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Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.1 by dl, Tue Jan 6 14:30:31 2009 UTC vs.
Revision 1.86 by dl, Mon Feb 20 18:20:06 2012 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Doug Lea with assistance from members of JCP JSR-166
3		* Expert Group and released to the public domain, as explained at
4	<	* http://creativecommons.org/licenses/publicdomain
4	>	* http://creativecommons.org/publicdomain/zero/1.0/
5		*/
6
7		package jsr166y;
8		import java.io.Serializable;
9	<	import java.util.*;
10	<	import java.util.concurrent.*;
11	<	import java.util.concurrent.atomic.*;
12	<	import sun.misc.Unsafe;
13	<	import java.lang.reflect.*;
9	>	import java.util.Collection;
10	>	import java.util.List;
11	>	import java.util.RandomAccess;
12	>	import java.lang.ref.WeakReference;
13	>	import java.lang.ref.ReferenceQueue;
14	>	import java.util.concurrent.Callable;
15	>	import java.util.concurrent.CancellationException;
16	>	import java.util.concurrent.ExecutionException;
17	>	import java.util.concurrent.Future;
18	>	import java.util.concurrent.RejectedExecutionException;
19	>	import java.util.concurrent.RunnableFuture;
20	>	import java.util.concurrent.TimeUnit;
21	>	import java.util.concurrent.TimeoutException;
22	>	import java.util.concurrent.locks.ReentrantLock;
23	>	import java.lang.reflect.Constructor;
24
25		/**
26	<	* Abstract base class for tasks that run within a ForkJoinPool.  A
27	<	* ForkJoinTask is a thread-like entity that is much lighter weight
28	<	* than a normal thread.  Huge numbers of tasks and subtasks may be
29	<	* hosted by a small number of actual threads in a ForkJoinPool,
30	<	* at the price of some usage limitations.
31	<	*
32	<	* <p> ForkJoinTasks are forms of <tt>Futures</tt> supporting a
33	<	* limited range of use.  The "lightness" of ForkJoinTasks is due to a
34	<	* set of restrictions (that are only partially statically
35	<	* enforceable) reflecting their intended use as computational tasks
36	<	* calculating pure functions or operating on purely isolated objects.
37	<	* The primary coordination mechanisms supported for ForkJoinTasks are
38	<	* <tt>fork</tt>, that arranges asynchronous execution, and
39	<	* <tt>join</tt>, that doesn't proceed until the task's result has
40	<	* been computed. (Cancellation is also supported).  The computation
41	<	* defined in the <tt>compute</tt> method should avoid
42	<	* <tt>synchronized</tt> methods or blocks, and should minimize
43	<	* blocking synchronization apart from joining other tasks or using
44	<	* synchronizers such as Phasers that are advertised to cooperate with
45	<	* fork/join scheduling. Tasks should also not perform blocking IO,
46	<	* and should ideally access variables that are completely independent
47	<	* of those accessed by other running tasks. Minor breaches of these
48	<	* restrictions, for example using shared output streams, may be
49	<	* tolerable in practice, but frequent use may result in poor
50	<	* performance, and the potential to indefinitely stall if the number
51	<	* of threads not waiting for external synchronization becomes
52	<	* exhausted. This usage restriction is in part enforced by not
53	<	* permitting checked exceptions such as IOExceptions to be
26	>	* Abstract base class for tasks that run within a {@link ForkJoinPool}.
27	>	* A {@code ForkJoinTask} is a thread-like entity that is much
28	>	* lighter weight than a normal thread.  Huge numbers of tasks and
29	>	* subtasks may be hosted by a small number of actual threads in a
30	>	* ForkJoinPool, at the price of some usage limitations.
31	>	*
32	>	* <p>A "main" {@code ForkJoinTask} begins execution when submitted
33	>	* to a {@link ForkJoinPool}.  Once started, it will usually in turn
34	>	* start other subtasks.  As indicated by the name of this class,
35	>	* many programs using {@code ForkJoinTask} employ only methods
36	>	* {@link #fork} and {@link #join}, or derivatives such as {@link
37	>	* #invokeAll(ForkJoinTask...) invokeAll}.  However, this class also
38	>	* provides a number of other methods that can come into play in
39	>	* advanced usages, as well as extension mechanics that allow
40	>	* support of new forms of fork/join processing.
41	>	*
42	>	* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
43	>	* The efficiency of {@code ForkJoinTask}s stems from a set of
44	>	* restrictions (that are only partially statically enforceable)
45	>	* reflecting their main use as computational tasks calculating pure
46	>	* functions or operating on purely isolated objects.  The primary
47	>	* coordination mechanisms are {@link #fork}, that arranges
48	>	* asynchronous execution, and {@link #join}, that doesn't proceed
49	>	* until the task's result has been computed.  Computations should
50	>	* ideally avoid {@code synchronized} methods or blocks, and should
51	>	* minimize other blocking synchronization apart from joining other
52	>	* tasks or using synchronizers such as Phasers that are advertised to
53	>	* cooperate with fork/join scheduling. Subdividable tasks should also
54	>	* not perform blocking IO, and should ideally access variables that
55	>	* are completely independent of those accessed by other running
56	>	* tasks. These guidelines are loosely enforced by not permitting
57	>	* checked exceptions such as {@code IOExceptions} to be
58		* thrown. However, computations may still encounter unchecked
59	<	* exceptions, that are rethrown to callers attempting join
60	<	* them. These exceptions may additionally include
61	<	* RejectedExecutionExceptions stemming from internal resource
62	<	* exhaustion such as failure to allocate internal task queues.
