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

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Date:   Fri, 25 Jun 2021 19:45:14 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Cc:     Zou Wei <zou_wei@...wei.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Lee Jones <lee.jones@...aro.org>,
        Linux PWM List <linux-pwm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH -next] pwm: img: Fix PM reference leak in img_pwm_enable()

On Wed, May 12, 2021 at 6:52 AM Uwe Kleine-König
<u.kleine-koenig@...gutronix.de> 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()?

I think so.

And calling pm_runtime_put_autosuspend() in the img_pwm_enable() error
path would work too.