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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.13 by dl, Wed Jul 22 19:04:11 2009 UTC vs.
Revision 1.58 by dl, Mon Sep 6 11:55:39 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 {@link
21	<	* ForkJoinPool}.  A ForkJoinTask is a thread-like entity that is much
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> A "main" ForkJoinTask begins execution when submitted to a
27	<	* {@link ForkJoinPool}. Once started, it will usually in turn start
28	<	* other subtasks.  As indicated by the name of this class, many
29	<	* programs using ForkJoinTasks employ only methods {@code fork}
30	<	* and {@code join}, or derivatives such as
31	<	* {@code invokeAll}.  However, this class also provides a number
32	<	* of other methods that can come into play in advanced usages, as
33	<	* well as extension mechanics that allow support of new forms of
34	<	* fork/join processing.
26	>	* <p>A "main" {@code ForkJoinTask} begins execution when submitted
27	>	* to a {@link ForkJoinPool}.  Once started, it will usually in turn
28	>	* start other subtasks.  As indicated by the name of this class,
29	>	* many programs using {@code ForkJoinTask} employ only methods
30	>	* {@link #fork} and {@link #join}, or derivatives such as {@link
31	>	* #invokeAll}.  However, this class also provides a number of other
32	>	* methods that can come into play in advanced usages, as well as
33	>	* extension mechanics that allow support of new forms of fork/join
34	>	* processing.
35		*
36	<	* <p>A ForkJoinTask is a lightweight form of {@link Future}.  The
37	<	* efficiency of ForkJoinTasks stems from a set of restrictions (that
38	<	* are only partially statically enforceable) reflecting their
39	<	* intended use as computational tasks calculating pure functions or
40	<	* operating on purely isolated objects.  The primary coordination
41	<	* mechanisms are {@link #fork}, that arranges asynchronous execution,
42	<	* and {@link #join}, that doesn't proceed until the task's result has
43	<	* been computed.  Computations should avoid {@code synchronized}
44	<	* methods or blocks, and should minimize other blocking
45	<	* synchronization apart from joining other tasks or using
46	<	* synchronizers such as Phasers that are advertised to cooperate with
47	<	* fork/join scheduling. Tasks should also not perform blocking IO,
48	<	* and should ideally access variables that are completely independent
49	<	* of those accessed by other running tasks. Minor breaches of these
50	<	* restrictions, for example using shared output streams, may be
51	<	* tolerable in practice, but frequent use may result in poor
52	<	* performance, and the potential to indefinitely stall if the number
53	<	* of threads not waiting for IO or other external synchronization
54	<	* becomes exhausted. This usage restriction is in part enforced by
55	<	* not permitting checked exceptions such as {@code IOExceptions}
56	<	* to be thrown. However, computations may still encounter unchecked
57	<	* exceptions, that are rethrown to callers attempting join
58	<	* them. These exceptions may additionally include
59	<	* RejectedExecutionExceptions stemming from internal resource
60	<	* exhaustion such as failure to allocate internal task queues.
36	>	* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
37	>	* The efficiency of {@code ForkJoinTask}s stems from a set of
38	>	* restrictions (that are only partially statically enforceable)
39	>	* reflecting their intended use as computational tasks calculating
40	>	* pure functions or operating on purely isolated objects.  The
41	>	* primary coordination mechanisms are {@link #fork}, that arranges
42	>	* asynchronous execution, and {@link #join}, that doesn't proceed
43	>	* until the task's result has been computed.  Computations should
44	>	* avoid {@code synchronized} methods or blocks, and should minimize
45	>	* other blocking synchronization apart from joining other tasks or
46	>	* using synchronizers such as Phasers that are advertised to
47	>	* cooperate with fork/join scheduling. Tasks should also not perform
48	>	* blocking IO, and should ideally access variables that are
49	>	* completely independent of those accessed by other running
50	>	* tasks. Minor breaches of these restrictions, for example using
51	>	* shared output streams, may be tolerable in practice, but frequent
52	>	* use may result in poor performance, and the potential to
53	>	* indefinitely stall if the number of threads not waiting for IO or
54	>	* other external synchronization becomes exhausted. This usage
55	>	* restriction is in part enforced by not permitting checked
56	>	* exceptions such as {@code IOExceptions} to be thrown. However,
57	>	* computations may still encounter unchecked exceptions, that are
58	>	* rethrown to callers attempting to join them. These exceptions may
59	>	* additionally include {@link RejectedExecutionException} stemming
60	>	* from internal resource exhaustion, such as failure to allocate
61	>	* internal task queues.
62		*
63		* <p>The primary method for awaiting completion and extracting
64		* results of a task is {@link #join}, but there are several variants:
65		* The {@link Future#get} methods support interruptible and/or timed
66		* waits for completion and report results using {@code Future}
67	<	* conventions. Method {@link #helpJoin} enables callers to actively
68	<	* execute other tasks while awaiting joins, which is sometimes more
69	<	* efficient but only applies when all subtasks are known to be
70	<	* strictly tree-structured. Method {@link #invoke} is semantically
66	<	* equivalent to {@code fork(); join()} but always attempts to
67	<	* begin execution in the current thread. The "<em>quiet</em>" forms
68	<	* of these methods do not extract results or report exceptions. These
67	>	* conventions. Method {@link #invoke} is semantically
68	>	* equivalent to {@code fork(); join()} but always attempts to begin
69	>	* execution in the current thread. The "<em>quiet</em>" forms of
70	>	* these methods do not extract results or report exceptions. These
71		* may be useful when a set of tasks are being executed, and you need
72		* to delay processing of results or exceptions until all complete.
73		* Method {@code invokeAll} (available in multiple versions)
74		* performs the most common form of parallel invocation: forking a set
75		* of tasks and joining them all.
76		*
77	<	* <p> The ForkJoinTask class is not usually directly subclassed.
77	>	* <p>The execution status of tasks may be queried at several levels
78	>	* of detail: {@link #isDone} is true if a task completed in any way
79	>	* (including the case where a task was cancelled without executing);
80	>	* {@link #isCompletedNormally} is true if a task completed without
81	>	* cancellation or encountering an exception; {@link #isCancelled} is
82	>	* true if the task was cancelled (in which case {@link #getException}
83	>	* returns a {@link java.util.concurrent.CancellationException}); and
84	>	* {@link #isCompletedAbnormally} is true if a task was either
85	>	* cancelled or encountered an exception, in which case {@link
86	>	* #getException} will return either the encountered exception or
87	>	* {@link java.util.concurrent.CancellationException}.
88	>	*
89	>	* <p>The ForkJoinTask class is not usually directly subclassed.
90		* Instead, you subclass one of the abstract classes that support a
91	<	* particular style of fork/join processing.  Normally, a concrete
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 others
98	>	* instances of different task subclasses to call each other's
99		* methods), some of them may only be called from within other
100		* ForkJoinTasks (as may be determined using method {@link
101		* #inForkJoinPool}).  Attempts to invoke them in other contexts
102	<	* result in exceptions or errors possibly including
103	<	* ClassCastException.
102	>	* result in exceptions or errors, possibly including
103	>	* {@code ClassCastException}.
104		*
105	<	* <p>Most base support methods are {@code final} because their
106	<	* implementations are intrinsically tied to the underlying
107	<	* lightweight task scheduling framework, and so cannot be overridden.
108	<	* Developers creating new basic styles of fork/join processing should
109	<	* minimally implement {@code protected} methods
110	<	* {@code exec}, {@code setRawResult}, and
111	<	* {@code getRawResult}, while also introducing an abstract
112	<	* computational method that can be implemented in its subclasses,
113	<	* possibly relying on other {@code protected} methods provided
98	<	* by this class.
