss_barrierCheckMask, 0);
202 : barrier_generation =
203 23890 : pg_atomic_read_u64(&ProcSignal->psh_barrierGeneration);
204 23890 : pg_atomic_write_u64(&slot->pss_barrierGeneration, barrier_generation);
205 :
206 23890 : if (cancel_key_len > 0)
207 14114 : memcpy(slot->pss_cancel_key, cancel_key, cancel_key_len);
208 23890 : slot->pss_cancel_key_len = cancel_key_len;
209 23890 : pg_atomic_write_u32(&slot->pss_pid, MyProcPid);
210 :
211 23890 : SpinLockRelease(&slot->pss_mutex);
212 :
213 : /* Spinlock is released, do the check */
214 23890 : if (old_pss_pid != 0)
215 0 : elog(LOG, "process %d taking over ProcSignal slot %d, but it's not empty",
216 : MyProcPid, MyProcNumber);
217 :
218 : /* Remember slot location for CheckProcSignal */
219 23890 : MyProcSignalSlot = slot;
220 :
221 : /* Set up to release the slot on process exit */
222 23890 : on_shmem_exit(CleanupProcSignalState, (Datum) 0);
223 23890 : }
224 :
225 : /*
226 : * CleanupProcSignalState
227 : * Remove current process from ProcSignal mechanism
228 : *
229 : * This function is called via on_shmem_exit() during backend shutdown.
230 : */
231 : static void
232 23890 : CleanupProcSignalState(int status, Datum arg)
233 : {
234 : pid_t old_pid;
235 23890 : ProcSignalSlot *slot = MyProcSignalSlot;
236 :
237 : /*
238 : * Clear MyProcSignalSlot, so that a SIGUSR1 received after this point
239 : * won't try to access it after it's no longer ours (and perhaps even
240 : * after we've unmapped the shared memory segment).
241 : */
242 : Assert(MyProcSignalSlot != NULL);
243 23890 : MyProcSignalSlot = NULL;
244 :
245 : /* sanity check */
246 23890 : SpinLockAcquire(&slot->pss_mutex);
247 23890 : old_pid = pg_atomic_read_u32(&slot->pss_pid);
248 23890 : if (old_pid != MyProcPid)
249 : {
250 : /*
251 : * don't ERROR here. We're exiting anyway, and don't want to get into
252 : * infinite loop trying to exit
253 : */
254 0 : SpinLockRelease(&slot->pss_mutex);
255 0 : elog(LOG, "process %d releasing ProcSignal slot %d, but it contains %d",
256 : MyProcPid, (int) (slot - ProcSignal->psh_slot), (int) old_pid);
257 0 : return; /* XXX better to zero the slot anyway? */
258 : }
259 :
260 : /* Mark the slot as unused */
261 23890 : pg_atomic_write_u32(&slot->pss_pid, 0);
262 23890 : slot->pss_cancel_key_len = 0;
263 :
264 : /*
265 : * Make this slot look like it's absorbed all possible barriers, so that
266 : * no barrier waits block on it.
267 : */
268 23890 : pg_atomic_write_u64(&slot->pss_barrierGeneration, PG_UINT64_MAX);
269 :
270 23890 : SpinLockRelease(&slot->pss_mutex);
271 :
272 23890 : ConditionVariableBroadcast(&slot->pss_barrierCV);
273 : }
274 :
275 : /*
276 : * SendProcSignal
277 : * Send a signal to a Postgres process
278 : *
279 : * Providing procNumber is optional, but it will speed up the operation.
280 : *
281 : * On success (a signal was sent), zero is returned.
282 : * On error, -1 is returned, and errno is set (typically to ESRCH or EPERM).
