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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.10 by jsr166, Mon Jul 20 23:07:43 2009 UTC vs.
Revision 1.50 by dl, Fri Dec 4 12:09:46 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.*;
12	<	import sun.misc.Unsafe;
13	<	import java.lang.reflect.*;
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
20	<	* submitted tasks. Otherwise, use would not usually outweigh the
21	<	* construction and bookkeeping overhead of creating a large set of
22	<	* 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
93		*/
94		public class ForkJoinPool extends AbstractExecutorService {
95
#	Line 71 | 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		}
122
123		/**
124	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
124	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
125		* new ForkJoinWorkerThread.
126		*/
127		static class  DefaultForkJoinWorkerThreadFactory
#	Line 181 | Line 215 | public class ForkJoinPool extends Abstra
215		private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
216
217		/**
218	<	* Head of Treiber stack for barrier sync. See below for explanation
218	>	* Head of Treiber stack for barrier sync. See below for explanation.
219		*/
220		private volatile WaitQueueNode syncStack;
221
#	Line 216 | Line 250 | public class ForkJoinPool extends Abstra
250		* threads, packed into one int to ensure consistent snapshot when
251		* making decisions about creating and suspending spare
252		* threads. Updated only by CAS.  Note: CASes in
253	<	* updateRunningCount and preJoin running active count is in low
254	<	* word, so need to be modified if this changes
253	>	* updateRunningCount and preJoin assume that running active count
254	>	* is in low word, so need to be modified if this changes.
255		*/
256		private volatile int workerCounts;
257
#	Line 229 | Line 263 | public class ForkJoinPool extends Abstra
263		* Adds delta (which may be negative) to running count.  This must
264		* be called before (with negative arg) and after (with positive)
265		* any managed synchronization (i.e., mainly, joins).
266	+	*
267		* @param delta the number to add
268		*/
269		final void updateRunningCount(int delta) {
270		int s;
271	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
271	>	do {} while (!casWorkerCounts(s = workerCounts, s + delta));
272		}
273
274		/**
275		* Adds delta (which may be negative) to both total and running
276		* count.  This must be called upon creation and termination of
277		* worker threads.
278	+	*
279		* @param delta the number to add
280		*/
281		private void updateWorkerCount(int delta) {
282		int d = delta + (delta << 16); // add to both lo and hi parts
283		int s;
284	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
284	>	do {} while (!casWorkerCounts(s = workerCounts, s + d));
285		}
286
287		/**
#	Line 271 | Line 307 | public class ForkJoinPool extends Abstra
307		private static int runControlFor(int r, int a)   { return (r << 16) + a; }
308
309		/**
310	<	* Try incrementing active count; fail on contention. Called by
311	<	* workers before/during executing tasks.
312	<	* @return true on success;
310	>	* Tries incrementing active count; fails on contention.
311	>	* Called by workers before/during executing tasks.
312	>	*
313	>	* @return true on success
314		*/
315		final boolean tryIncrementActiveCount() {
316		int c = runControl;
#	Line 284 | Line 321 | public class ForkJoinPool extends Abstra
321		* Tries decrementing active count; fails on contention.
322		* Possibly triggers termination on success.
323		* Called by workers when they can't find tasks.
324	+	*
325		* @return true on success
326		*/
327		final boolean tryDecrementActiveCount() {
#	Line 297 | 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) {
343	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
343	>	// i.e. least bit is nonzero runState bit
344	>	return ((c & -c) >>> 16) != 0;
345		}
346
347		/**
#	Line 327 | 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 and 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
375		*         because it does not hold {@link
376	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
376	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
377		*/
378		public ForkJoinPool() {
379		this(Runtime.getRuntime().availableProcessors(),
#	Line 341 | 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,
386	<	* @param parallelism the number of worker threads
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 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
394	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
394	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
395		*/
396		public ForkJoinPool(int parallelism) {
397		this(parallelism, defaultForkJoinWorkerThreadFactory);
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
410	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
410	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
411		*/
412		public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
413		this(Runtime.getRuntime().availableProcessors(), factory);
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
428	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
428	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
429		*/
430		public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
431		if (parallelism <= 0 || parallelism > MAX_THREADS)
#	Line 402 | Line 446 | public class ForkJoinPool extends Abstra
446		}
447
448		/**
449	<	* Create new worker using factory.
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 424 | Line 469 | public class ForkJoinPool extends Abstra
469		* Returns a good size for worker array given pool size.
470		* Currently requires size to be a power of two.
471		*/
472	<	private static int arraySizeFor(int ps) {
473	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
472	>	private static int arraySizeFor(int poolSize) {
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		/**
486		* Creates or resizes array if necessary to hold newLength.
487	<	* Call only under exclusion or lock.
487	>	* Call only under exclusion.
488	>	*
489		* @return the array
490		*/
491		private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
#	Line 444 | Line 499 | public class ForkJoinPool extends Abstra
499		}
500
501		/**
502	<	* Try to shrink workers into smaller array after one or more terminate
502	>	* Tries to shrink workers into smaller array after one or more terminate.
503		*/
504		private void tryShrinkWorkerArray() {
505		ForkJoinWorkerThread[] ws = workers;
#	Line 460 | Line 515 | public class ForkJoinPool extends Abstra
515		}
516
517		/**
518	<	* Initialize workers if necessary
518	>	* Initializes workers if necessary.
519		*/
520		final void ensureWorkerInitialization() {
521		ForkJoinWorkerThread[] ws = workers;
#	Line 471 | Line 526 | public class ForkJoinPool extends Abstra
526		ws = workers;
527		if (ws == null) {
528		int ps = parallelism;
529	+	updateWorkerCount(ps);
530		ws = ensureWorkerArrayCapacity(ps);
531		for (int i = 0; i < ps; ++i) {
532		ForkJoinWorkerThread w = createWorker(i);
533		if (w != null) {
534		ws[i] = w;
535		w.start();
480	–	updateWorkerCount(1);
536		}
537	+	else
538	+	updateWorkerCount(-1);
539		}
540		}
541		} finally {
#	Line 527 | Line 584 | public class ForkJoinPool extends Abstra
584		* Common code for execute, invoke and submit
585		*/
586		private <T> void doSubmit(ForkJoinTask<T> task) {
587	+	if (task == null)
588	+	throw new NullPointerException();
589		if (isShutdown())
590		throw new RejectedExecutionException();
591		if (workers == null)
#	Line 536 | Line 595 | public class ForkJoinPool extends Abstra
595		}
596
597		/**
598	<	* Performs the given task; returning its result upon completion
598	>	* Performs the given task, returning its result upon completion.
599	>	*
600		* @param task the task
601		* @return the task's result
602	<	* @throws NullPointerException if task is null
603	<	* @throws RejectedExecutionException if pool is shut down
602	>	* @throws NullPointerException if the task is null
603	>	* @throws RejectedExecutionException if the task cannot be
604	>	*         scheduled for execution
605		*/
606		public <T> T invoke(ForkJoinTask<T> task) {
607		doSubmit(task);
#	Line 549 | Line 610 | public class ForkJoinPool extends Abstra
610
611		/**
612		* Arranges for (asynchronous) execution of the given task.
