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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.7 by jsr166, Mon Jul 20 21:45:06 2009 UTC vs.
Revision 1.51 by dl, Fri Jul 23 16:49:11 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</code>
30	<	* and <code>join</code>, or derivatives such as
31	<	* <code>invokeAll</code>.  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</code>
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</code>
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</code>
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()</code> 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
66	>	* waits for completion and report results using {@code Future}
67	>	* conventions. Method {@link #invoke} is semantically
68	>	* equivalent to {@code fork(); join()} but always attempts to begin
69	>	* execution in the current thread. The "<em>quiet</em>" forms of
70	>	* these methods do not extract results or report exceptions. These
71		* may be useful when a set of tasks are being executed, and you need
72		* to delay processing of results or exceptions until all complete.
73	<	* Method <code>invokeAll</code> (available in multiple versions)
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</code>
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</code> access (to allow
98	<	* instances of different task subclasses to call each others
97	>	* class. While these methods have {@code public} access (to allow
98	>	* instances of different task subclasses to call each other's
99		* methods), some of them may only be called from within other
100	<	* ForkJoinTasks. Attempts to invoke them in other contexts result in
101	<	* exceptions or errors possibly including ClassCastException.
100	>	* ForkJoinTasks (as may be determined using method {@link
101	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
102	>	* result in exceptions or errors, possibly including
103	>	* ClassCastException.
104		*
105	<	* <p>Most base support methods are <code>final</code> 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</code> methods
110	<	* <code>exec</code>, <code>setRawResult</code>, and
111	<	* <code>getRawResult</code>, while also introducing an abstract
112	<	* computational method that can be implemented in its subclasses,
113	<	* possibly relying on other <code>protected</code> methods provided
96	<	* 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, othewise splitting into smaller tasks. As a very
117	<	* rough rule of thumb, a task should perform more than 100 and less
118	<	* than 10000 basic computational steps. If tasks are too big, then
119	<	* parellelism cannot improve throughput. If too small, then memory
120	<	* and internal task maintenance overhead may overwhelm processing.
116	>	* computation. Large tasks should be split into smaller subtasks,
117	>	* usually via recursive decomposition. As a very rough rule of thumb,
118	>	* a task should perform more than 100 and less than 10000 basic
119	>	* computational steps. If tasks are too big, then parallelism cannot
120	>	* improve throughput. If too small, then memory and internal task
121	>	* maintenance overhead may overwhelm processing.
122		*
123	<	* <p>ForkJoinTasks are <code>Serializable</code>, 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.
155	<	*/
156	<	volatile int status; // accessed directy by pool and workers
157	<
158	<	static final int COMPLETION_MASK      = 0xe0000000;
159	<	static final int NORMAL               = 0xe0000000; // == mask
160	<	static final int CANCELLED            = 0xc0000000;
161	<	static final int EXCEPTIONAL          = 0xa0000000;
162	<	static final int SIGNAL_MASK          = 0x0000ffff;
163	<	static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
164	<	static final int EXTERNAL_SIGNAL      = 0x00008000; // top bit of low word
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.
148	>	*/
149	>
150	>	/*
151	>	* The status field holds run control status bits packed into a
152	>	* single int to minimize footprint and to ensure atomicity (via
153	>	* CAS).  Status is initially zero, and takes on nonnegative
154	>	* values until completed, upon which status holds value
155	>	* COMPLETED. CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
156	>	* waits by other threads have the SIGNAL bit set.  Completion of
157	>	* a stolen task with SIGNAL set awakens any waiters via
158	>	* notifyAll. Even though suboptimal for some purposes, we use
159	>	* basic builtin wait/notify to take advantage of "monitor
160	>	* inflation" in JVMs that we would otherwise need to emulate to
161	>	* avoid adding further per-task bookkeeping overhead.  We want
162	>	* these monitors to be "fat", i.e., not use biasing or thin-lock
163	>	* techniques, so use some odd coding idioms that tend to avoid
164	>	* them.
165	>	*/
166	>
167	>	/** Run status of this task */
168	>	volatile int status; // accessed directly by pool and workers
169	>
170	>	private static final int NORMAL      = -1;
171	>	private static final int CANCELLED   = -2;
172	>	private static final int EXCEPTIONAL = -3;
173	>	private static final int SIGNAL      =  1;
174
175		/**
176		* Table of exceptions thrown by tasks, to enable reporting by
177		* callers. Because exceptions are rare, we don't directly keep
178	<	* them with task objects, but instead us a weak ref table.  Note
178	>	* them with task objects, but instead use a weak ref table.  Note
179		* that cancellation exceptions don't appear in the table, but are
180		* instead recorded as status values.
181	<	* Todo: Use ConcurrentReferenceHashMap
181	>	* TODO: Use ConcurrentReferenceHashMap
182		*/
183		static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
184		Collections.synchronizedMap
185		(new WeakHashMap<ForkJoinTask<?>, Throwable>());
186
187	<	// within-package utilities
154	<
155	<	/**
156	<	* Get current worker thread, or null if not a worker thread
157	<	*/
158	<	static ForkJoinWorkerThread getWorker() {
159	<	Thread t = Thread.currentThread();
160	<	return ((t instanceof ForkJoinWorkerThread)?
161	<	(ForkJoinWorkerThread)t : null);
162	<	}
163	<
164	<	final boolean casStatus(int cmp, int val) {
165	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
166	<	}
167	<
168	<	/**
169	<	* Workaround for not being able to rethrow unchecked exceptions.
170	<	*/
171	<	static void rethrowException(Throwable ex) {
172	<	if (ex != null)
173	<	_unsafe.throwException(ex);
174	<	}
175	<
176	<	// Setting completion status
187	>	// Maintaining completion status
188
189		/**
190	<	* Mark completion and wake up threads waiting to join this task.
190	>	* Marks completion and wakes up threads waiting to join this task,
191	>	* also clearing signal request bits.
192	>	*
193		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
194	+	* @return status on exit
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) {
189	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
190	<	pool.updateRunningCount(s);
191	<	synchronized(this) { notifyAll(); }
196	>	private int 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	>	return completion;
203		}
204		}
205	<	else
195	<	externallySetCompletion(completion);
196	<	}
197	<
198	<	/**
199	<	* Version of setCompletion for non-FJ threads.  Leaves signal
200	<	* bits for unblocked threads to adjust, and always notifies.
201	<	*/
202	<	private void externallySetCompletion(int completion) {
203	<	int s;
204	<	do;while ((s = status) >= 0 &&
205	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
206	<	synchronized(this) { notifyAll(); }
207	<	}
208	<
209	<	/**
210	<	* Sets status to indicate normal completion
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
215	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
216	<	setCompletion(NORMAL);
205	>	return s;
206		}
207
219	–	// internal waiting and notification
220	–
208		/**
209	<	* Performs the actual monitor wait for awaitDone
209	>	* Record exception and set exceptional completion
210	>	* @return status on exit
211		*/
212	<	private void doAwaitDone() {
213	<	// Minimize lock bias and in/de-flation effects by maximizing
214	<	// chances of waiting inside sync
227	<	try {
228	<	while (status >= 0)
229	<	synchronized(this) { if (status >= 0) wait(); }
230	<	} catch (InterruptedException ie) {
231	<	onInterruptedWait();
232	<	}
212	>	private int setExceptionalCompletion(Throwable rex) {
213	>	exceptionMap.put(this, rex);
214	>	return setCompletion(EXCEPTIONAL);
215		}
216
217		/**
218	<	* Performs the actual monitor wait for awaitDone
218	>	* Blocks a worker thread until completion. Called only by pool.
