Add QSBR minimal example
authorMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Mon, 3 Jun 2013 20:18:34 +0000 (16:18 -0400)
committerMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fri, 14 Jun 2013 21:29:32 +0000 (17:29 -0400)
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
configure.ac
doc/Makefile.am
doc/examples/Makefile.am [new file with mode: 0644]
doc/examples/qsbr-minimal/Makefile [new file with mode: 0644]
doc/examples/qsbr-minimal/qsbr-minimal.c [new file with mode: 0644]

index da560a4ad885b668ec6785c36cee18c759b9055a..058be2065dfd62215a8960efcefe6843b94b7511 100644 (file)
@@ -290,6 +290,7 @@ AC_CONFIG_LINKS([
 AC_CONFIG_FILES([
        Makefile
        doc/Makefile
+       doc/examples/Makefile
        tests/Makefile
        liburcu.pc
        liburcu-bp.pc
index 34226531250d5568c52b5c1149474dcf43d2213f..d98f16ba8f3e7bb80a6a6c63cbe3e02095d0a699 100644 (file)
@@ -1 +1,3 @@
+SUBDIRS = examples
+
 dist_doc_DATA = rcu-api.txt cds-api.txt uatomic-api.txt
diff --git a/doc/examples/Makefile.am b/doc/examples/Makefile.am
new file mode 100644 (file)
index 0000000..4583b5b
--- /dev/null
@@ -0,0 +1,12 @@
+SUBDIRS = qsbr-minimal
+
+doc_examplesdir = ${docdir}/examples
+
+doc_examples_qsbr_minimaldir = ${doc_examplesdir}/qsbr-minimal
+
+doc_examples_qsbr_minimal_DATA = \
+       qsbr-minimal/Makefile \
+       qsbr-minimal/qsbr-minimal.c
+
+BUILD_EXAMPLES_FROM_TREE = 1
+export
diff --git a/doc/examples/qsbr-minimal/Makefile b/doc/examples/qsbr-minimal/Makefile
new file mode 100644 (file)
index 0000000..53f1380
--- /dev/null
@@ -0,0 +1,43 @@
+# Copyright (C) 2013  Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+#
+# THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
+# OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
+#
+# Permission is hereby granted to use or copy this program for any
+# purpose,  provided the above notices are retained on all copies.
+# Permission to modify the code and to distribute modified code is
+# granted, provided the above notices are retained, and a notice that
+# the code was modified is included with the above copyright notice.
+
+CC = gcc
+LIBS = -lurcu-qsbr
+CFLAGS = -g -O2 -Wall
+
+# Only necessary when building from the source tree and userspace RCU is
+# not installed
+ifdef BUILD_EXAMPLES_FROM_TREE
+LOCAL_CPPFLAGS += -I../../../urcu/ -I../../../
+LIBURCU_QSBR_PATH = ../../../.libs/
+override LDFLAGS += -L$(LIBURCU_QSBR_PATH) -Wl,-rpath='$$ORIGIN/$(LIBURCU_QSBR_PATH)'
+
+# Third-party Makefiles have to define these targets to integrate with an
+# automake project
+EMPTY_AUTOMAKE_TARGETS = distdir install install-data install-exec uninstall \
+       install-dvi install-html install-info install-ps install-pdf \
+       installdirs check installcheck mostlyclean distclean maintainer-clean \
+       dvi pdf ps info tags ctags
+.PHONY: $(EMPTY_AUTOMAKE_TARGETS)
+$(EMPTY_AUTOMAKE_TARGETS):
+endif
+
+all: qsbr-minimal
+
+qsbr-minimal: qsbr-minimal.o
+       $(CC) -o $@ $^ $(LDFLAGS) $(LIBS)
+
+qsbr-minimal.o: qsbr-minimal.c
+       $(CC) $(CPPFLAGS) $(LOCAL_CPPFLAGS) $(CFLAGS) -c -o $@ $<
+
+.PHONY: clean
+clean:
+       rm -f *.o qsbr-minimal
diff --git a/doc/examples/qsbr-minimal/qsbr-minimal.c b/doc/examples/qsbr-minimal/qsbr-minimal.c
new file mode 100644 (file)
index 0000000..cc7278d
--- /dev/null
@@ -0,0 +1,137 @@
+/*
+ * 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
+ */
+
+#define _LGPL_SOURCE
+#include <urcu-qsbr.h>
+#include <urcu/rculist.h>
+#include <urcu/compiler.h>
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <inttypes.h>
+
+/*
+ * 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 explicitely
+        * 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.
+        */
+       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 is a good practice.
+        */
+       rcu_barrier();
+
+end:
+       rcu_unregister_thread();
+       return ret;
+}
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