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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.5 by jsr166, Thu Mar 19 05:10:42 2009 UTC vs.
Revision 1.16 by jsr166, Fri Jul 24 23:47:01 2009 UTC

#	Line 9 | Line 9 | import java.io.Serializable;
9		import java.util.*;
10		import java.util.concurrent.*;
11		import java.util.concurrent.atomic.*;
12	–	import sun.misc.Unsafe;
13	–	import java.lang.reflect.*;
12
13		/**
14		* Abstract base class for tasks that run within a {@link
#	Line 22 | Line 20 | import java.lang.reflect.*;
20		* <p> A "main" ForkJoinTask begins execution when submitted to a
21		* {@link ForkJoinPool}. Once started, it will usually in turn start
22		* other subtasks.  As indicated by the name of this class, many
23	<	* programs using ForkJoinTasks employ only methods <code>fork</code>
24	<	* and <code>join</code>, or derivatives such as
25	<	* <code>invokeAll</code>.  However, this class also provides a number
23	>	* programs using ForkJoinTasks employ only methods {@code fork}
24	>	* and {@code join}, or derivatives such as
25	>	* {@code invokeAll}.  However, this class also provides a number
26		* of other methods that can come into play in advanced usages, as
27		* well as extension mechanics that allow support of new forms of
28		* fork/join processing.
#	Line 36 | Line 34 | import java.lang.reflect.*;
34		* operating on purely isolated objects.  The primary coordination
35		* mechanisms are {@link #fork}, that arranges asynchronous execution,
36		* and {@link #join}, that doesn't proceed until the task's result has
37	<	* been computed.  Computations should avoid <code>synchronized</code>
37	>	* been computed.  Computations should avoid {@code synchronized}
38		* methods or blocks, and should minimize other blocking
39		* synchronization apart from joining other tasks or using
40		* synchronizers such as Phasers that are advertised to cooperate with
#	Line 48 | Line 46 | import java.lang.reflect.*;
46		* performance, and the potential to indefinitely stall if the number
47		* of threads not waiting for IO or other external synchronization
48		* becomes exhausted. This usage restriction is in part enforced by
49	<	* not permitting checked exceptions such as <code>IOExceptions</code>
49	>	* not permitting checked exceptions such as {@code IOExceptions}
50		* to be thrown. However, computations may still encounter unchecked
51		* exceptions, that are rethrown to callers attempting join
52		* them. These exceptions may additionally include
#	Line 58 | Line 56 | import java.lang.reflect.*;
56		* <p>The primary method for awaiting completion and extracting
57		* results of a task is {@link #join}, but there are several variants:
58		* The {@link Future#get} methods support interruptible and/or timed
59	<	* waits for completion and report results using <code>Future</code>
59	>	* waits for completion and report results using {@code Future}
60		* conventions. Method {@link #helpJoin} enables callers to actively
61		* execute other tasks while awaiting joins, which is sometimes more
62		* efficient but only applies when all subtasks are known to be
63		* strictly tree-structured. Method {@link #invoke} is semantically
64	<	* equivalent to <code>fork(); join()</code> but always attempts to
64	>	* equivalent to {@code fork(); join()} but always attempts to
65		* begin execution in the current thread. The "<em>quiet</em>" forms
66		* of these methods do not extract results or report exceptions. These
67		* may be useful when a set of tasks are being executed, and you need
68		* to delay processing of results or exceptions until all complete.
69	<	* Method <code>invokeAll</code> (available in multiple versions)
69	>	* Method {@code invokeAll} (available in multiple versions)
70		* performs the most common form of parallel invocation: forking a set
71		* of tasks and joining them all.
72		*
#	Line 76 | Line 74 | import java.lang.reflect.*;
74		* Instead, you subclass one of the abstract classes that support a
75		* particular style of fork/join processing.  Normally, a concrete
76		* ForkJoinTask subclass declares fields comprising its parameters,
77	<	* established in a constructor, and then defines a <code>compute</code>
77	>	* established in a constructor, and then defines a {@code compute}
78		* method that somehow uses the control methods supplied by this base
79	<	* class. While these methods have <code>public</code> access (to allow
79	>	* class. While these methods have {@code public} access (to allow
80		* instances of different task subclasses to call each others
81		* methods), some of them may only be called from within other
82	<	* ForkJoinTasks. Attempts to invoke them in other contexts result in
83	<	* exceptions or errors possibly including ClassCastException.
82	>	* ForkJoinTasks (as may be determined using method {@link
83	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
84	>	* result in exceptions or errors, possibly including
85	>	* ClassCastException.
86		*
87	<	* <p>Most base support methods are <code>final</code> because their
87	>	* <p>Most base support methods are {@code final} because their
88		* implementations are intrinsically tied to the underlying
89		* lightweight task scheduling framework, and so cannot be overridden.
