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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.28 by jsr166, Sun Aug 2 17:02:06 2009 UTC vs.
Revision 1.67 by dl, Sun Nov 21 14:43:27 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;
12		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 27 | 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 54 | Line 63 | import java.util.WeakHashMap;
63		* restriction is in part enforced by not permitting checked
64		* exceptions such as {@code IOExceptions} to be thrown. However,
65		* computations may still encounter unchecked exceptions, that are
66	<	* rethrown to callers attempting join them. These exceptions may
67	<	* additionally include RejectedExecutionExceptions stemming from
68	<	* internal resource exhaustion such as failure to allocate internal
69	<	* task queues.
66	>	* rethrown to callers attempting to join them. These exceptions may
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
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
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 85 | Line 103 | import java.util.WeakHashMap;
103		* established in a constructor, and then defines a {@code compute}
104		* method that somehow uses the control methods supplied by this base
105		* class. While these methods have {@code public} access (to allow
106	<	* instances of different task subclasses to call each others
106	>	* instances of different task subclasses to call each other's
107		* methods), some of them may only be called from within other
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>Most base support methods are {@code final} because their
114	<	* implementations are intrinsically tied to the underlying
115	<	* lightweight task scheduling framework, and so cannot be overridden.
116	<	* Developers creating new basic styles of fork/join processing should
117	<	* minimally implement {@code protected} methods
118	<	* {@link #exec}, {@link #setRawResult}, and
119	<	* {@link #getRawResult}, while also introducing an abstract
120	<	* computational method that can be implemented in its subclasses,
121	<	* possibly relying on other {@code protected} methods provided
104	<	* by this class.
113	>	* <p>Most base support methods are {@code final}, to prevent
114	>	* overriding of implementations that are intrinsically tied to the
115	>	* underlying lightweight task scheduling framework.  Developers
116	>	* creating new basic styles of fork/join processing should minimally
117	>	* implement {@code protected} methods {@link #exec}, {@link
118	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
119	>	* an abstract computational method that can be implemented in its
120	>	* subclasses, possibly relying on other {@code protected} methods
121	>	* provided by this class.
122		*
123		* <p>ForkJoinTasks should perform relatively small amounts of
124	<	* computations, otherwise splitting into smaller tasks. As a very
125	<	* rough rule of thumb, a task should perform more than 100 and less
126	<	* than 10000 basic computational steps. If tasks are too big, then
127	<	* parallelism cannot improve throughput. If too small, then memory
128	<	* and internal task maintenance overhead may overwhelm processing.
124	>	* computation. Large tasks should be split into smaller subtasks,
125	>	* usually via recursive decomposition. As a very rough rule of thumb,
126	>	* a task should perform more than 100 and less than 10000 basic
127	>	* computational steps. If tasks are too big, then parallelism cannot
128	>	* improve throughput. If too small, then memory and internal task
129	>	* maintenance overhead may overwhelm processing.
130		*
131	<	* <p>This class provides {@code adapt} methods for {@link
132	<	* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
133	<	* may be of use when mixing execution of ForkJoinTasks with other
134	<	* kinds of tasks. When all tasks are of this form, consider using a
117	<	* pool in {@link ForkJoinPool#setAsyncMode}.
131	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
132	>	* and {@link Callable}, that may be of use when mixing execution of
133	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
134	>	* of this form, consider using a pool constructed in <em>asyncMode</em>.
135		*
136	<	* <p>ForkJoinTasks are {@code Serializable}, which enables them
137	<	* to be used in extensions such as remote execution frameworks. It is
138	<	* in general sensible to serialize tasks only before or after, but
139	<	* not during execution. Serialization is not relied on during
123	<	* execution itself.
136	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
137	>	* used in extensions such as remote execution frameworks. It is
138	>	* sensible to serialize tasks only before or after, but not during,
139	>	* execution. Serialization is not relied on during execution itself.
140		*
141		* @since 1.7
142		* @author Doug Lea
143		*/
144		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
145
146	<	/**
147	<	* Run control status bits packed into a single int to minimize
148	<	* footprint and to ensure atomicity (via CAS).  Status is
149	<	* initially zero, and takes on nonnegative values until
150	<	* completed, upon which status holds COMPLETED. CANCELLED, or
151	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
152	<	* blocking waits by other threads have SIGNAL_MASK bits set --
153	<	* bit 15 for external (nonFJ) waits, and the rest a count of
154	<	* waiting FJ threads.  (This representation relies on
155	<	* ForkJoinPool max thread limits). Completion of a stolen task
156	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
157	<	* though suboptimal for some purposes, we use basic builtin
158	<	* wait/notify to take advantage of "monitor inflation" in JVMs
159	<	* that we would otherwise need to emulate to avoid adding further
160	<	* per-task bookkeeping overhead. Note that bits 16-28 are
161	<	* currently unused. Also value 0x80000000 is available as spare
162	<	* completion value.
146	>	/*
147	>	* See the internal documentation of class ForkJoinPool for a
148	>	* general implementation overview.  ForkJoinTasks are mainly
149	>	* responsible for maintaining their "status" field amidst relays
150	>	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
151	>	* methods of this class are more-or-less layered into (1) basic
152	>	* status maintenance (2) execution and awaiting completion (3)
153	>	* user-level methods that additionally report results. This is
154	>	* sometimes hard to see because this file orders exported methods
155	>	* in a way that flows well in javadocs. In particular, most
156	>	* join mechanics are in method quietlyJoin, below.
