Hi Peter,
On Fri, Aug 28, 2015 at 01:36:14PM +0200, Peter Zijlstra wrote:
> On Fri, Aug 28, 2015 at 10:48:16AM +0800, Boqun Feng wrote:
> > Some architectures may have their special barriers for acquire, release
> > and fence semantics, general memory barriers(smp_mb__*_atomic()) in
> > __atomic_op_*() may be too strong, so arch_atomic_op_*() helpers are
> > introduced for architectures to provide their own version helpers to
> > build different variants based on _relaxed variants.
> >
> > Signed-off-by: Boqun Feng <boqun.f...@gmail.com>
> > ---
> > include/linux/atomic.h | 16 ++++++++++++++++
> > 1 file changed, 16 insertions(+)
> >
> > diff --git a/include/linux/atomic.h b/include/linux/atomic.h
> > index 00a5763..622255b 100644
> > --- a/include/linux/atomic.h
> > +++ b/include/linux/atomic.h
> > @@ -34,20 +34,33 @@
> > * The idea here is to build acquire/release variants by adding explicit
> > * barriers on top of the relaxed variant. In the case where the relaxed
> > * variant is already fully ordered, no additional barriers are needed.
> > + *
> > + * Besides, if an arch has a special barrier for acquire/release, it could
> > + * implement its own arch_atomic_op_* and use the same framework for
> > building
> > + * variants
> > */
> > +#ifndef arch_atomic_op_acquire
> > #define __atomic_op_acquire(op, args...) \
> > ({ \
> > typeof(op##_relaxed(args)) __ret = op##_relaxed(args); \
> > smp_mb__after_atomic(); \
> > __ret; \
> > })
> > +#else
> > +#define __atomic_op_acquire arch_atomic_op_acquire
> > +#endif
>
> Not really a fan of this, its not consistent with the existing #ifndef
> guard style.
You suggestion is that I should:
#ifndef __atomic_op_acquire
#define __atomic_op_acquire(op, args...)
({
...
})
#endif
... and define powerpc specific __atomic_op_acquire in asm/atomic.h?
Regards,
Boqun
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