Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * proc.c
4 : * routines to manage per-process shared memory data structure
5 : *
6 : * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
7 : * Portions Copyright (c) 1994, Regents of the University of California
8 : *
9 : *
10 : * IDENTIFICATION
11 : * src/backend/storage/lmgr/proc.c
12 : *
13 : *-------------------------------------------------------------------------
14 : */
15 : /*
16 : * Interface (a):
17 : * ProcSleep(), ProcWakeup(),
18 : * ProcQueueAlloc() -- create a shm queue for sleeping processes
19 : * ProcQueueInit() -- create a queue without allocing memory
20 : *
21 : * Waiting for a lock causes the backend to be put to sleep. Whoever releases
22 : * the lock wakes the process up again (and gives it an error code so it knows
23 : * whether it was awoken on an error condition).
24 : *
25 : * Interface (b):
26 : *
27 : * ProcReleaseLocks -- frees the locks associated with current transaction
28 : *
29 : * ProcKill -- destroys the shared memory state (and locks)
30 : * associated with the process.
31 : */
32 : #include "postgres.h"
33 :
34 : #include <signal.h>
35 : #include <unistd.h>
36 : #include <sys/time.h>
37 :
38 : #include "access/transam.h"
39 : #include "access/twophase.h"
40 : #include "access/xact.h"
41 : #include "miscadmin.h"
42 : #include "pgstat.h"
43 : #include "postmaster/autovacuum.h"
44 : #include "replication/slot.h"
45 : #include "replication/syncrep.h"
46 : #include "storage/condition_variable.h"
47 : #include "storage/standby.h"
48 : #include "storage/ipc.h"
49 : #include "storage/lmgr.h"
50 : #include "storage/pmsignal.h"
51 : #include "storage/proc.h"
52 : #include "storage/procarray.h"
53 : #include "storage/procsignal.h"
54 : #include "storage/spin.h"
55 : #include "utils/timeout.h"
56 : #include "utils/timestamp.h"
57 :
58 :
59 : /* GUC variables */
60 : int DeadlockTimeout = 1000;
61 : int StatementTimeout = 0;
62 : int LockTimeout = 0;
63 : int IdleInTransactionSessionTimeout = 0;
64 : bool log_lock_waits = false;
65 :
66 : /* Pointer to this process's PGPROC and PGXACT structs, if any */
67 : PGPROC *MyProc = NULL;
68 : PGXACT *MyPgXact = NULL;
69 :
70 : /*
71 : * This spinlock protects the freelist of recycled PGPROC structures.
72 : * We cannot use an LWLock because the LWLock manager depends on already
73 : * having a PGPROC and a wait semaphore! But these structures are touched
74 : * relatively infrequently (only at backend startup or shutdown) and not for
75 : * very long, so a spinlock is okay.
76 : */
77 : NON_EXEC_STATIC slock_t *ProcStructLock = NULL;
78 :
79 : /* Pointers to shared-memory structures */
80 : PROC_HDR *ProcGlobal = NULL;
81 : NON_EXEC_STATIC PGPROC *AuxiliaryProcs = NULL;
82 : PGPROC *PreparedXactProcs = NULL;
83 :
84 : /* If we are waiting for a lock, this points to the associated LOCALLOCK */
85 : static LOCALLOCK *lockAwaited = NULL;
86 :
87 : static DeadLockState deadlock_state = DS_NOT_YET_CHECKED;
88 :
89 : /* Is a deadlock check pending? */
90 : static volatile sig_atomic_t got_deadlock_timeout;
91 :
92 : static void RemoveProcFromArray(int code, Datum arg);
93 : static void ProcKill(int code, Datum arg);
94 : static void AuxiliaryProcKill(int code, Datum arg);
95 : static void CheckDeadLock(void);
96 :
97 :
98 : /*
99 : * Report shared-memory space needed by InitProcGlobal.
100 : */
101 : Size
102 5 : ProcGlobalShmemSize(void)
103 : {
104 5 : Size size = 0;
105 :
106 : /* ProcGlobal */
107 5 : size = add_size(size, sizeof(PROC_HDR));
108 : /* MyProcs, including autovacuum workers and launcher */
109 5 : size = add_size(size, mul_size(MaxBackends, sizeof(PGPROC)));
110 : /* AuxiliaryProcs */
111 5 : size = add_size(size, mul_size(NUM_AUXILIARY_PROCS, sizeof(PGPROC)));
112 : /* Prepared xacts */
113 5 : size = add_size(size, mul_size(max_prepared_xacts, sizeof(PGPROC)));
114 : /* ProcStructLock */
115 5 : size = add_size(size, sizeof(slock_t));
116 :
117 5 : size = add_size(size, mul_size(MaxBackends, sizeof(PGXACT)));
118 5 : size = add_size(size, mul_size(NUM_AUXILIARY_PROCS, sizeof(PGXACT)));
119 5 : size = add_size(size, mul_size(max_prepared_xacts, sizeof(PGXACT)));
120 :
121 5 : return size;
122 : }
123 :
124 : /*
125 : * Report number of semaphores needed by InitProcGlobal.
126 : */
127 : int
128 5 : ProcGlobalSemas(void)
129 : {
130 : /*
131 : * We need a sema per backend (including autovacuum), plus one for each
132 : * auxiliary process.
133 : */
134 5 : return MaxBackends + NUM_AUXILIARY_PROCS;
135 : }
136 :
137 : /*
138 : * InitProcGlobal -
139 : * Initialize the global process table during postmaster or standalone
140 : * backend startup.
141 : *
142 : * We also create all the per-process semaphores we will need to support
143 : * the requested number of backends. We used to allocate semaphores
144 : * only when backends were actually started up, but that is bad because
145 : * it lets Postgres fail under load --- a lot of Unix systems are
146 : * (mis)configured with small limits on the number of semaphores, and
147 : * running out when trying to start another backend is a common failure.
148 : * So, now we grab enough semaphores to support the desired max number
149 : * of backends immediately at initialization --- if the sysadmin has set
150 : * MaxConnections, max_worker_processes, or autovacuum_max_workers higher
151 : * than his kernel will support, he'll find out sooner rather than later.
152 : *
153 : * Another reason for creating semaphores here is that the semaphore
154 : * implementation typically requires us to create semaphores in the
155 : * postmaster, not in backends.
156 : *
157 : * Note: this is NOT called by individual backends under a postmaster,
158 : * not even in the EXEC_BACKEND case. The ProcGlobal and AuxiliaryProcs
159 : * pointers must be propagated specially for EXEC_BACKEND operation.
160 : */
161 : void
162 5 : InitProcGlobal(void)
163 : {
164 : PGPROC *procs;
165 : PGXACT *pgxacts;
166 : int i,
167 : j;
168 : bool found;
169 5 : uint32 TotalProcs = MaxBackends + NUM_AUXILIARY_PROCS + max_prepared_xacts;
170 :
171 : /* Create the ProcGlobal shared structure */
172 5 : ProcGlobal = (PROC_HDR *)
173 5 : ShmemInitStruct("Proc Header", sizeof(PROC_HDR), &found);
174 5 : Assert(!found);
175 :
176 : /*
177 : * Initialize the data structures.
178 : */
179 5 : ProcGlobal->spins_per_delay = DEFAULT_SPINS_PER_DELAY;
180 5 : ProcGlobal->freeProcs = NULL;
181 5 : ProcGlobal->autovacFreeProcs = NULL;
182 5 : ProcGlobal->bgworkerFreeProcs = NULL;
183 5 : ProcGlobal->startupProc = NULL;
184 5 : ProcGlobal->startupProcPid = 0;
185 5 : ProcGlobal->startupBufferPinWaitBufId = -1;
186 5 : ProcGlobal->walwriterLatch = NULL;
187 5 : ProcGlobal->checkpointerLatch = NULL;
188 5 : pg_atomic_init_u32(&ProcGlobal->procArrayGroupFirst, INVALID_PGPROCNO);
189 5 : pg_atomic_init_u32(&ProcGlobal->clogGroupFirst, INVALID_PGPROCNO);
190 :
191 : /*
192 : * Create and initialize all the PGPROC structures we'll need. There are
193 : * five separate consumers: (1) normal backends, (2) autovacuum workers
194 : * and the autovacuum launcher, (3) background workers, (4) auxiliary
195 : * processes, and (5) prepared transactions. Each PGPROC structure is
196 : * dedicated to exactly one of these purposes, and they do not move
197 : * between groups.
198 : */
199 5 : procs = (PGPROC *) ShmemAlloc(TotalProcs * sizeof(PGPROC));
200 5 : MemSet(procs, 0, TotalProcs * sizeof(PGPROC));
201 5 : ProcGlobal->allProcs = procs;
202 : /* XXX allProcCount isn't really all of them; it excludes prepared xacts */
203 5 : ProcGlobal->allProcCount = MaxBackends + NUM_AUXILIARY_PROCS;
204 :
205 : /*
206 : * Also allocate a separate array of PGXACT structures. This is separate
207 : * from the main PGPROC array so that the most heavily accessed data is
208 : * stored contiguously in memory in as few cache lines as possible. This
209 : * provides significant performance benefits, especially on a
210 : * multiprocessor system. There is one PGXACT structure for every PGPROC
211 : * structure.
