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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.3 by dl, Wed Jan 7 19:12:36 2009 UTC vs.
Revision 1.22 by jsr166, Sat Jul 25 00:34:00 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
#	Line 27 | Line 34 | import java.lang.reflect.*;
34		* (eventually blocking if none exist). This makes them efficient when
35		* most tasks spawn other subtasks (as do most ForkJoinTasks), as well
36		* as the mixed execution of some plain Runnable- or Callable- based
37	<	* activities along with ForkJoinTasks. Otherwise, other
37	>	* activities along with ForkJoinTasks. When setting
38	>	* {@code setAsyncMode}, a ForkJoinPools may also be appropriate for
39	>	* use with fine-grained tasks that are never joined. Otherwise, other
40		* ExecutorService implementations are typically more appropriate
41		* choices.
42		*
#	Line 36 | Line 45 | import java.lang.reflect.*;
45		* adding, suspending, or resuming threads, even if some tasks are
46		* waiting to join others. However, no such adjustments are performed
47		* in the face of blocked IO or other unmanaged synchronization. The
48	<	* nested <code>ManagedBlocker</code> interface enables extension of
48	>	* nested {@code ManagedBlocker} interface enables extension of
49		* the kinds of synchronization accommodated.  The target parallelism
50	<	* level may also be changed dynamically (<code>setParallelism</code>)
51	<	* and dynamically thread construction can be limited using methods
52	<	* <code>setMaximumPoolSize</code> and/or
53	<	* <code>setMaintainsParallelism</code>.
50	>	* level may also be changed dynamically ({@code setParallelism})
51	>	* and thread construction can be limited using methods
52	>	* {@code setMaximumPoolSize} and/or
53	>	* {@code setMaintainsParallelism}.
54		*
55		* <p>In addition to execution and lifecycle control methods, this
56		* class provides status check methods (for example
57	<	* <code>getStealCount</code>) that are intended to aid in developing,
57	>	* {@code getStealCount}) that are intended to aid in developing,
58		* tuning, and monitoring fork/join applications. Also, method
59	<	* <code>toString</code> returns indications of pool state in a
59	>	* {@code toString} returns indications of pool state in a
60		* convenient form for informal monitoring.
61		*
62		* <p><b>Implementation notes</b>: This implementation restricts the
63		* maximum number of running threads to 32767. Attempts to create
64		* pools with greater than the maximum result in
65		* IllegalArgumentExceptions.
66	+	*
67	+	* @since 1.7
68	+	* @author Doug Lea
69		*/
70		public class ForkJoinPool extends AbstractExecutorService {
71
#	Line 79 | Line 91 | public class ForkJoinPool extends Abstra
91		* Returns a new worker thread operating in the given pool.
92		*
93		* @param pool the pool this thread works in
94	<	* @throws NullPointerException if pool is null;
94	>	* @throws NullPointerException if pool is null
95		*/
96		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
97		}
98
99		/**
100	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
100	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
101		* new ForkJoinWorkerThread.
102		*/
103		static class  DefaultForkJoinWorkerThreadFactory
#	Line 131 | Line 143 | public class ForkJoinPool extends Abstra
143		new AtomicInteger();
144
145		/**
146	<	* Array holding all worker threads in the pool. Array size must
147	<	* be a power of two.  Updates and replacements are protected by
148	<	* workerLock, but it is always kept in a consistent enough state
149	<	* to be randomly accessed without locking by workers performing
150	<	* work-stealing.
146	>	* Array holding all worker threads in the pool. Initialized upon
147	>	* first use. Array size must be a power of two.  Updates and
148	>	* replacements are protected by workerLock, but it is always kept
149	>	* in a consistent enough state to be randomly accessed without
150	>	* locking by workers performing work-stealing.
151		*/
152		volatile ForkJoinWorkerThread[] workers;
153
#	Line 151 | Line 163 | public class ForkJoinPool extends Abstra
163
164		/**
165		* The uncaught exception handler used when any worker
166	<	* abrupty terminates
166	>	* abruptly terminates
167		*/
168		private Thread.UncaughtExceptionHandler ueh;
169
#	Line 179 | Line 191 | public class ForkJoinPool extends Abstra
191		private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
192
193		/**
194	<	* Head of Treiber stack for barrier sync. See below for explanation
194	>	* Head of Treiber stack for barrier sync. See below for explanation.
195		*/
196	<	private volatile WaitQueueNode barrierStack;
196	>	private volatile WaitQueueNode syncStack;
197
198		/**
199		* The count for event barrier
#	Line 204 | Line 216 | public class ForkJoinPool extends Abstra
216		private volatile int parallelism;
217
218		/**
219	+	* True if use local fifo, not default lifo, for local polling
220	+	*/
221	+	private volatile boolean locallyFifo;
222	+
223	+	/**
224		* Holds number of total (i.e., created and not yet terminated)
225		* and running (i.e., not blocked on joins or other managed sync)
226		* threads, packed into one int to ensure consistent snapshot when
227		* making decisions about creating and suspending spare
228		* threads. Updated only by CAS.  Note: CASes in
229	<	* updateRunningCount and preJoin running active count is in low
230	<	* word, so need to be modified if this changes
229	>	* updateRunningCount and preJoin assume that running active count
230	>	* is in low word, so need to be modified if this changes.
231		*/
232		private volatile int workerCounts;
233
#	Line 219 | Line 236 | public class ForkJoinPool extends Abstra
236		private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
237
238		/**
239	<	* Add delta (which may be negative) to running count.  This must
239	>	* Adds delta (which may be negative) to running count.  This must
240		* be called before (with negative arg) and after (with positive)
241	<	* any managed synchronization (i.e., mainly, joins)
241	>	* any managed synchronization (i.e., mainly, joins).
242	>	*
243		* @param delta the number to add
244		*/
245		final void updateRunningCount(int delta) {
246		int s;
247	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
247	>	do {} while (!casWorkerCounts(s = workerCounts, s + delta));
248		}
249
250		/**
251	<	* Add delta (which may be negative) to both total and running
251	>	* Adds delta (which may be negative) to both total and running
252		* count.  This must be called upon creation and termination of
253		* worker threads.
254	+	*
255		* @param delta the number to add
256		*/
257		private void updateWorkerCount(int delta) {
258		int d = delta + (delta << 16); // add to both lo and hi parts
259		int s;
260	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
260	>	do {} while (!casWorkerCounts(s = workerCounts, s + d));
261		}
262
263		/**
#	Line 264 | Line 283 | public class ForkJoinPool extends Abstra
283		private static int runControlFor(int r, int a)   { return (r << 16) + a; }
284
285		/**
286	<	* Increment active count. Called by workers before/during
287	<	* executing tasks.
286	>	* Tries incrementing active count; fails on contention.
287	>	* Called by workers before/during executing tasks.
288	>	*
289	>	* @return true on success
290		*/
291	<	final void incrementActiveCount() {
292	<	int c;
293	<	do;while (!casRunControl(c = runControl, c+1));
291	>	final boolean tryIncrementActiveCount() {
292	>	int c = runControl;
293	>	return casRunControl(c, c+1);
294		}
295
296		/**
297	<	* Decrement active count; possibly trigger termination.
297	>	* Tries decrementing active count; fails on contention.
298	>	* Possibly triggers termination on success.
299		* Called by workers when they can't find tasks.
300	+	*
301	+	* @return true on success
302		*/
303	<	final void decrementActiveCount() {
304	<	int c, nextc;
305	<	do;while (!casRunControl(c = runControl, nextc = c-1));
303	>	final boolean tryDecrementActiveCount() {
304	>	int c = runControl;
305	>	int nextc = c - 1;
306	>	if (!casRunControl(c, nextc))
307	>	return false;
308		if (canTerminateOnShutdown(nextc))
309		terminateOnShutdown();
310	+	return true;
311		}
312
313		/**
314	<	* Return true if argument represents zero active count and
314	>	* Returns true if argument represents zero active count and
315		* nonzero runstate, which is the triggering condition for
316		* terminating on shutdown.
317		*/
318		private static boolean canTerminateOnShutdown(int c) {
319	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
319	>	// i.e. least bit is nonzero runState bit
320	>	return ((c & -c) >>> 16) != 0;
321		}
322
323		/**
#	Line 315 | Line 343 | public class ForkJoinPool extends Abstra
343
344		/**
345		* Creates a ForkJoinPool with a pool size equal to the number of
346	<	* processors available on the system and using the default
347	<	* ForkJoinWorkerThreadFactory,
346	>	* processors available on the system, using the default
347	>	* ForkJoinWorkerThreadFactory.
