linux-kernel - Re: [PATCH v10 1/8] rust: types: add `NotThreadSafe`

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Message-ID: <20240915163850.6af9c78d.gary@garyguo.net>
Date: Sun, 15 Sep 2024 16:38:50 +0100
From: Gary Guo <gary@...yguo.net>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
 "Serge E. Hallyn" <serge@...lyn.com>, Miguel Ojeda <ojeda@...nel.org>,
 Christian Brauner <brauner@...nel.org>, Alex Gaynor
 <alex.gaynor@...il.com>, Wedson Almeida Filho <wedsonaf@...il.com>, Boqun
 Feng <boqun.feng@...il.com>, "Björn Roy Baron"
 <bjorn3_gh@...tonmail.com>, Benno Lossin <benno.lossin@...ton.me>, Andreas
 Hindborg <a.hindborg@...sung.com>, Peter Zijlstra <peterz@...radead.org>,
 Alexander Viro <viro@...iv.linux.org.uk>, Greg Kroah-Hartman
 <gregkh@...uxfoundation.org>, "Arve Hjønnevåg"
 <arve@...roid.com>, Todd Kjos <tkjos@...roid.com>, Martijn Coenen
 <maco@...roid.com>, Joel Fernandes <joel@...lfernandes.org>, Carlos Llamas
 <cmllamas@...gle.com>, Suren Baghdasaryan <surenb@...gle.com>, Dan Williams
 <dan.j.williams@...el.com>, Matthew Wilcox <willy@...radead.org>, Thomas
 Gleixner <tglx@...utronix.de>, Daniel Xu <dxu@...uu.xyz>, Martin Rodriguez
 Reboredo <yakoyoku@...il.com>, Trevor Gross <tmgross@...ch.edu>,
 linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org,
 rust-for-linux@...r.kernel.org, linux-fsdevel@...r.kernel.org, Kees Cook
 <kees@...nel.org>
Subject: Re: [PATCH v10 1/8] rust: types: add `NotThreadSafe`

On Sun, 15 Sep 2024 14:31:27 +0000
Alice Ryhl <aliceryhl@...gle.com> wrote:

> This introduces a new marker type for types that shouldn't be thread
> safe. By adding a field of this type to a struct, it becomes non-Send
> and non-Sync, which means that it cannot be accessed in any way from
> threads other than the one it was created on.
> 
> This is useful for APIs that require globals such as `current` to remain
> constant while the value exists.
> 
> We update two existing users in the Kernel to use this helper:
> 
>  * `Task::current()` - moving the return type of this value to a
>    different thread would not be safe as you can no longer be guaranteed
>    that the `current` pointer remains valid.
>  * Lock guards. Mutexes and spinlocks should be unlocked on the same
>    thread as where they were locked, so we enforce this using the Send
>    trait.
> 
> There are also additional users in later patches of this patchset. See
> [1] and [2] for the discussion that led to the introduction of this
> patch.
> 
> Link: https://lore.kernel.org/all/nFDPJFnzE9Q5cqY7FwSMByRH2OAn_BpI4H53NQfWIlN6I2qfmAqnkp2wRqn0XjMO65OyZY4h6P4K2nAGKJpAOSzksYXaiAK_FoH_8QbgBI4=@proton.me/ [1]
> Link: https://lore.kernel.org/all/nFDPJFnzE9Q5cqY7FwSMByRH2OAn_BpI4H53NQfWIlN6I2qfmAqnkp2wRqn0XjMO65OyZY4h6P4K2nAGKJpAOSzksYXaiAK_FoH_8QbgBI4=@proton.me/ [2]
> Suggested-by: Benno Lossin <benno.lossin@...ton.me>
> Reviewed-by: Benno Lossin <benno.lossin@...ton.me>
> Reviewed-by: Trevor Gross <tmgross@...ch.edu>
> Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@...il.com>
> Reviewed-by: Björn Roy Baron <bjorn3_gh@...tonmail.com>
> Reviewed-by: Gary Guo <gary@...yguo.net>
> Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>

Miguel, can we apply this patch now without having it wait on the rest
of file abstractions because it'll be useful to other?

Best,
Gary

> ---
>  rust/kernel/sync/lock.rs | 13 +++++++++----
>  rust/kernel/task.rs      | 10 ++++++----
>  rust/kernel/types.rs     | 21 +++++++++++++++++++++
>  3 files changed, 36 insertions(+), 8 deletions(-)