Age Owner Branch data TLA Line data Source code
1 : : /*--------------------------------------------------------------------
2 : : * bgworker.c
3 : : * POSTGRES pluggable background workers implementation
4 : : *
5 : : * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
6 : : *
7 : : * IDENTIFICATION
8 : : * src/backend/postmaster/bgworker.c
9 : : *
10 : : *-------------------------------------------------------------------------
11 : : */
12 : :
13 : : #include "postgres.h"
14 : :
15 : : #include "access/parallel.h"
16 : : #include "libpq/pqsignal.h"
17 : : #include "miscadmin.h"
18 : : #include "pgstat.h"
19 : : #include "port/atomics.h"
20 : : #include "postmaster/bgworker_internals.h"
21 : : #include "postmaster/postmaster.h"
22 : : #include "replication/logicallauncher.h"
23 : : #include "replication/logicalworker.h"
24 : : #include "storage/ipc.h"
25 : : #include "storage/latch.h"
26 : : #include "storage/lwlock.h"
27 : : #include "storage/pmsignal.h"
28 : : #include "storage/proc.h"
29 : : #include "storage/procsignal.h"
30 : : #include "storage/shmem.h"
31 : : #include "tcop/tcopprot.h"
32 : : #include "utils/ascii.h"
33 : : #include "utils/memutils.h"
34 : : #include "utils/ps_status.h"
35 : : #include "utils/timeout.h"
36 : :
37 : : /*
38 : : * The postmaster's list of registered background workers, in private memory.
39 : : */
40 : : dlist_head BackgroundWorkerList = DLIST_STATIC_INIT(BackgroundWorkerList);
41 : :
42 : : /*
43 : : * BackgroundWorkerSlots exist in shared memory and can be accessed (via
44 : : * the BackgroundWorkerArray) by both the postmaster and by regular backends.
45 : : * However, the postmaster cannot take locks, even spinlocks, because this
46 : : * might allow it to crash or become wedged if shared memory gets corrupted.
47 : : * Such an outcome is intolerable. Therefore, we need a lockless protocol
48 : : * for coordinating access to this data.
49 : : *
50 : : * The 'in_use' flag is used to hand off responsibility for the slot between
51 : : * the postmaster and the rest of the system. When 'in_use' is false,
52 : : * the postmaster will ignore the slot entirely, except for the 'in_use' flag
53 : : * itself, which it may read. In this state, regular backends may modify the
54 : : * slot. Once a backend sets 'in_use' to true, the slot becomes the
55 : : * responsibility of the postmaster. Regular backends may no longer modify it,
56 : : * but the postmaster may examine it. Thus, a backend initializing a slot
57 : : * must fully initialize the slot - and insert a write memory barrier - before
58 : : * marking it as in use.
59 : : *
60 : : * As an exception, however, even when the slot is in use, regular backends
61 : : * may set the 'terminate' flag for a slot, telling the postmaster not
62 : : * to restart it. Once the background worker is no longer running, the slot
63 : : * will be released for reuse.
64 : : *
65 : : * In addition to coordinating with the postmaster, backends modifying this
66 : : * data structure must coordinate with each other. Since they can take locks,
67 : : * this is straightforward: any backend wishing to manipulate a slot must
68 : : * take BackgroundWorkerLock in exclusive mode. Backends wishing to read
69 : : * data that might get concurrently modified by other backends should take
70 : : * this lock in shared mode. No matter what, backends reading this data
71 : : * structure must be able to tolerate concurrent modifications by the
72 : : * postmaster.
73 : : */
74 : : typedef struct BackgroundWorkerSlot
75 : : {
76 : : bool in_use;
77 : : bool terminate;
78 : : pid_t pid; /* InvalidPid = not started yet; 0 = dead */
79 : : uint64 generation; /* incremented when slot is recycled */
80 : : BackgroundWorker worker;
81 : : } BackgroundWorkerSlot;
82 : :
83 : : /*
84 : : * In order to limit the total number of parallel workers (according to
85 : : * max_parallel_workers GUC), we maintain the number of active parallel
86 : : * workers. Since the postmaster cannot take locks, two variables are used for
87 : : * this purpose: the number of registered parallel workers (modified by the
88 : : * backends, protected by BackgroundWorkerLock) and the number of terminated
89 : : * parallel workers (modified only by the postmaster, lockless). The active
90 : : * number of parallel workers is the number of registered workers minus the
91 : : * terminated ones. These counters can of course overflow, but it's not
92 : : * important here since the subtraction will still give the right number.
93 : : */
94 : : typedef struct BackgroundWorkerArray
95 : : {
96 : : int total_slots;
97 : : uint32 parallel_register_count;
98 : : uint32 parallel_terminate_count;
99 : : BackgroundWorkerSlot slot[FLEXIBLE_ARRAY_MEMBER];
100 : : } BackgroundWorkerArray;
101 : :
102 : : struct BackgroundWorkerHandle
103 : : {
104 : : int slot;
105 : : uint64 generation;
106 : : };
107 : :
108 : : static BackgroundWorkerArray *BackgroundWorkerData;
109 : :
110 : : /*
111 : : * List of internal background worker entry points. We need this for
112 : : * reasons explained in LookupBackgroundWorkerFunction(), below.
113 : : */
114 : : static const struct
115 : : {
116 : : const char *fn_name;
117 : : bgworker_main_type fn_addr;
118 : : } InternalBGWorkers[] =
119 : :
120 : : {
121 : : {
122 : : "ParallelWorkerMain", ParallelWorkerMain
123 : : },
124 : : {
125 : : "ApplyLauncherMain", ApplyLauncherMain
126 : : },
127 : : {
128 : : "ApplyWorkerMain", ApplyWorkerMain
129 : : },
130 : : {
131 : : "ParallelApplyWorkerMain", ParallelApplyWorkerMain
132 : : },
133 : : {
134 : : "TablesyncWorkerMain", TablesyncWorkerMain
135 : : }
136 : : };
137 : :
138 : : /* Private functions. */
139 : : static bgworker_main_type LookupBackgroundWorkerFunction(const char *libraryname, const char *funcname);
140 : :
141 : :
142 : : /*
143 : : * Calculate shared memory needed.
144 : : */
145 : : Size
4435 rhaas@postgresql.org 146 :CBC 2938 : BackgroundWorkerShmemSize(void)
147 : : {
148 : : Size size;
149 : :
150 : : /* Array of workers is variably sized. */
151 : 2938 : size = offsetof(BackgroundWorkerArray, slot);
152 : 2938 : size = add_size(size, mul_size(max_worker_processes,
153 : : sizeof(BackgroundWorkerSlot)));
154 : :
155 : 2938 : return size;
156 : : }
157 : :
158 : : /*
159 : : * Initialize shared memory.
160 : : */
161 : : void
162 : 1029 : BackgroundWorkerShmemInit(void)
163 : : {
164 : : bool found;
165 : :
166 : 1029 : BackgroundWorkerData = ShmemInitStruct("Background Worker Data",
167 : : BackgroundWorkerShmemSize(),
168 : : &found);
169 [ + - ]: 1029 : if (!IsUnderPostmaster)
170 : : {
171 : : dlist_iter iter;
172 : 1029 : int slotno = 0;
173 : :
174 : 1029 : BackgroundWorkerData->total_slots = max_worker_processes;
3200 175 : 1029 : BackgroundWorkerData->parallel_register_count = 0;
176 : 1029 : BackgroundWorkerData->parallel_terminate_count = 0;
177 : :
178 : : /*
179 : : * Copy contents of worker list into shared memory. Record the shared
180 : : * memory slot assigned to each worker. This ensures a 1-to-1
181 : : * correspondence between the postmaster's private list and the array
182 : : * in shared memory.
183 : : */
393 heikki.linnakangas@i 184 [ + - + + ]: 1791 : dlist_foreach(iter, &BackgroundWorkerList)
185 : : {
4435 rhaas@postgresql.org 186 : 762 : BackgroundWorkerSlot *slot = &BackgroundWorkerData->slot[slotno];
187 : : RegisteredBgWorker *rw;
188 : :
393 heikki.linnakangas@i 189 : 762 : rw = dlist_container(RegisteredBgWorker, rw_lnode, iter.cur);
4435 rhaas@postgresql.org 190 [ - + ]: 762 : Assert(slotno < max_worker_processes);
191 : 762 : slot->in_use = true;
4341 192 : 762 : slot->terminate = false;
4392 193 : 762 : slot->pid = InvalidPid;
194 : 762 : slot->generation = 0;
4435 195 : 762 : rw->rw_shmem_slot = slotno;
4141 bruce@momjian.us 196 : 762 : rw->rw_worker.bgw_notify_pid = 0; /* might be reinit after crash */
4435 rhaas@postgresql.org 197 : 762 : memcpy(&slot->worker, &rw->rw_worker, sizeof(BackgroundWorker));
198 : 762 : ++slotno;
199 : : }
200 : :
201 : : /*
202 : : * Mark any remaining slots as not in use.
