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Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.12 by jsr166, Tue Jul 21 18:11:44 2009 UTC vs.
Revision 1.42 by dl, Mon Aug 3 13:01:15 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 waiting to join others. However, no such adjustments are
49	>	* 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 explictly {@link
73	+	* #shutdown} such a pool upon program exit.
74	+	*
75	+	* <pre>
76	+	* static final ForkJoinPool mainPool = new ForkJoinPool();
77	+	* ...
78	+	* public void sort(long[] array) {
79	+	*   mainPool.invoke(new SortTask(array, 0, array.length));
80	+	* }
81	+	* </pre>
82	+	*
83		* <p><b>Implementation notes</b>: This implementation restricts the
84		* maximum number of running threads to 32767. Attempts to create
85		* pools with greater than the maximum result in
86	<	* IllegalArgumentExceptions.
86	>	* {@code IllegalArgumentException}.
87	>	*
88	>	* @since 1.7
89	>	* @author Doug Lea
90		*/
91		public class ForkJoinPool extends AbstractExecutorService {
92
#	Line 71 | Line 102 | public class ForkJoinPool extends Abstra
102		private static final int MAX_THREADS =  0x7FFF;
103
104		/**
105	<	* Factory for creating new ForkJoinWorkerThreads.  A
106	<	* ForkJoinWorkerThreadFactory must be defined and used for
107	<	* ForkJoinWorkerThread subclasses that extend base functionality
108	<	* or initialize threads with different contexts.
105	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
106	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
107	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
108	>	* functionality or initialize threads with different contexts.
109		*/
110		public static interface ForkJoinWorkerThreadFactory {
111		/**
#	Line 87 | Line 118 | public class ForkJoinPool extends Abstra
118		}
119
120		/**
121	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
121	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
122		* new ForkJoinWorkerThread.
123		*/
124		static class  DefaultForkJoinWorkerThreadFactory
#	Line 181 | Line 212 | public class ForkJoinPool extends Abstra
212		private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
213
214		/**
215	<	* Head of Treiber stack for barrier sync. See below for explanation
215	>	* Head of Treiber stack for barrier sync. See below for explanation.
216		*/
217		private volatile WaitQueueNode syncStack;
218
#	Line 216 | Line 247 | public class ForkJoinPool extends Abstra
247		* threads, packed into one int to ensure consistent snapshot when
248		* making decisions about creating and suspending spare
249		* threads. Updated only by CAS.  Note: CASes in
250	<	* updateRunningCount and preJoin running active count is in low
251	<	* word, so need to be modified if this changes
250	>	* updateRunningCount and preJoin assume that running active count
251	>	* is in low word, so need to be modified if this changes.
252		*/
253		private volatile int workerCounts;
254
#	Line 229 | Line 260 | public class ForkJoinPool extends Abstra
260		* Adds delta (which may be negative) to running count.  This must
261		* be called before (with negative arg) and after (with positive)
262		* any managed synchronization (i.e., mainly, joins).
263	+	*
264		* @param delta the number to add
265		*/
266		final void updateRunningCount(int delta) {
267		int s;
268	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
268	>	do {} while (!casWorkerCounts(s = workerCounts, s + delta));
269		}
270
271		/**
272		* Adds delta (which may be negative) to both total and running
273		* count.  This must be called upon creation and termination of
274		* worker threads.
275	+	*
276		* @param delta the number to add
277		*/
278		private void updateWorkerCount(int delta) {
279		int d = delta + (delta << 16); // add to both lo and hi parts
280		int s;
281	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
281	>	do {} while (!casWorkerCounts(s = workerCounts, s + d));
282		}
283
284		/**
#	Line 271 | Line 304 | public class ForkJoinPool extends Abstra
304		private static int runControlFor(int r, int a)   { return (r << 16) + a; }
305
306		/**
307	<	* Try incrementing active count; fail on contention. Called by
308	<	* workers before/during executing tasks.
307	>	* Tries incrementing active count; fails on contention.
308	>	* Called by workers before/during executing tasks.
309	>	*
310		* @return true on success
311		*/
312		final boolean tryIncrementActiveCount() {
#	Line 284 | Line 318 | public class ForkJoinPool extends Abstra
318		* Tries decrementing active count; fails on contention.
319		* Possibly triggers termination on success.
320		* Called by workers when they can't find tasks.
321	+	*
322		* @return true on success
323		*/
324		final boolean tryDecrementActiveCount() {
#	Line 297 | Line 332 | public class ForkJoinPool extends Abstra
332		}
333
334		/**
335	<	* Returns true if argument represents zero active count and
336	<	* nonzero runstate, which is the triggering condition for
335	>	* Returns {@code true} if argument represents zero active count
336	>	* and nonzero runstate, which is the triggering condition for
337		* terminating on shutdown.
338		*/
339		private static boolean canTerminateOnShutdown(int c) {
340	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
340	>	// i.e. least bit is nonzero runState bit
341	>	return ((c & -c) >>> 16) != 0;
342		}
343
344		/**
#	Line 327 | Line 363 | public class ForkJoinPool extends Abstra
363		// Constructors
364
365		/**
366	<	* Creates a ForkJoinPool with a pool size equal to the number of
367	<	* processors available on the system and using the default
368	<	* ForkJoinWorkerThreadFactory,
366	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
367	>	* java.lang.Runtime#availableProcessors}, and using the {@linkplain
368	>	* #defaultForkJoinWorkerThreadFactory default thread factory}.
369	>	*
370		* @throws SecurityException if a security manager exists and
371		*         the caller is not permitted to modify threads
372		*         because it does not hold {@link
373	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
373	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
374		*/
375		public ForkJoinPool() {
376		this(Runtime.getRuntime().availableProcessors(),
#	Line 341 | Line 378 | public class ForkJoinPool extends Abstra
378		}
379
380		/**
381	<	* Creates a ForkJoinPool with the indicated parallelism level
382	<	* threads, and using the default ForkJoinWorkerThreadFactory,
383	<	* @param parallelism the number of worker threads
381	>	* Creates a {@code ForkJoinPool} with the indicated parallelism
382	>	* level and using the {@linkplain
383	>	* #defaultForkJoinWorkerThreadFactory default thread factory}.