90		* Developers creating new basic styles of fork/join processing should
91	<	* minimally implement <code>protected</code> methods
92	<	* <code>exec</code>, <code>setRawResult</code>, and
93	<	* <code>getRawResult</code>, while also introducing an abstract
91	>	* minimally implement {@code protected} methods
92	>	* {@code exec}, {@code setRawResult}, and
93	>	* {@code getRawResult}, while also introducing an abstract
94		* computational method that can be implemented in its subclasses,
95	<	* possibly relying on other <code>protected</code> methods provided
95	>	* possibly relying on other {@code protected} methods provided
96		* by this class.
97		*
98		* <p>ForkJoinTasks should perform relatively small amounts of
99	<	* computations, othewise splitting into smaller tasks. As a very
99	>	* computations, otherwise splitting into smaller tasks. As a very
100		* rough rule of thumb, a task should perform more than 100 and less
101		* than 10000 basic computational steps. If tasks are too big, then
102	<	* parellelism cannot improve throughput. If too small, then memory
102	>	* parallelism cannot improve throughput. If too small, then memory
103		* and internal task maintenance overhead may overwhelm processing.
104		*
105	<	* <p>ForkJoinTasks are <code>Serializable</code>, which enables them
105	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them
106		* to be used in extensions such as remote execution frameworks. It is
107		* in general sensible to serialize tasks only before or after, but
108		* not during execution. Serialization is not relied on during
109		* execution itself.
110	+	*
111	+	* @since 1.7
112	+	* @author Doug Lea
113		*/
114		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
115
#	Line 128 | Line 131 | public abstract class ForkJoinTask<V> im
131		* currently unused. Also value 0x80000000 is available as spare
132		* completion value.
133		*/
134	<	volatile int status; // accessed directy by pool and workers
134	>	volatile int status; // accessed directly by pool and workers
135
136		static final int COMPLETION_MASK      = 0xe0000000;
137		static final int NORMAL               = 0xe0000000; // == mask
#	Line 141 | Line 144 | public abstract class ForkJoinTask<V> im
144		/**
145		* Table of exceptions thrown by tasks, to enable reporting by
146		* callers. Because exceptions are rare, we don't directly keep
147	<	* them with task objects, but instead us a weak ref table.  Note
147	>	* them with task objects, but instead use a weak ref table.  Note
148		* that cancellation exceptions don't appear in the table, but are
149		* instead recorded as status values.
150	<	* Todo: Use ConcurrentReferenceHashMap
150	>	* TODO: Use ConcurrentReferenceHashMap
151		*/
152		static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
153		Collections.synchronizedMap
#	Line 153 | Line 156 | public abstract class ForkJoinTask<V> im
156		// within-package utilities
157
158		/**
159	<	* Get current worker thread, or null if not a worker thread
159	>	* Gets current worker thread, or null if not a worker thread.
160		*/
161		static ForkJoinWorkerThread getWorker() {
162		Thread t = Thread.currentThread();
163	<	return ((t instanceof ForkJoinWorkerThread)?
164	<	(ForkJoinWorkerThread)t : null);
163	>	return ((t instanceof ForkJoinWorkerThread) ?
164	>	(ForkJoinWorkerThread) t : null);
165		}
166
167		final boolean casStatus(int cmp, int val) {
168	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
168	>	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
169		}
170
171		/**
#	Line 170 | Line 173 | public abstract class ForkJoinTask<V> im
173		*/
174		static void rethrowException(Throwable ex) {
175		if (ex != null)
176	<	_unsafe.throwException(ex);
176	>	UNSAFE.throwException(ex);
177		}
178
179		// Setting completion status
180
181		/**
182	<	* Mark completion and wake up threads waiting to join this task.
182	>	* Marks completion and wakes up threads waiting to join this task.
183	>	*
184		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
185		*/
186		final void setCompletion(int completion) {
187		ForkJoinPool pool = getPool();
188		if (pool != null) {
189		int s; // Clear signal bits while setting completion status
190	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
190	>	do {} while ((s = status) >= 0 && !casStatus(s, completion));
191
192		if ((s & SIGNAL_MASK) != 0) {
193		if ((s &= INTERNAL_SIGNAL_MASK) != 0)
194		pool.updateRunningCount(s);
195	<	synchronized(this) { notifyAll(); }
195	>	synchronized (this) { notifyAll(); }
196		}
197		}
198		else
#	Line 201 | Line 205 | public abstract class ForkJoinTask<V> im
205		*/
206		private void externallySetCompletion(int completion) {
207		int s;
208	<	do;while ((s = status) >= 0 &&
209	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
210	<	synchronized(this) { notifyAll(); }
208	>	do {} while ((s = status) >= 0 &&
209	>	!casStatus(s, (s & SIGNAL_MASK) | completion));
210	>	synchronized (this) { notifyAll(); }
211		}
212
213		/**
214	<	* Sets status to indicate normal completion
214	>	* Sets status to indicate normal completion.
215		*/
216		final void setNormalCompletion() {
217		// Try typical fast case -- single CAS, no signal, not already done.
218		// Manually expand casStatus to improve chances of inlining it
219	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
219	>	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
220		setCompletion(NORMAL);
221		}
222
223		// internal waiting and notification
224
225		/**
226	<	* Performs the actual monitor wait for awaitDone
226	>	* Performs the actual monitor wait for awaitDone.
