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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.49 by dl, Wed Jul 7 19:52:31 2010 UTC vs.
Revision 1.70 by dl, Tue Nov 23 00:10:39 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 100 | 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>Method {@link #join} and its variants are appropriate for use
114	>	* only when completion dependencies are acyclic; that is, the
115	>	* parallel computation can be described as a directed acyclic graph
116	>	* (DAG). Otherwise, executions may encounter a form of deadlock as
117	>	* tasks cyclically wait for each other.  However, this framework
118	>	* supports other methods and techniques (for example the use of
119	>	* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that
120	>	* may be of use in constructing custom subclasses for problems that
121	>	* are not statically structured as DAGs.
122		*
123		* <p>Most base support methods are {@code final}, to prevent
124		* overriding of implementations that are intrinsically tied to the
#	Line 116 | Line 134 | import java.util.WeakHashMap;
134		* computation. Large tasks should be split into smaller subtasks,
135		* usually via recursive decomposition. As a very rough rule of thumb,
136		* a task should perform more than 100 and less than 10000 basic
137	<	* computational steps. If tasks are too big, then parallelism cannot
138	<	* improve throughput. If too small, then memory and internal task
139	<	* maintenance overhead may overwhelm processing.
137	>	* computational steps, and should avoid indefinite looping. If tasks
138	>	* are too big, then parallelism cannot improve throughput. If too
139	>	* small, then memory and internal task maintenance overhead may
140	>	* overwhelm processing.
141		*
142		* <p>This class provides {@code adapt} methods for {@link Runnable}
143		* and {@link Callable}, that may be of use when mixing execution of
#	Line 144 | Line 163 | public abstract class ForkJoinTask<V> im
163		* status maintenance (2) execution and awaiting completion (3)
164		* user-level methods that additionally report results. This is
165		* sometimes hard to see because this file orders exported methods
166	<	* in a way that flows well in javadocs.
166	>	* in a way that flows well in javadocs. In particular, most
167	>	* join mechanics are in method quietlyJoin, below.
168		*/
169
170	<	/**
171	<	* Run control status bits packed into a single int to minimize
172	<	* footprint and to ensure atomicity (via CAS).  Status is
173	<	* initially zero, and takes on nonnegative values until
174	<	* completed, upon which status holds value COMPLETED. CANCELLED,
175	<	* or EXCEPTIONAL. Tasks undergoing blocking waits by other
176	<	* threads have the SIGNAL bit set.  Completion of a stolen task
177	<	* with SIGNAL set awakens any waiters via notifyAll. Even though
178	<	* suboptimal for some purposes, we use basic builtin wait/notify
179	<	* to take advantage of "monitor inflation" in JVMs that we would
180	<	* otherwise need to emulate to avoid adding further per-task
181	<	* bookkeeping overhead.  We want these monitors to be "fat",
182	<	* i.e., not use biasing or thin-lock techniques, so use some odd
183	<	* coding idioms that tend to avoid them.
170	>	/*
171	>	* The status field holds run control status bits packed into a
172	>	* single int to minimize footprint and to ensure atomicity (via
173	>	* CAS).  Status is initially zero, and takes on nonnegative
174	>	* values until completed, upon which status holds value
175	>	* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
176	>	* waits by other threads have the SIGNAL bit set.  Completion of
177	>	* a stolen task with SIGNAL set awakens any waiters via
178	>	* notifyAll. Even though suboptimal for some purposes, we use
179	>	* basic builtin wait/notify to take advantage of "monitor
180	>	* inflation" in JVMs that we would otherwise need to emulate to
181	>	* avoid adding further per-task bookkeeping overhead.  We want
182	>	* these monitors to be "fat", i.e., not use biasing or thin-lock
183	>	* techniques, so use some odd coding idioms that tend to avoid
184	>	* them.
185		*/
186	+
187	+	/** The run status of this task */
188		volatile int status; // accessed directly by pool and workers
189
190		private static final int NORMAL      = -1;
#	Line 188 | Line 211 | public abstract class ForkJoinTask<V> im
211		* also clearing signal request bits.
