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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.6 by dl, Thu Jul 16 15:32:34 2009 UTC vs.
Revision 1.22 by jsr166, Sun Jul 26 17:33:37 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}, 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.
611	<	*/
612	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
613	<	if (!(tasks instanceof List)) {
614	<	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
615	<	return;
609	>	* @return the tasks argument, to simplify usage
610	>	* @throws NullPointerException if tasks or any element are null
611	>	* @throws RuntimeException or Error if any task did so
612	>	*/
613	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
614	>	if (!(tasks instanceof List<?>)) {
615	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
616	>	return tasks;
617		}
618	+	@SuppressWarnings("unchecked")
619		List<? extends ForkJoinTask<?>> ts =
620	<	(List<? extends ForkJoinTask<?>>)tasks;
620	>	(List<? extends ForkJoinTask<?>>) tasks;
621		Throwable ex = null;
622		int last = ts.size() - 1;
623		for (int i = last; i >= 0; --i) {
#	Line 618 | Line 648 | public abstract class ForkJoinTask<V> im
648		}
649		if (ex != null)
650		rethrowException(ex);
651	+	return tasks;
652		}
653
654		/**
655		* Returns true if the computation performed by this task has
656		* completed (or has been cancelled).
657	+	*
658		* @return true if this computation has completed
659		*/
660		public final boolean isDone() {
#	Line 631 | Line 663 | public abstract class ForkJoinTask<V> im
663
664		/**
665		* Returns true if this task was cancelled.
666	+	*
667		* @return true if this task was cancelled
668		*/
669		public final boolean isCancelled() {
#	Line 639 | Line 672 | public abstract class ForkJoinTask<V> im
672
673		/**
674		* Asserts that the results of this task's computation will not be
675	<	* used. If a cancellation occurs before atempting to execute this
676	<	* task, then execution will be suppressed, <code>isCancelled</code>
677	<	* will report true, and <code>join</code> will result in a
678	<	* <code>CancellationException</code> being thrown. Otherwise, when
675	>	* used. If a cancellation occurs before attempting to execute this
676	>	* task, then execution will be suppressed, {@code isCancelled}
677	>	* will report true, and {@code join} will result in a
678	>	* {@code CancellationException} being thrown. Otherwise, when
679		* cancellation races with completion, there are no guarantees
680	<	* about whether <code>isCancelled</code> will report true, whether
681	<	* <code>join</code> will return normally or via an exception, or
680	>	* about whether {@code isCancelled} will report true, whether
681	>	* {@code join} will return normally or via an exception, or
682		* whether these behaviors will remain consistent upon repeated
683		* invocation.
684		*
#	Line 656 | Line 689 | public abstract class ForkJoinTask<V> im
689		* <p> This method is designed to be invoked by <em>other</em>
690		* tasks. To terminate the current task, you can just return or
691		* throw an unchecked exception from its computation method, or
692	<	* invoke <code>completeExceptionally</code>.
692	>	* invoke {@code completeExceptionally}.
693		*
694		* @param mayInterruptIfRunning this value is ignored in the
695		* default implementation because tasks are not in general
696	<	* cancelled via interruption.
696	>	* cancelled via interruption
697		*
698		* @return true if this task is now cancelled
699		*/
#	Line 670 | Line 703 | public abstract class ForkJoinTask<V> im
703		}
704
705		/**
706	<	* Returns true if this task threw an exception or was cancelled
706	>	* Returns true if this task threw an exception or was cancelled.
707	>	*
708		* @return true if this task threw an exception or was cancelled
709		*/
710		public final boolean isCompletedAbnormally() {
#	Line 681 | Line 715 | public abstract class ForkJoinTask<V> im
715		* Returns the exception thrown by the base computation, or a
716		* CancellationException if cancelled, or null if none or if the
717		* method has not yet completed.
