linux-kernel - Re: [PATCH v3 6/7] asm-generic: percpu: Add assembly guard

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Message-Id: <a10395f7-6666-4bdb-9aa0-bdd873029cc9@app.fastmail.com>
Date: Mon, 15 Sep 2025 09:40:35 +0200
From: "Arnd Bergmann" <arnd@...db.de>
To: "Tiwei Bie" <tiwei.bie@...ux.dev>, "Richard Weinberger" <richard@....at>,
 "Anton Ivanov" <anton.ivanov@...bridgegreys.com>,
 "Johannes Berg" <johannes@...solutions.net>
Cc: linux-um@...ts.infradead.org, linux-kernel@...r.kernel.org,
 benjamin@...solutions.net, "Tiwei Bie" <tiwei.btw@...group.com>,
 Linux-Arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH v3 6/7] asm-generic: percpu: Add assembly guard

On Sun, Sep 14, 2025, at 17:56, Tiwei Bie wrote:
> From: Tiwei Bie <tiwei.btw@...group.com>
>
> Currently, asm/percpu.h is directly or indirectly included by
> some assembly files on x86. Some of them (e.g., checksum_32.S)
> are also used on um. But x86 and um provide different versions
> of asm/percpu.h -- um uses asm-generic/percpu.h directly.
>
> When SMP is enabled, asm-generic/percpu.h will introduce C code
> that cannot be assembled. Since asm-generic/percpu.h currently
> is not designed for use in assembly, and these assembly files
> do not actually need asm/percpu.h on um, let's add the assembly
> guard in asm-generic/percpu.h to fix this issue.
>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: linux-arch@...r.kernel.org
> Signed-off-by: Tiwei Bie <tiwei.btw@...group.com>

Have you tried if you can remove the percpu.h dependency from
the files that currently include it? In many cases it should
be enough to use percpu-defs.h.

If that doesn't work, I have no objections to this patch either.

Acked-by: Arnd Bergmann <arnd@...db.de>