text: #ifndef _LINUX_LIST_H
  #define _LINUX_LIST_H
  
  #include <linux/stddef.h>
  #include <linux/poison.h>
  
  #ifndef ARCH_HAS_PREFETCH
  #define ARCH_HAS_PREFETCH
  static inline void prefetch(const void *x) {;}
  #endif
  
  /*
   * Simple doubly linked list implementation.
   *
   * Some of the internal functions ("__xxx") are useful when
   * manipulating whole lists rather than single entries, as
   * sometimes we already know the next/prev entries and we can
   * generate better code by using them directly rather than
   * using the generic single-entry routines.
   */
  
  struct list_head {
  	struct list_head *next, *prev;
  };
  
  #define LIST_HEAD_INIT(name) { &(name), &(name) }
  
  #define LIST_HEAD(name) \
  	struct list_head name = LIST_HEAD_INIT(name)
  
  static inline void INIT_LIST_HEAD(struct list_head *list)
  {
  	list->next = list;
  	list->prev = list;
  }
  
  /*
   * Insert a new entry between two known consecutive entries.
   *
   * This is only for internal list manipulation where we know
   * the prev/next entries already!
   */
  static inline void __list_add(struct list_head *new,
  			      struct list_head *prev,
  			      struct list_head *next)
  {
  	next->prev = new;
  	new->next = next;
  	new->prev = prev;
  	prev->next = new;
  }
  
  /**
   * list_add - add a new entry
   * @new: new entry to be added
   * @head: list head to add it after
   *
   * Insert a new entry after the specified head.
   * This is good for implementing stacks.
   */
  static inline void list_add(struct list_head *new, struct list_head *head)
  {
  	__list_add(new, head, head->next);
  }
  
  /**
   * list_add_tail - add a new entry
   * @new: new entry to be added
   * @head: list head to add it before
   *
   * Insert a new entry before the specified head.
   * This is useful for implementing queues.
   */
  static inline void list_add_tail(struct list_head *new, struct list_head *head)
  {
  	__list_add(new, head->prev, head);
  }
  
  /*
   * Delete a list entry by making the prev/next entries
   * point to each other.
   *
   * This is only for internal list manipulation where we know
   * the prev/next entries already!
   */
  static inline void __list_del(struct list_head *prev, struct list_head *next)
  {
  	next->prev = prev;
  	prev->next = next;
  }
  
  /**
   * list_del - deletes entry from list.
   * @entry: the element to delete from the list.
   * Note: list_empty() on entry does not return true after this, the entry is
   * in an undefined state.
   */
  static inline void list_del(struct list_head *entry)
  {
  	__list_del(entry->prev, entry->next);
  	entry->next = LIST_POISON1;
  	entry->prev = LIST_POISON2;
  }
  
  /**
   * list_replace - replace old entry by new one
   * @old : the element to be replaced
   * @new : the new element to insert
   *
   * If @old was empty, it will be overwritten.
   */
  static inline void list_replace(struct list_head *old,
  				struct list_head *new)
  {
  	new->next = old->next;
  	new->next->prev = new;
  	new->prev = old->prev;
  	new->prev->next = new;
  }
  
  static inline void list_replace_init(struct list_head *old,
  					struct list_head *new)
  {
  	list_replace(old, new);
  	INIT_LIST_HEAD(old);
  }
  
  /**
   * list_del_init - deletes entry from list and reinitialize it.
   * @entry: the element to delete from the list.
   */
  static inline void list_del_init(struct list_head *entry)
  {
  	__list_del(entry->prev, entry->next);
  	INIT_LIST_HEAD(entry);
  }
  
  /**
   * list_move - delete from one list and add as another's head
   * @list: the entry to move
   * @head: the head that will precede our entry
   */
  static inline void list_move(struct list_head *list, struct list_head *head)
  {
  	__list_del(list->prev, list->next);
  	list_add(list, head);
  }
  
  /**
   * list_move_tail - delete from one list and add as another's tail
   * @list: the entry to move
   * @head: the head that will follow our entry
   */
  static inline void list_move_tail(struct list_head *list,
  				  struct list_head *head)
  {
  	__list_del(list->prev, list->next);
  	list_add_tail(list, head);
  }
  
