selftests, sched/membarrier: Add multi-threaded test

membarrier commands cover very different code paths if they are in
a single-threaded vs multi-threaded process. Therefore, exercise both
scenarios in the kernel selftests to increase coverage of this selftest.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Kirill Tkhai <tkhai@yandex.ru>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190919173705.2181-6-mathieu.desnoyers@efficios.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

tools/testing/selftests/membarrier/.gitignore

@@ -1 +1,2 @@
-membarrier_test
+membarrier_test_multi_thread
+membarrier_test_single_thread

tools/testing/selftests/membarrier/Makefile

@@ -1,7 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0-only
 CFLAGS += -g -I../../../../usr/include/
+LDLIBS += -lpthread
 
-TEST_GEN_PROGS := membarrier_test
+TEST_GEN_PROGS := membarrier_test_single_thread \
+		membarrier_test_multi_thread
 
 include ../lib.mk
-

tools/testing/selftests/membarrier/membarrier_test_impl.h

@@ -1,10 +1,11 @@
-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 #define _GNU_SOURCE
 #include <linux/membarrier.h>
 #include <syscall.h>
 #include <stdio.h>
 #include <errno.h>
 #include <string.h>
+#include <pthread.h>
 
 #include "../kselftest.h"
 
@@ -223,7 +224,7 @@ static int test_membarrier_global_expedited_success(void)
 	return 0;
 }
 
-static int test_membarrier(void)
+static int test_membarrier_fail(void)
 {
 	int status;
 
@@ -233,10 +234,27 @@ static int test_membarrier(void)
 	status = test_membarrier_flags_fail();
 	if (status)
 		return status;
-	status = test_membarrier_global_success();
+	status = test_membarrier_private_expedited_fail();
 	if (status)
 		return status;
-	status = test_membarrier_private_expedited_fail();
+	status = sys_membarrier(MEMBARRIER_CMD_QUERY, 0);
+	if (status < 0) {
+		ksft_test_result_fail("sys_membarrier() failed\n");
+		return status;
+	}
+	if (status & MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE) {
+		status = test_membarrier_private_expedited_sync_core_fail();
+		if (status)
+			return status;
+	}
+	return 0;
+}
+
+static int test_membarrier_success(void)
+{
+	int status;
+
+	status = test_membarrier_global_success();
 	if (status)
 		return status;
 	status = test_membarrier_register_private_expedited_success();
@@ -251,9 +269,6 @@ static int test_membarrier(void)
 		return status;
 	}
 	if (status & MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE) {
-		status = test_membarrier_private_expedited_sync_core_fail();
-		if (status)
-			return status;
 		status = test_membarrier_register_private_expedited_sync_core_success();
 		if (status)
 			return status;
@@ -300,14 +315,3 @@ static int test_membarrier_query(void)
 	ksft_test_result_pass("sys_membarrier available\n");
 	return 0;
 }
-
-int main(int argc, char **argv)
-{
-	ksft_print_header();
-	ksft_set_plan(13);
-
-	test_membarrier_query();
-	test_membarrier();
-
-	return ksft_exit_pass();
-}

tools/testing/selftests/membarrier/membarrier_test_multi_thread.c

@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <linux/membarrier.h>
+#include <syscall.h>
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <pthread.h>
+
+#include "membarrier_test_impl.h"
+
+static int thread_ready, thread_quit;
+static pthread_mutex_t test_membarrier_thread_mutex =
+	PTHREAD_MUTEX_INITIALIZER;
+static pthread_cond_t test_membarrier_thread_cond =
+	PTHREAD_COND_INITIALIZER;
+
+void *test_membarrier_thread(void *arg)
+{
+	pthread_mutex_lock(&test_membarrier_thread_mutex);
+	thread_ready = 1;
+	pthread_cond_broadcast(&test_membarrier_thread_cond);
+	pthread_mutex_unlock(&test_membarrier_thread_mutex);
+
+	pthread_mutex_lock(&test_membarrier_thread_mutex);
+	while (!thread_quit)
+		pthread_cond_wait(&test_membarrier_thread_cond,
+				  &test_membarrier_thread_mutex);
+	pthread_mutex_unlock(&test_membarrier_thread_mutex);
+
+	return NULL;
+}
+
+static int test_mt_membarrier(void)
+{
+	int i;
+	pthread_t test_thread;
+
+	pthread_create(&test_thread, NULL,
+		       test_membarrier_thread, NULL);
+
+	pthread_mutex_lock(&test_membarrier_thread_mutex);
+	while (!thread_ready)
+		pthread_cond_wait(&test_membarrier_thread_cond,
+				  &test_membarrier_thread_mutex);
+	pthread_mutex_unlock(&test_membarrier_thread_mutex);
+
+	test_membarrier_fail();
+
+	test_membarrier_success();
+
+	pthread_mutex_lock(&test_membarrier_thread_mutex);
+	thread_quit = 1;
+	pthread_cond_broadcast(&test_membarrier_thread_cond);
+	pthread_mutex_unlock(&test_membarrier_thread_mutex);
+
+	pthread_join(test_thread, NULL);
+
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	ksft_print_header();
+	ksft_set_plan(13);
+
+	test_membarrier_query();
+
+	/* Multi-threaded */
+	test_mt_membarrier();
+
+	return ksft_exit_pass();
+}

tools/testing/selftests/membarrier/membarrier_test_single_thread.c

@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <linux/membarrier.h>
+#include <syscall.h>
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <pthread.h>
+
+#include "membarrier_test_impl.h"
+
+int main(int argc, char **argv)
+{
+	ksft_print_header();
+	ksft_set_plan(13);
+
+	test_membarrier_query();
+
+	test_membarrier_fail();
+
+	test_membarrier_success();
+
+	return ksft_exit_pass();
+}