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00131368 MD |
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> | |
f6e888c5 | 35 | #include <assert.h> |
00131368 MD |
36 | |
37 | #include <urcu-rbtree.h> | |
38 | #include <urcu-pointer.h> | |
39 | ||
40 | /* | |
41 | * TODO | |
42 | * Deal with memory allocation errors. | |
43 | * Can be ensured by reserving a pool of memory entries before doing the | |
44 | * insertion, which will have to be function of number of | |
45 | * transplantations/rotations required for the operation. | |
46 | */ | |
47 | ||
48 | /* Sentinel (bottom nodes). Don't care about p, left, right and key values */ | |
db5b1669 | 49 | struct rcu_rbtree_node rcu_rbtree_nil = { |
00131368 MD |
50 | .color = COLOR_BLACK, |
51 | }; | |
52 | ||
53 | /* | |
54 | * Iterative rbtree search. | |
55 | */ | |
56 | struct rcu_rbtree_node* rcu_rbtree_search(struct rcu_rbtree_node *x, | |
57 | void *k, rcu_rbtree_comp comp) | |
58 | { | |
59 | x = rcu_dereference(x); | |
60 | ||
a23deda7 | 61 | while (x != &rcu_rbtree_nil && k != x->key) { |
00131368 MD |
62 | if (k < x->key) |
63 | x = rcu_dereference(x->left); | |
64 | else | |
65 | x = rcu_dereference(x->right); | |
66 | } | |
67 | return x; | |
68 | } | |
69 | ||
70 | struct rcu_rbtree_node *rcu_rbtree_min(struct rcu_rbtree_node *x, | |
71 | rcu_rbtree_comp comp) | |
72 | { | |
73 | struct rcu_rbtree_node *xl; | |
74 | ||
75 | x = rcu_dereference(x); | |
76 | ||
a23deda7 | 77 | while ((xl = rcu_dereference(x->left)) != &rcu_rbtree_nil) |
00131368 MD |
78 | x = xl; |
79 | return x; | |
80 | } | |
81 | ||
82 | struct rcu_rbtree_node *rcu_rbtree_max(struct rcu_rbtree_node *x, | |
83 | rcu_rbtree_comp comp) | |
84 | { | |
85 | struct rcu_rbtree_node *xr; | |
86 | ||
87 | x = rcu_dereference(x); | |
88 | ||
a23deda7 | 89 | while ((xr = rcu_dereference(x->right)) != &rcu_rbtree_nil) |
00131368 MD |
90 | x = xr; |
91 | return x; | |
92 | } | |
93 | ||
94 | /* | |
95 | * next and prev need to have mutex held to ensure that parent pointer is | |
96 | * coherent. | |
97 | */ | |
98 | struct rcu_rbtree_node *rcu_rbtree_next(struct rcu_rbtree_node *x, | |
99 | rcu_rbtree_comp comp) | |
100 | { | |
f6e888c5 | 101 | struct rcu_rbtree_node *xr, *y, *yredir; |
00131368 MD |
102 | |
103 | x = rcu_dereference(x); | |
104 | ||
a23deda7 | 105 | if ((xr = rcu_dereference(x->right)) != &rcu_rbtree_nil) |
00131368 MD |
106 | return rcu_rbtree_min(xr, comp); |
107 | y = rcu_dereference(x->p); | |
f6e888c5 MD |
108 | while ((yredir = rcu_dereference(y->redir)) != NULL) |
109 | y = yredir; | |
a23deda7 | 110 | while (y != &rcu_rbtree_nil && x == rcu_dereference(y->right)) { |
00131368 MD |
111 | x = y; |
112 | y = rcu_dereference(y->p); | |
f6e888c5 MD |
113 | while ((yredir = rcu_dereference(y->redir)) != NULL) |
114 | y = yredir; | |
00131368 MD |
115 | } |
116 | return y; | |
117 | } | |
118 | ||
119 | struct rcu_rbtree_node *rcu_rbtree_prev(struct rcu_rbtree_node *x, | |
120 | rcu_rbtree_comp comp) | |
121 | { | |
f6e888c5 | 122 | struct rcu_rbtree_node *xl, *y, *yredir; |
00131368 MD |
123 | |
124 | x = rcu_dereference(x); | |
