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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.15 by jsr166, Wed Jul 22 20:55:22 2009 UTC vs.
Revision 1.41 by jsr166, Mon Aug 3 01:11:58 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
27	<	* submitted tasks. Otherwise, use would not usually outweigh the
28	<	* construction and bookkeeping overhead of creating a large set of
29	<	* threads.
23	>	* An {@link ExecutorService} for running {@link ForkJoinTask}s.
24	>	* A {@code ForkJoinPool} provides the entry point for submissions
25	>	* from non-{@code ForkJoinTask}s, as well as management and
26	>	* monitoring operations.  Normally a single {@code ForkJoinPool} is
27	>	* used for a large number of submitted tasks. Otherwise, use would
28	>	* not usually outweigh the construction and bookkeeping overhead of
29	>	* creating a large set of threads.
30		*
31	<	* <p>ForkJoinPools differ from other kinds of Executors mainly in
32	<	* that they provide <em>work-stealing</em>: all threads in the pool
33	<	* attempt to find and execute subtasks created by other active tasks
34	<	* (eventually blocking if none exist). This makes them efficient when
35	<	* most tasks spawn other subtasks (as do most ForkJoinTasks), as well
36	<	* as the mixed execution of some plain Runnable- or Callable- based
37	<	* activities along with ForkJoinTasks. When setting
38	<	* <tt>setAsyncMode</tt>, a ForkJoinPools may also be appropriate for
39	<	* use with fine-grained tasks that are never joined. Otherwise, other
40	<	* ExecutorService implementations are typically more appropriate
41	<	* choices.
31	>	* <p>{@code ForkJoinPool}s differ from other kinds of {@link
32	>	* Executor}s mainly in that they provide <em>work-stealing</em>: all
33	>	* threads in the pool attempt to find and execute subtasks created by
34	>	* other active tasks (eventually blocking if none exist). This makes
35	>	* them efficient when most tasks spawn other subtasks (as do most
36	>	* {@code ForkJoinTask}s), as well as the mixed execution of some
37	>	* plain {@code Runnable}- or {@code Callable}- based activities along
38	>	* with {@code ForkJoinTask}s. When setting {@linkplain #setAsyncMode
39	>	* async mode}, a {@code ForkJoinPool} may also be appropriate for use
40	>	* with fine-grained tasks that are never joined. Otherwise, other
41	>	* {@code ExecutorService} implementations are typically more
42	>	* appropriate choices.
43		*
44	<	* <p>A ForkJoinPool may be constructed with a given parallelism level
45	<	* (target pool size), which it attempts to maintain by dynamically
46	<	* adding, suspending, or resuming threads, even if some tasks are
47	<	* waiting to join others. However, no such adjustments are performed
48	<	* in the face of blocked IO or other unmanaged synchronization. The
49	<	* nested <code>ManagedBlocker</code> interface enables extension of
50	<	* the kinds of synchronization accommodated.  The target parallelism
51	<	* level may also be changed dynamically (<code>setParallelism</code>)
52	<	* and thread construction can be limited using methods
53	<	* <code>setMaximumPoolSize</code> and/or
54	<	* <code>setMaintainsParallelism</code>.
44	>	* <p>A {@code ForkJoinPool} may be constructed with a given
45	>	* parallelism level (target pool size), which it attempts to maintain
46	>	* by dynamically adding, suspending, or resuming threads, even if
47	>	* some tasks are waiting to join others. However, no such adjustments
48	>	* are performed in the face of blocked IO or other unmanaged
49	>	* synchronization. The nested {@link ManagedBlocker} interface
50	>	* enables extension of the kinds of synchronization accommodated.
51	>	* The target parallelism level may also be changed dynamically
52	>	* ({@link #setParallelism}) and thread construction can be limited
53	>	* using methods {@link #setMaximumPoolSize} and/or {@link
54	>	* #setMaintainsParallelism}.
55		*
56		* <p>In addition to execution and lifecycle control methods, this
57		* class provides status check methods (for example
58	<	* <code>getStealCount</code>) that are intended to aid in developing,
58	>	* {@link #getStealCount}) that are intended to aid in developing,
59		* tuning, and monitoring fork/join applications. Also, method
60	<	* <code>toString</code> returns indications of pool state in a
60	>	* {@link #toString} returns indications of pool state in a
61		* convenient form for informal monitoring.
62		*
63		* <p><b>Implementation notes</b>: This implementation restricts the
64		* maximum number of running threads to 32767. Attempts to create
65		* pools with greater than the maximum result in
66	<	* IllegalArgumentExceptions.
66	>	* {@code IllegalArgumentException}.
67	>	*
68	>	* @since 1.7
69	>	* @author Doug Lea
70		*/
71		public class ForkJoinPool extends AbstractExecutorService {
72
#	Line 71 | Line 82 | public class ForkJoinPool extends Abstra
82		private static final int MAX_THREADS =  0x7FFF;
83
84		/**
85	<	* Factory for creating new ForkJoinWorkerThreads.  A
86	<	* ForkJoinWorkerThreadFactory must be defined and used for
87	<	* ForkJoinWorkerThread subclasses that extend base functionality
88	<	* or initialize threads with different contexts.
85	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
86	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
87	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
88	>	* functionality or initialize threads with different contexts.
89		*/
90		public static interface ForkJoinWorkerThreadFactory {
91		/**
92		* Returns a new worker thread operating in the given pool.
93		*
94		* @param pool the pool this thread works in
95	<	* @throws NullPointerException if pool is null;
95	>	* @throws NullPointerException if pool is null
96		*/
97		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
98		}
99
100		/**
101	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
101	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
102		* new ForkJoinWorkerThread.
103		*/
104		static class  DefaultForkJoinWorkerThreadFactory
#	Line 153 | Line 164 | public class ForkJoinPool extends Abstra
164
165		/**
166		* The uncaught exception handler used when any worker
167	<	* abrupty terminates
167	>	* abruptly terminates
168		*/
169		private Thread.UncaughtExceptionHandler ueh;
170
#	Line 181 | Line 192 | public class ForkJoinPool extends Abstra
192		private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
193
194		/**
195	<	* Head of Treiber stack for barrier sync. See below for explanation
195	>	* Head of Treiber stack for barrier sync. See below for explanation.
196		*/
197		private volatile WaitQueueNode syncStack;
198
#	Line 217 | Line 228 | public class ForkJoinPool extends Abstra
228		* making decisions about creating and suspending spare
229		* threads. Updated only by CAS.  Note: CASes in
230		* updateRunningCount and preJoin assume that running active count
231	<	* is in low word, so need to be modified if this changes
231	>	* is in low word, so need to be modified if this changes.
232		*/
233		private volatile int workerCounts;
234
#	Line 226 | Line 237 | public class ForkJoinPool extends Abstra
237		private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
238
239		/**
240	<	* Add delta (which may be negative) to running count.  This must
240	>	* Adds delta (which may be negative) to running count.  This must
241		* be called before (with negative arg) and after (with positive)
242	<	* any managed synchronization (i.e., mainly, joins)
242	>	* any managed synchronization (i.e., mainly, joins).
