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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.9 by jsr166, Mon Jul 20 22:26:03 2009 UTC vs.
Revision 1.27 by dl, Sun Aug 2 11:54:31 2009 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.io.Serializable;
9	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
11	<	import sun.misc.Unsafe;
12	<	import java.lang.reflect.*;
10	>
11	>	import java.io.Serializable;
12	>	import java.util.Collection;
13	>	import java.util.Collections;
14	>	import java.util.List;
15	>	import java.util.Map;
16	>	import java.util.WeakHashMap;
17
18		/**
19	<	* Abstract base class for tasks that run within a {@link
20	<	* ForkJoinPool}.  A ForkJoinTask is a thread-like entity that is much
19	>	* Abstract base class for tasks that run within a {@link ForkJoinPool}.
20	>	* A {@code ForkJoinTask} is a thread-like entity that is much
21		* lighter weight than a normal thread.  Huge numbers of tasks and
22		* subtasks may be hosted by a small number of actual threads in a
23		* ForkJoinPool, at the price of some usage limitations.
#	Line 22 | Line 25 | import java.lang.reflect.*;
25		* <p> A "main" ForkJoinTask begins execution when submitted to a
26		* {@link ForkJoinPool}. Once started, it will usually in turn start
27		* other subtasks.  As indicated by the name of this class, many
28	<	* programs using ForkJoinTasks employ only methods {@code fork}
29	<	* and {@code join}, or derivatives such as
30	<	* {@code invokeAll}.  However, this class also provides a number
31	<	* of other methods that can come into play in advanced usages, as
32	<	* well as extension mechanics that allow support of new forms of
30	<	* fork/join processing.
28	>	* programs using ForkJoinTasks employ only methods {@code fork} and
29	>	* {@code join}, or derivatives such as {@code invokeAll}.  However,
30	>	* this class also provides a number of other methods that can come
31	>	* into play in advanced usages, as well as extension mechanics that
32	>	* allow support of new forms of fork/join processing.
33		*
34		* <p>A ForkJoinTask is a lightweight form of {@link Future}.  The
35		* efficiency of ForkJoinTasks stems from a set of restrictions (that
#	Line 74 | Line 76 | import java.lang.reflect.*;
76		*
77		* <p> The ForkJoinTask class is not usually directly subclassed.
78		* Instead, you subclass one of the abstract classes that support a
79	<	* particular style of fork/join processing.  Normally, a concrete
79	>	* particular style of fork/join processing, typically {@link
80	>	* RecursiveAction} for computations that do not return results, or
81	>	* {@link RecursiveTask} for those that do.  Normally, a concrete
82		* ForkJoinTask subclass declares fields comprising its parameters,
83		* established in a constructor, and then defines a {@code compute}
84		* method that somehow uses the control methods supplied by this base
85		* class. While these methods have {@code public} access (to allow
86		* instances of different task subclasses to call each others
87		* methods), some of them may only be called from within other
88	<	* ForkJoinTasks. Attempts to invoke them in other contexts result in
89	<	* exceptions or errors possibly including ClassCastException.
88	>	* ForkJoinTasks (as may be determined using method {@link
89	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
90	>	* result in exceptions or errors, possibly including
91	>	* ClassCastException.
92		*
93		* <p>Most base support methods are {@code final} because their
94		* implementations are intrinsically tied to the underlying
95		* lightweight task scheduling framework, and so cannot be overridden.
96		* Developers creating new basic styles of fork/join processing should
97		* minimally implement {@code protected} methods
98	<	* {@code exec}, {@code setRawResult}, and
99	<	* {@code getRawResult}, while also introducing an abstract
98	>	* {@link #exec}, {@link #setRawResult}, and
99	>	* {@link #getRawResult}, while also introducing an abstract
100		* computational method that can be implemented in its subclasses,
101		* possibly relying on other {@code protected} methods provided
102		* by this class.
#	Line 102 | Line 108 | import java.lang.reflect.*;
108		* parallelism cannot improve throughput. If too small, then memory
109		* and internal task maintenance overhead may overwhelm processing.
110		*
111	+	* <p>This class provides {@code adapt} methods for {@link
112	+	* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
113	+	* may be of use when mixing execution of ForkJoinTasks with other
114	+	* kinds of tasks. When all tasks are of this form, consider using a
115	+	* pool in {@link ForkJoinPool#setAsyncMode}.
116	+	*
117		* <p>ForkJoinTasks are {@code Serializable}, which enables them
118		* to be used in extensions such as remote execution frameworks. It is
119		* in general sensible to serialize tasks only before or after, but
120		* not during execution. Serialization is not relied on during
121		* execution itself.
122	+	*
123	+	* @since 1.7
124	+	* @author Doug Lea
125		*/
126		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
127
#	Line 141 | Line 156 | public abstract class ForkJoinTask<V> im
156		/**
157		* Table of exceptions thrown by tasks, to enable reporting by
158		* callers. Because exceptions are rare, we don't directly keep
159	<	* them with task objects, but instead us a weak ref table.  Note
159	>	* them with task objects, but instead use a weak ref table.  Note
160		* that cancellation exceptions don't appear in the table, but are
161		* instead recorded as status values.
162	<	* Todo: Use ConcurrentReferenceHashMap
162	>	* TODO: Use ConcurrentReferenceHashMap
163		*/
164		static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
165		Collections.synchronizedMap
#	Line 153 | Line 168 | public abstract class ForkJoinTask<V> im
168		// within-package utilities
169
170		/**
171	<	* Get current worker thread, or null if not a worker thread
171	>	* Gets current worker thread, or null if not a worker thread.
