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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.31 by jsr166, Sun Aug 2 22:58:50 2009 UTC vs.
Revision 1.64 by jsr166, Mon Sep 20 20:42:37 2010 UTC

#	Line 7 | Line 7
7		package jsr166y;
8
9		import java.util.concurrent.*;
10	–
10		import java.io.Serializable;
11		import java.util.Collection;
12		import java.util.Collections;
13		import java.util.List;
14	+	import java.util.RandomAccess;
15		import java.util.Map;
16		import java.util.WeakHashMap;
17
#	Line 27 | Line 27 | import java.util.WeakHashMap;
27		* start other subtasks.  As indicated by the name of this class,
28		* many programs using {@code ForkJoinTask} employ only methods
29		* {@link #fork} and {@link #join}, or derivatives such as {@link
30	<	* #invokeAll}.  However, this class also provides a number of other
31	<	* methods that can come into play in advanced usages, as well as
32	<	* extension mechanics that allow support of new forms of fork/join
33	<	* processing.
30	>	* #invokeAll(ForkJoinTask...) invokeAll}.  However, this class also
31	>	* provides a number of other methods that can come into play in
32	>	* advanced usages, as well as extension mechanics that allow
33	>	* support of new forms of fork/join processing.
34		*
35		* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
36		* The efficiency of {@code ForkJoinTask}s stems from a set of
#	Line 54 | Line 54 | import java.util.WeakHashMap;
54		* restriction is in part enforced by not permitting checked
55		* exceptions such as {@code IOExceptions} to be thrown. However,
56		* computations may still encounter unchecked exceptions, that are
57	<	* rethrown to callers attempting join them. These exceptions may
58	<	* additionally include RejectedExecutionExceptions stemming from
59	<	* internal resource exhaustion such as failure to allocate internal
60	<	* task queues.
57	>	* rethrown to callers attempting to join them. These exceptions may
58	>	* additionally include {@link RejectedExecutionException} stemming
59	>	* from internal resource exhaustion, such as failure to allocate
60	>	* internal task queues.
61		*
62		* <p>The primary method for awaiting completion and extracting
63		* results of a task is {@link #join}, but there are several variants:
64		* The {@link Future#get} methods support interruptible and/or timed
65		* waits for completion and report results using {@code Future}
66	<	* conventions. Method {@link #helpJoin} enables callers to actively
67	<	* execute other tasks while awaiting joins, which is sometimes more
68	<	* efficient but only applies when all subtasks are known to be
69	<	* strictly tree-structured. Method {@link #invoke} is semantically
70	<	* equivalent to {@code fork(); join()} but always attempts to
71	<	* begin execution in the current thread. The "<em>quiet</em>" forms
72	<	* of these methods do not extract results or report exceptions. These
66	>	* conventions. Method {@link #invoke} is semantically
67	>	* equivalent to {@code fork(); join()} but always attempts to begin
68	>	* execution in the current thread. The "<em>quiet</em>" forms of
69	>	* these methods do not extract results or report exceptions. These
70		* may be useful when a set of tasks are being executed, and you need
71		* to delay processing of results or exceptions until all complete.
72		* Method {@code invokeAll} (available in multiple versions)
73		* performs the most common form of parallel invocation: forking a set
74		* of tasks and joining them all.
75		*
76	+	* <p>The execution status of tasks may be queried at several levels
77	+	* of detail: {@link #isDone} is true if a task completed in any way
78	+	* (including the case where a task was cancelled without executing);
79	+	* {@link #isCompletedNormally} is true if a task completed without
80	+	* cancellation or encountering an exception; {@link #isCancelled} is
81	+	* true if the task was cancelled (in which case {@link #getException}
82	+	* returns a {@link java.util.concurrent.CancellationException}); and
83	+	* {@link #isCompletedAbnormally} is true if a task was either
84	+	* cancelled or encountered an exception, in which case {@link
85	+	* #getException} will return either the encountered exception or
86	+	* {@link java.util.concurrent.CancellationException}.
87	+	*
88		* <p>The ForkJoinTask class is not usually directly subclassed.
89		* Instead, you subclass one of the abstract classes that support a
90		* particular style of fork/join processing, typically {@link
#	Line 85 | Line 94 | import java.util.WeakHashMap;
94		* established in a constructor, and then defines a {@code compute}
95		* method that somehow uses the control methods supplied by this base
96		* class. While these methods have {@code public} access (to allow
97	<	* instances of different task subclasses to call each others
97	>	* instances of different task subclasses to call each other's
98		* methods), some of them may only be called from within other
99		* ForkJoinTasks (as may be determined using method {@link
100		* #inForkJoinPool}).  Attempts to invoke them in other contexts
101		* result in exceptions or errors, possibly including
102	<	* ClassCastException.
102	>	* {@code ClassCastException}.
103		*
104	<	* <p>Most base support methods are {@code final} because their
105	<	* implementations are intrinsically tied to the underlying
106	<	* lightweight task scheduling framework, and so cannot be overridden.
107	<	* Developers creating new basic styles of fork/join processing should
108	<	* minimally implement {@code protected} methods
109	<	* {@link #exec}, {@link #setRawResult}, and
110	<	* {@link #getRawResult}, while also introducing an abstract
111	<	* computational method that can be implemented in its subclasses,
112	<	* possibly relying on other {@code protected} methods provided
104	<	* by this class.
104	>	* <p>Most base support methods are {@code final}, to prevent
105	>	* overriding of implementations that are intrinsically tied to the
106	>	* underlying lightweight task scheduling framework.  Developers
107	>	* creating new basic styles of fork/join processing should minimally
108	>	* implement {@code protected} methods {@link #exec}, {@link
109	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
110	>	* an abstract computational method that can be implemented in its
111	>	* subclasses, possibly relying on other {@code protected} methods
112	>	* provided by this class.
113		*
114		* <p>ForkJoinTasks should perform relatively small amounts of
115	<	* computations, otherwise splitting into smaller tasks. As a very
116	<	* rough rule of thumb, a task should perform more than 100 and less
117	<	* than 10000 basic computational steps. If tasks are too big, then
118	<	* parallelism cannot improve throughput. If too small, then memory
119	<	* and internal task maintenance overhead may overwhelm processing.
