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Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.16 by jsr166, Fri Jul 24 23:47:01 2009 UTC vs.
Revision 1.71 by dl, Tue Nov 23 10:51:18 2010 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	+
9		import java.io.Serializable;
10	<	import java.util.*;
11	<	import java.util.concurrent.*;
12	<	import java.util.concurrent.atomic.*;
10	>	import java.util.Collection;
11	>	import java.util.Collections;
12	>	import java.util.List;
13	>	import java.util.RandomAccess;
14	>	import java.util.Map;
15	>	import java.util.WeakHashMap;
16	>	import java.util.concurrent.Callable;
17	>	import java.util.concurrent.CancellationException;
18	>	import java.util.concurrent.ExecutionException;
19	>	import java.util.concurrent.Executor;
20	>	import java.util.concurrent.ExecutorService;
21	>	import java.util.concurrent.Future;
22	>	import java.util.concurrent.RejectedExecutionException;
23	>	import java.util.concurrent.RunnableFuture;
24	>	import java.util.concurrent.TimeUnit;
25	>	import java.util.concurrent.TimeoutException;
26
27		/**
28	<	* Abstract base class for tasks that run within a {@link
29	<	* ForkJoinPool}.  A ForkJoinTask is a thread-like entity that is much
28	>	* Abstract base class for tasks that run within a {@link ForkJoinPool}.
29	>	* A {@code ForkJoinTask} is a thread-like entity that is much
30		* lighter weight than a normal thread.  Huge numbers of tasks and
31		* subtasks may be hosted by a small number of actual threads in a
32		* ForkJoinPool, at the price of some usage limitations.
33		*
34	<	* <p> A "main" ForkJoinTask begins execution when submitted to a
35	<	* {@link ForkJoinPool}. Once started, it will usually in turn start
36	<	* other subtasks.  As indicated by the name of this class, many
37	<	* programs using ForkJoinTasks employ only methods {@code fork}
38	<	* and {@code join}, or derivatives such as
39	<	* {@code invokeAll}.  However, this class also provides a number
40	<	* of other methods that can come into play in advanced usages, as
41	<	* well as extension mechanics that allow support of new forms of
42	<	* fork/join processing.
34	>	* <p>A "main" {@code ForkJoinTask} begins execution when submitted
35	>	* to a {@link ForkJoinPool}.  Once started, it will usually in turn
36	>	* start other subtasks.  As indicated by the name of this class,
37	>	* many programs using {@code ForkJoinTask} employ only methods
38	>	* {@link #fork} and {@link #join}, or derivatives such as {@link
39	>	* #invokeAll(ForkJoinTask...) invokeAll}.  However, this class also
40	>	* provides a number of other methods that can come into play in
41	>	* advanced usages, as well as extension mechanics that allow
42	>	* support of new forms of fork/join processing.
43		*
44	<	* <p>A ForkJoinTask is a lightweight form of {@link Future}.  The
45	<	* efficiency of ForkJoinTasks stems from a set of restrictions (that
46	<	* are only partially statically enforceable) reflecting their
47	<	* intended use as computational tasks calculating pure functions or
48	<	* operating on purely isolated objects.  The primary coordination
49	<	* mechanisms are {@link #fork}, that arranges asynchronous execution,
50	<	* and {@link #join}, that doesn't proceed until the task's result has
51	<	* been computed.  Computations should avoid {@code synchronized}
52	<	* methods or blocks, and should minimize other blocking
53	<	* synchronization apart from joining other tasks or using
54	<	* synchronizers such as Phasers that are advertised to cooperate with
55	<	* fork/join scheduling. Tasks should also not perform blocking IO,
56	<	* and should ideally access variables that are completely independent
57	<	* of those accessed by other running tasks. Minor breaches of these
58	<	* restrictions, for example using shared output streams, may be
59	<	* tolerable in practice, but frequent use may result in poor
60	<	* performance, and the potential to indefinitely stall if the number
61	<	* of threads not waiting for IO or other external synchronization
62	<	* becomes exhausted. This usage restriction is in part enforced by
63	<	* not permitting checked exceptions such as {@code IOExceptions}
64	<	* to be thrown. However, computations may still encounter unchecked
65	<	* exceptions, that are rethrown to callers attempting join
66	<	* them. These exceptions may additionally include
67	<	* RejectedExecutionExceptions stemming from internal resource
68	<	* exhaustion such as failure to allocate internal task queues.
44	>	* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
45	>	* The efficiency of {@code ForkJoinTask}s stems from a set of
46	>	* restrictions (that are only partially statically enforceable)
47	>	* reflecting their intended use as computational tasks calculating
48	>	* pure functions or operating on purely isolated objects.  The
49	>	* primary coordination mechanisms are {@link #fork}, that arranges
50	>	* asynchronous execution, and {@link #join}, that doesn't proceed
51	>	* until the task's result has been computed.  Computations should
52	>	* avoid {@code synchronized} methods or blocks, and should minimize
53	>	* other blocking synchronization apart from joining other tasks or
54	>	* using synchronizers such as Phasers that are advertised to
55	>	* cooperate with fork/join scheduling. Tasks should also not perform
56	>	* blocking IO, and should ideally access variables that are
57	>	* completely independent of those accessed by other running
58	>	* tasks. Minor breaches of these restrictions, for example using
59	>	* shared output streams, may be tolerable in practice, but frequent
60	>	* use may result in poor performance, and the potential to
61	>	* indefinitely stall if the number of threads not waiting for IO or
62	>	* other external synchronization becomes exhausted. This usage
63	>	* restriction is in part enforced by not permitting checked
64	>	* exceptions such as {@code IOExceptions} to be thrown. However,
65	>	* computations may still encounter unchecked exceptions, that are
66	>	* rethrown to callers attempting to join them. These exceptions may
67	>	* additionally include {@link RejectedExecutionException} stemming
68	>	* from internal resource exhaustion, such as failure to allocate
69	>	* internal task queues.
70		*
71		* <p>The primary method for awaiting completion and extracting
72		* results of a task is {@link #join}, but there are several variants:
73		* The {@link Future#get} methods support interruptible and/or timed
74		* waits for completion and report results using {@code Future}
75	<	* conventions. Method {@link #helpJoin} enables callers to actively
76	<	* execute other tasks while awaiting joins, which is sometimes more
77	<	* efficient but only applies when all subtasks are known to be
78	<	* strictly tree-structured. Method {@link #invoke} is semantically
64	<	* equivalent to {@code fork(); join()} but always attempts to
65	<	* begin execution in the current thread. The "<em>quiet</em>" forms
66	<	* of these methods do not extract results or report exceptions. These
75	>	* conventions. Method {@link #invoke} is semantically
76	>	* equivalent to {@code fork(); join()} but always attempts to begin
77	>	* execution in the current thread. The "<em>quiet</em>" forms of
78	>	* these methods do not extract results or report exceptions. These
79		* may be useful when a set of tasks are being executed, and you need
80		* to delay processing of results or exceptions until all complete.
81		* Method {@code invokeAll} (available in multiple versions)
82		* performs the most common form of parallel invocation: forking a set
83		* of tasks and joining them all.
84		*
85	<	* <p> The ForkJoinTask class is not usually directly subclassed.
85	>	* <p>The execution status of tasks may be queried at several levels
86	>	* of detail: {@link #isDone} is true if a task completed in any way
87	>	* (including the case where a task was cancelled without executing);
88	>	* {@link #isCompletedNormally} is true if a task completed without
89	>	* cancellation or encountering an exception; {@link #isCancelled} is
90	>	* true if the task was cancelled (in which case {@link #getException}
91	>	* returns a {@link java.util.concurrent.CancellationException}); and
92	>	* {@link #isCompletedAbnormally} is true if a task was either
93	>	* cancelled or encountered an exception, in which case {@link
94	>	* #getException} will return either the encountered exception or
95	>	* {@link java.util.concurrent.CancellationException}.
96	>	*
97	>	* <p>The ForkJoinTask class is not usually directly subclassed.
98		* Instead, you subclass one of the abstract classes that support a
99	<	* particular style of fork/join processing.  Normally, a concrete
99	>	* particular style of fork/join processing, typically {@link
100	>	* RecursiveAction} for computations that do not return results, or
101	>	* {@link RecursiveTask} for those that do.  Normally, a concrete
102		* ForkJoinTask subclass declares fields comprising its parameters,
103		* established in a constructor, and then defines a {@code compute}
104		* method that somehow uses the control methods supplied by this base
105		* class. While these methods have {@code public} access (to allow
106	<	* instances of different task subclasses to call each others
106	>	* instances of different task subclasses to call each other's
107		* methods), some of them may only be called from within other
108		* ForkJoinTasks (as may be determined using method {@link
109		* #inForkJoinPool}).  Attempts to invoke them in other contexts
110		* result in exceptions or errors, possibly including
111	<	* ClassCastException.
