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Date:	Sat, 6 May 2017 20:27:47 -0700
From:	Noah Misch <noah AT leadboat DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: cygserver - Postgres Multiple connection Load Testing - Inifinte Loop
Message-ID:	<20170507032747.GA876495@rfd.leadboat.com>
References:	<200408030333 DOT i733XEXn023894 AT mx3 DOT redhat DOT com> <20040803100612 DOT GP31522 AT cygbert DOT vinschen DOT de> <20170321025614 DOT GA2100214 AT tornado DOT leadboat DOT com> <20170324171101 DOT GI29995 AT calimero DOT vinschen DOT de> <20170328052652 DOT GA2351961 AT tornado DOT leadboat DOT com> <20170402023624 DOT GA2561924 AT tornado DOT leadboat DOT com>
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On Sat, Apr 01, 2017 at 10:36:24PM -0400, Noah Misch wrote:
> On Tue, Mar 28, 2017 at 01:26:52AM -0400, Noah Misch wrote:
> > On Fri, Mar 24, 2017 at 06:11:01PM +0100, Corinna Vinschen wrote:
> > > I pushed a patchset now, and uploaded new developer snapshots for
> > > testing to https://cygwin.com/snapshots/
> > 
> > > Please give it a try
> 
> > I call the cygwin-20170324 freezes "limited" because the symptoms differ from
> > the classic freeze I described upthread.  "strace /bin/true" and "cat
> > /proc/sysvipc/sem" do not hang, but every PostgreSQL backend process is stuck
> > waiting on a synchronization primitive.
> > 
> > I can distill another self-contained test case for the limited freeze seen in
> > cygwin-20170324, but that make take awhile.  I'm sending this early report so
> > you're aware of the possible regression in cygwin-20170324.
> 
> I'm attaching a new test program that demonstrates the regression.  My previous
> test program created sixteen processes that each picked a random semaphore to
> lock.  Now, each process picks two semaphores and locks them in order.  This
> proceeds smoothly on GNU/Linux and on cygwin-20170321.tar.xz "cygserver -r 40".
> It freezes within one second on cygwin-20170324.tar.xz "cygserver -r 40".

I suggest reverting the cygwin-20170324 cygserver changes for now.  Older
versions can be configured to have reliable sysv semaphores, but I think no
settings render sysv semaphores reliable in Cygwin 2.8.0.  What do you think?

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