Centralize setup of SIGQUIT handling for postmaster child processes.

We decided that the policy established in commit 7634bd4f6 for
the bgwriter, checkpointer, walwriter, and walreceiver processes,
namely that they should accept SIGQUIT at all times, really ought
to apply uniformly to all postmaster children.  Therefore, get
rid of the duplicative and inconsistent per-process code for
establishing that signal handler and removing SIGQUIT from BlockSig.
Instead, make InitPostmasterChild do it.

The handler set up by InitPostmasterChild is SignalHandlerForCrashExit,
which just summarily does _exit(2).  In interactive backends, we
almost immediately replace that with quickdie, since we would prefer
to try to tell the client that we're dying.  However, this patch is
changing the behavior of autovacuum (both launcher and workers), as
well as walsenders.  Those processes formerly also used quickdie,
but AFAICS that was just mindless copy-and-paste: they don't have
any interactive client that's likely to benefit from being told this.

The stats collector continues to be an outlier, in that it thinks
SIGQUIT means normal exit.  That should probably be changed for
consistency, but there's another patch set where that's being
dealt with, so I didn't do so here.

Discussion: https://postgr.es/m/644875.1599933441@sss.pgh.pa.us

8 files changed, 18 insertions, 32 deletions

diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 19ba26b914..2cef56f115 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -454,8 +454,8 @@ AutoVacLauncherMain(int argc, char *argv[])
 	pqsignal(SIGHUP, SignalHandlerForConfigReload);
 	pqsignal(SIGINT, StatementCancelHandler);
 	pqsignal(SIGTERM, SignalHandlerForShutdownRequest);
+	/* SIGQUIT handler was already set up by InitPostmasterChild */
 
-	pqsignal(SIGQUIT, quickdie);
 	InitializeTimeouts();		/* establishes SIGALRM handler */
 
 	pqsignal(SIGPIPE, SIG_IGN);
@@ -498,9 +498,10 @@ AutoVacLauncherMain(int argc, char *argv[])
 	 *
 	 * Note that we use sigsetjmp(..., 1), so that the prevailing signal mask
 	 * (to wit, BlockSig) will be restored when longjmp'ing to here.  Thus,
-	 * signals will be blocked until we complete error recovery.  It might
-	 * seem that this policy makes the HOLD_INTERRUPTS() call redundant, but
-	 * it is not since InterruptPending might be set already.
+	 * signals other than SIGQUIT will be blocked until we complete error
+	 * recovery.  It might seem that this policy makes the HOLD_INTERRUPTS()
+	 * call redundant, but it is not since InterruptPending might be set
+	 * already.
 	 */
 	if (sigsetjmp(local_sigjmp_buf, 1) != 0)
 	{
@@ -1531,7 +1532,8 @@ AutoVacWorkerMain(int argc, char *argv[])
 	 */
 	pqsignal(SIGINT, StatementCancelHandler);
 	pqsignal(SIGTERM, die);
-	pqsignal(SIGQUIT, quickdie);
+	/* SIGQUIT handler was already set up by InitPostmasterChild */
+
 	InitializeTimeouts();		/* establishes SIGALRM handler */
 
 	pqsignal(SIGPIPE, SIG_IGN);
@@ -1562,9 +1564,9 @@ AutoVacWorkerMain(int argc, char *argv[])
 	 *
 	 * Note that we use sigsetjmp(..., 1), so that the prevailing signal mask
 	 * (to wit, BlockSig) will be restored when longjmp'ing to here.  Thus,
-	 * signals will be blocked until we exit.  It might seem that this policy
-	 * makes the HOLD_INTERRUPTS() call redundant, but it is not since
-	 * InterruptPending might be set already.
+	 * signals other than SIGQUIT will be blocked until we exit.  It might
+	 * seem that this policy makes the HOLD_INTERRUPTS() call redundant, but
+	 * it is not since InterruptPending might be set already.
 	 */
 	if (sigsetjmp(local_sigjmp_buf, 1) != 0)
 	{
diff --git a/src/backend/postmaster/bgworker.c b/src/backend/postmaster/bgworker.c
index d043ced686..5a9a0e3435 100644
--- a/src/backend/postmaster/bgworker.c
+++ b/src/backend/postmaster/bgworker.c
@@ -731,9 +731,9 @@ StartBackgroundWorker(void)
 		pqsignal(SIGFPE, SIG_IGN);
 	}
 	pqsignal(SIGTERM, bgworker_die);
+	/* SIGQUIT handler was already set up by InitPostmasterChild */
 	pqsignal(SIGHUP, SIG_IGN);
 
-	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 c96568149f..a7afa758b6 100644
--- a/src/backend/postmaster/bgwriter.c
+++ b/src/backend/postmaster/bgwriter.c
@@ -104,7 +104,7 @@ BackgroundWriterMain(void)
 	pqsignal(SIGHUP, SignalHandlerForConfigReload);
 	pqsignal(SIGINT, SIG_IGN);
 	pqsignal(SIGTERM, SignalHandlerForShutdownRequest);
-	pqsignal(SIGQUIT, SignalHandlerForCrashExit);
+	/* SIGQUIT handler was already set up by InitPostmasterChild */
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
@@ -115,10 +115,6 @@ BackgroundWriterMain(void)
 	 */
 	pqsignal(SIGCHLD, SIG_DFL);
 
