From: Michel Lespinasse <wal...@google.com>
In rb_erase, move the easy case (node to erase has no more than
1 child) first. I feel the code reads easier that way.
Signed-off-by: Michel Lespinasse <wal...@google.com>
Reviewed-by: Rik van Riel <r...@redhat.com>
Cc: Peter Zijlstra <a.p.zijls...@chello.nl>
Cc: Andrea Arcangeli <aarca...@redhat.com>
Cc: David Woodhouse <dw...@infradead.org>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
[Linux commit 60670b8034d6e2ba860af79c9379b7788d09db73]
Ported to Xen.
Signed-off-by: Praveen Kumar <kpraveen.l...@gmail.com>
---
xen/common/rbtree.c | 35 ++++++++++++++++++-----------------
1 file changed, 18 insertions(+), 17 deletions(-)
diff --git a/xen/common/rbtree.c b/xen/common/rbtree.c
index 8d836cef81..13a622326d 100644
--- a/xen/common/rbtree.c
+++ b/xen/common/rbtree.c
@@ -368,17 +368,28 @@ static void __rb_erase_color(struct rb_node *node, struct
rb_node *parent,
void rb_erase(struct rb_node *node, struct rb_root *root)
{
- struct rb_node *child, *parent;
+ struct rb_node *child = node->rb_right, *tmp = node->rb_left;
+ struct rb_node *parent;
int color;
- if (!node->rb_left)
- child = node->rb_right;
- else if (!node->rb_right)
- child = node->rb_left;
- else {
+ if (!tmp) {
+ case1:
+ /* Case 1: node to erase has no more than 1 child (easy!) */
+
+ parent = rb_parent(node);
+ color = rb_color(node);
+
+ if (child)
+ rb_set_parent(child, parent);
+ __rb_change_child(node, child, parent, root);
+ } else if (!child) {
+ /* Still case 1, but this time the child is node->rb_left */
+ child = tmp;
+ goto case1;
+ } else {
struct rb_node *old = node, *left;
- node = node->rb_right;
+ node = child;
while ((left = node->rb_left) != NULL)
node = left;
@@ -402,18 +413,8 @@ void rb_erase(struct rb_node *node, struct rb_root *root)
node->__rb_parent_color = old->__rb_parent_color;
node->rb_left = old->rb_left;
rb_set_parent(old->rb_left, node);
-
- goto color;
}
- parent = rb_parent(node);
- color = rb_color(node);
-
- if (child)
- rb_set_parent(child, parent);
- __rb_change_child(node, child, parent, root);
-
-color:
if (color == RB_BLACK)
__rb_erase_color(child, parent, root);
}
--
2.13.1
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel
