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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 1.45 by dl, Tue Aug 4 12:41:27 2009 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.locks.*;
11	<	import java.util.concurrent.atomic.*;
12	<	import sun.misc.Unsafe;
13	<	import java.lang.reflect.*;
10	>
11	>	import java.util.ArrayList;
12	>	import java.util.Arrays;
13	>	import java.util.Collection;
14	>	import java.util.Collections;
15	>	import java.util.List;
16	>	import java.util.concurrent.locks.Condition;
17	>	import java.util.concurrent.locks.LockSupport;
18	>	import java.util.concurrent.locks.ReentrantLock;
19	>	import java.util.concurrent.atomic.AtomicInteger;
20	>	import java.util.concurrent.atomic.AtomicLong;
21
22		/**
23	<	* An {@link ExecutorService} for running {@link ForkJoinTask}s.  A
24	<	* ForkJoinPool provides the entry point for submissions from
25	<	* non-ForkJoinTasks, as well as management and monitoring operations.
26	<	* Normally a single ForkJoinPool is used for a large number of
20	<	* submitted tasks. Otherwise, use would not usually outweigh the
21	<	* construction and bookkeeping overhead of creating a large set of
22	<	* threads.
23	>	* An {@link ExecutorService} for running {@link ForkJoinTask}s.
24	>	* A {@code ForkJoinPool} provides the entry point for submissions
25	>	* from non-{@code ForkJoinTask}s, as well as management and
26	>	* monitoring operations.
27		*
28	<	* <p>ForkJoinPools differ from other kinds of Executors mainly in
29	<	* that they provide <em>work-stealing</em>: all threads in the pool
30	<	* attempt to find and execute subtasks created by other active tasks
31	<	* (eventually blocking if none exist). This makes them efficient when
32	<	* most tasks spawn other subtasks (as do most ForkJoinTasks), as well
33	<	* as the mixed execution of some plain Runnable- or Callable- based
34	<	* activities along with ForkJoinTasks. When setting
35	<	* <tt>setAsyncMode</tt>, a ForkJoinPools may also be appropriate for
36	<	* use with fine-grained tasks that are never joined. Otherwise, other
37	<	* ExecutorService implementations are typically more appropriate
38	<	* choices.
28	>	* <p>A {@code ForkJoinPool} differs from other kinds of {@link
29	>	* ExecutorService} mainly by virtue of employing
30	>	* <em>work-stealing</em>: all threads in the pool attempt to find and
31	>	* execute subtasks created by other active tasks (eventually blocking
32	>	* waiting for work if none exist). This enables efficient processing
33	>	* when most tasks spawn other subtasks (as do most {@code
34	>	* ForkJoinTask}s). A {@code ForkJoinPool} may also be used for mixed
35	>	* execution of some plain {@code Runnable}- or {@code Callable}-
36	>	* based activities along with {@code ForkJoinTask}s. When setting
37	>	* {@linkplain #setAsyncMode async mode}, a {@code ForkJoinPool} may
38	>	* also be appropriate for use with fine-grained tasks of any form
39	>	* that are never joined. Otherwise, other {@code ExecutorService}
40	>	* implementations are typically more appropriate choices.
41		*
42	<	* <p>A ForkJoinPool may be constructed with a given parallelism level
43	<	* (target pool size), which it attempts to maintain by dynamically
44	<	* adding, suspending, or resuming threads, even if some tasks are
45	<	* waiting to join others. However, no such adjustments are performed
46	<	* in the face of blocked IO or other unmanaged synchronization. The
47	<	* nested <code>ManagedBlocker</code> interface enables extension of
48	<	* the kinds of synchronization accommodated.  The target parallelism
49	<	* level may also be changed dynamically (<code>setParallelism</code>)
50	<	* and thread construction can be limited using methods
51	<	* <code>setMaximumPoolSize</code> and/or
52	<	* <code>setMaintainsParallelism</code>.
42	>	* <p>A {@code ForkJoinPool} is constructed with a given target
43	>	* parallelism level; by default, equal to the number of available
44	>	* processors. Unless configured otherwise via {@link
45	>	* #setMaintainsParallelism}, the pool attempts to maintain this
46	>	* number of active (or available) threads by dynamically adding,
47	>	* suspending, or resuming internal worker threads, even if some tasks
48	>	* are stalled waiting to join others. However, no such adjustments
49	>	* are performed in the face of blocked IO or other unmanaged
50	>	* synchronization. The nested {@link ManagedBlocker} interface
51	>	* enables extension of the kinds of synchronization accommodated.
52	>	* The target parallelism level may also be changed dynamically
53	>	* ({@link #setParallelism}). The total number of threads may be
54	>	* limited using method {@link #setMaximumPoolSize}, in which case it
55	>	* may become possible for the activities of a pool to stall due to
56	>	* the lack of available threads to process new tasks.
57		*
58		* <p>In addition to execution and lifecycle control methods, this
59		* class provides status check methods (for example
60	<	* <code>getStealCount</code>) that are intended to aid in developing,
60	>	* {@link #getStealCount}) that are intended to aid in developing,
61		* tuning, and monitoring fork/join applications. Also, method
62	<	* <code>toString</code> returns indications of pool state in a
62	>	* {@link #toString} returns indications of pool state in a
63		* convenient form for informal monitoring.
64		*
65	+	* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
66	+	* used for all parallel task execution in a program or subsystem.
67	+	* Otherwise, use would not usually outweigh the construction and
68	+	* bookkeeping overhead of creating a large set of threads. For
69	+	* example, a common pool could be used for the {@code SortTasks}
70	+	* illustrated in {@link RecursiveAction}. Because {@code
71	+	* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
72	+	* daemon} mode, there is typically no need to explicitly {@link
73	+	* #shutdown} such a pool upon program exit.
74	+	*
75	+	* <pre>
76	+	* static final ForkJoinPool mainPool = new ForkJoinPool();
77	+	* ...
78	+	* public void sort(long[] array) {
79	+	*   mainPool.invoke(new SortTask(array, 0, array.length));
80	+	* }
81	+	* </pre>
82	+	*
83		* <p><b>Implementation notes</b>: This implementation restricts the
84		* maximum number of running threads to 32767. Attempts to create
85		* pools with greater than the maximum result in
86	<	* IllegalArgumentExceptions.
86	>	* {@code IllegalArgumentException}.
87	>	*
88	>	* @since 1.7
89	>	* @author Doug Lea
90		*/
91		public class ForkJoinPool extends AbstractExecutorService {
92
#	Line 71 | Line 102 | public class ForkJoinPool extends Abstra
102		private static final int MAX_THREADS =  0x7FFF;
103
104		/**
105	<	* Factory for creating new ForkJoinWorkerThreads.  A
106	<	* ForkJoinWorkerThreadFactory must be defined and used for
107	<	* ForkJoinWorkerThread subclasses that extend base functionality
108	<	* or initialize threads with different contexts.
105	>	* Factory for creating new {@link ForkJoinWorkerThread}s.
106	>	* A {@code ForkJoinWorkerThreadFactory} must be defined and used
107	>	* for {@code ForkJoinWorkerThread} subclasses that extend base
108	>	* functionality or initialize threads with different contexts.
109		*/
110		public static interface ForkJoinWorkerThreadFactory {
111		/**
112		* Returns a new worker thread operating in the given pool.
113		*
114		* @param pool the pool this thread works in
115	<	* @throws NullPointerException if pool is null;
115	>	* @throws NullPointerException if pool is null
116		*/
117		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
118		}
119
120		/**
121	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
121	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
122		* new ForkJoinWorkerThread.
123		*/
124		static class  DefaultForkJoinWorkerThreadFactory
#	Line 153 | Line 184 | public class ForkJoinPool extends Abstra
184
185		/**
186		* The uncaught exception handler used when any worker
187	<	* abrupty terminates
187	>	* abruptly terminates
188		*/
189		private Thread.UncaughtExceptionHandler ueh;
190
#	Line 181 | Line 212 | public class ForkJoinPool extends Abstra
212		private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
213
214		/**
215	<	* Head of Treiber stack for barrier sync. See below for explanation
215	>	* Head of Treiber stack for barrier sync. See below for explanation.