219		*/
220	<	private void doAwaitDone(long startTime, long nanos) {
221	<	synchronized(this) {
220	>	final void internalAwaitDone() {
221	>	int s;         // the odd construction reduces lock bias effects
222	>	while ((s = status) >= 0) {
223		try {
224	<	while (status >= 0) {
225	<	long nt = nanos - System.nanoTime() - startTime;
226	<	if (nt <= 0)
244	<	break;
245	<	wait(nt / 1000000, (int)(nt % 1000000));
224	>	synchronized(this) {
225	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
226	>	wait();
227		}
228		} catch (InterruptedException ie) {
229	<	onInterruptedWait();
249	<	}
250	<	}
251	<	}
252	<
253	<	// Awaiting completion
254	<
255	<	/**
256	<	* Sets status to indicate there is joiner, then waits for join,
257	<	* surrounded with pool notifications.
258	<	* @return status upon exit
259	<	*/
260	<	private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
261	<	ForkJoinPool pool = w == null? null : w.pool;
262	<	int s;
263	<	while ((s = status) >= 0) {
264	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
265	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
266	<	doAwaitDone();
267	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
268	<	adjustPoolCountsOnUnblock(pool);
269	<	break;
229	>	cancelIfTerminating();
230		}
231		}
272	–	return s;
232		}
233
234		/**
235	<	* Timed version of awaitDone
236	<	* @return status upon exit
235	>	* Blocks a non-worker-thread until completion.
236	>	* @return status on exit
237		*/
238	<	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
280	<	ForkJoinPool pool = w == null? null : w.pool;
238	>	private int externalAwaitDone() {
239		int s;
240		while ((s = status) >= 0) {
241	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
242	<	long startTime = System.nanoTime();
243	<	if (pool == null || !pool.preJoin(this, false))
244	<	doAwaitDone(startTime, nanos);
245	<	if ((s = status) >= 0) {
246	<	adjustPoolCountsOnCancelledWait(pool);
247	<	s = status;
241	>	synchronized(this) {
242	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
243	>	boolean interrupted = false;
244	>	while ((s = status) >= 0) {
245	>	try {
246	>	wait();
247	>	} catch (InterruptedException ie) {
248	>	interrupted = true;
249	>	}
250	>	}
251	>	if (interrupted)
252	>	Thread.currentThread().interrupt();
253	>	break;
254		}
291	–	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
292	–	adjustPoolCountsOnUnblock(pool);
293	–	break;
255		}
256		}
257		return s;
258		}
259
260		/**
261	<	* Notify pool that thread is unblocked. Called by signalled
262	<	* threads when woken by non-FJ threads (which is atypical).
261	>	* Unless done, calls exec and records status if completed, but
262	>	* doesn't wait for completion otherwise. Primary execution method
263	>	* for ForkJoinWorkerThread.
264		*/
265	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
266	<	int s;
267	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
268	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
269	<	pool.updateRunningCount(s);
265	>	final void tryExec() {
266	>	try {
267	>	if (status < 0 || !exec())
268	>	return;
269	>	} catch (Throwable rex) {
270	>	setExceptionalCompletion(rex);
271	>	return;
272	>	}
273	>	setCompletion(NORMAL); // must be outside try block
274		}
275
276		/**
277	<	* Notify pool to adjust counts on cancelled or timed out wait
277	>	* If not done and this task is next in worker queue, runs it,
278	>	* else waits for it.
279	>	* @return status on exit
280		*/
281	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
282	<	if (pool != null) {
283	<	int s;
284	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
285	<	if (casStatus(s, s - 1)) {
286	<	pool.updateRunningCount(1);
287	<	break;
281	>	private int doJoin() {
282	>	int stat;
283	>	if ((stat = status) < 0)
284	>	return stat;
285	>	Thread t = Thread.currentThread();
286	>	ForkJoinWorkerThread w;
287	>	if (t instanceof ForkJoinWorkerThread) {
288	>	if ((w = (ForkJoinWorkerThread) t).unpushTask(this)) {
289	>	boolean completed;
290	>	try {
291	>	completed = exec();
292	>	} catch (Throwable rex) {
293	>	return setExceptionalCompletion(rex);
294		}
295	+	if (completed)
296	+	return setCompletion(NORMAL);
297		}
298	+	return w.joinTask(this);
299		}
300	+	return externalAwaitDone();
301		}
302
303		/**
304	<	* Handle interruptions during waits.
305	<	*/
306	<	private void onInterruptedWait() {
329	<	ForkJoinWorkerThread w = getWorker();
330	<	if (w == null)
331	<	Thread.currentThread().interrupt(); // re-interrupt
332	<	else if (w.isTerminating())
333	<	cancelIgnoringExceptions();
334	<	// else if FJworker, ignore interrupt
335	<	}
336	<
337	<	// Recording and reporting exceptions
338	<
339	<	private void setDoneExceptionally(Throwable rex) {
340	<	exceptionMap.put(this, rex);
341	<	setCompletion(EXCEPTIONAL);
342	<	}
343	<
344	<	/**
345	<	* Throws the exception associated with status s;
346	<	* @throws the exception
304	>	* Unless done, calls exec and records status if completed, or
305	>	* waits for completion otherwise.
306	>	* @return status on exit
307		*/
308	<	private void reportException(int s) {
309	<	if ((s &= COMPLETION_MASK) < NORMAL) {
310	<	if (s == CANCELLED)
311	<	throw new CancellationException();
352	<	else
353	<	rethrowException(exceptionMap.get(this));
354	<	}
355	<	}
356	<
357	<	/**
358	<	* Returns result or throws exception using j.u.c.Future conventions
359	<	* Only call when isDone known to be true.
