数据结构的基石链表头FreeRTOS 的所有内核对象（任务、队列、事件组等）都通过List_t组织。它本质上是一个带哨兵节点的双向循环链表，并且链表中的元素按xItemValue升序排列。//list.h typedef struct xLIST { listFIRST_LIST_INTEGRITY_CHECK_VALUE /** Set to a known value if configUSE_LIST_DATA_INTEGRITY_CHECK_BYTES is set to 1. */ configLIST_VOLATILE UBaseType_t uxNumberOfItems; ListItem_t * configLIST_VOLATILE pxIndex; /** Used to walk through the list. Points to the last item returned by a call to listGET_OWNER_OF_NEXT_ENTRY (). */ MiniListItem_t 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. */ listSECOND_