net: force a reload of first item in hlist_nulls_for_each_entry_rcu

[pandora-kernel.git] / include / linux / rculist_nulls.h

diff --git a/include/linux/rculist_nulls.h b/include/linux/rculist_nulls.h
index b70ffe5..1c33dd7 100644 (file)
--- a/include/linux/rculist_nulls.h
+++ b/include/linux/rculist_nulls.h
@@ -37,6 +37,12 @@ static inline void hlist_nulls_del_init_rcu(struct hlist_nulls_node *n)
        }
 }
 
+#define hlist_nulls_first_rcu(head) \
+       (*((struct hlist_nulls_node __rcu __force **)&(head)->first))
+
+#define hlist_nulls_next_rcu(node) \
+       (*((struct hlist_nulls_node __rcu __force **)&(node)->next))
+
 /**
  * hlist_nulls_del_rcu - deletes entry from hash list without re-initialization
  * @n: the element to delete from the hash list.
@@ -88,7 +94,7 @@ static inline void hlist_nulls_add_head_rcu(struct hlist_nulls_node *n,
 
        n->next = first;
        n->pprev = &h->first;
-       rcu_assign_pointer(h->first, n);
+       rcu_assign_pointer(hlist_nulls_first_rcu(h), n);
        if (!is_a_nulls(first))
                first->pprev = &n->next;
 }
@@ -99,12 +105,17 @@ static inline void hlist_nulls_add_head_rcu(struct hlist_nulls_node *n,
  * @head:      the head for your list.
  * @member:    the name of the hlist_nulls_node within the struct.
  *
+ * The barrier() is needed to make sure compiler doesn't cache first element [1],
+ * as this loop can be restarted [2]
+ * [1] Documentation/atomic_ops.txt around line 114
+ * [2] Documentation/RCU/rculist_nulls.txt around line 146
  */
-#define hlist_nulls_for_each_entry_rcu(tpos, pos, head, member) \
-       for (pos = rcu_dereference_raw((head)->first);                   \
-               (!is_a_nulls(pos)) &&                   \
+#define hlist_nulls_for_each_entry_rcu(tpos, pos, head, member)                        \
+       for (({barrier();}),                                                    \
+            pos = rcu_dereference_raw(hlist_nulls_first_rcu(head));            \
+               (!is_a_nulls(pos)) &&                                           \
                ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1; }); \
-               pos = rcu_dereference_raw(pos->next))
+               pos = rcu_dereference_raw(hlist_nulls_next_rcu(pos)))
 
 #endif
 #endif