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 "commands/repack.h"
23 : #include "miscadmin.h"
24 : #include "pgstat.h"
25 : #include "port/pg_bitutils.h"
26 : #include "postmaster/datachecksum_state.h"
27 : #include "replication/logicalctl.h"
28 : #include "replication/logicalworker.h"
29 : #include "replication/slotsync.h"
30 : #include "replication/walsender.h"
31 : #include "storage/condition_variable.h"
32 : #include "storage/ipc.h"
33 : #include "storage/latch.h"
34 : #include "storage/proc.h"
35 : #include "storage/shmem.h"
36 : #include "storage/sinval.h"
37 : #include "storage/smgr.h"
38 : #include "storage/subsystems.h"
39 : #include "tcop/tcopprot.h"
40 : #include "utils/memutils.h"
41 : #include "utils/wait_event.h"
42 :
43 : /*
44 : * The SIGUSR1 signal is multiplexed to support signaling multiple event
45 : * types. The specific reason is communicated via flags in shared memory.
46 : * We keep a boolean flag for each possible "reason", so that different
47 : * reasons can be signaled to a process concurrently. (However, if the same
48 : * reason is signaled more than once nearly simultaneously, the process may
49 : * observe it only once.)
50 : *
51 : * Each process that wants to receive signals registers its process ID
52 : * in the ProcSignalSlots array. The array is indexed by ProcNumber to make
53 : * slot allocation simple, and to avoid having to search the array when you
54 : * know the ProcNumber of the process you're signaling. (We do support
55 : * signaling without ProcNumber, but it's a bit less efficient.)
56 : *
57 : * The fields in each slot are protected by a spinlock, pss_mutex. pss_pid can
58 : * also be read without holding the spinlock, as a quick preliminary check
59 : * when searching for a particular PID in the array.
60 : *
61 : * pss_signalFlags are intended to be set in cases where we don't need to
62 : * keep track of whether or not the target process has handled the signal,
63 : * but sometimes we need confirmation, as when making a global state change
64 : * that cannot be considered complete until all backends have taken notice
65 : * of it. For such use cases, we set a bit in pss_barrierCheckMask and then
66 : * increment the current "barrier generation"; when the new barrier generation
67 : * (or greater) appears in the pss_barrierGeneration flag of every process,
68 : * we know that the message has been received everywhere.
69 : */
70 : typedef struct
71 : {
72 : pg_atomic_uint32 pss_pid;
73 : int pss_cancel_key_len; /* 0 means no cancellation is possible */
74 : uint8 pss_cancel_key[MAX_CANCEL_KEY_LENGTH];
75 : volatile sig_atomic_t pss_signalFlags[NUM_PROCSIGNALS];
76 : slock_t pss_mutex; /* protects the above fields */
77 :
78 : /* Barrier-related fields (not protected by pss_mutex) */
79 : pg_atomic_uint64 pss_barrierGeneration;
80 : pg_atomic_uint32 pss_barrierCheckMask;
81 : ConditionVariable pss_barrierCV;
82 : } ProcSignalSlot;
83 :
84 : /*
85 : * Information that is global to the entire ProcSignal system can be stored
86 : * here.
87 : *
88 : * psh_barrierGeneration is the highest barrier generation in existence.
89 : */
90 : struct ProcSignalHeader
91 : {
92 : pg_atomic_uint64 psh_barrierGeneration;
93 : ProcSignalSlot psh_slot[FLEXIBLE_ARRAY_MEMBER];
94 : };
95 :
96 : /*
97 : * We reserve a slot for each possible ProcNumber, plus one for each
98 : * possible auxiliary process type. (This scheme assumes there is not
99 : * more than one of any auxiliary process type at a time, except for
100 : * IO workers.)
