liblttng-ht/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
  33 #include "urcu-flavor.h"
  34
  35 #ifdef __cplusplus
  36 extern "C" {
  37 #endif
  38
  39 /*
  40  * cds_lfht_node: Contains the next pointers and reverse-hash
  41  * value required for lookup and traversal of the hash table.
  42  *
  43  * struct cds_lfht_node should be aligned on 8-bytes boundaries because
  44  * the three lower bits are used as flags. It is worth noting that the
  45  * information contained within these three bits could be represented on
  46  * two bits by re-using the same bit for REMOVAL_OWNER_FLAG and
  47  * BUCKET_FLAG. This can be done if we ensure that no iterator nor
  48  * updater check the BUCKET_FLAG after it detects that the REMOVED_FLAG
  49  * is set. Given the minimum size of struct cds_lfht_node is 8 bytes on
  50  * 32-bit architectures, we choose to go for simplicity and reserve
  51  * three bits.
  52  *
  53  * struct cds_lfht_node can be embedded into a structure (as a field).
  54  * caa_container_of() can be used to get the structure from the struct
  55  * cds_lfht_node after a lookup.
  56  *
  57  * The structure which embeds it typically holds the key (or key-value
  58  * pair) of the object. The caller code is responsible for calculation
  59  * of the hash value for cds_lfht APIs.
  60  */
  61 struct cds_lfht_node {
  62         struct cds_lfht_node *next;     /* ptr | REMOVAL_OWNER_FLAG | BUCKET_FLAG | REMOVED_FLAG */
  63         unsigned long reverse_hash;
  64 } __attribute__((aligned(8)));
  65
  66 /* cds_lfht_iter: Used to track state while traversing a hash chain. */
  67 struct cds_lfht_iter {
  68         struct cds_lfht_node *node, *next;
  69 };
  70
  71 static inline
  72 struct cds_lfht_node *cds_lfht_iter_get_node(struct cds_lfht_iter *iter)
  73 {
  74         return iter->node;
  75 }
  76
  77 struct cds_lfht;
  78
  79 /*
  80  * Caution !
  81  * Ensure reader and writer threads are registered as urcu readers.
  82  */
  83
  84 typedef int (*cds_lfht_match_fct)(struct cds_lfht_node *node, const void *key);
  85
  86 /*
  87  * cds_lfht_node_init - initialize a hash table node
  88  * @node: the node to initialize.
  89  *
  90  * This function is kept to be eventually used for debugging purposes
  91  * (detection of memory corruption).
  92  */
  93 static inline
  94 void cds_lfht_node_init(struct cds_lfht_node *node)
  95 {
  96 }
  97
  98 /*
  99  * Hash table creation flags.
 100  */
 101 enum {
 102         CDS_LFHT_AUTO_RESIZE = (1U << 0),
 103         CDS_LFHT_ACCOUNTING = (1U << 1),
 104 };
 105
 106 struct cds_lfht_mm_type {
 107         struct cds_lfht *(*alloc_cds_lfht)(unsigned long min_nr_alloc_buckets,
 108                         unsigned long max_nr_buckets);
 109         void (*alloc_bucket_table)(struct cds_lfht *ht, unsigned long order);
 110         void (*free_bucket_table)(struct cds_lfht *ht, unsigned long order);
 111         struct cds_lfht_node *(*bucket_at)(struct cds_lfht *ht,
 112                         unsigned long index);
 113 };
 114
 115 extern const struct cds_lfht_mm_type cds_lfht_mm_order;
 116 extern const struct cds_lfht_mm_type cds_lfht_mm_chunk;
 117 extern const struct cds_lfht_mm_type cds_lfht_mm_mmap;
 118
 119 /*
 120  * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
 121  */
 122 struct cds_lfht *_cds_lfht_new(unsigned long init_size,
 123                         unsigned long min_nr_alloc_buckets,
 124                         unsigned long max_nr_buckets,
 125                         int flags,
 126                         const struct cds_lfht_mm_type *mm,
 127                         const struct rcu_flavor_struct *flavor,
 128                         pthread_attr_t *attr);
 129
 130 /*
 131  * cds_lfht_new - allocate a hash table.
