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

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Message-ID: <4E969EA6.9060400@linux.intel.com>
Date:	Thu, 13 Oct 2011 16:17:42 +0800
From:	Chen Gong <gong.chen@...ux.intel.com>
To:	Don Zickus <dzickus@...hat.com>
CC:	Ingo Molnar <mingo@...e.hu>, 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

于 2011/10/12 20:51, Don Zickus 写道:
> On Wed, Oct 12, 2011 at 10:35:42AM +0800, Chen Gong wrote:
>> 于 2011/10/11 23:24, Don Zickus 写道:
>>> +
>>> +		/* sync above data before sending NMI */
>>> +		wmb();
>>> +
>>> +		apic->send_IPI_allbutself(NMI_VECTOR);
>>> +
>>> +		/*
>>> +		 * Don't wait longer than a second if the caller
>>> +		 * didn't ask us to wait.
>>> +		 */
>>> +		timeout = USEC_PER_SEC;
>>> +		while (num_online_cpus()>   1&&   (wait || timeout--))
>>> +			udelay(1);
>>
>> In this patch and next patch, how about using the same logic in commit 74d91e3c6
>
> I guess I don't understand why I would do that.  That commit doesn't seem
> to have a way to break out of the while loop and it does not take into account
> the 'wait' variable the virt folks needed.  The only thing that could be
> usable seems to be the 'touch_nmi_watchdog', but in that case if the other
> cpus haven't hit the NMI yet, I would be happy for other NMI sources to
> trigger to, to help move things along. :-)

Maybe two birds with on stone :-)

>
> The above code snippet is what is currently there and that seems to work
> well, so I didn't want to change to much when moving from the IRQ path to
> the NMI path.

Fine, if so, I have no objection.

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