rculfhash: support replacement operation
[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
48ed1c18 37 * 8-bytes boundaries because the two lower bits are used as flags.
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38 */
39
14044b37 40struct _cds_lfht_node {
48ed1c18 41 struct cds_lfht_node *next; /* ptr | DUMMY_FLAG | GC_FLAG | REMOVED_FLAG */
abc490a1 42 unsigned long reverse_hash;
48ed1c18 43} __attribute__((aligned(8)));
cc4fcb10 44
14044b37 45struct cds_lfht_node {
cc4fcb10 46 /* cache-hot for iteration */
14044b37 47 struct _cds_lfht_node p; /* needs to be first field */
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48 void *key;
49 unsigned int key_len;
9b35f1e4 50 /* cache-cold for iteration */
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51 struct rcu_head head;
52};
53
14044b37 54struct cds_lfht;
ab7d5fc6 55
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56/*
57 * Caution !
abc490a1 58 * Ensure reader and writer threads are registered as urcu readers.
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59 */
60
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61typedef unsigned long (*cds_lfht_hash_fct)(void *key, size_t length,
62 unsigned long seed);
63typedef unsigned long (*cds_lfht_compare_fct)(void *key1, size_t key1_len,
64 void *key2, size_t key2_len);
abc490a1 65
f0c29ed7 66/*
14044b37 67 * cds_lfht_node_init - initialize a hash table node
f0c29ed7 68 */
abc490a1 69static inline
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70void cds_lfht_node_init(struct cds_lfht_node *node, void *key,
71 size_t key_len)
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72{
73 node->key = key;
732ad076 74 node->key_len = key_len;
abc490a1 75}
674f7a69 76
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77/*
78 * Hash table creation flags.
79 */
80enum {
81 CDS_LFHT_AUTO_RESIZE = (1U << 0),
82};
83
674f7a69 84/*
7a9dcf9b 85 * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
674f7a69 86 */
7a9dcf9b 87struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
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88 cds_lfht_compare_fct compare_fct,
89 unsigned long hash_seed,
90 unsigned long init_size,
b8af5011 91 int flags,
14044b37 92 void (*cds_lfht_call_rcu)(struct rcu_head *head,
1475579c 93 void (*func)(struct rcu_head *head)),
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94 void (*cds_lfht_synchronize_rcu)(void),
95 void (*cds_lfht_rcu_read_lock)(void),
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96 void (*cds_lfht_rcu_read_unlock)(void),
97 void (*cds_lfht_rcu_thread_offline)(void),
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98 void (*cds_lfht_rcu_thread_online)(void),
99 void (*cds_lfht_rcu_register_thread)(void),
100 void (*cds_lfht_rcu_unregister_thread)(void),
101 pthread_attr_t *attr);
ab7d5fc6 102
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103/*
104 * cds_lfht_new - allocate a hash table.
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105 * @hash_fct: the hashing function.
106 * @compare_fct: the key comparison function.
107 * @hash_seed: the seed for hash function.
108 * @init_size: number of nodes to allocate initially. Must be power of two.
109 * @flags: hash table creation flags (can be combined with bitwise or: '|').
110 * 0: no flags.
111 * CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
b7d619b0 112 * @attr: optional resize worker thread attributes. NULL for default.
7a9dcf9b 113 *
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114 * Return NULL on error.
115 * Note: the RCU flavor must be already included before the hash table header.
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116 *
117 * The programmer is responsible for ensuring that resize operation has a
118 * priority equal to hash table updater threads. It should be performed by
119 * specifying the appropriate priority in the pthread "attr" argument, and,
120 * for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
121 * this priority level. Having lower priority for call_rcu and resize threads
122 * does not pose any correctness issue, but the resize operations could be
123 * starved by updates, thus leading to long hash table bucket chains.
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124 */
125static inline
126struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_fct,
127 cds_lfht_compare_fct compare_fct,
128 unsigned long hash_seed,
129 unsigned long init_size,
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130 int flags,
131 pthread_attr_t *attr)
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132{
133 return _cds_lfht_new(hash_fct, compare_fct, hash_seed,
134 init_size, flags,
135 call_rcu, synchronize_rcu, rcu_read_lock,
136 rcu_read_unlock, rcu_thread_offline,
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137 rcu_thread_online, rcu_register_thread,
138 rcu_unregister_thread, attr);
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139}
140
f0c29ed7 141/*
14044b37 142 * cds_lfht_destroy - destroy a hash table.
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143 * @ht: the hash table to destroy.
