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

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.2 by dl, Wed Jan 7 16:07:37 2009 UTC vs.
Revision 1.21 by jsr166, Fri Jul 24 23:47:01 2009 UTC

#	Line 9 | Line 9 | import java.util.*;
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.*;
12
13		/**
14		* An {@link ExecutorService} for running {@link ForkJoinTask}s.  A
#	Line 27 | Line 25 | import java.lang.reflect.*;
25		* (eventually blocking if none exist). This makes them efficient when
26		* most tasks spawn other subtasks (as do most ForkJoinTasks), as well
27		* as the mixed execution of some plain Runnable- or Callable- based
28	<	* activities along with ForkJoinTasks. Otherwise, other
28	>	* activities along with ForkJoinTasks. When setting
29	>	* {@code setAsyncMode}, a ForkJoinPools may also be appropriate for
30	>	* use with fine-grained tasks that are never joined. Otherwise, other
31		* ExecutorService implementations are typically more appropriate
32		* choices.
33		*
#	Line 36 | Line 36 | import java.lang.reflect.*;
36		* adding, suspending, or resuming threads, even if some tasks are
37		* waiting to join others. However, no such adjustments are performed
38		* in the face of blocked IO or other unmanaged synchronization. The
39	<	* nested <code>ManagedBlocker</code> interface enables extension of
39	>	* nested {@code ManagedBlocker} interface enables extension of
40		* the kinds of synchronization accommodated.  The target parallelism
41	<	* level may also be changed dynamically (<code>setParallelism</code>)
42	<	* and dynamically thread construction can be limited using methods
43	<	* <code>setMaximumPoolSize</code> and/or
44	<	* <code>setMaintainsParallelism</code>.
41	>	* level may also be changed dynamically ({@code setParallelism})
42	>	* and thread construction can be limited using methods
43	>	* {@code setMaximumPoolSize} and/or
44	>	* {@code setMaintainsParallelism}.
45		*
46		* <p>In addition to execution and lifecycle control methods, this
47		* class provides status check methods (for example
48	<	* <code>getStealCount</code>) that are intended to aid in developing,
48	>	* {@code getStealCount}) that are intended to aid in developing,
49		* tuning, and monitoring fork/join applications. Also, method
50	<	* <code>toString</code> returns indications of pool state in a
50	>	* {@code toString} returns indications of pool state in a
51		* convenient form for informal monitoring.
52		*
53		* <p><b>Implementation notes</b>: This implementation restricts the
54		* maximum number of running threads to 32767. Attempts to create
55		* pools with greater than the maximum result in
56		* IllegalArgumentExceptions.
57	+	*
58	+	* @since 1.7
59	+	* @author Doug Lea
60		*/
61		public class ForkJoinPool extends AbstractExecutorService {
62
#	Line 79 | Line 82 | public class ForkJoinPool extends Abstra
82		* Returns a new worker thread operating in the given pool.
83		*
84		* @param pool the pool this thread works in
85	<	* @throws NullPointerException if pool is null;
85	>	* @throws NullPointerException if pool is null
86		*/
87		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
88		}
89
90		/**
91	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
91	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
92		* new ForkJoinWorkerThread.
93		*/
94		static class  DefaultForkJoinWorkerThreadFactory
#	Line 131 | Line 134 | public class ForkJoinPool extends Abstra
134		new AtomicInteger();
135
136		/**
137	<	* Array holding all worker threads in the pool. Array size must
138	<	* be a power of two.  Updates and replacements are protected by
139	<	* workerLock, but it is always kept in a consistent enough state
140	<	* to be randomly accessed without locking by workers performing
141	<	* work-stealing.
137	>	* Array holding all worker threads in the pool. Initialized upon
138	>	* first use. Array size must be a power of two.  Updates and
139	>	* replacements are protected by workerLock, but it is always kept
140	>	* in a consistent enough state to be randomly accessed without
141	>	* locking by workers performing work-stealing.
142		*/
143		volatile ForkJoinWorkerThread[] workers;
144
#	Line 151 | Line 154 | public class ForkJoinPool extends Abstra
154
155		/**
156		* The uncaught exception handler used when any worker
157	<	* abrupty terminates
157	>	* abruptly terminates
158		*/
159		private Thread.UncaughtExceptionHandler ueh;
160
#	Line 179 | Line 182 | public class ForkJoinPool extends Abstra
182		private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
183
184		/**
185	<	* Head of Treiber stack for barrier sync. See below for explanation
185	>	* Head of Treiber stack for barrier sync. See below for explanation.
186		*/
187	<	private volatile WaitQueueNode barrierStack;
187	>	private volatile WaitQueueNode syncStack;
188
189		/**
190		* The count for event barrier
#	Line 204 | Line 207 | public class ForkJoinPool extends Abstra
207		private volatile int parallelism;
208
209		/**
210	+	* True if use local fifo, not default lifo, for local polling
211	+	*/
212	+	private volatile boolean locallyFifo;
213	+
214	+	/**
215		* Holds number of total (i.e., created and not yet terminated)
216		* and running (i.e., not blocked on joins or other managed sync)
217		* threads, packed into one int to ensure consistent snapshot when
218		* making decisions about creating and suspending spare
219		* threads. Updated only by CAS.  Note: CASes in
220	<	* updateRunningCount and preJoin running active count is in low
221	<	* word, so need to be modified if this changes
220	>	* updateRunningCount and preJoin assume that running active count
221	>	* is in low word, so need to be modified if this changes.
222		*/
223		private volatile int workerCounts;
224
#	Line 219 | Line 227 | public class ForkJoinPool extends Abstra
227		private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
228
229		/**
230	<	* Add delta (which may be negative) to running count.  This must
230	>	* Adds delta (which may be negative) to running count.  This must
231		* be called before (with negative arg) and after (with positive)
232	<	* any managed synchronization (i.e., mainly, joins)
232	>	* any managed synchronization (i.e., mainly, joins).
233	>	*
234		* @param delta the number to add
235		*/
236		final void updateRunningCount(int delta) {
237		int s;
238	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
238	>	do {} while (!casWorkerCounts(s = workerCounts, s + delta));
239		}
240
241		/**
242	<	* Add delta (which may be negative) to both total and running
242	>	* Adds delta (which may be negative) to both total and running
243		* count.  This must be called upon creation and termination of
244		* worker threads.
245	+	*
246		* @param delta the number to add
247		*/
248		private void updateWorkerCount(int delta) {
249		int d = delta + (delta << 16); // add to both lo and hi parts
250		int s;
251	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
251	>	do {} while (!casWorkerCounts(s = workerCounts, s + d));
252		}
253
254		/**
#	Line 264 | Line 274 | public class ForkJoinPool extends Abstra
274		private static int runControlFor(int r, int a)   { return (r << 16) + a; }
275
276		/**
277	<	* Increment active count. Called by workers before/during
278	<	* executing tasks.
277	>	* Tries incrementing active count; fails on contention.
278	>	* Called by workers before/during executing tasks.
279	>	*
280	>	* @return true on success
281		*/
282	<	final void incrementActiveCount() {
283	<	int c;
284	<	do;while (!casRunControl(c = runControl, c+1));
282	>	final boolean tryIncrementActiveCount() {
283	>	int c = runControl;
284	>	return casRunControl(c, c+1);
285		}
286
287		/**
288	<	* Decrement active count; possibly trigger termination.
288	>	* Tries decrementing active count; fails on contention.
289	>	* Possibly triggers termination on success.
290		* Called by workers when they can't find tasks.
291	+	*
292	+	* @return true on success
293		*/
294	<	final void decrementActiveCount() {
295	<	int c, nextc;
296	<	do;while (!casRunControl(c = runControl, nextc = c-1));
294	>	final boolean tryDecrementActiveCount() {
295	>	int c = runControl;
296	>	int nextc = c - 1;
297	>	if (!casRunControl(c, nextc))
298	>	return false;
299		if (canTerminateOnShutdown(nextc))
300		terminateOnShutdown();
301	+	return true;
302		}
303
304		/**
305	<	* Return true if argument represents zero active count and
305	>	* Returns true if argument represents zero active count and
306		* nonzero runstate, which is the triggering condition for
307		* terminating on shutdown.