172		*/
173		static ForkJoinWorkerThread getWorker() {
174		Thread t = Thread.currentThread();
175	<	return ((t instanceof ForkJoinWorkerThread)?
176	<	(ForkJoinWorkerThread)t : null);
175	>	return ((t instanceof ForkJoinWorkerThread) ?
176	>	(ForkJoinWorkerThread) t : null);
177		}
178
179		final boolean casStatus(int cmp, int val) {
180	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
180	>	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
181		}
182
183		/**
#	Line 170 | Line 185 | public abstract class ForkJoinTask<V> im
185		*/
186		static void rethrowException(Throwable ex) {
187		if (ex != null)
188	<	_unsafe.throwException(ex);
188	>	UNSAFE.throwException(ex);
189		}
190
191		// Setting completion status
192
193		/**
194	<	* Mark completion and wake up threads waiting to join this task.
194	>	* Marks completion and wakes up threads waiting to join this task.
195	>	*
196		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
197		*/
198		final void setCompletion(int completion) {
199		ForkJoinPool pool = getPool();
200		if (pool != null) {
201		int s; // Clear signal bits while setting completion status
202	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
202	>	do {} while ((s = status) >= 0 && !casStatus(s, completion));
203
204		if ((s & SIGNAL_MASK) != 0) {
205		if ((s &= INTERNAL_SIGNAL_MASK) != 0)
206		pool.updateRunningCount(s);
207	<	synchronized(this) { notifyAll(); }
207	>	synchronized (this) { notifyAll(); }
208		}
209		}
210		else
#	Line 201 | Line 217 | public abstract class ForkJoinTask<V> im
217		*/
218		private void externallySetCompletion(int completion) {
219		int s;
220	<	do;while ((s = status) >= 0 &&
221	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
222	<	synchronized(this) { notifyAll(); }
220	>	do {} while ((s = status) >= 0 &&
221	>	!casStatus(s, (s & SIGNAL_MASK) | completion));
222	>	synchronized (this) { notifyAll(); }
223		}
224
225		/**
226	<	* Sets status to indicate normal completion
226	>	* Sets status to indicate normal completion.
227		*/
228		final void setNormalCompletion() {
229		// Try typical fast case -- single CAS, no signal, not already done.
230		// Manually expand casStatus to improve chances of inlining it
231	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
231	>	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
232		setCompletion(NORMAL);
233		}
234
235		// internal waiting and notification
236
237		/**
238	<	* Performs the actual monitor wait for awaitDone
238	>	* Performs the actual monitor wait for awaitDone.
239		*/
240		private void doAwaitDone() {
241		// Minimize lock bias and in/de-flation effects by maximizing
242		// chances of waiting inside sync
243		try {
244		while (status >= 0)
245	<	synchronized(this) { if (status >= 0) wait(); }
245	>	synchronized (this) { if (status >= 0) wait(); }
246		} catch (InterruptedException ie) {
247		onInterruptedWait();
248		}
249		}
250
251		/**
252	<	* Performs the actual monitor wait for awaitDone
252	>	* Performs the actual timed monitor wait for awaitDone.
253		*/
254		private void doAwaitDone(long startTime, long nanos) {
255	<	synchronized(this) {
255	>	synchronized (this) {
256		try {
257		while (status >= 0) {
258	<	long nt = nanos - System.nanoTime() - startTime;
258	>	long nt = nanos - (System.nanoTime() - startTime);
259		if (nt <= 0)
260		break;
261	<	wait(nt / 1000000, (int)(nt % 1000000));
261	>	wait(nt / 1000000, (int) (nt % 1000000));
262		}
263		} catch (InterruptedException ie) {
264		onInterruptedWait();
#	Line 255 | Line 271 | public abstract class ForkJoinTask<V> im
271		/**
272		* Sets status to indicate there is joiner, then waits for join,
273		* surrounded with pool notifications.
274	+	*
275		* @return status upon exit
276		*/
277	<	private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
278	<	ForkJoinPool pool = w == null? null : w.pool;
277	>	private int awaitDone(ForkJoinWorkerThread w,
278	>	boolean maintainParallelism) {
279	>	ForkJoinPool pool = (w == null) ? null : w.pool;
280		int s;
281		while ((s = status) >= 0) {
282	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
282	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
283		if (pool == null || !pool.preJoin(this, maintainParallelism))
284		doAwaitDone();
285		if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
#	Line 274 | Line 292 | public abstract class ForkJoinTask<V> im
292
293		/**
294		* Timed version of awaitDone
295	+	*
296		* @return status upon exit
297		*/
298		private int awaitDone(ForkJoinWorkerThread w, long nanos) {
299	<	ForkJoinPool pool = w == null? null : w.pool;
299	>	ForkJoinPool pool = (w == null) ? null : w.pool;
300		int s;
301		while ((s = status) >= 0) {
302	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
302	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
303		long startTime = System.nanoTime();
304		if (pool == null || !pool.preJoin(this, false))
305		doAwaitDone(startTime, nanos);
#	Line 297 | Line 316 | public abstract class ForkJoinTask<V> im
316		}
317
318		/**
319	<	* Notify pool that thread is unblocked. Called by signalled
319	>	* Notifies pool that thread is unblocked. Called by signalled
320		* threads when woken by non-FJ threads (which is atypical).
321		*/
322		private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
323		int s;
324	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
324	>	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
325		if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
326		pool.updateRunningCount(s);
327		}
328
329		/**
330	<	* Notify pool to adjust counts on cancelled or timed out wait
330	>	* Notifies pool to adjust counts on cancelled or timed out wait.