243	>	*
244		* @param delta the number to add
245		*/
246		final void updateRunningCount(int delta) {
247		int s;
248	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
248	>	do {} while (!casWorkerCounts(s = workerCounts, s + delta));
249		}
250
251		/**
252	<	* Add delta (which may be negative) to both total and running
252	>	* Adds delta (which may be negative) to both total and running
253		* count.  This must be called upon creation and termination of
254		* worker threads.
255	+	*
256		* @param delta the number to add
257		*/
258		private void updateWorkerCount(int delta) {
259		int d = delta + (delta << 16); // add to both lo and hi parts
260		int s;
261	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
261	>	do {} while (!casWorkerCounts(s = workerCounts, s + d));
262		}
263
264		/**
#	Line 271 | Line 284 | public class ForkJoinPool extends Abstra
284		private static int runControlFor(int r, int a)   { return (r << 16) + a; }
285
286		/**
287	<	* Try incrementing active count; fail on contention. Called by
288	<	* workers before/during executing tasks.
289	<	* @return true on success;
287	>	* Tries incrementing active count; fails on contention.
288	>	* Called by workers before/during executing tasks.
289	>	*
290	>	* @return true on success
291		*/
292		final boolean tryIncrementActiveCount() {
293		int c = runControl;
#	Line 281 | Line 295 | public class ForkJoinPool extends Abstra
295		}
296
297		/**
298	<	* Try decrementing active count; fail on contention.
299	<	* Possibly trigger termination on success
298	>	* Tries decrementing active count; fails on contention.
299	>	* Possibly triggers termination on success.
300		* Called by workers when they can't find tasks.
301	+	*
302		* @return true on success
303		*/
304		final boolean tryDecrementActiveCount() {
#	Line 297 | Line 312 | public class ForkJoinPool extends Abstra
312		}
313
314		/**
315	<	* Return true if argument represents zero active count and
316	<	* nonzero runstate, which is the triggering condition for
315	>	* Returns {@code true} if argument represents zero active count
316	>	* and nonzero runstate, which is the triggering condition for
317		* terminating on shutdown.
318		*/
319		private static boolean canTerminateOnShutdown(int c) {
320	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
320	>	// i.e. least bit is nonzero runState bit
321	>	return ((c & -c) >>> 16) != 0;
322		}
323
324		/**
#	Line 327 | Line 343 | public class ForkJoinPool extends Abstra
343		// Constructors
344
345		/**
346	<	* Creates a ForkJoinPool with a pool size equal to the number of
347	<	* processors available on the system and using the default
348	<	* ForkJoinWorkerThreadFactory,
346	>	* Creates a {@code ForkJoinPool} with a pool size equal to the
347	>	* number of processors available on the system, using the
348	>	* {@linkplain #defaultForkJoinWorkerThreadFactory default thread factory}.
349	>	*
350		* @throws SecurityException if a security manager exists and
351		*         the caller is not permitted to modify threads
352		*         because it does not hold {@link
353	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
353	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
354		*/
355		public ForkJoinPool() {
356		this(Runtime.getRuntime().availableProcessors(),
#	Line 341 | Line 358 | public class ForkJoinPool extends Abstra
358		}
359
360		/**
361	<	* Creates a ForkJoinPool with the indicated parellelism level
362	<	* threads, and using the default ForkJoinWorkerThreadFactory,
361	>	* Creates a {@code ForkJoinPool} with the indicated parallelism level
362	>	* threads and using the
363	>	* {@linkplain #defaultForkJoinWorkerThreadFactory default thread factory}.
364	>	*
365		* @param parallelism the number of worker threads
366		* @throws IllegalArgumentException if parallelism less than or
367		* equal to zero
368		* @throws SecurityException if a security manager exists and
369		*         the caller is not permitted to modify threads
370		*         because it does not hold {@link
371	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
371	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
372		*/
373		public ForkJoinPool(int parallelism) {
374		this(parallelism, defaultForkJoinWorkerThreadFactory);
375		}
376
377		/**
378	<	* Creates a ForkJoinPool with parallelism equal to the number of
379	<	* processors available on the system and using the given
380	<	* ForkJoinWorkerThreadFactory,
378	>	* Creates a {@code ForkJoinPool} with parallelism equal to the
379	>	* number of processors available on the system and using the
380	>	* given thread factory.
381	>	*
382		* @param factory the factory for creating new threads
383		* @throws NullPointerException if factory is null
384		* @throws SecurityException if a security manager exists and
385		*         the caller is not permitted to modify threads
386		*         because it does not hold {@link
387	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
387	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
388		*/
389		public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
390		this(Runtime.getRuntime().availableProcessors(), factory);
391		}
392
393		/**
394	<	* Creates a ForkJoinPool with the given parallelism and factory.
394	>	* Creates a {@code ForkJoinPool} with the given parallelism and
395	>	* thread factory.
396		*
397		* @param parallelism the targeted number of worker threads
398		* @param factory the factory for creating new threads
399		* @throws IllegalArgumentException if parallelism less than or
400	<	* equal to zero, or greater than implementation limit.
400	>	* equal to zero, or greater than implementation limit
401		* @throws NullPointerException if factory is null
402		* @throws SecurityException if a security manager exists and
403		*         the caller is not permitted to modify threads
404		*         because it does not hold {@link
405	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
405	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
406		*/
407		public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
408		if (parallelism <= 0 || parallelism > MAX_THREADS)
#	Line 402 | Line 423 | public class ForkJoinPool extends Abstra
423		}
424
425		/**
426	<	* Create new worker using factory.
426	>	* Creates a new worker thread using factory.
427	>	*
428		* @param index the index to assign worker
429	<	* @return new worker, or null of factory failed
429	>	* @return new worker, or null if factory failed
430		*/
431		private ForkJoinWorkerThread createWorker(int index) {
432		Thread.UncaughtExceptionHandler h = ueh;
#	Line 421 | Line 443 | public class ForkJoinPool extends Abstra
443		}
444
445		/**
446	<	* Return a good size for worker array given pool size.
446	>	* Returns a good size for worker array given pool size.
447		* Currently requires size to be a power of two.
448		*/
449	<	private static int arraySizeFor(int ps) {
450	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
449	>	private static int arraySizeFor(int poolSize) {
450	>	return (poolSize <= 1) ? 1 :
451	>	(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1)));
452		}
453
454		/**
455	<	* Create or resize array if necessary to hold newLength.
456	<	* Call only under exclusion
455	>	* Creates or resizes array if necessary to hold newLength.
456	>	* Call only under exclusion.
457	>	*
458		* @return the array
459		*/
460		private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
#	Line 444 | Line 468 | public class ForkJoinPool extends Abstra
468		}
469
470		/**
471	<	* Try to shrink workers into smaller array after one or more terminate
471	>	* Tries to shrink workers into smaller array after one or more terminate.
472		*/
473		private void tryShrinkWorkerArray() {
474		ForkJoinWorkerThread[] ws = workers;
#	Line 460 | Line 484 | public class ForkJoinPool extends Abstra
484		}
485
486		/**
487	<	* Initialize workers if necessary
487	>	* Initializes workers if necessary.
