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Date:   Wed, 13 Mar 2019 21:52:35 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Patrick Bellasi <patrick.bellasi@arm.com>
Cc:     linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
        linux-api@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
        Tejun Heo <tj@kernel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Paul Turner <pjt@google.com>,
        Quentin Perret <quentin.perret@arm.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Morten Rasmussen <morten.rasmussen@arm.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Todd Kjos <tkjos@google.com>,
        Joel Fernandes <joelaf@google.com>,
        Steve Muckle <smuckle@google.com>,
        Suren Baghdasaryan <surenb@google.com>
Subject: Re: [PATCH v7 06/15] sched/core: uclamp: Reset uclamp values on
 RESET_ON_FORK
Message-ID: <20190313205235.GX2482@worktop.programming.kicks-ass.net>
References: <20190208100554.32196-1-patrick.bellasi@arm.com>
 <20190208100554.32196-7-patrick.bellasi@arm.com>
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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);
> +	}
>  }