rculfhash: rename _next into _next_duplicate
[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
7f61a77f 35/*
14044b37 36 * struct cds_lfht_node and struct _cds_lfht_node should be aligned on
b198f0fd 37 * 4-bytes boundaries because the two lower bits are used as flags.
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38 */
39
14044b37 40struct _cds_lfht_node {
b198f0fd 41 struct cds_lfht_node *next; /* ptr | DUMMY_FLAG | REMOVED_FLAG */
abc490a1 42 unsigned long reverse_hash;
58ca0741 43} __attribute__((aligned(4)));
cc4fcb10 44
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45/*
46 * struct cds_lfht_node can be embedded into a structure (as a field).
47 * caa_container_of() can be used to get the structure from the struct
48 * cds_lfht_node after a lookup.
49 */
14044b37 50struct cds_lfht_node {
cc4fcb10 51 /* cache-hot for iteration */
14044b37 52 struct _cds_lfht_node p; /* needs to be first field */
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53 void *key;
54 unsigned int key_len;
9b35f1e4 55 /* cache-cold for iteration */
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56 struct rcu_head head;
57};
58
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59struct cds_lfht_iter {
60 struct cds_lfht_node *node, *next;
61};
62
63static inline
64struct cds_lfht_node *cds_lfht_iter_get_node(struct cds_lfht_iter *iter)
65{
66 return iter->node;
67}
68
14044b37 69struct cds_lfht;
ab7d5fc6 70
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71/*
72 * Caution !
abc490a1 73 * Ensure reader and writer threads are registered as urcu readers.
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74 */
75
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76typedef unsigned long (*cds_lfht_hash_fct)(void *key, size_t length,
77 unsigned long seed);
78typedef unsigned long (*cds_lfht_compare_fct)(void *key1, size_t key1_len,
79 void *key2, size_t key2_len);
abc490a1 80
f0c29ed7 81/*
14044b37 82 * cds_lfht_node_init - initialize a hash table node
f0c29ed7 83 */
abc490a1 84static inline
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85void cds_lfht_node_init(struct cds_lfht_node *node, void *key,
86 size_t key_len)
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87{
88 node->key = key;
732ad076 89 node->key_len = key_len;
abc490a1 90}
674f7a69 91
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92/*
93 * Hash table creation flags.
94 */
95enum {
96 CDS_LFHT_AUTO_RESIZE = (1U << 0),
97};
98
674f7a69 99/*
7a9dcf9b 100 * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
674f7a69 101 */
7a9dcf9b 102struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
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103 cds_lfht_compare_fct compare_fct,
104 unsigned long hash_seed,
105 unsigned long init_size,
b8af5011 106 int flags,
14044b37 107 void (*cds_lfht_call_rcu)(struct rcu_head *head,
1475579c 108 void (*func)(struct rcu_head *head)),
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109 void (*cds_lfht_synchronize_rcu)(void),
110 void (*cds_lfht_rcu_read_lock)(void),
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111 void (*cds_lfht_rcu_read_unlock)(void),
112 void (*cds_lfht_rcu_thread_offline)(void),
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113 void (*cds_lfht_rcu_thread_online)(void),
114 void (*cds_lfht_rcu_register_thread)(void),
115 void (*cds_lfht_rcu_unregister_thread)(void),
116 pthread_attr_t *attr);
ab7d5fc6 117
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118/*
119 * cds_lfht_new - allocate a hash table.
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120 * @hash_fct: the hashing function.
121 * @compare_fct: the key comparison function.
122 * @hash_seed: the seed for hash function.
123 * @init_size: number of nodes to allocate initially. Must be power of two.
124 * @flags: hash table creation flags (can be combined with bitwise or: '|').
125 * 0: no flags.
126 * CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
b7d619b0 127 * @attr: optional resize worker thread attributes. NULL for default.
7a9dcf9b 128 *
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129 * Return NULL on error.
130 * Note: the RCU flavor must be already included before the hash table header.
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131 *
132 * The programmer is responsible for ensuring that resize operation has a
133 * priority equal to hash table updater threads. It should be performed by
134 * specifying the appropriate priority in the pthread "attr" argument, and,
135 * for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
136 * this priority level. Having lower priority for call_rcu and resize threads
137 * does not pose any correctness issue, but the resize operations could be
138 * starved by updates, thus leading to long hash table bucket chains.
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139 */
140static inline
141struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_fct,
142 cds_lfht_compare_fct compare_fct,
143 unsigned long hash_seed,
144 unsigned long init_size,
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145 int flags,
146 pthread_attr_t *attr)
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147{
148 return _cds_lfht_new(hash_fct, compare_fct, hash_seed,
149 init_size, flags,
150 call_rcu, synchronize_rcu, rcu_read_lock,
151 rcu_read_unlock, rcu_thread_offline,
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152 rcu_thread_online, rcu_register_thread,
153 rcu_unregister_thread, attr);
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154}
155
f0c29ed7 156/*
14044b37 157 * cds_lfht_destroy - destroy a hash table.
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158 * @ht: the hash table to destroy.
159 * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
160 * The caller will typically want to free this pointer if dynamically
161 * allocated.
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162 *
163 * Return 0 on success, negative error value on error.
f0c29ed7 164 */
b7d619b0 165int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
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166
167/*
14044b37 168 * cds_lfht_count_nodes - count the number of nodes in the hash table.
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169 *
170 * Call with rcu_read_lock held.
