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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.7 by jsr166, Mon Jul 20 21:45:06 2009 UTC vs.
Revision 1.12 by jsr166, Wed Jul 22 01:36:51 2009 UTC

#	Line 22 | Line 22 | import java.lang.reflect.*;
22		* <p> A "main" ForkJoinTask begins execution when submitted to a
23		* {@link ForkJoinPool}. Once started, it will usually in turn start
24		* other subtasks.  As indicated by the name of this class, many
25	<	* programs using ForkJoinTasks employ only methods <code>fork</code>
26	<	* and <code>join</code>, or derivatives such as
27	<	* <code>invokeAll</code>.  However, this class also provides a number
25	>	* programs using ForkJoinTasks employ only methods {@code fork}
26	>	* and {@code join}, or derivatives such as
27	>	* {@code invokeAll}.  However, this class also provides a number
28		* of other methods that can come into play in advanced usages, as
29		* well as extension mechanics that allow support of new forms of
30		* fork/join processing.
#	Line 36 | Line 36 | import java.lang.reflect.*;
36		* operating on purely isolated objects.  The primary coordination
37		* mechanisms are {@link #fork}, that arranges asynchronous execution,
38		* and {@link #join}, that doesn't proceed until the task's result has
39	<	* been computed.  Computations should avoid <code>synchronized</code>
39	>	* been computed.  Computations should avoid {@code synchronized}
40		* methods or blocks, and should minimize other blocking
41		* synchronization apart from joining other tasks or using
42		* synchronizers such as Phasers that are advertised to cooperate with
#	Line 48 | Line 48 | import java.lang.reflect.*;
48		* performance, and the potential to indefinitely stall if the number
49		* of threads not waiting for IO or other external synchronization
50		* becomes exhausted. This usage restriction is in part enforced by
51	<	* not permitting checked exceptions such as <code>IOExceptions</code>
51	>	* not permitting checked exceptions such as {@code IOExceptions}
52		* to be thrown. However, computations may still encounter unchecked
53		* exceptions, that are rethrown to callers attempting join
54		* them. These exceptions may additionally include
#	Line 58 | Line 58 | import java.lang.reflect.*;
58		* <p>The primary method for awaiting completion and extracting
59		* results of a task is {@link #join}, but there are several variants:
60		* The {@link Future#get} methods support interruptible and/or timed
61	<	* waits for completion and report results using <code>Future</code>
61	>	* waits for completion and report results using {@code Future}
62		* conventions. Method {@link #helpJoin} enables callers to actively
63		* execute other tasks while awaiting joins, which is sometimes more
64		* efficient but only applies when all subtasks are known to be
65		* strictly tree-structured. Method {@link #invoke} is semantically
66	<	* equivalent to <code>fork(); join()</code> but always attempts to
66	>	* equivalent to {@code fork(); join()} but always attempts to
67		* begin execution in the current thread. The "<em>quiet</em>" forms
68		* of these methods do not extract results or report exceptions. These
69		* may be useful when a set of tasks are being executed, and you need
70		* to delay processing of results or exceptions until all complete.
71	<	* Method <code>invokeAll</code> (available in multiple versions)
71	>	* Method {@code invokeAll} (available in multiple versions)
72		* performs the most common form of parallel invocation: forking a set
73		* of tasks and joining them all.
74		*
#	Line 76 | Line 76 | import java.lang.reflect.*;
76		* Instead, you subclass one of the abstract classes that support a
77		* particular style of fork/join processing.  Normally, a concrete
78		* ForkJoinTask subclass declares fields comprising its parameters,
79	<	* established in a constructor, and then defines a <code>compute</code>
79	>	* established in a constructor, and then defines a {@code compute}
80		* method that somehow uses the control methods supplied by this base
81	<	* class. While these methods have <code>public</code> access (to allow
81	>	* class. While these methods have {@code public} access (to allow
82		* instances of different task subclasses to call each others
83		* methods), some of them may only be called from within other
84		* ForkJoinTasks. Attempts to invoke them in other contexts result in
85		* exceptions or errors possibly including 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();
#	Line 162 | Line 165 | public abstract class ForkJoinTask<V> im
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) {
#	Line 212 | Line 216 | public abstract class ForkJoinTask<V> im
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
#	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) {
#	Line 297 | Line 302 | public abstract class ForkJoinTask<V> im
302		}
303
304		/**
305	<	* Notify pool that thread is unblocked. Called by signalled
305	>	* Notifies pool that thread is unblocked. Called by signalled
306		* threads when woken by non-FJ threads (which is atypical).
