From 2c47fe16a709e01dea403643a1ff4d00c8c8c1ad Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Thu, 23 Apr 2015 21:25:44 +0300 Subject: [PATCH] Fix deadlock at startup, if max_prepared_transactions is too small. When the startup process recovers transactions by scanning pg_twophase directory, it should clear MyLockedGxact after it's done processing each transaction. Like we do during normal operation, at PREPARE TRANSACTION. Otherwise, if the startup process exits due to an error, it will try to clear the locking_backend field of the last recovered transaction. That's usually harmless, but if the error happens in MarkAsPreparing, while holding TwoPhaseStateLock, the shmem-exit hook will try to acquire TwoPhaseStateLock again, and deadlock with itself. This fixes bug #13128 reported by Grant McAlister. The bug was introduced by commit bb38fb0d, so backpatch to all supported versions like that commit. --- src/backend/access/transam/twophase.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c index b85a666ca1..3ac339bebf 100644 --- a/src/backend/access/transam/twophase.c +++ b/src/backend/access/transam/twophase.c @@ -2054,6 +2054,12 @@ RecoverPreparedTransactions(void) if (InHotStandby) StandbyReleaseLockTree(xid, hdr->nsubxacts, subxids); + /* + * We're done with recovering this transaction. Clear MyLockedGxact, + * like we do in PrepareTransaction() during normal operation. + */ + PostPrepare_Twophase(); + pfree(buf); } } -- 2.40.0