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rcu: Add list_next_or_null_rcu

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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>
This commit is contained in:
Tom Herbert 2016-03-07 14:11:00 -08:00 committed by David S. Miller
parent 26e9093110
commit ff3c44e675
1 changed files with 21 additions and 0 deletions
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21
include/linux/rculist.h
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@ -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.