157	>	*/
158	>
159	>	/*
160	>	* The status field holds run control status bits packed into a
161	>	* single int to minimize footprint and to ensure atomicity (via
162	>	* CAS).  Status is initially zero, and takes on nonnegative
163	>	* values until completed, upon which status holds value
164	>	* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
165	>	* waits by other threads have the SIGNAL bit set.  Completion of
166	>	* a stolen task with SIGNAL set awakens any waiters via
167	>	* notifyAll. Even though suboptimal for some purposes, we use
168	>	* basic builtin wait/notify to take advantage of "monitor
169	>	* inflation" in JVMs that we would otherwise need to emulate to
170	>	* avoid adding further per-task bookkeeping overhead.  We want
171	>	* these monitors to be "fat", i.e., not use biasing or thin-lock
172	>	* techniques, so use some odd coding idioms that tend to avoid
173	>	* them.
174		*/
175	+
176	+	/** The run status of this task */
177		volatile int status; // accessed directly by pool and workers
178
179	<	static final int COMPLETION_MASK      = 0xe0000000;
180	<	static final int NORMAL               = 0xe0000000; // == mask
181	<	static final int CANCELLED            = 0xc0000000;
182	<	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
179	>	private static final int NORMAL      = -1;
180	>	private static final int CANCELLED   = -2;
181	>	private static final int EXCEPTIONAL = -3;
182	>	private static final int SIGNAL      =  1;
183
184		/**
185		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 167 | Line 193 | public abstract class ForkJoinTask<V> im
193		Collections.synchronizedMap
194		(new WeakHashMap<ForkJoinTask<?>, Throwable>());
195
196	<	// within-package utilities
171	<
172	<	/**
173	<	* Gets current worker thread, or null if not a worker thread.
174	<	*/
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	<	}
196	>	// Maintaining completion status
197
198		/**
199	<	* Workaround for not being able to rethrow unchecked exceptions.
200	<	*/
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.
199	>	* Marks completion and wakes up threads waiting to join this task,
200	>	* also clearing signal request bits.
201		*
202		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
203		*/
204	<	final void setCompletion(int completion) {
205	<	ForkJoinPool pool = getPool();
206	<	if (pool != null) {
207	<	int s; // Clear signal bits while setting completion status
208	<	do {} while ((s = status) >= 0 && !casStatus(s, completion));
209	<
210	<	if ((s & SIGNAL_MASK) != 0) {
207	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
208	<	pool.updateRunningCount(s);
209	<	synchronized (this) { notifyAll(); }
204	>	private void setCompletion(int completion) {
205	>	int s;
206	>	while ((s = status) >= 0) {
207	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
208	>	if (s != 0)
209	>	synchronized (this) { notifyAll(); }
210	>	break;
211		}
212		}
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);
213		}
214
237	–	// internal waiting and notification
238	–
215		/**
216	<	* Performs the actual monitor wait for awaitDone.
216	>	* Records exception and sets exceptional completion.
217	>	*
218	>	* @return status on exit
219		*/
220	<	private void doAwaitDone() {
221	<	// Minimize lock bias and in/de-flation effects by maximizing
222	<	// 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	<	}
220	>	private void setExceptionalCompletion(Throwable rex) {
221	>	exceptionMap.put(this, rex);
222	>	setCompletion(EXCEPTIONAL);
223		}
224
225		/**
226	<	* Performs the actual timed monitor wait for awaitDone.
226	>	* Blocks a worker thread until completion. Called only by
227	>	* pool. Currently unused -- pool-based waits use timeout
228	>	* version below.
229		*/
230	<	private void doAwaitDone(long startTime, long nanos) {
231	<	synchronized (this) {
230	>	final void internalAwaitDone() {
231	>	int s;         // the odd construction reduces lock bias effects
232	>	while ((s = status) >= 0) {
233		try {
234	<	while (status >= 0) {
235	<	long nt = nanos - (System.nanoTime() - startTime);
236	<	if (nt <= 0)
262	<	break;
263	<	wait(nt / 1000000, (int) (nt % 1000000));
234	>	synchronized (this) {
235	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
236	>	wait();
237		}
238		} catch (InterruptedException ie) {
239	<	onInterruptedWait();
239	>	cancelIfTerminating();
240		}
241		}
242		}
243
271	–	// Awaiting completion
272	–
244		/**
245	<	* Sets status to indicate there is joiner, then waits for join,
246	<	* surrounded with pool notifications.
245	>	* Blocks a worker thread until completed or timed out.  Called
246	>	* only by pool.
247		*
248	<	* @return status upon exit
248	>	* @return status on exit
249		*/
250	<	private int awaitDone(ForkJoinWorkerThread w,
280	<	boolean maintainParallelism) {
281	<	ForkJoinPool pool = (w == null) ? null : w.pool;
250	>	final int internalAwaitDone(long millis, int nanos) {
251		int s;
252	<	while ((s = status) >= 0) {
253	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
254	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
255	<	doAwaitDone();
256	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
288	<	adjustPoolCountsOnUnblock(pool);
289	<	break;
290	<	}
291	<	}
292	<	return s;
293	<	}
294	<
295	<	/**
296	<	* Timed version of awaitDone
297	<	*
298	<	* @return status upon exit
299	<	*/
300	<	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
301	<	ForkJoinPool pool = (w == null) ? null : w.pool;
302	<	int s;
303	<	while ((s = status) >= 0) {
304	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
305	<	long startTime = System.nanoTime();
306	<	if (pool == null || !pool.preJoin(this, false))
307	<	doAwaitDone(startTime, nanos);
308	<	if ((s = status) >= 0) {
309	<	adjustPoolCountsOnCancelledWait(pool);
310	<	s = status;
252	>	if ((s = status) >= 0) {
253	>	try {
254	>	synchronized (this) {
255	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
256	>	wait(millis, nanos);
257		}
258	<	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
259	<	adjustPoolCountsOnUnblock(pool);
314	<	break;
258	>	} catch (InterruptedException ie) {
259	>	cancelIfTerminating();
260		}
261	+	s = status;
262		}
263		return s;
264		}
265
266		/**
267	<	* Notifies pool that thread is unblocked. Called by signalled
322	<	* threads when woken by non-FJ threads (which is atypical).
