netdev - Re: [vlan_device_event] BUG: unable to handle kernel paging request at 6b6b6ccf

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Message-ID: <20171109074315.fbm6heji62zbcdgp@wfg-t540p.sh.intel.com>
Date:   Thu, 9 Nov 2017 15:43:15 +0800
From:   Fengguang Wu <fengguang.wu@...el.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Alexander Duyck <alexander.duyck@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        Network Development <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        intel-wired-lan <intel-wired-lan@...ts.osuosl.org>,
        Girish Moodalbail <girish.moodalbail@...cle.com>
Subject: Re: [vlan_device_event] BUG: unable to handle kernel paging request
 at 6b6b6ccf

On Thu, Nov 09, 2017 at 02:55:10PM +0800, Fengguang Wu wrote:
>On Wed, Nov 08, 2017 at 10:34:10PM -0800, Cong Wang wrote:
>>On Wed, Nov 8, 2017 at 7:12 PM, Fengguang Wu <fengguang.wu@...el.com> wrote:
>>> Hi Alex,
>>>
>>>> So looking over the trace the panic seems to be happening after a
>>>> decnet interface is getting deleted. Is there any chance we could try
>>>> compiling the kernel without decnet support to see if that is the
>>>> source of these issues? I don't know if anyone on the Intel Wired Lan
>>>> team is testing with that enabled so if we can eliminate that as a
>>>> possible cause that would be useful.
>>>
>>>
>>> Sure and thank you for the suggestion!
>>>
>>> It looks disabling DECNET still triggers the vlan_device_event BUG.
>>> However when looking at the dmesgs, I find another warning just before
>>> the vlan_device_event BUG. Not sure if it's related one or independent
>>> now-fixed issue.
>>
>>Those decnet symbols are probably noises.
>
>Yes it's not related to CONFIG_DECNET.
>
>>How do you reproduce it? And what is your setup? Vlan device on
>>top of your eth0 (e1000)?
>
>It can basically be reproduced in one of our test machines --
>lkp-wsx03, which is a Westmere EX server.

Anyway if you'd like to try, here are the steps. It'll auto download
the images and run QEMU.

        apt-get install lib32gcc-7-dev # or lib32gcc-6-dev
        git clone https://github.com/intel/lkp-tests.git
        cd lkp-tests
        bin/lkp qemu -k <bzImage> job-script  # job-script is attached in this email

Note that even in our lkp-wsx03 machine, the chance of reproducing it
is only 3% (3 out of 100 boots).

Thanks,
Fengguang

View attachment "job-script" of type "text/plain" (3928 bytes)