svn merge -c 1517989 merging from trunk to branch-2 to fix HDFS-5132.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1517990 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -169,6 +169,9 @@ Release 2.1.1-beta - UNRELEASED
     HDFS-5124. DelegationTokenSecretManager#retrievePassword can cause deadlock 
     in NameNode. (Daryn Sharp via jing9)
 
+    HDFS-5132. Deadlock in NameNode between SafeModeMonitor#run and 
+    DatanodeManager#handleHeartbeat. (kihwal)
+
 Release 2.1.0-beta - 2013-08-22
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java

@@ -4781,7 +4781,21 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
      */
     @Override
     public void run() {
-      while (fsRunning && (safeMode != null && !safeMode.canLeave())) {
+      while (fsRunning) {
+        writeLock();
+        try {
+          if (safeMode == null) { // Not in safe mode.
+            break;
+          }
+          if (safeMode.canLeave()) {
+            // Leave safe mode.
+            safeMode.leave();
+            break;
+          }
+        } finally {
+          writeUnlock();
+        }
+
         try {
           Thread.sleep(recheckInterval);
         } catch (InterruptedException ie) {
@@ -4790,9 +4804,6 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
       }
       if (!fsRunning) {
         LOG.info("NameNode is being shutdown, exit SafeModeMonitor thread");
-      } else {
-        // leave safe mode and stop the monitor
-        leaveSafeMode();
       }
       smmthread = null;
     }