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LockManagerImpl.java
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LockManagerImpl.java
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/*
* Copyright (c) 2002-2016 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.kernel.impl.locking.community;
import java.time.Clock;
import java.util.HashMap;
import java.util.Map;
import org.neo4j.graphdb.factory.GraphDatabaseSettings;
import org.neo4j.helpers.collection.Visitor;
import org.neo4j.kernel.DeadlockDetectedException;
import org.neo4j.kernel.configuration.Config;
import org.neo4j.kernel.impl.transaction.IllegalResourceException;
import org.neo4j.logging.Logger;
public class LockManagerImpl
{
private final Map<Object,RWLock> resourceLockMap = new HashMap<>();
private final RagManager ragManager;
private Clock clock;
/**
* Time within which any particular lock should be acquired.
* @see GraphDatabaseSettings#lock_acquisition_timeout
*/
private long lockAcquisitionTimeoutMillis;
public LockManagerImpl( RagManager ragManager, Config config, Clock clock )
{
this.ragManager = ragManager;
this.clock = clock;
this.lockAcquisitionTimeoutMillis = config.get( GraphDatabaseSettings.lock_acquisition_timeout );
}
public boolean getReadLock( LockResource resource, Object tx )
throws DeadlockDetectedException, IllegalResourceException
{
return unusedResourceGuard( resource, tx, getRWLockForAcquiring( resource, tx ).acquireReadLock( tx ) );
}
public boolean tryReadLock( LockResource resource, Object tx )
throws IllegalResourceException
{
return unusedResourceGuard( resource, tx, getRWLockForAcquiring( resource, tx ).tryAcquireReadLock( tx ) );
}
public boolean getWriteLock( LockResource resource, Object tx )
throws DeadlockDetectedException, IllegalResourceException
{
return unusedResourceGuard( resource, tx, getRWLockForAcquiring( resource, tx ).acquireWriteLock( tx ) );
}
public boolean tryWriteLock( LockResource resource, Object tx )
throws IllegalResourceException
{
return unusedResourceGuard( resource, tx, getRWLockForAcquiring( resource, tx ).tryAcquireWriteLock( tx ) );
}
public void releaseReadLock( Object resource, Object tx )
throws LockNotFoundException, IllegalResourceException
{
getRWLockForReleasing( resource, tx, 1, 0, true ).releaseReadLock( tx );
}
public void releaseWriteLock( Object resource, Object tx )
throws LockNotFoundException, IllegalResourceException
{
getRWLockForReleasing( resource, tx, 0, 1, true ).releaseWriteLock( tx );
}
public void dumpLocksOnResource( final Object resource, Logger logger )
{
final RWLock lock;
synchronized ( resourceLockMap )
{
if ( !resourceLockMap.containsKey( resource ) )
{
logger.log( "No locks on " + resource );
return;
}
lock = resourceLockMap.get( resource );
}
logger.bulk( bulkLogger -> {
bulkLogger.log( "Dump locks on resource %s", resource );
lock.logTo( bulkLogger );
} );
}
/**
* Check if lock was obtained and in case if not will try to clear optimistically allocated lock from global
* resource map
*
* @return {@code lockObtained }
**/
private boolean unusedResourceGuard( Object resource, Object tx, boolean lockObtained )
{
if ( !lockObtained )
{
// if lock was not acquired cleaning up optimistically allocated value
// for case when it was only used by current call, if it was used by somebody else
// lock will be released during release call
getRWLockForReleasing( resource, tx, 0, 0, false );
}
return lockObtained;
}
/**
* Visit all locks.
* <p/>
* The supplied visitor may not block.
*
* @param visitor visitor for visiting each lock.
*/
public void accept( Visitor<RWLock,RuntimeException> visitor )
{
synchronized ( resourceLockMap )
{
for ( RWLock lock : resourceLockMap.values() )
{
if ( visitor.visit( lock ) )
{
break;
}
}
}
}
private void assertValidArguments( Object resource, Object tx )
{
if ( resource == null || tx == null )
{
throw new IllegalResourceException( "Null parameter: resource = " + resource + ", tx = " + tx );
}
}
private RWLock getRWLockForAcquiring( LockResource resource, Object tx )
{
assertValidArguments( resource, tx );
synchronized ( resourceLockMap )
{
RWLock lock = resourceLockMap.get( resource );
if ( lock == null )
{
lock = createLock( resource );
resourceLockMap.put( resource, lock );
}
lock.mark();
return lock;
}
}
// visible for testing
protected RWLock createLock( LockResource resource )
{
return new RWLock( resource, ragManager, clock, lockAcquisitionTimeoutMillis );
}
private RWLock getRWLockForReleasing( Object resource, Object tx, int readCountPrerequisite,
int writeCountPrerequisite, boolean strict )
{
assertValidArguments( resource, tx );
synchronized ( resourceLockMap )
{
RWLock lock = resourceLockMap.get( resource );
if ( lock == null )
{
if ( !strict )
{
return null;
}
throw new LockNotFoundException( "Lock not found for: "
+ resource + " tx:" + tx );
}
// we need to get info from a couple of synchronized methods
// to make it info consistent we need to synchronized lock to make sure it will not change between
// various calls
//noinspection SynchronizationOnLocalVariableOrMethodParameter
synchronized ( lock )
{
if ( !lock.isMarked() && lock.getReadCount() == readCountPrerequisite &&
lock.getWriteCount() == writeCountPrerequisite &&
lock.getWaitingThreadsCount() == 0 )
{
resourceLockMap.remove( resource );
}
}
return lock;
}
}
}