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Date: Thu, 24 Mar 2011 12:09:44 -0500
From: Jack Steiner <steiner@....com>
To: Don Zickus <dzickus@...hat.com>
Cc: Cyrill Gorcunov <gorcunov@...il.com>, Ingo Molnar <mingo@...e.hu>,
tglx@...utronix.de, hpa@...or.com, x86@...nel.org,
linux-kernel@...r.kernel.org,
Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] x86, UV: Fix NMI handler for UV platforms
On Wed, Mar 23, 2011 at 05:23:58PM -0400, Don Zickus wrote:
> On Wed, Mar 23, 2011 at 03:46:47PM -0500, Jack Steiner wrote:
> > On Wed, Mar 23, 2011 at 04:00:08PM -0400, Don Zickus wrote:
> > > On Wed, Mar 23, 2011 at 01:53:20PM -0400, Don Zickus wrote:
> > > > Let me know if the patch fixes that problem. Then it will be one less
> > > > thing to worry about. :-)
> > >
> > > Ok, I was an idiot and made the patch against RHEL-6. Here is the one
> > > against 2.6.38. Sorry about that.
> >
> > No problem.
> >
> > I applied the patch below. However, I still see the "dazed" messages with
> > about the same frequency.
>
> Crap. It fixed acme's problem though where he was using 3 counters at
> high frequency. The problem must be elsewhere. I'll have to figure out a
> new strategy. I'll probably put together a patch full of trace_printk
> output to see if I can characterize it.
I added tracing to see if I could get more clues on the cause
of the "dazed" message. Unfortunately, I don't see anything - maybe
you do.
I used a tracing module that I've used for other things. I'm sure
there are other facilities available, but I've used this for a long time & it's
easy to update for specific purposes.
rtc = usec clock
rtc-delta = usec since previous trace entry
id = trace identifier (not particularily useful here)
p1, p2 = tracepoint specific data. See patch below
For hw_perf
p1 [63:32] this_nmi
[31:0] handled
p2 [63:32] pmu_nmi.marked
[31:0] pmu_nmi.handled
Here is a trace leading up to a failure. Times are in usec:
cpu rtc rtc-delta id p1 p2 desc
10 80996952 44005 1 0 0 NMI handler
10 80996952 0 40 0 0 perf_event_nmi_handler
10 80996952 0 40 0 0 perf_event_nmi_handler NMI
10 80996955 3 40 343000000001 33bc00000002 perf_event_nmi_handler NMI handled - this/handled pmumarked/handled
10 80996955 0 1 0 0 NMI handler OK
10 81036965 40010 1 0 0 NMI handler
10 81036965 0 40 0 0 perf_event_nmi_handler
10 81036966 1 40 0 0 perf_event_nmi_handler NMI
10 81036968 2 40 343100000001 33bc00000002 perf_event_nmi_handler NMI handled - this/handled pmumarked/handled
10 81036968 0 1 0 0 NMI handler OK
10 81064135 27167 1 0 0 NMI handler
10 81064136 1 40 0 0 perf_event_nmi_handler
10 81064137 1 40 0 0 perf_event_nmi_handler NMI
10 81064138 1 40 0 0 perf_event_nmi_handler - not handled
10 81064138 0 3 0 0 NMI handler failed
10 81064146 8 4 0 0 Unknown NMI handler
10 81064147 1 20 95 0 UV NMI not received
10 81064147 0 40 0 0 perf_event_nmi_handler
10 81064148 1 40 3432 33bc perf_event_nmi_handler NMIUNKNOWN
10 81064148 0 99 0 0 Unknown NMI handler
The last trace is just prior to a "dazed" failure.
I dont see anything unusual. Just looks like a spurious NMI with no cause. The PMU did not
see an NMI cause. The previous couple of NMIs looked (at least to me) normal.
NMIs are occuring every ~40msec. No UV NMIs were recently received. No multiple PMU
events handled.
Here is a trace where a UV NMI was received:
0 371742833 2453 1 0 0 NMI handler
0 371742834 1 40 0 0 perf_event_nmi_handler
0 371742834 0 40 0 0 perf_event_nmi_handler NMI
0 371742836 2 40 0 0 perf_event_nmi_handler - not handled
0 371742836 0 3 0 0 NMI handler failed
0 371742856 20 4 0 0 Unknown NMI handler
0 371742913 57 21 f1 0 UV NMI received
I've include the patch (latest x86 tree) so you can see exactly where the trace points
were inserted.
Index: linux/arch/x86/kernel/apic/x2apic_uv_x.c
===================================================================
--- linux.orig/arch/x86/kernel/apic/x2apic_uv_x.c 2011-03-23 10:30:35.000000000 -0500
+++ linux/arch/x86/kernel/apic/x2apic_uv_x.c 2011-03-24 10:47:59.865562087 -0500
@@ -23,6 +23,7 @@
#include <linux/io.h>
#include <linux/pci.h>
#include <linux/kdebug.h>
+#include <linux/utrace.h>
#include <asm/uv/uv_mmrs.h>
#include <asm/uv/uv_hub.h>
@@ -54,6 +55,9 @@ unsigned int uv_apicid_hibits;
EXPORT_SYMBOL_GPL(uv_apicid_hibits);
static DEFINE_SPINLOCK(uv_nmi_lock);
+void (*utrace_func)(int id, unsigned long, unsigned long, const char*);
+EXPORT_SYMBOL_GPL(utrace_func);
+
/* Should be part of uv_hub_info but that breas the KABI */
static struct uv_nmi_info {
spinlock_t nmi_lock;
@@ -692,11 +696,14 @@ int uv_handle_nmi(struct notifier_block
* if a hw_perf and BMC NMI are received at about the same time
* and both events are processed with the first NMI.
