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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.32 by dl, Mon Aug 3 13:01:15 2009 UTC vs.
Revision 1.78 by jsr166, Fri Jun 3 14:20:43 2011 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Doug Lea with assistance from members of JCP JSR-166
3		* Expert Group and released to the public domain, as explained at
4	<	* http://creativecommons.org/licenses/publicdomain
4	>	* http://creativecommons.org/publicdomain/zero/1.0/
5		*/
6
7		package jsr166y;
8
9	–	import java.util.concurrent.*;
10	–
9		import java.io.Serializable;
10		import java.util.Collection;
11		import java.util.Collections;
12		import java.util.List;
13		import java.util.RandomAccess;
14		import java.util.Map;
15	<	import java.util.WeakHashMap;
15	>	import java.lang.ref.WeakReference;
16	>	import java.lang.ref.ReferenceQueue;
17	>	import java.util.concurrent.Callable;
18	>	import java.util.concurrent.CancellationException;
19	>	import java.util.concurrent.ExecutionException;
20	>	import java.util.concurrent.Executor;
21	>	import java.util.concurrent.ExecutorService;
22	>	import java.util.concurrent.Future;
23	>	import java.util.concurrent.RejectedExecutionException;
24	>	import java.util.concurrent.RunnableFuture;
25	>	import java.util.concurrent.TimeUnit;
26	>	import java.util.concurrent.TimeoutException;
27	>	import java.util.concurrent.locks.ReentrantLock;
28	>	import java.lang.reflect.Constructor;
29
30		/**
31		* Abstract base class for tasks that run within a {@link ForkJoinPool}.
#	Line 28 | Line 39 | import java.util.WeakHashMap;
39		* start other subtasks.  As indicated by the name of this class,
40		* many programs using {@code ForkJoinTask} employ only methods
41		* {@link #fork} and {@link #join}, or derivatives such as {@link
42	<	* #invokeAll}.  However, this class also provides a number of other
43	<	* methods that can come into play in advanced usages, as well as
44	<	* extension mechanics that allow support of new forms of fork/join
45	<	* processing.
42	>	* #invokeAll(ForkJoinTask...) invokeAll}.  However, this class also
43	>	* provides a number of other methods that can come into play in
44	>	* advanced usages, as well as extension mechanics that allow
45	>	* support of new forms of fork/join processing.
46		*
47		* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
48		* The efficiency of {@code ForkJoinTask}s stems from a set of
#	Line 56 | Line 67 | import java.util.WeakHashMap;
67		* exceptions such as {@code IOExceptions} to be thrown. However,
68		* computations may still encounter unchecked exceptions, that are
69		* rethrown to callers attempting to join them. These exceptions may
70	<	* additionally include RejectedExecutionExceptions stemming from
71	<	* internal resource exhaustion such as failure to allocate internal
72	<	* task queues.
70	>	* additionally include {@link RejectedExecutionException} stemming
71	>	* from internal resource exhaustion, such as failure to allocate
72	>	* internal task queues. Rethrown exceptions behave in the same way as
73	>	* regular exceptions, but, when possible, contain stack traces (as
74	>	* displayed for example using {@code ex.printStackTrace()}) of both
75	>	* the thread that initiated the computation as well as the thread
76	>	* actually encountering the exception; minimally only the latter.
77		*
78		* <p>The primary method for awaiting completion and extracting
79		* results of a task is {@link #join}, but there are several variants:
80		* The {@link Future#get} methods support interruptible and/or timed
81		* waits for completion and report results using {@code Future}
82	<	* conventions. Method {@link #helpJoin} enables callers to actively
83	<	* execute other tasks while awaiting joins, which is sometimes more
84	<	* efficient but only applies when all subtasks are known to be
85	<	* strictly tree-structured. Method {@link #invoke} is semantically
71	<	* equivalent to {@code fork(); join()} but always attempts to
72	<	* begin execution in the current thread. The "<em>quiet</em>" forms
73	<	* of these methods do not extract results or report exceptions. These
82	>	* conventions. Method {@link #invoke} is semantically
83	>	* equivalent to {@code fork(); join()} but always attempts to begin
84	>	* execution in the current thread. The "<em>quiet</em>" forms of
85	>	* these methods do not extract results or report exceptions. These
86		* may be useful when a set of tasks are being executed, and you need
87		* to delay processing of results or exceptions until all complete.
88		* Method {@code invokeAll} (available in multiple versions)
89		* performs the most common form of parallel invocation: forking a set
90		* of tasks and joining them all.
91		*
92	+	* <p>The execution status of tasks may be queried at several levels
93	+	* of detail: {@link #isDone} is true if a task completed in any way
94	+	* (including the case where a task was cancelled without executing);
95	+	* {@link #isCompletedNormally} is true if a task completed without
96	+	* cancellation or encountering an exception; {@link #isCancelled} is
97	+	* true if the task was cancelled (in which case {@link #getException}
98	+	* returns a {@link java.util.concurrent.CancellationException}); and
99	+	* {@link #isCompletedAbnormally} is true if a task was either
100	+	* cancelled or encountered an exception, in which case {@link
101	+	* #getException} will return either the encountered exception or
102	+	* {@link java.util.concurrent.CancellationException}.
103	+	*
104		* <p>The ForkJoinTask class is not usually directly subclassed.
105		* Instead, you subclass one of the abstract classes that support a
106		* particular style of fork/join processing, typically {@link
#	Line 91 | Line 115 | import java.util.WeakHashMap;
115		* ForkJoinTasks (as may be determined using method {@link
116		* #inForkJoinPool}).  Attempts to invoke them in other contexts
117		* result in exceptions or errors, possibly including
118	<	* ClassCastException.
118	>	* {@code ClassCastException}.
119	>	*
120	>	* <p>Method {@link #join} and its variants are appropriate for use
121	>	* only when completion dependencies are acyclic; that is, the
122	>	* parallel computation can be described as a directed acyclic graph
123	>	* (DAG). Otherwise, executions may encounter a form of deadlock as
124	>	* tasks cyclically wait for each other.  However, this framework
125	>	* supports other methods and techniques (for example the use of
126	>	* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that
127	>	* may be of use in constructing custom subclasses for problems that
128	>	* are not statically structured as DAGs.
129		*
130		* <p>Most base support methods are {@code final}, to prevent
131		* overriding of implementations that are intrinsically tied to the
#	Line 107 | Line 141 | import java.util.WeakHashMap;
141		* computation. Large tasks should be split into smaller subtasks,
142		* usually via recursive decomposition. As a very rough rule of thumb,
143		* a task should perform more than 100 and less than 10000 basic
144	<	* computational steps. If tasks are too big, then parallelism cannot
145	<	* improve throughput. If too small, then memory and internal task
146	<	* maintenance overhead may overwhelm processing.
144	>	* computational steps, and should avoid indefinite looping. If tasks
145	>	* are too big, then parallelism cannot improve throughput. If too
146	>	* small, then memory and internal task maintenance overhead may
147	>	* overwhelm processing.
148		*
149	<	* <p>This class provides {@code adapt} methods for {@link
150	<	* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
151	<	* may be of use when mixing execution of ForkJoinTasks with other
152	<	* kinds of tasks. When all tasks are of this form, consider using a
118	<	* pool in {@link ForkJoinPool#setAsyncMode}.
149	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
150	>	* and {@link Callable}, that may be of use when mixing execution of
151	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
152	>	* of this form, consider using a pool constructed in <em>asyncMode</em>.
