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 struct _cds_lfht_node {
  41         struct cds_lfht_node *next;     /* ptr | DUMMY_FLAG | REMOVED_FLAG */
  42         unsigned long reverse_hash;
  43 } __attribute__((aligned(4)));
  44
  45 /*
  46  * struct cds_lfht_node can be embedded into a structure (as a field).
  47  * caa_container_of() can be used to get the structure from the struct
  48  * cds_lfht_node after a lookup.
  49  */
  50 struct cds_lfht_node {
  51         /* cache-hot for iteration */
  52         struct _cds_lfht_node p;          /* needs to be first field */
  53         void *key;
  54         unsigned int key_len;
  55         /* cache-cold for iteration */
  56         struct rcu_head head;
  57 };
  58
  59 struct cds_lfht_iter {
  60         struct cds_lfht_node *node, *next;
  61 };
  62
  63 static inline
  64 struct cds_lfht_node *cds_lfht_iter_get_node(struct cds_lfht_iter *iter)
  65 {
  66         return iter->node;
  67 }
  68
  69 struct cds_lfht;
  70
  71 /*
  72  * Caution !
  73  * Ensure reader and writer threads are registered as urcu readers.
  74  */
  75
  76 typedef unsigned long (*cds_lfht_hash_fct)(void *key, size_t length,
  77                                         unsigned long seed);
  78 typedef unsigned long (*cds_lfht_compare_fct)(void *key1, size_t key1_len,
  79                                         void *key2, size_t key2_len);
  80
  81 /*
  82  * cds_lfht_node_init - initialize a hash table node
  83  */
  84 static inline
  85 void cds_lfht_node_init(struct cds_lfht_node *node, void *key,
  86                         size_t key_len)
  87 {
  88         node->key = key;
  89         node->key_len = key_len;
  90 }
  91
  92 /*
  93  * Hash table creation flags.
  94  */
  95 enum {
  96         CDS_LFHT_AUTO_RESIZE = (1U << 0),
  97 };
  98
  99 /*
 100  * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
 101  */
 102 struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
 103                         cds_lfht_compare_fct compare_fct,
 104                         unsigned long hash_seed,
 105                         unsigned long init_size,
 106                         int flags,
 107                         void (*cds_lfht_call_rcu)(struct rcu_head *head,
 108                                 void (*func)(struct rcu_head *head)),
 109                         void (*cds_lfht_synchronize_rcu)(void),
 110                         void (*cds_lfht_rcu_read_lock)(void),
 111                         void (*cds_lfht_rcu_read_unlock)(void),
 112                         void (*cds_lfht_rcu_thread_offline)(void),
 113                         void (*cds_lfht_rcu_thread_online)(void),
 114                         void (*cds_lfht_rcu_register_thread)(void),
 115                         void (*cds_lfht_rcu_unregister_thread)(void),
 116                         pthread_attr_t *attr);
 117
 118 /*
 119  * cds_lfht_new - allocate a hash table.
 120  * @hash_fct: the hashing function.
 121  * @compare_fct: the key comparison function.
 122  * @hash_seed: the seed for hash function.
 123  * @init_size: number of nodes to allocate initially. Must be power of two.
 124  * @flags: hash table creation flags (can be combined with bitwise or: '|').
 125  *           0: no flags.
 126  *           CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
 127  * @attr: optional resize worker thread attributes. NULL for default.
 128  *
 129  * Return NULL on error.
 130  * Note: the RCU flavor must be already included before the hash table header.
 131  *
 132  * The programmer is responsible for ensuring that resize operation has a
 133  * priority equal to hash table updater threads. It should be performed by
 134  * specifying the appropriate priority in the pthread "attr" argument, and,
 135  * for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
 136  * this priority level. Having lower priority for call_rcu and resize threads
 137  * does not pose any correctness issue, but the resize operations could be
 138  * starved by updates, thus leading to long hash table bucket chains.
 139  */
 140 static inline
 141 struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_fct,
 142                         cds_lfht_compare_fct compare_fct,
 143                         unsigned long hash_seed,
 144                         unsigned long init_size,
 145                         int flags,
 146                         pthread_attr_t *attr)
 147 {
 148         return _cds_lfht_new(hash_fct, compare_fct, hash_seed,
 149                         init_size, flags,
 150                         call_rcu, synchronize_rcu, rcu_read_lock,
 151                         rcu_read_unlock, rcu_thread_offline,
 152                         rcu_thread_online, rcu_register_thread,
 153                         rcu_unregister_thread, attr);
 154 }
 155
 156 /*
 157  * cds_lfht_destroy - destroy a hash table.
 158  * @ht: the hash table to destroy.
 159  * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
 160  *        The caller will typically want to free this pointer if dynamically
 161  *        allocated.
 162  *
 163  * Return 0 on success, negative error value on error.
 164  */
 165 int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
 166
 167 /*
 168  * cds_lfht_count_nodes - count the number of nodes in the hash table.
 169  *
 170  * Call with rcu_read_lock held.