63	<	*
64	<	* <p> The <tt>ForkJoinTask</tt> class is not usually directly
65	<	* subclassed.  Instead, you subclass one of the abstract classes that
66	<	* support different styles of fork/join processing.  Normally, a
67	<	* concrete ForkJoinTask subclass declares fields comprising its
68	<	* parameters, established in a constructor, and then defines a
69	<	* <tt>compute</tt> method that somehow uses the control methods
70	<	* supplied by this base class. While these methods have
71	<	* <tt>public</tt> access, some of them may only be called from within
72	<	* other ForkJoinTasks. Attempts to invoke them in other contexts
73	<	* result in exceptions or errors including ClassCastException.  The
74	<	* only way to invoke a "main" driver task is to submit it to a
75	<	* ForkJoinPool. Once started, this will usually in turn start other
76	<	* subtasks.
77	<	*
78	<	* <p>Most base support methods are <tt>final</tt> because their
79	<	* implementations are intrinsically tied to the underlying
80	<	* lightweight task scheduling framework, and so cannot be overridden.
81	<	* Developers creating new basic styles of fork/join processing should
82	<	* minimally implement protected methods <tt>exec</tt>,
83	<	* <tt>setRawResult</tt>, and <tt>getRawResult</tt>, while also
84	<	* introducing an abstract computational method that can be
85	<	* implemented in its subclasses. To support such extensions,
86	<	* instances of ForkJoinTasks maintain an atomically updated
87	<	* <tt>short</tt> representing user-defined control state.  Control
88	<	* state is guaranteed initially to be zero, and to be negative upon
89	<	* completion, but may otherwise be used for any other control
90	<	* purposes, such as maintaining join counts.  The {@link
91	<	* ForkJoinWorkerThread} class supports additional inspection and
92	<	* tuning methods that can be useful when developing extensions.
59	>	* exceptions, that are rethrown to callers attempting to join
60	>	* them. These exceptions may additionally include {@link
61	>	* RejectedExecutionException} stemming from internal resource
62	>	* exhaustion, such as failure to allocate internal task
63	>	* queues. Rethrown exceptions behave in the same way as regular
64	>	* exceptions, but, when possible, contain stack traces (as displayed
65	>	* for example using {@code ex.printStackTrace()}) of both the thread
66	>	* that initiated the computation as well as the thread actually
67	>	* encountering the exception; minimally only the latter.
68	>	*
69	>	* <p>It is possible to define and use ForkJoinTasks that may block,
70	>	* but doing do requires three further considerations: (1) Completion
71	>	* of few if any <em>other</em> tasks should be dependent on a task
72	>	* that blocks on external synchronization or IO. Event-style async
73	>	* tasks that are never joined often fall into this category.  (2) To
74	>	* minimize resource impact, tasks should be small; ideally performing
75	>	* only the (possibly) blocking action. (3) Unless the {@link
76	>	* ForkJoinPool.ManagedBlocker} API is used, or the number of possibly
77	>	* blocked tasks is known to be less than the pool's {@link
78	>	* ForkJoinPool#getParallelism} level, the pool cannot guarantee that
79	>	* enough threads will be available to ensure progress or good
80	>	* performance.
81	>	*
82	>	* <p>The primary method for awaiting completion and extracting
83	>	* results of a task is {@link #join}, but there are several variants:
84	>	* The {@link Future#get} methods support interruptible and/or timed
85	>	* waits for completion and report results using {@code Future}
86	>	* conventions. Method {@link #invoke} is semantically
87	>	* equivalent to {@code fork(); join()} but always attempts to begin
88	>	* execution in the current thread. The "<em>quiet</em>" forms of
89	>	* these methods do not extract results or report exceptions. These
90	>	* may be useful when a set of tasks are being executed, and you need
91	>	* to delay processing of results or exceptions until all complete.
92	>	* Method {@code invokeAll} (available in multiple versions)
93	>	* performs the most common form of parallel invocation: forking a set
94	>	* of tasks and joining them all.
95	>	*
96	>	* <p>In the most typical usages, a fork-join pair act like a call
97	>	* (fork) and return (join) from a parallel recursive function. As is
98	>	* the case with other forms of recursive calls, returns (joins)
99	>	* should be performed innermost-first. For example, {@code a.fork();
100	>	* b.fork(); b.join(); a.join();} is likely to be substantially more
101	>	* efficient than joining {@code a} before {@code b}.
102	>	*
103	>	* <p>The execution status of tasks may be queried at several levels
104	>	* of detail: {@link #isDone} is true if a task completed in any way
105	>	* (including the case where a task was cancelled without executing);
106	>	* {@link #isCompletedNormally} is true if a task completed without
107	>	* cancellation or encountering an exception; {@link #isCancelled} is
108	>	* true if the task was cancelled (in which case {@link #getException}
109	>	* returns a {@link java.util.concurrent.CancellationException}); and
110	>	* {@link #isCompletedAbnormally} is true if a task was either
111	>	* cancelled or encountered an exception, in which case {@link
112	>	* #getException} will return either the encountered exception or
113	>	* {@link java.util.concurrent.CancellationException}.
114	>	*
115	>	* <p>The ForkJoinTask class is not usually directly subclassed.
116	>	* Instead, you subclass one of the abstract classes that support a
117	>	* particular style of fork/join processing, typically {@link
118	>	* RecursiveAction} for computations that do not return results, or
119	>	* {@link RecursiveTask} for those that do.  Normally, a concrete
120	>	* ForkJoinTask subclass declares fields comprising its parameters,
121	>	* established in a constructor, and then defines a {@code compute}
122	>	* method that somehow uses the control methods supplied by this base
123	>	* class. While these methods have {@code public} access (to allow
124	>	* instances of different task subclasses to call each other's
125	>	* methods), some of them may only be called from within other
126	>	* ForkJoinTasks (as may be determined using method {@link
127	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
128	>	* result in exceptions or errors, possibly including
129	>	* {@code ClassCastException}.
