1 /* SPDX-License-Identifier: GPL-2.0-or-later */ 2 /* 3 Red Black Trees 4 (C) 1999 Andrea Arcangeli <andrea@suse.de> 5 6 7 linux/include/linux/rbtree.h 8 9 To use rbtrees you'll have to implement your own insert and search cores. 10 This will avoid us to use callbacks and to drop drammatically performances. 11 I know it's not the cleaner way, but in C (not in C++) to get 12 performances and genericity... 13 14 See Documentation/core-api/rbtree.rst for documentation and samples. 15 */ 16 17 #ifndef _LINUX_RBTREE_H 18 #define _LINUX_RBTREE_H 19 20 #include <linux/container_of.h> 21 #include <linux/rbtree_types.h> 22 23 #include <linux/stddef.h> 24 #include <linux/rcupdate.h> 25 26 #define rb_parent(r) ((struct rb_node *)((r)->__rb_parent_color & ~3)) 27 28 #define rb_entry(ptr, type, member) container_of(ptr, type, member) 29 30 #define RB_EMPTY_ROOT(root) (READ_ONCE((root)->rb_node) == NULL) 31 32 /* 'empty' nodes are nodes that are known not to be inserted in an rbtree */ 33 #define RB_EMPTY_NODE(node) \ 34 ((node)->__rb_parent_color == (unsigned long)(node)) 35 #define RB_CLEAR_NODE(node) \ 36 ((node)->__rb_parent_color = (unsigned long)(node)) 37 38 39 extern void rb_insert_color(struct rb_node *, struct rb_root *); 40 extern void rb_erase(struct rb_node *, struct rb_root *); 41 42 43 /* Find logical next and previous nodes in a tree */ 44 extern struct rb_node *rb_next(const struct rb_node *); 45 extern struct rb_node *rb_prev(const struct rb_node *); 46 extern struct rb_node *rb_first(const struct rb_root *); 47 extern struct rb_node *rb_last(const struct rb_root *); 48 49 /* Postorder iteration - always visit the parent after its children */ 50 extern struct rb_node *rb_first_postorder(const struct rb_root *); 51 extern struct rb_node *rb_next_postorder(const struct rb_node *); 52 53 /* Fast replacement of a single node without remove/rebalance/add/rebalance */ 54 extern void rb_replace_node(struct rb_node *victim, struct rb_node *new, 55 struct rb_root *root); 56 extern void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new, 57 struct rb_root *root); 58 59 static inline void rb_link_node(struct rb_node *node, struct rb_node *parent, 60 struct rb_node **rb_link) 61 { 62 node->__rb_parent_color = (unsigned long)parent; 63 node->rb_left = node->rb_right = NULL; 64 65 *rb_link = node; 66 } 67 68 static inline void rb_link_node_rcu(struct rb_node *node, struct rb_node *parent, 69 struct rb_node **rb_link) 70 { 71 node->__rb_parent_color = (unsigned long)parent; 72 node->rb_left = node->rb_right = NULL; 73 74 rcu_assign_pointer(*rb_link, node); 75 } 76 77 #define rb_entry_safe(ptr, type, member) \ 78 ({ typeof(ptr) ____ptr = (ptr); \ 79 ____ptr ? rb_entry(____ptr, type, member) : NULL; \ 80 }) 81 82 /** 83 * rbtree_postorder_for_each_entry_safe - iterate in post-order over rb_root of 84 * given type allowing the backing memory of @pos to be invalidated 85 * 86 * @pos: the 'type *' to use as a loop cursor. 87 * @n: another 'type *' to use as temporary storage 88 * @root: 'rb_root *' of the rbtree. 89 * @field: the name of the rb_node field within 'type'. 90 * 91 * rbtree_postorder_for_each_entry_safe() provides a similar guarantee as 92 * list_for_each_entry_safe() and allows the iteration to continue independent 93 * of changes to @pos by the body of the loop. 94 * 95 * Note, however, that it cannot handle other modifications that re-order the 96 * rbtree it is iterating over. This includes calling rb_erase() on @pos, as 97 * rb_erase() may rebalance the tree, causing us to miss some nodes. 