216		*/
217		private volatile WaitQueueNode syncStack;
218
#	Line 217 | Line 248 | public class ForkJoinPool extends Abstra
248		* making decisions about creating and suspending spare
249		* threads. Updated only by CAS.  Note: CASes in
250		* updateRunningCount and preJoin assume that running active count
251	<	* is in low word, so need to be modified if this changes
251	>	* is in low word, so need to be modified if this changes.
252		*/
253		private volatile int workerCounts;
254
#	Line 226 | Line 257 | public class ForkJoinPool extends Abstra
257		private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
258
259		/**
260	<	* Add delta (which may be negative) to running count.  This must
260	>	* Adds delta (which may be negative) to running count.  This must
261		* be called before (with negative arg) and after (with positive)
262	<	* any managed synchronization (i.e., mainly, joins)
262	>	* any managed synchronization (i.e., mainly, joins).
263	>	*
264		* @param delta the number to add
265		*/
266		final void updateRunningCount(int delta) {
267		int s;
268	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
268	>	do {} while (!casWorkerCounts(s = workerCounts, s + delta));
269		}
270
271		/**
272	<	* Add delta (which may be negative) to both total and running
272	>	* Adds delta (which may be negative) to both total and running
273		* count.  This must be called upon creation and termination of
274		* worker threads.
275	+	*
276		* @param delta the number to add
277		*/
278		private void updateWorkerCount(int delta) {
279		int d = delta + (delta << 16); // add to both lo and hi parts
280		int s;
281	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
281	>	do {} while (!casWorkerCounts(s = workerCounts, s + d));
282		}
283
284		/**
#	Line 271 | Line 304 | public class ForkJoinPool extends Abstra
304		private static int runControlFor(int r, int a)   { return (r << 16) + a; }
305
306		/**
307	<	* Try incrementing active count; fail on contention. Called by
308	<	* workers before/during executing tasks.
309	<	* @return true on success;
307	>	* Tries incrementing active count; fails on contention.
308	>	* Called by workers before/during executing tasks.
309	>	*
310	>	* @return true on success
311		*/
312		final boolean tryIncrementActiveCount() {
313		int c = runControl;
#	Line 281 | Line 315 | public class ForkJoinPool extends Abstra
315		}
316
317		/**
318	<	* Try decrementing active count; fail on contention.
319	<	* Possibly trigger termination on success
318	>	* Tries decrementing active count; fails on contention.
319	>	* Possibly triggers termination on success.
320		* Called by workers when they can't find tasks.
321	+	*
322		* @return true on success
323		*/
324		final boolean tryDecrementActiveCount() {
#	Line 297 | Line 332 | public class ForkJoinPool extends Abstra
332		}
333
334		/**
335	<	* Return true if argument represents zero active count and
336	<	* nonzero runstate, which is the triggering condition for
335	>	* Returns {@code true} if argument represents zero active count
336	>	* and nonzero runstate, which is the triggering condition for
337		* terminating on shutdown.
338		*/
339		private static boolean canTerminateOnShutdown(int c) {
340	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
340	>	// i.e. least bit is nonzero runState bit
341	>	return ((c & -c) >>> 16) != 0;
342		}
343
344		/**
#	Line 327 | Line 363 | public class ForkJoinPool extends Abstra
363		// Constructors
364
365		/**
366	<	* Creates a ForkJoinPool with a pool size equal to the number of
367	<	* processors available on the system and using the default
368	<	* ForkJoinWorkerThreadFactory,
366	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
367	>	* java.lang.Runtime#availableProcessors}, and using the {@linkplain
368	>	* #defaultForkJoinWorkerThreadFactory default thread factory}.
369	>	*
370		* @throws SecurityException if a security manager exists and
371		*         the caller is not permitted to modify threads
372		*         because it does not hold {@link
373	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
373	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
374		*/
375		public ForkJoinPool() {
376		this(Runtime.getRuntime().availableProcessors(),
#	Line 341 | Line 378 | public class ForkJoinPool extends Abstra
378		}
379
380		/**
381	<	* Creates a ForkJoinPool with the indicated parellelism level
382	<	* threads, and using the default ForkJoinWorkerThreadFactory,
383	<	* @param parallelism the number of worker threads
381	>	* Creates a {@code ForkJoinPool} with the indicated parallelism
382	>	* level and using the {@linkplain
383	>	* #defaultForkJoinWorkerThreadFactory default thread factory}.
384	>	*
385	>	* @param parallelism the parallelism level
386		* @throws IllegalArgumentException if parallelism less than or
387		* equal to zero
388		* @throws SecurityException if a security manager exists and
389		*         the caller is not permitted to modify threads
390		*         because it does not hold {@link
391	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
391	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
392		*/
393		public ForkJoinPool(int parallelism) {
394		this(parallelism, defaultForkJoinWorkerThreadFactory);
395		}
396
397		/**
398	<	* Creates a ForkJoinPool with parallelism equal to the number of
399	<	* processors available on the system and using the given
400	<	* ForkJoinWorkerThreadFactory,
398	>	* Creates a {@code ForkJoinPool} with parallelism equal to {@link
399	>	* java.lang.Runtime#availableProcessors}, and using the given
400	>	* thread factory.
401	>	*
402		* @param factory the factory for creating new threads
403		* @throws NullPointerException if factory is null
404		* @throws SecurityException if a security manager exists and
405		*         the caller is not permitted to modify threads
406		*         because it does not hold {@link
407	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
407	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
408		*/
409		public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
410		this(Runtime.getRuntime().availableProcessors(), factory);
411		}
412
413		/**
414	<	* Creates a ForkJoinPool with the given parallelism and factory.
414	>	* Creates a {@code ForkJoinPool} with the given parallelism and
415	>	* thread factory.
416		*
417	<	* @param parallelism the targeted number of worker threads
417	>	* @param parallelism the parallelism level
418		* @param factory the factory for creating new threads
419		* @throws IllegalArgumentException if parallelism less than or
420	<	* equal to zero, or greater than implementation limit.
420	>	* equal to zero, or greater than implementation limit
421		* @throws NullPointerException if factory is null
422		* @throws SecurityException if a security manager exists and
423		*         the caller is not permitted to modify threads
424		*         because it does not hold {@link
425	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
425	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
426		*/
427		public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
428		if (parallelism <= 0 || parallelism > MAX_THREADS)
#	Line 402 | Line 443 | public class ForkJoinPool extends Abstra
443		}
444
445		/**
446	<	* Create new worker using factory.
446	>	* Creates a new worker thread using factory.
447	>	*
448		* @param index the index to assign worker
449	<	* @return new worker, or null of factory failed
449	>	* @return new worker, or null if factory failed
450		*/
451		private ForkJoinWorkerThread createWorker(int index) {
452		Thread.UncaughtExceptionHandler h = ueh;
#	Line 421 | Line 463 | public class ForkJoinPool extends Abstra
463		}
464
465		/**
466	<	* Return a good size for worker array given pool size.
466	>	* Returns a good size for worker array given pool size.
467		* Currently requires size to be a power of two.
468		*/
469	<	private static int arraySizeFor(int ps) {
470	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
469	>	private static int arraySizeFor(int poolSize) {
470	>	if (poolSize <= 1)
471	>	return 1;
472	>	// See Hackers Delight, sec 3.2
473	>	int c = poolSize >= MAX_THREADS ? MAX_THREADS : (poolSize - 1);
474	>	c |= c >>>  1;
475	>	c |= c >>>  2;
476	>	c |= c >>>  4;
477	>	c |= c >>>  8;
478	>	c |= c >>> 16;
479	>	return c + 1;
480		}
481
482		/**
483	<	* Create or resize array if necessary to hold newLength.
