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Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.7 by jsr166, Mon Jul 20 21:45:06 2009 UTC vs.
Revision 1.18 by dl, Sat Jul 25 15:50:57 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
#	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</code>
29	<	* and <code>join</code>, or derivatives such as
30	<	* <code>invokeAll</code>.  However, this class also provides a number
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
33		* fork/join processing.
#	Line 36 | Line 39 | import java.lang.reflect.*;
39		* operating on purely isolated objects.  The primary coordination
40		* mechanisms are {@link #fork}, that arranges asynchronous execution,
41		* and {@link #join}, that doesn't proceed until the task's result has
42	<	* been computed.  Computations should avoid <code>synchronized</code>
42	>	* been computed.  Computations should avoid {@code synchronized}
43		* methods or blocks, and should minimize other blocking
44		* synchronization apart from joining other tasks or using
45		* synchronizers such as Phasers that are advertised to cooperate with
#	Line 48 | Line 51 | import java.lang.reflect.*;
51		* performance, and the potential to indefinitely stall if the number
52		* of threads not waiting for IO or other external synchronization
53		* becomes exhausted. This usage restriction is in part enforced by
54	<	* not permitting checked exceptions such as <code>IOExceptions</code>
54	>	* not permitting checked exceptions such as {@code IOExceptions}
55		* to be thrown. However, computations may still encounter unchecked
56		* exceptions, that are rethrown to callers attempting join
57		* them. These exceptions may additionally include
#	Line 58 | Line 61 | import java.lang.reflect.*;
61		* <p>The primary method for awaiting completion and extracting
62		* results of a task is {@link #join}, but there are several variants:
63		* The {@link Future#get} methods support interruptible and/or timed
64	<	* waits for completion and report results using <code>Future</code>
64	>	* waits for completion and report results using {@code Future}
65		* conventions. Method {@link #helpJoin} enables callers to actively
66		* execute other tasks while awaiting joins, which is sometimes more
67		* efficient but only applies when all subtasks are known to be
68		* strictly tree-structured. Method {@link #invoke} is semantically
69	<	* equivalent to <code>fork(); join()</code> but always attempts to
69	>	* equivalent to {@code fork(); join()} but always attempts to
70		* begin execution in the current thread. The "<em>quiet</em>" forms
71		* of these methods do not extract results or report exceptions. These
72		* may be useful when a set of tasks are being executed, and you need
73		* to delay processing of results or exceptions until all complete.
74	<	* Method <code>invokeAll</code> (available in multiple versions)
74	>	* Method {@code invokeAll} (available in multiple versions)
75		* performs the most common form of parallel invocation: forking a set
76		* of tasks and joining them all.
77		*
#	Line 76 | Line 79 | import java.lang.reflect.*;
79		* Instead, you subclass one of the abstract classes that support a
80		* particular style of fork/join processing.  Normally, a concrete
81		* ForkJoinTask subclass declares fields comprising its parameters,
82	<	* established in a constructor, and then defines a <code>compute</code>
82	>	* established in a constructor, and then defines a {@code compute}
83		* method that somehow uses the control methods supplied by this base
84	<	* class. While these methods have <code>public</code> access (to allow
84	>	* class. While these methods have {@code public} access (to allow
85		* instances of different task subclasses to call each others
86		* methods), some of them may only be called from within other
87	<	* ForkJoinTasks. Attempts to invoke them in other contexts result in
88	<	* exceptions or errors possibly including ClassCastException.
87	>	* ForkJoinTasks (as may be determined using method {@link
88	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
89	>	* result in exceptions or errors, possibly including
90	>	* ClassCastException.
91		*
92	<	* <p>Most base support methods are <code>final</code> because their
92	>	* <p>Most base support methods are {@code final} because their
93		* implementations are intrinsically tied to the underlying
94		* lightweight task scheduling framework, and so cannot be overridden.
95		* Developers creating new basic styles of fork/join processing should
96	<	* minimally implement <code>protected</code> methods
97	<	* <code>exec</code>, <code>setRawResult</code>, and
98	<	* <code>getRawResult</code>, while also introducing an abstract
96	>	* minimally implement {@code protected} methods
97	>	* {@code exec}, {@code setRawResult}, and
98	>	* {@code getRawResult}, while also introducing an abstract
99		* computational method that can be implemented in its subclasses,
100	<	* possibly relying on other <code>protected</code> methods provided
100	>	* possibly relying on other {@code protected} methods provided
101		* by this class.
102		*
103		* <p>ForkJoinTasks should perform relatively small amounts of
104	<	* computations, othewise splitting into smaller tasks. As a very
104	>	* computations, otherwise splitting into smaller tasks. As a very
105		* rough rule of thumb, a task should perform more than 100 and less
106		* than 10000 basic computational steps. If tasks are too big, then
107	<	* parellelism cannot improve throughput. If too small, then memory
107	>	* parallelism cannot improve throughput. If too small, then memory
108		* and internal task maintenance overhead may overwhelm processing.
