sched: add kernel thread creation and SMP-aware thread scheduling

sched/runqueue.c

@@ -27,6 +27,10 @@ struct thread *rq_dequeue(struct runqueue *rq)
 
 	struct thread *thr = QUEUE_CONTAINER(struct thread, tr_rqentry, qe);
 
+	if (rq->rq_nthreads > 0) {
+		rq->rq_nthreads--;
+	}
+
 	if (queue_empty(q)) {
 		rq->rq_readybits &= ~PRIO_MASK(prio);
 	}