488		*/
489		final void ensureWorkerInitialization() {
490		ForkJoinWorkerThread[] ws = workers;
#	Line 527 | Line 551 | public class ForkJoinPool extends Abstra
551		* Common code for execute, invoke and submit
552		*/
553		private <T> void doSubmit(ForkJoinTask<T> task) {
554	+	if (task == null)
555	+	throw new NullPointerException();
556		if (isShutdown())
557		throw new RejectedExecutionException();
558		if (workers == null)
#	Line 536 | Line 562 | public class ForkJoinPool extends Abstra
562		}
563
564		/**
565	<	* Performs the given task; returning its result upon completion
565	>	* Performs the given task, returning its result upon completion.
566	>	*
567		* @param task the task
568		* @return the task's result
569		* @throws NullPointerException if task is null
#	Line 549 | Line 576 | public class ForkJoinPool extends Abstra
576
577		/**
578		* Arranges for (asynchronous) execution of the given task.
579	+	*
580		* @param task the task
581		* @throws NullPointerException if task is null
582		* @throws RejectedExecutionException if pool is shut down
583		*/
584	<	public <T> void execute(ForkJoinTask<T> task) {
584	>	public void execute(ForkJoinTask<?> task) {
585		doSubmit(task);
586		}
587
588		// AbstractExecutorService methods
589
590		public void execute(Runnable task) {
591	<	doSubmit(new AdaptedRunnable<Void>(task, null));
591	>	ForkJoinTask<?> job;
592	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
593	>	job = (ForkJoinTask<?>) task;
594	>	else
595	>	job = ForkJoinTask.adapt(task, null);
596	>	doSubmit(job);
597		}
598
599		public <T> ForkJoinTask<T> submit(Callable<T> task) {
600	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
600	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
601		doSubmit(job);
602		return job;
603		}
604
605		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
606	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
606	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
607		doSubmit(job);
608		return job;
609		}
610
611		public ForkJoinTask<?> submit(Runnable task) {
612	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
612	>	ForkJoinTask<?> job;
613	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
614	>	job = (ForkJoinTask<?>) task;
615	>	else
616	>	job = ForkJoinTask.adapt(task, null);
617		doSubmit(job);
618		return job;
619		}
620
621		/**
622	<	* Adaptor for Runnables. This implements RunnableFuture
623	<	* to be compliant with AbstractExecutorService constraints
622	>	* Submits a ForkJoinTask for execution.
623	>	*
624	>	* @param task the task to submit
625	>	* @return the task
626	>	* @throws RejectedExecutionException if the task cannot be
627	>	*         scheduled for execution
628	>	* @throws NullPointerException if the task is null
629		*/
630	<	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
631	<	implements RunnableFuture<T> {
632	<	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(); }
630	>	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
631	>	doSubmit(task);
632	>	return task;
633		}
634
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	–	}
635
636		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
637	<	ArrayList<ForkJoinTask<T>> ts =
637	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
638		new ArrayList<ForkJoinTask<T>>(tasks.size());
639	<	for (Callable<T> c : tasks)
640	<	ts.add(new AdaptedCallable<T>(c));
641	<	invoke(new InvokeAll<T>(ts));
642	<	return (List<Future<T>>)(List)ts;
639	>	for (Callable<T> task : tasks)
640	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
641	>	invoke(new InvokeAll<T>(forkJoinTasks));
642	>
643	>	@SuppressWarnings({"unchecked", "rawtypes"})
644	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
645	>	return futures;
646		}
647
648		static final class InvokeAll<T> extends RecursiveAction {
649		final ArrayList<ForkJoinTask<T>> tasks;
650		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
651		public void compute() {
652	<	try { invokeAll(tasks); } catch(Exception ignore) {}
652	>	try { invokeAll(tasks); }
653	>	catch (Exception ignore) {}
654		}
655	+	private static final long serialVersionUID = -7914297376763021607L;
656		}
657
658		// Configuration and status settings and queries
659
660		/**
661	<	* Returns the factory used for constructing new workers
661	>	* Returns the factory used for constructing new workers.
662		*
663		* @return the factory used for constructing new workers
664		*/
#	Line 664 | Line 669 | public class ForkJoinPool extends Abstra
669		/**
670		* Returns the handler for internal worker threads that terminate
671		* due to unrecoverable errors encountered while executing tasks.
672	<	* @return the handler, or null if none
672	>	*
673	>	* @return the handler, or {@code null} if none
674		*/
675		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
676		Thread.UncaughtExceptionHandler h;
#	Line 685 | Line 691 | public class ForkJoinPool extends Abstra
691		* as handler.
692		*
693		* @param h the new handler
694	<	* @return the old handler, or null if none
694	>	* @return the old handler, or {@code null} if none
695		* @throws SecurityException if a security manager exists and
696		*         the caller is not permitted to modify threads
697		*         because it does not hold {@link
698	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
698	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
699		*/
700		public Thread.UncaughtExceptionHandler
701		setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
#	Line 716 | Line 722 | public class ForkJoinPool extends Abstra
722
723
724		/**
725	<	* Sets the target paralleism level of this pool.
725	>	* Sets the target parallelism level of this pool.
726	>	*
727		* @param parallelism the target parallelism
728		* @throws IllegalArgumentException if parallelism less than or
729	<	* equal to zero or greater than maximum size bounds.
729	>	* equal to zero or greater than maximum size bounds
730		* @throws SecurityException if a security manager exists and
731		*         the caller is not permitted to modify threads
732		*         because it does not hold {@link
733	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
733	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
734		*/
735		public void setParallelism(int parallelism) {
736		checkPermission();
#	Line 758 | Line 765 | public class ForkJoinPool extends Abstra
765		/**
766		* Returns the number of worker threads that have started but not
767		* yet terminated.  This result returned by this method may differ
768	<	* from <code>getParallelism</code> when threads are created to
768	>	* from {@link #getParallelism} when threads are created to
769		* maintain parallelism when others are cooperatively blocked.
770		*
771		* @return the number of worker threads
#	Line 770 | Line 777 | public class ForkJoinPool extends Abstra
777		/**
778		* Returns the maximum number of threads allowed to exist in the
779		* pool, even if there are insufficient unblocked running threads.
780	+	*
781		* @return the maximum
782		*/
783		public int getMaximumPoolSize() {
#	Line 781 | Line 789 | public class ForkJoinPool extends Abstra
789		* pool, even if there are insufficient unblocked running threads.
790		* Setting this value has no effect on current pool size. It
791		* controls construction of new threads.
792	<	* @throws IllegalArgumentException if negative or greater then
793	<	* internal implementation limit.
792	>	*
793	>	* @throws IllegalArgumentException if negative or greater than
794	>	* internal implementation limit
795		*/
796		public void setMaximumPoolSize(int newMax) {
797		if (newMax < 0 || newMax > MAX_THREADS)
#	Line 792 | Line 801 | public class ForkJoinPool extends Abstra
801
802
803		/**
804	<	* Returns true if this pool dynamically maintains its target
805	<	* parallelism level. If false, new threads are added only to
806	<	* avoid possible starvation.
