FreeRTOS進階之任務建立完全解析

        BaseType_t xTaskCreate(
                            TaskFunction_tp vTaskCode,
                            const char * constpcName,
                            unsigned short usStackDepth,
                            void *pvParameters,
                            UBaseType_t uxPriority,
                            TaskHandle_t *pvCreatedTask
                          );

#define xTaskCreate( pvTaskCode, pcName, usStackDepth,pvParameters, uxPriority, pxCreatedTask )    
      xTaskGenericCreate( ( pvTaskCode ),( pcName ), ( usStackDepth ), ( pvParameters ), ( uxPriority ), ( pxCreatedTask), ( NULL ), ( NULL ), ( NULL ) )

typedef struct tskTaskControlBlock
{
    volatile StackType_t    *pxTopOfStack; /*當前堆疊的棧頂,必須位於結構體的第一項*/
    #if ( portUSING_MPU_WRAPPERS == 1 )
        xMPU_SETTINGS   xMPUSettings;      /*MPU設定,必須位於結構體的第二項*/
    #endif
    ListItem_t          xStateListItem; /*任務的狀態列表項，以參照的方式表示任務的狀態*/
    ListItem_t          xEventListItem;    /*事件列表項，用於將任務以參照的方式掛接到事件列表*/
    UBaseType_t         uxPriority;        /*儲存任務優先順序，0表示最低優先順序*/
    StackType_t         *pxStack;           /*指向堆疊的起始位置*/
    char               pcTaskName[ configMAX_TASK_NAME_LEN ];/*任務名字*/
    #if ( portSTACK_GROWTH > 0 )
        StackType_t     *pxEndOfStack;     /*指向堆疊的尾部*/
    #endif
    #if ( portCRITICAL_NESTING_IN_TCB == 1 )
        UBaseType_t     uxCriticalNesting; /*儲存臨界區巢狀深度*/
    #endif
    #if ( configUSE_TRACE_FACILITY == 1 )
        UBaseType_t     uxTCBNumber;       /*儲存一個數值，每個任務都有唯一的值*/
        UBaseType_t     uxTaskNumber;      /*儲存一個特定數值*/
    #endif
    #if ( configUSE_MUTEXES == 1 )
        UBaseType_t     uxBasePriority;    /*儲存任務的基礎優先順序*/
        UBaseType_t     uxMutexesHeld;
    #endif
    #if ( configUSE_APPLICATION_TASK_TAG == 1 )
        TaskHookFunction_t pxTaskTag;
    #endif
    #if( configNUM_THREAD_LOCAL_STORAGE_POINTERS > 0 )
        void *pvThreadLocalStoragePointers[configNUM_THREAD_LOCAL_STORAGE_POINTERS ];
    #endif
    #if( configGENERATE_RUN_TIME_STATS == 1 )
        uint32_t        ulRunTimeCounter;  /*記錄任務在執行狀態下執行的總時間*/
    #endif
    #if ( configUSE_NEWLIB_REENTRANT == 1 )
        /* 為任務分配一個Newlibreent結構體變數。Newlib是一個C庫函數，並非FreeRTOS維護，FreeRTOS也不對使用結果負責。如果使用者使用Newlib，必須熟知Newlib的細節*/
        struct _reent xNewLib_reent;
    #endif
    #if( configUSE_TASK_NOTIFICATIONS == 1 )
        volatile uint32_t ulNotifiedValue; /*與任務通知相關*/
        volatile uint8_t ucNotifyState;
    #endif
    #if( configSUPPORT_STATIC_ALLOCATION == 1 )
        uint8_t ucStaticAllocationFlags; /* 如果堆疊由靜態陣列分配，則設定為pdTRUE，如果堆疊是動態分配的，則設定為pdFALSE*/
    #endif
    #if( INCLUDE_xTaskAbortDelay == 1 )
        uint8_t ucDelayAborted;
    #endif
} tskTCB;
typedef tskTCB TCB_t;

    TaskHandle_t xHandle；
    xTaskCreate(vTask_A,」Task A」,120,NULL,1,&xHandle);

static TCB_t *prvAllocateTCBAndStack( const uint16_t usStackDepth, StackType_t * const puxStackBuffer, TCB_t * const pxTaskBuffer )
{
TCB_t *pxNewTCB;
StackType_t *pxStack;
 
