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Cosmetic adjustments for postmaster's handling of checkpointer. 

Correct some comments, order some operations a bit more consistently.
No functional changes.
This commit is contained in:
Tom Lane 2012-05-11 17:46:08 -04:00
parent 2cfb1c6f77
commit d0c231d132
2 changed files with 34 additions and 26 deletions
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6
src/backend/postmaster/bgwriter.c
View File

@ -15,9 +15,9 @@
* The bgwriter is started by the postmaster as soon as the startup subprocess
* finishes, or as soon as recovery begins if we are doing archive recovery.
* It remains alive until the postmaster commands it to terminate.
* Normal termination is by SIGUSR2, which instructs the bgwriter to exit(0).
* Emergency termination is by SIGQUIT; like any
* backend, the bgwriter will simply abort and exit on SIGQUIT.
* Normal termination is by SIGTERM, which instructs the bgwriter to exit(0).
* Emergency termination is by SIGQUIT; like any backend, the bgwriter will
* simply abort and exit on SIGQUIT.
*
* If the bgwriter exits unexpectedly, the postmaster treats that the same
* as a backend crash: shared memory may be corrupted, so remaining backends

54
src/backend/postmaster/postmaster.c
View File

@ -239,13 +239,13 @@ static bool RecoveryError = false; /* T if WAL recovery failed */
* hot standby during archive recovery.
*
* When the startup process is ready to start archive recovery, it signals the
* postmaster, and we switch to PM_RECOVERY state. The background writer is
* launched, while the startup process continues applying WAL. If Hot Standby
* is enabled, then, after reaching a consistent point in WAL redo, startup
* process signals us again, and we switch to PM_HOT_STANDBY state and
* begin accepting connections to perform read-only queries. When archive
* recovery is finished, the startup process exits with exit code 0 and we
* switch to PM_RUN state.
* postmaster, and we switch to PM_RECOVERY state. The background writer and
* checkpointer are launched, while the startup process continues applying WAL.
* If Hot Standby is enabled, then, after reaching a consistent point in WAL
* redo, startup process signals us again, and we switch to PM_HOT_STANDBY
* state and begin accepting connections to perform read-only queries. When
* archive recovery is finished, the startup process exits with exit code 0
* and we switch to PM_RUN state.
*
* Normal child backends can only be launched when we are in PM_RUN or
* PM_HOT_STANDBY state. (We also allow launch of normal
@ -1038,7 +1038,7 @@ PostmasterMain(int argc, char *argv[])
* handling setup of child processes. See tcop/postgres.c,
* bootstrap/bootstrap.c, postmaster/bgwriter.c, postmaster/walwriter.c,
* postmaster/autovacuum.c, postmaster/pgarch.c, postmaster/pgstat.c,
* postmaster/syslogger.c and postmaster/checkpointer.c
* postmaster/syslogger.c and postmaster/checkpointer.c.
*/
pqinitmask();
PG_SETMASK(&BlockSig);
@ -1373,10 +1373,10 @@ ServerLoop(void)
/*
* If no background writer process is running, and we are not in a
* state that prevents it, start one. It doesn't matter if this
* fails, we'll just try again later.
* fails, we'll just try again later. Likewise for the checkpointer.
*/
if (pmState == PM_RUN || pmState == PM_RECOVERY ||
pmState == PM_HOT_STANDBY)
pmState == PM_HOT_STANDBY)
{
if (BgWriterPID == 0)
BgWriterPID = StartBackgroundWriter();
@ -1386,7 +1386,8 @@ ServerLoop(void)
/*
* Likewise, if we have lost the walwriter process, try to start a new
* one.
* one. But this is needed only in normal operation (else we cannot
* be writing any new WAL).
*/
if (WalWriterPID == 0 && pmState == PM_RUN)
WalWriterPID = StartWalWriter();
@ -2131,11 +2132,12 @@ pmdie(SIGNAL_ARGS)
/* and the autovac launcher too */
if (AutoVacPID != 0)
signal_child(AutoVacPID, SIGTERM);
/* and the bgwriter too */
if (BgWriterPID != 0)
signal_child(BgWriterPID, SIGTERM);
/* and the walwriter too */
if (WalWriterPID != 0)
signal_child(WalWriterPID, SIGTERM);
if (BgWriterPID != 0)
signal_child(BgWriterPID, SIGTERM);
/*
* If we're in recovery, we can't kill the startup process
@ -2174,13 +2176,17 @@ pmdie(SIGNAL_ARGS)
if (StartupPID != 0)
signal_child(StartupPID, SIGTERM);
if (WalReceiverPID != 0)
signal_child(WalReceiverPID, SIGTERM);
if (BgWriterPID != 0)
signal_child(BgWriterPID, SIGTERM);
if (WalReceiverPID != 0)
signal_child(WalReceiverPID, SIGTERM);
if (pmState == PM_RECOVERY)
{
/* only checkpointer is active in this state */
/*
* Only startup, bgwriter, and checkpointer should be active
* in this state; we just signaled the first two, and we don't
* want to kill checkpointer yet.
*/
pmState = PM_WAIT_BACKENDS;
}
else if (pmState == PM_RUN ||
@ -2362,7 +2368,7 @@ reaper(SIGNAL_ARGS)
}
/*
* Crank up background tasks, if we didn't do that already
* Crank up the background tasks, if we didn't do that already
* when we entered consistent recovery state. It doesn't matter
* if this fails, we'll just try again later.
*/
@ -2370,13 +2376,13 @@ reaper(SIGNAL_ARGS)
BgWriterPID = StartBackgroundWriter();
if (CheckpointerPID == 0)
CheckpointerPID = StartCheckpointer();
if (WalWriterPID == 0)
WalWriterPID = StartWalWriter();
/*
* Likewise, start other special children as needed. In a restart
* situation, some of them may be alive already.
*/
if (WalWriterPID == 0)
WalWriterPID = StartWalWriter();
if (!IsBinaryUpgrade && AutoVacuumingActive() && AutoVacPID == 0)
AutoVacPID = StartAutoVacLauncher();
if (XLogArchivingActive() && PgArchPID == 0)
@ -2392,7 +2398,9 @@ reaper(SIGNAL_ARGS)
}
/*
* Was it the bgwriter?
* Was it the bgwriter? Normal exit can be ignored; we'll start a
* new one at the next iteration of the postmaster's main loop, if
* necessary. Any other exit condition is treated as a crash.
*/
if (pid == BgWriterPID)
{
@ -4228,13 +4236,13 @@ sigusr1_handler(SIGNAL_ARGS)
FatalError = false;
/*
* Crank up the background writers. It doesn't matter if this fails,
* Crank up the background tasks. It doesn't matter if this fails,
* we'll just try again later.
*/
Assert(CheckpointerPID == 0);
CheckpointerPID = StartCheckpointer();
Assert(BgWriterPID == 0);
BgWriterPID = StartBackgroundWriter();
Assert(CheckpointerPID == 0);
CheckpointerPID = StartCheckpointer();
pmState = PM_RECOVERY;
}