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latch.c
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1 /*-------------------------------------------------------------------------
2  *
3  * latch.c
4  * Routines for inter-process latches
5  *
6  * The poll() implementation uses the so-called self-pipe trick to overcome the
7  * race condition involved with poll() and setting a global flag in the signal
8  * handler. When a latch is set and the current process is waiting for it, the
9  * signal handler wakes up the poll() in WaitLatch by writing a byte to a pipe.
10  * A signal by itself doesn't interrupt poll() on all platforms, and even on
11  * platforms where it does, a signal that arrives just before the poll() call
12  * does not prevent poll() from entering sleep. An incoming byte on a pipe
13  * however reliably interrupts the sleep, and causes poll() to return
14  * immediately even if the signal arrives before poll() begins.
15  *
16  * The epoll() implementation overcomes the race with a different technique: it
17  * keeps SIGURG blocked and consumes from a signalfd() descriptor instead. We
18  * don't need to register a signal handler or create our own self-pipe. We
19  * assume that any system that has Linux epoll() also has Linux signalfd().
20  *
21  * The kqueue() implementation waits for SIGURG with EVFILT_SIGNAL.
22  *
23  * The Windows implementation uses Windows events that are inherited by all
24  * postmaster child processes. There's no need for the self-pipe trick there.
25  *
26  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
27  * Portions Copyright (c) 1994, Regents of the University of California
28  *
29  * IDENTIFICATION
30  * src/backend/storage/ipc/latch.c
31  *
32  *-------------------------------------------------------------------------
33  */
34 #include "postgres.h"
35 
36 #include <fcntl.h>
37 #include <limits.h>
38 #include <signal.h>
39 #include <unistd.h>
40 #ifdef HAVE_SYS_EPOLL_H
41 #include <sys/epoll.h>
42 #endif
43 #ifdef HAVE_SYS_EVENT_H
44 #include <sys/event.h>
45 #endif
46 #ifdef HAVE_POLL_H
47 #include <poll.h>
48 #endif
49 
50 #include "libpq/pqsignal.h"
51 #include "miscadmin.h"
52 #include "pgstat.h"
53 #include "port/atomics.h"
54 #include "portability/instr_time.h"
55 #include "postmaster/postmaster.h"
56 #include "storage/fd.h"
57 #include "storage/ipc.h"
58 #include "storage/latch.h"
59 #include "storage/pmsignal.h"
60 #include "storage/shmem.h"
61 #include "utils/memutils.h"
62 
63 /*
64  * Select the fd readiness primitive to use. Normally the "most modern"
65  * primitive supported by the OS will be used, but for testing it can be
66  * useful to manually specify the used primitive. If desired, just add a
67  * define somewhere before this block.
68  */
69 #if defined(WAIT_USE_EPOLL) || defined(WAIT_USE_POLL) || \
70  defined(WAIT_USE_KQUEUE) || defined(WAIT_USE_WIN32)
71 /* don't overwrite manual choice */
72 #elif defined(HAVE_SYS_EPOLL_H)
73 #define WAIT_USE_EPOLL
74 #elif defined(HAVE_KQUEUE)
75 #define WAIT_USE_KQUEUE
76 #elif defined(HAVE_POLL)
77 #define WAIT_USE_POLL
78 #elif WIN32
79 #define WAIT_USE_WIN32
80 #else
81 #error "no wait set implementation available"
82 #endif
83 
84 #ifdef WAIT_USE_EPOLL
85 #include <sys/signalfd.h>
86 #endif
87 
88 /* typedef in latch.h */
90 {
91  int nevents; /* number of registered events */
92  int nevents_space; /* maximum number of events in this set */
93 
94  /*
95  * Array, of nevents_space length, storing the definition of events this
96  * set is waiting for.
97  */
99 
100  /*
101  * If WL_LATCH_SET is specified in any wait event, latch is a pointer to
102  * said latch, and latch_pos the offset in the ->events array. This is
103  * useful because we check the state of the latch before performing doing
104  * syscalls related to waiting.
105  */
108 
109  /*
110  * WL_EXIT_ON_PM_DEATH is converted to WL_POSTMASTER_DEATH, but this flag
111  * is set so that we'll exit immediately if postmaster death is detected,
112  * instead of returning.
113  */
115 
116 #if defined(WAIT_USE_EPOLL)
117  int epoll_fd;
118  /* epoll_wait returns events in a user provided arrays, allocate once */
119  struct epoll_event *epoll_ret_events;
120 #elif defined(WAIT_USE_KQUEUE)
121  int kqueue_fd;
122  /* kevent returns events in a user provided arrays, allocate once */
123  struct kevent *kqueue_ret_events;
124  bool report_postmaster_not_running;
125 #elif defined(WAIT_USE_POLL)
126  /* poll expects events to be waited on every poll() call, prepare once */
127  struct pollfd *pollfds;
128 #elif defined(WAIT_USE_WIN32)
129 
130  /*
131  * Array of windows events. The first element always contains
132  * pgwin32_signal_event, so the remaining elements are offset by one (i.e.
133  * event->pos + 1).
134  */
135  HANDLE *handles;
136 #endif
137 };
138 
139 /* A common WaitEventSet used to implement WatchLatch() */
141 
142 /* The position of the latch in LatchWaitSet. */
143 #define LatchWaitSetLatchPos 0
144 
145 #ifndef WIN32
146 /* Are we currently in WaitLatch? The signal handler would like to know. */
147 static volatile sig_atomic_t waiting = false;
148 #endif
149 
150 #ifdef WAIT_USE_EPOLL
151 /* On Linux, we'll receive SIGURG via a signalfd file descriptor. */
152 static int signal_fd = -1;
153 #endif
154 
155 #if defined(WAIT_USE_POLL)
156 /* Read and write ends of the self-pipe */
157 static int selfpipe_readfd = -1;
158 static int selfpipe_writefd = -1;
159 
160 /* Process owning the self-pipe --- needed for checking purposes */
161 static int selfpipe_owner_pid = 0;
162 
163 /* Private function prototypes */
164 static void latch_sigurg_handler(SIGNAL_ARGS);
165 static void sendSelfPipeByte(void);
166 #endif
167 
168 #if defined(WAIT_USE_POLL) || defined(WAIT_USE_EPOLL)
169 static void drain(void);
170 #endif
171 
172 #if defined(WAIT_USE_EPOLL)
173 static void WaitEventAdjustEpoll(WaitEventSet *set, WaitEvent *event, int action);
174 #elif defined(WAIT_USE_KQUEUE)
175 static void WaitEventAdjustKqueue(WaitEventSet *set, WaitEvent *event, int old_events);
176 #elif defined(WAIT_USE_POLL)
177 static void WaitEventAdjustPoll(WaitEventSet *set, WaitEvent *event);
178 #elif defined(WAIT_USE_WIN32)
179 static void WaitEventAdjustWin32(WaitEventSet *set, WaitEvent *event);
180 #endif
181 
182 static inline int WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
183  WaitEvent *occurred_events, int nevents);
184 
185 /*
186  * Initialize the process-local latch infrastructure.
187  *
188  * This must be called once during startup of any process that can wait on
189  * latches, before it issues any InitLatch() or OwnLatch() calls.
190  */
191 void
193 {
194 #if defined(WAIT_USE_POLL)
195  int pipefd[2];
196 
197  if (IsUnderPostmaster)
198  {
199  /*
200  * We might have inherited connections to a self-pipe created by the
201  * postmaster. It's critical that child processes create their own
202  * self-pipes, of course, and we really want them to close the
203  * inherited FDs for safety's sake.
204  */
205  if (selfpipe_owner_pid != 0)
206  {
207  /* Assert we go through here but once in a child process */
208  Assert(selfpipe_owner_pid != MyProcPid);
209  /* Release postmaster's pipe FDs; ignore any error */
210  (void) close(selfpipe_readfd);
211  (void) close(selfpipe_writefd);
212  /* Clean up, just for safety's sake; we'll set these below */
213  selfpipe_readfd = selfpipe_writefd = -1;
214  selfpipe_owner_pid = 0;
215  /* Keep fd.c's accounting straight */
218  }
219  else
220  {
221  /*
222  * Postmaster didn't create a self-pipe ... or else we're in an
223  * EXEC_BACKEND build, in which case it doesn't matter since the
224  * postmaster's pipe FDs were closed by the action of FD_CLOEXEC.
225  * fd.c won't have state to clean up, either.
226  */
227  Assert(selfpipe_readfd == -1);
228  }
229  }
230  else
231  {
232  /* In postmaster or standalone backend, assert we do this but once */
233  Assert(selfpipe_readfd == -1);
234  Assert(selfpipe_owner_pid == 0);
235  }
236 
237  /*
238  * Set up the self-pipe that allows a signal handler to wake up the
239  * poll()/epoll_wait() in WaitLatch. Make the write-end non-blocking, so
240  * that SetLatch won't block if the event has already been set many times
241  * filling the kernel buffer. Make the read-end non-blocking too, so that
242  * we can easily clear the pipe by reading until EAGAIN or EWOULDBLOCK.
243  * Also, make both FDs close-on-exec, since we surely do not want any
244  * child processes messing with them.
