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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.1 by dl, Tue Jan 6 14:30:31 2009 UTC vs.
Revision 1.12 by jsr166, Wed Jul 22 01:36:51 2009 UTC

#	Line 13 | Line 13 | import sun.misc.Unsafe;
13		import java.lang.reflect.*;
14
15		/**
16	<	* Abstract base class for tasks that run within a ForkJoinPool.  A
17	<	* ForkJoinTask is a thread-like entity that is much lighter weight
18	<	* than a normal thread.  Huge numbers of tasks and subtasks may be
19	<	* hosted by a small number of actual threads in a ForkJoinPool,
20	<	* at the price of some usage limitations.
16	>	* Abstract base class for tasks that run within a {@link
17	>	* ForkJoinPool}.  A ForkJoinTask is a thread-like entity that is much
18	>	* lighter weight than a normal thread.  Huge numbers of tasks and
19	>	* subtasks may be hosted by a small number of actual threads in a
20	>	* ForkJoinPool, at the price of some usage limitations.
21		*
22	<	* <p> ForkJoinTasks are forms of <tt>Futures</tt> supporting a
23	<	* limited range of use.  The "lightness" of ForkJoinTasks is due to a
24	<	* set of restrictions (that are only partially statically
25	<	* enforceable) reflecting their intended use as computational tasks
26	<	* calculating pure functions or operating on purely isolated objects.
27	<	* The primary coordination mechanisms supported for ForkJoinTasks are
28	<	* <tt>fork</tt>, that arranges asynchronous execution, and
29	<	* <tt>join</tt>, that doesn't proceed until the task's result has
30	<	* been computed. (Cancellation is also supported).  The computation
31	<	* defined in the <tt>compute</tt> method should avoid
32	<	* <tt>synchronized</tt> methods or blocks, and should minimize
33	<	* blocking synchronization apart from joining other tasks or using
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}
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.
31	>	*
32	>	* <p>A ForkJoinTask is a lightweight form of {@link Future}.  The
33	>	* efficiency of ForkJoinTasks stems from a set of restrictions (that
34	>	* are only partially statically enforceable) reflecting their
35	>	* intended use as computational tasks calculating pure functions or
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}
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
43		* fork/join scheduling. Tasks should also not perform blocking IO,
44		* and should ideally access variables that are completely independent
#	Line 38 | Line 46 | import java.lang.reflect.*;
46		* restrictions, for example using shared output streams, may be
47		* tolerable in practice, but frequent use may result in poor
48		* performance, and the potential to indefinitely stall if the number
49	<	* of threads not waiting for external synchronization becomes
50	<	* exhausted. This usage restriction is in part enforced by not
51	<	* permitting checked exceptions such as IOExceptions to be
52	<	* thrown. However, computations may still encounter unchecked
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}
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
55		* RejectedExecutionExceptions stemming from internal resource
56		* exhaustion such as failure to allocate internal task queues.
57		*
58	<	* <p> The <tt>ForkJoinTask</tt> class is not usually directly
59	<	* subclassed.  Instead, you subclass one of the abstract classes that
60	<	* support different styles of fork/join processing.  Normally, a
61	<	* concrete ForkJoinTask subclass declares fields comprising its
62	<	* parameters, established in a constructor, and then defines a
63	<	* <tt>compute</tt> method that somehow uses the control methods
64	<	* supplied by this base class. While these methods have
65	<	* <tt>public</tt> access, some of them may only be called from within
66	<	* other ForkJoinTasks. Attempts to invoke them in other contexts
67	<	* result in exceptions or errors including ClassCastException.  The
68	<	* only way to invoke a "main" driver task is to submit it to a
69	<	* ForkJoinPool. Once started, this will usually in turn start other
70	<	* subtasks.
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}
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()} 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} (available in multiple versions)
72	>	* performs the most common form of parallel invocation: forking a set
73	>	* of tasks and joining them all.
