v12-0002-Centralize-resetting-SIGCHLD-handler.patch

From 2616894d546d94e790dc294c950f425105f7382a Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Thu, 8 Jan 2026 20:22:43 +0200
Subject: [PATCH v12 2/4] Centralize resetting SIGCHLD handler

---
 src/backend/postmaster/autovacuum.c        |  2 --
 src/backend/postmaster/bgworker.c          |  1 -
 src/backend/postmaster/bgwriter.c          |  5 -----
 src/backend/postmaster/checkpointer.c      |  5 -----
 src/backend/postmaster/pgarch.c            |  3 ---
 src/backend/postmaster/startup.c           |  5 -----
 src/backend/postmaster/syslogger.c         |  5 -----
 src/backend/postmaster/walsummarizer.c     |  5 -----
 src/backend/postmaster/walwriter.c         |  5 -----
 src/backend/replication/logical/slotsync.c |  1 -
 src/backend/replication/walreceiver.c      |  3 ---
 src/backend/replication/walsender.c        |  3 ---
 src/backend/tcop/postgres.c                |  7 -------
 src/backend/utils/init/miscinit.c          | 14 ++++++++++++++
 14 files changed, 14 insertions(+), 50 deletions(-)

diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 5d4eea4a1e3..0a730fb5b45 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -409,7 +409,6 @@ AutoVacLauncherMain(const void *startup_data, size_t startup_data_len)
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, avl_sigusr2_handler);
 	pqsignal(SIGFPE, FloatExceptionHandler);
-	pqsignal(SIGCHLD, SIG_DFL);
 
 	/*
 	 * Create a per-backend PGPROC struct in shared memory.  We must do this
@@ -1416,7 +1415,6 @@ AutoVacWorkerMain(const void *startup_data, size_t startup_data_len)
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, SIG_IGN);
 	pqsignal(SIGFPE, FloatExceptionHandler);
-	pqsignal(SIGCHLD, SIG_DFL);
 
 	/*
 	 * Create a per-backend PGPROC struct in shared memory.  We must do this
diff --git a/src/backend/postmaster/bgworker.c b/src/backend/postmaster/bgworker.c
index 8678ea4e139..133af5aee97 100644
--- a/src/backend/postmaster/bgworker.c
+++ b/src/backend/postmaster/bgworker.c
@@ -781,7 +781,6 @@ BackgroundWorkerMain(const void *startup_data, size_t startup_data_len)
 
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR2, SIG_IGN);
-	pqsignal(SIGCHLD, SIG_DFL);
 
 	/*
 	 * If an exception is encountered, processing resumes here.
diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c
index 0956bd39a85..dbd670c16cc 100644
--- a/src/backend/postmaster/bgwriter.c
+++ b/src/backend/postmaster/bgwriter.c
@@ -108,11 +108,6 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len)
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, SIG_IGN);
 
-	/*
-	 * Reset some signals that are accepted by postmaster but not here
-	 */
-	pqsignal(SIGCHLD, SIG_DFL);
-
 	/*
 	 * 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 f1439d9a363..978a7d0e649 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -221,11 +221,6 @@ CheckpointerMain(const void *startup_data, size_t startup_data_len)
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, SignalHandlerForShutdownRequest);
 
-	/*
-	 * Reset some signals that are accepted by postmaster but not here
-	 */
-	pqsignal(SIGCHLD, SIG_DFL);
-
 	/*
 	 * 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 82731e452fc..10a5ef9e15c 100644
--- a/src/backend/postmaster/pgarch.c
+++ b/src/backend/postmaster/pgarch.c
@@ -237,9 +237,6 @@ PgArchiverMain(const void *startup_data, size_t startup_data_len)
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, pgarch_waken_stop);
 
-	/* Reset some signals that are accepted by postmaster but not here */
-	pqsignal(SIGCHLD, SIG_DFL);
-
 	/* Unblock signals (they were blocked when the postmaster forked us) */
 	sigprocmask(SIG_SETMASK, &UnBlockSig, NULL);
 
diff --git a/src/backend/postmaster/startup.c b/src/backend/postmaster/startup.c
index cdbe53dd262..330c10ddb0b 100644
--- a/src/backend/postmaster/startup.c
+++ b/src/backend/postmaster/startup.c
@@ -234,11 +234,6 @@ StartupProcessMain(const void *startup_data, size_t startup_data_len)
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, StartupProcTriggerHandler);
 
-	/*
-	 * Reset some signals that are accepted by postmaster but not here
-	 */
-	pqsignal(SIGCHLD, SIG_DFL);
-
 	/*
 	 * Register timeouts needed for standby mode
 	 */
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index 86c5e376b40..8515bfb9653 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -283,11 +283,6 @@ SysLoggerMain(const void *startup_data, size_t startup_data_len)
 	pqsignal(SIGUSR1, sigUsr1Handler);	/* request log rotation */
 	pqsignal(SIGUSR2, SIG_IGN);
 
