X-Recipient:	archive-cygwin AT delorie DOT com
DomainKey-Signature:	a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:date:from:to:subject:message-id:reply-to
	:references:mime-version:content-type:in-reply-to; q=dns; s=
	default; b=M9SJcULzsOZmyAGL1lMoULBT+biuIR3lgH4zzw/PnZ6nN0Iraxhc4
	1YeKNlq0auPjwo9d5cI85szw0uBrkU4F6kqxBtaudtjvhhn4I6F2QLk1WbetEUie
	TnnJwBEMAgmoeP2NGMZXW07z4SrQ7wOOzYWp/ukZ6V1JQO7rxSLsJE=
DKIM-Signature:	v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:date:from:to:subject:message-id:reply-to
	:references:mime-version:content-type:in-reply-to; s=default;
	bh=JajbhA+vBBZlKKRO/sVJ9AA7/Vk=; b=NGiVm40hKKM5hWySFPr/H6PulOaB
	dNcWELV0SMNcq4xXuwbkdHyeUBr6xQOrAPNlk1w2FbpYondMfUvHRLdS2+5g5BXb
	tezFdHaMj1WPu99Db56LWKoHhXbaPTfehmDZazmPZjDeczJOcJvU142IM9TckCE1
	7/3wByz8U8m4pQE=
Mailing-List:	contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id:	<cygwin.cygwin.com>
List-Subscribe:	<mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive:	<http://sourceware.org/ml/cygwin/>
List-Post:	<mailto:cygwin AT cygwin DOT com>
List-Help:	<mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender:	cygwin-owner AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
Delivered-To:	mailing list cygwin AT cygwin DOT com
X-Spam-SWARE-Status:	No, score=2.1 required=5.0 tests=AWL,BAYES_50,RDNS_NONE,URIBL_BLACK autolearn=no version=3.3.1
Date:	Tue, 23 Jul 2013 16:39:10 +0200
From:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: Win32 error in C program using openmp and fork()
Message-ID:	<20130723143910.GI9689@calimero.vinschen.de>
Reply-To:	cygwin AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
References:	<57302C57257EF2428CCAAF9BA83EC0448222C0EA AT mbx08 DOT adf DOT bham DOT ac DOT uk> <20130722080657 DOT GD2661 AT calimero DOT vinschen DOT de> <51EE7700 DOT 50803 AT star DOT sr DOT bham DOT ac DOT uk> <20130723130851 DOT GG9689 AT calimero DOT vinschen DOT de> <20130723141855 DOT GH9689 AT calimero DOT vinschen DOT de>
MIME-Version:	1.0
In-Reply-To:	<20130723141855.GH9689@calimero.vinschen.de>
User-Agent:	Mutt/1.5.21 (2010-09-15)

On Jul 23 16:18, Corinna Vinschen wrote:
> On Jul 23 15:08, Corinna Vinschen wrote:
> > On Jul 23 13:28, Daniel Brown wrote:
> > > and that still had the fork error. I have also tried running in safe
> > > mode and
> > > stopping all my anti-virus software just incase that was interfering
> > > somehow.
> > > So I get as an output now...
> > > 
> > > Daniel AT XPS15z ~
> > > $ uname -r
> > > 1.7.22s(0.268/5/3)
> > > 
> > > Daniel AT XPS15z ~
> > > $ ./a.exe
> > > I'm an openmp thread...
> > > I'm an openmp thread...
> > > I'm an openmp thread...
> > > I'm an openmp thread...
> > > Parent fork 1 [main] a 5832 C:\cygwin\home\Daniel\a.exe: *** fatal
> > > error in forked process - failed
> > > to create new win32 semaphore, currentvalue -2, Win32 error 87
> > > 
> > > However if I reduce the number of threads from 4 to 2 with:
> > > 
> > > #pragma omp parallel num_threads(2)
> > > {
> > > printf("I'm an openmp thread...\n");
> > > }
> > 
> > Ah, now there's something different.  If I set the number of threads to
> > 4, I can reproduce this problem almost every try with currentvalue -2,
> > occassionally with currentvalue -1.
> > 
> > > Looking at the source in thread.cc _fixup_after_fork() the win32
> > > error 87 is ERROR_INVALID_PARAMETER
> > > which is due to currentvalue < 0.
> > > 
> > > My only guess is that there is a race condition on the
> > > currentvalue-- operations perhaps?
> > 
> > Apparently.  I investigate...
> 
> Yes, there was a race condition in setting the value of the semaphore
> private "currentvalue" member.  The only reason to keep track of the
> value is to allow _fixup_after_fork to set the right value, but here the
> race comes into play.  I redesigned this part so that it only sets
> currentvalue once, right from fork itself, to propagate the correct
> value to the child process.
> 
> I'm just building new 32 and 64 bit snapshots.  They should be available
> on http://cygwin.com/snapshots/ in an hour at the latest.  Please give
> it a try.

Both snapshots are up.  Test away.


Corinna

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

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple

- Raw text -