From 2a2352e07df9ccc70689061b6453e226a56e7c79 Mon Sep 17 00:00:00 2001 From: Tom Lane 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 a7762eafcd..70b2e1cbeb 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); /*