74	>	*
75	>	* <p> The ForkJoinTask class is not usually directly subclassed.
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}
80	>	* method that somehow uses the control methods supplied by this base
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 <tt>final</tt> 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 protected methods <tt>exec</tt>,
92	<	* <tt>setRawResult</tt>, and <tt>getRawResult</tt>, while also
93	<	* introducing an abstract computational method that can be
94	<	* implemented in its subclasses. To support such extensions,
95	<	* instances of ForkJoinTasks maintain an atomically updated
96	<	* <tt>short</tt> representing user-defined control state.  Control
74	<	* state is guaranteed initially to be zero, and to be negative upon
75	<	* completion, but may otherwise be used for any other control
76	<	* purposes, such as maintaining join counts.  The {@link
77	<	* ForkJoinWorkerThread} class supports additional inspection and
78	<	* tuning methods that can be useful when developing extensions.
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} 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 <tt>Serializable</tt>, which enables them to
106	<	* be used in extensions such as remote execution frameworks. However,
107	<	* it is in general safe to serialize tasks only before or after, but
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	+
116		/**
117	<	* Status field holding all run status. We pack this into a single
118	<	* int both to minimize footprint overhead and to ensure atomicity
119	<	* (updates are via CAS).
98	<	*
99	<	* Status is initially zero, and takes on nonnegative values until
117	>	* Run control status bits packed into a single int to minimize
118	>	* footprint and to ensure atomicity (via CAS).  Status is
119	>	* initially zero, and takes on nonnegative values until
120		* completed, upon which status holds COMPLETED. CANCELLED, or
121		* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
122		* blocking waits by other threads have SIGNAL_MASK bits set --
#	Line 111 | 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 124 | 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 136 | 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 144 | Line 164 | public abstract class ForkJoinTask<V> im
164		(ForkJoinWorkerThread)t : null);
165		}
166
147	–	/**
148	–	* Get pool of current worker thread, or null if not a worker thread
149	–	*/
150	–	static ForkJoinPool getWorkerPool() {
151	–	Thread t = Thread.currentThread();
152	–	return ((t instanceof ForkJoinWorkerThread)?
153	–	((ForkJoinWorkerThread)t).pool : null);
154	–	}
155	–
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 162 | 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 = getWorkerPool();
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));
#	Line 204 | 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 247 | 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	<	final int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
265	>	private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
266		ForkJoinPool pool = w == null? null : w.pool;
267		int s;
268		while ((s = status) >= 0) {
#	Line 268 | Line 281 | public abstract class ForkJoinTask<V> im
281		* Timed version of awaitDone
282		* @return status upon exit
283		*/
284	<	final int awaitDone(ForkJoinWorkerThread w, long nanos) {
284	>	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
285		ForkJoinPool pool = w == null? null : w.pool;
286		int s;
287		while ((s = status) >= 0) {
#	Line 289 | 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 300 | 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 314 | Line 327 | public abstract class ForkJoinTask<V> im
327		}
328		}
329
330	+	/**
331	+	* Handles interruptions during waits.