115	>	* computation. Large tasks should be split into smaller subtasks,
116	>	* usually via recursive decomposition. As a very rough rule of thumb,
117	>	* a task should perform more than 100 and less than 10000 basic
118	>	* computational steps. If tasks are too big, then parallelism cannot
119	>	* improve throughput. If too small, then memory and internal task
120	>	* maintenance overhead may overwhelm processing.
121		*
122	<	* <p>This class provides {@code adapt} methods for {@link
123	<	* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
124	<	* may be of use when mixing execution of ForkJoinTasks with other
125	<	* kinds of tasks. When all tasks are of this form, consider using a
117	<	* pool in {@link ForkJoinPool#setAsyncMode}.
122	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
123	>	* and {@link Callable}, that may be of use when mixing execution of
124	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
125	>	* of this form, consider using a pool constructed in <em>asyncMode</em>.
126		*
127	<	* <p>ForkJoinTasks are {@code Serializable}, which enables them
128	<	* to be used in extensions such as remote execution frameworks. It is
129	<	* in general sensible to serialize tasks only before or after, but
130	<	* not during execution. Serialization is not relied on during
123	<	* execution itself.
127	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
128	>	* used in extensions such as remote execution frameworks. It is
129	>	* sensible to serialize tasks only before or after, but not during,
130	>	* execution. Serialization is not relied on during execution itself.
131		*
132		* @since 1.7
133		* @author Doug Lea
134		*/
135		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
136
137	<	/**
138	<	* Run control status bits packed into a single int to minimize
139	<	* footprint and to ensure atomicity (via CAS).  Status is
140	<	* initially zero, and takes on nonnegative values until
141	<	* completed, upon which status holds COMPLETED. CANCELLED, or
142	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
143	<	* blocking waits by other threads have SIGNAL_MASK bits set --
144	<	* bit 15 for external (nonFJ) waits, and the rest a count of
145	<	* waiting FJ threads.  (This representation relies on
146	<	* ForkJoinPool max thread limits). Completion of a stolen task
147	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
148	<	* though suboptimal for some purposes, we use basic builtin
149	<	* wait/notify to take advantage of "monitor inflation" in JVMs
150	<	* that we would otherwise need to emulate to avoid adding further
151	<	* per-task bookkeeping overhead. Note that bits 16-28 are
152	<	* currently unused. Also value 0x80000000 is available as spare
153	<	* completion value.
137	>	/*
138	>	* See the internal documentation of class ForkJoinPool for a
139	>	* general implementation overview.  ForkJoinTasks are mainly
140	>	* responsible for maintaining their "status" field amidst relays
141	>	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
142	>	* methods of this class are more-or-less layered into (1) basic
143	>	* status maintenance (2) execution and awaiting completion (3)
144	>	* user-level methods that additionally report results. This is
145	>	* sometimes hard to see because this file orders exported methods
146	>	* in a way that flows well in javadocs. In particular, most
147	>	* join mechanics are in method quietlyJoin, below.
148	>	*/
149	>
150	>	/*
151	>	* The status field holds run control status bits packed into a
152	>	* single int to minimize footprint and to ensure atomicity (via
153	>	* CAS).  Status is initially zero, and takes on nonnegative
154	>	* values until completed, upon which status holds value
155	>	* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
156	>	* waits by other threads have the SIGNAL bit set.  Completion of
157	>	* a stolen task with SIGNAL set awakens any waiters via
158	>	* notifyAll. Even though suboptimal for some purposes, we use
159	>	* basic builtin wait/notify to take advantage of "monitor
160	>	* inflation" in JVMs that we would otherwise need to emulate to
161	>	* avoid adding further per-task bookkeeping overhead.  We want
162	>	* these monitors to be "fat", i.e., not use biasing or thin-lock
163	>	* techniques, so use some odd coding idioms that tend to avoid
164	>	* them.
165		*/
166	+
167	+	/** The run status of this task */
168		volatile int status; // accessed directly by pool and workers
169
170	<	static final int COMPLETION_MASK      = 0xe0000000;
171	<	static final int NORMAL               = 0xe0000000; // == mask
172	<	static final int CANCELLED            = 0xc0000000;
173	<	static final int EXCEPTIONAL          = 0xa0000000;
154	<	static final int SIGNAL_MASK          = 0x0000ffff;
155	<	static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
156	<	static final int EXTERNAL_SIGNAL      = 0x00008000; // top bit of low word
170	>	private static final int NORMAL      = -1;
171	>	private static final int CANCELLED   = -2;
172	>	private static final int EXCEPTIONAL = -3;
173	>	private static final int SIGNAL      =  1;
174
175		/**
176		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 167 | Line 184 | public abstract class ForkJoinTask<V> im
184		Collections.synchronizedMap
185		(new WeakHashMap<ForkJoinTask<?>, Throwable>());
186
187	<	// within-package utilities
187	>	// Maintaining completion status
188
189		/**
190	<	* Gets current worker thread, or null if not a worker thread.
191	<	*/
175	<	static ForkJoinWorkerThread getWorker() {
176	<	Thread t = Thread.currentThread();
177	<	return ((t instanceof ForkJoinWorkerThread) ?
178	<	(ForkJoinWorkerThread) t : null);
179	<	}
180	<
181	<	final boolean casStatus(int cmp, int val) {
182	<	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
183	<	}
184	<
185	<	/**
186	<	* Workaround for not being able to rethrow unchecked exceptions.
187	<	*/
188	<	static void rethrowException(Throwable ex) {
189	<	if (ex != null)
190	<	UNSAFE.throwException(ex);
191	<	}
192	<
193	<	// Setting completion status
194	<
195	<	/**
196	<	* Marks completion and wakes up threads waiting to join this task.
190	>	* Marks completion and wakes up threads waiting to join this task,
191	>	* also clearing signal request bits.
