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

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, Dec 18, 2017 at 08:16:56PM -0700, Sameer Goel wrote:
> Port WARN_ON_ONCE macro from Linux.
> 
> Signed-off-by: Sameer Goel <sameer.goel@xxxxxxxxxx>
> ---
>  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; \

You introduced a new section without corresponding changes to
{arm,x86}/xen.lds.S

> +    int __ret_warn_once = !!(p);                    \
> +                                                    \
> +    if (unlikely(__ret_warn_once && !__warned)) {   \
> +        __warned = true;                            \
> +        WARN_ON(1);                                 \

This isn't really a direct port from Linux. At this point I wonder why
you didn't use WARN() directly?

Wei.

> +    }                                               \
> +    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 ")"); })
> -- 
> 2.14.1
> 

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