212		*
213		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
191	–	* @return status on exit
214		*/
215	<	private int setCompletion(int completion) {
215	>	private void setCompletion(int completion) {
216		int s;
217		while ((s = status) >= 0) {
218		if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
219	<	if (s == SIGNAL)
219	>	if (s != 0)
220		synchronized (this) { notifyAll(); }
221	<	return completion;
221	>	break;
222		}
223		}
202	–	return s;
224		}
225
226		/**
227	<	* Record exception and set exceptional completion
227	>	* Records exception and sets exceptional completion.
228	>	*
229		* @return status on exit
230		*/
231	<	private int setExceptionalCompletion(Throwable rex) {
231	>	private void setExceptionalCompletion(Throwable rex) {
232		exceptionMap.put(this, rex);
233	<	return setCompletion(EXCEPTIONAL);
233	>	setCompletion(EXCEPTIONAL);
234		}
235
236		/**
237	<	* Blocks a worker thread until completion. Called only by pool.
237	>	* Blocks a worker thread until completed or timed out.  Called
238	>	* only by pool.
239		*/
240	<	final int internalAwaitDone() {
241	<	int s;
242	<	while ((s = status) >= 0) {
243	<	synchronized(this) {
244	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
245	<	do {
246	<	try {
247	<	wait();
225	<	} catch (InterruptedException ie) {
226	<	cancelIfTerminating();
227	<	}
228	<	} while ((s = status) >= 0);
229	<	break;
240	>	final void internalAwaitDone(long millis, int nanos) {
241	>	if (status >= 0) {
242	>	try {     // the odd construction reduces lock bias effects
243	>	synchronized (this) {
244	>	if (status > 0 ||
245	>	UNSAFE.compareAndSwapInt(this, statusOffset,
246	>	0, SIGNAL))
247	>	wait(millis, nanos);
248		}
249	+	} catch (InterruptedException ie) {
250	+	cancelIfTerminating();
251		}
252		}
233	–	return s;
253		}
254
255		/**
256		* Blocks a non-worker-thread until completion.
238	–	* @return status on exit
257		*/
258	<	private int externalAwaitDone() {
259	<	int s;
260	<	while ((s = status) >= 0) {
258	>	private void externalAwaitDone() {
259	>	if (status >= 0) {
260	>	boolean interrupted = false;
261	>	synchronized(this) {
262	>	int s;
263	>	while ((s = status) >= 0) {
264	>	if (s == 0 &&
265	>	!UNSAFE.compareAndSwapInt(this, statusOffset,
266	>	0, SIGNAL))
267	>	continue;
268	>	try {
269	>	wait();
270	>	} catch (InterruptedException ie) {
271	>	interrupted = true;
272	>	}
273	>	}
274	>	}
275	>	if (interrupted)
276	>	Thread.currentThread().interrupt();
277	>	}
278	>	}
279	>
280	>	/**
281	>	* Blocks a non-worker-thread until completion or interruption or timeout
282	>	*/
283	>	private void externalInterruptibleAwaitDone(boolean timed, long nanos)
284	>	throws InterruptedException {
285	>	if (Thread.interrupted())
286	>	throw new InterruptedException();
287	>	if (status >= 0) {
288	>	long startTime = timed ? System.nanoTime() : 0L;
289		synchronized(this) {
290	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
291	<	boolean interrupted = false;
292	<	do {
293	<	try {
294	<	wait();
295	<	} catch (InterruptedException ie) {
296	<	interrupted = true;
297	<	}
298	<	} while ((s = status) >= 0);
299	<	if (interrupted)
300	<	Thread.currentThread().interrupt();
301	<	break;
290	>	int s;
291	>	while ((s = status) >= 0) {
292	>	long nt;
293	>	if (s == 0 &&
294	>	!UNSAFE.compareAndSwapInt(this, statusOffset,
295	>	0, SIGNAL))
296	>	continue;
297	>	else if (!timed)
298	>	wait();
299	>	else if ((nt = nanos - (System.nanoTime()-startTime)) > 0L)
300	>	wait(nt / 1000000, (int)(nt % 1000000));
301	>	else
302	>	break;
303		}
304		}
305		}
259	–	return s;
306		}
307
308		/**
#	Line 264 | Line 310 | public abstract class ForkJoinTask<V> im
310		* doesn't wait for completion otherwise. Primary execution method
311		* for ForkJoinWorkerThread.
