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, 0 is accepted, means
137 * @flags: hash table creation flags (can be combined with bitwise or: '|').
139 * CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
140 * CDS_LFHT_ACCOUNTING: count the number of node addition
141 * and removal in the table
142 * @attr: optional resize worker thread attributes. NULL for default.
144 * Return NULL on error.
145 * Note: the RCU flavor must be already included before the hash table header.
147 * The programmer is responsible for ensuring that resize operation has a
148 * priority equal to hash table updater threads. It should be performed by
149 * specifying the appropriate priority in the pthread "attr" argument, and,
150 * for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
151 * this priority level. Having lower priority for call_rcu and resize threads
152 * does not pose any correctness issue, but the resize operations could be
153 * starved by updates, thus leading to long hash table bucket chains.
154 * Threads calling cds_lfht_new are NOT required to be registered RCU
155 * read-side threads. It can be called very early. (e.g. before RCU is
159 struct cds_lfht
*cds_lfht_new(unsigned long init_size
,
160 unsigned long min_nr_alloc_buckets
,
161 unsigned long max_nr_buckets
,
163 pthread_attr_t
*attr
)
165 return _cds_lfht_new(init_size
, min_nr_alloc_buckets
, max_nr_buckets
,
166 flags
, NULL
, &rcu_flavor
, attr
);
170 * cds_lfht_destroy - destroy a hash table.
171 * @ht: the hash table to destroy.
172 * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
173 * The caller will typically want to free this pointer if dynamically
174 * allocated. The attr point can be NULL if the caller does not
175 * need to be informed of the value passed to cds_lfht_new().
177 * Return 0 on success, negative error value on error.
178 * Threads calling this API need to be registered RCU read-side threads.
179 * cds_lfht_destroy should *not* be called from a RCU read-side critical
180 * section. It should *not* be called from call_rcu thread context
182 * In userspace RCU 0.7.x, for QSBR RCU flavor, cds_lfht_destroy() has a
183 * side-effect: it puts the caller thread in "online" state. This will
184 * be fixed in userspace RCU 0.8.x.
186 int cds_lfht_destroy(struct cds_lfht
*ht
, pthread_attr_t
**attr
);
189 * cds_lfht_count_nodes - count the number of nodes in the hash table.
190 * @ht: the hash table.
191 * @split_count_before: sample the node count split-counter before traversal.
192 * @count: traverse the hash table, count the number of nodes observed.
193 * @split_count_after: sample the node count split-counter after traversal.
195 * Call with rcu_read_lock held.
196 * Threads calling this API need to be registered RCU read-side threads.
198 void cds_lfht_count_nodes(struct cds_lfht
*ht
,
199 long *split_count_before
,
200 unsigned long *count
,
201 long *split_count_after
);
204 * cds_lfht_lookup - lookup a node by key.
205 * @ht: the hash table.
206 * @hash: the key hash.
207 * @match: the key match function.
208 * @key: the current node key.
209 * @iter: node, if found (output). *iter->node set to NULL if not found.
211 * Call with rcu_read_lock held.
212 * Threads calling this API need to be registered RCU read-side threads.
213 * This function acts as a rcu_dereference() to read the node pointer.
215 void cds_lfht_lookup(struct cds_lfht
*ht
, unsigned long hash
,
216 cds_lfht_match_fct match
, const void *key
,
217 struct cds_lfht_iter
*iter
);
220 * cds_lfht_next_duplicate - get the next item with same key, after iterator.
221 * @ht: the hash table.
222 * @match: the key match function.
223 * @key: the current node key.
224 * @iter: input: current iterator.
225 * output: node, if found. *iter->node set to NULL if not found.
227 * Uses an iterator initialized by a lookup or traversal. Important: the
228 * iterator _needs_ to be initialized before calling
229 * cds_lfht_next_duplicate.
230 * Sets *iter-node to the following node with same key.
231 * Sets *iter->node to NULL if no following node exists with same key.
232 * RCU read-side lock must be held across cds_lfht_lookup and
233 * cds_lfht_next calls, and also between cds_lfht_next calls using the
234 * node returned by a previous cds_lfht_next.
235 * Call with rcu_read_lock held.
236 * Threads calling this API need to be registered RCU read-side threads.
237 * This function acts as a rcu_dereference() to read the node pointer.