807	<	* This setting is by default true;
808	<	* @return true if maintains parallelism
804	>	* Returns {@code true} if this pool dynamically maintains its
805	>	* target parallelism level. If false, new threads are added only
806	>	* to avoid possible starvation.  This setting is by default true.
807	>	*
808	>	* @return {@code true} if maintains parallelism
809		*/
810		public boolean getMaintainsParallelism() {
811		return maintainsParallelism;
#	Line 806 | Line 815 | public class ForkJoinPool extends Abstra
815		* Sets whether this pool dynamically maintains its target
816		* parallelism level. If false, new threads are added only to
817		* avoid possible starvation.
818	<	* @param enable true to maintains parallelism
818	>	*
819	>	* @param enable {@code true} to maintain parallelism
820		*/
821		public void setMaintainsParallelism(boolean enable) {
822		maintainsParallelism = enable;
#	Line 817 | Line 827 | public class ForkJoinPool extends Abstra
827		* tasks that are never joined. This mode may be more appropriate
828		* than default locally stack-based mode in applications in which
829		* worker threads only process asynchronous tasks.  This method is
830	<	* designed to be invoked only when pool is quiescent, and
830	>	* designed to be invoked only when the pool is quiescent, and
831		* typically only before any tasks are submitted. The effects of
832	<	* invocations at ather times may be unpredictable.
832	>	* invocations at other times may be unpredictable.
833		*
834	<	* @param async if true, use locally FIFO scheduling
835	<	* @return the previous mode.
834	>	* @param async if {@code true}, use locally FIFO scheduling
835	>	* @return the previous mode
836	>	* @see #getAsyncMode
837		*/
838		public boolean setAsyncMode(boolean async) {
839		boolean oldMode = locallyFifo;
#	Line 839 | Line 850 | public class ForkJoinPool extends Abstra
850		}
851
852		/**
853	<	* Returns true if this pool uses local first-in-first-out
854	<	* scheduling mode for forked tasks that are never joined.
853	>	* Returns {@code true} if this pool uses local first-in-first-out
854	>	* scheduling mode for forked tasks that are never joined.
855		*
856	<	* @return true if this pool uses async mode.
856	>	* @return {@code true} if this pool uses async mode
857	>	* @see #setAsyncMode
858		*/
859		public boolean getAsyncMode() {
860		return locallyFifo;
#	Line 863 | Line 875 | public class ForkJoinPool extends Abstra
875		* Returns an estimate of the number of threads that are currently
876		* stealing or executing tasks. This method may overestimate the
877		* number of active threads.
878	<	* @return the number of active threads.
878	>	*
879	>	* @return the number of active threads
880		*/
881		public int getActiveThreadCount() {
882		return activeCountOf(runControl);
#	Line 873 | Line 886 | public class ForkJoinPool extends Abstra
886		* Returns an estimate of the number of threads that are currently
887		* idle waiting for tasks. This method may underestimate the
888		* number of idle threads.
889	<	* @return the number of idle threads.
889	>	*
890	>	* @return the number of idle threads
891		*/
892		final int getIdleThreadCount() {
893		int c = runningCountOf(workerCounts) - activeCountOf(runControl);
894	<	return (c <= 0)? 0 : c;
894	>	return (c <= 0) ? 0 : c;
895		}
896
897		/**
898	<	* Returns true if all worker threads are currently idle. An idle
899	<	* worker is one that cannot obtain a task to execute because none
900	<	* are available to steal from other threads, and there are no
901	<	* pending submissions to the pool. This method is conservative:
902	<	* It might not return true immediately upon idleness of all
903	<	* threads, but will eventually become true if threads remain
904	<	* inactive.
905	<	* @return true if all threads are currently idle
898	>	* Returns {@code true} if all worker threads are currently idle.
899	>	* An idle worker is one that cannot obtain a task to execute
900	>	* because none are available to steal from other threads, and
901	>	* there are no pending submissions to the pool. This method is
902	>	* conservative; it might not return {@code true} immediately upon
903	>	* idleness of all threads, but will eventually become true if
904	>	* threads remain inactive.
905	>	*
906	>	* @return {@code true} if all threads are currently idle
907		*/
908		public boolean isQuiescent() {
909		return activeCountOf(runControl) == 0;
#	Line 899 | Line 914 | public class ForkJoinPool extends Abstra
914		* one thread's work queue by another. The reported value
915		* underestimates the actual total number of steals when the pool
916		* is not quiescent. This value may be useful for monitoring and
917	<	* tuning fork/join programs: In general, steal counts should be
917	>	* tuning fork/join programs: in general, steal counts should be
918		* high enough to keep threads busy, but low enough to avoid
919		* overhead and contention across threads.
920	<	* @return the number of steals.
920	>	*
921	>	* @return the number of steals
922		*/
923		public long getStealCount() {
924		return stealCount.get();
925		}
926
927		/**
928	<	* Accumulate steal count from a worker. Call only
929	<	* when worker known to be idle.
928	>	* Accumulates steal count from a worker.
929	>	* Call only when worker known to be idle.
930		*/
931		private void updateStealCount(ForkJoinWorkerThread w) {
932		int sc = w.getAndClearStealCount();
#	Line 925 | Line 941 | public class ForkJoinPool extends Abstra
941		* an approximation, obtained by iterating across all threads in
942		* the pool. This method may be useful for tuning task
943		* granularities.
944	<	* @return the number of queued tasks.
944	>	*
945	>	* @return the number of queued tasks
946		*/
947		public long getQueuedTaskCount() {
948		long count = 0;
#	Line 941 | Line 958 | public class ForkJoinPool extends Abstra
958		}
959
960		/**
961	<	* Returns an estimate of the number tasks submitted to this pool
962	<	* that have not yet begun executing. This method takes time
961	>	* Returns an estimate of the number of tasks submitted to this
962	>	* pool that have not yet begun executing.  This method takes time
963		* proportional to the number of submissions.
964	<	* @return the number of queued submissions.
964	>	*
965	>	* @return the number of queued submissions
966		*/
967		public int getQueuedSubmissionCount() {
968		return submissionQueue.size();
969		}
970
971		/**
972	<	* Returns true if there are any tasks submitted to this pool
973	<	* that have not yet begun executing.
974	<	* @return <code>true</code> if there are any queued submissions.
972	>	* Returns {@code true} if there are any tasks submitted to this
973	>	* pool that have not yet begun executing.
974	>	*
975	>	* @return {@code true} if there are any queued submissions
976		*/
977		public boolean hasQueuedSubmissions() {
978		return !submissionQueue.isEmpty();
#	Line 963 | Line 982 | public class ForkJoinPool extends Abstra
982		* Removes and returns the next unexecuted submission if one is
983		* available.  This method may be useful in extensions to this
984		* class that re-assign work in systems with multiple pools.
