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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.27 by dl, Sun Aug 2 11:54:31 2009 UTC vs.
Revision 1.53 by dl, Wed Aug 11 18:45:12 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 22 | Line 23 | import java.util.WeakHashMap;
23		* subtasks may be hosted by a small number of actual threads in a
24		* ForkJoinPool, at the price of some usage limitations.
25		*
26	<	* <p> A "main" ForkJoinTask begins execution when submitted to a
27	<	* {@link ForkJoinPool}. Once started, it will usually in turn start
28	<	* other subtasks.  As indicated by the name of this class, many
29	<	* programs using ForkJoinTasks employ only methods {@code fork} and
30	<	* {@code join}, or derivatives such as {@code invokeAll}.  However,
31	<	* this class also provides a number of other methods that can come
32	<	* into play in advanced usages, as well as extension mechanics that
33	<	* allow support of new forms of fork/join processing.
26	>	* <p>A "main" {@code ForkJoinTask} begins execution when submitted
27	>	* to a {@link ForkJoinPool}.  Once started, it will usually in turn
28	>	* start other subtasks.  As indicated by the name of this class,
29	>	* many programs using {@code ForkJoinTask} employ only methods
30	>	* {@link #fork} and {@link #join}, or derivatives such as {@link
31	>	* #invokeAll}.  However, this class also provides a number of other
32	>	* methods that can come into play in advanced usages, as well as
33	>	* extension mechanics that allow support of new forms of fork/join
34	>	* processing.
35		*
36	<	* <p>A ForkJoinTask is a lightweight form of {@link Future}.  The
37	<	* efficiency of ForkJoinTasks stems from a set of restrictions (that
38	<	* are only partially statically enforceable) reflecting their
39	<	* intended use as computational tasks calculating pure functions or
40	<	* operating on purely isolated objects.  The primary coordination
41	<	* mechanisms are {@link #fork}, that arranges asynchronous execution,
42	<	* and {@link #join}, that doesn't proceed until the task's result has
43	<	* been computed.  Computations should avoid {@code synchronized}
44	<	* methods or blocks, and should minimize other blocking
45	<	* synchronization apart from joining other tasks or using
46	<	* synchronizers such as Phasers that are advertised to cooperate with
47	<	* fork/join scheduling. Tasks should also not perform blocking IO,
48	<	* and should ideally access variables that are completely independent
49	<	* of those accessed by other running tasks. Minor breaches of these
50	<	* restrictions, for example using shared output streams, may be
51	<	* tolerable in practice, but frequent use may result in poor
52	<	* performance, and the potential to indefinitely stall if the number
53	<	* of threads not waiting for IO or other external synchronization
54	<	* becomes exhausted. This usage restriction is in part enforced by
55	<	* not permitting checked exceptions such as {@code IOExceptions}
56	<	* to be thrown. However, computations may still encounter unchecked
57	<	* exceptions, that are rethrown to callers attempting join
58	<	* them. These exceptions may additionally include
59	<	* RejectedExecutionExceptions stemming from internal resource
60	<	* exhaustion such as failure to allocate internal task queues.
36	>	* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
37	>	* The efficiency of {@code ForkJoinTask}s stems from a set of
38	>	* restrictions (that are only partially statically enforceable)
39	>	* reflecting their intended use as computational tasks calculating
40	>	* pure functions or operating on purely isolated objects.  The
41	>	* primary coordination mechanisms are {@link #fork}, that arranges
42	>	* asynchronous execution, and {@link #join}, that doesn't proceed
43	>	* until the task's result has been computed.  Computations should
44	>	* avoid {@code synchronized} methods or blocks, and should minimize
45	>	* other blocking synchronization apart from joining other tasks or
46	>	* using synchronizers such as Phasers that are advertised to
47	>	* cooperate with fork/join scheduling. Tasks should also not perform
48	>	* blocking IO, and should ideally access variables that are
49	>	* completely independent of those accessed by other running
50	>	* tasks. Minor breaches of these restrictions, for example using
51	>	* shared output streams, may be tolerable in practice, but frequent
52	>	* use may result in poor performance, and the potential to
53	>	* indefinitely stall if the number of threads not waiting for IO or
54	>	* other external synchronization becomes exhausted. This usage
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 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
68	<	* equivalent to {@code fork(); join()} but always attempts to
69	<	* begin execution in the current thread. The "<em>quiet</em>" forms
70	<	* 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 ForkJoinTask class is not usually directly subclassed.
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
92		* RecursiveAction} for computations that do not return results, or
#	Line 83 | 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
102	<	* 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
115	<	* 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
121	<	* 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. In particular, most
148	>	* join mechanics are in method quietlyJoin, below.
149	>	*/
150	>
151	>	/*
152	>	* The status field holds run control status bits packed into a
153	>	* single int to minimize footprint and to ensure atomicity (via
154	>	* CAS).  Status is initially zero, and takes on nonnegative
155	>	* values until completed, upon which status holds value
156	>	* COMPLETED. CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
157	>	* waits by other threads have the SIGNAL bit set.  Completion of
158	>	* a stolen task with SIGNAL set awakens any waiters via
159	>	* notifyAll. Even though suboptimal for some purposes, we use
160	>	* basic builtin wait/notify to take advantage of "monitor
161	>	* inflation" in JVMs that we would otherwise need to emulate to
162	>	* avoid adding further per-task bookkeeping overhead.  We want
163	>	* these monitors to be "fat", i.e., not use biasing or thin-lock
164	>	* techniques, so use some odd coding idioms that tend to avoid
165	>	* them.
166		*/
167	+
168	+	/** The run status of this task */
169		volatile int status; // accessed directly by pool and workers
170
171	<	static final int COMPLETION_MASK      = 0xe0000000;
172	<	static final int NORMAL               = 0xe0000000; // == mask
173	<	static final int CANCELLED            = 0xc0000000;
174	<	static final int EXCEPTIONAL          = 0xa0000000;
152	<	static final int SIGNAL_MASK          = 0x0000ffff;
153	<	static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
154	<	static final int EXTERNAL_SIGNAL      = 0x00008000; // top bit of low word
171	>	private static final int NORMAL      = -1;
172	>	private static final int CANCELLED   = -2;
173	>	private static final int EXCEPTIONAL = -3;
174	>	private static final int SIGNAL      =  1;
175
176		/**
177		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 165 | Line 185 | public abstract class ForkJoinTask<V> im
185		Collections.synchronizedMap
186		(new WeakHashMap<ForkJoinTask<?>, Throwable>());
187
188	<	// within-package utilities
169	<
170	<	/**
171	<	* Gets current worker thread, or null if not a worker thread.
