urcu-rbtree.c

   1 /*
   2  * urcu-rbtree.c
   3  *
   4  * Userspace RCU library - Red-Black Tree
   5  *
   6  * Copyright (c) 2010 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  *
  22  * Implementation of RCU-adapted data structures and operations based on the RB
  23  * tree algorithms found in chapter 12 of:
  24  *
  25  * Thomas H. Cormen, Charles E. Leiserson, Ronald L. Rivest, and
  26  * Clifford Stein. Introduction to Algorithms, Third Edition. The MIT
  27  * Press, September 2009.
  28  */
  29
  30 #define _BSD_SOURCE
  31 #define _LGPL_SOURCE
  32
  33 #include <stdio.h>
  34 #include <pthread.h>
  35 #include <assert.h>
  36 #include <string.h>
  37 #include <unistd.h>
  38
  39 #include <urcu/rcurbtree.h>
  40 #include <urcu-pointer.h>
  41 #include <urcu-call-rcu.h>
  42 #include <urcu/compiler.h>
  43
  44 #ifdef DEBUG
  45 #define dbg_printf(args...)     printf(args)
  46 #define dbg_usleep(usecs)       usleep(usecs)
  47 #else
  48 #define dbg_printf(args...)
  49 #define dbg_usleep(usecs)
  50 #endif
  51
  52 /*
  53  * Undefine this to enable the non-RCU rotate and transplant functions
  54  * (for debugging).
  55  */
  56 #define RBTREE_RCU_SUPPORT_ROTATE_LEFT
  57 #define RBTREE_RCU_SUPPORT_ROTATE_RIGHT
  58 #define RBTREE_RCU_SUPPORT_TRANSPLANT
  59
  60 #ifdef EXTRA_DEBUG
  61 static pthread_mutex_t test_mutex = PTHREAD_MUTEX_INITIALIZER;
  62 static pthread_mutex_t outer_mutex = PTHREAD_MUTEX_INITIALIZER;
  63
  64 static
  65 void lock_outer_mutex(void)
  66 {
  67         pthread_mutex_lock(&outer_mutex);
  68 }
  69
  70 static
  71 void unlock_outer_mutex(void)
  72 {
  73         pthread_mutex_unlock(&outer_mutex);
  74 }
  75
  76 static
  77 void lock_test_mutex(void)
  78 {
  79         pthread_mutex_lock(&test_mutex);
  80 }
  81
  82 static
  83 void unlock_test_mutex(void)
  84 {
  85         pthread_mutex_unlock(&test_mutex);
  86 }
  87 #endif
  88
  89 static
  90 void set_parent(struct rcu_rbtree_node *node,
  91                 struct rcu_rbtree_node *parent,
  92                 unsigned int pos)
  93 {
  94         _CMM_STORE_SHARED(node->parent, ((unsigned long) parent) | pos);
  95 }
  96
  97 static
  98 struct rcu_rbtree_node *get_parent(struct rcu_rbtree_node *node)
  99 {
 100         return (struct rcu_rbtree_node *) (node->parent & ~1UL);
 101 }
 102
 103 static
 104 unsigned int get_pos(struct rcu_rbtree_node *node)
 105 {
 106         return (unsigned int) (node->parent & 1UL);
 107 }
 108
 109 static
 110 struct rcu_rbtree_node *get_parent_and_pos(struct rcu_rbtree_node *node,
 111                                 unsigned int *pos)
 112 {
 113         unsigned long parent_pos = rcu_dereference(node->parent);
 114
 115         *pos = (unsigned int) (parent_pos & 1UL);
 116         return (struct rcu_rbtree_node *) (parent_pos & ~1UL);
 117 }
 118
 119 static
 120 void set_decay(struct rcu_rbtree_node *x, struct rcu_rbtree_node *xc)
 121 {
 122         x->decay_next = xc;
 123 }
 124
 125 static
 126 struct rcu_rbtree_node *get_decay(struct rcu_rbtree_node *x)
 127 {
 128         if (!x)
 129                 return NULL;
 130         while (x->decay_next)
 131                 x = x->decay_next;
 132         return x;
 133 }
 134
 135 static
 136 struct rcu_rbtree_node *is_decay(struct rcu_rbtree_node *x)
 137 {
 138         return x->decay_next;
 139 }
 140
 141 static
 142 struct rcu_rbtree_node *dup_decay_node(struct rcu_rbtree *rbtree,
 143                                 struct rcu_rbtree_node *x)
 144 {
 145         struct rcu_rbtree_node *xc;
 146
 147         if (rcu_rbtree_is_nil(rbtree, x))
 148                 return x;
 149
 150         xc = rbtree->rballoc();
 151         memcpy(xc, x, sizeof(struct rcu_rbtree_node));
 152         xc->decay_next = NULL;
 153         set_decay(x, xc);
 154         call_rcu(&x->head, rbtree->rbfree);
 155         return xc;
 156 }
 157
 158 /*
 159  * Info for range lookups:
 160  * Range lookup information is only valid when used when searching for
 161  * ranges. It should never be used in next/prev traversal because the
 162  * pointers to parents are not in sync with the parent vision of the
 163  * children range.
