4 * Userspace RCU library - Red-Black Tree
6 * Copyright (c) 2010 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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.
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.
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
22 * Implementation of RCU-adapted data structures and operations based on the RB
23 * tree algorithms found in chapter 12 of:
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.
40 #include <urcu/rcurbtree.h>
41 #include <urcu-pointer.h>
42 #include <urcu-call-rcu.h>
43 #include <urcu/compiler.h>
46 * Explanation of next/prev walk coherency and search coherency when
47 * performed concurrently with updates.
49 * next/prev walk coherency with respect to concurrent updates:
51 * There are 3 scenarios for which we need to model and validate this:
52 * rotation, transplant and "teleportation" (the latter being a remote
53 * transplant in a remove non-nil case).
55 * - rotation left (right is symmetric)
56 * xl and yr point to the same parent nodes before/after left
57 * rotation. yll and ylr also point to the same parent node
58 * before/after left rotation.
59 * As we are copying x, y and yl (the 3 nodes which parent/child
60 * relationship are changed) to "new" version of this node cluster,
61 * all external references to the cluster either point to the old
62 * cluster or the new one. If we take this cluster as a "black box"
63 * from the point of view of next/prev traversal, all we have to
64 * ensure is that the old and the new cluster behave in the exact same
65 * way with respect to traversal order.
68 * In this operation, we transplant a copy of "v" into its parent
69 * location (u), thus replacing it. The children of "v", vl and vr,
70 * still point to v (new version) after the transplant, so it does not
71 * change the behavior when considering the next/prev traversal. "v"
72 * being copied to a new version ensures that the parent pointers of v
73 * are pointing to its new parent (parent of u) before it is published
74 * to readers (by setting the child pointer of u's parent to the new
78 * This one is probably the most tricky and will require some ascii
81 * We want to remove z from this tree:
99 * What we are going to do is to "teleport" y into z's location,
100 * reparenting yr to b. We are taking care to create a new cluster
101 * copy that is isolated from any reader. We will represent the new
102 * members of the cluster with capital letters.
118 * In this transient state, we notice that the pointers within the
119 * cluster all point to the new cluster nodes, and they point to the
120 * correct external nodes. However, no external pointer point to the
121 * cluster (yet). The first pointer to point to this cluster will be
122 * "zp->right". It will therefore make the cluster visible for search.
124 * In this intermediate state, we can walk through the new cluster
125 * when coming from the top (in a next/prev traversal), but can come
126 * back to the old cluster when going back up from the children nodes.
127 * All we have to ensure is that the two clusters, taken as a black
128 * box from a next/prev traversal perspective, yield to the exact same
131 * Search coherency with concurrent updates:
133 * Simple "search" (only going down the tree) is also handled by this
134 * cluster scheme. The explanation is a subset of the prev/next
135 * explanation, where we don't have to care about the intermediate
136 * stages where the children point to the old cluster, because we only
137 * ever use the top level pointers to go down into the children nodes,
138 * we never go back up. So by simply making sure that all the cluster
139 * internal nodes pointers are setup correctly before making the
140 * cluster visible to the readers (by setting the parent pointer to
141 * the topmost new node in the cluster), we are sure that readers will
142 * see a coherent view of the cluster at all times.
146 #define dbg_printf(args...) printf(args)
147 #define dbg_usleep(usecs) usleep(usecs)
149 #define dbg_printf(args...)
150 #define dbg_usleep(usecs)
154 * Undefine this to enable the non-RCU rotate and transplant functions
155 * (for debugging). Note that these versions don't support the tree
156 * max_end updates, so lookups must be performed with
157 * rcu_rbtree_search_begin_key when using this debug facility.
159 #define RBTREE_RCU_SUPPORT_ROTATE_LEFT
160 #define RBTREE_RCU_SUPPORT_ROTATE_RIGHT
161 #define RBTREE_RCU_SUPPORT_TRANSPLANT
164 static pthread_mutex_t test_mutex
= PTHREAD_MUTEX_INITIALIZER
;
165 static pthread_mutex_t outer_mutex
= PTHREAD_MUTEX_INITIALIZER
;
168 void lock_outer_mutex(void)
170 pthread_mutex_lock(&outer_mutex
);
174 void unlock_outer_mutex(void)
176 pthread_mutex_unlock(&outer_mutex
);
180 void lock_test_mutex(void)
182 pthread_mutex_lock(&test_mutex
);
186 void unlock_test_mutex(void)
188 pthread_mutex_unlock(&test_mutex
);
193 void set_parent(struct rcu_rbtree_node
*node
,
194 struct rcu_rbtree_node
*parent
,
197 _CMM_STORE_SHARED(node
->parent
, ((unsigned long) parent
) | pos
);
201 struct rcu_rbtree_node
*get_parent(struct rcu_rbtree_node
*node
