/* $Id: LockObject.java 988245 2010-08-23 18:39:35Z kwright $ */
/**
* 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.manifoldcf.core.lockmanager;
import org.apache.manifoldcf.core.interfaces.*;
import org.apache.manifoldcf.core.system.ManifoldCF;
import org.apache.manifoldcf.core.system.Logging;
import java.io.*;
/** Base class. One instance of this object exists for each lock on each JVM!
*/
public class LockObject
{
public static final String _rcsid = "@(#)$Id: LockObject.java 988245 2010-08-23 18:39:35Z kwright $";
protected final Object lockKey;
private LockPool lockPool;
private volatile boolean obtainedWrite = false; // Set to true if this object already owns the permission to exclusively write
private volatile int obtainedRead = 0; // Set to a count if this object already owns the permission to read
private volatile int obtainedNonExWrite = 0; // Set to a count if this object already owns the permission to non-exclusively write
protected static final String LOCKEDANOTHERTHREAD = "Locked by another thread in this JVM";
protected static final String LOCKEDANOTHERJVM = "Locked by another JVM";
public LockObject(LockPool lockPool, Object lockKey)
{
this.lockPool = lockPool;
this.lockKey = lockKey;
}
public synchronized void makeInvalid()
{
this.lockPool = null;
}
/** This method WILL NOT BE CALLED UNLESS we are actually committing a write lock for the
* first time for a given thread.
*/
public synchronized void enterWriteLock()
throws ManifoldCFException, InterruptedException, ExpiredObjectException
{
while (true)
{
if (lockPool == null)
throw new ExpiredObjectException("Invalid");
try
{
// Does another thread in this JVM have the writelock?
if (obtainedWrite)
throw new LocalLockException(LOCKEDANOTHERTHREAD);
// Got the write token!
if (obtainedRead > 0 || obtainedNonExWrite > 0)
throw new LocalLockException(LOCKEDANOTHERTHREAD);
// Attempt to obtain a global write lock
obtainGlobalWriteLock();
obtainedWrite = true;
return;
}
catch (LocalLockException le)
{
wait();
}
}
}
/** Note well: Upgrading a read lock to a non-ex write lock is tricky. The code inside the
* lock should execute only when there are NO threads that are executing in a read-locked area that
* aren't waiting to enter the non-ex write lock area! This is therefore essentially an illegal codepath,
* because it will lead inevitably to deadlock, as is going from a read-locked area into a write-locked area,
* or from a non-ex write area into an
* exclusive write area.
*/
public synchronized void enterWriteLockNoWait()
throws ManifoldCFException, LockException, LocalLockException, InterruptedException, ExpiredObjectException
{
if (lockPool == null)
throw new ExpiredObjectException("Invalid");
// Does another thread in this JVM have the writelock?
if (obtainedWrite)
throw new LocalLockException(LOCKEDANOTHERTHREAD);
// Got the write token!
if (obtainedRead > 0 || obtainedNonExWrite > 0)
throw new LocalLockException(LOCKEDANOTHERTHREAD);
// Attempt to obtain a global write lock
obtainGlobalWriteLockNoWait();
obtainedWrite = true;
}
protected void obtainGlobalWriteLockNoWait()
throws ManifoldCFException, LockException, InterruptedException
{
}
protected void obtainGlobalWriteLock()
throws ManifoldCFException, InterruptedException
{
while (true)
{
try
{
obtainGlobalWriteLockNoWait();
return;
}
catch (LockException e)
{
// Cross JVM lock; sleep!
ManifoldCF.sleep(10L);
}
}
}
public synchronized boolean leaveWriteLock()
throws ManifoldCFException, InterruptedException, ExpiredObjectException
{
if (lockPool == null)
throw new ExpiredObjectException("Invalid");
if (obtainedWrite == false)
throw new RuntimeException("JVM failure: Don't hold lock for object "+this.toString());
clearGlobalWriteLock();
obtainedWrite = false;
notifyAll();
return true;
}
protected void clearGlobalWriteLockNoWait()
throws ManifoldCFException, LockException, InterruptedException
{
}
protected void clearGlobalWriteLock()
throws ManifoldCFException, InterruptedException
{
while (true)
{
try
{
clearGlobalWriteLockNoWait();
return;
}
catch (LockException e)
{
ManifoldCF.sleep(10L);
}
}
}
public synchronized void enterNonExWriteLock()
throws ManifoldCFException, InterruptedException, ExpiredObjectException
{
// System.out.println("Entering write lock for resource "+lockFileName);
while (true)
{
if (lockPool == null)
throw new ExpiredObjectException("Invalid");
try
{
// Does another thread in this JVM have the lock?
if (obtainedWrite || obtainedRead > 0)
throw new LocalLockException(LOCKEDANOTHERTHREAD);
// We've got the local non-ex write token
if (obtainedNonExWrite > 0)
{
obtainedNonExWrite++;
return;
}
obtainGlobalNonExWriteLock();
obtainedNonExWrite++;
return;
}
catch (LocalLockException le)
{
wait();
}
}
}
/** Note well: Upgrading a read lock to a non-ex write lock is tricky. The code inside the
* lock should execute only when there are NO threads that are executing in a read-locked area that
* aren't waiting to enter the non-ex write lock area! This is therefore essentially an illegal codepath,
* because it will lead inevitably to deadlock, as is going from a read-locked area into a write-locked area,
* or from a non-ex write area into an
* exclusive write area.
