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

From: Alice Ryhl
Date: Fri Feb 09 2024 - 14:44:59 EST

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/ | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/rust/kernel/sync/ b/rust/kernel/sync/
index f12a684bc957..7711c6313e14 100644
--- a/rust/kernel/sync/
+++ b/rust/kernel/sync/
@@ -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 {
+ }

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>.