urcu/rculfhash.h

   1 #ifndef _URCU_RCULFHASH_H
   2 #define _URCU_RCULFHASH_H
   3
   4 /*
   5  * urcu/rculfhash.h
   6  *
   7  * Userspace RCU library - Lock-Free RCU Hash Table
   8  *
   9  * Copyright 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  10  * Copyright 2011 - Lai Jiangshan <laijs@cn.fujitsu.com>
  11  *
  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.
  16  *
  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.
  21  *
  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
  25  *
  26  * Include this file _after_ including your URCU flavor.
  27  */
  28
  29 #include <stdint.h>
  30 #include <urcu/compiler.h>
  31 #include <urcu-call-rcu.h>
  32 #include <urcu-flavor.h>
  33
  34 #ifdef __cplusplus
  35 extern "C" {
  36 #endif
  37
  38 /*
  39  * cds_lfht_node: Contains the next pointers and reverse-hash
  40  * value required for lookup and traversal of the hash table.
  41  *
  42  * struct cds_lfht_node should be aligned on 4-bytes boundaries because
  43  * the two lower bits are used as flags.
  44  *
  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.
  48  *
  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.
  52  */
  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)));
  57
  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;
  61 };
  62
  63 static inline
  64 struct cds_lfht_node *cds_lfht_iter_get_node(struct cds_lfht_iter *iter)
  65 {
  66         return iter->node;
  67 }
  68
  69 struct cds_lfht;
  70
  71 /*
  72  * Caution !
  73  * Ensure reader and writer threads are registered as urcu readers.
  74  */
  75
  76 typedef int (*cds_lfht_match_fct)(struct cds_lfht_node *node, const void *key);
  77
  78 /*
  79  * cds_lfht_node_init - initialize a hash table node
  80  * @node: the node to initialize.
  81  *
  82  * This function is kept to be eventually used for debugging purposes
  83  * (detection of memory corruption).
  84  */
  85 static inline
  86 void cds_lfht_node_init(struct cds_lfht_node *node)
  87 {
  88 }
  89
  90 /*
  91  * Hash table creation flags.
  92  */
  93 enum {
  94         CDS_LFHT_AUTO_RESIZE = (1U << 0),
  95         CDS_LFHT_ACCOUNTING = (1U << 1),
  96 };
  97
  98 /*
  99  * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
 100  */
 101 struct cds_lfht *_cds_lfht_new(unsigned long init_size,
 102                         unsigned long min_nr_alloc_buckets,
 103                         unsigned long max_nr_buckets,
 104                         int flags,
 105                         const struct rcu_flavor_struct *flavor,
 106                         pthread_attr_t *attr);
 107
 108 /*
 109  * cds_lfht_new - allocate a hash table.
 110  * @init_size: number of buckets to allocate initially. Must be power of two.
 111  * @min_nr_alloc_buckets: the minimum number of allocated buckets.
 112  *                        (must be power of two)
 113  * @max_nr_buckets: the maximum number of hash table buckets allowed.
 114  *                  (must be power of two)
 115  * @flags: hash table creation flags (can be combined with bitwise or: '|').
 116  *           0: no flags.
 117  *           CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
 118  *           CDS_LFHT_ACCOUNTING: count the number of node addition
 119  *                                and removal in the table
 120  * @attr: optional resize worker thread attributes. NULL for default.
 121  *
 122  * Return NULL on error.
 123  * Note: the RCU flavor must be already included before the hash table header.
 124  *
 125  * The programmer is responsible for ensuring that resize operation has a
 126  * priority equal to hash table updater threads. It should be performed by
 127  * specifying the appropriate priority in the pthread "attr" argument, and,
 128  * for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
 129  * this priority level. Having lower priority for call_rcu and resize threads
 130  * does not pose any correctness issue, but the resize operations could be
 131  * starved by updates, thus leading to long hash table bucket chains.
 132  * Threads calling this API are NOT required to be registered RCU read-side
 133  * threads. It can be called very early.(before rcu is initialized ...etc.)
 134  */
 135 static inline
 136 struct cds_lfht *cds_lfht_new(unsigned long init_size,
 137                         unsigned long min_nr_alloc_buckets,
 138                         unsigned long max_nr_buckets,
 139                         int flags,
 140                         pthread_attr_t *attr)
 141 {
 142         return _cds_lfht_new(init_size, min_nr_alloc_buckets, max_nr_buckets,
 143                         flags, &rcu_flavor, attr);
 144 }
 145
 146 /*
 147  * cds_lfht_destroy - destroy a hash table.
 148  * @ht: the hash table to destroy.
 149  * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
 150  *        The caller will typically want to free this pointer if dynamically
 151  *        allocated. The attr point can be NULL if the caller does not
 152  *        need to be informed of the value passed to cds_lfht_new().
 153  *
 154  * Return 0 on success, negative error value on error.
 155  * Threads calling this API need to be registered RCU read-side threads.
 156  */
 157 int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
 158
 159 /*
 160  * cds_lfht_count_nodes - count the number of nodes in the hash table.
 161  * @ht: the hash table.
 162  * @split_count_before: Sample the node count split-counter before traversal.
