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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 1.55 by dl, Sun Aug 29 23:34:46 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
102	>	* result in exceptions or errors, possibly including
103		* 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	>	* COMPLETED. CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
157	>	* waits by other threads have the SIGNAL bit set.  Completion of
158	>	* a stolen task with SIGNAL set awakens any waiters via
159	>	* notifyAll. Even though suboptimal for some purposes, we use
160	>	* basic builtin wait/notify to take advantage of "monitor
161	>	* inflation" in JVMs that we would otherwise need to emulate to
162	>	* avoid adding further per-task bookkeeping overhead.  We want
163	>	* these monitors to be "fat", i.e., not use biasing or thin-lock
164	>	* techniques, so use some odd coding idioms that tend to avoid
165	>	* them.
166		*/
167	+
168	+	/** The run status of this task */
169		volatile int status; // accessed directly by pool and workers
170
171	<	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	>	* Record exception and set exceptional completion
209	>	* @return status on exit
210		*/
211	<	final void setNormalCompletion() {
212	<	// Try typical fast case -- single CAS, no signal, not already done.
213	<	// 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	<	}
211	>	private void setExceptionalCompletion(Throwable rex) {
212	>	exceptionMap.put(this, rex);
213	>	setCompletion(EXCEPTIONAL);
214		}
215
216		/**
217	<	* Performs the actual monitor wait for awaitDone
217	>	* Blocks a worker thread until completion. Called only by
218	>	* pool. Currently unused -- pool-based waits use timeout
219	>	* version below.
220		*/
221	<	private void doAwaitDone(long startTime, long nanos) {
222	<	synchronized(this) {
221	>	final void internalAwaitDone() {
222	>	int s;         // the odd construction reduces lock bias effects
223	>	while ((s = status) >= 0) {
224		try {
225	<	while (status >= 0) {
226	<	long nt = nanos - System.nanoTime() - startTime;
227	<	if (nt <= 0)
250	<	break;
251	<	wait(nt / 1000000, (int)(nt % 1000000));
225	>	synchronized(this) {
226	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
227	>	wait();
228		}
229		} catch (InterruptedException ie) {
230	<	onInterruptedWait();
230	>	cancelIfTerminating();
231		}
232		}
233		}
234
259	–	// Awaiting completion
260	–
235		/**
236	<	* Sets status to indicate there is joiner, then waits for join,
237	<	* surrounded with pool notifications.
236	>	* Blocks a worker thread until completed or timed out.  Called
237	>	* only by pool.
238		*
239	<	* @return status upon exit
266	<	*/
267	<	private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
268	<	ForkJoinPool pool = w == null? null : w.pool;
269	<	int s;
270	<	while ((s = status) >= 0) {
271	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
272	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
273	<	doAwaitDone();
274	<	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
239	>	* @return status on exit
240		*/
241	<	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
287	<	ForkJoinPool pool = w == null? null : w.pool;
241	>	final int internalAwaitDone(long millis) {
242		int s;
243	<	while ((s = status) >= 0) {
244	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
245	<	long startTime = System.nanoTime();
246	<	if (pool == null || !pool.preJoin(this, false))
247	<	doAwaitDone(startTime, nanos);
294	<	if ((s = status) >= 0) {
295	<	adjustPoolCountsOnCancelledWait(pool);
296	<	s = status;
243	>	if ((s = status) >= 0) {
244	>	try {
245	>	synchronized(this) {
246	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
247	>	wait(millis, 0);
248		}
249	<	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
250	<	adjustPoolCountsOnUnblock(pool);
300	<	break;
249	>	} catch (InterruptedException ie) {
250	>	cancelIfTerminating();
251		}
252	+	s = status;
253		}
254		return s;
255		}
256
257		/**
258	<	* Notifies pool that thread is unblocked. Called by signalled
308	<	* threads when woken by non-FJ threads (which is atypical).
258	>	* Blocks a non-worker-thread until completion.
259		*/
260	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
260	>	private void externalAwaitDone() {
261		int s;
262	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
263	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
264	<	pool.updateRunningCount(s);
265	<	}
266	<
267	<	/**
268	<	* Notifies pool to adjust counts on cancelled or timed out wait.
269	<	*/
270	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
271	<	if (pool != null) {
272	<	int s;
273	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
274	<	if (casStatus(s, s - 1)) {
325	<	pool.updateRunningCount(1);
262	>	while ((s = status) >= 0) {
263	>	synchronized(this) {
264	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
265	>	boolean interrupted = false;
266	>	while (status >= 0) {
267	>	try {
268	>	wait();
269	>	} catch (InterruptedException ie) {
270	>	interrupted = true;
271	>	}
272	>	}
273	>	if (interrupted)
274	>	Thread.currentThread().interrupt();
275		break;
276		}
277		}
#	Line 330 | Line 279 | public abstract class ForkJoinTask<V> im
279		}
280
281		/**
282	<	* Handles interruptions during waits.
283	<	*/
284	<	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.
282	>	* Unless done, calls exec and records status if completed, but
283	>	* doesn't wait for completion otherwise. Primary execution method
284	>	* for ForkJoinWorkerThread.
