linux-kernel - [PATCH v4 1/4] tools/memory-model: Add an exception for limitations on

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Message-Id: <20200326024022.7566-2-boqun.feng@gmail.com>
Date:   Thu, 26 Mar 2020 10:40:19 +0800
From:   Boqun Feng <boqun.feng@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Alan Stern <stern@...land.harvard.edu>,
        Andrea Parri <parri.andrea@...il.com>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Boqun Feng <boqun.feng@...il.com>,
        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>,
        Joel Fernandes <joel@...lfernandes.org>,
        linux-arch@...r.kernel.org, linux-doc@...r.kernel.org
Subject: [PATCH v4 1/4] tools/memory-model: Add an exception for limitations on _unless() family

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>
Acked-by: Andrea Parri <parri.andrea@...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..b9c562e92981 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
+		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
-- 
2.25.1