xref: /openbmc/linux/kernel/locking/test-ww_mutex.c (revision 70207686)

/*
 * Module-based API test facility for ww_mutexes
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, you can access it online at
 * http://www.gnu.org/licenses/gpl-2.0.html.
 */

#include <linux/kernel.h>

#include <linux/completion.h>
#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/ww_mutex.h>

static DEFINE_WW_CLASS(ww_class);

struct test_mutex {
	struct work_struct work;
	struct ww_mutex mutex;
	struct completion ready, go, done;
	unsigned int flags;
};

#define TEST_MTX_SPIN BIT(0)
#define TEST_MTX_TRY BIT(1)
#define TEST_MTX_CTX BIT(2)
#define __TEST_MTX_LAST BIT(3)

static void test_mutex_work(struct work_struct *work)
{
	struct test_mutex *mtx = container_of(work, typeof(*mtx), work);

	complete(&mtx->ready);
	wait_for_completion(&mtx->go);

	if (mtx->flags & TEST_MTX_TRY) {
		while (!ww_mutex_trylock(&mtx->mutex))
			cpu_relax();
	} else {
		ww_mutex_lock(&mtx->mutex, NULL);
	}
	complete(&mtx->done);
	ww_mutex_unlock(&mtx->mutex);
}

static int __test_mutex(unsigned int flags)
{
#define TIMEOUT (HZ / 16)
	struct test_mutex mtx;
	struct ww_acquire_ctx ctx;
	int ret;

	ww_mutex_init(&mtx.mutex, &ww_class);
	ww_acquire_init(&ctx, &ww_class);

	INIT_WORK_ONSTACK(&mtx.work, test_mutex_work);
	init_completion(&mtx.ready);
	init_completion(&mtx.go);
	init_completion(&mtx.done);
	mtx.flags = flags;

	schedule_work(&mtx.work);

	wait_for_completion(&mtx.ready);
	ww_mutex_lock(&mtx.mutex, (flags & TEST_MTX_CTX) ? &ctx : NULL);
	complete(&mtx.go);
	if (flags & TEST_MTX_SPIN) {
		unsigned long timeout = jiffies + TIMEOUT;

		ret = 0;
		do {
			if (completion_done(&mtx.done)) {
				ret = -EINVAL;
				break;
			}
			cpu_relax();
		} while (time_before(jiffies, timeout));
	} else {
		ret = wait_for_completion_timeout(&mtx.done, TIMEOUT);
	}
	ww_mutex_unlock(&mtx.mutex);
	ww_acquire_fini(&ctx);

	if (ret) {
		pr_err("%s(flags=%x): mutual exclusion failure\n",
		       __func__, flags);
		ret = -EINVAL;
	}

	flush_work(&mtx.work);
	destroy_work_on_stack(&mtx.work);
	return ret;
#undef TIMEOUT
}

static int test_mutex(void)
{
	int ret;
	int i;

	for (i = 0; i < __TEST_MTX_LAST; i++) {
		ret = __test_mutex(i);
		if (ret)
			return ret;
	}

	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;
}

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;

	ret = test_mutex();
	if (ret)
		return ret;

	ret = test_aa();
	if (ret)
		return ret;

	ret = test_abba(false);
	if (ret)
		return ret;

	ret = test_abba(true);
	if (ret)
		return ret;

	return 0;
}

static void __exit test_ww_mutex_exit(void)
{
}

module_init(test_ww_mutex_init);
module_exit(test_ww_mutex_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Intel Corporation");