v3-0001-Add-errdetail-with-PID-and-UID-about-source-of-te.patch

From 1959b4133f33a4e0cbb98ce257b7517f8f3c46dc Mon Sep 17 00:00:00 2001
From: Jakub Wartak <jakub.wartak@enterprisedb.com>
Date: Tue, 17 Feb 2026 12:41:01 +0100
Subject: [PATCH v3] Add errdetail() with PID and UID about source of
 termination signal.

On Linux and FreeBSD we can use SA_SIGINFO to fetch additional information
about sender of the signal, which can aid troubleshooting. Sample log:
  FATAL:  terminating connection due to administrator command
  DETAIL:  Signal sent by PID 508477, UID 1000.

Author: Jakub Wartak <jakub.wartak@enterprisedb.com>
Reviewed-by: Jim Jones <jim.jones@uni-muenster.de>
Discussion: https://www.postgresql.org/message-id/CAKZiRmyrOWovZSdixpLd3PGMQXuQL_zw2Ght5XhHCkQ1uDsxjw%40mail.gmail.com
---
 configure                         | 42 +++++++++++++++++++++++++++++++
 configure.ac                      | 18 +++++++++++++
 meson.build                       |  4 +++
 src/backend/replication/syncrep.c | 12 +++++++--
 src/backend/tcop/postgres.c       | 42 +++++++++++++++++++++++++------
 src/backend/utils/init/globals.c  |  2 ++
 src/bin/psql/t/001_basic.pl       |  7 +++---
 src/include/miscadmin.h           |  2 ++
 src/include/pg_config.h.in        |  3 +++
 src/port/pqsignal.c               | 35 +++++++++++++++++++++++---
 10 files changed, 151 insertions(+), 16 deletions(-)

diff --git a/configure b/configure
index a285a6ec3d7..704c88aee3d 100755
--- a/configure
+++ b/configure
@@ -15693,6 +15693,48 @@ if test "$ac_cv_sizeof_off_t" -lt 8; then
   fi
 fi
 
+# Check for SA_SIGINFO extended signal handler availability
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for SA_SIGINFO" >&5
+$as_echo_n "checking for SA_SIGINFO... " >&6; }
+if ${ac_cv_have_sa_siginfo+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+    cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+
+            #include <signal.h>
+            #include <stddef.h>
+
+int
+main ()
+{
+
+            struct sigaction sa;
+            sa.sa_flags = SA_SIGINFO;
+
+  ;
+  return 0;
+}
+
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  ac_cv_have_sa_siginfo=yes
+else
+  ac_cv_have_sa_siginfo=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_have_sa_siginfo" >&5
+$as_echo "$ac_cv_have_sa_siginfo" >&6; }
+
+if test "x$ac_cv_have_sa_siginfo" = "xyes"; then
+
+$as_echo "#define HAVE_SA_SIGINFO 1" >>confdefs.h
+
+fi
 
 ##
 ## Functions, global variables
diff --git a/configure.ac b/configure.ac
index 476a76c7991..183bc992126 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1822,6 +1822,24 @@ if test "$ac_cv_sizeof_off_t" -lt 8; then
   fi
 fi
 
+# Check for SA_SIGINFO extended signal handler availability
+AC_CACHE_CHECK([for SA_SIGINFO], [ac_cv_have_sa_siginfo], [
+    AC_COMPILE_IFELSE([
+        AC_LANG_PROGRAM([[
+            #include <signal.h>
+            #include <stddef.h>
+        ]], [[
+            struct sigaction sa;
+            sa.sa_flags = SA_SIGINFO;
+        ]])
+    ],
+    [ac_cv_have_sa_siginfo=yes],
+    [ac_cv_have_sa_siginfo=no])
+])
+
+if test "x$ac_cv_have_sa_siginfo" = "xyes"; then
+    AC_DEFINE([HAVE_SA_SIGINFO], 1, [Define to 1 if you have SA_SIGINFO available.])
+fi
 
 ##
 ## Functions, global variables
diff --git a/meson.build b/meson.build
index 5122706477d..3aa675e7ebb 100644
--- a/meson.build
+++ b/meson.build
@@ -2879,6 +2879,10 @@ if cc.has_member('struct sockaddr', 'sa_len',
   cdata.set('HAVE_STRUCT_SOCKADDR_SA_LEN', 1)
 endif
 
