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root/jsr166/jsr166/src/jsr166y/ForkJoinTask.java

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.48 by dl, Thu May 27 16:46:48 2010 UTC vs.
Revision 1.66 by dl, Sun Oct 24 19:37:26 2010 UTC

#	Line 6 | Line 6
6
7		package jsr166y;
8
9	–	import java.util.concurrent.*;
10	–
9		import java.io.Serializable;
10		import java.util.Collection;
11		import java.util.Collections;
#	Line 15 | Line 13 | import java.util.List;
13		import java.util.RandomAccess;
14		import java.util.Map;
15		import java.util.WeakHashMap;
16	+	import java.util.concurrent.Callable;
17	+	import java.util.concurrent.CancellationException;
18	+	import java.util.concurrent.ExecutionException;
19	+	import java.util.concurrent.Executor;
20	+	import java.util.concurrent.ExecutorService;
21	+	import java.util.concurrent.Future;
22	+	import java.util.concurrent.RejectedExecutionException;
23	+	import java.util.concurrent.RunnableFuture;
24	+	import java.util.concurrent.TimeUnit;
25	+	import java.util.concurrent.TimeoutException;
26
27		/**
28		* Abstract base class for tasks that run within a {@link ForkJoinPool}.
#	Line 28 | Line 36 | import java.util.WeakHashMap;
36		* start other subtasks.  As indicated by the name of this class,
37		* many programs using {@code ForkJoinTask} employ only methods
38		* {@link #fork} and {@link #join}, or derivatives such as {@link
39	<	* #invokeAll}.  However, this class also provides a number of other
40	<	* methods that can come into play in advanced usages, as well as
41	<	* extension mechanics that allow support of new forms of fork/join
42	<	* processing.
39	>	* #invokeAll(ForkJoinTask...) invokeAll}.  However, this class also
40	>	* provides a number of other methods that can come into play in
41	>	* advanced usages, as well as extension mechanics that allow
42	>	* support of new forms of fork/join processing.
43		*
44		* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
45		* The efficiency of {@code ForkJoinTask}s stems from a set of
#	Line 64 | Line 72 | import java.util.WeakHashMap;
72		* results of a task is {@link #join}, but there are several variants:
73		* The {@link Future#get} methods support interruptible and/or timed
74		* waits for completion and report results using {@code Future}
75	<	* conventions. Method {@link #helpJoin} enables callers to actively
68	<	* execute other tasks while awaiting joins, which is sometimes more
69	<	* efficient but only applies when all subtasks are known to be
70	<	* strictly tree-structured. Method {@link #invoke} is semantically
75	>	* conventions. Method {@link #invoke} is semantically
76		* equivalent to {@code fork(); join()} but always attempts to begin
77		* execution in the current thread. The "<em>quiet</em>" forms of
78		* these methods do not extract results or report exceptions. These
#	Line 103 | Line 108 | import java.util.WeakHashMap;
108		* ForkJoinTasks (as may be determined using method {@link
109		* #inForkJoinPool}).  Attempts to invoke them in other contexts
110		* result in exceptions or errors, possibly including
111	<	* ClassCastException.
111	>	* {@code ClassCastException}.
112		*
113		* <p>Most base support methods are {@code final}, to prevent
114		* overriding of implementations that are intrinsically tied to the
#	Line 125 | Line 130 | import java.util.WeakHashMap;
130		*
131		* <p>This class provides {@code adapt} methods for {@link Runnable}
132		* and {@link Callable}, that may be of use when mixing execution of
133	<	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks
134	<	* are of this form, consider using a pool in
130	<	* {@linkplain ForkJoinPool#setAsyncMode async mode}.
133	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
134	>	* of this form, consider using a pool constructed in <em>asyncMode</em>.
135		*
136		* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
137		* used in extensions such as remote execution frameworks. It is
#	Line 148 | Line 152 | public abstract class ForkJoinTask<V> im
152		* status maintenance (2) execution and awaiting completion (3)
153		* user-level methods that additionally report results. This is
154		* sometimes hard to see because this file orders exported methods
155	<	* in a way that flows well in javadocs.
