list: test: Add test for list_del_init_careful()

The list_del_init_careful() function was added[1] after the list KUnit
test. Add a very basic test to cover it.

Note that this test only covers the single-threaded behaviour (which
matches list_del_init()), as is already the case with the test for
list_empty_careful().

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c6fe44d96fc1536af5b11cd859686453d1b7bfd1

Signed-off-by: David Gow <davidgow@google.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

lib/list-test.c

@@ -161,6 +161,26 @@ static void list_test_list_del_init(struct kunit *test)
 	KUNIT_EXPECT_TRUE(test, list_empty_careful(&a));
 }
 
+static void list_test_list_del_init_careful(struct kunit *test)
+{
+	/* NOTE: This test only checks the behaviour of this function in
+	 * isolation. It does not verify memory model guarantees.
+	 */
+	struct list_head a, b;
+	LIST_HEAD(list);
+
+	list_add_tail(&a, &list);
+	list_add_tail(&b, &list);
+
+	/* before: [list] -> a -> b */
+	list_del_init_careful(&a);
+	/* after: [list] -> b, a initialised */
+
+	KUNIT_EXPECT_PTR_EQ(test, list.next, &b);
+	KUNIT_EXPECT_PTR_EQ(test, b.prev, &list);
+	KUNIT_EXPECT_TRUE(test, list_empty_careful(&a));
+}
+
 static void list_test_list_move(struct kunit *test)
 {
 	struct list_head a, b;
@@ -707,6 +727,7 @@ static struct kunit_case list_test_cases[] = {
 	KUNIT_CASE(list_test_list_replace_init),
 	KUNIT_CASE(list_test_list_swap),
 	KUNIT_CASE(list_test_list_del_init),
+	KUNIT_CASE(list_test_list_del_init_careful),
 	KUNIT_CASE(list_test_list_move),
 	KUNIT_CASE(list_test_list_move_tail),
 	KUNIT_CASE(list_test_list_bulk_move_tail),