245  */
246  if (pipe(pipefd) < 0)
247  elog(FATAL, "pipe() failed: %m");
248  if (fcntl(pipefd[0], F_SETFL, O_NONBLOCK) == -1)
249  elog(FATAL, "fcntl(F_SETFL) failed on read-end of self-pipe: %m");
250  if (fcntl(pipefd[1], F_SETFL, O_NONBLOCK) == -1)
251  elog(FATAL, "fcntl(F_SETFL) failed on write-end of self-pipe: %m");
252  if (fcntl(pipefd[0], F_SETFD, FD_CLOEXEC) == -1)
253  elog(FATAL, "fcntl(F_SETFD) failed on read-end of self-pipe: %m");
254  if (fcntl(pipefd[1], F_SETFD, FD_CLOEXEC) == -1)
255  elog(FATAL, "fcntl(F_SETFD) failed on write-end of self-pipe: %m");
256 
257  selfpipe_readfd = pipefd[0];
258  selfpipe_writefd = pipefd[1];
259  selfpipe_owner_pid = MyProcPid;
260 
261  /* Tell fd.c about these two long-lived FDs */
264 
265  pqsignal(SIGURG, latch_sigurg_handler);
266 #endif
267 
268 #ifdef WAIT_USE_EPOLL
269  sigset_t signalfd_mask;
270 
271  /* Block SIGURG, because we'll receive it through a signalfd. */
272  sigaddset(&UnBlockSig, SIGURG);
273 
274  /* Set up the signalfd to receive SIGURG notifications. */
275  sigemptyset(&signalfd_mask);
276  sigaddset(&signalfd_mask, SIGURG);
277  signal_fd = signalfd(-1, &signalfd_mask, SFD_NONBLOCK | SFD_CLOEXEC);
278  if (signal_fd < 0)
279  elog(FATAL, "signalfd() failed");
281 #endif
282 
283 #ifdef WAIT_USE_KQUEUE
284  /* Ignore SIGURG, because we'll receive it via kqueue. */
285  pqsignal(SIGURG, SIG_IGN);
286 #endif
287 }
288 
289 void
291 {
293 
294  Assert(LatchWaitSet == NULL);
295 
296  /* Set up the WaitEventSet used by WaitLatch(). */
297  LatchWaitSet = CreateWaitEventSet(TopMemoryContext, 2);
299  MyLatch, NULL);
300  if (IsUnderPostmaster)
302  PGINVALID_SOCKET, NULL, NULL);
303 
305 }
306 
307 void
309 {
310 #if defined(WAIT_USE_POLL)
311  pqsignal(SIGURG, SIG_IGN);
312 #endif
313 
314  if (LatchWaitSet)
315  {
316  FreeWaitEventSet(LatchWaitSet);
317  LatchWaitSet = NULL;
318  }
319 
320 #if defined(WAIT_USE_POLL)
321  close(selfpipe_readfd);
322  close(selfpipe_writefd);
323  selfpipe_readfd = -1;
324  selfpipe_writefd = -1;
325  selfpipe_owner_pid = InvalidPid;
326 #endif
327 
328 #if defined(WAIT_USE_EPOLL)
329  close(signal_fd);
330  signal_fd = -1;
331 #endif
332 }
333 
334 /*
335  * Initialize a process-local latch.
336  */
337 void
339 {
340  latch->is_set = false;
341  latch->maybe_sleeping = false;
342  latch->owner_pid = MyProcPid;
343  latch->is_shared = false;
344 
345 #if defined(WAIT_USE_POLL)
346  /* Assert InitializeLatchSupport has been called in this process */
347  Assert(selfpipe_readfd >= 0 && selfpipe_owner_pid == MyProcPid);
348 #elif defined(WAIT_USE_WIN32)
349  latch->event = CreateEvent(NULL, TRUE, FALSE, NULL);
350  if (latch->event == NULL)
351  elog(ERROR, "CreateEvent failed: error code %lu", GetLastError());
352 #endif /* WIN32 */
353 }
354 
355 /*
356  * Initialize a shared latch that can be set from other processes. The latch
357  * is initially owned by no-one; use OwnLatch to associate it with the
358  * current process.
359  *
360  * InitSharedLatch needs to be called in postmaster before forking child
361  * processes, usually right after allocating the shared memory block
362  * containing the latch with ShmemInitStruct. (The Unix implementation
363  * doesn't actually require that, but the Windows one does.) Because of
364  * this restriction, we have no concurrency issues to worry about here.
365  *
366  * Note that other handles created in this module are never marked as
367  * inheritable. Thus we do not need to worry about cleaning up child
368  * process references to postmaster-private latches or WaitEventSets.
369  */
370 void
372 {
373 #ifdef WIN32
374  SECURITY_ATTRIBUTES sa;
375 
376  /*
377  * Set up security attributes to specify that the events are inherited.
378  */
379  ZeroMemory(&sa, sizeof(sa));
380  sa.nLength = sizeof(sa);
381  sa.bInheritHandle = TRUE;
382 
383  latch->event = CreateEvent(&sa, TRUE, FALSE, NULL);
384  if (latch->event == NULL)
385  elog(ERROR, "CreateEvent failed: error code %lu", GetLastError());
386 #endif
387 
388  latch->is_set = false;
389  latch->maybe_sleeping = false;
390  latch->owner_pid = 0;
391  latch->is_shared = true;
392 }
393 
394 /*
395  * Associate a shared latch with the current process, allowing it to
396  * wait on the latch.
397  *
398  * Although there is a sanity check for latch-already-owned, we don't do
399  * any sort of locking here, meaning that we could fail to detect the error
400  * if two processes try to own the same latch at about the same time. If
401  * there is any risk of that, caller must provide an interlock to prevent it.
402  */
403 void
405 {
406  /* Sanity checks */
407  Assert(latch->is_shared);
408 
409 #if defined(WAIT_USE_POLL)
410  /* Assert InitializeLatchSupport has been called in this process */
411  Assert(selfpipe_readfd >= 0 && selfpipe_owner_pid == MyProcPid);
412 #endif
413 
414  if (latch->owner_pid != 0)
415  elog(ERROR, "latch already owned");
416 
417  latch->owner_pid = MyProcPid;
418 }
419 
420 /*
421  * Disown a shared latch currently owned by the current process.
422  */
423 void
425 {
426  Assert(latch->is_shared);
427  Assert(latch->owner_pid == MyProcPid);
428 
429  latch->owner_pid = 0;
430 }
431 
432 /*
433  * Wait for a given latch to be set, or for postmaster death, or until timeout
434  * is exceeded. 'wakeEvents' is a bitmask that specifies which of those events
435  * to wait for. If the latch is already set (and WL_LATCH_SET is given), the
436  * function returns immediately.
437  *
438  * The "timeout" is given in milliseconds. It must be >= 0 if WL_TIMEOUT flag
439  * is given. Although it is declared as "long", we don't actually support
440  * timeouts longer than INT_MAX milliseconds. Note that some extra overhead
441  * is incurred when WL_TIMEOUT is given, so avoid using a timeout if possible.
442  *
443  * The latch must be owned by the current process, ie. it must be a
444  * process-local latch initialized with InitLatch, or a shared latch
445  * associated with the current process by calling OwnLatch.
446  *
447  * Returns bit mask indicating which condition(s) caused the wake-up. Note
448  * that if multiple wake-up conditions are true, there is no guarantee that
449  * we return all of them in one call, but we will return at least one.
450  */
451 int
452 WaitLatch(Latch *latch, int wakeEvents, long timeout,
453  uint32 wait_event_info)
454 {
455  WaitEvent event;
456 
457  /* Postmaster-managed callers must handle postmaster death somehow. */
459  (wakeEvents & WL_EXIT_ON_PM_DEATH) ||
460  (wakeEvents & WL_POSTMASTER_DEATH));
461 
462  /*
463  * Some callers may have a latch other than MyLatch, or no latch at all,
464  * or want to handle postmaster death differently. It's cheap to assign
465  * those, so just do it every time.
466  */
467  if (!(wakeEvents & WL_LATCH_SET))
468  latch = NULL;
469  ModifyWaitEvent(LatchWaitSet, LatchWaitSetLatchPos, WL_LATCH_SET, latch);
470  LatchWaitSet->exit_on_postmaster_death =
471  ((wakeEvents & WL_EXIT_ON_PM_DEATH) != 0);
472 
473  if (WaitEventSetWait(LatchWaitSet,
474  (wakeEvents & WL_TIMEOUT) ? timeout : -1,
475  &event, 1,
476  wait_event_info) == 0)
477  return WL_TIMEOUT;
478  else
479  return event.events;
480 }
481 
482 /*
483  * Like WaitLatch, but with an extra socket argument for WL_SOCKET_*
484  * conditions.
485  *
486  * When waiting on a socket, EOF and error conditions always cause the socket
487  * to be reported as readable/writable/connected, so that the caller can deal
488  * with the condition.
489  *
490  * wakeEvents must include either WL_EXIT_ON_PM_DEATH for automatic exit
491  * if the postmaster dies or WL_POSTMASTER_DEATH for a flag set in the
492  * return value if the postmaster dies. The latter is useful for rare cases
493  * where some behavior other than immediate exit is needed.
494  *
495  * NB: These days this is just a wrapper around the WaitEventSet API. When
496  * using a latch very frequently, consider creating a longer living
497  * WaitEventSet instead; that's more efficient.
