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

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Date:	Tue, 22 Apr 2008 03:30:25 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Jiri Slaby <jirislaby@...il.com>, 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>
Subject: Re: 2.6.25-git2: BUG: unable to handle kernel paging request at ffffffffffffffff

On Tuesday, 22 of April 2008, Linus Torvalds wrote:
> 
> 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.
> 
> The nybble pattern looked intriguing (especially as it apparently also hit 
> a normal page cache page!) but obviously not everything matches that 
> pattern (eg your value of 1).
> 
> 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?

I've seen that only once, so far.  Jiri seems to be able to trigger it more often.

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

I always have CONFIG_DEBUG_PAGEALLOC set.

> 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?

Well, I thought about that too.  However, I had a hang before 2.6.25-git2 that
I suspect was related (I couldn't get any information from the box, as it just
hung solid), so I'd rather suspect some x86 changes.

> Or maybe it's the x86 code changes themselves, and it really is about the 
> suspend/resume sequence itself.

It seems to be specific to x86-64, AFAICS.

> Are all the people who see this doing suspends? 

I'm not sure.

Thanks,
Rafael
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