Commit | Line | Data |
---|---|---|
1c87adb3 MJ |
1 | // SPDX-FileCopyrightText: 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
2 | // | |
3 | // SPDX-License-Identifier: MIT | |
4 | ||
f7e7a1b8 | 5 | /* |
f7e7a1b8 MD |
6 | * This example shows how to remove nodes from a RCU lock-free hash table. |
7 | * This hash table requires using a RCU scheme. | |
8 | */ | |
9 | ||
10 | #include <stdio.h> | |
11 | #include <stdlib.h> | |
12 | #include <time.h> | |
13 | ||
b9050d91 | 14 | #include <urcu/urcu-memb.h> /* RCU flavor */ |
f7e7a1b8 MD |
15 | #include <urcu/rculfhash.h> /* RCU Lock-free hash table */ |
16 | #include <urcu/compiler.h> /* For CAA_ARRAY_SIZE */ | |
17 | #include "jhash.h" /* Example hash function */ | |
18 | ||
19 | /* | |
20 | * Nodes populated into the hash table. | |
21 | */ | |
22 | struct mynode { | |
23 | int value; /* Node content */ | |
24 | struct cds_lfht_node node; /* Chaining in hash table */ | |
25 | struct rcu_head rcu_head; /* For call_rcu() */ | |
26 | }; | |
27 | ||
34b3f359 | 28 | static |
f7e7a1b8 MD |
29 | int match(struct cds_lfht_node *ht_node, const void *_key) |
30 | { | |
31 | struct mynode *node = | |
32 | caa_container_of(ht_node, struct mynode, node); | |
83e334d0 | 33 | const int *key = _key; |
f7e7a1b8 MD |
34 | |
35 | return *key == node->value; | |
36 | } | |
37 | ||
34b3f359 MD |
38 | static |
39 | void free_node(struct rcu_head *head) | |
40 | { | |
41 | struct mynode *node = caa_container_of(head, struct mynode, rcu_head); | |
42 | ||
43 | free(node); | |
44 | } | |
45 | ||
70469b43 | 46 | int main(void) |
f7e7a1b8 MD |
47 | { |
48 | int values[] = { -5, 42, 42, 36, 24, }; /* 42 is duplicated */ | |
49 | int remove_values[] = { 42, 36, 24, 123, }; | |
50 | struct cds_lfht *ht; /* Hash table */ | |
51 | unsigned int i; | |
52 | int ret = 0; | |
53 | uint32_t seed; | |
54 | struct cds_lfht_iter iter; /* For iteration on hash table */ | |
55 | struct cds_lfht_node *ht_node; | |
56 | struct mynode *node; | |
57 | ||
58 | /* | |
59 | * Each thread need using RCU read-side need to be explicitly | |
60 | * registered. | |
61 | */ | |
b9050d91 | 62 | urcu_memb_register_thread(); |
f7e7a1b8 MD |
63 | |
64 | /* Use time as seed for hash table hashing. */ | |
65 | seed = (uint32_t) time(NULL); | |
66 | ||
67 | /* | |
68 | * Allocate hash table. | |
69 | */ | |
b9050d91 | 70 | ht = cds_lfht_new_flavor(1, 1, 0, |
f7e7a1b8 | 71 | CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, |
b9050d91 | 72 | &urcu_memb_flavor, NULL); |
f7e7a1b8 MD |
73 | if (!ht) { |
74 | printf("Error allocating hash table\n"); | |
75 | ret = -1; | |
76 | goto end; | |
77 | } | |
78 | ||
79 | /* | |
80 | * Add nodes to hash table. | |
81 | */ | |
82 | for (i = 0; i < CAA_ARRAY_SIZE(values); i++) { | |
83 | unsigned long hash; | |
84 | int value; | |
85 | ||
86 | node = malloc(sizeof(*node)); | |
87 | if (!node) { | |
88 | ret = -1; | |
89 | goto end; | |
90 | } | |
91 | ||
92 | cds_lfht_node_init(&node->node); | |
93 | value = values[i]; | |
94 | node->value = value; | |
95 | hash = jhash(&value, sizeof(value), seed); | |
96 | ||
97 | /* | |
98 | * cds_lfht_add() needs to be called from RCU read-side | |
99 | * critical section. | |
100 | */ | |
b9050d91 | 101 | urcu_memb_read_lock(); |
f7e7a1b8 | 102 | cds_lfht_add(ht, hash, &node->node); |
b9050d91 | 103 | urcu_memb_read_unlock(); |
f7e7a1b8 MD |
104 | } |
105 | ||
106 | /* | |
107 | * Iterate over each hash table node. Those will appear in | |
108 | * random order, depending on the hash seed. Iteration needs to | |
109 | * be performed within RCU read-side critical section. | |
110 | */ | |
111 | printf("hash table content (random order):"); | |
b9050d91 | 112 | urcu_memb_read_lock(); |
f7e7a1b8 MD |
113 | cds_lfht_for_each_entry(ht, &iter, node, node) { |
114 | printf(" %d", node->value); | |
115 | } | |
b9050d91 | 116 | urcu_memb_read_unlock(); |
f7e7a1b8 MD |
117 | printf("\n"); |
118 | ||
119 | /* | |
120 | * Remove one node for each key, if such a node is present. | |
121 | */ | |
122 | printf("removing keys (single key, not duplicates):"); | |
123 | for (i = 0; i < CAA_ARRAY_SIZE(remove_values); i++) { | |
124 | unsigned long hash; | |
125 | int value; | |
126 | ||
127 | value = remove_values[i]; | |
128 | hash = jhash(&value, sizeof(value), seed); | |
129 | printf(" %d", value); | |
b9050d91 | 130 | urcu_memb_read_lock(); |
f7e7a1b8 MD |
131 | cds_lfht_lookup(ht, hash, match, &value, &iter); |
132 | ht_node = cds_lfht_iter_get_node(&iter); | |
133 | if (ht_node) { | |
134 | ret = cds_lfht_del(ht, ht_node); | |
135 | if (ret) { | |
136 | printf(" (concurrently deleted)"); | |
34b3f359 MD |
137 | } else { |
138 | struct mynode *del_node = | |
139 | caa_container_of(ht_node, | |
140 | struct mynode, node); | |
b9050d91 | 141 | urcu_memb_call_rcu(&del_node->rcu_head, free_node); |
f7e7a1b8 MD |
142 | } |
143 | } else { | |
144 | printf(" (not found)"); | |
145 | } | |
b9050d91 | 146 | urcu_memb_read_unlock(); |
f7e7a1b8 MD |
147 | } |
148 | printf("\n"); | |
149 | ||
150 | printf("hash table content (random order):"); | |
b9050d91 | 151 | urcu_memb_read_lock(); |
f7e7a1b8 MD |
152 | cds_lfht_for_each_entry(ht, &iter, node, node) { |
153 | printf(" %d", node->value); | |
154 | } | |
b9050d91 | 155 | urcu_memb_read_unlock(); |
f7e7a1b8 MD |
156 | printf("\n"); |
157 | ||
158 | end: | |
b9050d91 | 159 | urcu_memb_unregister_thread(); |
f7e7a1b8 MD |
160 | return ret; |
161 | } |