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>
32 #include <urcu-flavor.h>
39 * cds_lfht_node: Contains the next pointers and reverse-hash
40 * value required for lookup and traversal of the hash table.
42 * struct cds_lfht_node should be aligned on 4-bytes boundaries because
43 * the two lower bits are used as flags.
45 * struct cds_lfht_node can be embedded into a structure (as a field).
46 * caa_container_of() can be used to get the structure from the struct
47 * cds_lfht_node after a lookup.
49 * The structure which embeds it typically holds the key (or key-value
50 * pair) of the object. The caller code is responsible for calculation
51 * of the hash value for cds_lfht APIs.
53 struct cds_lfht_node
{
54 struct cds_lfht_node
*next
; /* ptr | BUCKET_FLAG | REMOVED_FLAG */
55 unsigned long reverse_hash
;
56 } __attribute__((aligned(4)));
58 /* cds_lfht_iter: Used to track state while traversing a hash chain. */
59 struct cds_lfht_iter
{
60 struct cds_lfht_node
*node
, *next
;
64 struct cds_lfht_node
*cds_lfht_iter_get_node(struct cds_lfht_iter
*iter
)
73 * Ensure reader and writer threads are registered as urcu readers.
76 typedef int (*cds_lfht_match_fct
)(struct cds_lfht_node
*node
, const 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),
98 struct cds_lfht_mm_type
{
99 struct cds_lfht
*(*alloc_cds_lfht
)(unsigned long min_nr_alloc_buckets
,
100 unsigned long max_nr_buckets
);
101 void (*alloc_bucket_table
)(struct cds_lfht
*ht
, unsigned long order
);
102 void (*free_bucket_table
)(struct cds_lfht
*ht
, unsigned long order
);
103 struct cds_lfht_node
*(*bucket_at
)(struct cds_lfht
*ht
,
104 unsigned long index
);
107 extern const struct cds_lfht_mm_type cds_lfht_mm_order
;
110 * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
112 struct cds_lfht
*_cds_lfht_new(unsigned long init_size
,
113 unsigned long min_nr_alloc_buckets
,
114 unsigned long max_nr_buckets
,
116 const struct cds_lfht_mm_type
*mm
,
117 const struct rcu_flavor_struct
*flavor
,
118 pthread_attr_t
*attr
);
121 * cds_lfht_new - allocate a hash table.
122 * @init_size: number of buckets to allocate initially. Must be power of two.
123 * @min_nr_alloc_buckets: the minimum number of allocated buckets.
124 * (must be power of two)
125 * @max_nr_buckets: the maximum number of hash table buckets allowed.
126 * (must be power of two)
127 * @flags: hash table creation flags (can be combined with bitwise or: '|').
129 * CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
130 * CDS_LFHT_ACCOUNTING: count the number of node addition
131 * and removal in the table
132 * @attr: optional resize worker thread attributes. NULL for default.
134 * Return NULL on error.
135 * Note: the RCU flavor must be already included before the hash table header.
137 * The programmer is responsible for ensuring that resize operation has a
138 * priority equal to hash table updater threads. It should be performed by
139 * specifying the appropriate priority in the pthread "attr" argument, and,
140 * for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
141 * this priority level. Having lower priority for call_rcu and resize threads
142 * does not pose any correctness issue, but the resize operations could be
143 * starved by updates, thus leading to long hash table bucket chains.
144 * Threads calling this API are NOT required to be registered RCU read-side
145 * threads. It can be called very early.(before rcu is initialized ...etc.)
148 struct cds_lfht
*cds_lfht_new(unsigned long init_size
,
149 unsigned long min_nr_alloc_buckets
,
150 unsigned long max_nr_buckets
,
152 pthread_attr_t
*attr
)
154 return _cds_lfht_new(init_size
, min_nr_alloc_buckets
, max_nr_buckets
,
155 flags
, &cds_lfht_mm_order
, &rcu_flavor
, attr
);
159 * cds_lfht_destroy - destroy a hash table.
160 * @ht: the hash table to destroy.
161 * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
162 * The caller will typically want to free this pointer if dynamically
163 * allocated. The attr point can be NULL if the caller does not
164 * need to be informed of the value passed to cds_lfht_new().
166 * Return 0 on success, negative error value on error.
167 * Threads calling this API need to be registered RCU read-side threads.
169 int cds_lfht_destroy(struct cds_lfht
*ht
, pthread_attr_t
**attr
);
172 * cds_lfht_count_nodes - count the number of nodes in the hash table.
173 * @ht: the hash table.
174 * @split_count_before: Sample the node count split-counter before traversal.
