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SubjectRe: [PATCH] clockevent: don't remove broadcast device when cpu is dead
On Wed, 13 Jan 2010, Xiaotian Feng wrote:
> On 01/12/2010 09:20 PM, Thomas Gleixner wrote:
> > On Thu, 7 Jan 2010, Xiaotian Feng wrote:
> >
> > > Marc reported BUG during shutdown, after debugging, kernel is trying
> > > to remove a broadcast device which mode is CLOCK_EVT_MODE_ONESHOT.
> > >
> > > The root cause for this bug is that in clockevents_notify,
> > > "cpumask_weight(dev->cpumask) == 1" is always true even if dev is a
> >
> > Why is cpumask_weight(dev->cpumask) == 1 always true when we shutdown
> > a non boot cpu ?
> >
> > The broadcast device is not a per cpu device and the cpumask should
> > not only contain the CPU which is shut down !
>
> At least for hpet broadcast dev, it's dev->cpumask is only contain the CPU
> which it is initialized from.

Which is fundamentaly wrong and the root cause of the problem. I'll
have a look tomorrow morning when my brain is more awake than now.

> And for broadcast device, kernel is using tick_broadcast_mask not
> dev->cpumask, right?

No, tick_broadcast_mask is the bitmask which tells us which cpus get
the broadcast IPI.

Thanks,

tglx


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