+if cc.has_header_symbol('signal.h', 'SA_SIGINFO')
+  cdata.set('HAVE_SA_SIGINFO', 1)
+endif
+
 if cc.has_member('struct tm', 'tm_zone',
     args: test_c_args, include_directories: postgres_inc,
     prefix: '''
diff --git a/src/backend/replication/syncrep.c b/src/backend/replication/syncrep.c
index d1582a5d711..74cd41adfd4 100644
--- a/src/backend/replication/syncrep.c
+++ b/src/backend/replication/syncrep.c
@@ -302,7 +302,11 @@ SyncRepWaitForLSN(XLogRecPtr lsn, bool commit)
 			ereport(WARNING,
 					(errcode(ERRCODE_ADMIN_SHUTDOWN),
 					 errmsg("canceling the wait for synchronous replication and terminating connection due to administrator command"),
-					 errdetail("The transaction has already committed locally, but might not have been replicated to the standby.")));
+					 errdetail("The transaction has already committed locally, but might not have been replicated to the standby."),
+						proc_die_sender_pid == 0 ? 0 :
+							errdetail("Signal sent by PID %lld, UID %lld.",
+								(long long)proc_die_sender_pid, (long long)proc_die_sender_uid)
+						));
 			whereToSendOutput = DestNone;
 			SyncRepCancelWait();
 			break;
@@ -319,7 +323,11 @@ SyncRepWaitForLSN(XLogRecPtr lsn, bool commit)
 			QueryCancelPending = false;
 			ereport(WARNING,
 					(errmsg("canceling wait for synchronous replication due to user request"),
-					 errdetail("The transaction has already committed locally, but might not have been replicated to the standby.")));
+					 errdetail("The transaction has already committed locally, but might not have been replicated to the standby."),
+						proc_die_sender_pid == 0 ? 0 :
+							errdetail("Signal sent by PID %lld, UID %lld.",
+								(long long)proc_die_sender_pid, (long long)proc_die_sender_uid)
+						));
 			SyncRepCancelWait();
 			break;
 		}
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index d01a09dd0c4..6e3a0ec8655 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -3357,15 +3357,27 @@ ProcessInterrupts(void)
 		else if (AmAutoVacuumWorkerProcess())
 			ereport(FATAL,
 					(errcode(ERRCODE_ADMIN_SHUTDOWN),
-					 errmsg("terminating autovacuum process due to administrator command")));
+					 errmsg("terminating autovacuum process due to administrator command"),
+					 proc_die_sender_pid == 0 ? 0 :
+						errdetail("Signal sent by PID %lld, UID %lld.",
+							(long long)proc_die_sender_pid, (long long)proc_die_sender_uid)
+					));
 		else if (IsLogicalWorker())
 			ereport(FATAL,
 					(errcode(ERRCODE_ADMIN_SHUTDOWN),
-					 errmsg("terminating logical replication worker due to administrator command")));
+					 errmsg("terminating logical replication worker due to administrator command"),
+					 proc_die_sender_pid == 0 ? 0 :
+						errdetail("Signal sent by PID %lld, UID %lld.",
+							(long long)proc_die_sender_pid, (long long)proc_die_sender_uid)
+					));
 		else if (IsLogicalLauncher())
 		{
 			ereport(DEBUG1,
-					(errmsg_internal("logical replication launcher shutting down")));
+					(errmsg_internal("logical replication launcher shutting down"),
+					 proc_die_sender_pid == 0 ? 0 :
+						errdetail("Signal sent by PID %lld, UID %lld.",
+							(long long)proc_die_sender_pid, (long long)proc_die_sender_uid)
+					));
 
