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Date: Sat, 14 Jan 2012 06:49:38 -0800
From: Greg KH <gregkh@suse.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
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Subject: Re: x86/mce: machine check warning during poweroff
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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@linux.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