rculfhash: flip order of removal
[urcu.git] / rculfhash.c
CommitLineData
5e28c532 1/*
abc490a1
MD
2 * rculfhash.c
3 *
4 * Userspace RCU library - Lock-Free Expandable RCU Hash Table
5 *
6 * Copyright 2010-2011 - 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
5e28c532
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21 */
22
2ed95849
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23#define _LGPL_SOURCE
24#include <stdlib.h>
e0ba718a
MD
25#include <errno.h>
26#include <assert.h>
27#include <stdio.h>
abc490a1 28#include <stdint.h>
f000907d 29#include <string.h>
e0ba718a 30
2ed95849 31#include <urcu.h>
abc490a1 32#include <urcu-call-rcu.h>
a42cc659
MD
33#include <urcu/arch.h>
34#include <urcu/uatomic.h>
674f7a69 35#include <urcu/jhash.h>
a42cc659 36#include <urcu/compiler.h>
abc490a1 37#include <urcu/rculfhash.h>
5e28c532 38#include <stdio.h>
464a1ec9 39#include <pthread.h>
44395fb7 40
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41#define DEBUG /* Test */
42
43#ifdef DEBUG
44#define dbg_printf(args...) printf(args)
45#else
46#define dbg_printf(args...)
47#endif
48
65e8e729
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49#define CHAIN_LEN_TARGET 1
50#define CHAIN_LEN_RESIZE_THRESHOLD 2
2ed95849 51
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52#ifndef max
53#define max(a, b) ((a) > (b) ? (a) : (b))
54#endif
2ed95849 55
395270b6 56struct rcu_table {
abc490a1 57 unsigned long size; /* always a power of 2 */
f9830efd 58 unsigned long resize_target;
11519af6 59 int resize_initiated;
abc490a1 60 struct rcu_head head;
395270b6
MD
61 struct rcu_ht_node *tbl[0];
62};
63
2ed95849 64struct rcu_ht {
395270b6 65 struct rcu_table *t; /* shared */
2ed95849 66 ht_hash_fct hash_fct;
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67 ht_compare_fct compare_fct;
68 unsigned long hash_seed;
464a1ec9 69 pthread_mutex_t resize_mutex; /* resize mutex: add/del mutex */
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70 void (*ht_call_rcu)(struct rcu_head *head,
71 void (*func)(struct rcu_head *head));
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MD
72};
73
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74struct rcu_resize_work {
75 struct rcu_head head;
2ed95849 76 struct rcu_ht *ht;
abc490a1 77};
2ed95849 78
abc490a1
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79/*
80 * Algorithm to reverse bits in a word by lookup table, extended to
81 * 64-bit words.
f9830efd 82 * Source:
abc490a1 83 * http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
f9830efd 84 * Originally from Public Domain.
abc490a1
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85 */
86
87static const uint8_t BitReverseTable256[256] =
2ed95849 88{
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89#define R2(n) (n), (n) + 2*64, (n) + 1*64, (n) + 3*64
90#define R4(n) R2(n), R2((n) + 2*16), R2((n) + 1*16), R2((n) + 3*16)
91#define R6(n) R4(n), R4((n) + 2*4 ), R4((n) + 1*4 ), R4((n) + 3*4 )
92 R6(0), R6(2), R6(1), R6(3)
93};
94#undef R2
95#undef R4
96#undef R6
2ed95849 97
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98static
99uint8_t bit_reverse_u8(uint8_t v)
100{
101 return BitReverseTable256[v];
102}
ab7d5fc6 103
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104static __attribute__((unused))
105uint32_t bit_reverse_u32(uint32_t v)
106{
107 return ((uint32_t) bit_reverse_u8(v) << 24) |
108 ((uint32_t) bit_reverse_u8(v >> 8) << 16) |
109 ((uint32_t) bit_reverse_u8(v >> 16) << 8) |
110 ((uint32_t) bit_reverse_u8(v >> 24));
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111}
112
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113static __attribute__((unused))
114uint64_t bit_reverse_u64(uint64_t v)
2ed95849 115{
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116 return ((uint64_t) bit_reverse_u8(v) << 56) |
117 ((uint64_t) bit_reverse_u8(v >> 8) << 48) |
118 ((uint64_t) bit_reverse_u8(v >> 16) << 40) |
119 ((uint64_t) bit_reverse_u8(v >> 24) << 32) |
120 ((uint64_t) bit_reverse_u8(v >> 32) << 24) |
121 ((uint64_t) bit_reverse_u8(v >> 40) << 16) |
122 ((uint64_t) bit_reverse_u8(v >> 48) << 8) |
123 ((uint64_t) bit_reverse_u8(v >> 56));
124}
125
126static
127unsigned long bit_reverse_ulong(unsigned long v)
128{
129#if (CAA_BITS_PER_LONG == 32)
130 return bit_reverse_u32(v);
131#else
132 return bit_reverse_u64(v);
133#endif
134}
135
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136/*
137 * Algorithm to find the log2 of a 32-bit unsigned integer.
