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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 1.58 by dl, Mon Sep 6 11:55:39 2010 UTC

#	Line 64 | Line 64 | import java.util.WeakHashMap;
64		* results of a task is {@link #join}, but there are several variants:
65		* The {@link Future#get} methods support interruptible and/or timed
66		* waits for completion and report results using {@code Future}
67	<	* 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
67	>	* conventions. Method {@link #invoke} is semantically
68		* equivalent to {@code fork(); join()} but always attempts to begin
69		* execution in the current thread. The "<em>quiet</em>" forms of
70		* these methods do not extract results or report exceptions. These
#	Line 103 | Line 100 | import java.util.WeakHashMap;
100		* ForkJoinTasks (as may be determined using method {@link
101		* #inForkJoinPool}).  Attempts to invoke them in other contexts
102		* result in exceptions or errors, possibly including
103	<	* ClassCastException.
103	>	* {@code ClassCastException}.
104		*
105		* <p>Most base support methods are {@code final}, to prevent
106		* overriding of implementations that are intrinsically tied to the
#	Line 125 | Line 122 | import java.util.WeakHashMap;
122		*
123		* <p>This class provides {@code adapt} methods for {@link Runnable}
124		* and {@link Callable}, that may be of use when mixing execution of
125	<	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks
126	<	* are of this form, consider using a pool in
130	<	* {@linkplain ForkJoinPool#setAsyncMode async mode}.
125	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
126	>	* of this form, consider using a pool constructed in <em>asyncMode</em>.
127		*
128		* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
129		* used in extensions such as remote execution frameworks. It is
#	Line 148 | Line 144 | public abstract class ForkJoinTask<V> im
144		* status maintenance (2) execution and awaiting completion (3)
145		* user-level methods that additionally report results. This is
146		* sometimes hard to see because this file orders exported methods
147	<	* in a way that flows well in javadocs.
147	>	* in a way that flows well in javadocs. In particular, most
148	>	* join mechanics are in method quietlyJoin, below.
149		*/
150
151	<	/**
152	<	* Run control status bits packed into a single int to minimize
153	<	* footprint and to ensure atomicity (via CAS).  Status is
154	<	* initially zero, and takes on nonnegative values until
155	<	* completed, upon which status holds COMPLETED. CANCELLED, or
156	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
157	<	* blocking waits by other threads have the SIGNAL bit set.
158	<	*
159	<	* Completion of a stolen task with SIGNAL set awakens any waiters
163	<	* via notifyAll. Even though suboptimal for some purposes, we use
151	>	/*
152	>	* The status field holds run control status bits packed into a
153	>	* single int to minimize footprint and to ensure atomicity (via
154	>	* CAS).  Status is initially zero, and takes on nonnegative
155	>	* values until completed, upon which status holds value
156	>	* NORMAL. CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
157	>	* waits by other threads have the SIGNAL bit set.  Completion of
158	>	* a stolen task with SIGNAL set awakens any waiters via
159	>	* notifyAll. Even though suboptimal for some purposes, we use
160		* basic builtin wait/notify to take advantage of "monitor
161		* inflation" in JVMs that we would otherwise need to emulate to
162		* avoid adding further per-task bookkeeping overhead.  We want
163		* these monitors to be "fat", i.e., not use biasing or thin-lock
164		* techniques, so use some odd coding idioms that tend to avoid
165		* them.
170	–	*
171	–	* Note that bits 1-28 are currently unused. Also value
172	–	* 0x80000000 is available as spare completion value.
166		*/
167	+
168	+	/** The run status of this task */
169		volatile int status; // accessed directly by pool and workers
170
171	<	private static final int COMPLETION_MASK      = 0xe0000000;
172	<	private static final int NORMAL               = 0xe0000000; // == mask
173	<	private static final int CANCELLED            = 0xc0000000;
174	<	private static final int EXCEPTIONAL          = 0xa0000000;
180	<	private static final int SIGNAL               = 0x00000001;
171	>	private static final int NORMAL      = -1;
172	>	private static final int CANCELLED   = -2;
173	>	private static final int EXCEPTIONAL = -3;
174	>	private static final int SIGNAL      =  1;
175
176		/**
177		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 198 | Line 192 | public abstract class ForkJoinTask<V> im
192		* also clearing signal request bits.