153		*
154		* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
155		* used in extensions such as remote execution frameworks. It is
#	Line 127 | Line 161 | import java.util.WeakHashMap;
161		*/
162		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
163
164	<	/**
165	<	* Run control status bits packed into a single int to minimize
166	<	* footprint and to ensure atomicity (via CAS).  Status is
167	<	* initially zero, and takes on nonnegative values until
168	<	* completed, upon which status holds COMPLETED. CANCELLED, or
169	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
170	<	* blocking waits by other threads have SIGNAL_MASK bits set --
171	<	* bit 15 for external (nonFJ) waits, and the rest a count of
172	<	* waiting FJ threads.  (This representation relies on
173	<	* ForkJoinPool max thread limits). Completion of a stolen task
174	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
175	<	* though suboptimal for some purposes, we use basic builtin
176	<	* wait/notify to take advantage of "monitor inflation" in JVMs
177	<	* that we would otherwise need to emulate to avoid adding further
178	<	* per-task bookkeeping overhead. Note that bits 16-28 are
179	<	* currently unused. Also value 0x80000000 is available as spare
180	<	* completion value.
181	<	*/
182	<	volatile int status; // accessed directly by pool and workers
183	<
184	<	static final int COMPLETION_MASK      = 0xe0000000;
185	<	static final int NORMAL               = 0xe0000000; // == mask
186	<	static final int CANCELLED            = 0xc0000000;
187	<	static final int EXCEPTIONAL          = 0xa0000000;
188	<	static final int SIGNAL_MASK          = 0x0000ffff;
189	<	static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
190	<	static final int EXTERNAL_SIGNAL      = 0x00008000; // top bit of low word
157	<
158	<	/**
159	<	* Table of exceptions thrown by tasks, to enable reporting by
160	<	* callers. Because exceptions are rare, we don't directly keep
161	<	* them with task objects, but instead use a weak ref table.  Note
162	<	* that cancellation exceptions don't appear in the table, but are
163	<	* instead recorded as status values.
164	<	* TODO: Use ConcurrentReferenceHashMap
165	<	*/
166	<	static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
167	<	Collections.synchronizedMap
168	<	(new WeakHashMap<ForkJoinTask<?>, Throwable>());
169	<
170	<	// within-package utilities
171	<
172	<	/**
173	<	* Gets current worker thread, or null if not a worker thread.
164	>	/*
165	>	* See the internal documentation of class ForkJoinPool for a
166	>	* general implementation overview.  ForkJoinTasks are mainly
167	>	* responsible for maintaining their "status" field amidst relays
168	>	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
169	>	* methods of this class are more-or-less layered into (1) basic
170	>	* status maintenance (2) execution and awaiting completion (3)
171	>	* user-level methods that additionally report results. This is
172	>	* sometimes hard to see because this file orders exported methods
173	>	* in a way that flows well in javadocs.
174	>	*/
175	>
176	>	/*
177	>	* The status field holds run control status bits packed into a
178	>	* single int to minimize footprint and to ensure atomicity (via
179	>	* CAS).  Status is initially zero, and takes on nonnegative
180	>	* values until completed, upon which status holds value
181	>	* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
182	>	* waits by other threads have the SIGNAL bit set.  Completion of
183	>	* a stolen task with SIGNAL set awakens any waiters via
184	>	* notifyAll. Even though suboptimal for some purposes, we use
185	>	* basic builtin wait/notify to take advantage of "monitor
186	>	* inflation" in JVMs that we would otherwise need to emulate to
187	>	* avoid adding further per-task bookkeeping overhead.  We want
188	>	* these monitors to be "fat", i.e., not use biasing or thin-lock
189	>	* techniques, so use some odd coding idioms that tend to avoid
190	>	* them.
191		*/
175	–	static ForkJoinWorkerThread getWorker() {
176	–	Thread t = Thread.currentThread();
177	–	return ((t instanceof ForkJoinWorkerThread) ?
178	–	(ForkJoinWorkerThread) t : null);
179	–	}
180	–
181	–	final boolean casStatus(int cmp, int val) {
182	–	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
183	–	}
192
193	<	/**
194	<	* Workaround for not being able to rethrow unchecked exceptions.
195	<	*/
196	<	static void rethrowException(Throwable ex) {
197	<	if (ex != null)
198	<	UNSAFE.throwException(ex);
191	<	}
192	<
193	<	// Setting completion status
193	>	/** The run status of this task */
194	>	volatile int status; // accessed directly by pool and workers
195	>	private static final int NORMAL      = -1;
196	>	private static final int CANCELLED   = -2;
197	>	private static final int EXCEPTIONAL = -3;
198	>	private static final int SIGNAL      =  1;
199
200		/**
201	<	* Marks completion and wakes up threads waiting to join this task.
201	>	* Marks completion and wakes up threads waiting to join this task,
202	>	* also clearing signal request bits.
203		*
204		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
205	+	* @return completion status on exit
206		*/
207	<	final void setCompletion(int completion) {
208	<	ForkJoinPool pool = getPool();
209	<	if (pool != null) {
210	<	int s; // Clear signal bits while setting completion status
211	<	do {} while ((s = status) >= 0 && !casStatus(s, completion));
212	<
213	<	if ((s & SIGNAL_MASK) != 0) {
214	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
208	<	pool.updateRunningCount(s);
209	<	synchronized (this) { notifyAll(); }
207	>	private int setCompletion(int completion) {
208	>	for (int s;;) {
209	>	if ((s = status) < 0)
210	>	return s;
211	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
212	>	if (s != 0)
213	>	synchronized (this) { notifyAll(); }
214	>	return completion;
215		}
216		}
212	–	else
213	–	externallySetCompletion(completion);
217		}
218
219		/**
220	<	* Version of setCompletion for non-FJ threads.  Leaves signal
221	<	* bits for unblocked threads to adjust, and always notifies.
220	>	* Tries to block a worker thread until completed or timed out.
221	>	* Uses Object.wait time argument conventions.
222	>	* May fail on contention or interrupt.
223	>	*
224	>	* @param millis if > 0, wait time.
225		*/
226	<	private void externallySetCompletion(int completion) {
226	>	final void tryAwaitDone(long millis) {
227		int s;
222	–	do {} while ((s = status) >= 0 &&
223	–	!casStatus(s, (s & SIGNAL_MASK) | completion));
224	–	synchronized (this) { notifyAll(); }
225	–	}
226	–
227	–	/**
228	–	* Sets status to indicate normal completion.
229	–	*/
230	–	final void setNormalCompletion() {
231	–	// Try typical fast case -- single CAS, no signal, not already done.
232	–	// Manually expand casStatus to improve chances of inlining it
233	–	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
234	–	setCompletion(NORMAL);
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
228		try {
229	<	while (status >= 0)
230	<	synchronized (this) { if (status >= 0) wait(); }
231	<	} catch (InterruptedException ie) {
232	<	onInterruptedWait();
233	<	}
234	<	}
235	<
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));
229	>	if (((s = status) > 0 ||
230	>	(s == 0 &&
231	>	UNSAFE.compareAndSwapInt(this, statusOffset, 0, SIGNAL))) &&
232	>	status > 0) {
233	>	synchronized (this) {
234	>	if (status > 0)
235	>	wait(millis);
236		}
265	–	} catch (InterruptedException ie) {
266	–	onInterruptedWait();
237		}
238	+	} catch (InterruptedException ie) {
239	+	// caller must check termination
240		}
241		}
242
271	–	// Awaiting completion
272	–
243		/**
244	<	* Sets status to indicate there is joiner, then waits for join,
245	<	* surrounded with pool notifications.
