c3c1cbc2b797afbbc022f1bedbc146abd7cdb61e
[urcu.git] / urcu / rculfhash.h
1 #ifndef _URCU_RCULFHASH_H
2 #define _URCU_RCULFHASH_H
3
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
24 *
25 * Include this file _after_ including your URCU flavor.
26 */
27
28 #include <stdint.h>
29 #include <urcu-call-rcu.h>
30
31 #ifdef __cplusplus
32 extern "C" {
33 #endif
34
35 /*
36 * struct cds_lfht_node and struct _cds_lfht_node should be aligned on
37 * 8-bytes boundaries because the two lower bits are used as flags.
38 */
39
40 struct _cds_lfht_node {
41 struct cds_lfht_node *next; /* ptr | DUMMY_FLAG | GC_FLAG | REMOVED_FLAG */
42 unsigned long reverse_hash;
43 } __attribute__((aligned(8)));
44
45 struct cds_lfht_node {
46 /* cache-hot for iteration */
47 struct _cds_lfht_node p; /* needs to be first field */
48 void *key;
49 unsigned int key_len;
50 /* cache-cold for iteration */
51 struct rcu_head head;
52 };
53
54 struct cds_lfht_iter {
55 struct cds_lfht_node *node, *next;
56 };
57
58 static inline
59 struct cds_lfht_node *cds_lfht_iter_get_node(struct cds_lfht_iter *iter)
60 {
61 return iter->node;
62 }
63
64 struct cds_lfht;
65
66 /*
67 * Caution !
68 * Ensure reader and writer threads are registered as urcu readers.
69 */
70
71 typedef unsigned long (*cds_lfht_hash_fct)(void *key, size_t length,
72 unsigned long seed);
73 typedef unsigned long (*cds_lfht_compare_fct)(void *key1, size_t key1_len,
74 void *key2, size_t key2_len);
75
76 /*
77 * cds_lfht_node_init - initialize a hash table node
78 */
79 static inline
80 void cds_lfht_node_init(struct cds_lfht_node *node, void *key,
81 size_t key_len)
82 {
83 node->key = key;
84 node->key_len = key_len;
85 }
86
87 /*
88 * Hash table creation flags.
89 */
90 enum {
91 CDS_LFHT_AUTO_RESIZE = (1U << 0),
92 };
93
94 /*
95 * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
96 */
97 struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
98 cds_lfht_compare_fct compare_fct,
99 unsigned long hash_seed,
100 unsigned long init_size,
101 int flags,
102 void (*cds_lfht_call_rcu)(struct rcu_head *head,
103 void (*func)(struct rcu_head *head)),
104 void (*cds_lfht_synchronize_rcu)(void),
105 void (*cds_lfht_rcu_read_lock)(void),
106 void (*cds_lfht_rcu_read_unlock)(void),
107 void (*cds_lfht_rcu_thread_offline)(void),
108 void (*cds_lfht_rcu_thread_online)(void),
109 void (*cds_lfht_rcu_register_thread)(void),
110 void (*cds_lfht_rcu_unregister_thread)(void),
111 pthread_attr_t *attr);
112
113 /*
114 * cds_lfht_new - allocate a hash table.
115 * @hash_fct: the hashing function.
116 * @compare_fct: the key comparison function.
117 * @hash_seed: the seed for hash function.
118 * @init_size: number of nodes to allocate initially. Must be power of two.
119 * @flags: hash table creation flags (can be combined with bitwise or: '|').
120 * 0: no flags.
121 * CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
122 * @attr: optional resize worker thread attributes. NULL for default.
123 *
124 * Return NULL on error.
125 * Note: the RCU flavor must be already included before the hash table header.
126 *
127 * The programmer is responsible for ensuring that resize operation has a
128 * priority equal to hash table updater threads. It should be performed by
129 * specifying the appropriate priority in the pthread "attr" argument, and,
130 * for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
131 * this priority level. Having lower priority for call_rcu and resize threads
132 * does not pose any correctness issue, but the resize operations could be
133 * starved by updates, thus leading to long hash table bucket chains.
