linux-kernel - Re: [PATCH 6/9] sched/clock: Remove watchdog touching

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Date:   Fri, 21 Apr 2017 17:28:11 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     tglx@...utronix.de, mingo@...nel.org
Cc:     linux-kernel@...r.kernel.org, ville.syrjala@...ux.intel.com,
        daniel.lezcano@...aro.org, rafael.j.wysocki@...el.com,
        marta.lofstedt@...el.com, martin.peres@...ux.intel.com,
        pasha.tatashin@...cle.com, daniel.vetter@...ll.ch
Subject: Re: [PATCH 6/9] sched/clock: Remove watchdog touching

On Fri, Apr 21, 2017 at 04:58:02PM +0200, Peter Zijlstra wrote:
> Commit:
> 
>   2bacec8c318c ("sched: touch softlockup watchdog after idling")
> 
> introduced the touch_softlockup_watchdog_sched() call without
> justification and I feel sched_clock management is not the right
> place, it should only be concerned with producing semi coherent time.
> 
> If this causes watchdog thingies, we can find a better place.

Hurmph, the rest should've gone in the next patch, which calls
sched_clock_idle_wakeup_event() from a place with IRQs enabled.

> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  kernel/sched/clock.c |   12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> --- a/kernel/sched/clock.c
> +++ b/kernel/sched/clock.c
> @@ -410,15 +410,21 @@ void sched_clock_idle_sleep_event(void)
>  EXPORT_SYMBOL_GPL(sched_clock_idle_sleep_event);
>  
>  /*
> - * We just idled; resync with ktime. (called with irqs disabled):
> + * We just idled; resync with ktime.
>   */
>  void sched_clock_idle_wakeup_event(void)
>  {
> -	if (timekeeping_suspended)
> +	unsigned long flags;
> +
> +	if (sched_clock_stable())
> +		return;
> +
> +	if (unlikely(timekeeping_suspended))
>  		return;
>  
> +	local_irq_save(flags);
>  	sched_clock_tick();
> -	touch_softlockup_watchdog_sched();
> +	local_irq_restore(flags);
>  }
>  EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event);
>  
> 
>