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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.29 by jsr166, Sun Aug 2 17:19:24 2009 UTC vs.
Revision 1.51 by dl, Fri Jul 23 16:49:11 2010 UTC

#	Line 12 | Line 12 | import java.io.Serializable;
12		import java.util.Collection;
13		import java.util.Collections;
14		import java.util.List;
15	+	import java.util.RandomAccess;
16		import java.util.Map;
17		import java.util.WeakHashMap;
18
#	Line 54 | Line 55 | import java.util.WeakHashMap;
55		* restriction is in part enforced by not permitting checked
56		* exceptions such as {@code IOExceptions} to be thrown. However,
57		* computations may still encounter unchecked exceptions, that are
58	<	* rethrown to callers attempting join them. These exceptions may
59	<	* additionally include RejectedExecutionExceptions stemming from
60	<	* internal resource exhaustion such as failure to allocate internal
61	<	* task queues.
58	>	* rethrown to callers attempting to join them. These exceptions may
59	>	* additionally include {@link RejectedExecutionException} stemming
60	>	* from internal resource exhaustion, such as failure to allocate
61	>	* internal task queues.
62		*
63		* <p>The primary method for awaiting completion and extracting
64		* results of a task is {@link #join}, but there are several variants:
65		* The {@link Future#get} methods support interruptible and/or timed
66		* waits for completion and report results using {@code Future}
67	<	* conventions. Method {@link #helpJoin} enables callers to actively
68	<	* execute other tasks while awaiting joins, which is sometimes more
69	<	* efficient but only applies when all subtasks are known to be
70	<	* 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
67	>	* conventions. Method {@link #invoke} is semantically
68	>	* equivalent to {@code fork(); join()} but always attempts to begin
69	>	* execution in the current thread. The "<em>quiet</em>" forms of
70	>	* these methods do not extract results or report exceptions. These
71		* may be useful when a set of tasks are being executed, and you need
72		* to delay processing of results or exceptions until all complete.
73		* Method {@code invokeAll} (available in multiple versions)
74		* performs the most common form of parallel invocation: forking a set
75		* of tasks and joining them all.
76		*
77	+	* <p>The execution status of tasks may be queried at several levels
78	+	* of detail: {@link #isDone} is true if a task completed in any way
79	+	* (including the case where a task was cancelled without executing);
80	+	* {@link #isCompletedNormally} is true if a task completed without
81	+	* cancellation or encountering an exception; {@link #isCancelled} is
82	+	* true if the task was cancelled (in which case {@link #getException}
83	+	* returns a {@link java.util.concurrent.CancellationException}); and
84	+	* {@link #isCompletedAbnormally} is true if a task was either
85	+	* cancelled or encountered an exception, in which case {@link
86	+	* #getException} will return either the encountered exception or
87	+	* {@link java.util.concurrent.CancellationException}.
88	+	*
89		* <p>The ForkJoinTask class is not usually directly subclassed.
90		* Instead, you subclass one of the abstract classes that support a
91		* particular style of fork/join processing, typically {@link
#	Line 85 | Line 95 | import java.util.WeakHashMap;
95		* established in a constructor, and then defines a {@code compute}
96		* method that somehow uses the control methods supplied by this base
97		* class. While these methods have {@code public} access (to allow
98	<	* instances of different task subclasses to call each others
98	>	* instances of different task subclasses to call each other's
99		* methods), some of them may only be called from within other
100		* ForkJoinTasks (as may be determined using method {@link
101		* #inForkJoinPool}).  Attempts to invoke them in other contexts
102		* result in exceptions or errors, possibly including
103		* ClassCastException.
104		*
105	<	* <p>Most base support methods are {@code final} because their
106	<	* implementations are intrinsically tied to the underlying
107	<	* lightweight task scheduling framework, and so cannot be overridden.
108	<	* Developers creating new basic styles of fork/join processing should
109	<	* minimally implement {@code protected} methods
110	<	* {@link #exec}, {@link #setRawResult}, and
111	<	* {@link #getRawResult}, while also introducing an abstract
112	<	* computational method that can be implemented in its subclasses,
113	<	* possibly relying on other {@code protected} methods provided
104	<	* by this class.
105	>	* <p>Most base support methods are {@code final}, to prevent
106	>	* overriding of implementations that are intrinsically tied to the
107	>	* underlying lightweight task scheduling framework.  Developers
108	>	* creating new basic styles of fork/join processing should minimally
109	>	* implement {@code protected} methods {@link #exec}, {@link
110	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
111	>	* an abstract computational method that can be implemented in its
112	>	* subclasses, possibly relying on other {@code protected} methods
113	>	* provided by this class.
114		*
115		* <p>ForkJoinTasks should perform relatively small amounts of
116	<	* computations, otherwise splitting into smaller tasks. As a very
117	<	* rough rule of thumb, a task should perform more than 100 and less
118	<	* than 10000 basic computational steps. If tasks are too big, then
119	<	* parallelism cannot improve throughput. If too small, then memory
120	<	* and internal task maintenance overhead may overwhelm processing.
116	>	* computation. Large tasks should be split into smaller subtasks,
117	>	* usually via recursive decomposition. As a very rough rule of thumb,
118	>	* a task should perform more than 100 and less than 10000 basic
119	>	* computational steps. If tasks are too big, then parallelism cannot
120	>	* improve throughput. If too small, then memory and internal task
121	>	* maintenance overhead may overwhelm processing.
122		*
123	<	* <p>This class provides {@code adapt} methods for {@link
124	<	* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
125	<	* may be of use when mixing execution of ForkJoinTasks with other
126	<	* kinds of tasks. When all tasks are of this form, consider using a
117	<	* pool in {@link ForkJoinPool#setAsyncMode}.
123	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
124	>	* and {@link Callable}, that may be of use when mixing execution of
125	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
126	>	* of this form, consider using a pool constructed in <em>asyncMode</em>.
