On Mon, Sep 10, 2007 at 02:05:47PM +0200, Johannes Berg wrote: > 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. Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> > 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 > > - To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