 163  * @count: Traverse the hash table, count the number of nodes observed.
 164  * @removed: Number of logically removed nodes observed during traversal.
 165  * @split_count_after: Sample the node count split-counter after traversal.
 166  *
 167  * Call with rcu_read_lock held.
 168  * Threads calling this API need to be registered RCU read-side threads.
 169  */
 170 void cds_lfht_count_nodes(struct cds_lfht *ht,
 171                 long *split_count_before,
 172                 unsigned long *count,
 173                 unsigned long *removed,
 174                 long *split_count_after);
 175
 176 /*
 177  * cds_lfht_lookup - lookup a node by key.
 178  * @ht: the hash table.
 179  * @hash: the key hash.
 180  * @match: the key match function.
 181  * @key: the current node key.
 182  * @iter: Node, if found (output). *iter->node set to NULL if not found.
 183  *
 184  * Call with rcu_read_lock held.
 185  * Threads calling this API need to be registered RCU read-side threads.
 186  */
 187 void cds_lfht_lookup(struct cds_lfht *ht, unsigned long hash,
 188                 cds_lfht_match_fct match, const void *key,
 189                 struct cds_lfht_iter *iter);
 190
 191 /*
 192  * cds_lfht_next_duplicate - get the next item with same key (after a lookup).
 193  * @ht: the hash table.
 194  * @match: the key match function.
 195  * @key: the current node key.
 196  * @iter: Node, if found (output). *iter->node set to NULL if not found.
 197  *
 198  * Uses an iterator initialized by a lookup.
 199  * Sets *iter-node to the following node with same key.
 200  * Sets *iter->node to NULL if no following node exists with same key.
 201  * RCU read-side lock must be held across cds_lfht_lookup and
 202  * cds_lfht_next calls, and also between cds_lfht_next calls using the
 203  * node returned by a previous cds_lfht_next.
 204  * Call with rcu_read_lock held.
 205  * Threads calling this API need to be registered RCU read-side threads.
 206  */
 207 void cds_lfht_next_duplicate(struct cds_lfht *ht,
 208                 cds_lfht_match_fct match, const void *key,
 209                 struct cds_lfht_iter *iter);
 210
 211 /*
 212  * cds_lfht_first - get the first node in the table.
 213  * @ht: the hash table.
 214  * @iter: First node, if exists (output). *iter->node set to NULL if not found.
 215  *
 216  * Output in "*iter". *iter->node set to NULL if table is empty.
 217  * Call with rcu_read_lock held.
 218  * Threads calling this API need to be registered RCU read-side threads.
 219  */
 220 void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 221
 222 /*
 223  * cds_lfht_next - get the next node in the table.
 224  * @ht: the hash table.
 225  * @iter: Next node, if exists (output). *iter->node set to NULL if not found.
 226  *
 227  * Input/Output in "*iter". *iter->node set to NULL if *iter was
 228  * pointing to the last table node.
 229  * Call with rcu_read_lock held.
 230  * Threads calling this API need to be registered RCU read-side threads.
 231  */
 232 void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 233
 234 /*
 235  * cds_lfht_add - add a node to the hash table.
 236  * @ht: the hash table.
 237  * @hash: the key hash.
 238  * @node: the node to add.
 239  *
 240  * This function supports adding redundant keys into the table.
 241  * Call with rcu_read_lock held.
 242  * Threads calling this API need to be registered RCU read-side threads.
 243  */
 244 void cds_lfht_add(struct cds_lfht *ht, unsigned long hash,
 245                 struct cds_lfht_node *node);
 246
 247 /*
 248  * cds_lfht_add_unique - add a node to hash table, if key is not present.
 249  * @ht: the hash table.
 250  * @hash: the node's hash.
 251  * @match: the key match function.
 252  * @key: the node's key.
 253  * @node: the node to try adding.
 254  *
 255  * Return the node added upon success.
 256  * Return the unique node already present upon failure. If
 257  * cds_lfht_add_unique fails, the node passed as parameter should be
 258  * freed by the caller.
 259  * Call with rcu_read_lock held.
 260  * Threads calling this API need to be registered RCU read-side threads.
 261  *
 262  * The semantic of this function is that if only this function is used
 263  * to add keys into the table, no duplicated keys should ever be
 264  * observable in the table. The same guarantee apply for combination of
 265  * add_unique and add_replace (see below).
 266  */
 267 struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
 268                 unsigned long hash,
 269                 cds_lfht_match_fct match,
 270                 const void *key,
 271                 struct cds_lfht_node *node);
 272
 273 /*
 274  * cds_lfht_add_replace - replace or add a node within hash table.
 275  * @ht: the hash table.
 276  * @hash: the node's hash.
 277  * @match: the key match function.
 278  * @key: the node's key.
 279  * @node: the node to add.
 280  *
 281  * Return the node replaced upon success. If no node matching the key
 282  * was present, return NULL, which also means the operation succeeded.
 283  * This replacement operation should never fail.
 284  * Call with rcu_read_lock held.
 285  * Threads calling this API need to be registered RCU read-side threads.
