[PATCH 3/5] backlight: led_bl: add led_access locking

[Daniel Thompson]

On Fri, Apr 17, 2020 at 02:33:10PM +0300, Tomi Valkeinen wrote:
> led_bl does not lock 'led_access' when calling led_sysfs_disable and
> led_sysfs_enable, causing the below WARN. Add the locking.
> 
> WARNING: CPU: 0 PID: 223 at drivers/leds/led-core.c:353 led_sysfs_disable+0x4c/0x5c
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen at ti.com>

I did wonder if it might be better to provide self-locking API from the
LED sub-sys but it looks like elsewhere led_sysfs_disable() is
frequently paired with led_trigger_set() (and both under the same
lock)...

Reviewed-by: Daniel Thompson <daniel.thompson at linaro.org>


> ---
>  drivers/video/backlight/led_bl.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/video/backlight/led_bl.c b/drivers/video/backlight/led_bl.c
> index c46ecdfe8b0a..63693c4f0883 100644
> --- a/drivers/video/backlight/led_bl.c
> +++ b/drivers/video/backlight/led_bl.c
> @@ -216,8 +216,11 @@ static int led_bl_probe(struct platform_device *pdev)
>  		return PTR_ERR(priv->bl_dev);
>  	}
>  
> -	for (i = 0; i < priv->nb_leds; i++)
> +	for (i = 0; i < priv->nb_leds; i++) {
> +		mutex_lock(&priv->leds[i]->led_access);
>  		led_sysfs_disable(priv->leds[i]);
> +		mutex_unlock(&priv->leds[i]->led_access);
> +	}
>  
>  	backlight_update_status(priv->bl_dev);
>  
> @@ -233,8 +236,11 @@ static int led_bl_remove(struct platform_device *pdev)
>  	backlight_device_unregister(bl);
>  
>  	led_bl_power_off(priv);
> -	for (i = 0; i < priv->nb_leds; i++)
> +	for (i = 0; i < priv->nb_leds; i++) {
> +		mutex_lock(&priv->leds[i]->led_access);
>  		led_sysfs_enable(priv->leds[i]);
> +		mutex_unlock(&priv->leds[i]->led_access);
> +	}
>  
>  	return 0;
>  }
> -- 
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