Re: [PATCH v7 02/15] sched/core: uclamp: Enforce last task UCLAMP_MAX

Peter Zijlstra
2019-03-13T14:12:53Z

On Fri, Feb 08, 2019 at 10:05:41AM +0000, Patrick Bellasi wrote:
> +static inline void uclamp_idle_reset(struct rq *rq, unsigned int clamp_id,
> + unsigned int clamp_value)
> +{
> + /* Reset max-clamp retention only on idle exit */
> + if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE))
> + return;
> +
> + WRITE_ONCE(rq->uclamp[clamp_id].value, clamp_value);
> +
> + /*
> + * This function is called for both UCLAMP_MIN (before) and UCLAMP_MAX
> + * (after). The idle flag is reset only the second time, when we know
> + * that UCLAMP_MIN has been already updated.

Why do we care? That is, what is this comment trying to tell us.

> + */
> + if (clamp_id == UCLAMP_MAX)
> + rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
> +}