Re: [PATCH v3 04/14] sched/core: uclamp: update CPU's refcount on clamp changes

Dietmar Eggemann
2018-08-15T15:02:42Z

On 08/06/2018 06:39 PM, Patrick Bellasi wrote:

[...]

> +/**
> + * uclamp_task_active: check if a task is currently clamping a CPU
> + * @p: the task to check
> + *
> + * A task actively affects the utilization clamp of a CPU if:
> + * - it's currently enqueued or running on that CPU
> + * - it's refcounted in at least one clamp group of that CPU
> + *
> + * Return: true if p is currently clamping the utilization of its CPU.
> + */
> +static inline bool uclamp_task_active(struct task_struct *p)
> +{
> + struct rq *rq = task_rq(p);
> + int clamp_id;
> +
> + lockdep_assert_held(&p->pi_lock);
> + lockdep_assert_held(&rq->lock);
> +
> + if (!task_on_rq_queued(p) && !p->on_cpu)
> + return false;
> +
> + for (clamp_id = 0; clamp_id < UCLAMP_CNT; ++clamp_id) {
> + if (uclamp_task_affects(p, clamp_id))
> + return true;
> + }
> +
> + return false;
> +}

Looks like that uclamp_task_active() is only used once (in
uclamp_task_update_active()). Can you not code the if condition and the
for loop directly in uclamp_task_update_active()? This would save code
(lockdep_assert_held() etc.) and comment lines. …