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

From: Matthias Kaehlcke <[email-masked]>
Date: Wed, 18 Sep 2019 14:41:11 -0700

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 <[email-masked]>
> ---
>  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 <[email-masked]>

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