111	>	* {@code ClassCastException}.
112	>	*
113	>	* <p>Method {@link #join} and its variants are appropriate for use
114	>	* only when completion dependencies are acyclic; that is, the
115	>	* parallel computation can be described as a directed acyclic graph
116	>	* (DAG). Otherwise, executions may encounter a form of deadlock as
117	>	* tasks cyclically wait for each other.  However, this framework
118	>	* supports other methods and techniques (for example the use of
119	>	* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that
120	>	* may be of use in constructing custom subclasses for problems that
121	>	* are not statically structured as DAGs.
122		*
123	<	* <p>Most base support methods are {@code final} because their
124	<	* implementations are intrinsically tied to the underlying
125	<	* lightweight task scheduling framework, and so cannot be overridden.
126	<	* Developers creating new basic styles of fork/join processing should
127	<	* minimally implement {@code protected} methods
128	<	* {@code exec}, {@code setRawResult}, and
129	<	* {@code getRawResult}, while also introducing an abstract
130	<	* computational method that can be implemented in its subclasses,
131	<	* possibly relying on other {@code protected} methods provided
96	<	* by this class.
123	>	* <p>Most base support methods are {@code final}, to prevent
124	>	* overriding of implementations that are intrinsically tied to the
125	>	* underlying lightweight task scheduling framework.  Developers
126	>	* creating new basic styles of fork/join processing should minimally
127	>	* implement {@code protected} methods {@link #exec}, {@link
128	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
129	>	* an abstract computational method that can be implemented in its
130	>	* subclasses, possibly relying on other {@code protected} methods
131	>	* provided by this class.
132		*
133		* <p>ForkJoinTasks should perform relatively small amounts of
134	<	* computations, otherwise splitting into smaller tasks. As a very
135	<	* rough rule of thumb, a task should perform more than 100 and less
136	<	* than 10000 basic computational steps. If tasks are too big, then
137	<	* parallelism cannot improve throughput. If too small, then memory
138	<	* and internal task maintenance overhead may overwhelm processing.
134	>	* computation. Large tasks should be split into smaller subtasks,
135	>	* usually via recursive decomposition. As a very rough rule of thumb,
136	>	* a task should perform more than 100 and less than 10000 basic
137	>	* computational steps, and should avoid indefinite looping. If tasks
138	>	* are too big, then parallelism cannot improve throughput. If too
139	>	* small, then memory and internal task maintenance overhead may
140	>	* overwhelm processing.
141		*
142	<	* <p>ForkJoinTasks are {@code Serializable}, which enables them
143	<	* to be used in extensions such as remote execution frameworks. It is
144	<	* in general sensible to serialize tasks only before or after, but
145	<	* not during execution. Serialization is not relied on during
146	<	* execution itself.
142	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
143	>	* and {@link Callable}, that may be of use when mixing execution of
144	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
145	>	* of this form, consider using a pool constructed in <em>asyncMode</em>.
146	>	*
147	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
148	>	* used in extensions such as remote execution frameworks. It is
149	>	* sensible to serialize tasks only before or after, but not during,
150	>	* execution. Serialization is not relied on during execution itself.
151		*
152		* @since 1.7
153		* @author Doug Lea
154		*/
155		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
156
157	<	/**
158	<	* Run control status bits packed into a single int to minimize
159	<	* footprint and to ensure atomicity (via CAS).  Status is
160	<	* initially zero, and takes on nonnegative values until
161	<	* completed, upon which status holds COMPLETED. CANCELLED, or
162	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
163	<	* blocking waits by other threads have SIGNAL_MASK bits set --
164	<	* bit 15 for external (nonFJ) waits, and the rest a count of
165	<	* waiting FJ threads.  (This representation relies on
166	<	* ForkJoinPool max thread limits). Completion of a stolen task
167	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
168	<	* though suboptimal for some purposes, we use basic builtin
169	<	* wait/notify to take advantage of "monitor inflation" in JVMs
170	<	* that we would otherwise need to emulate to avoid adding further
171	<	* per-task bookkeeping overhead. Note that bits 16-28 are
172	<	* currently unused. Also value 0x80000000 is available as spare
173	<	* completion value.
157	>	/*
158	>	* See the internal documentation of class ForkJoinPool for a
159	>	* general implementation overview.  ForkJoinTasks are mainly
160	>	* responsible for maintaining their "status" field amidst relays
161	>	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
162	>	* methods of this class are more-or-less layered into (1) basic
163	>	* status maintenance (2) execution and awaiting completion (3)
164	>	* user-level methods that additionally report results. This is
165	>	* sometimes hard to see because this file orders exported methods
166	>	* in a way that flows well in javadocs. In particular, most
167	>	* join mechanics are in method quietlyJoin, below.
168	>	*/
169	>
170	>	/*
171	>	* The status field holds run control status bits packed into a
172	>	* single int to minimize footprint and to ensure atomicity (via
173	>	* CAS).  Status is initially zero, and takes on nonnegative
174	>	* values until completed, upon which status holds value
175	>	* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
176	>	* waits by other threads have the SIGNAL bit set.  Completion of
177	>	* a stolen task with SIGNAL set awakens any waiters via
178	>	* notifyAll. Even though suboptimal for some purposes, we use
179	>	* basic builtin wait/notify to take advantage of "monitor
180	>	* inflation" in JVMs that we would otherwise need to emulate to
181	>	* avoid adding further per-task bookkeeping overhead.  We want
182	>	* these monitors to be "fat", i.e., not use biasing or thin-lock
183	>	* techniques, so use some odd coding idioms that tend to avoid
184	>	* them.
185		*/
186	+
187	+	/** The run status of this task */
188		volatile int status; // accessed directly by pool and workers
189
190	<	static final int COMPLETION_MASK      = 0xe0000000;
191	<	static final int NORMAL               = 0xe0000000; // == mask
192	<	static final int CANCELLED            = 0xc0000000;
193	<	static final int EXCEPTIONAL          = 0xa0000000;
140	<	static final int SIGNAL_MASK          = 0x0000ffff;
141	<	static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
142	<	static final int EXTERNAL_SIGNAL      = 0x00008000; // top bit of low word
190	>	private static final int NORMAL      = -1;
191	>	private static final int CANCELLED   = -2;
192	>	private static final int EXCEPTIONAL = -3;
193	>	private static final int SIGNAL      =  1;
194
195		/**
196		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 153 | Line 204 | public abstract class ForkJoinTask<V> im
204		Collections.synchronizedMap
205		(new WeakHashMap<ForkJoinTask<?>, Throwable>());
206
207	<	// within-package utilities
207	>	// Maintaining completion status
208
209		/**
210	<	* Gets current worker thread, or null if not a worker thread.
211	<	*/
161	<	static ForkJoinWorkerThread getWorker() {
162	<	Thread t = Thread.currentThread();
163	<	return ((t instanceof ForkJoinWorkerThread) ?
164	<	(ForkJoinWorkerThread) t : null);
165	<	}
166	<
167	<	final boolean casStatus(int cmp, int val) {
168	<	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
169	<	}
170	<
171	<	/**
172	<	* Workaround for not being able to rethrow unchecked exceptions.
173	<	*/
174	<	static void rethrowException(Throwable ex) {
175	<	if (ex != null)
176	<	UNSAFE.throwException(ex);
177	<	}
178	<
179	<	// Setting completion status
180	<
181	<	/**
182	<	* Marks completion and wakes up threads waiting to join this task.
210	>	* Marks completion and wakes up threads waiting to join this task,
211	>	* also clearing signal request bits.
212		*
213		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
214		*/
215	<	final void setCompletion(int completion) {
187	<	ForkJoinPool pool = getPool();
188	<	if (pool != null) {
189	<	int s; // Clear signal bits while setting completion status
190	<	do {} while ((s = status) >= 0 && !casStatus(s, completion));
191	<
192	<	if ((s & SIGNAL_MASK) != 0) {
193	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
194	<	pool.updateRunningCount(s);
195	<	synchronized (this) { notifyAll(); }
196	<	}
197	<	}
198	<	else
199	<	externallySetCompletion(completion);
200	<	}
201	<
202	<	/**
203	<	* Version of setCompletion for non-FJ threads.  Leaves signal
204	<	* bits for unblocked threads to adjust, and always notifies.