138 * source: http://graphics.stanford.edu/~seander/bithacks.html#IntegerLogLookup
139 * Originally from Public Domain.
140 */
141static const char LogTable256[256] =
142{
143#define LT(n) n, n, n, n, n, n, n, n, n, n, n, n, n, n, n, n
144 -1, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3,
145 LT(4), LT(5), LT(5), LT(6), LT(6), LT(6), LT(6),
146 LT(7), LT(7), LT(7), LT(7), LT(7), LT(7), LT(7), LT(7)
147};
148
149uint32_t log2_u32(uint32_t v)
150{
151 uint32_t t, tt;
152
153 if ((tt = (v >> 16)))
154 return (t = (tt >> 8))
155 ? 24 + LogTable256[t]
156 : 16 + LogTable256[tt];
157 else
158 return (t = (v >> 8))
159 ? 8 + LogTable256[t]
160 : LogTable256[v];
161}
162
163static
164void ht_resize_lazy(struct rcu_ht *ht, struct rcu_table *t, int growth);
165
166static
167void check_resize(struct rcu_ht *ht, struct rcu_table *t,
168 uint32_t chain_len)
169{
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170 if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD)
171 ht_resize_lazy(ht, t,
65e8e729 172 log2_u32(chain_len - CHAIN_LEN_TARGET - 1));
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173}
174
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175static
176struct rcu_ht_node *clear_flag(struct rcu_ht_node *node)
177{
178 return (struct rcu_ht_node *) (((unsigned long) node) & ~0x1);
179}
180
181static
182int is_removed(struct rcu_ht_node *node)
183{
184 return ((unsigned long) node) & 0x1;
185}
186
187static
188struct rcu_ht_node *flag_removed(struct rcu_ht_node *node)
189{
190 return (struct rcu_ht_node *) (((unsigned long) node) | 0x1);
191}
192
193static
f9830efd 194unsigned long _uatomic_max(unsigned long *ptr, unsigned long v)
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195{
196 unsigned long old1, old2;
197
198 old1 = uatomic_read(ptr);
199 do {
200 old2 = old1;
201 if (old2 >= v)
f9830efd 202 return old2;
abc490a1 203 } while ((old1 = uatomic_cmpxchg(ptr, old2, v)) != old2);
f9830efd 204 return v;
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205}
206
207static
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208int _ht_add(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node,
209 int unique)
abc490a1 210{
11519af6 211 struct rcu_ht_node *iter_prev, *iter, *iter_prev_next, *next;
abc490a1 212
f000907d 213 if (!t->size)
3eca1b8c 214 return 0;
abc490a1 215 for (;;) {
f9830efd 216 uint32_t chain_len = 0;
abc490a1 217
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218 /*
219 * iter_prev points to the non-removed node prior to the
220 * insert location.
221 * iter iterates until it finds the next non-removed
222 * node.
