Re: pgsql: Add isolationtester spec for old heapam.c bug

Tom Lane wrote:
> I wrote:
> > Alvaro Herrera <alvherre@alvh.no-ip.org> writes:
> >> Add isolationtester spec for old heapam.c bug
>
> > Hmmm ....
>
> > http://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=spoonbill&dt=2016-02-27%2000%3A00%3A06
>
> > This failure looks a lot like the timing-related problems I was chasing
> > last week with deadlock-hard on the CLOBBER_CACHE_ALWAYS critters.
> > spoonbill isn't CLOBBER_CACHE_ALWAYS, but it uses some weird malloc debug
> > stuff that slows it down by similar orders of magnitude.  You seem to need
> > to think about how to make this test less timing-dependent.
>
> The plot thickens:
>
> http://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=guaibasaurus&dt=2016-02-29%2016%3A17%3A01
>
> guaibasaurus is not a particularly slow machine, and it's not using any
> special build flags AFAICT.  So I'm not sure what to make of this case,
> except that it proves the timing problem can manifest on normal builds.

Hmm, I suppose I could fix this by using three different advisory locks
rather than a single one.  (My assumption is that the timing dependency
is the order in which the backends are awakened when the advisory lock
is released.)  I would release the locks one by one rather than all
together.

--
Álvaro Herrera                http://www.2ndQuadrant.com/
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