    /* 分配堆疊空間*/
    pxStack = ( StackType_t * ) pvPortMallocAligned( ( ( ( size_t ) usStackDepth ) * sizeof( StackType_t ) ), puxStackBuffer );
    if( pxStack != NULL )
    {
        /* 分配TCB空間 */
        pxNewTCB = ( TCB_t * ) pvPortMallocAligned( sizeof( TCB_t ), pxTaskBuffer );
        if( pxNewTCB != NULL )
        {
            /* 將堆疊起始位置存入TCB*/
            pxNewTCB->pxStack = pxStack;
        }
        else
        {
            /* 如果TCB分配失敗，釋放之前申請的堆疊空間 */
            if( puxStackBuffer == NULL )
            {
                vPortFree( pxStack );
            }
        }
    }
    else
    {
        pxNewTCB = NULL;
    }
    if( pxNewTCB != NULL )
    {
        /* 如果需要，使用固定值填充堆疊 */
        #if( ( configCHECK_FOR_STACK_OVERFLOW> 1 ) || ( configUSE_TRACE_FACILITY == 1 ) || ( INCLUDE_uxTaskGetStackHighWaterMark== 1 ) )
        {
            /* 僅用於偵錯 */
            ( void ) memset( pxNewTCB->pxStack, ( int ) tskSTACK_FILL_BYTE, ( size_t ) usStackDepth * sizeof( StackType_t ) );
        }
        #endif
    }
    return pxNewTCB;
}

static void prvInitialiseTCBVariables( TCB_t * const pxTCB, const char * const pcName, UBaseType_t uxPriority,   
                              const MemoryRegion_t * const xRegions, const uint16_t usStackDepth )
{
UBaseType_t x;
    /* 將任務描述存入TCB */
    for( x = ( UBaseType_t ) 0; x < ( UBaseType_t ) configMAX_TASK_NAME_LEN; x++ )
    {
        pxTCB->pcTaskName[ x ] = pcName[ x ];
        if( pcName[ x ] == 0x00 )
        {
            break;
        }
    }
    /* 確保字串有結束 */
    pxTCB->pcTaskName[ configMAX_TASK_NAME_LEN - 1 ] = '';
 
    /* 調整優先順序，宏configMAX_PRIORITIES的值在FreeRTOSConfig.h中設定 */
    if( uxPriority >= ( UBaseType_t ) configMAX_PRIORITIES )
    {
        uxPriority = ( UBaseType_t ) configMAX_PRIORITIES - ( UBaseType_t ) 1U;
    }
    pxTCB->uxPriority = uxPriority;
    #if ( configUSE_MUTEXES == 1 )              /*使用互斥量*/
    {  
        pxTCB->uxBasePriority = uxPriority;
        pxTCB->uxMutexesHeld = 0;
    }
    #endif /* configUSE_MUTEXES */
    /*初始化列表項*/
    vListInitialiseItem( &( pxTCB->xStateListItem ) );
    vListInitialiseItem( &( pxTCB->xEventListItem ) );
    /* 設定列表項xStateListItem的成員pvOwner指向當前任務控制塊 */
    listSET_LIST_ITEM_OWNER( &( pxTCB->xStateListItem ), pxTCB );
    /* 設定列表項xEventListItem的成員xItemValue*/
    listSET_LIST_ITEM_VALUE( &( pxTCB->xEventListItem ), ( TickType_t ) configMAX_PRIORITIES - ( TickType_t ) uxPriority );
    /* 設定列表項xEventListItem的成員pvOwner指向當前任務控制塊 */
    listSET_LIST_ITEM_OWNER( &( pxTCB->xEventListItem ), pxTCB );
    #if ( portCRITICAL_NESTING_IN_TCB ==1 )    /*使能臨界區巢狀功能*/
    {  
        pxTCB->uxCriticalNesting = ( UBaseType_t ) 0U;
    }
    #endif /* portCRITICAL_NESTING_IN_TCB */
    #if ( configUSE_APPLICATION_TASK_TAG == 1 ) /*使能任務標籤功能*/
    {  
        pxTCB->pxTaskTag = NULL;
    }
    #endif /* configUSE_APPLICATION_TASK_TAG */
    #if ( configGENERATE_RUN_TIME_STATS == 1 )  /*使能事件統計功能*/
    {
        pxTCB->ulRunTimeCounter = 0UL;
    }
    #endif /* configGENERATE_RUN_TIME_STATS */
    #if ( portUSING_MPU_WRAPPERS == 1 )         /*使用MPU功能*/
    {
        vPortStoreTaskMPUSettings( &( pxTCB->xMPUSettings ), xRegions, pxTCB->pxStack, usStackDepth );
    }
    #else /* portUSING_MPU_WRAPPERS */
    {
        ( void ) xRegions;
        ( void ) usStackDepth;
    }
    #endif /* portUSING_MPU_WRAPPERS */
    #if( configNUM_THREAD_LOCAL_STORAGE_POINTERS != 0 )/*使能執行緒本地儲存指標*/
    {
        for( x = 0; x < ( UBaseType_t )configNUM_THREAD_LOCAL_STORAGE_POINTERS; x++ )
        {
            pxTCB->pvThreadLocalStoragePointers[ x ] = NULL;
        }
    }
    #endif
    #if ( configUSE_TASK_NOTIFICATIONS == 1 )   /*使能任務通知功能*/
    {
        pxTCB->ulNotifiedValue = 0;
        pxTCB->ucNotifyState = taskNOT_WAITING_NOTIFICATION;
    }
    #endif
    #if ( configUSE_NEWLIB_REENTRANT == 1 )     /*使用Newlib*/
    {
        _REENT_INIT_PTR( ( &( pxTCB->xNewLib_reent ) ) );
    }
    #endif
    #if( INCLUDE_xTaskAbortDelay == 1 )
    {
        pxTCB->ucDelayAborted = pdFALSE;
    }
    #endif
}

