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Re: [PATCH] asm-generic: fix compilation failure in cmpxchg_double()

From Dmitry Vyukov <dvyukov@google.com>
Newsgroups linux.kernel
Subject Re: [PATCH] asm-generic: fix compilation failure in cmpxchg_double()
Date 2017-03-23 10:00 +0100
Message-ID <to6L8-8hs-11@gated-at.bofh.it> (permalink)
References <tnMt3-1zh-15@gated-at.bofh.it> <tnMCK-1Dh-15@gated-at.bofh.it> <tnVZn-rc-1@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Wed, Mar 22, 2017 at 10:27 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> On Wed, Mar 22, 2017 at 12:27 PM, Arnd Bergmann <arnd@arndb.de> wrote:
>> On Wed, Mar 22, 2017 at 12:10 PM, Dmitry Vyukov <dvyukov@google.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


I can't reproduce it with gcc 4.8.4, 7.0.0, 7.0.1.

Are you sure it's related to my recent change? I did not touch set_64bit.

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Thread

[PATCH] asm-generic: fix compilation failure in cmpxchg_double() Dmitry Vyukov <dvyukov@google.com> - 2017-03-22 12:20 +0100
  Re: [PATCH] asm-generic: fix compilation failure in cmpxchg_double() Arnd Bergmann <arnd@arndb.de> - 2017-03-22 12:30 +0100
    Re: [PATCH] asm-generic: fix compilation failure in cmpxchg_double() Arnd Bergmann <arnd@arndb.de> - 2017-03-22 22:30 +0100
      Re: [PATCH] asm-generic: fix compilation failure in cmpxchg_double() Dmitry Vyukov <dvyukov@google.com> - 2017-03-23 10:00 +0100
        Re: [PATCH] asm-generic: fix compilation failure in cmpxchg_double() Arnd Bergmann <arnd@arndb.de> - 2017-03-23 14:40 +0100

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