127		*
128	<	* <p>ForkJoinTasks are {@code Serializable}, which enables them
129	<	* to be used in extensions such as remote execution frameworks. It is
130	<	* in general sensible to serialize tasks only before or after, but
131	<	* not during execution. Serialization is not relied on during
123	<	* execution itself.
128	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
129	>	* used in extensions such as remote execution frameworks. It is
130	>	* sensible to serialize tasks only before or after, but not during,
131	>	* execution. Serialization is not relied on during execution itself.
132		*
133		* @since 1.7
134		* @author Doug Lea
135		*/
136		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
137
138	<	/**
139	<	* Run control status bits packed into a single int to minimize
140	<	* footprint and to ensure atomicity (via CAS).  Status is
141	<	* initially zero, and takes on nonnegative values until
142	<	* completed, upon which status holds COMPLETED. CANCELLED, or
143	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
144	<	* blocking waits by other threads have SIGNAL_MASK bits set --
145	<	* bit 15 for external (nonFJ) waits, and the rest a count of
146	<	* waiting FJ threads.  (This representation relies on
147	<	* ForkJoinPool max thread limits). Completion of a stolen task
148	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
149	<	* though suboptimal for some purposes, we use basic builtin
150	<	* wait/notify to take advantage of "monitor inflation" in JVMs
151	<	* that we would otherwise need to emulate to avoid adding further
152	<	* per-task bookkeeping overhead. Note that bits 16-28 are
153	<	* currently unused. Also value 0x80000000 is available as spare
154	<	* completion value.
138	>	/*
139	>	* See the internal documentation of class ForkJoinPool for a
140	>	* general implementation overview.  ForkJoinTasks are mainly
141	>	* responsible for maintaining their "status" field amidst relays
142	>	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
143	>	* methods of this class are more-or-less layered into (1) basic
144	>	* status maintenance (2) execution and awaiting completion (3)
145	>	* user-level methods that additionally report results. This is
146	>	* sometimes hard to see because this file orders exported methods
147	>	* in a way that flows well in javadocs.
148	>	*/
149	>
150	>	/*
151	>	* The status field holds run control status bits packed into a
152	>	* single int to minimize footprint and to ensure atomicity (via
153	>	* CAS).  Status is initially zero, and takes on nonnegative
154	>	* values until completed, upon which status holds value
155	>	* COMPLETED. CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
156	>	* waits by other threads have the SIGNAL bit set.  Completion of
157	>	* a stolen task with SIGNAL set awakens any waiters via
158	>	* notifyAll. Even though suboptimal for some purposes, we use
159	>	* basic builtin wait/notify to take advantage of "monitor
160	>	* inflation" in JVMs that we would otherwise need to emulate to
161	>	* avoid adding further per-task bookkeeping overhead.  We want
162	>	* these monitors to be "fat", i.e., not use biasing or thin-lock
163	>	* techniques, so use some odd coding idioms that tend to avoid
164	>	* them.
165		*/
166	+
167	+	/** Run status of this task */
168		volatile int status; // accessed directly by pool and workers
169
170	<	static final int COMPLETION_MASK      = 0xe0000000;
171	<	static final int NORMAL               = 0xe0000000; // == mask
172	<	static final int CANCELLED            = 0xc0000000;
173	<	static final int EXCEPTIONAL          = 0xa0000000;
154	<	static final int SIGNAL_MASK          = 0x0000ffff;
155	<	static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
156	<	static final int EXTERNAL_SIGNAL      = 0x00008000; // top bit of low word
170	>	private static final int NORMAL      = -1;
171	>	private static final int CANCELLED   = -2;
172	>	private static final int EXCEPTIONAL = -3;
173	>	private static final int SIGNAL      =  1;
174
175		/**
176		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 167 | Line 184 | public abstract class ForkJoinTask<V> im
184		Collections.synchronizedMap
185		(new WeakHashMap<ForkJoinTask<?>, Throwable>());
186
187	<	// within-package utilities
187	>	// Maintaining completion status
188
189		/**
190	<	* Gets current worker thread, or null if not a worker thread.
191	<	*/
175	<	static ForkJoinWorkerThread getWorker() {
176	<	Thread t = Thread.currentThread();
177	<	return ((t instanceof ForkJoinWorkerThread) ?
178	<	(ForkJoinWorkerThread) t : null);
179	<	}
180	<
181	<	final boolean casStatus(int cmp, int val) {
182	<	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
183	<	}
184	<
185	<	/**
186	<	* Workaround for not being able to rethrow unchecked exceptions.
187	<	*/
188	<	static void rethrowException(Throwable ex) {
189	<	if (ex != null)
190	<	UNSAFE.throwException(ex);
191	<	}
192	<
193	<	// Setting completion status
194	<
195	<	/**
196	<	* Marks completion and wakes up threads waiting to join this task.
190	>	* Marks completion and wakes up threads waiting to join this task,
191	>	* also clearing signal request bits.
192		*
193		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
194	+	* @return status on exit
195		*/
196	<	final void setCompletion(int completion) {
197	<	ForkJoinPool pool = getPool();
198	<	if (pool != null) {
199	<	int s; // Clear signal bits while setting completion status
200	<	do {} while ((s = status) >= 0 && !casStatus(s, completion));
201	<
202	<	if ((s & SIGNAL_MASK) != 0) {
207	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
208	<	pool.updateRunningCount(s);
209	<	synchronized (this) { notifyAll(); }
196	>	private int setCompletion(int completion) {
197	>	int s;
198	>	while ((s = status) >= 0) {
199	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
200	>	if (s != 0)
201	>	synchronized (this) { notifyAll(); }
202	>	return completion;
203		}
204		}
205	<	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);
205	>	return s;
206		}
207
237	–	// internal waiting and notification
238	–
208		/**
209	<	* Performs the actual monitor wait for awaitDone.