332	+	*/
333		private void onInterruptedWait() {
334	<	Thread t = Thread.currentThread();
335	<	if (t instanceof ForkJoinWorkerThread) {
336	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)t;
337	<	if (w.isTerminating())
338	<	cancelIgnoreExceptions();
339	<	}
324	<	else { // re-interrupt
325	<	try {
326	<	t.interrupt();
327	<	} catch (SecurityException ignore) {
328	<	}
329	<	}
334	>	ForkJoinWorkerThread w = getWorker();
335	>	if (w == null)
336	>	Thread.currentThread().interrupt(); // re-interrupt
337	>	else if (w.isTerminating())
338	>	cancelIgnoringExceptions();
339	>	// else if FJworker, ignore interrupt
340		}
341
342		// Recording and reporting exceptions
#	Line 337 | 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 350 | 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 370 | 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 391 | 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 409 | 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 425 | 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 442 | 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 cancelIgnoreExceptions() {
460	>	final void cancelIgnoringExceptions() {
461		try {
462		cancel(false);
463		} catch(Throwable ignore) {
464		}
465		}
466
467	+	/**
468	+	* Main implementation of helpJoin
469	+	*/
470	+	private int busyJoin(ForkJoinWorkerThread w) {
471	+	int s;
472	+	ForkJoinTask<?> t;
473	+	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
474	+	t.quietlyExec();
475	+	return (s >= 0)? awaitDone(w, false) : s; // block if no work
476	+	}
477	+
478		// public methods
479
480		/**
481		* Arranges to asynchronously execute this task.  While it is not
482		* necessarily enforced, it is a usage error to fork a task more
483		* than once unless it has completed and been reinitialized.  This
484	<	* method may be invoked only from within other ForkJoinTask
484	>	* method may be invoked only from within ForkJoinTask
485		* computations. Attempts to invoke in other contexts result in
486	<	* exceptions or errors including ClassCastException.
486	>	* exceptions or errors possibly including ClassCastException.
487		*/
488		public final void fork() {
489		((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
#	Line 467 | 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 <tt>get</tt> 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 480 | Line 504 | public abstract class ForkJoinTask<V> im
504		return getRawResult();
505		}
506
483	–	public final V get() throws InterruptedException, ExecutionException {
484	–	ForkJoinWorkerThread w = getWorker();
485	–	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
486	–	awaitDone(w, true);
487	–	return reportFutureResult();
488	–	}
489	–
490	–	public final V get(long timeout, TimeUnit unit)
491	–	throws InterruptedException, ExecutionException, TimeoutException {
492	–	ForkJoinWorkerThread w = getWorker();
493	–	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
494	–	awaitDone(w, unit.toNanos(timeout));
495	–	return reportTimedFutureResult();
496	–	}
497	–
507		/**
508	<	* Possibly executes other tasks until this task is ready, then
509	<	* returns the result of the computation.  This method may be more
510	<	* efficient than <tt>join</tt>, but is only applicable when there
502	<	* are no potemtial dependencies between continuation of the
503	<	* current task and that of any other task that might be executed
504	<	* while helping. (This usually holds for pure divide-and-conquer
505	<	* tasks).
506	<	* @return the computed result
507	<	*/
508	<	public final V helpJoin() {
509	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
510	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
511	<	reportException(w.helpJoinTask(this));
512	<	return getRawResult();
513	<	}
514	<
515	<	/**
516	<	* Performs this task, awaits its completion if necessary, and
517	<	* return its result.
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 527 | Line 520 | public abstract class ForkJoinTask<V> im
520		}
521
522		/**
523	<	* Joins this task, without returning its result or throwing an
524	<	* exception. This method may be useful when processing
525	<	* collections of tasks when some have been cancelled or otherwise
526	<	* known to have aborted.
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
533		*/
534	<	public final void quietlyJoin() {
535	<	if (status >= 0) {
536	<	ForkJoinWorkerThread w = getWorker();
537	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
539	<	awaitDone(w, true);
540	<	}
534	>	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
535	>	t2.fork();
536	>	t1.invoke();
537	>	t2.join();
538		}
539
540		/**
541	<	* Possibly executes other tasks until this task is ready.