985	<	* @return the next submission, or null if none
985	>	*
986	>	* @return the next submission, or {@code null} if none
987		*/
988		protected ForkJoinTask<?> pollSubmission() {
989		return submissionQueue.poll();
#	Line 973 | Line 993 | public class ForkJoinPool extends Abstra
993		* Removes all available unexecuted submitted and forked tasks
994		* from scheduling queues and adds them to the given collection,
995		* without altering their execution status. These may include
996	<	* artifically generated or wrapped tasks. This method id designed
997	<	* to be invoked only when the pool is known to be
996	>	* artificially generated or wrapped tasks. This method is
997	>	* designed to be invoked only when the pool is known to be
998		* quiescent. Invocations at other times may not remove all
999		* tasks. A failure encountered while attempting to add elements
1000	<	* to collection <tt>c</tt> may result in elements being in
1000	>	* to collection {@code c} may result in elements being in
1001		* neither, either or both collections when the associated
1002		* exception is thrown.  The behavior of this operation is
1003		* undefined if the specified collection is modified while the
1004		* operation is in progress.
1005	+	*
1006		* @param c the collection to transfer elements into
1007		* @return the number of elements transferred
1008		*/
1009	<	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
1009	>	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1010		int n = submissionQueue.drainTo(c);
1011		ForkJoinWorkerThread[] ws = workers;
1012		if (ws != null) {
#	Line 1042 | Line 1063 | public class ForkJoinPool extends Abstra
1063		* Invocation has no additional effect if already shut down.
1064		* Tasks that are in the process of being submitted concurrently
1065		* during the course of this method may or may not be rejected.
1066	+	*
1067		* @throws SecurityException if a security manager exists and
1068		*         the caller is not permitted to modify threads
1069		*         because it does not hold {@link
1070	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1070	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1071		*/
1072		public void shutdown() {
1073		checkPermission();
1074		transitionRunStateTo(SHUTDOWN);
1075	<	if (canTerminateOnShutdown(runControl))
1075	>	if (canTerminateOnShutdown(runControl)) {
1076	>	if (workers == null) { // shutting down before workers created
1077	>	final ReentrantLock lock = this.workerLock;
1078	>	lock.lock();
1079	>	try {
1080	>	if (workers == null) {
1081	>	terminate();
1082	>	transitionRunStateTo(TERMINATED);
1083	>	termination.signalAll();
1084	>	}
1085	>	} finally {
1086	>	lock.unlock();
1087	>	}
1088	>	}
1089		terminateOnShutdown();
1090	+	}
1091		}
1092
1093		/**
#	Line 1061 | Line 1097 | public class ForkJoinPool extends Abstra
1097		* method may or may not be rejected. Unlike some other executors,
1098		* this method cancels rather than collects non-executed tasks
1099		* upon termination, so always returns an empty list. However, you
1100	<	* can use method <code>drainTasksTo</code> before invoking this
1100	>	* can use method {@link #drainTasksTo} before invoking this
1101		* method to transfer unexecuted tasks to another collection.
1102	+	*
1103		* @return an empty list
1104		* @throws SecurityException if a security manager exists and
1105		*         the caller is not permitted to modify threads
1106		*         because it does not hold {@link
1107	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1107	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1108		*/
1109		public List<Runnable> shutdownNow() {
1110		checkPermission();
#	Line 1076 | Line 1113 | public class ForkJoinPool extends Abstra
1113		}
1114
1115		/**
1116	<	* Returns <code>true</code> if all tasks have completed following shut down.
1116	>	* Returns {@code true} if all tasks have completed following shut down.
1117		*
1118	<	* @return <code>true</code> if all tasks have completed following shut down
1118	>	* @return {@code true} if all tasks have completed following shut down
1119		*/
1120		public boolean isTerminated() {
1121		return runStateOf(runControl) == TERMINATED;
1122		}
1123
1124		/**
1125	<	* Returns <code>true</code> if the process of termination has
1125	>	* Returns {@code true} if the process of termination has
1126		* commenced but possibly not yet completed.
1127		*
1128	<	* @return <code>true</code> if terminating
1128	>	* @return {@code true} if terminating
1129		*/
1130		public boolean isTerminating() {
1131		return runStateOf(runControl) >= TERMINATING;
1132		}
1133
1134		/**
1135	<	* Returns <code>true</code> if this pool has been shut down.
1135	>	* Returns {@code true} if this pool has been shut down.
1136		*
1137	<	* @return <code>true</code> if this pool has been shut down
1137	>	* @return {@code true} if this pool has been shut down
1138		*/
1139		public boolean isShutdown() {
1140		return runStateOf(runControl) >= SHUTDOWN;
#	Line 1110 | Line 1147 | public class ForkJoinPool extends Abstra
1147		*
1148		* @param timeout the maximum time to wait
1149		* @param unit the time unit of the timeout argument
1150	<	* @return <code>true</code> if this executor terminated and
1151	<	*         <code>false</code> if the timeout elapsed before termination
1150	>	* @return {@code true} if this executor terminated and
1151	>	*         {@code false} if the timeout elapsed before termination
1152		* @throws InterruptedException if interrupted while waiting
1153		*/
1154		public boolean awaitTermination(long timeout, TimeUnit unit)
#	Line 1135 | Line 1172 | public class ForkJoinPool extends Abstra
1172		// Shutdown and termination support
1173
1174		/**
1175	<	* Callback from terminating worker. Null out the corresponding
1176	<	* workers slot, and if terminating, try to terminate, else try to
1177	<	* shrink workers array.
1175	>	* Callback from terminating worker. Nulls out the corresponding
1176	>	* workers slot, and if terminating, tries to terminate; else
1177	>	* tries to shrink workers array.
1178	>	*
1179		* @param w the worker
1180		*/
1181		final void workerTerminated(ForkJoinWorkerThread w) {
#	Line 1168 | Line 1206 | public class ForkJoinPool extends Abstra
1206		}
1207
1208		/**
1209	<	* Initiate termination.
1209	>	* Initiates termination.
1210		*/
1211		private void terminate() {
1212		if (transitionRunStateTo(TERMINATING)) {
#	Line 1183 | Line 1221 | public class ForkJoinPool extends Abstra
1221		}
1222
1223		/**
1224	<	* Possibly terminate when on shutdown state
1224	>	* Possibly terminates when on shutdown state.
1225		*/
1226		private void terminateOnShutdown() {
1227		if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
#	Line 1191 | Line 1229 | public class ForkJoinPool extends Abstra
1229		}
1230
1231		/**
1232	<	* Clear out and cancel submissions
1232	>	* Clears out and cancels submissions.
1233		*/
1234		private void cancelQueuedSubmissions() {
1235		ForkJoinTask<?> task;
#	Line 1200 | Line 1238 | public class ForkJoinPool extends Abstra
1238		}
1239
1240		/**
1241	<	* Clean out worker queues.
1241	>	* Cleans out worker queues.
1242		*/
1243		private void cancelQueuedWorkerTasks() {
1244		final ReentrantLock lock = this.workerLock;
#	Line 1220 | Line 1258 | public class ForkJoinPool extends Abstra
1258		}
1259
1260		/**
1261	<	* Set each worker's status to terminating. Requires lock to avoid
1262	<	* conflicts with add/remove
1261	>	* Sets each worker's status to terminating. Requires lock to avoid
1262	>	* conflicts with add/remove.
