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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 1.49 by dl, Wed Jul 7 19:52:31 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	+	* 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		* Run control status bits packed into a single int to minimize
152		* footprint and to ensure atomicity (via CAS).  Status is
153		* initially zero, and takes on nonnegative values until
154	<	* completed, upon which status holds COMPLETED. CANCELLED, or
155	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
156	<	* blocking waits by other threads have SIGNAL_MASK bits set --
157	<	* bit 15 for external (nonFJ) waits, and the rest a count of
158	<	* waiting FJ threads.  (This representation relies on
159	<	* ForkJoinPool max thread limits). Completion of a stolen task
160	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
161	<	* though suboptimal for some purposes, we use basic builtin
162	<	* wait/notify to take advantage of "monitor inflation" in JVMs
163	<	* that we would otherwise need to emulate to avoid adding further
144	<	* per-task bookkeeping overhead. Note that bits 16-28 are
145	<	* currently unused. Also value 0x80000000 is available as spare
146	<	* completion value.
154	>	* completed, upon which status holds value COMPLETED. CANCELLED,
155	>	* or EXCEPTIONAL. Tasks undergoing blocking waits by other
156	>	* threads have the SIGNAL bit set.  Completion of a stolen task
157	>	* with SIGNAL set awakens any waiters via notifyAll. Even though
158	>	* suboptimal for some purposes, we use basic builtin wait/notify
159	>	* to take advantage of "monitor inflation" in JVMs that we would
160	>	* otherwise need to emulate to avoid adding further per-task
161	>	* bookkeeping overhead.  We want these monitors to be "fat",
162	>	* i.e., not use biasing or thin-lock techniques, so use some odd
163	>	* coding idioms that tend to avoid them.
164		*/
165		volatile int status; // accessed directly by pool and workers
166
167	<	static final int COMPLETION_MASK      = 0xe0000000;
168	<	static final int NORMAL               = 0xe0000000; // == mask
169	<	static final int CANCELLED            = 0xc0000000;
170	<	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
167	>	private static final int NORMAL      = -1;
168	>	private static final int CANCELLED   = -2;
169	>	private static final int EXCEPTIONAL = -3;
170	>	private static final int SIGNAL      =  1;
171
172		/**
173		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 167 | Line 181 | public abstract class ForkJoinTask<V> im
181		Collections.synchronizedMap
182		(new WeakHashMap<ForkJoinTask<?>, Throwable>());
183
184	<	// within-package utilities
184	>	// Maintaining completion status
185
186		/**
187	<	* Gets current worker thread, or null if not a worker thread.
188	<	*/
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.
187	>	* Marks completion and wakes up threads waiting to join this task,
188	>	* also clearing signal request bits.
189		*
190		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
191	+	* @return status on exit
192		*/
193	<	final void setCompletion(int completion) {
201	<	ForkJoinPool pool = getPool();
202	<	if (pool != null) {
203	<	int s; // Clear signal bits while setting completion status
204	<	do {} while ((s = status) >= 0 && !casStatus(s, completion));
205	<
206	<	if ((s & SIGNAL_MASK) != 0) {
207	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
208	<	pool.updateRunningCount(s);
209	<	synchronized (this) { notifyAll(); }
210	<	}
211	<	}
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) {
193	>	private int setCompletion(int completion) {
194		int s;
195	<	do {} while ((s = status) >= 0 &&
196	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
197	<	synchronized (this) { notifyAll(); }
198	<	}
199	<
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);
235	<	}
236	<
237	<	// internal waiting and notification
238	<
239	<	/**
240	<	* Performs the actual monitor wait for awaitDone.
241	<	*/
242	<	private void doAwaitDone() {
243	<	// Minimize lock bias and in/de-flation effects by maximizing
244	<	// 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	<	}
251	<	}
252	<
253	<	/**
254	<	* Performs the actual timed monitor wait for awaitDone.
255	<	*/
256	<	private void doAwaitDone(long startTime, long nanos) {
257	<	synchronized (this) {
258	<	try {
259	<	while (status >= 0) {
260	<	long nt = nanos - (System.nanoTime() - startTime);
261	<	if (nt <= 0)
262	<	break;
263	<	wait(nt / 1000000, (int) (nt % 1000000));
264	<	}
265	<	} catch (InterruptedException ie) {
266	<	onInterruptedWait();
195	>	while ((s = status) >= 0) {
196	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
197	>	if (s == SIGNAL)
198	>	synchronized (this) { notifyAll(); }
199	>	return completion;
200		}
201		}
202	+	return s;
203		}
204
271	–	// Awaiting completion
272	–
205		/**
206	<	* Sets status to indicate there is joiner, then waits for join,
207	<	* surrounded with pool notifications.
