linux-kernel - Re: [RFC 1/2] rust: Introduce atomic API helpers

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Date: Fri, 14 Jun 2024 11:31:33 +0100
From: Mark Rutland <mark.rutland@....com>
To: Boqun Feng <boqun.feng@...il.com>
Cc: 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>,
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	kent.overstreet@...il.com,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, elver@...gle.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>,
	torvalds@...ux-foundation.org, linux-arm-kernel@...ts.infradead.org,
	linux-fsdevel@...r.kernel.org, Trevor Gross <tmgross@...ch.edu>,
	dakr@...hat.com
Subject: Re: [RFC 1/2] rust: Introduce atomic API helpers

On Wed, Jun 12, 2024 at 03:30:24PM -0700, Boqun Feng wrote:
> In order to support LKMM atomics in Rust, add rust_helper_* for atomic
> APIs. These helpers ensure the implementation of LKMM atomics in Rust is
> the same as in C. This could save the maintenance burden of having two
> similar atomic implementations in asm.
> 
> Originally-by: Mark Rutland <mark.rutland@....com>
> Signed-off-by: Boqun Feng <boqun.feng@...il.com>

FWIW, I'm happy with the concept; I have a couple of minor comments
below.

> ---
>  rust/atomic_helpers.h                     | 1035 +++++++++++++++++++++
>  rust/helpers.c                            |    2 +
>  scripts/atomic/gen-atomics.sh             |    1 +
>  scripts/atomic/gen-rust-atomic-helpers.sh |   64 ++
>  4 files changed, 1102 insertions(+)
>  create mode 100644 rust/atomic_helpers.h
>  create mode 100755 scripts/atomic/gen-rust-atomic-helpers.sh

[...]

> +#gen_proto_order_variant(meta, pfx, name, sfx, order, atomic, int, raw, arg...)
> +gen_proto_order_variant()
> +{
> +	local meta="$1"; shift
> +	local pfx="$1"; shift
> +	local name="$1"; shift
> +	local sfx="$1"; shift
> +	local order="$1"; shift
> +	local atomic="$1"; shift
> +	local int="$1"; shift
> +	local raw="$1"; shift
> +	local attrs="${raw:+noinstr }"

You removed the 'raw_' atomic generation below, so you can drop the
'raw' parameter and the 'attrs' variable (both here and in the
template)...

> +	local atomicname="${raw}${atomic}_${pfx}${name}${sfx}${order}"
> +
> +	local ret="$(gen_ret_type "${meta}" "${int}")"
> +	local params="$(gen_params "${int}" "${atomic}" "$@")"
> +	local args="$(gen_args "$@")"
> +	local retstmt="$(gen_ret_stmt "${meta}")"
> +
> +cat <<EOF
> +__rust_helper ${attrs}${ret}

... e.g. you can remove '${attrs}' here.

[...]

> +grep '^[a-z]' "$1" | while read name meta args; do
> +	gen_proto "${meta}" "${name}" "atomic" "int" "" ${args}
> +done
> +
> +grep '^[a-z]' "$1" | while read name meta args; do
> +	gen_proto "${meta}" "${name}" "atomic64" "s64" "" ${args}
> +done

With the 'raw' parameter removed above, the '""' argument can be
dropped.

Any reason to not have the atomic_long_*() API? It seems like an odd
ommision.

Mark.