130	>	*
131	>	* <p>Method {@link #join} and its variants are appropriate for use
132	>	* only when completion dependencies are acyclic; that is, the
133	>	* parallel computation can be described as a directed acyclic graph
134	>	* (DAG). Otherwise, executions may encounter a form of deadlock as
135	>	* tasks cyclically wait for each other.  However, this framework
136	>	* supports other methods and techniques (for example the use of
137	>	* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that
138	>	* may be of use in constructing custom subclasses for problems that
139	>	* are not statically structured as DAGs. To support such usages a
140	>	* ForkJoinTask may be atomically <em>marked</em> using {@link
141	>	* #markForkJoinTask} and checked for marking using {@link
142	>	* #isMarkedForkJoinTask}. The ForkJoinTask implementation does not
143	>	* use these {@code protected} methods or marks for any purpose, but
144	>	* they may be of use in the construction of specialized subclasses.
145	>	* For example, parallel graph traversals can use the supplied methods
146	>	* to avoid revisiting nodes/tasks that have already been processed.
147	>	* Also, completion based designs can use them to record that one
148	>	* subtask has completed. (Method names for marking are bulky in part
149	>	* to encourage definition of methods that reflect their usage
150	>	* patterns.)
151	>	*
152	>	* <p>Most base support methods are {@code final}, to prevent
153	>	* overriding of implementations that are intrinsically tied to the
154	>	* underlying lightweight task scheduling framework.  Developers
155	>	* creating new basic styles of fork/join processing should minimally
156	>	* implement {@code protected} methods {@link #exec}, {@link
157	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
158	>	* an abstract computational method that can be implemented in its
159	>	* subclasses, possibly relying on other {@code protected} methods
160	>	* provided by this class.
161		*
162		* <p>ForkJoinTasks should perform relatively small amounts of
163	<	* computations, othewise splitting into smaller tasks. As a very
164	<	* rough rule of thumb, a task should perform more than 100 and less
165	<	* than 10000 basic computational steps. If tasks are too big, then
166	<	* parellelism cannot improve throughput. If too small, then memory
167	<	* and internal task maintenance overhead may overwhelm processing.
168	<	*
169	<	* <p>ForkJoinTasks are <tt>Serializable</tt>, which enables them to
170	<	* be used in extensions such as remote execution frameworks. However,
171	<	* it is in general safe to serialize tasks only before or after, but
172	<	* not during execution. Serialization is not relied on during
173	<	* execution itself.
163	>	* computation. Large tasks should be split into smaller subtasks,
164	>	* usually via recursive decomposition. As a very rough rule of thumb,
165	>	* a task should perform more than 100 and less than 10000 basic
166	>	* computational steps, and should avoid indefinite looping. If tasks
167	>	* are too big, then parallelism cannot improve throughput. If too
168	>	* small, then memory and internal task maintenance overhead may
169	>	* overwhelm processing.
170	>	*
171	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
172	>	* and {@link Callable}, that may be of use when mixing execution of
173	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
174	>	* of this form, consider using a pool constructed in <em>asyncMode</em>.
175	>	*
176	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
177	>	* used in extensions such as remote execution frameworks. It is
178	>	* sensible to serialize tasks only before or after, but not during,
179	>	* execution. Serialization is not relied on during execution itself.
180	>	*
181	>	* @since 1.7
182	>	* @author Doug Lea
183		*/
184		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
94	–	/**
95	–	* Status field holding all run status. We pack this into a single
96	–	* int both to minimize footprint overhead and to ensure atomicity
97	–	* (updates are via CAS).
98	–	*
99	–	* Status is initially zero, and takes on nonnegative values until
100	–	* completed, upon which status holds COMPLETED. CANCELLED, or
101	–	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
102	–	* blocking waits by other threads have SIGNAL_MASK bits set --
103	–	* bit 15 for external (nonFJ) waits, and the rest a count of
104	–	* waiting FJ threads.  (This representation relies on
105	–	* ForkJoinPool max thread limits). Completion of a stolen task
106	–	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
107	–	* though suboptimal for some purposes, we use basic builtin
108	–	* wait/notify to take advantage of "monitor inflation" in JVMs
109	–	* that we would otherwise need to emulate to avoid adding further
110	–	* per-task bookkeeping overhead. Note that bits 16-28 are
111	–	* currently unused. Also value 0x80000000 is available as spare
112	–	* completion value.
113	–	*/
114	–	volatile int status; // accessed directy by pool and workers
115	–
116	–	static final int COMPLETION_MASK      = 0xe0000000;
117	–	static final int NORMAL               = 0xe0000000; // == mask
118	–	static final int CANCELLED            = 0xc0000000;
119	–	static final int EXCEPTIONAL          = 0xa0000000;
120	–	static final int SIGNAL_MASK          = 0x0000ffff;
121	–	static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
122	–	static final int EXTERNAL_SIGNAL      = 0x00008000; // top bit of low word
185
186	<	/**
187	<	* Table of exceptions thrown by tasks, to enable reporting by
188	<	* callers. Because exceptions are rare, we don't directly keep
189	<	* them with task objects, but instead us a weak ref table.  Note
190	<	* that cancellation exceptions don't appear in the table, but are
191	<	* instead recorded as status values.
192	<	* Todo: Use ConcurrentReferenceHashMap
186	>	/*
187	>	* See the internal documentation of class ForkJoinPool for a
188	>	* general implementation overview.  ForkJoinTasks are mainly
189	>	* responsible for maintaining their "status" field amidst relays
190	>	* to methods in ForkJoinWorkerThread and ForkJoinPool.
