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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.5 by jsr166, Thu Mar 19 05:10:42 2009 UTC vs.
Revision 1.20 by jsr166, Fri Jul 24 22:05:22 2009 UTC

#	Line 27 | Line 27 | import java.lang.reflect.*;
27		* (eventually blocking if none exist). This makes them efficient when
28		* most tasks spawn other subtasks (as do most ForkJoinTasks), as well
29		* as the mixed execution of some plain Runnable- or Callable- based
30	<	* activities along with ForkJoinTasks. Otherwise, other
30	>	* activities along with ForkJoinTasks. When setting
31	>	* {@code setAsyncMode}, a ForkJoinPools may also be appropriate for
32	>	* use with fine-grained tasks that are never joined. Otherwise, other
33		* ExecutorService implementations are typically more appropriate
34		* choices.
35		*
#	Line 36 | Line 38 | import java.lang.reflect.*;
38		* adding, suspending, or resuming threads, even if some tasks are
39		* waiting to join others. However, no such adjustments are performed
40		* in the face of blocked IO or other unmanaged synchronization. The
41	<	* nested <code>ManagedBlocker</code> interface enables extension of
41	>	* nested {@code ManagedBlocker} interface enables extension of
42		* the kinds of synchronization accommodated.  The target parallelism
43	<	* level may also be changed dynamically (<code>setParallelism</code>)
44	<	* and dynamically thread construction can be limited using methods
45	<	* <code>setMaximumPoolSize</code> and/or
46	<	* <code>setMaintainsParallelism</code>.
43	>	* level may also be changed dynamically ({@code setParallelism})
44	>	* and thread construction can be limited using methods
45	>	* {@code setMaximumPoolSize} and/or
46	>	* {@code setMaintainsParallelism}.
47		*
48		* <p>In addition to execution and lifecycle control methods, this
49		* class provides status check methods (for example
50	<	* <code>getStealCount</code>) that are intended to aid in developing,
50	>	* {@code getStealCount}) that are intended to aid in developing,
51		* tuning, and monitoring fork/join applications. Also, method
52	<	* <code>toString</code> returns indications of pool state in a
52	>	* {@code toString} returns indications of pool state in a
53		* convenient form for informal monitoring.
54		*
55		* <p><b>Implementation notes</b>: This implementation restricts the
56		* maximum number of running threads to 32767. Attempts to create
57		* pools with greater than the maximum result in
58		* IllegalArgumentExceptions.
59	+	*
60	+	* @since 1.7
61	+	* @author Doug Lea
62		*/
63		public class ForkJoinPool extends AbstractExecutorService {
64
#	Line 79 | Line 84 | public class ForkJoinPool extends Abstra
84		* Returns a new worker thread operating in the given pool.
85		*
86		* @param pool the pool this thread works in
87	<	* @throws NullPointerException if pool is null;
87	>	* @throws NullPointerException if pool is null
88		*/
89		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
90		}
91
92		/**
93	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
93	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
94		* new ForkJoinWorkerThread.
95		*/
96		static class  DefaultForkJoinWorkerThreadFactory
#	Line 131 | Line 136 | public class ForkJoinPool extends Abstra
136		new AtomicInteger();
137
138		/**
139	<	* Array holding all worker threads in the pool. Array size must
140	<	* be a power of two.  Updates and replacements are protected by
141	<	* workerLock, but it is always kept in a consistent enough state
142	<	* to be randomly accessed without locking by workers performing
143	<	* work-stealing.
139	>	* Array holding all worker threads in the pool. Initialized upon
140	>	* first use. Array size must be a power of two.  Updates and
141	>	* replacements are protected by workerLock, but it is always kept
142	>	* in a consistent enough state to be randomly accessed without
143	>	* locking by workers performing work-stealing.
144		*/
145		volatile ForkJoinWorkerThread[] workers;
146
#	Line 151 | Line 156 | public class ForkJoinPool extends Abstra
156
157		/**
158		* The uncaught exception handler used when any worker
159	<	* abrupty terminates
159	>	* abruptly terminates
160		*/
161		private Thread.UncaughtExceptionHandler ueh;
162
#	Line 179 | Line 184 | public class ForkJoinPool extends Abstra
184		private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
185
186		/**
187	<	* Head of Treiber stack for barrier sync. See below for explanation
187	>	* Head of Treiber stack for barrier sync. See below for explanation.
188		*/
189		private volatile WaitQueueNode syncStack;
190
#	Line 204 | Line 209 | public class ForkJoinPool extends Abstra
209		private volatile int parallelism;
210
211		/**
212	+	* True if use local fifo, not default lifo, for local polling
213	+	*/
214	+	private volatile boolean locallyFifo;
215	+
216	+	/**
217		* Holds number of total (i.e., created and not yet terminated)
218		* and running (i.e., not blocked on joins or other managed sync)
219		* threads, packed into one int to ensure consistent snapshot when
220		* making decisions about creating and suspending spare
221		* threads. Updated only by CAS.  Note: CASes in
222	<	* updateRunningCount and preJoin running active count is in low
223	<	* word, so need to be modified if this changes
222	>	* updateRunningCount and preJoin assume that running active count
223	>	* is in low word, so need to be modified if this changes.
224		*/
225		private volatile int workerCounts;
226
#	Line 219 | Line 229 | public class ForkJoinPool extends Abstra
229		private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
230
231		/**
232	<	* Add delta (which may be negative) to running count.  This must
232	>	* Adds delta (which may be negative) to running count.  This must
233		* be called before (with negative arg) and after (with positive)
234	<	* any managed synchronization (i.e., mainly, joins)
234	>	* any managed synchronization (i.e., mainly, joins).
235	>	*
236		* @param delta the number to add
237		*/
238		final void updateRunningCount(int delta) {
239		int s;
240	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
240	>	do {} while (!casWorkerCounts(s = workerCounts, s + delta));
241		}
242
243		/**
244	<	* Add delta (which may be negative) to both total and running
244	>	* Adds delta (which may be negative) to both total and running
245		* count.  This must be called upon creation and termination of
246		* worker threads.
247	+	*
248		* @param delta the number to add
249		*/
250		private void updateWorkerCount(int delta) {
251		int d = delta + (delta << 16); // add to both lo and hi parts
252		int s;
253	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
253	>	do {} while (!casWorkerCounts(s = workerCounts, s + d));
254		}
255
256		/**
#	Line 264 | Line 276 | public class ForkJoinPool extends Abstra
276		private static int runControlFor(int r, int a)   { return (r << 16) + a; }
277
278		/**
279	<	* Try incrementing active count; fail on contention. Called by
280	<	* workers before/during executing tasks.
281	<	* @return true on success;
279	>	* Tries incrementing active count; fails on contention.
280	>	* Called by workers before/during executing tasks.
