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// SPDX-FileCopyrightText: 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
//
// SPDX-License-Identifier: MIT
/*
* This example shows how to replace a node within a linked-list safely
* against concurrent RCU traversals.
*/
#include <stdio.h>
#include <urcu/urcu-memb.h> /* Userspace RCU flavor */
#include <urcu/rculist.h> /* RCU list */
#include <urcu/compiler.h> /* For CAA_ARRAY_SIZE */
/*
* Nodes populated into the list.
*/
struct mynode {
int value; /* Node content */
struct cds_list_head node; /* Linked-list chaining */
struct rcu_head rcu_head; /* For call_rcu() */
};
static
void free_node_rcu(struct rcu_head *head)
{
struct mynode *node = caa_container_of(head, struct mynode, rcu_head);
free(node);
}
int main(void)
{
int values[] = { -5, 42, 36, 24, };
CDS_LIST_HEAD(mylist); /* Defines an empty list head */
unsigned int i;
int ret = 0;
struct mynode *node, *n;
/*
* Adding nodes to the linked-list. Safe against concurrent
* RCU traversals, require mutual exclusion with list updates.
*/
for (i = 0; i < CAA_ARRAY_SIZE(values); i++) {
node = malloc(sizeof(*node));
if (!node) {
ret = -1;
goto end;
}
node->value = values[i];
cds_list_add_tail_rcu(&node->node, &mylist);
}
/*
* Replacing all values by their negated value. Safe against
* concurrent RCU traversals, require mutual exclusion with list
* updates. Notice the "safe" iteration: it is safe against
* removal (and thus replacement) of nodes as we iterate on the
* list.
*/
cds_list_for_each_entry_safe(node, n, &mylist, node) {
struct mynode *new_node;
new_node = malloc(sizeof(*node));
if (!new_node) {
ret = -1;
goto end;
}
/* Replacement node value is negated original value. */
new_node->value = -node->value;
cds_list_replace_rcu(&node->node, &new_node->node);
urcu_memb_call_rcu(&node->rcu_head, free_node_rcu);
}
/*
* Just show the list content. This is _not_ an RCU-safe
* iteration on the list.
*/
printf("mylist content:");
cds_list_for_each_entry(node, &mylist, node) {
printf(" %d", node->value);
}
printf("\n");
end:
return ret;
}
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