 164  */
 165 static
 166 void set_left(struct rcu_rbtree *rbtree, struct rcu_rbtree_node *node,
 167                         struct rcu_rbtree_node *left)
 168 {
 169         node->_left = left;
 170 }
 171
 172 static
 173 void set_right(struct rcu_rbtree *rbtree, struct rcu_rbtree_node *node,
 174                         struct rcu_rbtree_node *right)
 175 {
 176         node->_right = right;
 177 }
 178
 179 /*
 180  * TODO
 181  * Deal with memory allocation errors.
 182  * Can be ensured by reserving a pool of memory entries before doing the
 183  * insertion, which will have to be function of number of
 184  * transplantations/rotations required for the operation.
 185  */
 186
 187 #ifdef DEBUG
 188 static
 189 void show_tree(struct rcu_rbtree *rbtree)
 190 {
 191         struct rcu_rbtree_node *node;
 192
 193         node = rcu_rbtree_min(rbtree, rbtree->root);
 194         while (!rcu_rbtree_is_nil(rbtree, node)) {
 195                 assert(!is_decay(node));
 196                 printf("{ b:%lX e:%lX pb: %lX pe: %lX r:%lX l:%lX %s %s %s} ",
 197                         (unsigned long) node->begin,
 198                         (unsigned long) node->end,
 199                         (unsigned long) get_parent(node)->begin,
 200                         (unsigned long) get_parent(node)->end,
 201                         (unsigned long) node->_right->key,
 202                         (unsigned long) node->_left->key,
 203                         node->color ? "red" : "black",
 204                         get_pos(node) ? "right" : "left",
 205                         rcu_rbtree_is_nil(rbtree, node) ? "nil" : "");
 206                 node = rcu_rbtree_next(rbtree, node);
 207         }
 208         printf("\n");
 209 }
 210 #else /* DEBUG */
 211 static
 212 void show_tree(struct rcu_rbtree *rbtree)
 213 {
 214 }
 215 #endif /* DEBUG */
 216
 217 static
 218 struct rcu_rbtree_node *make_nil(struct rcu_rbtree *rbtree)
 219 {
 220         return &rbtree->nil_node;
 221 }
 222
 223 /*
 224  * Iterative rbtree search.
 225  */
 226 struct rcu_rbtree_node *rcu_rbtree_search(struct rcu_rbtree *rbtree,
 227                                           struct rcu_rbtree_node *x,
 228                                           void *k)
 229 {
 230         x = rcu_dereference(x);
 231         int comp;
 232
 233         while (!rcu_rbtree_is_nil(rbtree, x) && (comp = rbtree->comp(k, x->begin)) != 0) {
 234                 dbg_usleep(10);
 235                 if (comp < 0)
 236                         x = rcu_dereference(x->_left);
 237                 else
 238                         x = rcu_dereference(x->_right);
 239         }
 240         return x;
 241 }
 242
 243 static
 244 struct rcu_rbtree_node *rcu_rbtree_min_dup_decay(struct rcu_rbtree *rbtree,
 245                                                  struct rcu_rbtree_node *x,
 246                                                  struct rcu_rbtree_node **zr)
 247 {
 248         struct rcu_rbtree_node *xl;
 249
 250         x = rcu_dereference(x);
 251
 252         if (rcu_rbtree_is_nil(rbtree, x)) {
 253                 *zr = x;
 254                 return x;
 255         } else
 256                 *zr = x = dup_decay_node(rbtree, x);
 257
 258         while (!rcu_rbtree_is_nil(rbtree, xl = rcu_dereference(x->_left))) {
 259                 x = dup_decay_node(rbtree, xl);
 260                 set_parent(x, get_decay(get_parent(x)), get_pos(x));
 261                 get_parent(x)->_left = get_decay(get_parent(x)->_left);
 262         }
 263         return x;
 264 }
 265
 266 static
 267 struct rcu_rbtree_node *rcu_rbtree_min_update_decay(struct rcu_rbtree *rbtree,
 268                                                     struct rcu_rbtree_node *x)
 269 {
 270         struct rcu_rbtree_node *xl;
 271
 272         x = rcu_dereference(x);
 273
 274         if (rcu_rbtree_is_nil(rbtree, x))
 275                 return x;
 276         else {