101 : */
102 : #define NumProcSignalSlots (MaxBackends + NUM_AUXILIARY_PROCS)
103 :
104 : /* Check whether the relevant type bit is set in the flags. */
105 : #define BARRIER_SHOULD_CHECK(flags, type) \
106 : (((flags) & (((uint32) 1) << (uint32) (type))) != 0)
107 :
108 : /* Clear the relevant type bit from the flags. */
109 : #define BARRIER_CLEAR_BIT(flags, type) \
110 : ((flags) &= ~(((uint32) 1) << (uint32) (type)))
111 :
112 : static void ProcSignalShmemRequest(void *arg);
113 : static void ProcSignalShmemInit(void *arg);
114 :
115 : const ShmemCallbacks ProcSignalShmemCallbacks = {
116 : .request_fn = ProcSignalShmemRequest,
117 : .init_fn = ProcSignalShmemInit,
118 : };
119 :
120 : NON_EXEC_STATIC ProcSignalHeader *ProcSignal = NULL;
121 :
122 : static ProcSignalSlot *MyProcSignalSlot = NULL;
123 :
124 : static bool CheckProcSignal(ProcSignalReason reason);
125 : static void CleanupProcSignalState(int status, Datum arg);
126 : static void ResetProcSignalBarrierBits(uint32 flags);
127 :
128 : /*
129 : * ProcSignalShmemRequest
130 : * Register ProcSignal's shared memory needs at postmaster startup
131 : */
132 : static void
133 1255 : ProcSignalShmemRequest(void *arg)
134 : {
135 : Size size;
136 :
137 1255 : size = mul_size(NumProcSignalSlots, sizeof(ProcSignalSlot));
138 1255 : size = add_size(size, offsetof(ProcSignalHeader, psh_slot));
139 :
140 1255 : ShmemRequestStruct(.name = "ProcSignal",
141 : .size = size,
142 : .ptr = (void **) &ProcSignal,
143 : );
144 1255 : }
145 :
146 : static void
147 1252 : ProcSignalShmemInit(void *arg)
148 : {
149 1252 : pg_atomic_init_u64(&ProcSignal->psh_barrierGeneration, 0);
150 :
151 165470 : for (int i = 0; i < NumProcSignalSlots; ++i)
152 : {
153 164218 : ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
154 :
155 164218 : SpinLockInit(&slot->pss_mutex);
156 164218 : pg_atomic_init_u32(&slot->pss_pid, 0);
157 164218 : slot->pss_cancel_key_len = 0;
158 985308 : MemSet(slot->pss_signalFlags, 0, sizeof(slot->pss_signalFlags));
159 164218 : pg_atomic_init_u64(&slot->pss_barrierGeneration, PG_UINT64_MAX);
160 164218 : pg_atomic_init_u32(&slot->pss_barrierCheckMask, 0);
161 164218 : ConditionVariableInit(&slot->pss_barrierCV);
162 : }
163 1252 : }
164 :
165 : /*
166 : * ProcSignalInit
167 : * Register the current process in the ProcSignal array
168 : */
169 : void
170 24728 : ProcSignalInit(const uint8 *cancel_key, int cancel_key_len)
171 : {
172 : ProcSignalSlot *slot;
173 : uint64 barrier_generation;
174 : uint32 old_pss_pid;
175 :
176 : Assert(cancel_key_len >= 0 && cancel_key_len <= MAX_CANCEL_KEY_LENGTH);
177 24728 : if (MyProcNumber < 0)
178 0 : elog(ERROR, "MyProcNumber not set");
179 24728 : if (MyProcNumber >= NumProcSignalSlots)
180 0 : elog(ERROR, "unexpected MyProcNumber %d in ProcSignalInit (max %d)", MyProcNumber, NumProcSignalSlots);
181 24728 : slot = &ProcSignal->psh_slot[MyProcNumber];
182 :
183 24728 : SpinLockAcquire(&slot->pss_mutex);
184 :
185 : /* Value used for sanity check below */
186 24728 : old_pss_pid = pg_atomic_read_u32(&slot->pss_pid);
187 :
188 : /* Clear out any leftover signal reasons */
189 148368 : MemSet(slot->pss_signalFlags, 0, NUM_PROCSIGNALS * sizeof(sig_atomic_t));
190 :
191 : /*
192 : * Publish the PID before reading the global barrier generation to ensure
193 : * that EmitProcSignalBarrier() doesn't skip us while we are grabbing an
194 : * older generation. We need a memory barrier here to make sure that the
195 : * update of pss_pid is ordered before the subsequent load of
196 : * psh_barrierGeneration.
