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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 1.54 by dl, Wed Aug 11 19:44:30 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}.  However, this class also provides a number of other
32	>	* methods that can come into play in advanced usages, as well as
33	>	* extension mechanics that allow support of new forms of fork/join
34	>	* processing.
35		*
36	<	* <p> 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	>	* 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	>	* COMPLETED. CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
157	>	* waits by other threads have the SIGNAL bit set.  Completion of
158	>	* a stolen task with SIGNAL set awakens any waiters via
159	>	* notifyAll. Even though suboptimal for some purposes, we use
160	>	* basic builtin wait/notify to take advantage of "monitor
161	>	* inflation" in JVMs that we would otherwise need to emulate to
162	>	* avoid adding further per-task bookkeeping overhead.  We want
163	>	* these monitors to be "fat", i.e., not use biasing or thin-lock
164	>	* techniques, so use some odd coding idioms that tend to avoid
165	>	* them.
166	>	*/
167	>
168	>	/** The run status of this task */
169	>	volatile int status; // accessed directly by pool and workers
170	>
171	>	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
188	>	// Maintaining completion status
189
190		/**
191	<	* Get current worker thread, or null if not a worker thread
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	<	static ForkJoinWorkerThread getWorker() {
197	<	Thread t = Thread.currentThread();
198	<	return ((t instanceof ForkJoinWorkerThread)?
199	<	(ForkJoinWorkerThread)t : null);
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	>	}
205		}
206
207		/**
208	<	* Get pool of current worker thread, or null if not a worker thread
208	>	* Record exception and set exceptional completion
209	>	* @return status on exit
210		*/
211	<	static ForkJoinPool getWorkerPool() {
212	<	Thread t = Thread.currentThread();
213	<	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);
211	>	private void setExceptionalCompletion(Throwable rex) {
212	>	exceptionMap.put(this, rex);
213	>	setCompletion(EXCEPTIONAL);
214		}
215
216		/**
217	<	* Workaround for not being able to rethrow unchecked exceptions.
217	>	* Blocks a worker thread until completion. Called only by pool.
218		*/
219	<	static void rethrowException(Throwable ex) {
220	<	if (ex != null)
221	<	_unsafe.throwException(ex);
219	>	final void internalAwaitDone() {
220	>	int s;         // the odd construction reduces lock bias effects
221	>	while ((s = status) >= 0) {
222	>	try {
223	>	synchronized(this) {
224	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
225	>	wait();
226	>	}
227	>	} catch (InterruptedException ie) {
228	>	cancelIfTerminating();
229	>	}
230	>	}
231		}
232
168	–	// Setting completion status
169	–
233		/**
234	<	* Mark completion and wake up threads waiting to join this task.
172	<	* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
234	>	* Blocks a non-worker-thread until completion.
235		*/
236	<	final void setCompletion(int completion) {
237	<	ForkJoinPool pool = getWorkerPool();
238	<	if (pool != null) {
239	<	int s; // Clear signal bits while setting completion status
240	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
241	<
242	<	if ((s & SIGNAL_MASK) != 0) {
243	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
244	<	pool.updateRunningCount(s);
245	<	synchronized(this) { notifyAll(); }
236	>	private void externalAwaitDone() {
237	>	int s;
238	>	while ((s = status) >= 0) {
239	>	synchronized(this) {
240	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
241	>	boolean interrupted = false;
242	>	while (status >= 0) {
243	>	try {
244	>	wait();
245	>	} catch (InterruptedException ie) {
246	>	interrupted = true;
247	>	}
248	>	}
249	>	if (interrupted)
250	>	Thread.currentThread().interrupt();
251	>	break;
252	>	}
253		}
254		}
186	–	else
187	–	externallySetCompletion(completion);
255		}
256
257		/**
258	<	* Version of setCompletion for non-FJ threads.  Leaves signal
259	<	* bits for unblocked threads to adjust, and always notifies.
258	>	* Unless done, calls exec and records status if completed, but
259	>	* doesn't wait for completion otherwise. Primary execution method
260	>	* for ForkJoinWorkerThread.
261		*/
262	<	private void externallySetCompletion(int completion) {
263	<	int s;
264	<	do;while ((s = status) >= 0 &&
265	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
266	<	synchronized(this) { notifyAll(); }
262	>	final void quietlyExec() {
263	>	try {
264	>	if (status < 0 || !exec())
265	>	return;
266	>	} catch (Throwable rex) {
267	>	setExceptionalCompletion(rex);
268	>	return;
269	>	}
270	>	setCompletion(NORMAL); // must be outside try block
271		}
272
273	+	// public methods
274	+
275		/**
276	<	* Sets status to indicate normal completion
276	>	* Arranges to asynchronously execute this task.  While it is not
277	>	* necessarily enforced, it is a usage error to fork a task more
278	>	* than once unless it has completed and been reinitialized.
279	>	* Subsequent modifications to the state of this task or any data
280	>	* it operates on are not necessarily consistently observable by
281	>	* any thread other than the one executing it unless preceded by a
282	>	* call to {@link #join} or related methods, or a call to {@link
283	>	* #isDone} returning {@code true}.
284	>	*
285	>	* <p>This method may be invoked only from within {@code
286	>	* ForkJoinTask} computations (as may be determined using method
287	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
288	>	* result in exceptions or errors, possibly including {@code
289	>	* ClassCastException}.
290	>	*
291	>	* @return {@code this}, to simplify usage
292		*/
293	<	final void setNormalCompletion() {
294	<	// Try typical fast case -- single CAS, no signal, not already done.
295	<	// Manually expand casStatus to improve chances of inlining it
296	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
208	<	setCompletion(NORMAL);
293	>	public final ForkJoinTask<V> fork() {
294	>	((ForkJoinWorkerThread) Thread.currentThread())
295	>	.pushTask(this);
296	>	return this;
297		}
298
211	–	// internal waiting and notification
212	–
299		/**
300	<	* Performs the actual monitor wait for awaitDone
300	>	* Returns the result of the computation when it {@link #isDone is done}.
301	>	* This method differs from {@link #get()} in that
302	>	* abnormal completion results in {@code RuntimeException} or
303	>	* {@code Error}, not {@code ExecutionException}.
304	>	*
305	>	* @return the computed result
306		*/
307	<	private void doAwaitDone() {
308	<	// Minimize lock bias and in/de-flation effects by maximizing
309	<	// chances of waiting inside sync
310	<	try {
311	<	while (status >= 0)
312	<	synchronized(this) { if (status >= 0) wait(); }
222	<	} catch (InterruptedException ie) {
223	<	onInterruptedWait();
224	<	}
307	>	public final V join() {
308	>	quietlyJoin();
309	>	Throwable ex;
310	>	if (status < NORMAL && (ex = getException()) != null)
311	>	UNSAFE.throwException(ex);
312	>	return getRawResult();
313		}
314
315		/**
316	<	* Performs the actual monitor wait for awaitDone
316	>	* Commences performing this task, awaits its completion if
317	>	* necessary, and return its result, or throws an (unchecked)
318	>	* exception if the underlying computation did so.