109		*
110	<	* <p>ForkJoinTasks are <code>Serializable</code>, which enables them
110	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them
111		* to be used in extensions such as remote execution frameworks. It is
112		* in general sensible to serialize tasks only before or after, but
113		* not during execution. Serialization is not relied on during
114		* execution itself.
115	+	*
116	+	* @since 1.7
117	+	* @author Doug Lea
118		*/
119		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
120
#	Line 128 | Line 136 | public abstract class ForkJoinTask<V> im
136		* currently unused. Also value 0x80000000 is available as spare
137		* completion value.
138		*/
139	<	volatile int status; // accessed directy by pool and workers
139	>	volatile int status; // accessed directly by pool and workers
140
141		static final int COMPLETION_MASK      = 0xe0000000;
142		static final int NORMAL               = 0xe0000000; // == mask
#	Line 141 | Line 149 | public abstract class ForkJoinTask<V> im
149		/**
150		* Table of exceptions thrown by tasks, to enable reporting by
151		* callers. Because exceptions are rare, we don't directly keep
152	<	* them with task objects, but instead us a weak ref table.  Note
152	>	* them with task objects, but instead use a weak ref table.  Note
153		* that cancellation exceptions don't appear in the table, but are
154		* instead recorded as status values.
155	<	* Todo: Use ConcurrentReferenceHashMap
155	>	* TODO: Use ConcurrentReferenceHashMap
156		*/
157		static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
158		Collections.synchronizedMap
#	Line 153 | Line 161 | public abstract class ForkJoinTask<V> im
161		// within-package utilities
162
163		/**
164	<	* Get current worker thread, or null if not a worker thread
164	>	* Gets current worker thread, or null if not a worker thread.
165		*/
166		static ForkJoinWorkerThread getWorker() {
167		Thread t = Thread.currentThread();
168	<	return ((t instanceof ForkJoinWorkerThread)?
169	<	(ForkJoinWorkerThread)t : null);
168	>	return ((t instanceof ForkJoinWorkerThread) ?
169	>	(ForkJoinWorkerThread) t : null);
170		}
171
172		final boolean casStatus(int cmp, int val) {
173	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
173	>	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
174		}
175
176		/**
#	Line 170 | Line 178 | public abstract class ForkJoinTask<V> im
178		*/
179		static void rethrowException(Throwable ex) {
180		if (ex != null)
181	<	_unsafe.throwException(ex);
181	>	UNSAFE.throwException(ex);
182		}
183
184		// Setting completion status
185
186		/**
187	<	* Mark completion and wake up threads waiting to join this task.
187	>	* Marks completion and wakes up threads waiting to join this task.
188	>	*
189		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
190		*/
191		final void setCompletion(int completion) {
192		ForkJoinPool pool = getPool();
193		if (pool != null) {
194		int s; // Clear signal bits while setting completion status
195	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
195	>	do {} while ((s = status) >= 0 && !casStatus(s, completion));
196
197		if ((s & SIGNAL_MASK) != 0) {
198		if ((s &= INTERNAL_SIGNAL_MASK) != 0)
199		pool.updateRunningCount(s);
200	<	synchronized(this) { notifyAll(); }
200	>	synchronized (this) { notifyAll(); }
201		}
202		}
203		else
#	Line 201 | Line 210 | public abstract class ForkJoinTask<V> im
210		*/
211		private void externallySetCompletion(int completion) {
212		int s;
213	<	do;while ((s = status) >= 0 &&
214	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
215	<	synchronized(this) { notifyAll(); }
213	>	do {} while ((s = status) >= 0 &&
214	>	!casStatus(s, (s & SIGNAL_MASK) | completion));
215	>	synchronized (this) { notifyAll(); }
216		}
217
218		/**
219	<	* Sets status to indicate normal completion
219	>	* Sets status to indicate normal completion.
220		*/
221		final void setNormalCompletion() {
222		// Try typical fast case -- single CAS, no signal, not already done.
223		// Manually expand casStatus to improve chances of inlining it
224	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
224	>	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
225		setCompletion(NORMAL);
226		}
227
228		// internal waiting and notification
229
230		/**
231	<	* Performs the actual monitor wait for awaitDone
231	>	* Performs the actual monitor wait for awaitDone.
232		*/
233		private void doAwaitDone() {
234		// Minimize lock bias and in/de-flation effects by maximizing
235		// chances of waiting inside sync
236		try {
237		while (status >= 0)
238	<	synchronized(this) { if (status >= 0) wait(); }
238	>	synchronized (this) { if (status >= 0) wait(); }
239		} catch (InterruptedException ie) {
240		onInterruptedWait();
241		}
242		}
243
244		/**
245	<	* Performs the actual monitor wait for awaitDone
245	>	* Performs the actual timed monitor wait for awaitDone.
