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" <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"
<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: Thu, 19 Sep 2019 12:16:59 -0700 [thread overview]
Message-ID: <20190919191659.GV133864@google.com> (raw)
In-Reply-To: <VI1PR04MB702350FA21534747D540C04FEE890@VI1PR04MB7023.eurprd04.prod.outlook.com>
On Thu, Sep 19, 2019 at 06:52:07PM +0000, Leonard Crestez wrote:
> On 19.09.2019 02:29, 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.
>
> Old code did "devfreq = NULL" just so that the later kfree did nothing.
> There were already two unwind paths, it's just that the second one was
> less obvious. I will add a comment.
>
> >> err_dev:
> >
> > This code path should include
> >
> > mutex_destroy(&devfreq->lock);
> >
> > That was already missing in the original code though.
>
> Yes, that would be a separate patch.
>
> > 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
> Next patch already removes mutex_lock before device_register (that's the
> purpose of the cleanup). If you're suggesting to move mutex_init around
> it's not clear what would be gained?
As per my earlier reply to self: I didn't look at the next patch
before writing this, it's all good, nothing to do here :)
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next prev parent reply other threads:[~2019-09-19 19:17 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
2019-09-19 18:52 ` Leonard Crestez
2019-09-19 19:16 ` Matthias Kaehlcke [this message]
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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