From 3335e502446b1542fc99c0c831e0542e53eac6f1 Mon Sep 17 00:00:00 2001
From: Tsz-wo Sze <szetszwo@apache.org>
Date: Fri, 26 Oct 2012 18:22:49 +0000
Subject: [PATCH] HDFS-3616. Fix a ConcurrentModificationException bug that BP
 actor threads may not be shutdown properly in DataNode.  Contributed by Jing
 Zhao

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1402608 13f79535-47bb-0310-9956-ffa450edef68
---
 hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt    |  3 +++
 .../hdfs/server/datanode/BlockPoolManager.java | 18 +++++++++---------
 .../hadoop/hdfs/server/datanode/DataNode.java  |  8 +++++++-
 3 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index 3571a4fe8a1..e98ac82bd1e 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -504,6 +504,9 @@ Release 2.0.3-alpha - Unreleased
     out stream returned by WebHdfsFileSystem does not support it. (Jing Zhao
     via szetszwo)
 
+    HDFS-3616. Fix a ConcurrentModificationException bug that BP actor threads
+    may not be shutdown properly in DataNode.  (Jing Zhao via szetszwo)
+
 Release 2.0.2-alpha - 2012-09-07 
 
   INCOMPATIBLE CHANGES
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockPoolManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockPoolManager.java
index eb4f403c4df..54cbb184bf6 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockPoolManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockPoolManager.java
@@ -106,15 +106,15 @@ synchronized void remove(BPOfferService t) {
     }
   }
   
-  void shutDownAll() throws InterruptedException {
-    BPOfferService[] bposArray = this.getAllNamenodeThreads();
-    
-    for (BPOfferService bpos : bposArray) {
-      bpos.stop(); //interrupts the threads
-    }
-    //now join
-    for (BPOfferService bpos : bposArray) {
-      bpos.join();
+  void shutDownAll(BPOfferService[] bposArray) throws InterruptedException {
+    if (bposArray != null) {
+      for (BPOfferService bpos : bposArray) {
+        bpos.stop(); //interrupts the threads
+      }
+      //now join
+      for (BPOfferService bpos : bposArray) {
+        bpos.join();
+      }
     }
   }
   
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java
index 1983f40243b..b64c41b1ca7 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java
@@ -1095,6 +1095,12 @@ public void shutdown() {
       }
     }
     
+    // We need to make a copy of the original blockPoolManager#offerServices to
+    // make sure blockPoolManager#shutDownAll() can still access all the 
+    // BPOfferServices, since after setting DataNode#shouldRun to false the 
+    // offerServices may be modified.
+    BPOfferService[] bposArray = this.blockPoolManager == null ? null
+        : this.blockPoolManager.getAllNamenodeThreads();
     this.shouldRun = false;
     shutdownPeriodicScanners();
     
@@ -1141,7 +1147,7 @@ public void shutdown() {
     
     if(blockPoolManager != null) {
       try {
-        this.blockPoolManager.shutDownAll();
+        this.blockPoolManager.shutDownAll(bposArray);
       } catch (InterruptedException ie) {
         LOG.warn("Received exception in BlockPoolManager#shutDownAll: ", ie);
       }