209	>	* Record exception and set exceptional completion
210	>	* @return status on exit
211		*/
212	<	private void doAwaitDone() {
213	<	// Minimize lock bias and in/de-flation effects by maximizing
214	<	// 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	<	}
212	>	private int setExceptionalCompletion(Throwable rex) {
213	>	exceptionMap.put(this, rex);
214	>	return setCompletion(EXCEPTIONAL);
215		}
216
217		/**
218	<	* Performs the actual timed monitor wait for awaitDone.
218	>	* Blocks a worker thread until completion. Called only by pool.
219		*/
220	<	private void doAwaitDone(long startTime, long nanos) {
221	<	synchronized (this) {
220	>	final void internalAwaitDone() {
221	>	int s;         // the odd construction reduces lock bias effects
222	>	while ((s = status) >= 0) {
223		try {
224	<	while (status >= 0) {
225	<	long nt = nanos - (System.nanoTime() - startTime);
226	<	if (nt <= 0)
262	<	break;
263	<	wait(nt / 1000000, (int) (nt % 1000000));
224	>	synchronized(this) {
225	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
226	>	wait();
227		}
228		} catch (InterruptedException ie) {
229	<	onInterruptedWait();
229	>	cancelIfTerminating();
230		}
231		}
232		}
233
271	–	// Awaiting completion
272	–
234		/**
235	<	* Sets status to indicate there is joiner, then waits for join,
236	<	* surrounded with pool notifications.
276	<	*
277	<	* @return status upon exit
235	>	* Blocks a non-worker-thread until completion.
236	>	* @return status on exit
237		*/
238	<	private int awaitDone(ForkJoinWorkerThread w,
280	<	boolean maintainParallelism) {
281	<	ForkJoinPool pool = (w == null) ? null : w.pool;
238	>	private int externalAwaitDone() {
239		int s;
240		while ((s = status) >= 0) {
241	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
242	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
243	<	doAwaitDone();
244	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
245	<	adjustPoolCountsOnUnblock(pool);
246	<	break;
247	<	}
248	<	}
249	<	return s;
250	<	}
251	<
252	<	/**
253	<	* 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;
241	>	synchronized(this) {
242	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
243	>	boolean interrupted = false;
244	>	while ((s = status) >= 0) {
245	>	try {
246	>	wait();
247	>	} catch (InterruptedException ie) {
248	>	interrupted = true;
249	>	}
250	>	}
251	>	if (interrupted)
252	>	Thread.currentThread().interrupt();
253	>	break;
254		}
312	–	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
313	–	adjustPoolCountsOnUnblock(pool);
314	–	break;
255		}
256		}
257		return s;
258		}
259
260		/**
261	<	* Notifies pool that thread is unblocked. Called by signalled
262	<	* threads when woken by non-FJ threads (which is atypical).
261	>	* Unless done, calls exec and records status if completed, but
262	>	* doesn't wait for completion otherwise. Primary execution method
263	>	* for ForkJoinWorkerThread.
264		*/
265	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
266	<	int s;
267	<	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
268	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
269	<	pool.updateRunningCount(s);
265	>	final void tryExec() {
266	>	try {
267	>	if (status < 0 || !exec())
268	>	return;
269	>	} catch (Throwable rex) {
270	>	setExceptionalCompletion(rex);
271	>	return;
272	>	}
273	>	setCompletion(NORMAL); // must be outside try block
274		}
275
276		/**
277	<	* Notifies pool to adjust counts on cancelled or timed out wait.
277	>	* If not done and this task is next in worker queue, runs it,
278	>	* else waits for it.
279	>	* @return status on exit
280		*/
281	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
282	<	if (pool != null) {
283	<	int s;
284	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
285	<	if (casStatus(s, s - 1)) {
286	<	pool.updateRunningCount(1);
287	<	break;
281	>	private int doJoin() {
282	>	int stat;
283	>	if ((stat = status) < 0)
284	>	return stat;
285	>	Thread t = Thread.currentThread();
286	>	ForkJoinWorkerThread w;
287	>	if (t instanceof ForkJoinWorkerThread) {
288	>	if ((w = (ForkJoinWorkerThread) t).unpushTask(this)) {
289	>	boolean completed;
290	>	try {
291	>	completed = exec();
292	>	} catch (Throwable rex) {
293	>	return setExceptionalCompletion(rex);
294		}
295	+	if (completed)
296	+	return setCompletion(NORMAL);
297		}
298	+	return w.joinTask(this);
299		}
300	+	return externalAwaitDone();
301		}
302
303		/**
304	<	* Handles interruptions during waits.
305	<	*/
306	<	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.
304	>	* Unless done, calls exec and records status if completed, or
305	>	* waits for completion otherwise.
306	>	* @return status on exit
307		*/
308	<	private V reportTimedFutureResult()
309	<	throws InterruptedException, ExecutionException, TimeoutException {
310	<	Throwable ex;
311	<	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.
441	<	*/
442	<	final void quietlyExec() {
443	<	if (status >= 0) {
308	>	private int doInvoke() {
309	>	int stat;
310	>	if ((stat = status) >= 0) {
311	>	boolean completed;
312		try {
313	<	if (!exec())
446	<	return;
313	>	completed = exec();
314		} catch (Throwable rex) {
315	<	setDoneExceptionally(rex);
449	<	return;
315	>	return setExceptionalCompletion(rex);
316		}
317	<	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() {
462	<	try {
463	<	if (!exec())
464	<	return false;
465	<	} catch (Throwable rex) {
466	<	setDoneExceptionally(rex);
467	<	return false;
317	>	stat = completed ? setCompletion(NORMAL) : doJoin();
318		}
319	<	setNormalCompletion();
470	<	return true;
319	>	return stat;
320		}
321
322		/**
323	<	* Cancels, ignoring any exceptions it throws.
323	>	* Returns result or throws exception associated with given status.
