gstreamer 1.20: v4l2bufferpool spams "newly allocated buffer is not free"

[Michiel Konstapel]

On 28-06-2022 22:13, Michiel Konstapel wrote:
> On 27-06-2022 22:24, Nicolas Dufresne via gstreamer-devel wrote:
>> Le dimanche 26 juin 2022 à 14:30 +0200, Michiel Konstapel a écrit :
>>> On 25-06-2022 17:34, Nicolas Dufresne via gstreamer-devel wrote:
>>>>> It's a very common Logitech C920 webcam (but I've seen the same 
>>>>> message
>>>>> with a Z-Cam M3 camera). I think that uses a generic UVC driver? 
>>>>> Anything
>>>>> I can run to get you more info?
>>>>>
>>>> I'm asking as I cannot reproduce, and from the look of it, the 
>>>> trace implies
>>>> is will leak data. Which Kernel? Have you tested with your own 
>>>> GStreamer
>>>> build (main branch)?
>>> $ uname -a
>>>   Linux xubuntux 5.4.0-121-generic #137-Ubuntu SMP Wed Jun 15 
>>> 13:33:07 UTC 2022
>> That might explain the discrepancy, this is an old kernel, its quite 
>> likely this
>> is a kernel bug and its fixed in newer kernels. Make sure to try more 
>> recently
>> Ubuntu and check. If it is, you likely can request a backport to Ubuntu,
>> assuming this isn't an EOL version you are using.
>>
>>> x86_64 x86_64 x86_64 GNU/Linux
>>> Gstreamer is built from source, from the 1.20.3 tag.
>>> I have also just built it from main (commit
>>> 0e551871c45a1b9fd67d99d2d4f31a983f1b3217) and that shows the effect 
>>> as well.
>>> Michiel
>
> Alas, not quite. I've upgraded to Ubuntu 22.04 which has
>
> $ uname -a
> Linux xubuntux 5.15.0-40-generic #43-Ubuntu SMP Wed Jun 15 12:54:21 
> UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
>
> But the problem persists.


Another data point: I have another video device, on /dev/video0, which 
is the webcam inside my Valve Index VR headset. That one does NOT 
produce the warnings! I tried unplugging the headset and replugging the 
Logitech C920 so that's on /dev/video0 (and the only webcam) but that 
doesn't help: it still spews warnings.