276	<	*
277	<	* @return status upon exit
244	>	* Blocks a non-worker-thread until completion.
245	>	* @return status upon completion
246		*/
247	<	private int awaitDone(ForkJoinWorkerThread w,
280	<	boolean maintainParallelism) {
281	<	ForkJoinPool pool = (w == null) ? null : w.pool;
247	>	private int externalAwaitDone() {
248		int s;
249	<	while ((s = status) >= 0) {
250	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
251	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
252	<	doAwaitDone();
253	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
254	<	adjustPoolCountsOnUnblock(pool);
255	<	break;
249	>	if ((s = status) >= 0) {
250	>	boolean interrupted = false;
251	>	synchronized (this) {
252	>	while ((s = status) >= 0) {
253	>	if (s == 0)
254	>	UNSAFE.compareAndSwapInt(this, statusOffset,
255	>	0, SIGNAL);
256	>	else {
257	>	try {
258	>	wait();
259	>	} catch (InterruptedException ie) {
260	>	interrupted = true;
261	>	}
262	>	}
263	>	}
264		}
265	+	if (interrupted)
266	+	Thread.currentThread().interrupt();
267		}
268		return s;
269		}
270
271		/**
272	<	* Timed version of awaitDone
297	<	*
298	<	* @return status upon exit
272	>	* Blocks a non-worker-thread until completion or interruption or timeout.
273		*/
274	<	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
275	<	ForkJoinPool pool = (w == null) ? null : w.pool;
274	>	private int externalInterruptibleAwaitDone(long millis)
275	>	throws InterruptedException {
276		int s;
277	<	while ((s = status) >= 0) {
278	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
279	<	long startTime = System.nanoTime();
280	<	if (pool == null || !pool.preJoin(this, false))
281	<	doAwaitDone(startTime, nanos);
282	<	if ((s = status) >= 0) {
283	<	adjustPoolCountsOnCancelledWait(pool);
284	<	s = status;
277	>	if (Thread.interrupted())
278	>	throw new InterruptedException();
279	>	if ((s = status) >= 0) {
280	>	synchronized (this) {
281	>	while ((s = status) >= 0) {
282	>	if (s == 0)
283	>	UNSAFE.compareAndSwapInt(this, statusOffset,
284	>	0, SIGNAL);
285	>	else {
286	>	wait(millis);
287	>	if (millis > 0L)
288	>	break;
289	>	}
290		}
312	–	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
313	–	adjustPoolCountsOnUnblock(pool);
314	–	break;
291		}
292		}
293		return s;
294		}
295
296		/**
297	<	* Notifies pool that thread is unblocked. Called by signalled
298	<	* threads when woken by non-FJ threads (which is atypical).
297	>	* Primary execution method for stolen tasks. Unless done, calls
298	>	* exec and records status if completed, but doesn't wait for
299	>	* completion otherwise.
300		*/
301	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
302	<	int s;
303	<	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
304	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
305	<	pool.updateRunningCount(s);
301	>	final void doExec() {
302	>	if (status >= 0) {
303	>	boolean completed;
304	>	try {
305	>	completed = exec();
306	>	} catch (Throwable rex) {
307	>	setExceptionalCompletion(rex);
308	>	return;
309	>	}
310	>	if (completed)
311	>	setCompletion(NORMAL); // must be outside try block
312	>	}
313		}
314
315		/**
316	<	* Notifies pool to adjust counts on cancelled or timed out wait.
316	>	* Primary mechanics for join, get, quietlyJoin.
317	>	* @return status upon completion
318		*/
319	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
320	<	if (pool != null) {
321	<	int s;
322	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
323	<	if (casStatus(s, s - 1)) {
324	<	pool.updateRunningCount(1);
325	<	break;
319	>	private int doJoin() {
320	>	Thread t; ForkJoinWorkerThread w; int s; boolean completed;
321	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
322	>	if ((s = status) < 0)
323	>	return s;
324	>	if ((w = (ForkJoinWorkerThread)t).unpushTask(this)) {
325	>	try {
326	>	completed = exec();
327	>	} catch (Throwable rex) {
328	>	return setExceptionalCompletion(rex);
329		}
330	+	if (completed)
331	+	return setCompletion(NORMAL);
332		}
333	+	return w.joinTask(this);
334		}
335	+	else
336	+	return externalAwaitDone();
337		}
338
339		/**
340	<	* Handles interruptions during waits.
340	>	* Primary mechanics for invoke, quietlyInvoke.
341	>	* @return status upon completion
342		*/
343	<	private void onInterruptedWait() {
344	<	ForkJoinWorkerThread w = getWorker();
345	<	if (w == null)
346	<	Thread.currentThread().interrupt(); // re-interrupt
347	<	else if (w.isTerminating())
348	<	cancelIgnoringExceptions();
349	<	// else if FJworker, ignore interrupt
343	>	private int doInvoke() {
344	>	int s; boolean completed;
345	>	if ((s = status) < 0)
346	>	return s;
347	>	try {
348	>	completed = exec();
349	>	} catch (Throwable rex) {
350	>	return setExceptionalCompletion(rex);
351	>	}
352	>	if (completed)
353	>	return setCompletion(NORMAL);
354	>	else
355	>	return doJoin();
356		}
357
358	<	// Recording and reporting exceptions
359	<
360	<	private void setDoneExceptionally(Throwable rex) {
361	<	exceptionMap.put(this, rex);
362	<	setCompletion(EXCEPTIONAL);
363	<	}
358	>	// Exception table support
359
360		/**
361	<	* Throws the exception associated with status s.
361	>	* Table of exceptions thrown by tasks, to enable reporting by
362	>	* callers. Because exceptions are rare, we don't directly keep
363	>	* them with task objects, but instead use a weak ref table.  Note
364	>	* that cancellation exceptions don't appear in the table, but are
365	>	* instead recorded as status values.
366		*
367	<	* @throws the exception
367	>	* Note: These statics are initialized below in static block.
368		*/
369	<	private void reportException(int s) {
370	<	if ((s &= COMPLETION_MASK) < NORMAL) {
371	<	if (s == CANCELLED)
373	<	throw new CancellationException();
374	<	else
375	<	rethrowException(exceptionMap.get(this));
376	<	}
377	<	}
369	>	private static final ExceptionNode[] exceptionTable;
370	>	private static final ReentrantLock exceptionTableLock;
371	>	private static final ReferenceQueue<Object> exceptionTableRefQueue;
372
373		/**
374	<	* Returns result or throws exception using j.u.c.Future conventions.
381	<	* Only call when {@code isDone} known to be true.
374	>	* Fixed capacity for exceptionTable.
375		*/
376	<	private V reportFutureResult()
384	<	throws ExecutionException, InterruptedException {
385	<	int s = status & COMPLETION_MASK;
386	<	if (s < NORMAL) {
387	<	Throwable ex;
388	<	if (s == CANCELLED)
389	<	throw new CancellationException();
390	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
391	<	throw new ExecutionException(ex);
392	<	if (Thread.interrupted())
393	<	throw new InterruptedException();
394	<	}
395	<	return getRawResult();
396	<	}
376	>	private static final int EXCEPTION_MAP_CAPACITY = 32;
377
378		/**
379	<	* Returns result or throws exception using j.u.c.Future conventions
380	<	* with timeouts.