205	<	*/
206	<	private void externallySetCompletion(int completion) {
207	<	int s;
208	<	do {} while ((s = status) >= 0 &&
209	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
210	<	synchronized (this) { notifyAll(); }
211	<	}
212	<
213	<	/**
214	<	* Sets status to indicate normal completion.
215	<	*/
216	<	final void setNormalCompletion() {
217	<	// Try typical fast case -- single CAS, no signal, not already done.
218	<	// Manually expand casStatus to improve chances of inlining it
219	<	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
220	<	setCompletion(NORMAL);
221	<	}
222	<
223	<	// internal waiting and notification
224	<
225	<	/**
226	<	* Performs the actual monitor wait for awaitDone.
227	<	*/
228	<	private void doAwaitDone() {
229	<	// Minimize lock bias and in/de-flation effects by maximizing
230	<	// chances of waiting inside sync
231	<	try {
232	<	while (status >= 0)
233	<	synchronized (this) { if (status >= 0) wait(); }
234	<	} catch (InterruptedException ie) {
235	<	onInterruptedWait();
236	<	}
237	<	}
238	<
239	<	/**
240	<	* Performs the actual timed monitor wait for awaitDone.
241	<	*/
242	<	private void doAwaitDone(long startTime, long nanos) {
243	<	synchronized (this) {
244	<	try {
245	<	while (status >= 0) {
246	<	long nt = nanos - System.nanoTime() - startTime;
247	<	if (nt <= 0)
248	<	break;
249	<	wait(nt / 1000000, (int) (nt % 1000000));
250	<	}
251	<	} catch (InterruptedException ie) {
252	<	onInterruptedWait();
253	<	}
254	<	}
255	<	}
256	<
257	<	// Awaiting completion
258	<
259	<	/**
260	<	* Sets status to indicate there is joiner, then waits for join,
261	<	* surrounded with pool notifications.
262	<	*
263	<	* @return status upon exit
264	<	*/
265	<	private int awaitDone(ForkJoinWorkerThread w,
266	<	boolean maintainParallelism) {
267	<	ForkJoinPool pool = (w == null) ? null : w.pool;
215	>	private void setCompletion(int completion) {
216		int s;
217		while ((s = status) >= 0) {
218	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
219	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
220	<	doAwaitDone();
273	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
274	<	adjustPoolCountsOnUnblock(pool);
218	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
219	>	if (s != 0)
220	>	synchronized (this) { notifyAll(); }
221		break;
222		}
223		}
278	–	return s;
224		}
225
226		/**
227	<	* Timed version of awaitDone
227	>	* Records exception and sets exceptional completion.
228		*
229	<	* @return status upon exit
229	>	* @return status on exit
230		*/
231	<	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
287	<	ForkJoinPool pool = (w == null) ? null : w.pool;
288	<	int s;
289	<	while ((s = status) >= 0) {
290	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
291	<	long startTime = System.nanoTime();
292	<	if (pool == null || !pool.preJoin(this, false))
293	<	doAwaitDone(startTime, nanos);
294	<	if ((s = status) >= 0) {
295	<	adjustPoolCountsOnCancelledWait(pool);
296	<	s = status;
297	<	}
298	<	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
299	<	adjustPoolCountsOnUnblock(pool);
300	<	break;
301	<	}
302	<	}
303	<	return s;
304	<	}
305	<
306	<	/**
307	<	* Notifies pool that thread is unblocked. Called by signalled
308	<	* threads when woken by non-FJ threads (which is atypical).
309	<	*/
310	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
311	<	int s;
312	<	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
313	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
314	<	pool.updateRunningCount(s);
315	<	}
316	<
317	<	/**
318	<	* Notifies pool to adjust counts on cancelled or timed out wait.
319	<	*/
320	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
321	<	if (pool != null) {
322	<	int s;
323	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
324	<	if (casStatus(s, s - 1)) {
325	<	pool.updateRunningCount(1);
326	<	break;
327	<	}
328	<	}
329	<	}
330	<	}
331	<
332	<	/**
333	<	* Handles interruptions during waits.
334	<	*/
335	<	private void onInterruptedWait() {
336	<	ForkJoinWorkerThread w = getWorker();
337	<	if (w == null)
338	<	Thread.currentThread().interrupt(); // re-interrupt
339	<	else if (w.isTerminating())
340	<	cancelIgnoringExceptions();
341	<	// else if FJworker, ignore interrupt
342	<	}
343	<
344	<	// Recording and reporting exceptions
345	<
346	<	private void setDoneExceptionally(Throwable rex) {
231	>	private void setExceptionalCompletion(Throwable rex) {
232		exceptionMap.put(this, rex);
233		setCompletion(EXCEPTIONAL);
234		}
235
236		/**
237	<	* Throws the exception associated with status s.
238	<	*
354	<	* @throws the exception
237	>	* Blocks a worker thread until completed or timed out.  Called
238	>	* only by pool.
239		*/
240	<	private void reportException(int s) {
241	<	if ((s &= COMPLETION_MASK) < NORMAL) {
242	<	if (s == CANCELLED)
243	<	throw new CancellationException();
244	<	else
245	<	rethrowException(exceptionMap.get(this));
240	>	final void internalAwaitDone(long millis, int nanos) {
241	>	if (status >= 0) {
242	>	try {     // the odd construction reduces lock bias effects
243	>	synchronized (this) {
244	>	if (status > 0 ||
245	>	UNSAFE.compareAndSwapInt(this, statusOffset,
246	>	0, SIGNAL))
247	>	wait(millis, nanos);
248	>	}
249	>	} catch (InterruptedException ie) {
250	>	cancelIfTerminating();
251	>	}
252		}
253		}
254
255		/**
256	<	* Returns result or throws exception using j.u.c.Future conventions.
367	<	* Only call when {@code isDone} known to be true.
256	>	* Blocks a non-worker-thread until completion.
257		*/
258	<	private V reportFutureResult()
259	<	throws ExecutionException, InterruptedException {
260	<	int s = status & COMPLETION_MASK;
261	<	if (s < NORMAL) {
262	<	Throwable ex;
263	<	if (s == CANCELLED)
264	<	throw new CancellationException();
265	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
266	<	throw new ExecutionException(ex);
267	<	if (Thread.interrupted())
268	<	throw new InterruptedException();
258	>	private void externalAwaitDone() {
259	>	if (status >= 0) {
260	>	boolean interrupted = false;
261	>	synchronized(this) {
262	>	int s;
263	>	while ((s = status) >= 0) {
264	>	if (s == 0 &&
265	>	!UNSAFE.compareAndSwapInt(this, statusOffset,
266	>	0, SIGNAL))
267	>	continue;
268	>	try {
269	>	wait();
270	>	} catch (InterruptedException ie) {
271	>	interrupted = true;
272	>	}
273	>	}
274	>	}
275	>	if (interrupted)
276	>	Thread.currentThread().interrupt();
277		}
381	–	return getRawResult();
278		}
279
280		/**
281	<	* Returns result or throws exception using j.u.c.Future conventions
386	<	* with timeouts.
281	>	* Blocks a non-worker-thread until completion or interruption or timeout.
282		*/
283	<	private V reportTimedFutureResult()
284	<	throws InterruptedException, ExecutionException, TimeoutException {
390	<	Throwable ex;
391	<	int s = status & COMPLETION_MASK;
392	<	if (s == NORMAL)
393	<	return getRawResult();
394	<	if (s == CANCELLED)
395	<	throw new CancellationException();
396	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
397	<	throw new ExecutionException(ex);
283	>	private void externalInterruptibleAwaitDone(boolean timed, long nanos)
284	>	throws InterruptedException {
285		if (Thread.interrupted())
286		throw new InterruptedException();
400	–	throw new TimeoutException();
401	–	}
402	–
403	–	// internal execution methods
404	–
405	–	/**
406	–	* Calls exec, recording completion, and rethrowing exception if
407	–	* encountered. Caller should normally check status before calling.
408	–	*
409	–	* @return true if completed normally
410	–	*/
411	–	private boolean tryExec() {
412	–	try { // try block must contain only call to exec
413	–	if (!exec())
414	–	return false;
415	–	} catch (Throwable rex) {
416	–	setDoneExceptionally(rex);
417	–	rethrowException(rex);
418	–	return false; // not reached
419	–	}
420	–	setNormalCompletion();
421	–	return true;
422	–	}
423	–
424	–	/**
425	–	* Main execution method used by worker threads. Invokes
426	–	* base computation unless already complete.
