2021-05-11 12:46:13

by Pratyush Yadav

Subject: [PATCH] media: i2c: ov5648: Plug runtime pm counter leak

When the stream is being enabled, the runtime pm usage counter is
incremented. Then if ov5648_sw_standby() fails, the function returns
error without decrementing the counter, leaking it.

Signed-off-by: Pratyush Yadav <[email protected]>
---

Hi,

I spotted this when converting OV5640 driver to use runtime PM using
this driver as reference. I only have a very surface level understanding
of runtime PM system as of now so please review with that in mind.

This patch is only compile-tested since I don't have the hardware with
me.

drivers/media/i2c/ov5648.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/media/i2c/ov5648.c b/drivers/media/i2c/ov5648.c
index 3ecb4a3e8773..6aa2c950f505 100644
--- a/drivers/media/i2c/ov5648.c
+++ b/drivers/media/i2c/ov5648.c
@@ -2143,8 +2143,12 @@ static int ov5648_s_stream(struct v4l2_subdev *subdev, int enable)
ret = ov5648_sw_standby(sensor, !enable);
mutex_unlock(&sensor->mutex);

- if (ret)
+ if (ret) {
+ if (enable)
+ pm_runtime_put(sensor->dev);
+
return ret;
+ }

state->streaming = !!enable;

--
2.30.0

2021-05-21 20:18:19

by Sakari Ailus

Subject: Re: [PATCH] media: i2c: ov5648: Plug runtime pm counter leak

Hi Pratyush,

Thanks for the patch.

On Tue, May 11, 2021 at 06:14:37PM +0530, Pratyush Yadav wrote:
> When the stream is being enabled, the runtime pm usage counter is
> incremented. Then if ov5648_sw_standby() fails, the function returns
> error without decrementing the counter, leaking it.
>
> Signed-off-by: Pratyush Yadav <[email protected]>
> ---
>
> Hi,
>
> I spotted this when converting OV5640 driver to use runtime PM using
> this driver as reference. I only have a very surface level understanding
> of runtime PM system as of now so please review with that in mind.
>
> This patch is only compile-tested since I don't have the hardware with
> me.
>
> drivers/media/i2c/ov5648.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/i2c/ov5648.c b/drivers/media/i2c/ov5648.c
> index 3ecb4a3e8773..6aa2c950f505 100644
> --- a/drivers/media/i2c/ov5648.c
> +++ b/drivers/media/i2c/ov5648.c
> @@ -2143,8 +2143,12 @@ static int ov5648_s_stream(struct v4l2_subdev *subdev, int enable)
> ret = ov5648_sw_standby(sensor, !enable);
> mutex_unlock(&sensor->mutex);
>
> - if (ret)
> + if (ret) {
> + if (enable)
> + pm_runtime_put(sensor->dev);

The function powers the sensor off at the end if streaming was to be
disabled. You could do:

if (ret || !enable)
pm_runtime_put(sensor->dev);

> +
> return ret;
> + }
>
> state->streaming = !!enable;

state->streaming is assigned when not holding the lock. Could you address
that at the same time?

--
Kind regards,

Sakari Ailus