On Wed, Oct 11, 2017 at 05:07:05PM +0100, David Howells wrote:
> Paul E. McKenney <paul...@linux.vnet.ibm.com> wrote:
>
> > It does not. In most cases, the barriered version would be
> > smp_store_release().
>
> Ummm... Is that good enough? Is:
>
> WRITE_ONCE(x, 1);
> WRITE_ONCE(x, 2);
>
> equivalent to:
>
> smp_store_release(x, 1);
> smp_store_release(x, 2);
>
> if CONFIG_SMP=n?
Almost; it ends up being:
barrier();
WRITE_ONCE(x, 1);
barrier();
WRITE_ONCE(x, 2);
> (Consider what happens if an interrupt messes with x).
>
> If it is good enough, should we be using smp_load_acquire() rather than
> READ_ONCE()?
No, smp_load_acquire() is strictly stronger (and far more expensive on
!Alpha).
Dependent loads do not require barriers (except Alpha, and we want to
kill that special case).
