Import hashtable files from URCU upstream git
[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
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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 */
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50struct cds_lfht_node {
51 /* cache-hot for iteration */
52 struct _cds_lfht_node p; /* needs to be first field */
53 void *key;
54 unsigned int key_len;
55 /* cache-cold for iteration */
56 struct rcu_head head;
57};
58
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
69struct cds_lfht;
70
71/*
72 * Caution !
73 * Ensure reader and writer threads are registered as urcu readers.
74 */
75
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);
80
81/*
82 * cds_lfht_node_init - initialize a hash table node
83 */
84static inline
85void cds_lfht_node_init(struct cds_lfht_node *node, void *key,
86 size_t key_len)
87{
88 node->key = key;
89 node->key_len = key_len;
90}
91
92/*
93 * Hash table creation flags.
94 */
95enum {
96 CDS_LFHT_AUTO_RESIZE = (1U << 0),
97};
98
99/*
100 * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
101 */
102struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
103 cds_lfht_compare_fct compare_fct,
104 unsigned long hash_seed,
105 unsigned long init_size,
106 int flags,
107 void (*cds_lfht_call_rcu)(struct rcu_head *head,
108 void (*func)(struct rcu_head *head)),
109 void (*cds_lfht_synchronize_rcu)(void),
110 void (*cds_lfht_rcu_read_lock)(void),
111 void (*cds_lfht_rcu_read_unlock)(void),
112 void (*cds_lfht_rcu_thread_offline)(void),
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);
117
118/*
119 * cds_lfht_new - allocate a hash table.
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.
127 * @attr: optional resize worker thread attributes. NULL for default.
128 *
129 * Return NULL on error.
130 * Note: the RCU flavor must be already included before the hash table header.
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.
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,
145 int flags,
146 pthread_attr_t *attr)
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,
152 rcu_thread_online, rcu_register_thread,
153 rcu_unregister_thread, attr);
154}
155
156/*
157 * cds_lfht_destroy - destroy a hash table.
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.
162 *
163 * Return 0 on success, negative error value on error.
164 */
165int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
166
167/*
168 * cds_lfht_count_nodes - count the number of nodes in the hash table.
169 *
170 * Call with rcu_read_lock held.
171 */
172void cds_lfht_count_nodes(struct cds_lfht *ht,
173 long *approx_before,
174 unsigned long *count,
175 unsigned long *removed,
176 long *approx_after);
177
178/*
179 * cds_lfht_lookup - lookup a node by key.
180 *
181 * Output in "*iter". *iter->node set to NULL if not found.
182 * Call with rcu_read_lock held.
183 */
184void cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len,
185 struct cds_lfht_iter *iter);
186
187/*
f6a9efaa 188 * cds_lfht_next_duplicate - get the next item with same key (after a lookup).
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189 *
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.
197 */
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198void cds_lfht_next_duplicate(struct cds_lfht *ht, struct cds_lfht_iter *iter);
199
200/*
201 * cds_lfht_first - get the first node in the table.
202 *
203 * Output in "*iter". *iter->node set to NULL if table is empty.
204 * Call with rcu_read_lock held.
205 */
206void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter);
207
208/*
209 * cds_lfht_next - get the next node in the table.
210 *
211 * Input/Output in "*iter". *iter->node set to NULL if *iter was
212 * pointing to the last table node.
213 * Call with rcu_read_lock held.
214 */
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215void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter);
216
217/*
218 * cds_lfht_add - add a node to the hash table.
219 *
220 * Call with rcu_read_lock held.
221 * This function supports adding redundant keys into the table.
222 */
223void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node);
224
225/*
226 * cds_lfht_add_unique - add a node to hash table, if key is not present.
227 *
228 * Return the node added upon success.
229 * Return the unique node already present upon failure. If
230 * cds_lfht_add_unique fails, the node passed as parameter should be
231 * freed by the caller.
232 * Call with rcu_read_lock held.
233 *
234 * The semantic of this function is that if only this function is used
235 * to add keys into the table, no duplicated keys should ever be
236 * observable in the table. The same guarantee apply for combination of
237 * add_unique and add_replace (see below).
238 */
239struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
240 struct cds_lfht_node *node);
241
242/*
243 * cds_lfht_add_replace - replace or add a node within hash table.
244 *
245 * Return the node replaced upon success. If no node matching the key
246 * was present, return NULL, which also means the operation succeeded.
247 * This replacement operation should never fail.
248 * Call with rcu_read_lock held.
249 * After successful replacement, a grace period must be waited for before
250 * freeing the memory reserved for the returned node.
251 *
252 * The semantic of replacement vs lookups is the following: if lookups
253 * are performed between a key unique insertion and its removal, we
254 * guarantee that the lookups and get next will always find exactly one
255 * instance of the key if it is replaced concurrently with the lookups.
256 *
257 * Providing this semantic allows us to ensure that replacement-only
258 * schemes will never generate duplicated keys. It also allows us to
259 * guarantee that a combination of add_replace and add_unique updates
260 * will never generate duplicated keys.
261 */
262struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
263 struct cds_lfht_node *node);
264
265/*
266 * cds_lfht_replace - replace a node pointer to by iter within hash table.
267 *
268 * Return 0 if replacement is successful, negative value otherwise.
269 * Replacing a NULL old node or an already removed node will fail with a
270 * negative value.
271 * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
272 * RCU read-side lock must be held between lookup and replacement.
273 * Call with rcu_read_lock held.
274 * After successful replacement, a grace period must be waited for before
275 * freeing the memory reserved for the old node (which can be accessed
276 * with cds_lfht_iter_get_node).
277 *
278 * The semantic of replacement vs lookups is the following: if lookups
279 * are performed between a key unique insertion and its removal, we
280 * guarantee that the lookups and get next will always find exactly one
281 * instance of the key if it is replaced concurrently with the lookups.
282 *
283 * Providing this semantic allows us to ensure that replacement-only
284 * schemes will never generate duplicated keys. It also allows us to
285 * guarantee that a combination of add_replace and add_unique updates
286 * will never generate duplicated keys.
287 */
288int cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_iter *old_iter,
289 struct cds_lfht_node *new_node);
290
291/*
292 * cds_lfht_del - remove node pointed to by iterator from hash table.
293 *
294 * Return 0 if the node is successfully removed, negative value
295 * otherwise.
296 * Replacing a NULL node or an already removed node will fail with a
297 * negative value.
298 * Node can be looked up with cds_lfht_lookup and cds_lfht_next.
299 * cds_lfht_iter_get_node.
300 * RCU read-side lock must be held between lookup and removal.
301 * Call with rcu_read_lock held.
302 * After successful removal, a grace period must be waited for before
303 * freeing the memory reserved for old node (which can be accessed with
304 * cds_lfht_iter_get_node).
305 */
306int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_iter *iter);
307
308/*
309 * cds_lfht_resize - Force a hash table resize
310 * @new_size: update to this hash table size.
311 */
312void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);
313
314#ifdef __cplusplus
315}
316#endif
317
318#endif /* _URCU_RCULFHASH_H */
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