diff --git a/hadoop-mapreduce/CHANGES.txt b/hadoop-mapreduce/CHANGES.txt
index 1f719ab107..57c44cf1f5 100644
--- a/hadoop-mapreduce/CHANGES.txt
+++ b/hadoop-mapreduce/CHANGES.txt
@@ -1133,7 +1133,10 @@ Trunk (unreleased changes)
     MAPREDUCE-2838. Fix MapReduce builds to use new hadoop-common test jars.
     (gkesavan via acmurthy) 
    
-    MAPREDUCE-2859 - Fix eclipse plugin contrib module compilation (gkesavan) 
+    MAPREDUCE-2859. Fix eclipse plugin contrib module compilation (gkesavan) 
+
+    MAPREDUCE-2846. Fix missing synchronization in the task log management.
+    (omalley)
 
 Release 0.22.0 - Unreleased
 
diff --git a/hadoop-mapreduce/hadoop-mr-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/TaskLog.java b/hadoop-mapreduce/hadoop-mr-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/TaskLog.java
index 810eea3a41..7e978e9cf9 100644
--- a/hadoop-mapreduce/hadoop-mr-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/TaskLog.java
+++ b/hadoop-mapreduce/hadoop-mr-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/TaskLog.java
@@ -183,9 +183,9 @@ static File getAttemptDir(TaskAttemptID taskid, boolean isCleanup) {
   private static long prevErrLength;
   private static long prevLogLength;
   
-  private static void writeToIndexFile(String logLocation,
-                                       boolean isCleanup) 
-  throws IOException {
+  private static synchronized 
+  void writeToIndexFile(String logLocation,
+                        boolean isCleanup) throws IOException {
     // To ensure atomicity of updates to index file, write to temporary index
     // file first and then rename.
     File tmpIndexFile = getTmpIndexFile(currentTaskid, isCleanup);