498  */
499 int
500 WaitLatchOrSocket(Latch *latch, int wakeEvents, pgsocket sock,
501  long timeout, uint32 wait_event_info)
502 {
503  int ret = 0;
504  int rc;
505  WaitEvent event;
507 
508  if (wakeEvents & WL_TIMEOUT)
509  Assert(timeout >= 0);
510  else
511  timeout = -1;
512 
513  if (wakeEvents & WL_LATCH_SET)
514  AddWaitEventToSet(set, WL_LATCH_SET, PGINVALID_SOCKET,
515  latch, NULL);
516 
517  /* Postmaster-managed callers must handle postmaster death somehow. */
519  (wakeEvents & WL_EXIT_ON_PM_DEATH) ||
520  (wakeEvents & WL_POSTMASTER_DEATH));
521 
522  if ((wakeEvents & WL_POSTMASTER_DEATH) && IsUnderPostmaster)
523  AddWaitEventToSet(set, WL_POSTMASTER_DEATH, PGINVALID_SOCKET,
524  NULL, NULL);
525 
526  if ((wakeEvents & WL_EXIT_ON_PM_DEATH) && IsUnderPostmaster)
527  AddWaitEventToSet(set, WL_EXIT_ON_PM_DEATH, PGINVALID_SOCKET,
528  NULL, NULL);
529 
530  if (wakeEvents & WL_SOCKET_MASK)
531  {
532  int ev;
533 
534  ev = wakeEvents & WL_SOCKET_MASK;
535  AddWaitEventToSet(set, ev, sock, NULL, NULL);
536  }
537 
538  rc = WaitEventSetWait(set, timeout, &event, 1, wait_event_info);
539 
540  if (rc == 0)
541  ret |= WL_TIMEOUT;
542  else
543  {
544  ret |= event.events & (WL_LATCH_SET |
545  WL_POSTMASTER_DEATH |
547  }
548 
549  FreeWaitEventSet(set);
550 
551  return ret;
552 }
553 
554 /*
555  * Sets a latch and wakes up anyone waiting on it.
556  *
557  * This is cheap if the latch is already set, otherwise not so much.
558  *
559  * NB: when calling this in a signal handler, be sure to save and restore
560  * errno around it. (That's standard practice in most signal handlers, of
561  * course, but we used to omit it in handlers that only set a flag.)
562  *
563  * NB: this function is called from critical sections and signal handlers so
564  * throwing an error is not a good idea.
565  */
566 void
568 {
569 #ifndef WIN32
570  pid_t owner_pid;
571 #else
572  HANDLE handle;
573 #endif
574 
575  /*
576  * The memory barrier has to be placed here to ensure that any flag
577  * variables possibly changed by this process have been flushed to main
578  * memory, before we check/set is_set.
579  */
581 
582  /* Quick exit if already set */
583  if (latch->is_set)
584  return;
585 
586  latch->is_set = true;
587 
589  if (!latch->maybe_sleeping)
590  return;
591 
592 #ifndef WIN32
593 
594  /*
595  * See if anyone's waiting for the latch. It can be the current process if
596  * we're in a signal handler. We use the self-pipe or SIGURG to ourselves
597  * to wake up WaitEventSetWaitBlock() without races in that case. If it's
598  * another process, send a signal.
599  *
600  * Fetch owner_pid only once, in case the latch is concurrently getting
601  * owned or disowned. XXX: This assumes that pid_t is atomic, which isn't
602  * guaranteed to be true! In practice, the effective range of pid_t fits
603  * in a 32 bit integer, and so should be atomic. In the worst case, we
604  * might end up signaling the wrong process. Even then, you're very
605  * unlucky if a process with that bogus pid exists and belongs to
606  * Postgres; and PG database processes should handle excess SIGUSR1
607  * interrupts without a problem anyhow.
608  *
609  * Another sort of race condition that's possible here is for a new
610  * process to own the latch immediately after we look, so we don't signal
611  * it. This is okay so long as all callers of ResetLatch/WaitLatch follow
612  * the standard coding convention of waiting at the bottom of their loops,
613  * not the top, so that they'll correctly process latch-setting events
614  * that happen before they enter the loop.
615  */
616  owner_pid = latch->owner_pid;
617  if (owner_pid == 0)
618  return;
619  else if (owner_pid == MyProcPid)
620  {
621 #if defined(WAIT_USE_POLL)
622  if (waiting)
623  sendSelfPipeByte();
624 #else
625  if (waiting)
626  kill(MyProcPid, SIGURG);
627 #endif
628  }
629  else
630  kill(owner_pid, SIGURG);
631 
632 #else
633 
634  /*
635  * See if anyone's waiting for the latch. It can be the current process if
636  * we're in a signal handler.
637  *
638  * Use a local variable here just in case somebody changes the event field
639  * concurrently (which really should not happen).
640  */
641  handle = latch->event;
642  if (handle)
643  {
644  SetEvent(handle);
645 
646  /*
647  * Note that we silently ignore any errors. We might be in a signal
648  * handler or other critical path where it's not safe to call elog().
649  */
650  }
651 #endif
652 
653 }
654 
655 /*
656  * Clear the latch. Calling WaitLatch after this will sleep, unless
657  * the latch is set again before the WaitLatch call.
658  */
659 void
661 {
662  /* Only the owner should reset the latch */
663  Assert(latch->owner_pid == MyProcPid);
664  Assert(latch->maybe_sleeping == false);
665 
666  latch->is_set = false;
667 
668  /*
669  * Ensure that the write to is_set gets flushed to main memory before we
670  * examine any flag variables. Otherwise a concurrent SetLatch might
671  * falsely conclude that it needn't signal us, even though we have missed
672  * seeing some flag updates that SetLatch was supposed to inform us of.
673  */
675 }
676 
677 /*
678  * Create a WaitEventSet with space for nevents different events to wait for.
679  *
680  * These events can then be efficiently waited upon together, using
681  * WaitEventSetWait().
682  */
683 WaitEventSet *
685 {
686  WaitEventSet *set;
687  char *data;
688  Size sz = 0;
689 
690  /*
691  * Use MAXALIGN size/alignment to guarantee that later uses of memory are
692  * aligned correctly. E.g. epoll_event might need 8 byte alignment on some
693  * platforms, but earlier allocations like WaitEventSet and WaitEvent
694  * might not sized to guarantee that when purely using sizeof().
695  */
696  sz += MAXALIGN(sizeof(WaitEventSet));
697  sz += MAXALIGN(sizeof(WaitEvent) * nevents);
698 
699 #if defined(WAIT_USE_EPOLL)
700  sz += MAXALIGN(sizeof(struct epoll_event) * nevents);
701 #elif defined(WAIT_USE_KQUEUE)
702  sz += MAXALIGN(sizeof(struct kevent) * nevents);
703 #elif defined(WAIT_USE_POLL)
704  sz += MAXALIGN(sizeof(struct pollfd) * nevents);
705 #elif defined(WAIT_USE_WIN32)
706  /* need space for the pgwin32_signal_event */
707  sz += MAXALIGN(sizeof(HANDLE) * (nevents + 1));
708 #endif
709 
710  data = (char *) MemoryContextAllocZero(context, sz);
711 
712  set = (WaitEventSet *) data;
713  data += MAXALIGN(sizeof(WaitEventSet));
714 
715  set->events = (WaitEvent *) data;
716  data += MAXALIGN(sizeof(WaitEvent) * nevents);
717 
718 #if defined(WAIT_USE_EPOLL)
719  set->epoll_ret_events = (struct epoll_event *) data;
720  data += MAXALIGN(sizeof(struct epoll_event) * nevents);
721 #elif defined(WAIT_USE_KQUEUE)
722  set->kqueue_ret_events = (struct kevent *) data;
723  data += MAXALIGN(sizeof(struct kevent) * nevents);
724 #elif defined(WAIT_USE_POLL)
725  set->pollfds = (struct pollfd *) data;
726  data += MAXALIGN(sizeof(struct pollfd) * nevents);
727 #elif defined(WAIT_USE_WIN32)
728  set->handles = (HANDLE) data;
729  data += MAXALIGN(sizeof(HANDLE) * nevents);
730 #endif
731 
732  set->latch = NULL;
733  set->nevents_space = nevents;
734  set->exit_on_postmaster_death = false;
735 
736 #if defined(WAIT_USE_EPOLL)
737  if (!AcquireExternalFD())
738  {
739  /* treat this as though epoll_create1 itself returned EMFILE */
740  elog(ERROR, "epoll_create1 failed: %m");
741  }
742  set->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
743  if (set->epoll_fd < 0)
744  {
746  elog(ERROR, "epoll_create1 failed: %m");
747  }
748 #elif defined(WAIT_USE_KQUEUE)
749  if (!AcquireExternalFD())
750  {
751  /* treat this as though kqueue itself returned EMFILE */
752  elog(ERROR, "kqueue failed: %m");
753  }
754  set->kqueue_fd = kqueue();
755  if (set->kqueue_fd < 0)
756  {
758  elog(ERROR, "kqueue failed: %m");
759  }
760  if (fcntl(set->kqueue_fd, F_SETFD, FD_CLOEXEC) == -1)
761  {
762  int save_errno = errno;
763 
764  close(set->kqueue_fd);
766  errno = save_errno;
767  elog(ERROR, "fcntl(F_SETFD) failed on kqueue descriptor: %m");
768  }
769  set->report_postmaster_not_running = false;
770 #elif defined(WAIT_USE_WIN32)
771 
772  /*
773  * To handle signals while waiting, we need to add a win32 specific event.
774  * We accounted for the additional event at the top of this routine. See
775  * port/win32/signal.c for more details.
776  *
777  * Note: pgwin32_signal_event should be first to ensure that it will be
778  * reported when multiple events are set. We want to guarantee that
779  * pending signals are serviced.
780  */
781  set->handles[0] = pgwin32_signal_event;
782  StaticAssertStmt(WSA_INVALID_EVENT == NULL, "");
783 #endif
784 
785  return set;
786 }
787 
788 /*
789  * Free a previously created WaitEventSet.
790  *
791  * Note: preferably, this shouldn't have to free any resources that could be
792  * inherited across an exec(). If it did, we'd likely leak those resources in
793  * many scenarios. For the epoll case, we ensure that by setting EPOLL_CLOEXEC
794  * when the FD is created. For the Windows case, we assume that the handles
795  * involved are non-inheritable.
