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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.52 by dl, Sat Jul 24 20:28:18 2010 UTC vs.
Revision 1.59 by jsr166, Tue Sep 7 07:51:13 2010 UTC

#	Line 100 | 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 144 | 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		/*
#	Line 152 | Line 153 | public abstract class ForkJoinTask<V> im
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	<	* COMPLETED. CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
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
#	Line 164 | Line 165 | public abstract class ForkJoinTask<V> im
165		* them.
166		*/
167
168	<	/** Run status of this task */
168	>	/** The run status of this task */
169		volatile int status; // accessed directly by pool and workers
170
171		private static final int NORMAL      = -1;
#	Line 191 | Line 192 | public abstract class ForkJoinTask<V> im
192		* also clearing signal request bits.
193		*
194		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
194	–	* @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 != 0)
201		synchronized (this) { notifyAll(); }
202	<	return completion;
202	>	break;
203		}
204		}
205	–	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;         // the odd construction reduces lock bias effects
#	Line 232 | Line 234 | public abstract class ForkJoinTask<V> im
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, SIGNAL)){
266		boolean interrupted = false;
267	<	while ((s = status) >= 0) {
267	>	while (status >= 0) {
268		try {
269		wait();
270		} catch (InterruptedException ie) {
#	Line 254 | Line 277 | public abstract class ForkJoinTask<V> im
277		}
278		}
279		}
257	–	return s;
280		}
281
282		/**
#	Line 262 | Line 284 | public abstract class ForkJoinTask<V> im
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 273 | Line 295 | public abstract class ForkJoinTask<V> im
295		setCompletion(NORMAL); // must be outside try block
296		}
297
276	–	/**
277	–	* If not done and this task is next in worker queue, runs it,
278	–	* else waits for it.
279	–	* @return status on exit
280	–	*/
281	–	private int doJoin() {
282	–	int stat;
283	–	Thread t;
284	–	ForkJoinWorkerThread w;
285	–	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
286	–	if ((stat = status) < 0)
287	–	return stat;
288	–	if ((w = (ForkJoinWorkerThread) t).unpushTask(this)) {
289	–	boolean completed;
290	–	try {
291	–	completed = exec();
292	–	} catch (Throwable rex) {
293	–	return setExceptionalCompletion(rex);
294	–	}
295	–	if (completed)
296	–	return setCompletion(NORMAL);
297	–	}
298	–	return w.joinTask(this);
299	–	}
300	–	return externalAwaitDone();
301	–	}
302	–
303	–	/**
304	–	* Unless done, calls exec and records status if completed, or
305	–	* waits for completion otherwise.
306	–	* @return status on exit
307	–	*/
308	–	private int doInvoke() {
309	–	int stat;
310	–	if ((stat = status) >= 0) {
311	–	boolean completed;
312	–	try {
313	–	completed = exec();
314	–	} catch (Throwable rex) {
315	–	return setExceptionalCompletion(rex);
316	–	}
317	–	stat = completed ? setCompletion(NORMAL) : doJoin();
318	–	}
319	–	return stat;
320	–	}
321	–
322	–	/**
323	–	* Returns result or throws exception associated with given status.
324	–	* @param s the status
325	–	*/
326	–	private V reportResult(int s) {
327	–	Throwable ex;
328	–	if (s < NORMAL && (ex = getException()) != null)
329	–	UNSAFE.throwException(ex);
330	–	return getRawResult();
331	–	}
332	–
298		// public methods
299
300		/**
#	Line 365 | Line 330 | public abstract class ForkJoinTask<V> im
330		* @return the computed result
331		*/
332		public final V join() {
333	<	return reportResult(doJoin());
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(doInvoke());
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 407 | 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 434 | Line 414 | public abstract class ForkJoinTask<V> im
414		}
415		else if (i != 0)
416		t.fork();
417	<	else if (t.doInvoke() < 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.doJoin() < 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 453 | 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 490 | Line 477 | public abstract class ForkJoinTask<V> im
477		}
478		else if (i != 0)
479		t.fork();
480	<	else if (t.doInvoke() < 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.doJoin() < 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 532 | Line 525 | public abstract class ForkJoinTask<V> im
525		* @return {@code true} if this task is now cancelled
526		*/
527		public boolean cancel(boolean mayInterruptIfRunning) {
528	<	return setCompletion(CANCELLED) == CANCELLED;
528	>	setCompletion(CANCELLED);
529	>	return status == CANCELLED;
530		}
531
532		/**
#	Line 549 | 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		final void cancelIfTerminating() {
550		Thread t = Thread.currentThread();
#	Line 626 | 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 647 | Line 643 | public abstract class ForkJoinTask<V> im
643		}
644
645		public final V get() throws InterruptedException, ExecutionException {
646	<	int s = doJoin();
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 667 | 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
#	Line 681 | 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		}
#	Line 691 | Line 689 | public abstract class ForkJoinTask<V> im
689		break;
690		if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
691		long startTime = System.nanoTime();
694	–	long nanos = unit.toNanos(timeout);
692		long nt; // wait time
693		while (status >= 0 &&
694		(nt = nanos - (System.nanoTime() - startTime)) > 0) {
#	Line 735 | Line 732 | public abstract class ForkJoinTask<V> im
732		}
733
734		/**
735	<	* 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	<	doJoin();
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
751	<	* collections of tasks when some have been cancelled or otherwise
752	<	* known to have aborted.
767	>	* necessary, without returning its result or throwing its
768	>	* exception.
769		*/
770		public final void quietlyInvoke() {
771	<	doInvoke();
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 1074 | 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 1087 | 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		*/

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