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Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.21 by jsr166, Fri Jul 24 23:47:01 2009 UTC vs.
Revision 1.47 by jsr166, Wed Aug 5 15:40:09 2009 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.locks.*;
11	<	import java.util.concurrent.atomic.*;
10	>
11	>	import java.util.ArrayList;
12	>	import java.util.Arrays;
13	>	import java.util.Collection;
14	>	import java.util.Collections;
15	>	import java.util.List;
16	>	import java.util.concurrent.locks.Condition;
17	>	import java.util.concurrent.locks.LockSupport;
18	>	import java.util.concurrent.locks.ReentrantLock;
19	>	import java.util.concurrent.atomic.AtomicInteger;
20	>	import java.util.concurrent.atomic.AtomicLong;
21
22		/**
23	<	* An {@link ExecutorService} for running {@link ForkJoinTask}s.  A
24	<	* ForkJoinPool provides the entry point for submissions from
25	<	* non-ForkJoinTasks, as well as management and monitoring operations.
26	<	* Normally a single ForkJoinPool is used for a large number of
18	<	* submitted tasks. Otherwise, use would not usually outweigh the
19	<	* construction and bookkeeping overhead of creating a large set of
20	<	* threads.
23	>	* An {@link ExecutorService} for running {@link ForkJoinTask}s.
24	>	* A {@code ForkJoinPool} provides the entry point for submissions
25	>	* from non-{@code ForkJoinTask}s, as well as management and
26	>	* monitoring operations.
27		*
28	<	* <p>ForkJoinPools differ from other kinds of Executors mainly in
29	<	* that they provide <em>work-stealing</em>: all threads in the pool
30	<	* attempt to find and execute subtasks created by other active tasks
31	<	* (eventually blocking if none exist). This makes them efficient when
32	<	* most tasks spawn other subtasks (as do most ForkJoinTasks), as well
33	<	* as the mixed execution of some plain Runnable- or Callable- based
34	<	* activities along with ForkJoinTasks. When setting
35	<	* {@code setAsyncMode}, a ForkJoinPools may also be appropriate for
36	<	* use with fine-grained tasks that are never joined. Otherwise, other
37	<	* ExecutorService implementations are typically more appropriate
38	<	* choices.
28	>	* <p>A {@code ForkJoinPool} differs from other kinds of {@link
29	>	* ExecutorService} mainly by virtue of employing
30	>	* <em>work-stealing</em>: all threads in the pool attempt to find and
31	>	* execute subtasks created by other active tasks (eventually blocking
32	>	* waiting for work if none exist). This enables efficient processing
33	>	* when most tasks spawn other subtasks (as do most {@code
34	>	* ForkJoinTask}s). A {@code ForkJoinPool} may also be used for mixed
35	>	* execution of some plain {@code Runnable}- or {@code Callable}-
36	>	* based activities along with {@code ForkJoinTask}s. When setting
37	>	* {@linkplain #setAsyncMode async mode}, a {@code ForkJoinPool} may
38	>	* also be appropriate for use with fine-grained tasks of any form
39	>	* that are never joined. Otherwise, other {@code ExecutorService}
40	>	* implementations are typically more appropriate choices.
41		*
42	<	* <p>A ForkJoinPool may be constructed with a given parallelism level
43	<	* (target pool size), which it attempts to maintain by dynamically
44	<	* adding, suspending, or resuming threads, even if some tasks are
45	<	* waiting to join others. However, no such adjustments are performed
46	<	* in the face of blocked IO or other unmanaged synchronization. The
47	<	* nested {@code ManagedBlocker} interface enables extension of
48	<	* the kinds of synchronization accommodated.  The target parallelism
49	<	* level may also be changed dynamically ({@code setParallelism})
50	<	* and thread construction can be limited using methods
51	<	* {@code setMaximumPoolSize} and/or
52	<	* {@code setMaintainsParallelism}.
42	>	* <p>A {@code ForkJoinPool} is constructed with a given target
43	>	* parallelism level; by default, equal to the number of available
44	>	* processors. Unless configured otherwise via {@link
45	>	* #setMaintainsParallelism}, the pool attempts to maintain this
46	>	* number of active (or available) threads by dynamically adding,
47	>	* suspending, or resuming internal worker threads, even if some tasks
48	>	* are stalled waiting to join others. However, no such adjustments
49	>	* are performed in the face of blocked IO or other unmanaged
50	>	* synchronization. The nested {@link ManagedBlocker} interface
51	>	* enables extension of the kinds of synchronization accommodated.
52	>	* The target parallelism level may also be changed dynamically
53	>	* ({@link #setParallelism}). The total number of threads may be
54	>	* limited using method {@link #setMaximumPoolSize}, in which case it
55	>	* may become possible for the activities of a pool to stall due to
56	>	* the lack of available threads to process new tasks.
