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Date: Mon, 3 Jun 2013 12:01:02 +0200
From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: pthread_join() problem
Message-ID: <20130603100102.GA14318@calimero.vinschen.de>
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References: <51ABC0BE.5080408@tiscali.co.uk>
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User-Agent: Mutt/1.5.21 (2010-09-15)

On Jun  2 23:01, David Stacey wrote:
> I'm trying to get Poco[1] working under Cygwin, and have hit a
> problem with the way it manages its threads. A short example
> (attached) shows what's going on.
> 
> Poco creates a global object that is used for managing various
> threads. In the destructor, the class calls pthread_join() to wait
> for the threads to finish. This works in Fedora (and presumably
> other Linux variants), but under Cygwin this call never returns.
> Note that the object is global, and so pthread_join() is being
> called after main() has returned and the global variables are being
> mopped up.
> 
> In the attached example, the problem only exists if the
> 'thread_container' object is global. When run in this way,
> pthread_join() never returns and the programme locks up. If
> 'thread_container' is moved local to main() then the programme works
> correctly. Sadly, I can't make such a trivial fix to the Poco code,
> which rather relies on this object being global.
> 
> The attached example (and indeed Poco) runs fine under Fedora 18
> x64, but locks up on Cygwin (32-bit; haven't tried 64-bit). Problem
> exists with a vanilla cygwin-1.7.18-1 and the most recent snapshot
> (2013-06-02).

Thanks for the simple testcase!

I tracked this down to a problem in the process exit handling which
disallowed pthreads to exit when process exit was in progress (and
running the global destructors is part of the process exit).  I fixed
that in CVS.

I'm just uploading a 2013-06-03 snapshot to http://cygwin.com/snapshots/
as well as generating a 1.7.9-10 cygwin package for the 64 bit test
distro.  Please give either one of them a try, especially with poco.


Thanks,
Corinna


-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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