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Subject: Re: apparent regression (crash) - 2.6.38.6
From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Jiri Slaby <jslaby@suse.cz>
Cc: Michael Tokarev <mjt@tls.msk.ru>,
        Linux-kernel <linux-kernel@vger.kernel.org>,
        "James E.J. Bottomley" <jejb@parisc-linux.org>, stable@kernel.org
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Date: Wed, 11 May 2011 14:19:17 -0500
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On Wed, 2011-05-11 at 08:30 +0200, Jiri Slaby wrote:
> On 05/10/2011 09:55 PM, Michael Tokarev wrote:
> > Hello.
> > 
> > I just tried 2.6.38.6 (which has been released today), and
> > discovered that it crashes during bootup on my machine.
> > 2.6.38.5 with exactly the same config works.
> 
> Is it reproducible?
> 
> > Unfortunately I don't have time _right now_ to debug the
> > issue, but will try tomorrow.
> > 
> > For now, here's a part of dmesg with an oops, captured
> > using netconsole.  If someone have a clue, please speak
> > up ;)
> > 
> > What I also noticed is that for some reason, udev now loads
> > option driver (option: v0.7.2:USB Driver for GSM modems),
> > even if I don't have any modems connected to the system.
> > This is obviously not related to the issue at hand.
> ...
> > [  106.761932] input: Logitech USB-PS/2 Optical Mouse as /devices/pci0000:00/0000:00:12.1/usb2/2-2/2-2:1.0/input/input6
> > [  106.762170] generic-usb 0003:046D:C044.0004: input,hidraw0: USB HID v1.10 Mouse [Logitech USB-PS/2 Optical Mouse] on usb-0000:00:12.1-2/input0
> > [  106.994177] scsi 10:0:0:0: Direct-Access     Kingston DT HyperX        HMAP PQ: 0 ANSI: 0 CCS
> > [  106.994458] sd 10:0:0:0: Attached scsi generic sg3 type 0
> > [  106.994628] BUG: unable to handle kernel NULL pointer dereference at 0000000000000048
> > [  106.994755] IP: [<ffffffff811bec1b>] elv_queue_empty+0x1b/0x30

Hmm, it's another missing elevator guard, like this patch:

http://marc.info/?l=linux-scsi&m=130348673628282

I think the bug here is that q->elevator is null, so dereferencing
elevator->ops gives the bug.

James


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