246		*/
247		private void doAwaitDone(long startTime, long nanos) {
248	<	synchronized(this) {
248	>	synchronized (this) {
249		try {
250		while (status >= 0) {
251		long nt = nanos - System.nanoTime() - startTime;
252		if (nt <= 0)
253		break;
254	<	wait(nt / 1000000, (int)(nt % 1000000));
254	>	wait(nt / 1000000, (int) (nt % 1000000));
255		}
256		} catch (InterruptedException ie) {
257		onInterruptedWait();
#	Line 255 | Line 264 | public abstract class ForkJoinTask<V> im
264		/**
265		* Sets status to indicate there is joiner, then waits for join,
266		* surrounded with pool notifications.
267	+	*
268		* @return status upon exit
269		*/
270	<	private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
271	<	ForkJoinPool pool = w == null? null : w.pool;
270	>	private int awaitDone(ForkJoinWorkerThread w,
271	>	boolean maintainParallelism) {
272	>	ForkJoinPool pool = (w == null) ? null : w.pool;
273		int s;
274		while ((s = status) >= 0) {
275	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
275	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
276		if (pool == null || !pool.preJoin(this, maintainParallelism))
277		doAwaitDone();
278		if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
#	Line 274 | Line 285 | public abstract class ForkJoinTask<V> im
285
286		/**
287		* Timed version of awaitDone
288	+	*
289		* @return status upon exit
290		*/
291		private int awaitDone(ForkJoinWorkerThread w, long nanos) {
292	<	ForkJoinPool pool = w == null? null : w.pool;
292	>	ForkJoinPool pool = (w == null) ? null : w.pool;
293		int s;
294		while ((s = status) >= 0) {
295	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
295	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
296		long startTime = System.nanoTime();
297		if (pool == null || !pool.preJoin(this, false))
298		doAwaitDone(startTime, nanos);
#	Line 297 | Line 309 | public abstract class ForkJoinTask<V> im
309		}
310
311		/**
312	<	* Notify pool that thread is unblocked. Called by signalled
312	>	* Notifies pool that thread is unblocked. Called by signalled
313		* threads when woken by non-FJ threads (which is atypical).
314		*/
315		private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
316		int s;
317	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
317	>	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
318		if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
319		pool.updateRunningCount(s);
320		}
321
322		/**
323	<	* Notify pool to adjust counts on cancelled or timed out wait
323	>	* Notifies pool to adjust counts on cancelled or timed out wait.
324		*/
325		private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
326		if (pool != null) {
#	Line 323 | Line 335 | public abstract class ForkJoinTask<V> im
335		}
336
337		/**
338	<	* Handle interruptions during waits.
338	>	* Handles interruptions during waits.
339		*/
340		private void onInterruptedWait() {
341		ForkJoinWorkerThread w = getWorker();
#	Line 342 | Line 354 | public abstract class ForkJoinTask<V> im
354		}
355
356		/**
357	<	* Throws the exception associated with status s;
357	>	* Throws the exception associated with status s.
358	>	*
359		* @throws the exception
360		*/
361		private void reportException(int s) {
#	Line 355 | Line 368 | public abstract class ForkJoinTask<V> im
368		}
369
370		/**
371	<	* Returns result or throws exception using j.u.c.Future conventions
372	<	* Only call when isDone known to be true.
371	>	* Returns result or throws exception using j.u.c.Future conventions.
372	>	* Only call when {@code isDone} known to be true.
373		*/
374		private V reportFutureResult()
375		throws ExecutionException, InterruptedException {
#	Line 375 | Line 388 | public abstract class ForkJoinTask<V> im
388
389		/**
390		* Returns result or throws exception using j.u.c.Future conventions
391	<	* with timeouts
391	>	* with timeouts.
392		*/
393		private V reportTimedFutureResult()
394		throws InterruptedException, ExecutionException, TimeoutException {
#	Line 396 | Line 409 | public abstract class ForkJoinTask<V> im
409
410		/**
411		* Calls exec, recording completion, and rethrowing exception if
412	<	* encountered. Caller should normally check status before calling
412	>	* encountered. Caller should normally check status before calling.
413	>	*
414		* @return true if completed normally
415		*/
416		private boolean tryExec() {
#	Line 414 | Line 428 | public abstract class ForkJoinTask<V> im
428
429		/**
430		* Main execution method used by worker threads. Invokes
431	<	* base computation unless already complete
431	>	* base computation unless already complete.
432		*/
433		final void quietlyExec() {
434		if (status >= 0) {
435		try {
436		if (!exec())
437		return;
438	<	} catch(Throwable rex) {
438	>	} catch (Throwable rex) {
439		setDoneExceptionally(rex);
440		return;
441		}
#	Line 430 | Line 444 | public abstract class ForkJoinTask<V> im
444		}
445
446		/**
447	<	* Calls exec, recording but not rethrowing exception
448	<	* Caller should normally check status before calling
447	>	* Calls exec(), recording but not rethrowing exception.
448	>	* Caller should normally check status before calling.
449	>	*
450		* @return true if completed normally
451		*/
452		private boolean tryQuietlyInvoke() {
#	Line 447 | Line 462 | public abstract class ForkJoinTask<V> im
462		}
463
464		/**
465	<	* Cancel, ignoring any exceptions it throws
465	>	* Cancels, ignoring any exceptions it throws.