)
203 return (struct rcu_rbtree_node
*) (node
->parent
& ~1UL);
207 unsigned int get_pos(struct rcu_rbtree_node
*node
)
209 return (unsigned int) (node
->parent
& 1UL);
213 struct rcu_rbtree_node
*get_parent_and_pos(struct rcu_rbtree_node
*node
,
216 unsigned long parent_pos
= rcu_dereference(node
->parent
);
218 *pos
= (unsigned int) (parent_pos
& 1UL);
219 return (struct rcu_rbtree_node
*) (parent_pos
& ~1UL);
223 void set_decay(struct rcu_rbtree_node
*x
, struct rcu_rbtree_node
*xc
)
229 struct rcu_rbtree_node
*get_decay(struct rcu_rbtree_node
*x
)
233 while (x
->decay_next
)
239 struct rcu_rbtree_node
*is_decay(struct rcu_rbtree_node
*x
)
241 return x
->decay_next
;
245 struct rcu_rbtree_node
*_rcu_rbtree_alloc_node(struct rcu_rbtree
*rbtree
)
247 return rbtree
->rballoc(sizeof(struct rcu_rbtree_node
));
251 void _rcu_rbtree_free_node(struct rcu_head
*head
)
253 struct rcu_rbtree_node
*node
=
254 caa_container_of(head
, struct rcu_rbtree_node
, head
);
255 node
->rbtree
->rbfree(node
);
259 struct rcu_rbtree_node
*dup_decay_node(struct rcu_rbtree
*rbtree
,
260 struct rcu_rbtree_node
*x
)
262 struct rcu_rbtree_node
*xc
;
264 if (rcu_rbtree_is_nil(rbtree
, x
))
267 xc
= _rcu_rbtree_alloc_node(rbtree
);
268 memcpy(xc
, x
, sizeof(*xc
));
269 xc
->decay_next
= NULL
;
271 call_rcu(&x
->head
, _rcu_rbtree_free_node
);
276 * Info for range lookups:
277 * Range lookup information is only valid when used when searching for
278 * ranges. It should never be used in next/prev traversal because the
279 * pointers to parents are not in sync with the parent vision of the
283 void set_left(struct rcu_rbtree
*rbtree
, struct rcu_rbtree_node
*node
,
284 struct rcu_rbtree_node
*left
)
290 void set_right(struct rcu_rbtree
*rbtree
, struct rcu_rbtree_node
*node
,
291 struct rcu_rbtree_node
*right
)
293 node
->_right
= right
;
297 void *calculate_node_max_end(struct rcu_rbtree
*rbtree
, struct rcu_rbtree_node
*node
)
302 if (!rcu_rbtree_is_nil(rbtree
, node
->_right
)) {
303 if (rbtree
->comp(max_end
, node
->_right
->max_end
) < 0)
304 max_end
= node
->_right
->max_end
;
306 if (!rcu_rbtree_is_nil(rbtree
, node
->_left
)) {
307 if (rbtree
->comp(max_end
, node
->_left
->max_end
) < 0)
308 max_end
= node
->_left
->max_end
;
315 * Deal with memory allocation errors.
316 * Can be ensured by reserving a pool of memory entries before doing the
317 * insertion, which will have to be function of number of
318 * transplantations/rotations required for the operation (which is a
319 * multiple of the tree height).
324 void show_tree(struct rcu_rbtree
*rbtree
)
326 struct rcu_rbtree_node
*node
;
328 node
= rcu_rbtree_min(rbtree
, rbtree
->root
);
329 while (!rcu_rbtree_is_nil(rbtree
, node
)) {
330 assert(!is_decay(node
));
331 printf("{ b:%lX e:%lX pb: %lX r:%lX l:%lX %s %s %s} ",
332 (unsigned long) node
->begin
,
333 (unsigned long) node
->end
,
334 (unsigned long) get_parent(node
)->begin
,
335 (unsigned long) node
->_right
->begin
,
336 (unsigned long) node
->_left
->begin
,
337 node
->color
? "red" : "black",
338 get_pos(node
) ? "right" : "left",
339 rcu_rbtree_is_nil(rbtree
, node
) ? "nil" : "");
340 node
= rcu_rbtree_next(rbtree
, node
);
345 #define check_max_end(rbtree, x) \
347 if (rcu_rbtree_is_nil(rbtree, x)) \
349 assert(rbtree->comp(x->max_end, \
350 calculate_node_max_end(rbtree, x)) == 0); \
355 void show_tree(struct rcu_rbtree
*rbtree
)
360 void check_max_end(struct rcu_rbtree
*rbtree
, struct rcu_rbtree_node
*x
)
366 struct rcu_rbtree_node
*make_nil(struct rcu_rbtree
*rbtree
)
368 return &rbtree
->nil_node
;
372 * Iterative rbtree search.
374 struct rcu_rbtree_node
*rcu_rbtree_search(struct rcu_rbtree
*rbtree
,
375 struct rcu_rbtree_node
*x
,
378 struct rcu_rbtree_node
*xl
;
380 dbg_printf("searching point 0x%lx\n", (unsigned long) point
);
381 x
= rcu_dereference(x
);
383 while (!rcu_rbtree_is_nil(rbtree
, x
)) {
385 xl
= rcu_dereference(x
->_left
);
386 dbg_printf("search x %lx x_end %lx x_max_end %lx\n", (unsigned long) x
->begin
,
387 (unsigned long) x
->end
, (unsigned long) x
->max_end
);
388 dbg_printf("search xl %lx xl_end %lx xl_max_end %lx\n", (unsigned long) xl
->begin
,
389 (unsigned long) xl
->end
, (unsigned long) xl
->max_end
);
390 if (!rcu_rbtree_is_nil(rbtree
, xl
)
391 && (rbtree
->comp(xl
->max_end
, point
) > 0)) {
392 dbg_printf("go left\n");
394 } else if (rbtree
->comp(x
->begin
, point
) <= 0
395 && rbtree
->comp(point
, x
->end
) < 0) {
396 dbg_printf("got it!\n");
398 } else if (rbtree
->comp(point
, x
->begin
) > 0) {
399 dbg_printf("go right\n");
400 x
= rcu_dereference(x
->_right
);
402 dbg_printf("not found!\n");
403 x
= make_nil(rbtree
);
406 if (rcu_rbtree_is_nil(rbtree
, x
))
407 dbg_printf("Reached bottom of tree.\n");
412 struct rcu_rbtree_node
*rcu_rbtree_search_range(struct rcu_rbtree
*rbtree
,
413 struct rcu_rbtree_node
*x
,
414 void *begin
, void *end
)
416 struct rcu_rbtree_node
*node
;
418 node
= rcu_rbtree_search(rbtree
, x
, begin
);
419 if (rcu_rbtree_is_nil(rbtree
, node
))
421 if (rbtree
->comp(node
->end
, end
) < 0)
422 return NULL
; /* High is outside lookup range */
427 * Search by exact range start value.
