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 int (*cds_lfht_match_fct)(struct cds_lfht_node *node, void *key);
  88
  89 /*
  90  * cds_lfht_node_init - initialize a hash table node
  91  * @node: the node to initialize.
  92  * @key: pointer to the key to use.
  93  * @key_len: the length of the key, in bytes.
  94  */
  95 static inline
  96 void cds_lfht_node_init(struct cds_lfht_node *node, void *key,
  97                         size_t key_len)
  98 {
  99         node->key = key;
 100         node->key_len = key_len;
 101 }
 102
 103 /*
 104  * Hash table creation flags.
 105  */
 106 enum {
 107         CDS_LFHT_AUTO_RESIZE = (1U << 0),
 108         CDS_LFHT_ACCOUNTING = (1U << 1),
 109 };
 110
 111 /*
 112  * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
 113  */
 114 struct cds_lfht *_cds_lfht_new(unsigned long init_size,
 115                         unsigned long min_alloc_size,
 116                         int flags,
 117                         void (*cds_lfht_call_rcu)(struct rcu_head *head,
 118                                 void (*func)(struct rcu_head *head)),
 119                         void (*cds_lfht_synchronize_rcu)(void),
 120                         void (*cds_lfht_rcu_read_lock)(void),
 121                         void (*cds_lfht_rcu_read_unlock)(void),
 122                         void (*cds_lfht_rcu_thread_offline)(void),
 123                         void (*cds_lfht_rcu_thread_online)(void),
 124                         void (*cds_lfht_rcu_register_thread)(void),
 125                         void (*cds_lfht_rcu_unregister_thread)(void),
 126                         pthread_attr_t *attr);
 127
 128 /*
 129  * cds_lfht_new - allocate a hash table.
 130  * @init_size: number of nodes to allocate initially. Must be power of two.
 131  * @min_alloc_size: the smallest allocation size to use. Must be power of two.
 132  * @flags: hash table creation flags (can be combined with bitwise or: '|').
 133  *           0: no flags.
 134  *           CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
 135  * @attr: optional resize worker thread attributes. NULL for default.
 136  *
 137  * Return NULL on error.
 138  * Note: the RCU flavor must be already included before the hash table header.
 139  *
 140  * The programmer is responsible for ensuring that resize operation has a
 141  * priority equal to hash table updater threads. It should be performed by
 142  * specifying the appropriate priority in the pthread "attr" argument, and,
 143  * for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
 144  * this priority level. Having lower priority for call_rcu and resize threads
 145  * does not pose any correctness issue, but the resize operations could be
 146  * starved by updates, thus leading to long hash table bucket chains.
 147  * Threads calling this API need to be registered RCU read-side threads.
 148  */
 149 static inline
 150 struct cds_lfht *cds_lfht_new(unsigned long init_size,
 151                         unsigned long min_alloc_size,
 152                         int flags,
 153                         pthread_attr_t *attr)
 154 {
 155         return _cds_lfht_new(init_size, min_alloc_size, flags,
 156                         call_rcu, synchronize_rcu, rcu_read_lock,
 157                         rcu_read_unlock, rcu_thread_offline,
 158                         rcu_thread_online, rcu_register_thread,
 159                         rcu_unregister_thread, attr);
 160 }
 161
 162 /*
 163  * cds_lfht_destroy - destroy a hash table.
 164  * @ht: the hash table to destroy.
 165  * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
 166  *        The caller will typically want to free this pointer if dynamically
 167  *        allocated. The attr point can be NULL if the caller does not
 168  *        need to be informed of the value passed to cds_lfht_new().
 169  *
 170  * Return 0 on success, negative error value on error.
 171  * Threads calling this API need to be registered RCU read-side threads.
 172  */
 173 int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
 174
 175 /*
 176  * cds_lfht_count_nodes - count the number of nodes in the hash table.
 177  * @ht: the hash table.
 178  * @split_count_before: Sample the node count split-counter before traversal.