308		*/
309		private static boolean canTerminateOnShutdown(int c) {
310	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
310	>	// i.e. least bit is nonzero runState bit
311	>	return ((c & -c) >>> 16) != 0;
312		}
313
314		/**
#	Line 315 | Line 334 | public class ForkJoinPool extends Abstra
334
335		/**
336		* Creates a ForkJoinPool with a pool size equal to the number of
337	<	* processors available on the system and using the default
338	<	* ForkJoinWorkerThreadFactory,
337	>	* processors available on the system, using the default
338	>	* ForkJoinWorkerThreadFactory.
339	>	*
340		* @throws SecurityException if a security manager exists and
341		*         the caller is not permitted to modify threads
342		*         because it does not hold {@link
343	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
343	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
344		*/
345		public ForkJoinPool() {
346		this(Runtime.getRuntime().availableProcessors(),
#	Line 328 | Line 348 | public class ForkJoinPool extends Abstra
348		}
349
350		/**
351	<	* Creates a ForkJoinPool with the indicated parellelism level
352	<	* threads, and using the default ForkJoinWorkerThreadFactory,
351	>	* Creates a ForkJoinPool with the indicated parallelism level
352	>	* threads and using the default ForkJoinWorkerThreadFactory.
353	>	*
354		* @param parallelism the number of worker threads
355		* @throws IllegalArgumentException if parallelism less than or
356		* equal to zero
357		* @throws SecurityException if a security manager exists and
358		*         the caller is not permitted to modify threads
359		*         because it does not hold {@link
360	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
360	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
361		*/
362		public ForkJoinPool(int parallelism) {
363		this(parallelism, defaultForkJoinWorkerThreadFactory);
#	Line 345 | Line 366 | public class ForkJoinPool extends Abstra
366		/**
367		* Creates a ForkJoinPool with parallelism equal to the number of
368		* processors available on the system and using the given
369	<	* ForkJoinWorkerThreadFactory,
369	>	* ForkJoinWorkerThreadFactory.
370	>	*
371		* @param factory the factory for creating new threads
372		* @throws NullPointerException if factory is null
373		* @throws SecurityException if a security manager exists and
374		*         the caller is not permitted to modify threads
375		*         because it does not hold {@link
376	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
376	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
377		*/
378		public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
379		this(Runtime.getRuntime().availableProcessors(), factory);
#	Line 363 | Line 385 | public class ForkJoinPool extends Abstra
385		* @param parallelism the targeted number of worker threads
386		* @param factory the factory for creating new threads
387		* @throws IllegalArgumentException if parallelism less than or
388	<	* equal to zero, or greater than implementation limit.
388	>	* equal to zero, or greater than implementation limit
389		* @throws NullPointerException if factory is null
390		* @throws SecurityException if a security manager exists and
391		*         the caller is not permitted to modify threads
392		*         because it does not hold {@link
393	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
393	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
394		*/
395		public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
396		if (parallelism <= 0 || parallelism > MAX_THREADS)
#	Line 385 | Line 407 | public class ForkJoinPool extends Abstra
407		this.termination = workerLock.newCondition();
408		this.stealCount = new AtomicLong();
409		this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
410	<	createAndStartInitialWorkers(parallelism);
410	>	// worker array and workers are lazily constructed
411		}
412
413		/**
414	<	* Create new worker using factory.
414	>	* Creates a new worker thread using factory.
415	>	*
416		* @param index the index to assign worker
417		* @return new worker, or null of factory failed
418		*/
#	Line 399 | Line 422 | public class ForkJoinPool extends Abstra
422		if (w != null) {
423		w.poolIndex = index;
424		w.setDaemon(true);
425	+	w.setAsyncMode(locallyFifo);
426		w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
427		if (h != null)
428		w.setUncaughtExceptionHandler(h);
#	Line 407 | Line 431 | public class ForkJoinPool extends Abstra
431		}
432
433		/**
434	<	* Return a good size for worker array given pool size.
434	>	* Returns a good size for worker array given pool size.
435		* Currently requires size to be a power of two.
436		*/
437	<	private static int arraySizeFor(int ps) {
438	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
437	>	private static int arraySizeFor(int poolSize) {
438	>	return (poolSize <= 1) ? 1 :
439	>	(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1)));
440		}
441
442		/**
443	<	* Create or resize array if necessary to hold newLength
443	>	* Creates or resizes array if necessary to hold newLength.
444	>	* Call only under exclusion.
445	>	*
446		* @return the array
447		*/
448		private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
#	Line 429 | Line 456 | public class ForkJoinPool extends Abstra
456		}
457
458		/**
459	<	* Try to shrink workers into smaller array after one or more terminate
459	>	* Tries to shrink workers into smaller array after one or more terminate.
460		*/
461		private void tryShrinkWorkerArray() {
462		ForkJoinWorkerThread[] ws = workers;
463	<	int len = ws.length;
464	<	int last = len - 1;
465	<	while (last >= 0 && ws[last] == null)
466	<	--last;
467	<	int newLength = arraySizeFor(last+1);
468	<	if (newLength < len)
469	<	workers = Arrays.copyOf(ws, newLength);
463	>	if (ws != null) {
464	>	int len = ws.length;
465	>	int last = len - 1;
466	>	while (last >= 0 && ws[last] == null)
467	>	--last;
468	>	int newLength = arraySizeFor(last+1);
469	>	if (newLength < len)
470	>	workers = Arrays.copyOf(ws, newLength);
471	>	}
472		}
473
474		/**
475	<	* 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.)
475	>	* Initializes workers if necessary.
476		*/
477	<	private void createAndStartInitialWorkers(int ps) {
478	<	final ReentrantLock lock = this.workerLock;
479	<	lock.lock();
480	<	try {
481	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
482	<	for (int i = 0; i < ps; ++i) {
483	<	ForkJoinWorkerThread w = createWorker(i);
484	<	if (w != null) {
485	<	ws[i] = w;
486	<	w.start();
487	<	updateWorkerCount(1);
477	>	final void ensureWorkerInitialization() {
478	>	ForkJoinWorkerThread[] ws = workers;
479	>	if (ws == null) {
480	>	final ReentrantLock lock = this.workerLock;
481	>	lock.lock();
482	>	try {
483	>	ws = workers;
484	>	if (ws == null) {
485	>	int ps = parallelism;
486	>	ws = ensureWorkerArrayCapacity(ps);
487	>	for (int i = 0; i < ps; ++i) {
488	>	ForkJoinWorkerThread w = createWorker(i);
489	>	if (w != null) {
490	>	ws[i] = w;
491	>	w.start();
492	>	updateWorkerCount(1);
493	>	}
494	>	}
495		}
496	+	} finally {
497	+	lock.unlock();
498		}
463	–	} finally {
464	–	lock.unlock();
499		}
500		}
501
#	Line 507 | Line 541 | public class ForkJoinPool extends Abstra
541		private <T> void doSubmit(ForkJoinTask<T> task) {
542		if (isShutdown())
543		throw new RejectedExecutionException();
544	+	if (workers == null)
545	+	ensureWorkerInitialization();
546		submissionQueue.offer(task);
547	<	signalIdleWorkers(true);
547	>	signalIdleWorkers();
548		}
549
550		/**
551	<	* Performs the given task; returning its result upon completion
551	>	* Performs the given task, returning its result upon completion.
552	>	*
553		* @param task the task
554		* @return the task's result
555		* @throws NullPointerException if task is null
#	Line 525 | Line 562 | public class ForkJoinPool extends Abstra
562
563		/**
564		* Arranges for (asynchronous) execution of the given task.
565	+	*
566		* @param task the task
567		* @throws NullPointerException if task is null
568		* @throws RejectedExecutionException if pool is shut down
#	Line 559 | Line 597 | public class ForkJoinPool extends Abstra
597
598		/**
599		* Adaptor for Runnables. This implements RunnableFuture
600	<	* to be compliant with AbstractExecutorService constraints
600	>	* to be compliant with AbstractExecutorService constraints.