-	/* We allow SIGQUIT (SignalHandlerForCrashExit) at all times */
-	sigdelset(&BlockSig, SIGQUIT);
-	PG_SETMASK(&BlockSig);
-
 	/*
 	 * We just started, assume there has been either a shutdown or
 	 * end-of-recovery snapshot.
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index 45f5deca72..3e7dcd4f76 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -198,7 +198,7 @@ CheckpointerMain(void)
 	pqsignal(SIGHUP, SignalHandlerForConfigReload);
 	pqsignal(SIGINT, ReqCheckpointHandler); /* request checkpoint */
 	pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */
-	pqsignal(SIGQUIT, SignalHandlerForCrashExit);
+	/* SIGQUIT handler was already set up by InitPostmasterChild */
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
@@ -209,10 +209,6 @@ CheckpointerMain(void)
 	 */
 	pqsignal(SIGCHLD, SIG_DFL);
 
-	/* We allow SIGQUIT (SignalHandlerForCrashExit) at all times */
-	sigdelset(&BlockSig, SIGQUIT);
-	PG_SETMASK(&BlockSig);
-
 	/*
 	 * Initialize so that first time-driven event happens at the correct time.
 	 */
diff --git a/src/backend/postmaster/pgarch.c b/src/backend/postmaster/pgarch.c
index 37be0e2bbb..ed1b65358d 100644
--- a/src/backend/postmaster/pgarch.c
+++ b/src/backend/postmaster/pgarch.c
@@ -228,7 +228,7 @@ PgArchiverMain(int argc, char *argv[])
 	pqsignal(SIGHUP, SignalHandlerForConfigReload);
 	pqsignal(SIGINT, SIG_IGN);
 	pqsignal(SIGTERM, SignalHandlerForShutdownRequest);
-	pqsignal(SIGQUIT, SignalHandlerForCrashExit);
+	/* SIGQUIT handler was already set up by InitPostmasterChild */
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, pgarch_waken);
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 3cd6fa30eb..959e3b8873 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -4355,7 +4355,7 @@ BackendInitialize(Port *port)
 	 * cleaned up.
 	 */
 	pqsignal(SIGTERM, process_startup_packet_die);
-	pqsignal(SIGQUIT, SignalHandlerForCrashExit);
+	/* SIGQUIT handler was already set up by InitPostmasterChild */
 	InitializeTimeouts();		/* establishes SIGALRM handler */
 	PG_SETMASK(&StartupBlockSig);
 
@@ -4435,7 +4435,7 @@ BackendInitialize(Port *port)
 	status = ProcessStartupPacket(port, false, false);
 
 	/*
-	 * Disable the timeout, and prevent SIGTERM/SIGQUIT again.
+	 * Disable the timeout, and prevent SIGTERM again.
 	 */
 	disable_timeout(STARTUP_PACKET_TIMEOUT, false);
 	PG_SETMASK(&BlockSig);
@@ -4983,10 +4983,6 @@ SubPostmasterMain(int argc, char *argv[])
 	if (strcmp(argv[1], "--forkavworker") == 0)
 		AutovacuumWorkerIAm();
 
-	/* In EXEC_BACKEND case we will not have inherited these settings */
-	pqinitmask();
-	PG_SETMASK(&BlockSig);
-
 	/* Read in remaining GUC variables */
 	read_nondefault_variables();
 
diff --git a/src/backend/postmaster/startup.c b/src/backend/postmaster/startup.c
index fd9ac35dac..64af7b8707 100644
--- a/src/backend/postmaster/startup.c
+++ b/src/backend/postmaster/startup.c
@@ -175,7 +175,7 @@ StartupProcessMain(void)
 	pqsignal(SIGHUP, StartupProcSigHupHandler); /* reload config file */
 	pqsignal(SIGINT, SIG_IGN);	/* ignore query cancel */
 	pqsignal(SIGTERM, StartupProcShutdownHandler);	/* request shutdown */
-	pqsignal(SIGQUIT, SignalHandlerForCrashExit);
+	/* SIGQUIT handler was already set up by InitPostmasterChild */
 	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 358c0916ac..a52832fe90 100644
--- a/src/backend/postmaster/walwriter.c
+++ b/src/backend/postmaster/walwriter.c
@@ -101,7 +101,7 @@ WalWriterMain(void)
 	pqsignal(SIGHUP, SignalHandlerForConfigReload);
 	pqsignal(SIGINT, SignalHandlerForShutdownRequest);
 	pqsignal(SIGTERM, SignalHandlerForShutdownRequest);
-	pqsignal(SIGQUIT, SignalHandlerForCrashExit);
+	/* SIGQUIT handler was already set up by InitPostmasterChild */
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
@@ -112,10 +112,6 @@ WalWriterMain(void)
 	 */
 	pqsignal(SIGCHLD, SIG_DFL);
 
-	/* We allow SIGQUIT (SignalHandlerForCrashExit) at all times */
-	sigdelset(&BlockSig, SIGQUIT);
-	PG_SETMASK(&BlockSig);
-
 	/*
 	 * Create a memory context that we will do all our work in.  We do this so
 	 * that we can reset the context during error recovery and thereby avoid