v13-0002-Centralize-resetting-SIGCHLD-handler.patch

From 72bbc1428c4da0dbfdbbe9a506917e687acbc448 Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Tue, 16 Jun 2026 22:06:39 +0300
Subject: [PATCH v13 2/9] 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 777acaa7c84..31cad5df015 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -447,7 +447,6 @@ 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, PG_SIG_DFL);
 
 	/*
 	 * Create a per-backend PGPROC struct in shared memory.  We must do this
@@ -1454,7 +1453,6 @@ AutoVacWorkerMain(const void *startup_data, size_t startup_data_len)
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, PG_SIG_IGN);
 	pqsignal(SIGFPE, FloatExceptionHandler);
-	pqsignal(SIGCHLD, PG_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 2e4acad4f00..2f51814c93d 100644
--- a/src/backend/postmaster/bgworker.c
+++ b/src/backend/postmaster/bgworker.c
@@ -797,7 +797,6 @@ BackgroundWorkerMain(const void *startup_data, size_t startup_data_len)
 
 	pqsignal(SIGPIPE, PG_SIG_IGN);
 	pqsignal(SIGUSR2, PG_SIG_IGN);
-	pqsignal(SIGCHLD, PG_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 d364382303a..d6121f2b4fe 100644
--- a/src/backend/postmaster/bgwriter.c
+++ b/src/backend/postmaster/bgwriter.c
@@ -109,11 +109,6 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len)
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, PG_SIG_IGN);
 
-	/*
-	 * Reset some signals that are accepted by postmaster but not here
-	 */
-	pqsignal(SIGCHLD, PG_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 a09d4097d51..4b051eb3128 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -231,11 +231,6 @@ 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, PG_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 0f207ac0356..a3fd4f83201 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, PG_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 d91b7caac01..63624e8caa1 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, PG_SIG_DFL);
-
 	/*
 	 * Register timeouts needed for standby mode
 	 */
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index 7645c495a81..b399adcce75 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -303,11 +303,6 @@ SysLoggerMain(const void *startup_data, size_t startup_data_len)
 	pqsignal(SIGUSR1, sigUsr1Handler);	/* request log rotation */
 	pqsignal(SIGUSR2, PG_SIG_IGN);
 
-	/*
-	 * Reset some signals that are accepted by postmaster but not here
-	 */
-	pqsignal(SIGCHLD, PG_SIG_DFL);
-
 	sigprocmask(SIG_SETMASK, &UnBlockSig, NULL);
 
 #ifdef WIN32
diff --git a/src/backend/postmaster/walsummarizer.c b/src/backend/postmaster/walsummarizer.c
index 4f12eaf2c85..89301815dc3 100644
--- a/src/backend/postmaster/walsummarizer.c
+++ b/src/backend/postmaster/walsummarizer.c
@@ -264,11 +264,6 @@ 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, PG_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 68dd5047c20..3493be8e630 100644
--- a/src/backend/postmaster/walwriter.c
+++ b/src/backend/postmaster/walwriter.c
@@ -109,11 +109,6 @@ WalWriterMain(const void *startup_data, size_t startup_data_len)
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, PG_SIG_IGN);	/* not used */
 
-	/*
-	 * Reset some signals that are accepted by postmaster but not here
-	 */
-	pqsignal(SIGCHLD, PG_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 05637344363..7d2999d77fd 100644
--- a/src/backend/replication/logical/slotsync.c
+++ b/src/backend/replication/logical/slotsync.c
@@ -1632,7 +1632,6 @@ ReplSlotSyncWorkerMain(const void *startup_data, size_t startup_data_len)
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, PG_SIG_IGN);
 	pqsignal(SIGPIPE, PG_SIG_IGN);
-	pqsignal(SIGCHLD, PG_SIG_DFL);
 
 	check_and_set_sync_info(MyProcPid);
 
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index 05e2f690fa7..4319cb6fd43 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -256,9 +256,6 @@ WalReceiverMain(const void *startup_data, size_t startup_data_len)
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, PG_SIG_IGN);
 
-	/* Reset some signals that are accepted by postmaster but not here */
-	pqsignal(SIGCHLD, PG_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 c931d9b4fa8..795393b0be0 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -3977,9 +3977,6 @@ 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, PG_SIG_DFL);
 }
 
 /* Register shared-memory space needed by walsender */
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index dbef734a93f..1f2fc3cce9b 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -4332,13 +4332,6 @@ PostgresMain(const char *dbname, const char *username)
 		pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 		pqsignal(SIGUSR2, PG_SIG_IGN);
 		pqsignal(SIGFPE, FloatExceptionHandler);
-
-		/*
-		 * Reset some signals that are accepted by postmaster but not by
-		 * backend
-		 */
-		pqsignal(SIGCHLD, PG_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 7ffc808073a..5343d4219ae 100644
--- a/src/backend/utils/init/miscinit.c
+++ b/src/backend/utils/init/miscinit.c
@@ -143,6 +143,15 @@ 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, PG_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
@@ -155,6 +164,11 @@ 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