#ifndef _LINUX_RCULIST_H
  #define _LINUX_RCULIST_H
  
  #ifdef __KERNEL__
  
  /*
   * RCU-protected list version
   */
  #include <linux/list.h>

  #include <linux/rcupdate.h>

  
  /*
   * 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_rcu(struct list_head *new,
  		struct list_head *prev, struct list_head *next)
  {
  	new->next = next;
  	new->prev = prev;

  	rcu_assign_pointer(prev->next, new);

  	next->prev = new;

  }
  
  /**
   * list_add_rcu - add a new entry to rcu-protected list
   * @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.
   *
   * The caller must take whatever precautions are necessary
   * (such as holding appropriate locks) to avoid racing
   * with another list-mutation primitive, such as list_add_rcu()
   * or list_del_rcu(), running on this same list.
   * However, it is perfectly legal to run concurrently with
   * the _rcu list-traversal primitives, such as
   * list_for_each_entry_rcu().
   */
  static inline void list_add_rcu(struct list_head *new, struct list_head *head)
  {
  	__list_add_rcu(new, head, head->next);
  }
  
  /**
   * list_add_tail_rcu - add a new entry to rcu-protected list
   * @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.
   *
   * The caller must take whatever precautions are necessary
   * (such as holding appropriate locks) to avoid racing
   * with another list-mutation primitive, such as list_add_tail_rcu()
   * or list_del_rcu(), running on this same list.
   * However, it is perfectly legal to run concurrently with
   * the _rcu list-traversal primitives, such as
   * list_for_each_entry_rcu().
   */
  static inline void list_add_tail_rcu(struct list_head *new,
  					struct list_head *head)
  {
  	__list_add_rcu(new, head->prev, head);
  }
  
  /**
   * list_del_rcu - deletes entry from list without re-initialization
   * @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. It is useful for RCU based
   * lockfree traversal.
   *
   * In particular, it means that we can not poison the forward
   * pointers that may still be used for walking the list.
   *
   * The caller must take whatever precautions are necessary
   * (such as holding appropriate locks) to avoid racing
   * with another list-mutation primitive, such as list_del_rcu()
   * or list_add_rcu(), running on this same list.
   * However, it is perfectly legal to run concurrently with
   * the _rcu list-traversal primitives, such as
   * list_for_each_entry_rcu().
   *
   * Note that the caller is not permitted to immediately free
   * the newly deleted entry.  Instead, either synchronize_rcu()
   * or call_rcu() must be used to defer freeing until an RCU
   * grace period has elapsed.
   */
  static inline void list_del_rcu(struct list_head *entry)
  {
  	__list_del(entry->prev, entry->next);
  	entry->prev = LIST_POISON2;
  }
  
  /**

   * hlist_del_init_rcu - deletes entry from hash list with re-initialization
   * @n: the element to delete from the hash list.
   *
   * Note: list_unhashed() on the node return true after this. It is
   * useful for RCU based read lockfree traversal if the writer side
   * must know if the list entry is still hashed or already unhashed.
   *
   * In particular, it means that we can not poison the forward pointers
   * that may still be used for walking the hash list and we can only
   * zero the pprev pointer so list_unhashed() will return true after
   * this.
   *
   * The caller must take whatever precautions are necessary (such as
   * holding appropriate locks) to avoid racing with another
   * list-mutation primitive, such as hlist_add_head_rcu() or
   * hlist_del_rcu(), running on this same list.  However, it is
   * perfectly legal to run concurrently with the _rcu list-traversal
   * primitives, such as hlist_for_each_entry_rcu().
   */
  static inline void hlist_del_init_rcu(struct hlist_node *n)
  {
  	if (!hlist_unhashed(n)) {
  		__hlist_del(n);
  		n->pprev = NULL;
  	}
  }
  
  /**

   * list_replace_rcu - replace old entry by new one
   * @old : the element to be replaced
   * @new : the new element to insert
   *
   * The @old entry will be replaced with the @new entry atomically.
   * Note: @old should not be empty.
   */
  static inline void list_replace_rcu(struct list_head *old,
  				struct list_head *new)
  {
  	new->next = old->next;
  	new->prev = old->prev;

  	rcu_assign_pointer(new->prev->next, new);

  	new->next->prev = new;

  	old->prev = LIST_POISON2;
  }
  
  /**
   * list_splice_init_rcu - splice an RCU-protected list into an existing list.
   * @list:	the RCU-protected list to splice
   * @head:	the place in the list to splice the first list into
   * @sync:	function to sync: synchronize_rcu(), synchronize_sched(), ...
   *
   * @head can be RCU-read traversed concurrently with this function.
   *
   * Note that this function blocks.
   *
   * Important note: the caller must take whatever action is necessary to
   *	prevent any other updates to @head.  In principle, it is possible
   *	to modify the list as soon as sync() begins execution.
   *	If this sort of thing becomes necessary, an alternative version
   *	based on call_rcu() could be created.  But only if -really-
   *	needed -- there is no shortage of RCU API members.
   */
  static inline void list_splice_init_rcu(struct list_head *list,
  					struct list_head *head,
  					void (*sync)(void))
  {
  	struct list_head *first = list->next;
  	struct list_head *last = list->prev;
  	struct list_head *at = head->next;
  
  	if (list_empty(head))
  		return;
  
