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 cds_lfht_new are NOT required to be registered RCU
154 * read-side threads. It can be called very early. (e.g. before RCU is
158 struct cds_lfht
*cds_lfht_new(unsigned long init_size
,
159 unsigned long min_nr_alloc_buckets
,
160 unsigned long max_nr_buckets
,
162 pthread_attr_t
*attr
)
164 return _cds_lfht_new(init_size
, min_nr_alloc_buckets
, max_nr_buckets
,
165 flags
, NULL
, &rcu_flavor
, attr
);
169 * cds_lfht_destroy - destroy a hash table.
170 * @ht: the hash table to destroy.
171 * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
172 * The caller will typically want to free this pointer if dynamically
173 * allocated. The attr point can be NULL if the caller does not
174 * need to be informed of the value passed to cds_lfht_new().
176 * Return 0 on success, negative error value on error.
177 * Threads calling this API need to be registered RCU read-side threads.
179 int cds_lfht_destroy(struct cds_lfht
*ht
, pthread_attr_t
**attr
);
182 * cds_lfht_count_nodes - count the number of nodes in the hash table.
183 * @ht: the hash table.
184 * @split_count_before: sample the node count split-counter before traversal.
185 * @count: traverse the hash table, count the number of nodes observed.
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 long *split_count_after
);
197 * cds_lfht_lookup - lookup a node by key.
198 * @ht: the hash table.
199 * @hash: the key hash.
200 * @match: the key match function.
201 * @key: the current node key.
202 * @iter: node, if found (output). *iter->node set to NULL if not found.
204 * Call with rcu_read_lock held.
205 * Threads calling this API need to be registered RCU read-side threads.
206 * This function acts as a rcu_dereference() to read the node pointer.
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 iterator.
214 * @ht: the hash table.
215 * @match: the key match function.
216 * @key: the current node key.
217 * @iter: input: current iterator.
218 * output: node, if found. *iter->node set to NULL if not found.
220 * Uses an iterator initialized by a lookup or traversal. Important: the
221 * iterator _needs_ to be initialized before calling
222 * cds_lfht_next_duplicate.
223 * Sets *iter-node to the following node with same key.
224 * Sets *iter->node to NULL if no following node exists with same key.
225 * RCU read-side lock must be held across cds_lfht_lookup and
226 * cds_lfht_next calls, and also between cds_lfht_next calls using the
227 * node returned by a previous cds_lfht_next.
228 * Call with rcu_read_lock held.
229 * Threads calling this API need to be registered RCU read-side threads.
230 * This function acts as a rcu_dereference() to read the node pointer.
232 void cds_lfht_next_duplicate(struct cds_lfht
*ht
,
233 cds_lfht_match_fct match
, const void *key
,
234 struct cds_lfht_iter
*iter
);
237 * cds_lfht_first - get the first node in the table.
238 * @ht: the hash table.
239 * @iter: First node, if exists (output). *iter->node set to NULL if not found.
241 * Output in "*iter". *iter->node set to NULL if table is empty.
242 * Call with rcu_read_lock held.
243 * Threads calling this API need to be registered RCU read-side threads.
244 * This function acts as a rcu_dereference() to read the node pointer.
246 void cds_lfht_first(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
249 * cds_lfht_next - get the next node in the table.
250 * @ht: the hash table.
251 * @iter: input: current iterator.
252 * output: next node, if exists. *iter->node set to NULL if not found.
254 * Input/Output in "*iter". *iter->node set to NULL if *iter was
255 * pointing to the last table node.
256 * Call with rcu_read_lock held.
257 * Threads calling this API need to be registered RCU read-side threads.
258 * This function acts as a rcu_dereference() to read the node pointer.
260 void cds_lfht_next(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
263 * cds_lfht_add - add a node to the hash table.
264 * @ht: the hash table.
265 * @hash: the key hash.
266 * @node: the node to add.
268 * This function supports adding redundant keys into the table.
269 * Call with rcu_read_lock held.
270 * Threads calling this API need to be registered RCU read-side threads.
271 * This function issues a full memory barrier before and after its
274 void cds_lfht_add(struct cds_lfht
*ht
, unsigned long hash
,
275 struct cds_lfht_node
*node
);
278 * cds_lfht_add_unique - add a node to hash table, if key is not present.
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 try adding.
285 * Return the node added upon success.
286 * Return the unique node already present upon failure. If
287 * cds_lfht_add_unique fails, the node passed as parameter should be
288 * freed by the caller. In this case, the caller does NOT need to wait
289 * for a grace period before freeing the node.
290 * Call with rcu_read_lock held.
291 * Threads calling this API need to be registered RCU read-side threads.
293 * The semantic of this function is that if only this function is used
294 * to add keys into the table, no duplicated keys should ever be
295 * observable in the table. The same guarantee apply for combination of
296 * add_unique and add_replace (see below).
298 * Upon success, this function issues a full memory barrier before and
299 * after its atomic commit. Upon failure, this function acts like a
300 * simple lookup operation: it acts as a rcu_dereference() to read the
301 * node pointer. The failure case does not guarantee any other memory
304 struct cds_lfht_node
*cds_lfht_add_unique(struct cds_lfht
*ht
,
306 cds_lfht_match_fct match
,
308 struct cds_lfht_node
*node
);
311 * cds_lfht_add_replace - replace or add a node within hash table.
312 * @ht: the hash table.
313 * @hash: the node's hash.
314 * @match: the key match function.
315 * @key: the node's key.
316 * @node: the node to add.
318 * Return the node replaced upon success. If no node matching the key
319 * was present, return NULL, which also means the operation succeeded.
320 * This replacement operation should never fail.