285		*/
286		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() {
287		try {
288	<	if (!exec())
289	<	return false;
288	>	if (status < 0 || !exec())
289	>	return;
290		} catch (Throwable rex) {
291	<	setDoneExceptionally(rex);
292	<	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) {
291	>	setExceptionalCompletion(rex);
292	>	return;
293		}
294	<	}
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
294	>	setCompletion(NORMAL); // must be outside try block
295		}
296
297		// public methods
#	Line 482 | Line 299 | public abstract class ForkJoinTask<V> im
299		/**
300		* Arranges to asynchronously execute this task.  While it is not
301		* necessarily enforced, it is a usage error to fork a task more
302	<	* than once unless it has completed and been reinitialized.  This
303	<	* method may be invoked only from within ForkJoinTask
304	<	* computations (as may be determined using method {@link
305	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
306	<	* in exceptions or errors possibly including ClassCastException.
307	<	*/
308	<	public final void fork() {
309	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
302	>	* than once unless it has completed and been reinitialized.
303	>	* Subsequent modifications to the state of this task or any data
304	>	* it operates on are not necessarily consistently observable by
305	>	* any thread other than the one executing it unless preceded by a
306	>	* call to {@link #join} or related methods, or a call to {@link
307	>	* #isDone} returning {@code true}.
308	>	*
309	>	* <p>This method may be invoked only from within {@code
310	>	* ForkJoinTask} computations (as may be determined using method
311	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
312	>	* result in exceptions or errors, possibly including {@code
313	>	* ClassCastException}.
314	>	*
315	>	* @return {@code this}, to simplify usage
316	>	*/
317	>	public final ForkJoinTask<V> fork() {
318	>	((ForkJoinWorkerThread) Thread.currentThread())
319	>	.pushTask(this);
320	>	return this;
321		}
322
323		/**
324	<	* Returns the result of the computation when it is ready.
325	<	* This method differs from {@code get} in that abnormal
326	<	* completion results in RuntimeExceptions or Errors, not
327	<	* ExecutionExceptions.
324	>	* Returns the result of the computation when it {@link #isDone is done}.
325	>	* This method differs from {@link #get()} in that
326	>	* abnormal completion results in {@code RuntimeException} or
327	>	* {@code Error}, not {@code ExecutionException}.
328		*
329		* @return the computed result
330		*/
331		public final V join() {
332	<	ForkJoinWorkerThread w = getWorker();
333	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
334	<	reportException(awaitDone(w, true));
332	>	quietlyJoin();
333	>	Throwable ex;
334	>	if (status < NORMAL && (ex = getException()) != null)
335	>	UNSAFE.throwException(ex);
336		return getRawResult();
337		}
338
339		/**
340		* Commences performing this task, awaits its completion if
341	<	* necessary, and return its result.
341	>	* necessary, and return its result, or throws an (unchecked)
342	>	* exception if the underlying computation did so.
343		*
514	–	* @throws Throwable (a RuntimeException, Error, or unchecked
515	–	* exception) if the underlying computation did so
344		* @return the computed result
345		*/
346		public final V invoke() {
347	<	if (status >= 0 && tryExec())
348	<	return getRawResult();
349	<	else
350	<	return join();
347	>	quietlyInvoke();
348	>	Throwable ex;
349	>	if (status < NORMAL && (ex = getException()) != null)
350	>	UNSAFE.throwException(ex);
351	>	return getRawResult();
352		}
353
354		/**
355	<	* Forks both tasks, returning when {@code isDone} holds for
356	<	* both of them or an exception is encountered. This method may be
357	<	* invoked only from within ForkJoinTask computations (as may be
358	<	* determined using method {@link #inForkJoinPool}). Attempts to
359	<	* invoke in other contexts result in exceptions or errors
360	<	* possibly including ClassCastException.
361	<	*
362	<	* @param t1 one task
363	<	* @param t2 the other task
364	<	* @throws NullPointerException if t1 or t2 are null
365	<	* @throws RuntimeException or Error if either task did so
355	>	* Forks the given tasks, returning when {@code isDone} holds for
356	>	* each task or an (unchecked) exception is encountered, in which
357	>	* case the exception is rethrown.  If either task encounters an
358	>	* exception, the other one may be, but is not guaranteed to be,
359	>	* cancelled.  If both tasks throw an exception, then this method
360	>	* throws one of them.  The individual status of each task may be
361	>	* checked using {@link #getException()} and related methods.
362	>	*
363	>	* <p>This method may be invoked only from within {@code
364	>	* ForkJoinTask} computations (as may be determined using method
365	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
366	>	* result in exceptions or errors, possibly including {@code
367	>	* ClassCastException}.
368	>	*
369	>	* @param t1 the first task
370	>	* @param t2 the second task
371	>	* @throws NullPointerException if any task is null
372		*/
373	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
373	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
374		t2.fork();
375		t1.invoke();
376		t2.join();
377		}
378
379		/**
380	<	* Forks the given tasks, returning when {@code isDone} holds
381	<	* for all of them. If any task encounters an exception, others
382	<	* may be cancelled.  This method may be invoked only from within
383	<	* ForkJoinTask computations (as may be determined using method
384	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
385	<	* result in exceptions or errors possibly including
386	<	* ClassCastException.
387	<	* @param tasks the array of tasks
388	<	* @throws NullPointerException if tasks or any element are null
389	<	* @throws RuntimeException or Error if any task did so
380	>	* Forks the given tasks, returning when {@code isDone} holds for
381	>	* each task or an (unchecked) exception is encountered, in which
382	>	* case the exception is rethrown. If any task encounters an
383	>	* exception, others may be, but are not guaranteed to be,
384	>	* cancelled.  If more than one task encounters an exception, then
385	>	* this method throws any one of these exceptions.  The individual
386	>	* status of each task may be checked using {@link #getException()}
387	>	* and related methods.
