[RESEND PATCH V2] leds: sc27xx: Move mutex_init() to the end of probe

[RESEND PATCH V2] leds: sc27xx: Move mutex_init() to the end of probe

[Chunyan Zhang]

Move the mutex_init() to avoid redundant mutex_destroy() calls after
that for each time the probe fails.

Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
---
Rebased onto linux-next.

V2:
- Move the mutex_init() to the end of .probe() instead of adding
mutex_destroy() according to Lee's comments.
---
 drivers/leds/leds-sc27xx-bltc.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/leds/leds-sc27xx-bltc.c b/drivers/leds/leds-sc27xx-bltc.c
index af1f00a2f328..ef57e57ecf07 100644
--- a/drivers/leds/leds-sc27xx-bltc.c
+++ b/drivers/leds/leds-sc27xx-bltc.c
@@ -296,7 +296,6 @@ static int sc27xx_led_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	platform_set_drvdata(pdev, priv);
-	mutex_init(&priv->lock);
 	priv->base = base;
 	priv->regmap = dev_get_regmap(dev->parent, NULL);
 	if (!priv->regmap) {
@@ -309,13 +308,11 @@ static int sc27xx_led_probe(struct platform_device *pdev)
 		err = of_property_read_u32(child, "reg", &reg);
 		if (err) {
 			of_node_put(child);
-			mutex_destroy(&priv->lock);
 			return err;
 		}
 
 		if (reg >= SC27XX_LEDS_MAX || priv->leds[reg].active) {
 			of_node_put(child);
-			mutex_destroy(&priv->lock);
 			return -EINVAL;
 		}
 
@@ -325,9 +322,11 @@ static int sc27xx_led_probe(struct platform_device *pdev)
 
 	err = sc27xx_led_register(dev, priv);
 	if (err)
-		mutex_destroy(&priv->lock);
+		return err;
 
-	return err;
+	mutex_init(&priv->lock);
+
+	return 0;
 }
 
 static void sc27xx_led_remove(struct platform_device *pdev)
-- 
2.41.0

Re: [RESEND PATCH V2] leds: sc27xx: Move mutex_init() to the end of probe

[Baolin Wang]

On 10/12/2023 11:47 AM, Chunyan Zhang wrote:
> Move the mutex_init() to avoid redundant mutex_destroy() calls after
> that for each time the probe fails.
> 
> Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
> ---
> Rebased onto linux-next.
> 
> V2:
> - Move the mutex_init() to the end of .probe() instead of adding
> mutex_destroy() according to Lee's comments.
> ---
>   drivers/leds/leds-sc27xx-bltc.c | 9 ++++-----
>   1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/leds/leds-sc27xx-bltc.c b/drivers/leds/leds-sc27xx-bltc.c
> index af1f00a2f328..ef57e57ecf07 100644
> --- a/drivers/leds/leds-sc27xx-bltc.c
> +++ b/drivers/leds/leds-sc27xx-bltc.c
> @@ -296,7 +296,6 @@ static int sc27xx_led_probe(struct platform_device *pdev)
>   		return -ENOMEM;
>   
>   	platform_set_drvdata(pdev, priv);
> -	mutex_init(&priv->lock);
>   	priv->base = base;
>   	priv->regmap = dev_get_regmap(dev->parent, NULL);
>   	if (!priv->regmap) {
> @@ -309,13 +308,11 @@ static int sc27xx_led_probe(struct platform_device *pdev)
>   		err = of_property_read_u32(child, "reg", &reg);
>   		if (err) {
>   			of_node_put(child);
> -			mutex_destroy(&priv->lock);
>   			return err;
>   		}
>   
>   		if (reg >= SC27XX_LEDS_MAX || priv->leds[reg].active) {
>   			of_node_put(child);
> -			mutex_destroy(&priv->lock);
>   			return -EINVAL;
>   		}
>   
> @@ -325,9 +322,11 @@ static int sc27xx_led_probe(struct platform_device *pdev)
>   
>   	err = sc27xx_led_register(dev, priv);
>   	if (err)
> -		mutex_destroy(&priv->lock);
> +		return err;
>   
> -	return err;
> +	mutex_init(&priv->lock);

I think it is better to prepare all the required resources before 
registering the led device, what I mean is moving mutex_init() before 
calling sc27xx_led_register().

