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/compiler.h>
30 #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 | BUCKET_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 int (*cds_lfht_match_fct
)(struct cds_lfht_node
*node
, const void *key
);
77 * cds_lfht_node_init - initialize a hash table node
78 * @node: the node to initialize.
80 * This function is kept to be eventually used for debugging purposes
81 * (detection of memory corruption).
84 void cds_lfht_node_init(struct cds_lfht_node
*node
)
89 * Hash table creation flags.
92 CDS_LFHT_AUTO_RESIZE
= (1U << 0),
93 CDS_LFHT_ACCOUNTING
= (1U << 1),
97 * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
99 struct cds_lfht
*_cds_lfht_new(unsigned long init_size
,
100 unsigned long min_alloc_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 * @init_size: number of nodes to allocate initially. Must be power of two.
116 * @min_alloc_size: the smallest allocation size to use. Must be power of two.
117 * @flags: hash table creation flags (can be combined with bitwise or: '|').
119 * CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
120 * CDS_LFHT_ACCOUNTING: count the number of node addition
121 * and removal in the 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 are NOT required to be registered RCU read-side
135 * threads. It can be called very early.(before rcu is initialized ...etc.)
138 struct cds_lfht
*cds_lfht_new(unsigned long init_size
,
139 unsigned long min_alloc_size
,
141 pthread_attr_t
*attr
)
143 return _cds_lfht_new(init_size
, min_alloc_size
, flags
,
144 call_rcu
, synchronize_rcu
, rcu_read_lock
,
145 rcu_read_unlock
, rcu_thread_offline
,
146 rcu_thread_online
, rcu_register_thread
,
147 rcu_unregister_thread
, attr
);
151 * cds_lfht_destroy - destroy a hash table.
152 * @ht: the hash table to destroy.
153 * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
154 * The caller will typically want to free this pointer if dynamically
155 * allocated. The attr point can be NULL if the caller does not
156 * need to be informed of the value passed to cds_lfht_new().
158 * Return 0 on success, negative error value on error.
159 * Threads calling this API need to be registered RCU read-side threads.
161 int cds_lfht_destroy(struct cds_lfht
*ht
, pthread_attr_t
**attr
);
164 * cds_lfht_count_nodes - count the number of nodes in the hash table.
165 * @ht: the hash table.
166 * @split_count_before: Sample the node count split-counter before traversal.
167 * @count: Traverse the hash table, count the number of nodes observed.
168 * @removed: Number of logically removed nodes observed during traversal.
169 * @split_count_after: Sample the node count split-counter after traversal.
171 * Call with rcu_read_lock held.
172 * Threads calling this API need to be registered RCU read-side threads.
174 void cds_lfht_count_nodes(struct cds_lfht
*ht
,
175 long *split_count_before
,
176 unsigned long *count
,
177 unsigned long *removed
,
178 long *split_count_after
);
181 * cds_lfht_lookup - lookup a node by key.
182 * @ht: the hash table.
183 * @hash: the key hash.
184 * @match: the key match function.
185 * @key: the current node key.
186 * @iter: Node, if found (output). *iter->node set to NULL if not found.
188 * Call with rcu_read_lock held.
189 * Threads calling this API need to be registered RCU read-side threads.
191 void cds_lfht_lookup(struct cds_lfht
*ht
, unsigned long hash
,
192 cds_lfht_match_fct match
, const void *key
,
193 struct cds_lfht_iter
*iter
);
196 * cds_lfht_next_duplicate - get the next item with same key (after a lookup).
197 * @ht: the hash table.
198 * @match: the key match function.
199 * @key: the current node key.
200 * @iter: Node, if found (output). *iter->node set to NULL if not found.
202 * Uses an iterator initialized by a lookup.
203 * Sets *iter-node to the following node with same key.
204 * Sets *iter->node to NULL if no following node exists with same key.
205 * RCU read-side lock must be held across cds_lfht_lookup and
206 * cds_lfht_next calls, and also between cds_lfht_next calls using the
207 * node returned by a previous cds_lfht_next.
208 * Call with rcu_read_lock held.
209 * Threads calling this API need to be registered RCU read-side threads.
211 void cds_lfht_next_duplicate(struct cds_lfht
*ht
,
212 cds_lfht_match_fct match
, const void *key
,
213 struct cds_lfht_iter
*iter
);
216 * cds_lfht_first - get the first node in the table.
217 * @ht: the hash table.
218 * @iter: First node, if exists (output). *iter->node set to NULL if not found.
220 * Output in "*iter". *iter->node set to NULL if table is empty.
221 * Call with rcu_read_lock held.
222 * Threads calling this API need to be registered RCU read-side threads.
224 void cds_lfht_first(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
227 * cds_lfht_next - get the next node in the table.
228 * @ht: the hash table.
229 * @iter: Next node, if exists (output). *iter->node set to NULL if not found.
231 * Input/Output in "*iter". *iter->node set to NULL if *iter was
232 * pointing to the last table node.
233 * Call with rcu_read_lock held.
234 * Threads calling this API need to be registered RCU read-side threads.
236 void cds_lfht_next(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
239 * cds_lfht_add - add a node to the hash table.
240 * @ht: the hash table.
241 * @hash: the key hash.
242 * @node: the node to add.
244 * This function supports adding redundant keys into the table.
245 * Call with rcu_read_lock held.
246 * Threads calling this API need to be registered RCU read-side threads.
248 void cds_lfht_add(struct cds_lfht
*ht
, unsigned long hash
,
249 struct cds_lfht_node
*node
);
252 * cds_lfht_add_unique - add a node to hash table, if key is not present.
253 * @ht: the hash table.
254 * @hash: the node's hash.
255 * @match: the key match function.
