X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=doc%2Fexamples%2Furcu-flavors%2Fqsbr.c;fp=doc%2Fexamples%2Furcu-flavors%2Fqsbr.c;h=1c50b8aedaf9b368309acc92e3b5bf840437f7a0;hp=0000000000000000000000000000000000000000;hb=6df9f02d9de67572ab8bd34855eca233c16ced47;hpb=71ea53b1c44c78bac18de7ac205bf1bdc4125353

diff --git a/doc/examples/urcu-flavors/qsbr.c b/doc/examples/urcu-flavors/qsbr.c
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+++ b/doc/examples/urcu-flavors/qsbr.c
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+/*
+ * 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 <stdlib.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <inttypes.h>
+
+#include <urcu-qsbr.h>		/* QSBR RCU flavor */
+#include <urcu/rculist.h>	/* List example */
+#include <urcu/compiler.h>	/* For CAA_ARRAY_SIZE */
+
+/*
+ * Example showing how to use the QSBR 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;
+	}
+
+	/*
+	 * For all RCU flavors except QSBR, 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(&node->rcu_head, rcu_free_node);
+	}
+
+	/*
+	 * For QSBR flavor, we need to explicitly announce quiescent
+	 * states. Here is how it is done. This should be performed by
+	 * every online registered RCU threads in the program
+	 * periodically.
+	 */
+	rcu_quiescent_state();
+
+	/*
+	 * For QSBR flavor, when a thread needs to be in a quiescent
+	 * state for a long period of time, we use rcu_thread_offline()
+	 * and rcu_thread_online().
+	 */
+	rcu_thread_offline();
+
+	sleep(1);
+
+	rcu_thread_online();
+
+	/*
+	 * 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;
+}