global / super barriers (for checksums)

diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index a84042a4ea..58b360d225 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -3765,6 +3765,9 @@ pgstat_get_wait_ipc(WaitEventIPC w)
 		case WAIT_EVENT_EXECUTE_GATHER:
 			event_name = "ExecuteGather";
 			break;
+		case WAIT_EVENT_GLOBAL_BARRIER:
+			event_name = "GlobalBarrier";
+			break;
 		case WAIT_EVENT_HASH_BATCH_ALLOCATING:
 			event_name = "Hash/Batch/Allocating";
 			break;
diff --git a/src/backend/storage/ipc/procsignal.c b/src/backend/storage/ipc/procsignal.c
index 4e3e4a4893..9aed52df4a 100644
--- a/src/backend/storage/ipc/procsignal.c
+++ b/src/backend/storage/ipc/procsignal.c
@@ -21,6 +21,7 @@
 #include "access/twophase.h"
 #include "commands/async.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "replication/walsender.h"
 #include "storage/latch.h"
 #include "storage/ipc.h"
@@ -368,6 +369,7 @@ EmitGlobalBarrier(GlobalBarrierKind kind)
 void
 WaitForGlobalBarrier(uint64 generation)
 {
+	pgstat_report_wait_start(WAIT_EVENT_GLOBAL_BARRIER);
 	for (int i = 0; i < (MaxBackends + max_prepared_xacts); i++)
 	{
 		PGPROC *proc = &ProcGlobal->allProcs[i];
@@ -389,6 +391,7 @@ WaitForGlobalBarrier(uint64 generation)
 			oldval = pg_atomic_read_u64(&proc->barrierGen);
 		}
 	}
+	pgstat_report_wait_end();
 }
 
 /*
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 2b656a8168..0d35b19420 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -827,6 +827,7 @@ typedef enum
 	WAIT_EVENT_CHECKPOINT_DONE,
 	WAIT_EVENT_CHECKPOINT_START,
 	WAIT_EVENT_EXECUTE_GATHER,
+	WAIT_EVENT_GLOBAL_BARRIER,
 	WAIT_EVENT_HASH_BATCH_ALLOCATING,
 	WAIT_EVENT_HASH_BATCH_ELECTING,
 	WAIT_EVENT_HASH_BATCH_LOADING,

diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index c1dd8168ca..d6b8738d28 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -140,7 +140,6 @@ static bool am_autovacuum_worker = false;
 /* Flags set by signal handlers */
 static volatile sig_atomic_t got_SIGHUP = false;
 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 +343,6 @@ static void autovac_report_workitem(AutoVacuumWorkItem *workitem,
 									const char *nspname, const char *relname);
 static void av_sighup_handler(SIGNAL_ARGS);
 static void avl_sigusr2_handler(SIGNAL_ARGS);
-static void avl_sigterm_handler(SIGNAL_ARGS);
 static void autovac_refresh_stats(void);
 
 
@@ -452,7 +450,7 @@ AutoVacLauncherMain(int argc, char *argv[])
 	 */
 	pqsignal(SIGHUP, av_sighup_handler);
 	pqsignal(SIGINT, StatementCancelHandler);
-	pqsignal(SIGTERM, avl_sigterm_handler);
+	pqsignal(SIGTERM, die);
 
 	pqsignal(SIGQUIT, quickdie);
 	InitializeTimeouts();		/* establishes SIGALRM handler */
@@ -552,9 +550,8 @@ AutoVacLauncherMain(int argc, char *argv[])
 		/* Now we can allow interrupts again */
 		RESUME_INTERRUPTS();
 
-		/* if in shutdown mode, no need for anything further; just go away */
-		if (got_SIGTERM)
-			goto shutdown;
+		/* And check for them, too */
+		CHECK_FOR_INTERRUPTS();
 
 		/*
 		 * Sleep at least 1 second after any error.  We don't want to be
@@ -605,8 +602,8 @@ AutoVacLauncherMain(int argc, char *argv[])
 	 */
 	if (!AutoVacuumingActive())
 	{
-		if (!got_SIGTERM)
-			do_start_worker();
+		CHECK_FOR_INTERRUPTS();
+		do_start_worker();
 		proc_exit(0);			/* done */
 	}
 
@@ -622,12 +619,14 @@ AutoVacLauncherMain(int argc, char *argv[])
 	rebuild_database_list(InvalidOid);
 
 	/* loop until shutdown request */
-	while (!got_SIGTERM)
+	while (1)
 	{
 		struct timeval nap;
 		TimestampTz current_time = 0;
 		bool		can_launch;
 
+		CHECK_FOR_INTERRUPTS();
+
 		/*
 		 * This loop is a bit different from the normal use of WaitLatch,
 		 * because we'd like to sleep before the first launch of a child
@@ -652,10 +651,6 @@ AutoVacLauncherMain(int argc, char *argv[])
 		/* Process sinval catchup interrupts that happened while sleeping */
 		ProcessCatchupInterrupt();
 
-		/* the normal shutdown case */
-		if (got_SIGTERM)
-			break;
-
 		if (got_SIGHUP)
 		{
 			got_SIGHUP = false;
@@ -814,7 +809,6 @@ AutoVacLauncherMain(int argc, char *argv[])
 	}
 
 	/* Normal exit from the autovac launcher is here */
-shutdown:
 	ereport(DEBUG1,
 			(errmsg("autovacuum launcher shutting down")));
 	AutoVacuumShmem->av_launcherpid = 0;
@@ -1411,18 +1405,6 @@ 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

From 19feb5a34b9d79d4052b4ad5b499e3d19bc328b3 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Mon, 2 Dec 2019 11:53:25 -0500
Subject: [PATCH v2 5/5] Not for commit: test code.

---
 src/backend/storage/ipc/signalfuncs.c | 11 +++++++++++
 src/include/catalog/pg_proc.dat       |  5 +++++
 2 files changed, 16 insertions(+)

diff --git a/src/backend/storage/ipc/signalfuncs.c b/src/backend/storage/ipc/signalfuncs.c
index ade8d713aa..f6deebcb5a 100644
--- a/src/backend/storage/ipc/signalfuncs.c
+++ b/src/backend/storage/ipc/signalfuncs.c
@@ -215,3 +215,14 @@ pg_rotate_logfile_v2(PG_FUNCTION_ARGS)
 	SendPostmasterSignal(PMSIGNAL_ROTATE_LOGFILE);
 	PG_RETURN_BOOL(true);
 }
+
+Datum
+sample_barrier(PG_FUNCTION_ARGS)
+{
+	uint64	bgen;
+
+	bgen = EmitProcSignalBarrier(PROCSIGNAL_BARRIER_SAMPLE);
+	elog(NOTICE, "emitted barrier");
+	WaitForProcSignalBarrier(bgen);
+	PG_RETURN_VOID();
+}
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index ac8f64b219..380bdfea45 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -10729,4 +10729,9 @@
   proname => 'pg_partition_root', prorettype => 'regclass',
   proargtypes => 'regclass', prosrc => 'pg_partition_root' },
 
+# function to get the top-most partition root parent
+{ oid => '9758', descr => 'send sample barrier',
+  proname => 'sample_barrier', prorettype => 'void',
+  proargtypes => '', prosrc => 'sample_barrier' },
+
 ]
-- 
2.17.2 (Apple Git-113)

From 033e790f544d107a914aab432bca7b9c82ac8f41 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Tue, 26 Nov 2019 13:14:13 -0500
Subject: [PATCH v2 1/5] Move interrupting-handling code into subroutines.

Some auxiliary processes, as well as the autovacuum launcher,
have interrupt handling code directly in their main loops.
Try to abstract things a little better by moving it into
separate functions.

This doesn't make any functional difference, and leaves
in place relatively large differences among processes in how
interrupts are handled, but hopefully it at least makes it
easier to see the commonalities and differences across
process types.
---
 src/backend/postmaster/autovacuum.c   | 72 +++++++++++++++++----------
 src/backend/postmaster/bgwriter.c     | 42 ++++++++++------
 src/backend/postmaster/checkpointer.c | 71 ++++++++++++++------------
 src/backend/postmaster/walwriter.c    | 34 ++++++++-----
 4 files changed, 133 insertions(+), 86 deletions(-)

diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index c1dd8168ca..5766203aaf 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -311,6 +311,8 @@ NON_EXEC_STATIC void AutoVacWorkerMain(int argc, char *argv[]) pg_attribute_nore
 NON_EXEC_STATIC void AutoVacLauncherMain(int argc, char *argv[]) pg_attribute_noreturn();
 
 static Oid	do_start_worker(void);
+static void HandleAutoVacLauncherInterrupts(void);
+static void AutoVacLauncherShutdown() pg_attribute_noreturn();
 static void launcher_determine_sleep(bool canlaunch, bool recursing,
 									 struct timeval *nap);
 static void launch_worker(TimestampTz now);
@@ -554,7 +556,7 @@ AutoVacLauncherMain(int argc, char *argv[])
 
 		/* if in shutdown mode, no need for anything further; just go away */
 		if (got_SIGTERM)
-			goto shutdown;
+			AutoVacLauncherShutdown();
 
 		/*
 		 * Sleep at least 1 second after any error.  We don't want to be
@@ -649,30 +651,7 @@ AutoVacLauncherMain(int argc, char *argv[])
 
 		ResetLatch(MyLatch);
 
-		/* Process sinval catchup interrupts that happened while sleeping */
-		ProcessCatchupInterrupt();
-
-		/* the normal shutdown case */
-		if (got_SIGTERM)
-			break;
-
-		if (got_SIGHUP)
-		{
-			got_SIGHUP = false;
-			ProcessConfigFile(PGC_SIGHUP);
-
-			/* shutdown requested in config file? */
-			if (!AutoVacuumingActive())
-				break;
-
-			/* rebalance in case the default cost parameters changed */
-			LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
-			autovac_balance_cost();
-			LWLockRelease(AutovacuumLock);
-
-			/* rebuild the list in case the naptime changed */
-			rebuild_database_list(InvalidOid);
-		}
+		HandleAutoVacLauncherInterrupts();
 
 		/*
 		 * a worker finished, or postmaster signalled failure to start a
@@ -813,8 +792,47 @@ AutoVacLauncherMain(int argc, char *argv[])
 		}
 	}
 
-	/* Normal exit from the autovac launcher is here */
-shutdown:
+	AutoVacLauncherShutdown();
+}
+
+/*
+ * Process any new interrupts.
+ */
+static void
+HandleAutoVacLauncherInterrupts(void)
+{
+	/* the normal shutdown case */
+	if (got_SIGTERM)
+		AutoVacLauncherShutdown();
+
+	if (got_SIGHUP)
+	{
+		got_SIGHUP = false;
+		ProcessConfigFile(PGC_SIGHUP);
+
+		/* shutdown requested in config file? */
+		if (!AutoVacuumingActive())
+			AutoVacLauncherShutdown();
+
+		/* rebalance in case the default cost parameters changed */
+		LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
+		autovac_balance_cost();
+		LWLockRelease(AutovacuumLock);
+
+		/* rebuild the list in case the naptime changed */
+		rebuild_database_list(InvalidOid);
+	}
+
+	/* Process sinval catchup interrupts that happened while sleeping */
+	ProcessCatchupInterrupt();
+}
+
+/*
+ * Perform a normal exit from the autovac launcher.
+ */
+static void
+AutoVacLauncherShutdown()
+{
 	ereport(DEBUG1,
 			(errmsg("autovacuum launcher shutting down")));
 	AutoVacuumShmem->av_launcherpid = 0;
diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c
index 2fa631ea7a..c7500f1d71 100644
--- a/src/backend/postmaster/bgwriter.c
+++ b/src/backend/postmaster/bgwriter.c
@@ -92,6 +92,8 @@ static XLogRecPtr last_snapshot_lsn = InvalidXLogRecPtr;
 static volatile sig_atomic_t got_SIGHUP = false;
 static volatile sig_atomic_t shutdown_requested = false;
 
+static void HandleBackgroundWriterInterrupts(void);
+
 /* Signal handlers */
 
 static void bg_quickdie(SIGNAL_ARGS);
@@ -241,21 +243,7 @@ BackgroundWriterMain(void)
 		/* Clear any already-pending wakeups */
 		ResetLatch(MyLatch);
 
-		if (got_SIGHUP)
-		{
-			got_SIGHUP = 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 */
-		}
+		HandleBackgroundWriterInterrupts();
 
 		/*
 		 * Do one cycle of dirty-buffer writing.
@@ -369,6 +357,30 @@ BackgroundWriterMain(void)
 	}
 }
 
+/*
+ * Process any new interrupts.
+ */
+static void
+HandleBackgroundWriterInterrupts(void)
+{
+	if (got_SIGHUP)
+	{
+		got_SIGHUP = 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
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index d93c941871..d087ee9c74 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -169,6 +169,7 @@ static pg_time_t last_xlog_switch_time;
 
 /* Prototypes for private functions */
 
+static void HandleCheckpointerInterrupts();
 static void CheckArchiveTimeout(void);
 static bool IsCheckpointOnSchedule(double progress);
 static bool ImmediateCheckpointRequested(void);
@@ -350,37 +351,7 @@ CheckpointerMain(void)
 		 * Process any requests or signals received recently.
 		 */
 		AbsorbSyncRequests();
-
-		if (got_SIGHUP)
-		{
-			got_SIGHUP = false;
-			ProcessConfigFile(PGC_SIGHUP);
-
-			/*
-			 * Checkpointer is the last process to shut down, so we ask it to
-			 * hold the keys for a range of other tasks required most of which
-			 * have nothing to do with checkpointing at all.
-			 *
-			 * For various reasons, some config values can change dynamically
-			 * so the primary copy of them is held in shared memory to make
-			 * sure all backends see the same value.  We make Checkpointer
-			 * responsible for updating the shared memory copy if the
-			 * parameter setting changes because of SIGHUP.
-			 */
-			UpdateSharedMemoryConfig();
-		}
-		if (shutdown_requested)
-		{
-			/*
-			 * From here on, elog(ERROR) should end with exit(1), not send
-			 * control back to the sigsetjmp block above
-			 */
-			ExitOnAnyError = true;
-			/* Close down the database */
-			ShutdownXLOG(0, 0);
-			/* Normal exit from the checkpointer is here */
-			proc_exit(0);		/* done */
-		}
+		HandleCheckpointerInterrupts();
 
 		/*
 		 * Detect a pending checkpoint request by checking whether the flags
@@ -558,6 +529,44 @@ CheckpointerMain(void)
 	}
 }
 
+/*
+ * Process any new interrupts.
+ */
+static void
+HandleCheckpointerInterrupts(void)
+{
+	if (got_SIGHUP)
+	{
+		got_SIGHUP = false;
+		ProcessConfigFile(PGC_SIGHUP);
+
+		/*
+		 * Checkpointer is the last process to shut down, so we ask it to
+		 * hold the keys for a range of other tasks required most of which
+		 * have nothing to do with checkpointing at all.
+		 *
+		 * For various reasons, some config values can change dynamically
+		 * so the primary copy of them is held in shared memory to make
+		 * sure all backends see the same value.  We make Checkpointer
+		 * responsible for updating the shared memory copy if the
+		 * parameter setting changes because of SIGHUP.
+		 */
+		UpdateSharedMemoryConfig();
+	}
+	if (shutdown_requested)
+	{
+		/*
+		 * From here on, elog(ERROR) should end with exit(1), not send
+		 * control back to the sigsetjmp block above
+		 */
+		ExitOnAnyError = true;
+		/* Close down the database */
+		ShutdownXLOG(0, 0);
+		/* Normal exit from the checkpointer is here */
+		proc_exit(0);		/* done */
+	}
+}
+
 /*
  * CheckArchiveTimeout -- check for archive_timeout and switch xlog files
  *
diff --git a/src/backend/postmaster/walwriter.c b/src/backend/postmaster/walwriter.c
index cce9713408..5a3573503c 100644
--- a/src/backend/postmaster/walwriter.c
+++ b/src/backend/postmaster/walwriter.c
@@ -83,6 +83,8 @@ int			WalWriterFlushAfter = 128;
 static volatile sig_atomic_t got_SIGHUP = false;
 static volatile sig_atomic_t shutdown_requested = false;
 
+static void HandleWalWriterInterrupts(void);
+
 /* Signal handlers */
 static void wal_quickdie(SIGNAL_ARGS);
 static void WalSigHupHandler(SIGNAL_ARGS);
@@ -242,19 +244,7 @@ WalWriterMain(void)
 		/* Clear any already-pending wakeups */
 		ResetLatch(MyLatch);
 
-		/*
-		 * Process any requests or signals received recently.
-		 */
-		if (got_SIGHUP)
-		{
-			got_SIGHUP = false;
-			ProcessConfigFile(PGC_SIGHUP);
-		}
-		if (shutdown_requested)
-		{
-			/* Normal exit from the walwriter is here */
-			proc_exit(0);		/* done */
-		}
+		HandleWalWriterInterrupts();
 
 		/*
 		 * Do what we're here for; then, if XLogBackgroundFlush() found useful
@@ -282,6 +272,24 @@ WalWriterMain(void)
 	}
 }
 
+/*
+ * Process any new interrupts.
+ */
+static void
+HandleWalWriterInterrupts(void)
+{
+	if (got_SIGHUP)
+	{
+		got_SIGHUP = false;
+		ProcessConfigFile(PGC_SIGHUP);
+	}
+	if (shutdown_requested)
+	{
+		/* Normal exit from the walwriter is here */
+		proc_exit(0);		/* done */
+	}
+}
+
 
 /* --------------------------------
  *		signal handler routines
-- 
2.17.2 (Apple Git-113)

From 8b6122932d9458015d3e468e4f30c2bffb7b9696 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Wed, 27 Nov 2019 09:01:16 -0500
Subject: [PATCH v2 2/5] Use PostgresSigHupHandler in more places.

There seems to be no reason for every background process to have
its own flag indicating that a config-file reload is needed.
Instead, let's just use ConfigFilePending for that purpose
everywhere.
---
 src/backend/postmaster/autovacuum.c        | 30 ++++++----------------
 src/backend/postmaster/bgwriter.c          | 20 +++------------
 src/backend/postmaster/checkpointer.c      | 24 ++++-------------
 src/backend/postmaster/pgarch.c            | 25 ++++--------------
 src/backend/postmaster/pgstat.c            | 28 +++++---------------
 src/backend/postmaster/walwriter.c         | 20 +++------------
 src/backend/replication/logical/launcher.c | 23 +++--------------
 src/backend/replication/logical/worker.c   | 23 +++--------------
 8 files changed, 37 insertions(+), 156 deletions(-)

diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 5766203aaf..b1c2b0a01c 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -138,7 +138,6 @@ static bool am_autovacuum_launcher = false;
 static bool am_autovacuum_worker = false;
 
 /* Flags set by signal handlers */
-static volatile sig_atomic_t got_SIGHUP = false;
 static volatile sig_atomic_t got_SIGUSR2 = false;
 static volatile sig_atomic_t got_SIGTERM = false;
 
@@ -344,7 +343,6 @@ static void perform_work_item(AutoVacuumWorkItem *workitem);
 static void autovac_report_activity(autovac_table *tab);
 static void autovac_report_workitem(AutoVacuumWorkItem *workitem,
 									const char *nspname, const char *relname);
-static void av_sighup_handler(SIGNAL_ARGS);
 static void avl_sigusr2_handler(SIGNAL_ARGS);
 static void avl_sigterm_handler(SIGNAL_ARGS);
 static void autovac_refresh_stats(void);
@@ -452,7 +450,7 @@ AutoVacLauncherMain(int argc, char *argv[])
 	 * backend, so we use the same signal handling.  See equivalent code in
 	 * tcop/postgres.c.
 	 */
-	pqsignal(SIGHUP, av_sighup_handler);
+	pqsignal(SIGHUP, PostgresSigHupHandler);
 	pqsignal(SIGINT, StatementCancelHandler);
 	pqsignal(SIGTERM, avl_sigterm_handler);
 
@@ -805,9 +803,9 @@ HandleAutoVacLauncherInterrupts(void)
 	if (got_SIGTERM)
 		AutoVacLauncherShutdown();
 
-	if (got_SIGHUP)
+	if (ConfigReloadPending)
 	{
-		got_SIGHUP = false;
+		ConfigReloadPending = false;
 		ProcessConfigFile(PGC_SIGHUP);
 
 		/* shutdown requested in config file? */
@@ -1405,18 +1403,6 @@ AutoVacWorkerFailed(void)
 	AutoVacuumShmem->av_signal[AutoVacForkFailed] = true;
 }
 
-/* SIGHUP: set flag to re-read config file at next convenient time */
-static void
-av_sighup_handler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	got_SIGHUP = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /* SIGUSR2: a worker is up and running, or just finished, or failed to fork */
 static void
 avl_sigusr2_handler(SIGNAL_ARGS)
@@ -1539,7 +1525,7 @@ AutoVacWorkerMain(int argc, char *argv[])
 	 * backend, so we use the same signal handling.  See equivalent code in
 	 * tcop/postgres.c.
 	 */
-	pqsignal(SIGHUP, av_sighup_handler);
+	pqsignal(SIGHUP, PostgresSigHupHandler);
 
 	/*
 	 * SIGINT is used to signal canceling the current table's vacuum; SIGTERM
@@ -2332,9 +2318,9 @@ do_autovacuum(void)
 		/*
 		 * Check for config changes before processing each collected table.
 		 */
-		if (got_SIGHUP)
+		if (ConfigReloadPending)
 		{
-			got_SIGHUP = false;
+			ConfigReloadPending = false;
 			ProcessConfigFile(PGC_SIGHUP);
 
 			/*
@@ -2580,9 +2566,9 @@ deleted:
 		 * Check for config changes before acquiring lock for further jobs.
 		 */
 		CHECK_FOR_INTERRUPTS();
-		if (got_SIGHUP)
+		if (ConfigReloadPending)
 		{
-			got_SIGHUP = false;
+			ConfigReloadPending = false;
 			ProcessConfigFile(PGC_SIGHUP);
 		}
 
diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c
index c7500f1d71..bca46de6d5 100644
--- a/src/backend/postmaster/bgwriter.c
+++ b/src/backend/postmaster/bgwriter.c
@@ -89,7 +89,6 @@ static XLogRecPtr last_snapshot_lsn = InvalidXLogRecPtr;
 /*
  * Flags set by interrupt handlers for later service in the main loop.
  */
-static volatile sig_atomic_t got_SIGHUP = false;
 static volatile sig_atomic_t shutdown_requested = false;
 
 static void HandleBackgroundWriterInterrupts(void);
@@ -97,7 +96,6 @@ static void HandleBackgroundWriterInterrupts(void);
 /* Signal handlers */
 
 static void bg_quickdie(SIGNAL_ARGS);
-static void BgSigHupHandler(SIGNAL_ARGS);
 static void ReqShutdownHandler(SIGNAL_ARGS);
 
 
@@ -118,7 +116,7 @@ BackgroundWriterMain(void)
 	/*
 	 * Properly accept or ignore signals that might be sent to us.
 	 */
-	pqsignal(SIGHUP, BgSigHupHandler);	/* set flag to read config file */
+	pqsignal(SIGHUP, PostgresSigHupHandler);	/* set flag to read config file */
 	pqsignal(SIGINT, SIG_IGN);
 	pqsignal(SIGTERM, ReqShutdownHandler);	/* shutdown */
 	pqsignal(SIGQUIT, bg_quickdie); /* hard crash time */
@@ -363,9 +361,9 @@ BackgroundWriterMain(void)
 static void
 HandleBackgroundWriterInterrupts(void)
 {
-	if (got_SIGHUP)
+	if (ConfigReloadPending)
 	{
-		got_SIGHUP = false;
+		ConfigReloadPending = false;
 		ProcessConfigFile(PGC_SIGHUP);
 	}
 
@@ -413,18 +411,6 @@ bg_quickdie(SIGNAL_ARGS)
 	_exit(2);
 }
 
-/* SIGHUP: set flag to re-read config file at next convenient time */
-static void
-BgSigHupHandler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	got_SIGHUP = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /* SIGTERM: set flag to shutdown and exit */
 static void
 ReqShutdownHandler(SIGNAL_ARGS)
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index d087ee9c74..9cf91b0d35 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -151,7 +151,6 @@ double		CheckPointCompletionTarget = 0.5;
 /*
  * Flags set by interrupt handlers for later service in the main loop.
  */
-static volatile sig_atomic_t got_SIGHUP = false;
 static volatile sig_atomic_t shutdown_requested = false;
 
 /*
@@ -179,7 +178,6 @@ static void UpdateSharedMemoryConfig(void);
 /* Signal handlers */
 
 static void chkpt_quickdie(SIGNAL_ARGS);
-static void ChkptSigHupHandler(SIGNAL_ARGS);
 static void ReqCheckpointHandler(SIGNAL_ARGS);
 static void ReqShutdownHandler(SIGNAL_ARGS);
 
@@ -206,7 +204,7 @@ CheckpointerMain(void)
 	 * want to wait for the backends to exit, whereupon the postmaster will
 	 * tell us it's okay to shut down (via SIGUSR2).
 	 */
-	pqsignal(SIGHUP, ChkptSigHupHandler);	/* set flag to read config file */
+	pqsignal(SIGHUP, PostgresSigHupHandler);	/* set flag to read config file */
 	pqsignal(SIGINT, ReqCheckpointHandler); /* request checkpoint */
 	pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */
 	pqsignal(SIGQUIT, chkpt_quickdie);	/* hard crash time */
@@ -535,9 +533,9 @@ CheckpointerMain(void)
 static void
 HandleCheckpointerInterrupts(void)
 {
-	if (got_SIGHUP)
+	if (ConfigReloadPending)
 	{
-		got_SIGHUP = false;
+		ConfigReloadPending = false;
 		ProcessConfigFile(PGC_SIGHUP);
 
