001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hdfs.util;
019
020/** Read-write lock interface. */
021public interface RwLock {
022  /** Acquire read lock. */
023  public void readLock();
024  
025  /**
026   * Acquire the long read lock, unless interrupted while waiting. The long
027   * read lock should also serve to block all concurrent writers.
028   **/
029  void longReadLockInterruptibly() throws InterruptedException;
030  
031  /** Release the long read lock. */
032  public void longReadUnlock();
033
034  /** Release read lock. */
035  public void readUnlock();
036
037  /** Check if the current thread holds read lock. */
038  public boolean hasReadLock();
039
040  /** Acquire write lock. */
041  public void writeLock();
042  
043  /** Acquire write lock, unless interrupted while waiting  */
044  void writeLockInterruptibly() throws InterruptedException;
045
046  /** Release write lock. */
047  public void writeUnlock();
048
049  /** Check if the current thread holds write lock. */
050  public boolean hasWriteLock();
051}