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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.14 by dl, Wed Jul 22 19:04:11 2009 UTC vs.
Revision 1.37 by dl, Sun Aug 2 11:54:31 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
23	>	* An {@link ExecutorService} for running {@link ForkJoinTask}s.
24	>	* A 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
#	Line 27 | Line 34 | import java.lang.reflect.*;
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.
37	>	* activities along with ForkJoinTasks. When setting {@linkplain
38	>	* #setAsyncMode async mode}, a ForkJoinPool may also be appropriate
39	>	* for use with fine-grained tasks that are never joined. Otherwise,
40	>	* other ExecutorService implementations are typically more
41	>	* appropriate choices.
42		*
43		* <p>A ForkJoinPool may be constructed with a given parallelism level
44		* (target pool size), which it attempts to maintain by dynamically
45		* adding, suspending, or resuming threads, even if some tasks are
46		* waiting to join others. However, no such adjustments are performed
47		* in the face of blocked IO or other unmanaged synchronization. The
48	<	* nested <code>ManagedBlocker</code> interface enables extension of
48	>	* nested {@link ManagedBlocker} interface enables extension of
49		* the kinds of synchronization accommodated.  The target parallelism
50	<	* level may also be changed dynamically (<code>setParallelism</code>)
50	>	* level may also be changed dynamically ({@link #setParallelism})
51		* and thread construction can be limited using methods
52	<	* <code>setMaximumPoolSize</code> and/or
53	<	* <code>setMaintainsParallelism</code>.
52	>	* {@link #setMaximumPoolSize} and/or
53	>	* {@link #setMaintainsParallelism}.
54		*
55		* <p>In addition to execution and lifecycle control methods, this
56		* class provides status check methods (for example
57	<	* <code>getStealCount</code>) that are intended to aid in developing,
57	>	* {@link #getStealCount}) that are intended to aid in developing,
58		* tuning, and monitoring fork/join applications. Also, method
59	<	* <code>toString</code> returns indications of pool state in a
59	>	* {@link #toString} returns indications of pool state in a
60		* convenient form for informal monitoring.
61		*
62		* <p><b>Implementation notes</b>: This implementation restricts the
63		* maximum number of running threads to 32767. Attempts to create
64		* pools with greater than the maximum result in
65		* IllegalArgumentExceptions.
66	+	*
67	+	* @since 1.7
68	+	* @author Doug Lea
69		*/
70		public class ForkJoinPool extends AbstractExecutorService {
71
#	Line 71 | Line 81 | public class ForkJoinPool extends Abstra
81		private static final int MAX_THREADS =  0x7FFF;
82
83		/**
84	<	* Factory for creating new ForkJoinWorkerThreads.  A
85	<	* ForkJoinWorkerThreadFactory must be defined and used for
86	<	* ForkJoinWorkerThread subclasses that extend base functionality
87	<	* or initialize threads with different contexts.
84	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
85	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
86	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
87	>	* functionality or initialize threads with different contexts.
88		*/
89		public static interface ForkJoinWorkerThreadFactory {
90		/**
91		* Returns a new worker thread operating in the given pool.
92		*
93		* @param pool the pool this thread works in
94	<	* @throws NullPointerException if pool is null;
94	>	* @throws NullPointerException if pool is null
95		*/
96		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
97		}
98
99		/**
100	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
100	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
101		* new ForkJoinWorkerThread.
102		*/
103		static class  DefaultForkJoinWorkerThreadFactory
#	Line 153 | Line 163 | public class ForkJoinPool extends Abstra
163
164		/**
165		* The uncaught exception handler used when any worker
166	<	* abrupty terminates
166	>	* abruptly terminates
167		*/
168		private Thread.UncaughtExceptionHandler ueh;
169
#	Line 181 | Line 191 | public class ForkJoinPool extends Abstra
191		private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
192
193		/**
194	<	* Head of Treiber stack for barrier sync. See below for explanation
194	>	* Head of Treiber stack for barrier sync. See below for explanation.
195		*/
196		private volatile WaitQueueNode syncStack;
197
#	Line 217 | Line 227 | public class ForkJoinPool extends Abstra
227		* making decisions about creating and suspending spare
228		* threads. Updated only by CAS.  Note: CASes in
229		* updateRunningCount and preJoin assume that running active count
230	<	* is in low word, so need to be modified if this changes
230	>	* is in low word, so need to be modified if this changes.
231		*/
232		private volatile int workerCounts;
233
#	Line 226 | Line 236 | public class ForkJoinPool extends Abstra
236		private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
237
238		/**
239	<	* Add delta (which may be negative) to running count.  This must
239	>	* Adds delta (which may be negative) to running count.  This must
240		* be called before (with negative arg) and after (with positive)
241	<	* any managed synchronization (i.e., mainly, joins)
241	>	* any managed synchronization (i.e., mainly, joins).
242	>	*
243		* @param delta the number to add
244		*/
245		final void updateRunningCount(int delta) {
246		int s;
247	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
247	>	do {} while (!casWorkerCounts(s = workerCounts, s + delta));
248		}
249
250		/**
251	<	* Add delta (which may be negative) to both total and running
251	>	* Adds delta (which may be negative) to both total and running
252		* count.  This must be called upon creation and termination of
253		* worker threads.
254	+	*
255		* @param delta the number to add
256		*/
257		private void updateWorkerCount(int delta) {
258		int d = delta + (delta << 16); // add to both lo and hi parts
259		int s;
260	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
260	>	do {} while (!casWorkerCounts(s = workerCounts, s + d));
261		}
262
263		/**
#	Line 271 | Line 283 | public class ForkJoinPool extends Abstra
283		private static int runControlFor(int r, int a)   { return (r << 16) + a; }
284
285		/**
286	<	* Try incrementing active count; fail on contention. Called by
287	<	* workers before/during executing tasks.
288	<	* @return true on success;
286	>	* Tries incrementing active count; fails on contention.
287	>	* Called by workers before/during executing tasks.
288	>	*
289	>	* @return true on success
290		*/
291		final boolean tryIncrementActiveCount() {
292		int c = runControl;
#	Line 281 | Line 294 | public class ForkJoinPool extends Abstra
294		}
295
296		/**
297	<	* Try decrementing active count; fail on contention.
298	<	* Possibly trigger termination on success
297	>	* Tries decrementing active count; fails on contention.
298	>	* Possibly triggers termination on success.
299		* Called by workers when they can't find tasks.
300	+	*
301		* @return true on success
302		*/
303		final boolean tryDecrementActiveCount() {
#	Line 297 | Line 311 | public class ForkJoinPool extends Abstra
311		}
312
313		/**
314	<	* Return true if argument represents zero active count and
315	<	* nonzero runstate, which is the triggering condition for
314	>	* Returns {@code true} if argument represents zero active count
315	>	* and nonzero runstate, which is the triggering condition for
316		* terminating on shutdown.
