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

  • To: "Tian, Kevin" <kevin.tian@xxxxxxxxx>, "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
  • Date: Fri, 2 Feb 2007 21:57:26 +0800
  • Delivery-date: Fri, 02 Feb 2007 05:57:12 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-topic: [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.

>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
>>next_timer_interrupt(), which only searches timer wheels and hrtimers.
>>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
>>it would return a sooner value if softlockup is the next 
>event to fire.
>>Do you want to try coding this up?
>> -- Keir

Attachment: softlockup_fix.patch
Description: softlockup_fix.patch

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