From: Boqun Feng <boqun.feng@gmail.com>
To: mathys35.gasnier@gmail.com
Cc: "Miguel Ojeda" <ojeda@kernel.org>,
"Alex Gaynor" <alex.gaynor@gmail.com>,
"Wedson Almeida Filho" <wedsonaf@gmail.com>,
"Gary Guo" <gary@garyguo.net>,
"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
"Benno Lossin" <benno.lossin@proton.me>,
"Andreas Hindborg" <a.hindborg@samsung.com>,
"Alice Ryhl" <aliceryhl@google.com>,
rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
"Martin Rodriguez Reboredo" <yakoyoku@gmail.com>
Subject: Re: [PATCH v4] rust: locks: Add `get_mut` method to `Lock`
Date: Wed, 28 Feb 2024 10:51:06 -0800 [thread overview]
Message-ID: <Zd-AmppAQtTXlOdo@boqun-archlinux> (raw)
In-Reply-To: <20240226-rust-locks-get-mut-v4-1-24abf57707a8@gmail.com>
On Mon, Feb 26, 2024 at 02:55:47PM +0100, Mathys-Gasnier via B4 Relay wrote:
> From: Mathys-Gasnier <mathys35.gasnier@gmail.com>
>
> 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.
>
> Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
> Signed-off-by: Mathys-Gasnier <mathys35.gasnier@gmail.com>
> ---
> Changes in v4:
> - Improved documentation
> - Link to v3: https://lore.kernel.org/r/20240222-rust-locks-get-mut-v3-1-d38a6f4bde3d@gmail.com
>
> Changes in v3:
> - Changing the function to take a `Pin<&mut self>` instead of a `&mut self`
> - Removed reviewed-by's since big changes were made. Please take another
> look.
> - Link to v2: https://lore.kernel.org/r/20240212-rust-locks-get-mut-v2-1-5ccd34c2b70b@gmail.com
>
> Changes in v2:
> - Improved doc comment.
> - Link to v1: https://lore.kernel.org/r/20240209-rust-locks-get-mut-v1-1-ce351fc3de47@gmail.com
> ---
> rust/kernel/sync/lock.rs | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
> index f12a684bc957..a563991bf851 100644
> --- a/rust/kernel/sync/lock.rs
> +++ b/rust/kernel/sync/lock.rs
> @@ -7,7 +7,11 @@
>
> use super::LockClassKey;
> use crate::{bindings, init::PinInit, pin_init, str::CStr, types::Opaque, types::ScopeGuard};
> -use core::{cell::UnsafeCell, marker::PhantomData, marker::PhantomPinned};
> +use core::{
> + cell::UnsafeCell,
> + marker::{PhantomData, PhantomPinned},
> + pin::Pin,
> +};
> use macros::pin_data;
>
> pub mod mutex;
> @@ -121,6 +125,17 @@ 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.
> + ///
> + /// Having a mutable reference to the lock guarantees that no other threads have access to the lock.
> + /// And because `data` is not structurally pinned,
> + /// it is safe to get a mutable reference to the lock content.
This looks good! But I forgot to mention this last time: it'll be good
to add an "# Example" session which would act as both a document and a
test. Do you mind to send a follow up patch?
Anyway,
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Regards,
Boqun
> + pub fn get_mut(self: Pin<&mut Self>) -> &mut T {
> + // SAFETY: The lock will only be used to get a reference to the data, therefore self won't get moved
> + let lock = unsafe { self.get_unchecked_mut() };
> + lock.data.get_mut()
> + }
> }
>
> /// A lock guard.
>
> ---
> base-commit: 711cbfc717650532624ca9f56fbaf191bed56e67
> change-id: 20240118-rust-locks-get-mut-c42072101d7a
>
> Best regards,
> --
> Mathys-Gasnier <mathys35.gasnier@gmail.com>
>
prev parent reply other threads:[~2024-02-28 18:51 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-26 13:55 [PATCH v4] rust: locks: Add `get_mut` method to `Lock` Mathys-Gasnier via B4 Relay
2024-02-27 14:51 ` Alice Ryhl
2024-02-28 18:51 ` Boqun Feng [this message]
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