212 : */
213 5 : pgxacts = (PGXACT *) ShmemAlloc(TotalProcs * sizeof(PGXACT));
214 5 : MemSet(pgxacts, 0, TotalProcs * sizeof(PGXACT));
215 5 : ProcGlobal->allPgXact = pgxacts;
216 :
217 587 : for (i = 0; i < TotalProcs; i++)
218 : {
219 : /* Common initialization for all PGPROCs, regardless of type. */
220 :
221 : /*
222 : * Set up per-PGPROC semaphore, latch, and backendLock. Prepared xact
223 : * dummy PGPROCs don't need these though - they're never associated
224 : * with a real process
225 : */
226 582 : if (i < MaxBackends + NUM_AUXILIARY_PROCS)
227 : {
228 580 : procs[i].sem = PGSemaphoreCreate();
229 580 : InitSharedLatch(&(procs[i].procLatch));
230 580 : LWLockInitialize(&(procs[i].backendLock), LWTRANCHE_PROC);
231 : }
232 582 : procs[i].pgprocno = i;
233 :
234 : /*
235 : * Newly created PGPROCs for normal backends, autovacuum and bgworkers
236 : * must be queued up on the appropriate free list. Because there can
237 : * only ever be a small, fixed number of auxiliary processes, no free
238 : * list is used in that case; InitAuxiliaryProcess() instead uses a
239 : * linear search. PGPROCs for prepared transactions are added to a
240 : * free list by TwoPhaseShmemInit().
241 : */
242 582 : if (i < MaxConnections)
243 : {
244 : /* PGPROC for normal backend, add to freeProcs list */
245 500 : procs[i].links.next = (SHM_QUEUE *) ProcGlobal->freeProcs;
246 500 : ProcGlobal->freeProcs = &procs[i];
247 500 : procs[i].procgloballist = &ProcGlobal->freeProcs;
248 : }
249 82 : else if (i < MaxConnections + autovacuum_max_workers + 1)
250 : {
251 : /* PGPROC for AV launcher/worker, add to autovacFreeProcs list */
252 20 : procs[i].links.next = (SHM_QUEUE *) ProcGlobal->autovacFreeProcs;
253 20 : ProcGlobal->autovacFreeProcs = &procs[i];
254 20 : procs[i].procgloballist = &ProcGlobal->autovacFreeProcs;
255 : }
256 62 : else if (i < MaxBackends)
257 : {
258 : /* PGPROC for bgworker, add to bgworkerFreeProcs list */
259 40 : procs[i].links.next = (SHM_QUEUE *) ProcGlobal->bgworkerFreeProcs;
260 40 : ProcGlobal->bgworkerFreeProcs = &procs[i];
261 40 : procs[i].procgloballist = &ProcGlobal->bgworkerFreeProcs;
262 : }
263 :
264 : /* Initialize myProcLocks[] shared memory queues. */
265 9894 : for (j = 0; j < NUM_LOCK_PARTITIONS; j++)
266 9312 : SHMQueueInit(&(procs[i].myProcLocks[j]));
267 :
268 : /* Initialize lockGroupMembers list. */
269 582 : dlist_init(&procs[i].lockGroupMembers);
270 : }
271 :
272 : /*
273 : * Save pointers to the blocks of PGPROC structures reserved for auxiliary
274 : * processes and prepared transactions.
275 : */
276 5 : AuxiliaryProcs = &procs[MaxBackends];
277 5 : PreparedXactProcs = &procs[MaxBackends + NUM_AUXILIARY_PROCS];
278 :
279 : /* Create ProcStructLock spinlock, too */
280 5 : ProcStructLock = (slock_t *) ShmemAlloc(sizeof(slock_t));
281 5 : SpinLockInit(ProcStructLock);
282 5 : }
283 :
284 : /*
285 : * InitProcess -- initialize a per-process data structure for this backend
286 : */
287 : void
288 338 : InitProcess(void)
289 : {
290 : PGPROC *volatile *procgloballist;
291 :
292 : /*
293 : * ProcGlobal should be set up already (if we are a backend, we inherit
294 : * this by fork() or EXEC_BACKEND mechanism from the postmaster).
295 : */
296 338 : if (ProcGlobal == NULL)
297 0 : elog(PANIC, "proc header uninitialized");
298 :
299 338 : if (MyProc != NULL)
300 0 : elog(ERROR, "you already exist");
301 :
302 : /* Decide which list should supply our PGPROC. */
303 338 : if (IsAnyAutoVacuumProcess())
304 5 : procgloballist = &ProcGlobal->autovacFreeProcs;
305 333 : else if (IsBackgroundWorker)
306 116 : procgloballist = &ProcGlobal->bgworkerFreeProcs;
307 : else
308 217 : procgloballist = &ProcGlobal->freeProcs;
309 :
310 : /*
311 : * Try to get a proc struct from the appropriate free list. If this
312 : * fails, we must be out of PGPROC structures (not to mention semaphores).
313 : *
314 : * While we are holding the ProcStructLock, also copy the current shared
315 : * estimate of spins_per_delay to local storage.
316 : */
317 338 : SpinLockAcquire(ProcStructLock);
318 :
319 338 : set_spins_per_delay(ProcGlobal->spins_per_delay);
320 :
321 338 : MyProc = *procgloballist;
322 :
323 338 : if (MyProc != NULL)
324 : {
325 338 : *procgloballist = (PGPROC *) MyProc->links.next;
326 338 : SpinLockRelease(ProcStructLock);
327 : }
328 : else
329 : {
330 : /*
331 : * If we reach here, all the PGPROCs are in use. This is one of the
332 : * possible places to detect "too many backends", so give the standard
333 : * error message. XXX do we need to give a different failure message
334 : * in the autovacuum case?
335 : */
336 0 : SpinLockRelease(ProcStructLock);
337 0 : ereport(FATAL,
338 : (errcode(ERRCODE_TOO_MANY_CONNECTIONS),
339 : errmsg("sorry, too many clients already")));
340 : }
341 338 : MyPgXact = &ProcGlobal->allPgXact[MyProc->pgprocno];
342 :
343 : /*
344 : * Cross-check that the PGPROC is of the type we expect; if this were not
345 : * the case, it would get returned to the wrong list.
346 : */
347 338 : Assert(MyProc->procgloballist == procgloballist);
348 :
349 : /*
350 : * Now that we have a PGPROC, mark ourselves as an active postmaster
351 : * child; this is so that the postmaster can detect it if we exit without
352 : * cleaning up. (XXX autovac launcher currently doesn't participate in
353 : * this; it probably should.)
354 : */
355 338 : if (IsUnderPostmaster && !IsAutoVacuumLauncherProcess())
356 335 : MarkPostmasterChildActive();
357 :
358 : /*
359 : * Initialize all fields of MyProc, except for those previously
360 : * initialized by InitProcGlobal.
361 : */
362 338 : SHMQueueElemInit(&(MyProc->links));
363 338 : MyProc->waitStatus = STATUS_OK;
364 338 : MyProc->lxid = InvalidLocalTransactionId;
365 338 : MyProc->fpVXIDLock = false;
366 338 : MyProc->fpLocalTransactionId = InvalidLocalTransactionId;
367 338 : MyPgXact->xid = InvalidTransactionId;
368 338 : MyPgXact->xmin = InvalidTransactionId;
369 338 : MyProc->pid = MyProcPid;
370 : /* backendId, databaseId and roleId will be filled in later */
371 338 : MyProc->backendId = InvalidBackendId;
372 338 : MyProc->databaseId = InvalidOid;
373 338 : MyProc->roleId = InvalidOid;
374 338 : MyProc->isBackgroundWorker = IsBackgroundWorker;
375 338 : MyPgXact->delayChkpt = false;
376 338 : MyPgXact->vacuumFlags = 0;
377 : /* NB -- autovac launcher intentionally does not set IS_AUTOVACUUM */
378 338 : if (IsAutoVacuumWorkerProcess())
379 4 : MyPgXact->vacuumFlags |= PROC_IS_AUTOVACUUM;
380 338 : MyProc->lwWaiting = false;
381 338 : MyProc->lwWaitMode = 0;
382 338 : MyProc->waitLock = NULL;
383 338 : MyProc->waitProcLock = NULL;
384 : #ifdef USE_ASSERT_CHECKING
385 : {
386 : int i;
387 :
388 : /* Last process should have released all locks. */
389 5746 : for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
390 5408 : Assert(SHMQueueEmpty(&(MyProc->myProcLocks[i])));
391 : }
392 : #endif
393 338 : MyProc->recoveryConflictPending = false;
394 :
395 : /* Initialize fields for sync rep */
396 338 : MyProc->waitLSN = 0;
397 338 : MyProc->syncRepState = SYNC_REP_NOT_WAITING;
398 338 : SHMQueueElemInit(&(MyProc->syncRepLinks));
399 :
400 : /* Initialize fields for group XID clearing. */
401 338 : MyProc->procArrayGroupMember = false;
402 338 : MyProc->procArrayGroupMemberXid = InvalidTransactionId;
403 338 : pg_atomic_init_u32(&MyProc->procArrayGroupNext, INVALID_PGPROCNO);
404 :
405 : /* Check that group locking fields are in a proper initial state. */
406 338 : Assert(MyProc->lockGroupLeader == NULL);
407 338 : Assert(dlist_is_empty(&MyProc->lockGroupMembers));
408 :
409 : /* Initialize wait event information. */
410 338 : MyProc->wait_event_info = 0;
411 :
412 : /* Initialize fields for group transaction status update. */
413 338 : MyProc->clogGroupMember = false;
414 338 : MyProc->clogGroupMemberXid = InvalidTransactionId;
415 338 : MyProc->clogGroupMemberXidStatus = TRANSACTION_STATUS_IN_PROGRESS;
416 338 : MyProc->clogGroupMemberPage = -1;
417 338 : MyProc->clogGroupMemberLsn = InvalidXLogRecPtr;
418 338 : pg_atomic_init_u32(&MyProc->clogGroupNext, INVALID_PGPROCNO);
419 :
420 : /*
421 : * Acquire ownership of the PGPROC's latch, so that we can use WaitLatch
422 : * on it. That allows us to repoint the process latch, which so far
423 : * points to process local one, to the shared one.
424 : */
425 338 : OwnLatch(&MyProc->procLatch);
426 338 : SwitchToSharedLatch();
427 :
428 : /*
429 : * We might be reusing a semaphore that belonged to a failed process. So
430 : * be careful and reinitialize its value here. (This is not strictly
431 : * necessary anymore, but seems like a good idea for cleanliness.)