PRIVILEGED_DATAstatic List_t pxReadyTasksLists[ configMAX_PRIORITIES ];/*按照優先順序排序的就緒態任務*/
PRIVILEGED_DATAstatic List_t xDelayedTaskList1;                        /*延時的任務 */
PRIVILEGED_DATAstatic List_t xDelayedTaskList2;                        /*延時的任務 */
PRIVILEGED_DATAstatic List_t xPendingReadyList;                        /*任務已就緒,但排程器被掛起 */
#if (INCLUDE_vTaskDelete == 1 )
    PRIVILEGED_DATA static List_t xTasksWaitingTermination;             /*任務已經被刪除,但記憶體尚未釋放*/
#endif
#if (INCLUDE_vTaskSuspend == 1 )
    PRIVILEGED_DATA static List_t xSuspendedTaskList;                   /*當前掛起的任務*/
#endif

static void prvInitialiseTaskLists( void )
{
UBaseType_tuxPriority;
    for( uxPriority = ( UBaseType_t ) 0U; uxPriority < ( UBaseType_t ) configMAX_PRIORITIES; uxPriority++ )
    {
        vListInitialise( &( pxReadyTasksLists[ uxPriority ] ) );
    }
    vListInitialise( &xDelayedTaskList1 );
    vListInitialise( &xDelayedTaskList2 );
    vListInitialise( &xPendingReadyList );
    #if ( INCLUDE_vTaskDelete == 1 )
    {
        vListInitialise( &xTasksWaitingTermination );
    }
    #endif /* INCLUDE_vTaskDelete */
 
    #if ( INCLUDE_vTaskSuspend == 1 )
    {
        vListInitialise( &xSuspendedTaskList );
    }
    #endif /* INCLUDE_vTaskSuspend */
    /* Start with pxDelayedTaskList using list1 and the pxOverflowDelayedTaskListusing list2. */
    pxDelayedTaskList = &xDelayedTaskList1;
    pxOverflowDelayedTaskList = &xDelayedTaskList2;
}

if( xSchedulerRunning == pdFALSE )
{
    if( pxCurrentTCB->uxPriority <= uxPriority )
    {
        pxCurrentTCB = pxNewTCB;
    }
    else
    {
        mtCOVERAGE_TEST_MARKER();
    }
}

#defineprvAddTaskToReadyList( pxTCB )                        
    taskRECORD_READY_PRIORITY( ( pxTCB)->uxPriority );       
    vListInsertEnd( &( pxReadyTasksLists[ (pxTCB )->uxPriority ] ), &( ( pxTCB )->xStateListItem ) );

 if( xReturn == pdPASS )
    {
        if( xSchedulerRunning != pdFALSE )
        {
            /* 如果新建立的任務優先順序大於當前任務優先順序，則新建立的任務應該被立即執行。*/
            if(pxCurrentTCB->uxPriority < uxPriority )
            {
                taskYIELD_IF_USING_PREEMPTION();
            }
        }
    }