本次学习版本为5.2.0
*******************File:list.h & list.c*************************
1、几个重要的数据结构
struct xLIST_ITEM
{
portTickType xItemValue; /*< The value being listed. In most cases this is used to sort the list in descending order. */
volatile struct xLIST_ITEM * pxNext; /*< Pointer to the next xListItem in the list. */
volatile struct xLIST_ITEM * pxPrevious;/*< Pointer to the previous xListItem in the list. */
void * pvOwner; /*< Pointer to the object (normally a TCB) that contains the list item. There is therefore a two way link between the object containing the list item and the list item itself. */
void * pvContainer; /*< Pointer to the list in which this list item is placed (if any). */
};
typedef struct xLIST_ITEM xListItem; /* For some reason lint wants this as two separate definitions. */
| xItemValue |
| * pxNext |
| * pxPrevious |
| * pvOwner |
| * pvContainer |
xListItem的结构
struct xMINI_LIST_ITEM
{
portTickType xItemValue;
volatile struct xLIST_ITEM *pxNext;
volatile struct xLIST_ITEM *pxPrevious;
};
typedef struct xMINI_LIST_ITEM xMiniListItem;
typedef struct xLIST
{
volatile unsigned portBASE_TYPE uxNumberOfItems;
volatile xListItem * pxIndex; /*< Used to walk through the list. Points to the last item returned by a call to pvListGetOwnerOfNextEntry (). */
volatile xMiniListItem xListEnd; /*< List item that contains the maximum possible item value meaning it is always at the end of the list and is therefore used as a marker. */
} xList;
| uxNumberOfItems |
| * pxIndex |
xListEnd
|
xList的结构
xList是一个双向量表。xListEnd 只是作为一个标志，标志你此刻访问的是链表的尾部。它不存放有效的数据。它的next节点指向xList的头节点。
一个疑问：pxList->xListEnd.xItemValue到底做什么用？
2. 几个宏定义实现了对链表上节点的各种操作：
#define listSET_LIST_ITEM_OWNER( pxListItem, pxOwner ) ( pxListItem )->pvOwner = ( void * ) pxOwner
#define listSET_LIST_ITEM_VALUE( pxListItem, xValue ) ( pxListItem )->xItemValue = xValue
#define listGET_LIST_ITEM_VALUE( pxListItem ) ( ( pxListItem )->xItemValue )
#define listLIST_IS_EMPTY( pxList ) ( ( pxList )->uxNumberOfItems == ( unsigned portBASE_TYPE ) 0 )
#define listCURRENT_LIST_LENGTH( pxList ) ( ( pxList )->uxNumberOfItems )
#define listGET_OWNER_OF_NEXT_ENTRY( pxTCB, pxList )
#define listGET_OWNER_OF_HEAD_ENTRY( pxList ) ( ( pxList->uxNumberOfItems != ( unsigned portBASE_TYPE ) 0 ) ? ( (&( pxList->xListEnd ))->pxNext->pvOwner ) : ( NULL ) )
#define listIS_CONTAINED_WITHIN( pxList, pxListItem ) ( ( pxListItem )->pvContainer == ( void * ) pxList )
3.定义了几个链表操作函数：
void vListInitialise( xList *pxList );
void vListInitialiseItem( xListItem *pxItem );
void vListInsert( xList *pxList, xListItem *pxNewListItem ); 按照xListItem上的xItemValue值排序，然后插入。保证xItemValue是递增的。
void vListInsertEnd( xList *pxList, xListItem *pxNewListItem ); 直接插到pxList->index的后面。
void vListRemove( xListItem *pxItemToRemove );
*******************File:task.h & task.c*************************
1、任务控制块结构
typedef struct tskTaskControlBlock
{
volatile portSTACK_TYPE *pxTopOfStack; /*< Points to the location of the last item placed on the tasks stack. THIS MUST BE THE FIRST MEMBER OF THE STRUCT. */
xListItem xGenericListItem; /*< List item used to place the TCB in ready and blocked queues. */
xListItem xEventListItem; /*< List item used to place the TCB in event lists. */
unsigned portBASE_TYPE uxPriority; /*< The priority of the task where 0 is the lowest priority. */
portSTACK_TYPE *pxStack; /*< Points to the start of the stack. */
signed portCHAR pcTaskName[ configMAX_TASK_NAME_LEN ];/*< Descriptive name given to the task when created. Facilitates debugging only. */
#if ( portSTACK_GROWTH > 0 )
portSTACK_TYPE *pxEndOfStack; /*< Used for stack overflow checking on architectures where the stack grows up from low memory. */
#endif
#if ( portCRITICAL_NESTING_IN_TCB == 1 )
unsigned portBASE_TYPE uxCriticalNesting;
#endif
#if ( configUSE_TRACE_FACILITY == 1 )
unsigned portBASE_TYPE uxTCBNumber; /*< This is used for tracing the scheduler and making debugging easier only. */
#endif
#if ( configUSE_MUTEXES == 1 )
unsigned portBASE_TYPE uxBasePriority;
#endif
#if ( configUSE_APPLICATION_TASK_TAG == 1 )
pdTASK_HOOK_CODE pxTaskTag;
#endif
} tskTCB;
*pxTopOfStack
|
xGenericListItem
|
xEventListItem
|
uxPriority
|
*pxStack
|
pcTaskName
|
*pxEndOfStack
|
uxCriticalNesting
|
uxTCBNumber
|
uxBasePriority
|
pxTaskTag
|
任务控制块的结构
2、各个API函数。
/*-----------------------------------------------------------
* TASK CREATION API
*----------------------------------------------------------*/
portBASE_TYPE xTaskCreate(
pdTASK_CODE pvTaskCode,
const portCHAR * const pcName,
unsigned portSHORT usStackDepth,
void *pvParameters,
unsigned portBASE_TYPE uxPriority,
xTaskHandle *pvCreatedTask
);
void vTaskCode( void * pvParameters )
{
for( ;; )
{
// Task code goes here.