466		*/
467		final void cancelIgnoringExceptions() {
468		try {
469		cancel(false);
470	<	} catch(Throwable ignore) {
470	>	} catch (Throwable ignore) {
471		}
472		}
473
#	Line 464 | Line 479 | public abstract class ForkJoinTask<V> im
479		ForkJoinTask<?> t;
480		while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
481		t.quietlyExec();
482	<	return (s >= 0)? awaitDone(w, false) : s; // block if no work
482	>	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
483		}
484
485		// public methods
#	Line 474 | Line 489 | public abstract class ForkJoinTask<V> im
489		* necessarily enforced, it is a usage error to fork a task more
490		* than once unless it has completed and been reinitialized.  This
491		* method may be invoked only from within ForkJoinTask
492	<	* computations. Attempts to invoke in other contexts result in
493	<	* exceptions or errors possibly including ClassCastException.
492	>	* computations (as may be determined using method {@link
493	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
494	>	* in exceptions or errors, possibly including ClassCastException.
495	>	*
496	>	* @return <code>this</code>, to simplify usage.
497		*/
498	<	public final void fork() {
499	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
498	>	public final ForkJoinTask<V> fork() {
499	>	((ForkJoinWorkerThread) Thread.currentThread())
500	>	.pushTask(this);
501	>	return this;
502		}
503
504		/**
505		* Returns the result of the computation when it is ready.
506	<	* This method differs from <code>get</code> in that abnormal
506	>	* This method differs from {@code get} in that abnormal
507		* completion results in RuntimeExceptions or Errors, not
508		* ExecutionExceptions.
509		*
#	Line 499 | Line 519 | public abstract class ForkJoinTask<V> im
519		/**
520		* Commences performing this task, awaits its completion if
521		* necessary, and return its result.
522	+	*
523		* @throws Throwable (a RuntimeException, Error, or unchecked
524	<	* exception) if the underlying computation did so.
524	>	* exception) if the underlying computation did so
525		* @return the computed result
526		*/
527		public final V invoke() {
#	Line 511 | Line 532 | public abstract class ForkJoinTask<V> im
532		}
533
534		/**
535	<	* Forks both tasks, returning when <code>isDone</code> holds for
535	>	* Forks both tasks, returning when {@code isDone} holds for
536		* both of them or an exception is encountered. This method may be
537	<	* invoked only from within ForkJoinTask computations. Attempts to
538	<	* invoke in other contexts result in exceptions or errors
537	>	* invoked only from within ForkJoinTask computations (as may be
538	>	* determined using method {@link #inForkJoinPool}). Attempts to
539	>	* invoke in other contexts result in exceptions or errors,
540		* possibly including ClassCastException.
541	+	*
542		* @param t1 one task
543		* @param t2 the other task
544		* @throws NullPointerException if t1 or t2 are null
545	<	* @throws RuntimeException or Error if either task did so.
545	>	* @throws RuntimeException or Error if either task did so
546		*/
547		public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
548		t2.fork();
#	Line 528 | Line 551 | public abstract class ForkJoinTask<V> im
551		}
552
553		/**
554	<	* Forks the given tasks, returning when <code>isDone</code> holds
554	>	* Forks the given tasks, returning when {@code isDone} holds
555		* for all of them. If any task encounters an exception, others
556		* may be cancelled.  This method may be invoked only from within
557	<	* ForkJoinTask computations. Attempts to invoke in other contexts
558	<	* result in exceptions or errors possibly including ClassCastException.
557	>	* ForkJoinTask computations (as may be determined using method
558	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
559	>	* result in exceptions or errors, possibly including
560	>	* ClassCastException.
561	>	*
562		* @param tasks the array of tasks
563	<	* @throws NullPointerException if tasks or any element are null.
564	<	* @throws RuntimeException or Error if any task did so.
563	>	* @throws NullPointerException if tasks or any element are null
564	>	* @throws RuntimeException or Error if any task did so
565		*/
566		public static void invokeAll(ForkJoinTask<?>... tasks) {
567		Throwable ex = null;
#	Line 572 | Line 598 | public abstract class ForkJoinTask<V> im
598
599		/**
600		* Forks all tasks in the collection, returning when
601	<	* <code>isDone</code> holds for all of them. If any task
601	>	* {@code isDone} holds for all of them. If any task
602		* encounters an exception, others may be cancelled.  This method
603	<	* may be invoked only from within ForkJoinTask
604	<	* computations. Attempts to invoke in other contexts resul!t in
605	<	* exceptions or errors possibly including ClassCastException.
603	>	* may be invoked only from within ForkJoinTask computations (as
604	>	* may be determined using method {@link
605	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
606	>	* in exceptions or errors, possibly including ClassCastException.
607	>	*
608		* @param tasks the collection of tasks
609	<	* @throws NullPointerException if tasks or any element are null.
610	<	* @throws RuntimeException or Error if any task did so.