317		*/
318		private static boolean canTerminateOnShutdown(int c) {
319	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
319	>	// i.e. least bit is nonzero runState bit
320	>	return ((c & -c) >>> 16) != 0;
321		}
322
323		/**
#	Line 328 | Line 343 | public class ForkJoinPool extends Abstra
343
344		/**
345		* Creates a ForkJoinPool with a pool size equal to the number of
346	<	* processors available on the system and using the default
347	<	* ForkJoinWorkerThreadFactory,
346	>	* processors available on the system, using the default
347	>	* ForkJoinWorkerThreadFactory.
348	>	*
349		* @throws SecurityException if a security manager exists and
350		*         the caller is not permitted to modify threads
351		*         because it does not hold {@link
352	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
352	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
353		*/
354		public ForkJoinPool() {
355		this(Runtime.getRuntime().availableProcessors(),
#	Line 341 | Line 357 | public class ForkJoinPool extends Abstra
357		}
358
359		/**
360	<	* Creates a ForkJoinPool with the indicated parellelism level
361	<	* threads, and using the default ForkJoinWorkerThreadFactory,
360	>	* Creates a ForkJoinPool with the indicated parallelism level
361	>	* threads and using the default ForkJoinWorkerThreadFactory.
362	>	*
363		* @param parallelism the number of worker threads
364		* @throws IllegalArgumentException if parallelism less than or
365		* equal to zero
366		* @throws SecurityException if a security manager exists and
367		*         the caller is not permitted to modify threads
368		*         because it does not hold {@link
369	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
369	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
370		*/
371		public ForkJoinPool(int parallelism) {
372		this(parallelism, defaultForkJoinWorkerThreadFactory);
#	Line 358 | Line 375 | public class ForkJoinPool extends Abstra
375		/**
376		* Creates a ForkJoinPool with parallelism equal to the number of
377		* processors available on the system and using the given
378	<	* ForkJoinWorkerThreadFactory,
378	>	* ForkJoinWorkerThreadFactory.
379	>	*
380		* @param factory the factory for creating new threads
381		* @throws NullPointerException if factory is null
382		* @throws SecurityException if a security manager exists and
383		*         the caller is not permitted to modify threads
384		*         because it does not hold {@link
385	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
385	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
386		*/
387		public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
388		this(Runtime.getRuntime().availableProcessors(), factory);
#	Line 376 | Line 394 | public class ForkJoinPool extends Abstra
394		* @param parallelism the targeted number of worker threads
395		* @param factory the factory for creating new threads
396		* @throws IllegalArgumentException if parallelism less than or
397	<	* equal to zero, or greater than implementation limit.
397	>	* equal to zero, or greater than implementation limit
398		* @throws NullPointerException if factory is null
399		* @throws SecurityException if a security manager exists and
400		*         the caller is not permitted to modify threads
401		*         because it does not hold {@link
402	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
402	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
403		*/
404		public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
405		if (parallelism <= 0 || parallelism > MAX_THREADS)
#	Line 402 | Line 420 | public class ForkJoinPool extends Abstra
420		}
421
422		/**
423	<	* Create new worker using factory.
423	>	* Creates a new worker thread using factory.
424	>	*
425		* @param index the index to assign worker
426		* @return new worker, or null of factory failed
427		*/
#	Line 421 | Line 440 | public class ForkJoinPool extends Abstra
440		}
441
442		/**
443	<	* Return a good size for worker array given pool size.
443	>	* Returns a good size for worker array given pool size.
444		* Currently requires size to be a power of two.
445		*/
446	<	private static int arraySizeFor(int ps) {
447	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
446	>	private static int arraySizeFor(int poolSize) {
447	>	return (poolSize <= 1) ? 1 :
448	>	(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1)));
449		}
450
451		/**
452	<	* Create or resize array if necessary to hold newLength.
453	<	* Call only under exclusion
452	>	* Creates or resizes array if necessary to hold newLength.
453	>	* Call only under exclusion.
454	>	*
455		* @return the array
456		*/
457		private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
#	Line 444 | Line 465 | public class ForkJoinPool extends Abstra
465		}
466
467		/**
468	<	* Try to shrink workers into smaller array after one or more terminate
468	>	* Tries to shrink workers into smaller array after one or more terminate.
469		*/
470		private void tryShrinkWorkerArray() {
471		ForkJoinWorkerThread[] ws = workers;
#	Line 460 | Line 481 | public class ForkJoinPool extends Abstra
481		}
482
483		/**
484	<	* Initialize workers if necessary
484	>	* Initializes workers if necessary.
485		*/
486		final void ensureWorkerInitialization() {
487		ForkJoinWorkerThread[] ws = workers;
#	Line 527 | Line 548 | public class ForkJoinPool extends Abstra
548		* Common code for execute, invoke and submit
549		*/
550		private <T> void doSubmit(ForkJoinTask<T> task) {
551	+	if (task == null)
552	+	throw new NullPointerException();
553		if (isShutdown())
554		throw new RejectedExecutionException();
555		if (workers == null)
#	Line 536 | Line 559 | public class ForkJoinPool extends Abstra
559		}
560
561		/**
562	<	* Performs the given task; returning its result upon completion
562	>	* Performs the given task, returning its result upon completion.
563	>	*
564		* @param task the task
565		* @return the task's result
566		* @throws NullPointerException if task is null
#	Line 549 | Line 573 | public class ForkJoinPool extends Abstra
573
574		/**
575		* Arranges for (asynchronous) execution of the given task.
576	+	*
577		* @param task the task
578		* @throws NullPointerException if task is null
579		* @throws RejectedExecutionException if pool is shut down
580		*/
581	<	public <T> void execute(ForkJoinTask<T> task) {
581	>	public void execute(ForkJoinTask<?> task) {
582		doSubmit(task);
583		}
584
585		// AbstractExecutorService methods
586
587		public void execute(Runnable task) {
588	<	doSubmit(new AdaptedRunnable<Void>(task, null));
588	>	ForkJoinTask<?> job;
589	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
590	>	job = (ForkJoinTask<?>) task;
591	>	else
592	>	job = ForkJoinTask.adapt(task, null);
593	>	doSubmit(job);
594		}
595
596		public <T> ForkJoinTask<T> submit(Callable<T> task) {
597	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
597	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
598		doSubmit(job);
599		return job;
600		}
601
602		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
603	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
603	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
604		doSubmit(job);
605		return job;
606		}
607
608		public ForkJoinTask<?> submit(Runnable task) {
609	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
609	>	ForkJoinTask<?> job;
610	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
611	>	job = (ForkJoinTask<?>) task;
612	>	else
613	>	job = ForkJoinTask.adapt(task, null);
614		doSubmit(job);
615		return job;
616		}
617
618		/**
619	<	* Adaptor for Runnables. This implements RunnableFuture
620	<	* to be compliant with AbstractExecutorService constraints
619	>	* Submits a ForkJoinTask for execution.
