linux-kernel - Re: [PATCH] asm-generic: fix compilation failure in cmpxchg

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Date:   Wed, 22 Mar 2017 22:27:12 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Mark Rutland <mark.rutland@....com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will.deacon@....com>,
        Linux-MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] asm-generic: fix compilation failure in cmpxchg_double()

On Wed, Mar 22, 2017 at 12:27 PM, Arnd Bergmann <arnd@...db.de> wrote:
> On Wed, Mar 22, 2017 at 12:10 PM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
>> Arnd reported that the new code leads to compilation failures
>> with some versions of gcc. I've filed gcc issue 72873,
>> but we need a kernel fix as well.
>>
>> Remove instrumentation from cmpxchg_double() for now.
>
> Thanks, I also checked that fixes the build error for me.

I got a new variant of the bug in
arch/x86/include/asm/cmpxchg_32.h:set_64bit() now.

In file included from /git/arm-soc/arch/x86/include/asm/cmpxchg.h:142:0,
                 from /git/arm-soc/arch/x86/include/asm/atomic.h:7,
                 from /git/arm-soc/arch/x86/include/asm/msr.h:66,
                 from /git/arm-soc/arch/x86/include/asm/processor.h:20,
                 from /git/arm-soc/arch/x86/include/asm/cpufeature.h:4,
                 from /git/arm-soc/arch/x86/include/asm/thread_info.h:52,
                 from /git/arm-soc/include/linux/thread_info.h:25,
                 from /git/arm-soc/arch/x86/include/asm/preempt.h:6,
                 from /git/arm-soc/include/linux/preempt.h:80,
                 from /git/arm-soc/include/linux/spinlock.h:50,
                 from /git/arm-soc/include/linux/mmzone.h:7,
                 from /git/arm-soc/include/linux/gfp.h:5,
                 from /git/arm-soc/include/linux/mm.h:9,
                 from /git/arm-soc/mm/khugepaged.c:3:
/git/arm-soc/mm/khugepaged.c: In function 'khugepaged':
/git/arm-soc/arch/x86/include/asm/cmpxchg_32.h:29:2: error: 'asm'
operand has impossible constraints
  asm volatile("\n1:\t"

Defconfig is at http://pastebin.com/raw/Pthhv5iU

       Arnd