Branch data Line data Source code
1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * proc.c
4 : : * routines to manage per-process shared memory data structure
5 : : *
6 : : * Portions Copyright (c) 1996-2026, 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 : : * JoinWaitQueue(), ProcSleep(), ProcWakeup()
18 : : *
19 : : * Waiting for a lock causes the backend to be put to sleep. Whoever releases
20 : : * the lock wakes the process up again (and gives it an error code so it knows
21 : : * whether it was awoken on an error condition).
22 : : *
23 : : * Interface (b):
24 : : *
25 : : * ProcReleaseLocks -- frees the locks associated with current transaction
26 : : *
27 : : * ProcKill -- destroys the shared memory state (and locks)
28 : : * associated with the process.
29 : : */
30 : : #include "postgres.h"
31 : :
32 : : #include <signal.h>
33 : : #include <unistd.h>
34 : : #include <sys/time.h>
35 : :
36 : : #include "access/clog.h"
37 : : #include "access/transam.h"
38 : : #include "access/twophase.h"
39 : : #include "access/xlogutils.h"
40 : : #include "access/xlogwait.h"
41 : : #include "miscadmin.h"
42 : : #include "pgstat.h"
43 : : #include "postmaster/autovacuum.h"
44 : : #include "replication/slotsync.h"
45 : : #include "replication/syncrep.h"
46 : : #include "storage/condition_variable.h"
47 : : #include "storage/ipc.h"
48 : : #include "storage/lmgr.h"
49 : : #include "storage/pmsignal.h"
50 : : #include "storage/proc.h"
51 : : #include "storage/procarray.h"
52 : : #include "storage/procsignal.h"
53 : : #include "storage/spin.h"
54 : : #include "storage/standby.h"
55 : : #include "storage/subsystems.h"
56 : : #include "utils/injection_point.h"
57 : : #include "utils/timeout.h"
58 : : #include "utils/timestamp.h"
59 : : #include "utils/wait_event.h"
60 : :
61 : : /* GUC variables */
62 : : int DeadlockTimeout = 1000;
63 : : int StatementTimeout = 0;
64 : : int LockTimeout = 0;
65 : : int IdleInTransactionSessionTimeout = 0;
66 : : int TransactionTimeout = 0;
67 : : int IdleSessionTimeout = 0;
68 : : bool log_lock_waits = true;
69 : :
70 : : /* Pointer to this process's PGPROC struct, if any */
71 : : PGPROC *MyProc = NULL;
72 : :
73 : : /* Pointers to shared-memory structures */
74 : : PROC_HDR *ProcGlobal = NULL;
75 : : static void *AllProcsShmemPtr;
76 : : static void *FastPathLockArrayShmemPtr;
77 : : NON_EXEC_STATIC PGPROC *AuxiliaryProcs = NULL;
78 : : PGPROC *PreparedXactProcs = NULL;
79 : :
80 : : static void ProcGlobalShmemRequest(void *arg);
81 : : static void ProcGlobalShmemInit(void *arg);
82 : :
83 : : const ShmemCallbacks ProcGlobalShmemCallbacks = {
84 : : .request_fn = ProcGlobalShmemRequest,
85 : : .init_fn = ProcGlobalShmemInit,
86 : : };
87 : :
88 : : static uint32 TotalProcs;
89 : : static size_t ProcGlobalAllProcsShmemSize;
90 : : static size_t FastPathLockArrayShmemSize;
91 : :
92 : : /* Is a deadlock check pending? */
93 : : static volatile sig_atomic_t got_deadlock_timeout;
94 : :
95 : : static void RemoveProcFromArray(int code, Datum arg);
96 : : static void ProcKill(int code, Datum arg);
97 : : static void AuxiliaryProcKill(int code, Datum arg);
98 : : static DeadLockState CheckDeadLock(void);
99 : :
100 : :
101 : : /*
102 : : * Calculate shared-memory space needed by Fast-Path locks.
103 : : */
104 : : static Size
105 : 1259 : CalculateFastPathLockShmemSize(void)
106 : : {
107 : 1259 : Size size = 0;
108 : : Size fpLockBitsSize,
109 : : fpRelIdSize;
110 : :
111 : : /*
112 : : * Memory needed for PGPROC fast-path lock arrays. Make sure the sizes are
113 : : * nicely aligned in each backend.
114 : : */
115 : 1259 : fpLockBitsSize = MAXALIGN(FastPathLockGroupsPerBackend * sizeof(uint64));
116 : 1259 : fpRelIdSize = MAXALIGN(FastPathLockSlotsPerBackend() * sizeof(Oid));
117 : :
118 : 1259 : size = add_size(size, mul_size(TotalProcs, (fpLockBitsSize + fpRelIdSize)));
119 : :
120 : : Assert(TotalProcs > 0);
121 : : Assert(size > 0);
122 : :
123 : 1259 : return size;
124 : : }
125 : :
126 : : /*
127 : : * Report number of semaphores needed by ProcGlobalShmemInit.
128 : : */
129 : : int
130 : 3598 : ProcGlobalSemas(void)
131 : : {
132 : : /*
133 : : * We need a sema per backend (including autovacuum), plus one for each
134 : : * auxiliary process.
135 : : */
136 : 3598 : return MaxBackends + NUM_AUXILIARY_PROCS;
137 : : }
138 : :
139 : : /*
140 : : * ProcGlobalShmemRequest
141 : : * Register shared memory needs.
142 : : *
143 : : * This is called during postmaster or standalone backend startup, and also
144 : : * during backend startup in EXEC_BACKEND mode.
145 : : */
146 : : static void
147 : 1259 : ProcGlobalShmemRequest(void *arg)
148 : : {
149 : : Size size;
150 : :
151 : : /*
152 : : * Reserve all the PGPROC structures we'll need. There are six separate
153 : : * consumers: (1) normal backends, (2) autovacuum workers and special
154 : : * workers, (3) background workers, (4) walsenders, (5) auxiliary
155 : : * processes, and (6) prepared transactions. (For largely-historical
156 : : * reasons, we combine autovacuum and special workers into one category
157 : : * with a single freelist.) Each PGPROC structure is dedicated to exactly
158 : : * one of these purposes, and they do not move between groups.
159 : : */
160 : 1259 : TotalProcs =
161 : 1259 : add_size(MaxBackends, add_size(NUM_AUXILIARY_PROCS, max_prepared_xacts));
162 : :
163 : 1259 : size = 0;
164 : 1259 : size = add_size(size, mul_size(TotalProcs, sizeof(PGPROC)));
165 : 1259 : size = add_size(size, mul_size(TotalProcs, sizeof(*ProcGlobal->xids)));
166 : 1259 : size = add_size(size, mul_size(TotalProcs, sizeof(*ProcGlobal->subxidStates)));
167 : 1259 : size = add_size(size, mul_size(TotalProcs, sizeof(*ProcGlobal->statusFlags)));
168 : 1259 : ProcGlobalAllProcsShmemSize = size;
169 : 1259 : ShmemRequestStruct(.name = "PGPROC structures",
170 : : .size = ProcGlobalAllProcsShmemSize,
171 : : .ptr = &AllProcsShmemPtr,
172 : : );
173 : :
174 [ + - ]: 1259 : if (!IsUnderPostmaster)
175 : 1259 : size = FastPathLockArrayShmemSize = CalculateFastPathLockShmemSize();
176 : : else
177 : 0 : size = SHMEM_ATTACH_UNKNOWN_SIZE;
178 : 1259 : ShmemRequestStruct(.name = "Fast-Path Lock Array",
179 : : .size = size,
180 : : .ptr = &FastPathLockArrayShmemPtr,
181 : : );
182 : :
183 : : /*
184 : : * ProcGlobal is registered here in .ptr as usual, but it needs to be
185 : : * propagated specially in EXEC_BACKEND mode, because ProcGlobal needs to
186 : : * be accessed early at backend startup, before ShmemAttachRequested() has
187 : : * been called.
188 : : */
189 : 1259 : ShmemRequestStruct(.name = "Proc Header",
190 : : .size = sizeof(PROC_HDR),
191 : : .ptr = (void **) &ProcGlobal,
192 : : );
193 : :
194 : : /* Let the semaphore implementation register its shared memory needs */
195 : 1259 : PGSemaphoreShmemRequest(ProcGlobalSemas());
196 : 1259 : }
197 : :
198 : :
199 : : /*
200 : : * ProcGlobalShmemInit -
201 : : * Initialize the global process table during postmaster or standalone
202 : : * backend startup.
203 : : *
204 : : * We also create all the per-process semaphores we will need to support
205 : : * the requested number of backends. We used to allocate semaphores
206 : : * only when backends were actually started up, but that is bad because
207 : : * it lets Postgres fail under load --- a lot of Unix systems are
208 : : * (mis)configured with small limits on the number of semaphores, and
209 : : * running out when trying to start another backend is a common failure.
210 : : * So, now we grab enough semaphores to support the desired max number
211 : : * of backends immediately at initialization --- if the sysadmin has set
212 : : * MaxConnections, max_worker_processes, max_wal_senders, or
213 : : * autovacuum_worker_slots higher than his kernel will support, he'll
214 : : * find out sooner rather than later.
215 : : *
216 : : * Another reason for creating semaphores here is that the semaphore
217 : : * implementation typically requires us to create semaphores in the
218 : : * postmaster, not in backends.
219 : : */
220 : : static void
221 : 1256 : ProcGlobalShmemInit(void *arg)
222 : : {
223 : : char *ptr;
224 : : size_t requestSize;
225 : : PGPROC *procs;
226 : : int i,
227 : : j;
228 : :
229 : : /* Used for setup of per-backend fast-path slots. */
230 : : char *fpPtr,
231 : : *fpEndPtr PG_USED_FOR_ASSERTS_ONLY;
232 : : Size fpLockBitsSize,
233 : : fpRelIdSize;
234 : :
235 : : Assert(ProcGlobal);
236 : 1256 : ProcGlobal->spins_per_delay = DEFAULT_SPINS_PER_DELAY;
237 : 1256 : SpinLockInit(&ProcGlobal->freeProcsLock);
238 : 1256 : dlist_init(&ProcGlobal->freeProcs);
239 : 1256 : dlist_init(&ProcGlobal->autovacFreeProcs);
240 : 1256 : dlist_init(&ProcGlobal->bgworkerFreeProcs);
241 : 1256 : dlist_init(&ProcGlobal->walsenderFreeProcs);
242 : 1256 : ProcGlobal->startupBufferPinWaitBufId = -1;
243 : 1256 : pg_atomic_init_u32(&ProcGlobal->avLauncherProc, INVALID_PROC_NUMBER);
244 : 1256 : pg_atomic_init_u32(&ProcGlobal->walwriterProc, INVALID_PROC_NUMBER);
245 : 1256 : pg_atomic_init_u32(&ProcGlobal->checkpointerProc, INVALID_PROC_NUMBER);
246 : 1256 : pg_atomic_init_u32(&ProcGlobal->procArrayGroupFirst, INVALID_PROC_NUMBER);
247 : 1256 : pg_atomic_init_u32(&ProcGlobal->clogGroupFirst, INVALID_PROC_NUMBER);
248 : :
249 : 1256 : ptr = AllProcsShmemPtr;
250 : 1256 : requestSize = ProcGlobalAllProcsShmemSize;
251 [ + - + + : 1256 : MemSet(ptr, 0, requestSize);
+ - - + -
- ]
252 : :
253 : : /* Carve out the allProcs array from the shared memory area */
254 : 1256 : procs = (PGPROC *) ptr;
255 : 1256 : ptr = ptr + TotalProcs * sizeof(PGPROC);
256 : :
257 : 1256 : ProcGlobal->allProcs = procs;
258 : : /* XXX allProcCount isn't really all of them; it excludes prepared xacts */
259 : 1256 : ProcGlobal->allProcCount = MaxBackends + NUM_AUXILIARY_PROCS;
260 : :
261 : : /*
262 : : * Carve out arrays mirroring PGPROC fields in a dense manner. See
263 : : * PROC_HDR.
264 : : *
265 : : * XXX: It might make sense to increase padding for these arrays, given
266 : : * how hotly they are accessed.
267 : : */
268 : 1256 : ProcGlobal->xids = (TransactionId *) ptr;
269 : 1256 : ptr = ptr + (TotalProcs * sizeof(*ProcGlobal->xids));
270 : :
271 : 1256 : ProcGlobal->subxidStates = (XidCacheStatus *) ptr;
272 : 1256 : ptr = ptr + (TotalProcs * sizeof(*ProcGlobal->subxidStates));
273 : :
274 : 1256 : ProcGlobal->statusFlags = (uint8 *) ptr;
275 : 1256 : ptr = ptr + (TotalProcs * sizeof(*ProcGlobal->statusFlags));
276 : :
277 : : /* make sure we didn't overflow */
278 : : Assert((ptr > (char *) procs) && (ptr <= (char *) procs + requestSize));
279 : :
280 : : /*
281 : : * Initialize arrays for fast-path locks. Those are variable-length, so
282 : : * can't be included in PGPROC directly. We allocate a separate piece of
283 : : * shared memory and then divide that between backends.