432 : */
433 338 : PGSemaphoreReset(MyProc->sem);
434 :
435 : /*
436 : * Arrange to clean up at backend exit.
437 : */
438 338 : on_shmem_exit(ProcKill, 0);
439 :
440 : /*
441 : * Now that we have a PGPROC, we could try to acquire locks, so initialize
442 : * local state needed for LWLocks, and the deadlock checker.
443 : */
444 338 : InitLWLockAccess();
445 338 : InitDeadLockChecking();
446 338 : }
447 :
448 : /*
449 : * InitProcessPhase2 -- make MyProc visible in the shared ProcArray.
450 : *
451 : * This is separate from InitProcess because we can't acquire LWLocks until
452 : * we've created a PGPROC, but in the EXEC_BACKEND case ProcArrayAdd won't
453 : * work until after we've done CreateSharedMemoryAndSemaphores.
454 : */
455 : void
456 338 : InitProcessPhase2(void)
457 : {
458 338 : Assert(MyProc != NULL);
459 :
460 : /*
461 : * Add our PGPROC to the PGPROC array in shared memory.
462 : */
463 338 : ProcArrayAdd(MyProc);
464 :
465 : /*
466 : * Arrange to clean that up at backend exit.
467 : */
468 338 : on_shmem_exit(RemoveProcFromArray, 0);
469 338 : }
470 :
471 : /*
472 : * InitAuxiliaryProcess -- create a per-auxiliary-process data structure
473 : *
474 : * This is called by bgwriter and similar processes so that they will have a
475 : * MyProc value that's real enough to let them wait for LWLocks. The PGPROC
476 : * and sema that are assigned are one of the extra ones created during
477 : * InitProcGlobal.
478 : *
479 : * Auxiliary processes are presently not expected to wait for real (lockmgr)
480 : * locks, so we need not set up the deadlock checker. They are never added
481 : * to the ProcArray or the sinval messaging mechanism, either. They also
482 : * don't get a VXID assigned, since this is only useful when we actually
483 : * hold lockmgr locks.
484 : *
485 : * Startup process however uses locks but never waits for them in the
486 : * normal backend sense. Startup process also takes part in sinval messaging
487 : * as a sendOnly process, so never reads messages from sinval queue. So
488 : * Startup process does have a VXID and does show up in pg_locks.
489 : */
490 : void
491 4 : InitAuxiliaryProcess(void)
492 : {
493 : PGPROC *auxproc;
494 : int proctype;
495 :
496 : /*
497 : * ProcGlobal should be set up already (if we are a backend, we inherit
498 : * this by fork() or EXEC_BACKEND mechanism from the postmaster).
499 : */
500 4 : if (ProcGlobal == NULL || AuxiliaryProcs == NULL)
501 0 : elog(PANIC, "proc header uninitialized");
502 :
503 4 : if (MyProc != NULL)
504 0 : elog(ERROR, "you already exist");
505 :
506 : /*
507 : * We use the ProcStructLock to protect assignment and releasing of
508 : * AuxiliaryProcs entries.
509 : *
510 : * While we are holding the ProcStructLock, also copy the current shared
511 : * estimate of spins_per_delay to local storage.
512 : */
513 4 : SpinLockAcquire(ProcStructLock);
514 :
515 4 : set_spins_per_delay(ProcGlobal->spins_per_delay);
516 :
517 : /*
518 : * Find a free auxproc ... *big* trouble if there isn't one ...
519 : */
520 7 : for (proctype = 0; proctype < NUM_AUXILIARY_PROCS; proctype++)
521 : {
522 7 : auxproc = &AuxiliaryProcs[proctype];
523 7 : if (auxproc->pid == 0)
524 4 : break;
525 : }
526 4 : if (proctype >= NUM_AUXILIARY_PROCS)
527 : {
528 0 : SpinLockRelease(ProcStructLock);
529 0 : elog(FATAL, "all AuxiliaryProcs are in use");
530 : }
531 :
532 : /* Mark auxiliary proc as in use by me */
533 : /* use volatile pointer to prevent code rearrangement */
534 4 : ((volatile PGPROC *) auxproc)->pid = MyProcPid;
535 :
536 4 : MyProc = auxproc;
537 4 : MyPgXact = &ProcGlobal->allPgXact[auxproc->pgprocno];
538 :
539 4 : SpinLockRelease(ProcStructLock);
540 :
541 : /*
542 : * Initialize all fields of MyProc, except for those previously
543 : * initialized by InitProcGlobal.
544 : */
545 4 : SHMQueueElemInit(&(MyProc->links));
546 4 : MyProc->waitStatus = STATUS_OK;
547 4 : MyProc->lxid = InvalidLocalTransactionId;
548 4 : MyProc->fpVXIDLock = false;
549 4 : MyProc->fpLocalTransactionId = InvalidLocalTransactionId;
550 4 : MyPgXact->xid = InvalidTransactionId;
551 4 : MyPgXact->xmin = InvalidTransactionId;
552 4 : MyProc->backendId = InvalidBackendId;
553 4 : MyProc->databaseId = InvalidOid;
554 4 : MyProc->roleId = InvalidOid;
555 4 : MyProc->isBackgroundWorker = IsBackgroundWorker;
556 4 : MyPgXact->delayChkpt = false;
557 4 : MyPgXact->vacuumFlags = 0;
558 4 : MyProc->lwWaiting = false;
559 4 : MyProc->lwWaitMode = 0;
560 4 : MyProc->waitLock = NULL;
561 4 : MyProc->waitProcLock = NULL;
562 : #ifdef USE_ASSERT_CHECKING
563 : {
564 : int i;
565 :
566 : /* Last process should have released all locks. */
567 68 : for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
568 64 : Assert(SHMQueueEmpty(&(MyProc->myProcLocks[i])));
569 : }
570 : #endif
571 :
572 : /*
573 : * Acquire ownership of the PGPROC's latch, so that we can use WaitLatch
574 : * on it. That allows us to repoint the process latch, which so far
575 : * points to process local one, to the shared one.
576 : */
577 4 : OwnLatch(&MyProc->procLatch);
578 4 : SwitchToSharedLatch();
579 :
580 : /* Check that group locking fields are in a proper initial state. */
581 4 : Assert(MyProc->lockGroupLeader == NULL);
582 4 : Assert(dlist_is_empty(&MyProc->lockGroupMembers));
583 :
584 : /*
585 : * We might be reusing a semaphore that belonged to a failed process. So
586 : * be careful and reinitialize its value here. (This is not strictly
587 : * necessary anymore, but seems like a good idea for cleanliness.)
588 : */
589 4 : PGSemaphoreReset(MyProc->sem);
590 :
591 : /*
592 : * Arrange to clean up at process exit.
593 : */
594 4 : on_shmem_exit(AuxiliaryProcKill, Int32GetDatum(proctype));
595 4 : }
596 :
597 : /*
598 : * Record the PID and PGPROC structures for the Startup process, for use in
599 : * ProcSendSignal(). See comments there for further explanation.
600 : */
601 : void
602 0 : PublishStartupProcessInformation(void)
603 : {
604 0 : SpinLockAcquire(ProcStructLock);
605 :
606 0 : ProcGlobal->startupProc = MyProc;
607 0 : ProcGlobal->startupProcPid = MyProcPid;
608 :
609 0 : SpinLockRelease(ProcStructLock);
610 0 : }
611 :
612 : /*
613 : * Used from bufgr to share the value of the buffer that Startup waits on,
614 : * or to reset the value to "not waiting" (-1). This allows processing
615 : * of recovery conflicts for buffer pins. Set is made before backends look
616 : * at this value, so locking not required, especially since the set is
617 : * an atomic integer set operation.
618 : */
619 : void
620 0 : SetStartupBufferPinWaitBufId(int bufid)
621 : {
622 : /* use volatile pointer to prevent code rearrangement */
623 0 : volatile PROC_HDR *procglobal = ProcGlobal;
624 :
625 0 : procglobal->startupBufferPinWaitBufId = bufid;
626 0 : }
627 :
628 : /*
629 : * Used by backends when they receive a request to check for buffer pin waits.
630 : */
631 : int
632 0 : GetStartupBufferPinWaitBufId(void)
633 : {
634 : /* use volatile pointer to prevent code rearrangement */
635 0 : volatile PROC_HDR *procglobal = ProcGlobal;
636 :
637 0 : return procglobal->startupBufferPinWaitBufId;
638 : }
639 :
640 : /*
641 : * Check whether there are at least N free PGPROC objects.
642 : *
643 : * Note: this is designed on the assumption that N will generally be small.
644 : */
645 : bool
646 0 : HaveNFreeProcs(int n)
647 : {
648 : PGPROC *proc;
649 :
650 0 : SpinLockAcquire(ProcStructLock);
651 :
652 0 : proc = ProcGlobal->freeProcs;
653 :
654 0 : while (n > 0 && proc != NULL)
655 : {
656 0 : proc = (PGPROC *) proc->links.next;
657 0 : n--;
658 : }
659 :
660 0 : SpinLockRelease(ProcStructLock);
661 :
662 0 : return (n <= 0);
663 : }
664 :
665 : /*
666 : * Check if the current process is awaiting a lock.
667 : */
668 : bool
669 0 : IsWaitingForLock(void)
670 : {
671 0 : if (lockAwaited == NULL)
672 0 : return false;
673 :
674 0 : return true;
675 : }
676 :
677 : /*
678 : * Cancel any pending wait for lock, when aborting a transaction, and revert
679 : * any strong lock count acquisition for a lock being acquired.
680 : *
681 : * (Normally, this would only happen if we accept a cancel/die
682 : * interrupt while waiting; but an ereport(ERROR) before or during the lock
683 : * wait is within the realm of possibility, too.)