609	>	* @throws NullPointerException if tasks or any element are null
610	>	* @throws RuntimeException or Error if any task did so
611		*/
612		public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
613	<	if (!(tasks instanceof List)) {
614	<	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
613	>	if (!(tasks instanceof List<?>)) {
614	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
615		return;
616		}
617	+	@SuppressWarnings("unchecked")
618		List<? extends ForkJoinTask<?>> ts =
619	<	(List<? extends ForkJoinTask<?>>)tasks;
619	>	(List<? extends ForkJoinTask<?>>) tasks;
620		Throwable ex = null;
621		int last = ts.size() - 1;
622		for (int i = last; i >= 0; --i) {
#	Line 623 | Line 652 | public abstract class ForkJoinTask<V> im
652		/**
653		* Returns true if the computation performed by this task has
654		* completed (or has been cancelled).
655	+	*
656		* @return true if this computation has completed
657		*/
658		public final boolean isDone() {
#	Line 631 | Line 661 | public abstract class ForkJoinTask<V> im
661
662		/**
663		* Returns true if this task was cancelled.
664	+	*
665		* @return true if this task was cancelled
666		*/
667		public final boolean isCancelled() {
#	Line 639 | Line 670 | public abstract class ForkJoinTask<V> im
670
671		/**
672		* Asserts that the results of this task's computation will not be
673	<	* used. If a cancellation occurs before atempting to execute this
674	<	* task, then execution will be suppressed, <code>isCancelled</code>
675	<	* will report true, and <code>join</code> will result in a
676	<	* <code>CancellationException</code> being thrown. Otherwise, when
673	>	* used. If a cancellation occurs before attempting to execute this
674	>	* task, then execution will be suppressed, {@code isCancelled}
675	>	* will report true, and {@code join} will result in a
676	>	* {@code CancellationException} being thrown. Otherwise, when
677		* cancellation races with completion, there are no guarantees
678	<	* about whether <code>isCancelled</code> will report true, whether
679	<	* <code>join</code> will return normally or via an exception, or
678	>	* about whether {@code isCancelled} will report true, whether
679	>	* {@code join} will return normally or via an exception, or
680		* whether these behaviors will remain consistent upon repeated
681		* invocation.
682		*
#	Line 656 | Line 687 | public abstract class ForkJoinTask<V> im
687		* <p> This method is designed to be invoked by <em>other</em>
688		* tasks. To terminate the current task, you can just return or
689		* throw an unchecked exception from its computation method, or
690	<	* invoke <code>completeExceptionally</code>.
690	>	* invoke {@code completeExceptionally}.
691		*
692		* @param mayInterruptIfRunning this value is ignored in the
693		* default implementation because tasks are not in general
694	<	* cancelled via interruption.
694	>	* cancelled via interruption
695		*
696		* @return true if this task is now cancelled
697		*/
#	Line 670 | Line 701 | public abstract class ForkJoinTask<V> im
701		}
702
703		/**
704	<	* Returns true if this task threw an exception or was cancelled
704	>	* Returns true if this task threw an exception or was cancelled.
705	>	*
706		* @return true if this task threw an exception or was cancelled
707		*/
708		public final boolean isCompletedAbnormally() {
#	Line 681 | Line 713 | public abstract class ForkJoinTask<V> im
713		* Returns the exception thrown by the base computation, or a
714		* CancellationException if cancelled, or null if none or if the
715		* method has not yet completed.
716	+	*
717		* @return the exception, or null if none
718		*/
719		public final Throwable getException() {
#	Line 695 | Line 728 | public abstract class ForkJoinTask<V> im
728		/**
729		* Completes this task abnormally, and if not already aborted or
730		* cancelled, causes it to throw the given exception upon
731	<	* <code>join</code> and related operations. This method may be used
731	>	* {@code join} and related operations. This method may be used
732		* to induce exceptions in asynchronous tasks, or to force
733		* completion of tasks that would not otherwise complete.  Its use
734		* in other situations is likely to be wrong.  This method is
735	<	* overridable, but overridden versions must invoke <code>super</code>
735	>	* overridable, but overridden versions must invoke {@code super}
736		* implementation to maintain guarantees.
737		*
738		* @param ex the exception to throw. If this exception is
#	Line 708 | Line 741 | public abstract class ForkJoinTask<V> im
741		*/
742		public void completeExceptionally(Throwable ex) {
743		setDoneExceptionally((ex instanceof RuntimeException) ||
744	<	(ex instanceof Error)? ex :
744	>	(ex instanceof Error) ? ex :
745		new RuntimeException(ex));
746		}
747
748		/**
749		* Completes this task, and if not already aborted or cancelled,
750	<	* returning a <code>null</code> result upon <code>join</code> and related
750	>	* returning a {@code null} result upon {@code join} and related
751		* operations. This method may be used to provide results for
752		* asynchronous tasks, or to provide alternative handling for
753		* tasks that would not otherwise complete normally. Its use in
754		* other situations is likely to be wrong. This method is
755	<	* overridable, but overridden versions must invoke <code>super</code>
755	>	* overridable, but overridden versions must invoke {@code super}
756		* implementation to maintain guarantees.
