Re: [Xen-devel] [PATCH 1/7] Port WARN_ON_ONCE() from Linux

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Feb 08, 2018 at 08:10:49PM -0700, Sameer Goel wrote:
> diff --git a/xen/include/xen/lib.h b/xen/include/xen/lib.h
> index 1d9771340c..697212a061 100644
> --- a/xen/include/xen/lib.h
> +++ b/xen/include/xen/lib.h
> @@ -11,6 +11,19 @@
>  #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);                    \
       ^ bool

> +                                                    \
> +    if ( unlikely(__ret_warn_once && !__warned) )     \
> +    {                                               \
> +        __warned = true;                            \
> +        WARN();                                     \
> +    }                                               \
> +    unlikely(__ret_warn_once);                      \

Does this macro really need to return something? It seems weird to me
to allow usages like: if ( WARN_ON_ONCE...

Nit: could you please align the '\'?

Thanks, Roger.

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