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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Mon, 19 Apr 2021 10:14:49 -0700
Message-ID: <CAHk-=wjSrOcA0567rpn1PbYkGEgnw_sOmZ13JX87isrMq1dL-Q@mail.gmail.com>
Subject: Re: [PATCH 00/13] [RFC] Rust support
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Wedson Almeida Filho <wedsonaf@google.com>, ojeda@kernel.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        rust-for-linux@vger.kernel.org,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Will Deacon <will@kernel.org>
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On Mon, Apr 19, 2021 at 2:36 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> I also don't see how this is better than seq_cst.
>
> But yes, not broken, but also very much not optimal.

I continue to feel like kernel people should just entirely ignore the
C++ memory ordering standard.

It's inferior to what we already have, and simply not helpful. It
doesn't actually solve any problems as far as the kernel is concerned,
and it generates its own set of issues (ie assuming that the compiler
supports it, and assuming the compiler gets it right).

The really subtle cases that it could have been helpful for (eg RCU,
or the load-store control dependencies) were _too_ subtle for the
standard.

And I do not believe Rust changes _any_ of that.

Any kernel Rust code will simply have to follow the LKMM rules, and
use the kernel model for the interfaces. Things like the C++ memory
model is simply not _relevant_ to the kernel.

         Linus