Pick the first available vcpu within cpumask from the run queue. Run queue is sorted
schedule function for rtglobal scheduler
Remove vcpu from run queue
runq_tickle picks a vcpu on a cpu to kick out to place the vcpu candidate chosen by schedule
Wake up a runnable vcpu, insert it back to run queue
rtglobal_context_saved insert the finished vcpu to runq and pick the next vcpu to run
init variable sched_rtglobal_def of struct scheduler