796  */
797 void
799 {
800 #if defined(WAIT_USE_EPOLL)
801  close(set->epoll_fd);
803 #elif defined(WAIT_USE_KQUEUE)
804  close(set->kqueue_fd);
806 #elif defined(WAIT_USE_WIN32)
807  WaitEvent *cur_event;
808 
809  for (cur_event = set->events;
810  cur_event < (set->events + set->nevents);
811  cur_event++)
812  {
813  if (cur_event->events & WL_LATCH_SET)
814  {
815  /* uses the latch's HANDLE */
816  }
817  else if (cur_event->events & WL_POSTMASTER_DEATH)
818  {
819  /* uses PostmasterHandle */
820  }
821  else
822  {
823  /* Clean up the event object we created for the socket */
824  WSAEventSelect(cur_event->fd, NULL, 0);
825  WSACloseEvent(set->handles[cur_event->pos + 1]);
826  }
827  }
828 #endif
829 
830  pfree(set);
831 }
832 
833 /* ---
834  * Add an event to the set. Possible events are:
835  * - WL_LATCH_SET: Wait for the latch to be set
836  * - WL_POSTMASTER_DEATH: Wait for postmaster to die
837  * - WL_SOCKET_READABLE: Wait for socket to become readable,
838  * can be combined in one event with other WL_SOCKET_* events
839  * - WL_SOCKET_WRITEABLE: Wait for socket to become writeable,
840  * can be combined with other WL_SOCKET_* events
841  * - WL_SOCKET_CONNECTED: Wait for socket connection to be established,
842  * can be combined with other WL_SOCKET_* events (on non-Windows
843  * platforms, this is the same as WL_SOCKET_WRITEABLE)
844  * - WL_EXIT_ON_PM_DEATH: Exit immediately if the postmaster dies
845  *
846  * Returns the offset in WaitEventSet->events (starting from 0), which can be
847  * used to modify previously added wait events using ModifyWaitEvent().
848  *
849  * In the WL_LATCH_SET case the latch must be owned by the current process,
850  * i.e. it must be a process-local latch initialized with InitLatch, or a
851  * shared latch associated with the current process by calling OwnLatch.
852  *
853  * In the WL_SOCKET_READABLE/WRITEABLE/CONNECTED cases, EOF and error
854  * conditions cause the socket to be reported as readable/writable/connected,
855  * so that the caller can deal with the condition.
856  *
857  * The user_data pointer specified here will be set for the events returned
858  * by WaitEventSetWait(), allowing to easily associate additional data with
859  * events.
860  */
861 int
863  void *user_data)
864 {
865  WaitEvent *event;
866 
867  /* not enough space */
868  Assert(set->nevents < set->nevents_space);
869 
870  if (events == WL_EXIT_ON_PM_DEATH)
871  {
872  events = WL_POSTMASTER_DEATH;
873  set->exit_on_postmaster_death = true;
874  }
875 
876  if (latch)
877  {
878  if (latch->owner_pid != MyProcPid)
879  elog(ERROR, "cannot wait on a latch owned by another process");
880  if (set->latch)
881  elog(ERROR, "cannot wait on more than one latch");
882  if ((events & WL_LATCH_SET) != WL_LATCH_SET)
883  elog(ERROR, "latch events only support being set");
884  }
885  else
886  {
887  if (events & WL_LATCH_SET)
888  elog(ERROR, "cannot wait on latch without a specified latch");
889  }
890 
891  /* waiting for socket readiness without a socket indicates a bug */
892  if (fd == PGINVALID_SOCKET && (events & WL_SOCKET_MASK))
893  elog(ERROR, "cannot wait on socket event without a socket");
894 
895  event = &set->events[set->nevents];
896  event->pos = set->nevents++;
897  event->fd = fd;
898  event->events = events;
899  event->user_data = user_data;
900 #ifdef WIN32
901  event->reset = false;
902 #endif
903 
904  if (events == WL_LATCH_SET)
905  {
906  set->latch = latch;
907  set->latch_pos = event->pos;
908 #if defined(WAIT_USE_POLL)
909  event->fd = selfpipe_readfd;
910 #elif defined(WAIT_USE_EPOLL)
911  event->fd = signal_fd;
912 #else
913  event->fd = PGINVALID_SOCKET;
914 #ifdef WAIT_USE_EPOLL
915  return event->pos;
916 #endif
917 #endif
918  }
919  else if (events == WL_POSTMASTER_DEATH)
920  {
921 #ifndef WIN32
923 #endif
924  }
925 
926  /* perform wait primitive specific initialization, if needed */
927 #if defined(WAIT_USE_EPOLL)
928  WaitEventAdjustEpoll(set, event, EPOLL_CTL_ADD);
929 #elif defined(WAIT_USE_KQUEUE)
930  WaitEventAdjustKqueue(set, event, 0);
931 #elif defined(WAIT_USE_POLL)
932  WaitEventAdjustPoll(set, event);
933 #elif defined(WAIT_USE_WIN32)
934  WaitEventAdjustWin32(set, event);
935 #endif
936 
937  return event->pos;
938 }
939 
940 /*
941  * Change the event mask and, in the WL_LATCH_SET case, the latch associated
942  * with the WaitEvent. The latch may be changed to NULL to disable the latch
943  * temporarily, and then set back to a latch later.
944  *
945  * 'pos' is the id returned by AddWaitEventToSet.
946  */
947 void
949 {
950  WaitEvent *event;
951 #if defined(WAIT_USE_KQUEUE)
952  int old_events;
953 #endif
954 
955  Assert(pos < set->nevents);
956 
957  event = &set->events[pos];
958 #if defined(WAIT_USE_KQUEUE)
959  old_events = event->events;
960 #endif
961 
962  /*
963  * If neither the event mask nor the associated latch changes, return
964  * early. That's an important optimization for some sockets, where
965  * ModifyWaitEvent is frequently used to switch from waiting for reads to
966  * waiting on writes.
967  */
968  if (events == event->events &&
969  (!(event->events & WL_LATCH_SET) || set->latch == latch))
970  return;
971 
972  if (event->events & WL_LATCH_SET &&
973  events != event->events)
974  {
975  elog(ERROR, "cannot modify latch event");
976  }
977 
978  if (event->events & WL_POSTMASTER_DEATH)
979  {
980  elog(ERROR, "cannot modify postmaster death event");
981  }
982 
983  /* FIXME: validate event mask */
984  event->events = events;
985 
986  if (events == WL_LATCH_SET)
987  {
988  if (latch && latch->owner_pid != MyProcPid)
989  elog(ERROR, "cannot wait on a latch owned by another process");
990  set->latch = latch;
991 
992  /*
993  * On Unix, we don't need to modify the kernel object because the
994  * underlying pipe (if there is one) is the same for all latches so we
995  * can return immediately. On Windows, we need to update our array of
996  * handles, but we leave the old one in place and tolerate spurious
997  * wakeups if the latch is disabled.
998  */
999 #if defined(WAIT_USE_WIN32)
1000  if (!latch)
1001  return;
1002 #else
1003  return;
1004 #endif
1005  }
1006 
1007 #if defined(WAIT_USE_EPOLL)
1008  WaitEventAdjustEpoll(set, event, EPOLL_CTL_MOD);
1009 #elif defined(WAIT_USE_KQUEUE)
1010  WaitEventAdjustKqueue(set, event, old_events);
1011 #elif defined(WAIT_USE_POLL)
1012  WaitEventAdjustPoll(set, event);
1013 #elif defined(WAIT_USE_WIN32)
1014  WaitEventAdjustWin32(set, event);
1015 #endif
1016 }
1017 
1018 #if defined(WAIT_USE_EPOLL)
1019 /*
1020  * action can be one of EPOLL_CTL_ADD | EPOLL_CTL_MOD | EPOLL_CTL_DEL
1021  */
1022 static void
1023 WaitEventAdjustEpoll(WaitEventSet *set, WaitEvent *event, int action)
1024 {
1025  struct epoll_event epoll_ev;
1026  int rc;
1027 
1028  /* pointer to our event, returned by epoll_wait */
1029  epoll_ev.data.ptr = event;
1030  /* always wait for errors */
1031  epoll_ev.events = EPOLLERR | EPOLLHUP;
1032 
1033  /* prepare pollfd entry once */
1034  if (event->events == WL_LATCH_SET)
1035  {
1036  Assert(set->latch != NULL);
1037  epoll_ev.events |= EPOLLIN;
1038  }
1039  else if (event->events == WL_POSTMASTER_DEATH)
1040  {
1041  epoll_ev.events |= EPOLLIN;
1042  }
1043  else
1044  {
1045  Assert(event->fd != PGINVALID_SOCKET);
1047 
1048  if (event->events & WL_SOCKET_READABLE)
1049  epoll_ev.events |= EPOLLIN;
1050  if (event->events & WL_SOCKET_WRITEABLE)
1051  epoll_ev.events |= EPOLLOUT;
1052  }
1053 
1054  /*
1055  * Even though unused, we also pass epoll_ev as the data argument if
1056  * EPOLL_CTL_DEL is passed as action. There used to be an epoll bug
1057  * requiring that, and actually it makes the code simpler...
1058  */
1059  rc = epoll_ctl(set->epoll_fd, action, event->fd, &epoll_ev);
1060 
1061  if (rc < 0)
1062  ereport(ERROR,
1064  errmsg("%s() failed: %m",
1065  "epoll_ctl")));
1066 }
1067 #endif
1068 
1069 #if defined(WAIT_USE_POLL)
1070 static void
1071 WaitEventAdjustPoll(WaitEventSet *set, WaitEvent *event)
1072 {
1073  struct pollfd *pollfd = &set->pollfds[event->pos];
1074 
1075  pollfd->revents = 0;
1076  pollfd->fd = event->fd;
1077 
1078  /* prepare pollfd entry once */
1079  if (event->events == WL_LATCH_SET)
1080  {
1081  Assert(set->latch != NULL);
1082  pollfd->events = POLLIN;
1083  }
1084  else if (event->events == WL_POSTMASTER_DEATH)
1085  {
1086  pollfd->events = POLLIN;
1087  }
1088  else
1089  {
1091  pollfd->events = 0;
1092  if (event->events & WL_SOCKET_READABLE)
1093  pollfd->events |= POLLIN;
1094  if (event->events & WL_SOCKET_WRITEABLE)
1095  pollfd->events |= POLLOUT;
1096  }
1097 
1098  Assert(event->fd != PGINVALID_SOCKET);
1099 }
1100 #endif
1101 
1102 #if defined(WAIT_USE_KQUEUE)
1103 
1104 /*
1105  * On most BSD family systems, the udata member of struct kevent is of type
1106  * void *, so we could directly convert to/from WaitEvent *. Unfortunately,
1107  * NetBSD has it as intptr_t, so here we wallpaper over that difference with
1108  * an lvalue cast.