360	<	*/
361	<	private V reportFutureResult()
362	<	throws ExecutionException, InterruptedException {
363	<	int s = status & COMPLETION_MASK;
364	<	if (s < NORMAL) {
365	<	Throwable ex;
366	<	if (s == CANCELLED)
367	<	throw new CancellationException();
368	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
369	<	throw new ExecutionException(ex);
370	<	if (Thread.interrupted())
371	<	throw new InterruptedException();
372	<	}
373	<	return getRawResult();
374	<	}
375	<
376	<	/**
377	<	* Returns result or throws exception using j.u.c.Future conventions
378	<	* with timeouts
379	<	*/
380	<	private V reportTimedFutureResult()
381	<	throws InterruptedException, ExecutionException, TimeoutException {
382	<	Throwable ex;
383	<	int s = status & COMPLETION_MASK;
384	<	if (s == NORMAL)
385	<	return getRawResult();
386	<	if (s == CANCELLED)
387	<	throw new CancellationException();
388	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
389	<	throw new ExecutionException(ex);
390	<	if (Thread.interrupted())
391	<	throw new InterruptedException();
392	<	throw new TimeoutException();
393	<	}
394	<
395	<	// internal execution methods
396	<
397	<	/**
398	<	* Calls exec, recording completion, and rethrowing exception if
399	<	* encountered. Caller should normally check status before calling
400	<	* @return true if completed normally
401	<	*/
402	<	private boolean tryExec() {
403	<	try { // try block must contain only call to exec
404	<	if (!exec())
405	<	return false;
406	<	} catch (Throwable rex) {
407	<	setDoneExceptionally(rex);
408	<	rethrowException(rex);
409	<	return false; // not reached
410	<	}
411	<	setNormalCompletion();
412	<	return true;
413	<	}
414	<
415	<	/**
416	<	* Main execution method used by worker threads. Invokes
417	<	* base computation unless already complete
418	<	*/
419	<	final void quietlyExec() {
420	<	if (status >= 0) {
308	>	private int doInvoke() {
309	>	int stat;
310	>	if ((stat = status) >= 0) {
311	>	boolean completed;
312		try {
313	<	if (!exec())
314	<	return;
315	<	} catch(Throwable rex) {
425	<	setDoneExceptionally(rex);
426	<	return;
313	>	completed = exec();
314	>	} catch (Throwable rex) {
315	>	return setExceptionalCompletion(rex);
316		}
317	<	setNormalCompletion();
317	>	stat = completed ? setCompletion(NORMAL) : doJoin();
318		}
319	+	return stat;
320		}
321
322		/**
323	<	* Calls exec, recording but not rethrowing exception
324	<	* Caller should normally check status before calling
435	<	* @return true if completed normally
323	>	* Returns result or throws exception associated with given status.
324	>	* @param s the status
325		*/
326	<	private boolean tryQuietlyInvoke() {
327	<	try {
328	<	if (!exec())
329	<	return false;
330	<	} catch (Throwable rex) {
442	<	setDoneExceptionally(rex);
443	<	return false;
444	<	}
445	<	setNormalCompletion();
446	<	return true;
447	<	}
448	<
449	<	/**
450	<	* Cancel, ignoring any exceptions it throws
451	<	*/
452	<	final void cancelIgnoringExceptions() {
453	<	try {
454	<	cancel(false);
455	<	} catch(Throwable ignore) {
456	<	}
457	<	}
458	<
459	<	/**
460	<	* Main implementation of helpJoin
461	<	*/
462	<	private int busyJoin(ForkJoinWorkerThread w) {
463	<	int s;
464	<	ForkJoinTask<?> t;
465	<	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
466	<	t.quietlyExec();
467	<	return (s >= 0)? awaitDone(w, false) : s; // block if no work
326	>	private V reportResult(int s) {
327	>	Throwable ex;
328	>	if (s < NORMAL && (ex = getException()) != null)
329	>	UNSAFE.throwException(ex);
330	>	return getRawResult();
331		}
332
333		// public methods
#	Line 472 | Line 335 | public abstract class ForkJoinTask<V> im
335		/**
336		* Arranges to asynchronously execute this task.  While it is not
337		* necessarily enforced, it is a usage error to fork a task more
338	<	* than once unless it has completed and been reinitialized.  This
339	<	* method may be invoked only from within ForkJoinTask
340	<	* computations. Attempts to invoke in other contexts result in
341	<	* exceptions or errors possibly including ClassCastException.
338	>	* than once unless it has completed and been reinitialized.
339	>	* Subsequent modifications to the state of this task or any data
340	>	* it operates on are not necessarily consistently observable by
341	>	* any thread other than the one executing it unless preceded by a
342	>	* call to {@link #join} or related methods, or a call to {@link
343	>	* #isDone} returning {@code true}.
344	>	*
345	>	* <p>This method may be invoked only from within {@code
346	>	* ForkJoinTask} computations (as may be determined using method
347	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
348	>	* result in exceptions or errors, possibly including {@code
349	>	* ClassCastException}.
350	>	*
351	>	* @return {@code this}, to simplify usage
352		*/
353	<	public final void fork() {
354	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
353	>	public final ForkJoinTask<V> fork() {
354	>	((ForkJoinWorkerThread) Thread.currentThread())
355	>	.pushTask(this);
356	>	return this;
357		}
358
359		/**
360	<	* Returns the result of the computation when it is ready.
361	<	* This method differs from <code>get</code> in that abnormal
362	<	* completion results in RuntimeExceptions or Errors, not
363	<	* ExecutionExceptions.
360	>	* Returns the result of the computation when it {@link #isDone is done}.
361	>	* This method differs from {@link #get()} in that
362	>	* abnormal completion results in {@code RuntimeException} or
363	>	* {@code Error}, not {@code ExecutionException}.
364		*
365		* @return the computed result
366		*/
367		public final V join() {
368	<	ForkJoinWorkerThread w = getWorker();
494	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
495	<	reportException(awaitDone(w, true));
496	<	return getRawResult();
368	>	return reportResult(doJoin());
369		}
370
371		/**
372		* Commences performing this task, awaits its completion if
373	<	* necessary, and return its result.
374	<	* @throws Throwable (a RuntimeException, Error, or unchecked
375	<	* exception) if the underlying computation did so.
373	>	* necessary, and return its result, or throws an (unchecked)
374	>	* exception if the underlying computation did so.
375	>	*
376		* @return the computed result
377		*/
378		public final V invoke() {
379	<	if (status >= 0 && tryExec())
508	<	return getRawResult();
509	<	else
510	<	return join();
379	>	return reportResult(doInvoke());
380		}
381
382		/**
383	<	* Forks both tasks, returning when <code>isDone</code> holds for
384	<	* both of them or an exception is encountered. This method may be
385	<	* invoked only from within ForkJoinTask computations. Attempts to
386	<	* invoke in other contexts result in exceptions or errors
387	<	* possibly including ClassCastException.
388	<	* @param t1 one task
389	<	* @param t2 the other task
390	<	* @throws NullPointerException if t1 or t2 are null
391	<	* @throws RuntimeException or Error if either task did so.
383	>	* Forks the given tasks, returning when {@code isDone} holds for
384	>	* each task or an (unchecked) exception is encountered, in which
385	>	* case the exception is rethrown.  If either task encounters an
386	>	* exception, the other one may be, but is not guaranteed to be,
387	>	* cancelled.  If both tasks throw an exception, then this method
388	>	* throws one of them.  The individual status of each task may be
389	>	* checked using {@link #getException()} and related methods.
390	>	*
391	>	* <p>This method may be invoked only from within {@code
392	>	* ForkJoinTask} computations (as may be determined using method
393	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
394	>	* result in exceptions or errors, possibly including {@code
395	>	* ClassCastException}.
396	>	*
397	>	* @param t1 the first task
398	>	* @param t2 the second task
399	>	* @throws NullPointerException if any task is null
400		*/
401	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
401	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
402		t2.fork();
403		t1.invoke();
404		t2.join();
405		}
406
407		/**
408	<	* Forks the given tasks, returning when <code>isDone</code> holds
409	<	* for all of them. If any task encounters an exception, others
410	<	* may be cancelled.  This method may be invoked only from within
411	<	* ForkJoinTask computations. Attempts to invoke in other contexts
412	<	* result in exceptions or errors possibly including ClassCastException.