57		*
58		* <p>In addition to execution and lifecycle control methods, this
59		* class provides status check methods (for example
60	<	* {@code getStealCount}) that are intended to aid in developing,
60	>	* {@link #getStealCount}) that are intended to aid in developing,
61		* tuning, and monitoring fork/join applications. Also, method
62	<	* {@code toString} returns indications of pool state in a
62	>	* {@link #toString} returns indications of pool state in a
63		* convenient form for informal monitoring.
64		*
65	+	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
66	+	* used for all parallel task execution in a program or subsystem.
67	+	* Otherwise, use would not usually outweigh the construction and
68	+	* bookkeeping overhead of creating a large set of threads. For
69	+	* example, a common pool could be used for the {@code SortTasks}
70	+	* illustrated in {@link RecursiveAction}. Because {@code
71	+	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
72	+	* daemon} mode, there is typically no need to explicitly {@link
73	+	* #shutdown} such a pool upon program exit.
74	+	*
75	+	* <pre>
76	+	* static final ForkJoinPool mainPool = new ForkJoinPool();
77	+	* ...
78	+	* public void sort(long[] array) {
79	+	*   mainPool.invoke(new SortTask(array, 0, array.length));
80	+	* }
81	+	* </pre>
82	+	*
83		* <p><b>Implementation notes</b>: This implementation restricts the
84		* maximum number of running threads to 32767. Attempts to create
85		* pools with greater than the maximum result in
86	<	* IllegalArgumentExceptions.
86	>	* {@code IllegalArgumentException}.
87		*
88		* @since 1.7
89		* @author Doug Lea
#	Line 72 | Line 102 | public class ForkJoinPool extends Abstra
102		private static final int MAX_THREADS =  0x7FFF;
103
104		/**
105	<	* Factory for creating new ForkJoinWorkerThreads.  A
106	<	* ForkJoinWorkerThreadFactory must be defined and used for
107	<	* ForkJoinWorkerThread subclasses that extend base functionality
108	<	* or initialize threads with different contexts.
105	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
106	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
107	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
108	>	* functionality or initialize threads with different contexts.
109		*/
110		public static interface ForkJoinWorkerThreadFactory {
111		/**
#	Line 302 | Line 332 | public class ForkJoinPool extends Abstra
332		}
333
334		/**
335	<	* Returns true if argument represents zero active count and
336	<	* nonzero runstate, which is the triggering condition for
335	>	* Returns {@code true} if argument represents zero active count
336	>	* and nonzero runstate, which is the triggering condition for
337		* terminating on shutdown.
338		*/
339		private static boolean canTerminateOnShutdown(int c) {
#	Line 333 | Line 363 | public class ForkJoinPool extends Abstra
363		// Constructors
364
365		/**
366	<	* Creates a ForkJoinPool with a pool size equal to the number of
367	<	* processors available on the system, using the default
368	<	* ForkJoinWorkerThreadFactory.
366	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
367	>	* java.lang.Runtime#availableProcessors}, and using the {@linkplain
368	>	* #defaultForkJoinWorkerThreadFactory default thread factory}.
369		*
370		* @throws SecurityException if a security manager exists and
371		*         the caller is not permitted to modify threads
#	Line 348 | Line 378 | public class ForkJoinPool extends Abstra
378		}
379
380		/**
381	<	* Creates a ForkJoinPool with the indicated parallelism level
382	<	* threads and using the default ForkJoinWorkerThreadFactory.
381	>	* Creates a {@code ForkJoinPool} with the indicated parallelism
382	>	* level and using the {@linkplain
383	>	* #defaultForkJoinWorkerThreadFactory default thread factory}.
384		*
385	<	* @param parallelism the number of worker threads
385	>	* @param parallelism the parallelism level
386		* @throws IllegalArgumentException if parallelism less than or
387	<	* equal to zero
387	>	*         equal to zero, or greater than implementation limit
388		* @throws SecurityException if a security manager exists and
389		*         the caller is not permitted to modify threads
390		*         because it does not hold {@link
#	Line 364 | Line 395 | public class ForkJoinPool extends Abstra
395		}
396
397		/**
398	<	* Creates a ForkJoinPool with parallelism equal to the number of
399	<	* processors available on the system and using the given
400	<	* ForkJoinWorkerThreadFactory.
398	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
399	>	* java.lang.Runtime#availableProcessors}, and using the given
400	>	* thread factory.
401		*
402		* @param factory the factory for creating new threads
403		* @throws NullPointerException if factory is null
#	Line 380 | Line 411 | public class ForkJoinPool extends Abstra
411		}
412
413		/**
414	<	* Creates a ForkJoinPool with the given parallelism and factory.
414	>	* Creates a {@code ForkJoinPool} with the given parallelism and
415	>	* thread factory.
416		*
417	<	* @param parallelism the targeted number of worker threads
417	>	* @param parallelism the parallelism level
418		* @param factory the factory for creating new threads
419		* @throws IllegalArgumentException if parallelism less than or
420	<	* equal to zero, or greater than implementation limit
420	>	*         equal to zero, or greater than implementation limit
421		* @throws NullPointerException if factory is null
422		* @throws SecurityException if a security manager exists and
423		*         the caller is not permitted to modify threads
#	Line 414 | Line 446 | public class ForkJoinPool extends Abstra
446		* Creates a new worker thread using factory.
