linux-kernel - Re: [PATCH v1 1/2] rust: specify when `ARef` is thread safe

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Date:   Fri, 19 May 2023 09:42:14 +0000
From:   Alice Ryhl <aliceryhl@...gle.com>
To:     boqun.feng@...il.com
Cc:     alex.gaynor@...il.com, aliceryhl@...gle.com,
        benno.lossin@...ton.me, bjorn3_gh@...tonmail.com, gary@...yguo.net,
        linux-kernel@...r.kernel.org, mark.rutland@....com,
        mingo@...hat.com, ojeda@...nel.org, patches@...ts.linux.dev,
        peterz@...radead.org, rust-for-linux@...r.kernel.org,
        wedsonaf@...il.com, will@...nel.org
Subject: Re: [PATCH v1 1/2] rust: specify when `ARef` is thread safe

On 5/18/23 23:24, Boqun Feng wrote:
> On Wed, May 17, 2023 at 09:59:04AM +0000, Alice Ryhl wrote:
>> +// SAFETY: It is safe to send `ARef<T>` to another thread when the underlying `T` is `Sync` because
>> +// it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally, it needs
>> +// `T` to be `Send` because any thread that has an `ARef<T>` may ultimately access `T` directly, for
>
> Does the "ultimately access `T` directly" here imply mutably or
> exclusively? If so, it makes sense to me to call it out. I'm trying to
> make sure we can agree on some "common terminologies" ;)

It means "access using a mutable reference". I agree that "directly" is a bit
unclear - I copied it from the safety comment on Arc.

Alice