 277                 set_parent(x->_right, get_decay(get_parent(x->_right)),
 278                            get_pos(x->_right));
 279                 set_parent(x->_left, get_decay(get_parent(x->_left)),
 280                            get_pos(x->_left));
 281         }
 282
 283         while (!rcu_rbtree_is_nil(rbtree, xl = rcu_dereference(x->_left))) {
 284                 x = xl;
 285                 set_parent(x->_right, get_decay(get_parent(x->_right)),
 286                            get_pos(x->_right));
 287                 set_parent(x->_left, get_decay(get_parent(x->_left)),
 288                            get_pos(x->_left));
 289         }
 290         return x;
 291 }
 292
 293 struct rcu_rbtree_node *rcu_rbtree_min(struct rcu_rbtree *rbtree,
 294                                        struct rcu_rbtree_node *x)
 295 {
 296         struct rcu_rbtree_node *xl;
 297
 298         x = rcu_dereference(x);
 299
 300         if (rcu_rbtree_is_nil(rbtree, x))
 301                 return x;
 302
 303         while (!rcu_rbtree_is_nil(rbtree, xl = rcu_dereference(x->_left)))
 304                 x = xl;
 305         return x;
 306 }
 307
 308 struct rcu_rbtree_node *rcu_rbtree_max(struct rcu_rbtree *rbtree,
 309                                        struct rcu_rbtree_node *x)
 310 {
 311         struct rcu_rbtree_node *xr;
 312
 313         x = rcu_dereference(x);
 314
 315         if (rcu_rbtree_is_nil(rbtree, x))
 316                 return x;
 317
 318         while (!rcu_rbtree_is_nil(rbtree, xr = rcu_dereference(x->_right)))
 319                 x = xr;
 320         return x;
 321 }
 322
 323 /*
 324  * FIXME:
 325  * Updates should wait for a grace period between update of the
 326  * redirect pointer and update of the parent child pointer. This is to make sure
 327  * that no reference to the old entry exist.
 328  */
 329
 330 /*
 331  * RCU read lock must be held across the next/prev calls to ensure validity of
 332  * the returned node.
 333  */
 334 struct rcu_rbtree_node *rcu_rbtree_next(struct rcu_rbtree *rbtree,
 335                                         struct rcu_rbtree_node *x)
 336 {
 337         struct rcu_rbtree_node *xr, *y;
 338         unsigned int x_pos;
 339
 340         x = rcu_dereference(x);
 341
 342         if (!rcu_rbtree_is_nil(rbtree, xr = rcu_dereference(x->_right)))
 343                 return rcu_rbtree_min(rbtree, xr);
 344         y = get_parent_and_pos(x, &x_pos);
 345         while (!rcu_rbtree_is_nil(rbtree, y) && x_pos == IS_RIGHT) {
 346                 x = y;
 347                 y = get_parent_and_pos(y, &x_pos);
 348         }
 349         return y;
 350 }
 351
 352 struct rcu_rbtree_node *rcu_rbtree_prev(struct rcu_rbtree *rbtree,
 353                                         struct rcu_rbtree_node *x)
 354 {
 355         struct rcu_rbtree_node *xl, *y;
 356         unsigned int x_pos;
 357
 358         x = rcu_dereference(x);
 359
 360         if (!rcu_rbtree_is_nil(rbtree, xl = rcu_dereference(x->_left)))
 361                 return rcu_rbtree_max(rbtree, xl);
 362         y = get_parent_and_pos(x, &x_pos);
 363         while (!rcu_rbtree_is_nil(rbtree, y) && x_pos == IS_LEFT) {
 364                 x = y;
 365                 y = get_parent_and_pos(y, &x_pos);
 366         }
 367         return y;
 368 }
 369
 370 /*
 371  * We have to ensure these assumptions are correct for prev/next
 372  * traversal:
 373  *
 374  * with x being a right child, the assumption that:
 375  *   get_parent(x)->_right == x
 376  * or if x is a left child, the assumption that:
 377  *   get_parent(x)->_left == x
 378  *
 379  * This explains why we have to allocate a vc copy of the node for left_rotate,
 380  * right_rotate and transplant operations.
 381  *
 382  * We always ensure that the right/left child and correct parent is set in the
 383  * node copies *before* we reparent the children and make the upper-level point
 384  * to the copy.