601		*/
602		static final class AdaptedRunnable<T> extends ForkJoinTask<T>
603		implements RunnableFuture<T> {
#	Line 579 | Line 617 | public class ForkJoinPool extends Abstra
617		return true;
618		}
619		public void run() { invoke(); }
620	+	private static final long serialVersionUID = 5232453952276885070L;
621		}
622
623		/**
#	Line 607 | Line 646 | public class ForkJoinPool extends Abstra
646		}
647		}
648		public void run() { invoke(); }
649	+	private static final long serialVersionUID = 2838392045355241008L;
650		}
651
652		public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
653	<	ArrayList<ForkJoinTask<T>> ts =
653	>	ArrayList<ForkJoinTask<T>> forkJoinTasks =
654		new ArrayList<ForkJoinTask<T>>(tasks.size());
655	<	for (Callable<T> c : tasks)
656	<	ts.add(new AdaptedCallable<T>(c));
657	<	invoke(new InvokeAll<T>(ts));
658	<	return (List<Future<T>>)(List)ts;
655	>	for (Callable<T> task : tasks)
656	>	forkJoinTasks.add(new AdaptedCallable<T>(task));
657	>	invoke(new InvokeAll<T>(forkJoinTasks));
658	>
659	>	@SuppressWarnings({"unchecked", "rawtypes"})
660	>	List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
661	>	return futures;
662		}
663
664		static final class InvokeAll<T> extends RecursiveAction {
665		final ArrayList<ForkJoinTask<T>> tasks;
666		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
667		public void compute() {
668	<	try { invokeAll(tasks); } catch(Exception ignore) {}
668	>	try { invokeAll(tasks); }
669	>	catch (Exception ignore) {}
670		}
671	+	private static final long serialVersionUID = -7914297376763021607L;
672		}
673
674		// Configuration and status settings and queries
675
676		/**
677	<	* Returns the factory used for constructing new workers
677	>	* Returns the factory used for constructing new workers.
678		*
679		* @return the factory used for constructing new workers
680		*/
#	Line 640 | Line 685 | public class ForkJoinPool extends Abstra
685		/**
686		* Returns the handler for internal worker threads that terminate
687		* due to unrecoverable errors encountered while executing tasks.
688	+	*
689		* @return the handler, or null if none
690		*/
691		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
#	Line 665 | Line 711 | public class ForkJoinPool extends Abstra
711		* @throws SecurityException if a security manager exists and
712		*         the caller is not permitted to modify threads
713		*         because it does not hold {@link
714	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
714	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
715		*/
716		public Thread.UncaughtExceptionHandler
717		setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
#	Line 677 | Line 723 | public class ForkJoinPool extends Abstra
723		old = ueh;
724		ueh = h;
725		ForkJoinWorkerThread[] ws = workers;
726	<	for (int i = 0; i < ws.length; ++i) {
727	<	ForkJoinWorkerThread w = ws[i];
728	<	if (w != null)
729	<	w.setUncaughtExceptionHandler(h);
726	>	if (ws != null) {
727	>	for (int i = 0; i < ws.length; ++i) {
728	>	ForkJoinWorkerThread w = ws[i];
729	>	if (w != null)
730	>	w.setUncaughtExceptionHandler(h);
731	>	}
732		}
733		} finally {
734		lock.unlock();
#	Line 690 | Line 738 | public class ForkJoinPool extends Abstra
738
739
740		/**
741	<	* Sets the target paralleism level of this pool.
741	>	* Sets the target parallelism level of this pool.
742	>	*
743		* @param parallelism the target parallelism
744		* @throws IllegalArgumentException if parallelism less than or
745	<	* equal to zero or greater than maximum size bounds.
745	>	* equal to zero or greater than maximum size bounds
746		* @throws SecurityException if a security manager exists and
747		*         the caller is not permitted to modify threads
748		*         because it does not hold {@link
749	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
749	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
750		*/
751		public void setParallelism(int parallelism) {
752		checkPermission();
#	Line 717 | Line 766 | public class ForkJoinPool extends Abstra
766		} finally {
767		lock.unlock();
768		}
769	<	signalIdleWorkers(false);
769	>	signalIdleWorkers();
770		}
771
772		/**
#	Line 732 | Line 781 | public class ForkJoinPool extends Abstra
781		/**
782		* Returns the number of worker threads that have started but not
783		* yet terminated.  This result returned by this method may differ
784	<	* from <code>getParallelism</code> when threads are created to
784	>	* from {@code getParallelism} when threads are created to
785		* maintain parallelism when others are cooperatively blocked.
786		*
787		* @return the number of worker threads
#	Line 744 | Line 793 | public class ForkJoinPool extends Abstra
793		/**
794		* Returns the maximum number of threads allowed to exist in the
795		* pool, even if there are insufficient unblocked running threads.
796	+	*
797		* @return the maximum
798		*/
799		public int getMaximumPoolSize() {
#	Line 755 | Line 805 | public class ForkJoinPool extends Abstra
805		* pool, even if there are insufficient unblocked running threads.
806		* Setting this value has no effect on current pool size. It
807		* controls construction of new threads.
808	+	*
809		* @throws IllegalArgumentException if negative or greater then
810	<	* internal implementation limit.
810	>	* internal implementation limit
811		*/
812		public void setMaximumPoolSize(int newMax) {
813		if (newMax < 0 || newMax > MAX_THREADS)
#	Line 769 | Line 820 | public class ForkJoinPool extends Abstra
820		* Returns true if this pool dynamically maintains its target
821		* parallelism level. If false, new threads are added only to
822		* avoid possible starvation.
823	<	* This setting is by default true;
823	>	* This setting is by default true.
824	>	*
825		* @return true if maintains parallelism
826		*/
827		public boolean getMaintainsParallelism() {
#	Line 780 | Line 832 | public class ForkJoinPool extends Abstra
832		* Sets whether this pool dynamically maintains its target
833		* parallelism level. If false, new threads are added only to
834		* avoid possible starvation.
835	+	*
836		* @param enable true to maintains parallelism
837		*/
838		public void setMaintainsParallelism(boolean enable) {
#	Line 787 | Line 840 | public class ForkJoinPool extends Abstra
840		}
841
842		/**
843	+	* Establishes local first-in-first-out scheduling mode for forked
844	+	* tasks that are never joined. This mode may be more appropriate
845	+	* than default locally stack-based mode in applications in which
846	+	* worker threads only process asynchronous tasks.  This method is
847	+	* designed to be invoked only when pool is quiescent, and
848	+	* typically only before any tasks are submitted. The effects of
849	+	* invocations at other times may be unpredictable.
850	+	*
851	+	* @param async if true, use locally FIFO scheduling
852	+	* @return the previous mode
853	+	*/
854	+	public boolean setAsyncMode(boolean async) {
855	+	boolean oldMode = locallyFifo;
856	+	locallyFifo = async;
857	+	ForkJoinWorkerThread[] ws = workers;
858	+	if (ws != null) {
859	+	for (int i = 0; i < ws.length; ++i) {
860	+	ForkJoinWorkerThread t = ws[i];
861	+	if (t != null)
862	+	t.setAsyncMode(async);
863	+	}
864	+	}
865	+	return oldMode;
866	+	}
867	+
868	+	/**
869	+	* Returns true if this pool uses local first-in-first-out
870	+	* scheduling mode for forked tasks that are never joined.
871	+	*
872	+	* @return true if this pool uses async mode
873	+	*/
874	+	public boolean getAsyncMode() {
875	+	return locallyFifo;
876	+	}
877	+
878	+	/**
879		* Returns an estimate of the number of worker threads that are
880		* not blocked waiting to join tasks or for other managed
881		* synchronization.
#	Line 801 | Line 890 | public class ForkJoinPool extends Abstra
890		* Returns an estimate of the number of threads that are currently
891		* stealing or executing tasks. This method may overestimate the
892		* number of active threads.
893	<	* @return the number of active threads.
893	>	*
894	>	* @return the number of active threads
895		*/
896		public int getActiveThreadCount() {
897		return activeCountOf(runControl);
#	Line 811 | Line 901 | public class ForkJoinPool extends Abstra
901		* Returns an estimate of the number of threads that are currently
902		* idle waiting for tasks. This method may underestimate the
903		* number of idle threads.
904	<	* @return the number of idle threads.
