From: Tom Lane <tgl@sss.pgh.pa.us>
To: Masahiko Sawada <masahiko.sawada@2ndquadrant.com>
Cc: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: Fujii Masao <masao.fujii@oss.nttdata.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Race condition in SyncRepGetSyncStandbysPriority
Date: Sat, 18 Apr 2020 12:00:19 -0400
Message-ID: <22664.1587225619@sss.pgh.pa.us> (raw)
In-Reply-To: <CA+fd4k4oJZYmi8+U=_8_CH3Lwk2ZQoeV2rmGkYtvoAnHXsQsTQ@mail.gmail.com>
References: <23215.1587051546@sss.pgh.pa.us>
<20200417.145834.1847060913969327935.horikyota.ntt@gmail.com>
<3f58063d-2544-aea8-07aa-7e0c35484187@oss.nttdata.com>
<20200417.170706.1152908438290368702.horikyota.ntt@gmail.com>
<3020.1587137510@sss.pgh.pa.us>
<CA+fd4k4oJZYmi8+U=_8_CH3Lwk2ZQoeV2rmGkYtvoAnHXsQsTQ@mail.gmail.com>
Masahiko Sawada <masahiko.sawada@2ndquadrant.com> writes:
> On Sat, 18 Apr 2020 at 00:31, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> + /* Quick out if not even configured to be synchronous */
>> + if (SyncRepConfig == NULL)
>> + return false;
> I felt strange a bit that we do the above check in
> SyncRepGetSyncRecPtr() because SyncRepReleaseWaiters() which is the
> only caller says the following before calling it:
Notice there was such a test in SyncRepGetSyncRecPtr already --- I just
moved it to be before doing some work instead of after.
> Can we either change it to an assertion, move it to before acquiring
> SyncRepLock in SyncRepReleaseWaiters or just remove it?
I have no objection to that in principle, but it seems like it's a
change in SyncRepGetSyncRecPtr's API that is not necessary to fix
this bug. So I'd rather leave it to happen along with the larger
API changes (getting rid of am_sync) that are proposed for v14.
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, masahiko.sawada@2ndquadrant.com, horikyota.ntt@gmail.com, masao.fujii@oss.nttdata.com, pgsql-hackers@lists.postgresql.org
Subject: Re: Race condition in SyncRepGetSyncStandbysPriority
In-Reply-To: <22664.1587225619@sss.pgh.pa.us>
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