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RE: [Xen-devel] [PATCH 2/4] CPUIDLE: Avoid remnant LAPIC timerintr while

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>, "Tian, Kevin" <kevin.tian@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH 2/4] CPUIDLE: Avoid remnant LAPIC timerintr while force hpetbroadcast
From: "Wei, Gang" <gang.wei@xxxxxxxxx>
Date: Thu, 11 Sep 2008 23:22:26 +0800
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Thread-topic: [Xen-devel] [PATCH 2/4] CPUIDLE: Avoid remnant LAPIC timerintr while force hpetbroadcast
On Thursday, September 11, 2008 7:07 PM, Keir Fraser wrote:
> On 11/9/08 11:59, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:
>>> Also, in your patch, you unmask LVTT after reprogramming the
>>> LAPIC counter.
>>> Isn't there a race where the LAPIC timer generates an
>>> interrupt event before
>>> you unmask the LVTT and hence you lose the interrupt (since I
>>> assume the
>>> LAPIC interrupt is basically an internal one-shot signal which
>>> does not get
>>> latched in any way)? So you'd probably need to reprogram_timer(0), then
>>> enable the timer, then reprogram_timer(<actual value>).
>> You're correct. It will be fixed.
> Thanks. I'm not sure whether the reprogram_timer(0) before re-enabling is
> really required. It looks like Linux doesn't do similar (although if course
> it does re-programming after re-enabling to avoid the above race).
> I suppose repogram_timer(0) is cheap so you might choose to do it anyway.
> It's up to you...

Do reprogram_timer(0) anyway make things well controlled. So let's do it this 
way. Attached is the additional patch.


Attachment: disable_apic_timer_in_c3_0911.patch
Description: disable_apic_timer_in_c3_0911.patch

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