904	>	*
905	>	* @return the number of idle threads
906		*/
907		final int getIdleThreadCount() {
908		int c = runningCountOf(workerCounts) - activeCountOf(runControl);
909	<	return (c <= 0)? 0 : c;
909	>	return (c <= 0) ? 0 : c;
910		}
911
912		/**
913		* Returns true if all worker threads are currently idle. An idle
914		* worker is one that cannot obtain a task to execute because none
915		* are available to steal from other threads, and there are no
916	<	* pending submissions to the pool. This method is conservative:
917	<	* It might not return true immediately upon idleness of all
916	>	* pending submissions to the pool. This method is conservative;
917	>	* it might not return true immediately upon idleness of all
918		* threads, but will eventually become true if threads remain
919		* inactive.
920	+	*
921		* @return true if all threads are currently idle
922		*/
923		public boolean isQuiescent() {
#	Line 837 | Line 929 | public class ForkJoinPool extends Abstra
929		* one thread's work queue by another. The reported value
930		* underestimates the actual total number of steals when the pool
931		* is not quiescent. This value may be useful for monitoring and
932	<	* tuning fork/join programs: In general, steal counts should be
932	>	* tuning fork/join programs: in general, steal counts should be
933		* high enough to keep threads busy, but low enough to avoid
934		* overhead and contention across threads.
935	<	* @return the number of steals.
935	>	*
936	>	* @return the number of steals
937		*/
938		public long getStealCount() {
939		return stealCount.get();
940		}
941
942		/**
943	<	* Accumulate steal count from a worker. Call only
944	<	* when worker known to be idle.
943	>	* Accumulates steal count from a worker.
944	>	* Call only when worker known to be idle.
945		*/
946		private void updateStealCount(ForkJoinWorkerThread w) {
947		int sc = w.getAndClearStealCount();
#	Line 863 | Line 956 | public class ForkJoinPool extends Abstra
956		* an approximation, obtained by iterating across all threads in
957		* the pool. This method may be useful for tuning task
958		* granularities.
959	<	* @return the number of queued tasks.
959	>	*
960	>	* @return the number of queued tasks
961		*/
962		public long getQueuedTaskCount() {
963		long count = 0;
964		ForkJoinWorkerThread[] ws = workers;
965	<	for (int i = 0; i < ws.length; ++i) {
966	<	ForkJoinWorkerThread t = ws[i];
967	<	if (t != null)
968	<	count += t.getQueueSize();
965	>	if (ws != null) {
966	>	for (int i = 0; i < ws.length; ++i) {
967	>	ForkJoinWorkerThread t = ws[i];
968	>	if (t != null)
969	>	count += t.getQueueSize();
970	>	}
971		}
972		return count;
973		}
#	Line 880 | Line 976 | public class ForkJoinPool extends Abstra
976		* Returns an estimate of the number tasks submitted to this pool
977		* that have not yet begun executing. This method takes time
978		* proportional to the number of submissions.
979	<	* @return the number of queued submissions.
979	>	*
980	>	* @return the number of queued submissions
981		*/
982		public int getQueuedSubmissionCount() {
983		return submissionQueue.size();
#	Line 889 | Line 986 | public class ForkJoinPool extends Abstra
986		/**
987		* Returns true if there are any tasks submitted to this pool
988		* that have not yet begun executing.
989	<	* @return <code>true</code> if there are any queued submissions.
989	>	*
990	>	* @return {@code true} if there are any queued submissions
991		*/
992		public boolean hasQueuedSubmissions() {
993		return !submissionQueue.isEmpty();
#	Line 899 | Line 997 | public class ForkJoinPool extends Abstra
997		* Removes and returns the next unexecuted submission if one is
998		* available.  This method may be useful in extensions to this
999		* class that re-assign work in systems with multiple pools.
1000	+	*
1001		* @return the next submission, or null if none
1002		*/
1003		protected ForkJoinTask<?> pollSubmission() {
#	Line 906 | Line 1005 | public class ForkJoinPool extends Abstra
1005		}
1006
1007		/**
1008	+	* Removes all available unexecuted submitted and forked tasks
1009	+	* from scheduling queues and adds them to the given collection,
1010	+	* without altering their execution status. These may include
1011	+	* artificially generated or wrapped tasks. This method is designed
1012	+	* to be invoked only when the pool is known to be
1013	+	* quiescent. Invocations at other times may not remove all
1014	+	* tasks. A failure encountered while attempting to add elements
1015	+	* to collection {@code c} may result in elements being in
1016	+	* neither, either or both collections when the associated
1017	+	* exception is thrown.  The behavior of this operation is
1018	+	* undefined if the specified collection is modified while the
1019	+	* operation is in progress.
1020	+	*
1021	+	* @param c the collection to transfer elements into
1022	+	* @return the number of elements transferred
1023	+	*/
1024	+	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
1025	+	int n = submissionQueue.drainTo(c);
1026	+	ForkJoinWorkerThread[] ws = workers;
1027	+	if (ws != null) {
1028	+	for (int i = 0; i < ws.length; ++i) {
1029	+	ForkJoinWorkerThread w = ws[i];
1030	+	if (w != null)
1031	+	n += w.drainTasksTo(c);
1032	+	}
1033	+	}
1034	+	return n;
1035	+	}
1036	+
1037	+	/**
1038		* Returns a string identifying this pool, as well as its state,
1039		* including indications of run state, parallelism level, and
1040		* worker and task counts.
#	Line 949 | Line 1078 | public class ForkJoinPool extends Abstra
1078		* Invocation has no additional effect if already shut down.
1079		* Tasks that are in the process of being submitted concurrently
1080		* during the course of this method may or may not be rejected.
1081	+	*
1082		* @throws SecurityException if a security manager exists and
1083		*         the caller is not permitted to modify threads
1084		*         because it does not hold {@link
1085	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1085	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1086		*/
1087		public void shutdown() {
1088		checkPermission();
#	Line 966 | Line 1096 | public class ForkJoinPool extends Abstra
1096		* waiting tasks.  Tasks that are in the process of being
1097		* submitted or executed concurrently during the course of this
1098		* method may or may not be rejected. Unlike some other executors,
1099	<	* this method cancels rather than collects non-executed tasks,
1100	<	* so always returns an empty list.
1099	>	* this method cancels rather than collects non-executed tasks
1100	>	* upon termination, so always returns an empty list. However, you
1101	>	* can use method {@code drainTasksTo} before invoking this
1102	>	* method to transfer unexecuted tasks to another collection.
1103	>	*
1104		* @return an empty list
1105		* @throws SecurityException if a security manager exists and
1106		*         the caller is not permitted to modify threads
1107		*         because it does not hold {@link
1108	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1108	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1109		*/
1110		public List<Runnable> shutdownNow() {
1111		checkPermission();
#	Line 981 | Line 1114 | public class ForkJoinPool extends Abstra
1114		}
1115
1116		/**
1117	<	* Returns <code>true</code> if all tasks have completed following shut down.
1117	>	* Returns {@code true} if all tasks have completed following shut down.
1118		*
1119	<	* @return <code>true</code> if all tasks have completed following shut down
1119	>	* @return {@code true} if all tasks have completed following shut down
1120		*/
1121		public boolean isTerminated() {
1122		return runStateOf(runControl) == TERMINATED;
1123		}
1124
1125		/**
1126	<	* Returns <code>true</code> if the process of termination has
1126	>	* Returns {@code true} if the process of termination has
1127		* commenced but possibly not yet completed.
1128		*
1129	<	* @return <code>true</code> if terminating
1129	>	* @return {@code true} if terminating
1130		*/
1131		public boolean isTerminating() {
1132		return runStateOf(runControl) >= TERMINATING;
1133		}
1134
1135		/**
1136	<	* Returns <code>true</code> if this pool has been shut down.
1136	>	* Returns {@code true} if this pool has been shut down.