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
550		*/
551	<	public final void quietlyHelpJoin() {
552	<	if (status >= 0) {
553	<	ForkJoinWorkerThread w =
554	<	(ForkJoinWorkerThread)(Thread.currentThread());
555	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
556	<	w.helpJoinTask(this);
551	>	public static void invokeAll(ForkJoinTask<?>... tasks) {
552	>	Throwable ex = null;
553	>	int last = tasks.length - 1;
554	>	for (int i = last; i >= 0; --i) {
555	>	ForkJoinTask<?> t = tasks[i];
556	>	if (t == null) {
557	>	if (ex == null)
558	>	ex = new NullPointerException();
559	>	}
560	>	else if (i != 0)
561	>	t.fork();
562	>	else {
563	>	t.quietlyInvoke();
564	>	if (ex == null)
565	>	ex = t.getException();
566	>	}
567		}
568	+	for (int i = 1; i <= last; ++i) {
569	+	ForkJoinTask<?> t = tasks[i];
570	+	if (t != null) {
571	+	if (ex != null)
572	+	t.cancel(false);
573	+	else {
574	+	t.quietlyJoin();
575	+	if (ex == null)
576	+	ex = t.getException();
577	+	}
578	+	}
579	+	}
580	+	if (ex != null)
581	+	rethrowException(ex);
582		}
583
584		/**
585	<	* Performs this task and awaits its completion if necessary,
586	<	* without returning its result or throwing an exception. This
587	<	* method may be useful when processing collections of tasks when
588	<	* some have been cancelled or otherwise known to have aborted.
585	>	* Forks all tasks in the collection, returning when
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 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
595		*/
596	<	public final void quietlyInvoke() {
597	<	if (status >= 0 && !tryQuietlyInvoke())
598	<	quietlyJoin();
596	>	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
597	>	if (!(tasks instanceof List)) {
598	>	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
599	>	return;
600	>	}
601	>	List<? extends ForkJoinTask<?>> ts =
602	>	(List<? extends ForkJoinTask<?>>)tasks;
603	>	Throwable ex = null;
604	>	int last = ts.size() - 1;
605	>	for (int i = last; i >= 0; --i) {
606	>	ForkJoinTask<?> t = ts.get(i);
607	>	if (t == null) {
608	>	if (ex == null)
609	>	ex = new NullPointerException();
610	>	}
611	>	else if (i != 0)
612	>	t.fork();
613	>	else {
614	>	t.quietlyInvoke();
615	>	if (ex == null)
616	>	ex = t.getException();
617	>	}
618	>	}
619	>	for (int i = 1; i <= last; ++i) {
620	>	ForkJoinTask<?> t = ts.get(i);
621	>	if (t != null) {
622	>	if (ex != null)
623	>	t.cancel(false);
624	>	else {
625	>	t.quietlyJoin();
626	>	if (ex == null)
627	>	ex = t.getException();
628	>	}
629	>	}
630	>	}
631	>	if (ex != null)
632	>	rethrowException(ex);
633		}
634
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 574 | 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 581 | Line 652 | public abstract class ForkJoinTask<V> im
652		}
653
654		/**
584	–	* Returns true if this task threw an exception or was cancelled
585	–	* @return true if this task threw an exception or was cancelled
586	–	*/
587	–	public final boolean completedAbnormally() {
588	–	return (status & COMPLETION_MASK) < NORMAL;
589	–	}
590	–
591	–	/**
592	–	* Returns the exception thrown by the base computation, or a
593	–	* CancellationException if cancelled, or null if none or if the
594	–	* method has not yet completed.
595	–	* @return the exception, or null if none
596	–	*/
597	–	public final Throwable getException() {
598	–	int s = status & COMPLETION_MASK;
599	–	if (s >= NORMAL)
600	–	return null;
601	–	if (s == CANCELLED)
602	–	return new CancellationException();
603	–	return exceptionMap.get(this);
604	–	}
605	–
606	–	/**
655		* Asserts that the results of this task's computation will not be
656	<	* used. If a cancellation occurs before this task is processed,
657	<	* then its <tt>compute</tt> method will not be executed,
658	<	* <tt>isCancelled</tt> will report true, and <tt>join</tt> will
659	<	* result in a CancellationException 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 <tt>isCancelled</tt> will report true, whether
662	<	* <tt>join</tt> 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 622 | 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 <tt>completeExceptionally(someException)</tt>.
673	>	* invoke {@code completeExceptionally}.
