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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 1.17 by jsr166, Thu Jul 23 23:07:57 2009 UTC

#	Line 27 | Line 27 | import java.lang.reflect.*;
27		* (eventually blocking if none exist). This makes them efficient when
28		* most tasks spawn other subtasks (as do most ForkJoinTasks), as well
29		* as the mixed execution of some plain Runnable- or Callable- based
30	<	* activities along with ForkJoinTasks. Otherwise, other
30	>	* activities along with ForkJoinTasks. When setting
31	>	* {@code setAsyncMode}, a ForkJoinPools may also be appropriate for
32	>	* use with fine-grained tasks that are never joined. Otherwise, other
33		* ExecutorService implementations are typically more appropriate
34		* choices.
35		*
#	Line 36 | Line 38 | import java.lang.reflect.*;
38		* adding, suspending, or resuming threads, even if some tasks are
39		* waiting to join others. However, no such adjustments are performed
40		* in the face of blocked IO or other unmanaged synchronization. The
41	<	* nested <code>ManagedBlocker</code> interface enables extension of
41	>	* nested {@code ManagedBlocker} interface enables extension of
42		* the kinds of synchronization accommodated.  The target parallelism
43	<	* level may also be changed dynamically (<code>setParallelism</code>)
44	<	* and dynamically thread construction can be limited using methods
45	<	* <code>setMaximumPoolSize</code> and/or
46	<	* <code>setMaintainsParallelism</code>.
43	>	* level may also be changed dynamically ({@code setParallelism})
44	>	* and thread construction can be limited using methods
45	>	* {@code setMaximumPoolSize} and/or
46	>	* {@code setMaintainsParallelism}.
47		*
48		* <p>In addition to execution and lifecycle control methods, this
49		* class provides status check methods (for example
50	<	* <code>getStealCount</code>) that are intended to aid in developing,
50	>	* {@code getStealCount}) that are intended to aid in developing,
51		* tuning, and monitoring fork/join applications. Also, method
52	<	* <code>toString</code> returns indications of pool state in a
52	>	* {@code toString} returns indications of pool state in a
53		* convenient form for informal monitoring.
54		*
55		* <p><b>Implementation notes</b>: This implementation restricts the
56		* maximum number of running threads to 32767. Attempts to create
57		* pools with greater than the maximum result in
58		* IllegalArgumentExceptions.
59	+	*
60	+	* @since 1.7
61	+	* @author Doug Lea
62		*/
63		public class ForkJoinPool extends AbstractExecutorService {
64
#	Line 79 | Line 84 | public class ForkJoinPool extends Abstra
84		* Returns a new worker thread operating in the given pool.
85		*
86		* @param pool the pool this thread works in
87	<	* @throws NullPointerException if pool is null;
87	>	* @throws NullPointerException if pool is null
88		*/
89		public ForkJoinWorkerThread newThread(ForkJoinPool pool);
90		}
91
92		/**
93	<	* Default ForkJoinWorkerThreadFactory implementation, creates a
93	>	* Default ForkJoinWorkerThreadFactory implementation; creates a
94		* new ForkJoinWorkerThread.
95		*/
96		static class  DefaultForkJoinWorkerThreadFactory
#	Line 131 | Line 136 | public class ForkJoinPool extends Abstra
136		new AtomicInteger();
137
138		/**
139	<	* Array holding all worker threads in the pool. Array size must
140	<	* be a power of two.  Updates and replacements are protected by
141	<	* workerLock, but it is always kept in a consistent enough state
142	<	* to be randomly accessed without locking by workers performing
143	<	* work-stealing.
139	>	* Array holding all worker threads in the pool. Initialized upon
140	>	* first use. Array size must be a power of two.  Updates and
141	>	* replacements are protected by workerLock, but it is always kept
142	>	* in a consistent enough state to be randomly accessed without
143	>	* locking by workers performing work-stealing.
144		*/
145		volatile ForkJoinWorkerThread[] workers;
146
#	Line 151 | Line 156 | public class ForkJoinPool extends Abstra
156
157		/**
158		* The uncaught exception handler used when any worker
159	<	* abrupty terminates
159	>	* abruptly terminates
160		*/
161		private Thread.UncaughtExceptionHandler ueh;
162
#	Line 179 | Line 184 | public class ForkJoinPool extends Abstra
184		private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
185
186		/**
187	<	* Head of Treiber stack for barrier sync. See below for explanation
187	>	* Head of Treiber stack for barrier sync. See below for explanation.
188		*/
189	<	private volatile WaitQueueNode barrierStack;
189	>	private volatile WaitQueueNode syncStack;
190
191		/**
192		* The count for event barrier
#	Line 204 | Line 209 | public class ForkJoinPool extends Abstra
209		private volatile int parallelism;
210
211		/**
212	+	* True if use local fifo, not default lifo, for local polling
213	+	*/
214	+	private volatile boolean locallyFifo;
215	+
216	+	/**
217		* Holds number of total (i.e., created and not yet terminated)
218		* and running (i.e., not blocked on joins or other managed sync)
219		* threads, packed into one int to ensure consistent snapshot when
220		* making decisions about creating and suspending spare
221		* threads. Updated only by CAS.  Note: CASes in
222	<	* updateRunningCount and preJoin running active count is in low
223	<	* word, so need to be modified if this changes
222	>	* updateRunningCount and preJoin assume that running active count
223	>	* is in low word, so need to be modified if this changes.
224		*/
225		private volatile int workerCounts;
226
#	Line 219 | Line 229 | public class ForkJoinPool extends Abstra
229		private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
230
231		/**
232	<	* Add delta (which may be negative) to running count.  This must
232	>	* Adds delta (which may be negative) to running count.  This must
233		* be called before (with negative arg) and after (with positive)
234	<	* any managed synchronization (i.e., mainly, joins)
234	>	* any managed synchronization (i.e., mainly, joins).
235	>	*
236		* @param delta the number to add
237		*/
238		final void updateRunningCount(int delta) {
239		int s;
240	<	do;while (!casWorkerCounts(s = workerCounts, s + delta));
240	>	do {} while (!casWorkerCounts(s = workerCounts, s + delta));
241		}
242
243		/**
244	<	* Add delta (which may be negative) to both total and running
244	>	* Adds delta (which may be negative) to both total and running
245		* count.  This must be called upon creation and termination of
246		* worker threads.
247	+	*
248		* @param delta the number to add
249		*/
250		private void updateWorkerCount(int delta) {
251		int d = delta + (delta << 16); // add to both lo and hi parts
252		int s;
253	<	do;while (!casWorkerCounts(s = workerCounts, s + d));
253	>	do {} while (!casWorkerCounts(s = workerCounts, s + d));
254		}
255
256		/**
#	Line 264 | Line 276 | public class ForkJoinPool extends Abstra
276		private static int runControlFor(int r, int a)   { return (r << 16) + a; }
277
278		/**
279	<	* Increment active count. Called by workers before/during
280	<	* executing tasks.
279	>	* Tries incrementing active count; fails on contention.
280	>	* Called by workers before/during executing tasks.
281	>	*
282	>	* @return true on success
283		*/
284	<	final void incrementActiveCount() {
285	<	int c;
286	<	do;while (!casRunControl(c = runControl, c+1));
284	>	final boolean tryIncrementActiveCount() {
285	>	int c = runControl;
286	>	return casRunControl(c, c+1);
287		}
288
289		/**
290	<	* Decrement active count; possibly trigger termination.
290	>	* Tries decrementing active count; fails on contention.
291	>	* Possibly triggers termination on success.
292		* Called by workers when they can't find tasks.
293	+	*
294	+	* @return true on success
295		*/
296	<	final void decrementActiveCount() {
297	<	int c, nextc;
298	<	do;while (!casRunControl(c = runControl, nextc = c-1));
296	>	final boolean tryDecrementActiveCount() {
297	>	int c = runControl;
298	>	int nextc = c - 1;
299	>	if (!casRunControl(c, nextc))
300	>	return false;
301		if (canTerminateOnShutdown(nextc))
302		terminateOnShutdown();
303	+	return true;
304		}
305
306		/**
307	<	* Return true if argument represents zero active count and
307	>	* Returns true if argument represents zero active count and
308		* nonzero runstate, which is the triggering condition for
309		* terminating on shutdown.