203 : : */
204 [ + + ]: 8497 : while (slotno < max_worker_processes)
205 : : {
206 : 7468 : BackgroundWorkerSlot *slot = &BackgroundWorkerData->slot[slotno];
207 : :
208 : 7468 : slot->in_use = false;
209 : 7468 : ++slotno;
210 : : }
211 : : }
212 : : else
4435 rhaas@postgresql.org 213 [ # # ]:UBC 0 : Assert(found);
4435 rhaas@postgresql.org 214 :CBC 1029 : }
215 : :
216 : : /*
217 : : * Search the postmaster's backend-private list of RegisteredBgWorker objects
218 : : * for the one that maps to the given slot number.
219 : : */
220 : : static RegisteredBgWorker *
221 : 4169 : FindRegisteredWorkerBySlotNumber(int slotno)
222 : : {
223 : : dlist_iter iter;
224 : :
393 heikki.linnakangas@i 225 [ + - + + ]: 10282 : dlist_foreach(iter, &BackgroundWorkerList)
226 : : {
227 : : RegisteredBgWorker *rw;
228 : :
229 : 8344 : rw = dlist_container(RegisteredBgWorker, rw_lnode, iter.cur);
4435 rhaas@postgresql.org 230 [ + + ]: 8344 : if (rw->rw_shmem_slot == slotno)
231 : 2231 : return rw;
232 : : }
233 : :
234 : 1938 : return NULL;
235 : : }
236 : :
237 : : /*
238 : : * Notice changes to shared memory made by other backends.
239 : : * Accept new worker requests only if allow_new_workers is true.
240 : : *
241 : : * This code runs in the postmaster, so we must be very careful not to assume
242 : : * that shared memory contents are sane. Otherwise, a rogue backend could
243 : : * take out the postmaster.
244 : : */
245 : : void
1717 tgl@sss.pgh.pa.us 246 : 1250 : BackgroundWorkerStateChange(bool allow_new_workers)
247 : : {
248 : : int slotno;
249 : :
250 : : /*
251 : : * The total number of slots stored in shared memory should match our
252 : : * notion of max_worker_processes. If it does not, something is very
253 : : * wrong. Further down, we always refer to this value as
254 : : * max_worker_processes, in case shared memory gets corrupted while we're
255 : : * looping.
256 : : */
4435 rhaas@postgresql.org 257 [ - + ]: 1250 : if (max_worker_processes != BackgroundWorkerData->total_slots)
258 : : {
1737 peter@eisentraut.org 259 [ # # ]:UBC 0 : ereport(LOG,
260 : : (errmsg("inconsistent background worker state (\"max_worker_processes\"=%d, total slots=%d)",
261 : : max_worker_processes,
262 : : BackgroundWorkerData->total_slots)));
4435 rhaas@postgresql.org 263 : 0 : return;
264 : : }
265 : :
266 : : /*
267 : : * Iterate through slots, looking for newly-registered workers or workers
268 : : * who must die.
269 : : */
4435 rhaas@postgresql.org 270 [ + + ]:CBC 11394 : for (slotno = 0; slotno < max_worker_processes; ++slotno)
271 : : {
272 : 10144 : BackgroundWorkerSlot *slot = &BackgroundWorkerData->slot[slotno];
273 : : RegisteredBgWorker *rw;
274 : :
275 [ + + ]: 10144 : if (!slot->in_use)
276 : 5975 : continue;
277 : :
278 : : /*
279 : : * Make sure we don't see the in_use flag before the updated slot
280 : : * contents.
281 : : */
282 : 4169 : pg_read_barrier();
283 : :
284 : : /* See whether we already know about this worker. */
285 : 4169 : rw = FindRegisteredWorkerBySlotNumber(slotno);
286 [ + + ]: 4169 : if (rw != NULL)
287 : : {
288 : : /*
289 : : * In general, the worker data can't change after it's initially
290 : : * registered. However, someone can set the terminate flag.
291 : : */
4341 292 [ + + + - ]: 2231 : if (slot->terminate && !rw->rw_terminate)
293 : : {
294 : 6 : rw->rw_terminate = true;
295 [ + - ]: 6 : if (rw->rw_pid != 0)
296 : 6 : kill(rw->rw_pid, SIGTERM);
297 : : else
298 : : {
299 : : /* Report never-started, now-terminated worker as dead. */
3824 rhaas@postgresql.org 300 :UBC 0 : ReportBackgroundWorkerPID(rw);
301 : : }
302 : : }
4435 rhaas@postgresql.org 303 :CBC 2231 : continue;
304 : : }
305 : :
306 : : /*
307 : : * If we aren't allowing new workers, then immediately mark it for
308 : : * termination; the next stanza will take care of cleaning it up.
309 : : * Doing this ensures that any process waiting for the worker will get
310 : : * awoken, even though the worker will never be allowed to run.
311 : : */
1717 tgl@sss.pgh.pa.us 312 [ + + ]: 1938 : if (!allow_new_workers)
313 : 3 : slot->terminate = true;
314 : :
315 : : /*
316 : : * If the worker is marked for termination, we don't need to add it to
317 : : * the registered workers list; we can just free the slot. However, if
318 : : * bgw_notify_pid is set, the process that registered the worker may
319 : : * need to know that we've processed the terminate request, so be sure
320 : : * to signal it.
321 : : */
4341 rhaas@postgresql.org 322 [ + + ]: 1938 : if (slot->terminate)
323 : 3 : {
324 : : int notify_pid;
325 : :
326 : : /*
327 : : * We need a memory barrier here to make sure that the load of
328 : : * bgw_notify_pid and the update of parallel_terminate_count
329 : : * complete before the store to in_use.
330 : : */
3824 331 : 3 : notify_pid = slot->worker.bgw_notify_pid;
3200 332 [ - + ]: 3 : if ((slot->worker.bgw_flags & BGWORKER_CLASS_PARALLEL) != 0)
3200 rhaas@postgresql.org 333 :UBC 0 : BackgroundWorkerData->parallel_terminate_count++;
3824 rhaas@postgresql.org 334 :CBC 3 : slot->pid = 0;
335 : :
1575 tgl@sss.pgh.pa.us 336 : 3 : pg_memory_barrier();
4341 rhaas@postgresql.org 337 : 3 : slot->in_use = false;
338 : :
3824 339 [ + - ]: 3 : if (notify_pid != 0)
340 : 3 : kill(notify_pid, SIGUSR1);
341 : :
4341 342 : 3 : continue;
343 : : }
344 : :
345 : : /*
346 : : * Copy the registration data into the registered workers list.
347 : : */
698 heikki.linnakangas@i 348 : 1935 : rw = MemoryContextAllocExtended(PostmasterContext,
349 : : sizeof(RegisteredBgWorker),
350 : : MCXT_ALLOC_NO_OOM | MCXT_ALLOC_ZERO);
4435 rhaas@postgresql.org 351 [ - + ]: 1935 : if (rw == NULL)
352 : : {
4435 rhaas@postgresql.org 353 [ # # ]:UBC 0 : ereport(LOG,
354 : : (errcode(ERRCODE_OUT_OF_MEMORY),
355 : : errmsg("out of memory")));
356 : 0 : return;
357 : : }
358 : :
359 : : /*
360 : : * Copy strings in a paranoid way. If shared memory is corrupted, the
361 : : * source data might not even be NUL-terminated.
362 : : */
4435 rhaas@postgresql.org 363 :CBC 1935 : ascii_safe_strlcpy(rw->rw_worker.bgw_name,
364 : 1935 : slot->worker.bgw_name, BGW_MAXLEN);
2928 peter_e@gmx.net 365 : 1935 : ascii_safe_strlcpy(rw->rw_worker.bgw_type,
366 : 1935 : slot->worker.bgw_type, BGW_MAXLEN);
4435 rhaas@postgresql.org 367 : 1935 : ascii_safe_strlcpy(rw->rw_worker.bgw_library_name,
796 nathan@postgresql.or 368 : 1935 : slot->worker.bgw_library_name, MAXPGPATH);
4435 rhaas@postgresql.org 369 : 1935 : ascii_safe_strlcpy(rw->rw_worker.bgw_function_name,
370 : 1935 : slot->worker.bgw_function_name, BGW_MAXLEN);
371 : :
372 : : /*
373 : : * Copy various fixed-size fields.
