--- /dev/null	2018-12-03 11:58:50.256341286 +0100
+++ new/test/hotspot/jtreg/gc/shenandoah/TestRefprocSanity.java	2018-12-03 17:49:17.621620610 +0100
@@ -0,0 +1,100 @@
+/*
+ * Copyright (c) 2018, Red Hat, Inc. All rights reserved.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+/*
+ * @test TestRefprocSanity
+ * @summary Test that null references/referents work fine
+ * @key gc
+ * @requires vm.gc.Shenandoah
+ *
+ * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -Xms1g                                                             TestRefprocSanity
+ * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -Xms1g -XX:+ShenandoahVerify                                       TestRefprocSanity
+ * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -Xms1g                       -XX:ShenandoahGCHeuristics=aggressive TestRefprocSanity
+ * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -Xms1g -XX:+ShenandoahVerify -XX:ShenandoahGCHeuristics=traversal  TestRefprocSanity
+ * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -Xms1g                       -XX:ShenandoahGCHeuristics=traversal  TestRefprocSanity
+ */
+
+import java.lang.ref.*;
+
+public class TestRefprocSanity {
+
+    static final long TARGET_MB = Long.getLong("target", 10_000); // 10 Gb allocation
+    static final int WINDOW = 10_000;
+
+    static final Reference<MyObject>[] refs = new Reference[WINDOW];
+
+    public static void main(String[] args) throws Exception {
+        long count = TARGET_MB * 1024 * 1024 / 32;
+        int rIdx = 0;
+
+        ReferenceQueue rq = new ReferenceQueue();
+
+        for (int c = 0; c < WINDOW; c++) {
+            refs[c] = select(c, new MyObject(c), rq);
+        }
+
+        for (int c = 0; c < count; c++) {
+            verifyRefAt(rIdx);
+            refs[rIdx] = select(c, new MyObject(rIdx), rq);
+
+            rIdx++;
+            if (rIdx >= WINDOW) {
+                rIdx = 0;
+            }
+            while (rq.poll() != null); // drain
+        }
+    }
+
+    static Reference<MyObject> select(int v, MyObject ext, ReferenceQueue rq) {
+        switch (v % 10) {
+            case 0:  return new SoftReference<MyObject>(null);
+            case 1:  return new SoftReference<MyObject>(null, rq);
+            case 2:  return new SoftReference<MyObject>(ext);
+            case 3:  return new SoftReference<MyObject>(ext, rq);
+            case 4:  return new WeakReference<MyObject>(null);
+            case 5:  return new WeakReference<MyObject>(null, rq);
+            case 6:  return new WeakReference<MyObject>(ext);
+            case 7:  return new WeakReference<MyObject>(ext, rq);
+            case 8:  return new PhantomReference<MyObject>(null, rq);
+            case 9:  return new PhantomReference<MyObject>(ext, rq);
+            default: throw new IllegalStateException();
+        }
+    }
+
+    static void verifyRefAt(int idx) {
+        Reference<MyObject> ref = refs[idx];
+        MyObject mo = ref.get();
+        if (mo != null && mo.x != idx) {
+            throw new IllegalStateException("Referent tag is incorrect: " + mo.x + ", should be " + idx);
+        }
+    }
+
+    static class MyObject {
+        final int x;
+
+        public MyObject(int x) {
+            this.x = x;
+        }
+    }
+
+}