From: Matthias Kaehlcke <mka@chromium.org>
To: Leonard Crestez <leonard.crestez@nxp.com>
Cc: "Artur Świgoń" <a.swigon@partner.samsung.com>,
"Abel Vesa" <abel.vesa@nxp.com>,
"Saravana Kannan" <saravanak@google.com>,
linux-pm@vger.kernel.org,
"Viresh Kumar" <viresh.kumar@linaro.org>,
"Krzysztof Kozlowski" <krzk@kernel.org>,
"Chanwoo Choi" <cw00.choi@samsung.com>,
"Kyungmin Park" <kyungmin.park@samsung.com>,
"MyungJoo Ham" <myungjoo.ham@samsung.com>,
"Alexandre Bailon" <abailon@baylibre.com>,
"Georgi Djakov" <georgi.djakov@linaro.org>,
linux-arm-kernel@lists.infradead.org,
"Jacky Bai" <ping.bai@nxp.com>
Subject: Re: [PATCH 3/8] PM / devfreq: Move more initialization before registration
Date: Wed, 18 Sep 2019 17:14:54 -0700 [thread overview]
Message-ID: <20190919001454.GQ133864@google.com> (raw)
In-Reply-To: <20190918232904.GP133864@google.com>
On Wed, Sep 18, 2019 at 04:29:04PM -0700, Matthias Kaehlcke wrote:
> Hi Leonard,
>
> On Wed, Sep 18, 2019 at 03:18:22AM +0300, Leonard Crestez wrote:
> > In general it is a better to initialize an object before making it
> > accessible externally (through device_register).
> >
> > This make it possible to avoid relying on locking a partially
> > initialized object.
> >
> > Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
> > ---
> > drivers/devfreq/devfreq.c | 38 ++++++++++++++++++++------------------
> > 1 file changed, 20 insertions(+), 18 deletions(-)
> >
> > diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> > index a715f27f35fd..57a217fc92de 100644
> > --- a/drivers/devfreq/devfreq.c
> > +++ b/drivers/devfreq/devfreq.c
> > @@ -589,10 +589,12 @@ static void devfreq_dev_release(struct device *dev)
> >
> > if (devfreq->profile->exit)
> > devfreq->profile->exit(devfreq->dev.parent);
> >
> > mutex_destroy(&devfreq->lock);
> > + kfree(devfreq->time_in_state);
> > + kfree(devfreq->trans_table);
> > kfree(devfreq);
> > }
> >
> > /**
> > * devfreq_add_device() - Add devfreq feature to the device
> > @@ -671,44 +673,43 @@ struct devfreq *devfreq_add_device(struct device *dev,
> > devfreq->max_freq = devfreq->scaling_max_freq;
> >
> > devfreq->suspend_freq = dev_pm_opp_get_suspend_opp_freq(dev);
> > atomic_set(&devfreq->suspend_count, 0);
> >
> > - dev_set_name(&devfreq->dev, "devfreq%d",
> > - atomic_inc_return(&devfreq_no));
> > - err = device_register(&devfreq->dev);
> > - if (err) {
> > - mutex_unlock(&devfreq->lock);
> > - put_device(&devfreq->dev);
> > - goto err_out;
> > - }
> > -
> > - devfreq->trans_table = devm_kzalloc(&devfreq->dev,
> > + devfreq->trans_table = kzalloc(
> > array3_size(sizeof(unsigned int),
> > devfreq->profile->max_state,
> > devfreq->profile->max_state),
> > GFP_KERNEL);
> > if (!devfreq->trans_table) {
> > mutex_unlock(&devfreq->lock);
> > err = -ENOMEM;
> > - goto err_devfreq;
> > + goto err_dev;
> > }
> >
> > - devfreq->time_in_state = devm_kcalloc(&devfreq->dev,
> > - devfreq->profile->max_state,
> > - sizeof(unsigned long),
> > - GFP_KERNEL);
> > + devfreq->time_in_state = kcalloc(devfreq->profile->max_state,
> > + sizeof(unsigned long),
> > + GFP_KERNEL);
> > if (!devfreq->time_in_state) {