  	/* "first" and "last" tracking list, so initialize it. */
  
  	INIT_LIST_HEAD(list);
  
  	/*
  	 * At this point, the list body still points to the source list.
  	 * Wait for any readers to finish using the list before splicing
  	 * the list body into the new list.  Any new readers will see
  	 * an empty list.
  	 */
  
  	sync();
  
  	/*
  	 * Readers are finished with the source list, so perform splice.
  	 * The order is important if the new list is global and accessible
  	 * to concurrent RCU readers.  Note that RCU readers are not
  	 * permitted to traverse the prev pointers without excluding
  	 * this function.
  	 */
  
  	last->next = at;

  	rcu_assign_pointer(head->next, first);

  	first->prev = head;
  	at->prev = last;
  }

  /**
   * list_entry_rcu - 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.
   *
   * This primitive may safely run concurrently with the _rcu list-mutation
   * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
   */
  #define list_entry_rcu(ptr, type, member) \

  	container_of(rcu_dereference_raw(ptr), type, member)

  
  /**
   * list_first_entry_rcu - 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.
   *
   * This primitive may safely run concurrently with the _rcu list-mutation
   * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
   */
  #define list_first_entry_rcu(ptr, type, member) \
  	list_entry_rcu((ptr)->next, type, member)

  #define __list_for_each_rcu(pos, head) \

  	for (pos = rcu_dereference_raw((head)->next); \

  		pos != (head); \

  		pos = rcu_dereference_raw(pos->next))

  
  /**
   * list_for_each_entry_rcu	-	iterate over rcu 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.
   *
   * This list-traversal primitive may safely run concurrently with
   * the _rcu list-mutation primitives such as list_add_rcu()
   * as long as the traversal is guarded by rcu_read_lock().
   */
  #define list_for_each_entry_rcu(pos, head, member) \

  	for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \

  		prefetch(pos->member.next), &pos->member != (head); \

  		pos = list_entry_rcu(pos->member.next, typeof(*pos), member))

  
  
  /**
   * list_for_each_continue_rcu
   * @pos:	the &struct list_head to use as a loop cursor.
   * @head:	the head for your list.
   *
   * Iterate over an rcu-protected list, continuing after current point.
   *
   * This list-traversal primitive may safely run concurrently with
   * the _rcu list-mutation primitives such as list_add_rcu()
   * as long as the traversal is guarded by rcu_read_lock().
   */
  #define list_for_each_continue_rcu(pos, head) \

  	for ((pos) = rcu_dereference_raw((pos)->next); \

  		prefetch((pos)->next), (pos) != (head); \

  		(pos) = rcu_dereference_raw((pos)->next))

  
  /**

   * list_for_each_entry_continue_rcu - 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_rcu(pos, head, member) 		\
  	for (pos = list_entry_rcu(pos->member.next, typeof(*pos), member); \
  	     prefetch(pos->member.next), &pos->member != (head);	\
  	     pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
  
  /**

   * hlist_del_rcu - deletes entry from hash list without re-initialization
   * @n: the element to delete from the hash list.
   *
   * Note: list_unhashed() on entry does not return true after this,
   * the entry is in an undefined state. It is useful for RCU based
   * lockfree traversal.
   *
   * In particular, it means that we can not poison the forward
   * pointers that may still be used for walking the hash list.
   *
   * The caller must take whatever precautions are necessary
   * (such as holding appropriate locks) to avoid racing
   * with another list-mutation primitive, such as hlist_add_head_rcu()
   * or hlist_del_rcu(), running on this same list.
   * However, it is perfectly legal to run concurrently with
   * the _rcu list-traversal primitives, such as
   * hlist_for_each_entry().
   */
  static inline void hlist_del_rcu(struct hlist_node *n)
  {
  	__hlist_del(n);
  	n->pprev = LIST_POISON2;
  }
  
  /**
   * hlist_replace_rcu - replace old entry by new one
   * @old : the element to be replaced
   * @new : the new element to insert
   *
   * The @old entry will be replaced with the @new entry atomically.
   */
  static inline void hlist_replace_rcu(struct hlist_node *old,
  					struct hlist_node *new)
  {
  	struct hlist_node *next = old->next;
  
  	new->next = next;
  	new->pprev = old->pprev;

  	rcu_assign_pointer(*new->pprev, new);

  	if (next)
  		new->next->pprev = &new->next;