284 : : */
285 : 1256 : fpLockBitsSize = MAXALIGN(FastPathLockGroupsPerBackend * sizeof(uint64));
286 : 1256 : fpRelIdSize = MAXALIGN(FastPathLockSlotsPerBackend() * sizeof(Oid));
287 : :
288 : 1256 : fpPtr = FastPathLockArrayShmemPtr;
289 : 1256 : requestSize = FastPathLockArrayShmemSize;
290 : 1256 : memset(fpPtr, 0, requestSize);
291 : :
292 : : /* For asserts checking we did not overflow. */
293 : 1256 : fpEndPtr = fpPtr + requestSize;
294 : :
295 : : /* Initialize semaphores */
296 : 1256 : PGSemaphoreInit(ProcGlobalSemas());
297 : :
298 [ + + ]: 166003 : for (i = 0; i < TotalProcs; i++)
299 : : {
300 : 164747 : PGPROC *proc = &procs[i];
301 : :
302 : : /* Common initialization for all PGPROCs, regardless of type. */
303 : :
304 : : /*
305 : : * Set the fast-path lock arrays, and move the pointer. We interleave
306 : : * the two arrays, to (hopefully) get some locality for each backend.
307 : : */
308 : 164747 : proc->fpLockBits = (uint64 *) fpPtr;
309 : 164747 : fpPtr += fpLockBitsSize;
310 : :
311 : 164747 : proc->fpRelId = (Oid *) fpPtr;
312 : 164747 : fpPtr += fpRelIdSize;
313 : :
314 : : Assert(fpPtr <= fpEndPtr);
315 : :
316 : : /*
317 : : * Set up per-PGPROC semaphore, latch, and fpInfoLock. Prepared xact
318 : : * dummy PGPROCs don't need these though - they're never associated
319 : : * with a real process
320 : : */
321 [ + + ]: 164747 : if (i < FIRST_PREPARED_XACT_PROC_NUMBER)
322 : : {
323 : 163861 : proc->sem = PGSemaphoreCreate();
324 : 163861 : InitSharedLatch(&(proc->procLatch));
325 : 163861 : LWLockInitialize(&(proc->fpInfoLock), LWTRANCHE_LOCK_FASTPATH);
326 : : }
327 : :
328 : : /*
329 : : * Newly created PGPROCs for normal backends, autovacuum workers,
330 : : * special workers, bgworkers, and walsenders must be queued up on the
331 : : * appropriate free list. Because there can only ever be a small,
332 : : * fixed number of auxiliary processes, no free list is used in that
333 : : * case; InitAuxiliaryProcess() instead uses a linear search. PGPROCs
334 : : * for prepared transactions are added to a free list by
335 : : * TwoPhaseShmemInit().
336 : : */
337 [ + + ]: 164747 : if (i < MaxConnections)
338 : : {
339 : : /* PGPROC for normal backend, add to freeProcs list */
340 : 81696 : dlist_push_tail(&ProcGlobal->freeProcs, &proc->freeProcsLink);
341 : 81696 : proc->procgloballist = &ProcGlobal->freeProcs;
342 : : }
343 [ + + ]: 83051 : else if (i < MaxConnections + autovacuum_worker_slots + NUM_SPECIAL_WORKER_PROCS)
344 : : {
345 : : /* PGPROC for AV or special worker, add to autovacFreeProcs list */
346 : 16314 : dlist_push_tail(&ProcGlobal->autovacFreeProcs, &proc->freeProcsLink);
347 : 16314 : proc->procgloballist = &ProcGlobal->autovacFreeProcs;
348 : : }
349 [ + + ]: 66737 : else if (i < MaxConnections + autovacuum_worker_slots + NUM_SPECIAL_WORKER_PROCS + max_worker_processes)
350 : : {
351 : : /* PGPROC for bgworker, add to bgworkerFreeProcs list */
352 : 10041 : dlist_push_tail(&ProcGlobal->bgworkerFreeProcs, &proc->freeProcsLink);
353 : 10041 : proc->procgloballist = &ProcGlobal->bgworkerFreeProcs;
354 : : }
355 [ + + ]: 56696 : else if (i < MaxBackends)
356 : : {
357 : : /* PGPROC for walsender, add to walsenderFreeProcs list */
358 : 8082 : dlist_push_tail(&ProcGlobal->walsenderFreeProcs, &proc->freeProcsLink);
359 : 8082 : proc->procgloballist = &ProcGlobal->walsenderFreeProcs;
360 : : }
361 : :
362 : : /* Initialize myProcLocks[] shared memory queues. */
363 [ + + ]: 2800699 : for (j = 0; j < NUM_LOCK_PARTITIONS; j++)
364 : 2635952 : dlist_init(&(proc->myProcLocks[j]));
365 : :
366 : : /* Initialize lockGroupMembers list. */
367 : 164747 : dlist_init(&proc->lockGroupMembers);
368 : :
369 : : /*
370 : : * Initialize the atomic variables, otherwise, it won't be safe to
371 : : * access them for backends that aren't currently in use.
372 : : */
373 : 164747 : pg_atomic_init_u32(&(proc->procArrayGroupNext), INVALID_PROC_NUMBER);
374 : 164747 : pg_atomic_init_u32(&(proc->clogGroupNext), INVALID_PROC_NUMBER);
375 : 164747 : pg_atomic_init_u64(&(proc->waitStart), 0);
376 : : }
377 : :
378 : : /* Should have consumed exactly the expected amount of fast-path memory. */
379 : : Assert(fpPtr == fpEndPtr);
380 : :
381 : : /*
382 : : * Save pointers to the blocks of PGPROC structures reserved for auxiliary
383 : : * processes and prepared transactions.
384 : : */
385 : 1256 : AuxiliaryProcs = &procs[MaxBackends];
386 : 1256 : PreparedXactProcs = &procs[FIRST_PREPARED_XACT_PROC_NUMBER];
387 : 1256 : }
388 : :
389 : : /*
390 : : * InitProcess -- initialize a per-process PGPROC entry for this backend
391 : : */
392 : : void
393 : 20597 : InitProcess(void)
394 : : {
395 : : dlist_head *procgloballist;
396 : :
397 : : /*
398 : : * ProcGlobal should be set up already (if we are a backend, we inherit
399 : : * this by fork() or EXEC_BACKEND mechanism from the postmaster).
400 : : */
401 [ - + ]: 20597 : if (ProcGlobal == NULL)
402 [ # # ]: 0 : elog(PANIC, "proc header uninitialized");
403 : :
404 [ - + ]: 20597 : if (MyProc != NULL)
405 [ # # ]: 0 : elog(ERROR, "you already exist");
406 : :
407 : : /*
408 : : * Before we start accessing the shared memory in a serious way, mark
409 : : * ourselves as an active postmaster child; this is so that the postmaster
410 : : * can detect it if we exit without cleaning up.
411 : : */
412 [ + + ]: 20597 : if (IsUnderPostmaster)
413 : 20464 : RegisterPostmasterChildActive();
414 : :
415 : : /*
416 : : * Decide which list should supply our PGPROC. This logic must match the
417 : : * way the freelists were constructed in ProcGlobalShmemInit().
418 : : */
419 [ + + + + : 20597 : if (AmAutoVacuumWorkerProcess() || AmSpecialWorkerProcess())
+ + ]
420 : 2292 : procgloballist = &ProcGlobal->autovacFreeProcs;
421 [ + + ]: 18305 : else if (AmBackgroundWorkerProcess())
422 : 3240 : procgloballist = &ProcGlobal->bgworkerFreeProcs;
423 [ + + ]: 15065 : else if (AmWalSenderProcess())
424 : 1336 : procgloballist = &ProcGlobal->walsenderFreeProcs;
425 : : else
426 : 13729 : procgloballist = &ProcGlobal->freeProcs;
427 : :
428 : : /*
429 : : * Try to get a proc struct from the appropriate free list. If this
430 : : * fails, we must be out of PGPROC structures (not to mention semaphores).
431 : : *
432 : : * While we are holding the spinlock, also copy the current shared
433 : : * estimate of spins_per_delay to local storage.
434 : : */
435 : 20597 : SpinLockAcquire(&ProcGlobal->freeProcsLock);
436 : :
437 : 20597 : set_spins_per_delay(ProcGlobal->spins_per_delay);
438 : :
439 [ + + ]: 20597 : if (!dlist_is_empty(procgloballist))
440 : : {
441 : 20594 : MyProc = dlist_container(PGPROC, freeProcsLink, dlist_pop_head_node(procgloballist));
442 : 20594 : SpinLockRelease(&ProcGlobal->freeProcsLock);
443 : : }
444 : : else
445 : : {
446 : : /*
447 : : * If we reach here, all the PGPROCs are in use. This is one of the
448 : : * possible places to detect "too many backends", so give the standard
449 : : * error message. XXX do we need to give a different failure message
450 : : * in the autovacuum case?
451 : : */
452 : 3 : SpinLockRelease(&ProcGlobal->freeProcsLock);
453 [ + + ]: 3 : if (AmWalSenderProcess())
454 [ + - ]: 2 : ereport(FATAL,
455 : : (errcode(ERRCODE_TOO_MANY_CONNECTIONS),
456 : : errmsg("number of requested standby connections exceeds \"max_wal_senders\" (currently %d)",
457 : : max_wal_senders)));
458 [ + - ]: 1 : ereport(FATAL,
459 : : (errcode(ERRCODE_TOO_MANY_CONNECTIONS),
460 : : errmsg("sorry, too many clients already")));
461 : : }
462 : 20594 : MyProcNumber = GetNumberFromPGProc(MyProc);
463 : :
464 : : /*
465 : : * Cross-check that the PGPROC is of the type we expect; if this were not
466 : : * the case, it would get returned to the wrong list.
467 : : */
468 : : Assert(MyProc->procgloballist == procgloballist);
469 : :
470 : : /*
471 : : * Initialize all fields of MyProc, except for those previously
472 : : * initialized by ProcGlobalShmemInit.
473 : : */
474 : 20594 : dlist_node_init(&MyProc->freeProcsLink);
475 : 20594 : MyProc->waitStatus = PROC_WAIT_STATUS_OK;
476 : 20594 : MyProc->fpVXIDLock = false;
477 : 20594 : MyProc->fpLocalTransactionId = InvalidLocalTransactionId;
478 : 20594 : MyProc->xid = InvalidTransactionId;
479 : 20594 : MyProc->xmin = InvalidTransactionId;
480 : 20594 : MyProc->pid = MyProcPid;
481 : 20594 : MyProc->vxid.procNumber = MyProcNumber;
482 : 20594 : MyProc->vxid.lxid = InvalidLocalTransactionId;
483 : : /* databaseId and roleId will be filled in later */
484 : 20594 : MyProc->databaseId = InvalidOid;
485 : 20594 : MyProc->roleId = InvalidOid;
486 : 20594 : MyProc->tempNamespaceId = InvalidOid;
487 : 20594 : MyProc->backendType = MyBackendType;
488 : 20594 : MyProc->delayChkptFlags = 0;
489 : 20594 : MyProc->statusFlags = 0;
490 : : /* NB -- autovac launcher intentionally does not set IS_AUTOVACUUM */
491 [ + + ]: 20594 : if (AmAutoVacuumWorkerProcess())
492 : 1806 : MyProc->statusFlags |= PROC_IS_AUTOVACUUM;
493 : 20594 : MyProc->lwWaiting = LW_WS_NOT_WAITING;
494 : 20594 : MyProc->lwWaitMode = 0;
495 : 20594 : MyProc->waitLock = NULL;
496 : 20594 : dlist_node_init(&MyProc->waitLink);
497 : 20594 : MyProc->waitProcLock = NULL;
498 : 20594 : pg_atomic_write_u64(&MyProc->waitStart, 0);
499 : : #ifdef USE_ASSERT_CHECKING
500 : : {
501 : : int i;
502 : :
503 : : /* Last process should have released all locks. */
504 : : for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
505 : : Assert(dlist_is_empty(&(MyProc->myProcLocks[i])));
506 : : }
507 : : #endif
508 : 20594 : pg_atomic_write_u32(&MyProc->pendingRecoveryConflicts, 0);
509 : :
510 : : /* Initialize fields for sync rep */
511 : 20594 : MyProc->waitLSN = InvalidXLogRecPtr;
512 : 20594 : MyProc->syncRepState = SYNC_REP_NOT_WAITING;
513 : 20594 : dlist_node_init(&MyProc->syncRepLinks);
514 : :
515 : : /* Initialize fields for group XID clearing. */
516 : 20594 : MyProc->procArrayGroupMember = false;
517 : 20594 : MyProc->procArrayGroupMemberXid = InvalidTransactionId;
518 : : Assert(pg_atomic_read_u32(&MyProc->procArrayGroupNext) == INVALID_PROC_NUMBER);
519 : :
520 : : /* Check that group locking fields are in a proper initial state. */
521 : : Assert(MyProc->lockGroupLeader == NULL);
522 : : Assert(dlist_is_empty(&MyProc->lockGroupMembers));
523 : :
524 : : /* Initialize wait event information. */
525 : 20594 : MyProc->wait_event_info = 0;
526 : :
527 : : /* Initialize fields for group transaction status update. */
528 : 20594 : MyProc->clogGroupMember = false;
529 : 20594 : MyProc->clogGroupMemberXid = InvalidTransactionId;
530 : 20594 : MyProc->clogGroupMemberXidStatus = TRANSACTION_STATUS_IN_PROGRESS;
531 : 20594 : MyProc->clogGroupMemberPage = -1;
532 : 20594 : MyProc->clogGroupMemberLsn = InvalidXLogRecPtr;
533 : : Assert(pg_atomic_read_u32(&MyProc->clogGroupNext) == INVALID_PROC_NUMBER);
534 : :
535 : : /*
536 : : * Acquire ownership of the PGPROC's latch, so that we can use WaitLatch
537 : : * on it. That allows us to repoint the process latch, which so far
538 : : * points to process local one, to the shared one.
