[bob1029]

What if you have multiple CPUs and you don't want the task to yield (i.e. for performance or latency reasons)?

[dmitrygr]

That limits your OS to numThreads < numCpus

[bob1029]

What if we have multiple classes of threads with varying scheduling and interruption policies?

[dmitrygr]

Either you have interrupts to interrupt them, you have more cores than threads, or you risk starvation. Simple.

[bob1029]

No opportunity for nuance wherein some of the compute resources are reserved for certain types of threads?