427	–	*/
428	–	final void quietlyExec() {
287		if (status >= 0) {
288	<	try {
289	<	if (!exec())
290	<	return;
291	<	} catch (Throwable rex) {
292	<	setDoneExceptionally(rex);
293	<	return;
288	>	long startTime = timed ? System.nanoTime() : 0L;
289	>	synchronized(this) {
290	>	int s;
291	>	while ((s = status) >= 0) {
292	>	long nt;
293	>	if (s == 0 &&
294	>	!UNSAFE.compareAndSwapInt(this, statusOffset,
295	>	0, SIGNAL))
296	>	continue;
297	>	else if (!timed)
298	>	wait();
299	>	else if ((nt = nanos - (System.nanoTime()-startTime)) > 0L)
300	>	wait(nt / 1000000, (int)(nt % 1000000));
301	>	else
302	>	break;
303	>	}
304		}
437	–	setNormalCompletion();
305		}
306		}
307
308		/**
309	<	* Calls exec(), recording but not rethrowing exception.
310	<	* Caller should normally check status before calling.
311	<	*
445	<	* @return true if completed normally
309	>	* Unless done, calls exec and records status if completed, but
310	>	* doesn't wait for completion otherwise. Primary execution method
311	>	* for ForkJoinWorkerThread.
312		*/
313	<	private boolean tryQuietlyInvoke() {
313	>	final void quietlyExec() {
314		try {
315	<	if (!exec())
316	<	return false;
315	>	if (status < 0 || !exec())
316	>	return;
317		} catch (Throwable rex) {
318	<	setDoneExceptionally(rex);
319	<	return false;
454	<	}
455	<	setNormalCompletion();
456	<	return true;
457	<	}
458	<
459	<	/**
460	<	* Cancels, ignoring any exceptions it throws.
461	<	*/
462	<	final void cancelIgnoringExceptions() {
463	<	try {
464	<	cancel(false);
465	<	} catch (Throwable ignore) {
318	>	setExceptionalCompletion(rex);
319	>	return;
320		}
321	<	}
468	<
469	<	/**
470	<	* Main implementation of helpJoin
471	<	*/
472	<	private int busyJoin(ForkJoinWorkerThread w) {
473	<	int s;
474	<	ForkJoinTask<?> t;
475	<	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
476	<	t.quietlyExec();
477	<	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
321	>	setCompletion(NORMAL); // must be outside try block
322		}
323
324		// public methods
#	Line 482 | Line 326 | public abstract class ForkJoinTask<V> im
326		/**
327		* Arranges to asynchronously execute this task.  While it is not
328		* necessarily enforced, it is a usage error to fork a task more
329	<	* than once unless it has completed and been reinitialized.  This
330	<	* method may be invoked only from within ForkJoinTask
331	<	* computations (as may be determined using method {@link
332	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
333	<	* in exceptions or errors, possibly including ClassCastException.
329	>	* than once unless it has completed and been reinitialized.
330	>	* Subsequent modifications to the state of this task or any data
331	>	* it operates on are not necessarily consistently observable by
332	>	* any thread other than the one executing it unless preceded by a
333	>	* call to {@link #join} or related methods, or a call to {@link
334	>	* #isDone} returning {@code true}.
335	>	*
336	>	* <p>This method may be invoked only from within {@code
337	>	* ForkJoinPool} computations (as may be determined using method
338	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
339	>	* result in exceptions or errors, possibly including {@code
340	>	* ClassCastException}.
341	>	*
342	>	* @return {@code this}, to simplify usage
343		*/
344	<	public final void fork() {
344	>	public final ForkJoinTask<V> fork() {
345		((ForkJoinWorkerThread) Thread.currentThread())
346		.pushTask(this);
347	+	return this;
348		}
349
350		/**
351	<	* Returns the result of the computation when it is ready.
352	<	* This method differs from {@code get} in that abnormal
353	<	* completion results in RuntimeExceptions or Errors, not
354	<	* ExecutionExceptions.
351	>	* Returns the result of the computation when it {@link #isDone is
352	>	* done}.  This method differs from {@link #get()} in that
353	>	* abnormal completion results in {@code RuntimeException} or
354	>	* {@code Error}, not {@code ExecutionException}, and that
355	>	* interrupts of the calling thread do <em>not</em> cause the
356	>	* method to abruptly return by throwing {@code
357	>	* InterruptedException}.
358		*
359		* @return the computed result
360		*/
361		public final V join() {
362	<	ForkJoinWorkerThread w = getWorker();
363	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
364	<	reportException(awaitDone(w, true));
362	>	quietlyJoin();
363	>	Throwable ex;
364	>	if (status < NORMAL && (ex = getException()) != null)
365	>	UNSAFE.throwException(ex);
366		return getRawResult();
367		}
368
369		/**
370		* Commences performing this task, awaits its completion if
371	<	* necessary, and return its result.
371	>	* necessary, and returns its result, or throws an (unchecked)
372	>	* {@code RuntimeException} or {@code Error} if the underlying
373	>	* computation did so.
374		*
515	–	* @throws Throwable (a RuntimeException, Error, or unchecked
516	–	* exception) if the underlying computation did so
375		* @return the computed result
376		*/
377		public final V invoke() {
378	<	if (status >= 0 && tryExec())
379	<	return getRawResult();
380	<	else
381	<	return join();
378	>	quietlyInvoke();
379	>	Throwable ex;
380	>	if (status < NORMAL && (ex = getException()) != null)
381	>	UNSAFE.throwException(ex);
382	>	return getRawResult();
383		}
384
385		/**
386	<	* Forks both tasks, returning when {@code isDone} holds for
387	<	* both of them or an exception is encountered. This method may be
388	<	* invoked only from within ForkJoinTask computations (as may be
389	<	* determined using method {@link #inForkJoinPool}). Attempts to
390	<	* invoke in other contexts result in exceptions or errors,
391	<	* possibly including ClassCastException.
392	<	*
393	<	* @param t1 one task
394	<	* @param t2 the other task
395	<	* @throws NullPointerException if t1 or t2 are null
396	<	* @throws RuntimeException or Error if either task did so
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, the
391	>	* other may be cancelled. However, the execution status of
392	>	* individual tasks is not guaranteed upon exceptional return. The
393	>	* status of each task may be obtained using {@link
394	>	* #getException()} and related methods to check if they have been
395	>	* cancelled, completed normally or exceptionally, or left
396	>	* unprocessed.
397	>	*
398	>	* <p>This method may be invoked only from within {@code
399	>	* ForkJoinPool} computations (as may be determined using method
400	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
401	>	* result in exceptions or errors, possibly including {@code
402	>	* ClassCastException}.
403	>	*
404	>	* @param t1 the first task
405	>	* @param t2 the second task
406	>	* @throws NullPointerException if any task is null
407		*/
408	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
408	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
409		t2.fork();
410		t1.invoke();
411		t2.join();
412		}
413
414		/**
415	<	* Forks the given tasks, returning when {@code isDone} holds
416	<	* for all of them. If any task encounters an exception, others
417	<	* may be cancelled.  This method may be invoked only from within
418	<	* ForkJoinTask computations (as may be determined using method
419	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
420	<	* result in exceptions or errors, possibly including
421	<	* ClassCastException.
415	>	* Forks the given tasks, returning when {@code isDone} holds for
416	>	* each task or an (unchecked) exception is encountered, in which
417	>	* case the exception is rethrown. If more than one task
418	>	* encounters an exception, then this method throws any one of
419	>	* these exceptions. If any task encounters an exception, others
420	>	* may be cancelled. However, the execution status of individual
421	>	* tasks is not guaranteed upon exceptional return. The status of
422	>	* each task may be obtained using {@link #getException()} and
423	>	* related methods to check if they have been cancelled, completed
424	>	* normally or exceptionally, or left unprocessed.
425	>	*
426	>	* <p>This method may be invoked only from within {@code
427	>	* ForkJoinPool} computations (as may be determined using method
428	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
429	>	* result in exceptions or errors, possibly including {@code
430	>	* ClassCastException}.
