--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/lib/jdk/test/lib/LockFreeLogger.java	Wed May 24 15:21:14 2017 -0700
@@ -0,0 +1,84 @@
+/*
+ * Copyright (c) 2014, 2017, 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 jdk.test.lib;
+
+import java.util.Collection;
+import java.util.Comparator;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.stream.Collectors;
+
+/**
+ * A logger designed specifically to allow collecting ordered log messages
+ * in a multi-threaded environment without involving any kind of locking.
+ * <p>
+ * It is particularly useful in situations when one needs to assert various
+ * details about the tested thread state or the locks it hold while also wanting
+ * to produce diagnostic log messages.
+ * <p>
+ * The logger does not provide any guarantees about the completness of the
+ * logs written from different threads - it is up to the caller to make sure
+ * {@code toString()} method is called only when all the activity has ceased
+ * and the per-thread logs contain all the necessary data.
+ *
+ * @author Jaroslav Bachorik
+ **/
+public class LockFreeLogger {
+    private final AtomicInteger logCntr = new AtomicInteger(0);
+    private final Collection<Map<Integer, String>> allRecords = new ConcurrentLinkedQueue<>();
+    private final ThreadLocal<Map<Integer, String>> records = ThreadLocal.withInitial(ConcurrentHashMap::new);
+
+    public LockFreeLogger() {
+        allRecords.add(records.get());
+    }
+
+    /**
+     * Log a message
+     * @param format Message format
+     * @param params Message parameters
+     */
+    public void log(String format, Object ... params) {
+        int id = logCntr.getAndIncrement();
+        records.get().put(id, String.format(format, params));
+    }
+
+    /**
+     * Will generate an aggregated log of chronologically ordered messages.
+     * <p>
+     * Make sure that you call this method only when all the related threads
+     * have finished; otherwise you might get incomplete data.
+     *
+     * @return An aggregated log of chronologically ordered messages
+     */
+    @Override
+    public String toString() {
+        return allRecords.stream()
+            .flatMap(m -> m.entrySet().stream())
+            .sorted(Comparator.comparing(Map.Entry::getKey))
+            .map(Map.Entry::getValue)
+            .collect(Collectors.joining());
+    }
+}