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

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Date:   Tue, 29 Jun 2021 11:23:41 +0800
From:   Samuel Zou <zou_wei@...wei.com>
To:     Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
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()

Hi Uwe,

Sorry for the delayed reply.
Thanks for all the review,.
To keep the consistency, it's better to clean this up accordingly, and I 
will send a new patch soon.

On 2021/6/29 1:01, Uwe Kleine-König wrote:
> 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
>