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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 1.13 by dl, Wed Jul 22 19:04:11 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 (as may be determined using method {@link
85	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
86	>	* result in exceptions or errors possibly including
87	>	* ClassCastException.
88		*
89	<	* <p>Most base support methods are <tt>final</tt> because their
89	>	* <p>Most base support methods are {@code final} because their
90		* implementations are intrinsically tied to the underlying
91		* lightweight task scheduling framework, and so cannot be overridden.
92		* Developers creating new basic styles of fork/join processing should
93	<	* minimally implement protected methods <tt>exec</tt>,
94	<	* <tt>setRawResult</tt>, and <tt>getRawResult</tt>, while also
95	<	* introducing an abstract computational method that can be
96	<	* implemented in its subclasses. To support such extensions,
97	<	* instances of ForkJoinTasks maintain an atomically updated
98	<	* <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.
93	>	* minimally implement {@code protected} methods
94	>	* {@code exec}, {@code setRawResult}, and
95	>	* {@code getRawResult}, while also introducing an abstract
96	>	* computational method that can be implemented in its subclasses,
97	>	* possibly relying on other {@code protected} methods provided
98	>	* by this class.
99		*
100		* <p>ForkJoinTasks should perform relatively small amounts of
101	<	* computations, othewise splitting into smaller tasks. As a very
101	>	* computations, otherwise splitting into smaller tasks. As a very
102		* rough rule of thumb, a task should perform more than 100 and less
103		* than 10000 basic computational steps. If tasks are too big, then
104	<	* parellelism cannot improve throughput. If too small, then memory
104	>	* parallelism cannot improve throughput. If too small, then memory
105		* and internal task maintenance overhead may overwhelm processing.
106		*
107	<	* <p>ForkJoinTasks are <tt>Serializable</tt>, which enables them to
108	<	* be used in extensions such as remote execution frameworks. However,
109	<	* it is in general safe to serialize tasks only before or after, but
107	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them
108	>	* to be used in extensions such as remote execution frameworks. It is
109	>	* in general sensible to serialize tasks only before or after, but
110		* not during execution. Serialization is not relied on during
111		* execution itself.
112	+	*
113	+	* @since 1.7
114	+	* @author Doug Lea
115		*/
116		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
117	+
118		/**
119	<	* Status field holding all run status. We pack this into a single
120	<	* int both to minimize footprint overhead and to ensure atomicity
121	<	* (updates are via CAS).
98	<	*
99	<	* Status is initially zero, and takes on nonnegative values until
119	>	* Run control status bits packed into a single int to minimize
120	>	* footprint and to ensure atomicity (via CAS).  Status is
121	>	* initially zero, and takes on nonnegative values until
122		* completed, upon which status holds COMPLETED. CANCELLED, or
123		* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
124		* blocking waits by other threads have SIGNAL_MASK bits set --
#	Line 111 | Line 133 | public abstract class ForkJoinTask<V> im
133		* currently unused. Also value 0x80000000 is available as spare
134		* completion value.
135		*/
136	<	volatile int status; // accessed directy by pool and workers
136	>	volatile int status; // accessed directly by pool and workers
137
138		static final int COMPLETION_MASK      = 0xe0000000;
139		static final int NORMAL               = 0xe0000000; // == mask
#	Line 124 | Line 146 | public abstract class ForkJoinTask<V> im
146		/**
147		* Table of exceptions thrown by tasks, to enable reporting by
148		* callers. Because exceptions are rare, we don't directly keep
149	<	* them with task objects, but instead us a weak ref table.  Note
149	>	* them with task objects, but instead use a weak ref table.  Note
150		* that cancellation exceptions don't appear in the table, but are
151		* instead recorded as status values.
152	<	* Todo: Use ConcurrentReferenceHashMap
152	>	* TODO: Use ConcurrentReferenceHashMap
153		*/
154		static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
155		Collections.synchronizedMap
#	Line 136 | Line 158 | public abstract class ForkJoinTask<V> im
158		// within-package utilities
159
160		/**
161	<	* Get current worker thread, or null if not a worker thread
161	>	* Gets current worker thread, or null if not a worker thread.