388	>	*
389	>	* <p>This method may be invoked only from within {@code
390	>	* ForkJoinTask} computations (as may be determined using method
391	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
392	>	* result in exceptions or errors, possibly including {@code
393	>	* ClassCastException}.
394	>	*
395	>	* @param tasks the tasks
396	>	* @throws NullPointerException if any task is null
397		*/
398		public static void invokeAll(ForkJoinTask<?>... tasks) {
399		Throwable ex = null;
#	Line 566 | Line 408 | public abstract class ForkJoinTask<V> im
408		t.fork();
409		else {
410		t.quietlyInvoke();
411	<	if (ex == null)
411	>	if (ex == null && t.status < NORMAL)
412		ex = t.getException();
413		}
414		}
#	Line 577 | Line 419 | public abstract class ForkJoinTask<V> im
419		t.cancel(false);
420		else {
421		t.quietlyJoin();
422	<	if (ex == null)
422	>	if (ex == null && t.status < NORMAL)
423		ex = t.getException();
424		}
425		}
426		}
427		if (ex != null)
428	<	rethrowException(ex);
428	>	UNSAFE.throwException(ex);
429		}
430
431		/**
432	<	* Forks all tasks in the collection, returning when
433	<	* {@code isDone} holds for all of them. If any task
434	<	* encounters an exception, others may be cancelled.  This method
435	<	* may be invoked only from within ForkJoinTask computations (as
436	<	* may be determined using method {@link
437	<	* #inForkJoinPool}). Attempts to invoke in other contexts resul!t
438	<	* in exceptions or errors possibly including ClassCastException.
432	>	* Forks all tasks in the specified collection, returning when
433	>	* {@code isDone} holds for each task or an (unchecked) exception
434	>	* is encountered.  If any task encounters an exception, others
435	>	* may be, but are not guaranteed to be, cancelled.  If more than
436	>	* one task encounters an exception, then this method throws any
437	>	* one of these exceptions.  The individual status of each task
438	>	* may be checked using {@link #getException()} and related
439	>	* methods.  The behavior of this operation is undefined if the
440	>	* specified collection is modified while the operation is in
441	>	* progress.
442	>	*
443	>	* <p>This method may be invoked only from within {@code
444	>	* ForkJoinTask} computations (as may be determined using method
445	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
446	>	* result in exceptions or errors, possibly including {@code
447	>	* ClassCastException}.
448		*
449		* @param tasks the collection of tasks
450	+	* @return the tasks argument, to simplify usage
451		* @throws NullPointerException if tasks or any element are null
600	–	* @throws RuntimeException or Error if any task did so
452		*/
453	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
454	<	if (!(tasks instanceof List)) {
455	<	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
456	<	return;
453	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
454	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
455	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
456	>	return tasks;
457		}
458	+	@SuppressWarnings("unchecked")
459		List<? extends ForkJoinTask<?>> ts =
460	<	(List<? extends ForkJoinTask<?>>)tasks;
460	>	(List<? extends ForkJoinTask<?>>) tasks;
461		Throwable ex = null;
462		int last = ts.size() - 1;
463		for (int i = last; i >= 0; --i) {
#	Line 618 | Line 470 | public abstract class ForkJoinTask<V> im
470		t.fork();
471		else {
472		t.quietlyInvoke();
473	<	if (ex == null)
473	>	if (ex == null && t.status < NORMAL)
474		ex = t.getException();
475		}
476		}
#	Line 629 | Line 481 | public abstract class ForkJoinTask<V> im
481		t.cancel(false);
482		else {
483		t.quietlyJoin();
484	<	if (ex == null)
484	>	if (ex == null && t.status < NORMAL)
485		ex = t.getException();
486		}
487		}
488		}
489		if (ex != null)
490	<	rethrowException(ex);
491	<	}
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;
490	>	UNSAFE.throwException(ex);
491	>	return tasks;
492		}
493
494		/**
495	<	* Asserts that the results of this task's computation will not be
496	<	* used. If a cancellation occurs before attempting to execute this
497	<	* task, then execution will be suppressed, {@code isCancelled}
498	<	* will report true, and {@code join} will result in a
499	<	* {@code CancellationException} being thrown. Otherwise, when
500	<	* cancellation races with completion, there are no guarantees
501	<	* 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.
495	>	* Attempts to cancel execution of this task. This attempt will
496	>	* fail if the task has already completed, has already been
497	>	* cancelled, or could not be cancelled for some other reason. If
498	>	* successful, and this task has not started when cancel is
499	>	* called, execution of this task is suppressed, {@link
500	>	* #isCancelled} will report true, and {@link #join} will result
501	>	* in a {@code CancellationException} being thrown.
502		*
503		* <p>This method may be overridden in subclasses, but if so, must
504		* still ensure that these minimal properties hold. In particular,
505	<	* the cancel method itself must not throw exceptions.
505	>	* the {@code cancel} method itself must not throw exceptions.
506		*
507	<	* <p> This method is designed to be invoked by <em>other</em>
507	>	* <p>This method is designed to be invoked by <em>other</em>
508		* tasks. To terminate the current task, you can just return or
509		* throw an unchecked exception from its computation method, or
510	<	* invoke {@code completeExceptionally}.
510	>	* invoke {@link #completeExceptionally}.
511		*
512		* @param mayInterruptIfRunning this value is ignored in the
513	<	* default implementation because tasks are not in general
514	<	* cancelled via interruption.
