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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.1 by dl, Tue Jan 6 14:30:31 2009 UTC vs.
Revision 1.62 by dl, Fri Sep 17 14:24:56 2010 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.io.Serializable;
9	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
11	<	import sun.misc.Unsafe;
12	<	import java.lang.reflect.*;
10	>
11	>	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
19		/**
20	<	* Abstract base class for tasks that run within a ForkJoinPool.  A
21	<	* ForkJoinTask is a thread-like entity that is much lighter weight
22	<	* than a normal thread.  Huge numbers of tasks and subtasks may be
23	<	* hosted by a small number of actual threads in a ForkJoinPool,
24	<	* at the price of some usage limitations.
20	>	* Abstract base class for tasks that run within a {@link ForkJoinPool}.
21	>	* A {@code ForkJoinTask} is a thread-like entity that is much
22	>	* lighter weight than a normal thread.  Huge numbers of tasks and
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> ForkJoinTasks are forms of <tt>Futures</tt> supporting a
27	<	* limited range of use.  The "lightness" of ForkJoinTasks is due to a
28	<	* set of restrictions (that are only partially statically
29	<	* enforceable) reflecting their intended use as computational tasks
30	<	* calculating pure functions or operating on purely isolated objects.
31	<	* The primary coordination mechanisms supported for ForkJoinTasks are
32	<	* <tt>fork</tt>, that arranges asynchronous execution, and
33	<	* <tt>join</tt>, that doesn't proceed until the task's result has
34	<	* been computed. (Cancellation is also supported).  The computation
31	<	* defined in the <tt>compute</tt> method should avoid
32	<	* <tt>synchronized</tt> methods or blocks, and should minimize
33	<	* blocking synchronization apart from joining other tasks or using
34	<	* synchronizers such as Phasers that are advertised to cooperate with
35	<	* fork/join scheduling. Tasks should also not perform blocking IO,
36	<	* and should ideally access variables that are completely independent
37	<	* of those accessed by other running tasks. Minor breaches of these
38	<	* restrictions, for example using shared output streams, may be
39	<	* tolerable in practice, but frequent use may result in poor
40	<	* performance, and the potential to indefinitely stall if the number
41	<	* of threads not waiting for external synchronization becomes
42	<	* exhausted. This usage restriction is in part enforced by not
43	<	* permitting checked exceptions such as IOExceptions to be
44	<	* thrown. However, computations may still encounter unchecked
45	<	* exceptions, that are rethrown to callers attempting join
46	<	* them. These exceptions may additionally include
47	<	* RejectedExecutionExceptions stemming from internal resource
48	<	* exhaustion such as failure to allocate internal task queues.
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(ForkJoinTask...) invokeAll}.  However, this class also
32	>	* provides a number of other methods that can come into play in
33	>	* advanced usages, as well as extension mechanics that allow
34	>	* support of new forms of fork/join processing.
35		*
36	<	* <p> The <tt>ForkJoinTask</tt> class is not usually directly
37	<	* subclassed.  Instead, you subclass one of the abstract classes that
38	<	* support different styles of fork/join processing.  Normally, a
39	<	* concrete ForkJoinTask subclass declares fields comprising its
40	<	* parameters, established in a constructor, and then defines a
41	<	* <tt>compute</tt> method that somehow uses the control methods
42	<	* supplied by this base class. While these methods have
43	<	* <tt>public</tt> access, some of them may only be called from within
44	<	* other ForkJoinTasks. Attempts to invoke them in other contexts
45	<	* result in exceptions or errors including ClassCastException.  The
46	<	* only way to invoke a "main" driver task is to submit it to a
47	<	* ForkJoinPool. Once started, this will usually in turn start other
48	<	* subtasks.
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>Most base support methods are <tt>final</tt> because their
64	<	* implementations are intrinsically tied to the underlying
65	<	* lightweight task scheduling framework, and so cannot be overridden.
66	<	* Developers creating new basic styles of fork/join processing should
67	<	* minimally implement protected methods <tt>exec</tt>,
68	<	* <tt>setRawResult</tt>, and <tt>getRawResult</tt>, while also
69	<	* introducing an abstract computational method that can be
70	<	* implemented in its subclasses. To support such extensions,
71	<	* instances of ForkJoinTasks maintain an atomically updated
72	<	* <tt>short</tt> representing user-defined control state.  Control
73	<	* state is guaranteed initially to be zero, and to be negative upon
74	<	* completion, but may otherwise be used for any other control
75	<	* purposes, such as maintaining join counts.  The {@link
76	<	* ForkJoinWorkerThread} class supports additional inspection and
77	<	* tuning methods that can be useful when developing extensions.
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 #invoke} is semantically
68	>	* equivalent to {@code fork(); join()} but always attempts to begin
69	>	* execution in the current thread. The "<em>quiet</em>" forms of
70	>	* these methods do not extract results or report exceptions. These
71	>	* may be useful when a set of tasks are being executed, and you need
72	>	* to delay processing of results or exceptions until all complete.
73	>	* Method {@code invokeAll} (available in multiple versions)
74	>	* performs the most common form of parallel invocation: forking a set
75	>	* of tasks and joining them all.
76	>	*
77	>	* <p>The execution status of tasks may be queried at several levels
78	>	* of detail: {@link #isDone} is true if a task completed in any way
79	>	* (including the case where a task was cancelled without executing);
80	>	* {@link #isCompletedNormally} is true if a task completed without
81	>	* cancellation or encountering an exception; {@link #isCancelled} is
82	>	* true if the task was cancelled (in which case {@link #getException}
83	>	* returns a {@link java.util.concurrent.CancellationException}); and
84	>	* {@link #isCompletedAbnormally} is true if a task was either
85	>	* cancelled or encountered an exception, in which case {@link
86	>	* #getException} will return either the encountered exception or
87	>	* {@link java.util.concurrent.CancellationException}.
88	>	*
89	>	* <p>The ForkJoinTask class is not usually directly subclassed.
90	>	* Instead, you subclass one of the abstract classes that support a
91	>	* particular style of fork/join processing, typically {@link
92	>	* RecursiveAction} for computations that do not return results, or
93	>	* {@link RecursiveTask} for those that do.  Normally, a concrete
94	>	* ForkJoinTask subclass declares fields comprising its parameters,
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 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	>	* {@code ClassCastException}.
104	>	*
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, othewise 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	<	* parellelism 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 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 <tt>Serializable</tt>, which enables them to
129	<	* be used in extensions such as remote execution frameworks. However,
130	<	* it is in general safe to serialize tasks only before or after, but
131	<	* not during execution. Serialization is not relied on during
132	<	* 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	<	* Status field holding all run status. We pack this into a single
139	<	* int both to minimize footprint overhead and to ensure atomicity
140	<	* (updates are via CAS).
141	<	*
142	<	* Status is initially zero, and takes on nonnegative values until
143	<	* completed, upon which status holds COMPLETED. CANCELLED, or
144	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
145	<	* blocking waits by other threads have SIGNAL_MASK bits set --
146	<	* bit 15 for external (nonFJ) waits, and the rest a count of
147	<	* waiting FJ threads.  (This representation relies on
148	<	* ForkJoinPool max thread limits). Completion of a stolen task
149	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
150	<	* though suboptimal for some purposes, we use basic builtin
151	<	* wait/notify to take advantage of "monitor inflation" in JVMs
152	<	* that we would otherwise need to emulate to avoid adding further
153	<	* per-task bookkeeping overhead. Note that bits 16-28 are
154	<	* currently unused. Also value 0x80000000 is available as spare
155	<	* completion value.
156	<	*/
157	<	volatile int status; // accessed directy by pool and workers
158	<
159	<	static final int COMPLETION_MASK      = 0xe0000000;
160	<	static final int NORMAL               = 0xe0000000; // == mask
161	<	static final int CANCELLED            = 0xc0000000;
162	<	static final int EXCEPTIONAL          = 0xa0000000;
163	<	static final int SIGNAL_MASK          = 0x0000ffff;
164	<	static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
165	<	static final int EXTERNAL_SIGNAL      = 0x00008000; // top bit of low word
137	>
138	>	/*
139	>	* See the internal documentation of class ForkJoinPool for a
140	>	* general implementation overview.  ForkJoinTasks are mainly
141	>	* responsible for maintaining their "status" field amidst relays
142	>	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
143	>	* methods of this class are more-or-less layered into (1) basic
144	>	* status maintenance (2) execution and awaiting completion (3)
145	>	* user-level methods that additionally report results. This is
146	>	* sometimes hard to see because this file orders exported methods
147	>	* in a way that flows well in javadocs. 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	>	* NORMAL, 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	>	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
178		* callers. Because exceptions are rare, we don't directly keep
179	<	* them with task objects, but instead us a weak ref table.  Note
179	>	* them with task objects, but instead use a weak ref table.  Note
180		* that cancellation exceptions don't appear in the table, but are
181		* instead recorded as status values.