162		*/
163		static ForkJoinWorkerThread getWorker() {
164		Thread t = Thread.currentThread();
#	Line 144 | Line 166 | public abstract class ForkJoinTask<V> im
166		(ForkJoinWorkerThread)t : null);
167		}
168
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	–
169		final boolean casStatus(int cmp, int val) {
170	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
170	>	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
171		}
172
173		/**
#	Line 162 | Line 175 | public abstract class ForkJoinTask<V> im
175		*/
176		static void rethrowException(Throwable ex) {
177		if (ex != null)
178	<	_unsafe.throwException(ex);
178	>	UNSAFE.throwException(ex);
179		}
180
181		// Setting completion status
182
183		/**
184	<	* Mark completion and wake up threads waiting to join this task.
184	>	* Marks completion and wakes up threads waiting to join this task.
185	>	*
186		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
187		*/
188		final void setCompletion(int completion) {
189	<	ForkJoinPool pool = getWorkerPool();
189	>	ForkJoinPool pool = getPool();
190		if (pool != null) {
191		int s; // Clear signal bits while setting completion status
192		do;while ((s = status) >= 0 && !casStatus(s, completion));
#	Line 204 | Line 218 | public abstract class ForkJoinTask<V> im
218		final void setNormalCompletion() {
219		// Try typical fast case -- single CAS, no signal, not already done.
220		// Manually expand casStatus to improve chances of inlining it
221	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
221	>	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
222		setCompletion(NORMAL);
223		}
224
#	Line 247 | Line 261 | public abstract class ForkJoinTask<V> im
261		/**
262		* Sets status to indicate there is joiner, then waits for join,
263		* surrounded with pool notifications.
264	+	*
265		* @return status upon exit
266		*/
267	<	final int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
267	>	private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
268		ForkJoinPool pool = w == null? null : w.pool;
269		int s;
270		while ((s = status) >= 0) {
#	Line 268 | Line 283 | public abstract class ForkJoinTask<V> im
283		* Timed version of awaitDone
284		* @return status upon exit
285		*/
286	<	final int awaitDone(ForkJoinWorkerThread w, long nanos) {
286	>	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
287		ForkJoinPool pool = w == null? null : w.pool;
288		int s;
289		while ((s = status) >= 0) {
#	Line 289 | 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) {
#	Line 300 | Line 315 | public abstract class ForkJoinTask<V> im
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 314 | Line 329 | public abstract class ForkJoinTask<V> im
329		}
330		}
331
332	+	/**
333	+	* Handles interruptions during waits.
334	+	*/
335		private void onInterruptedWait() {
336	<	Thread t = Thread.currentThread();
337	<	if (t instanceof ForkJoinWorkerThread) {
338	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)t;
339	<	if (w.isTerminating())
340	<	cancelIgnoreExceptions();
341	<	}
324	<	else { // re-interrupt
325	<	try {
326	<	t.interrupt();
327	<	} catch (SecurityException ignore) {
328	<	}
329	<	}
336	>	ForkJoinWorkerThread w = getWorker();
337	>	if (w == null)
338	>	Thread.currentThread().interrupt(); // re-interrupt
339	>	else if (w.isTerminating())
340	>	cancelIgnoringExceptions();
341	>	// else if FJworker, ignore interrupt
342		}
343
344		// Recording and reporting exceptions
#	Line 337 | 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 350 | Line 363 | public abstract class ForkJoinTask<V> im
363		}
364
365		/**
366	<	* Returns result or throws exception using j.u.c.Future conventions
366	>	* Returns result or throws exception using j.u.c.Future conventions.
367		* Only call when isDone known to be true.
368		*/
369		private V reportFutureResult()
#	Line 370 | 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 391 | 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 409 | 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) {
#	Line 425 | 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 442 | 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 cancelIgnoreExceptions() {
462	>	final void cancelIgnoringExceptions() {
463		try {
464		cancel(false);
465		} catch(Throwable ignore) {
466		}
467		}
468
469	+	/**
470	+	* Main implementation of helpJoin
471	+	*/
472	+	private int busyJoin(ForkJoinWorkerThread w) {
473	+	int s;
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
478	+	}
479	+
480		// public methods
481
482		/**
483		* Arranges to asynchronously execute this task.  While it is not
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 other ForkJoinTask
487	<	* computations. Attempts to invoke in other contexts result in
488	<	* exceptions or errors including ClassCastException.
486	>	* method may be invoked only from within ForkJoinTask
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);
#	Line 467 | Line 494 | public abstract class ForkJoinTask<V> im
494
495		/**
496		* Returns the result of the computation when it is ready.
497	<	* This method differs from <tt>get</tt> in that abnormal
497	>	* This method differs from {@code get} in that abnormal
498		* completion results in RuntimeExceptions or Errors, not
499		* ExecutionExceptions.
