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    SubjectRe: [RFC PATCH] ARM: smp: Fix the CPU hotplug race with scheduler.
    On 6/20/2011 3:20 PM, Russell King - ARM Linux wrote:
    > On Mon, Jun 20, 2011 at 02:53:59PM +0530, Santosh Shilimkar wrote:
    >> The current ARM CPU hotplug code suffers from couple of race conditions
    >> in CPU online path with scheduler.
    >> The ARM CPU hotplug code doesn't wait for hot-plugged CPU to be marked
    >> active as part of cpu_notify() by the CPU which brought it up before
    >> enabling interrupts.
    >
    > Hmm, why not just move the set_cpu_online() call before notify_cpu_starting()
    > and add the wait after the set_cpu_online() ?
    I think that's what patch is doing. Do you mean, calling hotplug
    notifier chain immediately after CPU marked as online. Something
    like below.

    set_cpu_online(cpu, true);
    notify_cpu_starting(cpu);
    while (!cpumask_test_cpu(smp_processor_id(), cpu_active_mask))
    cpu_relax();

    /*
    * Enable local interrupts.
    */
    local_irq_enable();
    local_fiq_enable();


    Regards
    Santosh



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