431		*
432	<	* @param tasks the array of tasks
433	<	* @throws NullPointerException if tasks or any element are null
556	<	* @throws RuntimeException or Error if any task did so
432	>	* @param tasks the tasks
433	>	* @throws NullPointerException if any task is null
434		*/
435		public static void invokeAll(ForkJoinTask<?>... tasks) {
436		Throwable ex = null;
#	Line 568 | Line 445 | public abstract class ForkJoinTask<V> im
445		t.fork();
446		else {
447		t.quietlyInvoke();
448	<	if (ex == null)
448	>	if (ex == null && t.status < NORMAL)
449		ex = t.getException();
450		}
451		}
#	Line 579 | Line 456 | public abstract class ForkJoinTask<V> im
456		t.cancel(false);
457		else {
458		t.quietlyJoin();
459	<	if (ex == null)
459	>	if (ex == null && t.status < NORMAL)
460		ex = t.getException();
461		}
462		}
463		}
464		if (ex != null)
465	<	rethrowException(ex);
465	>	UNSAFE.throwException(ex);
466		}
467
468		/**
469	<	* Forks all tasks in the collection, returning when
470	<	* {@code isDone} holds for all of them. If any task
471	<	* encounters an exception, others may be cancelled.  This method
472	<	* may be invoked only from within ForkJoinTask computations (as
473	<	* may be determined using method {@link
474	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
475	<	* in exceptions or errors, possibly including ClassCastException.
469	>	* Forks all tasks in the specified collection, returning when
470	>	* {@code isDone} holds for each task or an (unchecked) exception
471	>	* is encountered, in which case the exception is rethrown. If
472	>	* more than one task encounters an exception, then this method
473	>	* throws any one of these exceptions. If any task encounters an
474	>	* exception, others may be cancelled. However, the execution
475	>	* status of individual tasks is not guaranteed upon exceptional
476	>	* return. The status of each task may be obtained using {@link
477	>	* #getException()} and related methods to check if they have been
478	>	* cancelled, completed normally or exceptionally, or left
479	>	* unprocessed.
480	>	*
481	>	* <p>This method may be invoked only from within {@code
482	>	* ForkJoinPool} computations (as may be determined using method
483	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
484	>	* result in exceptions or errors, possibly including {@code
485	>	* ClassCastException}.
486		*
487		* @param tasks the collection of tasks
488	+	* @return the tasks argument, to simplify usage
489		* @throws NullPointerException if tasks or any element are null
602	–	* @throws RuntimeException or Error if any task did so
490		*/
491	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
492	<	if (!(tasks instanceof List<?>)) {
491	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
492	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
493		invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
494	<	return;
494	>	return tasks;
495		}
496		@SuppressWarnings("unchecked")
497		List<? extends ForkJoinTask<?>> ts =
#	Line 621 | Line 508 | public abstract class ForkJoinTask<V> im
508		t.fork();
509		else {
510		t.quietlyInvoke();
511	<	if (ex == null)
511	>	if (ex == null && t.status < NORMAL)
512		ex = t.getException();
513		}
514		}
#	Line 632 | Line 519 | public abstract class ForkJoinTask<V> im
519		t.cancel(false);
520		else {
521		t.quietlyJoin();
522	<	if (ex == null)
522	>	if (ex == null && t.status < NORMAL)
523		ex = t.getException();
524		}
525		}
526		}
527		if (ex != null)
528	<	rethrowException(ex);
528	>	UNSAFE.throwException(ex);
529	>	return tasks;
530		}
531
532		/**
533	<	* Returns true if the computation performed by this task has
534	<	* completed (or has been cancelled).
533	>	* Attempts to cancel execution of this task. This attempt will
534	>	* fail if the task has already completed or could not be
535	>	* cancelled for some other reason. If successful, and this task
536	>	* has not started when {@code cancel} is called, execution of
537	>	* this task is suppressed. After this method returns
538	>	* successfully, unless there is an intervening call to {@link
539	>	* #reinitialize}, subsequent calls to {@link #isCancelled},
540	>	* {@link #isDone}, and {@code cancel} will return {@code true}
541	>	* and calls to {@link #join} and related methods will result in
542	>	* {@code CancellationException}.
543	>	*
544	>	* <p>This method may be overridden in subclasses, but if so, must
545	>	* still ensure that these properties hold. In particular, the
546	>	* {@code cancel} method itself must not throw exceptions.
547	>	*
548	>	* <p>This method is designed to be invoked by <em>other</em>
549	>	* tasks. To terminate the current task, you can just return or
550	>	* throw an unchecked exception from its computation method, or
551	>	* invoke {@link #completeExceptionally}.
552	>	*
553	>	* @param mayInterruptIfRunning this value has no effect in the
554	>	* default implementation because interrupts are not used to
555	>	* control cancellation.
556		*
557	<	* @return true if this computation has completed
557	>	* @return {@code true} if this task is now cancelled
558		*/
559	<	public final boolean isDone() {
560	<	return status < 0;
559	>	public boolean cancel(boolean mayInterruptIfRunning) {
560	>	setCompletion(CANCELLED);
561	>	return status == CANCELLED;
562		}
563
564		/**
565	<	* Returns true if this task was cancelled.
566	<	*
567	<	* @return true if this task was cancelled
565	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
566	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
567	>	* exceptions, but if it does anyway, we have no recourse during
568	>	* shutdown, so guard against this case.
569		*/
570	+	final void cancelIgnoringExceptions() {
571	+	try {
572	+	cancel(false);
573	+	} catch (Throwable ignore) {
574	+	}
575	+	}
576	+
577	+	/**
578	+	* Cancels if current thread is a terminating worker thread,
579	+	* ignoring any exceptions thrown by cancel.
580	+	*/
581	+	final void cancelIfTerminating() {
582	+	Thread t = Thread.currentThread();
583	+	if ((t instanceof ForkJoinWorkerThread) &&
584	+	((ForkJoinWorkerThread) t).isTerminating()) {
585	+	try {
586	+	cancel(false);
587	+	} catch (Throwable ignore) {
588	+	}
589	+	}
590	+	}
591	+
592	+	public final boolean isDone() {
593	+	return status < 0;
594	+	}
595	+
596		public final boolean isCancelled() {
597	<	return (status & COMPLETION_MASK) == CANCELLED;
597	>	return status == CANCELLED;
598		}
599
600		/**
601	<	* Asserts that the results of this task's computation will not be
665	<	* used. If a cancellation occurs before attempting to execute this
666	<	* task, then execution will be suppressed, {@code isCancelled}
667	<	* will report true, and {@code join} will result in a
668	<	* {@code CancellationException} being thrown. Otherwise, when
669	<	* cancellation races with completion, there are no guarantees
670	<	* about whether {@code isCancelled} will report true, whether
671	<	* {@code join} will return normally or via an exception, or
672	<	* whether these behaviors will remain consistent upon repeated
673	<	* invocation.
674	<	*
675	<	* <p>This method may be overridden in subclasses, but if so, must
676	<	* still ensure that these minimal properties hold. In particular,
677	<	* the cancel method itself must not throw exceptions.
678	<	*
679	<	* <p> This method is designed to be invoked by <em>other</em>
680	<	* tasks. To terminate the current task, you can just return or
681	<	* throw an unchecked exception from its computation method, or
682	<	* invoke {@code completeExceptionally}.
601	>	* Returns {@code true} if this task threw an exception or was cancelled.
602		*
603	<	* @param mayInterruptIfRunning this value is ignored in the
685	<	* default implementation because tasks are not in general
686	<	* cancelled via interruption
687	<	*
688	<	* @return true if this task is now cancelled
603	>	* @return {@code true} if this task threw an exception or was cancelled
604		*/
605	<	public boolean cancel(boolean mayInterruptIfRunning) {
606	<	setCompletion(CANCELLED);
692	<	return (status & COMPLETION_MASK) == CANCELLED;
605	>	public final boolean isCompletedAbnormally() {
606	>	return status < NORMAL;
607		}
608
609		/**
610	<	* Returns true if this task threw an exception or was cancelled.
610	>	* Returns {@code true} if this task completed without throwing an
611	>	* exception and was not cancelled.
612		*
613	<	* @return true if this task threw an exception or was cancelled
613	>	* @return {@code true} if this task completed without throwing an
614	>	* exception and was not cancelled
615		*/
616	<	public final boolean isCompletedAbnormally() {
617	<	return (status & COMPLETION_MASK) < NORMAL;
616	>	public final boolean isCompletedNormally() {
617	>	return status == NORMAL;
618		}
619
620		/**
621		* Returns the exception thrown by the base computation, or a
622	<	* CancellationException if cancelled, or null if none or if the
623	<	* method has not yet completed.