684 : */
685 : void
686 29771 : LockErrorCleanup(void)
687 : {
688 : LWLock *partitionLock;
689 : DisableTimeoutParams timeouts[2];
690 :
691 29771 : HOLD_INTERRUPTS();
692 :
693 29771 : AbortStrongLockAcquire();
694 :
695 : /* Nothing to do if we weren't waiting for a lock */
696 29771 : if (lockAwaited == NULL)
697 : {
698 29771 : RESUME_INTERRUPTS();
699 59542 : return;
700 : }
701 :
702 : /*
703 : * Turn off the deadlock and lock timeout timers, if they are still
704 : * running (see ProcSleep). Note we must preserve the LOCK_TIMEOUT
705 : * indicator flag, since this function is executed before
706 : * ProcessInterrupts when responding to SIGINT; else we'd lose the
707 : * knowledge that the SIGINT came from a lock timeout and not an external
708 : * source.
709 : */
710 0 : timeouts[0].id = DEADLOCK_TIMEOUT;
711 0 : timeouts[0].keep_indicator = false;
712 0 : timeouts[1].id = LOCK_TIMEOUT;
713 0 : timeouts[1].keep_indicator = true;
714 0 : disable_timeouts(timeouts, 2);
715 :
716 : /* Unlink myself from the wait queue, if on it (might not be anymore!) */
717 0 : partitionLock = LockHashPartitionLock(lockAwaited->hashcode);
718 0 : LWLockAcquire(partitionLock, LW_EXCLUSIVE);
719 :
720 0 : if (MyProc->links.next != NULL)
721 : {
722 : /* We could not have been granted the lock yet */
723 0 : RemoveFromWaitQueue(MyProc, lockAwaited->hashcode);
724 : }
725 : else
726 : {
727 : /*
728 : * Somebody kicked us off the lock queue already. Perhaps they
729 : * granted us the lock, or perhaps they detected a deadlock. If they
730 : * did grant us the lock, we'd better remember it in our local lock
731 : * table.
732 : */
733 0 : if (MyProc->waitStatus == STATUS_OK)
734 0 : GrantAwaitedLock();
735 : }
736 :
737 0 : lockAwaited = NULL;
738 :
739 0 : LWLockRelease(partitionLock);
740 :
741 0 : RESUME_INTERRUPTS();
742 : }
743 :
744 :
745 : /*
746 : * ProcReleaseLocks() -- release locks associated with current transaction
747 : * at main transaction commit or abort
748 : *
749 : * At main transaction commit, we release standard locks except session locks.
750 : * At main transaction abort, we release all locks including session locks.
751 : *
752 : * Advisory locks are released only if they are transaction-level;
753 : * session-level holds remain, whether this is a commit or not.
754 : *
755 : * At subtransaction commit, we don't release any locks (so this func is not
756 : * needed at all); we will defer the releasing to the parent transaction.
757 : * At subtransaction abort, we release all locks held by the subtransaction;
758 : * this is implemented by retail releasing of the locks under control of
759 : * the ResourceOwner mechanism.
760 : */
761 : void
762 26167 : ProcReleaseLocks(bool isCommit)
763 : {
764 26167 : if (!MyProc)
765 26167 : return;
766 : /* If waiting, get off wait queue (should only be needed after error) */
767 26167 : LockErrorCleanup();
768 : /* Release standard locks, including session-level if aborting */
769 26167 : LockReleaseAll(DEFAULT_LOCKMETHOD, !isCommit);
770 : /* Release transaction-level advisory locks */
771 26167 : LockReleaseAll(USER_LOCKMETHOD, false);
772 : }
773 :
774 :
775 : /*
776 : * RemoveProcFromArray() -- Remove this process from the shared ProcArray.
777 : */
778 : static void
779 338 : RemoveProcFromArray(int code, Datum arg)
780 : {
781 338 : Assert(MyProc != NULL);
782 338 : ProcArrayRemove(MyProc, InvalidTransactionId);
783 338 : }
784 :
785 : /*
786 : * ProcKill() -- Destroy the per-proc data structure for
787 : * this process. Release any of its held LW locks.
788 : */
789 : static void
790 338 : ProcKill(int code, Datum arg)
791 : {
792 : PGPROC *proc;
793 : PGPROC *volatile *procgloballist;
794 :
795 338 : Assert(MyProc != NULL);
796 :
797 : /* Make sure we're out of the sync rep lists */
798 338 : SyncRepCleanupAtProcExit();
799 :
800 : #ifdef USE_ASSERT_CHECKING
801 : {
802 : int i;
803 :
804 : /* Last process should have released all locks. */
805 5746 : for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
806 5408 : Assert(SHMQueueEmpty(&(MyProc->myProcLocks[i])));
807 : }
808 : #endif
809 :
810 : /*
811 : * Release any LW locks I am holding. There really shouldn't be any, but
812 : * it's cheap to check again before we cut the knees off the LWLock
813 : * facility by releasing our PGPROC ...
814 : */
815 338 : LWLockReleaseAll();
816 :
817 : /* Cancel any pending condition variable sleep, too */
818 338 : ConditionVariableCancelSleep();
819 :
820 : /* Make sure active replication slots are released */
821 338 : if (MyReplicationSlot != NULL)
822 0 : ReplicationSlotRelease();
823 :
824 : /* Also cleanup all the temporary slots. */
825 338 : ReplicationSlotCleanup();
826 :
827 : /*
828 : * Detach from any lock group of which we are a member. If the leader
829 : * exist before all other group members, it's PGPROC will remain allocated
830 : * until the last group process exits; that process must return the
831 : * leader's PGPROC to the appropriate list.
832 : */
833 338 : if (MyProc->lockGroupLeader != NULL)
834 : {
835 116 : PGPROC *leader = MyProc->lockGroupLeader;
836 116 : LWLock *leader_lwlock = LockHashPartitionLockByProc(leader);
837 :
838 116 : LWLockAcquire(leader_lwlock, LW_EXCLUSIVE);
839 116 : Assert(!dlist_is_empty(&leader->lockGroupMembers));
840 116 : dlist_delete(&MyProc->lockGroupLink);
841 116 : if (dlist_is_empty(&leader->lockGroupMembers))
842 : {
843 1 : leader->lockGroupLeader = NULL;
844 1 : if (leader != MyProc)
845 : {
846 0 : procgloballist = leader->procgloballist;
847 :
848 : /* Leader exited first; return its PGPROC. */
849 0 : SpinLockAcquire(ProcStructLock);
850 0 : leader->links.next = (SHM_QUEUE *) *procgloballist;
851 0 : *procgloballist = leader;
852 0 : SpinLockRelease(ProcStructLock);
853 : }
854 : }
855 115 : else if (leader != MyProc)
856 115 : MyProc->lockGroupLeader = NULL;
857 116 : LWLockRelease(leader_lwlock);
858 : }
859 :
860 : /*
861 : * Reset MyLatch to the process local one. This is so that signal
862 : * handlers et al can continue using the latch after the shared latch
863 : * isn't ours anymore. After that clear MyProc and disown the shared
864 : * latch.
865 : */
866 338 : SwitchBackToLocalLatch();
867 338 : proc = MyProc;
868 338 : MyProc = NULL;
869 338 : DisownLatch(&proc->procLatch);
870 :
871 338 : procgloballist = proc->procgloballist;
872 338 : SpinLockAcquire(ProcStructLock);
873 :
874 : /*
875 : * If we're still a member of a locking group, that means we're a leader
876 : * which has somehow exited before its children. The last remaining child
877 : * will release our PGPROC. Otherwise, release it now.
878 : */
879 338 : if (proc->lockGroupLeader == NULL)
880 : {
881 : /* Since lockGroupLeader is NULL, lockGroupMembers should be empty. */
882 338 : Assert(dlist_is_empty(&proc->lockGroupMembers));
883 :
884 : /* Return PGPROC structure (and semaphore) to appropriate freelist */
885 338 : proc->links.next = (SHM_QUEUE *) *procgloballist;
886 338 : *procgloballist = proc;
887 : }
888 :
889 : /* Update shared estimate of spins_per_delay */
890 338 : ProcGlobal->spins_per_delay = update_spins_per_delay(ProcGlobal->spins_per_delay);
891 :
892 338 : SpinLockRelease(ProcStructLock);
893 :
894 : /*
895 : * This process is no longer present in shared memory in any meaningful
896 : * way, so tell the postmaster we've cleaned up acceptably well. (XXX
897 : * autovac launcher should be included here someday)
898 : */
899 338 : if (IsUnderPostmaster && !IsAutoVacuumLauncherProcess())
900 335 : MarkPostmasterChildInactive();
901 :
902 : /* wake autovac launcher if needed -- see comments in FreeWorkerInfo */
903 338 : if (AutovacuumLauncherPid != 0)
904 3 : kill(AutovacuumLauncherPid, SIGUSR2);
905 338 : }
906 :
907 : /*
908 : * AuxiliaryProcKill() -- Cut-down version of ProcKill for auxiliary
909 : * processes (bgwriter, etc). The PGPROC and sema are not released, only
910 : * marked as not-in-use.
911 : */
912 : static void
913 4 : AuxiliaryProcKill(int code, Datum arg)
914 : {
915 4 : int proctype = DatumGetInt32(arg);
916 : PGPROC *auxproc PG_USED_FOR_ASSERTS_ONLY;
917 : PGPROC *proc;
918 :
919 4 : Assert(proctype >= 0 && proctype < NUM_AUXILIARY_PROCS);
920 :
921 4 : auxproc = &AuxiliaryProcs[proctype];
922 :
923 4 : Assert(MyProc == auxproc);
924 :
925 : /* Release any LW locks I am holding (see notes above) */
926 4 : LWLockReleaseAll();
927 :
928 : /* Cancel any pending condition variable sleep, too */
929 4 : ConditionVariableCancelSleep();
930 :
931 : /*
932 : * Reset MyLatch to the process local one. This is so that signal
933 : * handlers et al can continue using the latch after the shared latch
934 : * isn't ours anymore. After that clear MyProc and disown the shared
935 : * latch.
936 : */
937 4 : SwitchBackToLocalLatch();
938 4 : proc = MyProc;
939 4 : MyProc = NULL;
940 4 : DisownLatch(&proc->procLatch);
941 :
942 4 : SpinLockAcquire(ProcStructLock);
943 :
944 : /* Mark auxiliary proc no longer in use */
945 4 : proc->pid = 0;
946 :
947 : /* Update shared estimate of spins_per_delay */
948 4 : ProcGlobal->spins_per_delay = update_spins_per_delay(ProcGlobal->spins_per_delay);
949 :
950 4 : SpinLockRelease(ProcStructLock);
951 4 : }
952 :
953 : /*
954 : * AuxiliaryPidGetProc -- get PGPROC for an auxiliary process
955 : * given its PID
956 : *
957 : * Returns NULL if not found.
958 : */
959 : PGPROC *
960 0 : AuxiliaryPidGetProc(int pid)
961 : {
962 0 : PGPROC *result = NULL;
963 : int index;
964 :
965 0 : if (pid == 0) /* never match dummy PGPROCs */
966 0 : return NULL;
967 :
968 0 : for (index = 0; index < NUM_AUXILIARY_PROCS; index++)
969 : {
970 0 : PGPROC *proc = &AuxiliaryProcs[index];
971 :
972 0 : if (proc->pid == pid)
973 : {
974 0 : result = proc;
975 0 : break;
976 : }
977 : }
978 0 : return result;
979 : }
980 :
981 : /*
982 : * ProcQueue package: routines for putting processes to sleep
983 : * and waking them up
984 : */
985 :
986 : /*
987 : * ProcQueueAlloc -- alloc/attach to a shared memory process queue
988 : *
989 : * Returns: a pointer to the queue
990 : * Side Effects: Initializes the queue if it wasn't there before
991 : */
992 : #ifdef NOT_USED
993 : PROC_QUEUE *
994 : ProcQueueAlloc(const char *name)
995 : {
996 : PROC_QUEUE *queue;
997 : bool found;
998 :
999 : queue = (PROC_QUEUE *)
1000 : ShmemInitStruct(name, sizeof(PROC_QUEUE), &found);
1001 :
1002 : if (!found)
1003 : ProcQueueInit(queue);
1004 :
1005 : return queue;
1006 : }
1007 : #endif
1008 :
1009 : /*
1010 : * ProcQueueInit -- initialize a shared memory process queue
1011 : */
1012 : void
1013 86353 : ProcQueueInit(PROC_QUEUE *queue)
1014 : {
1015 86353 : SHMQueueInit(&(queue->links));
1016 86353 : queue->size = 0;
1017 86353 : }
1018 :
1019 :
1020 : /*
1021 : * ProcSleep -- put a process to sleep on the specified lock
1022 : *
1023 : * Caller must have set MyProc->heldLocks to reflect locks already held
1024 : * on the lockable object by this process (under all XIDs).
1025 : *
1026 : * The lock table's partition lock must be held at entry, and will be held
1027 : * at exit.
1028 : *
1029 : * Result: STATUS_OK if we acquired the lock, STATUS_ERROR if not (deadlock).
1030 : *
1031 : * ASSUME: that no one will fiddle with the queue until after
1032 : * we release the partition lock.
1033 : *
1034 : * NOTES: The process queue is now a priority queue for locking.
1035 : */
1036 : int
1037 19 : ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable)
1038 : {
1039 19 : LOCKMODE lockmode = locallock->tag.mode;
1040 19 : LOCK *lock = locallock->lock;
1041 19 : PROCLOCK *proclock = locallock->proclock;
1042 19 : uint32 hashcode = locallock->hashcode;
1043 19 : LWLock *partitionLock = LockHashPartitionLock(hashcode);
1044 19 : PROC_QUEUE *waitQueue = &(lock->waitProcs);
1045 19 : LOCKMASK myHeldLocks = MyProc->heldLocks;
1046 19 : bool early_deadlock = false;
1047 19 : bool allow_autovacuum_cancel = true;
1048 : int myWaitStatus;
1049 : PGPROC *proc;
1050 19 : PGPROC *leader = MyProc->lockGroupLeader;
1051 : int i;
1052 :
1053 : /*
1054 : * If group locking is in use, locks held by members of my locking group
1055 : * need to be included in myHeldLocks.
1056 : */
1057 19 : if (leader != NULL)
1058 : {
1059 0 : SHM_QUEUE *procLocks = &(lock->procLocks);
1060 : PROCLOCK *otherproclock;
1061 :
1062 0 : otherproclock = (PROCLOCK *)
1063 : SHMQueueNext(procLocks, procLocks, offsetof(PROCLOCK, lockLink));
1064 0 : while (otherproclock != NULL)
1065 : {
1066 0 : if (otherproclock->groupLeader == leader)
1067 0 : myHeldLocks |= otherproclock->holdMask;
1068 0 : otherproclock = (PROCLOCK *)
1069 0 : SHMQueueNext(procLocks, &otherproclock->lockLink,
1070 : offsetof(PROCLOCK, lockLink));
1071 : }
1072 : }
1073 :
1074 : /*
1075 : * Determine where to add myself in the wait queue.
1076 : *
1077 : * Normally I should go at the end of the queue. However, if I already
1078 : * hold locks that conflict with the request of any previous waiter, put
1079 : * myself in the queue just in front of the first such waiter. This is not
1080 : * a necessary step, since deadlock detection would move me to before that
1081 : * waiter anyway; but it's relatively cheap to detect such a conflict
1082 : * immediately, and avoid delaying till deadlock timeout.
1083 : *
1084 : * Special case: if I find I should go in front of some waiter, check to
1085 : * see if I conflict with already-held locks or the requests before that
1086 : * waiter. If not, then just grant myself the requested lock immediately.
1087 : * This is the same as the test for immediate grant in LockAcquire, except
1088 : * we are only considering the part of the wait queue before my insertion
1089 : * point.
1090 : */
1091 19 : if (myHeldLocks != 0)
1092 : {
1093 1 : LOCKMASK aheadRequests = 0;
1094 :
1095 1 : proc = (PGPROC *) waitQueue->links.next;
1096 1 : for (i = 0; i < waitQueue->size; i++)
1097 : {
1098 : /*
1099 : * If we're part of the same locking group as this waiter, its
1100 : * locks neither conflict with ours nor contribute to
1101 : * aheadRequests.
1102 : */
1103 1 : if (leader != NULL && leader == proc->lockGroupLeader)
1104 : {
1105 0 : proc = (PGPROC *) proc->links.next;
1106 0 : continue;
1107 : }
1108 : /* Must he wait for me? */
1109 1 : if (lockMethodTable->conflictTab[proc->waitLockMode] & myHeldLocks)
1110 : {
1111 : /* Must I wait for him ? */
1112 1 : if (lockMethodTable->conflictTab[lockmode] & proc->heldLocks)
1113 : {
1114 : /*
1115 : * Yes, so we have a deadlock. Easiest way to clean up
1116 : * correctly is to call RemoveFromWaitQueue(), but we
1117 : * can't do that until we are *on* the wait queue. So, set
1118 : * a flag to check below, and break out of loop. Also,
1119 : * record deadlock info for later message.
1120 : */
1121 0 : RememberSimpleDeadLock(MyProc, lockmode, lock, proc);
1122 0 : early_deadlock = true;
1123 0 : break;
1124 : }
1125 : /* I must go before this waiter. Check special case. */
1126 2 : if ((lockMethodTable->conflictTab[lockmode] & aheadRequests) == 0 &&
1127 1 : LockCheckConflicts(lockMethodTable,
1128 : lockmode,
1129 : lock,
1130 : proclock) == STATUS_OK)
1131 : {
1132 : /* Skip the wait and just grant myself the lock. */
1133 1 : GrantLock(lock, proclock, lockmode);
1134 1 : GrantAwaitedLock();
1135 1 : return STATUS_OK;
1136 : }
1137 : /* Break out of loop to put myself before him */
1138 0 : break;
1139 : }
1140 : /* Nope, so advance to next waiter */
1141 0 : aheadRequests |= LOCKBIT_ON(proc->waitLockMode);
1142 0 : proc = (PGPROC *) proc->links.next;
1143 : }
1144 :
1145 : /*
1146 : * If we fall out of loop normally, proc points to waitQueue head, so
1147 : * we will insert at tail of queue as desired.
1148 : */
1149 : }
1150 : else
1151 : {
1152 : /* I hold no locks, so I can't push in front of anyone. */
1153 18 : proc = (PGPROC *) &(waitQueue->links);
1154 : }
1155 :
1156 : /*
1157 : * Insert self into queue, ahead of the given proc (or at tail of queue).
1158 : */
1159 18 : SHMQueueInsertBefore(&(proc->links), &(MyProc->links));
1160 18 : waitQueue->size++;
1161 :
1162 18 : lock->waitMask |= LOCKBIT_ON(lockmode);
1163 :
1164 : /* Set up wait information in PGPROC object, too */
1165 18 : MyProc->waitLock = lock;
1166 18 : MyProc->waitProcLock = proclock;
1167 18 : MyProc->waitLockMode = lockmode;
1168 :
1169 18 : MyProc->waitStatus = STATUS_WAITING;
1170 :
1171 : /*
1172 : * If we detected deadlock, give up without waiting. This must agree with
1173 : * CheckDeadLock's recovery code, except that we shouldn't release the
1174 : * semaphore since we haven't tried to lock it yet.
1175 : */
1176 18 : if (early_deadlock)
1177 : {
1178 0 : RemoveFromWaitQueue(MyProc, hashcode);
1179 0 : return STATUS_ERROR;
1180 : }
1181 :
1182 : /* mark that we are waiting for a lock */
1183 18 : lockAwaited = locallock;
1184 :
1185 : /*
1186 : * Release the lock table's partition lock.
1187 : *
1188 : * NOTE: this may also cause us to exit critical-section state, possibly
1189 : * allowing a cancel/die interrupt to be accepted. This is OK because we
1190 : * have recorded the fact that we are waiting for a lock, and so
1191 : * LockErrorCleanup will clean up if cancel/die happens.