319	>	*
320	>	* @return the computed result
321		*/
322	<	private void doAwaitDone(long startTime, long nanos) {
323	<	synchronized(this) {
324	<	try {
325	<	while (status >= 0) {
326	<	long nt = nanos - System.nanoTime() - startTime;
327	<	if (nt <= 0)
236	<	break;
237	<	wait(nt / 1000000, (int)(nt % 1000000));
238	<	}
239	<	} catch (InterruptedException ie) {
240	<	onInterruptedWait();
241	<	}
242	<	}
322	>	public final V invoke() {
323	>	quietlyInvoke();
324	>	Throwable ex;
325	>	if (status < NORMAL && (ex = getException()) != null)
326	>	UNSAFE.throwException(ex);
327	>	return getRawResult();
328		}
329
330	<	// Awaiting completion
330	>	/**
331	>	* Forks the given tasks, returning when {@code isDone} holds for
332	>	* each task or an (unchecked) exception is encountered, in which
333	>	* case the exception is rethrown.  If either task encounters an
334	>	* exception, the other one may be, but is not guaranteed to be,
335	>	* cancelled.  If both tasks throw an exception, then this method
336	>	* throws one of them.  The individual status of each task may be
337	>	* checked using {@link #getException()} and related methods.
338	>	*
339	>	* <p>This method may be invoked only from within {@code
340	>	* ForkJoinTask} computations (as may be determined using method
341	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
342	>	* result in exceptions or errors, possibly including {@code
343	>	* ClassCastException}.
344	>	*
345	>	* @param t1 the first task
346	>	* @param t2 the second task
347	>	* @throws NullPointerException if any task is null
348	>	*/
349	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
350	>	t2.fork();
351	>	t1.invoke();
352	>	t2.join();
353	>	}
354
355		/**
356	<	* Sets status to indicate there is joiner, then waits for join,
357	<	* surrounded with pool notifications.
358	<	* @return status upon exit
356	>	* Forks the given tasks, returning when {@code isDone} holds for
357	>	* each task or an (unchecked) exception is encountered, in which
358	>	* case the exception is rethrown. If any task encounters an
359	>	* exception, others may be, but are not guaranteed to be,
360	>	* cancelled.  If more than one task encounters an exception, then
361	>	* this method throws any one of these exceptions.  The individual
362	>	* status of each task may be checked using {@link #getException()}
363	>	* and related methods.
364	>	*
365	>	* <p>This method may be invoked only from within {@code
366	>	* ForkJoinTask} computations (as may be determined using method
367	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
368	>	* result in exceptions or errors, possibly including {@code
369	>	* ClassCastException}.
370	>	*
371	>	* @param tasks the tasks
372	>	* @throws NullPointerException if any task is null
373		*/
374	<	final int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
375	<	ForkJoinPool pool = w == null? null : w.pool;
376	<	int s;
377	<	while ((s = status) >= 0) {
378	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
379	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
380	<	doAwaitDone();
381	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
382	<	adjustPoolCountsOnUnblock(pool);
383	<	break;
374	>	public static void invokeAll(ForkJoinTask<?>... tasks) {
375	>	Throwable ex = null;
376	>	int last = tasks.length - 1;
377	>	for (int i = last; i >= 0; --i) {
378	>	ForkJoinTask<?> t = tasks[i];
379	>	if (t == null) {
380	>	if (ex == null)
381	>	ex = new NullPointerException();
382	>	}
383	>	else if (i != 0)
384	>	t.fork();
385	>	else {
386	>	t.quietlyInvoke();
387	>	if (ex == null && t.status < NORMAL)
388	>	ex = t.getException();
389		}
390		}
391	<	return s;
391	>	for (int i = 1; i <= last; ++i) {
392	>	ForkJoinTask<?> t = tasks[i];
393	>	if (t != null) {
394	>	if (ex != null)
395	>	t.cancel(false);
396	>	else {
397	>	t.quietlyJoin();
398	>	if (ex == null && t.status < NORMAL)
399	>	ex = t.getException();
400	>	}
401	>	}
402	>	}
403	>	if (ex != null)
404	>	UNSAFE.throwException(ex);
405		}
406
407		/**
408	<	* Timed version of awaitDone
409	<	* @return status upon exit
408	>	* Forks all tasks in the specified collection, returning when
409	>	* {@code isDone} holds for each task or an (unchecked) exception
410	>	* is encountered.  If any task encounters an exception, others
411	>	* may be, but are not guaranteed to be, cancelled.  If more than
412	>	* one task encounters an exception, then this method throws any
413	>	* one of these exceptions.  The individual status of each task
414	>	* may be checked using {@link #getException()} and related
415	>	* methods.  The behavior of this operation is undefined if the
416	>	* specified collection is modified while the operation is in
417	>	* progress.
418	>	*
419	>	* <p>This method may be invoked only from within {@code
420	>	* ForkJoinTask} computations (as may be determined using method
421	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
422	>	* result in exceptions or errors, possibly including {@code
423	>	* ClassCastException}.
424	>	*
425	>	* @param tasks the collection of tasks
426	>	* @return the tasks argument, to simplify usage
427	>	* @throws NullPointerException if tasks or any element are null
428		*/
429	<	final int awaitDone(ForkJoinWorkerThread w, long nanos) {
430	<	ForkJoinPool pool = w == null? null : w.pool;
431	<	int s;
432	<	while ((s = status) >= 0) {
433	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
434	<	long startTime = System.nanoTime();
435	<	if (pool == null || !pool.preJoin(this, false))
436	<	doAwaitDone(startTime, nanos);
437	<	if ((s = status) >= 0) {
438	<	adjustPoolCountsOnCancelledWait(pool);
439	<	s = status;
429	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
430	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
431	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
432	>	return tasks;
433	>	}
434	>	@SuppressWarnings("unchecked")
435	>	List<? extends ForkJoinTask<?>> ts =
436	>	(List<? extends ForkJoinTask<?>>) tasks;
437	>	Throwable ex = null;
438	>	int last = ts.size() - 1;
439	>	for (int i = last; i >= 0; --i) {
440	>	ForkJoinTask<?> t = ts.get(i);
441	>	if (t == null) {
442	>	if (ex == null)
443	>	ex = new NullPointerException();
444	>	}
445	>	else if (i != 0)
446	>	t.fork();
447	>	else {
448	>	t.quietlyInvoke();
449	>	if (ex == null && t.status < NORMAL)
450	>	ex = t.getException();
451	>	}
452	>	}
453	>	for (int i = 1; i <= last; ++i) {
454	>	ForkJoinTask<?> t = ts.get(i);
455	>	if (t != null) {
456	>	if (ex != null)
457	>	t.cancel(false);
458	>	else {
459	>	t.quietlyJoin();
460	>	if (ex == null && t.status < NORMAL)
461	>	ex = t.getException();
462		}
283	–	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
284	–	adjustPoolCountsOnUnblock(pool);
285	–	break;
463		}
464		}
465	<	return s;
465	>	if (ex != null)
466	>	UNSAFE.throwException(ex);
467	>	return tasks;
468		}
469
470		/**
471	<	* Notify pool that thread is unblocked. Called by signalled
472	<	* threads when woken by non-FJ threads (which is atypical).
