Recalculate max end values on rotation

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/urcu-rbtree.c b/urcu-rbtree.c
index b2982bb4f442e1fbe31fcb95e21df7faf5061c2b..b0f57fdc2ff019b48f292cb29b3d53e7ad82e99a 100644 (file)
--- a/urcu-rbtree.c
+++ b/urcu-rbtree.c
@@ -366,6 +366,23 @@ struct rcu_rbtree_node *rcu_rbtree_prev(struct rcu_rbtree *rbtree,
        return y;
 }
 
+static
+void *calculate_node_max_end(struct rcu_rbtree *rbtree, struct rcu_rbtree_node *node)
+{
+       void *max_end;
+
+       max_end = node->end;
+       if (!rcu_rbtree_is_nil(rbtree, node->_right)) {
+               if (rbtree->comp(max_end, node->_right->max_end) < 0)
+                       max_end = node->_right->max_end;
+       }
+       if (!rcu_rbtree_is_nil(rbtree, node->_left)) {
+               if (rbtree->comp(max_end, node->_left->max_end) < 0)
+                       max_end = node->_left->max_end;
+       }
+       return max_end;
+}
+
 /*
  * "node" needs to be non-visible by readers.
  */
@@ -380,16 +397,8 @@ void populate_node_end(struct rcu_rbtree *rbtree, struct rcu_rbtree_node *node,
 
                assert(node);
                assert(!rcu_rbtree_is_nil(rbtree, node));
-               max_end = node->end;
-               if (!rcu_rbtree_is_nil(rbtree, node->_right)) {
-                       if (rbtree->comp(max_end, node->_right->max_end) < 0)
-                               max_end = node->_right->max_end;
-               }
-               if (!rcu_rbtree_is_nil(rbtree, node->_left)) {
-                       if (rbtree->comp(max_end, node->_left->max_end) < 0)
-                               max_end = node->_left->max_end;
-               }
 
+               max_end = calculate_node_max_end(rbtree, node);
                if (rbtree->comp(max_end, node->max_end) != 0) {
                        if (prev && copy_parents) {
                                node = dup_decay_node(rbtree, node);
@@ -492,6 +501,15 @@ void left_rotate(struct rcu_rbtree *rbtree,
        if (!rcu_rbtree_is_nil(rbtree, y_left))
                set_parent(y_left, x, IS_RIGHT);
 
+       /*
+        * We only changed the relative position of x and y wrt their
+        * children, and reparented y (but are keeping the same nodes in
+        * place, so its parent does not need to have end value
+        * recalculated).
+        */
+       x->max_end = calculate_node_max_end(rbtree, x);
+       y->max_end = calculate_node_max_end(rbtree, y);
+
        cmm_smp_wmb();  /* write into node before publish */
 
        /* External references update (visible by readers) */
@@ -587,6 +605,15 @@ void right_rotate(struct rcu_rbtree *rbtree,
        if (!rcu_rbtree_is_nil(rbtree, y_right))
                set_parent(y_right, x, IS_LEFT);
 
+       /*
+        * We only changed the relative position of x and y wrt their
+        * children, and reparented y (but are keeping the same nodes in
+        * place, so its parent does not need to have end value
+        * recalculated).
+        */
+       x->max_end = calculate_node_max_end(rbtree, x);
+       y->max_end = calculate_node_max_end(rbtree, y);
+
        cmm_smp_wmb();  /* write into node before publish */
 
        /* External references update (visible by readers) */