613	+	*
614		* @param task the task
615	<	* @throws NullPointerException if task is null
616	<	* @throws RejectedExecutionException if pool is shut down
615	>	* @throws NullPointerException if the task is null
616	>	* @throws RejectedExecutionException if the task cannot be
617	>	*         scheduled for execution
618		*/
619	<	public <T> void execute(ForkJoinTask<T> task) {
619	>	public void execute(ForkJoinTask<?> task) {
620		doSubmit(task);
621		}
622
623		// AbstractExecutorService methods
624
625	+	/**
626	+	* @throws NullPointerException if the task is null
627	+	* @throws RejectedExecutionException if the task cannot be
628	+	*         scheduled for execution
629	+	*/
630		public void execute(Runnable task) {
631	<	doSubmit(new AdaptedRunnable<Void>(task, null));
631	>	ForkJoinTask<?> job;
632	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
633	>	job = (ForkJoinTask<?>) task;
634	>	else
635	>	job = ForkJoinTask.adapt(task, null);
636	>	doSubmit(job);
637		}
638
639	+	/**
640	+	* @throws NullPointerException if the task is null
641	+	* @throws RejectedExecutionException if the task cannot be
642	+	*         scheduled for execution
643	+	*/
644		public <T> ForkJoinTask<T> submit(Callable<T> task) {
645	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
645	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
646		doSubmit(job);
647		return job;
648		}
649
650	+	/**
651	+	* @throws NullPointerException if the task is null
652	+	* @throws RejectedExecutionException if the task cannot be
653	+	*         scheduled for execution
654	+	*/
655		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
656	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
656	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
657		doSubmit(job);
658		return job;
659		}
660
661	+	/**
662	+	* @throws NullPointerException if the task is null
663	+	* @throws RejectedExecutionException if the task cannot be
664	+	*         scheduled for execution
665	+	*/
666		public ForkJoinTask<?> submit(Runnable task) {
667	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
667	>	ForkJoinTask<?> job;
668	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
669	>	job = (ForkJoinTask<?>) task;
670	>	else
671	>	job = ForkJoinTask.adapt(task, null);
672		doSubmit(job);
673		return job;
674		}
675
676		/**
677	<	* Adaptor for Runnables. This implements RunnableFuture
678	<	* to be compliant with AbstractExecutorService constraints
677	>	* Submits a ForkJoinTask for execution.
678	>	*
679	>	* @param task the task to submit
680	>	* @return the task
681	>	* @throws NullPointerException if the task is null
682	>	* @throws RejectedExecutionException if the task cannot be
683	>	*         scheduled for execution
684		*/
685	<	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
686	<	implements RunnableFuture<T> {
687	<	final Runnable runnable;
591	<	final T resultOnCompletion;
592	<	T result;
593	<	AdaptedRunnable(Runnable runnable, T result) {
594	<	if (runnable == null) throw new NullPointerException();
595	<	this.runnable = runnable;
596	<	this.resultOnCompletion = result;
597	<	}
598	<	public T getRawResult() { return result; }
599	<	public void setRawResult(T v) { result = v; }
600	<	public boolean exec() {
601	<	runnable.run();
602	<	result = resultOnCompletion;
603	<	return true;
604	<	}
605	<	public void run() { invoke(); }
685	>	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
686	>	doSubmit(task);
687	>	return task;
688		}
689
690	+
691		/**
692	<	* Adaptor for Callables
692	>	* @throws NullPointerException       {@inheritDoc}
693	>	* @throws RejectedExecutionException {@inheritDoc}
694		*/
611	–	static final class AdaptedCallable<T> extends ForkJoinTask<T>
612	–	implements RunnableFuture<T> {
613	–	final Callable<T> callable;
614	–	T result;
615	–	AdaptedCallable(Callable<T> callable) {
616	–	if (callable == null) throw new NullPointerException();
617	–	this.callable = callable;
618	–	}
619	–	public T getRawResult() { return result; }
620	–	public void setRawResult(T v) { result = v; }
621	–	public boolean exec() {
622	–	try {
623	–	result = callable.call();
624	–	return true;
625	–	} catch (Error err) {
626	–	throw err;
627	–	} catch (RuntimeException rex) {
628	–	throw rex;
629	–	} catch (Exception ex) {
630	–	throw new RuntimeException(ex);
631	–	}
632	–	}
633	–	public void run() { invoke(); }
634	–	}
635	–
695		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
696	<	ArrayList<ForkJoinTask<T>> ts =
696	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
697		new ArrayList<ForkJoinTask<T>>(tasks.size());
698	<	for (Callable<T> c : tasks)
699	<	ts.add(new AdaptedCallable<T>(c));
700	<	invoke(new InvokeAll<T>(ts));
701	<	return (List<Future<T>>)(List)ts;
698	>	for (Callable<T> task : tasks)
699	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
700	>	invoke(new InvokeAll<T>(forkJoinTasks));
701	>
702	>	@SuppressWarnings({"unchecked", "rawtypes"})
703	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
704	>	return futures;
705		}
706
707		static final class InvokeAll<T> extends RecursiveAction {
708		final ArrayList<ForkJoinTask<T>> tasks;
709		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
710		public void compute() {
711	<	try { invokeAll(tasks); } catch(Exception ignore) {}
711	>	try { invokeAll(tasks); }
712	>	catch (Exception ignore) {}
713		}
714	+	private static final long serialVersionUID = -7914297376763021607L;
715		}
716
717		// Configuration and status settings and queries
718
719		/**
720	<	* Returns the factory used for constructing new workers
720	>	* Returns the factory used for constructing new workers.
721		*
722		* @return the factory used for constructing new workers
723		*/
#	Line 664 | Line 728 | public class ForkJoinPool extends Abstra
728		/**
729		* Returns the handler for internal worker threads that terminate
730		* due to unrecoverable errors encountered while executing tasks.
731	<	* @return the handler, or null if none
731	>	*
732	>	* @return the handler, or {@code null} if none
733		*/
734		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
735		Thread.UncaughtExceptionHandler h;
#	Line 685 | Line 750 | public class ForkJoinPool extends Abstra
750		* as handler.
751		*
752		* @param h the new handler
753	<	* @return the old handler, or null if none
753	>	* @return the old handler, or {@code null} if none
754		* @throws SecurityException if a security manager exists and
755		*         the caller is not permitted to modify threads
756		*         because it does not hold {@link
757	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
757	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
758		*/
759		public Thread.UncaughtExceptionHandler
760		setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
#	Line 717 | Line 782 | public class ForkJoinPool extends Abstra
782
783		/**
784		* Sets the target parallelism level of this pool.
785	+	*
786		* @param parallelism the target parallelism
787		* @throws IllegalArgumentException if parallelism less than or
788	<	* equal to zero or greater than maximum size bounds.
