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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.33 by dl, Tue Aug 4 00:36:45 2009 UTC vs.
Revision 1.69 by dl, Mon Nov 22 12:24:34 2010 UTC

#	Line 6 | Line 6
6
7		package jsr166y;
8
9	–	import java.util.concurrent.*;
10	–
9		import java.io.Serializable;
10		import java.util.Collection;
11		import java.util.Collections;
#	Line 15 | Line 13 | import java.util.List;
13		import java.util.RandomAccess;
14		import java.util.Map;
15		import java.util.WeakHashMap;
16	+	import java.util.concurrent.Callable;
17	+	import java.util.concurrent.CancellationException;
18	+	import java.util.concurrent.ExecutionException;
19	+	import java.util.concurrent.Executor;
20	+	import java.util.concurrent.ExecutorService;
21	+	import java.util.concurrent.Future;
22	+	import java.util.concurrent.RejectedExecutionException;
23	+	import java.util.concurrent.RunnableFuture;
24	+	import java.util.concurrent.TimeUnit;
25	+	import java.util.concurrent.TimeoutException;
26
27		/**
28		* Abstract base class for tasks that run within a {@link ForkJoinPool}.
#	Line 28 | Line 36 | import java.util.WeakHashMap;
36		* start other subtasks.  As indicated by the name of this class,
37		* many programs using {@code ForkJoinTask} employ only methods
38		* {@link #fork} and {@link #join}, or derivatives such as {@link
39	<	* #invokeAll}.  However, this class also provides a number of other
40	<	* methods that can come into play in advanced usages, as well as
41	<	* extension mechanics that allow support of new forms of fork/join
42	<	* processing.
39	>	* #invokeAll(ForkJoinTask...) invokeAll}.  However, this class also
40	>	* provides a number of other methods that can come into play in
41	>	* advanced usages, as well as extension mechanics that allow
42	>	* support of new forms of fork/join processing.
43		*
44		* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
45		* The efficiency of {@code ForkJoinTask}s stems from a set of
#	Line 56 | Line 64 | import java.util.WeakHashMap;
64		* exceptions such as {@code IOExceptions} to be thrown. However,
65		* computations may still encounter unchecked exceptions, that are
66		* rethrown to callers attempting to join them. These exceptions may
67	<	* additionally include RejectedExecutionExceptions stemming from
68	<	* internal resource exhaustion such as failure to allocate internal
69	<	* task queues.
67	>	* additionally include {@link RejectedExecutionException} stemming
68	>	* from internal resource exhaustion, such as failure to allocate
69	>	* internal task queues.
70		*
71		* <p>The primary method for awaiting completion and extracting
72		* results of a task is {@link #join}, but there are several variants:
73		* The {@link Future#get} methods support interruptible and/or timed
74		* waits for completion and report results using {@code Future}
75	<	* conventions. Method {@link #helpJoin} enables callers to actively
76	<	* execute other tasks while awaiting joins, which is sometimes more
77	<	* efficient but only applies when all subtasks are known to be
78	<	* strictly tree-structured. Method {@link #invoke} is semantically
71	<	* equivalent to {@code fork(); join()} but always attempts to
72	<	* begin execution in the current thread. The "<em>quiet</em>" forms
73	<	* of these methods do not extract results or report exceptions. These
75	>	* conventions. Method {@link #invoke} is semantically
76	>	* equivalent to {@code fork(); join()} but always attempts to begin
77	>	* execution in the current thread. The "<em>quiet</em>" forms of
78	>	* these methods do not extract results or report exceptions. These
79		* may be useful when a set of tasks are being executed, and you need
80		* to delay processing of results or exceptions until all complete.
81		* Method {@code invokeAll} (available in multiple versions)
82		* performs the most common form of parallel invocation: forking a set
83		* of tasks and joining them all.
84		*
85	+	* <p>The execution status of tasks may be queried at several levels
86	+	* of detail: {@link #isDone} is true if a task completed in any way
87	+	* (including the case where a task was cancelled without executing);
88	+	* {@link #isCompletedNormally} is true if a task completed without
89	+	* cancellation or encountering an exception; {@link #isCancelled} is
90	+	* true if the task was cancelled (in which case {@link #getException}
91	+	* returns a {@link java.util.concurrent.CancellationException}); and
92	+	* {@link #isCompletedAbnormally} is true if a task was either
93	+	* cancelled or encountered an exception, in which case {@link
94	+	* #getException} will return either the encountered exception or
95	+	* {@link java.util.concurrent.CancellationException}.
96	+	*
97		* <p>The ForkJoinTask class is not usually directly subclassed.
98		* Instead, you subclass one of the abstract classes that support a
99		* particular style of fork/join processing, typically {@link
#	Line 91 | Line 108 | import java.util.WeakHashMap;
108		* ForkJoinTasks (as may be determined using method {@link
109		* #inForkJoinPool}).  Attempts to invoke them in other contexts
110		* result in exceptions or errors, possibly including
111	<	* ClassCastException.
111	>	* {@code ClassCastException}.
112	>	*
113	>	* <p>Method {@link #join} and its variants are appropriate for use
114	>	* only when completion dependencies are acyclic; that is, the
115	>	* parallel computation can be described as a directed acyclic graph
116	>	* (DAG). Otherwise, executions may encounter a form of deadlock as
117	>	* tasks cyclically wait for each other.  However, this framework
118	>	* supports other methods and techniques (for example the use of
119	>	* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that
120	>	* may be of use in constructing custom subclasses for problems that
121	>	* are not statically structured as DAGs.