1192 : */
1193 18 : LWLockRelease(partitionLock);
1194 :
1195 : /*
1196 : * Also, now that we will successfully clean up after an ereport, it's
1197 : * safe to check to see if there's a buffer pin deadlock against the
1198 : * Startup process. Of course, that's only necessary if we're doing Hot
1199 : * Standby and are not the Startup process ourselves.
1200 : */
1201 18 : if (RecoveryInProgress() && !InRecovery)
1202 0 : CheckRecoveryConflictDeadlock();
1203 :
1204 : /* Reset deadlock_state before enabling the timeout handler */
1205 18 : deadlock_state = DS_NOT_YET_CHECKED;
1206 18 : got_deadlock_timeout = false;
1207 :
1208 : /*
1209 : * Set timer so we can wake up after awhile and check for a deadlock. If a
1210 : * deadlock is detected, the handler releases the process's semaphore and
1211 : * sets MyProc->waitStatus = STATUS_ERROR, allowing us to know that we
1212 : * must report failure rather than success.
1213 : *
1214 : * By delaying the check until we've waited for a bit, we can avoid
1215 : * running the rather expensive deadlock-check code in most cases.
1216 : *
1217 : * If LockTimeout is set, also enable the timeout for that. We can save a
1218 : * few cycles by enabling both timeout sources in one call.
1219 : *
1220 : * If InHotStandby we set lock waits slightly later for clarity with other
1221 : * code.
1222 : */
1223 18 : if (!InHotStandby)
1224 : {
1225 18 : if (LockTimeout > 0)
1226 : {
1227 : EnableTimeoutParams timeouts[2];
1228 :
1229 0 : timeouts[0].id = DEADLOCK_TIMEOUT;
1230 0 : timeouts[0].type = TMPARAM_AFTER;
1231 0 : timeouts[0].delay_ms = DeadlockTimeout;
1232 0 : timeouts[1].id = LOCK_TIMEOUT;
1233 0 : timeouts[1].type = TMPARAM_AFTER;
1234 0 : timeouts[1].delay_ms = LockTimeout;
1235 0 : enable_timeouts(timeouts, 2);
1236 : }
1237 : else
1238 18 : enable_timeout_after(DEADLOCK_TIMEOUT, DeadlockTimeout);
1239 : }
1240 :
1241 : /*
1242 : * If somebody wakes us between LWLockRelease and WaitLatch, the latch
1243 : * will not wait. But a set latch does not necessarily mean that the lock
1244 : * is free now, as there are many other sources for latch sets than
1245 : * somebody releasing the lock.
1246 : *
1247 : * We process interrupts whenever the latch has been set, so cancel/die
1248 : * interrupts are processed quickly. This means we must not mind losing
1249 : * control to a cancel/die interrupt here. We don't, because we have no
1250 : * shared-state-change work to do after being granted the lock (the
1251 : * grantor did it all). We do have to worry about canceling the deadlock
1252 : * timeout and updating the locallock table, but if we lose control to an
1253 : * error, LockErrorCleanup will fix that up.
1254 : */
1255 : do
1256 : {
1257 19 : if (InHotStandby)
1258 : {
1259 : /* Set a timer and wait for that or for the Lock to be granted */
1260 0 : ResolveRecoveryConflictWithLock(locallock->tag.lock);
1261 : }
1262 : else
1263 : {
1264 19 : WaitLatch(MyLatch, WL_LATCH_SET, 0,
1265 19 : PG_WAIT_LOCK | locallock->tag.lock.locktag_type);
1266 19 : ResetLatch(MyLatch);
1267 : /* check for deadlocks first, as that's probably log-worthy */
1268 19 : if (got_deadlock_timeout)
1269 : {
1270 0 : CheckDeadLock();
1271 0 : got_deadlock_timeout = false;
1272 : }
1273 19 : CHECK_FOR_INTERRUPTS();
1274 : }
1275 :
1276 : /*
1277 : * waitStatus could change from STATUS_WAITING to something else
1278 : * asynchronously. Read it just once per loop to prevent surprising
1279 : * behavior (such as missing log messages).
1280 : */
1281 19 : myWaitStatus = *((volatile int *) &MyProc->waitStatus);
1282 :
1283 : /*
1284 : * If we are not deadlocked, but are waiting on an autovacuum-induced
1285 : * task, send a signal to interrupt it.
1286 : */
1287 19 : if (deadlock_state == DS_BLOCKED_BY_AUTOVACUUM && allow_autovacuum_cancel)
1288 : {
1289 0 : PGPROC *autovac = GetBlockingAutoVacuumPgproc();
1290 0 : PGXACT *autovac_pgxact = &ProcGlobal->allPgXact[autovac->pgprocno];
1291 :
1292 0 : LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
1293 :
1294 : /*
1295 : * Only do it if the worker is not working to protect against Xid
1296 : * wraparound.
1297 : */
1298 0 : if ((autovac_pgxact->vacuumFlags & PROC_IS_AUTOVACUUM) &&
1299 0 : !(autovac_pgxact->vacuumFlags & PROC_VACUUM_FOR_WRAPAROUND))
1300 0 : {
1301 0 : int pid = autovac->pid;
1302 : StringInfoData locktagbuf;
1303 : StringInfoData logbuf; /* errdetail for server log */
1304 :
1305 0 : initStringInfo(&locktagbuf);
1306 0 : initStringInfo(&logbuf);
1307 0 : DescribeLockTag(&locktagbuf, &lock->tag);
1308 0 : appendStringInfo(&logbuf,
1309 : _("Process %d waits for %s on %s."),
1310 : MyProcPid,
1311 0 : GetLockmodeName(lock->tag.locktag_lockmethodid,
1312 : lockmode),
1313 : locktagbuf.data);
1314 :
1315 : /* release lock as quickly as possible */
1316 0 : LWLockRelease(ProcArrayLock);
1317 :
1318 : /* send the autovacuum worker Back to Old Kent Road */
1319 0 : ereport(DEBUG1,
1320 : (errmsg("sending cancel to blocking autovacuum PID %d",
1321 : pid),
1322 : errdetail_log("%s", logbuf.data)));
1323 :
1324 0 : if (kill(pid, SIGINT) < 0)
1325 : {
1326 : /*
1327 : * There's a race condition here: once we release the
1328 : * ProcArrayLock, it's possible for the autovac worker to
1329 : * close up shop and exit before we can do the kill().
1330 : * Therefore, we do not whinge about no-such-process.
1331 : * Other errors such as EPERM could conceivably happen if
1332 : * the kernel recycles the PID fast enough, but such cases
1333 : * seem improbable enough that it's probably best to issue
1334 : * a warning if we see some other errno.
1335 : */
1336 0 : if (errno != ESRCH)
1337 0 : ereport(WARNING,
1338 : (errmsg("could not send signal to process %d: %m",
1339 : pid)));
1340 : }
1341 :
1342 0 : pfree(logbuf.data);
1343 0 : pfree(locktagbuf.data);
1344 : }
1345 : else
1346 0 : LWLockRelease(ProcArrayLock);
1347 :
1348 : /* prevent signal from being resent more than once */
1349 0 : allow_autovacuum_cancel = false;
1350 : }
1351 :
1352 : /*
1353 : * If awoken after the deadlock check interrupt has run, and
1354 : * log_lock_waits is on, then report about the wait.
1355 : */
1356 19 : if (log_lock_waits && deadlock_state != DS_NOT_YET_CHECKED)
1357 : {
1358 : StringInfoData buf,
1359 : lock_waiters_sbuf,
1360 : lock_holders_sbuf;
1361 : const char *modename;
1362 : long secs;
1363 : int usecs;
1364 : long msecs;
1365 : SHM_QUEUE *procLocks;
1366 : PROCLOCK *proclock;
1367 0 : bool first_holder = true,
1368 0 : first_waiter = true;
1369 0 : int lockHoldersNum = 0;
1370 :
1371 0 : initStringInfo(&buf);
1372 0 : initStringInfo(&lock_waiters_sbuf);
1373 0 : initStringInfo(&lock_holders_sbuf);
1374 :
1375 0 : DescribeLockTag(&buf, &locallock->tag.lock);
1376 0 : modename = GetLockmodeName(locallock->tag.lock.locktag_lockmethodid,
1377 : lockmode);
1378 0 : TimestampDifference(get_timeout_start_time(DEADLOCK_TIMEOUT),
1379 : GetCurrentTimestamp(),
1380 : &secs, &usecs);
1381 0 : msecs = secs * 1000 + usecs / 1000;
1382 0 : usecs = usecs % 1000;
1383 :
1384 : /*
1385 : * we loop over the lock's procLocks to gather a list of all
1386 : * holders and waiters. Thus we will be able to provide more
1387 : * detailed information for lock debugging purposes.
1388 : *
1389 : * lock->procLocks contains all processes which hold or wait for
1390 : * this lock.