312		*/
313	<	final void tryExec() {
313	>	final void quietlyExec() {
314		try {
315		if (status < 0 || !exec())
316		return;
#	Line 275 | Line 321 | public abstract class ForkJoinTask<V> im
321		setCompletion(NORMAL); // must be outside try block
322		}
323
278	–	/**
279	–	* If not done and this task is next in worker queue, runs it,
280	–	* else waits for it.
281	–	* @return status on exit
282	–	*/
283	–	private int doJoin() {
284	–	int stat;
285	–	if ((stat = status) < 0)
286	–	return stat;
287	–	Thread t = Thread.currentThread();
288	–	ForkJoinWorkerThread w;
289	–	if (t instanceof ForkJoinWorkerThread) {
290	–	if ((w = (ForkJoinWorkerThread) t).unpushTask(this)) {
291	–	boolean completed;
292	–	try {
293	–	completed = exec();
294	–	} catch (Throwable rex) {
295	–	return setExceptionalCompletion(rex);
296	–	}
297	–	if (completed)
298	–	return setCompletion(NORMAL);
299	–	}
300	–	w.joinTask(this);
301	–	return status;
302	–	}
303	–	return externalAwaitDone();
304	–	}
305	–
306	–	/**
307	–	* Unless done, calls exec and records status if completed, or
308	–	* waits for completion otherwise.
309	–	* @return status on exit
310	–	*/
311	–	private int doInvoke() {
312	–	int stat;
313	–	if ((stat = status) >= 0) {
314	–	boolean completed;
315	–	try {
316	–	completed = exec();
317	–	} catch (Throwable rex) {
318	–	return setExceptionalCompletion(rex);
319	–	}
320	–	if (completed)
321	–	stat = setCompletion(NORMAL);
322	–	else
323	–	stat = doJoin();
324	–	}
325	–	return stat;
326	–	}
327	–
328	–	/**
329	–	* Returns result or throws exception associated with given status.
330	–	* @param s the status
331	–	*/
332	–	private V reportResult(int s) {
333	–	Throwable ex;
334	–	if (s < NORMAL && (ex = getException()) != null)
335	–	UNSAFE.throwException(ex);
336	–	return getRawResult();
337	–	}
338	–
324		// public methods
325
326		/**
#	Line 349 | Line 334 | public abstract class ForkJoinTask<V> im
334		* #isDone} returning {@code true}.
335		*
336		* <p>This method may be invoked only from within {@code
337	<	* ForkJoinTask} computations (as may be determined using method
337	>	* ForkJoinPool} computations (as may be determined using method
338		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
339		* result in exceptions or errors, possibly including {@code
340		* ClassCastException}.
#	Line 363 | Line 348 | public abstract class ForkJoinTask<V> im
348		}
349
350		/**
351	<	* Returns the result of the computation when it {@link #isDone is done}.
352	<	* This method differs from {@link #get()} in that
351	>	* Returns the result of the computation when it {@link #isDone is
352	>	* done}.  This method differs from {@link #get()} in that
353		* abnormal completion results in {@code RuntimeException} or
354	<	* {@code Error}, not {@code ExecutionException}.
354	>	* {@code Error}, not {@code ExecutionException}, and that
355	>	* interrupts of the calling thread do <em>not</em> cause the
356	>	* method to abruptly return by throwing {@code
357	>	* InterruptedException}.
358		*
359		* @return the computed result
360		*/
361		public final V join() {
362	<	return reportResult(doJoin());
362	>	quietlyJoin();
363	>	Throwable ex;
364	>	if (status < NORMAL && (ex = getException()) != null)
365	>	UNSAFE.throwException(ex);
366	>	return getRawResult();
367		}
368
369		/**
370		* Commences performing this task, awaits its completion if
371	<	* necessary, and return its result, or throws an (unchecked)
372	<	* exception if the underlying computation did so.
