Re: BUG #15036: Un-killable queries Hanging in BgWorkerShutdown

On Thu, Feb 8, 2018 at 1:34 PM, Thomas Munro
<thomas.munro@enterprisedb.com> wrote:
> On Thu, Feb 8, 2018 at 7:06 AM, David Kohn <djk447@gmail.com> wrote:
>> I'm not clear on when we do a SetLatch on those message queues during a
>> cancel of parallel workers, and a number of other things that could
>> definitely invalidate this analysis, but I think there could be a plausible
>> explanation in there somewhere.
>
> shm_mq_detach_internal() does SetLatch(&victim->procLatch) ("victim"
> being the counterparty process) after setting mq_detached.  So ideally
> no one should ever be able to wait forever on a queue from which the
> other end has detached, but perhaps there is some race condition style
> bug lurking in here.  I'm going to do some testing and see if I can
> break this...

I tried, but didn't get anywhere with this.

-- 
Thomas Munro
http://www.enterprisedb.com