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, const 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  *           CDS_LFHT_ACCOUNTING: count the number of node addition
 121  *                                and removal in the table
 122  * @attr: optional resize worker thread attributes. NULL for default.
 123  *
 124  * Return NULL on error.
 125  * Note: the RCU flavor must be already included before the hash table header.
 126  *
 127  * The programmer is responsible for ensuring that resize operation has a
 128  * priority equal to hash table updater threads. It should be performed by
 129  * specifying the appropriate priority in the pthread "attr" argument, and,
 130  * for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
 131  * this priority level. Having lower priority for call_rcu and resize threads
 132  * does not pose any correctness issue, but the resize operations could be
 133  * starved by updates, thus leading to long hash table bucket chains.
 134  * Threads calling this API are NOT required to be registered RCU read-side
 135  * threads. It can be called very early.(before rcu is initialized ...etc.)
 136  */
 137 static inline
 138 struct cds_lfht *cds_lfht_new(unsigned long init_size,
 139                         unsigned long min_alloc_size,
 140                         int flags,
 141                         pthread_attr_t *attr)
 142 {
 143         return _cds_lfht_new(init_size, min_alloc_size, flags,
 144                         call_rcu, synchronize_rcu, rcu_read_lock,
 145                         rcu_read_unlock, rcu_thread_offline,
 146                         rcu_thread_online, rcu_register_thread,
 147                         rcu_unregister_thread, attr);
 148 }
 149
 150 /*
 151  * cds_lfht_destroy - destroy a hash table.
 152  * @ht: the hash table to destroy.
 153  * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
 154  *        The caller will typically want to free this pointer if dynamically
 155  *        allocated. The attr point can be NULL if the caller does not
 156  *        need to be informed of the value passed to cds_lfht_new().
 157  *
 158  * Return 0 on success, negative error value on error.
 159  * Threads calling this API need to be registered RCU read-side threads.
 160  */
 161 int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
 162
 163 /*
 164  * cds_lfht_count_nodes - count the number of nodes in the hash table.
 165  * @ht: the hash table.
 166  * @split_count_before: Sample the node count split-counter before traversal.
 167  * @count: Traverse the hash table, count the number of nodes observed.
 168  * @removed: Number of logically removed nodes observed during traversal.
 169  * @split_count_after: Sample the node count split-counter after traversal.
 170  *
 171  * Call with rcu_read_lock held.
 172  * Threads calling this API need to be registered RCU read-side threads.
 173  */
 174 void cds_lfht_count_nodes(struct cds_lfht *ht,
 175                 long *split_count_before,
 176                 unsigned long *count,
 177                 unsigned long *removed,
 178                 long *split_count_after);
 179
 180 /*
 181  * cds_lfht_lookup - lookup a node by key.
 182  * @ht: the hash table.
 183  * @hash: the key hash.
 184  * @match: the key match function.
 185  * @key: the current node key.
 186  * @iter: Node, if found (output). *iter->node set to NULL if not found.
 187  *
 188  * Call with rcu_read_lock held.
 189  * Threads calling this API need to be registered RCU read-side threads.
 190  */
 191 void cds_lfht_lookup(struct cds_lfht *ht, unsigned long hash,
 192                 cds_lfht_match_fct match, const void *key,
 193                 struct cds_lfht_iter *iter);
 194
 195 /*
 196  * cds_lfht_next_duplicate - get the next item with same key (after a lookup).
 197  * @ht: the hash table.
 198  * @match: the key match function.
 199  * @key: the current node key.
 200  * @iter: Node, if found (output). *iter->node set to NULL if not found.
 201  *
 202  * Uses an iterator initialized by a lookup.
 203  * Sets *iter-node to the following node with same key.
 204  * Sets *iter->node to NULL if no following node exists with same key.
 205  * RCU read-side lock must be held across cds_lfht_lookup and
 206  * cds_lfht_next calls, and also between cds_lfht_next calls using the
 207  * node returned by a previous cds_lfht_next.
 208  * Call with rcu_read_lock held.
 209  * Threads calling this API need to be registered RCU read-side threads.
