linux-kernel - Re: [PATCH] cpufreq: scpi/scmi: Fix freeing of dynamic OPPs

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Date:   Fri, 11 Jan 2019 11:37:57 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Sudeep Holla <sudeep.holla@....com>,
        Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Valentin Schneider <valentin.schneider@....com>,
        Nishanth Menon <nm@...com>, Stephen Boyd <sboyd@...nel.org>,
        linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        quentin.perret@....com, dietmar.eggemann@....com,
        Douglas.Raillard@....com, "4 . 20" <stable@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq: scpi/scmi: Fix freeing of dynamic OPPs

On Friday, January 4, 2019 12:01:42 PM CET Sudeep Holla wrote:
> On Fri, Jan 04, 2019 at 03:14:33PM +0530, Viresh Kumar wrote:
> > Since the commit 2a4eb7358aba ("OPP: Don't remove dynamic OPPs from
> > _dev_pm_opp_remove_table()"), dynamically created OPP aren't
> > automatically removed anymore by dev_pm_opp_cpumask_remove_table(). This
> > affects the scpi and scmi cpufreq drivers which no longer free OPPs on
> > failures or on invocations of the policy->exit() callback.
> >
> > Create a generic OPP helper dev_pm_opp_remove_all_dynamic() which can be
> > called from these drivers instead of dev_pm_opp_cpumask_remove_table().
> >
> > In dev_pm_opp_remove_all_dynamic(), we need to make sure that the
> > opp_list isn't getting accessed simultaneously from other parts of the
> > OPP core while the helper is freeing dynamic OPPs, i.e. we can't drop
> > the opp_table->lock while traversing through the OPP list. And to
> > accomplish that, this patch also creates _opp_kref_release_unlocked()
> > which can be called from this new helper with the opp_table lock already
> > held.
> >
> 
> I did test it but since I couldn't reproduce the original issue, my
> tested-by is not that worth. Anyways the changes look fine to me.
> 
> Reviewed-by: Sudeep Holla <sudeep.holla@....com>

Applied and pushed to Linus, thanks!