diff -r 2c3cc4b01880 -r c16ac7a2eba4 test/jdk/jdk/jfr/api/consumer/recordingstream/TestStart.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/jdk/jdk/jfr/api/consumer/recordingstream/TestStart.java	Wed Oct 30 19:43:52 2019 +0100
@@ -0,0 +1,151 @@
+/*
+ * Copyright (c) 2019, 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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 jdk.jfr.api.consumer.recordingstream;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import jdk.jfr.Event;
+import jdk.jfr.consumer.RecordingStream;
+
+/**
+ * @test
+ * @summary Tests RecordingStream::start()
+ * @key jfr
+ * @requires vm.hasJFR
+ * @library /test/lib /test/jdk
+ * @build jdk.jfr.api.consumer.recordingstream.EventProducer
+ * @run main/othervm jdk.jfr.api.consumer.recordingstream.TestStart
+ */
+public class TestStart {
+    static class StartEvent extends Event {
+    }
+    public static void main(String... args) throws Exception {
+        testStart();
+        testStartOnEvent();
+        testStartTwice();
+        testStartClosed();
+    }
+
+    private static void testStartTwice() throws Exception {
+        log("Entering testStartTwice()");
+        CountDownLatch started = new CountDownLatch(1);
+        try (RecordingStream rs = new RecordingStream()) {
+            EventProducer t = new EventProducer();
+            t.start();
+            Thread thread = new Thread() {
+                public void run() {
+                    rs.start();
+                }
+            };
+            thread.start();
+            rs.onEvent(e -> {
+                if (started.getCount() > 0) {
+                    started.countDown();
+                }
+            });
+            started.await();
+            t.kill();
+            try {
+                rs.start();
+                throw new AssertionError("Expected IllegalStateException if started twice");
+            } catch (IllegalStateException ise) {
+                // OK, as expected
+            }
+        }
+        log("Leaving testStartTwice()");
+    }
+
+    static void testStart() throws Exception {
+        log("Entering testStart()");
+        CountDownLatch started = new CountDownLatch(1);
+        try (RecordingStream rs = new RecordingStream()) {
+            rs.onEvent(e -> {
+                started.countDown();
+            });
+            EventProducer t = new EventProducer();
+            t.start();
+            Thread thread = new Thread() {
+                public void run() {
+                    rs.start();
+                }
+            };
+            thread.start();
+            started.await();
+            t.kill();
+        }
+        log("Leaving testStart()");
+    }
+
+    static void testStartOnEvent() throws Exception {
+        log("Entering testStartOnEvent()");
+        AtomicBoolean ISE = new AtomicBoolean(false);
+        CountDownLatch startedTwice = new CountDownLatch(1);
+        try (RecordingStream rs = new RecordingStream()) {
+            rs.onEvent(e -> {
+                try {
+                    rs.start(); // must not deadlock
+                } catch (IllegalStateException ise) {
+                    if (!ISE.get())  {
+                        ISE.set(true);
+                        startedTwice.countDown();
+                    }
+                }
+            });
+            EventProducer t = new EventProducer();
+            t.start();
+            Thread thread = new Thread() {
+                public void run() {
+                    rs.start();
+                }
+            };
+            thread.start();
+            startedTwice.await();
+            t.kill();
+            if (!ISE.get()) {
+                throw new AssertionError("Expected IllegalStateException");
+            }
+        }
+        log("Leaving testStartOnEvent()");
+    }
+
+    static void testStartClosed() {
+        log("Entering testStartClosed()");
+        RecordingStream rs = new RecordingStream();
+        rs.close();
+        try {
+            rs.start();
+            throw new AssertionError("Expected IllegalStateException");
+        } catch (IllegalStateException ise) {
+            // OK, as expected.
+        }
+        log("Leaving testStartClosed()");
+    }
+
+    private static void log(String msg) {
+        System.out.println(msg);
+    }
+}