193		*
194		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
201	–	* @return status on exit
195		*/
196	<	private int setCompletion(int completion) {
196	>	private void setCompletion(int completion) {
197		int s;
198		while ((s = status) >= 0) {
199		if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
200	<	if ((s & SIGNAL) != 0)
200	>	if (s != 0)
201		synchronized (this) { notifyAll(); }
202	<	return completion;
202	>	break;
203		}
204		}
212	–	return s;
205		}
206
207		/**
208	<	* Record exception and set exceptional completion
208	>	* Records exception and sets exceptional completion.
209	>	*
210		* @return status on exit
211		*/
212	<	private int setExceptionalCompletion(Throwable rex) {
212	>	private void setExceptionalCompletion(Throwable rex) {
213		exceptionMap.put(this, rex);
214	<	return setCompletion(EXCEPTIONAL);
214	>	setCompletion(EXCEPTIONAL);
215		}
216
217		/**
218	<	* Blocks a worker thread until completion. Called only by pool.
218	>	* Blocks a worker thread until completion. Called only by
219	>	* pool. Currently unused -- pool-based waits use timeout
220	>	* version below.
221		*/
222		final void internalAwaitDone() {
223	<	int s;
223	>	int s;         // the odd construction reduces lock bias effects
224		while ((s = status) >= 0) {
225	<	synchronized(this) {
226	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, s|SIGNAL)){
227	<	do {
228	<	try {
234	<	wait();
235	<	} catch (InterruptedException ie) {
236	<	cancelIfTerminating();
237	<	}
238	<	} while (status >= 0);
239	<	break;
225	>	try {
226	>	synchronized(this) {
227	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
228	>	wait();
229		}
230	+	} catch (InterruptedException ie) {
231	+	cancelIfTerminating();
232		}
233		}
234		}
235
236		/**
237	<	* Blocks a non-worker-thread until completion.
237	>	* Blocks a worker thread until completed or timed out.  Called
238	>	* only by pool.
239	>	*
240		* @return status on exit
241		*/
242	<	private int externalAwaitDone() {
242	>	final int internalAwaitDone(long millis) {
243	>	int s;
244	>	if ((s = status) >= 0) {
245	>	try {
246	>	synchronized(this) {
247	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
248	>	wait(millis, 0);
249	>	}
250	>	} catch (InterruptedException ie) {
251	>	cancelIfTerminating();
252	>	}
253	>	s = status;
254	>	}
255	>	return s;
256	>	}
257	>
258	>	/**
259	>	* Blocks a non-worker-thread until completion.
260	>	*/
261	>	private void externalAwaitDone() {
262		int s;
263		while ((s = status) >= 0) {
264		synchronized(this) {
265	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, s|SIGNAL)){
265	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
266		boolean interrupted = false;
267	<	do {
267	>	while (status >= 0) {
268		try {
269		wait();
270		} catch (InterruptedException ie) {
271		interrupted = true;
272		}
273	<	} while ((s = status) >= 0);
273	>	}
274		if (interrupted)
275		Thread.currentThread().interrupt();
276		break;
277		}
278		}
279		}
268	–	return s;
280		}
281
282		/**
283		* Unless done, calls exec and records status if completed, but
284	<	* doesn't wait for completion otherwise.
284	>	* doesn't wait for completion otherwise. Primary execution method
285	>	* for ForkJoinWorkerThread.
