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authorMichel Lespinasse <walken@google.com>2012-10-08 16:30:42 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-10-09 16:22:33 +0900
commit1f0528653e41ec230c60f5738820e8a544731399 (patch)
treef07f4eb1ed58122b810b586839833e0c015b681c /lib
parent910a742d4ba863848c7283d69c21bfa779d3b9a8 (diff)
downloadvexpress-lsk-1f0528653e41ec230c60f5738820e8a544731399.tar.gz
rbtree: break out of rb_insert_color loop after tree rotation
It is a well known property of rbtrees that insertion never requires more than two tree rotations. In our implementation, after one loop iteration identified one or two necessary tree rotations, we would iterate and look for more. However at that point the node's parent would always be black, which would cause us to exit the loop. We can make the code flow more obvious by just adding a break statement after the tree rotations, where we know we are done. Additionally, in the cases where two tree rotations are necessary, we don't have to update the 'node' pointer as it wouldn't be used until the next loop iteration, which we now avoid due to this break statement. Signed-off-by: Michel Lespinasse <walken@google.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Acked-by: David Woodhouse <David.Woodhouse@intel.com> Cc: Rik van Riel <riel@redhat.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Daniel Santos <daniel.santos@pobox.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/rbtree.c14
1 files changed, 4 insertions, 10 deletions
diff --git a/lib/rbtree.c b/lib/rbtree.c
index ccada9abe6f..12abb8abf44 100644
--- a/lib/rbtree.c
+++ b/lib/rbtree.c
@@ -109,18 +109,15 @@ void rb_insert_color(struct rb_node *node, struct rb_root *root)
}
}
- if (parent->rb_right == node)
- {
- register struct rb_node *tmp;
+ if (parent->rb_right == node) {
__rb_rotate_left(parent, root);
- tmp = parent;
parent = node;
- node = tmp;
}
rb_set_black(parent);
rb_set_red(gparent);
__rb_rotate_right(gparent, root);
+ break;
} else {
{
register struct rb_node *uncle = gparent->rb_left;
@@ -134,18 +131,15 @@ void rb_insert_color(struct rb_node *node, struct rb_root *root)
}
}
- if (parent->rb_left == node)
- {
- register struct rb_node *tmp;
+ if (parent->rb_left == node) {
__rb_rotate_right(parent, root);
- tmp = parent;
parent = node;
- node = tmp;
}
rb_set_black(parent);
rb_set_red(gparent);
__rb_rotate_left(gparent, root);
+ break;
}
}