310		*/
311		private static boolean canTerminateOnShutdown(int c) {
312	<	return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
312	>	// i.e. least bit is nonzero runState bit
313	>	return ((c & -c) >>> 16) != 0;
314		}
315
316		/**
#	Line 315 | Line 336 | public class ForkJoinPool extends Abstra
336
337		/**
338		* Creates a ForkJoinPool with a pool size equal to the number of
339	<	* processors available on the system and using the default
340	<	* ForkJoinWorkerThreadFactory,
339	>	* processors available on the system, using the default
340	>	* ForkJoinWorkerThreadFactory.
341	>	*
342		* @throws SecurityException if a security manager exists and
343		*         the caller is not permitted to modify threads
344		*         because it does not hold {@link
345	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
345	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
346		*/
347		public ForkJoinPool() {
348		this(Runtime.getRuntime().availableProcessors(),
#	Line 328 | Line 350 | public class ForkJoinPool extends Abstra
350		}
351
352		/**
353	<	* Creates a ForkJoinPool with the indicated parellelism level
354	<	* threads, and using the default ForkJoinWorkerThreadFactory,
353	>	* Creates a ForkJoinPool with the indicated parallelism level
354	>	* threads and using the default ForkJoinWorkerThreadFactory.
355	>	*
356		* @param parallelism the number of worker threads
357		* @throws IllegalArgumentException if parallelism less than or
358		* equal to zero
359		* @throws SecurityException if a security manager exists and
360		*         the caller is not permitted to modify threads
361		*         because it does not hold {@link
362	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
362	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
363		*/
364		public ForkJoinPool(int parallelism) {
365		this(parallelism, defaultForkJoinWorkerThreadFactory);
#	Line 345 | Line 368 | public class ForkJoinPool extends Abstra
368		/**
369		* Creates a ForkJoinPool with parallelism equal to the number of
370		* processors available on the system and using the given
371	<	* ForkJoinWorkerThreadFactory,
371	>	* ForkJoinWorkerThreadFactory.
372	>	*
373		* @param factory the factory for creating new threads
374		* @throws NullPointerException if factory is null
375		* @throws SecurityException if a security manager exists and
376		*         the caller is not permitted to modify threads
377		*         because it does not hold {@link
378	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
378	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
379		*/
380		public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
381		this(Runtime.getRuntime().availableProcessors(), factory);
#	Line 363 | Line 387 | public class ForkJoinPool extends Abstra
387		* @param parallelism the targeted number of worker threads
388		* @param factory the factory for creating new threads
389		* @throws IllegalArgumentException if parallelism less than or
390	<	* equal to zero, or greater than implementation limit.
390	>	* equal to zero, or greater than implementation limit
391		* @throws NullPointerException if factory is null
392		* @throws SecurityException if a security manager exists and
393		*         the caller is not permitted to modify threads
394		*         because it does not hold {@link
395	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
395	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
396		*/
397		public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
398		if (parallelism <= 0 || parallelism > MAX_THREADS)
#	Line 385 | Line 409 | public class ForkJoinPool extends Abstra
409		this.termination = workerLock.newCondition();
410		this.stealCount = new AtomicLong();
411		this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
412	<	createAndStartInitialWorkers(parallelism);
412	>	// worker array and workers are lazily constructed
413		}
414
415		/**
416	<	* Create new worker using factory.
416	>	* Creates a new worker thread using factory.
417	>	*
418		* @param index the index to assign worker
419		* @return new worker, or null of factory failed
420		*/
#	Line 399 | Line 424 | public class ForkJoinPool extends Abstra
424		if (w != null) {
425		w.poolIndex = index;
426		w.setDaemon(true);
427	+	w.setAsyncMode(locallyFifo);
428		w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
429		if (h != null)
430		w.setUncaughtExceptionHandler(h);
#	Line 407 | Line 433 | public class ForkJoinPool extends Abstra
433		}
434
435		/**
436	<	* Return a good size for worker array given pool size.
436	>	* Returns a good size for worker array given pool size.
437		* Currently requires size to be a power of two.
438		*/
439	<	private static int arraySizeFor(int ps) {
440	<	return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
439	>	private static int arraySizeFor(int poolSize) {
440	>	return (poolSize <= 1) ? 1 :
441	>	(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1)));
442		}
443
444		/**
445	<	* Create or resize array if necessary to hold newLength
445	>	* Creates or resizes array if necessary to hold newLength.
446	>	* Call only under exclusion.
447	>	*
448		* @return the array
449		*/
450		private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
#	Line 429 | Line 458 | public class ForkJoinPool extends Abstra
458		}
459
460		/**
461	<	* Try to shrink workers into smaller array after one or more terminate
461	>	* Tries to shrink workers into smaller array after one or more terminate.
462		*/
463		private void tryShrinkWorkerArray() {
464		ForkJoinWorkerThread[] ws = workers;
465	<	int len = ws.length;
466	<	int last = len - 1;
467	<	while (last >= 0 && ws[last] == null)
468	<	--last;
469	<	int newLength = arraySizeFor(last+1);
470	<	if (newLength < len)
471	<	workers = Arrays.copyOf(ws, newLength);
465	>	if (ws != null) {
466	>	int len = ws.length;
467	>	int last = len - 1;
468	>	while (last >= 0 && ws[last] == null)
469	>	--last;
470	>	int newLength = arraySizeFor(last+1);
471	>	if (newLength < len)
472	>	workers = Arrays.copyOf(ws, newLength);
473	>	}
474		}
475
476		/**
477	<	* Initial worker array and worker creation and startup. (This
447	<	* must be done under lock to avoid interference by some of the
448	<	* newly started threads while creating others.)
477	>	* Initializes workers if necessary.
478		*/
479	<	private void createAndStartInitialWorkers(int ps) {
480	<	final ReentrantLock lock = this.workerLock;
481	<	lock.lock();
482	<	try {
483	<	ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
484	<	for (int i = 0; i < ps; ++i) {
485	<	ForkJoinWorkerThread w = createWorker(i);
486	<	if (w != null) {
487	<	ws[i] = w;
488	<	w.start();
489	<	updateWorkerCount(1);
479	>	final void ensureWorkerInitialization() {
480	>	ForkJoinWorkerThread[] ws = workers;
481	>	if (ws == null) {
482	>	final ReentrantLock lock = this.workerLock;
483	>	lock.lock();
484	>	try {
485	>	ws = workers;
486	>	if (ws == null) {
487	>	int ps = parallelism;
488	>	ws = ensureWorkerArrayCapacity(ps);
489	>	for (int i = 0; i < ps; ++i) {
490	>	ForkJoinWorkerThread w = createWorker(i);
491	>	if (w != null) {
492	>	ws[i] = w;
493	>	w.start();
494	>	updateWorkerCount(1);
495	>	}
496	>	}
497		}
498	+	} finally {
499	+	lock.unlock();
500		}
463	–	} finally {
464	–	lock.unlock();
501		}
502		}
503
#	Line 507 | Line 543 | public class ForkJoinPool extends Abstra
543		private <T> void doSubmit(ForkJoinTask<T> task) {
544		if (isShutdown())
545		throw new RejectedExecutionException();
546	+	if (workers == null)
547	+	ensureWorkerInitialization();
548		submissionQueue.offer(task);
549	<	signalIdleWorkers(true);
549	>	signalIdleWorkers();
550		}
551
552		/**
553	<	* Performs the given task; returning its result upon completion
553	>	* Performs the given task, returning its result upon completion.
554	>	*
555		* @param task the task
556		* @return the task's result
557		* @throws NullPointerException if task is null
#	Line 525 | Line 564 | public class ForkJoinPool extends Abstra
564
565		/**
566		* Arranges for (asynchronous) execution of the given task.