227		*/
228		private void doAwaitDone() {
229		// Minimize lock bias and in/de-flation effects by maximizing
230		// chances of waiting inside sync
231		try {
232		while (status >= 0)
233	<	synchronized(this) { if (status >= 0) wait(); }
233	>	synchronized (this) { if (status >= 0) wait(); }
234		} catch (InterruptedException ie) {
235		onInterruptedWait();
236		}
237		}
238
239		/**
240	<	* Performs the actual monitor wait for awaitDone
240	>	* Performs the actual timed monitor wait for awaitDone.
241		*/
242		private void doAwaitDone(long startTime, long nanos) {
243	<	synchronized(this) {
243	>	synchronized (this) {
244		try {
245		while (status >= 0) {
246		long nt = nanos - System.nanoTime() - startTime;
247		if (nt <= 0)
248		break;
249	<	wait(nt / 1000000, (int)(nt % 1000000));
249	>	wait(nt / 1000000, (int) (nt % 1000000));
250		}
251		} catch (InterruptedException ie) {
252		onInterruptedWait();
#	Line 255 | Line 259 | public abstract class ForkJoinTask<V> im
259		/**
260		* Sets status to indicate there is joiner, then waits for join,
261		* surrounded with pool notifications.
262	+	*
263		* @return status upon exit
264		*/
265	<	private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
266	<	ForkJoinPool pool = w == null? null : w.pool;
265	>	private int awaitDone(ForkJoinWorkerThread w,
266	>	boolean maintainParallelism) {
267	>	ForkJoinPool pool = (w == null) ? null : w.pool;
268		int s;
269		while ((s = status) >= 0) {
270	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
270	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
271		if (pool == null || !pool.preJoin(this, maintainParallelism))
272		doAwaitDone();
273		if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
#	Line 274 | Line 280 | public abstract class ForkJoinTask<V> im
280
281		/**
282		* Timed version of awaitDone
283	+	*
284		* @return status upon exit
285		*/
286		private int awaitDone(ForkJoinWorkerThread w, long nanos) {
287	<	ForkJoinPool pool = w == null? null : w.pool;
287	>	ForkJoinPool pool = (w == null) ? null : w.pool;
288		int s;
289		while ((s = status) >= 0) {
290	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
290	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
291		long startTime = System.nanoTime();
292		if (pool == null || !pool.preJoin(this, false))
293		doAwaitDone(startTime, nanos);
#	Line 297 | Line 304 | public abstract class ForkJoinTask<V> im
304		}
305
306		/**
307	<	* Notify pool that thread is unblocked. Called by signalled
307	>	* Notifies pool that thread is unblocked. Called by signalled
308		* threads when woken by non-FJ threads (which is atypical).
309		*/
310		private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
311		int s;
312	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
312	>	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
313		if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
314		pool.updateRunningCount(s);
315		}
316
317		/**
318	<	* Notify pool to adjust counts on cancelled or timed out wait
318	>	* Notifies pool to adjust counts on cancelled or timed out wait.
319		*/
320		private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
321		if (pool != null) {
#	Line 323 | Line 330 | public abstract class ForkJoinTask<V> im
330		}
331
332		/**
333	<	* Handle interruptions during waits.
333	>	* Handles interruptions during waits.
334		*/
335		private void onInterruptedWait() {
336		ForkJoinWorkerThread w = getWorker();
#	Line 342 | Line 349 | public abstract class ForkJoinTask<V> im
349		}
350
351		/**
352	<	* Throws the exception associated with status s;
352	>	* Throws the exception associated with status s.
353	>	*
354		* @throws the exception
355		*/
356		private void reportException(int s) {
#	Line 355 | Line 363 | public abstract class ForkJoinTask<V> im
363		}
364
365		/**
366	<	* Returns result or throws exception using j.u.c.Future conventions
367	<	* Only call when isDone known to be true.
366	>	* Returns result or throws exception using j.u.c.Future conventions.
367	>	* Only call when {@code isDone} known to be true.
368		*/
369		private V reportFutureResult()
370		throws ExecutionException, InterruptedException {
#	Line 375 | Line 383 | public abstract class ForkJoinTask<V> im
383
384		/**
385		* Returns result or throws exception using j.u.c.Future conventions
386	<	* with timeouts
386	>	* with timeouts.
387		*/
388		private V reportTimedFutureResult()
389		throws InterruptedException, ExecutionException, TimeoutException {
#	Line 396 | Line 404 | public abstract class ForkJoinTask<V> im
404
405		/**
406		* Calls exec, recording completion, and rethrowing exception if
407	<	* encountered. Caller should normally check status before calling
407	>	* encountered. Caller should normally check status before calling.
408	>	*
409		* @return true if completed normally
410		*/
411		private boolean tryExec() {
#	Line 414 | Line 423 | public abstract class ForkJoinTask<V> im
423
424		/**
425		* Main execution method used by worker threads. Invokes
426	<	* base computation unless already complete
426	>	* base computation unless already complete.
