--- /dev/null
+# 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 makefile is purposefully kept simple to support GNU and BSD make.
+
+EXAMPLE_NAME = membarrier
+
+SOURCES = $(EXAMPLE_NAME).c
+OBJECTS = $(EXAMPLE_NAME).o
+BINARY = $(EXAMPLE_NAME)
+LIBS = -lurcu
+
+include ../Makefile.examples.template
--- /dev/null
+/*
+ * Copyright (C) 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <inttypes.h>
+
+#include <urcu.h> /* Default: sys_membarrier() RCU flavor */
+#include <urcu/rculist.h> /* List example */
+#include <urcu/compiler.h> /* For CAA_ARRAY_SIZE */
+
+/*
+ * Example showing how to use the sys_membarrier()-based Userspace RCU
+ * flavor.
+ *
+ * This is a mock-up example where updates and RCU traversals are
+ * performed by the same thread to keep things simple on purpose.
+ */
+
+static CDS_LIST_HEAD(mylist);
+
+struct mynode {
+ uint64_t value;
+ struct cds_list_head node; /* linked-list chaining */
+ struct rcu_head rcu_head; /* for call_rcu() */
+};
+
+static
+int add_node(uint64_t v)
+{
+ struct mynode *node;
+
+ node = calloc(sizeof(*node), 1);
+ if (!node)
+ return -1;
+ node->value = v;
+ cds_list_add_rcu(&node->node, &mylist);
+ return 0;
+}
+
+static
+void rcu_free_node(struct rcu_head *rh)
+{
+ struct mynode *node = caa_container_of(rh, struct mynode, rcu_head);
+
+ free(node);
+}
+
+int main(int argc, char **argv)
+{
+ uint64_t values[] = { 42, 36, 24, };
+ unsigned int i;
+ int ret;
+ struct mynode *node, *n;
+
+ /*
+ * Each thread need using RCU read-side need to be explicitly
+ * registered.
+ */
+ rcu_register_thread();
+
+ /*
+ * 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++) {
+ ret = add_node(values[i]);
+ if (ret)
+ goto end;
+ }
+
+ /*
+ * We need to explicitly mark RCU read-side critical sections
+ * with rcu_read_lock() and rcu_read_unlock(). They can be
+ * nested. Those are no-ops for the QSBR flavor.
+ */
+ rcu_read_lock();
+
+ /*
+ * RCU traversal of the linked list.
+ */
+ cds_list_for_each_entry_rcu(node, &mylist, node) {
+ printf("Value: %" PRIu64 "\n", node->value);
+ }
+ rcu_read_unlock();
+
+ /*
+ * Removing nodes from linked list. Safe against concurrent RCU
+ * traversals, require mutual exclusion with list updates.
+ */
+ cds_list_for_each_entry_safe(node, n, &mylist, node) {
+ cds_list_del_rcu(&node->node);
+ /*
+ * call_rcu() will ensure that the handler
+ * "rcu_free_node" is executed after a grace period.
+ * call_rcu() can be called from RCU read-side critical
+ * sections.
+ */
+ call_rcu(&node->rcu_head, rcu_free_node);
+ }
+
+ sleep(1);
+
+ /*
+ * Waiting for previously called call_rcu handlers to complete
+ * before program exits, or in library destructors, is a good
+ * practice.
+ */
+ rcu_barrier();
+
+end:
+ rcu_unregister_thread();
+ return ret;
+}
projects / userspace-rcu.git / commitdiff