283 : *
284 : * Not to be confused with ProcSendSignal
285 : */
286 : int
287 6092 : SendProcSignal(pid_t pid, ProcSignalReason reason, ProcNumber procNumber)
288 : {
289 : volatile ProcSignalSlot *slot;
290 :
291 6092 : if (procNumber != INVALID_PROC_NUMBER)
292 : {
293 : Assert(procNumber < NumProcSignalSlots);
294 6030 : slot = &ProcSignal->psh_slot[procNumber];
295 :
296 6030 : SpinLockAcquire(&slot->pss_mutex);
297 6030 : if (pg_atomic_read_u32(&slot->pss_pid) == pid)
298 : {
299 : /* Atomically set the proper flag */
300 6030 : slot->pss_signalFlags[reason] = true;
301 6030 : SpinLockRelease(&slot->pss_mutex);
302 : /* Send signal */
303 6030 : return kill(pid, SIGUSR1);
304 : }
305 0 : SpinLockRelease(&slot->pss_mutex);
306 : }
307 : else
308 : {
309 : /*
310 : * procNumber not provided, so search the array using pid. We search
311 : * the array back to front so as to reduce search overhead. Passing
312 : * INVALID_PROC_NUMBER means that the target is most likely an
313 : * auxiliary process, which will have a slot near the end of the
314 : * array.
315 : */
316 : int i;
317 :
318 2796 : for (i = NumProcSignalSlots - 1; i >= 0; i--)
319 : {
320 2796 : slot = &ProcSignal->psh_slot[i];
321 :
322 2796 : if (pg_atomic_read_u32(&slot->pss_pid) == pid)
323 : {
324 62 : SpinLockAcquire(&slot->pss_mutex);
325 62 : if (pg_atomic_read_u32(&slot->pss_pid) == pid)
326 : {
327 : /* Atomically set the proper flag */
328 62 : slot->pss_signalFlags[reason] = true;
329 62 : SpinLockRelease(&slot->pss_mutex);
330 : /* Send signal */
331 62 : return kill(pid, SIGUSR1);
332 : }
333 0 : SpinLockRelease(&slot->pss_mutex);
334 : }
335 : }
336 : }
337 :
338 0 : errno = ESRCH;
339 0 : return -1;
340 : }
341 :
342 : /*
343 : * EmitProcSignalBarrier
344 : * Send a signal to every Postgres process
345 : *
346 : * The return value of this function is the barrier "generation" created
347 : * by this operation. This value can be passed to WaitForProcSignalBarrier
348 : * to wait until it is known that every participant in the ProcSignal
349 : * mechanism has absorbed the signal (or started afterwards).
350 : *
351 : * Note that it would be a bad idea to use this for anything that happens
352 : * frequently, as interrupting every backend could cause a noticeable
353 : * performance hit.
354 : *
355 : * Callers are entitled to assume that this function will not throw ERROR
356 : * or FATAL.
357 : */
358 : uint64
359 598 : EmitProcSignalBarrier(ProcSignalBarrierType type)
360 : {
361 598 : uint32 flagbit = 1 << (uint32) type;
362 : uint64 generation;
363 :
364 : /*
365 : * Set all the flags.
366 : *
367 : * Note that pg_atomic_fetch_or_u32 has full barrier semantics, so this is
368 : * totally ordered with respect to anything the caller did before, and
369 : * anything that we do afterwards. (This is also true of the later call to
370 : * pg_atomic_add_fetch_u64.)
371 : */
372 62380 : for (int i = 0; i < NumProcSignalSlots; i++)
373 : {
374 61782 : volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
375 :
376 61782 : pg_atomic_fetch_or_u32(&slot->pss_barrierCheckMask, flagbit);
377 : }
378 :
379 : /*
380 : * Increment the generation counter.
381 : */
382 : generation =
383 598 : pg_atomic_add_fetch_u64(&ProcSignal->psh_barrierGeneration, 1);
384 :
385 : /*
386 : * Signal all the processes, so that they update their advertised barrier
387 : * generation.
