| /** |
| * 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.bookkeeper.mledger.util; |
| |
| import java.util.concurrent.Semaphore; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| /** |
| * Mutex object that can be acquired from a thread and released from a different thread. |
| * |
| * <p/>This is meant to be acquired when calling an asynchronous method and released in its callback which is probably |
| * executed in a different thread. |
| */ |
| public class CallbackMutex { |
| |
| private Semaphore semaphore = new Semaphore(1, true); |
| |
| String owner; |
| String position; |
| |
| public void lock() { |
| semaphore.acquireUninterruptibly(); |
| |
| if (log.isDebugEnabled()) { |
| owner = Thread.currentThread().getName(); |
| position = Thread.currentThread().getStackTrace()[2].toString(); |
| log.debug("<<< Lock {} acquired at {}", this.hashCode(), position); |
| } |
| } |
| |
| public boolean tryLock() { |
| if (!semaphore.tryAcquire()) { |
| return false; |
| } |
| |
| if (log.isDebugEnabled()) { |
| owner = Thread.currentThread().getName(); |
| position = Thread.currentThread().getStackTrace()[2].toString(); |
| log.debug("<<< Lock {} acquired at {}", this.hashCode(), position); |
| } |
| return true; |
| } |
| |
| public void unlock() { |
| if (log.isDebugEnabled()) { |
| owner = null; |
| position = null; |
| log.debug(">>> Lock {} released at {}", this.hashCode(), |
| Thread.currentThread().getStackTrace()[2]); |
| } |
| |
| semaphore.release(); |
| } |
| |
| private static final Logger log = LoggerFactory.getLogger(CallbackMutex.class); |
| } |