622	>	* {@code CancellationException} if cancelled, or {@code null} if
623	>	* none or if the method has not yet completed.
624		*
625	<	* @return the exception, or null if none
625	>	* @return the exception, or {@code null} if none
626		*/
627		public final Throwable getException() {
628	<	int s = status & COMPLETION_MASK;
629	<	if (s >= NORMAL)
630	<	return null;
631	<	if (s == CANCELLED)
716	<	return new CancellationException();
717	<	return exceptionMap.get(this);
628	>	int s = status;
629	>	return ((s >= NORMAL)    ? null :
630	>	(s == CANCELLED) ? new CancellationException() :
631	>	exceptionMap.get(this));
632		}
633
634		/**
#	Line 723 | Line 637 | public abstract class ForkJoinTask<V> im
637		* {@code join} and related operations. This method may be used
638		* to induce exceptions in asynchronous tasks, or to force
639		* completion of tasks that would not otherwise complete.  Its use
640	<	* in other situations is likely to be wrong.  This method is
640	>	* in other situations is discouraged.  This method is
641		* overridable, but overridden versions must invoke {@code super}
642		* implementation to maintain guarantees.
643		*
644	<	* @param ex the exception to throw. If this exception is
645	<	* not a RuntimeException or Error, the actual exception thrown
646	<	* will be a RuntimeException with cause ex.
644	>	* @param ex the exception to throw. If this exception is not a
645	>	* {@code RuntimeException} or {@code Error}, the actual exception
646	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
647		*/
648		public void completeExceptionally(Throwable ex) {
649	<	setDoneExceptionally((ex instanceof RuntimeException) ||
650	<	(ex instanceof Error) ? ex :
651	<	new RuntimeException(ex));
649	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
650	>	(ex instanceof Error) ? ex :
651	>	new RuntimeException(ex));
652		}
653
654		/**
655		* Completes this task, and if not already aborted or cancelled,
656	<	* returning a {@code null} result upon {@code join} and related
657	<	* operations. This method may be used to provide results for
658	<	* asynchronous tasks, or to provide alternative handling for
659	<	* tasks that would not otherwise complete normally. Its use in
660	<	* other situations is likely to be wrong. This method is
661	<	* overridable, but overridden versions must invoke {@code super}
662	<	* implementation to maintain guarantees.
656	>	* returning the given value as the result of subsequent
657	>	* invocations of {@code join} and related operations. This method
658	>	* may be used to provide results for asynchronous tasks, or to
659	>	* provide alternative handling for tasks that would not otherwise
660	>	* complete normally. Its use in other situations is
661	>	* discouraged. This method is overridable, but overridden
662	>	* versions must invoke {@code super} implementation to maintain
663	>	* guarantees.
664		*
665		* @param value the result value for this task
666		*/
#	Line 753 | Line 668 | public abstract class ForkJoinTask<V> im
668		try {
669		setRawResult(value);
670		} catch (Throwable rex) {
671	<	setDoneExceptionally(rex);
671	>	setExceptionalCompletion(rex);
672		return;
673		}
674	<	setNormalCompletion();
760	<	}
761	<
762	<	public final V get() throws InterruptedException, ExecutionException {
763	<	ForkJoinWorkerThread w = getWorker();
764	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
765	<	awaitDone(w, true);
766	<	return reportFutureResult();
767	<	}
768	<
769	<	public final V get(long timeout, TimeUnit unit)
770	<	throws InterruptedException, ExecutionException, TimeoutException {
771	<	ForkJoinWorkerThread w = getWorker();
772	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
773	<	awaitDone(w, unit.toNanos(timeout));
774	<	return reportTimedFutureResult();
674	>	setCompletion(NORMAL);
675		}
676
677		/**
678	<	* Possibly executes other tasks until this task is ready, then
679	<	* returns the result of the computation.  This method may be more
780	<	* efficient than {@code join}, but is only applicable when
781	<	* there are no potential dependencies between continuation of the
782	<	* current task and that of any other task that might be executed
783	<	* while helping. (This usually holds for pure divide-and-conquer
784	<	* tasks). This method may be invoked only from within
785	<	* ForkJoinTask computations (as may be determined using method
786	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
787	<	* result in exceptions or errors, possibly including
788	<	* ClassCastException.
678	>	* Waits if necessary for the computation to complete, and then
679	>	* retrieves its result.
680		*
681		* @return the computed result
682	+	* @throws CancellationException if the computation was cancelled
683	+	* @throws ExecutionException if the computation threw an
684	+	* exception
685	+	* @throws InterruptedException if the current thread is not a
686	+	* member of a ForkJoinPool and was interrupted while waiting
687		*/
688	<	public final V helpJoin() {
689	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
690	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
691	<	reportException(busyJoin(w));
688	>	public final V get() throws InterruptedException, ExecutionException {
689	>	Thread t = Thread.currentThread();
690	>	if (t instanceof ForkJoinWorkerThread)
691	>	quietlyJoin();
692	>	else
693	>	externalInterruptibleAwaitDone(false, 0L);
694	>	int s = status;
695	>	if (s != NORMAL) {
696	>	Throwable ex;
697	>	if (s == CANCELLED)
698	>	throw new CancellationException();
699	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
700	>	throw new ExecutionException(ex);
701	>	}
702		return getRawResult();
703		}
704
705		/**
706	<	* Possibly executes other tasks until this task is ready.  This
707	<	* method may be invoked only from within ForkJoinTask
708	<	* computations (as may be determined using method {@link
709	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
710	<	* in exceptions or errors, possibly including ClassCastException.
706	>	* Waits if necessary for at most the given time for the computation
707	>	* to complete, and then retrieves its result, if available.
708	>	*
709	>	* @param timeout the maximum time to wait
710	>	* @param unit the time unit of the timeout argument
711	>	* @return the computed result
712	>	* @throws CancellationException if the computation was cancelled
713	>	* @throws ExecutionException if the computation threw an
714	>	* exception
715	>	* @throws InterruptedException if the current thread is not a
716	>	* member of a ForkJoinPool and was interrupted while waiting
717	>	* @throws TimeoutException if the wait timed out
718		*/
719	<	public final void quietlyHelpJoin() {
720	<	if (status >= 0) {
721	<	ForkJoinWorkerThread w =
722	<	(ForkJoinWorkerThread) Thread.currentThread();
723	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
724	<	busyJoin(w);
719	>	public final V get(long timeout, TimeUnit unit)
720	>	throws InterruptedException, ExecutionException, TimeoutException {
721	>	long nanos = unit.toNanos(timeout);
722	>	Thread t = Thread.currentThread();
723	>	if (t instanceof ForkJoinWorkerThread)
724	>	((ForkJoinWorkerThread)t).joinTask(this, true, nanos);
725	>	else
726	>	externalInterruptibleAwaitDone(true, nanos);
727	>	int s = status;
728	>	if (s != NORMAL) {
729	>	Throwable ex;
730	>	if (s == CANCELLED)
731	>	throw new CancellationException();
732	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
733	>	throw new ExecutionException(ex);
734	>	throw new TimeoutException();
735		}
736	+	return getRawResult();
737		}
738
739		/**
740	<	* Joins this task, without returning its result or throwing an
740	>	* Joins this task, without returning its result or throwing its
741		* exception. This method may be useful when processing
742		* collections of tasks when some have been cancelled or otherwise
743		* known to have aborted.
744		*/
745		public final void quietlyJoin() {
746	<	if (status >= 0) {
747	<	ForkJoinWorkerThread w = getWorker();
748	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
749	<	awaitDone(w, true);
746	>	Thread t;
747	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
748	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
749	>	if (status >= 0) {
750	>	if (w.unpushTask(this)) {
751	>	boolean completed;
752	>	try {
753	>	completed = exec();
754	>	} catch (Throwable rex) {
755	>	setExceptionalCompletion(rex);
756	>	return;
757	>	}
758	>	if (completed) {
759	>	setCompletion(NORMAL);
760	>	return;
761	>	}
762	>	}
763	>	w.joinTask(this, false, 0L);
764	>	}
765		}
766	+	else
767	+	externalAwaitDone();
768		}
769
770		/**
771		* Commences performing this task and awaits its completion if
772	<	* necessary, without returning its result or throwing an
773	<	* exception. This method may be useful when processing
833	<	* collections of tasks when some have been cancelled or otherwise
834	<	* known to have aborted.
