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root/jsr166/jsr166/src/jsr166y/ForkJoinPool.java

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.25 by jsr166, Sun Jul 26 05:55:34 2009 UTC vs.
Revision 1.48 by jsr166, Thu Aug 6 06:41:34 2009 UTC

#	Line 20 | Line 20 | import java.util.concurrent.atomic.Atomi
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
27	<	* submitted tasks. Otherwise, use would not usually outweigh the
28	<	* construction and bookkeeping overhead of creating a large set of
29	<	* 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.
85	>	* pools with greater than the maximum number result in
86	>	* {@code IllegalArgumentException}.
87	>	*
88	>	* <p>This implementation rejects submitted tasks (that is, by throwing
89	>	* {@link RejectedExecutionException}) only when the pool is shut down.
90		*
91		* @since 1.7
92		* @author Doug Lea
#	Line 81 | Line 105 | public class ForkJoinPool extends Abstra
105		private static final int MAX_THREADS =  0x7FFF;
106
107		/**
108	<	* Factory for creating new ForkJoinWorkerThreads.  A
109	<	* ForkJoinWorkerThreadFactory must be defined and used for
110	<	* ForkJoinWorkerThread subclasses that extend base functionality
111	<	* or initialize threads with different contexts.
108	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
109	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
110	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
111	>	* functionality or initialize threads with different contexts.
112		*/
113		public static interface ForkJoinWorkerThreadFactory {
114		/**
115		* Returns a new worker thread operating in the given pool.
116		*
117		* @param pool the pool this thread works in
118	<	* @throws NullPointerException if pool is null
118	>	* @throws NullPointerException if the pool is null
119		*/
120		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
121		}
#	Line 311 | Line 335 | public class ForkJoinPool extends Abstra
335		}
336
337		/**
338	<	* Returns true if argument represents zero active count and
339	<	* nonzero runstate, which is the triggering condition for
338	>	* Returns {@code true} if argument represents zero active count
339	>	* and nonzero runstate, which is the triggering condition for
340		* terminating on shutdown.
341		*/
342		private static boolean canTerminateOnShutdown(int c) {
#	Line 342 | Line 366 | public class ForkJoinPool extends Abstra
366		// Constructors
367
368		/**
369	<	* Creates a ForkJoinPool with a pool size equal to the number of
370	<	* processors available on the system, using the default
371	<	* ForkJoinWorkerThreadFactory.
369	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
370	>	* java.lang.Runtime#availableProcessors}, and using the {@linkplain
371	>	* #defaultForkJoinWorkerThreadFactory default thread factory}.
372		*
373		* @throws SecurityException if a security manager exists and
374		*         the caller is not permitted to modify threads
#	Line 357 | Line 381 | public class ForkJoinPool extends Abstra
381		}
382
383		/**
384	<	* Creates a ForkJoinPool with the indicated parallelism level
385	<	* threads and using the default ForkJoinWorkerThreadFactory.
384	>	* Creates a {@code ForkJoinPool} with the indicated parallelism
385	>	* level and using the {@linkplain
386	>	* #defaultForkJoinWorkerThreadFactory default thread factory}.
387		*
388	<	* @param parallelism the number of worker threads
388	>	* @param parallelism the parallelism level
389		* @throws IllegalArgumentException if parallelism less than or
390	<	* equal to zero
390	>	*         equal to zero, or greater than implementation limit
391		* @throws SecurityException if a security manager exists and
392		*         the caller is not permitted to modify threads
393		*         because it does not hold {@link
#	Line 373 | Line 398 | public class ForkJoinPool extends Abstra
398		}
399
400		/**
401	<	* Creates a ForkJoinPool with parallelism equal to the number of
402	<	* processors available on the system and using the given
403	<	* ForkJoinWorkerThreadFactory.
401	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
402	>	* java.lang.Runtime#availableProcessors}, and using the given
403	>	* thread factory.
404		*
405		* @param factory the factory for creating new threads
406	<	* @throws NullPointerException if factory is null
406	>	* @throws NullPointerException if the factory is null
407		* @throws SecurityException if a security manager exists and
408		*         the caller is not permitted to modify threads
409		*         because it does not hold {@link
#	Line 389 | Line 414 | public class ForkJoinPool extends Abstra
414		}
415
416		/**
417	<	* Creates a ForkJoinPool with the given parallelism and factory.
417	>	* Creates a {@code ForkJoinPool} with the given parallelism and
418	>	* thread factory.
