linux-kernel - Re: [PATCH] cpufreq: Move cancelling of policy update work just after removing notifiers

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Date:   Tue, 22 Oct 2019 11:46:43 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        Sudeep Holla <sudeep.holla@....com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH] cpufreq: Move cancelling of policy update work just after
 removing notifiers

On Tue, Oct 22, 2019 at 4:25 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> On 21-10-19, 14:28, Sudeep Holla wrote:
> > Commit 099967699ad9 ("cpufreq: Cancel policy update work scheduled before freeing")
> > added cancel_work_sync(policy->update) after the frequency QoS were
> > removed. We can cancel the work just after taking the last CPU in the
> > policy offline and unregistering the notifiers as policy->update cannot
> > be scheduled from anywhere at this point.
> >
> > However, due to other bugs, doing so still triggered the race between
> > freeing of policy and scheduled policy update work. Now that all those
> > issues are resolved, we can move this cancelling of any scheduled policy
> > update work just after removing min/max notifiers.
> >
> > Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> > ---
> >  drivers/cpufreq/cpufreq.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > Hi Rafael,
> >
> > Based on Viresh's suggestion, I am posting a patch to move this
> > cancel_work_sync earlier though it's not a must have change.
>
> For me it is :)
>
> > I will leave it up to your preference.
> >
> > Regards,
> > Sudeep
> >
> > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > index 829a3764df1b..48a224a6b178 100644
> > --- a/drivers/cpufreq/cpufreq.c
> > +++ b/drivers/cpufreq/cpufreq.c
> > @@ -1268,6 +1268,9 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
> >       freq_qos_remove_notifier(&policy->constraints, FREQ_QOS_MIN,
> >                                &policy->nb_min);
> >
> > +     /* Cancel any pending policy->update work before freeing the policy. */
> > +     cancel_work_sync(&policy->update);
> > +
> >       if (policy->max_freq_req) {
> >               /*
> >                * CPUFREQ_CREATE_POLICY notification is sent only after
> > @@ -1279,8 +1282,6 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
> >       }
> >
> >       freq_qos_remove_request(policy->min_freq_req);
> > -     /* Cancel any pending policy->update work before freeing the policy. */
> > -     cancel_work_sync(&policy->update);
> >       kfree(policy->min_freq_req);
> >
> >       cpufreq_policy_put_kobj(policy);
>
> Thanks for doing this.
>
> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

Folded into the previous patch and applied.

Please double check the result in the current linux-next branch in my tree.