772	>	* necessary, without returning its result or throwing its
773	>	* exception.
774		*/
775		public final void quietlyInvoke() {
776	<	if (status >= 0 && !tryQuietlyInvoke())
777	<	quietlyJoin();
776	>	if (status >= 0) {
777	>	boolean completed;
778	>	try {
779	>	completed = exec();
780	>	} catch (Throwable rex) {
781	>	setExceptionalCompletion(rex);
782	>	return;
783	>	}
784	>	if (completed)
785	>	setCompletion(NORMAL);
786	>	else
787	>	quietlyJoin();
788	>	}
789		}
790
791		/**
792		* Possibly executes tasks until the pool hosting the current task
793	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
794	<	* designs in which many tasks are forked, but none are explicitly
795	<	* joined, instead executing them until all are processed.
793	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
794	>	* be of use in designs in which many tasks are forked, but none
795	>	* are explicitly joined, instead executing them until all are
796	>	* processed.
797	>	*
798	>	* <p>This method may be invoked only from within {@code
799	>	* ForkJoinPool} computations (as may be determined using method
800	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
801	>	* result in exceptions or errors, possibly including {@code
802	>	* ClassCastException}.
803		*/
804		public static void helpQuiesce() {
805		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 855 | Line 812 | public abstract class ForkJoinTask<V> im
812		* this task, but only if reuse occurs when this task has either
813		* never been forked, or has been forked, then completed and all
814		* outstanding joins of this task have also completed. Effects
815	<	* under any other usage conditions are not guaranteed, and are
816	<	* almost surely wrong. This method may be useful when executing
815	>	* under any other usage conditions are not guaranteed.
816	>	* This method may be useful when executing
817		* pre-constructed trees of subtasks in loops.
818	+	*
819	+	* <p>Upon completion of this method, {@code isDone()} reports
820	+	* {@code false}, and {@code getException()} reports {@code
821	+	* null}. However, the value returned by {@code getRawResult} is
822	+	* unaffected. To clear this value, you can invoke {@code
823	+	* setRawResult(null)}.
824		*/
825		public void reinitialize() {
826	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
826	>	if (status == EXCEPTIONAL)
827		exceptionMap.remove(this);
828		status = 0;
829		}
#	Line 869 | Line 832 | public abstract class ForkJoinTask<V> im
832		* Returns the pool hosting the current task execution, or null
833		* if this task is executing outside of any ForkJoinPool.
834		*
835	<	* @return the pool, or null if none
835	>	* @see #inForkJoinPool
836	>	* @return the pool, or {@code null} if none
837		*/
838		public static ForkJoinPool getPool() {
839		Thread t = Thread.currentThread();
#	Line 878 | Line 842 | public abstract class ForkJoinTask<V> im
842		}
843
844		/**
845	<	* Returns {@code true} if the current thread is executing as a
846	<	* ForkJoinPool computation.
845	>	* Returns {@code true} if the current thread is a {@link
846	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation.
847		*
848	<	* @return {@code true} if the current thread is executing as a
849	<	* ForkJoinPool computation, or false otherwise
848	>	* @return {@code true} if the current thread is a {@link
849	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation,
850	>	* or {@code false} otherwise
851		*/
852		public static boolean inForkJoinPool() {
853		return Thread.currentThread() instanceof ForkJoinWorkerThread;
#	Line 894 | Line 859 | public abstract class ForkJoinTask<V> im
859		* by the current thread, and has not commenced executing in
860		* another thread.  This method may be useful when arranging
861		* alternative local processing of tasks that could have been, but
862	<	* were not, stolen. This method may be invoked only from within
898	<	* ForkJoinTask computations (as may be determined using method
899	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
900	<	* result in exceptions or errors, possibly including
901	<	* ClassCastException.
862	>	* were not, stolen.
863		*
864	<	* @return true if unforked
864	>	* <p>This method may be invoked only from within {@code
865	>	* ForkJoinPool} computations (as may be determined using method
866	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
867	>	* result in exceptions or errors, possibly including {@code
868	>	* ClassCastException}.
869	>	*
870	>	* @return {@code true} if unforked
871		*/
872		public boolean tryUnfork() {
873		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 913 | Line 880 | public abstract class ForkJoinTask<V> im
880		* value may be useful for heuristic decisions about whether to
881		* fork other tasks.
882		*
883	+	* <p>This method may be invoked only from within {@code
884	+	* ForkJoinPool} computations (as may be determined using method
885	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
886	+	* result in exceptions or errors, possibly including {@code
887	+	* ClassCastException}.
888	+	*
889		* @return the number of tasks
890		*/
891		public static int getQueuedTaskCount() {
#	Line 930 | Line 903 | public abstract class ForkJoinTask<V> im
903		* tasks, and to process computations locally if this threshold is
904		* exceeded.
905		*
906	+	* <p>This method may be invoked only from within {@code
907	+	* ForkJoinPool} computations (as may be determined using method
908	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
909	+	* result in exceptions or errors, possibly including {@code
910	+	* ClassCastException}.
911	+	*
912		* @return the surplus number of tasks, which may be negative
913		*/
914		public static int getSurplusQueuedTaskCount() {
#	Line 940 | Line 919 | public abstract class ForkJoinTask<V> im
919		// Extension methods
920
921		/**
922	<	* Returns the result that would be returned by {@code join},
923	<	* even if this task completed abnormally, or null if this task is
924	<	* not known to have been completed.  This method is designed to
925	<	* aid debugging, as well as to support extensions. Its use in any
926	<	* other context is discouraged.
922	>	* Returns the result that would be returned by {@link #join}, even
923	>	* if this task completed abnormally, or {@code null} if this task
924	>	* is not known to have been completed.  This method is designed
925	>	* to aid debugging, as well as to support extensions. Its use in
926	>	* any other context is discouraged.
927		*
928	<	* @return the result, or null if not completed
928	>	* @return the result, or {@code null} if not completed
929		*/
930		public abstract V getRawResult();
931
#	Line 965 | Line 944 | public abstract class ForkJoinTask<V> im
944		* called otherwise. The return value controls whether this task
945		* is considered to be done normally. It may return false in
946		* asynchronous actions that require explicit invocations of
947	<	* {@code complete} to become joinable. It may throw exceptions
948	<	* to indicate abnormal exit.
947	>	* {@link #complete} to become joinable. It may also throw an
948	>	* (unchecked) exception to indicate abnormal exit.
949		*
950	<	* @return true if completed normally
972	<	* @throws Error or RuntimeException if encountered during computation
950	>	* @return {@code true} if completed normally
951		*/
952		protected abstract boolean exec();
953
954		/**
955	<	* Returns, but does not unschedule or execute, the task queued by
956	<	* the current thread but not yet executed, if one is
955	>	* Returns, but does not unschedule or execute, a task queued by
956	>	* the current thread but not yet executed, if one is immediately
957		* available. There is no guarantee that this task will actually
958	<	* be polled or executed next.  This method is designed primarily
959	<	* to support extensions, and is unlikely to be useful otherwise.
960	<	* This method may be invoked only from within ForkJoinTask
961	<	* computations (as may be determined using method {@link
962	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
963	<	* in exceptions or errors, possibly including ClassCastException.
958	>	* be polled or executed next. Conversely, this method may return
959	>	* null even if a task exists but cannot be accessed without
960	>	* contention with other threads.  This method is designed
961	>	* primarily to support extensions, and is unlikely to be useful
962	>	* otherwise.
963	>	*
964	>	* <p>This method may be invoked only from within {@code
965	>	* ForkJoinPool} computations (as may be determined using method
966	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
967	>	* result in exceptions or errors, possibly including {@code
968	>	* ClassCastException}.
969		*
970	<	* @return the next task, or null if none are available
970	>	* @return the next task, or {@code null} if none are available
971		*/
972		protected static ForkJoinTask<?> peekNextLocalTask() {
973		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 995 | Line 978 | public abstract class ForkJoinTask<V> im
978		* Unschedules and returns, without executing, the next task
979		* queued by the current thread but not yet executed.  This method
980		* is designed primarily to support extensions, and is unlikely to
981	<	* be useful otherwise.  This method may be invoked only from
999	<	* within ForkJoinTask computations (as may be determined using
1000	<	* method {@link #inForkJoinPool}). Attempts to invoke in other
1001	<	* contexts result in exceptions or errors, possibly including
1002	<	* ClassCastException.
981	>	* be useful otherwise.
