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    SubjectRe: 2.6.38-rc2: Uhhuh. NMI received for unknown reason 2d on CPU 0.
    On 02/01/2011 07:27 PM, George Spelvin wrote:
    > Since upgrading to -rc2 (-rc3 is compiling right now), I've been getting
    > complaints at irregular intervals. This didn't used to happen with 2.6.37.
    >
    ...
    > Should I bisect this, or does someone know what might be happening?
    >
    > Thank you!
    >

    I fear it's known issue at moment, we're trying to resolve it. There is
    an option -- to disable nmi_watchdog (nmi_watchdog=0 boot option).

    But if you have a will or would like to help debug the problem -- mind to
    try the patch below? Note the patch is ugly at moment and must *not* be
    running on non-P4 system (and I only compile-tested it so no guarantees
    at all, and I've CC'ed a couple of people as well)

    Cyrill

    ---
    arch/x86/kernel/cpu/perf_event.c | 12 +++++++++++-
    arch/x86/kernel/cpu/perf_event_p4.c | 8 +++++++-
    2 files changed, 18 insertions(+), 2 deletions(-)

    Index: linux-2.6.git/arch/x86/kernel/cpu/perf_event.c
    =====================================================================
    --- linux-2.6.git.orig/arch/x86/kernel/cpu/perf_event.c
    +++ linux-2.6.git/arch/x86/kernel/cpu/perf_event.c
    @@ -1075,7 +1075,17 @@ static void x86_pmu_start(struct perf_ev

    cpuc->events[idx] = event;
    __set_bit(idx, cpuc->active_mask);
    - __set_bit(idx, cpuc->running);
    + if (1) {
    + /* running mask is shared across a core */
    + int leader_cpu;
    + struct cpu_hw_events *leader_cpuc;
    +
    + leader_cpu = cpumask_first(__get_cpu_var(cpu_sibling_map));
    + leader_cpuc = &per_cpu(cpu_hw_events, leader_cpu);
    +
    + __set_bit(idx, leader_cpuc->running);
    + } else
    + __set_bit(idx, cpuc->running);
    x86_pmu.enable(event);
    perf_event_update_userpage(event);
    }
    Index: linux-2.6.git/arch/x86/kernel/cpu/perf_event_p4.c
    =====================================================================
    --- linux-2.6.git.orig/arch/x86/kernel/cpu/perf_event_p4.c
    +++ linux-2.6.git/arch/x86/kernel/cpu/perf_event_p4.c
    @@ -907,8 +907,14 @@ static int p4_pmu_handle_irq(struct pt_r
    int overflow;

    if (!test_bit(idx, cpuc->active_mask)) {
    + int leader_cpu;
    + struct cpu_hw_events *leader_cpuc;
    +
    + leader_cpu = cpumask_first(__get_cpu_var(cpu_sibling_map));
    + leader_cpuc = &per_cpu(cpu_hw_events, leader_cpu);
    +
    /* catch in-flight IRQs */
    - if (__test_and_clear_bit(idx, cpuc->running))
    + if (__test_and_clear_bit(idx, leader_cpuc->running))
    handled++;
    continue;
    }


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