267	>	* Blocks a non-worker-thread until completion.
268		*/
269	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
269	>	private void externalAwaitDone() {
270		int s;
271	<	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
272	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
273	<	pool.updateRunningCount(s);
274	<	}
275	<
276	<	/**
277	<	* Notifies pool to adjust counts on cancelled or timed out wait.
278	<	*/
279	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
280	<	if (pool != null) {
281	<	int s;
282	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
283	<	if (casStatus(s, s - 1)) {
339	<	pool.updateRunningCount(1);
271	>	while ((s = status) >= 0) {
272	>	synchronized (this) {
273	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
274	>	boolean interrupted = false;
275	>	while (status >= 0) {
276	>	try {
277	>	wait();
278	>	} catch (InterruptedException ie) {
279	>	interrupted = true;
280	>	}
281	>	}
282	>	if (interrupted)
283	>	Thread.currentThread().interrupt();
284		break;
285		}
286		}
#	Line 344 | Line 288 | public abstract class ForkJoinTask<V> im
288		}
289
290		/**
291	<	* Handles interruptions during waits.
292	<	*/
293	<	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.
291	>	* Unless done, calls exec and records status if completed, but
292	>	* doesn't wait for completion otherwise. Primary execution method
293	>	* for ForkJoinWorkerThread.
294		*/
295		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() {
296		try {
297	<	if (!exec())
298	<	return false;
297	>	if (status < 0 || !exec())
298	>	return;
299		} catch (Throwable rex) {
300	<	setDoneExceptionally(rex);
301	<	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) {
300	>	setExceptionalCompletion(rex);
301	>	return;
302		}
303	<	}
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
303	>	setCompletion(NORMAL); // must be outside try block
304		}
305
306		// public methods
#	Line 496 | Line 308 | public abstract class ForkJoinTask<V> im
308		/**
309		* Arranges to asynchronously execute this task.  While it is not
310		* necessarily enforced, it is a usage error to fork a task more
311	<	* than once unless it has completed and been reinitialized.  This
312	<	* method may be invoked only from within ForkJoinTask
313	<	* computations (as may be determined using method {@link
314	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
315	<	* in exceptions or errors, possibly including ClassCastException.
311	>	* than once unless it has completed and been reinitialized.
312	>	* Subsequent modifications to the state of this task or any data
313	>	* it operates on are not necessarily consistently observable by
314	>	* any thread other than the one executing it unless preceded by a
315	>	* call to {@link #join} or related methods, or a call to {@link
316	>	* #isDone} returning {@code true}.
317	>	*
318	>	* <p>This method may be invoked only from within {@code
319	>	* ForkJoinTask} computations (as may be determined using method
320	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
321	>	* result in exceptions or errors, possibly including {@code
322	>	* ClassCastException}.
323		*
324	<	* @return {@code this}, to simplify usage.
324	>	* @return {@code this}, to simplify usage
325		*/
326		public final ForkJoinTask<V> fork() {
327		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 511 | Line 330 | public abstract class ForkJoinTask<V> im
330		}
331
332		/**
333	<	* Returns the result of the computation when it is ready.
334	<	* This method differs from {@code get} in that abnormal
335	<	* completion results in RuntimeExceptions or Errors, not
336	<	* ExecutionExceptions.
333	>	* Returns the result of the computation when it {@link #isDone is done}.
334	>	* This method differs from {@link #get()} in that
335	>	* abnormal completion results in {@code RuntimeException} or
336	>	* {@code Error}, not {@code ExecutionException}.
337		*
338		* @return the computed result
339		*/
340		public final V join() {
341	<	ForkJoinWorkerThread w = getWorker();
342	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
343	<	reportException(awaitDone(w, true));
341	>	quietlyJoin();
342	>	Throwable ex;
343	>	if (status < NORMAL && (ex = getException()) != null)
344	>	UNSAFE.throwException(ex);
345		return getRawResult();
346		}
347
348		/**
349		* Commences performing this task, awaits its completion if
350	<	* necessary, and return its result.
350	>	* necessary, and returns its result, or throws an (unchecked)
351	>	* {@code RuntimeException} or {@code Error} if the underlying
352	>	* computation did so.
353		*
532	–	* @throws Throwable (a RuntimeException, Error, or unchecked
533	–	* exception) if the underlying computation did so
354		* @return the computed result
355		*/
356		public final V invoke() {
357	<	if (status >= 0 && tryExec())
358	<	return getRawResult();
359	<	else
360	<	return join();
357	>	quietlyInvoke();
358	>	Throwable ex;
359	>	if (status < NORMAL && (ex = getException()) != null)
360	>	UNSAFE.throwException(ex);
361	>	return getRawResult();
362		}
363
364		/**
365		* Forks the given tasks, returning when {@code isDone} holds for
366	<	* each task or an exception is encountered. This method may be
367	<	* invoked only from within ForkJoinTask computations (as may be
368	<	* determined using method {@link #inForkJoinPool}). Attempts to
369	<	* invoke in other contexts result in exceptions or errors,
370	<	* possibly including ClassCastException.
366	>	* each task or an (unchecked) exception is encountered, in which
367	>	* case the exception is rethrown. If more than one task
368	>	* encounters an exception, then this method throws any one of
369	>	* these exceptions. If any task encounters an exception, the
370	>	* other may be cancelled. However, the execution status of
371	>	* individual tasks is not guaranteed upon exceptional return. The
372	>	* status of each task may be obtained using {@link
373	>	* #getException()} and related methods to check if they have been
374	>	* cancelled, completed normally or exceptionally, or left
375	>	* unprocessed.
376	>	*
377	>	* <p>This method may be invoked only from within {@code
378	>	* ForkJoinTask} computations (as may be determined using method
379	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
380	>	* result in exceptions or errors, possibly including {@code
381	>	* ClassCastException}.
