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