192		*
193		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
194		*/
195	<	final void setCompletion(int completion) {
196	<	ForkJoinPool pool = getPool();
197	<	if (pool != null) {
198	<	int s; // Clear signal bits while setting completion status
199	<	do {} while ((s = status) >= 0 && !casStatus(s, completion));
200	<
201	<	if ((s & SIGNAL_MASK) != 0) {
207	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
208	<	pool.updateRunningCount(s);
209	<	synchronized (this) { notifyAll(); }
195	>	private void setCompletion(int completion) {
196	>	int s;
197	>	while ((s = status) >= 0) {
198	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
199	>	if (s != 0)
200	>	synchronized (this) { notifyAll(); }
201	>	break;
202		}
203		}
212	–	else
213	–	externallySetCompletion(completion);
214	–	}
215	–
216	–	/**
217	–	* Version of setCompletion for non-FJ threads.  Leaves signal
218	–	* bits for unblocked threads to adjust, and always notifies.
219	–	*/
220	–	private void externallySetCompletion(int completion) {
221	–	int s;
222	–	do {} while ((s = status) >= 0 &&
223	–	!casStatus(s, (s & SIGNAL_MASK) | completion));
224	–	synchronized (this) { notifyAll(); }
225	–	}
226	–
227	–	/**
228	–	* Sets status to indicate normal completion.
229	–	*/
230	–	final void setNormalCompletion() {
231	–	// Try typical fast case -- single CAS, no signal, not already done.
232	–	// Manually expand casStatus to improve chances of inlining it
233	–	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
234	–	setCompletion(NORMAL);
204		}
205
237	–	// internal waiting and notification
238	–
206		/**
207	<	* Performs the actual monitor wait for awaitDone.
207	>	* Records exception and sets exceptional completion.
208	>	*
209	>	* @return status on exit
210		*/
211	<	private void doAwaitDone() {
212	<	// Minimize lock bias and in/de-flation effects by maximizing
213	<	// chances of waiting inside sync
245	<	try {
246	<	while (status >= 0)
247	<	synchronized (this) { if (status >= 0) wait(); }
248	<	} catch (InterruptedException ie) {
249	<	onInterruptedWait();
250	<	}
211	>	private void setExceptionalCompletion(Throwable rex) {
212	>	exceptionMap.put(this, rex);
213	>	setCompletion(EXCEPTIONAL);
214		}
215
216		/**
217	<	* Performs the actual timed monitor wait for awaitDone.
217	>	* Blocks a worker thread until completion. Called only by
218	>	* pool. Currently unused -- pool-based waits use timeout
219	>	* version below.
220		*/
221	<	private void doAwaitDone(long startTime, long nanos) {
222	<	synchronized (this) {
221	>	final void internalAwaitDone() {
222	>	int s;         // the odd construction reduces lock bias effects
223	>	while ((s = status) >= 0) {
224		try {
225	<	while (status >= 0) {
226	<	long nt = nanos - (System.nanoTime() - startTime);
227	<	if (nt <= 0)
262	<	break;
263	<	wait(nt / 1000000, (int) (nt % 1000000));
225	>	synchronized (this) {
226	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
227	>	wait();
228		}
229		} catch (InterruptedException ie) {
230	<	onInterruptedWait();
267	<	}
268	<	}
269	<	}
270	<
271	<	// Awaiting completion
272	<
273	<	/**
274	<	* Sets status to indicate there is joiner, then waits for join,
275	<	* surrounded with pool notifications.
276	<	*
277	<	* @return status upon exit
278	<	*/
279	<	private int awaitDone(ForkJoinWorkerThread w,
280	<	boolean maintainParallelism) {
281	<	ForkJoinPool pool = (w == null) ? null : w.pool;
282	<	int s;
283	<	while ((s = status) >= 0) {
284	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
285	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
286	<	doAwaitDone();
287	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
288	<	adjustPoolCountsOnUnblock(pool);
289	<	break;
230	>	cancelIfTerminating();
231		}
232		}
292	–	return s;
233		}
234
235		/**
236	<	* Timed version of awaitDone
236	>	* Blocks a worker thread until completed or timed out.  Called
237	>	* only by pool.
238		*
239	<	* @return status upon exit
239	>	* @return status on exit
240		*/
241	<	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
301	<	ForkJoinPool pool = (w == null) ? null : w.pool;
241	>	final int internalAwaitDone(long millis) {
242		int s;
243	<	while ((s = status) >= 0) {
244	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
245	<	long startTime = System.nanoTime();
246	<	if (pool == null || !pool.preJoin(this, false))
247	<	doAwaitDone(startTime, nanos);
308	<	if ((s = status) >= 0) {
309	<	adjustPoolCountsOnCancelledWait(pool);
310	<	s = status;
243	>	if ((s = status) >= 0) {
244	>	try {
245	>	synchronized (this) {
246	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
247	>	wait(millis, 0);
248		}
249	<	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
250	<	adjustPoolCountsOnUnblock(pool);
314	<	break;
249	>	} catch (InterruptedException ie) {
250	>	cancelIfTerminating();
251		}
252	+	s = status;
253		}
254		return s;
255		}
256
257		/**
258	<	* Notifies pool that thread is unblocked. Called by signalled
322	<	* threads when woken by non-FJ threads (which is atypical).
258	>	* Blocks a non-worker-thread until completion.
259		*/
260	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
260	>	private void externalAwaitDone() {
261		int s;
262	<	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
263	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
264	<	pool.updateRunningCount(s);
265	<	}
266	<
267	<	/**
268	<	* Notifies pool to adjust counts on cancelled or timed out wait.
269	<	*/
270	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
271	<	if (pool != null) {
272	<	int s;
273	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
274	<	if (casStatus(s, s - 1)) {
339	<	pool.updateRunningCount(1);
262	>	while ((s = status) >= 0) {
263	>	synchronized (this) {
264	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
265	>	boolean interrupted = false;
266	>	while (status >= 0) {
267	>	try {
268	>	wait();
269	>	} catch (InterruptedException ie) {
270	>	interrupted = true;
271	>	}
272	>	}
273	>	if (interrupted)
274	>	Thread.currentThread().interrupt();
275		break;
276		}
277		}
#	Line 344 | Line 279 | public abstract class ForkJoinTask<V> im
279		}
280
281		/**
282	<	* Handles interruptions during waits.