331		*/
332		private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
333		if (pool != null) {
#	Line 323 | Line 342 | public abstract class ForkJoinTask<V> im
342		}
343
344		/**
345	<	* Handle interruptions during waits.
345	>	* Handles interruptions during waits.
346		*/
347		private void onInterruptedWait() {
348		ForkJoinWorkerThread w = getWorker();
#	Line 342 | Line 361 | public abstract class ForkJoinTask<V> im
361		}
362
363		/**
364	<	* Throws the exception associated with status s;
364	>	* Throws the exception associated with status s.
365	>	*
366		* @throws the exception
367		*/
368		private void reportException(int s) {
#	Line 355 | Line 375 | public abstract class ForkJoinTask<V> im
375		}
376
377		/**
378	<	* Returns result or throws exception using j.u.c.Future conventions
379	<	* Only call when isDone known to be true.
378	>	* Returns result or throws exception using j.u.c.Future conventions.
379	>	* Only call when {@code isDone} known to be true.
380		*/
381		private V reportFutureResult()
382		throws ExecutionException, InterruptedException {
#	Line 375 | Line 395 | public abstract class ForkJoinTask<V> im
395
396		/**
397		* Returns result or throws exception using j.u.c.Future conventions
398	<	* with timeouts
398	>	* with timeouts.
399		*/
400		private V reportTimedFutureResult()
401		throws InterruptedException, ExecutionException, TimeoutException {
#	Line 396 | Line 416 | public abstract class ForkJoinTask<V> im
416
417		/**
418		* Calls exec, recording completion, and rethrowing exception if
419	<	* encountered. Caller should normally check status before calling
419	>	* encountered. Caller should normally check status before calling.
420	>	*
421		* @return true if completed normally
422		*/
423		private boolean tryExec() {
#	Line 414 | Line 435 | public abstract class ForkJoinTask<V> im
435
436		/**
437		* Main execution method used by worker threads. Invokes
438	<	* base computation unless already complete
438	>	* base computation unless already complete.
439		*/
440		final void quietlyExec() {
441		if (status >= 0) {
442		try {
443		if (!exec())
444		return;
445	<	} catch(Throwable rex) {
445	>	} catch (Throwable rex) {
446		setDoneExceptionally(rex);
447		return;
448		}
#	Line 430 | Line 451 | public abstract class ForkJoinTask<V> im
451		}
452
453		/**
454	<	* Calls exec, recording but not rethrowing exception
455	<	* Caller should normally check status before calling
454	>	* Calls exec(), recording but not rethrowing exception.
455	>	* Caller should normally check status before calling.
456	>	*
457		* @return true if completed normally
458		*/
459		private boolean tryQuietlyInvoke() {
#	Line 447 | Line 469 | public abstract class ForkJoinTask<V> im
469		}
470
471		/**
472	<	* Cancel, ignoring any exceptions it throws
472	>	* Cancels, ignoring any exceptions it throws.
473		*/
474		final void cancelIgnoringExceptions() {
475		try {
476		cancel(false);
477	<	} catch(Throwable ignore) {
477	>	} catch (Throwable ignore) {
478		}
479		}
480
#	Line 464 | Line 486 | public abstract class ForkJoinTask<V> im
486		ForkJoinTask<?> t;
487		while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
488		t.quietlyExec();
489	<	return (s >= 0)? awaitDone(w, false) : s; // block if no work
489	>	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
490		}
491
492		// public methods
#	Line 474 | Line 496 | public abstract class ForkJoinTask<V> im
496		* necessarily enforced, it is a usage error to fork a task more
497		* than once unless it has completed and been reinitialized.  This
498		* method may be invoked only from within ForkJoinTask
499	<	* computations. Attempts to invoke in other contexts result in
500	<	* exceptions or errors possibly including ClassCastException.
499	>	* computations (as may be determined using method {@link
500	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
501	>	* in exceptions or errors, possibly including ClassCastException.
502	>	*
503	>	* @return {@code this}, to simplify usage.
504		*/
505	<	public final void fork() {
506	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
505	>	public final ForkJoinTask<V> fork() {
506	>	((ForkJoinWorkerThread) Thread.currentThread())
507	>	.pushTask(this);
508	>	return this;
509		}
510
511		/**
#	Line 499 | Line 526 | public abstract class ForkJoinTask<V> im
526		/**
527		* Commences performing this task, awaits its completion if
528		* necessary, and return its result.
529	+	*
530		* @throws Throwable (a RuntimeException, Error, or unchecked
531	<	* exception) if the underlying computation did so.
531	>	* exception) if the underlying computation did so
532		* @return the computed result
533		*/
534		public final V invoke() {
#	Line 511 | Line 539 | public abstract class ForkJoinTask<V> im
539		}
540
541		/**
542	<	* Forks both tasks, returning when {@code isDone} holds for
543	<	* both of them or an exception is encountered. This method may be
544	<	* invoked only from within ForkJoinTask computations. Attempts to
545	<	* invoke in other contexts result in exceptions or errors
542	>	* Forks the given tasks, returning when {@code isDone} holds for
543	>	* each task or an exception is encountered. This method may be
544	>	* invoked only from within ForkJoinTask computations (as may be
545	>	* determined using method {@link #inForkJoinPool}). Attempts to
546	>	* invoke in other contexts result in exceptions or errors,
547		* possibly including ClassCastException.
