Line data Source code
1 : /* SPDX-License-Identifier: GPL-2.0-or-later */
2 : /*
3 : Red Black Trees
4 : (C) 1999 Andrea Arcangeli <andrea@suse.de>
5 : (C) 2002 David Woodhouse <dwmw2@infradead.org>
6 : (C) 2012 Michel Lespinasse <walken@google.com>
7 :
8 :
9 : linux/include/linux/rbtree_augmented.h
10 : */
11 :
12 : #ifndef _LINUX_RBTREE_AUGMENTED_H
13 : #define _LINUX_RBTREE_AUGMENTED_H
14 :
15 : #include <linux/compiler.h>
16 : #include <linux/rbtree.h>
17 : #include <linux/rcupdate.h>
18 :
19 : /*
20 : * Please note - only struct rb_augment_callbacks and the prototypes for
21 : * rb_insert_augmented() and rb_erase_augmented() are intended to be public.
22 : * The rest are implementation details you are not expected to depend on.
23 : *
24 : * See Documentation/core-api/rbtree.rst for documentation and samples.
25 : */
26 :
27 : struct rb_augment_callbacks {
28 : void (*propagate)(struct rb_node *node, struct rb_node *stop);
29 : void (*copy)(struct rb_node *old, struct rb_node *new);
30 : void (*rotate)(struct rb_node *old, struct rb_node *new);
31 : };
32 :
33 : extern void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
34 : void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
35 :
36 : /*
37 : * Fixup the rbtree and update the augmented information when rebalancing.
38 : *
39 : * On insertion, the user must update the augmented information on the path
40 : * leading to the inserted node, then call rb_link_node() as usual and
41 : * rb_insert_augmented() instead of the usual rb_insert_color() call.
42 : * If rb_insert_augmented() rebalances the rbtree, it will callback into
43 : * a user provided function to update the augmented information on the
44 : * affected subtrees.
45 : */
46 : static inline void
47 17 : rb_insert_augmented(struct rb_node *node, struct rb_root *root,
48 : const struct rb_augment_callbacks *augment)
49 : {
50 17 : __rb_insert_augmented(node, root, augment->rotate);
51 17 : }
52 :
53 : static inline void
54 : rb_insert_augmented_cached(struct rb_node *node,
55 : struct rb_root_cached *root, bool newleft,
56 : const struct rb_augment_callbacks *augment)
57 : {
58 0 : if (newleft)
59 0 : root->rb_leftmost = node;
60 0 : rb_insert_augmented(node, &root->rb_root, augment);
61 : }
62 :
63 : /*
64 : * Template for declaring augmented rbtree callbacks (generic case)
65 : *
66 : * RBSTATIC: 'static' or empty
67 : * RBNAME: name of the rb_augment_callbacks structure
68 : * RBSTRUCT: struct type of the tree nodes
69 : * RBFIELD: name of struct rb_node field within RBSTRUCT
70 : * RBAUGMENTED: name of field within RBSTRUCT holding data for subtree
71 : * RBCOMPUTE: name of function that recomputes the RBAUGMENTED data
72 : */
73 :
74 : #define RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME, \
75 : RBSTRUCT, RBFIELD, RBAUGMENTED, RBCOMPUTE) \
76 : static inline void \
77 : RBNAME ## _propagate(struct rb_node *rb, struct rb_node *stop) \
78 : { \
79 : while (rb != stop) { \
80 : RBSTRUCT *node = rb_entry(rb, RBSTRUCT, RBFIELD); \
81 : if (RBCOMPUTE(node, true)) \
82 : break; \
83 : rb = rb_parent(&node->RBFIELD); \
84 : } \
85 : } \
86 : static inline void \
87 : RBNAME ## _copy(struct rb_node *rb_old, struct rb_node *rb_new) \
88 : { \
89 : RBSTRUCT *old = rb_entry(rb_old, RBSTRUCT, RBFIELD); \
90 : RBSTRUCT *new = rb_entry(rb_new, RBSTRUCT, RBFIELD); \
91 : new->RBAUGMENTED = old->RBAUGMENTED; \
92 : } \
93 : static void \
94 : RBNAME ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new) \
95 : { \
96 : RBSTRUCT *old = rb_entry(rb_old, RBSTRUCT, RBFIELD); \
97 : RBSTRUCT *new = rb_entry(rb_new, RBSTRUCT, RBFIELD); \
98 : new->RBAUGMENTED = old->RBAUGMENTED; \
99 : RBCOMPUTE(old, false); \
100 : } \
101 : RBSTATIC const struct rb_augment_callbacks RBNAME = { \
102 : .propagate = RBNAME ## _propagate, \
103 : .copy = RBNAME ## _copy, \
104 : .rotate = RBNAME ## _rotate \
105 : };
106 :
107 : /*
108 : * Template for declaring augmented rbtree callbacks,
109 : * computing RBAUGMENTED scalar as max(RBCOMPUTE(node)) for all subtree nodes.
