[Bug 742074] New: v4l2videodec: leaks filedescriptors

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=742074
  GStreamer | gst-plugins-good | git

           Summary: v4l2videodec: leaks filedescriptors
    Classification: Platform
           Product: GStreamer
           Version: git
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-good
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: sjoerd at luon.net
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


Created an attachment (id=293414)
 --> (https://bugzilla.gnome.org/attachment.cgi?id=293414)
Strawmen patch

After playing back a video file on exynos 2 file descriptors stay open
referring to the video device. Tracing those down points to the BufferPool and
Allocate attached to the src pad (output object).

What happens when the decoder is torn down is that the pool is de-activate and
dropped (from gst_v4l2_object_stop):
  gst_buffer_pool_set_active (v4l2object->pool, FALSE);
  gst_object_unref (v4l2object->pool);
  v4l2object->pool = NULL;

The idea being that the BufferPool will get disposed once all buffers have been
returned to it. However for _OUTPUT the buffers enqueued in the video device
are also acquired out of the pool (as opposed to _CAPTURE buffers, which are
seenas "in" the pool while enqueued). Unfortunately, this means that if there
are any buffers still enqueued in the _OUTPUT queue when gst_v4l2_object_stop
is called, then the BufferPool will never get all its buffers back, thus never
gets cleaned up.


This is "solved" in the attached patch by calling stream off and dropping all
enqueued buffers once the pool is set to flushing. However I'm not entirely
happy with that solution, it might be nicer & more in line with the handling
of_CAPTURE buffers to regard enqueued _OUTPUT buffers as part of the pool
rather then buffers taken out of the pool, which prevents this issue and might
make the handling more aligned.

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