419		*
420	<	* @param parallelism the targeted number of worker threads
420	>	* @param parallelism the parallelism level
421		* @param factory the factory for creating new threads
422		* @throws IllegalArgumentException if parallelism less than or
423	<	* equal to zero, or greater than implementation limit
424	<	* @throws NullPointerException if factory is null
423	>	*         equal to zero, or greater than implementation limit
424	>	* @throws NullPointerException if the factory is null
425		* @throws SecurityException if a security manager exists and
426		*         the caller is not permitted to modify threads
427		*         because it does not hold {@link
#	Line 423 | Line 449 | public class ForkJoinPool extends Abstra
449		* Creates a new worker thread using factory.
450		*
451		* @param index the index to assign worker
452	<	* @return new worker, or null of factory failed
452	>	* @return new worker, or null if factory failed
453		*/
454		private ForkJoinWorkerThread createWorker(int index) {
455		Thread.UncaughtExceptionHandler h = ueh;
#	Line 444 | Line 470 | public class ForkJoinPool extends Abstra
470		* Currently requires size to be a power of two.
471		*/
472		private static int arraySizeFor(int poolSize) {
473	<	return (poolSize <= 1) ? 1 :
474	<	(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1)));
473	>	if (poolSize <= 1)
474	>	return 1;
475	>	// See Hackers Delight, sec 3.2
476	>	int c = poolSize >= MAX_THREADS ? MAX_THREADS : (poolSize - 1);
477	>	c |= c >>>  1;
478	>	c |= c >>>  2;
479	>	c |= c >>>  4;
480	>	c |= c >>>  8;
481	>	c |= c >>> 16;
482	>	return c + 1;
483		}
484
485		/**
#	Line 563 | Line 597 | public class ForkJoinPool extends Abstra
597		*
598		* @param task the task
599		* @return the task's result
600	<	* @throws NullPointerException if task is null
601	<	* @throws RejectedExecutionException if pool is shut down
600	>	* @throws NullPointerException if the task is null
601	>	* @throws RejectedExecutionException if the task cannot be
602	>	*         scheduled for execution
603		*/
604		public <T> T invoke(ForkJoinTask<T> task) {
605		doSubmit(task);
#	Line 575 | Line 610 | public class ForkJoinPool extends Abstra
610		* Arranges for (asynchronous) execution of the given task.
611		*
612		* @param task the task
613	<	* @throws NullPointerException if task is null
614	<	* @throws RejectedExecutionException if pool is shut down
613	>	* @throws NullPointerException if the task is null
614	>	* @throws RejectedExecutionException if the task cannot be
615	>	*         scheduled for execution
616		*/
617	<	public <T> void execute(ForkJoinTask<T> task) {
617	>	public void execute(ForkJoinTask<?> task) {
618		doSubmit(task);
619		}
620
621		// AbstractExecutorService methods
622
623	+	/**
624	+	* @throws NullPointerException if the task is null
625	+	* @throws RejectedExecutionException if the task cannot be
626	+	*         scheduled for execution
627	+	*/
628		public void execute(Runnable task) {
629		ForkJoinTask<?> job;
630	<	if (task instanceof ForkJoinTask) // avoid re-wrap
631	<	job = (ForkJoinTask<?>)task;
630	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
631	>	job = (ForkJoinTask<?>) task;
632		else
633	<	job = new AdaptedRunnable<Void>(task, null);
633	>	job = ForkJoinTask.adapt(task, null);
634		doSubmit(job);
635		}
636
637	+	/**
638	+	* @throws NullPointerException if the task is null
639	+	* @throws RejectedExecutionException if the task cannot be
640	+	*         scheduled for execution
641	+	*/
642		public <T> ForkJoinTask<T> submit(Callable<T> task) {
643	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
643	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
644		doSubmit(job);
645		return job;
646		}
647
648	+	/**
649	+	* @throws NullPointerException if the task is null
650	+	* @throws RejectedExecutionException if the task cannot be
651	+	*         scheduled for execution
652	+	*/
653		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
654	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
654	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
655		doSubmit(job);
656		return job;
657		}
658
659	+	/**
660	+	* @throws NullPointerException if the task is null
661	+	* @throws RejectedExecutionException if the task cannot be
662	+	*         scheduled for execution
663	+	*/
664		public ForkJoinTask<?> submit(Runnable task) {
665		ForkJoinTask<?> job;
666	<	if (task instanceof ForkJoinTask) // avoid re-wrap
667	<	job = (ForkJoinTask<?>)task;
666	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
667	>	job = (ForkJoinTask<?>) task;
668		else
669	<	job = new AdaptedRunnable<Void>(task, null);
669	>	job = ForkJoinTask.adapt(task, null);
670		doSubmit(job);
671		return job;
672		}
#	Line 620 | Line 676 | public class ForkJoinPool extends Abstra
676		*
677		* @param task the task to submit
678		* @return the task
679	+	* @throws NullPointerException if the task is null
680		* @throws RejectedExecutionException if the task cannot be
681		*         scheduled for execution
625	–	* @throws NullPointerException if the task is null
682		*/
683		public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
684		doSubmit(task);
685		return task;
686		}
687
632	–	/**
633	–	* Adaptor for Runnables. This implements RunnableFuture
634	–	* to be compliant with AbstractExecutorService constraints.
