Re: [RFC 3/3] tools/memory-model: Add litmus test for RMW + smp_mb__after_atomic()

From: Boqun Feng <boqun.feng@gmail.com>
To: Andrea Parri <parri.andrea@gmail.com>
Cc: linux-kernel@vger.kernel.org,
	Alan Stern <stern@rowland.harvard.edu>,
	Will Deacon <will@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Nicholas Piggin <npiggin@gmail.com>,
	David Howells <dhowells@redhat.com>,
	Jade Alglave <j.alglave@ucl.ac.uk>,
	Luc Maranget <luc.maranget@inria.fr>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Akira Yokosawa <akiyks@gmail.com>,
	Daniel Lustig <dlustig@nvidia.com>,
	Jonathan Corbet <corbet@lwn.net>,
	linux-arch@vger.kernel.org, linux-doc@vger.kernel.org
Subject: Re: [RFC 3/3] tools/memory-model: Add litmus test for RMW + smp_mb__after_atomic()
Date: Fri, 14 Feb 2020 16:20:42 +0800	[thread overview]
Message-ID: <20200214082042.GB20408@debian-boqun.qqnc3lrjykvubdpftowmye0fmh.lx.internal.cloudapp.net> (raw)
In-Reply-To: <20200214081826.GB17708@andrea>

On Fri, Feb 14, 2020 at 09:18:26AM +0100, Andrea Parri wrote:
> > > @@ -0,0 +1,29 @@
> > > +C Atomic-RMW+mb__after_atomic-is-strong-acquire
> > > +
> > > +(*
> > > + * Result: Never
> > > + *
> > > + * Test of an atomic RMW followed by a smp_mb__after_atomic() is
> > > + * "strong-acquire": both the read and write part of the RMW is ordered before
> > > + * the subsequential memory accesses.
> > > + *)
> > > +
> > > +{
> > > +}
> > > +
> > > +P0(int *x, atomic_t *y)
> > > +{
> > > +	r0 = READ_ONCE(*x);
> > > +	smp_rmb();
> > > +	r1 = atomic_read(y);
> 
> IIRC, klitmus7 needs a declaration for these local variables, say
> (trying to keep herd7 happy):
> 

Got it. I will add the declaration in the next version. It's just that
herd doesn't need those so I haven't put them in this version ;-)

Thanks!

Regards,
Boqun

> P0(int *x, atomic_t *y)
> {
> 	int r0;
> 	int r1;
> 
> 	r0 = READ_ONCE(*x);
> 	smp_rmb();
> 	r1 = atomic_read(y);
> }
> 
> Thanks,
>   Andrea