linux-kernel - Re: 2.6.26-git: NULL pointer deref in __switch

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Message-ID: <20080616174948.GB7788@linux-os.sc.intel.com>
Date:	Mon, 16 Jun 2008 10:49:48 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Simon Holm Thøgersen <odie@...aau.dk>
Cc:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	Vegard Nossum <vegard.nossum@...il.com>,
	Patrick McHardy <kaber@...sh.net>,
	Linux Kernel Mailinglist <linux-kernel@...r.kernel.org>,
	Chuck Ebbert <cebbert@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>
Subject: Re: 2.6.26-git: NULL pointer deref in __switch_to

On Mon, Jun 16, 2008 at 03:15:39AM -0700, Simon Holm Thøgersen wrote:
> fre, 13 06 2008 kl. 15:47 -0700, skrev Suresh Siddha:
> > On Fri, Jun 13, 2008 at 11:24:01AM -0700, Vegard Nossum wrote:
> > > On Fri, Jun 13, 2008 at 7:42 PM, Patrick McHardy <kaber@...sh.net> wrote:
> > > > I get this oops once a day, its apparently triggered by something
> > > > run by cron, but the process is a different one each time.
> > > >
> > > > Kernel is -git from yesterday shortly before the -rc6 release
> > > > (last commit is the usb-2.6 merge, the x86 patches are missing),
> > > > .config is attached.
> > > >
> > > > I'll retry with current -git, but the patches that have gone in
> > > > since I last updated don't look related.
> > > >
> > >
> > > Thanks for the report.
> > >
> > > >
> > > > [62060.043009] BUG: unable to handle kernel NULL pointer dereference at
> > > > 000001ff
> > > > [62060.043009] IP: [<c0102a9b>] __switch_to+0x2f/0x118
> > > > [62060.043009] *pde = 00000000
> > > > [62060.043009] Oops: 0002 [#1] PREEMPT
> >
> > Patrick, Do you see any other error messages before this BUG stmt? Can you
> > please provide the complete kernel log till the point of failure?
> >
> Suresh, I'm pretty sure this is the same problem that I reported two
> weeks ago [1]. I suggested that you tried running lguest and reproduced
> the problem locally, but I did not hear back from you. Now Patrick is
> reporting the same problem and is also indicating that the problem is
> correlated with his use of lguest, so I'd really like you to follow up
> on this.

I am on this and did try reproducing with lguest last week but couldn't
reproduce the issue with the initrd image. May be I need a full blown
disk image.

> At least for me, with this patch applied on top of -rc4 or -rc6+ the
> problem still triggered after running an lguest guest for less than 30
> seconds (the guest didn't even finish the boot of an image of Ubuntu
> with no X-server).

Please post the oops you captured.

> If you or anybody else would like to use the same guest image I use
> please just ask and I'll make it available somehow.

Can you please upload it some where? I will also try with another guest
image meanwhile.

thanks,
suresh
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