388 : *
389 : * Concurrency is not a problem here. Backends that have exited don't
390 : * matter, and new backends that have joined since we entered this
391 : * function must already have current state, since the caller is
392 : * responsible for making sure that the relevant state is entirely visible
393 : * before calling this function in the first place. We still have to wake
394 : * them up - because we can't distinguish between such backends and older
395 : * backends that need to update state - but they won't actually need to
396 : * change any state.
397 : */
398 62380 : for (int i = NumProcSignalSlots - 1; i >= 0; i--)
399 : {
400 61782 : volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
401 61782 : pid_t pid = pg_atomic_read_u32(&slot->pss_pid);
402 :
403 61782 : if (pid != 0)
404 : {
405 3480 : SpinLockAcquire(&slot->pss_mutex);
406 3480 : pid = pg_atomic_read_u32(&slot->pss_pid);
407 3480 : if (pid != 0)
408 : {
409 : /* see SendProcSignal for details */
410 3480 : slot->pss_signalFlags[PROCSIG_BARRIER] = true;
411 3480 : SpinLockRelease(&slot->pss_mutex);
412 3480 : kill(pid, SIGUSR1);
413 : }
414 : else
415 0 : SpinLockRelease(&slot->pss_mutex);
416 : }
417 : }
418 :
419 598 : return generation;
420 : }
421 :
422 : /*
423 : * WaitForProcSignalBarrier - wait until it is guaranteed that all changes
424 : * requested by a specific call to EmitProcSignalBarrier() have taken effect.
425 : */
426 : void
427 582 : WaitForProcSignalBarrier(uint64 generation)
428 : {
429 : Assert(generation <= pg_atomic_read_u64(&ProcSignal->psh_barrierGeneration));
430 :
431 582 : elog(DEBUG1,
432 : "waiting for all backends to process ProcSignalBarrier generation "
433 : UINT64_FORMAT,
434 : generation);
435 :
436 61234 : for (int i = NumProcSignalSlots - 1; i >= 0; i--)
437 : {
438 60652 : ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
439 : uint64 oldval;
440 :
441 : /*
442 : * It's important that we check only pss_barrierGeneration here and
443 : * not pss_barrierCheckMask. Bits in pss_barrierCheckMask get cleared
444 : * before the barrier is actually absorbed, but pss_barrierGeneration
445 : * is updated only afterward.
446 : */
447 60652 : oldval = pg_atomic_read_u64(&slot->pss_barrierGeneration);
448 63488 : while (oldval < generation)
449 : {
450 2836 : if (ConditionVariableTimedSleep(&slot->pss_barrierCV,
451 : 5000,
452 : WAIT_EVENT_PROC_SIGNAL_BARRIER))
453 0 : ereport(LOG,
454 : (errmsg("still waiting for backend with PID %d to accept ProcSignalBarrier",
455 : (int) pg_atomic_read_u32(&slot->pss_pid))));
456 2836 : oldval = pg_atomic_read_u64(&slot->pss_barrierGeneration);
457 : }
458 60652 : ConditionVariableCancelSleep();
459 : }
460 :
461 582 : elog(DEBUG1,
462 : "finished waiting for all backends to process ProcSignalBarrier generation "
463 : UINT64_FORMAT,
464 : generation);
465 :
466 : /*
467 : * The caller is probably calling this function because it wants to read
468 : * the shared state or perform further writes to shared state once all
469 : * backends are known to have absorbed the barrier. However, the read of
470 : * pss_barrierGeneration was performed unlocked; insert a memory barrier
471 : * to separate it from whatever follows.
472 : */
473 582 : pg_memory_barrier();
474 582 : }
475 :
476 : /*
477 : * Handle receipt of an interrupt indicating a global barrier event.
478 : *
479 : * All the actual work is deferred to ProcessProcSignalBarrier(), because we
480 : * cannot safely access the barrier generation inside the signal handler as
481 : * 64bit atomics might use spinlock based emulation, even for reads. As this
482 : * routine only gets called when PROCSIG_BARRIER is sent that won't cause a
483 : * lot of unnecessary work.
