Date: Sun, 4 Jun 2017 22:24:30 +0000
From: Noah Misch <noah@leadboat.com>
To: simon@2ndquadrant.com
Cc: Michael Paquier <michael.paquier@gmail.com>, wangchuanting@huawei.com,
	PostgreSQL mailing lists <pgsql-bugs@postgresql.org>,
	Tom Lane <tgl@sss.pgh.pa.us>, pgsql-hackers@postgresql.org
Subject: Re: BUG #14680: startup process on standby encounter a deadlock of
 TwoPhaseStateLock when redo 2PC xlog
Message-ID: <20170604222430.GA1547727@rfd.leadboat.com>
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On Thu, Jun 01, 2017 at 01:07:53AM -0700, Michael Paquier wrote:
> On Wed, May 31, 2017 at 12:30 PM, Michael Paquier
> <michael.paquier@gmail.com> wrote:
> > 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?
> 
> Attached is what I was thinking about for reference. I just came back
> from a long flight and I am pretty tired, so my brain may have missed
> something. I'll take again a look at this issue on Monday, an open
> item has been added for now.

[Action required within three days.  This is a generic notification.]

The above-described topic is currently a PostgreSQL 10 open item.  Simon,
since you committed the patch believed to have created it, you own this open
item.  If some other commit is more relevant or if this does not belong as a
v10 open item, please let us know.  Otherwise, please observe the policy on
open item ownership[1] and send a status update within three calendar days of
this message.  Include a date for your subsequent status update.  Testers may
discover new open items at any time, and I want to plan to get them all fixed
well in advance of shipping v10.  Consequently, I will appreciate your efforts
toward speedy resolution.  Thanks.

[1] https://www.postgresql.org/message-id/20170404140717.GA2675809%40tornado.leadboat.com


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