Partially deduplicate interrupt handling for background processes.

Where possible, share signal handler code and main loop interrupt
checking. This saves quite a bit of code and should simplify
maintenance, too.

This commit intends not to change the way anything works, even
though that might allow more code to be unified. It does unify
a bunch of individual variables into a ShutdownRequestPending
flag that has is now used by a bunch of different process types,
though.

Patch by me, reviewed by Andres Freund and Daniel Gustafsson.

Discussion: http://postgr.es/m/CA+TgmoZwDk=BguVDVa+qdA6SBKef=PKbaKDQALTC_9qoz1mJqg@mail.gmail.com

Author: robertmhaas

src/backend/postmaster/Makefile

@@ -18,6 +18,7 @@ OBJS = \
 	bgwriter.o \
 	checkpointer.o \
 	fork_process.o \
+	interrupt.o \
 	pgarch.o \
 	pgstat.o \
 	postmaster.o \

src/backend/postmaster/autovacuum.c

@@ -84,6 +84,7 @@
 #include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "postmaster/fork_process.h"
+#include "postmaster/interrupt.h"
 #include "postmaster/postmaster.h"
 #include "storage/bufmgr.h"
 #include "storage/ipc.h"
@@ -139,7 +140,6 @@ static bool am_autovacuum_worker = false;
 
 /* Flags set by signal handlers */
 static volatile sig_atomic_t got_SIGUSR2 = false;
-static volatile sig_atomic_t got_SIGTERM = false;
 
 /* Comparison points for determining whether freeze_max_age is exceeded */
 static TransactionId recentXid;
@@ -344,7 +344,6 @@ static void autovac_report_activity(autovac_table *tab);
 static void autovac_report_workitem(AutoVacuumWorkItem *workitem,
 									const char *nspname, const char *relname);
 static void avl_sigusr2_handler(SIGNAL_ARGS);
-static void avl_sigterm_handler(SIGNAL_ARGS);
 static void autovac_refresh_stats(void);
 
 
@@ -450,9 +449,9 @@ AutoVacLauncherMain(int argc, char *argv[])
 	 * backend, so we use the same signal handling.  See equivalent code in
 	 * tcop/postgres.c.
 	 */
-	pqsignal(SIGHUP, PostgresSigHupHandler);
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
 	pqsignal(SIGINT, StatementCancelHandler);
-	pqsignal(SIGTERM, avl_sigterm_handler);
+	pqsignal(SIGTERM, SignalHandlerForShutdownRequest);
 
 	pqsignal(SIGQUIT, quickdie);
 	InitializeTimeouts();		/* establishes SIGALRM handler */
@@ -553,7 +552,7 @@ AutoVacLauncherMain(int argc, char *argv[])
 		RESUME_INTERRUPTS();
 
 		/* if in shutdown mode, no need for anything further; just go away */
-		if (got_SIGTERM)
+		if (ShutdownRequestPending)
 			AutoVacLauncherShutdown();
 
 		/*
@@ -605,7 +604,7 @@ AutoVacLauncherMain(int argc, char *argv[])
 	 */
 	if (!AutoVacuumingActive())
 	{
-		if (!got_SIGTERM)
+		if (!ShutdownRequestPending)
 			do_start_worker();
 		proc_exit(0);			/* done */
 	}
@@ -622,7 +621,7 @@ AutoVacLauncherMain(int argc, char *argv[])
 	rebuild_database_list(InvalidOid);
 
 	/* loop until shutdown request */
-	while (!got_SIGTERM)
+	while (!ShutdownRequestPending)
 	{
 		struct timeval nap;
 		TimestampTz current_time = 0;
@@ -800,7 +799,7 @@ static void
 HandleAutoVacLauncherInterrupts(void)
 {
 	/* the normal shutdown case */
-	if (got_SIGTERM)
+	if (ShutdownRequestPending)
 		AutoVacLauncherShutdown();
 
 	if (ConfigReloadPending)
@@ -1415,18 +1414,6 @@ avl_sigusr2_handler(SIGNAL_ARGS)
 	errno = save_errno;
 }
 
-/* SIGTERM: time to die */
-static void
-avl_sigterm_handler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	got_SIGTERM = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 
 /********************************************************************
  *					  AUTOVACUUM WORKER CODE
@@ -1525,7 +1512,7 @@ AutoVacWorkerMain(int argc, char *argv[])
 	 * backend, so we use the same signal handling.  See equivalent code in
 	 * tcop/postgres.c.
 	 */
-	pqsignal(SIGHUP, PostgresSigHupHandler);
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
 
 	/*
 	 * SIGINT is used to signal canceling the current table's vacuum; SIGTERM

src/backend/postmaster/bgworker.c

@@ -12,14 +12,13 @@
 
 #include "postgres.h"
 
-#include <unistd.h>
-
 #include "access/parallel.h"
 #include "libpq/pqsignal.h"
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "port/atomics.h"
 #include "postmaster/bgworker_internals.h"
+#include "postmaster/interrupt.h"
 #include "postmaster/postmaster.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalworker.h"
@@ -641,26 +640,6 @@ SanityCheckBackgroundWorker(BackgroundWorker *worker, int elevel)
 	return true;
 }
 