447		*
448		* @param index the index to assign worker
449	<	* @return new worker, or null of factory failed
449	>	* @return new worker, or null if factory failed
450		*/
451		private ForkJoinWorkerThread createWorker(int index) {
452		Thread.UncaughtExceptionHandler h = ueh;
#	Line 435 | Line 467 | public class ForkJoinPool extends Abstra
467		* Currently requires size to be a power of two.
468		*/
469		private static int arraySizeFor(int poolSize) {
470	<	return (poolSize <= 1) ? 1 :
471	<	(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1)));
470	>	if (poolSize <= 1)
471	>	return 1;
472	>	// See Hackers Delight, sec 3.2
473	>	int c = poolSize >= MAX_THREADS ? MAX_THREADS : (poolSize - 1);
474	>	c |= c >>>  1;
475	>	c |= c >>>  2;
476	>	c |= c >>>  4;
477	>	c |= c >>>  8;
478	>	c |= c >>> 16;
479	>	return c + 1;
480		}
481
482		/**
#	Line 539 | Line 579 | public class ForkJoinPool extends Abstra
579		* Common code for execute, invoke and submit
580		*/
581		private <T> void doSubmit(ForkJoinTask<T> task) {
582	+	if (task == null)
583	+	throw new NullPointerException();
584		if (isShutdown())
585		throw new RejectedExecutionException();
586		if (workers == null)
#	Line 567 | Line 609 | public class ForkJoinPool extends Abstra
609		* @throws NullPointerException if task is null
610		* @throws RejectedExecutionException if pool is shut down
611		*/
612	<	public <T> void execute(ForkJoinTask<T> task) {
612	>	public void execute(ForkJoinTask<?> task) {
613		doSubmit(task);
614		}
615
616		// AbstractExecutorService methods
617
618		public void execute(Runnable task) {
619	<	doSubmit(new AdaptedRunnable<Void>(task, null));
619	>	ForkJoinTask<?> job;
620	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
621	>	job = (ForkJoinTask<?>) task;
622	>	else
623	>	job = ForkJoinTask.adapt(task, null);
624	>	doSubmit(job);
625		}
626
627		public <T> ForkJoinTask<T> submit(Callable<T> task) {
628	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
628	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
629		doSubmit(job);
630		return job;
631		}
632
633		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
634	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
634	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
635		doSubmit(job);
636		return job;
637		}
638
639		public ForkJoinTask<?> submit(Runnable task) {
640	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
640	>	ForkJoinTask<?> job;
641	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
642	>	job = (ForkJoinTask<?>) task;
643	>	else
644	>	job = ForkJoinTask.adapt(task, null);
645		doSubmit(job);
646		return job;
647		}
648
649		/**
650	<	* Adaptor for Runnables. This implements RunnableFuture
651	<	* to be compliant with AbstractExecutorService constraints.
650	>	* Submits a ForkJoinTask for execution.
651	>	*
652	>	* @param task the task to submit
653	>	* @return the task
654	>	* @throws RejectedExecutionException if the task cannot be
655	>	*         scheduled for execution
656	>	* @throws NullPointerException if the task is null
657		*/
658	<	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
659	<	implements RunnableFuture<T> {
660	<	final Runnable runnable;
605	<	final T resultOnCompletion;
606	<	T result;
607	<	AdaptedRunnable(Runnable runnable, T result) {
608	<	if (runnable == null) throw new NullPointerException();
609	<	this.runnable = runnable;
610	<	this.resultOnCompletion = result;
611	<	}
612	<	public T getRawResult() { return result; }
613	<	public void setRawResult(T v) { result = v; }
614	<	public boolean exec() {
615	<	runnable.run();
616	<	result = resultOnCompletion;
617	<	return true;
618	<	}
619	<	public void run() { invoke(); }
620	<	private static final long serialVersionUID = 5232453952276885070L;
658	>	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
659	>	doSubmit(task);
660	>	return task;
661		}
662
623	–	/**
624	–	* Adaptor for Callables
625	–	*/
626	–	static final class AdaptedCallable<T> extends ForkJoinTask<T>
627	–	implements RunnableFuture<T> {
628	–	final Callable<T> callable;
629	–	T result;
630	–	AdaptedCallable(Callable<T> callable) {
631	–	if (callable == null) throw new NullPointerException();
632	–	this.callable = callable;
633	–	}
634	–	public T getRawResult() { return result; }
635	–	public void setRawResult(T v) { result = v; }
636	–	public boolean exec() {
637	–	try {
638	–	result = callable.call();
639	–	return true;
640	–	} catch (Error err) {
641	–	throw err;
642	–	} catch (RuntimeException rex) {
643	–	throw rex;
644	–	} catch (Exception ex) {
645	–	throw new RuntimeException(ex);
646	–	}
647	–	}
648	–	public void run() { invoke(); }
649	–	private static final long serialVersionUID = 2838392045355241008L;
650	–	}
663
664		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
665		ArrayList<ForkJoinTask<T>> forkJoinTasks =
666		new ArrayList<ForkJoinTask<T>>(tasks.size());
667		for (Callable<T> task : tasks)
668	<	forkJoinTasks.add(new AdaptedCallable<T>(task));
668	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
669		invoke(new InvokeAll<T>(forkJoinTasks));
670
671		@SuppressWarnings({"unchecked", "rawtypes"})
#	Line 686 | Line 698 | public class ForkJoinPool extends Abstra
698		* Returns the handler for internal worker threads that terminate
699		* due to unrecoverable errors encountered while executing tasks.
