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

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Message-ID: <20210625173316.pfsk7rvlplv4bzef@pengutronix.de>
Date:   Fri, 25 Jun 2021 19:33:16 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>, linux-pm@...r.kernel.org
Cc:     Zou Wei <zou_wei@...wei.com>, thierry.reding@...il.com,
        lee.jones@...aro.org, linux-pwm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] pwm: img: Fix PM reference leak in img_pwm_enable()

Hello Rafael, Kevin and Ulf,

On Wed, May 12, 2021 at 06:52:22AM +0200, Uwe Kleine-König wrote:
> 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()?

Can you give some feedback here?

Best regards
Uwe

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

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