122		*
123		* <p>Most base support methods are {@code final}, to prevent
124		* overriding of implementations that are intrinsically tied to the
#	Line 111 | Line 138 | import java.util.WeakHashMap;
138		* improve throughput. If too small, then memory and internal task
139		* maintenance overhead may overwhelm processing.
140		*
141	<	* <p>This class provides {@code adapt} methods for {@link
142	<	* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
143	<	* may be of use when mixing execution of ForkJoinTasks with other
144	<	* kinds of tasks. When all tasks are of this form, consider using a
118	<	* pool in {@link ForkJoinPool#setAsyncMode}.
141	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
142	>	* and {@link Callable}, that may be of use when mixing execution of
143	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
144	>	* of this form, consider using a pool constructed in <em>asyncMode</em>.
145		*
146		* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
147		* used in extensions such as remote execution frameworks. It is
#	Line 127 | Line 153 | import java.util.WeakHashMap;
153		*/
154		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
155
156	<	/**
157	<	* Run control status bits packed into a single int to minimize
158	<	* footprint and to ensure atomicity (via CAS).  Status is
159	<	* initially zero, and takes on nonnegative values until
160	<	* completed, upon which status holds COMPLETED. CANCELLED, or
161	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
162	<	* blocking waits by other threads have SIGNAL_MASK bits set --
163	<	* bit 15 for external (nonFJ) waits, and the rest a count of
164	<	* waiting FJ threads.  (This representation relies on
165	<	* ForkJoinPool max thread limits). Completion of a stolen task
166	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
167	<	* though suboptimal for some purposes, we use basic builtin
168	<	* wait/notify to take advantage of "monitor inflation" in JVMs
169	<	* that we would otherwise need to emulate to avoid adding further
170	<	* per-task bookkeeping overhead. Note that bits 16-28 are
171	<	* currently unused. Also value 0x80000000 is available as spare
172	<	* completion value.
156	>	/*
157	>	* See the internal documentation of class ForkJoinPool for a
158	>	* general implementation overview.  ForkJoinTasks are mainly
159	>	* responsible for maintaining their "status" field amidst relays
160	>	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
161	>	* methods of this class are more-or-less layered into (1) basic
162	>	* status maintenance (2) execution and awaiting completion (3)
163	>	* user-level methods that additionally report results. This is
164	>	* sometimes hard to see because this file orders exported methods
165	>	* in a way that flows well in javadocs. In particular, most
166	>	* join mechanics are in method quietlyJoin, below.
167	>	*/
168	>
169	>	/*
170	>	* The status field holds run control status bits packed into a
171	>	* single int to minimize footprint and to ensure atomicity (via
172	>	* CAS).  Status is initially zero, and takes on nonnegative
173	>	* values until completed, upon which status holds value
174	>	* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
175	>	* waits by other threads have the SIGNAL bit set.  Completion of
176	>	* a stolen task with SIGNAL set awakens any waiters via
177	>	* notifyAll. Even though suboptimal for some purposes, we use
178	>	* basic builtin wait/notify to take advantage of "monitor
179	>	* inflation" in JVMs that we would otherwise need to emulate to
180	>	* avoid adding further per-task bookkeeping overhead.  We want
181	>	* these monitors to be "fat", i.e., not use biasing or thin-lock
182	>	* techniques, so use some odd coding idioms that tend to avoid
183	>	* them.
184		*/
185	+
186	+	/** The run status of this task */
187		volatile int status; // accessed directly by pool and workers
188
189	<	static final int COMPLETION_MASK      = 0xe0000000;
190	<	static final int NORMAL               = 0xe0000000; // == mask
191	<	static final int CANCELLED            = 0xc0000000;
192	<	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
189	>	private static final int NORMAL      = -1;
190	>	private static final int CANCELLED   = -2;
191	>	private static final int EXCEPTIONAL = -3;
192	>	private static final int SIGNAL      =  1;
193
194		/**
195		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 167 | Line 203 | public abstract class ForkJoinTask<V> im
203		Collections.synchronizedMap
204		(new WeakHashMap<ForkJoinTask<?>, Throwable>());
205
206	<	// within-package utilities
206	>	// Maintaining completion status
207
208		/**
209	<	* Gets current worker thread, or null if not a worker thread.
210	<	*/
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.
209	>	* Marks completion and wakes up threads waiting to join this task,
210	>	* also clearing signal request bits.
211		*
212		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
213		*/
214	<	final void setCompletion(int completion) {
215	<	ForkJoinPool pool = getPool();
216	<	if (pool != null) {
217	<	int s; // Clear signal bits while setting completion status
218	<	do {} while ((s = status) >= 0 && !casStatus(s, completion));
219	<
220	<	if ((s & SIGNAL_MASK) != 0) {
207	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
208	<	pool.updateRunningCount(s);
209	<	synchronized (this) { notifyAll(); }
214	>	private void setCompletion(int completion) {
215	>	int s;
216	>	while ((s = status) >= 0) {
217	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
218	>	if (s != 0)
219	>	synchronized (this) { notifyAll(); }
220	>	break;
221		}
222		}
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);
223		}
224
237	–	// internal waiting and notification
238	–
225		/**
226	<	* Performs the actual monitor wait for awaitDone.