 385  */
 386
 387 /* RCU: copy x and y, atomically point to new versions. GC old. */
 388 /* Should be eventually followed by a cmm_smp_wmc() */
 389
 390 #ifdef RBTREE_RCU_SUPPORT_ROTATE_LEFT
 391
 392 static
 393 void left_rotate(struct rcu_rbtree *rbtree,
 394                  struct rcu_rbtree_node *x)
 395 {
 396         struct rcu_rbtree_node *y, *y_left;
 397
 398         y = x->_right;
 399         y_left = y->_left;
 400
 401         /* Now operate on new copy, decay old versions */
 402         x = dup_decay_node(rbtree, x);
 403         y = dup_decay_node(rbtree, y);
 404         y_left = dup_decay_node(rbtree, y_left);
 405
 406         /* Internal node modifications */
 407         set_parent(y, get_parent(x), get_pos(x));
 408         set_parent(x, y, IS_LEFT);
 409         set_left(rbtree, y, x);
 410         set_right(rbtree, x, y_left);
 411
 412         if (!rcu_rbtree_is_nil(rbtree, y_left))
 413                 set_parent(y_left, x, IS_RIGHT);
 414
 415         cmm_smp_wmb();  /* write into node before publish */
 416
 417         /* External references update (visible by readers) */
 418         if (rcu_rbtree_is_nil(rbtree, get_parent(y)))
 419                 _CMM_STORE_SHARED(rbtree->root, y);
 420         else if (get_pos(y) == IS_LEFT)
 421                 _CMM_STORE_SHARED(get_parent(y)->_left, y);
 422         else
 423                 _CMM_STORE_SHARED(get_parent(y)->_right, y);
 424
 425         /* Point children to new copy (parent only used by updates/next/prev) */
 426         set_parent(x->_left, get_decay(get_parent(x->_left)),
 427                 get_pos(x->_left));
 428         set_parent(y->_right, get_decay(get_parent(y->_right)),
 429                 get_pos(y->_right));
 430         if (!rcu_rbtree_is_nil(rbtree, y_left)) {
 431                 set_parent(y_left->_right,
 432                         get_decay(get_parent(y_left->_right)),
 433                         get_pos(y_left->_right));
 434                 set_parent(y_left->_left,
 435                         get_decay(get_parent(y_left->_left)),
 436                         get_pos(y_left->_left));
 437         }
 438
 439         /* Sanity checks */
 440         assert(y == rbtree->root || get_parent(y)->_left == y
 441                 || get_parent(y)->_right == y);
 442         assert(x == rbtree->root || get_parent(x)->_left == x
 443                 || get_parent(x)->_right == x);
 444         assert(rcu_rbtree_is_nil(rbtree, x->_right) || get_parent(x->_right) == x);
 445         assert(rcu_rbtree_is_nil(rbtree, x->_left) || get_parent(x->_left) == x);
 446         assert(rcu_rbtree_is_nil(rbtree, y->_right) || get_parent(y->_right) == y);
 447         assert(rcu_rbtree_is_nil(rbtree, y->_left) || get_parent(y->_left) == y);
 448         assert(!is_decay(rbtree->root));
 449         assert(!is_decay(x));
 450         assert(!is_decay(y));
 451         assert(!is_decay(x->_right));
 452         assert(!is_decay(x->_left));
 453         assert(!is_decay(y->_right));
 454         assert(!is_decay(y->_left));
 455 }
 456
 457 #else
 458
 459 /* non-rcu version */
 460 static
 461 void left_rotate(struct rcu_rbtree *rbtree,
 462                  struct rcu_rbtree_node *x)
 463 {
 464         struct rcu_rbtree_node *y;
 465
 466         lock_test_mutex();
 467         y = x->_right;
 468         x->_right = y->_left;
 469         if (!rcu_rbtree_is_nil(rbtree, y->_left))
 470                 set_parent(y->_left, x, IS_RIGHT);
 471         set_parent(y, get_parent(x), get_pos(x));
 472         if (rcu_rbtree_is_nil(rbtree, get_parent(x)))
 473                 rbtree->root = y;
 474         else if (x == get_parent(x)->_left) {
 475                 get_parent(x)->_left = y;
 476         } else {
 477                 get_parent(x)->_right = y;
 478         }
 479         y->_left = x;
 480         set_parent(x, y, IS_LEFT);
 481         unlock_test_mutex();
 482 }
 483
 484 #endif
 485
 486 #ifdef RBTREE_RCU_SUPPORT_ROTATE_RIGHT
 487 static
 488 void right_rotate(struct rcu_rbtree *rbtree,
 489                   struct rcu_rbtree_node *x)
 490 {
 491         struct rcu_rbtree_node *y, *y_right;
 492
 493         y = x->_left;
 494         y_right = y->_right;
 495
 496         /* Now operate on new copy, decay old versions */
 497         x = dup_decay_node(rbtree, x);
 498         y = dup_decay_node(rbtree, y);
 499         y_right = dup_decay_node(rbtree, y_right);
 500
 501         /* Internal node modifications */
 502         set_parent(y, get_parent(x), get_pos(x));
 503         set_parent(x, y, IS_RIGHT);
 504         set_right(rbtree, y, x);
 505         set_left(rbtree, x, y_right);
 506
 507         if (!rcu_rbtree_is_nil(rbtree, y_right))
 508                 set_parent(y_right, x, IS_LEFT);
 509
 510         cmm_smp_wmb();  /* write into node before publish */
 511
 512         /* External references update (visible by readers) */
 513         if (rcu_rbtree_is_nil(rbtree, get_parent(y)))
 514                 _CMM_STORE_SHARED(rbtree->root, y);
 515         else if (get_pos(y) == IS_RIGHT)
 516                 _CMM_STORE_SHARED(get_parent(y)->_right, y);
 517         else
 518                 _CMM_STORE_SHARED(get_parent(y)->_left, y);
 519
 520         /* Point children to new copy (parent only used by updates/next/prev) */
 521         set_parent(x->_right, get_decay(get_parent(x->_right)),
 522                 get_pos(x->_right));
 523         set_parent(y->_left, get_decay(get_parent(y->_left)),
 524                 get_pos(y->_left));
