YARN-6263. NMTokenSecretManagerInRM.createAndGetNMToken is not thread safe. Contributed by Haibo Chen

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/security/NMTokenSecretManagerInRM.java

@@ -192,7 +192,7 @@ public class NMTokenSecretManagerInRM extends BaseNMTokenSecretManager {
   public NMToken createAndGetNMToken(String applicationSubmitter,
       ApplicationAttemptId appAttemptId, Container container) {
     try {
-      this.readLock.lock();
+      this.writeLock.lock();
       HashSet<NodeId> nodeSet = this.appAttemptToNodeKeyMap.get(appAttemptId);
       NMToken nmToken = null;
       if (nodeSet != null) {
@@ -208,7 +208,7 @@ public class NMTokenSecretManagerInRM extends BaseNMTokenSecretManager {
       }
       return nmToken;
     } finally {
-      this.readLock.unlock();
+      this.writeLock.unlock();
     }
   }