513	>	* default implementation because tasks are not
514	>	* cancelled via interruption
515		*
516	<	* @return true if this task is now cancelled
516	>	* @return {@code true} if this task is now cancelled
517		*/
518		public boolean cancel(boolean mayInterruptIfRunning) {
519		setCompletion(CANCELLED);
520	<	return (status & COMPLETION_MASK) == CANCELLED;
520	>	return status == CANCELLED;
521	>	}
522	>
523	>	/**
524	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
525	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
526	>	* exceptions, but if it does anyway, we have no recourse during
527	>	* shutdown, so guard against this case.
528	>	*/
529	>	final void cancelIgnoringExceptions() {
530	>	try {
531	>	cancel(false);
532	>	} catch (Throwable ignore) {
533	>	}
534	>	}
535	>
536	>	/**
537	>	* Cancels ignoring exceptions if worker is terminating
538	>	*/
539	>	final void cancelIfTerminating() {
540	>	Thread t = Thread.currentThread();
541	>	if ((t instanceof ForkJoinWorkerThread) &&
542	>	((ForkJoinWorkerThread) t).isTerminating()) {
543	>	try {
544	>	cancel(false);
545	>	} catch (Throwable ignore) {
546	>	}
547	>	}
548	>	}
549	>
550	>	public final boolean isDone() {
551	>	return status < 0;
552	>	}
553	>
554	>	public final boolean isCancelled() {
555	>	return status == CANCELLED;
556		}
557
558		/**
559	<	* Returns true if this task threw an exception or was cancelled.
559	>	* Returns {@code true} if this task threw an exception or was cancelled.
560		*
561	<	* @return true if this task threw an exception or was cancelled
561	>	* @return {@code true} if this task threw an exception or was cancelled
562		*/
563		public final boolean isCompletedAbnormally() {
564	<	return (status & COMPLETION_MASK) < NORMAL;
564	>	return status < NORMAL;
565	>	}
566	>
567	>	/**
568	>	* Returns {@code true} if this task completed without throwing an
569	>	* exception and was not cancelled.
570	>	*
571	>	* @return {@code true} if this task completed without throwing an
572	>	* exception and was not cancelled
573	>	*/
574	>	public final boolean isCompletedNormally() {
575	>	return status == NORMAL;
576		}
577
578		/**
579		* Returns the exception thrown by the base computation, or a
580	<	* CancellationException if cancelled, or null if none or if the
581	<	* method has not yet completed.
580	>	* {@code CancellationException} if cancelled, or {@code null} if
581	>	* none or if the method has not yet completed.
582		*
583	<	* @return the exception, or null if none
583	>	* @return the exception, or {@code null} if none
584		*/
585		public final Throwable getException() {
586	<	int s = status & COMPLETION_MASK;
587	<	if (s >= NORMAL)
588	<	return null;
589	<	if (s == CANCELLED)
713	<	return new CancellationException();
714	<	return exceptionMap.get(this);
586	>	int s = status;
587	>	return ((s >= NORMAL)    ? null :
588	>	(s == CANCELLED) ? new CancellationException() :
589	>	exceptionMap.get(this));
590		}
591
592		/**
#	Line 720 | Line 595 | public abstract class ForkJoinTask<V> im
595		* {@code join} and related operations. This method may be used
596		* to induce exceptions in asynchronous tasks, or to force
597		* completion of tasks that would not otherwise complete.  Its use
598	<	* in other situations is likely to be wrong.  This method is
598	>	* in other situations is discouraged.  This method is
599		* overridable, but overridden versions must invoke {@code super}
600		* implementation to maintain guarantees.
601		*
602	<	* @param ex the exception to throw. If this exception is
603	<	* not a RuntimeException or Error, the actual exception thrown
604	<	* will be a RuntimeException with cause ex.
602	>	* @param ex the exception to throw. If this exception is not a
603	>	* {@code RuntimeException} or {@code Error}, the actual exception
604	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
605		*/
606		public void completeExceptionally(Throwable ex) {
607	<	setDoneExceptionally((ex instanceof RuntimeException) ||
608	<	(ex instanceof Error)? ex :
609	<	new RuntimeException(ex));
607	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
608	>	(ex instanceof Error) ? ex :
609	>	new RuntimeException(ex));
610		}
611
612		/**
#	Line 740 | Line 615 | public abstract class ForkJoinTask<V> im
615		* operations. This method may be used to provide results for
616		* asynchronous tasks, or to provide alternative handling for
617		* tasks that would not otherwise complete normally. Its use in
618	<	* other situations is likely to be wrong. This method is
618	>	* other situations is discouraged. This method is
619		* overridable, but overridden versions must invoke {@code super}
620		* implementation to maintain guarantees.
