Re: [PATCH] rust: sync: lock: Add an example for Guard::lock_ref()

Andreas Hindborg
2025-02-24T08:08:19Z

Boqun Feng <boqun.feng@gmail.com> writes:

> To provide examples on usage of `Guard::lock_ref()` along with the unit
> test, an "assert a lock is held by a guard" example is added.
>
> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
> ---
> This depends on Alice's patch:
>
> https://lore.kernel.org/all/20250130-guard-get-lock-v1-1-8ed87899920a@google.com/
>
> I'm also OK to fold this in if Alice thinks it's fine.
>
> rust/kernel/sync/lock.rs | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
> index 3701fac6ebf6..6d868e35b0a3 100644
> --- a/rust/kernel/sync/lock.rs
> +++ b/rust/kernel/sync/lock.rs
> @@ -201,6 +201,30 @@ unsafe impl<T: Sync + ?Sized, B: Backend> Sync for Guard<'_, T, B> {}
>
> impl<'a, T: ?Sized, B: Backend> Guard<'a, T, B> {
> /// Returns the lock that this guard originates from.
> + ///
> + /// # Examples
> + ///
> + /// The following example shows how to use [`Guard::lock_ref()`] to assert the corresponding
> + /// lock is held.
> + ///
> + /// ```
> + /// # use kernel::{new_spinlock, stack_pin_init, sync::lock::{Backend, Guard, Lock}};
> + ///
> + /// fn assert_held<T, B: Backend>(guard: &Guard<'_, T, B>, lock: &Lock<T, B>) {
> + /// // Address-equal means the same lock.
> + /// assert!(core::ptr::eq(guard.lock_ref(), lock));
> + /// }

This seems super useful. Perhaps add this method as part of the lock api
instead of just having it in the example?

Best regards,
Andreas Hindborg