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 <[e-mail]>
Signed-off-by: Peter Zijlstra (Intel) <[e-mail]>
Cc: Chris Metcalf <[e-mail]>
Cc: Christoph Lameter <[e-mail]>
Cc: Eric W. Biederman <[e-mail]>
Cc: Kirill Tkhai <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Mike Galbraith <[e-mail]>
Cc: Oleg Nesterov <[e-mail]>
Cc: Paul E. McKenney <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Russell King - ARM Linux admin <[e-mail]>
Cc: Shuah Khan <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

tools/testing/selftests/membarrier/.gitignore

···
-membarrier_test
+membarrier_test_multi_thread
+membarrier_test_single_thread

tools/testing/selftests/membarrier/Makefile

···
 # 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.c tools/testing/selftests/membarrier/membarrier_test_impl.h

···
-// 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"
 
···
 	return 0;
 }
 
-static int test_membarrier(void)
+static int test_membarrier_fail(void)
 {
 	int status;
 
···
 	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();
···
 		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;
···
 
 	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

···
+// 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

···
+// 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();
+}