1391 : */
1392 :
1393 0 : LWLockAcquire(partitionLock, LW_SHARED);
1394 :
1395 0 : procLocks = &(lock->procLocks);
1396 0 : proclock = (PROCLOCK *) SHMQueueNext(procLocks, procLocks,
1397 : offsetof(PROCLOCK, lockLink));
1398 :
1399 0 : while (proclock)
1400 : {
1401 : /*
1402 : * we are a waiter if myProc->waitProcLock == proclock; we are
1403 : * a holder if it is NULL or something different
1404 : */
1405 0 : if (proclock->tag.myProc->waitProcLock == proclock)
1406 : {
1407 0 : if (first_waiter)
1408 : {
1409 0 : appendStringInfo(&lock_waiters_sbuf, "%d",
1410 0 : proclock->tag.myProc->pid);
1411 0 : first_waiter = false;
1412 : }
1413 : else
1414 0 : appendStringInfo(&lock_waiters_sbuf, ", %d",
1415 0 : proclock->tag.myProc->pid);
1416 : }
1417 : else
1418 : {
1419 0 : if (first_holder)
1420 : {
1421 0 : appendStringInfo(&lock_holders_sbuf, "%d",
1422 0 : proclock->tag.myProc->pid);
1423 0 : first_holder = false;
1424 : }
1425 : else
1426 0 : appendStringInfo(&lock_holders_sbuf, ", %d",
1427 0 : proclock->tag.myProc->pid);
1428 :
1429 0 : lockHoldersNum++;
1430 : }
1431 :
1432 0 : proclock = (PROCLOCK *) SHMQueueNext(procLocks, &proclock->lockLink,
1433 : offsetof(PROCLOCK, lockLink));
1434 : }
1435 :
1436 0 : LWLockRelease(partitionLock);
1437 :
1438 0 : if (deadlock_state == DS_SOFT_DEADLOCK)
1439 0 : ereport(LOG,
1440 : (errmsg("process %d avoided deadlock for %s on %s by rearranging queue order after %ld.%03d ms",
1441 : MyProcPid, modename, buf.data, msecs, usecs),
1442 : (errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
1443 : "Processes holding the lock: %s. Wait queue: %s.",
1444 : lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
1445 0 : else if (deadlock_state == DS_HARD_DEADLOCK)
1446 : {
1447 : /*
1448 : * This message is a bit redundant with the error that will be
1449 : * reported subsequently, but in some cases the error report
1450 : * might not make it to the log (eg, if it's caught by an
1451 : * exception handler), and we want to ensure all long-wait
1452 : * events get logged.
1453 : */
1454 0 : ereport(LOG,
1455 : (errmsg("process %d detected deadlock while waiting for %s on %s after %ld.%03d ms",
1456 : MyProcPid, modename, buf.data, msecs, usecs),
1457 : (errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
1458 : "Processes holding the lock: %s. Wait queue: %s.",
1459 : lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
1460 : }
1461 :
1462 0 : if (myWaitStatus == STATUS_WAITING)
1463 0 : ereport(LOG,
1464 : (errmsg("process %d still waiting for %s on %s after %ld.%03d ms",
1465 : MyProcPid, modename, buf.data, msecs, usecs),
1466 : (errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
1467 : "Processes holding the lock: %s. Wait queue: %s.",
1468 : lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
1469 0 : else if (myWaitStatus == STATUS_OK)
1470 0 : ereport(LOG,
1471 : (errmsg("process %d acquired %s on %s after %ld.%03d ms",
1472 : MyProcPid, modename, buf.data, msecs, usecs)));
1473 : else
1474 : {
1475 0 : Assert(myWaitStatus == STATUS_ERROR);
1476 :
1477 : /*
1478 : * Currently, the deadlock checker always kicks its own
1479 : * process, which means that we'll only see STATUS_ERROR when
1480 : * deadlock_state == DS_HARD_DEADLOCK, and there's no need to
1481 : * print redundant messages. But for completeness and
1482 : * future-proofing, print a message if it looks like someone
1483 : * else kicked us off the lock.
1484 : */
1485 0 : if (deadlock_state != DS_HARD_DEADLOCK)
1486 0 : ereport(LOG,
1487 : (errmsg("process %d failed to acquire %s on %s after %ld.%03d ms",
1488 : MyProcPid, modename, buf.data, msecs, usecs),
1489 : (errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
1490 : "Processes holding the lock: %s. Wait queue: %s.",
1491 : lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
1492 : }
1493 :
1494 : /*
1495 : * At this point we might still need to wait for the lock. Reset
1496 : * state so we don't print the above messages again.
1497 : */
1498 0 : deadlock_state = DS_NO_DEADLOCK;
1499 :
1500 0 : pfree(buf.data);
1501 0 : pfree(lock_holders_sbuf.data);
1502 0 : pfree(lock_waiters_sbuf.data);
1503 : }
1504 19 : } while (myWaitStatus == STATUS_WAITING);
1505 :
1506 : /*
1507 : * Disable the timers, if they are still running. As in LockErrorCleanup,
1508 : * we must preserve the LOCK_TIMEOUT indicator flag: if a lock timeout has
1509 : * already caused QueryCancelPending to become set, we want the cancel to
1510 : * be reported as a lock timeout, not a user cancel.
1511 : */
1512 18 : if (!InHotStandby)
1513 : {
1514 18 : if (LockTimeout > 0)
1515 : {
1516 : DisableTimeoutParams timeouts[2];
1517 :
1518 0 : timeouts[0].id = DEADLOCK_TIMEOUT;
1519 0 : timeouts[0].keep_indicator = false;
1520 0 : timeouts[1].id = LOCK_TIMEOUT;
1521 0 : timeouts[1].keep_indicator = true;
1522 0 : disable_timeouts(timeouts, 2);
1523 : }
1524 : else
1525 18 : disable_timeout(DEADLOCK_TIMEOUT, false);
1526 : }
1527 :
1528 : /*
1529 : * Re-acquire the lock table's partition lock. We have to do this to hold
1530 : * off cancel/die interrupts before we can mess with lockAwaited (else we
1531 : * might have a missed or duplicated locallock update).
1532 : */
1533 18 : LWLockAcquire(partitionLock, LW_EXCLUSIVE);
1534 :
1535 : /*
1536 : * We no longer want LockErrorCleanup to do anything.
1537 : */
1538 18 : lockAwaited = NULL;
1539 :
1540 : /*
1541 : * If we got the lock, be sure to remember it in the locallock table.
1542 : */
1543 18 : if (MyProc->waitStatus == STATUS_OK)
1544 18 : GrantAwaitedLock();
1545 :
1546 : /*
1547 : * We don't have to do anything else, because the awaker did all the
1548 : * necessary update of the lock table and MyProc.
1549 : */
1550 18 : return MyProc->waitStatus;
1551 : }
1552 :
1553 :
1554 : /*
1555 : * ProcWakeup -- wake up a process by releasing its private semaphore.
1556 : *
1557 : * Also remove the process from the wait queue and set its links invalid.
1558 : * RETURN: the next process in the wait queue.
1559 : *
1560 : * The appropriate lock partition lock must be held by caller.
1561 : *
1562 : * XXX: presently, this code is only used for the "success" case, and only
1563 : * works correctly for that case. To clean up in failure case, would need
1564 : * to twiddle the lock's request counts too --- see RemoveFromWaitQueue.
1565 : * Hence, in practice the waitStatus parameter must be STATUS_OK.
1566 : */
1567 : PGPROC *
1568 18 : ProcWakeup(PGPROC *proc, int waitStatus)
1569 : {
1570 : PGPROC *retProc;
1571 :
1572 : /* Proc should be sleeping ... */
1573 36 : if (proc->links.prev == NULL ||
1574 18 : proc->links.next == NULL)
1575 0 : return NULL;
1576 18 : Assert(proc->waitStatus == STATUS_WAITING);
1577 :
1578 : /* Save next process before we zap the list link */
1579 18 : retProc = (PGPROC *) proc->links.next;
1580 :
1581 : /* Remove process from wait queue */
1582 18 : SHMQueueDelete(&(proc->links));
1583 18 : (proc->waitLock->waitProcs.size)--;
1584 :
1585 : /* Clean up process' state and pass it the ok/fail signal */
1586 18 : proc->waitLock = NULL;
1587 18 : proc->waitProcLock = NULL;
1588 18 : proc->waitStatus = waitStatus;
1589 :
1590 : /* And awaken it */
1591 18 : SetLatch(&proc->procLatch);
1592 :
1593 18 : return retProc;
1594 : }
1595 :
1596 : /*
1597 : * ProcLockWakeup -- routine for waking up processes when a lock is
1598 : * released (or a prior waiter is aborted). Scan all waiters
1599 : * for lock, waken any that are no longer blocked.
1600 : *
1601 : * The appropriate lock partition lock must be held by caller.
1602 : */
1603 : void
1604 15 : ProcLockWakeup(LockMethod lockMethodTable, LOCK *lock)
1605 : {
1606 15 : PROC_QUEUE *waitQueue = &(lock->waitProcs);
1607 15 : int queue_size = waitQueue->size;
1608 : PGPROC *proc;
1609 15 : LOCKMASK aheadRequests = 0;
1610 :
1611 15 : Assert(queue_size >= 0);
1612 :
1613 15 : if (queue_size == 0)
1614 15 : return;
1615 :
1616 15 : proc = (PGPROC *) waitQueue->links.next;
1617 :
1618 71 : while (queue_size-- > 0)
1619 : {
1620 41 : LOCKMODE lockmode = proc->waitLockMode;
1621 :
1622 : /*
1623 : * Waken if (a) doesn't conflict with requests of earlier waiters, and
1624 : * (b) doesn't conflict with already-held locks.
1625 : */
1626 71 : if ((lockMethodTable->conflictTab[lockmode] & aheadRequests) == 0 &&
1627 30 : LockCheckConflicts(lockMethodTable,
1628 : lockmode,
1629 : lock,
1630 : proc->waitProcLock) == STATUS_OK)
1631 : {
1632 : /* OK to waken */
1633 18 : GrantLock(lock, proc->waitProcLock, lockmode);
1634 18 : proc = ProcWakeup(proc, STATUS_OK);
1635 :
1636 : /*
1637 : * ProcWakeup removes proc from the lock's waiting process queue
1638 : * and returns the next proc in chain; don't use proc's next-link,
1639 : * because it's been cleared.
1640 : */
1641 : }
1642 : else
1643 : {
1644 : /*
1645 : * Cannot wake this guy. Remember his request for later checks.
1646 : */
1647 23 : aheadRequests |= LOCKBIT_ON(lockmode);
1648 23 : proc = (PGPROC *) proc->links.next;
1649 : }
1650 : }
1651 :
1652 15 : Assert(waitQueue->size >= 0);
1653 : }
1654 :
1655 : /*
1656 : * CheckDeadLock
1657 : *
1658 : * We only get to this routine, if DEADLOCK_TIMEOUT fired while waiting for a
1659 : * lock to be released by some other process. Check if there's a deadlock; if
1660 : * not, just return. (But signal ProcSleep to log a message, if
1661 : * log_lock_waits is true.) If we have a real deadlock, remove ourselves from
1662 : * the lock's wait queue and signal an error to ProcSleep.
