src/java.base/share/classes/jdk/internal/ref/CleanerImpl.java - platform/libcore - Git at Google

 /*
  * Copyright (c) 2015, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this
  * particular file as subject to the "Classpath" exception as provided
  * by Oracle in the LICENSE file that accompanied this code.
  *
  * This code 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
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  */

 package jdk.internal.ref;

 import java.lang.ref.Cleaner;
 import java.lang.ref.Cleaner.Cleanable;
 import java.lang.ref.ReferenceQueue;
 import java.security.AccessController;
 import java.security.PrivilegedAction;
 import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.Function;

 import jdk.internal.misc.InnocuousThread;

 /**
  * CleanerImpl manages a set of object references and corresponding cleaning actions.
  * CleanerImpl provides the functionality of {@link java.lang.ref.Cleaner}.
  */
 public final class CleanerImpl implements Runnable {

     /**
      * An object to access the CleanerImpl from a Cleaner; set by Cleaner init.
      */
     private static Function<Cleaner, CleanerImpl> cleanerImplAccess = null;

     /**
      * Heads of a CleanableList for each reference type.
      */
     final PhantomCleanable<?> phantomCleanableList;

     final WeakCleanable<?> weakCleanableList;

     final SoftCleanable<?> softCleanableList;

     // The ReferenceQueue of pending cleaning actions
     final ReferenceQueue<Object> queue;

     /**
      * Called by Cleaner static initialization to provide the function
      * to map from Cleaner to CleanerImpl.
      * @param access a function to map from Cleaner to CleanerImpl
      */
     public static void setCleanerImplAccess(Function<Cleaner, CleanerImpl> access) {
         if (cleanerImplAccess == null) {
             cleanerImplAccess = access;
         } else {
             throw new InternalError("cleanerImplAccess");
         }
     }

     /**
      * Called to get the CleanerImpl for a Cleaner.
      * @param cleaner the cleaner
      * @return the corresponding CleanerImpl
      */
     static CleanerImpl getCleanerImpl(Cleaner cleaner) {
         return cleanerImplAccess.apply(cleaner);
     }

     /**
      * Constructor for CleanerImpl.
      */
     public CleanerImpl() {
         queue = new ReferenceQueue<>();
         phantomCleanableList = new PhantomCleanableRef();
         weakCleanableList = new WeakCleanableRef();
         softCleanableList = new SoftCleanableRef();
     }

     /**
      * Starts the Cleaner implementation.
      * Ensure this is the CleanerImpl for the Cleaner.
      * When started waits for Cleanables to be queued.
      * @param cleaner the cleaner
      * @param threadFactory the thread factory
      */
     public void start(Cleaner cleaner, ThreadFactory threadFactory) {
         if (getCleanerImpl(cleaner) != this) {
             throw new AssertionError("wrong cleaner");
         }
         // schedule a nop cleaning action for the cleaner, so the associated thread
         // will continue to run at least until the cleaner is reclaimable.
         new CleanerCleanable(cleaner);

         if (threadFactory == null) {
             threadFactory = CleanerImpl.InnocuousThreadFactory.factory();
         }

         // now that there's at least one cleaning action, for the cleaner,
         // we can start the associated thread, which runs until
         // all cleaning actions have been run.
         Thread thread = threadFactory.newThread(this);
         thread.setDaemon(true);
         thread.start();
     }

     /**
      * Process queued Cleanables as long as the cleanable lists are not empty.
      * A Cleanable is in one of the lists for each Object and for the Cleaner
      * itself.
      * Terminates when the Cleaner is no longer reachable and
      * has been cleaned and there are no more Cleanable instances
      * for which the object is reachable.
      * <p>
      * If the thread is a ManagedLocalsThread, the threadlocals
      * are erased before each cleanup
      */
     @Override
     public void run() {
         Thread t = Thread.currentThread();
         InnocuousThread mlThread = (t instanceof InnocuousThread)
                 ? (InnocuousThread) t
                 : null;
         while (!phantomCleanableList.isListEmpty() ||
                 !weakCleanableList.isListEmpty() ||
                 !softCleanableList.isListEmpty()) {
             if (mlThread != null) {
                 // Clear the thread locals
                 mlThread.eraseThreadLocals();
             }
             try {
                 // Wait for a Ref, with a timeout to avoid getting hung
                 // due to a race with clear/clean
                 Cleanable ref = (Cleanable) queue.remove(60 * 1000L);
                 if (ref != null) {
                     ref.clean();
                 }
             } catch (Throwable e) {
                 // ignore exceptions from the cleanup action
                 // (including interruption of cleanup thread)
             }
         }
     }