  	old->pprev = LIST_POISON2;
  }
  
  /**
   * hlist_add_head_rcu
   * @n: the element to add to the hash list.
   * @h: the list to add to.
   *
   * Description:
   * Adds the specified element to the specified hlist,
   * while permitting racing traversals.
   *
   * The caller must take whatever precautions are necessary
   * (such as holding appropriate locks) to avoid racing
   * with another list-mutation primitive, such as hlist_add_head_rcu()
   * or hlist_del_rcu(), running on this same list.
   * However, it is perfectly legal to run concurrently with
   * the _rcu list-traversal primitives, such as
   * hlist_for_each_entry_rcu(), used to prevent memory-consistency
   * problems on Alpha CPUs.  Regardless of the type of CPU, the
   * list-traversal primitive must be guarded by rcu_read_lock().
   */
  static inline void hlist_add_head_rcu(struct hlist_node *n,
  					struct hlist_head *h)
  {
  	struct hlist_node *first = h->first;

  	n->next = first;
  	n->pprev = &h->first;

  	rcu_assign_pointer(h->first, n);

  	if (first)
  		first->pprev = &n->next;

  }
  
  /**
   * hlist_add_before_rcu
   * @n: the new element to add to the hash list.
   * @next: the existing element to add the new element before.
   *
   * Description:
   * Adds the specified element to the specified hlist
   * before the specified node while permitting racing traversals.
   *
   * The caller must take whatever precautions are necessary
   * (such as holding appropriate locks) to avoid racing
   * with another list-mutation primitive, such as hlist_add_head_rcu()
   * or hlist_del_rcu(), running on this same list.
   * However, it is perfectly legal to run concurrently with
   * the _rcu list-traversal primitives, such as
   * hlist_for_each_entry_rcu(), used to prevent memory-consistency
   * problems on Alpha CPUs.
   */
  static inline void hlist_add_before_rcu(struct hlist_node *n,
  					struct hlist_node *next)
  {
  	n->pprev = next->pprev;
  	n->next = next;

  	rcu_assign_pointer(*(n->pprev), n);

  	next->pprev = &n->next;

  }
  
  /**
   * hlist_add_after_rcu
   * @prev: the existing element to add the new element after.
   * @n: the new element to add to the hash list.
   *
   * Description:
   * Adds the specified element to the specified hlist
   * after the specified node while permitting racing traversals.
   *
   * The caller must take whatever precautions are necessary
   * (such as holding appropriate locks) to avoid racing
   * with another list-mutation primitive, such as hlist_add_head_rcu()
   * or hlist_del_rcu(), running on this same list.
   * However, it is perfectly legal to run concurrently with
   * the _rcu list-traversal primitives, such as
   * hlist_for_each_entry_rcu(), used to prevent memory-consistency
   * problems on Alpha CPUs.
   */
  static inline void hlist_add_after_rcu(struct hlist_node *prev,
  				       struct hlist_node *n)
  {
  	n->next = prev->next;
  	n->pprev = &prev->next;

  	rcu_assign_pointer(prev->next, n);

  	if (n->next)
  		n->next->pprev = &n->next;
  }

  #define __hlist_for_each_rcu(pos, head)			\
  	for (pos = rcu_dereference((head)->first);	\
  	     pos && ({ prefetch(pos->next); 1; });	\
  	     pos = rcu_dereference(pos->next))

  /**
   * hlist_for_each_entry_rcu - iterate over rcu 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.
   *
   * This list-traversal primitive may safely run concurrently with
   * the _rcu list-mutation primitives such as hlist_add_head_rcu()
   * as long as the traversal is guarded by rcu_read_lock().
   */
  #define hlist_for_each_entry_rcu(tpos, pos, head, member)		 \

  	for (pos = rcu_dereference_raw((head)->first);			 \

  		pos && ({ prefetch(pos->next); 1; }) &&			 \

  		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \

  		pos = rcu_dereference_raw(pos->next))

  /**

   * hlist_for_each_entry_rcu_bh - iterate over rcu 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.
   *
   * This list-traversal primitive may safely run concurrently with
   * the _rcu list-mutation primitives such as hlist_add_head_rcu()
   * as long as the traversal is guarded by rcu_read_lock().
   */
  #define hlist_for_each_entry_rcu_bh(tpos, pos, head, member)		 \
  	for (pos = rcu_dereference_bh((head)->first);			 \
  		pos && ({ prefetch(pos->next); 1; }) &&			 \
  		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \
  		pos = rcu_dereference_bh(pos->next))
  
  /**

   * hlist_for_each_entry_continue_rcu - 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_rcu(tpos, pos, member)		\
  	for (pos = rcu_dereference((pos)->next);			\
  	     pos && ({ prefetch(pos->next); 1; }) &&			\
  	     ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; });  \
  	     pos = rcu_dereference(pos->next))

  /**
   * hlist_for_each_entry_continue_rcu_bh - 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_rcu_bh(tpos, pos, member)		\
  	for (pos = rcu_dereference_bh((pos)->next);			\
  	     pos && ({ prefetch(pos->next); 1; }) &&			\
  	     ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; });  \
  	     pos = rcu_dereference_bh(pos->next))

  #endif	/* __KERNEL__ */
  #endif