98 */ 99 #define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \ 100 for (pos = rb_entry_safe(rb_first_postorder(root), typeof(*pos), field); \ 101 pos && ({ n = rb_entry_safe(rb_next_postorder(&pos->field), \ 102 typeof(*pos), field); 1; }); \ 103 pos = n) 104 105 /* Same as rb_first(), but O(1) */ 106 #define rb_first_cached(root) (root)->rb_leftmost 107 108 static inline void rb_insert_color_cached(struct rb_node *node, 109 struct rb_root_cached *root, 110 bool leftmost) 111 { 112 if (leftmost) 113 root->rb_leftmost = node; 114 rb_insert_color(node, &root->rb_root); 115 } 116 117 118 static inline struct rb_node * 119 rb_erase_cached(struct rb_node *node, struct rb_root_cached *root) 120 { 121 struct rb_node *leftmost = NULL; 122 123 if (root->rb_leftmost == node) 124 leftmost = root->rb_leftmost = rb_next(node); 125 126 rb_erase(node, &root->rb_root); 127 128 return leftmost; 129 } 130 131 static inline void rb_replace_node_cached(struct rb_node *victim, 132 struct rb_node *new, 133 struct rb_root_cached *root) 134 { 135 if (root->rb_leftmost == victim) 136 root->rb_leftmost = new; 137 rb_replace_node(victim, new, &root->rb_root); 138 } 139 140 /* 141 * The below helper functions use 2 operators with 3 different 142 * calling conventions. The operators are related like: 143 * 144 * comp(a->key,b) < 0 := less(a,b) 145 * comp(a->key,b) > 0 := less(b,a) 146 * comp(a->key,b) == 0 := !less(a,b) && !less(b,a) 147 * 148 * If these operators define a partial order on the elements we make no 149 * guarantee on which of the elements matching the key is found. See 150 * rb_find(). 151 * 152 * The reason for this is to allow the find() interface without requiring an 153 * on-stack dummy object, which might not be feasible due to object size. 154 */ 155 156 /** 157 * rb_add_cached() - insert @node into the leftmost cached tree @tree 158 * @node: node to insert 159 * @tree: leftmost cached tree to insert @node into 160 * @less: operator defining the (partial) node order 161 * 162 * Returns @node when it is the new leftmost, or NULL. 163 */ 164 static __always_inline struct rb_node * 165 rb_add_cached(struct rb_node *node, struct rb_root_cached *tree, 166 bool (*less)(struct rb_node *, const struct rb_node *)) 167 { 168 struct rb_node **link = &tree->rb_root.rb_node; 169 struct rb_node *parent = NULL; 170 bool leftmost = true; 171 172 while (*link) { 173 parent = *link; 174 if (less(node, parent)) { 175 link = &parent->rb_left; 176 } else { 177 link = &parent->rb_right; 178 leftmost = false; 179 } 180 } 181 182 rb_link_node(node, parent, link); 183 rb_insert_color_cached(node, tree, leftmost); 184 185 return leftmost ? node : NULL; 186 } 187 188 /** 189 * rb_add() - insert @node into @tree 190 * @node: node to insert 191 * @tree: tree to insert @node into 192 * @less: operator defining the (partial) node order 193 */ 194 static __always_inline void 195 rb_add(struct rb_node *node, struct rb_root *tree, 196 bool (*less)(struct rb_node *, const struct rb_node *)) 197 { 198 struct rb_node **link = &tree->rb_node; 199 struct rb_node *parent = NULL; 200 201 while (*link) { 202 parent = *link; 203 if (less(node, parent)) 204 link = &parent->rb_left; 205 else 206 link = &parent->rb_right; 207 } 208 209 rb_link_node(node, parent, link); 210 rb_insert_color(node, tree); 211 } 212 213 /** 214 * rb_find_add() - find equivalent @node in @tree, or add @node 215 * @node: node to look-for / insert 216 * @tree: tree to search / modify 217 * @cmp: operator defining the node order 218 * 219 * Returns the rb_node matching @node, or NULL when no match is found and @node 220 * is inserted. 221 */ 222 static __always_inline struct rb_node * 223 rb_find_add(struct rb_node *node, struct rb_root *tree, 224 int (*cmp)(struct rb_node *, const struct rb_node *)) 225 { 226 struct rb_node **link = &tree->rb_node; 227 struct rb_node *parent = NULL; 228 int c; 229 230 while (*link) { 231 parent = *link; 232 c = cmp(node, parent); 233 234 if (c < 0) 235 link = &parent->rb_left; 236 else if (c > 0) 237 link = &parent->rb_right; 238 else 239 return parent; 240 } 241 242 rb_link_node(node, parent, link); 243 rb_insert_color(node, tree); 244 return NULL; 245 } 246 247 /** 248 * rb_find_add_rcu() - find equivalent @node in @tree, or add @node 249 * @node: node to look-for / insert 250 * @tree: tree to search / modify 251 * @cmp: operator defining the node order 252 * 253 * Adds a Store-Release for link_node. 254 * 255 * Returns the rb_node matching @node, or NULL when no match is found and @node 256 * is inserted. 