125 | ||
a23deda7 | 126 | if ((xl = rcu_dereference(x->left)) != &rcu_rbtree_nil) |
00131368 MD |
127 | return rcu_rbtree_max(xl, comp); |
128 | y = rcu_dereference(x->p); | |
f6e888c5 MD |
129 | while ((yredir = rcu_dereference(y->redir)) != NULL) |
130 | y = yredir; | |
a23deda7 | 131 | while (y != &rcu_rbtree_nil && x == rcu_dereference(y->left)) { |
00131368 MD |
132 | x = y; |
133 | y = rcu_dereference(y->p); | |
f6e888c5 MD |
134 | while ((yredir = rcu_dereference(y->redir)) != NULL) |
135 | y = yredir; | |
00131368 MD |
136 | } |
137 | return y; | |
138 | } | |
139 | ||
140 | /* | |
141 | * We have to ensure these assumptions are correct for prev/next | |
142 | * traversal: | |
143 | * | |
144 | * with x being a right child, the assumption that: | |
145 | * x->p->right == x | |
146 | * or if x is a left child, the assumption that: | |
147 | * x->p->left == x | |
148 | * | |
149 | * This explains why we have to allocate a vc copy of the node for left_rotate, | |
150 | * right_rotate and transplant operations. | |
151 | * | |
152 | * We always ensure that the right/left child and correct parent is set in the | |
153 | * node copies *before* we reparent the children and make the upper-level point | |
154 | * to the copy. | |
155 | */ | |
156 | ||
157 | /* RCU: copy x and y, atomically point to new versions. GC old. */ | |
158 | /* Should be eventually followed by a smp_wmc() */ | |
159 | /* Returns the new x. Previous x->right references are changed to yc. */ | |
160 | static struct rcu_rbtree_node *left_rotate(struct rcu_rbtree_node **root, | |
161 | struct rcu_rbtree_node *x, | |
162 | rcu_rbtree_alloc rballoc, | |
163 | rcu_rbtree_free rbfree) | |
164 | { | |
165 | struct rcu_rbtree_node *xc, *y, *yc; | |
166 | ||
167 | y = x->right; | |
168 | ||
21cddea3 MD |
169 | if (x != &rcu_rbtree_nil) { |
170 | xc = rballoc(); | |
171 | *xc = *x; | |
a23deda7 MD |
172 | } |
173 | ||
174 | if (y != &rcu_rbtree_nil) { | |
175 | yc = rballoc(); | |
176 | *yc = *y; | |
177 | } | |
178 | ||
179 | /* Modify children and parents in the node copies */ | |
180 | if (x != &rcu_rbtree_nil) { | |
21cddea3 MD |
181 | xc->right = y->left; |
182 | xc->p = yc; | |
183 | } else | |
184 | xc = &rcu_rbtree_nil; | |
185 | ||
186 | if (y != &rcu_rbtree_nil) { | |
21cddea3 MD |
187 | yc->left = xc; |
188 | yc->p = x->p; | |
189 | } else | |
190 | yc = &rcu_rbtree_nil; | |
00131368 MD |
191 | |
192 | /* | |
193 | * Order stores to node copies (children/parents) before stores that | |
194 | * will make the copies visible to the rest of the tree. | |
195 | */ | |
196 | smp_wmb(); | |
197 | ||
f6e888c5 MD |
198 | /* |
199 | * redirect old nodes to new. | |
200 | */ | |
9a9703e6 MD |
201 | _STORE_SHARED(x->redir, xc); |
202 | _STORE_SHARED(y->redir, yc); | |
f6e888c5 MD |
203 | |
204 | /* | |
205 | * Ensure that redirections are visible before updating external | |
206 | * pointers. | |
207 | */ | |
208 | smp_wmb(); | |
209 | ||
00131368 | 210 | /* Make parents point to the copies */ |
db5b1669 | 211 | if (x->p == &rcu_rbtree_nil) |
00131368 MD |
212 | _STORE_SHARED(*root, yc); |
