【FreeRTOS】任务管理与调度

文章目录

调度：
总结

调度：

相同优先级的任务轮流运行
最高优先级的任务先运行

可以得出结论如下：

a 高优先级的任务在运行，未执行完，更低优先级的任务无法运行
b 一旦高优先级任务就绪，它会马上运行（假设厨房着火了，会马上去灭火）
c 如果最高优先级的任务有多个，他们轮流运行

他们都是使用链表进行管理

打开CubeMX，最高优先级56
在这里插入图片描述

56个List，

RadeyList[55] —>优先级为55的，处于就绪态的任务
RadeyList[54] —>优先级为54的，处于就绪态的任务
……
RadeyList[N] —>优先级为N的，处于就绪态的任务
……
RadeyList[0]

我们一开始创建了好几个任务，优先级默认都是osPriorityNormal=24

  defaultTaskHandle = osThreadNew(StartDefaultTask, NULL, &defaultTask_attributes); // 默认任务

  /* 创建任务：光 */ 
  // 创建一个静态分配内存的任务
  xLightTaskHandle = xTaskCreateStatic(
            Led_Test,           //LED测试函数，PC13以500ms间隔亮灭一次
            "LightTask",        //光任务
            128,                //栈大小，这里提供了栈的大小（长度）
            NULL,               //无传入的参数
            osPriorityNormal,   //优先级默认
            g_pucStackOfLightTask,  // 静态分配的栈，一个buffer，这里只提供了首地址，长度就是栈的大小，最开始栈的类型不对，栈的类型uint32_t
            &g_TCBofLightTask       // 取址TCB
  );
  


  /* 创建任务：色 */ 
  xColorTaskHandle = xTaskCreateStatic(
            ColorLED_Test,           //LED测试函数，PC13以500ms间隔亮灭一次
            "ColorTask",        //光任务
            128,                //栈大小，这里提供了栈的大小（长度）
            NULL,               //无传入的参数
            osPriorityNormal,   //优先级默认
            g_pucStackOfColorTask,  // 静态分配的栈，一个buffer，这里只提供了首地址，长度就是栈的大小
            &g_TCBofColorTask       // 取址TCB
  );

执行完上面的程序之后，会创建三个任务，放在 RadeyList[24] 这个链表里面~其他链表都是空的

这里是怎么调度的呢？

启动调度器后
执行

osStatus_t osKernelStart (void) {
  osStatus_t stat;

  if (IS_IRQ()) {
    stat = osErrorISR;
  }
  else {
    if (KernelState == osKernelReady) {
      KernelState = osKernelRunning;
      vTaskStartScheduler();
      stat = osOK;
    } else {
      stat = osError;
    }
  }
  return (stat);
}

执行完之后，这里就创建了一个空闲的任务

在这里插入图片描述

void vTaskStartScheduler( void )
{
BaseType_t xReturn;

	/* Add the idle task at the lowest priority. */
	#if( configSUPPORT_STATIC_ALLOCATION == 1 )
	{
		StaticTask_t *pxIdleTaskTCBBuffer = NULL;
		StackType_t *pxIdleTaskStackBuffer = NULL;
		uint32_t ulIdleTaskStackSize;

		/* The Idle task is created using user provided RAM - obtain the
		address of the RAM then create the idle task. */
		vApplicationGetIdleTaskMemory( &pxIdleTaskTCBBuffer, &pxIdleTaskStackBuffer, &ulIdleTaskStackSize );
		xIdleTaskHandle = xTaskCreateStatic(	prvIdleTask,
												configIDLE_TASK_NAME,
												ulIdleTaskStackSize,
												( void * ) NULL, /*lint !e961.  The cast is not redundant for all compilers. */
												( tskIDLE_PRIORITY | portPRIVILEGE_BIT ),
												pxIdleTaskStackBuffer,
												pxIdleTaskTCBBuffer ); /*lint !e961 MISRA exception, justified as it is not a redundant explicit cast to all supported compilers. */

		if( xIdleTaskHandle != NULL )
		{
			xReturn = pdPASS;
		}
		else
		{
			xReturn = pdFAIL;
		}
	}
	#else
	{
		/* The Idle task is being created using dynamically allocated RAM. */
		xReturn = xTaskCreate(	prvIdleTask,
								configIDLE_TASK_NAME,
								configMINIMAL_STACK_SIZE,
								( void * ) NULL,
								( tskIDLE_PRIORITY | portPRIVILEGE_BIT ),
								&xIdleTaskHandle ); /*lint !e961 MISRA exception, justified as it is not a redundant explicit cast to all supported compilers. */
	}
	#endif /* configSUPPORT_STATIC_ALLOCATION */

	#if ( configUSE_TIMERS == 1 )
	{
		if( xReturn == pdPASS )
		{
			xReturn = xTimerCreateTimerTask();
		}
		else
		{
			mtCOVERAGE_TEST_MARKER();
		}
	}
	#endif /* configUSE_TIMERS */

	if( xReturn == pdPASS )
	{
		/* freertos_tasks_c_additions_init() should only be called if the user
		definable macro FREERTOS_TASKS_C_ADDITIONS_INIT() is defined, as that is
		the only macro called by the function. */
		#ifdef FREERTOS_TASKS_C_ADDITIONS_INIT
		{
			freertos_tasks_c_additions_init();
		}
		#endif

		/* Interrupts are turned off here, to ensure a tick does not occur
		before or during the call to xPortStartScheduler().  The stacks of
		the created tasks contain a status word with interrupts switched on
		so interrupts will automatically get re-enabled when the first task
		starts to run. */
		portDISABLE_INTERRUPTS();

		#if ( configUSE_NEWLIB_REENTRANT == 1 )
		{
			/* Switch Newlib's _impure_ptr variable to point to the _reent
			structure specific to the task that will run first. */
			_impure_ptr = &( pxCurrentTCB->xNewLib_reent );
		}
		#endif /* configUSE_NEWLIB_REENTRANT */

		xNextTaskUnblockTime = portMAX_DELAY;
		xSchedulerRunning = pdTRUE;
		xTickCount = ( TickType_t ) 0U;

		/* If configGENERATE_RUN_TIME_STATS is defined then the following
		macro must be defined to configure the timer/counter used to generate
		the run time counter time base.   NOTE:  If configGENERATE_RUN_TIME_STATS
		is set to 0 and the following line fails to build then ensure you do not
		have portCONFIGURE_TIMER_FOR_RUN_TIME_STATS() defined in your
		FreeRTOSConfig.h file. */
		portCONFIGURE_TIMER_FOR_RUN_TIME_STATS();

		/* Setting up the timer tick is hardware specific and thus in the
		portable interface. */
		if( xPortStartScheduler() != pdFALSE )
		{
			/* Should not reach here as if the scheduler is running the
			function will not return. */
		}
		else
		{
			/* Should only reach here if a task calls xTaskEndScheduler(). */
		}
	}
	else
	{
		/* This line will only be reached if the kernel could not be started,
		because there was not enough FreeRTOS heap to create the idle task
		or the timer task. */
		configASSERT( xReturn != errCOULD_NOT_ALLOCATE_REQUIRED_MEMORY );
	}

	/* Prevent compiler warnings if INCLUDE_xTaskGetIdleTaskHandle is set to 0,
	meaning xIdleTaskHandle is not used anywhere else. */
	( void ) xIdleTaskHandle;
}