From c16c46aac4af029d807d7060d3fb09a7b707ee4d Mon Sep 17 00:00:00 2001
From: Nathan Bossart <nathandbossart@gmail.com>
Date: Fri, 3 Feb 2023 10:24:14 -0800
Subject: [PATCH v4 2/3] do not call proc_exit in process forked for
 restore_command

---
 src/backend/postmaster/startup.c | 14 +++++++++++++-
 src/backend/storage/ipc/ipc.c    |  3 +++
 src/backend/storage/lmgr/proc.c  |  2 ++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/backend/postmaster/startup.c b/src/backend/postmaster/startup.c
index bcd23542f1..503eb1a5a6 100644
--- a/src/backend/postmaster/startup.c
+++ b/src/backend/postmaster/startup.c
@@ -19,6 +19,8 @@
  */
 #include "postgres.h"
 
+#include <unistd.h>
+
 #include "access/xlog.h"
 #include "access/xlogrecovery.h"
 #include "access/xlogutils.h"
@@ -121,7 +123,17 @@ StartupProcShutdownHandler(SIGNAL_ARGS)
 	int			save_errno = errno;
 
 	if (in_restore_command)
-		proc_exit(1);
+	{
+		/*
+		 * If we are in a child process (e.g., forked by system() in
+		 * shell_restore()), we don't want to call any exit callbacks.  The
+		 * parent will take care of that.
+		 */
+		if (MyProcPid == (int) getpid())
+			proc_exit(1);
+		else
+			_exit(1);
+	}
 	else
 		shutdown_requested = true;
 	WakeupRecovery();
diff --git a/src/backend/storage/ipc/ipc.c b/src/backend/storage/ipc/ipc.c
index 1904d21795..6796cabc3e 100644
--- a/src/backend/storage/ipc/ipc.c
+++ b/src/backend/storage/ipc/ipc.c
@@ -103,6 +103,9 @@ static int	on_proc_exit_index,
 void
 proc_exit(int code)
 {
+	/* proc_exit() is not safe in forked processes from system(), etc. */
+	Assert(MyProcPid == getpid());
+
 	/* Clean up everything that must be cleaned up */
 	proc_exit_prepare(code);
 
diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c
index 22b4278610..5bc53f34a4 100644
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -805,6 +805,7 @@ ProcKill(int code, Datum arg)
 	dlist_head *procgloballist;
 
 	Assert(MyProc != NULL);
+	Assert(MyProcPid == getpid());	/* not safe if forked by system(), etc. */
 
 	/* Make sure we're out of the sync rep lists */
 	SyncRepCleanupAtProcExit();
@@ -925,6 +926,7 @@ AuxiliaryProcKill(int code, Datum arg)
 	PGPROC	   *proc;
 
 	Assert(proctype >= 0 && proctype < NUM_AUXILIARY_PROCS);
+	Assert(MyProcPid == getpid());  /* not safe if forked by system(), etc. */
 
 	auxproc = &AuxiliaryProcs[proctype];
 
-- 
2.25.1