I'm not an OS dev either but I think core count makes a difference here. In that a while(true) loop brings down your single core system but doesn't for a multi-core system. Could see the tradeoffs being different today than back when the fundamentals of the OSes we use today were built.
This is a reasonable point. With containerization and the cloud, this abstraction is taken even further.
In the end though, all this really does is perhaps change how aggressive a pre-emptive system needs to be. It could wait longer to pre-empt. Fundamentally though, the design would still need to be pre-emptive.
I don't think it needs to be system pre-emptable. If we reserve 1 core for the OS then the user can always interact with the system. The OS can tell them "App X has pegged the 15 userland cores. Do you wish to kill it?".
In practice, I'm not sure how relevant pre-empting is any more. Software is much better behaved than it used to and I rarely see these runaway processes anymore. And when they do it's usually pegging a single core at 100% while other processes share the remaining core.
