We've had an important change to computers since then in that essentially every processor you might be running an OS on will have multiple threads of execution

We've had an important change to computers since then in that essentially every processor you might be running an OS on will have multiple threads of execution available. As long as some thread returns to the OS and the OS there does a check for excess resource usage it looks like Fomos's model could be made to work. Except in the case where you have some task that uses more threads than the system has which then all try to grab the same lost mutex or something. But you could always just ensure that the OS has at least one thread at any given time, which could be pretty expensive depending on how many threads are available.