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

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Message-ID: <20210628170105.apt7numxkdyxf6q5@pengutronix.de>
Date:   Mon, 28 Jun 2021 19:01:05 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Zou Wei <zou_wei@...wei.com>
Cc:     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>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH -next] pwm: img: Fix PM reference leak in img_pwm_enable()

Hello Zou,
On Mon, Jun 28, 2021 at 08:38:39AM +0200, Uwe Kleine-König wrote:
> On Fri, Jun 25, 2021 at 07:45:14PM +0200, Rafael J. Wysocki wrote:
> > On Wed, May 12, 2021 at 6:52 AM Uwe Kleine-König
> > <u.kleine-koenig@...gutronix.de> wrote:
> > > 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.
> 
> Do you care to clean this up accordingly and send a new patch?

Note that Thierry applied your initial patch regardless of the
inconsistency. Still I'd like to see this done in a consistent way. Do
you care to follow up with a patch that unifies the behaviour?

Best regards
Uwe

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

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