-static void
-bgworker_quickdie(SIGNAL_ARGS)
-{
-	/*
-	 * We DO NOT want to run proc_exit() or atexit() callbacks -- we're here
-	 * because shared memory may be corrupted, so we don't want to try to
-	 * clean up our transaction.  Just nail the windows shut and get out of
-	 * town.  The callbacks wouldn't be safe to run from a signal handler,
-	 * anyway.
-	 *
-	 * Note we do _exit(2) not _exit(0).  This is to force the postmaster into
-	 * a system reset cycle if someone sends a manual SIGQUIT to a random
-	 * backend.  This is necessary precisely because we don't clean up our
-	 * shared memory state.  (The "dead man switch" mechanism in pmsignal.c
-	 * should ensure the postmaster sees this as a crash, too, but no harm in
-	 * being doubly sure.)
-	 */
-	_exit(2);
-}
-
 /*
  * Standard SIGTERM handler for background workers
  */
@@ -754,7 +733,7 @@ StartBackgroundWorker(void)
 	pqsignal(SIGTERM, bgworker_die);
 	pqsignal(SIGHUP, SIG_IGN);
 
-	pqsignal(SIGQUIT, bgworker_quickdie);
+	pqsignal(SIGQUIT, SignalHandlerForCrashExit);
 	InitializeTimeouts();		/* establishes SIGALRM handler */
 
 	pqsignal(SIGPIPE, SIG_IGN);

src/backend/postmaster/bgwriter.c

@@ -34,16 +34,13 @@
  */
 #include "postgres.h"
 
-#include <signal.h>
-#include <sys/time.h>
-#include <unistd.h>
-
 #include "access/xlog.h"
 #include "access/xlog_internal.h"
 #include "libpq/pqsignal.h"
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "postmaster/bgwriter.h"
+#include "postmaster/interrupt.h"
 #include "storage/buf_internals.h"
 #include "storage/bufmgr.h"
 #include "storage/condition_variable.h"
@@ -86,18 +83,6 @@ int			BgWriterDelay = 200;
 static TimestampTz last_snapshot_ts;
 static XLogRecPtr last_snapshot_lsn = InvalidXLogRecPtr;
 
-/*
- * Flags set by interrupt handlers for later service in the main loop.
- */
-static volatile sig_atomic_t shutdown_requested = false;
-
-static void HandleBackgroundWriterInterrupts(void);
-
-/* Signal handlers */
-
-static void bg_quickdie(SIGNAL_ARGS);
-static void ReqShutdownHandler(SIGNAL_ARGS);
-
 
 /*
  * Main entry point for bgwriter process
@@ -116,10 +101,10 @@ BackgroundWriterMain(void)
 	/*
 	 * Properly accept or ignore signals that might be sent to us.
 	 */
-	pqsignal(SIGHUP, PostgresSigHupHandler);	/* set flag to read config file */
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
 	pqsignal(SIGINT, SIG_IGN);
-	pqsignal(SIGTERM, ReqShutdownHandler);	/* shutdown */
-	pqsignal(SIGQUIT, bg_quickdie); /* hard crash time */
+	pqsignal(SIGTERM, SignalHandlerForShutdownRequest);
+	pqsignal(SIGQUIT, SignalHandlerForCrashExit);
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
@@ -241,7 +226,7 @@ BackgroundWriterMain(void)
 		/* Clear any already-pending wakeups */
 		ResetLatch(MyLatch);
 
-		HandleBackgroundWriterInterrupts();
+		HandleMainLoopInterrupts();
 
 		/*
 		 * Do one cycle of dirty-buffer writing.
@@ -354,71 +339,3 @@ BackgroundWriterMain(void)
 		prev_hibernate = can_hibernate;
 	}
 }
-
-/*
- * Process any new interrupts.
- */
-static void
-HandleBackgroundWriterInterrupts(void)
-{
-	if (ConfigReloadPending)
-	{
-		ConfigReloadPending = false;
-		ProcessConfigFile(PGC_SIGHUP);
-	}
-
-	if (shutdown_requested)
-	{
-		/*
-		 * From here on, elog(ERROR) should end with exit(1), not send
-		 * control back to the sigsetjmp block above
-		 */
-		ExitOnAnyError = true;
-		/* Normal exit from the bgwriter is here */
-		proc_exit(0);		/* done */
-	}
-}
-
-
-/* --------------------------------
- *		signal handler routines
- * --------------------------------
- */
-
-/*
- * bg_quickdie() occurs when signalled SIGQUIT by the postmaster.
- *
- * Some backend has bought the farm,
- * so we need to stop what we're doing and exit.
- */
-static void
-bg_quickdie(SIGNAL_ARGS)
-{
-	/*
-	 * We DO NOT want to run proc_exit() or atexit() callbacks -- we're here
-	 * because shared memory may be corrupted, so we don't want to try to
-	 * clean up our transaction.  Just nail the windows shut and get out of
-	 * town.  The callbacks wouldn't be safe to run from a signal handler,
-	 * anyway.
-	 *
-	 * Note we do _exit(2) not _exit(0).  This is to force the postmaster into
-	 * a system reset cycle if someone sends a manual SIGQUIT to a random
-	 * backend.  This is necessary precisely because we don't clean up our
-	 * shared memory state.  (The "dead man switch" mechanism in pmsignal.c
-	 * should ensure the postmaster sees this as a crash, too, but no harm in
-	 * being doubly sure.)
-	 */
-	_exit(2);
-}
-
-/* SIGTERM: set flag to shutdown and exit */
-static void
-ReqShutdownHandler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	shutdown_requested = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}