429 struct rcu_rbtree_node
*rcu_rbtree_search_begin_key(struct rcu_rbtree
*rbtree
,
430 struct rcu_rbtree_node
*x
,
433 x
= rcu_dereference(x
);
436 while (!rcu_rbtree_is_nil(rbtree
, x
) && (comp
= rbtree
->comp(k
, x
->begin
)) != 0) {
439 x
= rcu_dereference(x
->_left
);
441 x
= rcu_dereference(x
->_right
);
447 struct rcu_rbtree_node
*rcu_rbtree_min_dup_decay(struct rcu_rbtree
*rbtree
,
448 struct rcu_rbtree_node
*x
,
449 struct rcu_rbtree_node
**zr
)
451 struct rcu_rbtree_node
*xl
;
453 x
= rcu_dereference(x
);
455 if (rcu_rbtree_is_nil(rbtree
, x
)) {
459 *zr
= x
= dup_decay_node(rbtree
, x
);
461 while (!rcu_rbtree_is_nil(rbtree
, xl
= rcu_dereference(x
->_left
))) {
462 x
= dup_decay_node(rbtree
, xl
);
463 set_parent(x
, get_decay(get_parent(x
)), get_pos(x
));
464 get_parent(x
)->_left
= get_decay(get_parent(x
)->_left
);
470 struct rcu_rbtree_node
*rcu_rbtree_min_update_decay(struct rcu_rbtree
*rbtree
,
471 struct rcu_rbtree_node
*x
)
473 struct rcu_rbtree_node
*xl
;
475 x
= rcu_dereference(x
);
477 if (rcu_rbtree_is_nil(rbtree
, x
))
480 set_parent(x
->_right
, get_decay(get_parent(x
->_right
)),
482 set_parent(x
->_left
, get_decay(get_parent(x
->_left
)),
486 while (!rcu_rbtree_is_nil(rbtree
, xl
= rcu_dereference(x
->_left
))) {
488 set_parent(x
->_right
, get_decay(get_parent(x
->_right
)),
490 set_parent(x
->_left
, get_decay(get_parent(x
->_left
)),
496 struct rcu_rbtree_node
*rcu_rbtree_min(struct rcu_rbtree
*rbtree
,
497 struct rcu_rbtree_node
*x
)
499 struct rcu_rbtree_node
*xl
;
501 x
= rcu_dereference(x
);
503 if (rcu_rbtree_is_nil(rbtree
, x
))
506 while (!rcu_rbtree_is_nil(rbtree
, xl
= rcu_dereference(x
->_left
)))
511 struct rcu_rbtree_node
*rcu_rbtree_max(struct rcu_rbtree
*rbtree
,
512 struct rcu_rbtree_node
*x
)
514 struct rcu_rbtree_node
*xr
;
516 x
= rcu_dereference(x
);
518 if (rcu_rbtree_is_nil(rbtree
, x
))
521 while (!rcu_rbtree_is_nil(rbtree
, xr
= rcu_dereference(x
->_right
)))
527 * RCU read lock must be held across the next/prev calls to ensure validity of
530 struct rcu_rbtree_node
*rcu_rbtree_next(struct rcu_rbtree
*rbtree
,
531 struct rcu_rbtree_node
*x
)
533 struct rcu_rbtree_node
*xr
, *y
;
536 x
= rcu_dereference(x
);
538 if (!rcu_rbtree_is_nil(rbtree
, xr
= rcu_dereference(x
->_right
)))
539 return rcu_rbtree_min(rbtree
, xr
);
540 y
= get_parent_and_pos(x
, &x_pos
);
541 while (!rcu_rbtree_is_nil(rbtree
, y
) && x_pos
== IS_RIGHT
) {
543 y
= get_parent_and_pos(y
, &x_pos
);
548 struct rcu_rbtree_node
*rcu_rbtree_prev(struct rcu_rbtree
*rbtree
,
549 struct rcu_rbtree_node
*x
)
551 struct rcu_rbtree_node
*xl
, *y
;
554 x
= rcu_dereference(x
);
556 if (!rcu_rbtree_is_nil(rbtree
, xl
= rcu_dereference(x
->_left
)))
557 return rcu_rbtree_max(rbtree
, xl
);
558 y
= get_parent_and_pos(x
, &x_pos
);
559 while (!rcu_rbtree_is_nil(rbtree
, y
) && x_pos
== IS_LEFT
) {
561 y
= get_parent_and_pos(y
, &x_pos
);
567 * "node" needs to be non-visible by readers.