384	>	*
385	>	* @param parallelism the parallelism level
386		* @throws IllegalArgumentException if parallelism less than or
387		* equal to zero
388		* @throws SecurityException if a security manager exists and
389		*         the caller is not permitted to modify threads
390		*         because it does not hold {@link
391	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
391	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
392		*/
393		public ForkJoinPool(int parallelism) {
394		this(parallelism, defaultForkJoinWorkerThreadFactory);
395		}
396
397		/**
398	<	* Creates a ForkJoinPool with parallelism equal to the number of
399	<	* processors available on the system and using the given
400	<	* ForkJoinWorkerThreadFactory,
398	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
399	>	* java.lang.Runtime#availableProcessors}, and using the given
400	>	* thread factory.
401	>	*
402		* @param factory the factory for creating new threads
403		* @throws NullPointerException if factory is null
404		* @throws SecurityException if a security manager exists and
405		*         the caller is not permitted to modify threads
406		*         because it does not hold {@link
407	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
407	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
408		*/
409		public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
410		this(Runtime.getRuntime().availableProcessors(), factory);
411		}
412
413		/**
414	<	* Creates a ForkJoinPool with the given parallelism and factory.
414	>	* Creates a {@code ForkJoinPool} with the given parallelism and
415	>	* thread factory.
416		*
417	<	* @param parallelism the targeted number of worker threads
417	>	* @param parallelism the parallelism level
418		* @param factory the factory for creating new threads
419		* @throws IllegalArgumentException if parallelism less than or
420		* equal to zero, or greater than implementation limit
#	Line 381 | Line 422 | public class ForkJoinPool extends Abstra
422		* @throws SecurityException if a security manager exists and
423		*         the caller is not permitted to modify threads
424		*         because it does not hold {@link
425	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
425	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
426		*/
427		public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
428		if (parallelism <= 0 || parallelism > MAX_THREADS)
#	Line 402 | Line 443 | public class ForkJoinPool extends Abstra
443		}
444
445		/**
446	<	* Create new worker using factory.
446	>	* Creates a new worker thread using factory.
447	>	*
448		* @param index the index to assign worker
449	<	* @return new worker, or null of factory failed
449	>	* @return new worker, or null if factory failed
450		*/
451		private ForkJoinWorkerThread createWorker(int index) {
452		Thread.UncaughtExceptionHandler h = ueh;
#	Line 424 | Line 466 | public class ForkJoinPool extends Abstra
466		* Returns a good size for worker array given pool size.
467		* Currently requires size to be a power of two.
468		*/
469	<	private static int arraySizeFor(int ps) {
470	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
469	>	private static int arraySizeFor(int poolSize) {
470	>	if (poolSize <= 1)
471	>	return 1;
472	>	// See Hackers Delight, sec 3.2
473	>	int c = poolSize >= MAX_THREADS ? MAX_THREADS : (poolSize - 1);
474	>	c |= c >>>  1;
475	>	c |= c >>>  2;
476	>	c |= c >>>  4;
477	>	c |= c >>>  8;
478	>	c |= c >>> 16;
479	>	return c + 1;
480		}
481
482		/**
483		* Creates or resizes array if necessary to hold newLength.
484	<	* Call only under exclusion or lock.
484	>	* Call only under exclusion.
485	>	*
486		* @return the array
487		*/
488		private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
#	Line 444 | Line 496 | public class ForkJoinPool extends Abstra
496		}
497
498		/**
499	<	* Try to shrink workers into smaller array after one or more terminate
499	>	* Tries to shrink workers into smaller array after one or more terminate.
500		*/
501		private void tryShrinkWorkerArray() {
502		ForkJoinWorkerThread[] ws = workers;
#	Line 460 | Line 512 | public class ForkJoinPool extends Abstra
512		}
513
514		/**
515	<	* Initialize workers if necessary
515	>	* Initializes workers if necessary.
516		*/
517		final void ensureWorkerInitialization() {
518		ForkJoinWorkerThread[] ws = workers;
#	Line 527 | Line 579 | public class ForkJoinPool extends Abstra
579		* Common code for execute, invoke and submit
580		*/
581		private <T> void doSubmit(ForkJoinTask<T> task) {
582	+	if (task == null)
583	+	throw new NullPointerException();
584		if (isShutdown())
585		throw new RejectedExecutionException();
586		if (workers == null)
#	Line 536 | Line 590 | public class ForkJoinPool extends Abstra
590		}
591
592		/**
593	<	* Performs the given task; returning its result upon completion
593	>	* Performs the given task, returning its result upon completion.
594	>	*
595		* @param task the task
596		* @return the task's result
597		* @throws NullPointerException if task is null
#	Line 549 | Line 604 | public class ForkJoinPool extends Abstra
604
605		/**
606		* Arranges for (asynchronous) execution of the given task.
607	+	*
608		* @param task the task
609		* @throws NullPointerException if task is null
610		* @throws RejectedExecutionException if pool is shut down
611		*/
612	<	public <T> void execute(ForkJoinTask<T> task) {
612	>	public void execute(ForkJoinTask<?> task) {
613		doSubmit(task);
614		}
615
616		// AbstractExecutorService methods
617
618		public void execute(Runnable task) {
619	<	doSubmit(new AdaptedRunnable<Void>(task, null));
619	>	ForkJoinTask<?> job;
620	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
621	>	job = (ForkJoinTask<?>) task;
622	>	else
623	>	job = ForkJoinTask.adapt(task, null);
624	>	doSubmit(job);
625		}
626
627		public <T> ForkJoinTask<T> submit(Callable<T> task) {
628	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
628	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
629		doSubmit(job);
630		return job;
631		}
632
633		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
634	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
634	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
635		doSubmit(job);
636		return job;
637		}
638
639		public ForkJoinTask<?> submit(Runnable task) {
640	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
640	>	ForkJoinTask<?> job;
641	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
642	>	job = (ForkJoinTask<?>) task;
643	>	else
644	>	job = ForkJoinTask.adapt(task, null);
645		doSubmit(job);
646		return job;
647		}
648
649		/**
650	<	* Adaptor for Runnables. This implements RunnableFuture
651	<	* to be compliant with AbstractExecutorService constraints
650	>	* Submits a ForkJoinTask for execution.