281	>	*
282	>	* @return true on success
283		*/
284		final boolean tryIncrementActiveCount() {
285		int c = runControl;
#	Line 274 | Line 287 | public class ForkJoinPool extends Abstra
287		}
288
289		/**
290	<	* Try decrementing active count; fail on contention.
291	<	* Possibly trigger termination on success
290	>	* Tries decrementing active count; fails on contention.
291	>	* Possibly triggers termination on success.
292		* Called by workers when they can't find tasks.
293	+	*
294		* @return true on success
295		*/
296		final boolean tryDecrementActiveCount() {
#	Line 290 | Line 304 | public class ForkJoinPool extends Abstra
304		}
305
306		/**
307	<	* Return true if argument represents zero active count and
307	>	* Returns true if argument represents zero active count and
308		* nonzero runstate, which is the triggering condition for
309		* terminating on shutdown.
310		*/
311		private static boolean canTerminateOnShutdown(int c) {
312	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
312	>	// i.e. least bit is nonzero runState bit
313	>	return ((c & -c) >>> 16) != 0;
314		}
315
316		/**
#	Line 321 | Line 336 | public class ForkJoinPool extends Abstra
336
337		/**
338		* Creates a ForkJoinPool with a pool size equal to the number of
339	<	* processors available on the system and using the default
340	<	* ForkJoinWorkerThreadFactory,
339	>	* processors available on the system, using the default
340	>	* ForkJoinWorkerThreadFactory.
341	>	*
342		* @throws SecurityException if a security manager exists and
343		*         the caller is not permitted to modify threads
344		*         because it does not hold {@link
345	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
345	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
346		*/
347		public ForkJoinPool() {
348		this(Runtime.getRuntime().availableProcessors(),
#	Line 334 | Line 350 | public class ForkJoinPool extends Abstra
350		}
351
352		/**
353	<	* Creates a ForkJoinPool with the indicated parellelism level
354	<	* threads, and using the default ForkJoinWorkerThreadFactory,
353	>	* Creates a ForkJoinPool with the indicated parallelism level
354	>	* threads and using the default ForkJoinWorkerThreadFactory.
355	>	*
356		* @param parallelism the number of worker threads
357		* @throws IllegalArgumentException if parallelism less than or
358		* equal to zero
359		* @throws SecurityException if a security manager exists and
360		*         the caller is not permitted to modify threads
361		*         because it does not hold {@link
362	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
362	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
363		*/
364		public ForkJoinPool(int parallelism) {
365		this(parallelism, defaultForkJoinWorkerThreadFactory);
#	Line 351 | Line 368 | public class ForkJoinPool extends Abstra
368		/**
369		* Creates a ForkJoinPool with parallelism equal to the number of
370		* processors available on the system and using the given
371	<	* ForkJoinWorkerThreadFactory,
371	>	* ForkJoinWorkerThreadFactory.
372	>	*
373		* @param factory the factory for creating new threads
374		* @throws NullPointerException if factory is null
375		* @throws SecurityException if a security manager exists and
376		*         the caller is not permitted to modify threads
377		*         because it does not hold {@link
378	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
378	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
379		*/
380		public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
381		this(Runtime.getRuntime().availableProcessors(), factory);
#	Line 369 | Line 387 | public class ForkJoinPool extends Abstra
387		* @param parallelism the targeted number of worker threads
388		* @param factory the factory for creating new threads
389		* @throws IllegalArgumentException if parallelism less than or
390	<	* equal to zero, or greater than implementation limit.
390	>	* equal to zero, or greater than implementation limit
391		* @throws NullPointerException if factory is null
392		* @throws SecurityException if a security manager exists and
393		*         the caller is not permitted to modify threads
394		*         because it does not hold {@link
395	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
395	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
396		*/
397		public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
398		if (parallelism <= 0 || parallelism > MAX_THREADS)
#	Line 391 | Line 409 | public class ForkJoinPool extends Abstra
409		this.termination = workerLock.newCondition();
410		this.stealCount = new AtomicLong();
411		this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
412	<	createAndStartInitialWorkers(parallelism);
412	>	// worker array and workers are lazily constructed
413		}
414
415		/**
416	<	* Create new worker using factory.
416	>	* Creates a new worker thread using factory.
417	>	*
418		* @param index the index to assign worker
419		* @return new worker, or null of factory failed
420		*/
#	Line 405 | Line 424 | public class ForkJoinPool extends Abstra
424		if (w != null) {
425		w.poolIndex = index;
426		w.setDaemon(true);
427	+	w.setAsyncMode(locallyFifo);
428		w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
429		if (h != null)
430		w.setUncaughtExceptionHandler(h);
#	Line 413 | Line 433 | public class ForkJoinPool extends Abstra
433		}
434
435		/**
436	<	* Return a good size for worker array given pool size.
436	>	* Returns a good size for worker array given pool size.
437		* Currently requires size to be a power of two.
438		*/
439	<	private static int arraySizeFor(int ps) {
440	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
439	>	private static int arraySizeFor(int poolSize) {
440	>	return (poolSize <= 1) ? 1 :
441	>	(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1)));
442		}
443
444		/**
445	<	* Create or resize array if necessary to hold newLength
445	>	* Creates or resizes array if necessary to hold newLength.
446	>	* Call only under exclusion.
447	>	*
448		* @return the array
449		*/
450		private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
#	Line 435 | Line 458 | public class ForkJoinPool extends Abstra
458		}
459
460		/**
461	<	* Try to shrink workers into smaller array after one or more terminate
461	>	* Tries to shrink workers into smaller array after one or more terminate.
462		*/
463		private void tryShrinkWorkerArray() {
464		ForkJoinWorkerThread[] ws = workers;
465	<	int len = ws.length;
466	<	int last = len - 1;
467	<	while (last >= 0 && ws[last] == null)
468	<	--last;
469	<	int newLength = arraySizeFor(last+1);
470	<	if (newLength < len)
471	<	workers = Arrays.copyOf(ws, newLength);
465	>	if (ws != null) {
466	>	int len = ws.length;
467	>	int last = len - 1;
468	>	while (last >= 0 && ws[last] == null)
469	>	--last;
470	>	int newLength = arraySizeFor(last+1);
471	>	if (newLength < len)
472	>	workers = Arrays.copyOf(ws, newLength);
473	>	}
474		}
475
476		/**
477	<	* Initial worker array and worker creation and startup. (This
453	<	* must be done under lock to avoid interference by some of the
454	<	* newly started threads while creating others.)
477	>	* Initializes workers if necessary.