182	<	* Todo: Use ConcurrentReferenceHashMap
182	>	* TODO: Use ConcurrentReferenceHashMap
183		*/
184		static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
185		Collections.synchronizedMap
186		(new WeakHashMap<ForkJoinTask<?>, Throwable>());
187
188	<	// within-package utilities
137	<
138	<	/**
139	<	* Get current worker thread, or null if not a worker thread
140	<	*/
141	<	static ForkJoinWorkerThread getWorker() {
142	<	Thread t = Thread.currentThread();
143	<	return ((t instanceof ForkJoinWorkerThread)?
144	<	(ForkJoinWorkerThread)t : null);
145	<	}
146	<
147	<	/**
148	<	* Get pool of current worker thread, or null if not a worker thread
149	<	*/
150	<	static ForkJoinPool getWorkerPool() {
151	<	Thread t = Thread.currentThread();
152	<	return ((t instanceof ForkJoinWorkerThread)?
153	<	((ForkJoinWorkerThread)t).pool : null);
154	<	}
155	<
156	<	final boolean casStatus(int cmp, int val) {
157	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
158	<	}
188	>	// Maintaining completion status
189
190		/**
191	<	* Workaround for not being able to rethrow unchecked exceptions.
192	<	*/
193	<	static void rethrowException(Throwable ex) {
164	<	if (ex != null)
165	<	_unsafe.throwException(ex);
166	<	}
167	<
168	<	// Setting completion status
169	<
170	<	/**
171	<	* Mark completion and wake 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 = getWorkerPool();
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) {
181	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
182	<	pool.updateRunningCount(s);
183	<	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		}
186	–	else
187	–	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.
210	<	*/
194	<	private void externallySetCompletion(int completion) {
195	<	int s;
196	<	do;while ((s = status) >= 0 &&
197	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
198	<	synchronized(this) { notifyAll(); }
199	<	}
200	<
201	<	/**
202	<	* Sets status to indicate normal completion
203	<	*/
204	<	final void setNormalCompletion() {
205	<	// Try typical fast case -- single CAS, no signal, not already done.
206	<	// Manually expand casStatus to improve chances of inlining it
207	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
208	<	setCompletion(NORMAL);
209	<	}
210	<
211	<	// internal waiting and notification
212	<
213	<	/**
214	<	* Performs the actual monitor wait for awaitDone
208	>	* Records exception and sets exceptional completion.
209	>	*
210	>	* @return status on exit
211		*/
212	<	private void doAwaitDone() {
213	<	// Minimize lock bias and in/de-flation effects by maximizing
214	<	// chances of waiting inside sync
219	<	try {
220	<	while (status >= 0)
221	<	synchronized(this) { if (status >= 0) wait(); }
222	<	} catch (InterruptedException ie) {
223	<	onInterruptedWait();
224	<	}
212	>	private void setExceptionalCompletion(Throwable rex) {
213	>	exceptionMap.put(this, rex);
214	>	setCompletion(EXCEPTIONAL);
215		}
216
217		/**
218	<	* Performs the actual monitor wait for awaitDone
218	>	* Blocks a worker thread until completion. Called only by
219	>	* pool. Currently unused -- pool-based waits use timeout
220	>	* version below.
221		*/
222	<	private void doAwaitDone(long startTime, long nanos) {
223	<	synchronized(this) {
222	>	final void internalAwaitDone() {
223	>	int s;         // the odd construction reduces lock bias effects
224	>	while ((s = status) >= 0) {
225		try {
226	<	while (status >= 0) {
227	<	long nt = nanos - System.nanoTime() - startTime;
228	<	if (nt <= 0)
236	<	break;
237	<	wait(nt / 1000000, (int)(nt % 1000000));
226	>	synchronized (this) {
227	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
228	>	wait();
229		}
230		} catch (InterruptedException ie) {
231	<	onInterruptedWait();
231	>	cancelIfTerminating();
232		}
233		}
234		}
235
245	–	// Awaiting completion
246	–
236		/**
237	<	* Sets status to indicate there is joiner, then waits for join,
238	<	* surrounded with pool notifications.
239	<	* @return status upon exit
237	>	* Blocks a worker thread until completed or timed out.  Called
238	>	* only by pool.
239	>	*
240	>	* @return status on exit
241		*/
242	<	final int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
253	<	ForkJoinPool pool = w == null? null : w.pool;
242	>	final int internalAwaitDone(long millis) {
243		int s;
244	<	while ((s = status) >= 0) {
245	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
246	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
247	<	doAwaitDone();
248	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
249	<	adjustPoolCountsOnUnblock(pool);
250	<	break;
244	>	if ((s = status) >= 0) {
245	>	try {
246	>	synchronized (this) {
247	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
248	>	wait(millis, 0);
249	>	}
250	>	} catch (InterruptedException ie) {
251	>	cancelIfTerminating();
252		}
253	+	s = status;
254		}
255		return s;
256		}
257
258		/**
259	<	* Timed version of awaitDone
269	<	* @return status upon exit
259	>	* Blocks a non-worker-thread until completion.
260		*/
261	<	final int awaitDone(ForkJoinWorkerThread w, long nanos) {
272	<	ForkJoinPool pool = w == null? null : w.pool;
261	>	private void externalAwaitDone() {
262		int s;
263		while ((s = status) >= 0) {
264	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
265	<	long startTime = System.nanoTime();
266	<	if (pool == null || !pool.preJoin(this, false))
267	<	doAwaitDone(startTime, nanos);
268	<	if ((s = status) >= 0) {
269	<	adjustPoolCountsOnCancelledWait(pool);
270	<	s = status;
264	>	synchronized (this) {
265	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
266	>	boolean interrupted = false;
267	>	while (status >= 0) {
268	>	try {
269	>	wait();
270	>	} catch (InterruptedException ie) {
271	>	interrupted = true;
272	>	}
273	>	}
274	>	if (interrupted)
275	>	Thread.currentThread().interrupt();
276	>	break;
277		}
283	–	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
284	–	adjustPoolCountsOnUnblock(pool);
285	–	break;
278		}
279		}
288	–	return s;
280		}
281
282		/**
283	<	* Notify pool that thread is unblocked. Called by signalled
284	<	* threads when woken by non-FJ threads (which is atypical).
283	>	* Unless done, calls exec and records status if completed, but
284	>	* doesn't wait for completion otherwise. Primary execution method
285	>	* for ForkJoinWorkerThread.
286		*/
287	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
288	<	int s;
289	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
290	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
291	<	pool.updateRunningCount(s);
287	>	final void quietlyExec() {
288	>	try {
289	>	if (status < 0 || !exec())
290	>	return;
291	>	} catch (Throwable rex) {
292	>	setExceptionalCompletion(rex);
293	>	return;
294	>	}
295	>	setCompletion(NORMAL); // must be outside try block
296		}
297
298	+	// public methods
299	+
300		/**
301	<	* Notify pool to adjust counts on cancelled or timed out wait
301	>	* Arranges to asynchronously execute this task.  While it is not
302	>	* necessarily enforced, it is a usage error to fork a task more
303	>	* than once unless it has completed and been reinitialized.
304	>	* Subsequent modifications to the state of this task or any data
305	>	* it operates on are not necessarily consistently observable by
306	>	* any thread other than the one executing it unless preceded by a
307	>	* call to {@link #join} or related methods, or a call to {@link
308	>	* #isDone} returning {@code true}.
309	>	*
310	>	* <p>This method may be invoked only from within {@code
311	>	* ForkJoinTask} computations (as may be determined using method
312	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
313	>	* result in exceptions or errors, possibly including {@code
314	>	* ClassCastException}.
