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  * struct cds_lfht_node and struct _cds_lfht_node should be aligned on
  37  * 4-bytes boundaries because the two lower bits are used as flags.
  38  */
  39
  40 /*
  41  * _cds_lfht_node: Contains the internal pointers and reverse-hash
  42  * value required for lookup and traversal of the hash table.
  43  */
  44 struct _cds_lfht_node {
  45         struct cds_lfht_node *next;     /* ptr | DUMMY_FLAG | REMOVED_FLAG */
  46         unsigned long reverse_hash;
  47 } __attribute__((aligned(4)));
  48
  49 /*
  50  * cds_lfht_node: Contains the full key and length required to check for
  51  * an actual match, and also contains an rcu_head structure that is used
  52  * by RCU to track a node through a given RCU grace period.  There is an
  53  * instance of _cds_lfht_node enclosed as a field within each
  54  * _cds_lfht_node structure.
  55  *
  56  * struct cds_lfht_node can be embedded into a structure (as a field).
  57  * caa_container_of() can be used to get the structure from the struct
  58  * cds_lfht_node after a lookup.
  59  */
  60 struct cds_lfht_node {
  61         /* cache-hot for iteration */
  62         struct _cds_lfht_node p;          /* needs to be first field */
  63         void *key;
  64         unsigned int key_len;
  65 };
  66
  67 /* cds_lfht_iter: Used to track state while traversing a hash chain. */
  68 struct cds_lfht_iter {
  69         struct cds_lfht_node *node, *next;
  70 };
  71
  72 static inline
  73 struct cds_lfht_node *cds_lfht_iter_get_node(struct cds_lfht_iter *iter)
  74 {
  75         return iter->node;
  76 }
  77
  78 struct cds_lfht;
  79
  80 /*
  81  * Caution !
  82  * Ensure reader and writer threads are registered as urcu readers.
  83  */
  84
  85 typedef unsigned long (*cds_lfht_hash_fct)(void *key, size_t length,
  86                                         unsigned long seed);
  87 typedef unsigned long (*cds_lfht_compare_fct)(void *key1, size_t key1_len,
  88                                         void *key2, size_t key2_len);
  89
  90 /*
  91  * cds_lfht_node_init - initialize a hash table node
  92  */
  93 static inline
  94 void cds_lfht_node_init(struct cds_lfht_node *node, void *key,
  95                         size_t key_len)
  96 {
  97         node->key = key;
  98         node->key_len = key_len;
  99 }
 100
 101 /*
 102  * Hash table creation flags.
 103  */
 104 enum {
 105         CDS_LFHT_AUTO_RESIZE = (1U << 0),
 106         CDS_LFHT_ACCOUNTING = (1U << 1),
 107 };
 108
 109 /*
 110  * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
 111  */
 112 struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
 113                         cds_lfht_compare_fct compare_fct,
 114                         unsigned long hash_seed,
 115                         unsigned long init_size,
 116                         unsigned long min_alloc_size,
 117                         int flags,
 118                         void (*cds_lfht_call_rcu)(struct rcu_head *head,
 119                                 void (*func)(struct rcu_head *head)),
 120                         void (*cds_lfht_synchronize_rcu)(void),
 121                         void (*cds_lfht_rcu_read_lock)(void),
 122                         void (*cds_lfht_rcu_read_unlock)(void),
 123                         void (*cds_lfht_rcu_thread_offline)(void),
 124                         void (*cds_lfht_rcu_thread_online)(void),
 125                         void (*cds_lfht_rcu_register_thread)(void),
 126                         void (*cds_lfht_rcu_unregister_thread)(void),
 127                         pthread_attr_t *attr);
 128
 129 /*
 130  * cds_lfht_new - allocate a hash table.
 131  * @hash_fct: the hashing function.
 132  * @compare_fct: the key comparison function.
 133  * @hash_seed: the seed for hash function.
 134  * @init_size: number of nodes to allocate initially. Must be power of two.
 135  * @min_alloc_size: the smallest allocation size to use. 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  * @attr: optional resize worker thread attributes. NULL for default.
 140  *
 141  * Return NULL on error.