155	>	* in a way that flows well in javadocs. In particular, most
156	>	* join mechanics are in method quietlyJoin, below.
157		*/
158
159	<	/**
160	<	* Run control status bits packed into a single int to minimize
161	<	* footprint and to ensure atomicity (via CAS).  Status is
162	<	* initially zero, and takes on nonnegative values until
163	<	* completed, upon which status holds COMPLETED. CANCELLED, or
164	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
165	<	* blocking waits by other threads have the SIGNAL bit set.
166	<	*
167	<	* Completion of a stolen task with SIGNAL set awakens any waiters
163	<	* via notifyAll. Even though suboptimal for some purposes, we use
159	>	/*
160	>	* The status field holds run control status bits packed into a
161	>	* single int to minimize footprint and to ensure atomicity (via
162	>	* CAS).  Status is initially zero, and takes on nonnegative
163	>	* values until completed, upon which status holds value
164	>	* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
165	>	* waits by other threads have the SIGNAL bit set.  Completion of
166	>	* a stolen task with SIGNAL set awakens any waiters via
167	>	* notifyAll. Even though suboptimal for some purposes, we use
168		* basic builtin wait/notify to take advantage of "monitor
169		* inflation" in JVMs that we would otherwise need to emulate to
170		* avoid adding further per-task bookkeeping overhead.  We want
171		* these monitors to be "fat", i.e., not use biasing or thin-lock
172		* techniques, so use some odd coding idioms that tend to avoid
173		* them.
170	–	*
171	–	* Note that bits 1-28 are currently unused. Also value
172	–	* 0x80000000 is available as spare completion value.
174		*/
175	+
176	+	/** The run status of this task */
177		volatile int status; // accessed directly by pool and workers
178
179	<	private static final int COMPLETION_MASK      = 0xe0000000;
180	<	private static final int NORMAL               = 0xe0000000; // == mask
181	<	private static final int CANCELLED            = 0xc0000000;
182	<	private static final int EXCEPTIONAL          = 0xa0000000;
180	<	private static final int SIGNAL               = 0x00000001;
179	>	private static final int NORMAL      = -1;
180	>	private static final int CANCELLED   = -2;
181	>	private static final int EXCEPTIONAL = -3;
182	>	private static final int SIGNAL      =  1;
183
184		/**
185		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 198 | Line 200 | public abstract class ForkJoinTask<V> im
200		* also clearing signal request bits.
201		*
202		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
201	–	* @return status on exit
203		*/
204	<	private int setCompletion(int completion) {
204	>	private void setCompletion(int completion) {
205		int s;
206		while ((s = status) >= 0) {
207		if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
208	<	if ((s & SIGNAL) != 0)
208	>	if (s != 0)
209		synchronized (this) { notifyAll(); }
210	<	return completion;
210	>	break;
211		}
212		}
212	–	return s;
213		}
214
215		/**
216	<	* Record exception and set exceptional completion
216	>	* Records exception and sets exceptional completion.
217	>	*
218		* @return status on exit
219		*/
220	<	private int setExceptionalCompletion(Throwable rex) {
220	>	private void setExceptionalCompletion(Throwable rex) {
221		exceptionMap.put(this, rex);
222	<	return setCompletion(EXCEPTIONAL);
222	>	setCompletion(EXCEPTIONAL);
223		}
224
225		/**
226	<	* Blocks a worker thread until completion. Called only by pool.
226	>	* Blocks a worker thread until completion. Called only by
227	>	* pool. Currently unused -- pool-based waits use timeout
228	>	* version below.
229		*/
230		final void internalAwaitDone() {
231	<	int s;
231	>	int s;         // the odd construction reduces lock bias effects
232		while ((s = status) >= 0) {
233	<	synchronized(this) {
234	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, s|SIGNAL)){
235	<	do {
236	<	try {
234	<	wait();
235	<	} catch (InterruptedException ie) {
236	<	cancelIfTerminating();
237	<	}
238	<	} while (status >= 0);
239	<	break;
233	>	try {
234	>	synchronized (this) {
235	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
236	>	wait();
237		}
238	+	} catch (InterruptedException ie) {
239	+	cancelIfTerminating();
240		}
241		}
242		}
243
244		/**
245	<	* Blocks a non-worker-thread until completion.