718	+	*
719		* @return the exception, or null if none
720		*/
721		public final Throwable getException() {
#	Line 695 | Line 730 | public abstract class ForkJoinTask<V> im
730		/**
731		* Completes this task abnormally, and if not already aborted or
732		* cancelled, causes it to throw the given exception upon
733	<	* <code>join</code> and related operations. This method may be used
733	>	* {@code join} and related operations. This method may be used
734		* to induce exceptions in asynchronous tasks, or to force
735		* completion of tasks that would not otherwise complete.  Its use
736		* in other situations is likely to be wrong.  This method is
737	<	* overridable, but overridden versions must invoke <code>super</code>
737	>	* overridable, but overridden versions must invoke {@code super}
738		* implementation to maintain guarantees.
739		*
740		* @param ex the exception to throw. If this exception is
#	Line 708 | Line 743 | public abstract class ForkJoinTask<V> im
743		*/
744		public void completeExceptionally(Throwable ex) {
745		setDoneExceptionally((ex instanceof RuntimeException) ||
746	<	(ex instanceof Error)? ex :
746	>	(ex instanceof Error) ? ex :
747		new RuntimeException(ex));
748		}
749
750		/**
751		* Completes this task, and if not already aborted or cancelled,
752	<	* returning a <code>null</code> result upon <code>join</code> and related
752	>	* returning a {@code null} result upon {@code join} and related
753		* operations. This method may be used to provide results for
754		* asynchronous tasks, or to provide alternative handling for
755		* tasks that would not otherwise complete normally. Its use in
756		* other situations is likely to be wrong. This method is
757	<	* overridable, but overridden versions must invoke <code>super</code>
757	>	* overridable, but overridden versions must invoke {@code super}
758		* implementation to maintain guarantees.
759		*
760	<	* @param value the result value for this task.
760	>	* @param value the result value for this task
761		*/
762		public void complete(V value) {
763		try {
764		setRawResult(value);
765	<	} catch(Throwable rex) {
765	>	} catch (Throwable rex) {
766		setDoneExceptionally(rex);
767		return;
768		}
#	Line 752 | Line 787 | public abstract class ForkJoinTask<V> im
787		/**
788		* Possibly executes other tasks until this task is ready, then
789		* returns the result of the computation.  This method may be more
790	<	* efficient than <code>join</code>, but is only applicable when
791	<	* there are no potemtial dependencies between continuation of the
790	>	* efficient than {@code join}, but is only applicable when
791	>	* there are no potential dependencies between continuation of the
792		* current task and that of any other task that might be executed
793		* while helping. (This usually holds for pure divide-and-conquer
794		* tasks). This method may be invoked only from within
795	<	* ForkJoinTask computations. Attempts to invoke in other contexts
796	<	* resul!t in exceptions or errors possibly including ClassCastException.
795	>	* ForkJoinTask computations (as may be determined using method
796	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
797	>	* result in exceptions or errors, possibly including
798	>	* ClassCastException.
799	>	*
800		* @return the computed result
801		*/
802		public final V helpJoin() {
803	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
803	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
804		if (status < 0 || !w.unpushTask(this) || !tryExec())
805		reportException(busyJoin(w));
806		return getRawResult();
#	Line 771 | Line 809 | public abstract class ForkJoinTask<V> im
809		/**
810		* Possibly executes other tasks until this task is ready.  This
811		* method may be invoked only from within ForkJoinTask
812	<	* computations. Attempts to invoke in other contexts resul!t in
813	<	* exceptions or errors possibly including ClassCastException.
812	>	* computations (as may be determined using method {@link
813	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
814	>	* in exceptions or errors, possibly including ClassCastException.
815		*/
816		public final void quietlyHelpJoin() {
817		if (status >= 0) {
818		ForkJoinWorkerThread w =
819	<	(ForkJoinWorkerThread)(Thread.currentThread());
819	>	(ForkJoinWorkerThread) Thread.currentThread();
820		if (!w.unpushTask(this) || !tryQuietlyInvoke())
821		busyJoin(w);
822		}
#	Line 816 | Line 855 | public abstract class ForkJoinTask<V> im
855		* joined, instead executing them until all are processed.