382		*
383		* @param t1 the first task
384		* @param t2 the second task
385		* @throws NullPointerException if any task is null
554	–	* @throws RuntimeException or Error if a task did so
386		*/
387	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
387	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
388		t2.fork();
389		t1.invoke();
390		t2.join();
#	Line 561 | Line 392 | public abstract class ForkJoinTask<V> im
392
393		/**
394		* Forks the given tasks, returning when {@code isDone} holds for
395	<	* each task or an exception is encountered. If any task
396	<	* encounters an exception, others may be, but are not guaranteed
397	<	* to be, cancelled.  This method may be invoked only from within
398	<	* ForkJoinTask computations (as may be determined using method
399	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
400	<	* result in exceptions or errors, possibly including
401	<	* ClassCastException.
402	<	*
403	<	* Overloadings of this method exist for the special cases
404	<	* of one to four arguments.
395	>	* each task or an (unchecked) exception is encountered, in which
396	>	* case the exception is rethrown. If more than one task
397	>	* encounters an exception, then this method throws any one of
398	>	* these exceptions. If any task encounters an exception, others
399	>	* may be cancelled. However, the execution status of individual
400	>	* tasks is not guaranteed upon exceptional return. The status of
401	>	* each task may be obtained using {@link #getException()} and
402	>	* related methods to check if they have been cancelled, completed
403	>	* normally or exceptionally, or left unprocessed.
404	>	*
405	>	* <p>This method may be invoked only from within {@code
406	>	* ForkJoinTask} computations (as may be determined using method
407	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
408	>	* result in exceptions or errors, possibly including {@code
409	>	* ClassCastException}.
410		*
411		* @param tasks the tasks
412	<	* @throws NullPointerException if tasks or any element are null
577	<	* @throws RuntimeException or Error if any task did so
412	>	* @throws NullPointerException if any task is null
413		*/
414		public static void invokeAll(ForkJoinTask<?>... tasks) {
415		Throwable ex = null;
#	Line 589 | Line 424 | public abstract class ForkJoinTask<V> im
424		t.fork();
425		else {
426		t.quietlyInvoke();
427	<	if (ex == null)
427	>	if (ex == null && t.status < NORMAL)
428		ex = t.getException();
429		}
430		}
#	Line 600 | Line 435 | public abstract class ForkJoinTask<V> im
435		t.cancel(false);
436		else {
437		t.quietlyJoin();
438	<	if (ex == null)
438	>	if (ex == null && t.status < NORMAL)
439		ex = t.getException();
440		}
441		}
442		}
443		if (ex != null)
444	<	rethrowException(ex);
444	>	UNSAFE.throwException(ex);
445		}
446
447		/**
448	<	* Forks all tasks in the collection, returning when {@code
449	<	* isDone} holds for each task or an exception is encountered. If
450	<	* any task encounters an exception, others may be, but are not
451	<	* guaranteed to be, cancelled.  This method may be invoked only
452	<	* from within ForkJoinTask computations (as may be determined
453	<	* using method {@link #inForkJoinPool}). Attempts to invoke in
454	<	* other contexts result in exceptions or errors, possibly
455	<	* including ClassCastException.
448	>	* Forks all tasks in the specified collection, returning when
449	>	* {@code isDone} holds for each task or an (unchecked) exception
450	>	* is encountered, in which case the exception is rethrown. If
451	>	* more than one task encounters an exception, then this method
452	>	* throws any one of these exceptions. If any task encounters an
453	>	* exception, others may be cancelled. However, the execution
454	>	* status of individual tasks is not guaranteed upon exceptional
455	>	* return. The status of each task may be obtained using {@link
456	>	* #getException()} and related methods to check if they have been
457	>	* cancelled, completed normally or exceptionally, or left
458	>	* unprocessed.
459	>	*
460	>	* <p>This method may be invoked only from within {@code
461	>	* ForkJoinTask} computations (as may be determined using method
462	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
463	>	* result in exceptions or errors, possibly including {@code
464	>	* ClassCastException}.
465		*
466		* @param tasks the collection of tasks
467		* @return the tasks argument, to simplify usage
468		* @throws NullPointerException if tasks or any element are null
625	–	* @throws RuntimeException or Error if any task did so
469		*/
470		public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
471	<	if (!(tasks instanceof List<?>)) {
471	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
472		invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
473		return tasks;
474		}
#	Line 644 | Line 487 | public abstract class ForkJoinTask<V> im
487		t.fork();
488		else {
489		t.quietlyInvoke();
490	<	if (ex == null)
490	>	if (ex == null && t.status < NORMAL)
491		ex = t.getException();
492		}
493		}
#	Line 655 | Line 498 | public abstract class ForkJoinTask<V> im
498		t.cancel(false);
499		else {
500		t.quietlyJoin();
501	<	if (ex == null)
501	>	if (ex == null && t.status < NORMAL)
502		ex = t.getException();
503		}
504		}
505		}
506		if (ex != null)
507	<	rethrowException(ex);
507	>	UNSAFE.throwException(ex);
508		return tasks;
509		}
510
511		/**
512	<	* Returns {@code true} if the computation performed by this task
513	<	* has completed (or has been cancelled).
514	<	*
515	<	* @return {@code true} if this computation has completed
516	<	*/
517	<	public final boolean isDone() {
518	<	return status < 0;
676	<	}
677	<
678	<	/**
679	<	* Returns {@code true} if this task was cancelled.
680	<	*
681	<	* @return {@code true} if this task was cancelled
682	<	*/
683	<	public final boolean isCancelled() {
684	<	return (status & COMPLETION_MASK) == CANCELLED;
685	<	}
686	<
687	<	/**
688	<	* Asserts that the results of this task's computation will not be
689	<	* used. If a cancellation occurs before attempting to execute this
690	<	* task, execution will be suppressed, {@link #isCancelled}
691	<	* will report true, and {@link #join} will result in a
692	<	* {@code CancellationException} being thrown. Otherwise, when
693	<	* cancellation races with completion, there are no guarantees
694	<	* about whether {@code isCancelled} will report {@code true},
695	<	* whether {@code join} will return normally or via an exception,
696	<	* or whether these behaviors will remain consistent upon repeated
697	<	* invocation.