651	>	*
652	>	* @param task the task to submit
653	>	* @return the task
654	>	* @throws RejectedExecutionException if the task cannot be
655	>	*         scheduled for execution
656	>	* @throws NullPointerException if the task is null
657		*/
658	<	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
659	<	implements RunnableFuture<T> {
660	<	final Runnable runnable;
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(); }
658	>	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
659	>	doSubmit(task);
660	>	return task;
661		}
662
608	–	/**
609	–	* Adaptor for Callables
610	–	*/
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	–	}
663
664		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
665	<	ArrayList<ForkJoinTask<T>> ts =
665	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
666		new ArrayList<ForkJoinTask<T>>(tasks.size());
667	<	for (Callable<T> c : tasks)
668	<	ts.add(new AdaptedCallable<T>(c));
669	<	invoke(new InvokeAll<T>(ts));
670	<	return (List<Future<T>>)(List)ts;
667	>	for (Callable<T> task : tasks)
668	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
669	>	invoke(new InvokeAll<T>(forkJoinTasks));
670	>
671	>	@SuppressWarnings({"unchecked", "rawtypes"})
672	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
673	>	return futures;
674		}
675
676		static final class InvokeAll<T> extends RecursiveAction {
677		final ArrayList<ForkJoinTask<T>> tasks;
678		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
679		public void compute() {
680	<	try { invokeAll(tasks); } catch(Exception ignore) {}
680	>	try { invokeAll(tasks); }
681	>	catch (Exception ignore) {}
682		}
683	+	private static final long serialVersionUID = -7914297376763021607L;
684		}
685
686		// Configuration and status settings and queries
687
688		/**
689	<	* Returns the factory used for constructing new workers
689	>	* Returns the factory used for constructing new workers.
690		*
691		* @return the factory used for constructing new workers
692		*/
#	Line 664 | Line 697 | public class ForkJoinPool extends Abstra
697		/**
698		* Returns the handler for internal worker threads that terminate
699		* due to unrecoverable errors encountered while executing tasks.
700	<	* @return the handler, or null if none
700	>	*
701	>	* @return the handler, or {@code null} if none
702		*/
703		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
704		Thread.UncaughtExceptionHandler h;
#	Line 685 | Line 719 | public class ForkJoinPool extends Abstra
719		* as handler.
720		*
721		* @param h the new handler
722	<	* @return the old handler, or null if none
722	>	* @return the old handler, or {@code null} if none
723		* @throws SecurityException if a security manager exists and
724		*         the caller is not permitted to modify threads
725		*         because it does not hold {@link
726	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
726	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
727		*/
728		public Thread.UncaughtExceptionHandler
729		setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
#	Line 717 | Line 751 | public class ForkJoinPool extends Abstra
751
752		/**
753		* Sets the target parallelism level of this pool.
754	+	*
755		* @param parallelism the target parallelism
756		* @throws IllegalArgumentException if parallelism less than or
757		* equal to zero or greater than maximum size bounds
758		* @throws SecurityException if a security manager exists and
759		*         the caller is not permitted to modify threads
760		*         because it does not hold {@link
761	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
761	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
762		*/
763		public void setParallelism(int parallelism) {
764		checkPermission();
#	Line 732 | Line 767 | public class ForkJoinPool extends Abstra
767		final ReentrantLock lock = this.workerLock;
768		lock.lock();
769		try {
770	<	if (!isTerminating()) {
770	>	if (isProcessingTasks()) {
771		int p = this.parallelism;
772		this.parallelism = parallelism;
773		if (parallelism > p)
#	Line 747 | Line 782 | public class ForkJoinPool extends Abstra
782		}
783
784		/**
785	<	* Returns the targeted number of worker threads in this pool.
785	>	* Returns the targeted parallelism level of this pool.
786		*
787	<	* @return the targeted number of worker threads in this pool
787	>	* @return the targeted parallelism level of this pool
788		*/
789		public int getParallelism() {
790		return parallelism;
#	Line 758 | Line 793 | public class ForkJoinPool extends Abstra
793		/**
794		* Returns the number of worker threads that have started but not
795		* yet terminated.  This result returned by this method may differ
796	<	* from {@code getParallelism} when threads are created to
796	>	* from {@link #getParallelism} when threads are created to
797		* maintain parallelism when others are cooperatively blocked.
798		*
799		* @return the number of worker threads
#	Line 769 | Line 804 | public class ForkJoinPool extends Abstra
804
805		/**
806		* Returns the maximum number of threads allowed to exist in the
807	<	* pool, even if there are insufficient unblocked running threads.
807	>	* pool.  Unless set using {@link #setMaximumPoolSize}, the
808	>	* maximum is an implementation-defined value designed only to
809	>	* prevent runaway growth.
810	>	*
811		* @return the maximum
812		*/
813		public int getMaximumPoolSize() {
#	Line 778 | Line 816 | public class ForkJoinPool extends Abstra
816
817		/**
818		* Sets the maximum number of threads allowed to exist in the
819	<	* pool, even if there are insufficient unblocked running threads.
820	<	* Setting this value has no effect on current pool size. It
821	<	* controls construction of new threads.
822	<	* @throws IllegalArgumentException if negative or greater then
819	>	* pool.  Setting this value has no effect on current pool
820	>	* size. It controls construction of new threads.
821	>	*
822	>	* @throws IllegalArgumentException if negative or greater than
823		* internal implementation limit
824		*/
825		public void setMaximumPoolSize(int newMax) {
#	Line 792 | Line 830 | public class ForkJoinPool extends Abstra
830
831
832		/**
833	<	* Returns true if this pool dynamically maintains its target
834	<	* parallelism level. If false, new threads are added only to
835	<	* avoid possible starvation.