539 : : */
540 : 20594 : OwnLatch(&MyProc->procLatch);
541 : 20594 : SwitchToSharedLatch();
542 : :
543 : : /* now that we have a proc, report wait events to shared memory */
544 : 20594 : pgstat_set_wait_event_storage(&MyProc->wait_event_info);
545 : :
546 : : /*
547 : : * We might be reusing a semaphore that belonged to a failed process. So
548 : : * be careful and reinitialize its value here. (This is not strictly
549 : : * necessary anymore, but seems like a good idea for cleanliness.)
550 : : */
551 : 20594 : PGSemaphoreReset(MyProc->sem);
552 : :
553 : : /* autovacuum launcher is specially advertised in ProcGlobal */
554 [ + + ]: 20594 : if (MyBackendType == B_AUTOVAC_LAUNCHER)
555 : 480 : pg_atomic_write_u32(&ProcGlobal->avLauncherProc, MyProcNumber);
556 : :
557 : : /*
558 : : * Arrange to clean up at backend exit.
559 : : */
560 : 20594 : on_shmem_exit(ProcKill, 0);
561 : :
562 : : /*
563 : : * Now that we have a PGPROC, we could try to acquire locks, so initialize
564 : : * local state needed for LWLocks, and the deadlock checker.
565 : : */
566 : 20594 : InitLWLockAccess();
567 : 20594 : InitDeadLockChecking();
568 : :
569 : : #ifdef EXEC_BACKEND
570 : :
571 : : /*
572 : : * Initialize backend-local pointers to all the shared data structures.
573 : : * (We couldn't do this until now because it needs LWLocks.)
574 : : */
575 : : if (IsUnderPostmaster)
576 : : AttachSharedMemoryStructs();
577 : : #endif
578 : 20594 : }
579 : :
580 : : /*
581 : : * InitProcessPhase2 -- make MyProc visible in the shared ProcArray.
582 : : *
583 : : * This is separate from InitProcess because we can't acquire LWLocks until
584 : : * we've created a PGPROC, but in the EXEC_BACKEND case ProcArrayAdd won't
585 : : * work until after we've done AttachSharedMemoryStructs.
586 : : */
587 : : void
588 : 20581 : InitProcessPhase2(void)
589 : : {
590 : : Assert(MyProc != NULL);
591 : :
592 : : /*
593 : : * Add our PGPROC to the PGPROC array in shared memory.
594 : : */
595 : 20581 : ProcArrayAdd(MyProc);
596 : :
597 : : /*
598 : : * Arrange to clean that up at backend exit.
599 : : */
600 : 20581 : on_shmem_exit(RemoveProcFromArray, 0);
601 : 20581 : }
602 : :
603 : : /*
604 : : * InitAuxiliaryProcess -- create a PGPROC entry for an auxiliary process
605 : : *
606 : : * This is called by bgwriter and similar processes so that they will have a
607 : : * MyProc value that's real enough to let them wait for LWLocks. The PGPROC
608 : : * and sema that are assigned are one of the extra ones created during
609 : : * ProcGlobalShmemInit.
610 : : *
611 : : * Auxiliary processes are presently not expected to wait for real (lockmgr)
612 : : * locks, so we need not set up the deadlock checker. They are never added
613 : : * to the ProcArray or the sinval messaging mechanism, either. They also
614 : : * don't get a VXID assigned, since this is only useful when we actually
615 : : * hold lockmgr locks.
616 : : *
617 : : * Startup process however uses locks but never waits for them in the
618 : : * normal backend sense. Startup process also takes part in sinval messaging
619 : : * as a sendOnly process, so never reads messages from sinval queue. So
620 : : * Startup process does have a VXID and does show up in pg_locks.
621 : : */
622 : : void
623 : 4442 : InitAuxiliaryProcess(void)
624 : : {
625 : : PGPROC *auxproc;
626 : : int proctype;
627 : :
628 : : /*
629 : : * ProcGlobal should be set up already (if we are a backend, we inherit
630 : : * this by fork() or EXEC_BACKEND mechanism from the postmaster).
631 : : */
632 [ + - - + ]: 4442 : if (ProcGlobal == NULL || AuxiliaryProcs == NULL)
633 [ # # ]: 0 : elog(PANIC, "proc header uninitialized");
634 : :
635 [ - + ]: 4442 : if (MyProc != NULL)
636 [ # # ]: 0 : elog(ERROR, "you already exist");
637 : :
638 [ + - ]: 4442 : if (IsUnderPostmaster)
639 : 4442 : RegisterPostmasterChildActive();
640 : :
641 : : /*
642 : : * We use the freeProcsLock to protect assignment and releasing of
643 : : * AuxiliaryProcs entries.
644 : : *
645 : : * While we are holding the spinlock, also copy the current shared
646 : : * estimate of spins_per_delay to local storage.
647 : : */
648 : 4442 : SpinLockAcquire(&ProcGlobal->freeProcsLock);
649 : :
650 : 4442 : set_spins_per_delay(ProcGlobal->spins_per_delay);
651 : :
652 : : /*
653 : : * Find a free auxproc ... *big* trouble if there isn't one ...
654 : : */
655 [ + - ]: 15397 : for (proctype = 0; proctype < NUM_AUXILIARY_PROCS; proctype++)
656 : : {
657 : 15397 : auxproc = &AuxiliaryProcs[proctype];
658 [ + + ]: 15397 : if (auxproc->pid == 0)
659 : 4442 : break;
660 : : }
661 [ - + ]: 4442 : if (proctype >= NUM_AUXILIARY_PROCS)
662 : : {
663 : 0 : SpinLockRelease(&ProcGlobal->freeProcsLock);
664 [ # # ]: 0 : elog(FATAL, "all AuxiliaryProcs are in use");
665 : : }
666 : :
667 : : /* Mark auxiliary proc as in use by me */
668 : 4442 : auxproc->pid = MyProcPid;
669 : :
670 : 4442 : SpinLockRelease(&ProcGlobal->freeProcsLock);
671 : :
672 : 4442 : MyProc = auxproc;
673 : 4442 : MyProcNumber = GetNumberFromPGProc(MyProc);
674 : :
675 : : /*
676 : : * Initialize all fields of MyProc, except for those previously
677 : : * initialized by ProcGlobalShmemInit.
678 : : */
679 : 4442 : dlist_node_init(&MyProc->freeProcsLink);
680 : 4442 : MyProc->waitStatus = PROC_WAIT_STATUS_OK;
681 : 4442 : MyProc->fpVXIDLock = false;
682 : 4442 : MyProc->fpLocalTransactionId = InvalidLocalTransactionId;
683 : 4442 : MyProc->xid = InvalidTransactionId;
684 : 4442 : MyProc->xmin = InvalidTransactionId;
685 : 4442 : MyProc->vxid.procNumber = INVALID_PROC_NUMBER;
686 : 4442 : MyProc->vxid.lxid = InvalidLocalTransactionId;
687 : 4442 : MyProc->databaseId = InvalidOid;
688 : 4442 : MyProc->roleId = InvalidOid;
689 : 4442 : MyProc->tempNamespaceId = InvalidOid;
690 : 4442 : MyProc->backendType = MyBackendType;
691 : 4442 : MyProc->delayChkptFlags = 0;
692 : 4442 : MyProc->statusFlags = 0;
693 : 4442 : MyProc->lwWaiting = LW_WS_NOT_WAITING;
694 : 4442 : MyProc->lwWaitMode = 0;
695 : 4442 : MyProc->waitLock = NULL;
696 : 4442 : dlist_node_init(&MyProc->waitLink);
697 : 4442 : MyProc->waitProcLock = NULL;
698 : 4442 : pg_atomic_write_u64(&MyProc->waitStart, 0);
699 : : #ifdef USE_ASSERT_CHECKING
700 : : {
701 : : int i;
702 : :
703 : : /* Last process should have released all locks. */
704 : : for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
705 : : Assert(dlist_is_empty(&(MyProc->myProcLocks[i])));
706 : : }
707 : : #endif
708 : 4442 : pg_atomic_write_u32(&MyProc->pendingRecoveryConflicts, 0);
709 : :
710 : : /*
711 : : * Acquire ownership of the PGPROC's latch, so that we can use WaitLatch
712 : : * on it. That allows us to repoint the process latch, which so far
713 : : * points to process local one, to the shared one.
714 : : */
715 : 4442 : OwnLatch(&MyProc->procLatch);
716 : 4442 : SwitchToSharedLatch();
717 : :
718 : : /* now that we have a proc, report wait events to shared memory */
719 : 4442 : pgstat_set_wait_event_storage(&MyProc->wait_event_info);
720 : :
721 : : /* Check that group locking fields are in a proper initial state. */
722 : : Assert(MyProc->lockGroupLeader == NULL);
723 : : Assert(dlist_is_empty(&MyProc->lockGroupMembers));
724 : :
725 : : /*
726 : : * We might be reusing a semaphore that belonged to a failed process. So
727 : : * be careful and reinitialize its value here. (This is not strictly
728 : : * necessary anymore, but seems like a good idea for cleanliness.)
729 : : */
730 : 4442 : PGSemaphoreReset(MyProc->sem);
731 : :
732 : : /* Some aux processes are also advertised in ProcGlobal */
733 [ + + ]: 4442 : if (MyBackendType == B_WAL_WRITER)
734 : 576 : pg_atomic_write_u32(&ProcGlobal->walwriterProc, MyProcNumber);
735 [ + + ]: 4442 : if (MyBackendType == B_CHECKPOINTER)
736 : 642 : pg_atomic_write_u32(&ProcGlobal->checkpointerProc, MyProcNumber);
737 : :
738 : : /*
739 : : * Arrange to clean up at process exit.
740 : : */
741 : 4442 : on_shmem_exit(AuxiliaryProcKill, Int32GetDatum(proctype));
742 : :
743 : : /*
744 : : * Now that we have a PGPROC, we could try to acquire lightweight locks.
745 : : * Initialize local state needed for them. (Heavyweight locks cannot be
746 : : * acquired in aux processes.)
747 : : */
748 : 4442 : InitLWLockAccess();
749 : :
750 : : #ifdef EXEC_BACKEND
751 : :
752 : : /*
753 : : * Initialize backend-local pointers to all the shared data structures.
754 : : * (We couldn't do this until now because it needs LWLocks.)
755 : : */
756 : : if (IsUnderPostmaster)
757 : : AttachSharedMemoryStructs();
758 : : #endif
759 : 4442 : }
760 : :
761 : : /*
762 : : * Used from bufmgr to share the value of the buffer that Startup waits on,
763 : : * or to reset the value to "not waiting" (-1). This allows processing
764 : : * of recovery conflicts for buffer pins. Set is made before backends look
765 : : * at this value, so locking not required, especially since the set is
766 : : * an atomic integer set operation.
767 : : */
768 : : void
769 : 18 : SetStartupBufferPinWaitBufId(int bufid)
770 : : {
771 : : /* use volatile pointer to prevent code rearrangement */
772 : 18 : volatile PROC_HDR *procglobal = ProcGlobal;
773 : :
774 : 18 : procglobal->startupBufferPinWaitBufId = bufid;
775 : 18 : }
776 : :
777 : : /*
778 : : * Used by backends when they receive a request to check for buffer pin waits.
779 : : */
780 : : int
781 : 3 : GetStartupBufferPinWaitBufId(void)
782 : : {
783 : : /* use volatile pointer to prevent code rearrangement */
784 : 3 : volatile PROC_HDR *procglobal = ProcGlobal;
785 : :
786 : 3 : return procglobal->startupBufferPinWaitBufId;
787 : : }
788 : :
789 : : /*
790 : : * Check whether there are at least N free PGPROC objects. If false is
791 : : * returned, *nfree will be set to the number of free PGPROC objects.
792 : : * Otherwise, *nfree will be set to n.
793 : : *
794 : : * Note: this is designed on the assumption that N will generally be small.