348	>	*
349		* @throws SecurityException if a security manager exists and
350		*         the caller is not permitted to modify threads
351		*         because it does not hold {@link
352	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
352	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
353		*/
354		public ForkJoinPool() {
355		this(Runtime.getRuntime().availableProcessors(),
#	Line 328 | Line 357 | public class ForkJoinPool extends Abstra
357		}
358
359		/**
360	<	* Creates a ForkJoinPool with the indicated parellelism level
361	<	* threads, and using the default ForkJoinWorkerThreadFactory,
360	>	* Creates a ForkJoinPool with the indicated parallelism level
361	>	* threads and using the default ForkJoinWorkerThreadFactory.
362	>	*
363		* @param parallelism the number of worker threads
364		* @throws IllegalArgumentException if parallelism less than or
365		* equal to zero
366		* @throws SecurityException if a security manager exists and
367		*         the caller is not permitted to modify threads
368		*         because it does not hold {@link
369	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
369	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
370		*/
371		public ForkJoinPool(int parallelism) {
372		this(parallelism, defaultForkJoinWorkerThreadFactory);
#	Line 345 | Line 375 | public class ForkJoinPool extends Abstra
375		/**
376		* Creates a ForkJoinPool with parallelism equal to the number of
377		* processors available on the system and using the given
378	<	* ForkJoinWorkerThreadFactory,
378	>	* ForkJoinWorkerThreadFactory.
379	>	*
380		* @param factory the factory for creating new threads
381		* @throws NullPointerException if factory is null
382		* @throws SecurityException if a security manager exists and
383		*         the caller is not permitted to modify threads
384		*         because it does not hold {@link
385	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
385	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
386		*/
387		public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
388		this(Runtime.getRuntime().availableProcessors(), factory);
#	Line 363 | Line 394 | public class ForkJoinPool extends Abstra
394		* @param parallelism the targeted number of worker threads
395		* @param factory the factory for creating new threads
396		* @throws IllegalArgumentException if parallelism less than or
397	<	* equal to zero, or greater than implementation limit.
397	>	* equal to zero, or greater than implementation limit
398		* @throws NullPointerException if factory is null
399		* @throws SecurityException if a security manager exists and
400		*         the caller is not permitted to modify threads
401		*         because it does not hold {@link
402	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
402	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
403		*/
404		public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
405		if (parallelism <= 0 || parallelism > MAX_THREADS)
#	Line 385 | Line 416 | public class ForkJoinPool extends Abstra
416		this.termination = workerLock.newCondition();
417		this.stealCount = new AtomicLong();
418		this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
419	<	createAndStartInitialWorkers(parallelism);
419	>	// worker array and workers are lazily constructed
420		}
421
422		/**
423	<	* Create new worker using factory.
423	>	* Creates a new worker thread using factory.
424	>	*
425		* @param index the index to assign worker
426		* @return new worker, or null of factory failed
427		*/
#	Line 399 | Line 431 | public class ForkJoinPool extends Abstra
431		if (w != null) {
432		w.poolIndex = index;
433		w.setDaemon(true);
434	+	w.setAsyncMode(locallyFifo);
435		w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
436		if (h != null)
437		w.setUncaughtExceptionHandler(h);
#	Line 407 | Line 440 | public class ForkJoinPool extends Abstra
440		}
441
442		/**
443	<	* Return a good size for worker array given pool size.
443	>	* Returns a good size for worker array given pool size.
444		* Currently requires size to be a power of two.
445		*/
446	<	private static int arraySizeFor(int ps) {
447	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
446	>	private static int arraySizeFor(int poolSize) {
447	>	return (poolSize <= 1) ? 1 :
448	>	(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1)));
449		}
450
451		/**
452	<	* Create or resize array if necessary to hold newLength
452	>	* Creates or resizes array if necessary to hold newLength.
453	>	* Call only under exclusion.
454	>	*
455		* @return the array
456		*/
457		private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
#	Line 429 | Line 465 | public class ForkJoinPool extends Abstra
465		}
466
467		/**
468	<	* Try to shrink workers into smaller array after one or more terminate
468	>	* Tries to shrink workers into smaller array after one or more terminate.
469		*/
470		private void tryShrinkWorkerArray() {
471		ForkJoinWorkerThread[] ws = workers;
472	<	int len = ws.length;
473	<	int last = len - 1;
474	<	while (last >= 0 && ws[last] == null)
475	<	--last;
476	<	int newLength = arraySizeFor(last+1);
477	<	if (newLength < len)
478	<	workers = Arrays.copyOf(ws, newLength);
472	>	if (ws != null) {
473	>	int len = ws.length;
474	>	int last = len - 1;
475	>	while (last >= 0 && ws[last] == null)
476	>	--last;
477	>	int newLength = arraySizeFor(last+1);
478	>	if (newLength < len)
479	>	workers = Arrays.copyOf(ws, newLength);
480	>	}
481		}
482
483		/**
484	<	* Initial worker array and worker creation and startup. (This
447	<	* must be done under lock to avoid interference by some of the
448	<	* newly started threads while creating others.)
484	>	* Initializes workers if necessary.
485		*/
486	<	private void createAndStartInitialWorkers(int ps) {
487	<	final ReentrantLock lock = this.workerLock;
488	<	lock.lock();
489	<	try {
490	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
491	<	for (int i = 0; i < ps; ++i) {
492	<	ForkJoinWorkerThread w = createWorker(i);
493	<	if (w != null) {
494	<	ws[i] = w;
495	<	w.start();
496	<	updateWorkerCount(1);
486	>	final void ensureWorkerInitialization() {
487	>	ForkJoinWorkerThread[] ws = workers;
488	>	if (ws == null) {
489	>	final ReentrantLock lock = this.workerLock;
490	>	lock.lock();
491	>	try {
492	>	ws = workers;
493	>	if (ws == null) {
494	>	int ps = parallelism;
495	>	ws = ensureWorkerArrayCapacity(ps);
496	>	for (int i = 0; i < ps; ++i) {
497	>	ForkJoinWorkerThread w = createWorker(i);
498	>	if (w != null) {
499	>	ws[i] = w;
500	>	w.start();
501	>	updateWorkerCount(1);
502	>	}
503	>	}
504		}
505	+	} finally {
506	+	lock.unlock();
507		}
463	–	} finally {
464	–	lock.unlock();
508		}
509		}
510
#	Line 507 | Line 550 | public class ForkJoinPool extends Abstra
550		private <T> void doSubmit(ForkJoinTask<T> task) {
551		if (isShutdown())
552		throw new RejectedExecutionException();
553	+	if (workers == null)
554	+	ensureWorkerInitialization();
555		submissionQueue.offer(task);
556	<	signalIdleWorkers(true);
556	>	signalIdleWorkers();
557		}
558
559		/**
560	<	* Performs the given task; returning its result upon completion
560	>	* Performs the given task, returning its result upon completion.
561	>	*
562		* @param task the task
563		* @return the task's result
564		* @throws NullPointerException if task is null
#	Line 525 | Line 571 | public class ForkJoinPool extends Abstra
571
572		/**
573		* Arranges for (asynchronous) execution of the given task.
574	+	*
575		* @param task the task
576		* @throws NullPointerException if task is null
577		* @throws RejectedExecutionException if pool is shut down
#	Line 559 | Line 606 | public class ForkJoinPool extends Abstra
606
607		/**
608		* Adaptor for Runnables. This implements RunnableFuture
609	<	* to be compliant with AbstractExecutorService constraints
609	>	* to be compliant with AbstractExecutorService constraints.
610		*/
611		static final class AdaptedRunnable<T> extends ForkJoinTask<T>
612		implements RunnableFuture<T> {
#	Line 579 | Line 626 | public class ForkJoinPool extends Abstra
626		return true;
627		}
628		public void run() { invoke(); }
629	+	private static final long serialVersionUID = 5232453952276885070L;
630		}
631
632		/**
#	Line 607 | Line 655 | public class ForkJoinPool extends Abstra
655		}
656		}
657		public void run() { invoke(); }
658	+	private static final long serialVersionUID = 2838392045355241008L;
659		}
660
661		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
662	<	ArrayList<ForkJoinTask<T>> ts =
662	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
663		new ArrayList<ForkJoinTask<T>>(tasks.size());
664	<	for (Callable<T> c : tasks)
665	<	ts.add(new AdaptedCallable<T>(c));
666	<	invoke(new InvokeAll<T>(ts));
667	<	return (List<Future<T>>)(List)ts;
664	>	for (Callable<T> task : tasks)
665	>	forkJoinTasks.add(new AdaptedCallable<T>(task));
666	>	invoke(new InvokeAll<T>(forkJoinTasks));
667	>
668	>	@SuppressWarnings({"unchecked", "rawtypes"})
669	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
670	>	return futures;
671		}
672
673		static final class InvokeAll<T> extends RecursiveAction {
674		final ArrayList<ForkJoinTask<T>> tasks;
675		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
676		public void compute() {
677	<	try { invokeAll(tasks); } catch(Exception ignore) {}
677	>	try { invokeAll(tasks); }
678	>	catch (Exception ignore) {}
679		}
680	+	private static final long serialVersionUID = -7914297376763021607L;
681		}
682
683		// Configuration and status settings and queries
684
685		/**
686	<	* Returns the factory used for constructing new workers
686	>	* Returns the factory used for constructing new workers.
