> User space mutexes were in QNX over two decades ago Futexes were in Linux over two decades ago: https://www.kernel.org/doc/ols/2002/ols2002-pages-479-495.pdf

> User space mutexes were in QNX over two decades ago Futexes were in Linux over two decades ago: https://www.kernel.org/doc/ols/2002/ols2002-pages-479-495.pdf https://www.kernel.org/doc/ols/2002/ols2002-pages-479-495.pd... :) And before that I believe glibc did something similar to what I described in the post, using signals