linux-kernel - [PATCH RFC tools/memory-model 2/5] tools/memory-model: Add litmus test for multicopy atomicity

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Date:   Mon, 16 Apr 2018 09:22:48 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Cc:     mingo@...nel.org, stern@...land.harvard.edu,
        parri.andrea@...il.com, will.deacon@....com, peterz@...radead.org,
        boqun.feng@...il.com, npiggin@...il.com, dhowells@...hat.com,
        j.alglave@....ac.uk, luc.maranget@...ia.fr, akiyks@...il.com,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH RFC tools/memory-model 2/5] tools/memory-model: Add litmus test for multicopy atomicity

This commit adds a litmus test suggested by Alan Stern that is forbidden
on multicopy atomic systems, but allowed on non-multicopy atomic systems.
Note that other-multicopy atomic systems are examples of non-multicopy
atomic systems.

Suggested-by: Alan Stern <stern@...land.harvard.edu>
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 .../litmus-tests/SB+poonceoncescoh.litmus          | 31 ++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 tools/memory-model/litmus-tests/SB+poonceoncescoh.litmus

diff --git a/tools/memory-model/litmus-tests/SB+poonceoncescoh.litmus b/tools/memory-model/litmus-tests/SB+poonceoncescoh.litmus
new file mode 100644
index 000000000000..991a2d6dec63
--- /dev/null
+++ b/tools/memory-model/litmus-tests/SB+poonceoncescoh.litmus
@@ -0,0 +1,31 @@
+C SB+poonceoncescoh
+
+(*
+ * Result: Sometimes
+ *
+ * This litmus test demonstrates that LKMM is not multicopy atomic.
+ *)
+
+{}
+
+P0(int *x, int *y)
+{
+	int r1;
+	int r2;
+
+	WRITE_ONCE(*x, 1);
+	r1 = READ_ONCE(*x);
+	r2 = READ_ONCE(*y);
+}
+
+P1(int *x, int *y)
+{
+	int r3;
+	int r4;
+
+	WRITE_ONCE(*y, 1);
+	r3 = READ_ONCE(*y);
+	r4 = READ_ONCE(*x);
+}
+
+exists (0:r2=0 /\ 1:r4=0 /\ 0:r1=1 /\ 1:r3=1)
-- 
2.5.2