列表项的pxNext和pxPrevious是在什么地方初始化？

struct xLIST_ITEM
{
        listFIRST_LIST_ITEM_INTEGRITY_CHECK_VALUE                        /*< Set to a known value if configUSE_LIST_DATA_INTEGRITY_CHECK_BYTES is set to 1. */
        configLIST_VOLAtiLE TickType_t xItemValue;                        /*< The value being listed.  In most cases this is used to sort the list in descending order. */
        struct xLIST_ITEM * configLIST_VOLATILE pxNext;                /*< Pointer to the next ListItem_t in the list. */
        struct xLIST_ITEM * configLIST_VOLATILE pxPrevious;        /*< Pointer to the previous ListItem_t 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 * configLIST_VOLATILE pvContainer;                                /*< Pointer to the list in which this list item is placed (if any). */
        listSECOND_LIST_ITEM_INTEGRITY_CHECK_VALUE                        /*< Set to a known value if configUSE_LIST_DATA_INTEGRITY_CHECK_BYTES is set to 1. */
};
typedef struct xLIST_ITEM ListItem_t;                                        /* For some reason lint wants this as two separate definitions. */