VEdit::render checking out Cache::check_out 1 Cache::check_out 2 VEdit::draw checking out Cache::check_out 1 VEdit::render checking in ATrack::render checking out Cache::check_out 1 Cache::check_in 1 Cache::check_out 2 Cache::check_in 2 VEdit::render done VRender::process_buffer age video Cache::age_type 1 Cache::lock_all 1 Cache::lock_all 2 but ATrack::render has locked check_out at this point. VEdit::draw checking in Cache::check_in 1 but Cache::age_type has locked check_in and check_out can't be unlocked until VEdit completes