500		*
#	Line 480 | Line 507 | public abstract class ForkJoinTask<V> im
507		return getRawResult();
508		}
509
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	–
510		/**
511	<	* Possibly executes other tasks until this task is ready, then
512	<	* returns the result of the computation.  This method may be more
513	<	* 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.
511	>	* Commences performing this task, awaits its completion if
512	>	* necessary, and return its result.
513	>	*
514		* @throws Throwable (a RuntimeException, Error, or unchecked
515	<	* exception) if the underlying computation did so.
515	>	* exception) if the underlying computation did so
516		* @return the computed result
517		*/
518		public final V invoke() {
#	Line 527 | Line 523 | public abstract class ForkJoinTask<V> im
523		}
524
525		/**
526	<	* Joins this task, without returning its result or throwing an
527	<	* exception. This method may be useful when processing
528	<	* collections of tasks when some have been cancelled or otherwise
529	<	* known to have aborted.
526	>	* Forks both tasks, returning when {@code isDone} holds for
527	>	* both of them or an exception is encountered. This method may be
528	>	* invoked only from within ForkJoinTask computations (as may be
529	>	* determined using method {@link #inForkJoinPool}). Attempts to
530	>	* invoke in other contexts result in exceptions or errors
531	>	* possibly including ClassCastException.
532	>	*
533	>	* @param t1 one task
534	>	* @param t2 the other task
535	>	* @throws NullPointerException if t1 or t2 are null
536	>	* @throws RuntimeException or Error if either task did so
537		*/
538	<	public final void quietlyJoin() {
539	<	if (status >= 0) {
540	<	ForkJoinWorkerThread w = getWorker();
541	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
539	<	awaitDone(w, true);
540	<	}
538	>	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
539	>	t2.fork();
540	>	t1.invoke();
541	>	t2.join();
542		}
543
544		/**
545	<	* Possibly executes other tasks until this task is ready.
545	>	* Forks the given tasks, returning when {@code isDone} holds
546	>	* for all of them. If any task encounters an exception, others
547	>	* may be cancelled.  This method may be invoked only from within
548	>	* ForkJoinTask computations (as may be determined using method
549	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
550	>	* result in exceptions or errors possibly including
551	>	* ClassCastException.
552	>	* @param tasks the array of tasks
553	>	* @throws NullPointerException if tasks or any element are null
554	>	* @throws RuntimeException or Error if any task did so
555		*/
556	<	public final void quietlyHelpJoin() {
557	<	if (status >= 0) {
558	<	ForkJoinWorkerThread w =
559	<	(ForkJoinWorkerThread)(Thread.currentThread());
560	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
561	<	w.helpJoinTask(this);
556	>	public static void invokeAll(ForkJoinTask<?>... tasks) {
557	>	Throwable ex = null;
558	>	int last = tasks.length - 1;
559	>	for (int i = last; i >= 0; --i) {
560	>	ForkJoinTask<?> t = tasks[i];
561	>	if (t == null) {
562	>	if (ex == null)
563	>	ex = new NullPointerException();
564	>	}
565	>	else if (i != 0)
566	>	t.fork();
567	>	else {
568	>	t.quietlyInvoke();
569	>	if (ex == null)
570	>	ex = t.getException();
571	>	}
572	>	}
573	>	for (int i = 1; i <= last; ++i) {
574	>	ForkJoinTask<?> t = tasks[i];
575	>	if (t != null) {
576	>	if (ex != null)
577	>	t.cancel(false);
578	>	else {
579	>	t.quietlyJoin();
580	>	if (ex == null)
581	>	ex = t.getException();
582	>	}
583	>	}
584		}
585	+	if (ex != null)
586	+	rethrowException(ex);
587		}
588
589		/**
590	<	* Performs this task and awaits its completion if necessary,
591	<	* without returning its result or throwing an exception. This
592	<	* method may be useful when processing collections of tasks when
593	<	* some have been cancelled or otherwise known to have aborted.
590	>	* Forks all tasks in the collection, returning when
591	>	* {@code isDone} holds for all of them. If any task
592	>	* encounters an exception, others may be cancelled.  This method
593	>	* may be invoked only from within ForkJoinTask computations (as
594	>	* may be determined using method {@link
595	>	* #inForkJoinPool}). Attempts to invoke in other contexts resul!t
596	>	* in exceptions or errors possibly including ClassCastException.