197 : */
198 24728 : pg_atomic_write_membarrier_u32(&slot->pss_pid, MyProcPid);
199 :
200 : /*
201 : * Initialize barrier state. Since we're a brand-new process, there
202 : * shouldn't be any leftover backend-private state that needs to be
203 : * updated. Therefore, we can broadcast the latest barrier generation and
204 : * disregard any previously-set check bits.
205 : *
206 : * NB: This only works if this initialization happens early enough in the
207 : * startup sequence that we haven't yet cached any state that might need
208 : * to be invalidated. That's also why we have a memory barrier here, to be
209 : * sure that any later reads of memory happen strictly after this.
210 : */
211 24728 : pg_atomic_write_u32(&slot->pss_barrierCheckMask, 0);
212 : barrier_generation =
213 24728 : pg_atomic_read_u64(&ProcSignal->psh_barrierGeneration);
214 24728 : pg_atomic_write_u64(&slot->pss_barrierGeneration, barrier_generation);
215 :
216 24728 : if (cancel_key_len > 0)
217 14857 : memcpy(slot->pss_cancel_key, cancel_key, cancel_key_len);
218 24728 : slot->pss_cancel_key_len = cancel_key_len;
219 :
220 24728 : SpinLockRelease(&slot->pss_mutex);
221 :
222 : /* Spinlock is released, do the check */
223 24728 : if (old_pss_pid != 0)
224 0 : elog(LOG, "process %d taking over ProcSignal slot %d, but it's not empty",
225 : MyProcPid, MyProcNumber);
226 :
227 : /* Remember slot location for CheckProcSignal */
228 24728 : MyProcSignalSlot = slot;
229 :
230 : /* Set up to release the slot on process exit */
231 24728 : on_shmem_exit(CleanupProcSignalState, (Datum) 0);
232 24728 : }
233 :
234 : /*
235 : * CleanupProcSignalState
236 : * Remove current process from ProcSignal mechanism
237 : *
238 : * This function is called via on_shmem_exit() during backend shutdown.
239 : */
240 : static void
241 24728 : CleanupProcSignalState(int status, Datum arg)
242 : {
243 : pid_t old_pid;
244 24728 : ProcSignalSlot *slot = MyProcSignalSlot;
245 :
246 : /*
247 : * Clear MyProcSignalSlot, so that a SIGUSR1 received after this point
248 : * won't try to access it after it's no longer ours (and perhaps even
249 : * after we've unmapped the shared memory segment).
250 : */
251 : Assert(MyProcSignalSlot != NULL);
252 24728 : MyProcSignalSlot = NULL;
253 :
254 : /* sanity check */
255 24728 : SpinLockAcquire(&slot->pss_mutex);
256 24728 : old_pid = pg_atomic_read_u32(&slot->pss_pid);
257 24728 : if (old_pid != MyProcPid)
258 : {
259 : /*
260 : * don't ERROR here. We're exiting anyway, and don't want to get into
261 : * infinite loop trying to exit
262 : */
263 0 : SpinLockRelease(&slot->pss_mutex);
264 0 : elog(LOG, "process %d releasing ProcSignal slot %d, but it contains %d",
265 : MyProcPid, (int) (slot - ProcSignal->psh_slot), (int) old_pid);
266 0 : return; /* XXX better to zero the slot anyway? */
267 : }
268 :
269 : /* Mark the slot as unused */
270 24728 : pg_atomic_write_u32(&slot->pss_pid, 0);
271 24728 : slot->pss_cancel_key_len = 0;
272 :
273 : /*
274 : * Make this slot look like it's absorbed all possible barriers, so that
275 : * no barrier waits block on it.
276 : */
277 24728 : pg_atomic_write_u64(&slot->pss_barrierGeneration, PG_UINT64_MAX);
278 :
279 24728 : SpinLockRelease(&slot->pss_mutex);
280 :
281 24728 : ConditionVariableBroadcast(&slot->pss_barrierCV);
282 : }
283 :
284 : /*
285 : * SendProcSignal
286 : * Send a signal to a Postgres process
287 : *
288 : * Providing procNumber is optional, but it will speed up the operation.
289 : *
290 : * On success (a signal was sent), zero is returned.
