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/rbtree.txt 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 rb_insert_augmented(struct rb_node *node, struct rb_root *root,
48 const struct rb_augment_callbacks *augment)
49 {
50 __rb_insert_augmented(node, root, augment->rotate);
51 }
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 if (newleft)
59 root->rb_leftmost = node;
60 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 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 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 if (parent) {
173 if (parent->rb_left == old)
174 WRITE_ONCE(parent->rb_left, new);
175 else
176 WRITE_ONCE(parent->rb_right, new);
177 } else
178 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 if (parent) {
186 if (parent->rb_left == old)
187 rcu_assign_pointer(parent->rb_left, new);
188 else
189 rcu_assign_pointer(parent->rb_right, new);
190 } else
191 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 struct rb_node *child = node->rb_right;
202 struct rb_node *tmp = node->rb_left;
203 struct rb_node *parent, *rebalance;
204 unsigned long pc;
205
206 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 pc = node->__rb_parent_color;
215 parent = __rb_parent(pc);
216 __rb_change_child(node, child, parent, root);
217 if (child) {
218 child->__rb_parent_color = pc;
219 rebalance = NULL;
220 } else
221 rebalance = __rb_is_black(pc) ? parent : NULL;
222 tmp = parent;
223 } else if (!child) {
224 /* Still case 1, but this time the child is node->rb_left */
225 tmp->__rb_parent_color = pc = node->__rb_parent_color;
226 parent = __rb_parent(pc);
227 __rb_change_child(node, tmp, parent, root);
228 rebalance = NULL;
229 tmp = parent;
230 } else {
231 struct rb_node *successor = child, *child2;
232
233 tmp = child->rb_left;
234 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 parent = successor;
245 child2 = successor->rb_right;
246
247 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 parent = successor;
265 successor = tmp;
266 tmp = tmp->rb_left;
267 } while (tmp);
268 child2 = successor->rb_right;
269 WRITE_ONCE(parent->rb_left, child2);
270 WRITE_ONCE(successor->rb_right, child);
271 rb_set_parent(child, successor);
272
273 augment->copy(node, successor);
274 augment->propagate(parent, successor);
275 }
276
277 tmp = node->rb_left;
278 WRITE_ONCE(successor->rb_left, tmp);
279 rb_set_parent(tmp, successor);
280
281 pc = node->__rb_parent_color;
282 tmp = __rb_parent(pc);
283 __rb_change_child(node, successor, tmp, root);
284
285 if (child2) {
286 successor->__rb_parent_color = pc;
287 rb_set_parent_color(child2, parent, RB_BLACK);
288 rebalance = NULL;
289 } else {
290 unsigned long pc2 = successor->__rb_parent_color;
291 successor->__rb_parent_color = pc;
292 rebalance = __rb_is_black(pc2) ? parent : NULL;
293 }
294 tmp = successor;
295 }
296
297 augment->propagate(tmp, NULL);
298 return rebalance;
299 }
300
301 static __always_inline void
302 rb_erase_augmented(struct rb_node *node, struct rb_root *root,
303 const struct rb_augment_callbacks *augment)
304 {
305 struct rb_node *rebalance = __rb_erase_augmented(node, root, augment);
306 if (rebalance)
307 __rb_erase_color(rebalance, root, augment->rotate);
308 }
309
310 static __always_inline void
311 rb_erase_augmented_cached(struct rb_node *node, struct rb_root_cached *root,
312 const struct rb_augment_callbacks *augment)
313 {
314 if (root->rb_leftmost == node)
315 root->rb_leftmost = rb_next(node);
316 rb_erase_augmented(node, &root->rb_root, augment);
317 }
318
319 #endif /* _LINUX_RBTREE_AUGMENTED_H */