locking/ww_mutex: Add kselftests for ww_mutex AA deadlock detection

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maarten Lankhorst <dev@mblankhorst.nl>
Cc: Nicolai Hähnle <nhaehnle@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20161201114711.28697-5-chris@chris-wilson.co.uk
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/locking/test-ww_mutex.c

@@ -118,6 +118,41 @@ static int test_mutex(void)
 	return 0;
 }
 
+static int test_aa(void)
+{
+	struct ww_mutex mutex;
+	struct ww_acquire_ctx ctx;
+	int ret;
+
+	ww_mutex_init(&mutex, &ww_class);
+	ww_acquire_init(&ctx, &ww_class);
+
+	ww_mutex_lock(&mutex, &ctx);
+
+	if (ww_mutex_trylock(&mutex))  {
+		pr_err("%s: trylocked itself!\n", __func__);
+		ww_mutex_unlock(&mutex);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	ret = ww_mutex_lock(&mutex, &ctx);
+	if (ret != -EALREADY) {
+		pr_err("%s: missed deadlock for recursing, ret=%d\n",
+		       __func__, ret);
+		if (!ret)
+			ww_mutex_unlock(&mutex);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	ret = 0;
+out:
+	ww_mutex_unlock(&mutex);
+	ww_acquire_fini(&ctx);
+	return ret;
+}
+
 static int __init test_ww_mutex_init(void)
 {
 	int ret;
@@ -126,6 +161,10 @@ static int __init test_ww_mutex_init(void)
 	if (ret)
 		return ret;
 
+	ret = test_aa();
+	if (ret)
+		return ret;
+
 	return 0;
 }