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Date: Thu, 31 Oct 2013 23:05:53 -0400
From: Christopher Faylor <cgf-use-the-mailinglist-please AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Problem with multiprocessing module from Python
Message-ID: <20131101030553.GA2729@ednor.casa.cgf.cx>
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On Thu, Oct 31, 2013 at 02:41:14PM -0400, Christopher Faylor wrote:
>On Thu, Oct 31, 2013 at 06:27:39PM +0000, Jean-Pierre Flori wrote:
>>Le Wed, 30 Oct 2013 10:33:13 +0100, Corinna Vinschen a ??crit??:
>>
>>> On Oct 29 21:22, Jean-Pierre Flori wrote:
>>>> Le Tue, 29 Oct 2013 21:19:14 +0000, Jean-Pierre Flori a ??crit??:
>>>> 
>>>> > Le Tue, 29 Oct 2013 16:59:35 -0400, Christopher Faylor a ??crit??:
>>>> >> If you want this fixed, the easiest way to get that to happen is to
>>>> >> post a simple test case which reproduces the problem.  That is not
>>>> >> the code snippet that you sent.  A real working example would be
>>>> >> required.
>>>> > Sorry about that.
>>>> > 
>>>> > Here you go:
>>>> > """
>>>> > from multiprocessing import Pool
>>>> > 
>>>> > def f(x): return x
>>>> > 
>>>> > p = pool(2)
>>>> > 
>>>> > p.map(f, [1, 2])
>>>> > """
>>>> And I managed to introduce a typo. The third line should read Pool, so
>>>> it is:
>>>> """
>>>> from multiprocessing import Pool
>>>> 
>>>> def f(x): return x
>>>> 
>>>> p = Pool(2)
>>>> 
>>>> p.map(f, [1, 2])
>>>> """
>>> 
>>> Works for me.  I guess.  At least, if I run the script, nothing happens:
>>> 
>>>   $ python x.py $
>>> 
>>> Same on 32 and 64 bit Cygwin.
>>> 
>>> 
>>> Corinna
>>
>>I think I got to the bottom of this.
>>It seems the new implem of sem_getvalue in cgwin1.dll is the cause, see:
>>http://cygwin.com/ml/cygwin-patches/2013-q3/msg00006.html
>>It may also explain the random reproducibility if sval stays uninitialized 
>>or something like that (I did not check it is the case though).
>
>I doubt that was the problem.  More likely it is something related to
>the changes in thread.cc that followed that change.

Actually I misread the CVS log.  It's more likely that this is due to changes
that happened just prior to the above change.

cgf

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