836	<	* This setting is by default true;
837	<	* @return true if maintains parallelism
833	>	* Returns {@code true} if this pool dynamically maintains its
834	>	* target parallelism level. If false, new threads are added only
835	>	* to avoid possible starvation.  This setting is by default true.
836	>	*
837	>	* @return {@code true} if maintains parallelism
838		*/
839		public boolean getMaintainsParallelism() {
840		return maintainsParallelism;
#	Line 806 | Line 844 | public class ForkJoinPool extends Abstra
844		* Sets whether this pool dynamically maintains its target
845		* parallelism level. If false, new threads are added only to
846		* avoid possible starvation.
847	<	* @param enable true to maintains parallelism
847	>	*
848	>	* @param enable {@code true} to maintain parallelism
849		*/
850		public void setMaintainsParallelism(boolean enable) {
851		maintainsParallelism = enable;
#	Line 817 | Line 856 | public class ForkJoinPool extends Abstra
856		* tasks that are never joined. This mode may be more appropriate
857		* than default locally stack-based mode in applications in which
858		* worker threads only process asynchronous tasks.  This method is
859	<	* designed to be invoked only when pool is quiescent, and
859	>	* designed to be invoked only when the pool is quiescent, and
860		* typically only before any tasks are submitted. The effects of
861		* invocations at other times may be unpredictable.
862		*
863	<	* @param async if true, use locally FIFO scheduling
863	>	* @param async if {@code true}, use locally FIFO scheduling
864		* @return the previous mode
865	+	* @see #getAsyncMode
866		*/
867		public boolean setAsyncMode(boolean async) {
868		boolean oldMode = locallyFifo;
#	Line 839 | Line 879 | public class ForkJoinPool extends Abstra
879		}
880
881		/**
882	<	* Returns true if this pool uses local first-in-first-out
882	>	* Returns {@code true} if this pool uses local first-in-first-out
883		* scheduling mode for forked tasks that are never joined.
884		*
885	<	* @return true if this pool uses async mode
885	>	* @return {@code true} if this pool uses async mode
886	>	* @see #setAsyncMode
887		*/
888		public boolean getAsyncMode() {
889		return locallyFifo;
#	Line 863 | Line 904 | public class ForkJoinPool extends Abstra
904		* Returns an estimate of the number of threads that are currently
905		* stealing or executing tasks. This method may overestimate the
906		* number of active threads.
907	+	*
908		* @return the number of active threads
909		*/
910		public int getActiveThreadCount() {
#	Line 873 | Line 915 | public class ForkJoinPool extends Abstra
915		* Returns an estimate of the number of threads that are currently
916		* idle waiting for tasks. This method may underestimate the
917		* number of idle threads.
918	+	*
919		* @return the number of idle threads
920		*/
921		final int getIdleThreadCount() {
922		int c = runningCountOf(workerCounts) - activeCountOf(runControl);
923	<	return (c <= 0)? 0 : c;
923	>	return (c <= 0) ? 0 : c;
924		}
925
926		/**
927	<	* Returns true if all worker threads are currently idle. An idle
928	<	* worker is one that cannot obtain a task to execute because none
929	<	* are available to steal from other threads, and there are no
930	<	* pending submissions to the pool. This method is conservative:
931	<	* It might not return true immediately upon idleness of all
932	<	* threads, but will eventually become true if threads remain
933	<	* inactive.
934	<	* @return true if all threads are currently idle
927	>	* Returns {@code true} if all worker threads are currently idle.
928	>	* An idle worker is one that cannot obtain a task to execute
929	>	* because none are available to steal from other threads, and
930	>	* there are no pending submissions to the pool. This method is
931	>	* conservative; it might not return {@code true} immediately upon
932	>	* idleness of all threads, but will eventually become true if
933	>	* threads remain inactive.
934	>	*
935	>	* @return {@code true} if all threads are currently idle
936		*/
937		public boolean isQuiescent() {
938		return activeCountOf(runControl) == 0;
#	Line 899 | Line 943 | public class ForkJoinPool extends Abstra
943		* one thread's work queue by another. The reported value
944		* underestimates the actual total number of steals when the pool
945		* is not quiescent. This value may be useful for monitoring and
946	<	* tuning fork/join programs: In general, steal counts should be
946	>	* tuning fork/join programs: in general, steal counts should be
947		* high enough to keep threads busy, but low enough to avoid
948		* overhead and contention across threads.
949	+	*
950		* @return the number of steals
951		*/
952		public long getStealCount() {
#	Line 909 | Line 954 | public class ForkJoinPool extends Abstra
954		}
955
956		/**
957	<	* Accumulate steal count from a worker. Call only
958	<	* when worker known to be idle.
957	>	* Accumulates steal count from a worker.
958	>	* Call only when worker known to be idle.
959		*/
960		private void updateStealCount(ForkJoinWorkerThread w) {
961		int sc = w.getAndClearStealCount();
#	Line 925 | Line 970 | public class ForkJoinPool extends Abstra
970		* an approximation, obtained by iterating across all threads in
971		* the pool. This method may be useful for tuning task
972		* granularities.
973	+	*
974		* @return the number of queued tasks
975		*/
976		public long getQueuedTaskCount() {
#	Line 941 | Line 987 | public class ForkJoinPool extends Abstra
987		}
988
989		/**
990	<	* Returns an estimate of the number tasks submitted to this pool
991	<	* that have not yet begun executing. This method takes time
990	>	* Returns an estimate of the number of tasks submitted to this
991	>	* pool that have not yet begun executing.  This method takes time
992		* proportional to the number of submissions.
993	+	*
994		* @return the number of queued submissions
995		*/
996		public int getQueuedSubmissionCount() {
#	Line 951 | Line 998 | public class ForkJoinPool extends Abstra
998		}
999
1000		/**
1001	<	* Returns true if there are any tasks submitted to this pool
1002	<	* that have not yet begun executing.
