diff options
Diffstat (limited to 'src/backend/storage/ipc/latch.c')
| -rw-r--r-- | src/backend/storage/ipc/latch.c | 56 |
1 files changed, 52 insertions, 4 deletions
diff --git a/src/backend/storage/ipc/latch.c b/src/backend/storage/ipc/latch.c index 91fa4b619b8..4153cc85579 100644 --- a/src/backend/storage/ipc/latch.c +++ b/src/backend/storage/ipc/latch.c @@ -56,6 +56,7 @@ #include "storage/latch.h" #include "storage/pmsignal.h" #include "storage/shmem.h" +#include "utils/memutils.h" /* * Select the fd readiness primitive to use. Normally the "most modern" @@ -129,6 +130,12 @@ struct WaitEventSet #endif }; +/* A common WaitEventSet used to implement WatchLatch() */ +static WaitEventSet *LatchWaitSet; + +/* The position of the latch in LatchWaitSet. */ +#define LatchWaitSetLatchPos 0 + #ifndef WIN32 /* Are we currently in WaitLatch? The signal handler would like to know. */ static volatile sig_atomic_t waiting = false; @@ -242,6 +249,24 @@ InitializeLatchSupport(void) #endif } +void +InitializeLatchWaitSet(void) +{ + int latch_pos PG_USED_FOR_ASSERTS_ONLY; + + Assert(LatchWaitSet == NULL); + + /* Set up the WaitEventSet used by WaitLatch(). */ + LatchWaitSet = CreateWaitEventSet(TopMemoryContext, 2); + latch_pos = AddWaitEventToSet(LatchWaitSet, WL_LATCH_SET, PGINVALID_SOCKET, + MyLatch, NULL); + if (IsUnderPostmaster) + AddWaitEventToSet(LatchWaitSet, WL_EXIT_ON_PM_DEATH, + PGINVALID_SOCKET, NULL, NULL); + + Assert(latch_pos == LatchWaitSetLatchPos); +} + /* * Initialize a process-local latch. */ @@ -365,8 +390,31 @@ int WaitLatch(Latch *latch, int wakeEvents, long timeout, uint32 wait_event_info) { - return WaitLatchOrSocket(latch, wakeEvents, PGINVALID_SOCKET, timeout, - wait_event_info); + WaitEvent event; + + /* Postmaster-managed callers must handle postmaster death somehow. */ + Assert(!IsUnderPostmaster || + (wakeEvents & WL_EXIT_ON_PM_DEATH) || + (wakeEvents & WL_POSTMASTER_DEATH)); + + /* + * Some callers may have a latch other than MyLatch, or no latch at all, + * or want to handle postmaster death differently. It's cheap to assign + * those, so just do it every time. + */ + if (!(wakeEvents & WL_LATCH_SET)) + latch = NULL; + ModifyWaitEvent(LatchWaitSet, LatchWaitSetLatchPos, WL_LATCH_SET, latch); + LatchWaitSet->exit_on_postmaster_death = + ((wakeEvents & WL_EXIT_ON_PM_DEATH) != 0); + + if (WaitEventSetWait(LatchWaitSet, + (wakeEvents & WL_TIMEOUT) ? timeout : -1, + &event, 1, + wait_event_info) == 0) + return WL_TIMEOUT; + else + return event.events; } /* @@ -830,7 +878,8 @@ AddWaitEventToSet(WaitEventSet *set, uint32 events, pgsocket fd, Latch *latch, /* * Change the event mask and, in the WL_LATCH_SET case, the latch associated - * with the WaitEvent. + * with the WaitEvent. The latch may be changed to NULL to disable the latch + * temporarily, and then set back to a latch later. * * 'pos' is the id returned by AddWaitEventToSet. */ @@ -862,7 +911,6 @@ ModifyWaitEvent(WaitEventSet *set, int pos, uint32 events, Latch *latch) if (event->events & WL_LATCH_SET && events != event->events) { - /* we could allow to disable latch events for a while */ elog(ERROR, "cannot modify latch event"); } |