linux-kernel - Re: [RFC 3/3] tools/memory-model: Add litmus test for RMW + smp_mb__after

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

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