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Message-ID: <3E04939F.1020404@BitWagon.com>
Date: Sat, 21 Dec 2002 08:15:27 -0800
From: John Reiser <jreiser@BitWagon.com>
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To: Jeff Dike <jdike@karaya.com>
CC: linux-kernel@vger.kernel.org, Jeremy Fitzhardinge <jeremy@goop.org>,
       Julian Seward <jseward@acm.org>
Subject: Re: Valgrind meets UML
References: <200212211607.LAA01515@ccure.karaya.com>
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Jeff Dike wrote:
> jreiser@BitWagon.com said:
> 
>>In order to prevent races between valgrind for UML and kernel
>>allocators which valgrind does not "know", then the VALGRIND_*
>>declarations being added to kernel allocators should allow for
>>expressing the concept "atomically change state in both allocator and
>>valgrind".
> 
> 
> What are you talking about?
> 
> There are no atomicity problems between UML and valgrind.

If so, then you are fortunate.  But in the abstract, and more importantly
in the mind of the maintainer of a lock-free SMP allocator who is trying
to allow simultaneous allocation and valgrind of the allocator, then such
atomicity problems are real.  The VALGRIND_* statements should allow
the conscientious and meticulous maintainer to express the correct
semantics, even though the current implementation of valgrind for UML
might not [have to] take advantage of all of the properties of such a
precise description.  If nothing else, then such a maintainer will invent
his own VALGRIND_* usage to express simultaneous {allocator, valgrind}
state transitions precisely.

-- 
John Reiser, jreiser@BitWagon.com

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