283	<	*/
284	<	private void onInterruptedWait() {
350	<	ForkJoinWorkerThread w = getWorker();
351	<	if (w == null)
352	<	Thread.currentThread().interrupt(); // re-interrupt
353	<	else if (w.isTerminating())
354	<	cancelIgnoringExceptions();
355	<	// else if FJworker, ignore interrupt
356	<	}
357	<
358	<	// Recording and reporting exceptions
359	<
360	<	private void setDoneExceptionally(Throwable rex) {
361	<	exceptionMap.put(this, rex);
362	<	setCompletion(EXCEPTIONAL);
363	<	}
364	<
365	<	/**
366	<	* Throws the exception associated with status s.
367	<	*
368	<	* @throws the exception
369	<	*/
370	<	private void reportException(int s) {
371	<	if ((s &= COMPLETION_MASK) < NORMAL) {
372	<	if (s == CANCELLED)
373	<	throw new CancellationException();
374	<	else
375	<	rethrowException(exceptionMap.get(this));
376	<	}
377	<	}
378	<
379	<	/**
380	<	* Returns result or throws exception using j.u.c.Future conventions.
381	<	* Only call when {@code isDone} known to be true.
382	<	*/
383	<	private V reportFutureResult()
384	<	throws ExecutionException, InterruptedException {
385	<	int s = status & COMPLETION_MASK;
386	<	if (s < NORMAL) {
387	<	Throwable ex;
388	<	if (s == CANCELLED)
389	<	throw new CancellationException();
390	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
391	<	throw new ExecutionException(ex);
392	<	if (Thread.interrupted())
393	<	throw new InterruptedException();
394	<	}
395	<	return getRawResult();
396	<	}
397	<
398	<	/**
399	<	* Returns result or throws exception using j.u.c.Future conventions
400	<	* with timeouts.
401	<	*/
402	<	private V reportTimedFutureResult()
403	<	throws InterruptedException, ExecutionException, TimeoutException {
404	<	Throwable ex;
405	<	int s = status & COMPLETION_MASK;
406	<	if (s == NORMAL)
407	<	return getRawResult();
408	<	if (s == CANCELLED)
409	<	throw new CancellationException();
410	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
411	<	throw new ExecutionException(ex);
412	<	if (Thread.interrupted())
413	<	throw new InterruptedException();
414	<	throw new TimeoutException();
415	<	}
416	<
417	<	// internal execution methods
418	<
419	<	/**
420	<	* Calls exec, recording completion, and rethrowing exception if
421	<	* encountered. Caller should normally check status before calling.
422	<	*
423	<	* @return true if completed normally
424	<	*/
425	<	private boolean tryExec() {
426	<	try { // try block must contain only call to exec
427	<	if (!exec())
428	<	return false;
429	<	} catch (Throwable rex) {
430	<	setDoneExceptionally(rex);
431	<	rethrowException(rex);
432	<	return false; // not reached
433	<	}
434	<	setNormalCompletion();
435	<	return true;
436	<	}
437	<
438	<	/**
439	<	* Main execution method used by worker threads. Invokes
440	<	* base computation unless already complete.
282	>	* Unless done, calls exec and records status if completed, but
283	>	* doesn't wait for completion otherwise. Primary execution method
284	>	* for ForkJoinWorkerThread.
285		*/
286		final void quietlyExec() {
443	–	if (status >= 0) {
444	–	try {
445	–	if (!exec())
446	–	return;
447	–	} catch (Throwable rex) {
448	–	setDoneExceptionally(rex);
449	–	return;
450	–	}
451	–	setNormalCompletion();
452	–	}
453	–	}
454	–
455	–	/**
456	–	* Calls exec(), recording but not rethrowing exception.
457	–	* Caller should normally check status before calling.
458	–	*
459	–	* @return true if completed normally
460	–	*/
461	–	private boolean tryQuietlyInvoke() {
287		try {
288	<	if (!exec())
289	<	return false;
288	>	if (status < 0 || !exec())
289	>	return;
290		} catch (Throwable rex) {
291	<	setDoneExceptionally(rex);
292	<	return false;
468	<	}
469	<	setNormalCompletion();
470	<	return true;
471	<	}
472	<
473	<	/**
474	<	* Cancels, ignoring any exceptions it throws.
475	<	*/
476	<	final void cancelIgnoringExceptions() {
477	<	try {
478	<	cancel(false);
479	<	} catch (Throwable ignore) {
291	>	setExceptionalCompletion(rex);
292	>	return;
293		}
294	<	}
482	<
483	<	/**
484	<	* Main implementation of helpJoin
485	<	*/
486	<	private int busyJoin(ForkJoinWorkerThread w) {
487	<	int s;
488	<	ForkJoinTask<?> t;
489	<	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
490	<	t.quietlyExec();
491	<	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
294	>	setCompletion(NORMAL); // must be outside try block
295		}
296
297		// public methods
#	Line 497 | Line 300 | public abstract class ForkJoinTask<V> im
300		* Arranges to asynchronously execute this task.  While it is not
301		* necessarily enforced, it is a usage error to fork a task more
302		* than once unless it has completed and been reinitialized.
303	+	* Subsequent modifications to the state of this task or any data
304	+	* it operates on are not necessarily consistently observable by
305	+	* any thread other than the one executing it unless preceded by a
306	+	* call to {@link #join} or related methods, or a call to {@link
307	+	* #isDone} returning {@code true}.
308		*
309		* <p>This method may be invoked only from within {@code
310		* ForkJoinTask} computations (as may be determined using method
#	Line 513 | Line 321 | public abstract class ForkJoinTask<V> im
321		}
322
323		/**
324	<	* Returns the result of the computation when it is ready.
324	>	* Returns the result of the computation when it {@link #isDone is done}.
