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    SubjectRe: PATCH: Fix race in cpu_down (hotplug cpu)
    On Mon, Sep 19, 2005 at 04:11:11PM +1000, Nigel Cunningham wrote:
    > > Ok, that makes sense. Nigel, could you confirm which idle routine you are
    > > using?
    >
    > >From dmesg:
    >
    > monitor/mwait feature present.
    > using mwait in idle threads.

    Ok, that may explain why __cpu_die is timing out for you! Can you try a
    (untested, I am afraid) patch on these lines:

    --- process.c.org 2005-09-19 11:44:57.000000000 +0530
    +++ process.c 2005-09-19 11:48:28.000000000 +0530
    @@ -245,16 +245,18 @@ EXPORT_SYMBOL_GPL(cpu_idle_wait);
    */
    static void mwait_idle(void)
    {
    + int cpu = raw_smp_processor_id();
    +
    local_irq_enable();

    if (!need_resched()) {
    set_thread_flag(TIF_POLLING_NRFLAG);
    do {
    __monitor((void *)&current_thread_info()->flags, 0, 0);
    - if (need_resched())
    + if (need_resched() || cpu_is_offline(cpu))
    break;
    __mwait(0, 0);
    - } while (!need_resched());
    + } while (!need_resched() || !cpu_is_offline(cpu));
    clear_thread_flag(TIF_POLLING_NRFLAG);
    }
    }

    Other idle routines will need similar fix.

    > Ok, but what about default_idle?

    default_idle should be fine as it is. IOW it should not cause __cpu_die to
    timeout.

    --


    Thanks and Regards,
    Srivatsa Vaddagiri,
    Linux Technology Center,
    IBM Software Labs,
    Bangalore, INDIA - 560017
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