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[lttng-tools.git] / hashtable / rculfhash.h
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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
32extern "C" {
33#endif
34
35/*
36 * struct cds_lfht_node and struct _cds_lfht_node should be aligned on
37 * 4-bytes boundaries because the two lower bits are used as flags.
38 */
39
40struct _cds_lfht_node {
41 struct cds_lfht_node *next; /* ptr | DUMMY_FLAG | REMOVED_FLAG */
42 unsigned long reverse_hash;
43} __attribute__((aligned(4)));
44
45struct 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
54struct cds_lfht_iter {
55 struct cds_lfht_node *node, *next;
56};
57
58static inline
59struct cds_lfht_node *cds_lfht_iter_get_node(struct cds_lfht_iter *iter)
60{
61 return iter->node;
62}
63
64struct cds_lfht;
65
66/*
67 * Caution !
68 * Ensure reader and writer threads are registered as urcu readers.
69 */
70
71typedef unsigned long (*cds_lfht_hash_fct)(void *key, size_t length,
72 unsigned long seed);
73typedef 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 */
79static inline
80void 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 */
90enum {
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 */
97struct 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 */
135static inline
136struct 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 */
160int 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 */
167void cds_lfht_count_nodes(struct cds_lfht *ht,
168 long *approx_before,
169 unsigned long *count,
170 unsigned long *removed,
171 long *approx_after);
172
173/*
174 * cds_lfht_lookup - lookup a node by key.
175 *
176 * Output in "*iter". *iter->node set to NULL if not found.
177 * Call with rcu_read_lock held.
178 */
179void cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len,
180 struct cds_lfht_iter *iter);
181
182/*
183 * cds_lfht_next - get the next item with same key (after a lookup).
184 *
185 * Uses an iterator initialized by a lookup.
186 * Sets *iter-node to the following node with same key.
187 * Sets *iter->node to NULL if no following node exists with same key.
188 * RCU read-side lock must be held across cds_lfht_lookup and
189 * cds_lfht_next calls, and also between cds_lfht_next calls using the
190 * node returned by a previous cds_lfht_next.
191 * Call with rcu_read_lock held.
192 */
193void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter);
194
195/*
196 * cds_lfht_add - add a node to the hash table.
197 *
198 * Call with rcu_read_lock held.
199 * This function supports adding redundant keys into the table.
200 */
201void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node);
202
203/*
204 * cds_lfht_add_unique - add a node to hash table, if key is not present.
205 *
206 * Return the node added upon success.
207 * Return the unique node already present upon failure. If
208 * cds_lfht_add_unique fails, the node passed as parameter should be
209 * freed by the caller.
210 * Call with rcu_read_lock held.
211 *
212 * The semantic of this function is that if only this function is used
213 * to add keys into the table, no duplicated keys should ever be
214 * observable in the table. The same guarantee apply for combination of
215 * add_unique and add_replace (see below).
216 */
217struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
218 struct cds_lfht_node *node);
219
220/*
221 * cds_lfht_add_replace - replace or add a node within hash table.
222 *
223 * Return the node replaced upon success. If no node matching the key
224 * was present, return NULL, which also means the operation succeeded.
225 * This replacement operation should never fail.
226 * Call with rcu_read_lock held.
227 * After successful replacement, a grace period must be waited for before
228 * freeing the memory reserved for the returned node.
229 *
230 * The semantic of replacement vs lookups is the following: if lookups
231 * are performed between a key unique insertion and its removal, we
232 * guarantee that the lookups and get next will always find exactly one
233 * instance of the key if it is replaced concurrently with the lookups.
234 *
235 * Providing this semantic allows us to ensure that replacement-only
236 * schemes will never generate duplicated keys. It also allows us to
237 * guarantee that a combination of add_replace and add_unique updates
238 * will never generate duplicated keys.
239 */
240struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
241 struct cds_lfht_node *node);
242
243/*
244 * cds_lfht_replace - replace a node pointer to by iter within hash table.
245 *
246 * Return 0 if replacement is successful, negative value otherwise.
247 * Replacing a NULL old node or an already removed node will fail with a
248 * negative value.
249 * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
250 * RCU read-side lock must be held between lookup and replacement.
251 * Call with rcu_read_lock held.
252 * After successful replacement, a grace period must be waited for before
253 * freeing the memory reserved for the old node (which can be accessed
254 * with cds_lfht_iter_get_node).
255 *
256 * The semantic of replacement vs lookups is the following: if lookups
257 * are performed between a key unique insertion and its removal, we
258 * guarantee that the lookups and get next will always find exactly one
259 * instance of the key if it is replaced concurrently with the lookups.
260 *
261 * Providing this semantic allows us to ensure that replacement-only
262 * schemes will never generate duplicated keys. It also allows us to
263 * guarantee that a combination of add_replace and add_unique updates
264 * will never generate duplicated keys.
265 */
266int cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_iter *old_iter,
267 struct cds_lfht_node *new_node);
268
269/*
270 * cds_lfht_del - remove node pointed to by iterator from hash table.
271 *
272 * Return 0 if the node is successfully removed, negative value
273 * otherwise.
274 * Replacing a NULL node or an already removed node will fail with a
275 * negative value.
276 * Node can be looked up with cds_lfht_lookup and cds_lfht_next.
277 * cds_lfht_iter_get_node.
278 * RCU read-side lock must be held between lookup and removal.
279 * Call with rcu_read_lock held.
280 * After successful removal, a grace period must be waited for before
281 * freeing the memory reserved for old node (which can be accessed with
282 * cds_lfht_iter_get_node).
283 */
284int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_iter *iter);
285
286/*
287 * cds_lfht_resize - Force a hash table resize
288 * @new_size: update to this hash table size.
289 */
290void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);
291
292#ifdef __cplusplus
293}
294#endif
295
296#endif /* _URCU_RCULFHASH_H */
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