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1c87adb3 MJ |
1 | // SPDX-FileCopyrightText: 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
2 | // | |
3 | // SPDX-License-Identifier: MIT | |
4 | ||
34b3f359 | 5 | /* |
34b3f359 MD |
6 | * This example shows how to add nodes into a RCU lock-free hash table |
7 | * with cds_lfht_add_replace(), which replaces existing nodes with the | |
8 | * same key if found. | |
9 | * We use a "seqnum" field to show which node is staying in the hash | |
10 | * table. This hash table requires using a RCU scheme. | |
11 | */ | |
12 | ||
13 | #include <stdio.h> | |
14 | #include <stdlib.h> | |
15 | #include <time.h> | |
16 | ||
b9050d91 | 17 | #include <urcu/urcu-memb.h> /* RCU flavor */ |
34b3f359 MD |
18 | #include <urcu/rculfhash.h> /* RCU Lock-free hash table */ |
19 | #include <urcu/compiler.h> /* For CAA_ARRAY_SIZE */ | |
20 | #include "jhash.h" /* Example hash function */ | |
21 | ||
22 | /* | |
23 | * Nodes populated into the hash table. | |
24 | */ | |
25 | struct mynode { | |
26 | int value; /* Node content */ | |
27 | int seqnum; /* Our node sequence number */ | |
28 | struct cds_lfht_node node; /* Chaining in hash table */ | |
29 | struct rcu_head rcu_head; /* For call_rcu() */ | |
30 | }; | |
31 | ||
32 | static | |
33 | int match(struct cds_lfht_node *ht_node, const void *_key) | |
34 | { | |
35 | struct mynode *node = | |
36 | caa_container_of(ht_node, struct mynode, node); | |
83e334d0 | 37 | const int *key = _key; |
34b3f359 MD |
38 | |
39 | return *key == node->value; | |
40 | } | |
41 | ||
42 | static | |
43 | void free_node(struct rcu_head *head) | |
44 | { | |
45 | struct mynode *node = caa_container_of(head, struct mynode, rcu_head); | |
46 | ||
47 | free(node); | |
48 | } | |
49 | ||
70469b43 | 50 | int main(void) |
34b3f359 MD |
51 | { |
52 | int values[] = { -5, 42, 42, 36, 24, }; /* 42 is duplicated */ | |
53 | struct cds_lfht *ht; /* Hash table */ | |
54 | unsigned int i; | |
55 | int ret = 0, seqnum = 0; | |
56 | uint32_t seed; | |
57 | struct cds_lfht_iter iter; /* For iteration on hash table */ | |
58 | struct cds_lfht_node *ht_node; | |
59 | struct mynode *node; | |
60 | ||
61 | /* | |
62 | * Each thread need using RCU read-side need to be explicitly | |
63 | * registered. | |
64 | */ | |
b9050d91 | 65 | urcu_memb_register_thread(); |
34b3f359 MD |
66 | |
67 | /* Use time as seed for hash table hashing. */ | |
68 | seed = (uint32_t) time(NULL); | |
69 | ||
70 | /* | |
71 | * Allocate hash table. | |
72 | */ | |
b9050d91 | 73 | ht = cds_lfht_new_flavor(1, 1, 0, |
34b3f359 | 74 | CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, |
b9050d91 | 75 | &urcu_memb_flavor, NULL); |
34b3f359 MD |
76 | if (!ht) { |
77 | printf("Error allocating hash table\n"); | |
78 | ret = -1; | |
79 | goto end; | |
80 | } | |
81 | ||
82 | /* | |
83 | * Add nodes to hash table. | |
84 | */ | |
85 | for (i = 0; i < CAA_ARRAY_SIZE(values); i++) { | |
86 | unsigned long hash; | |
87 | int value; | |
88 | ||
89 | node = malloc(sizeof(*node)); | |
90 | if (!node) { | |
91 | ret = -1; | |
92 | goto end; | |
93 | } | |
94 | ||
95 | cds_lfht_node_init(&node->node); | |
96 | value = values[i]; | |
97 | node->value = value; | |
98 | node->seqnum = seqnum++; | |
99 | hash = jhash(&value, sizeof(value), seed); | |
100 | ||
101 | /* | |
102 | * cds_lfht_add() needs to be called from RCU read-side | |
103 | * critical section. | |
104 | */ | |
b9050d91 | 105 | urcu_memb_read_lock(); |
34b3f359 MD |
106 | ht_node = cds_lfht_add_replace(ht, hash, match, &value, |
107 | &node->node); | |
108 | if (ht_node) { | |
109 | struct mynode *ret_node = | |
110 | caa_container_of(ht_node, struct mynode, node); | |
111 | ||
112 | printf("Replaced node (key: %d, seqnum: %d) by (key: %d, seqnum: %d)\n", | |
113 | ret_node->value, ret_node->seqnum, | |
114 | node->value, node->seqnum); | |
b9050d91 | 115 | urcu_memb_call_rcu(&ret_node->rcu_head, free_node); |
34b3f359 MD |
116 | } else { |
117 | printf("Add (key: %d, seqnum: %d)\n", | |
118 | node->value, node->seqnum); | |
119 | } | |
b9050d91 | 120 | urcu_memb_read_unlock(); |
34b3f359 MD |
121 | } |
122 | ||
123 | /* | |
124 | * Iterate over each hash table node. Those will appear in | |
125 | * random order, depending on the hash seed. Iteration needs to | |
126 | * be performed within RCU read-side critical section. | |
127 | */ | |
128 | printf("hash table content (random order):"); | |
b9050d91 | 129 | urcu_memb_read_lock(); |
34b3f359 MD |
130 | cds_lfht_for_each_entry(ht, &iter, node, node) { |
131 | printf(" (key: %d, seqnum: %d)", | |
132 | node->value, node->seqnum); | |
133 | } | |
b9050d91 | 134 | urcu_memb_read_unlock(); |
34b3f359 MD |
135 | printf("\n"); |
136 | ||
137 | end: | |
b9050d91 | 138 | urcu_memb_unregister_thread(); |
34b3f359 MD |
139 | return ret; |
140 | } |