1001	>	* Returns {@code true} if there are any tasks submitted to this
1002	>	* pool that have not yet begun executing.
1003	>	*
1004		* @return {@code true} if there are any queued submissions
1005		*/
1006		public boolean hasQueuedSubmissions() {
#	Line 963 | Line 1011 | public class ForkJoinPool extends Abstra
1011		* Removes and returns the next unexecuted submission if one is
1012		* available.  This method may be useful in extensions to this
1013		* class that re-assign work in systems with multiple pools.
1014	<	* @return the next submission, or null if none
1014	>	*
1015	>	* @return the next submission, or {@code null} if none
1016		*/
1017		protected ForkJoinTask<?> pollSubmission() {
1018		return submissionQueue.poll();
#	Line 973 | Line 1022 | public class ForkJoinPool extends Abstra
1022		* Removes all available unexecuted submitted and forked tasks
1023		* from scheduling queues and adds them to the given collection,
1024		* without altering their execution status. These may include
1025	<	* artificially generated or wrapped tasks. This method is designed
1026	<	* to be invoked only when the pool is known to be
1025	>	* artificially generated or wrapped tasks. This method is
1026	>	* designed to be invoked only when the pool is known to be
1027		* quiescent. Invocations at other times may not remove all
1028		* tasks. A failure encountered while attempting to add elements
1029		* to collection {@code c} may result in elements being in
#	Line 982 | Line 1031 | public class ForkJoinPool extends Abstra
1031		* exception is thrown.  The behavior of this operation is
1032		* undefined if the specified collection is modified while the
1033		* operation is in progress.
1034	+	*
1035		* @param c the collection to transfer elements into
1036		* @return the number of elements transferred
1037		*/
1038	<	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
1038	>	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1039		int n = submissionQueue.drainTo(c);
1040		ForkJoinWorkerThread[] ws = workers;
1041		if (ws != null) {
#	Line 1042 | Line 1092 | public class ForkJoinPool extends Abstra
1092		* Invocation has no additional effect if already shut down.
1093		* Tasks that are in the process of being submitted concurrently
1094		* during the course of this method may or may not be rejected.
1095	+	*
1096		* @throws SecurityException if a security manager exists and
1097		*         the caller is not permitted to modify threads
1098		*         because it does not hold {@link
1099	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
1099	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1100		*/
1101		public void shutdown() {
1102		checkPermission();
1103		transitionRunStateTo(SHUTDOWN);
1104	<	if (canTerminateOnShutdown(runControl))
1104	>	if (canTerminateOnShutdown(runControl)) {
1105	>	if (workers == null) { // shutting down before workers created
1106	>	final ReentrantLock lock = this.workerLock;
1107	>	lock.lock();
1108	>	try {
1109	>	if (workers == null) {
1110	>	terminate();
1111	>	transitionRunStateTo(TERMINATED);
1112	>	termination.signalAll();
1113	>	}
1114	>	} finally {
1115	>	lock.unlock();
1116	>	}
1117	>	}
1118		terminateOnShutdown();
1119	+	}
1120		}
1121
1122		/**
1123	<	* Attempts to stop all actively executing tasks, and cancels all
1124	<	* waiting tasks.  Tasks that are in the process of being
1125	<	* submitted or executed concurrently during the course of this
1126	<	* method may or may not be rejected. Unlike some other executors,
1127	<	* this method cancels rather than collects non-executed tasks
1128	<	* upon termination, so always returns an empty list. However, you
1129	<	* can use method {@code drainTasksTo} before invoking this
1130	<	* method to transfer unexecuted tasks to another collection.
1123	>	* Attempts to cancel and/or stop all tasks, and reject all
1124	>	* subsequently submitted tasks.  Tasks that are in the process of
1125	>	* being submitted or executed concurrently during the course of
1126	>	* this method may or may not be rejected. This method cancels
1127	>	* both existing and unexecuted tasks, in order to permit
1128	>	* termination in the presence of task dependencies. So the method
1129	>	* always returns an empty list (unlike the case for some other
1130	>	* Executors).
1131	>	*
1132		* @return an empty list
1133		* @throws SecurityException if a security manager exists and
1134		*         the caller is not permitted to modify threads
1135		*         because it does not hold {@link
1136	<	*         java.lang.RuntimePermission}{@code ("modifyThread")},
1136	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1137		*/
1138		public List<Runnable> shutdownNow() {
1139		checkPermission();
#	Line 1086 | Line 1152 | public class ForkJoinPool extends Abstra
1152
1153		/**
1154		* Returns {@code true} if the process of termination has
1155	<	* commenced but possibly not yet completed.
1155	>	* commenced but not yet completed.  This method may be useful for
1156	>	* debugging. A return of {@code true} reported a sufficient
1157	>	* period after shutdown may indicate that submitted tasks have
1158	>	* ignored or suppressed interruption, causing this executor not
1159	>	* to properly terminate.
1160		*
1161	<	* @return {@code true} if terminating
1161	>	* @return {@code true} if terminating but not yet terminated
1162		*/
1163		public boolean isTerminating() {
1164	<	return runStateOf(runControl) >= TERMINATING;
1164	>	return runStateOf(runControl) == TERMINATING;
1165		}
1166
1167		/**
#	Line 1104 | Line 1174 | public class ForkJoinPool extends Abstra
1174		}
1175
1176		/**
1177	+	* Returns true if pool is not terminating or terminated.
1178	+	* Used internally to suppress execution when terminating.
1179	+	*/
1180	+	final boolean isProcessingTasks() {
1181	+	return runStateOf(runControl) < TERMINATING;
1182	+	}
1183	+
1184	+	/**
1185		* Blocks until all tasks have completed execution after a shutdown
1186		* request, or the timeout occurs, or the current thread is
1187		* interrupted, whichever happens first.
#	Line 1135 | Line 1213 | public class ForkJoinPool extends Abstra
1213		// Shutdown and termination support
1214
1215		/**
1216	<	* Callback from terminating worker. Null out the corresponding
1217	<	* workers slot, and if terminating, try to terminate, else try to
1218	<	* shrink workers array.