     /**
      * Perform cleaning on an unreachable PhantomReference.
      */
     public static final class PhantomCleanableRef extends PhantomCleanable<Object> {
         private final Runnable action;

         /**
          * Constructor for a phantom cleanable reference.
          * @param obj the object to monitor
          * @param cleaner the cleaner
          * @param action the action Runnable
          */
         public PhantomCleanableRef(Object obj, Cleaner cleaner, Runnable action) {
             super(obj, cleaner);
             this.action = action;
         }

         /**
          * Constructor used only for root of phantom cleanable list.
          */
         PhantomCleanableRef() {
             super();
             this.action = null;
         }

         @Override
         protected void performCleanup() {
             action.run();
         }

         /**
          * Prevent access to referent even when it is still alive.
          *
          * @throws UnsupportedOperationException always
          */
         @Override
         public Object get() {
             throw new UnsupportedOperationException("get");
         }

         /**
          * Direct clearing of the referent is not supported.
          *
          * @throws UnsupportedOperationException always
          */
         @Override
         public void clear() {
             throw new UnsupportedOperationException("clear");
         }
     }

     /**
      * Perform cleaning on an unreachable WeakReference.
      */
     public static final class WeakCleanableRef extends WeakCleanable<Object> {
         private final Runnable action;

         /**
          * Constructor for a weak cleanable reference.
          * @param obj the object to monitor
          * @param cleaner the cleaner
          * @param action the action Runnable
          */
         WeakCleanableRef(Object obj, Cleaner cleaner, Runnable action) {
             super(obj, cleaner);
             this.action = action;
         }

         /**
          * Constructor used only for root of weak cleanable list.
          */
         WeakCleanableRef() {
             super();
             this.action = null;
         }

         @Override
         protected void performCleanup() {
             action.run();
         }

         /**
          * Prevent access to referent even when it is still alive.
          *
          * @throws UnsupportedOperationException always
          */
         @Override
         public Object get() {
             throw new UnsupportedOperationException("get");
         }

         /**
          * Direct clearing of the referent is not supported.
          *
          * @throws UnsupportedOperationException always
          */
         @Override
         public void clear() {
             throw new UnsupportedOperationException("clear");
         }
     }

     /**
      * Perform cleaning on an unreachable SoftReference.
      */
     public static final class SoftCleanableRef extends SoftCleanable<Object> {
         private final Runnable action;

         /**
          * Constructor for a soft cleanable reference.
          * @param obj the object to monitor
          * @param cleaner the cleaner
          * @param action the action Runnable
          */
         SoftCleanableRef(Object obj, Cleaner cleaner, Runnable action) {
             super(obj, cleaner);
             this.action = action;
         }

         /**
          * Constructor used only for root of soft cleanable list.
          */
         SoftCleanableRef() {
             super();
             this.action = null;
         }

         @Override
         protected void performCleanup() {
             action.run();
         }

         /**
          * Prevent access to referent even when it is still alive.
          *
          * @throws UnsupportedOperationException always
          */
         @Override
         public Object get() {
             throw new UnsupportedOperationException("get");
         }

         /**
          * Direct clearing of the referent is not supported.
          *
          * @throws UnsupportedOperationException always
          */
         @Override
         public void clear() {
             throw new UnsupportedOperationException("clear");
         }

     }

     /**
      * A ThreadFactory for InnocuousThreads.
      * The factory is a singleton.
      */
     static final class InnocuousThreadFactory implements ThreadFactory {
         final static ThreadFactory factory = new InnocuousThreadFactory();

         static ThreadFactory factory() {
             return factory;
         }

         final AtomicInteger cleanerThreadNumber = new AtomicInteger();

         public Thread newThread(Runnable r) {
             return AccessController.doPrivileged(new PrivilegedAction<>() {
                 @Override
                 public Thread run() {
                     Thread t = InnocuousThread.newThread(r);
                     t.setPriority(Thread.MAX_PRIORITY - 2);
                     t.setName("Cleaner-" + cleanerThreadNumber.getAndIncrement());
                     return t;
                 }
             });
         }
     }

     /**
      * A PhantomCleanable implementation for tracking the Cleaner itself.
      */
     static final class CleanerCleanable extends PhantomCleanable<Cleaner> {
         CleanerCleanable(Cleaner cleaner) {
             super(cleaner, cleaner);
         }