427		*/
428		final void quietlyExec() {
429		if (status >= 0) {
430		try {
431		if (!exec())
432		return;
433	<	} catch(Throwable rex) {
433	>	} catch (Throwable rex) {
434		setDoneExceptionally(rex);
435		return;
436		}
#	Line 430 | Line 439 | public abstract class ForkJoinTask<V> im
439		}
440
441		/**
442	<	* Calls exec, recording but not rethrowing exception
443	<	* Caller should normally check status before calling
442	>	* Calls exec(), recording but not rethrowing exception.
443	>	* Caller should normally check status before calling.
444	>	*
445		* @return true if completed normally
446		*/
447		private boolean tryQuietlyInvoke() {
#	Line 447 | Line 457 | public abstract class ForkJoinTask<V> im
457		}
458
459		/**
460	<	* Cancel, ignoring any exceptions it throws
460	>	* Cancels, ignoring any exceptions it throws.
461		*/
462		final void cancelIgnoringExceptions() {
463		try {
464		cancel(false);
465	<	} catch(Throwable ignore) {
465	>	} catch (Throwable ignore) {
466		}
467		}
468
#	Line 464 | Line 474 | public abstract class ForkJoinTask<V> im
474		ForkJoinTask<?> t;
475		while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
476		t.quietlyExec();
477	<	return (s >= 0)? awaitDone(w, false) : s; // block if no work
477	>	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
478		}
479
480		// public methods
#	Line 474 | Line 484 | public abstract class ForkJoinTask<V> im
484		* necessarily enforced, it is a usage error to fork a task more
485		* than once unless it has completed and been reinitialized.  This
486		* method may be invoked only from within ForkJoinTask
487	<	* computations. Attempts to invoke in other contexts result in
488	<	* exceptions or errors possibly including ClassCastException.
487	>	* computations (as may be determined using method {@link
488	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
489	>	* in exceptions or errors, possibly including ClassCastException.
490		*/
491		public final void fork() {
492	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
492	>	((ForkJoinWorkerThread) Thread.currentThread())
493	>	.pushTask(this);
494		}
495
496		/**
497		* Returns the result of the computation when it is ready.
498	<	* This method differs from <code>get</code> in that abnormal
498	>	* This method differs from {@code get} in that abnormal
499		* completion results in RuntimeExceptions or Errors, not
500		* ExecutionExceptions.
501		*
#	Line 499 | Line 511 | public abstract class ForkJoinTask<V> im
511		/**
512		* Commences performing this task, awaits its completion if
513		* necessary, and return its result.
514	+	*
515		* @throws Throwable (a RuntimeException, Error, or unchecked
516	<	* exception) if the underlying computation did so.
516	>	* exception) if the underlying computation did so
517		* @return the computed result
518		*/
519		public final V invoke() {
#	Line 511 | Line 524 | public abstract class ForkJoinTask<V> im
524		}
525
526		/**
527	<	* Forks both tasks, returning when <code>isDone</code> holds for
527	>	* Forks both tasks, returning when {@code isDone} holds for
528		* both of them or an exception is encountered. This method may be
529	<	* invoked only from within ForkJoinTask computations. Attempts to
530	<	* invoke in other contexts result in exceptions or errors
529	>	* invoked only from within ForkJoinTask computations (as may be
530	>	* determined using method {@link #inForkJoinPool}). Attempts to
531	>	* invoke in other contexts result in exceptions or errors,
532		* possibly including ClassCastException.
533	+	*
534		* @param t1 one task
535		* @param t2 the other task
536		* @throws NullPointerException if t1 or t2 are null
537	<	* @throws RuntimeException or Error if either task did so.
537	>	* @throws RuntimeException or Error if either task did so
538		*/
539		public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
540		t2.fork();
#	Line 528 | Line 543 | public abstract class ForkJoinTask<V> im
543		}
544
545		/**
546	<	* Forks the given tasks, returning when <code>isDone</code> holds
546	>	* Forks the given tasks, returning when {@code isDone} holds
547		* for all of them. If any task encounters an exception, others
548		* may be cancelled.  This method may be invoked only from within
549	<	* ForkJoinTask computations. Attempts to invoke in other contexts
550	<	* result in exceptions or errors possibly including ClassCastException.
549	>	* ForkJoinTask computations (as may be determined using method
550	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
551	>	* result in exceptions or errors, possibly including
552	>	* ClassCastException.
553	>	*
554		* @param tasks the array of tasks
555	<	* @throws NullPointerException if tasks or any element are null.
556	<	* @throws RuntimeException or Error if any task did so.
555	>	* @throws NullPointerException if tasks or any element are null
556	>	* @throws RuntimeException or Error if any task did so
557		*/
558		public static void invokeAll(ForkJoinTask<?>... tasks) {
559		Throwable ex = null;
#	Line 572 | Line 590 | public abstract class ForkJoinTask<V> im
590
591		/**
592		* Forks all tasks in the collection, returning when
593	<	* <code>isDone</code> holds for all of them. If any task
593	>	* {@code isDone} holds for all of them. If any task
594		* encounters an exception, others may be cancelled.  This method
595	<	* may be invoked only from within ForkJoinTask
596	<	* computations. Attempts to invoke in other contexts resul!t in
597	<	* exceptions or errors possibly including ClassCastException.
