linux-kernel - Re: Kernel 3.0: Instant kernel crash when mounting CIFS (also crashes with linux-3.1-rc2

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Date:	Wed, 17 Aug 2011 17:11:32 -0400
From:	Arnaud Lacombe <lacombar@...il.com>
To:	Justin Piszcz <jpiszcz@...idpixels.com>
Cc:	Jeff Layton <jlayton@...ba.org>, Jesper Juhl <jj@...osbits.net>,
	linux-kernel@...r.kernel.org, Alan Piszcz <ap@...arrain.com>,
	Steve French <sfrench@...ba.org>, linux-cifs@...r.kernel.org
Subject: Re: Kernel 3.0: Instant kernel crash when mounting CIFS (also crashes
 with linux-3.1-rc2

Hi,

On Wed, Aug 17, 2011 at 4:45 PM, Justin Piszcz <jpiszcz@...idpixels.com> wrote:
>
>
> On Wed, 17 Aug 2011, Jeff Layton wrote:
>
>> The crash is happening in the bowels of the slab allocator.
>> Specifically, it looks like it's hitting this:
>>
>>               /*
>>                * The slab was either on partial or free list so
>>                * there must be at least one object available for
>>                * allocation.
>>                */
>>               BUG_ON(slabp->inuse >= cachep->num);
>>
>> ...which looks like maybe the accounting of in-use objects is off. This
>> really sounds like some sort of memory corruption. I've not been able
>> to reproduce this so far, but I also had someone report panic here that
>> might be related:
>>
>>   https://bugzilla.redhat.com/show_bug.cgi?id=731278
>>
>> One thing that might be helpful is turning on page poisoning and
>> redoing this test, that might make it crash sooner and point out the
>> source of the corruption.
>>
>> Even better would be a bisect to track down the cause...
>
>
> Hi Jeff,
>
> root@...rlw:/usr/src/linux# grep CONFIG_PAGE_POISONING .config
> root@...rlw:/usr/src/linux# ls -l ../linux
> lrwxrwxrwx 1 root root 13 Aug 17 14:41 ../linux -> linux-3.1-rc2/
> root@...rlw:/usr/src/linux#
>
> In what kernel is that feature available, or, how do I enable it?
>
It is selected by "Kernel hacking" -> "Debug page memory allocations",
provided your arch support pagealloc debug.

 - Arnaud

> Justin.
>
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