245	>	* Blocks a worker thread until completed or timed out.  Called
246	>	* only by pool.
247	>	*
248		* @return status on exit
249		*/
250	<	private int externalAwaitDone() {
250	>	final int internalAwaitDone(long millis, int nanos) {
251	>	int s;
252	>	if ((s = status) >= 0) {
253	>	try {
254	>	synchronized (this) {
255	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
256	>	wait(millis, nanos);
257	>	}
258	>	} catch (InterruptedException ie) {
259	>	cancelIfTerminating();
260	>	}
261	>	s = status;
262	>	}
263	>	return s;
264	>	}
265	>
266	>	/**
267	>	* Blocks a non-worker-thread until completion.
268	>	*/
269	>	private void externalAwaitDone() {
270		int s;
271		while ((s = status) >= 0) {
272	<	synchronized(this) {
273	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, s|SIGNAL)){
272	>	synchronized (this) {
273	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
274		boolean interrupted = false;
275	<	do {
275	>	while (status >= 0) {
276		try {
277		wait();
278		} catch (InterruptedException ie) {
279		interrupted = true;
280		}
281	<	} while ((s = status) >= 0);
281	>	}
282		if (interrupted)
283		Thread.currentThread().interrupt();
284		break;
285		}
286		}
287		}
268	–	return s;
288		}
289
290		/**
291		* Unless done, calls exec and records status if completed, but
292	<	* doesn't wait for completion otherwise.
292	>	* doesn't wait for completion otherwise. Primary execution method
293	>	* for ForkJoinWorkerThread.
294		*/
295	<	final void tryExec() {
295	>	final void quietlyExec() {
296		try {
297		if (status < 0 || !exec())
298		return;
#	Line 283 | Line 303 | public abstract class ForkJoinTask<V> im
303		setCompletion(NORMAL); // must be outside try block
304		}
305
286	–	/**
287	–	* If not done and this task is next in worker queue, runs it,
288	–	* else waits for it.
289	–	* @return status on exit
290	–	*/
291	–	private int waitingJoin() {
292	–	int s = status;
293	–	if (s < 0)
294	–	return s;
295	–	Thread t = Thread.currentThread();
296	–	if (t instanceof ForkJoinWorkerThread) {
297	–	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
298	–	if (w.unpushTask(this)) {
299	–	boolean completed;
300	–	try {
301	–	completed = exec();
302	–	} catch (Throwable rex) {
303	–	return setExceptionalCompletion(rex);
304	–	}
305	–	if (completed)
306	–	return setCompletion(NORMAL);
307	–	}
308	–	return w.pool.awaitJoin(this);
309	–	}
310	–	else
311	–	return externalAwaitDone();
312	–	}
313	–
314	–	/**
315	–	* Unless done, calls exec and records status if completed, or
316	–	* waits for completion otherwise.
317	–	* @return status on exit
318	–	*/
319	–	private int waitingInvoke() {
320	–	int s = status;
321	–	if (s < 0)
322	–	return s;
323	–	boolean completed;
324	–	try {
325	–	completed = exec();
326	–	} catch (Throwable rex) {
327	–	return setExceptionalCompletion(rex);
328	–	}
329	–	if (completed)
330	–	return setCompletion(NORMAL);
331	–	return waitingJoin();
332	–	}
333	–
334	–	/**
335	–	* If this task is next in worker queue, runs it, else processes other
336	–	* tasks until complete.
337	–	* @return status on exit
338	–	*/
339	–	private int busyJoin() {
340	–	int s = status;
341	–	if (s < 0)
342	–	return s;
343	–	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
344	–	if (w.unpushTask(this)) {
345	–	boolean completed;
346	–	try {
347	–	completed = exec();
348	–	} catch (Throwable rex) {
349	–	return setExceptionalCompletion(rex);
350	–	}
351	–	if (completed)
352	–	return setCompletion(NORMAL);
353	–	}
354	–	return w.execWhileJoining(this);
355	–	}
356	–
357	–	/**
358	–	* Returns result or throws exception associated with given status.