379	>	* Key-value nodes for exception table.  The chained hash table
380	>	* uses identity comparisons, full locking, and weak references
381	>	* for keys. The table has a fixed capacity because it only
382	>	* maintains task exceptions long enough for joiners to access
383	>	* them, so should never become very large for sustained
384	>	* periods. However, since we do not know when the last joiner
385	>	* completes, we must use weak references and expunge them. We do
386	>	* so on each operation (hence full locking). Also, some thread in
387	>	* any ForkJoinPool will call helpExpungeStaleExceptions when its
388	>	* pool becomes isQuiescent.
389		*/
390	<	private V reportTimedFutureResult()
391	<	throws InterruptedException, ExecutionException, TimeoutException {
392	<	Throwable ex;
393	<	int s = status & COMPLETION_MASK;
394	<	if (s == NORMAL)
395	<	return getRawResult();
396	<	if (s == CANCELLED)
397	<	throw new CancellationException();
398	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
399	<	throw new ExecutionException(ex);
412	<	if (Thread.interrupted())
413	<	throw new InterruptedException();
414	<	throw new TimeoutException();
390	>	static final class ExceptionNode extends WeakReference<ForkJoinTask<?>>{
391	>	final Throwable ex;
392	>	ExceptionNode next;
393	>	final long thrower;  // use id not ref to avoid weak cycles
394	>	ExceptionNode(ForkJoinTask<?> task, Throwable ex, ExceptionNode next) {
395	>	super(task, exceptionTableRefQueue);
396	>	this.ex = ex;
397	>	this.next = next;
398	>	this.thrower = Thread.currentThread().getId();
399	>	}
400		}
401
417	–	// internal execution methods
418	–
402		/**
403	<	* Calls exec, recording completion, and rethrowing exception if
421	<	* encountered. Caller should normally check status before calling.
403	>	* Records exception and sets exceptional completion.
404		*
405	<	* @return true if completed normally
405	>	* @return status on exit
406		*/
407	<	private boolean tryExec() {
408	<	try { // try block must contain only call to exec
409	<	if (!exec())
410	<	return false;
411	<	} catch (Throwable rex) {
412	<	setDoneExceptionally(rex);
413	<	rethrowException(rex);
414	<	return false; // not reached
407	>	private int setExceptionalCompletion(Throwable ex) {
408	>	int h = System.identityHashCode(this);
409	>	final ReentrantLock lock = exceptionTableLock;
410	>	lock.lock();
411	>	try {
412	>	expungeStaleExceptions();
413	>	ExceptionNode[] t = exceptionTable;
414	>	int i = h & (t.length - 1);
415	>	for (ExceptionNode e = t[i]; ; e = e.next) {
416	>	if (e == null) {
417	>	t[i] = new ExceptionNode(this, ex, t[i]);
418	>	break;
419	>	}
420	>	if (e.get() == this) // already present
421	>	break;
422	>	}
423	>	} finally {
424	>	lock.unlock();
425		}
426	<	setNormalCompletion();
435	<	return true;
426	>	return setCompletion(EXCEPTIONAL);
427		}
428
429		/**
430	<	* Main execution method used by worker threads. Invokes
440	<	* base computation unless already complete.
430	>	* Removes exception node and clears status
431		*/
432	<	final void quietlyExec() {
433	<	if (status >= 0) {
434	<	try {
435	<	if (!exec())
436	<	return;
437	<	} catch (Throwable rex) {
438	<	setDoneExceptionally(rex);
439	<	return;
432	>	private void clearExceptionalCompletion() {
433	>	int h = System.identityHashCode(this);
434	>	final ReentrantLock lock = exceptionTableLock;
435	>	lock.lock();
436	>	try {
437	>	ExceptionNode[] t = exceptionTable;
438	>	int i = h & (t.length - 1);
439	>	ExceptionNode e = t[i];
440	>	ExceptionNode pred = null;
441	>	while (e != null) {
442	>	ExceptionNode next = e.next;
443	>	if (e.get() == this) {
444	>	if (pred == null)
445	>	t[i] = next;
446	>	else
447	>	pred.next = next;
448	>	break;
449	>	}
450	>	pred = e;
451	>	e = next;
452		}
453	<	setNormalCompletion();
453	>	expungeStaleExceptions();
454	>	status = 0;
455	>	} finally {
456	>	lock.unlock();
457		}
458		}
459
460		/**
461	<	* Calls exec(), recording but not rethrowing exception.
462	<	* Caller should normally check status before calling.
461	>	* Returns a rethrowable exception for the given task, if
462	>	* available. To provide accurate stack traces, if the exception
463	>	* was not thrown by the current thread, we try to create a new
464	>	* exception of the same type as the one thrown, but with the
465	>	* recorded exception as its cause. If there is no such
466	>	* constructor, we instead try to use a no-arg constructor,
467	>	* followed by initCause, to the same effect. If none of these
468	>	* apply, or any fail due to other exceptions, we return the
469	>	* recorded exception, which is still correct, although it may
470	>	* contain a misleading stack trace.
471		*
472	<	* @return true if completed normally
472	>	* @return the exception, or null if none
473		*/
474	<	private boolean tryQuietlyInvoke() {
474	>	private Throwable getThrowableException() {
475	>	if (status != EXCEPTIONAL)
476	>	return null;
477	>	int h = System.identityHashCode(this);
478	>	ExceptionNode e;
479	>	final ReentrantLock lock = exceptionTableLock;
480	>	lock.lock();
481		try {
482	<	if (!exec())
483	<	return false;
484	<	} catch (Throwable rex) {
485	<	setDoneExceptionally(rex);
486	<	return false;
482	>	expungeStaleExceptions();
483	>	ExceptionNode[] t = exceptionTable;
484	>	e = t[h & (t.length - 1)];
485	>	while (e != null && e.get() != this)
486	>	e = e.next;
487	>	} finally {
488	>	lock.unlock();
489	>	}
490	>	Throwable ex;
491	>	if (e == null || (ex = e.ex) == null)
492	>	return null;
493	>	if (e.thrower != Thread.currentThread().getId()) {
494	>	Class<? extends Throwable> ec = ex.getClass();
495	>	try {
496	>	Constructor<?> noArgCtor = null;
497	>	Constructor<?>[] cs = ec.getConstructors();// public ctors only
498	>	for (int i = 0; i < cs.length; ++i) {
499	>	Constructor<?> c = cs[i];
500	>	Class<?>[] ps = c.getParameterTypes();
501	>	if (ps.length == 0)
502	>	noArgCtor = c;
503	>	else if (ps.length == 1 && ps[0] == Throwable.class)
504	>	return (Throwable)(c.newInstance(ex));
505	>	}
506	>	if (noArgCtor != null) {
507	>	Throwable wx = (Throwable)(noArgCtor.newInstance());
508	>	wx.initCause(ex);
509	>	return wx;
510	>	}
511	>	} catch (Exception ignore) {
512	>	}
513		}
514	<	setNormalCompletion();
470	<	return true;
514	>	return ex;
515		}
516
517		/**
518	<	* Cancels, ignoring any exceptions it throws.
518	>	* Poll stale refs and remove them. Call only while holding lock.
519		*/
520	<	final void cancelIgnoringExceptions() {
521	<	try {
522	<	cancel(false);
523	<	} catch (Throwable ignore) {
520	>	private static void expungeStaleExceptions() {
521	>	for (Object x; (x = exceptionTableRefQueue.poll()) != null;) {
522	>	if (x instanceof ExceptionNode) {
523	>	ForkJoinTask<?> key = ((ExceptionNode)x).get();
524	>	ExceptionNode[] t = exceptionTable;
525	>	int i = System.identityHashCode(key) & (t.length - 1);
526	>	ExceptionNode e = t[i];
527	>	ExceptionNode pred = null;
528	>	while (e != null) {
529	>	ExceptionNode next = e.next;
530	>	if (e == x) {
531	>	if (pred == null)
532	>	t[i] = next;
533	>	else
534	>	pred.next = next;
535	>	break;
536	>	}
537	>	pred = e;
538	>	e = next;
539	>	}
540	>	}
541		}
542		}
543
544		/**
545	<	* Main implementation of helpJoin
545	>	* If lock is available, poll stale refs and remove them.