674		*
675		* @param mayInterruptIfRunning this value is ignored in the
676		* default implementation because tasks are not in general
#	Line 636 | Line 684 | public abstract class ForkJoinTask<V> im
684		}
685
686		/**
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() {
692	+	return (status & COMPLETION_MASK) < NORMAL;
693	+	}
694	+
695	+	/**
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() {
703	+	int s = status & COMPLETION_MASK;
704	+	if (s >= NORMAL)
705	+	return null;
706	+	if (s == CANCELLED)
707	+	return new CancellationException();
708	+	return exceptionMap.get(this);
709	+	}
710	+
711	+	/**
712		* Completes this task abnormally, and if not already aborted or
713		* cancelled, causes it to throw the given exception upon
714	<	* <tt>join</tt> 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.  This
717	<	* method is overridable, but overridden versions must invoke
718	<	* <tt>super</tt> implementation to maintain guarantees.
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}
719	>	* implementation to maintain guarantees.
720	>	*
721		* @param ex the exception to throw. If this exception is
722		* not a RuntimeException or Error, the actual exception thrown
723		* will be a RuntimeException with cause ex.
#	Line 655 | Line 730 | public abstract class ForkJoinTask<V> im
730
731		/**
732		* Completes this task, and if not already aborted or cancelled,
733	<	* returning a <tt>null</tt> result upon <tt>join</tt> 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.
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}
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 672 | Line 750 | public abstract class ForkJoinTask<V> im
750		setNormalCompletion();
751		}
752
753	<	/**
754	<	* Resets the internal bookkeeping state of this task, allowing a
755	<	* subsequent <tt>fork</tt>. This method allows repeated reuse of
756	<	* this task, but only if reuse occurs when this task has either
757	<	* never been forked, or has been forked, then completed and all
758	<	* outstanding joins of this task have also completed. Effects
759	<	* under any other usage conditions are not guaranteed, and are
760	<	* almost surely wrong. This method may be useful when executing
761	<	* pre-constructed trees of subtasks in loops.
762	<	*/
763	<	public void reinitialize() {
764	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
765	<	exceptionMap.remove(this);
688	<	status = 0;
753	>	public final V get() throws InterruptedException, ExecutionException {
754	>	ForkJoinWorkerThread w = getWorker();
755	>	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
756	>	awaitDone(w, true);
757	>	return reportFutureResult();
758	>	}
759	>
760	>	public final V get(long timeout, TimeUnit unit)
761	>	throws InterruptedException, ExecutionException, TimeoutException {
762	>	ForkJoinWorkerThread w = getWorker();
763	>	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
764	>	awaitDone(w, unit.toNanos(timeout));
765	>	return reportTimedFutureResult();
766		}
767
768		/**
769	<	* Tries to unschedule this task for execution. This method will
770	<	* typically succeed if this task is the next task that would be
771	<	* executed by the current thread, and will typically fail (return
772	<	* false) otherwise. This method may be useful when arranging
773	<	* faster local processing of tasks that could have been, but were
774	<	* not, stolen.
775	<	* @return true if unforked
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}, 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	>	* result in exceptions or errors possibly including ClassCastException.
778	>	*
779	>	* @return the computed result
780		*/
781	<	public boolean tryUnfork() {
782	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
781	>	public final V helpJoin() {
782	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
783	>	if (status < 0 || !w.unpushTask(this) || !tryExec())
784	>	reportException(busyJoin(w));
785	>	return getRawResult();
786		}
787
788		/**
789	<	* Forks both tasks, returning when <tt>isDone</tt> holds for both
790	<	* of them or an exception is encountered. This method may be
707	<	* invoked only from within other ForkJoinTask
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 result in
792	<	* exceptions or errors including ClassCastException.
710	<	* @param t1 one task
711	<	* @param t2 the other task
712	<	* @throws NullPointerException if t1 or t2 are null
713	<	* @throws RuntimeException or Error if either task did so.
792	>	* exceptions or errors possibly including ClassCastException.