226	>	* Records exception and sets exceptional completion.
227	>	*
228	>	* @return status on exit
229		*/
230	<	private void doAwaitDone() {
231	<	// Minimize lock bias and in/de-flation effects by maximizing
232	<	// 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	<	}
230	>	private void setExceptionalCompletion(Throwable rex) {
231	>	exceptionMap.put(this, rex);
232	>	setCompletion(EXCEPTIONAL);
233		}
234
235		/**
236	<	* Performs the actual timed monitor wait for awaitDone.
236	>	* Blocks a worker thread until completion. Called only by
237	>	* pool. Currently unused -- pool-based waits use timeout
238	>	* version below.
239		*/
240	<	private void doAwaitDone(long startTime, long nanos) {
241	<	synchronized (this) {
240	>	final void internalAwaitDone() {
241	>	int s;         // the odd construction reduces lock bias effects
242	>	while ((s = status) >= 0) {
243		try {
244	<	while (status >= 0) {
245	<	long nt = nanos - (System.nanoTime() - startTime);
246	<	if (nt <= 0)
262	<	break;
263	<	wait(nt / 1000000, (int) (nt % 1000000));
244	>	synchronized (this) {
245	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
246	>	wait();
247		}
248		} catch (InterruptedException ie) {
249	<	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;
249	>	cancelIfTerminating();
250		}
251		}
292	–	return s;
252		}
253
254		/**
255	<	* Timed version of awaitDone
255	>	* Blocks a worker thread until completed or timed out.  Called
256	>	* only by pool.
257		*
258	<	* @return status upon exit
258	>	* @return status on exit
259		*/
260	<	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
301	<	ForkJoinPool pool = (w == null) ? null : w.pool;
260	>	final int internalAwaitDone(long millis, int nanos) {
261		int s;
262	<	while ((s = status) >= 0) {
263	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
264	<	long startTime = System.nanoTime();
265	<	if (pool == null || !pool.preJoin(this, false))
266	<	doAwaitDone(startTime, nanos);
308	<	if ((s = status) >= 0) {
309	<	adjustPoolCountsOnCancelledWait(pool);
310	<	s = status;
262	>	if ((s = status) >= 0) {
263	>	try {
264	>	synchronized (this) {
265	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
266	>	wait(millis, nanos);
267		}
268	<	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
269	<	adjustPoolCountsOnUnblock(pool);
314	<	break;
268	>	} catch (InterruptedException ie) {
269	>	cancelIfTerminating();
270		}
271	+	s = status;
272		}
273		return s;
274		}
275
276		/**
277	<	* Notifies pool that thread is unblocked. Called by signalled
322	<	* threads when woken by non-FJ threads (which is atypical).
277	>	* Blocks a non-worker-thread until completion.
278		*/
279	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
279	>	private void externalAwaitDone() {
280		int s;
281	<	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
282	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
283	<	pool.updateRunningCount(s);
284	<	}
285	<
286	<	/**
287	<	* Notifies pool to adjust counts on cancelled or timed out wait.
288	<	*/
289	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
290	<	if (pool != null) {
291	<	int s;
292	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
293	<	if (casStatus(s, s - 1)) {
339	<	pool.updateRunningCount(1);
281	>	while ((s = status) >= 0) {
282	>	synchronized (this) {
283	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
284	>	boolean interrupted = false;
285	>	while (status >= 0) {
286	>	try {
287	>	wait();
288	>	} catch (InterruptedException ie) {
289	>	interrupted = true;
290	>	}
291	>	}
292	>	if (interrupted)
293	>	Thread.currentThread().interrupt();
294		break;
295		}
296		}
#	Line 344 | Line 298 | public abstract class ForkJoinTask<V> im
298		}
299
300		/**
301	<	* Handles interruptions during waits.
302	<	*/
303	<	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.
301	>	* Unless done, calls exec and records status if completed, but
302	>	* doesn't wait for completion otherwise. Primary execution method
303	>	* for ForkJoinWorkerThread.
304		*/
305		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() {
306		try {
307	<	if (!exec())
308	<	return false;
307	>	if (status < 0 || !exec())
308	>	return;
309		} catch (Throwable rex) {
310	<	setDoneExceptionally(rex);
311	<	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) {
310	>	setExceptionalCompletion(rex);
311	>	return;
312		}
313	<	}
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
313	>	setCompletion(NORMAL); // must be outside try block
314		}
315
316		// public methods
#	Line 497 | Line 319 | public abstract class ForkJoinTask<V> im
319		* Arranges to asynchronously execute this task.  While it is not
320		* necessarily enforced, it is a usage error to fork a task more
321		* than once unless it has completed and been reinitialized.
322	+	* Subsequent modifications to the state of this task or any data
323	+	* it operates on are not necessarily consistently observable by
324	+	* any thread other than the one executing it unless preceded by a
325	+	* call to {@link #join} or related methods, or a call to {@link
326	+	* #isDone} returning {@code true}.
327		*
328		* <p>This method may be invoked only from within {@code
329		* ForkJoinTask} computations (as may be determined using method
#	Line 513 | Line 340 | public abstract class ForkJoinTask<V> im
340		}
341
342		/**
343	<	* Returns the result of the computation when it is ready.
344	<	* This method differs from {@link #get()} in that
343	>	* Returns the result of the computation when it {@link #isDone is
344	>	* done}.  This method differs from {@link #get()} in that
345		* abnormal completion results in {@code RuntimeException} or
346	<	* {@code Error}, not {@code ExecutionException}.