570 void populate_node_end(struct rcu_rbtree
*rbtree
, struct rcu_rbtree_node
*node
,
571 unsigned int copy_parents
, struct rcu_rbtree_node
*stop
)
573 struct rcu_rbtree_node
*prev
= NULL
, *orig_node
= node
, *top
;
579 assert(!rcu_rbtree_is_nil(rbtree
, node
));
581 if (prev
&& copy_parents
) {
582 node
= dup_decay_node(rbtree
, node
);
583 if (get_pos(prev
) == IS_RIGHT
)
587 set_parent(prev
, node
, get_pos(prev
));
590 max_end
= calculate_node_max_end(rbtree
, node
);
592 * Compare the node max_end keys to make sure we replace
593 * references to a key belonging to a node we remove
594 * from the tree. Otherwise we would still be using this
595 * pointer as an invalid reference after garbage
596 * collection of the node and of its associated
597 * begin/end pointers.
599 if (max_end
!= node
->max_end
) {
600 node
->max_end
= max_end
;
602 top
= get_parent(node
);
603 cmm_smp_wmb(); /* write into node before publish */
604 /* make new branch visible to readers */
605 if (rcu_rbtree_is_nil(rbtree
, top
))
606 _CMM_STORE_SHARED(rbtree
->root
, node
);
607 if (get_pos(node
) == IS_LEFT
)
608 _CMM_STORE_SHARED(top
->_left
, node
);
610 _CMM_STORE_SHARED(top
->_right
, node
);
614 /* Check for propagation stop */
619 node
= get_parent(node
);
620 } while (!rcu_rbtree_is_nil(rbtree
, node
));
622 top
= node
; /* nil */
623 cmm_smp_wmb(); /* write into node before publish */
624 /* make new branch visible to readers */
625 _CMM_STORE_SHARED(rbtree
->root
, prev
);
630 /* update children */
633 assert(!rcu_rbtree_is_nil(rbtree
, node
));
634 set_parent(node
->_left
, get_decay(get_parent(node
->_left
)), IS_LEFT
);
635 set_parent(node
->_right
, get_decay(get_parent(node
->_right
)), IS_RIGHT
);
636 } while ((node
= get_parent(node
)) != top
);
640 * We have to ensure these assumptions are correct for prev/next
643 * with x being a right child, the assumption that:
644 * get_parent(x)->_right == x
645 * or if x is a left child, the assumption that:
646 * get_parent(x)->_left == x
648 * This explains why we have to allocate a vc copy of the node for left_rotate,
649 * right_rotate and transplant operations.
651 * We always ensure that the right/left child and correct parent is set in the
652 * node copies *before* we reparent the children and make the upper-level point
656 /* RCU: copy x and y, atomically point to new versions. GC old. */
657 /* Should be eventually followed by a cmm_smp_wmc() */
659 #ifdef RBTREE_RCU_SUPPORT_ROTATE_LEFT
662 void left_rotate(struct rcu_rbtree
*rbtree
,
663 struct rcu_rbtree_node
*x
)
665 struct rcu_rbtree_node
*y
, *y_left
;
667 dbg_printf("left rotate %lx\n", (unsigned long) x
->begin
);
672 /* Now operate on new copy, decay old versions */
673 x
= dup_decay_node(rbtree
, x
);
674 y
= dup_decay_node(rbtree
, y
);
675 y_left
= dup_decay_node(rbtree
, y_left
);
677 check_max_end(rbtree
, get_parent(x
));
678 check_max_end(rbtree
, x
);
679 check_max_end(rbtree
, y
);
681 /* Internal node modifications */
682 set_parent(y
, get_parent(x
), get_pos(x
));
683 set_parent(x
, y
, IS_LEFT
);
684 set_left(rbtree
, y
, x
);
685 set_right(rbtree
, x
, y_left
);
687 if (!rcu_rbtree_is_nil(rbtree
, y_left
))
688 set_parent(y_left
, x
, IS_RIGHT
);
691 * We only changed the relative position of x and y wrt their
692 * children, and reparented y (but are keeping the same nodes in
693 * place, so its parent does not need to have end value
696 x
->max_end
= calculate_node_max_end(rbtree
, x
);
697 y
->max_end
= calculate_node_max_end(rbtree
, y
);
699 cmm_smp_wmb(); /* write into node before publish */
701 /* External references update (visible by readers) */
702 if (rcu_rbtree_is_nil(rbtree
, get_parent(y
)))
703 _CMM_STORE_SHARED(rbtree
->root
, y
);
704 else if (get_pos(y
) == IS_LEFT
)
705 _CMM_STORE_SHARED(get_parent(y
)->_left
, y
);
707 _CMM_STORE_SHARED(get_parent(y
)->_right
, y
);
709 /* Point children to new copy (parent only used by updates/next/prev) */
710 set_parent(x
->_left
, get_decay(get_parent(x
->_left
)),
712 set_parent(y
->_right
, get_decay(get_parent(y