478		*/
479	<	private void createAndStartInitialWorkers(int ps) {
480	<	final ReentrantLock lock = this.workerLock;
481	<	lock.lock();
482	<	try {
483	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
484	<	for (int i = 0; i < ps; ++i) {
485	<	ForkJoinWorkerThread w = createWorker(i);
486	<	if (w != null) {
487	<	ws[i] = w;
488	<	w.start();
489	<	updateWorkerCount(1);
479	>	final void ensureWorkerInitialization() {
480	>	ForkJoinWorkerThread[] ws = workers;
481	>	if (ws == null) {
482	>	final ReentrantLock lock = this.workerLock;
483	>	lock.lock();
484	>	try {
485	>	ws = workers;
486	>	if (ws == null) {
487	>	int ps = parallelism;
488	>	ws = ensureWorkerArrayCapacity(ps);
489	>	for (int i = 0; i < ps; ++i) {
490	>	ForkJoinWorkerThread w = createWorker(i);
491	>	if (w != null) {
492	>	ws[i] = w;
493	>	w.start();
494	>	updateWorkerCount(1);
495	>	}
496	>	}
497		}
498	+	} finally {
499	+	lock.unlock();
500		}
469	–	} finally {
470	–	lock.unlock();
501		}
502		}
503
#	Line 513 | Line 543 | public class ForkJoinPool extends Abstra
543		private <T> void doSubmit(ForkJoinTask<T> task) {
544		if (isShutdown())
545		throw new RejectedExecutionException();
546	+	if (workers == null)
547	+	ensureWorkerInitialization();
548		submissionQueue.offer(task);
549		signalIdleWorkers();
550		}
551
552		/**
553	<	* Performs the given task; returning its result upon completion
553	>	* Performs the given task, returning its result upon completion.
554	>	*
555		* @param task the task
556		* @return the task's result
557		* @throws NullPointerException if task is null
#	Line 531 | Line 564 | public class ForkJoinPool extends Abstra
564
565		/**
566		* Arranges for (asynchronous) execution of the given task.
567	+	*
568		* @param task the task
569		* @throws NullPointerException if task is null
570		* @throws RejectedExecutionException if pool is shut down
#	Line 565 | Line 599 | public class ForkJoinPool extends Abstra
599
600		/**
601		* Adaptor for Runnables. This implements RunnableFuture
602	<	* to be compliant with AbstractExecutorService constraints
602	>	* to be compliant with AbstractExecutorService constraints.
603		*/
604		static final class AdaptedRunnable<T> extends ForkJoinTask<T>
605		implements RunnableFuture<T> {
#	Line 585 | Line 619 | public class ForkJoinPool extends Abstra
619		return true;
620		}
621		public void run() { invoke(); }
622	+	private static final long serialVersionUID = 5232453952276885070L;
623		}
624
625		/**
#	Line 613 | Line 648 | public class ForkJoinPool extends Abstra
648		}
649		}
650		public void run() { invoke(); }
651	+	private static final long serialVersionUID = 2838392045355241008L;
652		}
653
654		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
655	<	ArrayList<ForkJoinTask<T>> ts =
655	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
656		new ArrayList<ForkJoinTask<T>>(tasks.size());
657	<	for (Callable<T> c : tasks)
658	<	ts.add(new AdaptedCallable<T>(c));
659	<	invoke(new InvokeAll<T>(ts));
660	<	return (List<Future<T>>)(List)ts;
657	>	for (Callable<T> task : tasks)
658	>	forkJoinTasks.add(new AdaptedCallable<T>(task));
659	>	invoke(new InvokeAll<T>(forkJoinTasks));
660	>
661	>	@SuppressWarnings({"unchecked", "rawtypes"})
662	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
663	>	return futures;
664		}
665
666		static final class InvokeAll<T> extends RecursiveAction {
667		final ArrayList<ForkJoinTask<T>> tasks;
668		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
669		public void compute() {
670	<	try { invokeAll(tasks); } catch(Exception ignore) {}
670	>	try { invokeAll(tasks); }
671	>	catch (Exception ignore) {}
672		}
673	+	private static final long serialVersionUID = -7914297376763021607L;
674		}
675
676		// Configuration and status settings and queries
677
678		/**
679	<	* Returns the factory used for constructing new workers
679	>	* Returns the factory used for constructing new workers.
680		*
681		* @return the factory used for constructing new workers
682		*/
#	Line 646 | Line 687 | public class ForkJoinPool extends Abstra
687		/**
688		* Returns the handler for internal worker threads that terminate
689		* due to unrecoverable errors encountered while executing tasks.
690	+	*
691		* @return the handler, or null if none
692		*/
693		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
#	Line 671 | Line 713 | public class ForkJoinPool extends Abstra
713		* @throws SecurityException if a security manager exists and
714		*         the caller is not permitted to modify threads
715		*         because it does not hold {@link
716	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
716	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
717		*/
718		public Thread.UncaughtExceptionHandler
719		setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
#	Line 683 | Line 725 | public class ForkJoinPool extends Abstra
725		old = ueh;
726		ueh = h;
727		ForkJoinWorkerThread[] ws = workers;
728	<	for (int i = 0; i < ws.length; ++i) {
729	<	ForkJoinWorkerThread w = ws[i];
730	<	if (w != null)
731	<	w.setUncaughtExceptionHandler(h);
728	>	if (ws != null) {
729	>	for (int i = 0; i < ws.length; ++i) {
730	>	ForkJoinWorkerThread w = ws[i];
731	>	if (w != null)
732	>	w.setUncaughtExceptionHandler(h);
733	>	}
734		}
735		} finally {
736		lock.unlock();
#	Line 696 | Line 740 | public class ForkJoinPool extends Abstra
740
741
742		/**
743	<	* Sets the target paralleism level of this pool.
743	>	* Sets the target parallelism level of this pool.
744	>	*
745		* @param parallelism the target parallelism
746		* @throws IllegalArgumentException if parallelism less than or
747	<	* equal to zero or greater than maximum size bounds.
747	>	* equal to zero or greater than maximum size bounds
748		* @throws SecurityException if a security manager exists and
749		*         the caller is not permitted to modify threads
750		*         because it does not hold {@link
751	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
751	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
752		*/
753		public void setParallelism(int parallelism) {
754		checkPermission();
#	Line 738 | Line 783 | public class ForkJoinPool extends Abstra
783		/**
784		* Returns the number of worker threads that have started but not
785		* yet terminated.  This result returned by this method may differ
786	<	* from <code>getParallelism</code> when threads are created to
786	>	* from {@code getParallelism} when threads are created to
787		* maintain parallelism when others are cooperatively blocked.
788		*
789		* @return the number of worker threads
#	Line 750 | Line 795 | public class ForkJoinPool extends Abstra
795		/**
796		* Returns the maximum number of threads allowed to exist in the
797		* pool, even if there are insufficient unblocked running threads.
798	+	*
799		* @return the maximum
800		*/
801		public int getMaximumPoolSize() {
#	Line 761 | Line 807 | public class ForkJoinPool extends Abstra
807		* pool, even if there are insufficient unblocked running threads.