286		*/
287	<	final void tryExec() {
287	>	final void quietlyExec() {
288		try {
289		if (status < 0 || !exec())
290		return;
#	Line 283 | Line 295 | public abstract class ForkJoinTask<V> im
295		setCompletion(NORMAL); // must be outside try block
296		}
297
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	–
298		// public methods
299
300		/**
#	Line 400 | Line 330 | public abstract class ForkJoinTask<V> im
330		* @return the computed result
331		*/
332		public final V join() {
333	<	return reportResult(waitingJoin());
333	>	quietlyJoin();
334	>	Throwable ex;
335	>	if (status < NORMAL && (ex = getException()) != null)
336	>	UNSAFE.throwException(ex);
337	>	return getRawResult();
338		}
339
340		/**
341		* Commences performing this task, awaits its completion if
342	<	* necessary, and return its result, or throws an (unchecked)
343	<	* exception if the underlying computation did so.
342	>	* necessary, and returns its result, or throws an (unchecked)
343	>	* {@code RuntimeException} or {@code Error} if the underlying
344	>	* computation did so.
345		*
346		* @return the computed result
347		*/
348		public final V invoke() {
349	<	return reportResult(waitingInvoke());
349	>	quietlyInvoke();
350	>	Throwable ex;
351	>	if (status < NORMAL && (ex = getException()) != null)
352	>	UNSAFE.throwException(ex);
353	>	return getRawResult();
354		}
355
356		/**
357		* Forks the given tasks, returning when {@code isDone} holds for
358		* each task or an (unchecked) exception is encountered, in which
359	<	* case the exception is rethrown.  If either task encounters an
360	<	* exception, the other one may be, but is not guaranteed to be,
361	<	* cancelled.  If both tasks throw an exception, then this method
362	<	* throws one of them.  The individual status of each task may be
363	<	* checked using {@link #getException()} and related methods.
359	>	* case the exception is rethrown. If more than one task
360	>	* encounters an exception, then this method throws any one of
361	>	* these exceptions. If any task encounters an exception, the
362	>	* other may be cancelled. However, the execution status of
363	>	* individual tasks is not guaranteed upon exceptional return. The
364	>	* status of each task may be obtained using {@link
365	>	* #getException()} and related methods to check if they have been
366	>	* cancelled, completed normally or exceptionally, or left
367	>	* unprocessed.
368		*
369		* <p>This method may be invoked only from within {@code
370		* ForkJoinTask} computations (as may be determined using method
#	Line 442 | Line 385 | public abstract class ForkJoinTask<V> im
385		/**
386		* Forks the given tasks, returning when {@code isDone} holds for
387		* each task or an (unchecked) exception is encountered, in which
388	<	* case the exception is rethrown. If any task encounters an
389	<	* exception, others may be, but are not guaranteed to be,
390	<	* cancelled.  If more than one task encounters an exception, then
391	<	* this method throws any one of these exceptions.  The individual
392	<	* status of each task may be checked using {@link #getException()}
393	<	* and related methods.
388	>	* case the exception is rethrown. If more than one task
389	>	* encounters an exception, then this method throws any one of
390	>	* these exceptions. If any task encounters an exception, others
391	>	* may be cancelled. However, the execution status of individual
392	>	* tasks is not guaranteed upon exceptional return. The status of
393	>	* each task may be obtained using {@link #getException()} and
394	>	* related methods to check if they have been cancelled, completed
395	>	* normally or exceptionally, or left unprocessed.
