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Date: Wed, 12 Oct 2011 18:33:59 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Don Zickus <dzickus@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>, x86@kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
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        vgoyal@redhat.com, mjg@redhat.com, tony.luck@intel.com,
        gong.chen@intel.com, satoru.moriya@hds.com, avi@redhat.com
Subject: Re: [PATCH 1/3] x86, reboot:  Use NMI instead of REBOOT_VECTOR to
 stop cpus
Message-ID: <20111012163358.GD31857@elte.hu>
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* Don Zickus <dzickus@redhat.com> wrote:

> On Wed, Oct 12, 2011 at 09:30:25AM +0200, Ingo Molnar wrote:
> > 
> > * Don Zickus <dzickus@redhat.com> wrote:
> > 
> > > +		if (register_nmi_handler(NMI_LOCAL, smp_stop_nmi_callback,
> > > +					 NMI_FLAG_FIRST, "smp_stop"))
> > > +			return;		/* return what? */
> > 
> > That comment looks a bit odd.
> 
> Yeah, I copied it from the kdump code because it seemed relevant.  
> The point was to express the paranoid concern, if we can't register 
> the NMI handler for whatever reason, what happens!?.  How do we 
> explain to anyone we failed to shut down the other cpus?
> 
> I can expand the comment to be more specific in the paranoia.  I 
> just wasn't sure the right way to handle that failure case.

Just add something like:

	/* Note: we ignore failures here */

if there's nothing intelligent possible.

Thanks,

	Ingo