256 * @key: the node's key.
257 * @node: the node to try adding.
259 * Return the node added upon success.
260 * Return the unique node already present upon failure. If
261 * cds_lfht_add_unique fails, the node passed as parameter should be
262 * freed by the caller.
263 * Call with rcu_read_lock held.
264 * Threads calling this API need to be registered RCU read-side threads.
266 * The semantic of this function is that if only this function is used
267 * to add keys into the table, no duplicated keys should ever be
268 * observable in the table. The same guarantee apply for combination of
269 * add_unique and add_replace (see below).
271 struct cds_lfht_node
*cds_lfht_add_unique(struct cds_lfht
*ht
,
273 cds_lfht_match_fct match
,
275 struct cds_lfht_node
*node
);
278 * cds_lfht_add_replace - replace or add a node within hash table.
279 * @ht: the hash table.
280 * @hash: the node's hash.
281 * @match: the key match function.
282 * @key: the node's key.
283 * @node: the node to add.
285 * Return the node replaced upon success. If no node matching the key
286 * was present, return NULL, which also means the operation succeeded.
287 * This replacement operation should never fail.
288 * Call with rcu_read_lock held.
289 * Threads calling this API need to be registered RCU read-side threads.
290 * After successful replacement, a grace period must be waited for before
291 * freeing the memory reserved for the returned node.
293 * The semantic of replacement vs lookups is the following: if lookups
294 * are performed between a key unique insertion and its removal, we
295 * guarantee that the lookups and get next will always find exactly one
296 * instance of the key if it is replaced concurrently with the lookups.
298 * Providing this semantic allows us to ensure that replacement-only
299 * schemes will never generate duplicated keys. It also allows us to
300 * guarantee that a combination of add_replace and add_unique updates
301 * will never generate duplicated keys.
303 struct cds_lfht_node
*cds_lfht_add_replace(struct cds_lfht
*ht
,
305 cds_lfht_match_fct match
,
307 struct cds_lfht_node
*node
);
310 * cds_lfht_replace - replace a node pointer to by iter within hash table.
311 * @ht: the hash table.
312 * @old_iter: the iterator position of the node to replace.
313 * @now_node: the new node to try using for replacement.
315 * Return 0 if replacement is successful, negative value otherwise.
316 * Replacing a NULL old node or an already removed node will fail with a
318 * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
319 * RCU read-side lock must be held between lookup and replacement.
320 * Call with rcu_read_lock held.
321 * Threads calling this API need to be registered RCU read-side threads.
322 * After successful replacement, a grace period must be waited for before
323 * freeing the memory reserved for the old node (which can be accessed
324 * with cds_lfht_iter_get_node).
326 * The semantic of replacement vs lookups is the following: if lookups
327 * are performed between a key unique insertion and its removal, we
328 * guarantee that the lookups and get next will always find exactly one
329 * instance of the key if it is replaced concurrently with the lookups.
331 * Providing this semantic allows us to ensure that replacement-only
332 * schemes will never generate duplicated keys. It also allows us to
333 * guarantee that a combination of add_replace and add_unique updates
334 * will never generate duplicated keys.
336 int cds_lfht_replace(struct cds_lfht
*ht
, struct cds_lfht_iter
*old_iter
,
337 struct cds_lfht_node
*new_node
);
340 * cds_lfht_del - remove node pointed to by iterator from hash table.
341 * @ht: the hash table.
342 * @iter: the iterator position of the node to delete.
344 * Return 0 if the node is successfully removed, negative value
346 * Replacing a NULL node or an already removed node will fail with a
348 * Node can be looked up with cds_lfht_lookup and cds_lfht_next.
349 * cds_lfht_iter_get_node.
350 * RCU read-side lock must be held between lookup and removal.
351 * Call with rcu_read_lock held.
352 * Threads calling this API need to be registered RCU read-side threads.
353 * After successful removal, a grace period must be waited for before
354 * freeing the memory reserved for old node (which can be accessed with
355 * cds_lfht_iter_get_node).
357 int cds_lfht_del(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
360 * cds_lfht_resize - Force a hash table resize
361 * @ht: the hash table.
362 * @new_size: update to this hash table size.
364 * Threads calling this API need to be registered RCU read-side threads.
366 void cds_lfht_resize(struct cds_lfht
*ht
, unsigned long new_size
);
369 * Note: cds_lfht_for_each are safe for element removal during
372 #define cds_lfht_for_each(ht, iter, node) \
373 for (cds_lfht_first(ht, iter), \
374 node = cds_lfht_iter_get_node(iter); \
376 cds_lfht_next(ht, iter), \
377 node = cds_lfht_iter_get_node(iter))
379 #define cds_lfht_for_each_duplicate(ht, hash, match, key, iter, node) \
380 for (cds_lfht_lookup(ht, hash, match, key, iter), \
381 node = cds_lfht_iter_get_node(iter); \
383 cds_lfht_next_duplicate(ht, match, key, iter), \
384 node = cds_lfht_iter_get_node(iter))
386 #define cds_lfht_for_each_entry(ht, iter, pos, member) \
387 for (cds_lfht_first(ht, iter), \
388 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
389 typeof(*(pos)), member); \
390 &(pos)->member != NULL; \
391 cds_lfht_next(ht, iter), \
392 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
393 typeof(*(pos)), member))
395 #define cds_lfht_for_each_entry_duplicate(ht, hash, match, key, \
397 for (cds_lfht_lookup(ht, hash, match, key, iter), \
398 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
399 typeof(*(pos)), member); \
400 &(pos)->member != NULL; \
401 cds_lfht_next_duplicate(ht, match, key, iter), \
402 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
403 typeof(*(pos)), member))
409 #endif /* _URCU_RCULFHASH_H */