Don't clobber postmaster sigmask in dsm_impl_resize.

macdice · macdice · commit a05f40ef874b · 2022-07-15T02:06:01.000+12:00
Commit 4518c79 intended to block signals in regular backends that allocate DSM segments, but dsm_impl_resize() is also reached by dsm_postmaster_startup(). It's not OK to clobber the postmaster's signal mask, so only manipulate the signal mask when under the postmaster. Back-patch to all releases, like 4518c79. Discussion: https://postgr.es/m/CA%2BhUKGKNpK%3D2OMeea_AZwpLg7Bm4%3DgYWk7eDjZ5F6YbozfOf8w%40mail.gmail.com
diff --git a/src/backend/storage/ipc/dsm_impl.c b/src/backend/storage/ipc/dsm_impl.c
@@ -352,7 +352,8 @@ dsm_impl_posix_resize(int fd, off_t size)
 	 * allowed SIGUSR1 to interrupt us repeatedly (for example, due to recovery
 	 * conflicts), the retry loop might never succeed.
 	 */
-	PG_SETMASK(&BlockSig);
+	if (IsUnderPostmaster)
+		PG_SETMASK(&BlockSig);
 
 	/* Truncate (or extend) the file to the requested size. */
 	do
@@ -390,9 +391,12 @@ dsm_impl_posix_resize(int fd, off_t size)
 	}
 #endif							/* HAVE_POSIX_FALLOCATE && __linux__ */
 
-	save_errno = errno;
-	PG_SETMASK(&UnBlockSig);
-	errno = save_errno;
+	if (IsUnderPostmaster)
+	{
+		save_errno = errno;
+		PG_SETMASK(&UnBlockSig);
+		errno = save_errno;
+	}
 
 	return rc;
 }