191	>	*
192	>	* The methods of this class are more-or-less layered into
193	>	* (1) basic status maintenance
194	>	* (2) execution and awaiting completion
195	>	* (3) user-level methods that additionally report results.
196	>	* This is sometimes hard to see because this file orders exported
197	>	* methods in a way that flows well in javadocs.
198	>	*/
199	>
200	>	/*
201	>	* The status field holds run control status bits packed into a
202	>	* single int to minimize footprint and to ensure atomicity (via
203	>	* CAS).  Status is initially zero, and takes on nonnegative
204	>	* values until completed, upon which status (anded with
205	>	* DONE_MASK) holds value NORMAL, CANCELLED, or EXCEPTIONAL. Tasks
206	>	* undergoing blocking waits by other threads have the SIGNAL bit
207	>	* set.  Completion of a stolen task with SIGNAL set awakens any
208	>	* waiters via notifyAll. Even though suboptimal for some
209	>	* purposes, we use basic builtin wait/notify to take advantage of
210	>	* "monitor inflation" in JVMs that we would otherwise need to
211	>	* emulate to avoid adding further per-task bookkeeping overhead.
212	>	* We want these monitors to be "fat", i.e., not use biasing or
213	>	* thin-lock techniques, so use some odd coding idioms that tend
214	>	* to avoid them, mainly by arranging that every synchronized
215	>	* block performs a wait, notifyAll or both.
216	>	*/
217	>
218	>	/** The run status of this task */
219	>	volatile int status; // accessed directly by pool and workers
220	>	static final int DONE_MASK   = 0xf0000000;  // mask out non-completion bits
221	>	static final int NORMAL      = 0xf0000000;  // must be negative
222	>	static final int CANCELLED   = 0xc0000000;  // must be < NORMAL
223	>	static final int EXCEPTIONAL = 0x80000000;  // must be < CANCELLED
224	>	static final int SIGNAL      = 0x00000001;
225	>	static final int MARKED      = 0x00000002;
226	>
227	>	/**
228	>	* Marks completion and wakes up threads waiting to join this
229	>	* task. A specialization for NORMAL completion is in method
230	>	* doExec.
231	>	*
232	>	* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
233	>	* @return completion status on exit
234		*/
235	<	static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
236	<	Collections.synchronizedMap
237	<	(new WeakHashMap<ForkJoinTask<?>, Throwable>());
238	<
239	<	// within-package utilities
235	>	private int setCompletion(int completion) {
236	>	for (int s;;) {
237	>	if ((s = status) < 0)
238	>	return s;
239	>	if (U.compareAndSwapInt(this, STATUS, s, s | completion)) {
240	>	if ((s & SIGNAL) != 0)
241	>	synchronized (this) { notifyAll(); }
242	>	return completion;
243	>	}
244	>	}
245	>	}
246
247		/**
248	<	* Get current worker thread, or null if not a worker thread
248	>	* Primary execution method for stolen tasks. Unless done, calls
249	>	* exec and records status if completed, but doesn't wait for
250	>	* completion otherwise.
251	>	*
252	>	* @return status on exit from this method
253		*/
254	<	static ForkJoinWorkerThread getWorker() {
255	<	Thread t = Thread.currentThread();
256	<	return ((t instanceof ForkJoinWorkerThread)?
257	<	(ForkJoinWorkerThread)t : null);
254	>	final int doExec() {
255	>	int s; boolean completed;
256	>	if ((s = status) >= 0) {
257	>	try {
258	>	completed = exec();
259	>	} catch (Throwable rex) {
260	>	return setExceptionalCompletion(rex);
261	>	}
262	>	while ((s = status) >= 0 && completed) {
263	>	if (U.compareAndSwapInt(this, STATUS, s, s | NORMAL)) {
264	>	if ((s & SIGNAL) != 0)
265	>	synchronized (this) { notifyAll(); }
266	>	return NORMAL;
267	>	}
268	>	}
269	>	}
270	>	return s;
271		}
272
273		/**
274	<	* Get pool of current worker thread, or null if not a worker thread
274	>	* Tries to set SIGNAL status. Used by ForkJoinPool. Other
275	>	* variants are directly incorporated into externalAwaitDone etc.
276	>	*
277	>	* @return true if successful
278		*/
279	<	static ForkJoinPool getWorkerPool() {
280	<	Thread t = Thread.currentThread();
281	<	return ((t instanceof ForkJoinWorkerThread)?
153	<	((ForkJoinWorkerThread)t).pool : null);
279	>	final boolean trySetSignal() {
280	>	int s;
281	>	return U.compareAndSwapInt(this, STATUS, s = status, s | SIGNAL);
282		}
283
284	<	final boolean casStatus(int cmp, int val) {
285	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
284	>	/**
285	>	* Blocks a non-worker-thread until completion.
286	>	* @return status upon completion
287	>	*/
288	>	private int externalAwaitDone() {
289	>	boolean interrupted = false;
290	>	int s;
291	>	while ((s = status) >= 0) {
292	>	if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
293	>	synchronized (this) {
294	>	if (status >= 0) {
295	>	try {
296	>	wait();
297	>	} catch (InterruptedException ie) {
298	>	interrupted = true;
299	>	}
300	>	}
301	>	else
302	>	notifyAll();
303	>	}
304	>	}
305	>	}
306	>	if (interrupted)
307	>	Thread.currentThread().interrupt();
308	>	return s;
309		}
310
311		/**
312	<	* Workaround for not being able to rethrow unchecked exceptions.