795 : : */
796 : : bool
797 : 284 : HaveNFreeProcs(int n, int *nfree)
798 : : {
799 : : dlist_iter iter;
800 : :
801 : : Assert(n > 0);
802 : : Assert(nfree);
803 : :
804 : 284 : SpinLockAcquire(&ProcGlobal->freeProcsLock);
805 : :
806 : 284 : *nfree = 0;
807 [ + - + + ]: 849 : dlist_foreach(iter, &ProcGlobal->freeProcs)
808 : : {
809 : 845 : (*nfree)++;
810 [ + + ]: 845 : if (*nfree == n)
811 : 280 : break;
812 : : }
813 : :
814 : 284 : SpinLockRelease(&ProcGlobal->freeProcsLock);
815 : :
816 : 284 : return (*nfree == n);
817 : : }
818 : :
819 : : /*
820 : : * Cancel any pending wait for lock, when aborting a transaction, and revert
821 : : * any strong lock count acquisition for a lock being acquired.
822 : : *
823 : : * (Normally, this would only happen if we accept a cancel/die
824 : : * interrupt while waiting; but an ereport(ERROR) before or during the lock
825 : : * wait is within the realm of possibility, too.)
826 : : */
827 : : void
828 : 711102 : LockErrorCleanup(void)
829 : : {
830 : : LOCALLOCK *lockAwaited;
831 : : LWLock *partitionLock;
832 : : DisableTimeoutParams timeouts[2];
833 : :
834 : 711102 : HOLD_INTERRUPTS();
835 : :
836 : 711102 : AbortStrongLockAcquire();
837 : :
838 : : /* Nothing to do if we weren't waiting for a lock */
839 : 711102 : lockAwaited = GetAwaitedLock();
840 [ + + ]: 711102 : if (lockAwaited == NULL)
841 : : {
842 : 711060 : RESUME_INTERRUPTS();
843 : 711060 : return;
844 : : }
845 : :
846 : : /*
847 : : * Turn off the deadlock and lock timeout timers, if they are still
848 : : * running (see ProcSleep). Note we must preserve the LOCK_TIMEOUT
849 : : * indicator flag, since this function is executed before
850 : : * ProcessInterrupts when responding to SIGINT; else we'd lose the
851 : : * knowledge that the SIGINT came from a lock timeout and not an external
852 : : * source.
853 : : */
854 : 42 : timeouts[0].id = DEADLOCK_TIMEOUT;
855 : 42 : timeouts[0].keep_indicator = false;
856 : 42 : timeouts[1].id = LOCK_TIMEOUT;
857 : 42 : timeouts[1].keep_indicator = true;
858 : 42 : disable_timeouts(timeouts, 2);
859 : :
860 : : /* Unlink myself from the wait queue, if on it (might not be anymore!) */
861 : 42 : partitionLock = LockHashPartitionLock(lockAwaited->hashcode);
862 : 42 : LWLockAcquire(partitionLock, LW_EXCLUSIVE);
863 : :
864 [ + + ]: 42 : if (!dlist_node_is_detached(&MyProc->waitLink))
865 : : {
866 : : /* We could not have been granted the lock yet */
867 : 41 : RemoveFromWaitQueue(MyProc, lockAwaited->hashcode);
868 : : }
869 : : else
870 : : {
871 : : /*
872 : : * Somebody kicked us off the lock queue already. Perhaps they
873 : : * granted us the lock, or perhaps they detected a deadlock. If they
874 : : * did grant us the lock, we'd better remember it in our local lock
875 : : * table.
876 : : */
877 [ + - ]: 1 : if (MyProc->waitStatus == PROC_WAIT_STATUS_OK)
878 : 1 : GrantAwaitedLock();
879 : : }
880 : :
881 : 42 : ResetAwaitedLock();
882 : :
883 : 42 : LWLockRelease(partitionLock);
884 : :
885 : 42 : RESUME_INTERRUPTS();
886 : : }
887 : :
888 : :
889 : : /*
890 : : * ProcReleaseLocks() -- release locks associated with current transaction
891 : : * at main transaction commit or abort
892 : : *
893 : : * At main transaction commit, we release standard locks except session locks.
894 : : * At main transaction abort, we release all locks including session locks.
895 : : *
896 : : * Advisory locks are released only if they are transaction-level;
897 : : * session-level holds remain, whether this is a commit or not.
898 : : *
899 : : * At subtransaction commit, we don't release any locks (so this func is not
900 : : * needed at all); we will defer the releasing to the parent transaction.
901 : : * At subtransaction abort, we release all locks held by the subtransaction;
902 : : * this is implemented by retail releasing of the locks under control of
903 : : * the ResourceOwner mechanism.
904 : : */
905 : : void
906 : 668841 : ProcReleaseLocks(bool isCommit)
907 : : {
908 [ - + ]: 668841 : if (!MyProc)
909 : 0 : return;
910 : : /* If waiting, get off wait queue (should only be needed after error) */
911 : 668841 : LockErrorCleanup();
912 : : /* Release standard locks, including session-level if aborting */
913 : 668841 : LockReleaseAll(DEFAULT_LOCKMETHOD, !isCommit);
914 : : /* Release transaction-level advisory locks */
915 : 668841 : LockReleaseAll(USER_LOCKMETHOD, false);
916 : : }
917 : :
918 : :
919 : : /*
920 : : * RemoveProcFromArray() -- Remove this process from the shared ProcArray.
921 : : */
922 : : static void
923 : 20581 : RemoveProcFromArray(int code, Datum arg)
924 : : {
925 : : Assert(MyProc != NULL);
926 : 20581 : ProcArrayRemove(MyProc, InvalidTransactionId);
927 : 20581 : }
928 : :
929 : : /*
930 : : * ProcKill() -- Destroy the per-proc data structure for
931 : : * this process. Release any of its held LW locks.
932 : : */
933 : : static void
934 : 20594 : ProcKill(int code, Datum arg)
935 : : {
936 : : PGPROC *proc;
937 : : PGPROC *leader;
938 : : dlist_head *procgloballist;
939 : : bool push_leader;
940 : : bool push_self;
941 : :
942 : : Assert(MyProc != NULL);
943 : :
944 : : /* not safe if forked by system(), etc. */
945 [ - + ]: 20594 : if (MyProc->pid != (int) getpid())
946 [ # # ]: 0 : elog(PANIC, "ProcKill() called in child process");
947 : :
948 : : /* Make sure we're out of the sync rep lists */
949 : 20594 : SyncRepCleanupAtProcExit();
950 : :
951 : : #ifdef USE_ASSERT_CHECKING
952 : : {
953 : : int i;
954 : :
955 : : /* Last process should have released all locks. */
956 : : for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
957 : : Assert(dlist_is_empty(&(MyProc->myProcLocks[i])));
958 : : }
959 : : #endif
960 : :
961 : : /*
962 : : * Release any LW locks I am holding. There really shouldn't be any, but
963 : : * it's cheap to check again before we cut the knees off the LWLock
964 : : * facility by releasing our PGPROC ...
965 : : */
966 : 20594 : LWLockReleaseAll();
967 : :
968 : : /*
969 : : * Cleanup waiting for LSN if any.
970 : : */
971 : 20594 : WaitLSNCleanup();
972 : :
973 : : /* Cancel any pending condition variable sleep, too */
974 : 20594 : ConditionVariableCancelSleep();
975 : :
976 : : /*
977 : : * Reset MyLatch to the process local one and disown the shared latch, so
978 : : * that signal handlers et al can continue using the latch after the
979 : : * shared latch isn't ours anymore.
980 : : *
981 : : * DisownLatch() must happen before our PGPROC can appear on a freelist: a
982 : : * newly-forked backend that pops our slot and calls OwnLatch() would
983 : : * PANIC on a still-owned latch.
984 : : *
985 : : * pgstat_reset_wait_event_storage() is intentionally deferred until after
986 : : * the lock-group block so that wait_event_info remains visible in our
987 : : * PGPROC slot while we may be observed there. It is safe to defer
988 : : * because our slot is not yet on any freelist at this point, and useful
989 : : * for testing purposes.
990 : : */
991 : 20594 : SwitchBackToLocalLatch();
992 : 20594 : DisownLatch(&MyProc->procLatch);
993 : :
994 [ + + ]: 20594 : if (MyBackendType == B_AUTOVAC_LAUNCHER)
995 : : {
996 : : Assert(pg_atomic_read_u32(&ProcGlobal->avLauncherProc) == MyProcNumber);
997 : 480 : pg_atomic_write_u32(&ProcGlobal->avLauncherProc, INVALID_PROC_NUMBER);
998 : : }
999 : :
1000 : 20594 : proc = MyProc;
1001 : 20594 : procgloballist = proc->procgloballist;
1002 : :
1003 : : /*
1004 : : * Detach from any lock group of which we are a member, deciding under
1005 : : * leader_lwlock whether we (via push_self) and/or the leader (via
1006 : : * push_leader) need to be pushed onto a freelist. The actual pushes
1007 : : * happen after evaluating if any of these are required, under a single
1008 : : * ProcGlobal->freeProcsLock.
1009 : : *
1010 : : * The decision whether any of the freelists needs to be updated is taken
1011 : : * under a single leader_lwlock.
1012 : : */
1013 : 20594 : push_leader = false;
1014 : 20594 : push_self = true;
1015 : 20594 : leader = NULL;
1016 : :
1017 [ + + ]: 20594 : if (proc->lockGroupLeader != NULL)
1018 : : {
1019 : : LWLock *leader_lwlock;
1020 : :
1021 : 2142 : leader = proc->lockGroupLeader;
1022 : 2142 : leader_lwlock = LockHashPartitionLockByProc(leader);
1023 : :
1024 : 2142 : LWLockAcquire(leader_lwlock, LW_EXCLUSIVE);
1025 : : Assert(!dlist_is_empty(&leader->lockGroupMembers));
1026 : 2142 : dlist_delete(&proc->lockGroupLink);
1027 [ + + ]: 2142 : if (dlist_is_empty(&leader->lockGroupMembers))
1028 : : {
1029 : 124 : leader->lockGroupLeader = NULL;
1030 [ - + ]: 124 : if (leader != proc)
1031 : : {
1032 : : /*
1033 : : * We are the last follower and the leader exited earlier; its
1034 : : * PGPROC is still allocated and must be pushed here.
1035 : : */
1036 : 0 : push_leader = true;
1037 : 0 : proc->lockGroupLeader = NULL;
1038 : : }
1039 : : }
1040 [ + - ]: 2018 : else if (leader != proc)
1041 : : {
1042 : : /* Non-last follower; leader still present in the group. */
1043 : 2018 : proc->lockGroupLeader = NULL;
1044 : : }
1045 : : else
1046 : : {
1047 : : /*
1048 : : * We are the leader and followers remain. Skip our own push; the
1049 : : * last follower to exit will push us back to the freelist.
1050 : : */
1051 : 0 : push_self = false;
1052 : : }
1053 : 2142 : LWLockRelease(leader_lwlock);
1054 : : }
1055 : :
1056 : : /* See comment above, close to DisownLatch() */
1057 : 20594 : pgstat_reset_wait_event_storage();
1058 : :
1059 : 20594 : MyProc = NULL;
1060 : 20594 : MyProcNumber = INVALID_PROC_NUMBER;
1061 : :
1062 : : /* Mark the proc no longer in use */
1063 : 20594 : proc->pid = 0;
1064 : 20594 : proc->vxid.procNumber = INVALID_PROC_NUMBER;
1065 : 20594 : proc->vxid.lxid = InvalidTransactionId;
1066 : :
1067 : 20594 : SpinLockAcquire(&ProcGlobal->freeProcsLock);
1068 [ - + ]: 20594 : if (push_leader)
1069 : : {
1070 : : /* Return leader PGPROC (and semaphore) to appropriate freelist */
1071 : 0 : dlist_push_head(leader->procgloballist, &leader->freeProcsLink);
1072 : : }
1073 [ + - ]: 20594 : if (push_self)
1074 : : {
1075 : : Assert(proc->lockGroupLeader == NULL);
1076 : : /* Since lockGroupLeader is NULL, lockGroupMembers should be empty. */
1077 : : Assert(dlist_is_empty(&proc->lockGroupMembers));
1078 : :
1079 : : /* Return PGPROC structure (and semaphore) to appropriate freelist */
1080 : 20594 : dlist_push_tail(procgloballist, &proc->freeProcsLink);
1081 : : }
1082 : :
1083 : : /* Update shared estimate of spins_per_delay */
1084 : 20594 : ProcGlobal->spins_per_delay = update_spins_per_delay(ProcGlobal->spins_per_delay);
1085 : :
1086 : 20594 : SpinLockRelease(&ProcGlobal->freeProcsLock);
1087 : 20594 : }
1088 : :
1089 : : /*
1090 : : * AuxiliaryProcKill() -- Cut-down version of ProcKill for auxiliary
1091 : : * processes (bgwriter, etc). The PGPROC and sema are not released, only
1092 : : * marked as not-in-use.
