互斥量:
上图意思是Task L抢占了Task H的资源(获得二值信号量,高优先级任务被阻塞无法执行),我们想要Take H能够尽快运行起来,就要让Task L尽快执行完任务,释放信号量,让Task H获取信号量然后运行,但如果Task M来了,但它不需要信号量就能执行,这时候Task L就停下了,Task M运行起来了,就会延长Task L的运行时间,从而延长Task H获取信号量的时间,这是我们不希望看见的,所以就要用到互斥量,让Task L继承Task H的优先级。
优先级继承:
实操
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
实验1:
cubeMX配置:
/* 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 myMutex01Handle;
osSemaphoreId myBinarySem01Handle;
/* Private function prototypes -----------------------------------------------*/
/* USER CODE BEGIN FunctionPrototypes */
/* USER CODE END FunctionPrototypes */
void StartTaskH(void const * argument);
void StartTaskM(void const *