105	>	* <p>Most base support methods are {@code final}, to prevent
106	>	* overriding of implementations that are intrinsically tied to the
107	>	* underlying lightweight task scheduling framework.  Developers
108	>	* creating new basic styles of fork/join processing should minimally
109	>	* implement {@code protected} methods {@link #exec}, {@link
110	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
111	>	* an abstract computational method that can be implemented in its
112	>	* subclasses, possibly relying on other {@code protected} methods
113	>	* provided by this class.
114		*
115		* <p>ForkJoinTasks should perform relatively small amounts of
116	<	* computations, otherwise splitting into smaller tasks. As a very
117	<	* rough rule of thumb, a task should perform more than 100 and less
118	<	* than 10000 basic computational steps. If tasks are too big, then
119	<	* parallelism cannot improve throughput. If too small, then memory
120	<	* and internal task maintenance overhead may overwhelm processing.
116	>	* computation. Large tasks should be split into smaller subtasks,
117	>	* usually via recursive decomposition. As a very rough rule of thumb,
118	>	* a task should perform more than 100 and less than 10000 basic
119	>	* computational steps. If tasks are too big, then parallelism cannot
120	>	* improve throughput. If too small, then memory and internal task
121	>	* maintenance overhead may overwhelm processing.
122		*
123	<	* <p>ForkJoinTasks are {@code Serializable}, which enables them
124	<	* to be used in extensions such as remote execution frameworks. It is
125	<	* in general sensible to serialize tasks only before or after, but
126	<	* not during execution. Serialization is not relied on during
127	<	* execution itself.
123	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
124	>	* and {@link Callable}, that may be of use when mixing execution of
125	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
126	>	* of this form, consider using a pool constructed in <em>asyncMode</em>.
127	>	*
128	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
129	>	* used in extensions such as remote execution frameworks. It is
130	>	* sensible to serialize tasks only before or after, but not during,
131	>	* execution. Serialization is not relied on during execution itself.
132		*
133		* @since 1.7
134		* @author Doug Lea
135		*/
136		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
137
138	<	/**
139	<	* Run control status bits packed into a single int to minimize
140	<	* footprint and to ensure atomicity (via CAS).  Status is
141	<	* initially zero, and takes on nonnegative values until
142	<	* completed, upon which status holds COMPLETED. CANCELLED, or
143	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
144	<	* blocking waits by other threads have SIGNAL_MASK bits set --
145	<	* bit 15 for external (nonFJ) waits, and the rest a count of
146	<	* waiting FJ threads.  (This representation relies on
147	<	* ForkJoinPool max thread limits). Completion of a stolen task
148	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
149	<	* though suboptimal for some purposes, we use basic builtin
150	<	* wait/notify to take advantage of "monitor inflation" in JVMs
151	<	* that we would otherwise need to emulate to avoid adding further
152	<	* per-task bookkeeping overhead. Note that bits 16-28 are
153	<	* currently unused. Also value 0x80000000 is available as spare
154	<	* completion value.
138	>	/*
139	>	* See the internal documentation of class ForkJoinPool for a
140	>	* general implementation overview.  ForkJoinTasks are mainly
141	>	* responsible for maintaining their "status" field amidst relays
142	>	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
143	>	* methods of this class are more-or-less layered into (1) basic
144	>	* status maintenance (2) execution and awaiting completion (3)
145	>	* user-level methods that additionally report results. This is
146	>	* sometimes hard to see because this file orders exported methods
147	>	* in a way that flows well in javadocs. In particular, most
148	>	* join mechanics are in method quietlyJoin, below.
149	>	*/
150	>
151	>	/*
152	>	* The status field holds run control status bits packed into a
153	>	* single int to minimize footprint and to ensure atomicity (via
154	>	* CAS).  Status is initially zero, and takes on nonnegative
155	>	* values until completed, upon which status holds value
156	>	* NORMAL. CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
157	>	* waits by other threads have the SIGNAL bit set.  Completion of
158	>	* a stolen task with SIGNAL set awakens any waiters via
159	>	* notifyAll. Even though suboptimal for some purposes, we use
160	>	* basic builtin wait/notify to take advantage of "monitor
161	>	* inflation" in JVMs that we would otherwise need to emulate to
162	>	* avoid adding further per-task bookkeeping overhead.  We want
163	>	* these monitors to be "fat", i.e., not use biasing or thin-lock
164	>	* techniques, so use some odd coding idioms that tend to avoid
165	>	* them.
166		*/
167	+
168	+	/** The run status of this task */
169		volatile int status; // accessed directly by pool and workers
170
171	<	static final int COMPLETION_MASK      = 0xe0000000;
172	<	static final int NORMAL               = 0xe0000000; // == mask
173	<	static final int CANCELLED            = 0xc0000000;
174	<	static final int EXCEPTIONAL          = 0xa0000000;
142	<	static final int SIGNAL_MASK          = 0x0000ffff;
143	<	static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
144	<	static final int EXTERNAL_SIGNAL      = 0x00008000; // top bit of low word
171	>	private static final int NORMAL      = -1;
172	>	private static final int CANCELLED   = -2;
173	>	private static final int EXCEPTIONAL = -3;
174	>	private static final int SIGNAL      =  1;
175
176		/**
177		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 155 | Line 185 | public abstract class ForkJoinTask<V> im
185		Collections.synchronizedMap
186		(new WeakHashMap<ForkJoinTask<?>, Throwable>());
187
188	<	// within-package utilities
188	>	// Maintaining completion status
189
190		/**
191	<	* Gets current worker thread, or null if not a worker thread.
192	<	*/
163	<	static ForkJoinWorkerThread getWorker() {
164	<	Thread t = Thread.currentThread();
165	<	return ((t instanceof ForkJoinWorkerThread)?
166	<	(ForkJoinWorkerThread)t : null);
167	<	}
168	<
169	<	final boolean casStatus(int cmp, int val) {
170	<	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
171	<	}
172	<
173	<	/**
174	<	* Workaround for not being able to rethrow unchecked exceptions.
175	<	*/
176	<	static void rethrowException(Throwable ex) {
177	<	if (ex != null)
178	<	UNSAFE.throwException(ex);
179	<	}
180	<
181	<	// Setting completion status
182	<
183	<	/**
184	<	* Marks completion and wakes up threads waiting to join this task.
191	>	* Marks completion and wakes up threads waiting to join this task,
192	>	* also clearing signal request bits.
193		*
194		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
195		*/
196	<	final void setCompletion(int completion) {
197	<	ForkJoinPool pool = getPool();
198	<	if (pool != null) {
199	<	int s; // Clear signal bits while setting completion status
200	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
201	<
202	<	if ((s & SIGNAL_MASK) != 0) {
195	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
196	<	pool.updateRunningCount(s);
197	<	synchronized(this) { notifyAll(); }
196	>	private void setCompletion(int completion) {
197	>	int s;
198	>	while ((s = status) >= 0) {
199	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
200	>	if (s != 0)
201	>	synchronized (this) { notifyAll(); }
202	>	break;
203		}
204		}
200	–	else
201	–	externallySetCompletion(completion);
202	–	}
203	–
204	–	/**
205	–	* Version of setCompletion for non-FJ threads.  Leaves signal
206	–	* bits for unblocked threads to adjust, and always notifies.
207	–	*/
208	–	private void externallySetCompletion(int completion) {
209	–	int s;
210	–	do;while ((s = status) >= 0 &&
211	–	!casStatus(s, (s & SIGNAL_MASK) | completion));
212	–	synchronized(this) { notifyAll(); }
205		}
206
207		/**
208	<	* Sets status to indicate normal completion
208	>	* Records exception and sets exceptional completion.
209	>	*
210	>	* @return status on exit
211		*/
212	<	final void setNormalCompletion() {
213	<	// Try typical fast case -- single CAS, no signal, not already done.