548	<	* @param t1 one task
549	<	* @param t2 the other task
550	<	* @throws NullPointerException if t1 or t2 are null
551	<	* @throws RuntimeException or Error if either task did so.
548	>	*
549	>	* @param t1 the first task
550	>	* @param t2 the second task
551	>	* @throws NullPointerException if any task is null
552	>	* @throws RuntimeException or Error if a task did so
553		*/
554		public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
555		t2.fork();
#	Line 528 | Line 558 | public abstract class ForkJoinTask<V> im
558		}
559
560		/**
561	<	* Forks the given tasks, returning when {@code isDone} holds
562	<	* for all of them. If any task encounters an exception, others
563	<	* may be cancelled.  This method may be invoked only from within
564	<	* ForkJoinTask computations. Attempts to invoke in other contexts
565	<	* result in exceptions or errors possibly including ClassCastException.
566	<	* @param tasks the array of tasks
567	<	* @throws NullPointerException if tasks or any element are null.
568	<	* @throws RuntimeException or Error if any task did so.
561	>	* Forks the given tasks, returning when {@code isDone} holds for
562	>	* each task or an exception is encountered. If any task
563	>	* encounters an exception, others may be, but are not guaranteed
564	>	* to be, cancelled.  This method may be invoked only from within
565	>	* ForkJoinTask computations (as may be determined using method
566	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
567	>	* result in exceptions or errors, possibly including
568	>	* ClassCastException.
569	>	*
570	>	* Overloadings of this method exist for the special cases
571	>	* of one to four arguments.
572	>	*
573	>	* @param tasks the tasks
574	>	* @throws NullPointerException if tasks or any element are null
575	>	* @throws RuntimeException or Error if any task did so
576		*/
577		public static void invokeAll(ForkJoinTask<?>... tasks) {
578		Throwable ex = null;
#	Line 571 | Line 608 | public abstract class ForkJoinTask<V> im
608		}
609
610		/**
611	<	* Forks all tasks in the collection, returning when
612	<	* {@code isDone} holds for all of them. If any task
613	<	* encounters an exception, others may be cancelled.  This method
614	<	* may be invoked only from within ForkJoinTask
615	<	* computations. Attempts to invoke in other contexts result in
616	<	* exceptions or errors possibly including ClassCastException.
611	>	* Forks all tasks in the collection, returning when {@code
612	>	* isDone} holds for each task or an exception is encountered. If
613	>	* any task encounters an exception, others may be, but are not
614	>	* guaranteed to be, cancelled.  This method may be invoked only
615	>	* from within ForkJoinTask computations (as may be determined
616	>	* using method {@link #inForkJoinPool}). Attempts to invoke in
617	>	* other contexts result in exceptions or errors, possibly
618	>	* including ClassCastException.
619	>	*
620		* @param tasks the collection of tasks
621	<	* @throws NullPointerException if tasks or any element are null.
622	<	* @throws RuntimeException or Error if any task did so.
623	<	*/
624	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
625	<	if (!(tasks instanceof List)) {
626	<	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
627	<	return;
621	>	* @return the tasks argument, to simplify usage
622	>	* @throws NullPointerException if tasks or any element are null
623	>	* @throws RuntimeException or Error if any task did so
624	>	*/
625	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
626	>	if (!(tasks instanceof List<?>)) {
627	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
628	>	return tasks;
629		}
630	+	@SuppressWarnings("unchecked")
631		List<? extends ForkJoinTask<?>> ts =
632	<	(List<? extends ForkJoinTask<?>>)tasks;
632	>	(List<? extends ForkJoinTask<?>>) tasks;
633		Throwable ex = null;
634		int last = ts.size() - 1;
635		for (int i = last; i >= 0; --i) {
#	Line 618 | Line 660 | public abstract class ForkJoinTask<V> im
660		}
661		if (ex != null)
662		rethrowException(ex);
663	+	return tasks;
664		}
665
666		/**
667	<	* Returns true if the computation performed by this task has
668	<	* completed (or has been cancelled).
669	<	* @return true if this computation has completed
667	>	* Returns {@code true} if the computation performed by this task
668	>	* has completed (or has been cancelled).
669	>	*
670	>	* @return {@code true} if this computation has completed
671		*/
672		public final boolean isDone() {
673		return status < 0;
674		}
675
676		/**
677	<	* Returns true if this task was cancelled.
678	<	* @return true if this task was cancelled
677	>	* Returns {@code true} if this task was cancelled.
678	>	*
679	>	* @return {@code true} if this task was cancelled
680		*/
681		public final boolean isCancelled() {
682		return (status & COMPLETION_MASK) == CANCELLED;
#	Line 640 | Line 685 | public abstract class ForkJoinTask<V> im
685		/**
686		* Asserts that the results of this task's computation will not be
687		* used. If a cancellation occurs before attempting to execute this
688	<	* task, then execution will be suppressed, {@code isCancelled}
689	<	* will report true, and {@code join} will result in a
688	>	* task, execution will be suppressed, {@link #isCancelled}
689	>	* will report true, and {@link #join} will result in a
690		* {@code CancellationException} being thrown. Otherwise, when
691		* cancellation races with completion, there are no guarantees
692	<	* about whether {@code isCancelled} will report true, whether
693	<	* {@code join} will return normally or via an exception, or
694	<	* whether these behaviors will remain consistent upon repeated
692	>	* about whether {@code isCancelled} will report {@code true},
693	>	* whether {@code join} will return normally or via an exception,
694	>	* or whether these behaviors will remain consistent upon repeated
695		* invocation.