-	/*
-	 * Reset some signals that are accepted by postmaster but not here
-	 */
-	pqsignal(SIGCHLD, SIG_DFL);
-
 	sigprocmask(SIG_SETMASK, &UnBlockSig, NULL);
 
 #ifdef WIN32
diff --git a/src/backend/postmaster/walsummarizer.c b/src/backend/postmaster/walsummarizer.c
index 742137edad6..4e4eed4d076 100644
--- a/src/backend/postmaster/walsummarizer.c
+++ b/src/backend/postmaster/walsummarizer.c
@@ -263,11 +263,6 @@ WalSummarizerMain(const void *startup_data, size_t startup_data_len)
 									ALLOCSET_DEFAULT_SIZES);
 	MemoryContextSwitchTo(context);
 
-	/*
-	 * Reset some signals that are accepted by postmaster but not here
-	 */
-	pqsignal(SIGCHLD, SIG_DFL);
-
 	/*
 	 * If an exception is encountered, processing resumes here.
 	 */
diff --git a/src/backend/postmaster/walwriter.c b/src/backend/postmaster/walwriter.c
index a0ed1e61420..1851417ad1b 100644
--- a/src/backend/postmaster/walwriter.c
+++ b/src/backend/postmaster/walwriter.c
@@ -108,11 +108,6 @@ WalWriterMain(const void *startup_data, size_t startup_data_len)
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, SIG_IGN); /* not used */
 
-	/*
-	 * Reset some signals that are accepted by postmaster but not here
-	 */
-	pqsignal(SIGCHLD, SIG_DFL);
-
 	/*
 	 * 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
diff --git a/src/backend/replication/logical/slotsync.c b/src/backend/replication/logical/slotsync.c
index 062a08ccb88..5e1ee7e4728 100644
--- a/src/backend/replication/logical/slotsync.c
+++ b/src/backend/replication/logical/slotsync.c
@@ -1536,7 +1536,6 @@ ReplSlotSyncWorkerMain(const void *startup_data, size_t startup_data_len)
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
-	pqsignal(SIGCHLD, SIG_DFL);
 
 	check_and_set_sync_info(MyProcPid);
 
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index 7c1b8757d7d..ec6c516530d 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -257,9 +257,6 @@ WalReceiverMain(const void *startup_data, size_t startup_data_len)
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, SIG_IGN);
 
-	/* Reset some signals that are accepted by postmaster but not here */
-	pqsignal(SIGCHLD, SIG_DFL);
-
 	/* Load the libpq-specific functions */
 	load_file("libpqwalreceiver", false);
 	if (WalReceiverFunctions == NULL)
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 2cde8ebc729..5acc8ee3ac8 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -3743,9 +3743,6 @@ WalSndSignals(void)
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, WalSndLastCycleHandler);	/* request a last cycle and
 												 * shutdown */
-
-	/* Reset some signals that are accepted by postmaster but not here */
-	pqsignal(SIGCHLD, SIG_DFL);
 }
 
 /* Report shared-memory space needed by WalSndShmemInit */
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index d01a09dd0c4..5d66c80567c 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -4285,13 +4285,6 @@ PostgresMain(const char *dbname, const char *username)
 		pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 		pqsignal(SIGUSR2, SIG_IGN);
 		pqsignal(SIGFPE, FloatExceptionHandler);
-
-		/*
-		 * Reset some signals that are accepted by postmaster but not by
-		 * backend
-		 */
-		pqsignal(SIGCHLD, SIG_DFL); /* system() requires this on some
-									 * platforms */
 	}
 
 	/* Early initialization */
diff --git a/src/backend/utils/init/miscinit.c b/src/backend/utils/init/miscinit.c
index 03f6c8479f2..fadf856d9bc 100644
--- a/src/backend/utils/init/miscinit.c
+++ b/src/backend/utils/init/miscinit.c
@@ -142,6 +142,15 @@ InitPostmasterChild(void)
 		elog(FATAL, "setsid() failed: %m");
 #endif
 
+	/*
+	 * Reset signals that are used by postmaster but not by child processes.
+	 *
+	 * Currently just SIGCHLD.  The handlers for other signals are overridden
+	 * later, depending on the child process type.
+	 */
+	pqsignal(SIGCHLD, SIG_DFL); /* system() requires this to be SIG_DFL rather
+								 * than SIG_IGN on some platforms */
+
 	/*
 	 * Every postmaster child process is expected to respond promptly to
 	 * SIGQUIT at all times.  Therefore we centrally remove SIGQUIT from
@@ -154,6 +163,11 @@ InitPostmasterChild(void)
 	sigdelset(&BlockSig, SIGQUIT);
 	sigprocmask(SIG_SETMASK, &BlockSig, NULL);
 
+	/*
+	 * It is up to the *Main() function to set signal handlers appropriate for
+	 * the child process and unblock the rest of the signals.
+	 */
+
 	/* Request a signal if the postmaster dies, if possible. */
 	PostmasterDeathSignalInit();
 
-- 
2.47.3