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/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch 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.elasticsearch.common.util.concurrent;
import org.elasticsearch.Assertions;
import org.elasticsearch.common.lease.Releasable;
import org.elasticsearch.index.engine.EngineException;
import java.util.concurrent.locks.Lock;
/**
* Releasable lock used inside of Engine implementations
*/
public class ReleasableLock implements Releasable {
private final Lock lock;
// a per-thread count indicating how many times the thread has entered the lock; only works if assertions are enabled
private final ThreadLocal holdingThreads;
public ReleasableLock(Lock lock) {
this.lock = lock;
if (Assertions.ENABLED) {
holdingThreads = new ThreadLocal<>();
} else {
holdingThreads = null;
}
}
@Override
public void close() {
lock.unlock();
assert removeCurrentThread();
}
public ReleasableLock acquire() throws EngineException {
lock.lock();
assert addCurrentThread();
return this;
}
private boolean addCurrentThread() {
final Integer current = holdingThreads.get();
holdingThreads.set(current == null ? 1 : current + 1);
return true;
}
private boolean removeCurrentThread() {
final Integer count = holdingThreads.get();
assert count != null && count > 0;
if (count == 1) {
holdingThreads.remove();
} else {
holdingThreads.set(count - 1);
}
return true;
}
public boolean isHeldByCurrentThread() {
if (holdingThreads == null) {
throw new UnsupportedOperationException("asserts must be enabled");
}
final Integer count = holdingThreads.get();
return count != null && count > 0;
}
}