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[urcu.git] / urcu / rculfhash.h
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1#ifndef _URCU_RCULFHASH_H
2#define _URCU_RCULFHASH_H
ab7d5fc6 3
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4/*
5 * urcu/rculfhash.h
6 *
7 * Userspace RCU library - Lock-Free RCU Hash Table
8 *
9 * Copyright 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
10 *
11 * This library is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU Lesser General Public
13 * License as published by the Free Software Foundation; either
14 * version 2.1 of the License, or (at your option) any later version.
15 *
16 * This library is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
19 * Lesser General Public License for more details.
20 *
21 * You should have received a copy of the GNU Lesser General Public
22 * License along with this library; if not, write to the Free Software
23 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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24 *
25 * Include this file _after_ including your URCU flavor.
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26 */
27
674f7a69 28#include <stdint.h>
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29#include <urcu-call-rcu.h>
30
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31#ifdef __cplusplus
32extern "C" {
33#endif
34
7f52427b 35/*
04db56f8 36 * cds_lfht_node: Contains the next pointers and reverse-hash
7f52427b 37 * value required for lookup and traversal of the hash table.
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38 *
39 * struct cds_lfht_node should be aligned on 4-bytes boundaries because
40 * the two lower bits are used as flags.
7f52427b 41 *
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42 * struct cds_lfht_node can be embedded into a structure (as a field).
43 * caa_container_of() can be used to get the structure from the struct
44 * cds_lfht_node after a lookup.
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45 *
46 * The structure which embeds it typically holds the key (or key-value
47 * pair) of the object. The caller code is responsible for calculation
48 * of the hash value for cds_lfht APIs.
ae62aa6a 49 */
14044b37 50struct cds_lfht_node {
1ee8f000 51 struct cds_lfht_node *next; /* ptr | BUCKET_FLAG | REMOVED_FLAG */
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52 unsigned long reverse_hash;
53} __attribute__((aligned(4)));
abc490a1 54
7f52427b 55/* cds_lfht_iter: Used to track state while traversing a hash chain. */
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56struct cds_lfht_iter {
57 struct cds_lfht_node *node, *next;
58};
59
60static inline
61struct cds_lfht_node *cds_lfht_iter_get_node(struct cds_lfht_iter *iter)
62{
63 return iter->node;
64}
65
14044b37 66struct cds_lfht;
ab7d5fc6 67
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68/*
69 * Caution !
abc490a1 70 * Ensure reader and writer threads are registered as urcu readers.
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71 */
72
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73typedef unsigned long (*cds_lfht_hash_fct)(void *key, size_t length,
74 unsigned long seed);
0422d92c 75typedef int (*cds_lfht_match_fct)(struct cds_lfht_node *node, void *key);
abc490a1 76
f0c29ed7 77/*
14044b37 78 * cds_lfht_node_init - initialize a hash table node
0422d92c 79 * @node: the node to initialize.
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80 *
81 * This function is kept to be eventually used for debugging purposes
82 * (detection of memory corruption).
f0c29ed7 83 */
abc490a1 84static inline
04db56f8 85void cds_lfht_node_init(struct cds_lfht_node *node)
abc490a1 86{
abc490a1 87}
674f7a69 88
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89/*
90 * Hash table creation flags.
91 */
92enum {
93 CDS_LFHT_AUTO_RESIZE = (1U << 0),
5afadd12 94 CDS_LFHT_ACCOUNTING = (1U << 1),
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95};
96
674f7a69 97/*
7a9dcf9b 98 * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
674f7a69 99 */
0422d92c 100struct cds_lfht *_cds_lfht_new(unsigned long init_size,
5488222b 101 unsigned long min_alloc_size,
b8af5011 102 int flags,
14044b37 103 void (*cds_lfht_call_rcu)(struct rcu_head *head,
1475579c 104 void (*func)(struct rcu_head *head)),
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105 void (*cds_lfht_synchronize_rcu)(void),
106 void (*cds_lfht_rcu_read_lock)(void),
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107 void (*cds_lfht_rcu_read_unlock)(void),
108 void (*cds_lfht_rcu_thread_offline)(void),
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109 void (*cds_lfht_rcu_thread_online)(void),
110 void (*cds_lfht_rcu_register_thread)(void),
111 void (*cds_lfht_rcu_unregister_thread)(void),
112 pthread_attr_t *attr);
ab7d5fc6 113
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114/*
115 * cds_lfht_new - allocate a hash table.
f22dd01d 116 * @init_size: number of nodes to allocate initially. Must be power of two.