359	–	* @param s the status
360	–	*/
361	–	private V reportResult(int s) {
362	–	Throwable ex;
363	–	if (s < NORMAL && (ex = getException()) != null)
364	–	UNSAFE.throwException(ex);
365	–	return getRawResult();
366	–	}
367	–
306		// public methods
307
308		/**
#	Line 400 | Line 338 | public abstract class ForkJoinTask<V> im
338		* @return the computed result
339		*/
340		public final V join() {
341	<	return reportResult(waitingJoin());
341	>	quietlyJoin();
342	>	Throwable ex;
343	>	if (status < NORMAL && (ex = getException()) != null)
344	>	UNSAFE.throwException(ex);
345	>	return getRawResult();
346		}
347
348		/**
349		* Commences performing this task, awaits its completion if
350	<	* necessary, and return its result, or throws an (unchecked)
351	<	* exception if the underlying computation did so.
350	>	* necessary, and returns its result, or throws an (unchecked)
351	>	* {@code RuntimeException} or {@code Error} if the underlying
352	>	* computation did so.
353		*
354		* @return the computed result
355		*/
356		public final V invoke() {
357	<	return reportResult(waitingInvoke());
357	>	quietlyInvoke();
358	>	Throwable ex;
359	>	if (status < NORMAL && (ex = getException()) != null)
360	>	UNSAFE.throwException(ex);
361	>	return getRawResult();
362		}
363
364		/**
365		* Forks the given tasks, returning when {@code isDone} holds for
366		* each task or an (unchecked) exception is encountered, in which
367	<	* case the exception is rethrown.  If either task encounters an
368	<	* exception, the other one may be, but is not guaranteed to be,
369	<	* cancelled.  If both tasks throw an exception, then this method
370	<	* throws one of them.  The individual status of each task may be
371	<	* checked using {@link #getException()} and related methods.
367	>	* case the exception is rethrown. If more than one task
368	>	* encounters an exception, then this method throws any one of
369	>	* these exceptions. If any task encounters an exception, the
370	>	* other may be cancelled. However, the execution status of
371	>	* individual tasks is not guaranteed upon exceptional return. The
372	>	* status of each task may be obtained using {@link
373	>	* #getException()} and related methods to check if they have been
374	>	* cancelled, completed normally or exceptionally, or left
375	>	* unprocessed.
376		*
377		* <p>This method may be invoked only from within {@code
378		* ForkJoinTask} computations (as may be determined using method
#	Line 442 | Line 393 | public abstract class ForkJoinTask<V> im
393		/**
394		* Forks the given tasks, returning when {@code isDone} holds for
395		* each task or an (unchecked) exception is encountered, in which
396	<	* case the exception is rethrown. If any task encounters an
397	<	* exception, others may be, but are not guaranteed to be,
398	<	* cancelled.  If more than one task encounters an exception, then
399	<	* this method throws any one of these exceptions.  The individual
400	<	* status of each task may be checked using {@link #getException()}
401	<	* and related methods.
396	>	* case the exception is rethrown. If more than one task
397	>	* encounters an exception, then this method throws any one of
398	>	* these exceptions. If any task encounters an exception, others
399	>	* may be cancelled. However, the execution status of individual
400	>	* tasks is not guaranteed upon exceptional return. The status of
401	>	* each task may be obtained using {@link #getException()} and
402	>	* related methods to check if they have been cancelled, completed
403	>	* normally or exceptionally, or left unprocessed.