276	<	*
277	<	* @return status upon exit
206	>	* Record exception and set exceptional completion
207	>	* @return status on exit
208		*/
209	<	private int awaitDone(ForkJoinWorkerThread w,
210	<	boolean maintainParallelism) {
211	<	ForkJoinPool pool = (w == null) ? null : w.pool;
282	<	int s;
283	<	while ((s = status) >= 0) {
284	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
285	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
286	<	doAwaitDone();
287	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
288	<	adjustPoolCountsOnUnblock(pool);
289	<	break;
290	<	}
291	<	}
292	<	return s;
209	>	private int setExceptionalCompletion(Throwable rex) {
210	>	exceptionMap.put(this, rex);
211	>	return setCompletion(EXCEPTIONAL);
212		}
213
214		/**
215	<	* Timed version of awaitDone
297	<	*
298	<	* @return status upon exit
215	>	* Blocks a worker thread until completion. Called only by pool.
216		*/
217	<	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
301	<	ForkJoinPool pool = (w == null) ? null : w.pool;
217	>	final int internalAwaitDone() {
218		int s;
219		while ((s = status) >= 0) {
220	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
221	<	long startTime = System.nanoTime();
222	<	if (pool == null || !pool.preJoin(this, false))
223	<	doAwaitDone(startTime, nanos);
224	<	if ((s = status) >= 0) {
225	<	adjustPoolCountsOnCancelledWait(pool);
226	<	s = status;
220	>	synchronized(this) {
221	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
222	>	do {
223	>	try {
224	>	wait();
225	>	} catch (InterruptedException ie) {
226	>	cancelIfTerminating();
227	>	}
228	>	} while ((s = status) >= 0);
229	>	break;
230		}
312	–	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
313	–	adjustPoolCountsOnUnblock(pool);
314	–	break;
231		}
232		}
233		return s;
234		}
235
236		/**
237	<	* Notifies pool that thread is unblocked. Called by signalled
238	<	* threads when woken by non-FJ threads (which is atypical).
237	>	* Blocks a non-worker-thread until completion.
238	>	* @return status on exit
239		*/
240	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
240	>	private int externalAwaitDone() {
241		int s;
242	<	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
243	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
244	<	pool.updateRunningCount(s);
245	<	}
246	<
247	<	/**
248	<	* Notifies pool to adjust counts on cancelled or timed out wait.
249	<	*/
250	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
251	<	if (pool != null) {
252	<	int s;
253	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
254	<	if (casStatus(s, s - 1)) {
339	<	pool.updateRunningCount(1);
242	>	while ((s = status) >= 0) {
243	>	synchronized(this) {
244	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
245	>	boolean interrupted = false;
246	>	do {
247	>	try {
248	>	wait();
249	>	} catch (InterruptedException ie) {
250	>	interrupted = true;
251	>	}
252	>	} while ((s = status) >= 0);
253	>	if (interrupted)
254	>	Thread.currentThread().interrupt();
255		break;
256		}
257		}
258		}
259	+	return s;
260		}
261
262		/**
263	<	* Handles interruptions during waits.
264	<	*/
265	<	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.
263	>	* Unless done, calls exec and records status if completed, but
264	>	* doesn't wait for completion otherwise. Primary execution method
265	>	* for ForkJoinWorkerThread.
266		*/
267	<	private V reportFutureResult()
268	<	throws ExecutionException, InterruptedException {
269	<	int s = status & COMPLETION_MASK;
270	<	if (s < NORMAL) {
271	<	Throwable ex;
272	<	if (s == CANCELLED)
273	<	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();
267	>	final void tryExec() {
268	>	try {
269	>	if (status < 0 || !exec())
270	>	return;
271	>	} catch (Throwable rex) {
272	>	setExceptionalCompletion(rex);
273	>	return;
274		}
275	<	return getRawResult();
275	>	setCompletion(NORMAL); // must be outside try block
276		}
277
278		/**
279	<	* Returns result or throws exception using j.u.c.Future conventions
280	<	* with timeouts.
279	>	* If not done and this task is next in worker queue, runs it,
280	>	* else waits for it.
281	>	* @return status on exit
282		*/
283	<	private V reportTimedFutureResult()
284	<	throws InterruptedException, ExecutionException, TimeoutException {
285	<	Throwable ex;
286	<	int s = status & COMPLETION_MASK;
287	<	if (s == NORMAL)
288	<	return getRawResult();
289	<	if (s == CANCELLED)
290	<	throw new CancellationException();
291	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
292	<	throw new ExecutionException(ex);
293	<	if (Thread.interrupted())
294	<	throw new InterruptedException();
295	<	throw new TimeoutException();
296	<	}
297	<
298	<	// internal execution methods
299	<
300	<	/**
301	<	* 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
283	>	private int doJoin() {
284	>	int stat;
285	>	if ((stat = status) < 0)
286	>	return stat;
287	>	Thread t = Thread.currentThread();
288	>	ForkJoinWorkerThread w;
289	>	if (t instanceof ForkJoinWorkerThread) {
290	>	if ((w = (ForkJoinWorkerThread) t).unpushTask(this)) {
291	>	boolean completed;
292	>	try {
293	>	completed = exec();
294	>	} catch (Throwable rex) {
295	>	return setExceptionalCompletion(rex);
296	>	}
297	>	if (completed)
298	>	return setCompletion(NORMAL);
299	>	}
300	>	w.joinTask(this);
301	>	return status;
302		}
303	<	setNormalCompletion();
435	<	return true;
303	>	return externalAwaitDone();
304		}
305
306		/**
307	<	* Main execution method used by worker threads. Invokes
308	<	* base computation unless already complete.