546	>	* Called from ForkJoinPool when pools become quiescent.
547		*/
548	<	private int busyJoin(ForkJoinWorkerThread w) {
549	<	int s;
550	<	ForkJoinTask<?> t;
551	<	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
552	<	t.quietlyExec();
553	<	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
548	>	static final void helpExpungeStaleExceptions() {
549	>	final ReentrantLock lock = exceptionTableLock;
550	>	if (lock.tryLock()) {
551	>	try {
552	>	expungeStaleExceptions();
553	>	} finally {
554	>	lock.unlock();
555	>	}
556	>	}
557	>	}
558	>
559	>	/**
560	>	* Report the result of invoke or join; called only upon
561	>	* non-normal return of internal versions.
562	>	*/
563	>	private V reportResult() {
564	>	int s; Throwable ex;
565	>	if ((s = status) == CANCELLED)
566	>	throw new CancellationException();
567	>	if (s == EXCEPTIONAL && (ex = getThrowableException()) != null)
568	>	UNSAFE.throwException(ex);
569	>	return getRawResult();
570		}
571
572		// public methods
#	Line 497 | Line 575 | public abstract class ForkJoinTask<V> im
575		* Arranges to asynchronously execute this task.  While it is not
576		* necessarily enforced, it is a usage error to fork a task more
577		* than once unless it has completed and been reinitialized.
578	+	* Subsequent modifications to the state of this task or any data
579	+	* it operates on are not necessarily consistently observable by
580	+	* any thread other than the one executing it unless preceded by a
581	+	* call to {@link #join} or related methods, or a call to {@link
582	+	* #isDone} returning {@code true}.
583		*
584		* <p>This method may be invoked only from within {@code
585	<	* ForkJoinTask} computations (as may be determined using method
585	>	* ForkJoinPool} computations (as may be determined using method
586		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
587		* result in exceptions or errors, possibly including {@code
588		* ClassCastException}.
#	Line 513 | Line 596 | public abstract class ForkJoinTask<V> im
596		}
597
598		/**
599	<	* Returns the result of the computation when it is ready.
600	<	* This method differs from {@link #get()} in that
599	>	* Returns the result of the computation when it {@link #isDone is
600	>	* done}.  This method differs from {@link #get()} in that
601		* abnormal completion results in {@code RuntimeException} or
602	<	* {@code Error}, not {@code ExecutionException}.
602	>	* {@code Error}, not {@code ExecutionException}, and that
603	>	* interrupts of the calling thread do <em>not</em> cause the
604	>	* method to abruptly return by throwing {@code
605	>	* InterruptedException}.
606		*
607		* @return the computed result
608		*/
609		public final V join() {
610	<	ForkJoinWorkerThread w = getWorker();
611	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
612	<	reportException(awaitDone(w, true));
613	<	return getRawResult();
610	>	if (doJoin() != NORMAL)
611	>	return reportResult();
612	>	else
613	>	return getRawResult();
614		}
615
616		/**
617		* Commences performing this task, awaits its completion if
618	<	* necessary, and return its result.
618	>	* necessary, and returns its result, or throws an (unchecked)
619	>	* {@code RuntimeException} or {@code Error} if the underlying
620	>	* computation did so.
621		*
534	–	* @throws Throwable (a RuntimeException, Error, or unchecked
535	–	* exception) if the underlying computation did so
622		* @return the computed result
623		*/
624		public final V invoke() {
625	<	if (status >= 0 && tryExec())
626	<	return getRawResult();
625	>	if (doInvoke() != NORMAL)
626	>	return reportResult();
627		else
628	<	return join();
628	>	return getRawResult();
629		}
630
631		/**
632	<	* Forks the given tasks, returning when {@code isDone} holds
633	<	* for each task or an exception is encountered.
632	>	* Forks the given tasks, returning when {@code isDone} holds for
633	>	* each task or an (unchecked) exception is encountered, in which
634	>	* case the exception is rethrown. If more than one task
635	>	* encounters an exception, then this method throws any one of
636	>	* these exceptions. If any task encounters an exception, the
637	>	* other may be cancelled. However, the execution status of
638	>	* individual tasks is not guaranteed upon exceptional return. The
639	>	* status of each task may be obtained using {@link
640	>	* #getException()} and related methods to check if they have been
641	>	* cancelled, completed normally or exceptionally, or left
642	>	* unprocessed.
643		*
644		* <p>This method may be invoked only from within {@code
645	<	* ForkJoinTask} computations (as may be determined using method
645	>	* ForkJoinPool} computations (as may be determined using method
646		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
647		* result in exceptions or errors, possibly including {@code
648		* ClassCastException}.
#	Line 555 | Line 650 | public abstract class ForkJoinTask<V> im
650		* @param t1 the first task
651		* @param t2 the second task
652		* @throws NullPointerException if any task is null
558	–	* @throws RuntimeException or Error if a task did so
653		*/
654		public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
655		t2.fork();
#	Line 565 | Line 659 | public abstract class ForkJoinTask<V> im
659
660		/**
661		* Forks the given tasks, returning when {@code isDone} holds for
662	<	* each task or an exception is encountered. If any task
663	<	* encounters an exception, others may be, but are not guaranteed
664	<	* to be, cancelled.
662	>	* each task or an (unchecked) exception is encountered, in which
663	>	* case the exception is rethrown. If more than one task
664	>	* encounters an exception, then this method throws any one of
665	>	* these exceptions. If any task encounters an exception, others
666	>	* may be cancelled. However, the execution status of individual
667	>	* tasks is not guaranteed upon exceptional return. The status of
668	>	* each task may be obtained using {@link #getException()} and
669	>	* related methods to check if they have been cancelled, completed
670	>	* normally or exceptionally, or left unprocessed.
671		*
672		* <p>This method may be invoked only from within {@code
673	<	* ForkJoinTask} computations (as may be determined using method
673	>	* ForkJoinPool} computations (as may be determined using method
674		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
675		* result in exceptions or errors, possibly including {@code
676		* ClassCastException}.
677		*
678		* @param tasks the tasks
679	<	* @throws NullPointerException if tasks or any element are null
580	<	* @throws RuntimeException or Error if any task did so
679	>	* @throws NullPointerException if any task is null
680		*/
681		public static void invokeAll(ForkJoinTask<?>... tasks) {
682		Throwable ex = null;
#	Line 590 | Line 689 | public abstract class ForkJoinTask<V> im
689		}
690		else if (i != 0)
691		t.fork();
692	<	else {
693	<	t.quietlyInvoke();
595	<	if (ex == null)
596	<	ex = t.getException();
597	<	}
692	>	else if (t.doInvoke() < NORMAL && ex == null)
693	>	ex = t.getException();
694		}
695		for (int i = 1; i <= last; ++i) {
696		ForkJoinTask<?> t = tasks[i];
697		if (t != null) {
698		if (ex != null)
699		t.cancel(false);
700	<	else {
701	<	t.quietlyJoin();
606	<	if (ex == null)
607	<	ex = t.getException();
608	<	}
700	>	else if (t.doJoin() < NORMAL && ex == null)
701	>	ex = t.getException();
702		}
703		}
704		if (ex != null)
705	<	rethrowException(ex);
705	>	UNSAFE.throwException(ex);
706		}
707
708		/**
709		* Forks all tasks in the specified collection, returning when
710	<	* {@code isDone} holds for each task or an exception is
711	<	* encountered.  If any task encounters an exception, others may
712	<	* be, but are not guaranteed to be, cancelled. The behavior of
713	<	* this operation is undefined if the specified collection is
714	<	* modified while the operation is in progress.