512	>	* Attempts to cancel execution of this task. This attempt will
513	>	* fail if the task has already completed, has already been
514	>	* cancelled, or could not be cancelled for some other reason. If
515	>	* successful, and this task has not started when cancel is
516	>	* called, execution of this task is suppressed, {@link
517	>	* #isCancelled} will report true, and {@link #join} will result
518	>	* in a {@code CancellationException} being thrown.
519		*
520		* <p>This method may be overridden in subclasses, but if so, must
521		* still ensure that these minimal properties hold. In particular,
522	<	* the cancel method itself must not throw exceptions.
522	>	* the {@code cancel} method itself must not throw exceptions.
523		*
524		* <p>This method is designed to be invoked by <em>other</em>
525		* tasks. To terminate the current task, you can just return or
#	Line 706 | Line 527 | public abstract class ForkJoinTask<V> im
527		* invoke {@link #completeExceptionally}.
528		*
529		* @param mayInterruptIfRunning this value is ignored in the
530	<	* default implementation because tasks are not in general
530	>	* default implementation because tasks are not
531		* cancelled via interruption
532		*
533		* @return {@code true} if this task is now cancelled
534		*/
535		public boolean cancel(boolean mayInterruptIfRunning) {
536		setCompletion(CANCELLED);
537	<	return (status & COMPLETION_MASK) == CANCELLED;
537	>	return status == CANCELLED;
538	>	}
539	>
540	>	/**
541	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
542	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
543	>	* exceptions, but if it does anyway, we have no recourse during
544	>	* shutdown, so guard against this case.
545	>	*/
546	>	final void cancelIgnoringExceptions() {
547	>	try {
548	>	cancel(false);
549	>	} catch (Throwable ignore) {
550	>	}
551	>	}
552	>
553	>	/**
554	>	* Cancels if current thread is a terminating worker thread,
555	>	* ignoring any exceptions thrown by cancel.
556	>	*/
557	>	final void cancelIfTerminating() {
558	>	Thread t = Thread.currentThread();
559	>	if ((t instanceof ForkJoinWorkerThread) &&
560	>	((ForkJoinWorkerThread) t).isTerminating()) {
561	>	try {
562	>	cancel(false);
563	>	} catch (Throwable ignore) {
564	>	}
565	>	}
566	>	}
567	>
568	>	public final boolean isDone() {
569	>	return status < 0;
570	>	}
571	>
572	>	public final boolean isCancelled() {
573	>	return status == CANCELLED;
574		}
575
576		/**
#	Line 722 | Line 579 | public abstract class ForkJoinTask<V> im
579		* @return {@code true} if this task threw an exception or was cancelled
580		*/
581		public final boolean isCompletedAbnormally() {
582	<	return (status & COMPLETION_MASK) < NORMAL;
582	>	return status < NORMAL;
583	>	}
584	>
585	>	/**
586	>	* Returns {@code true} if this task completed without throwing an
587	>	* exception and was not cancelled.
588	>	*
589	>	* @return {@code true} if this task completed without throwing an
590	>	* exception and was not cancelled
591	>	*/
592	>	public final boolean isCompletedNormally() {
593	>	return status == NORMAL;
594		}
595
596		/**
597		* Returns the exception thrown by the base computation, or a
598	<	* CancellationException if cancelled, or null if none or if the
599	<	* method has not yet completed.
598	>	* {@code CancellationException} if cancelled, or {@code null} if
599	>	* none or if the method has not yet completed.
600		*
601		* @return the exception, or {@code null} if none
602		*/
603		public final Throwable getException() {
604	<	int s = status & COMPLETION_MASK;
605	<	if (s >= NORMAL)
606	<	return null;
607	<	if (s == CANCELLED)
740	<	return new CancellationException();
741	<	return exceptionMap.get(this);
604	>	int s = status;
605	>	return ((s >= NORMAL)    ? null :
606	>	(s == CANCELLED) ? new CancellationException() :
607	>	exceptionMap.get(this));
608		}
609
610		/**
#	Line 751 | Line 617 | public abstract class ForkJoinTask<V> im
617		* overridable, but overridden versions must invoke {@code super}
618		* implementation to maintain guarantees.
619		*
620	<	* @param ex the exception to throw. If this exception is
621	<	* not a RuntimeException or Error, the actual exception thrown
622	<	* will be a RuntimeException with cause ex.
620	>	* @param ex the exception to throw. If this exception is not a
621	>	* {@code RuntimeException} or {@code Error}, the actual exception
622	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
623		*/
624		public void completeExceptionally(Throwable ex) {
625	<	setDoneExceptionally((ex instanceof RuntimeException) ||
626	<	(ex instanceof Error) ? ex :
627	<	new RuntimeException(ex));
625	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
626	>	(ex instanceof Error) ? ex :
627	>	new RuntimeException(ex));
628		}
629
630		/**
631		* Completes this task, and if not already aborted or cancelled,
632	<	* returning a {@code null} result upon {@code join} and related
633	<	* operations. This method may be used to provide results for
634	<	* asynchronous tasks, or to provide alternative handling for
635	<	* tasks that would not otherwise complete normally. Its use in
636	<	* other situations is discouraged. This method is
637	<	* overridable, but overridden versions must invoke {@code super}
638	<	* implementation to maintain guarantees.
632	>	* returning the given value as the result of subsequent
633	>	* invocations of {@code join} and related operations. This method
634	>	* may be used to provide results for asynchronous tasks, or to
635	>	* provide alternative handling for tasks that would not otherwise
636	>	* complete normally. Its use in other situations is
637	>	* discouraged. This method is overridable, but overridden
638	>	* versions must invoke {@code super} implementation to maintain
639	>	* guarantees.