396		*
397		* <p>This method may be invoked only from within {@code
398		* ForkJoinTask} computations (as may be determined using method
#	Line 469 | Line 414 | public abstract class ForkJoinTask<V> im
414		}
415		else if (i != 0)
416		t.fork();
417	<	else if (t.waitingInvoke() < NORMAL && ex == null)
418	<	ex = t.getException();
417	>	else {
418	>	t.quietlyInvoke();
419	>	if (ex == null && t.status < NORMAL)
420	>	ex = t.getException();
421	>	}
422		}
423		for (int i = 1; i <= last; ++i) {
424		ForkJoinTask<?> t = tasks[i];
425		if (t != null) {
426		if (ex != null)
427		t.cancel(false);
428	<	else if (t.waitingJoin() < NORMAL && ex == null)
429	<	ex = t.getException();
428	>	else {
429	>	t.quietlyJoin();
430	>	if (ex == null && t.status < NORMAL)
431	>	ex = t.getException();
432	>	}
433		}
434		}
435		if (ex != null)
#	Line 488 | Line 439 | public abstract class ForkJoinTask<V> im
439		/**
440		* Forks all tasks in the specified collection, returning when
441		* {@code isDone} holds for each task or an (unchecked) exception
442	<	* is encountered.  If any task encounters an exception, others
443	<	* may be, but are not guaranteed to be, cancelled.  If more than
444	<	* one task encounters an exception, then this method throws any
445	<	* one of these exceptions.  The individual status of each task
446	<	* may be checked using {@link #getException()} and related
447	<	* methods.  The behavior of this operation is undefined if the
448	<	* specified collection is modified while the operation is in
449	<	* progress.
442	>	* is encountered, in which case the exception is rethrown. If
443	>	* more than one task encounters an exception, then this method
444	>	* throws any one of these exceptions. If any task encounters an
445	>	* exception, others may be cancelled. However, the execution
446	>	* status of individual tasks is not guaranteed upon exceptional
447	>	* return. The status of each task may be obtained using {@link
448	>	* #getException()} and related methods to check if they have been
449	>	* cancelled, completed normally or exceptionally, or left
450	>	* unprocessed.
451		*
452		* <p>This method may be invoked only from within {@code
453		* ForkJoinTask} computations (as may be determined using method
#	Line 525 | Line 477 | public abstract class ForkJoinTask<V> im
477		}
478		else if (i != 0)
479		t.fork();
480	<	else if (t.waitingInvoke() < NORMAL && ex == null)
481	<	ex = t.getException();
480	>	else {
481	>	t.quietlyInvoke();
482	>	if (ex == null && t.status < NORMAL)
483	>	ex = t.getException();
484	>	}
485		}
486		for (int i = 1; i <= last; ++i) {
487		ForkJoinTask<?> t = ts.get(i);
488		if (t != null) {
489		if (ex != null)
490		t.cancel(false);
491	<	else if (t.waitingJoin() < NORMAL && ex == null)
492	<	ex = t.getException();
491	>	else {
492	>	t.quietlyJoin();
493	>	if (ex == null && t.status < NORMAL)
494	>	ex = t.getException();
495	>	}
496		}
497		}
498		if (ex != null)
#	Line 568 | Line 526 | public abstract class ForkJoinTask<V> im
526		*/
527		public boolean cancel(boolean mayInterruptIfRunning) {
528		setCompletion(CANCELLED);
529	<	return (status & COMPLETION_MASK) == CANCELLED;
529	>	return status == CANCELLED;
530		}
531
532		/**
533	<	* Cancels, ignoring any exceptions it throws. Used during worker
534	<	* and pool shutdown.
533	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
534	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
535	>	* exceptions, but if it does anyway, we have no recourse during
536	>	* shutdown, so guard against this case.
537		*/
538		final void cancelIgnoringExceptions() {
539		try {
#	Line 583 | Line 543 | public abstract class ForkJoinTask<V> im
543		}
544
545		/**
546	<	* Cancels ignoring exceptions if worker is terminating
546	>	* Cancels if current thread is a terminating worker thread,
547	>	* ignoring any exceptions thrown by cancel.
