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

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Message-ID: <CAJF2gTRrDMhL0YyZ=BYJ17sRp0oU610N+Wn+WtAgBASC_TPrOg@mail.gmail.com>
Date:   Sun, 13 Mar 2022 09:10:42 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Max Filippov <jcmvbkbc@...il.com>
Cc:     Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-csky@...r.kernel.org,
        linux-riscv <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

On Sun, Mar 13, 2022 at 7:50 AM Max Filippov <jcmvbkbc@...il.com> wrote:
>
> 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?
No, theoretical risk.

>
> --
> Thanks.
> -- Max



-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/