From ee0e525bfc3a3d0851e36d3d15dce3a8bd7ac029 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 16 Aug 2010 17:32:46 +0000
Subject: [PATCH] Arrange to fsync the contents of lockfiles (both
 postmaster.pid and the socket lockfile) when writing them.  The lack of an
 fsync here may well explain two different reports we've seen of corrupted
 lockfile contents, which doesn't particularly bother the running server but
 can prevent a new server from starting if the old one crashes.  Per
 suggestion from Alvaro.

Back-patch to all supported versions.
---
 src/backend/utils/init/miscinit.c | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/src/backend/utils/init/miscinit.c b/src/backend/utils/init/miscinit.c
index e6b6676706..973f584067 100644
--- a/src/backend/utils/init/miscinit.c
+++ b/src/backend/utils/init/miscinit.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/init/miscinit.c,v 1.184 2010/04/20 23:48:47 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/init/miscinit.c,v 1.185 2010/08/16 17:32:46 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -818,6 +818,9 @@ CreateLockFile(const char *filename, bool amPostmaster,
 		 * admin) but has left orphan backends behind.	Check for this by
 		 * looking to see if there is an associated shmem segment that is
 		 * still in use.
+		 *
+		 * Note: because postmaster.pid is written in two steps, we might not
+		 * find the shmem ID values in it; we can't treat that as an error.
 		 */
 		if (isDDLock)
 		{
@@ -881,7 +884,18 @@ CreateLockFile(const char *filename, bool amPostmaster,
 				(errcode_for_file_access(),
 				 errmsg("could not write lock file \"%s\": %m", filename)));
 	}
-	if (close(fd))
+	if (pg_fsync(fd) != 0)
+	{
+		int			save_errno = errno;
+
+		close(fd);
+		unlink(filename);
+		errno = save_errno;
+		ereport(FATAL,
+				(errcode_for_file_access(),
+				 errmsg("could not write lock file \"%s\": %m", filename)));
+	}
+	if (close(fd) != 0)
 	{
 		int			save_errno = errno;
 
@@ -1042,7 +1056,14 @@ RecordSharedMemoryInLockFile(unsigned long id1, unsigned long id2)
 		close(fd);
 		return;
 	}
-	if (close(fd))
+	if (pg_fsync(fd) != 0)
+	{
+		ereport(LOG,
+				(errcode_for_file_access(),
+				 errmsg("could not write to file \"%s\": %m",
+						DIRECTORY_LOCK_FILE)));
+	}
+	if (close(fd) != 0)
 	{
 		ereport(LOG,
 				(errcode_for_file_access(),