567	+	*
568		* @param task the task
569		* @throws NullPointerException if task is null
570		* @throws RejectedExecutionException if pool is shut down
#	Line 559 | Line 599 | public class ForkJoinPool extends Abstra
599
600		/**
601		* Adaptor for Runnables. This implements RunnableFuture
602	<	* to be compliant with AbstractExecutorService constraints
602	>	* to be compliant with AbstractExecutorService constraints.
603		*/
604		static final class AdaptedRunnable<T> extends ForkJoinTask<T>
605		implements RunnableFuture<T> {
#	Line 615 | Line 655 | public class ForkJoinPool extends Abstra
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;
658	>	return (List<Future<T>>) (List) ts;
659		}
660
661		static final class InvokeAll<T> extends RecursiveAction {
662		final ArrayList<ForkJoinTask<T>> tasks;
663		InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
664		public void compute() {
665	<	try { invokeAll(tasks); } catch(Exception ignore) {}
665	>	try { invokeAll(tasks); }
666	>	catch (Exception ignore) {}
667		}
668		}
669
670		// Configuration and status settings and queries
671
672		/**
673	<	* Returns the factory used for constructing new workers
673	>	* Returns the factory used for constructing new workers.
674		*
675		* @return the factory used for constructing new workers
676		*/
#	Line 640 | Line 681 | public class ForkJoinPool extends Abstra
681		/**
682		* Returns the handler for internal worker threads that terminate
683		* due to unrecoverable errors encountered while executing tasks.
684	+	*
685		* @return the handler, or null if none
686		*/
687		public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
#	Line 665 | Line 707 | public class ForkJoinPool extends Abstra
707		* @throws SecurityException if a security manager exists and
708		*         the caller is not permitted to modify threads
709		*         because it does not hold {@link
710	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
710	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
711		*/
712		public Thread.UncaughtExceptionHandler
713		setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
#	Line 677 | Line 719 | public class ForkJoinPool extends Abstra
719		old = ueh;
720		ueh = h;
721		ForkJoinWorkerThread[] ws = workers;
722	<	for (int i = 0; i < ws.length; ++i) {
723	<	ForkJoinWorkerThread w = ws[i];
724	<	if (w != null)
725	<	w.setUncaughtExceptionHandler(h);
722	>	if (ws != null) {
723	>	for (int i = 0; i < ws.length; ++i) {
724	>	ForkJoinWorkerThread w = ws[i];
725	>	if (w != null)
726	>	w.setUncaughtExceptionHandler(h);
727	>	}
728		}
729		} finally {
730		lock.unlock();
#	Line 690 | Line 734 | public class ForkJoinPool extends Abstra
734
735
736		/**
737	<	* Sets the target paralleism level of this pool.
737	>	* Sets the target parallelism level of this pool.
738	>	*
739		* @param parallelism the target parallelism
740		* @throws IllegalArgumentException if parallelism less than or
741	<	* equal to zero or greater than maximum size bounds.
741	>	* equal to zero or greater than maximum size bounds
742		* @throws SecurityException if a security manager exists and
743		*         the caller is not permitted to modify threads
744		*         because it does not hold {@link
745	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
745	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
746		*/
747		public void setParallelism(int parallelism) {
748		checkPermission();
#	Line 717 | Line 762 | public class ForkJoinPool extends Abstra
762		} finally {
763		lock.unlock();
764		}
765	<	signalIdleWorkers(false);
765	>	signalIdleWorkers();
766		}
767
768		/**
#	Line 732 | Line 777 | public class ForkJoinPool extends Abstra
777		/**
778		* Returns the number of worker threads that have started but not
779		* yet terminated.  This result returned by this method may differ
780	<	* from <code>getParallelism</code> when threads are created to
780	>	* from {@code getParallelism} when threads are created to
781		* maintain parallelism when others are cooperatively blocked.
782		*
783		* @return the number of worker threads
#	Line 744 | Line 789 | public class ForkJoinPool extends Abstra
789		/**
790		* Returns the maximum number of threads allowed to exist in the
791		* pool, even if there are insufficient unblocked running threads.
792	+	*
793		* @return the maximum
794		*/
795		public int getMaximumPoolSize() {
#	Line 755 | Line 801 | public class ForkJoinPool extends Abstra
801		* pool, even if there are insufficient unblocked running threads.
802		* Setting this value has no effect on current pool size. It
803		* controls construction of new threads.
804	+	*
805		* @throws IllegalArgumentException if negative or greater then
806	<	* internal implementation limit.
806	>	* internal implementation limit
807		*/
808		public void setMaximumPoolSize(int newMax) {
809		if (newMax < 0 || newMax > MAX_THREADS)
#	Line 769 | Line 816 | public class ForkJoinPool extends Abstra
816		* Returns true if this pool dynamically maintains its target
817		* parallelism level. If false, new threads are added only to
818		* avoid possible starvation.
819	<	* This setting is by default true;
819	>	* This setting is by default true.
820	>	*
821		* @return true if maintains parallelism
822		*/
823		public boolean getMaintainsParallelism() {
#	Line 780 | Line 828 | public class ForkJoinPool extends Abstra
828		* Sets whether this pool dynamically maintains its target
829		* parallelism level. If false, new threads are added only to
830		* avoid possible starvation.
831	+	*
832		* @param enable true to maintains parallelism
833		*/
834		public void setMaintainsParallelism(boolean enable) {
#	Line 787 | Line 836 | public class ForkJoinPool extends Abstra
836		}
837
838		/**
839	+	* Establishes local first-in-first-out scheduling mode for forked
840	+	* tasks that are never joined. This mode may be more appropriate
841	+	* than default locally stack-based mode in applications in which
842	+	* worker threads only process asynchronous tasks.  This method is
843	+	* designed to be invoked only when pool is quiescent, and
844	+	* typically only before any tasks are submitted. The effects of
845	+	* invocations at other times may be unpredictable.
846	+	*
847	+	* @param async if true, use locally FIFO scheduling
848	+	* @return the previous mode
849	+	*/
850	+	public boolean setAsyncMode(boolean async) {
851	+	boolean oldMode = locallyFifo;
852	+	locallyFifo = async;
853	+	ForkJoinWorkerThread[] ws = workers;
854	+	if (ws != null) {
855	+	for (int i = 0; i < ws.length; ++i) {
856	+	ForkJoinWorkerThread t = ws[i];
857	+	if (t != null)
858	+	t.setAsyncMode(async);
859	+	}
860	+	}
861	+	return oldMode;
862	+	}
863	+
864	+	/**
865	+	* Returns true if this pool uses local first-in-first-out
866	+	* scheduling mode for forked tasks that are never joined.
867	+	*
868	+	* @return true if this pool uses async mode
869	+	*/
870	+	public boolean getAsyncMode() {
871	+	return locallyFifo;
872	+	}
873	+
874	+	/**
875		* Returns an estimate of the number of worker threads that are
876		* not blocked waiting to join tasks or for other managed
877		* synchronization.
#	Line 801 | Line 886 | public class ForkJoinPool extends Abstra
886		* Returns an estimate of the number of threads that are currently
887		* stealing or executing tasks. This method may overestimate the
888		* number of active threads.
889	<	* @return the number of active threads.
889	>	*
890	>	* @return the number of active threads
891		*/
892		public int getActiveThreadCount() {
893		return activeCountOf(runControl);
#	Line 811 | Line 897 | public class ForkJoinPool extends Abstra
897		* Returns an estimate of the number of threads that are currently
898		* idle waiting for tasks. This method may underestimate the
899		* number of idle threads.
900	<	* @return the number of idle threads.
900	>	*
901	>	* @return the number of idle threads
902		*/
903		final int getIdleThreadCount() {
904		int c = runningCountOf(workerCounts) - activeCountOf(runControl);
905	<	return (c <= 0)? 0 : c;
905	>	return (c <= 0) ? 0 : c;
906		}
907
908		/**
909		* Returns true if all worker threads are currently idle. An idle
910		* worker is one that cannot obtain a task to execute because none
911		* are available to steal from other threads, and there are no
912	<	* pending submissions to the pool. This method is conservative:
913	<	* It might not return true immediately upon idleness of all
912	>	* pending submissions to the pool. This method is conservative;
913	>	* it might not return true immediately upon idleness of all
914		* threads, but will eventually become true if threads remain
915		* inactive.
