linux-kernel - Re: [PATCH 1/3] x86, reboot: Use NMI instead of REBOOT

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Message-ID: <20111012163358.GD31857@elte.hu>
Date:	Wed, 12 Oct 2011 18:33:59 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Don Zickus <dzickus@...hat.com>
Cc:	Andi Kleen <andi@...stfloor.org>, x86@...nel.org,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Robert Richter <robert.richter@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	seiji.aguchi@....com, vgoyal@...hat.com, mjg@...hat.com,
	tony.luck@...el.com, gong.chen@...el.com, satoru.moriya@....com,
	avi@...hat.com
Subject: Re: [PATCH 1/3] x86, reboot:  Use NMI instead of REBOOT_VECTOR to
 stop cpus


* Don Zickus <dzickus@...hat.com> wrote:

> On Wed, Oct 12, 2011 at 09:30:25AM +0200, Ingo Molnar wrote:
> > 
> > * Don Zickus <dzickus@...hat.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
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