 210  */
 211 void cds_lfht_next_duplicate(struct cds_lfht *ht,
 212                 cds_lfht_match_fct match, const void *key,
 213                 struct cds_lfht_iter *iter);
 214
 215 /*
 216  * cds_lfht_first - get the first node in the table.
 217  * @ht: the hash table.
 218  * @iter: First node, if exists (output). *iter->node set to NULL if not found.
 219  *
 220  * Output in "*iter". *iter->node set to NULL if table is empty.
 221  * Call with rcu_read_lock held.
 222  * Threads calling this API need to be registered RCU read-side threads.
 223  */
 224 void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 225
 226 /*
 227  * cds_lfht_next - get the next node in the table.
 228  * @ht: the hash table.
 229  * @iter: Next node, if exists (output). *iter->node set to NULL if not found.
 230  *
 231  * Input/Output in "*iter". *iter->node set to NULL if *iter was
 232  * pointing to the last table node.
 233  * Call with rcu_read_lock held.
 234  * Threads calling this API need to be registered RCU read-side threads.
 235  */
 236 void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 237
 238 /*
 239  * cds_lfht_add - add a node to the hash table.
 240  * @ht: the hash table.
 241  * @hash: the key hash.
 242  * @node: the node to add.
 243  *
 244  * This function supports adding redundant keys into the table.
 245  * Call with rcu_read_lock held.
 246  * Threads calling this API need to be registered RCU read-side threads.
 247  */
 248 void cds_lfht_add(struct cds_lfht *ht, unsigned long hash,
 249                 struct cds_lfht_node *node);
 250
 251 /*
 252  * cds_lfht_add_unique - add a node to hash table, if key is not present.
 253  * @ht: the hash table.
 254  * @hash: the node's hash.
 255  * @match: the key match function.
 256  * @key: the node's key.
 257  * @node: the node to try adding.
 258  *
 259  * Return the node added upon success.
 260  * Return the unique node already present upon failure. If
 261  * cds_lfht_add_unique fails, the node passed as parameter should be
 262  * freed by the caller.
 263  * Call with rcu_read_lock held.
 264  * Threads calling this API need to be registered RCU read-side threads.
 265  *
 266  * The semantic of this function is that if only this function is used
 267  * to add keys into the table, no duplicated keys should ever be
 268  * observable in the table. The same guarantee apply for combination of
 269  * add_unique and add_replace (see below).
 270  */
 271 struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
 272                 unsigned long hash,
 273                 cds_lfht_match_fct match,
 274                 const void *key,
 275                 struct cds_lfht_node *node);
 276
 277 /*
 278  * cds_lfht_add_replace - replace or add a node within hash table.
 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 add.
 284  *
 285  * Return the node replaced upon success. If no node matching the key
 286  * was present, return NULL, which also means the operation succeeded.
 287  * This replacement operation should never fail.
 288  * Call with rcu_read_lock held.
 289  * Threads calling this API need to be registered RCU read-side threads.
 290  * After successful replacement, a grace period must be waited for before
 291  * freeing the memory reserved for the returned node.
 292  *
 293  * The semantic of replacement vs lookups is the following: if lookups
 294  * are performed between a key unique insertion and its removal, we
 295  * guarantee that the lookups and get next will always find exactly one
 296  * instance of the key if it is replaced concurrently with the lookups.
 297  *
 298  * Providing this semantic allows us to ensure that replacement-only
 299  * schemes will never generate duplicated keys. It also allows us to
 300  * guarantee that a combination of add_replace and add_unique updates
 301  * will never generate duplicated keys.
 302  */
 303 struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
 304                 unsigned long hash,
 305                 cds_lfht_match_fct match,
 306                 const void *key,
 307                 struct cds_lfht_node *node);
 308
 309 /*
 310  * cds_lfht_replace - replace a node pointer to by iter within hash table.
 311  * @ht: the hash table.
 312  * @old_iter: the iterator position of the node to replace.
 313  * @now_node: the new node to try using for replacement.
 314  *
 315  * Return 0 if replacement is successful, negative value otherwise.