239 void cds_lfht_next_duplicate(struct cds_lfht
*ht
,
240 cds_lfht_match_fct match
, const void *key
,
241 struct cds_lfht_iter
*iter
);
244 * cds_lfht_first - get the first node in the table.
245 * @ht: the hash table.
246 * @iter: First node, if exists (output). *iter->node set to NULL if not found.
248 * Output in "*iter". *iter->node set to NULL if table is empty.
249 * Call with rcu_read_lock held.
250 * Threads calling this API need to be registered RCU read-side threads.
251 * This function acts as a rcu_dereference() to read the node pointer.
253 void cds_lfht_first(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
256 * cds_lfht_next - get the next node in the table.
257 * @ht: the hash table.
258 * @iter: input: current iterator.
259 * output: next node, if exists. *iter->node set to NULL if not found.
261 * Input/Output in "*iter". *iter->node set to NULL if *iter was
262 * pointing to the last table node.
263 * Call with rcu_read_lock held.
264 * Threads calling this API need to be registered RCU read-side threads.
265 * This function acts as a rcu_dereference() to read the node pointer.
267 void cds_lfht_next(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
);
270 * cds_lfht_add - add a node to the hash table.
271 * @ht: the hash table.
272 * @hash: the key hash.
273 * @node: the node to add.
275 * This function supports adding redundant keys into the table.
276 * Call with rcu_read_lock held.
277 * Threads calling this API need to be registered RCU read-side threads.
278 * This function issues a full memory barrier before and after its
281 void cds_lfht_add(struct cds_lfht
*ht
, unsigned long hash
,
282 struct cds_lfht_node
*node
);
285 * cds_lfht_add_unique - add a node to hash table, if key is not present.
286 * @ht: the hash table.
287 * @hash: the node's hash.
288 * @match: the key match function.
289 * @key: the node's key.
290 * @node: the node to try adding.
292 * Return the node added upon success.
293 * Return the unique node already present upon failure. If
294 * cds_lfht_add_unique fails, the node passed as parameter should be
295 * freed by the caller. In this case, the caller does NOT need to wait
296 * for a grace period before freeing the node.
297 * Call with rcu_read_lock held.
298 * Threads calling this API need to be registered RCU read-side threads.
300 * The semantic of this function is that if only this function is used
301 * to add keys into the table, no duplicated keys should ever be
302 * observable in the table. The same guarantee apply for combination of
303 * add_unique and add_replace (see below).
305 * Upon success, this function issues a full memory barrier before and
306 * after its atomic commit. Upon failure, this function acts like a
307 * simple lookup operation: it acts as a rcu_dereference() to read the
308 * node pointer. The failure case does not guarantee any other memory
311 struct cds_lfht_node
*cds_lfht_add_unique(struct cds_lfht
*ht
,
313 cds_lfht_match_fct match
,
315 struct cds_lfht_node
*node
);
318 * cds_lfht_add_replace - replace or add a node within hash table.
319 * @ht: the hash table.
320 * @hash: the node's hash.
321 * @match: the key match function.
322 * @key: the node's key.
323 * @node: the node to add.
325 * Return the node replaced upon success. If no node matching the key
326 * was present, return NULL, which also means the operation succeeded.
327 * This replacement operation should never fail.
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 returned node.
333 * The semantic of replacement vs lookups and traversals is the
334 * following: if lookups and traversals are performed between a key
335 * unique insertion and its removal, we guarantee that the lookups and
336 * traversals will always find exactly one instance of the key if it is
337 * 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 * This function issues a full memory barrier before and after its
347 struct cds_lfht_node
*cds_lfht_add_replace(struct cds_lfht
*ht
,
349 cds_lfht_match_fct match
,
351 struct cds_lfht_node
*node
);
354 * cds_lfht_replace - replace a node pointed to by iter within hash table.
355 * @ht: the hash table.
356 * @old_iter: the iterator position of the node to replace.
357 * @hash: the node's hash.
358 * @match: the key match function.
359 * @key: the node's key.
360 * @new_node: the new node to use as replacement.
362 * Return 0 if replacement is successful, negative value otherwise.
363 * Replacing a NULL old node or an already removed node will fail with
365 * If the hash or value of the node to replace and the new node differ,
366 * this function returns -EINVAL without proceeding to the replacement.
367 * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
368 * RCU read-side lock must be held between lookup and replacement.
369 * Call with rcu_read_lock held.
370 * Threads calling this API need to be registered RCU read-side threads.