635	–	*/
636	–	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
637	–	implements RunnableFuture<T> {
638	–	final Runnable runnable;
639	–	final T resultOnCompletion;
640	–	T result;
641	–	AdaptedRunnable(Runnable runnable, T result) {
642	–	if (runnable == null) throw new NullPointerException();
643	–	this.runnable = runnable;
644	–	this.resultOnCompletion = result;
645	–	}
646	–	public T getRawResult() { return result; }
647	–	public void setRawResult(T v) { result = v; }
648	–	public boolean exec() {
649	–	runnable.run();
650	–	result = resultOnCompletion;
651	–	return true;
652	–	}
653	–	public void run() { invoke(); }
654	–	private static final long serialVersionUID = 5232453952276885070L;
655	–	}
688
689		/**
690	<	* Adaptor for Callables
690	>	* @throws NullPointerException       {@inheritDoc}
691	>	* @throws RejectedExecutionException {@inheritDoc}
692		*/
660	–	static final class AdaptedCallable<T> extends ForkJoinTask<T>
661	–	implements RunnableFuture<T> {
662	–	final Callable<T> callable;
663	–	T result;
664	–	AdaptedCallable(Callable<T> callable) {
665	–	if (callable == null) throw new NullPointerException();
666	–	this.callable = callable;
667	–	}
668	–	public T getRawResult() { return result; }
669	–	public void setRawResult(T v) { result = v; }
670	–	public boolean exec() {
671	–	try {
672	–	result = callable.call();
673	–	return true;
674	–	} catch (Error err) {
675	–	throw err;
676	–	} catch (RuntimeException rex) {
677	–	throw rex;
678	–	} catch (Exception ex) {
679	–	throw new RuntimeException(ex);
680	–	}
681	–	}
682	–	public void run() { invoke(); }
683	–	private static final long serialVersionUID = 2838392045355241008L;
684	–	}
685	–
693		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
694		ArrayList<ForkJoinTask<T>> forkJoinTasks =
695		new ArrayList<ForkJoinTask<T>>(tasks.size());
696		for (Callable<T> task : tasks)
697	<	forkJoinTasks.add(new AdaptedCallable<T>(task));
697	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
698		invoke(new InvokeAll<T>(forkJoinTasks));
699
700		@SuppressWarnings({"unchecked", "rawtypes"})
#	Line 720 | Line 727 | public class ForkJoinPool extends Abstra
727		* Returns the handler for internal worker threads that terminate
728		* due to unrecoverable errors encountered while executing tasks.
729		*
730	<	* @return the handler, or null if none
730	>	* @return the handler, or {@code null} if none
731		*/
732		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
733		Thread.UncaughtExceptionHandler h;
#	Line 741 | Line 748 | public class ForkJoinPool extends Abstra
748		* as handler.
749		*
750		* @param h the new handler
751	<	* @return the old handler, or null if none
751	>	* @return the old handler, or {@code null} if none
752		* @throws SecurityException if a security manager exists and
753		*         the caller is not permitted to modify threads
754		*         because it does not hold {@link
#	Line 789 | Line 796 | public class ForkJoinPool extends Abstra
796		final ReentrantLock lock = this.workerLock;
797		lock.lock();
798		try {
799	<	if (!isTerminating()) {
799	>	if (isProcessingTasks()) {
800		int p = this.parallelism;
801		this.parallelism = parallelism;
802		if (parallelism > p)
#	Line 804 | Line 811 | public class ForkJoinPool extends Abstra
811		}
812
813		/**
814	<	* Returns the targeted number of worker threads in this pool.
814	>	* Returns the targeted parallelism level of this pool.
815		*
816	<	* @return the targeted number of worker threads in this pool
816	>	* @return the targeted parallelism level of this pool
817		*/
818		public int getParallelism() {
819		return parallelism;
#	Line 815 | Line 822 | public class ForkJoinPool extends Abstra
822		/**
823		* Returns the number of worker threads that have started but not
824		* yet terminated.  This result returned by this method may differ
825	<	* from {@code getParallelism} when threads are created to
825	>	* from {@link #getParallelism} when threads are created to
826		* maintain parallelism when others are cooperatively blocked.
