From: Tom Lane <tgl@sss.pgh.pa.us>
To: Noah Misch <noah@leadboat.com>
cc: pgsql-hackers@lists.postgresql.org
Subject: Re: Unexpected "shared memory block is still in use"
In-reply-to: <20190510072213.GA1098093@rfd.leadboat.com>
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Comments: In-reply-to Noah Misch <noah@leadboat.com>
	message dated "Fri, 10 May 2019 00:22:13 -0700"
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Date: Fri, 10 May 2019 10:55:41 -0400
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Noah Misch <noah@leadboat.com> writes:
> Looks good.  That is basically a defect in commit c09850992; the race pa=
ssed
> from irrelevance to relevance when that commit subjected more segments t=
o the
> test.  Thanks for diagnosing it.

The bug's far older than that, surely, since before c09850992 we treated
*any* shmat failure as meaning we'd better fail.  I think you're right
that c09850992 might've made it slightly more probable, but most likely
the bottom line here is just that we haven't been doing parallel
check-worlds a lot until relatively recently.  The buildfarm would be
kind of unlikely to hit this I think --- AFAIK it doesn't launch multiple
postmasters using the same port number concurrently.  But parallel
invocation of TAP test scripts makes the hazard real.

Will go fix/backpatch in a minute.

			regards, tom lane