257 */ 258 static __always_inline struct rb_node * 259 rb_find_add_rcu(struct rb_node *node, struct rb_root *tree, 260 int (*cmp)(struct rb_node *, const struct rb_node *)) 261 { 262 struct rb_node **link = &tree->rb_node; 263 struct rb_node *parent = NULL; 264 int c; 265 266 while (*link) { 267 parent = *link; 268 c = cmp(node, parent); 269 270 if (c < 0) 271 link = &parent->rb_left; 272 else if (c > 0) 273 link = &parent->rb_right; 274 else 275 return parent; 276 } 277 278 rb_link_node_rcu(node, parent, link); 279 rb_insert_color(node, tree); 280 return NULL; 281 } 282 283 /** 284 * rb_find() - find @key in tree @tree 285 * @key: key to match 286 * @tree: tree to search 287 * @cmp: operator defining the node order 288 * 289 * Returns the rb_node matching @key or NULL. 290 */ 291 static __always_inline struct rb_node * 292 rb_find(const void *key, const struct rb_root *tree, 293 int (*cmp)(const void *key, const struct rb_node *)) 294 { 295 struct rb_node *node = tree->rb_node; 296 297 while (node) { 298 int c = cmp(key, node); 299 300 if (c < 0) 301 node = node->rb_left; 302 else if (c > 0) 303 node = node->rb_right; 304 else 305 return node; 306 } 307 308 return NULL; 309 } 310 311 /** 312 * rb_find_rcu() - find @key in tree @tree 313 * @key: key to match 314 * @tree: tree to search 315 * @cmp: operator defining the node order 316 * 317 * Notably, tree descent vs concurrent tree rotations is unsound and can result 318 * in false-negatives. 319 * 320 * Returns the rb_node matching @key or NULL. 321 */ 322 static __always_inline struct rb_node * 323 rb_find_rcu(const void *key, const struct rb_root *tree, 324 int (*cmp)(const void *key, const struct rb_node *)) 325 { 326 struct rb_node *node = tree->rb_node; 327 328 while (node) { 329 int c = cmp(key, node); 330 331 if (c < 0) 332 node = rcu_dereference_raw(node->rb_left); 333 else if (c > 0) 334 node = rcu_dereference_raw(node->rb_right); 335 else 336 return node; 337 } 338 339 return NULL; 340 } 341 342 /** 343 * rb_find_first() - find the first @key in @tree 344 * @key: key to match 345 * @tree: tree to search 346 * @cmp: operator defining node order 347 * 348 * Returns the leftmost node matching @key, or NULL. 349 */ 350 static __always_inline struct rb_node * 351 rb_find_first(const void *key, const struct rb_root *tree, 352 int (*cmp)(const void *key, const struct rb_node *)) 353 { 354 struct rb_node *node = tree->rb_node; 355 struct rb_node *match = NULL; 356 357 while (node) { 358 int c = cmp(key, node); 359 360 if (c <= 0) { 361 if (!c) 362 match = node; 363 node = node->rb_left; 364 } else if (c > 0) { 365 node = node->rb_right; 366 } 367 } 368 369 return match; 370 } 371 372 /** 373 * rb_next_match() - find the next @key in @tree 374 * @key: key to match 375 * @tree: tree to search 376 * @cmp: operator defining node order 377 * 378 * Returns the next node matching @key, or NULL. 379 */ 380 static __always_inline struct rb_node * 381 rb_next_match(const void *key, struct rb_node *node, 382 int (*cmp)(const void *key, const struct rb_node *)) 383 { 384 node = rb_next(node); 385 if (node && cmp(key, node)) 386 node = NULL; 387 return node; 388 } 389 390 /** 391 * rb_for_each() - iterates a subtree matching @key 392 * @node: iterator 393 * @key: key to match 394 * @tree: tree to search 395 * @cmp: operator defining node order 396 */ 397 #define rb_for_each(node, key, tree, cmp) \ 398 for ((node) = rb_find_first((key), (tree), (cmp)); \ 399 (node); (node) = rb_next_match((key), (node), (cmp))) 400 401 #endif /* _LINUX_RBTREE_H */ 402