 			/*
 			 * The logical replication launcher can be stopped at any time.
@@ -3376,23 +3388,39 @@ ProcessInterrupts(void)
 		else if (AmWalReceiverProcess())
 			ereport(FATAL,
 					(errcode(ERRCODE_ADMIN_SHUTDOWN),
-					 errmsg("terminating walreceiver process due to administrator command")));
+					 errmsg("terminating walreceiver process due to administrator command"),
+					 proc_die_sender_pid == 0 ? 0 :
+						errdetail("Signal sent by PID %lld, UID %lld.",
+							(long long)proc_die_sender_pid, (long long)proc_die_sender_uid)
+					));
 		else if (AmBackgroundWorkerProcess())
 			ereport(FATAL,
 					(errcode(ERRCODE_ADMIN_SHUTDOWN),
 					 errmsg("terminating background worker \"%s\" due to administrator command",
-							MyBgworkerEntry->bgw_type)));
+							MyBgworkerEntry->bgw_type),
+					 proc_die_sender_pid == 0 ? 0 :
+						errdetail("Signal sent by PID %lld, UID %lld.",
+							(long long)proc_die_sender_pid, (long long)proc_die_sender_uid)
+					));
 		else if (AmIoWorkerProcess())
 		{
 			ereport(DEBUG1,
-					(errmsg_internal("io worker shutting down due to administrator command")));
+					(errmsg_internal("io worker shutting down due to administrator command"),
+					 proc_die_sender_pid == 0 ? 0 :
+						errdetail("Signal sent by PID %lld, UID %lld.",
+							(long long)proc_die_sender_pid, (long long)proc_die_sender_uid)
+					));
 
 			proc_exit(0);
 		}
 		else
 			ereport(FATAL,
 					(errcode(ERRCODE_ADMIN_SHUTDOWN),
-					 errmsg("terminating connection due to administrator command")));
+					 errmsg("terminating connection due to administrator command"),
+					 proc_die_sender_pid == 0 ? 0 :
+						errdetail("Signal sent by PID %lld, UID %lld.",
+							(long long)proc_die_sender_pid, (long long)proc_die_sender_uid)
+					));
 	}
 
 	if (CheckClientConnectionPending)
diff --git a/src/backend/utils/init/globals.c b/src/backend/utils/init/globals.c
index 36ad708b360..927c98b45ee 100644
--- a/src/backend/utils/init/globals.c
+++ b/src/backend/utils/init/globals.c
@@ -32,6 +32,8 @@ ProtocolVersion FrontendProtocol;
 volatile sig_atomic_t InterruptPending = false;
 volatile sig_atomic_t QueryCancelPending = false;
 volatile sig_atomic_t ProcDiePending = false;
+volatile uint32 proc_die_sender_pid = 0;
+volatile uint32 proc_die_sender_uid = 0;
 volatile sig_atomic_t CheckClientConnectionPending = false;
 volatile sig_atomic_t ClientConnectionLost = false;
 volatile sig_atomic_t IdleInTransactionSessionTimeoutPending = false;
diff --git a/src/bin/psql/t/001_basic.pl b/src/bin/psql/t/001_basic.pl
index 6839f27cbe5..7bd585d40e3 100644
--- a/src/bin/psql/t/001_basic.pl
+++ b/src/bin/psql/t/001_basic.pl
@@ -142,12 +142,11 @@ my ($ret, $out, $err) = $node->psql('postgres',
 is($ret, 2, 'server crash: psql exit code');
 like($out, qr/before/, 'server crash: output before crash');
 unlike($out, qr/AFTER/, 'server crash: no output after crash');
-is( $err,
-	'psql:<stdin>:2: FATAL:  terminating connection due to administrator command
-psql:<stdin>:2: server closed the connection unexpectedly
+like( $err, qr/psql:<stdin>:2: FATAL:  terminating connection due to administrator command
+(?:DETAIL:  Signal sent by PID \d+, UID \d+.\n)?psql:<stdin>:2: server closed the connection unexpectedly
 	This probably means the server terminated abnormally
 	before or while processing the request.
-psql:<stdin>:2: error: connection to server was lost',
+psql:<stdin>:2: error: connection to server was lost/,
 	'server crash: error message');
 
