diff options
Diffstat (limited to 'java/lang/ref')
-rw-r--r-- | java/lang/ref/Reference.java | 13 | ||||
-rw-r--r-- | java/lang/ref/ReferenceQueue.java | 57 |
2 files changed, 44 insertions, 26 deletions
diff --git a/java/lang/ref/Reference.java b/java/lang/ref/Reference.java index 8a7501863..ce224b891 100644 --- a/java/lang/ref/Reference.java +++ b/java/lang/ref/Reference.java @@ -1,5 +1,5 @@ /* java.lang.ref.Reference - Copyright (C) 1999, 2002, 2003, 2004 Free Software Foundation, Inc. + Copyright (C) 1999, 2002, 2003, 2004, 2006 Free Software Foundation, Inc. This file is part of GNU Classpath. @@ -82,7 +82,7 @@ public abstract class Reference<T> * The queue this reference is registered on. This is null, if this * wasn't registered to any queue or reference was already enqueued. */ - ReferenceQueue<? super T> queue; + volatile ReferenceQueue<? super T> queue; /** * Link to the next entry on the queue. If this is null, this @@ -91,7 +91,7 @@ public abstract class Reference<T> * (not to null, that value is used to mark a not enqueued * reference). */ - Reference nextOnQueue; + volatile Reference nextOnQueue; /** * This lock should be taken by the garbage collector, before @@ -166,11 +166,10 @@ public abstract class Reference<T> */ public boolean enqueue() { - if (queue != null && nextOnQueue == null) + ReferenceQueue q = queue; + if (q != null) { - queue.enqueue(this); - queue = null; - return true; + return q.enqueue(this); } return false; } diff --git a/java/lang/ref/ReferenceQueue.java b/java/lang/ref/ReferenceQueue.java index 189b81b17..281628779 100644 --- a/java/lang/ref/ReferenceQueue.java +++ b/java/lang/ref/ReferenceQueue.java @@ -1,5 +1,5 @@ /* java.lang.ref.ReferenceQueue - Copyright (C) 1999, 2004 Free Software Foundation, Inc. + Copyright (C) 1999, 2004, 2006 Free Software Foundation, Inc. This file is part of GNU Classpath. @@ -63,6 +63,12 @@ public class ReferenceQueue<T> private Reference<? extends T> first; /** + * This is the lock that protects our linked list and is used to signal + * a thread waiting in remove(). + */ + private final Object lock = new Object(); + + /** * Creates a new empty reference queue. */ public ReferenceQueue() @@ -76,7 +82,7 @@ public class ReferenceQueue<T> * @return a reference on the queue, if there is one, * <code>null</code> otherwise. */ - public synchronized Reference<? extends T> poll() + public Reference<? extends T> poll() { return dequeue(); } @@ -84,14 +90,23 @@ public class ReferenceQueue<T> /** * This is called by reference to enqueue itself on this queue. * @param ref the reference that should be enqueued. + * @return true if successful, false if not. */ - synchronized void enqueue(Reference<? extends T> ref) - { - /* last reference will point to itself */ - ref.nextOnQueue = first == null ? ref : first; - first = ref; - /* this wakes only one remove thread. */ - notify(); + final boolean enqueue(Reference<? extends T> ref) + { + synchronized (lock) + { + if (ref.queue != this) + return false; + + /* last reference will point to itself */ + ref.nextOnQueue = first == null ? ref : first; + ref.queue = null; + first = ref; + /* this wakes only one remove thread. */ + lock.notify(); + return true; + } } /** @@ -100,13 +115,16 @@ public class ReferenceQueue<T> */ private Reference<? extends T> dequeue() { - if (first == null) - return null; - - Reference<? extends T> result = first; - first = (first == first.nextOnQueue) ? null : first.nextOnQueue; - result.nextOnQueue = null; - return result; + synchronized (lock) + { + if (first == null) + return null; + + Reference<? extends T> result = first; + first = (first == first.nextOnQueue) ? null : first.nextOnQueue; + result.nextOnQueue = null; + return result; + } } /** @@ -118,12 +136,13 @@ public class ReferenceQueue<T> * <code>null</code> if timeout period expired. * @exception InterruptedException if the wait was interrupted. */ - public synchronized Reference<? extends T> remove(long timeout) + public Reference<? extends T> remove(long timeout) throws InterruptedException { - if (first == null) + synchronized (lock) { - wait(timeout); + if (first == null) + lock.wait(timeout); } return dequeue(); |