[Bug 680091] [0.11] dvbsuboverlay: mangles video timestamps (?), crash on composition unref

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=680091
  GStreamer | gst-plugins-bad | 0.11.x

--- Comment #3 from Mark Nauwelaerts <mnauw at users.sourceforge.net> 2012-07-18 13:29:42 UTC ---
Created an attachment (id=219122)
 View: https://bugzilla.gnome.org/attachment.cgi?id=219122
 Review: https://bugzilla.gnome.org/review?bug=680091&attachment=219122

tests: gstbuffer: extend buffer copy test

Looks like we may still be having some problems in coming up with really
independent buffer copies and that that is biting here.

In particular, adding some debug shows that dvbsuboverlay (occasionally) gets
incoming buffers whose object_lock state is 0x20103, which means it is
owned/locked EXCLUSIVELY twice but ended up mapped writable (possibly twice). 
So 2 buffers can still end up playing around with the same memory.

Reading code suggests this can indeed happen in the sequence:
* locking EXCLUSIVE some fresh memory
* mapping it WRITE
* then making a buffer copy, adding another EXCLUSIVE lock
* mapping it WRITE again

Attached patch extends the unit test to illustrate/test this.

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