linux-kernel - Re: [PATCH] futex: Set USER_DS for the futex_detect

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Message-ID: <alpine.DEB.2.21.1809282224090.1432@nanos.tec.linutronix.de>
Date:   Fri, 28 Sep 2018 22:26:48 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Max Filippov <jcmvbkbc@...il.com>
cc:     Andy Lutomirski <luto@...capital.net>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Andrew Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Darren Hart <dvhart@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        fthain@...egraphics.com.au
Subject: Re: [PATCH] futex: Set USER_DS for the futex_detect_cmpxchg() test

On Fri, 28 Sep 2018, Max Filippov wrote:

> On Fri, Sep 28, 2018 at 11:02 AM, Andy Lutomirski <luto@...capital.net> wrote:
> > There may be a much nicer solution.  Unless I missed something, only
> > mips and xtensa even have the possibility of cmpxchg being missing.
> > We could just make those arches supply a futex-detecting helper.
> 
> In case of xtensa availability of cmpxchg is known at build time.

That makes it even simpler. Could you provide a patch which selects
CONFIG_HAVE_FUTEX_CMPXCHG for the right set of CPUs please?

Thanks,

	tglx