From 59f71a0d0b56b2df48db4bf1738aece5551f7a47 Mon Sep 17 00:00:00 2001
From: Andres Freund <andres@anarazel.de>
Date: Wed, 14 Jan 2015 18:45:22 +0100
Subject: [PATCH] Add a default local latch for use in signal handlers.
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
---
src/backend/postmaster/autovacuum.c | 13 +++-----
src/backend/postmaster/bgworker.c | 4 +--
src/backend/postmaster/bgwriter.c | 12 +++----
src/backend/postmaster/checkpointer.c | 13 +++-----
src/backend/postmaster/pgarch.c | 21 ++++--------
src/backend/postmaster/pgstat.c | 19 ++++-------
src/backend/postmaster/syslogger.c | 21 ++++--------
src/backend/postmaster/walwriter.c | 10 +++---
src/backend/replication/syncrep.c | 4 +--
src/backend/storage/ipc/procsignal.c | 4 +--
src/backend/storage/ipc/shm_mq.c | 12 +++----
src/backend/storage/lmgr/proc.c | 42 ++++++++++--------------
src/backend/tcop/postgres.c | 12 +++----
src/backend/utils/adt/misc.c | 4 +--
src/backend/utils/init/globals.c | 9 +++++
src/backend/utils/init/miscinit.c | 37 +++++++++++++++++++++
src/backend/utils/misc/timeout.c | 6 ++--
src/include/miscadmin.h | 4 +++
src/include/storage/latch.h | 2 +-
src/test/modules/test_shm_mq/setup.c | 4 +--
src/test/modules/test_shm_mq/test.c | 4 +--
src/test/modules/test_shm_mq/worker.c | 3 +-
src/test/modules/worker_spi/worker_spi.c | 10 +++---
23 files changed, 136 insertions(+), 134 deletions(-)
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index a26eee25d46..02f871ce22b 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -589,11 +589,11 @@ AutoVacLauncherMain(int argc, char *argv[])
* Wait until naptime expires or we get some type of signal (all the
* signal handlers will wake us by calling SetLatch).
*/
- rc = WaitLatch(&MyProc->procLatch,
+ rc = WaitLatch(MyLatch,
WL_LATCH_SET | WL_TIMEOUT | WL_POSTMASTER_DEATH,
(nap.tv_sec * 1000L) + (nap.tv_usec / 1000L));
- ResetLatch(&MyProc->procLatch);
+ ResetLatch(MyLatch);
DisableCatchupInterrupt();
@@ -1341,8 +1341,7 @@ avl_sighup_handler(SIGNAL_ARGS)
int save_errno = errno;
got_SIGHUP = true;
- if (MyProc)
- SetLatch(&MyProc->procLatch);
+ SetLatch(MyLatch);
errno = save_errno;
}
@@ -1354,8 +1353,7 @@ avl_sigusr2_handler(SIGNAL_ARGS)
int save_errno = errno;
got_SIGUSR2 = true;
- if (MyProc)
- SetLatch(&MyProc->procLatch);
+ SetLatch(MyLatch);
errno = save_errno;
}
@@ -1367,8 +1365,7 @@ avl_sigterm_handler(SIGNAL_ARGS)
int save_errno = errno;
got_SIGTERM = true;
- if (MyProc)
- SetLatch(&MyProc->procLatch);
+ SetLatch(MyLatch);
errno = save_errno;
}
diff --git a/src/backend/postmaster/bgworker.c b/src/backend/postmaster/bgworker.c
index 6673f5ba622..267b9163271 100644
--- a/src/backend/postmaster/bgworker.c
+++ b/src/backend/postmaster/bgworker.c
@@ -942,7 +942,7 @@ WaitForBackgroundWorkerStartup(BackgroundWorkerHandle *handle, pid_t *pidp)
if (status != BGWH_NOT_YET_STARTED)
break;
- rc = WaitLatch(&MyProc->procLatch,
+ rc = WaitLatch(MyLatch,
WL_LATCH_SET | WL_POSTMASTER_DEATH, 0);
if (rc & WL_POSTMASTER_DEATH)
@@ -951,7 +951,7 @@ WaitForBackgroundWorkerStartup(BackgroundWorkerHandle *handle, pid_t *pidp)
break;
}
- ResetLatch(&MyProc->procLatch);
+ ResetLatch(MyLatch);
}
}
PG_CATCH();
diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c
index f138eb7473b..b6cf65d4950 100644
--- a/src/backend/postmaster/bgwriter.c
+++ b/src/backend/postmaster/bgwriter.c
@@ -248,7 +248,7 @@ BackgroundWriterMain(void)
int rc;
/* Clear any already-pending wakeups */
- ResetLatch(&MyProc->procLatch);
+ ResetLatch(MyLatch);
if (got_SIGHUP)
{
@@ -336,7 +336,7 @@ BackgroundWriterMain(void)
* down with latch events that are likely to happen frequently during
* normal operation.