172	<	*/
173	<	static ForkJoinWorkerThread getWorker() {
174	<	Thread t = Thread.currentThread();
175	<	return ((t instanceof ForkJoinWorkerThread) ?
176	<	(ForkJoinWorkerThread) t : null);
177	<	}
178	<
179	<	final boolean casStatus(int cmp, int val) {
180	<	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
181	<	}
188	>	// Maintaining completion status
189
190		/**
191	<	* Workaround for not being able to rethrow unchecked exceptions.
192	<	*/
186	<	static void rethrowException(Throwable ex) {
187	<	if (ex != null)
188	<	UNSAFE.throwException(ex);
189	<	}
190	<
191	<	// Setting completion status
192	<
193	<	/**
194	<	* Marks completion and wakes up threads waiting to join this task.
191	>	* Marks completion and wakes up threads waiting to join this task,
192	>	* also clearing signal request bits.
193		*
194		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
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) {
205	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
206	<	pool.updateRunningCount(s);
207	<	synchronized (this) { notifyAll(); }
196	>	private void 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	>	break;
203		}
204		}
210	–	else
211	–	externallySetCompletion(completion);
205		}
206
207		/**
208	<	* Version of setCompletion for non-FJ threads.  Leaves signal
209	<	* bits for unblocked threads to adjust, and always notifies.
217	<	*/
218	<	private void externallySetCompletion(int completion) {
219	<	int s;
220	<	do {} while ((s = status) >= 0 &&
221	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
222	<	synchronized (this) { notifyAll(); }
223	<	}
224	<
225	<	/**
226	<	* Sets status to indicate normal completion.
227	<	*/
228	<	final void setNormalCompletion() {
229	<	// Try typical fast case -- single CAS, no signal, not already done.
230	<	// Manually expand casStatus to improve chances of inlining it
231	<	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
232	<	setCompletion(NORMAL);
233	<	}
234	<
235	<	// internal waiting and notification
236	<
237	<	/**
238	<	* Performs the actual monitor wait for awaitDone.
208	>	* Record exception and set exceptional completion
209	>	* @return status on exit
210		*/
211	<	private void doAwaitDone() {
212	<	// Minimize lock bias and in/de-flation effects by maximizing
213	<	// chances of waiting inside sync
243	<	try {
244	<	while (status >= 0)
245	<	synchronized (this) { if (status >= 0) wait(); }
246	<	} catch (InterruptedException ie) {
247	<	onInterruptedWait();
248	<	}
211	>	private void setExceptionalCompletion(Throwable rex) {
212	>	exceptionMap.put(this, rex);
213	>	setCompletion(EXCEPTIONAL);
214		}
215
216		/**
217	<	* Performs the actual timed monitor wait for awaitDone.
217	>	* Blocks a worker thread until completion. Called only by pool.
218		*/
219	<	private void doAwaitDone(long startTime, long nanos) {
220	<	synchronized (this) {
219	>	final void internalAwaitDone() {
220	>	int s;         // the odd construction reduces lock bias effects
221	>	while ((s = status) >= 0) {
222		try {
223	<	while (status >= 0) {
224	<	long nt = nanos - (System.nanoTime() - startTime);
225	<	if (nt <= 0)
260	<	break;
261	<	wait(nt / 1000000, (int) (nt % 1000000));
223	>	synchronized(this) {
224	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
225	>	wait();
226		}
227		} catch (InterruptedException ie) {
228	<	onInterruptedWait();
228	>	cancelIfTerminating();
229		}
230		}
231		}
232
269	–	// Awaiting completion
270	–
233		/**
234	<	* Sets status to indicate there is joiner, then waits for join,
273	<	* surrounded with pool notifications.
274	<	*
275	<	* @return status upon exit
234	>	* Blocks a non-worker-thread until completion.
235		*/
236	<	private int awaitDone(ForkJoinWorkerThread w,
278	<	boolean maintainParallelism) {
279	<	ForkJoinPool pool = (w == null) ? null : w.pool;
236	>	private void externalAwaitDone() {
237		int s;
238		while ((s = status) >= 0) {
239	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
240	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
241	<	doAwaitDone();
242	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
243	<	adjustPoolCountsOnUnblock(pool);
244	<	break;
245	<	}
246	<	}
247	<	return s;
248	<	}
249	<
250	<	/**
294	<	* Timed version of awaitDone
295	<	*
296	<	* @return status upon exit
297	<	*/
298	<	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
299	<	ForkJoinPool pool = (w == null) ? null : w.pool;
300	<	int s;
301	<	while ((s = status) >= 0) {
302	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
303	<	long startTime = System.nanoTime();
304	<	if (pool == null || !pool.preJoin(this, false))
305	<	doAwaitDone(startTime, nanos);
306	<	if ((s = status) >= 0) {
307	<	adjustPoolCountsOnCancelledWait(pool);
308	<	s = status;
309	<	}
310	<	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
311	<	adjustPoolCountsOnUnblock(pool);
312	<	break;
313	<	}
314	<	}
315	<	return s;
316	<	}
317	<
318	<	/**
319	<	* Notifies pool that thread is unblocked. Called by signalled
320	<	* threads when woken by non-FJ threads (which is atypical).
321	<	*/
322	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
323	<	int s;
324	<	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
325	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
326	<	pool.updateRunningCount(s);
327	<	}
328	<
329	<	/**
330	<	* Notifies pool to adjust counts on cancelled or timed out wait.