144 * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
145 * The caller will typically want to free this pointer if dynamically
146 * allocated.
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147 *
148 * Return 0 on success, negative error value on error.
f0c29ed7 149 */
b7d619b0 150int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
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151
152/*
14044b37 153 * cds_lfht_count_nodes - count the number of nodes in the hash table.
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154 *
155 * Call with rcu_read_lock held.
156 */
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157void cds_lfht_count_nodes(struct cds_lfht *ht,
158 unsigned long *count,
159 unsigned long *removed);
ab7d5fc6 160
f0c29ed7 161/*
14044b37 162 * cds_lfht_lookup - lookup a node by key.
f0c29ed7 163 *
6878c72b 164 * Return NULL if not found.
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165 * Call with rcu_read_lock held.
166 */
14044b37 167struct cds_lfht_node *cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len);
ab7d5fc6 168
f0c29ed7 169/*
14044b37 170 * cds_lfht_next - get the next item with same key (after a lookup).
f0c29ed7 171 *
6878c72b 172 * Return NULL if no following node exists with same key.
14044b37 173 * RCU read-side lock must be held across cds_lfht_lookup and cds_lfht_next calls, and also
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174 * between cds_lfht_next calls using the node returned by a previous
175 * cds_lfht_next. Call with rcu_read_lock held.
f0c29ed7 176 */
14044b37 177struct cds_lfht_node *cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_node *node);
ab7d5fc6 178
18117871 179/*
14044b37 180 * cds_lfht_add - add a node to the hash table.
f0c29ed7 181 *
18117871 182 * Call with rcu_read_lock held.
48ed1c18 183 * This function supports adding redundant keys into the table.
f0c29ed7 184 */
14044b37 185void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node);
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186
187/*
14044b37 188 * cds_lfht_add_unique - add a node to hash table, if key is not present.
f0c29ed7 189 *
6878c72b 190 * Return the node added upon success.
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191 * Return the unique node already present upon failure. If
192 * cds_lfht_add_unique fails, the node passed as parameter should be
193 * freed by the caller.
f0c29ed7 194 * Call with rcu_read_lock held.
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195 *
196 * The semantic of this function is that if only this function is used
197 * to add keys into the table, no duplicated keys should ever be
198 * observable in the table. The same guarantee apply for combination of
199 * add_unique and replace (see below).
18117871 200 */
14044b37 201struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht, struct cds_lfht_node *node);
3eca1b8c 202
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203/*
204 * cds_lfht_replace - replace a node within hash table.
205 *
206 * Return the node replaced upon success. If no node matching the key
207 * was present, return NULL, which also means the operation succeeded.
208 * This replacement operation should never fail.
209 * Call with rcu_read_lock held.
210 * After successful replacement, a grace period must be waited for before
211 * freeing the memory reserved for the returned node.
212 *
213 * The semantic of replacement vs lookups is the following: if lookups
214 * are performed between a key insertion and its removal, we guarantee
215 * that the lookups will always find the key if it is replaced
216 * concurrently with the lookups. Providing this guarantee require us to
217 * pin the node to remove in place (disallowing any insertion after this
218 * node temporarily) before we can proceed to its exchange with the new
219 * node atomically. This renders the "replace" operation not strictly
220 * lock-free, because a thread crashing in the middle of the replace
221 * operation could stop progress for other updaters.
222 *
223 * Providing this semantic allows us to ensure that replacement-only
224 * schemes will never generate duplicated keys. It also allows us to
225 * guarantee that a combination of replacement and add_unique updates
226 * will never generate duplicated keys.
227 */
228struct cds_lfht_node *cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_node *node);
229
f0c29ed7 230/*
860d07e8 231 * cds_lfht_del - remove node from hash table.
f0c29ed7 232 *
48ed1c18 233 * Return 0 if the node is successfully removed.
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234 * Node can be looked up with cds_lfht_lookup. RCU read-side lock must
235 * be held between lookup and removal.
f0c29ed7 236 * Call with rcu_read_lock held.
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237 * After successful removal, a grace period must be waited for before
238 * freeing the memory reserved for node.
f0c29ed7 239 */
860d07e8 240int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node);
ab7d5fc6 241
f0c29ed7 242/*
14044b37 243 * cds_lfht_resize - Force a hash table resize
1475579c 244 * @new_size: update to this hash table size.
f0c29ed7 245 */
1475579c 246void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);
464a1ec9 247
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248#ifdef __cplusplus
249}
250#endif
251
a42cc659 252#endif /* _URCU_RCULFHASH_H */
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