Re: [PATCH 14/15] futex: convert futex_pi_state.refcount to refcount_t

[Peter Zijlstra]

On Fri, Sep 01, 2017 at 05:03:55PM +0000, Reshetova, Elena wrote:
> > On Fri, Sep 01, 2017 at 01:24:16PM +0000, Reshetova, Elena wrote:
> > >
> > > > On Fri, Sep 01, 2017 at 11:05:33AM +0000, Reshetova, Elena wrote:
> > > > > Actually on the second thought: does the above memory ordering differences
> > > > > really apply when  we have ARCH_HAS_REFCOUNT? To me it looks like the way
> > > > > how it is currently implemented for x86 is the same way as it is for atomic
> > cases.
> > > >
> > > > Never look to x86 for memory ordering, its boring.
> > > >
> > > > And yes, for the ARM implementation it can certainly make a difference.
> > >
> > > So, yes, what I am trying to say is that it can really depend if you have
> > ARCH_HAS_REFCOUNT
> > > enabled or not and then also based on architecture. Thus I believe is also true for
> > atomic: there
> > > might be differences when you use arch. dependent version of function or not.
> > 
> > So the generic one in lib/refcount.c is already weaker on ARM, they
> > don't need to do a ARCH specific 'fast' implementation for the
> > difference to show up.
> 
> But can they make "fast" implementation on ARM that would give stronger memory guarantees?

Whatever for?