471	>	* Attempts to cancel execution of this task. This attempt will
472	>	* fail if the task has already completed, has already been
473	>	* cancelled, or could not be cancelled for some other reason. If
474	>	* successful, and this task has not started when cancel is
475	>	* called, execution of this task is suppressed, {@link
476	>	* #isCancelled} will report true, and {@link #join} will result
477	>	* in a {@code CancellationException} being thrown.
478	>	*
479	>	* <p>This method may be overridden in subclasses, but if so, must
480	>	* still ensure that these minimal properties hold. In particular,
481	>	* the {@code cancel} method itself must not throw exceptions.
482	>	*
483	>	* <p>This method is designed to be invoked by <em>other</em>
484	>	* tasks. To terminate the current task, you can just return or
485	>	* throw an unchecked exception from its computation method, or
486	>	* invoke {@link #completeExceptionally}.
487	>	*
488	>	* @param mayInterruptIfRunning this value is ignored in the
489	>	* default implementation because tasks are not
490	>	* cancelled via interruption
491	>	*
492	>	* @return {@code true} if this task is now cancelled
493		*/
494	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
495	<	int s;
496	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
298	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
299	<	pool.updateRunningCount(s);
494	>	public boolean cancel(boolean mayInterruptIfRunning) {
495	>	setCompletion(CANCELLED);
496	>	return status == CANCELLED;
497		}
498
499		/**
500	<	* Notify pool to adjust counts on cancelled or timed out wait
500	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
501	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
502	>	* exceptions, but if it does anyway, we have no recourse during
503	>	* shutdown, so guard against this case.
504		*/
505	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
506	<	if (pool != null) {
507	<	int s;
508	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
309	<	if (casStatus(s, s - 1)) {
310	<	pool.updateRunningCount(1);
311	<	break;
312	<	}
313	<	}
505	>	final void cancelIgnoringExceptions() {
506	>	try {
507	>	cancel(false);
508	>	} catch (Throwable ignore) {
509		}
510		}
511
512	<	private void onInterruptedWait() {
512	>	/**
513	>	* Cancels ignoring exceptions if worker is terminating
514	>	*/
515	>	final void cancelIfTerminating() {
516		Thread t = Thread.currentThread();
517	<	if (t instanceof ForkJoinWorkerThread) {
518	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)t;
321	<	if (w.isTerminating())
322	<	cancelIgnoreExceptions();
323	<	}
324	<	else { // re-interrupt
517	>	if ((t instanceof ForkJoinWorkerThread) &&
518	>	((ForkJoinWorkerThread) t).isTerminating()) {
519		try {
520	<	t.interrupt();
521	<	} catch (SecurityException ignore) {
520	>	cancel(false);
521	>	} catch (Throwable ignore) {
522		}
523		}
524		}
525
526	<	// Recording and reporting exceptions
527	<
334	<	private void setDoneExceptionally(Throwable rex) {
335	<	exceptionMap.put(this, rex);
336	<	setCompletion(EXCEPTIONAL);
526	>	public final boolean isDone() {
527	>	return status < 0;
528		}
529
530	<	/**
531	<	* Throws the exception associated with status s;
341	<	* @throws the exception
342	<	*/
343	<	private void reportException(int s) {
344	<	if ((s &= COMPLETION_MASK) < NORMAL) {
345	<	if (s == CANCELLED)
346	<	throw new CancellationException();
347	<	else
348	<	rethrowException(exceptionMap.get(this));
349	<	}
530	>	public final boolean isCancelled() {
531	>	return status == CANCELLED;
532		}
533
534		/**
535	<	* Returns result or throws exception using j.u.c.Future conventions
536	<	* Only call when isDone known to be true.
535	>	* Returns {@code true} if this task threw an exception or was cancelled.
536	>	*
537	>	* @return {@code true} if this task threw an exception or was cancelled
538		*/
539	<	private V reportFutureResult()
540	<	throws ExecutionException, InterruptedException {
358	<	int s = status & COMPLETION_MASK;
359	<	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();
367	<	}
368	<	return getRawResult();
539	>	public final boolean isCompletedAbnormally() {
540	>	return status < NORMAL;
541		}
542
543		/**
544	<	* Returns result or throws exception using j.u.c.Future conventions
545	<	* with timeouts
544	>	* Returns {@code true} if this task completed without throwing an
545	>	* exception and was not cancelled.
546	>	*
547	>	* @return {@code true} if this task completed without throwing an
548	>	* exception and was not cancelled
549		*/
550	<	private V reportTimedFutureResult()
551	<	throws InterruptedException, ExecutionException, TimeoutException {
377	<	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();
550	>	public final boolean isCompletedNormally() {
551	>	return status == NORMAL;
552		}
553
390	–	// internal execution methods
391	–
554		/**
555	<	* Calls exec, recording completion, and rethrowing exception if
556	<	* encountered. Caller should normally check status before calling
557	<	* @return true if completed normally
555	>	* Returns the exception thrown by the base computation, or a
556	>	* {@code CancellationException} if cancelled, or {@code null} if
557	>	* none or if the method has not yet completed.