214	<	// Manually expand casStatus to improve chances of inlining it
221	<	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
222	<	setCompletion(NORMAL);
223	<	}
224	<
225	<	// internal waiting and notification
226	<
227	<	/**
228	<	* Performs the actual monitor wait for awaitDone
229	<	*/
230	<	private void doAwaitDone() {
231	<	// Minimize lock bias and in/de-flation effects by maximizing
232	<	// chances of waiting inside sync
233	<	try {
234	<	while (status >= 0)
235	<	synchronized(this) { if (status >= 0) wait(); }
236	<	} catch (InterruptedException ie) {
237	<	onInterruptedWait();
238	<	}
212	>	private void setExceptionalCompletion(Throwable rex) {
213	>	exceptionMap.put(this, rex);
214	>	setCompletion(EXCEPTIONAL);
215		}
216
217		/**
218	<	* Performs the actual monitor wait for awaitDone
218	>	* Blocks a worker thread until completion. Called only by
219	>	* pool. Currently unused -- pool-based waits use timeout
220	>	* version below.
221		*/
222	<	private void doAwaitDone(long startTime, long nanos) {
223	<	synchronized(this) {
222	>	final void internalAwaitDone() {
223	>	int s;         // the odd construction reduces lock bias effects
224	>	while ((s = status) >= 0) {
225		try {
226	<	while (status >= 0) {
227	<	long nt = nanos - System.nanoTime() - startTime;
228	<	if (nt <= 0)
250	<	break;
251	<	wait(nt / 1000000, (int)(nt % 1000000));
226	>	synchronized(this) {
227	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
228	>	wait();
229		}
230		} catch (InterruptedException ie) {
231	<	onInterruptedWait();
231	>	cancelIfTerminating();
232		}
233		}
234		}
235
259	–	// Awaiting completion
260	–
236		/**
237	<	* Sets status to indicate there is joiner, then waits for join,
238	<	* surrounded with pool notifications.
237	>	* Blocks a worker thread until completed or timed out.  Called
238	>	* only by pool.
239		*
240	<	* @return status upon exit
240	>	* @return status on exit
241		*/
242	<	private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
268	<	ForkJoinPool pool = w == null? null : w.pool;
242	>	final int internalAwaitDone(long millis) {
243		int s;
244	<	while ((s = status) >= 0) {
245	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
246	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
247	<	doAwaitDone();
248	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
275	<	adjustPoolCountsOnUnblock(pool);
276	<	break;
277	<	}
278	<	}
279	<	return s;
280	<	}
281	<
282	<	/**
283	<	* Timed version of awaitDone
284	<	* @return status upon exit
285	<	*/
286	<	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;
244	>	if ((s = status) >= 0) {
245	>	try {
246	>	synchronized(this) {
247	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
248	>	wait(millis, 0);
249		}
250	<	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
251	<	adjustPoolCountsOnUnblock(pool);
300	<	break;
250	>	} catch (InterruptedException ie) {
251	>	cancelIfTerminating();
252		}
253	+	s = status;
254		}
255		return s;
256		}
257
258		/**
259	<	* Notifies pool that thread is unblocked. Called by signalled
308	<	* threads when woken by non-FJ threads (which is atypical).
259	>	* Blocks a non-worker-thread until completion.
260		*/
261	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
261	>	private void externalAwaitDone() {
262		int s;
263	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
264	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
265	<	pool.updateRunningCount(s);
266	<	}
267	<
268	<	/**
269	<	* Notifies pool to adjust counts on cancelled or timed out wait.
270	<	*/
271	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
272	<	if (pool != null) {
273	<	int s;
274	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
275	<	if (casStatus(s, s - 1)) {
325	<	pool.updateRunningCount(1);
263	>	while ((s = status) >= 0) {
264	>	synchronized(this) {
265	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
266	>	boolean interrupted = false;
267	>	while (status >= 0) {
268	>	try {
269	>	wait();
270	>	} catch (InterruptedException ie) {
271	>	interrupted = true;
272	>	}
273	>	}
274	>	if (interrupted)
275	>	Thread.currentThread().interrupt();
276		break;
277		}
278		}
#	Line 330 | Line 280 | public abstract class ForkJoinTask<V> im
280		}
281
282		/**
283	<	* Handles interruptions during waits.
284	<	*/
285	<	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) {
347	<	exceptionMap.put(this, rex);
348	<	setCompletion(EXCEPTIONAL);
349	<	}
350	<
351	<	/**
352	<	* Throws the exception associated with status s.
353	<	*
354	<	* @throws the exception
355	<	*/
356	<	private void reportException(int s) {
357	<	if ((s &= COMPLETION_MASK) < NORMAL) {
358	<	if (s == CANCELLED)
359	<	throw new CancellationException();
360	<	else
361	<	rethrowException(exceptionMap.get(this));
362	<	}
363	<	}
364	<
365	<	/**
366	<	* Returns result or throws exception using j.u.c.Future conventions.
367	<	* Only call when isDone known to be true.
368	<	*/
369	<	private V reportFutureResult()
370	<	throws ExecutionException, InterruptedException {
371	<	int s = status & COMPLETION_MASK;
372	<	if (s < NORMAL) {
373	<	Throwable ex;
374	<	if (s == CANCELLED)
375	<	throw new CancellationException();
376	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
377	<	throw new ExecutionException(ex);
378	<	if (Thread.interrupted())
379	<	throw new InterruptedException();
380	<	}
381	<	return getRawResult();
382	<	}
383	<
384	<	/**
385	<	* Returns result or throws exception using j.u.c.Future conventions
386	<	* with timeouts.
387	<	*/
388	<	private V reportTimedFutureResult()
389	<	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);
398	<	if (Thread.interrupted())
399	<	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.
283	>	* Unless done, calls exec and records status if completed, but
284	>	* doesn't wait for completion otherwise. Primary execution method
285	>	* for ForkJoinWorkerThread.
286		*/
287		final void quietlyExec() {
429	–	if (status >= 0) {
430	–	try {
431	–	if (!exec())
432	–	return;
433	–	} catch(Throwable rex) {
434	–	setDoneExceptionally(rex);
435	–	return;
436	–	}
437	–	setNormalCompletion();
438	–	}
439	–	}
440	–
441	–	/**
442	–	* Calls exec(), recording but not rethrowing exception.
443	–	* Caller should normally check status before calling.
444	–	*
445	–	* @return true if completed normally
446	–	*/
447	–	private boolean tryQuietlyInvoke() {
288		try {
289	<	if (!exec())
290	<	return false;
289	>	if (status < 0 || !exec())
290	>	return;
291		} catch (Throwable rex) {
292	<	setDoneExceptionally(rex);
293	<	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) {
292	>	setExceptionalCompletion(rex);
293	>	return;
294		}
295	<	}
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
295	>	setCompletion(NORMAL); // must be outside try block
296		}
297
298		// public methods
#	Line 482 | Line 300 | public abstract class ForkJoinTask<V> im
300		/**
301		* Arranges to asynchronously execute this task.  While it is not
302		* necessarily enforced, it is a usage error to fork a task more
303	<	* than once unless it has completed and been reinitialized.  This
304	<	* method may be invoked only from within ForkJoinTask
305	<	* computations (as may be determined using method {@link
306	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
307	<	* in exceptions or errors possibly including ClassCastException.
308	<	*/
309	<	public final void fork() {
310	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
303	>	* than once unless it has completed and been reinitialized.
304	>	* Subsequent modifications to the state of this task or any data
305	>	* it operates on are not necessarily consistently observable by
306	>	* any thread other than the one executing it unless preceded by a
307	>	* call to {@link #join} or related methods, or a call to {@link
308	>	* #isDone} returning {@code true}.
309	>	*
310	>	* <p>This method may be invoked only from within {@code
311	>	* ForkJoinTask} computations (as may be determined using method
312	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
313	>	* result in exceptions or errors, possibly including {@code
314	>	* ClassCastException}.
