linux-kernel - Re: [PATCH] fix BUG using smp_processor_id() in touch_nmi_watchdog and touch_softlockup

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Date:	Tue, 17 Aug 2010 12:27:05 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Don Zickus <dzickus@...hat.com>
Cc:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	fweisbec@...il.com
Subject: Re: [PATCH] fix BUG using smp_processor_id() in touch_nmi_watchdog
 and touch_softlockup_watchdog

On Mon, Aug 16, 2010 at 10:30 PM, Don Zickus <dzickus@...hat.com> wrote:
>> Patch also removes double smp_processor_id call (smp_processor_id itself and in
>> __get_cpu_var) in __touch_watchdog.

After checking touch_softlockup_watchdog() and touch_nmi_watchdog() in
before version, __raw_get_cpu_var() is used there.

Thanks,
Yong

>>
>> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
>
> Acked-by: Don Zickus <dzickus@...hat.com>
>
>>
>> ---
>>
>> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
>> index 613bc1f..8822f1e 100644
>> --- a/kernel/watchdog.c
>> +++ b/kernel/watchdog.c
>> @@ -116,13 +116,14 @@ static unsigned long get_sample_period(void)
>>  static void __touch_watchdog(void)
>>  {
>>       int this_cpu = smp_processor_id();
>> -
>> -     __get_cpu_var(watchdog_touch_ts) = get_timestamp(this_cpu);
>> +     per_cpu(watchdog_touch_ts, this_cpu) = get_timestamp(this_cpu);
>>  }
>>
>>  void touch_softlockup_watchdog(void)
>>  {
>> -     __get_cpu_var(watchdog_touch_ts) = 0;
>> +     int this_cpu = get_cpu();
>> +     per_cpu(watchdog_touch_ts, this_cpu) = 0;
>> +     put_cpu();
>>  }
>>  EXPORT_SYMBOL(touch_softlockup_watchdog);
>>
>> @@ -142,7 +143,9 @@ void touch_all_softlockup_watchdogs(void)
>>  #ifdef CONFIG_HARDLOCKUP_DETECTOR
>>  void touch_nmi_watchdog(void)
>>  {
>> -     __get_cpu_var(watchdog_nmi_touch) = true;
>> +     int this_cpu = get_cpu();
>> +     per_cpu(watchdog_nmi_touch, this_cpu) = true;
>> +     put_cpu();
>>       touch_softlockup_watchdog();
>>  }
>>  EXPORT_SYMBOL(touch_nmi_watchdog);
>>
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