[PATCH v6 4/7] add KUnit coverage on Rust ww_mutex implementation

Onur Özkan
2025-09-03T13:14:00Z

Adds coverage around the core `ww_mutex` functionality

Signed-off-by: Onur Özkan <work@onurozkan.dev>
---
rust/kernel/sync/lock/ww_mutex.rs | 127 ++++++++++++++++++++++++++++++
1 file changed, 127 insertions(+)

diff --git a/rust/kernel/sync/lock/ww_mutex.rs b/rust/kernel/sync/lock/ww_mutex.rs
index 314360632953..d289718d2c98 100644
--- a/rust/kernel/sync/lock/ww_mutex.rs
+++ b/rust/kernel/sync/lock/ww_mutex.rs
@@ -421,3 +421,130 @@ fn drop(&mut self) {
unsafe { bindings::ww_mutex_unlock(self.mutex.as_ptr()) };
}
}
+
+#[kunit_tests(rust_kernel_ww_mutex)]
+mod tests {
+ use crate::c_str;
+ use crate::prelude::*;
+ use crate::sync::Arc;
+ use pin_init::stack_pin_init;
+
+ use super::*;
+
+ // A simple coverage on `define_ww_class` macro.
+ define_ww_class!(TEST_WOUND_WAIT_CLASS, wound_wait, c_str!("test_wound_wait"));
+ define_ww_class!(TEST_WAIT_DIE_CLASS, wait_die, c_str!("test_wait_die"));
+
+ #[test]
+ fn test_ww_mutex_basic_lock_unlock() -> Result {
+ stack_pin_init!(let class = WwClass::new_wound_wait(c_str!("test_mutex_class")));
+
+ let mutex = Arc::pin_init(WwMutex::new(42, &class), GFP_KERNEL)?;
+
+ let ctx = KBox::pin_init(WwAcquireCtx::new(&class), GFP_KERNEL)?;
+
+ // Lock.
+ let guard = ctx.lock(&mutex)?;
+ assert_eq!(*guard, 42);
+
+ // Drop the lock.
+ drop(guard);
+
+ // Lock it again.
+ let mut guard = ctx.lock(&mutex)?;
+ *guard = 100;
+ assert_eq!(*guard, 100);
+
+ Ok(())
+ }
+
+ #[test]
+ fn test_ww_mutex_trylock() -> Result {
+ stack_pin_init!(let class = WwClass::new_wound_wait(c_str!("trylock_class")));
+
+ let mutex = Arc::pin_init(WwMutex::new(123, &class), GFP_KERNEL)?;
+
+ let ctx = KBox::pin_init(WwAcquireCtx::new(&class), GFP_KERNEL)?;
+
+ // `try_lock` on unlocked mutex should succeed.
+ let guard = ctx.try_lock(&mutex)?;
+ assert_eq!(*guard, 123);
+
+ // Now it should fail immediately as it's already locked.
+ assert!(ctx.try_lock(&mutex).is_err());
+
+ Ok(())
+ }
+
+ #[test]
+ fn test_ww_mutex_is_locked() -> Result {
+ stack_pin_init!(let class = WwClass::new_wait_die(c_str!("locked_check_class")));
+
+ let mutex = Arc::pin_init(WwMutex::new("hello", &class), GFP_KERNEL)?;
+
+ let ctx = KBox::pin_init(WwAcquireCtx::new(&class), GFP_KERNEL)?;
+
+ // Should not be locked initially.
+ assert!(!mutex.is_locked());
+
+ let guard = ctx.lock(&mutex)?;
+ assert!(mutex.is_locked());
+
+ drop(guard);
+ assert!(!mutex.is_locked());
+
+ Ok(())
+ }
+
+ #[test]
+ fn test_ww_acquire_context() -> Result {
+ stack_pin_init!(let class = WwClass::new_wound_wait(c_str!("ctx_class")));
+
+ let mutex1 = Arc::pin_init(WwMutex::new(1, &class), GFP_KERNEL)?;
+ let mutex2 = Arc::pin_init(WwMutex::new(2, &class), GFP_KERNEL)?;
+
+ let ctx = KBox::pin_init(WwAcquireCtx::new(&class), GFP_KERNEL)?;
+
+ // Acquire multiple mutexes with the same context.
+ let guard1 = ctx.lock(&mutex1)?;
+ let guard2 = ctx.lock(&mutex2)?;
+
+ assert_eq!(*guard1, 1);
+ assert_eq!(*guard2, 2);
+
+ ctx.done();
+
+ // We shouldn't be able to lock once it's `done`.
+ assert!(ctx.lock(&mutex1).is_err());
+ assert!(ctx.lock(&mutex2).is_err());
+
+ Ok(())
+ }
+
+ #[test]
+ fn test_with_global_classes() -> Result {
+ let wound_wait_mutex =
+ Arc::pin_init(WwMutex::new(100, &TEST_WOUND_WAIT_CLASS), GFP_KERNEL)?;
+ let wait_die_mutex = Arc::pin_init(WwMutex::new(200, &TEST_WAIT_DIE_CLASS), GFP_KERNEL)?;
+
+ let ww_ctx = KBox::pin_init(WwAcquireCtx::new(&TEST_WOUND_WAIT_CLASS), GFP_KERNEL)?;
+ let wd_ctx = KBox::pin_init(WwAcquireCtx::new(&TEST_WAIT_DIE_CLASS), GFP_KERNEL)?;
+
+ let ww_guard = ww_ctx.lock(&wound_wait_mutex)?;
+ let wd_guard = wd_ctx.lock(&wait_die_mutex)?;
+
+ assert_eq!(*ww_guard, 100);
+ assert_eq!(*wd_guard, 200);
+
+ assert!(wound_wait_mutex.is_locked());
+ assert!(wait_die_mutex.is_locked());
+
+ drop(ww_guard);
+ drop(wd_guard);
+
+ assert!(!wound_wait_mutex.is_locked());
+ assert!(!wait_die_mutex.is_locked());
+
+ Ok(())
+ }
+}
--
2.50.0