1093 : : */
1094 : : static void
1095 : 4442 : AuxiliaryProcKill(int code, Datum arg)
1096 : : {
1097 : 4442 : int proctype = DatumGetInt32(arg);
1098 : : PGPROC *auxproc PG_USED_FOR_ASSERTS_ONLY;
1099 : : PGPROC *proc;
1100 : :
1101 : : Assert(proctype >= 0 && proctype < NUM_AUXILIARY_PROCS);
1102 : :
1103 : : /* not safe if forked by system(), etc. */
1104 [ - + ]: 4442 : if (MyProc->pid != (int) getpid())
1105 [ # # ]: 0 : elog(PANIC, "AuxiliaryProcKill() called in child process");
1106 : :
1107 : 4442 : auxproc = &AuxiliaryProcs[proctype];
1108 : :
1109 : : Assert(MyProc == auxproc);
1110 : :
1111 : : /* Release any LW locks I am holding (see notes above) */
1112 : 4442 : LWLockReleaseAll();
1113 : :
1114 : : /* Cancel any pending condition variable sleep, too */
1115 : 4442 : ConditionVariableCancelSleep();
1116 : :
1117 : : /* look at the equivalent ProcKill() code for comments */
1118 : 4442 : SwitchBackToLocalLatch();
1119 : 4442 : pgstat_reset_wait_event_storage();
1120 : :
1121 : : /*
1122 : : * If this was one of the aux processes advertised in ProcGlobal, clear it
1123 : : */
1124 [ + + ]: 4442 : if (MyBackendType == B_WAL_WRITER)
1125 : : {
1126 : : Assert(pg_atomic_read_u32(&ProcGlobal->walwriterProc) == MyProcNumber);
1127 : 576 : pg_atomic_write_u32(&ProcGlobal->walwriterProc, INVALID_PROC_NUMBER);
1128 : : }
1129 [ + + ]: 4442 : if (MyBackendType == B_CHECKPOINTER)
1130 : : {
1131 : : Assert(pg_atomic_read_u32(&ProcGlobal->checkpointerProc) == MyProcNumber);
1132 : 642 : pg_atomic_write_u32(&ProcGlobal->checkpointerProc, INVALID_PROC_NUMBER);
1133 : : }
1134 : :
1135 : 4442 : proc = MyProc;
1136 : 4442 : MyProc = NULL;
1137 : 4442 : MyProcNumber = INVALID_PROC_NUMBER;
1138 : 4442 : DisownLatch(&proc->procLatch);
1139 : :
1140 : 4442 : SpinLockAcquire(&ProcGlobal->freeProcsLock);
1141 : :
1142 : : /* Mark auxiliary proc no longer in use */
1143 : 4442 : proc->pid = 0;
1144 : 4442 : proc->vxid.procNumber = INVALID_PROC_NUMBER;
1145 : 4442 : proc->vxid.lxid = InvalidTransactionId;
1146 : :
1147 : : /* Update shared estimate of spins_per_delay */
1148 : 4442 : ProcGlobal->spins_per_delay = update_spins_per_delay(ProcGlobal->spins_per_delay);
1149 : :
1150 : 4442 : SpinLockRelease(&ProcGlobal->freeProcsLock);
1151 : 4442 : }
1152 : :
1153 : : /*
1154 : : * AuxiliaryPidGetProc -- get PGPROC for an auxiliary process
1155 : : * given its PID
1156 : : *
1157 : : * Returns NULL if not found.
1158 : : */
1159 : : PGPROC *
1160 : 3810 : AuxiliaryPidGetProc(int pid)
1161 : : {
1162 : 3810 : PGPROC *result = NULL;
1163 : : int index;
1164 : :
1165 [ + + ]: 3810 : if (pid == 0) /* never match dummy PGPROCs */
1166 : 4 : return NULL;
1167 : :
1168 [ + - ]: 14191 : for (index = 0; index < NUM_AUXILIARY_PROCS; index++)
1169 : : {
1170 : 14191 : PGPROC *proc = &AuxiliaryProcs[index];
1171 : :
1172 [ + + ]: 14191 : if (proc->pid == pid)
1173 : : {
1174 : 3806 : result = proc;
1175 : 3806 : break;
1176 : : }
1177 : : }
1178 : 3806 : return result;
1179 : : }
1180 : :
1181 : :
1182 : : /*
1183 : : * JoinWaitQueue -- join the wait queue on the specified lock
1184 : : *
1185 : : * It's not actually guaranteed that we need to wait when this function is
1186 : : * called, because it could be that when we try to find a position at which
1187 : : * to insert ourself into the wait queue, we discover that we must be inserted
1188 : : * ahead of everyone who wants a lock that conflict with ours. In that case,
1189 : : * we get the lock immediately. Because of this, it's sensible for this function
1190 : : * to have a dontWait argument, despite the name.
1191 : : *
1192 : : * On entry, the caller has already set up LOCK and PROCLOCK entries to
1193 : : * reflect that we have "requested" the lock. The caller is responsible for
1194 : : * cleaning that up, if we end up not joining the queue after all.
1195 : : *
1196 : : * The lock table's partition lock must be held at entry, and is still held
1197 : : * at exit. The caller must release it before calling ProcSleep().
1198 : : *
1199 : : * Result is one of the following:
1200 : : *
1201 : : * PROC_WAIT_STATUS_OK - lock was immediately granted
1202 : : * PROC_WAIT_STATUS_WAITING - joined the wait queue; call ProcSleep()
1203 : : * PROC_WAIT_STATUS_ERROR - immediate deadlock was detected, or would
1204 : : * need to wait and dontWait == true
1205 : : *
1206 : : * NOTES: The process queue is now a priority queue for locking.
1207 : : */
1208 : : ProcWaitStatus
1209 : 2206 : JoinWaitQueue(LOCALLOCK *locallock, LockMethod lockMethodTable, bool dontWait)
1210 : : {
1211 : 2206 : LOCKMODE lockmode = locallock->tag.mode;
1212 : 2206 : LOCK *lock = locallock->lock;
1213 : 2206 : PROCLOCK *proclock = locallock->proclock;
1214 : 2206 : uint32 hashcode = locallock->hashcode;
1215 : 2206 : LWLock *partitionLock PG_USED_FOR_ASSERTS_ONLY = LockHashPartitionLock(hashcode);
1216 : 2206 : dclist_head *waitQueue = &lock->waitProcs;
1217 : 2206 : PGPROC *insert_before = NULL;
1218 : : LOCKMASK myProcHeldLocks;
1219 : : LOCKMASK myHeldLocks;
1220 : 2206 : bool early_deadlock = false;
1221 : 2206 : PGPROC *leader = MyProc->lockGroupLeader;
1222 : :
1223 : : Assert(LWLockHeldByMeInMode(partitionLock, LW_EXCLUSIVE));
1224 : :
1225 : : /*
1226 : : * Set bitmask of locks this process already holds on this object.
1227 : : */
1228 : 2206 : myHeldLocks = MyProc->heldLocks = proclock->holdMask;
1229 : :
1230 : : /*
1231 : : * Determine which locks we're already holding.
1232 : : *
1233 : : * If group locking is in use, locks held by members of my locking group
1234 : : * need to be included in myHeldLocks. This is not required for relation
1235 : : * extension lock which conflict among group members. However, including
1236 : : * them in myHeldLocks will give group members the priority to get those
1237 : : * locks as compared to other backends which are also trying to acquire
1238 : : * those locks. OTOH, we can avoid giving priority to group members for
1239 : : * that kind of locks, but there doesn't appear to be a clear advantage of
1240 : : * the same.
1241 : : */
1242 : 2206 : myProcHeldLocks = proclock->holdMask;
1243 : 2206 : myHeldLocks = myProcHeldLocks;
1244 [ + + ]: 2206 : if (leader != NULL)
1245 : : {
1246 : : dlist_iter iter;
1247 : :
1248 [ + - + + ]: 42 : dlist_foreach(iter, &lock->procLocks)
1249 : : {
1250 : : PROCLOCK *otherproclock;
1251 : :
1252 : 31 : otherproclock = dlist_container(PROCLOCK, lockLink, iter.cur);
1253 : :
1254 [ + + ]: 31 : if (otherproclock->groupLeader == leader)
1255 : 15 : myHeldLocks |= otherproclock->holdMask;
1256 : : }
1257 : : }
1258 : :
1259 : : /*
1260 : : * Determine where to add myself in the wait queue.
1261 : : *
1262 : : * Normally I should go at the end of the queue. However, if I already
1263 : : * hold locks that conflict with the request of any previous waiter, put
1264 : : * myself in the queue just in front of the first such waiter. This is not
1265 : : * a necessary step, since deadlock detection would move me to before that
1266 : : * waiter anyway; but it's relatively cheap to detect such a conflict
1267 : : * immediately, and avoid delaying till deadlock timeout.
1268 : : *
1269 : : * Special case: if I find I should go in front of some waiter, check to
1270 : : * see if I conflict with already-held locks or the requests before that
1271 : : * waiter. If not, then just grant myself the requested lock immediately.
1272 : : * This is the same as the test for immediate grant in LockAcquire, except
1273 : : * we are only considering the part of the wait queue before my insertion
1274 : : * point.
1275 : : */
1276 [ + + + + ]: 2206 : if (myHeldLocks != 0 && !dclist_is_empty(waitQueue))
1277 : : {
1278 : 7 : LOCKMASK aheadRequests = 0;
1279 : : dlist_iter iter;
1280 : :
1281 [ + - + - ]: 7 : dclist_foreach(iter, waitQueue)
1282 : : {
1283 : 7 : PGPROC *proc = dlist_container(PGPROC, waitLink, iter.cur);
1284 : :
1285 : : /*
1286 : : * If we're part of the same locking group as this waiter, its
1287 : : * locks neither conflict with ours nor contribute to
1288 : : * aheadRequests.
1289 : : */
1290 [ - + - - ]: 7 : if (leader != NULL && leader == proc->lockGroupLeader)
1291 : 0 : continue;
1292 : :
1293 : : /* Must he wait for me? */
1294 [ + - ]: 7 : if (lockMethodTable->conflictTab[proc->waitLockMode] & myHeldLocks)
1295 : : {
1296 : : /* Must I wait for him ? */
1297 [ + + ]: 7 : if (lockMethodTable->conflictTab[lockmode] & proc->heldLocks)
1298 : : {
1299 : : /*
1300 : : * Yes, so we have a deadlock. Easiest way to clean up
1301 : : * correctly is to call RemoveFromWaitQueue(), but we
1302 : : * can't do that until we are *on* the wait queue. So, set
1303 : : * a flag to check below, and break out of loop. Also,
1304 : : * record deadlock info for later message.
1305 : : */
1306 : 1 : RememberSimpleDeadLock(MyProc, lockmode, lock, proc);
1307 : 1 : early_deadlock = true;
1308 : 1 : break;
1309 : : }
1310 : : /* I must go before this waiter. Check special case. */
1311 [ + - ]: 6 : if ((lockMethodTable->conflictTab[lockmode] & aheadRequests) == 0 &&
1312 [ + - ]: 6 : !LockCheckConflicts(lockMethodTable, lockmode, lock,
1313 : : proclock))
1314 : : {
1315 : : /* Skip the wait and just grant myself the lock. */
1316 : 6 : GrantLock(lock, proclock, lockmode);
1317 : 6 : return PROC_WAIT_STATUS_OK;
1318 : : }
1319 : :
1320 : : /* Put myself into wait queue before conflicting process */
1321 : 0 : insert_before = proc;
1322 : 0 : break;
1323 : : }
1324 : : /* Nope, so advance to next waiter */
1325 : 0 : aheadRequests |= LOCKBIT_ON(proc->waitLockMode);
1326 : : }
1327 : : }
1328 : :
1329 : : /*
1330 : : * If we detected deadlock, give up without waiting. This must agree with
1331 : : * CheckDeadLock's recovery code.
1332 : : */
1333 [ + + ]: 2200 : if (early_deadlock)
1334 : 1 : return PROC_WAIT_STATUS_ERROR;
1335 : :
1336 : : /*
1337 : : * At this point we know that we'd really need to sleep. If we've been
1338 : : * commanded not to do that, bail out.
1339 : : */
1340 [ + + ]: 2199 : if (dontWait)
1341 : 735 : return PROC_WAIT_STATUS_ERROR;
1342 : :
1343 : : /*
1344 : : * Insert self into queue, at the position determined above.
1345 : : */
1346 [ - + ]: 1464 : if (insert_before)
1347 : 0 : dclist_insert_before(waitQueue, &insert_before->waitLink, &MyProc->waitLink);
1348 : : else
1349 : 1464 : dclist_push_tail(waitQueue, &MyProc->waitLink);
1350 : :
1351 : 1464 : lock->waitMask |= LOCKBIT_ON(lockmode);
1352 : :
1353 : : /* Set up wait information in PGPROC object, too */
1354 : 1464 : MyProc->heldLocks = myProcHeldLocks;
1355 : 1464 : MyProc->waitLock = lock;
1356 : 1464 : MyProc->waitProcLock = proclock;
1357 : 1464 : MyProc->waitLockMode = lockmode;
1358 : :
1359 : 1464 : MyProc->waitStatus = PROC_WAIT_STATUS_WAITING;
1360 : :
1361 : 1464 : return PROC_WAIT_STATUS_WAITING;
1362 : : }
1363 : :
1364 : : /*
1365 : : * ProcSleep -- put process to sleep waiting on lock
1366 : : *
1367 : : * This must be called when JoinWaitQueue() returns PROC_WAIT_STATUS_WAITING.
