Re: [PATCH][RESEND]RE: [Xen-devel] [PATCH] Fix softlockup issue aftervcpu hotplug

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

I'm travelling so I'm not getting through the patch queue as quickly as
usual. The patch looks fine -- it may get checked in today.

 -- Keir

On 4/2/07 12:30, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:

> Keir, how about your opinion about this version? Maybe I missed
> your reply...
> 
> Thanks,
> Kevin 
> 
>> -----Original Message-----
>> From: Tian, Kevin
>> Sent: 2007年2月2日 21:57
>> To: Tian, Kevin; Keir Fraser; xen-devel@xxxxxxxxxxxxxxxxxxx
>> Subject: RE: [PATCH][RESEND]RE: [Xen-devel] [PATCH] Fix
>> softlockup issue aftervcpu hotplug
>> 
>> Hi, Keir,
>> Please check whether attached patch matches
>> your suggestion. Test OK with vcpu hotplug and save/restore.
>> 
>> Thanks,
>> Kevin
>> 
>>> From: Tian, Kevin
>>> Sent: 2007年2月2日 10:49
>>>> Okay, I now see how this works -- the thread is kicked from
>>>> softlockup_tick(), from the timer ISR. So this wakeup event is hidden
>>>> from
>>>> next_timer_interrupt(), which only searches timer wheels and
>> hrtimers.
>>> 
>>> Exactly.
>>> 
>>>> 
>>>> The strictly correct fix here is to make next_timer_interrupt()
>>>> softlockup-aware. I would say it is currently incorrect in
>>> the presence of
>>>> softlockup since it is not doing its job (telling an idle
>>> process what the
>>>> next time-based event is that it must wake up for).
>>>> 
>>>> We can do this by adding a softlockup_get_next_event(),
>>> called from the
>>>> bottom of next_timer_interrupt(). I would pass it the current
>>> return value
>>>> and have it return an adjusted value: so in the absence of
>>> softlockup it
>>>> would simply return its argument unmodified. In the presence of
>>>> softlockup
>>>> it would return a sooner value if softlockup is the next
>>> event to fire.
>>>> 
>>>> Do you want to try coding this up?
>>>> 
>>>> -- Keir
>>> 
>>> Sure.
>>> 
>>> Thanks,
>>> Kevin
>> 



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