Re: [PATCH] rust: locks: Add `get_mut` method to `Lock`

[Alice Ryhl]

On 2/9/24 17:22, Mathys-Gasnier via B4 Relay wrote:
> From: Mathys-Gasnier <mathys35.gasnier@xxxxxxxxx>
>
> Having a mutable reference guarantees that no other threads have
> access to the lock, so we can take advantage of that to grant callers
> access to the protected data without the the cost of acquiring and
> releasing the locks. Since the lifetime of the data is tied to the
> mutable reference, the borrow checker guarantees that the usage is safe.
>
> Signed-off-by: Mathys-Gasnier <mathys35.gasnier@xxxxxxxxx>
> ---
>   rust/kernel/sync/lock.rs | 5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
> index f12a684bc957..7711c6313e14 100644
> --- a/rust/kernel/sync/lock.rs
> +++ b/rust/kernel/sync/lock.rs
> @@ -121,6 +121,11 @@ pub fn lock(&self) -> Guard<'_, T, B> {
>           // SAFETY: The lock was just acquired.
>           unsafe { Guard::new(self, state) }
>       }
> +
> +    /// Gets the data contained in the lock
> +    pub fn get_mut(&mut self) -> &mut T {
> +        self.data.get_mut()
> +    }

You can never have a mutable reference to a Linux mutex because we pin 
our locks. At most, you can have a Pin<&mut Self>.

Alice