To implement the multicast list callback in mac80211 we need to
do partial list iteration. Since I want to convert the interface
list to an RCU list, I need a new list walking primitive:
list_for_each_entry_continue_rcu().
Additional help text was provided by Paul McKenney.
Signed-off-by: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
John, I don't know if you want to merge this or not. There's no clear
list.h maintainer and this patch is requisite for the bugfix I'm going
to send in a minute so it'd probably be best if this goes into the tree
together.
If you don't want to take it, however, I have no idea how to handle the
situation :)
include/linux/list.h | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
--- wireless-dev.orig/include/linux/list.h 2007-09-07 22:00:41.234425862 +0200
+++ wireless-dev/include/linux/list.h 2007-09-07 22:05:08.184425862 +0200
@@ -665,6 +665,32 @@ static inline void list_splice_init_rcu(
prefetch(rcu_dereference((pos))->next), (pos) != (head); \
(pos) = (pos)->next)
+
+/**
+ * list_for_each_entry_continue_rcu - continue iteration over rcu list
+ * @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 rcu list of given type, continuing after
+ * the current position.
+ *
+ * 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().
+ *
+ * Note that the caller is responsible for making sure that
+ * the element remains in place between the earlier iterator
+ * and this one. One way to do this is to ensure that
+ * both iterators are covered by the same rcu_read_lock(),
+ * while others involve reference counts, flags, or mutexes.
+ */
+#define list_for_each_entry_continue_rcu(pos, head, member) \
+ for ((pos) = list_entry((pos)->member.next, typeof(*pos), member); \
+ prefetch(rcu_dereference((pos))->member.next), \
+ &pos->member != (head); \
+ (pos) = list_entry(pos->member.next, typeof(*pos), member))
+
/*
* Double linked lists with a single pointer list head.
* Mostly useful for hash tables where the two pointer list head is
-
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