1368 : : * Returns after the lock has been granted, or if a deadlock is detected. Can
1369 : : * also bail out with ereport(ERROR), if some other error condition, or a
1370 : : * timeout or cancellation is triggered.
1371 : : *
1372 : : * Result is one of the following:
1373 : : *
1374 : : * PROC_WAIT_STATUS_OK - lock was granted
1375 : : * PROC_WAIT_STATUS_ERROR - a deadlock was detected
1376 : : */
1377 : : ProcWaitStatus
1378 : 1464 : ProcSleep(LOCALLOCK *locallock)
1379 : : {
1380 : 1464 : LOCKMODE lockmode = locallock->tag.mode;
1381 : 1464 : LOCK *lock = locallock->lock;
1382 : 1464 : uint32 hashcode = locallock->hashcode;
1383 : 1464 : LWLock *partitionLock = LockHashPartitionLock(hashcode);
1384 : 1464 : TimestampTz standbyWaitStart = 0;
1385 : 1464 : bool allow_autovacuum_cancel = true;
1386 : 1464 : bool logged_recovery_conflict = false;
1387 : 1464 : bool logged_lock_wait = false;
1388 : : ProcWaitStatus myWaitStatus;
1389 : : DeadLockState deadlock_state;
1390 : :
1391 : : /* The caller must've armed the on-error cleanup mechanism */
1392 : : Assert(GetAwaitedLock() == locallock);
1393 : : Assert(!LWLockHeldByMe(partitionLock));
1394 : :
1395 : : /*
1396 : : * Now that we will successfully clean up after an ereport, it's safe to
1397 : : * check to see if there's a buffer pin deadlock against the Startup
1398 : : * process. Of course, that's only necessary if we're doing Hot Standby
1399 : : * and are not the Startup process ourselves.
1400 : : */
1401 [ + + + + ]: 1464 : if (RecoveryInProgress() && !InRecovery)
1402 : 1 : CheckRecoveryConflictDeadlock();
1403 : :
1404 : : /* Reset deadlock_state before enabling the timeout handler */
1405 : 1464 : deadlock_state = DS_NOT_YET_CHECKED;
1406 : 1464 : got_deadlock_timeout = false;
1407 : :
1408 : : /*
1409 : : * Set timer so we can wake up after awhile and check for a deadlock. If a
1410 : : * deadlock is detected, the handler sets MyProc->waitStatus =
1411 : : * PROC_WAIT_STATUS_ERROR, allowing us to know that we must report failure
1412 : : * rather than success.
1413 : : *
1414 : : * By delaying the check until we've waited for a bit, we can avoid
1415 : : * running the rather expensive deadlock-check code in most cases.
1416 : : *
1417 : : * If LockTimeout is set, also enable the timeout for that. We can save a
1418 : : * few cycles by enabling both timeout sources in one call.
1419 : : *
1420 : : * If InHotStandby we set lock waits slightly later for clarity with other
1421 : : * code.
1422 : : */
1423 [ + + ]: 1464 : if (!InHotStandby)
1424 : : {
1425 [ + + ]: 1463 : if (LockTimeout > 0)
1426 : : {
1427 : : EnableTimeoutParams timeouts[2];
1428 : :
1429 : 114 : timeouts[0].id = DEADLOCK_TIMEOUT;
1430 : 114 : timeouts[0].type = TMPARAM_AFTER;
1431 : 114 : timeouts[0].delay_ms = DeadlockTimeout;
1432 : 114 : timeouts[1].id = LOCK_TIMEOUT;
1433 : 114 : timeouts[1].type = TMPARAM_AFTER;
1434 : 114 : timeouts[1].delay_ms = LockTimeout;
1435 : 114 : enable_timeouts(timeouts, 2);
1436 : : }
1437 : : else
1438 : 1349 : enable_timeout_after(DEADLOCK_TIMEOUT, DeadlockTimeout);
1439 : :
1440 : : /*
1441 : : * Use the current time obtained for the deadlock timeout timer as
1442 : : * waitStart (i.e., the time when this process started waiting for the
1443 : : * lock). Since getting the current time newly can cause overhead, we
1444 : : * reuse the already-obtained time to avoid that overhead.
1445 : : *
1446 : : * Note that waitStart is updated without holding the lock table's
1447 : : * partition lock, to avoid the overhead by additional lock
1448 : : * acquisition. This can cause "waitstart" in pg_locks to become NULL
1449 : : * for a very short period of time after the wait started even though
1450 : : * "granted" is false. This is OK in practice because we can assume
1451 : : * that users are likely to look at "waitstart" when waiting for the
1452 : : * lock for a long time.
1453 : : */
1454 : 1463 : pg_atomic_write_u64(&MyProc->waitStart,
1455 : 1463 : get_timeout_start_time(DEADLOCK_TIMEOUT));
1456 : : }
1457 [ + - ]: 1 : else if (log_recovery_conflict_waits)
1458 : : {
1459 : : /*
1460 : : * Set the wait start timestamp if logging is enabled and in hot
1461 : : * standby.
1462 : : */
1463 : 1 : standbyWaitStart = GetCurrentTimestamp();
1464 : : }
1465 : :
1466 : : /*
1467 : : * If somebody wakes us between LWLockRelease and WaitLatch, the latch
1468 : : * will not wait. But a set latch does not necessarily mean that the lock
1469 : : * is free now, as there are many other sources for latch sets than
1470 : : * somebody releasing the lock.
1471 : : *
1472 : : * We process interrupts whenever the latch has been set, so cancel/die
1473 : : * interrupts are processed quickly. This means we must not mind losing
1474 : : * control to a cancel/die interrupt here. We don't, because we have no
1475 : : * shared-state-change work to do after being granted the lock (the
1476 : : * grantor did it all). We do have to worry about canceling the deadlock
1477 : : * timeout and updating the locallock table, but if we lose control to an
1478 : : * error, LockErrorCleanup will fix that up.
1479 : : */
1480 : : do
1481 : : {
1482 [ + + ]: 3497 : if (InHotStandby)
1483 : : {
1484 : 4 : bool maybe_log_conflict =
1485 [ + - + + ]: 4 : (standbyWaitStart != 0 && !logged_recovery_conflict);
1486 : :
1487 : : /* Set a timer and wait for that or for the lock to be granted */
1488 : 4 : ResolveRecoveryConflictWithLock(locallock->tag.lock,
1489 : : maybe_log_conflict);
1490 : :
1491 : : /*
1492 : : * Emit the log message if the startup process is waiting longer
1493 : : * than deadlock_timeout for recovery conflict on lock.
1494 : : */
1495 [ + + ]: 4 : if (maybe_log_conflict)
1496 : : {
1497 : 2 : TimestampTz now = GetCurrentTimestamp();
1498 : :
1499 [ + + ]: 2 : if (TimestampDifferenceExceeds(standbyWaitStart, now,
1500 : : DeadlockTimeout))
1501 : : {
1502 : : VirtualTransactionId *vxids;
1503 : : int cnt;
1504 : :
1505 : 1 : vxids = GetLockConflicts(&locallock->tag.lock,
1506 : : AccessExclusiveLock, &cnt);
1507 : :
1508 : : /*
1509 : : * Log the recovery conflict and the list of PIDs of
1510 : : * backends holding the conflicting lock. Note that we do
1511 : : * logging even if there are no such backends right now
1512 : : * because the startup process here has already waited
1513 : : * longer than deadlock_timeout.
1514 : : */
1515 : 1 : LogRecoveryConflict(RECOVERY_CONFLICT_LOCK,
1516 : : standbyWaitStart, now,
1517 [ + - ]: 1 : cnt > 0 ? vxids : NULL, true);
1518 : 1 : logged_recovery_conflict = true;
1519 : : }
1520 : : }
1521 : : }
1522 : : else
1523 : : {
1524 : 3493 : (void) WaitLatch(MyLatch, WL_LATCH_SET | WL_EXIT_ON_PM_DEATH, 0,
1525 : 3493 : PG_WAIT_LOCK | locallock->tag.lock.locktag_type);
1526 : 3493 : ResetLatch(MyLatch);
1527 : : /* check for deadlocks first, as that's probably log-worthy */
1528 [ + + ]: 3493 : if (got_deadlock_timeout)
1529 : : {
1530 : 35 : deadlock_state = CheckDeadLock();
1531 : 35 : got_deadlock_timeout = false;
1532 : : }
1533 [ + + ]: 3493 : CHECK_FOR_INTERRUPTS();
1534 : : }
1535 : :
1536 : : /*
1537 : : * waitStatus could change from PROC_WAIT_STATUS_WAITING to something
1538 : : * else asynchronously. Read it just once per loop to prevent
1539 : : * surprising behavior (such as missing log messages).
1540 : : */
1541 : 3454 : myWaitStatus = *((volatile ProcWaitStatus *) &MyProc->waitStatus);
1542 : :
1543 : : /*
1544 : : * If we are not deadlocked, but are waiting on an autovacuum-induced
1545 : : * task, send a signal to interrupt it.
1546 : : */
1547 [ - + - - ]: 3454 : if (deadlock_state == DS_BLOCKED_BY_AUTOVACUUM && allow_autovacuum_cancel)
1548 : : {
1549 : 0 : PGPROC *autovac = GetBlockingAutoVacuumPgproc();
1550 : : uint8 statusFlags;
1551 : : uint8 lockmethod_copy;
1552 : : LOCKTAG locktag_copy;
1553 : :
1554 : : /*
1555 : : * Grab info we need, then release lock immediately. Note this
1556 : : * coding means that there is a tiny chance that the process
1557 : : * terminates its current transaction and starts a different one
1558 : : * before we have a change to send the signal; the worst possible
1559 : : * consequence is that a for-wraparound vacuum is canceled. But
1560 : : * that could happen in any case unless we were to do kill() with
1561 : : * the lock held, which is much more undesirable.
1562 : : */
1563 : 0 : LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
1564 : 0 : statusFlags = ProcGlobal->statusFlags[autovac->pgxactoff];
1565 : 0 : lockmethod_copy = lock->tag.locktag_lockmethodid;
1566 : 0 : locktag_copy = lock->tag;
1567 : 0 : LWLockRelease(ProcArrayLock);
1568 : :
1569 : : /*
1570 : : * Only do it if the worker is not working to protect against Xid
1571 : : * wraparound.
1572 : : */
1573 [ # # ]: 0 : if ((statusFlags & PROC_IS_AUTOVACUUM) &&
1574 [ # # ]: 0 : !(statusFlags & PROC_VACUUM_FOR_WRAPAROUND))
1575 : : {
1576 : 0 : int pid = autovac->pid;
1577 : :
1578 : : /* report the case, if configured to do so */
1579 [ # # ]: 0 : if (message_level_is_interesting(DEBUG1))
1580 : : {
1581 : : StringInfoData locktagbuf;
1582 : : StringInfoData logbuf; /* errdetail for server log */
1583 : :
1584 : 0 : initStringInfo(&locktagbuf);
1585 : 0 : initStringInfo(&logbuf);
1586 : 0 : DescribeLockTag(&locktagbuf, &locktag_copy);
1587 : 0 : appendStringInfo(&logbuf,
1588 : : "Process %d waits for %s on %s.",
1589 : : MyProcPid,
1590 : : GetLockmodeName(lockmethod_copy, lockmode),
1591 : : locktagbuf.data);
1592 : :
1593 [ # # ]: 0 : ereport(DEBUG1,
1594 : : (errmsg_internal("sending cancel to blocking autovacuum PID %d",
1595 : : pid),
1596 : : errdetail_log("%s", logbuf.data)));
1597 : :
1598 : 0 : pfree(locktagbuf.data);
1599 : 0 : pfree(logbuf.data);
1600 : : }
1601 : :
1602 : : /* send the autovacuum worker Back to Old Kent Road */
1603 [ # # ]: 0 : if (kill(pid, SIGINT) < 0)
1604 : : {
1605 : : /*
1606 : : * There's a race condition here: once we release the
1607 : : * ProcArrayLock, it's possible for the autovac worker to
1608 : : * close up shop and exit before we can do the kill().
1609 : : * Therefore, we do not whinge about no-such-process.
1610 : : * Other errors such as EPERM could conceivably happen if
1611 : : * the kernel recycles the PID fast enough, but such cases
1612 : : * seem improbable enough that it's probably best to issue
1613 : : * a warning if we see some other errno.