700		*
701	<	* @return the handler, or null if none
701	>	* @return the handler, or {@code null} if none
702		*/
703		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
704		Thread.UncaughtExceptionHandler h;
#	Line 707 | Line 719 | public class ForkJoinPool extends Abstra
719		* as handler.
720		*
721		* @param h the new handler
722	<	* @return the old handler, or null if none
722	>	* @return the old handler, or {@code null} if none
723		* @throws SecurityException if a security manager exists and
724		*         the caller is not permitted to modify threads
725		*         because it does not hold {@link
#	Line 755 | Line 767 | public class ForkJoinPool extends Abstra
767		final ReentrantLock lock = this.workerLock;
768		lock.lock();
769		try {
770	<	if (!isTerminating()) {
770	>	if (isProcessingTasks()) {
771		int p = this.parallelism;
772		this.parallelism = parallelism;
773		if (parallelism > p)
#	Line 770 | Line 782 | public class ForkJoinPool extends Abstra
782		}
783
784		/**
785	<	* Returns the targeted number of worker threads in this pool.
785	>	* Returns the targeted parallelism level of this pool.
786		*
787	<	* @return the targeted number of worker threads in this pool
787	>	* @return the targeted parallelism level of this pool
788		*/
789		public int getParallelism() {
790		return parallelism;
#	Line 781 | Line 793 | public class ForkJoinPool extends Abstra
793		/**
794		* Returns the number of worker threads that have started but not
795		* yet terminated.  This result returned by this method may differ
796	<	* from {@code getParallelism} when threads are created to
796	>	* from {@link #getParallelism} when threads are created to
797		* maintain parallelism when others are cooperatively blocked.
798		*
799		* @return the number of worker threads
#	Line 792 | Line 804 | public class ForkJoinPool extends Abstra
804
805		/**
806		* Returns the maximum number of threads allowed to exist in the
807	<	* pool, even if there are insufficient unblocked running threads.
807	>	* pool. Unless set using {@link #setMaximumPoolSize}, the
808	>	* maximum is an implementation-defined value designed only to
809	>	* prevent runaway growth.
810		*
811		* @return the maximum
812		*/
#	Line 802 | Line 816 | public class ForkJoinPool extends Abstra
816
817		/**
818		* Sets the maximum number of threads allowed to exist in the
819	<	* pool, even if there are insufficient unblocked running threads.
820	<	* Setting this value has no effect on current pool size. It
821	<	* controls construction of new threads.
819	>	* pool. The given value should normally be greater than or equal
820	>	* to the {@link #getParallelism parallelism} level. Setting this
821	>	* value has no effect on current pool size. It controls
822	>	* construction of new threads.
823		*
824	<	* @throws IllegalArgumentException if negative or greater then
824	>	* @throws IllegalArgumentException if negative or greater than
825		* internal implementation limit
826		*/
827		public void setMaximumPoolSize(int newMax) {
#	Line 817 | Line 832 | public class ForkJoinPool extends Abstra
832
833
834		/**
835	<	* Returns true if this pool dynamically maintains its target
836	<	* parallelism level. If false, new threads are added only to
837	<	* avoid possible starvation.
823	<	* This setting is by default true.
835	>	* Returns {@code true} if this pool dynamically maintains its
836	>	* target parallelism level. If false, new threads are added only
837	>	* to avoid possible starvation.  This setting is by default true.
838		*
839	<	* @return true if maintains parallelism
839	>	* @return {@code true} if maintains parallelism
840		*/
841		public boolean getMaintainsParallelism() {
842		return maintainsParallelism;
#	Line 833 | Line 847 | public class ForkJoinPool extends Abstra
847		* parallelism level. If false, new threads are added only to
848		* avoid possible starvation.
849		*
850	<	* @param enable true to maintains parallelism
850	>	* @param enable {@code true} to maintain parallelism
851		*/
852		public void setMaintainsParallelism(boolean enable) {
853		maintainsParallelism = enable;
#	Line 844 | Line 858 | public class ForkJoinPool extends Abstra
858		* tasks that are never joined. This mode may be more appropriate
859		* than default locally stack-based mode in applications in which
860		* worker threads only process asynchronous tasks.  This method is
861	<	* designed to be invoked only when pool is quiescent, and
861	>	* designed to be invoked only when the pool is quiescent, and
862		* typically only before any tasks are submitted. The effects of
863		* invocations at other times may be unpredictable.
