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1c87adb3 MJ |
1 | // SPDX-FileCopyrightText: 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
2 | // | |
3 | // SPDX-License-Identifier: MIT | |
4 | ||
17fb3188 | 5 | /* |
8fd9af4a | 6 | * This example shows how to do a RCU linked list traversal, safely |
17fb3188 MD |
7 | * against concurrent RCU updates. cds_list_for_each_rcu() iterates on |
8 | * struct cds_list_head, and thus, either caa_container_of() or | |
9 | * cds_list_entry() are needed to access the container structure. | |
10 | */ | |
11 | ||
12 | #include <stdio.h> | |
13 | ||
b9050d91 | 14 | #include <urcu/urcu-memb.h> /* Userspace RCU flavor */ |
17fb3188 MD |
15 | #include <urcu/rculist.h> /* RCU list */ |
16 | #include <urcu/compiler.h> /* For CAA_ARRAY_SIZE */ | |
17 | ||
18 | /* | |
19 | * Nodes populated into the list. | |
20 | */ | |
21 | struct mynode { | |
22 | int value; /* Node content */ | |
23 | struct cds_list_head node; /* Linked-list chaining */ | |
24 | }; | |
25 | ||
70469b43 | 26 | int main(void) |
17fb3188 MD |
27 | { |
28 | int values[] = { -5, 42, 36, 24, }; | |
29 | CDS_LIST_HEAD(mylist); /* Defines an empty list head */ | |
30 | unsigned int i; | |
31 | int ret = 0; | |
32 | struct cds_list_head *pos; | |
33 | ||
34 | /* | |
8fd9af4a | 35 | * Each thread need using RCU read-side need to be explicitly |
17fb3188 MD |
36 | * registered. |
37 | */ | |
b9050d91 | 38 | urcu_memb_register_thread(); |
17fb3188 MD |
39 | |
40 | /* | |
41 | * Adding nodes to the linked-list. Safe against concurrent | |
42 | * RCU traversals, require mutual exclusion with list updates. | |
43 | */ | |
44 | for (i = 0; i < CAA_ARRAY_SIZE(values); i++) { | |
45 | struct mynode *node; | |
46 | ||
47 | node = malloc(sizeof(*node)); | |
48 | if (!node) { | |
49 | ret = -1; | |
50 | goto end; | |
51 | } | |
52 | node->value = values[i]; | |
53 | cds_list_add_tail_rcu(&node->node, &mylist); | |
54 | } | |
55 | ||
56 | /* | |
57 | * RCU-safe iteration on the list. | |
58 | */ | |
59 | printf("mylist content:"); | |
60 | ||
61 | /* | |
b9050d91 MD |
62 | * Surround the RCU read-side critical section with urcu_memb_read_lock() |
63 | * and urcu_memb_read_unlock(). | |
17fb3188 | 64 | */ |
b9050d91 | 65 | urcu_memb_read_lock(); |
17fb3188 MD |
66 | |
67 | /* | |
68 | * This traversal can be performed concurrently with RCU | |
69 | * updates. | |
70 | */ | |
71 | cds_list_for_each_rcu(pos, &mylist) { | |
72 | struct mynode *node = cds_list_entry(pos, struct mynode, node); | |
73 | ||
74 | printf(" %d", node->value); | |
75 | } | |
76 | ||
b9050d91 | 77 | urcu_memb_read_unlock(); |
17fb3188 MD |
78 | |
79 | printf("\n"); | |
80 | end: | |
b9050d91 | 81 | urcu_memb_unregister_thread(); |
17fb3188 MD |
82 | return ret; |
83 | } |