595	>	* may be invoked only from within ForkJoinTask computations (as
596	>	* may be determined using method {@link
597	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
598	>	* in exceptions or errors, possibly including ClassCastException.
599	>	*
600		* @param tasks the collection of tasks
601	<	* @throws NullPointerException if tasks or any element are null.
602	<	* @throws RuntimeException or Error if any task did so.
601	>	* @throws NullPointerException if tasks or any element are null
602	>	* @throws RuntimeException or Error if any task did so
603		*/
604		public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
605	<	if (!(tasks instanceof List)) {
606	<	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
605	>	if (!(tasks instanceof List<?>)) {
606	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
607		return;
608		}
609	+	@SuppressWarnings("unchecked")
610		List<? extends ForkJoinTask<?>> ts =
611	<	(List<? extends ForkJoinTask<?>>)tasks;
611	>	(List<? extends ForkJoinTask<?>>) tasks;
612		Throwable ex = null;
613		int last = ts.size() - 1;
614		for (int i = last; i >= 0; --i) {
#	Line 623 | Line 644 | public abstract class ForkJoinTask<V> im
644		/**
645		* Returns true if the computation performed by this task has
646		* completed (or has been cancelled).
647	+	*
648		* @return true if this computation has completed
649		*/
650		public final boolean isDone() {
#	Line 631 | Line 653 | public abstract class ForkJoinTask<V> im
653
654		/**
655		* Returns true if this task was cancelled.
656	+	*
657		* @return true if this task was cancelled
658		*/
659		public final boolean isCancelled() {
#	Line 639 | Line 662 | public abstract class ForkJoinTask<V> im
662
663		/**
664		* Asserts that the results of this task's computation will not be
665	<	* used. If a cancellation occurs before atempting to execute this
666	<	* task, then execution will be suppressed, <code>isCancelled</code>
667	<	* will report true, and <code>join</code> will result in a
668	<	* <code>CancellationException</code> being thrown. Otherwise, when
665	>	* used. If a cancellation occurs before attempting to execute this
666	>	* task, then execution will be suppressed, {@code isCancelled}
667	>	* will report true, and {@code join} will result in a
668	>	* {@code CancellationException} being thrown. Otherwise, when
669		* cancellation races with completion, there are no guarantees
670	<	* about whether <code>isCancelled</code> will report true, whether
671	<	* <code>join</code> will return normally or via an exception, or
670	>	* about whether {@code isCancelled} will report true, whether
671	>	* {@code join} will return normally or via an exception, or
672		* whether these behaviors will remain consistent upon repeated
673		* invocation.
674		*
#	Line 656 | Line 679 | public abstract class ForkJoinTask<V> im
679		* <p> This method is designed to be invoked by <em>other</em>
680		* tasks. To terminate the current task, you can just return or
681		* throw an unchecked exception from its computation method, or
682	<	* invoke <code>completeExceptionally</code>.
682	>	* invoke {@code completeExceptionally}.
683		*
684		* @param mayInterruptIfRunning this value is ignored in the
685		* default implementation because tasks are not in general
686	<	* cancelled via interruption.
686	>	* cancelled via interruption
687		*
688		* @return true if this task is now cancelled
689		*/
#	Line 670 | Line 693 | public abstract class ForkJoinTask<V> im
693		}
694
695		/**
696	<	* Returns true if this task threw an exception or was cancelled
696	>	* Returns true if this task threw an exception or was cancelled.
697	>	*
698		* @return true if this task threw an exception or was cancelled
699		*/
700		public final boolean isCompletedAbnormally() {
#	Line 681 | Line 705 | public abstract class ForkJoinTask<V> im
705		* Returns the exception thrown by the base computation, or a
706		* CancellationException if cancelled, or null if none or if the
707		* method has not yet completed.
708	+	*
709		* @return the exception, or null if none
710		*/
711		public final Throwable getException() {
#	Line 695 | Line 720 | public abstract class ForkJoinTask<V> im
720		/**
721		* Completes this task abnormally, and if not already aborted or
722		* cancelled, causes it to throw the given exception upon
723	<	* <code>join</code> and related operations. This method may be used
723	>	* {@code join} and related operations. This method may be used
724		* to induce exceptions in asynchronous tasks, or to force
725		* completion of tasks that would not otherwise complete.  Its use
726		* in other situations is likely to be wrong.  This method is
727	<	* overridable, but overridden versions must invoke <code>super</code>
727	>	* overridable, but overridden versions must invoke {@code super}
728		* implementation to maintain guarantees.
