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

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Message-ID: <20100816143052.GV4879@redhat.com>
Date:	Mon, 16 Aug 2010 10:30:52 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:	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

cc'ing Frederic

On Mon, Aug 16, 2010 at 05:08:29PM +0300, Sergey Senozhatsky wrote:
> Fix: acpi_os_stall calls touch_nmi_watchdog and touch_softlockup_watchdog
> with preemption enabled causing 'BUG: using smp_processor_id() in preemptible
> code'.
>      
> Patch also removes double smp_processor_id call (smp_processor_id itself and in
> __get_cpu_var) in __touch_watchdog.
> 
> 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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