 		/*
@@ -685,9 +683,9 @@ CheckpointWriteDelay(int flags, double progress)
 		!ImmediateCheckpointRequested() &&
 		IsCheckpointOnSchedule(progress))
 	{
-		if (got_SIGHUP)
+		if (ConfigReloadPending)
 		{
-			got_SIGHUP = false;
+			ConfigReloadPending = false;
 			ProcessConfigFile(PGC_SIGHUP);
 			/* update shmem copies of config variables */
 			UpdateSharedMemoryConfig();
@@ -835,18 +833,6 @@ chkpt_quickdie(SIGNAL_ARGS)
 	_exit(2);
 }
 
-/* SIGHUP: set flag to re-read config file at next convenient time */
-static void
-ChkptSigHupHandler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	got_SIGHUP = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /* SIGINT: set flag to run a normal checkpoint right away */
 static void
 ReqCheckpointHandler(SIGNAL_ARGS)
diff --git a/src/backend/postmaster/pgarch.c b/src/backend/postmaster/pgarch.c
index f84f882c4c..09a9c66b4b 100644
--- a/src/backend/postmaster/pgarch.c
+++ b/src/backend/postmaster/pgarch.c
@@ -83,7 +83,6 @@ static time_t last_sigterm_time = 0;
 /*
  * Flags set by interrupt handlers for later service in the main loop.
  */
-static volatile sig_atomic_t got_SIGHUP = false;
 static volatile sig_atomic_t got_SIGTERM = false;
 static volatile sig_atomic_t wakened = false;
 static volatile sig_atomic_t ready_to_stop = false;
@@ -98,7 +97,6 @@ static pid_t pgarch_forkexec(void);
 
 NON_EXEC_STATIC void PgArchiverMain(int argc, char *argv[]) pg_attribute_noreturn();
 static void pgarch_exit(SIGNAL_ARGS);
-static void ArchSigHupHandler(SIGNAL_ARGS);
 static void ArchSigTermHandler(SIGNAL_ARGS);
 static void pgarch_waken(SIGNAL_ARGS);
 static void pgarch_waken_stop(SIGNAL_ARGS);
@@ -229,7 +227,7 @@ PgArchiverMain(int argc, char *argv[])
 	 * Ignore all signals usually bound to some action in the postmaster,
 	 * except for SIGHUP, SIGTERM, SIGUSR1, SIGUSR2, and SIGQUIT.
 	 */
-	pqsignal(SIGHUP, ArchSigHupHandler);
+	pqsignal(SIGHUP, PostgresSigHupHandler);
 	pqsignal(SIGINT, SIG_IGN);
 	pqsignal(SIGTERM, ArchSigTermHandler);
 	pqsignal(SIGQUIT, pgarch_exit);
@@ -259,19 +257,6 @@ pgarch_exit(SIGNAL_ARGS)
 	exit(1);
 }
 
-/* SIGHUP signal handler for archiver process */
-static void
-ArchSigHupHandler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	/* set flag to re-read config file at next convenient time */
-	got_SIGHUP = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /* SIGTERM signal handler for archiver process */
 static void
 ArchSigTermHandler(SIGNAL_ARGS)
@@ -348,9 +333,9 @@ pgarch_MainLoop(void)
 		time_to_stop = ready_to_stop;
 
 		/* Check for config update */
-		if (got_SIGHUP)
+		if (ConfigReloadPending)
 		{
-			got_SIGHUP = false;
+			ConfigReloadPending = false;
 			ProcessConfigFile(PGC_SIGHUP);
 		}
 
@@ -457,9 +442,9 @@ pgarch_ArchiverCopyLoop(void)
 			 * setting for archive_command as soon as possible, even if there
 			 * is a backlog of files to be archived.
 			 */
-			if (got_SIGHUP)
+			if (ConfigReloadPending)
 			{
-				got_SIGHUP = false;
+				ConfigReloadPending = false;
 				ProcessConfigFile(PGC_SIGHUP);
 			}
 
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index fabcf31de8..96a9e09ced 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -264,7 +264,6 @@ static List *pending_write_requests = NIL;
 
 /* Signal handler flags */
 static volatile bool need_exit = false;
-static volatile bool got_SIGHUP = false;
 
 /*
  * Total time charged to functions so far in the current backend.
@@ -285,7 +284,6 @@ static pid_t pgstat_forkexec(void);
 NON_EXEC_STATIC void PgstatCollectorMain(int argc, char *argv[]) pg_attribute_noreturn();
 static void pgstat_exit(SIGNAL_ARGS);
 static void pgstat_beshutdown_hook(int code, Datum arg);
-static void pgstat_sighup_handler(SIGNAL_ARGS);
 
 static PgStat_StatDBEntry *pgstat_get_db_entry(Oid databaseid, bool create);
 static PgStat_StatTabEntry *pgstat_get_tab_entry(PgStat_StatDBEntry *dbentry,
@@ -4434,7 +4432,7 @@ PgstatCollectorMain(int argc, char *argv[])
 	 * except SIGHUP and SIGQUIT.  Note we don't need a SIGUSR1 handler to
 	 * support latch operations, because we only use a local latch.
 	 */
-	pqsignal(SIGHUP, pgstat_sighup_handler);
+	pqsignal(SIGHUP, PostgresSigHupHandler);
 	pqsignal(SIGINT, SIG_IGN);
 	pqsignal(SIGTERM, SIG_IGN);
 	pqsignal(SIGQUIT, pgstat_exit);
@@ -4466,10 +4464,10 @@ PgstatCollectorMain(int argc, char *argv[])
 	 * message.  (This effectively means that if backends are sending us stuff
 	 * like mad, we won't notice postmaster death until things slack off a
 	 * bit; which seems fine.)	To do that, we have an inner loop that
-	 * iterates as long as recv() succeeds.  We do recognize got_SIGHUP inside
-	 * the inner loop, which means that such interrupts will get serviced but
-	 * the latch won't get cleared until next time there is a break in the
-	 * action.
+	 * iterates as long as recv() succeeds.  We do check ConfigReloadPending
+	 * inside the inner loop, which means that such interrupts will get
+	 * serviced but the latch won't get cleared until next time there is a
+	 * break in the action.
 	 */
 	for (;;)
 	{
@@ -4491,9 +4489,9 @@ PgstatCollectorMain(int argc, char *argv[])
 			/*
 			 * Reload configuration if we got SIGHUP from the postmaster.
 			 */
-			if (got_SIGHUP)
+			if (ConfigReloadPending)
 			{
-				got_SIGHUP = false;
+				ConfigReloadPending = false;
 				ProcessConfigFile(PGC_SIGHUP);
 			}
 
@@ -4691,18 +4689,6 @@ pgstat_exit(SIGNAL_ARGS)
 	errno = save_errno;
 }
 
-/* SIGHUP handler for collector process */
-static void
-pgstat_sighup_handler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	got_SIGHUP = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /*
  * Subroutine to clear stats in a database entry
  *
diff --git a/src/backend/postmaster/walwriter.c b/src/backend/postmaster/walwriter.c
index 5a3573503c..599478530f 100644
--- a/src/backend/postmaster/walwriter.c
+++ b/src/backend/postmaster/walwriter.c
@@ -80,14 +80,12 @@ int			WalWriterFlushAfter = 128;
 /*
  * Flags set by interrupt handlers for later service in the main loop.
  */
-static volatile sig_atomic_t got_SIGHUP = false;
 static volatile sig_atomic_t shutdown_requested = false;
 
 static void HandleWalWriterInterrupts(void);
 
 /* Signal handlers */
 static void wal_quickdie(SIGNAL_ARGS);
-static void WalSigHupHandler(SIGNAL_ARGS);
 static void WalShutdownHandler(SIGNAL_ARGS);
 
 /*
@@ -110,7 +108,7 @@ WalWriterMain(void)
 	 * We have no particular use for SIGINT at the moment, but seems
 	 * reasonable to treat like SIGTERM.
 	 */
-	pqsignal(SIGHUP, WalSigHupHandler); /* set flag to read config file */
+	pqsignal(SIGHUP, PostgresSigHupHandler); /* set flag to read config file */
 	pqsignal(SIGINT, WalShutdownHandler);	/* request shutdown */
 	pqsignal(SIGTERM, WalShutdownHandler);	/* request shutdown */
 	pqsignal(SIGQUIT, wal_quickdie);	/* hard crash time */
@@ -278,9 +276,9 @@ WalWriterMain(void)
 static void
 HandleWalWriterInterrupts(void)
 {
-	if (got_SIGHUP)
+	if (ConfigReloadPending)
 	{
-		got_SIGHUP = false;
+		ConfigReloadPending = false;
 		ProcessConfigFile(PGC_SIGHUP);
 	}
 	if (shutdown_requested)
@@ -322,18 +320,6 @@ wal_quickdie(SIGNAL_ARGS)
 	_exit(2);
 }
 
-/* SIGHUP: set flag to re-read config file at next convenient time */
-static void
-WalSigHupHandler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	got_SIGHUP = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /* SIGTERM: set flag to exit normally */
 static void
 WalShutdownHandler(SIGNAL_ARGS)
diff --git a/src/backend/replication/logical/launcher.c b/src/backend/replication/logical/launcher.c
index 4643af95fe..edca70c58c 100644
--- a/src/backend/replication/logical/launcher.c
+++ b/src/backend/replication/logical/launcher.c
@@ -92,9 +92,6 @@ static void logicalrep_worker_onexit(int code, Datum arg);
 static void logicalrep_worker_detach(void);
 static void logicalrep_worker_cleanup(LogicalRepWorker *worker);
 
-/* Flags set by signal handlers */
-static volatile sig_atomic_t got_SIGHUP = false;
-
 static bool on_commit_launcher_wakeup = false;
 
 Datum		pg_stat_get_subscription(PG_FUNCTION_ARGS);
@@ -714,20 +711,6 @@ logicalrep_worker_onexit(int code, Datum arg)
 	ApplyLauncherWakeup();
 }
 
-/* SIGHUP: set flag to reload configuration at next convenient time */
-static void
-logicalrep_launcher_sighup(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	got_SIGHUP = true;
-
-	/* Waken anything waiting on the process latch */
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /*
  * Count the number of registered (not necessarily running) sync workers
  * for a subscription.
@@ -972,7 +955,7 @@ ApplyLauncherMain(Datum main_arg)
 	LogicalRepCtx->launcher_pid = MyProcPid;
 
 	/* Establish signal handlers. */
-	pqsignal(SIGHUP, logicalrep_launcher_sighup);
+	pqsignal(SIGTERM, PostgresSigHupHandler);
 	pqsignal(SIGTERM, die);
 	BackgroundWorkerUnblockSignals();
 
@@ -1061,9 +1044,9 @@ ApplyLauncherMain(Datum main_arg)
 			CHECK_FOR_INTERRUPTS();
 		}
 
-		if (got_SIGHUP)
+		if (ConfigReloadPending)
 		{
-			got_SIGHUP = false;
+			ConfigReloadPending = false;
 			ProcessConfigFile(PGC_SIGHUP);
 		}
 	}
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index ced0d191c2..3b12ad6400 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -111,9 +111,6 @@ static void store_flush_position(XLogRecPtr remote_lsn);
 
 static void maybe_reread_subscription(void);
 
-/* Flags set by signal handlers */
-static volatile sig_atomic_t got_SIGHUP = false;
-
 /*
  * Should this worker apply changes for given relation.
  *
@@ -1270,9 +1267,9 @@ LogicalRepApplyLoop(XLogRecPtr last_received)
 			CHECK_FOR_INTERRUPTS();
 		}
 
-		if (got_SIGHUP)
+		if (ConfigReloadPending)
 		{
-			got_SIGHUP = false;
+			ConfigReloadPending = false;
 			ProcessConfigFile(PGC_SIGHUP);
 		}
 
@@ -1563,20 +1560,6 @@ subscription_change_cb(Datum arg, int cacheid, uint32 hashvalue)
 	MySubscriptionValid = false;
 }
 
-/* SIGHUP: set flag to reload configuration at next convenient time */
-static void
-logicalrep_worker_sighup(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	got_SIGHUP = true;
-
-	/* Waken anything waiting on the process latch */
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /* Logical Replication Apply worker entry point */
 void
 ApplyWorkerMain(Datum main_arg)
@@ -1592,7 +1575,7 @@ ApplyWorkerMain(Datum main_arg)
 	logicalrep_worker_attach(worker_slot);
 
 	/* Setup signal handling */
-	pqsignal(SIGHUP, logicalrep_worker_sighup);
+	pqsignal(SIGHUP, PostgresSigHupHandler);
 	pqsignal(SIGTERM, die);
 	BackgroundWorkerUnblockSignals();
 
-- 
2.17.2 (Apple Git-113)

From dc57da67787fcbd736d98b97faacd2903121bccd Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Wed, 27 Nov 2019 11:19:37 -0500
Subject: [PATCH v2 3/5] 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.
---
 src/backend/postmaster/Makefile            |   1 +
 src/backend/postmaster/autovacuum.c        |  29 ++----
 src/backend/postmaster/bgworker.c          |  25 +----
 src/backend/postmaster/bgwriter.c          |  93 +-----------------
 src/backend/postmaster/checkpointer.c      |  60 ++----------
 src/backend/postmaster/interrupt.c         | 108 +++++++++++++++++++++
 src/backend/postmaster/pgarch.c            |  29 +-----
 src/backend/postmaster/pgstat.c            |  28 ++----
 src/backend/postmaster/startup.c           |  34 +------
 src/backend/postmaster/walwriter.c         |  84 ++--------------
 src/backend/replication/logical/launcher.c |   3 +-
 src/backend/replication/logical/worker.c   |   3 +-
 src/backend/replication/walreceiver.c      |  31 +-----
 src/backend/replication/walsender.c        |   4 +-
 src/backend/tcop/postgres.c                |  22 +----
 src/backend/utils/init/globals.c           |   1 -
 src/include/miscadmin.h                    |   3 -
 src/include/postmaster/interrupt.h         |  32 ++++++
 18 files changed, 191 insertions(+), 399 deletions(-)
 create mode 100644 src/backend/postmaster/interrupt.c
 create mode 100644 src/include/postmaster/interrupt.h

diff --git a/src/backend/postmaster/Makefile b/src/backend/postmaster/Makefile
index 03e3d3650a..bfdf6a833d 100644
--- a/src/backend/postmaster/Makefile
+++ b/src/backend/postmaster/Makefile
@@ -18,6 +18,7 @@ OBJS = \
 	bgwriter.o \
 	checkpointer.o \
 	fork_process.o \
+	interrupt.o \
 	pgarch.o \
 	pgstat.o \
 	postmaster.o \
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index b1c2b0a01c..1792008ebe 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/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
diff --git a/src/backend/postmaster/bgworker.c b/src/backend/postmaster/bgworker.c
index 5f8a007e73..a4c347d524 100644
--- a/src/backend/postmaster/bgworker.c
+++ b/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);
diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c
index bca46de6d5..9cc343b74f 100644
--- a/src/backend/postmaster/bgwriter.c
+++ b/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;
-}
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index 9cf91b0d35..3f35b324c3 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -36,10 +36,7 @@
  */
 #include "postgres.h"
 
-#include <signal.h>
 #include <sys/time.h>
-#include <time.h>
-#include <unistd.h>
 
 #include "access/xlog.h"
 #include "access/xlog_internal.h"
@@ -47,6 +44,7 @@
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "postmaster/bgwriter.h"
+#include "postmaster/interrupt.h"
 #include "replication/syncrep.h"
 #include "storage/bufmgr.h"
 #include "storage/condition_variable.h"
@@ -148,11 +146,6 @@ int			CheckPointTimeout = 300;
 int			CheckPointWarning = 30;
 double		CheckPointCompletionTarget = 0.5;
 
-/*
- * Flags set by interrupt handlers for later service in the main loop.
- */
-static volatile sig_atomic_t shutdown_requested = false;
-
 /*
  * Private state
  */
@@ -176,10 +169,7 @@ static bool CompactCheckpointerRequestQueue(void);
 static void UpdateSharedMemoryConfig(void);
 
 /* Signal handlers */
-
-static void chkpt_quickdie(SIGNAL_ARGS);
 static void ReqCheckpointHandler(SIGNAL_ARGS);
-static void ReqShutdownHandler(SIGNAL_ARGS);
 
 
 /*
@@ -204,14 +194,14 @@ CheckpointerMain(void)
 	 * want to wait for the backends to exit, whereupon the postmaster will
 	 * tell us it's okay to shut down (via SIGUSR2).
 	 */
-	pqsignal(SIGHUP, PostgresSigHupHandler);	/* set flag to read config file */
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
 	pqsignal(SIGINT, ReqCheckpointHandler); /* request checkpoint */
 	pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */
-	pqsignal(SIGQUIT, chkpt_quickdie);	/* hard crash time */
+	pqsignal(SIGQUIT, SignalHandlerForCrashExit);
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
-	pqsignal(SIGUSR2, ReqShutdownHandler);	/* request shutdown */
+	pqsignal(SIGUSR2, SignalHandlerForShutdownRequest);
 
 	/*
 	 * Reset some signals that are accepted by postmaster but not here
@@ -551,7 +541,7 @@ HandleCheckpointerInterrupts(void)
 		 */
 		UpdateSharedMemoryConfig();
 	}
-	if (shutdown_requested)
+	if (ShutdownRequestPending)
 	{
 		/*
 		 * From here on, elog(ERROR) should end with exit(1), not send
@@ -679,7 +669,7 @@ CheckpointWriteDelay(int flags, double progress)
 	 * in which case we just try to catch up as quickly as possible.
 	 */
 	if (!(flags & CHECKPOINT_IMMEDIATE) &&
-		!shutdown_requested &&
+		!ShutdownRequestPending &&
 		!ImmediateCheckpointRequested() &&
 		IsCheckpointOnSchedule(progress))
 	{
@@ -807,32 +797,6 @@ IsCheckpointOnSchedule(double progress)
  * --------------------------------
  */
 
-/*
- * chkpt_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
-chkpt_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);
-}
-
 /* SIGINT: set flag to run a normal checkpoint right away */
 static void
 ReqCheckpointHandler(SIGNAL_ARGS)
@@ -848,18 +812,6 @@ ReqCheckpointHandler(SIGNAL_ARGS)
 	errno = save_errno;
 }
 
-/* SIGUSR2: set flag to run a shutdown checkpoint and exit */
-static void
-ReqShutdownHandler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	shutdown_requested = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 
 /* --------------------------------
  *		communication with backends
diff --git a/src/backend/postmaster/interrupt.c b/src/backend/postmaster/interrupt.c
new file mode 100644
index 0000000000..6900cd02f6
--- /dev/null
+++ b/src/backend/postmaster/interrupt.c
@@ -0,0 +1,108 @@
+/*-------------------------------------------------------------------------
+ *
+ * interrupt.c
+ *	  Interrupt handling routines.
+ *
+ * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  src/backend/postmaster/interrupt.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <unistd.h>
+
+#include "miscadmin.h"
+#include "postmaster/interrupt.h"
+#include "storage/ipc.h"
+#include "storage/latch.h"
+#include "utils/guc.h"
+
+volatile sig_atomic_t ConfigReloadPending = false;
+volatile sig_atomic_t ShutdownRequestPending = false;
+
+/*
+ * Simple interrupt handler for main loops of background processes.
+ */
+void
+HandleMainLoopInterrupts(void)
+{
+	if (ConfigReloadPending)
+	{
+		ConfigReloadPending = false;
+		ProcessConfigFile(PGC_SIGHUP);
+	}
+
+	if (ShutdownRequestPending)
+		proc_exit(0);
+}
+
+/*
+ * Simple signal handler for triggering a configuration reload.
+ *
+ * Normally, this handler would be used for SIGHUP. The idea is that code
+ * which uses it would arrange to check the ConfigReloadPending flag at
+ * convenient places inside main loops, or else call HandleMainLoopInterrupts.
+ */
+void
+SignalHandlerForConfigReload(SIGNAL_ARGS)
+{
+	int			save_errno = errno;
+
+	ConfigReloadPending = true;
+	SetLatch(MyLatch);
+
+	errno = save_errno;
+}
+
+/*
+ * Simple signal handler for exiting quickly as if due to a crash.
+ *
+ * Normally, this would be used for handling SIGQUIT.
+ */
+void
+SignalHandlerForCrashExit(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);
+}
+
+/*
+ * Simple signal handler for triggering a long-running background process to
+ * shut down and exit.
+ *
+ * Typically, this handler would be used for SIGTERM, but some procesess use
+ * other signals. In particular, the checkpointer exits on SIGUSR2, the
+ * stats collector on SIGQUIT, and the WAL writer exits on either SIGINT
+ * or SIGTERM.
+ *
+ * ShutdownRequestPending should be checked at a convenient place within the
+ * main loop, or else the main loop should call HandleMainLoopInterrupts.
+ */
+void
+SignalHandlerForShutdownRequest(SIGNAL_ARGS)
+{
+	int			save_errno = errno;
+
+	ShutdownRequestPending = true;
+	SetLatch(MyLatch);
+
+	errno = save_errno;
+}
diff --git a/src/backend/postmaster/pgarch.c b/src/backend/postmaster/pgarch.c
index 09a9c66b4b..7824180ac7 100644
--- a/src/backend/postmaster/pgarch.c
+++ b/src/backend/postmaster/pgarch.c
@@ -39,6 +39,7 @@
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "postmaster/fork_process.h"
+#include "postmaster/interrupt.h"
 #include "postmaster/pgarch.h"
 #include "postmaster/postmaster.h"
 #include "storage/dsm.h"
@@ -83,7 +84,6 @@ static time_t last_sigterm_time = 0;
 /*
  * Flags set by interrupt handlers for later service in the main loop.
  */
-static volatile sig_atomic_t got_SIGTERM = false;
 static volatile sig_atomic_t wakened = false;
 static volatile sig_atomic_t ready_to_stop = false;
 
@@ -97,7 +97,6 @@ static pid_t pgarch_forkexec(void);
 
 NON_EXEC_STATIC void PgArchiverMain(int argc, char *argv[]) pg_attribute_noreturn();
 static void pgarch_exit(SIGNAL_ARGS);
-static void ArchSigTermHandler(SIGNAL_ARGS);
 static void pgarch_waken(SIGNAL_ARGS);
 static void pgarch_waken_stop(SIGNAL_ARGS);
 static void pgarch_MainLoop(void);
@@ -227,9 +226,9 @@ PgArchiverMain(int argc, char *argv[])
 	 * Ignore all signals usually bound to some action in the postmaster,
 	 * except for SIGHUP, SIGTERM, SIGUSR1, SIGUSR2, and SIGQUIT.
 	 */
-	pqsignal(SIGHUP, PostgresSigHupHandler);
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
 	pqsignal(SIGINT, SIG_IGN);
-	pqsignal(SIGTERM, ArchSigTermHandler);
+	pqsignal(SIGTERM, SignalHandlerForShutdownRequest);
 	pqsignal(SIGQUIT, pgarch_exit);
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
@@ -257,24 +256,6 @@ pgarch_exit(SIGNAL_ARGS)
 	exit(1);
 }
 
-/* SIGTERM signal handler for archiver process */
-static void
-ArchSigTermHandler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	/*
-	 * The postmaster never sends us SIGTERM, so we assume that this means
-	 * that init is trying to shut down the whole system.  If we hang around
-	 * too long we'll get SIGKILL'd.  Set flag to prevent starting any more
-	 * archive commands.
-	 */
-	got_SIGTERM = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /* SIGUSR1 signal handler for archiver process */
 static void
 pgarch_waken(SIGNAL_ARGS)
@@ -346,7 +327,7 @@ pgarch_MainLoop(void)
 		 * idea.  If more than 60 seconds pass since SIGTERM, exit anyway, so
 		 * that the postmaster can start a new archiver if needed.
 		 */
-		if (got_SIGTERM)
+		if (ShutdownRequestPending)
 		{
 			time_t		curtime = time(NULL);
 
@@ -434,7 +415,7 @@ pgarch_ArchiverCopyLoop(void)
 			 * command, and the second is to avoid conflicts with another
 			 * archiver spawned by a newer postmaster.
 			 */
-			if (got_SIGTERM || !PostmasterIsAlive())
+			if (ShutdownRequestPending || !PostmasterIsAlive())
 				return;
 
 			/*
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index 96a9e09ced..e931512203 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -49,6 +49,7 @@
 #include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "postmaster/fork_process.h"
+#include "postmaster/interrupt.h"
 #include "postmaster/postmaster.h"
 #include "replication/walsender.h"
 #include "storage/backendid.h"
@@ -262,9 +263,6 @@ static PgStat_GlobalStats globalStats;
  */
 static List *pending_write_requests = NIL;
 
-/* Signal handler flags */
-static volatile bool need_exit = false;
-
 /*
  * Total time charged to functions so far in the current backend.
  * We use this to help separate "self" and "other" time charges.
@@ -282,7 +280,6 @@ static pid_t pgstat_forkexec(void);
 #endif
 