 525         if (!rcu_rbtree_is_nil(rbtree, y_right)) {
 526                 set_parent(y_right->_left,
 527                         get_decay(get_parent(y_right->_left)),
 528                         get_pos(y_right->_left));
 529                 set_parent(y_right->_right,
 530                         get_decay(get_parent(y_right->_right)),
 531                         get_pos(y_right->_right));
 532         }
 533
 534         /* Sanity checks */
 535         assert(y == rbtree->root || get_parent(y)->_right == y
 536                 || get_parent(y)->_left == y);
 537         assert(x == rbtree->root || get_parent(x)->_right == x
 538                 || get_parent(x)->_left == x);
 539         assert(rcu_rbtree_is_nil(rbtree, x->_left) || get_parent(x->_left) == x);
 540         assert(rcu_rbtree_is_nil(rbtree, x->_right) || get_parent(x->_right) == x);
 541         assert(rcu_rbtree_is_nil(rbtree, y->_left) || get_parent(y->_left) == y);
 542         assert(rcu_rbtree_is_nil(rbtree, y->_right) || get_parent(y->_right) == y);
 543         assert(!is_decay(rbtree->root));
 544         assert(!is_decay(x));
 545         assert(!is_decay(y));
 546         assert(!is_decay(x->_left));
 547         assert(!is_decay(x->_right));
 548         assert(!is_decay(y->_left));
 549         assert(!is_decay(y->_right));
 550 }
 551
 552 #else
 553
 554 /* non-rcu version */
 555 static
 556 void right_rotate(struct rcu_rbtree *rbtree,
 557                   struct rcu_rbtree_node *x)
 558 {
 559         struct rcu_rbtree_node *y;
 560
 561         lock_test_mutex();
 562         y = x->_left;
 563         x->_left = y->_right;
 564         if (!rcu_rbtree_is_nil(rbtree, y->_right))
 565                 set_parent(y->_right, x, IS_LEFT);
 566         set_parent(y, get_parent(x), get_pos(x));
 567         if (rcu_rbtree_is_nil(rbtree, get_parent(x)))
 568                 rbtree->root = y;
 569         else if (x == get_parent(x)->_right) {
 570                 get_parent(x)->_right = y;
 571         } else {
 572                 get_parent(x)->_left = y;
 573         }
 574         y->_right = x;
 575         set_parent(x, y, IS_RIGHT);
 576         unlock_test_mutex();
 577 }
 578
 579 #endif
 580
 581 static void rcu_rbtree_insert_fixup(struct rcu_rbtree *rbtree,
 582                                     struct rcu_rbtree_node *z)
 583 {
 584         struct rcu_rbtree_node *y;
 585
 586         dbg_printf("insert fixup %p\n", z->begin);
 587         assert(!is_decay(rbtree->root));
 588
 589         while (get_parent(z)->color == COLOR_RED) {
 590                 if (get_parent(z) == get_parent(get_parent(z))->_left) {
 591                         y = get_parent(get_parent(z))->_right;
 592                         if (y->color == COLOR_RED) {
 593                                 get_parent(z)->color = COLOR_BLACK;
 594                                 y->color = COLOR_BLACK;
 595                                 get_parent(get_parent(z))->color = COLOR_RED;
 596                                 z = get_parent(get_parent(z));
 597                         } else {
 598                                 if (z == get_parent(z)->_right) {
 599                                         z = get_parent(z);
 600                                         left_rotate(rbtree, z);
 601                                         z = get_decay(z);
 602                                         assert(!is_decay(rbtree->root));
 603                                 }
 604                                 get_parent(z)->color = COLOR_BLACK;
 605                                 get_parent(get_parent(z))->color = COLOR_RED;
 606                                 assert(!is_decay(z));
 607                                 assert(!is_decay(get_parent(z)));
 608                                 assert(!is_decay(get_parent(get_parent(z))));
 609                                 right_rotate(rbtree, get_parent(get_parent(z)));
 610                                 assert(!is_decay(z));
 611                                 assert(!is_decay(rbtree->root));
 612                         }
 613                 } else {
 614                         y = get_parent(get_parent(z))->_left;
 615                         if (y->color == COLOR_RED) {
 616                                 get_parent(z)->color = COLOR_BLACK;
 617                                 y->color = COLOR_BLACK;
 618                                 get_parent(get_parent(z))->color = COLOR_RED;
 619                                 z = get_parent(get_parent(z));
 620                         } else {
 621                                 if (z == get_parent(z)->_left) {
 622                                         z = get_parent(z);
 623                                         right_rotate(rbtree, z);
 624                                         z = get_decay(z);
 625                                         assert(!is_decay(rbtree->root));
 626                                 }
 627                                 get_parent(z)->color = COLOR_BLACK;
 628                                 get_parent(get_parent(z))->color = COLOR_RED;
 629                                 left_rotate(rbtree, get_parent(get_parent(z)));
 630                                 assert(!is_decay(z));
 631                                 assert(!is_decay(rbtree->root));
 632                         }
 633                 }
 634         }
 635         rbtree->root->color = COLOR_BLACK;
 636 }
 637
 638 /*
 639  * rcu_rbtree_insert - Insert a node in the RCU rbtree
 640  *
 641  * Returns 0 on success, or < 0 on error.
