--- /dev/null	2020-06-15 17:34:57.000000000 -0400
+++ new/test/hotspot/jtreg/runtime/whitebox/TestWBDeflateIdleMonitors.java	2020-06-15 17:34:57.000000000 -0400
@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * 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.
+ */
+
+package runtime.whitebox;
+
+/*
+ * @test TestWBDeflateIdleMonitors
+ * @bug 8246477
+ * @summary Test verify that WB method deflateIdleMonitors works correctly.
+ * @library /test/lib
+ * @modules java.base/jdk.internal.misc
+ *          java.management
+ * @build sun.hotspot.WhiteBox
+ * @run driver ClassFileInstaller sun.hotspot.WhiteBox
+ * @run driver runtime.whitebox.TestWBDeflateIdleMonitors
+ */
+import jdk.test.lib.Asserts;
+import jdk.test.lib.process.ProcessTools;
+import jdk.test.lib.process.OutputAnalyzer;
+import sun.hotspot.WhiteBox;
+
+public class TestWBDeflateIdleMonitors {
+
+    public static void main(String args[]) throws Exception {
+        ProcessBuilder pb = ProcessTools.createTestJvm(
+                "-Xbootclasspath/a:.",
+                "-XX:+UnlockDiagnosticVMOptions",
+                "-XX:+WhiteBoxAPI",
+                "-Xlog:monitorinflation=info",
+                InflateMonitorsTest.class.getName());
+
+        OutputAnalyzer output = new OutputAnalyzer(pb.start());
+        System.out.println(output.getStdout());
+        output.shouldHaveExitValue(0);
+        output.shouldContain("WhiteBox initiated DeflateIdleMonitors");
+    }
+
+    public static class InflateMonitorsTest {
+        static WhiteBox wb = WhiteBox.getWhiteBox();
+        public static Object obj;
+
+        public static void main(String args[]) {
+            obj = new Object();
+            synchronized (obj) {
+                // HotSpot implementation detail: asking for the hash code
+                // when the object is locked causes monitor inflation.
+                if (obj.hashCode() == 0xBAD) System.out.println("!");
+                Asserts.assertEQ(wb.isMonitorInflated(obj), true,
+                                 "Monitor should be inflated.");
+            }
+            boolean did_deflation = wb.deflateIdleMonitors();
+            Asserts.assertEQ(did_deflation, true,
+                             "deflateIdleMonitors() should have worked.");
+            Asserts.assertEQ(wb.isMonitorInflated(obj), false,
+                             "Monitor should be deflated.");
+        }
+    }
+}