1109  */
1110 #define AccessWaitEvent(k_ev) (*((WaitEvent **)(&(k_ev)->udata)))
1111 
1112 static inline void
1113 WaitEventAdjustKqueueAdd(struct kevent *k_ev, int filter, int action,
1114  WaitEvent *event)
1115 {
1116  k_ev->ident = event->fd;
1117  k_ev->filter = filter;
1118  k_ev->flags = action;
1119  k_ev->fflags = 0;
1120  k_ev->data = 0;
1121  AccessWaitEvent(k_ev) = event;
1122 }
1123 
1124 static inline void
1125 WaitEventAdjustKqueueAddPostmaster(struct kevent *k_ev, WaitEvent *event)
1126 {
1127  /* For now postmaster death can only be added, not removed. */
1128  k_ev->ident = PostmasterPid;
1129  k_ev->filter = EVFILT_PROC;
1130  k_ev->flags = EV_ADD;
1131  k_ev->fflags = NOTE_EXIT;
1132  k_ev->data = 0;
1133  AccessWaitEvent(k_ev) = event;
1134 }
1135 
1136 static inline void
1137 WaitEventAdjustKqueueAddLatch(struct kevent *k_ev, WaitEvent *event)
1138 {
1139  /* For now latch can only be added, not removed. */
1140  k_ev->ident = SIGURG;
1141  k_ev->filter = EVFILT_SIGNAL;
1142  k_ev->flags = EV_ADD;
1143  k_ev->fflags = 0;
1144  k_ev->data = 0;
1145  AccessWaitEvent(k_ev) = event;
1146 }
1147 
1148 /*
1149  * old_events is the previous event mask, used to compute what has changed.
1150  */
1151 static void
1152 WaitEventAdjustKqueue(WaitEventSet *set, WaitEvent *event, int old_events)
1153 {
1154  int rc;
1155  struct kevent k_ev[2];
1156  int count = 0;
1157  bool new_filt_read = false;
1158  bool old_filt_read = false;
1159  bool new_filt_write = false;
1160  bool old_filt_write = false;
1161 
1162  if (old_events == event->events)
1163  return;
1164 
1165  Assert(event->events != WL_LATCH_SET || set->latch != NULL);
1166  Assert(event->events == WL_LATCH_SET ||
1167  event->events == WL_POSTMASTER_DEATH ||
1169 
1170  if (event->events == WL_POSTMASTER_DEATH)
1171  {
1172  /*
1173  * Unlike all the other implementations, we detect postmaster death
1174  * using process notification instead of waiting on the postmaster
1175  * alive pipe.
1176  */
1177  WaitEventAdjustKqueueAddPostmaster(&k_ev[count++], event);
1178  }
1179  else if (event->events == WL_LATCH_SET)
1180  {
1181  /* We detect latch wakeup using a signal event. */
1182  WaitEventAdjustKqueueAddLatch(&k_ev[count++], event);
1183  }
1184  else
1185  {
1186  /*
1187  * We need to compute the adds and deletes required to get from the
1188  * old event mask to the new event mask, since kevent treats readable
1189  * and writable as separate events.
1190  */
1191  if (old_events & WL_SOCKET_READABLE)
1192  old_filt_read = true;
1193  if (event->events & WL_SOCKET_READABLE)
1194  new_filt_read = true;
1195  if (old_events & WL_SOCKET_WRITEABLE)
1196  old_filt_write = true;
1197  if (event->events & WL_SOCKET_WRITEABLE)
1198  new_filt_write = true;
1199  if (old_filt_read && !new_filt_read)
1200  WaitEventAdjustKqueueAdd(&k_ev[count++], EVFILT_READ, EV_DELETE,
1201  event);
1202  else if (!old_filt_read && new_filt_read)
1203  WaitEventAdjustKqueueAdd(&k_ev[count++], EVFILT_READ, EV_ADD,
1204  event);
1205  if (old_filt_write && !new_filt_write)
1206  WaitEventAdjustKqueueAdd(&k_ev[count++], EVFILT_WRITE, EV_DELETE,
1207  event);
1208  else if (!old_filt_write && new_filt_write)
1209  WaitEventAdjustKqueueAdd(&k_ev[count++], EVFILT_WRITE, EV_ADD,
1210  event);
1211  }
1212 
1213  Assert(count > 0);
1214  Assert(count <= 2);
1215 
1216  rc = kevent(set->kqueue_fd, &k_ev[0], count, NULL, 0, NULL);
1217 
1218  /*
1219  * When adding the postmaster's pid, we have to consider that it might
1220  * already have exited and perhaps even been replaced by another process
1221  * with the same pid. If so, we have to defer reporting this as an event
1222  * until the next call to WaitEventSetWaitBlock().
1223  */
1224 
1225  if (rc < 0)
1226  {
1227  if (event->events == WL_POSTMASTER_DEATH &&
1228  (errno == ESRCH || errno == EACCES))
1229  set->report_postmaster_not_running = true;
1230  else
1231  ereport(ERROR,
1233  errmsg("%s() failed: %m",
1234  "kevent")));
1235  }
1236  else if (event->events == WL_POSTMASTER_DEATH &&
1237  PostmasterPid != getppid() &&
1238  !PostmasterIsAlive())
1239  {
1240  /*
1241  * The extra PostmasterIsAliveInternal() check prevents false alarms
1242  * on systems that give a different value for getppid() while being
1243  * traced by a debugger.
1244  */
1245  set->report_postmaster_not_running = true;
1246  }
1247 }
1248 
1249 #endif
1250 
1251 #if defined(WAIT_USE_WIN32)
1252 static void
1253 WaitEventAdjustWin32(WaitEventSet *set, WaitEvent *event)
1254 {
1255  HANDLE *handle = &set->handles[event->pos + 1];
1256 
1257  if (event->events == WL_LATCH_SET)
1258  {
1259  Assert(set->latch != NULL);
1260  *handle = set->latch->event;
1261  }
1262  else if (event->events == WL_POSTMASTER_DEATH)
1263  {
1264  *handle = PostmasterHandle;
1265  }
1266  else
1267  {
1268  int flags = FD_CLOSE; /* always check for errors/EOF */
1269 
1270  if (event->events & WL_SOCKET_READABLE)
1271  flags |= FD_READ;
1272  if (event->events & WL_SOCKET_WRITEABLE)
1273  flags |= FD_WRITE;
1274  if (event->events & WL_SOCKET_CONNECTED)
1275  flags |= FD_CONNECT;
1276 
1277  if (*handle == WSA_INVALID_EVENT)
1278  {
1279  *handle = WSACreateEvent();
1280  if (*handle == WSA_INVALID_EVENT)
1281  elog(ERROR, "failed to create event for socket: error code %d",
1282  WSAGetLastError());
1283  }
1284  if (WSAEventSelect(event->fd, *handle, flags) != 0)
1285  elog(ERROR, "failed to set up event for socket: error code %d",
1286  WSAGetLastError());
1287 
1288  Assert(event->fd != PGINVALID_SOCKET);
1289  }
1290 }
1291 #endif
1292 
1293 /*
1294  * Wait for events added to the set to happen, or until the timeout is
1295  * reached. At most nevents occurred events are returned.
1296  *
1297  * If timeout = -1, block until an event occurs; if 0, check sockets for
1298  * readiness, but don't block; if > 0, block for at most timeout milliseconds.
1299  *
1300  * Returns the number of events occurred, or 0 if the timeout was reached.
1301  *
1302  * Returned events will have the fd, pos, user_data fields set to the
1303  * values associated with the registered event.
1304  */
1305 int
1306 WaitEventSetWait(WaitEventSet *set, long timeout,
1307  WaitEvent *occurred_events, int nevents,
1308  uint32 wait_event_info)
1309 {
1310  int returned_events = 0;
1312  instr_time cur_time;
1313  long cur_timeout = -1;
1314 
1315  Assert(nevents > 0);
1316 
1317  /*
1318  * Initialize timeout if requested. We must record the current time so
1319  * that we can determine the remaining timeout if interrupted.
1320  */
1321  if (timeout >= 0)
1322  {
1323  INSTR_TIME_SET_CURRENT(start_time);
1324  Assert(timeout >= 0 && timeout <= INT_MAX);
1325  cur_timeout = timeout;
1326  }
1327 
1328  pgstat_report_wait_start(wait_event_info);
1329 
1330 #ifndef WIN32
1331  waiting = true;
1332 #else
1333  /* Ensure that signals are serviced even if latch is already set */
1335 #endif
1336  while (returned_events == 0)
1337  {
1338  int rc;
1339 
1340  /*
1341  * Check if the latch is set already. If so, leave the loop
1342  * immediately, avoid blocking again. We don't attempt to report any
1343  * other events that might also be satisfied.
1344  *
1345  * If someone sets the latch between this and the
1346  * WaitEventSetWaitBlock() below, the setter will write a byte to the
1347  * pipe (or signal us and the signal handler will do that), and the
1348  * readiness routine will return immediately.
