diff --git a/hadoop-yarn-project/CHANGES.txt b/hadoop-yarn-project/CHANGES.txt
index 946fc408013..34bdc0fe5b3 100644
--- a/hadoop-yarn-project/CHANGES.txt
+++ b/hadoop-yarn-project/CHANGES.txt
@@ -266,7 +266,10 @@ Release 2.3.1 - UNRELEASED
 
   OPTIMIZATIONS
 
-  BUG FIXES 
+  BUG FIXES
+
+    YARN-1692. ConcurrentModificationException in fair scheduler AppSchedulable
+    (Sangjin Lee via Sandy Ryza)
 
 Release 2.3.0 - 2014-02-18
 
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/SchedulerApplicationAttempt.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/SchedulerApplicationAttempt.java
index 7785e56bdb3..553338d7ab0 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/SchedulerApplicationAttempt.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/SchedulerApplicationAttempt.java
@@ -150,7 +150,7 @@ public class SchedulerApplicationAttempt {
     return appSchedulingInfo.getPriorities();
   }
   
-  public ResourceRequest getResourceRequest(Priority priority, String resourceName) {
+  public synchronized ResourceRequest getResourceRequest(Priority priority, String resourceName) {
     return this.appSchedulingInfo.getResourceRequest(priority, resourceName);
   }
 
@@ -158,7 +158,7 @@ public class SchedulerApplicationAttempt {
     return getResourceRequest(priority, ResourceRequest.ANY).getNumContainers();
   }
 
-  public Resource getResource(Priority priority) {
+  public synchronized Resource getResource(Priority priority) {
     return appSchedulingInfo.getResource(priority);
   }
 
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/common/fica/FiCaSchedulerApp.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/common/fica/FiCaSchedulerApp.java
index 9c34f2f5995..4be6b941d12 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/common/fica/FiCaSchedulerApp.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/common/fica/FiCaSchedulerApp.java
@@ -192,7 +192,7 @@ public class FiCaSchedulerApp extends SchedulerApplicationAttempt {
     return Math.min(((float)requiredResources / clusterNodes), 1.0f);
   }
 
-  public Resource getTotalPendingRequests() {
+  public synchronized Resource getTotalPendingRequests() {
     Resource ret = Resource.newInstance(0, 0);
     for (ResourceRequest rr : appSchedulingInfo.getAllResourceRequests()) {
       // to avoid double counting we count only "ANY" resource requests
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/AppSchedulable.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/AppSchedulable.java
index 275061a5fa1..b488e780fa2 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/AppSchedulable.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/AppSchedulable.java
@@ -82,10 +82,12 @@ public class AppSchedulable extends Schedulable {
     Resources.addTo(demand, app.getCurrentConsumption());
 
     // Add up outstanding resource requests
-    for (Priority p : app.getPriorities()) {
-      for (ResourceRequest r : app.getResourceRequests(p).values()) {
-        Resource total = Resources.multiply(r.getCapability(), r.getNumContainers());
-        Resources.addTo(demand, total);
+    synchronized (app) {
+      for (Priority p : app.getPriorities()) {
+        for (ResourceRequest r : app.getResourceRequests(p).values()) {
+          Resource total = Resources.multiply(r.getCapability(), r.getNumContainers());
+          Resources.addTo(demand, total);
+        }
       }
     }
   }