331	<	*/
332	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
333	<	if (pool != null) {
334	<	int s;
335	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
336	<	if (casStatus(s, s - 1)) {
337	<	pool.updateRunningCount(1);
239	>	synchronized(this) {
240	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
241	>	boolean interrupted = false;
242	>	while (status >= 0) {
243	>	try {
244	>	wait();
245	>	} catch (InterruptedException ie) {
246	>	interrupted = true;
247	>	}
248	>	}
249	>	if (interrupted)
250	>	Thread.currentThread().interrupt();
251		break;
252		}
253		}
#	Line 342 | Line 255 | public abstract class ForkJoinTask<V> im
255		}
256
257		/**
258	<	* Handles interruptions during waits.
259	<	*/
260	<	private void onInterruptedWait() {
348	<	ForkJoinWorkerThread w = getWorker();
349	<	if (w == null)
350	<	Thread.currentThread().interrupt(); // re-interrupt
351	<	else if (w.isTerminating())
352	<	cancelIgnoringExceptions();
353	<	// else if FJworker, ignore interrupt
354	<	}
355	<
356	<	// Recording and reporting exceptions
357	<
358	<	private void setDoneExceptionally(Throwable rex) {
359	<	exceptionMap.put(this, rex);
360	<	setCompletion(EXCEPTIONAL);
361	<	}
362	<
363	<	/**
364	<	* Throws the exception associated with status s.
365	<	*
366	<	* @throws the exception
367	<	*/
368	<	private void reportException(int s) {
369	<	if ((s &= COMPLETION_MASK) < NORMAL) {
370	<	if (s == CANCELLED)
371	<	throw new CancellationException();
372	<	else
373	<	rethrowException(exceptionMap.get(this));
374	<	}
375	<	}
376	<
377	<	/**
378	<	* Returns result or throws exception using j.u.c.Future conventions.
379	<	* Only call when {@code isDone} known to be true.
380	<	*/
381	<	private V reportFutureResult()
382	<	throws ExecutionException, InterruptedException {
383	<	int s = status & COMPLETION_MASK;
384	<	if (s < NORMAL) {
385	<	Throwable ex;
386	<	if (s == CANCELLED)
387	<	throw new CancellationException();
388	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
389	<	throw new ExecutionException(ex);
390	<	if (Thread.interrupted())
391	<	throw new InterruptedException();
392	<	}
393	<	return getRawResult();
394	<	}
395	<
396	<	/**
397	<	* Returns result or throws exception using j.u.c.Future conventions
398	<	* with timeouts.
399	<	*/
400	<	private V reportTimedFutureResult()
401	<	throws InterruptedException, ExecutionException, TimeoutException {
402	<	Throwable ex;
403	<	int s = status & COMPLETION_MASK;
404	<	if (s == NORMAL)
405	<	return getRawResult();
406	<	if (s == CANCELLED)
407	<	throw new CancellationException();
408	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
409	<	throw new ExecutionException(ex);
410	<	if (Thread.interrupted())
411	<	throw new InterruptedException();
412	<	throw new TimeoutException();
413	<	}
414	<
415	<	// internal execution methods
416	<
417	<	/**
418	<	* Calls exec, recording completion, and rethrowing exception if
419	<	* encountered. Caller should normally check status before calling.
420	<	*
421	<	* @return true if completed normally
422	<	*/
423	<	private boolean tryExec() {
424	<	try { // try block must contain only call to exec
425	<	if (!exec())
426	<	return false;
427	<	} catch (Throwable rex) {
428	<	setDoneExceptionally(rex);
429	<	rethrowException(rex);
430	<	return false; // not reached
431	<	}
432	<	setNormalCompletion();
433	<	return true;
434	<	}
435	<
436	<	/**
437	<	* Main execution method used by worker threads. Invokes
438	<	* base computation unless already complete.
258	>	* Unless done, calls exec and records status if completed, but
259	>	* doesn't wait for completion otherwise. Primary execution method
260	>	* for ForkJoinWorkerThread.
261		*/
262		final void quietlyExec() {
441	–	if (status >= 0) {
442	–	try {
443	–	if (!exec())
444	–	return;
445	–	} catch (Throwable rex) {
446	–	setDoneExceptionally(rex);
447	–	return;
448	–	}
449	–	setNormalCompletion();
450	–	}
451	–	}
452	–
453	–	/**
454	–	* Calls exec(), recording but not rethrowing exception.
455	–	* Caller should normally check status before calling.
456	–	*
457	–	* @return true if completed normally
458	–	*/
459	–	private boolean tryQuietlyInvoke() {
263		try {
264	<	if (!exec())
265	<	return false;
264	>	if (status < 0 || !exec())
265	>	return;
266		} catch (Throwable rex) {
267	<	setDoneExceptionally(rex);
268	<	return false;
466	<	}
467	<	setNormalCompletion();
468	<	return true;
469	<	}
470	<
471	<	/**
472	<	* Cancels, ignoring any exceptions it throws.
473	<	*/
474	<	final void cancelIgnoringExceptions() {
475	<	try {
476	<	cancel(false);
477	<	} catch (Throwable ignore) {
267	>	setExceptionalCompletion(rex);
268	>	return;
269		}
270	<	}
480	<
481	<	/**
482	<	* Main implementation of helpJoin
483	<	*/
484	<	private int busyJoin(ForkJoinWorkerThread w) {
485	<	int s;
486	<	ForkJoinTask<?> t;
487	<	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
488	<	t.quietlyExec();
489	<	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
270	>	setCompletion(NORMAL); // must be outside try block
271		}
272
273		// public methods
#	Line 494 | Line 275 | public abstract class ForkJoinTask<V> im
275		/**
276		* Arranges to asynchronously execute this task.  While it is not
277		* necessarily enforced, it is a usage error to fork a task more
278	<	* than once unless it has completed and been reinitialized.  This
279	<	* method may be invoked only from within ForkJoinTask
280	<	* computations (as may be determined using method {@link
281	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
282	<	* in exceptions or errors, possibly including ClassCastException.
278	>	* than once unless it has completed and been reinitialized.