621		*
#	Line 749 | Line 624 | public abstract class ForkJoinTask<V> im
624		public void complete(V value) {
625		try {
626		setRawResult(value);
627	<	} catch(Throwable rex) {
628	<	setDoneExceptionally(rex);
627	>	} catch (Throwable rex) {
628	>	setExceptionalCompletion(rex);
629		return;
630		}
631	<	setNormalCompletion();
631	>	setCompletion(NORMAL);
632		}
633
634		public final V get() throws InterruptedException, ExecutionException {
635	<	ForkJoinWorkerThread w = getWorker();
636	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
637	<	awaitDone(w, true);
638	<	return reportFutureResult();
635	>	quietlyJoin();
636	>	if (Thread.interrupted())
637	>	throw new InterruptedException();
638	>	int s = status;
639	>	if (s < NORMAL) {
640	>	Throwable ex;
641	>	if (s == CANCELLED)
642	>	throw new CancellationException();
643	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
644	>	throw new ExecutionException(ex);
645	>	}
646	>	return getRawResult();
647		}
648
649		public final V get(long timeout, TimeUnit unit)
650		throws InterruptedException, ExecutionException, TimeoutException {
651	<	ForkJoinWorkerThread w = getWorker();
652	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
653	<	awaitDone(w, unit.toNanos(timeout));
654	<	return reportTimedFutureResult();
655	<	}
656	<
657	<	/**
658	<	* Possibly executes other tasks until this task is ready, then
659	<	* returns the result of the computation.  This method may be more
660	<	* efficient than {@code join}, but is only applicable when
661	<	* there are no potential dependencies between continuation of the
662	<	* current task and that of any other task that might be executed
663	<	* while helping. (This usually holds for pure divide-and-conquer
664	<	* tasks). This method may be invoked only from within
665	<	* ForkJoinTask computations (as may be determined using method
666	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
667	<	* resul!t in exceptions or errors possibly including
668	<	* ClassCastException.
669	<	*
670	<	* @return the computed result
671	<	*/
672	<	public final V helpJoin() {
673	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
674	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
675	<	reportException(busyJoin(w));
676	<	return getRawResult();
677	<	}
678	<
679	<	/**
680	<	* Possibly executes other tasks until this task is ready.  This
681	<	* method may be invoked only from within ForkJoinTask
682	<	* computations (as may be determined using method {@link
683	<	* #inForkJoinPool}). Attempts to invoke in other contexts resul!t
684	<	* in exceptions or errors possibly including ClassCastException.
685	<	*/
686	<	public final void quietlyHelpJoin() {
687	<	if (status >= 0) {
688	<	ForkJoinWorkerThread w =
689	<	(ForkJoinWorkerThread)(Thread.currentThread());
690	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
691	<	busyJoin(w);
651	>	Thread t = Thread.currentThread();
652	>	ForkJoinPool pool;
653	>	if (t instanceof ForkJoinWorkerThread) {
654	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
655	>	if (status >= 0 && w.unpushTask(this))
656	>	quietlyExec();
657	>	pool = w.pool;
658	>	}
659	>	else
660	>	pool = null;
661	>	/*
662	>	* Timed wait loop intermixes cases for FJ (pool != null) and
663	>	* non FJ threads. For FJ, decrement pool count but don't try
664	>	* for replacement; increment count on completion. For non-FJ,
665	>	* deal with interrupts. This is messy, but a little less so
666	>	* than is splitting the FJ and nonFJ cases.
667	>	*/
668	>	boolean interrupted = false;
669	>	boolean dec = false; // true if pool count decremented
670	>	long nanos = unit.toNanos(timeout);
671	>	for (;;) {
672	>	if (Thread.interrupted() && pool == null) {
673	>	interrupted = true;
674	>	break;
675	>	}
676	>	int s = status;
677	>	if (s < 0)
678	>	break;
679	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
680	>	long startTime = System.nanoTime();
681	>	long nt; // wait time
682	>	while (status >= 0 &&
683	>	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
684	>	if (pool != null && !dec)
685	>	dec = pool.tryDecrementRunningCount();
686	>	else {
687	>	long ms = nt / 1000000;
688	>	int ns = (int) (nt % 1000000);
689	>	try {
690	>	synchronized(this) {
691	>	if (status >= 0)
692	>	wait(ms, ns);
693	>	}
694	>	} catch (InterruptedException ie) {
695	>	if (pool != null)
696	>	cancelIfTerminating();
697	>	else {
698	>	interrupted = true;
699	>	break;
700	>	}
701	>	}
702	>	}
703	>	}
704	>	break;
705	>	}
706	>	}
707	>	if (pool != null && dec)
708	>	pool.incrementRunningCount();
709	>	if (interrupted)
710	>	throw new InterruptedException();
711	>	int es = status;
712	>	if (es != NORMAL) {
713	>	Throwable ex;
714	>	if (es == CANCELLED)
715	>	throw new CancellationException();
716	>	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
717	>	throw new ExecutionException(ex);
718	>	throw new TimeoutException();
719		}
720	+	return getRawResult();
721		}
722
723		/**
724	<	* Joins this task, without returning its result or throwing an
724	>	* Joins this task, without returning its result or throwing its
725		* exception. This method may be useful when processing
726		* collections of tasks when some have been cancelled or otherwise
727		* known to have aborted.
728		*/
729		public final void quietlyJoin() {
730	<	if (status >= 0) {
731	<	ForkJoinWorkerThread w = getWorker();
732	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
733	<	awaitDone(w, true);
730	>	Thread t;
731	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
732	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
733	>	if (status >= 0) {
734	>	if (w.unpushTask(this)) {
735	>	boolean completed;
736	>	try {
737	>	completed = exec();
738	>	} catch (Throwable rex) {
739	>	setExceptionalCompletion(rex);
740	>	return;
741	>	}
742	>	if (completed) {
743	>	setCompletion(NORMAL);
744	>	return;
745	>	}
746	>	}
747	>	w.joinTask(this);
748	>	}
749		}
750	+	else
751	+	externalAwaitDone();
752		}
753
754		/**
755		* Commences performing this task and awaits its completion if
756	<	* necessary, without returning its result or throwing an
756	>	* necessary, without returning its result or throwing its
757		* exception. This method may be useful when processing
758		* collections of tasks when some have been cancelled or otherwise
759		* known to have aborted.