291 : * On error, -1 is returned, and errno is set (typically to ESRCH or EPERM).
292 : *
293 : * Not to be confused with ProcSendSignal
294 : */
295 : int
296 7660 : SendProcSignal(pid_t pid, ProcSignalReason reason, ProcNumber procNumber)
297 : {
298 : volatile ProcSignalSlot *slot;
299 :
300 7660 : if (procNumber != INVALID_PROC_NUMBER)
301 : {
302 : Assert(procNumber < NumProcSignalSlots);
303 7590 : slot = &ProcSignal->psh_slot[procNumber];
304 :
305 7590 : SpinLockAcquire(&slot->pss_mutex);
306 7590 : if (pg_atomic_read_u32(&slot->pss_pid) == pid)
307 : {
308 : /* Atomically set the proper flag */
309 7590 : slot->pss_signalFlags[reason] = true;
310 7590 : SpinLockRelease(&slot->pss_mutex);
311 : /* Send signal */
312 7590 : return kill(pid, SIGUSR1);
313 : }
314 0 : SpinLockRelease(&slot->pss_mutex);
315 : }
316 : else
317 : {
318 : /*
319 : * procNumber not provided, so search the array using pid. We search
320 : * the array back to front so as to reduce search overhead. Passing
321 : * INVALID_PROC_NUMBER means that the target is most likely an
322 : * auxiliary process, which will have a slot near the end of the
323 : * array.
324 : */
325 : int i;
326 :
327 3177 : for (i = NumProcSignalSlots - 1; i >= 0; i--)
328 : {
329 3177 : slot = &ProcSignal->psh_slot[i];
330 :
331 3177 : if (pg_atomic_read_u32(&slot->pss_pid) == pid)
332 : {
333 70 : SpinLockAcquire(&slot->pss_mutex);
334 70 : if (pg_atomic_read_u32(&slot->pss_pid) == pid)
335 : {
336 : /* Atomically set the proper flag */
337 70 : slot->pss_signalFlags[reason] = true;
338 70 : SpinLockRelease(&slot->pss_mutex);
339 : /* Send signal */
340 70 : return kill(pid, SIGUSR1);
341 : }
342 0 : SpinLockRelease(&slot->pss_mutex);
343 : }
344 : }
345 : }
346 :
347 0 : errno = ESRCH;
348 0 : return -1;
349 : }
350 :
351 : /*
352 : * EmitProcSignalBarrier
353 : * Send a signal to every Postgres process
354 : *
355 : * The return value of this function is the barrier "generation" created
356 : * by this operation. This value can be passed to WaitForProcSignalBarrier
357 : * to wait until it is known that every participant in the ProcSignal
358 : * mechanism has absorbed the signal (or started afterwards).
359 : *
360 : * Note that it would be a bad idea to use this for anything that happens
361 : * frequently, as interrupting every backend could cause a noticeable
362 : * performance hit.
363 : *
364 : * Callers are entitled to assume that this function will not throw ERROR
365 : * or FATAL.
366 : */
367 : uint64
368 678 : EmitProcSignalBarrier(ProcSignalBarrierType type)
369 : {
370 678 : uint32 flagbit = 1 << (uint32) type;
371 : uint64 generation;
372 :
373 : /*
374 : * Set all the flags.
375 : *
376 : * Note that pg_atomic_fetch_or_u32 has full barrier semantics, so this is
377 : * totally ordered with respect to anything the caller did before, and
378 : * anything that we do afterwards. (This is also true of the later call to
379 : * pg_atomic_add_fetch_u64.)
380 : */
381 72287 : for (int i = 0; i < NumProcSignalSlots; i++)
382 : {
383 71609 : volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
384 :
385 71609 : pg_atomic_fetch_or_u32(&slot->pss_barrierCheckMask, flagbit);
386 : }
387 :
388 : /*
389 : * Increment the generation counter.
390 : */
391 : generation =
392 678 : pg_atomic_add_fetch_u64(&ProcSignal->psh_barrierGeneration, 1);
393 :
394 : /*
395 : * Signal all the processes, so that they update their advertised barrier
396 : * generation.