325		* This method differs from {@link #get()} in that
326		* abnormal completion results in {@code RuntimeException} or
327		* {@code Error}, not {@code ExecutionException}.
#	Line 521 | Line 329 | public abstract class ForkJoinTask<V> im
329		* @return the computed result
330		*/
331		public final V join() {
332	<	ForkJoinWorkerThread w = getWorker();
333	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
334	<	reportException(awaitDone(w, true));
332	>	quietlyJoin();
333	>	Throwable ex;
334	>	if (status < NORMAL && (ex = getException()) != null)
335	>	UNSAFE.throwException(ex);
336		return getRawResult();
337		}
338
339		/**
340		* Commences performing this task, awaits its completion if
341	<	* necessary, and return its result.
341	>	* necessary, and returns its result, or throws an (unchecked)
342	>	* {@code RuntimeException} or {@code Error} if the underlying
343	>	* computation did so.
344		*
534	–	* @throws Throwable (a RuntimeException, Error, or unchecked
535	–	* exception) if the underlying computation did so
345		* @return the computed result
346		*/
347		public final V invoke() {
348	<	if (status >= 0 && tryExec())
349	<	return getRawResult();
350	<	else
351	<	return join();
348	>	quietlyInvoke();
349	>	Throwable ex;
350	>	if (status < NORMAL && (ex = getException()) != null)
351	>	UNSAFE.throwException(ex);
352	>	return getRawResult();
353		}
354
355		/**
356	<	* Forks the given tasks, returning when {@code isDone} holds
357	<	* for each task or an exception is encountered.
356	>	* Forks the given tasks, returning when {@code isDone} holds for
357	>	* each task or an (unchecked) exception is encountered, in which
358	>	* case the exception is rethrown. If more than one task
359	>	* encounters an exception, then this method throws any one of
360	>	* these exceptions. If any task encounters an exception, the
361	>	* other may be cancelled. However, the execution status of
362	>	* individual tasks is not guaranteed upon exceptional return. The
363	>	* status of each task may be obtained using {@link
364	>	* #getException()} and related methods to check if they have been
365	>	* cancelled, completed normally or exceptionally, or left
366	>	* unprocessed.
367		*
368		* <p>This method may be invoked only from within {@code
369		* ForkJoinTask} computations (as may be determined using method
#	Line 555 | Line 374 | public abstract class ForkJoinTask<V> im
374		* @param t1 the first task
375		* @param t2 the second task
376		* @throws NullPointerException if any task is null
558	–	* @throws RuntimeException or Error if a task did so
377		*/
378		public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
379		t2.fork();
#	Line 565 | Line 383 | public abstract class ForkJoinTask<V> im
383
384		/**
385		* Forks the given tasks, returning when {@code isDone} holds for
386	<	* each task or an exception is encountered. If any task
387	<	* encounters an exception, others may be, but are not guaranteed
388	<	* to be, cancelled.
386	>	* each task or an (unchecked) exception is encountered, in which
387	>	* case the exception is rethrown. If more than one task
388	>	* encounters an exception, then this method throws any one of
389	>	* these exceptions. If any task encounters an exception, others
390	>	* may be cancelled. However, the execution status of individual
391	>	* tasks is not guaranteed upon exceptional return. The status of
392	>	* each task may be obtained using {@link #getException()} and
393	>	* related methods to check if they have been cancelled, completed
394	>	* normally or exceptionally, or left unprocessed.
395		*
396		* <p>This method may be invoked only from within {@code
397		* ForkJoinTask} computations (as may be determined using method
#	Line 575 | Line 399 | public abstract class ForkJoinTask<V> im
399		* result in exceptions or errors, possibly including {@code
400		* ClassCastException}.
401		*
578	–	* <p>Overloadings of this method exist for the special cases
579	–	* of one to four arguments.
580	–	*
402		* @param tasks the tasks
403	<	* @throws NullPointerException if tasks or any element are null
583	<	* @throws RuntimeException or Error if any task did so
403	>	* @throws NullPointerException if any task is null
404		*/
405		public static void invokeAll(ForkJoinTask<?>... tasks) {
406		Throwable ex = null;
#	Line 595 | Line 415 | public abstract class ForkJoinTask<V> im
415		t.fork();
416		else {
417		t.quietlyInvoke();
418	<	if (ex == null)
418	>	if (ex == null && t.status < NORMAL)
419		ex = t.getException();
420		}
421		}
#	Line 606 | Line 426 | public abstract class ForkJoinTask<V> im
426		t.cancel(false);
427		else {
428		t.quietlyJoin();
429	<	if (ex == null)
429	>	if (ex == null && t.status < NORMAL)
430		ex = t.getException();
431		}
432		}
433		}
434		if (ex != null)
435	<	rethrowException(ex);
435	>	UNSAFE.throwException(ex);
436		}
437
438		/**
439	<	* Forks all tasks in the collection, returning when {@code
440	<	* isDone} holds for each task or an exception is encountered.
441	<	* If any task encounters an exception, others may be, but are
442	<	* not guaranteed to be, cancelled.
439	>	* Forks all tasks in the specified collection, returning when
440	>	* {@code isDone} holds for each task or an (unchecked) exception
441	>	* is encountered, in which case the exception is rethrown. If
442	>	* more than one task encounters an exception, then this method
443	>	* throws any one of these exceptions. If any task encounters an
444	>	* exception, others may be cancelled. However, the execution
445	>	* status of individual tasks is not guaranteed upon exceptional
446	>	* return. The status of each task may be obtained using {@link
447	>	* #getException()} and related methods to check if they have been
448	>	* cancelled, completed normally or exceptionally, or left
449	>	* unprocessed.