279	>	* Subsequent modifications to the state of this task or any data
280	>	* it operates on are not necessarily consistently observable by
281	>	* any thread other than the one executing it unless preceded by a
282	>	* call to {@link #join} or related methods, or a call to {@link
283	>	* #isDone} returning {@code true}.
284	>	*
285	>	* <p>This method may be invoked only from within {@code
286	>	* ForkJoinTask} computations (as may be determined using method
287	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
288	>	* result in exceptions or errors, possibly including {@code
289	>	* ClassCastException}.
290		*
291	<	* @return {@code this}, to simplify usage.
291	>	* @return {@code this}, to simplify usage
292		*/
293		public final ForkJoinTask<V> fork() {
294		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 509 | Line 297 | public abstract class ForkJoinTask<V> im
297		}
298
299		/**
300	<	* Returns the result of the computation when it is ready.
301	<	* This method differs from {@code get} in that abnormal
302	<	* completion results in RuntimeExceptions or Errors, not
303	<	* ExecutionExceptions.
300	>	* Returns the result of the computation when it {@link #isDone is done}.
301	>	* This method differs from {@link #get()} in that
302	>	* abnormal completion results in {@code RuntimeException} or
303	>	* {@code Error}, not {@code ExecutionException}.
304		*
305		* @return the computed result
306		*/
307		public final V join() {
308	<	ForkJoinWorkerThread w = getWorker();
309	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
310	<	reportException(awaitDone(w, true));
308	>	quietlyJoin();
309	>	Throwable ex;
310	>	if (status < NORMAL && (ex = getException()) != null)
311	>	UNSAFE.throwException(ex);
312		return getRawResult();
313		}
314
315		/**
316		* Commences performing this task, awaits its completion if
317	<	* necessary, and return its result.
317	>	* necessary, and return its result, or throws an (unchecked)
318	>	* exception if the underlying computation did so.
319		*
530	–	* @throws Throwable (a RuntimeException, Error, or unchecked
531	–	* exception) if the underlying computation did so
320		* @return the computed result
321		*/
322		public final V invoke() {
323	<	if (status >= 0 && tryExec())
324	<	return getRawResult();
325	<	else
326	<	return join();
323	>	quietlyInvoke();
324	>	Throwable ex;
325	>	if (status < NORMAL && (ex = getException()) != null)
326	>	UNSAFE.throwException(ex);
327	>	return getRawResult();
328		}
329
330		/**
331		* Forks the given tasks, returning when {@code isDone} holds for
332	<	* each task or an exception is encountered. This method may be
333	<	* invoked only from within ForkJoinTask computations (as may be
334	<	* determined using method {@link #inForkJoinPool}). Attempts to
335	<	* invoke in other contexts result in exceptions or errors,
336	<	* possibly including ClassCastException.
332	>	* each task or an (unchecked) exception is encountered, in which
333	>	* case the exception is rethrown.  If either task encounters an
334	>	* exception, the other one may be, but is not guaranteed to be,
335	>	* cancelled.  If both tasks throw an exception, then this method
336	>	* throws one of them.  The individual status of each task may be
337	>	* checked using {@link #getException()} and related methods.
338	>	*
339	>	* <p>This method may be invoked only from within {@code
340	>	* ForkJoinTask} computations (as may be determined using method
341	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
342	>	* result in exceptions or errors, possibly including {@code
343	>	* ClassCastException}.
344		*
345		* @param t1 the first task
346		* @param t2 the second task
347		* @throws NullPointerException if any task is null
552	–	* @throws RuntimeException or Error if a task did so
348		*/
349	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
349	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
350		t2.fork();
351		t1.invoke();
352		t2.join();
#	Line 559 | Line 354 | public abstract class ForkJoinTask<V> im
354
355		/**
356		* Forks the given tasks, returning when {@code isDone} holds for
357	<	* each task or an exception is encountered. If any task
358	<	* encounters an exception, others may be, but are not guaranteed
359	<	* to be, cancelled.  This method may be invoked only from within
360	<	* ForkJoinTask computations (as may be determined using method
361	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
362	<	* result in exceptions or errors, possibly including
363	<	* ClassCastException.
364	<	*
365	<	* Overloadings of this method exist for the special cases
366	<	* of one to four arguments.
357	>	* each task or an (unchecked) exception is encountered, in which
358	>	* case the exception is rethrown. If any task encounters an
359	>	* exception, others may be, but are not guaranteed to be,
360	>	* cancelled.  If more than one task encounters an exception, then
361	>	* this method throws any one of these exceptions.  The individual
362	>	* status of each task may be checked using {@link #getException()}
363	>	* and related methods.
364	>	*
365	>	* <p>This method may be invoked only from within {@code
366	>	* ForkJoinTask} computations (as may be determined using method
367	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
368	>	* result in exceptions or errors, possibly including {@code
369	>	* ClassCastException}.
370		*
371		* @param tasks the tasks
372	<	* @throws NullPointerException if tasks or any element are null
575	<	* @throws RuntimeException or Error if any task did so
372	>	* @throws NullPointerException if any task is null
373		*/
374		public static void invokeAll(ForkJoinTask<?>... tasks) {
375		Throwable ex = null;
#	Line 587 | Line 384 | public abstract class ForkJoinTask<V> im
384		t.fork();
385		else {
386		t.quietlyInvoke();
387	<	if (ex == null)
387	>	if (ex == null && t.status < NORMAL)
388		ex = t.getException();
389		}
390		}
#	Line 598 | Line 395 | public abstract class ForkJoinTask<V> im
395		t.cancel(false);
396		else {
397		t.quietlyJoin();
398	<	if (ex == null)
398	>	if (ex == null && t.status < NORMAL)
399		ex = t.getException();
400		}
401		}
402		}
403		if (ex != null)
404	<	rethrowException(ex);
404	>	UNSAFE.throwException(ex);
405		}
406
407		/**
408	<	* Forks all tasks in the collection, returning when {@code
409	<	* isDone} holds for each task or an exception is encountered. If
410	<	* any task encounters an exception, others may be, but are not
411	<	* guaranteed to be, cancelled.  This method may be invoked only
412	<	* from within ForkJoinTask computations (as may be determined
413	<	* using method {@link #inForkJoinPool}). Attempts to invoke in
414	<	* other contexts result in exceptions or errors, possibly
415	<	* including ClassCastException.
