linux-kernel - Re: kernel BUG at mm/slab.c:601

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Date:	Wed, 19 Nov 2008 23:19:12 +0100
From:	"Vegard Nossum" <vegard.nossum@...il.com>
To:	"Brian Phelps" <lm317t@...il.com>
Cc:	linux-kernel@...r.kernel.org, "Al Viro" <viro@...iv.linux.org.uk>,
	"Mikael Pettersson" <mikpe@...uu.se>,
	"Alexander Shaduri" <ashaduri@...il.com>,
	"Alexey Dobriyan" <adobriyan@...il.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: kernel BUG at mm/slab.c:601

On Wed, Nov 19, 2008 at 12:24 AM, Brian Phelps <lm317t@...il.com> wrote:
> This possible kernel bug (see bottom) is very reproducible when the
> pci bus gets loaded with traffic, specifically video data.
> It has been reproduced on 2 identical machines.
>
> Please let me know if you need more information

Hi,

Can you reproduce this with CONFIG_DEBUG_SLAB=y?

Can you reproduce this with CONFIG_SLUB=y instead of SLAB? If not,
could be a genuine bug in SLAB (but I doubt it). If yes, then SLUB
debugging might help us more than SLAB debugging can.

It sounds likely that bttv driver is involved somehow -- it would fit
with your description too. Maybe the fact that the same driver is
serving many devices on the same IRQ? But I guess that shouldn't
really be a problem.

It would also be interesting to see if you can find more different
crashes in other places, like the corrupted page tables. Those are
important clues. Like this:

> [ 2128.370257] PGD 10869067 PUD 23232323 BAD

That looks like a magic number of sorts. This was the only one I could
find, however:

crypto/anubis.c:      0x83838383U, 0x1b1b1b1bU, 0x0e0e0e0eU, 0x23232323U,

But google has some more info. A google for "23232323 bug" turned up
this thread:

http://lkml.org/lkml/2008/1/5/51

...which also involves bttv driver. I've added the Ccs of that discussion.

But it seems that it is not a regression at least. Did you try earlier
kernels as well?

Vegard

-- 
"The animistic metaphor of the bug that maliciously sneaked in while
the programmer was not looking is intellectually dishonest as it
disguises that the error is the programmer's own creation."
	-- E. W. Dijkstra, EWD1036
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