linux-kernel - Re: [RFC PATCH] arch: patch_text: Fixup last cpu should be master

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Date:   Sat, 12 Mar 2022 15:50:35 -0800
From:   Max Filippov <jcmvbkbc@...il.com>
To:     Guo Ren <guoren@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>, linux-csky@...r.kernel.org,
        linux-riscv@...ts.infradead.org,
        "open list:TENSILICA XTENSA PORT (xtensa)" 
        <linux-xtensa@...ux-xtensa.org>,
        Guo Ren <guoren@...ux.alibaba.com>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Chris Zankel <chris@...kel.net>, Arnd Bergmann <arnd@...db.de>
Subject: Re: [RFC PATCH] arch: patch_text: Fixup last cpu should be master

Hi Guo Ren,

On Sat, Mar 12, 2022 at 7:56 AM <guoren@...nel.org> wrote:
>
> From: Guo Ren <guoren@...ux.alibaba.com>
>
> These patch_text implementations are using stop_machine_cpuslocked
> infrastructure with atomic cpu_count. The origin idea is that when

The original

> the master CPU patch_text, others should wait for it. But current
> implementation is using the first CPU as master, which couldn't
> guarantee continue CPUs are waiting. This patch changes the last

guarantee that remaining CPUs are waiting.

> CPU as the master to solve the potaintial risk.

potential

>
> Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@...nel.org>
> Cc: Will Deacon <will@...nel.org>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Palmer Dabbelt <palmer@...belt.com>
> Cc: Peter Zijlstra <peterz@...radead.org
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> Cc: Chris Zankel <chris@...kel.net>
> Cc: Max Filippov <jcmvbkbc@...il.com>
> Cc: Arnd Bergmann <arnd@...db.de>
> ---
>  arch/arm64/kernel/patching.c      | 4 ++--
>  arch/csky/kernel/probes/kprobes.c | 2 +-
>  arch/riscv/kernel/patch.c         | 2 +-
>  arch/xtensa/kernel/jump_label.c   | 2 +-
>  4 files changed, 5 insertions(+), 5 deletions(-)

Reviewed-by: Max Filippov <jcmvbkbc@...il.com>

I'm curious, is there a specific issue that prompted this patch?

-- 
Thanks.
-- Max