->_right
)),
714 if (!rcu_rbtree_is_nil(rbtree
, y_left
)) {
715 set_parent(y_left
->_right
,
716 get_decay(get_parent(y_left
->_right
)),
717 get_pos(y_left
->_right
));
718 set_parent(y_left
->_left
,
719 get_decay(get_parent(y_left
->_left
)),
720 get_pos(y_left
->_left
));
724 assert(y
== rbtree
->root
|| get_parent(y
)->_left
== y
725 || get_parent(y
)->_right
== y
);
726 assert(x
== rbtree
->root
|| get_parent(x
)->_left
== x
727 || get_parent(x
)->_right
== x
);
728 assert(rcu_rbtree_is_nil(rbtree
, x
->_right
) || get_parent(x
->_right
) == x
);
729 assert(rcu_rbtree_is_nil(rbtree
, x
->_left
) || get_parent(x
->_left
) == x
);
730 assert(rcu_rbtree_is_nil(rbtree
, y
->_right
) || get_parent(y
->_right
) == y
);
731 assert(rcu_rbtree_is_nil(rbtree
, y
->_left
) || get_parent(y
->_left
) == y
);
732 assert(!is_decay(rbtree
->root
));
733 assert(!is_decay(x
));
734 assert(!is_decay(y
));
735 assert(!is_decay(x
->_right
));
736 assert(!is_decay(x
->_left
));
737 assert(!is_decay(y
->_right
));
738 assert(!is_decay(y
->_left
));
739 check_max_end(rbtree
, get_parent(y
));
740 check_max_end(rbtree
, x
);
741 check_max_end(rbtree
, y
);
746 /* non-rcu version */
748 void left_rotate(struct rcu_rbtree
*rbtree
,
749 struct rcu_rbtree_node
*x
)
751 struct rcu_rbtree_node
*y
;
755 x
->_right
= y
->_left
;
756 if (!rcu_rbtree_is_nil(rbtree
, y
->_left
))
757 set_parent(y
->_left
, x
, IS_RIGHT
);
758 set_parent(y
, get_parent(x
), get_pos(x
));
759 if (rcu_rbtree_is_nil(rbtree
, get_parent(x
)))
761 else if (x
== get_parent(x
)->_left
) {
762 get_parent(x
)->_left
= y
;
764 get_parent(x
)->_right
= y
;
767 set_parent(x
, y
, IS_LEFT
);
773 #ifdef RBTREE_RCU_SUPPORT_ROTATE_RIGHT
775 void right_rotate(struct rcu_rbtree
*rbtree
,
776 struct rcu_rbtree_node
*x
)
778 struct rcu_rbtree_node
*y
, *y_right
;
780 dbg_printf("right rotate %lx\n", (unsigned long) x
->begin
);
785 /* Now operate on new copy, decay old versions */
786 x
= dup_decay_node(rbtree
, x
);
787 y
= dup_decay_node(rbtree
, y
);
788 y_right
= dup_decay_node(rbtree
, y_right
);
790 check_max_end(rbtree
, get_parent(x
));
791 check_max_end(rbtree
, x
);
792 check_max_end(rbtree
, y
);
794 /* Internal node modifications */
795 set_parent(y
, get_parent(x
), get_pos(x
));
796 set_parent(x
, y
, IS_RIGHT
);
797 set_right(rbtree
, y
, x
);
798 set_left(rbtree
, x
, y_right
);
800 if (!rcu_rbtree_is_nil(rbtree
, y_right
))
801 set_parent(y_right
, x
, IS_LEFT
);
804 * We only changed the relative position of x and y wrt their
805 * children, and reparented y (but are keeping the same nodes in
806 * place, so its parent does not need to have end value
809 x
->max_end
= calculate_node_max_end(rbtree
, x
);
810 y
->max_end
= calculate_node_max_end(rbtree
, y
);
812 cmm_smp_wmb(); /* write into node before publish */
814 /* External references update (visible by readers) */
815 if (rcu_rbtree_is_nil(rbtree
, get_parent(y
)))
816 _CMM_STORE_SHARED(rbtree
->root
, y
);
817 else if (get_pos(y
) == IS_RIGHT
)
818 _CMM_STORE_SHARED(get_parent(y
)->_right
, y
);
820 _CMM_STORE_SHARED(get_parent(y
)->_left
, y
);
822 /* Point children to new copy (parent only used by updates/next/prev) */
823 set_parent(x
->_right
, get_decay(get_parent(x
->_right
)),
825 set_parent(y
->_left
, get_decay(get_parent(y
->_left
)),
827 if (!rcu_rbtree_is_nil(rbtree
, y_right
)) {
828 set_parent(y_right
->_left
,
829 get_decay(get_parent(y_right
->_left
)),
830 get_pos(y_right
->_left
));
831 set_parent(y_right
->_right
,
832 get_decay(get_parent(y_right
->_right
)),
833 get_pos(y_right
->_right
));
837 assert(y
== rbtree
->root
|| get_parent(y
)->_right
== y
838 || get_parent(y
)->_left
== y
);
839 assert(x
== rbtree
->root
|| get_parent(x
)->_right
== x
840 || get_parent(x
)->_left
== x
);
841 assert(rcu_rbtree_is_nil(rbtree
, x
->_left
) || get_parent(x
->_left
) == x
);
842 assert(rcu_rbtree_is_nil(rbtree
, x
->_right
) || get_parent(x
->_right
) == x
);
843 assert(rcu_rbtree_is_nil(rbtree
, y
->_left
) || get_parent(y
->_left
) == y
);