171 */
14044b37 172void cds_lfht_count_nodes(struct cds_lfht *ht,
d933dd0e 173 long *approx_before,
adc0de68 174 unsigned long *count,
973e5e1b 175 unsigned long *removed,
d933dd0e 176 long *approx_after);
ab7d5fc6 177
f0c29ed7 178/*
14044b37 179 * cds_lfht_lookup - lookup a node by key.
f0c29ed7 180 *
adc0de68 181 * Output in "*iter". *iter->node set to NULL if not found.
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182 * Call with rcu_read_lock held.
183 */
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184void cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len,
185 struct cds_lfht_iter *iter);
ab7d5fc6 186
f0c29ed7 187/*
3883c0e5 188 * cds_lfht_next_duplicate - get the next item with same key (after a lookup).
f0c29ed7 189 *
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190 * Uses an iterator initialized by a lookup.
191 * Sets *iter-node to the following node with same key.
192 * Sets *iter->node to NULL if no following node exists with same key.
193 * RCU read-side lock must be held across cds_lfht_lookup and
194 * cds_lfht_next calls, and also between cds_lfht_next calls using the
195 * node returned by a previous cds_lfht_next.
196 * Call with rcu_read_lock held.
f0c29ed7 197 */
3883c0e5 198void cds_lfht_next_duplicate(struct cds_lfht *ht, struct cds_lfht_iter *iter);
ab7d5fc6 199
18117871 200/*
14044b37 201 * cds_lfht_add - add a node to the hash table.
f0c29ed7 202 *
18117871 203 * Call with rcu_read_lock held.
48ed1c18 204 * This function supports adding redundant keys into the table.
f0c29ed7 205 */
14044b37 206void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node);
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207
208/*
14044b37 209 * cds_lfht_add_unique - add a node to hash table, if key is not present.
f0c29ed7 210 *
6878c72b 211 * Return the node added upon success.
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212 * Return the unique node already present upon failure. If
213 * cds_lfht_add_unique fails, the node passed as parameter should be
214 * freed by the caller.
f0c29ed7 215 * Call with rcu_read_lock held.
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216 *
217 * The semantic of this function is that if only this function is used
218 * to add keys into the table, no duplicated keys should ever be
219 * observable in the table. The same guarantee apply for combination of
9357c415 220 * add_unique and add_replace (see below).
18117871 221 */
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222struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
223 struct cds_lfht_node *node);
3eca1b8c 224
48ed1c18 225/*
9357c415 226 * cds_lfht_add_replace - replace or add a node within hash table.
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227 *
228 * Return the node replaced upon success. If no node matching the key
229 * was present, return NULL, which also means the operation succeeded.
230 * This replacement operation should never fail.
231 * Call with rcu_read_lock held.
232 * After successful replacement, a grace period must be waited for before
233 * freeing the memory reserved for the returned node.
234 *
235 * The semantic of replacement vs lookups is the following: if lookups
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236 * are performed between a key unique insertion and its removal, we
237 * guarantee that the lookups and get next will always find exactly one
238 * instance of the key if it is replaced concurrently with the lookups.
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239 *
240 * Providing this semantic allows us to ensure that replacement-only
241 * schemes will never generate duplicated keys. It also allows us to
9357c415 242 * guarantee that a combination of add_replace and add_unique updates
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243 * will never generate duplicated keys.
244 */
9357c415 245struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
adc0de68 246 struct cds_lfht_node *node);
48ed1c18 247
f0c29ed7 248/*
9357c415 249 * cds_lfht_replace - replace a node pointer to by iter within hash table.
f0c29ed7 250 *
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251 * Return 0 if replacement is successful, negative value otherwise.
252 * Replacing a NULL old node or an already removed node will fail with a
253 * negative value.
254 * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
255 * RCU read-side lock must be held between lookup and replacement.
256 * Call with rcu_read_lock held.
257 * After successful replacement, a grace period must be waited for before
258 * freeing the memory reserved for the old node (which can be accessed
259 * with cds_lfht_iter_get_node).
260 *
261 * The semantic of replacement vs lookups is the following: if lookups
262 * are performed between a key unique insertion and its removal, we
263 * guarantee that the lookups and get next will always find exactly one
264 * instance of the key if it is replaced concurrently with the lookups.
265 *
266 * Providing this semantic allows us to ensure that replacement-only
267 * schemes will never generate duplicated keys. It also allows us to
268 * guarantee that a combination of add_replace and add_unique updates
269 * will never generate duplicated keys.
270 */
271int cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_iter *old_iter,
272 struct cds_lfht_node *new_node);
273
274/*
275 * cds_lfht_del - remove node pointed to by iterator from hash table.
276 *
277 * Return 0 if the node is successfully removed, negative value
278 * otherwise.
279 * Replacing a NULL node or an already removed node will fail with a
280 * negative value.
281 * Node can be looked up with cds_lfht_lookup and cds_lfht_next.
282 * cds_lfht_iter_get_node.
283 * RCU read-side lock must be held between lookup and removal.
f0c29ed7 284 * Call with rcu_read_lock held.
48ed1c18 285 * After successful removal, a grace period must be waited for before
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286 * freeing the memory reserved for old node (which can be accessed with
287 * cds_lfht_iter_get_node).
f0c29ed7 288 */
9357c415 289int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_iter *iter);
ab7d5fc6 290
f0c29ed7 291/*
14044b37 292 * cds_lfht_resize - Force a hash table resize
1475579c 293 * @new_size: update to this hash table size.
f0c29ed7 294 */
1475579c 295void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);
464a1ec9 296
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297#ifdef __cplusplus
298}
299#endif
300
a42cc659 301#endif /* _URCU_RCULFHASH_H */
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