315	>	*
316	>	* @return {@code this}, to simplify usage
317		*/
318	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
319	<	if (pool != null) {
320	<	int s;
321	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
309	<	if (casStatus(s, s - 1)) {
310	<	pool.updateRunningCount(1);
311	<	break;
312	<	}
313	<	}
314	<	}
318	>	public final ForkJoinTask<V> fork() {
319	>	((ForkJoinWorkerThread) Thread.currentThread())
320	>	.pushTask(this);
321	>	return this;
322		}
323
324	<	private void onInterruptedWait() {
325	<	Thread t = Thread.currentThread();
326	<	if (t instanceof ForkJoinWorkerThread) {
327	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)t;
328	<	if (w.isTerminating())
329	<	cancelIgnoreExceptions();
330	<	}
331	<	else { // re-interrupt
332	<	try {
333	<	t.interrupt();
334	<	} catch (SecurityException ignore) {
335	<	}
336	<	}
324	>	/**
325	>	* Returns the result of the computation when it {@link #isDone is done}.
326	>	* This method differs from {@link #get()} in that
327	>	* abnormal completion results in {@code RuntimeException} or
328	>	* {@code Error}, not {@code ExecutionException}.
329	>	*
330	>	* @return the computed result
331	>	*/
332	>	public final V join() {
333	>	quietlyJoin();
334	>	Throwable ex;
335	>	if (status < NORMAL && (ex = getException()) != null)
336	>	UNSAFE.throwException(ex);
337	>	return getRawResult();
338		}
339
340	<	// Recording and reporting exceptions
340	>	/**
341	>	* Commences performing this task, awaits its completion if
342	>	* necessary, and returns its result, or throws an (unchecked)
343	>	* {@code RuntimeException} or {@code Error} if the underlying
344	>	* computation did so.
345	>	*
346	>	* @return the computed result
347	>	*/
348	>	public final V invoke() {
349	>	quietlyInvoke();
350	>	Throwable ex;
351	>	if (status < NORMAL && (ex = getException()) != null)
352	>	UNSAFE.throwException(ex);
353	>	return getRawResult();
354	>	}
355
356	<	private void setDoneExceptionally(Throwable rex) {
357	<	exceptionMap.put(this, rex);
358	<	setCompletion(EXCEPTIONAL);
356	>	/**
357	>	* Forks the given tasks, returning when {@code isDone} holds for
358	>	* each task or an (unchecked) exception is encountered, in which
359	>	* case the exception is rethrown. If more than one task
360	>	* encounters an exception, then this method throws any one of
361	>	* these exceptions. If any task encounters an exception, the
362	>	* other may be cancelled. However, the execution status of
363	>	* individual tasks is not guaranteed upon exceptional return. The
364	>	* status of each task may be obtained using {@link
365	>	* #getException()} and related methods to check if they have been
366	>	* cancelled, completed normally or exceptionally, or left
367	>	* unprocessed.
368	>	*
369	>	* <p>This method may be invoked only from within {@code
370	>	* ForkJoinTask} computations (as may be determined using method
371	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
372	>	* result in exceptions or errors, possibly including {@code
373	>	* ClassCastException}.
374	>	*
375	>	* @param t1 the first task
376	>	* @param t2 the second task
377	>	* @throws NullPointerException if any task is null
378	>	*/
379	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
380	>	t2.fork();
381	>	t1.invoke();
382	>	t2.join();
383		}
384
385		/**
386	<	* Throws the exception associated with status s;
387	<	* @throws the exception
386	>	* Forks the given tasks, returning when {@code isDone} holds for
387	>	* each task or an (unchecked) exception is encountered, in which
388	>	* case the exception is rethrown. If more than one task
389	>	* encounters an exception, then this method throws any one of
390	>	* these exceptions. If any task encounters an exception, others
391	>	* may be cancelled. However, the execution status of individual
392	>	* tasks is not guaranteed upon exceptional return. The status of
393	>	* each task may be obtained using {@link #getException()} and
394	>	* related methods to check if they have been cancelled, completed
395	>	* normally or exceptionally, or left unprocessed.
396	>	*
397	>	* <p>This method may be invoked only from within {@code
398	>	* ForkJoinTask} computations (as may be determined using method
399	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
400	>	* result in exceptions or errors, possibly including {@code
401	>	* ClassCastException}.
402	>	*
403	>	* @param tasks the tasks
404	>	* @throws NullPointerException if any task is null
405		*/
406	<	private void reportException(int s) {
407	<	if ((s &= COMPLETION_MASK) < NORMAL) {
408	<	if (s == CANCELLED)
409	<	throw new CancellationException();
410	<	else
411	<	rethrowException(exceptionMap.get(this));
406	>	public static void invokeAll(ForkJoinTask<?>... tasks) {
407	>	Throwable ex = null;
408	>	int last = tasks.length - 1;
409	>	for (int i = last; i >= 0; --i) {
410	>	ForkJoinTask<?> t = tasks[i];
411	>	if (t == null) {
412	>	if (ex == null)
413	>	ex = new NullPointerException();
414	>	}
415	>	else if (i != 0)
416	>	t.fork();
417	>	else {
418	>	t.quietlyInvoke();
419	>	if (ex == null && t.status < NORMAL)
420	>	ex = t.getException();
421	>	}
422	>	}
423	>	for (int i = 1; i <= last; ++i) {
424	>	ForkJoinTask<?> t = tasks[i];
425	>	if (t != null) {
426	>	if (ex != null)
427	>	t.cancel(false);
428	>	else {
429	>	t.quietlyJoin();
430	>	if (ex == null && t.status < NORMAL)
431	>	ex = t.getException();
432	>	}
433	>	}
434		}
435	+	if (ex != null)
436	+	UNSAFE.throwException(ex);
437		}
438
439		/**
440	<	* Returns result or throws exception using j.u.c.Future conventions
441	<	* Only call when isDone known to be true.
440	>	* Forks all tasks in the specified collection, returning when
441	>	* {@code isDone} holds for each task or an (unchecked) exception
442	>	* is encountered, in which case the exception is rethrown. If
443	>	* more than one task encounters an exception, then this method
444	>	* throws any one of these exceptions. If any task encounters an
445	>	* exception, others may be cancelled. However, the execution
446	>	* status of individual tasks is not guaranteed upon exceptional
447	>	* return. The status of each task may be obtained using {@link
448	>	* #getException()} and related methods to check if they have been
449	>	* cancelled, completed normally or exceptionally, or left
450	>	* unprocessed.
451	>	*
452	>	* <p>This method may be invoked only from within {@code
453	>	* ForkJoinTask} computations (as may be determined using method
454	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
455	>	* result in exceptions or errors, possibly including {@code
456	>	* ClassCastException}.
457	>	*
458	>	* @param tasks the collection of tasks
459	>	* @return the tasks argument, to simplify usage
460	>	* @throws NullPointerException if tasks or any element are null
461		*/
462	<	private V reportFutureResult()
463	<	throws ExecutionException, InterruptedException {
464	<	int s = status & COMPLETION_MASK;
465	<	if (s < NORMAL) {
360	<	Throwable ex;
361	<	if (s == CANCELLED)
362	<	throw new CancellationException();
363	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
364	<	throw new ExecutionException(ex);
365	<	if (Thread.interrupted())
366	<	throw new InterruptedException();
462	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
463	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
464	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
465	>	return tasks;
466		}
467	<	return getRawResult();
467	>	@SuppressWarnings("unchecked")
468	>	List<? extends ForkJoinTask<?>> ts =
469	>	(List<? extends ForkJoinTask<?>>) tasks;
470	>	Throwable ex = null;
471	>	int last = ts.size() - 1;
472	>	for (int i = last; i >= 0; --i) {
473	>	ForkJoinTask<?> t = ts.get(i);
474	>	if (t == null) {
475	>	if (ex == null)
476	>	ex = new NullPointerException();
477	>	}
478	>	else if (i != 0)
479	>	t.fork();
480	>	else {
481	>	t.quietlyInvoke();
482	>	if (ex == null && t.status < NORMAL)
483	>	ex = t.getException();
484	>	}
485	>	}
486	>	for (int i = 1; i <= last; ++i) {
487	>	ForkJoinTask<?> t = ts.get(i);
488	>	if (t != null) {
489	>	if (ex != null)
490	>	t.cancel(false);
491	>	else {
492	>	t.quietlyJoin();
493	>	if (ex == null && t.status < NORMAL)
494	>	ex = t.getException();
495	>	}
496	>	}
497	>	}
498	>	if (ex != null)
499	>	UNSAFE.throwException(ex);
500	>	return tasks;
501		}
502
503		/**
504	<	* Returns result or throws exception using j.u.c.Future conventions
505	<	* with timeouts
504	>	* Attempts to cancel execution of this task. This attempt will
505	>	* fail if the task has already completed, has already been
506	>	* cancelled, or could not be cancelled for some other reason. If
507	>	* successful, and this task has not started when cancel is
508	>	* called, execution of this task is suppressed, {@link
509	>	* #isCancelled} will report true, and {@link #join} will result
510	>	* in a {@code CancellationException} being thrown.