213 | else if (x == x->p->left) | |
214 | _STORE_SHARED(x->p->left, yc); | |
215 | else | |
216 | _STORE_SHARED(x->p->right, yc); | |
217 | ||
218 | /* Assign children parents to copies */ | |
21cddea3 MD |
219 | if (x != &rcu_rbtree_nil) { |
220 | _STORE_SHARED(xc->right->p, xc); | |
221 | _STORE_SHARED(xc->left->p, xc); | |
222 | defer_rcu(rbfree, x); | |
223 | } | |
224 | if (y != &rcu_rbtree_nil) { | |
225 | _STORE_SHARED(yc->right->p, yc); | |
226 | defer_rcu(rbfree, y); | |
227 | /* yc->left is xc, its parent is already set in node copy */ | |
228 | } | |
00131368 MD |
229 | return xc; |
230 | } | |
231 | ||
232 | #if 0 /* orig */ | |
233 | static void left_rotate(struct rcu_rbtree_node **root, | |
234 | struct rcu_rbtree_node *x, | |
235 | rcu_rbtree_alloc rballoc) | |
236 | { | |
237 | struct rcu_rbtree_node *y; | |
238 | ||
239 | y = x->right; | |
240 | x->right = y->left; | |
db5b1669 | 241 | if (y->left != &rcu_rbtree_nil) |
00131368 MD |
242 | y->left->p = x; |
243 | y->p = x->p; | |
db5b1669 | 244 | if (x->p == &rcu_rbtree_nil) |
00131368 MD |
245 | *root = y; |
246 | else if (x == x->p->left) | |
247 | x->p->left = y; | |
248 | else | |
249 | x->p->right = y; | |
250 | y->left = x; | |
251 | x->p = y; | |
252 | } | |
253 | #endif //0 | |
254 | ||
255 | /* RCU: copy x and y, atomically point to new versions. GC old. */ | |
256 | /* Should be eventually followed by a smp_wmc() */ | |
257 | /* Returns the new x. Previous x->left references are changed to yc. */ | |
258 | static struct rcu_rbtree_node *right_rotate(struct rcu_rbtree_node **root, | |
259 | struct rcu_rbtree_node *x, | |
260 | rcu_rbtree_alloc rballoc, | |
261 | rcu_rbtree_free rbfree) | |
262 | { | |
263 | struct rcu_rbtree_node *xc, *y, *yc; | |
264 | ||
265 | y = x->left; | |
266 | ||
21cddea3 MD |
267 | if (x != &rcu_rbtree_nil) { |
268 | xc = rballoc(); | |
269 | *xc = *x; | |
a23deda7 MD |
270 | } |
271 | ||
272 | if (y != &rcu_rbtree_nil) { | |
273 | yc = rballoc(); | |
274 | *yc = *y; | |
275 | } | |
276 | ||
277 | /* Modify children and parents in the node copies */ | |
278 | if (x != &rcu_rbtree_nil) { | |
21cddea3 MD |
279 | xc->left = y->right; |
280 | xc->p = yc; | |
281 | } else | |
282 | xc = &rcu_rbtree_nil; | |
283 | ||
284 | if (y != &rcu_rbtree_nil) { | |
21cddea3 MD |
285 | yc->right = xc; |
286 | yc->p = x->p; | |
287 | } else | |
288 | yc = &rcu_rbtree_nil; | |
00131368 MD |
289 | |
290 | /* | |
291 | * Order stores to node copies (children/parents) before stores that | |
292 | * will make the copies visible to the rest of the tree. | |
293 | */ | |
294 | smp_wmb(); | |
295 | ||
f6e888c5 MD |
296 | /* |
297 | * redirect old nodes to new. | |
298 | */ | |
9a9703e6 MD |
299 | _STORE_SHARED(x->redir, xc); |
300 | _STORE_SHARED(y->redir, yc); | |
f6e888c5 MD |
301 | |
302 | /* | |
303 | * Ensure that redirections are visible before updating external | |
304 | * pointers. | |
305 | */ | |
306 | smp_wmb(); | |
307 | ||
00131368 | 308 | /* Make parents point to the copies */ |
db5b1669 | 309 | if (x->p == &rcu_rbtree_nil) |
00131368 MD |
310 | _STORE_SHARED(*root, yc); |
311 | else if (x == x->p->right) | |