371 * After successful replacement, a grace period must be waited for before
372 * freeing the memory reserved for the old node (which can be accessed
373 * with cds_lfht_iter_get_node).
375 * The semantic of replacement vs lookups is the same as
376 * cds_lfht_add_replace().
378 * Upon success, this function issues a full memory barrier before and
379 * after its atomic commit. Upon failure, this function does not issue
380 * any memory barrier.
382 int cds_lfht_replace(struct cds_lfht
*ht
,
383 struct cds_lfht_iter
*old_iter
,
385 cds_lfht_match_fct match
,
387 struct cds_lfht_node
*new_node
);
390 * cds_lfht_del - remove node pointed to by iterator from hash table.
391 * @ht: the hash table.
392 * @node: the node to delete.
394 * Return 0 if the node is successfully removed, negative value
396 * Deleting a NULL node or an already removed node will fail with a
398 * Node can be looked up with cds_lfht_lookup and cds_lfht_next,
399 * followed by use of cds_lfht_iter_get_node.
400 * RCU read-side lock must be held between lookup and removal.
401 * Call with rcu_read_lock held.
402 * Threads calling this API need to be registered RCU read-side threads.
403 * After successful removal, a grace period must be waited for before
404 * freeing the memory reserved for old node (which can be accessed with
405 * cds_lfht_iter_get_node).
406 * Upon success, this function issues a full memory barrier before and
407 * after its atomic commit. Upon failure, this function does not issue
408 * any memory barrier.
410 int cds_lfht_del(struct cds_lfht
*ht
, struct cds_lfht_node
*node
);
413 * cds_lfht_is_node_deleted - query whether a node is removed from hash table.
415 * Return non-zero if the node is deleted from the hash table, 0
417 * Node can be looked up with cds_lfht_lookup and cds_lfht_next,
418 * followed by use of cds_lfht_iter_get_node.
419 * RCU read-side lock must be held between lookup and call to this
421 * Call with rcu_read_lock held.
422 * Threads calling this API need to be registered RCU read-side threads.
423 * This function does not issue any memory barrier.
425 int cds_lfht_is_node_deleted(struct cds_lfht_node
*node
);
428 * cds_lfht_resize - Force a hash table resize
429 * @ht: the hash table.
430 * @new_size: update to this hash table size.
432 * Threads calling this API need to be registered RCU read-side threads.
433 * This function does not (necessarily) issue memory barriers.
434 * cds_lfht_resize should *not* be called from a RCU read-side critical
436 * In userspace RCU 0.7.x, for QSBR RCU flavor, cds_lfht_resize() has a
437 * side-effect: it puts the caller thread in "online" state. This will
438 * be fixed in userspace RCU 0.8.x.
440 void cds_lfht_resize(struct cds_lfht
*ht
, unsigned long new_size
);
443 * Note: it is safe to perform element removal (del), replacement, or
444 * any hash table update operation during any of the following hash
446 * These functions act as rcu_dereference() to read the node pointers.
448 #define cds_lfht_for_each(ht, iter, node) \
449 for (cds_lfht_first(ht, iter), \
450 node = cds_lfht_iter_get_node(iter); \
452 cds_lfht_next(ht, iter), \
453 node = cds_lfht_iter_get_node(iter))
455 #define cds_lfht_for_each_duplicate(ht, hash, match, key, iter, node) \
456 for (cds_lfht_lookup(ht, hash, match, key, iter), \
457 node = cds_lfht_iter_get_node(iter); \
459 cds_lfht_next_duplicate(ht, match, key, iter), \
460 node = cds_lfht_iter_get_node(iter))
462 #define cds_lfht_for_each_entry(ht, iter, pos, member) \
463 for (cds_lfht_first(ht, iter), \
464 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
465 __typeof__(*(pos)), member); \
466 cds_lfht_iter_get_node(iter) != NULL; \
467 cds_lfht_next(ht, iter), \
468 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
469 __typeof__(*(pos)), member))
471 #define cds_lfht_for_each_entry_duplicate(ht, hash, match, key, \
473 for (cds_lfht_lookup(ht, hash, match, key, iter), \
474 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
475 __typeof__(*(pos)), member); \
476 cds_lfht_iter_get_node(iter) != NULL; \
477 cds_lfht_next_duplicate(ht, match, key, iter), \
478 pos = caa_container_of(cds_lfht_iter_get_node(iter), \
479 __typeof__(*(pos)), member))
485 #endif /* _URCU_RCULFHASH_H */