404		*
405		* <p>This method may be invoked only from within {@code
406		* ForkJoinTask} computations (as may be determined using method
#	Line 469 | Line 422 | public abstract class ForkJoinTask<V> im
422		}
423		else if (i != 0)
424		t.fork();
425	<	else if (t.waitingInvoke() < NORMAL && ex == null)
426	<	ex = t.getException();
425	>	else {
426	>	t.quietlyInvoke();
427	>	if (ex == null && t.status < NORMAL)
428	>	ex = t.getException();
429	>	}
430		}
431		for (int i = 1; i <= last; ++i) {
432		ForkJoinTask<?> t = tasks[i];
433		if (t != null) {
434		if (ex != null)
435		t.cancel(false);
436	<	else if (t.waitingJoin() < NORMAL && ex == null)
437	<	ex = t.getException();
436	>	else {
437	>	t.quietlyJoin();
438	>	if (ex == null && t.status < NORMAL)
439	>	ex = t.getException();
440	>	}
441		}
442		}
443		if (ex != null)
#	Line 488 | Line 447 | public abstract class ForkJoinTask<V> im
447		/**
448		* Forks all tasks in the specified collection, returning when
449		* {@code isDone} holds for each task or an (unchecked) exception
450	<	* is encountered.  If any task encounters an exception, others
451	<	* may be, but are not guaranteed to be, cancelled.  If more than
452	<	* one task encounters an exception, then this method throws any
453	<	* one of these exceptions.  The individual status of each task
454	<	* may be checked using {@link #getException()} and related
455	<	* methods.  The behavior of this operation is undefined if the
456	<	* specified collection is modified while the operation is in
457	<	* progress.
450	>	* is encountered, in which case the exception is rethrown. If
451	>	* more than one task encounters an exception, then this method
452	>	* throws any one of these exceptions. If any task encounters an
453	>	* exception, others may be cancelled. However, the execution
454	>	* status of individual tasks is not guaranteed upon exceptional
455	>	* return. The status of each task may be obtained using {@link
456	>	* #getException()} and related methods to check if they have been
457	>	* cancelled, completed normally or exceptionally, or left
458	>	* unprocessed.
459		*
460		* <p>This method may be invoked only from within {@code
461		* ForkJoinTask} computations (as may be determined using method
#	Line 525 | Line 485 | public abstract class ForkJoinTask<V> im
485		}
486		else if (i != 0)
487		t.fork();
488	<	else if (t.waitingInvoke() < NORMAL && ex == null)
489	<	ex = t.getException();
488	>	else {
489	>	t.quietlyInvoke();
490	>	if (ex == null && t.status < NORMAL)
491	>	ex = t.getException();
492	>	}
493		}
494		for (int i = 1; i <= last; ++i) {
495		ForkJoinTask<?> t = ts.get(i);
496		if (t != null) {
497		if (ex != null)
498		t.cancel(false);
499	<	else if (t.waitingJoin() < NORMAL && ex == null)
500	<	ex = t.getException();
499	>	else {
500	>	t.quietlyJoin();
501	>	if (ex == null && t.status < NORMAL)
502	>	ex = t.getException();
503	>	}
504		}
505		}
506		if (ex != null)
#	Line 568 | Line 534 | public abstract class ForkJoinTask<V> im
534		*/
535		public boolean cancel(boolean mayInterruptIfRunning) {
536		setCompletion(CANCELLED);
537	<	return (status & COMPLETION_MASK) == CANCELLED;
537	>	return status == CANCELLED;
538		}
539
540		/**
541	<	* Cancels, ignoring any exceptions it throws. Used during worker
542	<	* and pool shutdown.
541	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
542	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
543	>	* exceptions, but if it does anyway, we have no recourse during
544	>	* shutdown, so guard against this case.
545		*/
546		final void cancelIgnoringExceptions() {
547		try {
#	Line 583 | Line 551 | public abstract class ForkJoinTask<V> im
551		}
552
553		/**
554	<	* Cancels ignoring exceptions if worker is terminating
554	>	* Cancels if current thread is a terminating worker thread,
555	>	* ignoring any exceptions thrown by cancel.
