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From: Viresh Kumar <viresh.kumar@linaro.org>
To: Dmitry Osipenko <digetx@gmail.com>
Cc: Viresh Kumar <vireshk@kernel.org>, Nishanth Menon <nm@ti.com>,
	Stephen Boyd <sboyd@kernel.org>,
	linux-pm@vger.kernel.org,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Rafael Wysocki <rjw@rjwysocki.net>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] opp: Reinitialize the list_kref before adding the static OPPs again
Date: Mon, 21 Oct 2019 07:48:26 +0530	[thread overview]
Message-ID: <20191021021826.afb3yrh2r63mzghw@vireshk-i7> (raw)
In-Reply-To: <b1d263bb-f797-0f0d-5beb-0747c564ca90@gmail.com>

On 18-10-19, 18:35, Dmitry Osipenko wrote:
> 18.10.2019 12:28, Viresh Kumar пишет:
> > The list_kref reaches a count of 0 when all the static OPPs are removed,
> > for example when dev_pm_opp_of_cpumask_remove_table() is called, though
> > the actual OPP table may not get freed as it may still be referenced by
> > other parts of the kernel, like from a call to
> > dev_pm_opp_set_supported_hw(). And if we call
> > dev_pm_opp_of_cpumask_add_table() again at this point, we must
> > reinitialize the list_kref otherwise the kernel will hit a WARN() in
> > kref infrastructure for incrementing a kref with value 0.
> > 
> > Fixes: 11e1a1648298 ("opp: Don't decrement uninitialized list_kref")
> > Reported-by: Dmitry Osipenko <digetx@gmail.com>
> > Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> > ---
> >  drivers/opp/of.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/drivers/opp/of.c b/drivers/opp/of.c
> > index 6dc41faf74b5..1cbb58240b80 100644
> > --- a/drivers/opp/of.c
> > +++ b/drivers/opp/of.c
> > @@ -663,6 +663,13 @@ static int _of_add_opp_table_v2(struct device *dev, struct opp_table *opp_table)
> >  		return 0;
> >  	}
> >  
> > +	/*
> > +	 * Re-initialize list_kref every time we add static OPPs to the OPP
> > +	 * table as the reference count may be 0 after the last tie static OPPs
> > +	 * were removed.
> > +	 */
> > +	kref_init(&opp_table->list_kref);
> > +
> >  	/* We have opp-table node now, iterate over it and add OPPs */
> >  	for_each_available_child_of_node(opp_table->np, np) {
> >  		opp = _opp_add_static_v2(opp_table, dev, np);
> > 
> 
> I don't see the warning anymore, cpufreq-dt module reloading works fine
> now. Thank you very much!
> 
> Tested-by: Dmitry Osipenko <digetx@gmail.com>

Thanks for testing.

-- 
viresh

  reply	other threads:[~2019-10-21  2:18 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-18  9:28 [PATCH] opp: Reinitialize the list_kref before adding the static OPPs again Viresh Kumar
2019-10-18 15:35 ` Dmitry Osipenko
2019-10-21  2:18   ` Viresh Kumar [this message]
2019-10-18 21:12 ` Stephen Boyd
2019-10-21  2:25   ` Viresh Kumar
2019-10-28 12:01     ` Stephen Boyd
2019-10-30  7:50       ` Viresh Kumar
     [not found]         ` <20191030143400.1680D20656@mail.kernel.org>
2019-11-11  8:21           ` Viresh Kumar
2019-11-11 11:31             ` Viresh Kumar

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