互斥量（Mutex）

互斥量又称互斥信号量（本质也是一种信号量，不具备传递数据功能），是一种特殊的二值信号量，它和信号量不同的是，它支持互斥量所有权、递归访问以及防止优先级翻转的特性。比如有两个任务，A在运行，B就运行不了。

实验：创建三个任务，从高到低设置优先级，在任务一和三中使用互斥量，观察执行顺序。

实现：在【STM32】FreeRTOS消息队列和信号量学习基础上进行修改

void MX_FREERTOS_Init(void) {
  /* USER CODE BEGIN Init */

  /* USER CODE END Init */
  /* Create the mutex(es) */
  /* definition and creation of Mutex01 */
  osMutexDef(Mutex01);
  Mutex01Handle = osMutexCreate(osMutex(Mutex01));

  /* USER CODE BEGIN RTOS_MUTEX */
  /* add mutexes, ... */
  /* USER CODE END RTOS_MUTEX */

  /* Create the semaphores(s) */


  /* USER CODE BEGIN RTOS_SEMAPHORES */
  /* add semaphores, ... */
  /* USER CODE END RTOS_SEMAPHORES */

  /* USER CODE BEGIN RTOS_TIMERS */
  /* start timers, add new ones, ... */
  /* USER CODE END RTOS_TIMERS */

  /* USER CODE BEGIN RTOS_QUEUES */
  /* add queues, ... */
  /* USER CODE END RTOS_QUEUES */

  /* Create the thread(s) */
  /* definition and creation of Task1 */
  osThreadDef(Task1, StartDefaultTask, osPriorityHigh, 0, 128);
  Task1Handle = osThreadCreate(osThread(Task1), NULL);

  /* definition and creation of Task2 */
  osThreadDef(Task2, StartTask02, osPriorityAboveNormal, 0, 128);
  Task2Handle = osThreadCreate(osThread(Task2), NULL);

  /* definition and creation of Task3 */
  osThreadDef(Task3, StartTask03, osPriorityNormal, 0, 128);
  Task3Handle = osThreadCreate(osThread(Task3), NULL);

  /* USER CODE BEGIN RTOS_THREADS */
  /* add threads, ... */
  /* USER CODE END RTOS_THREADS */

}

/* USER CODE BEGIN Header_StartDefaultTask */
/**
  * @brief  Function implementing the Task1 thread.
  * @param  argument: Not used
  * @retval None
  */
/* USER CODE END Header_StartDefaultTask */
void StartDefaultTask(void const * argument)
{
  /* USER CODE BEGIN StartDefaultTask */
  /* Infinite loop */
  for(;;)
  {
		osDelay(10);//堵塞
		if(xSemaphoreTake(Mutex01Handle,portMAX_DELAY)!=pdTRUE)
		{
			printf("task1,进不去\r\n");
		}
		else
		{
			printf("task1,抢占进入\r\n");
		}
		xSemaphoreGive(Mutex01Handle);
		printf("task1,完成\r\n");
  }
  /* USER CODE END StartDefaultTask */
}

/* USER CODE BEGIN Header_StartTask02 */
/**
* @brief Function implementing the Task2 thread.
* @param argument: Not used
* @retval None
*/
/* USER CODE END Header_StartTask02 */
void StartTask02(void const * argument)
{
  /* USER CODE BEGIN StartTask02 */
  /* Infinite loop */
	
  for(;;)
  {
    osDelay(2);//堵塞
		printf("task2，运行\r\n");
  }
  /* USER CODE END StartTask02 */
}

/* USER CODE BEGIN Header_StartTask03 */
/**
* @brief Function implementing the Task3 thread.
* @param argument: Not used
* @retval None
*/
/* USER CODE END Header_StartTask03 */
void StartTask03(void const * argument)
{
  /* USER CODE BEGIN StartTask03 */
  /* Infinite loop */

  for(;;)
  {
		
		xSemaphoreTake(Mutex01Handle,0);
		printf("task3,进入\r\n");
		xSemaphoreGive(Mutex01Handle);
		printf("task3,完成\r\n");
  }
  /* USER CODE END StartTask03 */
}

 现象：

最低优先级先执行，最高优先级其次执行，最后是中间优先级执行。