* Andrew Morton <[email protected]> wrote:
> On Tue, 20 Nov 2007 09:46:11 +0100
> Ingo Molnar <[email protected]> wrote:
>
> > Subject: softlockup: do the wakeup from a hrtimer
> > From: Ingo Molnar <[email protected]>
> >
> > David Miller reported soft lockup false-positives that trigger on NOHZ
> > due to CPUs idling for more than 10 seconds.
> >
> > The solution is to drive the wakeup of the watchdog threads not from the
> > timer tick (which has no guaranteed frequency), but from the watchdog
> > tasks themselves.
> >
> > http://bugzilla.kernel.org/show_bug.cgi?id=9409
> >
> > Reported-by: David Miller <[email protected]>
> > Signed-off-by: Ingo Molnar <[email protected]>
> > ---
> > kernel/softlockup.c | 6 +-----
> > 1 file changed, 1 insertion(+), 5 deletions(-)
> >
> > Index: linux/kernel/softlockup.c
> > ===================================================================
> > --- linux.orig/kernel/softlockup.c
> > +++ linux/kernel/softlockup.c
> > @@ -100,10 +100,6 @@ void softlockup_tick(void)
> >
> > now = get_timestamp(this_cpu);
> >
> > - /* Wake up the high-prio watchdog task every second: */
> > - if (now > (touch_timestamp + 1))
> > - wake_up_process(per_cpu(watchdog_task, this_cpu));
> > -
> > /* Warn about unreasonable 10+ seconds delays: */
> > if (now <= (touch_timestamp + softlockup_thresh))
> > return;
> > @@ -141,7 +137,7 @@ static int watchdog(void *__bind_cpu)
> > while (!kthread_should_stop()) {
> > set_current_state(TASK_INTERRUPTIBLE);
> > touch_softlockup_watchdog();
> > - schedule();
> > + msleep(1000);
> > }
> >
> > return 0;
>
> I think you wanted msleep_interruptible() there to avoid contributing to
> load average?
>
> The set_current_state() can go away.
these can be fixed, but:
> This will introduce an up-to-one-second delay in responding to
> kthread_should_stop(). Is that bad?
grumble, it's bad. I guess David is right that this should be fixed the
right way ;-) So the above patch cannot go in.
Ingo
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