linux-kernel - Re: [PATCH v7 06/15] sched/core: uclamp: Reset uclamp values on RESET_ON

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Message-ID: <20190313205235.GX2482@worktop.programming.kicks-ass.net>
Date:   Wed, 13 Mar 2019 21:52:35 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Patrick Bellasi <patrick.bellasi@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-api@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Tejun Heo <tj@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Paul Turner <pjt@...gle.com>,
        Quentin Perret <quentin.perret@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Todd Kjos <tkjos@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Steve Muckle <smuckle@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>
Subject: Re: [PATCH v7 06/15] sched/core: uclamp: Reset uclamp values on
 RESET_ON_FORK

On Fri, Feb 08, 2019 at 10:05:45AM +0000, Patrick Bellasi wrote:
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 070caa1f72eb..8b282616e9c9 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1071,7 +1071,7 @@ static void __setscheduler_uclamp(struct task_struct *p,
>  	}
>  }
>  
> -static void uclamp_fork(struct task_struct *p)
> +static void uclamp_fork(struct task_struct *p, bool reset)
>  {
>  	unsigned int clamp_id;
>  
> @@ -1080,6 +1080,17 @@ static void uclamp_fork(struct task_struct *p)

IIRC there's an early return here if the class doesn't have uclamp
support, which I think is wrong now. You want the reset irrespective of
whether the class supports it, no?

>  
>  	for (clamp_id = 0; clamp_id < UCLAMP_CNT; ++clamp_id)
>  		p->uclamp[clamp_id].active = false;
> +
> +	if (likely(!reset))
> +		return;
> +
> +	for (clamp_id = 0; clamp_id < UCLAMP_CNT; ++clamp_id) {
> +		unsigned int clamp_value = uclamp_none(clamp_id);
> +
> +		p->uclamp[clamp_id].user_defined = false;
> +		p->uclamp[clamp_id].value = clamp_value;
> +		p->uclamp[clamp_id].bucket_id = uclamp_bucket_id(clamp_value);
> +	}
>  }