374 : : *
375 : : * flags, start_time, and restart_time are examined by the postmaster,
376 : : * but nothing too bad will happen if they are corrupted. The
377 : : * remaining fields will only be examined by the child process. It
378 : : * might crash, but we won't.
379 : : */
380 : 1935 : rw->rw_worker.bgw_flags = slot->worker.bgw_flags;
381 : 1935 : rw->rw_worker.bgw_start_time = slot->worker.bgw_start_time;
382 : 1935 : rw->rw_worker.bgw_restart_time = slot->worker.bgw_restart_time;
383 : 1935 : rw->rw_worker.bgw_main_arg = slot->worker.bgw_main_arg;
3593 384 : 1935 : memcpy(rw->rw_worker.bgw_extra, slot->worker.bgw_extra, BGW_EXTRALEN);
385 : :
386 : : /*
387 : : * Copy the PID to be notified about state changes, but only if the
388 : : * postmaster knows about a backend with that PID. It isn't an error
389 : : * if the postmaster doesn't know about the PID, because the backend
390 : : * that requested the worker could have died (or been killed) just
391 : : * after doing so. Nonetheless, at least until we get some experience
392 : : * with how this plays out in the wild, log a message at a relative
393 : : * high debug level.
394 : : */
4392 395 : 1935 : rw->rw_worker.bgw_notify_pid = slot->worker.bgw_notify_pid;
396 [ - + ]: 1935 : if (!PostmasterMarkPIDForWorkerNotify(rw->rw_worker.bgw_notify_pid))
397 : : {
1058 peter@eisentraut.org 398 [ # # ]:UBC 0 : elog(DEBUG1, "worker notification PID %d is not valid",
399 : : (int) rw->rw_worker.bgw_notify_pid);
4392 rhaas@postgresql.org 400 : 0 : rw->rw_worker.bgw_notify_pid = 0;
401 : : }
402 : :
403 : : /* Initialize postmaster bookkeeping. */
4435 rhaas@postgresql.org 404 :CBC 1935 : rw->rw_pid = 0;
405 : 1935 : rw->rw_crashed_at = 0;
406 : 1935 : rw->rw_shmem_slot = slotno;
4341 407 : 1935 : rw->rw_terminate = false;
408 : :
409 : : /* Log it! */
3725 410 [ + + ]: 1935 : ereport(DEBUG1,
411 : : (errmsg_internal("registering background worker \"%s\"",
412 : : rw->rw_worker.bgw_name)));
413 : :
393 heikki.linnakangas@i 414 : 1935 : dlist_push_head(&BackgroundWorkerList, &rw->rw_lnode);
415 : : }
416 : : }
417 : :
418 : : /*
419 : : * Forget about a background worker that's no longer needed.
420 : : *
421 : : * NOTE: The entry is unlinked from BackgroundWorkerList. If the caller is
422 : : * iterating through it, better use a mutable iterator!
423 : : *
424 : : * Caller is responsible for notifying bgw_notify_pid, if appropriate.
425 : : *
426 : : * This function must be invoked only in the postmaster.
427 : : */
428 : : void
429 : 1909 : ForgetBackgroundWorker(RegisteredBgWorker *rw)
430 : : {
431 : : BackgroundWorkerSlot *slot;
432 : :
4435 rhaas@postgresql.org 433 [ - + ]: 1909 : Assert(rw->rw_shmem_slot < max_worker_processes);
434 : 1909 : slot = &BackgroundWorkerData->slot[rw->rw_shmem_slot];
1575 tgl@sss.pgh.pa.us 435 [ - + ]: 1909 : Assert(slot->in_use);
436 : :
437 : : /*
438 : : * We need a memory barrier here to make sure that the update of
439 : : * parallel_terminate_count completes before the store to in_use.
440 : : */
3200 rhaas@postgresql.org 441 [ + + ]: 1909 : if ((rw->rw_worker.bgw_flags & BGWORKER_CLASS_PARALLEL) != 0)
442 : 1378 : BackgroundWorkerData->parallel_terminate_count++;
443 : :
1575 tgl@sss.pgh.pa.us 444 : 1909 : pg_memory_barrier();
4435 rhaas@postgresql.org 445 : 1909 : slot->in_use = false;
446 : :
3725 447 [ + + ]: 1909 : ereport(DEBUG1,
448 : : (errmsg_internal("unregistering background worker \"%s\"",
449 : : rw->rw_worker.bgw_name)));
450 : :
393 heikki.linnakangas@i 451 : 1909 : dlist_delete(&rw->rw_lnode);
698 452 : 1909 : pfree(rw);
4435 rhaas@postgresql.org 453 : 1909 : }
454 : :
455 : : /*
456 : : * Report the PID of a newly-launched background worker in shared memory.
457 : : *
458 : : * This function should only be called from the postmaster.
459 : : */
460 : : void
4392 461 : 2598 : ReportBackgroundWorkerPID(RegisteredBgWorker *rw)
462 : : {
463 : : BackgroundWorkerSlot *slot;
464 : :
465 [ - + ]: 2598 : Assert(rw->rw_shmem_slot < max_worker_processes);
466 : 2598 : slot = &BackgroundWorkerData->slot[rw->rw_shmem_slot];
467 : 2598 : slot->pid = rw->rw_pid;
468 : :
469 [ + + ]: 2598 : if (rw->rw_worker.bgw_notify_pid != 0)
470 : 1935 : kill(rw->rw_worker.bgw_notify_pid, SIGUSR1);
471 : 2598 : }
472 : :
473 : : /*
474 : : * Report that the PID of a background worker is now zero because a
475 : : * previously-running background worker has exited.
476 : : *
477 : : * NOTE: The entry may be unlinked from BackgroundWorkerList. If the caller
478 : : * is iterating through it, better use a mutable iterator!
479 : : *
480 : : * This function should only be called from the postmaster.
481 : : */
482 : : void
393 heikki.linnakangas@i 483 : 2293 : ReportBackgroundWorkerExit(RegisteredBgWorker *rw)
484 : : {
485 : : BackgroundWorkerSlot *slot;
486 : : int notify_pid;
487 : :
3109 rhaas@postgresql.org 488 [ - + ]: 2293 : Assert(rw->rw_shmem_slot < max_worker_processes);
489 : 2293 : slot = &BackgroundWorkerData->slot[rw->rw_shmem_slot];
490 : 2293 : slot->pid = rw->rw_pid;
3106 491 : 2293 : notify_pid = rw->rw_worker.bgw_notify_pid;
492 : :
493 : : /*
494 : : * If this worker is slated for deregistration, do that before notifying
495 : : * the process which started it. Otherwise, if that process tries to
496 : : * reuse the slot immediately, it might not be available yet. In theory
497 : : * that could happen anyway if the process checks slot->pid at just the
498 : : * wrong moment, but this makes the window narrower.
499 : : */
3109 500 [ + + ]: 2293 : if (rw->rw_terminate ||
501 [ + + ]: 612 : rw->rw_worker.bgw_restart_time == BGW_NEVER_RESTART)
393 heikki.linnakangas@i 502 : 1909 : ForgetBackgroundWorker(rw);
503 : :
3106 rhaas@postgresql.org 504 [ + + ]: 2293 : if (notify_pid != 0)
505 : 1877 : kill(notify_pid, SIGUSR1);
3109 506 : 2293 : }
507 : :
508 : : /*
509 : : * Cancel SIGUSR1 notifications for a PID belonging to an exiting backend.
510 : : *
511 : : * This function should only be called from the postmaster.
512 : : */
513 : : void
4392 514 : 246 : BackgroundWorkerStopNotifications(pid_t pid)
515 : : {
516 : : dlist_iter iter;
517 : :
393 heikki.linnakangas@i 518 [ + - + + ]: 838 : dlist_foreach(iter, &BackgroundWorkerList)
519 : : {
520 : : RegisteredBgWorker *rw;
521 : :
522 : 592 : rw = dlist_container(RegisteredBgWorker, rw_lnode, iter.cur);
4392 rhaas@postgresql.org 523 [ + + ]: 592 : if (rw->rw_worker.bgw_notify_pid == pid)
524 : 33 : rw->rw_worker.bgw_notify_pid = 0;
525 : : }
526 : 246 : }
527 : :
528 : : /*
529 : : * Cancel any not-yet-started worker requests that have waiting processes.
530 : : *
531 : : * This is called during a normal ("smart" or "fast") database shutdown.
532 : : * After this point, no new background workers will be started, so anything
533 : : * that might be waiting for them needs to be kicked off its wait. We do
534 : : * that by canceling the bgworker registration entirely, which is perhaps
535 : : * overkill, but since we're shutting down it does not matter whether the
536 : : * registration record sticks around.
537 : : *
538 : : * This function should only be called from the postmaster.