729		*
730		* @param ex the exception to throw. If this exception is
#	Line 708 | Line 733 | public abstract class ForkJoinTask<V> im
733		*/
734		public void completeExceptionally(Throwable ex) {
735		setDoneExceptionally((ex instanceof RuntimeException) ||
736	<	(ex instanceof Error)? ex :
736	>	(ex instanceof Error) ? ex :
737		new RuntimeException(ex));
738		}
739
740		/**
741		* Completes this task, and if not already aborted or cancelled,
742	<	* returning a <code>null</code> result upon <code>join</code> and related
742	>	* returning a {@code null} result upon {@code join} and related
743		* operations. This method may be used to provide results for
744		* asynchronous tasks, or to provide alternative handling for
745		* tasks that would not otherwise complete normally. Its use in
746		* other situations is likely to be wrong. This method is
747	<	* overridable, but overridden versions must invoke <code>super</code>
747	>	* overridable, but overridden versions must invoke {@code super}
748		* implementation to maintain guarantees.
749		*
750	<	* @param value the result value for this task.
750	>	* @param value the result value for this task
751		*/
752		public void complete(V value) {
753		try {
754		setRawResult(value);
755	<	} catch(Throwable rex) {
755	>	} catch (Throwable rex) {
756		setDoneExceptionally(rex);
757		return;
758		}
#	Line 752 | Line 777 | public abstract class ForkJoinTask<V> im
777		/**
778		* Possibly executes other tasks until this task is ready, then
779		* returns the result of the computation.  This method may be more
780	<	* efficient than <code>join</code>, but is only applicable when
781	<	* there are no potemtial dependencies between continuation of the
780	>	* efficient than {@code join}, but is only applicable when
781	>	* there are no potential dependencies between continuation of the
782		* current task and that of any other task that might be executed
783		* while helping. (This usually holds for pure divide-and-conquer
784		* tasks). This method may be invoked only from within
785	<	* ForkJoinTask computations. Attempts to invoke in other contexts
786	<	* resul!t in exceptions or errors possibly including ClassCastException.
785	>	* ForkJoinTask computations (as may be determined using method
786	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
787	>	* result in exceptions or errors, possibly including
788	>	* ClassCastException.
789	>	*
790		* @return the computed result
791		*/
792		public final V helpJoin() {
793	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
793	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
794		if (status < 0 || !w.unpushTask(this) || !tryExec())
795		reportException(busyJoin(w));
796		return getRawResult();
#	Line 771 | Line 799 | public abstract class ForkJoinTask<V> im
799		/**
800		* Possibly executes other tasks until this task is ready.  This
801		* method may be invoked only from within ForkJoinTask
802	<	* computations. Attempts to invoke in other contexts resul!t in
803	<	* exceptions or errors possibly including ClassCastException.
802	>	* computations (as may be determined using method {@link
803	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
804	>	* in exceptions or errors, possibly including ClassCastException.
805		*/
806		public final void quietlyHelpJoin() {
807		if (status >= 0) {
808		ForkJoinWorkerThread w =
809	<	(ForkJoinWorkerThread)(Thread.currentThread());
809	>	(ForkJoinWorkerThread) Thread.currentThread();
810		if (!w.unpushTask(this) || !tryQuietlyInvoke())
811		busyJoin(w);
812		}
#	Line 816 | Line 845 | public abstract class ForkJoinTask<V> im
845		* joined, instead executing them until all are processed.
846		*/
847		public static void helpQuiesce() {
848	<	((ForkJoinWorkerThread)(Thread.currentThread())).
849	<	helpQuiescePool();
848	>	((ForkJoinWorkerThread) Thread.currentThread())
849	>	.helpQuiescePool();
850		}
851
852		/**
853		* Resets the internal bookkeeping state of this task, allowing a
854	<	* subsequent <code>fork</code>. This method allows repeated reuse of
854	>	* subsequent {@code fork}. This method allows repeated reuse of
855		* this task, but only if reuse occurs when this task has either
856		* never been forked, or has been forked, then completed and all
857		* outstanding joins of this task have also completed. Effects
#	Line 838 | Line 867 | public abstract class ForkJoinTask<V> im
867
868		/**
869		* Returns the pool hosting the current task execution, or null
870	<	* if this task is executing outside of any pool.
871	<	* @return the pool, or null if none.
870	>	* if this task is executing outside of any ForkJoinPool.
871	>	*
872	>	* @return the pool, or null if none
873		*/
874		public static ForkJoinPool getPool() {
875		Thread t = Thread.currentThread();
876	<	return ((t instanceof ForkJoinWorkerThread)?
877	<	((ForkJoinWorkerThread)t).pool : null);
876	>	return (t instanceof ForkJoinWorkerThread) ?
877	>	((ForkJoinWorkerThread) t).pool : null;
878	>	}
879	>
880	>	/**
881	>	* Returns {@code true} if the current thread is executing as a
882	>	* ForkJoinPool computation.
883	>	*
884	>	* @return {@code true} if the current thread is executing as a
885	>	* ForkJoinPool computation, or false otherwise
886	>	*/
887	>	public static boolean inForkJoinPool() {
888	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
889		}
890
891		/**
#	Line 854 | Line 895 | public abstract class ForkJoinTask<V> im
895		* another thread.  This method may be useful when arranging
896		* alternative local processing of tasks that could have been, but
897		* were not, stolen. This method may be invoked only from within
898	<	* ForkJoinTask computations. Attempts to invoke in other contexts
899	<	* result in exceptions or errors possibly including ClassCastException.
