Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Tue, 10 Jul 2018 17:24:04 +0200
From:   Andrea Parri <andrea.parri@amarulasolutions.com>
To:     Alan Stern <stern@rowland.harvard.edu>
Cc:     "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        LKMM Maintainers -- Akira Yokosawa <akiyks@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        Daniel Lustig <dlustig@nvidia.com>,
        David Howells <dhowells@redhat.com>,
        Jade Alglave <j.alglave@ucl.ac.uk>,
        Luc Maranget <luc.maranget@inria.fr>,
        Nicholas Piggin <npiggin@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Will Deacon <will.deacon@arm.com>,
        Kernel development list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] tools/memory-model: Add extra ordering for locks and
 remove it for ordinary release/acquire
Message-ID: <20180710152404.GA11437@andrea>
References: <20180710093821.GA5414@andrea>
 <Pine.LNX.4.44L0.1807101039310.1449-100000@iolanthe.rowland.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <Pine.LNX.4.44L0.1807101039310.1449-100000@iolanthe.rowland.org>
User-Agent: Mutt/1.5.24 (2015-08-30)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

> >   ACQUIRE operations include LOCK operations and both smp_load_acquire()
> >   and smp_cond_acquire() operations.  [BTW, the latter was replaced by
> >   smp_cond_load_acquire() in 1f03e8d2919270 ...]
> > 
> >   RELEASE operations include UNLOCK operations and smp_store_release()
> >   operations. [...]
> > 
> >   [...] after an ACQUIRE on a given variable, all memory accesses
> >   preceding any prior RELEASE on that same variable are guaranteed
> >   to be visible.
> 
> As far as I can see, these statements remain valid.

Interesting; ;-)  What does these statement tells you ;-)  when applied
to a: and b: below?

  a: WRITE_ONCE(x, 1); // "preceding any prior RELEASE..."
  smp_store_release(&s, 1);
  smp_load_acquire(&s);
  b: WRITE_ONCE(y, 1); // "after an ACQUIRE..."

  Andrea