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.
29 #include "hashtable-symbols.h"
32 #include <urcu/compiler.h>
33 #include <urcu-call-rcu.h>
35 #include "urcu-flavor.h"
42 * cds_lfht_node: Contains the next pointers and reverse-hash
43 * value required for lookup and traversal of the hash table.
45 * struct cds_lfht_node should be aligned on 8-bytes boundaries because
46 * the three lower bits are used as flags. It is worth noting that the
47 * information contained within these three bits could be represented on
48 * two bits by re-using the same bit for REMOVAL_OWNER_FLAG and
49 * BUCKET_FLAG. This can be done if we ensure that no iterator nor
50 * updater check the BUCKET_FLAG after it detects that the REMOVED_FLAG
51 * is set. Given the minimum size of struct cds_lfht_node is 8 bytes on
52 * 32-bit architectures, we choose to go for simplicity and reserve
55 * struct cds_lfht_node can be embedded into a structure (as a field).
56 * caa_container_of() can be used to get the structure from the struct
57 * cds_lfht_node after a lookup.
59 * The structure which embeds it typically holds the key (or key-value
60 * pair) of the object. The caller code is responsible for calculation
61 * of the hash value for cds_lfht APIs.
63 struct cds_lfht_node
{
64 struct cds_lfht_node
*next
; /* ptr | REMOVAL_OWNER_FLAG | BUCKET_FLAG | REMOVED_FLAG */
65 unsigned long reverse_hash
;
66 } __attribute__((aligned(8)));
68 /* cds_lfht_iter: Used to track state while traversing a hash chain. */
69 struct cds_lfht_iter
{
70 struct cds_lfht_node
*node
, *next
;
74 struct cds_lfht_node
*cds_lfht_iter_get_node(struct cds_lfht_iter
*iter
)
83 * Ensure reader and writer threads are registered as urcu readers.
86 typedef int (*cds_lfht_match_fct
)(struct cds_lfht_node
*node
, const void *key
);
89 * cds_lfht_node_init - initialize a hash table node
90 * @node: the node to initialize.
92 * This function is kept to be eventually used for debugging purposes
93 * (detection of memory corruption).
96 void cds_lfht_node_init(struct cds_lfht_node
*node
)
101 * Hash table creation flags.
104 CDS_LFHT_AUTO_RESIZE
= (1U << 0),
105 CDS_LFHT_ACCOUNTING
= (1U << 1),
108 struct cds_lfht_mm_type
{
109 struct cds_lfht
*(*alloc_cds_lfht
)(unsigned long min_nr_alloc_buckets
,
110 unsigned long max_nr_buckets
);
111 void (*alloc_bucket_table
)(struct cds_lfht
*ht
, unsigned long order
);
112 void (*free_bucket_table
)(struct cds_lfht
*ht
, unsigned long order
);
113 struct cds_lfht_node
*(*bucket_at
)(struct cds_lfht
*ht
,
114 unsigned long index
);
117 extern const struct cds_lfht_mm_type cds_lfht_mm_order
;
118 extern const struct cds_lfht_mm_type cds_lfht_mm_chunk
;
119 extern const struct cds_lfht_mm_type cds_lfht_mm_mmap
;
122 * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
124 struct cds_lfht
*_cds_lfht_new(unsigned long init_size
,
125 unsigned long min_nr_alloc_buckets
,
126 unsigned long max_nr_buckets
,
128 const struct cds_lfht_mm_type
*mm
,
129 const struct rcu_flavor_struct
*flavor
,
130 pthread_attr_t
*attr
);
133 * cds_lfht_new - allocate a hash table.
134 * @init_size: number of buckets to allocate initially. Must be power of two.
135 * @min_nr_alloc_buckets: the minimum number of allocated buckets.
136 * (must be power of two)
137 * @max_nr_buckets: the maximum number of hash table buckets allowed.
138 * (must be power of two)
139 * @flags: hash table creation flags (can be combined with bitwise or: '|').
141 * CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
142 * CDS_LFHT_ACCOUNTING: count the number of node addition
143 * and removal in the table
144 * @attr: optional resize worker thread attributes. NULL for default.