788	>	* equal to zero or greater than maximum size bounds
789		* @throws SecurityException if a security manager exists and
790		*         the caller is not permitted to modify threads
791		*         because it does not hold {@link
792	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
792	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
793		*/
794		public void setParallelism(int parallelism) {
795		checkPermission();
#	Line 732 | Line 798 | public class ForkJoinPool extends Abstra
798		final ReentrantLock lock = this.workerLock;
799		lock.lock();
800		try {
801	<	if (!isTerminating()) {
801	>	if (isProcessingTasks()) {
802		int p = this.parallelism;
803		this.parallelism = parallelism;
804	<	if (parallelism > p)
805	<	createAndStartAddedWorkers();
806	<	else
807	<	trimSpares();
804	>	if (workers != null) {
805	>	if (parallelism > p)
806	>	createAndStartAddedWorkers();
807	>	else
808	>	trimSpares();
809	>	}
810		}
811		} finally {
812		lock.unlock();
#	Line 747 | Line 815 | public class ForkJoinPool extends Abstra
815		}
816
817		/**
818	<	* Returns the targeted number of worker threads in this pool.
818	>	* Returns the targeted parallelism level of this pool.
819		*
820	<	* @return the targeted number of worker threads in this pool
820	>	* @return the targeted parallelism level of this pool
821		*/
822		public int getParallelism() {
823		return parallelism;
#	Line 758 | Line 826 | public class ForkJoinPool extends Abstra
826		/**
827		* Returns the number of worker threads that have started but not
828		* yet terminated.  This result returned by this method may differ
829	<	* from {@code getParallelism} when threads are created to
829	>	* from {@link #getParallelism} when threads are created to
830		* maintain parallelism when others are cooperatively blocked.
831		*
832		* @return the number of worker threads
#	Line 769 | Line 837 | public class ForkJoinPool extends Abstra
837
838		/**
839		* Returns the maximum number of threads allowed to exist in the
840	<	* pool, even if there are insufficient unblocked running threads.
840	>	* pool. Unless set using {@link #setMaximumPoolSize}, the
841	>	* maximum is an implementation-defined value designed only to
842	>	* prevent runaway growth.
843	>	*
844		* @return the maximum
845		*/
846		public int getMaximumPoolSize() {
#	Line 778 | Line 849 | public class ForkJoinPool extends Abstra
849
850		/**
851		* Sets the maximum number of threads allowed to exist in the
852	<	* pool, even if there are insufficient unblocked running threads.
853	<	* Setting this value has no effect on current pool size. It
854	<	* controls construction of new threads.
855	<	* @throws IllegalArgumentException if negative or greater then
856	<	* internal implementation limit.
852	>	* pool. The given value should normally be greater than or equal
853	>	* to the {@link #getParallelism parallelism} level. Setting this
854	>	* value has no effect on current pool size. It controls
855	>	* construction of new threads.
856	>	*
857	>	* @throws IllegalArgumentException if negative or greater than
858	>	* internal implementation limit
859		*/
860		public void setMaximumPoolSize(int newMax) {
861		if (newMax < 0 || newMax > MAX_THREADS)
#	Line 792 | Line 865 | public class ForkJoinPool extends Abstra
865
866
867		/**
868	<	* Returns true if this pool dynamically maintains its target
869	<	* parallelism level. If false, new threads are added only to
870	<	* avoid possible starvation.
871	<	* This setting is by default true;
872	<	* @return true if maintains parallelism
868	>	* Returns {@code true} if this pool dynamically maintains its
869	>	* target parallelism level. If false, new threads are added only
870	>	* to avoid possible starvation.  This setting is by default true.
871	>	*
872	>	* @return {@code true} if maintains parallelism
873		*/
874		public boolean getMaintainsParallelism() {
875		return maintainsParallelism;
#	Line 806 | Line 879 | public class ForkJoinPool extends Abstra
879		* Sets whether this pool dynamically maintains its target
880		* parallelism level. If false, new threads are added only to
881		* avoid possible starvation.
882	<	* @param enable true to maintains parallelism
882	>	*
883	>	* @param enable {@code true} to maintain parallelism
884		*/
885		public void setMaintainsParallelism(boolean enable) {
886		maintainsParallelism = enable;
#	Line 817 | Line 891 | public class ForkJoinPool extends Abstra
891		* tasks that are never joined. This mode may be more appropriate
892		* than default locally stack-based mode in applications in which
893		* worker threads only process asynchronous tasks.  This method is
894	<	* designed to be invoked only when pool is quiescent, and
894	>	* designed to be invoked only when the pool is quiescent, and
895		* typically only before any tasks are submitted. The effects of
896		* invocations at other times may be unpredictable.
897		*
898	<	* @param async if true, use locally FIFO scheduling
899	<	* @return the previous mode.
898	>	* @param async if {@code true}, use locally FIFO scheduling
899	>	* @return the previous mode
900	>	* @see #getAsyncMode
901		*/
902		public boolean setAsyncMode(boolean async) {
903		boolean oldMode = locallyFifo;
#	Line 839 | Line 914 | public class ForkJoinPool extends Abstra
914		}
915
916		/**
917	<	* Returns true if this pool uses local first-in-first-out
917	>	* Returns {@code true} if this pool uses local first-in-first-out
918		* scheduling mode for forked tasks that are never joined.
919		*
920	<	* @return true if this pool uses async mode.
920	>	* @return {@code true} if this pool uses async mode
921	>	* @see #setAsyncMode
922		*/
923		public boolean getAsyncMode() {
924		return locallyFifo;
#	Line 863 | Line 939 | public class ForkJoinPool extends Abstra
939		* Returns an estimate of the number of threads that are currently
940		* stealing or executing tasks. This method may overestimate the
941		* number of active threads.
942	<	* @return the number of active threads.
942	>	*
943	>	* @return the number of active threads
944		*/
945		public int getActiveThreadCount() {
946		return activeCountOf(runControl);
#	Line 873 | Line 950 | public class ForkJoinPool extends Abstra
950		* Returns an estimate of the number of threads that are currently
951		* idle waiting for tasks. This method may underestimate the
952		* number of idle threads.
953	<	* @return the number of idle threads.
953	>	*
954	>	* @return the number of idle threads
955		*/
956		final int getIdleThreadCount() {
957		int c = runningCountOf(workerCounts) - activeCountOf(runControl);
958	<	return (c <= 0)? 0 : c;
958	>	return (c <= 0) ? 0 : c;
959		}
960
961		/**
962	<	* Returns true if all worker threads are currently idle. An idle
963	<	* worker is one that cannot obtain a task to execute because none
964	<	* are available to steal from other threads, and there are no
965	<	* pending submissions to the pool. This method is conservative:
966	<	* It might not return true immediately upon idleness of all
967	<	* threads, but will eventually become true if threads remain
968	<	* inactive.
969	<	* @return true if all threads are currently idle
962	>	* Returns {@code true} if all worker threads are currently idle.
