For some reason I thought SDL thread handling would be much simpler... but the migration to posix pthread went very smooth and painless. Less code even, and I even notice a slight performance increase! All threading code is still wrapped in blenlib/intern/threads.c Only real change was making the callback functions to return void pointer, instead of an int. The mutex handling is also different... there's no test anymore if a mutex was initialized, which is a bit confusing. But it appears to run all fine still. :) Nathan Letwory has been signalled already to provide the Windows pthread library and make/scons linking. For MSVC we might need help from someone else later though.