597	>	*
598	>	* @param tasks the collection of tasks
599	>	* @throws NullPointerException if tasks or any element are null
600	>	* @throws RuntimeException or Error if any task did so
601		*/
602	<	public final void quietlyInvoke() {
603	<	if (status >= 0 && !tryQuietlyInvoke())
604	<	quietlyJoin();
602	>	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
603	>	if (!(tasks instanceof List)) {
604	>	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
605	>	return;
606	>	}
607	>	List<? extends ForkJoinTask<?>> ts =
608	>	(List<? extends ForkJoinTask<?>>)tasks;
609	>	Throwable ex = null;
610	>	int last = ts.size() - 1;
611	>	for (int i = last; i >= 0; --i) {
612	>	ForkJoinTask<?> t = ts.get(i);
613	>	if (t == null) {
614	>	if (ex == null)
615	>	ex = new NullPointerException();
616	>	}
617	>	else if (i != 0)
618	>	t.fork();
619	>	else {
620	>	t.quietlyInvoke();
621	>	if (ex == null)
622	>	ex = t.getException();
623	>	}
624	>	}
625	>	for (int i = 1; i <= last; ++i) {
626	>	ForkJoinTask<?> t = ts.get(i);
627	>	if (t != null) {
628	>	if (ex != null)
629	>	t.cancel(false);
630	>	else {
631	>	t.quietlyJoin();
632	>	if (ex == null)
633	>	ex = t.getException();
634	>	}
635	>	}
636	>	}
637	>	if (ex != null)
638	>	rethrowException(ex);
639		}
640
641		/**
642		* Returns true if the computation performed by this task has
643		* completed (or has been cancelled).
644	+	*
645		* @return true if this computation has completed
646		*/
647		public final boolean isDone() {
#	Line 574 | Line 650 | public abstract class ForkJoinTask<V> im
650
651		/**
652		* Returns true if this task was cancelled.
653	+	*
654		* @return true if this task was cancelled
655		*/
656		public final boolean isCancelled() {
#	Line 581 | Line 658 | public abstract class ForkJoinTask<V> im
658		}
659
660		/**
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	–	/**
661		* Asserts that the results of this task's computation will not be
662	<	* used. If a cancellation occurs before this task is processed,
663	<	* then its <tt>compute</tt> method will not be executed,
664	<	* <tt>isCancelled</tt> will report true, and <tt>join</tt> will
665	<	* result in a CancellationException being thrown. Otherwise, when
662	>	* used. If a cancellation occurs before attempting to execute this
663	>	* task, then execution will be suppressed, {@code isCancelled}
664	>	* will report true, and {@code join} will result in a
665	>	* {@code CancellationException} being thrown. Otherwise, when
666		* cancellation races with completion, there are no guarantees
667	<	* about whether <tt>isCancelled</tt> will report true, whether
668	<	* <tt>join</tt> will return normally or via an exception, or
667	>	* about whether {@code isCancelled} will report true, whether
668	>	* {@code join} will return normally or via an exception, or
669		* whether these behaviors will remain consistent upon repeated
670		* invocation.
671		*
#	Line 622 | Line 676 | public abstract class ForkJoinTask<V> im
676		* <p> This method is designed to be invoked by <em>other</em>
677		* tasks. To terminate the current task, you can just return or
678		* throw an unchecked exception from its computation method, or
679	<	* invoke <tt>completeExceptionally(someException)</tt>.
679	>	* invoke {@code completeExceptionally}.
680		*
681		* @param mayInterruptIfRunning this value is ignored in the
682		* default implementation because tasks are not in general
#	Line 636 | Line 690 | public abstract class ForkJoinTask<V> im
690		}
691
692		/**
693	+	* Returns true if this task threw an exception or was cancelled.
694	+	*
695	+	* @return true if this task threw an exception or was cancelled
696	+	*/
697	+	public final boolean isCompletedAbnormally() {
698	+	return (status & COMPLETION_MASK) < NORMAL;
699	+	}
700	+
701	+	/**
702	+	* Returns the exception thrown by the base computation, or a
703	+	* CancellationException if cancelled, or null if none or if the
704	+	* method has not yet completed.
705	+	*
706	+	* @return the exception, or null if none
707	+	*/
708	+	public final Throwable getException() {
709	+	int s = status & COMPLETION_MASK;
710	+	if (s >= NORMAL)
711	+	return null;
712	+	if (s == CANCELLED)
713	+	return new CancellationException();
714	+	return exceptionMap.get(this);
715	+	}
716	+
717	+	/**
718		* Completes this task abnormally, and if not already aborted or
719		* cancelled, causes it to throw the given exception upon
720	<	* <tt>join</tt> and related operations. This method may be used
720	>	* {@code join} and related operations. This method may be used
721		* to induce exceptions in asynchronous tasks, or to force
722	<	* completion of tasks that would not otherwise complete.  This
723	<	* method is overridable, but overridden versions must invoke
724	<	* <tt>super</tt> implementation to maintain guarantees.