315	>	*
316	>	* @return {@code this}, to simplify usage
317	>	*/
318	>	public final ForkJoinTask<V> fork() {
319	>	((ForkJoinWorkerThread) Thread.currentThread())
320	>	.pushTask(this);
321	>	return this;
322		}
323
324		/**
325	<	* Returns the result of the computation when it is ready.
326	<	* This method differs from {@code get} in that abnormal
327	<	* completion results in RuntimeExceptions or Errors, not
328	<	* ExecutionExceptions.
325	>	* Returns the result of the computation when it {@link #isDone is done}.
326	>	* This method differs from {@link #get()} in that
327	>	* abnormal completion results in {@code RuntimeException} or
328	>	* {@code Error}, not {@code ExecutionException}.
329		*
330		* @return the computed result
331		*/
332		public final V join() {
333	<	ForkJoinWorkerThread w = getWorker();
334	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
335	<	reportException(awaitDone(w, true));
333	>	quietlyJoin();
334	>	Throwable ex;
335	>	if (status < NORMAL && (ex = getException()) != null)
336	>	UNSAFE.throwException(ex);
337		return getRawResult();
338		}
339
340		/**
341		* Commences performing this task, awaits its completion if
342	<	* necessary, and return its result.
342	>	* necessary, and returns its result, or throws an (unchecked)
343	>	* {@code RuntimeException} or {@code Error} if the underlying
344	>	* computation did so.
345		*
514	–	* @throws Throwable (a RuntimeException, Error, or unchecked
515	–	* exception) if the underlying computation did so
346		* @return the computed result
347		*/
348		public final V invoke() {
349	<	if (status >= 0 && tryExec())
350	<	return getRawResult();
351	<	else
352	<	return join();
349	>	quietlyInvoke();
350	>	Throwable ex;
351	>	if (status < NORMAL && (ex = getException()) != null)
352	>	UNSAFE.throwException(ex);
353	>	return getRawResult();
354		}
355
356		/**
357	<	* Forks both tasks, returning when {@code isDone} holds for
358	<	* both of them or an exception is encountered. This method may be
359	<	* invoked only from within ForkJoinTask computations (as may be
360	<	* determined using method {@link #inForkJoinPool}). Attempts to
361	<	* invoke in other contexts result in exceptions or errors
362	<	* possibly including ClassCastException.
363	<	*
364	<	* @param t1 one task
365	<	* @param t2 the other task
366	<	* @throws NullPointerException if t1 or t2 are null
367	<	* @throws RuntimeException or Error if either task did so
357	>	* Forks the given tasks, returning when {@code isDone} holds for
358	>	* each task or an (unchecked) exception is encountered, in which
359	>	* case the exception is rethrown. If more than one task
360	>	* encounters an exception, then this method throws any one of
361	>	* these exceptions. If any task encounters an exception, the
362	>	* other may be cancelled. However, the execution status of
363	>	* individual tasks is not guaranteed upon exceptional return. The
364	>	* status of each task may be obtained using {@link
365	>	* #getException()} and related methods to check if they have been
366	>	* cancelled, completed normally or exceptionally, or left
367	>	* unprocessed.
368	>	*
369	>	* <p>This method may be invoked only from within {@code
370	>	* ForkJoinTask} computations (as may be determined using method
371	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
372	>	* result in exceptions or errors, possibly including {@code
373	>	* ClassCastException}.
374	>	*
375	>	* @param t1 the first task
376	>	* @param t2 the second task
377	>	* @throws NullPointerException if any task is null
378		*/
379	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
379	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
380		t2.fork();
381		t1.invoke();
382		t2.join();
383		}
384
385		/**
386	<	* Forks the given tasks, returning when {@code isDone} holds
387	<	* for all of them. If any task encounters an exception, others
388	<	* may be cancelled.  This method may be invoked only from within
389	<	* ForkJoinTask computations (as may be determined using method
390	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
391	<	* result in exceptions or errors possibly including
392	<	* ClassCastException.
393	<	* @param tasks the array of tasks
394	<	* @throws NullPointerException if tasks or any element are null
395	<	* @throws RuntimeException or Error if any 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, others
391	>	* may be cancelled. However, the execution status of individual
392	>	* tasks is not guaranteed upon exceptional return. The status of
393	>	* each task may be obtained using {@link #getException()} and
394	>	* related methods to check if they have been cancelled, completed
395	>	* normally or exceptionally, or left unprocessed.
396	>	*
397	>	* <p>This method may be invoked only from within {@code
398	>	* ForkJoinTask} computations (as may be determined using method
399	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
400	>	* result in exceptions or errors, possibly including {@code
401	>	* ClassCastException}.
402	>	*
403	>	* @param tasks the tasks
404	>	* @throws NullPointerException if any task is null
405		*/
406		public static void invokeAll(ForkJoinTask<?>... tasks) {
407		Throwable ex = null;
#	Line 566 | Line 416 | public abstract class ForkJoinTask<V> im
416		t.fork();
417		else {
418		t.quietlyInvoke();
419	<	if (ex == null)
419	>	if (ex == null && t.status < NORMAL)
420		ex = t.getException();
421		}
422		}
#	Line 577 | Line 427 | public abstract class ForkJoinTask<V> im
427		t.cancel(false);
428		else {
429		t.quietlyJoin();
430	<	if (ex == null)
430	>	if (ex == null && t.status < NORMAL)
431		ex = t.getException();
432		}
433		}
434		}
435		if (ex != null)
436	<	rethrowException(ex);
436	>	UNSAFE.throwException(ex);
437		}
438
439		/**
440	<	* Forks all tasks in the collection, returning when
441	<	* {@code isDone} holds for all of them. If any task
442	<	* encounters an exception, others may be cancelled.  This method
443	<	* may be invoked only from within ForkJoinTask computations (as
444	<	* may be determined using method {@link
445	<	* #inForkJoinPool}). Attempts to invoke in other contexts resul!t
446	<	* in exceptions or errors possibly including ClassCastException.
440	>	* Forks all tasks in the specified collection, returning when
441	>	* {@code isDone} holds for each task or an (unchecked) exception
442	>	* is encountered, in which case the exception is rethrown. If
443	>	* more than one task encounters an exception, then this method
444	>	* throws any one of these exceptions. If any task encounters an
445	>	* exception, others may be cancelled. However, the execution
446	>	* status of individual tasks is not guaranteed upon exceptional
447	>	* return. The status of each task may be obtained using {@link
448	>	* #getException()} and related methods to check if they have been
449	>	* cancelled, completed normally or exceptionally, or left
450	>	* unprocessed.
451	>	*
452	>	* <p>This method may be invoked only from within {@code
453	>	* ForkJoinTask} computations (as may be determined using method
454	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
455	>	* result in exceptions or errors, possibly including {@code
456	>	* ClassCastException}.
457		*
458		* @param tasks the collection of tasks
459	+	* @return the tasks argument, to simplify usage
460		* @throws NullPointerException if tasks or any element are null
600	–	* @throws RuntimeException or Error if any task did so
461		*/
462	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
463	<	if (!(tasks instanceof List)) {
464	<	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
465	<	return;
462	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
463	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
464	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
465	>	return tasks;
466		}
467	+	@SuppressWarnings("unchecked")
468		List<? extends ForkJoinTask<?>> ts =
469	<	(List<? extends ForkJoinTask<?>>)tasks;
469	>	(List<? extends ForkJoinTask<?>>) tasks;
470		Throwable ex = null;
471		int last = ts.size() - 1;
472		for (int i = last; i >= 0; --i) {
#	Line 618 | Line 479 | public abstract class ForkJoinTask<V> im
479		t.fork();
480		else {
481		t.quietlyInvoke();
482	<	if (ex == null)
482	>	if (ex == null && t.status < NORMAL)
483		ex = t.getException();
484		}
485		}
#	Line 629 | Line 490 | public abstract class ForkJoinTask<V> im
490		t.cancel(false);
491		else {
492		t.quietlyJoin();
493	<	if (ex == null)
493	>	if (ex == null && t.status < NORMAL)
494		ex = t.getException();
495		}
496		}
497		}
498		if (ex != null)
499	<	rethrowException(ex);
500	<	}
640	<
641	<	/**
642	<	* Returns true if the computation performed by this task has
643	<	* completed (or has been cancelled).
