linux-kernel - Re: x86/mce: machine check warning during poweroff

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Date:	Sat, 14 Jan 2012 06:49:38 -0800
From:	Greg KH <gregkh@...e.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Ming Lei <tom.leiming@...il.com>,
	Djalal Harouni <tixxdz@...ndz.org>,
	Borislav Petkov <borislav.petkov@....com>,
	Tony Luck <tony.luck@...el.com>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Ingo Molnar <mingo@...e.hu>, Andi Kleen <ak@...ux.intel.com>,
	linux-kernel@...r.kernel.org, Kay Sievers <kay.sievers@...y.org>,
	gouders@...bocholt.fh-gelsenkirchen.de,
	Marcos Souza <marcos.mage@...il.com>,
	Linux PM mailing list <linux-pm@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	prasad@...ux.vnet.ibm.com, justinmattock@...il.com,
	Jeff Chua <jeff.chua.linux@...il.com>,
	Suresh B Siddha <suresh.b.siddha@...el.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mel Gorman <mgorman@...e.de>,
	Gilad Ben-Yossef <gilad@...yossef.com>
Subject: Re: x86/mce: machine check warning during poweroff

On Fri, Jan 13, 2012 at 06:53:04PM -0800, Linus Torvalds wrote:
> On Fri, Jan 13, 2012 at 6:41 PM, Srivatsa S. Bhat
> <srivatsa.bhat@...ux.vnet.ibm.com> wrote:
> >
> > YES!! Finally I have a fix for this whole MCE thing! :-)
> 
> Goodie.
> 
> > The patch below works perfectly for me - I tested multiple CPU hotplug
> > operations as well as multiple pm_test runs at core level. Please let me
> > know if this solves the suspend issue as well..
> 
> Ok, I'll try, and I bet it does.
> 
> HOWEVER.
> 
> I'd be a whole lot happier knowing exactly which field in "struct
> device" that needed to be NULL before it gets registered.
> 
> I don't like how
> 
>   device_register() + device_create_file(dev)..
> 
> is not sufficiently undone by
> 
>  .. device_remove_file(dev) +  device_unregister()
> 
> so that it can't be repeated. Exactly *what* state is stale and
> re-used incorrectly if you do that device_register() a second time.
> 
> It smells like a misfeature of the device core handling.

It has to do with the fact that this is a "static" device that is being
reused.  Normally it would be cleaned up properly in the release
function, but as there isn't one, some fields are being left in a bad
state.

I'll look into this Sunday better when I have the chance, I'm currently
on the road until late tonight, skiing, and it's hard to write patches
from a chair lift...

thanks,

greg k-h
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