864		*
865	<	* @param async if true, use locally FIFO scheduling
865	>	* @param async if {@code true}, use locally FIFO scheduling
866		* @return the previous mode
867	+	* @see #getAsyncMode
868		*/
869		public boolean setAsyncMode(boolean async) {
870		boolean oldMode = locallyFifo;
#	Line 866 | Line 881 | public class ForkJoinPool extends Abstra
881		}
882
883		/**
884	<	* Returns true if this pool uses local first-in-first-out
884	>	* Returns {@code true} if this pool uses local first-in-first-out
885		* scheduling mode for forked tasks that are never joined.
886		*
887	<	* @return true if this pool uses async mode
887	>	* @return {@code true} if this pool uses async mode
888	>	* @see #setAsyncMode
889		*/
890		public boolean getAsyncMode() {
891		return locallyFifo;
#	Line 910 | Line 926 | public class ForkJoinPool extends Abstra
926		}
927
928		/**
929	<	* Returns true if all worker threads are currently idle. An idle
930	<	* worker is one that cannot obtain a task to execute because none
931	<	* are available to steal from other threads, and there are no
932	<	* pending submissions to the pool. This method is conservative;
933	<	* it might not return true immediately upon idleness of all
934	<	* threads, but will eventually become true if threads remain
935	<	* inactive.
929	>	* Returns {@code true} if all worker threads are currently idle.
930	>	* An idle worker is one that cannot obtain a task to execute
931	>	* because none are available to steal from other threads, and
932	>	* there are no pending submissions to the pool. This method is
933	>	* conservative; it might not return {@code true} immediately upon
934	>	* idleness of all threads, but will eventually become true if
935	>	* threads remain inactive.
936		*
937	<	* @return true if all threads are currently idle
937	>	* @return {@code true} if all threads are currently idle
938		*/
939		public boolean isQuiescent() {
940		return activeCountOf(runControl) == 0;
#	Line 973 | Line 989 | public class ForkJoinPool extends Abstra
989		}
990
991		/**
992	<	* Returns an estimate of the number tasks submitted to this pool
993	<	* that have not yet begun executing. This method takes time
992	>	* Returns an estimate of the number of tasks submitted to this
993	>	* pool that have not yet begun executing.  This method takes time
994		* proportional to the number of submissions.
995		*
996		* @return the number of queued submissions
#	Line 984 | Line 1000 | public class ForkJoinPool extends Abstra
1000		}
1001
1002		/**
1003	<	* Returns true if there are any tasks submitted to this pool
1004	<	* that have not yet begun executing.
1003	>	* Returns {@code true} if there are any tasks submitted to this
1004	>	* pool that have not yet begun executing.
1005		*
1006		* @return {@code true} if there are any queued submissions
1007		*/
#	Line 998 | Line 1014 | public class ForkJoinPool extends Abstra
1014		* available.  This method may be useful in extensions to this
1015		* class that re-assign work in systems with multiple pools.
1016		*
1017	<	* @return the next submission, or null if none
1017	>	* @return the next submission, or {@code null} if none
1018		*/
1019		protected ForkJoinTask<?> pollSubmission() {
1020		return submissionQueue.poll();
#	Line 1008 | Line 1024 | public class ForkJoinPool extends Abstra
1024		* Removes all available unexecuted submitted and forked tasks
1025		* from scheduling queues and adds them to the given collection,
1026		* without altering their execution status. These may include
1027	<	* artificially generated or wrapped tasks. This method is designed
1028	<	* to be invoked only when the pool is known to be
1027	>	* artificially generated or wrapped tasks. This method is
1028	>	* designed to be invoked only when the pool is known to be
1029		* quiescent. Invocations at other times may not remove all
1030		* tasks. A failure encountered while attempting to add elements
1031		* to collection {@code c} may result in elements being in
#	Line 1021 | Line 1037 | public class ForkJoinPool extends Abstra
1037		* @param c the collection to transfer elements into
1038		* @return the number of elements transferred
1039		*/
1040	<	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
1040	>	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1041		int n = submissionQueue.drainTo(c);
1042		ForkJoinWorkerThread[] ws = workers;
1043		if (ws != null) {
#	Line 1087 | Line 1103 | public class ForkJoinPool extends Abstra
1103		public void shutdown() {
1104		checkPermission();
1105		transitionRunStateTo(SHUTDOWN);
1106	<	if (canTerminateOnShutdown(runControl))
1106	>	if (canTerminateOnShutdown(runControl)) {
1107	>	if (workers == null) { // shutting down before workers created
1108	>	final ReentrantLock lock = this.workerLock;
1109	>	lock.lock();
1110	>	try {
1111	>	if (workers == null) {
1112	>	terminate();
1113	>	transitionRunStateTo(TERMINATED);
1114	>	termination.signalAll();
1115	>	}
1116	>	} finally {
1117	>	lock.unlock();
1118	>	}
1119	>	}
1120		terminateOnShutdown();
1121	+	}
1122		}
1123
1124		/**
1125	<	* Attempts to stop all actively executing tasks, and cancels all
1126	<	* waiting tasks.  Tasks that are in the process of being
1127	<	* submitted or executed concurrently during the course of this
1128	<	* method may or may not be rejected. Unlike some other executors,
1129	<	* this method cancels rather than collects non-executed tasks
1130	<	* upon termination, so always returns an empty list. However, you
1131	<	* can use method {@code drainTasksTo} before invoking this
1132	<	* method to transfer unexecuted tasks to another collection.
