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SubjectRe: [PATCH V4 1/3] sched: cpufreq: Allow remote cpufreq callbacks
On Wed, Jul 26, 2017 at 02:52:32PM +0530, Viresh Kumar wrote:
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index 45fcf21ad685..bb834747e49b 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -72,10 +72,15 @@ static DEFINE_PER_CPU(struct sugov_cpu, sugov_cpu);
>
> /************************ Governor internals ***********************/
>
> -static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
> +static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time,
> + int target_cpu)
> {
> s64 delta_ns;
>
> + /* Don't allow remote callbacks */

So I think you can reduce confusion in general if we extend this comment
somewhat.

/*
* Since cpufreq_update_util() is called with rq->lock held for
* the @target_cpu, our per-cpu data is fully serialized.
*
* However, drivers cannot in general deal with cross-cpu
* requests, so while get_next_freq() will work, our
* sugov_update_commit() -> cpufreq_driver_fast_switch()
* call will not.
*
* Hence stop here for remote requests, as calculating the
* frequency is pointless if we cannot in fact act on it.
*/

> + if (smp_processor_id() != target_cpu)
> + return false;
> +
> if (sg_policy->work_in_progress)
> return false;
>

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