760		*/
761		public final void quietlyInvoke() {
762	<	if (status >= 0 && !tryQuietlyInvoke())
763	<	quietlyJoin();
762	>	if (status >= 0) {
763	>	boolean completed;
764	>	try {
765	>	completed = exec();
766	>	} catch (Throwable rex) {
767	>	setExceptionalCompletion(rex);
768	>	return;
769	>	}
770	>	if (completed)
771	>	setCompletion(NORMAL);
772	>	else
773	>	quietlyJoin();
774	>	}
775		}
776
777		/**
778		* Possibly executes tasks until the pool hosting the current task
779	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
780	<	* designs in which many tasks are forked, but none are explicitly
781	<	* joined, instead executing them until all are processed.
779	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
780	>	* be of use in designs in which many tasks are forked, but none
781	>	* are explicitly joined, instead executing them until all are
782	>	* processed.
783	>	*
784	>	* <p>This method may be invoked only from within {@code
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 {@code
788	>	* ClassCastException}.
789		*/
790		public static void helpQuiesce() {
791	<	((ForkJoinWorkerThread)(Thread.currentThread())).
792	<	helpQuiescePool();
791	>	((ForkJoinWorkerThread) Thread.currentThread())
792	>	.helpQuiescePool();
793		}
794
795		/**
#	Line 852 | Line 798 | public abstract class ForkJoinTask<V> im
798		* this task, but only if reuse occurs when this task has either
799		* never been forked, or has been forked, then completed and all
800		* outstanding joins of this task have also completed. Effects
801	<	* under any other usage conditions are not guaranteed, and are
802	<	* almost surely wrong. This method may be useful when executing
801	>	* under any other usage conditions are not guaranteed.
802	>	* This method may be useful when executing
803		* pre-constructed trees of subtasks in loops.
804		*/
805		public void reinitialize() {
806	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
806	>	if (status == EXCEPTIONAL)
807		exceptionMap.remove(this);
808		status = 0;
809		}
#	Line 866 | Line 812 | public abstract class ForkJoinTask<V> im
812		* Returns the pool hosting the current task execution, or null
813		* if this task is executing outside of any ForkJoinPool.
814		*
815	<	* @return the pool, or null if none.
815	>	* @see #inForkJoinPool
816	>	* @return the pool, or {@code null} if none
817		*/
818		public static ForkJoinPool getPool() {
819		Thread t = Thread.currentThread();
820	<	return ((t instanceof ForkJoinWorkerThread)?
821	<	((ForkJoinWorkerThread)t).pool : null);
820	>	return (t instanceof ForkJoinWorkerThread) ?
821	>	((ForkJoinWorkerThread) t).pool : null;
822		}
823
824		/**
825	<	* Returns true if the current thread is executing as a
825	>	* Returns {@code true} if the current thread is executing as a
826		* ForkJoinPool computation.
827	<	* @return <code>true</code> if the current thread is executing as a
827	>	*
828	>	* @return {@code true} if the current thread is executing as a
829		* ForkJoinPool computation, or false otherwise
830		*/
831		public static boolean inForkJoinPool() {
#	Line 890 | Line 838 | public abstract class ForkJoinTask<V> im
838		* by the current thread, and has not commenced executing in
839		* another thread.  This method may be useful when arranging
840		* alternative local processing of tasks that could have been, but
841	<	* were not, stolen. This method may be invoked only from within
842	<	* ForkJoinTask computations (as may be determined using method
843	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
844	<	* result in exceptions or errors possibly including
845	<	* ClassCastException.
841	>	* were not, stolen.
842	>	*
843	>	* <p>This method may be invoked only from within {@code
844	>	* ForkJoinTask} computations (as may be determined using method
845	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
846	>	* result in exceptions or errors, possibly including {@code
847	>	* ClassCastException}.
848		*
849	<	* @return true if unforked
849	>	* @return {@code true} if unforked
850		*/
851		public boolean tryUnfork() {
852	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
852	>	return ((ForkJoinWorkerThread) Thread.currentThread())
853	>	.unpushTask(this);
854		}
855
856		/**
#	Line 908 | Line 859 | public abstract class ForkJoinTask<V> im
859		* value may be useful for heuristic decisions about whether to
860		* fork other tasks.
861		*
862	+	* <p>This method may be invoked only from within {@code
863	+	* ForkJoinTask} computations (as may be determined using method
864	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
865	+	* result in exceptions or errors, possibly including {@code
866	+	* ClassCastException}.
867	+	*
868		* @return the number of tasks
869		*/
870		public static int getQueuedTaskCount() {
871	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
872	<	getQueueSize();
871	>	return ((ForkJoinWorkerThread) Thread.currentThread())
872	>	.getQueueSize();
873		}
874
875		/**
#	Line 925 | Line 882 | public abstract class ForkJoinTask<V> im
882		* tasks, and to process computations locally if this threshold is
883		* exceeded.
884		*
885	+	* <p>This method may be invoked only from within {@code
886	+	* ForkJoinTask} computations (as may be determined using method
887	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
888	+	* result in exceptions or errors, possibly including {@code
889	+	* ClassCastException}.
890	+	*
891		* @return the surplus number of tasks, which may be negative
892		*/
893		public static int getSurplusQueuedTaskCount() {
894	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
894	>	return ((ForkJoinWorkerThread) Thread.currentThread())
895		.getEstimatedSurplusTaskCount();
896		}
897
898		// Extension methods
899
900		/**
901	<	* Returns the result that would be returned by {@code join},
902	<	* even if this task completed abnormally, or null if this task is
903	<	* not known to have been completed.  This method is designed to
904	<	* aid debugging, as well as to support extensions. Its use in any
905	<	* other context is discouraged.
