FreeRTOS篇10：互斥量

最新推荐文章于 2025-05-30 00:03:58 发布

努力学习de小王

最新推荐文章于 2025-05-30 00:03:58 发布

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文章标签： stm32 嵌入式硬件单片机

本文链接：https://blog.youkuaiyun.com/2401_83811921/article/details/142690109

版权

一.什么是互斥量？

在多数情况下，互斥型信号量和二值型信号量非常相似，但是从功能上二值型信号量用于同步，而互斥型信号量用于资源保护。

互斥型信号量和二值型信号量还有一个最大的区别，互斥型信号量可以有效解决优先级反转现象。

二.什么是优先级翻转？

系统中有3个不同优先级的任务H/M/L，最高优先级任务H和最低优先级任务L通过信号量机制，共享资源。目前任务L占有资源，锁定了信号量，Task H运行后将被阻塞，直到Task L释放信号量后，Task H才能够退出阻塞状态继续运行。但是Task H在等待Task L释放信号量的过程中，中等优先级任务M抢占了任务L，从而延迟了信号量的释放时间，导致Task H阻塞了更长时间，这种现象称为优先级倒置或反转。

优先级继承：当一个互斥信号量正在被一个低优先级的任务持有时，如果此时有个高优先级的任务也尝试获取这个互斥信号量，那么这个高优先级的任务就会被阻塞。不过这个高优先级的任务会将低优先级任务的优先级提升到与自己相同的优先级。

优先级继承并不能完全的消除优先级翻转的问题，它只是尽可能的降低优先级翻转带来的影响。

三.互斥量相关 API 函数

互斥信号量不能用于中断服务函数中！

参数：

无

返回值：

成功，返回对应互斥量的句柄；失败，返回 NULL 。

四.实操

1.实验需求

1）演示优先级翻转

2）使用互斥量优化优先级翻转问题

2.cubeMX配置

1）演示优先级翻转

创建3个任务

创建二值信号量

2）使用互斥量优化优先级翻转问题

3.代码实现

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * File Name          : freertos.c
  * Description        : Code for freertos applications
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2024 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  */
/* USER CODE END Header */

/* Includes ------------------------------------------------------------------*/
#include "FreeRTOS.h"
#include "task.h"
#include "main.h"
#include "cmsis_os.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include <stdio.h>
/* USER CODE END Includes */

/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */

/* USER CODE END PTD */

/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */

/* USER CODE END PD */

/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */

/* USER CODE END PM */

/* Private variables ---------------------------------------------------------*/
/* USER CODE BEGIN Variables */

/* USER CODE END Variables */
osThreadId TaskHHandle;
osThreadId TaskMHandle;
osThreadId TaskLHandle;
osMutexId myMutexHandle;

/* Private function prototypes -----------------------------------------------*/
/* USER CODE BEGIN FunctionPrototypes */

/* USER CODE END FunctionPrototypes */

void StartTaskH(void const * argument);
void StartTaskM(void const * argument);
void StartTaskL(void const * argument);

void MX_FREERTOS_Init(void); /* (MISRA C 2004 rule 8.1) */

/* GetIdleTaskMemory prototype (linked to static allocation support) */
void vApplicationGetIdleTaskMemory( StaticTask_t **ppxIdleTaskTCBBuffer, StackType_t **ppxIdleTaskStackBuffer, uint32_t *pulIdleTaskStackSize );

/* USER CODE BEGIN GET_IDLE_TASK_MEMORY */
static StaticTask_t xIdleTaskTCBBuffer;
static StackType_t xIdleStack[configMINIMAL_STACK_SIZE];

void vApplicationGetIdleTaskMemory( StaticTask_t **ppxIdleTaskTCBBuffer, StackType_t **ppxIdleTaskStackBuffer, uint32_t *pulIdleTaskStackSize )
{
  *ppxIdleTaskTCBBuffer = &xIdleTaskTCBBuffer;
  *ppxIdleTaskStackBuffer = &xIdleStack[0];
  *pulIdleTaskStackSize = configMINIMAL_STACK_SIZE;
  /* place for user code */
}
/* USER CODE END GET_IDLE_TASK_MEMORY */

/**
  * @brief  FreeRTOS initialization
  * @param  None
  * @retval None
  */
void MX_FREERTOS_Init(void) {
  /* USER CODE BEGIN Init */

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

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

  /* 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 TaskH */
  osThreadDef(TaskH, StartTaskH, osPriorityAboveNormal, 0, 128);
  TaskHHandle = osThreadCreate(osThread(TaskH), NULL);

  /* definition and creation of TaskM */
  osThreadDef(TaskM, StartTaskM, osPriorityNormal, 0, 128);
  TaskMHandle = osThreadCreate(osThread(TaskM), NULL);

  /* definition and creation of TaskL */
  osThreadDef(TaskL, StartTaskL, osPriorityBelowNormal, 0, 128);
  TaskLHandle = osThreadCreate(osThread(TaskL), NULL);

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

}

/* USER CODE BEGIN Header_StartTaskH */
/**
  * @brief  Function implementing the TaskH thread.
  * @param  argument: Not used
  * @retval None
  */
/* USER CODE END Header_StartTaskH */
void StartTaskH(void const * argument)
{
  /* USER CODE BEGIN StartTaskH */
  /* Infinite loop */
  for(;;)
  {
		xSemaphoreTake(myMutexHandle,portMAX_DELAY);
		printf("TaskH：我开始进入厕所...\r\n");
		HAL_Delay(1000);
		printf("TaskH：我上完厕所了...\r\n");
		xSemaphoreGive(myMutexHandle);
    osDelay(1000);
  }
  /* USER CODE END StartTaskH */
}

/* USER CODE BEGIN Header_StartTaskM */
/**
* @brief Function implementing the TaskM thread.
* @param argument: Not used
* @retval None
*/
/* USER CODE END Header_StartTaskM */
void StartTaskM(void const * argument)
{
  /* USER CODE BEGIN StartTaskM */
  /* Infinite loop */
  for(;;)
  {
		printf("TaskM：占用CPU资源...\r\n");
    osDelay(1000);
  }
  /* USER CODE END StartTaskM */
}

/* USER CODE BEGIN Header_StartTaskL */
/**
* @brief Function implementing the TaskL thread.
* @param argument: Not used
* @retval None
*/
/* USER CODE END Header_StartTaskL */
void StartTaskL(void const * argument)
{
  /* USER CODE BEGIN StartTaskL */
  /* Infinite loop */
  for(;;)
  {
		xSemaphoreTake(myMutexHandle,portMAX_DELAY);
		printf("TaskL：我开始进入厕所...\r\n");
		HAL_Delay(3000);
		printf("TaskL：我上完厕所了...\r\n");
		xSemaphoreGive(myMutexHandle);
    osDelay(1000);
  }
  /* USER CODE END StartTaskL */
}

/* Private application code --------------------------------------------------*/
/* USER CODE BEGIN Application */

/* USER CODE END Application */