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  *
  11  * This library is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU Lesser General Public
  13  * License as published by the Free Software Foundation; either
  14  * version 2.1 of the License, or (at your option) any later version.
  15  *
  16  * This library is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  19  * Lesser General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU Lesser General Public
  22  * License along with this library; if not, write to the Free Software
  23  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  24  *
  25  * Include this file _after_ including your URCU flavor.
  26  */
  27
  28 #include <stdint.h>
  29 #include <urcu/compiler.h>
  30 #include <urcu-call-rcu.h>
  31
  32 #ifdef __cplusplus
  33 extern "C" {
  34 #endif
  35
  36 /*
  37  * cds_lfht_node: Contains the next pointers and reverse-hash
  38  * value required for lookup and traversal of the hash table.
  39  *
  40  * struct cds_lfht_node should be aligned on 4-bytes boundaries because
  41  * the two lower bits are used as flags.
  42  *
  43  * struct cds_lfht_node can be embedded into a structure (as a field).
  44  * caa_container_of() can be used to get the structure from the struct
  45  * cds_lfht_node after a lookup.
  46  *
  47  * The structure which embeds it typically holds the key (or key-value
  48  * pair) of the object. The caller code is responsible for calculation
  49  * of the hash value for cds_lfht APIs.
  50  */
  51 struct cds_lfht_node {
  52         struct cds_lfht_node *next;     /* ptr | BUCKET_FLAG | REMOVED_FLAG */
  53         unsigned long reverse_hash;
  54 } __attribute__((aligned(4)));
  55
  56 /* cds_lfht_iter: Used to track state while traversing a hash chain. */
  57 struct cds_lfht_iter {
  58         struct cds_lfht_node *node, *next;
  59 };
  60
  61 static inline
  62 struct cds_lfht_node *cds_lfht_iter_get_node(struct cds_lfht_iter *iter)
  63 {
  64         return iter->node;
  65 }
  66
  67 struct cds_lfht;
  68
  69 /*
  70  * Caution !
  71  * Ensure reader and writer threads are registered as urcu readers.
  72  */
  73
  74 typedef int (*cds_lfht_match_fct)(struct cds_lfht_node *node, void *key);
  75
  76 /*
  77  * cds_lfht_node_init - initialize a hash table node
  78  * @node: the node to initialize.
  79  *
  80  * This function is kept to be eventually used for debugging purposes
  81  * (detection of memory corruption).
  82  */
  83 static inline
  84 void cds_lfht_node_init(struct cds_lfht_node *node)
  85 {
  86 }
  87
  88 /*
  89  * Hash table creation flags.
  90  */
  91 enum {
  92         CDS_LFHT_AUTO_RESIZE = (1U << 0),
  93         CDS_LFHT_ACCOUNTING = (1U << 1),
  94 };
  95
  96 /*
  97  * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
  98  */
  99 struct cds_lfht *_cds_lfht_new(unsigned long init_size,
 100                         unsigned long min_alloc_size,
 101                         int flags,
 102                         void (*cds_lfht_call_rcu)(struct rcu_head *head,
 103                                 void (*func)(struct rcu_head *head)),
 104                         void (*cds_lfht_synchronize_rcu)(void),
 105                         void (*cds_lfht_rcu_read_lock)(void),
 106                         void (*cds_lfht_rcu_read_unlock)(void),
 107                         void (*cds_lfht_rcu_thread_offline)(void),
 108                         void (*cds_lfht_rcu_thread_online)(void),
 109                         void (*cds_lfht_rcu_register_thread)(void),
 110                         void (*cds_lfht_rcu_unregister_thread)(void),
 111                         pthread_attr_t *attr);
 112
 113 /*
 114  * cds_lfht_new - allocate a hash table.
 115  * @init_size: number of nodes to allocate initially. Must be power of two.
 116  * @min_alloc_size: the smallest allocation size to use. Must be power of two.