*/
- rc = WaitLatch(&MyProc->procLatch,
+ rc = WaitLatch(MyLatch,
WL_LATCH_SET | WL_TIMEOUT | WL_POSTMASTER_DEATH,
BgWriterDelay /* ms */ );
@@ -363,7 +363,7 @@ BackgroundWriterMain(void)
/* Ask for notification at next buffer allocation */
StrategyNotifyBgWriter(MyProc->pgprocno);
/* Sleep ... */
- rc = WaitLatch(&MyProc->procLatch,
+ rc = WaitLatch(MyLatch,
WL_LATCH_SET | WL_TIMEOUT | WL_POSTMASTER_DEATH,
BgWriterDelay * HIBERNATE_FACTOR);
/* Reset the notification request in case we timed out */
@@ -426,8 +426,7 @@ BgSigHupHandler(SIGNAL_ARGS)
int save_errno = errno;
got_SIGHUP = true;
- if (MyProc)
- SetLatch(&MyProc->procLatch);
+ SetLatch(MyLatch);
errno = save_errno;
}
@@ -439,8 +438,7 @@ ReqShutdownHandler(SIGNAL_ARGS)
int save_errno = errno;
shutdown_requested = true;
- if (MyProc)
- SetLatch(&MyProc->procLatch);
+ SetLatch(MyLatch);
errno = save_errno;
}
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index 3c9c216c6f1..237be121dd6 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -360,7 +360,7 @@ CheckpointerMain(void)
int rc;
/* Clear any already-pending wakeups */
- ResetLatch(&MyProc->procLatch);
+ ResetLatch(MyLatch);
/*
* Process any requests or signals received recently.
@@ -559,7 +559,7 @@ CheckpointerMain(void)
cur_timeout = Min(cur_timeout, XLogArchiveTimeout - elapsed_secs);
}
- rc = WaitLatch(&MyProc->procLatch,
+ rc = WaitLatch(MyLatch,
WL_LATCH_SET | WL_TIMEOUT | WL_POSTMASTER_DEATH,
cur_timeout * 1000L /* convert to ms */ );
@@ -832,8 +832,7 @@ ChkptSigHupHandler(SIGNAL_ARGS)
int save_errno = errno;
got_SIGHUP = true;
- if (MyProc)
- SetLatch(&MyProc->procLatch);
+ SetLatch(MyLatch);
errno = save_errno;
}
@@ -845,8 +844,7 @@ ReqCheckpointHandler(SIGNAL_ARGS)
int save_errno = errno;
checkpoint_requested = true;
- if (MyProc)
- SetLatch(&MyProc->procLatch);
+ SetLatch(MyLatch);
errno = save_errno;
}
@@ -869,8 +867,7 @@ ReqShutdownHandler(SIGNAL_ARGS)
int save_errno = errno;
shutdown_requested = true;
- if (MyProc)
- SetLatch(&MyProc->procLatch);
+ SetLatch(MyLatch);
errno = save_errno;
}
diff --git a/src/backend/postmaster/pgarch.c b/src/backend/postmaster/pgarch.c
index 78dec3a4c6f..9b689af9156 100644
--- a/src/backend/postmaster/pgarch.c
+++ b/src/backend/postmaster/pgarch.c
@@ -78,11 +78,6 @@ static volatile sig_atomic_t got_SIGTERM = false;
static volatile sig_atomic_t wakened = false;
static volatile sig_atomic_t ready_to_stop = false;
-/*
- * Latch used by signal handlers to wake up the sleep in the main loop.