901	>	* Returns the result that would be returned by {@link #join}, even
902	>	* if this task completed abnormally, or {@code null} if this task
903	>	* is not known to have been completed.  This method is designed
904	>	* to aid debugging, as well as to support extensions. Its use in
905	>	* any other context is discouraged.
906		*
907	<	* @return the result, or null if not completed
907	>	* @return the result, or {@code null} if not completed
908		*/
909		public abstract V getRawResult();
910
#	Line 960 | Line 923 | public abstract class ForkJoinTask<V> im
923		* called otherwise. The return value controls whether this task
924		* is considered to be done normally. It may return false in
925		* asynchronous actions that require explicit invocations of
926	<	* {@code complete} to become joinable. It may throw exceptions
927	<	* to indicate abnormal exit.
926	>	* {@link #complete} to become joinable. It may also throw an
927	>	* (unchecked) exception to indicate abnormal exit.
928		*
929	<	* @return true if completed normally
967	<	* @throws Error or RuntimeException if encountered during computation
929	>	* @return {@code true} if completed normally
930		*/
931		protected abstract boolean exec();
932
933		/**
934	<	* Returns, but does not unschedule or execute, the task queued by
935	<	* the current thread but not yet executed, if one is
934	>	* Returns, but does not unschedule or execute, a task queued by
935	>	* the current thread but not yet executed, if one is immediately
936		* available. There is no guarantee that this task will actually
937	<	* be polled or executed next.  This method is designed primarily
938	<	* to support extensions, and is unlikely to be useful otherwise.
939	<	* This method may be invoked only from within ForkJoinTask
940	<	* computations (as may be determined using method {@link
941	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
942	<	* in exceptions or errors possibly including ClassCastException.
937	>	* be polled or executed next. Conversely, this method may return
938	>	* null even if a task exists but cannot be accessed without
939	>	* contention with other threads.  This method is designed
940	>	* primarily to support extensions, and is unlikely to be useful
941	>	* otherwise.
942	>	*
943	>	* <p>This method may be invoked only from within {@code
944	>	* ForkJoinTask} computations (as may be determined using method
945	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
946	>	* result in exceptions or errors, possibly including {@code
947	>	* ClassCastException}.
948		*
949	<	* @return the next task, or null if none are available
949	>	* @return the next task, or {@code null} if none are available
950		*/
951		protected static ForkJoinTask<?> peekNextLocalTask() {
952	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask();
952	>	return ((ForkJoinWorkerThread) Thread.currentThread())
953	>	.peekTask();
954		}
955
956		/**
957		* Unschedules and returns, without executing, the next task
958		* queued by the current thread but not yet executed.  This method
959		* is designed primarily to support extensions, and is unlikely to
960	<	* 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.
960	>	* be useful otherwise.
961		*
962	<	* @return the next task, or null if none are available
962	>	* <p>This method may be invoked only from within {@code
963	>	* ForkJoinTask} computations (as may be determined using method
964	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
965	>	* result in exceptions or errors, possibly including {@code
966	>	* ClassCastException}.
967	>	*
968	>	* @return the next task, or {@code null} if none are available
969		*/
970		protected static ForkJoinTask<?> pollNextLocalTask() {
971	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).pollLocalTask();
971	>	return ((ForkJoinWorkerThread) Thread.currentThread())
972	>	.pollLocalTask();
973		}
974
975		/**
#	Line 1009 | Line 980 | public abstract class ForkJoinTask<V> im
980		* {@code null} result does not necessarily imply quiescence
981		* of the pool this task is operating in.  This method is designed
982		* primarily to support extensions, and is unlikely to be useful
983	<	* otherwise.  This method may be invoked only from within
984	<	* ForkJoinTask computations (as may be determined using method
985	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
986	<	* result in exceptions or errors possibly including
987	<	* ClassCastException.
983	>	* otherwise.
984	>	*
985	>	* <p>This method may be invoked only from within {@code
986	>	* ForkJoinTask} computations (as may be determined using method
987	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
988	>	* result in exceptions or errors, possibly including {@code
989	>	* ClassCastException}.
990		*
991	<	* @return a task, or null if none are available
991	>	* @return a task, or {@code null} if none are available
992		*/
993		protected static ForkJoinTask<?> pollTask() {
994	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
995	<	pollTask();
994	>	return ((ForkJoinWorkerThread) Thread.currentThread())
995	>	.pollTask();
996	>	}
997	>
998	>	/**
999	>	* Adaptor for Runnables. This implements RunnableFuture
1000	>	* to be compliant with AbstractExecutorService constraints
1001	>	* when used in ForkJoinPool.
