linux-kernel - Re: [PATCH v2] rust: add global lock support

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Message-ID: <CAH5fLgiZt3uVZiU1xXPcvYNR-Em2V3y+-C9EbsqrNvkScbiAYA@mail.gmail.com>
Date: Mon, 2 Sep 2024 13:42:53 +0200
From: Alice Ryhl <aliceryhl@...gle.com>
To: Benno Lossin <benno.lossin@...ton.me>
Cc: Miguel Ojeda <ojeda@...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>, 
	Andreas Hindborg <a.hindborg@...sung.com>, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] rust: add global lock support

On Mon, Sep 2, 2024 at 1:37 PM Alice Ryhl <aliceryhl@...gle.com> wrote:
>
> On Fri, Aug 30, 2024 at 3:22 PM Benno Lossin <benno.lossin@...ton.me> wrote:
> >
> > On 30.08.24 07:34, Alice Ryhl wrote:
> > > On Thu, Aug 29, 2024 at 8:17 PM Benno Lossin <benno.lossin@...ton.me> wrote:
> > >>
> > >> On 27.08.24 10:41, Alice Ryhl wrote:
> > >>> For architectures that don't use all-zeros for the unlocked case, we
> > >>> will most likely have to hard-code the correct representation on the
> > >>> Rust side.
> > >>
> > >> You mean in `unsafe_const_init`?
> > >
> > > No, I mean we would have `unsafe_const_new` directly set `state` to
> > > the right value and let `unsafe_const_init` be a no-op.
> >
> > But how do you set the right value of a list_head? The value will be
> > moved.
>
> Right ... we probably can't get around needing a macro. Can statics
> even reference themselves?

Looks like they can:

use std::ptr::addr_of;

struct MyStruct {
    ptr: *const MyStruct,
}

static mut MY_STRUCT: MyStruct = MyStruct {
    ptr: addr_of!(MY_STRUCT),
};

Alice