1614 : : */
1615 [ # # ]: 0 : if (errno != ESRCH)
1616 [ # # ]: 0 : ereport(WARNING,
1617 : : (errmsg("could not send signal to process %d: %m",
1618 : : pid)));
1619 : : }
1620 : : }
1621 : :
1622 : : /* prevent signal from being sent again more than once */
1623 : 0 : allow_autovacuum_cancel = false;
1624 : : }
1625 : :
1626 : : /*
1627 : : * If awoken after the deadlock check interrupt has run, increment the
1628 : : * lock statistics counters and if log_lock_waits is on, then report
1629 : : * about the wait.
1630 : : */
1631 [ + + ]: 3454 : if (deadlock_state != DS_NOT_YET_CHECKED)
1632 : : {
1633 : : long secs;
1634 : : int usecs;
1635 : : long msecs;
1636 : :
1637 : 1593 : INJECTION_POINT("deadlock-timeout-fired", NULL);
1638 : 1593 : TimestampDifference(get_timeout_start_time(DEADLOCK_TIMEOUT),
1639 : : GetCurrentTimestamp(),
1640 : : &secs, &usecs);
1641 : : /* Increment the lock statistics counters if done waiting. */
1642 [ + + ]: 1593 : if (myWaitStatus == PROC_WAIT_STATUS_OK)
1643 : 27 : pgstat_count_lock_waits(locallock->tag.lock.locktag_type,
1644 : 27 : (PgStat_Counter) secs * 1000000 + usecs);
1645 : :
1646 : 1593 : msecs = secs * 1000 + usecs / 1000;
1647 : 1593 : usecs = usecs % 1000;
1648 : :
1649 [ + + ]: 1593 : if (log_lock_waits)
1650 : : {
1651 : : StringInfoData buf,
1652 : : lock_waiters_sbuf,
1653 : : lock_holders_sbuf;
1654 : : const char *modename;
1655 : 1591 : int lockHoldersNum = 0;
1656 : :
1657 : 1591 : initStringInfo(&buf);
1658 : 1591 : initStringInfo(&lock_waiters_sbuf);
1659 : 1591 : initStringInfo(&lock_holders_sbuf);
1660 : :
1661 : 1591 : DescribeLockTag(&buf, &locallock->tag.lock);
1662 : 1591 : modename = GetLockmodeName(locallock->tag.lock.locktag_lockmethodid,
1663 : : lockmode);
1664 : :
1665 : : /* Gather a list of all lock holders and waiters */
1666 : 1591 : LWLockAcquire(partitionLock, LW_SHARED);
1667 : 1591 : GetLockHoldersAndWaiters(locallock, &lock_holders_sbuf,
1668 : : &lock_waiters_sbuf, &lockHoldersNum);
1669 : 1591 : LWLockRelease(partitionLock);
1670 : :
1671 [ + + ]: 1591 : if (deadlock_state == DS_SOFT_DEADLOCK)
1672 [ + - ]: 3 : ereport(LOG,
1673 : : (errmsg("process %d avoided deadlock for %s on %s by rearranging queue order after %ld.%03d ms",
1674 : : MyProcPid, modename, buf.data, msecs, usecs),
1675 : : (errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
1676 : : "Processes holding the lock: %s. Wait queue: %s.",
1677 : : lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
1678 [ + + ]: 1588 : else if (deadlock_state == DS_HARD_DEADLOCK)
1679 : : {
1680 : : /*
1681 : : * This message is a bit redundant with the error that
1682 : : * will be reported subsequently, but in some cases the
1683 : : * error report might not make it to the log (eg, if it's
1684 : : * caught by an exception handler), and we want to ensure
1685 : : * all long-wait events get logged.
1686 : : */
1687 [ + - ]: 5 : ereport(LOG,
1688 : : (errmsg("process %d detected deadlock while waiting for %s on %s after %ld.%03d ms",
1689 : : MyProcPid, modename, buf.data, msecs, usecs),
1690 : : (errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
1691 : : "Processes holding the lock: %s. Wait queue: %s.",
1692 : : lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
1693 : : }
1694 : :
1695 [ + + ]: 1591 : if (myWaitStatus == PROC_WAIT_STATUS_WAITING)
1696 : : {
1697 : : /*
1698 : : * Guard the "still waiting on lock" log message so it is
1699 : : * reported at most once while waiting for the lock.
1700 : : *
1701 : : * Without this guard, the message can be emitted whenever
1702 : : * the lock-wait sleep is interrupted (for example by
1703 : : * SIGHUP for config reload or by
1704 : : * client_connection_check_interval). For example, if
1705 : : * client_connection_check_interval is set very low (e.g.,
1706 : : * 100 ms), the message could be logged repeatedly,
1707 : : * flooding the log and making it difficult to use.
1708 : : */
1709 [ + + ]: 1560 : if (!logged_lock_wait)
1710 : : {
1711 [ + - ]: 28 : ereport(LOG,
1712 : : (errmsg("process %d still waiting for %s on %s after %ld.%03d ms",
1713 : : MyProcPid, modename, buf.data, msecs, usecs),
1714 : : (errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
1715 : : "Processes holding the lock: %s. Wait queue: %s.",
1716 : : lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
1717 : 28 : logged_lock_wait = true;
1718 : : }
1719 : : }
1720 [ + + ]: 31 : else if (myWaitStatus == PROC_WAIT_STATUS_OK)
1721 [ + - ]: 26 : ereport(LOG,
1722 : : (errmsg("process %d acquired %s on %s after %ld.%03d ms",
1723 : : MyProcPid, modename, buf.data, msecs, usecs)));
1724 : : else
1725 : : {
1726 : : Assert(myWaitStatus == PROC_WAIT_STATUS_ERROR);
1727 : :
1728 : : /*
1729 : : * Currently, the deadlock checker always kicks its own
1730 : : * process, which means that we'll only see
1731 : : * PROC_WAIT_STATUS_ERROR when deadlock_state ==
1732 : : * DS_HARD_DEADLOCK, and there's no need to print
1733 : : * redundant messages. But for completeness and
1734 : : * future-proofing, print a message if it looks like
1735 : : * someone else kicked us off the lock.
1736 : : */
1737 [ - + ]: 5 : if (deadlock_state != DS_HARD_DEADLOCK)
1738 [ # # ]: 0 : ereport(LOG,
1739 : : (errmsg("process %d failed to acquire %s on %s after %ld.%03d ms",
1740 : : MyProcPid, modename, buf.data, msecs, usecs),
1741 : : (errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
1742 : : "Processes holding the lock: %s. Wait queue: %s.",
1743 : : lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
1744 : : }
1745 : 1591 : pfree(buf.data);
1746 : 1591 : pfree(lock_holders_sbuf.data);
1747 : 1591 : pfree(lock_waiters_sbuf.data);
1748 : : }
1749 : :
1750 : : /*
1751 : : * At this point we might still need to wait for the lock. Reset
1752 : : * state so we don't print the above messages again if
1753 : : * log_lock_waits is on.
1754 : : */
1755 : 1593 : deadlock_state = DS_NO_DEADLOCK;
1756 : : }
1757 [ + + ]: 3454 : } while (myWaitStatus == PROC_WAIT_STATUS_WAITING);
1758 : :
1759 : : /*
1760 : : * Disable the timers, if they are still running. As in LockErrorCleanup,
1761 : : * we must preserve the LOCK_TIMEOUT indicator flag: if a lock timeout has
1762 : : * already caused QueryCancelPending to become set, we want the cancel to
1763 : : * be reported as a lock timeout, not a user cancel.
1764 : : */
1765 [ + + ]: 1421 : if (!InHotStandby)
1766 : : {
1767 [ + + ]: 1420 : if (LockTimeout > 0)
1768 : : {
1769 : : DisableTimeoutParams timeouts[2];
1770 : :
1771 : 108 : timeouts[0].id = DEADLOCK_TIMEOUT;
1772 : 108 : timeouts[0].keep_indicator = false;
1773 : 108 : timeouts[1].id = LOCK_TIMEOUT;
1774 : 108 : timeouts[1].keep_indicator = true;
1775 : 108 : disable_timeouts(timeouts, 2);
1776 : : }
1777 : : else
1778 : 1312 : disable_timeout(DEADLOCK_TIMEOUT, false);
1779 : : }
1780 : :
1781 : : /*
1782 : : * Emit the log message if recovery conflict on lock was resolved but the
1783 : : * startup process waited longer than deadlock_timeout for it.
1784 : : */
1785 [ + + + - ]: 1421 : if (InHotStandby && logged_recovery_conflict)
1786 : 1 : LogRecoveryConflict(RECOVERY_CONFLICT_LOCK,
1787 : : standbyWaitStart, GetCurrentTimestamp(),
1788 : : NULL, false);
1789 : :
1790 : : /*
1791 : : * We don't have to do anything else, because the awaker did all the
1792 : : * necessary updates of the lock table and MyProc. (The caller is
1793 : : * responsible for updating the local lock table.)
1794 : : */
1795 : 1421 : return myWaitStatus;
1796 : : }
1797 : :
1798 : :
1799 : : /*
1800 : : * ProcWakeup -- wake up a process by setting its latch.
1801 : : *
1802 : : * Also remove the process from the wait queue and set its waitLink invalid.
1803 : : *
1804 : : * The appropriate lock partition lock must be held by caller.
1805 : : *
1806 : : * XXX: presently, this code is only used for the "success" case, and only
1807 : : * works correctly for that case. To clean up in failure case, would need
1808 : : * to twiddle the lock's request counts too --- see RemoveFromWaitQueue.
1809 : : * Hence, in practice the waitStatus parameter must be PROC_WAIT_STATUS_OK.
1810 : : */
1811 : : void
1812 : 1418 : ProcWakeup(PGPROC *proc, ProcWaitStatus waitStatus)
1813 : : {
1814 [ - + ]: 1418 : if (dlist_node_is_detached(&proc->waitLink))
1815 : 0 : return;
1816 : :
1817 : : Assert(proc->waitStatus == PROC_WAIT_STATUS_WAITING);
1818 : :
1819 : : /* Remove process from wait queue */
1820 : 1418 : dclist_delete_from_thoroughly(&proc->waitLock->waitProcs, &proc->waitLink);
1821 : :
1822 : : /* Clean up process' state and pass it the ok/fail signal */
1823 : 1418 : proc->waitLock = NULL;
1824 : 1418 : proc->waitProcLock = NULL;
1825 : 1418 : proc->waitStatus = waitStatus;
1826 : 1418 : pg_atomic_write_u64(&proc->waitStart, 0);
1827 : :
1828 : : /* And awaken it */
1829 : 1418 : SetLatch(&proc->procLatch);
1830 : : }
1831 : :
1832 : : /*
1833 : : * ProcLockWakeup -- routine for waking up processes when a lock is
1834 : : * released (or a prior waiter is aborted). Scan all waiters
1835 : : * for lock, waken any that are no longer blocked.
1836 : : *
1837 : : * The appropriate lock partition lock must be held by caller.
1838 : : */
1839 : : void
1840 : 1422 : ProcLockWakeup(LockMethod lockMethodTable, LOCK *lock)
1841 : : {
1842 : 1422 : dclist_head *waitQueue = &lock->waitProcs;
1843 : 1422 : LOCKMASK aheadRequests = 0;
1844 : : dlist_mutable_iter miter;
1845 : :
1846 [ + + ]: 1422 : if (dclist_is_empty(waitQueue))
1847 : 46 : return;
1848 : :
1849 [ + - + + ]: 3148 : dclist_foreach_modify(miter, waitQueue)
1850 : : {
1851 : 1772 : PGPROC *proc = dlist_container(PGPROC, waitLink, miter.cur);
1852 : 1772 : LOCKMODE lockmode = proc->waitLockMode;
1853 : :
1854 : : /*
1855 : : * Waken if (a) doesn't conflict with requests of earlier waiters, and
1856 : : * (b) doesn't conflict with already-held locks.
1857 : : */
1858 [ + + ]: 1772 : if ((lockMethodTable->conflictTab[lockmode] & aheadRequests) == 0 &&
1859 [ + + ]: 1626 : !LockCheckConflicts(lockMethodTable, lockmode, lock,
1860 : : proc->waitProcLock))
1861 : : {
1862 : : /* OK to waken */
1863 : 1418 : GrantLock(lock, proc->waitProcLock, lockmode);
1864 : : /* removes proc from the lock's waiting process queue */
1865 : 1418 : ProcWakeup(proc, PROC_WAIT_STATUS_OK);
1866 : : }
1867 : : else
1868 : : {
1869 : : /*
1870 : : * Lock conflicts: Don't wake, but remember requested mode for
1871 : : * later checks.
1872 : : */
1873 : 354 : aheadRequests |= LOCKBIT_ON(lockmode);
1874 : : }
1875 : : }
1876 : : }
1877 : :
1878 : : /*
1879 : : * CheckDeadLock
1880 : : *
1881 : : * We only get to this routine, if DEADLOCK_TIMEOUT fired while waiting for a
1882 : : * lock to be released by some other process. Check if there's a deadlock; if
1883 : : * not, just return. If we have a real deadlock, remove ourselves from the
1884 : : * lock's wait queue.