484	<	* Call only under exclusion
483	>	* Creates or resizes array if necessary to hold newLength.
484	>	* Call only under exclusion.
485	>	*
486		* @return the array
487		*/
488		private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
#	Line 444 | Line 496 | public class ForkJoinPool extends Abstra
496		}
497
498		/**
499	<	* Try to shrink workers into smaller array after one or more terminate
499	>	* Tries to shrink workers into smaller array after one or more terminate.
500		*/
501		private void tryShrinkWorkerArray() {
502		ForkJoinWorkerThread[] ws = workers;
#	Line 460 | Line 512 | public class ForkJoinPool extends Abstra
512		}
513
514		/**
515	<	* Initialize workers if necessary
515	>	* Initializes workers if necessary.
516		*/
517		final void ensureWorkerInitialization() {
518		ForkJoinWorkerThread[] ws = workers;
#	Line 527 | Line 579 | public class ForkJoinPool extends Abstra
579		* Common code for execute, invoke and submit
580		*/
581		private <T> void doSubmit(ForkJoinTask<T> task) {
582	+	if (task == null)
583	+	throw new NullPointerException();
584		if (isShutdown())
585		throw new RejectedExecutionException();
586		if (workers == null)
#	Line 536 | Line 590 | public class ForkJoinPool extends Abstra
590		}
591
592		/**
593	<	* Performs the given task; returning its result upon completion
593	>	* Performs the given task, returning its result upon completion.
594	>	*
595		* @param task the task
596		* @return the task's result
597		* @throws NullPointerException if task is null
#	Line 549 | Line 604 | public class ForkJoinPool extends Abstra
604
605		/**
606		* Arranges for (asynchronous) execution of the given task.
607	+	*
608		* @param task the task
609		* @throws NullPointerException if task is null
610		* @throws RejectedExecutionException if pool is shut down
611		*/
612	<	public <T> void execute(ForkJoinTask<T> task) {
612	>	public void execute(ForkJoinTask<?> task) {
613		doSubmit(task);
614		}
615
616		// AbstractExecutorService methods
617
618		public void execute(Runnable task) {
619	<	doSubmit(new AdaptedRunnable<Void>(task, null));
619	>	ForkJoinTask<?> job;
620	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
621	>	job = (ForkJoinTask<?>) task;
622	>	else
623	>	job = ForkJoinTask.adapt(task, null);
624	>	doSubmit(job);
625		}
626
627		public <T> ForkJoinTask<T> submit(Callable<T> task) {
628	<	ForkJoinTask<T> job = new AdaptedCallable<T>(task);
628	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task);
629		doSubmit(job);
630		return job;
631		}
632
633		public <T> ForkJoinTask<T> submit(Runnable task, T result) {
634	<	ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result);
634	>	ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
635		doSubmit(job);
636		return job;
637		}
638
639		public ForkJoinTask<?> submit(Runnable task) {
640	<	ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null);
640	>	ForkJoinTask<?> job;
641	>	if (task instanceof ForkJoinTask<?>) // avoid re-wrap
642	>	job = (ForkJoinTask<?>) task;
643	>	else
644	>	job = ForkJoinTask.adapt(task, null);
645		doSubmit(job);
646		return job;
647		}
648
649		/**
650	<	* Adaptor for Runnables. This implements RunnableFuture
651	<	* to be compliant with AbstractExecutorService constraints
650	>	* Submits a ForkJoinTask for execution.
651	>	*
652	>	* @param task the task to submit
653	>	* @return the task
654	>	* @throws RejectedExecutionException if the task cannot be
655	>	*         scheduled for execution
656	>	* @throws NullPointerException if the task is null
657		*/
658	<	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
659	<	implements RunnableFuture<T> {
660	<	final Runnable runnable;
591	<	final T resultOnCompletion;
592	<	T result;
593	<	AdaptedRunnable(Runnable runnable, T result) {
594	<	if (runnable == null) throw new NullPointerException();
595	<	this.runnable = runnable;
596	<	this.resultOnCompletion = result;
597	<	}
598	<	public T getRawResult() { return result; }
599	<	public void setRawResult(T v) { result = v; }
600	<	public boolean exec() {
601	<	runnable.run();
602	<	result = resultOnCompletion;
603	<	return true;
604	<	}
605	<	public void run() { invoke(); }
658	>	public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
659	>	doSubmit(task);
660	>	return task;
661		}
662
608	–	/**
609	–	* Adaptor for Callables
610	–	*/
611	–	static final class AdaptedCallable<T> extends ForkJoinTask<T>
612	–	implements RunnableFuture<T> {
613	–	final Callable<T> callable;
614	–	T result;
615	–	AdaptedCallable(Callable<T> callable) {
616	–	if (callable == null) throw new NullPointerException();
617	–	this.callable = callable;
618	–	}
619	–	public T getRawResult() { return result; }
620	–	public void setRawResult(T v) { result = v; }
621	–	public boolean exec() {
622	–	try {
623	–	result = callable.call();
624	–	return true;
625	–	} catch (Error err) {
626	–	throw err;
627	–	} catch (RuntimeException rex) {
628	–	throw rex;
629	–	} catch (Exception ex) {
630	–	throw new RuntimeException(ex);
631	–	}
632	–	}
633	–	public void run() { invoke(); }
634	–	}
663
664		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
665	<	ArrayList<ForkJoinTask<T>> ts =
665	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
666		new ArrayList<ForkJoinTask<T>>(tasks.size());
667	<	for (Callable<T> c : tasks)
668	<	ts.add(new AdaptedCallable<T>(c));
669	<	invoke(new InvokeAll<T>(ts));
670	<	return (List<Future<T>>)(List)ts;
667	>	for (Callable<T> task : tasks)
668	>	forkJoinTasks.add(ForkJoinTask.adapt(task));
669	>	invoke(new InvokeAll<T>(forkJoinTasks));
670	>
671	>	@SuppressWarnings({"unchecked", "rawtypes"})
672	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
673	>	return futures;
674		}
675
676		static final class InvokeAll<T> extends RecursiveAction {
677		final ArrayList<ForkJoinTask<T>> tasks;
678		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
679		public void compute() {
680	<	try { invokeAll(tasks); } catch(Exception ignore) {}
680	>	try { invokeAll(tasks); }
681	>	catch (Exception ignore) {}
682		}
683	+	private static final long serialVersionUID = -7914297376763021607L;
684		}
685
686		// Configuration and status settings and queries
687
688		/**
689	<	* Returns the factory used for constructing new workers
689	>	* Returns the factory used for constructing new workers.
690		*
691		* @return the factory used for constructing new workers
692		*/
#	Line 664 | Line 697 | public class ForkJoinPool extends Abstra
697		/**
698		* Returns the handler for internal worker threads that terminate
699		* due to unrecoverable errors encountered while executing tasks.
700	<	* @return the handler, or null if none
700	>	*
701	>	* @return the handler, or {@code null} if none
702		*/
703		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
704		Thread.UncaughtExceptionHandler h;
#	Line 685 | Line 719 | public class ForkJoinPool extends Abstra
719		* as handler.
720		*
721		* @param h the new handler
722	<	* @return the old handler, or null if none
722	>	* @return the old handler, or {@code null} if none
723		* @throws SecurityException if a security manager exists and
724		*         the caller is not permitted to modify threads
725		*         because it does not hold {@link
726	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
726	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
727		*/
728		public Thread.UncaughtExceptionHandler
729		setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
#	Line 716 | Line 750 | public class ForkJoinPool extends Abstra
750
751
752		/**
753	<	* Sets the target paralleism level of this pool.
753	>	* Sets the target parallelism level of this pool.
754	>	*
755		* @param parallelism the target parallelism
756		* @throws IllegalArgumentException if parallelism less than or
757	<	* equal to zero or greater than maximum size bounds.
