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, 34 struct rb_root *root, 35 bool newleft, struct rb_node **leftmost, 36 void (*augment_rotate)(struct rb_node *old, struct rb_node *new)); 37 /* 38 * Fixup the rbtree and update the augmented information when rebalancing. 39 * 40 * On insertion, the user must update the augmented information on the path 41 * leading to the inserted node, then call rb_link_node() as usual and 42 * rb_insert_augmented() instead of the usual rb_insert_color() call. 43 * If rb_insert_augmented() rebalances the rbtree, it will callback into 44 * a user provided function to update the augmented information on the 45 * affected subtrees. 46 */ 47 static inline void 48 rb_insert_augmented(struct rb_node *node, struct rb_root *root, 49 const struct rb_augment_callbacks *augment) 50 { 51 __rb_insert_augmented(node, root, false, NULL, augment->rotate); 52 } 53 54 static inline void 55 rb_insert_augmented_cached(struct rb_node *node, 56 struct rb_root_cached *root, bool newleft, 57 const struct rb_augment_callbacks *augment) 58 { 59 __rb_insert_augmented(node, &root->rb_root, 60 newleft, &root->rb_leftmost, augment->rotate); 61 } 62 63 #define RB_DECLARE_CALLBACKS(rbstatic, rbname, rbstruct, rbfield, \ 64 rbtype, rbaugmented, rbcompute) \ 65 static inline void \ 66 rbname ## _propagate(struct rb_node *rb, struct rb_node *stop) \ 67 { \ 68 while (rb != stop) { \ 69 rbstruct *node = rb_entry(rb, rbstruct, rbfield); \ 70 rbtype augmented = rbcompute(node); \ 71 if (node->rbaugmented == augmented) \ 72 break; \ 73 node->rbaugmented = augmented; \ 74 rb = rb_parent(&node->rbfield); \ 75 } \ 76 } \ 77 static inline void \ 78 rbname ## _copy(struct rb_node *rb_old, struct rb_node *rb_new) \ 79 { \ 80 rbstruct *old = rb_entry(rb_old, rbstruct, rbfield); \ 81 rbstruct *new = rb_entry(rb_new, rbstruct, rbfield); \ 82 new->rbaugmented = old->rbaugmented; \ 83 } \ 84 static void \ 85 rbname ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new) \ 86 { \ 87 rbstruct *old = rb_entry(rb_old, rbstruct, rbfield); \ 88 rbstruct *new = rb_entry(rb_new, rbstruct, rbfield); \ 89 new->rbaugmented = old->rbaugmented; \ 90 old->rbaugmented = rbcompute(old); \ 91 } \ 92 rbstatic const struct rb_augment_callbacks rbname = { \ 93 .propagate = rbname ## _propagate, \ 94 .copy = rbname ## _copy, \ 95 .rotate = rbname ## _rotate \ 96 }; 97 98 99 #define RB_RED 0 100 #define RB_BLACK 1 101 102 #define __rb_parent(pc) ((struct rb_node *)(pc & ~3)) 103 104 #define __rb_color(pc) ((pc) & 1) 105 #define __rb_is_black(pc) __rb_color(pc) 106 #define __rb_is_red(pc) (!__rb_color(pc)) 107 #define rb_color(rb) __rb_color((rb)->__rb_parent_color) 108 #define rb_is_red(rb) __rb_is_red((rb)->__rb_parent_color) 109 #define rb_is_black(rb) __rb_is_black((rb)->__rb_parent_color) 110 111 static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p) 112 { 113 rb->__rb_parent_color = rb_color(rb) | (unsigned long)p; 114 } 115 116 static inline void rb_set_parent_color(struct rb_node *rb, 117 struct rb_node *p, int color) 118 { 119 rb->__rb_parent_color = (unsigned long)p | color; 120 } 121 122 static inline void 123 __rb_change_child(struct rb_node *old, struct rb_node *new, 124 struct rb_node *parent, struct rb_root *root) 125 { 126 if (parent) { 127 if (parent->rb_left == old) 128 WRITE_ONCE(parent->rb_left, new); 129 else 130 WRITE_ONCE(parent->rb_right, new); 131 } else 132 WRITE_ONCE(root->rb_node, new); 133 } 134 135 static inline void 136 __rb_change_child_rcu(struct rb_node *old, struct rb_node *new, 137 struct rb_node *parent, struct rb_root *root) 138 { 139 if (parent) { 140 if (parent->rb_left == old) 141 rcu_assign_pointer(parent->rb_left, new); 142 else 143 rcu_assign_pointer(parent->rb_right, new); 