  /**
   * list_is_last - tests whether @list is the last entry in list @head
   * @list: the entry to test
   * @head: the head of the list
   */
  static inline int list_is_last(const struct list_head *list,
  				const struct list_head *head)
  {
  	return list->next == head;
  }
  
  /**
   * list_empty - tests whether a list is empty
   * @head: the list to test.
   */
  static inline int list_empty(const struct list_head *head)
  {
  	return head->next == head;
  }
  
  /**
   * list_empty_careful - tests whether a list is empty and not being modified
   * @head: the list to test
   *
   * Description:
   * tests whether a list is empty _and_ checks that no other CPU might be
   * in the process of modifying either member (next or prev)
   *
   * NOTE: using list_empty_careful() without synchronization
   * can only be safe if the only activity that can happen
   * to the list entry is list_del_init(). Eg. it cannot be used
   * if another CPU could re-list_add() it.
   */
  static inline int list_empty_careful(const struct list_head *head)
  {
  	struct list_head *next = head->next;
  	return (next == head) && (next == head->prev);
  }
  
  /**
   * list_is_singular - tests whether a list has just one entry.
   * @head: the list to test.
   */
  static inline int list_is_singular(const struct list_head *head)
  {
  	return !list_empty(head) && (head->next == head->prev);
  }
  
  static inline void __list_cut_position(struct list_head *list,
  		struct list_head *head, struct list_head *entry)
  {
  	struct list_head *new_first = entry->next;
  	list->next = head->next;
  	list->next->prev = list;
  	list->prev = entry;
  	entry->next = list;
  	head->next = new_first;
  	new_first->prev = head;
  }
  
  /**
   * list_cut_position - cut a list into two
   * @list: a new list to add all removed entries
   * @head: a list with entries
   * @entry: an entry within head, could be the head itself
   *	and if so we won't cut the list
   *
   * This helper moves the initial part of @head, up to and
   * including @entry, from @head to @list. You should
   * pass on @entry an element you know is on @head. @list
   * should be an empty list or a list you do not care about
   * losing its data.
   *
   */
  static inline void list_cut_position(struct list_head *list,
  		struct list_head *head, struct list_head *entry)
  {
  	if (list_empty(head))
  		return;
  	if (list_is_singular(head) &&
  		(head->next != entry && head != entry))
  		return;
  	if (entry == head)
  		INIT_LIST_HEAD(list);
  	else
  		__list_cut_position(list, head, entry);
  }
  
  static inline void __list_splice(const struct list_head *list,
  				 struct list_head *prev,
  				 struct list_head *next)
  {
  	struct list_head *first = list->next;
  	struct list_head *last = list->prev;
  
  	first->prev = prev;
  	prev->next = first;
  
  	last->next = next;
  	next->prev = last;
  }
  
  /**
   * list_splice - join two lists, this is designed for stacks
   * @list: the new list to add.
   * @head: the place to add it in the first list.
   */
  static inline void list_splice(const struct list_head *list,
  				struct list_head *head)
  {
  	if (!list_empty(list))
  		__list_splice(list, head, head->next);
  }
  
  /**
   * list_splice_tail - join two lists, each list being a queue
   * @list: the new list to add.
   * @head: the place to add it in the first list.
   */
  static inline void list_splice_tail(struct list_head *list,
  				struct list_head *head)
  {
  	if (!list_empty(list))
  		__list_splice(list, head->prev, head);
  }
  
  /**
   * list_splice_init - join two lists and reinitialise the emptied list.
   * @list: the new list to add.
   * @head: the place to add it in the first list.
   *
   * The list at @list is reinitialised
   */
  static inline void list_splice_init(struct list_head *list,
  				    struct list_head *head)
  {
  	if (!list_empty(list)) {
  		__list_splice(list, head, head->next);
  		INIT_LIST_HEAD(list);
  	}
  }
  
  /**
   * list_splice_tail_init - join two lists and reinitialise the emptied list
   * @list: the new list to add.
   * @head: the place to add it in the first list.
   *
   * Each of the lists is a queue.
   * The list at @list is reinitialised
   */
  static inline void list_splice_tail_init(struct list_head *list,
  					 struct list_head *head)
  {
  	if (!list_empty(list)) {
  		__list_splice(list, head->prev, head);
  		INIT_LIST_HEAD(list);
  	}
  }
  