371	>	* necessary, and returns its result, or throws an (unchecked)
372	>	* {@code RuntimeException} or {@code Error} if the underlying
373	>	* computation did so.
374		*
375		* @return the computed result
376		*/
377		public final V invoke() {
378	<	return reportResult(doInvoke());
378	>	quietlyInvoke();
379	>	Throwable ex;
380	>	if (status < NORMAL && (ex = getException()) != null)
381	>	UNSAFE.throwException(ex);
382	>	return getRawResult();
383		}
384
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 either task encounters an
389	<	* exception, the other one may be, but is not guaranteed to be,
390	<	* cancelled.  If both tasks throw an exception, then this method
391	<	* throws one of them.  The individual status of each task may be
392	<	* checked using {@link #getException()} 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, the
391	>	* other may be cancelled. However, the execution status of
392	>	* individual tasks is not guaranteed upon exceptional return. The
393	>	* status of each task may be obtained using {@link
394	>	* #getException()} and related methods to check if they have been
395	>	* cancelled, completed normally or exceptionally, or left
396	>	* unprocessed.
397		*
398		* <p>This method may be invoked only from within {@code
399	<	* ForkJoinTask} computations (as may be determined using method
399	>	* ForkJoinPool} computations (as may be determined using method
400		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
401		* result in exceptions or errors, possibly including {@code
402		* ClassCastException}.
#	Line 413 | Line 414 | public abstract class ForkJoinTask<V> im
414		/**
415		* Forks the given tasks, returning when {@code isDone} holds for
416		* each task or an (unchecked) exception is encountered, in which
417	<	* case the exception is rethrown. If any task encounters an
418	<	* exception, others may be, but are not guaranteed to be,
419	<	* cancelled.  If more than one task encounters an exception, then
420	<	* this method throws any one of these exceptions.  The individual
421	<	* status of each task may be checked using {@link #getException()}
422	<	* and related methods.
417	>	* case the exception is rethrown. If more than one task
418	>	* encounters an exception, then this method throws any one of
419	>	* these exceptions. If any task encounters an exception, others
420	>	* may be cancelled. However, the execution status of individual
421	>	* tasks is not guaranteed upon exceptional return. The status of
422	>	* each task may be obtained using {@link #getException()} and
423	>	* related methods to check if they have been cancelled, completed
424	>	* normally or exceptionally, or left unprocessed.
425		*
426		* <p>This method may be invoked only from within {@code
427	<	* ForkJoinTask} computations (as may be determined using method
427	>	* ForkJoinPool} computations (as may be determined using method
428		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
429		* result in exceptions or errors, possibly including {@code
430		* ClassCastException}.
#	Line 440 | Line 443 | public abstract class ForkJoinTask<V> im
443		}
444		else if (i != 0)
445		t.fork();
446	<	else if (t.doInvoke() < NORMAL && ex == null)
447	<	ex = t.getException();
446	>	else {
447	>	t.quietlyInvoke();
448	>	if (ex == null && t.status < NORMAL)
449	>	ex = t.getException();
450	>	}
451		}
452		for (int i = 1; i <= last; ++i) {
453		ForkJoinTask<?> t = tasks[i];
454		if (t != null) {
455		if (ex != null)
456		t.cancel(false);
457	<	else if (t.doJoin() < NORMAL && ex == null)
458	<	ex = t.getException();
457	>	else {
458	>	t.quietlyJoin();
459	>	if (ex == null && t.status < NORMAL)
460	>	ex = t.getException();
461	>	}
462		}
463		}
464		if (ex != null)
#	Line 459 | Line 468 | public abstract class ForkJoinTask<V> im
468		/**
469		* Forks all tasks in the specified collection, returning when
470		* {@code isDone} holds for each task or an (unchecked) exception
471	<	* is encountered.  If any task encounters an exception, others
472	<	* may be, but are not guaranteed to be, cancelled.  If more than
473	<	* one task encounters an exception, then this method throws any
474	<	* one of these exceptions.  The individual status of each task
475	<	* may be checked using {@link #getException()} and related
476	<	* methods.  The behavior of this operation is undefined if the
477	<	* specified collection is modified while the operation is in
478	<	* progress.
