The streaming threads and GST_Seeking_SetPositions() contend for the same flushing locks.
GST_Seeking_SetPositions() needs to acquire all the flushing locks before doing the actual
stream seeking, having the streaming threads fighting for the same locks will make
GST_Seeking_SetPositions() wait for a unusually long time.
This reduces PowerPoint 2016 video seeking time from ~5s to almost an instant and fixes a regression
for Fallout 3.
Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=53403
--
https://gitlab.winehq.org/wine/wine/-/merge_requests/1239