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

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

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...

 -- Keir



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel