[PATCH for -tip 1/2] kernel.h: add MAYBE_BUILD_BUG_ON_NOT_POWER_OF_2

[Andi Kleen]

> +/* Force a compilation error if condition is constant and not a power of 2 */
> +#define MAYBE_BUILD_BUG_ON_NOT_POWER_OF_2(n)		\
> +	MAYBE_BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0))

Looks super-ugly. IMHO just writing MAYBE_BUILD_BUG_ON(!n || n & (n - 1)) directly
would be clear enough. If you really think that's unclear define a generic
is_power_of_two() macro.

-Andi