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调度器锁
同中断锁一样把调度器锁住也能让当前运行的任务不被换出,直到调度器解锁。但和中断锁有一点不相同的是,对调度器上锁,系统依然能响应外部中断,中断服务例程依然能进行相应的响应。所以在使用调度器上锁的方式进行任务同步时,需要考虑好任务访问的临界资源是否会被中断服务例程所修改,如果可能会被修改,那么将不适合采用此种方式进行同步。RT-Thread提供的调度锁操作API为:
- void rt_enter_critical(void); /* 进入临界区*/
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调用这个函数后,调度器将被上锁。在锁住调度器期间,系统依然响应中断,如果中断唤醒了更高优先级的线程,调度器并不会立刻执行它,直到调用解锁调度器函数时才会尝试进行下一次调度。
- void rt_exit_critical(void); /* 退出临界区*/
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当系统退出临界区的时候,系统会计算当前是否有更高优先级的线程就绪,如果有比当前线程更高优先级的线程就绪,将切换到这个高优先级线程中执行;如果无更高优先级线程就绪,将继续执行当前任务。
注: rt_enter_critical/rt_exit_critical可以多次嵌套调用,但每调用一次rt_enter_critical就必须相对应地调用一次rt_exit_critical退出操作,嵌套的最大深度是65535。
使用场合
调度器锁能够方便地使用于一些线程与线程间同步的场合,由于轻型,它不会对系统中断响应造成负担;但它的缺陷也很明显,就是它不能被用于中断与线程间的同步或通知,并且如果执行调度器锁的时间过长,会对系统的实时性造成影响(因为使用了调度器锁后,系统将不再具备优先级的关系,直到它脱离了调度器锁的状态)。
下面在机智云gokit上验证如何通过调度锁保护代码,程序创建2个不同优先级的线程,线程1的优先级比线程2高,低优先级线程会执行一段耗时比较长的代码:
(1)若不启用调度锁,即注释掉rt_enter_critical和rt_exit_critical这2行代码,则会发现线程2会被线程1打断,字符串被修改为gokit demo而不是期望打印的Gokit Demo,说明线程2被线程1打断;
(2)若启用调度锁,即不注释掉rt_enter_critical和rt_exit_critical这2行代码,则会发现线程2打印的是期望的Gokit Demo,说明线程2没有被线程1打断,调度锁起到了保护临界代码的作用;
- /**
- ****************************************************
- * File Name : main.c
- * Description : Main program body
- ****************************************************
- ** This notice applies to any and all portions of this file
- * that are not between comment pairs USER CODE BEGIN and
- * USER CODE END. Other portions of this file, whether
- * inserted by the user or by software development tools
- * are owned by their respective copyright owners.
- *
- * COPYRIGHT(c) 2017 STMicroelectronics
- *
- * Redistribution and use in source and binary forms, with or without modification,
- * are permitted provided that the following conditions are met:
- * 1. Redistributions of source code must retain the above copyright notice,
- * this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright notice,
- * this list of conditions and the following disclaimer in the documentation
- * and/or other materials provided with the distribution.
- * 3. Neither the name of STMicroelectronics nor the names of its contributors
- * may be used to endorse or promote products derived from this software
- * without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
- * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
- * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
- * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
- * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- ****************************************************
- */
- /* Includes ------------------------------------------------------------------*/
- #include "main.h"
- #include "STM32f1xx_hal.h"
- #include "usart.h"
- #include "gpio.h"
- /* USER CODE BEGIN Includes */
- #include "rtthread.h"
- #include "string.h"
- /* USER CODE END Includes */
- /* Private variables ---------------------------------------------------------*/
- /* USER CODE BEGIN PV */
- /* Private variables ---------------------------------------------------------*/
- /* USER CODE END PV */
- /* Private function prototypes -----------------------------------------------*/
- void SystemClock_Config(void);
- /* USER CODE BEGIN PFP */
- /* Private function prototypes -----------------------------------------------*/
- /* USER CODE END PFP */
- /* USER CODE BEGIN 0 */
- //重映射串口1到rt_kprintf
- void rt_hw_console_output(const char *str)
- {
- /* empty console output */
- char aa='\r';
- rt_enter_critical();
- while(*str!='\0')
- {
- if(*str=='\n')
- {
- HAL_UART_Transmit(&huart1, (uint8_t *)&aa, 1, 10);
- }
- HAL_UART_Transmit(&huart1, (uint8_t *)(str++), 1, 10);
- }
-
- rt_exit_critical();
- }
- void rt_hw_us_delay(int us)
- {
- rt_uint32_t delta;
- /* 获得延时经过的tick数 */
- us = us * (SysTick->LOAD/(1000000/RT_TICK_PER_SECOND));
- /* 获得当前时间 */
- delta = SysTick->VAL;
- /* 循环获得当前时间,直到达到指定的时间后退出循环 */
- while (delta - SysTick->VAL< us);
- }
- void rt_hw_ms_delay(int ms)
- {
- int i=0,j=0;
- for(j=0;j<ms;j++)
- {
- for (i=0;i<2;i++)
- rt_hw_us_delay(500);
- }
- }
- /*
- * 程序清单:通过调度锁保护临界区代码
- *线程1的优先级比线程2高,低优先级线程会执行一段耗时比较长的代码;
- *(1)若不启用调度锁,即注释掉rt_enter_critical和rt_exit_critical这2行代码,
- *则会发现线程2会被线程1打断,字符串被修改为gokit demo而不是期望打印的Gokit Demo,说明线程2被线程1打断;
- *(2)若启用调度锁,即不注释掉rt_enter_critical和rt_exit_critical这2行代码,
- *则会发现线程2打印的是期望的Gokit Demo,说明线程2没有被线程1打断,调度锁起到了保护临界代码的作用;
- */
- /* 指向线程控制块的指针 */
- static rt_thread_t tid1 = RT_NULL;