556		*/
557	<	private void cancelIfTerminating() {
557	>	final void cancelIfTerminating() {
558		Thread t = Thread.currentThread();
559		if ((t instanceof ForkJoinWorkerThread) &&
560		((ForkJoinWorkerThread) t).isTerminating()) {
#	Line 601 | Line 570 | public abstract class ForkJoinTask<V> im
570		}
571
572		public final boolean isCancelled() {
573	<	return (status & COMPLETION_MASK) == CANCELLED;
573	>	return status == CANCELLED;
574		}
575
576		/**
#	Line 610 | Line 579 | public abstract class ForkJoinTask<V> im
579		* @return {@code true} if this task threw an exception or was cancelled
580		*/
581		public final boolean isCompletedAbnormally() {
582	<	return (status & COMPLETION_MASK) < NORMAL;
582	>	return status < NORMAL;
583		}
584
585		/**
#	Line 621 | Line 590 | public abstract class ForkJoinTask<V> im
590		* exception and was not cancelled
591		*/
592		public final boolean isCompletedNormally() {
593	<	return (status & COMPLETION_MASK) == NORMAL;
593	>	return status == NORMAL;
594		}
595
596		/**
#	Line 632 | Line 601 | public abstract class ForkJoinTask<V> im
601		* @return the exception, or {@code null} if none
602		*/
603		public final Throwable getException() {
604	<	int s = status & COMPLETION_MASK;
604	>	int s = status;
605		return ((s >= NORMAL)    ? null :
606		(s == CANCELLED) ? new CancellationException() :
607		exceptionMap.get(this));
#	Line 660 | Line 629 | public abstract class ForkJoinTask<V> im
629
630		/**
631		* Completes this task, and if not already aborted or cancelled,
632	<	* returning a {@code null} result upon {@code join} and related
633	<	* operations. This method may be used to provide results for
634	<	* asynchronous tasks, or to provide alternative handling for
635	<	* tasks that would not otherwise complete normally. Its use in
636	<	* other situations is discouraged. This method is
637	<	* overridable, but overridden versions must invoke {@code super}
638	<	* implementation to maintain guarantees.
632	>	* returning the given value as the result of subsequent
633	>	* invocations of {@code join} and related operations. This method
634	>	* may be used to provide results for asynchronous tasks, or to
635	>	* provide alternative handling for tasks that would not otherwise
636	>	* complete normally. Its use in other situations is
637	>	* discouraged. This method is overridable, but overridden
638	>	* versions must invoke {@code super} implementation to maintain
639	>	* guarantees.
640		*
641		* @param value the result value for this task
642		*/
#	Line 680 | Line 650 | public abstract class ForkJoinTask<V> im
650		setCompletion(NORMAL);
651		}
652
653	+	/**
654	+	* Waits if necessary for the computation to complete, and then
655	+	* retrieves its result.
656	+	*
657	+	* @return the computed result
658	+	* @throws CancellationException if the computation was cancelled
659	+	* @throws ExecutionException if the computation threw an
660	+	* exception
661	+	* @throws InterruptedException if the current thread is not a
662	+	* member of a ForkJoinPool and was interrupted while waiting
663	+	*/
664		public final V get() throws InterruptedException, ExecutionException {
665	<	int s = waitingJoin() & COMPLETION_MASK;
666	<	if (Thread.interrupted())
667	<	throw new InterruptedException();
665	>	int s;
666	>	if (Thread.currentThread() instanceof ForkJoinWorkerThread) {
667	>	quietlyJoin();
668	>	s = status;
669	>	}
670	>	else {
671	>	while ((s = status) >= 0) {
672	>	synchronized (this) { // interruptible form of awaitDone
673	>	if (UNSAFE.compareAndSwapInt(this, statusOffset,
674	>	s, SIGNAL)) {
675	>	while (status >= 0)
676	>	wait();
677	>	}
678	>	}
679	>	}
680	>	}
681		if (s < NORMAL) {
682		Throwable ex;
683		if (s == CANCELLED)
#	Line 694 | Line 688 | public abstract class ForkJoinTask<V> im
688		return getRawResult();
689		}
690
691	+	/**
692	+	* Waits if necessary for at most the given time for the computation
693	+	* to complete, and then retrieves its result, if available.