 179  * @count: Traverse the hash table, count the number of nodes observed.
 180  * @removed: Number of logically removed nodes observed during traversal.
 181  * @split_count_after: Sample the node count split-counter after traversal.
 182  *
 183  * Call with rcu_read_lock held.
 184  * Threads calling this API need to be registered RCU read-side threads.
 185  */
 186 void cds_lfht_count_nodes(struct cds_lfht *ht,
 187                 long *split_count_before,
 188                 unsigned long *count,
 189                 unsigned long *removed,
 190                 long *split_count_after);
 191
 192 /*
 193  * cds_lfht_lookup - lookup a node by key.
 194  * @ht: the hash table.
 195  * @match: the key match function.
 196  * @hash: the key hash.
 197  * @iter: Node, if found (output). *iter->node set to NULL if not found.
 198  *
 199  * Call with rcu_read_lock held.
 200  * Threads calling this API need to be registered RCU read-side threads.
 201  */
 202 void cds_lfht_lookup(struct cds_lfht *ht, cds_lfht_match_fct match,
 203                 unsigned long hash, void *key, struct cds_lfht_iter *iter);
 204
 205 /*
 206  * cds_lfht_next_duplicate - get the next item with same key (after a lookup).
 207  * @ht: the hash table.
 208  * @match: the key match function.
 209  * @iter: Node, if found (output). *iter->node set to NULL if not found.
 210  *
 211  * Uses an iterator initialized by a lookup.
 212  * Sets *iter-node to the following node with same key.
 213  * Sets *iter->node to NULL if no following node exists with same key.
 214  * RCU read-side lock must be held across cds_lfht_lookup and
 215  * cds_lfht_next calls, and also between cds_lfht_next calls using the
 216  * node returned by a previous cds_lfht_next.
 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_next_duplicate(struct cds_lfht *ht,
 221                 cds_lfht_match_fct match, struct cds_lfht_iter *iter);
 222
 223 /*
 224  * cds_lfht_first - get the first node in the table.
 225  * @ht: the hash table.
 226  * @iter: First node, if exists (output). *iter->node set to NULL if not found.
 227  *
 228  * Output in "*iter". *iter->node set to NULL if table is empty.
 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_first(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 233
 234 /*
 235  * cds_lfht_next - get the next node in the table.
 236  * @ht: the hash table.
 237  * @iter: Next node, if exists (output). *iter->node set to NULL if not found.
 238  *
 239  * Input/Output in "*iter". *iter->node set to NULL if *iter was
 240  * pointing to the last table node.
 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_next(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 245
 246 /*
 247  * cds_lfht_add - add a node to the hash table.
 248  * @ht: the hash table.
 249  * @hash: the key hash.
 250  * @node: the node to add.
 251  *
 252  * This function supports adding redundant keys into the table.
 253  * Call with rcu_read_lock held.
 254  * Threads calling this API need to be registered RCU read-side threads.
 255  */
 256 void cds_lfht_add(struct cds_lfht *ht, unsigned long hash,
 257                 struct cds_lfht_node *node);
 258
 259 /*
 260  * cds_lfht_add_unique - add a node to hash table, if key is not present.
 261  * @ht: the hash table.
 262  * @match: the key match function.
 263  * @node: the node to try adding.
 264  *
 265  * Return the node added upon success.
 266  * Return the unique node already present upon failure. If
 267  * cds_lfht_add_unique fails, the node passed as parameter should be
 268  * freed by the caller.
 269  * Call with rcu_read_lock held.
 270  * Threads calling this API need to be registered RCU read-side threads.
 271  *
 272  * The semantic of this function is that if only this function is used
 273  * to add keys into the table, no duplicated keys should ever be
 274  * observable in the table. The same guarantee apply for combination of
 275  * add_unique and add_replace (see below).