511	>	*
512	>	* <p>This method may be overridden in subclasses, but if so, must
513	>	* still ensure that these minimal properties hold. In particular,
514	>	* the {@code cancel} method itself must not throw exceptions.
515	>	*
516	>	* <p>This method is designed to be invoked by <em>other</em>
517	>	* tasks. To terminate the current task, you can just return or
518	>	* throw an unchecked exception from its computation method, or
519	>	* invoke {@link #completeExceptionally}.
520	>	*
521	>	* @param mayInterruptIfRunning this value is ignored in the
522	>	* default implementation because tasks are not
523	>	* cancelled via interruption
524	>	*
525	>	* @return {@code true} if this task is now cancelled
526		*/
527	<	private V reportTimedFutureResult()
528	<	throws InterruptedException, ExecutionException, TimeoutException {
529	<	Throwable ex;
378	<	int s = status & COMPLETION_MASK;
379	<	if (s == NORMAL)
380	<	return getRawResult();
381	<	if (s == CANCELLED)
382	<	throw new CancellationException();
383	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
384	<	throw new ExecutionException(ex);
385	<	if (Thread.interrupted())
386	<	throw new InterruptedException();
387	<	throw new TimeoutException();
527	>	public boolean cancel(boolean mayInterruptIfRunning) {
528	>	setCompletion(CANCELLED);
529	>	return status == CANCELLED;
530		}
531
390	–	// internal execution methods
391	–
532		/**
533	<	* Calls exec, recording completion, and rethrowing exception if
534	<	* encountered. Caller should normally check status before calling
535	<	* @return true if completed normally
533	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
534	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
535	>	* exceptions, but if it does anyway, we have no recourse during
536	>	* shutdown, so guard against this case.
537		*/
538	<	private boolean tryExec() {
539	<	try { // try block must contain only call to exec
540	<	if (!exec())
541	<	return false;
401	<	} catch (Throwable rex) {
402	<	setDoneExceptionally(rex);
403	<	rethrowException(rex);
404	<	return false; // not reached
538	>	final void cancelIgnoringExceptions() {
539	>	try {
540	>	cancel(false);
541	>	} catch (Throwable ignore) {
542		}
406	–	setNormalCompletion();
407	–	return true;
543		}
544
545		/**
546	<	* Main execution method used by worker threads. Invokes
547	<	* base computation unless already complete
546	>	* Cancels if current thread is a terminating worker thread,
547	>	* ignoring any exceptions thrown by cancel.
548		*/
549	<	final void quietlyExec() {
550	<	if (status >= 0) {
549	>	final void cancelIfTerminating() {
550	>	Thread t = Thread.currentThread();
551	>	if ((t instanceof ForkJoinWorkerThread) &&
552	>	((ForkJoinWorkerThread) t).isTerminating()) {
553		try {
554	<	if (!exec())
555	<	return;
419	<	} catch(Throwable rex) {
420	<	setDoneExceptionally(rex);
421	<	return;
554	>	cancel(false);
555	>	} catch (Throwable ignore) {
556		}
423	–	setNormalCompletion();
557		}
558		}
559
560	<	/**
561	<	* Calls exec, recording but not rethrowing exception
562	<	* Caller should normally check status before calling
563	<	* @return true if completed normally
564	<	*/
565	<	private boolean tryQuietlyInvoke() {
433	<	try {
434	<	if (!exec())
435	<	return false;
436	<	} catch (Throwable rex) {
437	<	setDoneExceptionally(rex);
438	<	return false;
439	<	}
440	<	setNormalCompletion();
441	<	return true;
560	>	public final boolean isDone() {
561	>	return status < 0;
562	>	}
563	>
564	>	public final boolean isCancelled() {
565	>	return status == CANCELLED;
566		}
567
568		/**
569	<	* Cancel, ignoring any exceptions it throws
569	>	* Returns {@code true} if this task threw an exception or was cancelled.
570	>	*
571	>	* @return {@code true} if this task threw an exception or was cancelled
572		*/
573	<	final void cancelIgnoreExceptions() {
574	<	try {
449	<	cancel(false);
450	<	} catch(Throwable ignore) {
451	<	}
573	>	public final boolean isCompletedAbnormally() {
574	>	return status < NORMAL;
575		}
576
454	–	// public methods
455	–
577		/**
578	<	* Arranges to asynchronously execute this task.  While it is not
579	<	* necessarily enforced, it is a usage error to fork a task more
580	<	* than once unless it has completed and been reinitialized.  This
581	<	* method may be invoked only from within other ForkJoinTask
582	<	* computations. Attempts to invoke in other contexts result in
462	<	* exceptions or errors including ClassCastException.
578	>	* Returns {@code true} if this task completed without throwing an
579	>	* exception and was not cancelled.
580	>	*
581	>	* @return {@code true} if this task completed without throwing an
582	>	* exception and was not cancelled
583		*/
584	<	public final void fork() {
585	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
584	>	public final boolean isCompletedNormally() {
585	>	return status == NORMAL;
586		}
587
588		/**
589	<	* Returns the result of the computation when it is ready.
590	<	* This method differs from <tt>get</tt> in that abnormal
591	<	* completion results in RuntimeExceptions or Errors, not
472	<	* ExecutionExceptions.
589	>	* Returns the exception thrown by the base computation, or a
590	>	* {@code CancellationException} if cancelled, or {@code null} if
591	>	* none or if the method has not yet completed.
592		*
593	<	* @return the computed result
593	>	* @return the exception, or {@code null} if none
594		*/
595	<	public final V join() {
596	<	ForkJoinWorkerThread w = getWorker();
597	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
598	<	reportException(awaitDone(w, true));
599	<	return getRawResult();
595	>	public final Throwable getException() {
596	>	int s = status;
597	>	return ((s >= NORMAL)    ? null :
598	>	(s == CANCELLED) ? new CancellationException() :
599	>	exceptionMap.get(this));
600		}
601
602	<	public final V get() throws InterruptedException, ExecutionException {
603	<	ForkJoinWorkerThread w = getWorker();
604	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
605	<	awaitDone(w, true);
606	<	return reportFutureResult();
602	>	/**
603	>	* Completes this task abnormally, and if not already aborted or
604	>	* cancelled, causes it to throw the given exception upon
605	>	* {@code join} and related operations. This method may be used
606	>	* to induce exceptions in asynchronous tasks, or to force
607	>	* completion of tasks that would not otherwise complete.  Its use
608	>	* in other situations is discouraged.  This method is
609	>	* overridable, but overridden versions must invoke {@code super}
610	>	* implementation to maintain guarantees.
611	>	*
612	>	* @param ex the exception to throw. If this exception is not a
613	>	* {@code RuntimeException} or {@code Error}, the actual exception
614	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
615	>	*/
616	>	public void completeExceptionally(Throwable ex) {
617	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
618	>	(ex instanceof Error) ? ex :
619	>	new RuntimeException(ex));
620		}
621
622	<	public final V get(long timeout, TimeUnit unit)
623	<	throws InterruptedException, ExecutionException, TimeoutException {
624	<	ForkJoinWorkerThread w = getWorker();
625	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
626	<	awaitDone(w, unit.toNanos(timeout));
627	<	return reportTimedFutureResult();
622	>	/**
623	>	* Completes this task, and if not already aborted or cancelled,
624	>	* returning the given value as the result of subsequent
625	>	* invocations of {@code join} and related operations. This method
626	>	* may be used to provide results for asynchronous tasks, or to
627	>	* provide alternative handling for tasks that would not otherwise
628	>	* complete normally. Its use in other situations is
629	>	* discouraged. This method is overridable, but overridden
630	>	* versions must invoke {@code super} implementation to maintain
631	>	* guarantees.
