struct list {

  	struct list *next, *prev;

  };
  
  static inline void
  list_init(struct list *list)
  {

  	list->next = list;
  	list->prev = list;

  }
  
  static inline int
  list_empty(struct list *list)
  {

  	return list->next == list;

  }
  
  static inline void
  list_insert(struct list *link, struct list *new_link)
  {

  	new_link->prev		= link->prev;
  	new_link->next		= link;
  	new_link->prev->next	= new_link;
  	new_link->next->prev	= new_link;

  }
  
  static inline void
  list_append(struct list *list, struct list *new_link)
  {

  	list_insert((struct list *)list, new_link);

  }
  
  static inline void
  list_prepend(struct list *list, struct list *new_link)
  {

  	list_insert(list->next, new_link);

  }
  
  static inline void
  list_remove(struct list *link)
  {

  	link->prev->next = link->next;
  	link->next->prev = link->prev;

  }
  
  #define list_entry(link, type, member) \
  	((type *)((char *)(link)-(unsigned long)(&((type *)0)->member)))
  
  #define list_head(list, type, member)		\
  	list_entry((list)->next, type, member)
  
  #define list_tail(list, type, member)		\
  	list_entry((list)->prev, type, member)
  
  #define list_next(elm, member)					\
  	list_entry((elm)->member.next, typeof(*elm), member)
  
  #define list_for_each_entry(pos, list, member)			\
  	for (pos = list_head(list, typeof(*pos), member);	\
  	     &pos->member != (list);				\
  	     pos = list_next(pos, member))