694	+	*
695	+	* @param timeout the maximum time to wait
696	+	* @param unit the time unit of the timeout argument
697	+	* @return the computed result
698	+	* @throws CancellationException if the computation was cancelled
699	+	* @throws ExecutionException if the computation threw an
700	+	* exception
701	+	* @throws InterruptedException if the current thread is not a
702	+	* member of a ForkJoinPool and was interrupted while waiting
703	+	* @throws TimeoutException if the wait timed out
704	+	*/
705		public final V get(long timeout, TimeUnit unit)
706		throws InterruptedException, ExecutionException, TimeoutException {
707	<	Thread t = Thread.currentThread();
708	<	ForkJoinPool pool;
709	<	if (t instanceof ForkJoinWorkerThread) {
710	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
711	<	if (status >= 0 && w.unpushTask(this))
712	<	tryExec();
713	<	pool = w.pool;
714	<	}
715	<	else
716	<	pool = null;
717	<	/*
718	<	* Timed wait loop intermixes cases for fj (pool != null) and
719	<	* non FJ threads. For FJ, decrement pool count but don't try
720	<	* for replacement; increment count on completion. For non-FJ,
721	<	* deal with interrupts. This is messy, but a little less so
722	<	* than is splitting the FJ and nonFJ cases.
723	<	*/
716	<	boolean interrupted = false;
717	<	boolean dec = false; // true if pool count decremented
718	<	for (;;) {
719	<	if (Thread.interrupted() && pool == null) {
720	<	interrupted = true;
721	<	break;
707	>	long nanos = unit.toNanos(timeout);
708	>	if (status >= 0) {
709	>	Thread t = Thread.currentThread();
710	>	if (t instanceof ForkJoinWorkerThread) {
711	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
712	>	boolean completed = false; // timed variant of quietlyJoin
713	>	if (w.unpushTask(this)) {
714	>	try {
715	>	completed = exec();
716	>	} catch (Throwable rex) {
717	>	setExceptionalCompletion(rex);
718	>	}
719	>	}
720	>	if (completed)
721	>	setCompletion(NORMAL);
722	>	else if (status >= 0)
723	>	w.joinTask(this, true, nanos);
724		}
725	<	int s = status;
726	<	if (s < 0)
727	<	break;
726	<	if (UNSAFE.compareAndSwapInt(this, statusOffset,
727	<	s, s | SIGNAL)) {
725	>	else if (Thread.interrupted())
726	>	throw new InterruptedException();
727	>	else {
728		long startTime = System.nanoTime();
729	<	long nanos = unit.toNanos(timeout);
730	<	long nt; // wait time
731	<	while (status >= 0 &&
729	>	int s; long nt;
730	>	while ((s = status) >= 0 &&
731		(nt = nanos - (System.nanoTime() - startTime)) > 0) {
732	<	if (pool != null && !dec)
733	<	dec = pool.tryDecrementRunningCount();
735	<	else {
732	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,
733	>	SIGNAL)) {
734		long ms = nt / 1000000;
735		int ns = (int) (nt % 1000000);
736	<	try {
737	<	synchronized(this) {
738	<	if (status >= 0)
741	<	wait(ms, ns);
742	<	}
743	<	} catch (InterruptedException ie) {
744	<	if (pool != null)
745	<	cancelIfTerminating();
746	<	else {
747	<	interrupted = true;
748	<	break;
749	<	}
736	>	synchronized (this) {
737	>	if (status >= 0)
738	>	wait(ms, ns); // exit on IE throw
739		}
740		}
741		}
753	–	break;
742		}
743		}
744	<	if (pool != null && dec)
757	<	pool.updateRunningCount(1);
758	<	if (interrupted)
759	<	throw new InterruptedException();
760	<	int es = status & COMPLETION_MASK;
744	>	int es = status;
745		if (es != NORMAL) {
746		Throwable ex;
747		if (es == CANCELLED)
#	Line 770 | Line 754 | public abstract class ForkJoinTask<V> im
754		}
755
756		/**
757	<	* Possibly executes other tasks until this task {@link #isDone is
774	<	* done}, then returns the result of the computation.  This method
775	<	* may be more efficient than {@code join}, but is only applicable
776	<	* when there are no potential dependencies between continuation
777	<	* of the current task and that of any other task that might be
778	<	* executed while helping. (This usually holds for pure
779	<	* divide-and-conquer tasks).