1263		*/
1264		private void stopAllWorkers() {
1265		final ReentrantLock lock = this.workerLock;
#	Line 1241 | Line 1279 | public class ForkJoinPool extends Abstra
1279		}
1280
1281		/**
1282	<	* Interrupt all unterminated workers.  This is not required for
1282	>	* Interrupts all unterminated workers.  This is not required for
1283		* sake of internal control, but may help unstick user code during
1284		* shutdown.
1285		*/
#	Line 1311 | Line 1349 | public class ForkJoinPool extends Abstra
1349		}
1350
1351		/**
1352	<	* Wake up waiter, returning false if known to already
1352	>	* Wakes up waiter, returning false if known to already
1353		*/
1354		boolean signal() {
1355		ForkJoinWorkerThread t = thread;
#	Line 1323 | Line 1361 | public class ForkJoinPool extends Abstra
1361		}
1362
1363		/**
1364	<	* Await release on sync
1364	>	* Awaits release on sync.
1365		*/
1366		void awaitSyncRelease(ForkJoinPool p) {
1367		while (thread != null && !p.syncIsReleasable(this))
#	Line 1331 | Line 1369 | public class ForkJoinPool extends Abstra
1369		}
1370
1371		/**
1372	<	* Await resumption as spare
1372	>	* Awaits resumption as spare.
1373		*/
1374		void awaitSpareRelease() {
1375		while (thread != null) {
#	Line 1345 | Line 1383 | public class ForkJoinPool extends Abstra
1383		* Ensures that no thread is waiting for count to advance from the
1384		* current value of eventCount read on entry to this method, by
1385		* releasing waiting threads if necessary.
1386	+	*
1387		* @return the count
1388		*/
1389		final long ensureSync() {
#	Line 1366 | Line 1405 | public class ForkJoinPool extends Abstra
1405		*/
1406		private void signalIdleWorkers() {
1407		long c;
1408	<	do;while (!casEventCount(c = eventCount, c+1));
1408	>	do {} while (!casEventCount(c = eventCount, c+1));
1409		ensureSync();
1410		}
1411
1412		/**
1413	<	* Signal threads waiting to poll a task. Because method sync
1413	>	* Signals threads waiting to poll a task. Because method sync
1414		* rechecks availability, it is OK to only proceed if queue
1415		* appears to be non-empty, and OK to skip under contention to
1416		* increment count (since some other thread succeeded).
#	Line 1390 | Line 1429 | public class ForkJoinPool extends Abstra
1429		* Waits until event count advances from last value held by
1430		* caller, or if excess threads, caller is resumed as spare, or
1431		* caller or pool is terminating. Updates caller's event on exit.
1432	+	*
1433		* @param w the calling worker thread
1434		*/
1435		final void sync(ForkJoinWorkerThread w) {
#	Line 1417 | Line 1457 | public class ForkJoinPool extends Abstra
1457		}
1458
1459		/**
1460	<	* Returns true if worker waiting on sync can proceed:
1460	>	* Returns {@code true} if worker waiting on sync can proceed:
1461		*  - on signal (thread == null)
1462		*  - on event count advance (winning race to notify vs signaller)
1463	<	*  - on Interrupt
1463	>	*  - on interrupt
1464		*  - if the first queued node, we find work available
1465		* If node was not signalled and event count not advanced on exit,
1466		* then we also help advance event count.
1467	<	* @return true if node can be released
1467	>	*
1468	>	* @return {@code true} if node can be released
1469		*/
1470		final boolean syncIsReleasable(WaitQueueNode node) {
1471		long prev = node.count;
#	Line 1443 | Line 1484 | public class ForkJoinPool extends Abstra
1484		}
1485
1486		/**
1487	<	* Returns true if a new sync event occurred since last call to
1488	<	* sync or this method, if so, updating caller's count.
1487	>	* Returns {@code true} if a new sync event occurred since last
1488	>	* call to sync or this method, if so, updating caller's count.
1489		*/
1490		final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1491		long lc = w.lastEventCount;
#	Line 1458 | Line 1499 | public class ForkJoinPool extends Abstra
1499		//  Parallelism maintenance
1500
1501		/**
1502	<	* Decrement running count; if too low, add spare.
1502	>	* Decrements running count; if too low, adds spare.
1503		*
1504		* Conceptually, all we need to do here is add or resume a
1505		* spare thread when one is about to block (and remove or
1506		* suspend it later when unblocked -- see suspendIfSpare).
1507		* However, implementing this idea requires coping with
1508	<	* several problems: We have imperfect information about the
1508	>	* several problems: we have imperfect information about the
1509		* states of threads. Some count updates can and usually do
1510		* lag run state changes, despite arrangements to keep them
1511		* accurate (for example, when possible, updating counts
#	Line 1478 | Line 1519 | public class ForkJoinPool extends Abstra
1519		* only be suspended or removed when they are idle, not
1520		* immediately when they aren't needed. So adding threads will
1521		* raise parallelism level for longer than necessary.  Also,
1522	<	* FJ applications often enounter highly transient peaks when
1522	>	* FJ applications often encounter highly transient peaks when
1523		* many threads are blocked joining, but for less time than it
1524		* takes to create or resume spares.
1525		*
#	Line 1487 | Line 1528 | public class ForkJoinPool extends Abstra
1528		* target counts, else create only to avoid starvation
1529		* @return true if joinMe known to be done
1530		*/
1531	<	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1531	>	final boolean preJoin(ForkJoinTask<?> joinMe,
1532	>	boolean maintainParallelism) {
1533		maintainParallelism &= maintainsParallelism; // overrride
1534		boolean dec = false;  // true when running count decremented
1535		while (spareStack == null || !tryResumeSpare(dec)) {
1536		int counts = workerCounts;
1537	<	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1537	>	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1538	>	// CAS cheat
1539		if (!needSpare(counts, maintainParallelism))
1540		break;
1541		if (joinMe.status < 0)
#	Line 1526 | Line 1569 | public class ForkJoinPool extends Abstra
1569		}
1570
1571		/**
1572	<	* Returns true if a spare thread appears to be needed.  If
1573	<	* maintaining parallelism, returns true when the deficit in
1572	>	* Returns {@code true} if a spare thread appears to be needed.
1573	>	* If maintaining parallelism, returns true when the deficit in
1574		* running threads is more than the surplus of total threads, and
1575		* there is apparently some work to do.  This self-limiting rule
1576		* means that the more threads that have already been added, the
1577		* less parallelism we will tolerate before adding another.
1578	+	*
1579		* @param counts current worker counts
1580		* @param maintainParallelism try to maintain parallelism
1581		*/
#	Line 1549 | Line 1593 | public class ForkJoinPool extends Abstra
1593		}
1594
1595		/**
1596	<	* Add a spare worker if lock available and no more than the
1597	<	* expected numbers of threads exist
1596	>	* Adds a spare worker if lock available and no more than the
1597	>	* expected numbers of threads exist.