324	>	* @param s the status
325		*/
326	<	final void cancelIgnoringExceptions() {
327	<	try {
328	<	cancel(false);
329	<	} catch (Throwable ignore) {
330	<	}
481	<	}
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
326	>	private V reportResult(int s) {
327	>	Throwable ex;
328	>	if (s < NORMAL && (ex = getException()) != null)
329	>	UNSAFE.throwException(ex);
330	>	return getRawResult();
331		}
332
333		// public methods
#	Line 496 | Line 335 | public abstract class ForkJoinTask<V> im
335		/**
336		* Arranges to asynchronously execute this task.  While it is not
337		* necessarily enforced, it is a usage error to fork a task more
338	<	* than once unless it has completed and been reinitialized.  This
339	<	* method may be invoked only from within ForkJoinTask
340	<	* computations (as may be determined using method {@link
341	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
342	<	* in exceptions or errors, possibly including ClassCastException.
338	>	* than once unless it has completed and been reinitialized.
339	>	* Subsequent modifications to the state of this task or any data
340	>	* it operates on are not necessarily consistently observable by
341	>	* any thread other than the one executing it unless preceded by a
342	>	* call to {@link #join} or related methods, or a call to {@link
343	>	* #isDone} returning {@code true}.
344	>	*
345	>	* <p>This method may be invoked only from within {@code
346	>	* ForkJoinTask} computations (as may be determined using method
347	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
348	>	* result in exceptions or errors, possibly including {@code
349	>	* ClassCastException}.
350		*
351	<	* @return {@code this}, to simplify usage.
351	>	* @return {@code this}, to simplify usage
352		*/
353		public final ForkJoinTask<V> fork() {
354		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 511 | Line 357 | public abstract class ForkJoinTask<V> im
357		}
358
359		/**
360	<	* Returns the result of the computation when it is ready.
361	<	* This method differs from {@code get} in that abnormal
362	<	* completion results in RuntimeExceptions or Errors, not
363	<	* ExecutionExceptions.
360	>	* Returns the result of the computation when it {@link #isDone is done}.
361	>	* This method differs from {@link #get()} in that
362	>	* abnormal completion results in {@code RuntimeException} or
363	>	* {@code Error}, not {@code ExecutionException}.
364		*
365		* @return the computed result
366		*/
367		public final V join() {
368	<	ForkJoinWorkerThread w = getWorker();
523	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
524	<	reportException(awaitDone(w, true));
525	<	return getRawResult();
368	>	return reportResult(doJoin());
369		}
370
371		/**
372		* Commences performing this task, awaits its completion if
373	<	* necessary, and return its result.
373	>	* necessary, and return its result, or throws an (unchecked)
374	>	* exception if the underlying computation did so.
375		*
532	–	* @throws Throwable (a RuntimeException, Error, or unchecked
533	–	* exception) if the underlying computation did so
376		* @return the computed result
377		*/
378		public final V invoke() {
379	<	if (status >= 0 && tryExec())
538	<	return getRawResult();
539	<	else
540	<	return join();
379	>	return reportResult(doInvoke());
380		}
381
382		/**
383		* Forks the given tasks, returning when {@code isDone} holds for
384	<	* each task or an exception is encountered. This method may be
385	<	* invoked only from within ForkJoinTask computations (as may be
386	<	* determined using method {@link #inForkJoinPool}). Attempts to
387	<	* invoke in other contexts result in exceptions or errors,
388	<	* possibly including ClassCastException.
384	>	* each task or an (unchecked) exception is encountered, in which
385	>	* case the exception is rethrown.  If either task encounters an
386	>	* exception, the other one may be, but is not guaranteed to be,
387	>	* cancelled.  If both tasks throw an exception, then this method
388	>	* throws one of them.  The individual status of each task may be
389	>	* checked using {@link #getException()} and related methods.
390	>	*
391	>	* <p>This method may be invoked only from within {@code
392	>	* ForkJoinTask} computations (as may be determined using method
393	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
394	>	* result in exceptions or errors, possibly including {@code
395	>	* ClassCastException}.
396		*
397		* @param t1 the first task
398		* @param t2 the second task
399		* @throws NullPointerException if any task is null
554	–	* @throws RuntimeException or Error if a task did so
400		*/
401	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
401	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
402		t2.fork();
403		t1.invoke();
404		t2.join();
#	Line 561 | Line 406 | public abstract class ForkJoinTask<V> im
406
407		/**
408		* Forks the given tasks, returning when {@code isDone} holds for
409	<	* each task or an exception is encountered. If any task
410	<	* encounters an exception, others may be, but are not guaranteed
411	<	* to be, cancelled.  This method may be invoked only from within
412	<	* ForkJoinTask computations (as may be determined using method
413	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
414	<	* result in exceptions or errors, possibly including
415	<	* ClassCastException.
416	<	*
417	<	* Overloadings of this method exist for the special cases
418	<	* of one to four arguments.
409	>	* each task or an (unchecked) exception is encountered, in which
410	>	* case the exception is rethrown. If any task encounters an
411	>	* exception, others may be, but are not guaranteed to be,
412	>	* cancelled.  If more than one task encounters an exception, then
413	>	* this method throws any one of these exceptions.  The individual
414	>	* status of each task may be checked using {@link #getException()}
415	>	* and related methods.
416	>	*
417	>	* <p>This method may be invoked only from within {@code
418	>	* ForkJoinTask} computations (as may be determined using method
419	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
420	>	* result in exceptions or errors, possibly including {@code
421	>	* ClassCastException}.
