Github user jwagenleitner commented on a diff in the pull request:
https://github.com/apache/groovy/pull/489#discussion_r100162935
--- Diff:
subprojects/stress/src/test/java/org/codehaus/groovy/reflection/ClassInfoDeadlockStressTest.java
---
@@ -0,0 +1,140 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ *http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.codehaus.groovy.reflection;
+
+import groovy.lang.GroovyClassLoader;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import org.apache.groovy.stress.util.GCUtils;
+import org.junit.Test;
+import static org.junit.Assert.*;
+
+/**
+ * Tests for deadlocks in the ClassInfo caching.
+ *
+ */
+public class ClassInfoDeadlockStressTest {
+
+private static final int DEADLOCK_TRIES = 8;
+private static final int THREAD_COUNT = 8;
+
+private final CountDownLatch startLatch = new CountDownLatch(1);
+private final CountDownLatch completeLatch = new
CountDownLatch(THREAD_COUNT);
+private final GroovyClassLoader gcl = new GroovyClassLoader();
+private final AtomicInteger counter = new AtomicInteger();
+
+/**
+ * We first generate a large number of ClassInfo instances for classes
+ * that are no longer reachable. Then queue up threads to all request
+ * ClassInfo instances for new classes simultaneously to ensure that
+ * clearing the old references wont deadlock the creation of new
+ * instances.
+ *
+ * GROOVY-8067
+ */
+@Test
+public void testDeadlock() throws Exception {
+for (int i = 1; i <= DEADLOCK_TRIES; i++) {
+System.out.println("Test Number: " + i);
+generateGarbage();
+GCUtils.gc();
+attemptDeadlock(null);
+}
+}
+
+@Test
+public void testRequestsForSameClassInfo() throws Exception {
+Class newClass = createRandomClass();
+for (int i = 1; i <= DEADLOCK_TRIES; i++) {
+System.out.println("Test Number: " + i);
+generateGarbage();
+GCUtils.gc();
+attemptDeadlock(newClass);
+}
+ClassInfo newClassInfo = ClassInfo.getClassInfo(newClass);
+for (ClassInfo ci : ClassInfo.getAllClassInfo()) {
+if (ci.getTheClass() == newClass && ci != newClassInfo) {
+fail("Found multiple ClassInfo instances for class");
+}
+}
+}
+
+private void attemptDeadlock(final Class cls) throws Exception {
+for (int i = 0; i < THREAD_COUNT; i++) {
+Runnable runnable = new Runnable() {
+@Override
+public void run() {
+Class newClass = (cls == null) ?
createRandomClass() : cls;
+try {
+startLatch.await();
+} catch (InterruptedException ie) {
--- End diff --
can use `ThreadUtils.awaite()`
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