 # test \errverbose
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index f16f35659b9..38bae8bb809 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -90,6 +90,8 @@
 extern PGDLLIMPORT volatile sig_atomic_t InterruptPending;
 extern PGDLLIMPORT volatile sig_atomic_t QueryCancelPending;
 extern PGDLLIMPORT volatile sig_atomic_t ProcDiePending;
+extern PGDLLIMPORT volatile uint32 proc_die_sender_pid;
+extern PGDLLIMPORT volatile uint32 proc_die_sender_uid;
 extern PGDLLIMPORT volatile sig_atomic_t IdleInTransactionSessionTimeoutPending;
 extern PGDLLIMPORT volatile sig_atomic_t TransactionTimeoutPending;
 extern PGDLLIMPORT volatile sig_atomic_t IdleSessionTimeoutPending;
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index a0bd84376e7..1fbb2ce380a 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -340,6 +340,9 @@
 /* Define to 1 if you have the `rl_variable_bind' function. */
 #undef HAVE_RL_VARIABLE_BIND
 
+/* Define to 1 if you have SA_SIGINFO available. */
+#undef HAVE_SA_SIGINFO
+
 /* Define to 1 if you have the <security/pam_appl.h> header file. */
 #undef HAVE_SECURITY_PAM_APPL_H
 
diff --git a/src/port/pqsignal.c b/src/port/pqsignal.c
index fbdf9341c2f..5e61739fdc3 100644
--- a/src/port/pqsignal.c
+++ b/src/port/pqsignal.c
@@ -82,10 +82,19 @@ static volatile pqsigfunc pqsignal_handlers[PG_NSIG];
  *
  * This wrapper also handles restoring the value of errno.
  */
+#if !defined(FRONTEND) && defined(HAVE_SA_SIGINFO)
+static void
+wrapper_handler(int signo, siginfo_t *info, void *context)
+#else
 static void
 wrapper_handler(SIGNAL_ARGS)
+#endif
 {
 	int			save_errno = errno;
+#if !defined(FRONTEND) && defined(HAVE_SA_SIGINFO)
+	/* SIGNAL_ARGS defines postgres_signal_arg */
+	int			postgres_signal_arg = signo;
+#endif
 
 	Assert(postgres_signal_arg > 0);
 	Assert(postgres_signal_arg < PG_NSIG);
@@ -105,6 +114,14 @@ wrapper_handler(SIGNAL_ARGS)
 		raise(postgres_signal_arg);
 		return;
 	}
+
+#ifdef HAVE_SA_SIGINFO
+	if (signo == SIGTERM && info)
+	{
+		proc_die_sender_pid = info->si_pid;
+		proc_die_sender_uid = info->si_uid;
+	}
+#endif
 #endif
 
 	(*pqsignal_handlers[postgres_signal_arg]) (postgres_signal_arg);
@@ -125,6 +142,7 @@ pqsignal(int signo, pqsigfunc func)
 #if !(defined(WIN32) && defined(FRONTEND))
 	struct sigaction act;
 #endif
+	bool		use_wrapper = false;
 
 	Assert(signo > 0);
 	Assert(signo < PG_NSIG);
@@ -132,13 +150,24 @@ pqsignal(int signo, pqsigfunc func)
 	if (func != SIG_IGN && func != SIG_DFL)
 	{
 		pqsignal_handlers[signo] = func;	/* assumed atomic */
-		func = wrapper_handler;
+		use_wrapper = true;
 	}
 
 #if !(defined(WIN32) && defined(FRONTEND))
-	act.sa_handler = func;
 	sigemptyset(&act.sa_mask);
 	act.sa_flags = SA_RESTART;
+#if !defined(FRONTEND) && defined(HAVE_SA_SIGINFO)
+	if (use_wrapper)
+	{
+		act.sa_sigaction = wrapper_handler;
+		act.sa_flags |= SA_SIGINFO;
+	}
+	else
+		act.sa_handler = func;
+#else
+	act.sa_handler = use_wrapper ? wrapper_handler : func;
+#endif
+
 #ifdef SA_NOCLDSTOP
 	if (signo == SIGCHLD)
 		act.sa_flags |= SA_NOCLDSTOP;
@@ -147,7 +176,7 @@ pqsignal(int signo, pqsigfunc func)
 		Assert(false);			/* probably indicates coding error */
 #else
 	/* Forward to Windows native signal system. */
-	if (signal(signo, func) == SIG_ERR)
+	if (signal(signo, use_wrapper ? wrapper_handler : func) == SIG_ERR)
 		Assert(false);			/* probably indicates coding error */
 #endif
 }
-- 
2.43.0