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 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
  50  * three bits.
  51  *
  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.
  55  *
  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.
  59  */
  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)));
  64
  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;
  68 };
  69
  70 static inline
  71 struct cds_lfht_node *cds_lfht_iter_get_node(struct cds_lfht_iter *iter)
  72 {
  73         return iter->node;
  74 }
  75
  76 struct cds_lfht;
  77
  78 /*
  79  * Caution !
  80  * Ensure reader and writer threads are registered as urcu readers.
  81  */
  82
  83 typedef int (*cds_lfht_match_fct)(struct cds_lfht_node *node, const void *key);
  84
  85 /*
  86  * cds_lfht_node_init - initialize a hash table node
  87  * @node: the node to initialize.
  88  *
  89  * This function is kept to be eventually used for debugging purposes
  90  * (detection of memory corruption).
  91  */
  92 static inline
  93 void cds_lfht_node_init(struct cds_lfht_node *node)
  94 {
  95 }
  96
  97 /*
  98  * Hash table creation flags.
  99  */
 100 enum {
 101         CDS_LFHT_AUTO_RESIZE = (1U << 0),
 102         CDS_LFHT_ACCOUNTING = (1U << 1),
 103 };
 104
 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);
 112 };
 113
 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;
 117
 118 /*
 119  * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
 120  */
 121 struct cds_lfht *_cds_lfht_new(unsigned long init_size,
 122                         unsigned long min_nr_alloc_buckets,
 123                         unsigned long max_nr_buckets,
 124                         int flags,
 125                         const struct cds_lfht_mm_type *mm,
 126                         const struct rcu_flavor_struct *flavor,
 127                         pthread_attr_t *attr);
 128
 129 /*
 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)
 136  * @flags: hash table creation flags (can be combined with bitwise or: '|').
 137  *           0: no flags.
 138  *           CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
 139  *           CDS_LFHT_ACCOUNTING: count the number of node addition
 140  *                                and removal in the table
 141  * @attr: optional resize worker thread attributes. NULL for default.
 142  *
 143  * Return NULL on error.
 144  * Note: the RCU flavor must be already included before the hash table header.
 145  *
 146  * The programmer is responsible for ensuring that resize operation has a
 147  * priority equal to hash table updater threads. It should be performed by
 148  * specifying the appropriate priority in the pthread "attr" argument, and,
 149  * for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
 150  * this priority level. Having lower priority for call_rcu and resize threads
 151  * does not pose any correctness issue, but the resize operations could be
 152  * starved by updates, thus leading to long hash table bucket chains.
 153  * Threads calling this API are NOT required to be registered RCU read-side
 154  * threads. It can be called very early.(before rcu is initialized ...etc.)
 155  */
 156 static inline
 157 struct cds_lfht *cds_lfht_new(unsigned long init_size,
 158                         unsigned long min_nr_alloc_buckets,
 159                         unsigned long max_nr_buckets,
 160                         int flags,
 161                         pthread_attr_t *attr)
 162 {
 163         return _cds_lfht_new(init_size, min_nr_alloc_buckets, max_nr_buckets,
 164                         flags, NULL, &rcu_flavor, attr);
 165 }
 166
 167 /*
 168  * cds_lfht_destroy - destroy a hash table.
 169  * @ht: the hash table to destroy.
 170  * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
 171  *        The caller will typically want to free this pointer if dynamically
 172  *        allocated. The attr point can be NULL if the caller does not
 173  *        need to be informed of the value passed to cds_lfht_new().
 174  *
 175  * Return 0 on success, negative error value on error.
 176  * Threads calling this API need to be registered RCU read-side threads.
 177  */
 178 int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
 179
 180 /*
 181  * cds_lfht_count_nodes - count the number of nodes in the hash table.
 182  * @ht: the hash table.
 183  * @split_count_before: Sample the node count split-counter before traversal.
 184  * @count: Traverse the hash table, count the number of nodes observed.
 185  * @removed: Number of logically removed nodes observed during traversal.
 186  * @split_count_after: Sample the node count split-counter after traversal.
 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_count_nodes(struct cds_lfht *ht,
 192                 long *split_count_before,
 193                 unsigned long *count,
 194                 unsigned long *removed,
 195                 long *split_count_after);
 196
 197 /*
 198  * cds_lfht_lookup - lookup a node by key.
 199  * @ht: the hash table.
 200  * @hash: the key hash.
 201  * @match: the key match function.
 202  * @key: the current node key.
 203  * @iter: Node, if found (output). *iter->node set to NULL if not found.