722	>	* completion of tasks that would not otherwise complete.  Its use
723	>	* in other situations is likely to be wrong.  This method is
724	>	* overridable, but overridden versions must invoke {@code super}
725	>	* implementation to maintain guarantees.
726	>	*
727		* @param ex the exception to throw. If this exception is
728		* not a RuntimeException or Error, the actual exception thrown
729		* will be a RuntimeException with cause ex.
#	Line 655 | Line 736 | public abstract class ForkJoinTask<V> im
736
737		/**
738		* Completes this task, and if not already aborted or cancelled,
739	<	* returning a <tt>null</tt> result upon <tt>join</tt> and related
739	>	* returning a {@code null} result upon {@code join} and related
740		* operations. This method may be used to provide results for
741		* asynchronous tasks, or to provide alternative handling for
742	<	* tasks that would not otherwise complete normally.
742	>	* tasks that would not otherwise complete normally. Its use in
743	>	* other situations is likely to be wrong. This method is
744	>	* overridable, but overridden versions must invoke {@code super}
745	>	* implementation to maintain guarantees.
746		*
747	<	* @param value the result value for this task.
747	>	* @param value the result value for this task
748		*/
749		public void complete(V value) {
750		try {
#	Line 672 | Line 756 | public abstract class ForkJoinTask<V> im
756		setNormalCompletion();
757		}
758
759	+	public final V get() throws InterruptedException, ExecutionException {
760	+	ForkJoinWorkerThread w = getWorker();
761	+	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
762	+	awaitDone(w, true);
763	+	return reportFutureResult();
764	+	}
765	+
766	+	public final V get(long timeout, TimeUnit unit)
767	+	throws InterruptedException, ExecutionException, TimeoutException {
768	+	ForkJoinWorkerThread w = getWorker();
769	+	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
770	+	awaitDone(w, unit.toNanos(timeout));
771	+	return reportTimedFutureResult();
772	+	}
773	+
774	+	/**
775	+	* Possibly executes other tasks until this task is ready, then
776	+	* returns the result of the computation.  This method may be more
777	+	* efficient than {@code join}, but is only applicable when
778	+	* there are no potential dependencies between continuation of the
779	+	* current task and that of any other task that might be executed
780	+	* while helping. (This usually holds for pure divide-and-conquer
781	+	* tasks). This method may be invoked only from within
782	+	* ForkJoinTask computations (as may be determined using method
783	+	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
784	+	* resul!t in exceptions or errors possibly including
785	+	* ClassCastException.
786	+	*
787	+	* @return the computed result
788	+	*/
789	+	public final V helpJoin() {
790	+	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
791	+	if (status < 0 || !w.unpushTask(this) || !tryExec())
792	+	reportException(busyJoin(w));
793	+	return getRawResult();
794	+	}
795	+
796	+	/**
797	+	* Possibly executes other tasks until this task is ready.  This
798	+	* method may be invoked only from within ForkJoinTask
799	+	* computations (as may be determined using method {@link
800	+	* #inForkJoinPool}). Attempts to invoke in other contexts resul!t
801	+	* in exceptions or errors possibly including ClassCastException.
802	+	*/
803	+	public final void quietlyHelpJoin() {
804	+	if (status >= 0) {
805	+	ForkJoinWorkerThread w =
806	+	(ForkJoinWorkerThread)(Thread.currentThread());
807	+	if (!w.unpushTask(this) || !tryQuietlyInvoke())
808	+	busyJoin(w);
809	+	}
810	+	}
811	+
812	+	/**
813	+	* Joins this task, without returning its result or throwing an
814	+	* exception. This method may be useful when processing
815	+	* collections of tasks when some have been cancelled or otherwise
816	+	* known to have aborted.
817	+	*/
818	+	public final void quietlyJoin() {
819	+	if (status >= 0) {
820	+	ForkJoinWorkerThread w = getWorker();
821	+	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
822	+	awaitDone(w, true);
823	+	}
824	+	}
825	+
826	+	/**
827	+	* Commences performing this task and awaits its completion if
828	+	* necessary, without returning its result or throwing an
829	+	* exception. This method may be useful when processing
830	+	* collections of tasks when some have been cancelled or otherwise
831	+	* known to have aborted.
