2 * Copyright (C) 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
4 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
5 * OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
7 * Permission is hereby granted to use or copy this program for any
8 * purpose, provided the above notices are retained on all copies.
9 * Permission to modify the code and to distribute modified code is
10 * granted, provided the above notices are retained, and a notice that
11 * the code was modified is included with the above copyright notice.
13 * This example shows how to replace a node within a linked-list safely
14 * against concurrent RCU traversals.
19 #include <urcu/urcu-memb.h> /* Userspace RCU flavor */
20 #include <urcu/rculist.h> /* RCU list */
21 #include <urcu/compiler.h> /* For CAA_ARRAY_SIZE */
24 * Nodes populated into the list.
27 int value
; /* Node content */
28 struct cds_list_head node
; /* Linked-list chaining */
29 struct rcu_head rcu_head
; /* For call_rcu() */
33 void free_node_rcu(struct rcu_head
*head
)
35 struct mynode
*node
= caa_container_of(head
, struct mynode
, rcu_head
);
40 int main(int argc
, char **argv
)
42 int values
[] = { -5, 42, 36, 24, };
43 CDS_LIST_HEAD(mylist
); /* Defines an empty list head */
46 struct mynode
*node
, *n
;
49 * Adding nodes to the linked-list. Safe against concurrent
50 * RCU traversals, require mutual exclusion with list updates.
52 for (i
= 0; i
< CAA_ARRAY_SIZE(values
); i
++) {
53 node
= malloc(sizeof(*node
));
58 node
->value
= values
[i
];
59 cds_list_add_tail_rcu(&node
->node
, &mylist
);
63 * Replacing all values by their negated value. Safe against
64 * concurrent RCU traversals, require mutual exclusion with list
65 * updates. Notice the "safe" iteration: it is safe against
66 * removal (and thus replacement) of nodes as we iterate on the
69 cds_list_for_each_entry_safe(node
, n
, &mylist
, node
) {
70 struct mynode
*new_node
;
72 new_node
= malloc(sizeof(*node
));
77 /* Replacement node value is negated original value. */
78 new_node
->value
= -node
->value
;
79 cds_list_replace_rcu(&node
->node
, &new_node
->node
);
80 urcu_memb_call_rcu(&node
->rcu_head
, free_node_rcu
);
84 * Just show the list content. This is _not_ an RCU-safe
85 * iteration on the list.
87 printf("mylist content:");
88 cds_list_for_each_entry(node
, &mylist
, node
) {
89 printf(" %d", node
->value
);
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