346	>	* {@code Error}, not {@code ExecutionException}, and that
347	>	* interrupts of the calling thread do <em>not</em> cause the
348	>	* method to abruptly return by throwing {@code
349	>	* InterruptedException}.
350		*
351		* @return the computed result
352		*/
353		public final V join() {
354	<	ForkJoinWorkerThread w = getWorker();
355	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
356	<	reportException(awaitDone(w, true));
354	>	quietlyJoin();
355	>	Throwable ex;
356	>	if (status < NORMAL && (ex = getException()) != null)
357	>	UNSAFE.throwException(ex);
358		return getRawResult();
359		}
360
361		/**
362		* Commences performing this task, awaits its completion if
363	<	* necessary, and return its result.
363	>	* necessary, and returns its result, or throws an (unchecked)
364	>	* {@code RuntimeException} or {@code Error} if the underlying
365	>	* computation did so.
366		*
534	–	* @throws Throwable (a RuntimeException, Error, or unchecked
535	–	* exception) if the underlying computation did so
367		* @return the computed result
368		*/
369		public final V invoke() {
370	<	if (status >= 0 && tryExec())
371	<	return getRawResult();
372	<	else
373	<	return join();
370	>	quietlyInvoke();
371	>	Throwable ex;
372	>	if (status < NORMAL && (ex = getException()) != null)
373	>	UNSAFE.throwException(ex);
374	>	return getRawResult();
375		}
376
377		/**
378	<	* Forks the given tasks, returning when {@code isDone} holds
379	<	* for each task or an exception is encountered.
378	>	* Forks the given tasks, returning when {@code isDone} holds for
379	>	* each task or an (unchecked) exception is encountered, in which
380	>	* case the exception is rethrown. If more than one task
381	>	* encounters an exception, then this method throws any one of
382	>	* these exceptions. If any task encounters an exception, the
383	>	* other may be cancelled. However, the execution status of
384	>	* individual tasks is not guaranteed upon exceptional return. The
385	>	* status of each task may be obtained using {@link
386	>	* #getException()} and related methods to check if they have been
387	>	* cancelled, completed normally or exceptionally, or left
388	>	* unprocessed.
389		*
390		* <p>This method may be invoked only from within {@code
391	<	* ForkJoinTask} computations (as may be determined using method
391	>	* ForkJoinPool} computations (as may be determined using method
392		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
393		* result in exceptions or errors, possibly including {@code
394		* ClassCastException}.
#	Line 555 | Line 396 | public abstract class ForkJoinTask<V> im
396		* @param t1 the first task
397		* @param t2 the second task
398		* @throws NullPointerException if any task is null
558	–	* @throws RuntimeException or Error if a task did so
399		*/
400		public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
401		t2.fork();
#	Line 565 | Line 405 | public abstract class ForkJoinTask<V> im
405
406		/**
407		* Forks the given tasks, returning when {@code isDone} holds for
408	<	* each task or an exception is encountered. If any task
409	<	* encounters an exception, others may be, but are not guaranteed
410	<	* to be, cancelled.
408	>	* each task or an (unchecked) exception is encountered, in which
409	>	* case the exception is rethrown. If more than one task
410	>	* encounters an exception, then this method throws any one of
411	>	* these exceptions. If any task encounters an exception, others
412	>	* may be cancelled. However, the execution status of individual
413	>	* tasks is not guaranteed upon exceptional return. The status of
414	>	* each task may be obtained using {@link #getException()} and
415	>	* related methods to check if they have been cancelled, completed
416	>	* normally or exceptionally, or left unprocessed.
417		*
418		* <p>This method may be invoked only from within {@code
419	<	* ForkJoinTask} computations (as may be determined using method
419	>	* ForkJoinPool} computations (as may be determined using method
420		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
421		* result in exceptions or errors, possibly including {@code
422		* ClassCastException}.
423		*
424		* @param tasks the tasks
425	<	* @throws NullPointerException if tasks or any element are null
580	<	* @throws RuntimeException or Error if any task did so
425	>	* @throws NullPointerException if any task is null
426		*/
427		public static void invokeAll(ForkJoinTask<?>... tasks) {
428		Throwable ex = null;
#	Line 592 | Line 437 | public abstract class ForkJoinTask<V> im
437		t.fork();
438		else {
439		t.quietlyInvoke();
440	<	if (ex == null)
440	>	if (ex == null && t.status < NORMAL)
441		ex = t.getException();
442		}
443		}
#	Line 603 | Line 448 | public abstract class ForkJoinTask<V> im
448		t.cancel(false);
449		else {
450		t.quietlyJoin();
451	<	if (ex == null)
451	>	if (ex == null && t.status < NORMAL)
452		ex = t.getException();
453		}
454		}
455		}
456		if (ex != null)
457	<	rethrowException(ex);
457	>	UNSAFE.throwException(ex);
458		}
459
460		/**
461		* Forks all tasks in the specified collection, returning when
462	<	* {@code isDone} holds for each task or an exception is
463	<	* encountered.  If any task encounters an exception, others may
464	<	* be, but are not guaranteed to be, cancelled. The behavior of
465	<	* this operation is undefined if the specified collection is
466	<	* modified while the operation is in progress.