 286  * After successful replacement, a grace period must be waited for before
 287  * freeing the memory reserved for the returned node.
 288  *
 289  * The semantic of replacement vs lookups is the following: if lookups
 290  * are performed between a key unique insertion and its removal, we
 291  * guarantee that the lookups and get next will always find exactly one
 292  * instance of the key if it is replaced concurrently with the lookups.
 293  *
 294  * Providing this semantic allows us to ensure that replacement-only
 295  * schemes will never generate duplicated keys. It also allows us to
 296  * guarantee that a combination of add_replace and add_unique updates
 297  * will never generate duplicated keys.
 298  */
 299 struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
 300                 unsigned long hash,
 301                 cds_lfht_match_fct match,
 302                 const void *key,
 303                 struct cds_lfht_node *node);
 304
 305 /*
 306  * cds_lfht_replace - replace a node pointer to by iter within hash table.
 307  * @ht: the hash table.
 308  * @old_iter: the iterator position of the node to replace.
 309  * @now_node: the new node to try using for replacement.
 310  *
 311  * Return 0 if replacement is successful, negative value otherwise.
 312  * Replacing a NULL old node or an already removed node will fail with a
 313  * negative value.
 314  * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
 315  * RCU read-side lock must be held between lookup and replacement.
 316  * Call with rcu_read_lock held.
 317  * Threads calling this API need to be registered RCU read-side threads.
 318  * After successful replacement, a grace period must be waited for before
 319  * freeing the memory reserved for the old node (which can be accessed
 320  * with cds_lfht_iter_get_node).
 321  *
 322  * The semantic of replacement vs lookups is the following: if lookups
 323  * are performed between a key unique insertion and its removal, we
 324  * guarantee that the lookups and get next will always find exactly one
 325  * instance of the key if it is replaced concurrently with the lookups.
 326  *
 327  * Providing this semantic allows us to ensure that replacement-only
 328  * schemes will never generate duplicated keys. It also allows us to
 329  * guarantee that a combination of add_replace and add_unique updates
 330  * will never generate duplicated keys.
 331  */
 332 int cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_iter *old_iter,
 333                 struct cds_lfht_node *new_node);
 334
 335 /*
 336  * cds_lfht_del - remove node pointed to by iterator from hash table.
 337  * @ht: the hash table.
 338  * @iter: the iterator position of the node to delete.
 339  *
 340  * Return 0 if the node is successfully removed, negative value
 341  * otherwise.
 342  * Replacing a NULL node or an already removed node will fail with a
 343  * negative value.
 344  * Node can be looked up with cds_lfht_lookup and cds_lfht_next.
 345  * cds_lfht_iter_get_node.
 346  * RCU read-side lock must be held between lookup and removal.
 347  * Call with rcu_read_lock held.
 348  * Threads calling this API need to be registered RCU read-side threads.
 349  * After successful removal, a grace period must be waited for before
 350  * freeing the memory reserved for old node (which can be accessed with
 351  * cds_lfht_iter_get_node).
 352  */
 353 int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 354
 355 /*
 356  * cds_lfht_resize - Force a hash table resize
 357  * @ht: the hash table.
 358  * @new_size: update to this hash table size.
 359  *
 360  * Threads calling this API need to be registered RCU read-side threads.
 361  */
 362 void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);
 363
 364 /*
 365  * Note: cds_lfht_for_each are safe for element removal during
 366  * iteration.
 367  */
 368 #define cds_lfht_for_each(ht, iter, node)                               \
 369         for (cds_lfht_first(ht, iter),                                  \
 370                         node = cds_lfht_iter_get_node(iter);            \
 371                 node != NULL;                                           \
 372                 cds_lfht_next(ht, iter),                                \
 373                         node = cds_lfht_iter_get_node(iter))
 374
 375 #define cds_lfht_for_each_duplicate(ht, hash, match, key, iter, node)   \
 376         for (cds_lfht_lookup(ht, hash, match, key, iter),               \
 377                         node = cds_lfht_iter_get_node(iter);            \
 378                 node != NULL;                                           \
 379                 cds_lfht_next_duplicate(ht, match, key, iter),          \
 380                         node = cds_lfht_iter_get_node(iter))
 381
 382 #define cds_lfht_for_each_entry(ht, iter, pos, member)                  \
 383         for (cds_lfht_first(ht, iter),                                  \
 384                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 385                                         typeof(*(pos)), member);        \
 386                 &(pos)->member != NULL;                                 \
 387                 cds_lfht_next(ht, iter),                                \
 388                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 389                                         typeof(*(pos)), member))
 390
 391 #define cds_lfht_for_each_entry_duplicate(ht, hash, match, key,         \
 392                                 iter, pos, member)                      \
 393         for (cds_lfht_lookup(ht, hash, match, key, iter),               \
 394                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 395                                         typeof(*(pos)), member);        \
 396                 &(pos)->member != NULL;                                 \
 397                 cds_lfht_next_duplicate(ht, match, key, iter),          \
 398                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 399                                         typeof(*(pos)), member))
 400
 401 #ifdef __cplusplus
 402 }
 403 #endif
 404
 405 #endif /* _URCU_RCULFHASH_H */