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authorJie Chen <fykcee1@gmail.com>2016-12-12 16:46:17 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-12-12 18:55:09 -0800
commitce093a04543c403d52c1a5788d8cb92e47453aba (patch)
tree4f0dbd7ab08c3110cc45f2ce94662ea3e561c00c /lib
parent6b2a65c7ff612035deb1012388738b54e08ab2a6 (diff)
downloadlinux-stericsson-ce093a04543c403d52c1a5788d8cb92e47453aba.tar.gz
lib/rbtree.c: fix typo in comment of ____rb_erase_color
In Case 3 of `sibling == parent->rb_right': Right rotation will not change color of sl and S in the diagram (i.e. should not change "sl" to "Sl", "S" to "s") In Case 3 of `sibling == parent->rb_left': (p) (p) / \ / \ S N --> sr N / \ / Sl sr S / Sl This is actually left rotation at "S", not right rotation. In Case 4 of `sibling == parent->rb_left': (p) (s) / \ / \ S N --> Sl P / \ / \ sl (sr) (sr) N This is actually right rotation at "(p)" + color flips, not left rotation + color flips. Link: http://lkml.kernel.org/r/1472391115-3702-1-git-send-email-fykcee1@gmail.com Signed-off-by: Jie Chen <fykcee1@gmail.com> Cc: Wei Yang <weiyang@linux.vnet.ibm.com> Cc: Xiao Guangrong <guangrong.xiao@linux.intel.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.c23
1 files changed, 19 insertions, 4 deletions
diff --git a/lib/rbtree.c b/lib/rbtree.c
index eb8a19fee110..1f8b112a7c35 100644
--- a/lib/rbtree.c
+++ b/lib/rbtree.c
@@ -296,11 +296,26 @@ ____rb_erase_color(struct rb_node *parent, struct rb_root *root,
*
* (p) (p)
* / \ / \
- * N S --> N Sl
+ * N S --> N sl
* / \ \
- * sl Sr s
+ * sl Sr S
* \
* Sr
+ *
+ * Note: p might be red, and then both
+ * p and sl are red after rotation(which
+ * breaks property 4). This is fixed in
+ * Case 4 (in __rb_rotate_set_parents()
+ * which set sl the color of p
+ * and set p RB_BLACK)
+ *
+ * (p) (sl)
+ * / \ / \
+ * N sl --> P S
+ * \ / \
+ * S N Sr
+ * \
+ * Sr
*/
tmp1 = tmp2->rb_right;
WRITE_ONCE(sibling->rb_left, tmp1);
@@ -365,7 +380,7 @@ ____rb_erase_color(struct rb_node *parent, struct rb_root *root,
}
break;
}
- /* Case 3 - right rotate at sibling */
+ /* Case 3 - left rotate at sibling */
tmp1 = tmp2->rb_left;
WRITE_ONCE(sibling->rb_right, tmp1);
WRITE_ONCE(tmp2->rb_left, sibling);
@@ -377,7 +392,7 @@ ____rb_erase_color(struct rb_node *parent, struct rb_root *root,
tmp1 = sibling;
sibling = tmp2;
}
- /* Case 4 - left rotate at parent + color flips */
+ /* Case 4 - right rotate at parent + color flips */
tmp2 = sibling->rb_right;
WRITE_ONCE(parent->rb_left, tmp2);
WRITE_ONCE(sibling->rb_right, parent);