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Add a default local latch for use in signal handlers.

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To do so, move InitializeLatchSupport() into the new common process
initialization functions, and add a new global variable MyLatch.

MyLatch is usable as soon InitPostmasterChild() has been called
(i.e. very early during startup). Initially it points to a process
local latch that exists in all processes. InitProcess/InitAuxiliaryProcess
then replaces that local latch with PGPROC->procLatch. During shutdown
the reverse happens.

This is primarily advantageous for two reasons: For one it simplifies
dealing with the shared process latch, especially in signal handlers,
because instead of having to check for MyProc, MyLatch can be used
unconditionally. For another, a later patch that makes FEs/BE
communication use latches, now can rely on the existence of a latch,
even before having gone through InitProcess.

Discussion: 20140927191243.GD5423@alap3.anarazel.de
This commit is contained in:
Andres Freund
2015-01-14 18:45:22 +01:00
parent 85a2a8903f
commit 59f71a0d0b
23 changed files with 136 additions and 134 deletions
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19
src/backend/postmaster/pgstat.c
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@@ -130,8 +130,6 @@ PgStat_MsgBgWriter BgWriterStats;
*/
NON_EXEC_STATIC pgsocket pgStatSock = PGINVALID_SOCKET;
static Latch pgStatLatch;
static struct sockaddr_storage pgStatAddr;
static time_t last_pgstat_start_time;
@@ -3151,15 +3149,10 @@ PgstatCollectorMain(int argc, char *argv[])
PgStat_Msg msg;
int wr;
InitializeLatchSupport(); /* needed for latch waits */
/* Initialize private latch for use by signal handlers */
InitLatch(&pgStatLatch);
/*
* Ignore all signals usually bound to some action in the postmaster,
* except SIGHUP and SIGQUIT. Note we don't need a SIGUSR1 handler to
* support latch operations, because pgStatLatch is local not shared.
* support latch operations, because we only use a local latch.
*/
pqsignal(SIGHUP, pgstat_sighup_handler);
pqsignal(SIGINT, SIG_IGN);
@@ -3205,7 +3198,7 @@ PgstatCollectorMain(int argc, char *argv[])
for (;;)
{
/* Clear any already-pending wakeups */
ResetLatch(&pgStatLatch);
ResetLatch(MyLatch);
/*
* Quit if we get SIGQUIT from the postmaster.
@@ -3363,7 +3356,7 @@ PgstatCollectorMain(int argc, char *argv[])
/* Sleep until there's something to do */
#ifndef WIN32
wr = WaitLatchOrSocket(&pgStatLatch,
wr = WaitLatchOrSocket(MyLatch,
WL_LATCH_SET | WL_POSTMASTER_DEATH | WL_SOCKET_READABLE,
pgStatSock,
-1L);
@@ -3379,7 +3372,7 @@ PgstatCollectorMain(int argc, char *argv[])
* to not provoke "pgstat wait timeout" complaints from
* backend_read_statsfile.
*/
wr = WaitLatchOrSocket(&pgStatLatch,
wr = WaitLatchOrSocket(MyLatch,
WL_LATCH_SET | WL_POSTMASTER_DEATH | WL_SOCKET_READABLE | WL_TIMEOUT,
pgStatSock,
2 * 1000L /* msec */ );
@@ -3409,7 +3402,7 @@ pgstat_exit(SIGNAL_ARGS)
int save_errno = errno;
need_exit = true;
SetLatch(&pgStatLatch);
SetLatch(MyLatch);
errno = save_errno;
}
@@ -3421,7 +3414,7 @@ pgstat_sighup_handler(SIGNAL_ARGS)
int save_errno = errno;
got_SIGHUP = true;
SetLatch(&pgStatLatch);
SetLatch(MyLatch);
errno = save_errno;
}