Re: [PATCH -v3] perf, x86: try to handle unknown nmis with running perfctrs

Don Zickus
2010-08-24T21:48:51Z

On Fri, Aug 20, 2010 at 04:17:03PM +0200, Ingo Molnar wrote:
>
> it's not working so well, i'm getting:
>
> Uhhuh. NMI received for unknown reason 00 on CPU 9.
> Do you have a strange power saving mode enabled?
> Dazed and confused, but trying to continue
>
> on a nehalem box, after a perf top and perf stat run.

After applying the patch below, I ran the following commands on my nehalem
box without reproducing what you are seeing. Any thing else I can run
that might trigger it? (I also ran them on an amd phenom quad-core box).

I used 2.6.32-rc2 plus Robert's and 2 of PeterZ's patches.

perf top
perf stat -a -e cycles -e instructions -e cache-references -e cache-misses -e branch-misses -- sleep 5
perf record -f -a -e cycles -e instructions -e cache-references -e cache-misses -e branch-misses -- sleep 5

Cheers,
Don

>From 198be1044fa603bc9582a5c19134fdf9a433fff0 Mon Sep 17 00:00:00 2001
From: Don Zickus <dzickus@redhat.com>
Date: Tue, 24 Aug 2010 17:43:17 -0400
Subject: [PATCH] [x86] perf: rename nmi variable to avoid clash with entry point

There is already an entry point named .nmi in entry.S and that seems to clash
with the per_cpu variable nmi defined in commit f3a860d8. Renaming this
variable avoids the namespace collision.

Signed-off-by: Don Zickus <dzickus@redhat.com>
---
arch/x86/kernel/cpu/perf_event.c | 12 ++++++------
1 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index dd2fceb..2a05ea4 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -1205,7 +1205,7 @@ struct pmu_nmi_state {
int handled;
};

-static DEFINE_PER_CPU(struct pmu_nmi_state, nmi);
+static DEFINE_PER_CPU_PAGE_ALIGNED(struct pmu_nmi_state, pmu_nmi);

static int __kprobes
perf_event_nmi_handler(struct notifier_block *self,
@@ -1224,7 +1224,7 @@ perf_event_nmi_handler(struct notifier_block *self,
break;
case DIE_NMIUNKNOWN:
this_nmi = percpu_read(irq_stat.__nmi_count);
- if (this_nmi != __get_cpu_var(nmi).marked)
+ if (this_nmi != __get_cpu_var(pmu_nmi).marked)
/* let the kernel handle the unknown nmi */
return NOTIFY_DONE;
/*
@@ -1248,8 +1248,8 @@ perf_event_nmi_handler(struct notifier_block *self,
this_nmi = percpu_read(irq_stat.__nmi_count);
if ((handled > 1) ||
/* the next nmi could be a back-to-back nmi */
- ((__get_cpu_var(nmi).marked == this_nmi) &&
- (__get_cpu_var(nmi).handled > 1))) {
+ ((__get_cpu_var(pmu_nmi).marked == this_nmi) &&
+ (__get_cpu_var(pmu_nmi).handled > 1))) {
/*
* We could have two subsequent back-to-back nmis: The
* first handles more than one counter, the 2nd
@@ -1260,8 +1260,8 @@ perf_event_nmi_handler(struct notifier_block *self,
* handling more than one counter. We will mark the
* next (3rd) and then drop it if unhandled.
*/
- __get_cpu_var(nmi).marked = this_nmi + 1;
- __get_cpu_var(nmi).handled = handled;
+ __get_cpu_var(pmu_nmi).marked = this_nmi + 1;
+ __get_cpu_var(pmu_nmi).handled = handled;
}

return NOTIFY_STOP;
--
1.7.2.1