827		*
828		* @return the number of worker threads
#	Line 826 | Line 833 | public class ForkJoinPool extends Abstra
833
834		/**
835		* Returns the maximum number of threads allowed to exist in the
836	<	* pool, even if there are insufficient unblocked running threads.
836	>	* pool. Unless set using {@link #setMaximumPoolSize}, the
837	>	* maximum is an implementation-defined value designed only to
838	>	* prevent runaway growth.
839		*
840		* @return the maximum
841		*/
#	Line 836 | Line 845 | public class ForkJoinPool extends Abstra
845
846		/**
847		* Sets the maximum number of threads allowed to exist in the
848	<	* pool, even if there are insufficient unblocked running threads.
849	<	* Setting this value has no effect on current pool size. It
850	<	* controls construction of new threads.
848	>	* pool. The given value should normally be greater than or equal
849	>	* to the {@link #getParallelism parallelism} level. Setting this
850	>	* value has no effect on current pool size. It controls
851	>	* construction of new threads.
852		*
853	<	* @throws IllegalArgumentException if negative or greater then
853	>	* @throws IllegalArgumentException if negative or greater than
854		* internal implementation limit
855		*/
856		public void setMaximumPoolSize(int newMax) {
#	Line 851 | Line 861 | public class ForkJoinPool extends Abstra
861
862
863		/**
864	<	* Returns true if this pool dynamically maintains its target
865	<	* parallelism level. If false, new threads are added only to
866	<	* avoid possible starvation.
857	<	* This setting is by default true.
864	>	* Returns {@code true} if this pool dynamically maintains its
865	>	* target parallelism level. If false, new threads are added only
866	>	* to avoid possible starvation.  This setting is by default true.
867		*
868	<	* @return true if maintains parallelism
868	>	* @return {@code true} if maintains parallelism
869		*/
870		public boolean getMaintainsParallelism() {
871		return maintainsParallelism;
#	Line 867 | Line 876 | public class ForkJoinPool extends Abstra
876		* parallelism level. If false, new threads are added only to
877		* avoid possible starvation.
878		*
879	<	* @param enable true to maintains parallelism
879	>	* @param enable {@code true} to maintain parallelism
880		*/
881		public void setMaintainsParallelism(boolean enable) {
882		maintainsParallelism = enable;
#	Line 878 | Line 887 | public class ForkJoinPool extends Abstra
887		* tasks that are never joined. This mode may be more appropriate
888		* than default locally stack-based mode in applications in which
889		* worker threads only process asynchronous tasks.  This method is
890	<	* designed to be invoked only when pool is quiescent, and
890	>	* designed to be invoked only when the pool is quiescent, and
891		* typically only before any tasks are submitted. The effects of
892		* invocations at other times may be unpredictable.
893		*
894	<	* @param async if true, use locally FIFO scheduling
894	>	* @param async if {@code true}, use locally FIFO scheduling
895		* @return the previous mode
896	+	* @see #getAsyncMode
897		*/
898		public boolean setAsyncMode(boolean async) {
899		boolean oldMode = locallyFifo;
#	Line 900 | Line 910 | public class ForkJoinPool extends Abstra
910		}
911
912		/**
913	<	* Returns true if this pool uses local first-in-first-out
913	>	* Returns {@code true} if this pool uses local first-in-first-out
914		* scheduling mode for forked tasks that are never joined.
915		*
916	<	* @return true if this pool uses async mode
916	>	* @return {@code true} if this pool uses async mode
917	>	* @see #setAsyncMode
918		*/
919		public boolean getAsyncMode() {
920		return locallyFifo;
#	Line 944 | Line 955 | public class ForkJoinPool extends Abstra
955		}
956
957		/**
958	<	* Returns true if all worker threads are currently idle. An idle
959	<	* worker is one that cannot obtain a task to execute because none
960	<	* are available to steal from other threads, and there are no
961	<	* pending submissions to the pool. This method is conservative;
962	<	* it might not return true immediately upon idleness of all
963	<	* threads, but will eventually become true if threads remain
964	<	* inactive.
958	>	* Returns {@code true} if all worker threads are currently idle.
959	>	* An idle worker is one that cannot obtain a task to execute
960	>	* because none are available to steal from other threads, and
961	>	* there are no pending submissions to the pool. This method is
962	>	* conservative; it might not return {@code true} immediately upon
963	>	* idleness of all threads, but will eventually become true if
964	>	* threads remain inactive.