844 assert(rcu_rbtree_is_nil(rbtree
, y
->_right
) || get_parent(y
->_right
) == y
);
845 assert(!is_decay(rbtree
->root
));
846 assert(!is_decay(x
));
847 assert(!is_decay(y
));
848 assert(!is_decay(x
->_left
));
849 assert(!is_decay(x
->_right
));
850 assert(!is_decay(y
->_left
));
851 assert(!is_decay(y
->_right
));
852 check_max_end(rbtree
, x
);
853 check_max_end(rbtree
, y
);
854 check_max_end(rbtree
, get_parent(y
));
859 /* non-rcu version */
861 void right_rotate(struct rcu_rbtree
*rbtree
,
862 struct rcu_rbtree_node
*x
)
864 struct rcu_rbtree_node
*y
;
868 x
->_left
= y
->_right
;
869 if (!rcu_rbtree_is_nil(rbtree
, y
->_right
))
870 set_parent(y
->_right
, x
, IS_LEFT
);
871 set_parent(y
, get_parent(x
), get_pos(x
));
872 if (rcu_rbtree_is_nil(rbtree
, get_parent(x
)))
874 else if (x
== get_parent(x
)->_right
) {
875 get_parent(x
)->_right
= y
;
877 get_parent(x
)->_left
= y
;
880 set_parent(x
, y
, IS_RIGHT
);
886 static void rcu_rbtree_insert_fixup(struct rcu_rbtree
*rbtree
,
887 struct rcu_rbtree_node
*z
)
889 struct rcu_rbtree_node
*y
;
891 dbg_printf("insert fixup %p\n", z
->begin
);
892 assert(!is_decay(rbtree
->root
));
894 while (get_parent(z
)->color
== COLOR_RED
) {
895 if (get_parent(z
) == get_parent(get_parent(z
))->_left
) {
896 y
= get_parent(get_parent(z
))->_right
;
897 if (y
->color
== COLOR_RED
) {
898 get_parent(z
)->color
= COLOR_BLACK
;
899 y
->color
= COLOR_BLACK
;
900 get_parent(get_parent(z
))->color
= COLOR_RED
;
901 z
= get_parent(get_parent(z
));
903 if (z
== get_parent(z
)->_right
) {
905 left_rotate(rbtree
, z
);
907 assert(!is_decay(rbtree
->root
));
909 get_parent(z
)->color
= COLOR_BLACK
;
910 get_parent(get_parent(z
))->color
= COLOR_RED
;
911 assert(!is_decay(z
));
912 assert(!is_decay(get_parent(z
)));
913 assert(!is_decay(get_parent(get_parent(z
))));
914 right_rotate(rbtree
, get_parent(get_parent(z
)));
915 assert(!is_decay(z
));
916 assert(!is_decay(rbtree
->root
));
919 y
= get_parent(get_parent(z
))->_left
;
920 if (y
->color
== COLOR_RED
) {
921 get_parent(z
)->color
= COLOR_BLACK
;
922 y
->color
= COLOR_BLACK
;
923 get_parent(get_parent(z
))->color
= COLOR_RED
;
924 z
= get_parent(get_parent(z
));
926 if (z
== get_parent(z
)->_left
) {
928 right_rotate(rbtree
, z
);
930 assert(!is_decay(rbtree
->root
));
932 get_parent(z
)->color
= COLOR_BLACK
;
933 get_parent(get_parent(z
))->color
= COLOR_RED
;
934 left_rotate(rbtree
, get_parent(get_parent(z
)));
935 assert(!is_decay(z
));
936 assert(!is_decay(rbtree
->root
));
940 rbtree
->root
->color
= COLOR_BLACK
;
944 * rcu_rbtree_insert - Insert a node in the RCU rbtree
946 * Returns 0 on success, or < 0 on error.
948 int rcu_rbtree_insert(struct rcu_rbtree
*rbtree
,
949 void *begin
, void *end
)
951 struct rcu_rbtree_node
*x
, *y
, *z
;
953 z
= _rcu_rbtree_alloc_node(rbtree
);
959 dbg_printf("insert %p\n", z
->begin
);
960 assert(!is_decay(rbtree
->root
));
962 y
= make_nil(rbtree
);
964 while (!rcu_rbtree_is_nil(rbtree
, x
)) {
966 if (rbtree
->comp(z
->begin
, x
->begin
) < 0)
972 z
->_left
= make_nil(rbtree
);
973 z
->_right
= make_nil(rbtree
);
974 z
->color
= COLOR_RED
;
975 z
->decay_next
= NULL
;
979 if (rcu_rbtree_is_nil(rbtree
, y
)) {
980 set_parent(z
, y
, IS_RIGHT
); /* pos arbitrary for root node */
982 * Order stores to z (children/parents) before stores
983 * that will make it visible to the rest of the tree.
986 _CMM_STORE_SHARED(rbtree
->root
, z
);
987 } else if (rbtree
->comp(z
->begin
, y
->begin
) < 0) {
988 y
= dup_decay_node(rbtree
, y
);
989 set_parent(z
, y
, IS_LEFT
);
990 if (get_pos(z
) == IS_LEFT
)
991 _CMM_STORE_SHARED(y
->_left
, z
);
993 _CMM_STORE_SHARED(y
->_right
, z
);
994 populate_node_end(rbtree
, y
, 1, NULL
);
996 y
= dup_decay_node(rbtree
, y
);
997 set_parent(z
, y
, IS_RIGHT
);
998 if (get_pos(z
) == IS_LEFT
)
999 _CMM_STORE_SHARED(y
->_left
, z
);
1001 _CMM_STORE_SHARED(y
->_right
, z
);
1002 populate_node_end(rbtree
, y
, 1, NULL
);
1004 rcu_rbtree_insert_fixup(rbtree
, z
);
1006 * Make sure to commit all _CMM_STORE_SHARED() for non-coherent caches.
