【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 theaddress 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 userdefinable macro FREERTOS_TASKS_C_ADDITIONS_INIT() is defined, as that isthe 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 occurbefore or during the call to xPortStartScheduler().  The stacks ofthe created tasks contain a status word with interrupts switched onso interrupts will automatically get re-enabled when the first taskstarts to run. */portDISABLE_INTERRUPTS();#if ( configUSE_NEWLIB_REENTRANT == 1 ){/* Switch Newlib's _impure_ptr variable to point to the _reentstructure 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 followingmacro must be defined to configure the timer/counter used to generatethe run time counter time base.   NOTE:  If configGENERATE_RUN_TIME_STATSis set to 0 and the following line fails to build then ensure you do nothave portCONFIGURE_TIMER_FOR_RUN_TIME_STATS() defined in yourFreeRTOSConfig.h file. */portCONFIGURE_TIMER_FOR_RUN_TIME_STATS();/* Setting up the timer tick is hardware specific and thus in theportable interface. */if( xPortStartScheduler() != pdFALSE ){/* Should not reach here as if the scheduler is running thefunction 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 taskor 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;
}