Re: [sqlsmith] Crash reading pg_stat_activity

From: Andreas Seltenreich <seltenreich(at)gmx(dot)de>
To: Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>
Cc: Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, rhaas(at)postgresql(dot)org
Subject: Re: [sqlsmith] Crash reading pg_stat_activity
Date: 2016-12-27 23:28:09
Message-ID: 87inq5uf3q.fsf@ansel.ydns.eu
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Andreas Seltenreich writes:

> Thomas Munro writes:
>
>> It is safe, as long as the segment remains mapped. Each backend that
>> attaches calls LWLockRegisterTranche giving it the address of the name
>> in its virtual address space.
>
> Hmok, I was under the impression only backends participating in the IPC
> call the attach function, not necessarily the ones that could possible
> want to resolve the wait_event_info they found in the procArray via
> pgstat_get_wait_event().

Erm, ignore that question: They'll find a NULL in their
LWLockTrancheArray and run into the "extension" case you mentioned.

> But I really feel like I need to study the code a bit more before
> commenting further…

Following this advise now :-)

regards,
Andreas

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