134 */
135 static inline
136 struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_fct,
137 cds_lfht_compare_fct compare_fct,
138 unsigned long hash_seed,
139 unsigned long init_size,
140 int flags,
141 pthread_attr_t *attr)
142 {
143 return _cds_lfht_new(hash_fct, compare_fct, hash_seed,
144 init_size, flags,
145 call_rcu, synchronize_rcu, rcu_read_lock,
146 rcu_read_unlock, rcu_thread_offline,
147 rcu_thread_online, rcu_register_thread,
148 rcu_unregister_thread, attr);
149 }
150
151 /*
152 * cds_lfht_destroy - destroy a hash table.
153 * @ht: the hash table to destroy.
154 * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
155 * The caller will typically want to free this pointer if dynamically
156 * allocated.
157 *
158 * Return 0 on success, negative error value on error.
159 */
160 int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
161
162 /*
163 * cds_lfht_count_nodes - count the number of nodes in the hash table.
164 *
165 * Call with rcu_read_lock held.
166 */
167 void cds_lfht_count_nodes(struct cds_lfht *ht,
168 unsigned long *count,
169 unsigned long *removed);
170
171 /*
172 * cds_lfht_lookup - lookup a node by key.
173 *
174 * Output in "*iter". *iter->node set to NULL if not found.
175 * Call with rcu_read_lock held.
176 */
177 void cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len,
178 struct cds_lfht_iter *iter);
179
180 /*
181 * cds_lfht_next - get the next item with same key (after a lookup).
182 *
183 * Uses an iterator initialized by a lookup.
184 * Sets *iter-node to the following node with same key.
185 * Sets *iter->node to NULL if no following node exists with same key.
186 * RCU read-side lock must be held across cds_lfht_lookup and
187 * cds_lfht_next calls, and also between cds_lfht_next calls using the
188 * node returned by a previous cds_lfht_next.
189 * Call with rcu_read_lock held.
190 */
191 void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter);
192
193 /*
194 * cds_lfht_add - add a node to the hash table.
195 *
196 * Call with rcu_read_lock held.
197 * This function supports adding redundant keys into the table.
198 */
199 void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node);
200
201 /*
202 * cds_lfht_add_unique - add a node to hash table, if key is not present.
203 *
204 * Return the node added upon success.
205 * Return the unique node already present upon failure. If
206 * cds_lfht_add_unique fails, the node passed as parameter should be
207 * freed by the caller.
208 * Call with rcu_read_lock held.
209 *
210 * The semantic of this function is that if only this function is used
211 * to add keys into the table, no duplicated keys should ever be
212 * observable in the table. The same guarantee apply for combination of
213 * add_unique and replace (see below).
214 */
215 struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
216 struct cds_lfht_node *node);
217
218 /*
219 * cds_lfht_replace - replace a node within hash table.
220 *
221 * Return the node replaced upon success. If no node matching the key
222 * was present, return NULL, which also means the operation succeeded.
223 * This replacement operation should never fail.
224 * Call with rcu_read_lock held.
225 * After successful replacement, a grace period must be waited for before
226 * freeing the memory reserved for the returned node.
227 *
228 * The semantic of replacement vs lookups is the following: if lookups
229 * are performed between a key insertion and its removal, we guarantee
230 * that the lookups will always find the key if it is replaced
231 * concurrently with the lookups.
232 *
233 * Providing this semantic allows us to ensure that replacement-only
234 * schemes will never generate duplicated keys. It also allows us to
235 * guarantee that a combination of replacement and add_unique updates
236 * will never generate duplicated keys.
237 */
238 struct cds_lfht_node *cds_lfht_replace(struct cds_lfht *ht,
239 struct cds_lfht_node *node);
240
241 /*
242 * cds_lfht_del - remove node from hash table.
243 *
244 * Return 0 if the node is successfully removed.
245 * Node can be looked up with cds_lfht_lookup. RCU read-side lock must
246 * be held between lookup and removal.
247 * Call with rcu_read_lock held.
248 * After successful removal, a grace period must be waited for before
249 * freeing the memory reserved for node.
250 */
251 int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node);
252
253 /*
254 * cds_lfht_resize - Force a hash table resize
255 * @new_size: update to this hash table size.
256 */
257 void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);
258
259 #ifdef __cplusplus
260 }
261 #endif
262
263 #endif /* _URCU_RCULFHASH_H */
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