Re: Race condition in SyncRepGetSyncStandbysPriority

On Sun, 19 Apr 2020 at 01:00, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Masahiko Sawada <masahiko(dot)sawada(at)2ndquadrant(dot)com> writes:
> > On Sat, 18 Apr 2020 at 00:31, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)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.

Agreed.

Regards,

--
Masahiko Sawada http://www.2ndQuadrant.com/
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