632	>	*
633	>	* @param value the result value for this task
634	>	*/
635	>	public void complete(V value) {
636	>	try {
637	>	setRawResult(value);
638	>	} catch (Throwable rex) {
639	>	setExceptionalCompletion(rex);
640	>	return;
641	>	}
642	>	setCompletion(NORMAL);
643		}
644
645		/**
646	<	* Possibly executes other tasks until this task is ready, then
500	<	* returns the result of the computation.  This method may be more
501	<	* efficient than <tt>join</tt>, but is only applicable when there
502	<	* are no potemtial dependencies between continuation of the
503	<	* current task and that of any other task that might be executed
504	<	* while helping. (This usually holds for pure divide-and-conquer
505	<	* tasks).
506	<	* @return the computed result
646	>	* @throws CancellationException {@inheritDoc}
647		*/
648	<	public final V helpJoin() {
649	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
650	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
651	<	reportException(w.helpJoinTask(this));
648	>	public final V get() throws InterruptedException, ExecutionException {
649	>	int s;
650	>	if (Thread.currentThread() instanceof ForkJoinWorkerThread) {
651	>	quietlyJoin();
652	>	s = status;
653	>	}
654	>	else {
655	>	while ((s = status) >= 0) {
656	>	synchronized (this) { // interruptible form of awaitDone
657	>	if (UNSAFE.compareAndSwapInt(this, statusOffset,
658	>	s, SIGNAL)) {
659	>	while (status >= 0)
660	>	wait();
661	>	}
662	>	}
663	>	}
664	>	}
665	>	if (s < NORMAL) {
666	>	Throwable ex;
667	>	if (s == CANCELLED)
668	>	throw new CancellationException();
669	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
670	>	throw new ExecutionException(ex);
671	>	}
672		return getRawResult();
673		}
674
675		/**
676	<	* Performs this task, awaits its completion if necessary, and
517	<	* return its result.
518	<	* @throws Throwable (a RuntimeException, Error, or unchecked
519	<	* exception) if the underlying computation did so.
520	<	* @return the computed result
676	>	* @throws CancellationException {@inheritDoc}
677		*/
678	<	public final V invoke() {
679	<	if (status >= 0 && tryExec())
680	<	return getRawResult();
678	>	public final V get(long timeout, TimeUnit unit)
679	>	throws InterruptedException, ExecutionException, TimeoutException {
680	>	Thread t = Thread.currentThread();
681	>	ForkJoinPool pool;
682	>	if (t instanceof ForkJoinWorkerThread) {
683	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
684	>	if (status >= 0 && w.unpushTask(this))
685	>	quietlyExec();
686	>	pool = w.pool;
687	>	}
688		else
689	<	return join();
689	>	pool = null;
690	>	/*
691	>	* Timed wait loop intermixes cases for FJ (pool != null) and
692	>	* non FJ threads. For FJ, decrement pool count but don't try
693	>	* for replacement; increment count on completion. For non-FJ,
694	>	* deal with interrupts. This is messy, but a little less so
695	>	* than is splitting the FJ and nonFJ cases.
696	>	*/
697	>	boolean interrupted = false;
698	>	boolean dec = false; // true if pool count decremented
699	>	long nanos = unit.toNanos(timeout);
700	>	for (;;) {
701	>	if (pool == null && Thread.interrupted()) {
702	>	interrupted = true;
703	>	break;
704	>	}
705	>	int s = status;
706	>	if (s < 0)
707	>	break;
708	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
709	>	long startTime = System.nanoTime();
710	>	long nt; // wait time
711	>	while (status >= 0 &&
712	>	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
713	>	if (pool != null && !dec)
714	>	dec = pool.tryDecrementRunningCount();
715	>	else {
716	>	long ms = nt / 1000000;
717	>	int ns = (int) (nt % 1000000);
718	>	try {
719	>	synchronized (this) {
720	>	if (status >= 0)
721	>	wait(ms, ns);
722	>	}
723	>	} catch (InterruptedException ie) {
724	>	if (pool != null)
725	>	cancelIfTerminating();
726	>	else {
727	>	interrupted = true;
728	>	break;
729	>	}
730	>	}
731	>	}
732	>	}
733	>	break;
734	>	}
735	>	}
736	>	if (pool != null && dec)
737	>	pool.incrementRunningCount();
738	>	if (interrupted)
739	>	throw new InterruptedException();
740	>	int es = status;
741	>	if (es != NORMAL) {
742	>	Throwable ex;
743	>	if (es == CANCELLED)
744	>	throw new CancellationException();
745	>	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
746	>	throw new ExecutionException(ex);
747	>	throw new TimeoutException();
748	>	}
749	>	return getRawResult();
750		}
751
752		/**
753	<	* Joins this task, without returning its result or throwing an
753	>	* Joins this task, without returning its result or throwing its
754		* exception. This method may be useful when processing
755		* collections of tasks when some have been cancelled or otherwise
756		* known to have aborted.
757		*/
758		public final void quietlyJoin() {
759	<	if (status >= 0) {
760	<	ForkJoinWorkerThread w = getWorker();
761	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
762	<	awaitDone(w, true);
759	>	Thread t;
760	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
761	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
762	>	if (status >= 0) {
763	>	if (w.unpushTask(this)) {
764	>	boolean completed;
765	>	try {
766	>	completed = exec();
767	>	} catch (Throwable rex) {
768	>	setExceptionalCompletion(rex);
769	>	return;
770	>	}
771	>	if (completed) {
772	>	setCompletion(NORMAL);
773	>	return;
774	>	}
775	>	}
776	>	w.joinTask(this);
777	>	}
778		}
779	+	else
780	+	externalAwaitDone();
781		}
782
783		/**
784	<	* Possibly executes other tasks until this task is ready.
784	>	* Commences performing this task and awaits its completion if
785	>	* necessary, without returning its result or throwing its
786	>	* exception.
787		*/
788	<	public final void quietlyHelpJoin() {
788	>	public final void quietlyInvoke() {
789		if (status >= 0) {
790	<	ForkJoinWorkerThread w =
791	<	(ForkJoinWorkerThread)(Thread.currentThread());
792	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
793	<	w.helpJoinTask(this);
790	>	boolean completed;
791	>	try {
792	>	completed = exec();
793	>	} catch (Throwable rex) {
794	>	setExceptionalCompletion(rex);
795	>	return;
796	>	}
797	>	if (completed)
798	>	setCompletion(NORMAL);
799	>	else
800	>	quietlyJoin();
801		}
802		}
803
804		/**
805	<	* Performs this task and awaits its completion if necessary,
806	<	* without returning its result or throwing an exception. This
807	<	* method may be useful when processing collections of tasks when
808	<	* some have been cancelled or otherwise known to have aborted.
805	>	* Possibly executes tasks until the pool hosting the current task
806	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
807	>	* be of use in designs in which many tasks are forked, but none
808	>	* are explicitly joined, instead executing them until all are
809	>	* processed.
810	>	*
811	>	* <p>This method may be invoked only from within {@code
812	>	* ForkJoinTask} computations (as may be determined using method
813	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
814	>	* result in exceptions or errors, possibly including {@code
815	>	* ClassCastException}.
816		*/
817	<	public final void quietlyInvoke() {
818	<	if (status >= 0 && !tryQuietlyInvoke())
819	<	quietlyJoin();
817	>	public static void helpQuiesce() {
818	>	((ForkJoinWorkerThread) Thread.currentThread())
819	>	.helpQuiescePool();
820		}
821
822		/**
823	<	* Returns true if the computation performed by this task has
824	<	* completed (or has been cancelled).
825	<	* @return true if this computation has completed
823	>	* Resets the internal bookkeeping state of this task, allowing a
824	>	* subsequent {@code fork}. This method allows repeated reuse of
825	>	* this task, but only if reuse occurs when this task has either
826	>	* never been forked, or has been forked, then completed and all
827	>	* outstanding joins of this task have also completed. Effects
828	>	* under any other usage conditions are not guaranteed.