223 */
abc490a1 224 iter_prev = rcu_dereference(t->tbl[node->hash & (t->size - 1)]);
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225 /* We can always skip the dummy node initially */
226 iter_prev_next = next = rcu_dereference(iter_prev->next);
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227 assert(iter_prev);
228 assert(iter_prev->reverse_hash <= node->reverse_hash);
229 for (;;) {
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230 iter = next;
231 if (unlikely(!clear_flag(iter)))
abc490a1 232 break;
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233 next = rcu_dereference(clear_flag(iter)->next);
234 if (unlikely(is_removed(next)))
235 continue;
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MD
236 if (unique
237 && !clear_flag(iter)->dummy
238 && !ht->compare_fct(node->key, node->key_len,
239 clear_flag(iter)->key,
240 clear_flag(iter)->key_len))
241 return -EEXIST;
11519af6 242 if (clear_flag(iter)->reverse_hash > node->reverse_hash)
abc490a1 243 break;
11519af6
MD
244 /* Only account for identical reverse hash once */
245 if (iter_prev->reverse_hash != clear_flag(iter)->reverse_hash)
246 check_resize(ht, t, ++chain_len);
247 iter_prev = clear_flag(iter);
248 iter_prev_next = next;
abc490a1 249 }
7ec59d3b 250 assert(node != clear_flag(iter));
11519af6 251 assert(!is_removed(iter_prev));
f000907d 252 assert(iter_prev != node);
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MD
253 node->next = iter;
254 if (uatomic_cmpxchg(&iter_prev->next, iter_prev_next,
255 node) != iter_prev_next)
abc490a1 256 continue;
11519af6
MD
257 else
258 break;
464a1ec9 259 }
3eca1b8c 260 return 0;
abc490a1 261}
464a1ec9 262
abc490a1
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263static
264int _ht_remove(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
265{
11519af6 266 struct rcu_ht_node *iter_prev, *iter, *iter_prev_next, *next, *old;
11519af6 267 int found;
abc490a1 268 int flagged = 0;
5e28c532 269
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MD
270 /* logically delete the node */
271 old = rcu_dereference(node->next);
272 do {
273 next = old;
274 if (is_removed(next))
275 goto end;
276 old = uatomic_cmpxchg(&node->next, next,
277 flag_removed(next));
278 } while (old != next);
279
280 /* We performed the (logical) deletion. */
281 flagged = 1;
282
283 /*
284 * Ensure that the node is not visible to readers anymore: lookup for
285 * the node, and remove it if found.
286 */
abc490a1 287retry:
abc490a1 288 found = 0;
11519af6
MD
289 /*
290 * iter_prev points to the non-removed node prior to the remove
291 * location.
7ec59d3b 292 * next points to the non-removed node following the remove location.
11519af6 293 */
abc490a1 294 iter_prev = rcu_dereference(t->tbl[node->hash & (t->size - 1)]);
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MD
295 /* We can always skip the dummy node initially */
296 iter_prev_next = next = rcu_dereference(iter_prev->next);
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297 assert(iter_prev);
298 assert(iter_prev->reverse_hash <= node->reverse_hash);
2ed95849 299 for (;;) {
11519af6
MD
300 iter = next;
301 if (unlikely(!clear_flag(iter)))
abc490a1 302 break;
11519af6 303 next = rcu_dereference(clear_flag(iter)->next);
7ec59d3b 304 if (clear_flag(iter) == node) {
abc490a1 305 found = 1;
7ec59d3b 306 assert(is_removed(rcu_dereference(node->next)));
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MD
307 break;
308 }
11519af6
MD
309 if (unlikely(is_removed(next)))
310 continue;
311 if (clear_flag(iter)->reverse_hash > node->reverse_hash)
312 break;
313 iter_prev = clear_flag(iter);
314 iter_prev_next = next;
abc490a1 315 }
11519af6 316 if (!found)
abc490a1 317 goto end;
11519af6
MD
318 if (uatomic_cmpxchg(&iter_prev->next, iter_prev_next,
319 clear_flag(next)) != iter_prev_next)
abc490a1 320 goto retry;
2ed95849 321end:
11519af6
MD
322 /*
323 * Only the flagging action indicated that we (and no other)
324 * removed the node from the hash.