757	>	* equal to zero or greater than maximum size bounds
758		* @throws SecurityException if a security manager exists and
759		*         the caller is not permitted to modify threads
760		*         because it does not hold {@link
761	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
761	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
762		*/
763		public void setParallelism(int parallelism) {
764		checkPermission();
#	Line 732 | Line 767 | public class ForkJoinPool extends Abstra
767		final ReentrantLock lock = this.workerLock;
768		lock.lock();
769		try {
770	<	if (!isTerminating()) {
770	>	if (isProcessingTasks()) {
771		int p = this.parallelism;
772		this.parallelism = parallelism;
773		if (parallelism > p)
#	Line 747 | Line 782 | public class ForkJoinPool extends Abstra
782		}
783
784		/**
785	<	* Returns the targeted number of worker threads in this pool.
785	>	* Returns the targeted parallelism level of this pool.
786		*
787	<	* @return the targeted number of worker threads in this pool
787	>	* @return the targeted parallelism level of this pool
788		*/
789		public int getParallelism() {
790		return parallelism;
#	Line 758 | Line 793 | public class ForkJoinPool extends Abstra
793		/**
794		* Returns the number of worker threads that have started but not
795		* yet terminated.  This result returned by this method may differ
796	<	* from <code>getParallelism</code> when threads are created to
796	>	* from {@link #getParallelism} when threads are created to
797		* maintain parallelism when others are cooperatively blocked.
798		*
799		* @return the number of worker threads
#	Line 769 | Line 804 | public class ForkJoinPool extends Abstra
804
805		/**
806		* Returns the maximum number of threads allowed to exist in the
807	<	* pool, even if there are insufficient unblocked running threads.
807	>	* pool. Unless set using {@link #setMaximumPoolSize}, the
808	>	* maximum is an implementation-defined value designed only to
809	>	* prevent runaway growth.
810	>	*
811		* @return the maximum
812		*/
813		public int getMaximumPoolSize() {
#	Line 778 | Line 816 | public class ForkJoinPool extends Abstra
816
817		/**
818		* Sets the maximum number of threads allowed to exist in the
819	<	* pool, even if there are insufficient unblocked running threads.
820	<	* Setting this value has no effect on current pool size. It
821	<	* controls construction of new threads.
822	<	* @throws IllegalArgumentException if negative or greater then
823	<	* internal implementation limit.
819	>	* pool. The given value should normally be greater than or equal
820	>	* to the {@link #getParallelism parallelism} level. Setting this
821	>	* value has no effect on current pool size. It controls
822	>	* construction of new threads.
823	>	*
824	>	* @throws IllegalArgumentException if negative or greater than
825	>	* internal implementation limit
826		*/
827		public void setMaximumPoolSize(int newMax) {
828		if (newMax < 0 || newMax > MAX_THREADS)
#	Line 792 | Line 832 | public class ForkJoinPool extends Abstra
832
833
834		/**
835	<	* Returns true if this pool dynamically maintains its target
836	<	* parallelism level. If false, new threads are added only to
837	<	* avoid possible starvation.
838	<	* This setting is by default true;
839	<	* @return true if maintains parallelism
835	>	* Returns {@code true} if this pool dynamically maintains its
836	>	* target parallelism level. If false, new threads are added only
837	>	* to avoid possible starvation.  This setting is by default true.
838	>	*
839	>	* @return {@code true} if maintains parallelism
840		*/
841		public boolean getMaintainsParallelism() {
842		return maintainsParallelism;
#	Line 806 | Line 846 | public class ForkJoinPool extends Abstra
846		* Sets whether this pool dynamically maintains its target
847		* parallelism level. If false, new threads are added only to
848		* avoid possible starvation.
849	<	* @param enable true to maintains parallelism
849	>	*
850	>	* @param enable {@code true} to maintain parallelism
851		*/
852		public void setMaintainsParallelism(boolean enable) {
853		maintainsParallelism = enable;
#	Line 817 | Line 858 | public class ForkJoinPool extends Abstra
858		* tasks that are never joined. This mode may be more appropriate
859		* than default locally stack-based mode in applications in which
860		* worker threads only process asynchronous tasks.  This method is
861	<	* designed to be invoked only when pool is quiescent, and
861	>	* designed to be invoked only when the pool is quiescent, and
862		* typically only before any tasks are submitted. The effects of
863	<	* invocations at ather times may be unpredictable.
863	>	* invocations at other times may be unpredictable.
864		*
865	<	* @param async if true, use locally FIFO scheduling
866	<	* @return the previous mode.
865	>	* @param async if {@code true}, use locally FIFO scheduling
866	>	* @return the previous mode
867	>	* @see #getAsyncMode
868		*/
869		public boolean setAsyncMode(boolean async) {
870		boolean oldMode = locallyFifo;
#	Line 839 | Line 881 | public class ForkJoinPool extends Abstra
881		}
882
883		/**
884	<	* Returns true if this pool uses local first-in-first-out
885	<	* scheduling mode for forked tasks that are never joined.
884	>	* Returns {@code true} if this pool uses local first-in-first-out
885	>	* scheduling mode for forked tasks that are never joined.
886		*
887	<	* @return true if this pool uses async mode.
887	>	* @return {@code true} if this pool uses async mode
888	>	* @see #setAsyncMode
889		*/
890		public boolean getAsyncMode() {
891		return locallyFifo;
#	Line 863 | Line 906 | public class ForkJoinPool extends Abstra
906		* Returns an estimate of the number of threads that are currently
907		* stealing or executing tasks. This method may overestimate the
908		* number of active threads.
909	<	* @return the number of active threads.
909	>	*
910	>	* @return the number of active threads
911		*/
912		public int getActiveThreadCount() {
913		return activeCountOf(runControl);
#	Line 873 | Line 917 | public class ForkJoinPool extends Abstra
917		* Returns an estimate of the number of threads that are currently
918		* idle waiting for tasks. This method may underestimate the
919		* number of idle threads.
920	<	* @return the number of idle threads.
920	>	*
921	>	* @return the number of idle threads
922		*/
923		final int getIdleThreadCount() {
924		int c = runningCountOf(workerCounts) - activeCountOf(runControl);
925	<	return (c <= 0)? 0 : c;
925	>	return (c <= 0) ? 0 : c;
926		}
927
928		/**
929	<	* Returns true if all worker threads are currently idle. An idle
930	<	* worker is one that cannot obtain a task to execute because none
931	<	* are available to steal from other threads, and there are no
932	<	* pending submissions to the pool. This method is conservative:
933	<	* It might not return true immediately upon idleness of all
934	<	* threads, but will eventually become true if threads remain
935	<	* inactive.
936	<	* @return true if all threads are currently idle
929	>	* Returns {@code true} if all worker threads are currently idle.
930	>	* An idle worker is one that cannot obtain a task to execute
931	>	* because none are available to steal from other threads, and
932	>	* there are no pending submissions to the pool. This method is
933	>	* conservative; it might not return {@code true} immediately upon
934	>	* idleness of all threads, but will eventually become true if
935	>	* threads remain inactive.
936	>	*
937	>	* @return {@code true} if all threads are currently idle
938		*/
939		public boolean isQuiescent() {
940		return activeCountOf(runControl) == 0;
#	Line 899 | Line 945 | public class ForkJoinPool extends Abstra
945		* one thread's work queue by another. The reported value
946		* underestimates the actual total number of steals when the pool
947		* is not quiescent. This value may be useful for monitoring and
948	<	* tuning fork/join programs: In general, steal counts should be
948	>	* tuning fork/join programs: in general, steal counts should be
949		* high enough to keep threads busy, but low enough to avoid
950		* overhead and contention across threads.
951	<	* @return the number of steals.
951	>	*
952	>	* @return the number of steals
953		*/
954		public long getStealCount() {
955		return stealCount.get();
956		}
957
958		/**
959	<	* Accumulate steal count from a worker. Call only
960	<	* when worker known to be idle.
959	>	* Accumulates steal count from a worker.
960	>	* Call only when worker known to be idle.
