diff options
| author | Jie Chen <fykcee1@gmail.com> | 2016-12-12 16:46:17 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-12-12 18:55:09 -0800 |
| commit | ce093a04543c403d52c1a5788d8cb92e47453aba (patch) | |
| tree | 4f0dbd7ab08c3110cc45f2ce94662ea3e561c00c /lib/rbtree.c | |
| parent | 6b2a65c7ff612035deb1012388738b54e08ab2a6 (diff) | |
| download | lwn-ce093a04543c403d52c1a5788d8cb92e47453aba.tar.gz lwn-ce093a04543c403d52c1a5788d8cb92e47453aba.zip | |
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/rbtree.c')
| -rw-r--r-- | lib/rbtree.c | 23 |
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); |