For displays, instead of using the draw_callbacks_mutex and risk a
reverse mutual lock scenario, use a separate mutex to lock display size
data.
This bug was exposed when trying to reorder filters in the UI module.
The UI thread would try to reorder the filters, locking the filter mutex
of the source, and then the reorder would signal the UI to resize the
display, so the display would lock its draw_callbacks_mutex. Then, in
the graphics thread, it would lock the display's draw_callbacks_mutex,
try to draw the source, and then the source would try to lock that same
filter mutex.
A mutex trace:
UI thread -> lock source filter mutex -> waiting on display mutex
graphics thread -> lock display mutex -> waiting on source filter mutex
Closesjp9000/obs-studio#714
jp9000
e541e170a3