Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures

[Chris Snook <csnook@redhat.com>]

Christoph Lameter wrote:
> On Fri, 17 Aug 2007, Paul E. McKenney wrote:
>
> > On Sat, Aug 18, 2007 at 08:09:13AM +0800, Herbert Xu wrote:
> > > On Fri, Aug 17, 2007 at 04:59:12PM -0700, Paul E. McKenney wrote:
> > > > gcc bugzilla bug #33102, for whatever that ends up being worth.  ;-)
> > > I had totally forgotten that I'd already filed that bug more
> > > than six years ago until they just closed yours as a duplicate
> > > of mine :)
> > >
> > > Good luck in getting it fixed!
> > Well, just got done re-opening it for the third time.  And a local
> > gcc community member advised me not to give up too easily.  But I
> > must admit that I am impressed with the speed that it was identified
> > as duplicate.
> >
> > Should be entertaining!  ;-)
>
> Right. ROTFL... volatile actually breaks atomic_t instead of making it 
> safe. x++ becomes a register load, increment and a register store. Without 
> volatile we can increment the memory directly. It seems that volatile 
> requires that the variable is loaded into a register first and then 
> operated upon. Understandable when you think about volatile being used to 
> access memory mapped I/O registers where a RMW operation could be 
> problematic.

So, if we want consistent behavior, we're pretty much screwed unless we use 
inline assembler everywhere?

	-- Chris
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