307	>	* Unless done, calls exec and records status if completed, or
308	>	* waits for completion otherwise.
309	>	* @return status on exit
310		*/
311	<	final void quietlyExec() {
312	<	if (status >= 0) {
311	>	private int doInvoke() {
312	>	int stat;
313	>	if ((stat = status) >= 0) {
314	>	boolean completed;
315		try {
316	<	if (!exec())
446	<	return;
316	>	completed = exec();
317		} catch (Throwable rex) {
318	<	setDoneExceptionally(rex);
449	<	return;
318	>	return setExceptionalCompletion(rex);
319		}
320	<	setNormalCompletion();
321	<	}
322	<	}
323	<
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;
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) {
320	>	if (completed)
321	>	stat = setCompletion(NORMAL);
322	>	else
323	>	stat = doJoin();
324		}
325	+	return stat;
326		}
327
328		/**
329	<	* Main implementation of helpJoin
329	>	* Returns result or throws exception associated with given status.
330	>	* @param s the status
331		*/
332	<	private int busyJoin(ForkJoinWorkerThread w) {
333	<	int s;
334	<	ForkJoinTask<?> t;
335	<	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
336	<	t.quietlyExec();
491	<	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
332	>	private V reportResult(int s) {
333	>	Throwable ex;
334	>	if (s < NORMAL && (ex = getException()) != null)
335	>	UNSAFE.throwException(ex);
336	>	return getRawResult();
337		}
338
339		// public methods
#	Line 496 | Line 341 | public abstract class ForkJoinTask<V> im
341		/**
342		* Arranges to asynchronously execute this task.  While it is not
343		* necessarily enforced, it is a usage error to fork a task more
344	<	* than once unless it has completed and been reinitialized.  This
345	<	* method may be invoked only from within ForkJoinTask
346	<	* computations (as may be determined using method {@link
347	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
348	<	* in exceptions or errors, possibly including ClassCastException.
344	>	* than once unless it has completed and been reinitialized.
345	>	* Subsequent modifications to the state of this task or any data
346	>	* it operates on are not necessarily consistently observable by
347	>	* any thread other than the one executing it unless preceded by a
348	>	* call to {@link #join} or related methods, or a call to {@link
349	>	* #isDone} returning {@code true}.
350	>	*
351	>	* <p>This method may be invoked only from within {@code
352	>	* ForkJoinTask} computations (as may be determined using method
353	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
354	>	* result in exceptions or errors, possibly including {@code
355	>	* ClassCastException}.
356		*
357	<	* @return {@code this}, to simplify usage.
357	>	* @return {@code this}, to simplify usage
358		*/
359		public final ForkJoinTask<V> fork() {
360		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 511 | Line 363 | public abstract class ForkJoinTask<V> im
363		}
364
365		/**
366	<	* Returns the result of the computation when it is ready.
367	<	* This method differs from {@code get} in that abnormal
368	<	* completion results in RuntimeExceptions or Errors, not
369	<	* ExecutionExceptions.
366	>	* Returns the result of the computation when it {@link #isDone is done}.
367	>	* This method differs from {@link #get()} in that
368	>	* abnormal completion results in {@code RuntimeException} or
369	>	* {@code Error}, not {@code ExecutionException}.
370		*
371		* @return the computed result
372		*/
373		public final V join() {
374	<	ForkJoinWorkerThread w = getWorker();
523	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
524	<	reportException(awaitDone(w, true));
525	<	return getRawResult();
374	>	return reportResult(doJoin());
375		}
376
377		/**
378		* Commences performing this task, awaits its completion if
379	<	* necessary, and return its result.
379	>	* necessary, and return its result, or throws an (unchecked)
380	>	* exception if the underlying computation did so.
381		*
532	–	* @throws Throwable (a RuntimeException, Error, or unchecked
533	–	* exception) if the underlying computation did so
382		* @return the computed result
383		*/
384		public final V invoke() {
385	<	if (status >= 0 && tryExec())
538	<	return getRawResult();
539	<	else
540	<	return join();
385	>	return reportResult(doInvoke());
386		}
387
388		/**
389		* Forks the given tasks, returning when {@code isDone} holds for
390	<	* each task or an exception is encountered. This method may be
391	<	* invoked only from within ForkJoinTask computations (as may be
392	<	* determined using method {@link #inForkJoinPool}). Attempts to
393	<	* invoke in other contexts result in exceptions or errors,
394	<	* possibly including ClassCastException.
390	>	* each task or an (unchecked) exception is encountered, in which
391	>	* case the exception is rethrown.  If either task encounters an
392	>	* exception, the other one may be, but is not guaranteed to be,
393	>	* cancelled.  If both tasks throw an exception, then this method
394	>	* throws one of them.  The individual status of each task may be
395	>	* checked using {@link #getException()} and related methods.
396	>	*
397	>	* <p>This method may be invoked only from within {@code
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 {@code
401	>	* ClassCastException}.
