linux-kernel - Re: linux-next: Tree for July 9 (kmemcheck: Caught 8-bit read from freed memory (ffff880127c120e8))

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Date:	Thu, 10 Jul 2008 10:24:45 +0300
From:	"Pekka Enberg" <penberg@...helsinki.fi>
To:	"Vegard Nossum" <vegard.nossum@...il.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, linux-next@...r.kernel.org,
	"Stephen Rothwell" <sfr@...b.auug.org.au>,
	LKML <linux-kernel@...r.kernel.org>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Kernel Testers List" <kernel-testers@...r.kernel.org>,
	"Christoph Lameter" <cl@...ux-foundation.org>
Subject: Re: linux-next: Tree for July 9 (kmemcheck: Caught 8-bit read from freed memory (ffff880127c120e8))

Hi Vegard,

On Thu, Jul 10, 2008 at 10:19 AM, Vegard Nossum <vegard.nossum@...il.com> wrote:
> Also, the error report is bogus. We should make kmemcheck depend on
> !CONFIG_DEBUG_SLAB && !CONFIG_SLUB_DEBUG_ON for now, because these
> modes interfere with the checking that kmemcheck does.

Agreed.

On Thu, Jul 10, 2008 at 10:19 AM, Vegard Nossum <vegard.nossum@...il.com> wrote:
> That said, we *might* be able to do a kmemcheck_off()/kmemcheck_on()
> thing around the special code. Maybe a kmemcheck_read()  which
> bypasses the checking for a single read.
>
> But I really do think kmemcheck and slab/slub debugging should be
> mutually exclusive. They do essentially the same thing, except that
> kmemcheck is much more eager and detects problems right where they
> happen (though sometimes too eagerly too; the false positives).

I'm not so sure about this. You ought to be able to compile-in SLUB
debugging and kmemcheck support but only enable one of them at
run-time.

                         Pekka
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