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![Michel Lespinasse](/assets/img/avatar_default.png)
lib/rbtree.c declared __rb_erase_color() as __always_inline void, and then exported it with EXPORT_SYMBOL. This was because __rb_erase_color() must be exported for augmented rbtree users, but it must also be inlined into rb_erase() so that the dummy callback can get optimized out of that call site. (Actually with a modern compiler, none of the dummy callback functions should even be generated as separate text functions). The above usage is legal C, but it was unusual enough for some compilers to warn about it. This change makes things more explicit, with a static __always_inline ____rb_erase_color function for use in rb_erase(), and a separate non-inline __rb_erase_color function for use in rb_erase_augmented call sites. Signed-off-by: Michel Lespinasse <walken@google.com> Reported-by: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
520 lines
14 KiB
C
520 lines
14 KiB
C
/*
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Red Black Trees
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(C) 1999 Andrea Arcangeli <andrea@suse.de>
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(C) 2002 David Woodhouse <dwmw2@infradead.org>
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(C) 2012 Michel Lespinasse <walken@google.com>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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linux/lib/rbtree.c
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*/
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#include <linux/rbtree_augmented.h>
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#include <linux/export.h>
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/*
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* red-black trees properties: http://en.wikipedia.org/wiki/Rbtree
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*
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* 1) A node is either red or black
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* 2) The root is black
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* 3) All leaves (NULL) are black
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* 4) Both children of every red node are black
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* 5) Every simple path from root to leaves contains the same number
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* of black nodes.
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*
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* 4 and 5 give the O(log n) guarantee, since 4 implies you cannot have two
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* consecutive red nodes in a path and every red node is therefore followed by
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* a black. So if B is the number of black nodes on every simple path (as per
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* 5), then the longest possible path due to 4 is 2B.
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*
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* We shall indicate color with case, where black nodes are uppercase and red
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* nodes will be lowercase. Unknown color nodes shall be drawn as red within
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* parentheses and have some accompanying text comment.
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*/
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static inline void rb_set_black(struct rb_node *rb)
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{
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rb->__rb_parent_color |= RB_BLACK;
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}
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static inline struct rb_node *rb_red_parent(struct rb_node *red)
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{
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return (struct rb_node *)red->__rb_parent_color;
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}
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/*
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* Helper function for rotations:
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* - old's parent and color get assigned to new
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* - old gets assigned new as a parent and 'color' as a color.
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*/
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static inline void
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__rb_rotate_set_parents(struct rb_node *old, struct rb_node *new,
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struct rb_root *root, int color)
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{
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struct rb_node *parent = rb_parent(old);
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new->__rb_parent_color = old->__rb_parent_color;
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rb_set_parent_color(old, new, color);
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__rb_change_child(old, new, parent, root);
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}
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static __always_inline void
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__rb_insert(struct rb_node *node, struct rb_root *root,
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void (*augment_rotate)(struct rb_node *old, struct rb_node *new))
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{
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struct rb_node *parent = rb_red_parent(node), *gparent, *tmp;
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while (true) {
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/*
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* Loop invariant: node is red
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*
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* If there is a black parent, we are done.
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* Otherwise, take some corrective action as we don't
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* want a red root or two consecutive red nodes.
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*/
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if (!parent) {
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rb_set_parent_color(node, NULL, RB_BLACK);
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break;
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} else if (rb_is_black(parent))
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break;
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gparent = rb_red_parent(parent);
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tmp = gparent->rb_right;
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if (parent != tmp) { /* parent == gparent->rb_left */
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if (tmp && rb_is_red(tmp)) {
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/*
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* Case 1 - color flips
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*
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* G g
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* / \ / \
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* p u --> P U
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* / /
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* n N
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*
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* However, since g's parent might be red, and
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* 4) does not allow this, we need to recurse
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* at g.
