linux-kernel - Re: [PATCH v11 3/5] sched/core: uclamp: Propagate system defaults to root group

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Date:   Tue, 16 Jul 2019 19:00:08 +0100
From:   Patrick Bellasi <patrick.bellasi@....com>
To:     Michal Koutný <mkoutny@...e.com>
Cc:     Alessio Balsini <balsini@...roid.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Quentin Perret <quentin.perret@....com>,
        Joel Fernandes <joelaf@...gle.com>,
        Paul Turner <pjt@...gle.com>,
        Steve Muckle <smuckle@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Todd Kjos <tkjos@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Tejun Heo <tj@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v11 3/5] sched/core: uclamp: Propagate system defaults to
 root group

On 16-Jul 17:36, Michal Koutný wrote:
> On Tue, Jul 16, 2019 at 03:34:17PM +0100, Patrick Bellasi <patrick.bellasi@....com> wrote:
> > > cpu_util_update_eff internally calls css_for_each_descendant_pre() so
> > > this should be protected with rcu_read_lock().
> > 
> > Right, good catch! Will add in v12.
> When I responded to your other patch, it occurred to me that since
> cpu_util_update_eff goes writing down to child csses, it should take
> also uclamp_mutex here to avoid race with direct cgroup attribute
> writers.

Yep, I should drop the "dedicated" mutex we have now in
sysctl_sched_uclamp_handler() and use the uclamp_mutex we already
have.

Thanks, Patrick


-- 
#include <best/regards.h>

Patrick Bellasi