}
}
// Function that creates a task.
void vOtherFunction( void )
{
static unsigned char ucParameterToPass;
xTaskHandle xHandle;
// Create the task, storing the handle. Note that the passed parameter ucParameterToPass
// must exist for the lifetime of the task, so in this case is declared static. If it was just an
// an automatic stack variable it might no longer exist, or at least have been corrupted, by the time
// the new time attempts to access it.
xTaskCreate( vTaskCode, "NAME", STACK_SIZE, &ucParameterToPass, tskIDLE_PRIORITY, &xHandle );
// Use the handle to delete the task.
vTaskDelete( xHandle );
}
3、对于为什么要用到两个delaylist，我一直很不解。在vTaskIncrementTick（）函数中：
if( uxSchedulerSuspended == ( unsigned portBASE_TYPE ) pdFALSE )
{
++xTickCount;
if( xTickCount == ( portTickType ) 0 )
{
xList *pxTemp;
/* Tick count has overflowed so we need to swap the delay lists. XXXXXXXXXXXXXXXXXXXXXXXXXXXX
If there are any items in pxDelayedTaskList here then there is
an error! */
pxTemp = pxDelayedTaskList;
pxDelayedTaskList = pxOverflowDelayedTaskList;
pxOverflowDelayedTaskList = pxTemp;
xNumOfOverflows++;
}
/* See if this tick has made a timeout expire. */
prvCheckDelayedTasks();
}
明白是为什么了！因为FreeRTOS系统的时钟管理原理是，每发生一个始终节拍，xTimeCount加1.这样有一种可能是，xTimeCount会溢出。所以在挂起一个任务的时候，计算xTimeToWake值与xTimeCount的关系。如果大，则是计数器正常，任务进入pxDelayedTaskList里面。而如果小了，说明xTimeCount溢出了。则该任务要进入到pxOverflowDelayedTaskList里面。这样，随着时间节拍数的增加致溢出时，挂起队列自然而然要进行切换。这也是为什么学要两个delayedList的原因啦！
*******************File:queue.h & queue.c*************************
1、queue的结构定义。
typedef struct QueueDefinition
{
signed portCHAR *pcHead; /*< Points to the beginning of the queue storage area. */
signed portCHAR *pcTail; /*< Points to the byte at the end of the queue storage area. Once more byte is allocated than necessary to store the queue items, this is used as a marker. */
signed portCHAR *pcWriteTo; /*< Points to the free next place in the storage area. */
signed portCHAR *pcReadFrom; /*< Points to the last place that a queued item was read from. */
xList xTasksWaitingToSend; /*< List of tasks that are blocked waiting to post onto this queue. Stored in priority order. */
xList xTasksWaitingToReceive; /*< List of tasks that are blocked waiting to read from this queue. Stored in priority order. */
volatile unsigned portBASE_TYPE uxMessagesWaiting;/*< The number of items currently in the queue. */
unsigned portBASE_TYPE uxLength; /*< The length of the queue defined as the number of items it will hold, not the number of bytes. */
unsigned portBASE_TYPE uxItemSize; /*< The size of each items that the queue will hold. */
signed portBASE_TYPE xRxLock; /*< Stores the number of items received from the queue (removed from the queue) while the queue was locked. Set to queueUNLOCKED when the queue is not locked. */
signed portBASE_TYPE xTxLock; /*< Stores the number of items transmitted to the queue (added to the queue) while the queue was locked. Set to queueUNLOCKED when the queue is not locked. */
} xQUEUE;
*******************File:heap_2.c*************************
1、两个重要的数据结构
static struct xRTOS_HEAP
{
unsigned portLONG ulDummy;
unsigned portCHAR ucHeap[ configTOTAL_HEAP_SIZE ];
} xHeap;
typedef struct A_BLOCK_LINK
{
struct A_BLOCK_LINK *pxNextFreeBlock; /*<< The next free block in the list. */
size_t xBlockSize; /*<< The size of the free block. */
} xBlockLink;
接下来，就是移植咯！