1125	>	* Attempts to cancel and/or stop all tasks, and reject all
1126	>	* subsequently submitted tasks.  Tasks that are in the process of
1127	>	* being submitted or executed concurrently during the course of
1128	>	* this method may or may not be rejected. This method cancels
1129	>	* both existing and unexecuted tasks, in order to permit
1130	>	* termination in the presence of task dependencies. So the method
1131	>	* always returns an empty list (unlike the case for some other
1132	>	* Executors).
1133		*
1134		* @return an empty list
1135		* @throws SecurityException if a security manager exists and
#	Line 1124 | Line 1154 | public class ForkJoinPool extends Abstra
1154
1155		/**
1156		* Returns {@code true} if the process of termination has
1157	<	* commenced but possibly not yet completed.
1157	>	* commenced but not yet completed.  This method may be useful for
1158	>	* debugging. A return of {@code true} reported a sufficient
1159	>	* period after shutdown may indicate that submitted tasks have
1160	>	* ignored or suppressed interruption, causing this executor not
1161	>	* to properly terminate.
1162		*
1163	<	* @return {@code true} if terminating
1163	>	* @return {@code true} if terminating but not yet terminated
1164		*/
1165		public boolean isTerminating() {
1166	<	return runStateOf(runControl) >= TERMINATING;
1166	>	return runStateOf(runControl) == TERMINATING;
1167		}
1168
1169		/**
#	Line 1142 | Line 1176 | public class ForkJoinPool extends Abstra
1176		}
1177
1178		/**
1179	+	* Returns true if pool is not terminating or terminated.
1180	+	* Used internally to suppress execution when terminating.
1181	+	*/
1182	+	final boolean isProcessingTasks() {
1183	+	return runStateOf(runControl) < TERMINATING;
1184	+	}
1185	+
1186	+	/**
1187		* Blocks until all tasks have completed execution after a shutdown
1188		* request, or the timeout occurs, or the current thread is
1189		* interrupted, whichever happens first.
#	Line 1195 | Line 1237 | public class ForkJoinPool extends Abstra
1237		transitionRunStateTo(TERMINATED);
1238		termination.signalAll();
1239		}
1240	<	else if (!isTerminating()) {
1240	>	else if (isProcessingTasks()) {
1241		tryShrinkWorkerArray();
1242		tryResumeSpare(true); // allow replacement
1243		}
#	Line 1436 | Line 1478 | public class ForkJoinPool extends Abstra
1478		final void sync(ForkJoinWorkerThread w) {
1479		updateStealCount(w); // Transfer w's count while it is idle
1480
1481	<	while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) {
1481	>	while (!w.isShutdown() && isProcessingTasks() && !suspendIfSpare(w)) {
1482		long prev = w.lastEventCount;
1483		WaitQueueNode node = null;
1484		WaitQueueNode h;
#	Line 1458 | Line 1500 | public class ForkJoinPool extends Abstra
1500		}
1501
1502		/**
1503	<	* Returns true if worker waiting on sync can proceed:
1503	>	* Returns {@code true} if worker waiting on sync can proceed:
1504		*  - on signal (thread == null)
1505		*  - on event count advance (winning race to notify vs signaller)
1506		*  - on interrupt
#	Line 1466 | Line 1508 | public class ForkJoinPool extends Abstra
1508		* If node was not signalled and event count not advanced on exit,
1509		* then we also help advance event count.
1510		*
1511	<	* @return true if node can be released
1511	>	* @return {@code true} if node can be released
1512		*/
1513		final boolean syncIsReleasable(WaitQueueNode node) {
1514		long prev = node.count;
#	Line 1485 | Line 1527 | public class ForkJoinPool extends Abstra
1527		}
1528
1529		/**
1530	<	* Returns true if a new sync event occurred since last call to
1531	<	* sync or this method, if so, updating caller's count.
1530	>	* Returns {@code true} if a new sync event occurred since last
1531	>	* call to sync or this method, if so, updating caller's count.
1532		*/
1533		final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1534		long lc = w.lastEventCount;
#	Line 1536 | Line 1578 | public class ForkJoinPool extends Abstra
1578		while (spareStack == null || !tryResumeSpare(dec)) {
1579		int counts = workerCounts;
1580		if (dec || (dec = casWorkerCounts(counts, --counts))) {
1539	–	// CAS cheat
1581		if (!needSpare(counts, maintainParallelism))
1582		break;
1583		if (joinMe.status < 0)
#	Line 1570 | Line 1611 | public class ForkJoinPool extends Abstra
1611		}
1612
1613		/**
1614	<	* Returns true if a spare thread appears to be needed.  If
1615	<	* maintaining parallelism, returns true when the deficit in
1614	>	* Returns {@code true} if a spare thread appears to be needed.