687		*
688		* @return the factory used for constructing new workers
689		*/
#	Line 640 | Line 694 | public class ForkJoinPool extends Abstra
694		/**
695		* Returns the handler for internal worker threads that terminate
696		* due to unrecoverable errors encountered while executing tasks.
697	+	*
698		* @return the handler, or null if none
699		*/
700		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
#	Line 665 | Line 720 | public class ForkJoinPool extends Abstra
720		* @throws SecurityException if a security manager exists and
721		*         the caller is not permitted to modify threads
722		*         because it does not hold {@link
723	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
723	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
724		*/
725		public Thread.UncaughtExceptionHandler
726		setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
#	Line 677 | Line 732 | public class ForkJoinPool extends Abstra
732		old = ueh;
733		ueh = h;
734		ForkJoinWorkerThread[] ws = workers;
735	<	for (int i = 0; i < ws.length; ++i) {
736	<	ForkJoinWorkerThread w = ws[i];
737	<	if (w != null)
738	<	w.setUncaughtExceptionHandler(h);
735	>	if (ws != null) {
736	>	for (int i = 0; i < ws.length; ++i) {
737	>	ForkJoinWorkerThread w = ws[i];
738	>	if (w != null)
739	>	w.setUncaughtExceptionHandler(h);
740	>	}
741		}
742		} finally {
743		lock.unlock();
#	Line 690 | Line 747 | public class ForkJoinPool extends Abstra
747
748
749		/**
750	<	* Sets the target paralleism level of this pool.
750	>	* Sets the target parallelism level of this pool.
751	>	*
752		* @param parallelism the target parallelism
753		* @throws IllegalArgumentException if parallelism less than or
754	<	* equal to zero or greater than maximum size bounds.
754	>	* equal to zero or greater than maximum size bounds
755		* @throws SecurityException if a security manager exists and
756		*         the caller is not permitted to modify threads
757		*         because it does not hold {@link
758	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
758	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
759		*/
760		public void setParallelism(int parallelism) {
761		checkPermission();
#	Line 717 | Line 775 | public class ForkJoinPool extends Abstra
775		} finally {
776		lock.unlock();
777		}
778	<	signalIdleWorkers(false);
778	>	signalIdleWorkers();
779		}
780
781		/**
#	Line 732 | Line 790 | public class ForkJoinPool extends Abstra
790		/**
791		* Returns the number of worker threads that have started but not
792		* yet terminated.  This result returned by this method may differ
793	<	* from <code>getParallelism</code> when threads are created to
793	>	* from {@code getParallelism} when threads are created to
794		* maintain parallelism when others are cooperatively blocked.
795		*
796		* @return the number of worker threads
#	Line 744 | Line 802 | public class ForkJoinPool extends Abstra
802		/**
803		* Returns the maximum number of threads allowed to exist in the
804		* pool, even if there are insufficient unblocked running threads.
805	+	*
806		* @return the maximum
807		*/
808		public int getMaximumPoolSize() {
#	Line 755 | Line 814 | public class ForkJoinPool extends Abstra
814		* pool, even if there are insufficient unblocked running threads.
815		* Setting this value has no effect on current pool size. It
816		* controls construction of new threads.
817	+	*
818		* @throws IllegalArgumentException if negative or greater then
819	<	* internal implementation limit.
819	>	* internal implementation limit
820		*/
821		public void setMaximumPoolSize(int newMax) {
822		if (newMax < 0 || newMax > MAX_THREADS)
#	Line 769 | Line 829 | public class ForkJoinPool extends Abstra
829		* Returns true if this pool dynamically maintains its target
830		* parallelism level. If false, new threads are added only to
831		* avoid possible starvation.
832	<	* This setting is by default true;
832	>	* This setting is by default true.
833	>	*
834		* @return true if maintains parallelism
835		*/
836		public boolean getMaintainsParallelism() {
#	Line 780 | Line 841 | public class ForkJoinPool extends Abstra
841		* Sets whether this pool dynamically maintains its target
842		* parallelism level. If false, new threads are added only to
843		* avoid possible starvation.
844	+	*
845		* @param enable true to maintains parallelism
846		*/
847		public void setMaintainsParallelism(boolean enable) {
#	Line 787 | Line 849 | public class ForkJoinPool extends Abstra
849		}
850
851		/**
852	+	* Establishes local first-in-first-out scheduling mode for forked
853	+	* tasks that are never joined. This mode may be more appropriate
854	+	* than default locally stack-based mode in applications in which
855	+	* worker threads only process asynchronous tasks.  This method is
856	+	* designed to be invoked only when pool is quiescent, and
857	+	* typically only before any tasks are submitted. The effects of
858	+	* invocations at other times may be unpredictable.
859	+	*
860	+	* @param async if true, use locally FIFO scheduling
861	+	* @return the previous mode
862	+	*/
863	+	public boolean setAsyncMode(boolean async) {
864	+	boolean oldMode = locallyFifo;
865	+	locallyFifo = async;
866	+	ForkJoinWorkerThread[] ws = workers;
867	+	if (ws != null) {
868	+	for (int i = 0; i < ws.length; ++i) {
869	+	ForkJoinWorkerThread t = ws[i];
870	+	if (t != null)
871	+	t.setAsyncMode(async);
872	+	}
873	+	}
874	+	return oldMode;
875	+	}
876	+
877	+	/**
878	+	* Returns true if this pool uses local first-in-first-out
879	+	* scheduling mode for forked tasks that are never joined.
880	+	*
881	+	* @return true if this pool uses async mode
882	+	*/
883	+	public boolean getAsyncMode() {
884	+	return locallyFifo;
885	+	}
886	+
887	+	/**
888		* Returns an estimate of the number of worker threads that are
889		* not blocked waiting to join tasks or for other managed
890		* synchronization.
#	Line 801 | Line 899 | public class ForkJoinPool extends Abstra
899		* Returns an estimate of the number of threads that are currently
900		* stealing or executing tasks. This method may overestimate the
901		* number of active threads.
902	<	* @return the number of active threads.
902	>	*
903	>	* @return the number of active threads
904		*/
905		public int getActiveThreadCount() {
906		return activeCountOf(runControl);
#	Line 811 | Line 910 | public class ForkJoinPool extends Abstra
910		* Returns an estimate of the number of threads that are currently
911		* idle waiting for tasks. This method may underestimate the
912		* number of idle threads.
913	<	* @return the number of idle threads.
913	>	*
914	>	* @return the number of idle threads
915		*/
916		final int getIdleThreadCount() {
917		int c = runningCountOf(workerCounts) - activeCountOf(runControl);
918	<	return (c <= 0)? 0 : c;
918	>	return (c <= 0) ? 0 : c;
919		}
920
921		/**
922		* Returns true if all worker threads are currently idle. An idle
923		* worker is one that cannot obtain a task to execute because none
924		* are available to steal from other threads, and there are no
925	<	* pending submissions to the pool. This method is conservative:
926	<	* It might not return true immediately upon idleness of all
925	>	* pending submissions to the pool. This method is conservative;
926	>	* it might not return true immediately upon idleness of all
927		* threads, but will eventually become true if threads remain
928		* inactive.
929	+	*
930		* @return true if all threads are currently idle
931		*/
932		public boolean isQuiescent() {
#	Line 837 | Line 938 | public class ForkJoinPool extends Abstra
938		* one thread's work queue by another. The reported value
939		* underestimates the actual total number of steals when the pool
940		* is not quiescent. This value may be useful for monitoring and
941	<	* tuning fork/join programs: In general, steal counts should be
941	>	* tuning fork/join programs: in general, steal counts should be
942		* high enough to keep threads busy, but low enough to avoid
943		* overhead and contention across threads.
944	<	* @return the number of steals.