696		*
697		* <p>This method may be overridden in subclasses, but if so, must
#	Line 656 | Line 701 | public abstract class ForkJoinTask<V> im
701		* <p> This method is designed to be invoked by <em>other</em>
702		* tasks. To terminate the current task, you can just return or
703		* throw an unchecked exception from its computation method, or
704	<	* invoke {@code completeExceptionally}.
704	>	* invoke {@link #completeExceptionally}.
705		*
706		* @param mayInterruptIfRunning this value is ignored in the
707		* default implementation because tasks are not in general
708	<	* cancelled via interruption.
708	>	* cancelled via interruption
709		*
710	<	* @return true if this task is now cancelled
710	>	* @return {@code true} if this task is now cancelled
711		*/
712		public boolean cancel(boolean mayInterruptIfRunning) {
713		setCompletion(CANCELLED);
#	Line 670 | Line 715 | public abstract class ForkJoinTask<V> im
715		}
716
717		/**
718	<	* Returns true if this task threw an exception or was cancelled
719	<	* @return true if this task threw an exception or was cancelled
718	>	* Returns {@code true} if this task threw an exception or was cancelled.
719	>	*
720	>	* @return {@code true} if this task threw an exception or was cancelled
721		*/
722		public final boolean isCompletedAbnormally() {
723		return (status & COMPLETION_MASK) < NORMAL;
#	Line 681 | Line 727 | public abstract class ForkJoinTask<V> im
727		* Returns the exception thrown by the base computation, or a
728		* CancellationException if cancelled, or null if none or if the
729		* method has not yet completed.
730	<	* @return the exception, or null if none
730	>	*
731	>	* @return the exception, or {@code null} if none
732		*/
733		public final Throwable getException() {
734		int s = status & COMPLETION_MASK;
#	Line 698 | Line 745 | public abstract class ForkJoinTask<V> im
745		* {@code join} and related operations. This method may be used
746		* to induce exceptions in asynchronous tasks, or to force
747		* completion of tasks that would not otherwise complete.  Its use
748	<	* in other situations is likely to be wrong.  This method is
748	>	* in other situations is discouraged.  This method is
749		* overridable, but overridden versions must invoke {@code super}
750		* implementation to maintain guarantees.
751		*
#	Line 708 | Line 755 | public abstract class ForkJoinTask<V> im
755		*/
756		public void completeExceptionally(Throwable ex) {
757		setDoneExceptionally((ex instanceof RuntimeException) ||
758	<	(ex instanceof Error)? ex :
758	>	(ex instanceof Error) ? ex :
759		new RuntimeException(ex));
760		}
761
#	Line 718 | Line 765 | public abstract class ForkJoinTask<V> im
765		* operations. This method may be used to provide results for
766		* asynchronous tasks, or to provide alternative handling for
767		* tasks that would not otherwise complete normally. Its use in
768	<	* other situations is likely to be wrong. This method is
768	>	* other situations is discouraged. This method is
769		* overridable, but overridden versions must invoke {@code super}
770		* implementation to maintain guarantees.
771		*
772	<	* @param value the result value for this task.
772	>	* @param value the result value for this task
773		*/
774		public void complete(V value) {
775		try {
776		setRawResult(value);
777	<	} catch(Throwable rex) {
777	>	} catch (Throwable rex) {
778		setDoneExceptionally(rex);
779		return;
780		}
#	Line 743 | Line 790 | public abstract class ForkJoinTask<V> im
790
791		public final V get(long timeout, TimeUnit unit)
792		throws InterruptedException, ExecutionException, TimeoutException {
793	+	long nanos = unit.toNanos(timeout);
794		ForkJoinWorkerThread w = getWorker();
795		if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
796	<	awaitDone(w, unit.toNanos(timeout));
796	>	awaitDone(w, nanos);
797		return reportTimedFutureResult();
798		}
799
#	Line 757 | Line 805 | public abstract class ForkJoinTask<V> im
805		* current task and that of any other task that might be executed
806		* while helping. (This usually holds for pure divide-and-conquer
807		* tasks). This method may be invoked only from within
808	<	* ForkJoinTask computations. Attempts to invoke in other contexts
809	<	* result in exceptions or errors possibly including ClassCastException.
808	>	* ForkJoinTask computations (as may be determined using method
809	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
810	>	* result in exceptions or errors, possibly including
811	>	* ClassCastException.
812	>	*
813		* @return the computed result
814		*/
815		public final V helpJoin() {
816	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
816	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
817		if (status < 0 || !w.unpushTask(this) || !tryExec())
818		reportException(busyJoin(w));
819		return getRawResult();
#	Line 771 | Line 822 | public abstract class ForkJoinTask<V> im
822		/**
823		* Possibly executes other tasks until this task is ready.  This
824		* method may be invoked only from within ForkJoinTask
825	<	* computations. Attempts to invoke in other contexts result in
826	<	* exceptions or errors possibly including ClassCastException.
825	>	* computations (as may be determined using method {@link
826	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
827	>	* in exceptions or errors, possibly including ClassCastException.
828		*/
829		public final void quietlyHelpJoin() {
830		if (status >= 0) {
831		ForkJoinWorkerThread w =
832	<	(ForkJoinWorkerThread)(Thread.currentThread());
832	>	(ForkJoinWorkerThread) Thread.currentThread();
833		if (!w.unpushTask(this) || !tryQuietlyInvoke())
834		busyJoin(w);
835		}
#	Line 813 | Line 865 | public abstract class ForkJoinTask<V> im
865		* Possibly executes tasks until the pool hosting the current task
866		* {@link ForkJoinPool#isQuiescent}. This method may be of use in
867		* designs in which many tasks are forked, but none are explicitly
868	<	* joined, instead executing them until all are processed.