963	>	* An idle worker is one that cannot obtain a task to execute
964	>	* because none are available to steal from other threads, and
965	>	* there are no pending submissions to the pool. This method is
966	>	* conservative; it might not return {@code true} immediately upon
967	>	* idleness of all threads, but will eventually become true if
968	>	* threads remain inactive.
969	>	*
970	>	* @return {@code true} if all threads are currently idle
971		*/
972		public boolean isQuiescent() {
973		return activeCountOf(runControl) == 0;
#	Line 899 | Line 978 | public class ForkJoinPool extends Abstra
978		* one thread's work queue by another. The reported value
979		* underestimates the actual total number of steals when the pool
980		* is not quiescent. This value may be useful for monitoring and
981	<	* tuning fork/join programs: In general, steal counts should be
981	>	* tuning fork/join programs: in general, steal counts should be
982		* high enough to keep threads busy, but low enough to avoid
983		* overhead and contention across threads.
984	<	* @return the number of steals.
984	>	*
985	>	* @return the number of steals
986		*/
987		public long getStealCount() {
988		return stealCount.get();
989		}
990
991		/**
992	<	* Accumulate steal count from a worker. Call only
993	<	* when worker known to be idle.
992	>	* Accumulates steal count from a worker.
993	>	* Call only when worker known to be idle.
994		*/
995		private void updateStealCount(ForkJoinWorkerThread w) {
996		int sc = w.getAndClearStealCount();
#	Line 925 | Line 1005 | public class ForkJoinPool extends Abstra
1005		* an approximation, obtained by iterating across all threads in
1006		* the pool. This method may be useful for tuning task
1007		* granularities.
1008	<	* @return the number of queued tasks.
1008	>	*
1009	>	* @return the number of queued tasks
1010		*/
1011		public long getQueuedTaskCount() {
1012		long count = 0;
#	Line 941 | Line 1022 | public class ForkJoinPool extends Abstra
1022		}
1023
1024		/**
1025	<	* Returns an estimate of the number tasks submitted to this pool
1026	<	* that have not yet begun executing. This method takes time
1025	>	* Returns an estimate of the number of tasks submitted to this
1026	>	* pool that have not yet begun executing.  This method takes time
1027		* proportional to the number of submissions.
1028	<	* @return the number of queued submissions.
1028	>	*
1029	>	* @return the number of queued submissions
1030		*/
1031		public int getQueuedSubmissionCount() {
1032		return submissionQueue.size();
1033		}
1034
1035		/**
1036	<	* Returns true if there are any tasks submitted to this pool
1037	<	* that have not yet begun executing.
1038	<	* @return {@code true} if there are any queued submissions.
1036	>	* Returns {@code true} if there are any tasks submitted to this
1037	>	* pool that have not yet begun executing.
1038	>	*
1039	>	* @return {@code true} if there are any queued submissions
1040		*/
1041		public boolean hasQueuedSubmissions() {
1042		return !submissionQueue.isEmpty();
#	Line 963 | Line 1046 | public class ForkJoinPool extends Abstra
1046		* Removes and returns the next unexecuted submission if one is
1047		* available.  This method may be useful in extensions to this
1048		* class that re-assign work in systems with multiple pools.
1049	<	* @return the next submission, or null if none
1049	>	*
1050	>	* @return the next submission, or {@code null} if none
1051		*/
1052		protected ForkJoinTask<?> pollSubmission() {
1053		return submissionQueue.poll();
#	Line 973 | Line 1057 | public class ForkJoinPool extends Abstra
1057		* Removes all available unexecuted submitted and forked tasks
1058		* from scheduling queues and adds them to the given collection,
1059		* without altering their execution status. These may include
1060	<	* artificially generated or wrapped tasks. This method is designed
1061	<	* to be invoked only when the pool is known to be
1060	>	* artificially generated or wrapped tasks. This method is
1061	>	* designed to be invoked only when the pool is known to be
1062		* quiescent. Invocations at other times may not remove all
1063		* tasks. A failure encountered while attempting to add elements
1064		* to collection {@code c} may result in elements being in
#	Line 982 | Line 1066 | public class ForkJoinPool extends Abstra
1066		* exception is thrown.  The behavior of this operation is
1067		* undefined if the specified collection is modified while the
1068		* operation is in progress.
1069	+	*
1070		* @param c the collection to transfer elements into
1071		* @return the number of elements transferred
1072		*/
1073	<	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
1073	>	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1074		int n = submissionQueue.drainTo(c);
1075		ForkJoinWorkerThread[] ws = workers;
1076		if (ws != null) {
#	Line 1025 | Line 1110 | public class ForkJoinPool extends Abstra
1110		}
1111
1112		private static String runStateToString(int rs) {
1113	<	switch(rs) {
1113	>	switch (rs) {
1114		case RUNNING: return "Running";
1115		case SHUTDOWN: return "Shutting down";
1116		case TERMINATING: return "Terminating";
#	Line 1042 | Line 1127 | public class ForkJoinPool extends Abstra
1127		* Invocation has no additional effect if already shut down.
1128		* Tasks that are in the process of being submitted concurrently
1129		* during the course of this method may or may not be rejected.
1130	+	*
1131		* @throws SecurityException if a security manager exists and
1132		*         the caller is not permitted to modify threads
1133		*         because it does not hold {@link
1134	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
1134	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1135		*/
1136		public void shutdown() {
1137		checkPermission();
1138		transitionRunStateTo(SHUTDOWN);
1139	<	if (canTerminateOnShutdown(runControl))
1139	>	if (canTerminateOnShutdown(runControl)) {
1140	>	if (workers == null) { // shutting down before workers created
1141	>	final ReentrantLock lock = this.workerLock;
1142	>	lock.lock();
1143	>	try {
1144	>	if (workers == null) {
1145	>	terminate();
1146	>	transitionRunStateTo(TERMINATED);
1147	>	termination.signalAll();
1148	>	}
1149	>	} finally {
1150	>	lock.unlock();
1151	>	}
1152	>	}
1153		terminateOnShutdown();
1154	+	}
1155		}
1156
1157		/**
1158	<	* Attempts to stop all actively executing tasks, and cancels all
1159	<	* waiting tasks.  Tasks that are in the process of being
1160	<	* submitted or executed concurrently during the course of this
1161	<	* method may or may not be rejected. Unlike some other executors,
1162	<	* this method cancels rather than collects non-executed tasks
1163	<	* upon termination, so always returns an empty list. However, you
1164	<	* can use method {@code drainTasksTo} before invoking this
1165	<	* method to transfer unexecuted tasks to another collection.
1158	>	* Attempts to cancel and/or stop all tasks, and reject all
1159	>	* subsequently submitted tasks.  Tasks that are in the process of
1160	>	* being submitted or executed concurrently during the course of
1161	>	* this method may or may not be rejected. This method cancels
1162	>	* both existing and unexecuted tasks, in order to permit
1163	>	* termination in the presence of task dependencies. So the method
1164	>	* always returns an empty list (unlike the case for some other
1165	>	* Executors).
