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.
* (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)