868	>	* joined, instead executing them until all are processed.  This
869	>	* method may be invoked only from within ForkJoinTask
870	>	* computations (as may be determined using method {@link
871	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
872	>	* in exceptions or errors, possibly including ClassCastException.
873		*/
874		public static void helpQuiesce() {
875	<	((ForkJoinWorkerThread)(Thread.currentThread())).
876	<	helpQuiescePool();
875	>	((ForkJoinWorkerThread) Thread.currentThread())
876	>	.helpQuiescePool();
877		}
878
879		/**
#	Line 827 | Line 883 | public abstract class ForkJoinTask<V> im
883		* never been forked, or has been forked, then completed and all
884		* outstanding joins of this task have also completed. Effects
885		* under any other usage conditions are not guaranteed, and are
886	<	* almost surely wrong. This method may be useful when executing
886	>	* discouraged. This method may be useful when executing
887		* pre-constructed trees of subtasks in loops.
888		*/
889		public void reinitialize() {
#	Line 838 | Line 894 | public abstract class ForkJoinTask<V> im
894
895		/**
896		* Returns the pool hosting the current task execution, or null
897	<	* if this task is executing outside of any pool.
898	<	* @return the pool, or null if none.
897	>	* if this task is executing outside of any ForkJoinPool.
898	>	*
899	>	* @see #inForkJoinPool
900	>	* @return the pool, or {@code null} if none
901		*/
902		public static ForkJoinPool getPool() {
903		Thread t = Thread.currentThread();
904	<	return ((t instanceof ForkJoinWorkerThread)?
905	<	((ForkJoinWorkerThread)t).pool : null);
904	>	return (t instanceof ForkJoinWorkerThread) ?
905	>	((ForkJoinWorkerThread) t).pool : null;
906	>	}
907	>
908	>	/**
909	>	* Returns {@code true} if the current thread is executing as a
910	>	* ForkJoinPool computation.
911	>	*
912	>	* @return {@code true} if the current thread is executing as a
913	>	* ForkJoinPool computation, or false otherwise
914	>	*/
915	>	public static boolean inForkJoinPool() {
916	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
917		}
918
919		/**
#	Line 854 | Line 923 | public abstract class ForkJoinTask<V> im
923		* another thread.  This method may be useful when arranging
924		* alternative local processing of tasks that could have been, but
925		* were not, stolen. This method may be invoked only from within
926	<	* ForkJoinTask computations. Attempts to invoke in other contexts
927	<	* result in exceptions or errors possibly including ClassCastException.
928	<	* @return true if unforked
926	>	* ForkJoinTask computations (as may be determined using method
927	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
928	>	* result in exceptions or errors, possibly including
929	>	* ClassCastException.
930	>	*
931	>	* @return {@code true} if unforked
932		*/
933		public boolean tryUnfork() {
934	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
934	>	return ((ForkJoinWorkerThread) Thread.currentThread())
935	>	.unpushTask(this);
936		}
937
938		/**
939		* Returns an estimate of the number of tasks that have been
940		* forked by the current worker thread but not yet executed. This
941		* value may be useful for heuristic decisions about whether to
942	<	* fork other tasks.
942	>	* fork other tasks.  This method may be invoked only from within
943	>	* ForkJoinTask computations (as may be determined using method
944	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
945	>	* result in exceptions or errors, possibly including
946	>	* ClassCastException.
947		* @return the number of tasks
948		*/
949		public static int getQueuedTaskCount() {
950	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
951	<	getQueueSize();
950	>	return ((ForkJoinWorkerThread) Thread.currentThread())
951	>	.getQueueSize();
952		}
953
954		/**
955	<	* Returns a estimate of how many more locally queued tasks are
955	>	* Returns an estimate of how many more locally queued tasks are
956		* held by the current worker thread than there are other worker
957		* threads that might steal them.  This value may be useful for
958		* heuristic decisions about whether to fork other tasks. In many
959		* usages of ForkJoinTasks, at steady state, each worker should
960		* aim to maintain a small constant surplus (for example, 3) of
961		* tasks, and to process computations locally if this threshold is
962	<	* exceeded.
962	>	* exceeded.  This method may be invoked only from within
963	>	* ForkJoinTask computations (as may be determined using method
964	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
965	>	* result in exceptions or errors, possibly including
966	>	* ClassCastException.  *
967		* @return the surplus number of tasks, which may be negative
968		*/
969		public static int getSurplusQueuedTaskCount() {
970	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
970	>	return ((ForkJoinWorkerThread) Thread.currentThread())
971		.getEstimatedSurplusTaskCount();
972		}
973
974		// Extension methods
975
976		/**
977	<	* Returns the result that would be returned by {@code join},
978	<	* even if this task completed abnormally, or null if this task is
979	<	* not known to have been completed.  This method is designed to
980	<	* aid debugging, as well as to support extensions. Its use in any
981	<	* other context is discouraged.
977	>	* Returns the result that would be returned by {@link #join}, even
978	>	* if this task completed abnormally, or {@code null} if this task
979	>	* is not known to have been completed.  This method is designed
980	>	* to aid debugging, as well as to support extensions. Its use in
981	>	* any other context is discouraged.
982		*
983	<	* @return the result, or null if not completed.