402		*
403		* @param t1 the first task
404		* @param t2 the second task
405		* @throws NullPointerException if any task is null
554	–	* @throws RuntimeException or Error if a task did so
406		*/
407	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
407	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
408		t2.fork();
409		t1.invoke();
410		t2.join();
#	Line 561 | Line 412 | public abstract class ForkJoinTask<V> im
412
413		/**
414		* Forks the given tasks, returning when {@code isDone} holds for
415	<	* each task or an exception is encountered. If any task
416	<	* encounters an exception, others may be, but are not guaranteed
417	<	* to be, cancelled.  This method may be invoked only from within
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
421	<	* ClassCastException.
422	<	*
423	<	* Overloadings of this method exist for the special cases
424	<	* of one to four arguments.
415	>	* each task or an (unchecked) exception is encountered, in which
416	>	* case the exception is rethrown. If any task encounters an
417	>	* exception, others may be, but are not guaranteed to be,
418	>	* cancelled.  If more than one task encounters an exception, then
419	>	* this method throws any one of these exceptions.  The individual
420	>	* status of each task may be checked using {@link #getException()}
421	>	* and related methods.
422	>	*
423	>	* <p>This method may be invoked only from within {@code
424	>	* ForkJoinTask} computations (as may be determined using method
425	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
426	>	* result in exceptions or errors, possibly including {@code
427	>	* ClassCastException}.
428		*
429		* @param tasks the tasks
430	<	* @throws NullPointerException if tasks or any element are null
577	<	* @throws RuntimeException or Error if any task did so
430	>	* @throws NullPointerException if any task is null
431		*/
432		public static void invokeAll(ForkJoinTask<?>... tasks) {
433		Throwable ex = null;
#	Line 587 | Line 440 | public abstract class ForkJoinTask<V> im
440		}
441		else if (i != 0)
442		t.fork();
443	<	else {
444	<	t.quietlyInvoke();
592	<	if (ex == null)
593	<	ex = t.getException();
594	<	}
443	>	else if (t.doInvoke() < NORMAL && ex == null)
444	>	ex = t.getException();
445		}
446		for (int i = 1; i <= last; ++i) {
447		ForkJoinTask<?> t = tasks[i];
448		if (t != null) {
449		if (ex != null)
450		t.cancel(false);
451	<	else {
452	<	t.quietlyJoin();
603	<	if (ex == null)
604	<	ex = t.getException();
605	<	}
451	>	else if (t.doJoin() < NORMAL && ex == null)
452	>	ex = t.getException();
453		}
454		}
455		if (ex != null)
456	<	rethrowException(ex);
456	>	UNSAFE.throwException(ex);
457		}
458
459		/**
460	<	* Forks all tasks in the collection, returning when {@code
461	<	* isDone} holds for each task or an exception is encountered. If
462	<	* any task encounters an exception, others may be, but are not
463	<	* guaranteed to be, cancelled.  This method may be invoked only
464	<	* from within ForkJoinTask computations (as may be determined
465	<	* using method {@link #inForkJoinPool}). Attempts to invoke in
466	<	* other contexts result in exceptions or errors, possibly
467	<	* including ClassCastException.
460	>	* Forks all tasks in the specified collection, returning when
461	>	* {@code isDone} holds for each task or an (unchecked) exception
462	>	* is encountered.  If any task encounters an exception, others
463	>	* may be, but are not guaranteed to be, cancelled.  If more than
464	>	* one task encounters an exception, then this method throws any
465	>	* one of these exceptions.  The individual status of each task
466	>	* may be checked using {@link #getException()} and related
467	>	* methods.  The behavior of this operation is undefined if the
468	>	* specified collection is modified while the operation is in
469	>	* progress.
470	>	*
471	>	* <p>This method may be invoked only from within {@code
472	>	* ForkJoinTask} computations (as may be determined using method
473	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
474	>	* result in exceptions or errors, possibly including {@code
475	>	* ClassCastException}.
476		*
477		* @param tasks the collection of tasks
478		* @return the tasks argument, to simplify usage
479		* @throws NullPointerException if tasks or any element are null
625	–	* @throws RuntimeException or Error if any task did so
480		*/
481		public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
482	<	if (!(tasks instanceof List<?>)) {
482	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
483		invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
484		return tasks;
485		}
#	Line 642 | Line 496 | public abstract class ForkJoinTask<V> im
496		}
497		else if (i != 0)
498		t.fork();
499	<	else {
500	<	t.quietlyInvoke();
647	<	if (ex == null)
648	<	ex = t.getException();
649	<	}
499	>	else if (t.doInvoke() < NORMAL && ex == null)
500	>	ex = t.getException();
501		}
502		for (int i = 1; i <= last; ++i) {
503		ForkJoinTask<?> t = ts.get(i);
504		if (t != null) {
505		if (ex != null)
506		t.cancel(false);
507	<	else {
508	<	t.quietlyJoin();
658	<	if (ex == null)
659	<	ex = t.getException();
660	<	}
507	>	else if (t.doJoin() < NORMAL && ex == null)
508	>	ex = t.getException();
509		}
510		}
511		if (ex != null)
512	<	rethrowException(ex);
512	>	UNSAFE.throwException(ex);
513		return tasks;
514		}
515
516		/**
517	<	* Returns {@code true} if the computation performed by this task
518	<	* has completed (or has been cancelled).
