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 8-bytes boundaries because
43 * the three lower bits are used as flags. It is worth noting that the
44 * information contained within these three bits could be represented on
45 * two bits by re-using the same bit for REMOVAL_OWNER_FLAG and
46 * BUCKET_FLAG. This can be done if we ensure that no iterator nor
47 * updater check the BUCKET_FLAG after it detects that the REMOVED_FLAG
48 * is set. Given the minimum size of struct cds_lfht_node is 8 bytes on
49 * 32-bit architectures, we choose to go for simplicity and reserve
52 * struct cds_lfht_node can be embedded into a structure (as a field).
53 * caa_container_of() can be used to get the structure from the struct
54 * cds_lfht_node after a lookup.
56 * The structure which embeds it typically holds the key (or key-value
57 * pair) of the object. The caller code is responsible for calculation
58 * of the hash value for cds_lfht APIs.
60 struct cds_lfht_node
{
61 struct cds_lfht_node
*next
; /* ptr | REMOVAL_OWNER_FLAG | BUCKET_FLAG | REMOVED_FLAG */
62 unsigned long reverse_hash
;
63 } __attribute__((aligned(8)));
65 /* cds_lfht_iter: Used to track state while traversing a hash chain. */
66 struct cds_lfht_iter
{
67 struct cds_lfht_node
*node
, *next
;
71 struct cds_lfht_node
*cds_lfht_iter_get_node(struct cds_lfht_iter
*iter
)
80 * Ensure reader and writer threads are registered as urcu readers.
83 typedef int (*cds_lfht_match_fct
)(struct cds_lfht_node
*node
, const void *key
);
86 * cds_lfht_node_init - initialize a hash table node
87 * @node: the node to initialize.
89 * This function is kept to be eventually used for debugging purposes
90 * (detection of memory corruption).
93 void cds_lfht_node_init(struct cds_lfht_node
*node
)
98 * Hash table creation flags.
101 CDS_LFHT_AUTO_RESIZE
= (1U << 0),
102 CDS_LFHT_ACCOUNTING
= (1U << 1),
105 struct cds_lfht_mm_type
{
106 struct cds_lfht
*(*alloc_cds_lfht
)(unsigned long min_nr_alloc_buckets
,
107 unsigned long max_nr_buckets
);
108 void (*alloc_bucket_table
)(struct cds_lfht
*ht
, unsigned long order
);
109 void (*free_bucket_table
)(struct cds_lfht
*ht
, unsigned long order
);
110 struct cds_lfht_node
*(*bucket_at
)(struct cds_lfht
*ht
,
111 unsigned long index
);
114 extern const struct cds_lfht_mm_type cds_lfht_mm_order
;
115 extern const struct cds_lfht_mm_type cds_lfht_mm_chunk
;
116 extern const struct cds_lfht_mm_type cds_lfht_mm_mmap
;
119 * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
121 struct cds_lfht
*_cds_lfht_new(unsigned long init_size
,
122 unsigned long min_nr_alloc_buckets
,
123 unsigned long max_nr_buckets
,
125 const struct cds_lfht_mm_type
*mm
,
126 const struct rcu_flavor_struct
*flavor
,
127 pthread_attr_t
*attr
);
130 * cds_lfht_new - allocate a hash table.
131 * @init_size: number of buckets to allocate initially. Must be power of two.
132 * @min_nr_alloc_buckets: the minimum number of allocated buckets.
133 * (must be power of two)
134 * @max_nr_buckets: the maximum number of hash table buckets allowed.
135 * (must be power of two)
136 * @flags: hash table creation flags (can be combined with bitwise or: '|').
138 * CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
139 * CDS_LFHT_ACCOUNTING: count the number of node addition
140 * and removal in the table
141 * @attr: optional resize worker thread attributes. NULL for default.
143 * Return NULL on error.
144 * Note: the RCU flavor must be already included before the hash table header.
146 * The programmer is responsible for ensuring that resize operation has a
147 * priority equal to hash table updater threads. It should be performed by
148 * specifying the appropriate priority in the pthread "attr" argument, and,
149 * for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
150 * this priority level. Having lower priority for call_rcu and resize threads
151 * does not pose any correctness issue, but the resize operations could be
152 * starved by updates, thus leading to long hash table bucket chains.
153 * Threads calling this API are NOT required to be registered RCU read-side
154 * threads. It can be called very early.(before rcu is initialized ...etc.)
157 struct cds_lfht
*cds_lfht_new(unsigned long init_size
,
158 unsigned long min_nr_alloc_buckets
,
159 unsigned long max_nr_buckets
,
161 pthread_attr_t
*attr
)
163 return _cds_lfht_new(init_size
, min_nr_alloc_buckets
, max_nr_buckets
,
164 flags
, NULL
, &rcu_flavor
, attr
);
168 * cds_lfht_destroy - destroy a hash table.
