From 2a2352e07df9ccc70689061b6453e226a56e7c79 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 3 Sep 2012 15:38:42 -0400
Subject: [PATCH] Replace memcpy() calls in xlog.c critical sections with
 struct assignments.

This gets rid of a dangerous-looking use of the not-volatile XLogCtl
pointer in a couple of spinlock-protected sections, where the normal
coding rule is that you should only access shared memory through a
pointer-to-volatile.  I think the risk is only hypothetical not actual,
since for there to be a bug the compiler would have to move the spinlock
acquire or release across the memcpy() call, which one sincerely hopes
it will not.  Still, it looks cleaner this way.

Per comment from Daniel Farina and subsequent discussion.
---
 src/backend/access/transam/xlog.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index a7762eafcd0..70b2e1cbeb8 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -8158,8 +8158,8 @@ RecoveryRestartPoint(const CheckPoint *checkPoint)
 	 * work out the next time it wants to perform a restartpoint.
 	 */
 	SpinLockAcquire(&xlogctl->info_lck);
-	XLogCtl->lastCheckPointRecPtr = ReadRecPtr;
-	memcpy(&XLogCtl->lastCheckPoint, checkPoint, sizeof(CheckPoint));
+	xlogctl->lastCheckPointRecPtr = ReadRecPtr;
+	xlogctl->lastCheckPoint = *checkPoint;
 	SpinLockRelease(&xlogctl->info_lck);
 }
 
@@ -8194,7 +8194,7 @@ CreateRestartPoint(int flags)
 	/* Get a local copy of the last safe checkpoint record. */
 	SpinLockAcquire(&xlogctl->info_lck);
 	lastCheckPointRecPtr = xlogctl->lastCheckPointRecPtr;
-	memcpy(&lastCheckPoint, &XLogCtl->lastCheckPoint, sizeof(CheckPoint));
+	lastCheckPoint = xlogctl->lastCheckPoint;
 	SpinLockRelease(&xlogctl->info_lck);
 
 	/*
-- 
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