1216	>	* Callback from terminating worker. Nulls out the corresponding
1217	>	* workers slot, and if terminating, tries to terminate; else
1218	>	* tries to shrink workers array.
1219	>	*
1220		* @param w the worker
1221		*/
1222		final void workerTerminated(ForkJoinWorkerThread w) {
#	Line 1156 | Line 1235 | public class ForkJoinPool extends Abstra
1235		transitionRunStateTo(TERMINATED);
1236		termination.signalAll();
1237		}
1238	<	else if (!isTerminating()) {
1238	>	else if (isProcessingTasks()) {
1239		tryShrinkWorkerArray();
1240		tryResumeSpare(true); // allow replacement
1241		}
#	Line 1168 | Line 1247 | public class ForkJoinPool extends Abstra
1247		}
1248
1249		/**
1250	<	* Initiate termination.
1250	>	* Initiates termination.
1251		*/
1252		private void terminate() {
1253		if (transitionRunStateTo(TERMINATING)) {
#	Line 1345 | Line 1424 | public class ForkJoinPool extends Abstra
1424		* Ensures that no thread is waiting for count to advance from the
1425		* current value of eventCount read on entry to this method, by
1426		* releasing waiting threads if necessary.
1427	+	*
1428		* @return the count
1429		*/
1430		final long ensureSync() {
#	Line 1366 | Line 1446 | public class ForkJoinPool extends Abstra
1446		*/
1447		private void signalIdleWorkers() {
1448		long c;
1449	<	do;while (!casEventCount(c = eventCount, c+1));
1449	>	do {} while (!casEventCount(c = eventCount, c+1));
1450		ensureSync();
1451		}
1452
#	Line 1390 | Line 1470 | public class ForkJoinPool extends Abstra
1470		* Waits until event count advances from last value held by
1471		* caller, or if excess threads, caller is resumed as spare, or
1472		* caller or pool is terminating. Updates caller's event on exit.
1473	+	*
1474		* @param w the calling worker thread
1475		*/
1476		final void sync(ForkJoinWorkerThread w) {
1477		updateStealCount(w); // Transfer w's count while it is idle
1478
1479	<	while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) {
1479	>	while (!w.isShutdown() && isProcessingTasks() && !suspendIfSpare(w)) {
1480		long prev = w.lastEventCount;
1481		WaitQueueNode node = null;
1482		WaitQueueNode h;
#	Line 1417 | Line 1498 | public class ForkJoinPool extends Abstra
1498		}
1499
1500		/**
1501	<	* Returns true if worker waiting on sync can proceed:
1501	>	* Returns {@code true} if worker waiting on sync can proceed:
1502		*  - on signal (thread == null)
1503		*  - on event count advance (winning race to notify vs signaller)
1504	<	*  - on Interrupt
1504	>	*  - on interrupt
1505		*  - if the first queued node, we find work available
1506		* If node was not signalled and event count not advanced on exit,
1507		* then we also help advance event count.
1508	<	* @return true if node can be released
1508	>	*
1509	>	* @return {@code true} if node can be released
1510		*/
1511		final boolean syncIsReleasable(WaitQueueNode node) {
1512		long prev = node.count;
#	Line 1443 | Line 1525 | public class ForkJoinPool extends Abstra
1525		}
1526
1527		/**
1528	<	* Returns true if a new sync event occurred since last call to
1529	<	* sync or this method, if so, updating caller's count.
1528	>	* Returns {@code true} if a new sync event occurred since last
1529	>	* call to sync or this method, if so, updating caller's count.
1530		*/
1531		final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1532		long lc = w.lastEventCount;
#	Line 1464 | Line 1546 | public class ForkJoinPool extends Abstra
1546		* spare thread when one is about to block (and remove or
1547		* suspend it later when unblocked -- see suspendIfSpare).
1548		* However, implementing this idea requires coping with
1549	<	* several problems: We have imperfect information about the
1549	>	* several problems: we have imperfect information about the
1550		* states of threads. Some count updates can and usually do
1551		* lag run state changes, despite arrangements to keep them
1552		* accurate (for example, when possible, updating counts
#	Line 1487 | Line 1569 | public class ForkJoinPool extends Abstra
1569		* target counts, else create only to avoid starvation
1570		* @return true if joinMe known to be done
1571		*/
1572	<	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1572	>	final boolean preJoin(ForkJoinTask<?> joinMe,
1573	>	boolean maintainParallelism) {
1574		maintainParallelism &= maintainsParallelism; // overrride
1575		boolean dec = false;  // true when running count decremented
1576		while (spareStack == null || !tryResumeSpare(dec)) {
1577		int counts = workerCounts;
1578	<	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1578	>	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1579	>	// CAS cheat
1580		if (!needSpare(counts, maintainParallelism))
1581		break;
1582		if (joinMe.status < 0)
#	Line 1507 | Line 1591 | public class ForkJoinPool extends Abstra
1591		/**
1592		* Same idea as preJoin
1593		*/
1594	<	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1594	>	final boolean preBlock(ManagedBlocker blocker,
1595	>	boolean maintainParallelism) {
1596		maintainParallelism &= maintainsParallelism;
1597		boolean dec = false;
1598		while (spareStack == null || !tryResumeSpare(dec)) {
#	Line 1525 | Line 1610 | public class ForkJoinPool extends Abstra
1610		}
1611
1612		/**
1613	<	* Returns true if a spare thread appears to be needed.  If
1614	<	* maintaining parallelism, returns true when the deficit in
1613	>	* Returns {@code true} if a spare thread appears to be needed.
1614	>	* If maintaining parallelism, returns true when the deficit in
1615		* running threads is more than the surplus of total threads, and
1616		* there is apparently some work to do.  This self-limiting rule
1617		* means that the more threads that have already been added, the
1618		* less parallelism we will tolerate before adding another.
1619	+	*
1620		* @param counts current worker counts
1621		* @param maintainParallelism try to maintain parallelism
1622		*/
#	Line 1550 | Line 1636 | public class ForkJoinPool extends Abstra
1636		/**
1637		* Adds a spare worker if lock available and no more than the
1638		* expected numbers of threads exist.
