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Re: [Xen-devel] [PATCH] Fix softlockup issue after vcpu hotplug

  • To: "Graham, Simon" <Simon.Graham@xxxxxxxxxxx>, "Tian, Kevin" <kevin.tian@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
  • Date: Thu, 01 Feb 2007 23:26:54 +0000
  • Delivery-date: Thu, 01 Feb 2007 15:28:01 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcdESFqDCWsISfq5RGeHgxcxVzRqmQACelaDAAAZiDAAAQnwRAATVWmwABVdeuAAQqkN4AAKff/fAAh92KAAAhEUjg==
  • Thread-topic: [Xen-devel] [PATCH] Fix softlockup issue after vcpu hotplug

On 1/2/07 22:40, "Graham, Simon" <Simon.Graham@xxxxxxxxxxx> wrote:

> I also considered only touching the watchdog timer every 5s or so, but I
> think the code to do that would have more overhead than simply touching
> it for every do_timer() call (since it's just a call that copies jiffies
> to the per-cpu watchdog timer value).
> Take a look and let me know what you think (the printk could be removed
> -- I just put it in so I could tell the code was running).

The test inside the loop should check against NS_PER_TICK*100, not just 0.
You only want to override the usual running of the watchdog if you get a big
bunch of time stolen from you. Actually, five seconds (NS_PER_TICK*5*HZ)
would be good: no reason to make the comparison dependent on the duration of
a jiffy.

 -- Keir

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