Didn't most old operating systems use cooperative multitasking? I remember, at least, that classic Mac OS (i.e. pre-OSX) didn't use preemptive multitasking, either.
Anyway, this SO answer[0] explains why early Linux, much like the hobby kernel in this article, used cooperative scheduling inside the kernel, and only preempted user-space stuff.
Anyway, this SO answer[0] explains why early Linux, much like the hobby kernel in this article, used cooperative scheduling inside the kernel, and only preempted user-space stuff.
[0]: https://stackoverflow.com/a/16766562