 642  */
 643 int rcu_rbtree_insert(struct rcu_rbtree *rbtree,
 644                       struct rcu_rbtree_node *z)
 645 {
 646         struct rcu_rbtree_node *x, *y;
 647
 648         dbg_printf("insert %p\n", z->begin);
 649         assert(!is_decay(rbtree->root));
 650
 651         y = make_nil(rbtree);
 652         x = rbtree->root;
 653         while (!rcu_rbtree_is_nil(rbtree, x)) {
 654                 y = x;
 655                 if (rbtree->comp(z->begin, x->begin) < 0)
 656                         x = x->_left;
 657                 else
 658                         x = x->_right;
 659         }
 660
 661         z->_left = make_nil(rbtree);
 662         z->_right = make_nil(rbtree);
 663         z->color = COLOR_RED;
 664         z->decay_next = NULL;
 665
 666         if (rcu_rbtree_is_nil(rbtree, y))
 667                 set_parent(z, y, IS_RIGHT); /* pos arbitrary for root node */
 668         else if (rbtree->comp(z->begin, y->begin) < 0)
 669                 set_parent(z, y, IS_LEFT);
 670         else
 671                 set_parent(z, y, IS_RIGHT);
 672
 673         if (rcu_rbtree_is_nil(rbtree, y)) {
 674                 /*
 675                  * Order stores to z (children/parents) before stores
 676                  * that will make it visible to the rest of the tree.
 677                  */
 678                 cmm_smp_wmb();
 679                 _CMM_STORE_SHARED(rbtree->root, z);
 680         } else if (rbtree->comp(z->begin, y->begin) < 0) {
 681                 set_left(rbtree, y, z);
 682                 /*
 683                  * Order stores to z (children/parents) before stores
 684                  * that will make it visible to the rest of the tree.
 685                  */
 686                 cmm_smp_wmb();
 687                 if (rcu_rbtree_is_nil(rbtree, y))
 688                         _CMM_STORE_SHARED(rbtree->root, z);
 689                 else if (get_pos(z) == IS_LEFT)
 690                         _CMM_STORE_SHARED(y->_left, z);
 691                 else
 692                         _CMM_STORE_SHARED(y->_right, z);
 693         } else {
 694                 set_right(rbtree, y, z);
 695                 /*
 696                  * Order stores to z (children/parents) before stores
 697                  * that will make it visible to the rest of the tree.
 698                  */
 699                 cmm_smp_wmb();
 700                 if (rcu_rbtree_is_nil(rbtree, y))
 701                         _CMM_STORE_SHARED(rbtree->root, z);
 702                 else if (get_pos(z) == IS_LEFT)
 703                         _CMM_STORE_SHARED(y->_left, z);
 704                 else
 705                         _CMM_STORE_SHARED(y->_right, z);
 706         }
 707         rcu_rbtree_insert_fixup(rbtree, z);
 708         /*
 709          * Make sure to commit all _CMM_STORE_SHARED() for non-coherent caches.
 710          */
 711         cmm_smp_wmc();
 712         show_tree(rbtree);
 713
 714         return 0;
 715 }
 716
 717 /*
 718  * Transplant v into u position.