620	>	*
621	>	* @param task the task to submit
622	>	* @return the task
623	>	* @throws RejectedExecutionException if the task cannot be
624	>	*         scheduled for execution
625	>	* @throws NullPointerException if the task is null
626		*/
627	<	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
628	<	implements RunnableFuture<T> {
629	<	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(); }
627	>	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
628	>	doSubmit(task);
629	>	return task;
630		}
631
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	–	}
632
633		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
634	<	ArrayList<ForkJoinTask<T>> ts =
634	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
635		new ArrayList<ForkJoinTask<T>>(tasks.size());
636	<	for (Callable<T> c : tasks)
637	<	ts.add(new AdaptedCallable<T>(c));
638	<	invoke(new InvokeAll<T>(ts));
639	<	return (List<Future<T>>)(List)ts;
636	>	for (Callable<T> task : tasks)
637	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
638	>	invoke(new InvokeAll<T>(forkJoinTasks));
639	>
640	>	@SuppressWarnings({"unchecked", "rawtypes"})
641	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
642	>	return futures;
643		}
644
645		static final class InvokeAll<T> extends RecursiveAction {
646		final ArrayList<ForkJoinTask<T>> tasks;
647		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
648		public void compute() {
649	<	try { invokeAll(tasks); } catch(Exception ignore) {}
649	>	try { invokeAll(tasks); }
650	>	catch (Exception ignore) {}
651		}
652	+	private static final long serialVersionUID = -7914297376763021607L;
653		}
654
655		// Configuration and status settings and queries
656
657		/**
658	<	* Returns the factory used for constructing new workers
658	>	* Returns the factory used for constructing new workers.
659		*
660		* @return the factory used for constructing new workers
661		*/
#	Line 664 | Line 666 | public class ForkJoinPool extends Abstra
666		/**
667		* Returns the handler for internal worker threads that terminate
668		* due to unrecoverable errors encountered while executing tasks.
669	<	* @return the handler, or null if none
669	>	*
670	>	* @return the handler, or {@code null} if none
671		*/
672		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
673		Thread.UncaughtExceptionHandler h;
#	Line 685 | Line 688 | public class ForkJoinPool extends Abstra
688		* as handler.
689		*
690		* @param h the new handler
691	<	* @return the old handler, or null if none
691	>	* @return the old handler, or {@code null} if none
692		* @throws SecurityException if a security manager exists and
693		*         the caller is not permitted to modify threads
694		*         because it does not hold {@link
695	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
695	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
696		*/
697		public Thread.UncaughtExceptionHandler
698		setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
#	Line 716 | Line 719 | public class ForkJoinPool extends Abstra
719
720
721		/**
722	<	* Sets the target paralleism level of this pool.
722	>	* Sets the target parallelism level of this pool.
723	>	*
724		* @param parallelism the target parallelism
725		* @throws IllegalArgumentException if parallelism less than or
726	<	* equal to zero or greater than maximum size bounds.
726	>	* equal to zero or greater than maximum size bounds
727		* @throws SecurityException if a security manager exists and
728		*         the caller is not permitted to modify threads
729		*         because it does not hold {@link
730	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
730	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
731		*/
732		public void setParallelism(int parallelism) {
733		checkPermission();
#	Line 758 | Line 762 | public class ForkJoinPool extends Abstra
762		/**
763		* Returns the number of worker threads that have started but not
764		* yet terminated.  This result returned by this method may differ
765	<	* from <code>getParallelism</code> when threads are created to
765	>	* from {@link #getParallelism} when threads are created to
766		* maintain parallelism when others are cooperatively blocked.
767		*
768		* @return the number of worker threads
#	Line 770 | Line 774 | public class ForkJoinPool extends Abstra
774		/**
775		* Returns the maximum number of threads allowed to exist in the
776		* pool, even if there are insufficient unblocked running threads.
777	+	*
778		* @return the maximum
779		*/
780		public int getMaximumPoolSize() {
#	Line 781 | Line 786 | public class ForkJoinPool extends Abstra
786		* pool, even if there are insufficient unblocked running threads.
787		* Setting this value has no effect on current pool size. It
788		* controls construction of new threads.
789	<	* @throws IllegalArgumentException if negative or greater then
790	<	* internal implementation limit.
789	>	*
790	>	* @throws IllegalArgumentException if negative or greater than
791	>	* internal implementation limit
792		*/
793		public void setMaximumPoolSize(int newMax) {
794		if (newMax < 0 || newMax > MAX_THREADS)
#	Line 792 | Line 798 | public class ForkJoinPool extends Abstra
798
799
800		/**
801	<	* Returns true if this pool dynamically maintains its target
802	<	* parallelism level. If false, new threads are added only to
803	<	* avoid possible starvation.
804	<	* This setting is by default true;
805	<	* @return true if maintains parallelism
801	>	* Returns {@code true} if this pool dynamically maintains its
802	>	* target parallelism level. If false, new threads are added only
803	>	* to avoid possible starvation.  This setting is by default true.
804	>	*
805	>	* @return {@code true} if maintains parallelism
806		*/
807		public boolean getMaintainsParallelism() {
808		return maintainsParallelism;
#	Line 806 | Line 812 | public class ForkJoinPool extends Abstra
812		* Sets whether this pool dynamically maintains its target
813		* parallelism level. If false, new threads are added only to
814		* avoid possible starvation.
815	<	* @param enable true to maintains parallelism
815	>	*
816	>	* @param enable {@code true} to maintain parallelism
817		*/
818		public void setMaintainsParallelism(boolean enable) {
819		maintainsParallelism = enable;
#	Line 817 | Line 824 | public class ForkJoinPool extends Abstra
824		* tasks that are never joined. This mode may be more appropriate
825		* than default locally stack-based mode in applications in which
826		* worker threads only process asynchronous tasks.  This method is
827	<	* designed to be invoked only when pool is quiescent, and
827	>	* designed to be invoked only when the pool is quiescent, and
828		* typically only before any tasks are submitted. The effects of
829	<	* invocations at ather times may be unpredictable.
829	>	* invocations at other times may be unpredictable.
830		*
831	<	* @param async if true, use locally FIFO scheduling
832	<	* @return the previous mode.
