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

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Message-ID: <ZmwcBWjxf7gm89wA@J2N7QTR9R3.cambridge.arm.com>
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>,
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	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
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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.