944	>	*
945	>	* @return the number of steals
946		*/
947		public long getStealCount() {
948		return stealCount.get();
949		}
950
951		/**
952	<	* Accumulate steal count from a worker. Call only
953	<	* when worker known to be idle.
952	>	* Accumulates steal count from a worker.
953	>	* Call only when worker known to be idle.
954		*/
955		private void updateStealCount(ForkJoinWorkerThread w) {
956		int sc = w.getAndClearStealCount();
#	Line 863 | Line 965 | public class ForkJoinPool extends Abstra
965		* an approximation, obtained by iterating across all threads in
966		* the pool. This method may be useful for tuning task
967		* granularities.
968	<	* @return the number of queued tasks.
968	>	*
969	>	* @return the number of queued tasks
970		*/
971		public long getQueuedTaskCount() {
972		long count = 0;
973		ForkJoinWorkerThread[] ws = workers;
974	<	for (int i = 0; i < ws.length; ++i) {
975	<	ForkJoinWorkerThread t = ws[i];
976	<	if (t != null)
977	<	count += t.getQueueSize();
974	>	if (ws != null) {
975	>	for (int i = 0; i < ws.length; ++i) {
976	>	ForkJoinWorkerThread t = ws[i];
977	>	if (t != null)
978	>	count += t.getQueueSize();
979	>	}
980		}
981		return count;
982		}
#	Line 880 | Line 985 | public class ForkJoinPool extends Abstra
985		* Returns an estimate of the number tasks submitted to this pool
986		* that have not yet begun executing. This method takes time
987		* proportional to the number of submissions.
988	<	* @return the number of queued submissions.
988	>	*
989	>	* @return the number of queued submissions
990		*/
991		public int getQueuedSubmissionCount() {
992		return submissionQueue.size();
#	Line 889 | Line 995 | public class ForkJoinPool extends Abstra
995		/**
996		* Returns true if there are any tasks submitted to this pool
997		* that have not yet begun executing.
998	<	* @return <code>true</code> if there are any queued submissions.
998	>	*
999	>	* @return {@code true} if there are any queued submissions
1000		*/
1001		public boolean hasQueuedSubmissions() {
1002		return !submissionQueue.isEmpty();
#	Line 899 | Line 1006 | public class ForkJoinPool extends Abstra
1006		* Removes and returns the next unexecuted submission if one is
1007		* available.  This method may be useful in extensions to this
1008		* class that re-assign work in systems with multiple pools.
1009	+	*
1010		* @return the next submission, or null if none
1011		*/
1012		protected ForkJoinTask<?> pollSubmission() {
#	Line 906 | Line 1014 | public class ForkJoinPool extends Abstra
1014		}
1015
1016		/**
1017	+	* Removes all available unexecuted submitted and forked tasks
1018	+	* from scheduling queues and adds them to the given collection,
1019	+	* without altering their execution status. These may include
1020	+	* artificially generated or wrapped tasks. This method is designed
1021	+	* to be invoked only when the pool is known to be
1022	+	* quiescent. Invocations at other times may not remove all
1023	+	* tasks. A failure encountered while attempting to add elements
1024	+	* to collection {@code c} may result in elements being in
1025	+	* neither, either or both collections when the associated
1026	+	* exception is thrown.  The behavior of this operation is
1027	+	* undefined if the specified collection is modified while the
1028	+	* operation is in progress.
1029	+	*
1030	+	* @param c the collection to transfer elements into
1031	+	* @return the number of elements transferred
1032	+	*/
1033	+	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
1034	+	int n = submissionQueue.drainTo(c);
1035	+	ForkJoinWorkerThread[] ws = workers;
1036	+	if (ws != null) {
1037	+	for (int i = 0; i < ws.length; ++i) {
1038	+	ForkJoinWorkerThread w = ws[i];
1039	+	if (w != null)
1040	+	n += w.drainTasksTo(c);
1041	+	}
1042	+	}
1043	+	return n;
1044	+	}
1045	+
1046	+	/**
1047		* Returns a string identifying this pool, as well as its state,
1048		* including indications of run state, parallelism level, and
1049		* worker and task counts.
#	Line 949 | Line 1087 | public class ForkJoinPool extends Abstra
1087		* Invocation has no additional effect if already shut down.
1088		* Tasks that are in the process of being submitted concurrently
1089		* during the course of this method may or may not be rejected.
1090	+	*
1091		* @throws SecurityException if a security manager exists and
1092		*         the caller is not permitted to modify threads
1093		*         because it does not hold {@link
1094	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1094	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1095		*/
1096		public void shutdown() {
1097		checkPermission();
#	Line 966 | Line 1105 | public class ForkJoinPool extends Abstra
1105		* waiting tasks.  Tasks that are in the process of being
1106		* submitted or executed concurrently during the course of this
1107		* method may or may not be rejected. Unlike some other executors,
1108	<	* this method cancels rather than collects non-executed tasks,
1109	<	* so always returns an empty list.
1108	>	* this method cancels rather than collects non-executed tasks
1109	>	* upon termination, so always returns an empty list. However, you
1110	>	* can use method {@code drainTasksTo} before invoking this
1111	>	* method to transfer unexecuted tasks to another collection.
1112	>	*
1113		* @return an empty list
1114		* @throws SecurityException if a security manager exists and
1115		*         the caller is not permitted to modify threads
1116		*         because it does not hold {@link
1117	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1117	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1118		*/
1119		public List<Runnable> shutdownNow() {
1120		checkPermission();
#	Line 981 | Line 1123 | public class ForkJoinPool extends Abstra
1123		}
1124
1125		/**
1126	<	* Returns <code>true</code> if all tasks have completed following shut down.
1126	>	* Returns {@code true} if all tasks have completed following shut down.
1127		*
1128	<	* @return <code>true</code> if all tasks have completed following shut down
1128	>	* @return {@code true} if all tasks have completed following shut down
1129		*/
1130		public boolean isTerminated() {
1131		return runStateOf(runControl) == TERMINATED;
1132		}
1133
1134		/**
1135	<	* Returns <code>true</code> if the process of termination has
1135	>	* Returns {@code true} if the process of termination has
1136		* commenced but possibly not yet completed.
1137		*
1138	<	* @return <code>true</code> if terminating
1138	>	* @return {@code true} if terminating
1139		*/
1140		public boolean isTerminating() {
1141		return runStateOf(runControl) >= TERMINATING;
1142		}
1143
1144		/**
1145	<	* Returns <code>true</code> if this pool has been shut down.
1145	>	* Returns {@code true} if this pool has been shut down.
1146		*
1147	<	* @return <code>true</code> if this pool has been shut down
1147	>	* @return {@code true} if this pool has been shut down
1148		*/
1149		public boolean isShutdown() {
1150		return runStateOf(runControl) >= SHUTDOWN;
#	Line 1015 | Line 1157 | public class ForkJoinPool extends Abstra
1157		*
1158		* @param timeout the maximum time to wait
1159		* @param unit the time unit of the timeout argument
1160	<	* @return <code>true</code> if this executor terminated and
1161	<	*         <code>false</code> if the timeout elapsed before termination
1160	>	* @return {@code true} if this executor terminated and
1161	>	*         {@code false} if the timeout elapsed before termination
1162		* @throws InterruptedException if interrupted while waiting
1163		*/
1164		public boolean awaitTermination(long timeout, TimeUnit unit)
#	Line 1040 | Line 1182 | public class ForkJoinPool extends Abstra
1182		// Shutdown and termination support
1183
1184		/**
1185	<	* Callback from terminating worker. Null out the corresponding
1186	<	* workers slot, and if terminating, try to terminate, else try to
1187	<	* shrink workers array.
1185	>	* Callback from terminating worker. Nulls out the corresponding
1186	>	* workers slot, and if terminating, tries to terminate; else
1187	>	* tries to shrink workers array.