450		*
451		* <p>This method may be invoked only from within {@code
452		* ForkJoinTask} computations (as may be determined using method
#	Line 630 | Line 457 | public abstract class ForkJoinTask<V> im
457		* @param tasks the collection of tasks
458		* @return the tasks argument, to simplify usage
459		* @throws NullPointerException if tasks or any element are null
633	–	* @throws RuntimeException or Error if any task did so
460		*/
461		public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
462	<	if (!(tasks instanceof List<?>)) {
462	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
463		invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
464		return tasks;
465		}
#	Line 652 | Line 478 | public abstract class ForkJoinTask<V> im
478		t.fork();
479		else {
480		t.quietlyInvoke();
481	<	if (ex == null)
481	>	if (ex == null && t.status < NORMAL)
482		ex = t.getException();
483		}
484		}
#	Line 663 | Line 489 | public abstract class ForkJoinTask<V> im
489		t.cancel(false);
490		else {
491		t.quietlyJoin();
492	<	if (ex == null)
492	>	if (ex == null && t.status < NORMAL)
493		ex = t.getException();
494		}
495		}
496		}
497		if (ex != null)
498	<	rethrowException(ex);
498	>	UNSAFE.throwException(ex);
499		return tasks;
500		}
501
502		/**
503	<	* Returns {@code true} if the computation performed by this task
504	<	* has completed (or has been cancelled).
505	<	*
506	<	* @return {@code true} if this computation has completed
507	<	*/
508	<	public final boolean isDone() {
509	<	return status < 0;
684	<	}
685	<
686	<	/**
687	<	* Returns {@code true} if this task was cancelled.
688	<	*
689	<	* @return {@code true} if this task was cancelled
690	<	*/
691	<	public final boolean isCancelled() {
692	<	return (status & COMPLETION_MASK) == CANCELLED;
693	<	}
694	<
695	<	/**
696	<	* Asserts that the results of this task's computation will not be
697	<	* used. If a cancellation occurs before attempting to execute this
698	<	* task, execution will be suppressed, {@link #isCancelled}
699	<	* will report true, and {@link #join} will result in a
700	<	* {@code CancellationException} being thrown. Otherwise, when
701	<	* cancellation races with completion, there are no guarantees
702	<	* about whether {@code isCancelled} will report {@code true},
703	<	* whether {@code join} will return normally or via an exception,
704	<	* or whether these behaviors will remain consistent upon repeated
705	<	* invocation.
503	>	* Attempts to cancel execution of this task. This attempt will
504	>	* fail if the task has already completed, has already been
505	>	* cancelled, or could not be cancelled for some other reason. If
506	>	* successful, and this task has not started when cancel is
507	>	* called, execution of this task is suppressed, {@link
508	>	* #isCancelled} will report true, and {@link #join} will result
509	>	* in a {@code CancellationException} being thrown.
510		*
511		* <p>This method may be overridden in subclasses, but if so, must
512		* still ensure that these minimal properties hold. In particular,
#	Line 714 | Line 518 | public abstract class ForkJoinTask<V> im
518		* invoke {@link #completeExceptionally}.
519		*
520		* @param mayInterruptIfRunning this value is ignored in the
521	<	* default implementation because tasks are not in general
521	>	* default implementation because tasks are not
522		* cancelled via interruption
523		*
524		* @return {@code true} if this task is now cancelled
525		*/
526		public boolean cancel(boolean mayInterruptIfRunning) {
527		setCompletion(CANCELLED);
528	<	return (status & COMPLETION_MASK) == CANCELLED;
528	>	return status == CANCELLED;
529	>	}
530	>
531	>	/**
532	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
533	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
534	>	* exceptions, but if it does anyway, we have no recourse during
535	>	* shutdown, so guard against this case.
536	>	*/
537	>	final void cancelIgnoringExceptions() {
538	>	try {
539	>	cancel(false);
540	>	} catch (Throwable ignore) {
541	>	}
542	>	}
543	>
544	>	/**
545	>	* Cancels if current thread is a terminating worker thread,
546	>	* ignoring any exceptions thrown by cancel.
547	>	*/
548	>	final void cancelIfTerminating() {
549	>	Thread t = Thread.currentThread();
550	>	if ((t instanceof ForkJoinWorkerThread) &&
551	>	((ForkJoinWorkerThread) t).isTerminating()) {
552	>	try {
553	>	cancel(false);
554	>	} catch (Throwable ignore) {
555	>	}
556	>	}
557	>	}
558	>
559	>	public final boolean isDone() {
560	>	return status < 0;
561	>	}
562	>
563	>	public final boolean isCancelled() {
564	>	return status == CANCELLED;
565		}
566
567		/**
#	Line 730 | Line 570 | public abstract class ForkJoinTask<V> im
570		* @return {@code true} if this task threw an exception or was cancelled
571		*/
572		public final boolean isCompletedAbnormally() {
573	<	return (status & COMPLETION_MASK) < NORMAL;
573	>	return status < NORMAL;
574	>	}
575	>
576	>	/**
577	>	* Returns {@code true} if this task completed without throwing an
578	>	* exception and was not cancelled.
579	>	*
580	>	* @return {@code true} if this task completed without throwing an
581	>	* exception and was not cancelled
582	>	*/
583	>	public final boolean isCompletedNormally() {
584	>	return status == NORMAL;
585		}
586
587		/**
#	Line 741 | Line 592 | public abstract class ForkJoinTask<V> im
592		* @return the exception, or {@code null} if none
593		*/
594		public final Throwable getException() {
595	<	int s = status & COMPLETION_MASK;
596	<	if (s >= NORMAL)
597	<	return null;
598	<	if (s == CANCELLED)
748	<	return new CancellationException();
749	<	return exceptionMap.get(this);
595	>	int s = status;
596	>	return ((s >= NORMAL)    ? null :
597	>	(s == CANCELLED) ? new CancellationException() :
598	>	exceptionMap.get(this));
599		}
600
601		/**
#	Line 759 | Line 608 | public abstract class ForkJoinTask<V> im
608		* overridable, but overridden versions must invoke {@code super}
609		* implementation to maintain guarantees.
610		*
611	<	* @param ex the exception to throw. If this exception is
612	<	* not a RuntimeException or Error, the actual exception thrown
613	<	* will be a RuntimeException with cause ex.
