Re: [PATCH] counter: rz-mtu3-cnt: Unlock on error in rz_mtu3_count_write()

[William Breathitt Gray <william.gray@linaro.org>]

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On Wed, Apr 19, 2023 at 05:23:55PM +0300, Dan Carpenter wrote:
> The return -ERANGE error paths need to call mutex_unlock(&priv->lock);
> before returning.
> 
> Fixes: 25d21447d896 ("counter: Add Renesas RZ/G2L MTU3a counter driver")
> Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>

The changes in this patch are for rz_mtu3_count_ceiling_write(), so the
title of this patch should be fixed.

> ---
>  drivers/counter/rz-mtu3-cnt.c | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/counter/rz-mtu3-cnt.c b/drivers/counter/rz-mtu3-cnt.c
> index a371bab68499..aeadce5e2853 100644
> --- a/drivers/counter/rz-mtu3-cnt.c
> +++ b/drivers/counter/rz-mtu3-cnt.c
> @@ -358,19 +358,23 @@ static int rz_mtu3_count_ceiling_write(struct counter_device *counter,
>  	switch (count->id) {
>  	case RZ_MTU3_16_BIT_MTU1_CH:
>  	case RZ_MTU3_16_BIT_MTU2_CH:
> -		if (ceiling > U16_MAX)
> -			return -ERANGE;
> +		if (ceiling > U16_MAX) {
> +			ret = -ERANGE;
> +			goto unlock;
> +		}
>  		priv->mtu_16bit_max[ch_id] = ceiling;
>  		break;
>  	case RZ_MTU3_32_BIT_CH:
> -		if (ceiling > U32_MAX)
> -			return -ERANGE;
> +		if (ceiling > U32_MAX) {
> +			ret = -ERANGE;
> +			goto unlock;
> +		}
>  		priv->mtu_32bit_max = ceiling;
>  		break;
>  	default:
>  		/* should never reach this path */
> -		mutex_unlock(&priv->lock);
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		goto unlock;
>  	}

Normally, I like "goto unlock" patterns, but I think in this context it
makes the flow of code confusing with the mix-match of the switch cases;
default case jumps with a goto, but RZ_MTU3_* cases passes will break,
yet RZ_MUT3_* failures have a goto path. Rather than a "goto unlock"
pattern, I'd prefer to see simply mutex_lock() called for these ceiling
checks. That also has the benefit of reducing the number of changes we
have to make for this fix.

William Breathitt Gray

>  
>  	pm_runtime_get_sync(ch->dev);
> @@ -381,9 +385,9 @@ static int rz_mtu3_count_ceiling_write(struct counter_device *counter,
>  
>  	rz_mtu3_8bit_ch_write(ch, RZ_MTU3_TCR, RZ_MTU3_TCR_CCLR_TGRA);
>  	pm_runtime_put(ch->dev);
> +unlock:
>  	mutex_unlock(&priv->lock);
> -
> -	return 0;
> +	return ret;
>  }
>  
>  static void rz_mtu3_32bit_cnt_setting(struct counter_device *counter)
> -- 
> 2.39.2
> 

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