710	>	* {@code isDone} holds for each task or an (unchecked) exception
711	>	* is encountered, in which case the exception is rethrown. If
712	>	* more than one task encounters an exception, then this method
713	>	* throws any one of these exceptions. If any task encounters an
714	>	* exception, others may be cancelled. However, the execution
715	>	* status of individual tasks is not guaranteed upon exceptional
716	>	* return. The status of each task may be obtained using {@link
717	>	* #getException()} and related methods to check if they have been
718	>	* cancelled, completed normally or exceptionally, or left
719	>	* unprocessed.
720		*
721		* <p>This method may be invoked only from within {@code
722	<	* ForkJoinTask} computations (as may be determined using method
722	>	* ForkJoinPool} computations (as may be determined using method
723		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
724		* result in exceptions or errors, possibly including {@code
725		* ClassCastException}.
#	Line 629 | Line 727 | public abstract class ForkJoinTask<V> im
727		* @param tasks the collection of tasks
728		* @return the tasks argument, to simplify usage
729		* @throws NullPointerException if tasks or any element are null
632	–	* @throws RuntimeException or Error if any task did so
730		*/
731		public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
732		if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
#	Line 649 | Line 746 | public abstract class ForkJoinTask<V> im
746		}
747		else if (i != 0)
748		t.fork();
749	<	else {
750	<	t.quietlyInvoke();
654	<	if (ex == null)
655	<	ex = t.getException();
656	<	}
749	>	else if (t.doInvoke() < NORMAL && ex == null)
750	>	ex = t.getException();
751		}
752		for (int i = 1; i <= last; ++i) {
753		ForkJoinTask<?> t = ts.get(i);
754		if (t != null) {
755		if (ex != null)
756		t.cancel(false);
757	<	else {
758	<	t.quietlyJoin();
665	<	if (ex == null)
666	<	ex = t.getException();
667	<	}
757	>	else if (t.doJoin() < NORMAL && ex == null)
758	>	ex = t.getException();
759		}
760		}
761		if (ex != null)
762	<	rethrowException(ex);
762	>	UNSAFE.throwException(ex);
763		return tasks;
764		}
765
766		/**
767	<	* Returns {@code true} if the computation performed by this task
768	<	* has completed (or has been cancelled).
769	<	*
770	<	* @return {@code true} if this computation has completed
771	<	*/
772	<	public final boolean isDone() {
773	<	return status < 0;
774	<	}
775	<
776	<	/**
686	<	* Returns {@code true} if this task was cancelled.
687	<	*
688	<	* @return {@code true} if this task was cancelled
689	<	*/
690	<	public final boolean isCancelled() {
691	<	return (status & COMPLETION_MASK) == CANCELLED;
692	<	}
693	<
694	<	/**
695	<	* Asserts that the results of this task's computation will not be
696	<	* used. If a cancellation occurs before attempting to execute this
697	<	* task, execution will be suppressed, {@link #isCancelled}
698	<	* will report true, and {@link #join} will result in a
699	<	* {@code CancellationException} being thrown. Otherwise, when
700	<	* cancellation races with completion, there are no guarantees
701	<	* about whether {@code isCancelled} will report {@code true},
702	<	* whether {@code join} will return normally or via an exception,
703	<	* or whether these behaviors will remain consistent upon repeated
704	<	* invocation.
767	>	* Attempts to cancel execution of this task. This attempt will
768	>	* fail if the task has already completed or could not be
769	>	* cancelled for some other reason. If successful, and this task
770	>	* has not started when {@code cancel} is called, execution of
771	>	* this task is suppressed. After this method returns
772	>	* successfully, unless there is an intervening call to {@link
773	>	* #reinitialize}, subsequent calls to {@link #isCancelled},
774	>	* {@link #isDone}, and {@code cancel} will return {@code true}
775	>	* and calls to {@link #join} and related methods will result in
776	>	* {@code CancellationException}.
777		*
778		* <p>This method may be overridden in subclasses, but if so, must
779	<	* still ensure that these minimal properties hold. In particular,
780	<	* the {@code cancel} method itself must not throw exceptions.
779	>	* still ensure that these properties hold. In particular, the
780	>	* {@code cancel} method itself must not throw exceptions.
781		*
782		* <p>This method is designed to be invoked by <em>other</em>
783		* tasks. To terminate the current task, you can just return or
784		* throw an unchecked exception from its computation method, or
785		* invoke {@link #completeExceptionally}.
786		*
787	<	* @param mayInterruptIfRunning this value is ignored in the
788	<	* default implementation because tasks are not in general
789	<	* cancelled via interruption
787	>	* @param mayInterruptIfRunning this value has no effect in the
788	>	* default implementation because interrupts are not used to
789	>	* control cancellation.
790		*
791		* @return {@code true} if this task is now cancelled
792		*/
793		public boolean cancel(boolean mayInterruptIfRunning) {
794	<	setCompletion(CANCELLED);
795	<	return (status & COMPLETION_MASK) == CANCELLED;
794	>	return setCompletion(CANCELLED) == CANCELLED;
795	>	}
796	>
797	>	/**
798	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
799	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
800	>	* exceptions, but if it does anyway, we have no recourse during
801	>	* shutdown, so guard against this case.
802	>	*/
803	>	final void cancelIgnoringExceptions() {
804	>	try {
805	>	cancel(false);
806	>	} catch (Throwable ignore) {
807	>	}
808	>	}
809	>
810	>	public final boolean isDone() {
811	>	return status < 0;
812	>	}
813	>
814	>	public final boolean isCancelled() {
815	>	return status == CANCELLED;
816		}
817
818		/**
#	Line 729 | Line 821 | public abstract class ForkJoinTask<V> im
821		* @return {@code true} if this task threw an exception or was cancelled
822		*/
823		public final boolean isCompletedAbnormally() {
824	<	return (status & COMPLETION_MASK) < NORMAL;
824	>	return status < NORMAL;
825	>	}
826	>
827	>	/**
828	>	* Returns {@code true} if this task completed without throwing an
829	>	* exception and was not cancelled.
830	>	*
831	>	* @return {@code true} if this task completed without throwing an
832	>	* exception and was not cancelled
833	>	*/
834	>	public final boolean isCompletedNormally() {
835	>	return status == NORMAL;
836		}
837
838		/**
#	Line 740 | Line 843 | public abstract class ForkJoinTask<V> im
843		* @return the exception, or {@code null} if none
844		*/
845		public final Throwable getException() {
846	<	int s = status & COMPLETION_MASK;
847	<	if (s >= NORMAL)
848	<	return null;
849	<	if (s == CANCELLED)
747	<	return new CancellationException();
748	<	return exceptionMap.get(this);
846	>	int s = status;
847	>	return ((s >= NORMAL)    ? null :
848	>	(s == CANCELLED) ? new CancellationException() :
849	>	getThrowableException());
850		}
851
852		/**
#	Line 758 | Line 859 | public abstract class ForkJoinTask<V> im
859		* overridable, but overridden versions must invoke {@code super}
860		* implementation to maintain guarantees.