110 : *
111 : * RBSTATIC: 'static' or empty
112 : * RBNAME: name of the rb_augment_callbacks structure
113 : * RBSTRUCT: struct type of the tree nodes
114 : * RBFIELD: name of struct rb_node field within RBSTRUCT
115 : * RBTYPE: type of the RBAUGMENTED field
116 : * RBAUGMENTED: name of RBTYPE field within RBSTRUCT holding data for subtree
117 : * RBCOMPUTE: name of function that returns the per-node RBTYPE scalar
118 : */
119 :
120 : #define RB_DECLARE_CALLBACKS_MAX(RBSTATIC, RBNAME, RBSTRUCT, RBFIELD, \
121 : RBTYPE, RBAUGMENTED, RBCOMPUTE) \
122 : static inline bool RBNAME ## _compute_max(RBSTRUCT *node, bool exit) \
123 : { \
124 : RBSTRUCT *child; \
125 : RBTYPE max = RBCOMPUTE(node); \
126 : if (node->RBFIELD.rb_left) { \
127 : child = rb_entry(node->RBFIELD.rb_left, RBSTRUCT, RBFIELD); \
128 : if (child->RBAUGMENTED > max) \
129 : max = child->RBAUGMENTED; \
130 : } \
131 : if (node->RBFIELD.rb_right) { \
132 : child = rb_entry(node->RBFIELD.rb_right, RBSTRUCT, RBFIELD); \
133 : if (child->RBAUGMENTED > max) \
134 : max = child->RBAUGMENTED; \
135 : } \
136 : if (exit && node->RBAUGMENTED == max) \
137 : return true; \
138 : node->RBAUGMENTED = max; \
139 : return false; \
140 : } \
141 : RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME, \
142 : RBSTRUCT, RBFIELD, RBAUGMENTED, RBNAME ## _compute_max)
143 :
144 :
145 : #define RB_RED 0
146 : #define RB_BLACK 1
147 :
148 : #define __rb_parent(pc) ((struct rb_node *)(pc & ~3))
149 :
150 : #define __rb_color(pc) ((pc) & 1)
151 : #define __rb_is_black(pc) __rb_color(pc)
152 : #define __rb_is_red(pc) (!__rb_color(pc))
153 : #define rb_color(rb) __rb_color((rb)->__rb_parent_color)
154 : #define rb_is_red(rb) __rb_is_red((rb)->__rb_parent_color)
155 : #define rb_is_black(rb) __rb_is_black((rb)->__rb_parent_color)
156 :
157 : static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
158 : {
159 44 : rb->__rb_parent_color = rb_color(rb) + (unsigned long)p;
160 : }
161 :
162 : static inline void rb_set_parent_color(struct rb_node *rb,
163 : struct rb_node *p, int color)
164 : {
165 16682 : rb->__rb_parent_color = (unsigned long)p + color;
166 : }
167 :
168 : static inline void
169 : __rb_change_child(struct rb_node *old, struct rb_node *new,
170 : struct rb_node *parent, struct rb_root *root)
171 : {
172 3849 : if (parent) {
173 1361 : if (parent->rb_left == old)
174 726 : WRITE_ONCE(parent->rb_left, new);
175 : else
176 635 : WRITE_ONCE(parent->rb_right, new);
177 : } else
178 2488 : WRITE_ONCE(root->rb_node, new);
179 : }
180 :
181 : static inline void
182 : __rb_change_child_rcu(struct rb_node *old, struct rb_node *new,
183 : struct rb_node *parent, struct rb_root *root)
184 : {
185 0 : if (parent) {
186 0 : if (parent->rb_left == old)
187 0 : rcu_assign_pointer(parent->rb_left, new);
188 : else
189 0 : rcu_assign_pointer(parent->rb_right, new);
190 : } else
191 0 : rcu_assign_pointer(root->rb_node, new);
192 : }
193 :
194 : extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
195 : void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
196 :
197 : static __always_inline struct rb_node *
198 : __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
199 : const struct rb_augment_callbacks *augment)
200 : {
201 1246 : struct rb_node *child = node->rb_right;
202 1246 : struct rb_node *tmp = node->rb_left;
203 : struct rb_node *parent, *rebalance;
204 : unsigned long pc;
205 :
206 1246 : if (!tmp) {
207 : /*
208 : * Case 1: node to erase has no more than 1 child (easy!)