832	+	*/
833	+	public final void quietlyInvoke() {
834	+	if (status >= 0 && !tryQuietlyInvoke())
835	+	quietlyJoin();
836	+	}
837	+
838	+	/**
839	+	* Possibly executes tasks until the pool hosting the current task
840	+	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
841	+	* designs in which many tasks are forked, but none are explicitly
842	+	* joined, instead executing them until all are processed.
843	+	*/
844	+	public static void helpQuiesce() {
845	+	((ForkJoinWorkerThread)(Thread.currentThread())).
846	+	helpQuiescePool();
847	+	}
848	+
849		/**
850		* Resets the internal bookkeeping state of this task, allowing a
851	<	* subsequent <tt>fork</tt>. This method allows repeated reuse of
851	>	* subsequent {@code fork}. This method allows repeated reuse of
852		* this task, but only if reuse occurs when this task has either
853		* never been forked, or has been forked, then completed and all
854		* outstanding joins of this task have also completed. Effects
#	Line 689 | Line 863 | public abstract class ForkJoinTask<V> im
863		}
864
865		/**
866	<	* Tries to unschedule this task for execution. This method will
867	<	* typically succeed if this task is the next task that would be
868	<	* executed by the current thread, and will typically fail (return
869	<	* false) otherwise. This method may be useful when arranging
696	<	* faster local processing of tasks that could have been, but were
697	<	* not, stolen.
698	<	* @return true if unforked
866	>	* Returns the pool hosting the current task execution, or null
867	>	* if this task is executing outside of any ForkJoinPool.
868	>	*
869	>	* @return the pool, or null if none.
870		*/
871	<	public boolean tryUnfork() {
872	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
871	>	public static ForkJoinPool getPool() {
872	>	Thread t = Thread.currentThread();
873	>	return ((t instanceof ForkJoinWorkerThread)?
874	>	((ForkJoinWorkerThread)t).pool : null);
875		}
876
877		/**
878	<	* Forks both tasks, returning when <tt>isDone</tt> holds for both
879	<	* of them or an exception is encountered. This method may be
880	<	* invoked only from within other ForkJoinTask
881	<	* computations. Attempts to invoke in other contexts result in
709	<	* 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.
878	>	* Returns true if the current thread is executing as a
879	>	* ForkJoinPool computation.
880	>	* @return <code>true</code> if the current thread is executing as a
881	>	* ForkJoinPool computation, or false otherwise
882		*/
883	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
884	<	t2.fork();
717	<	t1.invoke();
718	<	t2.join();
883	>	public static boolean inForkJoinPool() {
884	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
885		}
886
887		/**
888	<	* Forks the given tasks, returning when <tt>isDone</tt> holds for
889	<	* all of them. If any task encounters an exception, others may be
890	<	* cancelled.  This method may be invoked only from within other
891	<	* ForkJoinTask computations. Attempts to invoke in other contexts
892	<	* result in exceptions or errors including ClassCastException.
893	<	* @param tasks the array of tasks
894	<	* @throws NullPointerException if tasks or any element are null.
895	<	* @throws RuntimeException or Error if any task did so.
896	<	*/
897	<	public static void invokeAll(ForkJoinTask<?>... tasks) {
898	<	Throwable ex = null;
899	<	int last = tasks.length - 1;
734	<	for (int i = last; i >= 0; --i) {
735	<	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	<	}
759	<	}
760	<	if (ex != null)
761	<	rethrowException(ex);
762	<	}
763	<
764	<	/**
765	<	* Forks all tasks in the collection, returning when
766	<	* <tt>isDone</tt> holds for all of them. If any task encounters
767	<	* an exception, others may be cancelled.  This method may be
768	<	* invoked only from within other ForkJoinTask
769	<	* 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.
888	>	* Tries to unschedule this task for execution. This method will
889	>	* typically succeed if this task is the most recently forked task
890	>	* by the current thread, and has not commenced executing in
891	>	* another thread.  This method may be useful when arranging
892	>	* alternative local processing of tasks that could have been, but
893	>	* were not, stolen. This method may be invoked only from within
894	>	* ForkJoinTask computations (as may be determined using method
895	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
896	>	* result in exceptions or errors possibly including
897	>	* ClassCastException.