1010 check_max_end(rbtree
, z
);
1011 check_max_end(rbtree
, y
);
1017 * Transplant v into u position.
1020 #ifdef RBTREE_RCU_SUPPORT_TRANSPLANT
1023 void rcu_rbtree_transplant(struct rcu_rbtree
*rbtree
,
1024 struct rcu_rbtree_node
*u
,
1025 struct rcu_rbtree_node
*v
,
1026 unsigned int copy_parents
,
1027 struct rcu_rbtree_node
*stop
)
1029 dbg_printf("transplant %p\n", v
->begin
);
1031 if (!rcu_rbtree_is_nil(rbtree
, v
))
1032 v
= dup_decay_node(rbtree
, v
);
1034 if (rcu_rbtree_is_nil(rbtree
, get_parent(u
))) {
1035 /* pos is arbitrary for root node */
1036 set_parent(v
, get_parent(u
), IS_RIGHT
);
1037 cmm_smp_wmb(); /* write into node before publish */
1038 _CMM_STORE_SHARED(rbtree
->root
, v
);
1040 struct rcu_rbtree_node
*vp
;
1044 vp
= dup_decay_node(rbtree
, vp
);
1045 set_parent(v
, vp
, get_pos(u
));
1046 if (get_pos(v
) == IS_LEFT
)
1047 _CMM_STORE_SHARED(vp
->_left
, v
);
1049 _CMM_STORE_SHARED(vp
->_right
, v
);
1050 populate_node_end(rbtree
, vp
, copy_parents
, stop
);
1051 check_max_end(rbtree
, vp
);
1054 /* Point children to new copy (parent only used by updates/next/prev) */
1055 if (!rcu_rbtree_is_nil(rbtree
, v
)) {
1056 set_parent(v
->_right
, get_decay(get_parent(v
->_right
)),
1057 get_pos(v
->_right
));
1058 set_parent(v
->_left
, get_decay(get_parent(v
->_left
)),
1061 assert(!is_decay(rbtree
->root
));
1062 check_max_end(rbtree
, v
);
1067 /* Non-RCU version */
1069 void rcu_rbtree_transplant(struct rcu_rbtree
*rbtree
,
1070 struct rcu_rbtree_node
*u
,
1071 struct rcu_rbtree_node
*v
,
1072 unsigned int copy_parents
,
1073 struct rcu_rbtree_node
*stop
)
1075 dbg_printf("transplant %p\n", v
->begin
);
1078 if (rcu_rbtree_is_nil(rbtree
, get_parent(u
)))
1080 else if (u
== get_parent(u
)->_left
)
1081 get_parent(u
)->_left
= v
;
1083 get_parent(u
)->_right
= v
;
1084 set_parent(v
, get_parent(u
), get_pos(u
));
1085 unlock_test_mutex();
1090 static void rcu_rbtree_remove_fixup(struct rcu_rbtree
*rbtree
,
1091 struct rcu_rbtree_node
*x
)
1093 dbg_printf("remove fixup %p\n", x
->begin
);
1095 while (x
!= rbtree
->root
&& x
->color
== COLOR_BLACK
) {
1096 assert(!is_decay(get_parent(x
)));
1097 assert(!is_decay(get_parent(x
)->_left
));
1098 if (x
== get_parent(x
)->_left
) {
1099 struct rcu_rbtree_node
*w
;
1101 w
= get_parent(x
)->_right
;
1103 if (w
->color
== COLOR_RED
) {
1104 w
->color
= COLOR_BLACK
;
1105 get_parent(x
)->color
= COLOR_RED
;
1106 left_rotate(rbtree
, get_parent(x
));
1108 assert(!is_decay(rbtree
->root
));
1109 w
= get_parent(x
)->_right
;
1111 if (w
->_left
->color
== COLOR_BLACK
1112 && w
->_right
->color
== COLOR_BLACK
) {
1113 w
->color
= COLOR_RED
;
1115 assert(!is_decay(rbtree
->root
));
1116 assert(!is_decay(x
));
1118 if (w
->_right
->color
== COLOR_BLACK
) {
1119 w
->_left
->color
= COLOR_BLACK
;
1120 w
->color
= COLOR_RED
;
1121 right_rotate(rbtree
, w
);
1122 assert(!is_decay(rbtree
->root
));
1124 w
= get_parent(x
)->_right
;
1126 w
->color
= get_parent(x
)->color
;
1127 get_parent(x
)->color
= COLOR_BLACK
;
1128 w
->_right
->color
= COLOR_BLACK
;
1129 left_rotate(rbtree
, get_parent(x
));
1130 assert(!is_decay(rbtree
->root
));
1134 struct rcu_rbtree_node
*w
;
1136 w
= get_parent(x
)->_left
;
1138 if (w
->color
== COLOR_RED
) {
1139 w
->color
= COLOR_BLACK
;
1140 get_parent(x
)->color
= COLOR_RED
;
1141 right_rotate(rbtree
, get_parent(x
));
1142 assert(!is_decay(rbtree
->root
));
1144 w
= get_parent(x
)->_left
;
1146 if (w
->_right
->color
== COLOR_BLACK
1147 && w
->_left
->color
== COLOR_BLACK
) {
1148 w
->color
= COLOR_RED
;
1150 assert(!is_decay(rbtree
->root
));
1151 assert(!is_decay(x
));
1153 if (w
->_left
->color
== COLOR_BLACK
) {
1154 w
->_right
->color
= COLOR_BLACK
;
1155 w
->color
= COLOR_RED
;
1156 left_rotate(rbtree
, w
);
1157 assert(!is_decay(rbtree
->root
));
1159 w
= get_parent(x
)->_left
;
1161 w
->color
= get_parent(x
)->color
;
1162 get_parent(x
)->color
= COLOR_BLACK
;
1163 w
->_left
->color
= COLOR_BLACK
;
1164 right_rotate(rbtree
, get_parent(x
));
1165 assert(!is_decay(rbtree
->root
));
1170 x
->color
= COLOR_BLACK
;
1174 * Delete z. All non-copied children left/right positions are unchanged.