831	>	* @param async if {@code true}, use locally FIFO scheduling
832	>	* @return the previous mode
833	>	* @see #getAsyncMode
834		*/
835		public boolean setAsyncMode(boolean async) {
836		boolean oldMode = locallyFifo;
#	Line 839 | Line 847 | public class ForkJoinPool extends Abstra
847		}
848
849		/**
850	<	* Returns true if this pool uses local first-in-first-out
851	<	* scheduling mode for forked tasks that are never joined.
850	>	* Returns {@code true} if this pool uses local first-in-first-out
851	>	* scheduling mode for forked tasks that are never joined.
852		*
853	<	* @return true if this pool uses async mode.
853	>	* @return {@code true} if this pool uses async mode
854	>	* @see #setAsyncMode
855		*/
856		public boolean getAsyncMode() {
857		return locallyFifo;
#	Line 863 | Line 872 | public class ForkJoinPool extends Abstra
872		* Returns an estimate of the number of threads that are currently
873		* stealing or executing tasks. This method may overestimate the
874		* number of active threads.
875	<	* @return the number of active threads.
875	>	*
876	>	* @return the number of active threads
877		*/
878		public int getActiveThreadCount() {
879		return activeCountOf(runControl);
#	Line 873 | Line 883 | public class ForkJoinPool extends Abstra
883		* Returns an estimate of the number of threads that are currently
884		* idle waiting for tasks. This method may underestimate the
885		* number of idle threads.
886	<	* @return the number of idle threads.
886	>	*
887	>	* @return the number of idle threads
888		*/
889		final int getIdleThreadCount() {
890		int c = runningCountOf(workerCounts) - activeCountOf(runControl);
891	<	return (c <= 0)? 0 : c;
891	>	return (c <= 0) ? 0 : c;
892		}
893
894		/**
895	<	* Returns true if all worker threads are currently idle. An idle
896	<	* worker is one that cannot obtain a task to execute because none
897	<	* are available to steal from other threads, and there are no
898	<	* pending submissions to the pool. This method is conservative:
899	<	* It might not return true immediately upon idleness of all
900	<	* threads, but will eventually become true if threads remain
901	<	* inactive.
902	<	* @return true if all threads are currently idle
895	>	* Returns {@code true} if all worker threads are currently idle.
896	>	* An idle worker is one that cannot obtain a task to execute
897	>	* because none are available to steal from other threads, and
898	>	* there are no pending submissions to the pool. This method is
899	>	* conservative; it might not return {@code true} immediately upon
900	>	* idleness of all threads, but will eventually become true if
901	>	* threads remain inactive.
902	>	*
903	>	* @return {@code true} if all threads are currently idle
904		*/
905		public boolean isQuiescent() {
906		return activeCountOf(runControl) == 0;
#	Line 899 | Line 911 | public class ForkJoinPool extends Abstra
911		* one thread's work queue by another. The reported value
912		* underestimates the actual total number of steals when the pool
913		* is not quiescent. This value may be useful for monitoring and
914	<	* tuning fork/join programs: In general, steal counts should be
914	>	* tuning fork/join programs: in general, steal counts should be
915		* high enough to keep threads busy, but low enough to avoid
916		* overhead and contention across threads.
917	<	* @return the number of steals.
917	>	*
918	>	* @return the number of steals
919		*/
920		public long getStealCount() {
921		return stealCount.get();
922		}
923
924		/**
925	<	* Accumulate steal count from a worker. Call only
926	<	* when worker known to be idle.
925	>	* Accumulates steal count from a worker.
926	>	* Call only when worker known to be idle.
927		*/
928		private void updateStealCount(ForkJoinWorkerThread w) {
929		int sc = w.getAndClearStealCount();
#	Line 925 | Line 938 | public class ForkJoinPool extends Abstra
938		* an approximation, obtained by iterating across all threads in
939		* the pool. This method may be useful for tuning task
940		* granularities.
941	<	* @return the number of queued tasks.
941	>	*
942	>	* @return the number of queued tasks
943		*/
944		public long getQueuedTaskCount() {
945		long count = 0;
#	Line 944 | Line 958 | public class ForkJoinPool extends Abstra
958		* Returns an estimate of the number tasks submitted to this pool
959		* that have not yet begun executing. This method takes time
960		* proportional to the number of submissions.
961	<	* @return the number of queued submissions.
961	>	*
962	>	* @return the number of queued submissions
963		*/
964		public int getQueuedSubmissionCount() {
965		return submissionQueue.size();
966		}
967
968		/**
969	<	* Returns true if there are any tasks submitted to this pool
970	<	* that have not yet begun executing.
971	<	* @return <code>true</code> if there are any queued submissions.
969	>	* Returns {@code true} if there are any tasks submitted to this
970	>	* pool that have not yet begun executing.
971	>	*
972	>	* @return {@code true} if there are any queued submissions
973		*/
974		public boolean hasQueuedSubmissions() {
975		return !submissionQueue.isEmpty();
#	Line 963 | Line 979 | public class ForkJoinPool extends Abstra
979		* Removes and returns the next unexecuted submission if one is
980		* available.  This method may be useful in extensions to this
981		* class that re-assign work in systems with multiple pools.
982	<	* @return the next submission, or null if none
982	>	*
983	>	* @return the next submission, or {@code null} if none
984		*/
985		protected ForkJoinTask<?> pollSubmission() {
986		return submissionQueue.poll();
#	Line 973 | Line 990 | public class ForkJoinPool extends Abstra
990		* Removes all available unexecuted submitted and forked tasks
991		* from scheduling queues and adds them to the given collection,
992		* without altering their execution status. These may include
993	<	* artifically generated or wrapped tasks. This method id designed
993	>	* artificially generated or wrapped tasks. This method is designed
994		* to be invoked only when the pool is known to be
995		* quiescent. Invocations at other times may not remove all
996		* tasks. A failure encountered while attempting to add elements
997	<	* to collection <tt>c</tt> may result in elements being in
997	>	* to collection {@code c} may result in elements being in
998		* neither, either or both collections when the associated
999		* exception is thrown.  The behavior of this operation is
1000		* undefined if the specified collection is modified while the
1001		* operation is in progress.
1002	+	*
1003		* @param c the collection to transfer elements into
1004		* @return the number of elements transferred
1005		*/
1006	<	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
1006	>	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1007		int n = submissionQueue.drainTo(c);
1008		ForkJoinWorkerThread[] ws = workers;
1009		if (ws != null) {
#	Line 1042 | Line 1060 | public class ForkJoinPool extends Abstra
1060		* Invocation has no additional effect if already shut down.
1061		* Tasks that are in the process of being submitted concurrently
1062		* during the course of this method may or may not be rejected.
