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Date:   Tue, 6 Aug 2019 18:11:53 +0200
From:   Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>
To:     Patrick Bellasi <patrick.bellasi@arm.com>
Cc:     linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
        linux-api@vger.kernel.org, cgroups@vger.kernel.org,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        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>,
        Alessio Balsini <balsini@android.com>
Subject: Re: [PATCH v13 2/6] sched/core: uclamp: Propagate parent clamps
Message-ID: <20190806161153.GA19991@blackbody.suse.cz>
References: <20190802090853.4810-1-patrick.bellasi@arm.com>
 <20190802090853.4810-3-patrick.bellasi@arm.com>
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On Fri, Aug 02, 2019 at 10:08:49AM +0100, Patrick Bellasi <patrick.bellasi@=
arm.com> wrote:
> @@ -7095,6 +7149,7 @@ static ssize_t cpu_uclamp_write(struct kernfs_open_=
file *of, char *buf,
>  	if (req.ret)
>  		return req.ret;
> =20
> +	mutex_lock(&uclamp_mutex);
>  	rcu_read_lock();
> =20
>  	tg =3D css_tg(of_css(of));
> @@ -7107,7 +7162,11 @@ static ssize_t cpu_uclamp_write(struct kernfs_open=
_file *of, char *buf,
>  	 */
>  	tg->uclamp_pct[clamp_id] =3D req.percent;
> =20
> +	/* Update effective clamps to track the most restrictive value */
> +	cpu_util_update_eff(of_css(of));
> +
>  	rcu_read_unlock();
> +	mutex_unlock(&uclamp_mutex);
Following my remarks to "[PATCH v13 1/6] sched/core: uclamp: Extend
CPU's cgroup", I wonder if the rcu_read_lock() couldn't be moved right
before cpu_util_update_eff(). And by extension rcu_read_(un)lock could
be hidden into cpu_util_update_eff() closer to its actual need.


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