[Bug 708661] New: elements/multiqueue test_output_order racy

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=708661
  GStreamer | gstreamer (core) | git

           Summary: elements/multiqueue test_output_order racy
    Classification: Platform
           Product: GStreamer
           Version: git
        OS/Version: All
            Status: NEW
          Severity: major
          Priority: Normal
         Component: gstreamer (core)
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: bilboed at bilboed.com
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


the test_output_order "check" is racy.

 (CK_FORK=no GST_CHECK=test_output_order make elements/multiqueue.forever).

The problem is indeed the test and not the actual element behaviour.

The objects to push are being pulled out of the single internal queues in the
right order and at the right time...

But between:
* the moment the global multiqueue lock is released (which was used to detect
if we should pop and push downstream the next buffer)
* and the moment it is received by the source pad (which does the check)

=> another single queue (like the unlinked pad) might pop and push a buffer
downstream

What should we do ? Putting a bigger margin of error (say 5 buffers) doesn't
help, it'll eventually fail.

I can't see how we can detect this reliably.

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