 117  * @flags: hash table creation flags (can be combined with bitwise or: '|').
 118  *           0: no flags.
 119  *           CDS_LFHT_AUTO_RESIZE: automatically resize hash 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 need to be registered RCU read-side threads.
 133  */
 134 static inline
 135 struct cds_lfht *cds_lfht_new(unsigned long init_size,
 136                         unsigned long min_alloc_size,
 137                         int flags,
 138                         pthread_attr_t *attr)
 139 {
 140         return _cds_lfht_new(init_size, min_alloc_size, flags,
 141                         call_rcu, synchronize_rcu, rcu_read_lock,
 142                         rcu_read_unlock, rcu_thread_offline,
 143                         rcu_thread_online, rcu_register_thread,
 144                         rcu_unregister_thread, attr);
 145 }
 146
 147 /*
 148  * cds_lfht_destroy - destroy a hash table.
 149  * @ht: the hash table to destroy.
 150  * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
 151  *        The caller will typically want to free this pointer if dynamically
 152  *        allocated. The attr point can be NULL if the caller does not
 153  *        need to be informed of the value passed to cds_lfht_new().
 154  *
 155  * Return 0 on success, negative error value on error.
 156  * Threads calling this API need to be registered RCU read-side threads.
 157  */
 158 int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
 159
 160 /*
 161  * cds_lfht_count_nodes - count the number of nodes in the hash table.
 162  * @ht: the hash table.
 163  * @split_count_before: Sample the node count split-counter before traversal.
 164  * @count: Traverse the hash table, count the number of nodes observed.
 165  * @removed: Number of logically removed nodes observed during traversal.
 166  * @split_count_after: Sample the node count split-counter after traversal.
 167  *
 168  * Call with rcu_read_lock held.
 169  * Threads calling this API need to be registered RCU read-side threads.
 170  */
 171 void cds_lfht_count_nodes(struct cds_lfht *ht,
 172                 long *split_count_before,
 173                 unsigned long *count,
 174                 unsigned long *removed,
 175                 long *split_count_after);
 176
 177 /*
 178  * cds_lfht_lookup - lookup a node by key.
 179  * @ht: the hash table.
 180  * @hash: the key hash.
 181  * @match: the key match function.
 182  * @key: the current node key.
 183  * @iter: Node, if found (output). *iter->node set to NULL if not found.
 184  *
 185  * Call with rcu_read_lock held.
 186  * Threads calling this API need to be registered RCU read-side threads.
 187  */
 188 void cds_lfht_lookup(struct cds_lfht *ht, unsigned long hash,
 189                 cds_lfht_match_fct match, void *key,
 190                 struct cds_lfht_iter *iter);
 191
 192 /*
 193  * cds_lfht_next_duplicate - get the next item with same key (after a lookup).
 194  * @ht: the hash table.
 195  * @match: the key match function.
 196  * @key: the current node key.
 197  * @iter: Node, if found (output). *iter->node set to NULL if not found.
 198  *
 199  * Uses an iterator initialized by a lookup.
 200  * Sets *iter-node to the following node with same key.
 201  * Sets *iter->node to NULL if no following node exists with same key.
 202  * RCU read-side lock must be held across cds_lfht_lookup and
 203  * cds_lfht_next calls, and also between cds_lfht_next calls using the
 204  * node returned by a previous cds_lfht_next.
 205  * Call with rcu_read_lock held.
 206  * Threads calling this API need to be registered RCU read-side threads.
 207  */
 208 void cds_lfht_next_duplicate(struct cds_lfht *ht,
 209                 cds_lfht_match_fct match, void *key,
 210                 struct cds_lfht_iter *iter);
 211
 212 /*
 213  * cds_lfht_first - get the first node in the table.
 214  * @ht: the hash table.
 215  * @iter: First node, if exists (output). *iter->node set to NULL if not found.
 216  *
 217  * Output in "*iter". *iter->node set to NULL if table is empty.