793		*/
794	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
795	<	t2.fork();
796	<	t1.invoke();
797	<	t2.join();
794	>	public final void quietlyHelpJoin() {
795	>	if (status >= 0) {
796	>	ForkJoinWorkerThread w =
797	>	(ForkJoinWorkerThread)(Thread.currentThread());
798	>	if (!w.unpushTask(this) || !tryQuietlyInvoke())
799	>	busyJoin(w);
800	>	}
801		}
802
803		/**
804	<	* Forks the given tasks, returning when <tt>isDone</tt> holds for
805	<	* all of them. If any task encounters an exception, others may be
806	<	* cancelled.  This method may be invoked only from within other
807	<	* ForkJoinTask computations. Attempts to invoke in other contexts
726	<	* result in exceptions or errors including ClassCastException.
727	<	* @param tasks the array of tasks
728	<	* @throws NullPointerException if tasks or any element are null.
729	<	* @throws RuntimeException or Error if any task did so.
804	>	* Joins this task, without returning its result or throwing an
805	>	* exception. This method may be useful when processing
806	>	* collections of tasks when some have been cancelled or otherwise
807	>	* known to have aborted.
808		*/
809	<	public static void invokeAll(ForkJoinTask<?>... tasks) {
810	<	Throwable ex = null;
811	<	int last = tasks.length - 1;
812	<	for (int i = last; i >= 0; --i) {
813	<	ForkJoinTask<?> t = tasks[i];
736	<	if (t == null) {
737	<	if (ex == null)
738	<	ex = new NullPointerException();
739	<	}
740	<	else if (i != 0)
741	<	t.fork();
742	<	else {
743	<	t.quietlyInvoke();
744	<	if (ex == null)
745	<	ex = t.getException();
746	<	}
747	<	}
748	<	for (int i = 1; i <= last; ++i) {
749	<	ForkJoinTask<?> t = tasks[i];
750	<	if (t != null) {
751	<	if (ex != null)
752	<	t.cancel(false);
753	<	else {
754	<	t.quietlyJoin();
755	<	if (ex == null)
756	<	ex = t.getException();
757	<	}
758	<	}
809	>	public final void quietlyJoin() {
810	>	if (status >= 0) {
811	>	ForkJoinWorkerThread w = getWorker();
812	>	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
813	>	awaitDone(w, true);
814		}
760	–	if (ex != null)
761	–	rethrowException(ex);
815		}
816
817		/**
818	<	* Forks all tasks in the collection, returning when
819	<	* <tt>isDone</tt> holds for all of them. If any task encounters
820	<	* an exception, others may be cancelled.  This method may be
821	<	* invoked only from within other ForkJoinTask
822	<	* computations. Attempts to invoke in other contexts result in
770	<	* exceptions or errors including ClassCastException.
771	<	* @param tasks the collection of tasks
772	<	* @throws NullPointerException if tasks or any element are null.
773	<	* @throws RuntimeException or Error if any task did so.
818	>	* Commences performing this task and awaits its completion if
819	>	* necessary, without returning its result or throwing an
820	>	* exception. This method may be useful when processing
821	>	* collections of tasks when some have been cancelled or otherwise
822	>	* known to have aborted.