Re: [RESEND PATCH V2] leds: sc27xx: Move mutex_init() to the end of probe

[Lee Jones]

On Thu, 12 Oct 2023, Baolin Wang wrote:

> 
> 
> On 10/12/2023 11:47 AM, Chunyan Zhang wrote:
> > Move the mutex_init() to avoid redundant mutex_destroy() calls after
> > that for each time the probe fails.
> > 
> > Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
> > ---
> > Rebased onto linux-next.
> > 
> > V2:
> > - Move the mutex_init() to the end of .probe() instead of adding
> > mutex_destroy() according to Lee's comments.
> > ---
> >   drivers/leds/leds-sc27xx-bltc.c | 9 ++++-----
> >   1 file changed, 4 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/leds/leds-sc27xx-bltc.c b/drivers/leds/leds-sc27xx-bltc.c
> > index af1f00a2f328..ef57e57ecf07 100644
> > --- a/drivers/leds/leds-sc27xx-bltc.c
> > +++ b/drivers/leds/leds-sc27xx-bltc.c
> > @@ -296,7 +296,6 @@ static int sc27xx_led_probe(struct platform_device *pdev)
> >   		return -ENOMEM;
> >   	platform_set_drvdata(pdev, priv);
> > -	mutex_init(&priv->lock);
> >   	priv->base = base;
> >   	priv->regmap = dev_get_regmap(dev->parent, NULL);
> >   	if (!priv->regmap) {
> > @@ -309,13 +308,11 @@ static int sc27xx_led_probe(struct platform_device *pdev)
> >   		err = of_property_read_u32(child, "reg", &reg);
> >   		if (err) {
> >   			of_node_put(child);
> > -			mutex_destroy(&priv->lock);
> >   			return err;
> >   		}
> >   		if (reg >= SC27XX_LEDS_MAX || priv->leds[reg].active) {
> >   			of_node_put(child);
> > -			mutex_destroy(&priv->lock);
> >   			return -EINVAL;
> >   		}
> > @@ -325,9 +322,11 @@ static int sc27xx_led_probe(struct platform_device *pdev)
> >   	err = sc27xx_led_register(dev, priv);
> >   	if (err)
> > -		mutex_destroy(&priv->lock);
> > +		return err;
> > -	return err;
> > +	mutex_init(&priv->lock);
> 
> I think it is better to prepare all the required resources before
> registering the led device, what I mean is moving mutex_init() before
> calling sc27xx_led_register().

Is the mutex used before this point?

If not, I don't see any reason to initialise it sooner.

-- 
Lee Jones [李琼斯]

Re: [RESEND PATCH V2] leds: sc27xx: Move mutex_init() to the end of probe

[Baolin Wang]

On 10/12/2023 5:16 PM, Lee Jones wrote:
> On Thu, 12 Oct 2023, Baolin Wang wrote:
> 
>>
>>
>> On 10/12/2023 11:47 AM, Chunyan Zhang wrote:
>>> Move the mutex_init() to avoid redundant mutex_destroy() calls after
>>> that for each time the probe fails.
>>>
>>> Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
>>> ---
>>> Rebased onto linux-next.
>>>
>>> V2:
>>> - Move the mutex_init() to the end of .probe() instead of adding
>>> mutex_destroy() according to Lee's comments.
>>> ---
>>>    drivers/leds/leds-sc27xx-bltc.c | 9 ++++-----
>>>    1 file changed, 4 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/leds/leds-sc27xx-bltc.c b/drivers/leds/leds-sc27xx-bltc.c
>>> index af1f00a2f328..ef57e57ecf07 100644
>>> --- a/drivers/leds/leds-sc27xx-bltc.c
>>> +++ b/drivers/leds/leds-sc27xx-bltc.c
>>> @@ -296,7 +296,6 @@ static int sc27xx_led_probe(struct platform_device *pdev)
>>>    		return -ENOMEM;
>>>    	platform_set_drvdata(pdev, priv);
>>> -	mutex_init(&priv->lock);
>>>    	priv->base = base;
>>>    	priv->regmap = dev_get_regmap(dev->parent, NULL);
>>>    	if (!priv->regmap) {
>>> @@ -309,13 +308,11 @@ static int sc27xx_led_probe(struct platform_device *pdev)
>>>    		err = of_property_read_u32(child, "reg", &reg);
>>>    		if (err) {
>>>    			of_node_put(child);
>>> -			mutex_destroy(&priv->lock);
>>>    			return err;
>>>    		}
>>>    		if (reg >= SC27XX_LEDS_MAX || priv->leds[reg].active) {
>>>    			of_node_put(child);
>>> -			mutex_destroy(&priv->lock);
>>>    			return -EINVAL;
>>>    		}
>>> @@ -325,9 +322,11 @@ static int sc27xx_led_probe(struct platform_device *pdev)
>>>    	err = sc27xx_led_register(dev, priv);
>>>    	if (err)
>>> -		mutex_destroy(&priv->lock);
>>> +		return err;
>>> -	return err;
>>> +	mutex_init(&priv->lock);
>>
>> I think it is better to prepare all the required resources before
>> registering the led device, what I mean is moving mutex_init() before
>> calling sc27xx_led_register().
> 
> Is the mutex used before this point?
> 
> If not, I don't see any reason to initialise it sooner.