965		*
966	<	* @return true if all threads are currently idle
966	>	* @return {@code true} if all threads are currently idle
967		*/
968		public boolean isQuiescent() {
969		return activeCountOf(runControl) == 0;
#	Line 1007 | Line 1018 | public class ForkJoinPool extends Abstra
1018		}
1019
1020		/**
1021	<	* Returns an estimate of the number tasks submitted to this pool
1022	<	* that have not yet begun executing. This method takes time
1021	>	* Returns an estimate of the number of tasks submitted to this
1022	>	* pool that have not yet begun executing.  This method takes time
1023		* proportional to the number of submissions.
1024		*
1025		* @return the number of queued submissions
#	Line 1018 | Line 1029 | public class ForkJoinPool extends Abstra
1029		}
1030
1031		/**
1032	<	* Returns true if there are any tasks submitted to this pool
1033	<	* that have not yet begun executing.
1032	>	* Returns {@code true} if there are any tasks submitted to this
1033	>	* pool that have not yet begun executing.
1034		*
1035		* @return {@code true} if there are any queued submissions
1036		*/
#	Line 1032 | Line 1043 | public class ForkJoinPool extends Abstra
1043		* available.  This method may be useful in extensions to this
1044		* class that re-assign work in systems with multiple pools.
1045		*
1046	<	* @return the next submission, or null if none
1046	>	* @return the next submission, or {@code null} if none
1047		*/
1048		protected ForkJoinTask<?> pollSubmission() {
1049		return submissionQueue.poll();
#	Line 1042 | Line 1053 | public class ForkJoinPool extends Abstra
1053		* Removes all available unexecuted submitted and forked tasks
1054		* from scheduling queues and adds them to the given collection,
1055		* without altering their execution status. These may include
1056	<	* artificially generated or wrapped tasks. This method is designed
1057	<	* to be invoked only when the pool is known to be
1056	>	* artificially generated or wrapped tasks. This method is
1057	>	* designed to be invoked only when the pool is known to be
1058		* quiescent. Invocations at other times may not remove all
1059		* tasks. A failure encountered while attempting to add elements
1060		* to collection {@code c} may result in elements being in
#	Line 1055 | Line 1066 | public class ForkJoinPool extends Abstra
1066		* @param c the collection to transfer elements into
1067		* @return the number of elements transferred
1068		*/
1069	<	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
1069	>	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1070		int n = submissionQueue.drainTo(c);
1071		ForkJoinWorkerThread[] ws = workers;
1072		if (ws != null) {
#	Line 1121 | Line 1132 | public class ForkJoinPool extends Abstra
1132		public void shutdown() {
1133		checkPermission();
1134		transitionRunStateTo(SHUTDOWN);
1135	<	if (canTerminateOnShutdown(runControl))
1135	>	if (canTerminateOnShutdown(runControl)) {
1136	>	if (workers == null) { // shutting down before workers created
1137	>	final ReentrantLock lock = this.workerLock;
1138	>	lock.lock();
1139	>	try {
1140	>	if (workers == null) {
1141	>	terminate();
1142	>	transitionRunStateTo(TERMINATED);
1143	>	termination.signalAll();
1144	>	}
1145	>	} finally {
1146	>	lock.unlock();
1147	>	}
1148	>	}
1149		terminateOnShutdown();
1150	+	}
1151		}
1152
1153		/**
1154	<	* Attempts to stop all actively executing tasks, and cancels all
1155	<	* waiting tasks.  Tasks that are in the process of being
1156	<	* submitted or executed concurrently during the course of this
1157	<	* method may or may not be rejected. Unlike some other executors,
1158	<	* this method cancels rather than collects non-executed tasks
1159	<	* upon termination, so always returns an empty list. However, you
1160	<	* can use method {@code drainTasksTo} before invoking this
1161	<	* method to transfer unexecuted tasks to another collection.
1154	>	* Attempts to cancel and/or stop all tasks, and reject all
1155	>	* subsequently submitted tasks.  Tasks that are in the process of
1156	>	* being submitted or executed concurrently during the course of
1157	>	* this method may or may not be rejected. This method cancels
1158	>	* both existing and unexecuted tasks, in order to permit
1159	>	* termination in the presence of task dependencies. So the method
1160	>	* always returns an empty list (unlike the case for some other
1161	>	* Executors).