 316  * Replacing a NULL old node or an already removed node will fail with a
 317  * negative value.
 318  * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
 319  * RCU read-side lock must be held between lookup and replacement.
 320  * Call with rcu_read_lock held.
 321  * Threads calling this API need to be registered RCU read-side threads.
 322  * After successful replacement, a grace period must be waited for before
 323  * freeing the memory reserved for the old node (which can be accessed
 324  * with cds_lfht_iter_get_node).
 325  *
 326  * The semantic of replacement vs lookups is the following: if lookups
 327  * are performed between a key unique insertion and its removal, we
 328  * guarantee that the lookups and get next will always find exactly one
 329  * instance of the key if it is replaced concurrently with the lookups.
 330  *
 331  * Providing this semantic allows us to ensure that replacement-only
 332  * schemes will never generate duplicated keys. It also allows us to
 333  * guarantee that a combination of add_replace and add_unique updates
 334  * will never generate duplicated keys.
 335  */
 336 int cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_iter *old_iter,
 337                 struct cds_lfht_node *new_node);
 338
 339 /*
 340  * cds_lfht_del - remove node pointed to by iterator from hash table.
 341  * @ht: the hash table.
 342  * @iter: the iterator position of the node to delete.
 343  *
 344  * Return 0 if the node is successfully removed, negative value
 345  * otherwise.
 346  * Replacing a NULL node or an already removed node will fail with a
 347  * negative value.
 348  * Node can be looked up with cds_lfht_lookup and cds_lfht_next.
 349  * cds_lfht_iter_get_node.
 350  * RCU read-side lock must be held between lookup and removal.
 351  * Call with rcu_read_lock held.
 352  * Threads calling this API need to be registered RCU read-side threads.
 353  * After successful removal, a grace period must be waited for before
 354  * freeing the memory reserved for old node (which can be accessed with
 355  * cds_lfht_iter_get_node).
 356  */
 357 int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 358
 359 /*
 360  * cds_lfht_resize - Force a hash table resize
 361  * @ht: the hash table.
 362  * @new_size: update to this hash table size.
 363  *
 364  * Threads calling this API need to be registered RCU read-side threads.
 365  */
 366 void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);
 367
 368 /*
 369  * Note: cds_lfht_for_each are safe for element removal during
 370  * iteration.
 371  */
 372 #define cds_lfht_for_each(ht, iter, node)                               \
 373         for (cds_lfht_first(ht, iter),                                  \
 374                         node = cds_lfht_iter_get_node(iter);            \
 375                 node != NULL;                                           \
 376                 cds_lfht_next(ht, iter),                                \
 377                         node = cds_lfht_iter_get_node(iter))
 378
 379 #define cds_lfht_for_each_duplicate(ht, hash, match, key, iter, node)   \
 380         for (cds_lfht_lookup(ht, hash, match, key, iter),               \
 381                         node = cds_lfht_iter_get_node(iter);            \
 382                 node != NULL;                                           \
 383                 cds_lfht_next_duplicate(ht, match, key, iter),          \
 384                         node = cds_lfht_iter_get_node(iter))
 385
 386 #define cds_lfht_for_each_entry(ht, iter, pos, member)                  \
 387         for (cds_lfht_first(ht, iter),                                  \
 388                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 389                                         typeof(*(pos)), member);        \
 390                 &(pos)->member != NULL;                                 \
 391                 cds_lfht_next(ht, iter),                                \
 392                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 393                                         typeof(*(pos)), member))
 394
 395 #define cds_lfht_for_each_entry_duplicate(ht, hash, match, key,         \
 396                                 iter, pos, member)                      \
 397         for (cds_lfht_lookup(ht, hash, match, key, iter),               \
 398                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 399                                         typeof(*(pos)), member);        \
 400                 &(pos)->member != NULL;                                 \
 401                 cds_lfht_next_duplicate(ht, match, key, iter),          \
 402                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 403                                         typeof(*(pos)), member))
 404
 405 #ifdef __cplusplus
 406 }
 407 #endif
 408
 409 #endif /* _URCU_RCULFHASH_H */