Messages in this thread | | | Date | Tue, 27 Nov 2007 11:36:42 +0100 | From | Ingo Molnar <> | Subject | Re: [patch] softlockup: do the wakeup from a hrtimer |
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* Andrew Morton <akpm@linux-foundation.org> wrote:
> On Tue, 20 Nov 2007 09:46:11 +0100 > Ingo Molnar <mingo@elte.hu> wrote: > > > Subject: softlockup: do the wakeup from a hrtimer > > From: Ingo Molnar <mingo@elte.hu> > > > > 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 <davem@davemloft.net> > > Signed-off-by: Ingo Molnar <mingo@elte.hu> > > --- > > 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.
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