413	<	* @param tasks the array of tasks
414	<	* @throws NullPointerException if tasks or any element are null.
415	<	* @throws RuntimeException or Error if any task did so.
408	>	* Forks the given tasks, returning when {@code isDone} holds for
409	>	* each task or an (unchecked) exception is encountered, in which
410	>	* case the exception is rethrown. If any task encounters an
411	>	* exception, others may be, but are not guaranteed to be,
412	>	* cancelled.  If more than one task encounters an exception, then
413	>	* this method throws any one of these exceptions.  The individual
414	>	* status of each task may be checked using {@link #getException()}
415	>	* and related methods.
416	>	*
417	>	* <p>This method may be invoked only from within {@code
418	>	* ForkJoinTask} computations (as may be determined using method
419	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
420	>	* result in exceptions or errors, possibly including {@code
421	>	* ClassCastException}.
422	>	*
423	>	* @param tasks the tasks
424	>	* @throws NullPointerException if any task is null
425		*/
426		public static void invokeAll(ForkJoinTask<?>... tasks) {
427		Throwable ex = null;
#	Line 548 | Line 434 | public abstract class ForkJoinTask<V> im
434		}
435		else if (i != 0)
436		t.fork();
437	<	else {
438	<	t.quietlyInvoke();
553	<	if (ex == null)
554	<	ex = t.getException();
555	<	}
437	>	else if (t.doInvoke() < NORMAL && ex == null)
438	>	ex = t.getException();
439		}
440		for (int i = 1; i <= last; ++i) {
441		ForkJoinTask<?> t = tasks[i];
442		if (t != null) {
443		if (ex != null)
444		t.cancel(false);
445	<	else {
446	<	t.quietlyJoin();
564	<	if (ex == null)
565	<	ex = t.getException();
566	<	}
445	>	else if (t.doJoin() < NORMAL && ex == null)
446	>	ex = t.getException();
447		}
448		}
449		if (ex != null)
450	<	rethrowException(ex);
450	>	UNSAFE.throwException(ex);
451		}
452
453		/**
454	<	* Forks all tasks in the collection, returning when
455	<	* <code>isDone</code> holds for all of them. If any task
456	<	* encounters an exception, others may be cancelled.  This method
457	<	* may be invoked only from within ForkJoinTask
458	<	* computations. Attempts to invoke in other contexts resul!t in
459	<	* exceptions or errors possibly including ClassCastException.
454	>	* Forks all tasks in the specified collection, returning when
455	>	* {@code isDone} holds for each task or an (unchecked) exception
456	>	* is encountered.  If any task encounters an exception, others
457	>	* may be, but are not guaranteed to be, cancelled.  If more than
458	>	* one task encounters an exception, then this method throws any
459	>	* one of these exceptions.  The individual status of each task
460	>	* may be checked using {@link #getException()} and related
461	>	* methods.  The behavior of this operation is undefined if the
462	>	* specified collection is modified while the operation is in
463	>	* progress.
464	>	*
465	>	* <p>This method may be invoked only from within {@code
466	>	* ForkJoinTask} computations (as may be determined using method
467	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
468	>	* result in exceptions or errors, possibly including {@code
469	>	* ClassCastException}.
470	>	*
471		* @param tasks the collection of tasks
472	<	* @throws NullPointerException if tasks or any element are null.
473	<	* @throws RuntimeException or Error if any task did so.
472	>	* @return the tasks argument, to simplify usage
473	>	* @throws NullPointerException if tasks or any element are null
474		*/
475	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
476	<	if (!(tasks instanceof List)) {
477	<	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
478	<	return;
475	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
476	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
477	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
478	>	return tasks;
479		}
480	+	@SuppressWarnings("unchecked")
481		List<? extends ForkJoinTask<?>> ts =
482	<	(List<? extends ForkJoinTask<?>>)tasks;
482	>	(List<? extends ForkJoinTask<?>>) tasks;
483		Throwable ex = null;
484		int last = ts.size() - 1;
485		for (int i = last; i >= 0; --i) {
#	Line 598 | Line 490 | public abstract class ForkJoinTask<V> im
490		}
491		else if (i != 0)
492		t.fork();
493	<	else {
494	<	t.quietlyInvoke();
603	<	if (ex == null)
604	<	ex = t.getException();
605	<	}
493	>	else if (t.doInvoke() < NORMAL && ex == null)
494	>	ex = t.getException();
495		}
496		for (int i = 1; i <= last; ++i) {
497		ForkJoinTask<?> t = ts.get(i);
498		if (t != null) {
499		if (ex != null)
500		t.cancel(false);
501	<	else {
502	<	t.quietlyJoin();
614	<	if (ex == null)
615	<	ex = t.getException();
616	<	}
501	>	else if (t.doJoin() < NORMAL && ex == null)
502	>	ex = t.getException();
503		}
504		}
505		if (ex != null)
506	<	rethrowException(ex);
507	<	}
622	<
623	<	/**
624	<	* Returns true if the computation performed by this task has
625	<	* completed (or has been cancelled).
626	<	* @return true if this computation has completed
627	<	*/
628	<	public final boolean isDone() {
629	<	return status < 0;
630	<	}
631	<
632	<	/**
633	<	* Returns true if this task was cancelled.
634	<	* @return true if this task was cancelled
635	<	*/
636	<	public final boolean isCancelled() {
637	<	return (status & COMPLETION_MASK) == CANCELLED;
506	>	UNSAFE.throwException(ex);
507	>	return tasks;
508		}
509
510		/**
511	<	* Asserts that the results of this task's computation will not be
512	<	* used. If a cancellation occurs before atempting to execute this
513	<	* task, then execution will be suppressed, <code>isCancelled</code>
514	<	* will report true, and <code>join</code> will result in a
515	<	* <code>CancellationException</code> being thrown. Otherwise, when
516	<	* cancellation races with completion, there are no guarantees
517	<	* about whether <code>isCancelled</code> will report true, whether
648	<	* <code>join</code> will return normally or via an exception, or
649	<	* whether these behaviors will remain consistent upon repeated
650	<	* invocation.
511	>	* Attempts to cancel execution of this task. This attempt will
512	>	* fail if the task has already completed, has already been
513	>	* cancelled, or could not be cancelled for some other reason. If
514	>	* successful, and this task has not started when cancel is
515	>	* called, execution of this task is suppressed, {@link
516	>	* #isCancelled} will report true, and {@link #join} will result
517	>	* in a {@code CancellationException} being thrown.
518		*
519		* <p>This method may be overridden in subclasses, but if so, must
520		* still ensure that these minimal properties hold. In particular,
521	<	* the cancel method itself must not throw exceptions.
521	>	* the {@code cancel} method itself must not throw exceptions.
522		*
523	<	* <p> This method is designed to be invoked by <em>other</em>
523	>	* <p>This method is designed to be invoked by <em>other</em>
524		* tasks. To terminate the current task, you can just return or
525		* throw an unchecked exception from its computation method, or
526	<	* invoke <code>completeExceptionally</code>.
526	>	* invoke {@link #completeExceptionally}.
