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>
10 * Copyright 2011 - Lai Jiangshan <laijs@cn.fujitsu.com>
12 * This library is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU Lesser General Public
14 * License as published by the Free Software Foundation; either
15 * version 2.1 of the License, or (at your option) any later version.
17 * This library is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
20 * Lesser General Public License for more details.
22 * You should have received a copy of the GNU Lesser General Public
23 * License along with this library; if not, write to the Free Software
24 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
26 * Include this file _after_ including your URCU flavor.
30 #include <urcu/compiler.h>
31 #include <urcu-call-rcu.h>
38 * cds_lfht_node: Contains the next pointers and reverse-hash
39 * value required for lookup and traversal of the hash table.
41 * struct cds_lfht_node should be aligned on 4-bytes boundaries because
42 * the two lower bits are used as flags.
44 * struct cds_lfht_node can be embedded into a structure (as a field).
45 * caa_container_of() can be used to get the structure from the struct
46 * cds_lfht_node after a lookup.
48 * The structure which embeds it typically holds the key (or key-value
49 * pair) of the object. The caller code is responsible for calculation
50 * of the hash value for cds_lfht APIs.
52 struct cds_lfht_node
{
53 struct cds_lfht_node
*next
; /* ptr | BUCKET_FLAG | REMOVED_FLAG */
54 unsigned long reverse_hash
;
55 } __attribute__((aligned(4)));
57 /* cds_lfht_iter: Used to track state while traversing a hash chain. */
58 struct cds_lfht_iter
{
59 struct cds_lfht_node
*node
, *next
;
63 struct cds_lfht_node
*cds_lfht_iter_get_node(struct cds_lfht_iter
*iter
)
72 * Ensure reader and writer threads are registered as urcu readers.
75 typedef int (*cds_lfht_match_fct
)(struct cds_lfht_node
*node
, const void *key
);
78 * cds_lfht_node_init - initialize a hash table node
79 * @node: the node to initialize.
81 * This function is kept to be eventually used for debugging purposes
82 * (detection of memory corruption).
85 void cds_lfht_node_init(struct cds_lfht_node
*node
)
90 * Hash table creation flags.
93 CDS_LFHT_AUTO_RESIZE
= (1U << 0),
94 CDS_LFHT_ACCOUNTING
= (1U << 1),
98 * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
100 struct cds_lfht
*_cds_lfht_new(unsigned long init_size
,
101 unsigned long min_nr_alloc_buckets
,
102 unsigned long max_nr_buckets
,
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 buckets to allocate initially. Must be power of two.
118 * @min_nr_alloc_buckets: the minimum number of allocated buckets.
119 * (must be power of two)
120 * @max_nr_buckets: the maximum number of hash table buckets allowed.
121 * (must be power of two)
122 * @flags: hash table creation flags (can be combined with bitwise or: '|').
124 * CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
125 * CDS_LFHT_ACCOUNTING: count the number of node addition
126 * and removal in the table
127 * @attr: optional resize worker thread attributes. NULL for default.
129 * Return NULL on error.
130 * Note: the RCU flavor must be already included before the hash table header.
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 * Threads calling this API are NOT required to be registered RCU read-side
140 * threads. It can be called very early.(before rcu is initialized ...etc.)
143 struct cds_lfht
*cds_lfht_new(unsigned long init_size
,
144 unsigned long min_nr_alloc_buckets
,
145 unsigned long max_nr_buckets
,
147 pthread_attr_t
*attr
)
149 return _cds_lfht_new(init_size
, min_nr_alloc_buckets
, max_nr_buckets
, 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
);
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. The attr point can be NULL if the caller does not
162 * need to be informed of the value passed to cds_lfht_new().
164 * Return 0 on success, negative error value on error.
165 * Threads calling this API need to be registered RCU read-side threads.
167 int cds_lfht_destroy(struct cds_lfht
*ht
, pthread_attr_t
**attr
);
170 * cds_lfht_count_nodes - count the number of nodes in the hash table.
171 * @ht: the hash table.
172 * @split_count_before: Sample the node count split-counter before traversal.
173 * @count: Traverse the hash table, count the number of nodes observed.
174 * @removed: Number of logically removed nodes observed during traversal.
175 * @split_count_after: Sample the node count split-counter after traversal.
177 * Call with rcu_read_lock held.
178 * Threads calling this API need to be registered RCU read-side threads.
