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Message-ID: <20200227175240.GA12046@andrea>
Date: Thu, 27 Feb 2020 18:52:40 +0100
From: Andrea Parri <parri.andrea@...il.com>
To: Boqun Feng <boqun.feng@...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>,
Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
"David S. Miller" <davem@...emloft.net>,
Rob Herring <robh@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jonathan Cameron <Jonathan.Cameron@...wei.com>,
linux-arch@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v3 1/5] tools/memory-model: Add an exception for
limitations on _unless() family
On Thu, Feb 27, 2020 at 08:40:45AM +0800, 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().
>
> Cc: Luc Maranget <luc.maranget@...ia.fr>
> Signed-off-by: Boqun Feng <boqun.feng@...il.com>
> ---
> tools/memory-model/README | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/tools/memory-model/README b/tools/memory-model/README
> index fc07b52f2028..409211b1c544 100644
> --- a/tools/memory-model/README
> +++ b/tools/memory-model/README
> @@ -207,11 +207,15 @@ The Linux-kernel memory model (LKMM) has the following limitations:
> case as a store release.
>
> b. The "unless" RMW operations are not currently modeled:
> - atomic_long_add_unless(), atomic_add_unless(),
> - atomic_inc_unless_negative(), and
> - atomic_dec_unless_positive(). These can be emulated
> + atomic_long_add_unless(), atomic_inc_unless_negative(),
> + and atomic_dec_unless_positive(). These can be emulated
> in litmus tests, for example, by using atomic_cmpxchg().
>
> + One exception of this limitation is atomic_add_unless(),
> + which is provided directly by herd7 (so no corresponding
> + definition in linux-kernel.def). atomic_add_unless() is
Nit: Two spaces after period?
Andrea
> + modeled by herd7 therefore it can be used in litmus tests.
> +
> c. The call_rcu() function is not modeled. It can be
> emulated in litmus tests by adding another process that
> invokes synchronize_rcu() and the body of the callback
> --
> 2.25.0
>
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