         @Override
         protected void performCleanup() {
             // no action
         }
     }
 }
	/*
	* Copyright (c) 2015, 2016, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code 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
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package jdk.internal.ref;

	import java.lang.ref.Cleaner;
	import java.lang.ref.Cleaner.Cleanable;
	import java.lang.ref.ReferenceQueue;
	import java.security.AccessController;
	import java.security.PrivilegedAction;
	import java.util.concurrent.ThreadFactory;
	import java.util.concurrent.atomic.AtomicInteger;
	import java.util.function.Function;

	import jdk.internal.misc.InnocuousThread;

	/**
	* CleanerImpl manages a set of object references and corresponding cleaning actions.
	* CleanerImpl provides the functionality of {@link java.lang.ref.Cleaner}.
	*/
	public final class CleanerImpl implements Runnable {

	/**
	* An object to access the CleanerImpl from a Cleaner; set by Cleaner init.
	*/
	private static Function<Cleaner, CleanerImpl> cleanerImplAccess = null;

	/**
	* Heads of a CleanableList for each reference type.
	*/
	final PhantomCleanable<?> phantomCleanableList;

	final WeakCleanable<?> weakCleanableList;

	final SoftCleanable<?> softCleanableList;

	// The ReferenceQueue of pending cleaning actions
	final ReferenceQueue<Object> queue;

	/**
	* Called by Cleaner static initialization to provide the function
	* to map from Cleaner to CleanerImpl.
	* @param access a function to map from Cleaner to CleanerImpl
	*/
	public static void setCleanerImplAccess(Function<Cleaner, CleanerImpl> access) {
	if (cleanerImplAccess == null) {
	cleanerImplAccess = access;
	} else {
	throw new InternalError("cleanerImplAccess");
	}
	}

	/**
	* Called to get the CleanerImpl for a Cleaner.
	* @param cleaner the cleaner
	* @return the corresponding CleanerImpl
	*/
	static CleanerImpl getCleanerImpl(Cleaner cleaner) {
	return cleanerImplAccess.apply(cleaner);
	}

	/**
	* Constructor for CleanerImpl.
	*/
	public CleanerImpl() {
	queue = new ReferenceQueue<>();
	phantomCleanableList = new PhantomCleanableRef();
	weakCleanableList = new WeakCleanableRef();
	softCleanableList = new SoftCleanableRef();
	}

	/**
	* Starts the Cleaner implementation.
	* Ensure this is the CleanerImpl for the Cleaner.
	* When started waits for Cleanables to be queued.
	* @param cleaner the cleaner
	* @param threadFactory the thread factory
	*/
	public void start(Cleaner cleaner, ThreadFactory threadFactory) {
	if (getCleanerImpl(cleaner) != this) {
	throw new AssertionError("wrong cleaner");
	}
	// schedule a nop cleaning action for the cleaner, so the associated thread
	// will continue to run at least until the cleaner is reclaimable.
	new CleanerCleanable(cleaner);

	if (threadFactory == null) {
	threadFactory = CleanerImpl.InnocuousThreadFactory.factory();
	}

	// now that there's at least one cleaning action, for the cleaner,
	// we can start the associated thread, which runs until
	// all cleaning actions have been run.
	Thread thread = threadFactory.newThread(this);
	thread.setDaemon(true);
	thread.start();
	}

	/**
	* Process queued Cleanables as long as the cleanable lists are not empty.
	* A Cleanable is in one of the lists for each Object and for the Cleaner
	* itself.
	* Terminates when the Cleaner is no longer reachable and
	* has been cleaned and there are no more Cleanable instances
	* for which the object is reachable.
	* <p>
	* If the thread is a ManagedLocalsThread, the threadlocals
	* are erased before each cleanup
	*/
	@Override
	public void run() {
	Thread t = Thread.currentThread();
	InnocuousThread mlThread = (t instanceof InnocuousThread)
	? (InnocuousThread) t
	: null;
	while (!phantomCleanableList.isListEmpty() \|\|
	!weakCleanableList.isListEmpty() \|\|
	!softCleanableList.isListEmpty()) {
	if (mlThread != null) {
	// Clear the thread locals
	mlThread.eraseThreadLocals();
	}
	try {
	// Wait for a Ref, with a timeout to avoid getting hung
	// due to a race with clear/clean
	Cleanable ref = (Cleanable) queue.remove(60 * 1000L);
	if (ref != null) {
	ref.clean();
	}
	} catch (Throwable e) {
	// ignore exceptions from the cleanup action
	// (including interruption of cleanup thread)
	}
	}
	}

