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    SubjectRe: [PATCH] x86: fix duplicate calls of the nmi handler
    On 13.09.10 16:37:13, Robert Richter wrote:
    > Ingo, Peter,
    > I finally found a system here, will start debugging

    I found the reason why we get the unknown nmi. For some reason
    cpuc->active_mask in x86_pmu_handle_irq() is zero. Thus, no counters
    are handled when we get an nmi. It seems there is somewhere a race
    accessing the active_mask. So far I don't have a fix available.
    Changing x86_pmu_stop() did not help:

    static void x86_pmu_stop(struct perf_event *event, int flags)
    struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
    struct hw_perf_event *hwc = &event->hw;

    if (test_bit(hwc->idx, cpuc->active_mask)) {
    __clear_bit(hwc->idx, cpuc->active_mask);
    cpuc->events[hwc->idx] = NULL;
    WARN_ON_ONCE(hwc->state & PERF_HES_STOPPED);
    hwc->state |= PERF_HES_STOPPED;


    Advanced Micro Devices, Inc.
    Operating System Research Center

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