462	>	* {@code isDone} holds for each task or an (unchecked) exception
463	>	* is encountered, in which case the exception is rethrown. If
464	>	* more than one task encounters an exception, then this method
465	>	* throws any one of these exceptions. If any task encounters an
466	>	* exception, others may be cancelled. However, the execution
467	>	* status of individual tasks is not guaranteed upon exceptional
468	>	* return. The status of each task may be obtained using {@link
469	>	* #getException()} and related methods to check if they have been
470	>	* cancelled, completed normally or exceptionally, or left
471	>	* unprocessed.
472		*
473		* <p>This method may be invoked only from within {@code
474	<	* ForkJoinTask} computations (as may be determined using method
474	>	* ForkJoinPool} computations (as may be determined using method
475		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
476		* result in exceptions or errors, possibly including {@code
477		* ClassCastException}.
#	Line 629 | Line 479 | public abstract class ForkJoinTask<V> im
479		* @param tasks the collection of tasks
480		* @return the tasks argument, to simplify usage
481		* @throws NullPointerException if tasks or any element are null
632	–	* @throws RuntimeException or Error if any task did so
482		*/
483		public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
484		if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
#	Line 651 | Line 500 | public abstract class ForkJoinTask<V> im
500		t.fork();
501		else {
502		t.quietlyInvoke();
503	<	if (ex == null)
503	>	if (ex == null && t.status < NORMAL)
504		ex = t.getException();
505		}
506		}
#	Line 662 | Line 511 | public abstract class ForkJoinTask<V> im
511		t.cancel(false);
512		else {
513		t.quietlyJoin();
514	<	if (ex == null)
514	>	if (ex == null && t.status < NORMAL)
515		ex = t.getException();
516		}
517		}
518		}
519		if (ex != null)
520	<	rethrowException(ex);
520	>	UNSAFE.throwException(ex);
521		return tasks;
522		}
523
524		/**
676	–	* Returns {@code true} if the computation performed by this task
677	–	* has completed (or has been cancelled).
678	–	*
679	–	* @return {@code true} if this computation has completed
680	–	*/
681	–	public final boolean isDone() {
682	–	return status < 0;
683	–	}
684	–
685	–	/**
686	–	* Returns {@code true} if this task was cancelled.
687	–	*
688	–	* @return {@code true} if this task was cancelled
689	–	*/
690	–	public final boolean isCancelled() {
691	–	return (status & COMPLETION_MASK) == CANCELLED;
692	–	}
693	–
694	–	/**
525		* Attempts to cancel execution of this task. This attempt will
526	<	* fail if the task has already completed, has already been
527	<	* cancelled, or could not be cancelled for some other reason. If
528	<	* successful, and this task has not started when cancel is
529	<	* called, execution of this task is suppressed, {@link
530	<	* #isCancelled} will report true, and {@link #join} will result
531	<	* in a {@code CancellationException} being thrown.
526	>	* fail if the task has already completed or could not be
527	>	* cancelled for some other reason. If successful, and this task
528	>	* has not started when {@code cancel} is called, execution of
529	>	* this task is suppressed. After this method returns
530	>	* successfully, unless there is an intervening call to {@link
531	>	* #reinitialize}, subsequent calls to {@link #isCancelled},
532	>	* {@link #isDone}, and {@code cancel} will return {@code true}
533	>	* and calls to {@link #join} and related methods will result in
534	>	* {@code CancellationException}.
535		*
536		* <p>This method may be overridden in subclasses, but if so, must
537	<	* still ensure that these minimal properties hold. In particular,
538	<	* the {@code cancel} method itself must not throw exceptions.
537	>	* still ensure that these properties hold. In particular, the
538	>	* {@code cancel} method itself must not throw exceptions.
539		*
540		* <p>This method is designed to be invoked by <em>other</em>
541		* tasks. To terminate the current task, you can just return or
542		* throw an unchecked exception from its computation method, or
543		* invoke {@link #completeExceptionally}.
544		*
545	<	* @param mayInterruptIfRunning this value is ignored in the
546	<	* default implementation because tasks are not
547	<	* cancelled via interruption
545	>	* @param mayInterruptIfRunning this value has no effect in the
546	>	* default implementation because interrupts are not used to
547	>	* control cancellation.
548		*
549		* @return {@code true} if this task is now cancelled
550		*/
551		public boolean cancel(boolean mayInterruptIfRunning) {
552		setCompletion(CANCELLED);
553	<	return (status & COMPLETION_MASK) == CANCELLED;
553	>	return status == CANCELLED;
554	>	}
555	>
556	>	/**
557	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
558	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
559	>	* exceptions, but if it does anyway, we have no recourse during
560	>	* shutdown, so guard against this case.
561	>	*/
562	>	final void cancelIgnoringExceptions() {
563	>	try {
564	>	cancel(false);
565	>	} catch (Throwable ignore) {
566	>	}
567	>	}
568	>
569	>	/**
570	>	* Cancels if current thread is a terminating worker thread,
571	>	* ignoring any exceptions thrown by cancel.