484 : */
485 : static void
486 2530 : HandleProcSignalBarrierInterrupt(void)
487 : {
488 2530 : InterruptPending = true;
489 2530 : ProcSignalBarrierPending = true;
490 : /* latch will be set by procsignal_sigusr1_handler */
491 2530 : }
492 :
493 : /*
494 : * Perform global barrier related interrupt checking.
495 : *
496 : * Any backend that participates in ProcSignal signaling must arrange to
497 : * call this function periodically. It is called from CHECK_FOR_INTERRUPTS(),
498 : * which is enough for normal backends, but not necessarily for all types of
499 : * background processes.
500 : */
501 : void
502 2527 : ProcessProcSignalBarrier(void)
503 : {
504 : uint64 local_gen;
505 : uint64 shared_gen;
506 : volatile uint32 flags;
507 :
508 : Assert(MyProcSignalSlot);
509 :
510 : /* Exit quickly if there's no work to do. */
511 2527 : if (!ProcSignalBarrierPending)
512 0 : return;
513 2527 : ProcSignalBarrierPending = false;
514 :
515 : /*
516 : * It's not unlikely to process multiple barriers at once, before the
517 : * signals for all the barriers have arrived. To avoid unnecessary work in
518 : * response to subsequent signals, exit early if we already have processed
519 : * all of them.
520 : */
521 2527 : local_gen = pg_atomic_read_u64(&MyProcSignalSlot->pss_barrierGeneration);
522 2527 : shared_gen = pg_atomic_read_u64(&ProcSignal->psh_barrierGeneration);
523 :
524 : Assert(local_gen <= shared_gen);
525 :
526 2527 : if (local_gen == shared_gen)
527 2 : return;
528 :
529 : /*
530 : * Get and clear the flags that are set for this backend. Note that
531 : * pg_atomic_exchange_u32 is a full barrier, so we're guaranteed that the
532 : * read of the barrier generation above happens before we atomically
533 : * extract the flags, and that any subsequent state changes happen
534 : * afterward.
535 : *
536 : * NB: In order to avoid race conditions, we must zero
537 : * pss_barrierCheckMask first and only afterwards try to do barrier
538 : * processing. If we did it in the other order, someone could send us
539 : * another barrier of some type right after we called the
540 : * barrier-processing function but before we cleared the bit. We would
541 : * have no way of knowing that the bit needs to stay set in that case, so
542 : * the need to call the barrier-processing function again would just get
543 : * forgotten. So instead, we tentatively clear all the bits and then put
544 : * back any for which we don't manage to successfully absorb the barrier.
545 : */
546 2525 : flags = pg_atomic_exchange_u32(&MyProcSignalSlot->pss_barrierCheckMask, 0);
547 :
548 : /*
549 : * If there are no flags set, then we can skip doing any real work.
550 : * Otherwise, establish a PG_TRY block, so that we don't lose track of
551 : * which types of barrier processing are needed if an ERROR occurs.
552 : */
553 2525 : if (flags != 0)
554 : {
555 2525 : bool success = true;
556 :
557 2525 : PG_TRY();
558 : {
559 : /*
560 : * Process each type of barrier. The barrier-processing functions
561 : * should normally return true, but may return false if the
562 : * barrier can't be absorbed at the current time. This should be
563 : * rare, because it's pretty expensive. Every single
564 : * CHECK_FOR_INTERRUPTS() will return here until we manage to
565 : * absorb the barrier, and that cost will add up in a hurry.
566 : *
567 : * NB: It ought to be OK to call the barrier-processing functions
568 : * unconditionally, but it's more efficient to call only the ones
569 : * that might need us to do something based on the flags.