961		*/
962		private void updateStealCount(ForkJoinWorkerThread w) {
963		int sc = w.getAndClearStealCount();
#	Line 925 | Line 972 | public class ForkJoinPool extends Abstra
972		* an approximation, obtained by iterating across all threads in
973		* the pool. This method may be useful for tuning task
974		* granularities.
975	<	* @return the number of queued tasks.
975	>	*
976	>	* @return the number of queued tasks
977		*/
978		public long getQueuedTaskCount() {
979		long count = 0;
#	Line 941 | Line 989 | public class ForkJoinPool extends Abstra
989		}
990
991		/**
992	<	* Returns an estimate of the number tasks submitted to this pool
993	<	* that have not yet begun executing. This method takes time
992	>	* Returns an estimate of the number of tasks submitted to this
993	>	* pool that have not yet begun executing.  This method takes time
994		* proportional to the number of submissions.
995	<	* @return the number of queued submissions.
995	>	*
996	>	* @return the number of queued submissions
997		*/
998		public int getQueuedSubmissionCount() {
999		return submissionQueue.size();
1000		}
1001
1002		/**
1003	<	* Returns true if there are any tasks submitted to this pool
1004	<	* that have not yet begun executing.
1005	<	* @return <code>true</code> if there are any queued submissions.
1003	>	* Returns {@code true} if there are any tasks submitted to this
1004	>	* pool that have not yet begun executing.
1005	>	*
1006	>	* @return {@code true} if there are any queued submissions
1007		*/
1008		public boolean hasQueuedSubmissions() {
1009		return !submissionQueue.isEmpty();
#	Line 963 | Line 1013 | public class ForkJoinPool extends Abstra
1013		* Removes and returns the next unexecuted submission if one is
1014		* available.  This method may be useful in extensions to this
1015		* class that re-assign work in systems with multiple pools.
1016	<	* @return the next submission, or null if none
1016	>	*
1017	>	* @return the next submission, or {@code null} if none
1018		*/
1019		protected ForkJoinTask<?> pollSubmission() {
1020		return submissionQueue.poll();
#	Line 973 | Line 1024 | public class ForkJoinPool extends Abstra
1024		* Removes all available unexecuted submitted and forked tasks
1025		* from scheduling queues and adds them to the given collection,
1026		* without altering their execution status. These may include
1027	<	* artifically generated or wrapped tasks. This method id designed
1028	<	* to be invoked only when the pool is known to be
1027	>	* artificially generated or wrapped tasks. This method is
1028	>	* designed to be invoked only when the pool is known to be
1029		* quiescent. Invocations at other times may not remove all
1030		* tasks. A failure encountered while attempting to add elements
1031	<	* to collection <tt>c</tt> may result in elements being in
1031	>	* to collection {@code c} may result in elements being in
1032		* neither, either or both collections when the associated
1033		* exception is thrown.  The behavior of this operation is
1034		* undefined if the specified collection is modified while the
1035		* operation is in progress.
1036	+	*
1037		* @param c the collection to transfer elements into
1038		* @return the number of elements transferred
1039		*/
1040	<	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
1040	>	protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
1041		int n = submissionQueue.drainTo(c);
1042		ForkJoinWorkerThread[] ws = workers;
1043		if (ws != null) {
#	Line 1042 | Line 1094 | public class ForkJoinPool extends Abstra
1094		* Invocation has no additional effect if already shut down.
1095		* Tasks that are in the process of being submitted concurrently
1096		* during the course of this method may or may not be rejected.
1097	+	*
1098		* @throws SecurityException if a security manager exists and
1099		*         the caller is not permitted to modify threads
1100		*         because it does not hold {@link
1101	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1101	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1102		*/
1103		public void shutdown() {
1104		checkPermission();
1105		transitionRunStateTo(SHUTDOWN);
1106	<	if (canTerminateOnShutdown(runControl))
1106	>	if (canTerminateOnShutdown(runControl)) {
1107	>	if (workers == null) { // shutting down before workers created
1108	>	final ReentrantLock lock = this.workerLock;
1109	>	lock.lock();
1110	>	try {
1111	>	if (workers == null) {
1112	>	terminate();
1113	>	transitionRunStateTo(TERMINATED);
1114	>	termination.signalAll();
1115	>	}
1116	>	} finally {
1117	>	lock.unlock();
1118	>	}
1119	>	}
1120		terminateOnShutdown();
1121	+	}
1122		}
1123
1124		/**
1125	<	* Attempts to stop all actively executing tasks, and cancels all
1126	<	* waiting tasks.  Tasks that are in the process of being
1127	<	* submitted or executed concurrently during the course of this
1128	<	* method may or may not be rejected. Unlike some other executors,
1129	<	* this method cancels rather than collects non-executed tasks
1130	<	* upon termination, so always returns an empty list. However, you
1131	<	* can use method <code>drainTasksTo</code> before invoking this
1132	<	* method to transfer unexecuted tasks to another collection.
1125	>	* Attempts to cancel and/or stop all tasks, and reject all
1126	>	* subsequently submitted tasks.  Tasks that are in the process of
1127	>	* being submitted or executed concurrently during the course of
1128	>	* this method may or may not be rejected. This method cancels
1129	>	* both existing and unexecuted tasks, in order to permit
1130	>	* termination in the presence of task dependencies. So the method
1131	>	* always returns an empty list (unlike the case for some other
1132	>	* Executors).
1133	>	*
1134		* @return an empty list
1135		* @throws SecurityException if a security manager exists and
1136		*         the caller is not permitted to modify threads
1137		*         because it does not hold {@link
1138	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1138	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1139		*/
1140		public List<Runnable> shutdownNow() {
1141		checkPermission();
#	Line 1076 | Line 1144 | public class ForkJoinPool extends Abstra
1144		}
1145
1146		/**
1147	<	* Returns <code>true</code> if all tasks have completed following shut down.
1147	>	* Returns {@code true} if all tasks have completed following shut down.
1148		*
1149	<	* @return <code>true</code> if all tasks have completed following shut down
1149	>	* @return {@code true} if all tasks have completed following shut down
1150		*/
1151		public boolean isTerminated() {
1152		return runStateOf(runControl) == TERMINATED;
1153		}
1154
1155		/**
1156	<	* Returns <code>true</code> if the process of termination has
1157	<	* commenced but possibly not yet completed.
1156	>	* Returns {@code true} if the process of termination has
1157	>	* commenced but not yet completed.  This method may be useful for
1158	>	* debugging. A return of {@code true} reported a sufficient
1159	>	* period after shutdown may indicate that submitted tasks have
1160	>	* ignored or suppressed interruption, causing this executor not
1161	>	* to properly terminate.
1162		*
1163	<	* @return <code>true</code> if terminating
1163	>	* @return {@code true} if terminating but not yet terminated
1164		*/
1165		public boolean isTerminating() {
1166	<	return runStateOf(runControl) >= TERMINATING;
1166	>	return runStateOf(runControl) == TERMINATING;
1167		}
1168
1169		/**
1170	<	* Returns <code>true</code> if this pool has been shut down.
1170	>	* Returns {@code true} if this pool has been shut down.
1171		*
1172	<	* @return <code>true</code> if this pool has been shut down
1172	>	* @return {@code true} if this pool has been shut down
1173		*/
1174		public boolean isShutdown() {
1175		return runStateOf(runControl) >= SHUTDOWN;
1176		}
1177
1178		/**
1179	+	* Returns true if pool is not terminating or terminated.
1180	+	* Used internally to suppress execution when terminating.
1181	+	*/
1182	+	final boolean isProcessingTasks() {
1183	+	return runStateOf(runControl) < TERMINATING;
1184	+	}
1185	+
1186	+	/**
1187		* Blocks until all tasks have completed execution after a shutdown
1188		* request, or the timeout occurs, or the current thread is
1189		* interrupted, whichever happens first.
