linux-kernel - [Patch v2 1/2] lib/rbtree: set successor's parent unconditionally

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20191028021442.5450-1-richardw.yang@linux.intel.com>
Date:   Mon, 28 Oct 2019 10:14:41 +0800
From:   Wei Yang <richardw.yang@...ux.intel.com>
To:     akpm@...ux-foundation.org, peterz@...radead.org, walken@...gle.com,
        richardw.yang@...ux.intel.com, dbueso@...e.de, tglx@...utronix.de
Cc:     linux-kernel@...r.kernel.org
Subject: [Patch v2 1/2] lib/rbtree: set successor's parent unconditionally

Both in Case 2 and 3, we exchange n and s. This mean no matter whether
child2 is NULL or not, successor's parent should be assigned to node's.

This patch takes this step out to make it explicit and reduce the
ambiguity.

Besides, this step reduces some symbol size like rb_erase().

   KERN_CONFIG       upstream       patched
   OPT_FOR_PERF      877            870
   OPT_FOR_SIZE      635            621

Signed-off-by: Wei Yang <richardw.yang@...ux.intel.com>
---
 include/linux/rbtree_augmented.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/include/linux/rbtree_augmented.h b/include/linux/rbtree_augmented.h
index fdd421b8d9ae..99c42e1a74b8 100644
--- a/include/linux/rbtree_augmented.h
+++ b/include/linux/rbtree_augmented.h
@@ -283,14 +283,13 @@ __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 		__rb_change_child(node, successor, tmp, root);
 
 		if (child2) {
-			successor->__rb_parent_color = pc;
 			rb_set_parent_color(child2, parent, RB_BLACK);
 			rebalance = NULL;
 		} else {
 			unsigned long pc2 = successor->__rb_parent_color;
-			successor->__rb_parent_color = pc;
 			rebalance = __rb_is_black(pc2) ? parent : NULL;
 		}
+		successor->__rb_parent_color = pc;
 		tmp = successor;
 	}
 
-- 
2.17.1