519	<	*
520	<	* @return {@code true} if this computation has completed
521	<	*/
522	<	public final boolean isDone() {
523	<	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.
517	>	* Attempts to cancel execution of this task. This attempt will
518	>	* fail if the task has already completed, has already been
519	>	* cancelled, or could not be cancelled for some other reason. If
520	>	* successful, and this task has not started when cancel is
521	>	* called, execution of this task is suppressed, {@link
522	>	* #isCancelled} will report true, and {@link #join} will result
523	>	* in a {@code CancellationException} being thrown.
524		*
525		* <p>This method may be overridden in subclasses, but if so, must
526		* still ensure that these minimal properties hold. In particular,
#	Line 706 | Line 532 | public abstract class ForkJoinTask<V> im
532		* invoke {@link #completeExceptionally}.
533		*
534		* @param mayInterruptIfRunning this value is ignored in the
535	<	* default implementation because tasks are not in general
535	>	* default implementation because tasks are not
536		* cancelled via interruption
537		*
538		* @return {@code true} if this task is now cancelled
539		*/
540		public boolean cancel(boolean mayInterruptIfRunning) {
541		setCompletion(CANCELLED);
542	<	return (status & COMPLETION_MASK) == CANCELLED;
542	>	return status == CANCELLED;
543	>	}
544	>
545	>	/**
546	>	* Cancels, ignoring any exceptions it throws. Used during worker
547	>	* and pool shutdown.
548	>	*/
549	>	final void cancelIgnoringExceptions() {
550	>	try {
551	>	cancel(false);
552	>	} catch (Throwable ignore) {
553	>	}
554	>	}
555	>
556	>	/**
557	>	* Cancels ignoring exceptions if worker is terminating
558	>	*/
559	>	private void cancelIfTerminating() {
560	>	Thread t = Thread.currentThread();
561	>	if ((t instanceof ForkJoinWorkerThread) &&
562	>	((ForkJoinWorkerThread) t).isTerminating()) {
563	>	try {
564	>	cancel(false);
565	>	} catch (Throwable ignore) {
566	>	}
567	>	}
568	>	}
569	>
570	>	public final boolean isDone() {
571	>	return status < 0;
572	>	}
573	>
574	>	public final boolean isCancelled() {
575	>	return status == CANCELLED;
576		}
577
578		/**
#	Line 722 | Line 581 | public abstract class ForkJoinTask<V> im
581		* @return {@code true} if this task threw an exception or was cancelled
582		*/
583		public final boolean isCompletedAbnormally() {
584	<	return (status & COMPLETION_MASK) < NORMAL;
584	>	return status < NORMAL;
585	>	}
586	>
587	>	/**
588	>	* Returns {@code true} if this task completed without throwing an
589	>	* exception and was not cancelled.
590	>	*
591	>	* @return {@code true} if this task completed without throwing an
592	>	* exception and was not cancelled
593	>	*/
594	>	public final boolean isCompletedNormally() {
595	>	return status == NORMAL;
596		}
597
598		/**
#	Line 733 | Line 603 | public abstract class ForkJoinTask<V> im
603		* @return the exception, or {@code null} if none
604		*/
605		public final Throwable getException() {
606	<	int s = status & COMPLETION_MASK;
607	<	if (s >= NORMAL)
608	<	return null;
609	<	if (s == CANCELLED)
740	<	return new CancellationException();
741	<	return exceptionMap.get(this);
606	>	int s = status;
607	>	return ((s >= NORMAL)    ? null :
608	>	(s == CANCELLED) ? new CancellationException() :
609	>	exceptionMap.get(this));
610		}
611
612		/**
#	Line 751 | Line 619 | public abstract class ForkJoinTask<V> im
619		* overridable, but overridden versions must invoke {@code super}
620		* implementation to maintain guarantees.
621		*
622	<	* @param ex the exception to throw. If this exception is
623	<	* not a RuntimeException or Error, the actual exception thrown
624	<	* will be a RuntimeException with cause ex.
