Re: [PATCH 13/13] rcutorture: formal: prepare for ACCESS_ONCE() removal

[Paul E. McKenney]

On Tue, Oct 10, 2017 at 10:54:14AM +0100, Mark Rutland wrote:
> On Mon, Oct 09, 2017 at 12:51:12PM -0700, Paul E. McKenney wrote:
> > On Mon, Oct 09, 2017 at 07:28:50PM +0100, Mark Rutland wrote:
> > > diff --git a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/barriers.h b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/barriers.h
> > > index 6687acc..ee4e4f8 100644
> > > --- a/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/barriers.h
> > > +++ b/tools/testing/selftests/rcutorture/formal/srcu-cbmc/src/barriers.h
> > > @@ -34,8 +34,9 @@
> > >  #define rs_smp_mb() do {} while (0)
> > >  #endif
> > > 
> > > -#define ACCESS_ONCE(x) (*(volatile typeof(x) *) &(x))
> > > -#define READ_ONCE(x) ACCESS_ONCE(x)
> > > -#define WRITE_ONCE(x, val) (ACCESS_ONCE(x) = (val))
> > > +#define __ACCESS_ONCE(x) (*(volatile typeof(x) *) &(x))
> > > +#define ACCESS_ONCE(x) __ACCESS_ONCE(x)
> > > +#define READ_ONCE(x) __ACCESS_ONCE(x)
> > > +#define WRITE_ONCE(x, val) (__ACCESS_ONCE(x) = (val))
> > 
> > How about something like the following?
> > 
> > #define READ_ONCE(x) (*(volatile typeof(x) *) &(x))
> > #define WRITE_ONCE(x) ((*(volatile typeof(x) *) &(x)) = (val))
> 
> Sure; folded in and pushed out. :)

Thank you!

> I've assumed that the ACCESS_ONCE() definition needs to be kept until
> that's ripped out treewide. Please shout if that's not the case!

You have it right.  This case is an exception because this code is
used only by RCU, which has long since had ACCESS_ONCE() ripped out.

							Thanx, Paul