postgres.git / summary / log / commit / refs

commit    2c47fe16a709e01dea403643a1ff4d00c8c8c1ad
Author:   Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date:     Thu Apr 23 18:25:44 2015 +0000
First released in: 9.5.0, 9.0.20, 9.1.16, 9.2.11, 9.3.7, 9.4.2

    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 b85a666ca1c..3ac339bebfc 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);
 		}
 	}


[parent: 2aa0fb032ecd]