From 462a2f1f019fa16087fe2f59e96e339a703923b2 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Wed, 13 May 2015 09:44:43 +0300 Subject: [PATCH] Fix RBM_ZERO_AND_LOCK mode to not acquire lock on local buffers. Commit 81c45081 introduced a new RBM_ZERO_AND_LOCK mode to ReadBuffer, which takes a lock on the buffer before zeroing it. However, you cannot take a lock on a local buffer, and you got a segfault instead. The version of that patch committed to master included a check for !isLocalBuf, and therefore didn't crash, but oddly I missed that in the back-patched versions. This patch adds that check to the back-branches too. RBM_ZERO_AND_LOCK mode is only used during WAL replay, and in hash indexes. WAL replay only deals with shared buffers, so the only way to trigger the bug is with a temporary hash index. Reported by Artem Ignatyev, analysis by Tom Lane. --- src/backend/storage/buffer/bufmgr.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c index 2f753e52db..19ec7eb231 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -515,7 +515,8 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum, * (Note that we cannot use LockBuffer() of LockBufferForCleanup() here, * because they assert that the buffer is already valid.) */ - if (mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK) + if ((mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK) && + !isLocalBuf) LWLockAcquire(bufHdr->content_lock, LW_EXCLUSIVE); if (isLocalBuf) -- 2.40.0