 719  */
 720
 721 #ifdef RBTREE_RCU_SUPPORT_TRANSPLANT
 722
 723 static
 724 void rcu_rbtree_transplant(struct rcu_rbtree *rbtree,
 725                         struct rcu_rbtree_node *u,
 726                         struct rcu_rbtree_node *v,
 727                         unsigned int copy_parents)
 728 {
 729         dbg_printf("transplant %p\n", v->begin);
 730
 731         if (!rcu_rbtree_is_nil(rbtree, v))
 732                 v = dup_decay_node(rbtree, v);
 733
 734         if (rcu_rbtree_is_nil(rbtree, get_parent(u))) {
 735                 /* pos is arbitrary for root node */
 736                 set_parent(v, get_parent(u), IS_RIGHT);
 737                 cmm_smp_wmb();  /* write into node before publish */
 738                 _CMM_STORE_SHARED(rbtree->root, v);
 739         } else {
 740                 set_parent(v, get_parent(u), get_pos(u));
 741
 742                 if (get_pos(u) == IS_LEFT)
 743                         set_left(rbtree, get_parent(u), v);
 744                 else
 745                         set_right(rbtree, get_parent(u), v);
 746
 747                 cmm_smp_wmb();  /* write into node before publish */
 748
 749                 if (rcu_rbtree_is_nil(rbtree, get_parent(u)))
 750                         _CMM_STORE_SHARED(rbtree->root, v);
 751                 else if (get_pos(u) == IS_LEFT)
 752                         _CMM_STORE_SHARED(get_parent(u)->_left, v);
 753                 else
 754                         _CMM_STORE_SHARED(get_parent(u)->_right, v);
 755         }
 756
 757         /* Point children to new copy (parent only used by updates/next/prev) */
 758         if (!rcu_rbtree_is_nil(rbtree, v)) {
 759                 set_parent(v->_right, get_decay(get_parent(v->_right)),
 760                         get_pos(v->_right));
 761                 set_parent(v->_left, get_decay(get_parent(v->_left)),
 762                         get_pos(v->_left));
 763         }
 764         assert(!is_decay(rbtree->root));
 765 }
 766
 767 #else
 768
 769 /* Non-RCU version */
 770 static
 771 void rcu_rbtree_transplant(struct rcu_rbtree *rbtree,
 772                            struct rcu_rbtree_node *u,
 773                            struct rcu_rbtree_node *v,
 774                            unsigned int copy_parents)
 775 {
 776         dbg_printf("transplant %p\n", v->begin);
 777
 778         lock_test_mutex();
 779         if (rcu_rbtree_is_nil(rbtree, get_parent(u)))
 780                 rbtree->root = v;
 781         else if (u == get_parent(u)->_left)
 782                 get_parent(u)->_left = v;
 783         else
 784                 get_parent(u)->_right = v;
 785         set_parent(v, get_parent(u), get_pos(u));
 786         unlock_test_mutex();
 787 }
 788
 789 #endif
 790
 791 static void rcu_rbtree_remove_fixup(struct rcu_rbtree *rbtree,
 792                                     struct rcu_rbtree_node *x)
 793 {
 794         dbg_printf("remove fixup %p\n", x->begin);
 795
 796         while (x != rbtree->root && x->color == COLOR_BLACK) {
 797                 assert(!is_decay(get_parent(x)));
 798                 assert(!is_decay(get_parent(x)->_left));
 799                 if (x == get_parent(x)->_left) {
 800                         struct rcu_rbtree_node *w;
 801
 802                         w = get_parent(x)->_right;
 803
 804                         if (w->color == COLOR_RED) {
 805                                 w->color = COLOR_BLACK;
 806                                 get_parent(x)->color = COLOR_RED;
 807                                 left_rotate(rbtree, get_parent(x));
 808                                 x = get_decay(x);
 809                                 assert(!is_decay(rbtree->root));
 810                                 w = get_parent(x)->_right;
 811                         }
 812                         if (w->_left->color == COLOR_BLACK
 813                             && w->_right->color == COLOR_BLACK) {
 814                                 w->color = COLOR_RED;
 815                                 x = get_parent(x);
 816                                 assert(!is_decay(rbtree->root));
 817                                 assert(!is_decay(x));
 818                         } else {
 819                                 if (w->_right->color == COLOR_BLACK) {
 820                                         w->_left->color = COLOR_BLACK;
 821                                         w->color = COLOR_RED;
 822                                         right_rotate(rbtree, w);
 823                                         assert(!is_decay(rbtree->root));
 824                                         x = get_decay(x);
 825                                         w = get_parent(x)->_right;
 826                                 }
 827                                 w->color = get_parent(x)->color;
 828                                 get_parent(x)->color = COLOR_BLACK;
 829                                 w->_right->color = COLOR_BLACK;
 830                                 left_rotate(rbtree, get_parent(x));
 831                                 assert(!is_decay(rbtree->root));
 832                                 x = rbtree->root;
 833                         }
 834                 } else {
 835                         struct rcu_rbtree_node *w;
 836
 837                         w = get_parent(x)->_left;
 838
 839                         if (w->color == COLOR_RED) {
 840                                 w->color = COLOR_BLACK;
 841                                 get_parent(x)->color = COLOR_RED;
 842                                 right_rotate(rbtree, get_parent(x));
 843                                 assert(!is_decay(rbtree->root));
 844                                 x = get_decay(x);
 845                                 w = get_parent(x)->_left;
 846                         }
 847                         if (w->_right->color == COLOR_BLACK
 848                             && w->_left->color == COLOR_BLACK) {
 849                                 w->color = COLOR_RED;
 850                                 x = get_parent(x);
 851                                 assert(!is_decay(rbtree->root));
 852                                 assert(!is_decay(x));
 853                         } else {
 854                                 if (w->_left->color == COLOR_BLACK) {
 855                                         w->_right->color = COLOR_BLACK;
 856                                         w->color = COLOR_RED;
 857                                         left_rotate(rbtree, w);
 858                                         assert(!is_decay(rbtree->root));
 859                                         x = get_decay(x);
 860                                         w = get_parent(x)->_left;
 861                                 }
 862                                 w->color = get_parent(x)->color;
 863                                 get_parent(x)->color = COLOR_BLACK;
 864                                 w->_left->color = COLOR_BLACK;
 865                                 right_rotate(rbtree, get_parent(x));
 866                                 assert(!is_decay(rbtree->root));
 867                                 x = rbtree->root;
 868                         }
 869                 }
 870         }
 871         x->color = COLOR_BLACK;
 872 }
 873
 874 /*
 875  * Delete z. All non-copied children left/right positions are unchanged.