644	<	*
645	<	* @return true if this computation has completed
646	<	*/
647	<	public final boolean isDone() {
648	<	return status < 0;
649	<	}
650	<
651	<	/**
652	<	* Returns true if this task was cancelled.
653	<	*
654	<	* @return true if this task was cancelled
655	<	*/
656	<	public final boolean isCancelled() {
657	<	return (status & COMPLETION_MASK) == CANCELLED;
499	>	UNSAFE.throwException(ex);
500	>	return tasks;
501		}
502
503		/**
504	<	* Asserts that the results of this task's computation will not be
505	<	* used. If a cancellation occurs before attempting to execute this
506	<	* task, then execution will be suppressed, {@code isCancelled}
507	<	* will report true, and {@code join} will result in a
508	<	* {@code CancellationException} being thrown. Otherwise, when
509	<	* cancellation races with completion, there are no guarantees
510	<	* about whether {@code isCancelled} will report true, whether
668	<	* {@code join} will return normally or via an exception, or
669	<	* whether these behaviors will remain consistent upon repeated
670	<	* invocation.
504	>	* Attempts to cancel execution of this task. This attempt will
505	>	* fail if the task has already completed, has already been
506	>	* cancelled, or could not be cancelled for some other reason. If
507	>	* successful, and this task has not started when cancel is
508	>	* called, execution of this task is suppressed, {@link
509	>	* #isCancelled} will report true, and {@link #join} will result
510	>	* in a {@code CancellationException} being thrown.
511		*
512		* <p>This method may be overridden in subclasses, but if so, must
513		* still ensure that these minimal properties hold. In particular,
514	<	* the cancel method itself must not throw exceptions.
514	>	* the {@code cancel} method itself must not throw exceptions.
515		*
516	<	* <p> This method is designed to be invoked by <em>other</em>
516	>	* <p>This method is designed to be invoked by <em>other</em>
517		* tasks. To terminate the current task, you can just return or
518		* throw an unchecked exception from its computation method, or
519	<	* invoke {@code completeExceptionally}.
519	>	* invoke {@link #completeExceptionally}.
520		*
521		* @param mayInterruptIfRunning this value is ignored in the
522	<	* default implementation because tasks are not in general
523	<	* cancelled via interruption.
522	>	* default implementation because tasks are not
523	>	* cancelled via interruption
524		*
525	<	* @return true if this task is now cancelled
525	>	* @return {@code true} if this task is now cancelled
526		*/
527		public boolean cancel(boolean mayInterruptIfRunning) {
528		setCompletion(CANCELLED);
529	<	return (status & COMPLETION_MASK) == CANCELLED;
529	>	return status == CANCELLED;
530	>	}
531	>
532	>	/**
533	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
534	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
535	>	* exceptions, but if it does anyway, we have no recourse during
536	>	* shutdown, so guard against this case.
537	>	*/
538	>	final void cancelIgnoringExceptions() {
539	>	try {
540	>	cancel(false);
541	>	} catch (Throwable ignore) {
542	>	}
543	>	}
544	>
545	>	/**
546	>	* Cancels if current thread is a terminating worker thread,
547	>	* ignoring any exceptions thrown by cancel.
548	>	*/
549	>	final void cancelIfTerminating() {
550	>	Thread t = Thread.currentThread();
551	>	if ((t instanceof ForkJoinWorkerThread) &&
552	>	((ForkJoinWorkerThread) t).isTerminating()) {
553	>	try {
554	>	cancel(false);
555	>	} catch (Throwable ignore) {
556	>	}
557	>	}
558	>	}
559	>
560	>	public final boolean isDone() {
561	>	return status < 0;
562	>	}
563	>
564	>	public final boolean isCancelled() {
565	>	return status == CANCELLED;
566		}
567
568		/**
569	<	* Returns true if this task threw an exception or was cancelled.
569	>	* Returns {@code true} if this task threw an exception or was cancelled.
570		*
571	<	* @return true if this task threw an exception or was cancelled
571	>	* @return {@code true} if this task threw an exception or was cancelled
572		*/
573		public final boolean isCompletedAbnormally() {
574	<	return (status & COMPLETION_MASK) < NORMAL;
574	>	return status < NORMAL;
575	>	}
576	>
577	>	/**
578	>	* Returns {@code true} if this task completed without throwing an
579	>	* exception and was not cancelled.
580	>	*
581	>	* @return {@code true} if this task completed without throwing an
582	>	* exception and was not cancelled
583	>	*/
584	>	public final boolean isCompletedNormally() {
585	>	return status == NORMAL;
586		}
587
588		/**
589		* Returns the exception thrown by the base computation, or a
590	<	* CancellationException if cancelled, or null if none or if the
591	<	* method has not yet completed.
590	>	* {@code CancellationException} if cancelled, or {@code null} if
591	>	* none or if the method has not yet completed.
592		*
593	<	* @return the exception, or null if none
593	>	* @return the exception, or {@code null} if none
594		*/
595		public final Throwable getException() {
596	<	int s = status & COMPLETION_MASK;
597	<	if (s >= NORMAL)
598	<	return null;
599	<	if (s == CANCELLED)
713	<	return new CancellationException();
714	<	return exceptionMap.get(this);
596	>	int s = status;
597	>	return ((s >= NORMAL)    ? null :
598	>	(s == CANCELLED) ? new CancellationException() :
599	>	exceptionMap.get(this));
600		}
601
602		/**
#	Line 720 | Line 605 | public abstract class ForkJoinTask<V> im
605		* {@code join} and related operations. This method may be used
606		* to induce exceptions in asynchronous tasks, or to force
607		* completion of tasks that would not otherwise complete.  Its use
608	<	* in other situations is likely to be wrong.  This method is
608	>	* in other situations is discouraged.  This method is
609		* overridable, but overridden versions must invoke {@code super}
610		* implementation to maintain guarantees.
611		*
612	<	* @param ex the exception to throw. If this exception is
613	<	* not a RuntimeException or Error, the actual exception thrown
614	<	* will be a RuntimeException with cause ex.
612	>	* @param ex the exception to throw. If this exception is not a
613	>	* {@code RuntimeException} or {@code Error}, the actual exception
614	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
615		*/
616		public void completeExceptionally(Throwable ex) {
617	<	setDoneExceptionally((ex instanceof RuntimeException) ||
618	<	(ex instanceof Error)? ex :
619	<	new RuntimeException(ex));
617	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
618	>	(ex instanceof Error) ? ex :
619	>	new RuntimeException(ex));
620		}
621
622		/**
623		* Completes this task, and if not already aborted or cancelled,
624	<	* returning a {@code null} result upon {@code join} and related
625	<	* operations. This method may be used to provide results for
626	<	* asynchronous tasks, or to provide alternative handling for
627	<	* tasks that would not otherwise complete normally. Its use in
628	<	* other situations is likely to be wrong. This method is
629	<	* overridable, but overridden versions must invoke {@code super}
630	<	* implementation to maintain guarantees.
624	>	* returning the given value as the result of subsequent
625	>	* invocations of {@code join} and related operations. This method
626	>	* may be used to provide results for asynchronous tasks, or to
627	>	* provide alternative handling for tasks that would not otherwise
628	>	* complete normally. Its use in other situations is
629	>	* discouraged. This method is overridable, but overridden
630	>	* versions must invoke {@code super} implementation to maintain
631	>	* guarantees.
