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.
This will introduce an up-to-one-second delay in responding to
kthread_should_stop(). Is that bad?
-
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