 NON_EXEC_STATIC void PgstatCollectorMain(int argc, char *argv[]) pg_attribute_noreturn();
-static void pgstat_exit(SIGNAL_ARGS);
 static void pgstat_beshutdown_hook(int code, Datum arg);
 
 static PgStat_StatDBEntry *pgstat_get_db_entry(Oid databaseid, bool create);
@@ -4432,10 +4429,10 @@ PgstatCollectorMain(int argc, char *argv[])
 	 * except SIGHUP and SIGQUIT.  Note we don't need a SIGUSR1 handler to
 	 * support latch operations, because we only use a local latch.
 	 */
-	pqsignal(SIGHUP, PostgresSigHupHandler);
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
 	pqsignal(SIGINT, SIG_IGN);
 	pqsignal(SIGTERM, SIG_IGN);
-	pqsignal(SIGQUIT, pgstat_exit);
+	pqsignal(SIGQUIT, SignalHandlerForShutdownRequest);
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, SIG_IGN);
@@ -4477,14 +4474,14 @@ PgstatCollectorMain(int argc, char *argv[])
 		/*
 		 * Quit if we get SIGQUIT from the postmaster.
 		 */
-		if (need_exit)
+		if (ShutdownRequestPending)
 			break;
 
 		/*
 		 * Inner loop iterates as long as we keep getting messages, or until
-		 * need_exit becomes set.
+		 * ShutdownRequestPending becomes set.
 		 */
-		while (!need_exit)
+		while (!ShutdownRequestPending)
 		{
 			/*
 			 * Reload configuration if we got SIGHUP from the postmaster.
@@ -4676,19 +4673,6 @@ PgstatCollectorMain(int argc, char *argv[])
 	exit(0);
 }
 
-
-/* SIGQUIT signal handler for collector process */
-static void
-pgstat_exit(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	need_exit = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /*
  * Subroutine to clear stats in a database entry
  *
diff --git a/src/backend/postmaster/startup.c b/src/backend/postmaster/startup.c
index f43e57dadb..4f59c71f73 100644
--- a/src/backend/postmaster/startup.c
+++ b/src/backend/postmaster/startup.c
@@ -19,13 +19,11 @@
  */
 #include "postgres.h"
 
-#include <signal.h>
-#include <unistd.h>
-
 #include "access/xlog.h"
 #include "libpq/pqsignal.h"
 #include "miscadmin.h"
 #include "pgstat.h"
+#include "postmaster/interrupt.h"
 #include "postmaster/startup.h"
 #include "storage/ipc.h"
 #include "storage/latch.h"
@@ -50,7 +48,6 @@ static volatile sig_atomic_t promote_triggered = false;
 static volatile sig_atomic_t in_restore_command = false;
 
 /* Signal handlers */
-static void startupproc_quickdie(SIGNAL_ARGS);
 static void StartupProcTriggerHandler(SIGNAL_ARGS);
 static void StartupProcSigHupHandler(SIGNAL_ARGS);
 
@@ -60,33 +57,6 @@ static void StartupProcSigHupHandler(SIGNAL_ARGS);
  * --------------------------------
  */
 
-/*
- * startupproc_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
-startupproc_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);
-}
-
-
 /* SIGUSR2: set flag to finish recovery */
 static void
 StartupProcTriggerHandler(SIGNAL_ARGS)
@@ -167,7 +137,7 @@ StartupProcessMain(void)
 	pqsignal(SIGHUP, StartupProcSigHupHandler); /* reload config file */
 	pqsignal(SIGINT, SIG_IGN);	/* ignore query cancel */
 	pqsignal(SIGTERM, StartupProcShutdownHandler);	/* request shutdown */
-	pqsignal(SIGQUIT, startupproc_quickdie);	/* hard crash time */
+	pqsignal(SIGQUIT, SignalHandlerForCrashExit);
 	InitializeTimeouts();		/* establishes SIGALRM handler */
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
diff --git a/src/backend/postmaster/walwriter.c b/src/backend/postmaster/walwriter.c
index 599478530f..38e9eb1304 100644
--- a/src/backend/postmaster/walwriter.c
+++ b/src/backend/postmaster/walwriter.c
@@ -48,6 +48,7 @@
 #include "libpq/pqsignal.h"
 #include "miscadmin.h"
 #include "pgstat.h"
+#include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
 #include "storage/bufmgr.h"
 #include "storage/condition_variable.h"
@@ -77,17 +78,6 @@ int			WalWriterFlushAfter = 128;
 #define LOOPS_UNTIL_HIBERNATE		50
 #define HIBERNATE_FACTOR			25
 
-/*
- * Flags set by interrupt handlers for later service in the main loop.
- */
-static volatile sig_atomic_t shutdown_requested = false;
-
-static void HandleWalWriterInterrupts(void);
-
-/* Signal handlers */
-static void wal_quickdie(SIGNAL_ARGS);
-static void WalShutdownHandler(SIGNAL_ARGS);
-
 /*
  * Main entry point for walwriter process
  *
@@ -108,10 +98,10 @@ WalWriterMain(void)
 	 * We have no particular use for SIGINT at the moment, but seems
 	 * reasonable to treat like SIGTERM.
 	 */
-	pqsignal(SIGHUP, PostgresSigHupHandler); /* set flag to read config file */
-	pqsignal(SIGINT, WalShutdownHandler);	/* request shutdown */
-	pqsignal(SIGTERM, WalShutdownHandler);	/* request shutdown */
-	pqsignal(SIGQUIT, wal_quickdie);	/* hard crash time */
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
+	pqsignal(SIGINT, SignalHandlerForShutdownRequest);
+	pqsignal(SIGTERM, SignalHandlerForShutdownRequest);
+	pqsignal(SIGQUIT, SignalHandlerForCrashExit);
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
@@ -242,7 +232,7 @@ WalWriterMain(void)
 		/* Clear any already-pending wakeups */
 		ResetLatch(MyLatch);
 
-		HandleWalWriterInterrupts();
+		HandleMainLoopInterrupts();
 
 		/*
 		 * Do what we're here for; then, if XLogBackgroundFlush() found useful
@@ -269,65 +259,3 @@ WalWriterMain(void)
 						 WAIT_EVENT_WAL_WRITER_MAIN);
 	}
 }
-
-/*
- * Process any new interrupts.
- */
-static void
-HandleWalWriterInterrupts(void)
-{
-	if (ConfigReloadPending)
-	{
-		ConfigReloadPending = false;
-		ProcessConfigFile(PGC_SIGHUP);
-	}
-	if (shutdown_requested)
-	{
-		/* Normal exit from the walwriter is here */
-		proc_exit(0);		/* done */
-	}
-}
-
-
-/* --------------------------------
- *		signal handler routines
- * --------------------------------
- */
-
-/*
- * wal_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
-wal_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 exit normally */
-static void
-WalShutdownHandler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	shutdown_requested = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
diff --git a/src/backend/replication/logical/launcher.c b/src/backend/replication/logical/launcher.c
index edca70c58c..99cfa5d8b4 100644
--- a/src/backend/replication/logical/launcher.c
+++ b/src/backend/replication/logical/launcher.c
@@ -30,6 +30,7 @@
 #include "pgstat.h"
 #include "postmaster/bgworker.h"
 #include "postmaster/fork_process.h"
+#include "postmaster/interrupt.h"
 #include "postmaster/postmaster.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalworker.h"
@@ -955,7 +956,7 @@ ApplyLauncherMain(Datum main_arg)
 	LogicalRepCtx->launcher_pid = MyProcPid;
 
 	/* Establish signal handlers. */
-	pqsignal(SIGTERM, PostgresSigHupHandler);
+	pqsignal(SIGTERM, SignalHandlerForConfigReload);
 	pqsignal(SIGTERM, die);
 	BackgroundWorkerUnblockSignals();
 
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 3b12ad6400..4bf6f5e427 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -45,6 +45,7 @@
 #include "parser/parse_relation.h"
 #include "pgstat.h"
 #include "postmaster/bgworker.h"
+#include "postmaster/interrupt.h"
 #include "postmaster/postmaster.h"
 #include "postmaster/walwriter.h"
 #include "replication/decode.h"
@@ -1575,7 +1576,7 @@ ApplyWorkerMain(Datum main_arg)
 	logicalrep_worker_attach(worker_slot);
 
 	/* Setup signal handling */
-	pqsignal(SIGHUP, PostgresSigHupHandler);
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
 	pqsignal(SIGTERM, die);
 	BackgroundWorkerUnblockSignals();
 
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index 72acb10767..06214b213b 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -43,7 +43,6 @@
  */
 #include "postgres.h"
 
-#include <signal.h>
 #include <unistd.h>
 
 #include "access/htup_details.h"
@@ -58,6 +57,7 @@
 #include "libpq/pqsignal.h"
 #include "miscadmin.h"
 #include "pgstat.h"
+#include "postmaster/interrupt.h"
 #include "replication/walreceiver.h"
 #include "replication/walsender.h"
 #include "storage/ipc.h"
@@ -127,7 +127,6 @@ static void ProcessWalSndrMessage(XLogRecPtr walEnd, TimestampTz sendTime);
 /* Signal handlers */
 static void WalRcvSigHupHandler(SIGNAL_ARGS);
 static void WalRcvShutdownHandler(SIGNAL_ARGS);
-static void WalRcvQuickDieHandler(SIGNAL_ARGS);
 
 
 /*
@@ -249,7 +248,7 @@ WalReceiverMain(void)
 	pqsignal(SIGHUP, WalRcvSigHupHandler);	/* set flag to read config file */
 	pqsignal(SIGINT, SIG_IGN);
 	pqsignal(SIGTERM, WalRcvShutdownHandler);	/* request shutdown */
-	pqsignal(SIGQUIT, WalRcvQuickDieHandler);	/* hard crash time */
+	pqsignal(SIGQUIT, SignalHandlerForCrashExit);
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
@@ -780,32 +779,6 @@ WalRcvShutdownHandler(SIGNAL_ARGS)
 	errno = save_errno;
 }
 
-/*
- * WalRcvQuickDieHandler() 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
-WalRcvQuickDieHandler(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 use _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);
-}
-
 /*
  * Accept the message from XLOG stream, and process it.
  */
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 8bafa65e50..1361f34198 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -66,6 +66,7 @@
 #include "miscadmin.h"
 #include "nodes/replnodes.h"
 #include "pgstat.h"
+#include "postmaster/interrupt.h"
 #include "replication/basebackup.h"
 #include "replication/decode.h"
 #include "replication/logical.h"
@@ -2962,8 +2963,7 @@ void
 WalSndSignals(void)
 {
 	/* Set up signal handlers */
-	pqsignal(SIGHUP, PostgresSigHupHandler);	/* set flag to read config
-												 * file */
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
 	pqsignal(SIGINT, StatementCancelHandler);	/* query cancel */
 	pqsignal(SIGTERM, die);		/* request shutdown */
 	pqsignal(SIGQUIT, quickdie);	/* hard crash time */
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 3b85e48333..d894c3ddf4 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -57,6 +57,7 @@
 #include "pg_trace.h"
 #include "pgstat.h"
 #include "postmaster/autovacuum.h"
+#include "postmaster/interrupt.h"
 #include "postmaster/postmaster.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalworker.h"
@@ -2843,24 +2844,6 @@ FloatExceptionHandler(SIGNAL_ARGS)
 					   "invalid operation, such as division by zero.")));
 }
 
-/*
- * SIGHUP: set flag to re-read config file at next convenient time.
- *
- * Sets the ConfigReloadPending flag, which should be checked at convenient
- * places inside main loops. (Better than doing the reading in the signal
- * handler, ey?)
- */
-void
-PostgresSigHupHandler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	ConfigReloadPending = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /*
  * RecoveryConflictInterrupt: out-of-line portion of recovery conflict
  * handling following receipt of SIGUSR1. Designed to be similar to die()
@@ -3809,8 +3792,7 @@ PostgresMain(int argc, char *argv[],
 		WalSndSignals();
 	else
 	{
-		pqsignal(SIGHUP, PostgresSigHupHandler);	/* set flag to read config
-													 * file */
+		pqsignal(SIGHUP, SignalHandlerForConfigReload);
 		pqsignal(SIGINT, StatementCancelHandler);	/* cancel current query */
 		pqsignal(SIGTERM, die); /* cancel current query and exit */
 
diff --git a/src/backend/utils/init/globals.c b/src/backend/utils/init/globals.c
index 3bf96de256..4473e18e53 100644
--- a/src/backend/utils/init/globals.c
+++ b/src/backend/utils/init/globals.c
@@ -32,7 +32,6 @@ volatile sig_atomic_t QueryCancelPending = false;
 volatile sig_atomic_t ProcDiePending = false;
 volatile sig_atomic_t ClientConnectionLost = false;
 volatile sig_atomic_t IdleInTransactionSessionTimeoutPending = false;
-volatile sig_atomic_t ConfigReloadPending = false;
 volatile uint32 InterruptHoldoffCount = 0;
 volatile uint32 QueryCancelHoldoffCount = 0;
 volatile uint32 CritSectionCount = 0;
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index bc6e03fbc7..24f43ad686 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -82,7 +82,6 @@ extern PGDLLIMPORT volatile sig_atomic_t InterruptPending;
 extern PGDLLIMPORT volatile sig_atomic_t QueryCancelPending;
 extern PGDLLIMPORT volatile sig_atomic_t ProcDiePending;
 extern PGDLLIMPORT volatile sig_atomic_t IdleInTransactionSessionTimeoutPending;
-extern PGDLLIMPORT volatile sig_atomic_t ConfigReloadPending;
 
 extern PGDLLIMPORT volatile sig_atomic_t ClientConnectionLost;
 
@@ -279,8 +278,6 @@ extern void restore_stack_base(pg_stack_base_t base);
 extern void check_stack_depth(void);
 extern bool stack_is_too_deep(void);
 
-extern void PostgresSigHupHandler(SIGNAL_ARGS);
-
 /* in tcop/utility.c */
 extern void PreventCommandIfReadOnly(const char *cmdname);
 extern void PreventCommandIfParallelMode(const char *cmdname);
diff --git a/src/include/postmaster/interrupt.h b/src/include/postmaster/interrupt.h
new file mode 100644
index 0000000000..8f4e43be20
--- /dev/null
+++ b/src/include/postmaster/interrupt.h
@@ -0,0 +1,32 @@
+/*-------------------------------------------------------------------------
+ *
+ * interrupt.h
+ *	  Interrupt handling routines.
+ *
+ * Responses to interrupts are fairly varied and many types of backends
+ * have their own implementations, but we provide a few generic things
+ * here to facilitate code reuse.
+ *
+ * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  src/include/postmaster/interrupt.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef INTERRUPT_H
+#define INTERRUPT_H
+
+#include <signal.h>
+
+extern PGDLLIMPORT volatile sig_atomic_t ConfigReloadPending;
+extern PGDLLIMPORT volatile sig_atomic_t ShutdownRequestPending;
+
+extern void HandleMainLoopInterrupts(void);
+extern void SignalHandlerForConfigReload(SIGNAL_ARGS);
+extern void SignalHandlerForCrashExit(SIGNAL_ARGS);
+extern void SignalHandlerForShutdownRequest(SIGNAL_ARGS);
+
+#endif
-- 
2.17.2 (Apple Git-113)

From e9bfcbc3a1b1aa4a01a5a281bc71c6f019f5d46b Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Wed, 27 Nov 2019 11:29:25 -0500
Subject: [PATCH v2 4/5] Extend the ProcSignal mechanism to support barriers.

A new function EmitProcSignalBarrier() can be used to emit a global
barrier which all backends that participate in the ProcSignal
mechanism must absorb, and a new function WaitForProcSignalBarrier()
can be used to wait until all relevant backends have in fact
absorbed the barrier.

This can be used to coordinate global state changes, such as turning
checksums on while the system is running.

Andres Freund and Robert Haas
---
 doc/src/sgml/monitoring.sgml          |   4 +
 src/backend/postmaster/autovacuum.c   |   4 +
 src/backend/postmaster/checkpointer.c |   7 +
 src/backend/postmaster/interrupt.c    |   4 +
 src/backend/postmaster/pgstat.c       |   3 +
 src/backend/postmaster/startup.c      |   6 +-
 src/backend/replication/walreceiver.c |   3 +-
 src/backend/storage/buffer/bufmgr.c   |  10 +
 src/backend/storage/ipc/procsignal.c  | 289 +++++++++++++++++++++++++-
 src/backend/tcop/postgres.c           |   3 +
 src/backend/utils/init/globals.c      |   1 +
 src/include/miscadmin.h               |   1 +
 src/include/pgstat.h                  |   1 +
 src/include/storage/procsignal.h      |   9 +
 14 files changed, 332 insertions(+), 13 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index a3c5f86b7e..76957c0a43 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -1593,6 +1593,10 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
          <entry><literal>LogicalRewriteWrite</literal></entry>
          <entry>Waiting for a write of logical rewrite mappings.</entry>
         </row>
+        <row>
+         <entry><literal>ProcSignalBarrier</literal></entry>
+         <entry>Waiting for a barrier event to be processed by all backends.</entry>
+        </row>
         <row>
          <entry><literal>RelationMapRead</literal></entry>
          <entry>Waiting for a read of the relation map file.</entry>
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 1792008ebe..52ad99f716 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -820,6 +820,10 @@ HandleAutoVacLauncherInterrupts(void)
 		rebuild_database_list(InvalidOid);
 	}
 
+	/* Process barrier events */
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
+
 	/* Process sinval catchup interrupts that happened while sleeping */
 	ProcessCatchupInterrupt();
 }
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index 3f35b324c3..d1185cc135 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -523,6 +523,9 @@ CheckpointerMain(void)
 static void
 HandleCheckpointerInterrupts(void)
 {
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
+
 	if (ConfigReloadPending)
 	{
 		ConfigReloadPending = false;
@@ -709,6 +712,10 @@ CheckpointWriteDelay(int flags, double progress)
 		AbsorbSyncRequests();
 		absorb_counter = WRITES_PER_ABSORB;
 	}
+
+	/* Check for barrier events. */
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
 }
 
 /*
diff --git a/src/backend/postmaster/interrupt.c b/src/backend/postmaster/interrupt.c
index 6900cd02f6..214ccaf34b 100644
--- a/src/backend/postmaster/interrupt.c
+++ b/src/backend/postmaster/interrupt.c
@@ -20,6 +20,7 @@
 #include "postmaster/interrupt.h"
 #include "storage/ipc.h"
 #include "storage/latch.h"
+#include "storage/procsignal.h"
 #include "utils/guc.h"
 
 volatile sig_atomic_t ConfigReloadPending = false;
@@ -31,6 +32,9 @@ volatile sig_atomic_t ShutdownRequestPending = false;
 void
 HandleMainLoopInterrupts(void)
 {
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
+
 	if (ConfigReloadPending)
 	{
 		ConfigReloadPending = false;
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index e931512203..7410b2ff5e 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -3988,6 +3988,9 @@ pgstat_get_wait_io(WaitEventIO w)
 		case WAIT_EVENT_LOGICAL_REWRITE_WRITE:
 			event_name = "LogicalRewriteWrite";
 			break;
+		case WAIT_EVENT_PROC_SIGNAL_BARRIER:
+			event_name = "ProcSignalBarrier";
+			break;
 		case WAIT_EVENT_RELATION_MAP_READ:
 			event_name = "RelationMapRead";
 			break;
diff --git a/src/backend/postmaster/startup.c b/src/backend/postmaster/startup.c
index 4f59c71f73..11f7052e78 100644
--- a/src/backend/postmaster/startup.c
+++ b/src/backend/postmaster/startup.c
@@ -96,7 +96,7 @@ StartupProcShutdownHandler(SIGNAL_ARGS)
 	errno = save_errno;
 }
 
-/* Handle SIGHUP and SIGTERM signals of startup process */
+/* Handle various signals that might be sent to the startup process */
 void
 HandleStartupProcInterrupts(void)
 {
@@ -121,6 +121,10 @@ HandleStartupProcInterrupts(void)
 	 */
 	if (IsUnderPostmaster && !PostmasterIsAlive())
 		exit(1);
+
+	/* Process barrier events */
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
 }
 
 
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index 06214b213b..5c23e7db2d 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -148,7 +148,8 @@ ProcessWalRcvInterrupts(void)
 	/*
 	 * Although walreceiver interrupt handling doesn't use the same scheme as
 	 * regular backends, call CHECK_FOR_INTERRUPTS() to make sure we receive
-	 * any incoming signals on Win32.
+	 * any incoming signals on Win32, and also to make sure we process any
+	 * barrier events.
 	 */
 	CHECK_FOR_INTERRUPTS();
 
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 7ad10736d5..1f10a97dc7 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -1852,6 +1852,10 @@ BufferSync(int flags)
 		}
 
 		UnlockBufHdr(bufHdr, buf_state);
+
+		/* Check for barrier events in case NBuffers is large. */
+		if (ProcSignalBarrierPending)
+			ProcessProcSignalBarrier();
 	}
 
 	if (num_to_scan == 0)
@@ -1930,6 +1934,10 @@ BufferSync(int flags)
 		}
 
 		s->num_to_scan++;
+
+		/* Check for barrier events. */
+		if (ProcSignalBarrierPending)
+			ProcessProcSignalBarrier();
 	}
 
 	Assert(num_spaces > 0);
@@ -2018,6 +2026,8 @@ BufferSync(int flags)
 
 		/*
 		 * Sleep to throttle our I/O rate.
+		 *
+		 * (This will check for barrier events even if it doesn't sleep.)
 		 */
 		CheckpointWriteDelay(flags, (double) num_processed / num_to_scan);
 	}
diff --git a/src/backend/storage/ipc/procsignal.c b/src/backend/storage/ipc/procsignal.c
index fde97a1036..4c249d58b1 100644
--- a/src/backend/storage/ipc/procsignal.c
+++ b/src/backend/storage/ipc/procsignal.c
@@ -20,6 +20,7 @@
 #include "access/parallel.h"
 #include "commands/async.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "replication/walsender.h"
 #include "storage/ipc.h"
 #include "storage/latch.h"
@@ -45,13 +46,36 @@
  * The flags are actually declared as "volatile sig_atomic_t" for maximum
  * portability.  This should ensure that loads and stores of the flag
  * values are atomic, allowing us to dispense with any explicit locking.
+ *
+ * pss_signalFlags are intended to be set in cases where we don't need to
+ * keep track of whether or not the target process has handled the signal,
+ * but sometimes we need confirmation, as when making a global state change
+ * that cannot be considered complete until all backends have taken notice
+ * of it. For such use cases, we set a bit in pss_barrierCheckMask and then
+ * increment the current "barrier generation"; when the new barrier generation
+ * (or greater) appears in the pss_barrierGeneration flag of every process,
+ * we know that the message has been received everywhere.
  */
 typedef struct
 {
 	pid_t		pss_pid;
 	sig_atomic_t pss_signalFlags[NUM_PROCSIGNALS];
+	pg_atomic_uint64	pss_barrierGeneration;
+	pg_atomic_uint32	pss_barrierCheckMask;
 } ProcSignalSlot;
 
+/*
+ * Information that is global to the entire ProcSignal system can be stored
+ * here.
+ *
+ * psh_barrierGeneration is the highest barrier generation in existence.
+ */
+typedef struct
+{
+	pg_atomic_uint64	psh_barrierGeneration;
+	ProcSignalSlot		psh_slot[FLEXIBLE_ARRAY_MEMBER];
+} ProcSignalHeader;
+
 /*
  * We reserve a slot for each possible BackendId, plus one for each
  * possible auxiliary process type.  (This scheme assumes there is not
@@ -59,11 +83,16 @@ typedef struct
  */
 #define NumProcSignalSlots	(MaxBackends + NUM_AUXPROCTYPES)
 
-static ProcSignalSlot *ProcSignalSlots = NULL;
+/* Check whether the relevant type bit is set in the flags. */
+#define BARRIER_SHOULD_CHECK(flags, type) \
+	(((flags) & (((uint32) 1) << (uint32) (type))) != 0)
+
+static ProcSignalHeader *ProcSignal = NULL;
 static volatile ProcSignalSlot *MyProcSignalSlot = NULL;
 
 static bool CheckProcSignal(ProcSignalReason reason);
 static void CleanupProcSignalState(int status, Datum arg);
+static void ProcessBarrierSample(void);
 
 /*
  * ProcSignalShmemSize
@@ -72,7 +101,11 @@ static void CleanupProcSignalState(int status, Datum arg);
 Size
 ProcSignalShmemSize(void)
 {
-	return NumProcSignalSlots * sizeof(ProcSignalSlot);
+	Size	size;
+
+	size = mul_size(NumProcSignalSlots, sizeof(ProcSignalSlot));
+	size = add_size(size, offsetof(ProcSignalHeader, psh_slot));
+	return size;
 }
 
 /*
@@ -85,12 +118,26 @@ ProcSignalShmemInit(void)
 	Size		size = ProcSignalShmemSize();
 	bool		found;
 
-	ProcSignalSlots = (ProcSignalSlot *)
-		ShmemInitStruct("ProcSignalSlots", size, &found);
+	ProcSignal = (ProcSignalHeader *)
+		ShmemInitStruct("ProcSignal", size, &found);
 
-	/* If we're first, set everything to zeroes */
+	/* If we're first, initialize. */
 	if (!found)
-		MemSet(ProcSignalSlots, 0, size);
+	{
+		int		i;
+
+		pg_atomic_init_u64(&ProcSignal->psh_barrierGeneration, 0);
+
+		for (i = 0; i < NumProcSignalSlots; ++i)
+		{
+			ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
+
+			slot->pss_pid = 0;
+			MemSet(slot->pss_signalFlags, 0, sizeof(slot->pss_signalFlags));
+			pg_atomic_init_u64(&slot->pss_barrierGeneration, PG_UINT64_MAX);
+			pg_atomic_init_u32(&slot->pss_barrierCheckMask, 0);
+		}
+	}
 }
 
