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  * 8-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 | GC_FLAG | REMOVED_FLAG */
  42         unsigned long reverse_hash;
  43 } __attribute__((aligned(8)));
  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;
  55
  56 /*
  57  * Caution !
  58  * Ensure reader and writer threads are registered as urcu readers.
  59  */
  60
  61 typedef unsigned long (*cds_lfht_hash_fct)(void *key, size_t length,
  62                                         unsigned long seed);
  63 typedef unsigned long (*cds_lfht_compare_fct)(void *key1, size_t key1_len,
  64                                         void *key2, size_t key2_len);
  65
  66 /*
  67  * cds_lfht_node_init - initialize a hash table node
  68  */
  69 static inline
  70 void cds_lfht_node_init(struct cds_lfht_node *node, void *key,
  71                         size_t key_len)
  72 {
  73         node->key = key;
  74         node->key_len = key_len;
  75 }
  76
  77 /*
  78  * Hash table creation flags.
  79  */
  80 enum {
  81         CDS_LFHT_AUTO_RESIZE = (1U << 0),
  82 };
  83
  84 /*
  85  * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
  86  */
  87 struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
  88                         cds_lfht_compare_fct compare_fct,
  89                         unsigned long hash_seed,
  90                         unsigned long init_size,
  91                         int flags,
  92                         void (*cds_lfht_call_rcu)(struct rcu_head *head,
  93                                 void (*func)(struct rcu_head *head)),
  94                         void (*cds_lfht_synchronize_rcu)(void),
  95                         void (*cds_lfht_rcu_read_lock)(void),
  96                         void (*cds_lfht_rcu_read_unlock)(void),
  97                         void (*cds_lfht_rcu_thread_offline)(void),
  98                         void (*cds_lfht_rcu_thread_online)(void),
  99                         void (*cds_lfht_rcu_register_thread)(void),
 100                         void (*cds_lfht_rcu_unregister_thread)(void),
 101                         pthread_attr_t *attr);
 102
 103 /*
 104  * cds_lfht_new - allocate a hash table.
 105  * @hash_fct: the hashing function.
 106  * @compare_fct: the key comparison function.
 107  * @hash_seed: the seed for hash function.
 108  * @init_size: number of nodes to allocate initially. Must be power of two.
 109  * @flags: hash table creation flags (can be combined with bitwise or: '|').
 110  *           0: no flags.
 111  *           CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
 112  * @attr: optional resize worker thread attributes. NULL for default.
 113  *
 114  * Return NULL on error.
 115  * Note: the RCU flavor must be already included before the hash table header.
 116  *
 117  * The programmer is responsible for ensuring that resize operation has a
 118  * priority equal to hash table updater threads. It should be performed by
 119  * specifying the appropriate priority in the pthread "attr" argument, and,
 120  * for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
 121  * this priority level. Having lower priority for call_rcu and resize threads
 122  * does not pose any correctness issue, but the resize operations could be
 123  * starved by updates, thus leading to long hash table bucket chains.
 124  */
 125 static inline
 126 struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_fct,
 127                         cds_lfht_compare_fct compare_fct,
 128                         unsigned long hash_seed,
 129                         unsigned long init_size,
 130                         int flags,
 131                         pthread_attr_t *attr)
 132 {
 133         return _cds_lfht_new(hash_fct, compare_fct, hash_seed,
 134                         init_size, flags,
 135                         call_rcu, synchronize_rcu, rcu_read_lock,
 136                         rcu_read_unlock, rcu_thread_offline,
 137                         rcu_thread_online, rcu_register_thread,
 138                         rcu_unregister_thread, attr);
 139 }
 140
 141 /*
 142  * cds_lfht_destroy - destroy a hash table.
 143  * @ht: the hash table to destroy.
 144  * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
 145  *        The caller will typically want to free this pointer if dynamically
 146  *        allocated.
 147  *
 148  * Return 0 on success, negative error value on error.
