doc/examples: cds_list_replace_rcu

[urcu.git] / doc / examples / list / cds_list_replace_rcu.c

diff --git a/doc/examples/list/cds_list_replace_rcu.c b/doc/examples/list/cds_list_replace_rcu.c
new file mode 100644 (file)
index 0000000..4ccc1df
--- /dev/null
+++ b/doc/examples/list/cds_list_replace_rcu.c
@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2013  Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
+ * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
+ *
+ * Permission is hereby granted to use or copy this program for any
+ * purpose,  provided the above notices are retained on all copies.
+ * Permission to modify the code and to distribute modified code is
+ * granted, provided the above notices are retained, and a notice that
+ * the code was modified is included with the above copyright notice.
+ *
+ * This example shows how to replace a node within a linked-list safely
+ * against concurrent RCU traversals.
+ */
+
+#include <stdio.h>
+
+#include <urcu.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(int argc, char **argv)
+{
+       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);
+               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;
+}