640		*
641		* @param value the result value for this task
642		*/
#	Line 777 | Line 644 | public abstract class ForkJoinTask<V> im
644		try {
645		setRawResult(value);
646		} catch (Throwable rex) {
647	<	setDoneExceptionally(rex);
647	>	setExceptionalCompletion(rex);
648		return;
649		}
650	<	setNormalCompletion();
784	<	}
785	<
786	<	public final V get() throws InterruptedException, ExecutionException {
787	<	ForkJoinWorkerThread w = getWorker();
788	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
789	<	awaitDone(w, true);
790	<	return reportFutureResult();
791	<	}
792	<
793	<	public final V get(long timeout, TimeUnit unit)
794	<	throws InterruptedException, ExecutionException, TimeoutException {
795	<	long nanos = unit.toNanos(timeout);
796	<	ForkJoinWorkerThread w = getWorker();
797	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
798	<	awaitDone(w, nanos);
799	<	return reportTimedFutureResult();
650	>	setCompletion(NORMAL);
651		}
652
653		/**
654	<	* Possibly executes other tasks until this task is ready, then
655	<	* returns the result of the computation.  This method may be more
805	<	* efficient than {@code join}, but is only applicable when
806	<	* there are no potential dependencies between continuation of the
807	<	* current task and that of any other task that might be executed
808	<	* while helping. (This usually holds for pure divide-and-conquer
809	<	* tasks). This method may be invoked only from within
810	<	* ForkJoinTask computations (as may be determined using method
811	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
812	<	* result in exceptions or errors, possibly including
813	<	* ClassCastException.
654	>	* Waits if necessary for the computation to complete, and then
655	>	* retrieves its result.
656		*
657		* @return the computed result
658	+	* @throws CancellationException if the computation was cancelled
659	+	* @throws ExecutionException if the computation threw an
660	+	* exception
661	+	* @throws InterruptedException if the current thread is not a
662	+	* member of a ForkJoinPool and was interrupted while waiting
663		*/
664	<	public final V helpJoin() {
665	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
666	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
667	<	reportException(busyJoin(w));
664	>	public final V get() throws InterruptedException, ExecutionException {
665	>	int s;
666	>	if (Thread.currentThread() instanceof ForkJoinWorkerThread) {
667	>	quietlyJoin();
668	>	s = status;
669	>	}
670	>	else {
671	>	while ((s = status) >= 0) {
672	>	synchronized (this) { // interruptible form of awaitDone
673	>	if (UNSAFE.compareAndSwapInt(this, statusOffset,
674	>	s, SIGNAL)) {
675	>	while (status >= 0)
676	>	wait();
677	>	}
678	>	}
679	>	}
680	>	}
681	>	if (s < NORMAL) {
682	>	Throwable ex;
683	>	if (s == CANCELLED)
684	>	throw new CancellationException();
685	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
686	>	throw new ExecutionException(ex);
687	>	}
688		return getRawResult();
689		}
690
691		/**
692	<	* Possibly executes other tasks until this task is ready.  This
693	<	* method may be invoked only from within ForkJoinTask
694	<	* computations (as may be determined using method {@link
695	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
696	<	* in exceptions or errors, possibly including ClassCastException.
692	>	* Waits if necessary for at most the given time for the computation
693	>	* to complete, and then retrieves its result, if available.
694	>	*
695	>	* @param timeout the maximum time to wait
696	>	* @param unit the time unit of the timeout argument
697	>	* @return the computed result
698	>	* @throws CancellationException if the computation was cancelled
699	>	* @throws ExecutionException if the computation threw an
700	>	* exception
701	>	* @throws InterruptedException if the current thread is not a
702	>	* member of a ForkJoinPool and was interrupted while waiting
703	>	* @throws TimeoutException if the wait timed out
704		*/
705	<	public final void quietlyHelpJoin() {
705	>	public final V get(long timeout, TimeUnit unit)
706	>	throws InterruptedException, ExecutionException, TimeoutException {
707	>	long nanos = unit.toNanos(timeout);
708		if (status >= 0) {
709	<	ForkJoinWorkerThread w =
710	<	(ForkJoinWorkerThread) Thread.currentThread();
711	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
712	<	busyJoin(w);
709	>	Thread t = Thread.currentThread();
710	>	if (t instanceof ForkJoinWorkerThread) {
711	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
712	>	boolean completed = false; // timed variant of quietlyJoin
713	>	if (w.unpushTask(this)) {
714	>	try {
715	>	completed = exec();
716	>	} catch (Throwable rex) {
717	>	setExceptionalCompletion(rex);
718	>	}
719	>	}
720	>	if (completed)
721	>	setCompletion(NORMAL);
722	>	else if (status >= 0)
723	>	w.joinTask(this, true, nanos);
724	>	}
725	>	else if (Thread.interrupted())
726	>	throw new InterruptedException();
727	>	else {
728	>	long startTime = System.nanoTime();
729	>	int s; long nt;
730	>	while ((s = status) >= 0 &&
731	>	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
732	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,
733	>	SIGNAL)) {
734	>	long ms = nt / 1000000;
735	>	int ns = (int) (nt % 1000000);
736	>	synchronized (this) {
737	>	if (status >= 0)
738	>	wait(ms, ns); // exit on IE throw
739	>	}
740	>	}
741	>	}
742	>	}
743	>	}
744	>	int es = status;
745	>	if (es != NORMAL) {
746	>	Throwable ex;
747	>	if (es == CANCELLED)
748	>	throw new CancellationException();
749	>	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
750	>	throw new ExecutionException(ex);
751	>	throw new TimeoutException();
752		}
753	+	return getRawResult();
754		}
755
756		/**
757	<	* Joins this task, without returning its result or throwing an
757	>	* Joins this task, without returning its result or throwing its
758		* exception. This method may be useful when processing
759		* collections of tasks when some have been cancelled or otherwise
760		* known to have aborted.