471	>	* is encountered, in which case the exception is rethrown. If
472	>	* more than one task encounters an exception, then this method
473	>	* throws any one of these exceptions. If any task encounters an
474	>	* exception, others may be cancelled. However, the execution
475	>	* status of individual tasks is not guaranteed upon exceptional
476	>	* return. The status of each task may be obtained using {@link
477	>	* #getException()} and related methods to check if they have been
478	>	* cancelled, completed normally or exceptionally, or left
479	>	* unprocessed.
480		*
481		* <p>This method may be invoked only from within {@code
482	<	* ForkJoinTask} computations (as may be determined using method
482	>	* ForkJoinPool} computations (as may be determined using method
483		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
484		* result in exceptions or errors, possibly including {@code
485		* ClassCastException}.
#	Line 496 | Line 506 | public abstract class ForkJoinTask<V> im
506		}
507		else if (i != 0)
508		t.fork();
509	<	else if (t.doInvoke() < NORMAL && ex == null)
510	<	ex = t.getException();
509	>	else {
510	>	t.quietlyInvoke();
511	>	if (ex == null && t.status < NORMAL)
512	>	ex = t.getException();
513	>	}
514		}
515		for (int i = 1; i <= last; ++i) {
516		ForkJoinTask<?> t = ts.get(i);
517		if (t != null) {
518		if (ex != null)
519		t.cancel(false);
520	<	else if (t.doJoin() < NORMAL && ex == null)
521	<	ex = t.getException();
520	>	else {
521	>	t.quietlyJoin();
522	>	if (ex == null && t.status < NORMAL)
523	>	ex = t.getException();
524	>	}
525		}
526		}
527		if (ex != null)
#	Line 515 | Line 531 | public abstract class ForkJoinTask<V> im
531
532		/**
533		* Attempts to cancel execution of this task. This attempt will
534	<	* fail if the task has already completed, has already been
535	<	* cancelled, or could not be cancelled for some other reason. If
536	<	* successful, and this task has not started when cancel is
537	<	* called, execution of this task is suppressed, {@link
538	<	* #isCancelled} will report true, and {@link #join} will result
539	<	* in a {@code CancellationException} being thrown.
534	>	* fail if the task has already completed or could not be
535	>	* cancelled for some other reason. If successful, and this task
536	>	* has not started when {@code cancel} is called, execution of
537	>	* this task is suppressed. After this method returns
538	>	* successfully, unless there is an intervening call to {@link
539	>	* #reinitialize}, subsequent calls to {@link #isCancelled},
540	>	* {@link #isDone}, and {@code cancel} will return {@code true}
541	>	* and calls to {@link #join} and related methods will result in
542	>	* {@code CancellationException}.
543		*
544		* <p>This method may be overridden in subclasses, but if so, must
545	<	* still ensure that these minimal properties hold. In particular,
546	<	* the {@code cancel} method itself must not throw exceptions.
545	>	* still ensure that these properties hold. In particular, the
546	>	* {@code cancel} method itself must not throw exceptions.
547		*
548		* <p>This method is designed to be invoked by <em>other</em>
549		* tasks. To terminate the current task, you can just return or
550		* throw an unchecked exception from its computation method, or
551		* invoke {@link #completeExceptionally}.
552		*
553	<	* @param mayInterruptIfRunning this value is ignored in the
554	<	* default implementation because tasks are not
555	<	* cancelled via interruption
553	>	* @param mayInterruptIfRunning this value has no effect in the
554	>	* default implementation because interrupts are not used to
555	>	* control cancellation.
556		*
557		* @return {@code true} if this task is now cancelled
558		*/
#	Line 543 | Line 562 | public abstract class ForkJoinTask<V> im
562		}
563
564		/**
565	<	* Cancels, ignoring any exceptions it throws. Used during worker
566	<	* and pool shutdown.
565	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
566	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
567	>	* exceptions, but if it does anyway, we have no recourse during
568	>	* shutdown, so guard against this case.
569		*/
570		final void cancelIgnoringExceptions() {
571		try {
#	Line 554 | Line 575 | public abstract class ForkJoinTask<V> im
575		}
576
577		/**
578	<	* Cancels ignoring exceptions if worker is terminating
578	>	* Cancels if current thread is a terminating worker thread,
579	>	* ignoring any exceptions thrown by cancel.
