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

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
...@@ -318,6 +318,27 @@ static inline void list_splice_tail_init_rcu(struct list_head *list, ...@@ -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; \ 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 * list_for_each_entry_rcu - iterate over rcu list of given type
* @pos: the type * to use as a loop cursor. * @pos: the type * to use as a loop cursor.
......
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