1188	>	*
1189		* @param w the worker
1190		*/
1191		final void workerTerminated(ForkJoinWorkerThread w) {
#	Line 1052 | Line 1195 | public class ForkJoinPool extends Abstra
1195		lock.lock();
1196		try {
1197		ForkJoinWorkerThread[] ws = workers;
1198	<	int idx = w.poolIndex;
1199	<	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1200	<	ws[idx] = null;
1201	<	if (totalCountOf(workerCounts) == 0) {
1202	<	terminate(); // no-op if already terminating
1203	<	transitionRunStateTo(TERMINATED);
1204	<	termination.signalAll();
1205	<	}
1206	<	else if (!isTerminating()) {
1207	<	tryShrinkWorkerArray();
1208	<	tryResumeSpare(true); // allow replacement
1198	>	if (ws != null) {
1199	>	int idx = w.poolIndex;
1200	>	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1201	>	ws[idx] = null;
1202	>	if (totalCountOf(workerCounts) == 0) {
1203	>	terminate(); // no-op if already terminating
1204	>	transitionRunStateTo(TERMINATED);
1205	>	termination.signalAll();
1206	>	}
1207	>	else if (!isTerminating()) {
1208	>	tryShrinkWorkerArray();
1209	>	tryResumeSpare(true); // allow replacement
1210	>	}
1211		}
1212		} finally {
1213		lock.unlock();
1214		}
1215	<	signalIdleWorkers(false);
1215	>	signalIdleWorkers();
1216		}
1217
1218		/**
1219	<	* Initiate termination.
1219	>	* Initiates termination.
1220		*/
1221		private void terminate() {
1222		if (transitionRunStateTo(TERMINATING)) {
1223		stopAllWorkers();
1224		resumeAllSpares();
1225	<	signalIdleWorkers(true);
1225	>	signalIdleWorkers();
1226		cancelQueuedSubmissions();
1227		cancelQueuedWorkerTasks();
1228		interruptUnterminatedWorkers();
1229	<	signalIdleWorkers(true); // resignal after interrupt
1229	>	signalIdleWorkers(); // resignal after interrupt
1230		}
1231		}
1232
1233		/**
1234	<	* Possibly terminate when on shutdown state
1234	>	* Possibly terminates when on shutdown state.
1235		*/
1236		private void terminateOnShutdown() {
1237		if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
#	Line 1094 | Line 1239 | public class ForkJoinPool extends Abstra
1239		}
1240
1241		/**
1242	<	* Clear out and cancel submissions
1242	>	* Clears out and cancels submissions.
1243		*/
1244		private void cancelQueuedSubmissions() {
1245		ForkJoinTask<?> task;
#	Line 1103 | Line 1248 | public class ForkJoinPool extends Abstra
1248		}
1249
1250		/**
1251	<	* Clean out worker queues.
1251	>	* Cleans out worker queues.
1252		*/
1253		private void cancelQueuedWorkerTasks() {
1254		final ReentrantLock lock = this.workerLock;
1255		lock.lock();
1256		try {
1257		ForkJoinWorkerThread[] ws = workers;
1258	<	for (int i = 0; i < ws.length; ++i) {
1259	<	ForkJoinWorkerThread t = ws[i];
1260	<	if (t != null)
1261	<	t.cancelTasks();
1258	>	if (ws != null) {
1259	>	for (int i = 0; i < ws.length; ++i) {
1260	>	ForkJoinWorkerThread t = ws[i];
1261	>	if (t != null)
1262	>	t.cancelTasks();
1263	>	}
1264		}
1265		} finally {
1266		lock.unlock();
#	Line 1121 | Line 1268 | public class ForkJoinPool extends Abstra
1268		}
1269
1270		/**
1271	<	* Set each worker's status to terminating. Requires lock to avoid
1272	<	* conflicts with add/remove
1271	>	* Sets each worker's status to terminating. Requires lock to avoid
1272	>	* conflicts with add/remove.
1273		*/
1274		private void stopAllWorkers() {
1275		final ReentrantLock lock = this.workerLock;
1276		lock.lock();
1277		try {
1278		ForkJoinWorkerThread[] ws = workers;
1279	<	for (int i = 0; i < ws.length; ++i) {
1280	<	ForkJoinWorkerThread t = ws[i];
1281	<	if (t != null)
1282	<	t.shutdownNow();
1279	>	if (ws != null) {
1280	>	for (int i = 0; i < ws.length; ++i) {
1281	>	ForkJoinWorkerThread t = ws[i];
1282	>	if (t != null)
1283	>	t.shutdownNow();
1284	>	}
1285		}
1286		} finally {
1287		lock.unlock();
#	Line 1140 | Line 1289 | public class ForkJoinPool extends Abstra
1289		}
1290
1291		/**
1292	<	* Interrupt all unterminated workers.  This is not required for
1292	>	* Interrupts all unterminated workers.  This is not required for
1293		* sake of internal control, but may help unstick user code during
1294		* shutdown.
1295		*/
#	Line 1149 | Line 1298 | public class ForkJoinPool extends Abstra
1298		lock.lock();
1299		try {
1300		ForkJoinWorkerThread[] ws = workers;
1301	<	for (int i = 0; i < ws.length; ++i) {
1302	<	ForkJoinWorkerThread t = ws[i];
1303	<	if (t != null && !t.isTerminated()) {
1304	<	try {
1305	<	t.interrupt();
1306	<	} catch (SecurityException ignore) {
1301	>	if (ws != null) {
1302	>	for (int i = 0; i < ws.length; ++i) {
1303	>	ForkJoinWorkerThread t = ws[i];
1304	>	if (t != null && !t.isTerminated()) {
1305	>	try {
1306	>	t.interrupt();
1307	>	} catch (SecurityException ignore) {
1308	>	}
1309		}
1310		}
1311		}
#	Line 1165 | Line 1316 | public class ForkJoinPool extends Abstra
1316
1317
1318		/*
1319	<	* Nodes for event barrier to manage idle threads.
1319	>	* Nodes for event barrier to manage idle threads.  Queue nodes
1320	>	* are basic Treiber stack nodes, also used for spare stack.
1321		*
1322		* The event barrier has an event count and a wait queue (actually
1323		* a Treiber stack).  Workers are enabled to look for work when
1324	<	* the eventCount is incremented. If they fail to find some,
1325	<	* they may wait for next count. Synchronization events occur only
1326	<	* in enough contexts to maintain overall liveness:
1324	>	* the eventCount is incremented. If they fail to find work, they
1325	>	* may wait for next count. Upon release, threads help others wake
1326	>	* up.
1327	>	*
1328	>	* Synchronization events occur only in enough contexts to
1329	>	* maintain overall liveness:
1330		*
1331		*   - Submission of a new task to the pool
1332	<	*   - Creation or termination of a worker
1332	>	*   - Resizes or other changes to the workers array
1333		*   - pool termination
1334		*   - A worker pushing a task on an empty queue
1335		*
1336	<	* The last case (pushing a task) occurs often enough, and is
1337	<	* heavy enough compared to simple stack pushes to require some
1338	<	* special handling: Method signalNonEmptyWorkerQueue returns
1339	<	* without advancing count if the queue appears to be empty.  This
1340	<	* would ordinarily result in races causing some queued waiters
1341	<	* not to be woken up. To avoid this, a worker in sync
1342	<	* rescans for tasks after being enqueued if it was the first to
1343	<	* enqueue, and aborts the wait if finding one, also helping to
1344	<	* signal others. This works well because the worker has nothing
1345	<	* better to do anyway, and so might as well help alleviate the
1346	<	* overhead and contention on the threads actually doing work.
1347	<	*
1348	<	* Queue nodes are basic Treiber stack nodes, also used for spare
1349	<	* stack.
1336	>	* The case of pushing a task occurs often enough, and is heavy
1337	>	* enough compared to simple stack pushes, to require special
1338	>	* handling: Method signalWork returns without advancing count if
1339	>	* the queue appears to be empty.  This would ordinarily result in
1340	>	* races causing some queued waiters not to be woken up. To avoid
1341	>	* this, the first worker enqueued in method sync (see
1342	>	* syncIsReleasable) rescans for tasks after being enqueued, and
1343	>	* helps signal if any are found. This works well because the
1344	>	* worker has nothing better to do, and so might as well help
1345	>	* alleviate the overhead and contention on the threads actually
1346	>	* doing work.  Also, since event counts increments on task
1347	>	* availability exist to maintain liveness (rather than to force
1348	>	* refreshes etc), it is OK for callers to exit early if
1349	>	* contending with another signaller.
1350		*/
1351		static final class WaitQueueNode {
1352		WaitQueueNode next; // only written before enqueued
1353		volatile ForkJoinWorkerThread thread; // nulled to cancel wait
1354		final long count; // unused for spare stack
1355	<	WaitQueueNode(ForkJoinWorkerThread w, long c) {
1355	>
1356	>	WaitQueueNode(long c, ForkJoinWorkerThread w) {
1357		count = c;
1358		thread = w;
1359		}
1360	<	final boolean signal() {
1360	>
1361	>	/**
1362	>	* Wakes up waiter, returning false if known to already
1363	>	*/
1364	>	boolean signal() {
1365		ForkJoinWorkerThread t = thread;
1366	+	if (t == null)
1367	+	return false;
1368		thread = null;
1369	<	if (t != null) {
1370	<	LockSupport.unpark(t);
1371	<	return true;
1369	>	LockSupport.unpark(t);
1370	>	return true;
1371	>	}
1372	>
1373	>	/**
1374	>	* Awaits release on sync.