- */
-static Latch mainloop_latch;
-
/* ----------
* Local function forward declarations
* ----------
@@ -220,10 +215,6 @@ pgarch_forkexec(void)
NON_EXEC_STATIC void
PgArchiverMain(int argc, char *argv[])
{
- InitializeLatchSupport(); /* needed for latch waits */
-
- InitLatch(&mainloop_latch); /* initialize latch used in main loop */
-
/*
* Ignore all signals usually bound to some action in the postmaster,
* except for SIGHUP, SIGTERM, SIGUSR1, SIGUSR2, and SIGQUIT.
@@ -269,7 +260,7 @@ ArchSigHupHandler(SIGNAL_ARGS)
/* set flag to re-read config file at next convenient time */
got_SIGHUP = true;
- SetLatch(&mainloop_latch);
+ SetLatch(MyLatch);
errno = save_errno;
}
@@ -287,7 +278,7 @@ ArchSigTermHandler(SIGNAL_ARGS)
* archive commands.
*/
got_SIGTERM = true;
- SetLatch(&mainloop_latch);
+ SetLatch(MyLatch);
errno = save_errno;
}
@@ -300,7 +291,7 @@ pgarch_waken(SIGNAL_ARGS)
/* set flag that there is work to be done */
wakened = true;
- SetLatch(&mainloop_latch);
+ SetLatch(MyLatch);
errno = save_errno;
}
@@ -313,7 +304,7 @@ pgarch_waken_stop(SIGNAL_ARGS)
/* set flag to do a final cycle and shut down afterwards */
ready_to_stop = true;
- SetLatch(&mainloop_latch);
+ SetLatch(MyLatch);
errno = save_errno;
}
@@ -344,7 +335,7 @@ pgarch_MainLoop(void)
*/
do
{
- ResetLatch(&mainloop_latch);
+ ResetLatch(MyLatch);
/* When we get SIGUSR2, we do one more archive cycle, then exit */
time_to_stop = ready_to_stop;
@@ -397,7 +388,7 @@ pgarch_MainLoop(void)
{
int rc;
- rc = WaitLatch(&mainloop_latch,
+ rc = WaitLatch(MyLatch,
WL_LATCH_SET | WL_TIMEOUT | WL_POSTMASTER_DEATH,
timeout * 1000L);
if (rc & WL_TIMEOUT)
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index fa87660baee..0cf498866a3 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -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;
}
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index d127fb57711..41b8dbb6c25 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -85,7 +85,6 @@ static FILE *csvlogFile = NULL;
NON_EXEC_STATIC pg_time_t first_syslogger_file_time = 0;
static char *last_file_name = NULL;
static char *last_csv_file_name = NULL;
-static Latch sysLoggerLatch;
/*
* Buffers for saving partial messages from different backends.
@@ -231,12 +230,6 @@ SysLoggerMain(int argc, char *argv[])
syslogPipe[1] = 0;
#endif
- InitializeLatchSupport(); /* needed for latch waits */
-
-
- /* Initialize private latch for use by signal handlers */
- InitLatch(&sysLoggerLatch);
-
/*
* Properly accept or ignore signals the postmaster might send us
*
@@ -302,7 +295,7 @@ SysLoggerMain(int argc, char *argv[])
#endif
/* Clear any already-pending wakeups */
- ResetLatch(&sysLoggerLatch);
+ ResetLatch(MyLatch);
/*
* Process any requests or signals received recently.