916	+	*
917		* @return true if all threads are currently idle
918		*/
919		public boolean isQuiescent() {
#	Line 837 | Line 925 | public class ForkJoinPool extends Abstra
925		* one thread's work queue by another. The reported value
926		* underestimates the actual total number of steals when the pool
927		* is not quiescent. This value may be useful for monitoring and
928	<	* tuning fork/join programs: In general, steal counts should be
928	>	* tuning fork/join programs: in general, steal counts should be
929		* high enough to keep threads busy, but low enough to avoid
930		* overhead and contention across threads.
931	<	* @return the number of steals.
931	>	*
932	>	* @return the number of steals
933		*/
934		public long getStealCount() {
935		return stealCount.get();
936		}
937
938		/**
939	<	* Accumulate steal count from a worker. Call only
940	<	* when worker known to be idle.
939	>	* Accumulates steal count from a worker.
940	>	* Call only when worker known to be idle.
941		*/
942		private void updateStealCount(ForkJoinWorkerThread w) {
943		int sc = w.getAndClearStealCount();
#	Line 863 | Line 952 | public class ForkJoinPool extends Abstra
952		* an approximation, obtained by iterating across all threads in
953		* the pool. This method may be useful for tuning task
954		* granularities.
955	<	* @return the number of queued tasks.
955	>	*
956	>	* @return the number of queued tasks
957		*/
958		public long getQueuedTaskCount() {
959		long count = 0;
960		ForkJoinWorkerThread[] ws = workers;
961	<	for (int i = 0; i < ws.length; ++i) {
962	<	ForkJoinWorkerThread t = ws[i];
963	<	if (t != null)
964	<	count += t.getQueueSize();
961	>	if (ws != null) {
962	>	for (int i = 0; i < ws.length; ++i) {
963	>	ForkJoinWorkerThread t = ws[i];
964	>	if (t != null)
965	>	count += t.getQueueSize();
966	>	}
967		}
968		return count;
969		}
#	Line 880 | Line 972 | public class ForkJoinPool extends Abstra
972		* Returns an estimate of the number tasks submitted to this pool
973		* that have not yet begun executing. This method takes time
974		* proportional to the number of submissions.
975	<	* @return the number of queued submissions.
975	>	*
976	>	* @return the number of queued submissions
977		*/
978		public int getQueuedSubmissionCount() {
979		return submissionQueue.size();
#	Line 889 | Line 982 | public class ForkJoinPool extends Abstra
982		/**
983		* Returns true if there are any tasks submitted to this pool
984		* that have not yet begun executing.
985	<	* @return <code>true</code> if there are any queued submissions.
985	>	*
986	>	* @return {@code true} if there are any queued submissions
987		*/
988		public boolean hasQueuedSubmissions() {
989		return !submissionQueue.isEmpty();
#	Line 899 | Line 993 | public class ForkJoinPool extends Abstra
993		* Removes and returns the next unexecuted submission if one is
994		* available.  This method may be useful in extensions to this
995		* class that re-assign work in systems with multiple pools.
996	+	*
997		* @return the next submission, or null if none
998		*/
999		protected ForkJoinTask<?> pollSubmission() {
#	Line 906 | Line 1001 | public class ForkJoinPool extends Abstra
1001		}
1002
1003		/**
1004	+	* Removes all available unexecuted submitted and forked tasks
1005	+	* from scheduling queues and adds them to the given collection,
1006	+	* without altering their execution status. These may include
1007	+	* artificially generated or wrapped tasks. This method is designed
1008	+	* to be invoked only when the pool is known to be
1009	+	* quiescent. Invocations at other times may not remove all
1010	+	* tasks. A failure encountered while attempting to add elements
1011	+	* to collection {@code c} may result in elements being in
1012	+	* neither, either or both collections when the associated
1013	+	* exception is thrown.  The behavior of this operation is
1014	+	* undefined if the specified collection is modified while the
1015	+	* operation is in progress.
1016	+	*
1017	+	* @param c the collection to transfer elements into
1018	+	* @return the number of elements transferred
1019	+	*/
1020	+	protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
1021	+	int n = submissionQueue.drainTo(c);
1022	+	ForkJoinWorkerThread[] ws = workers;
1023	+	if (ws != null) {
1024	+	for (int i = 0; i < ws.length; ++i) {
1025	+	ForkJoinWorkerThread w = ws[i];
1026	+	if (w != null)
1027	+	n += w.drainTasksTo(c);
1028	+	}
1029	+	}
1030	+	return n;
1031	+	}
1032	+
1033	+	/**
1034		* Returns a string identifying this pool, as well as its state,
1035		* including indications of run state, parallelism level, and
1036		* worker and task counts.
#	Line 949 | Line 1074 | public class ForkJoinPool extends Abstra
1074		* Invocation has no additional effect if already shut down.
1075		* Tasks that are in the process of being submitted concurrently
1076		* during the course of this method may or may not be rejected.
1077	+	*
1078		* @throws SecurityException if a security manager exists and
1079		*         the caller is not permitted to modify threads
1080		*         because it does not hold {@link
1081	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1081	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1082		*/
1083		public void shutdown() {
1084		checkPermission();
#	Line 966 | Line 1092 | public class ForkJoinPool extends Abstra
1092		* waiting tasks.  Tasks that are in the process of being
1093		* submitted or executed concurrently during the course of this
1094		* method may or may not be rejected. Unlike some other executors,
1095	<	* this method cancels rather than collects non-executed tasks,
1096	<	* so always returns an empty list.
1095	>	* this method cancels rather than collects non-executed tasks
1096	>	* upon termination, so always returns an empty list. However, you
1097	>	* can use method {@code drainTasksTo} before invoking this
1098	>	* method to transfer unexecuted tasks to another collection.
1099	>	*
1100		* @return an empty list
1101		* @throws SecurityException if a security manager exists and
1102		*         the caller is not permitted to modify threads
1103		*         because it does not hold {@link
1104	<	*         java.lang.RuntimePermission}<code>("modifyThread")</code>,
1104	>	*         java.lang.RuntimePermission}{@code ("modifyThread")}
1105		*/
1106		public List<Runnable> shutdownNow() {
1107		checkPermission();
#	Line 981 | Line 1110 | public class ForkJoinPool extends Abstra
1110		}
1111
1112		/**
1113	<	* Returns <code>true</code> if all tasks have completed following shut down.
1113	>	* Returns {@code true} if all tasks have completed following shut down.
1114		*
1115	<	* @return <code>true</code> if all tasks have completed following shut down
1115	>	* @return {@code true} if all tasks have completed following shut down
1116		*/
1117		public boolean isTerminated() {
1118		return runStateOf(runControl) == TERMINATED;
1119		}
1120
1121		/**
1122	<	* Returns <code>true</code> if the process of termination has
1122	>	* Returns {@code true} if the process of termination has
1123		* commenced but possibly not yet completed.
1124		*
1125	<	* @return <code>true</code> if terminating
1125	>	* @return {@code true} if terminating
1126		*/
1127		public boolean isTerminating() {
1128		return runStateOf(runControl) >= TERMINATING;
1129		}
1130
1131		/**
1132	<	* Returns <code>true</code> if this pool has been shut down.
1132	>	* Returns {@code true} if this pool has been shut down.
1133		*
1134	<	* @return <code>true</code> if this pool has been shut down
1134	>	* @return {@code true} if this pool has been shut down
1135		*/
1136		public boolean isShutdown() {
1137		return runStateOf(runControl) >= SHUTDOWN;
#	Line 1015 | Line 1144 | public class ForkJoinPool extends Abstra
1144		*
1145		* @param timeout the maximum time to wait
1146		* @param unit the time unit of the timeout argument
1147	<	* @return <code>true</code> if this executor terminated and
1148	<	*         <code>false</code> if the timeout elapsed before termination
1147	>	* @return {@code true} if this executor terminated and
1148	>	*         {@code false} if the timeout elapsed before termination
1149		* @throws InterruptedException if interrupted while waiting
1150		*/
1151		public boolean awaitTermination(long timeout, TimeUnit unit)
#	Line 1040 | Line 1169 | public class ForkJoinPool extends Abstra
1169		// Shutdown and termination support
1170
1171		/**
1172	<	* Callback from terminating worker. Null out the corresponding
1173	<	* workers slot, and if terminating, try to terminate, else try to
1174	<	* shrink workers array.