622	>	* @param ex the exception to throw. If this exception is not a
623	>	* {@code RuntimeException} or {@code Error}, the actual exception
624	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
625		*/
626		public void completeExceptionally(Throwable ex) {
627	<	setDoneExceptionally((ex instanceof RuntimeException) ||
628	<	(ex instanceof Error) ? ex :
629	<	new RuntimeException(ex));
627	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
628	>	(ex instanceof Error) ? ex :
629	>	new RuntimeException(ex));
630		}
631
632		/**
#	Line 777 | Line 645 | public abstract class ForkJoinTask<V> im
645		try {
646		setRawResult(value);
647		} catch (Throwable rex) {
648	<	setDoneExceptionally(rex);
648	>	setExceptionalCompletion(rex);
649		return;
650		}
651	<	setNormalCompletion();
651	>	setCompletion(NORMAL);
652		}
653
654		public final V get() throws InterruptedException, ExecutionException {
655	<	ForkJoinWorkerThread w = getWorker();
656	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
657	<	awaitDone(w, true);
658	<	return reportFutureResult();
655	>	int s = doJoin();
656	>	if (Thread.interrupted())
657	>	throw new InterruptedException();
658	>	if (s < NORMAL) {
659	>	Throwable ex;
660	>	if (s == CANCELLED)
661	>	throw new CancellationException();
662	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
663	>	throw new ExecutionException(ex);
664	>	}
665	>	return getRawResult();
666		}
667
668		public final V get(long timeout, TimeUnit unit)
669		throws InterruptedException, ExecutionException, TimeoutException {
670	<	long nanos = unit.toNanos(timeout);
671	<	ForkJoinWorkerThread w = getWorker();
672	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
673	<	awaitDone(w, nanos);
674	<	return reportTimedFutureResult();
675	<	}
676	<
677	<	/**
678	<	* Possibly executes other tasks until this task is ready, then
679	<	* returns the result of the computation.  This method may be more
680	<	* efficient than {@code join}, but is only applicable when
681	<	* there are no potential dependencies between continuation of the
682	<	* current task and that of any other task that might be executed
683	<	* while helping. (This usually holds for pure divide-and-conquer
684	<	* tasks). This method may be invoked only from within
685	<	* ForkJoinTask computations (as may be determined using method
686	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
687	<	* result in exceptions or errors, possibly including
688	<	* ClassCastException.
689	<	*
690	<	* @return the computed result
691	<	*/
692	<	public final V helpJoin() {
693	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
694	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
695	<	reportException(busyJoin(w));
696	<	return getRawResult();
697	<	}
698	<
699	<	/**
700	<	* Possibly executes other tasks until this task is ready.  This
701	<	* method may be invoked only from within ForkJoinTask
702	<	* computations (as may be determined using method {@link
703	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
704	<	* in exceptions or errors, possibly including ClassCastException.
705	<	*/
706	<	public final void quietlyHelpJoin() {
707	<	if (status >= 0) {
708	<	ForkJoinWorkerThread w =
709	<	(ForkJoinWorkerThread) Thread.currentThread();
710	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
711	<	busyJoin(w);
670	>	Thread t = Thread.currentThread();
671	>	ForkJoinPool pool;
672	>	if (t instanceof ForkJoinWorkerThread) {
673	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
674	>	if (status >= 0 && w.unpushTask(this))
675	>	tryExec();
676	>	pool = w.pool;
677	>	}
678	>	else
679	>	pool = null;
680	>	/*
681	>	* Timed wait loop intermixes cases for fj (pool != null) and
682	>	* non FJ threads. For FJ, decrement pool count but don't try
683	>	* for replacement; increment count on completion. For non-FJ,
684	>	* deal with interrupts. This is messy, but a little less so
685	>	* than is splitting the FJ and nonFJ cases.
686	>	*/
687	>	boolean interrupted = false;
688	>	boolean dec = false; // true if pool count decremented
689	>	for (;;) {
690	>	if (Thread.interrupted() && pool == null) {
691	>	interrupted = true;
692	>	break;
693	>	}
694	>	int s = status;
695	>	if (s < 0)
696	>	break;
697	>	if (UNSAFE.compareAndSwapInt(this, statusOffset,
698	>	s, s | SIGNAL)) {
699	>	long startTime = System.nanoTime();
700	>	long nanos = unit.toNanos(timeout);
701	>	long nt; // wait time
702	>	while (status >= 0 &&
703	>	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
704	>	if (pool != null && !dec)
705	>	dec = pool.tryDecrementRunningCount();
706	>	else {
707	>	long ms = nt / 1000000;
708	>	int ns = (int) (nt % 1000000);
709	>	try {
710	>	synchronized(this) {
711	>	if (status >= 0)
712	>	wait(ms, ns);
713	>	}
714	>	} catch (InterruptedException ie) {
715	>	if (pool != null)
716	>	cancelIfTerminating();
717	>	else {
718	>	interrupted = true;
719	>	break;
720	>	}
721	>	}
722	>	}
723	>	}
724	>	break;
725	>	}
726	>	}
727	>	if (pool != null && dec)
728	>	pool.incrementRunningCount();
729	>	if (interrupted)
730	>	throw new InterruptedException();
731	>	int es = status;
732	>	if (es != NORMAL) {
733	>	Throwable ex;
734	>	if (es == CANCELLED)
735	>	throw new CancellationException();
736	>	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
737	>	throw new ExecutionException(ex);
738	>	throw new TimeoutException();
739		}
740	+	return getRawResult();
741		}
742
743		/**
#	Line 844 | Line 747 | public abstract class ForkJoinTask<V> im
747		* known to have aborted.
748		*/
749		public final void quietlyJoin() {
750	<	if (status >= 0) {
848	<	ForkJoinWorkerThread w = getWorker();
849	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
850	<	awaitDone(w, true);
851	<	}
750	>	doJoin();
751		}
752
753		/**
#	Line 859 | Line 758 | public abstract class ForkJoinTask<V> im
758		* known to have aborted.
