Re: [BUGS] BUG #14680: startup process on standby encounter adeadlock of TwoPhaseStateLock when redo 2PC xlog

On Wed, May 31, 2017 at 6:57 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> wangchuanting@huawei.com writes:
>> startup process on standby encounter a deadlock of TwoPhaseStateLock when
>> redo 2PC xlog.
>
> Please provide an example of how to get into this state.

That would help. Are you seeing in the logs something like "removing
future two-phase state from memory for XXX" or "removing stale
two-phase state from shared memory for XXX"?

Even with that, the light-weight lock sequence taken in those code
paths look definitely wrong to me, we should not take twice
TwoPhaseStateLock in the same code path. I think that we should remove
the lock acquisitions in RemoveGXact() and PrepareRedoRemove, and then
upgrade the locks of PrescanPreparedTransactions() and
StandbyRecoverPreparedTransactions() to be exclusive. We still need to
keep a lock as CheckPointTwoPhase() may still be triggered by the
checkpoint. Tom, what do you think?
-- 
Michael


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