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>
37 * cds_lfht_node: Contains the next pointers and reverse-hash
38 * value required for lookup and traversal of the hash table.
40 * struct cds_lfht_node should be aligned on 4-bytes boundaries because
41 * the two lower bits are used as flags.
43 * struct cds_lfht_node can be embedded into a structure (as a field).
44 * caa_container_of() can be used to get the structure from the struct
45 * cds_lfht_node after a lookup.
47 * The structure which embeds it typically holds the key (or key-value
48 * pair) of the object. The caller code is responsible for calculation
49 * of the hash value for cds_lfht APIs.
51 struct cds_lfht_node
{
52 struct cds_lfht_node
*next
; /* ptr | DUMMY_FLAG | REMOVED_FLAG */
53 unsigned long reverse_hash
;
54 } __attribute__((aligned(4)));
56 /* cds_lfht_iter: Used to track state while traversing a hash chain. */
57 struct cds_lfht_iter
{
58 struct cds_lfht_node
*node
, *next
;
62 struct cds_lfht_node
*cds_lfht_iter_get_node(struct cds_lfht_iter
*iter
)
71 * Ensure reader and writer threads are registered as urcu readers.
74 typedef unsigned long (*cds_lfht_hash_fct
)(void *key
, size_t length
,
76 typedef int (*cds_lfht_match_fct
)(struct cds_lfht_node
*node
, void *key
);
79 * cds_lfht_node_init - initialize a hash table node
80 * @node: the node to initialize.
82 * This function is kept to be eventually used for debugging purposes
83 * (detection of memory corruption).
86 void cds_lfht_node_init(struct cds_lfht_node
*node
)
91 * Hash table creation flags.
94 CDS_LFHT_AUTO_RESIZE
= (1U << 0),
95 CDS_LFHT_ACCOUNTING
= (1U << 1),
99 * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
101 struct cds_lfht
*_cds_lfht_new(unsigned long init_size
,
102 unsigned long min_alloc_size
,
104 void (*cds_lfht_call_rcu
)(struct rcu_head
*head
,
105 void (*func
)(struct rcu_head
*head
)),
106 void (*cds_lfht_synchronize_rcu
)(void),
107 void (*cds_lfht_rcu_read_lock
)(void),
108 void (*cds_lfht_rcu_read_unlock
)(void),
109 void (*cds_lfht_rcu_thread_offline
)(void),
110 void (*cds_lfht_rcu_thread_online
)(void),
111 void (*cds_lfht_rcu_register_thread
)(void),
112 void (*cds_lfht_rcu_unregister_thread
)(void),
113 pthread_attr_t
*attr
);
116 * cds_lfht_new - allocate a hash table.
117 * @init_size: number of nodes to allocate initially. Must be power of two.
118 * @min_alloc_size: the smallest allocation size to use. 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.
134 * Threads calling this API need to be registered RCU read-side threads.
137 struct cds_lfht
*cds_lfht_new(unsigned long init_size
,
138 unsigned long min_alloc_size
,
140 pthread_attr_t
*attr
)
142 return _cds_lfht_new(init_size
, min_alloc_size
, flags
,
143 call_rcu
, synchronize_rcu
, rcu_read_lock
,
144 rcu_read_unlock
, rcu_thread_offline
,
145 rcu_thread_online
, rcu_register_thread
,
146 rcu_unregister_thread
, attr
);
150 * cds_lfht_destroy - destroy a hash table.
151 * @ht: the hash table to destroy.
152 * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
153 * The caller will typically want to free this pointer if dynamically
154 * allocated. The attr point can be NULL if the caller does not
155 * need to be informed of the value passed to cds_lfht_new().
157 * Return 0 on success, negative error value on error.
158 * Threads calling this API need to be registered RCU read-side threads.
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.
164 * @ht: the hash table.
165 * @split_count_before: Sample the node count split-counter before traversal.
166 * @count: Traverse the hash table, count the number of nodes observed.
167 * @removed: Number of logically removed nodes observed during traversal.
168 * @split_count_after: Sample the node count split-counter after traversal.
170 * Call with rcu_read_lock held.
171 * Threads calling this API need to be registered RCU read-side threads.
173 void cds_lfht_count_nodes(struct cds_lfht
*ht
,
174 long *split_count_before
,
175 unsigned long *count
,
176 unsigned long *removed
,
177 long *split_count_after
);
180 * cds_lfht_lookup - lookup a node by key.
181 * @ht: the hash table.
182 * @match: the key match function.
183 * @hash: the key hash.
184 * @iter: Node, if found (output). *iter->node set to NULL if not found.
186 * Call with rcu_read_lock held.
187 * Threads calling this API need to be registered RCU read-side threads.
189 void cds_lfht_lookup(struct cds_lfht
*ht
, cds_lfht_match_fct match
,
190 unsigned long hash
, void *key
, struct cds_lfht_iter
*iter
);
193 * cds_lfht_next_duplicate - get the next item with same key (after a lookup).
194 * @ht: the hash table.
195 * @match: the key match function.
196 * @key: the current node key.
197 * @iter: Node, if found (output). *iter->node set to NULL if not found.
199 * Uses an iterator initialized by a lookup.
200 * Sets *iter-node to the following node with same key.
201 * Sets *iter->node to NULL if no following node exists with same key.
202 * RCU read-side lock must be held across cds_lfht_lookup and
203 * cds_lfht_next calls, and also between cds_lfht_next calls using the
204 * node returned by a previous cds_lfht_next.
205 * Call with rcu_read_lock held.
206 * Threads calling this API need to be registered RCU read-side threads.
208 void cds_lfht_next_duplicate(struct cds_lfht
*ht
,
209 cds_lfht_match_fct match
, void *key
,
210 struct cds_lfht_iter
*iter
);
213 * cds_lfht_first - get the first node in the table.