856		*/
857		public static void helpQuiesce() {
858	<	((ForkJoinWorkerThread)(Thread.currentThread())).
859	<	helpQuiescePool();
858	>	((ForkJoinWorkerThread) Thread.currentThread())
859	>	.helpQuiescePool();
860		}
861
862		/**
863		* Resets the internal bookkeeping state of this task, allowing a
864	<	* subsequent <code>fork</code>. This method allows repeated reuse of
864	>	* subsequent {@code fork}. This method allows repeated reuse of
865		* this task, but only if reuse occurs when this task has either
866		* never been forked, or has been forked, then completed and all
867		* outstanding joins of this task have also completed. Effects
#	Line 838 | Line 877 | public abstract class ForkJoinTask<V> im
877
878		/**
879		* Returns the pool hosting the current task execution, or null
880	<	* if this task is executing outside of any pool.
881	<	* @return the pool, or null if none.
880	>	* if this task is executing outside of any ForkJoinPool.
881	>	*
882	>	* @return the pool, or null if none
883		*/
884		public static ForkJoinPool getPool() {
885		Thread t = Thread.currentThread();
886	<	return ((t instanceof ForkJoinWorkerThread)?
887	<	((ForkJoinWorkerThread)t).pool : null);
886	>	return (t instanceof ForkJoinWorkerThread) ?
887	>	((ForkJoinWorkerThread) t).pool : null;
888	>	}
889	>
890	>	/**
891	>	* Returns {@code true} if the current thread is executing as a
892	>	* ForkJoinPool computation.
893	>	*
894	>	* @return {@code true} if the current thread is executing as a
895	>	* ForkJoinPool computation, or false otherwise
896	>	*/
897	>	public static boolean inForkJoinPool() {
898	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
899		}
900
901		/**
#	Line 854 | Line 905 | public abstract class ForkJoinTask<V> im
905		* another thread.  This method may be useful when arranging
906		* alternative local processing of tasks that could have been, but
907		* were not, stolen. This method may be invoked only from within
908	<	* ForkJoinTask computations. Attempts to invoke in other contexts
909	<	* result in exceptions or errors possibly including ClassCastException.
908	>	* ForkJoinTask computations (as may be determined using method
909	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
910	>	* result in exceptions or errors, possibly including
911	>	* ClassCastException.
912	>	*
913		* @return true if unforked
914		*/
915		public boolean tryUnfork() {
916	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
916	>	return ((ForkJoinWorkerThread) Thread.currentThread())
917	>	.unpushTask(this);
918		}
919
920		/**
#	Line 867 | Line 922 | public abstract class ForkJoinTask<V> im
922		* forked by the current worker thread but not yet executed. This
923		* value may be useful for heuristic decisions about whether to
924		* fork other tasks.
925	+	*
926		* @return the number of tasks
927		*/
928		public static int getQueuedTaskCount() {
929	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
930	<	getQueueSize();
929	>	return ((ForkJoinWorkerThread) Thread.currentThread())
930	>	.getQueueSize();
931		}
932
933		/**
934	<	* Returns a estimate of how many more locally queued tasks are
934	>	* Returns an estimate of how many more locally queued tasks are
935		* held by the current worker thread than there are other worker
936		* threads that might steal them.  This value may be useful for
937		* heuristic decisions about whether to fork other tasks. In many
#	Line 883 | Line 939 | public abstract class ForkJoinTask<V> im
939		* aim to maintain a small constant surplus (for example, 3) of
940		* tasks, and to process computations locally if this threshold is
941		* exceeded.
942	+	*
943		* @return the surplus number of tasks, which may be negative
944		*/
945		public static int getSurplusQueuedTaskCount() {
946	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
946	>	return ((ForkJoinWorkerThread) Thread.currentThread())
947		.getEstimatedSurplusTaskCount();
948		}
949
950		// Extension methods
951
952		/**
953	<	* Returns the result that would be returned by <code>join</code>,
953	>	* Returns the result that would be returned by {@code join},
954		* even if this task completed abnormally, or null if this task is
955		* not known to have been completed.  This method is designed to
956		* aid debugging, as well as to support extensions. Its use in any
957		* other context is discouraged.
