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9b4bf32b MD |
1 | /* |
2 | * Copyright (C) 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
3 | * | |
4 | * This library is free software; you can redistribute it and/or | |
5 | * modify it under the terms of the GNU Lesser General Public | |
6 | * License as published by the Free Software Foundation; either | |
7 | * version 2.1 of the License, or (at your option) any later version. | |
8 | * | |
9 | * This library is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
12 | * Lesser General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU Lesser General Public | |
15 | * License along with this library; if not, write to the Free Software | |
16 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
17 | */ | |
18 | ||
19 | #include <unistd.h> | |
20 | #include <stdlib.h> | |
21 | #include <stdio.h> | |
22 | #include <stdint.h> | |
23 | #include <inttypes.h> | |
24 | ||
b9050d91 | 25 | #include <urcu/urcu-bp.h> /* Bulletproof RCU flavor */ |
9b4bf32b MD |
26 | #include <urcu/rculist.h> /* List example */ |
27 | #include <urcu/compiler.h> /* For CAA_ARRAY_SIZE */ | |
28 | ||
29 | /* | |
30 | * Example showing how to use the Bulletproof Userspace RCU flavor. | |
31 | * | |
32 | * This is a mock-up example where updates and RCU traversals are | |
33 | * performed by the same thread to keep things simple on purpose. | |
34 | */ | |
35 | ||
36 | static CDS_LIST_HEAD(mylist); | |
37 | ||
38 | struct mynode { | |
39 | uint64_t value; | |
40 | struct cds_list_head node; /* linked-list chaining */ | |
41 | struct rcu_head rcu_head; /* for call_rcu() */ | |
42 | }; | |
43 | ||
44 | static | |
45 | int add_node(uint64_t v) | |
46 | { | |
47 | struct mynode *node; | |
48 | ||
49 | node = calloc(sizeof(*node), 1); | |
50 | if (!node) | |
51 | return -1; | |
52 | node->value = v; | |
53 | cds_list_add_rcu(&node->node, &mylist); | |
54 | return 0; | |
55 | } | |
56 | ||
17a8f206 | 57 | int main(void) |
9b4bf32b MD |
58 | { |
59 | uint64_t values[] = { 42, 36, 24, }; | |
60 | unsigned int i; | |
61 | int ret; | |
62 | struct mynode *node, *n; | |
63 | ||
64 | /* | |
65 | * Notice that with the bulletproof flavor, there is no need to | |
66 | * register/unregister RCU reader threads. | |
67 | */ | |
68 | ||
69 | /* | |
70 | * Adding nodes to the linked-list. Safe against concurrent | |
71 | * RCU traversals, require mutual exclusion with list updates. | |
72 | */ | |
73 | for (i = 0; i < CAA_ARRAY_SIZE(values); i++) { | |
74 | ret = add_node(values[i]); | |
75 | if (ret) | |
76 | goto end; | |
77 | } | |
78 | ||
79 | /* | |
80 | * We need to explicitly mark RCU read-side critical sections | |
81 | * with rcu_read_lock() and rcu_read_unlock(). They can be | |
82 | * nested. Those are no-ops for the QSBR flavor. | |
83 | */ | |
b9050d91 | 84 | urcu_bp_read_lock(); |
9b4bf32b MD |
85 | |
86 | /* | |
87 | * RCU traversal of the linked list. | |
88 | */ | |
89 | cds_list_for_each_entry_rcu(node, &mylist, node) { | |
90 | printf("Value: %" PRIu64 "\n", node->value); | |
91 | } | |
b9050d91 | 92 | urcu_bp_read_unlock(); |
9b4bf32b MD |
93 | |
94 | /* | |
95 | * Removing nodes from linked list. Safe against concurrent RCU | |
96 | * traversals, require mutual exclusion with list updates. | |
97 | */ | |
98 | cds_list_for_each_entry_safe(node, n, &mylist, node) { | |
99 | cds_list_del_rcu(&node->node); | |
100 | ||
101 | /* | |
102 | * Using synchronize_rcu() directly for synchronization | |
103 | * so we keep a minimal impact on the system by not | |
104 | * spawning any call_rcu() thread. It is slower though, | |
105 | * since there is no batching. | |
106 | */ | |
b9050d91 | 107 | urcu_bp_synchronize_rcu(); |
9b4bf32b MD |
108 | free(node); |
109 | } | |
110 | ||
111 | sleep(1); | |
112 | ||
113 | end: | |
114 | return ret; | |
115 | } |