312 | _STORE_SHARED(x->p->right, yc); | |
313 | else | |
314 | _STORE_SHARED(x->p->left, yc); | |
315 | ||
316 | /* Assign children parents to copies */ | |
21cddea3 MD |
317 | if (x != &rcu_rbtree_nil) { |
318 | _STORE_SHARED(xc->left->p, xc); | |
319 | _STORE_SHARED(xc->right->p, xc); | |
320 | defer_rcu(rbfree, x); | |
321 | } | |
322 | if (y != &rcu_rbtree_nil) { | |
323 | _STORE_SHARED(yc->left->p, yc); | |
324 | defer_rcu(rbfree, y); | |
325 | /* yc->right is xc, its parent is already set in node copy */ | |
326 | } | |
00131368 MD |
327 | return xc; |
328 | } | |
329 | ||
330 | #if 0 //orig | |
331 | static void right_rotate(struct rcu_rbtree_node **root, | |
332 | struct rcu_rbtree_node *x, | |
333 | rcu_rbtree_alloc rballoc) | |
334 | { | |
335 | struct rcu_rbtree_node *y; | |
336 | ||
337 | y = x->left; | |
338 | x->left = y->right; | |
db5b1669 | 339 | if (y->right != &rcu_rbtree_nil) |
00131368 MD |
340 | y->right->p = x; |
341 | y->p = x->p; | |
db5b1669 | 342 | if (x->p == &rcu_rbtree_nil) |
00131368 MD |
343 | *root = y; |
344 | else if (x == x->p->right) | |
345 | x->p->right = y; | |
346 | else | |
347 | x->p->left = y; | |
348 | y->right = x; | |
349 | x->p = y; | |
350 | } | |
351 | #endif //0 | |
352 | ||
353 | static void rcu_rbtree_insert_fixup(struct rcu_rbtree_node **root, | |
354 | struct rcu_rbtree_node *z, | |
355 | rcu_rbtree_alloc rballoc, | |
356 | rcu_rbtree_free rbfree) | |
357 | { | |
358 | struct rcu_rbtree_node *y; | |
359 | ||
360 | while (z->p->color == COLOR_RED) { | |
361 | if (z->p == z->p->p->left) { | |
362 | y = z->p->p->right; | |
363 | if (y->color == COLOR_RED) { | |
364 | z->p->color = COLOR_BLACK; | |
365 | y->color = COLOR_BLACK; | |
366 | z->p->p->color = COLOR_RED; | |
367 | z = z->p->p; | |
368 | } else { | |
369 | if (z == z->p->right) { | |
370 | z = z->p; | |
371 | z = left_rotate(root, z, | |
372 | rballoc, rbfree); | |
373 | } | |
374 | z->p->color = COLOR_BLACK; | |
375 | z->p->p->color = COLOR_RED; | |
a23deda7 | 376 | right_rotate(root, z->p->p, rballoc, rbfree); |
00131368 MD |
377 | } |
378 | } else { | |
379 | y = z->p->p->left; | |
380 | if (y->color == COLOR_RED) { | |
381 | z->p->color = COLOR_BLACK; | |
382 | y->color = COLOR_BLACK; | |
383 | z->p->p->color = COLOR_RED; | |
384 | z = z->p->p; | |
385 | } else { | |
386 | if (z == z->p->left) { | |
387 | z = z->p; | |
388 | z = right_rotate(root, z, | |
389 | rballoc, rbfree); | |
390 | } | |
391 | z->p->color = COLOR_BLACK; | |
392 | z->p->p->color = COLOR_RED; | |
a23deda7 | 393 | left_rotate(root, z->p->p, rballoc, rbfree); |
00131368 MD |
394 | } |
395 | } | |
396 | } | |
397 | (*root)->color = COLOR_BLACK; | |
398 | } | |
399 | ||
400 | /* | |
401 | * rcu_rbtree_insert - Insert a node in the RCU rbtree | |
402 | * | |
403 | * Returns 0 on success, or < 0 on error. | |
404 | */ | |
405 | int rcu_rbtree_insert(struct rcu_rbtree_node **root, | |
406 | struct rcu_rbtree_node *z, | |
407 | rcu_rbtree_comp comp, | |
408 | rcu_rbtree_alloc rballoc, | |
409 | rcu_rbtree_free rbfree) | |
410 | { | |
411 | struct rcu_rbtree_node *x, *y; | |
412 | ||
