Received-SPF: pass (google.com: domain of linux-kernel+bounces-201364-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223;
Precedence: bulk
MIME-Version: 1.0
References: <1dee481f-d584-41d6-a5f1-d84375be5fe8@paulmck-laptop> <20240604170437.2362545-4-paulmck@kernel.org>
In-Reply-To: <20240604170437.2362545-4-paulmck@kernel.org>
From: Linus Walleij <linus.walleij@linaro.org>
Date: Tue, 4 Jun 2024 22:52:23 +0200
Message-ID: <CACRpkdaYQWGsjtDPzbJS4C9Y9z8JGv=3ihQrVKvegJf8ujqSmA@mail.gmail.com>
Subject: Re: [PATCH v3 cmpxchg 4/4] ARM: Emulate one-byte cmpxchg
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, 
	kernel-team@meta.com, elver@google.com, akpm@linux-foundation.org, 
	tglx@linutronix.de, peterz@infradead.org, dianders@chromium.org, 
	pmladek@suse.com, torvalds@linux-foundation.org, arnd@arndb.de, 
	Mark Brown <broonie@kernel.org>, Naresh Kamboju <naresh.kamboju@linaro.org>, 
	Nathan Chancellor <nathan@kernel.org>, "Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>, 
	Andrew Davis <afd@ti.com>, Eric DeVolder <eric.devolder@oracle.com>, Rob Herring <robh@kernel.org>, 
	linux-arm-kernel@lists.infradead.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

Hi Paul,

thanks for your patch! This caught my eye:

On Tue, Jun 4, 2024 at 7:04=E2=80=AFPM Paul E. McKenney <paulmck@kernel.org=
> wrote:

> Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on ARM systems
> with ARCH < ARMv6K.

ARCH =3D=3D ARMv6.

This ARCH < ARMv6K comes from inversion of the the a bit terse
comment for ifndef CONFIG_CPU_V6, which means "out of the
post-v6 CPUs, the following applies to those > V6".

The code in the patch, IIUC make use of cmpxchg_emu_u8()
if and only if the CPU is V6.

> -#ifndef CONFIG_CPU_V6  /* min ARCH >=3D ARMv6K */
> +#ifdef CONFIG_CPU_V6   /* min ARCH < ARMv6K */

This is now a set with one member so this comment should say:

/* ARCH =3D=3D ARMv6 */

After this change.

Yours,
Linus Walleij