When inserting the led module, after registering the led device, users 
can set the led brightness or pattern trigger before initializing the 
mutex, which will crash the system. I know this may not be an actual 
scenario, but this patch opens a small race window, that's what I concerned.

Re: [RESEND PATCH V2] leds: sc27xx: Move mutex_init() to the end of probe

[Lee Jones]

On Thu, 12 Oct 2023, Baolin Wang wrote:

> 
> 
> On 10/12/2023 5:16 PM, Lee Jones wrote:
> > On Thu, 12 Oct 2023, Baolin Wang wrote:
> > 
> > > 
> > > 
> > > On 10/12/2023 11:47 AM, Chunyan Zhang wrote:
> > > > Move the mutex_init() to avoid redundant mutex_destroy() calls after
> > > > that for each time the probe fails.
> > > > 
> > > > Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
> > > > ---
> > > > Rebased onto linux-next.
> > > > 
> > > > V2:
> > > > - Move the mutex_init() to the end of .probe() instead of adding
> > > > mutex_destroy() according to Lee's comments.
> > > > ---
> > > >    drivers/leds/leds-sc27xx-bltc.c | 9 ++++-----
> > > >    1 file changed, 4 insertions(+), 5 deletions(-)
> > > > 
> > > > diff --git a/drivers/leds/leds-sc27xx-bltc.c b/drivers/leds/leds-sc27xx-bltc.c
> > > > index af1f00a2f328..ef57e57ecf07 100644
> > > > --- a/drivers/leds/leds-sc27xx-bltc.c
> > > > +++ b/drivers/leds/leds-sc27xx-bltc.c
> > > > @@ -296,7 +296,6 @@ static int sc27xx_led_probe(struct platform_device *pdev)
> > > >    		return -ENOMEM;
> > > >    	platform_set_drvdata(pdev, priv);
> > > > -	mutex_init(&priv->lock);
> > > >    	priv->base = base;
> > > >    	priv->regmap = dev_get_regmap(dev->parent, NULL);
> > > >    	if (!priv->regmap) {
> > > > @@ -309,13 +308,11 @@ static int sc27xx_led_probe(struct platform_device *pdev)
> > > >    		err = of_property_read_u32(child, "reg", &reg);
> > > >    		if (err) {
> > > >    			of_node_put(child);
> > > > -			mutex_destroy(&priv->lock);
> > > >    			return err;
> > > >    		}
> > > >    		if (reg >= SC27XX_LEDS_MAX || priv->leds[reg].active) {
> > > >    			of_node_put(child);
> > > > -			mutex_destroy(&priv->lock);
> > > >    			return -EINVAL;
> > > >    		}
> > > > @@ -325,9 +322,11 @@ static int sc27xx_led_probe(struct platform_device *pdev)
> > > >    	err = sc27xx_led_register(dev, priv);
> > > >    	if (err)
> > > > -		mutex_destroy(&priv->lock);
> > > > +		return err;
> > > > -	return err;
> > > > +	mutex_init(&priv->lock);
> > > 
> > > I think it is better to prepare all the required resources before
> > > registering the led device, what I mean is moving mutex_init() before
> > > calling sc27xx_led_register().
> > 
> > Is the mutex used before this point?
> > 
> > If not, I don't see any reason to initialise it sooner.
> 
> When inserting the led module, after registering the led device, users can
> set the led brightness or pattern trigger before initializing the mutex,
> which will crash the system. I know this may not be an actual scenario, but
> this patch opens a small race window, that's what I concerned.

If there's a good technical reason to move it, then we should.

-- 
Lee Jones [李琼斯]