1166	>	*
1167		* @return an empty list
1168		* @throws SecurityException if a security manager exists and
1169		*         the caller is not permitted to modify threads
1170		*         because it does not hold {@link
1171	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
1171	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1172		*/
1173		public List<Runnable> shutdownNow() {
1174		checkPermission();
#	Line 1086 | Line 1187 | public class ForkJoinPool extends Abstra
1187
1188		/**
1189		* Returns {@code true} if the process of termination has
1190	<	* commenced but possibly not yet completed.
1190	>	* commenced but not yet completed.  This method may be useful for
1191	>	* debugging. A return of {@code true} reported a sufficient
1192	>	* period after shutdown may indicate that submitted tasks have
1193	>	* ignored or suppressed interruption, causing this executor not
1194	>	* to properly terminate.
1195		*
1196	<	* @return {@code true} if terminating
1196	>	* @return {@code true} if terminating but not yet terminated
1197		*/
1198		public boolean isTerminating() {
1199	<	return runStateOf(runControl) >= TERMINATING;
1199	>	return runStateOf(runControl) == TERMINATING;
1200		}
1201
1202		/**
#	Line 1104 | Line 1209 | public class ForkJoinPool extends Abstra
1209		}
1210
1211		/**
1212	+	* Returns true if pool is not terminating or terminated.
1213	+	* Used internally to suppress execution when terminating.
1214	+	*/
1215	+	final boolean isProcessingTasks() {
1216	+	return runStateOf(runControl) < TERMINATING;
1217	+	}
1218	+
1219	+	/**
1220		* Blocks until all tasks have completed execution after a shutdown
1221		* request, or the timeout occurs, or the current thread is
1222		* interrupted, whichever happens first.
#	Line 1135 | Line 1248 | public class ForkJoinPool extends Abstra
1248		// Shutdown and termination support
1249
1250		/**
1251	<	* Callback from terminating worker. Null out the corresponding
1252	<	* workers slot, and if terminating, try to terminate, else try to
1253	<	* shrink workers array.
1251	>	* Callback from terminating worker. Nulls out the corresponding
1252	>	* workers slot, and if terminating, tries to terminate; else
1253	>	* tries to shrink workers array.
1254	>	*
1255		* @param w the worker
1256		*/
1257		final void workerTerminated(ForkJoinWorkerThread w) {
#	Line 1156 | Line 1270 | public class ForkJoinPool extends Abstra
1270		transitionRunStateTo(TERMINATED);
1271		termination.signalAll();
1272		}
1273	<	else if (!isTerminating()) {
1273	>	else if (isProcessingTasks()) {
1274		tryShrinkWorkerArray();
1275		tryResumeSpare(true); // allow replacement
1276		}
#	Line 1168 | Line 1282 | public class ForkJoinPool extends Abstra
1282		}
1283
1284		/**
1285	<	* Initiate termination.
1285	>	* Initiates termination.
1286		*/
1287		private void terminate() {
1288		if (transitionRunStateTo(TERMINATING)) {
#	Line 1266 | Line 1380 | public class ForkJoinPool extends Abstra
1380		}
1381		}
1382
1269	–
1383		/*
1384		* Nodes for event barrier to manage idle threads.  Queue nodes
1385		* are basic Treiber stack nodes, also used for spare stack.
#	Line 1290 | Line 1403 | public class ForkJoinPool extends Abstra
1403		* handling: Method signalWork returns without advancing count if
1404		* the queue appears to be empty.  This would ordinarily result in
1405		* races causing some queued waiters not to be woken up. To avoid
1406	<	* this, the first worker enqueued in method sync (see
1407	<	* syncIsReleasable) rescans for tasks after being enqueued, and
1408	<	* helps signal if any are found. This works well because the
1409	<	* worker has nothing better to do, and so might as well help
1410	<	* alleviate the overhead and contention on the threads actually
1411	<	* doing work.  Also, since event counts increments on task
1412	<	* availability exist to maintain liveness (rather than to force
1413	<	* refreshes etc), it is OK for callers to exit early if
1301	<	* contending with another signaller.
1406	>	* this, the first worker enqueued in method sync rescans for
1407	>	* tasks after being enqueued, and helps signal if any are
1408	>	* found. This works well because the worker has nothing better to
1409	>	* do, and so might as well help alleviate the overhead and
1410	>	* contention on the threads actually doing work.  Also, since
1411	>	* event counts increments on task availability exist to maintain
1412	>	* liveness (rather than to force refreshes etc), it is OK for
1413	>	* callers to exit early if contending with another signaller.
1414		*/
1415		static final class WaitQueueNode {
1416		WaitQueueNode next; // only written before enqueued
#	Line 1311 | Line 1423 | public class ForkJoinPool extends Abstra
1423		}
1424
1425		/**
1426	<	* Wakes up waiter, returning false if known to already
1426	>	* Wakes up waiter, returning false if known to already be awake
1427		*/
1428		boolean signal() {
1429		ForkJoinWorkerThread t = thread;
#	Line 1321 | Line 1433 | public class ForkJoinPool extends Abstra
1433		LockSupport.unpark(t);
1434		return true;
1435		}
1324	–
1325	–	/**
1326	–	* Awaits release on sync.
1327	–	*/
1328	–	void awaitSyncRelease(ForkJoinPool p) {
1329	–	while (thread != null && !p.syncIsReleasable(this))
1330	–	LockSupport.park(this);
1331	–	}
1332	–
1333	–	/**
1334	–	* Awaits resumption as spare.
1335	–	*/
1336	–	void awaitSpareRelease() {
1337	–	while (thread != null) {
1338	–	if (!Thread.interrupted())
1339	–	LockSupport.park(this);
1340	–	}
1341	–	}
1436		}
1437
1438		/**
1439		* Ensures that no thread is waiting for count to advance from the
1440		* current value of eventCount read on entry to this method, by
1441		* releasing waiting threads if necessary.
1348	–	* @return the count
1442		*/
1443	<	final long ensureSync() {
1443	>	final void ensureSync() {
1444		long c = eventCount;
1445		WaitQueueNode q;
1446		while ((q = syncStack) != null && q.count < c) {
#	Line 1358 | Line 1451 | public class ForkJoinPool extends Abstra
1451		break;
1452		}
1453		}
1361	–	return c;
1454		}
1455
1456		/**
#	Line 1366 | Line 1458 | public class ForkJoinPool extends Abstra
1458		*/
1459		private void signalIdleWorkers() {
1460		long c;
1461	<	do;while (!casEventCount(c = eventCount, c+1));
1461	>	do {} while (!casEventCount(c = eventCount, c+1));
1462		ensureSync();
1463		}
1464
1465		/**
1466		* Signals threads waiting to poll a task. Because method sync
1467		* rechecks availability, it is OK to only proceed if queue
1468	<	* appears to be non-empty, and OK to skip under contention to
1469	<	* increment count (since some other thread succeeded).