 /*
@@ -104,10 +151,11 @@ void
 ProcSignalInit(int pss_idx)
 {
 	volatile ProcSignalSlot *slot;
+	uint64		barrier_generation;
 
 	Assert(pss_idx >= 1 && pss_idx <= NumProcSignalSlots);
 
-	slot = &ProcSignalSlots[pss_idx - 1];
+	slot = &ProcSignal->psh_slot[pss_idx - 1];
 
 	/* sanity check */
 	if (slot->pss_pid != 0)
@@ -117,6 +165,23 @@ ProcSignalInit(int pss_idx)
 	/* Clear out any leftover signal reasons */
 	MemSet(slot->pss_signalFlags, 0, NUM_PROCSIGNALS * sizeof(sig_atomic_t));
 
+	/*
+	 * Initialize barrier state. Since we're a brand-new process, there
+	 * shouldn't be any leftover backend-private state that needs to be
+	 * updated. Therefore, we can broadcast the latest barrier generation
+	 * and disregard any previously-set check bits.
+	 *
+	 * NB: This only works if this initialization happens early enough in the
+	 * startup sequence that we haven't yet cached any state that might need
+	 * to be invalidated. That's also why we have a memory barrier here, to
+	 * be sure that any later reads of memory happen strictly after this.
+	 */
+	pg_atomic_write_u32(&slot->pss_barrierCheckMask, 0);
+	barrier_generation =
+		pg_atomic_read_u64(&ProcSignal->psh_barrierGeneration);
+	pg_atomic_write_u64(&slot->pss_barrierGeneration, barrier_generation);
+	pg_memory_barrier();
+
 	/* Mark slot with my PID */
 	slot->pss_pid = MyProcPid;
 
@@ -129,7 +194,7 @@ ProcSignalInit(int pss_idx)
 
 /*
  * CleanupProcSignalState
- *		Remove current process from ProcSignalSlots
+ *		Remove current process from ProcSignal mechanism
  *
  * This function is called via on_shmem_exit() during backend shutdown.
  */
@@ -139,7 +204,7 @@ CleanupProcSignalState(int status, Datum arg)
 	int			pss_idx = DatumGetInt32(arg);
 	volatile ProcSignalSlot *slot;
 
-	slot = &ProcSignalSlots[pss_idx - 1];
+	slot = &ProcSignal->psh_slot[pss_idx - 1];
 	Assert(slot == MyProcSignalSlot);
 
 	/*
@@ -161,6 +226,12 @@ CleanupProcSignalState(int status, Datum arg)
 		return;					/* XXX better to zero the slot anyway? */
 	}
 
+	/*
+	 * Make this slot look like it's absorbed all possible barriers, so that
+	 * no barrier waits block on it.
+	 */
+	pg_atomic_write_u64(&slot->pss_barrierGeneration, PG_UINT64_MAX);
+
 	slot->pss_pid = 0;
 }
 
@@ -182,7 +253,7 @@ SendProcSignal(pid_t pid, ProcSignalReason reason, BackendId backendId)
 
 	if (backendId != InvalidBackendId)
 	{
-		slot = &ProcSignalSlots[backendId - 1];
+		slot = &ProcSignal->psh_slot[backendId - 1];
 
 		/*
 		 * Note: Since there's no locking, it's possible that the target
@@ -212,7 +283,7 @@ SendProcSignal(pid_t pid, ProcSignalReason reason, BackendId backendId)
 
 		for (i = NumProcSignalSlots - 1; i >= 0; i--)
 		{
-			slot = &ProcSignalSlots[i];
+			slot = &ProcSignal->psh_slot[i];
 
 			if (slot->pss_pid == pid)
 			{
@@ -230,6 +301,175 @@ SendProcSignal(pid_t pid, ProcSignalReason reason, BackendId backendId)
 	return -1;
 }
 
+/*
+ * EmitProcSignalBarrier
+ *		Send a signal to every Postgres process
+ *
+ * The return value of this function is the barrier "generation" created
+ * by this operation. This value can be passed to WaitForProcSignalBarrier
+ * to wait until it is known that every participant in the ProcSignal
+ * mechanism has absorbed the signal (or started afterwards).
+ *
+ * Note that it would be a bad idea to use this for anything that happens
+ * frequently, as interrupting every backend could cause a noticeable
+ * performance hit.
+ *
+ * Callers are entitled to assume that this function will not throw ERROR
+ * or FATAL.
+ */
+uint64
+EmitProcSignalBarrier(ProcSignalBarrierType type)
+{
+	uint64	flagbit = UINT64CONST(1) << (uint64) type;
+	uint64	generation;
+
+	/*
+	 * Set all the flags.
+	 *
+	 * Note that pg_atomic_fetch_or_u32 has full barrier semantics, so this
+	 * is totally ordered with respect to anything the caller did before, and
+	 * anything that we do afterwards. (This is also true of the later call
+	 * to pg_atomic_add_fetch_u64.)
+	 */
+	for (int i = NumProcSignalSlots - 1; i >= 0; i--)
+	{
+		volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
+
+		pg_atomic_fetch_or_u32(&slot->pss_barrierCheckMask, flagbit);
+	}
+
+	/*
+	 * Increment the generation counter.
+	 */
+	generation =
+		pg_atomic_add_fetch_u64(&ProcSignal->psh_barrierGeneration, 1);
+
+	/*
+	 * Signal all the processes, so that they update their advertised barrier
+	 * generation.
+	 *
+	 * Concurrency is not a problem here. Backends that have exited don't
+	 * matter, and new backends that have joined since we entered this function
+	 * must already have current state, since the caller is responsible for
+	 * making sure that the relevant state is entirely visible before calling
+	 * this function in the first place. We still have to wake them up -
+	 * because we can't distinguish between such backends and older backends
+	 * that need to update state - but they won't actually need to change
+	 * any state.
+	 */
+	for (int i = NumProcSignalSlots - 1; i >= 0; i--)
+	{
+		volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
+		pid_t	pid = slot->pss_pid;
+
+		if (pid != 0)
+			kill(pid, SIGUSR1);
+	}
+
+	return generation;
+}
+
+/*
+ * WaitForProcSignalBarrier - wait until it is guaranteed that all changes
+ * requested by a specific call to EmitProcSignalBarrier() have taken effect.
+ *
+ * We expect that the barrier will normally be absorbed very quickly by other
+ * backends, so we start by waiting just 1/8 of a second and then back off
+ * by a factor of two every time we time out, to a maximum wait time of
+ * 1 second.
+ */
+void
+WaitForProcSignalBarrier(uint64 generation)
+{
+	long	timeout = 125L;
+
+	for (int i = NumProcSignalSlots - 1; i >= 0; i--)
+	{
+		volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
+		uint64	oldval;
+
+		oldval = pg_atomic_read_u64(&slot->pss_barrierGeneration);
+		while (oldval < generation)
+		{
+			int		events;
+
+			CHECK_FOR_INTERRUPTS();
+
+			events =
+				WaitLatch(MyLatch,
+						  WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
+						  timeout, WAIT_EVENT_PROC_SIGNAL_BARRIER);
+			ResetLatch(MyLatch);
+
+			oldval = pg_atomic_read_u64(&slot->pss_barrierGeneration);
+			if (events & WL_TIMEOUT)
+				timeout = Min(timeout * 2, 1000L);
+		}
+	}
+}
+
+/*
+ * Perform global barrier related interrupt checking.
+ *
+ * Any backend that participates in ProcSignal signalling must arrange to
+ * call this function periodically. It is called from CHECK_FOR_INTERRUPTS(),
+ * which is enough for normal backends, but not necessarily for all types of
+ * background processes.
+ */
+void
+ProcessProcSignalBarrier(void)
+{
+	uint64 generation;
+	uint32 flags;
+
+	/* Exit quickly if there's no work to do. */
+	if (!ProcSignalBarrierPending)
+		return;
+	ProcSignalBarrierPending = false;
+
+	/*
+	 * Read the current barrier generation, and then get the flags that
+	 * are set for this backend. Note that pg_atomic_exchange_u32 is a full
+	 * barrier, so we're guaranteed that the read of the barrier generation
+	 * happens before we atomically extract the flags, and that any subsequent
+	 * state changes happen afterward.
+	 */
+	generation = pg_atomic_read_u64(&ProcSignal->psh_barrierGeneration);
+	flags = pg_atomic_exchange_u32(&MyProcSignalSlot->pss_barrierCheckMask, 0);
+
+	/*
+	 * Process each type of barrier. It's important that nothing we call from
+	 * here throws an error, because pss_barrierCheckMask has already been
+	 * cleared. If we jumped out of here before processing all barrier types,
+	 * then we'd forget about the need to do so later.
+	 *
+	 * NB: It ought to be OK to call the barrier-processing functions
+	 * unconditionally, but it's more efficient to call only the ones that
+	 * might need us to do something based on the flags.
+	 */
+	if (BARRIER_SHOULD_CHECK(flags, PROCSIGNAL_BARRIER_SAMPLE))
+		ProcessBarrierSample();
+
+	/*
+	 * State changes related to all types of barriers that might have been
+	 * emitted have now been handled, so we can update our notion of the
+	 * generation to the one we observed before beginning the updates. If
+	 * things have changed further, it'll get fixed up when this function is
+	 * next called.
+	 */
+	pg_atomic_write_u64(&MyProcSignalSlot->pss_barrierGeneration, generation);
+}
+
+static void
+ProcessBarrierSample(void)
+{
+	/*
+	 * XXX. This should be something no-fail, which elog() is not, but this is
+	 * just for testing purposes.
+	 */
+	elog(LOG, "ProcessBarrierSample");
+}
+
 /*
  * CheckProcSignal - check to see if a particular reason has been
  * signaled, and clear the signal flag.  Should be called after receiving
@@ -253,6 +493,27 @@ CheckProcSignal(ProcSignalReason reason)
 	return false;
 }
 
+/*
+ * CheckProcSignalBarrier - check for new barriers we need to absorb
+ */
+static bool
+CheckProcSignalBarrier(void)
+{
+	volatile ProcSignalSlot *slot = MyProcSignalSlot;
+
+	if (slot != NULL)
+	{
+		uint64	mygen;
+		uint64	curgen;
+
+		mygen = pg_atomic_read_u64(&slot->pss_barrierGeneration);
+		curgen = pg_atomic_read_u64(&ProcSignal->psh_barrierGeneration);
+		return (mygen != curgen);
+	}
+
+	return false;
+}
+
 /*
  * procsignal_sigusr1_handler - handle SIGUSR1 signal.
  */
@@ -291,6 +552,12 @@ procsignal_sigusr1_handler(SIGNAL_ARGS)
 	if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN))
 		RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN);
 
+	if (CheckProcSignalBarrier())
+	{
+		InterruptPending = true;
+		ProcSignalBarrierPending = true;
+	}
+
 	SetLatch(MyLatch);
 
 	latch_sigusr1_handler();
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index d894c3ddf4..25e22bd63b 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -3162,6 +3162,9 @@ ProcessInterrupts(void)
 
 	}
 
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
+
 	if (ParallelMessagePending)
 		HandleParallelMessages();
 }
diff --git a/src/backend/utils/init/globals.c b/src/backend/utils/init/globals.c
index 4473e18e53..3a091022e2 100644
--- a/src/backend/utils/init/globals.c
+++ b/src/backend/utils/init/globals.c
@@ -32,6 +32,7 @@ volatile sig_atomic_t QueryCancelPending = false;
 volatile sig_atomic_t ProcDiePending = false;
 volatile sig_atomic_t ClientConnectionLost = false;
 volatile sig_atomic_t IdleInTransactionSessionTimeoutPending = false;
+volatile sig_atomic_t ProcSignalBarrierPending = false;
 volatile uint32 InterruptHoldoffCount = 0;
 volatile uint32 QueryCancelHoldoffCount = 0;
 volatile uint32 CritSectionCount = 0;
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index 24f43ad686..ed80f1d668 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -82,6 +82,7 @@ extern PGDLLIMPORT volatile sig_atomic_t InterruptPending;
 extern PGDLLIMPORT volatile sig_atomic_t QueryCancelPending;
 extern PGDLLIMPORT volatile sig_atomic_t ProcDiePending;
 extern PGDLLIMPORT volatile sig_atomic_t IdleInTransactionSessionTimeoutPending;
+extern PGDLLIMPORT volatile sig_atomic_t ProcSignalBarrierPending;
 
 extern PGDLLIMPORT volatile sig_atomic_t ClientConnectionLost;
 
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index fe076d823d..f2e873d048 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -908,6 +908,7 @@ typedef enum
 	WAIT_EVENT_LOGICAL_REWRITE_SYNC,
 	WAIT_EVENT_LOGICAL_REWRITE_TRUNCATE,
 	WAIT_EVENT_LOGICAL_REWRITE_WRITE,
+	WAIT_EVENT_PROC_SIGNAL_BARRIER,
 	WAIT_EVENT_RELATION_MAP_READ,
 	WAIT_EVENT_RELATION_MAP_SYNC,
 	WAIT_EVENT_RELATION_MAP_WRITE,
diff --git a/src/include/storage/procsignal.h b/src/include/storage/procsignal.h
index 05b186a05c..90eda29d15 100644
--- a/src/include/storage/procsignal.h
+++ b/src/include/storage/procsignal.h
@@ -45,6 +45,11 @@ typedef enum
 	NUM_PROCSIGNALS				/* Must be last! */
 } ProcSignalReason;
 
+typedef enum
+{
+	PROCSIGNAL_BARRIER_SAMPLE = 0
+} ProcSignalBarrierType;
+
 /*
  * prototypes for functions in procsignal.c
  */
@@ -55,6 +60,10 @@ extern void ProcSignalInit(int pss_idx);
 extern int	SendProcSignal(pid_t pid, ProcSignalReason reason,
 						   BackendId backendId);
 
+extern uint64 EmitProcSignalBarrier(ProcSignalBarrierType type);
+extern void WaitForProcSignalBarrier(uint64 generation);
+extern void ProcessProcSignalBarrier(void);
+
 extern void procsignal_sigusr1_handler(SIGNAL_ARGS);
 
 #endif							/* PROCSIGNAL_H */
-- 
2.17.2 (Apple Git-113)

From cd84336070bb3246360678cd79457327df3808a0 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Wed, 27 Nov 2019 11:19:37 -0500
Subject: [PATCH v3 3/5] 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.
---
 src/backend/postmaster/Makefile            |   1 +
 src/backend/postmaster/autovacuum.c        |  29 ++----
 src/backend/postmaster/bgworker.c          |  25 +----
 src/backend/postmaster/bgwriter.c          |  93 +-----------------
 src/backend/postmaster/checkpointer.c      |  60 ++----------
 src/backend/postmaster/interrupt.c         | 108 +++++++++++++++++++++
 src/backend/postmaster/pgarch.c            |  29 +-----
 src/backend/postmaster/pgstat.c            |  28 ++----
 src/backend/postmaster/startup.c           |  34 +------
 src/backend/postmaster/walwriter.c         |  84 ++--------------
 src/backend/replication/logical/launcher.c |   3 +-
 src/backend/replication/logical/worker.c   |   3 +-
 src/backend/replication/walreceiver.c      |  31 +-----
 src/backend/replication/walsender.c        |   4 +-
 src/backend/tcop/postgres.c                |  22 +----
 src/backend/utils/init/globals.c           |   1 -
 src/include/miscadmin.h                    |   3 -
 src/include/postmaster/interrupt.h         |  32 ++++++
 18 files changed, 191 insertions(+), 399 deletions(-)
 create mode 100644 src/backend/postmaster/interrupt.c
 create mode 100644 src/include/postmaster/interrupt.h

diff --git a/src/backend/postmaster/Makefile b/src/backend/postmaster/Makefile
index 03e3d3650a..bfdf6a833d 100644
--- a/src/backend/postmaster/Makefile
+++ b/src/backend/postmaster/Makefile
@@ -18,6 +18,7 @@ OBJS = \
 	bgwriter.o \
 	checkpointer.o \
 	fork_process.o \
+	interrupt.o \
 	pgarch.o \
 	pgstat.o \
 	postmaster.o \
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index b1c2b0a01c..1792008ebe 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/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
diff --git a/src/backend/postmaster/bgworker.c b/src/backend/postmaster/bgworker.c
index 5f8a007e73..a4c347d524 100644
--- a/src/backend/postmaster/bgworker.c
+++ b/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);
diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c
index bca46de6d5..9cc343b74f 100644
--- a/src/backend/postmaster/bgwriter.c
+++ b/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;
-}
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index 9cf91b0d35..3f35b324c3 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -36,10 +36,7 @@
  */
 #include "postgres.h"
 
-#include <signal.h>
 #include <sys/time.h>
-#include <time.h>
-#include <unistd.h>
 
 #include "access/xlog.h"
 #include "access/xlog_internal.h"
@@ -47,6 +44,7 @@
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "postmaster/bgwriter.h"
+#include "postmaster/interrupt.h"
 #include "replication/syncrep.h"
 #include "storage/bufmgr.h"
 #include "storage/condition_variable.h"
@@ -148,11 +146,6 @@ int			CheckPointTimeout = 300;
 int			CheckPointWarning = 30;
 double		CheckPointCompletionTarget = 0.5;
 
-/*
- * Flags set by interrupt handlers for later service in the main loop.
- */
-static volatile sig_atomic_t shutdown_requested = false;
-
 /*
  * Private state
  */
@@ -176,10 +169,7 @@ static bool CompactCheckpointerRequestQueue(void);
 static void UpdateSharedMemoryConfig(void);
 
 /* Signal handlers */
-
-static void chkpt_quickdie(SIGNAL_ARGS);
 static void ReqCheckpointHandler(SIGNAL_ARGS);
-static void ReqShutdownHandler(SIGNAL_ARGS);
 
 
 /*
@@ -204,14 +194,14 @@ CheckpointerMain(void)
 	 * want to wait for the backends to exit, whereupon the postmaster will
 	 * tell us it's okay to shut down (via SIGUSR2).
 	 */
-	pqsignal(SIGHUP, PostgresSigHupHandler);	/* set flag to read config file */
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
 	pqsignal(SIGINT, ReqCheckpointHandler); /* request checkpoint */
 	pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */
-	pqsignal(SIGQUIT, chkpt_quickdie);	/* hard crash time */
+	pqsignal(SIGQUIT, SignalHandlerForCrashExit);
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
-	pqsignal(SIGUSR2, ReqShutdownHandler);	/* request shutdown */
+	pqsignal(SIGUSR2, SignalHandlerForShutdownRequest);
 
 	/*
 	 * Reset some signals that are accepted by postmaster but not here
@@ -551,7 +541,7 @@ HandleCheckpointerInterrupts(void)
 		 */
 		UpdateSharedMemoryConfig();
 	}
-	if (shutdown_requested)
+	if (ShutdownRequestPending)
 	{
 		/*
 		 * From here on, elog(ERROR) should end with exit(1), not send
@@ -679,7 +669,7 @@ CheckpointWriteDelay(int flags, double progress)
 	 * in which case we just try to catch up as quickly as possible.
 	 */
 	if (!(flags & CHECKPOINT_IMMEDIATE) &&
-		!shutdown_requested &&
+		!ShutdownRequestPending &&
 		!ImmediateCheckpointRequested() &&
 		IsCheckpointOnSchedule(progress))
 	{
@@ -807,32 +797,6 @@ IsCheckpointOnSchedule(double progress)
  * --------------------------------
  */
 
-/*
- * chkpt_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
-chkpt_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);
-}
-
 /* SIGINT: set flag to run a normal checkpoint right away */
 static void
 ReqCheckpointHandler(SIGNAL_ARGS)
@@ -848,18 +812,6 @@ ReqCheckpointHandler(SIGNAL_ARGS)
 	errno = save_errno;
 }
 
-/* SIGUSR2: set flag to run a shutdown checkpoint and exit */
-static void
-ReqShutdownHandler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	shutdown_requested = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 
 /* --------------------------------
  *		communication with backends
diff --git a/src/backend/postmaster/interrupt.c b/src/backend/postmaster/interrupt.c
new file mode 100644
index 0000000000..6900cd02f6
--- /dev/null
+++ b/src/backend/postmaster/interrupt.c
@@ -0,0 +1,108 @@
+/*-------------------------------------------------------------------------
+ *
+ * interrupt.c
+ *	  Interrupt handling routines.
+ *
+ * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  src/backend/postmaster/interrupt.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <unistd.h>
+
+#include "miscadmin.h"
+#include "postmaster/interrupt.h"
+#include "storage/ipc.h"
+#include "storage/latch.h"
+#include "utils/guc.h"
+
+volatile sig_atomic_t ConfigReloadPending = false;
+volatile sig_atomic_t ShutdownRequestPending = false;
+
+/*
+ * Simple interrupt handler for main loops of background processes.
+ */
+void
+HandleMainLoopInterrupts(void)
+{
+	if (ConfigReloadPending)
+	{
+		ConfigReloadPending = false;
+		ProcessConfigFile(PGC_SIGHUP);
+	}
+
+	if (ShutdownRequestPending)
+		proc_exit(0);
+}
+
+/*
+ * Simple signal handler for triggering a configuration reload.
+ *
+ * Normally, this handler would be used for SIGHUP. The idea is that code
+ * which uses it would arrange to check the ConfigReloadPending flag at
+ * convenient places inside main loops, or else call HandleMainLoopInterrupts.
+ */
+void
+SignalHandlerForConfigReload(SIGNAL_ARGS)
+{
+	int			save_errno = errno;
+
+	ConfigReloadPending = true;
+	SetLatch(MyLatch);
+
+	errno = save_errno;
+}
+
+/*
+ * Simple signal handler for exiting quickly as if due to a crash.
+ *
+ * Normally, this would be used for handling SIGQUIT.
+ */
+void
+SignalHandlerForCrashExit(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);
+}
+
+/*
+ * Simple signal handler for triggering a long-running background process to
+ * shut down and exit.
+ *
+ * Typically, this handler would be used for SIGTERM, but some procesess use
+ * other signals. In particular, the checkpointer exits on SIGUSR2, the
+ * stats collector on SIGQUIT, and the WAL writer exits on either SIGINT
+ * or SIGTERM.
+ *
+ * ShutdownRequestPending should be checked at a convenient place within the
+ * main loop, or else the main loop should call HandleMainLoopInterrupts.
+ */
+void
+SignalHandlerForShutdownRequest(SIGNAL_ARGS)
+{
+	int			save_errno = errno;
+
+	ShutdownRequestPending = true;
+	SetLatch(MyLatch);
+
+	errno = save_errno;
+}
diff --git a/src/backend/postmaster/pgarch.c b/src/backend/postmaster/pgarch.c
index 09a9c66b4b..7824180ac7 100644
--- a/src/backend/postmaster/pgarch.c
+++ b/src/backend/postmaster/pgarch.c
@@ -39,6 +39,7 @@
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "postmaster/fork_process.h"
+#include "postmaster/interrupt.h"
 #include "postmaster/pgarch.h"
 #include "postmaster/postmaster.h"
 #include "storage/dsm.h"
@@ -83,7 +84,6 @@ static time_t last_sigterm_time = 0;
 /*
  * Flags set by interrupt handlers for later service in the main loop.
  */
-static volatile sig_atomic_t got_SIGTERM = false;
 static volatile sig_atomic_t wakened = false;
 static volatile sig_atomic_t ready_to_stop = false;
 
@@ -97,7 +97,6 @@ static pid_t pgarch_forkexec(void);
 
 NON_EXEC_STATIC void PgArchiverMain(int argc, char *argv[]) pg_attribute_noreturn();
 static void pgarch_exit(SIGNAL_ARGS);
-static void ArchSigTermHandler(SIGNAL_ARGS);
 static void pgarch_waken(SIGNAL_ARGS);
 static void pgarch_waken_stop(SIGNAL_ARGS);
 static void pgarch_MainLoop(void);
@@ -227,9 +226,9 @@ PgArchiverMain(int argc, char *argv[])
 	 * Ignore all signals usually bound to some action in the postmaster,
 	 * except for SIGHUP, SIGTERM, SIGUSR1, SIGUSR2, and SIGQUIT.
 	 */
-	pqsignal(SIGHUP, PostgresSigHupHandler);
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
 	pqsignal(SIGINT, SIG_IGN);
-	pqsignal(SIGTERM, ArchSigTermHandler);
+	pqsignal(SIGTERM, SignalHandlerForShutdownRequest);
 	pqsignal(SIGQUIT, pgarch_exit);
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
@@ -257,24 +256,6 @@ pgarch_exit(SIGNAL_ARGS)
 	exit(1);
 }
 
-/* SIGTERM signal handler for archiver process */
-static void
-ArchSigTermHandler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	/*
-	 * The postmaster never sends us SIGTERM, so we assume that this means
-	 * that init is trying to shut down the whole system.  If we hang around
-	 * too long we'll get SIGKILL'd.  Set flag to prevent starting any more
-	 * archive commands.
-	 */
-	got_SIGTERM = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /* SIGUSR1 signal handler for archiver process */
 static void
 pgarch_waken(SIGNAL_ARGS)
@@ -346,7 +327,7 @@ pgarch_MainLoop(void)
 		 * idea.  If more than 60 seconds pass since SIGTERM, exit anyway, so
 		 * that the postmaster can start a new archiver if needed.
 		 */
-		if (got_SIGTERM)
+		if (ShutdownRequestPending)
 		{
 			time_t		curtime = time(NULL);
 