@@ -428,7 +421,7 @@ SysLoggerMain(int argc, char *argv[])
* Sleep until there's something to do
*/
#ifndef WIN32
- rc = WaitLatchOrSocket(&sysLoggerLatch,
+ rc = WaitLatchOrSocket(MyLatch,
WL_LATCH_SET | WL_SOCKET_READABLE | cur_flags,
syslogPipe[0],
cur_timeout);
@@ -480,7 +473,7 @@ SysLoggerMain(int argc, char *argv[])
*/
LeaveCriticalSection(&sysloggerSection);
- (void) WaitLatch(&sysLoggerLatch,
+ (void) WaitLatch(MyLatch,
WL_LATCH_SET | cur_flags,
cur_timeout);
@@ -1061,7 +1054,7 @@ pipeThread(void *arg)
{
if (ftell(syslogFile) >= Log_RotationSize * 1024L ||
(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L))
- SetLatch(&sysLoggerLatch);
+ SetLatch(MyLatch);
}
LeaveCriticalSection(&sysloggerSection);
}
@@ -1073,7 +1066,7 @@ pipeThread(void *arg)
flush_pipe_input(logbuffer, &bytes_in_logbuffer);
/* set the latch to waken the main thread, which will quit */
- SetLatch(&sysLoggerLatch);
+ SetLatch(MyLatch);
LeaveCriticalSection(&sysloggerSection);
_endthread();
@@ -1353,7 +1346,7 @@ sigHupHandler(SIGNAL_ARGS)
int save_errno = errno;
got_SIGHUP = true;
- SetLatch(&sysLoggerLatch);
+ SetLatch(MyLatch);
errno = save_errno;
}
@@ -1365,7 +1358,7 @@ sigUsr1Handler(SIGNAL_ARGS)
int save_errno = errno;
rotation_requested = true;
- SetLatch(&sysLoggerLatch);
+ SetLatch(MyLatch);
errno = save_errno;
}
diff --git a/src/backend/postmaster/walwriter.c b/src/backend/postmaster/walwriter.c
index 044c30665e7..a44b5a80eb4 100644
--- a/src/backend/postmaster/walwriter.c
+++ b/src/backend/postmaster/walwriter.c
@@ -252,7 +252,7 @@ WalWriterMain(void)
}
/* Clear any already-pending wakeups */
- ResetLatch(&MyProc->procLatch);
+ ResetLatch(MyLatch);
/*
* Process any requests or signals received recently.
@@ -287,7 +287,7 @@ WalWriterMain(void)
else
cur_timeout = WalWriterDelay * HIBERNATE_FACTOR;
- rc = WaitLatch(&MyProc->procLatch,
+ rc = WaitLatch(MyLatch,
WL_LATCH_SET | WL_TIMEOUT | WL_POSTMASTER_DEATH,
cur_timeout);
@@ -345,8 +345,7 @@ WalSigHupHandler(SIGNAL_ARGS)
int save_errno = errno;
got_SIGHUP = true;
- if (MyProc)
- SetLatch(&MyProc->procLatch);
+ SetLatch(MyLatch);
errno = save_errno;
}
@@ -358,8 +357,7 @@ WalShutdownHandler(SIGNAL_ARGS)
int save_errno = errno;
shutdown_requested = true;
- if (MyProc)
- SetLatch(&MyProc->procLatch);
+ SetLatch(MyLatch);
errno = save_errno;
}
diff --git a/src/backend/replication/syncrep.c b/src/backend/replication/syncrep.c
index b2b3a81f54c..ec594cf3df8 100644
--- a/src/backend/replication/syncrep.c
+++ b/src/backend/replication/syncrep.c
@@ -162,7 +162,7 @@ SyncRepWaitForLSN(XLogRecPtr XactCommitLSN)
int syncRepState;
/* Must reset the latch before testing state. */
- ResetLatch(&MyProc->procLatch);
+ ResetLatch(MyLatch);
/*
* Try checking the state without the lock first. There's no
@@ -235,7 +235,7 @@ SyncRepWaitForLSN(XLogRecPtr XactCommitLSN)
* Wait on latch. Any condition that should wake us up will set the
* latch, so no need for timeout.