548		*/
549	<	private void cancelIfTerminating() {
549	>	final void cancelIfTerminating() {
550		Thread t = Thread.currentThread();
551		if ((t instanceof ForkJoinWorkerThread) &&
552		((ForkJoinWorkerThread) t).isTerminating()) {
#	Line 601 | Line 562 | public abstract class ForkJoinTask<V> im
562		}
563
564		public final boolean isCancelled() {
565	<	return (status & COMPLETION_MASK) == CANCELLED;
565	>	return status == CANCELLED;
566		}
567
568		/**
#	Line 610 | Line 571 | public abstract class ForkJoinTask<V> im
571		* @return {@code true} if this task threw an exception or was cancelled
572		*/
573		public final boolean isCompletedAbnormally() {
574	<	return (status & COMPLETION_MASK) < NORMAL;
574	>	return status < NORMAL;
575		}
576
577		/**
#	Line 621 | Line 582 | public abstract class ForkJoinTask<V> im
582		* exception and was not cancelled
583		*/
584		public final boolean isCompletedNormally() {
585	<	return (status & COMPLETION_MASK) == NORMAL;
585	>	return status == NORMAL;
586		}
587
588		/**
#	Line 632 | Line 593 | public abstract class ForkJoinTask<V> im
593		* @return the exception, or {@code null} if none
594		*/
595		public final Throwable getException() {
596	<	int s = status & COMPLETION_MASK;
596	>	int s = status;
597		return ((s >= NORMAL)    ? null :
598		(s == CANCELLED) ? new CancellationException() :
599		exceptionMap.get(this));
#	Line 660 | Line 621 | public abstract class ForkJoinTask<V> im
621
622		/**
623		* Completes this task, and if not already aborted or cancelled,
624	<	* returning a {@code null} result upon {@code join} and related
625	<	* operations. This method may be used to provide results for
626	<	* asynchronous tasks, or to provide alternative handling for
627	<	* tasks that would not otherwise complete normally. Its use in
628	<	* other situations is discouraged. This method is
629	<	* overridable, but overridden versions must invoke {@code super}
630	<	* implementation to maintain guarantees.
624	>	* returning the given value as the result of subsequent
625	>	* invocations of {@code join} and related operations. This method
626	>	* may be used to provide results for asynchronous tasks, or to
627	>	* provide alternative handling for tasks that would not otherwise
628	>	* complete normally. Its use in other situations is
629	>	* discouraged. This method is overridable, but overridden
630	>	* versions must invoke {@code super} implementation to maintain
631	>	* guarantees.
632		*
633		* @param value the result value for this task
634		*/
#	Line 681 | Line 643 | public abstract class ForkJoinTask<V> im
643		}
644
645		public final V get() throws InterruptedException, ExecutionException {
646	<	int s = waitingJoin() & COMPLETION_MASK;
646	>	quietlyJoin();
647		if (Thread.interrupted())
648		throw new InterruptedException();
649	+	int s = status;
650		if (s < NORMAL) {
651		Throwable ex;
652		if (s == CANCELLED)
#	Line 701 | Line 664 | public abstract class ForkJoinTask<V> im
664		if (t instanceof ForkJoinWorkerThread) {
665		ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
666		if (status >= 0 && w.unpushTask(this))
667	<	tryExec();
667	>	quietlyExec();
668		pool = w.pool;
669		}
670		else
671		pool = null;
672		/*
673	<	* Timed wait loop intermixes cases for fj (pool != null) and
673	>	* Timed wait loop intermixes cases for FJ (pool != null) and
674		* non FJ threads. For FJ, decrement pool count but don't try
675		* for replacement; increment count on completion. For non-FJ,
676		* deal with interrupts. This is messy, but a little less so
#	Line 715 | Line 678 | public abstract class ForkJoinTask<V> im
678		*/
679		boolean interrupted = false;
680		boolean dec = false; // true if pool count decremented
681	+	long nanos = unit.toNanos(timeout);
682		for (;;) {
683	<	if (Thread.interrupted() && pool == null) {
683	>	if (pool == null && Thread.interrupted()) {
684		interrupted = true;
685		break;
686		}
687		int s = status;
688		if (s < 0)
689		break;
690	<	if (UNSAFE.compareAndSwapInt(this, statusOffset,
727	<	s, s | SIGNAL)) {
690	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
691		long startTime = System.nanoTime();
729	–	long nanos = unit.toNanos(timeout);
692		long nt; // wait time
693		while (status >= 0 &&
694		(nt = nanos - (System.nanoTime() - startTime)) > 0) {
#	Line 754 | Line 716 | public abstract class ForkJoinTask<V> im
716		}
717		}
718		if (pool != null && dec)
719	<	pool.updateRunningCount(1);
719	>	pool.incrementRunningCount();
720		if (interrupted)
721		throw new InterruptedException();
722	<	int es = status & COMPLETION_MASK;
722	>	int es = status;
723		if (es != NORMAL) {
724		Throwable ex;
725		if (es == CANCELLED)
#	Line 770 | Line 732 | public abstract class ForkJoinTask<V> im
732		}
733
734		/**
735	<	* 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
735	>	* Joins this task, without returning its result or throwing its
736		* exception. This method may be useful when processing
737		* collections of tasks when some have been cancelled or otherwise
738		* known to have aborted.
