线程切换，打印出来的时间不对

发布于 2021-05-09 12:33:23 浏览：1277 订阅该版

开始内核学习，在潘多拉上进行线程切换实验，我想看thread1和thread2在时间轴上的切换，但打印出来的时间不对，与线程内的延时时间差了2、3个毫秒，请问这是正常的吗？是什么原因导致的呢？麻烦帮忙看一下，非常感谢！！
![线程切换问题.png](https://oss-club.rt-thread.org/uploads/20210509/41f45bcbbbd2c0e5eb0247d1344e3ece.png)

工程配置：
节拍：1ms
最大优先级数：32
MSH优先级：__FINSH_THREAD_PRIORITY     5
其他线程：无

代码如下：
```
/*
创建2个线程，高优先级静态线程thread1，低优先级动态线程thread2，
thread1 执行完后退出，thread2一直不停打印计数。
*/

#include <rtthread.h>

#define THREAD_PRIORITY		22
#define THREAD_STACK_SIZE	512
#define THREAD_TIMESLICE	5

ALIGN(RT_ALIGN_SIZE)
static rt_uint8_t thread1_stack[THREAD_STACK_SIZE];
static struct rt_thread thread1;
//thread1入口函数
static void thread1_entry(void *param)
{
	rt_uint32_t i = 0;
	//延时，让thread2先运行
	rt_thread_mdelay(2000);
	for(i = 0; i < 20; i++)
	{
		rt_kprintf("thread1: i = %d, time: %dms\n", i, rt_tick_get());
		rt_thread_mdelay(70);	
	}
	rt_kprintf("thread1 exit, time: %dms\n", rt_tick_get());
	
}

static rt_thread_t	tid2 = RT_NULL;
//thread2入口函数
static void thread2_entry(void *param)
{
	rt_uint32_t count = 0;

while(1)
	{
		rt_kprintf("thread2: count = %d, time: %dms\n", count++, rt_tick_get());
		rt_thread_mdelay(51);
	}
}

//thead测试代码
int thread_sample(void)
{
	rt_thread_init(&thread1, 
					"thread1", 
					thread1_entry,
					RT_NULL,
					thread1_stack,
					THREAD_STACK_SIZE,
					THREAD_PRIORITY - 1,
					THREAD_TIMESLICE);
	//rt_thread_startup(&thread1);

tid2 = rt_thread_create("thread2", 
						thread2_entry, 
						RT_NULL, 
						THREAD_STACK_SIZE, 
						THREAD_PRIORITY, 
						THREAD_TIMESLICE);
	if(RT_NULL != tid2)
	{
		//初始化时间轴
		rt_tick_set(0);
		//同时启动2个线程
		rt_thread_startup(&thread1);
		rt_thread_startup(tid2);
	}

return 0;
}

MSH_CMD_EXPORT(thread_sample, "thread sample");