422		*
423		* @param tasks the tasks
424	<	* @throws NullPointerException if tasks or any element are null
577	<	* @throws RuntimeException or Error if any task did so
424	>	* @throws NullPointerException if any task is null
425		*/
426		public static void invokeAll(ForkJoinTask<?>... tasks) {
427		Throwable ex = null;
#	Line 587 | Line 434 | public abstract class ForkJoinTask<V> im
434		}
435		else if (i != 0)
436		t.fork();
437	<	else {
438	<	t.quietlyInvoke();
592	<	if (ex == null)
593	<	ex = t.getException();
594	<	}
437	>	else if (t.doInvoke() < NORMAL && ex == null)
438	>	ex = t.getException();
439		}
440		for (int i = 1; i <= last; ++i) {
441		ForkJoinTask<?> t = tasks[i];
442		if (t != null) {
443		if (ex != null)
444		t.cancel(false);
445	<	else {
446	<	t.quietlyJoin();
603	<	if (ex == null)
604	<	ex = t.getException();
605	<	}
445	>	else if (t.doJoin() < NORMAL && ex == null)
446	>	ex = t.getException();
447		}
448		}
449		if (ex != null)
450	<	rethrowException(ex);
450	>	UNSAFE.throwException(ex);
451		}
452
453		/**
454	<	* Forks all tasks in the collection, returning when {@code
455	<	* isDone} holds for each task or an exception is encountered. If
456	<	* any task encounters an exception, others may be, but are not
457	<	* guaranteed to be, cancelled.  This method may be invoked only
458	<	* from within ForkJoinTask computations (as may be determined
459	<	* using method {@link #inForkJoinPool}). Attempts to invoke in
460	<	* other contexts result in exceptions or errors, possibly
461	<	* including ClassCastException.
454	>	* Forks all tasks in the specified collection, returning when
455	>	* {@code isDone} holds for each task or an (unchecked) exception
456	>	* is encountered.  If any task encounters an exception, others
457	>	* may be, but are not guaranteed to be, cancelled.  If more than
458	>	* one task encounters an exception, then this method throws any
459	>	* one of these exceptions.  The individual status of each task
460	>	* may be checked using {@link #getException()} and related
461	>	* methods.  The behavior of this operation is undefined if the
462	>	* specified collection is modified while the operation is in
463	>	* progress.
464	>	*
465	>	* <p>This method may be invoked only from within {@code
466	>	* ForkJoinTask} computations (as may be determined using method
467	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
468	>	* result in exceptions or errors, possibly including {@code
469	>	* ClassCastException}.
470		*
471		* @param tasks the collection of tasks
472		* @return the tasks argument, to simplify usage
473		* @throws NullPointerException if tasks or any element are null
625	–	* @throws RuntimeException or Error if any task did so
474		*/
475		public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
476	<	if (!(tasks instanceof List<?>)) {
476	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
477		invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
478		return tasks;
479		}
#	Line 642 | Line 490 | public abstract class ForkJoinTask<V> im
490		}
491		else if (i != 0)
492		t.fork();
493	<	else {
494	<	t.quietlyInvoke();
647	<	if (ex == null)
648	<	ex = t.getException();
649	<	}
493	>	else if (t.doInvoke() < NORMAL && ex == null)
494	>	ex = t.getException();
495		}
496		for (int i = 1; i <= last; ++i) {
497		ForkJoinTask<?> t = ts.get(i);
498		if (t != null) {
499		if (ex != null)
500		t.cancel(false);
501	<	else {
502	<	t.quietlyJoin();
658	<	if (ex == null)
659	<	ex = t.getException();
660	<	}
501	>	else if (t.doJoin() < NORMAL && ex == null)
502	>	ex = t.getException();
503		}
504		}
505		if (ex != null)
506	<	rethrowException(ex);
506	>	UNSAFE.throwException(ex);
507		return tasks;
508		}
509
510		/**
511	<	* Returns {@code true} if the computation performed by this task
512	<	* has completed (or has been cancelled).
513	<	*
514	<	* @return {@code true} if this computation has completed
515	<	*/
516	<	public final boolean isDone() {
517	<	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.
511	>	* Attempts to cancel execution of this task. This attempt will
512	>	* fail if the task has already completed, has already been
513	>	* cancelled, or could not be cancelled for some other reason. If
514	>	* successful, and this task has not started when cancel is
515	>	* called, execution of this task is suppressed, {@link
516	>	* #isCancelled} will report true, and {@link #join} will result
517	>	* in a {@code CancellationException} being thrown.
518		*
519		* <p>This method may be overridden in subclasses, but if so, must
520		* still ensure that these minimal properties hold. In particular,
#	Line 706 | Line 526 | public abstract class ForkJoinTask<V> im
526		* invoke {@link #completeExceptionally}.
527		*
528		* @param mayInterruptIfRunning this value is ignored in the
529	<	* default implementation because tasks are not in general
529	>	* default implementation because tasks are not
530		* cancelled via interruption
531		*
532		* @return {@code true} if this task is now cancelled
533		*/
534		public boolean cancel(boolean mayInterruptIfRunning) {
535	<	setCompletion(CANCELLED);
536	<	return (status & COMPLETION_MASK) == CANCELLED;
535	>	return setCompletion(CANCELLED) == CANCELLED;
536	>	}
537	>
538	>	/**
539	>	* Cancels, ignoring any exceptions it throws. Used during worker
540	>	* and pool shutdown.
541	>	*/
542	>	final void cancelIgnoringExceptions() {
543	>	try {
544	>	cancel(false);
545	>	} catch (Throwable ignore) {
546	>	}
547	>	}
548	>
549	>	/**
550	>	* Cancels ignoring exceptions if worker is terminating
551	>	*/
552	>	final void cancelIfTerminating() {
553	>	Thread t = Thread.currentThread();
554	>	if ((t instanceof ForkJoinWorkerThread) &&
555	>	((ForkJoinWorkerThread) t).isTerminating()) {
556	>	try {
557	>	cancel(false);
558	>	} catch (Throwable ignore) {
559	>	}
560	>	}
561	>	}
562	>
563	>	public final boolean isDone() {
564	>	return status < 0;
565	>	}
566	>
567	>	public final boolean isCancelled() {
568	>	return status == CANCELLED;
569		}
570
571		/**
#	Line 722 | Line 574 | public abstract class ForkJoinTask<V> im
574		* @return {@code true} if this task threw an exception or was cancelled
575		*/
576		public final boolean isCompletedAbnormally() {
577	<	return (status & COMPLETION_MASK) < NORMAL;
577	>	return status < NORMAL;
578	>	}
579	>
580	>	/**
581	>	* Returns {@code true} if this task completed without throwing an
582	>	* exception and was not cancelled.