580		*/
581	<	private void cancelIfTerminating() {
581	>	final void cancelIfTerminating() {
582		Thread t = Thread.currentThread();
583		if ((t instanceof ForkJoinWorkerThread) &&
584		((ForkJoinWorkerThread) t).isTerminating()) {
#	Line 631 | Line 653 | public abstract class ForkJoinTask<V> im
653
654		/**
655		* Completes this task, and if not already aborted or cancelled,
656	<	* returning a {@code null} result upon {@code join} and related
657	<	* operations. This method may be used to provide results for
658	<	* asynchronous tasks, or to provide alternative handling for
659	<	* tasks that would not otherwise complete normally. Its use in
660	<	* other situations is discouraged. This method is
661	<	* overridable, but overridden versions must invoke {@code super}
662	<	* implementation to maintain guarantees.
656	>	* returning the given value as the result of subsequent
657	>	* invocations of {@code join} and related operations. This method
658	>	* may be used to provide results for asynchronous tasks, or to
659	>	* provide alternative handling for tasks that would not otherwise
660	>	* complete normally. Its use in other situations is
661	>	* discouraged. This method is overridable, but overridden
662	>	* versions must invoke {@code super} implementation to maintain
663	>	* guarantees.
664		*
665		* @param value the result value for this task
666		*/
#	Line 651 | Line 674 | public abstract class ForkJoinTask<V> im
674		setCompletion(NORMAL);
675		}
676
677	+	/**
678	+	* Waits if necessary for the computation to complete, and then
679	+	* retrieves its result.
680	+	*
681	+	* @return the computed result
682	+	* @throws CancellationException if the computation was cancelled
683	+	* @throws ExecutionException if the computation threw an
684	+	* exception
685	+	* @throws InterruptedException if the current thread is not a
686	+	* member of a ForkJoinPool and was interrupted while waiting
687	+	*/
688		public final V get() throws InterruptedException, ExecutionException {
689	<	int s = doJoin();
690	<	if (Thread.interrupted())
691	<	throw new InterruptedException();
692	<	if (s < NORMAL) {
689	>	Thread t = Thread.currentThread();
690	>	if (t instanceof ForkJoinWorkerThread)
691	>	quietlyJoin();
692	>	else
693	>	externalInterruptibleAwaitDone(false, 0L);
694	>	int s = status;
695	>	if (s != NORMAL) {
696		Throwable ex;
697		if (s == CANCELLED)
698		throw new CancellationException();
#	Line 665 | Line 702 | public abstract class ForkJoinTask<V> im
702		return getRawResult();
703		}
704
705	+	/**
706	+	* Waits if necessary for at most the given time for the computation
707	+	* to complete, and then retrieves its result, if available.
708	+	*
709	+	* @param timeout the maximum time to wait
710	+	* @param unit the time unit of the timeout argument
711	+	* @return the computed result
712	+	* @throws CancellationException if the computation was cancelled
713	+	* @throws ExecutionException if the computation threw an
714	+	* exception
715	+	* @throws InterruptedException if the current thread is not a
716	+	* member of a ForkJoinPool and was interrupted while waiting
717	+	* @throws TimeoutException if the wait timed out
718	+	*/
719		public final V get(long timeout, TimeUnit unit)
720		throws InterruptedException, ExecutionException, TimeoutException {
721	+	long nanos = unit.toNanos(timeout);
722		Thread t = Thread.currentThread();
723	<	ForkJoinPool pool;
724	<	if (t instanceof ForkJoinWorkerThread) {
673	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
674	<	if (status >= 0 && w.unpushTask(this))
675	<	tryExec();
676	<	pool = w.pool;
677	<	}
723	>	if (t instanceof ForkJoinWorkerThread)
724	>	((ForkJoinWorkerThread)t).joinTask(this, true, nanos);
725		else
726	<	pool = null;
727	<	/*
728	<	* Timed wait loop intermixes cases for fj (pool != null) and
682	<	* non FJ threads. For FJ, decrement pool count but don't try
683	<	* for replacement; increment count on completion. For non-FJ,
684	<	* deal with interrupts. This is messy, but a little less so
685	<	* than is splitting the FJ and nonFJ cases.