397 : *
398 : * Concurrency is not a problem here. Backends that have exited don't
399 : * matter, and new backends that have joined since we entered this
400 : * function must already have current state, since the caller is
401 : * responsible for making sure that the relevant state is entirely visible
402 : * before calling this function in the first place. We still have to wake
403 : * them up - because we can't distinguish between such backends and older
404 : * backends that need to update state - but they won't actually need to
405 : * change any state.
406 : */
407 72287 : for (int i = NumProcSignalSlots - 1; i >= 0; i--)
408 : {
409 71609 : volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
410 71609 : pid_t pid = pg_atomic_read_u32(&slot->pss_pid);
411 :
412 71609 : if (pid != 0)
413 : {
414 3539 : SpinLockAcquire(&slot->pss_mutex);
415 3539 : pid = pg_atomic_read_u32(&slot->pss_pid);
416 3539 : if (pid != 0)
417 : {
418 : /* see SendProcSignal for details */
419 3539 : slot->pss_signalFlags[PROCSIG_BARRIER] = true;
420 3539 : SpinLockRelease(&slot->pss_mutex);
421 3539 : kill(pid, SIGUSR1);
422 : }
423 : else
424 0 : SpinLockRelease(&slot->pss_mutex);
425 : }
426 : }
427 :
428 678 : return generation;
429 : }
430 :
431 : /*
432 : * WaitForProcSignalBarrier - wait until it is guaranteed that all changes
433 : * requested by a specific call to EmitProcSignalBarrier() have taken effect.
434 : */
435 : void
436 657 : WaitForProcSignalBarrier(uint64 generation)
437 : {
438 : Assert(generation <= pg_atomic_read_u64(&ProcSignal->psh_barrierGeneration));
439 :
440 657 : elog(DEBUG1,
441 : "waiting for all backends to process ProcSignalBarrier generation "
442 : UINT64_FORMAT,
443 : generation);
444 :
445 70369 : for (int i = NumProcSignalSlots - 1; i >= 0; i--)
446 : {
447 69712 : ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
448 : uint64 oldval;
449 :
450 : /*
451 : * It's important that we check only pss_barrierGeneration here and
452 : * not pss_barrierCheckMask. Bits in pss_barrierCheckMask get cleared
453 : * before the barrier is actually absorbed, but pss_barrierGeneration
454 : * is updated only afterward.
455 : */
456 69712 : oldval = pg_atomic_read_u64(&slot->pss_barrierGeneration);
457 72608 : while (oldval < generation)
458 : {
459 2896 : if (ConditionVariableTimedSleep(&slot->pss_barrierCV,
460 : 5000,
461 : WAIT_EVENT_PROC_SIGNAL_BARRIER))
462 0 : ereport(LOG,
463 : (errmsg("still waiting for backend with PID %d to accept ProcSignalBarrier",
464 : (int) pg_atomic_read_u32(&slot->pss_pid))));
465 2896 : oldval = pg_atomic_read_u64(&slot->pss_barrierGeneration);
466 : }
467 69712 : ConditionVariableCancelSleep();
468 : }
469 :
470 657 : elog(DEBUG1,
471 : "finished waiting for all backends to process ProcSignalBarrier generation "
472 : UINT64_FORMAT,
473 : generation);
474 :
475 : /*
476 : * The caller is probably calling this function because it wants to read
477 : * the shared state or perform further writes to shared state once all
478 : * backends are known to have absorbed the barrier. However, the read of
479 : * pss_barrierGeneration was performed unlocked; insert a memory barrier
480 : * to separate it from whatever follows.
481 : */
482 657 : pg_memory_barrier();
483 657 : }
484 :
485 : /*
486 : * Handle receipt of an interrupt indicating a global barrier event.
487 : *
488 : * All the actual work is deferred to ProcessProcSignalBarrier(), because we
489 : * cannot safely access the barrier generation inside the signal handler as
490 : * 64bit atomics might use spinlock based emulation, even for reads. As this
491 : * routine only gets called when PROCSIG_BARRIER is sent that won't cause a
492 : * lot of unnecessary work.