861		*
862	<	* @param ex the exception to throw. If this exception is
863	<	* not a RuntimeException or Error, the actual exception thrown
864	<	* will be a RuntimeException with cause ex.
862	>	* @param ex the exception to throw. If this exception is not a
863	>	* {@code RuntimeException} or {@code Error}, the actual exception
864	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
865		*/
866		public void completeExceptionally(Throwable ex) {
867	<	setDoneExceptionally((ex instanceof RuntimeException) ||
868	<	(ex instanceof Error) ? ex :
869	<	new RuntimeException(ex));
867	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
868	>	(ex instanceof Error) ? ex :
869	>	new RuntimeException(ex));
870		}
871
872		/**
873		* Completes this task, and if not already aborted or cancelled,
874	<	* returning a {@code null} result upon {@code join} and related
875	<	* operations. This method may be used to provide results for
876	<	* asynchronous tasks, or to provide alternative handling for
877	<	* tasks that would not otherwise complete normally. Its use in
878	<	* other situations is discouraged. This method is
879	<	* overridable, but overridden versions must invoke {@code super}
880	<	* implementation to maintain guarantees.
874	>	* returning the given value as the result of subsequent
875	>	* invocations of {@code join} and related operations. This method
876	>	* may be used to provide results for asynchronous tasks, or to
877	>	* provide alternative handling for tasks that would not otherwise
878	>	* complete normally. Its use in other situations is
879	>	* discouraged. This method is overridable, but overridden
880	>	* versions must invoke {@code super} implementation to maintain
881	>	* guarantees.
882		*
883		* @param value the result value for this task
884		*/
#	Line 784 | Line 886 | public abstract class ForkJoinTask<V> im
886		try {
887		setRawResult(value);
888		} catch (Throwable rex) {
889	<	setDoneExceptionally(rex);
889	>	setExceptionalCompletion(rex);
890		return;
891		}
892	<	setNormalCompletion();
791	<	}
792	<
793	<	public final V get() throws InterruptedException, ExecutionException {
794	<	ForkJoinWorkerThread w = getWorker();
795	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
796	<	awaitDone(w, true);
797	<	return reportFutureResult();
798	<	}
799	<
800	<	public final V get(long timeout, TimeUnit unit)
801	<	throws InterruptedException, ExecutionException, TimeoutException {
802	<	long nanos = unit.toNanos(timeout);
803	<	ForkJoinWorkerThread w = getWorker();
804	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
805	<	awaitDone(w, nanos);
806	<	return reportTimedFutureResult();
892	>	setCompletion(NORMAL);
893		}
894
895		/**
896	<	* Possibly executes other tasks until this task is ready, then
897	<	* returns the result of the computation.  This method may be more
812	<	* efficient than {@code join}, but is only applicable when
813	<	* there are no potential dependencies between continuation of the
814	<	* current task and that of any other task that might be executed
815	<	* while helping. (This usually holds for pure divide-and-conquer
816	<	* tasks).
817	<	*
818	<	* <p>This method may be invoked only from within {@code
819	<	* ForkJoinTask} computations (as may be determined using method
820	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
821	<	* result in exceptions or errors, possibly including {@code
822	<	* ClassCastException}.
896	>	* Waits if necessary for the computation to complete, and then
897	>	* retrieves its result.
898		*
899		* @return the computed result
900	+	* @throws CancellationException if the computation was cancelled
901	+	* @throws ExecutionException if the computation threw an
902	+	* exception
903	+	* @throws InterruptedException if the current thread is not a
904	+	* member of a ForkJoinPool and was interrupted while waiting
905		*/
906	<	public final V helpJoin() {
907	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
908	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
909	<	reportException(busyJoin(w));
906	>	public final V get() throws InterruptedException, ExecutionException {
907	>	int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ?
908	>	doJoin() : externalInterruptibleAwaitDone(0L);
909	>	Throwable ex;
910	>	if (s == CANCELLED)
911	>	throw new CancellationException();
912	>	if (s == EXCEPTIONAL && (ex = getThrowableException()) != null)
913	>	throw new ExecutionException(ex);
914		return getRawResult();
915		}
916
917		/**
918	<	* Possibly executes other tasks until this task is ready.  This
919	<	* method may be useful when processing collections of tasks when
836	<	* some have been cancelled or otherwise known to have aborted.
918	>	* Waits if necessary for at most the given time for the computation
919	>	* to complete, and then retrieves its result, if available.
920		*
921	<	* <p>This method may be invoked only from within {@code
922	<	* ForkJoinTask} computations (as may be determined using method
923	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
924	<	* result in exceptions or errors, possibly including {@code
925	<	* ClassCastException}.
921	>	* @param timeout the maximum time to wait
922	>	* @param unit the time unit of the timeout argument
923	>	* @return the computed result
924	>	* @throws CancellationException if the computation was cancelled
925	>	* @throws ExecutionException if the computation threw an
926	>	* exception
927	>	* @throws InterruptedException if the current thread is not a
928	>	* member of a ForkJoinPool and was interrupted while waiting
929	>	* @throws TimeoutException if the wait timed out
930		*/
931	<	public final void quietlyHelpJoin() {
932	<	if (status >= 0) {
933	<	ForkJoinWorkerThread w =
934	<	(ForkJoinWorkerThread) Thread.currentThread();
935	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
936	<	busyJoin(w);
931	>	public final V get(long timeout, TimeUnit unit)
932	>	throws InterruptedException, ExecutionException, TimeoutException {
933	>	Thread t = Thread.currentThread();
934	>	if (t instanceof ForkJoinWorkerThread) {
935	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
936	>	long nanos = unit.toNanos(timeout);
937	>	if (status >= 0) {
938	>	boolean completed = false;
939	>	if (w.unpushTask(this)) {
940	>	try {
941	>	completed = exec();
942	>	} catch (Throwable rex) {
943	>	setExceptionalCompletion(rex);
944	>	}
945	>	}
946	>	if (completed)
947	>	setCompletion(NORMAL);
948	>	else if (status >= 0 && nanos > 0)
949	>	w.pool.timedAwaitJoin(this, nanos);
950	>	}
951	>	}
952	>	else {
953	>	long millis = unit.toMillis(timeout);
954	>	if (millis > 0)
955	>	externalInterruptibleAwaitDone(millis);
956		}
957	+	int s = status;
958	+	if (s != NORMAL) {
959	+	Throwable ex;
960	+	if (s == CANCELLED)
961	+	throw new CancellationException();
962	+	if (s != EXCEPTIONAL)
963	+	throw new TimeoutException();
964	+	if ((ex = getThrowableException()) != null)
965	+	throw new ExecutionException(ex);
966	+	}
967	+	return getRawResult();
968		}
969
970		/**
971	<	* Joins this task, without returning its result or throwing an
971	>	* Joins this task, without returning its result or throwing its
972		* exception. This method may be useful when processing
973		* collections of tasks when some have been cancelled or otherwise
974		* known to have aborted.
975		*/
976		public final void quietlyJoin() {
977	<	if (status >= 0) {
861	<	ForkJoinWorkerThread w = getWorker();
862	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
863	<	awaitDone(w, true);
864	<	}
977	>	doJoin();
978		}
979
980		/**
981		* Commences performing this task and awaits its completion if
982	<	* necessary, without returning its result or throwing an
983	<	* exception. This method may be useful when processing
871	<	* collections of tasks when some have been cancelled or otherwise
872	<	* known to have aborted.
982	>	* necessary, without returning its result or throwing its
983	>	* exception.