*/
- if (__get_cpu_var(cpu_last_nmi_count) == uv_nmi_info[blade].nmi_count)
+ if (__get_cpu_var(cpu_last_nmi_count) == uv_nmi_info[blade].nmi_count) {
+ UTRACE(20, __get_cpu_var(cpu_last_nmi_count), 0, "UV NMI not received");
return NOTIFY_DONE;
+ }
printk("ZZZ:%d NMI %ld %ld\n", smp_processor_id(), __get_cpu_var(cpu_last_nmi_count), uv_nmi_info[blade].nmi_count);
__get_cpu_var(cpu_last_nmi_count) = uv_nmi_info[blade].nmi_count;
+ UTRACE(21, __get_cpu_var(cpu_last_nmi_count), 0, "UV NMI received");
/*
* Use a lock so only one cpu prints at a time.
Index: linux/arch/x86/kernel/cpu/perf_event.c
===================================================================
--- linux.orig/arch/x86/kernel/cpu/perf_event.c 2011-03-23 15:33:48.000000000 -0500
+++ linux/arch/x86/kernel/cpu/perf_event.c 2011-03-24 10:47:20.101496911 -0500
@@ -25,6 +25,7 @@
#include <linux/highmem.h>
#include <linux/cpu.h>
#include <linux/bitops.h>
+#include <linux/utrace.h>
#include <asm/apic.h>
#include <asm/stacktrace.h>
@@ -1341,15 +1342,19 @@ perf_event_nmi_handler(struct notifier_b
struct die_args *args = __args;
unsigned int this_nmi;
int handled;
+ unsigned long tmp1, tmp2;
if (!atomic_read(&active_events))
return NOTIFY_DONE;
+ UTRACE(40, 0, 0, "perf_event_nmi_handler");
switch (cmd) {
case DIE_NMI:
+ UTRACE(40, 0, 0, "perf_event_nmi_handler NMI");
break;
case DIE_NMIUNKNOWN:
this_nmi = percpu_read(irq_stat.__nmi_count);
+ UTRACE(40, this_nmi, __this_cpu_read(pmu_nmi.marked), "perf_event_nmi_handler NMIUNKNOWN");
if (this_nmi != __this_cpu_read(pmu_nmi.marked))
/* let the kernel handle the unknown nmi */
return NOTIFY_DONE;
@@ -1368,10 +1373,15 @@ perf_event_nmi_handler(struct notifier_b
apic_write(APIC_LVTPC, APIC_DM_NMI);
handled = x86_pmu.handle_irq(args->regs);
- if (!handled)
+ if (!handled) {
+ UTRACE(40, handled, 0, "perf_event_nmi_handler - not handled");
return NOTIFY_DONE;
+ }
this_nmi = percpu_read(irq_stat.__nmi_count);
+ tmp1 = ((unsigned long)this_nmi << 32) | handled;
+ tmp2 = ((unsigned long)__this_cpu_read(pmu_nmi.marked) << 32) | __this_cpu_read(pmu_nmi.handled);
+ UTRACE(40, tmp1, tmp2, "perf_event_nmi_handler NMI handled - this/handled pmumarked/handled");
if ((handled > 1) ||
/* the next nmi could be a back-to-back nmi */
((__this_cpu_read(pmu_nmi.marked) == this_nmi) &&
Index: linux/arch/x86/kernel/traps.c
===================================================================
--- linux.orig/arch/x86/kernel/traps.c 2011-03-22 15:10:36.000000000 -0500
+++ linux/arch/x86/kernel/traps.c 2011-03-24 10:35:15.410168027 -0500
@@ -31,6 +31,7 @@
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/io.h>
+#include <linux/utrace.h>
#ifdef CONFIG_EISA
#include <linux/ioport.h>
@@ -371,9 +372,11 @@ io_check_error(unsigned char reason, str
static notrace __kprobes void
unknown_nmi_error(unsigned char reason, struct pt_regs *regs)
{
+ UTRACE(4, 0, 0, "Unknown NMI handler");
if (notify_die(DIE_NMIUNKNOWN, "nmi", regs, reason, 2, SIGINT) ==
NOTIFY_STOP)
return;
+ UTRACE(99, 0, 0, "Unknown NMI handler");
#ifdef CONFIG_MCA
/*
* Might actually be able to figure out what the guilty party
@@ -403,8 +406,12 @@ static notrace __kprobes void default_do
* NMI, otherwise we may lose it, because the CPU-specific
* NMI can not be detected/processed on other CPUs.
*/
- if (notify_die(DIE_NMI, "nmi", regs, 0, 2, SIGINT) == NOTIFY_STOP)
+ UTRACE(1, 0, 0, "NMI handler");
+ if (notify_die(DIE_NMI, "nmi", regs, 0, 2, SIGINT) == NOTIFY_STOP) {
+ UTRACE(1, 0, 0, "NMI handler OK");
return;
+ }
+ UTRACE(3, 0, 0, "NMI handler failed");
/* Non-CPU-specific NMI: NMI sources can be processed on any CPU */
raw_spin_lock(&nmi_reason_lock);
Index: linux/include/linux/utrace.h
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux/include/linux/utrace.h 2011-03-24 10:30:52.438555195 -0500
@@ -0,0 +1,14 @@
+#ifndef _LINUX_UTRACE_H_
+#define _LINUX_UTRACE_H_
+
+
+extern void (*utrace_func)(int id, unsigned long, unsigned long, const char *);
+
+#define UTRACE(id, a, b, c) \
+ do { \
+ if (unlikely(utrace_func)) \
+ (*utrace_func)(id, a, b, c); \
+ } while (0)
+
+#endif /* _LINUX_UTRACE_H_ */
+
--
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