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Date:	Mon, 7 Jan 2013 11:02:15 -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)
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On Mon, Jan 07, 2013 at 01:43:17AM -0500, Christopher Faylor wrote:
>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.

This is checked in and will be in the next snapshot at:
http://cygwin.com/snapshots/

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