572	>	*/
573	>	final void cancelIfTerminating() {
574	>	Thread t = Thread.currentThread();
575	>	if ((t instanceof ForkJoinWorkerThread) &&
576	>	((ForkJoinWorkerThread) t).isTerminating()) {
577	>	try {
578	>	cancel(false);
579	>	} catch (Throwable ignore) {
580	>	}
581	>	}
582	>	}
583	>
584	>	public final boolean isDone() {
585	>	return status < 0;
586	>	}
587	>
588	>	public final boolean isCancelled() {
589	>	return status == CANCELLED;
590		}
591
592		/**
#	Line 726 | Line 595 | public abstract class ForkJoinTask<V> im
595		* @return {@code true} if this task threw an exception or was cancelled
596		*/
597		public final boolean isCompletedAbnormally() {
598	<	return (status & COMPLETION_MASK) < NORMAL;
598	>	return status < NORMAL;
599	>	}
600	>
601	>	/**
602	>	* Returns {@code true} if this task completed without throwing an
603	>	* exception and was not cancelled.
604	>	*
605	>	* @return {@code true} if this task completed without throwing an
606	>	* exception and was not cancelled
607	>	*/
608	>	public final boolean isCompletedNormally() {
609	>	return status == NORMAL;
610		}
611
612		/**
#	Line 737 | Line 617 | public abstract class ForkJoinTask<V> im
617		* @return the exception, or {@code null} if none
618		*/
619		public final Throwable getException() {
620	<	int s = status & COMPLETION_MASK;
621	<	if (s >= NORMAL)
622	<	return null;
623	<	if (s == CANCELLED)
744	<	return new CancellationException();
745	<	return exceptionMap.get(this);
620	>	int s = status;
621	>	return ((s >= NORMAL)    ? null :
622	>	(s == CANCELLED) ? new CancellationException() :
623	>	exceptionMap.get(this));
624		}
625
626		/**
#	Line 755 | Line 633 | public abstract class ForkJoinTask<V> im
633		* overridable, but overridden versions must invoke {@code super}
634		* implementation to maintain guarantees.
635		*
636	<	* @param ex the exception to throw. If this exception is
637	<	* not a RuntimeException or Error, the actual exception thrown
638	<	* will be a RuntimeException with cause ex.
636	>	* @param ex the exception to throw. If this exception is not a
637	>	* {@code RuntimeException} or {@code Error}, the actual exception
638	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
639		*/
640		public void completeExceptionally(Throwable ex) {
641	<	setDoneExceptionally((ex instanceof RuntimeException) ||
642	<	(ex instanceof Error) ? ex :
643	<	new RuntimeException(ex));
641	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
642	>	(ex instanceof Error) ? ex :
643	>	new RuntimeException(ex));
644		}
645
646		/**
647		* Completes this task, and if not already aborted or cancelled,
648	<	* returning a {@code null} result upon {@code join} and related
649	<	* operations. This method may be used to provide results for
650	<	* asynchronous tasks, or to provide alternative handling for
651	<	* tasks that would not otherwise complete normally. Its use in
652	<	* other situations is discouraged. This method is
653	<	* overridable, but overridden versions must invoke {@code super}
654	<	* implementation to maintain guarantees.
648	>	* returning the given value as the result of subsequent
649	>	* invocations of {@code join} and related operations. This method
650	>	* may be used to provide results for asynchronous tasks, or to
651	>	* provide alternative handling for tasks that would not otherwise
652	>	* complete normally. Its use in other situations is
653	>	* discouraged. This method is overridable, but overridden
654	>	* versions must invoke {@code super} implementation to maintain
655	>	* guarantees.
656		*
657		* @param value the result value for this task
658		*/
#	Line 781 | Line 660 | public abstract class ForkJoinTask<V> im
660		try {
661		setRawResult(value);
662		} catch (Throwable rex) {
663	<	setDoneExceptionally(rex);
663	>	setExceptionalCompletion(rex);
664		return;
665		}
666	<	setNormalCompletion();
788	<	}
789	<
790	<	public final V get() throws InterruptedException, ExecutionException {
791	<	ForkJoinWorkerThread w = getWorker();
792	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
793	<	awaitDone(w, true);
794	<	return reportFutureResult();
795	<	}
796	<
797	<	public final V get(long timeout, TimeUnit unit)
798	<	throws InterruptedException, ExecutionException, TimeoutException {
799	<	long nanos = unit.toNanos(timeout);
800	<	ForkJoinWorkerThread w = getWorker();
801	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
802	<	awaitDone(w, nanos);
803	<	return reportTimedFutureResult();
666	>	setCompletion(NORMAL);
667		}
668
669		/**
670	<	* Possibly executes other tasks until this task is ready, then
671	<	* returns the result of the computation.  This method may be more
809	<	* efficient than {@code join}, but is only applicable when
810	<	* there are no potential dependencies between continuation of the
811	<	* current task and that of any other task that might be executed
812	<	* while helping. (This usually holds for pure divide-and-conquer
813	<	* tasks).
814	<	*
815	<	* <p>This method may be invoked only from within {@code
816	<	* ForkJoinTask} computations (as may be determined using method
817	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
818	<	* result in exceptions or errors, possibly including {@code
819	<	* ClassCastException}.
670	>	* Waits if necessary for the computation to complete, and then
671	>	* retrieves its result.
