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-call-rcu.h>
  30
  31 #ifdef __cplusplus
  32 extern "C" {
  33 #endif
  34
  35 /*
  36  * cds_lfht_node: Contains the next pointers and reverse-hash
  37  * value required for lookup and traversal of the hash table.
  38  *
  39  * struct cds_lfht_node should be aligned on 4-bytes boundaries because
  40  * the two lower bits are used as flags.
  41  *
  42  * struct cds_lfht_node can be embedded into a structure (as a field).
  43  * caa_container_of() can be used to get the structure from the struct
  44  * cds_lfht_node after a lookup.
  45  *
  46  * The structure which embeds it typically holds the key (or key-value
  47  * pair) of the object. The caller code is responsible for calculation
  48  * of the hash value for cds_lfht APIs.
  49  */
  50 struct cds_lfht_node {
  51         struct cds_lfht_node *next;     /* ptr | BUCKET_FLAG | REMOVED_FLAG */
  52         unsigned long reverse_hash;
  53 } __attribute__((aligned(4)));
  54
  55 /* cds_lfht_iter: Used to track state while traversing a hash chain. */
  56 struct cds_lfht_iter {
  57         struct cds_lfht_node *node, *next;
  58 };
  59
  60 static inline
  61 struct cds_lfht_node *cds_lfht_iter_get_node(struct cds_lfht_iter *iter)
  62 {
  63         return iter->node;
  64 }
  65
  66 struct cds_lfht;
  67
  68 /*
  69  * Caution !
  70  * Ensure reader and writer threads are registered as urcu readers.
  71  */
  72
  73 typedef unsigned long (*cds_lfht_hash_fct)(void *key, size_t length,
  74                                         unsigned long seed);
  75 typedef int (*cds_lfht_match_fct)(struct cds_lfht_node *node, void *key);
  76
  77 /*
  78  * cds_lfht_node_init - initialize a hash table node
  79  * @node: the node to initialize.
  80  *
  81  * This function is kept to be eventually used for debugging purposes
  82  * (detection of memory corruption).
  83  */
  84 static inline
  85 void cds_lfht_node_init(struct cds_lfht_node *node)
  86 {
  87 }
  88
  89 /*
  90  * Hash table creation flags.
  91  */
  92 enum {
  93         CDS_LFHT_AUTO_RESIZE = (1U << 0),
  94         CDS_LFHT_ACCOUNTING = (1U << 1),
  95 };
  96
  97 /*
  98  * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
  99  */
 100 struct cds_lfht *_cds_lfht_new(unsigned long init_size,
 101                         unsigned long min_alloc_size,
 102                         int flags,
 103                         void (*cds_lfht_call_rcu)(struct rcu_head *head,
 104                                 void (*func)(struct rcu_head *head)),
 105                         void (*cds_lfht_synchronize_rcu)(void),
 106                         void (*cds_lfht_rcu_read_lock)(void),
 107                         void (*cds_lfht_rcu_read_unlock)(void),
 108                         void (*cds_lfht_rcu_thread_offline)(void),
 109                         void (*cds_lfht_rcu_thread_online)(void),
 110                         void (*cds_lfht_rcu_register_thread)(void),
 111                         void (*cds_lfht_rcu_unregister_thread)(void),
 112                         pthread_attr_t *attr);
 113
 114 /*
 115  * cds_lfht_new - allocate a hash table.
 116  * @init_size: number of nodes to allocate initially. Must be power of two.
 117  * @min_alloc_size: the smallest allocation size to use. Must be power of two.
 118  * @flags: hash table creation flags (can be combined with bitwise or: '|').
 119  *           0: no flags.
 120  *           CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
 121  * @attr: optional resize worker thread attributes. NULL for default.
 122  *
 123  * Return NULL on error.
 124  * Note: the RCU flavor must be already included before the hash table header.
 125  *
 126  * The programmer is responsible for ensuring that resize operation has a
 127  * priority equal to hash table updater threads. It should be performed by
 128  * specifying the appropriate priority in the pthread "attr" argument, and,
 129  * for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
 130  * this priority level. Having lower priority for call_rcu and resize threads
 131  * does not pose any correctness issue, but the resize operations could be
 132  * starved by updates, thus leading to long hash table bucket chains.
 133  * Threads calling this API need to be registered RCU read-side threads.
 134  */
 135 static inline
 136 struct cds_lfht *cds_lfht_new(unsigned long init_size,
 137                         unsigned long min_alloc_size,
 138                         int flags,
 139                         pthread_attr_t *attr)
 140 {
 141         return _cds_lfht_new(init_size, min_alloc_size, flags,
 142                         call_rcu, synchronize_rcu, rcu_read_lock,
 143                         rcu_read_unlock, rcu_thread_offline,
 144                         rcu_thread_online, rcu_register_thread,
 145                         rcu_unregister_thread, attr);
 146 }
 147
 148 /*
 149  * cds_lfht_destroy - destroy a hash table.
 150  * @ht: the hash table to destroy.
 151  * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
 152  *        The caller will typically want to free this pointer if dynamically
 153  *        allocated. The attr point can be NULL if the caller does not
 154  *        need to be informed of the value passed to cds_lfht_new().
 155  *
 156  * Return 0 on success, negative error value on error.
 157  * Threads calling this API need to be registered RCU read-side threads.
 158  */
 159 int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
 160
 161 /*
 162  * cds_lfht_count_nodes - count the number of nodes in the hash table.
 163  * @ht: the hash table.
 164  * @split_count_before: Sample the node count split-counter before traversal.
 165  * @count: Traverse the hash table, count the number of nodes observed.
 166  * @removed: Number of logically removed nodes observed during traversal.
 167  * @split_count_after: Sample the node count split-counter after traversal.
 168  *
 169  * Call with rcu_read_lock held.
 170  * Threads calling this API need to be registered RCU read-side threads.
 171  */
 172 void cds_lfht_count_nodes(struct cds_lfht *ht,
 173                 long *split_count_before,
 174                 unsigned long *count,
 175                 unsigned long *removed,
 176                 long *split_count_after);
 177
 178 /*
 179  * cds_lfht_lookup - lookup a node by key.
 180  * @ht: the hash table.
 181  * @match: the key match function.
 182  * @hash: the key hash.
 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, cds_lfht_match_fct match,
 189                 unsigned long hash, void *key, 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, 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  * @match: the key match function.
 251  * @key: the node's key.
 252  * @hash: the node's hash.
 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                 cds_lfht_match_fct match,
 269                 void *key,
 270                 unsigned long hash,
 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  * @match: the key match function.
 277  * @key: the node's key.
 278  * @hash: the node's hash.
 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                 cds_lfht_match_fct match,
 301                 void *key,
 302                 unsigned long hash,
 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 #ifdef __cplusplus
 365 }
 366 #endif
 367
 368 #endif /* _URCU_RCULFHASH_H */