632		*
633		* @param value the result value for this task
634		*/
635		public void complete(V value) {
636		try {
637		setRawResult(value);
638	<	} catch(Throwable rex) {
639	<	setDoneExceptionally(rex);
638	>	} catch (Throwable rex) {
639	>	setExceptionalCompletion(rex);
640		return;
641		}
642	<	setNormalCompletion();
642	>	setCompletion(NORMAL);
643		}
644
645		public final V get() throws InterruptedException, ExecutionException {
646	<	ForkJoinWorkerThread w = getWorker();
647	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
648	<	awaitDone(w, true);
649	<	return reportFutureResult();
646	>	quietlyJoin();
647	>	if (Thread.interrupted())
648	>	throw new InterruptedException();
649	>	int s = status;
650	>	if (s < NORMAL) {
651	>	Throwable ex;
652	>	if (s == CANCELLED)
653	>	throw new CancellationException();
654	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
655	>	throw new ExecutionException(ex);
656	>	}
657	>	return getRawResult();
658		}
659
660		public final V get(long timeout, TimeUnit unit)
661		throws InterruptedException, ExecutionException, TimeoutException {
662	<	ForkJoinWorkerThread w = getWorker();
663	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
664	<	awaitDone(w, unit.toNanos(timeout));
665	<	return reportTimedFutureResult();
666	<	}
667	<
668	<	/**
775	<	* Possibly executes other tasks until this task is ready, then
776	<	* returns the result of the computation.  This method may be more
777	<	* efficient than {@code join}, but is only applicable when
778	<	* there are no potential dependencies between continuation of the
779	<	* current task and that of any other task that might be executed
780	<	* while helping. (This usually holds for pure divide-and-conquer
781	<	* tasks). This method may be invoked only from within
782	<	* ForkJoinTask computations (as may be determined using method
783	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
784	<	* resul!t in exceptions or errors possibly including
785	<	* ClassCastException.
786	<	*
787	<	* @return the computed result
788	<	*/
789	<	public final V helpJoin() {
790	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
791	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
792	<	reportException(busyJoin(w));
793	<	return getRawResult();
794	<	}
795	<
796	<	/**
797	<	* Possibly executes other tasks until this task is ready.  This
798	<	* method may be invoked only from within ForkJoinTask
799	<	* computations (as may be determined using method {@link
800	<	* #inForkJoinPool}). Attempts to invoke in other contexts resul!t
801	<	* in exceptions or errors possibly including ClassCastException.
802	<	*/
803	<	public final void quietlyHelpJoin() {
804	<	if (status >= 0) {
805	<	ForkJoinWorkerThread w =
806	<	(ForkJoinWorkerThread)(Thread.currentThread());
807	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
808	<	busyJoin(w);
662	>	Thread t = Thread.currentThread();
663	>	ForkJoinPool pool;
664	>	if (t instanceof ForkJoinWorkerThread) {
665	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
666	>	if (status >= 0 && w.unpushTask(this))
667	>	quietlyExec();
668	>	pool = w.pool;
669		}
670	+	else
671	+	pool = null;
672	+	/*
673	+	* Timed wait loop intermixes cases for FJ (pool != null) and
674	+	* non FJ threads. For FJ, decrement pool count but don't try
675	+	* for replacement; increment count on completion. For non-FJ,
676	+	* deal with interrupts. This is messy, but a little less so
677	+	* than is splitting the FJ and nonFJ cases.
678	+	*/
679	+	boolean interrupted = false;
680	+	boolean dec = false; // true if pool count decremented
681	+	long nanos = unit.toNanos(timeout);
682	+	for (;;) {
683	+	if (pool == null && Thread.interrupted()) {
684	+	interrupted = true;
685	+	break;
686	+	}
687	+	int s = status;
688	+	if (s < 0)
689	+	break;
690	+	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
691	+	long startTime = System.nanoTime();
692	+	long nt; // wait time
693	+	while (status >= 0 &&
694	+	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
695	+	if (pool != null && !dec)
696	+	dec = pool.tryDecrementRunningCount();
697	+	else {
698	+	long ms = nt / 1000000;
699	+	int ns = (int) (nt % 1000000);
700	+	try {
701	+	synchronized(this) {
702	+	if (status >= 0)
703	+	wait(ms, ns);
704	+	}
705	+	} catch (InterruptedException ie) {
706	+	if (pool != null)
707	+	cancelIfTerminating();
708	+	else {
709	+	interrupted = true;
710	+	break;
711	+	}
712	+	}
713	+	}
714	+	}
715	+	break;
716	+	}
717	+	}
718	+	if (pool != null && dec)
719	+	pool.incrementRunningCount();
720	+	if (interrupted)
721	+	throw new InterruptedException();
722	+	int es = status;
723	+	if (es != NORMAL) {
724	+	Throwable ex;
725	+	if (es == CANCELLED)
726	+	throw new CancellationException();
727	+	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
728	+	throw new ExecutionException(ex);
729	+	throw new TimeoutException();
730	+	}
731	+	return getRawResult();
732		}
733
734		/**
735	<	* Joins this task, without returning its result or throwing an
735	>	* Joins this task, without returning its result or throwing its
736		* exception. This method may be useful when processing
737		* collections of tasks when some have been cancelled or otherwise
738		* known to have aborted.
739		*/
740		public final void quietlyJoin() {
741	<	if (status >= 0) {
742	<	ForkJoinWorkerThread w = getWorker();
743	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
744	<	awaitDone(w, true);
741	>	Thread t;
742	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
743	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
744	>	if (status >= 0) {
745	>	if (w.unpushTask(this)) {
746	>	boolean completed;
747	>	try {
748	>	completed = exec();
749	>	} catch (Throwable rex) {
750	>	setExceptionalCompletion(rex);
751	>	return;
752	>	}
753	>	if (completed) {
754	>	setCompletion(NORMAL);
755	>	return;
756	>	}
757	>	}
758	>	w.joinTask(this);
759	>	}
760		}
761	+	else
762	+	externalAwaitDone();
763		}
764
765		/**
766		* Commences performing this task and awaits its completion if
767	<	* necessary, without returning its result or throwing an
768	<	* exception. This method may be useful when processing
830	<	* collections of tasks when some have been cancelled or otherwise
831	<	* known to have aborted.
767	>	* necessary, without returning its result or throwing its
768	>	* exception.
769		*/
770		public final void quietlyInvoke() {
771	<	if (status >= 0 && !tryQuietlyInvoke())
772	<	quietlyJoin();
771	>	if (status >= 0) {
772	>	boolean completed;
773	>	try {
774	>	completed = exec();
775	>	} catch (Throwable rex) {
776	>	setExceptionalCompletion(rex);
777	>	return;
778	>	}
779	>	if (completed)
780	>	setCompletion(NORMAL);
781	>	else
782	>	quietlyJoin();
783	>	}
784		}
785
786		/**
787		* Possibly executes tasks until the pool hosting the current task
788	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
789	<	* designs in which many tasks are forked, but none are explicitly
790	<	* joined, instead executing them until all are processed.
788	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
789	>	* be of use in designs in which many tasks are forked, but none
790	>	* are explicitly joined, instead executing them until all are
791	>	* processed.
792	>	*
793	>	* <p>This method may be invoked only from within {@code
794	>	* ForkJoinTask} computations (as may be determined using method
795	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
796	>	* result in exceptions or errors, possibly including {@code
797	>	* ClassCastException}.
798		*/
799		public static void helpQuiesce() {
800	<	((ForkJoinWorkerThread)(Thread.currentThread())).
801	<	helpQuiescePool();
800	>	((ForkJoinWorkerThread) Thread.currentThread())
801	>	.helpQuiescePool();
802		}
803
804		/**
#	Line 852 | Line 807 | public abstract class ForkJoinTask<V> im
807		* this task, but only if reuse occurs when this task has either
808		* never been forked, or has been forked, then completed and all
809		* outstanding joins of this task have also completed. Effects
810	<	* under any other usage conditions are not guaranteed, and are
811	<	* almost surely wrong. This method may be useful when executing
810	>	* under any other usage conditions are not guaranteed.