325 */
7ec59d3b
MD
326 if (flagged) {
327 assert(is_removed(rcu_dereference(node->next)));
11519af6 328 return 0;
7ec59d3b 329 } else
11519af6 330 return -ENOENT;
abc490a1 331}
2ed95849 332
abc490a1
MD
333static
334void init_table(struct rcu_ht *ht, struct rcu_table *t,
335 unsigned long first, unsigned long len)
336{
337 unsigned long i, end;
338
339 end = first + len;
340 for (i = first; i < end; i++) {
341 /* Update table size when power of two */
342 if (i != 0 && !(i & (i - 1)))
343 t->size = i;
344 t->tbl[i] = calloc(1, sizeof(struct rcu_ht_node));
345 t->tbl[i]->dummy = 1;
346 t->tbl[i]->hash = i;
347 t->tbl[i]->reverse_hash = bit_reverse_ulong(i);
3eca1b8c 348 (void) _ht_add(ht, t, t->tbl[i], 0);
abc490a1 349 }
f9830efd 350 t->resize_target = t->size = end;
11519af6 351 t->resize_initiated = 0;
2ed95849
MD
352}
353
abc490a1 354struct rcu_ht *ht_new(ht_hash_fct hash_fct,
732ad076
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355 ht_compare_fct compare_fct,
356 unsigned long hash_seed,
abc490a1
MD
357 unsigned long init_size,
358 void (*ht_call_rcu)(struct rcu_head *head,
359 void (*func)(struct rcu_head *head)))
360{
361 struct rcu_ht *ht;
362
363 ht = calloc(1, sizeof(struct rcu_ht));
364 ht->hash_fct = hash_fct;
732ad076
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365 ht->compare_fct = compare_fct;
366 ht->hash_seed = hash_seed;
f000907d 367 ht->ht_call_rcu = ht_call_rcu;
abc490a1
MD
368 /* this mutex should not nest in read-side C.S. */
369 pthread_mutex_init(&ht->resize_mutex, NULL);
370 ht->t = calloc(1, sizeof(struct rcu_table)
371 + (max(init_size, 1) * sizeof(struct rcu_ht_node *)));
372 ht->t->size = 0;
f000907d 373 pthread_mutex_lock(&ht->resize_mutex);
abc490a1 374 init_table(ht, ht->t, 0, max(init_size, 1));
f000907d 375 pthread_mutex_unlock(&ht->resize_mutex);
abc490a1
MD
376 return ht;
377}
378
732ad076 379struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key, size_t key_len)
2ed95849 380{
395270b6 381 struct rcu_table *t;
abc490a1
MD
382 struct rcu_ht_node *node;
383 unsigned long hash, reverse_hash;
2ed95849 384
732ad076 385 hash = ht->hash_fct(key, key_len, ht->hash_seed);
abc490a1 386 reverse_hash = bit_reverse_ulong(hash);
464a1ec9 387
395270b6 388 t = rcu_dereference(ht->t);
abc490a1 389 node = rcu_dereference(t->tbl[hash & (t->size - 1)]);
2ed95849 390 for (;;) {
abc490a1
MD
391 if (unlikely(!node))
392 break;
dd4505e0 393 if (unlikely(node->reverse_hash > reverse_hash)) {
abc490a1
MD
394 node = NULL;
395 break;
2ed95849 396 }
732ad076 397 if (!ht->compare_fct(node->key, node->key_len, key, key_len)) {
dd4505e0 398 if (unlikely(is_removed(rcu_dereference(node->next))))
abc490a1 399 node = NULL;
2ed95849
MD
400 break;
401 }
abc490a1 402 node = clear_flag(rcu_dereference(node->next));
2ed95849 403 }
abc490a1
MD
404 return node;
405}
e0ba718a 406
f000907d 407void ht_add(struct rcu_ht *ht, struct rcu_ht_node *node)
abc490a1
MD
408{
409 struct rcu_table *t;
ab7d5fc6 410
732ad076 411 node->hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed);
abc490a1 412 node->reverse_hash = bit_reverse_ulong((unsigned long) node->hash);
2ed95849 413
abc490a1 414 t = rcu_dereference(ht->t);
3eca1b8c
MD
415 (void) _ht_add(ht, t, node, 0);
416}
417
418int ht_add_unique(struct rcu_ht *ht, struct rcu_ht_node *node)
419{
420 struct rcu_table *t;
421
422 node->hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed);
423 node->reverse_hash = bit_reverse_ulong((unsigned long) node->hash);
424
425 t = rcu_dereference(ht->t);
426 return _ht_add(ht, t, node, 1);
2ed95849
MD
427}
428
abc490a1 429int ht_remove(struct rcu_ht *ht, struct rcu_ht_node *node)
2ed95849 430{
abc490a1
MD
431 struct rcu_table *t;
432
433 t = rcu_dereference(ht->t);
abc490a1 434 return _ht_remove(ht, t, node);
2ed95849 435}
ab7d5fc6 436
abc490a1
MD
437static
438int ht_delete_dummy(struct rcu_ht *ht)
674f7a69 439{
395270b6 440 struct rcu_table *t;
abc490a1
MD
441 struct rcu_ht_node *node;
442 unsigned long i;
674f7a69 443
abc490a1
MD
444 t = ht->t;
445 /* Check that the table is empty */
446 node = t->tbl[0];
447 do {
448 if (!node->dummy)
449 return -EPERM;
450 node = node->next;
451 } while (node);
452 /* Internal sanity check: all nodes left should be dummy */
395270b6 453 for (i = 0; i < t->size; i++) {
abc490a1
MD
454 assert(t->tbl[i]->dummy);
455 free(t->tbl[i]);
674f7a69 456 }
abc490a1 457 return 0;
674f7a69
MD
458}
459
460/*
461 * Should only be called when no more concurrent readers nor writers can
462 * possibly access the table.
