Darwin has its own set of futex primitives that it only fairly recently made public API, see https://developer.apple.com/documentation/os/os_sync_wait_on.... But there is a problem with this approach on Darwin, which is that the Darwin kernel has a Quality of Service thread priority implementation that differs from other kernels such that mutexes implemented with spinlocks or with primitives like this are vulnerable to priority inversion. Priority inversion is of course possible on other platforms, but other kernels typically guarantee even low-priority threads always eventually get serviced, whereas on Darwin a low-QoS thread will only get serviced if there are no higher-QoS threads that want to run.

For this reason, on Darwin if you want a mutex of the sort this article describes, you'll typically want to reach for os_unfair_lock, as that will donate the priority of the waiting threads to the thread that holds the lock, thus avoiding the priority inversion issue.