146 * Return NULL on error.
147 * Note: the RCU flavor must be already included before the hash table header.
149 * The programmer is responsible for ensuring that resize operation has a
150 * priority equal to hash table updater threads. It should be performed by
151 * specifying the appropriate priority in the pthread "attr" argument, and,
152 * for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
153 * this priority level. Having lower priority for call_rcu and resize threads
154 * does not pose any correctness issue, but the resize operations could be
155 * starved by updates, thus leading to long hash table bucket chains.
156 * Threads calling cds_lfht_new are NOT required to be registered RCU
157 * read-side threads. It can be called very early. (e.g. before RCU is
161 struct cds_lfht
*cds_lfht_new(unsigned long init_size
,
162 unsigned long min_nr_alloc_buckets
,
163 unsigned long max_nr_buckets
,
165 pthread_attr_t
*attr
)
167 return _cds_lfht_new(init_size
, min_nr_alloc_buckets
, max_nr_buckets
,
168 flags
, NULL
, &rcu_flavor
, attr
);
172 * cds_lfht_destroy - destroy a hash table.
173 * @ht: the hash table to destroy.
174 * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
175 * The caller will typically want to free this pointer if dynamically
176 * allocated. The attr point can be NULL if the caller does not
177 * need to be informed of the value passed to cds_lfht_new().
179 * Return 0 on success, negative error value on error.
180 * Threads calling this API need to be registered RCU read-side threads.
181 * cds_lfht_destroy should *not* be called from a RCU read-side critical
184 int cds_lfht_destroy(struct cds_lfht
*ht
, pthread_attr_t
**attr
);
187 * cds_lfht_count_nodes - count the number of nodes in the hash table.
188 * @ht: the hash table.
189 * @split_count_before: sample the node count split-counter before traversal.
190 * @count: traverse the hash table, count the number of nodes observed.
191 * @split_count_after: sample the node count split-counter after traversal.
193 * Call with rcu_read_lock held.
194 * Threads calling this API need to be registered RCU read-side threads.
196 void cds_lfht_count_nodes(struct cds_lfht
*ht
,
197 long *split_count_before
,
198 unsigned long *count
,
199 long *split_count_after
);
202 * cds_lfht_lookup - lookup a node by key.
203 * @ht: the hash table.
204 * @hash: the key hash.
205 * @match: the key match function.
206 * @key: the current node key.
207 * @iter: node, if found (output). *iter->node set to NULL if not found.
209 * Call with rcu_read_lock held.
210 * Threads calling this API need to be registered RCU read-side threads.
211 * This function acts as a rcu_dereference() to read the node pointer.
213 void cds_lfht_lookup(struct cds_lfht
*ht
, unsigned long hash
,
214 cds_lfht_match_fct match
, const void *key
,
215 struct cds_lfht_iter
*iter
);
218 * cds_lfht_next_duplicate - get the next item with same key, after iterator.
219 * @ht: the hash table.
220 * @match: the key match function.
221 * @key: the current node key.
222 * @iter: input: current iterator.
223 * output: node, if found. *iter->node set to NULL if not found.
225 * Uses an iterator initialized by a lookup or traversal. Important: the
226 * iterator _needs_ to be initialized before calling
227 * cds_lfht_next_duplicate.
228 * Sets *iter-node to the following node with same key.
229 * Sets *iter->node to NULL if no following node exists with same key.
230 * RCU read-side lock must be held across cds_lfht_lookup and
231 * cds_lfht_next calls, and also between cds_lfht_next calls using the
232 * node returned by a previous cds_lfht_next.
233 * Call with rcu_read_lock held.
234 * Threads calling this API need to be registered RCU read-side threads.
235 * This function acts as a rcu_dereference() to read the node pointer.
237 void cds_lfht_next_duplicate(struct cds_lfht
*ht
,
238 cds_lfht_match_fct match
, const void *key
,
239 struct cds_lfht_iter
*iter
);
242 * cds_lfht_first - get the first node in the table.
243 * @ht: the hash table.
244 * @iter: First node, if exists (output). *iter->node set to NULL if not found.
246 * Output in "*iter". *iter->node set to NULL if table is empty.