db5b1669 | 413 | y = &rcu_rbtree_nil; |
00131368 MD |
414 | x = *root; |
415 | ||
db5b1669 | 416 | while (x != &rcu_rbtree_nil) { |
00131368 MD |
417 | y = x; |
418 | if (comp(z->key, x->key) < 0) | |
419 | x = x->left; | |
420 | else | |
421 | x = x->right; | |
422 | } | |
423 | ||
424 | z->p = y; | |
db5b1669 MD |
425 | z->left = &rcu_rbtree_nil; |
426 | z->right = &rcu_rbtree_nil; | |
00131368 | 427 | z->color = COLOR_RED; |
f6e888c5 | 428 | z->redir = NULL; |
00131368 MD |
429 | |
430 | /* | |
431 | * Order stores to z (children/parents) before stores that will make it | |
432 | * visible to the rest of the tree. | |
433 | */ | |
434 | smp_wmb(); | |
435 | ||
db5b1669 | 436 | if (y == &rcu_rbtree_nil) |
00131368 MD |
437 | _STORE_SHARED(*root, z); |
438 | else if (comp(z->key, y->key) < 0) | |
439 | _STORE_SHARED(y->left, z); | |
440 | else | |
441 | _STORE_SHARED(y->right, z); | |
442 | rcu_rbtree_insert_fixup(root, z, rballoc, rbfree); | |
443 | /* | |
444 | * Make sure to commit all _STORE_SHARED() for non-coherent caches. | |
445 | */ | |
446 | smp_wmc(); | |
447 | ||
448 | return 0; | |
449 | } | |
450 | ||
451 | /* | |
452 | * Transplant v into u position. | |
453 | * Returns new copy of v. | |
454 | */ | |
455 | static struct rcu_rbtree_node * | |
456 | rcu_rbtree_transplant(struct rcu_rbtree_node **root, | |
457 | struct rcu_rbtree_node *u, | |
458 | struct rcu_rbtree_node *v, | |
459 | rcu_rbtree_alloc rballoc, | |
460 | rcu_rbtree_free rbfree) | |
461 | { | |
462 | struct rcu_rbtree_node *vc; | |
463 | ||
21cddea3 MD |
464 | if (v != &rcu_rbtree_nil) { |
465 | vc = rballoc(); | |
466 | *vc = *v; | |
00131368 | 467 | |
21cddea3 MD |
468 | /* Change vc parent pointer */ |
469 | vc->p = u->p; | |
00131368 | 470 | |
21cddea3 MD |
471 | /* |
472 | * Order stores to node copies (children/parents) before stores | |
473 | * that will make the copies visible to the rest of the tree. | |
474 | */ | |
475 | smp_wmb(); | |
f6e888c5 MD |
476 | |
477 | /* | |
478 | * redirect old node to new. | |
479 | */ | |
9a9703e6 | 480 | _STORE_SHARED(v->redir, vc); |
f6e888c5 MD |
481 | |
482 | /* | |
483 | * Ensure that redirections are visible before updating external | |
484 | * pointers. | |
485 | */ | |
486 | smp_wmb(); | |
21cddea3 MD |
487 | } else { |
488 | vc = &rcu_rbtree_nil; | |
489 | } | |
00131368 MD |
490 | |
491 | /* Assign upper-level pointer to vc, replacing u. */ | |
db5b1669 | 492 | if (u->p == &rcu_rbtree_nil) |
00131368 MD |
493 | _STORE_SHARED(*root, vc); |
494 | else if (u == u->p->left) | |
495 | _STORE_SHARED(u->p->left, vc); | |
496 | else | |
497 | _STORE_SHARED(u->p->right, vc); | |
498 | ||
21cddea3 MD |
499 | if (v != &rcu_rbtree_nil) { |
500 | /* | |
501 | * The children pointers in vc are the same as v. We can | |
502 | * therefore reparent v's children to vc safely. | |
503 | */ | |
504 | _STORE_SHARED(vc->right->p, vc); | |
505 | _STORE_SHARED(vc->left->p, vc); | |
00131368 | 506 | |
21cddea3 MD |
507 | defer_rcu(rbfree, v); |
508 | } | |
00131368 MD |
509 | return vc; |
510 | } | |
511 | ||
512 | static void rcu_rbtree_remove_fixup(struct rcu_rbtree_node **root, | |
