YARN-2594. Potential deadlock in RM when querying ApplicationResourceUsageReport. (Wangda Tan via kasha)

hadoop-yarn-project/CHANGES.txt

@@ -488,6 +488,9 @@ Release 2.6.0 - UNRELEASED
     YARN-2387. Resource Manager crashes with NPE due to lack of
     synchronization (Mit Desai via jlowe)
 
+    YARN-2594. Potential deadlock in RM when querying 
+    ApplicationResourceUsageReport. (Wangda Tan via kasha)
+
 Release 2.5.1 - 2014-09-05
 
   INCOMPATIBLE CHANGES

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/rmapp/RMAppImpl.java

@@ -128,7 +128,8 @@ public class RMAppImpl implements RMApp, Recoverable {
   private long startTime;
   private long finishTime = 0;
   private long storedFinishTime = 0;
-  private RMAppAttempt currentAttempt;
+  // This field isn't protected by readlock now.
+  private volatile RMAppAttempt currentAttempt;
   private String queue;
   private EventHandler handler;
   private static final AppFinishedTransition FINISHED_TRANSITION =
@@ -438,16 +439,11 @@ public class RMAppImpl implements RMApp, Recoverable {
 
   @Override
   public float getProgress() {
-    this.readLock.lock();
-
-    try {
-      if (this.currentAttempt != null) {
-        return this.currentAttempt.getProgress();
-      }
-      return 0;
-    } finally {
-      this.readLock.unlock();
+    RMAppAttempt attempt = this.currentAttempt;
+    if (attempt != null) {
+      return attempt.getProgress();
     }
+    return 0;
   }
 
   @Override
@@ -478,13 +474,7 @@ public class RMAppImpl implements RMApp, Recoverable {
 
   @Override
   public RMAppAttempt getCurrentAppAttempt() {
-    this.readLock.lock();
-
-    try {
-      return this.currentAttempt;
-    } finally {
-      this.readLock.unlock();
-    }
+    return this.currentAttempt;
   }
 
   @Override
@@ -655,30 +645,20 @@ public class RMAppImpl implements RMApp, Recoverable {
 
   @Override
   public String getTrackingUrl() {
-    this.readLock.lock();
-    
-    try {
-      if (this.currentAttempt != null) {
-        return this.currentAttempt.getTrackingUrl();
-      }
-      return null;
-    } finally {
-      this.readLock.unlock();
+    RMAppAttempt attempt = this.currentAttempt;
+    if (attempt != null) {
+      return attempt.getTrackingUrl();
     }
+    return null;
   }
 
   @Override
   public String getOriginalTrackingUrl() {
-    this.readLock.lock();
-    
-    try {
-      if (this.currentAttempt != null) {
-        return this.currentAttempt.getOriginalTrackingUrl();
-      }
-      return null;
-    } finally {
-      this.readLock.unlock();
+    RMAppAttempt attempt = this.currentAttempt;
+    if (attempt != null) {
+      return attempt.getOriginalTrackingUrl();
     }
+    return null;
   }
 
   @Override