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*/
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rb_set_parent_color(tmp, gparent, RB_BLACK);
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rb_set_parent_color(parent, gparent, RB_BLACK);
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node = gparent;
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parent = rb_parent(node);
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rb_set_parent_color(node, parent, RB_RED);
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continue;
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}
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tmp = parent->rb_right;
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if (node == tmp) {
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/*
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* Case 2 - left rotate at parent
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*
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* G G
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* / \ / \
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* p U --> n U
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* \ /
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* n p
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*
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* This still leaves us in violation of 4), the
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* continuation into Case 3 will fix that.
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*/
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parent->rb_right = tmp = node->rb_left;
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node->rb_left = parent;
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if (tmp)
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rb_set_parent_color(tmp, parent,
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RB_BLACK);
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rb_set_parent_color(parent, node, RB_RED);
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augment_rotate(parent, node);
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parent = node;
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tmp = node->rb_right;
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}
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/*
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* Case 3 - right rotate at gparent
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*
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* G P
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* / \ / \
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* p U --> n g
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* / \
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* n U
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*/
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gparent->rb_left = tmp; /* == parent->rb_right */
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parent->rb_right = gparent;
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if (tmp)
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rb_set_parent_color(tmp, gparent, RB_BLACK);
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__rb_rotate_set_parents(gparent, parent, root, RB_RED);
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augment_rotate(gparent, parent);
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break;
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} else {
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tmp = gparent->rb_left;
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if (tmp && rb_is_red(tmp)) {
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/* Case 1 - color flips */
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rb_set_parent_color(tmp, gparent, RB_BLACK);
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rb_set_parent_color(parent, gparent, RB_BLACK);
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node = gparent;
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parent = rb_parent(node);
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rb_set_parent_color(node, parent, RB_RED);
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continue;
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}
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tmp = parent->rb_left;
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if (node == tmp) {
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/* Case 2 - right rotate at parent */
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parent->rb_left = tmp = node->rb_right;
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node->rb_right = parent;
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if (tmp)
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rb_set_parent_color(tmp, parent,
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RB_BLACK);
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rb_set_parent_color(parent, node, RB_RED);
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augment_rotate(parent, node);
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parent = node;
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tmp = node->rb_left;
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}
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/* Case 3 - left rotate at gparent */
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gparent->rb_right = tmp; /* == parent->rb_left */
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parent->rb_left = gparent;
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if (tmp)
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rb_set_parent_color(tmp, gparent, RB_BLACK);
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__rb_rotate_set_parents(gparent, parent, root, RB_RED);
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augment_rotate(gparent, parent);
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break;
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}
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}
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}
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/*
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* Inline version for rb_erase() use - we want to be able to inline
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* and eliminate the dummy_rotate callback there
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*/
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static __always_inline void
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____rb_erase_color(struct rb_node *parent, struct rb_root *root,
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void (*augment_rotate)(struct rb_node *old, struct rb_node *new))
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{
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struct rb_node *node = NULL, *sibling, *tmp1, *tmp2;
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while (true) {
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/*
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* Loop invariants:
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* - node is black (or NULL on first iteration)
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* - node is not the root (parent is not NULL)
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* - All leaf paths going through parent and node have a
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* black node count that is 1 lower than other leaf paths.
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*/
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sibling = parent->rb_right;
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if (node != sibling) { /* node == parent->rb_left */
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if (rb_is_red(sibling)) {
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/*
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* Case 1 - left rotate at parent
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*
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* P S
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* / \ / \
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* N s --> p Sr
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* / \ / \
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* Sl Sr N Sl
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*/
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parent->rb_right = tmp1 = sibling->rb_left;
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sibling->rb_left = parent;
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rb_set_parent_color(tmp1, parent, RB_BLACK);
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__rb_rotate_set_parents(parent, sibling, root,
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RB_RED);
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augment_rotate(parent, sibling);
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sibling = tmp1;
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}
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tmp1 = sibling->rb_right;
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if (!tmp1 || rb_is_black(tmp1)) {
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tmp2 = sibling->rb_left;
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if (!tmp2 || rb_is_black(tmp2)) {
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/*
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* Case 2 - sibling color flip
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* (p could be either color here)
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*
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* (p) (p)
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* / \ / \
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* N S --> N s
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* / \ / \
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* Sl Sr Sl Sr
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*
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* This leaves us violating 5) which
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* can be fixed by flipping p to black
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* if it was red, or by recursing at p.
