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

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Message-ID: <CAH5fLgggtjNAAotBzwRQ4RYQ9+WDom0MRyYFMnQ+E5UXgOc3RQ@mail.gmail.com>
Date: Wed, 25 Sep 2024 13:06:10 +0200
From: Alice Ryhl <aliceryhl@...gle.com>
To: "Serge E. Hallyn" <serge@...lyn.com>
Cc: Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>, 
	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>, Gary Guo <gary@...yguo.net>, 
	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 Tue, Sep 24, 2024 at 9:45 PM Serge E. Hallyn <serge@...lyn.com> wrote:
>
> On Sun, Sep 15, 2024 at 02:31:27PM +0000, Alice Ryhl 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.
>
> Hi,
>
> this sounds useful, however from kernel side when I think thread-safe,
> I think must not be used across a sleep.  Would something like ThreadLocked
> or LockedToThread make sense?

Hmm, those names seem pretty similar to the current name to me?

Alice