X-Recipient:	archive-cygwin AT delorie DOT com
X-SWARE-Spam-Status:	No, hits=-1.4 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE,RCVD_IN_HOSTKARMA_YE
X-Spam-Check-By:	sourceware.org
X-Mail-Handler:	Dyn Standard SMTP by Dyn
X-Report-Abuse-To:	abuse AT dyndns DOT com (see http://www.dyndns.com/services/sendlabs/outbound_abuse.html for abuse reporting information)
X-MHO-User:	U2FsdGVkX1/x3qsIKmgQ7ar1lD1qLWsS
Date:	Mon, 7 Jan 2013 01:43:17 -0500
From:	Christopher Faylor <cgf-use-the-mailinglist-please AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: pthread_rwlock_tryrdlock bug (with test & patch)
Message-ID:	<20130107064317.GA29248@ednor.casa.cgf.cx>
Reply-To:	cygwin AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
References:	<50E9B35F DOT 7030307 AT iki DOT fi>
MIME-Version:	1.0
In-Reply-To:	<50E9B35F.7030307@iki.fi>
User-Agent:	Mutt/1.5.20 (2009-06-14)
Mailing-List:	contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id:	<cygwin.cygwin.com>
List-Unsubscribe:	<mailto:cygwin-unsubscribe-archive-cygwin=delorie DOT com AT cygwin DOT 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

On Sun, Jan 06, 2013 at 06:24:47PM +0100, Antti Kantee wrote:
>[I'd submit this to cygwin-patches, but the web page says only 
>subscribers can post to that list, so please bear with me for this 
>simple issue]
>
>Hi,
>
>Calling pthread_rwlock_tryrdlock() twice from the same thread always 
>fails with EBUSY the second time.  See attached test.c.  Replacing the 
>second tryrdlock() with rdlock() makes the call succeed, leading me to 
>believe there is a bug in tryrdlock().
>
>Assuming I was looking at the correct source file, the attached patch 
>should fix the issue.  I'm not sure why the lookup_reader() call was 
>there in the first place; perhaps a remnant from a time when recursive 
>read locking was not supported?
>
>While looking at tryrdlock(), the handling of ULONG_MAX also seems 
>wrong, as you'd probably want to return EAGAIN instead of allocating 
>another reader structure.  However, that problem is arguably more of an 
>academic issue and therefore I didn't touch it in my patch.

Thanks for the analysis and patch.  I've made a few more changes to this
function and should have everything checked in tomorrow.

cgf

--
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 -