513 | struct rcu_rbtree_node *x, | |
514 | rcu_rbtree_alloc rballoc, | |
515 | rcu_rbtree_free rbfree) | |
516 | { | |
517 | while (x != *root && x->color == COLOR_BLACK) { | |
518 | if (x == x->p->left) { | |
f6e888c5 | 519 | struct rcu_rbtree_node *w, *t; |
00131368 MD |
520 | |
521 | w = x->p->right; | |
522 | if (w->color == COLOR_RED) { | |
523 | w->color == COLOR_BLACK; | |
524 | x->p->color = COLOR_RED; | |
f6e888c5 MD |
525 | t = left_rotate(root, x->p, rballoc, rbfree); |
526 | assert(x->p->left == t->left); | |
00131368 MD |
527 | /* x is a left node, not copied by rotation */ |
528 | w = x->p->right; | |
529 | } | |
530 | if (w->left->color == COLOR_BLACK | |
531 | && w->right->color == COLOR_BLACK) { | |
532 | w->color = COLOR_RED; | |
533 | x = x->p; | |
534 | } else { | |
535 | if (w->right->color == COLOR_BLACK) { | |
536 | w->left->color = COLOR_BLACK; | |
537 | w->color = COLOR_RED; | |
538 | right_rotate(root, w, rballoc, rbfree); | |
539 | w = x->p->right; | |
540 | } | |
541 | w->color = x->p->color; | |
542 | x->p->color = COLOR_BLACK; | |
543 | w->right->color = COLOR_BLACK; | |
544 | left_rotate(root, x->p, rballoc, rbfree); | |
545 | x = *root; | |
546 | } | |
547 | } else { | |
548 | struct rcu_rbtree_node *w; | |
549 | ||
550 | w = x->p->left; | |
551 | if (w->color == COLOR_RED) { | |
552 | w->color == COLOR_BLACK; | |
553 | x->p->color = COLOR_RED; | |
554 | right_rotate(root, x->p, rballoc, rbfree); | |
555 | /* x is a right node, not copied by rotation */ | |
556 | w = x->p->left; | |
557 | } | |
558 | if (w->right->color == COLOR_BLACK | |
559 | && w->left->color == COLOR_BLACK) { | |
560 | w->color = COLOR_RED; | |
561 | x = x->p; | |
562 | } else { | |
563 | if (w->left->color == COLOR_BLACK) { | |
564 | w->right->color = COLOR_BLACK; | |
565 | w->color = COLOR_RED; | |
566 | left_rotate(root, w, rballoc, rbfree); | |
567 | w = x->p->left; | |
568 | } | |
569 | w->color = x->p->color; | |
570 | x->p->color = COLOR_BLACK; | |
571 | w->left->color = COLOR_BLACK; | |
572 | right_rotate(root, x->p, rballoc, rbfree); | |
573 | x = *root; | |
574 | } | |
575 | } | |
576 | } | |
577 | x->color = COLOR_BLACK; | |
578 | } | |
579 | ||
580 | /* Returns the new copy of y->right */ | |
581 | static struct rcu_rbtree_node * | |
582 | rcu_rbtree_remove_nonil(struct rcu_rbtree_node **root, | |
583 | struct rcu_rbtree_node *z, | |
584 | struct rcu_rbtree_node *y, | |
585 | rcu_rbtree_comp comp, | |
586 | rcu_rbtree_alloc rballoc, | |
587 | rcu_rbtree_free rbfree) | |
588 | { | |
589 | struct rcu_rbtree_node *x, *xc, *yc; | |
590 | ||
591 | x = y->right; | |
592 | ||
a23deda7 MD |
593 | if (x != &rcu_rbtree_nil) { |
594 | xc = rballoc(); | |
595 | *xc = *x; | |
596 | } else | |
597 | xc = &rcu_rbtree_nil; | |
598 | ||
00131368 | 599 | yc = rballoc(); |
00131368 MD |
600 | *yc = *y; |
601 | ||
602 | /* Update parent and children pointers within copies */ | |
603 | if (y->p == z) | |
604 | xc->p = yc; | |
605 | else { | |
606 | /* Transplant y->right (xc) into y, within copy */ | |
607 | xc->p = y->p; | |
608 | /* But also change the right pointer of yc */ | |