527		*
528		* @param mayInterruptIfRunning this value is ignored in the
529	<	* default implementation because tasks are not in general
530	<	* cancelled via interruption.
529	>	* default implementation because tasks are not
530	>	* cancelled via interruption
531		*
532	<	* @return true if this task is now cancelled
532	>	* @return {@code true} if this task is now cancelled
533		*/
534		public boolean cancel(boolean mayInterruptIfRunning) {
535	<	setCompletion(CANCELLED);
536	<	return (status & COMPLETION_MASK) == CANCELLED;
535	>	return setCompletion(CANCELLED) == CANCELLED;
536	>	}
537	>
538	>	/**
539	>	* Cancels, ignoring any exceptions it throws. Used during worker
540	>	* and pool shutdown.
541	>	*/
542	>	final void cancelIgnoringExceptions() {
543	>	try {
544	>	cancel(false);
545	>	} catch (Throwable ignore) {
546	>	}
547		}
548
549		/**
550	<	* Returns true if this task threw an exception or was cancelled
551	<	* @return true if this task threw an exception or was cancelled
550	>	* Cancels ignoring exceptions if worker is terminating
551	>	*/
552	>	final void cancelIfTerminating() {
553	>	Thread t = Thread.currentThread();
554	>	if ((t instanceof ForkJoinWorkerThread) &&
555	>	((ForkJoinWorkerThread) t).isTerminating()) {
556	>	try {
557	>	cancel(false);
558	>	} catch (Throwable ignore) {
559	>	}
560	>	}
561	>	}
562	>
563	>	public final boolean isDone() {
564	>	return status < 0;
565	>	}
566	>
567	>	public final boolean isCancelled() {
568	>	return status == CANCELLED;
569	>	}
570	>
571	>	/**
572	>	* Returns {@code true} if this task threw an exception or was cancelled.
573	>	*
574	>	* @return {@code true} if this task threw an exception or was cancelled
575		*/
576		public final boolean isCompletedAbnormally() {
577	<	return (status & COMPLETION_MASK) < NORMAL;
577	>	return status < NORMAL;
578	>	}
579	>
580	>	/**
581	>	* Returns {@code true} if this task completed without throwing an
582	>	* exception and was not cancelled.
583	>	*
584	>	* @return {@code true} if this task completed without throwing an
585	>	* exception and was not cancelled
586	>	*/
587	>	public final boolean isCompletedNormally() {
588	>	return status == NORMAL;
589		}
590
591		/**
592		* Returns the exception thrown by the base computation, or a
593	<	* CancellationException if cancelled, or null if none or if the
594	<	* method has not yet completed.
595	<	* @return the exception, or null if none
593	>	* {@code CancellationException} if cancelled, or {@code null} if
594	>	* none or if the method has not yet completed.
595	>	*
596	>	* @return the exception, or {@code null} if none
597		*/
598		public final Throwable getException() {
599	<	int s = status & COMPLETION_MASK;
600	<	if (s >= NORMAL)
601	<	return null;
602	<	if (s == CANCELLED)
691	<	return new CancellationException();
692	<	return exceptionMap.get(this);
599	>	int s = status;
600	>	return ((s >= NORMAL)    ? null :
601	>	(s == CANCELLED) ? new CancellationException() :
602	>	exceptionMap.get(this));
603		}
604
605		/**
606		* Completes this task abnormally, and if not already aborted or
607		* cancelled, causes it to throw the given exception upon
608	<	* <code>join</code> and related operations. This method may be used
608	>	* {@code join} and related operations. This method may be used
609		* to induce exceptions in asynchronous tasks, or to force
610		* completion of tasks that would not otherwise complete.  Its use
611	<	* in other situations is likely to be wrong.  This method is
612	<	* overridable, but overridden versions must invoke <code>super</code>
611	>	* in other situations is discouraged.  This method is
612	>	* overridable, but overridden versions must invoke {@code super}
613		* implementation to maintain guarantees.
614		*
615	<	* @param ex the exception to throw. If this exception is
616	<	* not a RuntimeException or Error, the actual exception thrown
617	<	* will be a RuntimeException with cause ex.
615	>	* @param ex the exception to throw. If this exception is not a
616	>	* {@code RuntimeException} or {@code Error}, the actual exception
617	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
618		*/
619		public void completeExceptionally(Throwable ex) {
620	<	setDoneExceptionally((ex instanceof RuntimeException) ||
621	<	(ex instanceof Error)? ex :
622	<	new RuntimeException(ex));
620	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
621	>	(ex instanceof Error) ? ex :
622	>	new RuntimeException(ex));
623		}
624
625		/**
626		* Completes this task, and if not already aborted or cancelled,
627	<	* returning a <code>null</code> result upon <code>join</code> and related
627	>	* returning a {@code null} result upon {@code join} and related
628		* operations. This method may be used to provide results for
629		* asynchronous tasks, or to provide alternative handling for
630		* tasks that would not otherwise complete normally. Its use in
631	<	* other situations is likely to be wrong. This method is
632	<	* overridable, but overridden versions must invoke <code>super</code>
631	>	* other situations is discouraged. This method is
632	>	* overridable, but overridden versions must invoke {@code super}
633		* implementation to maintain guarantees.
634		*
635	<	* @param value the result value for this task.
635	>	* @param value the result value for this task
636		*/
637		public void complete(V value) {
638		try {
639		setRawResult(value);
640	<	} catch(Throwable rex) {
641	<	setDoneExceptionally(rex);
640	>	} catch (Throwable rex) {
641	>	setExceptionalCompletion(rex);
642		return;
643		}
644	<	setNormalCompletion();
644	>	setCompletion(NORMAL);
645		}
646
647		public final V get() throws InterruptedException, ExecutionException {
648	<	ForkJoinWorkerThread w = getWorker();
649	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
650	<	awaitDone(w, true);
651	<	return reportFutureResult();
648	>	int s = doJoin();
649	>	if (Thread.interrupted())
650	>	throw new InterruptedException();
651	>	if (s < NORMAL) {
652	>	Throwable ex;
653	>	if (s == CANCELLED)
654	>	throw new CancellationException();
655	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
656	>	throw new ExecutionException(ex);
657	>	}
658	>	return getRawResult();
659		}
660
661		public final V get(long timeout, TimeUnit unit)
662		throws InterruptedException, ExecutionException, TimeoutException {
663	<	ForkJoinWorkerThread w = getWorker();
664	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
665	<	awaitDone(w, unit.toNanos(timeout));
666	<	return reportTimedFutureResult();
667	<	}
668	<
669	<	/**
670	<	* Possibly executes other tasks until this task is ready, then
671	<	* returns the result of the computation.  This method may be more
672	<	* efficient than <code>join</code>, but is only applicable when
673	<	* there are no potemtial dependencies between continuation of the
674	<	* current task and that of any other task that might be executed
675	<	* while helping. (This usually holds for pure divide-and-conquer
676	<	* tasks). This method may be invoked only from within
677	<	* ForkJoinTask computations. Attempts to invoke in other contexts
678	<	* resul!t in exceptions or errors possibly including ClassCastException.
