linux-kernel - Re: [BUG] null-pointer in task_rq

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Message-ID: <4E271A66.40307@colorfullife.com>
Date:	Wed, 20 Jul 2011 20:11:50 +0200
From:	Manfred Spraul <manfred@...orfullife.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Harald Laabs <kernelml@...r.de>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [BUG] null-pointer in task_rq_lock (2.6.35 to 3.0-rc7)

On 07/19/2011 11:14 PM, Eric Dumazet wrote:
> Le mardi 19 juillet 2011 à 22:03 +0200, Harald Laabs a écrit :Hi,
>>
>> I'm not able to fix or understand this bug myself, its already in
>> bugzilla with the call trace:
>> https://bugzilla.kernel.org/show_bug.cgi?id=27142
>>
>> Is there any more useful information I can provide? Anything to test?
Could you build a kernel with CONFIG_DEBUG_LIST enabled?
Does it report anything?
>> Does anyone know of changes from 2.6.34 to 2.6.35 that might have
>> broken this? (The diff and the changelog do not enlighten me, too
>> much changed and I understand little of it.)
> I feel commit 0a2b9d4c79671b059568 might be the bug origin
> (ipc/sem.c: move wake_up_process out of the spinlock section)
>
I'll try to reproduce the bug tomorrow.
Perhaps a race with multiple processes sleeping, some/all woken up by a 
signal an a concurrent IPC_RM.

But I don't see the bug yet.

--
     Manfred

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