180 void cds_lfht_count_nodes(struct cds_lfht
*ht
,
181 long *split_count_before
,
182 unsigned long *count
,
183 unsigned long *removed
,
184 long *split_count_after
);
187 * cds_lfht_lookup - lookup a node by key.
188 * @ht: the hash table.
189 * @hash: the key hash.
190 * @match: the key match function.
191 * @key: the current node key.
192 * @iter: Node, if found (output). *iter->node set to NULL if not found.
194 * Call with rcu_read_lock held.
195 * Threads calling this API need to be registered RCU read-side threads.
197 void cds_lfht_lookup(struct cds_lfht
*ht
, unsigned long hash
,
198 cds_lfht_match_fct match
, const void *key
,
199 struct cds_lfht_iter
*iter
);
202 * cds_lfht_next_duplicate - get the next item with same key (after a lookup).
203 * @ht: the hash table.
204 * @match: the key match function.
205 * @key: the current node key.
206 * @iter: Node, if found (output). *iter->node set to NULL if not found.
208 * Uses an iterator initialized by a lookup.
209 * Sets *iter-node to the following node with same key.
210 * Sets *iter->node to NULL if no following node exists with same key.
211 * RCU read-side lock must be held across cds_lfht_lookup and
212 * cds_lfht_next calls, and also between cds_lfht_next calls using the
213 * node returned by a previous cds_lfht_next.
214 * Call with rcu_read_lock held.
215 * Threads calling this API need to be registered RCU read-side threads.
217 void cds_lfht_next_duplicate(struct cds_lfht
*ht
,
218 cds_lfht_match_fct match
, const void *key
,
219 struct cds_lfht_iter
*iter
);
222 * cds_lfht_first - get the first node in the table.
223 * @ht: the hash table.
224 * @iter: First node, if exists (output). *iter->node set to NULL if not found.
226 * Output in "*iter". *iter->node set to NULL if table is empty.
227 * Call with rcu_read_lock held.
228 * Threads calling this API need to be registered RCU read-side threads.
230 void cds_lfht_first(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
233 * cds_lfht_next - get the next node in the table.
234 * @ht: the hash table.
235 * @iter: Next node, if exists (output). *iter->node set to NULL if not found.
237 * Input/Output in "*iter". *iter->node set to NULL if *iter was
238 * pointing to the last table node.
239 * Call with rcu_read_lock held.
240 * Threads calling this API need to be registered RCU read-side threads.
242 void cds_lfht_next(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
245 * cds_lfht_add - add a node to the hash table.
246 * @ht: the hash table.
247 * @hash: the key hash.
248 * @node: the node to add.
250 * This function supports adding redundant keys into the table.
251 * Call with rcu_read_lock held.
252 * Threads calling this API need to be registered RCU read-side threads.
254 void cds_lfht_add(struct cds_lfht
*ht
, unsigned long hash
,
255 struct cds_lfht_node
*node
);
258 * cds_lfht_add_unique - add a node to hash table, if key is not present.
259 * @ht: the hash table.
260 * @hash: the node's hash.
261 * @match: the key match function.
262 * @key: the node's key.
263 * @node: the node to try adding.
265 * Return the node added upon success.
266 * Return the unique node already present upon failure. If
267 * cds_lfht_add_unique fails, the node passed as parameter should be
268 * freed by the caller.
269 * Call with rcu_read_lock held.
270 * Threads calling this API need to be registered RCU read-side threads.
272 * The semantic of this function is that if only this function is used
273 * to add keys into the table, no duplicated keys should ever be
274 * observable in the table. The same guarantee apply for combination of
275 * add_unique and add_replace (see below).
277 struct cds_lfht_node
*cds_lfht_add_unique(struct cds_lfht
*ht
,
279 cds_lfht_match_fct match
,
281 struct cds_lfht_node
*node
);
284 * cds_lfht_add_replace - replace or add a node within hash table.
285 * @ht: the hash table.
286 * @hash: the node's hash.
287 * @match: the key match function.
288 * @key: the node's key.
289 * @node: the node to add.
291 * Return the node replaced upon success. If no node matching the key
292 * was present, return NULL, which also means the operation succeeded.
293 * This replacement operation should never fail.
294 * Call with rcu_read_lock held.
295 * Threads calling this API need to be registered RCU read-side threads.
296 * After successful replacement, a grace period must be waited for before
297 * freeing the memory reserved for the returned node.