686	<	*/
687	<	boolean interrupted = false;
688	<	boolean dec = false; // true if pool count decremented
689	<	for (;;) {
690	<	if (Thread.interrupted() && pool == null) {
691	<	interrupted = true;
692	<	break;
693	<	}
694	<	int s = status;
695	<	if (s < 0)
696	<	break;
697	<	if (UNSAFE.compareAndSwapInt(this, statusOffset,
698	<	s, s | SIGNAL)) {
699	<	long startTime = System.nanoTime();
700	<	long nanos = unit.toNanos(timeout);
701	<	long nt; // wait time
702	<	while (status >= 0 &&
703	<	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
704	<	if (pool != null && !dec)
705	<	dec = pool.tryDecrementRunningCount();
706	<	else {
707	<	long ms = nt / 1000000;
708	<	int ns = (int) (nt % 1000000);
709	<	try {
710	<	synchronized(this) {
711	<	if (status >= 0)
712	<	wait(ms, ns);
713	<	}
714	<	} catch (InterruptedException ie) {
715	<	if (pool != null)
716	<	cancelIfTerminating();
717	<	else {
718	<	interrupted = true;
719	<	break;
720	<	}
721	<	}
722	<	}
723	<	}
724	<	break;
725	<	}
726	<	}
727	<	if (pool != null && dec)
728	<	pool.incrementRunningCount();
729	<	if (interrupted)
730	<	throw new InterruptedException();
731	<	int es = status;
732	<	if (es != NORMAL) {
726	>	externalInterruptibleAwaitDone(true, nanos);
727	>	int s = status;
728	>	if (s != NORMAL) {
729		Throwable ex;
730	<	if (es == CANCELLED)
730	>	if (s == CANCELLED)
731		throw new CancellationException();
732	<	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
732	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
733		throw new ExecutionException(ex);
734		throw new TimeoutException();
735		}
#	Line 741 | Line 737 | public abstract class ForkJoinTask<V> im
737		}
738
739		/**
740	<	* Joins this task, without returning its result or throwing an
740	>	* Joins this task, without returning its result or throwing its
741		* exception. This method may be useful when processing
742		* collections of tasks when some have been cancelled or otherwise
743		* known to have aborted.
744		*/
745		public final void quietlyJoin() {
746	<	doJoin();
746	>	Thread t;
747	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
748	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
749	>	if (status >= 0) {
750	>	if (w.unpushTask(this)) {
751	>	boolean completed;
752	>	try {
753	>	completed = exec();
754	>	} catch (Throwable rex) {
755	>	setExceptionalCompletion(rex);
756	>	return;
757	>	}
758	>	if (completed) {
759	>	setCompletion(NORMAL);
760	>	return;
761	>	}
762	>	}
763	>	w.joinTask(this, false, 0L);
764	>	}
765	>	}
766	>	else
767	>	externalAwaitDone();
768		}
769
770		/**
771		* Commences performing this task and awaits its completion if
772	<	* necessary, without returning its result or throwing an
773	<	* exception. This method may be useful when processing
757	<	* collections of tasks when some have been cancelled or otherwise
758	<	* known to have aborted.
772	>	* necessary, without returning its result or throwing its
773	>	* exception.
774		*/
775		public final void quietlyInvoke() {
776	<	doInvoke();
776	>	if (status >= 0) {
777	>	boolean completed;
778	>	try {
779	>	completed = exec();
780	>	} catch (Throwable rex) {
781	>	setExceptionalCompletion(rex);
782	>	return;
783	>	}
784	>	if (completed)
785	>	setCompletion(NORMAL);
786	>	else
787	>	quietlyJoin();
788	>	}
789		}
790
791		/**
#	Line 769 | Line 796 | public abstract class ForkJoinTask<V> im
796		* processed.
797		*
798		* <p>This method may be invoked only from within {@code
799	<	* ForkJoinTask} computations (as may be determined using method
799	>	* ForkJoinPool} computations (as may be determined using method
800		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
801		* result in exceptions or errors, possibly including {@code
802		* ClassCastException}.