463 */
5e28c532 464int ht_destroy(struct rcu_ht *ht)
674f7a69 465{
5e28c532
MD
466 int ret;
467
abc490a1
MD
468 ret = ht_delete_dummy(ht);
469 if (ret)
470 return ret;
395270b6 471 free(ht->t);
674f7a69 472 free(ht);
5e28c532 473 return ret;
674f7a69
MD
474}
475
abc490a1
MD
476static
477void ht_free_table_cb(struct rcu_head *head)
478{
479 struct rcu_table *t =
480 caa_container_of(head, struct rcu_table, head);
481 free(t);
482}
483
484/* called with resize mutex held */
485static
486void _do_ht_resize(struct rcu_ht *ht)
464a1ec9 487{
abc490a1 488 unsigned long new_size, old_size;
395270b6 489 struct rcu_table *new_t, *old_t;
464a1ec9 490
395270b6
MD
491 old_t = ht->t;
492 old_size = old_t->size;
464a1ec9 493
f9830efd
MD
494 new_size = CMM_LOAD_SHARED(old_t->resize_target);
495 dbg_printf("rculfhash: resize from %lu to %lu buckets\n",
496 old_size, new_size);
abc490a1 497 if (old_size == new_size)
464a1ec9 498 return;
f000907d 499 new_t = malloc(sizeof(struct rcu_table)
abc490a1 500 + (new_size * sizeof(struct rcu_ht_node *)));
f000907d
MD
501 assert(new_size > old_size);
502 memcpy(&new_t->tbl, &old_t->tbl,
503 old_size * sizeof(struct rcu_ht_node *));
504 init_table(ht, new_t, old_size, new_size - old_size);
f000907d
MD
505 /* Changing table and size atomically wrt lookups */
506 rcu_assign_pointer(ht->t, new_t);
507 ht->ht_call_rcu(&old_t->head, ht_free_table_cb);
464a1ec9
MD
508}
509
abc490a1 510static
f9830efd
MD
511unsigned long resize_target_update(struct rcu_table *t,
512 int growth_order)
464a1ec9 513{
f9830efd
MD
514 return _uatomic_max(&t->resize_target,
515 t->size << growth_order);
464a1ec9
MD
516}
517
464a1ec9
MD
518void ht_resize(struct rcu_ht *ht, int growth)
519{
f9830efd
MD
520 struct rcu_table *t = rcu_dereference(ht->t);
521 unsigned long target_size;
522
523 target_size = resize_target_update(t, growth);
524 if (t->size < target_size) {
11519af6 525 CMM_STORE_SHARED(t->resize_initiated, 1);
f9830efd
MD
526 pthread_mutex_lock(&ht->resize_mutex);
527 _do_ht_resize(ht);
528 pthread_mutex_unlock(&ht->resize_mutex);
529 }
abc490a1 530}
464a1ec9 531
abc490a1
MD
532static
533void do_resize_cb(struct rcu_head *head)
534{
535 struct rcu_resize_work *work =
536 caa_container_of(head, struct rcu_resize_work, head);
537 struct rcu_ht *ht = work->ht;
538
539 pthread_mutex_lock(&ht->resize_mutex);
540 _do_ht_resize(ht);
541 pthread_mutex_unlock(&ht->resize_mutex);
542 free(work);
464a1ec9
MD
543}
544
abc490a1 545static
f000907d 546void ht_resize_lazy(struct rcu_ht *ht, struct rcu_table *t, int growth)
ab7d5fc6 547{
abc490a1 548 struct rcu_resize_work *work;
f9830efd 549 unsigned long target_size;
abc490a1 550
f9830efd 551 target_size = resize_target_update(t, growth);
11519af6 552 if (!CMM_LOAD_SHARED(t->resize_initiated) && t->size < target_size) {
f9830efd
MD
553 work = malloc(sizeof(*work));
554 work->ht = ht;
555 ht->ht_call_rcu(&work->head, do_resize_cb);
11519af6 556 CMM_STORE_SHARED(t->resize_initiated, 1);
f9830efd 557 }
ab7d5fc6 558}
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