312	>	* Blocks a non-worker-thread until completion or interruption.
313		*/
314	<	static void rethrowException(Throwable ex) {
315	<	if (ex != null)
316	<	_unsafe.throwException(ex);
314	>	private int externalInterruptibleAwaitDone() throws InterruptedException {
315	>	int s;
316	>	if (Thread.interrupted())
317	>	throw new InterruptedException();
318	>	while ((s = status) >= 0) {
319	>	if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
320	>	synchronized (this) {
321	>	if (status >= 0)
322	>	wait();
323	>	else
324	>	notifyAll();
325	>	}
326	>	}
327	>	}
328	>	return s;
329		}
330
168	–	// Setting completion status
331
332		/**
333	<	* Mark completion and wake up threads waiting to join this task.
334	<	* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
333	>	* Implementation for join, get, quietlyJoin. Directly handles
334	>	* only cases of already-completed, external wait, and
335	>	* unfork+exec.  Others are relayed to ForkJoinPool.awaitJoin.
336	>	*
337	>	* @return status upon completion
338		*/
339	<	final void setCompletion(int completion) {
340	<	ForkJoinPool pool = getWorkerPool();
341	<	if (pool != null) {
342	<	int s; // Clear signal bits while setting completion status
343	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
344	<
345	<	if ((s & SIGNAL_MASK) != 0) {
181	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
182	<	pool.updateRunningCount(s);
183	<	synchronized(this) { notifyAll(); }
339	>	private int doJoin() {
340	>	int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w;
341	>	if ((s = status) >= 0) {
342	>	if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) {
343	>	if (!(w = (wt = (ForkJoinWorkerThread)t).workQueue).
344	>	tryUnpush(this) || (s = doExec()) >= 0)
345	>	s = wt.pool.awaitJoin(w, this);
346		}
347	+	else
348	+	s = externalAwaitDone();
349		}
350	<	else
187	<	externallySetCompletion(completion);
350	>	return s;
351		}
352
353		/**
354	<	* Version of setCompletion for non-FJ threads.  Leaves signal
355	<	* bits for unblocked threads to adjust, and always notifies.
354	>	* Implementation for invoke, quietlyInvoke.
355	>	*
356	>	* @return status upon completion
357		*/
358	<	private void externallySetCompletion(int completion) {
359	<	int s;
360	<	do;while ((s = status) >= 0 &&
361	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
362	<	synchronized(this) { notifyAll(); }
358	>	private int doInvoke() {
359	>	int s; Thread t; ForkJoinWorkerThread wt;
360	>	if ((s = doExec()) >= 0) {
361	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
362	>	s = (wt = (ForkJoinWorkerThread)t).pool.awaitJoin(wt.workQueue,
363	>	this);
364	>	else
365	>	s = externalAwaitDone();
366	>	}
367	>	return s;
368		}
369
370	+	// Exception table support
371	+
372		/**
373	<	* Sets status to indicate normal completion
373	>	* Table of exceptions thrown by tasks, to enable reporting by
374	>	* callers. Because exceptions are rare, we don't directly keep
375	>	* them with task objects, but instead use a weak ref table.  Note
376	>	* that cancellation exceptions don't appear in the table, but are
377	>	* instead recorded as status values.
378	>	*
379	>	* Note: These statics are initialized below in static block.
380		*/
381	<	final void setNormalCompletion() {
382	<	// Try typical fast case -- single CAS, no signal, not already done.
383	<	// Manually expand casStatus to improve chances of inlining it
207	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
208	<	setCompletion(NORMAL);
209	<	}
381	>	private static final ExceptionNode[] exceptionTable;
382	>	private static final ReentrantLock exceptionTableLock;
383	>	private static final ReferenceQueue<Object> exceptionTableRefQueue;
384
385	<	// internal waiting and notification
385	>	/**
386	>	* Fixed capacity for exceptionTable.
387	>	*/
388	>	private static final int EXCEPTION_MAP_CAPACITY = 32;
389
390		/**
391	<	* Performs the actual monitor wait for awaitDone
391	>	* Key-value nodes for exception table.  The chained hash table
392	>	* uses identity comparisons, full locking, and weak references
393	>	* for keys. The table has a fixed capacity because it only
394	>	* maintains task exceptions long enough for joiners to access
395	>	* them, so should never become very large for sustained
396	>	* periods. However, since we do not know when the last joiner
397	>	* completes, we must use weak references and expunge them. We do
398	>	* so on each operation (hence full locking). Also, some thread in
399	>	* any ForkJoinPool will call helpExpungeStaleExceptions when its
400	>	* pool becomes isQuiescent.
401		*/
402	<	private void doAwaitDone() {
403	<	// Minimize lock bias and in/de-flation effects by maximizing
404	<	// chances of waiting inside sync
405	<	try {
406	<	while (status >= 0)
407	<	synchronized(this) { if (status >= 0) wait(); }
408	<	} catch (InterruptedException ie) {
409	<	onInterruptedWait();
402	>	static final class ExceptionNode extends WeakReference<ForkJoinTask<?>> {
403	>	final Throwable ex;
404	>	ExceptionNode next;
405	>	final long thrower;  // use id not ref to avoid weak cycles
406	>	ExceptionNode(ForkJoinTask<?> task, Throwable ex, ExceptionNode next) {
407	>	super(task, exceptionTableRefQueue);
408	>	this.ex = ex;
409	>	this.next = next;
410	>	this.thrower = Thread.currentThread().getId();
411		}
412		}
413
414		/**
415	<	* Performs the actual monitor wait for awaitDone
415	>	* Records exception and sets exceptional completion.