611	>	* @param ex the exception to throw. If this exception is not a
612	>	* {@code RuntimeException} or {@code Error}, the actual exception
613	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
614		*/
615		public void completeExceptionally(Throwable ex) {
616	<	setDoneExceptionally((ex instanceof RuntimeException) ||
617	<	(ex instanceof Error) ? ex :
618	<	new RuntimeException(ex));
616	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
617	>	(ex instanceof Error) ? ex :
618	>	new RuntimeException(ex));
619		}
620
621		/**
622		* Completes this task, and if not already aborted or cancelled,
623	<	* returning a {@code null} result upon {@code join} and related
624	<	* operations. This method may be used to provide results for
625	<	* asynchronous tasks, or to provide alternative handling for
626	<	* tasks that would not otherwise complete normally. Its use in
627	<	* other situations is discouraged. This method is
628	<	* overridable, but overridden versions must invoke {@code super}
629	<	* implementation to maintain guarantees.
623	>	* returning the given value as the result of subsequent
624	>	* invocations of {@code join} and related operations. This method
625	>	* may be used to provide results for asynchronous tasks, or to
626	>	* provide alternative handling for tasks that would not otherwise
627	>	* complete normally. Its use in other situations is
628	>	* discouraged. This method is overridable, but overridden
629	>	* versions must invoke {@code super} implementation to maintain
630	>	* guarantees.
631		*
632		* @param value the result value for this task
633		*/
#	Line 785 | Line 635 | public abstract class ForkJoinTask<V> im
635		try {
636		setRawResult(value);
637		} catch (Throwable rex) {
638	<	setDoneExceptionally(rex);
638	>	setExceptionalCompletion(rex);
639		return;
640		}
641	<	setNormalCompletion();
792	<	}
793	<
794	<	public final V get() throws InterruptedException, ExecutionException {
795	<	ForkJoinWorkerThread w = getWorker();
796	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
797	<	awaitDone(w, true);
798	<	return reportFutureResult();
799	<	}
800	<
801	<	public final V get(long timeout, TimeUnit unit)
802	<	throws InterruptedException, ExecutionException, TimeoutException {
803	<	long nanos = unit.toNanos(timeout);
804	<	ForkJoinWorkerThread w = getWorker();
805	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
806	<	awaitDone(w, nanos);
807	<	return reportTimedFutureResult();
641	>	setCompletion(NORMAL);
642		}
643
644		/**
645	<	* Possibly executes other tasks until this task is ready, then
646	<	* returns the result of the computation.  This method may be more
813	<	* efficient than {@code join}, but is only applicable when
814	<	* there are no potential dependencies between continuation of the
815	<	* current task and that of any other task that might be executed
816	<	* while helping. (This usually holds for pure divide-and-conquer
817	<	* tasks).
818	<	*
819	<	* <p>This method may be invoked only from within {@code
820	<	* ForkJoinTask} computations (as may be determined using method
821	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
822	<	* result in exceptions or errors, possibly including {@code
823	<	* ClassCastException}.
645	>	* Waits if necessary for the computation to complete, and then
646	>	* retrieves its result.
647		*
648		* @return the computed result
649	+	* @throws CancellationException if the computation was cancelled
650	+	* @throws ExecutionException if the computation threw an
651	+	* exception
652	+	* @throws InterruptedException if the current thread is not a
653	+	* member of a ForkJoinPool and was interrupted while waiting
654		*/
655	<	public final V helpJoin() {
656	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
657	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
658	<	reportException(busyJoin(w));
655	>	public final V get() throws InterruptedException, ExecutionException {
656	>	int s;
657	>	if (Thread.currentThread() instanceof ForkJoinWorkerThread) {
658	>	quietlyJoin();
659	>	s = status;
660	>	}
661	>	else {
662	>	while ((s = status) >= 0) {
663	>	synchronized (this) { // interruptible form of awaitDone
664	>	if (UNSAFE.compareAndSwapInt(this, statusOffset,
665	>	s, SIGNAL)) {
666	>	while (status >= 0)
667	>	wait();
668	>	}
669	>	}
670	>	}
671	>	}
672	>	if (s < NORMAL) {
673	>	Throwable ex;
674	>	if (s == CANCELLED)
675	>	throw new CancellationException();
676	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
677	>	throw new ExecutionException(ex);
678	>	}
679		return getRawResult();
680		}
681
682		/**
683	<	* Possibly executes other tasks until this task is ready.
683	>	* Waits if necessary for at most the given time for the computation
684	>	* to complete, and then retrieves its result, if available.
685		*
686	<	* <p>This method may be invoked only from within {@code
687	<	* ForkJoinTask} computations (as may be determined using method
688	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
689	<	* result in exceptions or errors, possibly including {@code
690	<	* ClassCastException}.
686	>	* @param timeout the maximum time to wait
687	>	* @param unit the time unit of the timeout argument
688	>	* @return the computed result
689	>	* @throws CancellationException if the computation was cancelled
690	>	* @throws ExecutionException if the computation threw an
691	>	* exception
692	>	* @throws InterruptedException if the current thread is not a
693	>	* member of a ForkJoinPool and was interrupted while waiting
694	>	* @throws TimeoutException if the wait timed out
695		*/
696	<	public final void quietlyHelpJoin() {
697	<	if (status >= 0) {
698	<	ForkJoinWorkerThread w =
699	<	(ForkJoinWorkerThread) Thread.currentThread();
700	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
701	<	busyJoin(w);
696	>	public final V get(long timeout, TimeUnit unit)
697	>	throws InterruptedException, ExecutionException, TimeoutException {
698	>	Thread t = Thread.currentThread();
699	>	ForkJoinPool pool;
700	>	if (t instanceof ForkJoinWorkerThread) {
701	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
702	>	if (status >= 0 && w.unpushTask(this))
703	>	quietlyExec();
704	>	pool = w.pool;
705	>	}
706	>	else
707	>	pool = null;
708	>	/*
709	>	* Timed wait loop intermixes cases for FJ (pool != null) and
710	>	* non FJ threads. For FJ, decrement pool count but don't try
711	>	* for replacement; increment count on completion. For non-FJ,
712	>	* deal with interrupts. This is messy, but a little less so
713	>	* than is splitting the FJ and nonFJ cases.