808		* Setting this value has no effect on current pool size. It
809		* controls construction of new threads.
810	+	*
811		* @throws IllegalArgumentException if negative or greater then
812	<	* internal implementation limit.
812	>	* internal implementation limit
813		*/
814		public void setMaximumPoolSize(int newMax) {
815		if (newMax < 0 || newMax > MAX_THREADS)
#	Line 775 | Line 822 | public class ForkJoinPool extends Abstra
822		* Returns true if this pool dynamically maintains its target
823		* parallelism level. If false, new threads are added only to
824		* avoid possible starvation.
825	<	* This setting is by default true;
825	>	* This setting is by default true.
826	>	*
827		* @return true if maintains parallelism
828		*/
829		public boolean getMaintainsParallelism() {
#	Line 786 | Line 834 | public class ForkJoinPool extends Abstra
834		* Sets whether this pool dynamically maintains its target
835		* parallelism level. If false, new threads are added only to
836		* avoid possible starvation.
837	+	*
838		* @param enable true to maintains parallelism
839		*/
840		public void setMaintainsParallelism(boolean enable) {
#	Line 793 | Line 842 | public class ForkJoinPool extends Abstra
842		}
843
844		/**
845	+	* Establishes local first-in-first-out scheduling mode for forked
846	+	* tasks that are never joined. This mode may be more appropriate
847	+	* than default locally stack-based mode in applications in which
848	+	* worker threads only process asynchronous tasks.  This method is
849	+	* designed to be invoked only when pool is quiescent, and
850	+	* typically only before any tasks are submitted. The effects of
851	+	* invocations at other times may be unpredictable.
852	+	*
853	+	* @param async if true, use locally FIFO scheduling
854	+	* @return the previous mode
855	+	*/
856	+	public boolean setAsyncMode(boolean async) {
857	+	boolean oldMode = locallyFifo;
858	+	locallyFifo = async;
859	+	ForkJoinWorkerThread[] ws = workers;
860	+	if (ws != null) {
861	+	for (int i = 0; i < ws.length; ++i) {
862	+	ForkJoinWorkerThread t = ws[i];
863	+	if (t != null)
864	+	t.setAsyncMode(async);
865	+	}
866	+	}
867	+	return oldMode;
868	+	}
869	+
870	+	/**
871	+	* Returns true if this pool uses local first-in-first-out
872	+	* scheduling mode for forked tasks that are never joined.
873	+	*
874	+	* @return true if this pool uses async mode
875	+	*/
876	+	public boolean getAsyncMode() {
877	+	return locallyFifo;
878	+	}
879	+
880	+	/**
881		* Returns an estimate of the number of worker threads that are
882		* not blocked waiting to join tasks or for other managed
883		* synchronization.
#	Line 807 | Line 892 | public class ForkJoinPool extends Abstra
892		* Returns an estimate of the number of threads that are currently
893		* stealing or executing tasks. This method may overestimate the
894		* number of active threads.
895	<	* @return the number of active threads.
895	>	*
896	>	* @return the number of active threads
897		*/
898		public int getActiveThreadCount() {
899		return activeCountOf(runControl);
#	Line 817 | Line 903 | public class ForkJoinPool extends Abstra
903		* Returns an estimate of the number of threads that are currently
904		* idle waiting for tasks. This method may underestimate the
905		* number of idle threads.
906	<	* @return the number of idle threads.
906	>	*
907	>	* @return the number of idle threads
908		*/
909		final int getIdleThreadCount() {
910		int c = runningCountOf(workerCounts) - activeCountOf(runControl);
911	<	return (c <= 0)? 0 : c;
911	>	return (c <= 0) ? 0 : c;
912		}
913
914		/**
915		* Returns true if all worker threads are currently idle. An idle
916		* worker is one that cannot obtain a task to execute because none
917		* are available to steal from other threads, and there are no
918	<	* pending submissions to the pool. This method is conservative:
919	<	* It might not return true immediately upon idleness of all
918	>	* pending submissions to the pool. This method is conservative;
919	>	* it might not return true immediately upon idleness of all
920		* threads, but will eventually become true if threads remain
921		* inactive.
922	+	*
923		* @return true if all threads are currently idle
924		*/
925		public boolean isQuiescent() {
#	Line 843 | Line 931 | public class ForkJoinPool extends Abstra
931		* one thread's work queue by another. The reported value
932		* underestimates the actual total number of steals when the pool
933		* is not quiescent. This value may be useful for monitoring and
934	<	* tuning fork/join programs: In general, steal counts should be
934	>	* tuning fork/join programs: in general, steal counts should be
935		* high enough to keep threads busy, but low enough to avoid
936		* overhead and contention across threads.
937	<	* @return the number of steals.
937	>	*
938	>	* @return the number of steals
939		*/
940		public long getStealCount() {
941		return stealCount.get();
942		}
943
944		/**
945	<	* Accumulate steal count from a worker. Call only
946	<	* when worker known to be idle.
945	>	* Accumulates steal count from a worker.
946	>	* Call only when worker known to be idle.
947		*/
948		private void updateStealCount(ForkJoinWorkerThread w) {
949		int sc = w.getAndClearStealCount();
#	Line 869 | Line 958 | public class ForkJoinPool extends Abstra
958		* an approximation, obtained by iterating across all threads in
959		* the pool. This method may be useful for tuning task
960		* granularities.
961	<	* @return the number of queued tasks.
961	>	*
962	>	* @return the number of queued tasks
963		*/
964		public long getQueuedTaskCount() {
965		long count = 0;
966		ForkJoinWorkerThread[] ws = workers;
967	<	for (int i = 0; i < ws.length; ++i) {
968	<	ForkJoinWorkerThread t = ws[i];
969	<	if (t != null)
970	<	count += t.getQueueSize();
967	>	if (ws != null) {
968	>	for (int i = 0; i < ws.length; ++i) {
969	>	ForkJoinWorkerThread t = ws[i];
970	>	if (t != null)
971	>	count += t.getQueueSize();
972	>	}
973		}
974		return count;
975		}
#	Line 886 | Line 978 | public class ForkJoinPool extends Abstra
978		* Returns an estimate of the number tasks submitted to this pool
979		* that have not yet begun executing. This method takes time
980		* proportional to the number of submissions.
981	<	* @return the number of queued submissions.
981	>	*
982	>	* @return the number of queued submissions
983		*/
984		public int getQueuedSubmissionCount() {
985		return submissionQueue.size();
#	Line 895 | Line 988 | public class ForkJoinPool extends Abstra
988		/**
989		* Returns true if there are any tasks submitted to this pool
990		* that have not yet begun executing.
991	<	* @return <code>true</code> if there are any queued submissions.
