From 331a6cface11c4a9706e4a4a9bf07e7f1bc07a1d Mon Sep 17 00:00:00 2001
From: Sean Busbey <busbey@apache.org>
Date: Fri, 28 Jul 2017 16:04:45 -0500
Subject: [PATCH] HBASE-18475 ensure only non-null procedures are sent to
 requireTableExclusiveLock

Signed-off-by: Umesh Agashe <uagashe@cloudera.com>
Signed-off-by: Michael Stack <stack@apache.org>
---
 .../master/procedure/MasterProcedureScheduler.java     | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/master/procedure/MasterProcedureScheduler.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/master/procedure/MasterProcedureScheduler.java
index 10e6aa06d88..564b86d6bf5 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/master/procedure/MasterProcedureScheduler.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/master/procedure/MasterProcedureScheduler.java
@@ -212,6 +212,9 @@ public class MasterProcedureScheduler extends AbstractProcedureScheduler {
     }
 
     final Procedure pollResult = rq.peek();
+    if (pollResult == null) {
+      return null;
+    }
     final boolean xlockReq = rq.requireExclusiveLock(pollResult);
     if (xlockReq && rq.getLockStatus().isLocked() && !rq.getLockStatus().hasLockAccess(pollResult)) {
       // someone is already holding the lock (e.g. shared lock). avoid a yield
@@ -586,6 +589,9 @@ public class MasterProcedureScheduler extends AbstractProcedureScheduler {
   // ============================================================================
   //  Table Locking Helpers
   // ============================================================================
+  /**
+   * @param proc must not be null
+   */
   private static boolean requireTableExclusiveLock(TableProcedureInterface proc) {
     switch (proc.getTableOperationType()) {
       case CREATE:
@@ -1007,6 +1013,10 @@ public class MasterProcedureScheduler extends AbstractProcedureScheduler {
   // ============================================================================
   private static abstract class Queue<TKey extends Comparable<TKey>>
       extends AvlLinkedNode<Queue<TKey>> {
+
+    /**
+     * @param proc must not be null
+     */
     abstract boolean requireExclusiveLock(Procedure proc);
 
     private final TKey key;