757		*
758	<	* @param value the result value for this task.
758	>	* @param value the result value for this task
759		*/
760		public void complete(V value) {
761		try {
762		setRawResult(value);
763	<	} catch(Throwable rex) {
763	>	} catch (Throwable rex) {
764		setDoneExceptionally(rex);
765		return;
766		}
#	Line 752 | Line 785 | public abstract class ForkJoinTask<V> im
785		/**
786		* Possibly executes other tasks until this task is ready, then
787		* returns the result of the computation.  This method may be more
788	<	* efficient than <code>join</code>, but is only applicable when
789	<	* there are no potemtial dependencies between continuation of the
788	>	* efficient than {@code join}, but is only applicable when
789	>	* there are no potential dependencies between continuation of the
790		* current task and that of any other task that might be executed
791		* while helping. (This usually holds for pure divide-and-conquer
792		* tasks). This method may be invoked only from within
793	<	* ForkJoinTask computations. Attempts to invoke in other contexts
794	<	* resul!t in exceptions or errors possibly including ClassCastException.
793	>	* ForkJoinTask computations (as may be determined using method
794	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
795	>	* result in exceptions or errors, possibly including
796	>	* ClassCastException.
797	>	*
798		* @return the computed result
799		*/
800		public final V helpJoin() {
801	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
801	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
802		if (status < 0 || !w.unpushTask(this) || !tryExec())
803		reportException(busyJoin(w));
804		return getRawResult();
#	Line 771 | Line 807 | public abstract class ForkJoinTask<V> im
807		/**
808		* Possibly executes other tasks until this task is ready.  This
809		* method may be invoked only from within ForkJoinTask
810	<	* computations. Attempts to invoke in other contexts resul!t in
811	<	* exceptions or errors possibly including ClassCastException.
810	>	* computations (as may be determined using method {@link
811	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
812	>	* in exceptions or errors, possibly including ClassCastException.
813		*/
814		public final void quietlyHelpJoin() {
815		if (status >= 0) {
816		ForkJoinWorkerThread w =
817	<	(ForkJoinWorkerThread)(Thread.currentThread());
817	>	(ForkJoinWorkerThread) Thread.currentThread();
818		if (!w.unpushTask(this) || !tryQuietlyInvoke())
819		busyJoin(w);
820		}
#	Line 816 | Line 853 | public abstract class ForkJoinTask<V> im
853		* joined, instead executing them until all are processed.
854		*/
855		public static void helpQuiesce() {
856	<	((ForkJoinWorkerThread)(Thread.currentThread())).
857	<	helpQuiescePool();
856	>	((ForkJoinWorkerThread) Thread.currentThread())
857	>	.helpQuiescePool();
858		}
859
860		/**
861		* Resets the internal bookkeeping state of this task, allowing a
862	<	* subsequent <code>fork</code>. This method allows repeated reuse of
862	>	* subsequent {@code fork}. This method allows repeated reuse of
863		* this task, but only if reuse occurs when this task has either
864		* never been forked, or has been forked, then completed and all
865		* outstanding joins of this task have also completed. Effects
#	Line 838 | Line 875 | public abstract class ForkJoinTask<V> im
875
876		/**
877		* Returns the pool hosting the current task execution, or null
878	<	* if this task is executing outside of any pool.
879	<	* @return the pool, or null if none.
878	>	* if this task is executing outside of any ForkJoinPool.
879	>	*
880	>	* @return the pool, or null if none
881		*/
882		public static ForkJoinPool getPool() {
883		Thread t = Thread.currentThread();
884	<	return ((t instanceof ForkJoinWorkerThread)?
885	<	((ForkJoinWorkerThread)t).pool : null);
884	>	return (t instanceof ForkJoinWorkerThread) ?
885	>	((ForkJoinWorkerThread) t).pool : null;
886	>	}
887	>
888	>	/**
889	>	* Returns {@code true} if the current thread is executing as a
890	>	* ForkJoinPool computation.
891	>	*
892	>	* @return {@code true} if the current thread is executing as a
893	>	* ForkJoinPool computation, or false otherwise
894	>	*/
895	>	public static boolean inForkJoinPool() {
896	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
897		}
898
899		/**
#	Line 854 | Line 903 | public abstract class ForkJoinTask<V> im
903		* another thread.  This method may be useful when arranging
904		* alternative local processing of tasks that could have been, but
905		* were not, stolen. This method may be invoked only from within
906	<	* ForkJoinTask computations. Attempts to invoke in other contexts
907	<	* result in exceptions or errors possibly including ClassCastException.
906	>	* ForkJoinTask computations (as may be determined using method
907	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
908	>	* result in exceptions or errors, possibly including
909	>	* ClassCastException.
