Re: [BUG] null-pointer in task_rq_lock (2.6.35 to 3.0-rc7)

From: Manfred Spraul
Date: Wed Jul 20 2011 - 14:08:14 EST

On 07/19/2011 11:14 PM, Eric Dumazet wrote:
Le mardi 19 juillet 2011 Ã 22:03 +0200, Harald Laabs a Ãcrit :Hi,

I'm not able to fix or understand this bug myself, its already in
bugzilla with the call trace:

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.


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