144 } else 145 rcu_assign_pointer(root->rb_node, new); 146 } 147 148 extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root, 149 void (*augment_rotate)(struct rb_node *old, struct rb_node *new)); 150 151 static __always_inline struct rb_node * 152 __rb_erase_augmented(struct rb_node *node, struct rb_root *root, 153 struct rb_node **leftmost, 154 const struct rb_augment_callbacks *augment) 155 { 156 struct rb_node *child = node->rb_right; 157 struct rb_node *tmp = node->rb_left; 158 struct rb_node *parent, *rebalance; 159 unsigned long pc; 160 161 if (leftmost && node == *leftmost) 162 *leftmost = rb_next(node); 163 164 if (!tmp) { 165 /* 166 * Case 1: node to erase has no more than 1 child (easy!) 167 * 168 * Note that if there is one child it must be red due to 5) 169 * and node must be black due to 4). We adjust colors locally 170 * so as to bypass __rb_erase_color() later on. 171 */ 172 pc = node->__rb_parent_color; 173 parent = __rb_parent(pc); 174 __rb_change_child(node, child, parent, root); 175 if (child) { 176 child->__rb_parent_color = pc; 177 rebalance = NULL; 178 } else 179 rebalance = __rb_is_black(pc) ? parent : NULL; 180 tmp = parent; 181 } else if (!child) { 182 /* Still case 1, but this time the child is node->rb_left */ 183 tmp->__rb_parent_color = pc = node->__rb_parent_color; 184 parent = __rb_parent(pc); 185 __rb_change_child(node, tmp, parent, root); 186 rebalance = NULL; 187 tmp = parent; 188 } else { 189 struct rb_node *successor = child, *child2; 190 191 tmp = child->rb_left; 192 if (!tmp) { 193 /* 194 * Case 2: node's successor is its right child 195 * 196 * (n) (s) 197 * / \ / \ 198 * (x) (s) -> (x) (c) 199 * \ 200 * (c) 201 */ 202 parent = successor; 203 child2 = successor->rb_right; 204 205 augment->copy(node, successor); 206 } else { 207 /* 208 * Case 3: node's successor is leftmost under 209 * node's right child subtree 210 * 211 * (n) (s) 212 * / \ / \ 213 * (x) (y) -> (x) (y) 214 * / / 215 * (p) (p) 216 * / / 217 * (s) (c) 218 * \ 219 * (c) 220 */ 221 do { 222 parent = successor; 223 successor = tmp; 224 tmp = tmp->rb_left; 225 } while (tmp); 226 child2 = successor->rb_right; 227 WRITE_ONCE(parent->rb_left, child2); 228 WRITE_ONCE(successor->rb_right, child); 229 rb_set_parent(child, successor); 230 231 augment->copy(node, successor); 232 augment->propagate(parent, successor); 233 } 234 235 tmp = node->rb_left; 236 WRITE_ONCE(successor->rb_left, tmp); 237 rb_set_parent(tmp, successor); 238 239 pc = node->__rb_parent_color; 240 tmp = __rb_parent(pc); 241 __rb_change_child(node, successor, tmp, root); 242 243 if (child2) { 244 successor->__rb_parent_color = pc; 245 rb_set_parent_color(child2, parent, RB_BLACK); 246 rebalance = NULL; 247 } else { 248 unsigned long pc2 = successor->__rb_parent_color; 249 successor->__rb_parent_color = pc; 250 rebalance = __rb_is_black(pc2) ? parent : NULL; 251 } 252 tmp = successor; 253 } 254 255 augment->propagate(tmp, NULL); 256 return rebalance; 257 } 258 259 static __always_inline void 260 rb_erase_augmented(struct rb_node *node, struct rb_root *root, 261 const struct rb_augment_callbacks *augment) 262 { 263 struct rb_node *rebalance = __rb_erase_augmented(node, root, 264 NULL, augment); 265 if (rebalance) 266 __rb_erase_color(rebalance, root, augment->rotate); 267 } 268 269 static __always_inline void 270 rb_erase_augmented_cached(struct rb_node *node, struct rb_root_cached *root, 271 const struct rb_augment_callbacks *augment) 272 { 273 struct rb_node *rebalance = __rb_erase_augmented(node, &root->rb_root, 274 &root->rb_leftmost, 275 augment); 276 if (rebalance) 277 __rb_erase_color(rebalance, &root->rb_root, augment->rotate); 278 } 279 280 #endif /* _LINUX_RBTREE_AUGMENTED_H */ 281