759		*/
760		public final void quietlyInvoke() {
761	<	if (status >= 0 && !tryQuietlyInvoke())
863	<	quietlyJoin();
761	>	doInvoke();
762		}
763
764		/**
765		* Possibly executes tasks until the pool hosting the current task
766	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
767	<	* designs in which many tasks are forked, but none are explicitly
768	<	* joined, instead executing them until all are processed.  This
769	<	* method may be invoked only from within ForkJoinTask
770	<	* computations (as may be determined using method {@link
771	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
772	<	* in exceptions or errors, possibly including ClassCastException.
766	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
767	>	* be of use in designs in which many tasks are forked, but none
768	>	* are explicitly joined, instead executing them until all are
769	>	* processed.
770	>	*
771	>	* <p>This method may be invoked only from within {@code
772	>	* ForkJoinTask} computations (as may be determined using method
773	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
774	>	* result in exceptions or errors, possibly including {@code
775	>	* ClassCastException}.
776		*/
777		public static void helpQuiesce() {
778		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 884 | Line 785 | public abstract class ForkJoinTask<V> im
785		* this task, but only if reuse occurs when this task has either
786		* never been forked, or has been forked, then completed and all
787		* outstanding joins of this task have also completed. Effects
788	<	* under any other usage conditions are not guaranteed, and are
789	<	* discouraged. This method may be useful when executing
788	>	* under any other usage conditions are not guaranteed.
789	>	* This method may be useful when executing
790		* pre-constructed trees of subtasks in loops.
791		*/
792		public void reinitialize() {
793	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
793	>	if (status == EXCEPTIONAL)
794		exceptionMap.remove(this);
795		status = 0;
796		}
#	Line 924 | Line 825 | public abstract class ForkJoinTask<V> im
825		* by the current thread, and has not commenced executing in
826		* another thread.  This method may be useful when arranging
827		* alternative local processing of tasks that could have been, but
828	<	* were not, stolen. This method may be invoked only from within
829	<	* ForkJoinTask computations (as may be determined using method
830	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
831	<	* result in exceptions or errors, possibly including
832	<	* ClassCastException.
828	>	* were not, stolen.
829	>	*
830	>	* <p>This method may be invoked only from within {@code
831	>	* ForkJoinTask} computations (as may be determined using method
832	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
833	>	* result in exceptions or errors, possibly including {@code
834	>	* ClassCastException}.
835		*
836		* @return {@code true} if unforked
837		*/
#	Line 941 | Line 844 | public abstract class ForkJoinTask<V> im
844		* Returns an estimate of the number of tasks that have been
845		* forked by the current worker thread but not yet executed. This
846		* value may be useful for heuristic decisions about whether to
847	<	* fork other tasks.  This method may be invoked only from within
848	<	* ForkJoinTask computations (as may be determined using method
849	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
850	<	* result in exceptions or errors, possibly including
851	<	* ClassCastException.
847	>	* fork other tasks.
848	>	*
849	>	* <p>This method may be invoked only from within {@code
850	>	* ForkJoinTask} computations (as may be determined using method
851	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
852	>	* result in exceptions or errors, possibly including {@code
853	>	* ClassCastException}.
854	>	*
855		* @return the number of tasks
856		*/
857		public static int getQueuedTaskCount() {
#	Line 961 | Line 867 | public abstract class ForkJoinTask<V> im
867		* usages of ForkJoinTasks, at steady state, each worker should
868		* aim to maintain a small constant surplus (for example, 3) of
869		* tasks, and to process computations locally if this threshold is
870	<	* exceeded.  This method may be invoked only from within
871	<	* ForkJoinTask computations (as may be determined using method
872	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
873	<	* result in exceptions or errors, possibly including
874	<	* ClassCastException.  *
870	>	* exceeded.
871	>	*
872	>	* <p>This method may be invoked only from within {@code
873	>	* ForkJoinTask} computations (as may be determined using method
874	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
875	>	* result in exceptions or errors, possibly including {@code
876	>	* ClassCastException}.
877	>	*
878		* @return the surplus number of tasks, which may be negative
879		*/
880		public static int getSurplusQueuedTaskCount() {
#	Line 1001 | Line 910 | public abstract class ForkJoinTask<V> im
910		* called otherwise. The return value controls whether this task
911		* is considered to be done normally. It may return false in
912		* asynchronous actions that require explicit invocations of
913	<	* {@link #complete} to become joinable. It may throw exceptions
914	<	* to indicate abnormal exit.
913	>	* {@link #complete} to become joinable. It may also throw an
914	>	* (unchecked) exception to indicate abnormal exit.
915		*
916		* @return {@code true} if completed normally
1008	–	* @throws Error or RuntimeException if encountered during computation
917		*/
918		protected abstract boolean exec();
919
#	Line 1017 | Line 925 | public abstract class ForkJoinTask<V> im
925		* null even if a task exists but cannot be accessed without
926		* contention with other threads.  This method is designed
927		* primarily to support extensions, and is unlikely to be useful
928	<	* otherwise.  This method may be invoked only from within
929	<	* ForkJoinTask computations (as may be determined using method
930	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
931	<	* result in exceptions or errors, possibly including
932	<	* ClassCastException.
