YARN-3487. CapacityScheduler scheduler lock obtained unnecessarily when calling getQueue (Jason Lowe via wangda)

(cherry picked from commit f47a5763acd55cb0b3f16152c7f8df06ec0e09a9)

hadoop-yarn-project/CHANGES.txt

@@ -11,6 +11,8 @@ Release 2.7.1 - UNRELEASED
   OPTIMIZATIONS
 
   BUG FIXES
+    YARN-3487. CapacityScheduler scheduler lock obtained unnecessarily when 
+    calling getQueue (Jason Lowe via wangda)
 
     YARN-3462. Patches applied for YARN-2424 are inconsistent between
     trunk and branch-2. (Naganarasimha G R via harsh)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/CapacityScheduler.java

@@ -627,7 +627,7 @@ public class CapacityScheduler extends
     return queue;
   }
 
-  public synchronized CSQueue getQueue(String queueName) {
+  public CSQueue getQueue(String queueName) {
     if (queueName == null) {
       return null;
     }
@@ -925,11 +925,7 @@ public class CapacityScheduler extends
       boolean includeChildQueues, boolean recursive) 
   throws IOException {
     CSQueue queue = null;
-
-    synchronized (this) {
-      queue = this.queues.get(queueName); 
-    }
-
+    queue = this.queues.get(queueName);
     if (queue == null) {
       throw new IOException("Unknown queue: " + queueName);
     }