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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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