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     */
018    package org.apache.hadoop.hdfs.util;
019    
020    /** Read-write lock interface. */
021    public interface RwLock {
022      /** Acquire read lock. */
023      public void readLock();
024    
025      /** Release read lock. */
026      public void readUnlock();
027    
028      /** Check if the current thread holds read lock. */
029      public boolean hasReadLock();
030    
031      /** Acquire write lock. */
032      public void writeLock();
033      
034      /** Acquire write lock, unless interrupted while waiting  */
035      void writeLockInterruptibly() throws InterruptedException;
036    
037      /** Release write lock. */
038      public void writeUnlock();
039    
040      /** Check if the current thread holds write lock. */
041      public boolean hasWriteLock();
042    
043      /** Check if the current thread holds read or write lock. */
044      public boolean hasReadOrWriteLock();
045    }