1137		*
1138	<	* @return <code>true</code> if this pool has been shut down
1138	>	* @return {@code true} if this pool has been shut down
1139		*/
1140		public boolean isShutdown() {
1141		return runStateOf(runControl) >= SHUTDOWN;
#	Line 1015 | Line 1148 | public class ForkJoinPool extends Abstra
1148		*
1149		* @param timeout the maximum time to wait
1150		* @param unit the time unit of the timeout argument
1151	<	* @return <code>true</code> if this executor terminated and
1152	<	*         <code>false</code> if the timeout elapsed before termination
1151	>	* @return {@code true} if this executor terminated and
1152	>	*         {@code false} if the timeout elapsed before termination
1153		* @throws InterruptedException if interrupted while waiting
1154		*/
1155		public boolean awaitTermination(long timeout, TimeUnit unit)
#	Line 1040 | Line 1173 | public class ForkJoinPool extends Abstra
1173		// Shutdown and termination support
1174
1175		/**
1176	<	* Callback from terminating worker. Null out the corresponding
1177	<	* workers slot, and if terminating, try to terminate, else try to
1178	<	* shrink workers array.
1176	>	* Callback from terminating worker. Nulls out the corresponding
1177	>	* workers slot, and if terminating, tries to terminate; else
1178	>	* tries to shrink workers array.
1179	>	*
1180		* @param w the worker
1181		*/
1182		final void workerTerminated(ForkJoinWorkerThread w) {
#	Line 1052 | Line 1186 | public class ForkJoinPool extends Abstra
1186		lock.lock();
1187		try {
1188		ForkJoinWorkerThread[] ws = workers;
1189	<	int idx = w.poolIndex;
1190	<	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1191	<	ws[idx] = null;
1192	<	if (totalCountOf(workerCounts) == 0) {
1193	<	terminate(); // no-op if already terminating
1194	<	transitionRunStateTo(TERMINATED);
1195	<	termination.signalAll();
1196	<	}
1197	<	else if (!isTerminating()) {
1198	<	tryShrinkWorkerArray();
1199	<	tryResumeSpare(true); // allow replacement
1189	>	if (ws != null) {
1190	>	int idx = w.poolIndex;
1191	>	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1192	>	ws[idx] = null;
1193	>	if (totalCountOf(workerCounts) == 0) {
1194	>	terminate(); // no-op if already terminating
1195	>	transitionRunStateTo(TERMINATED);
1196	>	termination.signalAll();
1197	>	}
1198	>	else if (!isTerminating()) {
1199	>	tryShrinkWorkerArray();
1200	>	tryResumeSpare(true); // allow replacement
1201	>	}
1202		}
1203		} finally {
1204		lock.unlock();
1205		}
1206	<	signalIdleWorkers(false);
1206	>	signalIdleWorkers();
1207		}
1208
1209		/**
1210	<	* Initiate termination.
1210	>	* Initiates termination.
1211		*/
1212		private void terminate() {
1213		if (transitionRunStateTo(TERMINATING)) {
1214		stopAllWorkers();
1215		resumeAllSpares();
1216	<	signalIdleWorkers(true);
1216	>	signalIdleWorkers();
1217		cancelQueuedSubmissions();
1218		cancelQueuedWorkerTasks();
1219		interruptUnterminatedWorkers();
1220	<	signalIdleWorkers(true); // resignal after interrupt
1220	>	signalIdleWorkers(); // resignal after interrupt
1221		}
1222		}
1223
1224		/**
1225	<	* Possibly terminate when on shutdown state
1225	>	* Possibly terminates when on shutdown state.
1226		*/
1227		private void terminateOnShutdown() {
1228		if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
#	Line 1094 | Line 1230 | public class ForkJoinPool extends Abstra
1230		}
1231
1232		/**
1233	<	* Clear out and cancel submissions
1233	>	* Clears out and cancels submissions.
1234		*/
1235		private void cancelQueuedSubmissions() {
1236		ForkJoinTask<?> task;
#	Line 1103 | Line 1239 | public class ForkJoinPool extends Abstra
1239		}
1240
1241		/**
1242	<	* Clean out worker queues.
1242	>	* Cleans out worker queues.
1243		*/
1244		private void cancelQueuedWorkerTasks() {
1245		final ReentrantLock lock = this.workerLock;
1246		lock.lock();
1247		try {
1248		ForkJoinWorkerThread[] ws = workers;
1249	<	for (int i = 0; i < ws.length; ++i) {
1250	<	ForkJoinWorkerThread t = ws[i];
1251	<	if (t != null)
1252	<	t.cancelTasks();
1249	>	if (ws != null) {
1250	>	for (int i = 0; i < ws.length; ++i) {
1251	>	ForkJoinWorkerThread t = ws[i];
1252	>	if (t != null)
1253	>	t.cancelTasks();
1254	>	}
1255		}
1256		} finally {
1257		lock.unlock();
#	Line 1121 | Line 1259 | public class ForkJoinPool extends Abstra
1259		}
1260
1261		/**
1262	<	* Set each worker's status to terminating. Requires lock to avoid
1263	<	* conflicts with add/remove
1262	>	* Sets each worker's status to terminating. Requires lock to avoid
1263	>	* conflicts with add/remove.
1264		*/
1265		private void stopAllWorkers() {
1266		final ReentrantLock lock = this.workerLock;
1267		lock.lock();
1268		try {
1269		ForkJoinWorkerThread[] ws = workers;
1270	<	for (int i = 0; i < ws.length; ++i) {
1271	<	ForkJoinWorkerThread t = ws[i];
1272	<	if (t != null)
1273	<	t.shutdownNow();
1270	>	if (ws != null) {
1271	>	for (int i = 0; i < ws.length; ++i) {
1272	>	ForkJoinWorkerThread t = ws[i];
1273	>	if (t != null)
1274	>	t.shutdownNow();
1275	>	}
1276		}
1277		} finally {
1278		lock.unlock();
#	Line 1140 | Line 1280 | public class ForkJoinPool extends Abstra
1280		}
1281
1282		/**
1283	<	* Interrupt all unterminated workers.  This is not required for
1283	>	* Interrupts all unterminated workers.  This is not required for
1284		* sake of internal control, but may help unstick user code during
1285		* shutdown.
1286		*/
#	Line 1149 | Line 1289 | public class ForkJoinPool extends Abstra
1289		lock.lock();
1290		try {
1291		ForkJoinWorkerThread[] ws = workers;
1292	<	for (int i = 0; i < ws.length; ++i) {
1293	<	ForkJoinWorkerThread t = ws[i];
1294	<	if (t != null && !t.isTerminated()) {
1295	<	try {
1296	<	t.interrupt();
1297	<	} catch (SecurityException ignore) {
1292	>	if (ws != null) {
1293	>	for (int i = 0; i < ws.length; ++i) {
1294	>	ForkJoinWorkerThread t = ws[i];
1295	>	if (t != null && !t.isTerminated()) {
1296	>	try {
1297	>	t.interrupt();
1298	>	} catch (SecurityException ignore) {
1299	>	}
1300		}
1301		}
1302		}
#	Line 1165 | Line 1307 | public class ForkJoinPool extends Abstra
1307
1308
1309		/*
1310	<	* Nodes for event barrier to manage idle threads.
1310	>	* Nodes for event barrier to manage idle threads.  Queue nodes
1311	>	* are basic Treiber stack nodes, also used for spare stack.
1312		*
1313		* The event barrier has an event count and a wait queue (actually
1314		* a Treiber stack).  Workers are enabled to look for work when
1315	<	* the eventCount is incremented. If they fail to find some,
1316	<	* they may wait for next count. Synchronization events occur only
1317	<	* in enough contexts to maintain overall liveness:
1315	>	* the eventCount is incremented. If they fail to find work, they
1316	>	* may wait for next count. Upon release, threads help others wake
1317	>	* up.
1318	>	*
1319	>	* Synchronization events occur only in enough contexts to
1320	>	* maintain overall liveness:
1321		*
1322		*   - Submission of a new task to the pool
1323	<	*   - Creation or termination of a worker
1323	>	*   - Resizes or other changes to the workers array
1324		*   - pool termination
1325		*   - A worker pushing a task on an empty queue
1326		*
1327	<	* The last case (pushing a task) occurs often enough, and is
1328	<	* heavy enough compared to simple stack pushes to require some
1329	<	* special handling: Method signalNonEmptyWorkerQueue returns
1330	<	* without advancing count if the queue appears to be empty.  This
1331	<	* would ordinarily result in races causing some queued waiters
1332	<	* not to be woken up. To avoid this, a worker in sync
1333	<	* rescans for tasks after being enqueued if it was the first to
1334	<	* enqueue, and aborts the wait if finding one, also helping to
1335	<	* signal others. This works well because the worker has nothing
1336	<	* better to do anyway, and so might as well help alleviate the
1337	<	* overhead and contention on the threads actually doing work.
