linux-kernel - Re: [PATCH -next] pwm: img: Fix PM reference leak in img_pwm

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Date:   Wed, 12 May 2021 06:52:22 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Zou Wei <zou_wei@...wei.com>
Cc:     thierry.reding@...il.com, lee.jones@...aro.org,
        linux-pwm@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>, linux-pm@...r.kernel.org
Subject: Re: [PATCH -next] pwm: img: Fix PM reference leak in img_pwm_enable()

Hello,

On Wed, May 12, 2021 at 11:57:17AM +0800, Zou Wei wrote:
> pm_runtime_get_sync will increment pm usage counter even it failed.
> Forgetting to putting operation will result in reference leak here.
> Fix it by replacing it with pm_runtime_resume_and_get to keep usage
> counter balanced.
> 
> Reported-by: Hulk Robot <hulkci@...wei.com>
> Signed-off-by: Zou Wei <zou_wei@...wei.com>
> ---
>  drivers/pwm/pwm-img.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pwm/pwm-img.c b/drivers/pwm/pwm-img.c
> index cc37054..11b16ec 100644
> --- a/drivers/pwm/pwm-img.c
> +++ b/drivers/pwm/pwm-img.c
> @@ -156,7 +156,7 @@ static int img_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
>  	struct img_pwm_chip *pwm_chip = to_img_pwm_chip(chip);
>  	int ret;
>  
> -	ret = pm_runtime_get_sync(chip->dev);
> +	ret = pm_runtime_resume_and_get(chip->dev);
>  	if (ret < 0)
>  		return ret;

This patch looks right with my limited understanding of pm_runtime. A
similar issue in this driver was fixed in commit

	ca162ce98110 ("pwm: img: Call pm_runtime_put() in pm_runtime_get_sync() failed case")

where (even though the commit log talks about pm_runtime_put()) a call
to pm_runtime_put_autosuspend() was added in the error path.

I added the PM guys to Cc, maybe they can advise about the right thing
to do here. Does it make sense to use the same idiom in both
img_pwm_enable() and img_pwm_config()?

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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