739		*/
740		public final void quietlyJoin() {
741	<	waitingJoin();
741	>	Thread t;
742	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
743	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
744	>	if (status >= 0) {
745	>	if (w.unpushTask(this)) {
746	>	boolean completed;
747	>	try {
748	>	completed = exec();
749	>	} catch (Throwable rex) {
750	>	setExceptionalCompletion(rex);
751	>	return;
752	>	}
753	>	if (completed) {
754	>	setCompletion(NORMAL);
755	>	return;
756	>	}
757	>	}
758	>	w.joinTask(this);
759	>	}
760	>	}
761	>	else
762	>	externalAwaitDone();
763		}
764
765		/**
766		* Commences performing this task and awaits its completion if
767	<	* necessary, without returning its result or throwing an
768	<	* exception. This method may be useful when processing
823	<	* collections of tasks when some have been cancelled or otherwise
824	<	* known to have aborted.
767	>	* necessary, without returning its result or throwing its
768	>	* exception.
769		*/
770		public final void quietlyInvoke() {
771	<	waitingInvoke();
771	>	if (status >= 0) {
772	>	boolean completed;
773	>	try {
774	>	completed = exec();
775	>	} catch (Throwable rex) {
776	>	setExceptionalCompletion(rex);
777	>	return;
778	>	}
779	>	if (completed)
780	>	setCompletion(NORMAL);
781	>	else
782	>	quietlyJoin();
783	>	}
784		}
785
786		/**
#	Line 856 | Line 812 | public abstract class ForkJoinTask<V> im
812		* pre-constructed trees of subtasks in loops.
813		*/
814		public void reinitialize() {
815	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
815	>	if (status == EXCEPTIONAL)
816		exceptionMap.remove(this);
817		status = 0;
818		}
#	Line 1146 | Line 1102 | public abstract class ForkJoinTask<V> im
1102		private static final long serialVersionUID = -7721805057305804111L;
1103
1104		/**
1105	<	* Saves the state to a stream.
1105	>	* Saves the state to a stream (that is, serializes it).
1106		*
1107		* @serialData the current run status and the exception thrown
1108		* during execution, or {@code null} if none
#	Line 1159 | Line 1115 | public abstract class ForkJoinTask<V> im
1115		}
1116
1117		/**
1118	<	* Reconstitutes the instance from a stream.
1118	>	* Reconstitutes the instance from a stream (that is, deserializes it).
1119		*
1120		* @param s the stream
1121		*/
1122		private void readObject(java.io.ObjectInputStream s)
1123		throws java.io.IOException, ClassNotFoundException {
1124		s.defaultReadObject();
1169	–	status |= SIGNAL; // conservatively set external signal
1125		Object ex = s.readObject();
1126		if (ex != null)
1127		setExceptionalCompletion((Throwable) ex);

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