Re: [RFC v4 1/8] Port WARN_ON_ONCE() from Linux

[Julien Grall <julien.grall@linaro.org>]

Hi Sameer,

On 19/12/17 03:16, Sameer Goel wrote:
> Port WARN_ON_ONCE macro from Linux.
> 
> Signed-off-by: Sameer Goel <sameer.goel@linaro.org>
> ---
>   xen/include/xen/lib.h | 11 +++++++++++
>   1 file changed, 11 insertions(+)
> 
> diff --git a/xen/include/xen/lib.h b/xen/include/xen/lib.h
> index ed00ae1379..83206c0848 100644
> --- a/xen/include/xen/lib.h
> +++ b/xen/include/xen/lib.h
> @@ -11,6 +11,17 @@
>   #define BUG_ON(p)  do { if (unlikely(p)) BUG();  } while (0)
>   #define WARN_ON(p) do { if (unlikely(p)) WARN(); } while (0)
>   
> +#define WARN_ON_ONCE(p)	({                          \
> +    static bool __section(".data.unlikely") __warned; \
> +    int __ret_warn_once = !!(p);                    \
> +                                                    \
> +    if (unlikely(__ret_warn_once && !__warned)) {   \

I realise BUG_ON/WARN_ON above is not using Xen coding style. However, 
can you make this code follow Xen coding style?

FWIW with the coding style change:

Acked-by: Julien Grall <julien.grall@linaro.org>

This will also require an ack from "THE REST" maintainers as this is 
common code.

Cheers,

> +        __warned = true;                            \
> +        WARN_ON(1);                                 \
> +    }                                               \
> +    unlikely(__ret_warn_once);                      \
> +})
> +
>   #if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
>   /* Force a compilation error if condition is true */
>   #define BUILD_BUG_ON(cond) ({ _Static_assert(!(cond), "!(" #cond ")"); })
> 

-- 
Julien Grall

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