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Commit ff3c44e6 authored by Tom Herbert's avatar Tom Herbert Committed by David S. Miller
Browse files

rcu: Add list_next_or_null_rcu 



This is a convenience function that returns the next entry in an RCU
list or NULL if at the end of the list.

Signed-off-by: default avatarTom Herbert <tom@herbertland.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 26e90931

include/linux/rculist.h

+21 −0
Original line number Diff line number Diff line
@@ -318,6 +318,27 @@ static inline void list_splice_tail_init_rcu(struct list_head *list, 
	likely(__ptr != __next) ? list_entry_rcu(__next, type, member) : NULL; \

})



/**

 * list_next_or_null_rcu - get the first element from a list

 * @head:	the head for the list.

 * @ptr:        the list head to take the next element from.

 * @type:       the type of the struct this is embedded in.

 * @member:     the name of the list_head within the struct.

 *

 * Note that if the ptr is at the end of the list, NULL is returned.

 *

 * 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_next_or_null_rcu(head, ptr, type, member) \

({ \

	struct list_head *__head = (head); \

	struct list_head *__ptr = (ptr); \

	struct list_head *__next = READ_ONCE(__ptr->next); \

	likely(__next != __head) ? list_entry_rcu(__next, type, \

						  member) : NULL; \

})



/**

 * list_for_each_entry_rcu	-	iterate over rcu list of given type

 * @pos:	the type * to use as a loop cursor.