558	>	*
559	>	* @return the exception, or {@code null} if none
560		*/
561	<	private boolean tryExec() {
562	<	try { // try block must contain only call to exec
563	<	if (!exec())
564	<	return false;
565	<	} catch (Throwable rex) {
402	<	setDoneExceptionally(rex);
403	<	rethrowException(rex);
404	<	return false; // not reached
405	<	}
406	<	setNormalCompletion();
407	<	return true;
561	>	public final Throwable getException() {
562	>	int s = status;
563	>	return ((s >= NORMAL)    ? null :
564	>	(s == CANCELLED) ? new CancellationException() :
565	>	exceptionMap.get(this));
566		}
567
568		/**
569	<	* Main execution method used by worker threads. Invokes
570	<	* base computation unless already complete
569	>	* Completes this task abnormally, and if not already aborted or
570	>	* cancelled, causes it to throw the given exception upon
571	>	* {@code join} and related operations. This method may be used
572	>	* to induce exceptions in asynchronous tasks, or to force
573	>	* completion of tasks that would not otherwise complete.  Its use
574	>	* in other situations is discouraged.  This method is
575	>	* overridable, but overridden versions must invoke {@code super}
576	>	* implementation to maintain guarantees.
577	>	*
578	>	* @param ex the exception to throw. If this exception is not a
579	>	* {@code RuntimeException} or {@code Error}, the actual exception
580	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
581		*/
582	<	final void quietlyExec() {
583	<	if (status >= 0) {
584	<	try {
585	<	if (!exec())
418	<	return;
419	<	} catch(Throwable rex) {
420	<	setDoneExceptionally(rex);
421	<	return;
422	<	}
423	<	setNormalCompletion();
424	<	}
582	>	public void completeExceptionally(Throwable ex) {
583	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
584	>	(ex instanceof Error) ? ex :
585	>	new RuntimeException(ex));
586		}
587
588		/**
589	<	* Calls exec, recording but not rethrowing exception
590	<	* Caller should normally check status before calling
591	<	* @return true if completed normally
589	>	* Completes this task, and if not already aborted or cancelled,
590	>	* returning a {@code null} result upon {@code join} and related
591	>	* operations. This method may be used to provide results for
592	>	* asynchronous tasks, or to provide alternative handling for
593	>	* tasks that would not otherwise complete normally. Its use in
594	>	* other situations is discouraged. This method is
595	>	* overridable, but overridden versions must invoke {@code super}
596	>	* implementation to maintain guarantees.
597	>	*
598	>	* @param value the result value for this task
599		*/
600	<	private boolean tryQuietlyInvoke() {
600	>	public void complete(V value) {
601		try {
602	<	if (!exec())
435	<	return false;
602	>	setRawResult(value);
603		} catch (Throwable rex) {
604	<	setDoneExceptionally(rex);
605	<	return false;
604	>	setExceptionalCompletion(rex);
605	>	return;
606		}
607	<	setNormalCompletion();
441	<	return true;
607	>	setCompletion(NORMAL);
608		}
609
610	<	/**
611	<	* Cancel, ignoring any exceptions it throws
612	<	*/
613	<	final void cancelIgnoreExceptions() {
614	<	try {
615	<	cancel(false);
616	<	} catch(Throwable ignore) {
610	>	public final V get() throws InterruptedException, ExecutionException {
611	>	quietlyJoin();
612	>	if (Thread.interrupted())
613	>	throw new InterruptedException();
614	>	int s = status;
615	>	if (s < NORMAL) {
616	>	Throwable ex;
617	>	if (s == CANCELLED)
618	>	throw new CancellationException();
619	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
620	>	throw new ExecutionException(ex);
621		}
452	–	}
453	–
454	–	// public methods
455	–
456	–	/**
457	–	* Arranges to asynchronously execute this task.  While it is not
458	–	* necessarily enforced, it is a usage error to fork a task more
459	–	* than once unless it has completed and been reinitialized.  This
460	–	* method may be invoked only from within other ForkJoinTask
461	–	* computations. Attempts to invoke in other contexts result in
462	–	* exceptions or errors including ClassCastException.
463	–	*/
464	–	public final void fork() {
465	–	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
466	–	}
467	–
468	–	/**
469	–	* Returns the result of the computation when it is ready.
470	–	* This method differs from <tt>get</tt> in that abnormal
471	–	* completion results in RuntimeExceptions or Errors, not
472	–	* ExecutionExceptions.
473	–	*
474	–	* @return the computed result
475	–	*/
476	–	public final V join() {
477	–	ForkJoinWorkerThread w = getWorker();
478	–	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
479	–	reportException(awaitDone(w, true));
622		return getRawResult();
623		}
624
483	–	public final V get() throws InterruptedException, ExecutionException {
484	–	ForkJoinWorkerThread w = getWorker();
485	–	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
486	–	awaitDone(w, true);
487	–	return reportFutureResult();
488	–	}
489	–
625		public final V get(long timeout, TimeUnit unit)
626		throws InterruptedException, ExecutionException, TimeoutException {
627	<	ForkJoinWorkerThread w = getWorker();
628	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
629	<	awaitDone(w, unit.toNanos(timeout));
630	<	return reportTimedFutureResult();
631	<	}
632	<
633	<	/**
634	<	* Possibly executes other tasks until this task is ready, then
635	<	* returns the result of the computation.  This method may be more
636	<	* efficient than <tt>join</tt>, but is only applicable when there
637	<	* are no potemtial dependencies between continuation of the
638	<	* current task and that of any other task that might be executed
639	<	* while helping. (This usually holds for pure divide-and-conquer
640	<	* tasks).
641	<	* @return the computed result
642	<	*/
643	<	public final V helpJoin() {
644	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
645	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
646	<	reportException(w.helpJoinTask(this));
627	>	Thread t = Thread.currentThread();
628	>	ForkJoinPool pool;
629	>	if (t instanceof ForkJoinWorkerThread) {
630	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
631	>	if (status >= 0 && w.unpushTask(this))
632	>	quietlyExec();
633	>	pool = w.pool;
634	>	}
635	>	else
636	>	pool = null;
637	>	/*
638	>	* Timed wait loop intermixes cases for FJ (pool != null) and
639	>	* non FJ threads. For FJ, decrement pool count but don't try
640	>	* for replacement; increment count on completion. For non-FJ,
641	>	* deal with interrupts. This is messy, but a little less so
642	>	* than is splitting the FJ and nonFJ cases.
