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34b3f359 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 add nodes into a RCU lock-free hash table | |
14 | * with cds_lfht_add_replace(), which replaces existing nodes with the | |
15 | * same key if found. | |
16 | * We use a "seqnum" field to show which node is staying in the hash | |
17 | * table. This hash table requires using a RCU scheme. | |
18 | */ | |
19 | ||
20 | #include <stdio.h> | |
21 | #include <stdlib.h> | |
22 | #include <time.h> | |
23 | ||
b9050d91 | 24 | #include <urcu/urcu-memb.h> /* RCU flavor */ |
34b3f359 MD |
25 | #include <urcu/rculfhash.h> /* RCU Lock-free hash table */ |
26 | #include <urcu/compiler.h> /* For CAA_ARRAY_SIZE */ | |
27 | #include "jhash.h" /* Example hash function */ | |
28 | ||
29 | /* | |
30 | * Nodes populated into the hash table. | |
31 | */ | |
32 | struct mynode { | |
33 | int value; /* Node content */ | |
34 | int seqnum; /* Our node sequence number */ | |
35 | struct cds_lfht_node node; /* Chaining in hash table */ | |
36 | struct rcu_head rcu_head; /* For call_rcu() */ | |
37 | }; | |
38 | ||
39 | static | |
40 | int match(struct cds_lfht_node *ht_node, const void *_key) | |
41 | { | |
42 | struct mynode *node = | |
43 | caa_container_of(ht_node, struct mynode, node); | |
83e334d0 | 44 | const int *key = _key; |
34b3f359 MD |
45 | |
46 | return *key == node->value; | |
47 | } | |
48 | ||
49 | static | |
50 | void free_node(struct rcu_head *head) | |
51 | { | |
52 | struct mynode *node = caa_container_of(head, struct mynode, rcu_head); | |
53 | ||
54 | free(node); | |
55 | } | |
56 | ||
57 | int main(int argc, char **argv) | |
58 | { | |
59 | int values[] = { -5, 42, 42, 36, 24, }; /* 42 is duplicated */ | |
60 | struct cds_lfht *ht; /* Hash table */ | |
61 | unsigned int i; | |
62 | int ret = 0, seqnum = 0; | |
63 | uint32_t seed; | |
64 | struct cds_lfht_iter iter; /* For iteration on hash table */ | |
65 | struct cds_lfht_node *ht_node; | |
66 | struct mynode *node; | |
67 | ||
68 | /* | |
69 | * Each thread need using RCU read-side need to be explicitly | |
70 | * registered. | |
71 | */ | |
b9050d91 | 72 | urcu_memb_register_thread(); |
34b3f359 MD |
73 | |
74 | /* Use time as seed for hash table hashing. */ | |
75 | seed = (uint32_t) time(NULL); | |
76 | ||
77 | /* | |
78 | * Allocate hash table. | |
79 | */ | |
b9050d91 | 80 | ht = cds_lfht_new_flavor(1, 1, 0, |
34b3f359 | 81 | CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, |
b9050d91 | 82 | &urcu_memb_flavor, NULL); |
34b3f359 MD |
83 | if (!ht) { |
84 | printf("Error allocating hash table\n"); | |
85 | ret = -1; | |
86 | goto end; | |
87 | } | |
88 | ||
89 | /* | |
90 | * Add nodes to hash table. | |
91 | */ | |
92 | for (i = 0; i < CAA_ARRAY_SIZE(values); i++) { | |
93 | unsigned long hash; | |
94 | int value; | |
95 | ||
96 | node = malloc(sizeof(*node)); | |
97 | if (!node) { | |
98 | ret = -1; | |
99 | goto end; | |
100 | } | |
101 | ||
102 | cds_lfht_node_init(&node->node); | |
103 | value = values[i]; | |
104 | node->value = value; | |
105 | node->seqnum = seqnum++; | |
106 | hash = jhash(&value, sizeof(value), seed); | |
107 | ||
108 | /* | |
109 | * cds_lfht_add() needs to be called from RCU read-side | |
110 | * critical section. | |
111 | */ | |
b9050d91 | 112 | urcu_memb_read_lock(); |
34b3f359 MD |
113 | ht_node = cds_lfht_add_replace(ht, hash, match, &value, |
114 | &node->node); | |
115 | if (ht_node) { | |
116 | struct mynode *ret_node = | |
117 | caa_container_of(ht_node, struct mynode, node); | |
118 | ||
119 | printf("Replaced node (key: %d, seqnum: %d) by (key: %d, seqnum: %d)\n", | |
120 | ret_node->value, ret_node->seqnum, | |
121 | node->value, node->seqnum); | |
b9050d91 | 122 | urcu_memb_call_rcu(&ret_node->rcu_head, free_node); |
34b3f359 MD |
123 | } else { |
124 | printf("Add (key: %d, seqnum: %d)\n", | |
125 | node->value, node->seqnum); | |
126 | } | |
b9050d91 | 127 | urcu_memb_read_unlock(); |
34b3f359 MD |
128 | } |
129 | ||
130 | /* | |
131 | * Iterate over each hash table node. Those will appear in | |
132 | * random order, depending on the hash seed. Iteration needs to | |
133 | * be performed within RCU read-side critical section. | |
134 | */ | |
135 | printf("hash table content (random order):"); | |
b9050d91 | 136 | urcu_memb_read_lock(); |
34b3f359 MD |
137 | cds_lfht_for_each_entry(ht, &iter, node, node) { |
138 | printf(" (key: %d, seqnum: %d)", | |
139 | node->value, node->seqnum); | |
140 | } | |
b9050d91 | 141 | urcu_memb_read_unlock(); |
34b3f359 MD |
142 | printf("\n"); |
143 | ||
144 | end: | |
b9050d91 | 145 | urcu_memb_unregister_thread(); |
34b3f359 MD |
146 | return ret; |
147 | } |