1639	+	*
1640		* @return true if successful
1641		*/
1642		private boolean tryAddSpare(int expectedCounts) {
#	Line 1594 | Line 1681 | public class ForkJoinPool extends Abstra
1681		for (k = 0; k < len && ws[k] != null; ++k)
1682		;
1683		}
1684	<	if (k < len && !isTerminating() && (w = createWorker(k)) != null) {
1684	>	if (k < len && isProcessingTasks() && (w = createWorker(k)) != null) {
1685		ws[k] = w;
1686		w.start();
1687		}
#	Line 1609 | Line 1696 | public class ForkJoinPool extends Abstra
1696		* the same WaitQueueNodes as barriers.  They are resumed mainly
1697		* in preJoin, but are also woken on pool events that require all
1698		* threads to check run state.
1699	+	*
1700		* @param w the caller
1701		*/
1702		private boolean suspendIfSpare(ForkJoinWorkerThread w) {
#	Line 1619 | Line 1707 | public class ForkJoinPool extends Abstra
1707		node = new WaitQueueNode(0, w);
1708		if (casWorkerCounts(s, s-1)) { // representation-dependent
1709		// push onto stack
1710	<	do;while (!casSpareStack(node.next = spareStack, node));
1710	>	do {} while (!casSpareStack(node.next = spareStack, node));
1711		// block until released by resumeSpare
1712		node.awaitSpareRelease();
1713		return true;
#	Line 1630 | Line 1718 | public class ForkJoinPool extends Abstra
1718
1719		/**
1720		* Tries to pop and resume a spare thread.
1721	+	*
1722		* @param updateCount if true, increment running count on success
1723		* @return true if successful
1724		*/
#	Line 1648 | Line 1737 | public class ForkJoinPool extends Abstra
1737
1738		/**
1739		* Pops and resumes all spare threads. Same idea as ensureSync.
1740	+	*
1741		* @return true if any spares released
1742		*/
1743		private boolean resumeAllSpares() {
#	Line 1689 | Line 1779 | public class ForkJoinPool extends Abstra
1779
1780		/**
1781		* Interface for extending managed parallelism for tasks running
1782	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1783	<	* Method {@code isReleasable} must return true if blocking is not
1784	<	* necessary. Method {@code block} blocks the current thread
1785	<	* if necessary (perhaps internally invoking isReleasable before
1786	<	* actually blocking.).
1782	>	* in {@link ForkJoinPool}s.
1783	>	*
1784	>	* <p>A {@code ManagedBlocker} provides two methods.
1785	>	* Method {@code isReleasable} must return {@code true} if
1786	>	* blocking is not necessary. Method {@code block} blocks the
1787	>	* current thread if necessary (perhaps internally invoking
1788	>	* {@code isReleasable} before actually blocking).
1789	>	*
1790		* <p>For example, here is a ManagedBlocker based on a
1791		* ReentrantLock:
1792	<	* <pre>
1793	<	*   class ManagedLocker implements ManagedBlocker {
1794	<	*     final ReentrantLock lock;
1795	<	*     boolean hasLock = false;
1796	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1797	<	*     public boolean block() {
1798	<	*        if (!hasLock)
1799	<	*           lock.lock();
1800	<	*        return true;
1708	<	*     }
1709	<	*     public boolean isReleasable() {
1710	<	*        return hasLock || (hasLock = lock.tryLock());
1711	<	*     }
1792	>	*  <pre> {@code
1793	>	* class ManagedLocker implements ManagedBlocker {
1794	>	*   final ReentrantLock lock;
1795	>	*   boolean hasLock = false;
1796	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1797	>	*   public boolean block() {
1798	>	*     if (!hasLock)
1799	>	*       lock.lock();
1800	>	*     return true;
1801		*   }
1802	<	* </pre>
1802	>	*   public boolean isReleasable() {
1803	>	*     return hasLock || (hasLock = lock.tryLock());
1804	>	*   }
1805	>	* }}</pre>
1806		*/
1807		public static interface ManagedBlocker {
1808		/**
1809		* Possibly blocks the current thread, for example waiting for
1810		* a lock or condition.
1811	<	* @return true if no additional blocking is necessary (i.e.,
1812	<	* if isReleasable would return true)
1811	>	*
1812	>	* @return {@code true} if no additional blocking is necessary
1813	>	* (i.e., if isReleasable would return true)
1814		* @throws InterruptedException if interrupted while waiting
1815	<	* (the method is not required to do so, but is allowed to).
1815	>	* (the method is not required to do so, but is allowed to)
1816		*/
1817		boolean block() throws InterruptedException;
1818
1819		/**
1820	<	* Returns true if blocking is unnecessary.
1820	>	* Returns {@code true} if blocking is unnecessary.
1821		*/
1822		boolean isReleasable();
1823		}
1824
1825		/**
1826		* Blocks in accord with the given blocker.  If the current thread
1827	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
1828	<	* spare thread to be activated if necessary to ensure parallelism
1829	<	* while the current thread is blocked.  If
1830	<	* {@code maintainParallelism} is true and the pool supports
1831	<	* it ({@link #getMaintainsParallelism}), this method attempts to
1832	<	* maintain the pool's nominal parallelism. Otherwise if activates
1833	<	* a thread only if necessary to avoid complete starvation. This
1834	<	* option may be preferable when blockages use timeouts, or are
1835	<	* almost always brief.
1836	<	*
1837	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1838	<	* equivalent to
1839	<	* <pre>
1840	<	*   while (!blocker.isReleasable())
1841	<	*      if (blocker.block())
1842	<	*         return;
1843	<	* </pre>
1844	<	* If the caller is a ForkJoinTask, then the pool may first
1845	<	* be expanded to ensure parallelism, and later adjusted.
1827	>	* is a {@link ForkJoinWorkerThread}, this method possibly
1828	>	* arranges for a spare thread to be activated if necessary to
1829	>	* ensure parallelism while the current thread is blocked.