679	<	* @return the computed result
680	<	*/
681	<	public final V helpJoin() {
682	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
683	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
684	<	reportException(busyJoin(w));
685	<	return getRawResult();
686	<	}
687	<
688	<	/**
689	<	* Possibly executes other tasks until this task is ready.  This
690	<	* method may be invoked only from within ForkJoinTask
691	<	* computations. Attempts to invoke in other contexts resul!t in
692	<	* exceptions or errors possibly including ClassCastException.
693	<	*/
694	<	public final void quietlyHelpJoin() {
695	<	if (status >= 0) {
696	<	ForkJoinWorkerThread w =
697	<	(ForkJoinWorkerThread)(Thread.currentThread());
698	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
699	<	busyJoin(w);
663	>	Thread t = Thread.currentThread();
664	>	ForkJoinPool pool;
665	>	if (t instanceof ForkJoinWorkerThread) {
666	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
667	>	if (status >= 0 && w.unpushTask(this))
668	>	tryExec();
669	>	pool = w.pool;
670	>	}
671	>	else
672	>	pool = null;
673	>	/*
674	>	* Timed wait loop intermixes cases for fj (pool != null) and
675	>	* non FJ threads. For FJ, decrement pool count but don't try
676	>	* for replacement; increment count on completion. For non-FJ,
677	>	* deal with interrupts. This is messy, but a little less so
678	>	* than is splitting the FJ and nonFJ cases.
679	>	*/
680	>	boolean interrupted = false;
681	>	boolean dec = false; // true if pool count decremented
682	>	for (;;) {
683	>	if (Thread.interrupted() && pool == null) {
684	>	interrupted = true;
685	>	break;
686	>	}
687	>	int s = status;
688	>	if (s < 0)
689	>	break;
690	>	if (UNSAFE.compareAndSwapInt(this, statusOffset,
691	>	s, s | SIGNAL)) {
692	>	long startTime = System.nanoTime();
693	>	long nanos = unit.toNanos(timeout);
694	>	long nt; // wait time
695	>	while (status >= 0 &&
696	>	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
697	>	if (pool != null && !dec)
698	>	dec = pool.tryDecrementRunningCount();
699	>	else {
700	>	long ms = nt / 1000000;
701	>	int ns = (int) (nt % 1000000);
702	>	try {
703	>	synchronized(this) {
704	>	if (status >= 0)
705	>	wait(ms, ns);
706	>	}
707	>	} catch (InterruptedException ie) {
708	>	if (pool != null)
709	>	cancelIfTerminating();
710	>	else {
711	>	interrupted = true;
712	>	break;
713	>	}
714	>	}
715	>	}
716	>	}
717	>	break;
718	>	}
719		}
720	+	if (pool != null && dec)
721	+	pool.incrementRunningCount();
722	+	if (interrupted)
723	+	throw new InterruptedException();
724	+	int es = status;
725	+	if (es != NORMAL) {
726	+	Throwable ex;
727	+	if (es == CANCELLED)
728	+	throw new CancellationException();
729	+	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
730	+	throw new ExecutionException(ex);
731	+	throw new TimeoutException();
732	+	}
733	+	return getRawResult();
734		}
735
736		/**
#	Line 790 | Line 740 | public abstract class ForkJoinTask<V> im
740		* known to have aborted.
741		*/
742		public final void quietlyJoin() {
743	<	if (status >= 0) {
794	<	ForkJoinWorkerThread w = getWorker();
795	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
796	<	awaitDone(w, true);
797	<	}
743	>	doJoin();
744		}
745
746		/**
#	Line 805 | Line 751 | public abstract class ForkJoinTask<V> im
751		* known to have aborted.
752		*/
753		public final void quietlyInvoke() {
754	<	if (status >= 0 && !tryQuietlyInvoke())
809	<	quietlyJoin();
754	>	doInvoke();
755		}
756
757		/**
758		* Possibly executes tasks until the pool hosting the current task
759	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
760	<	* designs in which many tasks are forked, but none are explicitly
761	<	* joined, instead executing them until all are processed.
759	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
760	>	* be of use in designs in which many tasks are forked, but none
761	>	* are explicitly joined, instead executing them until all are
762	>	* processed.
763	>	*
764	>	* <p>This method may be invoked only from within {@code
765	>	* ForkJoinTask} computations (as may be determined using method
766	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
767	>	* result in exceptions or errors, possibly including {@code
768	>	* ClassCastException}.
769		*/
770		public static void helpQuiesce() {
771	<	((ForkJoinWorkerThread)(Thread.currentThread())).
772	<	helpQuiescePool();
771	>	((ForkJoinWorkerThread) Thread.currentThread())
772	>	.helpQuiescePool();
773		}
774
775		/**
776		* Resets the internal bookkeeping state of this task, allowing a
777	<	* subsequent <code>fork</code>. This method allows repeated reuse of
777	>	* subsequent {@code fork}. This method allows repeated reuse of
778		* this task, but only if reuse occurs when this task has either
779		* never been forked, or has been forked, then completed and all
780		* outstanding joins of this task have also completed. Effects
781	<	* under any other usage conditions are not guaranteed, and are
782	<	* almost surely wrong. This method may be useful when executing
781	>	* under any other usage conditions are not guaranteed.
782	>	* This method may be useful when executing
783		* pre-constructed trees of subtasks in loops.
784		*/
785		public void reinitialize() {
786	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
786	>	if (status == EXCEPTIONAL)
787		exceptionMap.remove(this);
788		status = 0;
789		}
790
791		/**
792		* Returns the pool hosting the current task execution, or null
793	<	* if this task is executing outside of any pool.
794	<	* @return the pool, or null if none.
793	>	* if this task is executing outside of any ForkJoinPool.
794	>	*
795	>	* @see #inForkJoinPool
796	>	* @return the pool, or {@code null} if none
797		*/
798		public static ForkJoinPool getPool() {
799		Thread t = Thread.currentThread();
800	<	return ((t instanceof ForkJoinWorkerThread)?
801	<	((ForkJoinWorkerThread)t).pool : null);
800	>	return (t instanceof ForkJoinWorkerThread) ?
801	>	((ForkJoinWorkerThread) t).pool : null;
802	>	}
803	>
804	>	/**
805	>	* Returns {@code true} if the current thread is executing as a
806	>	* ForkJoinPool computation.
807	>	*
808	>	* @return {@code true} if the current thread is executing as a
809	>	* ForkJoinPool computation, or false otherwise
810	>	*/
811	>	public static boolean inForkJoinPool() {
812	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
813		}
814
815		/**
#	Line 853 | Line 818 | public abstract class ForkJoinTask<V> im
818		* by the current thread, and has not commenced executing in
819		* another thread.  This method may be useful when arranging
820		* alternative local processing of tasks that could have been, but
821	<	* were not, stolen. This method may be invoked only from within
822	<	* ForkJoinTask computations. Attempts to invoke in other contexts
823	<	* result in exceptions or errors possibly including ClassCastException.
824	<	* @return true if unforked
821	>	* were not, stolen.
822	>	*
823	>	* <p>This method may be invoked only from within {@code
824	>	* ForkJoinTask} computations (as may be determined using method
825	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
826	>	* result in exceptions or errors, possibly including {@code
827	>	* ClassCastException}.
