Re: f68f031d ("Documentation: atomic_t.txt: Explain ordering provided by smp_mb__{before,after}_atomic()")

[Peter Zijlstra]

On Fri, May 03, 2019 at 12:19:21PM -0400, Alan Stern wrote:
> On Fri, 3 May 2019, Peter Zijlstra wrote:
> 
> > On Fri, May 03, 2019 at 07:53:26AM -0700, Paul E. McKenney wrote:
> > > Hello, Alan,
> > > 
> > > Just following up on the -rcu commit below.  I believe that it needs
> > > some adjustment given Peter Zijlstra's addition of "memory" to the x86
> > > non-value-returning atomics, but thought I should double-check.
> > 
> > Right; I should get back to that thread...
> 
> The real question, still outstanding, is whether smp_mb__before_atomic 
> orders anything following the RMW instruction (and similarly, whether 
> smp_mb__after_atomic orders anything preceding the RMW instruction).

Yes -- that was very much the intent, and only (some) x86 ops and (some)
MIPS config have issues with that.