175 * @count: Traverse the hash table, count the number of nodes observed.
176 * @removed: Number of logically removed nodes observed during traversal.
177 * @split_count_after: Sample the node count split-counter after traversal.
179 * Call with rcu_read_lock held.
180 * Threads calling this API need to be registered RCU read-side threads.
182 void cds_lfht_count_nodes(struct cds_lfht
*ht
,
183 long *split_count_before
,
184 unsigned long *count
,
185 unsigned long *removed
,
186 long *split_count_after
);
189 * cds_lfht_lookup - lookup a node by key.
190 * @ht: the hash table.
191 * @hash: the key hash.
192 * @match: the key match function.
193 * @key: the current node key.
194 * @iter: Node, if found (output). *iter->node set to NULL if not found.
196 * Call with rcu_read_lock held.
197 * Threads calling this API need to be registered RCU read-side threads.
199 void cds_lfht_lookup(struct cds_lfht
*ht
, unsigned long hash
,
200 cds_lfht_match_fct match
, const void *key
,
201 struct cds_lfht_iter
*iter
);
204 * cds_lfht_next_duplicate - get the next item with same key (after a lookup).
205 * @ht: the hash table.
206 * @match: the key match function.
207 * @key: the current node key.
208 * @iter: Node, if found (output). *iter->node set to NULL if not found.
210 * Uses an iterator initialized by a lookup.
211 * Sets *iter-node to the following node with same key.
212 * Sets *iter->node to NULL if no following node exists with same key.
213 * RCU read-side lock must be held across cds_lfht_lookup and
214 * cds_lfht_next calls, and also between cds_lfht_next calls using the
215 * node returned by a previous cds_lfht_next.
216 * Call with rcu_read_lock held.
217 * Threads calling this API need to be registered RCU read-side threads.
219 void cds_lfht_next_duplicate(struct cds_lfht
*ht
,
220 cds_lfht_match_fct match
, const void *key
,
221 struct cds_lfht_iter
*iter
);
224 * cds_lfht_first - get the first node in the table.
225 * @ht: the hash table.
226 * @iter: First node, if exists (output). *iter->node set to NULL if not found.
228 * Output in "*iter". *iter->node set to NULL if table is empty.
229 * Call with rcu_read_lock held.
230 * Threads calling this API need to be registered RCU read-side threads.
232 void cds_lfht_first(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
235 * cds_lfht_next - get the next node in the table.
236 * @ht: the hash table.
237 * @iter: Next node, if exists (output). *iter->node set to NULL if not found.
239 * Input/Output in "*iter". *iter->node set to NULL if *iter was
240 * pointing to the last table node.
241 * Call with rcu_read_lock held.
242 * Threads calling this API need to be registered RCU read-side threads.
244 void cds_lfht_next(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
247 * cds_lfht_add - add a node to the hash table.
248 * @ht: the hash table.
249 * @hash: the key hash.
250 * @node: the node to add.
252 * This function supports adding redundant keys into the table.
253 * Call with rcu_read_lock held.
254 * Threads calling this API need to be registered RCU read-side threads.
256 void cds_lfht_add(struct cds_lfht
*ht
, unsigned long hash
,
257 struct cds_lfht_node
*node
);
260 * cds_lfht_add_unique - add a node to hash table, if key is not present.
261 * @ht: the hash table.
262 * @hash: the node's hash.
263 * @match: the key match function.
264 * @key: the node's key.
265 * @node: the node to try adding.
267 * Return the node added upon success.
268 * Return the unique node already present upon failure. If
269 * cds_lfht_add_unique fails, the node passed as parameter should be
270 * freed by the caller.
271 * Call with rcu_read_lock held.
272 * Threads calling this API need to be registered RCU read-side threads.
274 * The semantic of this function is that if only this function is used
275 * to add keys into the table, no duplicated keys should ever be
276 * observable in the table. The same guarantee apply for combination of
277 * add_unique and add_replace (see below).
279 struct cds_lfht_node
*cds_lfht_add_unique(struct cds_lfht
*ht
,
281 cds_lfht_match_fct match
,
283 struct cds_lfht_node
*node
);
286 * cds_lfht_add_replace - replace or add a node within hash table.
287 * @ht: the hash table.
288 * @hash: the node's hash.
289 * @match: the key match function.
290 * @key: the node's key.
291 * @node: the node to add.
293 * Return the node replaced upon success. If no node matching the key
294 * was present, return NULL, which also means the operation succeeded.
295 * This replacement operation should never fail.
296 * Call with rcu_read_lock held.