1162		*
1163		* @return an empty list
1164		* @throws SecurityException if a security manager exists and
#	Line 1158 | Line 1183 | public class ForkJoinPool extends Abstra
1183
1184		/**
1185		* Returns {@code true} if the process of termination has
1186	<	* commenced but possibly not yet completed.
1186	>	* commenced but not yet completed.  This method may be useful for
1187	>	* debugging. A return of {@code true} reported a sufficient
1188	>	* period after shutdown may indicate that submitted tasks have
1189	>	* ignored or suppressed interruption, causing this executor not
1190	>	* to properly terminate.
1191		*
1192	<	* @return {@code true} if terminating
1192	>	* @return {@code true} if terminating but not yet terminated
1193		*/
1194		public boolean isTerminating() {
1195	<	return runStateOf(runControl) >= TERMINATING;
1195	>	return runStateOf(runControl) == TERMINATING;
1196		}
1197
1198		/**
#	Line 1176 | Line 1205 | public class ForkJoinPool extends Abstra
1205		}
1206
1207		/**
1208	+	* Returns true if pool is not terminating or terminated.
1209	+	* Used internally to suppress execution when terminating.
1210	+	*/
1211	+	final boolean isProcessingTasks() {
1212	+	return runStateOf(runControl) < TERMINATING;
1213	+	}
1214	+
1215	+	/**
1216		* Blocks until all tasks have completed execution after a shutdown
1217		* request, or the timeout occurs, or the current thread is
1218		* interrupted, whichever happens first.
#	Line 1229 | Line 1266 | public class ForkJoinPool extends Abstra
1266		transitionRunStateTo(TERMINATED);
1267		termination.signalAll();
1268		}
1269	<	else if (!isTerminating()) {
1269	>	else if (isProcessingTasks()) {
1270		tryShrinkWorkerArray();
1271		tryResumeSpare(true); // allow replacement
1272		}
#	Line 1470 | Line 1507 | public class ForkJoinPool extends Abstra
1507		final void sync(ForkJoinWorkerThread w) {
1508		updateStealCount(w); // Transfer w's count while it is idle
1509
1510	<	while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) {
1510	>	while (!w.isShutdown() && isProcessingTasks() && !suspendIfSpare(w)) {
1511		long prev = w.lastEventCount;
1512		WaitQueueNode node = null;
1513		WaitQueueNode h;
#	Line 1492 | Line 1529 | public class ForkJoinPool extends Abstra
1529		}
1530
1531		/**
1532	<	* Returns true if worker waiting on sync can proceed:
1532	>	* Returns {@code true} if worker waiting on sync can proceed:
1533		*  - on signal (thread == null)
1534		*  - on event count advance (winning race to notify vs signaller)
1535		*  - on interrupt
#	Line 1500 | Line 1537 | public class ForkJoinPool extends Abstra
1537		* If node was not signalled and event count not advanced on exit,
1538		* then we also help advance event count.
1539		*
1540	<	* @return true if node can be released
1540	>	* @return {@code true} if node can be released
1541		*/
1542		final boolean syncIsReleasable(WaitQueueNode node) {
1543		long prev = node.count;
#	Line 1519 | Line 1556 | public class ForkJoinPool extends Abstra
1556		}
1557
1558		/**
1559	<	* Returns true if a new sync event occurred since last call to
1560	<	* sync or this method, if so, updating caller's count.
1559	>	* Returns {@code true} if a new sync event occurred since last
1560	>	* call to sync or this method, if so, updating caller's count.
1561		*/
1562		final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1563		long lc = w.lastEventCount;
#	Line 1570 | Line 1607 | public class ForkJoinPool extends Abstra
1607		while (spareStack == null || !tryResumeSpare(dec)) {
1608		int counts = workerCounts;
1609		if (dec || (dec = casWorkerCounts(counts, --counts))) {
1573	–	// CAS cheat
1610		if (!needSpare(counts, maintainParallelism))
1611		break;
1612		if (joinMe.status < 0)
#	Line 1604 | Line 1640 | public class ForkJoinPool extends Abstra
1640		}
1641
1642		/**
1643	<	* Returns true if a spare thread appears to be needed.  If
1644	<	* maintaining parallelism, returns true when the deficit in
1643	>	* Returns {@code true} if a spare thread appears to be needed.
