Re: LWLock deadlock and gdb advice

From: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
To: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
Cc: Peter Geoghegan <pg(at)heroku(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: LWLock deadlock and gdb advice
Date: 2015-06-30 18:19:29
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On 06/30/2015 07:37 PM, Alvaro Herrera wrote:
> Jeff Janes wrote:
>> I've gotten the LWLock deadlock again. User backend 24841 holds the
>> WALInsertLocks 7 and is blocked attempting to acquire 6 . So it seems to
>> be violating the lock ordering rules (although I don't see that rule
>> spelled out in xlog.c)
> Hmm, interesting -- pg_stat_statement is trying to re-do an operation
> that involves updating a GIN index, while WAL-logging for the original
> update is still ongoing, it seems.

I don't think pg_stat_statement has anything to do with this. You can
see from the backtrace that pg_stat_statement is enabled, as the call
went through the pgss_ExecutorRun executor hook, but that's all.

- Heikki

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