diff options
author | Tom Herbert <tom@herbertland.com> | 2016-03-08 01:11:00 +0300 |
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committer | David S. Miller <davem@davemloft.net> | 2016-03-10 00:36:13 +0300 |
commit | ff3c44e675054533403909ecb76e78c1d4efbd26 (patch) | |
tree | 5700cd86c182eaa9172de44d3151439e4ff745ed /include | |
parent | 26e9093110fb9ceb10093e4914b129b58d49a425 (diff) | |
download | linux-ff3c44e675054533403909ecb76e78c1d4efbd26.tar.xz |
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: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
-rw-r--r-- | include/linux/rculist.h | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/include/linux/rculist.h b/include/linux/rculist.h index 14ec1652daf4..17d4f849c65e 100644 --- a/include/linux/rculist.h +++ b/include/linux/rculist.h @@ -319,6 +319,27 @@ static inline void list_splice_tail_init_rcu(struct list_head *list, }) /** + * 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. * @head: the head for your list. |