672		*
673		* @return the computed result
674	+	* @throws CancellationException if the computation was cancelled
675	+	* @throws ExecutionException if the computation threw an
676	+	* exception
677	+	* @throws InterruptedException if the current thread is not a
678	+	* member of a ForkJoinPool and was interrupted while waiting
679		*/
680	<	public final V helpJoin() {
681	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
682	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
683	<	reportException(busyJoin(w));
680	>	public final V get() throws InterruptedException, ExecutionException {
681	>	int s;
682	>	if (Thread.currentThread() instanceof ForkJoinWorkerThread) {
683	>	quietlyJoin();
684	>	s = status;
685	>	}
686	>	else {
687	>	while ((s = status) >= 0) {
688	>	synchronized (this) { // interruptible form of awaitDone
689	>	if (UNSAFE.compareAndSwapInt(this, statusOffset,
690	>	s, SIGNAL)) {
691	>	while (status >= 0)
692	>	wait();
693	>	}
694	>	}
695	>	}
696	>	}
697	>	if (s < NORMAL) {
698	>	Throwable ex;
699	>	if (s == CANCELLED)
700	>	throw new CancellationException();
701	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
702	>	throw new ExecutionException(ex);
703	>	}
704		return getRawResult();
705		}
706
707		/**
708	<	* Possibly executes other tasks until this task is ready.  This
709	<	* method may be useful when processing collections of tasks when
833	<	* some have been cancelled or otherwise known to have aborted.
708	>	* Waits if necessary for at most the given time for the computation
709	>	* to complete, and then retrieves its result, if available.
710		*
711	<	* <p>This method may be invoked only from within {@code
712	<	* ForkJoinTask} computations (as may be determined using method
713	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
714	<	* result in exceptions or errors, possibly including {@code
715	<	* ClassCastException}.
711	>	* @param timeout the maximum time to wait
712	>	* @param unit the time unit of the timeout argument
713	>	* @return the computed result
714	>	* @throws CancellationException if the computation was cancelled
715	>	* @throws ExecutionException if the computation threw an
716	>	* exception
717	>	* @throws InterruptedException if the current thread is not a
718	>	* member of a ForkJoinPool and was interrupted while waiting
719	>	* @throws TimeoutException if the wait timed out
720		*/
721	<	public final void quietlyHelpJoin() {
721	>	public final V get(long timeout, TimeUnit unit)
722	>	throws InterruptedException, ExecutionException, TimeoutException {
723	>	long nanos = unit.toNanos(timeout);
724		if (status >= 0) {
725	<	ForkJoinWorkerThread w =
726	<	(ForkJoinWorkerThread) Thread.currentThread();
727	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
728	<	busyJoin(w);
725	>	Thread t = Thread.currentThread();
726	>	if (t instanceof ForkJoinWorkerThread) {
727	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
728	>	boolean completed = false; // timed variant of quietlyJoin
729	>	if (w.unpushTask(this)) {
730	>	try {
731	>	completed = exec();
732	>	} catch (Throwable rex) {
733	>	setExceptionalCompletion(rex);
734	>	}
735	>	}
736	>	if (completed)
737	>	setCompletion(NORMAL);
738	>	else if (status >= 0)
739	>	w.joinTask(this, true, nanos);
740	>	}
741	>	else if (Thread.interrupted())
742	>	throw new InterruptedException();
743	>	else {
744	>	long startTime = System.nanoTime();
745	>	int s; long nt;
746	>	while ((s = status) >= 0 &&
747	>	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
748	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,
749	>	SIGNAL)) {
750	>	long ms = nt / 1000000;
751	>	int ns = (int) (nt % 1000000);
752	>	synchronized (this) {
753	>	if (status >= 0)
754	>	wait(ms, ns); // exit on IE throw
755	>	}
756	>	}
757	>	}
758	>	}
759	>	}
760	>	int es = status;
761	>	if (es != NORMAL) {
762	>	Throwable ex;
763	>	if (es == CANCELLED)
764	>	throw new CancellationException();
765	>	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
766	>	throw new ExecutionException(ex);
767	>	throw new TimeoutException();
768		}
769	+	return getRawResult();
770		}
771
772		/**
773	<	* Joins this task, without returning its result or throwing an
773	>	* Joins this task, without returning its result or throwing its
774		* exception. This method may be useful when processing
775		* collections of tasks when some have been cancelled or otherwise
776		* known to have aborted.
777		*/
778		public final void quietlyJoin() {
779	<	if (status >= 0) {
780	<	ForkJoinWorkerThread w = getWorker();
781	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
782	<	awaitDone(w, true);
779	>	Thread t;
780	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
781	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
782	>	if (status >= 0) {
783	>	if (w.unpushTask(this)) {
784	>	boolean completed;
785	>	try {
786	>	completed = exec();
787	>	} catch (Throwable rex) {
788	>	setExceptionalCompletion(rex);
789	>	return;
790	>	}
791	>	if (completed) {
792	>	setCompletion(NORMAL);
793	>	return;
794	>	}
795	>	}
796	>	w.joinTask(this, false, 0L);
797	>	}
798		}
799	+	else
800	+	externalAwaitDone();
801		}
802
803		/**
804		* Commences performing this task and awaits its completion if
805	<	* necessary, without returning its result or throwing an
806	<	* exception. This method may be useful when processing
868	<	* collections of tasks when some have been cancelled or otherwise
869	<	* known to have aborted.
805	>	* necessary, without returning its result or throwing its
806	>	* exception.
807		*/
808		public final void quietlyInvoke() {
809	<	if (status >= 0 && !tryQuietlyInvoke())
810	<	quietlyJoin();
809	>	if (status >= 0) {
810	>	boolean completed;
811	>	try {
812	>	completed = exec();
813	>	} catch (Throwable rex) {
814	>	setExceptionalCompletion(rex);
815	>	return;
816	>	}
817	>	if (completed)
818	>	setCompletion(NORMAL);
819	>	else
820	>	quietlyJoin();
821	>	}
822		}
823
824		/**
#	Line 881 | Line 829 | public abstract class ForkJoinTask<V> im
829		* processed.
