From: Mathys-Gasnier <[email protected]>
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 <[email protected]>
---
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()
+ }
}
/// A lock guard.
---
base-commit: 711cbfc717650532624ca9f56fbaf191bed56e67
change-id: 20240118-rust-locks-get-mut-c42072101d7a
Best regards,
--
Mathys-Gasnier <[email protected]>
On 2/9/24 17:22, Mathys-Gasnier via B4 Relay wrote:
> From: Mathys-Gasnier <[email protected]>
>
> 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 <[email protected]>
> ---
> 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
On 2/9/24 13:22, Mathys-Gasnier wrote:
> From: Mathys-Gasnier <[email protected]>
>
> 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 <[email protected]>
> ---
> [...]
> + /// Gets the data contained in the lock
I wish that this doc comment mentioned what you've said about having a
mutable reference avoids locking, much like the documentation on
`std::sync::Mutex::get_mut`. If you do so then you can add my reviewed.
Reviewed-by: Martin Rodriguez Reboredo <[email protected]>
> + pub fn get_mut(&mut self) -> &mut T {
> + self.data.get_mut()
> + }
> }
> [...]