1375	>	*/
1376	>	void awaitSyncRelease(ForkJoinPool p) {
1377	>	while (thread != null && !p.syncIsReleasable(this))
1378	>	LockSupport.park(this);
1379	>	}
1380	>
1381	>	/**
1382	>	* Awaits resumption as spare.
1383	>	*/
1384	>	void awaitSpareRelease() {
1385	>	while (thread != null) {
1386	>	if (!Thread.interrupted())
1387	>	LockSupport.park(this);
1388		}
1211	–	return false;
1389		}
1390		}
1391
1392		/**
1393	<	* Release at least one thread waiting for event count to advance,
1394	<	* if one exists. If initial attempt fails, release all threads.
1395	<	* @param all if false, at first try to only release one thread
1396	<	* @return current event
1393	>	* Ensures that no thread is waiting for count to advance from the
1394	>	* current value of eventCount read on entry to this method, by
1395	>	* releasing waiting threads if necessary.
1396	>	*
1397	>	* @return the count
1398		*/
1399	<	private long releaseIdleWorkers(boolean all) {
1400	<	long c;
1401	<	for (;;) {
1402	<	WaitQueueNode q = barrierStack;
1403	<	c = eventCount;
1226	<	long qc;
1227	<	if (q == null || (qc = q.count) >= c)
1228	<	break;
1229	<	if (!all) {
1230	<	if (casBarrierStack(q, q.next) && q.signal())
1231	<	break;
1232	<	all = true;
1233	<	}
1234	<	else if (casBarrierStack(q, null)) {
1399	>	final long ensureSync() {
1400	>	long c = eventCount;
1401	>	WaitQueueNode q;
1402	>	while ((q = syncStack) != null && q.count < c) {
1403	>	if (casBarrierStack(q, null)) {
1404		do {
1405	<	q.signal();
1405	>	q.signal();
1406		} while ((q = q.next) != null);
1407		break;
1408		}
#	Line 1242 | Line 1411 | public class ForkJoinPool extends Abstra
1411		}
1412
1413		/**
1414	<	* Returns current barrier event count
1246	<	* @return current barrier event count
1247	<	*/
1248	<	final long getEventCount() {
1249	<	long ec = eventCount;
1250	<	releaseIdleWorkers(true); // release to ensure accurate result
1251	<	return ec;
1252	<	}
1253	<
1254	<	/**
1255	<	* Increment event count and release at least one waiting thread,
1256	<	* if one exists (released threads will in turn wake up others).
1257	<	* @param all if true, try to wake up all
1414	>	* Increments event count and releases waiting threads.
1415		*/
1416	<	final void signalIdleWorkers(boolean all) {
1416	>	private void signalIdleWorkers() {
1417		long c;
1418	<	do;while (!casEventCount(c = eventCount, c+1));
1419	<	releaseIdleWorkers(all);
1418	>	do {} while (!casEventCount(c = eventCount, c+1));
1419	>	ensureSync();
1420		}
1421
1422		/**
1423	<	* Wake up threads waiting to steal a task. Because method
1424	<	* sync rechecks availability, it is OK to only proceed if
1425	<	* queue appears to be non-empty.
1423	>	* Signals threads waiting to poll a task. Because method sync
1424	>	* rechecks availability, it is OK to only proceed if queue
1425	>	* appears to be non-empty, and OK to skip under contention to
1426	>	* increment count (since some other thread succeeded).
1427		*/
1428	<	final void signalNonEmptyWorkerQueue() {
1271	<	// If CAS fails another signaller must have succeeded
1428	>	final void signalWork() {
1429		long c;
1430	<	if (barrierStack != null && casEventCount(c = eventCount, c+1))
1431	<	releaseIdleWorkers(false);
1430	>	WaitQueueNode q;
1431	>	if (syncStack != null &&
1432	>	casEventCount(c = eventCount, c+1) &&
1433	>	(((q = syncStack) != null && q.count <= c) &&
1434	>	(!casBarrierStack(q, q.next) || !q.signal())))
1435	>	ensureSync();
1436		}
1437
1438		/**
1439	<	* Waits until event count advances from count, or some thread is
1440	<	* waiting on a previous count, or there is stealable work
1441	<	* available. Help wake up others on release.
1439	>	* Waits until event count advances from last value held by
1440	>	* caller, or if excess threads, caller is resumed as spare, or
1441	>	* caller or pool is terminating. Updates caller's event on exit.
1442	>	*
1443		* @param w the calling worker thread
1282	–	* @param prev previous value returned by sync (or 0)
1283	–	* @return current event count
1444		*/
1445	<	final long sync(ForkJoinWorkerThread w, long prev) {
1446	<	updateStealCount(w);
1445	>	final void sync(ForkJoinWorkerThread w) {
1446	>	updateStealCount(w); // Transfer w's count while it is idle
1447
1448	<	while (!w.isShutdown() && !isTerminating() &&
1449	<	(parallelism >= runningCountOf(workerCounts) ||
1290	<	!suspendIfSpare(w))) { // prefer suspend to waiting here
1448	>	while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) {
1449	>	long prev = w.lastEventCount;
1450		WaitQueueNode node = null;
1451	<	boolean queued = false;
1452	<	for (;;) {
1453	<	if (!queued) {
1454	<	if (eventCount != prev)
1455	<	break;
1456	<	WaitQueueNode h = barrierStack;
1457	<	if (h != null && h.count != prev)
1299	<	break; // release below and maybe retry
1300	<	if (node == null)
1301	<	node = new WaitQueueNode(w, prev);
1302	<	queued = casBarrierStack(node.next = h, node);
1303	<	}
1304	<	else if (Thread.interrupted() ||
1305	<	node.thread == null ||
1306	<	(node.next == null && w.prescan()) ||
1307	<	eventCount != prev) {
1308	<	node.thread = null;
1309	<	if (eventCount == prev) // help trigger
1310	<	casEventCount(prev, prev+1);
1451	>	WaitQueueNode h;
1452	>	while (eventCount == prev &&
1453	>	((h = syncStack) == null || h.count == prev)) {
1454	>	if (node == null)
1455	>	node = new WaitQueueNode(prev, w);
1456	>	if (casBarrierStack(node.next = h, node)) {
1457	>	node.awaitSyncRelease(this);
1458		break;
1459		}
1313	–	else
1314	–	LockSupport.park(this);
1460		}
1461	+	long ec = ensureSync();
1462	+	if (ec != prev) {
1463	+	w.lastEventCount = ec;
1464	+	break;
1465	+	}
1466	+	}
1467	+	}
1468	+
1469	+	/**
1470	+	* Returns true if worker waiting on sync can proceed:
1471	+	*  - on signal (thread == null)
1472	+	*  - on event count advance (winning race to notify vs signaller)
1473	+	*  - on interrupt
1474	+	*  - if the first queued node, we find work available
1475	+	* If node was not signalled and event count not advanced on exit,
1476	+	* then we also help advance event count.
1477	+	*
1478	+	* @return true if node can be released
1479	+	*/
1480	+	final boolean syncIsReleasable(WaitQueueNode node) {
1481	+	long prev = node.count;
1482	+	if (!Thread.interrupted() && node.thread != null &&
1483	+	(node.next != null ||
1484	+	!ForkJoinWorkerThread.hasQueuedTasks(workers)) &&
1485	+	eventCount == prev)
1486	+	return false;
1487	+	if (node.thread != null) {
1488	+	node.thread = null;
1489		long ec = eventCount;
1490	<	if (releaseIdleWorkers(false) != prev)
1491	<	return ec;
1490	>	if (prev <= ec) // help signal
1491	>	casEventCount(ec, ec+1);
1492		}
1493	<	return prev; // return old count if aborted
1493	>	return true;
1494	>	}
1495	>
1496	>	/**
1497	>	* Returns true if a new sync event occurred since last call to
1498	>	* sync or this method, if so, updating caller's count.
1499	>	*/
1500	>	final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1501	>	long lc = w.lastEventCount;
1502	>	long ec = ensureSync();
1503	>	if (ec == lc)
1504	>	return false;
1505	>	w.lastEventCount = ec;
1506	>	return true;
1507		}
1508
1509		//  Parallelism maintenance
1510
1511		/**
1512	<	* Decrement running count; if too low, add spare.
1512	>	* Decrements running count; if too low, adds spare.