1349  *
1350  * On unix, If there's a pending byte in the self pipe, we'll notice
1351  * whenever blocking. Only clearing the pipe in that case avoids
1352  * having to drain it every time WaitLatchOrSocket() is used. Should
1353  * the pipe-buffer fill up we're still ok, because the pipe is in
1354  * nonblocking mode. It's unlikely for that to happen, because the
1355  * self pipe isn't filled unless we're blocking (waiting = true), or
1356  * from inside a signal handler in latch_sigurg_handler().
1357  *
1358  * On windows, we'll also notice if there's a pending event for the
1359  * latch when blocking, but there's no danger of anything filling up,
1360  * as "Setting an event that is already set has no effect.".
1361  *
1362  * Note: we assume that the kernel calls involved in latch management
1363  * will provide adequate synchronization on machines with weak memory
1364  * ordering, so that we cannot miss seeing is_set if a notification
1365  * has already been queued.
1366  */
1367  if (set->latch && !set->latch->is_set)
1368  {
1369  /* about to sleep on a latch */
1370  set->latch->maybe_sleeping = true;
1372  /* and recheck */
1373  }
1374 
1375  if (set->latch && set->latch->is_set)
1376  {
1377  occurred_events->fd = PGINVALID_SOCKET;
1378  occurred_events->pos = set->latch_pos;
1379  occurred_events->user_data =
1380  set->events[set->latch_pos].user_data;
1381  occurred_events->events = WL_LATCH_SET;
1382  occurred_events++;
1383  returned_events++;
1384 
1385  /* could have been set above */
1386  set->latch->maybe_sleeping = false;
1387 
1388  break;
1389  }
1390 
1391  /*
1392  * Wait for events using the readiness primitive chosen at the top of
1393  * this file. If -1 is returned, a timeout has occurred, if 0 we have
1394  * to retry, everything >= 1 is the number of returned events.
1395  */
1396  rc = WaitEventSetWaitBlock(set, cur_timeout,
1397  occurred_events, nevents);
1398 
1399  if (set->latch)
1400  {
1401  Assert(set->latch->maybe_sleeping);
1402  set->latch->maybe_sleeping = false;
1403  }
1404 
1405  if (rc == -1)
1406  break; /* timeout occurred */
1407  else
1408  returned_events = rc;
1409 
1410  /* If we're not done, update cur_timeout for next iteration */
1411  if (returned_events == 0 && timeout >= 0)
1412  {
1413  INSTR_TIME_SET_CURRENT(cur_time);
1414  INSTR_TIME_SUBTRACT(cur_time, start_time);
1415  cur_timeout = timeout - (long) INSTR_TIME_GET_MILLISEC(cur_time);
1416  if (cur_timeout <= 0)
1417  break;
1418  }
1419  }
1420 #ifndef WIN32
1421  waiting = false;
1422 #endif
1423 
1425 
1426  return returned_events;
1427 }
1428 
1429 
1430 #if defined(WAIT_USE_EPOLL)
1431 
1432 /*
1433  * Wait using linux's epoll_wait(2).
1434  *
1435  * This is the preferable wait method, as several readiness notifications are
1436  * delivered, without having to iterate through all of set->events. The return
1437  * epoll_event struct contain a pointer to our events, making association
1438  * easy.
1439  */
1440 static inline int
1441 WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
1442  WaitEvent *occurred_events, int nevents)
1443 {
1444  int returned_events = 0;
1445  int rc;
1446  WaitEvent *cur_event;
1447  struct epoll_event *cur_epoll_event;
1448 
1449  /* Sleep */
1450  rc = epoll_wait(set->epoll_fd, set->epoll_ret_events,
1451  nevents, cur_timeout);
1452 
1453  /* Check return code */
1454  if (rc < 0)
1455  {
1456  /* EINTR is okay, otherwise complain */
1457  if (errno != EINTR)
1458  {
1459  waiting = false;
1460  ereport(ERROR,
1462  errmsg("%s() failed: %m",
1463  "epoll_wait")));
1464  }
1465  return 0;
1466  }
1467  else if (rc == 0)
1468  {
1469  /* timeout exceeded */
1470  return -1;
1471  }
1472 
1473  /*
1474  * At least one event occurred, iterate over the returned epoll events
1475  * until they're either all processed, or we've returned all the events
1476  * the caller desired.
1477  */
1478  for (cur_epoll_event = set->epoll_ret_events;
1479  cur_epoll_event < (set->epoll_ret_events + rc) &&
1480  returned_events < nevents;
1481  cur_epoll_event++)
1482  {
1483  /* epoll's data pointer is set to the associated WaitEvent */
1484  cur_event = (WaitEvent *) cur_epoll_event->data.ptr;
1485 
1486  occurred_events->pos = cur_event->pos;
1487  occurred_events->user_data = cur_event->user_data;
1488  occurred_events->events = 0;
1489 
1490  if (cur_event->events == WL_LATCH_SET &&
1491  cur_epoll_event->events & (EPOLLIN | EPOLLERR | EPOLLHUP))
1492  {
1493  /* Drain the signalfd. */
1494  drain();
1495 
1496  if (set->latch && set->latch->is_set)
1497  {
1498  occurred_events->fd = PGINVALID_SOCKET;
1499  occurred_events->events = WL_LATCH_SET;
1500  occurred_events++;
1501  returned_events++;
1502  }
1503  }
1504  else if (cur_event->events == WL_POSTMASTER_DEATH &&
1505  cur_epoll_event->events & (EPOLLIN | EPOLLERR | EPOLLHUP))
1506  {
1507  /*
1508  * We expect an EPOLLHUP when the remote end is closed, but
1509  * because we don't expect the pipe to become readable or to have
1510  * any errors either, treat those cases as postmaster death, too.
1511  *
1512  * Be paranoid about a spurious event signaling the postmaster as
1513  * being dead. There have been reports about that happening with
1514  * older primitives (select(2) to be specific), and a spurious
1515  * WL_POSTMASTER_DEATH event would be painful. Re-checking doesn't
1516  * cost much.
1517  */
1519  {
1520  if (set->exit_on_postmaster_death)
1521  proc_exit(1);
1522  occurred_events->fd = PGINVALID_SOCKET;
1523  occurred_events->events = WL_POSTMASTER_DEATH;
1524  occurred_events++;
1525  returned_events++;
1526  }
1527  }
1528  else if (cur_event->events & (WL_SOCKET_READABLE | WL_SOCKET_WRITEABLE))
1529  {
1530  Assert(cur_event->fd != PGINVALID_SOCKET);
1531 
1532  if ((cur_event->events & WL_SOCKET_READABLE) &&
1533  (cur_epoll_event->events & (EPOLLIN | EPOLLERR | EPOLLHUP)))
1534  {
1535  /* data available in socket, or EOF */
1536  occurred_events->events |= WL_SOCKET_READABLE;
1537  }
1538 
1539  if ((cur_event->events & WL_SOCKET_WRITEABLE) &&
1540  (cur_epoll_event->events & (EPOLLOUT | EPOLLERR | EPOLLHUP)))
1541  {
1542  /* writable, or EOF */
1543  occurred_events->events |= WL_SOCKET_WRITEABLE;
1544  }
1545 
1546  if (occurred_events->events != 0)
1547  {
1548  occurred_events->fd = cur_event->fd;
1549  occurred_events++;
1550  returned_events++;
1551  }
1552  }
1553  }
1554 
1555  return returned_events;
1556 }
1557 
1558 #elif defined(WAIT_USE_KQUEUE)
1559 
1560 /*
1561  * Wait using kevent(2) on BSD-family systems and macOS.
1562  *
1563  * For now this mirrors the epoll code, but in future it could modify the fd
1564  * set in the same call to kevent as it uses for waiting instead of doing that
1565  * with separate system calls.
1566  */
1567 static int
1568 WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
1569  WaitEvent *occurred_events, int nevents)
1570 {
1571  int returned_events = 0;
1572  int rc;
1573  WaitEvent *cur_event;
1574  struct kevent *cur_kqueue_event;
1575  struct timespec timeout;
1576  struct timespec *timeout_p;
1577 
1578  if (cur_timeout < 0)
1579  timeout_p = NULL;
1580  else
1581  {
1582  timeout.tv_sec = cur_timeout / 1000;
1583  timeout.tv_nsec = (cur_timeout % 1000) * 1000000;
1584  timeout_p = &timeout;
1585  }
1586 
1587  /*
1588  * Report postmaster events discovered by WaitEventAdjustKqueue() or an
1589  * earlier call to WaitEventSetWait().
1590  */
1591  if (unlikely(set->report_postmaster_not_running))
1592  {
1593  if (set->exit_on_postmaster_death)
1594  proc_exit(1);
1595  occurred_events->fd = PGINVALID_SOCKET;
1596  occurred_events->events = WL_POSTMASTER_DEATH;
1597  return 1;
1598  }
1599 
1600  /* Sleep */
1601  rc = kevent(set->kqueue_fd, NULL, 0,
1602  set->kqueue_ret_events, nevents,
1603  timeout_p);
1604 
1605  /* Check return code */
1606  if (rc < 0)
1607  {
1608  /* EINTR is okay, otherwise complain */
1609  if (errno != EINTR)
1610  {
1611  waiting = false;
1612  ereport(ERROR,
1614  errmsg("%s() failed: %m",
1615  "kevent")));
1616  }
1617  return 0;
1618  }
1619  else if (rc == 0)
1620  {
1621  /* timeout exceeded */
1622  return -1;
1623  }
1624 
1625  /*
1626  * At least one event occurred, iterate over the returned kqueue events
1627  * until they're either all processed, or we've returned all the events
1628  * the caller desired.
