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Subject[PATCH] lib/rbtree: set successor's parent unconditionally
Date
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@linux.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 179faab29f52..8fcddfef7876 100644
--- a/include/linux/rbtree_augmented.h
+++ b/include/linux/rbtree_augmented.h
@@ -237,14 +237,13 @@ __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
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