Merge branch 'WIP.x86/asm' into x86/urgent, because the topic is ready

Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/tools/memory-model/litmus-tests/LB+ctrlonceonce+mbonceonce.litmus b/tools/memory-model/litmus-tests/LB+ctrlonceonce+mbonceonce.litmus
new file mode 100644
index 000000000000..de6708229dd1
--- /dev/null
+++ b/tools/memory-model/litmus-tests/LB+ctrlonceonce+mbonceonce.litmus
@@ -0,0 +1,34 @@
+C LB+ctrlonceonce+mbonceonce
+
+(*
+ * Result: Never
+ *
+ * This litmus test demonstrates that lightweight ordering suffices for
+ * the load-buffering pattern, in other words, preventing all processes
+ * reading from the preceding process's write.  In this example, the
+ * combination of a control dependency and a full memory barrier are enough
+ * to do the trick.  (But the full memory barrier could be replaced with
+ * another control dependency and order would still be maintained.)
+ *)
+
+{}
+
+P0(int *x, int *y)
+{
+	int r0;
+
+	r0 = READ_ONCE(*x);
+	if (r0)
+		WRITE_ONCE(*y, 1);
+}
+
+P1(int *x, int *y)
+{
+	int r0;
+
+	r0 = READ_ONCE(*y);
+	smp_mb();
+	WRITE_ONCE(*x, 1);
+}
+
+exists (0:r0=1 /\ 1:r0=1)