214 * @ht: the hash table.
215 * @iter: First node, if exists (output). *iter->node set to NULL if not found.
217 * Output in "*iter". *iter->node set to NULL if table is empty.
218 * Call with rcu_read_lock held.
219 * Threads calling this API need to be registered RCU read-side threads.
221 void cds_lfht_first(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
224 * cds_lfht_next - get the next node in the table.
225 * @ht: the hash table.
226 * @iter: Next node, if exists (output). *iter->node set to NULL if not found.
228 * Input/Output in "*iter". *iter->node set to NULL if *iter was
229 * pointing to the last table node.
230 * Call with rcu_read_lock held.
231 * Threads calling this API need to be registered RCU read-side threads.
233 void cds_lfht_next(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
236 * cds_lfht_add - add a node to the hash table.
237 * @ht: the hash table.
238 * @hash: the key hash.
239 * @node: the node to add.
241 * This function supports adding redundant keys into the table.
242 * Call with rcu_read_lock held.
243 * Threads calling this API need to be registered RCU read-side threads.
245 void cds_lfht_add(struct cds_lfht
*ht
, unsigned long hash
,
246 struct cds_lfht_node
*node
);
249 * cds_lfht_add_unique - add a node to hash table, if key is not present.
250 * @ht: the hash table.
251 * @match: the key match function.
252 * @key: the node's key.
253 * @hash: the node's hash.
254 * @node: the node to try adding.
256 * Return the node added upon success.
257 * Return the unique node already present upon failure. If
258 * cds_lfht_add_unique fails, the node passed as parameter should be
259 * freed by the caller.
260 * Call with rcu_read_lock held.
261 * Threads calling this API need to be registered RCU read-side threads.
263 * The semantic of this function is that if only this function is used
264 * to add keys into the table, no duplicated keys should ever be
265 * observable in the table. The same guarantee apply for combination of
266 * add_unique and add_replace (see below).
268 struct cds_lfht_node
*cds_lfht_add_unique(struct cds_lfht
*ht
,
269 cds_lfht_match_fct match
,
272 struct cds_lfht_node
*node
);
275 * cds_lfht_add_replace - replace or add a node within hash table.
276 * @ht: the hash table.
277 * @match: the key match function.
278 * @key: the node's key.
279 * @hash: the node's hash.
280 * @node: the node to add.
282 * Return the node replaced upon success. If no node matching the key
283 * was present, return NULL, which also means the operation succeeded.
284 * This replacement operation should never fail.
285 * Call with rcu_read_lock held.
286 * Threads calling this API need to be registered RCU read-side threads.
287 * After successful replacement, a grace period must be waited for before
288 * freeing the memory reserved for the returned node.
290 * The semantic of replacement vs lookups is the following: if lookups
291 * are performed between a key unique insertion and its removal, we
292 * guarantee that the lookups and get next will always find exactly one
293 * instance of the key if it is replaced concurrently with the lookups.
295 * Providing this semantic allows us to ensure that replacement-only
296 * schemes will never generate duplicated keys. It also allows us to
297 * guarantee that a combination of add_replace and add_unique updates
298 * will never generate duplicated keys.
300 struct cds_lfht_node
*cds_lfht_add_replace(struct cds_lfht
*ht
,
301 cds_lfht_match_fct match
,
304 struct cds_lfht_node
*node
);
307 * cds_lfht_replace - replace a node pointer to by iter within hash table.
308 * @ht: the hash table.
309 * @old_iter: the iterator position of the node to replace.
310 * @now_node: the new node to try using for replacement.
312 * Return 0 if replacement is successful, negative value otherwise.
313 * Replacing a NULL old node or an already removed node will fail with a
315 * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
316 * RCU read-side lock must be held between lookup and replacement.
317 * Call with rcu_read_lock held.
318 * Threads calling this API need to be registered RCU read-side threads.
319 * After successful replacement, a grace period must be waited for before
320 * freeing the memory reserved for the old node (which can be accessed
321 * with cds_lfht_iter_get_node).
323 * The semantic of replacement vs lookups is the following: if lookups
324 * are performed between a key unique insertion and its removal, we
325 * guarantee that the lookups and get next will always find exactly one
326 * instance of the key if it is replaced concurrently with the lookups.
328 * Providing this semantic allows us to ensure that replacement-only
329 * schemes will never generate duplicated keys. It also allows us to
330 * guarantee that a combination of add_replace and add_unique updates
331 * will never generate duplicated keys.
333 int cds_lfht_replace(struct cds_lfht
*ht
, struct cds_lfht_iter
*old_iter
,
334 struct cds_lfht_node
*new_node
);
337 * cds_lfht_del - remove node pointed to by iterator from hash table.
338 * @ht: the hash table.
339 * @iter: the iterator position of the node to delete.
341 * Return 0 if the node is successfully removed, negative value
343 * Replacing a NULL node or an already removed node will fail with a
345 * Node can be looked up with cds_lfht_lookup and cds_lfht_next.
346 * cds_lfht_iter_get_node.
347 * RCU read-side lock must be held between lookup and removal.
348 * Call with rcu_read_lock held.
349 * Threads calling this API need to be registered RCU read-side threads.
350 * After successful removal, a grace period must be waited for before
351 * freeing the memory reserved for old node (which can be accessed with
352 * cds_lfht_iter_get_node).
354 int cds_lfht_del(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
357 * cds_lfht_resize - Force a hash table resize
358 * @ht: the hash table.
359 * @new_size: update to this hash table size.
361 * Threads calling this API need to be registered RCU read-side threads.
363 void cds_lfht_resize(struct cds_lfht
*ht
, unsigned long new_size
);
369 #endif /* _URCU_RCULFHASH_H */