958		*
959	<	* @return the result, or null if not completed.
959	>	* @return the result, or null if not completed
960		*/
961		public abstract V getRawResult();
962
#	Line 918 | Line 975 | public abstract class ForkJoinTask<V> im
975		* called otherwise. The return value controls whether this task
976		* is considered to be done normally. It may return false in
977		* asynchronous actions that require explicit invocations of
978	<	* <code>complete</code> to become joinable. It may throw exceptions
978	>	* {@code complete} to become joinable. It may throw exceptions
979		* to indicate abnormal exit.
980	+	*
981		* @return true if completed normally
982		* @throws Error or RuntimeException if encountered during computation
983		*/
#	Line 932 | Line 990 | public abstract class ForkJoinTask<V> im
990		* be polled or executed next.  This method is designed primarily
991		* to support extensions, and is unlikely to be useful otherwise.
992		* This method may be invoked only from within ForkJoinTask
993	<	* computations. Attempts to invoke in other contexts result in
994	<	* exceptions or errors possibly including ClassCastException.
993	>	* computations (as may be determined using method {@link
994	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
995	>	* in exceptions or errors, possibly including ClassCastException.
996		*
997		* @return the next task, or null if none are available
998		*/
999		protected static ForkJoinTask<?> peekNextLocalTask() {
1000	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask();
1000	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1001	>	.peekTask();
1002		}
1003
1004		/**
#	Line 946 | Line 1006 | public abstract class ForkJoinTask<V> im
1006		* queued by the current thread but not yet executed.  This method
1007		* is designed primarily to support extensions, and is unlikely to
1008		* be useful otherwise.  This method may be invoked only from
1009	<	* within ForkJoinTask computations. Attempts to invoke in other
1010	<	* contexts result in exceptions or errors possibly including
1009	>	* within ForkJoinTask computations (as may be determined using
1010	>	* method {@link #inForkJoinPool}). Attempts to invoke in other
1011	>	* contexts result in exceptions or errors, possibly including
1012		* ClassCastException.
1013		*
1014		* @return the next task, or null if none are available
1015		*/
1016		protected static ForkJoinTask<?> pollNextLocalTask() {
1017	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).pollLocalTask();
1017	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1018	>	.pollLocalTask();
1019		}
1020	<
1020	>
1021		/**
1022		* Unschedules and returns, without executing, the next task
1023		* queued by the current thread but not yet executed, if one is
1024		* available, or if not available, a task that was forked by some
1025		* other thread, if available. Availability may be transient, so a
1026	<	* <code>null</code> result does not necessarily imply quiecence
1026	>	* {@code null} result does not necessarily imply quiescence
1027		* of the pool this task is operating in.  This method is designed
1028		* primarily to support extensions, and is unlikely to be useful
1029		* otherwise.  This method may be invoked only from within
1030	<	* ForkJoinTask computations. Attempts to invoke in other contexts
1031	<	* result in exceptions or errors possibly including
1030	>	* ForkJoinTask computations (as may be determined using method
1031	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1032	>	* result in exceptions or errors, possibly including
1033		* ClassCastException.
1034		*
1035		* @return a task, or null if none are available
1036		*/
1037		protected static ForkJoinTask<?> pollTask() {
1038	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
1039	<	pollTask();
1038	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1039	>	.pollTask();
1040	>	}
1041	>
1042	>	// adaptors
1043	>
1044	>	/**
1045	>	* Returns a new ForkJoinTask that performs the {@code run}
1046	>	* method of the given Runnable as its action, and returns a null
1047	>	* result upon {@code join}.