@@ -434,7 +415,7 @@ pgarch_ArchiverCopyLoop(void)
 			 * command, and the second is to avoid conflicts with another
 			 * archiver spawned by a newer postmaster.
 			 */
-			if (got_SIGTERM || !PostmasterIsAlive())
+			if (ShutdownRequestPending || !PostmasterIsAlive())
 				return;
 
 			/*
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index 96a9e09ced..e931512203 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -49,6 +49,7 @@
 #include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "postmaster/fork_process.h"
+#include "postmaster/interrupt.h"
 #include "postmaster/postmaster.h"
 #include "replication/walsender.h"
 #include "storage/backendid.h"
@@ -262,9 +263,6 @@ static PgStat_GlobalStats globalStats;
  */
 static List *pending_write_requests = NIL;
 
-/* Signal handler flags */
-static volatile bool need_exit = false;
-
 /*
  * Total time charged to functions so far in the current backend.
  * We use this to help separate "self" and "other" time charges.
@@ -282,7 +280,6 @@ static pid_t pgstat_forkexec(void);
 #endif
 
 NON_EXEC_STATIC void PgstatCollectorMain(int argc, char *argv[]) pg_attribute_noreturn();
-static void pgstat_exit(SIGNAL_ARGS);
 static void pgstat_beshutdown_hook(int code, Datum arg);
 
 static PgStat_StatDBEntry *pgstat_get_db_entry(Oid databaseid, bool create);
@@ -4432,10 +4429,10 @@ PgstatCollectorMain(int argc, char *argv[])
 	 * except SIGHUP and SIGQUIT.  Note we don't need a SIGUSR1 handler to
 	 * support latch operations, because we only use a local latch.
 	 */
-	pqsignal(SIGHUP, PostgresSigHupHandler);
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
 	pqsignal(SIGINT, SIG_IGN);
 	pqsignal(SIGTERM, SIG_IGN);
-	pqsignal(SIGQUIT, pgstat_exit);
+	pqsignal(SIGQUIT, SignalHandlerForShutdownRequest);
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, SIG_IGN);
@@ -4477,14 +4474,14 @@ PgstatCollectorMain(int argc, char *argv[])
 		/*
 		 * Quit if we get SIGQUIT from the postmaster.
 		 */
-		if (need_exit)
+		if (ShutdownRequestPending)
 			break;
 
 		/*
 		 * Inner loop iterates as long as we keep getting messages, or until
-		 * need_exit becomes set.
+		 * ShutdownRequestPending becomes set.
 		 */
-		while (!need_exit)
+		while (!ShutdownRequestPending)
 		{
 			/*
 			 * Reload configuration if we got SIGHUP from the postmaster.
@@ -4676,19 +4673,6 @@ PgstatCollectorMain(int argc, char *argv[])
 	exit(0);
 }
 
-
-/* SIGQUIT signal handler for collector process */
-static void
-pgstat_exit(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	need_exit = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /*
  * Subroutine to clear stats in a database entry
  *
diff --git a/src/backend/postmaster/startup.c b/src/backend/postmaster/startup.c
index f43e57dadb..4f59c71f73 100644
--- a/src/backend/postmaster/startup.c
+++ b/src/backend/postmaster/startup.c
@@ -19,13 +19,11 @@
  */
 #include "postgres.h"
 
-#include <signal.h>
-#include <unistd.h>
-
 #include "access/xlog.h"
 #include "libpq/pqsignal.h"
 #include "miscadmin.h"
 #include "pgstat.h"
+#include "postmaster/interrupt.h"
 #include "postmaster/startup.h"
 #include "storage/ipc.h"
 #include "storage/latch.h"
@@ -50,7 +48,6 @@ static volatile sig_atomic_t promote_triggered = false;
 static volatile sig_atomic_t in_restore_command = false;
 
 /* Signal handlers */
-static void startupproc_quickdie(SIGNAL_ARGS);
 static void StartupProcTriggerHandler(SIGNAL_ARGS);
 static void StartupProcSigHupHandler(SIGNAL_ARGS);
 
@@ -60,33 +57,6 @@ static void StartupProcSigHupHandler(SIGNAL_ARGS);
  * --------------------------------
  */
 
-/*
- * startupproc_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
-startupproc_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);
-}
-
-
 /* SIGUSR2: set flag to finish recovery */
 static void
 StartupProcTriggerHandler(SIGNAL_ARGS)
@@ -167,7 +137,7 @@ StartupProcessMain(void)
 	pqsignal(SIGHUP, StartupProcSigHupHandler); /* reload config file */
 	pqsignal(SIGINT, SIG_IGN);	/* ignore query cancel */
 	pqsignal(SIGTERM, StartupProcShutdownHandler);	/* request shutdown */
-	pqsignal(SIGQUIT, startupproc_quickdie);	/* hard crash time */
+	pqsignal(SIGQUIT, SignalHandlerForCrashExit);
 	InitializeTimeouts();		/* establishes SIGALRM handler */
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
diff --git a/src/backend/postmaster/walwriter.c b/src/backend/postmaster/walwriter.c
index 599478530f..38e9eb1304 100644
--- a/src/backend/postmaster/walwriter.c
+++ b/src/backend/postmaster/walwriter.c
@@ -48,6 +48,7 @@
 #include "libpq/pqsignal.h"
 #include "miscadmin.h"
 #include "pgstat.h"
+#include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
 #include "storage/bufmgr.h"
 #include "storage/condition_variable.h"
@@ -77,17 +78,6 @@ int			WalWriterFlushAfter = 128;
 #define LOOPS_UNTIL_HIBERNATE		50
 #define HIBERNATE_FACTOR			25
 
-/*
- * Flags set by interrupt handlers for later service in the main loop.
- */
-static volatile sig_atomic_t shutdown_requested = false;
-
-static void HandleWalWriterInterrupts(void);
-
-/* Signal handlers */
-static void wal_quickdie(SIGNAL_ARGS);
-static void WalShutdownHandler(SIGNAL_ARGS);
-
 /*
  * Main entry point for walwriter process
  *
@@ -108,10 +98,10 @@ WalWriterMain(void)
 	 * We have no particular use for SIGINT at the moment, but seems
 	 * reasonable to treat like SIGTERM.
 	 */
-	pqsignal(SIGHUP, PostgresSigHupHandler); /* set flag to read config file */
-	pqsignal(SIGINT, WalShutdownHandler);	/* request shutdown */
-	pqsignal(SIGTERM, WalShutdownHandler);	/* request shutdown */
-	pqsignal(SIGQUIT, wal_quickdie);	/* hard crash time */
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
+	pqsignal(SIGINT, SignalHandlerForShutdownRequest);
+	pqsignal(SIGTERM, SignalHandlerForShutdownRequest);
+	pqsignal(SIGQUIT, SignalHandlerForCrashExit);
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
@@ -242,7 +232,7 @@ WalWriterMain(void)
 		/* Clear any already-pending wakeups */
 		ResetLatch(MyLatch);
 
-		HandleWalWriterInterrupts();
+		HandleMainLoopInterrupts();
 
 		/*
 		 * Do what we're here for; then, if XLogBackgroundFlush() found useful
@@ -269,65 +259,3 @@ WalWriterMain(void)
 						 WAIT_EVENT_WAL_WRITER_MAIN);
 	}
 }
-
-/*
- * Process any new interrupts.
- */
-static void
-HandleWalWriterInterrupts(void)
-{
-	if (ConfigReloadPending)
-	{
-		ConfigReloadPending = false;
-		ProcessConfigFile(PGC_SIGHUP);
-	}
-	if (shutdown_requested)
-	{
-		/* Normal exit from the walwriter is here */
-		proc_exit(0);		/* done */
-	}
-}
-
-
-/* --------------------------------
- *		signal handler routines
- * --------------------------------
- */
-
-/*
- * wal_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
-wal_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 exit normally */
-static void
-WalShutdownHandler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	shutdown_requested = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
diff --git a/src/backend/replication/logical/launcher.c b/src/backend/replication/logical/launcher.c
index edca70c58c..99cfa5d8b4 100644
--- a/src/backend/replication/logical/launcher.c
+++ b/src/backend/replication/logical/launcher.c
@@ -30,6 +30,7 @@
 #include "pgstat.h"
 #include "postmaster/bgworker.h"
 #include "postmaster/fork_process.h"
+#include "postmaster/interrupt.h"
 #include "postmaster/postmaster.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalworker.h"
@@ -955,7 +956,7 @@ ApplyLauncherMain(Datum main_arg)
 	LogicalRepCtx->launcher_pid = MyProcPid;
 
 	/* Establish signal handlers. */
-	pqsignal(SIGTERM, PostgresSigHupHandler);
+	pqsignal(SIGTERM, SignalHandlerForConfigReload);
 	pqsignal(SIGTERM, die);
 	BackgroundWorkerUnblockSignals();
 
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 3b12ad6400..4bf6f5e427 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -45,6 +45,7 @@
 #include "parser/parse_relation.h"
 #include "pgstat.h"
 #include "postmaster/bgworker.h"
+#include "postmaster/interrupt.h"
 #include "postmaster/postmaster.h"
 #include "postmaster/walwriter.h"
 #include "replication/decode.h"
@@ -1575,7 +1576,7 @@ ApplyWorkerMain(Datum main_arg)
 	logicalrep_worker_attach(worker_slot);
 
 	/* Setup signal handling */
-	pqsignal(SIGHUP, PostgresSigHupHandler);
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
 	pqsignal(SIGTERM, die);
 	BackgroundWorkerUnblockSignals();
 
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index c1e439adb4..c36bcc08ec 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -43,7 +43,6 @@
  */
 #include "postgres.h"
 
-#include <signal.h>
 #include <unistd.h>
 
 #include "access/htup_details.h"
@@ -58,6 +57,7 @@
 #include "libpq/pqsignal.h"
 #include "miscadmin.h"
 #include "pgstat.h"
+#include "postmaster/interrupt.h"
 #include "replication/walreceiver.h"
 #include "replication/walsender.h"
 #include "storage/ipc.h"
@@ -127,7 +127,6 @@ static void ProcessWalSndrMessage(XLogRecPtr walEnd, TimestampTz sendTime);
 /* Signal handlers */
 static void WalRcvSigHupHandler(SIGNAL_ARGS);
 static void WalRcvShutdownHandler(SIGNAL_ARGS);
-static void WalRcvQuickDieHandler(SIGNAL_ARGS);
 
 
 /*
@@ -249,7 +248,7 @@ WalReceiverMain(void)
 	pqsignal(SIGHUP, WalRcvSigHupHandler);	/* set flag to read config file */
 	pqsignal(SIGINT, SIG_IGN);
 	pqsignal(SIGTERM, WalRcvShutdownHandler);	/* request shutdown */
-	pqsignal(SIGQUIT, WalRcvQuickDieHandler);	/* hard crash time */
+	pqsignal(SIGQUIT, SignalHandlerForCrashExit);
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
@@ -780,32 +779,6 @@ WalRcvShutdownHandler(SIGNAL_ARGS)
 	errno = save_errno;
 }
 
-/*
- * WalRcvQuickDieHandler() 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
-WalRcvQuickDieHandler(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 use _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);
-}
-
 /*
  * Accept the message from XLOG stream, and process it.
  */
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 8b2a2be1c0..8e74177de4 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -66,6 +66,7 @@
 #include "miscadmin.h"
 #include "nodes/replnodes.h"
 #include "pgstat.h"
+#include "postmaster/interrupt.h"
 #include "replication/basebackup.h"
 #include "replication/decode.h"
 #include "replication/logical.h"
@@ -2969,8 +2970,7 @@ void
 WalSndSignals(void)
 {
 	/* Set up signal handlers */
-	pqsignal(SIGHUP, PostgresSigHupHandler);	/* set flag to read config
-												 * file */
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
 	pqsignal(SIGINT, StatementCancelHandler);	/* query cancel */
 	pqsignal(SIGTERM, die);		/* request shutdown */
 	pqsignal(SIGQUIT, quickdie);	/* hard crash time */
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 3b85e48333..d894c3ddf4 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -57,6 +57,7 @@
 #include "pg_trace.h"
 #include "pgstat.h"
 #include "postmaster/autovacuum.h"
+#include "postmaster/interrupt.h"
 #include "postmaster/postmaster.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalworker.h"
@@ -2843,24 +2844,6 @@ FloatExceptionHandler(SIGNAL_ARGS)
 					   "invalid operation, such as division by zero.")));
 }
 
-/*
- * SIGHUP: set flag to re-read config file at next convenient time.
- *
- * Sets the ConfigReloadPending flag, which should be checked at convenient
- * places inside main loops. (Better than doing the reading in the signal
- * handler, ey?)
- */
-void
-PostgresSigHupHandler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	ConfigReloadPending = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /*
  * RecoveryConflictInterrupt: out-of-line portion of recovery conflict
  * handling following receipt of SIGUSR1. Designed to be similar to die()
@@ -3809,8 +3792,7 @@ PostgresMain(int argc, char *argv[],
 		WalSndSignals();
 	else
 	{
-		pqsignal(SIGHUP, PostgresSigHupHandler);	/* set flag to read config
-													 * file */
+		pqsignal(SIGHUP, SignalHandlerForConfigReload);
 		pqsignal(SIGINT, StatementCancelHandler);	/* cancel current query */
 		pqsignal(SIGTERM, die); /* cancel current query and exit */
 
diff --git a/src/backend/utils/init/globals.c b/src/backend/utils/init/globals.c
index 3bf96de256..4473e18e53 100644
--- a/src/backend/utils/init/globals.c
+++ b/src/backend/utils/init/globals.c
@@ -32,7 +32,6 @@ volatile sig_atomic_t QueryCancelPending = false;
 volatile sig_atomic_t ProcDiePending = false;
 volatile sig_atomic_t ClientConnectionLost = false;
 volatile sig_atomic_t IdleInTransactionSessionTimeoutPending = false;
-volatile sig_atomic_t ConfigReloadPending = false;
 volatile uint32 InterruptHoldoffCount = 0;
 volatile uint32 QueryCancelHoldoffCount = 0;
 volatile uint32 CritSectionCount = 0;
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index bc6e03fbc7..24f43ad686 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -82,7 +82,6 @@ extern PGDLLIMPORT volatile sig_atomic_t InterruptPending;
 extern PGDLLIMPORT volatile sig_atomic_t QueryCancelPending;
 extern PGDLLIMPORT volatile sig_atomic_t ProcDiePending;
 extern PGDLLIMPORT volatile sig_atomic_t IdleInTransactionSessionTimeoutPending;
-extern PGDLLIMPORT volatile sig_atomic_t ConfigReloadPending;
 
 extern PGDLLIMPORT volatile sig_atomic_t ClientConnectionLost;
 
@@ -279,8 +278,6 @@ extern void restore_stack_base(pg_stack_base_t base);
 extern void check_stack_depth(void);
 extern bool stack_is_too_deep(void);
 
-extern void PostgresSigHupHandler(SIGNAL_ARGS);
-
 /* in tcop/utility.c */
 extern void PreventCommandIfReadOnly(const char *cmdname);
 extern void PreventCommandIfParallelMode(const char *cmdname);
diff --git a/src/include/postmaster/interrupt.h b/src/include/postmaster/interrupt.h
new file mode 100644
index 0000000000..8f4e43be20
--- /dev/null
+++ b/src/include/postmaster/interrupt.h
@@ -0,0 +1,32 @@
+/*-------------------------------------------------------------------------
+ *
+ * interrupt.h
+ *	  Interrupt handling routines.
+ *
+ * Responses to interrupts are fairly varied and many types of backends
+ * have their own implementations, but we provide a few generic things
+ * here to facilitate code reuse.
+ *
+ * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  src/include/postmaster/interrupt.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef INTERRUPT_H
+#define INTERRUPT_H
+
+#include <signal.h>
+
+extern PGDLLIMPORT volatile sig_atomic_t ConfigReloadPending;
+extern PGDLLIMPORT volatile sig_atomic_t ShutdownRequestPending;
+
+extern void HandleMainLoopInterrupts(void);
+extern void SignalHandlerForConfigReload(SIGNAL_ARGS);
+extern void SignalHandlerForCrashExit(SIGNAL_ARGS);
+extern void SignalHandlerForShutdownRequest(SIGNAL_ARGS);
+
+#endif
-- 
2.17.2 (Apple Git-113)

From f314b81c8c8e55326ccd095f8849a6ab91fa9004 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Wed, 27 Nov 2019 11:29:25 -0500
Subject: [PATCH v3 4/5] Extend the ProcSignal mechanism to support barriers.

A new function EmitProcSignalBarrier() can be used to emit a global
barrier which all backends that participate in the ProcSignal
mechanism must absorb, and a new function WaitForProcSignalBarrier()
can be used to wait until all relevant backends have in fact
absorbed the barrier.

This can be used to coordinate global state changes, such as turning
checksums on while the system is running.

Andres Freund and Robert Haas
---
 doc/src/sgml/monitoring.sgml          |   4 +
 src/backend/postmaster/autovacuum.c   |   4 +
 src/backend/postmaster/checkpointer.c |   7 +
 src/backend/postmaster/interrupt.c    |   4 +
 src/backend/postmaster/pgstat.c       |   3 +
 src/backend/postmaster/startup.c      |   6 +-
 src/backend/replication/walreceiver.c |   3 +-
 src/backend/storage/buffer/bufmgr.c   |  10 +
 src/backend/storage/ipc/procsignal.c  | 298 +++++++++++++++++++++++++-
 src/backend/tcop/postgres.c           |   3 +
 src/backend/utils/init/globals.c      |   1 +
 src/include/miscadmin.h               |   1 +
 src/include/pgstat.h                  |   1 +
 src/include/storage/procsignal.h      |   9 +
 14 files changed, 341 insertions(+), 13 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index a3c5f86b7e..76957c0a43 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -1593,6 +1593,10 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
          <entry><literal>LogicalRewriteWrite</literal></entry>
          <entry>Waiting for a write of logical rewrite mappings.</entry>
         </row>
+        <row>
+         <entry><literal>ProcSignalBarrier</literal></entry>
+         <entry>Waiting for a barrier event to be processed by all backends.</entry>
+        </row>
         <row>
          <entry><literal>RelationMapRead</literal></entry>
          <entry>Waiting for a read of the relation map file.</entry>
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 1792008ebe..52ad99f716 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -820,6 +820,10 @@ HandleAutoVacLauncherInterrupts(void)
 		rebuild_database_list(InvalidOid);
 	}
 
+	/* Process barrier events */
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
+
 	/* Process sinval catchup interrupts that happened while sleeping */
 	ProcessCatchupInterrupt();
 }
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index 3f35b324c3..d1185cc135 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -523,6 +523,9 @@ CheckpointerMain(void)
 static void
 HandleCheckpointerInterrupts(void)
 {
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
+
 	if (ConfigReloadPending)
 	{
 		ConfigReloadPending = false;
@@ -709,6 +712,10 @@ CheckpointWriteDelay(int flags, double progress)
 		AbsorbSyncRequests();
 		absorb_counter = WRITES_PER_ABSORB;
 	}
+
+	/* Check for barrier events. */
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
 }
 
 /*
diff --git a/src/backend/postmaster/interrupt.c b/src/backend/postmaster/interrupt.c
index 6900cd02f6..214ccaf34b 100644
--- a/src/backend/postmaster/interrupt.c
+++ b/src/backend/postmaster/interrupt.c
@@ -20,6 +20,7 @@
 #include "postmaster/interrupt.h"
 #include "storage/ipc.h"
 #include "storage/latch.h"
+#include "storage/procsignal.h"
 #include "utils/guc.h"
 
 volatile sig_atomic_t ConfigReloadPending = false;
@@ -31,6 +32,9 @@ volatile sig_atomic_t ShutdownRequestPending = false;
 void
 HandleMainLoopInterrupts(void)
 {
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
+
 	if (ConfigReloadPending)
 	{
 		ConfigReloadPending = false;
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index e931512203..7410b2ff5e 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -3988,6 +3988,9 @@ pgstat_get_wait_io(WaitEventIO w)
 		case WAIT_EVENT_LOGICAL_REWRITE_WRITE:
 			event_name = "LogicalRewriteWrite";
 			break;
+		case WAIT_EVENT_PROC_SIGNAL_BARRIER:
+			event_name = "ProcSignalBarrier";
+			break;
 		case WAIT_EVENT_RELATION_MAP_READ:
 			event_name = "RelationMapRead";
 			break;
diff --git a/src/backend/postmaster/startup.c b/src/backend/postmaster/startup.c
index 4f59c71f73..11f7052e78 100644
--- a/src/backend/postmaster/startup.c
+++ b/src/backend/postmaster/startup.c
@@ -96,7 +96,7 @@ StartupProcShutdownHandler(SIGNAL_ARGS)
 	errno = save_errno;
 }
 
-/* Handle SIGHUP and SIGTERM signals of startup process */
+/* Handle various signals that might be sent to the startup process */
 void
 HandleStartupProcInterrupts(void)
 {
@@ -121,6 +121,10 @@ HandleStartupProcInterrupts(void)
 	 */
 	if (IsUnderPostmaster && !PostmasterIsAlive())
 		exit(1);
+
+	/* Process barrier events */
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
 }
 
 
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index c36bcc08ec..a4de8a9cd8 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -148,7 +148,8 @@ ProcessWalRcvInterrupts(void)
 	/*
 	 * Although walreceiver interrupt handling doesn't use the same scheme as
 	 * regular backends, call CHECK_FOR_INTERRUPTS() to make sure we receive
-	 * any incoming signals on Win32.
+	 * any incoming signals on Win32, and also to make sure we process any
+	 * barrier events.
 	 */
 	CHECK_FOR_INTERRUPTS();
 
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 7ad10736d5..1f10a97dc7 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -1852,6 +1852,10 @@ BufferSync(int flags)
 		}
 
 		UnlockBufHdr(bufHdr, buf_state);
+
+		/* Check for barrier events in case NBuffers is large. */
+		if (ProcSignalBarrierPending)
+			ProcessProcSignalBarrier();
 	}
 
 	if (num_to_scan == 0)
@@ -1930,6 +1934,10 @@ BufferSync(int flags)
 		}
 
 		s->num_to_scan++;
+
+		/* Check for barrier events. */
+		if (ProcSignalBarrierPending)
+			ProcessProcSignalBarrier();
 	}
 
 	Assert(num_spaces > 0);
@@ -2018,6 +2026,8 @@ BufferSync(int flags)
 
 		/*
 		 * Sleep to throttle our I/O rate.
+		 *
+		 * (This will check for barrier events even if it doesn't sleep.)
 		 */
 		CheckpointWriteDelay(flags, (double) num_processed / num_to_scan);
 	}
diff --git a/src/backend/storage/ipc/procsignal.c b/src/backend/storage/ipc/procsignal.c
index fde97a1036..9399ab0be4 100644
--- a/src/backend/storage/ipc/procsignal.c
+++ b/src/backend/storage/ipc/procsignal.c
@@ -20,6 +20,7 @@
 #include "access/parallel.h"
 #include "commands/async.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "replication/walsender.h"
 #include "storage/ipc.h"
 #include "storage/latch.h"
@@ -45,13 +46,36 @@
  * The flags are actually declared as "volatile sig_atomic_t" for maximum
  * portability.  This should ensure that loads and stores of the flag
  * values are atomic, allowing us to dispense with any explicit locking.
+ *
+ * pss_signalFlags are intended to be set in cases where we don't need to
+ * keep track of whether or not the target process has handled the signal,
+ * but sometimes we need confirmation, as when making a global state change
+ * that cannot be considered complete until all backends have taken notice
+ * of it. For such use cases, we set a bit in pss_barrierCheckMask and then
+ * increment the current "barrier generation"; when the new barrier generation
+ * (or greater) appears in the pss_barrierGeneration flag of every process,
+ * we know that the message has been received everywhere.
  */
 typedef struct
 {
 	pid_t		pss_pid;
 	sig_atomic_t pss_signalFlags[NUM_PROCSIGNALS];
+	pg_atomic_uint64	pss_barrierGeneration;
+	pg_atomic_uint32	pss_barrierCheckMask;
 } ProcSignalSlot;
 
+/*
+ * Information that is global to the entire ProcSignal system can be stored
+ * here.
+ *
+ * psh_barrierGeneration is the highest barrier generation in existence.
+ */
+typedef struct
+{
+	pg_atomic_uint64	psh_barrierGeneration;
+	ProcSignalSlot		psh_slot[FLEXIBLE_ARRAY_MEMBER];
+} ProcSignalHeader;
+
 /*
  * We reserve a slot for each possible BackendId, plus one for each
  * possible auxiliary process type.  (This scheme assumes there is not
@@ -59,11 +83,16 @@ typedef struct
  */
 #define NumProcSignalSlots	(MaxBackends + NUM_AUXPROCTYPES)
 
-static ProcSignalSlot *ProcSignalSlots = NULL;
+/* Check whether the relevant type bit is set in the flags. */
+#define BARRIER_SHOULD_CHECK(flags, type) \
+	(((flags) & (((uint32) 1) << (uint32) (type))) != 0)
+
+static ProcSignalHeader *ProcSignal = NULL;
 static volatile ProcSignalSlot *MyProcSignalSlot = NULL;
 
 static bool CheckProcSignal(ProcSignalReason reason);
 static void CleanupProcSignalState(int status, Datum arg);
+static void ProcessBarrierSample(void);
 
