linux-kernel - [PATCH] oprofile: re-arm APIC_DM_NMI in ppro_check

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Date:	Mon, 10 Nov 2008 15:23:00 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Andi Kleen <andi@...stfloor.org>,
	Robert Richter <robert.richter@....com>,
	Ingo Molnar <mingo@...e.hu>
CC:	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] oprofile: re-arm APIC_DM_NMI in ppro_check_ctrs()

Andi Kleen a écrit :
> Eric Dumazet <dada1@...mosbay.com> writes:
> 
>> diff --git a/arch/x86/oprofile/op_model_ppro.c b/arch/x86/oprofile/op_model_ppro.c
>> index 3f1b81a..716d26f 100644
>> --- a/arch/x86/oprofile/op_model_ppro.c
>> +++ b/arch/x86/oprofile/op_model_ppro.c
>> @@ -69,7 +69,7 @@ static void ppro_setup_ctrs(struct op_msrs const * const msrs)
>>  	int i;
>>  
>>  	if (!reset_value) {
>> -		reset_value = kmalloc(sizeof(unsigned) * num_counters,
>> +		reset_value = kmalloc(sizeof(reset_value[0]) * num_counters,
> 
> Thanks for tracking this down.
> 
> But that still doesn't explain why 2.6.27 fails too?

Desesperatly Seeking Oprofile, next round.

I know *nothing* about APIC but spent few hours to try several tricks
and finally found something.

It solved my problem : oprofile can run several hours without
any freeze of NMI on any core.

# grep NMI /proc/interrupts
NMI:   10902884    9635871   10333815    8372989    7971483    8298373    8877495   10206963   Non-maskable interrupts
...
# grep NMI /proc/interrupts
NMI:   15518834   14340713   15038694   13078235   12676585   13003394   13582115   14912146   Non-maskable interrupts

Can anybody understand and explain what is happening ?

Is it a software or hardware problem ?

[PATCH] oprofile: re-arm APIC_DM_NMI in ppro_check_ctrs()

While using oprofile on my HP BL460c G1, (two quad core intel E5450 CPU),
I noticed that one CPU after the other could not get anymore NMI.

After a while, all cores where blocked (ie not generating events for oprofile)
I tried all major linux versions and all where affected by this freeze.

I found that we have to re-arm APIC_DM_NMI *before* writing to MSR counter
when we get event notification.

Signed-off-by: Eric Dumazet <dada1@...mosbay.com>
 arch/x86/oprofile/op_model_ppro.c |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)

View attachment "oprofile_msr.patch" of type "text/plain" (892 bytes)