811	>	* This method may be useful when executing
812		* pre-constructed trees of subtasks in loops.
813		*/
814		public void reinitialize() {
815	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
815	>	if (status == EXCEPTIONAL)
816		exceptionMap.remove(this);
817		status = 0;
818		}
#	Line 866 | Line 821 | public abstract class ForkJoinTask<V> im
821		* Returns the pool hosting the current task execution, or null
822		* if this task is executing outside of any ForkJoinPool.
823		*
824	<	* @return the pool, or null if none.
824	>	* @see #inForkJoinPool
825	>	* @return the pool, or {@code null} if none
826		*/
827		public static ForkJoinPool getPool() {
828		Thread t = Thread.currentThread();
829	<	return ((t instanceof ForkJoinWorkerThread)?
830	<	((ForkJoinWorkerThread)t).pool : null);
829	>	return (t instanceof ForkJoinWorkerThread) ?
830	>	((ForkJoinWorkerThread) t).pool : null;
831		}
832
833		/**
834	<	* Returns true if the current thread is executing as a
834	>	* Returns {@code true} if the current thread is executing as a
835		* ForkJoinPool computation.
836	<	* @return <code>true</code> if the current thread is executing as a
836	>	*
837	>	* @return {@code true} if the current thread is executing as a
838		* ForkJoinPool computation, or false otherwise
839		*/
840		public static boolean inForkJoinPool() {
#	Line 890 | Line 847 | public abstract class ForkJoinTask<V> im
847		* by the current thread, and has not commenced executing in
848		* another thread.  This method may be useful when arranging
849		* alternative local processing of tasks that could have been, but
850	<	* were not, stolen. This method may be invoked only from within
851	<	* ForkJoinTask computations (as may be determined using method
852	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
853	<	* result in exceptions or errors possibly including
854	<	* ClassCastException.
850	>	* were not, stolen.
851	>	*
852	>	* <p>This method may be invoked only from within {@code
853	>	* ForkJoinTask} computations (as may be determined using method
854	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
855	>	* result in exceptions or errors, possibly including {@code
856	>	* ClassCastException}.
857		*
858	<	* @return true if unforked
858	>	* @return {@code true} if unforked
859		*/
860		public boolean tryUnfork() {
861	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
861	>	return ((ForkJoinWorkerThread) Thread.currentThread())
862	>	.unpushTask(this);
863		}
864
865		/**
#	Line 908 | Line 868 | public abstract class ForkJoinTask<V> im
868		* value may be useful for heuristic decisions about whether to
869		* fork other tasks.
870		*
871	+	* <p>This method may be invoked only from within {@code
872	+	* ForkJoinTask} computations (as may be determined using method
873	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
874	+	* result in exceptions or errors, possibly including {@code
875	+	* ClassCastException}.
876	+	*
877		* @return the number of tasks
878		*/
879		public static int getQueuedTaskCount() {
880	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
881	<	getQueueSize();
880	>	return ((ForkJoinWorkerThread) Thread.currentThread())
881	>	.getQueueSize();
882		}
883
884		/**
#	Line 925 | Line 891 | public abstract class ForkJoinTask<V> im
891		* tasks, and to process computations locally if this threshold is
892		* exceeded.
893		*
894	+	* <p>This method may be invoked only from within {@code
895	+	* ForkJoinTask} computations (as may be determined using method
896	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
897	+	* result in exceptions or errors, possibly including {@code
898	+	* ClassCastException}.
899	+	*
900		* @return the surplus number of tasks, which may be negative
901		*/
902		public static int getSurplusQueuedTaskCount() {
903	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
903	>	return ((ForkJoinWorkerThread) Thread.currentThread())
904		.getEstimatedSurplusTaskCount();
905		}
906
907		// Extension methods
908
909		/**
910	<	* Returns the result that would be returned by {@code join},
911	<	* even if this task completed abnormally, or null if this task is
912	<	* not known to have been completed.  This method is designed to
913	<	* aid debugging, as well as to support extensions. Its use in any
914	<	* other context is discouraged.
910	>	* Returns the result that would be returned by {@link #join}, even
911	>	* if this task completed abnormally, or {@code null} if this task
912	>	* is not known to have been completed.  This method is designed
913	>	* to aid debugging, as well as to support extensions. Its use in
914	>	* any other context is discouraged.
915		*
916	<	* @return the result, or null if not completed
916	>	* @return the result, or {@code null} if not completed
917		*/
918		public abstract V getRawResult();
919
#	Line 960 | Line 932 | public abstract class ForkJoinTask<V> im
932		* called otherwise. The return value controls whether this task
933		* is considered to be done normally. It may return false in
934		* asynchronous actions that require explicit invocations of
935	<	* {@code complete} to become joinable. It may throw exceptions
936	<	* to indicate abnormal exit.
935	>	* {@link #complete} to become joinable. It may also throw an
936	>	* (unchecked) exception to indicate abnormal exit.
937		*
938	<	* @return true if completed normally
967	<	* @throws Error or RuntimeException if encountered during computation
938	>	* @return {@code true} if completed normally
939		*/
940		protected abstract boolean exec();
941
942		/**
943	<	* Returns, but does not unschedule or execute, the task queued by
944	<	* the current thread but not yet executed, if one is
943	>	* Returns, but does not unschedule or execute, a task queued by
944	>	* the current thread but not yet executed, if one is immediately
945		* available. There is no guarantee that this task will actually
946	<	* be polled or executed next.  This method is designed primarily
947	<	* to support extensions, and is unlikely to be useful otherwise.
948	<	* This method may be invoked only from within ForkJoinTask
949	<	* computations (as may be determined using method {@link
950	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
951	<	* in exceptions or errors possibly including ClassCastException.
946	>	* be polled or executed next. Conversely, this method may return
947	>	* null even if a task exists but cannot be accessed without
948	>	* contention with other threads.  This method is designed
949	>	* primarily to support extensions, and is unlikely to be useful
950	>	* otherwise.
951	>	*
952	>	* <p>This method may be invoked only from within {@code
953	>	* ForkJoinTask} computations (as may be determined using method
954	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
955	>	* result in exceptions or errors, possibly including {@code
956	>	* ClassCastException}.
957		*
958	<	* @return the next task, or null if none are available
958	>	* @return the next task, or {@code null} if none are available
959		*/
960		protected static ForkJoinTask<?> peekNextLocalTask() {
961	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask();
961	>	return ((ForkJoinWorkerThread) Thread.currentThread())
962	>	.peekTask();
963		}
964
965		/**
966		* Unschedules and returns, without executing, the next task
967		* queued by the current thread but not yet executed.  This method
968		* is designed primarily to support extensions, and is unlikely to
969	<	* be useful otherwise.  This method may be invoked only from
993	<	* within ForkJoinTask computations (as may be determined using
994	<	* method {@link #inForkJoinPool}). Attempts to invoke in other
995	<	* contexts result in exceptions or errors possibly including
996	<	* ClassCastException.
969	>	* be useful otherwise.
970		*
971	<	* @return the next task, or null if none are available
971	>	* <p>This method may be invoked only from within {@code
972	>	* ForkJoinTask} computations (as may be determined using method
973	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
974	>	* result in exceptions or errors, possibly including {@code
975	>	* ClassCastException}.
976	>	*
977	>	* @return the next task, or {@code null} if none are available
978		*/
979		protected static ForkJoinTask<?> pollNextLocalTask() {
980	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).pollLocalTask();
980	>	return ((ForkJoinWorkerThread) Thread.currentThread())
981	>	.pollLocalTask();
982		}
983
984		/**
#	Line 1009 | Line 989 | public abstract class ForkJoinTask<V> im
989		* {@code null} result does not necessarily imply quiescence
990		* of the pool this task is operating in.  This method is designed
991		* primarily to support extensions, and is unlikely to be useful
992	<	* otherwise.  This method may be invoked only from within
993	<	* ForkJoinTask computations (as may be determined using method
994	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
995	<	* result in exceptions or errors possibly including
996	<	* ClassCastException.