1063	+	*
1064		* @throws SecurityException if a security manager exists and
1065		*         the caller is not permitted to modify threads
1066		*         because it does not hold {@link
1067	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1067	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1068		*/
1069		public void shutdown() {
1070		checkPermission();
1071		transitionRunStateTo(SHUTDOWN);
1072	<	if (canTerminateOnShutdown(runControl))
1072	>	if (canTerminateOnShutdown(runControl)) {
1073	>	if (workers == null) { // shutting down before workers created
1074	>	final ReentrantLock lock = this.workerLock;
1075	>	lock.lock();
1076	>	try {
1077	>	if (workers == null) {
1078	>	terminate();
1079	>	transitionRunStateTo(TERMINATED);
1080	>	termination.signalAll();
1081	>	}
1082	>	} finally {
1083	>	lock.unlock();
1084	>	}
1085	>	}
1086		terminateOnShutdown();
1087	+	}
1088		}
1089
1090		/**
#	Line 1061 | Line 1094 | public class ForkJoinPool extends Abstra
1094		* method may or may not be rejected. Unlike some other executors,
1095		* this method cancels rather than collects non-executed tasks
1096		* upon termination, so always returns an empty list. However, you
1097	<	* can use method <code>drainTasksTo</code> before invoking this
1097	>	* can use method {@link #drainTasksTo} before invoking this
1098		* method to transfer unexecuted tasks to another collection.
1099	+	*
1100		* @return an empty list
1101		* @throws SecurityException if a security manager exists and
1102		*         the caller is not permitted to modify threads
1103		*         because it does not hold {@link
1104	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1104	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1105		*/
1106		public List<Runnable> shutdownNow() {
1107		checkPermission();
#	Line 1076 | Line 1110 | public class ForkJoinPool extends Abstra
1110		}
1111
1112		/**
1113	<	* Returns <code>true</code> if all tasks have completed following shut down.
1113	>	* Returns {@code true} if all tasks have completed following shut down.
1114		*
1115	<	* @return <code>true</code> if all tasks have completed following shut down
1115	>	* @return {@code true} if all tasks have completed following shut down
1116		*/
1117		public boolean isTerminated() {
1118		return runStateOf(runControl) == TERMINATED;
1119		}
1120
1121		/**
1122	<	* Returns <code>true</code> if the process of termination has
1122	>	* Returns {@code true} if the process of termination has
1123		* commenced but possibly not yet completed.
1124		*
1125	<	* @return <code>true</code> if terminating
1125	>	* @return {@code true} if terminating
1126		*/
1127		public boolean isTerminating() {
1128		return runStateOf(runControl) >= TERMINATING;
1129		}
1130
1131		/**
1132	<	* Returns <code>true</code> if this pool has been shut down.
1132	>	* Returns {@code true} if this pool has been shut down.
1133		*
1134	<	* @return <code>true</code> if this pool has been shut down
1134	>	* @return {@code true} if this pool has been shut down
1135		*/
1136		public boolean isShutdown() {
1137		return runStateOf(runControl) >= SHUTDOWN;
#	Line 1110 | Line 1144 | public class ForkJoinPool extends Abstra
1144		*
1145		* @param timeout the maximum time to wait
1146		* @param unit the time unit of the timeout argument
1147	<	* @return <code>true</code> if this executor terminated and
1148	<	*         <code>false</code> if the timeout elapsed before termination
1147	>	* @return {@code true} if this executor terminated and
1148	>	*         {@code false} if the timeout elapsed before termination
1149		* @throws InterruptedException if interrupted while waiting
1150		*/
1151		public boolean awaitTermination(long timeout, TimeUnit unit)
#	Line 1135 | Line 1169 | public class ForkJoinPool extends Abstra
1169		// Shutdown and termination support
1170
1171		/**
1172	<	* Callback from terminating worker. Null out the corresponding
1173	<	* workers slot, and if terminating, try to terminate, else try to
1174	<	* shrink workers array.
1172	>	* Callback from terminating worker. Nulls out the corresponding
1173	>	* workers slot, and if terminating, tries to terminate; else
1174	>	* tries to shrink workers array.
1175	>	*
1176		* @param w the worker
1177		*/
1178		final void workerTerminated(ForkJoinWorkerThread w) {
#	Line 1168 | Line 1203 | public class ForkJoinPool extends Abstra
1203		}
1204
1205		/**
1206	<	* Initiate termination.
1206	>	* Initiates termination.
1207		*/
1208		private void terminate() {
1209		if (transitionRunStateTo(TERMINATING)) {
#	Line 1183 | Line 1218 | public class ForkJoinPool extends Abstra
1218		}
1219
1220		/**
1221	<	* Possibly terminate when on shutdown state
1221	>	* Possibly terminates when on shutdown state.
1222		*/
1223		private void terminateOnShutdown() {
1224		if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
#	Line 1191 | Line 1226 | public class ForkJoinPool extends Abstra
1226		}
1227
1228		/**
1229	<	* Clear out and cancel submissions
1229	>	* Clears out and cancels submissions.
1230		*/
1231		private void cancelQueuedSubmissions() {
1232		ForkJoinTask<?> task;
#	Line 1200 | Line 1235 | public class ForkJoinPool extends Abstra
1235		}
1236
1237		/**
1238	<	* Clean out worker queues.
1238	>	* Cleans out worker queues.
1239		*/
1240		private void cancelQueuedWorkerTasks() {
1241		final ReentrantLock lock = this.workerLock;
#	Line 1220 | Line 1255 | public class ForkJoinPool extends Abstra
1255		}
1256
1257		/**
1258	<	* Set each worker's status to terminating. Requires lock to avoid
1259	<	* conflicts with add/remove
1258	>	* Sets each worker's status to terminating. Requires lock to avoid
1259	>	* conflicts with add/remove.
1260		*/
1261		private void stopAllWorkers() {
1262		final ReentrantLock lock = this.workerLock;
#	Line 1241 | Line 1276 | public class ForkJoinPool extends Abstra
1276		}
1277
1278		/**
1279	<	* Interrupt all unterminated workers.  This is not required for
1279	>	* Interrupts all unterminated workers.  This is not required for
1280		* sake of internal control, but may help unstick user code during
1281		* shutdown.
1282		*/
#	Line 1311 | Line 1346 | public class ForkJoinPool extends Abstra
1346		}
1347
1348		/**
1349	<	* Wake up waiter, returning false if known to already
1349	>	* Wakes up waiter, returning false if known to already
1350		*/
1351		boolean signal() {
1352		ForkJoinWorkerThread t = thread;
#	Line 1323 | Line 1358 | public class ForkJoinPool extends Abstra
1358		}
1359
1360		/**
1361	<	* Await release on sync
1361	>	* Awaits release on sync.
