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Date:   Thu, 27 Feb 2020 13:16:37 -0500 (EST)
From:   Alan Stern <stern@rowland.harvard.edu>
To:     Luc Maranget <luc.maranget@inria.fr>
cc:     Boqun Feng <boqun.feng@gmail.com>, <linux-kernel@vger.kernel.org>,
        Andrea Parri <parri.andrea@gmail.com>,
        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>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Akira Yokosawa <akiyks@gmail.com>,
        Daniel Lustig <dlustig@nvidia.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Rob Herring <robh@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        <linux-arch@vger.kernel.org>, <linux-doc@vger.kernel.org>
Subject: Re: [PATCH v3 1/5] tools/memory-model: Add an exception for limitations
 on _unless() family
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On Thu, 27 Feb 2020, Luc Maranget wrote:

> > On Thu, 27 Feb 2020, Boqun Feng wrote:
> > 
> > > According to Luc, atomic_add_unless() is directly provided by herd7,
> > > therefore it can be used in litmus tests. So change the limitation
> > > section in README to unlimit the use of atomic_add_unless().
> > 
> > Is this really true?  Why does herd treat atomic_add_unless() different
> > from all the other atomic RMS ops?  All the other ones we support do
> > have entries in linux-kernel.def.
> 
> I think this to be true :)
> 
> As far as I remember atomic_add_unless is quite different fron other atomic
> RMW ops and called for a specific all-OCaml implementation, without an
> entry in linux-kernel.def. As to  atomic_long_add_unless, I was not aware
> of its existence.

Can you explain what is so different about atomic_add_unless?

Alan