1 #ifndef _URCU_RCULFHASH_H
2 #define _URCU_RCULFHASH_H
7 * Userspace RCU library - Lock-Free RCU Hash Table
9 * Copyright 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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.
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.
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
25 * Include this file _after_ including your URCU flavor.
29 #include <urcu-call-rcu.h>
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.
40 struct _cds_lfht_node
{
41 struct cds_lfht_node
*next
; /* ptr | DUMMY_FLAG | REMOVED_FLAG */
42 unsigned long reverse_hash
;
43 } __attribute__((aligned(4)));
45 struct cds_lfht_node
{
46 /* cache-hot for iteration */
47 struct _cds_lfht_node p
; /* needs to be first field */
50 /* cache-cold for iteration */
54 struct cds_lfht_iter
{
55 struct cds_lfht_node
*node
, *next
;
59 struct cds_lfht_node
*cds_lfht_iter_get_node(struct cds_lfht_iter
*iter
)
68 * Ensure reader and writer threads are registered as urcu readers.
71 typedef unsigned long (*cds_lfht_hash_fct
)(void *key
, size_t length
,
73 typedef unsigned long (*cds_lfht_compare_fct
)(void *key1
, size_t key1_len
,
74 void *key2
, size_t key2_len
);
77 * cds_lfht_node_init - initialize a hash table node
80 void cds_lfht_node_init(struct cds_lfht_node
*node
, void *key
,
84 node
->key_len
= key_len
;
88 * Hash table creation flags.
91 CDS_LFHT_AUTO_RESIZE
= (1U << 0),
95 * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
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
,
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
);
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: '|').
121 * CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
122 * @attr: optional resize worker thread attributes. NULL for default.
124 * Return NULL on error.
125 * Note: the RCU flavor must be already included before the hash table header.
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.
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
,
141 pthread_attr_t
*attr
)
143 return _cds_lfht_new(hash_fct
, compare_fct
, hash_seed
,
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
);
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
158 * Return 0 on success, negative error value on error.
160 int cds_lfht_destroy(struct cds_lfht
*ht
, pthread_attr_t
**attr
);
163 * cds_lfht_count_nodes - count the number of nodes in the hash table.
165 * Call with rcu_read_lock held.
167 void cds_lfht_count_nodes(struct cds_lfht
*ht
,
169 unsigned long *count
,
170 unsigned long *removed
,
174 * cds_lfht_lookup - lookup a node by key.
176 * Output in "*iter". *iter->node set to NULL if not found.
177 * Call with rcu_read_lock held.
179 void cds_lfht_lookup(struct cds_lfht
*ht
, void *key
, size_t key_len
,
180 struct cds_lfht_iter
*iter
);
183 * cds_lfht_next - get the next item with same key (after a lookup).
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.
193 void cds_lfht_next(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
196 * cds_lfht_add - add a node to the hash table.
198 * Call with rcu_read_lock held.
199 * This function supports adding redundant keys into the table.
201 void cds_lfht_add(struct cds_lfht
*ht
, struct cds_lfht_node
*node
);
204 * cds_lfht_add_unique - add a node to hash table, if key is not present.
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.
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).
217 struct cds_lfht_node
*cds_lfht_add_unique(struct cds_lfht
*ht
,
218 struct cds_lfht_node
*node
);
221 * cds_lfht_add_replace - replace or add a node within hash table.
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.
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.
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.
240 struct cds_lfht_node
*cds_lfht_add_replace(struct cds_lfht
*ht
,
241 struct cds_lfht_node
*node
);
244 * cds_lfht_replace - replace a node pointer to by iter within hash table.
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
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).
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.
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.
266 int cds_lfht_replace(struct cds_lfht
*ht
, struct cds_lfht_iter
*old_iter
,
267 struct cds_lfht_node
*new_node
);
270 * cds_lfht_del - remove node pointed to by iterator from hash table.
272 * Return 0 if the node is successfully removed, negative value
274 * Replacing a NULL node or an already removed node will fail with a
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).
284 int cds_lfht_del(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
287 * cds_lfht_resize - Force a hash table resize
288 * @new_size: update to this hash table size.
290 void cds_lfht_resize(struct cds_lfht
*ht
, unsigned long new_size
);
296 #endif /* _URCU_RCULFHASH_H */