 /*
  * ProcSignalShmemSize
@@ -72,7 +101,11 @@ static void CleanupProcSignalState(int status, Datum arg);
 Size
 ProcSignalShmemSize(void)
 {
-	return NumProcSignalSlots * sizeof(ProcSignalSlot);
+	Size	size;
+
+	size = mul_size(NumProcSignalSlots, sizeof(ProcSignalSlot));
+	size = add_size(size, offsetof(ProcSignalHeader, psh_slot));
+	return size;
 }
 
 /*
@@ -85,12 +118,26 @@ ProcSignalShmemInit(void)
 	Size		size = ProcSignalShmemSize();
 	bool		found;
 
-	ProcSignalSlots = (ProcSignalSlot *)
-		ShmemInitStruct("ProcSignalSlots", size, &found);
+	ProcSignal = (ProcSignalHeader *)
+		ShmemInitStruct("ProcSignal", size, &found);
 
-	/* If we're first, set everything to zeroes */
+	/* If we're first, initialize. */
 	if (!found)
-		MemSet(ProcSignalSlots, 0, size);
+	{
+		int		i;
+
+		pg_atomic_init_u64(&ProcSignal->psh_barrierGeneration, 0);
+
+		for (i = 0; i < NumProcSignalSlots; ++i)
+		{
+			ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
+
+			slot->pss_pid = 0;
+			MemSet(slot->pss_signalFlags, 0, sizeof(slot->pss_signalFlags));
+			pg_atomic_init_u64(&slot->pss_barrierGeneration, PG_UINT64_MAX);
+			pg_atomic_init_u32(&slot->pss_barrierCheckMask, 0);
+		}
+	}
 }
 
 /*
@@ -104,10 +151,11 @@ void
 ProcSignalInit(int pss_idx)
 {
 	volatile ProcSignalSlot *slot;
+	uint64		barrier_generation;
 
 	Assert(pss_idx >= 1 && pss_idx <= NumProcSignalSlots);
 
-	slot = &ProcSignalSlots[pss_idx - 1];
+	slot = &ProcSignal->psh_slot[pss_idx - 1];
 
 	/* sanity check */
 	if (slot->pss_pid != 0)
@@ -117,6 +165,23 @@ ProcSignalInit(int pss_idx)
 	/* Clear out any leftover signal reasons */
 	MemSet(slot->pss_signalFlags, 0, NUM_PROCSIGNALS * sizeof(sig_atomic_t));
 
+	/*
+	 * Initialize barrier state. Since we're a brand-new process, there
+	 * shouldn't be any leftover backend-private state that needs to be
+	 * updated. Therefore, we can broadcast the latest barrier generation
+	 * and disregard any previously-set check bits.
+	 *
+	 * NB: This only works if this initialization happens early enough in the
+	 * startup sequence that we haven't yet cached any state that might need
+	 * to be invalidated. That's also why we have a memory barrier here, to
+	 * be sure that any later reads of memory happen strictly after this.
+	 */
+	pg_atomic_write_u32(&slot->pss_barrierCheckMask, 0);
+	barrier_generation =
+		pg_atomic_read_u64(&ProcSignal->psh_barrierGeneration);
+	pg_atomic_write_u64(&slot->pss_barrierGeneration, barrier_generation);
+	pg_memory_barrier();
+
 	/* Mark slot with my PID */
 	slot->pss_pid = MyProcPid;
 
@@ -129,7 +194,7 @@ ProcSignalInit(int pss_idx)
 
 /*
  * CleanupProcSignalState
- *		Remove current process from ProcSignalSlots
+ *		Remove current process from ProcSignal mechanism
  *
  * This function is called via on_shmem_exit() during backend shutdown.
  */
@@ -139,7 +204,7 @@ CleanupProcSignalState(int status, Datum arg)
 	int			pss_idx = DatumGetInt32(arg);
 	volatile ProcSignalSlot *slot;
 
-	slot = &ProcSignalSlots[pss_idx - 1];
+	slot = &ProcSignal->psh_slot[pss_idx - 1];
 	Assert(slot == MyProcSignalSlot);
 
 	/*
@@ -161,6 +226,12 @@ CleanupProcSignalState(int status, Datum arg)
 		return;					/* XXX better to zero the slot anyway? */
 	}
 
+	/*
+	 * Make this slot look like it's absorbed all possible barriers, so that
+	 * no barrier waits block on it.
+	 */
+	pg_atomic_write_u64(&slot->pss_barrierGeneration, PG_UINT64_MAX);
+
 	slot->pss_pid = 0;
 }
 
@@ -182,7 +253,7 @@ SendProcSignal(pid_t pid, ProcSignalReason reason, BackendId backendId)
 
 	if (backendId != InvalidBackendId)
 	{
-		slot = &ProcSignalSlots[backendId - 1];
+		slot = &ProcSignal->psh_slot[backendId - 1];
 
 		/*
 		 * Note: Since there's no locking, it's possible that the target
@@ -212,7 +283,7 @@ SendProcSignal(pid_t pid, ProcSignalReason reason, BackendId backendId)
 
 		for (i = NumProcSignalSlots - 1; i >= 0; i--)
 		{
-			slot = &ProcSignalSlots[i];
+			slot = &ProcSignal->psh_slot[i];
 
 			if (slot->pss_pid == pid)
 			{
@@ -230,6 +301,184 @@ SendProcSignal(pid_t pid, ProcSignalReason reason, BackendId backendId)
 	return -1;
 }
 
+/*
+ * EmitProcSignalBarrier
+ *		Send a signal to every Postgres process
+ *
+ * The return value of this function is the barrier "generation" created
+ * by this operation. This value can be passed to WaitForProcSignalBarrier
+ * to wait until it is known that every participant in the ProcSignal
+ * mechanism has absorbed the signal (or started afterwards).
+ *
+ * Note that it would be a bad idea to use this for anything that happens
+ * frequently, as interrupting every backend could cause a noticeable
+ * performance hit.
+ *
+ * Callers are entitled to assume that this function will not throw ERROR
+ * or FATAL.
+ */
+uint64
+EmitProcSignalBarrier(ProcSignalBarrierType type)
+{
+	uint64	flagbit = UINT64CONST(1) << (uint64) type;
+	uint64	generation;
+
+	/*
+	 * Set all the flags.
+	 *
+	 * Note that pg_atomic_fetch_or_u32 has full barrier semantics, so this
+	 * is totally ordered with respect to anything the caller did before, and
+	 * anything that we do afterwards. (This is also true of the later call
+	 * to pg_atomic_add_fetch_u64.)
+	 */
+	for (int i = 0; i < NumProcSignalSlots; i++)
+	{
+		volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
+
+		pg_atomic_fetch_or_u32(&slot->pss_barrierCheckMask, flagbit);
+	}
+
+	/*
+	 * Increment the generation counter.
+	 */
+	generation =
+		pg_atomic_add_fetch_u64(&ProcSignal->psh_barrierGeneration, 1);
+
+	/*
+	 * Signal all the processes, so that they update their advertised barrier
+	 * generation.
+	 *
+	 * Concurrency is not a problem here. Backends that have exited don't
+	 * matter, and new backends that have joined since we entered this function
+	 * must already have current state, since the caller is responsible for
+	 * making sure that the relevant state is entirely visible before calling
+	 * this function in the first place. We still have to wake them up -
+	 * because we can't distinguish between such backends and older backends
+	 * that need to update state - but they won't actually need to change
+	 * any state.
+	 */
+	for (int i = NumProcSignalSlots - 1; i >= 0; i--)
+	{
+		volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
+		pid_t	pid = slot->pss_pid;
+
+		if (pid != 0)
+			kill(pid, SIGUSR1);
+	}
+
+	return generation;
+}
+
+/*
+ * WaitForProcSignalBarrier - wait until it is guaranteed that all changes
+ * requested by a specific call to EmitProcSignalBarrier() have taken effect.
+ *
+ * We expect that the barrier will normally be absorbed very quickly by other
+ * backends, so we start by waiting just 1/8 of a second and then back off
+ * by a factor of two every time we time out, to a maximum wait time of
+ * 1 second.
+ */
+void
+WaitForProcSignalBarrier(uint64 generation)
+{
+	long	timeout = 125L;
+
+	for (int i = NumProcSignalSlots - 1; i >= 0; i--)
+	{
+		volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
+		uint64	oldval;
+
+		oldval = pg_atomic_read_u64(&slot->pss_barrierGeneration);
+		while (oldval < generation)
+		{
+			int		events;
+
+			CHECK_FOR_INTERRUPTS();
+
+			events =
+				WaitLatch(MyLatch,
+						  WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
+						  timeout, WAIT_EVENT_PROC_SIGNAL_BARRIER);
+			ResetLatch(MyLatch);
+
+			oldval = pg_atomic_read_u64(&slot->pss_barrierGeneration);
+			if (events & WL_TIMEOUT)
+				timeout = Min(timeout * 2, 1000L);
+		}
+	}
+
+	/*
+	 * The caller is probably calling this function because it wants to
+	 * read the shared state or perform further writes to shared state once
+	 * all backends are known to have absorbed the barrier. However, the
+	 * read of pss_barrierGeneration was performed unlocked; insert a memory
+	 * barrier to separate it from whatever follows.
+	 */
+	pg_memory_barrier();
+}
+
+/*
+ * Perform global barrier related interrupt checking.
+ *
+ * Any backend that participates in ProcSignal signalling must arrange to
+ * call this function periodically. It is called from CHECK_FOR_INTERRUPTS(),
+ * which is enough for normal backends, but not necessarily for all types of
+ * background processes.
+ */
+void
+ProcessProcSignalBarrier(void)
+{
+	uint64 generation;
+	uint32 flags;
+
+	/* Exit quickly if there's no work to do. */
+	if (!ProcSignalBarrierPending)
+		return;
+	ProcSignalBarrierPending = false;
+
+	/*
+	 * Read the current barrier generation, and then get the flags that
+	 * are set for this backend. Note that pg_atomic_exchange_u32 is a full
+	 * barrier, so we're guaranteed that the read of the barrier generation
+	 * happens before we atomically extract the flags, and that any subsequent
+	 * state changes happen afterward.
+	 */
+	generation = pg_atomic_read_u64(&ProcSignal->psh_barrierGeneration);
+	flags = pg_atomic_exchange_u32(&MyProcSignalSlot->pss_barrierCheckMask, 0);
+
+	/*
+	 * Process each type of barrier. It's important that nothing we call from
+	 * here throws an error, because pss_barrierCheckMask has already been
+	 * cleared. If we jumped out of here before processing all barrier types,
+	 * then we'd forget about the need to do so later.
+	 *
+	 * NB: It ought to be OK to call the barrier-processing functions
+	 * unconditionally, but it's more efficient to call only the ones that
+	 * might need us to do something based on the flags.
+	 */
+	if (BARRIER_SHOULD_CHECK(flags, PROCSIGNAL_BARRIER_SAMPLE))
+		ProcessBarrierSample();
+
+	/*
+	 * State changes related to all types of barriers that might have been
+	 * emitted have now been handled, so we can update our notion of the
+	 * generation to the one we observed before beginning the updates. If
+	 * things have changed further, it'll get fixed up when this function is
+	 * next called.
+	 */
+	pg_atomic_write_u64(&MyProcSignalSlot->pss_barrierGeneration, generation);
+}
+
+static void
+ProcessBarrierSample(void)
+{
+	/*
+	 * XXX. This should be something no-fail, which elog() is not, but this is
+	 * just for testing purposes.
+	 */
+	elog(LOG, "ProcessBarrierSample");
+}
+
 /*
  * CheckProcSignal - check to see if a particular reason has been
  * signaled, and clear the signal flag.  Should be called after receiving
@@ -253,6 +502,27 @@ CheckProcSignal(ProcSignalReason reason)
 	return false;
 }
 
+/*
+ * CheckProcSignalBarrier - check for new barriers we need to absorb
+ */
+static bool
+CheckProcSignalBarrier(void)
+{
+	volatile ProcSignalSlot *slot = MyProcSignalSlot;
+
+	if (slot != NULL)
+	{
+		uint64	mygen;
+		uint64	curgen;
+
+		mygen = pg_atomic_read_u64(&slot->pss_barrierGeneration);
+		curgen = pg_atomic_read_u64(&ProcSignal->psh_barrierGeneration);
+		return (mygen != curgen);
+	}
+
+	return false;
+}
+
 /*
  * procsignal_sigusr1_handler - handle SIGUSR1 signal.
  */
@@ -291,6 +561,12 @@ procsignal_sigusr1_handler(SIGNAL_ARGS)
 	if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN))
 		RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN);
 
+	if (CheckProcSignalBarrier())
+	{
+		InterruptPending = true;
+		ProcSignalBarrierPending = true;
+	}
+
 	SetLatch(MyLatch);
 
 	latch_sigusr1_handler();
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index d894c3ddf4..25e22bd63b 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -3162,6 +3162,9 @@ ProcessInterrupts(void)
 
 	}
 
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
+
 	if (ParallelMessagePending)
 		HandleParallelMessages();
 }
diff --git a/src/backend/utils/init/globals.c b/src/backend/utils/init/globals.c
index 4473e18e53..3a091022e2 100644
--- a/src/backend/utils/init/globals.c
+++ b/src/backend/utils/init/globals.c
@@ -32,6 +32,7 @@ volatile sig_atomic_t QueryCancelPending = false;
 volatile sig_atomic_t ProcDiePending = false;
 volatile sig_atomic_t ClientConnectionLost = false;
 volatile sig_atomic_t IdleInTransactionSessionTimeoutPending = false;
+volatile sig_atomic_t ProcSignalBarrierPending = false;
 volatile uint32 InterruptHoldoffCount = 0;
 volatile uint32 QueryCancelHoldoffCount = 0;
 volatile uint32 CritSectionCount = 0;
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index 24f43ad686..ed80f1d668 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -82,6 +82,7 @@ extern PGDLLIMPORT volatile sig_atomic_t InterruptPending;
 extern PGDLLIMPORT volatile sig_atomic_t QueryCancelPending;
 extern PGDLLIMPORT volatile sig_atomic_t ProcDiePending;
 extern PGDLLIMPORT volatile sig_atomic_t IdleInTransactionSessionTimeoutPending;
+extern PGDLLIMPORT volatile sig_atomic_t ProcSignalBarrierPending;
 
 extern PGDLLIMPORT volatile sig_atomic_t ClientConnectionLost;
 
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index fe076d823d..f2e873d048 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -908,6 +908,7 @@ typedef enum
 	WAIT_EVENT_LOGICAL_REWRITE_SYNC,
 	WAIT_EVENT_LOGICAL_REWRITE_TRUNCATE,
 	WAIT_EVENT_LOGICAL_REWRITE_WRITE,
+	WAIT_EVENT_PROC_SIGNAL_BARRIER,
 	WAIT_EVENT_RELATION_MAP_READ,
 	WAIT_EVENT_RELATION_MAP_SYNC,
 	WAIT_EVENT_RELATION_MAP_WRITE,
diff --git a/src/include/storage/procsignal.h b/src/include/storage/procsignal.h
index 05b186a05c..90eda29d15 100644
--- a/src/include/storage/procsignal.h
+++ b/src/include/storage/procsignal.h
@@ -45,6 +45,11 @@ typedef enum
 	NUM_PROCSIGNALS				/* Must be last! */
 } ProcSignalReason;
 
+typedef enum
+{
+	PROCSIGNAL_BARRIER_SAMPLE = 0
+} ProcSignalBarrierType;
+
 /*
  * prototypes for functions in procsignal.c
  */
@@ -55,6 +60,10 @@ extern void ProcSignalInit(int pss_idx);
 extern int	SendProcSignal(pid_t pid, ProcSignalReason reason,
 						   BackendId backendId);
 
+extern uint64 EmitProcSignalBarrier(ProcSignalBarrierType type);
+extern void WaitForProcSignalBarrier(uint64 generation);
+extern void ProcessProcSignalBarrier(void);
+
 extern void procsignal_sigusr1_handler(SIGNAL_ARGS);
 
 #endif							/* PROCSIGNAL_H */
-- 
2.17.2 (Apple Git-113)

From 2fd42691849f490b70cbd1003de6c4300a1ac465 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Mon, 2 Dec 2019 11:53:25 -0500
Subject: [PATCH v3 5/5] Not for commit: test code.

---
 src/backend/storage/ipc/signalfuncs.c | 11 +++++++++++
 src/include/catalog/pg_proc.dat       |  5 +++++
 2 files changed, 16 insertions(+)

diff --git a/src/backend/storage/ipc/signalfuncs.c b/src/backend/storage/ipc/signalfuncs.c
index ade8d713aa..f6deebcb5a 100644
--- a/src/backend/storage/ipc/signalfuncs.c
+++ b/src/backend/storage/ipc/signalfuncs.c
@@ -215,3 +215,14 @@ pg_rotate_logfile_v2(PG_FUNCTION_ARGS)
 	SendPostmasterSignal(PMSIGNAL_ROTATE_LOGFILE);
 	PG_RETURN_BOOL(true);
 }
+
+Datum
+sample_barrier(PG_FUNCTION_ARGS)
+{
+	uint64	bgen;
+
+	bgen = EmitProcSignalBarrier(PROCSIGNAL_BARRIER_SAMPLE);
+	elog(NOTICE, "emitted barrier");
+	WaitForProcSignalBarrier(bgen);
+	PG_RETURN_VOID();
+}
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index ac8f64b219..380bdfea45 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -10729,4 +10729,9 @@
   proname => 'pg_partition_root', prorettype => 'regclass',
   proargtypes => 'regclass', prosrc => 'pg_partition_root' },
 
+# function to get the top-most partition root parent
+{ oid => '9758', descr => 'send sample barrier',
+  proname => 'sample_barrier', prorettype => 'void',
+  proargtypes => '', prosrc => 'sample_barrier' },
+
 ]
-- 
2.17.2 (Apple Git-113)

From c9ad049519eab0bdbdb539dcca99c6f052291b14 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Wed, 27 Nov 2019 09:01:16 -0500
Subject: [PATCH v3 2/5] Use PostgresSigHupHandler in more places.

There seems to be no reason for every background process to have
its own flag indicating that a config-file reload is needed.
Instead, let's just use ConfigFilePending for that purpose
everywhere.
---
 src/backend/postmaster/autovacuum.c        | 30 ++++++----------------
 src/backend/postmaster/bgwriter.c          | 20 +++------------
 src/backend/postmaster/checkpointer.c      | 24 ++++-------------
 src/backend/postmaster/pgarch.c            | 25 ++++--------------
 src/backend/postmaster/pgstat.c            | 28 +++++---------------
 src/backend/postmaster/walwriter.c         | 20 +++------------
 src/backend/replication/logical/launcher.c | 23 +++--------------
 src/backend/replication/logical/worker.c   | 23 +++--------------
 8 files changed, 37 insertions(+), 156 deletions(-)

diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 5766203aaf..b1c2b0a01c 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -138,7 +138,6 @@ static bool am_autovacuum_launcher = false;
 static bool am_autovacuum_worker = false;
 
 /* Flags set by signal handlers */
-static volatile sig_atomic_t got_SIGHUP = false;
 static volatile sig_atomic_t got_SIGUSR2 = false;
 static volatile sig_atomic_t got_SIGTERM = false;
 
@@ -344,7 +343,6 @@ static void perform_work_item(AutoVacuumWorkItem *workitem);
 static void autovac_report_activity(autovac_table *tab);
 static void autovac_report_workitem(AutoVacuumWorkItem *workitem,
 									const char *nspname, const char *relname);
-static void av_sighup_handler(SIGNAL_ARGS);
 static void avl_sigusr2_handler(SIGNAL_ARGS);
 static void avl_sigterm_handler(SIGNAL_ARGS);
 static void autovac_refresh_stats(void);
@@ -452,7 +450,7 @@ AutoVacLauncherMain(int argc, char *argv[])
 	 * backend, so we use the same signal handling.  See equivalent code in
 	 * tcop/postgres.c.
 	 */
-	pqsignal(SIGHUP, av_sighup_handler);
+	pqsignal(SIGHUP, PostgresSigHupHandler);
 	pqsignal(SIGINT, StatementCancelHandler);
 	pqsignal(SIGTERM, avl_sigterm_handler);
 
@@ -805,9 +803,9 @@ HandleAutoVacLauncherInterrupts(void)
 	if (got_SIGTERM)
 		AutoVacLauncherShutdown();
 
-	if (got_SIGHUP)
+	if (ConfigReloadPending)
 	{
-		got_SIGHUP = false;
+		ConfigReloadPending = false;
 		ProcessConfigFile(PGC_SIGHUP);
 
 		/* shutdown requested in config file? */
@@ -1405,18 +1403,6 @@ AutoVacWorkerFailed(void)
 	AutoVacuumShmem->av_signal[AutoVacForkFailed] = true;
 }
 
-/* SIGHUP: set flag to re-read config file at next convenient time */
-static void
-av_sighup_handler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	got_SIGHUP = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /* SIGUSR2: a worker is up and running, or just finished, or failed to fork */
 static void
 avl_sigusr2_handler(SIGNAL_ARGS)
@@ -1539,7 +1525,7 @@ AutoVacWorkerMain(int argc, char *argv[])
 	 * backend, so we use the same signal handling.  See equivalent code in
 	 * tcop/postgres.c.
 	 */
-	pqsignal(SIGHUP, av_sighup_handler);
+	pqsignal(SIGHUP, PostgresSigHupHandler);
 
 	/*
 	 * SIGINT is used to signal canceling the current table's vacuum; SIGTERM
@@ -2332,9 +2318,9 @@ do_autovacuum(void)
 		/*
 		 * Check for config changes before processing each collected table.
 		 */
-		if (got_SIGHUP)
+		if (ConfigReloadPending)
 		{
-			got_SIGHUP = false;
+			ConfigReloadPending = false;
 			ProcessConfigFile(PGC_SIGHUP);
 
 			/*
@@ -2580,9 +2566,9 @@ deleted:
 		 * Check for config changes before acquiring lock for further jobs.
 		 */
 		CHECK_FOR_INTERRUPTS();
-		if (got_SIGHUP)
+		if (ConfigReloadPending)
 		{
-			got_SIGHUP = false;
+			ConfigReloadPending = false;
 			ProcessConfigFile(PGC_SIGHUP);
 		}
 
diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c
index c7500f1d71..bca46de6d5 100644
--- a/src/backend/postmaster/bgwriter.c
+++ b/src/backend/postmaster/bgwriter.c
@@ -89,7 +89,6 @@ static XLogRecPtr last_snapshot_lsn = InvalidXLogRecPtr;
 /*
  * Flags set by interrupt handlers for later service in the main loop.
  */
-static volatile sig_atomic_t got_SIGHUP = false;
 static volatile sig_atomic_t shutdown_requested = false;
 
 static void HandleBackgroundWriterInterrupts(void);
@@ -97,7 +96,6 @@ static void HandleBackgroundWriterInterrupts(void);
 /* Signal handlers */
 
 static void bg_quickdie(SIGNAL_ARGS);
-static void BgSigHupHandler(SIGNAL_ARGS);
 static void ReqShutdownHandler(SIGNAL_ARGS);
 
 
@@ -118,7 +116,7 @@ BackgroundWriterMain(void)
 	/*
 	 * Properly accept or ignore signals that might be sent to us.
 	 */
-	pqsignal(SIGHUP, BgSigHupHandler);	/* set flag to read config file */
+	pqsignal(SIGHUP, PostgresSigHupHandler);	/* set flag to read config file */
 	pqsignal(SIGINT, SIG_IGN);
 	pqsignal(SIGTERM, ReqShutdownHandler);	/* shutdown */
 	pqsignal(SIGQUIT, bg_quickdie); /* hard crash time */
@@ -363,9 +361,9 @@ BackgroundWriterMain(void)
 static void
 HandleBackgroundWriterInterrupts(void)
 {
-	if (got_SIGHUP)
+	if (ConfigReloadPending)
 	{
-		got_SIGHUP = false;
+		ConfigReloadPending = false;
 		ProcessConfigFile(PGC_SIGHUP);
 	}
 
@@ -413,18 +411,6 @@ bg_quickdie(SIGNAL_ARGS)
 	_exit(2);
 }
 
-/* SIGHUP: set flag to re-read config file at next convenient time */
-static void
-BgSigHupHandler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	got_SIGHUP = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /* SIGTERM: set flag to shutdown and exit */
 static void
 ReqShutdownHandler(SIGNAL_ARGS)
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index d087ee9c74..9cf91b0d35 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -151,7 +151,6 @@ double		CheckPointCompletionTarget = 0.5;
 /*
  * Flags set by interrupt handlers for later service in the main loop.
  */
-static volatile sig_atomic_t got_SIGHUP = false;
 static volatile sig_atomic_t shutdown_requested = false;
 
 /*
@@ -179,7 +178,6 @@ static void UpdateSharedMemoryConfig(void);
 /* Signal handlers */
 
 static void chkpt_quickdie(SIGNAL_ARGS);
-static void ChkptSigHupHandler(SIGNAL_ARGS);
 static void ReqCheckpointHandler(SIGNAL_ARGS);
 static void ReqShutdownHandler(SIGNAL_ARGS);
 