898	>	*
899	>	* @return true if unforked
900		*/
901	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
902	<	if (!(tasks instanceof List)) {
777	<	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);
901	>	public boolean tryUnfork() {
902	>	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
903		}
904
905		/**
906	<	* Possibly executes tasks until the pool hosting the current task
907	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
908	<	* designs in which many tasks are forked, but none are explicitly
909	<	* joined, instead executing them until all are processed.
906	>	* Returns an estimate of the number of tasks that have been
907	>	* forked by the current worker thread but not yet executed. This
908	>	* value may be useful for heuristic decisions about whether to
909	>	* fork other tasks.
910	>	*
911	>	* @return the number of tasks
912		*/
913	<	public static void helpQuiesce() {
914	<	((ForkJoinWorkerThread)(Thread.currentThread())).
915	<	helpQuiescePool();
913	>	public static int getQueuedTaskCount() {
914	>	return ((ForkJoinWorkerThread)(Thread.currentThread())).
915	>	getQueueSize();
916		}
917
918		/**
919	<	* Returns a estimate of how many more locally queued tasks are
919	>	* Returns an estimate of how many more locally queued tasks are
920		* held by the current worker thread than there are other worker
921	<	* threads that might want to steal them.  This value may be
922	<	* useful for heuristic decisions about whether to fork other
923	<	* tasks. In many usages of ForkJoinTasks, at steady state, each
924	<	* worker should aim to maintain a small constant surplus (for
925	<	* example, 3) of tasks, and to process computations locally if
926	<	* this threshold is exceeded.
921	>	* threads that might steal them.  This value may be useful for
922	>	* heuristic decisions about whether to fork other tasks. In many
923	>	* usages of ForkJoinTasks, at steady state, each worker should
924	>	* aim to maintain a small constant surplus (for example, 3) of
925	>	* tasks, and to process computations locally if this threshold is
926	>	* exceeded.
927	>	*
928		* @return the surplus number of tasks, which may be negative
929		*/
930	<	public static int surplus() {
930	>	public static int getSurplusQueuedTaskCount() {
931		return ((ForkJoinWorkerThread)(Thread.currentThread()))
932		.getEstimatedSurplusTaskCount();
933		}
934
935	<	// Extension kit
935	>	// Extension methods
936
937		/**
938	<	* Returns the result that would be returned by <tt>join</tt>, or
939	<	* null if this task is not known to have been completed.  This
940	<	* method is designed to aid debugging, as well as to support
941	<	* extensions. Its use in any other context is discouraged.
938	>	* Returns the result that would be returned by {@code join},
939	>	* even if this task completed abnormally, or null if this task is
940	>	* not known to have been completed.  This method is designed to
941	>	* aid debugging, as well as to support extensions. Its use in any
942	>	* other context is discouraged.
943		*
944	<	* @return the result, or null if not completed.
944	>	* @return the result, or null if not completed
945		*/
946		public abstract V getRawResult();
947
#	Line 865 | Line 960 | public abstract class ForkJoinTask<V> im
960		* called otherwise. The return value controls whether this task
961		* is considered to be done normally. It may return false in
962		* asynchronous actions that require explicit invocations of
963	<	* <tt>complete</tt> to become joinable. It may throw exceptions
963	>	* {@code complete} to become joinable. It may throw exceptions
964		* to indicate abnormal exit.
965	+	*
966		* @return true if completed normally
967		* @throws Error or RuntimeException if encountered during computation
968		*/
969		protected abstract boolean exec();
970
971	+	/**
972	+	* Returns, but does not unschedule or execute, the task queued by
973	+	* the current thread but not yet executed, if one is
974	+	* available. There is no guarantee that this task will actually
975	+	* be polled or executed next.  This method is designed primarily
976	+	* to support extensions, and is unlikely to be useful otherwise.
977	+	* This method may be invoked only from within ForkJoinTask
978	+	* computations (as may be determined using method {@link
979	+	* #inForkJoinPool}). Attempts to invoke in other contexts result
980	+	* in exceptions or errors possibly including ClassCastException.
981	+	*
982	+	* @return the next task, or null if none are available
983	+	*/
984	+	protected static ForkJoinTask<?> peekNextLocalTask() {
985	+	return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask();
986	+	}
987	+
988	+	/**
989	+	* Unschedules and returns, without executing, the next task
990	+	* queued by the current thread but not yet executed.  This method
991	+	* is designed primarily to support extensions, and is unlikely to
992	+	* be useful otherwise.  This method may be invoked only from
993	+	* within ForkJoinTask computations (as may be determined using
994	+	* method {@link #inForkJoinPool}). Attempts to invoke in other
995	+	* contexts result in exceptions or errors possibly including
996	+	* ClassCastException.