416	>	*
417	>	* @return status on exit
418		*/
419	<	private void doAwaitDone(long startTime, long nanos) {
420	<	synchronized(this) {
421	<	try {
422	<	while (status >= 0) {
423	<	long nt = nanos - System.nanoTime() - startTime;
424	<	if (nt <= 0)
425	<	break;
426	<	wait(nt / 1000000, (int)(nt % 1000000));
419	>	private int setExceptionalCompletion(Throwable ex) {
420	>	int h = System.identityHashCode(this);
421	>	final ReentrantLock lock = exceptionTableLock;
422	>	lock.lock();
423	>	try {
424	>	expungeStaleExceptions();
425	>	ExceptionNode[] t = exceptionTable;
426	>	int i = h & (t.length - 1);
427	>	for (ExceptionNode e = t[i]; ; e = e.next) {
428	>	if (e == null) {
429	>	t[i] = new ExceptionNode(this, ex, t[i]);
430	>	break;
431		}
432	<	} catch (InterruptedException ie) {
433	<	onInterruptedWait();
432	>	if (e.get() == this) // already present
433	>	break;
434		}
435	+	} finally {
436	+	lock.unlock();
437		}
438	+	return setCompletion(EXCEPTIONAL);
439		}
440
245	–	// Awaiting completion
246	–
441		/**
442	<	* Sets status to indicate there is joiner, then waits for join,
443	<	* surrounded with pool notifications.
444	<	* @return status upon exit
442	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
443	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
444	>	* exceptions, but if it does anyway, we have no recourse during
445	>	* shutdown, so guard against this case.
446		*/
447	<	final int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
448	<	ForkJoinPool pool = w == null? null : w.pool;
449	<	int s;
450	<	while ((s = status) >= 0) {
451	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
257	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
258	<	doAwaitDone();
259	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
260	<	adjustPoolCountsOnUnblock(pool);
261	<	break;
447	>	static final void cancelIgnoringExceptions(ForkJoinTask<?> t) {
448	>	if (t != null && t.status >= 0) {
449	>	try {
450	>	t.cancel(false);
451	>	} catch (Throwable ignore) {
452		}
453		}
264	–	return s;
454		}
455
456		/**
457	<	* Timed version of awaitDone
269	<	* @return status upon exit
457	>	* Removes exception node and clears status
458		*/
459	<	final int awaitDone(ForkJoinWorkerThread w, long nanos) {
460	<	ForkJoinPool pool = w == null? null : w.pool;
461	<	int s;
462	<	while ((s = status) >= 0) {
463	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
464	<	long startTime = System.nanoTime();
465	<	if (pool == null || !pool.preJoin(this, false))
466	<	doAwaitDone(startTime, nanos);
467	<	if ((s = status) >= 0) {
468	<	adjustPoolCountsOnCancelledWait(pool);
469	<	s = status;
459	>	private void clearExceptionalCompletion() {
460	>	int h = System.identityHashCode(this);
461	>	final ReentrantLock lock = exceptionTableLock;
462	>	lock.lock();
463	>	try {
464	>	ExceptionNode[] t = exceptionTable;
465	>	int i = h & (t.length - 1);
466	>	ExceptionNode e = t[i];
467	>	ExceptionNode pred = null;
468	>	while (e != null) {
469	>	ExceptionNode next = e.next;
470	>	if (e.get() == this) {
471	>	if (pred == null)
472	>	t[i] = next;
473	>	else
474	>	pred.next = next;
475	>	break;
476		}
477	<	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
478	<	adjustPoolCountsOnUnblock(pool);
285	<	break;
477	>	pred = e;
478	>	e = next;
479		}
480	+	expungeStaleExceptions();
481	+	status = 0;
482	+	} finally {
483	+	lock.unlock();
484		}
288	–	return s;
485		}
486
487		/**
488	<	* Notify pool that thread is unblocked. Called by signalled
489	<	* threads when woken by non-FJ threads (which is atypical).
488	>	* Returns a rethrowable exception for the given task, if
489	>	* available. To provide accurate stack traces, if the exception
490	>	* was not thrown by the current thread, we try to create a new
491	>	* exception of the same type as the one thrown, but with the
492	>	* recorded exception as its cause. If there is no such
493	>	* constructor, we instead try to use a no-arg constructor,
494	>	* followed by initCause, to the same effect. If none of these
495	>	* apply, or any fail due to other exceptions, we return the
496	>	* recorded exception, which is still correct, although it may
497	>	* contain a misleading stack trace.
498	>	*
499	>	* @return the exception, or null if none
500		*/
501	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
502	<	int s;
503	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
504	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
505	<	pool.updateRunningCount(s);
501	>	private Throwable getThrowableException() {
502	>	if ((status & DONE_MASK) != EXCEPTIONAL)
503	>	return null;
504	>	int h = System.identityHashCode(this);
505	>	ExceptionNode e;
506	>	final ReentrantLock lock = exceptionTableLock;
507	>	lock.lock();
508	>	try {
509	>	expungeStaleExceptions();
510	>	ExceptionNode[] t = exceptionTable;
511	>	e = t[h & (t.length - 1)];
512	>	while (e != null && e.get() != this)
513	>	e = e.next;
514	>	} finally {
515	>	lock.unlock();
516	>	}
517	>	Throwable ex;
518	>	if (e == null || (ex = e.ex) == null)
519	>	return null;
520	>	if (e.thrower != Thread.currentThread().getId()) {
521	>	Class<? extends Throwable> ec = ex.getClass();
522	>	try {
523	>	Constructor<?> noArgCtor = null;
524	>	Constructor<?>[] cs = ec.getConstructors();// public ctors only
525	>	for (int i = 0; i < cs.length; ++i) {
526	>	Constructor<?> c = cs[i];
527	>	Class<?>[] ps = c.getParameterTypes();
528	>	if (ps.length == 0)
529	>	noArgCtor = c;
530	>	else if (ps.length == 1 && ps[0] == Throwable.class)
531	>	return (Throwable)(c.newInstance(ex));
532	>	}
533	>	if (noArgCtor != null) {
534	>	Throwable wx = (Throwable)(noArgCtor.newInstance());
535	>	wx.initCause(ex);
536	>	return wx;
537	>	}
538	>	} catch (Exception ignore) {
539	>	}
540	>	}
541	>	return ex;
542		}
543
544		/**
545	<	* Notify pool to adjust counts on cancelled or timed out wait
545	>	* Poll stale refs and remove them. Call only while holding lock.