1172	>	* Callback from terminating worker. Nulls out the corresponding
1173	>	* workers slot, and if terminating, tries to terminate; else
1174	>	* tries to shrink workers array.
1175	>	*
1176		* @param w the worker
1177		*/
1178		final void workerTerminated(ForkJoinWorkerThread w) {
#	Line 1052 | Line 1182 | public class ForkJoinPool extends Abstra
1182		lock.lock();
1183		try {
1184		ForkJoinWorkerThread[] ws = workers;
1185	<	int idx = w.poolIndex;
1186	<	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1187	<	ws[idx] = null;
1188	<	if (totalCountOf(workerCounts) == 0) {
1189	<	terminate(); // no-op if already terminating
1190	<	transitionRunStateTo(TERMINATED);
1191	<	termination.signalAll();
1192	<	}
1193	<	else if (!isTerminating()) {
1194	<	tryShrinkWorkerArray();
1195	<	tryResumeSpare(true); // allow replacement
1185	>	if (ws != null) {
1186	>	int idx = w.poolIndex;
1187	>	if (idx >= 0 && idx < ws.length && ws[idx] == w)
1188	>	ws[idx] = null;
1189	>	if (totalCountOf(workerCounts) == 0) {
1190	>	terminate(); // no-op if already terminating
1191	>	transitionRunStateTo(TERMINATED);
1192	>	termination.signalAll();
1193	>	}
1194	>	else if (!isTerminating()) {
1195	>	tryShrinkWorkerArray();
1196	>	tryResumeSpare(true); // allow replacement
1197	>	}
1198		}
1199		} finally {
1200		lock.unlock();
1201		}
1202	<	signalIdleWorkers(false);
1202	>	signalIdleWorkers();
1203		}
1204
1205		/**
1206	<	* Initiate termination.
1206	>	* Initiates termination.
1207		*/
1208		private void terminate() {
1209		if (transitionRunStateTo(TERMINATING)) {
1210		stopAllWorkers();
1211		resumeAllSpares();
1212	<	signalIdleWorkers(true);
1212	>	signalIdleWorkers();
1213		cancelQueuedSubmissions();
1214		cancelQueuedWorkerTasks();
1215		interruptUnterminatedWorkers();
1216	<	signalIdleWorkers(true); // resignal after interrupt
1216	>	signalIdleWorkers(); // resignal after interrupt
1217		}
1218		}
1219
1220		/**
1221	<	* Possibly terminate when on shutdown state
1221	>	* Possibly terminates when on shutdown state.
1222		*/
1223		private void terminateOnShutdown() {
1224		if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
#	Line 1094 | Line 1226 | public class ForkJoinPool extends Abstra
1226		}
1227
1228		/**
1229	<	* Clear out and cancel submissions
1229	>	* Clears out and cancels submissions.
1230		*/
1231		private void cancelQueuedSubmissions() {
1232		ForkJoinTask<?> task;
#	Line 1103 | Line 1235 | public class ForkJoinPool extends Abstra
1235		}
1236
1237		/**
1238	<	* Clean out worker queues.
1238	>	* Cleans out worker queues.
1239		*/
1240		private void cancelQueuedWorkerTasks() {
1241		final ReentrantLock lock = this.workerLock;
1242		lock.lock();
1243		try {
1244		ForkJoinWorkerThread[] ws = workers;
1245	<	for (int i = 0; i < ws.length; ++i) {
1246	<	ForkJoinWorkerThread t = ws[i];
1247	<	if (t != null)
1248	<	t.cancelTasks();
1245	>	if (ws != null) {
1246	>	for (int i = 0; i < ws.length; ++i) {
1247	>	ForkJoinWorkerThread t = ws[i];
1248	>	if (t != null)
1249	>	t.cancelTasks();
1250	>	}
1251		}
1252		} finally {
1253		lock.unlock();
#	Line 1121 | Line 1255 | public class ForkJoinPool extends Abstra
1255		}
1256
1257		/**
1258	<	* Set each worker's status to terminating. Requires lock to avoid
1259	<	* conflicts with add/remove
1258	>	* Sets each worker's status to terminating. Requires lock to avoid
1259	>	* conflicts with add/remove.
1260		*/
1261		private void stopAllWorkers() {
1262		final ReentrantLock lock = this.workerLock;
1263		lock.lock();
1264		try {
1265		ForkJoinWorkerThread[] ws = workers;
1266	<	for (int i = 0; i < ws.length; ++i) {
1267	<	ForkJoinWorkerThread t = ws[i];
1268	<	if (t != null)
1269	<	t.shutdownNow();
1266	>	if (ws != null) {
1267	>	for (int i = 0; i < ws.length; ++i) {
1268	>	ForkJoinWorkerThread t = ws[i];
1269	>	if (t != null)
1270	>	t.shutdownNow();
1271	>	}
1272		}
1273		} finally {
1274		lock.unlock();
#	Line 1140 | Line 1276 | public class ForkJoinPool extends Abstra
1276		}
1277
1278		/**
1279	<	* Interrupt all unterminated workers.  This is not required for
1279	>	* Interrupts all unterminated workers.  This is not required for
1280		* sake of internal control, but may help unstick user code during
1281		* shutdown.
1282		*/
#	Line 1149 | Line 1285 | public class ForkJoinPool extends Abstra
1285		lock.lock();
1286		try {
1287		ForkJoinWorkerThread[] ws = workers;
1288	<	for (int i = 0; i < ws.length; ++i) {
1289	<	ForkJoinWorkerThread t = ws[i];
1290	<	if (t != null && !t.isTerminated()) {
1291	<	try {
1292	<	t.interrupt();
1293	<	} catch (SecurityException ignore) {
1288	>	if (ws != null) {
1289	>	for (int i = 0; i < ws.length; ++i) {
1290	>	ForkJoinWorkerThread t = ws[i];
1291	>	if (t != null && !t.isTerminated()) {
1292	>	try {
1293	>	t.interrupt();
1294	>	} catch (SecurityException ignore) {
1295	>	}
1296		}
1297		}
1298		}
#	Line 1165 | Line 1303 | public class ForkJoinPool extends Abstra
1303
1304
1305		/*
1306	<	* Nodes for event barrier to manage idle threads.
1306	>	* Nodes for event barrier to manage idle threads.  Queue nodes
1307	>	* are basic Treiber stack nodes, also used for spare stack.
1308		*
1309		* The event barrier has an event count and a wait queue (actually
1310		* a Treiber stack).  Workers are enabled to look for work when
1311	<	* the eventCount is incremented. If they fail to find some,
1312	<	* they may wait for next count. Synchronization events occur only
1313	<	* in enough contexts to maintain overall liveness:
1311	>	* the eventCount is incremented. If they fail to find work, they
1312	>	* may wait for next count. Upon release, threads help others wake
1313	>	* up.
1314	>	*
1315	>	* Synchronization events occur only in enough contexts to
1316	>	* maintain overall liveness:
1317		*
1318		*   - Submission of a new task to the pool
1319	<	*   - Creation or termination of a worker
1319	>	*   - Resizes or other changes to the workers array
1320		*   - pool termination
1321		*   - A worker pushing a task on an empty queue
1322		*
1323	<	* The last case (pushing a task) occurs often enough, and is
1324	<	* heavy enough compared to simple stack pushes to require some
1325	<	* special handling: Method signalNonEmptyWorkerQueue returns
1326	<	* without advancing count if the queue appears to be empty.  This
1327	<	* would ordinarily result in races causing some queued waiters
1328	<	* not to be woken up. To avoid this, a worker in sync
1329	<	* rescans for tasks after being enqueued if it was the first to
1330	<	* enqueue, and aborts the wait if finding one, also helping to
1331	<	* signal others. This works well because the worker has nothing
1332	<	* better to do anyway, and so might as well help alleviate the
1333	<	* overhead and contention on the threads actually doing work.
