/*
 * Definition of the only type of object that a list can contain.
 */
struct xLIST_ITEM
{
	configLIST_VOLATILE portTickType xItemValue;	/*< The value being listed.  In most cases this is used to sort the list in descending order. */
	struct xLIST_ITEM * configLIST_VOLATILE pxNext;	/*< 指向链表中下一个元素的指针. */
	struct xLIST_ITEM * configLIST_VOLATILE pxPrevious;/*< 指向链表中上一个元素的指针. */
	void * pvOwner;									/*< 指向链表元素(一般是任务控制块(TCB))的指针.  There is therefore a two way link between the object containing the list item and the list item itself. */
	void * configLIST_VOLATILE pvContainer;			/*< 指向存储元素的链表的指针. */
};
typedef struct xLIST_ITEM xListItem;				/* For some reason lint wants this as two separate definitions. */

struct xMINI_LIST_ITEM
{
	configLIST_VOLATILE portTickType xItemValue;
	struct xLIST_ITEM * configLIST_VOLATILE pxNext;
	struct xLIST_ITEM * configLIST_VOLATILE pxPrevious;
};
typedef struct xMINI_LIST_ITEM xMiniListItem;

/*
 * Definition of the type of queue used by the scheduler.
 */
typedef struct xLIST
{
	configLIST_VOLATILE unsigned portBASE_TYPE uxNumberOfItems;
	xListItem * configLIST_VOLATILE pxIndex;		/*< Used to walk through the list.  Points to the last item returned by a call to pvListGetOwnerOfNextEntry (). */
	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;

/*
 * Access function to obtain the owner of the next entry in a list.
 *
 * The list member pxIndex is used to walk through a list.  Calling
 * listGET_OWNER_OF_NEXT_ENTRY increments pxIndex to the next item in the list
 * and returns that entries pxOwner parameter.  Using multiple calls to this
 * function it is therefore possible to move through every item contained in
 * a list.
 *
 * The pxOwner parameter of a list item is a pointer to the object that owns
 * the list item.  In the scheduler this is normally a task control block.
 * The pxOwner parameter effectively creates a two way link between the list
 * item and its owner.
 *
 * @param pxList The list from which the next item owner is to be returned.
 *
 * \page listGET_OWNER_OF_NEXT_ENTRY listGET_OWNER_OF_NEXT_ENTRY
 * \ingroup LinkedList
 */
#define listGET_OWNER_OF_NEXT_ENTRY( pxTCB, pxList ) \
{	\
xList * const pxConstList = ( pxList );			\
	/* Increment the index to the next item and return the item, ensuring */\
	/* we don't return the marker used at the end of the list.  */	\
	( pxConstList )->pxIndex = ( pxConstList )->pxIndex->pxNext;	\
	if( ( void * ) ( pxConstList )->pxIndex == ( void * ) &( ( pxConstList )->xListEnd ) )	\
	{	    \
		( pxConstList )->pxIndex = ( pxConstList )->pxIndex->pxNext;	\
	}		\
	( pxTCB ) = ( pxConstList )->pxIndex->pvOwner;		\
}