遮蔽了具體的排程演算法，具體的排程演算法在冰山之下

schedule
	=>preempt_disable();
	=>cpu = smp_processor_id();
	rq = cpu_rq(cpu);
	rcu_sched_qs(cpu);
	prev = rq->curr;
	switch_count = &prev->nivcsw;
	=>if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
		if (unlikely(signal_pending_state(prev->state, prev)))
			prev->state = TASK_RUNNING;
		else
			deactivate_task(rq, prev, 1);//prev程序出佇列
		switch_count = &prev->nvcsw;
	}
	=>put_prev_task(rq, prev);//重新入佇列，在紅黑樹的位置可能不在以前的位置了
	=>next = pick_next_task(rq);//選擇最左節點作為下一次排程的程序next
	=>if (likely(prev != next)) {//prev和next不是同一程序則排程之
		sched_info_switch(prev, next);
		perf_event_task_sched_out(prev, next);

		rq->nr_switches++;
		rq->curr = next;
		++*switch_count;

		context_switch(rq, prev, next); /* unlocks the rq */
		/*
		 * the context switch might have flipped the stack from under
		 * us, hence refresh the local variables.
		 */
		cpu = smp_processor_id();
		rq = cpu_rq(cpu);
	}
	=>preempt_enable_no_resched();