408	>	* Forks all tasks in the specified collection, returning when
409	>	* {@code isDone} holds for each task or an (unchecked) exception
410	>	* is encountered.  If any task encounters an exception, others
411	>	* may be, but are not guaranteed to be, cancelled.  If more than
412	>	* one task encounters an exception, then this method throws any
413	>	* one of these exceptions.  The individual status of each task
414	>	* may be checked using {@link #getException()} and related
415	>	* methods.  The behavior of this operation is undefined if the
416	>	* specified collection is modified while the operation is in
417	>	* progress.
418	>	*
419	>	* <p>This method may be invoked only from within {@code
420	>	* ForkJoinTask} computations (as may be determined using method
421	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
422	>	* result in exceptions or errors, possibly including {@code
423	>	* ClassCastException}.
424		*
425		* @param tasks the collection of tasks
426		* @return the tasks argument, to simplify usage
427		* @throws NullPointerException if tasks or any element are null
623	–	* @throws RuntimeException or Error if any task did so
428		*/
429		public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
430	<	if (!(tasks instanceof List<?>)) {
430	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
431		invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
432		return tasks;
433		}
#	Line 642 | Line 446 | public abstract class ForkJoinTask<V> im
446		t.fork();
447		else {
448		t.quietlyInvoke();
449	<	if (ex == null)
449	>	if (ex == null && t.status < NORMAL)
450		ex = t.getException();
451		}
452		}
#	Line 653 | Line 457 | public abstract class ForkJoinTask<V> im
457		t.cancel(false);
458		else {
459		t.quietlyJoin();
460	<	if (ex == null)
460	>	if (ex == null && t.status < NORMAL)
461		ex = t.getException();
462		}
463		}
464		}
465		if (ex != null)
466	<	rethrowException(ex);
466	>	UNSAFE.throwException(ex);
467		return tasks;
468		}
469
470		/**
471	<	* Returns {@code true} if the computation performed by this task
472	<	* has completed (or has been cancelled).
473	<	*
474	<	* @return {@code true} if this computation has completed
475	<	*/
476	<	public final boolean isDone() {
477	<	return status < 0;
674	<	}
675	<
676	<	/**
677	<	* Returns {@code true} if this task was cancelled.
678	<	*
679	<	* @return {@code true} if this task was cancelled
680	<	*/
681	<	public final boolean isCancelled() {
682	<	return (status & COMPLETION_MASK) == CANCELLED;
683	<	}
684	<
685	<	/**
686	<	* Asserts that the results of this task's computation will not be
687	<	* used. If a cancellation occurs before attempting to execute this
688	<	* task, execution will be suppressed, {@link #isCancelled}
689	<	* will report true, and {@link #join} will result in a
690	<	* {@code CancellationException} being thrown. Otherwise, when
691	<	* cancellation races with completion, there are no guarantees
692	<	* about whether {@code isCancelled} will report {@code true},
693	<	* whether {@code join} will return normally or via an exception,
694	<	* or whether these behaviors will remain consistent upon repeated
695	<	* invocation.
471	>	* Attempts to cancel execution of this task. This attempt will
472	>	* fail if the task has already completed, has already been
473	>	* cancelled, or could not be cancelled for some other reason. If
474	>	* successful, and this task has not started when cancel is
475	>	* called, execution of this task is suppressed, {@link
476	>	* #isCancelled} will report true, and {@link #join} will result
477	>	* in a {@code CancellationException} being thrown.
478		*
479		* <p>This method may be overridden in subclasses, but if so, must
480		* still ensure that these minimal properties hold. In particular,
481	<	* the cancel method itself must not throw exceptions.
481	>	* the {@code cancel} method itself must not throw exceptions.
482		*
483	<	* <p> This method is designed to be invoked by <em>other</em>
483	>	* <p>This method is designed to be invoked by <em>other</em>
484		* tasks. To terminate the current task, you can just return or
485		* throw an unchecked exception from its computation method, or
486		* invoke {@link #completeExceptionally}.
487		*
488		* @param mayInterruptIfRunning this value is ignored in the
489	<	* default implementation because tasks are not in general
489	>	* default implementation because tasks are not
490		* cancelled via interruption
491		*
492		* @return {@code true} if this task is now cancelled
493		*/
494		public boolean cancel(boolean mayInterruptIfRunning) {
495		setCompletion(CANCELLED);
496	<	return (status & COMPLETION_MASK) == CANCELLED;
496	>	return status == CANCELLED;
497	>	}
498	>
499	>	/**
500	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
501	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
502	>	* exceptions, but if it does anyway, we have no recourse during
503	>	* shutdown, so guard against this case.
504	>	*/
505	>	final void cancelIgnoringExceptions() {
506	>	try {
507	>	cancel(false);
508	>	} catch (Throwable ignore) {
509	>	}
510	>	}
511	>
512	>	/**
513	>	* Cancels ignoring exceptions if worker is terminating
514	>	*/
515	>	final void cancelIfTerminating() {
516	>	Thread t = Thread.currentThread();
517	>	if ((t instanceof ForkJoinWorkerThread) &&
518	>	((ForkJoinWorkerThread) t).isTerminating()) {
519	>	try {
520	>	cancel(false);
521	>	} catch (Throwable ignore) {
522	>	}
523	>	}
524	>	}
525	>
526	>	public final boolean isDone() {
527	>	return status < 0;
528	>	}
529	>
530	>	public final boolean isCancelled() {
531	>	return status == CANCELLED;
532		}
533
534		/**
#	Line 720 | Line 537 | public abstract class ForkJoinTask<V> im
537		* @return {@code true} if this task threw an exception or was cancelled
538		*/
539		public final boolean isCompletedAbnormally() {
540	<	return (status & COMPLETION_MASK) < NORMAL;
540	>	return status < NORMAL;
541	>	}
542	>
543	>	/**
544	>	* Returns {@code true} if this task completed without throwing an
545	>	* exception and was not cancelled.
