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

[Chris Wilson]

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Maarten Lankhorst <d...@mblankhorst.nl>
Cc: Nicolai Hähnle <nhaeh...@gmail.com>
---
 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