 142  * Note: the RCU flavor must be already included before the hash table header.
 143  *
 144  * The programmer is responsible for ensuring that resize operation has a
 145  * priority equal to hash table updater threads. It should be performed by
 146  * specifying the appropriate priority in the pthread "attr" argument, and,
 147  * for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
 148  * this priority level. Having lower priority for call_rcu and resize threads
 149  * does not pose any correctness issue, but the resize operations could be
 150  * starved by updates, thus leading to long hash table bucket chains.
 151  * Threads calling this API need to be registered RCU read-side threads.
 152  */
 153 static inline
 154 struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_fct,
 155                         cds_lfht_compare_fct compare_fct,
 156                         unsigned long hash_seed,
 157                         unsigned long init_size,
 158                         unsigned long min_alloc_size,
 159                         int flags,
 160                         pthread_attr_t *attr)
 161 {
 162         return _cds_lfht_new(hash_fct, compare_fct, hash_seed,
 163                         init_size, min_alloc_size, flags,
 164                         call_rcu, synchronize_rcu, rcu_read_lock,
 165                         rcu_read_unlock, rcu_thread_offline,
 166                         rcu_thread_online, rcu_register_thread,
 167                         rcu_unregister_thread, attr);
 168 }
 169
 170 /*
 171  * cds_lfht_destroy - destroy a hash table.
 172  * @ht: the hash table to destroy.
 173  * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
 174  *        The caller will typically want to free this pointer if dynamically
 175  *        allocated. The attr point can be NULL if the caller does not
 176  *        need to be informed of the value passed to cds_lfht_new().
 177  *
 178  * Return 0 on success, negative error value on error.
 179  * Threads calling this API need to be registered RCU read-side threads.
 180  */
 181 int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
 182
 183 /*
 184  * cds_lfht_count_nodes - count the number of nodes in the hash table.
 185  * @ht: the hash table.
 186  * @split_count_before: Sample the node count split-counter before traversal.
 187  * @count: Traverse the hash table, count the number of nodes observed.
 188  * @removed: Number of logically removed nodes observed during traversal.
 189  * @split_count_after: Sample the node count split-counter after traversal.
 190  * Call with rcu_read_lock held.
 191  * Threads calling this API need to be registered RCU read-side threads.
 192  */
 193 void cds_lfht_count_nodes(struct cds_lfht *ht,
 194                 long *split_count_before,
 195                 unsigned long *count,
 196                 unsigned long *removed,
 197                 long *split_count_after);
 198
 199 /*
 200  * cds_lfht_lookup - lookup a node by key.
 201  *
 202  * Output in "*iter". *iter->node set to NULL if not found.
 203  * Call with rcu_read_lock held.
 204  * Threads calling this API need to be registered RCU read-side threads.
 205  */
 206 void cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len,
 207                 struct cds_lfht_iter *iter);
 208
 209 /*
 210  * cds_lfht_next_duplicate - get the next item with same key (after a lookup).
 211  *
 212  * Uses an iterator initialized by a lookup.
 213  * Sets *iter-node to the following node with same key.
 214  * Sets *iter->node to NULL if no following node exists with same key.
 215  * RCU read-side lock must be held across cds_lfht_lookup and
 216  * cds_lfht_next calls, and also between cds_lfht_next calls using the
 217  * node returned by a previous cds_lfht_next.
 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_next_duplicate(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 222
 223 /*
 224  * cds_lfht_first - get the first node in the table.
 225  *
 226  * Output in "*iter". *iter->node set to NULL if table is empty.
 227  * Call with rcu_read_lock held.
 228  * Threads calling this API need to be registered RCU read-side threads.
 229  */
 230 void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 231
 232 /*
 233  * cds_lfht_next - get the next node in the table.
 234  *
 235  * Input/Output in "*iter". *iter->node set to NULL if *iter was
 236  * pointing to the last table node.
 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_next(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 241
 242 /*
 243  * cds_lfht_add - add a node to the hash table.
 244  *
 245  * This function supports adding redundant keys into the table.
 246  * Call with rcu_read_lock held.
 247  * Threads calling this API need to be registered RCU read-side threads.