 132  * @init_size: number of buckets to allocate initially. Must be power of two.
 133  * @min_nr_alloc_buckets: the minimum number of allocated buckets.
 134  *                        (must be power of two)
 135  * @max_nr_buckets: the maximum number of hash table buckets allowed.
 136  *                  (must be power of two)
 137  * @flags: hash table creation flags (can be combined with bitwise or: '|').
 138  *           0: no flags.
 139  *           CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
 140  *           CDS_LFHT_ACCOUNTING: count the number of node addition
 141  *                                and removal in the table
 142  * @attr: optional resize worker thread attributes. NULL for default.
 143  *
 144  * Return NULL on error.
 145  * Note: the RCU flavor must be already included before the hash table header.
 146  *
 147  * The programmer is responsible for ensuring that resize operation has a
 148  * priority equal to hash table updater threads. It should be performed by
 149  * specifying the appropriate priority in the pthread "attr" argument, and,
 150  * for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
 151  * this priority level. Having lower priority for call_rcu and resize threads
 152  * does not pose any correctness issue, but the resize operations could be
 153  * starved by updates, thus leading to long hash table bucket chains.
 154  * Threads calling this API are NOT required to be registered RCU read-side
 155  * threads. It can be called very early.(before rcu is initialized ...etc.)
 156  */
 157 static inline
 158 struct cds_lfht *cds_lfht_new(unsigned long init_size,
 159                         unsigned long min_nr_alloc_buckets,
 160                         unsigned long max_nr_buckets,
 161                         int flags,
 162                         pthread_attr_t *attr)
 163 {
 164         return _cds_lfht_new(init_size, min_nr_alloc_buckets, max_nr_buckets,
 165                         flags, NULL, &rcu_flavor, attr);
 166 }
 167
 168 /*
 169  * cds_lfht_destroy - destroy a hash table.
 170  * @ht: the hash table to destroy.
 171  * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
 172  *        The caller will typically want to free this pointer if dynamically
 173  *        allocated. The attr point can be NULL if the caller does not
 174  *        need to be informed of the value passed to cds_lfht_new().
 175  *
 176  * Return 0 on success, negative error value on error.
 177  * Threads calling this API need to be registered RCU read-side threads.
 178  */
 179 int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
 180
 181 /*
 182  * cds_lfht_count_nodes - count the number of nodes in the hash table.
 183  * @ht: the hash table.
 184  * @split_count_before: Sample the node count split-counter before traversal.
 185  * @count: Traverse the hash table, count the number of nodes observed.
 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                 long *split_count_after);
 195
 196 /*
 197  * cds_lfht_lookup - lookup a node by key.
 198  * @ht: the hash table.
 199  * @hash: the key hash.
 200  * @match: the key match function.
 201  * @key: the current node key.
 202  * @iter: Node, if found (output). *iter->node set to NULL if not found.
 203  *
 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_lookup(struct cds_lfht *ht, unsigned long hash,
 208                 cds_lfht_match_fct match, const void *key,
 209                 struct cds_lfht_iter *iter);
 210
 211 /*
 212  * cds_lfht_next_duplicate - get the next item with same key (after a lookup).
 213  * @ht: the hash table.
 214  * @match: the key match function.
 215  * @key: the current node key.
 216  * @iter: Node, if found (output). *iter->node set to NULL if not found.
 217  *
 218  * Uses an iterator initialized by a lookup.
 219  * Sets *iter-node to the following node with same key.
 220  * Sets *iter->node to NULL if no following node exists with same key.
 221  * RCU read-side lock must be held across cds_lfht_lookup and
 222  * cds_lfht_next calls, and also between cds_lfht_next calls using the
 223  * node returned by a previous cds_lfht_next.
 224  * Call with rcu_read_lock held.
 225  * Threads calling this API need to be registered RCU read-side threads.
 226  */
 227 void cds_lfht_next_duplicate(struct cds_lfht *ht,
 228                 cds_lfht_match_fct match, const void *key,
 229                 struct cds_lfht_iter *iter);
 230
 231 /*
 232  * cds_lfht_first - get the first node in the table.
 233  * @ht: the hash table.
 234  * @iter: First node, if exists (output). *iter->node set to NULL if not found.
