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SubjectRe: [RFC] arch: Introduce new TSO memory barrier smp_tmb()
On Tue, Nov 05, 2013 at 02:05:48PM +0000, Will Deacon wrote:
> On Mon, Nov 04, 2013 at 08:53:44PM +0000, Paul E. McKenney wrote:
> > On Mon, Nov 04, 2013 at 08:11:27PM +0100, Peter Zijlstra wrote:
> > Some comments below. I believe that opcodes need to be fixed for IA64.
> > I am unsure of the ifdefs and opcodes for arm64, but the ARM folks should
> > be able to tell us.

[ . . . ]

> > > +} while (0)
> > > +
> > > +#define smp_load_acquire(p) \
> > > +do { \
> > > + typeof(p) ___p1; \
> > > + asm volatile ("ldar %w0, [%1]" \
> > > + : "=r" (___p1) : "r" (&p) : "memory"); \
> > > + return ___p1; \
>
> Similar comments here wrt Q constraint.
>
> Random other question: have you considered how these accessors should behave
> when presented with __iomem pointers?

Should we have something to make sparse yell if not __kernel or some such?

Thanx, Paul



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