0001-Make-dsm_impl_resize-more-future-proof.patch

From 17eb588af303873dbd76d0f24b536f74747cb3bf Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Fri, 15 Jul 2022 09:00:12 +1200
Subject: [PATCH] Make dsm_impl_resize more future-proof.

Commit 4518c798 blocks signals for a short region of code, but it
assumed that whatever calls it had the mask set to UnBlockSig on entry.
That may be true today, but it would be more resilient to save and
restore the caller's signal mask.

Previously we couldn't do this because our macro for abstracting signal
mask changes was based on the old pre-POSIX sigsetmask(), due to 1990s
portability concerns.  Since this is a POSIX-only code path, and since
a65e0864 established that supported Unix systems must have
sigprocmask(), we can just use sigprocmask() directly.  It would also be
implementable for Windows, but that's not needed for this.

Back-patch to all releases, like 4518c798 and 80845b7c.

Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CA%2BhUKGKx6Biq7_UuV0kn9DW%2B8QWcpJC1qwhizdtD9tN-fn0H0g%40mail.gmail.com
---
 src/backend/storage/ipc/dsm_impl.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/backend/storage/ipc/dsm_impl.c b/src/backend/storage/ipc/dsm_impl.c
index 0247d13a91..69c6df75b4 100644
--- a/src/backend/storage/ipc/dsm_impl.c
+++ b/src/backend/storage/ipc/dsm_impl.c
@@ -49,6 +49,7 @@
 #include "postgres.h"
 
 #include <fcntl.h>
+#include <signal.h>
 #include <unistd.h>
 #ifndef WIN32
 #include <sys/mman.h>
@@ -62,7 +63,7 @@
 #endif
 
 #include "common/file_perm.h"
-#include "libpq/pqsignal.h"		/* for PG_SETMASK macro */
+#include "libpq/pqsignal.h"
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "portability/mem.h"
@@ -355,6 +356,7 @@ dsm_impl_posix_resize(int fd, off_t size)
 {
 	int			rc;
 	int			save_errno;
+	sigset_t	save_sigmask;
 
 	/*
 	 * Block all blockable signals, except SIGQUIT.  posix_fallocate() can run
@@ -363,7 +365,7 @@ dsm_impl_posix_resize(int fd, off_t size)
 	 * conflicts), the retry loop might never succeed.
 	 */
 	if (IsUnderPostmaster)
-		PG_SETMASK(&BlockSig);
+		sigprocmask(SIG_SETMASK, &BlockSig, &save_sigmask);
 
 	pgstat_report_wait_start(WAIT_EVENT_DSM_ALLOCATE);
 #if defined(HAVE_POSIX_FALLOCATE) && defined(__linux__)
@@ -402,7 +404,7 @@ dsm_impl_posix_resize(int fd, off_t size)
 	if (IsUnderPostmaster)
 	{
 		save_errno = errno;
-		PG_SETMASK(&UnBlockSig);
+		sigprocmask(SIG_SETMASK, &save_sigmask, NULL);
 		errno = save_errno;
 	}
 
-- 
2.30.2