Re: [PATCH] bug: Fix CONFIG_BUG=n BUG_ON()

Arnd Bergmann
2014-06-19T17:00:25Z

On Thursday 19 June 2014 15:28:19 Bart Van Assche wrote:
> Patch "bug: Make BUG() always stop the machine" changed the
> behavior of BUG() with CONFIG_BUG=n from a no-op into an infinite
> loop. Modify the definition of BUG_ON() accordingly such that the
> behavior of BUG_ON(1) is identical to that of BUG().
>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Josh Triplett <josh@joshtriplett.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> ---
> include/asm-generic/bug.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
> index 630dd23..f3241cd 100644
> --- a/include/asm-generic/bug.h
> +++ b/include/asm-generic/bug.h
> @@ -142,7 +142,7 @@ extern void warn_slowpath_null(const char *file, const int line);
> #endif
>
> #ifndef HAVE_ARCH_BUG_ON
> -#define BUG_ON(condition) do { if (condition) ; } while (0)
> +#define BUG_ON(condition) do { } while (unlikely(condition))
> #endif
>
> #ifndef HAVE_ARCH_WARN_ON
>

How about making it

do { if (condition) BUG(); } while (0)

That way it can be optimized for architectures that have their own
BUG but not BUG_ON.

Arnd