714	>	*/
715	>	boolean interrupted = false;
716	>	boolean dec = false; // true if pool count decremented
717	>	long nanos = unit.toNanos(timeout);
718	>	for (;;) {
719	>	if (pool == null && Thread.interrupted()) {
720	>	interrupted = true;
721	>	break;
722	>	}
723	>	int s = status;
724	>	if (s < 0)
725	>	break;
726	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
727	>	long startTime = System.nanoTime();
728	>	long nt; // wait time
729	>	while (status >= 0 &&
730	>	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
731	>	if (pool != null && !dec)
732	>	dec = pool.tryDecrementRunningCount();
733	>	else {
734	>	long ms = nt / 1000000;
735	>	int ns = (int) (nt % 1000000);
736	>	try {
737	>	synchronized (this) {
738	>	if (status >= 0)
739	>	wait(ms, ns);
740	>	}
741	>	} catch (InterruptedException ie) {
742	>	if (pool != null)
743	>	cancelIfTerminating();
744	>	else {
745	>	interrupted = true;
746	>	break;
747	>	}
748	>	}
749	>	}
750	>	}
751	>	break;
752	>	}
753	>	}
754	>	if (pool != null && dec)
755	>	pool.incrementRunningCount();
756	>	if (interrupted)
757	>	throw new InterruptedException();
758	>	int es = status;
759	>	if (es != NORMAL) {
760	>	Throwable ex;
761	>	if (es == CANCELLED)
762	>	throw new CancellationException();
763	>	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
764	>	throw new ExecutionException(ex);
765	>	throw new TimeoutException();
766		}
767	+	return getRawResult();
768		}
769
770		/**
771	<	* Joins this task, without returning its result or throwing an
771	>	* Joins this task, without returning its result or throwing its
772		* exception. This method may be useful when processing
773		* collections of tasks when some have been cancelled or otherwise
774		* known to have aborted.
775		*/
776		public final void quietlyJoin() {
777	<	if (status >= 0) {
778	<	ForkJoinWorkerThread w = getWorker();
779	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
780	<	awaitDone(w, true);
777	>	Thread t;
778	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
779	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
780	>	if (status >= 0) {
781	>	if (w.unpushTask(this)) {
782	>	boolean completed;
783	>	try {
784	>	completed = exec();
785	>	} catch (Throwable rex) {
786	>	setExceptionalCompletion(rex);
787	>	return;
788	>	}
789	>	if (completed) {
790	>	setCompletion(NORMAL);
791	>	return;
792	>	}
793	>	}
794	>	w.joinTask(this);
795	>	}
796		}
797	+	else
798	+	externalAwaitDone();
799		}
800
801		/**
802		* Commences performing this task and awaits its completion if
803	<	* necessary, without returning its result or throwing an
804	<	* exception. This method may be useful when processing
870	<	* collections of tasks when some have been cancelled or otherwise
871	<	* known to have aborted.
803	>	* necessary, without returning its result or throwing its
804	>	* exception.
805		*/
806		public final void quietlyInvoke() {
807	<	if (status >= 0 && !tryQuietlyInvoke())
808	<	quietlyJoin();
807	>	if (status >= 0) {
808	>	boolean completed;
809	>	try {
810	>	completed = exec();
811	>	} catch (Throwable rex) {
812	>	setExceptionalCompletion(rex);
813	>	return;
814	>	}
815	>	if (completed)
816	>	setCompletion(NORMAL);
817	>	else
818	>	quietlyJoin();
819	>	}
820		}
821
822		/**
823		* Possibly executes tasks until the pool hosting the current task
824	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
825	<	* designs in which many tasks are forked, but none are explicitly
826	<	* joined, instead executing them until all are processed.
824	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
825	>	* be of use in designs in which many tasks are forked, but none
826	>	* are explicitly joined, instead executing them until all are
827	>	* processed.
828		*
829		* <p>This method may be invoked only from within {@code
830		* ForkJoinTask} computations (as may be determined using method
#	Line 903 | Line 848 | public abstract class ForkJoinTask<V> im
848		* pre-constructed trees of subtasks in loops.
849		*/
850		public void reinitialize() {
851	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
851	>	if (status == EXCEPTIONAL)
852		exceptionMap.remove(this);
853		status = 0;
854		}
#	Line 1023 | Line 968 | public abstract class ForkJoinTask<V> im
968		* called otherwise. The return value controls whether this task
969		* is considered to be done normally. It may return false in
970		* asynchronous actions that require explicit invocations of
971	<	* {@link #complete} to become joinable. It may throw exceptions
972	<	* to indicate abnormal exit.
971	>	* {@link #complete} to become joinable. It may also throw an
972	>	* (unchecked) exception to indicate abnormal exit.
973		*
974		* @return {@code true} if completed normally
1030	–	* @throws Error or RuntimeException if encountered during computation
975		*/
976		protected abstract boolean exec();
977
#	Line 1194 | Line 1138 | public abstract class ForkJoinTask<V> im
1138		private static final long serialVersionUID = -7721805057305804111L;
1139
1140		/**
1141	<	* Save the state to a stream.
1141	>	* Saves the state to a stream (that is, serializes it).
1142		*
1143		* @serialData the current run status and the exception thrown
1144		* during execution, or {@code null} if none
#	Line 1207 | Line 1151 | public abstract class ForkJoinTask<V> im
1151		}
1152
1153		/**
1154	<	* Reconstitute the instance from a stream.
1154	>	* Reconstitutes the instance from a stream (that is, deserializes it).
1155		*
1156		* @param s the stream
1157		*/
1158		private void readObject(java.io.ObjectInputStream s)
1159		throws java.io.IOException, ClassNotFoundException {
1160		s.defaultReadObject();
1217	–	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1218	–	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1161		Object ex = s.readObject();
1162		if (ex != null)
1163	<	setDoneExceptionally((Throwable) ex);
1163	>	setExceptionalCompletion((Throwable) ex);
1164		}
1165
1166		// Unsafe mechanics

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