 276  */
 277 struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
 278                 cds_lfht_match_fct match,
 279                 unsigned long hash,
 280                 struct cds_lfht_node *node);
 281
 282 /*
 283  * cds_lfht_add_replace - replace or add a node within hash table.
 284  * @ht: the hash table.
 285  * @match: the key match function.
 286  * @node: the node to add.
 287  *
 288  * Return the node replaced upon success. If no node matching the key
 289  * was present, return NULL, which also means the operation succeeded.
 290  * This replacement operation should never fail.
 291  * Call with rcu_read_lock held.
 292  * Threads calling this API need to be registered RCU read-side threads.
 293  * After successful replacement, a grace period must be waited for before
 294  * freeing the memory reserved for the returned node.
 295  *
 296  * The semantic of replacement vs lookups is the following: if lookups
 297  * are performed between a key unique insertion and its removal, we
 298  * guarantee that the lookups and get next will always find exactly one
 299  * instance of the key if it is replaced concurrently with the lookups.
 300  *
 301  * Providing this semantic allows us to ensure that replacement-only
 302  * schemes will never generate duplicated keys. It also allows us to
 303  * guarantee that a combination of add_replace and add_unique updates
 304  * will never generate duplicated keys.
 305  */
 306 struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
 307                 cds_lfht_match_fct match,
 308                 unsigned long hash,
 309                 struct cds_lfht_node *node);
 310
 311 /*
 312  * cds_lfht_replace - replace a node pointer to by iter within hash table.
 313  * @ht: the hash table.
 314  * @old_iter: the iterator position of the node to replace.
 315  * @now_node: the new node to try using for replacement.
 316  *
 317  * Return 0 if replacement is successful, negative value otherwise.
 318  * Replacing a NULL old node or an already removed node will fail with a
 319  * negative value.
 320  * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
 321  * RCU read-side lock must be held between lookup and replacement.
 322  * Call with rcu_read_lock held.
 323  * Threads calling this API need to be registered RCU read-side threads.
 324  * After successful replacement, a grace period must be waited for before
 325  * freeing the memory reserved for the old node (which can be accessed
 326  * with cds_lfht_iter_get_node).
 327  *
 328  * The semantic of replacement vs lookups is the following: if lookups
 329  * are performed between a key unique insertion and its removal, we
 330  * guarantee that the lookups and get next will always find exactly one
 331  * instance of the key if it is replaced concurrently with the lookups.
 332  *
 333  * Providing this semantic allows us to ensure that replacement-only
 334  * schemes will never generate duplicated keys. It also allows us to
 335  * guarantee that a combination of add_replace and add_unique updates
 336  * will never generate duplicated keys.
 337  */
 338 int cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_iter *old_iter,
 339                 struct cds_lfht_node *new_node);
 340
 341 /*
 342  * cds_lfht_del - remove node pointed to by iterator from hash table.
 343  * @ht: the hash table.
 344  * @iter: the iterator position of the node to delete.
 345  *
 346  * Return 0 if the node is successfully removed, negative value
 347  * otherwise.
 348  * Replacing a NULL node or an already removed node will fail with a
 349  * negative value.
 350  * Node can be looked up with cds_lfht_lookup and cds_lfht_next.
 351  * cds_lfht_iter_get_node.
 352  * RCU read-side lock must be held between lookup and removal.
 353  * Call with rcu_read_lock held.
 354  * Threads calling this API need to be registered RCU read-side threads.
 355  * After successful removal, a grace period must be waited for before
 356  * freeing the memory reserved for old node (which can be accessed with
 357  * cds_lfht_iter_get_node).
 358  */
 359 int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 360
 361 /*
 362  * cds_lfht_resize - Force a hash table resize
 363  * @ht: the hash table.
 364  * @new_size: update to this hash table size.
 365  *
 366  * Threads calling this API need to be registered RCU read-side threads.
 367  */
 368 void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);
 369
 370 #ifdef __cplusplus
 371 }
 372 #endif
 373
 374 #endif /* _URCU_RCULFHASH_H */