983	>	* @return the result, or {@code null} if not completed
984		*/
985		public abstract V getRawResult();
986
#	Line 918 | Line 999 | public abstract class ForkJoinTask<V> im
999		* called otherwise. The return value controls whether this task
1000		* is considered to be done normally. It may return false in
1001		* asynchronous actions that require explicit invocations of
1002	<	* {@code complete} to become joinable. It may throw exceptions
1002	>	* {@link #complete} to become joinable. It may throw exceptions
1003		* to indicate abnormal exit.
1004	<	* @return true if completed normally
1004	>	*
1005	>	* @return {@code true} if completed normally
1006		* @throws Error or RuntimeException if encountered during computation
1007		*/
1008		protected abstract boolean exec();
1009
1010		/**
1011	<	* Returns, but does not unschedule or execute, the task queued by
1012	<	* the current thread but not yet executed, if one is
1011	>	* Returns, but does not unschedule or execute, a task queued by
1012	>	* the current thread but not yet executed, if one is immediately
1013		* available. There is no guarantee that this task will actually
1014	<	* be polled or executed next.  This method is designed primarily
1015	<	* to support extensions, and is unlikely to be useful otherwise.
1016	<	* This method may be invoked only from within ForkJoinTask
1017	<	* computations. Attempts to invoke in other contexts result in
1018	<	* exceptions or errors possibly including ClassCastException.
1014	>	* be polled or executed next. Conversely, this method may return
1015	>	* null even if a task exists but cannot be accessed without
1016	>	* contention with other threads.  This method is designed
1017	>	* primarily to support extensions, and is unlikely to be useful
1018	>	* otherwise.  This method may be invoked only from within
1019	>	* ForkJoinTask computations (as may be determined using method
1020	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1021	>	* result in exceptions or errors, possibly including
1022	>	* ClassCastException.
1023		*
1024	<	* @return the next task, or null if none are available
1024	>	* @return the next task, or {@code null} if none are available
1025		*/
1026		protected static ForkJoinTask<?> peekNextLocalTask() {
1027	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask();
1027	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1028	>	.peekTask();
1029		}
1030
1031		/**
#	Line 946 | Line 1033 | public abstract class ForkJoinTask<V> im
1033		* queued by the current thread but not yet executed.  This method
1034		* is designed primarily to support extensions, and is unlikely to
1035		* be useful otherwise.  This method may be invoked only from
1036	<	* within ForkJoinTask computations. Attempts to invoke in other
1037	<	* contexts result in exceptions or errors possibly including
1036	>	* within ForkJoinTask computations (as may be determined using
1037	>	* method {@link #inForkJoinPool}). Attempts to invoke in other
1038	>	* contexts result in exceptions or errors, possibly including
1039		* ClassCastException.
1040		*
1041	<	* @return the next task, or null if none are available
1041	>	* @return the next task, or {@code null} if none are available
1042		*/
1043		protected static ForkJoinTask<?> pollNextLocalTask() {
1044	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).pollLocalTask();
1044	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1045	>	.pollLocalTask();
1046		}
1047
1048		/**
#	Line 965 | Line 1054 | public abstract class ForkJoinTask<V> im
1054		* of the pool this task is operating in.  This method is designed
1055		* primarily to support extensions, and is unlikely to be useful
1056		* otherwise.  This method may be invoked only from within
1057	<	* ForkJoinTask computations. Attempts to invoke in other contexts
1058	<	* result in exceptions or errors possibly including
1057	>	* ForkJoinTask computations (as may be determined using method
1058	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1059	>	* result in exceptions or errors, possibly including
1060		* ClassCastException.
1061		*
1062	<	* @return a task, or null if none are available
1062	>	* @return a task, or {@code null} if none are available
1063		*/
1064		protected static ForkJoinTask<?> pollTask() {
1065	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
1066	<	pollTask();
1065	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1066	>	.pollTask();
1067	>	}
1068	>
1069	>	/**
1070	>	* Adaptor for Runnables. This implements RunnableFuture
1071	>	* to be compliant with AbstractExecutorService constraints
1072	>	* when used in ForkJoinPool.
1073	>	*/
1074	>	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1075	>	implements RunnableFuture<T> {
1076	>	final Runnable runnable;
1077	>	final T resultOnCompletion;
1078	>	T result;
1079	>	AdaptedRunnable(Runnable runnable, T result) {
1080	>	if (runnable == null) throw new NullPointerException();
1081	>	this.runnable = runnable;
1082	>	this.resultOnCompletion = result;
1083	>	}
1084	>	public T getRawResult() { return result; }
1085	>	public void setRawResult(T v) { result = v; }
1086	>	public boolean exec() {
1087	>	runnable.run();
1088	>	result = resultOnCompletion;
1089	>	return true;
1090	>	}
1091	>	public void run() { invoke(); }
1092	>	private static final long serialVersionUID = 5232453952276885070L;
1093	>	}
1094	>
1095	>	/**
1096	>	* Adaptor for Callables
1097	>	*/
1098	>	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1099	>	implements RunnableFuture<T> {
1100	>	final Callable<? extends T> callable;
1101	>	T result;
1102	>	AdaptedCallable(Callable<? extends T> callable) {
1103	>	if (callable == null) throw new NullPointerException();
1104	>	this.callable = callable;
1105	>	}
1106	>	public T getRawResult() { return result; }
1107	>	public void setRawResult(T v) { result = v; }
1108	>	public boolean exec() {
1109	>	try {
1110	>	result = callable.call();
1111	>	return true;
1112	>	} catch (Error err) {
1113	>	throw err;
1114	>	} catch (RuntimeException rex) {
1115	>	throw rex;
1116	>	} catch (Exception ex) {
1117	>	throw new RuntimeException(ex);
1118	>	}
1119	>	}
1120	>	public void run() { invoke(); }
1121	>	private static final long serialVersionUID = 2838392045355241008L;
1122	>	}
1123	>
1124	>	/**
1125	>	* Returns a new ForkJoinTask that performs the {@code run}
1126	>	* method of the given Runnable as its action, and returns a null
1127	>	* result upon {@code join}.