829	>	* This method may be useful when executing
830	>	* pre-constructed trees of subtasks in loops.
831		*/
832	<	public final boolean isDone() {
833	<	return status < 0;
832	>	public void reinitialize() {
833	>	if (status == EXCEPTIONAL)
834	>	exceptionMap.remove(this);
835	>	status = 0;
836		}
837
838		/**
839	<	* Returns true if this task was cancelled.
840	<	* @return true if this task was cancelled
839	>	* Returns the pool hosting the current task execution, or null
840	>	* if this task is executing outside of any ForkJoinPool.
841	>	*
842	>	* @see #inForkJoinPool
843	>	* @return the pool, or {@code null} if none
844		*/
845	<	public final boolean isCancelled() {
846	<	return (status & COMPLETION_MASK) == CANCELLED;
845	>	public static ForkJoinPool getPool() {
846	>	Thread t = Thread.currentThread();
847	>	return (t instanceof ForkJoinWorkerThread) ?
848	>	((ForkJoinWorkerThread) t).pool : null;
849		}
850
851		/**
852	<	* Returns true if this task threw an exception or was cancelled
853	<	* @return true if this task threw an exception or was cancelled
852	>	* Returns {@code true} if the current thread is executing as a
853	>	* ForkJoinPool computation.
854	>	*
855	>	* @return {@code true} if the current thread is executing as a
856	>	* ForkJoinPool computation, or false otherwise
857		*/
858	<	public final boolean completedAbnormally() {
859	<	return (status & COMPLETION_MASK) < NORMAL;
858	>	public static boolean inForkJoinPool() {
859	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
860		}
861
862		/**
863	<	* Returns the exception thrown by the base computation, or a
864	<	* CancellationException if cancelled, or null if none or if the
865	<	* method has not yet completed.
866	<	* @return the exception, or null if none
863	>	* Tries to unschedule this task for execution. This method will
864	>	* typically succeed if this task is the most recently forked task
865	>	* by the current thread, and has not commenced executing in
866	>	* another thread.  This method may be useful when arranging
867	>	* alternative local processing of tasks that could have been, but
868	>	* were not, stolen.
869	>	*
870	>	* <p>This method may be invoked only from within {@code
871	>	* ForkJoinTask} computations (as may be determined using method
872	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
873	>	* result in exceptions or errors, possibly including {@code
874	>	* ClassCastException}.
875	>	*
876	>	* @return {@code true} if unforked
877		*/
878	<	public final Throwable getException() {
879	<	int s = status & COMPLETION_MASK;
880	<	if (s >= NORMAL)
600	<	return null;
601	<	if (s == CANCELLED)
602	<	return new CancellationException();
603	<	return exceptionMap.get(this);
878	>	public boolean tryUnfork() {
879	>	return ((ForkJoinWorkerThread) Thread.currentThread())
880	>	.unpushTask(this);
881		}
882
883		/**
884	<	* Asserts that the results of this task's computation will not be
885	<	* used. If a cancellation occurs before this task is processed,
886	<	* then its <tt>compute</tt> method will not be executed,
887	<	* <tt>isCancelled</tt> will report true, and <tt>join</tt> will
611	<	* result in a CancellationException being thrown. Otherwise, when
612	<	* cancellation races with completion, there are no guarantees
613	<	* about whether <tt>isCancelled</tt> will report true, whether
614	<	* <tt>join</tt> will return normally or via an exception, or
615	<	* whether these behaviors will remain consistent upon repeated
616	<	* invocation.
884	>	* Returns an estimate of the number of tasks that have been
885	>	* forked by the current worker thread but not yet executed. This
886	>	* value may be useful for heuristic decisions about whether to
887	>	* fork other tasks.
888		*
889	<	* <p>This method may be overridden in subclasses, but if so, must
890	<	* still ensure that these minimal properties hold. In particular,
891	<	* the cancel method itself must not throw exceptions.
889	>	* <p>This method may be invoked only from within {@code
890	>	* ForkJoinTask} computations (as may be determined using method
891	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
892	>	* result in exceptions or errors, possibly including {@code
893	>	* ClassCastException}.
894		*
895	<	* <p> This method is designed to be invoked by <em>other</em>
896	<	* tasks. To terminate the current task, you can just return or
897	<	* throw an unchecked exception from its computation method, or
898	<	* invoke <tt>completeExceptionally(someException)</tt>.
895	>	* @return the number of tasks
896	>	*/
897	>	public static int getQueuedTaskCount() {
898	>	return ((ForkJoinWorkerThread) Thread.currentThread())
899	>	.getQueueSize();
900	>	}
901	>
902	>	/**
903	>	* Returns an estimate of how many more locally queued tasks are
904	>	* held by the current worker thread than there are other worker
905	>	* threads that might steal them.  This value may be useful for
906	>	* heuristic decisions about whether to fork other tasks. In many
907	>	* usages of ForkJoinTasks, at steady state, each worker should
908	>	* aim to maintain a small constant surplus (for example, 3) of
909	>	* tasks, and to process computations locally if this threshold is
910	>	* exceeded.
911		*
912	<	* @param mayInterruptIfRunning this value is ignored in the
913	<	* default implementation because tasks are not in general
914	<	* cancelled via interruption.
912	>	* <p>This method may be invoked only from within {@code
913	>	* ForkJoinTask} computations (as may be determined using method
914	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
915	>	* result in exceptions or errors, possibly including {@code
916	>	* ClassCastException}.
917		*
918	<	* @return true if this task is now cancelled
918	>	* @return the surplus number of tasks, which may be negative
919		*/
920	<	public boolean cancel(boolean mayInterruptIfRunning) {
921	<	setCompletion(CANCELLED);
922	<	return (status & COMPLETION_MASK) == CANCELLED;
920	>	public static int getSurplusQueuedTaskCount() {
921	>	return ((ForkJoinWorkerThread) Thread.currentThread())
922	>	.getEstimatedSurplusTaskCount();
923		}
924
925	+	// Extension methods
926	+
927		/**
928	<	* Completes this task abnormally, and if not already aborted or
929	<	* cancelled, causes it to throw the given exception upon
930	<	* <tt>join</tt> and related operations. This method may be used
931	<	* to induce exceptions in asynchronous tasks, or to force
932	<	* completion of tasks that would not otherwise complete.  This
933	<	* method is overridable, but overridden versions must invoke
934	<	* <tt>super</tt> implementation to maintain guarantees.
646	<	* @param ex the exception to throw. If this exception is
647	<	* not a RuntimeException or Error, the actual exception thrown
648	<	* will be a RuntimeException with cause ex.
928	>	* Returns the result that would be returned by {@link #join}, even
929	>	* if this task completed abnormally, or {@code null} if this task
930	>	* is not known to have been completed.  This method is designed
931	>	* to aid debugging, as well as to support extensions. Its use in
932	>	* any other context is discouraged.
933	>	*
934	>	* @return the result, or {@code null} if not completed
935		*/
936	<	public void completeExceptionally(Throwable ex) {
651	<	setDoneExceptionally((ex instanceof RuntimeException) ||
652	<	(ex instanceof Error)? ex :
653	<	new RuntimeException(ex));
654	<	}
936	>	public abstract V getRawResult();
937
938		/**
939	<	* Completes this task, and if not already aborted or cancelled,
940	<	* returning a <tt>null</tt> result upon <tt>join</tt> and related
941	<	* operations. This method may be used to provide results for
660	<	* asynchronous tasks, or to provide alternative handling for
661	<	* tasks that would not otherwise complete normally.
939	>	* Forces the given value to be returned as a result.  This method
940	>	* is designed to support extensions, and should not in general be
941	>	* called otherwise.
942		*
943	<	* @param value the result value for this task.
943	>	* @param value the value
944		*/
945	<	public void complete(V value) {
666	<	try {
667	<	setRawResult(value);
668	<	} catch(Throwable rex) {
669	<	setDoneExceptionally(rex);
670	<	return;
671	<	}
672	<	setNormalCompletion();
673	<	}
945	>	protected abstract void setRawResult(V value);
946
947		/**
948	<	* Resets the internal bookkeeping state of this task, allowing a
949	<	* subsequent <tt>fork</tt>. This method allows repeated reuse of
950	<	* this task, but only if reuse occurs when this task has either
951	<	* never been forked, or has been forked, then completed and all
952	<	* outstanding joins of this task have also completed. Effects
953	<	* under any other usage conditions are not guaranteed, and are
954	<	* almost surely wrong. This method may be useful when executing
955	<	* pre-constructed trees of subtasks in loops.