1468	>	* appears to be non-empty, and OK if CAS to increment count
1469	>	* fails (since some other thread succeeded).
1470		*/
1471		final void signalWork() {
1472	<	long c;
1473	<	WaitQueueNode q;
1474	<	if (syncStack != null &&
1475	<	casEventCount(c = eventCount, c+1) &&
1476	<	(((q = syncStack) != null && q.count <= c) &&
1477	<	(!casBarrierStack(q, q.next) || !q.signal())))
1478	<	ensureSync();
1472	>	if (syncStack != null) {
1473	>	long c;
1474	>	casEventCount(c = eventCount, c+1);
1475	>	WaitQueueNode q = syncStack;
1476	>	if (q != null && q.count <= c &&
1477	>	(!casBarrierStack(q, q.next) || !q.signal()))
1478	>	ensureSync();
1479	>	}
1480		}
1481
1482		/**
1483		* Waits until event count advances from last value held by
1484		* caller, or if excess threads, caller is resumed as spare, or
1485		* caller or pool is terminating. Updates caller's event on exit.
1486	+	*
1487		* @param w the calling worker thread
1488		*/
1489		final void sync(ForkJoinWorkerThread w) {
1490		updateStealCount(w); // Transfer w's count while it is idle
1491
1492	<	while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) {
1492	>	if (!w.isShutdown() && isProcessingTasks() && !suspendIfSpare(w)) {
1493		long prev = w.lastEventCount;
1494		WaitQueueNode node = null;
1495		WaitQueueNode h;
1496	+	boolean helpSignal = false;
1497		while (eventCount == prev &&
1498		((h = syncStack) == null || h.count == prev)) {
1499		if (node == null)
1500		node = new WaitQueueNode(prev, w);
1501		if (casBarrierStack(node.next = h, node)) {
1502	<	node.awaitSyncRelease(this);
1502	>	if (!Thread.interrupted() && node.thread != null &&
1503	>	eventCount == prev) {
1504	>	if (h == null && // cover signalWork race
1505	>	ForkJoinWorkerThread.hasQueuedTasks(workers))
1506	>	helpSignal = true;
1507	>	else
1508	>	LockSupport.park(this);
1509	>	}
1510	>	if (node.thread != null)
1511	>	node.thread = null;
1512		break;
1513		}
1514		}
1515	<	long ec = ensureSync();
1516	<	if (ec != prev) {
1515	>	long ec = eventCount;
1516	>	if (ec != prev)
1517		w.lastEventCount = ec;
1518	<	break;
1519	<	}
1518	>	else if (helpSignal)
1519	>	casEventCount(ec, ec + 1);
1520	>	ensureSync();
1521		}
1522		}
1523
1419	–	/**
1420	–	* Returns true if worker waiting on sync can proceed:
1421	–	*  - on signal (thread == null)
1422	–	*  - on event count advance (winning race to notify vs signaller)
1423	–	*  - on Interrupt
1424	–	*  - if the first queued node, we find work available
1425	–	* If node was not signalled and event count not advanced on exit,
1426	–	* then we also help advance event count.
1427	–	* @return true if node can be released
1428	–	*/
1429	–	final boolean syncIsReleasable(WaitQueueNode node) {
1430	–	long prev = node.count;
1431	–	if (!Thread.interrupted() && node.thread != null &&
1432	–	(node.next != null ||
1433	–	!ForkJoinWorkerThread.hasQueuedTasks(workers)) &&
1434	–	eventCount == prev)
1435	–	return false;
1436	–	if (node.thread != null) {
1437	–	node.thread = null;
1438	–	long ec = eventCount;
1439	–	if (prev <= ec) // help signal
1440	–	casEventCount(ec, ec+1);
1441	–	}
1442	–	return true;
1443	–	}
1524
1525		/**
1526	<	* Returns true if a new sync event occurred since last call to
1527	<	* sync or this method, if so, updating caller's count.
1526	>	* Returns {@code true} if a new sync event occurred since last
1527	>	* call to sync or this method, if so, updating caller's count.
1528		*/
1529		final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1530		long lc = w.lastEventCount;
1531	<	long ec = ensureSync();
1532	<	if (ec == lc)
1533	<	return false;
1534	<	w.lastEventCount = ec;
1535	<	return true;
1531	>	long ec = eventCount;
1532	>	if (lc != ec)
1533	>	w.lastEventCount = ec;
1534	>	ensureSync();
1535	>	return lc != ec || lc != eventCount;
1536		}
1537
1538		//  Parallelism maintenance
#	Line 1464 | Line 1544 | public class ForkJoinPool extends Abstra
1544		* spare thread when one is about to block (and remove or
1545		* suspend it later when unblocked -- see suspendIfSpare).
1546		* However, implementing this idea requires coping with
1547	<	* several problems: We have imperfect information about the
1547	>	* several problems: we have imperfect information about the
1548		* states of threads. Some count updates can and usually do
1549		* lag run state changes, despite arrangements to keep them
1550		* accurate (for example, when possible, updating counts
#	Line 1487 | Line 1567 | public class ForkJoinPool extends Abstra
1567		* target counts, else create only to avoid starvation
1568		* @return true if joinMe known to be done
1569		*/
1570	<	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1570	>	final boolean preJoin(ForkJoinTask<?> joinMe,
1571	>	boolean maintainParallelism) {
1572		maintainParallelism &= maintainsParallelism; // overrride
1573		boolean dec = false;  // true when running count decremented
1574		while (spareStack == null || !tryResumeSpare(dec)) {
1575		int counts = workerCounts;
1576	<	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1576	>	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1577		if (!needSpare(counts, maintainParallelism))
1578		break;
1579		if (joinMe.status < 0)
#	Line 1507 | Line 1588 | public class ForkJoinPool extends Abstra
1588		/**
1589		* Same idea as preJoin
1590		*/
1591	<	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1591	>	final boolean preBlock(ManagedBlocker blocker,
1592	>	boolean maintainParallelism) {
1593		maintainParallelism &= maintainsParallelism;
1594		boolean dec = false;
1595		while (spareStack == null || !tryResumeSpare(dec)) {
#	Line 1525 | Line 1607 | public class ForkJoinPool extends Abstra
1607		}
1608
1609		/**
1610	<	* Returns true if a spare thread appears to be needed.  If
1611	<	* maintaining parallelism, returns true when the deficit in
1610	>	* Returns {@code true} if a spare thread appears to be needed.
1611	>	* If maintaining parallelism, returns true when the deficit in
1612		* running threads is more than the surplus of total threads, and
1613		* there is apparently some work to do.  This self-limiting rule
1614		* means that the more threads that have already been added, the
1615		* less parallelism we will tolerate before adding another.
1616	+	*
1617		* @param counts current worker counts
1618		* @param maintainParallelism try to maintain parallelism
1619		*/
#	Line 1550 | Line 1633 | public class ForkJoinPool extends Abstra
1633		/**
1634		* Adds a spare worker if lock available and no more than the
1635		* expected numbers of threads exist.
