diff --git a/mapreduce/src/test/mapred/org/apache/hadoop/mapred/TestTaskLauncherThreaded.java b/mapreduce/src/test/mapred/org/apache/hadoop/mapred/TestTaskLauncherThreaded.java
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index 0000000000..21378f16dd
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+++ b/mapreduce/src/test/mapred/org/apache/hadoop/mapred/TestTaskLauncherThreaded.java
@@ -0,0 +1,165 @@
+/**
+ * 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.apache.hadoop.mapred;
+
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.*;
+
+import java.io.IOException;
+import java.util.LinkedHashMap;
+import java.util.TreeMap;
+
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.mapred.JobConf;
+import org.apache.hadoop.mapred.TaskTracker.TaskInProgress;
+import org.apache.hadoop.mapred.TaskTracker.TaskLauncher;
+import org.apache.hadoop.mapred.TaskTracker.RunningJob;
+import org.apache.hadoop.mapreduce.TaskType;
+import org.apache.hadoop.security.UserGroupInformation;
+import org.junit.Test;
+
+/**
+ * Tests {@link TaskLauncherThreaded}
+ */
+public class TestTaskLauncherThreaded {
+  private static int jobLocalizedCount = 0;
+  private static int jobLaunchCount = 0;
+  private static boolean quitWaiting = false;
+  private static boolean firstJobStarted = false;
+  private static boolean firstJobFinished = false;
+
+  private static class MyTaskTracker extends TaskTracker {
+
+    // stub out functions called from startNewTask
+    @Override
+    RunningJob localizeJob(TaskInProgress tip)
+        throws IOException, InterruptedException {
+      if (firstJobStarted == false) {
+        firstJobStarted = true;
+        while (quitWaiting == false) {
+          Thread.sleep(100);
+        }
+        firstJobFinished = true;
+      }
+      // mock out a RunningJob
+      RunningJob rjob = mock(RunningJob.class);
+      when(rjob.getJobConf()).thenReturn(new JobConf());
+      jobLocalizedCount++;
+
+      return rjob;
+    }
+
+    @Override
+    protected void launchTaskForJob(TaskInProgress tip, JobConf jobConf,
+        UserGroupInformation ugi) throws IOException {
+      jobLaunchCount++;
+    }
+  }
+
+  /**
+   * Tests the case "task localizing doesn't block other tasks".
+   *
+   * Launches one task that simulates a task doing large localization,
+   * then starts a second task and verifies that second task is not
+   * blocked waiting behind the first task.
+   *
+   * @throws IOException
+   */
+  @Test
+  public void testLocalizationNotBlockingOtherTasks() throws IOException {
+    // setup a TaskTracker
+    JobConf ttConf = new JobConf();
+    ttConf.setInt("mapred.tasktracker.map.tasks.maximum", 4);
+    TaskTracker tt = new MyTaskTracker();
+
+    tt.runningJobs = new TreeMap<JobID, TaskTracker.RunningJob>();
+    tt.runningTasks = new LinkedHashMap<TaskAttemptID, TaskInProgress>();
+    tt.setIndexCache(new IndexCache(ttConf));
+    tt.setTaskMemoryManagerEnabledFlag();
+
+    // start map-task launcher with four slots
+    TaskLauncher mapLauncher = tt.new TaskLauncher(TaskType.MAP, 4);
+    mapLauncher.start();
+
+    // launch a task which simulates large localization
+    String jtId = "test";
+    TaskAttemptID attemptID = new TaskAttemptID(jtId, 1, true, 0, 0);
+    Task task = new MapTask(null, attemptID, 0, null, 2);
+    mapLauncher.addToTaskQueue(new LaunchTaskAction(task));
+    // verify that task is added to runningTasks
+    TaskInProgress runningTip = tt.runningTasks.get(attemptID);
+    assertNotNull(runningTip);
+
+    // wait for a while for the first task to start initializing
+    // this loop waits at most for 30 seconds
+    for (int i = 0; i < 300; i++) {
+      if (firstJobStarted == true) {
+        break;
+      }
+      UtilsForTests.waitFor(100);
+    }
+
+    // Now start a second task and make sure it doesn't wait while first one initializes
+    String secondjtId = "test2";
+    TaskAttemptID secondAttemptID = new TaskAttemptID(secondjtId, 1, true, 0, 0);
+    Task secondTask = new MapTask(null, secondAttemptID, 0, null, 2);
+    mapLauncher.addToTaskQueue(new LaunchTaskAction(secondTask));
+    // verify that task is added to runningTasks
+    TaskInProgress secondRunningTip = tt.runningTasks.get(secondAttemptID);
+    assertNotNull(secondRunningTip);
+
+    // wait for a while for the second task to be launched
+    // this loop waits at most for 30 seconds
+    for (int i = 0; i < 300; i++) {
+      if (jobLaunchCount > 0) {
+        break;
+      }
+      UtilsForTests.waitFor(100);
+    }
+
+    assertEquals("Second task didn't run or both ran", 1, jobLocalizedCount);
+    assertEquals("second task didn't try to launch", 1, jobLaunchCount);
+    assertFalse("Second task didn't finish first task initializing", firstJobFinished);
+
+    // tell first task to stop waiting
+    quitWaiting = true;
+
+    // wait for a while for the first task finishes initializing
+    // this loop waits at most for 30 seconds
+    for (int i = 0; i < 300; i++) {
+      if (firstJobFinished == true) {
+        break;
+      }
+      UtilsForTests.waitFor(100);
+    }
+    assertTrue("First task didn't finish initializing", firstJobFinished);
+
+    // wait for a while for the first task finishes
+    // this loop waits at most for 30 seconds
+    for (int i = 0; i < 300; i++) {
+      if (jobLaunchCount > 1) {
+        break;
+      }
+      UtilsForTests.waitFor(100);
+    }
+    assertEquals("Both tasks didn't run", 2, jobLocalizedCount);
+    assertEquals("First task didn't try to launch", 2, jobLaunchCount);
+
+  }
+
+}