546	>	*
547	>	* @return {@code true} if this task completed without throwing an
548	>	* exception and was not cancelled
549	>	*/
550	>	public final boolean isCompletedNormally() {
551	>	return status == NORMAL;
552		}
553
554		/**
555		* Returns the exception thrown by the base computation, or a
556	<	* CancellationException if cancelled, or null if none or if the
557	<	* method has not yet completed.
556	>	* {@code CancellationException} if cancelled, or {@code null} if
557	>	* none or if the method has not yet completed.
558		*
559		* @return the exception, or {@code null} if none
560		*/
561		public final Throwable getException() {
562	<	int s = status & COMPLETION_MASK;
563	<	if (s >= NORMAL)
564	<	return null;
565	<	if (s == CANCELLED)
738	<	return new CancellationException();
739	<	return exceptionMap.get(this);
562	>	int s = status;
563	>	return ((s >= NORMAL)    ? null :
564	>	(s == CANCELLED) ? new CancellationException() :
565	>	exceptionMap.get(this));
566		}
567
568		/**
#	Line 749 | Line 575 | public abstract class ForkJoinTask<V> im
575		* overridable, but overridden versions must invoke {@code super}
576		* implementation to maintain guarantees.
577		*
578	<	* @param ex the exception to throw. If this exception is
579	<	* not a RuntimeException or Error, the actual exception thrown
580	<	* will be a RuntimeException with cause ex.
578	>	* @param ex the exception to throw. If this exception is not a
579	>	* {@code RuntimeException} or {@code Error}, the actual exception
580	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
581		*/
582		public void completeExceptionally(Throwable ex) {
583	<	setDoneExceptionally((ex instanceof RuntimeException) ||
584	<	(ex instanceof Error) ? ex :
585	<	new RuntimeException(ex));
583	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
584	>	(ex instanceof Error) ? ex :
585	>	new RuntimeException(ex));
586		}
587
588		/**
#	Line 775 | Line 601 | public abstract class ForkJoinTask<V> im
601		try {
602		setRawResult(value);
603		} catch (Throwable rex) {
604	<	setDoneExceptionally(rex);
604	>	setExceptionalCompletion(rex);
605		return;
606		}
607	<	setNormalCompletion();
607	>	setCompletion(NORMAL);
608		}
609
610		public final V get() throws InterruptedException, ExecutionException {
611	<	ForkJoinWorkerThread w = getWorker();
612	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
613	<	awaitDone(w, true);
614	<	return reportFutureResult();
611	>	quietlyJoin();
612	>	if (Thread.interrupted())
613	>	throw new InterruptedException();
614	>	int s = status;
615	>	if (s < NORMAL) {
616	>	Throwable ex;
617	>	if (s == CANCELLED)
618	>	throw new CancellationException();
619	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
620	>	throw new ExecutionException(ex);
621	>	}
622	>	return getRawResult();
623		}
624
625		public final V get(long timeout, TimeUnit unit)
626		throws InterruptedException, ExecutionException, TimeoutException {
627	<	long nanos = unit.toNanos(timeout);
628	<	ForkJoinWorkerThread w = getWorker();
629	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
630	<	awaitDone(w, nanos);
631	<	return reportTimedFutureResult();
632	<	}
633	<
800	<	/**
801	<	* Possibly executes other tasks until this task is ready, then
802	<	* returns the result of the computation.  This method may be more
803	<	* efficient than {@code join}, but is only applicable when
804	<	* there are no potential dependencies between continuation of the
805	<	* current task and that of any other task that might be executed
806	<	* while helping. (This usually holds for pure divide-and-conquer
807	<	* tasks). This method may be invoked only from within
808	<	* ForkJoinTask computations (as may be determined using method
809	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
810	<	* result in exceptions or errors, possibly including
811	<	* ClassCastException.
812	<	*
813	<	* @return the computed result
814	<	*/
815	<	public final V helpJoin() {
816	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
817	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
818	<	reportException(busyJoin(w));
819	<	return getRawResult();
820	<	}
821	<
822	<	/**
823	<	* Possibly executes other tasks until this task is ready.  This
824	<	* method may be invoked only from within ForkJoinTask
825	<	* computations (as may be determined using method {@link
826	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
827	<	* in exceptions or errors, possibly including ClassCastException.
828	<	*/
829	<	public final void quietlyHelpJoin() {
830	<	if (status >= 0) {
831	<	ForkJoinWorkerThread w =
832	<	(ForkJoinWorkerThread) Thread.currentThread();
833	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
834	<	busyJoin(w);
627	>	Thread t = Thread.currentThread();
628	>	ForkJoinPool pool;
629	>	if (t instanceof ForkJoinWorkerThread) {
630	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
631	>	if (status >= 0 && w.unpushTask(this))
632	>	quietlyExec();
633	>	pool = w.pool;
634		}
635	+	else
636	+	pool = null;
637	+	/*
638	+	* Timed wait loop intermixes cases for FJ (pool != null) and
639	+	* non FJ threads. For FJ, decrement pool count but don't try
640	+	* for replacement; increment count on completion. For non-FJ,
641	+	* deal with interrupts. This is messy, but a little less so
642	+	* than is splitting the FJ and nonFJ cases.
