HDFS-16141. Address permission related issues with File / Directory

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/LatchLock.java

@@ -0,0 +1,64 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.util;
+
+/**
+ * LatchLock controls two hierarchical Read/Write locks:
+ * the topLock and the childLock.
+ * Typically an operation starts with the topLock already acquired.
+ * To acquire child lock LatchLock will
+ * first acquire the childLock, and then release the topLock.
+ */
+public abstract class LatchLock<C> {
+  // Interfaces methods to be defined for subclasses
+  /** @return true topLock is locked for read by any thread */
+  protected abstract boolean isReadTopLocked();
+  /** @return true topLock is locked for write by any thread */
+  protected abstract boolean isWriteTopLocked();
+  protected abstract void readTopUnlock();
+  protected abstract void writeTopUnlock();
+
+  protected abstract boolean hasReadChildLock();
+  protected abstract void readChildLock();
+  protected abstract void readChildUnlock();
+
+  protected abstract boolean hasWriteChildLock();
+  protected abstract void writeChildLock();
+  protected abstract void writeChildUnlock();
+
+  protected abstract LatchLock<C> clone();
+
+  // Public APIs to use with the class
+  public void readLock() {
+    readChildLock();
+    readTopUnlock();
+  }
+
+  public void readUnlock() {
+    readChildUnlock();
+  }
+
+  public void writeLock() {
+    writeChildLock();
+    writeTopUnlock();
+  }
+
+  public void writeUnlock() {
+    writeChildUnlock();
+  }
+}