 149  */
 150 int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
 151
 152 /*
 153  * cds_lfht_count_nodes - count the number of nodes in the hash table.
 154  *
 155  * Call with rcu_read_lock held.
 156  */
 157 void cds_lfht_count_nodes(struct cds_lfht *ht,
 158                         unsigned long *count,
 159                         unsigned long *removed);
 160
 161 /*
 162  * cds_lfht_lookup - lookup a node by key.
 163  *
 164  * Return NULL if not found.
 165  * Call with rcu_read_lock held.
 166  */
 167 struct cds_lfht_node *cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len);
 168
 169 /*
 170  * cds_lfht_next - get the next item with same key (after a lookup).
 171  *
 172  * Return NULL if no following node exists with same key.
 173  * RCU read-side lock must be held across cds_lfht_lookup and cds_lfht_next calls, and also
 174  * between cds_lfht_next calls using the node returned by a previous
 175  * cds_lfht_next.  Call with rcu_read_lock held.
 176  */
 177 struct cds_lfht_node *cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_node *node);
 178
 179 /*
 180  * cds_lfht_add - add a node to the hash table.
 181  *
 182  * Call with rcu_read_lock held.
 183  * This function supports adding redundant keys into the table.
 184  */
 185 void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node);
 186
 187 /*
 188  * cds_lfht_add_unique - add a node to hash table, if key is not present.
 189  *
 190  * Return the node added upon success.
 191  * Return the unique node already present upon failure. If
 192  * cds_lfht_add_unique fails, the node passed as parameter should be
 193  * freed by the caller.
 194  * Call with rcu_read_lock held.
 195  *
 196  * The semantic of this function is that if only this function is used
 197  * to add keys into the table, no duplicated keys should ever be
 198  * observable in the table. The same guarantee apply for combination of
 199  * add_unique and replace (see below).
 200  */
 201 struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht, struct cds_lfht_node *node);
 202
 203 /*
 204  * cds_lfht_replace - replace a node within hash table.
 205  *
 206  * Return the node replaced upon success. If no node matching the key
 207  * was present, return NULL, which also means the operation succeeded.
 208  * This replacement operation should never fail.
 209  * Call with rcu_read_lock held.
 210  * After successful replacement, a grace period must be waited for before
 211  * freeing the memory reserved for the returned node.
 212  *
 213  * The semantic of replacement vs lookups is the following: if lookups
 214  * are performed between a key insertion and its removal, we guarantee
 215  * that the lookups will always find the key if it is replaced
 216  * concurrently with the lookups. Providing this guarantee require us to
 217  * pin the node to remove in place (disallowing any insertion after this
 218  * node temporarily) before we can proceed to its exchange with the new
 219  * node atomically. This renders the "replace" operation not strictly
 220  * lock-free, because a thread crashing in the middle of the replace
 221  * operation could stop progress for other updaters.
 222  *
 223  * Providing this semantic allows us to ensure that replacement-only
 224  * schemes will never generate duplicated keys. It also allows us to
 225  * guarantee that a combination of replacement and add_unique updates
 226  * will never generate duplicated keys.
 227  */
 228 struct cds_lfht_node *cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_node *node);
 229
 230 /*
 231  * cds_lfht_del - remove node from hash table.
 232  *
 233  * Return 0 if the node is successfully removed.
 234  * Node can be looked up with cds_lfht_lookup. RCU read-side lock must
 235  * be held between lookup and removal.
 236  * Call with rcu_read_lock held.
 237  * After successful removal, a grace period must be waited for before
 238  * freeing the memory reserved for node.
 239  */
 240 int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node);
 241
 242 /*
 243  * cds_lfht_resize - Force a hash table resize
 244  * @new_size: update to this hash table size.
 245  */
 246 void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);
 247
 248 #ifdef __cplusplus
 249 }
 250 #endif
 251
 252 #endif /* _URCU_RCULFHASH_H */