linux-kernel - RE: [hv] BUG: kernel freezes after [ 13.356381] PCI: CLS 0 bytes, default 64

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Date:	Tue, 4 Jun 2013 23:36:23 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Greg KH <greg@...ah.com>, Fengguang Wu <fengguang.wu@...el.com>
CC:	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [hv] BUG: kernel freezes after [   13.356381] PCI: CLS 0 bytes,
 default 64



> -----Original Message-----
> From: Greg KH [mailto:greg@...ah.com]
> Sent: Tuesday, June 04, 2013 6:44 PM
> To: Fengguang Wu
> Cc: KY Srinivasan; devel@...uxdriverproject.org; Greg Kroah-Hartman; linux-
> kernel@...r.kernel.org
> Subject: Re: [hv] BUG: kernel freezes after [ 13.356381] PCI: CLS 0 bytes, default
> 64
> 
> On Tue, Jun 04, 2013 at 10:15:36PM +0800, Fengguang Wu wrote:
> > Greetings,
> >
> > I got the below dmesg (kernel freezes at the end of it) and the first bad commit
> is
> >
> > commit cf6a2eacbcb2593b5b91d0817915c4f0464bb534
> > Author: K. Y. Srinivasan <kys@...rosoft.com>
> > Date:   Thu Dec 1 09:59:34 2011 -0800
> >
> >     drivers: hv: Don't OOPS when you cannot init vmbus
> >
> >     The hv vmbus driver was causing an OOPS since it was trying to register
> drivers
> >     on top of the bus even if initialization of the bus has failed for some
> >     reason (such as the odd chance someone would run a hv enabled kernel in a
> >     non-hv environment).
> >
> >     Signed-off-by: Sasha Levin <levinsasha928@...il.com>
> >     Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
> >     Cc: stable <stable@...r.kernel.org>
> >     Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
> >
> > [   13.356381] PCI: CLS 0 bytes, default 64
> 
> Ick, not good.  K.Y., any reason why I shouldn't just revert this?

I have asked Wu for details. Examining the relevant VMBUS code, I cannot see
how this patch could be responsible for the freeze. For what it is worth looking at dmesg, it appears that
we are not running on a Hypervisor.

There was a bug in this patch and that was fixed a few days later:  

commit 8f257a142fc3868d69de3f996b95d7bdbc509560
Author: K. Y. Srinivasan <kys@...rosoft.com>
Date:   Tue Dec 27 13:49:37 2011 -0800

    Drivers:hv: Fix a bug in vmbus_driver_unregister()

    The function vmbus_exists() was introduced recently to deal with cases where
    the vmbus driver failed to initialize and yet other Hyper-V drivers attempted
    to register with the vmbus bus driver. This patch introduced a bug where
    vmbus_driver_unregister() would fail to unregister the driver. This patch
    fixes the problem.

    Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
    Signed-off-by: Fuzhou Chen <fuzhouch@...rosoft.com>
    Cc: Sasha Levin <levinsasha928@...il.com>
    Cc: stable <stable@...r.kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

Regards,

K. Y
 
> 
> thanks,
> 
> greg k-h
> 


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