@@ -206,7 +204,7 @@ CheckpointerMain(void)
 	 * want to wait for the backends to exit, whereupon the postmaster will
 	 * tell us it's okay to shut down (via SIGUSR2).
 	 */
-	pqsignal(SIGHUP, ChkptSigHupHandler);	/* set flag to read config file */
+	pqsignal(SIGHUP, PostgresSigHupHandler);	/* set flag to read config file */
 	pqsignal(SIGINT, ReqCheckpointHandler); /* request checkpoint */
 	pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */
 	pqsignal(SIGQUIT, chkpt_quickdie);	/* hard crash time */
@@ -535,9 +533,9 @@ CheckpointerMain(void)
 static void
 HandleCheckpointerInterrupts(void)
 {
-	if (got_SIGHUP)
+	if (ConfigReloadPending)
 	{
-		got_SIGHUP = false;
+		ConfigReloadPending = false;
 		ProcessConfigFile(PGC_SIGHUP);
 
 		/*
@@ -685,9 +683,9 @@ CheckpointWriteDelay(int flags, double progress)
 		!ImmediateCheckpointRequested() &&
 		IsCheckpointOnSchedule(progress))
 	{
-		if (got_SIGHUP)
+		if (ConfigReloadPending)
 		{
-			got_SIGHUP = false;
+			ConfigReloadPending = false;
 			ProcessConfigFile(PGC_SIGHUP);
 			/* update shmem copies of config variables */
 			UpdateSharedMemoryConfig();
@@ -835,18 +833,6 @@ chkpt_quickdie(SIGNAL_ARGS)
 	_exit(2);
 }
 
-/* SIGHUP: set flag to re-read config file at next convenient time */
-static void
-ChkptSigHupHandler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	got_SIGHUP = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /* SIGINT: set flag to run a normal checkpoint right away */
 static void
 ReqCheckpointHandler(SIGNAL_ARGS)
diff --git a/src/backend/postmaster/pgarch.c b/src/backend/postmaster/pgarch.c
index f84f882c4c..09a9c66b4b 100644
--- a/src/backend/postmaster/pgarch.c
+++ b/src/backend/postmaster/pgarch.c
@@ -83,7 +83,6 @@ static time_t last_sigterm_time = 0;
 /*
  * Flags set by interrupt handlers for later service in the main loop.
  */
-static volatile sig_atomic_t got_SIGHUP = false;
 static volatile sig_atomic_t got_SIGTERM = false;
 static volatile sig_atomic_t wakened = false;
 static volatile sig_atomic_t ready_to_stop = false;
@@ -98,7 +97,6 @@ static pid_t pgarch_forkexec(void);
 
 NON_EXEC_STATIC void PgArchiverMain(int argc, char *argv[]) pg_attribute_noreturn();
 static void pgarch_exit(SIGNAL_ARGS);
-static void ArchSigHupHandler(SIGNAL_ARGS);
 static void ArchSigTermHandler(SIGNAL_ARGS);
 static void pgarch_waken(SIGNAL_ARGS);
 static void pgarch_waken_stop(SIGNAL_ARGS);
@@ -229,7 +227,7 @@ PgArchiverMain(int argc, char *argv[])
 	 * Ignore all signals usually bound to some action in the postmaster,
 	 * except for SIGHUP, SIGTERM, SIGUSR1, SIGUSR2, and SIGQUIT.
 	 */
-	pqsignal(SIGHUP, ArchSigHupHandler);
+	pqsignal(SIGHUP, PostgresSigHupHandler);
 	pqsignal(SIGINT, SIG_IGN);
 	pqsignal(SIGTERM, ArchSigTermHandler);
 	pqsignal(SIGQUIT, pgarch_exit);
@@ -259,19 +257,6 @@ pgarch_exit(SIGNAL_ARGS)
 	exit(1);
 }
 
-/* SIGHUP signal handler for archiver process */
-static void
-ArchSigHupHandler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	/* set flag to re-read config file at next convenient time */
-	got_SIGHUP = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /* SIGTERM signal handler for archiver process */
 static void
 ArchSigTermHandler(SIGNAL_ARGS)
@@ -348,9 +333,9 @@ pgarch_MainLoop(void)
 		time_to_stop = ready_to_stop;
 
 		/* Check for config update */
-		if (got_SIGHUP)
+		if (ConfigReloadPending)
 		{
-			got_SIGHUP = false;
+			ConfigReloadPending = false;
 			ProcessConfigFile(PGC_SIGHUP);
 		}
 
@@ -457,9 +442,9 @@ pgarch_ArchiverCopyLoop(void)
 			 * setting for archive_command as soon as possible, even if there
 			 * is a backlog of files to be archived.
 			 */
-			if (got_SIGHUP)
+			if (ConfigReloadPending)
 			{
-				got_SIGHUP = false;
+				ConfigReloadPending = false;
 				ProcessConfigFile(PGC_SIGHUP);
 			}
 
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index fabcf31de8..96a9e09ced 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -264,7 +264,6 @@ static List *pending_write_requests = NIL;
 
 /* Signal handler flags */
 static volatile bool need_exit = false;
-static volatile bool got_SIGHUP = false;
 
 /*
  * Total time charged to functions so far in the current backend.
@@ -285,7 +284,6 @@ static pid_t pgstat_forkexec(void);
 NON_EXEC_STATIC void PgstatCollectorMain(int argc, char *argv[]) pg_attribute_noreturn();
 static void pgstat_exit(SIGNAL_ARGS);
 static void pgstat_beshutdown_hook(int code, Datum arg);
-static void pgstat_sighup_handler(SIGNAL_ARGS);
 
 static PgStat_StatDBEntry *pgstat_get_db_entry(Oid databaseid, bool create);
 static PgStat_StatTabEntry *pgstat_get_tab_entry(PgStat_StatDBEntry *dbentry,
@@ -4434,7 +4432,7 @@ PgstatCollectorMain(int argc, char *argv[])
 	 * except SIGHUP and SIGQUIT.  Note we don't need a SIGUSR1 handler to
 	 * support latch operations, because we only use a local latch.
 	 */
-	pqsignal(SIGHUP, pgstat_sighup_handler);
+	pqsignal(SIGHUP, PostgresSigHupHandler);
 	pqsignal(SIGINT, SIG_IGN);
 	pqsignal(SIGTERM, SIG_IGN);
 	pqsignal(SIGQUIT, pgstat_exit);
@@ -4466,10 +4464,10 @@ PgstatCollectorMain(int argc, char *argv[])
 	 * message.  (This effectively means that if backends are sending us stuff
 	 * like mad, we won't notice postmaster death until things slack off a
 	 * bit; which seems fine.)	To do that, we have an inner loop that
-	 * iterates as long as recv() succeeds.  We do recognize got_SIGHUP inside
-	 * the inner loop, which means that such interrupts will get serviced but
-	 * the latch won't get cleared until next time there is a break in the
-	 * action.
+	 * iterates as long as recv() succeeds.  We do check ConfigReloadPending
+	 * inside the inner loop, which means that such interrupts will get
+	 * serviced but the latch won't get cleared until next time there is a
+	 * break in the action.
 	 */
 	for (;;)
 	{
@@ -4491,9 +4489,9 @@ PgstatCollectorMain(int argc, char *argv[])
 			/*
 			 * Reload configuration if we got SIGHUP from the postmaster.
 			 */
-			if (got_SIGHUP)
+			if (ConfigReloadPending)
 			{
-				got_SIGHUP = false;
+				ConfigReloadPending = false;
 				ProcessConfigFile(PGC_SIGHUP);
 			}
 
@@ -4691,18 +4689,6 @@ pgstat_exit(SIGNAL_ARGS)
 	errno = save_errno;
 }
 
-/* SIGHUP handler for collector process */
-static void
-pgstat_sighup_handler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	got_SIGHUP = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /*
  * Subroutine to clear stats in a database entry
  *
diff --git a/src/backend/postmaster/walwriter.c b/src/backend/postmaster/walwriter.c
index 5a3573503c..599478530f 100644
--- a/src/backend/postmaster/walwriter.c
+++ b/src/backend/postmaster/walwriter.c
@@ -80,14 +80,12 @@ int			WalWriterFlushAfter = 128;
 /*
  * Flags set by interrupt handlers for later service in the main loop.
  */
-static volatile sig_atomic_t got_SIGHUP = false;
 static volatile sig_atomic_t shutdown_requested = false;
 
 static void HandleWalWriterInterrupts(void);
 
 /* Signal handlers */
 static void wal_quickdie(SIGNAL_ARGS);
-static void WalSigHupHandler(SIGNAL_ARGS);
 static void WalShutdownHandler(SIGNAL_ARGS);
 
 /*
@@ -110,7 +108,7 @@ WalWriterMain(void)
 	 * We have no particular use for SIGINT at the moment, but seems
 	 * reasonable to treat like SIGTERM.
 	 */
-	pqsignal(SIGHUP, WalSigHupHandler); /* set flag to read config file */
+	pqsignal(SIGHUP, PostgresSigHupHandler); /* set flag to read config file */
 	pqsignal(SIGINT, WalShutdownHandler);	/* request shutdown */
 	pqsignal(SIGTERM, WalShutdownHandler);	/* request shutdown */
 	pqsignal(SIGQUIT, wal_quickdie);	/* hard crash time */
@@ -278,9 +276,9 @@ WalWriterMain(void)
 static void
 HandleWalWriterInterrupts(void)
 {
-	if (got_SIGHUP)
+	if (ConfigReloadPending)
 	{
-		got_SIGHUP = false;
+		ConfigReloadPending = false;
 		ProcessConfigFile(PGC_SIGHUP);
 	}
 	if (shutdown_requested)
@@ -322,18 +320,6 @@ wal_quickdie(SIGNAL_ARGS)
 	_exit(2);
 }
 
-/* SIGHUP: set flag to re-read config file at next convenient time */
-static void
-WalSigHupHandler(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	got_SIGHUP = true;
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /* SIGTERM: set flag to exit normally */
 static void
 WalShutdownHandler(SIGNAL_ARGS)
diff --git a/src/backend/replication/logical/launcher.c b/src/backend/replication/logical/launcher.c
index 4643af95fe..edca70c58c 100644
--- a/src/backend/replication/logical/launcher.c
+++ b/src/backend/replication/logical/launcher.c
@@ -92,9 +92,6 @@ static void logicalrep_worker_onexit(int code, Datum arg);
 static void logicalrep_worker_detach(void);
 static void logicalrep_worker_cleanup(LogicalRepWorker *worker);
 
-/* Flags set by signal handlers */
-static volatile sig_atomic_t got_SIGHUP = false;
-
 static bool on_commit_launcher_wakeup = false;
 
 Datum		pg_stat_get_subscription(PG_FUNCTION_ARGS);
@@ -714,20 +711,6 @@ logicalrep_worker_onexit(int code, Datum arg)
 	ApplyLauncherWakeup();
 }
 
-/* SIGHUP: set flag to reload configuration at next convenient time */
-static void
-logicalrep_launcher_sighup(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	got_SIGHUP = true;
-
-	/* Waken anything waiting on the process latch */
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /*
  * Count the number of registered (not necessarily running) sync workers
  * for a subscription.
@@ -972,7 +955,7 @@ ApplyLauncherMain(Datum main_arg)
 	LogicalRepCtx->launcher_pid = MyProcPid;
 
 	/* Establish signal handlers. */
-	pqsignal(SIGHUP, logicalrep_launcher_sighup);
+	pqsignal(SIGTERM, PostgresSigHupHandler);
 	pqsignal(SIGTERM, die);
 	BackgroundWorkerUnblockSignals();
 
@@ -1061,9 +1044,9 @@ ApplyLauncherMain(Datum main_arg)
 			CHECK_FOR_INTERRUPTS();
 		}
 
-		if (got_SIGHUP)
+		if (ConfigReloadPending)
 		{
-			got_SIGHUP = false;
+			ConfigReloadPending = false;
 			ProcessConfigFile(PGC_SIGHUP);
 		}
 	}
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index ced0d191c2..3b12ad6400 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -111,9 +111,6 @@ static void store_flush_position(XLogRecPtr remote_lsn);
 
 static void maybe_reread_subscription(void);
 
-/* Flags set by signal handlers */
-static volatile sig_atomic_t got_SIGHUP = false;
-
 /*
  * Should this worker apply changes for given relation.
  *
@@ -1270,9 +1267,9 @@ LogicalRepApplyLoop(XLogRecPtr last_received)
 			CHECK_FOR_INTERRUPTS();
 		}
 
-		if (got_SIGHUP)
+		if (ConfigReloadPending)
 		{
-			got_SIGHUP = false;
+			ConfigReloadPending = false;
 			ProcessConfigFile(PGC_SIGHUP);
 		}
 
@@ -1563,20 +1560,6 @@ subscription_change_cb(Datum arg, int cacheid, uint32 hashvalue)
 	MySubscriptionValid = false;
 }
 
-/* SIGHUP: set flag to reload configuration at next convenient time */
-static void
-logicalrep_worker_sighup(SIGNAL_ARGS)
-{
-	int			save_errno = errno;
-
-	got_SIGHUP = true;
-
-	/* Waken anything waiting on the process latch */
-	SetLatch(MyLatch);
-
-	errno = save_errno;
-}
-
 /* Logical Replication Apply worker entry point */
 void
 ApplyWorkerMain(Datum main_arg)
@@ -1592,7 +1575,7 @@ ApplyWorkerMain(Datum main_arg)
 	logicalrep_worker_attach(worker_slot);
 
 	/* Setup signal handling */
-	pqsignal(SIGHUP, logicalrep_worker_sighup);
+	pqsignal(SIGHUP, PostgresSigHupHandler);
 	pqsignal(SIGTERM, die);
 	BackgroundWorkerUnblockSignals();
 
-- 
2.17.2 (Apple Git-113)

From be1b8bd29985572598fd5881ec6e0854f9138dac Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Tue, 26 Nov 2019 13:14:13 -0500
Subject: [PATCH v3 1/5] Move interrupting-handling code into subroutines.

Some auxiliary processes, as well as the autovacuum launcher,
have interrupt handling code directly in their main loops.
Try to abstract things a little better by moving it into
separate functions.

This doesn't make any functional difference, and leaves
in place relatively large differences among processes in how
interrupts are handled, but hopefully it at least makes it
easier to see the commonalities and differences across
process types.
---
 src/backend/postmaster/autovacuum.c   | 72 +++++++++++++++++----------
 src/backend/postmaster/bgwriter.c     | 42 ++++++++++------
 src/backend/postmaster/checkpointer.c | 71 ++++++++++++++------------
 src/backend/postmaster/walwriter.c    | 34 ++++++++-----
 4 files changed, 133 insertions(+), 86 deletions(-)

diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index c1dd8168ca..5766203aaf 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -311,6 +311,8 @@ NON_EXEC_STATIC void AutoVacWorkerMain(int argc, char *argv[]) pg_attribute_nore
 NON_EXEC_STATIC void AutoVacLauncherMain(int argc, char *argv[]) pg_attribute_noreturn();
 
 static Oid	do_start_worker(void);
+static void HandleAutoVacLauncherInterrupts(void);
+static void AutoVacLauncherShutdown() pg_attribute_noreturn();
 static void launcher_determine_sleep(bool canlaunch, bool recursing,
 									 struct timeval *nap);
 static void launch_worker(TimestampTz now);
@@ -554,7 +556,7 @@ AutoVacLauncherMain(int argc, char *argv[])
 
 		/* if in shutdown mode, no need for anything further; just go away */
 		if (got_SIGTERM)
-			goto shutdown;
+			AutoVacLauncherShutdown();
 
 		/*
 		 * Sleep at least 1 second after any error.  We don't want to be
@@ -649,30 +651,7 @@ AutoVacLauncherMain(int argc, char *argv[])
 
 		ResetLatch(MyLatch);
 
-		/* Process sinval catchup interrupts that happened while sleeping */
-		ProcessCatchupInterrupt();
-
-		/* the normal shutdown case */
-		if (got_SIGTERM)
-			break;
-
-		if (got_SIGHUP)
-		{
-			got_SIGHUP = false;
-			ProcessConfigFile(PGC_SIGHUP);
-
-			/* shutdown requested in config file? */
-			if (!AutoVacuumingActive())
-				break;
-
-			/* rebalance in case the default cost parameters changed */
-			LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
-			autovac_balance_cost();
-			LWLockRelease(AutovacuumLock);
-
-			/* rebuild the list in case the naptime changed */
-			rebuild_database_list(InvalidOid);
-		}
+		HandleAutoVacLauncherInterrupts();
 
 		/*
 		 * a worker finished, or postmaster signalled failure to start a
@@ -813,8 +792,47 @@ AutoVacLauncherMain(int argc, char *argv[])
 		}
 	}
 
-	/* Normal exit from the autovac launcher is here */
-shutdown:
+	AutoVacLauncherShutdown();
+}
+
+/*
+ * Process any new interrupts.
+ */
+static void
+HandleAutoVacLauncherInterrupts(void)
+{
+	/* the normal shutdown case */
+	if (got_SIGTERM)
+		AutoVacLauncherShutdown();
+
+	if (got_SIGHUP)
+	{
+		got_SIGHUP = false;
+		ProcessConfigFile(PGC_SIGHUP);
+
+		/* shutdown requested in config file? */
+		if (!AutoVacuumingActive())
+			AutoVacLauncherShutdown();
+
+		/* rebalance in case the default cost parameters changed */
+		LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
+		autovac_balance_cost();
+		LWLockRelease(AutovacuumLock);
+
+		/* rebuild the list in case the naptime changed */
+		rebuild_database_list(InvalidOid);
+	}
+
+	/* Process sinval catchup interrupts that happened while sleeping */
+	ProcessCatchupInterrupt();
+}
+
+/*
+ * Perform a normal exit from the autovac launcher.
+ */
+static void
+AutoVacLauncherShutdown()
+{
 	ereport(DEBUG1,
 			(errmsg("autovacuum launcher shutting down")));
 	AutoVacuumShmem->av_launcherpid = 0;
diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c
index 2fa631ea7a..c7500f1d71 100644
--- a/src/backend/postmaster/bgwriter.c
+++ b/src/backend/postmaster/bgwriter.c
@@ -92,6 +92,8 @@ static XLogRecPtr last_snapshot_lsn = InvalidXLogRecPtr;
 static volatile sig_atomic_t got_SIGHUP = false;
 static volatile sig_atomic_t shutdown_requested = false;
 
+static void HandleBackgroundWriterInterrupts(void);
+
 /* Signal handlers */
 
 static void bg_quickdie(SIGNAL_ARGS);
@@ -241,21 +243,7 @@ BackgroundWriterMain(void)
 		/* Clear any already-pending wakeups */
 		ResetLatch(MyLatch);
 
-		if (got_SIGHUP)
-		{
-			got_SIGHUP = 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 */
-		}
+		HandleBackgroundWriterInterrupts();
 
 		/*
 		 * Do one cycle of dirty-buffer writing.
@@ -369,6 +357,30 @@ BackgroundWriterMain(void)
 	}
 }
 
+/*
+ * Process any new interrupts.
+ */
+static void
+HandleBackgroundWriterInterrupts(void)
+{
+	if (got_SIGHUP)
+	{
+		got_SIGHUP = 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
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index d93c941871..d087ee9c74 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -169,6 +169,7 @@ static pg_time_t last_xlog_switch_time;
 
 /* Prototypes for private functions */
 
+static void HandleCheckpointerInterrupts();
 static void CheckArchiveTimeout(void);
 static bool IsCheckpointOnSchedule(double progress);
 static bool ImmediateCheckpointRequested(void);
@@ -350,37 +351,7 @@ CheckpointerMain(void)
 		 * Process any requests or signals received recently.
 		 */
 		AbsorbSyncRequests();
-
-		if (got_SIGHUP)
-		{
-			got_SIGHUP = false;
-			ProcessConfigFile(PGC_SIGHUP);
-
-			/*
-			 * Checkpointer is the last process to shut down, so we ask it to
-			 * hold the keys for a range of other tasks required most of which
-			 * have nothing to do with checkpointing at all.
-			 *
-			 * For various reasons, some config values can change dynamically
-			 * so the primary copy of them is held in shared memory to make
-			 * sure all backends see the same value.  We make Checkpointer
-			 * responsible for updating the shared memory copy if the
-			 * parameter setting changes because of SIGHUP.
-			 */
-			UpdateSharedMemoryConfig();
-		}
-		if (shutdown_requested)
-		{
-			/*
-			 * From here on, elog(ERROR) should end with exit(1), not send
-			 * control back to the sigsetjmp block above
-			 */
-			ExitOnAnyError = true;
-			/* Close down the database */
-			ShutdownXLOG(0, 0);
-			/* Normal exit from the checkpointer is here */
-			proc_exit(0);		/* done */
-		}
+		HandleCheckpointerInterrupts();
 
 		/*
 		 * Detect a pending checkpoint request by checking whether the flags
@@ -558,6 +529,44 @@ CheckpointerMain(void)
 	}
 }
 
+/*
+ * Process any new interrupts.
+ */
+static void
+HandleCheckpointerInterrupts(void)
+{
+	if (got_SIGHUP)
+	{
+		got_SIGHUP = false;
+		ProcessConfigFile(PGC_SIGHUP);
+
+		/*
+		 * Checkpointer is the last process to shut down, so we ask it to
+		 * hold the keys for a range of other tasks required most of which
+		 * have nothing to do with checkpointing at all.
+		 *
+		 * For various reasons, some config values can change dynamically
+		 * so the primary copy of them is held in shared memory to make
+		 * sure all backends see the same value.  We make Checkpointer
+		 * responsible for updating the shared memory copy if the
+		 * parameter setting changes because of SIGHUP.
+		 */
+		UpdateSharedMemoryConfig();
+	}
+	if (shutdown_requested)
+	{
+		/*
+		 * From here on, elog(ERROR) should end with exit(1), not send
+		 * control back to the sigsetjmp block above
+		 */
+		ExitOnAnyError = true;
+		/* Close down the database */
+		ShutdownXLOG(0, 0);
+		/* Normal exit from the checkpointer is here */
+		proc_exit(0);		/* done */
+	}
+}
+
 /*
  * CheckArchiveTimeout -- check for archive_timeout and switch xlog files
  *
diff --git a/src/backend/postmaster/walwriter.c b/src/backend/postmaster/walwriter.c
index cce9713408..5a3573503c 100644
--- a/src/backend/postmaster/walwriter.c
+++ b/src/backend/postmaster/walwriter.c
@@ -83,6 +83,8 @@ int			WalWriterFlushAfter = 128;
 static volatile sig_atomic_t got_SIGHUP = false;
 static volatile sig_atomic_t shutdown_requested = false;
 
+static void HandleWalWriterInterrupts(void);
+
 /* Signal handlers */
 static void wal_quickdie(SIGNAL_ARGS);
 static void WalSigHupHandler(SIGNAL_ARGS);
@@ -242,19 +244,7 @@ WalWriterMain(void)
 		/* Clear any already-pending wakeups */
 		ResetLatch(MyLatch);
 
-		/*
-		 * Process any requests or signals received recently.
-		 */
-		if (got_SIGHUP)
-		{
-			got_SIGHUP = false;
-			ProcessConfigFile(PGC_SIGHUP);
-		}
-		if (shutdown_requested)
-		{
-			/* Normal exit from the walwriter is here */
-			proc_exit(0);		/* done */
-		}
+		HandleWalWriterInterrupts();
 
 		/*
 		 * Do what we're here for; then, if XLogBackgroundFlush() found useful
@@ -282,6 +272,24 @@ WalWriterMain(void)
 	}
 }
 
+/*
+ * Process any new interrupts.
+ */
+static void
+HandleWalWriterInterrupts(void)
+{
+	if (got_SIGHUP)
+	{
+		got_SIGHUP = false;
+		ProcessConfigFile(PGC_SIGHUP);
+	}
+	if (shutdown_requested)
+	{
+		/* Normal exit from the walwriter is here */
+		proc_exit(0);		/* done */
+	}
+}
+
 
 /* --------------------------------
  *		signal handler routines
-- 
2.17.2 (Apple Git-113)

From 3c747e912b894ebe201e4f6200ff3d10947dbc54 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Tue, 17 Dec 2019 13:35:09 -0500
Subject: [PATCH v4] Extend the ProcSignal mechanism to support barriers.

A new function EmitProcSignalBarrier() can be used to emit a global
barrier which all backends that participate in the ProcSignal
mechanism must absorb, and a new function WaitForProcSignalBarrier()
can be used to wait until all relevant backends have in fact
absorbed the barrier.

This can be used to coordinate global state changes, such as turning
checksums on while the system is running.

Andres Freund and Robert Haas, reviewed by Daniel Gustafsson.