*/
public synchronized void enterNonExWriteLockNoWait()
throws ManifoldCFException, LockException, LocalLockException, InterruptedException, ExpiredObjectException
{
if (lockPool == null)
throw new ExpiredObjectException("Invalid");
// Does another thread in this JVM have the lock?
if (obtainedWrite || obtainedRead > 0)
throw new LocalLockException(LOCKEDANOTHERTHREAD);
// We've got the local non-ex write token
if (obtainedNonExWrite > 0)
{
obtainedNonExWrite++;
return;
}
obtainGlobalNonExWriteLockNoWait();
obtainedNonExWrite++;
}
protected void obtainGlobalNonExWriteLockNoWait()
throws ManifoldCFException, LockException, InterruptedException
{
}
protected void obtainGlobalNonExWriteLock()
throws ManifoldCFException, InterruptedException
{
while (true)
{
try
{
obtainGlobalNonExWriteLockNoWait();
return;
}
catch (LockException e)
{
// Cross JVM lock; sleep!
ManifoldCF.sleep(10L);
}
}
}
public synchronized boolean leaveNonExWriteLock()
throws ManifoldCFException, InterruptedException, ExpiredObjectException
{
if (lockPool == null)
throw new ExpiredObjectException("Invalid");
if (obtainedNonExWrite == 0)
throw new RuntimeException("JVM error: Don't hold lock for object "+this.toString());
if (obtainedNonExWrite > 1)
{
obtainedNonExWrite--;
return false;
}
clearGlobalNonExWriteLock();
obtainedNonExWrite--;
notifyAll();
return true;
}
protected void clearGlobalNonExWriteLockNoWait()
throws ManifoldCFException, LockException, InterruptedException
{
}
protected void clearGlobalNonExWriteLock()
throws ManifoldCFException, InterruptedException
{
while (true)
{
try
{
clearGlobalNonExWriteLockNoWait();
return;
}
catch (LockException e)
{
ManifoldCF.sleep(10L);
}
}
}
public synchronized void enterReadLock()
throws ManifoldCFException, InterruptedException, ExpiredObjectException
{
while (true)
{
if (lockPool == null)
throw new ExpiredObjectException("Invalid");
try
{
if (obtainedWrite || obtainedNonExWrite > 0)
throw new LocalLockException(LOCKEDANOTHERTHREAD);
if (obtainedRead > 0)
{
obtainedRead++;
return;
}
// Got the read token locally!
obtainGlobalReadLock();
obtainedRead = 1;
return;
}
catch (LocalLockException le)
{
wait();
}
}
}
public synchronized void enterReadLockNoWait()
throws ManifoldCFException, LockException, LocalLockException, InterruptedException, ExpiredObjectException
{
if (lockPool == null)
throw new ExpiredObjectException("Invalid");
if (obtainedWrite || obtainedNonExWrite > 0)
throw new LocalLockException(LOCKEDANOTHERTHREAD);
if (obtainedRead > 0)
{
obtainedRead++;
return;
}
// Got the read token locally!
obtainGlobalReadLockNoWait();
obtainedRead = 1;
}
protected void obtainGlobalReadLockNoWait()
throws ManifoldCFException, LockException, InterruptedException
{
}
protected void obtainGlobalReadLock()
throws ManifoldCFException, InterruptedException
{
while (true)
{
try
{
obtainGlobalReadLockNoWait();
return;
}
catch (LockException e)
{
// Cross JVM lock; sleep!
ManifoldCF.sleep(10L);
}
}
}
public synchronized boolean leaveReadLock()
throws ManifoldCFException, InterruptedException, ExpiredObjectException
{
if (lockPool == null)
throw new ExpiredObjectException("Invalid");
if (obtainedRead == 0)
throw new RuntimeException("JVM error: Don't hold lock for object "+this.toString());
if (obtainedRead > 1)
{
obtainedRead--;
return false;
}
clearGlobalReadLock();
obtainedRead--;
notifyAll();
return true;
}
protected void clearGlobalReadLockNoWait()
throws ManifoldCFException, LockException, InterruptedException
{
}
protected void clearGlobalReadLock()
throws ManifoldCFException, InterruptedException
{
while (true)
{
try
{
clearGlobalReadLockNoWait();
return;
}
catch (LockException e)
{
ManifoldCF.sleep(10L);
}
}
}
}