1048	>	*
1049	>	* @param runnable the runnable action
1050	>	* @return the task
1051	>	*/
1052	>	public static ForkJoinTask<Void> adapt(Runnable runnable) {
1053	>	return new ForkJoinPool.AdaptedRunnable<Void>(runnable, null);
1054	>	}
1055	>
1056	>	/**
1057	>	* Returns a new ForkJoinTask that performs the {@code run}
1058	>	* method of the given Runnable as its action, and returns the
1059	>	* given result upon {@code join}.
1060	>	*
1061	>	* @param runnable the runnable action
1062	>	* @param result the result upon completion
1063	>	* @return the task
1064	>	*/
1065	>	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1066	>	return new ForkJoinPool.AdaptedRunnable<T>(runnable, result);
1067	>	}
1068	>
1069	>	/**
1070	>	* Returns a new ForkJoinTask that performs the {@code call}
1071	>	* method of the given Callable as its action, and returns its
1072	>	* result upon {@code join}, translating any checked
1073	>	* exceptions encountered into {@code RuntimeException}.
1074	>	*
1075	>	* @param callable the callable action
1076	>	* @return the task
1077	>	*/
1078	>	public static <T> ForkJoinTask<T> adapt(Callable<T> callable) {
1079	>	return new ForkJoinPool.AdaptedCallable<T>(callable);
1080		}
1081
1082		// Serialization support
#	Line 984 | Line 1087 | public abstract class ForkJoinTask<V> im
1087		* Save the state to a stream.
1088		*
1089		* @serialData the current run status and the exception thrown
1090	<	* during execution, or null if none.
1090	>	* during execution, or null if none
1091		* @param s the stream
1092		*/
1093		private void writeObject(java.io.ObjectOutputStream s)
#	Line 995 | Line 1098 | public abstract class ForkJoinTask<V> im
1098
1099		/**
1100		* Reconstitute the instance from a stream.
1101	+	*
1102		* @param s the stream
1103		*/
1104		private void readObject(java.io.ObjectInputStream s)
#	Line 1004 | Line 1108 | public abstract class ForkJoinTask<V> im
1108		status |= EXTERNAL_SIGNAL; // conservatively set external signal
1109		Object ex = s.readObject();
1110		if (ex != null)
1111	<	setDoneExceptionally((Throwable)ex);
1111	>	setDoneExceptionally((Throwable) ex);
1112		}
1113
1114	<	// Temporary Unsafe mechanics for preliminary release
1115	<	private static Unsafe getUnsafe() throws Throwable {
1114	>	// Unsafe mechanics
1115	>
1116	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1117	>	private static final long statusOffset =
1118	>	objectFieldOffset("status", ForkJoinTask.class);
1119	>
1120	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1121		try {
1122	<	return Unsafe.getUnsafe();
1122	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1123	>	} catch (NoSuchFieldException e) {
1124	>	// Convert Exception to corresponding Error
1125	>	NoSuchFieldError error = new NoSuchFieldError(field);
1126	>	error.initCause(e);
1127	>	throw error;
1128	>	}
1129	>	}
1130	>
1131	>	/**
1132	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1133	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1134	>	* into a jdk.
1135	>	*
1136	>	* @return a sun.misc.Unsafe
1137	>	*/
1138	>	private static sun.misc.Unsafe getUnsafe() {
1139	>	try {
1140	>	return sun.misc.Unsafe.getUnsafe();
1141		} catch (SecurityException se) {
1142		try {
1143		return java.security.AccessController.doPrivileged
1144	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1145	<	public Unsafe run() throws Exception {
1146	<	return getUnsafePrivileged();
1144	>	(new java.security
1145	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1146	>	public sun.misc.Unsafe run() throws Exception {
1147	>	java.lang.reflect.Field f = sun.misc
1148	>	.Unsafe.class.getDeclaredField("theUnsafe");
1149	>	f.setAccessible(true);
1150	>	return (sun.misc.Unsafe) f.get(null);
1151		}});
1152		} catch (java.security.PrivilegedActionException e) {
1153	<	throw e.getCause();
1153	>	throw new RuntimeException("Could not initialize intrinsics",
1154	>	e.getCause());
1155		}
1156		}
1157		}
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	–
1158		}

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