539 : : */
540 : : void
1717 tgl@sss.pgh.pa.us 541 : 488 : ForgetUnstartedBackgroundWorkers(void)
542 : : {
543 : : dlist_mutable_iter iter;
544 : :
393 heikki.linnakangas@i 545 [ + - + + ]: 970 : dlist_foreach_modify(iter, &BackgroundWorkerList)
546 : : {
547 : : RegisteredBgWorker *rw;
548 : : BackgroundWorkerSlot *slot;
549 : :
550 : 482 : rw = dlist_container(RegisteredBgWorker, rw_lnode, iter.cur);
1717 tgl@sss.pgh.pa.us 551 [ - + ]: 482 : Assert(rw->rw_shmem_slot < max_worker_processes);
552 : 482 : slot = &BackgroundWorkerData->slot[rw->rw_shmem_slot];
553 : :
554 : : /* If it's not yet started, and there's someone waiting ... */
555 [ + + ]: 482 : if (slot->pid == InvalidPid &&
556 [ - + ]: 51 : rw->rw_worker.bgw_notify_pid != 0)
557 : : {
558 : : /* ... then zap it, and notify the waiter */
1717 tgl@sss.pgh.pa.us 559 :UBC 0 : int notify_pid = rw->rw_worker.bgw_notify_pid;
560 : :
393 heikki.linnakangas@i 561 : 0 : ForgetBackgroundWorker(rw);
1717 tgl@sss.pgh.pa.us 562 [ # # ]: 0 : if (notify_pid != 0)
563 : 0 : kill(notify_pid, SIGUSR1);
564 : : }
565 : : }
1717 tgl@sss.pgh.pa.us 566 :CBC 488 : }
567 : :
568 : : /*
569 : : * Reset background worker crash state.
570 : : *
571 : : * We assume that, after a crash-and-restart cycle, background workers without
572 : : * the never-restart flag should be restarted immediately, instead of waiting
573 : : * for bgw_restart_time to elapse. On the other hand, workers with that flag
574 : : * should be forgotten immediately, since we won't ever restart them.
575 : : *
576 : : * This function should only be called from the postmaster.
577 : : */
578 : : void
4140 rhaas@postgresql.org 579 : 4 : ResetBackgroundWorkerCrashTimes(void)
580 : : {
581 : : dlist_mutable_iter iter;
582 : :
393 heikki.linnakangas@i 583 [ + - + + ]: 8 : dlist_foreach_modify(iter, &BackgroundWorkerList)
584 : : {
585 : : RegisteredBgWorker *rw;
586 : :
587 : 4 : rw = dlist_container(RegisteredBgWorker, rw_lnode, iter.cur);
588 : :
3070 rhaas@postgresql.org 589 [ - + ]: 4 : if (rw->rw_worker.bgw_restart_time == BGW_NEVER_RESTART)
590 : : {
591 : : /*
592 : : * Workers marked BGW_NEVER_RESTART shouldn't get relaunched after
593 : : * the crash, so forget about them. (If we wait until after the
594 : : * crash to forget about them, and they are parallel workers,
595 : : * parallel_terminate_count will get incremented after we've
596 : : * already zeroed parallel_register_count, which would be bad.)
597 : : */
393 heikki.linnakangas@i 598 :UBC 0 : ForgetBackgroundWorker(rw);
599 : : }
600 : : else
601 : : {
602 : : /*
603 : : * The accounting which we do via parallel_register_count and
604 : : * parallel_terminate_count would get messed up if a worker marked
605 : : * parallel could survive a crash and restart cycle. All such
606 : : * workers should be marked BGW_NEVER_RESTART, and thus control
607 : : * should never reach this branch.
608 : : */
3070 rhaas@postgresql.org 609 [ - + ]:CBC 4 : Assert((rw->rw_worker.bgw_flags & BGWORKER_CLASS_PARALLEL) == 0);
610 : :
611 : : /*
612 : : * Allow this worker to be restarted immediately after we finish
613 : : * resetting.
614 : : */
3810 615 : 4 : rw->rw_crashed_at = 0;
43 fujii@postgresql.org 616 : 4 : rw->rw_pid = 0;
617 : :
618 : : /*
619 : : * If there was anyone waiting for it, they're history.
620 : : */
1717 tgl@sss.pgh.pa.us 621 : 4 : rw->rw_worker.bgw_notify_pid = 0;
622 : : }
623 : : }
4140 rhaas@postgresql.org 624 : 4 : }
625 : :
626 : : /*
627 : : * Complain about the BackgroundWorker definition using error level elevel.
628 : : * Return true if it looks ok, false if not (unless elevel >= ERROR, in
629 : : * which case we won't return at all in the not-OK case).
630 : : */
631 : : static bool
4435 632 : 2582 : SanityCheckBackgroundWorker(BackgroundWorker *worker, int elevel)
633 : : {
634 : : /* sanity check for flags */
635 : :
636 : : /*
637 : : * We used to support workers not connected to shared memory, but don't
638 : : * anymore. Thus this is a required flag now. We're not removing the flag
639 : : * for compatibility reasons and because the flag still provides some
640 : : * signal when reading code.
641 : : */
1485 andres@anarazel.de 642 [ - + ]: 2582 : if (!(worker->bgw_flags & BGWORKER_SHMEM_ACCESS))
643 : : {
1485 andres@anarazel.de 644 [ # # ]:UBC 0 : ereport(elevel,
645 : : (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
646 : : errmsg("background worker \"%s\": background workers without shared memory access are not supported",
647 : : worker->bgw_name)));
648 : 0 : return false;
649 : : }
650 : :
1485 andres@anarazel.de 651 [ + + ]:CBC 2582 : if (worker->bgw_flags & BGWORKER_BACKEND_DATABASE_CONNECTION)
652 : : {
4435 rhaas@postgresql.org 653 [ - + ]: 2573 : if (worker->bgw_start_time == BgWorkerStart_PostmasterStart)
654 : : {
4435 rhaas@postgresql.org 655 [ # # ]:UBC 0 : ereport(elevel,
656 : : (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
657 : : errmsg("background worker \"%s\": cannot request database access if starting at postmaster start",
658 : : worker->bgw_name)));
659 : 0 : return false;
660 : : }
661 : :
662 : : /* XXX other checks? */
663 : : }
664 : :
4435 rhaas@postgresql.org 665 [ + + ]:CBC 2582 : if ((worker->bgw_restart_time < 0 &&
666 [ + - ]: 1820 : worker->bgw_restart_time != BGW_NEVER_RESTART) ||
667 [ - + ]: 2582 : (worker->bgw_restart_time > USECS_PER_DAY / 1000))
668 : : {
4435 rhaas@postgresql.org 669 [ # # ]:UBC 0 : ereport(elevel,
670 : : (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
671 : : errmsg("background worker \"%s\": invalid restart interval",
672 : : worker->bgw_name)));
673 : 0 : return false;
674 : : }
675 : :
676 : : /*
677 : : * Parallel workers may not be configured for restart, because the
678 : : * parallel_register_count/parallel_terminate_count accounting can't
679 : : * handle parallel workers lasting through a crash-and-restart cycle.
680 : : */
3070 rhaas@postgresql.org 681 [ + + ]:CBC 2582 : if (worker->bgw_restart_time != BGW_NEVER_RESTART &&
682 [ - + ]: 762 : (worker->bgw_flags & BGWORKER_CLASS_PARALLEL) != 0)
683 : : {
3070 rhaas@postgresql.org 684 [ # # ]:UBC 0 : ereport(elevel,
685 : : (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
686 : : errmsg("background worker \"%s\": parallel workers may not be configured for restart",
687 : : worker->bgw_name)));
688 : 0 : return false;
689 : : }
690 : :
691 : : /*
692 : : * If bgw_type is not filled in, use bgw_name.
693 : : */
2928 peter_e@gmx.net 694 [ - + ]:CBC 2582 : if (strcmp(worker->bgw_type, "") == 0)
2928 peter_e@gmx.net 695 :UBC 0 : strcpy(worker->bgw_type, worker->bgw_name);
696 : :
4435 rhaas@postgresql.org 697 :CBC 2582 : return true;
698 : : }
699 : :
700 : : /*
701 : : * Standard SIGTERM handler for background workers
702 : : */
703 : : static void
4404 rhaas@postgresql.org 704 :UBC 0 : bgworker_die(SIGNAL_ARGS)
705 : : {
946 tmunro@postgresql.or 706 : 0 : sigprocmask(SIG_SETMASK, &BlockSig, NULL);
707 : :
4404 rhaas@postgresql.org 708 [ # # ]: 0 : ereport(FATAL,
709 : : (errcode(ERRCODE_ADMIN_SHUTDOWN),
710 : : errmsg("terminating background worker \"%s\" due to administrator command",
711 : : MyBgworkerEntry->bgw_type)));
712 : : }
713 : :
714 : : /*
715 : : * Main entry point for background worker processes.