898	>	* ForkJoinTask computations (as may be determined using method
899	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
900	>	* result in exceptions or errors, possibly including
901	>	* ClassCastException.
902	>	*
903		* @return true if unforked
904		*/
905		public boolean tryUnfork() {
906	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
906	>	return ((ForkJoinWorkerThread) Thread.currentThread())
907	>	.unpushTask(this);
908		}
909
910		/**
#	Line 867 | Line 912 | public abstract class ForkJoinTask<V> im
912		* forked by the current worker thread but not yet executed. This
913		* value may be useful for heuristic decisions about whether to
914		* fork other tasks.
915	+	*
916		* @return the number of tasks
917		*/
918		public static int getQueuedTaskCount() {
919	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
920	<	getQueueSize();
919	>	return ((ForkJoinWorkerThread) Thread.currentThread())
920	>	.getQueueSize();
921		}
922
923		/**
924	<	* Returns a estimate of how many more locally queued tasks are
924	>	* Returns an estimate of how many more locally queued tasks are
925		* held by the current worker thread than there are other worker
926		* threads that might steal them.  This value may be useful for
927		* heuristic decisions about whether to fork other tasks. In many
#	Line 883 | Line 929 | public abstract class ForkJoinTask<V> im
929		* aim to maintain a small constant surplus (for example, 3) of
930		* tasks, and to process computations locally if this threshold is
931		* exceeded.
932	+	*
933		* @return the surplus number of tasks, which may be negative
934		*/
935		public static int getSurplusQueuedTaskCount() {
936	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
936	>	return ((ForkJoinWorkerThread) Thread.currentThread())
937		.getEstimatedSurplusTaskCount();
938		}
939
940		// Extension methods
941
942		/**
943	<	* Returns the result that would be returned by <code>join</code>,
943	>	* Returns the result that would be returned by {@code join},
944		* even if this task completed abnormally, or null if this task is
945		* not known to have been completed.  This method is designed to
946		* aid debugging, as well as to support extensions. Its use in any
947		* other context is discouraged.
948		*
949	<	* @return the result, or null if not completed.
949	>	* @return the result, or null if not completed
950		*/
951		public abstract V getRawResult();
952
#	Line 918 | Line 965 | public abstract class ForkJoinTask<V> im
965		* called otherwise. The return value controls whether this task
966		* is considered to be done normally. It may return false in
967		* asynchronous actions that require explicit invocations of
968	<	* <code>complete</code> to become joinable. It may throw exceptions
968	>	* {@code complete} to become joinable. It may throw exceptions
969		* to indicate abnormal exit.
970	+	*
971		* @return true if completed normally
972		* @throws Error or RuntimeException if encountered during computation
973		*/
974		protected abstract boolean exec();
975
976		/**
977	<	* Returns, but does not unschedule or execute, the task most
978	<	* recently forked by the current thread but not yet executed, if
979	<	* one is available. There is no guarantee that this task will
980	<	* actually be polled or executed next.
981	<	* This method is designed primarily to support extensions,
982	<	* and is unlikely to be useful otherwise.
983	<	* This method may be invoked only from within
984	<	* ForkJoinTask computations. Attempts to invoke in other contexts
985	<	* result in exceptions or errors possibly including ClassCastException.
977	>	* Returns, but does not unschedule or execute, the task queued by
978	>	* the current thread but not yet executed, if one is
979	>	* available. There is no guarantee that this task will actually
980	>	* be polled or executed next.  This method is designed primarily
981	>	* to support extensions, and is unlikely to be useful otherwise.
982	>	* This method may be invoked only from within ForkJoinTask
983	>	* computations (as may be determined using method {@link
984	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
985	>	* in exceptions or errors, possibly including ClassCastException.
986		*
987		* @return the next task, or null if none are available
988		*/
989		protected static ForkJoinTask<?> peekNextLocalTask() {
990	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask();
990	>	return ((ForkJoinWorkerThread) Thread.currentThread())
991	>	.peekTask();
992		}
993
994		/**
995	<	* Unschedules and returns, without executing, the task most
996	<	* recently forked by the current thread but not yet executed.
997	<	* This method is designed primarily to support extensions,
998	<	* and is unlikely to be useful otherwise.
999	<	* This method may be invoked only from within
1000	<	* ForkJoinTask computations. Attempts to invoke in other contexts
1001	<	* result in exceptions or errors possibly including ClassCastException.
995	>	* Unschedules and returns, without executing, the next task
996	>	* queued by the current thread but not yet executed.  This method
997	>	* is designed primarily to support extensions, and is unlikely to
998	>	* be useful otherwise.  This method may be invoked only from
999	>	* within ForkJoinTask computations (as may be determined using
1000	>	* method {@link #inForkJoinPool}). Attempts to invoke in other
1001	>	* contexts result in exceptions or errors, possibly including
1002	>	* ClassCastException.