 171  */
 172 void cds_lfht_count_nodes(struct cds_lfht *ht,
 173                 long *approx_before,
 174                 unsigned long *count,
 175                 unsigned long *removed,
 176                 long *approx_after);
 177
 178 /*
 179  * cds_lfht_lookup - lookup a node by key.
 180  *
 181  * Output in "*iter". *iter->node set to NULL if not found.
 182  * Call with rcu_read_lock held.
 183  */
 184 void cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len,
 185                 struct cds_lfht_iter *iter);
 186
 187 /*
 188  * cds_lfht_next_duplicate - get the next item with same key (after a lookup).
 189  *
 190  * Uses an iterator initialized by a lookup.
 191  * Sets *iter-node to the following node with same key.
 192  * Sets *iter->node to NULL if no following node exists with same key.
 193  * RCU read-side lock must be held across cds_lfht_lookup and
 194  * cds_lfht_next calls, and also between cds_lfht_next calls using the
 195  * node returned by a previous cds_lfht_next.
 196  * Call with rcu_read_lock held.
 197  */
 198 void cds_lfht_next_duplicate(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 199
 200 /*
 201  * cds_lfht_add - add a node to the hash table.
 202  *
 203  * Call with rcu_read_lock held.
 204  * This function supports adding redundant keys into the table.
 205  */
 206 void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node);
 207
 208 /*
 209  * cds_lfht_add_unique - add a node to hash table, if key is not present.
 210  *
 211  * Return the node added upon success.
 212  * Return the unique node already present upon failure. If
 213  * cds_lfht_add_unique fails, the node passed as parameter should be
 214  * freed by the caller.
 215  * Call with rcu_read_lock held.
 216  *
 217  * The semantic of this function is that if only this function is used
 218  * to add keys into the table, no duplicated keys should ever be
 219  * observable in the table. The same guarantee apply for combination of
 220  * add_unique and add_replace (see below).
 221  */
 222 struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
 223                 struct cds_lfht_node *node);
 224
 225 /*
 226  * cds_lfht_add_replace - replace or add a node within hash table.
 227  *
 228  * Return the node replaced upon success. If no node matching the key
 229  * was present, return NULL, which also means the operation succeeded.
 230  * This replacement operation should never fail.
 231  * Call with rcu_read_lock held.
 232  * After successful replacement, a grace period must be waited for before
 233  * freeing the memory reserved for the returned node.
 234  *
 235  * The semantic of replacement vs lookups is the following: if lookups
 236  * are performed between a key unique insertion and its removal, we
 237  * guarantee that the lookups and get next will always find exactly one
 238  * instance of the key if it is replaced concurrently with the lookups.
 239  *
 240  * Providing this semantic allows us to ensure that replacement-only
 241  * schemes will never generate duplicated keys. It also allows us to
 242  * guarantee that a combination of add_replace and add_unique updates
 243  * will never generate duplicated keys.
 244  */
 245 struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
 246                 struct cds_lfht_node *node);
 247
 248 /*
 249  * cds_lfht_replace - replace a node pointer to by iter within hash table.
 250  *
 251  * Return 0 if replacement is successful, negative value otherwise.
 252  * Replacing a NULL old node or an already removed node will fail with a
 253  * negative value.
 254  * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
 255  * RCU read-side lock must be held between lookup and replacement.
 256  * Call with rcu_read_lock held.
 257  * After successful replacement, a grace period must be waited for before
 258  * freeing the memory reserved for the old node (which can be accessed
 259  * with cds_lfht_iter_get_node).
 260  *
 261  * The semantic of replacement vs lookups is the following: if lookups
 262  * are performed between a key unique insertion and its removal, we
 263  * guarantee that the lookups and get next will always find exactly one
 264  * instance of the key if it is replaced concurrently with the lookups.
 265  *
 266  * Providing this semantic allows us to ensure that replacement-only
 267  * schemes will never generate duplicated keys. It also allows us to
 268  * guarantee that a combination of add_replace and add_unique updates
 269  * will never generate duplicated keys.
 270  */
 271 int cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_iter *old_iter,
 272                 struct cds_lfht_node *new_node);
 273
 274 /*
 275  * cds_lfht_del - remove node pointed to by iterator from hash table.
 276  *
 277  * Return 0 if the node is successfully removed, negative value
 278  * otherwise.
 279  * Replacing a NULL node or an already removed node will fail with a
 280  * negative value.
 281  * Node can be looked up with cds_lfht_lookup and cds_lfht_next.
 282  * cds_lfht_iter_get_node.
 283  * RCU read-side lock must be held between lookup and removal.
 284  * Call with rcu_read_lock held.
 285  * After successful removal, a grace period must be waited for before
 286  * freeing the memory reserved for old node (which can be accessed with
 287  * cds_lfht_iter_get_node).
 288  */
 289 int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 290
 291 /*
 292  * cds_lfht_resize - Force a hash table resize
 293  * @new_size: update to this hash table size.
 294  */
 295 void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);
 296
 297 #ifdef __cplusplus
 298 }
 299 #endif
 300
 301 #endif /* _URCU_RCULFHASH_H */