#	Line 788 | Line 815 | public abstract class ForkJoinTask<V> im
815		* under any other usage conditions are not guaranteed.
816		* This method may be useful when executing
817		* pre-constructed trees of subtasks in loops.
818	+	*
819	+	* <p>Upon completion of this method, {@code isDone()} reports
820	+	* {@code false}, and {@code getException()} reports {@code
821	+	* null}. However, the value returned by {@code getRawResult} is
822	+	* unaffected. To clear this value, you can invoke {@code
823	+	* setRawResult(null)}.
824		*/
825		public void reinitialize() {
826		if (status == EXCEPTIONAL)
#	Line 828 | Line 861 | public abstract class ForkJoinTask<V> im
861		* were not, stolen.
862		*
863		* <p>This method may be invoked only from within {@code
864	<	* ForkJoinTask} computations (as may be determined using method
864	>	* ForkJoinPool} computations (as may be determined using method
865		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
866		* result in exceptions or errors, possibly including {@code
867		* ClassCastException}.
#	Line 847 | Line 880 | public abstract class ForkJoinTask<V> im
880		* fork other tasks.
881		*
882		* <p>This method may be invoked only from within {@code
883	<	* ForkJoinTask} computations (as may be determined using method
883	>	* ForkJoinPool} computations (as may be determined using method
884		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
885		* result in exceptions or errors, possibly including {@code
886		* ClassCastException}.
#	Line 870 | Line 903 | public abstract class ForkJoinTask<V> im
903		* exceeded.
904		*
905		* <p>This method may be invoked only from within {@code
906	<	* ForkJoinTask} computations (as may be determined using method
906	>	* ForkJoinPool} computations (as may be determined using method
907		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
908		* result in exceptions or errors, possibly including {@code
909		* ClassCastException}.
#	Line 928 | Line 961 | public abstract class ForkJoinTask<V> im
961		* otherwise.
962		*
963		* <p>This method may be invoked only from within {@code
964	<	* ForkJoinTask} computations (as may be determined using method
964	>	* ForkJoinPool} computations (as may be determined using method
965		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
966		* result in exceptions or errors, possibly including {@code
967		* ClassCastException}.
#	Line 947 | Line 980 | public abstract class ForkJoinTask<V> im
980		* be useful otherwise.
981		*
982		* <p>This method may be invoked only from within {@code
983	<	* ForkJoinTask} computations (as may be determined using method
983	>	* ForkJoinPool} computations (as may be determined using method
984		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
985		* result in exceptions or errors, possibly including {@code
986		* ClassCastException}.
#	Line 970 | Line 1003 | public abstract class ForkJoinTask<V> im
1003		* otherwise.
1004		*
1005		* <p>This method may be invoked only from within {@code
1006	<	* ForkJoinTask} computations (as may be determined using method
1006	>	* ForkJoinPool} computations (as may be determined using method
1007		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1008		* result in exceptions or errors, possibly including {@code
1009		* ClassCastException}.
#	Line 1080 | Line 1113 | public abstract class ForkJoinTask<V> im
1113		private static final long serialVersionUID = -7721805057305804111L;
1114
1115		/**
1116	<	* Saves the state to a stream.
1116	>	* Saves the state to a stream (that is, serializes it).
1117		*
1118		* @serialData the current run status and the exception thrown
1119		* during execution, or {@code null} if none
#	Line 1093 | Line 1126 | public abstract class ForkJoinTask<V> im
1126		}
1127
1128		/**
1129	<	* Reconstitutes the instance from a stream.
1129	>	* Reconstitutes the instance from a stream (that is, deserializes it).
1130		*
1131		* @param s the stream
1132		*/
#	Line 1103 | Line 1136 | public abstract class ForkJoinTask<V> im
1136		Object ex = s.readObject();
1137		if (ex != null)
1138		setExceptionalCompletion((Throwable) ex);
1106	–	if (status < 0)
1107	–	synchronized (this) { notifyAll(); }
1139		}
1140
1141		// Unsafe mechanics

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