Messages in this thread | | | From | Wedson Almeida Filho <> | Date | Thu, 15 Feb 2024 13:50:58 -0300 | Subject | Re: [PATCH v2] rust: locks: Add `get_mut` method to `Lock` |
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On Mon, 12 Feb 2024 at 11:22, Alice Ryhl <aliceryhl@google.com> wrote: > > On Mon, Feb 12, 2024 at 3:13 PM Mathys-Gasnier via B4 Relay > <devnull+mathys35.gasnier.gmail.com@kernel.org> wrote: > > + /// Gets the data contained in the lock > > + /// Having a mutable reference to the lock guarantees that no other threads have access to the lock. > > + /// Making it safe to get a mutable reference to the lock content. > > + pub fn get_mut(&mut self) -> &mut T { > > + self.data.get_mut() > > + } > > It's impossible to call this method. 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>.
Perhaps you meant to say that it's impossible to call this method without unsafe blocks? From a `Pin<&mut T>`, we can call `get_unchecked_mut` to get an `&mut T`.
This is addressing issue 924 opened by Björn some time back. The idea here is that if there's a path where avoiding the lock/unlock calls (which are expensive because of the memory barriers) is performance critical, we can do it as long as we use an unsafe block.
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