493 : */
494 : static void
495 2692 : HandleProcSignalBarrierInterrupt(void)
496 : {
497 2692 : InterruptPending = true;
498 2692 : ProcSignalBarrierPending = true;
499 : /* latch will be set by procsignal_sigusr1_handler */
500 2692 : }
501 :
502 : /*
503 : * Perform global barrier related interrupt checking.
504 : *
505 : * Any backend that participates in ProcSignal signaling must arrange to
506 : * call this function periodically. It is called from CHECK_FOR_INTERRUPTS(),
507 : * which is enough for normal backends, but not necessarily for all types of
508 : * background processes.
509 : */
510 : void
511 2687 : ProcessProcSignalBarrier(void)
512 : {
513 : uint64 local_gen;
514 : uint64 shared_gen;
515 : volatile uint32 flags;
516 :
517 : Assert(MyProcSignalSlot);
518 :
519 : /* Exit quickly if there's no work to do. */
520 2687 : if (!ProcSignalBarrierPending)
521 0 : return;
522 2687 : ProcSignalBarrierPending = false;
523 :
524 : /*
525 : * It's not unlikely to process multiple barriers at once, before the
526 : * signals for all the barriers have arrived. To avoid unnecessary work in
527 : * response to subsequent signals, exit early if we already have processed
528 : * all of them.
529 : */
530 2687 : local_gen = pg_atomic_read_u64(&MyProcSignalSlot->pss_barrierGeneration);
531 2687 : shared_gen = pg_atomic_read_u64(&ProcSignal->psh_barrierGeneration);
532 :
533 : Assert(local_gen <= shared_gen);
534 :
535 2687 : if (local_gen == shared_gen)
536 2 : return;
537 :
538 : /*
539 : * Get and clear the flags that are set for this backend. Note that
540 : * pg_atomic_exchange_u32 is a full barrier, so we're guaranteed that the
541 : * read of the barrier generation above happens before we atomically
542 : * extract the flags, and that any subsequent state changes happen
543 : * afterward.
544 : *
545 : * NB: In order to avoid race conditions, we must zero
546 : * pss_barrierCheckMask first and only afterwards try to do barrier
547 : * processing. If we did it in the other order, someone could send us
548 : * another barrier of some type right after we called the
549 : * barrier-processing function but before we cleared the bit. We would
550 : * have no way of knowing that the bit needs to stay set in that case, so
551 : * the need to call the barrier-processing function again would just get
552 : * forgotten. So instead, we tentatively clear all the bits and then put
553 : * back any for which we don't manage to successfully absorb the barrier.
554 : */
555 2685 : flags = pg_atomic_exchange_u32(&MyProcSignalSlot->pss_barrierCheckMask, 0);
556 :
557 : /*
558 : * If there are no flags set, then we can skip doing any real work.
559 : * Otherwise, establish a PG_TRY block, so that we don't lose track of
560 : * which types of barrier processing are needed if an ERROR occurs.
561 : */
562 2685 : if (flags != 0)
563 : {
564 2684 : bool success = true;
565 :
566 2684 : PG_TRY();
567 : {
568 : /*
569 : * Process each type of barrier. The barrier-processing functions
570 : * should normally return true, but may return false if the
571 : * barrier can't be absorbed at the current time. This should be
572 : * rare, because it's pretty expensive. Every single
573 : * CHECK_FOR_INTERRUPTS() will return here until we manage to
574 : * absorb the barrier, and that cost will add up in a hurry.
575 : *
576 : * NB: It ought to be OK to call the barrier-processing functions
577 : * unconditionally, but it's more efficient to call only the ones
578 : * that might need us to do something based on the flags.
579 : */
580 8052 : while (flags != 0)
581 : {
582 : ProcSignalBarrierType type;
583 2684 : bool processed = true;
584 :
585 2684 : type = (ProcSignalBarrierType) pg_rightmost_one_pos32(flags);
586 2684 : switch (type)
587 : {
588 662 : case PROCSIGNAL_BARRIER_SMGRRELEASE:
589 662 : processed = ProcessBarrierSmgrRelease();
590 662 : break;
591 1747 : case PROCSIGNAL_BARRIER_UPDATE_XLOG_LOGICAL_INFO:
592 1747 : processed = ProcessBarrierUpdateXLogLogicalInfo();
593 1747 : break;
594 :
595 275 : case PROCSIGNAL_BARRIER_CHECKSUM_INPROGRESS_ON:
596 : case PROCSIGNAL_BARRIER_CHECKSUM_ON:
597 : case PROCSIGNAL_BARRIER_CHECKSUM_INPROGRESS_OFF:
598 : case PROCSIGNAL_BARRIER_CHECKSUM_OFF:
599 275 : processed = AbsorbDataChecksumsBarrier(type);
600 275 : break;
601 : }
602 :
603 : /*
604 : * To avoid an infinite loop, we must always unset the bit in
605 : * flags.