716 : : */
717 : : void
197 peter@eisentraut.org 718 :CBC 2305 : BackgroundWorkerMain(const void *startup_data, size_t startup_data_len)
719 : : {
720 : : sigjmp_buf local_sigjmp_buf;
721 : : BackgroundWorker *worker;
722 : : bgworker_main_type entrypt;
723 : :
537 heikki.linnakangas@i 724 [ - + ]: 2305 : if (startup_data == NULL)
4404 rhaas@postgresql.org 725 [ # # ]:UBC 0 : elog(FATAL, "unable to find bgworker entry");
537 heikki.linnakangas@i 726 [ - + ]:CBC 2305 : Assert(startup_data_len == sizeof(BackgroundWorker));
727 : 2305 : worker = MemoryContextAlloc(TopMemoryContext, sizeof(BackgroundWorker));
728 : 2305 : memcpy(worker, startup_data, sizeof(BackgroundWorker));
729 : :
730 : : /*
731 : : * Now that we're done reading the startup data, release postmaster's
732 : : * working memory context.
733 : : */
734 [ + - ]: 2305 : if (PostmasterContext)
735 : : {
736 : 2305 : MemoryContextDelete(PostmasterContext);
737 : 2305 : PostmasterContext = NULL;
738 : : }
739 : :
740 : 2305 : MyBgworkerEntry = worker;
2005 peter@eisentraut.org 741 : 2305 : MyBackendType = B_BG_WORKER;
742 : 2305 : init_ps_display(worker->bgw_name);
743 : :
431 heikki.linnakangas@i 744 [ - + ]: 2305 : Assert(GetProcessingMode() == InitProcessing);
745 : :
746 : : /* Apply PostAuthDelay */
4404 rhaas@postgresql.org 747 [ - + ]: 2305 : if (PostAuthDelay > 0)
4404 rhaas@postgresql.org 748 :UBC 0 : pg_usleep(PostAuthDelay * 1000000L);
749 : :
750 : : /*
751 : : * Set up signal handlers.
752 : : */
4404 rhaas@postgresql.org 753 [ + + ]:CBC 2305 : if (worker->bgw_flags & BGWORKER_BACKEND_DATABASE_CONNECTION)
754 : : {
755 : : /*
756 : : * SIGINT is used to signal canceling the current action
757 : : */
758 : 2296 : pqsignal(SIGINT, StatementCancelHandler);
759 : 2296 : pqsignal(SIGUSR1, procsignal_sigusr1_handler);
760 : 2296 : pqsignal(SIGFPE, FloatExceptionHandler);
761 : :
762 : : /* XXX Any other handlers needed here? */
763 : : }
764 : : else
765 : : {
766 : 9 : pqsignal(SIGINT, SIG_IGN);
1650 tmunro@postgresql.or 767 : 9 : pqsignal(SIGUSR1, SIG_IGN);
4404 rhaas@postgresql.org 768 : 9 : pqsignal(SIGFPE, SIG_IGN);
769 : : }
770 : 2305 : pqsignal(SIGTERM, bgworker_die);
771 : : /* SIGQUIT handler was already set up by InitPostmasterChild */
772 : 2305 : pqsignal(SIGHUP, SIG_IGN);
773 : :
4141 bruce@momjian.us 774 : 2305 : InitializeTimeouts(); /* establishes SIGALRM handler */
775 : :
4404 rhaas@postgresql.org 776 : 2305 : pqsignal(SIGPIPE, SIG_IGN);
777 : 2305 : pqsignal(SIGUSR2, SIG_IGN);
778 : 2305 : pqsignal(SIGCHLD, SIG_DFL);
779 : :
780 : : /*
781 : : * If an exception is encountered, processing resumes here.
782 : : *
783 : : * We just need to clean up, report the error, and go away.
784 : : */
785 [ + + ]: 2305 : if (sigsetjmp(local_sigjmp_buf, 1) != 0)
786 : : {
787 : : /* Since not using PG_TRY, must reset error stack by hand */
788 : 129 : error_context_stack = NULL;
789 : :
790 : : /* Prevent interrupts while cleaning up */
791 : 129 : HOLD_INTERRUPTS();
792 : :
793 : : /*
794 : : * sigsetjmp will have blocked all signals, but we may need to accept
795 : : * signals while communicating with our parallel leader. Once we've
796 : : * done HOLD_INTERRUPTS() it should be safe to unblock signals.
797 : : */
1829 tgl@sss.pgh.pa.us 798 : 129 : BackgroundWorkerUnblockSignals();
799 : :
800 : : /* Report the error to the parallel leader and the server log */
4404 rhaas@postgresql.org 801 : 129 : EmitErrorReport();
802 : :
803 : : /*
804 : : * Do we need more cleanup here? For shmem-connected bgworkers, we
805 : : * will call InitProcess below, which will install ProcKill as exit
806 : : * callback. That will take care of releasing locks, etc.
807 : : */
808 : :
809 : : /* and go away */
810 : 129 : proc_exit(1);
811 : : }
812 : :
813 : : /* We can now handle ereport(ERROR) */
814 : 2305 : PG_exception_stack = &local_sigjmp_buf;
815 : :
816 : : /*
817 : : * Create a per-backend PGPROC struct in shared memory. We must do this
818 : : * before we can use LWLocks or access any shared memory.
819 : : */
1485 andres@anarazel.de 820 : 2305 : InitProcess();
821 : :
822 : : /*
823 : : * Early initialization.
824 : : */
825 : 2305 : BaseInit();
826 : :
827 : : /*
828 : : * Look up the entry point function, loading its library if necessary.
829 : : */
3067 tgl@sss.pgh.pa.us 830 : 4610 : entrypt = LookupBackgroundWorkerFunction(worker->bgw_library_name,
831 : 2305 : worker->bgw_function_name);
832 : :
833 : : /*
834 : : * Note that in normal processes, we would call InitPostgres here. For a
835 : : * worker, however, we don't know what database to connect to, yet; so we
836 : : * need to wait until the user code does it via
837 : : * BackgroundWorkerInitializeConnection().
838 : : */
839 : :
840 : : /*
841 : : * Now invoke the user-defined worker code
842 : : */
4404 rhaas@postgresql.org 843 : 2305 : entrypt(worker->bgw_main_arg);
844 : :
845 : : /* ... and if it returns, we're done */
846 : 1375 : proc_exit(0);
847 : : }
848 : :
849 : : /*
850 : : * Connect background worker to a database.
851 : : */
852 : : void
431 heikki.linnakangas@i 853 : 387 : BackgroundWorkerInitializeConnection(const char *dbname, const char *username, uint32 flags)
854 : : {
855 : 387 : BackgroundWorker *worker = MyBgworkerEntry;
856 : 387 : bits32 init_flags = 0; /* never honor session_preload_libraries */
857 : :
858 : : /* ignore datallowconn and ACL_CONNECT? */
859 [ - + ]: 387 : if (flags & BGWORKER_BYPASS_ALLOWCONN)
431 heikki.linnakangas@i 860 :UBC 0 : init_flags |= INIT_PG_OVERRIDE_ALLOW_CONNS;
861 : : /* ignore rolcanlogin? */
431 heikki.linnakangas@i 862 [ - + ]:CBC 387 : if (flags & BGWORKER_BYPASS_ROLELOGINCHECK)
431 heikki.linnakangas@i 863 :UBC 0 : init_flags |= INIT_PG_OVERRIDE_ROLE_LOGIN;
864 : :
865 : : /* XXX is this the right errcode? */
431 heikki.linnakangas@i 866 [ - + ]:CBC 387 : if (!(worker->bgw_flags & BGWORKER_BACKEND_DATABASE_CONNECTION))
431 heikki.linnakangas@i 867 [ # # ]:UBC 0 : ereport(FATAL,
868 : : (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
869 : : errmsg("database connection requirement not indicated during registration")));
870 : :
431 heikki.linnakangas@i 871 :CBC 387 : InitPostgres(dbname, InvalidOid, /* database to connect to */
872 : : username, InvalidOid, /* role to connect as */
873 : : init_flags,
874 : : NULL); /* no out_dbname */
875 : :
876 : : /* it had better not gotten out of "init" mode yet */
877 [ - + ]: 387 : if (!IsInitProcessingMode())
431 heikki.linnakangas@i 878 [ # # ]:UBC 0 : ereport(ERROR,
879 : : (errmsg("invalid processing mode in background worker")));
431 heikki.linnakangas@i 880 :CBC 387 : SetProcessingMode(NormalProcessing);
881 : 387 : }
882 : :
883 : : /*
884 : : * Connect background worker to a database using OIDs.