169 * @ht: the hash table to destroy.
170 * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
171 * The caller will typically want to free this pointer if dynamically
172 * allocated. The attr point can be NULL if the caller does not
173 * need to be informed of the value passed to cds_lfht_new().
175 * Return 0 on success, negative error value on error.
176 * Threads calling this API need to be registered RCU read-side threads.
178 int cds_lfht_destroy(struct cds_lfht
*ht
, pthread_attr_t
**attr
);
181 * cds_lfht_count_nodes - count the number of nodes in the hash table.
182 * @ht: the hash table.
183 * @split_count_before: Sample the node count split-counter before traversal.
184 * @count: Traverse the hash table, count the number of nodes observed.
185 * @removed: Number of logically removed nodes observed during traversal.
186 * @split_count_after: Sample the node count split-counter after traversal.
188 * Call with rcu_read_lock held.
189 * Threads calling this API need to be registered RCU read-side threads.
191 void cds_lfht_count_nodes(struct cds_lfht
*ht
,
192 long *split_count_before
,
193 unsigned long *count
,
194 unsigned long *removed
,
195 long *split_count_after
);
198 * cds_lfht_lookup - lookup a node by key.
199 * @ht: the hash table.
200 * @hash: the key hash.
201 * @match: the key match function.
202 * @key: the current node key.
203 * @iter: Node, if found (output). *iter->node set to NULL if not found.
205 * Call with rcu_read_lock held.
206 * Threads calling this API need to be registered RCU read-side threads.
208 void cds_lfht_lookup(struct cds_lfht
*ht
, unsigned long hash
,
209 cds_lfht_match_fct match
, const void *key
,
210 struct cds_lfht_iter
*iter
);
213 * cds_lfht_next_duplicate - get the next item with same key (after a lookup).
214 * @ht: the hash table.
215 * @match: the key match function.
216 * @key: the current node key.
217 * @iter: Node, if found (output). *iter->node set to NULL if not found.
219 * Uses an iterator initialized by a lookup.
220 * Sets *iter-node to the following node with same key.
221 * Sets *iter->node to NULL if no following node exists with same key.
222 * RCU read-side lock must be held across cds_lfht_lookup and
223 * cds_lfht_next calls, and also between cds_lfht_next calls using the
224 * node returned by a previous cds_lfht_next.
225 * Call with rcu_read_lock held.
226 * Threads calling this API need to be registered RCU read-side threads.
228 void cds_lfht_next_duplicate(struct cds_lfht
*ht
,
229 cds_lfht_match_fct match
, const void *key
,
230 struct cds_lfht_iter
*iter
);
233 * cds_lfht_first - get the first node in the table.
234 * @ht: the hash table.
235 * @iter: First node, if exists (output). *iter->node set to NULL if not found.
237 * Output in "*iter". *iter->node set to NULL if table is empty.
238 * Call with rcu_read_lock held.
239 * Threads calling this API need to be registered RCU read-side threads.
241 void cds_lfht_first(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
244 * cds_lfht_next - get the next node in the table.
245 * @ht: the hash table.
246 * @iter: Next node, if exists (output). *iter->node set to NULL if not found.
248 * Input/Output in "*iter". *iter->node set to NULL if *iter was
249 * pointing to the last table node.
250 * Call with rcu_read_lock held.
251 * Threads calling this API need to be registered RCU read-side threads.
253 void cds_lfht_next(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
256 * cds_lfht_add - add a node to the hash table.
257 * @ht: the hash table.
258 * @hash: the key hash.
259 * @node: the node to add.
261 * This function supports adding redundant keys into the table.
262 * Call with rcu_read_lock held.
263 * Threads calling this API need to be registered RCU read-side threads.
265 void cds_lfht_add(struct cds_lfht
*ht
, unsigned long hash
,
266 struct cds_lfht_node
*node
);
269 * cds_lfht_add_unique - add a node to hash table, if key is not present.
270 * @ht: the hash table.
271 * @hash: the node's hash.
272 * @match: the key match function.
273 * @key: the node's key.
274 * @node: the node to try adding.
276 * Return the node added upon success.
277 * Return the unique node already present upon failure. If
278 * cds_lfht_add_unique fails, the node passed as parameter should be
279 * freed by the caller.
280 * Call with rcu_read_lock held.
281 * Threads calling this API need to be registered RCU read-side threads.
283 * The semantic of this function is that if only this function is used
284 * to add keys into the table, no duplicated keys should ever be
285 * observable in the table. The same guarantee apply for combination of
286 * add_unique and add_replace (see below).
288 struct cds_lfht_node
*cds_lfht_add_unique(struct cds_lfht
*ht
,
290 cds_lfht_match_fct match
,
292 struct cds_lfht_node
*node
);
295 * cds_lfht_add_replace - replace or add a node within hash table.
296 * @ht: the hash table.
297 * @hash: the node's hash.