910	>	*
911		* @return true if unforked
912		*/
913		public boolean tryUnfork() {
914	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
914	>	return ((ForkJoinWorkerThread) Thread.currentThread())
915	>	.unpushTask(this);
916		}
917
918		/**
#	Line 867 | Line 920 | public abstract class ForkJoinTask<V> im
920		* forked by the current worker thread but not yet executed. This
921		* value may be useful for heuristic decisions about whether to
922		* fork other tasks.
923	+	*
924		* @return the number of tasks
925		*/
926		public static int getQueuedTaskCount() {
927	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
928	<	getQueueSize();
927	>	return ((ForkJoinWorkerThread) Thread.currentThread())
928	>	.getQueueSize();
929		}
930
931		/**
932	<	* Returns a estimate of how many more locally queued tasks are
932	>	* Returns an estimate of how many more locally queued tasks are
933		* held by the current worker thread than there are other worker
934		* threads that might steal them.  This value may be useful for
935		* heuristic decisions about whether to fork other tasks. In many
#	Line 883 | Line 937 | public abstract class ForkJoinTask<V> im
937		* aim to maintain a small constant surplus (for example, 3) of
938		* tasks, and to process computations locally if this threshold is
939		* exceeded.
940	+	*
941		* @return the surplus number of tasks, which may be negative
942		*/
943		public static int getSurplusQueuedTaskCount() {
944	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
944	>	return ((ForkJoinWorkerThread) Thread.currentThread())
945		.getEstimatedSurplusTaskCount();
946		}
947
948		// Extension methods
949
950		/**
951	<	* Returns the result that would be returned by <code>join</code>,
951	>	* Returns the result that would be returned by {@code join},
952		* even if this task completed abnormally, or null if this task is
953		* not known to have been completed.  This method is designed to
954		* aid debugging, as well as to support extensions. Its use in any
955		* other context is discouraged.
956		*
957	<	* @return the result, or null if not completed.
957	>	* @return the result, or null if not completed
958		*/
959		public abstract V getRawResult();
960
#	Line 918 | Line 973 | public abstract class ForkJoinTask<V> im
973		* called otherwise. The return value controls whether this task
974		* is considered to be done normally. It may return false in
975		* asynchronous actions that require explicit invocations of
976	<	* <code>complete</code> to become joinable. It may throw exceptions
976	>	* {@code complete} to become joinable. It may throw exceptions
977		* to indicate abnormal exit.
978	+	*
979		* @return true if completed normally
980		* @throws Error or RuntimeException if encountered during computation
981		*/
#	Line 932 | Line 988 | public abstract class ForkJoinTask<V> im
988		* be polled or executed next.  This method is designed primarily
989		* to support extensions, and is unlikely to be useful otherwise.
990		* This method may be invoked only from within ForkJoinTask
991	<	* computations. Attempts to invoke in other contexts result in
992	<	* exceptions or errors possibly including ClassCastException.
991	>	* computations (as may be determined using method {@link
992	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
993	>	* in exceptions or errors, possibly including ClassCastException.
994		*
995		* @return the next task, or null if none are available
996		*/
997		protected static ForkJoinTask<?> peekNextLocalTask() {
998	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask();
998	>	return ((ForkJoinWorkerThread) Thread.currentThread())
999	>	.peekTask();
1000		}
1001
1002		/**
#	Line 946 | Line 1004 | public abstract class ForkJoinTask<V> im
1004		* queued by the current thread but not yet executed.  This method
1005		* is designed primarily to support extensions, and is unlikely to
1006		* be useful otherwise.  This method may be invoked only from
1007	<	* within ForkJoinTask computations. Attempts to invoke in other
1008	<	* contexts result in exceptions or errors possibly including
1007	>	* within ForkJoinTask computations (as may be determined using
1008	>	* method {@link #inForkJoinPool}). Attempts to invoke in other
1009	>	* contexts result in exceptions or errors, possibly including
1010		* ClassCastException.
1011		*
1012		* @return the next task, or null if none are available
1013		*/
1014		protected static ForkJoinTask<?> pollNextLocalTask() {
1015	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).pollLocalTask();
1015	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1016	>	.pollLocalTask();
1017		}
1018
1019		/**
#	Line 961 | Line 1021 | public abstract class ForkJoinTask<V> im
1021		* queued by the current thread but not yet executed, if one is
1022		* available, or if not available, a task that was forked by some
1023		* other thread, if available. Availability may be transient, so a
1024	<	* <code>null</code> result does not necessarily imply quiecence
1024	>	* {@code null} result does not necessarily imply quiescence
1025		* of the pool this task is operating in.  This method is designed
1026		* primarily to support extensions, and is unlikely to be useful
1027		* otherwise.  This method may be invoked only from within
1028	<	* ForkJoinTask computations. Attempts to invoke in other contexts
1029	<	* result in exceptions or errors possibly including
1028	>	* ForkJoinTask computations (as may be determined using method
1029	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1030	>	* result in exceptions or errors, possibly including
1031		* ClassCastException.