583	>	*
584	>	* @return {@code true} if this task completed without throwing an
585	>	* exception and was not cancelled
586	>	*/
587	>	public final boolean isCompletedNormally() {
588	>	return status == NORMAL;
589		}
590
591		/**
#	Line 733 | Line 596 | public abstract class ForkJoinTask<V> im
596		* @return the exception, or {@code null} if none
597		*/
598		public final Throwable getException() {
599	<	int s = status & COMPLETION_MASK;
600	<	if (s >= NORMAL)
601	<	return null;
602	<	if (s == CANCELLED)
740	<	return new CancellationException();
741	<	return exceptionMap.get(this);
599	>	int s = status;
600	>	return ((s >= NORMAL)    ? null :
601	>	(s == CANCELLED) ? new CancellationException() :
602	>	exceptionMap.get(this));
603		}
604
605		/**
#	Line 751 | Line 612 | public abstract class ForkJoinTask<V> im
612		* overridable, but overridden versions must invoke {@code super}
613		* implementation to maintain guarantees.
614		*
615	<	* @param ex the exception to throw. If this exception is
616	<	* not a RuntimeException or Error, the actual exception thrown
617	<	* will be a RuntimeException with cause ex.
615	>	* @param ex the exception to throw. If this exception is not a
616	>	* {@code RuntimeException} or {@code Error}, the actual exception
617	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
618		*/
619		public void completeExceptionally(Throwable ex) {
620	<	setDoneExceptionally((ex instanceof RuntimeException) ||
621	<	(ex instanceof Error) ? ex :
622	<	new RuntimeException(ex));
620	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
621	>	(ex instanceof Error) ? ex :
622	>	new RuntimeException(ex));
623		}
624
625		/**
#	Line 777 | Line 638 | public abstract class ForkJoinTask<V> im
638		try {
639		setRawResult(value);
640		} catch (Throwable rex) {
641	<	setDoneExceptionally(rex);
641	>	setExceptionalCompletion(rex);
642		return;
643		}
644	<	setNormalCompletion();
644	>	setCompletion(NORMAL);
645		}
646
647		public final V get() throws InterruptedException, ExecutionException {
648	<	ForkJoinWorkerThread w = getWorker();
649	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
650	<	awaitDone(w, true);
651	<	return reportFutureResult();
648	>	int s = doJoin();
649	>	if (Thread.interrupted())
650	>	throw new InterruptedException();
651	>	if (s < NORMAL) {
652	>	Throwable ex;
653	>	if (s == CANCELLED)
654	>	throw new CancellationException();
655	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
656	>	throw new ExecutionException(ex);
657	>	}
658	>	return getRawResult();
659		}
660
661		public final V get(long timeout, TimeUnit unit)
662		throws InterruptedException, ExecutionException, TimeoutException {
663	<	long nanos = unit.toNanos(timeout);
664	<	ForkJoinWorkerThread w = getWorker();
665	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
666	<	awaitDone(w, nanos);
667	<	return reportTimedFutureResult();
668	<	}
669	<
670	<	/**
671	<	* Possibly executes other tasks until this task is ready, then
672	<	* returns the result of the computation.  This method may be more
673	<	* efficient than {@code join}, but is only applicable when
674	<	* there are no potential dependencies between continuation of the
675	<	* current task and that of any other task that might be executed
676	<	* while helping. (This usually holds for pure divide-and-conquer
677	<	* tasks). This method may be invoked only from within
678	<	* ForkJoinTask computations (as may be determined using method
679	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
680	<	* result in exceptions or errors, possibly including
681	<	* ClassCastException.
682	<	*
683	<	* @return the computed result
684	<	*/
685	<	public final V helpJoin() {
686	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
687	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
688	<	reportException(busyJoin(w));
689	<	return getRawResult();
690	<	}
691	<
692	<	/**
693	<	* Possibly executes other tasks until this task is ready.  This
694	<	* method may be invoked only from within ForkJoinTask
695	<	* computations (as may be determined using method {@link
696	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
697	<	* in exceptions or errors, possibly including ClassCastException.
698	<	*/
699	<	public final void quietlyHelpJoin() {
700	<	if (status >= 0) {
701	<	ForkJoinWorkerThread w =
702	<	(ForkJoinWorkerThread) Thread.currentThread();
703	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
704	<	busyJoin(w);
663	>	Thread t = Thread.currentThread();
664	>	ForkJoinPool pool;
665	>	if (t instanceof ForkJoinWorkerThread) {
666	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
667	>	if (status >= 0 && w.unpushTask(this))
668	>	tryExec();
669	>	pool = w.pool;
670	>	}
671	>	else
672	>	pool = null;
673	>	/*
674	>	* Timed wait loop intermixes cases for fj (pool != null) and
675	>	* non FJ threads. For FJ, decrement pool count but don't try
676	>	* for replacement; increment count on completion. For non-FJ,
677	>	* deal with interrupts. This is messy, but a little less so
678	>	* than is splitting the FJ and nonFJ cases.
