线程状态，即结构体struct rt_thread的成员stat=0x0a（RT_THREAD_STAT_YIELD | RT_THREAD_SUSPEND）

发布于 2023-05-19 11:25:19 浏览：521 订阅该版

2 个回答

宇宙码蚁 2023-05-19

接口与实现分离

应该说是有可能的：

搜索`RT_THREAD_STAT_YIELD`，发现在`src/clock.c`的`rt_tick_increase()`中使用了，
具体定义如下：
```
/**
 * This function will notify kernel there is one tick passed. Normally,
 * this function is invoked by clock ISR.
 */
void rt_tick_increase(void)
{
    struct rt_thread *thread;

/* increase the global tick */
#ifdef RT_USING_SMP
    rt_cpu_self()->tick ++;
#else
    ++ rt_tick;
#endif

/* check time slice */
    thread = rt_thread_self();

-- thread->remaining_tick;
    if (thread->remaining_tick == 0)
    {
        /* change to initialized tick */
        thread->remaining_tick = thread->init_tick;

thread->stat |= RT_THREAD_STAT_YIELD;

rt_schedule();
    }

/* check timer */
    rt_timer_check();
}
```
rt_tick_increase是系统定时器中断的回调，任何时候（除了关中断时）都有可能发生。
可以看到，实际被操作的线程是通过调用rt_thread_self()获取的，查看rt_thread_self的定义，其实就是读了个全局变量`rt_current_thread`，
再搜索这个全局变量，发现只在rt_schedule中更改。

再看RT_THREAD_SUSPEND，主要通过rt_thread_suspend函数操作，搜索rt_thread_suspend函数，使用的地方很多，最常用的在ipc.c中，rt_sem_take,下面摘自此函数
```

/* suspend thread */
            rt_ipc_list_suspend(&(sem->parent.suspend_thread),
                                thread,
                                sem->parent.parent.flag);

/* has waiting time, start thread timer */
            if (time > 0)
            {
                RT_DEBUG_LOG(RT_DEBUG_IPC, ("set thread:%s to timer list\n",
                                            thread->name));

/* reset the timeout of thread timer and start it */
                rt_timer_control(&(thread->thread_timer),
                                 RT_TIMER_CTRL_SET_TIME,
                                 &time);
                rt_timer_start(&(thread->thread_timer));
            }

/* enable interrupt */
            rt_hw_interrupt_enable(temp);

/* do schedule */
            rt_schedule();
```
可以看到，等不到资源就会先挂起线程，然后调用rt_schedule切到其他线程去，但rt_schedule前开了中断。

所以可能性就是：已经挂起但没切线程前，来了系统定时器中断，把线态状态又“或”上了RT_THREAD_STAT_YIELD