570 : */
571 7575 : while (flags != 0)
572 : {
573 : ProcSignalBarrierType type;
574 2525 : bool processed = true;
575 :
576 2525 : type = (ProcSignalBarrierType) pg_rightmost_one_pos32(flags);
577 2525 : switch (type)
578 : {
579 696 : case PROCSIGNAL_BARRIER_SMGRRELEASE:
580 696 : processed = ProcessBarrierSmgrRelease();
581 696 : break;
582 1829 : case PROCSIGNAL_BARRIER_UPDATE_XLOG_LOGICAL_INFO:
583 1829 : processed = ProcessBarrierUpdateXLogLogicalInfo();
584 1829 : break;
585 : }
586 :
587 : /*
588 : * To avoid an infinite loop, we must always unset the bit in
589 : * flags.
590 : */
591 2525 : BARRIER_CLEAR_BIT(flags, type);
592 :
593 : /*
594 : * If we failed to process the barrier, reset the shared bit
595 : * so we try again later, and set a flag so that we don't bump
596 : * our generation.
597 : */
598 2525 : if (!processed)
599 : {
600 0 : ResetProcSignalBarrierBits(((uint32) 1) << type);
601 0 : success = false;
602 : }
603 : }
604 : }
605 0 : PG_CATCH();
606 : {
607 : /*
608 : * If an ERROR occurred, we'll need to try again later to handle
609 : * that barrier type and any others that haven't been handled yet
610 : * or weren't successfully absorbed.
611 : */
612 0 : ResetProcSignalBarrierBits(flags);
613 0 : PG_RE_THROW();
614 : }
615 2525 : PG_END_TRY();
616 :
617 : /*
618 : * If some barrier types were not successfully absorbed, we will have
619 : * to try again later.
620 : */
621 2525 : if (!success)
622 0 : return;
623 : }
624 :
625 : /*
626 : * State changes related to all types of barriers that might have been
627 : * emitted have now been handled, so we can update our notion of the
628 : * generation to the one we observed before beginning the updates. If
629 : * things have changed further, it'll get fixed up when this function is
630 : * next called.
631 : */
632 2525 : pg_atomic_write_u64(&MyProcSignalSlot->pss_barrierGeneration, shared_gen);
633 2525 : ConditionVariableBroadcast(&MyProcSignalSlot->pss_barrierCV);
634 : }
635 :
636 : /*
637 : * If it turns out that we couldn't absorb one or more barrier types, either
638 : * because the barrier-processing functions returned false or due to an error,
639 : * arrange for processing to be retried later.
640 : */
641 : static void
642 0 : ResetProcSignalBarrierBits(uint32 flags)
643 : {
644 0 : pg_atomic_fetch_or_u32(&MyProcSignalSlot->pss_barrierCheckMask, flags);
645 0 : ProcSignalBarrierPending = true;
646 0 : InterruptPending = true;
647 0 : }
648 :
649 : /*
650 : * CheckProcSignal - check to see if a particular reason has been
651 : * signaled, and clear the signal flag. Should be called after receiving
652 : * SIGUSR1.
653 : */
654 : static bool
655 94360 : CheckProcSignal(ProcSignalReason reason)
656 : {
657 94360 : volatile ProcSignalSlot *slot = MyProcSignalSlot;
658 :
659 94360 : if (slot != NULL)
660 : {
661 : /*
662 : * Careful here --- don't clear flag if we haven't seen it set.
663 : * pss_signalFlags is of type "volatile sig_atomic_t" to allow us to
664 : * read it here safely, without holding the spinlock.
665 : */
666 94288 : if (slot->pss_signalFlags[reason])
667 : {
668 7212 : slot->pss_signalFlags[reason] = false;
669 7212 : return true;
670 : }
671 : }
672 :
673 87148 : return false;
674 : }
675 :
676 : /*
677 : * procsignal_sigusr1_handler - handle SIGUSR1 signal.