*/
- WaitLatch(&MyProc->procLatch, WL_LATCH_SET | WL_POSTMASTER_DEATH, -1);
+ WaitLatch(MyLatch, WL_LATCH_SET | WL_POSTMASTER_DEATH, -1);
}
/*
diff --git a/src/backend/storage/ipc/procsignal.c b/src/backend/storage/ipc/procsignal.c
index cf094187661..48573bef60b 100644
--- a/src/backend/storage/ipc/procsignal.c
+++ b/src/backend/storage/ipc/procsignal.c
@@ -292,8 +292,8 @@ procsignal_sigusr1_handler(SIGNAL_ARGS)
if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN))
RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN);
- if (set_latch_on_sigusr1 && MyProc != NULL)
- SetLatch(&MyProc->procLatch);
+ if (set_latch_on_sigusr1)
+ SetLatch(MyLatch);
latch_sigusr1_handler();
diff --git a/src/backend/storage/ipc/shm_mq.c b/src/backend/storage/ipc/shm_mq.c
index 7c41400d216..d42a8d1ae4d 100644
--- a/src/backend/storage/ipc/shm_mq.c
+++ b/src/backend/storage/ipc/shm_mq.c
@@ -827,13 +827,13 @@ shm_mq_send_bytes(shm_mq_handle *mqh, Size nbytes, const void *data,
* at top of loop, because setting an already-set latch is much
* cheaper than setting one that has been reset.
*/
- WaitLatch(&MyProc->procLatch, WL_LATCH_SET, 0);
+ WaitLatch(MyLatch, WL_LATCH_SET, 0);
/* An interrupt may have occurred while we were waiting. */
CHECK_FOR_INTERRUPTS();
/* Reset the latch so we don't spin. */
- ResetLatch(&MyProc->procLatch);
+ ResetLatch(MyLatch);
}
else
{
@@ -924,13 +924,13 @@ shm_mq_receive_bytes(shm_mq *mq, Size bytes_needed, bool nowait,
* loop, because setting an already-set latch is much cheaper than
* setting one that has been reset.
*/
- WaitLatch(&MyProc->procLatch, WL_LATCH_SET, 0);
+ WaitLatch(MyLatch, WL_LATCH_SET, 0);
/* An interrupt may have occurred while we were waiting. */
CHECK_FOR_INTERRUPTS();
/* Reset the latch so we don't spin. */
- ResetLatch(&MyProc->procLatch);
+ ResetLatch(MyLatch);
}
}
@@ -991,13 +991,13 @@ shm_mq_wait_internal(volatile shm_mq *mq, PGPROC *volatile * ptr,
}
/* Wait to be signalled. */
- WaitLatch(&MyProc->procLatch, WL_LATCH_SET, 0);
+ WaitLatch(MyLatch, WL_LATCH_SET, 0);
/* An interrupt may have occurred while we were waiting. */
CHECK_FOR_INTERRUPTS();
/* Reset the latch so we don't spin. */
- ResetLatch(&MyProc->procLatch);
+ ResetLatch(MyLatch);
}
}
PG_CATCH();
diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c
index 777c60b64d4..65e8afe457f 100644
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -290,13 +290,6 @@ InitProcess(void)
if (MyProc != NULL)
elog(ERROR, "you already exist");
- /*
- * Initialize process-local latch support. This could fail if the kernel
- * is low on resources, and if so we want to exit cleanly before acquiring
- * any shared-memory resources.
- */
- InitializeLatchSupport();
-
/*
* Try to get a proc struct from the free list. If this fails, we must be
* out of PGPROC structures (not to mention semaphores).
@@ -391,10 +384,12 @@ InitProcess(void)
SHMQueueElemInit(&(MyProc->syncRepLinks));
/*
- * Acquire ownership of the PGPROC's latch, so that we can use WaitLatch.
- * Note that there's no particular need to do ResetLatch here.
+ * Acquire ownership of the PGPROC's latch, so that we can use WaitLatch
+ * on it. That allows us to repoint the process latch, which so far
+ * points to process local one, to the shared one.
*/
OwnLatch(&MyProc->procLatch);
+ SwitchToSharedLatch();
/*
* We might be reusing a semaphore that belonged to a failed process. So
@@ -474,13 +469,6 @@ InitAuxiliaryProcess(void)
if (MyProc != NULL)
elog(ERROR, "you already exist");
- /*
- * Initialize process-local latch support. This could fail if the kernel
- * is low on resources, and if so we want to exit cleanly before acquiring
- * any shared-memory resources.
- */
- InitializeLatchSupport();
-
/*
* We use the ProcStructLock to protect assignment and releasing of
* AuxiliaryProcs entries.
@@ -547,10 +535,12 @@ InitAuxiliaryProcess(void)
#endif
/*
- * Acquire ownership of the PGPROC's latch, so that we can use WaitLatch.