761		*/
762		public final void quietlyJoin() {
763	<	if (status >= 0) {
764	<	ForkJoinWorkerThread w = getWorker();
765	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
766	<	awaitDone(w, true);
763	>	Thread t;
764	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
765	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
766	>	if (status >= 0) {
767	>	if (w.unpushTask(this)) {
768	>	boolean completed;
769	>	try {
770	>	completed = exec();
771	>	} catch (Throwable rex) {
772	>	setExceptionalCompletion(rex);
773	>	return;
774	>	}
775	>	if (completed) {
776	>	setCompletion(NORMAL);
777	>	return;
778	>	}
779	>	}
780	>	w.joinTask(this, false, 0L);
781	>	}
782		}
783	+	else
784	+	externalAwaitDone();
785		}
786
787		/**
788		* Commences performing this task and awaits its completion if
789	<	* necessary, without returning its result or throwing an
790	<	* exception. This method may be useful when processing
858	<	* collections of tasks when some have been cancelled or otherwise
859	<	* known to have aborted.
789	>	* necessary, without returning its result or throwing its
790	>	* exception.
791		*/
792		public final void quietlyInvoke() {
793	<	if (status >= 0 && !tryQuietlyInvoke())
794	<	quietlyJoin();
793	>	if (status >= 0) {
794	>	boolean completed;
795	>	try {
796	>	completed = exec();
797	>	} catch (Throwable rex) {
798	>	setExceptionalCompletion(rex);
799	>	return;
800	>	}
801	>	if (completed)
802	>	setCompletion(NORMAL);
803	>	else
804	>	quietlyJoin();
805	>	}
806		}
807
808		/**
809		* Possibly executes tasks until the pool hosting the current task
810	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
811	<	* designs in which many tasks are forked, but none are explicitly
812	<	* joined, instead executing them until all are processed.  This
813	<	* method may be invoked only from within ForkJoinTask
814	<	* computations (as may be determined using method {@link
815	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
816	<	* in exceptions or errors, possibly including ClassCastException.
810	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
811	>	* be of use in designs in which many tasks are forked, but none
812	>	* are explicitly joined, instead executing them until all are
813	>	* processed.
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}.
820		*/
821		public static void helpQuiesce() {
822		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 884 | Line 829 | public abstract class ForkJoinTask<V> im
829		* this task, but only if reuse occurs when this task has either
830		* never been forked, or has been forked, then completed and all
831		* outstanding joins of this task have also completed. Effects
832	<	* under any other usage conditions are not guaranteed, and are
833	<	* discouraged. This method may be useful when executing
832	>	* under any other usage conditions are not guaranteed.
833	>	* This method may be useful when executing
834		* pre-constructed trees of subtasks in loops.
835	+	*
836	+	* <p>Upon completion of this method, {@code isDone()} reports
837	+	* {@code false}, and {@code getException()} reports {@code
838	+	* null}. However, the value returned by {@code getRawResult} is
839	+	* unaffected. To clear this value, you can invoke {@code
840	+	* setRawResult(null)}.
841		*/
842		public void reinitialize() {
843	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
843	>	if (status == EXCEPTIONAL)
844		exceptionMap.remove(this);
845		status = 0;
846		}
#	Line 924 | Line 875 | public abstract class ForkJoinTask<V> im
875		* by the current thread, and has not commenced executing in
876		* another thread.  This method may be useful when arranging
877		* alternative local processing of tasks that could have been, but
878	<	* were not, stolen. This method may be invoked only from within
879	<	* ForkJoinTask computations (as may be determined using method
880	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
881	<	* result in exceptions or errors, possibly including
882	<	* ClassCastException.
878	>	* were not, stolen.
879	>	*
880	>	* <p>This method may be invoked only from within {@code
881	>	* ForkJoinTask} computations (as may be determined using method
882	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
883	>	* result in exceptions or errors, possibly including {@code
884	>	* ClassCastException}.
885		*
886		* @return {@code true} if unforked
887		*/
#	Line 941 | Line 894 | public abstract class ForkJoinTask<V> im
894		* Returns an estimate of the number of tasks that have been
895		* forked by the current worker thread but not yet executed. This
896		* value may be useful for heuristic decisions about whether to
897	<	* fork other tasks.  This method may be invoked only from within
898	<	* ForkJoinTask computations (as may be determined using method
899	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
900	<	* result in exceptions or errors, possibly including
901	<	* ClassCastException.
897	>	* fork other tasks.
898	>	*
899	>	* <p>This method may be invoked only from within {@code
900	>	* ForkJoinTask} computations (as may be determined using method
901	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
902	>	* result in exceptions or errors, possibly including {@code
903	>	* ClassCastException}.
904	>	*
905		* @return the number of tasks
906		*/
907		public static int getQueuedTaskCount() {
#	Line 961 | Line 917 | public abstract class ForkJoinTask<V> im
917		* usages of ForkJoinTasks, at steady state, each worker should
918		* aim to maintain a small constant surplus (for example, 3) of
919		* tasks, and to process computations locally if this threshold is
920	<	* exceeded.  This method may be invoked only from within
921	<	* ForkJoinTask computations (as may be determined using method
922	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
923	<	* result in exceptions or errors, possibly including
924	<	* ClassCastException.  *
920	>	* exceeded.
921	>	*
922	>	* <p>This method may be invoked only from within {@code
923	>	* ForkJoinTask} computations (as may be determined using method
924	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
925	>	* result in exceptions or errors, possibly including {@code
926	>	* ClassCastException}.