- static rt_thread_t tid2 = RT_NULL;
- char str[]="GOKIT DEMO";
- /* 线程1入口 */
- static void thread1_entry(void* parameter)
- {
- /* 高优先级线程1开始运行,会修改str内容 */
- while(1)
- {
- strcpy(str,"gokit demo");
- rt_kprintf("thread1: %s\n",str);
- rt_thread_delay(1000);
- }
- }
- /* 线程2入口 */
- static void thread2_entry(void* parameter)
- {
- /* 调度器上锁,上锁后,将不再切换到其他线程,仅响应中断 */
- rt_enter_critical();
- strcpy(str,"Gokit Demo");
- /*低优先级线程2执行耗时有点长的代码*/
- rt_hw_ms_delay(4000);
- rt_kprintf("thread2: %s\n",str);
- /* 调度器解锁 */
- rt_exit_critical();
- }
- /* USER CODE END 0 */
- int main(void)
- {
- /* USER CODE BEGIN 1 */
- /* USER CODE END 1 */
- /* MCU Configuration----------------------------------------------------------*/
- // /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
- // HAL_Init();
- // /* USER CODE BEGIN Init */
- // /* USER CODE END Init */
- // /* Configure the system clock */
- // SystemClock_Config();
- // /* USER CODE BEGIN SysInit */
- // /* USER CODE END SysInit */
- // /* Initialize all configured peripherals */
- // MX_GPIO_Init();
- // MX_USART1_UART_Init();
- /* USER CODE BEGIN 2 */
-
- /* 创建线程1 */
- tid1 = rt_thread_create("t1",
- thread1_entry,
- RT_NULL,
- 512,
- 2,
- 20);
- if (tid1 != RT_NULL)
- rt_thread_startup(tid1);
-
- /* 创建线程2 */
- tid2 = rt_thread_create("t2",
- thread2_entry,
- RT_NULL,
- 512,
- 3,
- 20);
- if (tid2 != RT_NULL)
- rt_thread_startup(tid2);
-
- printf("\r\n机智云 只为智能硬件而生\r\n");
- printf("Gizwits Smart Cloud for Smart Products\r\n");
- printf("链接|增值|开放|中立|安全|自有|自由|生态\r\n");
- printf("www.gizwits.com\r\n");
- printf("\r\nGokit RT-Thread Demo\r\n\r\n");
-
- return 0;
-
-
- /* USER CODE END 2 */
- /* Infinite loop */
- /* USER CODE BEGIN WHILE */
- // while (1)
- // {
- /* USER CODE END WHILE */
- /* USER CODE BEGIN 3 */
- //
- // }
- /* USER CODE END 3 */
- }
- /** System Clock Configuration
- */
- void SystemClock_Config(void)
- {
- RCC_OscInitTypeDef RCC_OscInitStruct;
- RCC_ClkInitTypeDef RCC_ClkInitStruct;
- /**Initializes the CPU, AHB and APB busses clocks
- */
- RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
- RCC_OscInitStruct.HSEState = RCC_HSE_ON;
- RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
- RCC_OscInitStruct.HSIState = RCC_HSI_ON;
- RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
- RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
- RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
- if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
- {
- _Error_Handler(__FILE__, __LINE__);
- }
- /**Initializes the CPU, AHB and APB busses clocks
- */
- RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
- |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
- RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
- RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
- RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
- RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
- if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
- {
- _Error_Handler(__FILE__, __LINE__);
- }
- /**Configure the Systick interrupt time
- */
- HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
- /**Configure the Systick
- */
- HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);
- /* SysTick_IRQn interrupt configuration */
- HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);
- }
- /* USER CODE BEGIN 4 */
- /* USER CODE END 4 */
- /**
- * @brief This function is executed in case of error occurrence.
- * @param None
- * @retval None
- */
- void _Error_Handler(char * file, int line)
- {
- /* USER CODE BEGIN Error_Handler_Debug */
- /* User can add his own implementation to report the HAL error return state */
- while(1)
- {
- }
- /* USER CODE END Error_Handler_Debug */
- }
- #ifdef USE_FULL_ASSERT
- /**
- * @brief Reports the name of the source file and the source line number
- * where the assert_param error has occurred.
- * @param file: pointer to the source file name
- * @param line: assert_param error line source number
- * @retval None
- */
- void assert_failed(uint8_t* file, uint32_t line)
- {
- /* USER CODE BEGIN 6 */
- /* User can add his own implementation to report the file name and line number,
- ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
- /* USER CODE END 6 */
- }
- #endif
- /**
- * @}
- */
- /**
- * @}
- */
- /**************** (C) COPYRIGHT STMicroelectronics ****END OF FILE***/
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源码下载:
Gokit_RT-Thread.zip
(8.7 MB, 下载次数: 2, 售价: 1 金钱)
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