997	+	*
998	+	* @return the next task, or null if none are available
999	+	*/
1000	+	protected static ForkJoinTask<?> pollNextLocalTask() {
1001	+	return ((ForkJoinWorkerThread)(Thread.currentThread())).pollLocalTask();
1002	+	}
1003	+
1004	+	/**
1005	+	* Unschedules and returns, without executing, the next task
1006	+	* queued by the current thread but not yet executed, if one is
1007	+	* available, or if not available, a task that was forked by some
1008	+	* other thread, if available. Availability may be transient, so a
1009	+	* {@code null} result does not necessarily imply quiescence
1010	+	* of the pool this task is operating in.  This method is designed
1011	+	* primarily to support extensions, and is unlikely to be useful
1012	+	* otherwise.  This method may be invoked only from within
1013	+	* ForkJoinTask computations (as may be determined using method
1014	+	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1015	+	* result in exceptions or errors possibly including
1016	+	* ClassCastException.
1017	+	*
1018	+	* @return a task, or null if none are available
1019	+	*/
1020	+	protected static ForkJoinTask<?> pollTask() {
1021	+	return ((ForkJoinWorkerThread)(Thread.currentThread())).
1022	+	pollTask();
1023	+	}
1024	+
1025		// Serialization support
1026
1027		private static final long serialVersionUID = -7721805057305804111L;
#	Line 880 | Line 1030 | public abstract class ForkJoinTask<V> im
1030		* Save the state to a stream.
1031		*
1032		* @serialData the current run status and the exception thrown
1033	<	* during execution, or null if none.
1033	>	* during execution, or null if none
1034		* @param s the stream
1035		*/
1036		private void writeObject(java.io.ObjectOutputStream s)
#	Line 891 | Line 1041 | public abstract class ForkJoinTask<V> im
1041
1042		/**
1043		* Reconstitute the instance from a stream.
1044	+	*
1045		* @param s the stream
1046		*/
1047		private void readObject(java.io.ObjectInputStream s)
1048		throws java.io.IOException, ClassNotFoundException {
1049		s.defaultReadObject();
1050	<	//        status &= ~INTERNAL_SIGNAL_MASK; //  todo: define policy
1050	>	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1051	>	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1052		Object ex = s.readObject();
1053		if (ex != null)
1054		setDoneExceptionally((Throwable)ex);
1055		}
1056
1057		// Temporary Unsafe mechanics for preliminary release
1058	+	private static Unsafe getUnsafe() throws Throwable {
1059	+	try {
1060	+	return Unsafe.getUnsafe();
1061	+	} catch (SecurityException se) {
1062	+	try {
1063	+	return java.security.AccessController.doPrivileged
1064	+	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1065	+	public Unsafe run() throws Exception {
1066	+	return getUnsafePrivileged();
1067	+	}});
1068	+	} catch (java.security.PrivilegedActionException e) {
1069	+	throw e.getCause();
1070	+	}
1071	+	}
1072	+	}
1073	+
1074	+	private static Unsafe getUnsafePrivileged()
1075	+	throws NoSuchFieldException, IllegalAccessException {
1076	+	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1077	+	f.setAccessible(true);
1078	+	return (Unsafe) f.get(null);
1079	+	}
1080	+
1081	+	private static long fieldOffset(String fieldName)
1082	+	throws NoSuchFieldException {
1083	+	return UNSAFE.objectFieldOffset
1084	+	(ForkJoinTask.class.getDeclaredField(fieldName));
1085	+	}
1086
1087	<	static final Unsafe _unsafe;
1087	>	static final Unsafe UNSAFE;
1088		static final long statusOffset;
1089
1090		static {
1091		try {
1092	<	if (ForkJoinTask.class.getClassLoader() != null) {
1093	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1094	<	f.setAccessible(true);
1095	<	_unsafe = (Unsafe)f.get(null);
1096	<	}
917	<	else
918	<	_unsafe = Unsafe.getUnsafe();
919	<	statusOffset = _unsafe.objectFieldOffset
920	<	(ForkJoinTask.class.getDeclaredField("status"));
921	<	} catch (Exception ex) { throw new Error(ex); }
1092	>	UNSAFE = getUnsafe();
1093	>	statusOffset = fieldOffset("status");
1094	>	} catch (Throwable e) {
1095	>	throw new RuntimeException("Could not initialize intrinsics", e);
1096	>	}
1097		}
1098
1099		}

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