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Revert "Get rid of the dedicated latch for signaling the startup process".

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Revert ac22929a26, as well as the followup fix 113d3591b8. Because it broke
the assumption that the startup process waiting for the recovery conflict
on buffer pin should be waken up only by buffer unpin or the timeout enabled
in ResolveRecoveryConflictWithBufferPin(). It caused, for example,
SIGHUP signal handler or walreceiver process to wake that startup process
up unnecessarily frequently.

Additionally, add the comments about why that dedicated latch that
the reverted patch tried to get rid of should not be removed.

Thanks to Kyotaro Horiguchi for the discussion.

Author: Fujii Masao
Discussion: https://postgr.es/m/d8c0c608-021b-3c73-fffd-3240829ee986@oss.nttdata.com
This commit is contained in:
Fujii Masao
2020-12-17 18:06:51 +09:00
parent 88e014c149
commit 00f690a239
3 changed files with 52 additions and 21 deletions
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24
src/backend/postmaster/startup.c
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@ -37,6 +37,7 @@
/*
* Flags set by interrupt handlers for later service in the redo loop.
*/
static volatile sig_atomic_t got_SIGHUP = false;
static volatile sig_atomic_t shutdown_requested = false;
static volatile sig_atomic_t promote_signaled = false;
@ -48,6 +49,7 @@ static volatile sig_atomic_t in_restore_command = false;
/* Signal handlers */
static void StartupProcTriggerHandler(SIGNAL_ARGS);
static void StartupProcSigHupHandler(SIGNAL_ARGS);
/* --------------------------------
@ -62,7 +64,19 @@ StartupProcTriggerHandler(SIGNAL_ARGS)
int save_errno = errno;
promote_signaled = true;
SetLatch(MyLatch);
WakeupRecovery();
errno = save_errno;
}
/* SIGHUP: set flag to re-read config file at next convenient time */
static void
StartupProcSigHupHandler(SIGNAL_ARGS)
{
int save_errno = errno;
got_SIGHUP = true;
WakeupRecovery();
errno = save_errno;
}
@ -77,7 +91,7 @@ StartupProcShutdownHandler(SIGNAL_ARGS)
proc_exit(1);
else
shutdown_requested = true;
SetLatch(MyLatch);
WakeupRecovery();
errno = save_errno;
}
@ -123,9 +137,9 @@ HandleStartupProcInterrupts(void)
/*
* Process any requests or signals received recently.
*/
if (ConfigReloadPending)
if (got_SIGHUP)
{
ConfigReloadPending = false;
got_SIGHUP = false;
StartupRereadConfig();
}
@ -158,7 +172,7 @@ StartupProcessMain(void)
/*
* Properly accept or ignore signals the postmaster might send us.
*/
pqsignal(SIGHUP, SignalHandlerForConfigReload); /* reload config file */
pqsignal(SIGHUP, StartupProcSigHupHandler); /* reload config file */
pqsignal(SIGINT, SIG_IGN); /* ignore query cancel */
pqsignal(SIGTERM, StartupProcShutdownHandler); /* request shutdown */
/* SIGQUIT handler was already set up by InitPostmasterChild */