643	+	*/
644	+	boolean interrupted = false;
645	+	boolean dec = false; // true if pool count decremented
646	+	for (;;) {
647	+	if (Thread.interrupted() && pool == null) {
648	+	interrupted = true;
649	+	break;
650	+	}
651	+	int s = status;
652	+	if (s < 0)
653	+	break;
654	+	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
655	+	long startTime = System.nanoTime();
656	+	long nanos = unit.toNanos(timeout);
657	+	long nt; // wait time
658	+	while (status >= 0 &&
659	+	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
660	+	if (pool != null && !dec)
661	+	dec = pool.tryDecrementRunningCount();
662	+	else {
663	+	long ms = nt / 1000000;
664	+	int ns = (int) (nt % 1000000);
665	+	try {
666	+	synchronized(this) {
667	+	if (status >= 0)
668	+	wait(ms, ns);
669	+	}
670	+	} catch (InterruptedException ie) {
671	+	if (pool != null)
672	+	cancelIfTerminating();
673	+	else {
674	+	interrupted = true;
675	+	break;
676	+	}
677	+	}
678	+	}
679	+	}
680	+	break;
681	+	}
682	+	}
683	+	if (pool != null && dec)
684	+	pool.incrementRunningCount();
685	+	if (interrupted)
686	+	throw new InterruptedException();
687	+	int es = status;
688	+	if (es != NORMAL) {
689	+	Throwable ex;
690	+	if (es == CANCELLED)
691	+	throw new CancellationException();
692	+	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
693	+	throw new ExecutionException(ex);
694	+	throw new TimeoutException();
695	+	}
696	+	return getRawResult();
697		}
698
699		/**
700	<	* Joins this task, without returning its result or throwing an
700	>	* Joins this task, without returning its result or throwing its
701		* exception. This method may be useful when processing
702		* collections of tasks when some have been cancelled or otherwise
703		* known to have aborted.
704		*/
705		public final void quietlyJoin() {
706	<	if (status >= 0) {
707	<	ForkJoinWorkerThread w = getWorker();
708	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
709	<	awaitDone(w, true);
706	>	Thread t;
707	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
708	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
709	>	if (status >= 0) {
710	>	if (w.unpushTask(this)) {
711	>	boolean completed;
712	>	try {
713	>	completed = exec();
714	>	} catch (Throwable rex) {
715	>	setExceptionalCompletion(rex);
716	>	return;
717	>	}
718	>	if (completed) {
719	>	setCompletion(NORMAL);
720	>	return;
721	>	}
722	>	}
723	>	w.joinTask(this);
724	>	}
725		}
726	+	else
727	+	externalAwaitDone();
728		}
729
730		/**
731		* Commences performing this task and awaits its completion if
732	<	* necessary, without returning its result or throwing an
732	>	* necessary, without returning its result or throwing its
733		* exception. This method may be useful when processing
734		* collections of tasks when some have been cancelled or otherwise
735		* known to have aborted.
736		*/
737		public final void quietlyInvoke() {
738	<	if (status >= 0 && !tryQuietlyInvoke())
739	<	quietlyJoin();
738	>	if (status >= 0) {
739	>	boolean completed;
740	>	try {
741	>	completed = exec();
742	>	} catch (Throwable rex) {
743	>	setExceptionalCompletion(rex);
744	>	return;
745	>	}
746	>	if (completed)
747	>	setCompletion(NORMAL);
748	>	else
749	>	quietlyJoin();
750	>	}
751		}
752
753		/**
754		* Possibly executes tasks until the pool hosting the current task
755	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
756	<	* designs in which many tasks are forked, but none are explicitly
757	<	* joined, instead executing them until all are processed.  This
758	<	* method may be invoked only from within ForkJoinTask
759	<	* computations (as may be determined using method {@link
760	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
761	<	* in exceptions or errors, possibly including ClassCastException.
755	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
756	>	* be of use in designs in which many tasks are forked, but none
757	>	* are explicitly joined, instead executing them until all are
758	>	* processed.
759	>	*
760	>	* <p>This method may be invoked only from within {@code
761	>	* ForkJoinTask} computations (as may be determined using method
762	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
763	>	* result in exceptions or errors, possibly including {@code
764	>	* ClassCastException}.
765		*/
766		public static void helpQuiesce() {
767		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 882 | Line 774 | public abstract class ForkJoinTask<V> im
774		* this task, but only if reuse occurs when this task has either
775		* never been forked, or has been forked, then completed and all
776		* outstanding joins of this task have also completed. Effects
777	<	* under any other usage conditions are not guaranteed, and are
778	<	* discouraged. This method may be useful when executing
777	>	* under any other usage conditions are not guaranteed.
778	>	* This method may be useful when executing
779		* pre-constructed trees of subtasks in loops.
780		*/
781		public void reinitialize() {
782	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
782	>	if (status == EXCEPTIONAL)
783		exceptionMap.remove(this);
784		status = 0;
785		}
#	Line 922 | Line 814 | public abstract class ForkJoinTask<V> im
814		* by the current thread, and has not commenced executing in
815		* another thread.  This method may be useful when arranging
816		* alternative local processing of tasks that could have been, but
817	<	* were not, stolen. This method may be invoked only from within
818	<	* ForkJoinTask computations (as may be determined using method
819	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
820	<	* result in exceptions or errors, possibly including
821	<	* ClassCastException.
817	>	* were not, stolen.
818	>	*
819	>	* <p>This method may be invoked only from within {@code
820	>	* ForkJoinTask} computations (as may be determined using method
821	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
822	>	* result in exceptions or errors, possibly including {@code
823	>	* ClassCastException}.
824		*
825		* @return {@code true} if unforked
826		*/
#	Line 939 | Line 833 | public abstract class ForkJoinTask<V> im
833		* Returns an estimate of the number of tasks that have been
834		* forked by the current worker thread but not yet executed. This
835		* value may be useful for heuristic decisions about whether to
836	<	* fork other tasks.  This method may be invoked only from within
837	<	* ForkJoinTask computations (as may be determined using method
838	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
839	<	* result in exceptions or errors, possibly including
840	<	* ClassCastException.
836	>	* fork other tasks.
837	>	*
838	>	* <p>This method may be invoked only from within {@code
839	>	* ForkJoinTask} computations (as may be determined using method
840	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
841	>	* result in exceptions or errors, possibly including {@code
842	>	* ClassCastException}.
843	>	*
844		* @return the number of tasks
845		*/
846		public static int getQueuedTaskCount() {
#	Line 959 | Line 856 | public abstract class ForkJoinTask<V> im
856		* usages of ForkJoinTasks, at steady state, each worker should
857		* aim to maintain a small constant surplus (for example, 3) of
858		* tasks, and to process computations locally if this threshold is
859	<	* exceeded.  This method may be invoked only from within
860	<	* ForkJoinTask computations (as may be determined using method
861	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
862	<	* result in exceptions or errors, possibly including
863	<	* ClassCastException.  *
859	>	* exceeded.
