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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.53 by dl, Wed Aug 11 18:45:12 2010 UTC vs.
Revision 1.62 by dl, Fri Sep 17 14:24:56 2010 UTC

#	Line 28 | Line 28 | import java.util.WeakHashMap;
28		* start other subtasks.  As indicated by the name of this class,
29		* many programs using {@code ForkJoinTask} employ only methods
30		* {@link #fork} and {@link #join}, or derivatives such as {@link
31	<	* #invokeAll}.  However, this class also provides a number of other
32	<	* methods that can come into play in advanced usages, as well as
33	<	* extension mechanics that allow support of new forms of fork/join
34	<	* processing.
31	>	* #invokeAll(ForkJoinTask...) invokeAll}.  However, this class also
32	>	* provides a number of other methods that can come into play in
33	>	* advanced usages, as well as extension mechanics that allow
34	>	* support of new forms of fork/join processing.
35		*
36		* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
37		* The efficiency of {@code ForkJoinTask}s stems from a set of
#	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 153 | 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 205 | Line 205 | public abstract class ForkJoinTask<V> im
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 void setExceptionalCompletion(Throwable rex) {
#	Line 214 | Line 215 | public abstract class ForkJoinTask<V> im
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
224		while ((s = status) >= 0) {
225		try {
226	<	synchronized(this) {
226	>	synchronized (this) {
227		if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
228		wait();
229		}
#	Line 231 | Line 234 | public abstract class ForkJoinTask<V> im
234		}
235
236		/**
237	+	* Blocks a worker thread until completed or timed out.  Called
238	+	* only by pool.
239	+	*
240	+	* @return status on exit
241	+	*/
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) {
264	>	synchronized (this) {
265		if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
266		boolean interrupted = false;
267		while (status >= 0) {
#	Line 314 | Line 339 | public abstract class ForkJoinTask<V> im
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		*/
#	Line 330 | Line 356 | public abstract class ForkJoinTask<V> im
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 355 | 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 407 | 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 510 | 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 587 | 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 607 | Line 642 | public abstract class ForkJoinTask<V> im
642		setCompletion(NORMAL);
643		}
644
645	+	/**
646	+	* @throws CancellationException {@inheritDoc}
647	+	*/
648		public final V get() throws InterruptedException, ExecutionException {
649	<	quietlyJoin();
650	<	if (Thread.interrupted())
651	<	throw new InterruptedException();
652	<	int s = status;
649	>	int s;
650	>	if (Thread.currentThread() instanceof ForkJoinWorkerThread) {
651	>	quietlyJoin();
652	>	s = status;
653	>	}
654	>	else {
655	>	while ((s = status) >= 0) {
656	>	synchronized (this) { // interruptible form of awaitDone
657	>	if (UNSAFE.compareAndSwapInt(this, statusOffset,
658	>	s, SIGNAL)) {
659	>	while (status >= 0)
660	>	wait();
661	>	}
662	>	}
663	>	}
664	>	}
665		if (s < NORMAL) {
666		Throwable ex;
667		if (s == CANCELLED)
#	Line 622 | Line 672 | public abstract class ForkJoinTask<V> im
672		return getRawResult();
673		}
674
675	+	/**
676	+	* @throws CancellationException {@inheritDoc}
677	+	*/
678		public final V get(long timeout, TimeUnit unit)
679		throws InterruptedException, ExecutionException, TimeoutException {
680		Thread t = Thread.currentThread();
#	Line 643 | Line 696 | public abstract class ForkJoinTask<V> im
696		*/
697		boolean interrupted = false;
698		boolean dec = false; // true if pool count decremented
699	+	long nanos = unit.toNanos(timeout);
700		for (;;) {
701	<	if (Thread.interrupted() && pool == null) {
701	>	if (pool == null && Thread.interrupted()) {
702		interrupted = true;
703		break;
704		}
#	Line 653 | Line 707 | public abstract class ForkJoinTask<V> im
707		break;
708		if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
709		long startTime = System.nanoTime();
656	–	long nanos = unit.toNanos(timeout);
710		long nt; // wait time
711		while (status >= 0 &&
712		(nt = nanos - (System.nanoTime() - startTime)) > 0) {
#	Line 663 | Line 716 | public abstract class ForkJoinTask<V> im
716		long ms = nt / 1000000;
717		int ns = (int) (nt % 1000000);
718		try {
719	<	synchronized(this) {
719	>	synchronized (this) {
720		if (status >= 0)
721		wait(ms, ns);
722		}
#	Line 730 | Line 783 | public abstract class ForkJoinTask<V> im
783		/**
784		* Commences performing this task and awaits its completion if
785		* necessary, without returning its result or throwing its
786	<	* exception. This method may be useful when processing
734	<	* collections of tasks when some have been cancelled or otherwise
735	<	* known to have aborted.
786	>	* exception.
787		*/
788		public final void quietlyInvoke() {
789		if (status >= 0) {
#	Line 1069 | Line 1120 | public abstract class ForkJoinTask<V> im
1120		private static final long serialVersionUID = -7721805057305804111L;
1121
1122		/**
1123	<	* Saves the state to a stream.
1123	>	* Saves the state to a stream (that is, serializes it).
1124		*
1125		* @serialData the current run status and the exception thrown
1126		* during execution, or {@code null} if none
#	Line 1082 | Line 1133 | public abstract class ForkJoinTask<V> im
1133		}
1134
1135		/**
1136	<	* Reconstitutes the instance from a stream.
1136	>	* Reconstitutes the instance from a stream (that is, deserializes it).
1137		*
1138		* @param s the stream
1139		*/

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