606 : */
607 2684 : BARRIER_CLEAR_BIT(flags, type);
608 :
609 : /*
610 : * If we failed to process the barrier, reset the shared bit
611 : * so we try again later, and set a flag so that we don't bump
612 : * our generation.
613 : */
614 2684 : if (!processed)
615 : {
616 0 : ResetProcSignalBarrierBits(((uint32) 1) << type);
617 0 : success = false;
618 : }
619 : }
620 : }
621 0 : PG_CATCH();
622 : {
623 : /*
624 : * If an ERROR occurred, we'll need to try again later to handle
625 : * that barrier type and any others that haven't been handled yet
626 : * or weren't successfully absorbed.
627 : */
628 0 : ResetProcSignalBarrierBits(flags);
629 0 : PG_RE_THROW();
630 : }
631 2684 : PG_END_TRY();
632 :
633 : /*
634 : * If some barrier types were not successfully absorbed, we will have
635 : * to try again later.
636 : */
637 2684 : if (!success)
638 0 : return;
639 : }
640 :
641 : /*
642 : * State changes related to all types of barriers that might have been
643 : * emitted have now been handled, so we can update our notion of the
644 : * generation to the one we observed before beginning the updates. If
645 : * things have changed further, it'll get fixed up when this function is
646 : * next called.
647 : */
648 2685 : pg_atomic_write_u64(&MyProcSignalSlot->pss_barrierGeneration, shared_gen);
649 2685 : ConditionVariableBroadcast(&MyProcSignalSlot->pss_barrierCV);
650 : }
651 :
652 : /*
653 : * If it turns out that we couldn't absorb one or more barrier types, either
654 : * because the barrier-processing functions returned false or due to an error,
655 : * arrange for processing to be retried later.
656 : */
657 : static void
658 0 : ResetProcSignalBarrierBits(uint32 flags)
659 : {
660 0 : pg_atomic_fetch_or_u32(&MyProcSignalSlot->pss_barrierCheckMask, flags);
661 0 : ProcSignalBarrierPending = true;
662 0 : InterruptPending = true;
663 0 : }
664 :
665 : /*
666 : * CheckProcSignal - check to see if a particular reason has been
667 : * signaled, and clear the signal flag. Should be called after receiving
668 : * SIGUSR1.
669 : */
670 : static bool
671 137710 : CheckProcSignal(ProcSignalReason reason)
672 : {
673 137710 : volatile ProcSignalSlot *slot = MyProcSignalSlot;
674 :
675 137710 : if (slot != NULL)
676 : {
677 : /*
678 : * Careful here --- don't clear flag if we haven't seen it set.
679 : * pss_signalFlags is of type "volatile sig_atomic_t" to allow us to
680 : * read it here safely, without holding the spinlock.
681 : */
682 137530 : if (slot->pss_signalFlags[reason])
683 : {
684 8101 : slot->pss_signalFlags[reason] = false;
685 8101 : return true;
686 : }
687 : }
688 :
689 129609 : return false;
690 : }
691 :
692 : /*
693 : * procsignal_sigusr1_handler - handle SIGUSR1 signal.