	/**
	* Perform cleaning on an unreachable PhantomReference.
	*/
	public static final class PhantomCleanableRef extends PhantomCleanable<Object> {
	private final Runnable action;

	/**
	* Constructor for a phantom cleanable reference.
	* @param obj the object to monitor
	* @param cleaner the cleaner
	* @param action the action Runnable
	*/
	public PhantomCleanableRef(Object obj, Cleaner cleaner, Runnable action) {
	super(obj, cleaner);
	this.action = action;
	}

	/**
	* Constructor used only for root of phantom cleanable list.
	*/
	PhantomCleanableRef() {
	super();
	this.action = null;
	}

	@Override
	protected void performCleanup() {
	action.run();
	}

	/**
	* Prevent access to referent even when it is still alive.
	*
	* @throws UnsupportedOperationException always
	*/
	@Override
	public Object get() {
	throw new UnsupportedOperationException("get");
	}

	/**
	* Direct clearing of the referent is not supported.
	*
	* @throws UnsupportedOperationException always
	*/
	@Override
	public void clear() {
	throw new UnsupportedOperationException("clear");
	}
	}

	/**
	* Perform cleaning on an unreachable WeakReference.
	*/
	public static final class WeakCleanableRef extends WeakCleanable<Object> {
	private final Runnable action;

	/**
	* Constructor for a weak cleanable reference.
	* @param obj the object to monitor
	* @param cleaner the cleaner
	* @param action the action Runnable
	*/
	WeakCleanableRef(Object obj, Cleaner cleaner, Runnable action) {
	super(obj, cleaner);
	this.action = action;
	}

	/**
	* Constructor used only for root of weak cleanable list.
	*/
	WeakCleanableRef() {
	super();
	this.action = null;
	}

	@Override
	protected void performCleanup() {
	action.run();
	}

	/**
	* Prevent access to referent even when it is still alive.
	*
	* @throws UnsupportedOperationException always
	*/
	@Override
	public Object get() {
	throw new UnsupportedOperationException("get");
	}

	/**
	* Direct clearing of the referent is not supported.
	*
	* @throws UnsupportedOperationException always
	*/
	@Override
	public void clear() {
	throw new UnsupportedOperationException("clear");
	}
	}

	/**
	* Perform cleaning on an unreachable SoftReference.
	*/
	public static final class SoftCleanableRef extends SoftCleanable<Object> {
	private final Runnable action;

	/**
	* Constructor for a soft cleanable reference.
	* @param obj the object to monitor
	* @param cleaner the cleaner
	* @param action the action Runnable
	*/
	SoftCleanableRef(Object obj, Cleaner cleaner, Runnable action) {
	super(obj, cleaner);
	this.action = action;
	}

	/**
	* Constructor used only for root of soft cleanable list.
	*/
	SoftCleanableRef() {
	super();
	this.action = null;
	}

	@Override
	protected void performCleanup() {
	action.run();
	}

	/**
	* Prevent access to referent even when it is still alive.
	*
	* @throws UnsupportedOperationException always
	*/
	@Override
	public Object get() {
	throw new UnsupportedOperationException("get");
	}

	/**
	* Direct clearing of the referent is not supported.
	*
	* @throws UnsupportedOperationException always
	*/
	@Override
	public void clear() {
	throw new UnsupportedOperationException("clear");
	}

	}

	/**
	* A ThreadFactory for InnocuousThreads.
	* The factory is a singleton.
	*/
	static final class InnocuousThreadFactory implements ThreadFactory {
	final static ThreadFactory factory = new InnocuousThreadFactory();

	static ThreadFactory factory() {
	return factory;
	}

	final AtomicInteger cleanerThreadNumber = new AtomicInteger();

	public Thread newThread(Runnable r) {
	return AccessController.doPrivileged(new PrivilegedAction<>() {
	@Override
	public Thread run() {
	Thread t = InnocuousThread.newThread(r);
	t.setPriority(Thread.MAX_PRIORITY - 2);
	t.setName("Cleaner-" + cleanerThreadNumber.getAndIncrement());
	return t;
	}
	});
	}
	}

	/**
	* A PhantomCleanable implementation for tracking the Cleaner itself.
	*/
	static final class CleanerCleanable extends PhantomCleanable<Cleaner> {
	CleanerCleanable(Cleaner cleaner) {
	super(cleaner, cleaner);
	}

	@Override
	protected void performCleanup() {
	// no action
	}
	}
	}