1362		*/
1363		void awaitSyncRelease(ForkJoinPool p) {
1364		while (thread != null && !p.syncIsReleasable(this))
#	Line 1331 | Line 1366 | public class ForkJoinPool extends Abstra
1366		}
1367
1368		/**
1369	<	* Await resumption as spare
1369	>	* Awaits resumption as spare.
1370		*/
1371		void awaitSpareRelease() {
1372		while (thread != null) {
#	Line 1345 | Line 1380 | public class ForkJoinPool extends Abstra
1380		* Ensures that no thread is waiting for count to advance from the
1381		* current value of eventCount read on entry to this method, by
1382		* releasing waiting threads if necessary.
1383	+	*
1384		* @return the count
1385		*/
1386		final long ensureSync() {
#	Line 1366 | Line 1402 | public class ForkJoinPool extends Abstra
1402		*/
1403		private void signalIdleWorkers() {
1404		long c;
1405	<	do;while (!casEventCount(c = eventCount, c+1));
1405	>	do {} while (!casEventCount(c = eventCount, c+1));
1406		ensureSync();
1407		}
1408
1409		/**
1410	<	* Signal threads waiting to poll a task. Because method sync
1410	>	* Signals threads waiting to poll a task. Because method sync
1411		* rechecks availability, it is OK to only proceed if queue
1412		* appears to be non-empty, and OK to skip under contention to
1413		* increment count (since some other thread succeeded).
#	Line 1390 | Line 1426 | public class ForkJoinPool extends Abstra
1426		* Waits until event count advances from last value held by
1427		* caller, or if excess threads, caller is resumed as spare, or
1428		* caller or pool is terminating. Updates caller's event on exit.
1429	+	*
1430		* @param w the calling worker thread
1431		*/
1432		final void sync(ForkJoinWorkerThread w) {
#	Line 1417 | Line 1454 | public class ForkJoinPool extends Abstra
1454		}
1455
1456		/**
1457	<	* Returns true if worker waiting on sync can proceed:
1457	>	* Returns {@code true} if worker waiting on sync can proceed:
1458		*  - on signal (thread == null)
1459		*  - on event count advance (winning race to notify vs signaller)
1460	<	*  - on Interrupt
1460	>	*  - on interrupt
1461		*  - if the first queued node, we find work available
1462		* If node was not signalled and event count not advanced on exit,
1463		* then we also help advance event count.
1464	<	* @return true if node can be released
1464	>	*
1465	>	* @return {@code true} if node can be released
1466		*/
1467		final boolean syncIsReleasable(WaitQueueNode node) {
1468		long prev = node.count;
#	Line 1443 | Line 1481 | public class ForkJoinPool extends Abstra
1481		}
1482
1483		/**
1484	<	* Returns true if a new sync event occurred since last call to
1485	<	* sync or this method, if so, updating caller's count.
1484	>	* Returns {@code true} if a new sync event occurred since last
1485	>	* call to sync or this method, if so, updating caller's count.
1486		*/
1487		final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1488		long lc = w.lastEventCount;
#	Line 1458 | Line 1496 | public class ForkJoinPool extends Abstra
1496		//  Parallelism maintenance
1497
1498		/**
1499	<	* Decrement running count; if too low, add spare.
1499	>	* Decrements running count; if too low, adds spare.
1500		*
1501		* Conceptually, all we need to do here is add or resume a
1502		* spare thread when one is about to block (and remove or
1503		* suspend it later when unblocked -- see suspendIfSpare).
1504		* However, implementing this idea requires coping with
1505	<	* several problems: We have imperfect information about the
1505	>	* several problems: we have imperfect information about the
1506		* states of threads. Some count updates can and usually do
1507		* lag run state changes, despite arrangements to keep them
1508		* accurate (for example, when possible, updating counts
#	Line 1478 | Line 1516 | public class ForkJoinPool extends Abstra
1516		* only be suspended or removed when they are idle, not
1517		* immediately when they aren't needed. So adding threads will
1518		* raise parallelism level for longer than necessary.  Also,
1519	<	* FJ applications often enounter highly transient peaks when
1519	>	* FJ applications often encounter highly transient peaks when
1520		* many threads are blocked joining, but for less time than it
1521		* takes to create or resume spares.
1522		*
#	Line 1487 | Line 1525 | public class ForkJoinPool extends Abstra
1525		* target counts, else create only to avoid starvation
1526		* @return true if joinMe known to be done
1527		*/
1528	<	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1528	>	final boolean preJoin(ForkJoinTask<?> joinMe,
1529	>	boolean maintainParallelism) {
1530		maintainParallelism &= maintainsParallelism; // overrride
1531		boolean dec = false;  // true when running count decremented
1532		while (spareStack == null || !tryResumeSpare(dec)) {
1533		int counts = workerCounts;
1534	<	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1534	>	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1535	>	// CAS cheat
1536		if (!needSpare(counts, maintainParallelism))
1537		break;
1538		if (joinMe.status < 0)
#	Line 1507 | Line 1547 | public class ForkJoinPool extends Abstra
1547		/**
1548		* Same idea as preJoin
1549		*/
1550	<	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1550	>	final boolean preBlock(ManagedBlocker blocker,
1551	>	boolean maintainParallelism) {
1552		maintainParallelism &= maintainsParallelism;
1553		boolean dec = false;
1554		while (spareStack == null || !tryResumeSpare(dec)) {
#	Line 1525 | Line 1566 | public class ForkJoinPool extends Abstra
1566		}
1567
1568		/**
1569	<	* Returns true if a spare thread appears to be needed.  If
1570	<	* maintaining parallelism, returns true when the deficit in
1569	>	* Returns {@code true} if a spare thread appears to be needed.
1570	>	* If maintaining parallelism, returns true when the deficit in
1571		* running threads is more than the surplus of total threads, and
1572		* there is apparently some work to do.  This self-limiting rule
1573		* means that the more threads that have already been added, the
1574		* less parallelism we will tolerate before adding another.
1575	+	*
1576		* @param counts current worker counts
1577		* @param maintainParallelism try to maintain parallelism
1578		*/
#	Line 1548 | Line 1590 | public class ForkJoinPool extends Abstra
1590		}
1591
1592		/**
1593	<	* Add a spare worker if lock available and no more than the
1594	<	* expected numbers of threads exist
1593	>	* Adds a spare worker if lock available and no more than the
1594	>	* expected numbers of threads exist.
