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f7e7a1b8 MD |
1 | /* |
2 | * Copyright (C) 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
3 | * | |
4 | * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED | |
5 | * OR IMPLIED. ANY USE IS AT YOUR OWN RISK. | |
6 | * | |
7 | * Permission is hereby granted to use or copy this program for any | |
8 | * purpose, provided the above notices are retained on all copies. | |
9 | * Permission to modify the code and to distribute modified code is | |
10 | * granted, provided the above notices are retained, and a notice that | |
11 | * the code was modified is included with the above copyright notice. | |
12 | * | |
13 | * This example shows how to remove nodes from a RCU lock-free hash table. | |
14 | * This hash table requires using a RCU scheme. | |
15 | */ | |
16 | ||
17 | #include <stdio.h> | |
18 | #include <stdlib.h> | |
19 | #include <time.h> | |
20 | ||
21 | #include <urcu.h> /* RCU flavor */ | |
22 | #include <urcu/rculfhash.h> /* RCU Lock-free hash table */ | |
23 | #include <urcu/compiler.h> /* For CAA_ARRAY_SIZE */ | |
24 | #include "jhash.h" /* Example hash function */ | |
25 | ||
26 | /* | |
27 | * Nodes populated into the hash table. | |
28 | */ | |
29 | struct mynode { | |
30 | int value; /* Node content */ | |
31 | struct cds_lfht_node node; /* Chaining in hash table */ | |
32 | struct rcu_head rcu_head; /* For call_rcu() */ | |
33 | }; | |
34 | ||
35 | int match(struct cds_lfht_node *ht_node, const void *_key) | |
36 | { | |
37 | struct mynode *node = | |
38 | caa_container_of(ht_node, struct mynode, node); | |
39 | const unsigned int *key = _key; | |
40 | ||
41 | return *key == node->value; | |
42 | } | |
43 | ||
44 | int main(int argc, char **argv) | |
45 | { | |
46 | int values[] = { -5, 42, 42, 36, 24, }; /* 42 is duplicated */ | |
47 | int remove_values[] = { 42, 36, 24, 123, }; | |
48 | struct cds_lfht *ht; /* Hash table */ | |
49 | unsigned int i; | |
50 | int ret = 0; | |
51 | uint32_t seed; | |
52 | struct cds_lfht_iter iter; /* For iteration on hash table */ | |
53 | struct cds_lfht_node *ht_node; | |
54 | struct mynode *node; | |
55 | ||
56 | /* | |
57 | * Each thread need using RCU read-side need to be explicitly | |
58 | * registered. | |
59 | */ | |
60 | rcu_register_thread(); | |
61 | ||
62 | /* Use time as seed for hash table hashing. */ | |
63 | seed = (uint32_t) time(NULL); | |
64 | ||
65 | /* | |
66 | * Allocate hash table. | |
67 | */ | |
68 | ht = cds_lfht_new(1, 1, 0, | |
69 | CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, | |
70 | NULL); | |
71 | if (!ht) { | |
72 | printf("Error allocating hash table\n"); | |
73 | ret = -1; | |
74 | goto end; | |
75 | } | |
76 | ||
77 | /* | |
78 | * Add nodes to hash table. | |
79 | */ | |
80 | for (i = 0; i < CAA_ARRAY_SIZE(values); i++) { | |
81 | unsigned long hash; | |
82 | int value; | |
83 | ||
84 | node = malloc(sizeof(*node)); | |
85 | if (!node) { | |
86 | ret = -1; | |
87 | goto end; | |
88 | } | |
89 | ||
90 | cds_lfht_node_init(&node->node); | |
91 | value = values[i]; | |
92 | node->value = value; | |
93 | hash = jhash(&value, sizeof(value), seed); | |
94 | ||
95 | /* | |
96 | * cds_lfht_add() needs to be called from RCU read-side | |
97 | * critical section. | |
98 | */ | |
99 | rcu_read_lock(); | |
100 | cds_lfht_add(ht, hash, &node->node); | |
101 | rcu_read_unlock(); | |
102 | } | |
103 | ||
104 | /* | |
105 | * Iterate over each hash table node. Those will appear in | |
106 | * random order, depending on the hash seed. Iteration needs to | |
107 | * be performed within RCU read-side critical section. | |
108 | */ | |
109 | printf("hash table content (random order):"); | |
110 | rcu_read_lock(); | |
111 | cds_lfht_for_each_entry(ht, &iter, node, node) { | |
112 | printf(" %d", node->value); | |
113 | } | |
114 | rcu_read_unlock(); | |
115 | printf("\n"); | |
116 | ||
117 | /* | |
118 | * Remove one node for each key, if such a node is present. | |
119 | */ | |
120 | printf("removing keys (single key, not duplicates):"); | |
121 | for (i = 0; i < CAA_ARRAY_SIZE(remove_values); i++) { | |
122 | unsigned long hash; | |
123 | int value; | |
124 | ||
125 | value = remove_values[i]; | |
126 | hash = jhash(&value, sizeof(value), seed); | |
127 | printf(" %d", value); | |
128 | rcu_read_lock(); | |
129 | cds_lfht_lookup(ht, hash, match, &value, &iter); | |
130 | ht_node = cds_lfht_iter_get_node(&iter); | |
131 | if (ht_node) { | |
132 | ret = cds_lfht_del(ht, ht_node); | |
133 | if (ret) { | |
134 | printf(" (concurrently deleted)"); | |
135 | } | |
136 | } else { | |
137 | printf(" (not found)"); | |
138 | } | |
139 | rcu_read_unlock(); | |
140 | } | |
141 | printf("\n"); | |
142 | ||
143 | printf("hash table content (random order):"); | |
144 | rcu_read_lock(); | |
145 | cds_lfht_for_each_entry(ht, &iter, node, node) { | |
146 | printf(" %d", node->value); | |
147 | } | |
148 | rcu_read_unlock(); | |
149 | printf("\n"); | |
150 | ||
151 | end: | |
152 | rcu_unregister_thread(); | |
153 | return ret; | |
154 | } |