[PATCH 1/2] rust: kunit: add config to fail kunit tests if a lockdep warning is triggered

[Malte Wechter <maltewechter@gmail.com>]

When running KUnit tests and a lockdep warning is triggered, the test is
still marked as passed based only on if test assertions are true.
Thus, add a Kconfig option CONFIG_RUST_LOCKDEP_KUNIT_DEBUG_LOCKS. When
this option selected, if lockdep triggers during a test, fail the test.

Signed-off-by: Malte Wechter <maltewechter@gmail.com>
---
 lib/kunit/Kconfig    | 13 +++++++++++++
 rust/macros/kunit.rs | 10 ++++++++++
 2 files changed, 23 insertions(+)

diff --git a/lib/kunit/Kconfig b/lib/kunit/Kconfig
index 94ff8e4089bfb..30bac00c42ce1 100644
--- a/lib/kunit/Kconfig
+++ b/lib/kunit/Kconfig
@@ -142,4 +142,17 @@ config KUNIT_UML_PCI
 
 	  If unsure, say N.
 
+config RUST_LOCKDEP_KUNIT_DEBUG_LOCKS
+	bool "Enable extra debug_locks assertion in Rust KUnit tests"
+	depends on RUST
+	depends on LOCKDEP
+	default n
+	help
+	  Adds an extra assertion to each Rust kunit test case that asserts
+	  that the debug_locks flag from `lockdep` is unchanged. This is useful
+	  when writing unit tests that could potentially trigger a lockdep warning,
+	  this makes it so the KUnit test does not succeed if the test assertions are
+	  true, but a lockdep warning is triggered.
+
+	  If unsure, say N.
 endif # KUNIT
diff --git a/rust/macros/kunit.rs b/rust/macros/kunit.rs
index ae20ed6768f15..d1cd0349f86f0 100644
--- a/rust/macros/kunit.rs
+++ b/rust/macros/kunit.rs
@@ -144,9 +144,19 @@ macro_rules! assert_eq {
                 // here to reduce the length of the assert message.
                 #(#cfg_attrs)*
                 {
+                    #[cfg(CONFIG_RUST_LOCKDEP_KUNIT_DEBUG_LOCKS)]
+                    let __debug_locks_snapshot = ::kernel::bindings::debug_locks;
+
                     (*_test).status = ::kernel::bindings::kunit_status_KUNIT_SUCCESS;
                     use ::kernel::kunit::is_test_result_ok;
                     assert!(is_test_result_ok(#test()));
+
+                    #[cfg(CONFIG_RUST_LOCKDEP_KUNIT_DEBUG_LOCKS)]
+                    {
+                        let __debug_locks_ok =
+                            ::kernel::bindings::debug_locks == __debug_locks_snapshot;
+                        assert!(__debug_locks_ok);
+                    }
                 }
             }
         });

-- 
2.51.2