885 : : */
886 : : void
887 : 1909 : BackgroundWorkerInitializeConnectionByOid(Oid dboid, Oid useroid, uint32 flags)
888 : : {
889 : 1909 : BackgroundWorker *worker = MyBgworkerEntry;
890 : 1909 : bits32 init_flags = 0; /* never honor session_preload_libraries */
891 : :
892 : : /* ignore datallowconn and ACL_CONNECT? */
893 [ + + ]: 1909 : if (flags & BGWORKER_BYPASS_ALLOWCONN)
894 : 1378 : init_flags |= INIT_PG_OVERRIDE_ALLOW_CONNS;
895 : : /* ignore rolcanlogin? */
896 [ + + ]: 1909 : if (flags & BGWORKER_BYPASS_ROLELOGINCHECK)
897 : 1378 : init_flags |= INIT_PG_OVERRIDE_ROLE_LOGIN;
898 : :
899 : : /* XXX is this the right errcode? */
900 [ - + ]: 1909 : if (!(worker->bgw_flags & BGWORKER_BACKEND_DATABASE_CONNECTION))
431 heikki.linnakangas@i 901 [ # # ]:UBC 0 : ereport(FATAL,
902 : : (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
903 : : errmsg("database connection requirement not indicated during registration")));
904 : :
431 heikki.linnakangas@i 905 :CBC 1909 : InitPostgres(NULL, dboid, /* database to connect to */
906 : : NULL, useroid, /* role to connect as */
907 : : init_flags,
908 : : NULL); /* no out_dbname */
909 : :
910 : : /* it had better not gotten out of "init" mode yet */
911 [ - + ]: 1903 : if (!IsInitProcessingMode())
431 heikki.linnakangas@i 912 [ # # ]:UBC 0 : ereport(ERROR,
913 : : (errmsg("invalid processing mode in background worker")));
431 heikki.linnakangas@i 914 :CBC 1903 : SetProcessingMode(NormalProcessing);
915 : 1903 : }
916 : :
917 : : /*
918 : : * Block/unblock signals in a background worker
919 : : */
920 : : void
431 heikki.linnakangas@i 921 :UBC 0 : BackgroundWorkerBlockSignals(void)
922 : : {
923 : 0 : sigprocmask(SIG_SETMASK, &BlockSig, NULL);
924 : 0 : }
925 : :
926 : : void
431 heikki.linnakangas@i 927 :CBC 2434 : BackgroundWorkerUnblockSignals(void)
928 : : {
929 : 2434 : sigprocmask(SIG_SETMASK, &UnBlockSig, NULL);
930 : 2434 : }
931 : :
932 : : /*
933 : : * Register a new static background worker.
934 : : *
935 : : * This can only be called directly from postmaster or in the _PG_init
936 : : * function of a module library that's loaded by shared_preload_libraries;
937 : : * otherwise it will have no effect.
938 : : */
939 : : void
4435 rhaas@postgresql.org 940 : 765 : RegisterBackgroundWorker(BackgroundWorker *worker)
941 : : {
942 : : RegisteredBgWorker *rw;
943 : : static int numworkers = 0;
944 : :
945 : : /*
946 : : * Static background workers can only be registered in the postmaster
947 : : * process.
948 : : */
698 heikki.linnakangas@i 949 [ + - - + ]: 765 : if (IsUnderPostmaster || !IsPostmasterEnvironment)
950 : : {
951 : : /*
952 : : * In EXEC_BACKEND or single-user mode, we process
953 : : * shared_preload_libraries in backend processes too. We cannot
954 : : * register static background workers at that stage, but many
955 : : * libraries' _PG_init() functions don't distinguish whether they're
956 : : * being loaded in the postmaster or in a backend, they just check
957 : : * process_shared_preload_libraries_in_progress. It's a bit sloppy,
958 : : * but for historical reasons we tolerate it. In EXEC_BACKEND mode,
959 : : * the background workers should already have been registered when the
960 : : * library was loaded in postmaster.
961 : : */
698 heikki.linnakangas@i 962 [ # # ]:UBC 0 : if (process_shared_preload_libraries_in_progress)
963 : 0 : return;
964 [ # # ]: 0 : ereport(LOG,
965 : : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
966 : : errmsg("background worker \"%s\": must be registered in \"shared_preload_libraries\"",
967 : : worker->bgw_name)));
4435 rhaas@postgresql.org 968 : 0 : return;
969 : : }
970 : :
971 : : /*
972 : : * Cannot register static background workers after calling
973 : : * BackgroundWorkerShmemInit().
974 : : */
698 heikki.linnakangas@i 975 [ - + ]:CBC 765 : if (BackgroundWorkerData != NULL)
698 heikki.linnakangas@i 976 [ # # ]:UBC 0 : elog(ERROR, "cannot register background worker \"%s\" after shmem init",
977 : : worker->bgw_name);
978 : :
698 heikki.linnakangas@i 979 [ + + ]:CBC 765 : ereport(DEBUG1,
980 : : (errmsg_internal("registering background worker \"%s\"", worker->bgw_name)));
981 : :
4435 rhaas@postgresql.org 982 [ - + ]: 765 : if (!SanityCheckBackgroundWorker(worker, LOG))
4435 rhaas@postgresql.org 983 :UBC 0 : return;
984 : :
4392 rhaas@postgresql.org 985 [ - + ]:CBC 765 : if (worker->bgw_notify_pid != 0)
986 : : {
4392 rhaas@postgresql.org 987 [ # # ]:UBC 0 : ereport(LOG,
988 : : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
989 : : errmsg("background worker \"%s\": only dynamic background workers can request notification",
990 : : worker->bgw_name)));
991 : 0 : return;
992 : : }
993 : :
994 : : /*
995 : : * Enforce maximum number of workers. Note this is overly restrictive: we
996 : : * could allow more non-shmem-connected workers, because these don't count
997 : : * towards the MAX_BACKENDS limit elsewhere. For now, it doesn't seem
998 : : * important to relax this restriction.
999 : : */
4435 rhaas@postgresql.org 1000 [ - + ]:CBC 765 : if (++numworkers > max_worker_processes)
1001 : : {
4435 rhaas@postgresql.org 1002 [ # # ]:UBC 0 : ereport(LOG,
1003 : : (errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
1004 : : errmsg("too many background workers"),
1005 : : errdetail_plural("Up to %d background worker can be registered with the current settings.",
1006 : : "Up to %d background workers can be registered with the current settings.",
1007 : : max_worker_processes,
1008 : : max_worker_processes),
1009 : : errhint("Consider increasing the configuration parameter \"%s\".", "max_worker_processes")));
1010 : 0 : return;
1011 : : }
1012 : :
1013 : : /*
1014 : : * Copy the registration data into the registered workers list.
1015 : : */
698 heikki.linnakangas@i 1016 :CBC 765 : rw = MemoryContextAllocExtended(PostmasterContext,
1017 : : sizeof(RegisteredBgWorker),
1018 : : MCXT_ALLOC_NO_OOM);
4435 rhaas@postgresql.org 1019 [ - + ]: 765 : if (rw == NULL)
1020 : : {
4435 rhaas@postgresql.org 1021 [ # # ]:UBC 0 : ereport(LOG,
1022 : : (errcode(ERRCODE_OUT_OF_MEMORY),
1023 : : errmsg("out of memory")));
1024 : 0 : return;
1025 : : }
1026 : :
4435 rhaas@postgresql.org 1027 :CBC 765 : rw->rw_worker = *worker;
1028 : 765 : rw->rw_pid = 0;
1029 : 765 : rw->rw_crashed_at = 0;
4341 1030 : 765 : rw->rw_terminate = false;
1031 : :
393 heikki.linnakangas@i 1032 : 765 : dlist_push_head(&BackgroundWorkerList, &rw->rw_lnode);
1033 : : }
1034 : :
1035 : : /*
1036 : : * Register a new background worker from a regular backend.
1037 : : *
1038 : : * Returns true on success and false on failure. Failure typically indicates
1039 : : * that no background worker slots are currently available.
1040 : : *
1041 : : * If handle != NULL, we'll set *handle to a pointer that can subsequently
1042 : : * be used as an argument to GetBackgroundWorkerPid(). The caller can
1043 : : * free this pointer using pfree(), if desired.