1338	<	*
1339	<	* Queue nodes are basic Treiber stack nodes, also used for spare
1340	<	* stack.
1327	>	* The case of pushing a task occurs often enough, and is heavy
1328	>	* enough compared to simple stack pushes, to require special
1329	>	* handling: Method signalWork returns without advancing count if
1330	>	* the queue appears to be empty.  This would ordinarily result in
1331	>	* races causing some queued waiters not to be woken up. To avoid
1332	>	* this, the first worker enqueued in method sync (see
1333	>	* syncIsReleasable) rescans for tasks after being enqueued, and
1334	>	* helps signal if any are found. This works well because the
1335	>	* worker has nothing better to do, and so might as well help
1336	>	* alleviate the overhead and contention on the threads actually
1337	>	* doing work.  Also, since event counts increments on task
1338	>	* availability exist to maintain liveness (rather than to force
1339	>	* refreshes etc), it is OK for callers to exit early if
1340	>	* contending with another signaller.
1341		*/
1342		static final class WaitQueueNode {
1343		WaitQueueNode next; // only written before enqueued
1344		volatile ForkJoinWorkerThread thread; // nulled to cancel wait
1345		final long count; // unused for spare stack
1346	<	WaitQueueNode(ForkJoinWorkerThread w, long c) {
1346	>
1347	>	WaitQueueNode(long c, ForkJoinWorkerThread w) {
1348		count = c;
1349		thread = w;
1350		}
1351	<	final boolean signal() {
1351	>
1352	>	/**
1353	>	* Wakes up waiter, returning false if known to already
1354	>	*/
1355	>	boolean signal() {
1356		ForkJoinWorkerThread t = thread;
1357	+	if (t == null)
1358	+	return false;
1359		thread = null;
1360	<	if (t != null) {
1361	<	LockSupport.unpark(t);
1362	<	return true;
1360	>	LockSupport.unpark(t);
1361	>	return true;
1362	>	}
1363	>
1364	>	/**
1365	>	* Awaits release on sync.
1366	>	*/
1367	>	void awaitSyncRelease(ForkJoinPool p) {
1368	>	while (thread != null && !p.syncIsReleasable(this))
1369	>	LockSupport.park(this);
1370	>	}
1371	>
1372	>	/**
1373	>	* Awaits resumption as spare.
1374	>	*/
1375	>	void awaitSpareRelease() {
1376	>	while (thread != null) {
1377	>	if (!Thread.interrupted())
1378	>	LockSupport.park(this);
1379		}
1211	–	return false;
1380		}
1381		}
1382
1383		/**
1384	<	* Release at least one thread waiting for event count to advance,
1385	<	* if one exists. If initial attempt fails, release all threads.
1386	<	* @param all if false, at first try to only release one thread
1387	<	* @return current event
1384	>	* Ensures that no thread is waiting for count to advance from the
1385	>	* current value of eventCount read on entry to this method, by
1386	>	* releasing waiting threads if necessary.
1387	>	*
1388	>	* @return the count
1389		*/
1390	<	private long releaseIdleWorkers(boolean all) {
1391	<	long c;
1392	<	for (;;) {
1393	<	WaitQueueNode q = barrierStack;
1394	<	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)) {
1390	>	final long ensureSync() {
1391	>	long c = eventCount;
1392	>	WaitQueueNode q;
1393	>	while ((q = syncStack) != null && q.count < c) {
1394	>	if (casBarrierStack(q, null)) {
1395		do {
1396	<	q.signal();
1396	>	q.signal();
1397		} while ((q = q.next) != null);
1398		break;
1399		}
#	Line 1242 | Line 1402 | public class ForkJoinPool extends Abstra
1402		}
1403
1404		/**
1405	<	* 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
1405	>	* Increments event count and releases waiting threads.
1406		*/
1407	<	final void signalIdleWorkers(boolean all) {
1407	>	private void signalIdleWorkers() {
1408		long c;
1409	<	do;while (!casEventCount(c = eventCount, c+1));
1410	<	releaseIdleWorkers(all);
1409	>	do {} while (!casEventCount(c = eventCount, c+1));
1410	>	ensureSync();
1411		}
1412
1413		/**
1414	<	* Wake up threads waiting to steal a task. Because method
1415	<	* sync rechecks availability, it is OK to only proceed if
1416	<	* queue appears to be non-empty.
1414	>	* Signals threads waiting to poll a task. Because method sync
1415	>	* rechecks availability, it is OK to only proceed if queue
1416	>	* appears to be non-empty, and OK to skip under contention to
1417	>	* increment count (since some other thread succeeded).
1418		*/
1419	<	final void signalNonEmptyWorkerQueue() {
1271	<	// If CAS fails another signaller must have succeeded
1419	>	final void signalWork() {
1420		long c;
1421	<	if (barrierStack != null && casEventCount(c = eventCount, c+1))
1422	<	releaseIdleWorkers(false);
1421	>	WaitQueueNode q;
1422	>	if (syncStack != null &&
1423	>	casEventCount(c = eventCount, c+1) &&
1424	>	(((q = syncStack) != null && q.count <= c) &&
1425	>	(!casBarrierStack(q, q.next) || !q.signal())))
1426	>	ensureSync();
1427		}
1428
1429		/**
1430	<	* Waits until event count advances from count, or some thread is
1431	<	* waiting on a previous count, or there is stealable work
1432	<	* available. Help wake up others on release.
1430	>	* Waits until event count advances from last value held by
1431	>	* caller, or if excess threads, caller is resumed as spare, or
1432	>	* caller or pool is terminating. Updates caller's event on exit.
1433	>	*
1434		* @param w the calling worker thread
1282	–	* @param prev previous value returned by sync (or 0)
1283	–	* @return current event count
1435		*/
1436	<	final long sync(ForkJoinWorkerThread w, long prev) {
1437	<	updateStealCount(w);
1436	>	final void sync(ForkJoinWorkerThread w) {
1437	>	updateStealCount(w); // Transfer w's count while it is idle
1438
1439	<	while (!w.isShutdown() && !isTerminating() &&
1440	<	(parallelism >= runningCountOf(workerCounts) ||
1290	<	!suspendIfSpare(w))) { // prefer suspend to waiting here
1439	>	while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) {
1440	>	long prev = w.lastEventCount;
1441		WaitQueueNode node = null;
1442	<	boolean queued = false;
1443	<	for (;;) {
1444	<	if (!queued) {
1445	<	if (eventCount != prev)
1446	<	break;
1447	<	WaitQueueNode h = barrierStack;
1448	<	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);
1442	>	WaitQueueNode h;
1443	>	while (eventCount == prev &&
1444	>	((h = syncStack) == null || h.count == prev)) {
1445	>	if (node == null)
1446	>	node = new WaitQueueNode(prev, w);
1447	>	if (casBarrierStack(node.next = h, node)) {
1448	>	node.awaitSyncRelease(this);
1449		break;
1450		}
1313	–	else
1314	–	LockSupport.park(this);
1451		}
1452	+	long ec = ensureSync();
1453	+	if (ec != prev) {
1454	+	w.lastEventCount = ec;
1455	+	break;
1456	+	}
1457	+	}
1458	+	}
1459	+
1460	+	/**
1461	+	* Returns true if worker waiting on sync can proceed:
1462	+	*  - on signal (thread == null)
1463	+	*  - on event count advance (winning race to notify vs signaller)
1464	+	*  - on interrupt
1465	+	*  - if the first queued node, we find work available
1466	+	* If node was not signalled and event count not advanced on exit,
1467	+	* then we also help advance event count.
1468	+	*
1469	+	* @return true if node can be released
1470	+	*/
1471	+	final boolean syncIsReleasable(WaitQueueNode node) {
1472	+	long prev = node.count;
1473	+	if (!Thread.interrupted() && node.thread != null &&
1474	+	(node.next != null ||
1475	+	!ForkJoinWorkerThread.hasQueuedTasks(workers)) &&
1476	+	eventCount == prev)
1477	+	return false;
1478	+	if (node.thread != null) {
1479	+	node.thread = null;
1480		long ec = eventCount;
1481	<	if (releaseIdleWorkers(false) != prev)
1482	<	return ec;
1481	>	if (prev <= ec) // help signal
1482	>	casEventCount(ec, ec+1);
1483		}
1484	<	return prev; // return old count if aborted
1484	>	return true;
1485	>	}
1486	>
1487	>	/**
1488	>	* Returns true if a new sync event occurred since last call to
1489	>	* sync or this method, if so, updating caller's count.
