[PATCH] kernel/sched/cpufreq_schedutil: remove stale comment

[PATCH] kernel/sched/cpufreq_schedutil: remove stale comment

[Juri Lelli]

After commit 794a56ebd9a57 ("sched/cpufreq: Change the worker kthread to
SCHED_DEADLINE") schedutil kthreads are "ignored" for a clock frequency
selection point of view, so the potential corner case for RT tasks is not
possible at all now.

Remove the stale comment mentioning it.

Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Claudio Scordino <claudio@evidence.eu.com>
Cc: Luca Abeni <luca.abeni@santannapisa.it>
---
 kernel/sched/cpufreq_schedutil.c | 13 -------------
 1 file changed, 13 deletions(-)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index d2c6083304b4..23ef19070137 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -396,19 +396,6 @@ static void sugov_irq_work(struct irq_work *irq_work)
 
 	sg_policy = container_of(irq_work, struct sugov_policy, irq_work);
 
-	/*
-	 * For RT tasks, the schedutil governor shoots the frequency to maximum.
-	 * Special care must be taken to ensure that this kthread doesn't result
-	 * in the same behavior.
-	 *
-	 * This is (mostly) guaranteed by the work_in_progress flag. The flag is
-	 * updated only at the end of the sugov_work() function and before that
-	 * the schedutil governor rejects all other frequency scaling requests.
-	 *
-	 * There is a very rare case though, where the RT thread yields right
-	 * after the work_in_progress flag is cleared. The effects of that are
-	 * neglected for now.
-	 */
 	kthread_queue_work(&sg_policy->worker, &sg_policy->work);
 }
 
-- 
2.14.3

Re: [PATCH] kernel/sched/cpufreq_schedutil: remove stale comment

[Viresh Kumar]

On 09-05-18, 10:40, Juri Lelli wrote:
> After commit 794a56ebd9a57 ("sched/cpufreq: Change the worker kthread to
> SCHED_DEADLINE") schedutil kthreads are "ignored" for a clock frequency
> selection point of view, so the potential corner case for RT tasks is not
> possible at all now.
> 
> Remove the stale comment mentioning it.
> 
> Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> Cc: Viresh Kumar <viresh.kumar@linaro.org>
> Cc: Claudio Scordino <claudio@evidence.eu.com>
> Cc: Luca Abeni <luca.abeni@santannapisa.it>
> ---
>  kernel/sched/cpufreq_schedutil.c | 13 -------------
>  1 file changed, 13 deletions(-)
> 
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index d2c6083304b4..23ef19070137 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -396,19 +396,6 @@ static void sugov_irq_work(struct irq_work *irq_work)
>  
>  	sg_policy = container_of(irq_work, struct sugov_policy, irq_work);
>  
> -	/*
> -	 * For RT tasks, the schedutil governor shoots the frequency to maximum.
> -	 * Special care must be taken to ensure that this kthread doesn't result
> -	 * in the same behavior.
> -	 *
> -	 * This is (mostly) guaranteed by the work_in_progress flag. The flag is
> -	 * updated only at the end of the sugov_work() function and before that
> -	 * the schedutil governor rejects all other frequency scaling requests.
> -	 *
> -	 * There is a very rare case though, where the RT thread yields right
> -	 * after the work_in_progress flag is cleared. The effects of that are
> -	 * neglected for now.
> -	 */
>  	kthread_queue_work(&sg_policy->worker, &sg_policy->work);
>  }

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

-- 
viresh

Re: [PATCH] kernel/sched/cpufreq_schedutil: remove stale comment

[Rafael J. Wysocki]

On Wednesday, May 9, 2018 10:41:54 AM CEST Viresh Kumar wrote:
> On 09-05-18, 10:40, Juri Lelli wrote:
> > After commit 794a56ebd9a57 ("sched/cpufreq: Change the worker kthread to
> > SCHED_DEADLINE") schedutil kthreads are "ignored" for a clock frequency
> > selection point of view, so the potential corner case for RT tasks is not
> > possible at all now.
> > 
> > Remove the stale comment mentioning it.
> > 
> > Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> > Cc: Viresh Kumar <viresh.kumar@linaro.org>
> > Cc: Claudio Scordino <claudio@evidence.eu.com>
> > Cc: Luca Abeni <luca.abeni@santannapisa.it>
> > ---
> >  kernel/sched/cpufreq_schedutil.c | 13 -------------
> >  1 file changed, 13 deletions(-)
> > 
> > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> > index d2c6083304b4..23ef19070137 100644
> > --- a/kernel/sched/cpufreq_schedutil.c
> > +++ b/kernel/sched/cpufreq_schedutil.c
> > @@ -396,19 +396,6 @@ static void sugov_irq_work(struct irq_work *irq_work)
> >  
> >  	sg_policy = container_of(irq_work, struct sugov_policy, irq_work);
> >  
> > -	/*
> > -	 * For RT tasks, the schedutil governor shoots the frequency to maximum.
> > -	 * Special care must be taken to ensure that this kthread doesn't result
> > -	 * in the same behavior.
> > -	 *
> > -	 * This is (mostly) guaranteed by the work_in_progress flag. The flag is
> > -	 * updated only at the end of the sugov_work() function and before that
> > -	 * the schedutil governor rejects all other frequency scaling requests.
> > -	 *
> > -	 * There is a very rare case though, where the RT thread yields right
> > -	 * after the work_in_progress flag is cleared. The effects of that are
> > -	 * neglected for now.
> > -	 */
> >  	kthread_queue_work(&sg_policy->worker, &sg_policy->work);
> >  }
> 
> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

Applied and pushed for 4.17-rc5.