1002	>	*/
1003	>	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1004	>	implements RunnableFuture<T> {
1005	>	final Runnable runnable;
1006	>	final T resultOnCompletion;
1007	>	T result;
1008	>	AdaptedRunnable(Runnable runnable, T result) {
1009	>	if (runnable == null) throw new NullPointerException();
1010	>	this.runnable = runnable;
1011	>	this.resultOnCompletion = result;
1012	>	}
1013	>	public T getRawResult() { return result; }
1014	>	public void setRawResult(T v) { result = v; }
1015	>	public boolean exec() {
1016	>	runnable.run();
1017	>	result = resultOnCompletion;
1018	>	return true;
1019	>	}
1020	>	public void run() { invoke(); }
1021	>	private static final long serialVersionUID = 5232453952276885070L;
1022	>	}
1023	>
1024	>	/**
1025	>	* Adaptor for Callables
1026	>	*/
1027	>	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1028	>	implements RunnableFuture<T> {
1029	>	final Callable<? extends T> callable;
1030	>	T result;
1031	>	AdaptedCallable(Callable<? extends T> callable) {
1032	>	if (callable == null) throw new NullPointerException();
1033	>	this.callable = callable;
1034	>	}
1035	>	public T getRawResult() { return result; }
1036	>	public void setRawResult(T v) { result = v; }
1037	>	public boolean exec() {
1038	>	try {
1039	>	result = callable.call();
1040	>	return true;
1041	>	} catch (Error err) {
1042	>	throw err;
1043	>	} catch (RuntimeException rex) {
1044	>	throw rex;
1045	>	} catch (Exception ex) {
1046	>	throw new RuntimeException(ex);
1047	>	}
1048	>	}
1049	>	public void run() { invoke(); }
1050	>	private static final long serialVersionUID = 2838392045355241008L;
1051	>	}
1052	>
1053	>	/**
1054	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1055	>	* method of the given {@code Runnable} as its action, and returns
1056	>	* a null result upon {@link #join}.
1057	>	*
1058	>	* @param runnable the runnable action
1059	>	* @return the task
1060	>	*/
1061	>	public static ForkJoinTask<?> adapt(Runnable runnable) {
1062	>	return new AdaptedRunnable<Void>(runnable, null);
1063	>	}
1064	>
1065	>	/**
1066	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1067	>	* method of the given {@code Runnable} as its action, and returns
1068	>	* the given result upon {@link #join}.
1069	>	*
1070	>	* @param runnable the runnable action
1071	>	* @param result the result upon completion
1072	>	* @return the task
1073	>	*/
1074	>	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1075	>	return new AdaptedRunnable<T>(runnable, result);
1076	>	}
1077	>
1078	>	/**
1079	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1080	>	* method of the given {@code Callable} as its action, and returns
1081	>	* its result upon {@link #join}, translating any checked exceptions
1082	>	* encountered into {@code RuntimeException}.
1083	>	*
1084	>	* @param callable the callable action
1085	>	* @return the task
1086	>	*/
1087	>	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1088	>	return new AdaptedCallable<T>(callable);
1089		}
1090
1091		// Serialization support
#	Line 1027 | Line 1093 | public abstract class ForkJoinTask<V> im
1093		private static final long serialVersionUID = -7721805057305804111L;
1094
1095		/**
1096	<	* Save the state to a stream.
1096	>	* Saves the state to a stream.
1097		*
1098		* @serialData the current run status and the exception thrown
1099	<	* during execution, or null if none
1099	>	* during execution, or {@code null} if none
1100		* @param s the stream
1101		*/
1102		private void writeObject(java.io.ObjectOutputStream s)
#	Line 1040 | Line 1106 | public abstract class ForkJoinTask<V> im
1106		}
1107
1108		/**
1109	<	* Reconstitute the instance from a stream.
1109	>	* Reconstitutes the instance from a stream.
1110		*
1111		* @param s the stream
1112		*/
1113		private void readObject(java.io.ObjectInputStream s)
1114		throws java.io.IOException, ClassNotFoundException {
1115		s.defaultReadObject();
1050	–	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1051	–	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1116		Object ex = s.readObject();
1117		if (ex != null)
1118	<	setDoneExceptionally((Throwable)ex);
1118	>	setExceptionalCompletion((Throwable) ex);
1119	>	}
1120	>
1121	>	// Unsafe mechanics
1122	>
1123	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1124	>	private static final long statusOffset =
1125	>	objectFieldOffset("status", ForkJoinTask.class);
1126	>
1127	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1128	>	try {
1129	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1130	>	} catch (NoSuchFieldException e) {
1131	>	// Convert Exception to corresponding Error
1132	>	NoSuchFieldError error = new NoSuchFieldError(field);
1133	>	error.initCause(e);
1134	>	throw error;
1135	>	}
1136		}
1137
1138	<	// Temporary Unsafe mechanics for preliminary release
1139	<	private static Unsafe getUnsafe() throws Throwable {
1138	>	/**
1139	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1140	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1141	>	* into a jdk.
1142	>	*
1143	>	* @return a sun.misc.Unsafe
1144	>	*/
1145	>	private static sun.misc.Unsafe getUnsafe() {
1146		try {
1147	<	return Unsafe.getUnsafe();
1147	>	return sun.misc.Unsafe.getUnsafe();
1148		} catch (SecurityException se) {
1149		try {
1150		return java.security.AccessController.doPrivileged
1151	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1152	<	public Unsafe run() throws Exception {
1153	<	return getUnsafePrivileged();
1151	>	(new java.security
1152	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1153	>	public sun.misc.Unsafe run() throws Exception {
1154	>	java.lang.reflect.Field f = sun.misc
1155	>	.Unsafe.class.getDeclaredField("theUnsafe");
1156	>	f.setAccessible(true);
1157	>	return (sun.misc.Unsafe) f.get(null);
1158		}});
1159		} catch (java.security.PrivilegedActionException e) {
1160	<	throw e.getCause();
1160	>	throw new RuntimeException("Could not initialize intrinsics",
1161	>	e.getCause());
1162		}
1163		}
1164		}
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	–
1165		}

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