991	>	*
992	>	* @return {@code true} if there are any queued submissions
993		*/
994		public boolean hasQueuedSubmissions() {
995		return !submissionQueue.isEmpty();
#	Line 905 | Line 999 | public class ForkJoinPool extends Abstra
999		* Removes and returns the next unexecuted submission if one is
1000		* available.  This method may be useful in extensions to this
1001		* class that re-assign work in systems with multiple pools.
1002	+	*
1003		* @return the next submission, or null if none
1004		*/
1005		protected ForkJoinTask<?> pollSubmission() {
#	Line 912 | Line 1007 | public class ForkJoinPool extends Abstra
1007		}
1008
1009		/**
1010	+	* Removes all available unexecuted submitted and forked tasks
1011	+	* from scheduling queues and adds them to the given collection,
1012	+	* without altering their execution status. These may include
1013	+	* artificially generated or wrapped tasks. This method is designed
1014	+	* to be invoked only when the pool is known to be
1015	+	* quiescent. Invocations at other times may not remove all
1016	+	* tasks. A failure encountered while attempting to add elements
1017	+	* to collection {@code c} may result in elements being in
1018	+	* neither, either or both collections when the associated
1019	+	* exception is thrown.  The behavior of this operation is
1020	+	* undefined if the specified collection is modified while the
1021	+	* operation is in progress.
1022	+	*
1023	+	* @param c the collection to transfer elements into
1024	+	* @return the number of elements transferred
1025	+	*/
1026	+	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
1027	+	int n = submissionQueue.drainTo(c);
1028	+	ForkJoinWorkerThread[] ws = workers;
1029	+	if (ws != null) {
1030	+	for (int i = 0; i < ws.length; ++i) {
1031	+	ForkJoinWorkerThread w = ws[i];
1032	+	if (w != null)
1033	+	n += w.drainTasksTo(c);
1034	+	}
1035	+	}
1036	+	return n;
1037	+	}
1038	+
1039	+	/**
1040		* Returns a string identifying this pool, as well as its state,
1041		* including indications of run state, parallelism level, and
1042		* worker and task counts.
#	Line 955 | Line 1080 | public class ForkJoinPool extends Abstra
1080		* Invocation has no additional effect if already shut down.
1081		* Tasks that are in the process of being submitted concurrently
1082		* during the course of this method may or may not be rejected.
1083	+	*
1084		* @throws SecurityException if a security manager exists and
1085		*         the caller is not permitted to modify threads
1086		*         because it does not hold {@link
1087	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1087	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1088		*/
1089		public void shutdown() {
1090		checkPermission();
#	Line 972 | Line 1098 | public class ForkJoinPool extends Abstra
1098		* waiting tasks.  Tasks that are in the process of being
1099		* submitted or executed concurrently during the course of this
1100		* method may or may not be rejected. Unlike some other executors,
1101	<	* this method cancels rather than collects non-executed tasks,
1102	<	* so always returns an empty list.
1101	>	* this method cancels rather than collects non-executed tasks
1102	>	* upon termination, so always returns an empty list. However, you
1103	>	* can use method {@code drainTasksTo} before invoking this
1104	>	* method to transfer unexecuted tasks to another collection.
1105	>	*
1106		* @return an empty list
1107		* @throws SecurityException if a security manager exists and
1108		*         the caller is not permitted to modify threads
1109		*         because it does not hold {@link
1110	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1110	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1111		*/
1112		public List<Runnable> shutdownNow() {
1113		checkPermission();
#	Line 987 | Line 1116 | public class ForkJoinPool extends Abstra
1116		}
1117
1118		/**
1119	<	* Returns <code>true</code> if all tasks have completed following shut down.
1119	>	* Returns {@code true} if all tasks have completed following shut down.
1120		*
1121	<	* @return <code>true</code> if all tasks have completed following shut down
1121	>	* @return {@code true} if all tasks have completed following shut down
1122		*/
1123		public boolean isTerminated() {
1124		return runStateOf(runControl) == TERMINATED;
1125		}
1126
1127		/**
1128	<	* Returns <code>true</code> if the process of termination has
1128	>	* Returns {@code true} if the process of termination has
1129		* commenced but possibly not yet completed.
1130		*
1131	<	* @return <code>true</code> if terminating
1131	>	* @return {@code true} if terminating
1132		*/
1133		public boolean isTerminating() {
1134		return runStateOf(runControl) >= TERMINATING;
1135		}
1136
1137		/**
1138	<	* Returns <code>true</code> if this pool has been shut down.
1138	>	* Returns {@code true} if this pool has been shut down.
1139		*
1140	<	* @return <code>true</code> if this pool has been shut down
1140	>	* @return {@code true} if this pool has been shut down
1141		*/
1142		public boolean isShutdown() {
1143		return runStateOf(runControl) >= SHUTDOWN;
#	Line 1021 | Line 1150 | public class ForkJoinPool extends Abstra
1150		*
1151		* @param timeout the maximum time to wait
1152		* @param unit the time unit of the timeout argument
1153	<	* @return <code>true</code> if this executor terminated and
1154	<	*         <code>false</code> if the timeout elapsed before termination
1153	>	* @return {@code true} if this executor terminated and
1154	>	*         {@code false} if the timeout elapsed before termination
1155		* @throws InterruptedException if interrupted while waiting
1156		*/
1157		public boolean awaitTermination(long timeout, TimeUnit unit)
#	Line 1046 | Line 1175 | public class ForkJoinPool extends Abstra
1175		// Shutdown and termination support
1176
1177		/**
1178	<	* Callback from terminating worker. Null out the corresponding
1179	<	* workers slot, and if terminating, try to terminate, else try to
1180	<	* shrink workers array.
1178	>	* Callback from terminating worker. Nulls out the corresponding
1179	>	* workers slot, and if terminating, tries to terminate; else
1180	>	* tries to shrink workers array.
1181	>	*
1182		* @param w the worker
1183		*/
1184		final void workerTerminated(ForkJoinWorkerThread w) {
#	Line 1058 | Line 1188 | public class ForkJoinPool extends Abstra
1188		lock.lock();
1189		try {
1190		ForkJoinWorkerThread[] ws = workers;
1191	<	int idx = w.poolIndex;
1192	<	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1193	<	ws[idx] = null;
1194	<	if (totalCountOf(workerCounts) == 0) {
1195	<	terminate(); // no-op if already terminating
1196	<	transitionRunStateTo(TERMINATED);
1197	<	termination.signalAll();
1198	<	}
1199	<	else if (!isTerminating()) {
1200	<	tryShrinkWorkerArray();
1201	<	tryResumeSpare(true); // allow replacement
1191	>	if (ws != null) {
1192	>	int idx = w.poolIndex;
1193	>	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1194	>	ws[idx] = null;
1195	>	if (totalCountOf(workerCounts) == 0) {
1196	>	terminate(); // no-op if already terminating
1197	>	transitionRunStateTo(TERMINATED);
1198	>	termination.signalAll();
1199	>	}
1200	>	else if (!isTerminating()) {
1201	>	tryShrinkWorkerArray();
1202	>	tryResumeSpare(true); // allow replacement
1203	>	}
1204		}
1205		} finally {
1206		lock.unlock();
#	Line 1077 | Line 1209 | public class ForkJoinPool extends Abstra
1209		}
1210
1211		/**
1212	<	* Initiate termination.
