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References: <20240222-rust-locks-get-mut-v3-1-d38a6f4bde3d@gmail.com> <ZdgIVxrwBfTEjuEe@boqun-archlinux>
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From: Alice Ryhl <aliceryhl@google.com>
Date: Fri, 23 Feb 2024 11:49:15 +0100
Message-ID: <CAH5fLgj8g1d47u0eFD83topKg2d7FEG+cHS5+Be6+TLt06NmHg@mail.gmail.com>
Subject: Re: [PATCH v3] rust: locks: Add `get_mut` method to `Lock`
To: Boqun Feng <boqun.feng@gmail.com>
Cc: mathys35.gasnier@gmail.com, Miguel Ojeda <ojeda@kernel.org>, 
	Alex Gaynor <alex.gaynor@gmail.com>, Wedson Almeida Filho <wedsonaf@gmail.com>, Gary Guo <gary@garyguo.net>, 
	=?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>, 
	Benno Lossin <benno.lossin@proton.me>, Andreas Hindborg <a.hindborg@samsung.com>, 
	rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org
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On Fri, Feb 23, 2024 at 3:52=E2=80=AFAM Boqun Feng <boqun.feng@gmail.com> w=
rote:
> BTW, while we are at it, I think we should document the
> "structural/non-structural pinning" design decisions somewhere, for
> example in the struct definition:
>
>         #[pin_data]
>         pub struct Lock<T: ?Sized, B: Backend> {
>             ...
>             /// The data protected by the lock.
>             /// This field is non-structural pinned.
>             pub(crate) data: UnsafeCell<T>,
>         }
>
> Thoughts? Or do we think "non-structural pinned" should be the default
> case so no need to document it? I want to have a clear document for each
> field to avoid the accidental "everyone forgets what's the decision
> here" ;-)

I would normally assume that "field is not marked #[pin]" implies that
it's not structurally pinned. But it could still be worth to call out
here.

I prefer the wording "not structurally pinnned" over "non-structural pinned=
".

Alice