823		*/
824	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
825	<	if (!(tasks instanceof List)) {
826	<	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
778	<	return;
779	<	}
780	<	List<? extends ForkJoinTask<?>> ts =
781	<	(List<? extends ForkJoinTask<?>>)tasks;
782	<	Throwable ex = null;
783	<	int last = ts.size() - 1;
784	<	for (int i = last; i >= 0; --i) {
785	<	ForkJoinTask<?> t = ts.get(i);
786	<	if (t == null) {
787	<	if (ex == null)
788	<	ex = new NullPointerException();
789	<	}
790	<	else if (i != 0)
791	<	t.fork();
792	<	else {
793	<	t.quietlyInvoke();
794	<	if (ex == null)
795	<	ex = t.getException();
796	<	}
797	<	}
798	<	for (int i = 1; i <= last; ++i) {
799	<	ForkJoinTask<?> t = ts.get(i);
800	<	if (t != null) {
801	<	if (ex != null)
802	<	t.cancel(false);
803	<	else {
804	<	t.quietlyJoin();
805	<	if (ex == null)
806	<	ex = t.getException();
807	<	}
808	<	}
809	<	}
810	<	if (ex != null)
811	<	rethrowException(ex);
824	>	public final void quietlyInvoke() {
825	>	if (status >= 0 && !tryQuietlyInvoke())
826	>	quietlyJoin();
827		}
828
829		/**
#	Line 823 | Line 838 | public abstract class ForkJoinTask<V> im
838		}
839
840		/**
841	<	* Returns a estimate of how many more locally queued tasks are
841	>	* Resets the internal bookkeeping state of this task, allowing a
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
846	>	* under any other usage conditions are not guaranteed, and are
847	>	* almost surely wrong. This method may be useful when executing
848	>	* pre-constructed trees of subtasks in loops.
849	>	*/
850	>	public void reinitialize() {
851	>	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
852	>	exceptionMap.remove(this);
853	>	status = 0;
854	>	}
855	>
856	>	/**
857	>	* Returns the pool hosting the current task execution, or null
858	>	* if this task is executing outside of any pool.
859	>	*
860	>	* @return the pool, or null if none
861	>	*/
862	>	public static ForkJoinPool getPool() {
863	>	Thread t = Thread.currentThread();
864	>	return ((t instanceof ForkJoinWorkerThread)?
865	>	((ForkJoinWorkerThread)t).pool : null);
866	>	}
867	>
868	>	/**
869	>	* Tries to unschedule this task for execution. This method will
870	>	* typically succeed if this task is the most recently forked task
871	>	* by the current thread, and has not commenced executing in
872	>	* another thread.  This method may be useful when arranging
873	>	* alternative local processing of tasks that could have been, but
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() {
881	>	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
882	>	}
883	>
884	>	/**
885	>	* Returns an estimate of the number of tasks that have been
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() {
893	>	return ((ForkJoinWorkerThread)(Thread.currentThread())).
894	>	getQueueSize();
895	>	}
896	>
897	>	/**
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 want to steal them.  This value may be
901	<	* useful for heuristic decisions about whether to fork other
902	<	* tasks. In many usages of ForkJoinTasks, at steady state, each
903	<	* worker should aim to maintain a small constant surplus (for
904	<	* example, 3) of tasks, and to process computations locally if
905	<	* this threshold is exceeded.
900	>	* threads that might steal them.  This value may be useful for
901	>	* heuristic decisions about whether to fork other tasks. In many
902	>	* usages of ForkJoinTasks, at steady state, each worker should
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 surplus() {
909	>	public static int getSurplusQueuedTaskCount() {
910		return ((ForkJoinWorkerThread)(Thread.currentThread()))
911		.getEstimatedSurplusTaskCount();
912		}
913
914	<	// Extension kit
914	>	// Extension methods
915
916		/**
917	<	* Returns the result that would be returned by <tt>join</tt>, or
918	<	* null if this task is not known to have been completed.  This
919	<	* method is designed to aid debugging, as well as to support
920	<	* extensions. Its use in any other context is discouraged.
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 865 | 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	<	* <tt>complete</tt> 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		*/
948		protected abstract boolean exec();
949
950	+	/**
951	+	* Returns, but does not unschedule or execute, the task queued by
952	+	* the current thread but not yet executed, if one is
953	+	* available. There is no guarantee that this task will actually
954	+	* be polled or executed next.  This method is designed primarily
955	+	* to support extensions, and is unlikely to be useful otherwise.
956	+	* This method may be invoked only from within ForkJoinTask
957	+	* computations. Attempts to invoke in other contexts result in
958	+	* exceptions or errors possibly including ClassCastException.