1190		*
1191		* @param timeout the maximum time to wait
1192		* @param unit the time unit of the timeout argument
1193	<	* @return <code>true</code> if this executor terminated and
1194	<	*         <code>false</code> if the timeout elapsed before termination
1193	>	* @return {@code true} if this executor terminated and
1194	>	*         {@code false} if the timeout elapsed before termination
1195		* @throws InterruptedException if interrupted while waiting
1196		*/
1197		public boolean awaitTermination(long timeout, TimeUnit unit)
#	Line 1135 | Line 1215 | public class ForkJoinPool extends Abstra
1215		// Shutdown and termination support
1216
1217		/**
1218	<	* Callback from terminating worker. Null out the corresponding
1219	<	* workers slot, and if terminating, try to terminate, else try to
1220	<	* shrink workers array.
1218	>	* Callback from terminating worker. Nulls out the corresponding
1219	>	* workers slot, and if terminating, tries to terminate; else
1220	>	* tries to shrink workers array.
1221	>	*
1222		* @param w the worker
1223		*/
1224		final void workerTerminated(ForkJoinWorkerThread w) {
#	Line 1156 | Line 1237 | public class ForkJoinPool extends Abstra
1237		transitionRunStateTo(TERMINATED);
1238		termination.signalAll();
1239		}
1240	<	else if (!isTerminating()) {
1240	>	else if (isProcessingTasks()) {
1241		tryShrinkWorkerArray();
1242		tryResumeSpare(true); // allow replacement
1243		}
#	Line 1168 | Line 1249 | public class ForkJoinPool extends Abstra
1249		}
1250
1251		/**
1252	<	* Initiate termination.
1252	>	* Initiates termination.
1253		*/
1254		private void terminate() {
1255		if (transitionRunStateTo(TERMINATING)) {
#	Line 1183 | Line 1264 | public class ForkJoinPool extends Abstra
1264		}
1265
1266		/**
1267	<	* Possibly terminate when on shutdown state
1267	>	* Possibly terminates when on shutdown state.
1268		*/
1269		private void terminateOnShutdown() {
1270		if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
#	Line 1191 | Line 1272 | public class ForkJoinPool extends Abstra
1272		}
1273
1274		/**
1275	<	* Clear out and cancel submissions
1275	>	* Clears out and cancels submissions.
1276		*/
1277		private void cancelQueuedSubmissions() {
1278		ForkJoinTask<?> task;
#	Line 1200 | Line 1281 | public class ForkJoinPool extends Abstra
1281		}
1282
1283		/**
1284	<	* Clean out worker queues.
1284	>	* Cleans out worker queues.
1285		*/
1286		private void cancelQueuedWorkerTasks() {
1287		final ReentrantLock lock = this.workerLock;
#	Line 1220 | Line 1301 | public class ForkJoinPool extends Abstra
1301		}
1302
1303		/**
1304	<	* Set each worker's status to terminating. Requires lock to avoid
1305	<	* conflicts with add/remove
1304	>	* Sets each worker's status to terminating. Requires lock to avoid
1305	>	* conflicts with add/remove.
1306		*/
1307		private void stopAllWorkers() {
1308		final ReentrantLock lock = this.workerLock;
#	Line 1241 | Line 1322 | public class ForkJoinPool extends Abstra
1322		}
1323
1324		/**
1325	<	* Interrupt all unterminated workers.  This is not required for
1325	>	* Interrupts all unterminated workers.  This is not required for
1326		* sake of internal control, but may help unstick user code during
1327		* shutdown.
1328		*/
#	Line 1311 | Line 1392 | public class ForkJoinPool extends Abstra
1392		}
1393
1394		/**
1395	<	* Wake up waiter, returning false if known to already
1395	>	* Wakes up waiter, returning false if known to already
1396		*/
1397		boolean signal() {
1398		ForkJoinWorkerThread t = thread;
#	Line 1323 | Line 1404 | public class ForkJoinPool extends Abstra
1404		}
1405
1406		/**
1407	<	* Await release on sync
1407	>	* Awaits release on sync.
1408		*/
1409		void awaitSyncRelease(ForkJoinPool p) {
1410		while (thread != null && !p.syncIsReleasable(this))
#	Line 1331 | Line 1412 | public class ForkJoinPool extends Abstra
1412		}
1413
1414		/**
1415	<	* Await resumption as spare
1415	>	* Awaits resumption as spare.
1416		*/
1417		void awaitSpareRelease() {
1418		while (thread != null) {
#	Line 1345 | Line 1426 | public class ForkJoinPool extends Abstra
1426		* Ensures that no thread is waiting for count to advance from the
1427		* current value of eventCount read on entry to this method, by
1428		* releasing waiting threads if necessary.
1429	+	*
1430		* @return the count
1431		*/
1432		final long ensureSync() {
#	Line 1366 | Line 1448 | public class ForkJoinPool extends Abstra
1448		*/
1449		private void signalIdleWorkers() {
1450		long c;
1451	<	do;while (!casEventCount(c = eventCount, c+1));
1451	>	do {} while (!casEventCount(c = eventCount, c+1));
1452		ensureSync();
1453		}
1454
1455		/**
1456	<	* Signal threads waiting to poll a task. Because method sync
1456	>	* Signals threads waiting to poll a task. Because method sync
1457		* rechecks availability, it is OK to only proceed if queue
1458		* appears to be non-empty, and OK to skip under contention to
1459		* increment count (since some other thread succeeded).
#	Line 1390 | Line 1472 | public class ForkJoinPool extends Abstra
1472		* Waits until event count advances from last value held by
1473		* caller, or if excess threads, caller is resumed as spare, or
1474		* caller or pool is terminating. Updates caller's event on exit.
1475	+	*
1476		* @param w the calling worker thread
1477		*/
1478		final void sync(ForkJoinWorkerThread w) {
1479		updateStealCount(w); // Transfer w's count while it is idle
1480
1481	<	while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) {
1481	>	while (!w.isShutdown() && isProcessingTasks() && !suspendIfSpare(w)) {
1482		long prev = w.lastEventCount;
1483		WaitQueueNode node = null;
1484		WaitQueueNode h;
#	Line 1417 | Line 1500 | public class ForkJoinPool extends Abstra
1500		}
1501
1502		/**
1503	<	* Returns true if worker waiting on sync can proceed:
1503	>	* Returns {@code true} if worker waiting on sync can proceed:
1504		*  - on signal (thread == null)
1505		*  - on event count advance (winning race to notify vs signaller)
1506	<	*  - on Interrupt
1506	>	*  - on interrupt
1507		*  - if the first queued node, we find work available
1508		* If node was not signalled and event count not advanced on exit,
1509		* then we also help advance event count.
1510	<	* @return true if node can be released
1510	>	*
1511	>	* @return {@code true} if node can be released
1512		*/
1513		final boolean syncIsReleasable(WaitQueueNode node) {
1514		long prev = node.count;
#	Line 1443 | Line 1527 | public class ForkJoinPool extends Abstra
1527		}
1528
1529		/**
1530	<	* Returns true if a new sync event occurred since last call to
1531	<	* sync or this method, if so, updating caller's count.
1530	>	* Returns {@code true} if a new sync event occurred since last
1531	>	* call to sync or this method, if so, updating caller's count.
1532		*/
1533		final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1534		long lc = w.lastEventCount;
#	Line 1458 | Line 1542 | public class ForkJoinPool extends Abstra
1542		//  Parallelism maintenance
1543
1544		/**
1545	<	* Decrement running count; if too low, add spare.
1545	>	* Decrements running count; if too low, adds spare.
1546		*
1547		* Conceptually, all we need to do here is add or resume a
1548		* spare thread when one is about to block (and remove or
1549		* suspend it later when unblocked -- see suspendIfSpare).