307		*/
308		private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
#	Line 308 | Line 313 | public abstract class ForkJoinTask<V> im
313		}
314
315		/**
316	<	* Notify pool to adjust counts on cancelled or timed out wait
316	>	* Notifies pool to adjust counts on cancelled or timed out wait.
317		*/
318		private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
319		if (pool != null) {
#	Line 323 | Line 328 | public abstract class ForkJoinTask<V> im
328		}
329
330		/**
331	<	* Handle interruptions during waits.
331	>	* Handles interruptions during waits.
332		*/
333		private void onInterruptedWait() {
334		ForkJoinWorkerThread w = getWorker();
#	Line 342 | Line 347 | public abstract class ForkJoinTask<V> im
347		}
348
349		/**
350	<	* Throws the exception associated with status s;
350	>	* Throws the exception associated with status s.
351	>	*
352		* @throws the exception
353		*/
354		private void reportException(int s) {
#	Line 355 | Line 361 | public abstract class ForkJoinTask<V> im
361		}
362
363		/**
364	<	* Returns result or throws exception using j.u.c.Future conventions
364	>	* Returns result or throws exception using j.u.c.Future conventions.
365		* Only call when isDone known to be true.
366		*/
367		private V reportFutureResult()
#	Line 375 | Line 381 | public abstract class ForkJoinTask<V> im
381
382		/**
383		* Returns result or throws exception using j.u.c.Future conventions
384	<	* with timeouts
384	>	* with timeouts.
385		*/
386		private V reportTimedFutureResult()
387		throws InterruptedException, ExecutionException, TimeoutException {
#	Line 396 | Line 402 | public abstract class ForkJoinTask<V> im
402
403		/**
404		* Calls exec, recording completion, and rethrowing exception if
405	<	* encountered. Caller should normally check status before calling
405	>	* encountered. Caller should normally check status before calling.
406	>	*
407		* @return true if completed normally
408		*/
409		private boolean tryExec() {
#	Line 414 | Line 421 | public abstract class ForkJoinTask<V> im
421
422		/**
423		* Main execution method used by worker threads. Invokes
424	<	* base computation unless already complete
424	>	* base computation unless already complete.
425		*/
426		final void quietlyExec() {
427		if (status >= 0) {
#	Line 430 | Line 437 | public abstract class ForkJoinTask<V> im
437		}
438
439		/**
440	<	* Calls exec, recording but not rethrowing exception
441	<	* Caller should normally check status before calling
440	>	* Calls exec(), recording but not rethrowing exception.
441	>	* Caller should normally check status before calling.
442	>	*
443		* @return true if completed normally
444		*/
445		private boolean tryQuietlyInvoke() {
#	Line 447 | Line 455 | public abstract class ForkJoinTask<V> im
455		}
456
457		/**
458	<	* Cancel, ignoring any exceptions it throws
458	>	* Cancels, ignoring any exceptions it throws.
459		*/
460		final void cancelIgnoringExceptions() {
461		try {
#	Line 483 | Line 491 | public abstract class ForkJoinTask<V> im
491
492		/**
493		* Returns the result of the computation when it is ready.
494	<	* This method differs from <code>get</code> in that abnormal
494	>	* This method differs from {@code get} in that abnormal
495		* completion results in RuntimeExceptions or Errors, not
496		* ExecutionExceptions.
497		*
#	Line 499 | Line 507 | public abstract class ForkJoinTask<V> im
507		/**
508		* Commences performing this task, awaits its completion if
509		* necessary, and return its result.
510	+	*
511		* @throws Throwable (a RuntimeException, Error, or unchecked
512	<	* exception) if the underlying computation did so.
512	>	* exception) if the underlying computation did so
513		* @return the computed result
514		*/
515		public final V invoke() {
#	Line 511 | Line 520 | public abstract class ForkJoinTask<V> im
520		}
521
522		/**
523	<	* Forks both tasks, returning when <code>isDone</code> holds for
523	>	* Forks both tasks, returning when {@code isDone} holds for
524		* both of them or an exception is encountered. This method may be
525		* invoked only from within ForkJoinTask computations. Attempts to
526		* invoke in other contexts result in exceptions or errors
527		* possibly including ClassCastException.
