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1c87adb3 MJ |
1 | // SPDX-FileCopyrightText: 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
2 | // | |
3 | // SPDX-License-Identifier: MIT | |
4 | ||
7eba9f88 | 5 | /* |
7eba9f88 MD |
6 | * This example shows how to replace a node within a linked-list safely |
7 | * against concurrent RCU traversals. | |
8 | */ | |
9 | ||
10 | #include <stdio.h> | |
11 | ||
b9050d91 | 12 | #include <urcu/urcu-memb.h> /* Userspace RCU flavor */ |
7eba9f88 MD |
13 | #include <urcu/rculist.h> /* RCU list */ |
14 | #include <urcu/compiler.h> /* For CAA_ARRAY_SIZE */ | |
15 | ||
16 | /* | |
17 | * Nodes populated into the list. | |
18 | */ | |
19 | struct mynode { | |
20 | int value; /* Node content */ | |
21 | struct cds_list_head node; /* Linked-list chaining */ | |
22 | struct rcu_head rcu_head; /* For call_rcu() */ | |
23 | }; | |
24 | ||
25 | static | |
26 | void free_node_rcu(struct rcu_head *head) | |
27 | { | |
28 | struct mynode *node = caa_container_of(head, struct mynode, rcu_head); | |
29 | ||
30 | free(node); | |
31 | } | |
32 | ||
70469b43 | 33 | int main(void) |
7eba9f88 MD |
34 | { |
35 | int values[] = { -5, 42, 36, 24, }; | |
36 | CDS_LIST_HEAD(mylist); /* Defines an empty list head */ | |
37 | unsigned int i; | |
38 | int ret = 0; | |
39 | struct mynode *node, *n; | |
40 | ||
41 | /* | |
42 | * Adding nodes to the linked-list. Safe against concurrent | |
43 | * RCU traversals, require mutual exclusion with list updates. | |
44 | */ | |
45 | for (i = 0; i < CAA_ARRAY_SIZE(values); i++) { | |
46 | node = malloc(sizeof(*node)); | |
47 | if (!node) { | |
48 | ret = -1; | |
49 | goto end; | |
50 | } | |
51 | node->value = values[i]; | |
52 | cds_list_add_tail_rcu(&node->node, &mylist); | |
53 | } | |
54 | ||
55 | /* | |
56 | * Replacing all values by their negated value. Safe against | |
57 | * concurrent RCU traversals, require mutual exclusion with list | |
58 | * updates. Notice the "safe" iteration: it is safe against | |
59 | * removal (and thus replacement) of nodes as we iterate on the | |
60 | * list. | |
61 | */ | |
62 | cds_list_for_each_entry_safe(node, n, &mylist, node) { | |
63 | struct mynode *new_node; | |
64 | ||
65 | new_node = malloc(sizeof(*node)); | |
66 | if (!new_node) { | |
67 | ret = -1; | |
68 | goto end; | |
69 | } | |
70 | /* Replacement node value is negated original value. */ | |
71 | new_node->value = -node->value; | |
72 | cds_list_replace_rcu(&node->node, &new_node->node); | |
b9050d91 | 73 | urcu_memb_call_rcu(&node->rcu_head, free_node_rcu); |
7eba9f88 MD |
74 | } |
75 | ||
76 | /* | |
77 | * Just show the list content. This is _not_ an RCU-safe | |
78 | * iteration on the list. | |
79 | */ | |
80 | printf("mylist content:"); | |
81 | cds_list_for_each_entry(node, &mylist, node) { | |
82 | printf(" %d", node->value); | |
83 | } | |
84 | printf("\n"); | |
85 | end: | |
86 | return ret; | |
87 | } |