1212	>	* Initiates termination.
1213		*/
1214		private void terminate() {
1215		if (transitionRunStateTo(TERMINATING)) {
#	Line 1092 | Line 1224 | public class ForkJoinPool extends Abstra
1224		}
1225
1226		/**
1227	<	* Possibly terminate when on shutdown state
1227	>	* Possibly terminates when on shutdown state.
1228		*/
1229		private void terminateOnShutdown() {
1230		if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
#	Line 1100 | Line 1232 | public class ForkJoinPool extends Abstra
1232		}
1233
1234		/**
1235	<	* Clear out and cancel submissions
1235	>	* Clears out and cancels submissions.
1236		*/
1237		private void cancelQueuedSubmissions() {
1238		ForkJoinTask<?> task;
#	Line 1109 | Line 1241 | public class ForkJoinPool extends Abstra
1241		}
1242
1243		/**
1244	<	* Clean out worker queues.
1244	>	* Cleans out worker queues.
1245		*/
1246		private void cancelQueuedWorkerTasks() {
1247		final ReentrantLock lock = this.workerLock;
1248		lock.lock();
1249		try {
1250		ForkJoinWorkerThread[] ws = workers;
1251	<	for (int i = 0; i < ws.length; ++i) {
1252	<	ForkJoinWorkerThread t = ws[i];
1253	<	if (t != null)
1254	<	t.cancelTasks();
1251	>	if (ws != null) {
1252	>	for (int i = 0; i < ws.length; ++i) {
1253	>	ForkJoinWorkerThread t = ws[i];
1254	>	if (t != null)
1255	>	t.cancelTasks();
1256	>	}
1257		}
1258		} finally {
1259		lock.unlock();
#	Line 1127 | Line 1261 | public class ForkJoinPool extends Abstra
1261		}
1262
1263		/**
1264	<	* Set each worker's status to terminating. Requires lock to avoid
1265	<	* conflicts with add/remove
1264	>	* Sets each worker's status to terminating. Requires lock to avoid
1265	>	* conflicts with add/remove.
1266		*/
1267		private void stopAllWorkers() {
1268		final ReentrantLock lock = this.workerLock;
1269		lock.lock();
1270		try {
1271		ForkJoinWorkerThread[] ws = workers;
1272	<	for (int i = 0; i < ws.length; ++i) {
1273	<	ForkJoinWorkerThread t = ws[i];
1274	<	if (t != null)
1275	<	t.shutdownNow();
1272	>	if (ws != null) {
1273	>	for (int i = 0; i < ws.length; ++i) {
1274	>	ForkJoinWorkerThread t = ws[i];
1275	>	if (t != null)
1276	>	t.shutdownNow();
1277	>	}
1278		}
1279		} finally {
1280		lock.unlock();
#	Line 1146 | Line 1282 | public class ForkJoinPool extends Abstra
1282		}
1283
1284		/**
1285	<	* Interrupt all unterminated workers.  This is not required for
1285	>	* Interrupts all unterminated workers.  This is not required for
1286		* sake of internal control, but may help unstick user code during
1287		* shutdown.
1288		*/
#	Line 1155 | Line 1291 | public class ForkJoinPool extends Abstra
1291		lock.lock();
1292		try {
1293		ForkJoinWorkerThread[] ws = workers;
1294	<	for (int i = 0; i < ws.length; ++i) {
1295	<	ForkJoinWorkerThread t = ws[i];
1296	<	if (t != null && !t.isTerminated()) {
1297	<	try {
1298	<	t.interrupt();
1299	<	} catch (SecurityException ignore) {
1294	>	if (ws != null) {
1295	>	for (int i = 0; i < ws.length; ++i) {
1296	>	ForkJoinWorkerThread t = ws[i];
1297	>	if (t != null && !t.isTerminated()) {
1298	>	try {
1299	>	t.interrupt();
1300	>	} catch (SecurityException ignore) {
1301	>	}
1302		}
1303		}
1304		}
#	Line 1214 | Line 1352 | public class ForkJoinPool extends Abstra
1352		}
1353
1354		/**
1355	<	* Wake up waiter, returning false if known to already
1355	>	* Wakes up waiter, returning false if known to already
1356		*/
1357		boolean signal() {
1358		ForkJoinWorkerThread t = thread;
#	Line 1226 | Line 1364 | public class ForkJoinPool extends Abstra
1364		}
1365
1366		/**
1367	<	* Await release on sync
1367	>	* Awaits release on sync.
1368		*/
1369		void awaitSyncRelease(ForkJoinPool p) {
1370		while (thread != null && !p.syncIsReleasable(this))
#	Line 1234 | Line 1372 | public class ForkJoinPool extends Abstra
1372		}
1373
1374		/**
1375	<	* Await resumption as spare
1375	>	* Awaits resumption as spare.
1376		*/
1377		void awaitSpareRelease() {
1378		while (thread != null) {
#	Line 1248 | Line 1386 | public class ForkJoinPool extends Abstra
1386		* Ensures that no thread is waiting for count to advance from the
1387		* current value of eventCount read on entry to this method, by
1388		* releasing waiting threads if necessary.
1389	+	*
1390		* @return the count
1391		*/
1392		final long ensureSync() {
#	Line 1269 | Line 1408 | public class ForkJoinPool extends Abstra
1408		*/
1409		private void signalIdleWorkers() {
1410		long c;
1411	<	do;while (!casEventCount(c = eventCount, c+1));
1411	>	do {} while (!casEventCount(c = eventCount, c+1));
1412		ensureSync();
1413		}
1414
1415		/**
1416	<	* Signal threads waiting to poll a task. Because method sync
1416	>	* Signals threads waiting to poll a task. Because method sync
1417		* rechecks availability, it is OK to only proceed if queue
1418		* appears to be non-empty, and OK to skip under contention to
1419		* increment count (since some other thread succeeded).
#	Line 1293 | Line 1432 | public class ForkJoinPool extends Abstra
1432		* Waits until event count advances from last value held by
1433		* caller, or if excess threads, caller is resumed as spare, or
1434		* caller or pool is terminating. Updates caller's event on exit.
