linux-kernel - Re: [PATCH] media: vsp1: Fix a reference count leak.

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Message-ID: <812c778d-2bdc-574c-eb72-fb2570ac2c11@xs4all.nl>
Date:   Mon, 22 Jun 2020 12:21:47 +0200
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        wu000273@....edu
Cc:     kjlu@....edu,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-media@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org, Dinghao Liu <dinghao.liu@....edu.cn>,
        Aditya Pakki <pakki001@....edu>
Subject: Re: [PATCH] media: vsp1: Fix a reference count leak.

On 16/06/2020 04:09, Laurent Pinchart wrote:
> On Tue, Jun 16, 2020 at 05:07:34AM +0300, Laurent Pinchart wrote:
>> Hi Qiushi,
>>
>> (CC'ing Rafael and Geert)
>>
>> Thank you for the patch.
>>
>> On Sat, Jun 13, 2020 at 06:23:57PM -0500, wu000273@....edu wrote:
>>> From: Qiushi Wu <wu000273@....edu>
>>>
>>> pm_runtime_get_sync() increments the runtime PM usage counter even
>>> when it returns an error code, causing incorrect ref count if
>>> pm_runtime_put_noidle() is not called in error handling paths.
>>> Thus call pm_runtime_put_noidle() if pm_runtime_get_sync() fails.
>>>
>>> Fixes: 1e6af546ee66 ("[media] v4l: vsp1: Implement runtime PM support")
>>> Signed-off-by: Qiushi Wu <wu000273@....edu>
>>
>> https://lore.kernel.org/dri-devel/20200614134655.GA5960@pendragon.ideasonboard.com/
>>
>> I really wonder if mass-patching all drivers is the best way forward.
> 
> Also,
> 
> https://lore.kernel.org/linux-media/20200608052919.4984-1-dinghao.liu@zju.edu.cn/

I also stop applying these patches. In part because of what Laurent says (I'd
like to have some consensus on this as well), and in part because there are
at least three different devs working on this (Qiushi Wu <wu000273@....edu>,
Aditya Pakki <pakki001@....edu> and Dinghao Liu <dinghao.liu@....edu.cn>) and
I am getting duplicate patches.

So I stop applying these pm_runtime_get_sync() patches until it is clear that
this is the way forward. Other ref count issues I will still apply, but it
would be great if Qiushi Wu, Aditya Pakki and Dinghao Liu can work together
to avoid duplicate patches.

Regards,

	Hans

> 
>>> ---
>>>  drivers/media/platform/vsp1/vsp1_drv.c | 4 +++-
>>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/media/platform/vsp1/vsp1_drv.c b/drivers/media/platform/vsp1/vsp1_drv.c
>>> index c650e45bb0ad..222c9e1261a0 100644
>>> --- a/drivers/media/platform/vsp1/vsp1_drv.c
>>> +++ b/drivers/media/platform/vsp1/vsp1_drv.c
>>> @@ -846,8 +846,10 @@ static int vsp1_probe(struct platform_device *pdev)
>>>  	pm_runtime_enable(&pdev->dev);
>>>  
>>>  	ret = pm_runtime_get_sync(&pdev->dev);
>>> -	if (ret < 0)
>>> +	if (ret < 0) {
>>> +		pm_runtime_put_noidle(&pdev->dev);
>>>  		goto done;
>>> +	}
>>>  
>>>  	vsp1->version = vsp1_read(vsp1, VI6_IP_VERSION);
>>>  	pm_runtime_put_sync(&pdev->dev);
>