528	+	*
529		* @param t1 one task
530		* @param t2 the other task
531		* @throws NullPointerException if t1 or t2 are null
532	<	* @throws RuntimeException or Error if either task did so.
532	>	* @throws RuntimeException or Error if either task did so
533		*/
534		public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
535		t2.fork();
#	Line 528 | Line 538 | public abstract class ForkJoinTask<V> im
538		}
539
540		/**
541	<	* Forks the given tasks, returning when <code>isDone</code> holds
541	>	* Forks the given tasks, returning when {@code isDone} holds
542		* for all of them. If any task encounters an exception, others
543		* may be cancelled.  This method may be invoked only from within
544		* ForkJoinTask computations. Attempts to invoke in other contexts
545		* result in exceptions or errors possibly including ClassCastException.
546	+	*
547		* @param tasks the array of tasks
548	<	* @throws NullPointerException if tasks or any element are null.
549	<	* @throws RuntimeException or Error if any task did so.
548	>	* @throws NullPointerException if tasks or any element are null
549	>	* @throws RuntimeException or Error if any task did so
550		*/
551		public static void invokeAll(ForkJoinTask<?>... tasks) {
552		Throwable ex = null;
#	Line 572 | Line 583 | public abstract class ForkJoinTask<V> im
583
584		/**
585		* Forks all tasks in the collection, returning when
586	<	* <code>isDone</code> holds for all of them. If any task
586	>	* {@code isDone} holds for all of them. If any task
587		* encounters an exception, others may be cancelled.  This method
588		* may be invoked only from within ForkJoinTask
589	<	* computations. Attempts to invoke in other contexts resul!t in
589	>	* computations. Attempts to invoke in other contexts result in
590		* exceptions or errors possibly including ClassCastException.
591	+	*
592		* @param tasks the collection of tasks
593	<	* @throws NullPointerException if tasks or any element are null.
594	<	* @throws RuntimeException or Error if any task did so.
593	>	* @throws NullPointerException if tasks or any element are null
594	>	* @throws RuntimeException or Error if any task did so
595		*/
596		public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
597		if (!(tasks instanceof List)) {
#	Line 623 | Line 635 | public abstract class ForkJoinTask<V> im
635		/**
636		* Returns true if the computation performed by this task has
637		* completed (or has been cancelled).
638	+	*
639		* @return true if this computation has completed
640		*/
641		public final boolean isDone() {
#	Line 631 | Line 644 | public abstract class ForkJoinTask<V> im
644
645		/**
646		* Returns true if this task was cancelled.
647	+	*
648		* @return true if this task was cancelled
649		*/
650		public final boolean isCancelled() {
#	Line 639 | Line 653 | public abstract class ForkJoinTask<V> im
653
654		/**
655		* Asserts that the results of this task's computation will not be
656	<	* used. If a cancellation occurs before atempting to execute this
657	<	* task, then execution will be suppressed, <code>isCancelled</code>
658	<	* will report true, and <code>join</code> will result in a
659	<	* <code>CancellationException</code> being thrown. Otherwise, when
656	>	* used. If a cancellation occurs before attempting to execute this
657	>	* task, then execution will be suppressed, {@code isCancelled}
658	>	* will report true, and {@code join} will result in a
659	>	* {@code CancellationException} being thrown. Otherwise, when
660		* cancellation races with completion, there are no guarantees
661	<	* about whether <code>isCancelled</code> will report true, whether
662	<	* <code>join</code> will return normally or via an exception, or
661	>	* about whether {@code isCancelled} will report true, whether
662	>	* {@code join} will return normally or via an exception, or
663		* whether these behaviors will remain consistent upon repeated
664		* invocation.
665		*
#	Line 656 | Line 670 | public abstract class ForkJoinTask<V> im
670		* <p> This method is designed to be invoked by <em>other</em>
671		* tasks. To terminate the current task, you can just return or
672		* throw an unchecked exception from its computation method, or
673	<	* invoke <code>completeExceptionally</code>.
673	>	* invoke {@code completeExceptionally}.
674		*
675		* @param mayInterruptIfRunning this value is ignored in the
676		* default implementation because tasks are not in general
#	Line 670 | Line 684 | public abstract class ForkJoinTask<V> im
684		}
685
686		/**
687	<	* Returns true if this task threw an exception or was cancelled
687	>	* Returns true if this task threw an exception or was cancelled.