1435	+	*
1436		* @param w the calling worker thread
1437		*/
1438		final void sync(ForkJoinWorkerThread w) {
#	Line 1323 | Line 1463 | public class ForkJoinPool extends Abstra
1463		* Returns true if worker waiting on sync can proceed:
1464		*  - on signal (thread == null)
1465		*  - on event count advance (winning race to notify vs signaller)
1466	<	*  - on Interrupt
1466	>	*  - on interrupt
1467		*  - if the first queued node, we find work available
1468		* If node was not signalled and event count not advanced on exit,
1469		* then we also help advance event count.
1470	+	*
1471		* @return true if node can be released
1472		*/
1473		final boolean syncIsReleasable(WaitQueueNode node) {
#	Line 1361 | Line 1502 | public class ForkJoinPool extends Abstra
1502		//  Parallelism maintenance
1503
1504		/**
1505	<	* Decrement running count; if too low, add spare.
1505	>	* Decrements running count; if too low, adds spare.
1506		*
1507		* Conceptually, all we need to do here is add or resume a
1508		* spare thread when one is about to block (and remove or
1509		* suspend it later when unblocked -- see suspendIfSpare).
1510		* However, implementing this idea requires coping with
1511	<	* several problems: We have imperfect information about the
1511	>	* several problems: we have imperfect information about the
1512		* states of threads. Some count updates can and usually do
1513		* lag run state changes, despite arrangements to keep them
1514		* accurate (for example, when possible, updating counts
#	Line 1381 | Line 1522 | public class ForkJoinPool extends Abstra
1522		* only be suspended or removed when they are idle, not
1523		* immediately when they aren't needed. So adding threads will
1524		* raise parallelism level for longer than necessary.  Also,
1525	<	* FJ applications often enounter highly transient peaks when
1525	>	* FJ applications often encounter highly transient peaks when
1526		* many threads are blocked joining, but for less time than it
1527		* takes to create or resume spares.
1528		*
#	Line 1390 | Line 1531 | public class ForkJoinPool extends Abstra
1531		* target counts, else create only to avoid starvation
1532		* @return true if joinMe known to be done
1533		*/
1534	<	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1534	>	final boolean preJoin(ForkJoinTask<?> joinMe,
1535	>	boolean maintainParallelism) {
1536		maintainParallelism &= maintainsParallelism; // overrride
1537		boolean dec = false;  // true when running count decremented
1538		while (spareStack == null || !tryResumeSpare(dec)) {
1539		int counts = workerCounts;
1540	<	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1540	>	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1541	>	// CAS cheat
1542		if (!needSpare(counts, maintainParallelism))
1543		break;
1544		if (joinMe.status < 0)
#	Line 1410 | Line 1553 | public class ForkJoinPool extends Abstra
1553		/**
1554		* Same idea as preJoin
1555		*/
1556	<	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1556	>	final boolean preBlock(ManagedBlocker blocker,
1557	>	boolean maintainParallelism) {
1558		maintainParallelism &= maintainsParallelism;
1559		boolean dec = false;
1560		while (spareStack == null || !tryResumeSpare(dec)) {
#	Line 1434 | Line 1578 | public class ForkJoinPool extends Abstra
1578		* there is apparently some work to do.  This self-limiting rule
1579		* means that the more threads that have already been added, the
1580		* less parallelism we will tolerate before adding another.
1581	+	*
1582		* @param counts current worker counts
1583		* @param maintainParallelism try to maintain parallelism
1584		*/
#	Line 1451 | Line 1596 | public class ForkJoinPool extends Abstra
1596		}
1597
1598		/**
1599	<	* Add a spare worker if lock available and no more than the
1600	<	* expected numbers of threads exist
1599	>	* Adds a spare worker if lock available and no more than the
1600	>	* expected numbers of threads exist.
1601	>	*
1602		* @return true if successful
1603		*/
1604		private boolean tryAddSpare(int expectedCounts) {
#	Line 1485 | Line 1631 | public class ForkJoinPool extends Abstra
1631		}
1632
1633		/**
1634	<	* Add the kth spare worker. On entry, pool coounts are already
1634	>	* Adds the kth spare worker. On entry, pool counts are already
1635		* adjusted to reflect addition.
1636		*/
1637		private void createAndStartSpare(int k) {
#	Line 1507 | Line 1653 | public class ForkJoinPool extends Abstra
1653		}
1654
1655		/**
1656	<	* Suspend calling thread w if there are excess threads.  Called
1657	<	* only from sync.  Spares are enqueued in a Treiber stack
1658	<	* using the same WaitQueueNodes as barriers.  They are resumed
1659	<	* mainly in preJoin, but are also woken on pool events that
1660	<	* require all threads to check run state.
1656	>	* Suspends calling thread w if there are excess threads.  Called
1657	>	* only from sync.  Spares are enqueued in a Treiber stack using
1658	>	* the same WaitQueueNodes as barriers.  They are resumed mainly
1659	>	* in preJoin, but are also woken on pool events that require all
1660	>	* threads to check run state.
1661	>	*
1662		* @param w the caller
1663		*/
1664		private boolean suspendIfSpare(ForkJoinWorkerThread w) {
#	Line 1522 | Line 1669 | public class ForkJoinPool extends Abstra
1669		node = new WaitQueueNode(0, w);
1670		if (casWorkerCounts(s, s-1)) { // representation-dependent
1671		// push onto stack
1672	<	do;while (!casSpareStack(node.next = spareStack, node));
1672	>	do {} while (!casSpareStack(node.next = spareStack, node));
1673		// block until released by resumeSpare
1674		node.awaitSpareRelease();
1675		return true;
#	Line 1532 | Line 1679 | public class ForkJoinPool extends Abstra
1679		}
1680
1681		/**
1682	<	* Try to pop and resume a spare thread.
1682	>	* Tries to pop and resume a spare thread.
1683	>	*
1684		* @param updateCount if true, increment running count on success
1685		* @return true if successful
1686		*/
#	Line 1550 | Line 1698 | public class ForkJoinPool extends Abstra
1698		}
1699
1700		/**
1701	<	* Pop and resume all spare threads. Same idea as ensureSync.
1701	>	* Pops and resumes all spare threads. Same idea as ensureSync.
1702	>	*
1703		* @return true if any spares released
1704		*/
1705		private boolean resumeAllSpares() {
#	Line 1568 | Line 1717 | public class ForkJoinPool extends Abstra
1717		}
1718
1719		/**
1720	<	* Pop and shutdown excessive spare threads. Call only while
1720	>	* Pops and shuts down excessive spare threads. Call only while
1721		* holding lock. This is not guaranteed to eliminate all excess
1722		* threads, only those suspended as spares, which are the ones
1723		* unlikely to be needed in the future.
