From 651094542847ccd42580faa94fb14ac7d9e6669a Mon Sep 17 00:00:00 2001
From: Michel Lespinasse <walken@google.com>
Date: Mon, 8 Oct 2012 16:30:50 -0700
Subject: [PATCH] --- yaml --- r: 332392 b: refs/heads/master c:
 d6ff1273928ebf15466a85b7e1810cd00e72998b h: refs/heads/master v: v3

---
 [refs]                                       |  2 +-
 trunk/lib/rbtree.c                           | 28 ++++++++++++--------
 trunk/tools/perf/util/include/linux/rbtree.h |  1 +
 3 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/[refs] b/[refs]
index 5e566c27024e..332d8c67514a 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 5bc9188aa207dafd47eab57df7c4fe5b3d3f636a
+refs/heads/master: d6ff1273928ebf15466a85b7e1810cd00e72998b
diff --git a/trunk/lib/rbtree.c b/trunk/lib/rbtree.c
index 41cf19b2fe51..baf7c835c57c 100644
--- a/trunk/lib/rbtree.c
+++ b/trunk/lib/rbtree.c
@@ -259,10 +259,22 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
 {
 	struct rb_node *other;
 
-	while ((!node || rb_is_black(node)) && node != root->rb_node)
-	{
-		if (parent->rb_left == node)
-		{
+	while (true) {
+		/*
+		 * Loop invariant: all leaf paths going through node have a
+		 * black node count that is 1 lower than other leaf paths.
+		 *
+		 * If node is red, we can flip it to black to adjust.
+		 * If node is the root, all leaf paths go through it.
+		 * Otherwise, we need to adjust the tree through color flips
+		 * and tree rotations as per one of the 4 cases below.
+		 */
+		if (node && rb_is_red(node)) {
+			rb_set_black(node);
+			break;
+		} else if (!parent) {
+			break;
+		} else if (parent->rb_left == node) {
 			other = parent->rb_right;
 			if (rb_is_red(other))
 			{
@@ -291,12 +303,9 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
 				rb_set_black(parent);
 				rb_set_black(other->rb_right);
 				__rb_rotate_left(parent, root);
-				node = root->rb_node;
 				break;
 			}
-		}
-		else
-		{
+		} else {
 			other = parent->rb_left;
 			if (rb_is_red(other))
 			{
@@ -325,13 +334,10 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
 				rb_set_black(parent);
 				rb_set_black(other->rb_left);
 				__rb_rotate_right(parent, root);
-				node = root->rb_node;
 				break;
 			}
 		}
 	}
-	if (node)
-		rb_set_black(node);
 }
 
 void rb_erase(struct rb_node *node, struct rb_root *root)
diff --git a/trunk/tools/perf/util/include/linux/rbtree.h b/trunk/tools/perf/util/include/linux/rbtree.h
index 2a030c5af3aa..9bcdc844b330 100644
--- a/trunk/tools/perf/util/include/linux/rbtree.h
+++ b/trunk/tools/perf/util/include/linux/rbtree.h
@@ -1,2 +1,3 @@
 #include <stdbool.h>
+#include <stdbool.h>
 #include "../../../../include/linux/rbtree.h"