[BRIDGE]: forwarding table RCU

Convert the bridge forwarding database over to using RCU.
This avoids a read_lock and atomic_inc/dec in the fast path
of output.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@redhat.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/include/linux/list.h b/include/linux/list.h
index 23e287fe4259..978876d258a9 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -678,6 +678,24 @@ static inline void hlist_add_after(struct hlist_node *n,
 	     pos && ({ n = pos->next; 1; }) && 				 \
 		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
 	     pos = n)
+
+/**
+ * hlist_for_each_entry_rcu - iterate over rcu list of given type
+ * @pos:	the type * to use as a loop counter.
+ * @pos:	the &struct hlist_node to use as a loop counter.
+ * @head:	the head for your list.
+ * @member:	the name of the hlist_node within the struct.
+ *
+ * This list-traversal primitive may safely run concurrently with
+ * the _rcu list-mutation primitives such as hlist_add_rcu()
+ * as long as the traversal is guarded by rcu_read_lock().
+ */
+#define hlist_for_each_entry_rcu(tpos, pos, head, member)		 \
+	for (pos = (head)->first;					 \
+	     pos && ({ prefetch(pos->next); 1;}) &&			 \
+		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
+	     pos = pos->next, ({ smp_read_barrier_depends(); 0; }) )
+
 #else
 #warning "don't include kernel headers in userspace"
 #endif /* __KERNEL__ */