 204  *
 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_lookup(struct cds_lfht *ht, unsigned long hash,
 209                 cds_lfht_match_fct match, const void *key,
 210                 struct cds_lfht_iter *iter);
 211
 212 /*
 213  * cds_lfht_next_duplicate - get the next item with same key (after a lookup).
 214  * @ht: the hash table.
 215  * @match: the key match function.
 216  * @key: the current node key.
 217  * @iter: Node, if found (output). *iter->node set to NULL if not found.
 218  *
 219  * Uses an iterator initialized by a lookup.
 220  * Sets *iter-node to the following node with same key.
 221  * Sets *iter->node to NULL if no following node exists with same key.
 222  * RCU read-side lock must be held across cds_lfht_lookup and
 223  * cds_lfht_next calls, and also between cds_lfht_next calls using the
 224  * node returned by a previous cds_lfht_next.
 225  * Call with rcu_read_lock held.
 226  * Threads calling this API need to be registered RCU read-side threads.
 227  */
 228 void cds_lfht_next_duplicate(struct cds_lfht *ht,
 229                 cds_lfht_match_fct match, const void *key,
 230                 struct cds_lfht_iter *iter);
 231
 232 /*
 233  * cds_lfht_first - get the first node in the table.
 234  * @ht: the hash table.
 235  * @iter: First node, if exists (output). *iter->node set to NULL if not found.
 236  *
 237  * Output in "*iter". *iter->node set to NULL if table is empty.
 238  * Call with rcu_read_lock held.
 239  * Threads calling this API need to be registered RCU read-side threads.
 240  */
 241 void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 242
 243 /*
 244  * cds_lfht_next - get the next node in the table.
 245  * @ht: the hash table.
 246  * @iter: Next node, if exists (output). *iter->node set to NULL if not found.
 247  *
 248  * Input/Output in "*iter". *iter->node set to NULL if *iter was
 249  * pointing to the last table node.
 250  * Call with rcu_read_lock held.
 251  * Threads calling this API need to be registered RCU read-side threads.
 252  */
 253 void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 254
 255 /*
 256  * cds_lfht_add - add a node to the hash table.
 257  * @ht: the hash table.
 258  * @hash: the key hash.
 259  * @node: the node to add.
 260  *
 261  * This function supports adding redundant keys into the table.
 262  * Call with rcu_read_lock held.
 263  * Threads calling this API need to be registered RCU read-side threads.
 264  */
 265 void cds_lfht_add(struct cds_lfht *ht, unsigned long hash,
 266                 struct cds_lfht_node *node);
 267
 268 /*
 269  * cds_lfht_add_unique - add a node to hash table, if key is not present.
 270  * @ht: the hash table.
 271  * @hash: the node's hash.
 272  * @match: the key match function.
 273  * @key: the node's key.
 274  * @node: the node to try adding.
 275  *
 276  * Return the node added upon success.
 277  * Return the unique node already present upon failure. If
 278  * cds_lfht_add_unique fails, the node passed as parameter should be
 279  * freed by the caller.
 280  * Call with rcu_read_lock held.
 281  * Threads calling this API need to be registered RCU read-side threads.
 282  *
 283  * The semantic of this function is that if only this function is used
 284  * to add keys into the table, no duplicated keys should ever be
 285  * observable in the table. The same guarantee apply for combination of
 286  * add_unique and add_replace (see below).
 287  */
 288 struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
 289                 unsigned long hash,
 290                 cds_lfht_match_fct match,
 291                 const void *key,
 292                 struct cds_lfht_node *node);
 293
 294 /*
 295  * cds_lfht_add_replace - replace or add a node within hash table.
 296  * @ht: the hash table.
 297  * @hash: the node's hash.
 298  * @match: the key match function.
 299  * @key: the node's key.
 300  * @node: the node to add.
 301  *
 302  * Return the node replaced upon success. If no node matching the key
 303  * was present, return NULL, which also means the operation succeeded.
 304  * This replacement operation should never fail.
 305  * Call with rcu_read_lock held.
 306  * Threads calling this API need to be registered RCU read-side threads.
 307  * After successful replacement, a grace period must be waited for before
 308  * freeing the memory reserved for the returned node.
 309  *
 310  * The semantic of replacement vs lookups is the following: if lookups
 311  * are performed between a key unique insertion and its removal, we
 312  * guarantee that the lookups and get next will always find exactly one
 313  * instance of the key if it is replaced concurrently with the lookups.
 314  *
 315  * Providing this semantic allows us to ensure that replacement-only
 316  * schemes will never generate duplicated keys. It also allows us to
 317  * guarantee that a combination of add_replace and add_unique updates
 318  * will never generate duplicated keys.
