atomic(3) on macOS
The text d39607cd377d, as Mac OS X 10.5.8, Mac OS X 10.5.7, Mac OS X 10.5.6, Mac OS X 10.5.5, Mac OS X 10.5.4, Mac OS X 10.5.3, Mac OS X 10.5.2, Mac OS X 10.5.1, Mac OS X 10.5 shipped it.
atomic add, increment, decrement, or, and, xor, compare and swap, test and set, test and clear, spinlocks, and lockless queues