From mboxrd@z Thu Jan 1 00:00:00 1970 From: Viresh Kumar Subject: Re: [PATCH] devfreq: rk3399_dmc: Don't use OPP structures outside of RCU locks Date: Fri, 2 Dec 2016 14:30:47 +0530 Message-ID: <20161202090047.GA22049@vireshk-i7> References: <22bf6dfc155a6a241c2ee4e2b44a615d0e82064d.1480588658.git.viresh.kumar@linaro.org> <584133F9.4080006@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: Received: from mail-pf0-f175.google.com ([209.85.192.175]:34142 "EHLO mail-pf0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751678AbcLBJAx (ORCPT ); Fri, 2 Dec 2016 04:00:53 -0500 Received: by mail-pf0-f175.google.com with SMTP id c4so51876802pfb.1 for ; Fri, 02 Dec 2016 01:00:52 -0800 (PST) Content-Disposition: inline In-Reply-To: <584133F9.4080006@samsung.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Chanwoo Choi Cc: Rafael Wysocki , MyungJoo Ham , Kyungmin Park , linaro-kernel@lists.linaro.org, linux-pm@vger.kernel.org, Stephen Boyd , nm@ti.com, Vincent Guittot Hi Chanwoo, Thanks for trying to review all these patches. On 02-12-16, 17:42, Chanwoo Choi wrote: > Hi Viresh, > > On 2016년 12월 01일 19:38, Viresh Kumar wrote: > > The OPP structures are abused to the best here, without understanding > > how the OPP core and RCU locks work. > > > > In short, the OPP pointer saved in 'rk3399_dmcfreq' can become invalid > > under your nose, as the OPP core may free it. > > > > Fix various abuses around OPP structures and calls. > > > > Compile tested only. > > > > Signed-off-by: Viresh Kumar > > --- > > I would like it to go via the PM tree. Perhaps that's already the > > default tree for this. > > > > drivers/devfreq/rk3399_dmc.c | 11 +++++------ > > 1 file changed, 5 insertions(+), 6 deletions(-) > > > > diff --git a/drivers/devfreq/rk3399_dmc.c b/drivers/devfreq/rk3399_dmc.c > > index 5063ac1a5939..cf14631b1945 100644 > > --- a/drivers/devfreq/rk3399_dmc.c > > +++ b/drivers/devfreq/rk3399_dmc.c > > @@ -80,7 +80,6 @@ struct rk3399_dmcfreq { > > struct regulator *vdd_center; > > unsigned long rate, target_rate; > > unsigned long volt, target_volt; > > - struct dev_pm_opp *curr_opp; > > }; > > > > static int rk3399_dmcfreq_target(struct device *dev, unsigned long *freq, > > @@ -102,9 +101,6 @@ static int rk3399_dmcfreq_target(struct device *dev, unsigned long *freq, > > target_rate = dev_pm_opp_get_freq(opp); > > target_volt = dev_pm_opp_get_voltage(opp); > > > > - dmcfreq->rate = dev_pm_opp_get_freq(dmcfreq->curr_opp); > > - dmcfreq->volt = dev_pm_opp_get_voltage(dmcfreq->curr_opp); > > - > > rcu_read_unlock(); > > > > if (dmcfreq->rate == target_rate) > > dmcfreq->rate is used on here. Are you trying to say that dmcfreq->rate is required to have the right value as we will be using it here for comparison? If yes, then ... > Maybe struct rk3399_dmcfreq need to add the new 'curr_freq' field. > > > > @@ -165,7 +161,9 @@ static int rk3399_dmcfreq_target(struct device *dev, unsigned long *freq, > > if (err) > > dev_err(dev, "Cannot to set vol %lu uV\n", target_volt); > > > > - dmcfreq->curr_opp = opp; > > + dmcfreq->rate = target_rate; > > + dmcfreq->volt = target_volt; This takes care of it for all cases except the first call to target()... > > + > > out: > > mutex_unlock(&dmcfreq->lock); > > return err; > > @@ -431,8 +429,9 @@ static int rk3399_dmcfreq_probe(struct platform_device *pdev) > > rcu_read_unlock(); > > return PTR_ERR(opp); > > } > > + dmcfreq->rate = dev_pm_opp_get_freq(opp); > > + dmcfreq->volt = dev_pm_opp_get_voltage(opp); And this takes care of the first call to target(). Am I still missing something ? > > rcu_read_unlock(); > > - data->curr_opp = opp; > > > > rk3399_devfreq_dmc_profile.initial_freq = data->rate; > > > > > > -- > Best Regards, > Chanwoo Choi -- viresh