1032		*
1033		* @return a task, or null if none are available
1034		*/
1035		protected static ForkJoinTask<?> pollTask() {
1036	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
1037	<	pollTask();
1036	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1037	>	.pollTask();
1038	>	}
1039	>
1040	>	// adaptors
1041	>
1042	>	/**
1043	>	* Returns a new ForkJoinTask that performs the <code>run</code>
1044	>	* method of the given Runnable as its action, and returns a null
1045	>	* result upon <code>join</code>.
1046	>	*
1047	>	* @param runnable the runnable action
1048	>	* @return the task
1049	>	*/
1050	>	public static ForkJoinTask<Void> adapt(Runnable runnable) {
1051	>	return new ForkJoinPool.AdaptedRunnable<Void>(runnable, null);
1052	>	}
1053	>
1054	>	/**
1055	>	* Returns a new ForkJoinTask that performs the <code>run</code>
1056	>	* method of the given Runnable as its action, and returns the
1057	>	* given result upon <code>join</code>.
1058	>	*
1059	>	* @param runnable the runnable action
1060	>	* @param result the result upon completion
1061	>	* @return the task
1062	>	*/
1063	>	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1064	>	return new ForkJoinPool.AdaptedRunnable<T>(runnable, result);
1065	>	}
1066	>
1067	>	/**
1068	>	* Returns a new ForkJoinTask that performs the <code>call</code>
1069	>	* method of the given Callable as its action, and returns its
1070	>	* result upon <code>join</code>, translating any checked
1071	>	* exceptions encountered into <code>RuntimeException<code>.
1072	>	*
1073	>	* @param callable the callable action
1074	>	* @return the task
1075	>	*/
1076	>	public static <T> ForkJoinTask<T> adapt(Callable<T> callable) {
1077	>	return new ForkJoinPool.AdaptedCallable<T>(callable);
1078		}
1079
1080		// Serialization support
#	Line 984 | Line 1085 | public abstract class ForkJoinTask<V> im
1085		* Save the state to a stream.
1086		*
1087		* @serialData the current run status and the exception thrown
1088	<	* during execution, or null if none.
1088	>	* during execution, or null if none
1089		* @param s the stream
1090		*/
1091		private void writeObject(java.io.ObjectOutputStream s)
#	Line 995 | Line 1096 | public abstract class ForkJoinTask<V> im
1096
1097		/**
1098		* Reconstitute the instance from a stream.
1099	+	*
1100		* @param s the stream
1101		*/
1102		private void readObject(java.io.ObjectInputStream s)
#	Line 1004 | Line 1106 | public abstract class ForkJoinTask<V> im
1106		status |= EXTERNAL_SIGNAL; // conservatively set external signal
1107		Object ex = s.readObject();
1108		if (ex != null)
1109	<	setDoneExceptionally((Throwable)ex);
1109	>	setDoneExceptionally((Throwable) ex);
1110		}
1111
1112	<	// Temporary Unsafe mechanics for preliminary release
1113	<	private static Unsafe getUnsafe() throws Throwable {
1112	>	// Unsafe mechanics for jsr166y 3rd party package.
1113	>	private static sun.misc.Unsafe getUnsafe() {
1114		try {
1115	<	return Unsafe.getUnsafe();
1115	>	return sun.misc.Unsafe.getUnsafe();
1116		} catch (SecurityException se) {
1117		try {
1118		return java.security.AccessController.doPrivileged
1119	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1120	<	public Unsafe run() throws Exception {
1121	<	return getUnsafePrivileged();
1119	>	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1120	>	public sun.misc.Unsafe run() throws Exception {
1121	>	return getUnsafeByReflection();
1122		}});
1123		} catch (java.security.PrivilegedActionException e) {
1124	<	throw e.getCause();
1124	>	throw new RuntimeException("Could not initialize intrinsics",
1125	>	e.getCause());
1126		}
1127		}
1128		}
1129
1130	<	private static Unsafe getUnsafePrivileged()
1130	>	private static sun.misc.Unsafe getUnsafeByReflection()
1131		throws NoSuchFieldException, IllegalAccessException {
1132	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1132	>	java.lang.reflect.Field f =
1133	>	sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
1134		f.setAccessible(true);
1135	<	return (Unsafe) f.get(null);
1135	>	return (sun.misc.Unsafe) f.get(null);
1136		}
1137
1138	<	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 {
1138	>	private static long fieldOffset(String fieldName, Class<?> klazz) {
1139		try {
1140	<	_unsafe = getUnsafe();
1141	<	statusOffset = fieldOffset("status");
1142	<	} catch (Throwable e) {
1143	<	throw new RuntimeException("Could not initialize intrinsics", e);
1140	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
1141	>	} catch (NoSuchFieldException e) {
1142	>	// Convert Exception to Error
1143	>	NoSuchFieldError error = new NoSuchFieldError(fieldName);
1144	>	error.initCause(e);
1145	>	throw error;
1146		}
1147		}
1148
1149	+	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1150	+	static final long statusOffset =
1151	+	fieldOffset("status", ForkJoinTask.class);
1152	+
1153		}

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