 218  * Call with rcu_read_lock held.
 219  * Threads calling this API need to be registered RCU read-side threads.
 220  */
 221 void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 222
 223 /*
 224  * cds_lfht_next - get the next node in the table.
 225  * @ht: the hash table.
 226  * @iter: Next node, if exists (output). *iter->node set to NULL if not found.
 227  *
 228  * Input/Output in "*iter". *iter->node set to NULL if *iter was
 229  * pointing to the last table node.
 230  * Call with rcu_read_lock held.
 231  * Threads calling this API need to be registered RCU read-side threads.
 232  */
 233 void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 234
 235 /*
 236  * cds_lfht_add - add a node to the hash table.
 237  * @ht: the hash table.
 238  * @hash: the key hash.
 239  * @node: the node to add.
 240  *
 241  * This function supports adding redundant keys into the table.
 242  * Call with rcu_read_lock held.
 243  * Threads calling this API need to be registered RCU read-side threads.
 244  */
 245 void cds_lfht_add(struct cds_lfht *ht, unsigned long hash,
 246                 struct cds_lfht_node *node);
 247
 248 /*
 249  * cds_lfht_add_unique - add a node to hash table, if key is not present.
 250  * @ht: the hash table.
 251  * @hash: the node's hash.
 252  * @match: the key match function.
 253  * @key: the node's key.
 254  * @node: the node to try adding.
 255  *
 256  * Return the node added upon success.
 257  * Return the unique node already present upon failure. If
 258  * cds_lfht_add_unique fails, the node passed as parameter should be
 259  * freed by the caller.
 260  * Call with rcu_read_lock held.
 261  * Threads calling this API need to be registered RCU read-side threads.
 262  *
 263  * The semantic of this function is that if only this function is used
 264  * to add keys into the table, no duplicated keys should ever be
 265  * observable in the table. The same guarantee apply for combination of
 266  * add_unique and add_replace (see below).
 267  */
 268 struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
 269                 unsigned long hash,
 270                 cds_lfht_match_fct match,
 271                 void *key,
 272                 struct cds_lfht_node *node);
 273
 274 /*
 275  * cds_lfht_add_replace - replace or add a node within hash table.
 276  * @ht: the hash table.
 277  * @hash: the node's hash.
 278  * @match: the key match function.
 279  * @key: the node's key.
 280  * @node: the node to add.
 281  *
 282  * Return the node replaced upon success. If no node matching the key
 283  * was present, return NULL, which also means the operation succeeded.
 284  * This replacement operation should never fail.
 285  * Call with rcu_read_lock held.
 286  * Threads calling this API need to be registered RCU read-side threads.
 287  * After successful replacement, a grace period must be waited for before
 288  * freeing the memory reserved for the returned node.
 289  *
 290  * The semantic of replacement vs lookups is the following: if lookups
 291  * are performed between a key unique insertion and its removal, we
 292  * guarantee that the lookups and get next will always find exactly one
 293  * instance of the key if it is replaced concurrently with the lookups.
 294  *
 295  * Providing this semantic allows us to ensure that replacement-only
 296  * schemes will never generate duplicated keys. It also allows us to
 297  * guarantee that a combination of add_replace and add_unique updates
 298  * will never generate duplicated keys.
 299  */
 300 struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
 301                 unsigned long hash,
 302                 cds_lfht_match_fct match,
 303                 void *key,
 304                 struct cds_lfht_node *node);
 305
 306 /*
 307  * cds_lfht_replace - replace a node pointer to by iter within hash table.
 308  * @ht: the hash table.
 309  * @old_iter: the iterator position of the node to replace.
 310  * @now_node: the new node to try using for replacement.
 311  *
 312  * Return 0 if replacement is successful, negative value otherwise.
 313  * Replacing a NULL old node or an already removed node will fail with a
 314  * negative value.
 315  * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
 316  * RCU read-side lock must be held between lookup and replacement.
