[PATCH 3/4] locking: Add kselftests for ww_mutex ABBA deadlock detection

[Chris Wilson]

Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Maarten Lankhorst <dev@xxxxxxxxxxxxxx>
Cc: Nicolai HÃhnle <nhaehnle@xxxxxxxxx>
---
 kernel/locking/test-ww_mutex.c | 75 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)

diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c
index 02a4bacf8aac..63a5031de138 100644
--- a/kernel/locking/test-ww_mutex.c
+++ b/kernel/locking/test-ww_mutex.c
@@ -153,6 +153,77 @@ static int test_aa(void)
 	return ret;
 }
 
+struct test_abba {
+	struct work_struct work;
+	struct ww_mutex a_mutex;
+	struct ww_mutex b_mutex;
+	struct completion a_ready;
+	struct completion b_ready;
+	struct completion done;
+	int ret;
+};
+
+static void test_abba_work(struct work_struct *work)
+{
+	struct test_abba *abba = container_of(work, typeof(*abba), work);
+	struct ww_acquire_ctx ctx;
+
+	ww_acquire_init(&ctx, &ww_class);
+	ww_mutex_lock(&abba->b_mutex, &ctx);
+
+	complete(&abba->b_ready);
+	wait_for_completion(&abba->a_ready);
+	abba->ret = ww_mutex_lock(&abba->a_mutex, &ctx);
+	if (!abba->ret)
+		ww_mutex_unlock(&abba->a_mutex);
+
+	ww_mutex_unlock(&abba->b_mutex);
+	ww_acquire_fini(&ctx);
+
+	complete(&abba->done);
+}
+
+static int test_abba(void)
+{
+	struct test_abba abba;
+	struct ww_acquire_ctx ctx;
+	int ret;
+
+	ww_mutex_init(&abba.a_mutex, &ww_class);
+	ww_mutex_init(&abba.b_mutex, &ww_class);
+	INIT_WORK_ONSTACK(&abba.work, test_abba_work);
+	init_completion(&abba.a_ready);
+	init_completion(&abba.b_ready);
+	init_completion(&abba.done);
+
+	schedule_work(&abba.work);
+
+	ww_acquire_init(&ctx, &ww_class);
+	ww_mutex_lock(&abba.a_mutex, &ctx);
+	complete(&abba.a_ready);
+	wait_for_completion(&abba.b_ready);
+	ret = ww_mutex_lock(&abba.b_mutex, &ctx);
+	if (!ret)
+		ww_mutex_unlock(&abba.b_mutex);
+	ww_mutex_unlock(&abba.a_mutex);
+
+	wait_for_completion(&abba.done);
+
+	if (ret != -EDEADLK && abba.ret != -EDEADLK) {
+		pr_err("%s: missed ABBA deadlock, A ret=%d, B ret=%d\n",
+		       __func__, ret, abba.ret);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	ret = 0;
+out:
+	ww_acquire_fini(&ctx);
+	flush_work(&abba.work);
+	destroy_work_on_stack(&abba.work);
+	return ret;
+}
+
 static int __init test_ww_mutex_init(void)
 {
 	int ret;
@@ -165,6 +236,10 @@ static int __init test_ww_mutex_init(void)
 	if (ret)
 		return ret;
 
+	ret = test_abba();
+	if (ret)
+		return ret;
+
 	return 0;
 }
 
-- 
2.10.2