1128	>	*
1129	>	* @param runnable the runnable action
1130	>	* @return the task
1131	>	*/
1132	>	public static ForkJoinTask<?> adapt(Runnable runnable) {
1133	>	return new AdaptedRunnable<Void>(runnable, null);
1134	>	}
1135	>
1136	>	/**
1137	>	* Returns a new ForkJoinTask that performs the {@code run}
1138	>	* method of the given Runnable as its action, and returns the
1139	>	* given result upon {@code join}.
1140	>	*
1141	>	* @param runnable the runnable action
1142	>	* @param result the result upon completion
1143	>	* @return the task
1144	>	*/
1145	>	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1146	>	return new AdaptedRunnable<T>(runnable, result);
1147	>	}
1148	>
1149	>	/**
1150	>	* Returns a new ForkJoinTask that performs the {@code call}
1151	>	* method of the given Callable as its action, and returns its
1152	>	* result upon {@code join}, translating any checked
1153	>	* exceptions encountered into {@code RuntimeException}.
1154	>	*
1155	>	* @param callable the callable action
1156	>	* @return the task
1157	>	*/
1158	>	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1159	>	return new AdaptedCallable<T>(callable);
1160		}
1161
1162		// Serialization support
#	Line 984 | Line 1167 | public abstract class ForkJoinTask<V> im
1167		* Save the state to a stream.
1168		*
1169		* @serialData the current run status and the exception thrown
1170	<	* during execution, or null if none.
1170	>	* during execution, or {@code null} if none
1171		* @param s the stream
1172		*/
1173		private void writeObject(java.io.ObjectOutputStream s)
#	Line 995 | Line 1178 | public abstract class ForkJoinTask<V> im
1178
1179		/**
1180		* Reconstitute the instance from a stream.
1181	+	*
1182		* @param s the stream
1183		*/
1184		private void readObject(java.io.ObjectInputStream s)
#	Line 1004 | Line 1188 | public abstract class ForkJoinTask<V> im
1188		status |= EXTERNAL_SIGNAL; // conservatively set external signal
1189		Object ex = s.readObject();
1190		if (ex != null)
1191	<	setDoneExceptionally((Throwable)ex);
1191	>	setDoneExceptionally((Throwable) ex);
1192		}
1193
1194	<	// Temporary Unsafe mechanics for preliminary release
1195	<	private static Unsafe getUnsafe() throws Throwable {
1194	>	// Unsafe mechanics
1195	>
1196	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1197	>	private static final long statusOffset =
1198	>	objectFieldOffset("status", ForkJoinTask.class);
1199	>
1200	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1201	>	try {
1202	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1203	>	} catch (NoSuchFieldException e) {
1204	>	// Convert Exception to corresponding Error
1205	>	NoSuchFieldError error = new NoSuchFieldError(field);
1206	>	error.initCause(e);
1207	>	throw error;
1208	>	}
1209	>	}
1210	>
1211	>	/**
1212	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1213	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1214	>	* into a jdk.
1215	>	*
1216	>	* @return a sun.misc.Unsafe
1217	>	*/
1218	>	private static sun.misc.Unsafe getUnsafe() {
1219		try {
1220	<	return Unsafe.getUnsafe();
1220	>	return sun.misc.Unsafe.getUnsafe();
1221		} catch (SecurityException se) {
1222		try {
1223		return java.security.AccessController.doPrivileged
1224	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1225	<	public Unsafe run() throws Exception {
1226	<	return getUnsafePrivileged();
1224	>	(new java.security
1225	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1226	>	public sun.misc.Unsafe run() throws Exception {
1227	>	java.lang.reflect.Field f = sun.misc
1228	>	.Unsafe.class.getDeclaredField("theUnsafe");
1229	>	f.setAccessible(true);
1230	>	return (sun.misc.Unsafe) f.get(null);
1231		}});
1232		} catch (java.security.PrivilegedActionException e) {
1233	<	throw e.getCause();
1233	>	throw new RuntimeException("Could not initialize intrinsics",
1234	>	e.getCause());
1235		}
1236		}
1237		}
1026	–
1027	–	private static Unsafe getUnsafePrivileged()
1028	–	throws NoSuchFieldException, IllegalAccessException {
1029	–	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1030	–	f.setAccessible(true);
1031	–	return (Unsafe) f.get(null);
1032	–	}
1033	–
1034	–	private static long fieldOffset(String fieldName)
1035	–	throws NoSuchFieldException {
1036	–	return _unsafe.objectFieldOffset
1037	–	(ForkJoinTask.class.getDeclaredField(fieldName));
1038	–	}
1039	–
1040	–	static final Unsafe _unsafe;
1041	–	static final long statusOffset;
1042	–
1043	–	static {
1044	–	try {
1045	–	_unsafe = getUnsafe();
1046	–	statusOffset = fieldOffset("status");
1047	–	} catch (Throwable e) {
1048	–	throw new RuntimeException("Could not initialize intrinsics", e);
1049	–	}
1050	–	}
1051	–
1238		}

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