679	>	*/
680	>	boolean interrupted = false;
681	>	boolean dec = false; // true if pool count decremented
682	>	for (;;) {
683	>	if (Thread.interrupted() && pool == null) {
684	>	interrupted = true;
685	>	break;
686	>	}
687	>	int s = status;
688	>	if (s < 0)
689	>	break;
690	>	if (UNSAFE.compareAndSwapInt(this, statusOffset,
691	>	s, s | SIGNAL)) {
692	>	long startTime = System.nanoTime();
693	>	long nanos = unit.toNanos(timeout);
694	>	long nt; // wait time
695	>	while (status >= 0 &&
696	>	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
697	>	if (pool != null && !dec)
698	>	dec = pool.tryDecrementRunningCount();
699	>	else {
700	>	long ms = nt / 1000000;
701	>	int ns = (int) (nt % 1000000);
702	>	try {
703	>	synchronized(this) {
704	>	if (status >= 0)
705	>	wait(ms, ns);
706	>	}
707	>	} catch (InterruptedException ie) {
708	>	if (pool != null)
709	>	cancelIfTerminating();
710	>	else {
711	>	interrupted = true;
712	>	break;
713	>	}
714	>	}
715	>	}
716	>	}
717	>	break;
718	>	}
719	>	}
720	>	if (pool != null && dec)
721	>	pool.incrementRunningCount();
722	>	if (interrupted)
723	>	throw new InterruptedException();
724	>	int es = status;
725	>	if (es != NORMAL) {
726	>	Throwable ex;
727	>	if (es == CANCELLED)
728	>	throw new CancellationException();
729	>	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
730	>	throw new ExecutionException(ex);
731	>	throw new TimeoutException();
732		}
733	+	return getRawResult();
734		}
735
736		/**
#	Line 844 | Line 740 | public abstract class ForkJoinTask<V> im
740		* known to have aborted.
741		*/
742		public final void quietlyJoin() {
743	<	if (status >= 0) {
848	<	ForkJoinWorkerThread w = getWorker();
849	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
850	<	awaitDone(w, true);
851	<	}
743	>	doJoin();
744		}
745
746		/**
#	Line 859 | Line 751 | public abstract class ForkJoinTask<V> im
751		* known to have aborted.
752		*/
753		public final void quietlyInvoke() {
754	<	if (status >= 0 && !tryQuietlyInvoke())
863	<	quietlyJoin();
754	>	doInvoke();
755		}
756
757		/**
758		* Possibly executes tasks until the pool hosting the current task
759	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
760	<	* designs in which many tasks are forked, but none are explicitly
761	<	* joined, instead executing them until all are processed.  This
762	<	* method may be invoked only from within ForkJoinTask
763	<	* computations (as may be determined using method {@link
764	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
765	<	* in exceptions or errors, possibly including ClassCastException.
759	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
760	>	* be of use in designs in which many tasks are forked, but none
761	>	* are explicitly joined, instead executing them until all are
762	>	* processed.
763	>	*
764	>	* <p>This method may be invoked only from within {@code
765	>	* ForkJoinTask} computations (as may be determined using method
766	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
767	>	* result in exceptions or errors, possibly including {@code
768	>	* ClassCastException}.
769		*/
770		public static void helpQuiesce() {
771		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 884 | Line 778 | public abstract class ForkJoinTask<V> im
778		* this task, but only if reuse occurs when this task has either
779		* never been forked, or has been forked, then completed and all
780		* outstanding joins of this task have also completed. Effects
781	<	* under any other usage conditions are not guaranteed, and are
782	<	* discouraged. This method may be useful when executing
781	>	* under any other usage conditions are not guaranteed.
782	>	* This method may be useful when executing
783		* pre-constructed trees of subtasks in loops.
784		*/
785		public void reinitialize() {
786	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
786	>	if (status == EXCEPTIONAL)
787		exceptionMap.remove(this);
788		status = 0;
789		}
#	Line 924 | Line 818 | public abstract class ForkJoinTask<V> im
818		* by the current thread, and has not commenced executing in
819		* another thread.  This method may be useful when arranging
820		* alternative local processing of tasks that could have been, but
821	<	* were not, stolen. This method may be invoked only from within
822	<	* ForkJoinTask computations (as may be determined using method
823	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
824	<	* result in exceptions or errors, possibly including
825	<	* ClassCastException.
821	>	* were not, stolen.
822	>	*
823	>	* <p>This method may be invoked only from within {@code
824	>	* ForkJoinTask} computations (as may be determined using method
825	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
826	>	* result in exceptions or errors, possibly including {@code
827	>	* ClassCastException}.
828		*
829		* @return {@code true} if unforked
830		*/
#	Line 941 | Line 837 | public abstract class ForkJoinTask<V> im
837		* Returns an estimate of the number of tasks that have been
838		* forked by the current worker thread but not yet executed. This
839		* value may be useful for heuristic decisions about whether to
840	<	* fork other tasks.  This method may be invoked only from within
841	<	* ForkJoinTask computations (as may be determined using method
842	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
843	<	* result in exceptions or errors, possibly including
844	<	* ClassCastException.
840	>	* fork other tasks.
841	>	*
842	>	* <p>This method may be invoked only from within {@code
843	>	* ForkJoinTask} computations (as may be determined using method
844	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
845	>	* result in exceptions or errors, possibly including {@code
846	>	* ClassCastException}.
847	>	*
848		* @return the number of tasks
849		*/
850		public static int getQueuedTaskCount() {
#	Line 961 | Line 860 | public abstract class ForkJoinTask<V> im
860		* usages of ForkJoinTasks, at steady state, each worker should
861		* aim to maintain a small constant surplus (for example, 3) of
862		* tasks, and to process computations locally if this threshold is
863	<	* exceeded.  This method may be invoked only from within
864	<	* ForkJoinTask computations (as may be determined using method
865	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
866	<	* result in exceptions or errors, possibly including
867	<	* ClassCastException.  *
863	>	* exceeded.
864	>	*
865	>	* <p>This method may be invoked only from within {@code
866	>	* ForkJoinTask} computations (as may be determined using method
867	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
868	>	* result in exceptions or errors, possibly including {@code
869	>	* ClassCastException}.