- * Note that there's no particular need to do ResetLatch here.
+ * Acquire ownership of the PGPROC's latch, so that we can use WaitLatch
+ * on it. That allows us to repoint the process latch, which so far
+ * points to process local one, to the shared one.
*/
OwnLatch(&MyProc->procLatch);
+ SwitchToSharedLatch();
/*
* We might be reusing a semaphore that belonged to a failed process. So
@@ -800,10 +790,12 @@ ProcKill(int code, Datum arg)
ReplicationSlotRelease();
/*
- * Clear MyProc first; then disown the process latch. This is so that
- * signal handlers won't try to clear the process latch after it's no
- * longer ours.
+ * Reset MyLatch to the process local one. This is so that signal
+ * handlers et al can continue using the latch after the shared latch
+ * isn't ours anymore. After that clear MyProc and disown the shared
+ * latch.
*/
+ SwitchBackToLocalLatch();
proc = MyProc;
MyProc = NULL;
DisownLatch(&proc->procLatch);
@@ -867,10 +859,12 @@ AuxiliaryProcKill(int code, Datum arg)
LWLockReleaseAll();
/*
- * Clear MyProc first; then disown the process latch. This is so that
- * signal handlers won't try to clear the process latch after it's no
- * longer ours.
+ * Reset MyLatch to the process local one. This is so that signal
+ * handlers et al can continue using the latch after the shared latch
+ * isn't ours anymore. After that clear MyProc and disown the shared
+ * latch.
*/
+ SwitchBackToLocalLatch();
proc = MyProc;
MyProc = NULL;
DisownLatch(&proc->procLatch);
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index f805368899a..8f743536cff 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -2607,8 +2607,7 @@ die(SIGNAL_ARGS)
}
/* If we're still here, waken anything waiting on the process latch */
- if (MyProc)
- SetLatch(&MyProc->procLatch);
+ SetLatch(MyLatch);
errno = save_errno;
}
@@ -2649,8 +2648,7 @@ StatementCancelHandler(SIGNAL_ARGS)
}
/* If we're still here, waken anything waiting on the process latch */
- if (MyProc)
- SetLatch(&MyProc->procLatch);
+ SetLatch(MyLatch);
errno = save_errno;
}
@@ -2675,8 +2673,7 @@ SigHupHandler(SIGNAL_ARGS)
int save_errno = errno;
got_SIGHUP = true;
- if (MyProc)
- SetLatch(&MyProc->procLatch);
+ SetLatch(MyLatch);
errno = save_errno;
}
@@ -2814,8 +2811,7 @@ RecoveryConflictInterrupt(ProcSignalReason reason)
* waiting on that latch, expecting to get interrupted by query cancels et
* al., would also need to set set_latch_on_sigusr1.
*/
- if (MyProc)
- SetLatch(&MyProc->procLatch);
+ SetLatch(MyLatch);
errno = save_errno;
}
diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index ed5a795bb0e..29f7c3badfd 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -413,10 +413,10 @@ pg_sleep(PG_FUNCTION_ARGS)
else
break;
- (void) WaitLatch(&MyProc->procLatch,
+ (void) WaitLatch(MyLatch,
WL_LATCH_SET | WL_TIMEOUT,
delay_ms);
- ResetLatch(&MyProc->procLatch);
+ ResetLatch(MyLatch);
}
PG_RETURN_VOID();
diff --git a/src/backend/utils/init/globals.c b/src/backend/utils/init/globals.c
index dc5c8d684a7..c35867bcfe9 100644
--- a/src/backend/utils/init/globals.c
+++ b/src/backend/utils/init/globals.c
@@ -40,6 +40,15 @@ struct Port *MyProcPort;
long MyCancelKey;
int MyPMChildSlot;
+/*
+ * MyLatch points to the latch that should be used for signal handling by the
+ * current process. It will either point to a process local latch if the
+ * current process does not have a PGPROC entry in that moment, or to
+ * PGPROC->procLatch if it has. Thus it can always be used in signal handlers,
+ * without checking for its existence.
+ */
+struct Latch *MyLatch;
+
/*
* DataDir is the absolute path to the top level of the PGDATA directory tree.