  /**
   * list_entry - get the struct for this entry
   * @ptr:	the &struct list_head pointer.
   * @type:	the type of the struct this is embedded in.
   * @member:	the name of the list_struct within the struct.
   */
  #define list_entry(ptr, type, member) \
  	container_of(ptr, type, member)
  
  /**
   * list_first_entry - get the first element from a list
   * @ptr:	the list head to take the element from.
   * @type:	the type of the struct this is embedded in.
   * @member:	the name of the list_struct within the struct.
   *
   * Note, that list is expected to be not empty.
   */
  #define list_first_entry(ptr, type, member) \
  	list_entry((ptr)->next, type, member)
  
  /**
   * list_for_each	-	iterate over a list
   * @pos:	the &struct list_head to use as a loop cursor.
   * @head:	the head for your list.
   */
  #define list_for_each(pos, head) \
  	for (pos = (head)->next; prefetch(pos->next), pos != (head); \
  		pos = pos->next)
  
  /**
   * __list_for_each	-	iterate over a list
   * @pos:	the &struct list_head to use as a loop cursor.
   * @head:	the head for your list.
   *
   * This variant differs from list_for_each() in that it's the
   * simplest possible list iteration code, no prefetching is done.
   * Use this for code that knows the list to be very short (empty
   * or 1 entry) most of the time.
   */
  #define __list_for_each(pos, head) \
  	for (pos = (head)->next; pos != (head); pos = pos->next)
  
  /**
   * list_for_each_prev	-	iterate over a list backwards
   * @pos:	the &struct list_head to use as a loop cursor.
   * @head:	the head for your list.
   */
  #define list_for_each_prev(pos, head) \
  	for (pos = (head)->prev; prefetch(pos->prev), pos != (head); \
  		pos = pos->prev)
  
  /**
   * list_for_each_safe - iterate over a list safe against removal of list entry
   * @pos:	the &struct list_head to use as a loop cursor.
   * @n:		another &struct list_head to use as temporary storage
   * @head:	the head for your list.
   */
  #define list_for_each_safe(pos, n, head) \
  	for (pos = (head)->next, n = pos->next; pos != (head); \
  		pos = n, n = pos->next)
  
  /**
   * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
   * @pos:	the &struct list_head to use as a loop cursor.
   * @n:		another &struct list_head to use as temporary storage
   * @head:	the head for your list.
   */
  #define list_for_each_prev_safe(pos, n, head) \
  	for (pos = (head)->prev, n = pos->prev; \
  	     prefetch(pos->prev), pos != (head); \
  	     pos = n, n = pos->prev)
  
  /**
   * list_for_each_entry	-	iterate over list of given type
   * @pos:	the type * to use as a loop cursor.
   * @head:	the head for your list.
   * @member:	the name of the list_struct within the struct.
   */
  #define list_for_each_entry(pos, head, member)				\
  	for (pos = list_entry((head)->next, typeof(*pos), member);	\
  	     prefetch(pos->member.next), &pos->member != (head);	\
  	     pos = list_entry(pos->member.next, typeof(*pos), member))
  
  /**
   * list_for_each_entry_reverse - iterate backwards over list of given type.
   * @pos:	the type * to use as a loop cursor.
   * @head:	the head for your list.
   * @member:	the name of the list_struct within the struct.
   */
  #define list_for_each_entry_reverse(pos, head, member)			\
  	for (pos = list_entry((head)->prev, typeof(*pos), member);	\
  	     prefetch(pos->member.prev), &pos->member != (head);	\
  	     pos = list_entry(pos->member.prev, typeof(*pos), member))
  
  /**
   * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
   * @pos:	the type * to use as a start point
   * @head:	the head of the list
   * @member:	the name of the list_struct within the struct.
   *
   * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
   */
  #define list_prepare_entry(pos, head, member) \
  	((pos) ? : list_entry(head, typeof(*pos), member))
  
