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Commit 70207686 authored by Chris Wilson's avatar Chris Wilson Committed by Ingo Molnar
Browse files

locking/ww_mutex: Add kselftests for ww_mutex ABBA deadlock detection 



Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: default avatarPeter 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/20161201114711.28697-6-chris@chris-wilson.co.uk


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent c22fb380

kernel/locking/test-ww_mutex.c

+98 −0
Original line number Original line Diff line number Diff line
@@ -153,6 +153,96 @@ static int test_aa(void) 
	return ret;

	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)

static int __init test_ww_mutex_init(void)

{

{

	int ret;

	int ret;
@@ -165,6 +255,14 @@ static int __init test_ww_mutex_init(void) 
	if (ret)

	if (ret)

		return ret;

		return ret;





	ret = test_abba(false);

	if (ret)

		return ret;



	ret = test_abba(true);

	if (ret)

		return ret;



	return 0;

	return 0;

}

}