1629  */
1630  for (cur_kqueue_event = set->kqueue_ret_events;
1631  cur_kqueue_event < (set->kqueue_ret_events + rc) &&
1632  returned_events < nevents;
1633  cur_kqueue_event++)
1634  {
1635  /* kevent's udata points to the associated WaitEvent */
1636  cur_event = AccessWaitEvent(cur_kqueue_event);
1637 
1638  occurred_events->pos = cur_event->pos;
1639  occurred_events->user_data = cur_event->user_data;
1640  occurred_events->events = 0;
1641 
1642  if (cur_event->events == WL_LATCH_SET &&
1643  cur_kqueue_event->filter == EVFILT_SIGNAL)
1644  {
1645  if (set->latch && set->latch->is_set)
1646  {
1647  occurred_events->fd = PGINVALID_SOCKET;
1648  occurred_events->events = WL_LATCH_SET;
1649  occurred_events++;
1650  returned_events++;
1651  }
1652  }
1653  else if (cur_event->events == WL_POSTMASTER_DEATH &&
1654  cur_kqueue_event->filter == EVFILT_PROC &&
1655  (cur_kqueue_event->fflags & NOTE_EXIT) != 0)
1656  {
1657  /*
1658  * The kernel will tell this kqueue object only once about the exit
1659  * of the postmaster, so let's remember that for next time so that
1660  * we provide level-triggered semantics.
1661  */
1662  set->report_postmaster_not_running = true;
1663 
1664  if (set->exit_on_postmaster_death)
1665  proc_exit(1);
1666  occurred_events->fd = PGINVALID_SOCKET;
1667  occurred_events->events = WL_POSTMASTER_DEATH;
1668  occurred_events++;
1669  returned_events++;
1670  }
1671  else if (cur_event->events & (WL_SOCKET_READABLE | WL_SOCKET_WRITEABLE))
1672  {
1673  Assert(cur_event->fd >= 0);
1674 
1675  if ((cur_event->events & WL_SOCKET_READABLE) &&
1676  (cur_kqueue_event->filter == EVFILT_READ))
1677  {
1678  /* readable, or EOF */
1679  occurred_events->events |= WL_SOCKET_READABLE;
1680  }
1681 
1682  if ((cur_event->events & WL_SOCKET_WRITEABLE) &&
1683  (cur_kqueue_event->filter == EVFILT_WRITE))
1684  {
1685  /* writable, or EOF */
1686  occurred_events->events |= WL_SOCKET_WRITEABLE;
1687  }
1688 
1689  if (occurred_events->events != 0)
1690  {
1691  occurred_events->fd = cur_event->fd;
1692  occurred_events++;
1693  returned_events++;
1694  }
1695  }
1696  }
1697 
1698  return returned_events;
1699 }
1700 
1701 #elif defined(WAIT_USE_POLL)
1702 
1703 /*
1704  * Wait using poll(2).
1705  *
1706  * This allows to receive readiness notifications for several events at once,
1707  * but requires iterating through all of set->pollfds.
1708  */
1709 static inline int
1710 WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
1711  WaitEvent *occurred_events, int nevents)
1712 {
1713  int returned_events = 0;
1714  int rc;
1715  WaitEvent *cur_event;
1716  struct pollfd *cur_pollfd;
1717 
1718  /* Sleep */
1719  rc = poll(set->pollfds, set->nevents, (int) cur_timeout);
1720 
1721  /* Check return code */
1722  if (rc < 0)
1723  {
1724  /* EINTR is okay, otherwise complain */
1725  if (errno != EINTR)
1726  {
1727  waiting = false;
1728  ereport(ERROR,
1730  errmsg("%s() failed: %m",
1731  "poll")));
1732  }
1733  return 0;
1734  }
1735  else if (rc == 0)
1736  {
1737  /* timeout exceeded */
1738  return -1;
1739  }
1740 
1741  for (cur_event = set->events, cur_pollfd = set->pollfds;
1742  cur_event < (set->events + set->nevents) &&
1743  returned_events < nevents;
1744  cur_event++, cur_pollfd++)
1745  {
1746  /* no activity on this FD, skip */
1747  if (cur_pollfd->revents == 0)
1748  continue;
1749 
1750  occurred_events->pos = cur_event->pos;
1751  occurred_events->user_data = cur_event->user_data;
1752  occurred_events->events = 0;
1753 
1754  if (cur_event->events == WL_LATCH_SET &&
1755  (cur_pollfd->revents & (POLLIN | POLLHUP | POLLERR | POLLNVAL)))
1756  {
1757  /* There's data in the self-pipe, clear it. */
1758  drain();
1759 
1760  if (set->latch && set->latch->is_set)
1761  {
1762  occurred_events->fd = PGINVALID_SOCKET;
1763  occurred_events->events = WL_LATCH_SET;
1764  occurred_events++;
1765  returned_events++;
1766  }
1767  }
1768  else if (cur_event->events == WL_POSTMASTER_DEATH &&
1769  (cur_pollfd->revents & (POLLIN | POLLHUP | POLLERR | POLLNVAL)))
1770  {
1771  /*
1772  * We expect an POLLHUP when the remote end is closed, but because
1773  * we don't expect the pipe to become readable or to have any
1774  * errors either, treat those cases as postmaster death, too.
1775  *
1776  * Be paranoid about a spurious event signaling the postmaster as
1777  * being dead. There have been reports about that happening with
1778  * older primitives (select(2) to be specific), and a spurious
1779  * WL_POSTMASTER_DEATH event would be painful. Re-checking doesn't
1780  * cost much.
1781  */
1783  {
1784  if (set->exit_on_postmaster_death)
1785  proc_exit(1);
1786  occurred_events->fd = PGINVALID_SOCKET;
1787  occurred_events->events = WL_POSTMASTER_DEATH;
1788  occurred_events++;
1789  returned_events++;
1790  }
1791  }
1792  else if (cur_event->events & (WL_SOCKET_READABLE | WL_SOCKET_WRITEABLE))
1793  {
1794  int errflags = POLLHUP | POLLERR | POLLNVAL;
1795 
1796  Assert(cur_event->fd >= PGINVALID_SOCKET);
1797 
1798  if ((cur_event->events & WL_SOCKET_READABLE) &&
1799  (cur_pollfd->revents & (POLLIN | errflags)))
1800  {
1801  /* data available in socket, or EOF */
1802  occurred_events->events |= WL_SOCKET_READABLE;
1803  }
1804 
1805  if ((cur_event->events & WL_SOCKET_WRITEABLE) &&
1806  (cur_pollfd->revents & (POLLOUT | errflags)))
1807  {
1808  /* writeable, or EOF */
1809  occurred_events->events |= WL_SOCKET_WRITEABLE;
1810  }
1811 
1812  if (occurred_events->events != 0)
1813  {
1814  occurred_events->fd = cur_event->fd;
1815  occurred_events++;
1816  returned_events++;
1817  }
1818  }
1819  }
1820  return returned_events;
1821 }
1822 
1823 #elif defined(WAIT_USE_WIN32)
1824 
1825 /*
1826  * Wait using Windows' WaitForMultipleObjects().
1827  *
1828  * Unfortunately this will only ever return a single readiness notification at
1829  * a time. Note that while the official documentation for
1830  * WaitForMultipleObjects is ambiguous about multiple events being "consumed"
1831  * with a single bWaitAll = FALSE call,
1832  * https://blogs.msdn.microsoft.com/oldnewthing/20150409-00/?p=44273 confirms
1833  * that only one event is "consumed".
1834  */
1835 static inline int
1836 WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
1837  WaitEvent *occurred_events, int nevents)
1838 {
1839  int returned_events = 0;
1840  DWORD rc;
1841  WaitEvent *cur_event;
1842 
1843  /* Reset any wait events that need it */
1844  for (cur_event = set->events;
1845  cur_event < (set->events + set->nevents);
1846  cur_event++)
1847  {
1848  if (cur_event->reset)
1849  {
1850  WaitEventAdjustWin32(set, cur_event);
1851  cur_event->reset = false;
1852  }
1853 
1854  /*
1855  * Windows does not guarantee to log an FD_WRITE network event
1856  * indicating that more data can be sent unless the previous send()
1857  * failed with WSAEWOULDBLOCK. While our caller might well have made
1858  * such a call, we cannot assume that here. Therefore, if waiting for
1859  * write-ready, force the issue by doing a dummy send(). If the dummy
1860  * send() succeeds, assume that the socket is in fact write-ready, and
1861  * return immediately. Also, if it fails with something other than
1862  * WSAEWOULDBLOCK, return a write-ready indication to let our caller
1863  * deal with the error condition.
1864  */
1865  if (cur_event->events & WL_SOCKET_WRITEABLE)
1866  {
1867  char c;
1868  WSABUF buf;
1869  DWORD sent;
1870  int r;
1871 
1872  buf.buf = &c;
1873  buf.len = 0;
1874 
1875  r = WSASend(cur_event->fd, &buf, 1, &sent, 0, NULL, NULL);
1876  if (r == 0 || WSAGetLastError() != WSAEWOULDBLOCK)
1877  {
1878  occurred_events->pos = cur_event->pos;
1879  occurred_events->user_data = cur_event->user_data;
1880  occurred_events->events = WL_SOCKET_WRITEABLE;
1881  occurred_events->fd = cur_event->fd;
1882  return 1;
1883  }
1884  }
1885  }
1886 
1887  /*
1888  * Sleep.
1889  *
1890  * Need to wait for ->nevents + 1, because signal handle is in [0].
