On 16-05-18, 20:18, Vincent Guittot wrote:
> With commit 8f111bc357aa ("cpufreq/schedutil: Rewrite CPUFREQ_RT support")
> schedutil governor uses rq->rt.rt_nr_running to detect whether a RT task is
> currently running on the CPU and to set frequency to max if necessary.
> cpufreq_update_util() is called in enqueue/dequeue_top_rt_rq() but
> rq->rt.rt_nr_running as not been updated yet when dequeue_top_rt_rq() is
> called so schedutil still considers that a RT task is running when the
> last task is dequeued. The update of rq->rt.rt_nr_running happens later
> in dequeue_rt_stack()
>
> Fixes: 8f111bc357aa ('cpufreq/schedutil: Rewrite CPUFREQ_RT support')
> Cc: <stable@xxxxxxxxxxxxxxx> # v4.16+
> Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
> ---
> kernel/sched/rt.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index 7aef6b4..6e74d3d 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -1001,8 +1001,6 @@ dequeue_top_rt_rq(struct rt_rq *rt_rq)
> sub_nr_running(rq, rt_rq->rt_nr_running);
> rt_rq->rt_queued = 0;
>
Remove this blank line as well ?
> - /* Kick cpufreq (see the comment in kernel/sched/sched.h). */
> - cpufreq_update_util(rq, 0);
> }
>
> static void
> @@ -1288,6 +1286,9 @@ static void dequeue_rt_stack(struct sched_rt_entity *rt_se, unsigned int flags)
> if (on_rt_rq(rt_se))
> __dequeue_rt_entity(rt_se, flags);
> }
> +
> + /* Kick cpufreq (see the comment in kernel/sched/sched.h). */
> + cpufreq_update_util(rq_of_rt_rq(rt_rq_of_se(back)), 0);
> }
>
> static void enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
> --
> 2.7.4
--
viresh