1003		*
1004		* @return the next task, or null if none are available
1005		*/
1006		protected static ForkJoinTask<?> pollNextLocalTask() {
1007	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).popTask();
1007	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1008	>	.pollLocalTask();
1009		}
1010
1011		/**
1012	<	* Unschedules and returns, without executing, the task most
1013	<	* recently forked by the current thread but not yet executed, if
1014	<	* one is available, or if not available, a task that was forked
1015	<	* by some other thread, if available. Availability may be
1016	<	* transient, so a <code>null</code> result does not necessarily
1017	<	* imply quiecence of the pool this task is operating in.
1018	<	* This method is designed primarily to support extensions,
1019	<	* and is unlikely to be useful otherwise.
1020	<	* This method may be invoked only from within
1021	<	* ForkJoinTask computations. Attempts to invoke in other contexts
1022	<	* result in exceptions or errors possibly including ClassCastException.
1012	>	* Unschedules and returns, without executing, the next task
1013	>	* queued by the current thread but not yet executed, if one is
1014	>	* available, or if not available, a task that was forked by some
1015	>	* other thread, if available. Availability may be transient, so a
1016	>	* {@code null} result does not necessarily imply quiescence
1017	>	* of the pool this task is operating in.  This method is designed
1018	>	* primarily to support extensions, and is unlikely to be useful
1019	>	* otherwise.  This method may be invoked only from within
1020	>	* ForkJoinTask computations (as may be determined using method
1021	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1022	>	* result in exceptions or errors, possibly including
1023	>	* ClassCastException.
1024		*
1025		* @return a task, or null if none are available
1026		*/
1027		protected static ForkJoinTask<?> pollTask() {
1028	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
1029	<	pollTask();
1028	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1029	>	.pollTask();
1030		}
1031
1032		// Serialization support
#	Line 985 | Line 1037 | public abstract class ForkJoinTask<V> im
1037		* Save the state to a stream.
1038		*
1039		* @serialData the current run status and the exception thrown
1040	<	* during execution, or null if none.
1040	>	* during execution, or null if none
1041		* @param s the stream
1042		*/
1043		private void writeObject(java.io.ObjectOutputStream s)
#	Line 996 | Line 1048 | public abstract class ForkJoinTask<V> im
1048
1049		/**
1050		* Reconstitute the instance from a stream.
1051	+	*
1052		* @param s the stream
1053		*/
1054		private void readObject(java.io.ObjectInputStream s)
#	Line 1005 | Line 1058 | public abstract class ForkJoinTask<V> im
1058		status |= EXTERNAL_SIGNAL; // conservatively set external signal
1059		Object ex = s.readObject();
1060		if (ex != null)
1061	<	setDoneExceptionally((Throwable)ex);
1061	>	setDoneExceptionally((Throwable) ex);
1062		}
1063
1064	<	// Temporary Unsafe mechanics for preliminary release
1065	<	private static Unsafe getUnsafe() throws Throwable {
1064	>	// Unsafe mechanics for jsr166y 3rd party package.
1065	>	private static sun.misc.Unsafe getUnsafe() {
1066		try {
1067	<	return Unsafe.getUnsafe();
1067	>	return sun.misc.Unsafe.getUnsafe();
1068		} catch (SecurityException se) {
1069		try {
1070		return java.security.AccessController.doPrivileged
1071	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1072	<	public Unsafe run() throws Exception {
1073	<	return getUnsafePrivileged();
1071	>	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1072	>	public sun.misc.Unsafe run() throws Exception {
1073	>	return getUnsafeByReflection();
1074		}});
1075		} catch (java.security.PrivilegedActionException e) {
1076	<	throw e.getCause();
1076	>	throw new RuntimeException("Could not initialize intrinsics",
1077	>	e.getCause());
1078		}
1079		}
1080		}
1081
1082	<	private static Unsafe getUnsafePrivileged()
1082	>	private static sun.misc.Unsafe getUnsafeByReflection()
1083		throws NoSuchFieldException, IllegalAccessException {
1084	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1084	>	java.lang.reflect.Field f =
1085	>	sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
1086		f.setAccessible(true);
1087	<	return (Unsafe) f.get(null);
1087	>	return (sun.misc.Unsafe) f.get(null);
1088		}
1089
1090	<	private static long fieldOffset(String fieldName)
1036	<	throws NoSuchFieldException {
1037	<	return _unsafe.objectFieldOffset
1038	<	(ForkJoinTask.class.getDeclaredField(fieldName));
1039	<	}
1040	<
1041	<	static final Unsafe _unsafe;
1042	<	static final long statusOffset;
1043	<
1044	<	static {
1090	>	private static long fieldOffset(String fieldName, Class<?> klazz) {
1091		try {
1092	<	_unsafe = getUnsafe();
1093	<	statusOffset = fieldOffset("status");
1094	<	} catch (Throwable e) {
1095	<	throw new RuntimeException("Could not initialize intrinsics", e);
1092	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
1093	>	} catch (NoSuchFieldException e) {
1094	>	// Convert Exception to Error
1095	>	NoSuchFieldError error = new NoSuchFieldError(fieldName);
1096	>	error.initCause(e);
1097	>	throw error;
1098		}
1099		}
1100
1101	+	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1102	+	static final long statusOffset =
1103	+	fieldOffset("status", ForkJoinTask.class);
1104	+
1105		}

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