1513		*
1514		* Conceptually, all we need to do here is add or resume a
1515		* spare thread when one is about to block (and remove or
1516		* suspend it later when unblocked -- see suspendIfSpare).
1517		* However, implementing this idea requires coping with
1518	<	* several problems: We have imperfect information about the
1518	>	* several problems: we have imperfect information about the
1519		* states of threads. Some count updates can and usually do
1520		* lag run state changes, despite arrangements to keep them
1521		* accurate (for example, when possible, updating counts
#	Line 1343 | Line 1529 | public class ForkJoinPool extends Abstra
1529		* only be suspended or removed when they are idle, not
1530		* immediately when they aren't needed. So adding threads will
1531		* raise parallelism level for longer than necessary.  Also,
1532	<	* FJ applications often enounter highly transient peaks when
1532	>	* FJ applications often encounter highly transient peaks when
1533		* many threads are blocked joining, but for less time than it
1534		* takes to create or resume spares.
1535		*
#	Line 1352 | Line 1538 | public class ForkJoinPool extends Abstra
1538		* target counts, else create only to avoid starvation
1539		* @return true if joinMe known to be done
1540		*/
1541	<	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1541	>	final boolean preJoin(ForkJoinTask<?> joinMe,
1542	>	boolean maintainParallelism) {
1543		maintainParallelism &= maintainsParallelism; // overrride
1544		boolean dec = false;  // true when running count decremented
1545		while (spareStack == null || !tryResumeSpare(dec)) {
1546		int counts = workerCounts;
1547	<	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1547	>	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1548	>	// CAS cheat
1549		if (!needSpare(counts, maintainParallelism))
1550		break;
1551		if (joinMe.status < 0)
#	Line 1372 | Line 1560 | public class ForkJoinPool extends Abstra
1560		/**
1561		* Same idea as preJoin
1562		*/
1563	<	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1563	>	final boolean preBlock(ManagedBlocker blocker,
1564	>	boolean maintainParallelism) {
1565		maintainParallelism &= maintainsParallelism;
1566		boolean dec = false;
1567		while (spareStack == null || !tryResumeSpare(dec)) {
#	Line 1396 | Line 1585 | public class ForkJoinPool extends Abstra
1585		* there is apparently some work to do.  This self-limiting rule
1586		* means that the more threads that have already been added, the
1587		* less parallelism we will tolerate before adding another.
1588	+	*
1589		* @param counts current worker counts
1590		* @param maintainParallelism try to maintain parallelism
1591		*/
#	Line 1408 | Line 1598 | public class ForkJoinPool extends Abstra
1598		return (tc < maxPoolSize &&
1599		(rc == 0 || totalSurplus < 0 ||
1600		(maintainParallelism &&
1601	<	runningDeficit > totalSurplus && mayHaveQueuedWork())));
1601	>	runningDeficit > totalSurplus &&
1602	>	ForkJoinWorkerThread.hasQueuedTasks(workers))));
1603		}
1604
1605		/**
1606	<	* Returns true if at least one worker queue appears to be
1607	<	* nonempty. This is expensive but not often called. It is not
1608	<	* critical that this be accurate, but if not, more or fewer
1418	<	* running threads than desired might be maintained.
1419	<	*/
1420	<	private boolean mayHaveQueuedWork() {
1421	<	ForkJoinWorkerThread[] ws = workers;
1422	<	int len = ws.length;
1423	<	ForkJoinWorkerThread v;
1424	<	for (int i = 0; i < len; ++i) {
1425	<	if ((v = ws[i]) != null && v.getRawQueueSize() > 0) {
1426	<	releaseIdleWorkers(false); // help wake up stragglers
1427	<	return true;
1428	<	}
1429	<	}
1430	<	return false;
1431	<	}
1432	<
1433	<	/**
1434	<	* Add a spare worker if lock available and no more than the
1435	<	* expected numbers of threads exist
1606	>	* Adds a spare worker if lock available and no more than the
1607	>	* expected numbers of threads exist.
1608	>	*
1609		* @return true if successful
1610		*/
1611		private boolean tryAddSpare(int expectedCounts) {
#	Line 1465 | Line 1638 | public class ForkJoinPool extends Abstra
1638		}
1639
1640		/**
1641	<	* Add the kth spare worker. On entry, pool coounts are already
1641	>	* Adds the kth spare worker. On entry, pool counts are already
1642		* adjusted to reflect addition.
1643		*/
1644		private void createAndStartSpare(int k) {
#	Line 1483 | Line 1656 | public class ForkJoinPool extends Abstra
1656		}
1657		else
1658		updateWorkerCount(-1); // adjust on failure
1659	<	signalIdleWorkers(false);
1659	>	signalIdleWorkers();
1660		}
1661
1662		/**
1663	<	* Suspend calling thread w if there are excess threads.  Called
1664	<	* only from sync.  Spares are enqueued in a Treiber stack
1665	<	* using the same WaitQueueNodes as barriers.  They are resumed
1666	<	* mainly in preJoin, but are also woken on pool events that
1667	<	* require all threads to check run state.
1663	>	* Suspends calling thread w if there are excess threads.  Called
1664	>	* only from sync.  Spares are enqueued in a Treiber stack using
1665	>	* the same WaitQueueNodes as barriers.  They are resumed mainly
1666	>	* in preJoin, but are also woken on pool events that require all
1667	>	* threads to check run state.
1668	>	*
1669		* @param w the caller
1670		*/
1671		private boolean suspendIfSpare(ForkJoinWorkerThread w) {
#	Line 1499 | Line 1673 | public class ForkJoinPool extends Abstra
1673		int s;
1674		while (parallelism < runningCountOf(s = workerCounts)) {
1675		if (node == null)
1676	<	node = new WaitQueueNode(w, 0);
1676	>	node = new WaitQueueNode(0, w);
1677		if (casWorkerCounts(s, s-1)) { // representation-dependent
1678		// push onto stack
1679	<	do;while (!casSpareStack(node.next = spareStack, node));
1506	<
1679	>	do {} while (!casSpareStack(node.next = spareStack, node));
1680		// block until released by resumeSpare
1681	<	while (node.thread != null) {
1509	<	if (!Thread.interrupted())
1510	<	LockSupport.park(this);
1511	<	}
1512	<	w.activate(); // help warm up
1681	>	node.awaitSpareRelease();
1682		return true;
1683		}
1684		}
#	Line 1517 | Line 1686 | public class ForkJoinPool extends Abstra
1686		}
1687
1688		/**
1689	<	* Try to pop and resume a spare thread.
1689	>	* Tries to pop and resume a spare thread.
1690	>	*
1691		* @param updateCount if true, increment running count on success
1692		* @return true if successful
1693		*/
#	Line 1535 | Line 1705 | public class ForkJoinPool extends Abstra
1705		}
1706
1707		/**
1708	<	* Pop and resume all spare threads. Same idea as
1709	<	* releaseIdleWorkers.
1708	>	* Pops and resumes all spare threads. Same idea as ensureSync.
1709	>	*
1710		* @return true if any spares released
1711		*/
1712		private boolean resumeAllSpares() {
#	Line 1554 | Line 1724 | public class ForkJoinPool extends Abstra
1724		}
1725
1726		/**
1727	<	* Pop and shutdown excessive spare threads. Call only while
1727	>	* Pops and shuts down excessive spare threads. Call only while
1728		* holding lock. This is not guaranteed to eliminate all excess
1729		* threads, only those suspended as spares, which are the ones
1730		* unlikely to be needed in the future.
#	Line 1577 | Line 1747 | public class ForkJoinPool extends Abstra
1747		}
1748
1749		/**
1580	–	* Returns approximate number of spares, just for diagnostics.
1581	–	*/
1582	–	private int countSpares() {
1583	–	int sum = 0;
1584	–	for (WaitQueueNode q = spareStack; q != null; q = q.next)
1585	–	++sum;
1586	–	return sum;
1587	–	}
1588	–
1589	–	/**
1750		* Interface for extending managed parallelism for tasks running
1751		* in ForkJoinPools. A ManagedBlocker provides two methods.
1752	<	* Method <code>isReleasable</code> must return true if blocking is not
1753	<	* necessary. Method <code>block</code> blocks the current thread
1754	<	* if necessary (perhaps internally invoking isReleasable before
1755	<	* actually blocking.).
1752	>	* Method {@code isReleasable} must return true if blocking is not
1753	>	* necessary. Method {@code block} blocks the current thread if
1754	>	* necessary (perhaps internally invoking {@code isReleasable}
1755	>	* before actually blocking.).
