YARN-8323. FairScheduler.allocConf should be declared as volatile. (Szilard Nemeth via Haibo Chen)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/FairScheduler.java

@@ -199,7 +199,7 @@ public class FairScheduler extends
 
   private AllocationFileLoaderService allocsLoader;
   @VisibleForTesting
-  AllocationConfiguration allocConf;
+  volatile AllocationConfiguration allocConf;
 
   // Container size threshold for making a reservation.
   @VisibleForTesting