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Fix WAL waiting in walproposer for v16.

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Just preparing cv right before waiting is not enough as we might have already
missed the flushptr change & wakeup, so re-checked before sleep.

https://neondb.slack.com/archives/C03QLRH7PPD/p1702830965396619?thread_ts=1702756761.836649&cid=C03QLRH7PPD
This commit is contained in:
Arseny Sher
2023-12-19 02:27:23 +03:00
committed by Arseny Sher
parent d89af4cf8e
commit b701394d7a
1 changed files with 15 additions and 0 deletions
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15
pgxn/neon/walproposer_pg.c
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@@ -1482,6 +1482,21 @@ walprop_pg_wait_event_set(WalProposer *wp, long timeout, Safekeeper **sk, uint32
#if PG_MAJORVERSION_NUM >= 16
if (WalSndCtl != NULL)
ConditionVariablePrepareToSleep(&WalSndCtl->wal_flush_cv);
/*
* Now that we prepared the condvar, check flush ptr again -- it might have
* changed before we subscribed to cv so we missed the wakeup.
*
* Do that only when we're interested in new WAL: without sync-safekeepers
* and if election already passed.
*/
if (!wp->config->syncSafekeepers && wp->availableLsn != InvalidXLogRecPtr && GetFlushRecPtr(NULL) > wp->availableLsn)
{
ConditionVariableCancelSleep();
ResetLatch(MyLatch);
*events = WL_LATCH_SET;
return 1;
}
#endif
/*