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    [W:0.024 / U:306.268 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site