992	>	* otherwise.
993	>	*
994	>	* <p>This method may be invoked only from within {@code
995	>	* ForkJoinTask} computations (as may be determined using method
996	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
997	>	* result in exceptions or errors, possibly including {@code
998	>	* ClassCastException}.
999		*
1000	<	* @return a task, or null if none are available
1000	>	* @return a task, or {@code null} if none are available
1001		*/
1002		protected static ForkJoinTask<?> pollTask() {
1003	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
1004	<	pollTask();
1003	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1004	>	.pollTask();
1005	>	}
1006	>
1007	>	/**
1008	>	* Adaptor for Runnables. This implements RunnableFuture
1009	>	* to be compliant with AbstractExecutorService constraints
1010	>	* when used in ForkJoinPool.
1011	>	*/
1012	>	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1013	>	implements RunnableFuture<T> {
1014	>	final Runnable runnable;
1015	>	final T resultOnCompletion;
1016	>	T result;
1017	>	AdaptedRunnable(Runnable runnable, T result) {
1018	>	if (runnable == null) throw new NullPointerException();
1019	>	this.runnable = runnable;
1020	>	this.resultOnCompletion = result;
1021	>	}
1022	>	public T getRawResult() { return result; }
1023	>	public void setRawResult(T v) { result = v; }
1024	>	public boolean exec() {
1025	>	runnable.run();
1026	>	result = resultOnCompletion;
1027	>	return true;
1028	>	}
1029	>	public void run() { invoke(); }
1030	>	private static final long serialVersionUID = 5232453952276885070L;
1031	>	}
1032	>
1033	>	/**
1034	>	* Adaptor for Callables
1035	>	*/
1036	>	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1037	>	implements RunnableFuture<T> {
1038	>	final Callable<? extends T> callable;
1039	>	T result;
1040	>	AdaptedCallable(Callable<? extends T> callable) {
1041	>	if (callable == null) throw new NullPointerException();
1042	>	this.callable = callable;
1043	>	}
1044	>	public T getRawResult() { return result; }
1045	>	public void setRawResult(T v) { result = v; }
1046	>	public boolean exec() {
1047	>	try {
1048	>	result = callable.call();
1049	>	return true;
1050	>	} catch (Error err) {
1051	>	throw err;
1052	>	} catch (RuntimeException rex) {
1053	>	throw rex;
1054	>	} catch (Exception ex) {
1055	>	throw new RuntimeException(ex);
1056	>	}
1057	>	}
1058	>	public void run() { invoke(); }
1059	>	private static final long serialVersionUID = 2838392045355241008L;
1060	>	}
1061	>
1062	>	/**
1063	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1064	>	* method of the given {@code Runnable} as its action, and returns
1065	>	* a null result upon {@link #join}.
1066	>	*
1067	>	* @param runnable the runnable action
1068	>	* @return the task
1069	>	*/
1070	>	public static ForkJoinTask<?> adapt(Runnable runnable) {
1071	>	return new AdaptedRunnable<Void>(runnable, null);
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	>	* the given result upon {@link #join}.
1078	>	*
1079	>	* @param runnable the runnable action
1080	>	* @param result the result upon completion
1081	>	* @return the task
1082	>	*/
1083	>	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1084	>	return new AdaptedRunnable<T>(runnable, result);
1085	>	}
1086	>
1087	>	/**
1088	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1089	>	* method of the given {@code Callable} as its action, and returns
1090	>	* its result upon {@link #join}, translating any checked exceptions
1091	>	* encountered into {@code RuntimeException}.
1092	>	*
1093	>	* @param callable the callable action
1094	>	* @return the task
1095	>	*/
1096	>	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1097	>	return new AdaptedCallable<T>(callable);
1098		}
1099
1100		// Serialization support
#	Line 1027 | Line 1102 | public abstract class ForkJoinTask<V> im
1102		private static final long serialVersionUID = -7721805057305804111L;
1103
1104		/**
1105	<	* Save the state to a stream.
1105	>	* Saves the state to a stream (that is, serializes it).
1106		*
1107		* @serialData the current run status and the exception thrown
1108	<	* during execution, or null if none
1108	>	* during execution, or {@code null} if none
1109		* @param s the stream
1110		*/
1111		private void writeObject(java.io.ObjectOutputStream s)
#	Line 1040 | Line 1115 | public abstract class ForkJoinTask<V> im
1115		}
1116
1117		/**
1118	<	* Reconstitute the instance from a stream.
1118	>	* Reconstitutes the instance from a stream (that is, deserializes it).
1119		*
1120		* @param s the stream
1121		*/
1122		private void readObject(java.io.ObjectInputStream s)
1123		throws java.io.IOException, ClassNotFoundException {
1124		s.defaultReadObject();
1050	–	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1051	–	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1125		Object ex = s.readObject();
1126		if (ex != null)
1127	<	setDoneExceptionally((Throwable)ex);
1127	>	setExceptionalCompletion((Throwable) ex);
1128	>	}
1129	>
1130	>	// Unsafe mechanics
1131	>
1132	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1133	>	private static final long statusOffset =
1134	>	objectFieldOffset("status", ForkJoinTask.class);
1135	>
1136	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1137	>	try {
1138	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1139	>	} catch (NoSuchFieldException e) {
1140	>	// Convert Exception to corresponding Error
1141	>	NoSuchFieldError error = new NoSuchFieldError(field);
1142	>	error.initCause(e);
1143	>	throw error;
1144	>	}
1145		}
1146
1147	<	// Temporary Unsafe mechanics for preliminary release
1148	<	private static Unsafe getUnsafe() throws Throwable {
1147	>	/**
1148	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1149	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1150	>	* into a jdk.
1151	>	*
1152	>	* @return a sun.misc.Unsafe
1153	>	*/
1154	>	private static sun.misc.Unsafe getUnsafe() {
1155		try {
1156	<	return Unsafe.getUnsafe();
1156	>	return sun.misc.Unsafe.getUnsafe();
1157		} catch (SecurityException se) {
1158		try {
1159		return java.security.AccessController.doPrivileged
1160	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1161	<	public Unsafe run() throws Exception {
1162	<	return getUnsafePrivileged();
1160	>	(new java.security
1161	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1162	>	public sun.misc.Unsafe run() throws Exception {
1163	>	java.lang.reflect.Field f = sun.misc
1164	>	.Unsafe.class.getDeclaredField("theUnsafe");
1165	>	f.setAccessible(true);
1166	>	return (sun.misc.Unsafe) f.get(null);
1167		}});
1168		} catch (java.security.PrivilegedActionException e) {
1169	<	throw e.getCause();
1169	>	throw new RuntimeException("Could not initialize intrinsics",
1170	>	e.getCause());
1171		}
1172		}
1173		}
1073	–
1074	–	private static Unsafe getUnsafePrivileged()
1075	–	throws NoSuchFieldException, IllegalAccessException {
1076	–	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1077	–	f.setAccessible(true);
1078	–	return (Unsafe) f.get(null);
1079	–	}
1080	–
1081	–	private static long fieldOffset(String fieldName)
1082	–	throws NoSuchFieldException {
1083	–	return UNSAFE.objectFieldOffset
1084	–	(ForkJoinTask.class.getDeclaredField(fieldName));
1085	–	}
1086	–
1087	–	static final Unsafe UNSAFE;
1088	–	static final long statusOffset;
1089	–
1090	–	static {
1091	–	try {
1092	–	UNSAFE = getUnsafe();
1093	–	statusOffset = fieldOffset("status");
1094	–	} catch (Throwable e) {
1095	–	throw new RuntimeException("Could not initialize intrinsics", e);
1096	–	}
1097	–	}
1098	–
1174		}

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