 876  */
 877 static
 878 void rcu_rbtree_remove_nonil(struct rcu_rbtree *rbtree,
 879                              struct rcu_rbtree_node *z,
 880                              struct rcu_rbtree_node *y)
 881 {
 882         struct rcu_rbtree_node *x;
 883
 884         dbg_printf("remove nonil %p\n", z->begin);
 885         show_tree(rbtree);
 886
 887         assert(!is_decay(z));
 888         assert(!is_decay(y));
 889         assert(!is_decay(y->_right));
 890         assert(!is_decay(get_parent(y)));
 891         x = y->_right;
 892         assert(!is_decay(x));
 893         if (get_parent(y) == z) {
 894                 y = dup_decay_node(rbtree, y);
 895                 set_parent(x, y, get_pos(x));   /* parent for nil */
 896                 /* y is z's right node: set left will just update y */
 897                 set_left(rbtree, y, z->_left);
 898                 rcu_rbtree_transplant(rbtree, z, y, 1);
 899         } else {
 900                 struct rcu_rbtree_node *oy_right, *z_right;
 901
 902                 /*
 903                  * Need to make sure y is always visible by readers.
 904                  */
 905                 y = rcu_rbtree_min_dup_decay(rbtree, z->_right, &z_right);
 906                 assert(!is_decay(y));
 907                 assert(!is_decay(z));
 908                 oy_right = y->_right;
 909
 910                 /*
 911                  * The max child begin of z_right does not change, because
 912                  * we're only changing its left children.
 913                  */
 914                 y->_right = z_right;
 915                 set_parent(y->_right, y, IS_RIGHT);
 916                 assert(!is_decay(z->_left));
 917                 y->_left = z->_left;
 918                 assert(!is_decay(oy_right));
 919                 /*
 920                  * Transplant of oy_right to old y's location will only
 921                  * trigger a min/max update of the already copied branch
 922                  * (which is not visible yet). We are transplanting
 923                  * oy_right as a left child of old y's parent, so the
 924                  * min values update propagated upward necessarily stops
 925                  * at z_right.
 926                  */
 927                 rcu_rbtree_transplant(rbtree, y, oy_right, 0);
 928                 rcu_rbtree_transplant(rbtree, z, y, 1);
 929                 /* Update children */
 930                 (void) rcu_rbtree_min_update_decay(rbtree, y->_right);
 931         }
 932         y = get_decay(y);
 933         assert(!is_decay(z));
 934         assert(!is_decay(z->_left));
 935         y->color = z->color;
 936         set_parent(y->_left, y, IS_LEFT);
 937         set_parent(y->_right, get_decay(get_parent(y->_right)), IS_RIGHT);
 938         assert(!is_decay(y->_left));
 939         assert(!is_decay(y->_right));
 940 }
 941
 942 int rcu_rbtree_remove(struct rcu_rbtree *rbtree,
 943                       struct rcu_rbtree_node *z)
 944 {
 945         struct rcu_rbtree_node *x, *y;
 946         unsigned int y_original_color;
 947
 948         assert(!is_decay(rbtree->root));
 949         dbg_printf("remove %p\n", z->begin);
 950         show_tree(rbtree);
 951
 952         assert(!is_decay(z));
 953         y = z;
 954         y_original_color = y->color;
 955
 956         if (rcu_rbtree_is_nil(rbtree, z->_left)) {
 957                 rcu_rbtree_transplant(rbtree, z, z->_right, 1);
 958                 assert(!is_decay(z));
 959                 x = get_decay(z->_right);
 960                 show_tree(rbtree);
 961         } else if (rcu_rbtree_is_nil(rbtree, z->_right)) {
 962                 rcu_rbtree_transplant(rbtree, z, z->_left, 1);
 963                 assert(!is_decay(z));
 964                 x = get_decay(z->_left);
 965                 show_tree(rbtree);
 966         } else {
 967                 y = rcu_rbtree_min(rbtree, z->_right);
 968                 assert(!is_decay(y));
 969                 y_original_color = y->color;
 970                 x = y->_right;
 971                 rcu_rbtree_remove_nonil(rbtree, z, y);
 972                 x = get_decay(x);
 973                 show_tree(rbtree);
 974         }
 975         if (y_original_color == COLOR_BLACK)
 976                 rcu_rbtree_remove_fixup(rbtree, x);
 977         show_tree(rbtree);
 978         /*
 979          * Commit all _CMM_STORE_SHARED().
 980          */
 981         cmm_smp_wmc();
 982
 983         return 0;
 984 }