  /**
   * list_for_each_entry_continue - continue iteration over list of given type
   * @pos:	the type * to use as a loop cursor.
   * @head:	the head for your list.
   * @member:	the name of the list_struct within the struct.
   *
   * Continue to iterate over list of given type, continuing after
   * the current position.
   */
  #define list_for_each_entry_continue(pos, head, member) 		\
  	for (pos = list_entry(pos->member.next, typeof(*pos), member);	\
  	     prefetch(pos->member.next), &pos->member != (head);	\
  	     pos = list_entry(pos->member.next, typeof(*pos), member))
  
  /**
   * list_for_each_entry_continue_reverse - iterate backwards from the given point
   * @pos:	the type * to use as a loop cursor.
   * @head:	the head for your list.
   * @member:	the name of the list_struct within the struct.
   *
   * Start to iterate over list of given type backwards, continuing after
   * the current position.
   */
  #define list_for_each_entry_continue_reverse(pos, head, member)		\
  	for (pos = list_entry(pos->member.prev, typeof(*pos), member);	\
  	     prefetch(pos->member.prev), &pos->member != (head);	\
  	     pos = list_entry(pos->member.prev, typeof(*pos), member))
  
  /**
   * list_for_each_entry_from - iterate over list of given type from the current point
   * @pos:	the type * to use as a loop cursor.
   * @head:	the head for your list.
   * @member:	the name of the list_struct within the struct.
   *
   * Iterate over list of given type, continuing from current position.
   */
  #define list_for_each_entry_from(pos, head, member)			\
  	for (; prefetch(pos->member.next), &pos->member != (head);	\
  	     pos = list_entry(pos->member.next, typeof(*pos), member))
  
  /**
   * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
   * @pos:	the type * to use as a loop cursor.
   * @n:		another type * to use as temporary storage
   * @head:	the head for your list.
   * @member:	the name of the list_struct within the struct.
   */
  #define list_for_each_entry_safe(pos, n, head, member)			\
  	for (pos = list_entry((head)->next, typeof(*pos), member),	\
  		n = list_entry(pos->member.next, typeof(*pos), member);	\
  	     &pos->member != (head);					\
  	     pos = n, n = list_entry(n->member.next, typeof(*n), member))
  
  /**
   * list_for_each_entry_safe_continue
   * @pos:	the type * to use as a loop cursor.
   * @n:		another type * to use as temporary storage
   * @head:	the head for your list.
   * @member:	the name of the list_struct within the struct.
   *
   * Iterate over list of given type, continuing after current point,
   * safe against removal of list entry.
   */
  #define list_for_each_entry_safe_continue(pos, n, head, member) 		\
  	for (pos = list_entry(pos->member.next, typeof(*pos), member),		\
  		n = list_entry(pos->member.next, typeof(*pos), member);		\
  	     &pos->member != (head);						\
  	     pos = n, n = list_entry(n->member.next, typeof(*n), member))
  
  /**
   * list_for_each_entry_safe_from
   * @pos:	the type * to use as a loop cursor.
   * @n:		another type * to use as temporary storage
   * @head:	the head for your list.
   * @member:	the name of the list_struct within the struct.
   *
   * Iterate over list of given type from current point, safe against
   * removal of list entry.
   */
  #define list_for_each_entry_safe_from(pos, n, head, member)			\
  	for (n = list_entry(pos->member.next, typeof(*pos), member);		\
  	     &pos->member != (head);						\
  	     pos = n, n = list_entry(n->member.next, typeof(*n), member))
  
  /**
   * list_for_each_entry_safe_reverse
   * @pos:	the type * to use as a loop cursor.
   * @n:		another type * to use as temporary storage
   * @head:	the head for your list.
   * @member:	the name of the list_struct within the struct.
   *
   * Iterate backwards over list of given type, safe against removal
   * of list entry.
   */
  #define list_for_each_entry_safe_reverse(pos, n, head, member)		\
  	for (pos = list_entry((head)->prev, typeof(*pos), member),	\
  		n = list_entry(pos->member.prev, typeof(*pos), member);	\
  	     &pos->member != (head);					\
  	     pos = n, n = list_entry(n->member.prev, typeof(*n), member))
  
  /*
   * Double linked lists with a single pointer list head.
   * Mostly useful for hash tables where the two pointer list head is
   * too wasteful.
   * You lose the ability to access the tail in O(1).
   */
  
  struct hlist_head {
  	struct hlist_node *first;
  };
  
  struct hlist_node {
  	struct hlist_node *next, **pprev;
  };
  
