net.sf.ehcache.constructs.nonstop.concurrency.ExplicitLockingContextThreadLocal Maven / Gradle / Ivy
/**
* Copyright Terracotta, Inc.
*
* Licensed 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 net.sf.ehcache.constructs.nonstop.concurrency;
import java.util.LinkedList;
import net.sf.ehcache.util.lang.VicariousThreadLocal;
/**
* A class that maintains a thread local to keep track of any explicit locks acquired by the app thread
*
* @author Abhishek Sanoujam
*
*/
public final class ExplicitLockingContextThreadLocal {
private final VicariousThreadLocal contextThreadLocal = new VicariousThreadLocal() {
@Override
protected ExplicitLockingContextImpl initialValue() {
return new ExplicitLockingContextImpl();
}
};
/**
* Public constructor
*/
public ExplicitLockingContextThreadLocal() {
// private constructor
}
/**
* Returns true if the thread has acquired any locks previously and not released yet
*
* @return true if the thread has acquired any locks previously and not released yet
*/
public boolean areAnyExplicitLocksAcquired() {
return contextThreadLocal.get().areAnyExplicitLocksAcquired();
}
/**
* Returns the thread local for the current thread
*
* @return the thread local for the current thread
*/
public ExplicitLockingContext getCurrentThreadLockContext() {
return contextThreadLocal.get();
}
/**
*
* This class doesn't need to be thread safe as there's 1-1 mapping between app thread and nonstop threads. And only one of the threads
* is using this class at a time.
*
*/
private static class ExplicitLockingContextImpl implements ExplicitLockingContext {
// volatile for visibility
private volatile boolean locksAcquired;
private final LinkedList lockAcquisitionStack = new LinkedList();
/**
* {@inheritDoc}
*/
public boolean areAnyExplicitLocksAcquired() {
return locksAcquired;
}
/**
* {@inheritDoc}
*/
public void lockAcquired(final long currentNonstopThreadUniqueId) {
locksAcquired = true;
lockAcquisitionStack.addFirst(Long.valueOf(currentNonstopThreadUniqueId));
}
/**
* {@inheritDoc}
*/
public void lockReleased() {
if (lockAcquisitionStack.peek() != null) {
lockAcquisitionStack.removeFirst();
}
// a litte perf than doing size() > 0
if (lockAcquisitionStack.peek() == null) {
locksAcquired = false;
}
}
/**
* {@inheritDoc}
*/
public boolean areLocksAcquiredByOtherThreads(long currentNonstopThreadUniqueId) {
for (Long nonstopThreadUniqueId : lockAcquisitionStack) {
if (nonstopThreadUniqueId.longValue() != currentNonstopThreadUniqueId) {
return true;
}
}
return false;
}
}
}