1756	>	*
1757		* <p>For example, here is a ManagedBlocker based on a
1758		* ReentrantLock:
1759	<	* <pre>
1760	<	*   class ManagedLocker implements ManagedBlocker {
1761	<	*     final ReentrantLock lock;
1762	<	*     boolean hasLock = false;
1763	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1764	<	*     public boolean block() {
1765	<	*        if (!hasLock)
1766	<	*           lock.lock();
1767	<	*        return true;
1768	<	*     }
1769	<	*     public boolean isReleasable() {
1770	<	*        return hasLock || (hasLock = lock.tryLock());
1610	<	*     }
1759	>	*  <pre> {@code
1760	>	* class ManagedLocker implements ManagedBlocker {
1761	>	*   final ReentrantLock lock;
1762	>	*   boolean hasLock = false;
1763	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1764	>	*   public boolean block() {
1765	>	*     if (!hasLock)
1766	>	*       lock.lock();
1767	>	*     return true;
1768	>	*   }
1769	>	*   public boolean isReleasable() {
1770	>	*     return hasLock || (hasLock = lock.tryLock());
1771		*   }
1772	<	* </pre>
1772	>	* }}</pre>
1773		*/
1774		public static interface ManagedBlocker {
1775		/**
1776		* Possibly blocks the current thread, for example waiting for
1777		* a lock or condition.
1778	+	*
1779		* @return true if no additional blocking is necessary (i.e.,
1780	<	* if isReleasable would return true).
1780	>	* if isReleasable would return true)
1781		* @throws InterruptedException if interrupted while waiting
1782	<	* (the method is not required to do so, but is allowe to).
1782	>	* (the method is not required to do so, but is allowed to)
1783		*/
1784		boolean block() throws InterruptedException;
1785
#	Line 1633 | Line 1794 | public class ForkJoinPool extends Abstra
1794		* is a ForkJoinWorkerThread, this method possibly arranges for a
1795		* spare thread to be activated if necessary to ensure parallelism
1796		* while the current thread is blocked.  If
1797	<	* <code>maintainParallelism</code> is true and the pool supports
1797	>	* {@code maintainParallelism} is true and the pool supports
1798		* it ({@link #getMaintainsParallelism}), this method attempts to
1799	<	* maintain the pool's nominal parallelism. Otherwise if activates
1799	>	* maintain the pool's nominal parallelism. Otherwise it activates
1800		* a thread only if necessary to avoid complete starvation. This
1801		* option may be preferable when blockages use timeouts, or are
1802		* almost always brief.
1803		*
1804		* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1805		* equivalent to
1806	<	* <pre>
1807	<	*   while (!blocker.isReleasable())
1808	<	*      if (blocker.block())
1809	<	*         return;
1810	<	* </pre>
1806	>	*  <pre> {@code
1807	>	* while (!blocker.isReleasable())
1808	>	*   if (blocker.block())
1809	>	*     return;
1810	>	* }</pre>
1811		* If the caller is a ForkJoinTask, then the pool may first
1812		* be expanded to ensure parallelism, and later adjusted.
1813		*
#	Line 1655 | Line 1816 | public class ForkJoinPool extends Abstra
1816		* attempt to maintain the pool's nominal parallelism; otherwise
1817		* activate a thread only if necessary to avoid complete
1818		* starvation.
1819	<	* @throws InterruptedException if blocker.block did so.
1819	>	* @throws InterruptedException if blocker.block did so
1820		*/
1821		public static void managedBlock(ManagedBlocker blocker,
1822		boolean maintainParallelism)
1823		throws InterruptedException {
1824		Thread t = Thread.currentThread();
1825	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1826	<	((ForkJoinWorkerThread)t).pool : null);
1825	>	ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ?
1826	>	((ForkJoinWorkerThread) t).pool : null);
1827		if (!blocker.isReleasable()) {
1828		try {
1829		if (pool == null ||
#	Line 1677 | Line 1838 | public class ForkJoinPool extends Abstra
1838
1839		private static void awaitBlocker(ManagedBlocker blocker)
1840		throws InterruptedException {
1841	<	do;while (!blocker.isReleasable() && !blocker.block());
1841	>	do {} while (!blocker.isReleasable() && !blocker.block());
1842		}
1843
1844		// AbstractExecutorService overrides
1845
1846		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1847	<	return new AdaptedRunnable(runnable, value);
1847	>	return new AdaptedRunnable<T>(runnable, value);
1848		}
1849
1850		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1851	<	return new AdaptedCallable(callable);
1851	>	return new AdaptedCallable<T>(callable);
1852		}
1853
1854
1855	<	// Temporary Unsafe mechanics for preliminary release
1855	>	// Unsafe mechanics for jsr166y 3rd party package.
1856	>	private static sun.misc.Unsafe getUnsafe() {
1857	>	try {
1858	>	return sun.misc.Unsafe.getUnsafe();
1859	>	} catch (SecurityException se) {
1860	>	try {
1861	>	return java.security.AccessController.doPrivileged
1862	>	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1863	>	public sun.misc.Unsafe run() throws Exception {
1864	>	return getUnsafeByReflection();
1865	>	}});
1866	>	} catch (java.security.PrivilegedActionException e) {
1867	>	throw new RuntimeException("Could not initialize intrinsics",
1868	>	e.getCause());
1869	>	}
1870	>	}
1871	>	}
1872
1873	<	static final Unsafe _unsafe;
1874	<	static final long eventCountOffset;
1875	<	static final long workerCountsOffset;
1876	<	static final long runControlOffset;
1877	<	static final long barrierStackOffset;
1878	<	static final long spareStackOffset;
1873	>	private static sun.misc.Unsafe getUnsafeByReflection()
1874	>	throws NoSuchFieldException, IllegalAccessException {
1875	>	java.lang.reflect.Field f =
1876	>	sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
1877	>	f.setAccessible(true);
1878	>	return (sun.misc.Unsafe) f.get(null);
1879	>	}
1880
1881	<	static {
1881	>	private static long fieldOffset(String fieldName, Class<?> klazz) {
1882		try {
1883	<	if (ForkJoinPool.class.getClassLoader() != null) {
1884	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1885	<	f.setAccessible(true);
1886	<	_unsafe = (Unsafe)f.get(null);
1887	<	}
1888	<	else
1711	<	_unsafe = Unsafe.getUnsafe();
1712	<	eventCountOffset = _unsafe.objectFieldOffset
1713	<	(ForkJoinPool.class.getDeclaredField("eventCount"));
1714	<	workerCountsOffset = _unsafe.objectFieldOffset
1715	<	(ForkJoinPool.class.getDeclaredField("workerCounts"));
1716	<	runControlOffset = _unsafe.objectFieldOffset
1717	<	(ForkJoinPool.class.getDeclaredField("runControl"));
1718	<	barrierStackOffset = _unsafe.objectFieldOffset
1719	<	(ForkJoinPool.class.getDeclaredField("barrierStack"));
1720	<	spareStackOffset = _unsafe.objectFieldOffset
1721	<	(ForkJoinPool.class.getDeclaredField("spareStack"));
1722	<	} catch (Exception e) {
1723	<	throw new RuntimeException("Could not initialize intrinsics", e);
1883	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
1884	>	} catch (NoSuchFieldException e) {
1885	>	// Convert Exception to Error
1886	>	NoSuchFieldError error = new NoSuchFieldError(fieldName);
1887	>	error.initCause(e);
1888	>	throw error;
1889		}
1890		}
1891
1892	+	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1893	+	static final long eventCountOffset =
1894	+	fieldOffset("eventCount", ForkJoinPool.class);
1895	+	static final long workerCountsOffset =
1896	+	fieldOffset("workerCounts", ForkJoinPool.class);
1897	+	static final long runControlOffset =
1898	+	fieldOffset("runControl", ForkJoinPool.class);
1899	+	static final long syncStackOffset =
1900	+	fieldOffset("syncStack",ForkJoinPool.class);
1901	+	static final long spareStackOffset =
1902	+	fieldOffset("spareStack", ForkJoinPool.class);
1903	+
1904		private boolean casEventCount(long cmp, long val) {
1905	<	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1905	>	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
1906		}
1907		private boolean casWorkerCounts(int cmp, int val) {
1908	<	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1908	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1909		}
1910		private boolean casRunControl(int cmp, int val) {
1911	<	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1911	>	return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
1912		}
1913		private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1914	<	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1914	>	return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
1915		}
1916		private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1917	<	return _unsafe.compareAndSwapObject(this, barrierStackOffset, cmp, val);
1917	>	return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1918		}
1919		}

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