Re: [PATCH 2/8] PM / devfreq: Don't fail devfreq_dev_release if not in list

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 2/8] PM / devfreq: Don't fail devfreq_dev_release if not in list
Date: Wed, 18 Sep 2019 14:41:11 -0700	[thread overview]
Message-ID: <20190918214111.GO133864@google.com> (raw)
In-Reply-To: <60f8aa909fe209632734b6c637dffbc7554f996c.1568764439.git.leonard.crestez@nxp.com>

On Wed, Sep 18, 2019 at 03:18:21AM +0300, Leonard Crestez wrote:
> Right now devfreq_dev_release will print a warning and abort the rest of
> the cleanup if the devfreq instance is not part of the global
> devfreq_list. But this is a valid scenario, for example it can happen if
> the governor can't be found or on any other init error that happens
> after device_register.
> 
> Initialize devfreq->node to an empty list head in devfreq_add_device so
> that list_del becomes a safe noop inside devfreq_dev_release and we can
> continue the rest of the cleanup.
> 
> Signed-off-by: Leonard Crestez <leonard.crestez@nxp•com>
> ---
>  drivers/devfreq/devfreq.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 665575228c4f..a715f27f35fd 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -582,15 +582,10 @@ static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type,
>  static void devfreq_dev_release(struct device *dev)
>  {
>  	struct devfreq *devfreq = to_devfreq(dev);
>  
>  	mutex_lock(&devfreq_list_lock);
> -	if (IS_ERR(find_device_devfreq(devfreq->dev.parent))) {
> -		mutex_unlock(&devfreq_list_lock);
> -		dev_warn(&devfreq->dev, "releasing devfreq which doesn't exist\n");
> -		return;
> -	}
>  	list_del(&devfreq->node);
>  	mutex_unlock(&devfreq_list_lock);
>  
>  	if (devfreq->profile->exit)
>  		devfreq->profile->exit(devfreq->dev.parent);
> @@ -641,10 +636,11 @@ struct devfreq *devfreq_add_device(struct device *dev,
>  	mutex_init(&devfreq->lock);
>  	mutex_lock(&devfreq->lock);
>  	devfreq->dev.parent = dev;
>  	devfreq->dev.class = devfreq_class;
>  	devfreq->dev.release = devfreq_dev_release;
> +	INIT_LIST_HEAD(&devfreq->node);
>  	devfreq->profile = profile;
>  	strncpy(devfreq->governor_name, governor_name, DEVFREQ_NAME_LEN);
>  	devfreq->previous_freq = profile->initial_freq;
>  	devfreq->last_status.current_frequency = profile->initial_freq;
>  	devfreq->data = data;

Reviewed-by: Matthias Kaehlcke <mka@chromium•org>

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