678 : */
679 : void
680 11795 : procsignal_sigusr1_handler(SIGNAL_ARGS)
681 : {
682 11795 : if (CheckProcSignal(PROCSIG_CATCHUP_INTERRUPT))
683 2942 : HandleCatchupInterrupt();
684 :
685 11795 : if (CheckProcSignal(PROCSIG_NOTIFY_INTERRUPT))
686 11 : HandleNotifyInterrupt();
687 :
688 11795 : if (CheckProcSignal(PROCSIG_PARALLEL_MESSAGE))
689 1642 : HandleParallelMessageInterrupt();
690 :
691 11795 : if (CheckProcSignal(PROCSIG_WALSND_INIT_STOPPING))
692 43 : HandleWalSndInitStopping();
693 :
694 11795 : if (CheckProcSignal(PROCSIG_BARRIER))
695 2530 : HandleProcSignalBarrierInterrupt();
696 :
697 11795 : if (CheckProcSignal(PROCSIG_LOG_MEMORY_CONTEXT))
698 9 : HandleLogMemoryContextInterrupt();
699 :
700 11795 : if (CheckProcSignal(PROCSIG_PARALLEL_APPLY_MESSAGE))
701 16 : HandleParallelApplyMessageInterrupt();
702 :
703 11795 : if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT))
704 19 : HandleRecoveryConflictInterrupt();
705 :
706 11795 : SetLatch(MyLatch);
707 11795 : }
708 :
709 : /*
710 : * Send a query cancellation signal to backend.
711 : *
712 : * Note: This is called from a backend process before authentication. We
713 : * cannot take LWLocks yet, but that's OK; we rely on atomic reads of the
714 : * fields in the ProcSignal slots.
715 : */
716 : void
717 16 : SendCancelRequest(int backendPID, const uint8 *cancel_key, int cancel_key_len)
718 : {
719 16 : if (backendPID == 0)
720 : {
721 0 : ereport(LOG, (errmsg("invalid cancel request with PID 0")));
722 0 : return;
723 : }
724 :
725 : /*
726 : * See if we have a matching backend. Reading the pss_pid and
727 : * pss_cancel_key fields is racy, a backend might die and remove itself
728 : * from the array at any time. The probability of the cancellation key
729 : * matching wrong process is miniscule, however, so we can live with that.
730 : * PIDs are reused too, so sending the signal based on PID is inherently
731 : * racy anyway, although OS's avoid reusing PIDs too soon.
732 : */
733 275 : for (int i = 0; i < NumProcSignalSlots; i++)
734 : {
735 275 : ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
736 : bool match;
737 :
738 275 : if (pg_atomic_read_u32(&slot->pss_pid) != backendPID)
739 259 : continue;
740 :
741 : /* Acquire the spinlock and re-check */
742 16 : SpinLockAcquire(&slot->pss_mutex);
743 16 : if (pg_atomic_read_u32(&slot->pss_pid) != backendPID)
744 : {
745 0 : SpinLockRelease(&slot->pss_mutex);
746 0 : continue;
747 : }
748 : else
749 : {
750 32 : match = slot->pss_cancel_key_len == cancel_key_len &&
751 16 : timingsafe_bcmp(slot->pss_cancel_key, cancel_key, cancel_key_len) == 0;
752 :
753 16 : SpinLockRelease(&slot->pss_mutex);
754 :
755 16 : if (match)
756 : {
757 : /* Found a match; signal that backend to cancel current op */
758 16 : ereport(DEBUG2,
759 : (errmsg_internal("processing cancel request: sending SIGINT to process %d",
760 : backendPID)));
761 :
762 : /*
763 : * If we have setsid(), signal the backend's whole process
764 : * group
765 : */
766 : #ifdef HAVE_SETSID
767 16 : kill(-backendPID, SIGINT);
768 : #else
769 : kill(backendPID, SIGINT);
770 : #endif
771 : }
772 : else
773 : {
774 : /* Right PID, wrong key: no way, Jose */
775 0 : ereport(LOG,
776 : (errmsg("wrong key in cancel request for process %d",
777 : backendPID)));
778 : }
779 16 : return;
780 : }
781 : }
782 :
783 : /* No matching backend */
784 0 : ereport(LOG,
785 : (errmsg("PID %d in cancel request did not match any process",
786 : backendPID)));
787 : }
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