Re: [PATCH v2 1/2] rust: sync: lock: Add Lock::get_mut_pinned()

[Alice Ryhl <aliceryhl@google.com>]

On Fri, May 29, 2026 at 01:30:41PM -0400, Lyude Paul wrote:
> These two functions are inspired by the Rust stdlib equivalent:
> 
>   https://doc.rust-lang.org/std/sync/struct.Mutex.html#method.get_mut()
> 
> The idea here is very simple - if the user has access to a Pin<&mut
> Mutex<…>>, we can guarantee that no one else can look at the data protected
> by the lock. Thus in such situations, locking the mutex isn't necessary to
> access its contents. This can be useful in situations like `Drop`
> implementations, where we may want to access the contents of a Mutex within
> a struct before dropping it.
> 
> So to do this, we add `get_mut_pinned()` to `Lock` - which provides a
> function to access the inner contents of a Mutex provided a Pin<&mut …>.
> 
> Signed-off-by: Lyude Paul <lyude@redhat.com>

Reviewed-by: Alice Ryhl <aliceryhl@google.com>

>  rust/kernel/sync/lock.rs | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
> index 10b6b5e9b024f..5ca36baed34f5 100644
> --- a/rust/kernel/sync/lock.rs
> +++ b/rust/kernel/sync/lock.rs
> @@ -190,6 +190,17 @@ pub fn try_lock(&self) -> Option<Guard<'_, T, B>> {
>          // that `init` was called.
>          unsafe { B::try_lock(self.state.get()).map(|state| Guard::new(self, state)) }
>      }
> +
> +    /// Returns a pinned mutable reference to the underlying data.
> +    ///
> +    /// Because this borrows the lock mutably, no actual locking needs to take place - as the
> +    /// mutable borrow statically guarantees no new locks can be acquired while this reference
> +    /// exists.
> +    #[inline(always)]

Normal #[inline] is sufficient.

> +    pub fn get_mut_pinned(self: Pin<&mut Self>) -> Pin<&mut T> {
> +        // SAFETY: We return a pinned T, ensuring we don't move T.
> +        unsafe { self.map_unchecked_mut(|data| data.data.get_mut()) }
> +    }
>  }
>  
>  /// A lock guard.
> -- 
> 2.54.0
>