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

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Message-ID: <96b57b5b-7c6f-2118-05a0-8a568d7cb245@arm.com>
Date:   Fri, 4 Jan 2019 10:40:07 +0000
From:   Valentin Schneider <valentin.schneider@....com>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        Sudeep Holla <sudeep.holla@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Nishanth Menon <nm@...com>, Stephen Boyd <sboyd@...nel.org>
Cc:     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

Hi,

On 04/01/2019 09:44, 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.
> 
> Cc: 4.20 <stable@...r.kernel.org> # v4.20
> Reported-by: Valentin Schneider <valentin.schneider@....com>
> Fixes: 2a4eb7358aba ("OPP: Don't remove dynamic OPPs from _dev_pm_opp_remove_table()")
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>

Gave it a spin on my Juno, and I don't see the refcount warning anymore so:

Tested-by: Valentin Schneider <valentin.schneider@....com>

Thanks for having a look at this.

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