609 | yc->right = z->right; | |
610 | } | |
611 | /* Transplant y into z, within copy */ | |
612 | yc->p = z->p; | |
613 | ||
614 | yc->left = z->left; | |
615 | yc->color = z->color; | |
616 | ||
617 | /* | |
618 | * Order stores to node copies (children/parents) before stores that | |
619 | * will make the copies visible to the rest of the tree. | |
620 | */ | |
621 | smp_wmb(); | |
622 | ||
f6e888c5 MD |
623 | /* |
624 | * redirect old nodes to new. | |
625 | */ | |
626 | if (x != &rcu_rbtree_nil) | |
9a9703e6 MD |
627 | _STORE_SHARED(x->redir, xc); |
628 | _STORE_SHARED(y->redir, yc); | |
f6e888c5 MD |
629 | |
630 | /* | |
631 | * Ensure that redirections are visible before updating external | |
632 | * pointers. | |
633 | */ | |
634 | smp_wmb(); | |
635 | ||
00131368 MD |
636 | /* Update external pointers */ |
637 | ||
638 | if (y->p != z) { | |
639 | /* Transplant y->right into y, external parent links */ | |
640 | ||
641 | /* Assign upper-level pointer to xc, replacing y. */ | |
db5b1669 | 642 | if (y->p == &rcu_rbtree_nil) |
00131368 MD |
643 | _STORE_SHARED(*root, xc); |
644 | else if (y == y->p->left) | |
645 | _STORE_SHARED(y->p->left, xc); | |
646 | else | |
647 | _STORE_SHARED(y->p->right, xc); | |
648 | } | |
649 | ||
650 | /* Transplant y into z, update external parent links */ | |
db5b1669 | 651 | if (z->p == &rcu_rbtree_nil) |
00131368 MD |
652 | _STORE_SHARED(*root, yc); |
653 | else if (z == z->p->left) | |
654 | _STORE_SHARED(z->p->left, yc); | |
655 | else | |
656 | _STORE_SHARED(z->p->right, yc); | |
657 | ||
a23deda7 MD |
658 | if (x != &rcu_rbtree_nil) { |
659 | /* Reparent xc's children to xc. */ | |
660 | _STORE_SHARED(xc->right->p, xc); | |
661 | _STORE_SHARED(xc->left->p, xc); | |
662 | defer_rcu(rbfree, x); | |
663 | } | |
664 | ||
00131368 MD |
665 | /* Reparent yc's children to yc */ |
666 | _STORE_SHARED(yc->right->p, yc); | |
667 | _STORE_SHARED(yc->left->p, yc); | |
00131368 MD |
668 | defer_rcu(rbfree, y); |
669 | ||
670 | return xc; | |
671 | } | |
672 | ||
673 | int rcu_rbtree_remove(struct rcu_rbtree_node **root, | |
674 | struct rcu_rbtree_node *z, | |
675 | rcu_rbtree_comp comp, | |
676 | rcu_rbtree_alloc rballoc, | |
677 | rcu_rbtree_free rbfree) | |
678 | { | |
679 | struct rcu_rbtree_node *x, *y; | |
680 | unsigned int y_original_color; | |
681 | ||
682 | y = z; | |
683 | y_original_color = y->color; | |
684 | ||
db5b1669 | 685 | if (z->left == &rcu_rbtree_nil) { |
00131368 | 686 | x = rcu_rbtree_transplant(root, z, z->right, rballoc, rbfree); |
db5b1669 | 687 | } else if (z->right == &rcu_rbtree_nil) { |
00131368 MD |
688 | x = rcu_rbtree_transplant(root, z, z->left, rballoc, rbfree); |
689 | } else { | |
690 | y = rcu_rbtree_min(z->right, comp); | |
691 | y_original_color = y->color; | |
692 | x = rcu_rbtree_remove_nonil(root, z, y, comp, rballoc, rbfree); | |
693 | } | |
694 | if (y_original_color == COLOR_BLACK) | |
695 | rcu_rbtree_remove_fixup(root, x, rballoc, rbfree); | |
696 | /* | |
697 | * Commit all _STORE_SHARED(). | |
698 | */ | |
699 | smp_wmc(); | |
700 | ||
701 | return 0; | |
702 | } |