828	>	*
829	>	* @return {@code true} if unforked
830		*/
831		public boolean tryUnfork() {
832	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
832	>	return ((ForkJoinWorkerThread) Thread.currentThread())
833	>	.unpushTask(this);
834		}
835
836		/**
#	Line 867 | Line 838 | public abstract class ForkJoinTask<V> im
838		* forked by the current worker thread but not yet executed. This
839		* value may be useful for heuristic decisions about whether to
840		* fork other tasks.
841	+	*
842	+	* <p>This method may be invoked only from within {@code
843	+	* ForkJoinTask} computations (as may be determined using method
844	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
845	+	* result in exceptions or errors, possibly including {@code
846	+	* ClassCastException}.
847	+	*
848		* @return the number of tasks
849		*/
850		public static int getQueuedTaskCount() {
851	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
852	<	getQueueSize();
851	>	return ((ForkJoinWorkerThread) Thread.currentThread())
852	>	.getQueueSize();
853		}
854
855		/**
856	<	* Returns a estimate of how many more locally queued tasks are
856	>	* Returns an estimate of how many more locally queued tasks are
857		* held by the current worker thread than there are other worker
858		* threads that might steal them.  This value may be useful for
859		* heuristic decisions about whether to fork other tasks. In many
#	Line 883 | Line 861 | public abstract class ForkJoinTask<V> im
861		* aim to maintain a small constant surplus (for example, 3) of
862		* tasks, and to process computations locally if this threshold is
863		* exceeded.
864	+	*
865	+	* <p>This method may be invoked only from within {@code
866	+	* ForkJoinTask} computations (as may be determined using method
867	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
868	+	* result in exceptions or errors, possibly including {@code
869	+	* ClassCastException}.
870	+	*
871		* @return the surplus number of tasks, which may be negative
872		*/
873		public static int getSurplusQueuedTaskCount() {
874	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
874	>	return ((ForkJoinWorkerThread) Thread.currentThread())
875		.getEstimatedSurplusTaskCount();
876		}
877
878		// Extension methods
879
880		/**
881	<	* Returns the result that would be returned by <code>join</code>,
882	<	* even if this task completed abnormally, or null if this task is
883	<	* not known to have been completed.  This method is designed to
884	<	* aid debugging, as well as to support extensions. Its use in any
885	<	* other context is discouraged.
881	>	* Returns the result that would be returned by {@link #join}, even
882	>	* if this task completed abnormally, or {@code null} if this task
883	>	* is not known to have been completed.  This method is designed
884	>	* to aid debugging, as well as to support extensions. Its use in
885	>	* any other context is discouraged.
886		*
887	<	* @return the result, or null if not completed.
887	>	* @return the result, or {@code null} if not completed
888		*/
889		public abstract V getRawResult();
890
#	Line 918 | Line 903 | public abstract class ForkJoinTask<V> im
903		* called otherwise. The return value controls whether this task
904		* is considered to be done normally. It may return false in
905		* asynchronous actions that require explicit invocations of
906	<	* <code>complete</code> to become joinable. It may throw exceptions
907	<	* to indicate abnormal exit.
908	<	* @return true if completed normally
909	<	* @throws Error or RuntimeException if encountered during computation
906	>	* {@link #complete} to become joinable. It may also throw an
907	>	* (unchecked) exception to indicate abnormal exit.
908	>	*
909	>	* @return {@code true} if completed normally
910		*/
911		protected abstract boolean exec();
912
913		/**
914	<	* Returns, but does not unschedule or execute, the task queued by
915	<	* the current thread but not yet executed, if one is
914	>	* Returns, but does not unschedule or execute, a task queued by
915	>	* the current thread but not yet executed, if one is immediately
916		* available. There is no guarantee that this task will actually
917	<	* be polled or executed next.  This method is designed primarily
918	<	* to support extensions, and is unlikely to be useful otherwise.
919	<	* This method may be invoked only from within ForkJoinTask
920	<	* computations. Attempts to invoke in other contexts result in
921	<	* exceptions or errors possibly including ClassCastException.
917	>	* be polled or executed next. Conversely, this method may return
918	>	* null even if a task exists but cannot be accessed without
919	>	* contention with other threads.  This method is designed
920	>	* primarily to support extensions, and is unlikely to be useful
921	>	* otherwise.
922	>	*
923	>	* <p>This method may be invoked only from within {@code
924	>	* ForkJoinTask} computations (as may be determined using method
925	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
926	>	* result in exceptions or errors, possibly including {@code
927	>	* ClassCastException}.
928		*
929	<	* @return the next task, or null if none are available
929	>	* @return the next task, or {@code null} if none are available
930		*/
931		protected static ForkJoinTask<?> peekNextLocalTask() {
932	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask();
932	>	return ((ForkJoinWorkerThread) Thread.currentThread())
933	>	.peekTask();
934		}
935
936		/**
937		* Unschedules and returns, without executing, the next task
938		* queued by the current thread but not yet executed.  This method
939		* is designed primarily to support extensions, and is unlikely to
940	<	* be useful otherwise.  This method may be invoked only from
949	<	* within ForkJoinTask computations. Attempts to invoke in other
950	<	* contexts result in exceptions or errors possibly including
951	<	* ClassCastException.
940	>	* be useful otherwise.
941		*
942	<	* @return the next task, or null if none are available
942	>	* <p>This method may be invoked only from within {@code
943	>	* ForkJoinTask} computations (as may be determined using method
944	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
945	>	* result in exceptions or errors, possibly including {@code
946	>	* ClassCastException}.
947	>	*
948	>	* @return the next task, or {@code null} if none are available
949		*/
950		protected static ForkJoinTask<?> pollNextLocalTask() {
951	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).pollLocalTask();
951	>	return ((ForkJoinWorkerThread) Thread.currentThread())
952	>	.pollLocalTask();
953		}
954
955		/**
#	Line 961 | Line 957 | public abstract class ForkJoinTask<V> im
957		* queued by the current thread but not yet executed, if one is
958		* available, or if not available, a task that was forked by some
959		* other thread, if available. Availability may be transient, so a
960	<	* <code>null</code> result does not necessarily imply quiecence
960	>	* {@code null} result does not necessarily imply quiescence
961		* of the pool this task is operating in.  This method is designed
962		* primarily to support extensions, and is unlikely to be useful
963	<	* otherwise.  This method may be invoked only from within
964	<	* ForkJoinTask computations. Attempts to invoke in other contexts
965	<	* result in exceptions or errors possibly including
966	<	* ClassCastException.
963	>	* otherwise.
964	>	*
965	>	* <p>This method may be invoked only from within {@code
966	>	* ForkJoinTask} computations (as may be determined using method
967	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
968	>	* result in exceptions or errors, possibly including {@code
969	>	* ClassCastException}.
970		*
971	<	* @return a task, or null if none are available
971	>	* @return a task, or {@code null} if none are available
972		*/
973		protected static ForkJoinTask<?> pollTask() {
974	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
975	<	pollTask();
974	>	return ((ForkJoinWorkerThread) Thread.currentThread())
975	>	.pollTask();
976	>	}
977	>
978	>	/**
979	>	* Adaptor for Runnables. This implements RunnableFuture
980	>	* to be compliant with AbstractExecutorService constraints
981	>	* when used in ForkJoinPool.
