linux-kernel - Re: [PATCH 1/2] futex: mark futex_detect

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Message-ID: <CAJF2gTQUPXzRL4P2ghoSt6t+pyAJ7A9dqdD6VWYNdOmJjd2HQg@mail.gmail.com>
Date:   Sun, 20 Dec 2020 23:44:01 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Marco Elver <elver@...gle.com>, Arnd Bergmann <arnd@...db.de>,
        Russell King <linux@...linux.org.uk>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Darren Hart <dvhart@...radead.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Elena Reshetova <elena.reshetova@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-csky@...r.kernel.org,
        sparclinux <sparclinux@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 1/2] futex: mark futex_detect_cmpxchg() as 'noinline'

Hi Arnd,

On Tue, Dec 15, 2020 at 7:26 PM Arnd Bergmann <arnd@...nel.org> wrote:
>
> On Tue, Dec 15, 2020 at 7:09 AM Guo Ren <guoren@...nel.org> wrote:
> > On Mon, Dec 14, 2020 at 9:15 PM Arnd Bergmann <arnd@...nel.org> wrote:
> > > I had a look at what other architectures always implement
> > > futex_atomic_cmpxchg_inatomic() or can use the asm-generic non-SMP version,
> > > and I found that it's pretty much all of them, the odd ones being just sparc32
> > > and csky, which use asm-generic/futex.h but do have an SMP option,
> > > as well as xtensa
> > >
> > > I would guess that for csky, this is a mistake, as the architecture is fairly
> > > new and should be able to implement it. Not sure about sparc32.
> >
> > The c610, c807, c810 don't support SMP, so futex_cmpxchg_enabled = 1
> > with asm-generic's implementation.
> > For c860, there is no HAVE_FUTEX_CMPXCHG and cmpxchg_inatomic/inuser
> > implementation, so futex_cmpxchg_enabled = 0.
> >
> > Thx for point it out, we'll implement cmpxchg_inatomic/inuser for C860
> > and still use asm-generic for non-smp CPUs.
>
> Sounds good to me.
Done: https://lore.kernel.org/linux-csky/1608478763-60148-3-git-send-email-guoren@kernel.org/T/#u

-- 
Best Regards
 Guo Ren

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