rb_tree: make clear distinction between two different cases in rb_erase()
There are two cases when a node, having 2 childs, is erased:
'normal case': the successor is not the right-hand-child of the node to be erased
'special case': the successor is the right-hand child of the node to be erased
Here some ascii-art, with following symbols (referring to the code):
O: node to be deleted
N: the successor of O
P: parent of N
C: child of N
L: some other node
normal case:
O N
/ \ / \
/ \ / \
L \ L \
/ \ P ----> / \ P
/ \ / \
/ /
N C
\ / \
\
C
/ \
special case:
O|P N
/ \ / \
/ \ / \
L \ L \
/ \ N ----> / C
\ / \
\
C
/ \
Notice that for the special case we don't have to reconnect C to N.
Signed-off-by: Wolfram Strepp <wstrepp@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/lib/rbtree.c b/lib/rbtree.c
index 0455685..4b4b29b 100644
--- a/lib/rbtree.c
+++ b/lib/rbtree.c
@@ -244,13 +244,13 @@
parent = rb_parent(node);
color = rb_color(node);
- if (child)
- rb_set_parent(child, parent);
if (parent == old) {
- parent->rb_right = child;
parent = node;
- } else
+ } else {
+ if (child)
+ rb_set_parent(child, parent);
parent->rb_left = child;
+ }
node->rb_parent_color = old->rb_parent_color;
node->rb_right = old->rb_right;