1334	<	*
1335	<	* Queue nodes are basic Treiber stack nodes, also used for spare
1336	<	* stack.
1323	>	* The case of pushing a task occurs often enough, and is heavy
1324	>	* enough compared to simple stack pushes, to require special
1325	>	* handling: Method signalWork returns without advancing count if
1326	>	* the queue appears to be empty.  This would ordinarily result in
1327	>	* races causing some queued waiters not to be woken up. To avoid
1328	>	* this, the first worker enqueued in method sync (see
1329	>	* syncIsReleasable) rescans for tasks after being enqueued, and
1330	>	* helps signal if any are found. This works well because the
1331	>	* worker has nothing better to do, and so might as well help
1332	>	* alleviate the overhead and contention on the threads actually
1333	>	* doing work.  Also, since event counts increments on task
1334	>	* availability exist to maintain liveness (rather than to force
1335	>	* refreshes etc), it is OK for callers to exit early if
1336	>	* contending with another signaller.
1337		*/
1338		static final class WaitQueueNode {
1339		WaitQueueNode next; // only written before enqueued
1340		volatile ForkJoinWorkerThread thread; // nulled to cancel wait
1341		final long count; // unused for spare stack
1342	<	WaitQueueNode(ForkJoinWorkerThread w, long c) {
1342	>
1343	>	WaitQueueNode(long c, ForkJoinWorkerThread w) {
1344		count = c;
1345		thread = w;
1346		}
1347	<	final boolean signal() {
1347	>
1348	>	/**
1349	>	* Wakes up waiter, returning false if known to already
1350	>	*/
1351	>	boolean signal() {
1352		ForkJoinWorkerThread t = thread;
1353	+	if (t == null)
1354	+	return false;
1355		thread = null;
1356	<	if (t != null) {
1357	<	LockSupport.unpark(t);
1358	<	return true;
1356	>	LockSupport.unpark(t);
1357	>	return true;
1358	>	}
1359	>
1360	>	/**
1361	>	* Awaits release on sync.
1362	>	*/
1363	>	void awaitSyncRelease(ForkJoinPool p) {
1364	>	while (thread != null && !p.syncIsReleasable(this))
1365	>	LockSupport.park(this);
1366	>	}
1367	>
1368	>	/**
1369	>	* Awaits resumption as spare.
1370	>	*/
1371	>	void awaitSpareRelease() {
1372	>	while (thread != null) {
1373	>	if (!Thread.interrupted())
1374	>	LockSupport.park(this);
1375		}
1211	–	return false;
1376		}
1377		}
1378
1379		/**
1380	<	* Release at least one thread waiting for event count to advance,
1381	<	* if one exists. If initial attempt fails, release all threads.
1382	<	* @param all if false, at first try to only release one thread
1383	<	* @return current event
1380	>	* Ensures that no thread is waiting for count to advance from the
1381	>	* current value of eventCount read on entry to this method, by
1382	>	* releasing waiting threads if necessary.
1383	>	*
1384	>	* @return the count
1385		*/
1386	<	private long releaseIdleWorkers(boolean all) {
1387	<	long c;
1388	<	for (;;) {
1389	<	WaitQueueNode q = barrierStack;
1390	<	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)) {
1386	>	final long ensureSync() {
1387	>	long c = eventCount;
1388	>	WaitQueueNode q;
1389	>	while ((q = syncStack) != null && q.count < c) {
1390	>	if (casBarrierStack(q, null)) {
1391		do {
1392	<	q.signal();
1392	>	q.signal();
1393		} while ((q = q.next) != null);
1394		break;
1395		}
#	Line 1242 | Line 1398 | public class ForkJoinPool extends Abstra
1398		}
1399
1400		/**
1401	<	* 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
1401	>	* Increments event count and releases waiting threads.
1402		*/
1403	<	final void signalIdleWorkers(boolean all) {
1403	>	private void signalIdleWorkers() {
1404		long c;
1405	<	do;while (!casEventCount(c = eventCount, c+1));
1406	<	releaseIdleWorkers(all);
1405	>	do {} while (!casEventCount(c = eventCount, c+1));
1406	>	ensureSync();
1407		}
1408
1409		/**
1410	<	* Wake up threads waiting to steal a task. Because method
1411	<	* sync rechecks availability, it is OK to only proceed if
1412	<	* queue appears to be non-empty.
1410	>	* Signals threads waiting to poll a task. Because method sync
1411	>	* rechecks availability, it is OK to only proceed if queue
1412	>	* appears to be non-empty, and OK to skip under contention to
1413	>	* increment count (since some other thread succeeded).
1414		*/
1415	<	final void signalNonEmptyWorkerQueue() {
1271	<	// If CAS fails another signaller must have succeeded
1415	>	final void signalWork() {
1416		long c;
1417	<	if (barrierStack != null && casEventCount(c = eventCount, c+1))
1418	<	releaseIdleWorkers(false);
1417	>	WaitQueueNode q;
1418	>	if (syncStack != null &&
1419	>	casEventCount(c = eventCount, c+1) &&
1420	>	(((q = syncStack) != null && q.count <= c) &&
1421	>	(!casBarrierStack(q, q.next) || !q.signal())))
1422	>	ensureSync();
1423		}
1424
1425		/**
1426	<	* Waits until event count advances from count, or some thread is
1427	<	* waiting on a previous count, or there is stealable work
1428	<	* available. Help wake up others on release.
1426	>	* Waits until event count advances from last value held by
1427	>	* caller, or if excess threads, caller is resumed as spare, or
1428	>	* caller or pool is terminating. Updates caller's event on exit.
1429	>	*
1430		* @param w the calling worker thread
1282	–	* @param prev previous value returned by sync (or 0)
1283	–	* @return current event count
1431		*/
1432	<	final long sync(ForkJoinWorkerThread w, long prev) {
1433	<	updateStealCount(w);
1432	>	final void sync(ForkJoinWorkerThread w) {
1433	>	updateStealCount(w); // Transfer w's count while it is idle
1434
1435	<	while (!w.isShutdown() && !isTerminating() &&
1436	<	(parallelism >= runningCountOf(workerCounts) ||
1290	<	!suspendIfSpare(w))) { // prefer suspend to waiting here
1435	>	while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) {
1436	>	long prev = w.lastEventCount;
1437		WaitQueueNode node = null;
1438	<	boolean queued = false;
1439	<	for (;;) {
1440	<	if (!queued) {
1441	<	if (eventCount != prev)
1442	<	break;
1443	<	WaitQueueNode h = barrierStack;
1444	<	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);
1438	>	WaitQueueNode h;
1439	>	while (eventCount == prev &&
1440	>	((h = syncStack) == null || h.count == prev)) {
1441	>	if (node == null)
1442	>	node = new WaitQueueNode(prev, w);
1443	>	if (casBarrierStack(node.next = h, node)) {
1444	>	node.awaitSyncRelease(this);
1445		break;
1446		}
1313	–	else
1314	–	LockSupport.park(this);
1447		}
1448	+	long ec = ensureSync();
1449	+	if (ec != prev) {
1450	+	w.lastEventCount = ec;
1451	+	break;
1452	+	}
1453	+	}
1454	+	}
1455	+
1456	+	/**
1457	+	* Returns true if worker waiting on sync can proceed:
1458	+	*  - on signal (thread == null)
1459	+	*  - on event count advance (winning race to notify vs signaller)
1460	+	*  - on interrupt
1461	+	*  - if the first queued node, we find work available
1462	+	* If node was not signalled and event count not advanced on exit,
1463	+	* then we also help advance event count.