* Except during early startup, this is also the server's working directory;
diff --git a/src/backend/utils/init/miscinit.c b/src/backend/utils/init/miscinit.c
index 414b05e3b8c..4646e0938e9 100644
--- a/src/backend/utils/init/miscinit.c
+++ b/src/backend/utils/init/miscinit.c
@@ -39,6 +39,7 @@
#include "postmaster/postmaster.h"
#include "storage/fd.h"
#include "storage/ipc.h"
+#include "storage/latch.h"
#include "storage/pg_shmem.h"
#include "storage/proc.h"
#include "storage/procarray.h"
@@ -55,6 +56,7 @@ ProcessingMode Mode = InitProcessing;
/* List of lock files to be removed at proc exit */
static List *lock_files = NIL;
+static Latch LocalLatchData;
/* ----------------------------------------------------------------
* ignoring system indexes support stuff
@@ -189,6 +191,11 @@ InitPostmasterChild(void)
/* We don't want the postmaster's proc_exit() handlers */
on_exit_reset();
+ /* Initialize process-local latch support */
+ InitializeLatchSupport();
+ MyLatch = &LocalLatchData;
+ InitLatch(MyLatch);
+
/*
* If possible, make this process a group leader, so that the postmaster
* can signal any child processes too. Not all processes will have
@@ -215,6 +222,11 @@ InitStandaloneProcess(const char *argv0)
MyStartTime = time(NULL); /* set our start time in case we call elog */
+ /* Initialize process-local latch support */
+ InitializeLatchSupport();
+ MyLatch = &LocalLatchData;
+ InitLatch(MyLatch);
+
/* Compute paths, no postmaster to inherit from */
if (my_exec_path[0] == '\0')
{
@@ -227,6 +239,31 @@ InitStandaloneProcess(const char *argv0)
get_pkglib_path(my_exec_path, pkglib_path);
}
+void
+SwitchToSharedLatch(void)
+{
+ Assert(MyLatch == &LocalLatchData);
+ Assert(MyProc != NULL);
+
+ MyLatch = &MyProc->procLatch;
+ /*
+ * Set the shared latch as the local one might have been set. This
+ * shouldn't normally be necessary as code is supposed to check the
+ * condition before waiting for the latch, but a bit care can't hurt.
+ */
+ SetLatch(MyLatch);
+}
+
+void
+SwitchBackToLocalLatch(void)
+{
+ Assert(MyLatch != &LocalLatchData);
+ Assert(MyProc != NULL && MyLatch == &MyProc->procLatch);
+
+ MyLatch = &LocalLatchData;
+ SetLatch(MyLatch);
+}
+
/*
* GetUserId - get the current effective user ID.
*
diff --git a/src/backend/utils/misc/timeout.c b/src/backend/utils/misc/timeout.c
index 1dec4928af0..ce4bc13ec3b 100644
--- a/src/backend/utils/misc/timeout.c
+++ b/src/backend/utils/misc/timeout.c
@@ -284,11 +284,9 @@ handle_sig_alarm(SIGNAL_ARGS)
/*
* SIGALRM is always cause for waking anything waiting on the process
- * latch. Cope with MyProc not being there, as the startup process also
- * uses this signal handler.
+ * latch.
*/
- if (MyProc)
- SetLatch(&MyProc->procLatch);
+ SetLatch(MyLatch);
/*
* Fire any pending timeouts, but only if we're enabled to do so.
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index b94a94499b7..6e33a172122 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -148,6 +148,7 @@ extern int max_worker_processes;
extern PGDLLIMPORT int MyProcPid;
extern PGDLLIMPORT pg_time_t MyStartTime;
extern PGDLLIMPORT struct Port *MyProcPort;
+extern PGDLLIMPORT struct Latch *MyLatch;
extern long MyCancelKey;
extern int MyPMChildSlot;
@@ -302,6 +303,9 @@ extern void SetCurrentRoleId(Oid roleid, bool is_superuser);
extern void SetDataDir(const char *dir);
extern void ChangeToDataDir(void);
+extern void SwitchToSharedLatch(void);
+extern void SwitchBackToLocalLatch(void);
+
/* in utils/misc/superuser.c */
extern bool superuser(void); /* current user is superuser */
extern bool superuser_arg(Oid roleid); /* given user is superuser */
diff --git a/src/include/storage/latch.h b/src/include/storage/latch.h
index f1577b00955..28fc684d240 100644
--- a/src/include/storage/latch.h
+++ b/src/include/storage/latch.h
@@ -85,7 +85,7 @@
* the public functions. It is defined here to allow embedding Latches as
* part of bigger structs.