1598	>	*
1599		* @return true if successful
1600		*/
1601		private boolean tryAddSpare(int expectedCounts) {
#	Line 1583 | Line 1628 | public class ForkJoinPool extends Abstra
1628		}
1629
1630		/**
1631	<	* Add the kth spare worker. On entry, pool coounts are already
1631	>	* Adds the kth spare worker. On entry, pool counts are already
1632		* adjusted to reflect addition.
1633		*/
1634		private void createAndStartSpare(int k) {
#	Line 1605 | Line 1650 | public class ForkJoinPool extends Abstra
1650		}
1651
1652		/**
1653	<	* Suspend calling thread w if there are excess threads.  Called
1654	<	* only from sync.  Spares are enqueued in a Treiber stack
1655	<	* using the same WaitQueueNodes as barriers.  They are resumed
1656	<	* mainly in preJoin, but are also woken on pool events that
1657	<	* require all threads to check run state.
1653	>	* Suspends calling thread w if there are excess threads.  Called
1654	>	* only from sync.  Spares are enqueued in a Treiber stack using
1655	>	* the same WaitQueueNodes as barriers.  They are resumed mainly
1656	>	* in preJoin, but are also woken on pool events that require all
1657	>	* threads to check run state.
1658	>	*
1659		* @param w the caller
1660		*/
1661		private boolean suspendIfSpare(ForkJoinWorkerThread w) {
#	Line 1620 | Line 1666 | public class ForkJoinPool extends Abstra
1666		node = new WaitQueueNode(0, w);
1667		if (casWorkerCounts(s, s-1)) { // representation-dependent
1668		// push onto stack
1669	<	do;while (!casSpareStack(node.next = spareStack, node));
1669	>	do {} while (!casSpareStack(node.next = spareStack, node));
1670		// block until released by resumeSpare
1671		node.awaitSpareRelease();
1672		return true;
#	Line 1630 | Line 1676 | public class ForkJoinPool extends Abstra
1676		}
1677
1678		/**
1679	<	* Try to pop and resume a spare thread.
1679	>	* Tries to pop and resume a spare thread.
1680	>	*
1681		* @param updateCount if true, increment running count on success
1682		* @return true if successful
1683		*/
#	Line 1648 | Line 1695 | public class ForkJoinPool extends Abstra
1695		}
1696
1697		/**
1698	<	* Pop and resume all spare threads. Same idea as ensureSync.
1698	>	* Pops and resumes all spare threads. Same idea as ensureSync.
1699	>	*
1700		* @return true if any spares released
1701		*/
1702		private boolean resumeAllSpares() {
#	Line 1666 | Line 1714 | public class ForkJoinPool extends Abstra
1714		}
1715
1716		/**
1717	<	* Pop and shutdown excessive spare threads. Call only while
1717	>	* Pops and shuts down excessive spare threads. Call only while
1718		* holding lock. This is not guaranteed to eliminate all excess
1719		* threads, only those suspended as spares, which are the ones
1720		* unlikely to be needed in the future.
#	Line 1690 | Line 1738 | public class ForkJoinPool extends Abstra
1738
1739		/**
1740		* Interface for extending managed parallelism for tasks running
1741	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1742	<	* Method <code>isReleasable</code> must return true if blocking is not
1743	<	* necessary. Method <code>block</code> blocks the current thread
1744	<	* if necessary (perhaps internally invoking isReleasable before
1745	<	* actually blocking.).
1741	>	* in {@link ForkJoinPool}s.
1742	>	*
1743	>	* <p>A {@code ManagedBlocker} provides two methods.
1744	>	* Method {@code isReleasable} must return {@code true} if
1745	>	* blocking is not necessary. Method {@code block} blocks the
1746	>	* current thread if necessary (perhaps internally invoking
1747	>	* {@code isReleasable} before actually blocking).
1748	>	*
1749		* <p>For example, here is a ManagedBlocker based on a
1750		* ReentrantLock:
1751	<	* <pre>
1752	<	*   class ManagedLocker implements ManagedBlocker {
1753	<	*     final ReentrantLock lock;
1754	<	*     boolean hasLock = false;
1755	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1756	<	*     public boolean block() {
1757	<	*        if (!hasLock)
1758	<	*           lock.lock();
1759	<	*        return true;
1760	<	*     }
1761	<	*     public boolean isReleasable() {
1762	<	*        return hasLock || (hasLock = lock.tryLock());
1712	<	*     }
1751	>	*  <pre> {@code
1752	>	* class ManagedLocker implements ManagedBlocker {
1753	>	*   final ReentrantLock lock;
1754	>	*   boolean hasLock = false;
1755	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1756	>	*   public boolean block() {
1757	>	*     if (!hasLock)
1758	>	*       lock.lock();
1759	>	*     return true;
1760	>	*   }
1761	>	*   public boolean isReleasable() {
1762	>	*     return hasLock || (hasLock = lock.tryLock());
1763		*   }
1764	<	* </pre>
1764	>	* }}</pre>
1765		*/
1766		public static interface ManagedBlocker {
1767		/**
1768		* Possibly blocks the current thread, for example waiting for
1769		* a lock or condition.
1770	<	* @return true if no additional blocking is necessary (i.e.,
1771	<	* if isReleasable would return true).
1770	>	*
1771	>	* @return {@code true} if no additional blocking is necessary
1772	>	* (i.e., if isReleasable would return true)
1773		* @throws InterruptedException if interrupted while waiting
1774	<	* (the method is not required to do so, but is allowe to).
1774	>	* (the method is not required to do so, but is allowed to)
1775		*/
1776		boolean block() throws InterruptedException;
1777
1778		/**
1779	<	* Returns true if blocking is unnecessary.
1779	>	* Returns {@code true} if blocking is unnecessary.
1780		*/
1781		boolean isReleasable();
1782		}
1783
1784		/**
1785		* Blocks in accord with the given blocker.  If the current thread
1786	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
1787	<	* spare thread to be activated if necessary to ensure parallelism
1788	<	* while the current thread is blocked.  If
1789	<	* <code>maintainParallelism</code> is true and the pool supports
1790	<	* it ({@link #getMaintainsParallelism}), this method attempts to
1791	<	* maintain the pool's nominal parallelism. Otherwise if activates
1792	<	* a thread only if necessary to avoid complete starvation. This
1793	<	* option may be preferable when blockages use timeouts, or are
1794	<	* almost always brief.
1795	<	*
1796	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1797	<	* equivalent to
1798	<	* <pre>
1799	<	*   while (!blocker.isReleasable())
1800	<	*      if (blocker.block())
1801	<	*         return;
1802	<	* </pre>
1803	<	* If the caller is a ForkJoinTask, then the pool may first
1804	<	* be expanded to ensure parallelism, and later adjusted.
1786	>	* is a {@link ForkJoinWorkerThread}, this method possibly
1787	>	* arranges for a spare thread to be activated if necessary to
1788	>	* ensure parallelism while the current thread is blocked.