830		*
831		* <p>This method may be invoked only from within {@code
832	<	* ForkJoinTask} computations (as may be determined using method
832	>	* ForkJoinPool} computations (as may be determined using method
833		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
834		* result in exceptions or errors, possibly including {@code
835		* ClassCastException}.
#	Line 900 | Line 848 | public abstract class ForkJoinTask<V> im
848		* under any other usage conditions are not guaranteed.
849		* This method may be useful when executing
850		* pre-constructed trees of subtasks in loops.
851	+	*
852	+	* <p>Upon completion of this method, {@code isDone()} reports
853	+	* {@code false}, and {@code getException()} reports {@code
854	+	* null}. However, the value returned by {@code getRawResult} is
855	+	* unaffected. To clear this value, you can invoke {@code
856	+	* setRawResult(null)}.
857		*/
858		public void reinitialize() {
859	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
859	>	if (status == EXCEPTIONAL)
860		exceptionMap.remove(this);
861		status = 0;
862		}
#	Line 940 | Line 894 | public abstract class ForkJoinTask<V> im
894		* were not, stolen.
895		*
896		* <p>This method may be invoked only from within {@code
897	<	* ForkJoinTask} computations (as may be determined using method
897	>	* ForkJoinPool} computations (as may be determined using method
898		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
899		* result in exceptions or errors, possibly including {@code
900		* ClassCastException}.
#	Line 959 | Line 913 | public abstract class ForkJoinTask<V> im
913		* fork other tasks.
914		*
915		* <p>This method may be invoked only from within {@code
916	<	* ForkJoinTask} computations (as may be determined using method
916	>	* ForkJoinPool} computations (as may be determined using method
917		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
918		* result in exceptions or errors, possibly including {@code
919		* ClassCastException}.
#	Line 982 | Line 936 | public abstract class ForkJoinTask<V> im
936		* exceeded.
937		*
938		* <p>This method may be invoked only from within {@code
939	<	* ForkJoinTask} computations (as may be determined using method
939	>	* ForkJoinPool} computations (as may be determined using method
940		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
941		* result in exceptions or errors, possibly including {@code
942		* ClassCastException}.
#	Line 1022 | Line 976 | public abstract class ForkJoinTask<V> im
976		* called otherwise. The return value controls whether this task
977		* is considered to be done normally. It may return false in
978		* asynchronous actions that require explicit invocations of
979	<	* {@link #complete} to become joinable. It may throw exceptions
980	<	* to indicate abnormal exit.
979	>	* {@link #complete} to become joinable. It may also throw an
980	>	* (unchecked) exception to indicate abnormal exit.
981		*
982		* @return {@code true} if completed normally
1029	–	* @throws Error or RuntimeException if encountered during computation
983		*/
984		protected abstract boolean exec();
985
#	Line 1041 | Line 994 | public abstract class ForkJoinTask<V> im
994		* otherwise.
995		*
996		* <p>This method may be invoked only from within {@code
997	<	* ForkJoinTask} computations (as may be determined using method
997	>	* ForkJoinPool} computations (as may be determined using method
998		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
999		* result in exceptions or errors, possibly including {@code
1000		* ClassCastException}.
#	Line 1060 | Line 1013 | public abstract class ForkJoinTask<V> im
1013		* be useful otherwise.
1014		*
1015		* <p>This method may be invoked only from within {@code
1016	<	* ForkJoinTask} computations (as may be determined using method
1016	>	* ForkJoinPool} computations (as may be determined using method
1017		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1018		* result in exceptions or errors, possibly including {@code
1019		* ClassCastException}.
#	Line 1083 | Line 1036 | public abstract class ForkJoinTask<V> im
1036		* otherwise.
1037		*
1038		* <p>This method may be invoked only from within {@code
1039	<	* ForkJoinTask} computations (as may be determined using method
1039	>	* ForkJoinPool} computations (as may be determined using method
1040		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1041		* result in exceptions or errors, possibly including {@code
1042		* ClassCastException}.
#	Line 1193 | Line 1146 | public abstract class ForkJoinTask<V> im
1146		private static final long serialVersionUID = -7721805057305804111L;
1147
1148		/**
1149	<	* Save the state to a stream.
1149	>	* Saves the state to a stream (that is, serializes it).
1150		*
1151		* @serialData the current run status and the exception thrown
1152		* during execution, or {@code null} if none
#	Line 1206 | Line 1159 | public abstract class ForkJoinTask<V> im
1159		}
1160
1161		/**
1162	<	* Reconstitute the instance from a stream.
1162	>	* Reconstitutes the instance from a stream (that is, deserializes it).
1163		*
1164		* @param s the stream
1165		*/
1166		private void readObject(java.io.ObjectInputStream s)
1167		throws java.io.IOException, ClassNotFoundException {
1168		s.defaultReadObject();
1216	–	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1217	–	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1169		Object ex = s.readObject();
1170		if (ex != null)
1171	<	setDoneExceptionally((Throwable) ex);
1171	>	setExceptionalCompletion((Throwable) ex);
1172		}
1173
1174		// Unsafe mechanics

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