643	>	*/
644	>	boolean interrupted = false;
645	>	boolean dec = false; // true if pool count decremented
646	>	long nanos = unit.toNanos(timeout);
647	>	for (;;) {
648	>	if (Thread.interrupted() && pool == null) {
649	>	interrupted = true;
650	>	break;
651	>	}
652	>	int s = status;
653	>	if (s < 0)
654	>	break;
655	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
656	>	long startTime = System.nanoTime();
657	>	long nt; // wait time
658	>	while (status >= 0 &&
659	>	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
660	>	if (pool != null && !dec)
661	>	dec = pool.tryDecrementRunningCount();
662	>	else {
663	>	long ms = nt / 1000000;
664	>	int ns = (int) (nt % 1000000);
665	>	try {
666	>	synchronized(this) {
667	>	if (status >= 0)
668	>	wait(ms, ns);
669	>	}
670	>	} catch (InterruptedException ie) {
671	>	if (pool != null)
672	>	cancelIfTerminating();
673	>	else {
674	>	interrupted = true;
675	>	break;
676	>	}
677	>	}
678	>	}
679	>	}
680	>	break;
681	>	}
682	>	}
683	>	if (pool != null && dec)
684	>	pool.incrementRunningCount();
685	>	if (interrupted)
686	>	throw new InterruptedException();
687	>	int es = status;
688	>	if (es != NORMAL) {
689	>	Throwable ex;
690	>	if (es == CANCELLED)
691	>	throw new CancellationException();
692	>	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
693	>	throw new ExecutionException(ex);
694	>	throw new TimeoutException();
695	>	}
696		return getRawResult();
697		}
698
699		/**
700	<	* Performs this task, awaits its completion if necessary, and
701	<	* return its result.
702	<	* @throws Throwable (a RuntimeException, Error, or unchecked
703	<	* exception) if the underlying computation did so.
520	<	* @return the computed result
700	>	* Joins this task, without returning its result or throwing its
701	>	* exception. This method may be useful when processing
702	>	* collections of tasks when some have been cancelled or otherwise
703	>	* known to have aborted.
704		*/
705	<	public final V invoke() {
706	<	if (status >= 0 && tryExec())
707	<	return getRawResult();
705	>	public final void quietlyJoin() {
706	>	Thread t;
707	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
708	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
709	>	if (status >= 0) {
710	>	if (w.unpushTask(this)) {
711	>	boolean completed;
712	>	try {
713	>	completed = exec();
714	>	} catch (Throwable rex) {
715	>	setExceptionalCompletion(rex);
716	>	return;
717	>	}
718	>	if (completed) {
719	>	setCompletion(NORMAL);
720	>	return;
721	>	}
722	>	}
723	>	w.joinTask(this);
724	>	}
725	>	}
726		else
727	<	return join();
727	>	externalAwaitDone();
728		}
729
730		/**
731	<	* Joins this task, without returning its result or throwing an
731	>	* Commences performing this task and awaits its completion if
732	>	* necessary, without returning its result or throwing its
733		* exception. This method may be useful when processing
734		* collections of tasks when some have been cancelled or otherwise
735		* known to have aborted.
736		*/
737	<	public final void quietlyJoin() {
737	>	public final void quietlyInvoke() {
738		if (status >= 0) {
739	<	ForkJoinWorkerThread w = getWorker();
740	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
741	<	awaitDone(w, true);
739	>	boolean completed;
740	>	try {
741	>	completed = exec();
742	>	} catch (Throwable rex) {
743	>	setExceptionalCompletion(rex);
744	>	return;
745	>	}
746	>	if (completed)
747	>	setCompletion(NORMAL);
748	>	else
749	>	quietlyJoin();
750		}
751		}
752
753		/**
754	<	* Possibly executes other tasks until this task is ready.
754	>	* Possibly executes tasks until the pool hosting the current task
755	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
756	>	* be of use in designs in which many tasks are forked, but none
757	>	* are explicitly joined, instead executing them until all are
758	>	* processed.
759	>	*
760	>	* <p>This method may be invoked only from within {@code
761	>	* ForkJoinTask} computations (as may be determined using method
762	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
763	>	* result in exceptions or errors, possibly including {@code
764	>	* ClassCastException}.
765		*/
766	<	public final void quietlyHelpJoin() {
767	<	if (status >= 0) {
768	<	ForkJoinWorkerThread w =
549	<	(ForkJoinWorkerThread)(Thread.currentThread());
550	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
551	<	w.helpJoinTask(this);
552	<	}
766	>	public static void helpQuiesce() {
767	>	((ForkJoinWorkerThread) Thread.currentThread())
768	>	.helpQuiescePool();
769		}
770
771		/**
772	<	* Performs this task and awaits its completion if necessary,
773	<	* without returning its result or throwing an exception. This
774	<	* method may be useful when processing collections of tasks when
775	<	* some have been cancelled or otherwise known to have aborted.
772	>	* Resets the internal bookkeeping state of this task, allowing a
773	>	* subsequent {@code fork}. This method allows repeated reuse of
774	>	* this task, but only if reuse occurs when this task has either
775	>	* never been forked, or has been forked, then completed and all
776	>	* outstanding joins of this task have also completed. Effects
777	>	* under any other usage conditions are not guaranteed.
778	>	* This method may be useful when executing
779	>	* pre-constructed trees of subtasks in loops.
780		*/
781	<	public final void quietlyInvoke() {
782	<	if (status >= 0 && !tryQuietlyInvoke())
783	<	quietlyJoin();
781	>	public void reinitialize() {
782	>	if (status == EXCEPTIONAL)
783	>	exceptionMap.remove(this);
784	>	status = 0;
785		}
786
787		/**
788	<	* Returns true if the computation performed by this task has
789	<	* completed (or has been cancelled).
790	<	* @return true if this computation has completed
788	>	* Returns the pool hosting the current task execution, or null
789	>	* if this task is executing outside of any ForkJoinPool.
790	>	*
791	>	* @see #inForkJoinPool
792	>	* @return the pool, or {@code null} if none
793		*/
794	<	public final boolean isDone() {
795	<	return status < 0;
794	>	public static ForkJoinPool getPool() {
795	>	Thread t = Thread.currentThread();
796	>	return (t instanceof ForkJoinWorkerThread) ?
797	>	((ForkJoinWorkerThread) t).pool : null;
798		}
799
800		/**
801	<	* Returns true if this task was cancelled.
802	<	* @return true if this task was cancelled
801	>	* Returns {@code true} if the current thread is executing as a
802	>	* ForkJoinPool computation.
803	>	*
804	>	* @return {@code true} if the current thread is executing as a
805	>	* ForkJoinPool computation, or false otherwise
806		*/
807	<	public final boolean isCancelled() {
808	<	return (status & COMPLETION_MASK) == CANCELLED;
807	>	public static boolean inForkJoinPool() {
808	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
809		}
810
811		/**
812	<	* Returns true if this task threw an exception or was cancelled
813	<	* @return true if this task threw an exception or was cancelled
812	>	* Tries to unschedule this task for execution. This method will
813	>	* typically succeed if this task is the most recently forked task
814	>	* by the current thread, and has not commenced executing in
815	>	* another thread.  This method may be useful when arranging
816	>	* alternative local processing of tasks that could have been, but
817	>	* were not, stolen.
