1 #ifndef _URCU_RCULFHASH_H
2 #define _URCU_RCULFHASH_H
7 * Userspace RCU library - Lock-Free RCU Hash Table
9 * Copyright 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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.
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.
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
25 * Include this file _after_ including your URCU flavor.
29 #include <urcu-call-rcu.h>
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.
40 struct _cds_lfht_node
{
41 struct cds_lfht_node
*next
; /* ptr | DUMMY_FLAG | REMOVED_FLAG */
42 unsigned long reverse_hash
;
45 struct cds_lfht_node
{
46 /* cache-hot for iteration */
47 struct _cds_lfht_node p
; /* needs to be first field */
50 /* cache-cold for iteration */
58 * Ensure reader and writer threads are registered as urcu readers.
61 typedef unsigned long (*cds_lfht_hash_fct
)(void *key
, size_t length
,
63 typedef unsigned long (*cds_lfht_compare_fct
)(void *key1
, size_t key1_len
,
64 void *key2
, size_t key2_len
);
67 * cds_lfht_node_init - initialize a hash table node
70 void cds_lfht_node_init(struct cds_lfht_node
*node
, void *key
,
74 node
->key_len
= key_len
;
78 * Hash table creation flags.
81 CDS_LFHT_AUTO_RESIZE
= (1U << 0),
85 * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
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
,
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
);
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: '|').
111 * CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
112 * @attr: optional resize worker thread attributes. NULL for default.
114 * Return NULL on error.
115 * Note: the RCU flavor must be already included before the hash table header.
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.
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
,
131 pthread_attr_t
*attr
)
133 return _cds_lfht_new(hash_fct
, compare_fct
, hash_seed
,
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
);
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
148 * Return 0 on success, negative error value on error.
150 int cds_lfht_destroy(struct cds_lfht
*ht
, pthread_attr_t
**attr
);
153 * cds_lfht_count_nodes - count the number of nodes in the hash table.
155 * Call with rcu_read_lock held.
157 void cds_lfht_count_nodes(struct cds_lfht
*ht
,
158 unsigned long *count
,
159 unsigned long *removed
);
162 * cds_lfht_lookup - lookup a node by key.
164 * Return NULL if not found.
165 * Call with rcu_read_lock held.
167 struct cds_lfht_node
*cds_lfht_lookup(struct cds_lfht
*ht
, void *key
, size_t key_len
);
170 * cds_lfht_next - get the next item with same key (after a lookup).
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.
177 struct cds_lfht_node
*cds_lfht_next(struct cds_lfht
*ht
, struct cds_lfht_node
*node
);
180 * cds_lfht_add - add a node to the hash table.
182 * Call with rcu_read_lock held.
184 void cds_lfht_add(struct cds_lfht
*ht
, struct cds_lfht_node
*node
);
187 * cds_lfht_add_unique - add a node to hash table, if key is not present.
189 * Return the node added upon success.
190 * Return the unique node already present upon failure. If
191 * cds_lfht_add_unique fails, the node passed as parameter should be
192 * freed by the caller.
193 * Call with rcu_read_lock held.
195 struct cds_lfht_node
*cds_lfht_add_unique(struct cds_lfht
*ht
, struct cds_lfht_node
*node
);
198 * cds_lfht_del - remove node from hash table.
200 * Node can be looked up with cds_lfht_lookup. RCU read-side lock must
201 * be held between lookup and removal.
202 * Call with rcu_read_lock held.
204 int cds_lfht_del(struct cds_lfht
*ht
, struct cds_lfht_node
*node
);
207 * cds_lfht_resize - Force a hash table resize
208 * @new_size: update to this hash table size.
210 void cds_lfht_resize(struct cds_lfht
*ht
, unsigned long new_size
);
216 #endif /* _URCU_RCULFHASH_H */