[pjtr]

I don't think Microsoft invented it:

> On the CDC CYBER, an interlock register is available ... Operation of this interlock register is similar to TEST AND SET

Concurrency in Operating Systems, October 1976 https://www.computer.org/csdl/magazine/co/1976/10/01647182/1...

[zinekeller]

To add to this, an interlock (which unfortunately is a dated term) is the part of the hardware checking for atomicity when required.