818	>	*
819	>	* <p>This method may be invoked only from within {@code
820	>	* ForkJoinTask} computations (as may be determined using method
821	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
822	>	* result in exceptions or errors, possibly including {@code
823	>	* ClassCastException}.
824	>	*
825	>	* @return {@code true} if unforked
826		*/
827	<	public final boolean completedAbnormally() {
828	<	return (status & COMPLETION_MASK) < NORMAL;
827	>	public boolean tryUnfork() {
828	>	return ((ForkJoinWorkerThread) Thread.currentThread())
829	>	.unpushTask(this);
830		}
831
832		/**
833	<	* Returns the exception thrown by the base computation, or a
834	<	* CancellationException if cancelled, or null if none or if the
835	<	* method has not yet completed.
836	<	* @return the exception, or null if none
833	>	* Returns an estimate of the number of tasks that have been
834	>	* forked by the current worker thread but not yet executed. This
835	>	* value may be useful for heuristic decisions about whether to
836	>	* fork other tasks.
837	>	*
838	>	* <p>This method may be invoked only from within {@code
839	>	* ForkJoinTask} computations (as may be determined using method
840	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
841	>	* result in exceptions or errors, possibly including {@code
842	>	* ClassCastException}.
843	>	*
844	>	* @return the number of tasks
845		*/
846	<	public final Throwable getException() {
847	<	int s = status & COMPLETION_MASK;
848	<	if (s >= NORMAL)
600	<	return null;
601	<	if (s == CANCELLED)
602	<	return new CancellationException();
603	<	return exceptionMap.get(this);
846	>	public static int getQueuedTaskCount() {
847	>	return ((ForkJoinWorkerThread) Thread.currentThread())
848	>	.getQueueSize();
849		}
850
851		/**
852	<	* Asserts that the results of this task's computation will not be
853	<	* used. If a cancellation occurs before this task is processed,
854	<	* then its <tt>compute</tt> method will not be executed,
855	<	* <tt>isCancelled</tt> will report true, and <tt>join</tt> will
856	<	* result in a CancellationException being thrown. Otherwise, when
857	<	* cancellation races with completion, there are no guarantees
858	<	* about whether <tt>isCancelled</tt> will report true, whether
859	<	* <tt>join</tt> will return normally or via an exception, or
615	<	* whether these behaviors will remain consistent upon repeated
616	<	* invocation.
617	<	*
618	<	* <p>This method may be overridden in subclasses, but if so, must
619	<	* still ensure that these minimal properties hold. In particular,
620	<	* the cancel method itself must not throw exceptions.
621	<	*
622	<	* <p> This method is designed to be invoked by <em>other</em>
623	<	* tasks. To terminate the current task, you can just return or
624	<	* throw an unchecked exception from its computation method, or
625	<	* invoke <tt>completeExceptionally(someException)</tt>.
852	>	* Returns an estimate of how many more locally queued tasks are
853	>	* held by the current worker thread than there are other worker
854	>	* threads that might steal them.  This value may be useful for
855	>	* heuristic decisions about whether to fork other tasks. In many
856	>	* usages of ForkJoinTasks, at steady state, each worker should
857	>	* aim to maintain a small constant surplus (for example, 3) of
858	>	* tasks, and to process computations locally if this threshold is
859	>	* exceeded.
860		*
861	<	* @param mayInterruptIfRunning this value is ignored in the
862	<	* default implementation because tasks are not in general
863	<	* cancelled via interruption.
861	>	* <p>This method may be invoked only from within {@code
862	>	* ForkJoinTask} computations (as may be determined using method
863	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
864	>	* result in exceptions or errors, possibly including {@code
865	>	* ClassCastException}.
866		*
867	<	* @return true if this task is now cancelled
867	>	* @return the surplus number of tasks, which may be negative
868		*/
869	<	public boolean cancel(boolean mayInterruptIfRunning) {
870	<	setCompletion(CANCELLED);
871	<	return (status & COMPLETION_MASK) == CANCELLED;
869	>	public static int getSurplusQueuedTaskCount() {
870	>	return ((ForkJoinWorkerThread) Thread.currentThread())
871	>	.getEstimatedSurplusTaskCount();
872		}
873
874	+	// Extension methods
875	+
876		/**
877	<	* Completes this task abnormally, and if not already aborted or
878	<	* cancelled, causes it to throw the given exception upon
879	<	* <tt>join</tt> and related operations. This method may be used
880	<	* to induce exceptions in asynchronous tasks, or to force
881	<	* completion of tasks that would not otherwise complete.  This
882	<	* method is overridable, but overridden versions must invoke
883	<	* <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.
877	>	* Returns the result that would be returned by {@link #join}, even
878	>	* if this task completed abnormally, or {@code null} if this task
879	>	* is not known to have been completed.  This method is designed
880	>	* to aid debugging, as well as to support extensions. Its use in
881	>	* any other context is discouraged.
882	>	*
883	>	* @return the result, or {@code null} if not completed
884		*/
885	<	public void completeExceptionally(Throwable ex) {
651	<	setDoneExceptionally((ex instanceof RuntimeException) ||
652	<	(ex instanceof Error)? ex :
653	<	new RuntimeException(ex));
654	<	}
885	>	public abstract V getRawResult();
886
887		/**
888	<	* Completes this task, and if not already aborted or cancelled,
889	<	* returning a <tt>null</tt> result upon <tt>join</tt> and related
890	<	* 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.
888	>	* Forces the given value to be returned as a result.  This method
889	>	* is designed to support extensions, and should not in general be
890	>	* called otherwise.
891		*
892	<	* @param value the result value for this task.
892	>	* @param value the value
893		*/
894	<	public void complete(V value) {
666	<	try {
667	<	setRawResult(value);
668	<	} catch(Throwable rex) {
669	<	setDoneExceptionally(rex);
670	<	return;
671	<	}
672	<	setNormalCompletion();
673	<	}
894	>	protected abstract void setRawResult(V value);
895
896		/**
897	<	* Resets the internal bookkeeping state of this task, allowing a
898	<	* subsequent <tt>fork</tt>. This method allows repeated reuse of
899	<	* this task, but only if reuse occurs when this task has either
900	<	* never been forked, or has been forked, then completed and all
901	<	* outstanding joins of this task have also completed. Effects
902	<	* under any other usage conditions are not guaranteed, and are
903	<	* almost surely wrong. This method may be useful when executing
904	<	* pre-constructed trees of subtasks in loops.
897	>	* Immediately performs the base action of this task.  This method
898	>	* is designed to support extensions, and should not in general be
899	>	* called otherwise. The return value controls whether this task
900	>	* is considered to be done normally. It may return false in
901	>	* asynchronous actions that require explicit invocations of
902	>	* {@link #complete} to become joinable. It may also throw an
903	>	* (unchecked) exception to indicate abnormal exit.