1595	>	*
1596		* @return true if successful
1597		*/
1598		private boolean tryAddSpare(int expectedCounts) {
#	Line 1582 | Line 1625 | public class ForkJoinPool extends Abstra
1625		}
1626
1627		/**
1628	<	* Add the kth spare worker. On entry, pool coounts are already
1628	>	* Adds the kth spare worker. On entry, pool counts are already
1629		* adjusted to reflect addition.
1630		*/
1631		private void createAndStartSpare(int k) {
#	Line 1604 | Line 1647 | public class ForkJoinPool extends Abstra
1647		}
1648
1649		/**
1650	<	* Suspend calling thread w if there are excess threads.  Called
1651	<	* only from sync.  Spares are enqueued in a Treiber stack
1652	<	* using the same WaitQueueNodes as barriers.  They are resumed
1653	<	* mainly in preJoin, but are also woken on pool events that
1654	<	* require all threads to check run state.
1650	>	* Suspends calling thread w if there are excess threads.  Called
1651	>	* only from sync.  Spares are enqueued in a Treiber stack using
1652	>	* the same WaitQueueNodes as barriers.  They are resumed mainly
1653	>	* in preJoin, but are also woken on pool events that require all
1654	>	* threads to check run state.
1655	>	*
1656		* @param w the caller
1657		*/
1658		private boolean suspendIfSpare(ForkJoinWorkerThread w) {
#	Line 1619 | Line 1663 | public class ForkJoinPool extends Abstra
1663		node = new WaitQueueNode(0, w);
1664		if (casWorkerCounts(s, s-1)) { // representation-dependent
1665		// push onto stack
1666	<	do;while (!casSpareStack(node.next = spareStack, node));
1666	>	do {} while (!casSpareStack(node.next = spareStack, node));
1667		// block until released by resumeSpare
1668		node.awaitSpareRelease();
1669		return true;
#	Line 1629 | Line 1673 | public class ForkJoinPool extends Abstra
1673		}
1674
1675		/**
1676	<	* Try to pop and resume a spare thread.
1676	>	* Tries to pop and resume a spare thread.
1677	>	*
1678		* @param updateCount if true, increment running count on success
1679		* @return true if successful
1680		*/
#	Line 1647 | Line 1692 | public class ForkJoinPool extends Abstra
1692		}
1693
1694		/**
1695	<	* Pop and resume all spare threads. Same idea as ensureSync.
1695	>	* Pops and resumes all spare threads. Same idea as ensureSync.
1696	>	*
1697		* @return true if any spares released
1698		*/
1699		private boolean resumeAllSpares() {
#	Line 1665 | Line 1711 | public class ForkJoinPool extends Abstra
1711		}
1712
1713		/**
1714	<	* Pop and shutdown excessive spare threads. Call only while
1714	>	* Pops and shuts down excessive spare threads. Call only while
1715		* holding lock. This is not guaranteed to eliminate all excess
1716		* threads, only those suspended as spares, which are the ones
1717		* unlikely to be needed in the future.
#	Line 1689 | Line 1735 | public class ForkJoinPool extends Abstra
1735
1736		/**
1737		* Interface for extending managed parallelism for tasks running
1738	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1739	<	* Method <code>isReleasable</code> must return true if blocking is not
1740	<	* necessary. Method <code>block</code> blocks the current thread
1741	<	* if necessary (perhaps internally invoking isReleasable before
1742	<	* actually blocking.).
1738	>	* in {@link ForkJoinPool}s.
1739	>	*
1740	>	* <p>A {@code ManagedBlocker} provides two methods.
1741	>	* Method {@code isReleasable} must return {@code true} if
1742	>	* blocking is not necessary. Method {@code block} blocks the
1743	>	* current thread if necessary (perhaps internally invoking
1744	>	* {@code isReleasable} before actually blocking.).
1745	>	*
1746		* <p>For example, here is a ManagedBlocker based on a
1747		* ReentrantLock:
1748	<	* <pre>
1749	<	*   class ManagedLocker implements ManagedBlocker {
1750	<	*     final ReentrantLock lock;
1751	<	*     boolean hasLock = false;
1752	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1753	<	*     public boolean block() {
1754	<	*        if (!hasLock)
1755	<	*           lock.lock();
1756	<	*        return true;
1757	<	*     }
1758	<	*     public boolean isReleasable() {
1759	<	*        return hasLock || (hasLock = lock.tryLock());
1711	<	*     }
1748	>	*  <pre> {@code
1749	>	* class ManagedLocker implements ManagedBlocker {
1750	>	*   final ReentrantLock lock;
1751	>	*   boolean hasLock = false;
1752	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1753	>	*   public boolean block() {
1754	>	*     if (!hasLock)
1755	>	*       lock.lock();
1756	>	*     return true;
1757	>	*   }
1758	>	*   public boolean isReleasable() {
1759	>	*     return hasLock || (hasLock = lock.tryLock());
1760		*   }
1761	<	* </pre>
1761	>	* }}</pre>
1762		*/
1763		public static interface ManagedBlocker {
1764		/**
1765		* Possibly blocks the current thread, for example waiting for
1766		* a lock or condition.
1767	<	* @return true if no additional blocking is necessary (i.e.,
1768	<	* if isReleasable would return true).
1767	>	*
1768	>	* @return {@code true} if no additional blocking is necessary
1769	>	* (i.e., if isReleasable would return true)
1770		* @throws InterruptedException if interrupted while waiting
1771	<	* (the method is not required to do so, but is allowe to).
1771	>	* (the method is not required to do so, but is allowed to)
1772		*/
1773		boolean block() throws InterruptedException;
1774
1775		/**
1776	<	* Returns true if blocking is unnecessary.
1776	>	* Returns {@code true} if blocking is unnecessary.
1777		*/
1778		boolean isReleasable();
1779		}
#	Line 1734 | Line 1783 | public class ForkJoinPool extends Abstra
1783		* is a ForkJoinWorkerThread, this method possibly arranges for a
1784		* spare thread to be activated if necessary to ensure parallelism
1785		* while the current thread is blocked.  If
1786	<	* <code>maintainParallelism</code> is true and the pool supports
1786	>	* {@code maintainParallelism} is {@code true} and the pool supports
1787		* it ({@link #getMaintainsParallelism}), this method attempts to
1788	<	* maintain the pool's nominal parallelism. Otherwise if activates
1788	>	* maintain the pool's nominal parallelism. Otherwise it activates
1789		* a thread only if necessary to avoid complete starvation. This
1790		* option may be preferable when blockages use timeouts, or are
1791		* almost always brief.
