linux-kernel - Re: [PATCH v4 01/13] rust: sync: introduce `LockClassKey`

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Message-ID: <a9428aa7-efc0-f6e8-6bc3-5a3173a09e7e@proton.me>
Date:   Thu, 13 Apr 2023 08:02:43 +0000
From:   Benno Lossin <benno.lossin@...ton.me>
To:     Wedson Almeida Filho <wedsonaf@...il.com>,
        rust-for-linux@...r.kernel.org
Cc:     Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>,
        linux-kernel@...r.kernel.org,
        Wedson Almeida Filho <walmeida@...rosoft.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Martin Rodriguez Reboredo <yakoyoku@...il.com>
Subject: Re: [PATCH v4 01/13] rust: sync: introduce `LockClassKey`

On 11.04.23 07:45, Wedson Almeida Filho wrote:
> From: Wedson Almeida Filho <walmeida@...rosoft.com>
>
> It is a wrapper around C's `lock_class_key`, which is used by the
> synchronisation primitives that are checked with lockdep. This is in
> preparation for introducing Rust abstractions for these primitives.
>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Waiman Long <longman@...hat.com>
> Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@...il.com>
> Co-developed-by: Boqun Feng <boqun.feng@...il.com>
> Signed-off-by: Boqun Feng <boqun.feng@...il.com>
> Signed-off-by: Wedson Almeida Filho <walmeida@...rosoft.com>

Reviewed-by: Benno Lossin <benno.lossin@...ton.me>

> ---
> v1 -> v2: Fixed a typo in comment
> v2 -> v3: Replaced `core` with `::core` in macro
> v3 -> v4:
> - Rebased on top of rust-next now that all dependencies are applied
>
>   rust/kernel/sync.rs | 45 +++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 45 insertions(+)
>
> diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs
> index 33da23e3076d..541d235ffbeb 100644
> --- a/rust/kernel/sync.rs
> +++ b/rust/kernel/sync.rs
> @@ -5,6 +5,51 @@
>   //! This module contains the kernel APIs related to synchronisation that have been ported or
>   //! wrapped for usage by Rust code in the kernel.
>
> +use crate::types::Opaque;
> +
>   mod arc;
>
>   pub use arc::{Arc, ArcBorrow, UniqueArc};
> +
> +/// Represents a lockdep class. It's a wrapper around C's `lock_class_key`.
> +#[repr(transparent)]
> +pub struct LockClassKey(Opaque<bindings::lock_class_key>);
> +
> +// SAFETY: `bindings::lock_class_key` is designed to be used concurrently from multiple threads and
> +// provides its own synchronization.
> +unsafe impl Sync for LockClassKey {}
> +
> +impl LockClassKey {
> +    /// Creates a new lock class key.
> +    pub const fn new() -> Self {
> +        Self(Opaque::uninit())
> +    }
> +
> +    #[allow(dead_code)]
> +    pub(crate) fn as_ptr(&self) -> *mut bindings::lock_class_key {
> +        self.0.get()
> +    }
> +}
> +
> +/// Defines a new static lock class and returns a pointer to it.
> +#[doc(hidden)]
> +#[macro_export]
> +macro_rules! static_lock_class {
> +    () => {{
> +        static CLASS: $crate::sync::LockClassKey = $crate::sync::LockClassKey::new();
> +        &CLASS
> +    }};
> +}
> +
> +/// Returns the given string, if one is provided, otherwise generates one based on the source code
> +/// location.
> +#[doc(hidden)]
> +#[macro_export]
> +macro_rules! optional_name {
> +    () => {
> +        $crate::c_str!(::core::concat!(::core::file!(), ":", ::core::line!()))
> +    };
> +    ($name:literal) => {
> +        $crate::c_str!($name)
> +    };
> +}
>
> base-commit: 2d0dec625d872a41632a68fce2e69453ed87df91
> --
> 2.34.1
>