5488222b 117 * @min_alloc_size: the smallest allocation size to use. Must be power of two.
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118 * @flags: hash table creation flags (can be combined with bitwise or: '|').
119 * 0: no flags.
120 * CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
b7d619b0 121 * @attr: optional resize worker thread attributes. NULL for default.
7a9dcf9b 122 *
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123 * Return NULL on error.
124 * Note: the RCU flavor must be already included before the hash table header.
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125 *
126 * The programmer is responsible for ensuring that resize operation has a
127 * priority equal to hash table updater threads. It should be performed by
128 * specifying the appropriate priority in the pthread "attr" argument, and,
129 * for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
130 * this priority level. Having lower priority for call_rcu and resize threads
131 * does not pose any correctness issue, but the resize operations could be
132 * starved by updates, thus leading to long hash table bucket chains.
3df0c49c 133 * Threads calling this API need to be registered RCU read-side threads.
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134 */
135static inline
0422d92c 136struct cds_lfht *cds_lfht_new(unsigned long init_size,
5488222b 137 unsigned long min_alloc_size,
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138 int flags,
139 pthread_attr_t *attr)
7a9dcf9b 140{
0422d92c 141 return _cds_lfht_new(init_size, min_alloc_size, flags,
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142 call_rcu, synchronize_rcu, rcu_read_lock,
143 rcu_read_unlock, rcu_thread_offline,
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144 rcu_thread_online, rcu_register_thread,
145 rcu_unregister_thread, attr);
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146}
147
f0c29ed7 148/*
14044b37 149 * cds_lfht_destroy - destroy a hash table.
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150 * @ht: the hash table to destroy.
151 * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
152 * The caller will typically want to free this pointer if dynamically
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153 * allocated. The attr point can be NULL if the caller does not
154 * need to be informed of the value passed to cds_lfht_new().
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155 *
156 * Return 0 on success, negative error value on error.
3df0c49c 157 * Threads calling this API need to be registered RCU read-side threads.
f0c29ed7 158 */
b7d619b0 159int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
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160
161/*
14044b37 162 * cds_lfht_count_nodes - count the number of nodes in the hash table.
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163 * @ht: the hash table.
164 * @split_count_before: Sample the node count split-counter before traversal.
165 * @count: Traverse the hash table, count the number of nodes observed.
166 * @removed: Number of logically removed nodes observed during traversal.
167 * @split_count_after: Sample the node count split-counter after traversal.
0422d92c 168 *
f0c29ed7 169 * Call with rcu_read_lock held.
3df0c49c 170 * Threads calling this API need to be registered RCU read-side threads.
f0c29ed7 171 */
14044b37 172void cds_lfht_count_nodes(struct cds_lfht *ht,
7f52427b 173 long *split_count_before,
adc0de68 174 unsigned long *count,
973e5e1b 175 unsigned long *removed,
7f52427b 176 long *split_count_after);
ab7d5fc6 177
f0c29ed7 178/*
14044b37 179 * cds_lfht_lookup - lookup a node by key.
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180 * @ht: the hash table.
181 * @match: the key match function.
182 * @hash: the key hash.
183 * @iter: Node, if found (output). *iter->node set to NULL if not found.
f0c29ed7 184 *
f0c29ed7 185 * Call with rcu_read_lock held.
