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locking: Add kselftests for ww_mutex

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  locking: Add kselftests for ww_mutex Chris Wilson <chris@chris-wilson.co.uk> - 2016-12-01 12:50 +0100
    [PATCH v2 8/8] locking: Add ww_mutex to tools/testing/selftests Chris Wilson <chris@chris-wilson.co.uk> - 2016-12-01 12:50 +0100
    [PATCH v2 5/8] locking: Add kselftests for ww_mutex ABBA deadlock detection Chris Wilson <chris@chris-wilson.co.uk> - 2016-12-01 12:50 +0100

#1533993 — locking: Add kselftests for ww_mutex

Nicolai Hähnle was looking into a deadlock within ww_mutexes (that has
been fixed by Peter's mutex rewrite) and to support his changes, I
thought it was be useful to have a small validation suite for ww_mutex.
-Chris

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#1533994 — [PATCH v2 8/8] locking: Add ww_mutex to tools/testing/selftests

Add the minimal test running (modprobe test-ww_mutex) to the kselftests
CI framework.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
---
 tools/testing/selftests/locking/ww_mutex.sh | 10 ++++++++++
 1 file changed, 10 insertions(+)
 create mode 100755 tools/testing/selftests/locking/ww_mutex.sh

diff --git a/tools/testing/selftests/locking/ww_mutex.sh b/tools/testing/selftests/locking/ww_mutex.sh
new file mode 100755
index 000000000000..6905da965f3b
--- /dev/null
+++ b/tools/testing/selftests/locking/ww_mutex.sh
@@ -0,0 +1,10 @@
+#!/bin/sh
+# Runs API tests for struct ww_mutex (Wait/Wound mutexes)
+
+if /sbin/modprobe -q test-ww_mutex; then
+       /sbin/modprobe -q -r test-ww_mutex
+       echo "locking/ww_mutex: ok"
+else
+       echo "locking/ww_mutex: [FAIL]"
+       exit 1
+fi
-- 
2.10.2

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#1533995 — [PATCH v2 5/8] locking: Add kselftests for ww_mutex ABBA deadlock detection

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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