linux-kernel - Re: [RFC PATCH 05/11] rust: add revocable objects

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Date: Fri, 31 May 2024 10:35:35 +0200
From: Dirk Behme <dirk.behme@...bosch.com>
To: Danilo Krummrich <dakr@...hat.com>, <gregkh@...uxfoundation.org>,
	<rafael@...nel.org>, <bhelgaas@...gle.com>, <ojeda@...nel.org>,
	<alex.gaynor@...il.com>, <wedsonaf@...il.com>, <boqun.feng@...il.com>,
	<gary@...yguo.net>, <bjorn3_gh@...tonmail.com>, <benno.lossin@...ton.me>,
	<a.hindborg@...sung.com>, <aliceryhl@...gle.com>, <airlied@...il.com>,
	<fujita.tomonori@...il.com>, <lina@...hilina.net>, <pstanner@...hat.com>,
	<ajanulgu@...hat.com>, <lyude@...hat.com>
CC: <rust-for-linux@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-pci@...r.kernel.org>
Subject: Re: [RFC PATCH 05/11] rust: add revocable objects

On 20.05.2024 19:25, Danilo Krummrich wrote:
> From: Wedson Almeida Filho <wedsonaf@...il.com>
> 
> This implements the Revocable and AsyncRevocable types.
> 
> Revocable allows access to objects to be safely revoked at run time.
> 
> This is useful, for example, for resources allocated during device probe;
> when the device is removed, the driver should stop accessing the device
> resources even if other state is kept in memory due to existing
> references (i.e., device context data is ref-counted and has a non-zero
> refcount after removal of the device).
> 
> AsyncRevocable allows access to objects to be revoked without having to
> wait for existing users to complete. This will be used to drop futures
> in tasks when executors are being torn down.
> 
> Co-developed-by: Andreas Hindborg <a.hindborg@...sung.com>
> Signed-off-by: Andreas Hindborg <a.hindborg@...sung.com>
> Signed-off-by: Wedson Almeida Filho <wedsonaf@...il.com>
> Signed-off-by: Danilo Krummrich <dakr@...hat.com>
> ---
>   rust/kernel/lib.rs       |   1 +
>   rust/kernel/revocable.rs | 441 +++++++++++++++++++++++++++++++++++++++
>   2 files changed, 442 insertions(+)
>   create mode 100644 rust/kernel/revocable.rs
> 
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index 698121c925f3..d7d415429517 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -40,6 +40,7 @@
>   pub mod net;
>   pub mod prelude;
>   pub mod print;
> +pub mod revocable;
>   mod static_assert;
>   #[doc(hidden)]
>   pub mod std_vendor;
> diff --git a/rust/kernel/revocable.rs b/rust/kernel/revocable.rs
> new file mode 100644
> index 000000000000..71408039a117
> --- /dev/null
> +++ b/rust/kernel/revocable.rs
> @@ -0,0 +1,441 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Revocable objects.
> +//!
> +//! The [`Revocable`] type wraps other types and allows access to them to be revoked. The existence
> +//! of a [`RevocableGuard`] ensures that objects remain valid.
> +
> +use crate::{
> +    bindings,
> +    init::{self},
> +    prelude::*,
> +    sync::rcu,
> +};
> +use core::{
> +    cell::UnsafeCell,
> +    marker::PhantomData,
> +    mem::MaybeUninit,
> +    ops::Deref,
> +    ptr::drop_in_place,
> +    sync::atomic::{fence, AtomicBool, AtomicU32, Ordering},
> +};
> +
> +/// An object that can become inaccessible at runtime.
> +///
> +/// Once access is revoked and all concurrent users complete (i.e., all existing instances of
> +/// [`RevocableGuard`] are dropped), the wrapped object is also dropped.
> +///
> +/// # Examples

You might want to enable the doctest and check if the Examples are at 
least compiling ;) Here and in devres as well.

Best regards

Dirk