1792		*
1793		* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1794		* equivalent to
1795	<	* <pre>
1796	<	*   while (!blocker.isReleasable())
1797	<	*      if (blocker.block())
1798	<	*         return;
1799	<	* </pre>
1795	>	*  <pre> {@code
1796	>	* while (!blocker.isReleasable())
1797	>	*   if (blocker.block())
1798	>	*     return;
1799	>	* }</pre>
1800		* If the caller is a ForkJoinTask, then the pool may first
1801		* be expanded to ensure parallelism, and later adjusted.
1802		*
1803		* @param blocker the blocker
1804	<	* @param maintainParallelism if true and supported by this pool,
1805	<	* attempt to maintain the pool's nominal parallelism; otherwise
1806	<	* activate a thread only if necessary to avoid complete
1807	<	* starvation.
1808	<	* @throws InterruptedException if blocker.block did so.
1804	>	* @param maintainParallelism if {@code true} and supported by
1805	>	* this pool, attempt to maintain the pool's nominal parallelism;
1806	>	* otherwise activate a thread only if necessary to avoid
1807	>	* complete starvation.
1808	>	* @throws InterruptedException if blocker.block did so
1809		*/
1810		public static void managedBlock(ManagedBlocker blocker,
1811		boolean maintainParallelism)
1812		throws InterruptedException {
1813		Thread t = Thread.currentThread();
1814	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1815	<	((ForkJoinWorkerThread)t).pool : null);
1814	>	ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ?
1815	>	((ForkJoinWorkerThread) t).pool : null);
1816		if (!blocker.isReleasable()) {
1817		try {
1818		if (pool == null ||
#	Line 1778 | Line 1827 | public class ForkJoinPool extends Abstra
1827
1828		private static void awaitBlocker(ManagedBlocker blocker)
1829		throws InterruptedException {
1830	<	do;while (!blocker.isReleasable() && !blocker.block());
1830	>	do {} while (!blocker.isReleasable() && !blocker.block());
1831		}
1832
1833	<	// AbstractExecutorService overrides
1833	>	// AbstractExecutorService overrides.  These rely on undocumented
1834	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1835	>	// implement RunnableFuture.
1836
1837		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1838	<	return new AdaptedRunnable(runnable, value);
1838	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
1839		}
1840
1841		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1842	<	return new AdaptedCallable(callable);
1842	>	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
1843		}
1844
1845	+	// Unsafe mechanics
1846
1847	<	// Temporary Unsafe mechanics for preliminary release
1848	<	private static Unsafe getUnsafe() throws Throwable {
1849	<	try {
1850	<	return Unsafe.getUnsafe();
1851	<	} catch (SecurityException se) {
1852	<	try {
1853	<	return java.security.AccessController.doPrivileged
1854	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1855	<	public Unsafe run() throws Exception {
1856	<	return getUnsafePrivileged();
1857	<	}});
1806	<	} catch (java.security.PrivilegedActionException e) {
1807	<	throw e.getCause();
1808	<	}
1809	<	}
1810	<	}
1811	<
1812	<	private static Unsafe getUnsafePrivileged()
1813	<	throws NoSuchFieldException, IllegalAccessException {
1814	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1815	<	f.setAccessible(true);
1816	<	return (Unsafe) f.get(null);
1817	<	}
1818	<
1819	<	private static long fieldOffset(String fieldName)
1820	<	throws NoSuchFieldException {
1821	<	return _unsafe.objectFieldOffset
1822	<	(ForkJoinPool.class.getDeclaredField(fieldName));
1823	<	}
1824	<
1825	<	static final Unsafe _unsafe;
1826	<	static final long eventCountOffset;
1827	<	static final long workerCountsOffset;
1828	<	static final long runControlOffset;
1829	<	static final long syncStackOffset;
1830	<	static final long spareStackOffset;
1831	<
1832	<	static {
1833	<	try {
1834	<	_unsafe = getUnsafe();
1835	<	eventCountOffset = fieldOffset("eventCount");
1836	<	workerCountsOffset = fieldOffset("workerCounts");
1837	<	runControlOffset = fieldOffset("runControl");
1838	<	syncStackOffset = fieldOffset("syncStack");
1839	<	spareStackOffset = fieldOffset("spareStack");
1840	<	} catch (Throwable e) {
1841	<	throw new RuntimeException("Could not initialize intrinsics", e);
1842	<	}
1843	<	}
1847	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1848	>	private static final long eventCountOffset =
1849	>	objectFieldOffset("eventCount", ForkJoinPool.class);
1850	>	private static final long workerCountsOffset =
1851	>	objectFieldOffset("workerCounts", ForkJoinPool.class);
1852	>	private static final long runControlOffset =
1853	>	objectFieldOffset("runControl", ForkJoinPool.class);
1854	>	private static final long syncStackOffset =
1855	>	objectFieldOffset("syncStack",ForkJoinPool.class);
1856	>	private static final long spareStackOffset =
1857	>	objectFieldOffset("spareStack", ForkJoinPool.class);
1858
1859		private boolean casEventCount(long cmp, long val) {
1860	<	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1860	>	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
1861		}
1862		private boolean casWorkerCounts(int cmp, int val) {
1863	<	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1863	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1864		}
1865		private boolean casRunControl(int cmp, int val) {
1866	<	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1866	>	return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
1867		}
1868		private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1869	<	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1869	>	return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
1870		}
1871		private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1872	<	return _unsafe.compareAndSwapObject(this, syncStackOffset, cmp, val);
1872	>	return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1873	>	}
1874	>
1875	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1876	>	try {
1877	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1878	>	} catch (NoSuchFieldException e) {
1879	>	// Convert Exception to corresponding Error
1880	>	NoSuchFieldError error = new NoSuchFieldError(field);
1881	>	error.initCause(e);
1882	>	throw error;
1883	>	}
1884	>	}
1885	>
1886	>	/**
1887	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1888	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1889	>	* into a jdk.
1890	>	*
1891	>	* @return a sun.misc.Unsafe
1892	>	*/
1893	>	private static sun.misc.Unsafe getUnsafe() {
1894	>	try {
1895	>	return sun.misc.Unsafe.getUnsafe();
1896	>	} catch (SecurityException se) {
1897	>	try {
1898	>	return java.security.AccessController.doPrivileged
1899	>	(new java.security
1900	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1901	>	public sun.misc.Unsafe run() throws Exception {
1902	>	java.lang.reflect.Field f = sun.misc
1903	>	.Unsafe.class.getDeclaredField("theUnsafe");
1904	>	f.setAccessible(true);
1905	>	return (sun.misc.Unsafe) f.get(null);
1906	>	}});
1907	>	} catch (java.security.PrivilegedActionException e) {
1908	>	throw new RuntimeException("Could not initialize intrinsics",
1909	>	e.getCause());
1910	>	}
1911	>	}
1912		}
1913		}

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