982	>	*/
983	>	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
984	>	implements RunnableFuture<T> {
985	>	final Runnable runnable;
986	>	final T resultOnCompletion;
987	>	T result;
988	>	AdaptedRunnable(Runnable runnable, T result) {
989	>	if (runnable == null) throw new NullPointerException();
990	>	this.runnable = runnable;
991	>	this.resultOnCompletion = result;
992	>	}
993	>	public T getRawResult() { return result; }
994	>	public void setRawResult(T v) { result = v; }
995	>	public boolean exec() {
996	>	runnable.run();
997	>	result = resultOnCompletion;
998	>	return true;
999	>	}
1000	>	public void run() { invoke(); }
1001	>	private static final long serialVersionUID = 5232453952276885070L;
1002	>	}
1003	>
1004	>	/**
1005	>	* Adaptor for Callables
1006	>	*/
1007	>	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1008	>	implements RunnableFuture<T> {
1009	>	final Callable<? extends T> callable;
1010	>	T result;
1011	>	AdaptedCallable(Callable<? extends T> callable) {
1012	>	if (callable == null) throw new NullPointerException();
1013	>	this.callable = callable;
1014	>	}
1015	>	public T getRawResult() { return result; }
1016	>	public void setRawResult(T v) { result = v; }
1017	>	public boolean exec() {
1018	>	try {
1019	>	result = callable.call();
1020	>	return true;
1021	>	} catch (Error err) {
1022	>	throw err;
1023	>	} catch (RuntimeException rex) {
1024	>	throw rex;
1025	>	} catch (Exception ex) {
1026	>	throw new RuntimeException(ex);
1027	>	}
1028	>	}
1029	>	public void run() { invoke(); }
1030	>	private static final long serialVersionUID = 2838392045355241008L;
1031	>	}
1032	>
1033	>	/**
1034	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1035	>	* method of the given {@code Runnable} as its action, and returns
1036	>	* a null result upon {@link #join}.
1037	>	*
1038	>	* @param runnable the runnable action
1039	>	* @return the task
1040	>	*/
1041	>	public static ForkJoinTask<?> adapt(Runnable runnable) {
1042	>	return new AdaptedRunnable<Void>(runnable, null);
1043	>	}
1044	>
1045	>	/**
1046	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1047	>	* method of the given {@code Runnable} as its action, and returns
1048	>	* the given result upon {@link #join}.
1049	>	*
1050	>	* @param runnable the runnable action
1051	>	* @param result the result upon completion
1052	>	* @return the task
1053	>	*/
1054	>	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1055	>	return new AdaptedRunnable<T>(runnable, result);
1056	>	}
1057	>
1058	>	/**
1059	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1060	>	* method of the given {@code Callable} as its action, and returns
1061	>	* its result upon {@link #join}, translating any checked exceptions
1062	>	* encountered into {@code RuntimeException}.
1063	>	*
1064	>	* @param callable the callable action
1065	>	* @return the task
1066	>	*/
1067	>	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1068	>	return new AdaptedCallable<T>(callable);
1069		}
1070
1071		// Serialization support
#	Line 981 | Line 1073 | public abstract class ForkJoinTask<V> im
1073		private static final long serialVersionUID = -7721805057305804111L;
1074
1075		/**
1076	<	* Save the state to a stream.
1076	>	* Saves the state to a stream.
1077		*
1078		* @serialData the current run status and the exception thrown
1079	<	* during execution, or null if none.
1079	>	* during execution, or {@code null} if none
1080		* @param s the stream
1081		*/
1082		private void writeObject(java.io.ObjectOutputStream s)
#	Line 994 | Line 1086 | public abstract class ForkJoinTask<V> im
1086		}
1087
1088		/**
1089	<	* Reconstitute the instance from a stream.
1089	>	* Reconstitutes the instance from a stream.
1090	>	*
1091		* @param s the stream
1092		*/
1093		private void readObject(java.io.ObjectInputStream s)
1094		throws java.io.IOException, ClassNotFoundException {
1095		s.defaultReadObject();
1003	–	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1004	–	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1096		Object ex = s.readObject();
1097		if (ex != null)
1098	<	setDoneExceptionally((Throwable)ex);
1098	>	setExceptionalCompletion((Throwable) ex);
1099		}
1100
1101	<	// Temporary Unsafe mechanics for preliminary release
1102	<	private static Unsafe getUnsafe() throws Throwable {
1101	>	// Unsafe mechanics
1102	>
1103	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1104	>	private static final long statusOffset =
1105	>	objectFieldOffset("status", ForkJoinTask.class);
1106	>
1107	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1108		try {
1109	<	return Unsafe.getUnsafe();
1109	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1110	>	} catch (NoSuchFieldException e) {
1111	>	// Convert Exception to corresponding Error
1112	>	NoSuchFieldError error = new NoSuchFieldError(field);
1113	>	error.initCause(e);
1114	>	throw error;
1115	>	}
1116	>	}
1117	>
1118	>	/**
1119	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1120	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1121	>	* into a jdk.
1122	>	*
1123	>	* @return a sun.misc.Unsafe
1124	>	*/
1125	>	private static sun.misc.Unsafe getUnsafe() {
1126	>	try {
1127	>	return sun.misc.Unsafe.getUnsafe();
1128		} catch (SecurityException se) {
1129		try {
1130		return java.security.AccessController.doPrivileged
1131	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1132	<	public Unsafe run() throws Exception {
1133	<	return getUnsafePrivileged();
1131	>	(new java.security
1132	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1133	>	public sun.misc.Unsafe run() throws Exception {
1134	>	java.lang.reflect.Field f = sun.misc
1135	>	.Unsafe.class.getDeclaredField("theUnsafe");
1136	>	f.setAccessible(true);
1137	>	return (sun.misc.Unsafe) f.get(null);
1138		}});
1139		} catch (java.security.PrivilegedActionException e) {
1140	<	throw e.getCause();
1140	>	throw new RuntimeException("Could not initialize intrinsics",
1141	>	e.getCause());
1142		}
1143		}
1144		}
1026	–
1027	–	private static Unsafe getUnsafePrivileged()
1028	–	throws NoSuchFieldException, IllegalAccessException {
1029	–	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1030	–	f.setAccessible(true);
1031	–	return (Unsafe) f.get(null);
1032	–	}
1033	–
1034	–	private static long fieldOffset(String fieldName)
1035	–	throws NoSuchFieldException {
1036	–	return _unsafe.objectFieldOffset
1037	–	(ForkJoinTask.class.getDeclaredField(fieldName));
1038	–	}
1039	–
1040	–	static final Unsafe _unsafe;
1041	–	static final long statusOffset;
1042	–
1043	–	static {
1044	–	try {
1045	–	_unsafe = getUnsafe();
1046	–	statusOffset = fieldOffset("status");
1047	–	} catch (Throwable e) {
1048	–	throw new RuntimeException("Could not initialize intrinsics", e);
1049	–	}
1050	–	}
1051	–
1145		}

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