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* p is red when coming from Case 1.
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*/
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rb_set_parent_color(sibling, parent,
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RB_RED);
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if (rb_is_red(parent))
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rb_set_black(parent);
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else {
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node = parent;
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parent = rb_parent(node);
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if (parent)
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continue;
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}
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break;
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}
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/*
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* Case 3 - right rotate at sibling
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* (p could be either color here)
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*
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* (p) (p)
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* / \ / \
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* N S --> N Sl
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* / \ \
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* sl Sr s
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* \
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* Sr
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*/
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sibling->rb_left = tmp1 = tmp2->rb_right;
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tmp2->rb_right = sibling;
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parent->rb_right = tmp2;
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if (tmp1)
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rb_set_parent_color(tmp1, sibling,
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RB_BLACK);
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augment_rotate(sibling, tmp2);
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tmp1 = sibling;
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sibling = tmp2;
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}
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/*
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* Case 4 - left rotate at parent + color flips
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* (p and sl could be either color here.
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* After rotation, p becomes black, s acquires
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* p's color, and sl keeps its color)
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*
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* (p) (s)
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* / \ / \
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* N S --> P Sr
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* / \ / \
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* (sl) sr N (sl)
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*/
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parent->rb_right = tmp2 = sibling->rb_left;
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sibling->rb_left = parent;
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rb_set_parent_color(tmp1, sibling, RB_BLACK);
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if (tmp2)
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rb_set_parent(tmp2, parent);
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__rb_rotate_set_parents(parent, sibling, root,
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RB_BLACK);
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augment_rotate(parent, sibling);
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break;
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} else {
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sibling = parent->rb_left;
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if (rb_is_red(sibling)) {
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/* Case 1 - right rotate at parent */
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parent->rb_left = tmp1 = sibling->rb_right;
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sibling->rb_right = parent;
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rb_set_parent_color(tmp1, parent, RB_BLACK);
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__rb_rotate_set_parents(parent, sibling, root,
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RB_RED);
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augment_rotate(parent, sibling);
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sibling = tmp1;
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}
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tmp1 = sibling->rb_left;
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if (!tmp1 || rb_is_black(tmp1)) {
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tmp2 = sibling->rb_right;
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if (!tmp2 || rb_is_black(tmp2)) {
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/* Case 2 - sibling color flip */
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rb_set_parent_color(sibling, parent,
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RB_RED);
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if (rb_is_red(parent))
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rb_set_black(parent);
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else {
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node = parent;
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parent = rb_parent(node);
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if (parent)
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continue;
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}
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break;
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}
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/* Case 3 - right rotate at sibling */
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sibling->rb_right = tmp1 = tmp2->rb_left;
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tmp2->rb_left = sibling;
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parent->rb_left = tmp2;
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if (tmp1)
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rb_set_parent_color(tmp1, sibling,
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RB_BLACK);
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augment_rotate(sibling, tmp2);
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tmp1 = sibling;
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sibling = tmp2;
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}
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/* Case 4 - left rotate at parent + color flips */
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parent->rb_left = tmp2 = sibling->rb_right;
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sibling->rb_right = parent;
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rb_set_parent_color(tmp1, sibling, RB_BLACK);
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if (tmp2)
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rb_set_parent(tmp2, parent);
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__rb_rotate_set_parents(parent, sibling, root,
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RB_BLACK);
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augment_rotate(parent, sibling);
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break;
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}
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}
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}
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/* Non-inline version for rb_erase_augmented() use */
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void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
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void (*augment_rotate)(struct rb_node *old, struct rb_node *new))
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{
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____rb_erase_color(parent, root, augment_rotate);
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}
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EXPORT_SYMBOL(__rb_erase_color);
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/*
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* Non-augmented rbtree manipulation functions.
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*
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* We use dummy augmented callbacks here, and have the compiler optimize them
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* out of the rb_insert_color() and rb_erase() function definitions.