3df0c49c 186 * Threads calling this API need to be registered RCU read-side threads.
f0c29ed7 187 */
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188void cds_lfht_lookup(struct cds_lfht *ht, cds_lfht_match_fct match,
189 unsigned long hash, void *key, struct cds_lfht_iter *iter);
ab7d5fc6 190
f0c29ed7 191/*
3883c0e5 192 * cds_lfht_next_duplicate - get the next item with same key (after a lookup).
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193 * @ht: the hash table.
194 * @match: the key match function.
04db56f8 195 * @key: the current node key.
0422d92c 196 * @iter: Node, if found (output). *iter->node set to NULL if not found.
f0c29ed7 197 *
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198 * Uses an iterator initialized by a lookup.
199 * Sets *iter-node to the following node with same key.
200 * Sets *iter->node to NULL if no following node exists with same key.
201 * RCU read-side lock must be held across cds_lfht_lookup and
202 * cds_lfht_next calls, and also between cds_lfht_next calls using the
203 * node returned by a previous cds_lfht_next.
204 * Call with rcu_read_lock held.
3df0c49c 205 * Threads calling this API need to be registered RCU read-side threads.
f0c29ed7 206 */
0422d92c 207void cds_lfht_next_duplicate(struct cds_lfht *ht,
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208 cds_lfht_match_fct match, void *key,
209 struct cds_lfht_iter *iter);
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210
211/*
212 * cds_lfht_first - get the first node in the table.
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213 * @ht: the hash table.
214 * @iter: First node, if exists (output). *iter->node set to NULL if not found.
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215 *
216 * Output in "*iter". *iter->node set to NULL if table is empty.
217 * Call with rcu_read_lock held.
3df0c49c 218 * Threads calling this API need to be registered RCU read-side threads.
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219 */
220void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter);
221
222/*
223 * cds_lfht_next - get the next node in the table.
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224 * @ht: the hash table.
225 * @iter: Next node, if exists (output). *iter->node set to NULL if not found.
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226 *
227 * Input/Output in "*iter". *iter->node set to NULL if *iter was
228 * pointing to the last table node.
229 * Call with rcu_read_lock held.
3df0c49c 230 * Threads calling this API need to be registered RCU read-side threads.
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231 */
232void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter);
ab7d5fc6 233
18117871 234/*
14044b37 235 * cds_lfht_add - add a node to the hash table.
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236 * @ht: the hash table.
237 * @hash: the key hash.
238 * @node: the node to add.
f0c29ed7 239 *
48ed1c18 240 * This function supports adding redundant keys into the table.
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241 * Call with rcu_read_lock held.
242 * Threads calling this API need to be registered RCU read-side threads.
f0c29ed7 243 */
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244void cds_lfht_add(struct cds_lfht *ht, unsigned long hash,
245 struct cds_lfht_node *node);
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246
247/*
14044b37 248 * cds_lfht_add_unique - add a node to hash table, if key is not present.
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249 * @ht: the hash table.
250 * @match: the key match function.
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251 * @key: the node's key.
252 * @hash: the node's hash.
0422d92c 253 * @node: the node to try adding.
f0c29ed7 254 *
6878c72b 255 * Return the node added upon success.
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256 * Return the unique node already present upon failure. If
257 * cds_lfht_add_unique fails, the node passed as parameter should be
258 * freed by the caller.
f0c29ed7 259 * Call with rcu_read_lock held.
3df0c49c 260 * Threads calling this API need to be registered RCU read-side threads.
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261 *
262 * The semantic of this function is that if only this function is used
263 * to add keys into the table, no duplicated keys should ever be
264 * observable in the table. The same guarantee apply for combination of
9357c415 265 * add_unique and add_replace (see below).
18117871 266 */
adc0de68 267struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
0422d92c 268 cds_lfht_match_fct match,
04db56f8 269 void *key,
0422d92c 270 unsigned long hash,
adc0de68 271 struct cds_lfht_node *node);
3eca1b8c 272
48ed1c18 273/*
9357c415 274 * cds_lfht_add_replace - replace or add a node within hash table.
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275 * @ht: the hash table.
276 * @match: the key match function.
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277 * @key: the node's key.
