HDFS-4106. Merging change r1403075 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1409039 13f79535-47bb-0310-9956-ffa450edef68

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -229,6 +229,9 @@ Release 2.0.3-alpha - Unreleased
     HDFS-3921. NN will prematurely consider blocks missing when entering active
     state while still in safe mode. (atm)
 
+    HDFS-4106. BPServiceActor#lastHeartbeat, lastBlockReport and
+    lastDeletedReport should be volatile. (Jing Zhao via suresh)
+
 Release 2.0.2-alpha - 2012-09-07 
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java

@@ -75,14 +75,18 @@ class BPServiceActor implements Runnable {
 
   BPOfferService bpos;
   
-  long lastBlockReport = 0;
-  long lastDeletedReport = 0;
+  // lastBlockReport, lastDeletedReport and lastHeartbeat may be assigned/read
+  // by testing threads (through BPServiceActor#triggerXXX), while also 
+  // assigned/read by the actor thread. Thus they should be declared as volatile
+  // to make sure the "happens-before" consistency.
+  volatile long lastBlockReport = 0;
+  volatile long lastDeletedReport = 0;
 
   boolean resetBlockReportTime = true;
 
   Thread bpThread;
   DatanodeProtocolClientSideTranslatorPB bpNamenode;
-  private long lastHeartbeat = 0;
+  private volatile long lastHeartbeat = 0;
   private volatile boolean initialized = false;
   
   /**