10 RT Thtead线程优先级问题（互斥量应用示例）

发布于 2022-11-15 15:42:32 浏览：609 订阅该版

RT-Thread优先级问题，官方文档互斥量一节，线程2的优先级比线程1高，但在线程2running的时候还是会被线程1抢占，达不到官方文档的仿真运行结果。下图是我的仿真运行结果，输出打印的number都是有间隔的

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20221115/d5d1fef577187a0d13885842936127fd.png)

代码都是官方文档代码，就改了优先级和线程2的while循环次数，代码如下：

```c
#include <rtthread.h>

#define THREAD_PRIORITY         21
#define THREAD_TIMESLICE        5

/* 指向互斥量的指针 */
static rt_mutex_t dynamic_mutex = RT_NULL;
static rt_uint8_t number1,number2 = 0;

ALIGN(RT_ALIGN_SIZE)
static char thread1_stack[1024];
static struct rt_thread thread1;
static void rt_thread_entry1(void *parameter)
{
      while(1)
      {
          /* 线程 1 获取到互斥量后，先后对 number1、number2 进行加 1 操作，然后释放互斥量 */
          //rt_kprintf("thread1.current_priority = %d\n",thread1.current_priority);
          rt_mutex_take(dynamic_mutex, RT_WAITING_FOREVER);
          //rt_kprintf("thread1.number1 = %d, mumber2 = %d \n",number1 ,number2);
          number1++;
          rt_thread_mdelay(10);
          number2++;
          rt_mutex_release(dynamic_mutex);
       }
}

ALIGN(RT_ALIGN_SIZE)
static char thread2_stack[1024];
static struct rt_thread thread2;
static void rt_thread_entry2(void *parameter)
{
      while(1)
      {
          /* 线程 2 获取到互斥量后，检查 number1、number2 的值是否相同，相同则表示 mutex 起到了锁的作用 */
          //rt_kprintf("thread2.current_priority = %d\n",thread2.current_priority);
          //rt_kprintf("thread1.current_priority = %d\n",thread1.current_priority);
          rt_mutex_take(dynamic_mutex, RT_WAITING_FOREVER);
          if(number1 != number2)
          {
            rt_kprintf("not protect.number1 = %d, mumber2 = %d \n",number1 ,number2);
          }
          else
          {
            rt_kprintf("mutex protect ,number1 = mumber2 is %d\n",number1);
          }

number1++;
           number2++;
           rt_mutex_release(dynamic_mutex);

if(number1>=10)
              return;
      }
}

/* 互斥量示例的初始化 */
int mutex_sample(void)
{
    /* 创建一个动态互斥量 */
    dynamic_mutex = rt_mutex_create("dmutex", RT_IPC_FLAG_PRIO);
    if (dynamic_mutex == RT_NULL)
    {
        rt_kprintf("create dynamic mutex failed.\n");
        return -1;
    }

rt_thread_init(&thread1,
                   "thread1",
                   rt_thread_entry1,
                   RT_NULL,
                   &thread1_stack[0],
                   sizeof(thread1_stack),
                   THREAD_PRIORITY, THREAD_TIMESLICE);
    
    rt_thread_startup(&thread1);

rt_thread_init(&thread2,
                   "thread2",
                   rt_thread_entry2,
                   RT_NULL,
                   &thread2_stack[0],
                   sizeof(thread2_stack),
                   THREAD_PRIORITY-1, THREAD_TIMESLICE);
    rt_thread_startup(&thread2);
    return 0;
}

/* 导出到 MSH 命令列表中 */
MSH_CMD_EXPORT(mutex_sample, mutex sample);

```

在代码仿真运行过程中也打印看了一下线程优先级，跟初始的线程优先级是一样的，没有变化，如下图：

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20221115/5b67a330eb4080d8e15fa30562283b7b.png)