928	>	* otherwise.
929	>	*
930	>	* <p>This method may be invoked only from within {@code
931	>	* ForkJoinTask} computations (as may be determined using method
932	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
933	>	* result in exceptions or errors, possibly including {@code
934	>	* ClassCastException}.
935		*
936		* @return the next task, or {@code null} if none are available
937		*/
#	Line 1034 | Line 944 | public abstract class ForkJoinTask<V> im
944		* Unschedules and returns, without executing, the next task
945		* queued by the current thread but not yet executed.  This method
946		* is designed primarily to support extensions, and is unlikely to
947	<	* be useful otherwise.  This method may be invoked only from
948	<	* within ForkJoinTask computations (as may be determined using
949	<	* method {@link #inForkJoinPool}). Attempts to invoke in other
950	<	* contexts result in exceptions or errors, possibly including
951	<	* ClassCastException.
947	>	* be useful otherwise.
948	>	*
949	>	* <p>This method may be invoked only from within {@code
950	>	* ForkJoinTask} computations (as may be determined using method
951	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
952	>	* result in exceptions or errors, possibly including {@code
953	>	* ClassCastException}.
954		*
955		* @return the next task, or {@code null} if none are available
956		*/
#	Line 1055 | Line 967 | public abstract class ForkJoinTask<V> im
967		* {@code null} result does not necessarily imply quiescence
968		* of the pool this task is operating in.  This method is designed
969		* primarily to support extensions, and is unlikely to be useful
970	<	* otherwise.  This method may be invoked only from within
971	<	* ForkJoinTask computations (as may be determined using method
972	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
973	<	* result in exceptions or errors, possibly including
974	<	* ClassCastException.
970	>	* otherwise.
971	>	*
972	>	* <p>This method may be invoked only from within {@code
973	>	* ForkJoinTask} computations (as may be determined using method
974	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
975	>	* result in exceptions or errors, possibly including {@code
976	>	* ClassCastException}.
977		*
978		* @return a task, or {@code null} if none are available
979		*/
#	Line 1124 | Line 1038 | public abstract class ForkJoinTask<V> im
1038		}
1039
1040		/**
1041	<	* Returns a new ForkJoinTask that performs the {@code run}
1042	<	* method of the given Runnable as its action, and returns a null
1043	<	* result upon {@code join}.
1041	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1042	>	* method of the given {@code Runnable} as its action, and returns
1043	>	* a null result upon {@link #join}.
1044		*
1045		* @param runnable the runnable action
1046		* @return the task
#	Line 1136 | Line 1050 | public abstract class ForkJoinTask<V> im
1050		}
1051
1052		/**
1053	<	* Returns a new ForkJoinTask that performs the {@code run}
1054	<	* method of the given Runnable as its action, and returns the
1055	<	* given result upon {@code join}.
1053	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1054	>	* method of the given {@code Runnable} as its action, and returns
1055	>	* the given result upon {@link #join}.
1056		*
1057		* @param runnable the runnable action
1058		* @param result the result upon completion
#	Line 1149 | Line 1063 | public abstract class ForkJoinTask<V> im
1063		}
1064
1065		/**
1066	<	* Returns a new ForkJoinTask that performs the {@code call}
1067	<	* method of the given Callable as its action, and returns its
1068	<	* result upon {@code join}, translating any checked
1069	<	* exceptions encountered into {@code RuntimeException}.
1066	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1067	>	* method of the given {@code Callable} as its action, and returns
1068	>	* its result upon {@link #join}, translating any checked exceptions
1069	>	* encountered into {@code RuntimeException}.
1070		*
1071		* @param callable the callable action
1072		* @return the task
#	Line 1166 | Line 1080 | public abstract class ForkJoinTask<V> im
1080		private static final long serialVersionUID = -7721805057305804111L;
1081
1082		/**
1083	<	* Save the state to a stream.
1083	>	* Saves the state to a stream.
1084		*
1085		* @serialData the current run status and the exception thrown
1086		* during execution, or {@code null} if none
#	Line 1179 | Line 1093 | public abstract class ForkJoinTask<V> im
1093		}
1094
1095		/**
1096	<	* Reconstitute the instance from a stream.
1096	>	* Reconstitutes the instance from a stream.
1097		*
1098		* @param s the stream
1099		*/
1100		private void readObject(java.io.ObjectInputStream s)
1101		throws java.io.IOException, ClassNotFoundException {
1102		s.defaultReadObject();
1189	–	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1190	–	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1103		Object ex = s.readObject();
1104		if (ex != null)
1105	<	setDoneExceptionally((Throwable) ex);
1105	>	setExceptionalCompletion((Throwable) ex);
1106	>	if (status < 0)
1107	>	synchronized (this) { notifyAll(); }
1108		}
1109
1110		// Unsafe mechanics

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