982		*
983	<	* @return the next task, or null if none are available
983	>	* <p>This method may be invoked only from within {@code
984	>	* ForkJoinPool} computations (as may be determined using method
985	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
986	>	* result in exceptions or errors, possibly including {@code
987	>	* ClassCastException}.
988	>	*
989	>	* @return the next task, or {@code null} if none are available
990		*/
991		protected static ForkJoinTask<?> pollNextLocalTask() {
992		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 1016 | Line 1001 | public abstract class ForkJoinTask<V> im
1001		* {@code null} result does not necessarily imply quiescence
1002		* of the pool this task is operating in.  This method is designed
1003		* primarily to support extensions, and is unlikely to be useful
1004	<	* otherwise.  This method may be invoked only from within
1005	<	* ForkJoinTask computations (as may be determined using method
1006	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1007	<	* result in exceptions or errors, possibly including
1008	<	* ClassCastException.
1004	>	* otherwise.
1005	>	*
1006	>	* <p>This method may be invoked only from within {@code
1007	>	* ForkJoinPool} computations (as may be determined using method
1008	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1009	>	* result in exceptions or errors, possibly including {@code
1010	>	* ClassCastException}.
1011		*
1012	<	* @return a task, or null if none are available
1012	>	* @return a task, or {@code null} if none are available
1013		*/
1014		protected static ForkJoinTask<?> pollTask() {
1015		return ((ForkJoinWorkerThread) Thread.currentThread())
1016		.pollTask();
1017		}
1018
1019	+	/**
1020	+	* Adaptor for Runnables. This implements RunnableFuture
1021	+	* to be compliant with AbstractExecutorService constraints
1022	+	* when used in ForkJoinPool.
1023	+	*/
1024	+	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1025	+	implements RunnableFuture<T> {
1026	+	final Runnable runnable;
1027	+	final T resultOnCompletion;
1028	+	T result;
1029	+	AdaptedRunnable(Runnable runnable, T result) {
1030	+	if (runnable == null) throw new NullPointerException();
1031	+	this.runnable = runnable;
1032	+	this.resultOnCompletion = result;
1033	+	}
1034	+	public T getRawResult() { return result; }
1035	+	public void setRawResult(T v) { result = v; }
1036	+	public boolean exec() {
1037	+	runnable.run();
1038	+	result = resultOnCompletion;
1039	+	return true;
1040	+	}
1041	+	public void run() { invoke(); }
1042	+	private static final long serialVersionUID = 5232453952276885070L;
1043	+	}
1044	+
1045	+	/**
1046	+	* Adaptor for Callables
1047	+	*/
1048	+	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1049	+	implements RunnableFuture<T> {
1050	+	final Callable<? extends T> callable;
1051	+	T result;
1052	+	AdaptedCallable(Callable<? extends T> callable) {
1053	+	if (callable == null) throw new NullPointerException();
1054	+	this.callable = callable;
1055	+	}
1056	+	public T getRawResult() { return result; }
1057	+	public void setRawResult(T v) { result = v; }
1058	+	public boolean exec() {
1059	+	try {
1060	+	result = callable.call();
1061	+	return true;
1062	+	} catch (Error err) {
1063	+	throw err;
1064	+	} catch (RuntimeException rex) {
1065	+	throw rex;
1066	+	} catch (Exception ex) {
1067	+	throw new RuntimeException(ex);
1068	+	}
1069	+	}
1070	+	public void run() { invoke(); }
1071	+	private static final long serialVersionUID = 2838392045355241008L;
1072	+	}
1073	+
1074	+	/**
1075	+	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1076	+	* method of the given {@code Runnable} as its action, and returns
1077	+	* a null result upon {@link #join}.
1078	+	*
1079	+	* @param runnable the runnable action
1080	+	* @return the task
1081	+	*/
1082	+	public static ForkJoinTask<?> adapt(Runnable runnable) {
1083	+	return new AdaptedRunnable<Void>(runnable, null);
1084	+	}
1085	+
1086	+	/**
1087	+	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1088	+	* method of the given {@code Runnable} as its action, and returns
1089	+	* the given result upon {@link #join}.
1090	+	*
1091	+	* @param runnable the runnable action
1092	+	* @param result the result upon completion
1093	+	* @return the task
1094	+	*/
1095	+	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1096	+	return new AdaptedRunnable<T>(runnable, result);
1097	+	}
1098	+
1099	+	/**
1100	+	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1101	+	* method of the given {@code Callable} as its action, and returns
1102	+	* its result upon {@link #join}, translating any checked exceptions
1103	+	* encountered into {@code RuntimeException}.
1104	+	*
1105	+	* @param callable the callable action
1106	+	* @return the task
1107	+	*/
1108	+	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1109	+	return new AdaptedCallable<T>(callable);
1110	+	}
1111	+
1112		// Serialization support
1113
1114		private static final long serialVersionUID = -7721805057305804111L;
1115
1116		/**
1117	<	* Save the state to a stream.
1117	>	* Saves the state to a stream (that is, serializes it).
1118		*
1119		* @serialData the current run status and the exception thrown
1120	<	* during execution, or null if none
1120	>	* during execution, or {@code null} if none
1121		* @param s the stream
1122		*/
1123		private void writeObject(java.io.ObjectOutputStream s)
#	Line 1047 | Line 1127 | public abstract class ForkJoinTask<V> im
1127		}
1128
1129		/**
1130	<	* Reconstitute the instance from a stream.
1130	>	* Reconstitutes the instance from a stream (that is, deserializes it).
1131		*
1132		* @param s the stream
1133		*/
1134		private void readObject(java.io.ObjectInputStream s)
1135		throws java.io.IOException, ClassNotFoundException {
1136		s.defaultReadObject();
1057	–	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1058	–	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1137		Object ex = s.readObject();
1138		if (ex != null)
1139	<	setDoneExceptionally((Throwable) ex);
1139	>	setExceptionalCompletion((Throwable) ex);
1140	>	}
1141	>
1142	>	// Unsafe mechanics
1143	>
1144	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1145	>	private static final long statusOffset =
1146	>	objectFieldOffset("status", ForkJoinTask.class);
1147	>
1148	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1149	>	try {
1150	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1151	>	} catch (NoSuchFieldException e) {
1152	>	// Convert Exception to corresponding Error
1153	>	NoSuchFieldError error = new NoSuchFieldError(field);
1154	>	error.initCause(e);
1155	>	throw error;
1156	>	}
1157		}
1158
1159	<	// Unsafe mechanics for jsr166y 3rd party package.
1159	>	/**
1160	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1161	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1162	>	* into a jdk.
1163	>	*
1164	>	* @return a sun.misc.Unsafe
1165	>	*/
1166		private static sun.misc.Unsafe getUnsafe() {
1167		try {
1168		return sun.misc.Unsafe.getUnsafe();
1169		} catch (SecurityException se) {
1170		try {
1171		return java.security.AccessController.doPrivileged
1172	<	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1172	>	(new java.security
1173	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1174		public sun.misc.Unsafe run() throws Exception {
1175	<	return getUnsafeByReflection();
1175	>	java.lang.reflect.Field f = sun.misc
1176	>	.Unsafe.class.getDeclaredField("theUnsafe");
1177	>	f.setAccessible(true);
1178	>	return (sun.misc.Unsafe) f.get(null);
1179		}});
1180		} catch (java.security.PrivilegedActionException e) {
1181		throw new RuntimeException("Could not initialize intrinsics",
#	Line 1078 | Line 1183 | public abstract class ForkJoinTask<V> im
1183		}
1184		}
1185		}
1081	–
1082	–	private static sun.misc.Unsafe getUnsafeByReflection()
1083	–	throws NoSuchFieldException, IllegalAccessException {
1084	–	java.lang.reflect.Field f =
1085	–	sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
1086	–	f.setAccessible(true);
1087	–	return (sun.misc.Unsafe) f.get(null);
1088	–	}
1089	–
1090	–	private static long fieldOffset(String fieldName, Class<?> klazz) {
1091	–	try {
1092	–	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
1093	–	} catch (NoSuchFieldException e) {
1094	–	// Convert Exception to Error
1095	–	NoSuchFieldError error = new NoSuchFieldError(fieldName);
1096	–	error.initCause(e);
1097	–	throw error;
1098	–	}
1099	–	}
1100	–
1101	–	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1102	–	static final long statusOffset =
1103	–	fieldOffset("status", ForkJoinTask.class);
1104	–
1186		}

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