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*/
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static inline void dummy_propagate(struct rb_node *node, struct rb_node *stop) {}
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static inline void dummy_copy(struct rb_node *old, struct rb_node *new) {}
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static inline void dummy_rotate(struct rb_node *old, struct rb_node *new) {}
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static const struct rb_augment_callbacks dummy_callbacks = {
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dummy_propagate, dummy_copy, dummy_rotate
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};
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void rb_insert_color(struct rb_node *node, struct rb_root *root)
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{
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__rb_insert(node, root, dummy_rotate);
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}
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EXPORT_SYMBOL(rb_insert_color);
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void rb_erase(struct rb_node *node, struct rb_root *root)
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{
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struct rb_node *rebalance;
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rebalance = __rb_erase_augmented(node, root, &dummy_callbacks);
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if (rebalance)
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____rb_erase_color(rebalance, root, dummy_rotate);
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}
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EXPORT_SYMBOL(rb_erase);
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/*
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* Augmented rbtree manipulation functions.
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*
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* This instantiates the same __always_inline functions as in the non-augmented
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* case, but this time with user-defined callbacks.
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*/
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void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
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void (*augment_rotate)(struct rb_node *old, struct rb_node *new))
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{
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__rb_insert(node, root, augment_rotate);
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}
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EXPORT_SYMBOL(__rb_insert_augmented);
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/*
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* This function returns the first node (in sort order) of the tree.
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*/
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struct rb_node *rb_first(const struct rb_root *root)
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{
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struct rb_node *n;
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n = root->rb_node;
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if (!n)
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return NULL;
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while (n->rb_left)
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n = n->rb_left;
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return n;
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}
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EXPORT_SYMBOL(rb_first);
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struct rb_node *rb_last(const struct rb_root *root)
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{
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struct rb_node *n;
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n = root->rb_node;
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if (!n)
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return NULL;
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while (n->rb_right)
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n = n->rb_right;
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return n;
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}
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EXPORT_SYMBOL(rb_last);
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struct rb_node *rb_next(const struct rb_node *node)
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{
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struct rb_node *parent;
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if (RB_EMPTY_NODE(node))
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return NULL;
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/*
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* If we have a right-hand child, go down and then left as far
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* as we can.
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*/
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if (node->rb_right) {
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node = node->rb_right;
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while (node->rb_left)
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node=node->rb_left;
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return (struct rb_node *)node;
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}
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/*
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* No right-hand children. Everything down and left is smaller than us,
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* so any 'next' node must be in the general direction of our parent.
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* Go up the tree; any time the ancestor is a right-hand child of its
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* parent, keep going up. First time it's a left-hand child of its
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* parent, said parent is our 'next' node.
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*/
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while ((parent = rb_parent(node)) && node == parent->rb_right)
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node = parent;
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return parent;
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}
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EXPORT_SYMBOL(rb_next);
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struct rb_node *rb_prev(const struct rb_node *node)
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{
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struct rb_node *parent;
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if (RB_EMPTY_NODE(node))
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return NULL;
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/*
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* If we have a left-hand child, go down and then right as far
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* as we can.
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*/
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if (node->rb_left) {
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node = node->rb_left;
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while (node->rb_right)
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node=node->rb_right;
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return (struct rb_node *)node;
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}
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/*
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* No left-hand children. Go up till we find an ancestor which
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* is a right-hand child of its parent.
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*/
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while ((parent = rb_parent(node)) && node == parent->rb_left)
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node = parent;
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return parent;
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}
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EXPORT_SYMBOL(rb_prev);
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void rb_replace_node(struct rb_node *victim, struct rb_node *new,
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struct rb_root *root)
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{
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struct rb_node *parent = rb_parent(victim);
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/* Set the surrounding nodes to point to the replacement */
|
|
__rb_change_child(victim, new, parent, root);
|
|
if (victim->rb_left)
|
|
rb_set_parent(victim->rb_left, new);
|
|
if (victim->rb_right)
|
|
rb_set_parent(victim->rb_right, new);
|
|
|
|
/* Copy the pointers/colour from the victim to the replacement */
|
|
*new = *victim;
|
|
}
|
|
EXPORT_SYMBOL(rb_replace_node);
|