 235  *
 236  * Output in "*iter". *iter->node set to NULL if table is empty.
 237  * Call with rcu_read_lock held.
 238  * Threads calling this API need to be registered RCU read-side threads.
 239  */
 240 void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 241
 242 /*
 243  * cds_lfht_next - get the next node in the table.
 244  * @ht: the hash table.
 245  * @iter: Next node, if exists (output). *iter->node set to NULL if not found.
 246  *
 247  * Input/Output in "*iter". *iter->node set to NULL if *iter was
 248  * pointing to the last table node.
 249  * Call with rcu_read_lock held.
 250  * Threads calling this API need to be registered RCU read-side threads.
 251  */
 252 void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 253
 254 /*
 255  * cds_lfht_add - add a node to the hash table.
 256  * @ht: the hash table.
 257  * @hash: the key hash.
 258  * @node: the node to add.
 259  *
 260  * This function supports adding redundant keys into the table.
 261  * Call with rcu_read_lock held.
 262  * Threads calling this API need to be registered RCU read-side threads.
 263  */
 264 void cds_lfht_add(struct cds_lfht *ht, unsigned long hash,
 265                 struct cds_lfht_node *node);
 266
 267 /*
 268  * cds_lfht_add_unique - add a node to hash table, if key is not present.
 269  * @ht: the hash table.
 270  * @hash: the node's hash.
 271  * @match: the key match function.
 272  * @key: the node's key.
 273  * @node: the node to try adding.
 274  *
 275  * Return the node added upon success.
 276  * Return the unique node already present upon failure. If
 277  * cds_lfht_add_unique fails, the node passed as parameter should be
 278  * freed by the caller.
 279  * Call with rcu_read_lock held.
 280  * Threads calling this API need to be registered RCU read-side threads.
 281  *
 282  * The semantic of this function is that if only this function is used
 283  * to add keys into the table, no duplicated keys should ever be
 284  * observable in the table. The same guarantee apply for combination of
 285  * add_unique and add_replace (see below).
 286  */
 287 struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
 288                 unsigned long hash,
 289                 cds_lfht_match_fct match,
 290                 const void *key,
 291                 struct cds_lfht_node *node);
 292
 293 /*
 294  * cds_lfht_add_replace - replace or add a node within hash table.
 295  * @ht: the hash table.
 296  * @hash: the node's hash.
 297  * @match: the key match function.
 298  * @key: the node's key.
 299  * @node: the node to add.
 300  *
 301  * Return the node replaced upon success. If no node matching the key
 302  * was present, return NULL, which also means the operation succeeded.
 303  * This replacement operation should never fail.
 304  * Call with rcu_read_lock held.
 305  * Threads calling this API need to be registered RCU read-side threads.
 306  * After successful replacement, a grace period must be waited for before
 307  * freeing the memory reserved for the returned node.
 308  *
 309  * The semantic of replacement vs lookups is the following: if lookups
 310  * are performed between a key unique insertion and its removal, we
 311  * guarantee that the lookups and get next will always find exactly one
 312  * instance of the key if it is replaced concurrently with the lookups.
 313  *
 314  * Providing this semantic allows us to ensure that replacement-only
 315  * schemes will never generate duplicated keys. It also allows us to
 316  * guarantee that a combination of add_replace and add_unique updates
 317  * will never generate duplicated keys.
 318  */
 319 struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
 320                 unsigned long hash,
 321                 cds_lfht_match_fct match,
 322                 const void *key,
 323                 struct cds_lfht_node *node);
 324
 325 /*
 326  * cds_lfht_replace - replace a node pointer to by iter within hash table.
 327  * @ht: the hash table.
 328  * @old_iter: the iterator position of the node to replace.
 329  * @hash: the node's hash.
 330  * @match: the key match function.
 331  * @key: the node's key.
 332  * @new_node: the new node to use as replacement.
 333  *
 334  * Return 0 if replacement is successful, negative value otherwise.
 335  * Replacing a NULL old node or an already removed node will fail with
 336  * -ENOENT.
 337  * If the hash or value of the node to replace and the new node differ,
 338  * this function returns -EINVAL without proceeding to the replacement.
 339  * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
 340  * RCU read-side lock must be held between lookup and replacement.
