Note that C++11 std::mutex and C11 mtx_t require a single total order of operations on the mutex, which means acquire plus release pairs equivalent on lock/unlo

Note that C++11 std::mutex and C11 mtx_t require a single total order of operations on the mutex, which means acquire plus release pairs equivalent on lock/unlock. That is actually weaker than acq rel write. POSIX requires memory barrier in addition to that on the pthread pair, making it get more different, and both major C++ library implementations defer to pthreads.