 248  */
 249 void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node);
 250
 251 /*
 252  * cds_lfht_add_unique - add a node to hash table, if key is not present.
 253  *
 254  * Return the node added upon success.
 255  * Return the unique node already present upon failure. If
 256  * cds_lfht_add_unique fails, the node passed as parameter should be
 257  * freed by the caller.
 258  * Call with rcu_read_lock held.
 259  * Threads calling this API need to be registered RCU read-side threads.
 260  *
 261  * The semantic of this function is that if only this function is used
 262  * to add keys into the table, no duplicated keys should ever be
 263  * observable in the table. The same guarantee apply for combination of
 264  * add_unique and add_replace (see below).
 265  */
 266 struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
 267                 struct cds_lfht_node *node);
 268
 269 /*
 270  * cds_lfht_add_replace - replace or add a node within hash table.
 271  *
 272  * Return the node replaced upon success. If no node matching the key
 273  * was present, return NULL, which also means the operation succeeded.
 274  * This replacement operation should never fail.
 275  * Call with rcu_read_lock held.
 276  * Threads calling this API need to be registered RCU read-side threads.
 277  * After successful replacement, a grace period must be waited for before
 278  * freeing the memory reserved for the returned node.
 279  *
 280  * The semantic of replacement vs lookups is the following: if lookups
 281  * are performed between a key unique insertion and its removal, we
 282  * guarantee that the lookups and get next will always find exactly one
 283  * instance of the key if it is replaced concurrently with the lookups.
 284  *
 285  * Providing this semantic allows us to ensure that replacement-only
 286  * schemes will never generate duplicated keys. It also allows us to
 287  * guarantee that a combination of add_replace and add_unique updates
 288  * will never generate duplicated keys.
 289  */
 290 struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
 291                 struct cds_lfht_node *node);
 292
 293 /*
 294  * cds_lfht_replace - replace a node pointer to by iter within hash table.
 295  *
 296  * Return 0 if replacement is successful, negative value otherwise.
 297  * Replacing a NULL old node or an already removed node will fail with a
 298  * negative value.
 299  * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
 300  * RCU read-side lock must be held between lookup and replacement.
 301  * Call with rcu_read_lock held.
 302  * Threads calling this API need to be registered RCU read-side threads.
 303  * After successful replacement, a grace period must be waited for before
 304  * freeing the memory reserved for the old node (which can be accessed
 305  * with cds_lfht_iter_get_node).
 306  *
 307  * The semantic of replacement vs lookups is the following: if lookups
 308  * are performed between a key unique insertion and its removal, we
 309  * guarantee that the lookups and get next will always find exactly one
 310  * instance of the key if it is replaced concurrently with the lookups.
 311  *
 312  * Providing this semantic allows us to ensure that replacement-only
 313  * schemes will never generate duplicated keys. It also allows us to
 314  * guarantee that a combination of add_replace and add_unique updates
 315  * will never generate duplicated keys.
 316  */
 317 int cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_iter *old_iter,
 318                 struct cds_lfht_node *new_node);
 319
 320 /*
 321  * cds_lfht_del - remove node pointed to by iterator from hash table.
 322  *
 323  * Return 0 if the node is successfully removed, negative value
 324  * otherwise.
 325  * Replacing a NULL node or an already removed node will fail with a
 326  * negative value.
 327  * Node can be looked up with cds_lfht_lookup and cds_lfht_next.
 328  * cds_lfht_iter_get_node.
 329  * RCU read-side lock must be held between lookup and removal.
 330  * Call with rcu_read_lock held.
 331  * Threads calling this API need to be registered RCU read-side threads.
 332  * After successful removal, a grace period must be waited for before
 333  * freeing the memory reserved for old node (which can be accessed with
 334  * cds_lfht_iter_get_node).
 335  */
 336 int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 337
 338 /*
 339  * cds_lfht_resize - Force a hash table resize
 340  * @new_size: update to this hash table size.
 341  *
 342  * Threads calling this API need to be registered RCU read-side threads.
 343  */
 344 void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);
 345
 346 #ifdef __cplusplus
 347 }
 348 #endif
 349
 350 #endif /* _URCU_RCULFHASH_H */