  #define HLIST_HEAD_INIT { .first = NULL }
  #define HLIST_HEAD(name) struct hlist_head name = {  .first = NULL }
  #define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
  static inline void INIT_HLIST_NODE(struct hlist_node *h)
  {
  	h->next = NULL;
  	h->pprev = NULL;
  }
  
  static inline int hlist_unhashed(const struct hlist_node *h)
  {
  	return !h->pprev;
  }
  
  static inline int hlist_empty(const struct hlist_head *h)
  {
  	return !h->first;
  }
  
  static inline void __hlist_del(struct hlist_node *n)
  {
  	struct hlist_node *next = n->next;
  	struct hlist_node **pprev = n->pprev;
  	*pprev = next;
  	if (next)
  		next->pprev = pprev;
  }
  
  static inline void hlist_del(struct hlist_node *n)
  {
  	__hlist_del(n);
  	n->next = LIST_POISON1;
  	n->pprev = LIST_POISON2;
  }
  
  static inline void hlist_del_init(struct hlist_node *n)
  {
  	if (!hlist_unhashed(n)) {
  		__hlist_del(n);
  		INIT_HLIST_NODE(n);
  	}
  }
  
  static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
  {
  	struct hlist_node *first = h->first;
  	n->next = first;
  	if (first)
  		first->pprev = &n->next;
  	h->first = n;
  	n->pprev = &h->first;
  }
  
  /* next must be != NULL */
  static inline void hlist_add_before(struct hlist_node *n,
  					struct hlist_node *next)
  {
  	n->pprev = next->pprev;
  	n->next = next;
  	next->pprev = &n->next;
  	*(n->pprev) = n;
  }
  
  static inline void hlist_add_after(struct hlist_node *n,
  					struct hlist_node *next)
  {
  	next->next = n->next;
  	n->next = next;
  	next->pprev = &n->next;
  
  	if(next->next)
  		next->next->pprev  = &next->next;
  }
  
  #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
  
  #define hlist_for_each(pos, head) \
  	for (pos = (head)->first; pos && ({ prefetch(pos->next); 1; }); \
  	     pos = pos->next)
  
  #define hlist_for_each_safe(pos, n, head) \
  	for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
  	     pos = n)
  
  /**
   * hlist_for_each_entry	- iterate over list of given type
   * @tpos:	the type * to use as a loop cursor.
   * @pos:	the &struct hlist_node to use as a loop cursor.
   * @head:	the head for your list.
   * @member:	the name of the hlist_node within the struct.
   */
  #define hlist_for_each_entry(tpos, pos, head, member)			 \
  	for (pos = (head)->first;					 \
  	     pos && ({ prefetch(pos->next); 1;}) &&			 \
  		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
  	     pos = pos->next)
  
  /**
   * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
   * @tpos:	the type * to use as a loop cursor.
   * @pos:	the &struct hlist_node to use as a loop cursor.
   * @member:	the name of the hlist_node within the struct.
   */
  #define hlist_for_each_entry_continue(tpos, pos, member)		 \
  	for (pos = (pos)->next;						 \
  	     pos && ({ prefetch(pos->next); 1;}) &&			 \
  		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
  	     pos = pos->next)
  
  /**
   * hlist_for_each_entry_from - iterate over a hlist continuing from current point
   * @tpos:	the type * to use as a loop cursor.
   * @pos:	the &struct hlist_node to use as a loop cursor.
   * @member:	the name of the hlist_node within the struct.
   */
  #define hlist_for_each_entry_from(tpos, pos, member)			 \
  	for (; pos && ({ prefetch(pos->next); 1;}) &&			 \
  		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
  	     pos = pos->next)
  
  /**
   * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
   * @tpos:	the type * to use as a loop cursor.
   * @pos:	the &struct hlist_node to use as a loop cursor.
   * @n:		another &struct hlist_node to use as temporary storage
   * @head:	the head for your list.
   * @member:	the name of the hlist_node within the struct.
   */
  #define hlist_for_each_entry_safe(tpos, pos, n, head, member)		 \
  	for (pos = (head)->first;					 \
  	     pos && ({ n = pos->next; 1; }) &&				 \
  		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
  	     pos = n)
  
  #endif
  