688	>	*
689		* @return true if this task threw an exception or was cancelled
690		*/
691		public final boolean isCompletedAbnormally() {
#	Line 681 | Line 696 | public abstract class ForkJoinTask<V> im
696		* Returns the exception thrown by the base computation, or a
697		* CancellationException if cancelled, or null if none or if the
698		* method has not yet completed.
699	+	*
700		* @return the exception, or null if none
701		*/
702		public final Throwable getException() {
#	Line 695 | Line 711 | public abstract class ForkJoinTask<V> im
711		/**
712		* Completes this task abnormally, and if not already aborted or
713		* cancelled, causes it to throw the given exception upon
714	<	* <code>join</code> and related operations. This method may be used
714	>	* {@code join} and related operations. This method may be used
715		* to induce exceptions in asynchronous tasks, or to force
716		* completion of tasks that would not otherwise complete.  Its use
717		* in other situations is likely to be wrong.  This method is
718	<	* overridable, but overridden versions must invoke <code>super</code>
718	>	* overridable, but overridden versions must invoke {@code super}
719		* implementation to maintain guarantees.
720		*
721		* @param ex the exception to throw. If this exception is
#	Line 714 | Line 730 | public abstract class ForkJoinTask<V> im
730
731		/**
732		* Completes this task, and if not already aborted or cancelled,
733	<	* returning a <code>null</code> result upon <code>join</code> and related
733	>	* returning a {@code null} result upon {@code join} and related
734		* operations. This method may be used to provide results for
735		* asynchronous tasks, or to provide alternative handling for
736		* tasks that would not otherwise complete normally. Its use in
737		* other situations is likely to be wrong. This method is
738	<	* overridable, but overridden versions must invoke <code>super</code>
738	>	* overridable, but overridden versions must invoke {@code super}
739		* implementation to maintain guarantees.
740		*
741	<	* @param value the result value for this task.
741	>	* @param value the result value for this task
742		*/
743		public void complete(V value) {
744		try {
#	Line 752 | Line 768 | public abstract class ForkJoinTask<V> im
768		/**
769		* Possibly executes other tasks until this task is ready, then
770		* returns the result of the computation.  This method may be more
771	<	* efficient than <code>join</code>, but is only applicable when
772	<	* there are no potemtial dependencies between continuation of the
771	>	* efficient than {@code join}, but is only applicable when
772	>	* there are no potential dependencies between continuation of the
773		* current task and that of any other task that might be executed
774		* while helping. (This usually holds for pure divide-and-conquer
775		* tasks). This method may be invoked only from within
776		* ForkJoinTask computations. Attempts to invoke in other contexts
777	<	* resul!t in exceptions or errors possibly including ClassCastException.
777	>	* result in exceptions or errors possibly including ClassCastException.
778	>	*
779		* @return the computed result
780		*/
781		public final V helpJoin() {
#	Line 771 | Line 788 | public abstract class ForkJoinTask<V> im
788		/**
789		* Possibly executes other tasks until this task is ready.  This
790		* method may be invoked only from within ForkJoinTask
791	<	* computations. Attempts to invoke in other contexts resul!t in
791	>	* computations. Attempts to invoke in other contexts result in
792		* exceptions or errors possibly including ClassCastException.
793		*/
794		public final void quietlyHelpJoin() {
#	Line 822 | Line 839 | public abstract class ForkJoinTask<V> im
839
840		/**
841		* Resets the internal bookkeeping state of this task, allowing a
842	<	* subsequent <code>fork</code>. This method allows repeated reuse of
842	>	* subsequent {@code fork}. This method allows repeated reuse of
843		* this task, but only if reuse occurs when this task has either
844		* never been forked, or has been forked, then completed and all
845		* outstanding joins of this task have also completed. Effects
#	Line 839 | Line 856 | public abstract class ForkJoinTask<V> im
856		/**
857		* Returns the pool hosting the current task execution, or null
858		* if this task is executing outside of any pool.
859	<	* @return the pool, or null if none.
859	>	*
860	>	* @return the pool, or null if none
861		*/
862		public static ForkJoinPool getPool() {
863		Thread t = Thread.currentThread();
#	Line 856 | Line 874 | public abstract class ForkJoinTask<V> im
874		* were not, stolen. This method may be invoked only from within
875		* ForkJoinTask computations. Attempts to invoke in other contexts
876		* result in exceptions or errors possibly including ClassCastException.
