Re: [PATCH v7 3/6] PM / devfreq: Don't take lock in devfreq_add_device

From: Chanwoo Choi <cw00.choi@samsung•com>
To: Leonard Crestez <leonard.crestez@nxp•com>,
	MyungJoo Ham <myungjoo.ham@samsung•com>,
	Kyungmin Park <kyungmin.park@samsung•com>,
	Matthias Kaehlcke <mka@chromium•org>
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>,
	"NXP Linux Team" <linux-imx@nxp•com>,
	"Krzysztof Kozlowski" <krzk@kernel•org>,
	"Lukasz Luba" <l.luba@partner•samsung.com>,
	"Alexandre Bailon" <abailon@baylibre•com>,
	"Martin Kepplinger" <martink@posteo•de>,
	"Georgi Djakov" <georgi.djakov@linaro•org>,
	linux-arm-kernel@lists•infradead.org,
	"Jacky Bai" <ping.bai@nxp•com>
Subject: Re: [PATCH v7 3/6] PM / devfreq: Don't take lock in devfreq_add_device
Date: Tue, 24 Sep 2019 12:13:54 +0900	[thread overview]
Message-ID: <03c0f372-930c-bb4e-6bc4-27366e20bc52@samsung.com> (raw)
In-Reply-To: <a88e8c73679fa01264732fe163704a0e748b5235.1569272883.git.leonard.crestez@nxp.com>

Hi,

On 19. 9. 24. 오전 6:10, Leonard Crestez wrote:
> A device usually doesn't need to lock itself during initialization
> because it is not yet reachable from other threads.
> 
> This simplifies the code and helps avoid recursive lock warnings.
> 
> Signed-off-by: Leonard Crestez <leonard.crestez@nxp•com>
> Reviewed-by: Matthias Kaehlcke <mka@chromium•org>
> ---
>  drivers/devfreq/devfreq.c | 10 ----------
>  1 file changed, 10 deletions(-)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 8bbcd4efa09f..1cec816d3d00 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -634,11 +634,10 @@ struct devfreq *devfreq_add_device(struct device *dev,
>  		err = -ENOMEM;
>  		goto err_out;
>  	}
>  
>  	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;
> @@ -647,28 +646,24 @@ struct devfreq *devfreq_add_device(struct device *dev,
>  	devfreq->last_status.current_frequency = profile->initial_freq;
>  	devfreq->data = data;
>  	devfreq->nb.notifier_call = devfreq_notifier_call;
>  
>  	if (!devfreq->profile->max_state && !devfreq->profile->freq_table) {
> -		mutex_unlock(&devfreq->lock);
>  		err = set_freq_table(devfreq);
>  		if (err < 0)
>  			goto err_dev;
> -		mutex_lock(&devfreq->lock);
>  	}
>  
>  	devfreq->scaling_min_freq = find_available_min_freq(devfreq);
>  	if (!devfreq->scaling_min_freq) {
> -		mutex_unlock(&devfreq->lock);
>  		err = -EINVAL;
>  		goto err_dev;
>  	}
>  	devfreq->min_freq = devfreq->scaling_min_freq;
>  
>  	devfreq->scaling_max_freq = find_available_max_freq(devfreq);
>  	if (!devfreq->scaling_max_freq) {
> -		mutex_unlock(&devfreq->lock);
>  		err = -EINVAL;
>  		goto err_dev;
>  	}
>  	devfreq->max_freq = devfreq->scaling_max_freq;
>  
> @@ -679,20 +674,18 @@ struct devfreq *devfreq_add_device(struct device *dev,
>  			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_dev;
>  	}
>  
>  	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_dev;
>  	}
>  
>  	devfreq->last_stat_updated = jiffies;
> @@ -701,17 +694,14 @@ struct devfreq *devfreq_add_device(struct device *dev,
>  
>  	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;
>  	}
>  
> -	mutex_unlock(&devfreq->lock);
> -
>  	mutex_lock(&devfreq_list_lock);
>  
>  	governor = try_then_request_governor(devfreq->governor_name);
>  	if (IS_ERR(governor)) {
>  		dev_err(dev, "%s: Unable to find governor for the device\n",
> 

Reviewed-by: Chanwoo Choi <cw00.choi@samsung•com>

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics

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