904	>	*
905	>	* @return {@code true} if completed normally
906		*/
907	<	public void reinitialize() {
686	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
687	<	exceptionMap.remove(this);
688	<	status = 0;
689	<	}
907	>	protected abstract boolean exec();
908
909		/**
910	<	* Tries to unschedule this task for execution. This method will
911	<	* typically succeed if this task is the next task that would be
912	<	* executed by the current thread, and will typically fail (return
913	<	* false) otherwise. This method may be useful when arranging
914	<	* faster local processing of tasks that could have been, but were
915	<	* not, stolen.
916	<	* @return true if unforked
910	>	* Returns, but does not unschedule or execute, a task queued by
911	>	* the current thread but not yet executed, if one is immediately
912	>	* available. There is no guarantee that this task will actually
913	>	* be polled or executed next. Conversely, this method may return
914	>	* null even if a task exists but cannot be accessed without
915	>	* contention with other threads.  This method is designed
916	>	* primarily to support extensions, and is unlikely to be useful
917	>	* otherwise.
918	>	*
919	>	* <p>This method may be invoked only from within {@code
920	>	* ForkJoinTask} computations (as may be determined using method
921	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
922	>	* result in exceptions or errors, possibly including {@code
923	>	* ClassCastException}.
924	>	*
925	>	* @return the next task, or {@code null} if none are available
926		*/
927	<	public boolean tryUnfork() {
928	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
927	>	protected static ForkJoinTask<?> peekNextLocalTask() {
928	>	return ((ForkJoinWorkerThread) Thread.currentThread())
929	>	.peekTask();
930		}
931
932		/**
933	<	* Forks both tasks, returning when <tt>isDone</tt> holds for both
934	<	* of them or an exception is encountered. This method may be
935	<	* invoked only from within other ForkJoinTask
936	<	* computations. Attempts to invoke in other contexts result in
937	<	* exceptions or errors including ClassCastException.
938	<	* @param t1 one task
939	<	* @param t2 the other task
940	<	* @throws NullPointerException if t1 or t2 are null
941	<	* @throws RuntimeException or Error if either task did so.
933	>	* Unschedules and returns, without executing, the next task
934	>	* queued by the current thread but not yet executed.  This method
935	>	* is designed primarily to support extensions, and is unlikely to
936	>	* be useful otherwise.
937	>	*
938	>	* <p>This method may be invoked only from within {@code
939	>	* ForkJoinTask} computations (as may be determined using method
940	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
941	>	* result in exceptions or errors, possibly including {@code
942	>	* ClassCastException}.
943	>	*
944	>	* @return the next task, or {@code null} if none are available
945		*/
946	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
947	<	t2.fork();
948	<	t1.invoke();
718	<	t2.join();
946	>	protected static ForkJoinTask<?> pollNextLocalTask() {
947	>	return ((ForkJoinWorkerThread) Thread.currentThread())
948	>	.pollLocalTask();
949		}
950
951		/**
952	<	* Forks the given tasks, returning when <tt>isDone</tt> holds for
953	<	* all of them. If any task encounters an exception, others may be
954	<	* cancelled.  This method may be invoked only from within other
955	<	* ForkJoinTask computations. Attempts to invoke in other contexts
956	<	* result in exceptions or errors including ClassCastException.
957	<	* @param tasks the array of tasks
958	<	* @throws NullPointerException if tasks or any element are null.
959	<	* @throws RuntimeException or Error if any task did so.
952	>	* Unschedules and returns, without executing, the next task
953	>	* queued by the current thread but not yet executed, if one is
954	>	* available, or if not available, a task that was forked by some
955	>	* other thread, if available. Availability may be transient, so a
956	>	* {@code null} result does not necessarily imply quiescence
957	>	* of the pool this task is operating in.  This method is designed
958	>	* primarily to support extensions, and is unlikely to be useful
959	>	* otherwise.
960	>	*
961	>	* <p>This method may be invoked only from within {@code
962	>	* ForkJoinTask} computations (as may be determined using method
963	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
964	>	* result in exceptions or errors, possibly including {@code
965	>	* ClassCastException}.
966	>	*
967	>	* @return a task, or {@code null} if none are available
968		*/
969	<	public static void invokeAll(ForkJoinTask<?>... tasks) {
970	<	Throwable ex = null;
971	<	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);
969	>	protected static ForkJoinTask<?> pollTask() {
970	>	return ((ForkJoinWorkerThread) Thread.currentThread())
971	>	.pollTask();
972		}
973
974		/**
975	<	* Forks all tasks in the collection, returning when
976	<	* <tt>isDone</tt> holds for all of them. If any task encounters
977	<	* 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.
975	>	* Adaptor for Runnables. This implements RunnableFuture
976	>	* to be compliant with AbstractExecutorService constraints
977	>	* when used in ForkJoinPool.
978		*/
979	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
980	<	if (!(tasks instanceof List)) {
981	<	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
982	<	return;
979	>	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
980	>	implements RunnableFuture<T> {
981	>	final Runnable runnable;
982	>	final T resultOnCompletion;
983	>	T result;
984	>	AdaptedRunnable(Runnable runnable, T result) {
985	>	if (runnable == null) throw new NullPointerException();
986	>	this.runnable = runnable;
987	>	this.resultOnCompletion = result;
988		}
989	<	List<? extends ForkJoinTask<?>> ts =
990	<	(List<? extends ForkJoinTask<?>>)tasks;
991	<	Throwable ex = null;
992	<	int last = ts.size() - 1;
993	<	for (int i = last; i >= 0; --i) {
994	<	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	<	}
989	>	public T getRawResult() { return result; }
990	>	public void setRawResult(T v) { result = v; }
991	>	public boolean exec() {
992	>	runnable.run();
993	>	result = resultOnCompletion;
994	>	return true;
995		}
996	<	for (int i = 1; i <= last; ++i) {
997	<	ForkJoinTask<?> t = ts.get(i);
800	<	if (t != null) {
801	<	if (ex != null)
802	<	t.cancel(false);
803	<	else {
804	<	t.quietlyJoin();
805	<	if (ex == null)
806	<	ex = t.getException();
807	<	}
808	<	}
809	<	}
810	<	if (ex != null)
811	<	rethrowException(ex);
996	>	public void run() { invoke(); }
997	>	private static final long serialVersionUID = 5232453952276885070L;
998		}
999
1000		/**
1001	<	* 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.
1001	>	* Adaptor for Callables
1002		*/
1003	<	public static void helpQuiesce() {
1004	<	((ForkJoinWorkerThread)(Thread.currentThread())).