*/
-typedef struct
+typedef struct Latch
{
sig_atomic_t is_set;
bool is_shared;
diff --git a/src/test/modules/test_shm_mq/setup.c b/src/test/modules/test_shm_mq/setup.c
index b049cff2d05..195099095de 100644
--- a/src/test/modules/test_shm_mq/setup.c
+++ b/src/test/modules/test_shm_mq/setup.c
@@ -285,13 +285,13 @@ wait_for_workers_to_become_ready(worker_state *wstate,
}
/* Wait to be signalled. */
- WaitLatch(&MyProc->procLatch, WL_LATCH_SET, 0);
+ WaitLatch(MyLatch, WL_LATCH_SET, 0);
/* An interrupt may have occurred while we were waiting. */
CHECK_FOR_INTERRUPTS();
/* Reset the latch so we don't spin. */
- ResetLatch(&MyProc->procLatch);
+ ResetLatch(MyLatch);
}
}
PG_CATCH();
diff --git a/src/test/modules/test_shm_mq/test.c b/src/test/modules/test_shm_mq/test.c
index 6428fcf51c4..732376daff2 100644
--- a/src/test/modules/test_shm_mq/test.c
+++ b/src/test/modules/test_shm_mq/test.c
@@ -230,9 +230,9 @@ test_shm_mq_pipelined(PG_FUNCTION_ARGS)
* have read or written data and therefore there may now be work
* for us to do.
*/
- WaitLatch(&MyProc->procLatch, WL_LATCH_SET, 0);
+ WaitLatch(MyLatch, WL_LATCH_SET, 0);
CHECK_FOR_INTERRUPTS();
- ResetLatch(&MyProc->procLatch);
+ ResetLatch(MyLatch);
}
}
diff --git a/src/test/modules/test_shm_mq/worker.c b/src/test/modules/test_shm_mq/worker.c
index dec058b55ea..a9d9e0e2552 100644
--- a/src/test/modules/test_shm_mq/worker.c
+++ b/src/test/modules/test_shm_mq/worker.c
@@ -211,8 +211,7 @@ handle_sigterm(SIGNAL_ARGS)
{
int save_errno = errno;
- if (MyProc)
- SetLatch(&MyProc->procLatch);
+ SetLatch(MyLatch);
if (!proc_exit_inprogress)
{
diff --git a/src/test/modules/worker_spi/worker_spi.c b/src/test/modules/worker_spi/worker_spi.c
index ac0f59c9886..94d3857364f 100644
--- a/src/test/modules/worker_spi/worker_spi.c
+++ b/src/test/modules/worker_spi/worker_spi.c
@@ -74,8 +74,7 @@ worker_spi_sigterm(SIGNAL_ARGS)
int save_errno = errno;
got_sigterm = true;
- if (MyProc)
- SetLatch(&MyProc->procLatch);
+ SetLatch(MyLatch);
errno = save_errno;
}
@@ -91,8 +90,7 @@ worker_spi_sighup(SIGNAL_ARGS)
int save_errno = errno;
got_sighup = true;
- if (MyProc)
- SetLatch(&MyProc->procLatch);
+ SetLatch(MyLatch);
errno = save_errno;
}
@@ -227,10 +225,10 @@ worker_spi_main(Datum main_arg)
* necessary, but is awakened if postmaster dies. That way the
* background process goes away immediately in an emergency.
*/
- rc = WaitLatch(&MyProc->procLatch,
+ rc = WaitLatch(MyLatch,
WL_LATCH_SET | WL_TIMEOUT | WL_POSTMASTER_DEATH,
worker_spi_naptime * 1000L);
- ResetLatch(&MyProc->procLatch);
+ ResetLatch(MyLatch);
/* emergency bailout if postmaster has died */
if (rc & WL_POSTMASTER_DEATH)
--
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