247 * Call with rcu_read_lock held.
248 * Threads calling this API need to be registered RCU read-side threads.
249 * This function acts as a rcu_dereference() to read the node pointer.
251 void cds_lfht_first(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
254 * cds_lfht_next - get the next node in the table.
255 * @ht: the hash table.
256 * @iter: input: current iterator.
257 * output: next node, if exists. *iter->node set to NULL if not found.
259 * Input/Output in "*iter". *iter->node set to NULL if *iter was
260 * pointing to the last table node.
261 * Call with rcu_read_lock held.
262 * Threads calling this API need to be registered RCU read-side threads.
263 * This function acts as a rcu_dereference() to read the node pointer.
265 void cds_lfht_next(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
268 * cds_lfht_add - add a node to the hash table.
269 * @ht: the hash table.
270 * @hash: the key hash.
271 * @node: the node to add.
273 * This function supports adding redundant keys into the table.
274 * Call with rcu_read_lock held.
275 * Threads calling this API need to be registered RCU read-side threads.
276 * This function issues a full memory barrier before and after its
279 void cds_lfht_add(struct cds_lfht
*ht
, unsigned long hash
,
280 struct cds_lfht_node
*node
);
283 * cds_lfht_add_unique - add a node to hash table, if key is not present.
284 * @ht: the hash table.
285 * @hash: the node's hash.
286 * @match: the key match function.
287 * @key: the node's key.
288 * @node: the node to try adding.
290 * Return the node added upon success.
291 * Return the unique node already present upon failure. If
292 * cds_lfht_add_unique fails, the node passed as parameter should be
293 * freed by the caller. In this case, the caller does NOT need to wait
294 * for a grace period before freeing the node.
295 * Call with rcu_read_lock held.
296 * Threads calling this API need to be registered RCU read-side threads.
298 * The semantic of this function is that if only this function is used
299 * to add keys into the table, no duplicated keys should ever be
300 * observable in the table. The same guarantee apply for combination of
301 * add_unique and add_replace (see below).
303 * Upon success, this function issues a full memory barrier before and
304 * after its atomic commit. Upon failure, this function acts like a
305 * simple lookup operation: it acts as a rcu_dereference() to read the
306 * node pointer. The failure case does not guarantee any other memory
309 struct cds_lfht_node
*cds_lfht_add_unique(struct cds_lfht
*ht
,
311 cds_lfht_match_fct match
,
313 struct cds_lfht_node
*node
);
316 * cds_lfht_add_replace - replace or add a node within hash table.
317 * @ht: the hash table.
318 * @hash: the node's hash.
319 * @match: the key match function.
320 * @key: the node's key.
321 * @node: the node to add.
323 * Return the node replaced upon success. If no node matching the key
324 * was present, return NULL, which also means the operation succeeded.
325 * This replacement operation should never fail.
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 returned node.
331 * The semantic of replacement vs lookups and traversals is the
332 * following: if lookups and traversals are performed between a key
333 * unique insertion and its removal, we guarantee that the lookups and
334 * traversals will always find exactly one instance of the key if it is
335 * 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 * This function issues a full memory barrier before and after its
345 struct cds_lfht_node
*cds_lfht_add_replace(struct cds_lfht
*ht
,
347 cds_lfht_match_fct match
,
349 struct cds_lfht_node
*node
);
352 * cds_lfht_replace - replace a node pointed to by iter within hash table.
353 * @ht: the hash table.
354 * @old_iter: the iterator position of the node to replace.
355 * @hash: the node's hash.
356 * @match: the key match function.
357 * @key: the node's key.
358 * @new_node: the new node to use as replacement.
360 * Return 0 if replacement is successful, negative value otherwise.
361 * Replacing a NULL old node or an already removed node will fail with
363 * If the hash or value of the node to replace and the new node differ,
364 * this function returns -EINVAL without proceeding to the replacement.
365 * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
366 * RCU read-side lock must be held between lookup and replacement.
367 * Call with rcu_read_lock held.
368 * Threads calling this API need to be registered RCU read-side threads.