1789	>	*
1790	>	* <p>If {@code maintainParallelism} is {@code true} and the pool
1791	>	* supports it ({@link #getMaintainsParallelism}), this method
1792	>	* attempts to maintain the pool's nominal parallelism. Otherwise
1793	>	* it activates a thread only if necessary to avoid complete
1794	>	* starvation. This option may be preferable when blockages use
1795	>	* timeouts, or are almost always brief.
1796	>	*
1797	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
1798	>	* behaviorally equivalent to
1799	>	*  <pre> {@code
1800	>	* while (!blocker.isReleasable())
1801	>	*   if (blocker.block())
1802	>	*     return;
1803	>	* }</pre>
1804	>	*
1805	>	* If the caller is a {@code ForkJoinTask}, then the pool may
1806	>	* first be expanded to ensure parallelism, and later adjusted.
1807		*
1808		* @param blocker the blocker
1809	<	* @param maintainParallelism if true and supported by this pool,
1810	<	* attempt to maintain the pool's nominal parallelism; otherwise
1811	<	* activate a thread only if necessary to avoid complete
1812	<	* starvation.
1813	<	* @throws InterruptedException if blocker.block did so.
1809	>	* @param maintainParallelism if {@code true} and supported by
1810	>	* this pool, attempt to maintain the pool's nominal parallelism;
1811	>	* otherwise activate a thread only if necessary to avoid
1812	>	* complete starvation.
1813	>	* @throws InterruptedException if blocker.block did so
1814		*/
1815		public static void managedBlock(ManagedBlocker blocker,
1816		boolean maintainParallelism)
1817		throws InterruptedException {
1818		Thread t = Thread.currentThread();
1819	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1820	<	((ForkJoinWorkerThread)t).pool : null);
1819	>	ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ?
1820	>	((ForkJoinWorkerThread) t).pool : null);
1821		if (!blocker.isReleasable()) {
1822		try {
1823		if (pool == null ||
#	Line 1779 | Line 1832 | public class ForkJoinPool extends Abstra
1832
1833		private static void awaitBlocker(ManagedBlocker blocker)
1834		throws InterruptedException {
1835	<	do;while (!blocker.isReleasable() && !blocker.block());
1835	>	do {} while (!blocker.isReleasable() && !blocker.block());
1836		}
1837
1838	<	// AbstractExecutorService overrides
1838	>	// AbstractExecutorService overrides.  These rely on undocumented
1839	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1840	>	// implement RunnableFuture.
1841
1842		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1843	<	return new AdaptedRunnable(runnable, value);
1843	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
1844		}
1845
1846		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1847	<	return new AdaptedCallable(callable);
1793	<	}
1794	<
1795	<
1796	<	// Temporary Unsafe mechanics for preliminary release
1797	<	private static Unsafe getUnsafe() throws Throwable {
1798	<	try {
1799	<	return Unsafe.getUnsafe();
1800	<	} catch (SecurityException se) {
1801	<	try {
1802	<	return java.security.AccessController.doPrivileged
1803	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1804	<	public Unsafe run() throws Exception {
1805	<	return getUnsafePrivileged();
1806	<	}});
1807	<	} catch (java.security.PrivilegedActionException e) {
1808	<	throw e.getCause();
1809	<	}
1810	<	}
1847	>	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
1848		}
1849
1850	<	private static Unsafe getUnsafePrivileged()
1814	<	throws NoSuchFieldException, IllegalAccessException {
1815	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1816	<	f.setAccessible(true);
1817	<	return (Unsafe) f.get(null);
1818	<	}
1850	>	// Unsafe mechanics
1851
1852	<	private static long fieldOffset(String fieldName)
1853	<	throws NoSuchFieldException {
1854	<	return _unsafe.objectFieldOffset
1855	<	(ForkJoinPool.class.getDeclaredField(fieldName));
1856	<	}
1857	<
1858	<	static final Unsafe _unsafe;
1859	<	static final long eventCountOffset;
1860	<	static final long workerCountsOffset;
1861	<	static final long runControlOffset;
1862	<	static final long syncStackOffset;
1831	<	static final long spareStackOffset;
1832	<
1833	<	static {
1834	<	try {
1835	<	_unsafe = getUnsafe();
1836	<	eventCountOffset = fieldOffset("eventCount");
1837	<	workerCountsOffset = fieldOffset("workerCounts");
1838	<	runControlOffset = fieldOffset("runControl");
1839	<	syncStackOffset = fieldOffset("syncStack");
1840	<	spareStackOffset = fieldOffset("spareStack");
1841	<	} catch (Throwable e) {
1842	<	throw new RuntimeException("Could not initialize intrinsics", e);
1843	<	}
1844	<	}
1852	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1853	>	private static final long eventCountOffset =
1854	>	objectFieldOffset("eventCount", ForkJoinPool.class);
1855	>	private static final long workerCountsOffset =
1856	>	objectFieldOffset("workerCounts", ForkJoinPool.class);
1857	>	private static final long runControlOffset =
1858	>	objectFieldOffset("runControl", ForkJoinPool.class);
1859	>	private static final long syncStackOffset =
1860	>	objectFieldOffset("syncStack",ForkJoinPool.class);
1861	>	private static final long spareStackOffset =
1862	>	objectFieldOffset("spareStack", ForkJoinPool.class);
1863
1864		private boolean casEventCount(long cmp, long val) {
1865	<	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1865	>	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
1866		}
1867		private boolean casWorkerCounts(int cmp, int val) {
1868	<	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1868	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1869		}
1870		private boolean casRunControl(int cmp, int val) {
1871	<	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1871	>	return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
1872		}
1873		private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1874	<	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1874	>	return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
1875		}
1876		private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1877	<	return _unsafe.compareAndSwapObject(this, syncStackOffset, cmp, val);
1877	>	return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1878	>	}
1879	>
1880	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1881	>	try {
1882	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1883	>	} catch (NoSuchFieldException e) {
1884	>	// Convert Exception to corresponding Error
1885	>	NoSuchFieldError error = new NoSuchFieldError(field);
1886	>	error.initCause(e);
1887	>	throw error;
1888	>	}
1889	>	}
1890	>
1891	>	/**
1892	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1893	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1894	>	* into a jdk.
1895	>	*
1896	>	* @return a sun.misc.Unsafe
1897	>	*/
1898	>	private static sun.misc.Unsafe getUnsafe() {
1899	>	try {
1900	>	return sun.misc.Unsafe.getUnsafe();
1901	>	} catch (SecurityException se) {
1902	>	try {
1903	>	return java.security.AccessController.doPrivileged
1904	>	(new java.security
1905	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1906	>	public sun.misc.Unsafe run() throws Exception {
1907	>	java.lang.reflect.Field f = sun.misc
1908	>	.Unsafe.class.getDeclaredField("theUnsafe");
1909	>	f.setAccessible(true);
1910	>	return (sun.misc.Unsafe) f.get(null);
1911	>	}});
1912	>	} catch (java.security.PrivilegedActionException e) {
1913	>	throw new RuntimeException("Could not initialize intrinsics",
1914	>	e.getCause());
1915	>	}
1916	>	}
1917		}
1918		}

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