1490	>	*/
1491	>	final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1492	>	long lc = w.lastEventCount;
1493	>	long ec = ensureSync();
1494	>	if (ec == lc)
1495	>	return false;
1496	>	w.lastEventCount = ec;
1497	>	return true;
1498		}
1499
1500		//  Parallelism maintenance
1501
1502		/**
1503	<	* Decrement running count; if too low, add spare.
1503	>	* Decrements running count; if too low, adds spare.
1504		*
1505		* Conceptually, all we need to do here is add or resume a
1506		* spare thread when one is about to block (and remove or
1507		* suspend it later when unblocked -- see suspendIfSpare).
1508		* However, implementing this idea requires coping with
1509	<	* several problems: We have imperfect information about the
1509	>	* several problems: we have imperfect information about the
1510		* states of threads. Some count updates can and usually do
1511		* lag run state changes, despite arrangements to keep them
1512		* accurate (for example, when possible, updating counts
#	Line 1343 | Line 1520 | public class ForkJoinPool extends Abstra
1520		* only be suspended or removed when they are idle, not
1521		* immediately when they aren't needed. So adding threads will
1522		* raise parallelism level for longer than necessary.  Also,
1523	<	* FJ applications often enounter highly transient peaks when
1523	>	* FJ applications often encounter highly transient peaks when
1524		* many threads are blocked joining, but for less time than it
1525		* takes to create or resume spares.
1526		*
#	Line 1352 | Line 1529 | public class ForkJoinPool extends Abstra
1529		* target counts, else create only to avoid starvation
1530		* @return true if joinMe known to be done
1531		*/
1532	<	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1532	>	final boolean preJoin(ForkJoinTask<?> joinMe,
1533	>	boolean maintainParallelism) {
1534		maintainParallelism &= maintainsParallelism; // overrride
1535		boolean dec = false;  // true when running count decremented
1536		while (spareStack == null || !tryResumeSpare(dec)) {
1537		int counts = workerCounts;
1538	<	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1538	>	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1539	>	// CAS cheat
1540		if (!needSpare(counts, maintainParallelism))
1541		break;
1542		if (joinMe.status < 0)
#	Line 1372 | Line 1551 | public class ForkJoinPool extends Abstra
1551		/**
1552		* Same idea as preJoin
1553		*/
1554	<	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1554	>	final boolean preBlock(ManagedBlocker blocker,
1555	>	boolean maintainParallelism) {
1556		maintainParallelism &= maintainsParallelism;
1557		boolean dec = false;
1558		while (spareStack == null || !tryResumeSpare(dec)) {
#	Line 1396 | Line 1576 | public class ForkJoinPool extends Abstra
1576		* there is apparently some work to do.  This self-limiting rule
1577		* means that the more threads that have already been added, the
1578		* less parallelism we will tolerate before adding another.
1579	+	*
1580		* @param counts current worker counts
1581		* @param maintainParallelism try to maintain parallelism
1582		*/
#	Line 1408 | Line 1589 | public class ForkJoinPool extends Abstra
1589		return (tc < maxPoolSize &&
1590		(rc == 0 || totalSurplus < 0 ||
1591		(maintainParallelism &&
1592	<	runningDeficit > totalSurplus && mayHaveQueuedWork())));
1593	<	}
1413	<
1414	<	/**
1415	<	* Returns true if at least one worker queue appears to be
1416	<	* nonempty. This is expensive but not often called. It is not
1417	<	* 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;
1592	>	runningDeficit > totalSurplus &&
1593	>	ForkJoinWorkerThread.hasQueuedTasks(workers))));
1594		}
1595
1596		/**
1597	<	* Add a spare worker if lock available and no more than the
1598	<	* expected numbers of threads exist
1597	>	* Adds a spare worker if lock available and no more than the
1598	>	* expected numbers of threads exist.
1599	>	*
1600		* @return true if successful
1601		*/
1602		private boolean tryAddSpare(int expectedCounts) {
#	Line 1465 | Line 1629 | public class ForkJoinPool extends Abstra
1629		}
1630
1631		/**
1632	<	* Add the kth spare worker. On entry, pool coounts are already
1632	>	* Adds the kth spare worker. On entry, pool counts are already
1633		* adjusted to reflect addition.
1634		*/
1635		private void createAndStartSpare(int k) {
#	Line 1477 | Line 1641 | public class ForkJoinPool extends Abstra
1641		for (k = 0; k < len && ws[k] != null; ++k)
1642		;
1643		}
1644	<	if (k < len && (w = createWorker(k)) != null) {
1644	>	if (k < len && !isTerminating() && (w = createWorker(k)) != null) {
1645		ws[k] = w;
1646		w.start();
1647		}
1648		else
1649		updateWorkerCount(-1); // adjust on failure
1650	<	signalIdleWorkers(false);
1650	>	signalIdleWorkers();
1651		}
1652
1653		/**
1654	<	* Suspend calling thread w if there are excess threads.  Called
1655	<	* only from sync.  Spares are enqueued in a Treiber stack
1656	<	* using the same WaitQueueNodes as barriers.  They are resumed
1657	<	* mainly in preJoin, but are also woken on pool events that
1658	<	* require all threads to check run state.
1654	>	* Suspends calling thread w if there are excess threads.  Called
1655	>	* only from sync.  Spares are enqueued in a Treiber stack using
1656	>	* the same WaitQueueNodes as barriers.  They are resumed mainly
1657	>	* in preJoin, but are also woken on pool events that require all
1658	>	* threads to check run state.
1659	>	*
1660		* @param w the caller
1661		*/
1662		private boolean suspendIfSpare(ForkJoinWorkerThread w) {
#	Line 1499 | Line 1664 | public class ForkJoinPool extends Abstra
1664		int s;
1665		while (parallelism < runningCountOf(s = workerCounts)) {
1666		if (node == null)
1667	<	node = new WaitQueueNode(w, 0);
1667	>	node = new WaitQueueNode(0, w);
1668		if (casWorkerCounts(s, s-1)) { // representation-dependent
1669		// push onto stack
1670	<	do;while (!casSpareStack(node.next = spareStack, node));
1506	<
1670	>	do {} while (!casSpareStack(node.next = spareStack, node));
1671		// block until released by resumeSpare
1672	<	while (node.thread != null) {
1509	<	if (!Thread.interrupted())
1510	<	LockSupport.park(this);
1511	<	}
1512	<	w.activate(); // help warm up
1672	>	node.awaitSpareRelease();
1673		return true;
1674		}
1675		}
#	Line 1517 | Line 1677 | public class ForkJoinPool extends Abstra
1677		}
1678
1679		/**
1680	<	* Try to pop and resume a spare thread.
1680	>	* Tries to pop and resume a spare thread.
1681	>	*
1682		* @param updateCount if true, increment running count on success
1683		* @return true if successful
1684		*/
#	Line 1535 | Line 1696 | public class ForkJoinPool extends Abstra
1696		}
1697
1698		/**
1699	<	* Pop and resume all spare threads. Same idea as
1700	<	* releaseIdleWorkers.
1699	>	* Pops and resumes all spare threads. Same idea as ensureSync.
1700	>	*
1701		* @return true if any spares released
1702		*/
1703		private boolean resumeAllSpares() {
#	Line 1554 | Line 1715 | public class ForkJoinPool extends Abstra
1715		}
1716
1717		/**
1718	<	* Pop and shutdown excessive spare threads. Call only while
1718	>	* Pops and shuts down excessive spare threads. Call only while
1719		* holding lock. This is not guaranteed to eliminate all excess
1720		* threads, only those suspended as spares, which are the ones
1721		* unlikely to be needed in the future.
#	Line 1577 | Line 1738 | public class ForkJoinPool extends Abstra
1738		}
1739
1740		/**
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	–	/**
1741		* Interface for extending managed parallelism for tasks running
1742		* in ForkJoinPools. A ManagedBlocker provides two methods.