1044 : : */
1045 : : bool
4392 rhaas@postgresql.org 1046 : 1817 : RegisterDynamicBackgroundWorker(BackgroundWorker *worker,
1047 : : BackgroundWorkerHandle **handle)
1048 : : {
1049 : : int slotno;
4141 bruce@momjian.us 1050 : 1817 : bool success = false;
1051 : : bool parallel;
1052 : 1817 : uint64 generation = 0;
1053 : :
1054 : : /*
1055 : : * We can't register dynamic background workers from the postmaster. If
1056 : : * this is a standalone backend, we're the only process and can't start
1057 : : * any more. In a multi-process environment, it might be theoretically
1058 : : * possible, but we don't currently support it due to locking
1059 : : * considerations; see comments on the BackgroundWorkerSlot data
1060 : : * structure.
1061 : : */
4435 rhaas@postgresql.org 1062 [ - + ]: 1817 : if (!IsUnderPostmaster)
4435 rhaas@postgresql.org 1063 :UBC 0 : return false;
1064 : :
4435 rhaas@postgresql.org 1065 [ - + ]:CBC 1817 : if (!SanityCheckBackgroundWorker(worker, ERROR))
4435 rhaas@postgresql.org 1066 :UBC 0 : return false;
1067 : :
3200 rhaas@postgresql.org 1068 :CBC 1817 : parallel = (worker->bgw_flags & BGWORKER_CLASS_PARALLEL) != 0;
1069 : :
4435 1070 : 1817 : LWLockAcquire(BackgroundWorkerLock, LW_EXCLUSIVE);
1071 : :
1072 : : /*
1073 : : * If this is a parallel worker, check whether there are already too many
1074 : : * parallel workers; if so, don't register another one. Our view of
1075 : : * parallel_terminate_count may be slightly stale, but that doesn't really
1076 : : * matter: we would have gotten the same result if we'd arrived here
1077 : : * slightly earlier anyway. There's no help for it, either, since the
1078 : : * postmaster must not take locks; a memory barrier wouldn't guarantee
1079 : : * anything useful.
1080 : : */
3200 1081 [ + + ]: 1817 : if (parallel && (BackgroundWorkerData->parallel_register_count -
1082 [ + + ]: 1392 : BackgroundWorkerData->parallel_terminate_count) >=
1083 : : max_parallel_workers)
1084 : : {
3070 1085 [ - + ]: 10 : Assert(BackgroundWorkerData->parallel_register_count -
1086 : : BackgroundWorkerData->parallel_terminate_count <=
1087 : : MAX_PARALLEL_WORKER_LIMIT);
3200 1088 : 10 : LWLockRelease(BackgroundWorkerLock);
1089 : 10 : return false;
1090 : : }
1091 : :
1092 : : /*
1093 : : * Look for an unused slot. If we find one, grab it.
1094 : : */
4435 1095 [ + + ]: 5722 : for (slotno = 0; slotno < BackgroundWorkerData->total_slots; ++slotno)
1096 : : {
1097 : 5718 : BackgroundWorkerSlot *slot = &BackgroundWorkerData->slot[slotno];
1098 : :
1099 [ + + ]: 5718 : if (!slot->in_use)
1100 : : {
1101 : 1803 : memcpy(&slot->worker, worker, sizeof(BackgroundWorker));
2999 tgl@sss.pgh.pa.us 1102 : 1803 : slot->pid = InvalidPid; /* indicates not started yet */
4392 rhaas@postgresql.org 1103 : 1803 : slot->generation++;
4341 1104 : 1803 : slot->terminate = false;
4392 1105 : 1803 : generation = slot->generation;
3200 1106 [ + + ]: 1803 : if (parallel)
1107 : 1378 : BackgroundWorkerData->parallel_register_count++;
1108 : :
1109 : : /*
1110 : : * Make sure postmaster doesn't see the slot as in use before it
1111 : : * sees the new contents.
1112 : : */
4435 1113 : 1803 : pg_write_barrier();
1114 : :
1115 : 1803 : slot->in_use = true;
1116 : 1803 : success = true;
1117 : 1803 : break;
1118 : : }
1119 : : }
1120 : :
1121 : 1807 : LWLockRelease(BackgroundWorkerLock);
1122 : :
1123 : : /* If we found a slot, tell the postmaster to notice the change. */
1124 [ + + ]: 1807 : if (success)
1125 : 1803 : SendPostmasterSignal(PMSIGNAL_BACKGROUND_WORKER_CHANGE);
1126 : :
1127 : : /*
1128 : : * If we found a slot and the user has provided a handle, initialize it.
1129 : : */
4392 1130 [ + + + - ]: 1807 : if (success && handle)
1131 : : {
1132 : 1803 : *handle = palloc(sizeof(BackgroundWorkerHandle));
1133 : 1803 : (*handle)->slot = slotno;
1134 : 1803 : (*handle)->generation = generation;
1135 : : }
1136 : :
4435 1137 : 1807 : return success;
1138 : : }
1139 : :
1140 : : /*
1141 : : * Get the PID of a dynamically-registered background worker.
1142 : : *
1143 : : * If the worker is determined to be running, the return value will be
1144 : : * BGWH_STARTED and *pidp will get the PID of the worker process. If the
1145 : : * postmaster has not yet attempted to start the worker, the return value will
1146 : : * be BGWH_NOT_YET_STARTED. Otherwise, the return value is BGWH_STOPPED.
1147 : : *
1148 : : * BGWH_STOPPED can indicate either that the worker is temporarily stopped
1149 : : * (because it is configured for automatic restart and exited non-zero),
1150 : : * or that the worker is permanently stopped (because it exited with exit
1151 : : * code 0, or was not configured for automatic restart), or even that the
1152 : : * worker was unregistered without ever starting (either because startup
1153 : : * failed and the worker is not configured for automatic restart, or because
1154 : : * TerminateBackgroundWorker was used before the worker was successfully
1155 : : * started).
1156 : : */
1157 : : BgwHandleStatus
4392 1158 : 2905176 : GetBackgroundWorkerPid(BackgroundWorkerHandle *handle, pid_t *pidp)
1159 : : {
1160 : : BackgroundWorkerSlot *slot;
1161 : : pid_t pid;
1162 : :
1163 [ - + ]: 2905176 : Assert(handle->slot < max_worker_processes);
1164 : 2905176 : slot = &BackgroundWorkerData->slot[handle->slot];
1165 : :
1166 : : /*
1167 : : * We could probably arrange to synchronize access to data using memory
1168 : : * barriers only, but for now, let's just keep it simple and grab the
1169 : : * lock. It seems unlikely that there will be enough traffic here to
1170 : : * result in meaningful contention.
1171 : : */
1172 : 2905176 : LWLockAcquire(BackgroundWorkerLock, LW_SHARED);
1173 : :
1174 : : /*
1175 : : * The generation number can't be concurrently changed while we hold the
1176 : : * lock. The pid, which is updated by the postmaster, can change at any
1177 : : * time, but we assume such changes are atomic. So the value we read
1178 : : * won't be garbage, but it might be out of date by the time the caller
1179 : : * examines it (but that's unavoidable anyway).
1180 : : *
1181 : : * The in_use flag could be in the process of changing from true to false,
1182 : : * but if it is already false then it can't change further.
1183 : : */
2831 1184 [ + + + + ]: 2905176 : if (handle->generation != slot->generation || !slot->in_use)
4392 1185 : 1379 : pid = 0;
1186 : : else
1187 : 2903797 : pid = slot->pid;
1188 : :
1189 : : /* All done. */
1190 : 2905176 : LWLockRelease(BackgroundWorkerLock);
1191 : :
1192 [ + + ]: 2905176 : if (pid == 0)
1193 : 1379 : return BGWH_STOPPED;
1194 [ + + ]: 2903797 : else if (pid == InvalidPid)
1195 : 145225 : return BGWH_NOT_YET_STARTED;
1196 : 2758572 : *pidp = pid;
1197 : 2758572 : return BGWH_STARTED;
1198 : : }
1199 : :
1200 : : /*
1201 : : * Wait for a background worker to start up.
1202 : : *
1203 : : * This is like GetBackgroundWorkerPid(), except that if the worker has not
1204 : : * yet started, we wait for it to do so; thus, BGWH_NOT_YET_STARTED is never
1205 : : * returned. However, if the postmaster has died, we give up and return
1206 : : * BGWH_POSTMASTER_DIED, since it that case we know that startup will not
1207 : : * take place.
1208 : : *
1209 : : * The caller *must* have set our PID as the worker's bgw_notify_pid,
1210 : : * else we will not be awoken promptly when the worker's state changes.