948	>	* Immediately performs the base action of this task.  This method
949	>	* is designed to support extensions, and should not in general be
950	>	* called otherwise. The return value controls whether this task
951	>	* is considered to be done normally. It may return false in
952	>	* asynchronous actions that require explicit invocations of
953	>	* {@link #complete} to become joinable. It may also throw an
954	>	* (unchecked) exception to indicate abnormal exit.
955	>	*
956	>	* @return {@code true} if completed normally
957		*/
958	<	public void reinitialize() {
686	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
687	<	exceptionMap.remove(this);
688	<	status = 0;
689	<	}
958	>	protected abstract boolean exec();
959
960		/**
961	<	* Tries to unschedule this task for execution. This method will
962	<	* typically succeed if this task is the next task that would be
963	<	* executed by the current thread, and will typically fail (return
964	<	* false) otherwise. This method may be useful when arranging
965	<	* faster local processing of tasks that could have been, but were
966	<	* not, stolen.
967	<	* @return true if unforked
961	>	* Returns, but does not unschedule or execute, a task queued by
962	>	* the current thread but not yet executed, if one is immediately
963	>	* available. There is no guarantee that this task will actually
964	>	* be polled or executed next. Conversely, this method may return
965	>	* null even if a task exists but cannot be accessed without
966	>	* contention with other threads.  This method is designed
967	>	* primarily to support extensions, and is unlikely to be useful
968	>	* otherwise.
969	>	*
970	>	* <p>This method may be invoked only from within {@code
971	>	* ForkJoinTask} computations (as may be determined using method
972	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
973	>	* result in exceptions or errors, possibly including {@code
974	>	* ClassCastException}.
975	>	*
976	>	* @return the next task, or {@code null} if none are available
977		*/
978	<	public boolean tryUnfork() {
979	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
978	>	protected static ForkJoinTask<?> peekNextLocalTask() {
979	>	return ((ForkJoinWorkerThread) Thread.currentThread())
980	>	.peekTask();
981		}
982
983		/**
984	<	* Forks both tasks, returning when <tt>isDone</tt> holds for both
985	<	* of them or an exception is encountered. This method may be
986	<	* invoked only from within other ForkJoinTask
987	<	* computations. Attempts to invoke in other contexts result in
988	<	* exceptions or errors including ClassCastException.
989	<	* @param t1 one task
990	<	* @param t2 the other task
991	<	* @throws NullPointerException if t1 or t2 are null
992	<	* @throws RuntimeException or Error if either task did so.
984	>	* Unschedules and returns, without executing, the next task
985	>	* queued by the current thread but not yet executed.  This method
986	>	* is designed primarily to support extensions, and is unlikely to
987	>	* be useful otherwise.
988	>	*
989	>	* <p>This method may be invoked only from within {@code
990	>	* ForkJoinTask} computations (as may be determined using method
991	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
992	>	* result in exceptions or errors, possibly including {@code
993	>	* ClassCastException}.
994	>	*
995	>	* @return the next task, or {@code null} if none are available
996		*/
997	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
998	<	t2.fork();
999	<	t1.invoke();
718	<	t2.join();
997	>	protected static ForkJoinTask<?> pollNextLocalTask() {
998	>	return ((ForkJoinWorkerThread) Thread.currentThread())
999	>	.pollLocalTask();
1000		}
1001
1002		/**
1003	<	* Forks the given tasks, returning when <tt>isDone</tt> holds for
1004	<	* all of them. If any task encounters an exception, others may be
1005	<	* cancelled.  This method may be invoked only from within other
1006	<	* ForkJoinTask computations. Attempts to invoke in other contexts
1007	<	* result in exceptions or errors including ClassCastException.
1008	<	* @param tasks the array of tasks
1009	<	* @throws NullPointerException if tasks or any element are null.
1010	<	* @throws RuntimeException or Error if any task did so.
1003	>	* Unschedules and returns, without executing, the next task
1004	>	* queued by the current thread but not yet executed, if one is
1005	>	* available, or if not available, a task that was forked by some
1006	>	* other thread, if available. Availability may be transient, so a
1007	>	* {@code null} result does not necessarily imply quiescence
1008	>	* of the pool this task is operating in.  This method is designed
1009	>	* primarily to support extensions, and is unlikely to be useful
1010	>	* otherwise.
1011	>	*
1012	>	* <p>This method may be invoked only from within {@code
1013	>	* ForkJoinTask} computations (as may be determined using method
1014	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1015	>	* result in exceptions or errors, possibly including {@code
1016	>	* ClassCastException}.
1017	>	*
1018	>	* @return a task, or {@code null} if none are available
1019		*/
1020	<	public static void invokeAll(ForkJoinTask<?>... tasks) {
1021	<	Throwable ex = null;
1022	<	int last = tasks.length - 1;
734	<	for (int i = last; i >= 0; --i) {
735	<	ForkJoinTask<?> t = tasks[i];
736	<	if (t == null) {
737	<	if (ex == null)
738	<	ex = new NullPointerException();
739	<	}
740	<	else if (i != 0)
741	<	t.fork();
742	<	else {
743	<	t.quietlyInvoke();
744	<	if (ex == null)
745	<	ex = t.getException();
746	<	}
747	<	}
748	<	for (int i = 1; i <= last; ++i) {
749	<	ForkJoinTask<?> t = tasks[i];
750	<	if (t != null) {
751	<	if (ex != null)
752	<	t.cancel(false);
753	<	else {
754	<	t.quietlyJoin();
755	<	if (ex == null)
756	<	ex = t.getException();
757	<	}
758	<	}
759	<	}
760	<	if (ex != null)
761	<	rethrowException(ex);
1020	>	protected static ForkJoinTask<?> pollTask() {
1021	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1022	>	.pollTask();
1023		}
1024
1025		/**
1026	<	* Forks all tasks in the collection, returning when
1027	<	* <tt>isDone</tt> holds for all of them. If any task encounters
1028	<	* an exception, others may be cancelled.  This method may be
768	<	* invoked only from within other ForkJoinTask
769	<	* computations. Attempts to invoke in other contexts result in
770	<	* exceptions or errors including ClassCastException.
771	<	* @param tasks the collection of tasks
772	<	* @throws NullPointerException if tasks or any element are null.
773	<	* @throws RuntimeException or Error if any task did so.
1026	>	* Adaptor for Runnables. This implements RunnableFuture
1027	>	* to be compliant with AbstractExecutorService constraints
1028	>	* when used in ForkJoinPool.
1029		*/
1030	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
1031	<	if (!(tasks instanceof List)) {
1032	<	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
1033	<	return;
1034	<	}
1035	<	List<? extends ForkJoinTask<?>> ts =
1036	<	(List<? extends ForkJoinTask<?>>)tasks;
1037	<	Throwable ex = null;
1038	<	int last = ts.size() - 1;
784	<	for (int i = last; i >= 0; --i) {
785	<	ForkJoinTask<?> t = ts.get(i);
786	<	if (t == null) {
787	<	if (ex == null)
788	<	ex = new NullPointerException();
789	<	}
790	<	else if (i != 0)
791	<	t.fork();
792	<	else {
793	<	t.quietlyInvoke();
794	<	if (ex == null)
795	<	ex = t.getException();
796	<	}
1030	>	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1031	>	implements RunnableFuture<T> {
1032	>	final Runnable runnable;
1033	>	final T resultOnCompletion;
1034	>	T result;
1035	>	AdaptedRunnable(Runnable runnable, T result) {
1036	>	if (runnable == null) throw new NullPointerException();
1037	>	this.runnable = runnable;
1038	>	this.resultOnCompletion = result;
1039		}
1040	<	for (int i = 1; i <= last; ++i) {
1041	<	ForkJoinTask<?> t = ts.get(i);
1042	<	if (t != null) {
1043	<	if (ex != null)
1044	<	t.cancel(false);
1045	<	else {
804	<	t.quietlyJoin();
805	<	if (ex == null)
806	<	ex = t.getException();
807	<	}
808	<	}
1040	>	public T getRawResult() { return result; }
1041	>	public void setRawResult(T v) { result = v; }
1042	>	public boolean exec() {
1043	>	runnable.run();
1044	>	result = resultOnCompletion;
1045	>	return true;
1046		}
1047	<	if (ex != null)
1048	<	rethrowException(ex);
1047	>	public void run() { invoke(); }
1048	>	private static final long serialVersionUID = 5232453952276885070L;
1049		}
1050
1051		/**
1052	<	* Possibly executes tasks until the pool hosting the current task
816	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
817	<	* designs in which many tasks are forked, but none are explicitly
818	<	* joined, instead executing them until all are processed.
