netdev - RE: [BUG] NULL pointer dereference in skb

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Message-ID: <EA929A9653AAE14F841771FB1DE5A1365F1FBE8ADD@rrsmsx501.amr.corp.intel.com>
Date:	Sat, 2 Aug 2008 03:36:49 -0600
From:	"Tantilov, Emil S" <emil.s.tantilov@...el.com>
To:	David Miller <davem@...emloft.net>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [BUG] NULL pointer dereference in skb_dequeue

David Miller wrote:
> From: David Miller <davem@...emloft.net>
> Date: Fri, 01 Aug 2008 18:03:37 -0700 (PDT)
>
>> Looks like two threads are accessing the qdisc SKB lists but one of
>> them isn't taking the proper qdisc locks.
>>
>> I can't see how this can happen currently but I'll try to figure it
>> out.
>
> I see what's going on.
>
> Once we decide on a root qdisc to process, we shouldn't use
> qdisc_root_lock() since that will resample qdisc->dev_queue->qdisc
> which might be different.
>
> This points out a core problem, and I might need to add a
> root_qdisc backpointer to struct Qdisc to make this all work
> out sanely for all cases.
>
> Anyways, please try this patch:

Still panics. Survived few MTU changes, but eventually I got this (see attached file - sorry for the partial dump, but that's all I can do remotely).

Thanks,
Emil

Download attachment "skb_dequeue.jpg" of type "image/jpeg" (94991 bytes)