lkml.org 
[lkml]   [2010]   [Aug]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] fix BUG using smp_processor_id() in touch_nmi_watchdog and touch_softlockup_watchdog
On Tue, Aug 17, 2010 at 01:39:48PM +0300, Sergey Senozhatsky wrote:
> Please kindly review.

I don't have a deep enough understanding of the subtleties between
per_cpu, __get_cpu_var, and __raw_get_cpu_var to really say which is
correct. To me, all three versions of your patch look they do the same
thing.

Technically, it seems like preempt_disable/enable would be the correct
thing to do. But as someone pointed out earlier, if the code is preempted
and switches cpu, then the touch_*_watchdog effectively becomes a no-op
(which I guess it can do even with the preempt_disable/enable surrounding
it). So I have no idea. I am going to wait for smarter people than me to
provide an opinion. :-)

Cheers,
Don

>
> ---
>
> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> index 613bc1f..22dd388 100644
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -116,13 +116,12 @@ 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;
> + __raw_get_cpu_var(watchdog_touch_ts) = 0;
> }
> EXPORT_SYMBOL(touch_softlockup_watchdog);
>
> @@ -142,7 +141,7 @@ void touch_all_softlockup_watchdogs(void)
> #ifdef CONFIG_HARDLOCKUP_DETECTOR
> void touch_nmi_watchdog(void)
> {
> - __get_cpu_var(watchdog_nmi_touch) = true;
> + __raw_get_cpu_var(watchdog_nmi_touch) = true;
> touch_softlockup_watchdog();
> }
> EXPORT_SYMBOL(touch_nmi_watchdog);
>


\
 
 \ /
  Last update: 2010-08-17 15:17    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site