Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab...

[firefly-linux-kernel-4.4.55.git] / include / linux / rculist_nulls.h

diff --git a/include/linux/rculist_nulls.h b/include/linux/rculist_nulls.h
index 2ae13714828bc42568e77684fedfc2cf929c291d..1c33dd7da4a7d860004264e00bd406645df1ed96 100644 (file)
--- a/include/linux/rculist_nulls.h
+++ b/include/linux/rculist_nulls.h
@@ -105,9 +105,14 @@ 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(hlist_nulls_first_rcu(head));            \
+       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(hlist_nulls_next_rcu(pos)))