 319  */
 320 struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
 321                 unsigned long hash,
 322                 cds_lfht_match_fct match,
 323                 const void *key,
 324                 struct cds_lfht_node *node);
 325
 326 /*
 327  * cds_lfht_replace - replace a node pointer to by iter within hash table.
 328  * @ht: the hash table.
 329  * @old_iter: the iterator position of the node to replace.
 330  * @now_node: the new node to try using for replacement.
 331  *
 332  * Return 0 if replacement is successful, negative value otherwise.
 333  * Replacing a NULL old node or an already removed node will fail with a
 334  * negative value.
 335  * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
 336  * RCU read-side lock must be held between lookup and replacement.
 337  * Call with rcu_read_lock held.
 338  * Threads calling this API need to be registered RCU read-side threads.
 339  * After successful replacement, a grace period must be waited for before
 340  * freeing the memory reserved for the old node (which can be accessed
 341  * with cds_lfht_iter_get_node).
 342  *
 343  * The semantic of replacement vs lookups is the following: if lookups
 344  * are performed between a key unique insertion and its removal, we
 345  * guarantee that the lookups and get next will always find exactly one
 346  * instance of the key if it is replaced concurrently with the lookups.
 347  *
 348  * Providing this semantic allows us to ensure that replacement-only
 349  * schemes will never generate duplicated keys. It also allows us to
 350  * guarantee that a combination of add_replace and add_unique updates
 351  * will never generate duplicated keys.
 352  */
 353 int cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_iter *old_iter,
 354                 struct cds_lfht_node *new_node);
 355
 356 /*
 357  * cds_lfht_del - remove node pointed to by iterator from hash table.
 358  * @ht: the hash table.
 359  * @iter: the iterator position of the node to delete.
 360  *
 361  * Return 0 if the node is successfully removed, negative value
 362  * otherwise.
 363  * Replacing a NULL node or an already removed node will fail with a
 364  * negative value.
 365  * Node can be looked up with cds_lfht_lookup and cds_lfht_next.
 366  * cds_lfht_iter_get_node.
 367  * RCU read-side lock must be held between lookup and removal.
 368  * Call with rcu_read_lock held.
 369  * Threads calling this API need to be registered RCU read-side threads.
 370  * After successful removal, a grace period must be waited for before
 371  * freeing the memory reserved for old node (which can be accessed with
 372  * cds_lfht_iter_get_node).
 373  */
 374 int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 375
 376 /*
 377  * cds_lfht_resize - Force a hash table resize
 378  * @ht: the hash table.
 379  * @new_size: update to this hash table size.
 380  *
 381  * Threads calling this API need to be registered RCU read-side threads.
 382  */
 383 void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);
 384
 385 /*
 386  * Note: cds_lfht_for_each are safe for element removal during
 387  * iteration.
 388  */
 389 #define cds_lfht_for_each(ht, iter, node)                               \
 390         for (cds_lfht_first(ht, iter),                                  \
 391                         node = cds_lfht_iter_get_node(iter);            \
 392                 node != NULL;                                           \
 393                 cds_lfht_next(ht, iter),                                \
 394                         node = cds_lfht_iter_get_node(iter))
 395
 396 #define cds_lfht_for_each_duplicate(ht, hash, match, key, iter, node)   \
 397         for (cds_lfht_lookup(ht, hash, match, key, iter),               \
 398                         node = cds_lfht_iter_get_node(iter);            \
 399                 node != NULL;                                           \
 400                 cds_lfht_next_duplicate(ht, match, key, iter),          \
 401                         node = cds_lfht_iter_get_node(iter))
 402
 403 #define cds_lfht_for_each_entry(ht, iter, pos, member)                  \
 404         for (cds_lfht_first(ht, iter),                                  \
 405                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 406                                         typeof(*(pos)), member);        \
 407                 &(pos)->member != NULL;                                 \
 408                 cds_lfht_next(ht, iter),                                \
 409                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 410                                         typeof(*(pos)), member))
 411
 412 #define cds_lfht_for_each_entry_duplicate(ht, hash, match, key,         \
 413                                 iter, pos, member)                      \
 414         for (cds_lfht_lookup(ht, hash, match, key, iter),               \
 415                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 416                                         typeof(*(pos)), member);        \
 417                 &(pos)->member != NULL;                                 \
 418                 cds_lfht_next_duplicate(ht, match, key, iter),          \
 419                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 420                                         typeof(*(pos)), member))
 421
 422 #ifdef __cplusplus
 423 }
 424 #endif
 425
 426 #endif /* _URCU_RCULFHASH_H */