546		*/
547	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
548	<	if (pool != null) {
549	<	int s;
550	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
551	<	if (casStatus(s, s - 1)) {
552	<	pool.updateRunningCount(1);
553	<	break;
547	>	private static void expungeStaleExceptions() {
548	>	for (Object x; (x = exceptionTableRefQueue.poll()) != null;) {
549	>	if (x instanceof ExceptionNode) {
550	>	ForkJoinTask<?> key = ((ExceptionNode)x).get();
551	>	ExceptionNode[] t = exceptionTable;
552	>	int i = System.identityHashCode(key) & (t.length - 1);
553	>	ExceptionNode e = t[i];
554	>	ExceptionNode pred = null;
555	>	while (e != null) {
556	>	ExceptionNode next = e.next;
557	>	if (e == x) {
558	>	if (pred == null)
559	>	t[i] = next;
560	>	else
561	>	pred.next = next;
562	>	break;
563	>	}
564	>	pred = e;
565	>	e = next;
566		}
567		}
568		}
569		}
570
571	<	private void onInterruptedWait() {
572	<	Thread t = Thread.currentThread();
573	<	if (t instanceof ForkJoinWorkerThread) {
574	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)t;
575	<	if (w.isTerminating())
576	<	cancelIgnoreExceptions();
577	<	}
324	<	else { // re-interrupt
571	>	/**
572	>	* If lock is available, poll stale refs and remove them.
573	>	* Called from ForkJoinPool when pools become quiescent.
574	>	*/
575	>	static final void helpExpungeStaleExceptions() {
576	>	final ReentrantLock lock = exceptionTableLock;
577	>	if (lock.tryLock()) {
578		try {
579	<	t.interrupt();
580	<	} catch (SecurityException ignore) {
579	>	expungeStaleExceptions();
580	>	} finally {
581	>	lock.unlock();
582		}
583		}
584		}
585
586	<	// Recording and reporting exceptions
587	<
588	<	private void setDoneExceptionally(Throwable rex) {
589	<	exceptionMap.put(this, rex);
590	<	setCompletion(EXCEPTIONAL);
586	>	/**
587	>	* Throws exception, if any, associated with the given status.
588	>	*/
589	>	private void reportException(int s) {
590	>	Throwable ex = ((s == CANCELLED) ?  new CancellationException() :
591	>	(s == EXCEPTIONAL) ? getThrowableException() :
592	>	null);
593	>	if (ex != null)
594	>	U.throwException(ex);
595		}
596
597	+	// public methods
598	+
599		/**
600	<	* Throws the exception associated with status s;
601	<	* @throws the exception
600	>	* Arranges to asynchronously execute this task.  While it is not
601	>	* necessarily enforced, it is a usage error to fork a task more
602	>	* than once unless it has completed and been reinitialized.
603	>	* Subsequent modifications to the state of this task or any data
604	>	* it operates on are not necessarily consistently observable by
605	>	* any thread other than the one executing it unless preceded by a
606	>	* call to {@link #join} or related methods, or a call to {@link
607	>	* #isDone} returning {@code true}.
608	>	*
609	>	* <p>This method may be invoked only from within {@code
610	>	* ForkJoinPool} computations (as may be determined using method
611	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
612	>	* result in exceptions or errors, possibly including {@code
613	>	* ClassCastException}.
614	>	*
615	>	* @return {@code this}, to simplify usage
616		*/
617	<	private void reportException(int s) {
618	<	if ((s &= COMPLETION_MASK) < NORMAL) {
619	<	if (s == CANCELLED)
346	<	throw new CancellationException();
347	<	else
348	<	rethrowException(exceptionMap.get(this));
349	<	}
617	>	public final ForkJoinTask<V> fork() {
618	>	((ForkJoinWorkerThread)Thread.currentThread()).workQueue.push(this);
619	>	return this;
620		}
621
622		/**
623	<	* Returns result or throws exception using j.u.c.Future conventions
624	<	* Only call when isDone known to be true.
623	>	* Returns the result of the computation when it {@link #isDone is
624	>	* done}.  This method differs from {@link #get()} in that
625	>	* abnormal completion results in {@code RuntimeException} or
626	>	* {@code Error}, not {@code ExecutionException}, and that
627	>	* interrupts of the calling thread do <em>not</em> cause the
628	>	* method to abruptly return by throwing {@code
629	>	* InterruptedException}.