870	>	*
871		* @return the surplus number of tasks, which may be negative
872		*/
873		public static int getSurplusQueuedTaskCount() {
#	Line 1001 | Line 903 | public abstract class ForkJoinTask<V> im
903		* called otherwise. The return value controls whether this task
904		* is considered to be done normally. It may return false in
905		* asynchronous actions that require explicit invocations of
906	<	* {@link #complete} to become joinable. It may throw exceptions
907	<	* to indicate abnormal exit.
906	>	* {@link #complete} to become joinable. It may also throw an
907	>	* (unchecked) exception to indicate abnormal exit.
908		*
909		* @return {@code true} if completed normally
1008	–	* @throws Error or RuntimeException if encountered during computation
910		*/
911		protected abstract boolean exec();
912
#	Line 1017 | Line 918 | public abstract class ForkJoinTask<V> im
918		* null even if a task exists but cannot be accessed without
919		* contention with other threads.  This method is designed
920		* primarily to support extensions, and is unlikely to be useful
921	<	* otherwise.  This method may be invoked only from within
922	<	* ForkJoinTask computations (as may be determined using method
923	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
924	<	* result in exceptions or errors, possibly including
925	<	* ClassCastException.
921	>	* otherwise.
922	>	*
923	>	* <p>This method may be invoked only from within {@code
924	>	* ForkJoinTask} computations (as may be determined using method
925	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
926	>	* result in exceptions or errors, possibly including {@code
927	>	* ClassCastException}.
928		*
929		* @return the next task, or {@code null} if none are available
930		*/
#	Line 1034 | Line 937 | public abstract class ForkJoinTask<V> im
937		* Unschedules and returns, without executing, the next task
938		* queued by the current thread but not yet executed.  This method
939		* is designed primarily to support extensions, and is unlikely to
940	<	* be useful otherwise.  This method may be invoked only from
941	<	* within ForkJoinTask computations (as may be determined using
942	<	* method {@link #inForkJoinPool}). Attempts to invoke in other
943	<	* contexts result in exceptions or errors, possibly including
944	<	* ClassCastException.
940	>	* be useful otherwise.
941	>	*
942	>	* <p>This method may be invoked only from within {@code
943	>	* ForkJoinTask} computations (as may be determined using method
944	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
945	>	* result in exceptions or errors, possibly including {@code
946	>	* ClassCastException}.
947		*
948		* @return the next task, or {@code null} if none are available
949		*/
#	Line 1055 | Line 960 | public abstract class ForkJoinTask<V> im
960		* {@code null} result does not necessarily imply quiescence
961		* of the pool this task is operating in.  This method is designed
962		* primarily to support extensions, and is unlikely to be useful
963	<	* otherwise.  This method may be invoked only from within
964	<	* ForkJoinTask computations (as may be determined using method
965	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
966	<	* result in exceptions or errors, possibly including
967	<	* ClassCastException.
963	>	* otherwise.
964	>	*
965	>	* <p>This method may be invoked only from within {@code
966	>	* ForkJoinTask} computations (as may be determined using method
967	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
968	>	* result in exceptions or errors, possibly including {@code
969	>	* ClassCastException}.
970		*
971		* @return a task, or {@code null} if none are available
972		*/
#	Line 1124 | Line 1031 | public abstract class ForkJoinTask<V> im
1031		}
1032
1033		/**
1034	<	* Returns a new ForkJoinTask that performs the {@code run}
1035	<	* method of the given Runnable as its action, and returns a null
1036	<	* result upon {@code join}.
1034	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1035	>	* method of the given {@code Runnable} as its action, and returns
1036	>	* a null result upon {@link #join}.
1037		*
1038		* @param runnable the runnable action
1039		* @return the task
#	Line 1136 | Line 1043 | public abstract class ForkJoinTask<V> im
1043		}
1044
1045		/**
1046	<	* Returns a new ForkJoinTask that performs the {@code run}
1047	<	* method of the given Runnable as its action, and returns the
1048	<	* given result upon {@code join}.
1046	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1047	>	* method of the given {@code Runnable} as its action, and returns
1048	>	* the given result upon {@link #join}.
1049		*
1050		* @param runnable the runnable action
1051		* @param result the result upon completion
#	Line 1149 | Line 1056 | public abstract class ForkJoinTask<V> im
1056		}
1057
1058		/**
1059	<	* Returns a new ForkJoinTask that performs the {@code call}
1060	<	* method of the given Callable as its action, and returns its
1061	<	* result upon {@code join}, translating any checked
1062	<	* exceptions encountered into {@code RuntimeException}.
1059	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1060	>	* method of the given {@code Callable} as its action, and returns
1061	>	* its result upon {@link #join}, translating any checked exceptions
1062	>	* encountered into {@code RuntimeException}.
1063		*
1064		* @param callable the callable action
1065		* @return the task
#	Line 1166 | Line 1073 | public abstract class ForkJoinTask<V> im
1073		private static final long serialVersionUID = -7721805057305804111L;
1074
1075		/**
1076	<	* Save the state to a stream.
1076	>	* Saves the state to a stream.
1077		*
1078		* @serialData the current run status and the exception thrown
1079		* during execution, or {@code null} if none
#	Line 1179 | Line 1086 | public abstract class ForkJoinTask<V> im
1086		}
1087
1088		/**
1089	<	* Reconstitute the instance from a stream.
1089	>	* Reconstitutes the instance from a stream.
1090		*
1091		* @param s the stream
1092		*/
1093		private void readObject(java.io.ObjectInputStream s)
1094		throws java.io.IOException, ClassNotFoundException {
1095		s.defaultReadObject();
1189	–	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1190	–	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1096		Object ex = s.readObject();
1097		if (ex != null)
1098	<	setDoneExceptionally((Throwable) ex);
1098	>	setExceptionalCompletion((Throwable) ex);
1099		}
1100
1101		// Unsafe mechanics

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