1615	>	* If maintaining parallelism, returns true when the deficit in
1616		* running threads is more than the surplus of total threads, and
1617		* there is apparently some work to do.  This self-limiting rule
1618		* means that the more threads that have already been added, the
#	Line 1641 | Line 1682 | public class ForkJoinPool extends Abstra
1682		for (k = 0; k < len && ws[k] != null; ++k)
1683		;
1684		}
1685	<	if (k < len && !isTerminating() && (w = createWorker(k)) != null) {
1685	>	if (k < len && isProcessingTasks() && (w = createWorker(k)) != null) {
1686		ws[k] = w;
1687		w.start();
1688		}
#	Line 1739 | Line 1780 | public class ForkJoinPool extends Abstra
1780
1781		/**
1782		* Interface for extending managed parallelism for tasks running
1783	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1784	<	* Method {@code isReleasable} must return true if blocking is not
1785	<	* necessary. Method {@code block} blocks the current thread if
1786	<	* necessary (perhaps internally invoking {@code isReleasable}
1787	<	* before actually blocking.).
1783	>	* in {@link ForkJoinPool}s.
1784	>	*
1785	>	* <p>A {@code ManagedBlocker} provides two methods.
1786	>	* Method {@code isReleasable} must return {@code true} if
1787	>	* blocking is not necessary. Method {@code block} blocks the
1788	>	* current thread if necessary (perhaps internally invoking
1789	>	* {@code isReleasable} before actually blocking).
1790		*
1791		* <p>For example, here is a ManagedBlocker based on a
1792		* ReentrantLock:
#	Line 1767 | Line 1810 | public class ForkJoinPool extends Abstra
1810		* Possibly blocks the current thread, for example waiting for
1811		* a lock or condition.
1812		*
1813	<	* @return true if no additional blocking is necessary (i.e.,
1814	<	* if isReleasable would return true)
1813	>	* @return {@code true} if no additional blocking is necessary
1814	>	* (i.e., if isReleasable would return true)
1815		* @throws InterruptedException if interrupted while waiting
1816		* (the method is not required to do so, but is allowed to)
1817		*/
1818		boolean block() throws InterruptedException;
1819
1820		/**
1821	<	* Returns true if blocking is unnecessary.
1821	>	* Returns {@code true} if blocking is unnecessary.
1822		*/
1823		boolean isReleasable();
1824		}
1825
1826		/**
1827		* Blocks in accord with the given blocker.  If the current thread
1828	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
1829	<	* spare thread to be activated if necessary to ensure parallelism
1830	<	* while the current thread is blocked.  If
1831	<	* {@code maintainParallelism} is true and the pool supports
1832	<	* it ({@link #getMaintainsParallelism}), this method attempts to
1833	<	* maintain the pool's nominal parallelism. Otherwise it activates
1834	<	* a thread only if necessary to avoid complete starvation. This
1835	<	* option may be preferable when blockages use timeouts, or are
1836	<	* almost always brief.
1828	>	* is a {@link ForkJoinWorkerThread}, this method possibly
1829	>	* arranges for a spare thread to be activated if necessary to
1830	>	* ensure parallelism while the current thread is blocked.
1831	>	*
1832	>	* <p>If {@code maintainParallelism} is {@code true} and the pool
1833	>	* supports it ({@link #getMaintainsParallelism}), this method
1834	>	* attempts to maintain the pool's nominal parallelism. Otherwise
1835	>	* it activates a thread only if necessary to avoid complete
1836	>	* starvation. This option may be preferable when blockages use
1837	>	* timeouts, or are almost always brief.
1838		*
1839	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1840	<	* equivalent to
1839	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
1840	>	* behaviorally equivalent to
1841		*  <pre> {@code
1842		* while (!blocker.isReleasable())
1843		*   if (blocker.block())
1844		*     return;
1845		* }</pre>
1846	<	* If the caller is a ForkJoinTask, then the pool may first
1847	<	* be expanded to ensure parallelism, and later adjusted.
1846	>	*
1847	>	* If the caller is a {@code ForkJoinTask}, then the pool may
1848	>	* first be expanded to ensure parallelism, and later adjusted.
1849		*
1850		* @param blocker the blocker
1851	<	* @param maintainParallelism if true and supported by this pool,
1852	<	* attempt to maintain the pool's nominal parallelism; otherwise
1853	<	* activate a thread only if necessary to avoid complete
1854	<	* starvation.
1851	>	* @param maintainParallelism if {@code true} and supported by
1852	>	* this pool, attempt to maintain the pool's nominal parallelism;
1853	>	* otherwise activate a thread only if necessary to avoid
1854	>	* complete starvation.