780	<	*
781	<	* <p>This method may be invoked only from within {@code
782	<	* ForkJoinTask} computations (as may be determined using method
783	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
784	<	* result in exceptions or errors, possibly including {@code
785	<	* ClassCastException}.
786	<	*
787	<	* @return the computed result
788	<	*/
789	<	public final V helpJoin() {
790	<	return reportResult(busyJoin());
791	<	}
792	<
793	<	/**
794	<	* Possibly executes other tasks until this task {@link #isDone is
795	<	* done}.  This method may be useful when processing collections
796	<	* of tasks when some have been cancelled or otherwise known to
797	<	* have aborted.
798	<	*
799	<	* <p>This method may be invoked only from within {@code
800	<	* ForkJoinTask} computations (as may be determined using method
801	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
802	<	* result in exceptions or errors, possibly including {@code
803	<	* ClassCastException}.
804	<	*/
805	<	public final void quietlyHelpJoin() {
806	<	busyJoin();
807	<	}
808	<
809	<	/**
810	<	* Joins this task, without returning its result or throwing an
757	>	* Joins this task, without returning its result or throwing its
758		* exception. This method may be useful when processing
759		* collections of tasks when some have been cancelled or otherwise
760		* known to have aborted.
761		*/
762		public final void quietlyJoin() {
763	<	waitingJoin();
763	>	Thread t;
764	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
765	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
766	>	if (status >= 0) {
767	>	if (w.unpushTask(this)) {
768	>	boolean completed;
769	>	try {
770	>	completed = exec();
771	>	} catch (Throwable rex) {
772	>	setExceptionalCompletion(rex);
773	>	return;
774	>	}
775	>	if (completed) {
776	>	setCompletion(NORMAL);
777	>	return;
778	>	}
779	>	}
780	>	w.joinTask(this, false, 0L);
781	>	}
782	>	}
783	>	else
784	>	externalAwaitDone();
785		}
786
787		/**
788		* Commences performing this task and awaits its completion if
789	<	* necessary, without returning its result or throwing an
790	<	* exception. This method may be useful when processing
823	<	* collections of tasks when some have been cancelled or otherwise
824	<	* known to have aborted.
789	>	* necessary, without returning its result or throwing its
790	>	* exception.
791		*/
792		public final void quietlyInvoke() {
793	<	waitingInvoke();
793	>	if (status >= 0) {
794	>	boolean completed;
795	>	try {
796	>	completed = exec();
797	>	} catch (Throwable rex) {
798	>	setExceptionalCompletion(rex);
799	>	return;
800	>	}
801	>	if (completed)
802	>	setCompletion(NORMAL);
803	>	else
804	>	quietlyJoin();
805	>	}
806		}
807
808		/**
#	Line 856 | Line 834 | public abstract class ForkJoinTask<V> im
834		* pre-constructed trees of subtasks in loops.
835		*/
836		public void reinitialize() {
837	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
837	>	if (status == EXCEPTIONAL)
838		exceptionMap.remove(this);
839		status = 0;
840		}
#	Line 1146 | Line 1124 | public abstract class ForkJoinTask<V> im
1124		private static final long serialVersionUID = -7721805057305804111L;
1125
1126		/**
1127	<	* Saves the state to a stream.
1127	>	* Saves the state to a stream (that is, serializes it).
1128		*
1129		* @serialData the current run status and the exception thrown
1130		* during execution, or {@code null} if none
#	Line 1159 | Line 1137 | public abstract class ForkJoinTask<V> im
1137		}
1138
1139		/**
1140	<	* Reconstitutes the instance from a stream.
1140	>	* Reconstitutes the instance from a stream (that is, deserializes it).
1141		*
1142		* @param s the stream
1143		*/
1144		private void readObject(java.io.ObjectInputStream s)
1145		throws java.io.IOException, ClassNotFoundException {
1146		s.defaultReadObject();
1169	–	status |= SIGNAL; // conservatively set external signal
1147		Object ex = s.readObject();
1148		if (ex != null)
1149		setExceptionalCompletion((Throwable) ex);

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