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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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