694 : */
695 : void
696 13771 : procsignal_sigusr1_handler(SIGNAL_ARGS)
697 : {
698 13771 : if (CheckProcSignal(PROCSIG_CATCHUP_INTERRUPT))
699 3187 : HandleCatchupInterrupt();
700 :
701 13771 : if (CheckProcSignal(PROCSIG_NOTIFY_INTERRUPT))
702 9 : HandleNotifyInterrupt();
703 :
704 13771 : if (CheckProcSignal(PROCSIG_PARALLEL_MESSAGE))
705 2111 : HandleParallelMessageInterrupt();
706 :
707 13771 : if (CheckProcSignal(PROCSIG_WALSND_INIT_STOPPING))
708 48 : HandleWalSndInitStopping();
709 :
710 13771 : if (CheckProcSignal(PROCSIG_BARRIER))
711 2692 : HandleProcSignalBarrierInterrupt();
712 :
713 13771 : if (CheckProcSignal(PROCSIG_LOG_MEMORY_CONTEXT))
714 12 : HandleLogMemoryContextInterrupt();
715 :
716 13771 : if (CheckProcSignal(PROCSIG_PARALLEL_APPLY_MESSAGE))
717 16 : HandleParallelApplyMessageInterrupt();
718 :
719 13771 : if (CheckProcSignal(PROCSIG_REPACK_MESSAGE))
720 7 : HandleRepackMessageInterrupt();
721 :
722 13771 : if (CheckProcSignal(PROCSIG_SLOTSYNC_MESSAGE))
723 1 : HandleSlotSyncMessageInterrupt();
724 :
725 13771 : if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT))
726 18 : HandleRecoveryConflictInterrupt();
727 :
728 13771 : SetLatch(MyLatch);
729 13771 : }
730 :
731 : /*
732 : * Send a query cancellation signal to backend.
733 : *
734 : * Note: This is called from a backend process before authentication. We
735 : * cannot take LWLocks yet, but that's OK; we rely on atomic reads of the
736 : * fields in the ProcSignal slots.
737 : */
738 : void
739 16 : SendCancelRequest(int backendPID, const uint8 *cancel_key, int cancel_key_len)
740 : {
741 16 : if (backendPID == 0)
742 : {
743 0 : ereport(LOG, (errmsg("invalid cancel request with PID 0")));
744 0 : return;
745 : }
746 :
747 : /*
748 : * See if we have a matching backend. Reading the pss_pid and
749 : * pss_cancel_key fields is racy, a backend might die and remove itself
750 : * from the array at any time. The probability of the cancellation key
751 : * matching wrong process is miniscule, however, so we can live with that.
752 : * PIDs are reused too, so sending the signal based on PID is inherently
753 : * racy anyway, although OS's avoid reusing PIDs too soon.
754 : */
755 278 : for (int i = 0; i < NumProcSignalSlots; i++)
756 : {
757 278 : ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
758 : bool match;
759 :
760 278 : if (pg_atomic_read_u32(&slot->pss_pid) != backendPID)
761 262 : continue;
762 :
763 : /* Acquire the spinlock and re-check */
764 16 : SpinLockAcquire(&slot->pss_mutex);
765 16 : if (pg_atomic_read_u32(&slot->pss_pid) != backendPID)
766 : {
767 0 : SpinLockRelease(&slot->pss_mutex);
768 0 : continue;
769 : }
770 : else
771 : {
772 32 : match = slot->pss_cancel_key_len == cancel_key_len &&
773 16 : timingsafe_bcmp(slot->pss_cancel_key, cancel_key, cancel_key_len) == 0;
774 :
775 16 : SpinLockRelease(&slot->pss_mutex);
776 :
777 16 : if (match)
778 : {
779 : /* Found a match; signal that backend to cancel current op */
780 16 : ereport(DEBUG2,
781 : (errmsg_internal("processing cancel request: sending SIGINT to process %d",
782 : backendPID)));
783 :
784 : /*
785 : * If we have setsid(), signal the backend's whole process
786 : * group
787 : */
788 : #ifdef HAVE_SETSID
789 16 : kill(-backendPID, SIGINT);
790 : #else
791 : kill(backendPID, SIGINT);
792 : #endif
793 : }
794 : else
795 : {
796 : /* Right PID, wrong key: no way, Jose */
797 0 : ereport(LOG,
798 : (errmsg("wrong key in cancel request for process %d",
799 : backendPID)));
800 : }
801 16 : return;
802 : }
803 : }
804 :
805 : /* No matching backend */
806 0 : ereport(LOG,
807 : (errmsg("PID %d in cancel request did not match any process",
808 : backendPID)));
809 : }
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