959	+	*
960	+	* @return the next task, or null if none are available
961	+	*/
962	+	protected static ForkJoinTask<?> peekNextLocalTask() {
963	+	return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask();
964	+	}
965	+
966	+	/**
967	+	* Unschedules and returns, without executing, the next task
968	+	* queued by the current thread but not yet executed.  This method
969	+	* is designed primarily to support extensions, and is unlikely to
970	+	* be useful otherwise.  This method may be invoked only from
971	+	* within ForkJoinTask computations. Attempts to invoke in other
972	+	* contexts result in exceptions or errors possibly including
973	+	* ClassCastException.
974	+	*
975	+	* @return the next task, or null if none are available
976	+	*/
977	+	protected static ForkJoinTask<?> pollNextLocalTask() {
978	+	return ((ForkJoinWorkerThread)(Thread.currentThread())).pollLocalTask();
979	+	}
980	+
981	+	/**
982	+	* Unschedules and returns, without executing, the next task
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} 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
990	+	* ForkJoinTask computations. Attempts to invoke in other contexts
991	+	* result in exceptions or errors possibly including
992	+	* ClassCastException.
993	+	*
994	+	* @return a task, or null if none are available
995	+	*/
996	+	protected static ForkJoinTask<?> pollTask() {
997	+	return ((ForkJoinWorkerThread)(Thread.currentThread())).
998	+	pollTask();
999	+	}
1000	+
1001		// Serialization support
1002
1003		private static final long serialVersionUID = -7721805057305804111L;
#	Line 880 | 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 891 | 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)
1024		throws java.io.IOException, ClassNotFoundException {
1025		s.defaultReadObject();
1026	<	//        status &= ~INTERNAL_SIGNAL_MASK; //  todo: define policy
1026	>	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1027	>	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1028		Object ex = s.readObject();
1029		if (ex != null)
1030		setDoneExceptionally((Throwable)ex);
1031		}
1032
1033		// Temporary Unsafe mechanics for preliminary release
1034	+	private static Unsafe getUnsafe() throws Throwable {
1035	+	try {
1036	+	return Unsafe.getUnsafe();
1037	+	} catch (SecurityException se) {
1038	+	try {
1039	+	return java.security.AccessController.doPrivileged
1040	+	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1041	+	public Unsafe run() throws Exception {
1042	+	return getUnsafePrivileged();
1043	+	}});
1044	+	} catch (java.security.PrivilegedActionException e) {
1045	+	throw e.getCause();
1046	+	}
1047	+	}
1048	+	}
1049
1050	<	static final Unsafe _unsafe;
1050	>	private static Unsafe getUnsafePrivileged()
1051	>	throws NoSuchFieldException, IllegalAccessException {
1052	>	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1053	>	f.setAccessible(true);
1054	>	return (Unsafe) f.get(null);
1055	>	}
1056	>
1057	>	private static long fieldOffset(String fieldName)
1058	>	throws NoSuchFieldException {
1059	>	return UNSAFE.objectFieldOffset
1060	>	(ForkJoinTask.class.getDeclaredField(fieldName));
1061	>	}
1062	>
1063	>	static final Unsafe UNSAFE;
1064		static final long statusOffset;
1065
1066		static {
1067		try {
1068	<	if (ForkJoinTask.class.getClassLoader() != null) {
1069	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1070	<	f.setAccessible(true);
1071	<	_unsafe = (Unsafe)f.get(null);
1072	<	}
917	<	else
918	<	_unsafe = Unsafe.getUnsafe();
919	<	statusOffset = _unsafe.objectFieldOffset
920	<	(ForkJoinTask.class.getDeclaredField("status"));
921	<	} catch (Exception ex) { throw new Error(ex); }
1068	>	UNSAFE = getUnsafe();
1069	>	statusOffset = fieldOffset("status");
1070	>	} catch (Throwable e) {
1071	>	throw new RuntimeException("Could not initialize intrinsics", e);
1072	>	}
1073		}
1074
1075		}

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