tools/memory-model: Add reference for 'Simplifying ARM concurrency'

The paper discusses the revised ARMv8 memory model; such revision
had an important impact on the design of the LKMM.
Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Akira Yokosawa <akiyks@gmail.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luc Maranget <luc.maranget@inria.fr>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/1526340837-12222-19-git-send-email-paulmck@linux.vnet.ibm.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

tools/memory-model/Documentation/references.txt

@@ -63,6 +63,12 @@ o	Shaked Flur, Susmit Sarkar, Christopher Pulte, Kyndylan Nienhuis,
 	Principles of Programming Languages (POPL 2017). ACM, New York,
 	NY, USA, 429–442.
 
+o	Christopher Pulte, Shaked Flur, Will Deacon, Jon French,
+	Susmit Sarkar, and Peter Sewell. 2018. "Simplifying ARM concurrency:
+	multicopy-atomic axiomatic and operational models for ARMv8". In
+	Proceedings of the ACM on Programming Languages, Volume 2, Issue
+	POPL, Article No. 19. ACM, New York, NY, USA.
+
 
 Linux-kernel memory model
 =========================