1550		* However, implementing this idea requires coping with
1551	<	* several problems: We have imperfect information about the
1551	>	* several problems: we have imperfect information about the
1552		* states of threads. Some count updates can and usually do
1553		* lag run state changes, despite arrangements to keep them
1554		* accurate (for example, when possible, updating counts
#	Line 1478 | Line 1562 | public class ForkJoinPool extends Abstra
1562		* only be suspended or removed when they are idle, not
1563		* immediately when they aren't needed. So adding threads will
1564		* raise parallelism level for longer than necessary.  Also,
1565	<	* FJ applications often enounter highly transient peaks when
1565	>	* FJ applications often encounter highly transient peaks when
1566		* many threads are blocked joining, but for less time than it
1567		* takes to create or resume spares.
1568		*
#	Line 1487 | Line 1571 | public class ForkJoinPool extends Abstra
1571		* target counts, else create only to avoid starvation
1572		* @return true if joinMe known to be done
1573		*/
1574	<	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1574	>	final boolean preJoin(ForkJoinTask<?> joinMe,
1575	>	boolean maintainParallelism) {
1576		maintainParallelism &= maintainsParallelism; // overrride
1577		boolean dec = false;  // true when running count decremented
1578		while (spareStack == null || !tryResumeSpare(dec)) {
1579		int counts = workerCounts;
1580	<	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1580	>	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1581	>	// CAS cheat
1582		if (!needSpare(counts, maintainParallelism))
1583		break;
1584		if (joinMe.status < 0)
#	Line 1507 | Line 1593 | public class ForkJoinPool extends Abstra
1593		/**
1594		* Same idea as preJoin
1595		*/
1596	<	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1596	>	final boolean preBlock(ManagedBlocker blocker,
1597	>	boolean maintainParallelism) {
1598		maintainParallelism &= maintainsParallelism;
1599		boolean dec = false;
1600		while (spareStack == null || !tryResumeSpare(dec)) {
#	Line 1525 | Line 1612 | public class ForkJoinPool extends Abstra
1612		}
1613
1614		/**
1615	<	* Returns true if a spare thread appears to be needed.  If
1616	<	* maintaining parallelism, returns true when the deficit in
1615	>	* Returns {@code true} if a spare thread appears to be needed.
1616	>	* If maintaining parallelism, returns true when the deficit in
1617		* running threads is more than the surplus of total threads, and
1618		* there is apparently some work to do.  This self-limiting rule
1619		* means that the more threads that have already been added, the
1620		* less parallelism we will tolerate before adding another.
1621	+	*
1622		* @param counts current worker counts
1623		* @param maintainParallelism try to maintain parallelism
1624		*/
#	Line 1548 | Line 1636 | public class ForkJoinPool extends Abstra
1636		}
1637
1638		/**
1639	<	* Add a spare worker if lock available and no more than the
1640	<	* expected numbers of threads exist
1639	>	* Adds a spare worker if lock available and no more than the
1640	>	* expected numbers of threads exist.
1641	>	*
1642		* @return true if successful
1643		*/
1644		private boolean tryAddSpare(int expectedCounts) {
#	Line 1582 | Line 1671 | public class ForkJoinPool extends Abstra
1671		}
1672
1673		/**
1674	<	* Add the kth spare worker. On entry, pool coounts are already
1674	>	* Adds the kth spare worker. On entry, pool counts are already
1675		* adjusted to reflect addition.
1676		*/
1677		private void createAndStartSpare(int k) {
#	Line 1594 | Line 1683 | public class ForkJoinPool extends Abstra
1683		for (k = 0; k < len && ws[k] != null; ++k)
1684		;
1685		}
1686	<	if (k < len && !isTerminating() && (w = createWorker(k)) != null) {
1686	>	if (k < len && isProcessingTasks() && (w = createWorker(k)) != null) {
1687		ws[k] = w;
1688		w.start();
1689		}
#	Line 1604 | Line 1693 | public class ForkJoinPool extends Abstra
1693		}
1694
1695		/**
1696	<	* Suspend calling thread w if there are excess threads.  Called
1697	<	* only from sync.  Spares are enqueued in a Treiber stack
1698	<	* using the same WaitQueueNodes as barriers.  They are resumed
1699	<	* mainly in preJoin, but are also woken on pool events that
1700	<	* require all threads to check run state.
1696	>	* Suspends calling thread w if there are excess threads.  Called
1697	>	* only from sync.  Spares are enqueued in a Treiber stack using
1698	>	* the same WaitQueueNodes as barriers.  They are resumed mainly
1699	>	* in preJoin, but are also woken on pool events that require all
1700	>	* threads to check run state.
1701	>	*
1702		* @param w the caller
1703		*/
1704		private boolean suspendIfSpare(ForkJoinWorkerThread w) {
#	Line 1619 | Line 1709 | public class ForkJoinPool extends Abstra
1709		node = new WaitQueueNode(0, w);
1710		if (casWorkerCounts(s, s-1)) { // representation-dependent
1711		// push onto stack
1712	<	do;while (!casSpareStack(node.next = spareStack, node));
1712	>	do {} while (!casSpareStack(node.next = spareStack, node));
1713		// block until released by resumeSpare
1714		node.awaitSpareRelease();
1715		return true;
#	Line 1629 | Line 1719 | public class ForkJoinPool extends Abstra
1719		}
1720
1721		/**
1722	<	* Try to pop and resume a spare thread.
1722	>	* Tries to pop and resume a spare thread.
1723	>	*
1724		* @param updateCount if true, increment running count on success
1725		* @return true if successful
1726		*/
#	Line 1647 | Line 1738 | public class ForkJoinPool extends Abstra
1738		}
1739
1740		/**
1741	<	* Pop and resume all spare threads. Same idea as ensureSync.
1741	>	* Pops and resumes all spare threads. Same idea as ensureSync.
1742	>	*
1743		* @return true if any spares released
1744		*/
1745		private boolean resumeAllSpares() {
#	Line 1665 | Line 1757 | public class ForkJoinPool extends Abstra
1757		}
1758
1759		/**
1760	<	* Pop and shutdown excessive spare threads. Call only while
1760	>	* Pops and shuts down excessive spare threads. Call only while
1761		* holding lock. This is not guaranteed to eliminate all excess
1762		* threads, only those suspended as spares, which are the ones
1763		* unlikely to be needed in the future.
#	Line 1689 | Line 1781 | public class ForkJoinPool extends Abstra
1781
1782		/**
1783		* Interface for extending managed parallelism for tasks running
1784	<	* in ForkJoinPools. A ManagedBlocker provides two methods.
1785	<	* Method <code>isReleasable</code> must return true if blocking is not
1786	<	* necessary. Method <code>block</code> blocks the current thread
1787	<	* if necessary (perhaps internally invoking isReleasable before
1788	<	* actually blocking.).
1784	>	* in {@link ForkJoinPool}s.
1785	>	*
1786	>	* <p>A {@code ManagedBlocker} provides two methods.
1787	>	* Method {@code isReleasable} must return {@code true} if
1788	>	* blocking is not necessary. Method {@code block} blocks the
1789	>	* current thread if necessary (perhaps internally invoking
1790	>	* {@code isReleasable} before actually blocking).
1791	>	*
1792		* <p>For example, here is a ManagedBlocker based on a
1793		* ReentrantLock:
1794	<	* <pre>
1795	<	*   class ManagedLocker implements ManagedBlocker {
1796	<	*     final ReentrantLock lock;
1797	<	*     boolean hasLock = false;
1798	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1799	<	*     public boolean block() {
1800	<	*        if (!hasLock)
1801	<	*           lock.lock();
1802	<	*        return true;
1803	<	*     }
1804	<	*     public boolean isReleasable() {
1805	<	*        return hasLock || (hasLock = lock.tryLock());
1711	<	*     }
1794	>	*  <pre> {@code
1795	>	* class ManagedLocker implements ManagedBlocker {
1796	>	*   final ReentrantLock lock;
1797	>	*   boolean hasLock = false;
1798	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1799	>	*   public boolean block() {
1800	>	*     if (!hasLock)
1801	>	*       lock.lock();
1802	>	*     return true;
1803	>	*   }
1804	>	*   public boolean isReleasable() {
1805	>	*     return hasLock || (hasLock = lock.tryLock());
1806		*   }
1807	<	* </pre>
1807	>	* }}</pre>
1808		*/
1809		public static interface ManagedBlocker {
1810		/**
1811		* Possibly blocks the current thread, for example waiting for
1812		* a lock or condition.
