From: Tom Lane <tgl@sss.pgh.pa.us>
To: Jeevan Chalke <jeevan.chalke@enterprisedb.com>
cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Server crash (FailedAssertion) due to catcache refcount
 mis-handling
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Comments: In-reply-to Jeevan Chalke <jeevan.chalke@enterprisedb.com>
	message dated "Tue, 08 Aug 2017 18:04:56 +0530"
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Date: Tue, 08 Aug 2017 11:36:17 -0400
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Jeevan Chalke <jeevan.chalke@enterprisedb.com> writes:
> We have observed a random server crash (FailedAssertion), while running few
> tests at our end. Stack-trace is attached.

> By looking at the stack-trace, and as discussed it with my team members;
> what we have observed that in SearchCatCacheList(), we are incrementing
> refcount and then decrementing it at the end. However for some reason, if
> we are in TRY() block (where we increment the refcount), and hit with any
> interrupt, we failed to decrement the refcount due to which later we get
> assertion failure.

Hm.  So SearchCatCacheList has a PG_TRY block that is meant to release
those refcounts, but if you hit the backend with a SIGTERM while it's
in that function, control goes out through elog(FATAL) which doesn't
execute the PG_CATCH cleanup.  But it does do AbortTransaction which
calls AtEOXact_CatCache, and that is expecting that all the cache
refcounts have reached zero.

We could respond to this by using PG_ENSURE_ERROR_CLEANUP there instead
of plain PG_TRY.  But I have an itchy feeling that there may be a lot
of places with similar issues.  Should we be revisiting the basic way
that elog(FATAL) works, to make it less unlike elog(ERROR)?

			regards, tom lane


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