1644	>	* If maintaining parallelism, returns true when the deficit in
1645		* running threads is more than the surplus of total threads, and
1646		* there is apparently some work to do.  This self-limiting rule
1647		* means that the more threads that have already been added, the
#	Line 1675 | Line 1711 | public class ForkJoinPool extends Abstra
1711		for (k = 0; k < len && ws[k] != null; ++k)
1712		;
1713		}
1714	<	if (k < len && !isTerminating() && (w = createWorker(k)) != null) {
1714	>	if (k < len && isProcessingTasks() && (w = createWorker(k)) != null) {
1715		ws[k] = w;
1716		w.start();
1717		}
#	Line 1773 | Line 1809 | public class ForkJoinPool extends Abstra
1809
1810		/**
1811		* Interface for extending managed parallelism for tasks running
1812	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1813	<	* Method {@code isReleasable} must return true if blocking is not
1814	<	* necessary. Method {@code block} blocks the current thread if
1815	<	* necessary (perhaps internally invoking {@code isReleasable}
1816	<	* before actually blocking.).
1812	>	* in {@link ForkJoinPool}s.
1813	>	*
1814	>	* <p>A {@code ManagedBlocker} provides two methods.
1815	>	* Method {@code isReleasable} must return {@code true} if
1816	>	* blocking is not necessary. Method {@code block} blocks the
1817	>	* current thread if necessary (perhaps internally invoking
1818	>	* {@code isReleasable} before actually blocking).
1819		*
1820		* <p>For example, here is a ManagedBlocker based on a
1821		* ReentrantLock:
#	Line 1801 | Line 1839 | public class ForkJoinPool extends Abstra
1839		* Possibly blocks the current thread, for example waiting for
1840		* a lock or condition.
1841		*
1842	<	* @return true if no additional blocking is necessary (i.e.,
1843	<	* if isReleasable would return true)
1842	>	* @return {@code true} if no additional blocking is necessary
1843	>	* (i.e., if isReleasable would return true)
1844		* @throws InterruptedException if interrupted while waiting
1845		* (the method is not required to do so, but is allowed to)
1846		*/
1847		boolean block() throws InterruptedException;
1848
1849		/**
1850	<	* Returns true if blocking is unnecessary.
1850	>	* Returns {@code true} if blocking is unnecessary.
1851		*/
1852		boolean isReleasable();
1853		}
1854
1855		/**
1856		* Blocks in accord with the given blocker.  If the current thread
1857	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
1858	<	* spare thread to be activated if necessary to ensure parallelism
1859	<	* while the current thread is blocked.  If
1860	<	* {@code maintainParallelism} is true and the pool supports
1861	<	* it ({@link #getMaintainsParallelism}), this method attempts to
1862	<	* maintain the pool's nominal parallelism. Otherwise it activates
1863	<	* a thread only if necessary to avoid complete starvation. This
1864	<	* option may be preferable when blockages use timeouts, or are
1865	<	* almost always brief.
1857	>	* is a {@link ForkJoinWorkerThread}, this method possibly
1858	>	* arranges for a spare thread to be activated if necessary to
1859	>	* ensure parallelism while the current thread is blocked.
1860	>	*
1861	>	* <p>If {@code maintainParallelism} is {@code true} and the pool
1862	>	* supports it ({@link #getMaintainsParallelism}), this method
1863	>	* attempts to maintain the pool's nominal parallelism. Otherwise
1864	>	* it activates a thread only if necessary to avoid complete
1865	>	* starvation. This option may be preferable when blockages use
1866	>	* timeouts, or are almost always brief.
1867		*
1868	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1869	<	* equivalent to
1868	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
1869	>	* behaviorally equivalent to
1870		*  <pre> {@code
1871		* while (!blocker.isReleasable())
1872		*   if (blocker.block())
1873		*     return;
1874		* }</pre>
1875	<	* If the caller is a ForkJoinTask, then the pool may first
1876	<	* be expanded to ensure parallelism, and later adjusted.
1875	>	*
1876	>	* If the caller is a {@code ForkJoinTask}, then the pool may
1877	>	* first be expanded to ensure parallelism, and later adjusted.
1878		*
1879		* @param blocker the blocker
1880	<	* @param maintainParallelism if true and supported by this pool,
1881	<	* attempt to maintain the pool's nominal parallelism; otherwise
1882	<	* activate a thread only if necessary to avoid complete
1883	<	* starvation.
1880	>	* @param maintainParallelism if {@code true} and supported by
1881	>	* this pool, attempt to maintain the pool's nominal parallelism;
1882	>	* otherwise activate a thread only if necessary to avoid
1883	>	* complete starvation.
1884		* @throws InterruptedException if blocker.block did so
1885		*/
1886		public static void managedBlock(ManagedBlocker blocker,
#	Line 1866 | Line 1906 | public class ForkJoinPool extends Abstra
1906		do {} while (!blocker.isReleasable() && !blocker.block());
1907		}
1908
1909	<	// AbstractExecutorService overrides
1909	>	// AbstractExecutorService overrides.  These rely on undocumented
1910	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1911	>	// implement RunnableFuture.
