rt_thread_delay延时不同时间导致线程切换间的时间不同

发布于 2023-07-06 09:20:22 浏览：642 订阅该版

新手，在尝试移植rt-nano中遇到了这个问题，
我只有两个简单的线程
```c
void led_thread_entry(void *parm)
{
    while (1)
    {
        rt_kprintf("[led_entry:%d]\r\n", rt_tick_get());
        rt_thread_delay(500);
    }
}
void screen_thread_entry(void *parameter)
{
    while(1)
    {
        rt_kprintf("[screen_entry:%d]\r\n", rt_tick_get());
        rt_thread_delay(500);

}
}
void screen_task(void)
{
    rt_sem_init(&sem_lock, "lock",     1,      RT_IPC_FLAG_FIFO);
    rt_sem_init(&sem_led, "led",   1, RT_IPC_FLAG_FIFO);
    rt_sem_init(&sem_screen, "screen",     0,      RT_IPC_FLAG_FIFO);
    rt_thread_t tid1;
    tid1 = rt_thread_create("led", led_thread_entry, RT_NULL,
                            1024, 8, 10);
    RT_ASSERT(tid1 != RT_NULL);
    rt_thread_startup(tid1);
    rt_thread_t tid2;
    tid2 = rt_thread_create("screen", screen_thread_entry, RT_NULL,
                            1024, 8, 10);
    RT_ASSERT(tid2 != RT_NULL);
    rt_thread_startup(tid2);
}
```
`#define RT_TICK_PER_SECOND  1000`在我delay500的时候，两个线程间切换的时间居然需要300ms
![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20230706/c773625fcf1eb4d40b5f505e5370e3da.png.webp)
而在delay100的时候，
![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20230706/a1e519b8d8ba7ce740dcf48f1ccb2083.png)
看上去就很正常
我实在是不理解为什么会这样，特来求助

lchnu 2023-07-06

Witness, Understand, Skill

yiansher 2023-07-06

这家伙很懒，什么也没写！

yiansher 2023-07-06

这家伙很懒，什么也没写！

yiansher 2023-07-06

这家伙很懒，什么也没写！

lchnu 2023-07-06

Witness, Understand, Skill

yiansher 2023-07-07

这家伙很懒，什么也没写！

谢谢大佬的回答
```c
void screen_task(void)
{
    MD_OLED_RST_Set(); //显示器复位拉高
    u8g2Init(&u8g2);   //显示器调用初始化函数
```
我将显示初始化放到了任务创建，当使用普通的delay时，线程间第一次同步，其后每次调度后会开始偏移
![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20230707/d03e559f82c988810387fc7b46b6cd4a.png)
然后换成delay_until,这时线程间同步。
![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20230707/70c0cb6befa7ebd052fe46eb58e5c1d0.png)
但是当超过100次调度后，会卡一下调度，表现为在此之前，灯亮，屏幕就显示1，灭就是0，当打印到100000时，就变成灯亮显示0了，屏幕明显顿在那里了，猜测是因为访问同一个变量导致的问题。
所以我又尝试学习了信号量，
```c
void led_thread_entry(void *parm)
{
    rt_tick_t tick = rt_tick_get();
    while (1)
    {
        tick = rt_tick_get();
        rt_kprintf("[led_entry:%d]\r\n", rt_tick_get());
        rt_sem_take(&sem_led, RT_WAITING_FOREVER);
        rt_sem_take(&sem_lock, RT_WAITING_FOREVER);
        HAL_GPIO_WritePin(LED_GPIO_Port, LED_Pin, (GPIO_PinState)led_onoff);
        led_onoff ^= 1;
        rt_sem_release(&sem_lock);
        rt_sem_release(&sem_screen);
        rt_thread_delay_until(&tick,D_T);
    }
}
void screen_thread_entry(void *parameter)
{
    rt_tick_t tick = rt_tick_get();
    while(1)
    {
        tick = rt_tick_get();
        rt_kprintf("[screen_entry:%d]\r\n", rt_tick_get());
        rt_sem_take(&sem_screen, RT_WAITING_FOREVER);
        rt_sem_take(&sem_lock, RT_WAITING_FOREVER);
        u8g2_ClearBuffer(&u8g2);
        PrintVarFormat(&u8g2, 60, 30, u8g2_font_inb24_mf, (short)led_onoff);
        rt_sem_release(&sem_lock);
        rt_sem_release(&sem_led);
        rt_thread_delay_until(&tick,D_T);
    }
}
void screen_task(void)
{
    MD_OLED_RST_Set(); //显示器复位拉高
    u8g2Init(&u8g2);   //显示器调用初始化函数
    #if 1
    rt_sem_init(&sem_lock, "lock",     1,      RT_IPC_FLAG_FIFO);
    rt_sem_init(&sem_led, "led",   1, RT_IPC_FLAG_FIFO);
    rt_sem_init(&sem_screen, "screen",     0,      RT_IPC_FLAG_FIFO);
    rt_thread_t tid1;
    tid1 = rt_thread_create("led", led_thread_entry, RT_NULL,
                            1024, 8, 1);
    RT_ASSERT(tid1 != RT_NULL);
    rt_thread_startup(tid1);
    rt_thread_t tid2;
    tid2 = rt_thread_create("screen", screen_thread_entry, RT_NULL,
                            1024, 7, 1);
    RT_ASSERT(tid2 != RT_NULL);
    rt_thread_startup(tid2);
```
其实就是抄了例程:-)，这下问题就解决了，总之还是感谢大佬的回答，谢谢