svn merge -c 1509565. Merging from trunk to branch-0.23 to fix HDFS-5028.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1510771 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -25,6 +25,9 @@ Release 0.23.10 - UNRELEASED
     HDFS-4943. WebHdfsFileSystem does not work when original file path has
     encoded chars. (Jerry He and Robert Parker via kihwal)
 
+    HDFS-5028. LeaseRenewer throws ConcurrentModificationException when timeout.
+    (zhaoyunjiong via szetszwo)
+
 Release 0.23.9 - 2013-07-08
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/LeaseRenewer.java

@@ -443,8 +443,8 @@ class LeaseRenewer {
           LOG.warn("Failed to renew lease for " + clientsString() + " for "
               + (elapsed/1000) + " seconds.  Aborting ...", ie);
           synchronized (this) {
-            for(DFSClient c : dfsclients) {
-              c.abort();
+            while (!dfsclients.isEmpty()) {
+              dfsclients.get(0).abort();
             }
           }
           break;