1912
1913		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1914	<	return new AdaptedRunnable<T>(runnable, value);
1914	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
1915		}
1916
1917		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1918	<	return new AdaptedCallable<T>(callable);
1877	<	}
1878	<
1879	<
1880	<	// Unsafe mechanics for jsr166y 3rd party package.
1881	<	private static sun.misc.Unsafe getUnsafe() {
1882	<	try {
1883	<	return sun.misc.Unsafe.getUnsafe();
1884	<	} catch (SecurityException se) {
1885	<	try {
1886	<	return java.security.AccessController.doPrivileged
1887	<	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1888	<	public sun.misc.Unsafe run() throws Exception {
1889	<	return getUnsafeByReflection();
1890	<	}});
1891	<	} catch (java.security.PrivilegedActionException e) {
1892	<	throw new RuntimeException("Could not initialize intrinsics",
1893	<	e.getCause());
1894	<	}
1895	<	}
1918	>	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
1919		}
1920
1921	<	private static sun.misc.Unsafe getUnsafeByReflection()
1899	<	throws NoSuchFieldException, IllegalAccessException {
1900	<	java.lang.reflect.Field f =
1901	<	sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
1902	<	f.setAccessible(true);
1903	<	return (sun.misc.Unsafe) f.get(null);
1904	<	}
1905	<
1906	<	private static long fieldOffset(String fieldName, Class<?> klazz) {
1907	<	try {
1908	<	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
1909	<	} catch (NoSuchFieldException e) {
1910	<	// Convert Exception to Error
1911	<	NoSuchFieldError error = new NoSuchFieldError(fieldName);
1912	<	error.initCause(e);
1913	<	throw error;
1914	<	}
1915	<	}
1921	>	// Unsafe mechanics
1922
1923		private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1924		private static final long eventCountOffset =
1925	<	fieldOffset("eventCount", ForkJoinPool.class);
1925	>	objectFieldOffset("eventCount", ForkJoinPool.class);
1926		private static final long workerCountsOffset =
1927	<	fieldOffset("workerCounts", ForkJoinPool.class);
1927	>	objectFieldOffset("workerCounts", ForkJoinPool.class);
1928		private static final long runControlOffset =
1929	<	fieldOffset("runControl", ForkJoinPool.class);
1929	>	objectFieldOffset("runControl", ForkJoinPool.class);
1930		private static final long syncStackOffset =
1931	<	fieldOffset("syncStack",ForkJoinPool.class);
1931	>	objectFieldOffset("syncStack",ForkJoinPool.class);
1932		private static final long spareStackOffset =
1933	<	fieldOffset("spareStack", ForkJoinPool.class);
1933	>	objectFieldOffset("spareStack", ForkJoinPool.class);
1934
1935		private boolean casEventCount(long cmp, long val) {
1936		return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
#	Line 1941 | Line 1947 | public class ForkJoinPool extends Abstra
1947		private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1948		return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1949		}
1950	+
1951	+	private static long objectFieldOffset(String field, Class<?> klazz) {
1952	+	try {
1953	+	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1954	+	} catch (NoSuchFieldException e) {
1955	+	// Convert Exception to corresponding Error
1956	+	NoSuchFieldError error = new NoSuchFieldError(field);
1957	+	error.initCause(e);
1958	+	throw error;
1959	+	}
1960	+	}
1961	+
1962	+	/**
1963	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1964	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1965	+	* into a jdk.
1966	+	*
1967	+	* @return a sun.misc.Unsafe
1968	+	*/
1969	+	private static sun.misc.Unsafe getUnsafe() {
1970	+	try {
1971	+	return sun.misc.Unsafe.getUnsafe();
1972	+	} catch (SecurityException se) {
1973	+	try {
1974	+	return java.security.AccessController.doPrivileged
1975	+	(new java.security
1976	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1977	+	public sun.misc.Unsafe run() throws Exception {
1978	+	java.lang.reflect.Field f = sun.misc
1979	+	.Unsafe.class.getDeclaredField("theUnsafe");
1980	+	f.setAccessible(true);
1981	+	return (sun.misc.Unsafe) f.get(null);
1982	+	}});
1983	+	} catch (java.security.PrivilegedActionException e) {
1984	+	throw new RuntimeException("Could not initialize intrinsics",
1985	+	e.getCause());
1986	+	}
1987	+	}
1988	+	}
1989		}

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