1830	>	*
1831	>	* <p>If {@code maintainParallelism} is {@code true} and the pool
1832	>	* supports it ({@link #getMaintainsParallelism}), this method
1833	>	* attempts to maintain the pool's nominal parallelism. Otherwise
1834	>	* it activates a thread only if necessary to avoid complete
1835	>	* starvation. This option may be preferable when blockages use
1836	>	* timeouts, or are almost always brief.
1837	>	*
1838	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
1839	>	* behaviorally equivalent to
1840	>	*  <pre> {@code
1841	>	* while (!blocker.isReleasable())
1842	>	*   if (blocker.block())
1843	>	*     return;
1844	>	* }</pre>
1845	>	*
1846	>	* If the caller is a {@code ForkJoinTask}, then the pool may
1847	>	* first be expanded to ensure parallelism, and later adjusted.
1848		*
1849		* @param blocker the blocker
1850	<	* @param maintainParallelism if true and supported by this pool,
1851	<	* attempt to maintain the pool's nominal parallelism; otherwise
1852	<	* activate a thread only if necessary to avoid complete
1853	<	* starvation.
1850	>	* @param maintainParallelism if {@code true} and supported by
1851	>	* this pool, attempt to maintain the pool's nominal parallelism;
1852	>	* otherwise activate a thread only if necessary to avoid
1853	>	* complete starvation.
1854		* @throws InterruptedException if blocker.block did so
1855		*/
1856		public static void managedBlock(ManagedBlocker blocker,
1857		boolean maintainParallelism)
1858		throws InterruptedException {
1859		Thread t = Thread.currentThread();
1860	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1861	<	((ForkJoinWorkerThread)t).pool : null);
1860	>	ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ?
1861	>	((ForkJoinWorkerThread) t).pool : null);
1862		if (!blocker.isReleasable()) {
1863		try {
1864		if (pool == null ||
#	Line 1778 | Line 1873 | public class ForkJoinPool extends Abstra
1873
1874		private static void awaitBlocker(ManagedBlocker blocker)
1875		throws InterruptedException {
1876	<	do;while (!blocker.isReleasable() && !blocker.block());
1876	>	do {} while (!blocker.isReleasable() && !blocker.block());
1877		}
1878
1879	<	// AbstractExecutorService overrides
1879	>	// AbstractExecutorService overrides.  These rely on undocumented
1880	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1881	>	// implement RunnableFuture.
1882
1883		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1884	<	return new AdaptedRunnable(runnable, value);
1884	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
1885		}
1886
1887		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1888	<	return new AdaptedCallable(callable);
1792	<	}
1793	<
1794	<
1795	<	// Temporary Unsafe mechanics for preliminary release
1796	<	private static Unsafe getUnsafe() throws Throwable {
1797	<	try {
1798	<	return Unsafe.getUnsafe();
1799	<	} catch (SecurityException se) {
1800	<	try {
1801	<	return java.security.AccessController.doPrivileged
1802	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1803	<	public Unsafe run() throws Exception {
1804	<	return getUnsafePrivileged();
1805	<	}});
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));
1888	>	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
1889		}
1890
1891	<	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;
1891	>	// Unsafe mechanics
1892
1893	<	static {
1894	<	try {
1895	<	UNSAFE = getUnsafe();
1896	<	eventCountOffset = fieldOffset("eventCount");
1897	<	workerCountsOffset = fieldOffset("workerCounts");
1898	<	runControlOffset = fieldOffset("runControl");
1899	<	syncStackOffset = fieldOffset("syncStack");
1900	<	spareStackOffset = fieldOffset("spareStack");
1901	<	} catch (Throwable e) {
1902	<	throw new RuntimeException("Could not initialize intrinsics", e);
1903	<	}
1843	<	}
1893	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1894	>	private static final long eventCountOffset =
1895	>	objectFieldOffset("eventCount", ForkJoinPool.class);
1896	>	private static final long workerCountsOffset =
1897	>	objectFieldOffset("workerCounts", ForkJoinPool.class);
1898	>	private static final long runControlOffset =
1899	>	objectFieldOffset("runControl", ForkJoinPool.class);
1900	>	private static final long syncStackOffset =
1901	>	objectFieldOffset("syncStack",ForkJoinPool.class);
1902	>	private static final long spareStackOffset =
1903	>	objectFieldOffset("spareStack", ForkJoinPool.class);
1904
1905		private boolean casEventCount(long cmp, long val) {
1906		return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
#	Line 1857 | Line 1917 | public class ForkJoinPool extends Abstra
1917		private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1918		return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1919		}
1920	+
1921	+	private static long objectFieldOffset(String field, Class<?> klazz) {
1922	+	try {
1923	+	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1924	+	} catch (NoSuchFieldException e) {
1925	+	// Convert Exception to corresponding Error
1926	+	NoSuchFieldError error = new NoSuchFieldError(field);
1927	+	error.initCause(e);
1928	+	throw error;
1929	+	}
1930	+	}
1931	+
1932	+	/**
1933	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1934	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1935	+	* into a jdk.
1936	+	*
1937	+	* @return a sun.misc.Unsafe
1938	+	*/
1939	+	private static sun.misc.Unsafe getUnsafe() {
1940	+	try {
1941	+	return sun.misc.Unsafe.getUnsafe();
1942	+	} catch (SecurityException se) {
1943	+	try {
1944	+	return java.security.AccessController.doPrivileged
1945	+	(new java.security
1946	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1947	+	public sun.misc.Unsafe run() throws Exception {
1948	+	java.lang.reflect.Field f = sun.misc
1949	+	.Unsafe.class.getDeclaredField("theUnsafe");
1950	+	f.setAccessible(true);
1951	+	return (sun.misc.Unsafe) f.get(null);
1952	+	}});
1953	+	} catch (java.security.PrivilegedActionException e) {
1954	+	throw new RuntimeException("Could not initialize intrinsics",
1955	+	e.getCause());
1956	+	}
1957	+	}
1958	+	}
1959		}

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