1211 : : */
1212 : : BgwHandleStatus
1213 : 7 : WaitForBackgroundWorkerStartup(BackgroundWorkerHandle *handle, pid_t *pidp)
1214 : : {
1215 : : BgwHandleStatus status;
1216 : : int rc;
1217 : :
1218 : : for (;;)
1219 : 9 : {
1220 : : pid_t pid;
1221 : :
3620 1222 [ - + ]: 16 : CHECK_FOR_INTERRUPTS();
1223 : :
1224 : 16 : status = GetBackgroundWorkerPid(handle, &pid);
1225 [ + + ]: 16 : if (status == BGWH_STARTED)
1226 : 7 : *pidp = pid;
1227 [ + + ]: 16 : if (status != BGWH_NOT_YET_STARTED)
1228 : 7 : break;
1229 : :
1230 : 9 : rc = WaitLatch(MyLatch,
1231 : : WL_LATCH_SET | WL_POSTMASTER_DEATH, 0,
1232 : : WAIT_EVENT_BGWORKER_STARTUP);
1233 : :
1234 [ - + ]: 9 : if (rc & WL_POSTMASTER_DEATH)
1235 : : {
3620 rhaas@postgresql.org 1236 :UBC 0 : status = BGWH_POSTMASTER_DIED;
1237 : 0 : break;
1238 : : }
1239 : :
3620 rhaas@postgresql.org 1240 :CBC 9 : ResetLatch(MyLatch);
1241 : : }
1242 : :
3782 1243 : 7 : return status;
1244 : : }
1245 : :
1246 : : /*
1247 : : * Wait for a background worker to stop.
1248 : : *
1249 : : * If the worker hasn't yet started, or is running, we wait for it to stop
1250 : : * and then return BGWH_STOPPED. However, if the postmaster has died, we give
1251 : : * up and return BGWH_POSTMASTER_DIED, because it's the postmaster that
1252 : : * notifies us when a worker's state changes.
1253 : : *
1254 : : * The caller *must* have set our PID as the worker's bgw_notify_pid,
1255 : : * else we will not be awoken promptly when the worker's state changes.
1256 : : */
1257 : : BgwHandleStatus
1258 : 1379 : WaitForBackgroundWorkerShutdown(BackgroundWorkerHandle *handle)
1259 : : {
1260 : : BgwHandleStatus status;
1261 : : int rc;
1262 : :
1263 : : for (;;)
1264 : 1583 : {
1265 : : pid_t pid;
1266 : :
3620 1267 [ + + ]: 2962 : CHECK_FOR_INTERRUPTS();
1268 : :
1269 : 2962 : status = GetBackgroundWorkerPid(handle, &pid);
1270 [ + + ]: 2962 : if (status == BGWH_STOPPED)
3320 tgl@sss.pgh.pa.us 1271 : 1379 : break;
1272 : :
3014 andres@anarazel.de 1273 : 1583 : rc = WaitLatch(MyLatch,
1274 : : WL_LATCH_SET | WL_POSTMASTER_DEATH, 0,
1275 : : WAIT_EVENT_BGWORKER_SHUTDOWN);
1276 : :
3620 rhaas@postgresql.org 1277 [ - + ]: 1583 : if (rc & WL_POSTMASTER_DEATH)
1278 : : {
3320 tgl@sss.pgh.pa.us 1279 :UBC 0 : status = BGWH_POSTMASTER_DIED;
1280 : 0 : break;
1281 : : }
1282 : :
3014 andres@anarazel.de 1283 :CBC 1583 : ResetLatch(MyLatch);
1284 : : }
1285 : :
4392 rhaas@postgresql.org 1286 : 1379 : return status;
1287 : : }
1288 : :
1289 : : /*
1290 : : * Instruct the postmaster to terminate a background worker.
1291 : : *
1292 : : * Note that it's safe to do this without regard to whether the worker is
1293 : : * still running, or even if the worker may already have exited and been
1294 : : * unregistered.
1295 : : */
1296 : : void
4341 1297 : 6 : TerminateBackgroundWorker(BackgroundWorkerHandle *handle)
1298 : : {
1299 : : BackgroundWorkerSlot *slot;
4141 bruce@momjian.us 1300 : 6 : bool signal_postmaster = false;
1301 : :
4341 rhaas@postgresql.org 1302 [ - + ]: 6 : Assert(handle->slot < max_worker_processes);
1303 : 6 : slot = &BackgroundWorkerData->slot[handle->slot];
1304 : :
1305 : : /* Set terminate flag in shared memory, unless slot has been reused. */
1306 : 6 : LWLockAcquire(BackgroundWorkerLock, LW_EXCLUSIVE);
1307 [ + - ]: 6 : if (handle->generation == slot->generation)
1308 : : {
1309 : 6 : slot->terminate = true;
1310 : 6 : signal_postmaster = true;
1311 : : }
1312 : 6 : LWLockRelease(BackgroundWorkerLock);
1313 : :
1314 : : /* Make sure the postmaster notices the change to shared memory. */
1315 [ + - ]: 6 : if (signal_postmaster)
1316 : 6 : SendPostmasterSignal(PMSIGNAL_BACKGROUND_WORKER_CHANGE);
1317 : 6 : }
1318 : :
1319 : : /*
1320 : : * Look up (and possibly load) a bgworker entry point function.
1321 : : *
1322 : : * For functions contained in the core code, we use library name "postgres"
1323 : : * and consult the InternalBGWorkers array. External functions are
1324 : : * looked up, and loaded if necessary, using load_external_function().
1325 : : *
1326 : : * The point of this is to pass function names as strings across process
1327 : : * boundaries. We can't pass actual function addresses because of the
1328 : : * possibility that the function has been loaded at a different address
1329 : : * in a different process. This is obviously a hazard for functions in
1330 : : * loadable libraries, but it can happen even for functions in the core code
1331 : : * on platforms using EXEC_BACKEND (e.g., Windows).
1332 : : *
1333 : : * At some point it might be worthwhile to get rid of InternalBGWorkers[]
1334 : : * in favor of applying load_external_function() for core functions too;
1335 : : * but that raises portability issues that are not worth addressing now.
1336 : : */
1337 : : static bgworker_main_type
3067 tgl@sss.pgh.pa.us 1338 : 2305 : LookupBackgroundWorkerFunction(const char *libraryname, const char *funcname)
1339 : : {
1340 : : /*
1341 : : * If the function is to be loaded from postgres itself, search the
1342 : : * InternalBGWorkers array.
1343 : : */
1344 [ + + ]: 2305 : if (strcmp(libraryname, "postgres") == 0)
1345 : : {
1346 : : int i;
1347 : :
1348 [ + - ]: 4139 : for (i = 0; i < lengthof(InternalBGWorkers); i++)
1349 : : {
1350 [ + + ]: 4139 : if (strcmp(InternalBGWorkers[i].fn_name, funcname) == 0)
1351 : 2292 : return InternalBGWorkers[i].fn_addr;
1352 : : }
1353 : :
1354 : : /* We can only reach this by programming error. */
3067 tgl@sss.pgh.pa.us 1355 [ # # ]:UBC 0 : elog(ERROR, "internal function \"%s\" not found", funcname);
1356 : : }
1357 : :
1358 : : /* Otherwise load from external library. */
3067 tgl@sss.pgh.pa.us 1359 :CBC 13 : return (bgworker_main_type)
1360 : 13 : load_external_function(libraryname, funcname, true, NULL);
1361 : : }
1362 : :
1363 : : /*
1364 : : * Given a PID, get the bgw_type of the background worker. Returns NULL if
1365 : : * not a valid background worker.
1366 : : *
1367 : : * The return value is in static memory belonging to this function, so it has
1368 : : * to be used before calling this function again. This is so that the caller
1369 : : * doesn't have to worry about the background worker locking protocol.
1370 : : */
1371 : : const char *
2928 peter_e@gmx.net 1372 : 833 : GetBackgroundWorkerTypeByPid(pid_t pid)
1373 : : {
1374 : : int slotno;
1375 : 833 : bool found = false;
1376 : : static char result[BGW_MAXLEN];
1377 : :
1378 : 833 : LWLockAcquire(BackgroundWorkerLock, LW_SHARED);
1379 : :
1380 [ + - ]: 947 : for (slotno = 0; slotno < BackgroundWorkerData->total_slots; slotno++)
1381 : : {
1382 : 947 : BackgroundWorkerSlot *slot = &BackgroundWorkerData->slot[slotno];
1383 : :
1384 [ + + + + ]: 947 : if (slot->pid > 0 && slot->pid == pid)
1385 : : {
1386 : 833 : strcpy(result, slot->worker.bgw_type);
1387 : 833 : found = true;
1388 : 833 : break;
1389 : : }
1390 : : }
1391 : :
1392 : 833 : LWLockRelease(BackgroundWorkerLock);
1393 : :
1394 [ - + ]: 833 : if (!found)
2928 peter_e@gmx.net 1395 :UBC 0 : return NULL;
1396 : :
2928 peter_e@gmx.net 1397 :CBC 833 : return result;
1398 : : }
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