1885 : : */
1886 : : static DeadLockState
1887 : 35 : CheckDeadLock(void)
1888 : : {
1889 : : int i;
1890 : : DeadLockState result;
1891 : :
1892 : : /*
1893 : : * Acquire exclusive lock on the entire shared lock data structures. Must
1894 : : * grab LWLocks in partition-number order to avoid LWLock deadlock.
1895 : : *
1896 : : * Note that the deadlock check interrupt had better not be enabled
1897 : : * anywhere that this process itself holds lock partition locks, else this
1898 : : * will wait forever. Also note that LWLockAcquire creates a critical
1899 : : * section, so that this routine cannot be interrupted by cancel/die
1900 : : * interrupts.
1901 : : */
1902 [ + + ]: 595 : for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
1903 : 560 : LWLockAcquire(LockHashPartitionLockByIndex(i), LW_EXCLUSIVE);
1904 : :
1905 : : /*
1906 : : * Check to see if we've been awoken by anyone in the interim.
1907 : : *
1908 : : * If we have, we can return and resume our transaction -- happy day.
1909 : : * Before we are awoken the process releasing the lock grants it to us so
1910 : : * we know that we don't have to wait anymore.
1911 : : *
1912 : : * We check by looking to see if we've been unlinked from the wait queue.
1913 : : * This is safe because we hold the lock partition lock.
1914 : : */
1915 [ - + ]: 35 : if (dlist_node_is_detached(&MyProc->waitLink))
1916 : : {
1917 : 0 : result = DS_NO_DEADLOCK;
1918 : 0 : goto check_done;
1919 : : }
1920 : :
1921 : : #ifdef LOCK_DEBUG
1922 : : if (Debug_deadlocks)
1923 : : DumpAllLocks();
1924 : : #endif
1925 : :
1926 : : /* Run the deadlock check */
1927 : 35 : result = DeadLockCheck(MyProc);
1928 : :
1929 [ + + ]: 35 : if (result == DS_HARD_DEADLOCK)
1930 : : {
1931 : : /*
1932 : : * Oops. We have a deadlock.
1933 : : *
1934 : : * Get this process out of wait state. (Note: we could do this more
1935 : : * efficiently by relying on lockAwaited, but use this coding to
1936 : : * preserve the flexibility to kill some other transaction than the
1937 : : * one detecting the deadlock.)
1938 : : *
1939 : : * RemoveFromWaitQueue sets MyProc->waitStatus to
1940 : : * PROC_WAIT_STATUS_ERROR, so ProcSleep will report an error after we
1941 : : * return.
1942 : : */
1943 : : Assert(MyProc->waitLock != NULL);
1944 : 5 : RemoveFromWaitQueue(MyProc, LockTagHashCode(&(MyProc->waitLock->tag)));
1945 : :
1946 : : /*
1947 : : * We're done here. Transaction abort caused by the error that
1948 : : * ProcSleep will raise will cause any other locks we hold to be
1949 : : * released, thus allowing other processes to wake up; we don't need
1950 : : * to do that here. NOTE: an exception is that releasing locks we
1951 : : * hold doesn't consider the possibility of waiters that were blocked
1952 : : * behind us on the lock we just failed to get, and might now be
1953 : : * wakable because we're not in front of them anymore. However,
1954 : : * RemoveFromWaitQueue took care of waking up any such processes.
1955 : : */
1956 : : }
1957 : :
1958 : : /*
1959 : : * And release locks. We do this in reverse order for two reasons: (1)
1960 : : * Anyone else who needs more than one of the locks will be trying to lock
1961 : : * them in increasing order; we don't want to release the other process
1962 : : * until it can get all the locks it needs. (2) This avoids O(N^2)
1963 : : * behavior inside LWLockRelease.
1964 : : */
1965 : 30 : check_done:
1966 [ + + ]: 595 : for (i = NUM_LOCK_PARTITIONS; --i >= 0;)
1967 : 560 : LWLockRelease(LockHashPartitionLockByIndex(i));
1968 : :
1969 : 35 : return result;
1970 : : }
1971 : :
1972 : : /*
1973 : : * CheckDeadLockAlert - Handle the expiry of deadlock_timeout.
1974 : : *
1975 : : * NB: Runs inside a signal handler, be careful.
1976 : : */
1977 : : void
1978 : 35 : CheckDeadLockAlert(void)
1979 : : {
1980 : 35 : int save_errno = errno;
1981 : :
1982 : 35 : got_deadlock_timeout = true;
1983 : :
1984 : : /*
1985 : : * Have to set the latch again, even if handle_sig_alarm already did. Back
1986 : : * then got_deadlock_timeout wasn't yet set... It's unlikely that this
1987 : : * ever would be a problem, but setting a set latch again is cheap.
1988 : : *
1989 : : * Note that, when this function runs inside procsignal_sigusr1_handler(),
1990 : : * the handler function sets the latch again after the latch is set here.
1991 : : */
1992 : 35 : SetLatch(MyLatch);
1993 : 35 : errno = save_errno;
1994 : 35 : }
1995 : :
1996 : : /*
1997 : : * GetLockHoldersAndWaiters - get lock holders and waiters for a lock
1998 : : *
1999 : : * Fill lock_holders_sbuf and lock_waiters_sbuf with the PIDs of processes holding
2000 : : * and waiting for the lock, and set lockHoldersNum to the number of lock holders.
2001 : : *
2002 : : * The lock table's partition lock must be held on entry and remains held on exit.
2003 : : */
2004 : : void
2005 : 1591 : GetLockHoldersAndWaiters(LOCALLOCK *locallock, StringInfo lock_holders_sbuf,
2006 : : StringInfo lock_waiters_sbuf, int *lockHoldersNum)
2007 : : {
2008 : : dlist_iter proc_iter;
2009 : : PROCLOCK *curproclock;
2010 : 1591 : LOCK *lock = locallock->lock;
2011 : 1591 : bool first_holder = true,
2012 : 1591 : first_waiter = true;
2013 : :
2014 : : #ifdef USE_ASSERT_CHECKING
2015 : : {
2016 : : uint32 hashcode = locallock->hashcode;
2017 : : LWLock *partitionLock = LockHashPartitionLock(hashcode);
2018 : :
2019 : : Assert(LWLockHeldByMe(partitionLock));
2020 : : }
2021 : : #endif
2022 : :
2023 : 1591 : *lockHoldersNum = 0;
2024 : :
2025 : : /*
2026 : : * Loop over the lock's procLocks to gather a list of all holders and
2027 : : * waiters. Thus we will be able to provide more detailed information for
2028 : : * lock debugging purposes.
2029 : : *
2030 : : * lock->procLocks contains all processes which hold or wait for this
2031 : : * lock.
2032 : : */
2033 [ + - + + ]: 4770 : dlist_foreach(proc_iter, &lock->procLocks)
2034 : : {
2035 : 3179 : curproclock =
2036 : 3179 : dlist_container(PROCLOCK, lockLink, proc_iter.cur);
2037 : :
2038 : : /*
2039 : : * We are a waiter if myProc->waitProcLock == curproclock; we are a
2040 : : * holder if it is NULL or something different.
2041 : : */
2042 [ + + ]: 3179 : if (curproclock->tag.myProc->waitProcLock == curproclock)
2043 : : {
2044 [ + + ]: 1581 : if (first_waiter)
2045 : : {
2046 : 1561 : appendStringInfo(lock_waiters_sbuf, "%d",
2047 : 1561 : curproclock->tag.myProc->pid);
2048 : 1561 : first_waiter = false;
2049 : : }
2050 : : else
2051 : 20 : appendStringInfo(lock_waiters_sbuf, ", %d",
2052 : 20 : curproclock->tag.myProc->pid);
2053 : : }
2054 : : else
2055 : : {
2056 [ + + ]: 1598 : if (first_holder)
2057 : : {
2058 : 1591 : appendStringInfo(lock_holders_sbuf, "%d",
2059 : 1591 : curproclock->tag.myProc->pid);
2060 : 1591 : first_holder = false;
2061 : : }
2062 : : else
2063 : 7 : appendStringInfo(lock_holders_sbuf, ", %d",
2064 : 7 : curproclock->tag.myProc->pid);
2065 : :
2066 : 1598 : (*lockHoldersNum)++;
2067 : : }
2068 : : }
2069 : 1591 : }
2070 : :
2071 : : /*
2072 : : * ProcWaitForSignal - wait for a signal from another backend.
2073 : : *
2074 : : * As this uses the generic process latch the caller has to be robust against
2075 : : * unrelated wakeups: Always check that the desired state has occurred, and
2076 : : * wait again if not.
2077 : : */
2078 : : void
2079 : 104 : ProcWaitForSignal(uint32 wait_event_info)
2080 : : {
2081 : 104 : (void) WaitLatch(MyLatch, WL_LATCH_SET | WL_EXIT_ON_PM_DEATH, 0,
2082 : : wait_event_info);
2083 : 104 : ResetLatch(MyLatch);
2084 [ - + ]: 104 : CHECK_FOR_INTERRUPTS();
2085 : 104 : }
2086 : :
2087 : : /*
2088 : : * ProcSendSignal - set the latch of a backend identified by ProcNumber
2089 : : */
2090 : : void
2091 : 92 : ProcSendSignal(ProcNumber procNumber)
2092 : : {
2093 [ + - - + ]: 92 : if (procNumber < 0 || procNumber >= ProcGlobal->allProcCount)
2094 [ # # ]: 0 : elog(ERROR, "procNumber out of range");
2095 : :
2096 : 92 : SetLatch(&GetPGProcByNumber(procNumber)->procLatch);
2097 : 92 : }
2098 : :
2099 : : /*
2100 : : * BecomeLockGroupLeader - designate process as lock group leader
2101 : : *
2102 : : * Once this function has returned, other processes can join the lock group
2103 : : * by calling BecomeLockGroupMember.
2104 : : */
2105 : : void
2106 : 869 : BecomeLockGroupLeader(void)
2107 : : {
2108 : : LWLock *leader_lwlock;
2109 : :
2110 : : /* If we already did it, we don't need to do it again. */
2111 [ + + ]: 869 : if (MyProc->lockGroupLeader == MyProc)
2112 : 745 : return;
2113 : :
2114 : : /* We had better not be a follower. */
2115 : : Assert(MyProc->lockGroupLeader == NULL);
2116 : :
2117 : : /* Create single-member group, containing only ourselves. */
2118 : 124 : leader_lwlock = LockHashPartitionLockByProc(MyProc);
2119 : 124 : LWLockAcquire(leader_lwlock, LW_EXCLUSIVE);
2120 : 124 : MyProc->lockGroupLeader = MyProc;
2121 : 124 : dlist_push_head(&MyProc->lockGroupMembers, &MyProc->lockGroupLink);
2122 : 124 : LWLockRelease(leader_lwlock);
2123 : : }
2124 : :
2125 : : /*
2126 : : * BecomeLockGroupMember - designate process as lock group member
2127 : : *
2128 : : * This is pretty straightforward except for the possibility that the leader
2129 : : * whose group we're trying to join might exit before we manage to do so;
2130 : : * and the PGPROC might get recycled for an unrelated process. To avoid
2131 : : * that, we require the caller to pass the PID of the intended PGPROC as
2132 : : * an interlock. Returns true if we successfully join the intended lock
2133 : : * group, and false if not.
2134 : : */
2135 : : bool
2136 : 2018 : BecomeLockGroupMember(PGPROC *leader, int pid)
2137 : : {
2138 : : LWLock *leader_lwlock;
2139 : 2018 : bool ok = false;
2140 : :
2141 : : /* Group leader can't become member of group */
2142 : : Assert(MyProc != leader);
2143 : :
2144 : : /* Can't already be a member of a group */
2145 : : Assert(MyProc->lockGroupLeader == NULL);
2146 : :
2147 : : /* PID must be valid. */
2148 : : Assert(pid != 0);
2149 : :
2150 : : /*
2151 : : * Get lock protecting the group fields. Note LockHashPartitionLockByProc
2152 : : * calculates the proc number based on the PGPROC slot without looking at
2153 : : * its contents, so we will acquire the correct lock even if the leader
2154 : : * PGPROC is in process of being recycled.
2155 : : */
2156 : 2018 : leader_lwlock = LockHashPartitionLockByProc(leader);
2157 : 2018 : LWLockAcquire(leader_lwlock, LW_EXCLUSIVE);
2158 : :
2159 : : /* Is this the leader we're looking for? */
2160 [ + - + - ]: 2018 : if (leader->pid == pid && leader->lockGroupLeader == leader)
2161 : : {
2162 : : /* OK, join the group */
2163 : 2018 : ok = true;
2164 : 2018 : MyProc->lockGroupLeader = leader;
2165 : 2018 : dlist_push_tail(&leader->lockGroupMembers, &MyProc->lockGroupLink);
2166 : : }
2167 : 2018 : LWLockRelease(leader_lwlock);
2168 : :
2169 : 2018 : return ok;
2170 : : }
|