1813	<	* @return true if no additional blocking is necessary (i.e.,
1814	<	* if isReleasable would return true).
1813	>	*
1814	>	* @return {@code true} if no additional blocking is necessary
1815	>	* (i.e., if isReleasable would return true)
1816		* @throws InterruptedException if interrupted while waiting
1817	<	* (the method is not required to do so, but is allowe to).
1817	>	* (the method is not required to do so, but is allowed to)
1818		*/
1819		boolean block() throws InterruptedException;
1820
1821		/**
1822	<	* Returns true if blocking is unnecessary.
1822	>	* Returns {@code true} if blocking is unnecessary.
1823		*/
1824		boolean isReleasable();
1825		}
1826
1827		/**
1828		* Blocks in accord with the given blocker.  If the current thread
1829	<	* is a ForkJoinWorkerThread, this method possibly arranges for a
1830	<	* spare thread to be activated if necessary to ensure parallelism
1831	<	* while the current thread is blocked.  If
1832	<	* <code>maintainParallelism</code> is true and the pool supports
1833	<	* it ({@link #getMaintainsParallelism}), this method attempts to
1834	<	* maintain the pool's nominal parallelism. Otherwise if activates
1835	<	* a thread only if necessary to avoid complete starvation. This
1836	<	* option may be preferable when blockages use timeouts, or are
1837	<	* almost always brief.
1838	<	*
1839	<	* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1840	<	* equivalent to
1841	<	* <pre>
1842	<	*   while (!blocker.isReleasable())
1843	<	*      if (blocker.block())
1844	<	*         return;
1845	<	* </pre>
1846	<	* If the caller is a ForkJoinTask, then the pool may first
1847	<	* be expanded to ensure parallelism, and later adjusted.
1829	>	* is a {@link ForkJoinWorkerThread}, this method possibly
1830	>	* arranges for a spare thread to be activated if necessary to
1831	>	* ensure parallelism while the current thread is blocked.
1832	>	*
1833	>	* <p>If {@code maintainParallelism} is {@code true} and the pool
1834	>	* supports it ({@link #getMaintainsParallelism}), this method
1835	>	* attempts to maintain the pool's nominal parallelism. Otherwise
1836	>	* it activates a thread only if necessary to avoid complete
1837	>	* starvation. This option may be preferable when blockages use
1838	>	* timeouts, or are almost always brief.
1839	>	*
1840	>	* <p>If the caller is not a {@link ForkJoinTask}, this method is
1841	>	* behaviorally equivalent to
1842	>	*  <pre> {@code
1843	>	* while (!blocker.isReleasable())
1844	>	*   if (blocker.block())
1845	>	*     return;
1846	>	* }</pre>
1847	>	*
1848	>	* If the caller is a {@code ForkJoinTask}, then the pool may
1849	>	* first be expanded to ensure parallelism, and later adjusted.
1850		*
1851		* @param blocker the blocker
1852	<	* @param maintainParallelism if true and supported by this pool,
1853	<	* attempt to maintain the pool's nominal parallelism; otherwise
1854	<	* activate a thread only if necessary to avoid complete
1855	<	* starvation.
1856	<	* @throws InterruptedException if blocker.block did so.
1852	>	* @param maintainParallelism if {@code true} and supported by
1853	>	* this pool, attempt to maintain the pool's nominal parallelism;
1854	>	* otherwise activate a thread only if necessary to avoid
1855	>	* complete starvation.
1856	>	* @throws InterruptedException if blocker.block did so
1857		*/
1858		public static void managedBlock(ManagedBlocker blocker,
1859		boolean maintainParallelism)
1860		throws InterruptedException {
1861		Thread t = Thread.currentThread();
1862	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1863	<	((ForkJoinWorkerThread)t).pool : null);
1862	>	ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ?
1863	>	((ForkJoinWorkerThread) t).pool : null);
1864		if (!blocker.isReleasable()) {
1865		try {
1866		if (pool == null ||
#	Line 1778 | Line 1875 | public class ForkJoinPool extends Abstra
1875
1876		private static void awaitBlocker(ManagedBlocker blocker)
1877		throws InterruptedException {
1878	<	do;while (!blocker.isReleasable() && !blocker.block());
1878	>	do {} while (!blocker.isReleasable() && !blocker.block());
1879		}
1880
1881	<	// AbstractExecutorService overrides
1881	>	// AbstractExecutorService overrides.  These rely on undocumented
1882	>	// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
1883	>	// implement RunnableFuture.
1884
1885		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1886	<	return new AdaptedRunnable(runnable, value);
1886	>	return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
1887		}
1888
1889		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1890	<	return new AdaptedCallable(callable);
1890	>	return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
1891		}
1892
1893	+	// Unsafe mechanics
1894
1895	<	// Temporary Unsafe mechanics for preliminary release
1896	<	private static Unsafe getUnsafe() throws Throwable {
1897	<	try {
1898	<	return Unsafe.getUnsafe();
1899	<	} catch (SecurityException se) {
1900	<	try {
1901	<	return java.security.AccessController.doPrivileged
1902	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1903	<	public Unsafe run() throws Exception {
1904	<	return getUnsafePrivileged();
1905	<	}});
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	<	}
1895	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1896	>	private static final long eventCountOffset =
1897	>	objectFieldOffset("eventCount", ForkJoinPool.class);
1898	>	private static final long workerCountsOffset =
1899	>	objectFieldOffset("workerCounts", ForkJoinPool.class);
1900	>	private static final long runControlOffset =
1901	>	objectFieldOffset("runControl", ForkJoinPool.class);
1902	>	private static final long syncStackOffset =
1903	>	objectFieldOffset("syncStack",ForkJoinPool.class);
1904	>	private static final long spareStackOffset =
1905	>	objectFieldOffset("spareStack", ForkJoinPool.class);
1906
1907		private boolean casEventCount(long cmp, long val) {
1908	<	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1908	>	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
1909		}
1910		private boolean casWorkerCounts(int cmp, int val) {
1911	<	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1911	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1912		}
1913		private boolean casRunControl(int cmp, int val) {
1914	<	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1914	>	return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
1915		}
1916		private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1917	<	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1917	>	return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
1918		}
1919		private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1920	<	return _unsafe.compareAndSwapObject(this, syncStackOffset, cmp, val);
1920	>	return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1921	>	}
1922	>
1923	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1924	>	try {
1925	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1926	>	} catch (NoSuchFieldException e) {
1927	>	// Convert Exception to corresponding Error
1928	>	NoSuchFieldError error = new NoSuchFieldError(field);
1929	>	error.initCause(e);
1930	>	throw error;
1931	>	}
1932	>	}
1933	>
1934	>	/**
1935	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1936	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1937	>	* into a jdk.
1938	>	*
1939	>	* @return a sun.misc.Unsafe
1940	>	*/
1941	>	private static sun.misc.Unsafe getUnsafe() {
1942	>	try {
1943	>	return sun.misc.Unsafe.getUnsafe();
1944	>	} catch (SecurityException se) {
1945	>	try {
1946	>	return java.security.AccessController.doPrivileged
1947	>	(new java.security
1948	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1949	>	public sun.misc.Unsafe run() throws Exception {
1950	>	java.lang.reflect.Field f = sun.misc
1951	>	.Unsafe.class.getDeclaredField("theUnsafe");
1952	>	f.setAccessible(true);
1953	>	return (sun.misc.Unsafe) f.get(null);
1954	>	}});
1955	>	} catch (java.security.PrivilegedActionException e) {
1956	>	throw new RuntimeException("Could not initialize intrinsics",
1957	>	e.getCause());
1958	>	}
1959	>	}
1960		}
1961		}

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