860	>	*
861	>	* <p>This method may be invoked only from within {@code
862	>	* ForkJoinTask} computations (as may be determined using method
863	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
864	>	* result in exceptions or errors, possibly including {@code
865	>	* ClassCastException}.
866	>	*
867		* @return the surplus number of tasks, which may be negative
868		*/
869		public static int getSurplusQueuedTaskCount() {
#	Line 999 | Line 899 | public abstract class ForkJoinTask<V> im
899		* called otherwise. The return value controls whether this task
900		* is considered to be done normally. It may return false in
901		* asynchronous actions that require explicit invocations of
902	<	* {@link #complete} to become joinable. It may throw exceptions
903	<	* to indicate abnormal exit.
902	>	* {@link #complete} to become joinable. It may also throw an
903	>	* (unchecked) exception to indicate abnormal exit.
904		*
905		* @return {@code true} if completed normally
1006	–	* @throws Error or RuntimeException if encountered during computation
906		*/
907		protected abstract boolean exec();
908
#	Line 1015 | Line 914 | public abstract class ForkJoinTask<V> im
914		* null even if a task exists but cannot be accessed without
915		* contention with other threads.  This method is designed
916		* primarily to support extensions, and is unlikely to be useful
917	<	* otherwise.  This method may be invoked only from within
918	<	* ForkJoinTask computations (as may be determined using method
919	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
920	<	* result in exceptions or errors, possibly including
921	<	* ClassCastException.
917	>	* otherwise.
918	>	*
919	>	* <p>This method may be invoked only from within {@code
920	>	* ForkJoinTask} computations (as may be determined using method
921	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
922	>	* result in exceptions or errors, possibly including {@code
923	>	* ClassCastException}.
924		*
925		* @return the next task, or {@code null} if none are available
926		*/
#	Line 1032 | Line 933 | public abstract class ForkJoinTask<V> im
933		* Unschedules and returns, without executing, the next task
934		* queued by the current thread but not yet executed.  This method
935		* is designed primarily to support extensions, and is unlikely to
936	<	* be useful otherwise.  This method may be invoked only from
937	<	* within ForkJoinTask computations (as may be determined using
938	<	* method {@link #inForkJoinPool}). Attempts to invoke in other
939	<	* contexts result in exceptions or errors, possibly including
940	<	* ClassCastException.
936	>	* be useful otherwise.
937	>	*
938	>	* <p>This method may be invoked only from within {@code
939	>	* ForkJoinTask} computations (as may be determined using method
940	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
941	>	* result in exceptions or errors, possibly including {@code
942	>	* ClassCastException}.
943		*
944		* @return the next task, or {@code null} if none are available
945		*/
#	Line 1053 | Line 956 | public abstract class ForkJoinTask<V> im
956		* {@code null} result does not necessarily imply quiescence
957		* of the pool this task is operating in.  This method is designed
958		* primarily to support extensions, and is unlikely to be useful
959	<	* otherwise.  This method may be invoked only from within
960	<	* ForkJoinTask computations (as may be determined using method
961	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
962	<	* result in exceptions or errors, possibly including
963	<	* ClassCastException.
959	>	* otherwise.
960	>	*
961	>	* <p>This method may be invoked only from within {@code
962	>	* ForkJoinTask} computations (as may be determined using method
963	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
964	>	* result in exceptions or errors, possibly including {@code
965	>	* ClassCastException}.
966		*
967		* @return a task, or {@code null} if none are available
968		*/
#	Line 1122 | Line 1027 | public abstract class ForkJoinTask<V> im
1027		}
1028
1029		/**
1030	<	* Returns a new ForkJoinTask that performs the {@code run}
1031	<	* method of the given Runnable as its action, and returns a null
1032	<	* result upon {@code join}.
1030	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1031	>	* method of the given {@code Runnable} as its action, and returns
1032	>	* a null result upon {@link #join}.
1033		*
1034		* @param runnable the runnable action
1035		* @return the task
#	Line 1134 | Line 1039 | public abstract class ForkJoinTask<V> im
1039		}
1040
1041		/**
1042	<	* Returns a new ForkJoinTask that performs the {@code run}
1043	<	* method of the given Runnable as its action, and returns the
1044	<	* given result upon {@code join}.
1042	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1043	>	* method of the given {@code Runnable} as its action, and returns
1044	>	* the given result upon {@link #join}.
1045		*
1046		* @param runnable the runnable action
1047		* @param result the result upon completion
#	Line 1147 | Line 1052 | public abstract class ForkJoinTask<V> im
1052		}
1053
1054		/**
1055	<	* Returns a new ForkJoinTask that performs the {@code call}
1056	<	* method of the given Callable as its action, and returns its
1057	<	* result upon {@code join}, translating any checked
1058	<	* exceptions encountered into {@code RuntimeException}.
1055	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1056	>	* method of the given {@code Callable} as its action, and returns
1057	>	* its result upon {@link #join}, translating any checked exceptions
1058	>	* encountered into {@code RuntimeException}.
1059		*
1060		* @param callable the callable action
1061		* @return the task
#	Line 1164 | Line 1069 | public abstract class ForkJoinTask<V> im
1069		private static final long serialVersionUID = -7721805057305804111L;
1070
1071		/**
1072	<	* Save the state to a stream.
1072	>	* Saves the state to a stream.
1073		*
1074		* @serialData the current run status and the exception thrown
1075		* during execution, or {@code null} if none
#	Line 1177 | Line 1082 | public abstract class ForkJoinTask<V> im
1082		}
1083
1084		/**
1085	<	* Reconstitute the instance from a stream.
1085	>	* Reconstitutes the instance from a stream.
1086		*
1087		* @param s the stream
1088		*/
1089		private void readObject(java.io.ObjectInputStream s)
1090		throws java.io.IOException, ClassNotFoundException {
1091		s.defaultReadObject();
1187	–	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1188	–	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1092		Object ex = s.readObject();
1093		if (ex != null)
1094	<	setDoneExceptionally((Throwable) ex);
1094	>	setExceptionalCompletion((Throwable) ex);
1095		}
1096
1097		// Unsafe mechanics

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