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Subject[PATCH v2 5/8] locking: Add kselftests for ww_mutex ABBA deadlock detection
Date
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Maarten Lankhorst <dev@mblankhorst.nl>
Cc: Nicolai Hähnle <nhaehnle@gmail.com>
---
kernel/locking/test-ww_mutex.c | 98 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 98 insertions(+)

diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c
index 835fa7a1036e..5a643ba2b020 100644
--- a/kernel/locking/test-ww_mutex.c
+++ b/kernel/locking/test-ww_mutex.c
@@ -153,6 +153,96 @@ 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;
+ bool resolve;
+ int result;
+};
+
+static void test_abba_work(struct work_struct *work)
+{
+ struct test_abba *abba = container_of(work, typeof(*abba), work);
+ struct ww_acquire_ctx ctx;
+ int err;
+
+ ww_acquire_init(&ctx, &ww_class);
+ ww_mutex_lock(&abba->b_mutex, &ctx);
+
+ complete(&abba->b_ready);
+ wait_for_completion(&abba->a_ready);
+
+ err = ww_mutex_lock(&abba->a_mutex, &ctx);
+ if (abba->resolve && err == -EDEADLK) {
+ ww_mutex_unlock(&abba->b_mutex);
+ ww_mutex_lock_slow(&abba->a_mutex, &ctx);
+ err = ww_mutex_lock(&abba->b_mutex, &ctx);
+ }
+
+ if (!err)
+ ww_mutex_unlock(&abba->a_mutex);
+ ww_mutex_unlock(&abba->b_mutex);
+ ww_acquire_fini(&ctx);
+
+ abba->result = err;
+}
+
+static int test_abba(bool resolve)
+{
+ struct test_abba abba;
+ struct ww_acquire_ctx ctx;
+ int err, 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);
+ abba.resolve = resolve;
+
+ 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);
+
+ err = ww_mutex_lock(&abba.b_mutex, &ctx);
+ if (resolve && err == -EDEADLK) {
+ ww_mutex_unlock(&abba.a_mutex);
+ ww_mutex_lock_slow(&abba.b_mutex, &ctx);
+ err = ww_mutex_lock(&abba.a_mutex, &ctx);
+ }
+
+ if (!err)
+ ww_mutex_unlock(&abba.b_mutex);
+ ww_mutex_unlock(&abba.a_mutex);
+ ww_acquire_fini(&ctx);
+
+ flush_work(&abba.work);
+ destroy_work_on_stack(&abba.work);
+
+ ret = 0;
+ if (resolve) {
+ if (err || abba.result) {
+ pr_err("%s: failed to resolve ABBA deadlock, A err=%d, B err=%d\n",
+ __func__, err, abba.result);
+ ret = -EINVAL;
+ }
+ } else {
+ if (err != -EDEADLK && abba.result != -EDEADLK) {
+ pr_err("%s: missed ABBA deadlock, A err=%d, B err=%d\n",
+ __func__, err, abba.result);
+ ret = -EINVAL;
+ }
+ }
+ return ret;
+}
+
static int __init test_ww_mutex_init(void)
{
int ret;
@@ -165,6 +255,14 @@ static int __init test_ww_mutex_init(void)
if (ret)
return ret;

+ ret = test_abba(false);
+ if (ret)
+ return ret;
+
+ ret = test_abba(true);
+ if (ret)
+ return ret;
+
return 0;
}

--
2.10.2
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