> > mutex_unlock(&devfreq->lock);
> > err = -ENOMEM;
> > - goto err_devfreq;
> > + goto err_dev;
> > }
> >
> > devfreq->last_stat_updated = jiffies;
> >
> > srcu_init_notifier_head(&devfreq->transition_notifier_list);
> >
> > + dev_set_name(&devfreq->dev, "devfreq%d",
> > + atomic_inc_return(&devfreq_no));
> > + err = device_register(&devfreq->dev);
> > + if (err) {
> > + mutex_unlock(&devfreq->lock);
> > + put_device(&devfreq->dev);
> > + goto err_out;
>
> goto err_dev;
>
> > + }
> > +
> > mutex_unlock(&devfreq->lock);
> >
> > mutex_lock(&devfreq_list_lock);
> >
> > governor = try_then_request_governor(devfreq->governor_name);
> > @@ -734,14 +735,15 @@ struct devfreq *devfreq_add_device(struct device *dev,
> >
> > return devfreq;
> >
> > err_init:
> > mutex_unlock(&devfreq_list_lock);
> > -err_devfreq:
> > devfreq_remove_device(devfreq);
> > - devfreq = NULL;
> > + return ERR_PTR(err);
>
> The two return paths in the unwind part are unorthodox, but I
> see why they are needed. Maybe add an empty line between the two paths
> to make it a bit more evident that they are separate.
>
> > err_dev:
>
> This code path should include
>
> mutex_destroy(&devfreq->lock);
>
> That was already missing in the original code though.
>
> Actually with the later device registration the mutex could be
> initialized later and doesn't need to be held. This would
> obsolete the mutex_unlock() calls in the error paths.
Just saw that you are already doing this in "[4/8] PM / devfreq:
Don't take lock in devfreq_add_device" :)
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next prev parent reply other threads:[~2019-09-19 0:15 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-18 0:18 [PATCH 0/8] PM / devfreq: Add dev_pm_qos support Leonard Crestez
2019-09-18 0:18 ` [PATCH 1/8] PM / devfreq: Lock devfreq in trans_stat_show Leonard Crestez
2019-09-18 21:28 ` Matthias Kaehlcke
2019-09-19 18:42 ` Leonard Crestez
2019-09-19 19:25 ` Matthias Kaehlcke
2019-09-18 0:18 ` [PATCH 2/8] PM / devfreq: Don't fail devfreq_dev_release if not in list Leonard Crestez
2019-09-18 21:41 ` Matthias Kaehlcke
2019-09-18 0:18 ` [PATCH 3/8] PM / devfreq: Move more initialization before registration Leonard Crestez
2019-09-18 23:29 ` Matthias Kaehlcke
2019-09-19 0:14 ` Matthias Kaehlcke [this message]
2019-09-19 18:52 ` Leonard Crestez
2019-09-19 19:16 ` Matthias Kaehlcke
2019-09-18 0:18 ` [PATCH 4/8] PM / devfreq: Don't take lock in devfreq_add_device Leonard Crestez
2019-09-19 0:20 ` Matthias Kaehlcke
2019-09-18 0:18 ` [PATCH 5/8] PM / devfreq: Introduce devfreq_get_freq_range Leonard Crestez
2019-09-19 18:07 ` Matthias Kaehlcke
2019-09-18 0:18 ` [PATCH 6/8] PM / devfreq: Add dev_pm_qos support Leonard Crestez
2019-09-19 19:12 ` Matthias Kaehlcke
2019-09-18 0:18 ` [PATCH 7/8] PM / devfreq: Use dev_pm_qos for sysfs min/max_freq Leonard Crestez
2019-09-19 19:59 ` Matthias Kaehlcke
2019-09-20 13:50 ` Leonard Crestez
2019-09-18 0:18 ` [PATCH 8/8] PM / devfreq: Move opp notifier registration to core Leonard Crestez
2019-09-30 21:49 ` Chanwoo Choi
2019-10-01 15:14 ` Leonard Crestez
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