1743	<	* Method <code>isReleasable</code> must return true if blocking is not
1744	<	* necessary. Method <code>block</code> blocks the current thread
1745	<	* if necessary (perhaps internally invoking isReleasable before
1746	<	* actually blocking.).
1743	>	* Method {@code isReleasable} must return true if blocking is not
1744	>	* necessary. Method {@code block} blocks the current thread if
1745	>	* necessary (perhaps internally invoking {@code isReleasable}
1746	>	* before actually blocking.).
1747	>	*
1748		* <p>For example, here is a ManagedBlocker based on a
1749		* ReentrantLock:
1750	<	* <pre>
1751	<	*   class ManagedLocker implements ManagedBlocker {
1752	<	*     final ReentrantLock lock;
1753	<	*     boolean hasLock = false;
1754	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1755	<	*     public boolean block() {
1756	<	*        if (!hasLock)
1757	<	*           lock.lock();
1758	<	*        return true;
1759	<	*     }
1760	<	*     public boolean isReleasable() {
1761	<	*        return hasLock || (hasLock = lock.tryLock());
1610	<	*     }
1750	>	*  <pre> {@code
1751	>	* class ManagedLocker implements ManagedBlocker {
1752	>	*   final ReentrantLock lock;
1753	>	*   boolean hasLock = false;
1754	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1755	>	*   public boolean block() {
1756	>	*     if (!hasLock)
1757	>	*       lock.lock();
1758	>	*     return true;
1759	>	*   }
1760	>	*   public boolean isReleasable() {
1761	>	*     return hasLock || (hasLock = lock.tryLock());
1762		*   }
1763	<	* </pre>
1763	>	* }}</pre>
1764		*/
1765		public static interface ManagedBlocker {
1766		/**
1767		* Possibly blocks the current thread, for example waiting for
1768		* a lock or condition.
1769	+	*
1770		* @return true if no additional blocking is necessary (i.e.,
1771	<	* if isReleasable would return true).
1771	>	* if isReleasable would return true)
1772		* @throws InterruptedException if interrupted while waiting
1773	<	* (the method is not required to do so, but is allowe to).
1773	>	* (the method is not required to do so, but is allowed to)
1774		*/
1775		boolean block() throws InterruptedException;
1776
#	Line 1633 | Line 1785 | public class ForkJoinPool extends Abstra
1785		* is a ForkJoinWorkerThread, this method possibly arranges for a
1786		* spare thread to be activated if necessary to ensure parallelism
1787		* while the current thread is blocked.  If
1788	<	* <code>maintainParallelism</code> is true and the pool supports
1788	>	* {@code maintainParallelism} is true and the pool supports
1789		* it ({@link #getMaintainsParallelism}), this method attempts to
1790	<	* maintain the pool's nominal parallelism. Otherwise if activates
1790	>	* maintain the pool's nominal parallelism. Otherwise it activates
1791		* a thread only if necessary to avoid complete starvation. This
1792		* option may be preferable when blockages use timeouts, or are
1793		* almost always brief.
1794		*
1795		* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1796		* equivalent to
1797	<	* <pre>
1798	<	*   while (!blocker.isReleasable())
1799	<	*      if (blocker.block())
1800	<	*         return;
1801	<	* </pre>
1797	>	*  <pre> {@code
1798	>	* while (!blocker.isReleasable())
1799	>	*   if (blocker.block())
1800	>	*     return;
1801	>	* }</pre>
1802		* If the caller is a ForkJoinTask, then the pool may first
1803		* be expanded to ensure parallelism, and later adjusted.
1804		*
#	Line 1655 | Line 1807 | public class ForkJoinPool extends Abstra
1807		* attempt to maintain the pool's nominal parallelism; otherwise
1808		* activate a thread only if necessary to avoid complete
1809		* starvation.
1810	<	* @throws InterruptedException if blocker.block did so.
1810	>	* @throws InterruptedException if blocker.block did so
1811		*/
1812		public static void managedBlock(ManagedBlocker blocker,
1813		boolean maintainParallelism)
1814		throws InterruptedException {
1815		Thread t = Thread.currentThread();
1816	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1817	<	((ForkJoinWorkerThread)t).pool : null);
1816	>	ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ?
1817	>	((ForkJoinWorkerThread) t).pool : null);
1818		if (!blocker.isReleasable()) {
1819		try {
1820		if (pool == null ||
#	Line 1677 | Line 1829 | public class ForkJoinPool extends Abstra
1829
1830		private static void awaitBlocker(ManagedBlocker blocker)
1831		throws InterruptedException {
1832	<	do;while (!blocker.isReleasable() && !blocker.block());
1832	>	do {} while (!blocker.isReleasable() && !blocker.block());
1833		}
1834
1835		// AbstractExecutorService overrides
1836
1837		protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
1838	<	return new AdaptedRunnable(runnable, value);
1838	>	return new AdaptedRunnable<T>(runnable, value);
1839		}
1840
1841		protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
1842	<	return new AdaptedCallable(callable);
1842	>	return new AdaptedCallable<T>(callable);
1843		}
1844
1845
1846	<	// Temporary Unsafe mechanics for preliminary release
1846	>	// Unsafe mechanics for jsr166y 3rd party package.
1847	>	private static sun.misc.Unsafe getUnsafe() {
1848	>	try {
1849	>	return sun.misc.Unsafe.getUnsafe();
1850	>	} catch (SecurityException se) {
1851	>	try {
1852	>	return java.security.AccessController.doPrivileged
1853	>	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1854	>	public sun.misc.Unsafe run() throws Exception {
1855	>	return getUnsafeByReflection();
1856	>	}});
1857	>	} catch (java.security.PrivilegedActionException e) {
1858	>	throw new RuntimeException("Could not initialize intrinsics",
1859	>	e.getCause());
1860	>	}
1861	>	}
1862	>	}
1863
1864	<	static final Unsafe _unsafe;
1865	<	static final long eventCountOffset;
1866	<	static final long workerCountsOffset;
1867	<	static final long runControlOffset;
1868	<	static final long barrierStackOffset;
1869	<	static final long spareStackOffset;
1864	>	private static sun.misc.Unsafe getUnsafeByReflection()
1865	>	throws NoSuchFieldException, IllegalAccessException {
1866	>	java.lang.reflect.Field f =
1867	>	sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
1868	>	f.setAccessible(true);
1869	>	return (sun.misc.Unsafe) f.get(null);
1870	>	}
1871
1872	<	static {
1872	>	private static long fieldOffset(String fieldName, Class<?> klazz) {
1873		try {
1874	<	if (ForkJoinPool.class.getClassLoader() != null) {
1875	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1876	<	f.setAccessible(true);
1877	<	_unsafe = (Unsafe)f.get(null);
1878	<	}
1879	<	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);
1874	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
1875	>	} catch (NoSuchFieldException e) {
1876	>	// Convert Exception to Error
1877	>	NoSuchFieldError error = new NoSuchFieldError(fieldName);
1878	>	error.initCause(e);
1879	>	throw error;
1880		}
1881		}
1882
1883	+	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1884	+	static final long eventCountOffset =
1885	+	fieldOffset("eventCount", ForkJoinPool.class);
1886	+	static final long workerCountsOffset =
1887	+	fieldOffset("workerCounts", ForkJoinPool.class);
1888	+	static final long runControlOffset =
1889	+	fieldOffset("runControl", ForkJoinPool.class);
1890	+	static final long syncStackOffset =
1891	+	fieldOffset("syncStack",ForkJoinPool.class);
1892	+	static final long spareStackOffset =
1893	+	fieldOffset("spareStack", ForkJoinPool.class);
1894	+
1895		private boolean casEventCount(long cmp, long val) {
1896	<	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1896	>	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
1897		}
1898		private boolean casWorkerCounts(int cmp, int val) {
1899	<	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1899	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1900		}
1901		private boolean casRunControl(int cmp, int val) {
1902	<	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1902	>	return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
1903		}
1904		private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1905	<	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1905	>	return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
1906		}
1907		private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1908	<	return _unsafe.compareAndSwapObject(this, barrierStackOffset, cmp, val);
1908	>	return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1909		}
1910		}

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