1636	+	*
1637		* @return true if successful
1638		*/
1639		private boolean tryAddSpare(int expectedCounts) {
#	Line 1594 | Line 1678 | public class ForkJoinPool extends Abstra
1678		for (k = 0; k < len && ws[k] != null; ++k)
1679		;
1680		}
1681	<	if (k < len && !isTerminating() && (w = createWorker(k)) != null) {
1681	>	if (k < len && isProcessingTasks() && (w = createWorker(k)) != null) {
1682		ws[k] = w;
1683		w.start();
1684		}
#	Line 1609 | Line 1693 | public class ForkJoinPool extends Abstra
1693		* the same WaitQueueNodes as barriers.  They are resumed mainly
1694		* in preJoin, but are also woken on pool events that require all
1695		* threads to check run state.
1696	+	*
1697		* @param w the caller
1698		*/
1699		private boolean suspendIfSpare(ForkJoinWorkerThread w) {
1700		WaitQueueNode node = null;
1701	<	int s;
1702	<	while (parallelism < runningCountOf(s = workerCounts)) {
1701	>	for (;;) {
1702	>	int p = parallelism;
1703	>	int s = workerCounts;
1704	>	int r = runningCountOf(s);
1705	>	int t = totalCountOf(s);
1706	>	// use t as bound if r transiently out of sync
1707	>	if (t <= p || r <= p)
1708	>	return false; // not a spare
1709		if (node == null)
1710		node = new WaitQueueNode(0, w);
1711	<	if (casWorkerCounts(s, s-1)) { // representation-dependent
1712	<	// push onto stack
1622	<	do;while (!casSpareStack(node.next = spareStack, node));
1623	<	// block until released by resumeSpare
1624	<	node.awaitSpareRelease();
1625	<	return true;
1626	<	}
1711	>	if (casWorkerCounts(s, workerCountsFor(t, r - 1)))
1712	>	break;
1713		}
1714	<	return false;
1714	>	// push onto stack
1715	>	do {} while (!casSpareStack(node.next = spareStack, node));
1716	>	// block until released by resumeSpare
1717	>	while (!Thread.interrupted() && node.thread != null)
1718	>	LockSupport.park(this);
1719	>	return true;
1720		}
1721
1722		/**
1723		* Tries to pop and resume a spare thread.
1724	+	*
1725		* @param updateCount if true, increment running count on success
1726		* @return true if successful
1727		*/
#	Line 1648 | Line 1740 | public class ForkJoinPool extends Abstra
1740
1741		/**
1742		* Pops and resumes all spare threads. Same idea as ensureSync.
1743	+	*
1744		* @return true if any spares released
1745		*/
1746		private boolean resumeAllSpares() {
#	Line 1689 | Line 1782 | public class ForkJoinPool extends Abstra
1782
1783		/**
1784		* Interface for extending managed parallelism for tasks running
1785	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1786	<	* Method {@code isReleasable} must return true if blocking is not
1787	<	* necessary. Method {@code block} blocks the current thread
1788	<	* if necessary (perhaps internally invoking isReleasable before
1789	<	* actually blocking.).
1785	>	* in {@link ForkJoinPool}s.
1786	>	*
1787	>	* <p>A {@code ManagedBlocker} provides two methods.
1788	>	* Method {@code isReleasable} must return {@code true} if
1789	>	* blocking is not necessary. Method {@code block} blocks the
1790	>	* current thread if necessary (perhaps internally invoking
1791	>	* {@code isReleasable} before actually blocking).
1792	>	*
1793		* <p>For example, here is a ManagedBlocker based on a
1794		* ReentrantLock:
1795	<	* <pre>
1796	<	*   class ManagedLocker implements ManagedBlocker {
1797	<	*     final ReentrantLock lock;
1798	<	*     boolean hasLock = false;
1799	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1800	<	*     public boolean block() {
1801	<	*        if (!hasLock)
1802	<	*           lock.lock();
1803	<	*        return true;
1708	<	*     }
1709	<	*     public boolean isReleasable() {
1710	<	*        return hasLock || (hasLock = lock.tryLock());
1711	<	*     }
1795	>	*  <pre> {@code
1796	>	* class ManagedLocker implements ManagedBlocker {
1797	>	*   final ReentrantLock lock;
1798	>	*   boolean hasLock = false;
1799	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1800	>	*   public boolean block() {
1801	>	*     if (!hasLock)
1802	>	*       lock.lock();
1803	>	*     return true;
1804		*   }
1805	<	* </pre>
1805	>	*   public boolean isReleasable() {
1806	>	*     return hasLock || (hasLock = lock.tryLock());
1807	>	*   }
1808	>	* }}</pre>
1809		*/
1810		public static interface ManagedBlocker {
1811		/**
1812		* Possibly blocks the current thread, for example waiting for
1813		* a lock or condition.
1814	<	* @return true if no additional blocking is necessary (i.e.,
1815	<	* if isReleasable would return true).
1814	>	*
1815	>	* @return {@code true} if no additional blocking is necessary
1816	>	* (i.e., if isReleasable would return true)
1817		* @throws InterruptedException if interrupted while waiting
1818	<	* (the method is not required to do so, but is allowed to).
1818	>	* (the method is not required to do so, but is allowed to)
1819		*/
1820		boolean block() throws InterruptedException;
1821
1822		/**
1823	<	* Returns true if blocking is unnecessary.
1823	>	* Returns {@code true} if blocking is unnecessary.
1824		*/
1825		boolean isReleasable();
1826		}
1827
1828		/**
1829		* Blocks in accord with the given blocker.  If the current thread
1830	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
1831	<	* spare thread to be activated if necessary to ensure parallelism
1832	<	* while the current thread is blocked.  If
1833	<	* {@code maintainParallelism} is true and the pool supports
1834	<	* it ({@link #getMaintainsParallelism}), this method attempts to
1835	<	* maintain the pool's nominal parallelism. Otherwise if activates
1836	<	* a thread only if necessary to avoid complete starvation. This
1837	<	* option may be preferable when blockages use timeouts, or are
1838	<	* almost always brief.
1839	<	*
1840	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1841	<	* equivalent to
1842	<	* <pre>
1843	<	*   while (!blocker.isReleasable())
1844	<	*      if (blocker.block())
1845	<	*         return;
1846	<	* </pre>
1847	<	* If the caller is a ForkJoinTask, then the pool may first
1848	<	* be expanded to ensure parallelism, and later adjusted.
1830	>	* is a {@link ForkJoinWorkerThread}, this method possibly
1831	>	* arranges for a spare thread to be activated if necessary to
1832	>	* ensure parallelism while the current thread is blocked.