1052	>	* Adaptor for Callables
1053		*/
1054	<	public static void helpQuiesce() {
1055	<	((ForkJoinWorkerThread)(Thread.currentThread())).
1056	<	helpQuiescePool();
1054	>	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1055	>	implements RunnableFuture<T> {
1056	>	final Callable<? extends T> callable;
1057	>	T result;
1058	>	AdaptedCallable(Callable<? extends T> callable) {
1059	>	if (callable == null) throw new NullPointerException();
1060	>	this.callable = callable;
1061	>	}
1062	>	public T getRawResult() { return result; }
1063	>	public void setRawResult(T v) { result = v; }
1064	>	public boolean exec() {
1065	>	try {
1066	>	result = callable.call();
1067	>	return true;
1068	>	} catch (Error err) {
1069	>	throw err;
1070	>	} catch (RuntimeException rex) {
1071	>	throw rex;
1072	>	} catch (Exception ex) {
1073	>	throw new RuntimeException(ex);
1074	>	}
1075	>	}
1076	>	public void run() { invoke(); }
1077	>	private static final long serialVersionUID = 2838392045355241008L;
1078		}
1079
1080		/**
1081	<	* Returns a estimate of how many more locally queued tasks are
1082	<	* held by the current worker thread than there are other worker
1083	<	* threads that might want to steal them.  This value may be
1084	<	* useful for heuristic decisions about whether to fork other
1085	<	* tasks. In many usages of ForkJoinTasks, at steady state, each
1086	<	* worker should aim to maintain a small constant surplus (for
832	<	* example, 3) of tasks, and to process computations locally if
833	<	* this threshold is exceeded.
834	<	* @return the surplus number of tasks, which may be negative
1081	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1082	>	* method of the given {@code Runnable} as its action, and returns
1083	>	* a null result upon {@link #join}.
1084	>	*
1085	>	* @param runnable the runnable action
1086	>	* @return the task
1087		*/
1088	<	public static int surplus() {
1089	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
838	<	.getEstimatedSurplusTaskCount();
1088	>	public static ForkJoinTask<?> adapt(Runnable runnable) {
1089	>	return new AdaptedRunnable<Void>(runnable, null);
1090		}
1091
841	–	// Extension kit
842	–
1092		/**
1093	<	* Returns the result that would be returned by <tt>join</tt>, or
1094	<	* null if this task is not known to have been completed.  This
1095	<	* method is designed to aid debugging, as well as to support
847	<	* extensions. Its use in any other context is discouraged.
1093	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1094	>	* method of the given {@code Runnable} as its action, and returns
1095	>	* the given result upon {@link #join}.
1096		*
1097	<	* @return the result, or null if not completed.
1097	>	* @param runnable the runnable action
1098	>	* @param result the result upon completion
1099	>	* @return the task
1100		*/
1101	<	public abstract V getRawResult();
1101	>	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1102	>	return new AdaptedRunnable<T>(runnable, result);
1103	>	}
1104
1105		/**
1106	<	* Forces the given value to be returned as a result.  This method
1107	<	* is designed to support extensions, and should not in general be
1108	<	* called otherwise.
1106	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1107	>	* method of the given {@code Callable} as its action, and returns
1108	>	* its result upon {@link #join}, translating any checked exceptions
1109	>	* encountered into {@code RuntimeException}.
1110		*
1111	<	* @param value the value
1112	<	*/
860	<	protected abstract void setRawResult(V value);
861	<
862	<	/**
863	<	* Immediately performs the base action of this task.  This method
864	<	* is designed to support extensions, and should not in general be
865	<	* called otherwise. The return value controls whether this task
866	<	* is considered to be done normally. It may return false in
867	<	* asynchronous actions that require explicit invocations of
868	<	* <tt>complete</tt> to become joinable. It may throw exceptions
869	<	* to indicate abnormal exit.
870	<	* @return true if completed normally
871	<	* @throws Error or RuntimeException if encountered during computation
1111	>	* @param callable the callable action
1112	>	* @return the task
1113		*/
1114	<	protected abstract boolean exec();
1114	>	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1115	>	return new AdaptedCallable<T>(callable);
1116	>	}
1117
1118		// Serialization support
1119
1120		private static final long serialVersionUID = -7721805057305804111L;
1121
1122		/**
1123	<	* Save the state to a stream.
1123	>	* Saves the state to a stream (that is, serializes it).
1124		*
1125		* @serialData the current run status and the exception thrown
1126	<	* during execution, or null if none.
1126	>	* during execution, or {@code null} if none
1127		* @param s the stream
1128		*/
1129		private void writeObject(java.io.ObjectOutputStream s)
#	Line 890 | Line 1133 | public abstract class ForkJoinTask<V> im
1133		}
1134
1135		/**
1136	<	* Reconstitute the instance from a stream.
1136	>	* Reconstitutes the instance from a stream (that is, deserializes it).
1137	>	*
1138		* @param s the stream
1139		*/
1140		private void readObject(java.io.ObjectInputStream s)
1141		throws java.io.IOException, ClassNotFoundException {
1142		s.defaultReadObject();
899	–	//        status &= ~INTERNAL_SIGNAL_MASK; //  todo: define policy
1143		Object ex = s.readObject();
1144		if (ex != null)
1145	<	setDoneExceptionally((Throwable)ex);
1145	>	setExceptionalCompletion((Throwable) ex);
1146		}
1147
1148	<	// Temporary Unsafe mechanics for preliminary release
1148	>	// Unsafe mechanics
1149
1150	<	static final Unsafe _unsafe;
1151	<	static final long statusOffset;
1150	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1151	>	private static final long statusOffset =
1152	>	objectFieldOffset("status", ForkJoinTask.class);
1153
1154	<	static {
1154	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1155		try {
1156	<	if (ForkJoinTask.class.getClassLoader() != null) {
1157	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1158	<	f.setAccessible(true);
1159	<	_unsafe = (Unsafe)f.get(null);
1160	<	}
1161	<	else
1162	<	_unsafe = Unsafe.getUnsafe();
919	<	statusOffset = _unsafe.objectFieldOffset
920	<	(ForkJoinTask.class.getDeclaredField("status"));
921	<	} catch (Exception ex) { throw new Error(ex); }
1156	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1157	>	} catch (NoSuchFieldException e) {
1158	>	// Convert Exception to corresponding Error
1159	>	NoSuchFieldError error = new NoSuchFieldError(field);
1160	>	error.initCause(e);
1161	>	throw error;
1162	>	}
1163		}
1164
1165	+	/**
1166	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1167	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1168	+	* into a jdk.
1169	+	*
1170	+	* @return a sun.misc.Unsafe
1171	+	*/
1172	+	private static sun.misc.Unsafe getUnsafe() {
1173	+	try {
1174	+	return sun.misc.Unsafe.getUnsafe();
1175	+	} catch (SecurityException se) {
1176	+	try {
1177	+	return java.security.AccessController.doPrivileged
1178	+	(new java.security
1179	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1180	+	public sun.misc.Unsafe run() throws Exception {
1181	+	java.lang.reflect.Field f = sun.misc
1182	+	.Unsafe.class.getDeclaredField("theUnsafe");
1183	+	f.setAccessible(true);
1184	+	return (sun.misc.Unsafe) f.get(null);
1185	+	}});
1186	+	} catch (java.security.PrivilegedActionException e) {
1187	+	throw new RuntimeException("Could not initialize intrinsics",
1188	+	e.getCause());
1189	+	}
1190	+	}
1191	+	}
1192		}

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