Thanks for the feedback,

On Mon, 2019-09-23 at 13:39 -0700, John Hubbard wrote:
> Please remember to include linux-mm if there is a v2.

Sure, I will include on v3.

> Nit: seems like it would be nicer to just put it all in one place, and use
> positive logic, and also I think people normally don't compress the empty
> functions quite that much. So like this:

I did this by following the default on the rest of this file.
As you can see, all other features use the standard of 
#ifndef SOMETHING
dummy/generic functions
#endif

Declaring the functions become responsibility of the arch.

> #ifdef __HAVE_ARCH_LOCKLESS_PGTBL_WALK_COUNTER
> void start_lockless_pgtbl_walk(struct mm_struct *mm); 
> void end_lockless_pgtbl_walk(struct mm_struct *mm); 
> int running_lockless_pgtbl_walk(struct mm_struct *mm); 
> 
> #else
> static inline void start_lockless_pgtbl_walk(struct mm_struct *mm)
> {
> }
> static inline void end_lockless_pgtbl_walk(struct mm_struct *mm)
> {
> }
> static inline int running_lockless_pgtbl_walk(struct mm_struct *mm)
> {
>         return 0;
> }
> #endif
> 
> thanks,