877	+	*
878		* @return true if unforked
879		*/
880		public boolean tryUnfork() {
#	Line 867 | Line 886 | public abstract class ForkJoinTask<V> im
886		* forked by the current worker thread but not yet executed. This
887		* value may be useful for heuristic decisions about whether to
888		* fork other tasks.
889	+	*
890		* @return the number of tasks
891		*/
892		public static int getQueuedTaskCount() {
#	Line 875 | Line 895 | public abstract class ForkJoinTask<V> im
895		}
896
897		/**
898	<	* Returns a estimate of how many more locally queued tasks are
898	>	* Returns an estimate of how many more locally queued tasks are
899		* held by the current worker thread than there are other worker
900		* threads that might steal them.  This value may be useful for
901		* heuristic decisions about whether to fork other tasks. In many
#	Line 883 | Line 903 | public abstract class ForkJoinTask<V> im
903		* aim to maintain a small constant surplus (for example, 3) of
904		* tasks, and to process computations locally if this threshold is
905		* exceeded.
906	+	*
907		* @return the surplus number of tasks, which may be negative
908		*/
909		public static int getSurplusQueuedTaskCount() {
#	Line 893 | Line 914 | public abstract class ForkJoinTask<V> im
914		// Extension methods
915
916		/**
917	<	* Returns the result that would be returned by <code>join</code>,
917	>	* Returns the result that would be returned by {@code join},
918		* even if this task completed abnormally, or null if this task is
919		* not known to have been completed.  This method is designed to
920		* aid debugging, as well as to support extensions. Its use in any
921		* other context is discouraged.
922		*
923	<	* @return the result, or null if not completed.
923	>	* @return the result, or null if not completed
924		*/
925		public abstract V getRawResult();
926
#	Line 918 | Line 939 | public abstract class ForkJoinTask<V> im
939		* called otherwise. The return value controls whether this task
940		* is considered to be done normally. It may return false in
941		* asynchronous actions that require explicit invocations of
942	<	* <code>complete</code> to become joinable. It may throw exceptions
942	>	* {@code complete} to become joinable. It may throw exceptions
943		* to indicate abnormal exit.
944	+	*
945		* @return true if completed normally
946		* @throws Error or RuntimeException if encountered during computation
947		*/
#	Line 961 | Line 983 | public abstract class ForkJoinTask<V> im
983		* queued by the current thread but not yet executed, if one is
984		* available, or if not available, a task that was forked by some
985		* other thread, if available. Availability may be transient, so a
986	<	* <code>null</code> result does not necessarily imply quiecence
986	>	* {@code null} result does not necessarily imply quiescence
987		* of the pool this task is operating in.  This method is designed
988		* primarily to support extensions, and is unlikely to be useful
989		* otherwise.  This method may be invoked only from within
#	Line 984 | Line 1006 | public abstract class ForkJoinTask<V> im
1006		* Save the state to a stream.
1007		*
1008		* @serialData the current run status and the exception thrown
1009	<	* during execution, or null if none.
1009	>	* during execution, or null if none
1010		* @param s the stream
1011		*/
1012		private void writeObject(java.io.ObjectOutputStream s)
#	Line 995 | Line 1017 | public abstract class ForkJoinTask<V> im
1017
1018		/**
1019		* Reconstitute the instance from a stream.
1020	+	*
1021		* @param s the stream
1022		*/
1023		private void readObject(java.io.ObjectInputStream s)
#	Line 1033 | Line 1056 | public abstract class ForkJoinTask<V> im
1056
1057		private static long fieldOffset(String fieldName)
1058		throws NoSuchFieldException {
1059	<	return _unsafe.objectFieldOffset
1059	>	return UNSAFE.objectFieldOffset
1060		(ForkJoinTask.class.getDeclaredField(fieldName));
1061		}
1062
1063	<	static final Unsafe _unsafe;
1063	>	static final Unsafe UNSAFE;
1064		static final long statusOffset;
1065
1066		static {
1067		try {
1068	<	_unsafe = getUnsafe();
1068	>	UNSAFE = getUnsafe();
1069		statusOffset = fieldOffset("status");
1070		} catch (Throwable e) {
1071		throw new RuntimeException("Could not initialize intrinsics", e);

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