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Message-ID: <ZmweL12SL7Unlfpe@J2N7QTR9R3.cambridge.arm.com>
Date: Fri, 14 Jun 2024 11:40:47 +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>,
Nathan Chancellor <nathan@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
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 2/2] rust: sync: Add atomic support
On Wed, Jun 12, 2024 at 03:30:25PM -0700, Boqun Feng wrote:
> Provide two atomic types: AtomicI32 and AtomicI64 with the existing
> implemenation of C atomics. These atomics have the same semantics of the
> corresponding LKMM C atomics, and using one memory (ordering) model
> certainly reduces the reasoning difficulty and potential bugs from the
> interaction of two different memory models.
>
> Also bump my role to the maintainer of ATOMIC INFRASTRUCTURE to reflect
> my responsiblity on these Rust APIs.
>
> Note that `Atomic*::new()`s are implemented vi open coding on struct
> atomic*_t. This allows `new()` being a `const` function, so that it can
> be used in constant contexts.
>
> Signed-off-by: Boqun Feng <boqun.feng@...il.com>
I have a few minor comments below.
> ---
> MAINTAINERS | 4 +-
> arch/arm64/kernel/cpufeature.c | 2 +
> rust/kernel/sync.rs | 1 +
> rust/kernel/sync/atomic.rs | 63 ++
> rust/kernel/sync/atomic/impl.rs | 1375 +++++++++++++++++++++++++++++
> scripts/atomic/gen-atomics.sh | 1 +
> scripts/atomic/gen-rust-atomic.sh | 136 +++
> 7 files changed, 1581 insertions(+), 1 deletion(-)
> create mode 100644 rust/kernel/sync/atomic.rs
> create mode 100644 rust/kernel/sync/atomic/impl.rs
> create mode 100755 scripts/atomic/gen-rust-atomic.sh
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index d6c90161c7bf..a8528d27b260 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -3458,7 +3458,7 @@ F: drivers/input/touchscreen/atmel_mxt_ts.c
> ATOMIC INFRASTRUCTURE
> M: Will Deacon <will@...nel.org>
> M: Peter Zijlstra <peterz@...radead.org>
> -R: Boqun Feng <boqun.feng@...il.com>
> +M: Boqun Feng <boqun.feng@...il.com>
> R: Mark Rutland <mark.rutland@....com>
> L: linux-kernel@...r.kernel.org
> S: Maintained
> @@ -3467,6 +3467,8 @@ F: arch/*/include/asm/atomic*.h
> F: include/*/atomic*.h
> F: include/linux/refcount.h
> F: scripts/atomic/
> +F: rust/kernel/sync/atomic.rs
> +F: rust/kernel/sync/atomic/
>
> ATTO EXPRESSSAS SAS/SATA RAID SCSI DRIVER
> M: Bradley Grove <linuxdrivers@...otech.com>
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 48e7029f1054..99e6e2b2867f 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -1601,6 +1601,8 @@ static bool
> has_cpuid_feature(const struct arm64_cpu_capabilities *entry, int scope)
> {
> u64 val = read_scoped_sysreg(entry, scope);
> + if (entry->capability == ARM64_HAS_LSE_ATOMICS)
> + return false;
> return feature_matches(val, entry);
> }
As per other replies, this'll obviously need to go.
> diff --git a/rust/kernel/sync/atomic.rs b/rust/kernel/sync/atomic.rs
> new file mode 100644
> index 000000000000..b0f852cf1741
> --- /dev/null
> +++ b/rust/kernel/sync/atomic.rs
> @@ -0,0 +1,63 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Atomic primitives.
> +//!
> +//! These primitives have the same semantics as their C counterparts, for precise definitions of
> +//! the semantics, please refer to tools/memory-model. Note that Linux Kernel Memory (Consistency)
> +//! Model is the only model for Rust development in kernel right now, please avoid to use Rust's
> +//! own atomics.
> +
> +use crate::bindings::{atomic64_t, atomic_t};
As with the last patch, why no atomic_long_t?
[...]
> +#gen_proto_order_variant(meta, pfx, name, sfx, order, atomic, ty, 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 ty="$1"; shift
> + local int="$1"; shift
> + local raw="$1"; shift
> +
> + local fn_name="${raw}${pfx}${name}${sfx}${order}"
> + local atomicname="${raw}${atomic}_${pfx}${name}${sfx}${order}"
> +
> + local ret="$(gen_ret_type "${meta}" "${int}")"
> + local params="$(gen_params "${int}" $@)"
> + local args="$(gen_args "$@")"
> + local retstmt="$(gen_ret_stmt "${meta}")"
> +
> +cat <<EOF
> + /// See \`${atomicname}\`.
> + #[inline(always)]
> + pub fn ${fn_name}(&self${params}) ${ret}{
> + // SAFETY:\`self.0.get()\` is a valid pointer.
> + unsafe {
> + ${retstmt}${atomicname}(${args});
> + }
> + }
> +EOF
> +}
AFAICT the 'ty' argument (AtomicI32/AtomicI64) isn't used and can be
removed.
Likewise for 'raw'.
> +
> +cat << EOF
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Generated by $0
> +//! DO NOT MODIFY THIS FILE DIRECTLY
> +
> +use super::*;
> +use crate::bindings::*;
> +
> +impl AtomicI32 {
> +EOF
> +
> +grep '^[a-z]' "$1" | while read name meta args; do
> + gen_proto "${meta}" "${name}" "atomic" "AtomicI32" "i32" "" ${args}
With 'ty' and 'raw' gone, this'd be:
gen_proto "${meta}" "${name}" "atomic" "i32" ${args}
> +done
> +
> +cat << EOF
> +}
> +
> +impl AtomicI64 {
> +EOF
> +
> +grep '^[a-z]' "$1" | while read name meta args; do
> + gen_proto "${meta}" "${name}" "atomic64" "AtomicI64" "i64" "" ${args}
With 'ty' and 'raw' gone, this'd be:
gen_proto "${meta}" "${name}" "atomic64" "i64" ${args}
Mark.
> +done
> +
> +cat << EOF
> +}
> +
> +EOF
> --
> 2.45.2
>
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