984		*/
985		public final void quietlyInvoke() {
986	<	if (status >= 0 && !tryQuietlyInvoke())
876	<	quietlyJoin();
986	>	doInvoke();
987		}
988
989		/**
990		* Possibly executes tasks until the pool hosting the current task
991	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
992	<	* designs in which many tasks are forked, but none are explicitly
993	<	* joined, instead executing them until all are processed.
991	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
992	>	* be of use in designs in which many tasks are forked, but none
993	>	* are explicitly joined, instead executing them until all are
994	>	* processed.
995		*
996		* <p>This method may be invoked only from within {@code
997	<	* ForkJoinTask} computations (as may be determined using method
997	>	* ForkJoinPool} computations (as may be determined using method
998		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
999		* result in exceptions or errors, possibly including {@code
1000		* ClassCastException}.
#	Line 902 | Line 1013 | public abstract class ForkJoinTask<V> im
1013		* under any other usage conditions are not guaranteed.
1014		* This method may be useful when executing
1015		* pre-constructed trees of subtasks in loops.
1016	+	*
1017	+	* <p>Upon completion of this method, {@code isDone()} reports
1018	+	* {@code false}, and {@code getException()} reports {@code
1019	+	* null}. However, the value returned by {@code getRawResult} is
1020	+	* unaffected. To clear this value, you can invoke {@code
1021	+	* setRawResult(null)}.
1022		*/
1023		public void reinitialize() {
1024	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
1025	<	exceptionMap.remove(this);
1026	<	status = 0;
1024	>	if (status == EXCEPTIONAL)
1025	>	clearExceptionalCompletion();
1026	>	else
1027	>	status = 0;
1028		}
1029
1030		/**
#	Line 923 | Line 1041 | public abstract class ForkJoinTask<V> im
1041		}
1042
1043		/**
1044	<	* Returns {@code true} if the current thread is executing as a
1045	<	* ForkJoinPool computation.
1044	>	* Returns {@code true} if the current thread is a {@link
1045	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation.
1046		*
1047	<	* @return {@code true} if the current thread is executing as a
1048	<	* ForkJoinPool computation, or false otherwise
1047	>	* @return {@code true} if the current thread is a {@link
1048	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation,
1049	>	* or {@code false} otherwise
1050		*/
1051		public static boolean inForkJoinPool() {
1052		return Thread.currentThread() instanceof ForkJoinWorkerThread;
#	Line 942 | Line 1061 | public abstract class ForkJoinTask<V> im
1061		* were not, stolen.
1062		*
1063		* <p>This method may be invoked only from within {@code
1064	<	* ForkJoinTask} computations (as may be determined using method
1064	>	* ForkJoinPool} computations (as may be determined using method
1065		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1066		* result in exceptions or errors, possibly including {@code
1067		* ClassCastException}.
#	Line 961 | Line 1080 | public abstract class ForkJoinTask<V> im
1080		* fork other tasks.
1081		*
1082		* <p>This method may be invoked only from within {@code
1083	<	* ForkJoinTask} computations (as may be determined using method
1083	>	* ForkJoinPool} computations (as may be determined using method
1084		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1085		* result in exceptions or errors, possibly including {@code
1086		* ClassCastException}.
#	Line 984 | Line 1103 | public abstract class ForkJoinTask<V> im
1103		* exceeded.
1104		*
1105		* <p>This method may be invoked only from within {@code
1106	<	* ForkJoinTask} computations (as may be determined using method
1106	>	* ForkJoinPool} computations (as may be determined using method
1107		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1108		* result in exceptions or errors, possibly including {@code
1109		* ClassCastException}.
#	Line 1024 | Line 1143 | public abstract class ForkJoinTask<V> im
1143		* called otherwise. The return value controls whether this task
1144		* is considered to be done normally. It may return false in
1145		* asynchronous actions that require explicit invocations of
1146	<	* {@link #complete} to become joinable. It may throw exceptions
1147	<	* to indicate abnormal exit.
1146	>	* {@link #complete} to become joinable. It may also throw an
1147	>	* (unchecked) exception to indicate abnormal exit.
1148		*
1149		* @return {@code true} if completed normally
1031	–	* @throws Error or RuntimeException if encountered during computation
1150		*/
1151		protected abstract boolean exec();
1152
#	Line 1043 | Line 1161 | public abstract class ForkJoinTask<V> im
1161		* otherwise.
1162		*
1163		* <p>This method may be invoked only from within {@code
1164	<	* ForkJoinTask} computations (as may be determined using method
1164	>	* ForkJoinPool} computations (as may be determined using method
1165		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1166		* result in exceptions or errors, possibly including {@code
1167		* ClassCastException}.
#	Line 1062 | Line 1180 | public abstract class ForkJoinTask<V> im
1180		* be useful otherwise.
1181		*
1182		* <p>This method may be invoked only from within {@code
1183	<	* ForkJoinTask} computations (as may be determined using method
1183	>	* ForkJoinPool} computations (as may be determined using method
1184		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1185		* result in exceptions or errors, possibly including {@code
1186		* ClassCastException}.
#	Line 1085 | Line 1203 | public abstract class ForkJoinTask<V> im
1203		* otherwise.
1204		*
1205		* <p>This method may be invoked only from within {@code
1206	<	* ForkJoinTask} computations (as may be determined using method
1206	>	* ForkJoinPool} computations (as may be determined using method
1207		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1208		* result in exceptions or errors, possibly including {@code
1209		* ClassCastException}.
#	Line 1195 | Line 1313 | public abstract class ForkJoinTask<V> im
1313		private static final long serialVersionUID = -7721805057305804111L;
1314
1315		/**
1316	<	* Save the state to a stream.
1316	>	* Saves the state to a stream (that is, serializes it).
1317		*
1318		* @serialData the current run status and the exception thrown
1319		* during execution, or {@code null} if none
#	Line 1208 | Line 1326 | public abstract class ForkJoinTask<V> im
1326		}
1327
1328		/**
1329	<	* Reconstitute the instance from a stream.
1329	>	* Reconstitutes the instance from a stream (that is, deserializes it).
1330		*
1331		* @param s the stream
1332		*/
1333		private void readObject(java.io.ObjectInputStream s)
1334		throws java.io.IOException, ClassNotFoundException {
1335		s.defaultReadObject();
1218	–	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1219	–	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1336		Object ex = s.readObject();
1337		if (ex != null)
1338	<	setDoneExceptionally((Throwable) ex);
1338	>	setExceptionalCompletion((Throwable)ex);
1339		}
1340
1341		// Unsafe mechanics
1342	<
1343	<	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1344	<	private static final long statusOffset =
1345	<	objectFieldOffset("status", ForkJoinTask.class);
1346	<
1347	<	private static long objectFieldOffset(String field, Class<?> klazz) {
1342	>	private static final sun.misc.Unsafe UNSAFE;
1343	>	private static final long statusOffset;
1344	>	static {
1345	>	exceptionTableLock = new ReentrantLock();
1346	>	exceptionTableRefQueue = new ReferenceQueue<Object>();
1347	>	exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY];
1348		try {
1349	<	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1350	<	} catch (NoSuchFieldException e) {
1351	<	// Convert Exception to corresponding Error
1352	<	NoSuchFieldError error = new NoSuchFieldError(field);
1353	<	error.initCause(e);
1238	<	throw error;
1349	>	UNSAFE = getUnsafe();
1350	>	statusOffset = UNSAFE.objectFieldOffset
1351	>	(ForkJoinTask.class.getDeclaredField("status"));
1352	>	} catch (Exception e) {
1353	>	throw new Error(e);
1354		}
1355		}
1356

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