1833	>	*
1834	>	* <p>If {@code maintainParallelism} is {@code true} and the pool
1835	>	* supports it ({@link #getMaintainsParallelism}), this method
1836	>	* attempts to maintain the pool's nominal parallelism. Otherwise
1837	>	* it activates a thread only if necessary to avoid complete
1838	>	* starvation. This option may be preferable when blockages use
1839	>	* timeouts, or are almost always brief.
1840	>	*
1841	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
1842	>	* behaviorally equivalent to
1843	>	*  <pre> {@code
1844	>	* while (!blocker.isReleasable())
1845	>	*   if (blocker.block())
1846	>	*     return;
1847	>	* }</pre>
1848	>	*
1849	>	* If the caller is a {@code ForkJoinTask}, then the pool may
1850	>	* first be expanded to ensure parallelism, and later adjusted.
1851		*
1852		* @param blocker the blocker
1853	<	* @param maintainParallelism if true and supported by this pool,
1854	<	* attempt to maintain the pool's nominal parallelism; otherwise
1855	<	* activate a thread only if necessary to avoid complete
1856	<	* starvation.
1857	<	* @throws InterruptedException if blocker.block did so.
1853	>	* @param maintainParallelism if {@code true} and supported by
1854	>	* this pool, attempt to maintain the pool's nominal parallelism;
1855	>	* otherwise activate a thread only if necessary to avoid
1856	>	* complete starvation.
1857	>	* @throws InterruptedException if blocker.block did so
1858		*/
1859		public static void managedBlock(ManagedBlocker blocker,
1860		boolean maintainParallelism)
1861		throws InterruptedException {
1862		Thread t = Thread.currentThread();
1863	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1864	<	((ForkJoinWorkerThread)t).pool : null);
1863	>	ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ?
1864	>	((ForkJoinWorkerThread) t).pool : null);
1865		if (!blocker.isReleasable()) {
1866		try {
1867		if (pool == null ||
#	Line 1778 | Line 1876 | public class ForkJoinPool extends Abstra
1876
1877		private static void awaitBlocker(ManagedBlocker blocker)
1878		throws InterruptedException {
1879	<	do;while (!blocker.isReleasable() && !blocker.block());
1879	>	do {} while (!blocker.isReleasable() && !blocker.block());
1880		}
1881
1882	<	// AbstractExecutorService overrides
1882	>	// AbstractExecutorService overrides.  These rely on undocumented
1883	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1884	>	// implement RunnableFuture.
1885
1886		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1887	<	return new AdaptedRunnable(runnable, value);
1887	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
1888		}
1889
1890		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1891	<	return new AdaptedCallable(callable);
1891	>	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
1892		}
1893
1894	+	// Unsafe mechanics
1895
1896	<	// Temporary Unsafe mechanics for preliminary release
1897	<	private static Unsafe getUnsafe() throws Throwable {
1898	<	try {
1899	<	return Unsafe.getUnsafe();
1900	<	} catch (SecurityException se) {
1901	<	try {
1902	<	return java.security.AccessController.doPrivileged
1903	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1904	<	public Unsafe run() throws Exception {
1905	<	return getUnsafePrivileged();
1906	<	}});
1806	<	} catch (java.security.PrivilegedActionException e) {
1807	<	throw e.getCause();
1808	<	}
1809	<	}
1810	<	}
1811	<
1812	<	private static Unsafe getUnsafePrivileged()
1813	<	throws NoSuchFieldException, IllegalAccessException {
1814	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1815	<	f.setAccessible(true);
1816	<	return (Unsafe) f.get(null);
1817	<	}
1818	<
1819	<	private static long fieldOffset(String fieldName)
1820	<	throws NoSuchFieldException {
1821	<	return _unsafe.objectFieldOffset
1822	<	(ForkJoinPool.class.getDeclaredField(fieldName));
1823	<	}
1824	<
1825	<	static final Unsafe _unsafe;
1826	<	static final long eventCountOffset;
1827	<	static final long workerCountsOffset;
1828	<	static final long runControlOffset;
1829	<	static final long syncStackOffset;
1830	<	static final long spareStackOffset;
1831	<
1832	<	static {
1833	<	try {
1834	<	_unsafe = getUnsafe();
1835	<	eventCountOffset = fieldOffset("eventCount");
1836	<	workerCountsOffset = fieldOffset("workerCounts");
1837	<	runControlOffset = fieldOffset("runControl");
1838	<	syncStackOffset = fieldOffset("syncStack");
1839	<	spareStackOffset = fieldOffset("spareStack");
1840	<	} catch (Throwable e) {
1841	<	throw new RuntimeException("Could not initialize intrinsics", e);
1842	<	}
1843	<	}
1896	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1897	>	private static final long eventCountOffset =
1898	>	objectFieldOffset("eventCount", ForkJoinPool.class);
1899	>	private static final long workerCountsOffset =
1900	>	objectFieldOffset("workerCounts", ForkJoinPool.class);
1901	>	private static final long runControlOffset =
1902	>	objectFieldOffset("runControl", ForkJoinPool.class);
1903	>	private static final long syncStackOffset =
1904	>	objectFieldOffset("syncStack",ForkJoinPool.class);
1905	>	private static final long spareStackOffset =
1906	>	objectFieldOffset("spareStack", ForkJoinPool.class);
1907
1908		private boolean casEventCount(long cmp, long val) {
1909	<	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1909	>	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
1910		}
1911		private boolean casWorkerCounts(int cmp, int val) {
1912	<	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1912	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1913		}
1914		private boolean casRunControl(int cmp, int val) {
1915	<	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1915	>	return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
1916		}
1917		private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1918	<	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1918	>	return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
1919		}
1920		private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1921	<	return _unsafe.compareAndSwapObject(this, syncStackOffset, cmp, val);
1921	>	return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1922	>	}
1923	>
1924	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1925	>	try {
1926	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1927	>	} catch (NoSuchFieldException e) {
1928	>	// Convert Exception to corresponding Error
1929	>	NoSuchFieldError error = new NoSuchFieldError(field);
1930	>	error.initCause(e);
1931	>	throw error;
1932	>	}
1933	>	}
1934	>
1935	>	/**
1936	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1937	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1938	>	* into a jdk.
1939	>	*
1940	>	* @return a sun.misc.Unsafe
1941	>	*/
1942	>	private static sun.misc.Unsafe getUnsafe() {
1943	>	try {
1944	>	return sun.misc.Unsafe.getUnsafe();
1945	>	} catch (SecurityException se) {
1946	>	try {
1947	>	return java.security.AccessController.doPrivileged
1948	>	(new java.security
1949	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1950	>	public sun.misc.Unsafe run() throws Exception {
1951	>	java.lang.reflect.Field f = sun.misc
1952	>	.Unsafe.class.getDeclaredField("theUnsafe");
1953	>	f.setAccessible(true);
1954	>	return (sun.misc.Unsafe) f.get(null);
1955	>	}});
1956	>	} catch (java.security.PrivilegedActionException e) {
1957	>	throw new RuntimeException("Could not initialize intrinsics",
1958	>	e.getCause());
1959	>	}
1960	>	}
1961		}
1962		}

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