Diff of /jsr166/src/main/java/util/concurrent/SynchronousQueue.java

	revision 1.55, Mon Aug 1 15:26:40 2005 UTC	revision 1.56, Wed Aug 3 18:57:28 2005 UTC
#	Line 47	Line 47
47	* Java Collections Framework</a>.	* Java Collections Framework</a>.
48	*	*
49	* @since 1.5	* @since 1.5
50	* @author Doug Lea	* @author Doug Lea and Bill Scherer and Michael Scott
51	* @param <E> the type of elements held in this collection	* @param <E> the type of elements held in this collection
52	*/	*/
53	public class SynchronousQueue<E> extends AbstractQueue<E>	public class SynchronousQueue<E> extends AbstractQueue<E>
#	Line 98	Line 98
98	* of further adaptations.	* of further adaptations.
99	* 2. SynchronousQueues must block threads waiting to become	* 2. SynchronousQueues must block threads waiting to become
100	* fulfilled.	* fulfilled.
101	* 3. Nodes/threads that have been cancelled due to timeouts	* 3. Support for cancellation via timeout and interrupts,
102	* or interruptions are cleaned out of the lists to	* including cleaning out cancelled nodes/threads
103	* avoid garbage retention and memory depletion.	* from lists to avoid garbage retention and memory depletion.
104	*	*
105	* Blocking is mainly accomplished using LockSupport park/unpark,	* Blocking is mainly accomplished using LockSupport park/unpark,
106	* except that nodes that appear to be the next ones to become	* except that nodes that appear to be the next ones to become
#	Line 156	Line 156
156	/**	/**
157	* The number of times to spin before blocking in timed waits.	* The number of times to spin before blocking in timed waits.
158	* The value is empirically derived -- it works well across a	* The value is empirically derived -- it works well across a
159	* variety of processors and OSes. Emprically, the best value	* variety of processors and OSes. Empirically, the best value
160	* seems not to vary with number of CPUs (beyond 2) so is just	* seems not to vary with number of CPUs (beyond 2) so is just
161	* a constant.	* a constant.
162	*/	*/
#	Line 430	Line 430
430	*/	*/
431	boolean shouldSpin(SNode s) {	boolean shouldSpin(SNode s) {
432	SNode h = head;	SNode h = head;
433	return (h == null \|\| h == s \|\| isFulfilling(h.mode));	return (h == s \|\| h == null \|\| isFulfilling(h.mode));
434	}	}
435
436	/**	/**
#	Line 522	Line 522
522	boolean isCancelled() {	boolean isCancelled() {
523	return item == this;	return item == this;
524	}	}
525
526		/**
527		* Return true if this node is known to be off the queue
528		* because its next pointer has been forgotten due to
529		* an advanceHead operation.
530		*/
531		boolean isOffList() {
532		return next == this;
533		}
534	}	}
535
536	/** Head of queue */	/** Head of queue */
#	Line 638	Line 647
647	return null;	return null;
648	}	}
649
650	if (s.next != s) { // not already unlinked	if (!s.isOffList()) { // not already unlinked
651	advanceHead(t, s); // unlink	advanceHead(t, s); // unlink if head
652	if (x != null) // and forget fields	if (x != null) // and forget fields
653	s.item = s;	s.item = s;
654	s.waiter = null;	s.waiter = null;
#	Line 764	Line 773
773	/**	/**
774	* The transferer. Set only in constructor, but cannot be declared	* The transferer. Set only in constructor, but cannot be declared
775	* as final without further complicating serialization. Since	* as final without further complicating serialization. Since
776	* this is accessed only once per public method, there isn't a	* this is accessed only at most once per public method, there
777	* noticeable performance penalty for using volatile instead of	* isn't a noticeable performance penalty for using volatile
778	* final here.	* instead of final here.
779	*/	*/
780	private transient volatile Transferer transferer;	private transient volatile Transferer transferer;
781

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