1855		* @throws InterruptedException if blocker.block did so
1856		*/
1857		public static void managedBlock(ManagedBlocker blocker,
#	Line 1832 | Line 1877 | public class ForkJoinPool extends Abstra
1877		do {} while (!blocker.isReleasable() && !blocker.block());
1878		}
1879
1880	<	// AbstractExecutorService overrides
1880	>	// AbstractExecutorService overrides.  These rely on undocumented
1881	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1882	>	// implement RunnableFuture.
1883
1884		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1885	<	return new AdaptedRunnable<T>(runnable, value);
1885	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
1886		}
1887
1888		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1889	<	return new AdaptedCallable<T>(callable);
1889	>	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
1890		}
1891
1892	<
1846	<	// Unsafe mechanics for jsr166y 3rd party package.
1847	<	private static sun.misc.Unsafe getUnsafe() {
1848	<	try {
1849	<	return sun.misc.Unsafe.getUnsafe();
1850	<	} catch (SecurityException se) {
1851	<	try {
1852	<	return java.security.AccessController.doPrivileged
1853	<	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1854	<	public sun.misc.Unsafe run() throws Exception {
1855	<	return getUnsafeByReflection();
1856	<	}});
1857	<	} catch (java.security.PrivilegedActionException e) {
1858	<	throw new RuntimeException("Could not initialize intrinsics",
1859	<	e.getCause());
1860	<	}
1861	<	}
1862	<	}
1863	<
1864	<	private static sun.misc.Unsafe getUnsafeByReflection()
1865	<	throws NoSuchFieldException, IllegalAccessException {
1866	<	java.lang.reflect.Field f =
1867	<	sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
1868	<	f.setAccessible(true);
1869	<	return (sun.misc.Unsafe) f.get(null);
1870	<	}
1871	<
1872	<	private static long fieldOffset(String fieldName, Class<?> klazz) {
1873	<	try {
1874	<	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
1875	<	} catch (NoSuchFieldException e) {
1876	<	// Convert Exception to Error
1877	<	NoSuchFieldError error = new NoSuchFieldError(fieldName);
1878	<	error.initCause(e);
1879	<	throw error;
1880	<	}
1881	<	}
1892	>	// Unsafe mechanics
1893
1894		private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1895	<	static final long eventCountOffset =
1896	<	fieldOffset("eventCount", ForkJoinPool.class);
1897	<	static final long workerCountsOffset =
1898	<	fieldOffset("workerCounts", ForkJoinPool.class);
1899	<	static final long runControlOffset =
1900	<	fieldOffset("runControl", ForkJoinPool.class);
1901	<	static final long syncStackOffset =
1902	<	fieldOffset("syncStack",ForkJoinPool.class);
1903	<	static final long spareStackOffset =
1904	<	fieldOffset("spareStack", ForkJoinPool.class);
1895	>	private static final long eventCountOffset =
1896	>	objectFieldOffset("eventCount", ForkJoinPool.class);
1897	>	private static final long workerCountsOffset =
1898	>	objectFieldOffset("workerCounts", ForkJoinPool.class);
1899	>	private static final long runControlOffset =
1900	>	objectFieldOffset("runControl", ForkJoinPool.class);
1901	>	private static final long syncStackOffset =
1902	>	objectFieldOffset("syncStack",ForkJoinPool.class);
1903	>	private static final long spareStackOffset =
1904	>	objectFieldOffset("spareStack", ForkJoinPool.class);
1905
1906		private boolean casEventCount(long cmp, long val) {
1907		return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
#	Line 1907 | Line 1918 | public class ForkJoinPool extends Abstra
1918		private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1919		return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1920		}
1921	+
1922	+	private static long objectFieldOffset(String field, Class<?> klazz) {
1923	+	try {
1924	+	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1925	+	} catch (NoSuchFieldException e) {
1926	+	// Convert Exception to corresponding Error
1927	+	NoSuchFieldError error = new NoSuchFieldError(field);
1928	+	error.initCause(e);
1929	+	throw error;
1930	+	}
1931	+	}
1932	+
1933	+	/**
1934	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1935	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1936	+	* into a jdk.
1937	+	*
1938	+	* @return a sun.misc.Unsafe
1939	+	*/
1940	+	private static sun.misc.Unsafe getUnsafe() {
1941	+	try {
1942	+	return sun.misc.Unsafe.getUnsafe();
1943	+	} catch (SecurityException se) {
1944	+	try {
1945	+	return java.security.AccessController.doPrivileged
1946	+	(new java.security
1947	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1948	+	public sun.misc.Unsafe run() throws Exception {
1949	+	java.lang.reflect.Field f = sun.misc
1950	+	.Unsafe.class.getDeclaredField("theUnsafe");
1951	+	f.setAccessible(true);
1952	+	return (sun.misc.Unsafe) f.get(null);
1953	+	}});
1954	+	} catch (java.security.PrivilegedActionException e) {
1955	+	throw new RuntimeException("Could not initialize intrinsics",
1956	+	e.getCause());
1957	+	}
1958	+	}
1959	+	}
1960		}

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