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To: John Reiser <jreiser@BitWagon.com>
Cc: linux-kernel@vger.kernel.org, Jeremy Fitzhardinge <jeremy@goop.org>,
       Julian Seward <jseward@acm.org>
Subject: Re: Valgrind meets UML 
In-Reply-To: Your message of "Fri, 20 Dec 2002 07:26:39 PST."
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Date: Fri, 20 Dec 2002 17:58:18 -0500
From: Jeff Dike <jdike@karaya.com>
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jreiser@BitWagon.com said:
> Implementors of allocators can have bugs in the valgrind declarations
> they add. An "independent" check based on documented
> externally-visible behavior can help. 

The problem is that valgrind is going to look under the covers of the kernel
allocators and see the externally-visible requirements being violated.

Either you implement a globally correct description, which includes the 
externally visible description as a subset, or you somehow tell valgrind not
to complain about stuff inside the allocator.

The second sounds complicated, and anyway hides bugs in the allocator.

> Nested allocators (inner allocator grabs a large region, outer
> allocator performs sub-allocations of small pieces from the large
> region) can be troublesome. 

And are another reason for implementing a globally correct description.

				Jeff

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