298 * @match: the key match function.
299 * @key: the node's key.
300 * @node: the node to add.
302 * Return the node replaced upon success. If no node matching the key
303 * was present, return NULL, which also means the operation succeeded.
304 * This replacement operation should never fail.
305 * Call with rcu_read_lock held.
306 * Threads calling this API need to be registered RCU read-side threads.
307 * After successful replacement, a grace period must be waited for before
308 * freeing the memory reserved for the returned node.
310 * The semantic of replacement vs lookups is the following: if lookups
311 * are performed between a key unique insertion and its removal, we
312 * guarantee that the lookups and get next will always find exactly one
313 * instance of the key if it is replaced concurrently with the lookups.
315 * Providing this semantic allows us to ensure that replacement-only
316 * schemes will never generate duplicated keys. It also allows us to
317 * guarantee that a combination of add_replace and add_unique updates
318 * will never generate duplicated keys.
320 struct cds_lfht_node
*cds_lfht_add_replace(struct cds_lfht
*ht
,
322 cds_lfht_match_fct match
,
324 struct cds_lfht_node
*node
);
327 * cds_lfht_replace - replace a node pointer to by iter within hash table.
328 * @ht: the hash table.
329 * @old_iter: the iterator position of the node to replace.
330 * @now_node: the new node to try using for replacement.
332 * Return 0 if replacement is successful, negative value otherwise.
333 * Replacing a NULL old node or an already removed node will fail with a
335 * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
336 * RCU read-side lock must be held between lookup and replacement.
337 * Call with rcu_read_lock held.
338 * Threads calling this API need to be registered RCU read-side threads.
339 * After successful replacement, a grace period must be waited for before
340 * freeing the memory reserved for the old node (which can be accessed
341 * with cds_lfht_iter_get_node).
343 * The semantic of replacement vs lookups is the following: if lookups
344 * are performed between a key unique insertion and its removal, we
345 * guarantee that the lookups and get next will always find exactly one
346 * instance of the key if it is replaced concurrently with the lookups.
348 * Providing this semantic allows us to ensure that replacement-only
349 * schemes will never generate duplicated keys. It also allows us to
350 * guarantee that a combination of add_replace and add_unique updates
351 * will never generate duplicated keys.
353 int cds_lfht_replace(struct cds_lfht
*ht
, struct cds_lfht_iter
*old_iter
,
354 struct cds_lfht_node
*new_node
);
357 * cds_lfht_del - remove node pointed to by iterator from hash table.
358 * @ht: the hash table.
359 * @iter: the iterator position of the node to delete.
361 * Return 0 if the node is successfully removed, negative value
363 * Replacing a NULL node or an already removed node will fail with a
365 * Node can be looked up with cds_lfht_lookup and cds_lfht_next.
366 * cds_lfht_iter_get_node.
367 * RCU read-side lock must be held between lookup and removal.
368 * Call with rcu_read_lock held.
369 * Threads calling this API need to be registered RCU read-side threads.
370 * After successful removal, a grace period must be waited for before
371 * freeing the memory reserved for old node (which can be accessed with
372 * cds_lfht_iter_get_node).
374 int cds_lfht_del(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
377 * cds_lfht_resize - Force a hash table resize
378 * @ht: the hash table.
379 * @new_size: update to this hash table size.
381 * Threads calling this API need to be registered RCU read-side threads.
383 void cds_lfht_resize(struct cds_lfht
*ht
, unsigned long new_size
);
386 * Note: cds_lfht_for_each are safe for element removal during
389 #define cds_lfht_for_each(ht, iter, node) \
390 for (cds_lfht_first(ht, iter), \
391 node = cds_lfht_iter_get_node(iter); \
393 cds_lfht_next(ht, iter), \
394 node = cds_lfht_iter_get_node(iter))
396 #define cds_lfht_for_each_duplicate(ht, hash, match, key, iter, node) \
397 for (cds_lfht_lookup(ht, hash, match, key, iter), \
398 node = cds_lfht_iter_get_node(iter); \
400 cds_lfht_next_duplicate(ht, match, key, iter), \
401 node = cds_lfht_iter_get_node(iter))
403 #define cds_lfht_for_each_entry(ht, iter, pos, member) \
404 for (cds_lfht_first(ht, iter), \
405 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
406 typeof(*(pos)), member); \
407 &(pos)->member != NULL; \
408 cds_lfht_next(ht, iter), \
409 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
410 typeof(*(pos)), member))
412 #define cds_lfht_for_each_entry_duplicate(ht, hash, match, key, \
414 for (cds_lfht_lookup(ht, hash, match, key, iter), \
415 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
416 typeof(*(pos)), member); \
417 &(pos)->member != NULL; \
418 cds_lfht_next_duplicate(ht, match, key, iter), \
419 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
420 typeof(*(pos)), member))
426 #endif /* _URCU_RCULFHASH_H */