1464	+	*
1465	+	* @return true if node can be released
1466	+	*/
1467	+	final boolean syncIsReleasable(WaitQueueNode node) {
1468	+	long prev = node.count;
1469	+	if (!Thread.interrupted() && node.thread != null &&
1470	+	(node.next != null ||
1471	+	!ForkJoinWorkerThread.hasQueuedTasks(workers)) &&
1472	+	eventCount == prev)
1473	+	return false;
1474	+	if (node.thread != null) {
1475	+	node.thread = null;
1476		long ec = eventCount;
1477	<	if (releaseIdleWorkers(false) != prev)
1478	<	return ec;
1477	>	if (prev <= ec) // help signal
1478	>	casEventCount(ec, ec+1);
1479		}
1480	<	return prev; // return old count if aborted
1480	>	return true;
1481	>	}
1482	>
1483	>	/**
1484	>	* Returns true if a new sync event occurred since last call to
1485	>	* sync or this method, if so, updating caller's count.
1486	>	*/
1487	>	final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
1488	>	long lc = w.lastEventCount;
1489	>	long ec = ensureSync();
1490	>	if (ec == lc)
1491	>	return false;
1492	>	w.lastEventCount = ec;
1493	>	return true;
1494		}
1495
1496		//  Parallelism maintenance
1497
1498		/**
1499	<	* Decrement running count; if too low, add spare.
1499	>	* Decrements running count; if too low, adds spare.
1500		*
1501		* Conceptually, all we need to do here is add or resume a
1502		* spare thread when one is about to block (and remove or
1503		* suspend it later when unblocked -- see suspendIfSpare).
1504		* However, implementing this idea requires coping with
1505	<	* several problems: We have imperfect information about the
1505	>	* several problems: we have imperfect information about the
1506		* states of threads. Some count updates can and usually do
1507		* lag run state changes, despite arrangements to keep them
1508		* accurate (for example, when possible, updating counts
#	Line 1343 | Line 1516 | public class ForkJoinPool extends Abstra
1516		* only be suspended or removed when they are idle, not
1517		* immediately when they aren't needed. So adding threads will
1518		* raise parallelism level for longer than necessary.  Also,
1519	<	* FJ applications often enounter highly transient peaks when
1519	>	* FJ applications often encounter highly transient peaks when
1520		* many threads are blocked joining, but for less time than it
1521		* takes to create or resume spares.
1522		*
#	Line 1352 | Line 1525 | public class ForkJoinPool extends Abstra
1525		* target counts, else create only to avoid starvation
1526		* @return true if joinMe known to be done
1527		*/
1528	<	final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
1528	>	final boolean preJoin(ForkJoinTask<?> joinMe,
1529	>	boolean maintainParallelism) {
1530		maintainParallelism &= maintainsParallelism; // overrride
1531		boolean dec = false;  // true when running count decremented
1532		while (spareStack == null || !tryResumeSpare(dec)) {
1533		int counts = workerCounts;
1534	<	if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
1534	>	if (dec || (dec = casWorkerCounts(counts, --counts))) {
1535	>	// CAS cheat
1536		if (!needSpare(counts, maintainParallelism))
1537		break;
1538		if (joinMe.status < 0)
#	Line 1372 | Line 1547 | public class ForkJoinPool extends Abstra
1547		/**
1548		* Same idea as preJoin
1549		*/
1550	<	final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
1550	>	final boolean preBlock(ManagedBlocker blocker,
1551	>	boolean maintainParallelism) {
1552		maintainParallelism &= maintainsParallelism;
1553		boolean dec = false;
1554		while (spareStack == null || !tryResumeSpare(dec)) {
#	Line 1396 | Line 1572 | public class ForkJoinPool extends Abstra
1572		* there is apparently some work to do.  This self-limiting rule
1573		* means that the more threads that have already been added, the
1574		* less parallelism we will tolerate before adding another.
1575	+	*
1576		* @param counts current worker counts
1577		* @param maintainParallelism try to maintain parallelism
1578		*/
#	Line 1408 | Line 1585 | public class ForkJoinPool extends Abstra
1585		return (tc < maxPoolSize &&
1586		(rc == 0 || totalSurplus < 0 ||
1587		(maintainParallelism &&
1588	<	runningDeficit > totalSurplus && mayHaveQueuedWork())));
1589	<	}
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;
1588	>	runningDeficit > totalSurplus &&
1589	>	ForkJoinWorkerThread.hasQueuedTasks(workers))));
1590		}
1591
1592		/**
1593	<	* Add a spare worker if lock available and no more than the
1594	<	* expected numbers of threads exist
1593	>	* Adds a spare worker if lock available and no more than the
1594	>	* expected numbers of threads exist.
1595	>	*
1596		* @return true if successful
1597		*/
1598		private boolean tryAddSpare(int expectedCounts) {
#	Line 1465 | Line 1625 | public class ForkJoinPool extends Abstra
1625		}
1626
1627		/**
1628	<	* Add the kth spare worker. On entry, pool coounts are already
1628	>	* Adds the kth spare worker. On entry, pool counts are already
1629		* adjusted to reflect addition.
1630		*/
1631		private void createAndStartSpare(int k) {
#	Line 1483 | Line 1643 | public class ForkJoinPool extends Abstra
1643		}
1644		else
1645		updateWorkerCount(-1); // adjust on failure
1646	<	signalIdleWorkers(false);
1646	>	signalIdleWorkers();
1647		}
1648
1649		/**
1650	<	* Suspend calling thread w if there are excess threads.  Called
1651	<	* only from sync.  Spares are enqueued in a Treiber stack
1652	<	* using the same WaitQueueNodes as barriers.  They are resumed
1653	<	* mainly in preJoin, but are also woken on pool events that
1654	<	* require all threads to check run state.
1650	>	* Suspends calling thread w if there are excess threads.  Called
1651	>	* only from sync.  Spares are enqueued in a Treiber stack using
1652	>	* the same WaitQueueNodes as barriers.  They are resumed mainly
1653	>	* in preJoin, but are also woken on pool events that require all
1654	>	* threads to check run state.
1655	>	*
1656		* @param w the caller
1657		*/
1658		private boolean suspendIfSpare(ForkJoinWorkerThread w) {
#	Line 1499 | Line 1660 | public class ForkJoinPool extends Abstra
1660		int s;
1661		while (parallelism < runningCountOf(s = workerCounts)) {
1662		if (node == null)
1663	<	node = new WaitQueueNode(w, 0);
1663	>	node = new WaitQueueNode(0, w);
1664		if (casWorkerCounts(s, s-1)) { // representation-dependent
1665		// push onto stack
1666	<	do;while (!casSpareStack(node.next = spareStack, node));
1506	<
1666	>	do {} while (!casSpareStack(node.next = spareStack, node));
1667		// block until released by resumeSpare
1668	<	while (node.thread != null) {
1509	<	if (!Thread.interrupted())
1510	<	LockSupport.park(this);
1511	<	}
1512	<	w.activate(); // help warm up
1668	>	node.awaitSpareRelease();
1669		return true;
1670		}
1671		}
#	Line 1517 | Line 1673 | public class ForkJoinPool extends Abstra
1673		}
1674
1675		/**
1676	<	* Try to pop and resume a spare thread.
1676	>	* Tries to pop and resume a spare thread.
1677	>	*
1678		* @param updateCount if true, increment running count on success
1679		* @return true if successful
1680		*/
#	Line 1535 | Line 1692 | public class ForkJoinPool extends Abstra
1692		}
1693
1694		/**
1695	<	* Pop and resume all spare threads. Same idea as
1696	<	* releaseIdleWorkers.
1695	>	* Pops and resumes all spare threads. Same idea as ensureSync.
1696	>	*
1697		* @return true if any spares released
1698		*/
1699		private boolean resumeAllSpares() {
#	Line 1554 | Line 1711 | public class ForkJoinPool extends Abstra
1711		}
1712
1713		/**
1714	<	* Pop and shutdown excessive spare threads. Call only while
1714	>	* Pops and shuts down excessive spare threads. Call only while
1715		* holding lock. This is not guaranteed to eliminate all excess
1716		* threads, only those suspended as spares, which are the ones
1717		* unlikely to be needed in the future.
