@rbernon The change which the blamed commit (unintentionally) introduced is that after loosing debug info critical sections started to use slower semaphore path. I sent a patch for that (https://gitlab.winehq.org/wine/wine/-/merge_requests/5379) which fixes mentioned 2 mf tests here. But I think that blamed patch most likely only uncovered a pre-existing race in either mf implementation or mf tests, I didn't debug that part.