linux-ext4 - Re: 2.6.25-git2: BUG: unable to handle kernel paging request at ffffffffffffffff

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Date:	Tue, 22 Apr 2008 11:49:07 +0200
From:	Jiri Slaby <jirislaby@...il.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	"Rafael J. Wysocki" <rjw@...k.pl>, paulmck@...ux.vnet.ibm.com,
	David Miller <davem@...emloft.net>,
	linux-kernel@...r.kernel.org, mingo@...e.hu,
	akpm@...ux-foundation.org, linux-ext4@...r.kernel.org,
	herbert@...dor.apana.org.au,
	Zdenek Kabelac <zdenek.kabelac@...il.com>, mingo@...e.hu
Subject: Re: 2.6.25-git2: BUG: unable to handle kernel paging request at ffffffffffffffff

Linus Torvalds napsal(a):
> 
> On Tue, 22 Apr 2008, Rafael J. Wysocki wrote:
>>> The same place, dentry.d_hash.next is 1. No slub debug clues... I think, I'll 
>>> give slab a try. Any other clues?
>> Well, SLUB uses some per CPU data structures.  Is it possible that they get
>> corrupted and which leads to the observed symptoms?
> 
> It really doesn't look like the slub allocations themselves would be 
> corrupted. It very much looks like wild pointers corrupting allocations 
> that themselves were fine.

Hmm, correct.

> What do you do to trigger this? Any particular load? Is it still just 
> doing suspend/resume, or do you have something else that you are playing 
> with?

Yesterday I did 2 suspend/resumes after 1 hour of uptime and ran git-status 
for a fraction of a second until it was killed. So I can perfectly reproduce 
it when I suspend, resume and produce some io load. I guess it's time to 
bisect 2.6.25-rc8-mm2 as I'm able to reproduce it the best and haven't seen 
that bug in -rc8-mm1 for over week of suspending and working.

> Also, have you tried CONFIG_DEBUG_PAGEALLOC? That can also be a very 
> powerful way to find memory corruption.

Not yet.

> Does anybody see any other patterns? Looking at the modules linked in in 
> the oopses from Zdenek, Rafael and Jiri, I don't see anything odd. You 
> both all have 80211 support, maybe the corruption comes from the wireless 
> layer?

May be, however I don't use that stack, it's a desktop machine, it's only 
sitting there not turned on, but sure, it's loaded.
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