linux-kernel - Re: [PATCH] locking/atomics: don't alias ___

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Message-ID: <20170628121246.qnk2csgzbgpqrmw3@linutronix.de>
Date:   Wed, 28 Jun 2017 14:12:52 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Ingo Molnar <mingo@...nel.org>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will.deacon@....com>,
        "H. Peter Anvin" <hpa@...or.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        "x86@...nel.org" <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] locking/atomics: don't alias ____ptr

On 2017-06-28 14:15:18 [+0300], Andrey Ryabinin wrote:
> The main problem here is that arch_cmpxchg64_local() calls cmpxhg_local() instead of using arch_cmpxchg_local().
> 
> So, the patch bellow should fix the problem, also this will fix double instrumentation of cmpcxchg64[_local]().
> But I haven't tested this patch yet.

tested, works. Next step?

> ---
>  arch/x86/include/asm/cmpxchg_64.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/include/asm/cmpxchg_64.h b/arch/x86/include/asm/cmpxchg_64.h
> index fafaebacca2d..7046a3cc2493 100644
> --- a/arch/x86/include/asm/cmpxchg_64.h
> +++ b/arch/x86/include/asm/cmpxchg_64.h
> @@ -9,13 +9,13 @@ static inline void set_64bit(volatile u64 *ptr, u64 val)
>  #define arch_cmpxchg64(ptr, o, n)					\
>  ({									\
>  	BUILD_BUG_ON(sizeof(*(ptr)) != 8);				\
> -	cmpxchg((ptr), (o), (n));					\
> +	arch_cmpxchg((ptr), (o), (n));					\
>  })
>  
>  #define arch_cmpxchg64_local(ptr, o, n)					\
>  ({									\
>  	BUILD_BUG_ON(sizeof(*(ptr)) != 8);				\
> -	cmpxchg_local((ptr), (o), (n));					\
> +	arch_cmpxchg_local((ptr), (o), (n));					\
>  })
>  
>  #define system_has_cmpxchg_double() boot_cpu_has(X86_FEATURE_CX16)

Sebastian