 317  * Call with rcu_read_lock held.
 318  * Threads calling this API need to be registered RCU read-side threads.
 319  * After successful replacement, a grace period must be waited for before
 320  * freeing the memory reserved for the old node (which can be accessed
 321  * with cds_lfht_iter_get_node).
 322  *
 323  * The semantic of replacement vs lookups is the following: if lookups
 324  * are performed between a key unique insertion and its removal, we
 325  * guarantee that the lookups and get next will always find exactly one
 326  * instance of the key if it is replaced concurrently with the lookups.
 327  *
 328  * Providing this semantic allows us to ensure that replacement-only
 329  * schemes will never generate duplicated keys. It also allows us to
 330  * guarantee that a combination of add_replace and add_unique updates
 331  * will never generate duplicated keys.
 332  */
 333 int cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_iter *old_iter,
 334                 struct cds_lfht_node *new_node);
 335
 336 /*
 337  * cds_lfht_del - remove node pointed to by iterator from hash table.
 338  * @ht: the hash table.
 339  * @iter: the iterator position of the node to delete.
 340  *
 341  * Return 0 if the node is successfully removed, negative value
 342  * otherwise.
 343  * Replacing a NULL node or an already removed node will fail with a
 344  * negative value.
 345  * Node can be looked up with cds_lfht_lookup and cds_lfht_next.
 346  * cds_lfht_iter_get_node.
 347  * RCU read-side lock must be held between lookup and removal.
 348  * Call with rcu_read_lock held.
 349  * Threads calling this API need to be registered RCU read-side threads.
 350  * After successful removal, a grace period must be waited for before
 351  * freeing the memory reserved for old node (which can be accessed with
 352  * cds_lfht_iter_get_node).
 353  */
 354 int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 355
 356 /*
 357  * cds_lfht_resize - Force a hash table resize
 358  * @ht: the hash table.
 359  * @new_size: update to this hash table size.
 360  *
 361  * Threads calling this API need to be registered RCU read-side threads.
 362  */
 363 void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);
 364
 365 /*
 366  * Note: cds_lfht_for_each are safe for element removal during
 367  * iteration.
 368  */
 369 #define cds_lfht_for_each(ht, iter, node)                               \
 370         for (cds_lfht_first(ht, iter),                                  \
 371                         node = cds_lfht_iter_get_node(iter);            \
 372                 node != NULL;                                           \
 373                 cds_lfht_next(ht, iter),                                \
 374                         node = cds_lfht_iter_get_node(iter))
 375
 376 #define cds_lfht_for_each_duplicate(ht, hash, match, key, iter, node)   \
 377         for (cds_lfht_lookup(ht, hash, match, key, iter),               \
 378                         node = cds_lfht_iter_get_node(iter);            \
 379                 node != NULL;                                           \
 380                 cds_lfht_next_duplicate(ht, match, key, iter),          \
 381                         node = cds_lfht_iter_get_node(iter))
 382
 383 #define cds_lfht_for_each_entry(ht, iter, pos, member)                  \
 384         for (cds_lfht_first(ht, iter),                                  \
 385                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 386                                         typeof(*(pos)), member);        \
 387                 &(pos)->member != NULL;                                 \
 388                 cds_lfht_next(ht, iter),                                \
 389                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 390                                         typeof(*(pos)), member))
 391
 392 #define cds_lfht_for_each_entry_duplicate(ht, hash, match, key,         \
 393                                 iter, pos, member)                      \
 394         for (cds_lfht_lookup(ht, hash, match, key, iter),               \
 395                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 396                                         typeof(*(pos)), member);        \
 397                 &(pos)->member != NULL;                                 \
 398                 cds_lfht_next_duplicate(ht, match, key, iter),          \
 399                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 400                                         typeof(*(pos)), member))
 401
 402 #ifdef __cplusplus
 403 }
 404 #endif
 405
 406 #endif /* _URCU_RCULFHASH_H */