#	Line 1593 | Line 1742 | public class ForkJoinPool extends Abstra
1742		/**
1743		* Interface for extending managed parallelism for tasks running
1744		* in ForkJoinPools. A ManagedBlocker provides two methods.
1745	<	* Method <code>isReleasable</code> must return true if blocking is not
1746	<	* necessary. Method <code>block</code> blocks the current thread
1747	<	* if necessary (perhaps internally invoking isReleasable before
1748	<	* actually blocking.).
1745	>	* Method {@code isReleasable} must return true if blocking is not
1746	>	* necessary. Method {@code block} blocks the current thread if
1747	>	* necessary (perhaps internally invoking {@code isReleasable}
1748	>	* before actually blocking.).
1749	>	*
1750		* <p>For example, here is a ManagedBlocker based on a
1751		* ReentrantLock:
1752	<	* <pre>
1753	<	*   class ManagedLocker implements ManagedBlocker {
1754	<	*     final ReentrantLock lock;
1755	<	*     boolean hasLock = false;
1756	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1757	<	*     public boolean block() {
1758	<	*        if (!hasLock)
1759	<	*           lock.lock();
1760	<	*        return true;
1761	<	*     }
1762	<	*     public boolean isReleasable() {
1763	<	*        return hasLock || (hasLock = lock.tryLock());
1614	<	*     }
1752	>	*  <pre> {@code
1753	>	* class ManagedLocker implements ManagedBlocker {
1754	>	*   final ReentrantLock lock;
1755	>	*   boolean hasLock = false;
1756	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1757	>	*   public boolean block() {
1758	>	*     if (!hasLock)
1759	>	*       lock.lock();
1760	>	*     return true;
1761	>	*   }
1762	>	*   public boolean isReleasable() {
1763	>	*     return hasLock || (hasLock = lock.tryLock());
1764		*   }
1765	<	* </pre>
1765	>	* }}</pre>
1766		*/
1767		public static interface ManagedBlocker {
1768		/**
1769		* Possibly blocks the current thread, for example waiting for
1770		* a lock or condition.
1771	+	*
1772		* @return true if no additional blocking is necessary (i.e.,
1773	<	* if isReleasable would return true).
1773	>	* if isReleasable would return true)
1774		* @throws InterruptedException if interrupted while waiting
1775	<	* (the method is not required to do so, but is allowe to).
1775	>	* (the method is not required to do so, but is allowed to)
1776		*/
1777		boolean block() throws InterruptedException;
1778
#	Line 1637 | Line 1787 | public class ForkJoinPool extends Abstra
1787		* is a ForkJoinWorkerThread, this method possibly arranges for a
1788		* spare thread to be activated if necessary to ensure parallelism
1789		* while the current thread is blocked.  If
1790	<	* <code>maintainParallelism</code> is true and the pool supports
1790	>	* {@code maintainParallelism} is true and the pool supports
1791		* it ({@link #getMaintainsParallelism}), this method attempts to
1792	<	* maintain the pool's nominal parallelism. Otherwise if activates
1792	>	* maintain the pool's nominal parallelism. Otherwise it activates
1793		* a thread only if necessary to avoid complete starvation. This
1794		* option may be preferable when blockages use timeouts, or are
1795		* almost always brief.
1796		*
1797		* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1798		* equivalent to
1799	<	* <pre>
1800	<	*   while (!blocker.isReleasable())
1801	<	*      if (blocker.block())
1802	<	*         return;
1803	<	* </pre>
1799	>	*  <pre> {@code
1800	>	* while (!blocker.isReleasable())
1801	>	*   if (blocker.block())
1802	>	*     return;
1803	>	* }</pre>
1804		* If the caller is a ForkJoinTask, then the pool may first
1805		* be expanded to ensure parallelism, and later adjusted.
1806		*
#	Line 1659 | Line 1809 | public class ForkJoinPool extends Abstra
1809		* attempt to maintain the pool's nominal parallelism; otherwise
1810		* activate a thread only if necessary to avoid complete
1811		* starvation.
1812	<	* @throws InterruptedException if blocker.block did so.
1812	>	* @throws InterruptedException if blocker.block did so
1813		*/
1814		public static void managedBlock(ManagedBlocker blocker,
1815		boolean maintainParallelism)
1816		throws InterruptedException {
1817		Thread t = Thread.currentThread();
1818	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1819	<	((ForkJoinWorkerThread)t).pool : null);
1818	>	ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ?
1819	>	((ForkJoinWorkerThread) t).pool : null);
1820		if (!blocker.isReleasable()) {
1821		try {
1822		if (pool == null ||
#	Line 1681 | Line 1831 | public class ForkJoinPool extends Abstra
1831
1832		private static void awaitBlocker(ManagedBlocker blocker)
1833		throws InterruptedException {
1834	<	do;while (!blocker.isReleasable() && !blocker.block());
1834	>	do {} while (!blocker.isReleasable() && !blocker.block());
1835		}
1836
1837		// AbstractExecutorService overrides
1838
1839		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1840	<	return new AdaptedRunnable(runnable, value);
1840	>	return new AdaptedRunnable<T>(runnable, value);
1841		}
1842
1843		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1844	<	return new AdaptedCallable(callable);
1844	>	return new AdaptedCallable<T>(callable);
1845		}
1846
1847
#	Line 1721 | Line 1871 | public class ForkJoinPool extends Abstra
1871
1872		private static long fieldOffset(String fieldName)
1873		throws NoSuchFieldException {
1874	<	return _unsafe.objectFieldOffset
1874	>	return UNSAFE.objectFieldOffset
1875		(ForkJoinPool.class.getDeclaredField(fieldName));
1876		}
1877
1878	<	static final Unsafe _unsafe;
1878	>	static final Unsafe UNSAFE;
1879		static final long eventCountOffset;
1880		static final long workerCountsOffset;
1881		static final long runControlOffset;
#	Line 1734 | Line 1884 | public class ForkJoinPool extends Abstra
1884
1885		static {
1886		try {
1887	<	_unsafe = getUnsafe();
1887	>	UNSAFE = getUnsafe();
1888		eventCountOffset = fieldOffset("eventCount");
1889		workerCountsOffset = fieldOffset("workerCounts");
1890		runControlOffset = fieldOffset("runControl");
#	Line 1746 | Line 1896 | public class ForkJoinPool extends Abstra
1896		}
1897
1898		private boolean casEventCount(long cmp, long val) {
1899	<	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1899	>	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
1900		}
1901		private boolean casWorkerCounts(int cmp, int val) {
1902	<	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1902	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1903		}
1904		private boolean casRunControl(int cmp, int val) {
1905	<	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1905	>	return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
1906		}
1907		private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1908	<	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1908	>	return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
1909		}
1910		private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1911	<	return _unsafe.compareAndSwapObject(this, syncStackOffset, cmp, val);
1911	>	return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1912		}
1913		}

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