Discussion: http://postgr.es/m/CA+TgmoZwDk=BguVDVa+qdA6SBKef=PKbaKDQALTC_9qoz1mJqg@mail.gmail.com
---
 doc/src/sgml/monitoring.sgml          |   4 +
 src/backend/postmaster/autovacuum.c   |   4 +
 src/backend/postmaster/checkpointer.c |   7 +
 src/backend/postmaster/interrupt.c    |   4 +
 src/backend/postmaster/pgstat.c       |   3 +
 src/backend/postmaster/startup.c      |   6 +-
 src/backend/replication/walreceiver.c |   3 +-
 src/backend/storage/buffer/bufmgr.c   |  10 +
 src/backend/storage/ipc/procsignal.c  | 301 +++++++++++++++++++++++++-
 src/backend/tcop/postgres.c           |   3 +
 src/backend/utils/init/globals.c      |   1 +
 src/include/miscadmin.h               |   1 +
 src/include/pgstat.h                  |   1 +
 src/include/storage/procsignal.h      |  14 ++
 14 files changed, 349 insertions(+), 13 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index a3c5f86b7e..76957c0a43 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -1593,6 +1593,10 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
          <entry><literal>LogicalRewriteWrite</literal></entry>
          <entry>Waiting for a write of logical rewrite mappings.</entry>
         </row>
+        <row>
+         <entry><literal>ProcSignalBarrier</literal></entry>
+         <entry>Waiting for a barrier event to be processed by all backends.</entry>
+        </row>
         <row>
          <entry><literal>RelationMapRead</literal></entry>
          <entry>Waiting for a read of the relation map file.</entry>
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 1792008ebe..52ad99f716 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -820,6 +820,10 @@ HandleAutoVacLauncherInterrupts(void)
 		rebuild_database_list(InvalidOid);
 	}
 
+	/* Process barrier events */
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
+
 	/* Process sinval catchup interrupts that happened while sleeping */
 	ProcessCatchupInterrupt();
 }
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index 3f35b324c3..d1185cc135 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -523,6 +523,9 @@ CheckpointerMain(void)
 static void
 HandleCheckpointerInterrupts(void)
 {
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
+
 	if (ConfigReloadPending)
 	{
 		ConfigReloadPending = false;
@@ -709,6 +712,10 @@ CheckpointWriteDelay(int flags, double progress)
 		AbsorbSyncRequests();
 		absorb_counter = WRITES_PER_ABSORB;
 	}
+
+	/* Check for barrier events. */
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
 }
 
 /*
diff --git a/src/backend/postmaster/interrupt.c b/src/backend/postmaster/interrupt.c
index 6900cd02f6..214ccaf34b 100644
--- a/src/backend/postmaster/interrupt.c
+++ b/src/backend/postmaster/interrupt.c
@@ -20,6 +20,7 @@
 #include "postmaster/interrupt.h"
 #include "storage/ipc.h"
 #include "storage/latch.h"
+#include "storage/procsignal.h"
 #include "utils/guc.h"
 
 volatile sig_atomic_t ConfigReloadPending = false;
@@ -31,6 +32,9 @@ volatile sig_atomic_t ShutdownRequestPending = false;
 void
 HandleMainLoopInterrupts(void)
 {
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
+
 	if (ConfigReloadPending)
 	{
 		ConfigReloadPending = false;
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index e931512203..7410b2ff5e 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -3988,6 +3988,9 @@ pgstat_get_wait_io(WaitEventIO w)
 		case WAIT_EVENT_LOGICAL_REWRITE_WRITE:
 			event_name = "LogicalRewriteWrite";
 			break;
+		case WAIT_EVENT_PROC_SIGNAL_BARRIER:
+			event_name = "ProcSignalBarrier";
+			break;
 		case WAIT_EVENT_RELATION_MAP_READ:
 			event_name = "RelationMapRead";
 			break;
diff --git a/src/backend/postmaster/startup.c b/src/backend/postmaster/startup.c
index 4f59c71f73..11f7052e78 100644
--- a/src/backend/postmaster/startup.c
+++ b/src/backend/postmaster/startup.c
@@ -96,7 +96,7 @@ StartupProcShutdownHandler(SIGNAL_ARGS)
 	errno = save_errno;
 }
 
-/* Handle SIGHUP and SIGTERM signals of startup process */
+/* Handle various signals that might be sent to the startup process */
 void
 HandleStartupProcInterrupts(void)
 {
@@ -121,6 +121,10 @@ HandleStartupProcInterrupts(void)
 	 */
 	if (IsUnderPostmaster && !PostmasterIsAlive())
 		exit(1);
+
+	/* Process barrier events */
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
 }
 
 
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index c36bcc08ec..a4de8a9cd8 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -148,7 +148,8 @@ ProcessWalRcvInterrupts(void)
 	/*
 	 * Although walreceiver interrupt handling doesn't use the same scheme as
 	 * regular backends, call CHECK_FOR_INTERRUPTS() to make sure we receive
-	 * any incoming signals on Win32.
+	 * any incoming signals on Win32, and also to make sure we process any
+	 * barrier events.
 	 */
 	CHECK_FOR_INTERRUPTS();
 
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 7ad10736d5..1f10a97dc7 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -1852,6 +1852,10 @@ BufferSync(int flags)
 		}
 
 		UnlockBufHdr(bufHdr, buf_state);
+
+		/* Check for barrier events in case NBuffers is large. */
+		if (ProcSignalBarrierPending)
+			ProcessProcSignalBarrier();
 	}
 
 	if (num_to_scan == 0)
@@ -1930,6 +1934,10 @@ BufferSync(int flags)
 		}
 
 		s->num_to_scan++;
+
+		/* Check for barrier events. */
+		if (ProcSignalBarrierPending)
+			ProcessProcSignalBarrier();
 	}
 
 	Assert(num_spaces > 0);
@@ -2018,6 +2026,8 @@ BufferSync(int flags)
 
 		/*
 		 * Sleep to throttle our I/O rate.
+		 *
+		 * (This will check for barrier events even if it doesn't sleep.)
 		 */
 		CheckpointWriteDelay(flags, (double) num_processed / num_to_scan);
 	}
diff --git a/src/backend/storage/ipc/procsignal.c b/src/backend/storage/ipc/procsignal.c
index fde97a1036..06e00eae15 100644
--- a/src/backend/storage/ipc/procsignal.c
+++ b/src/backend/storage/ipc/procsignal.c
@@ -20,6 +20,7 @@
 #include "access/parallel.h"
 #include "commands/async.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "replication/walsender.h"
 #include "storage/ipc.h"
 #include "storage/latch.h"
@@ -45,13 +46,36 @@
  * The flags are actually declared as "volatile sig_atomic_t" for maximum
  * portability.  This should ensure that loads and stores of the flag
  * values are atomic, allowing us to dispense with any explicit locking.
+ *
+ * pss_signalFlags are intended to be set in cases where we don't need to
+ * keep track of whether or not the target process has handled the signal,
+ * but sometimes we need confirmation, as when making a global state change
+ * that cannot be considered complete until all backends have taken notice
+ * of it. For such use cases, we set a bit in pss_barrierCheckMask and then
+ * increment the current "barrier generation"; when the new barrier generation
+ * (or greater) appears in the pss_barrierGeneration flag of every process,
+ * we know that the message has been received everywhere.
  */
 typedef struct
 {
 	pid_t		pss_pid;
 	sig_atomic_t pss_signalFlags[NUM_PROCSIGNALS];
+	pg_atomic_uint64	pss_barrierGeneration;
+	pg_atomic_uint32	pss_barrierCheckMask;
 } ProcSignalSlot;
 
+/*
+ * Information that is global to the entire ProcSignal system can be stored
+ * here.
+ *
+ * psh_barrierGeneration is the highest barrier generation in existence.
+ */
+typedef struct
+{
+	pg_atomic_uint64	psh_barrierGeneration;
+	ProcSignalSlot		psh_slot[FLEXIBLE_ARRAY_MEMBER];
+} ProcSignalHeader;
+
 /*
  * We reserve a slot for each possible BackendId, plus one for each
  * possible auxiliary process type.  (This scheme assumes there is not
@@ -59,11 +83,16 @@ typedef struct
  */
 #define NumProcSignalSlots	(MaxBackends + NUM_AUXPROCTYPES)
 
-static ProcSignalSlot *ProcSignalSlots = NULL;
+/* Check whether the relevant type bit is set in the flags. */
+#define BARRIER_SHOULD_CHECK(flags, type) \
+	(((flags) & (((uint32) 1) << (uint32) (type))) != 0)
+
+static ProcSignalHeader *ProcSignal = NULL;
 static volatile ProcSignalSlot *MyProcSignalSlot = NULL;
 
 static bool CheckProcSignal(ProcSignalReason reason);
 static void CleanupProcSignalState(int status, Datum arg);
+static void ProcessBarrierPlaceholder(void);
 
 /*
  * ProcSignalShmemSize
@@ -72,7 +101,11 @@ static void CleanupProcSignalState(int status, Datum arg);
 Size
 ProcSignalShmemSize(void)
 {
-	return NumProcSignalSlots * sizeof(ProcSignalSlot);
+	Size	size;
+
+	size = mul_size(NumProcSignalSlots, sizeof(ProcSignalSlot));
+	size = add_size(size, offsetof(ProcSignalHeader, psh_slot));
+	return size;
 }
 
 /*
@@ -85,12 +118,26 @@ ProcSignalShmemInit(void)
 	Size		size = ProcSignalShmemSize();
 	bool		found;
 
-	ProcSignalSlots = (ProcSignalSlot *)
-		ShmemInitStruct("ProcSignalSlots", size, &found);
+	ProcSignal = (ProcSignalHeader *)
+		ShmemInitStruct("ProcSignal", size, &found);
 
-	/* If we're first, set everything to zeroes */
+	/* If we're first, initialize. */
 	if (!found)
-		MemSet(ProcSignalSlots, 0, size);
+	{
+		int		i;
+
+		pg_atomic_init_u64(&ProcSignal->psh_barrierGeneration, 0);
+
+		for (i = 0; i < NumProcSignalSlots; ++i)
+		{
+			ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
+
+			slot->pss_pid = 0;
+			MemSet(slot->pss_signalFlags, 0, sizeof(slot->pss_signalFlags));
+			pg_atomic_init_u64(&slot->pss_barrierGeneration, PG_UINT64_MAX);
+			pg_atomic_init_u32(&slot->pss_barrierCheckMask, 0);
+		}
+	}
 }
 
 /*
@@ -104,10 +151,11 @@ void
 ProcSignalInit(int pss_idx)
 {
 	volatile ProcSignalSlot *slot;
+	uint64		barrier_generation;
 
 	Assert(pss_idx >= 1 && pss_idx <= NumProcSignalSlots);
 
-	slot = &ProcSignalSlots[pss_idx - 1];
+	slot = &ProcSignal->psh_slot[pss_idx - 1];
 
 	/* sanity check */
 	if (slot->pss_pid != 0)
@@ -117,6 +165,23 @@ ProcSignalInit(int pss_idx)
 	/* Clear out any leftover signal reasons */
 	MemSet(slot->pss_signalFlags, 0, NUM_PROCSIGNALS * sizeof(sig_atomic_t));
 
+	/*
+	 * Initialize barrier state. Since we're a brand-new process, there
+	 * shouldn't be any leftover backend-private state that needs to be
+	 * updated. Therefore, we can broadcast the latest barrier generation
+	 * and disregard any previously-set check bits.
+	 *
+	 * NB: This only works if this initialization happens early enough in the
+	 * startup sequence that we haven't yet cached any state that might need
+	 * to be invalidated. That's also why we have a memory barrier here, to
+	 * be sure that any later reads of memory happen strictly after this.
+	 */
+	pg_atomic_write_u32(&slot->pss_barrierCheckMask, 0);
+	barrier_generation =
+		pg_atomic_read_u64(&ProcSignal->psh_barrierGeneration);
+	pg_atomic_write_u64(&slot->pss_barrierGeneration, barrier_generation);
+	pg_memory_barrier();
+
 	/* Mark slot with my PID */
 	slot->pss_pid = MyProcPid;
 
@@ -129,7 +194,7 @@ ProcSignalInit(int pss_idx)
 
 /*
  * CleanupProcSignalState
- *		Remove current process from ProcSignalSlots
+ *		Remove current process from ProcSignal mechanism
  *
  * This function is called via on_shmem_exit() during backend shutdown.
  */
@@ -139,7 +204,7 @@ CleanupProcSignalState(int status, Datum arg)
 	int			pss_idx = DatumGetInt32(arg);
 	volatile ProcSignalSlot *slot;
 
-	slot = &ProcSignalSlots[pss_idx - 1];
+	slot = &ProcSignal->psh_slot[pss_idx - 1];
 	Assert(slot == MyProcSignalSlot);
 
 	/*
@@ -161,6 +226,12 @@ CleanupProcSignalState(int status, Datum arg)
 		return;					/* XXX better to zero the slot anyway? */
 	}
 
+	/*
+	 * Make this slot look like it's absorbed all possible barriers, so that
+	 * no barrier waits block on it.
+	 */
+	pg_atomic_write_u64(&slot->pss_barrierGeneration, PG_UINT64_MAX);
+
 	slot->pss_pid = 0;
 }
 
@@ -182,7 +253,7 @@ SendProcSignal(pid_t pid, ProcSignalReason reason, BackendId backendId)
 
 	if (backendId != InvalidBackendId)
 	{
-		slot = &ProcSignalSlots[backendId - 1];
+		slot = &ProcSignal->psh_slot[backendId - 1];
 
 		/*
 		 * Note: Since there's no locking, it's possible that the target
@@ -212,7 +283,7 @@ SendProcSignal(pid_t pid, ProcSignalReason reason, BackendId backendId)
 
 		for (i = NumProcSignalSlots - 1; i >= 0; i--)
 		{
-			slot = &ProcSignalSlots[i];
+			slot = &ProcSignal->psh_slot[i];
 
 			if (slot->pss_pid == pid)
 			{
@@ -230,6 +301,187 @@ SendProcSignal(pid_t pid, ProcSignalReason reason, BackendId backendId)
 	return -1;
 }
 
+/*
+ * EmitProcSignalBarrier
+ *		Send a signal to every Postgres process
+ *
+ * The return value of this function is the barrier "generation" created
+ * by this operation. This value can be passed to WaitForProcSignalBarrier
+ * to wait until it is known that every participant in the ProcSignal
+ * mechanism has absorbed the signal (or started afterwards).
+ *
+ * Note that it would be a bad idea to use this for anything that happens
+ * frequently, as interrupting every backend could cause a noticeable
+ * performance hit.
+ *
+ * Callers are entitled to assume that this function will not throw ERROR
+ * or FATAL.
+ */
+uint64
+EmitProcSignalBarrier(ProcSignalBarrierType type)
+{
+	uint64	flagbit = UINT64CONST(1) << (uint64) type;
+	uint64	generation;
+
+	/*
+	 * Set all the flags.
+	 *
+	 * Note that pg_atomic_fetch_or_u32 has full barrier semantics, so this
+	 * is totally ordered with respect to anything the caller did before, and
+	 * anything that we do afterwards. (This is also true of the later call
+	 * to pg_atomic_add_fetch_u64.)
+	 */
+	for (int i = 0; i < NumProcSignalSlots; i++)
+	{
+		volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
+
+		pg_atomic_fetch_or_u32(&slot->pss_barrierCheckMask, flagbit);
+	}
+
+	/*
+	 * Increment the generation counter.
+	 */
+	generation =
+		pg_atomic_add_fetch_u64(&ProcSignal->psh_barrierGeneration, 1);
+
+	/*
+	 * Signal all the processes, so that they update their advertised barrier
+	 * generation.
+	 *
+	 * Concurrency is not a problem here. Backends that have exited don't
+	 * matter, and new backends that have joined since we entered this function
+	 * must already have current state, since the caller is responsible for
+	 * making sure that the relevant state is entirely visible before calling
+	 * this function in the first place. We still have to wake them up -
+	 * because we can't distinguish between such backends and older backends
+	 * that need to update state - but they won't actually need to change
+	 * any state.
+	 */
+	for (int i = NumProcSignalSlots - 1; i >= 0; i--)
+	{
+		volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
+		pid_t	pid = slot->pss_pid;
+
+		if (pid != 0)
+			kill(pid, SIGUSR1);
+	}
+
+	return generation;
+}
+
+/*
+ * WaitForProcSignalBarrier - wait until it is guaranteed that all changes
+ * requested by a specific call to EmitProcSignalBarrier() have taken effect.
+ *
+ * We expect that the barrier will normally be absorbed very quickly by other
+ * backends, so we start by waiting just 1/8 of a second and then back off
+ * by a factor of two every time we time out, to a maximum wait time of
+ * 1 second.
+ */
+void
+WaitForProcSignalBarrier(uint64 generation)
+{
+	long	timeout = 125L;
+
+	for (int i = NumProcSignalSlots - 1; i >= 0; i--)
+	{
+		volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
+		uint64	oldval;
+
+		oldval = pg_atomic_read_u64(&slot->pss_barrierGeneration);
+		while (oldval < generation)
+		{
+			int		events;
+
+			CHECK_FOR_INTERRUPTS();
+
+			events =
+				WaitLatch(MyLatch,
+						  WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
+						  timeout, WAIT_EVENT_PROC_SIGNAL_BARRIER);
+			ResetLatch(MyLatch);
+
+			oldval = pg_atomic_read_u64(&slot->pss_barrierGeneration);
+			if (events & WL_TIMEOUT)
+				timeout = Min(timeout * 2, 1000L);
+		}
+	}
+
+	/*
+	 * The caller is probably calling this function because it wants to
+	 * read the shared state or perform further writes to shared state once
+	 * all backends are known to have absorbed the barrier. However, the
+	 * read of pss_barrierGeneration was performed unlocked; insert a memory
+	 * barrier to separate it from whatever follows.
+	 */
+	pg_memory_barrier();
+}
+
+/*
+ * Perform global barrier related interrupt checking.
+ *
+ * Any backend that participates in ProcSignal signalling must arrange to
+ * call this function periodically. It is called from CHECK_FOR_INTERRUPTS(),
+ * which is enough for normal backends, but not necessarily for all types of
+ * background processes.
+ */
+void
+ProcessProcSignalBarrier(void)
+{
+	uint64 generation;
+	uint32 flags;
+
+	/* Exit quickly if there's no work to do. */
+	if (!ProcSignalBarrierPending)
+		return;
+	ProcSignalBarrierPending = false;
+
+	/*
+	 * Read the current barrier generation, and then get the flags that
+	 * are set for this backend. Note that pg_atomic_exchange_u32 is a full
+	 * barrier, so we're guaranteed that the read of the barrier generation
+	 * happens before we atomically extract the flags, and that any subsequent
+	 * state changes happen afterward.
+	 */
+	generation = pg_atomic_read_u64(&ProcSignal->psh_barrierGeneration);
+	flags = pg_atomic_exchange_u32(&MyProcSignalSlot->pss_barrierCheckMask, 0);
+
+	/*
+	 * Process each type of barrier. It's important that nothing we call from
+	 * here throws an error, because pss_barrierCheckMask has already been
+	 * cleared. If we jumped out of here before processing all barrier types,
+	 * then we'd forget about the need to do so later.
+	 *
+	 * NB: It ought to be OK to call the barrier-processing functions
+	 * unconditionally, but it's more efficient to call only the ones that
+	 * might need us to do something based on the flags.
+	 */
+	if (BARRIER_SHOULD_CHECK(flags, PROCSIGNAL_BARRIER_PLACEHOLDER))
+		ProcessBarrierPlaceholder();
+
+	/*
+	 * State changes related to all types of barriers that might have been
+	 * emitted have now been handled, so we can update our notion of the
+	 * generation to the one we observed before beginning the updates. If
+	 * things have changed further, it'll get fixed up when this function is
+	 * next called.
+	 */
+	pg_atomic_write_u64(&MyProcSignalSlot->pss_barrierGeneration, generation);
+}
+
+static void
+ProcessBarrierPlaceholder(void)
+{
+	/*
+	 * XXX. This is just a placeholder until the first real user of this
+	 * machinery gets committed. Rename PROCSIGNAL_BARRIER_PLACEHOLDER to
+	 * PROCSIGNAL_BARRIER_SOMETHING_ELSE where SOMETHING_ELSE is something
+	 * appropriately descriptive. Get rid of this function and instead have
+	 * ProcessBarrierSomethingElse. Most likely, that function should live
+	 * in the file pertaining to that subsystem, rather than here.
+	 */
+}
+
 /*
  * CheckProcSignal - check to see if a particular reason has been
  * signaled, and clear the signal flag.  Should be called after receiving
@@ -253,6 +505,27 @@ CheckProcSignal(ProcSignalReason reason)
 	return false;
 }
 
+/*
+ * CheckProcSignalBarrier - check for new barriers we need to absorb
+ */
+static bool
+CheckProcSignalBarrier(void)
+{
+	volatile ProcSignalSlot *slot = MyProcSignalSlot;
+
+	if (slot != NULL)
+	{
+		uint64	mygen;
+		uint64	curgen;
+
+		mygen = pg_atomic_read_u64(&slot->pss_barrierGeneration);
+		curgen = pg_atomic_read_u64(&ProcSignal->psh_barrierGeneration);
+		return (mygen != curgen);
+	}
+
+	return false;
+}
+
 /*
  * procsignal_sigusr1_handler - handle SIGUSR1 signal.
  */
@@ -291,6 +564,12 @@ procsignal_sigusr1_handler(SIGNAL_ARGS)
 	if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN))
 		RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN);
 
+	if (CheckProcSignalBarrier())
+	{
+		InterruptPending = true;
+		ProcSignalBarrierPending = true;
+	}
+
 	SetLatch(MyLatch);
 
 	latch_sigusr1_handler();
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index ef5a952968..c42d9ce09a 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -3180,6 +3180,9 @@ ProcessInterrupts(void)
 
 	}
 
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
+
 	if (ParallelMessagePending)
 		HandleParallelMessages();
 }
diff --git a/src/backend/utils/init/globals.c b/src/backend/utils/init/globals.c
index 4473e18e53..3a091022e2 100644
--- a/src/backend/utils/init/globals.c
+++ b/src/backend/utils/init/globals.c
@@ -32,6 +32,7 @@ volatile sig_atomic_t QueryCancelPending = false;
 volatile sig_atomic_t ProcDiePending = false;
 volatile sig_atomic_t ClientConnectionLost = false;
 volatile sig_atomic_t IdleInTransactionSessionTimeoutPending = false;
+volatile sig_atomic_t ProcSignalBarrierPending = false;
 volatile uint32 InterruptHoldoffCount = 0;
 volatile uint32 QueryCancelHoldoffCount = 0;
 volatile uint32 CritSectionCount = 0;
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index 24f43ad686..ed80f1d668 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -82,6 +82,7 @@ extern PGDLLIMPORT volatile sig_atomic_t InterruptPending;
 extern PGDLLIMPORT volatile sig_atomic_t QueryCancelPending;
 extern PGDLLIMPORT volatile sig_atomic_t ProcDiePending;
 extern PGDLLIMPORT volatile sig_atomic_t IdleInTransactionSessionTimeoutPending;
+extern PGDLLIMPORT volatile sig_atomic_t ProcSignalBarrierPending;
 
 extern PGDLLIMPORT volatile sig_atomic_t ClientConnectionLost;
 
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index fe076d823d..f2e873d048 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -908,6 +908,7 @@ typedef enum
 	WAIT_EVENT_LOGICAL_REWRITE_SYNC,
 	WAIT_EVENT_LOGICAL_REWRITE_TRUNCATE,
 	WAIT_EVENT_LOGICAL_REWRITE_WRITE,
+	WAIT_EVENT_PROC_SIGNAL_BARRIER,
 	WAIT_EVENT_RELATION_MAP_READ,
 	WAIT_EVENT_RELATION_MAP_SYNC,
 	WAIT_EVENT_RELATION_MAP_WRITE,
diff --git a/src/include/storage/procsignal.h b/src/include/storage/procsignal.h
index 05b186a05c..b7d0d43f0d 100644
--- a/src/include/storage/procsignal.h
+++ b/src/include/storage/procsignal.h
@@ -45,6 +45,16 @@ typedef enum
 	NUM_PROCSIGNALS				/* Must be last! */
 } ProcSignalReason;
 
+typedef enum
+{
+	/*
+	 * XXX. PROCSIGNAL_BARRIER_PLACEHOLDER should be replaced when the first
+	 * real user of the ProcSignalBarrier mechanism is added. It's just here
+	 * for now because we can't have an empty enum.
+	 */
+	PROCSIGNAL_BARRIER_PLACEHOLDER = 0
+} ProcSignalBarrierType;
+
 /*
  * prototypes for functions in procsignal.c
  */
@@ -55,6 +65,10 @@ extern void ProcSignalInit(int pss_idx);
 extern int	SendProcSignal(pid_t pid, ProcSignalReason reason,
 						   BackendId backendId);
 
+extern uint64 EmitProcSignalBarrier(ProcSignalBarrierType type);
+extern void WaitForProcSignalBarrier(uint64 generation);
+extern void ProcessProcSignalBarrier(void);
+
 extern void procsignal_sigusr1_handler(SIGNAL_ARGS);
 
 #endif							/* PROCSIGNAL_H */
-- 
2.17.2 (Apple Git-113)

diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 1792008ebe..47b4bacadb 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -311,7 +311,7 @@ NON_EXEC_STATIC void AutoVacLauncherMain(int argc, char *argv[]) pg_attribute_no
 
 static Oid	do_start_worker(void);
 static void HandleAutoVacLauncherInterrupts(void);
-static void AutoVacLauncherShutdown() pg_attribute_noreturn();
+static void AutoVacLauncherShutdown(void) pg_attribute_noreturn();
 static void launcher_determine_sleep(bool canlaunch, bool recursing,
 									 struct timeval *nap);
 static void launch_worker(TimestampTz now);
@@ -828,7 +828,7 @@ HandleAutoVacLauncherInterrupts(void)
  * Perform a normal exit from the autovac launcher.
  */
 static void
-AutoVacLauncherShutdown()
+AutoVacLauncherShutdown(void)
 {
 	ereport(DEBUG1,
 			(errmsg("autovacuum launcher shutting down")));
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index 3f35b324c3..df527ac021 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -161,7 +161,7 @@ static pg_time_t last_xlog_switch_time;
 
 /* Prototypes for private functions */
 
-static void HandleCheckpointerInterrupts();
+static void HandleCheckpointerInterrupts(void);
 static void CheckArchiveTimeout(void);
 static bool IsCheckpointOnSchedule(double progress);
 static bool ImmediateCheckpointRequested(void);