1663 : */
1664 : static void
1665 0 : CheckDeadLock(void)
1666 : {
1667 : int i;
1668 :
1669 : /*
1670 : * Acquire exclusive lock on the entire shared lock data structures. Must
1671 : * grab LWLocks in partition-number order to avoid LWLock deadlock.
1672 : *
1673 : * Note that the deadlock check interrupt had better not be enabled
1674 : * anywhere that this process itself holds lock partition locks, else this
1675 : * will wait forever. Also note that LWLockAcquire creates a critical
1676 : * section, so that this routine cannot be interrupted by cancel/die
1677 : * interrupts.
1678 : */
1679 0 : for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
1680 0 : LWLockAcquire(LockHashPartitionLockByIndex(i), LW_EXCLUSIVE);
1681 :
1682 : /*
1683 : * Check to see if we've been awoken by anyone in the interim.
1684 : *
1685 : * If we have, we can return and resume our transaction -- happy day.
1686 : * Before we are awoken the process releasing the lock grants it to us so
1687 : * we know that we don't have to wait anymore.
1688 : *
1689 : * We check by looking to see if we've been unlinked from the wait queue.
1690 : * This is quicker than checking our semaphore's state, since no kernel
1691 : * call is needed, and it is safe because we hold the lock partition lock.
1692 : */
1693 0 : if (MyProc->links.prev == NULL ||
1694 0 : MyProc->links.next == NULL)
1695 : goto check_done;
1696 :
1697 : #ifdef LOCK_DEBUG
1698 : if (Debug_deadlocks)
1699 : DumpAllLocks();
1700 : #endif
1701 :
1702 : /* Run the deadlock check, and set deadlock_state for use by ProcSleep */
1703 0 : deadlock_state = DeadLockCheck(MyProc);
1704 :
1705 0 : if (deadlock_state == DS_HARD_DEADLOCK)
1706 : {
1707 : /*
1708 : * Oops. We have a deadlock.
1709 : *
1710 : * Get this process out of wait state. (Note: we could do this more
1711 : * efficiently by relying on lockAwaited, but use this coding to
1712 : * preserve the flexibility to kill some other transaction than the
1713 : * one detecting the deadlock.)
1714 : *
1715 : * RemoveFromWaitQueue sets MyProc->waitStatus to STATUS_ERROR, so
1716 : * ProcSleep will report an error after we return from the signal
1717 : * handler.
1718 : */
1719 0 : Assert(MyProc->waitLock != NULL);
1720 0 : RemoveFromWaitQueue(MyProc, LockTagHashCode(&(MyProc->waitLock->tag)));
1721 :
1722 : /*
1723 : * We're done here. Transaction abort caused by the error that
1724 : * ProcSleep will raise will cause any other locks we hold to be
1725 : * released, thus allowing other processes to wake up; we don't need
1726 : * to do that here. NOTE: an exception is that releasing locks we
1727 : * hold doesn't consider the possibility of waiters that were blocked
1728 : * behind us on the lock we just failed to get, and might now be
1729 : * wakable because we're not in front of them anymore. However,
1730 : * RemoveFromWaitQueue took care of waking up any such processes.
1731 : */
1732 : }
1733 :
1734 : /*
1735 : * And release locks. We do this in reverse order for two reasons: (1)
1736 : * Anyone else who needs more than one of the locks will be trying to lock
1737 : * them in increasing order; we don't want to release the other process
1738 : * until it can get all the locks it needs. (2) This avoids O(N^2)
1739 : * behavior inside LWLockRelease.
1740 : */
1741 : check_done:
1742 0 : for (i = NUM_LOCK_PARTITIONS; --i >= 0;)
1743 0 : LWLockRelease(LockHashPartitionLockByIndex(i));
1744 0 : }
1745 :
1746 : /*
1747 : * CheckDeadLockAlert - Handle the expiry of deadlock_timeout.
1748 : *
1749 : * NB: Runs inside a signal handler, be careful.
1750 : */
1751 : void
1752 0 : CheckDeadLockAlert(void)
1753 : {
1754 0 : int save_errno = errno;
1755 :
1756 0 : got_deadlock_timeout = true;
1757 :
1758 : /*
1759 : * Have to set the latch again, even if handle_sig_alarm already did. Back
1760 : * then got_deadlock_timeout wasn't yet set... It's unlikely that this
1761 : * ever would be a problem, but setting a set latch again is cheap.
1762 : */
1763 0 : SetLatch(MyLatch);
1764 0 : errno = save_errno;
1765 0 : }
1766 :
1767 : /*
1768 : * ProcWaitForSignal - wait for a signal from another backend.
1769 : *
1770 : * As this uses the generic process latch the caller has to be robust against
1771 : * unrelated wakeups: Always check that the desired state has occurred, and
1772 : * wait again if not.
1773 : */
1774 : void
1775 0 : ProcWaitForSignal(uint32 wait_event_info)
1776 : {
1777 0 : WaitLatch(MyLatch, WL_LATCH_SET, 0, wait_event_info);
1778 0 : ResetLatch(MyLatch);
1779 0 : CHECK_FOR_INTERRUPTS();
1780 0 : }
1781 :
1782 : /*
1783 : * ProcSendSignal - send a signal to a backend identified by PID
1784 : */
1785 : void
1786 0 : ProcSendSignal(int pid)
1787 : {
1788 0 : PGPROC *proc = NULL;
1789 :
1790 0 : if (RecoveryInProgress())
1791 : {
1792 0 : SpinLockAcquire(ProcStructLock);
1793 :
1794 : /*
1795 : * Check to see whether it is the Startup process we wish to signal.
1796 : * This call is made by the buffer manager when it wishes to wake up a
1797 : * process that has been waiting for a pin in so it can obtain a
1798 : * cleanup lock using LockBufferForCleanup(). Startup is not a normal
1799 : * backend, so BackendPidGetProc() will not return any pid at all. So
1800 : * we remember the information for this special case.
1801 : */
1802 0 : if (pid == ProcGlobal->startupProcPid)
1803 0 : proc = ProcGlobal->startupProc;
1804 :
1805 0 : SpinLockRelease(ProcStructLock);
1806 : }
1807 :
1808 0 : if (proc == NULL)
1809 0 : proc = BackendPidGetProc(pid);
1810 :
1811 0 : if (proc != NULL)
1812 : {
1813 0 : SetLatch(&proc->procLatch);
1814 : }
1815 0 : }
1816 :
1817 : /*
1818 : * BecomeLockGroupLeader - designate process as lock group leader
1819 : *
1820 : * Once this function has returned, other processes can join the lock group
1821 : * by calling BecomeLockGroupMember.
1822 : */
1823 : void
1824 32 : BecomeLockGroupLeader(void)
1825 : {
1826 : LWLock *leader_lwlock;
1827 :
1828 : /* If we already did it, we don't need to do it again. */
1829 32 : if (MyProc->lockGroupLeader == MyProc)
1830 63 : return;
1831 :
1832 : /* We had better not be a follower. */
1833 1 : Assert(MyProc->lockGroupLeader == NULL);
1834 :
1835 : /* Create single-member group, containing only ourselves. */
1836 1 : leader_lwlock = LockHashPartitionLockByProc(MyProc);
1837 1 : LWLockAcquire(leader_lwlock, LW_EXCLUSIVE);
1838 1 : MyProc->lockGroupLeader = MyProc;
1839 1 : dlist_push_head(&MyProc->lockGroupMembers, &MyProc->lockGroupLink);
1840 1 : LWLockRelease(leader_lwlock);
1841 : }
1842 :
1843 : /*
1844 : * BecomeLockGroupMember - designate process as lock group member
1845 : *
1846 : * This is pretty straightforward except for the possibility that the leader
1847 : * whose group we're trying to join might exit before we manage to do so;
1848 : * and the PGPROC might get recycled for an unrelated process. To avoid
1849 : * that, we require the caller to pass the PID of the intended PGPROC as
1850 : * an interlock. Returns true if we successfully join the intended lock
1851 : * group, and false if not.
1852 : */
1853 : bool
1854 115 : BecomeLockGroupMember(PGPROC *leader, int pid)
1855 : {
1856 : LWLock *leader_lwlock;
1857 115 : bool ok = false;
1858 :
1859 : /* Group leader can't become member of group */
1860 115 : Assert(MyProc != leader);
1861 :
1862 : /* Can't already be a member of a group */
1863 115 : Assert(MyProc->lockGroupLeader == NULL);
1864 :
1865 : /* PID must be valid. */
1866 115 : Assert(pid != 0);
1867 :
1868 : /*
1869 : * Get lock protecting the group fields. Note LockHashPartitionLockByProc
1870 : * accesses leader->pgprocno in a PGPROC that might be free. This is safe
1871 : * because all PGPROCs' pgprocno fields are set during shared memory
1872 : * initialization and never change thereafter; so we will acquire the
1873 : * correct lock even if the leader PGPROC is in process of being recycled.
1874 : */
1875 115 : leader_lwlock = LockHashPartitionLockByProc(leader);
1876 115 : LWLockAcquire(leader_lwlock, LW_EXCLUSIVE);
1877 :
1878 : /* Is this the leader we're looking for? */
1879 115 : if (leader->pid == pid && leader->lockGroupLeader == leader)
1880 : {
1881 : /* OK, join the group */
1882 115 : ok = true;
1883 115 : MyProc->lockGroupLeader = leader;
1884 115 : dlist_push_tail(&leader->lockGroupMembers, &MyProc->lockGroupLink);
1885 : }
1886 115 : LWLockRelease(leader_lwlock);
1887 :
1888 115 : return ok;
1889 : }
|