321 * Call with rcu_read_lock held.
322 * Threads calling this API need to be registered RCU read-side threads.
323 * After successful replacement, a grace period must be waited for before
324 * freeing the memory reserved for the returned node.
326 * The semantic of replacement vs lookups and traversals is the
327 * following: if lookups and traversals are performed between a key
328 * unique insertion and its removal, we guarantee that the lookups and
329 * traversals will always find exactly one instance of the key if it is
330 * replaced concurrently with the lookups.
332 * Providing this semantic allows us to ensure that replacement-only
333 * schemes will never generate duplicated keys. It also allows us to
334 * guarantee that a combination of add_replace and add_unique updates
335 * will never generate duplicated keys.
337 * This function issues a full memory barrier before and after its
340 struct cds_lfht_node
*cds_lfht_add_replace(struct cds_lfht
*ht
,
342 cds_lfht_match_fct match
,
344 struct cds_lfht_node
*node
);
347 * cds_lfht_replace - replace a node pointed to by iter within hash table.
348 * @ht: the hash table.
349 * @old_iter: the iterator position of the node to replace.
350 * @hash: the node's hash.
351 * @match: the key match function.
352 * @key: the node's key.
353 * @new_node: the new node to use as replacement.
355 * Return 0 if replacement is successful, negative value otherwise.
356 * Replacing a NULL old node or an already removed node will fail with
358 * If the hash or value of the node to replace and the new node differ,
359 * this function returns -EINVAL without proceeding to the replacement.
360 * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
361 * RCU read-side lock must be held between lookup and replacement.
362 * Call with rcu_read_lock held.
363 * Threads calling this API need to be registered RCU read-side threads.
364 * After successful replacement, a grace period must be waited for before
365 * freeing the memory reserved for the old node (which can be accessed
366 * with cds_lfht_iter_get_node).
368 * The semantic of replacement vs lookups is the same as
369 * cds_lfht_add_replace().
371 * Upon success, this function issues a full memory barrier before and
372 * after its atomic commit. Upon failure, this function does not issue
373 * any memory barrier.
375 int cds_lfht_replace(struct cds_lfht
*ht
,
376 struct cds_lfht_iter
*old_iter
,
378 cds_lfht_match_fct match
,
380 struct cds_lfht_node
*new_node
);
383 * cds_lfht_del - remove node pointed to by iterator from hash table.
384 * @ht: the hash table.
385 * @node: the node to delete.
387 * Return 0 if the node is successfully removed, negative value
389 * Deleting a NULL node or an already removed node will fail with a
391 * Node can be looked up with cds_lfht_lookup and cds_lfht_next,
392 * followed by use of cds_lfht_iter_get_node.
393 * RCU read-side lock must be held between lookup and removal.
394 * Call with rcu_read_lock held.
395 * Threads calling this API need to be registered RCU read-side threads.
396 * After successful removal, a grace period must be waited for before
397 * freeing the memory reserved for old node (which can be accessed with
398 * cds_lfht_iter_get_node).
399 * Upon success, this function issues a full memory barrier before and
400 * after its atomic commit. Upon failure, this function does not issue
401 * any memory barrier.
403 int cds_lfht_del(struct cds_lfht
*ht
, struct cds_lfht_node
*node
);
406 * cds_lfht_is_node_deleted - query whether a node is removed from hash table.
408 * Return non-zero if the node is deleted from the hash table, 0
410 * Node can be looked up with cds_lfht_lookup and cds_lfht_next,
411 * followed by use of cds_lfht_iter_get_node.
412 * RCU read-side lock must be held between lookup and call to this
414 * Call with rcu_read_lock held.
415 * Threads calling this API need to be registered RCU read-side threads.
416 * This function does not issue any memory barrier.
418 int cds_lfht_is_node_deleted(struct cds_lfht_node
*node
);
421 * cds_lfht_resize - Force a hash table resize
422 * @ht: the hash table.
423 * @new_size: update to this hash table size.
425 * Threads calling this API need to be registered RCU read-side threads.
426 * This function does not (necessarily) issue memory barriers.
428 void cds_lfht_resize(struct cds_lfht
*ht
, unsigned long new_size
);
431 * Note: it is safe to perform element removal (del), replacement, or
432 * any hash table update operation during any of the following hash
434 * These functions act as rcu_dereference() to read the node pointers.
436 #define cds_lfht_for_each(ht, iter, node) \
437 for (cds_lfht_first(ht, iter), \
438 node = cds_lfht_iter_get_node(iter); \
440 cds_lfht_next(ht, iter), \
441 node = cds_lfht_iter_get_node(iter))
443 #define cds_lfht_for_each_duplicate(ht, hash, match, key, iter, node) \
444 for (cds_lfht_lookup(ht, hash, match, key, iter), \
445 node = cds_lfht_iter_get_node(iter); \
447 cds_lfht_next_duplicate(ht, match, key, iter), \
448 node = cds_lfht_iter_get_node(iter))
450 #define cds_lfht_for_each_entry(ht, iter, pos, member) \
451 for (cds_lfht_first(ht, iter), \
452 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
453 typeof(*(pos)), member); \
454 &(pos)->member != NULL; \
455 cds_lfht_next(ht, iter), \
456 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
457 typeof(*(pos)), member))
459 #define cds_lfht_for_each_entry_duplicate(ht, hash, match, key, \
461 for (cds_lfht_lookup(ht, hash, match, key, iter), \
462 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
463 typeof(*(pos)), member); \
464 &(pos)->member != NULL; \
465 cds_lfht_next_duplicate(ht, match, key, iter), \
466 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
467 typeof(*(pos)), member))
473 #endif /* _URCU_RCULFHASH_H */