1177 void rcu_rbtree_remove_nonil(struct rcu_rbtree
*rbtree
,
1178 struct rcu_rbtree_node
*z
,
1179 struct rcu_rbtree_node
*y
)
1181 struct rcu_rbtree_node
*x
;
1183 dbg_printf("remove nonil %p\n", z
->begin
);
1186 assert(!is_decay(z
));
1187 assert(!is_decay(y
));
1188 assert(!is_decay(y
->_right
));
1189 assert(!is_decay(get_parent(y
)));
1191 assert(!is_decay(x
));
1192 if (get_parent(y
) == z
) {
1193 y
= dup_decay_node(rbtree
, y
);
1194 set_parent(x
, y
, get_pos(x
)); /* parent for nil */
1195 /* y is z's right node */
1196 set_left(rbtree
, y
, z
->_left
);
1197 y
->max_end
= calculate_node_max_end(rbtree
, y
);
1198 rcu_rbtree_transplant(rbtree
, z
, y
, 1, NULL
);
1200 struct rcu_rbtree_node
*oy_right
, *z_right
;
1203 * Need to make sure y is always visible by readers.
1205 y
= rcu_rbtree_min_dup_decay(rbtree
, z
->_right
, &z_right
);
1206 assert(!is_decay(y
));
1207 assert(!is_decay(z
));
1208 oy_right
= y
->_right
;
1211 * The max child begin of z_right does not change, because
1212 * we're only changing its left children.
1214 y
->_right
= z_right
;
1215 set_parent(y
->_right
, y
, IS_RIGHT
);
1216 assert(!is_decay(z
->_left
));
1217 y
->_left
= z
->_left
;
1218 assert(!is_decay(oy_right
));
1220 * Transplant of oy_right to old y's location will only
1221 * trigger a "end" value update of the already copied branch
1222 * (which is not visible yet). We are transplanting
1223 * oy_right as a left child of old y's parent, so the
1224 * min values update propagated upward necessarily stops
1227 rcu_rbtree_transplant(rbtree
, y
, oy_right
, 0, y
);
1228 y
->max_end
= calculate_node_max_end(rbtree
, y
);
1229 rcu_rbtree_transplant(rbtree
, z
, y
, 1, NULL
);
1230 /* Update children */
1231 (void) rcu_rbtree_min_update_decay(rbtree
, y
->_right
);
1234 assert(!is_decay(z
));
1235 assert(!is_decay(z
->_left
));
1236 y
->color
= z
->color
;
1237 set_parent(y
->_left
, y
, IS_LEFT
);
1238 set_parent(y
->_right
, get_decay(get_parent(y
->_right
)), IS_RIGHT
);
1239 assert(!is_decay(y
->_left
));
1240 assert(!is_decay(y
->_right
));
1243 int rcu_rbtree_remove(struct rcu_rbtree
*rbtree
,
1244 struct rcu_rbtree_node
*z
)
1246 struct rcu_rbtree_node
*x
, *y
;
1247 unsigned int y_original_color
;
1249 assert(!is_decay(rbtree
->root
));
1250 dbg_printf("remove %p\n", z
->begin
);
1253 assert(!is_decay(z
));
1255 y_original_color
= y
->color
;
1257 if (rcu_rbtree_is_nil(rbtree
, z
->_left
)) {
1258 rcu_rbtree_transplant(rbtree
, z
, z
->_right
, 1, NULL
);
1259 assert(!is_decay(z
));
1260 x
= get_decay(z
->_right
);
1262 } else if (rcu_rbtree_is_nil(rbtree
, z
->_right
)) {
1263 rcu_rbtree_transplant(rbtree
, z
, z
->_left
, 1, NULL
);
1264 assert(!is_decay(z
));
1265 x
= get_decay(z
->_left
);
1268 y
= rcu_rbtree_min(rbtree
, z
->_right
);
1269 assert(!is_decay(y
));
1270 y_original_color
= y
->color
;
1272 rcu_rbtree_remove_nonil(rbtree
, z
, y
);
1276 if (y_original_color
== COLOR_BLACK
)
1277 rcu_rbtree_remove_fixup(rbtree
, x
);
1279 check_max_end(rbtree
, x
);
1280 check_max_end(rbtree
, get_decay(y
));
1282 * Commit all _CMM_STORE_SHARED().
1285 call_rcu(&z
->head
, _rcu_rbtree_free_node
);