299 * The semantic of replacement vs lookups is the following: if lookups
300 * are performed between a key unique insertion and its removal, we
301 * guarantee that the lookups and get next will always find exactly one
302 * instance of the key if it is replaced concurrently with the lookups.
304 * Providing this semantic allows us to ensure that replacement-only
305 * schemes will never generate duplicated keys. It also allows us to
306 * guarantee that a combination of add_replace and add_unique updates
307 * will never generate duplicated keys.
309 struct cds_lfht_node
*cds_lfht_add_replace(struct cds_lfht
*ht
,
311 cds_lfht_match_fct match
,
313 struct cds_lfht_node
*node
);
316 * cds_lfht_replace - replace a node pointer to by iter within hash table.
317 * @ht: the hash table.
318 * @old_iter: the iterator position of the node to replace.
319 * @now_node: the new node to try using for replacement.
321 * Return 0 if replacement is successful, negative value otherwise.
322 * Replacing a NULL old node or an already removed node will fail with a
324 * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
325 * RCU read-side lock must be held between lookup and replacement.
326 * Call with rcu_read_lock held.
327 * Threads calling this API need to be registered RCU read-side threads.
328 * After successful replacement, a grace period must be waited for before
329 * freeing the memory reserved for the old node (which can be accessed
330 * with cds_lfht_iter_get_node).
332 * The semantic of replacement vs lookups is the following: if lookups
333 * are performed between a key unique insertion and its removal, we
334 * guarantee that the lookups and get next will always find exactly one
335 * instance of the key if it is replaced concurrently with the lookups.
337 * Providing this semantic allows us to ensure that replacement-only
338 * schemes will never generate duplicated keys. It also allows us to
339 * guarantee that a combination of add_replace and add_unique updates
340 * will never generate duplicated keys.
342 int cds_lfht_replace(struct cds_lfht
*ht
, struct cds_lfht_iter
*old_iter
,
343 struct cds_lfht_node
*new_node
);
346 * cds_lfht_del - remove node pointed to by iterator from hash table.
347 * @ht: the hash table.
348 * @iter: the iterator position of the node to delete.
350 * Return 0 if the node is successfully removed, negative value
352 * Replacing a NULL node or an already removed node will fail with a
354 * Node can be looked up with cds_lfht_lookup and cds_lfht_next.
355 * cds_lfht_iter_get_node.
356 * RCU read-side lock must be held between lookup and removal.
357 * Call with rcu_read_lock held.
358 * Threads calling this API need to be registered RCU read-side threads.
359 * After successful removal, a grace period must be waited for before
360 * freeing the memory reserved for old node (which can be accessed with
361 * cds_lfht_iter_get_node).
363 int cds_lfht_del(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
366 * cds_lfht_resize - Force a hash table resize
367 * @ht: the hash table.
368 * @new_size: update to this hash table size.
370 * Threads calling this API need to be registered RCU read-side threads.
372 void cds_lfht_resize(struct cds_lfht
*ht
, unsigned long new_size
);
375 * Note: cds_lfht_for_each are safe for element removal during
378 #define cds_lfht_for_each(ht, iter, node) \
379 for (cds_lfht_first(ht, iter), \
380 node = cds_lfht_iter_get_node(iter); \
382 cds_lfht_next(ht, iter), \
383 node = cds_lfht_iter_get_node(iter))
385 #define cds_lfht_for_each_duplicate(ht, hash, match, key, iter, node) \
386 for (cds_lfht_lookup(ht, hash, match, key, iter), \
387 node = cds_lfht_iter_get_node(iter); \
389 cds_lfht_next_duplicate(ht, match, key, iter), \
390 node = cds_lfht_iter_get_node(iter))
392 #define cds_lfht_for_each_entry(ht, iter, pos, member) \
393 for (cds_lfht_first(ht, iter), \
394 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
395 typeof(*(pos)), member); \
396 &(pos)->member != NULL; \
397 cds_lfht_next(ht, iter), \
398 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
399 typeof(*(pos)), member))
401 #define cds_lfht_for_each_entry_duplicate(ht, hash, match, key, \
403 for (cds_lfht_lookup(ht, hash, match, key, iter), \
404 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
405 typeof(*(pos)), member); \
406 &(pos)->member != NULL; \
407 cds_lfht_next_duplicate(ht, match, key, iter), \
408 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
409 typeof(*(pos)), member))
415 #endif /* _URCU_RCULFHASH_H */