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

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

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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