209 : *
210 : * Note that if there is one child it must be red due to 5)
211 : * and node must be black due to 4). We adjust colors locally
212 : * so as to bypass __rb_erase_color() later on.
213 : */
214 1182 : pc = node->__rb_parent_color;
215 1182 : parent = __rb_parent(pc);
216 1182 : __rb_change_child(node, child, parent, root);
217 1182 : if (child) {
218 349 : child->__rb_parent_color = pc;
219 349 : rebalance = NULL;
220 : } else
221 833 : rebalance = __rb_is_black(pc) ? parent : NULL;
222 : tmp = parent;
223 64 : } else if (!child) {
224 : /* Still case 1, but this time the child is node->rb_left */
225 24 : tmp->__rb_parent_color = pc = node->__rb_parent_color;
226 24 : parent = __rb_parent(pc);
227 : __rb_change_child(node, tmp, parent, root);
228 : rebalance = NULL;
229 : tmp = parent;
230 : } else {
231 40 : struct rb_node *successor = child, *child2;
232 :
233 40 : tmp = child->rb_left;
234 40 : if (!tmp) {
235 : /*
236 : * Case 2: node's successor is its right child
237 : *
238 : * (n) (s)
239 : * / \ / \
240 : * (x) (s) -> (x) (c)
241 : * \
242 : * (c)
243 : */
244 38 : parent = successor;
245 38 : child2 = successor->rb_right;
246 :
247 0 : augment->copy(node, successor);
248 : } else {
249 : /*
250 : * Case 3: node's successor is leftmost under
251 : * node's right child subtree
252 : *
253 : * (n) (s)
254 : * / \ / \
255 : * (x) (y) -> (x) (y)
256 : * / /
257 : * (p) (p)
258 : * / /
259 : * (s) (c)
260 : * \
261 : * (c)
262 : */
263 : do {
264 2 : parent = successor;
265 2 : successor = tmp;
266 2 : tmp = tmp->rb_left;
267 2 : } while (tmp);
268 2 : child2 = successor->rb_right;
269 2 : WRITE_ONCE(parent->rb_left, child2);
270 2 : WRITE_ONCE(successor->rb_right, child);
271 4 : rb_set_parent(child, successor);
272 :
273 0 : augment->copy(node, successor);
274 0 : augment->propagate(parent, successor);
275 : }
276 :
277 40 : tmp = node->rb_left;
278 40 : WRITE_ONCE(successor->rb_left, tmp);
279 80 : rb_set_parent(tmp, successor);
280 :
281 40 : pc = node->__rb_parent_color;
282 40 : tmp = __rb_parent(pc);
283 40 : __rb_change_child(node, successor, tmp, root);
284 :
285 40 : if (child2) {
286 1 : rb_set_parent_color(child2, parent, RB_BLACK);
287 : rebalance = NULL;
288 : } else {
289 39 : rebalance = rb_is_black(successor) ? parent : NULL;
290 : }
291 40 : successor->__rb_parent_color = pc;
292 40 : tmp = successor;
293 : }
294 :
295 0 : augment->propagate(tmp, NULL);
296 : return rebalance;
297 : }
298 :
299 : static __always_inline void
300 : rb_erase_augmented(struct rb_node *node, struct rb_root *root,
301 : const struct rb_augment_callbacks *augment)
302 : {
303 0 : struct rb_node *rebalance = __rb_erase_augmented(node, root, augment);
304 0 : if (rebalance)
305 0 : __rb_erase_color(rebalance, root, augment->rotate);
306 : }
307 :
308 : static __always_inline void
309 : rb_erase_augmented_cached(struct rb_node *node, struct rb_root_cached *root,
310 : const struct rb_augment_callbacks *augment)
311 : {
312 0 : if (root->rb_leftmost == node)
313 0 : root->rb_leftmost = rb_next(node);
314 0 : rb_erase_augmented(node, &root->rb_root, augment);
315 : }
316 :
317 : #endif /* _LINUX_RBTREE_AUGMENTED_H */
|
