关于RTT线程切换的疑问

发布于 2019-11-20 11:55:17 浏览：1617 订阅该版

rt_err_t rt_thread_yield(void)
{
    register rt_base_t level;
    struct rt_thread *thread;

/* disable interrupt */
    level = rt_hw_interrupt_disable();

/* set to current thread */
    thread = rt_current_thread;

/* if the thread stat is READY and on ready queue list */
    if ((thread->stat & RT_THREAD_STAT_MASK) == RT_THREAD_READY &&
        thread->tlist.next != thread->tlist.prev)
    {
        /* remove thread from thread list */
        rt_list_remove(&(thread->tlist));

/* put thread to end of ready queue */
        rt_list_insert_before(&(rt_thread_priority_table[thread->current_priority]),
                              &(thread->tlist));

/* enable interrupt */
        rt_hw_interrupt_enable(level);

rt_schedule();

return RT_EOK;
    }

/* enable interrupt */
    rt_hw_interrupt_enable(level);

return RT_EOK;
}

看RTT源码时，有点地方看不大明白，如上函数，
我假设是一个优先级最高的线程A时间片计时到了，进入了rt_thread_yield  函数中
我的理解是  执行 rt_list_remove(&(thread->tlist));  是把线程A从线程优先级链表中脱离
rt_list_insert_before    再把线程A接入线程优先级链表中
rt_schedule();   执行最高优先级线程
因为线程A优先级是最高，这样不就一直是执行A了吗。是我哪里理解的不对？