#	Line 1577 | Line 1734 | public class ForkJoinPool extends Abstra
1734		}
1735
1736		/**
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	–	/**
1737		* Interface for extending managed parallelism for tasks running
1738		* in ForkJoinPools. A ManagedBlocker provides two methods.
1739	<	* Method <code>isReleasable</code> must return true if blocking is not
1740	<	* necessary. Method <code>block</code> blocks the current thread
1741	<	* if necessary (perhaps internally invoking isReleasable before
1742	<	* actually blocking.).
1739	>	* Method {@code isReleasable} must return true if blocking is not
1740	>	* necessary. Method {@code block} blocks the current thread if
1741	>	* necessary (perhaps internally invoking {@code isReleasable}
1742	>	* before actually blocking.).
1743	>	*
1744		* <p>For example, here is a ManagedBlocker based on a
1745		* ReentrantLock:
1746	<	* <pre>
1747	<	*   class ManagedLocker implements ManagedBlocker {
1748	<	*     final ReentrantLock lock;
1749	<	*     boolean hasLock = false;
1750	<	*     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1751	<	*     public boolean block() {
1752	<	*        if (!hasLock)
1753	<	*           lock.lock();
1754	<	*        return true;
1607	<	*     }
1608	<	*     public boolean isReleasable() {
1609	<	*        return hasLock || (hasLock = lock.tryLock());
1610	<	*     }
1746	>	*  <pre> {@code
1747	>	* class ManagedLocker implements ManagedBlocker {
1748	>	*   final ReentrantLock lock;
1749	>	*   boolean hasLock = false;
1750	>	*   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
1751	>	*   public boolean block() {
1752	>	*     if (!hasLock)
1753	>	*       lock.lock();
1754	>	*     return true;
1755		*   }
1756	<	* </pre>
1756	>	*   public boolean isReleasable() {
1757	>	*     return hasLock || (hasLock = lock.tryLock());
1758	>	*   }
1759	>	* }}</pre>
1760		*/
1761		public static interface ManagedBlocker {
1762		/**
1763		* Possibly blocks the current thread, for example waiting for
1764		* a lock or condition.
1765	+	*
1766		* @return true if no additional blocking is necessary (i.e.,
1767	<	* if isReleasable would return true).
1767	>	* if isReleasable would return true)
1768		* @throws InterruptedException if interrupted while waiting
1769	<	* (the method is not required to do so, but is allowe to).
1769	>	* (the method is not required to do so, but is allowed to)
1770		*/
1771		boolean block() throws InterruptedException;
1772
#	Line 1633 | Line 1781 | public class ForkJoinPool extends Abstra
1781		* is a ForkJoinWorkerThread, this method possibly arranges for a
1782		* spare thread to be activated if necessary to ensure parallelism
1783		* while the current thread is blocked.  If
1784	<	* <code>maintainParallelism</code> is true and the pool supports
1784	>	* {@code maintainParallelism} is true and the pool supports
1785		* it ({@link #getMaintainsParallelism}), this method attempts to
1786	<	* maintain the pool's nominal parallelism. Otherwise if activates
1786	>	* maintain the pool's nominal parallelism. Otherwise it activates
1787		* a thread only if necessary to avoid complete starvation. This
1788		* option may be preferable when blockages use timeouts, or are
1789		* almost always brief.
1790		*
1791		* <p> If the caller is not a ForkJoinTask, this method is behaviorally
1792		* equivalent to
1793	<	* <pre>
1794	<	*   while (!blocker.isReleasable())
1795	<	*      if (blocker.block())
1796	<	*         return;
1797	<	* </pre>
1793	>	*  <pre> {@code
1794	>	* while (!blocker.isReleasable())
1795	>	*   if (blocker.block())
1796	>	*     return;
1797	>	* }</pre>
1798		* If the caller is a ForkJoinTask, then the pool may first
1799		* be expanded to ensure parallelism, and later adjusted.
1800		*
#	Line 1655 | Line 1803 | public class ForkJoinPool extends Abstra
1803		* attempt to maintain the pool's nominal parallelism; otherwise
1804		* activate a thread only if necessary to avoid complete
1805		* starvation.
1806	<	* @throws InterruptedException if blocker.block did so.
1806	>	* @throws InterruptedException if blocker.block did so
1807		*/
1808		public static void managedBlock(ManagedBlocker blocker,
1809		boolean maintainParallelism)
1810		throws InterruptedException {
1811		Thread t = Thread.currentThread();
1812	<	ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
1813	<	((ForkJoinWorkerThread)t).pool : null);
1812	>	ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ?
1813	>	((ForkJoinWorkerThread) t).pool : null);
1814		if (!blocker.isReleasable()) {
1815		try {
1816		if (pool == null ||
#	Line 1677 | Line 1825 | public class ForkJoinPool extends Abstra
1825
1826		private static void awaitBlocker(ManagedBlocker blocker)
1827		throws InterruptedException {
1828	<	do;while (!blocker.isReleasable() && !blocker.block());
1828	>	do {} while (!blocker.isReleasable() && !blocker.block());
1829		}
1830
1831		// AbstractExecutorService overrides
#	Line 1692 | Line 1840 | public class ForkJoinPool extends Abstra
1840
1841
1842		// Temporary Unsafe mechanics for preliminary release
1843	+	private static Unsafe getUnsafe() throws Throwable {
1844	+	try {
1845	+	return Unsafe.getUnsafe();
1846	+	} catch (SecurityException se) {
1847	+	try {
1848	+	return java.security.AccessController.doPrivileged
1849	+	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1850	+	public Unsafe run() throws Exception {
1851	+	return getUnsafePrivileged();
1852	+	}});
1853	+	} catch (java.security.PrivilegedActionException e) {
1854	+	throw e.getCause();
1855	+	}
1856	+	}
1857	+	}
1858	+
1859	+	private static Unsafe getUnsafePrivileged()
1860	+	throws NoSuchFieldException, IllegalAccessException {
1861	+	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1862	+	f.setAccessible(true);
1863	+	return (Unsafe) f.get(null);
1864	+	}
1865	+
1866	+	private static long fieldOffset(String fieldName)
1867	+	throws NoSuchFieldException {
1868	+	return UNSAFE.objectFieldOffset
1869	+	(ForkJoinPool.class.getDeclaredField(fieldName));
1870	+	}
1871
1872	<	static final Unsafe _unsafe;
1872	>	static final Unsafe UNSAFE;
1873		static final long eventCountOffset;
1874		static final long workerCountsOffset;
1875		static final long runControlOffset;
1876	<	static final long barrierStackOffset;
1876	>	static final long syncStackOffset;
1877		static final long spareStackOffset;
1878
1879		static {
1880		try {
1881	<	if (ForkJoinPool.class.getClassLoader() != null) {
1882	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1883	<	f.setAccessible(true);
1884	<	_unsafe = (Unsafe)f.get(null);
1885	<	}
1886	<	else
1887	<	_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) {
1881	>	UNSAFE = getUnsafe();
1882	>	eventCountOffset = fieldOffset("eventCount");
1883	>	workerCountsOffset = fieldOffset("workerCounts");
1884	>	runControlOffset = fieldOffset("runControl");
1885	>	syncStackOffset = fieldOffset("syncStack");
1886	>	spareStackOffset = fieldOffset("spareStack");
1887	>	} catch (Throwable e) {
1888		throw new RuntimeException("Could not initialize intrinsics", e);
1889		}
1890		}
1891
1892		private boolean casEventCount(long cmp, long val) {
1893	<	return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
1893	>	return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
1894		}
1895		private boolean casWorkerCounts(int cmp, int val) {
1896	<	return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1896	>	return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
1897		}
1898		private boolean casRunControl(int cmp, int val) {
1899	<	return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
1899	>	return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
1900		}
1901		private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
1902	<	return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
1902	>	return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
1903		}
1904		private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
1905	<	return _unsafe.compareAndSwapObject(this, barrierStackOffset, cmp, val);
1905	>	return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
1906		}
1907		}

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