linux-kernel - Re: [PATCH v2 2/2] io: prevent compiler reordering on the default readX() implementation

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Date:   Wed, 4 Apr 2018 17:55:37 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Sinan Kaya <okaya@...eaurora.org>
Cc:     Palmer Dabbelt <palmer@...ive.com>,
        Mark Rutland <mark.rutland@....com>,
        Timur Tabi <timur@...eaurora.org>, sulrich@...eaurora.org,
        linux-arm-msm@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] io: prevent compiler reordering on the default
 readX() implementation

On Wed, Apr 4, 2018 at 5:52 PM, Sinan Kaya <okaya@...eaurora.org> wrote:
> On 4/3/2018 6:29 PM, Palmer Dabbelt wrote:
>>
>
> Are we looking for something like this?

Yes, exactly, plus the same for write and in/out of course.

> diff --git a/inc
>  #ifndef readb
>  #define readb readb
> -static inline u8 readb(const volatile void __iomem *addr)
> -{
> -       return __raw_readb(addr);
> -}
> +#define readb(c)                               \
> +       ({ u8  __v;                             \
> +        __io_br();                             \
> +        __v = __raw_readb(c);                  \
> +        __io_ar();                             \
> +        __v; })
>  #endif

I would prefer leaving these as inline functions, but that's only
a cosmetic difference.

       Arnd