linux-kernel - Re: [WIP 0/3] Memory model and atomic API in Rust

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Date: Fri, 22 Mar 2024 20:21:23 -0400
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Boqun Feng <boqun.feng@...il.com>, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org, llvm@...ts.linux.dev, 
	Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, 
	Wedson Almeida Filho <wedsonaf@...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>, Alice Ryhl <aliceryhl@...gle.com>, 
	Alan Stern <stern@...land.harvard.edu>, Andrea Parri <parri.andrea@...il.com>, 
	Will Deacon <will@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Nicholas Piggin <npiggin@...il.com>, David Howells <dhowells@...hat.com>, 
	Jade Alglave <j.alglave@....ac.uk>, Luc Maranget <luc.maranget@...ia.fr>, 
	"Paul E. McKenney" <paulmck@...nel.org>, Akira Yokosawa <akiyks@...il.com>, 
	Daniel Lustig <dlustig@...dia.com>, Joel Fernandes <joel@...lfernandes.org>, 
	Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, 
	kent.overstreet@...il.com, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	elver@...gle.com, Mark Rutland <mark.rutland@....com>, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, 
	Catalin Marinas <catalin.marinas@....com>, linux-arm-kernel@...ts.infradead.org, 
	linux-fsdevel@...r.kernel.org
Subject: Re: [WIP 0/3] Memory model and atomic API in Rust

On Fri, Mar 22, 2024 at 05:12:29PM -0700, Linus Torvalds wrote:
> On Fri, 22 Mar 2024 at 16:57, Kent Overstreet <kent.overstreet@...ux.dev> wrote:
> >
> > I wonder about that. The disadvantage of only supporting LKMM atomics is
> > that we'll be incompatible with third party code, and we don't want to
> > be rolling all of our own data structures forever.
> 
> Honestly, having seen the shit-show that is language standards bodies
> and incomplete compiler support, I do not understand why people think
> that we wouldn't want to roll our own.
> 
> The C++ memory model may be reliable in another decade. And then a
> decade after *that*, we can drop support for the pre-reliable
> compilers.
> 
> People who think that compilers do things right just because they are
> automated simply don't know what they are talking about.
> 
> It was just a couple of days ago that I was pointed at
> 
>     https://github.com/llvm/llvm-project/issues/64188

Besides that there's cross arch support to think about - it's hard to
imagine us ever ditching our own atomics.

I was thinking about something more incremental - just an optional mode
where our atomics were C atomics underneath. It'd probably give the
compiler people a much more effective way to test their stuff than
anything they have now.