That leaves out the fact that the kernel scheduler does in fact issue timed interrupts to all kernel and userspace code running on a given core, except for "cri

That leaves out the fact that the kernel scheduler does in fact issue timed interrupts to all kernel and userspace code running on a given core, except for "critical sections" (where one or more locks are held). That being said, the scheduler is so reliable and so seamless that one need hardly ever worry about it unless a particular block of code must not be interrupted, usually for parts of parallel/multithreaded code that have shared memory or other resources, or sections within the kernel or scheduler itself. More info on the current Linux scheduler here: https://www.kernel.org/doc/html/latest/scheduler/sched-design-CFS.html https://www.kernel.org/doc/html/latest/scheduler/sched-desig... Check out the code here, if you're brave: https://github.com/torvalds/linux/blob/master/kernel/sched/fair.c https://github.com/torvalds/linux/blob/master/kernel/sched/f...