278 * @hash: the node's hash.
0422d92c 279 * @node: the node to add.
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280 *
281 * Return the node replaced upon success. If no node matching the key
282 * was present, return NULL, which also means the operation succeeded.
283 * This replacement operation should never fail.
284 * Call with rcu_read_lock held.
3df0c49c 285 * Threads calling this API need to be registered RCU read-side threads.
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286 * After successful replacement, a grace period must be waited for before
287 * freeing the memory reserved for the returned node.
288 *
289 * The semantic of replacement vs lookups is the following: if lookups
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290 * are performed between a key unique insertion and its removal, we
291 * guarantee that the lookups and get next will always find exactly one
292 * instance of the key if it is replaced concurrently with the lookups.
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293 *
294 * Providing this semantic allows us to ensure that replacement-only
295 * schemes will never generate duplicated keys. It also allows us to
9357c415 296 * guarantee that a combination of add_replace and add_unique updates
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297 * will never generate duplicated keys.
298 */
9357c415 299struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
0422d92c 300 cds_lfht_match_fct match,
04db56f8 301 void *key,
0422d92c 302 unsigned long hash,
adc0de68 303 struct cds_lfht_node *node);
48ed1c18 304
f0c29ed7 305/*
9357c415 306 * cds_lfht_replace - replace a node pointer to by iter within hash table.
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307 * @ht: the hash table.
308 * @old_iter: the iterator position of the node to replace.
309 * @now_node: the new node to try using for replacement.
f0c29ed7 310 *
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311 * Return 0 if replacement is successful, negative value otherwise.
312 * Replacing a NULL old node or an already removed node will fail with a
313 * negative value.
314 * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
315 * RCU read-side lock must be held between lookup and replacement.
316 * Call with rcu_read_lock held.
3df0c49c 317 * Threads calling this API need to be registered RCU read-side threads.
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318 * After successful replacement, a grace period must be waited for before
319 * freeing the memory reserved for the old node (which can be accessed
320 * with cds_lfht_iter_get_node).
321 *
322 * The semantic of replacement vs lookups is the following: if lookups
323 * are performed between a key unique insertion and its removal, we
324 * guarantee that the lookups and get next will always find exactly one
325 * instance of the key if it is replaced concurrently with the lookups.
326 *
327 * Providing this semantic allows us to ensure that replacement-only
328 * schemes will never generate duplicated keys. It also allows us to
329 * guarantee that a combination of add_replace and add_unique updates
330 * will never generate duplicated keys.
331 */
332int cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_iter *old_iter,
333 struct cds_lfht_node *new_node);
334
335/*
336 * cds_lfht_del - remove node pointed to by iterator from hash table.
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337 * @ht: the hash table.
338 * @iter: the iterator position of the node to delete.
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339 *
340 * Return 0 if the node is successfully removed, negative value
341 * otherwise.
342 * Replacing a NULL node or an already removed node will fail with a
343 * negative value.
344 * Node can be looked up with cds_lfht_lookup and cds_lfht_next.
345 * cds_lfht_iter_get_node.
346 * RCU read-side lock must be held between lookup and removal.
f0c29ed7 347 * Call with rcu_read_lock held.
3df0c49c 348 * Threads calling this API need to be registered RCU read-side threads.
48ed1c18 349 * After successful removal, a grace period must be waited for before
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350 * freeing the memory reserved for old node (which can be accessed with
351 * cds_lfht_iter_get_node).
f0c29ed7 352 */
9357c415 353int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_iter *iter);
ab7d5fc6 354
f0c29ed7 355/*
14044b37 356 * cds_lfht_resize - Force a hash table resize
0422d92c 357 * @ht: the hash table.
1475579c 358 * @new_size: update to this hash table size.
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359 *
360 * Threads calling this API need to be registered RCU read-side threads.
f0c29ed7 361 */
1475579c 362void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);
464a1ec9 363
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364#ifdef __cplusplus
365}
366#endif
367
a42cc659 368#endif /* _URCU_RCULFHASH_H */
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