| 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 | unsigned long *approx_before, |
| 169 | unsigned long *count, |
| 170 | unsigned long *removed, |
| 171 | unsigned 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 */ |