927	>	*
928		* @return the surplus number of tasks, which may be negative
929		*/
930		public static int getSurplusQueuedTaskCount() {
#	Line 1001 | Line 960 | public abstract class ForkJoinTask<V> im
960		* called otherwise. The return value controls whether this task
961		* is considered to be done normally. It may return false in
962		* asynchronous actions that require explicit invocations of
963	<	* {@link #complete} to become joinable. It may throw exceptions
964	<	* to indicate abnormal exit.
963	>	* {@link #complete} to become joinable. It may also throw an
964	>	* (unchecked) exception to indicate abnormal exit.
965		*
966		* @return {@code true} if completed normally
1008	–	* @throws Error or RuntimeException if encountered during computation
967		*/
968		protected abstract boolean exec();
969
#	Line 1017 | Line 975 | public abstract class ForkJoinTask<V> im
975		* null even if a task exists but cannot be accessed without
976		* contention with other threads.  This method is designed
977		* primarily to support extensions, and is unlikely to be useful
978	<	* otherwise.  This method may be invoked only from within
979	<	* ForkJoinTask computations (as may be determined using method
980	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
981	<	* result in exceptions or errors, possibly including
982	<	* ClassCastException.
978	>	* otherwise.
979	>	*
980	>	* <p>This method may be invoked only from within {@code
981	>	* ForkJoinTask} computations (as may be determined using method
982	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
983	>	* result in exceptions or errors, possibly including {@code
984	>	* ClassCastException}.
985		*
986		* @return the next task, or {@code null} if none are available
987		*/
#	Line 1034 | Line 994 | public abstract class ForkJoinTask<V> im
994		* Unschedules and returns, without executing, the next task
995		* queued by the current thread but not yet executed.  This method
996		* is designed primarily to support extensions, and is unlikely to
997	<	* be useful otherwise.  This method may be invoked only from
998	<	* within ForkJoinTask computations (as may be determined using
999	<	* method {@link #inForkJoinPool}). Attempts to invoke in other
1000	<	* contexts result in exceptions or errors, possibly including
1001	<	* ClassCastException.
997	>	* be useful otherwise.
998	>	*
999	>	* <p>This method may be invoked only from within {@code
1000	>	* ForkJoinTask} computations (as may be determined using method
1001	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1002	>	* result in exceptions or errors, possibly including {@code
1003	>	* ClassCastException}.
1004		*
1005		* @return the next task, or {@code null} if none are available
1006		*/
#	Line 1055 | Line 1017 | public abstract class ForkJoinTask<V> im
1017		* {@code null} result does not necessarily imply quiescence
1018		* of the pool this task is operating in.  This method is designed
1019		* primarily to support extensions, and is unlikely to be useful
1020	<	* otherwise.  This method may be invoked only from within
1021	<	* ForkJoinTask computations (as may be determined using method
1022	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1023	<	* result in exceptions or errors, possibly including
1024	<	* ClassCastException.
1020	>	* otherwise.
1021	>	*
1022	>	* <p>This method may be invoked only from within {@code
1023	>	* ForkJoinTask} computations (as may be determined using method
1024	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1025	>	* result in exceptions or errors, possibly including {@code
1026	>	* ClassCastException}.
1027		*
1028		* @return a task, or {@code null} if none are available
1029		*/
#	Line 1124 | Line 1088 | public abstract class ForkJoinTask<V> im
1088		}
1089
1090		/**
1091	<	* Returns a new ForkJoinTask that performs the {@code run}
1092	<	* method of the given Runnable as its action, and returns a null
1093	<	* result upon {@code join}.
1091	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1092	>	* method of the given {@code Runnable} as its action, and returns
1093	>	* a null result upon {@link #join}.
1094		*
1095		* @param runnable the runnable action
1096		* @return the task
#	Line 1136 | Line 1100 | public abstract class ForkJoinTask<V> im
1100		}
1101
1102		/**
1103	<	* Returns a new ForkJoinTask that performs the {@code run}
1104	<	* method of the given Runnable as its action, and returns the
1105	<	* given result upon {@code join}.
1103	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1104	>	* method of the given {@code Runnable} as its action, and returns
1105	>	* the given result upon {@link #join}.
1106		*
1107		* @param runnable the runnable action
1108		* @param result the result upon completion
#	Line 1149 | Line 1113 | public abstract class ForkJoinTask<V> im
1113		}
1114
1115		/**
1116	<	* Returns a new ForkJoinTask that performs the {@code call}
1117	<	* method of the given Callable as its action, and returns its
1118	<	* result upon {@code join}, translating any checked
1119	<	* exceptions encountered into {@code RuntimeException}.
1116	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1117	>	* method of the given {@code Callable} as its action, and returns
1118	>	* its result upon {@link #join}, translating any checked exceptions
1119	>	* encountered into {@code RuntimeException}.
1120		*
1121		* @param callable the callable action
1122		* @return the task
#	Line 1166 | Line 1130 | public abstract class ForkJoinTask<V> im
1130		private static final long serialVersionUID = -7721805057305804111L;
1131
1132		/**
1133	<	* Save the state to a stream.
1133	>	* Saves the state to a stream (that is, serializes it).
1134		*
1135		* @serialData the current run status and the exception thrown
1136		* during execution, or {@code null} if none
#	Line 1179 | Line 1143 | public abstract class ForkJoinTask<V> im
1143		}
1144
1145		/**
1146	<	* Reconstitute the instance from a stream.
1146	>	* Reconstitutes the instance from a stream (that is, deserializes it).
1147		*
1148		* @param s the stream
1149		*/
1150		private void readObject(java.io.ObjectInputStream s)
1151		throws java.io.IOException, ClassNotFoundException {
1152		s.defaultReadObject();
1189	–	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1190	–	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1153		Object ex = s.readObject();
1154		if (ex != null)
1155	<	setDoneExceptionally((Throwable) ex);
1155	>	setExceptionalCompletion((Throwable) ex);
1156		}
1157
1158		// Unsafe mechanics

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