1005	<	helpQuiescePool();
1003	>	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1004	>	implements RunnableFuture<T> {
1005	>	final Callable<? extends T> callable;
1006	>	T result;
1007	>	AdaptedCallable(Callable<? extends T> callable) {
1008	>	if (callable == null) throw new NullPointerException();
1009	>	this.callable = callable;
1010	>	}
1011	>	public T getRawResult() { return result; }
1012	>	public void setRawResult(T v) { result = v; }
1013	>	public boolean exec() {
1014	>	try {
1015	>	result = callable.call();
1016	>	return true;
1017	>	} catch (Error err) {
1018	>	throw err;
1019	>	} catch (RuntimeException rex) {
1020	>	throw rex;
1021	>	} catch (Exception ex) {
1022	>	throw new RuntimeException(ex);
1023	>	}
1024	>	}
1025	>	public void run() { invoke(); }
1026	>	private static final long serialVersionUID = 2838392045355241008L;
1027		}
1028
1029		/**
1030	<	* Returns a estimate of how many more locally queued tasks are
1031	<	* held by the current worker thread than there are other worker
1032	<	* threads that might want to steal them.  This value may be
1033	<	* useful for heuristic decisions about whether to fork other
1034	<	* tasks. In many usages of ForkJoinTasks, at steady state, each
1035	<	* 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
1030	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1031	>	* method of the given {@code Runnable} as its action, and returns
1032	>	* a null result upon {@link #join}.
1033	>	*
1034	>	* @param runnable the runnable action
1035	>	* @return the task
1036		*/
1037	<	public static int surplus() {
1038	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
838	<	.getEstimatedSurplusTaskCount();
1037	>	public static ForkJoinTask<?> adapt(Runnable runnable) {
1038	>	return new AdaptedRunnable<Void>(runnable, null);
1039		}
1040
841	–	// Extension kit
842	–
1041		/**
1042	<	* Returns the result that would be returned by <tt>join</tt>, or
1043	<	* null if this task is not known to have been completed.  This
1044	<	* method is designed to aid debugging, as well as to support
847	<	* extensions. Its use in any other context is discouraged.
1042	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1043	>	* method of the given {@code Runnable} as its action, and returns
1044	>	* the given result upon {@link #join}.
1045		*
1046	<	* @return the result, or null if not completed.
1046	>	* @param runnable the runnable action
1047	>	* @param result the result upon completion
1048	>	* @return the task
1049		*/
1050	<	public abstract V getRawResult();
1050	>	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1051	>	return new AdaptedRunnable<T>(runnable, result);
1052	>	}
1053
1054		/**
1055	<	* Forces the given value to be returned as a result.  This method
1056	<	* is designed to support extensions, and should not in general be
1057	<	* called otherwise.
1055	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1056	>	* method of the given {@code Callable} as its action, and returns
1057	>	* its result upon {@link #join}, translating any checked exceptions
1058	>	* encountered into {@code RuntimeException}.
1059		*
1060	<	* @param value the value
1061	<	*/
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
1060	>	* @param callable the callable action
1061	>	* @return the task
1062		*/
1063	<	protected abstract boolean exec();
1063	>	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1064	>	return new AdaptedCallable<T>(callable);
1065	>	}
1066
1067		// Serialization support
1068
1069		private static final long serialVersionUID = -7721805057305804111L;
1070
1071		/**
1072	<	* Save the state to a stream.
1072	>	* Saves the state to a stream.
1073		*
1074		* @serialData the current run status and the exception thrown
1075	<	* during execution, or null if none.
1075	>	* during execution, or {@code null} if none
1076		* @param s the stream
1077		*/
1078		private void writeObject(java.io.ObjectOutputStream s)
#	Line 890 | Line 1082 | public abstract class ForkJoinTask<V> im
1082		}
1083
1084		/**
1085	<	* Reconstitute the instance from a stream.
1085	>	* Reconstitutes the instance from a stream.
1086	>	*
1087		* @param s the stream
1088		*/
1089		private void readObject(java.io.ObjectInputStream s)
1090		throws java.io.IOException, ClassNotFoundException {
1091		s.defaultReadObject();
899	–	//        status &= ~INTERNAL_SIGNAL_MASK; //  todo: define policy
1092		Object ex = s.readObject();
1093		if (ex != null)
1094	<	setDoneExceptionally((Throwable)ex);
1094	>	setExceptionalCompletion((Throwable) ex);
1095		}
1096
1097	<	// Temporary Unsafe mechanics for preliminary release
1097	>	// Unsafe mechanics
1098
1099	<	static final Unsafe _unsafe;
1100	<	static final long statusOffset;
1099	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1100	>	private static final long statusOffset =
1101	>	objectFieldOffset("status", ForkJoinTask.class);
1102
1103	<	static {
1103	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1104		try {
1105	<	if (ForkJoinTask.class.getClassLoader() != null) {
1106	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1107	<	f.setAccessible(true);
1108	<	_unsafe = (Unsafe)f.get(null);
1109	<	}
1110	<	else
1111	<	_unsafe = Unsafe.getUnsafe();
919	<	statusOffset = _unsafe.objectFieldOffset
920	<	(ForkJoinTask.class.getDeclaredField("status"));
921	<	} catch (Exception ex) { throw new Error(ex); }
1105	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1106	>	} catch (NoSuchFieldException e) {
1107	>	// Convert Exception to corresponding Error
1108	>	NoSuchFieldError error = new NoSuchFieldError(field);
1109	>	error.initCause(e);
1110	>	throw error;
1111	>	}
1112		}
1113
1114	+	/**
1115	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1116	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1117	+	* into a jdk.
1118	+	*
1119	+	* @return a sun.misc.Unsafe
1120	+	*/
1121	+	private static sun.misc.Unsafe getUnsafe() {
1122	+	try {
1123	+	return sun.misc.Unsafe.getUnsafe();
1124	+	} catch (SecurityException se) {
1125	+	try {
1126	+	return java.security.AccessController.doPrivileged
1127	+	(new java.security
1128	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1129	+	public sun.misc.Unsafe run() throws Exception {
1130	+	java.lang.reflect.Field f = sun.misc
1131	+	.Unsafe.class.getDeclaredField("theUnsafe");
1132	+	f.setAccessible(true);
1133	+	return (sun.misc.Unsafe) f.get(null);
1134	+	}});
1135	+	} catch (java.security.PrivilegedActionException e) {
1136	+	throw new RuntimeException("Could not initialize intrinsics",
1137	+	e.getCause());
1138	+	}
1139	+	}
1140	+	}
1141		}

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