297 * Threads calling this API need to be registered RCU read-side threads.
298 * After successful replacement, a grace period must be waited for before
299 * freeing the memory reserved for the returned node.
301 * The semantic of replacement vs lookups is the following: if lookups
302 * are performed between a key unique insertion and its removal, we
303 * guarantee that the lookups and get next will always find exactly one
304 * instance of the key if it is replaced concurrently with the lookups.
306 * Providing this semantic allows us to ensure that replacement-only
307 * schemes will never generate duplicated keys. It also allows us to
308 * guarantee that a combination of add_replace and add_unique updates
309 * will never generate duplicated keys.
311 struct cds_lfht_node
*cds_lfht_add_replace(struct cds_lfht
*ht
,
313 cds_lfht_match_fct match
,
315 struct cds_lfht_node
*node
);
318 * cds_lfht_replace - replace a node pointer to by iter within hash table.
319 * @ht: the hash table.
320 * @old_iter: the iterator position of the node to replace.
321 * @now_node: the new node to try using for replacement.
323 * Return 0 if replacement is successful, negative value otherwise.
324 * Replacing a NULL old node or an already removed node will fail with a
326 * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
327 * RCU read-side lock must be held between lookup and replacement.
328 * Call with rcu_read_lock held.
329 * Threads calling this API need to be registered RCU read-side threads.
330 * After successful replacement, a grace period must be waited for before
331 * freeing the memory reserved for the old node (which can be accessed
332 * with cds_lfht_iter_get_node).
334 * The semantic of replacement vs lookups is the following: if lookups
335 * are performed between a key unique insertion and its removal, we
336 * guarantee that the lookups and get next will always find exactly one
337 * instance of the key if it is replaced concurrently with the lookups.
339 * Providing this semantic allows us to ensure that replacement-only
340 * schemes will never generate duplicated keys. It also allows us to
341 * guarantee that a combination of add_replace and add_unique updates
342 * will never generate duplicated keys.
344 int cds_lfht_replace(struct cds_lfht
*ht
, struct cds_lfht_iter
*old_iter
,
345 struct cds_lfht_node
*new_node
);
348 * cds_lfht_del - remove node pointed to by iterator from hash table.
349 * @ht: the hash table.
350 * @iter: the iterator position of the node to delete.
352 * Return 0 if the node is successfully removed, negative value
354 * Replacing a NULL node or an already removed node will fail with a
356 * Node can be looked up with cds_lfht_lookup and cds_lfht_next.
357 * cds_lfht_iter_get_node.
358 * RCU read-side lock must be held between lookup and removal.
359 * Call with rcu_read_lock held.
360 * Threads calling this API need to be registered RCU read-side threads.
361 * After successful removal, a grace period must be waited for before
362 * freeing the memory reserved for old node (which can be accessed with
363 * cds_lfht_iter_get_node).
365 int cds_lfht_del(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
368 * cds_lfht_resize - Force a hash table resize
369 * @ht: the hash table.
370 * @new_size: update to this hash table size.
372 * Threads calling this API need to be registered RCU read-side threads.
374 void cds_lfht_resize(struct cds_lfht
*ht
, unsigned long new_size
);
377 * Note: cds_lfht_for_each are safe for element removal during
380 #define cds_lfht_for_each(ht, iter, node) \
381 for (cds_lfht_first(ht, iter), \
382 node = cds_lfht_iter_get_node(iter); \
384 cds_lfht_next(ht, iter), \
385 node = cds_lfht_iter_get_node(iter))
387 #define cds_lfht_for_each_duplicate(ht, hash, match, key, iter, node) \
388 for (cds_lfht_lookup(ht, hash, match, key, iter), \
389 node = cds_lfht_iter_get_node(iter); \
391 cds_lfht_next_duplicate(ht, match, key, iter), \
392 node = cds_lfht_iter_get_node(iter))
394 #define cds_lfht_for_each_entry(ht, iter, pos, member) \
395 for (cds_lfht_first(ht, iter), \
396 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
397 typeof(*(pos)), member); \
398 &(pos)->member != NULL; \
399 cds_lfht_next(ht, iter), \
400 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
401 typeof(*(pos)), member))
403 #define cds_lfht_for_each_entry_duplicate(ht, hash, match, key, \
405 for (cds_lfht_lookup(ht, hash, match, key, iter), \
406 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
407 typeof(*(pos)), member); \
408 &(pos)->member != NULL; \
409 cds_lfht_next_duplicate(ht, match, key, iter), \
410 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
411 typeof(*(pos)), member))
417 #endif /* _URCU_RCULFHASH_H */