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Message-ID: <da560b11-4ee0-c534-6dd0-4e080a1e10f3@huawei.com>
Date: Sat, 29 May 2021 17:15:20 +0800
From: "yukuai (C)" <yukuai3@...wei.com>
To: Robert Foss <robert.foss@...aro.org>,
Johan Hovold <johan@...nel.org>
CC: Andrzej Hajda <a.hajda@...sung.com>,
Neil Armstrong <narmstrong@...libre.com>,
David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>,
dri-devel <dri-devel@...ts.freedesktop.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
<yi.zhang@...wei.com>
Subject: Re: [PATCH] drm: bridge: cdns-mhdp8546: Fix PM reference leak in
cdns_mhdp_probe()
ping ...
On 2021/05/18 20:58, Robert Foss wrote:
> On Tue, 18 May 2021 at 09:42, Johan Hovold <johan@...nel.org> wrote:
>>
>> On Mon, May 17, 2021 at 11:27:38AM +0200, Robert Foss wrote:
>>> Hey Yu,
>>>
>>> On Mon, 17 May 2021 at 10:08, Yu Kuai <yukuai3@...wei.com> 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: Yu Kuai <yukuai3@...wei.com>
>>>> ---
>>>> drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c | 2 +-
>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
>>>> index 0cd8f40fb690..305489d48c16 100644
>>>> --- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
>>>> +++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
>>>> @@ -2478,7 +2478,7 @@ static int cdns_mhdp_probe(struct platform_device *pdev)
>>>> clk_prepare_enable(clk);
>>>>
>>>> pm_runtime_enable(dev);
>>>> - ret = pm_runtime_get_sync(dev);
>>>> + ret = pm_runtime_resume_and_get(dev);
>>>> if (ret < 0) {
>>>> dev_err(dev, "pm_runtime_get_sync failed\n");
>
> This error message is a bit confusing now, could you update it.
>
>>>> pm_runtime_disable(dev);
>>>
>>> The code is correct as it is. If pm_runtime_get_sync() fails and
>>> increments[1] the pm.usage_count variable, that isn't a problem since
>>> pm_runtime_disable() disables pm, and resets pm.usage_count variable
>>> to zero[2].
>>
>> No it doesn't; pm_runtime_disable() does not reset the counter and you
>> still need to decrement the usage count when pm_runtime_get_sync()
>> fails.
>
> Thanks for chiming in Johan, you're absolutely right and I must have
> misread something.
>
> With the above fix, feel free to add my r-b.
>
> Reviewed-by: Robert Foss <robert.foss@...aro.org>
> .
>
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