1891  */
1892  rc = WaitForMultipleObjects(set->nevents + 1, set->handles, FALSE,
1893  cur_timeout);
1894 
1895  /* Check return code */
1896  if (rc == WAIT_FAILED)
1897  elog(ERROR, "WaitForMultipleObjects() failed: error code %lu",
1898  GetLastError());
1899  else if (rc == WAIT_TIMEOUT)
1900  {
1901  /* timeout exceeded */
1902  return -1;
1903  }
1904 
1905  if (rc == WAIT_OBJECT_0)
1906  {
1907  /* Service newly-arrived signals */
1909  return 0; /* retry */
1910  }
1911 
1912  /*
1913  * With an offset of one, due to the always present pgwin32_signal_event,
1914  * the handle offset directly corresponds to a wait event.
1915  */
1916  cur_event = (WaitEvent *) &set->events[rc - WAIT_OBJECT_0 - 1];
1917 
1918  occurred_events->pos = cur_event->pos;
1919  occurred_events->user_data = cur_event->user_data;
1920  occurred_events->events = 0;
1921 
1922  if (cur_event->events == WL_LATCH_SET)
1923  {
1924  /*
1925  * We cannot use set->latch->event to reset the fired event if we
1926  * aren't waiting on this latch now.
1927  */
1928  if (!ResetEvent(set->handles[cur_event->pos + 1]))
1929  elog(ERROR, "ResetEvent failed: error code %lu", GetLastError());
1930 
1931  if (set->latch && set->latch->is_set)
1932  {
1933  occurred_events->fd = PGINVALID_SOCKET;
1934  occurred_events->events = WL_LATCH_SET;
1935  occurred_events++;
1936  returned_events++;
1937  }
1938  }
1939  else if (cur_event->events == WL_POSTMASTER_DEATH)
1940  {
1941  /*
1942  * Postmaster apparently died. Since the consequences of falsely
1943  * returning WL_POSTMASTER_DEATH could be pretty unpleasant, we take
1944  * the trouble to positively verify this with PostmasterIsAlive(),
1945  * even though there is no known reason to think that the event could
1946  * be falsely set on Windows.
1947  */
1949  {
1950  if (set->exit_on_postmaster_death)
1951  proc_exit(1);
1952  occurred_events->fd = PGINVALID_SOCKET;
1953  occurred_events->events = WL_POSTMASTER_DEATH;
1954  occurred_events++;
1955  returned_events++;
1956  }
1957  }
1958  else if (cur_event->events & WL_SOCKET_MASK)
1959  {
1960  WSANETWORKEVENTS resEvents;
1961  HANDLE handle = set->handles[cur_event->pos + 1];
1962 
1963  Assert(cur_event->fd);
1964 
1965  occurred_events->fd = cur_event->fd;
1966 
1967  ZeroMemory(&resEvents, sizeof(resEvents));
1968  if (WSAEnumNetworkEvents(cur_event->fd, handle, &resEvents) != 0)
1969  elog(ERROR, "failed to enumerate network events: error code %d",
1970  WSAGetLastError());
1971  if ((cur_event->events & WL_SOCKET_READABLE) &&
1972  (resEvents.lNetworkEvents & FD_READ))
1973  {
1974  /* data available in socket */
1975  occurred_events->events |= WL_SOCKET_READABLE;
1976 
1977  /*------
1978  * WaitForMultipleObjects doesn't guarantee that a read event will
1979  * be returned if the latch is set at the same time. Even if it
1980  * did, the caller might drop that event expecting it to reoccur
1981  * on next call. So, we must force the event to be reset if this
1982  * WaitEventSet is used again in order to avoid an indefinite
1983  * hang. Refer https://msdn.microsoft.com/en-us/library/windows/desktop/ms741576(v=vs.85).aspx
1984  * for the behavior of socket events.
1985  *------
1986  */
1987  cur_event->reset = true;
1988  }
1989  if ((cur_event->events & WL_SOCKET_WRITEABLE) &&
1990  (resEvents.lNetworkEvents & FD_WRITE))
1991  {
1992  /* writeable */
1993  occurred_events->events |= WL_SOCKET_WRITEABLE;
1994  }
1995  if ((cur_event->events & WL_SOCKET_CONNECTED) &&
1996  (resEvents.lNetworkEvents & FD_CONNECT))
1997  {
1998  /* connected */
1999  occurred_events->events |= WL_SOCKET_CONNECTED;
2000  }
2001  if (resEvents.lNetworkEvents & FD_CLOSE)
2002  {
2003  /* EOF/error, so signal all caller-requested socket flags */
2004  occurred_events->events |= (cur_event->events & WL_SOCKET_MASK);
2005  }
2006 
2007  if (occurred_events->events != 0)
2008  {
2009  occurred_events++;
2010  returned_events++;
2011  }
2012  }
2013 
2014  return returned_events;
2015 }
2016 #endif
2017 
2018 /*
2019  * Get the number of wait events registered in a given WaitEventSet.
2020  */
2021 int
2023 {
2024  return set->nevents;
2025 }
2026 
2027 #if defined(WAIT_USE_POLL)
2028 
2029 /*
2030  * SetLatch uses SIGURG to wake up the process waiting on the latch.
2031  *
2032  * Wake up WaitLatch, if we're waiting.
2033  */
2034 static void
2035 latch_sigurg_handler(SIGNAL_ARGS)
2036 {
2037  int save_errno = errno;
2038 
2039  if (waiting)
2040  sendSelfPipeByte();
2041 
2042  errno = save_errno;
2043 }
2044 
2045 /* Send one byte to the self-pipe, to wake up WaitLatch */
2046 static void
2047 sendSelfPipeByte(void)
2048 {
2049  int rc;
2050  char dummy = 0;
2051 
2052 retry:
2053  rc = write(selfpipe_writefd, &dummy, 1);
2054  if (rc < 0)
2055  {
2056  /* If interrupted by signal, just retry */
2057  if (errno == EINTR)
2058  goto retry;
2059 
2060  /*
2061  * If the pipe is full, we don't need to retry, the data that's there
2062  * already is enough to wake up WaitLatch.
2063  */
2064  if (errno == EAGAIN || errno == EWOULDBLOCK)
2065  return;
2066 
2067  /*
2068  * Oops, the write() failed for some other reason. We might be in a
2069  * signal handler, so it's not safe to elog(). We have no choice but
2070  * silently ignore the error.
2071  */
2072  return;
2073  }
2074 }
2075 
2076 #endif
2077 
2078 #if defined(WAIT_USE_POLL) || defined(WAIT_USE_EPOLL)
2079 
2080 /*
2081  * Read all available data from self-pipe or signalfd.
2082  *
2083  * Note: this is only called when waiting = true. If it fails and doesn't
2084  * return, it must reset that flag first (though ideally, this will never
2085  * happen).
2086  */
2087 static void
2088 drain(void)
2089 {
2090  char buf[1024];
2091  int rc;
2092  int fd;
2093 
2094 #ifdef WAIT_USE_POLL
2095  fd = selfpipe_readfd;
2096 #else
2097  fd = signal_fd;
2098 #endif
2099 
2100  for (;;)
2101  {
2102  rc = read(fd, buf, sizeof(buf));
2103  if (rc < 0)
2104  {
2105  if (errno == EAGAIN || errno == EWOULDBLOCK)
2106  break; /* the descriptor is empty */
2107  else if (errno == EINTR)
2108  continue; /* retry */
2109  else
2110  {
2111  waiting = false;
2112 #ifdef WAIT_USE_POLL
2113  elog(ERROR, "read() on self-pipe failed: %m");
2114 #else
2115  elog(ERROR, "read() on signalfd failed: %m");
2116 #endif
2117  }
2118  }
2119  else if (rc == 0)
2120  {
2121  waiting = false;
2122 #ifdef WAIT_USE_POLL
2123  elog(ERROR, "unexpected EOF on self-pipe");
2124 #else
2125  elog(ERROR, "unexpected EOF on signalfd");
2126 #endif
2127  }
2128  else if (rc < sizeof(buf))
2129  {
2130  /* we successfully drained the pipe; no need to read() again */
2131  break;
2132  }
2133  /* else buffer wasn't big enough, so read again */
2134  }
2135 }
2136 
2137 #endif
int latch_pos
Definition: latch.c:107
void InitSharedLatch(Latch *latch)
Definition: latch.c:371
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Definition: latch.h:127
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Definition: latch.h:146
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Definition: latch.c:798
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Definition: latch.h:128
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Definition: latch.c:862
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Definition: instr_time.h:150
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Definition: win32_port.h:454
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Definition: latch.h:126
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Definition: latch.c:424
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Definition: pg_ctl.c:99
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Definition: latch.c:452
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Definition: latch.c:684
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Definition: signal.c:27
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Definition: signal.c:108
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Definition: elog.h:46
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Definition: latch.c:143
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Definition: latch.c:404
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Definition: instr_time.h:170
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Definition: fd.c:1130
Definition: latch.h:110
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Definition: latch.c:114
static int WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout, WaitEvent *occurred_events, int nevents)
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Definition: globals.c:112
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Definition: pmsignal.h:102
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Definition: latch.c:500
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Definition: c.h:441
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Definition: port.h:31
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Definition: pqsignal.c:22
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Definition: mcxt.c:42
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Definition: mcxt.c:48
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Definition: latch.c:2022
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Definition: globals.c:98
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Definition: postmaster.c:569
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Definition: latch.h:129
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Definition: port.h:33
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Definition: latch.c:192
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Definition: pmsignal.c:344
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Definition: fd.c:1095
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Definition: mcxt.c:906
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Definition: signal.c:170
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Definition: c.h:804
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Definition: latch.c:98
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Definition: latch.c:290
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Definition: c.h:540
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Definition: c.h:757
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Definition: instr_time.h:156
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Definition: latch.h:147
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Definition: fd.c:1148
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Definition: globals.c:57
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Definition: latch.c:140
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Definition: win32.h:12
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Definition: latch.h:135
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Definition: latch.c:106
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