Fix recovery of 2PC transaction during crash recovery A crash in the middle of a checkpoint with some two-phase state data already flushed to disk by this checkpoint could cause a follow-up crash recovery to recover twice the same transaction, once from what has been found in pg_twophase/ at the beginning of recovery and a second time when replaying its corresponding record.
This would lead to FATAL failures in the startup process during recovery, where the same transaction would have a state recovered twice instead of once: LOG: recovering prepared transaction 731 from shared memory LOG: recovering prepared transaction 731 from shared memory FATAL: lock ExclusiveLock on object 731/0/0 is already held This issue is fixed by skipping the addition of any 2PC state coming from a record whose equivalent 2PC state file has already been loaded in TwoPhaseState at the beginning of recovery by restoreTwoPhaseData(), which is OK as long as the system has not reached a consistent state. The timing to get a messed up recovery processing is very racy, and would very unlikely happen. The thread that has reported the issue has demonstrated the bug using injection points to force a PANIC in the middle of a checkpoint. Issue introduced in 728bd99, so backpatch all the way down. Reported-by: "suyu.cmj" <mengjuan....@alibaba-inc.com> Author: "suyu.cmj" <mengjuan....@alibaba-inc.com> Author: Michael Paquier Discussion: https://postgr.es/m/109e6994-b971-48cb-84f6-829646f18b4c.mengjuan....@alibaba-inc.com Backpatch-through: 11 Branch ------ REL_15_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/a878eff6b4b9600763db95ba9dd5725497847fa3 Modified Files -------------- src/backend/access/transam/twophase.c | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+)