 341  * Call with rcu_read_lock held.
 342  * Threads calling this API need to be registered RCU read-side threads.
 343  * After successful replacement, a grace period must be waited for before
 344  * freeing the memory reserved for the old node (which can be accessed
 345  * with cds_lfht_iter_get_node).
 346  *
 347  * The semantic of replacement vs lookups is the following: if lookups
 348  * are performed between a key unique insertion and its removal, we
 349  * guarantee that the lookups and get next will always find exactly one
 350  * instance of the key if it is replaced concurrently with the lookups.
 351  *
 352  * Providing this semantic allows us to ensure that replacement-only
 353  * schemes will never generate duplicated keys. It also allows us to
 354  * guarantee that a combination of add_replace and add_unique updates
 355  * will never generate duplicated keys.
 356  */
 357 int cds_lfht_replace(struct cds_lfht *ht,
 358                 struct cds_lfht_iter *old_iter,
 359                 unsigned long hash,
 360                 cds_lfht_match_fct match,
 361                 const void *key,
 362                 struct cds_lfht_node *new_node);
 363
 364 /*
 365  * cds_lfht_del - remove node pointed to by iterator from hash table.
 366  * @ht: the hash table.
 367  * @node: the node to delete.
 368  *
 369  * Return 0 if the node is successfully removed, negative value
 370  * otherwise.
 371  * Deleting a NULL node or an already removed node will fail with a
 372  * negative value.
 373  * Node can be looked up with cds_lfht_lookup and cds_lfht_next,
 374  * followed by use of cds_lfht_iter_get_node.
 375  * RCU read-side lock must be held between lookup and removal.
 376  * Call with rcu_read_lock held.
 377  * Threads calling this API need to be registered RCU read-side threads.
 378  * After successful removal, a grace period must be waited for before
 379  * freeing the memory reserved for old node (which can be accessed with
 380  * cds_lfht_iter_get_node).
 381  */
 382 int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node);
 383
 384 /*
 385  * cds_lfht_resize - Force a hash table resize
 386  * @ht: the hash table.
 387  * @new_size: update to this hash table size.
 388  *
 389  * Threads calling this API need to be registered RCU read-side threads.
 390  */
 391 void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);
 392
 393 /*
 394  * Note: cds_lfht_for_each are safe for element removal during
 395  * iteration.
 396  */
 397 #define cds_lfht_for_each(ht, iter, node)                               \
 398         for (cds_lfht_first(ht, iter),                                  \
 399                         node = cds_lfht_iter_get_node(iter);            \
 400                 node != NULL;                                           \
 401                 cds_lfht_next(ht, iter),                                \
 402                         node = cds_lfht_iter_get_node(iter))
 403
 404 #define cds_lfht_for_each_duplicate(ht, hash, match, key, iter, node)   \
 405         for (cds_lfht_lookup(ht, hash, match, key, iter),               \
 406                         node = cds_lfht_iter_get_node(iter);            \
 407                 node != NULL;                                           \
 408                 cds_lfht_next_duplicate(ht, match, key, iter),          \
 409                         node = cds_lfht_iter_get_node(iter))
 410
 411 #define cds_lfht_for_each_entry(ht, iter, pos, member)                  \
 412         for (cds_lfht_first(ht, iter),                                  \
 413                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 414                                         typeof(*(pos)), member);        \
 415                 &(pos)->member != NULL;                                 \
 416                 cds_lfht_next(ht, iter),                                \
 417                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 418                                         typeof(*(pos)), member))
 419
 420 #define cds_lfht_for_each_entry_duplicate(ht, hash, match, key,         \
 421                                 iter, pos, member)                      \
 422         for (cds_lfht_lookup(ht, hash, match, key, iter),               \
 423                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 424                                         typeof(*(pos)), member);        \
 425                 &(pos)->member != NULL;                                 \
 426                 cds_lfht_next_duplicate(ht, match, key, iter),          \
 427                         pos = caa_container_of(cds_lfht_iter_get_node(iter), \
 428                                         typeof(*(pos)), member))
 429
 430 #ifdef __cplusplus
 431 }
 432 #endif
 433
 434 #endif /* _URCU_RCULFHASH_H */