369 * After successful replacement, a grace period must be waited for before
370 * freeing the memory reserved for the old node (which can be accessed
371 * with cds_lfht_iter_get_node).
373 * The semantic of replacement vs lookups is the same as
374 * cds_lfht_add_replace().
376 * Upon success, this function issues a full memory barrier before and
377 * after its atomic commit. Upon failure, this function does not issue
378 * any memory barrier.
380 int cds_lfht_replace(struct cds_lfht
*ht
,
381 struct cds_lfht_iter
*old_iter
,
383 cds_lfht_match_fct match
,
385 struct cds_lfht_node
*new_node
);
388 * cds_lfht_del - remove node pointed to by iterator from hash table.
389 * @ht: the hash table.
390 * @node: the node to delete.
392 * Return 0 if the node is successfully removed, negative value
394 * Deleting a NULL node or an already removed node will fail with a
396 * Node can be looked up with cds_lfht_lookup and cds_lfht_next,
397 * followed by use of cds_lfht_iter_get_node.
398 * RCU read-side lock must be held between lookup and removal.
399 * Call with rcu_read_lock held.
400 * Threads calling this API need to be registered RCU read-side threads.
401 * After successful removal, a grace period must be waited for before
402 * freeing the memory reserved for old node (which can be accessed with
403 * cds_lfht_iter_get_node).
404 * Upon success, this function issues a full memory barrier before and
405 * after its atomic commit. Upon failure, this function does not issue
406 * any memory barrier.
408 int cds_lfht_del(struct cds_lfht
*ht
, struct cds_lfht_node
*node
);
411 * cds_lfht_is_node_deleted - query whether a node is removed from hash table.
413 * Return non-zero if the node is deleted from the hash table, 0
415 * Node can be looked up with cds_lfht_lookup and cds_lfht_next,
416 * followed by use of cds_lfht_iter_get_node.
417 * RCU read-side lock must be held between lookup and call to this
419 * Call with rcu_read_lock held.
420 * Threads calling this API need to be registered RCU read-side threads.
421 * This function does not issue any memory barrier.
423 int cds_lfht_is_node_deleted(struct cds_lfht_node
*node
);
426 * cds_lfht_resize - Force a hash table resize
427 * @ht: the hash table.
428 * @new_size: update to this hash table size.
430 * Threads calling this API need to be registered RCU read-side threads.
431 * This function does not (necessarily) issue memory barriers.
432 * cds_lfht_resize should *not* be called from a RCU read-side critical
435 void cds_lfht_resize(struct cds_lfht
*ht
, unsigned long new_size
);
438 * Note: it is safe to perform element removal (del), replacement, or
439 * any hash table update operation during any of the following hash
441 * These functions act as rcu_dereference() to read the node pointers.
443 #define cds_lfht_for_each(ht, iter, node) \
444 for (cds_lfht_first(ht, iter), \
445 node = cds_lfht_iter_get_node(iter); \
447 cds_lfht_next(ht, iter), \
448 node = cds_lfht_iter_get_node(iter))
450 #define cds_lfht_for_each_duplicate(ht, hash, match, key, iter, node) \
451 for (cds_lfht_lookup(ht, hash, match, key, iter), \
452 node = cds_lfht_iter_get_node(iter); \
454 cds_lfht_next_duplicate(ht, match, key, iter), \
455 node = cds_lfht_iter_get_node(iter))
457 #define cds_lfht_for_each_entry(ht, iter, pos, member) \
458 for (cds_lfht_first(ht, iter), \
459 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
460 __typeof__(*(pos)), member); \
461 cds_lfht_iter_get_node(iter) != NULL; \
462 cds_lfht_next(ht, iter), \
463 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
464 __typeof__(*(pos)), member))
466 #define cds_lfht_for_each_entry_duplicate(ht, hash, match, key, \
468 for (cds_lfht_lookup(ht, hash, match, key, iter), \
469 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
470 __typeof__(*(pos)), member); \
471 cds_lfht_iter_get_node(iter) != NULL; \
472 cds_lfht_next_duplicate(ht, match, key, iter), \
473 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
474 __typeof__(*(pos)), member))
480 #endif /* _URCU_RCULFHASH_H */