630	>	*
631	>	* @return the computed result
632		*/
633	<	private V reportFutureResult()
634	<	throws ExecutionException, InterruptedException {
635	<	int s = status & COMPLETION_MASK;
636	<	if (s < NORMAL) {
360	<	Throwable ex;
361	<	if (s == CANCELLED)
362	<	throw new CancellationException();
363	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
364	<	throw new ExecutionException(ex);
365	<	if (Thread.interrupted())
366	<	throw new InterruptedException();
367	<	}
633	>	public final V join() {
634	>	int s;
635	>	if ((s = doJoin() & DONE_MASK) != NORMAL)
636	>	reportException(s);
637		return getRawResult();
638		}
639
640		/**
641	<	* Returns result or throws exception using j.u.c.Future conventions
642	<	* with timeouts
641	>	* Commences performing this task, awaits its completion if
642	>	* necessary, and returns its result, or throws an (unchecked)
643	>	* {@code RuntimeException} or {@code Error} if the underlying
644	>	* computation did so.
645	>	*
646	>	* @return the computed result
647		*/
648	<	private V reportTimedFutureResult()
649	<	throws InterruptedException, ExecutionException, TimeoutException {
650	<	Throwable ex;
651	<	int s = status & COMPLETION_MASK;
652	<	if (s == NORMAL)
380	<	return getRawResult();
381	<	if (s == CANCELLED)
382	<	throw new CancellationException();
383	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
384	<	throw new ExecutionException(ex);
385	<	if (Thread.interrupted())
386	<	throw new InterruptedException();
387	<	throw new TimeoutException();
648	>	public final V invoke() {
649	>	int s;
650	>	if ((s = doInvoke() & DONE_MASK) != NORMAL)
651	>	reportException(s);
652	>	return getRawResult();
653		}
654
390	–	// internal execution methods
391	–
655		/**
656	<	* Calls exec, recording completion, and rethrowing exception if
657	<	* encountered. Caller should normally check status before calling
658	<	* @return true if completed normally
656	>	* Forks the given tasks, returning when {@code isDone} holds for
657	>	* each task or an (unchecked) exception is encountered, in which
658	>	* case the exception is rethrown. If more than one task
659	>	* encounters an exception, then this method throws any one of
660	>	* these exceptions. If any task encounters an exception, the
661	>	* other may be cancelled. However, the execution status of
662	>	* individual tasks is not guaranteed upon exceptional return. The
663	>	* status of each task may be obtained using {@link
664	>	* #getException()} and related methods to check if they have been
665	>	* cancelled, completed normally or exceptionally, or left
666	>	* unprocessed.
667	>	*
668	>	* <p>This method may be invoked only from within {@code
669	>	* ForkJoinPool} computations (as may be determined using method
670	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
671	>	* result in exceptions or errors, possibly including {@code
672	>	* ClassCastException}.
673	>	*
674	>	* @param t1 the first task
675	>	* @param t2 the second task
676	>	* @throws NullPointerException if any task is null
677		*/
678	<	private boolean tryExec() {
679	<	try { // try block must contain only call to exec
680	<	if (!exec())
681	<	return false;
682	<	} catch (Throwable rex) {
683	<	setDoneExceptionally(rex);
684	<	rethrowException(rex);
404	<	return false; // not reached
405	<	}
406	<	setNormalCompletion();
407	<	return true;
678	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
679	>	int s1, s2;
680	>	t2.fork();
681	>	if ((s1 = t1.doInvoke() & DONE_MASK) != NORMAL)
682	>	t1.reportException(s1);
683	>	if ((s2 = t2.doJoin() & DONE_MASK) != NORMAL)
684	>	t2.reportException(s2);
685		}
686
687		/**
688	<	* Main execution method used by worker threads. Invokes
689	<	* base computation unless already complete
688	>	* Forks the given tasks, returning when {@code isDone} holds for
689	>	* each task or an (unchecked) exception is encountered, in which
690	>	* case the exception is rethrown. If more than one task
691	>	* encounters an exception, then this method throws any one of
692	>	* these exceptions. If any task encounters an exception, others
693	>	* may be cancelled. However, the execution status of individual
694	>	* tasks is not guaranteed upon exceptional return. The status of
695	>	* each task may be obtained using {@link #getException()} and
696	>	* related methods to check if they have been cancelled, completed
697	>	* normally or exceptionally, or left unprocessed.
698	>	*
699	>	* <p>This method may be invoked only from within {@code
700	>	* ForkJoinPool} computations (as may be determined using method
701	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
702	>	* result in exceptions or errors, possibly including {@code
703	>	* ClassCastException}.
704	>	*
705	>	* @param tasks the tasks
706	>	* @throws NullPointerException if any task is null
707		*/
708	<	final void quietlyExec() {
709	<	if (status >= 0) {
710	<	try {
711	<	if (!exec())
712	<	return;
713	<	} catch(Throwable rex) {
714	<	setDoneExceptionally(rex);
715	<	return;
708	>	public static void invokeAll(ForkJoinTask<?>... tasks) {
709	>	Throwable ex = null;
710	>	int last = tasks.length - 1;
711	>	for (int i = last; i >= 0; --i) {
712	>	ForkJoinTask<?> t = tasks[i];
713	>	if (t == null) {
714	>	if (ex == null)
715	>	ex = new NullPointerException();
716	>	}
717	>	else if (i != 0)
718	>	t.fork();
719	>	else if (t.doInvoke() < NORMAL && ex == null)
720	>	ex = t.getException();
721	>	}
722	>	for (int i = 1; i <= last; ++i) {
723	>	ForkJoinTask<?> t = tasks[i];
724	>	if (t != null) {
725	>	if (ex != null)
726	>	t.cancel(false);
727	>	else if (t.doJoin() < NORMAL)
728	>	ex = t.getException();
729		}
423	–	setNormalCompletion();
730		}
731	+	if (ex != null)
732	+	U.throwException(ex);
733		}
734
735		/**
736	<	* Calls exec, recording but not rethrowing exception
737	<	* Caller should normally check status before calling
738	<	* @return true if completed normally
736	>	* Forks all tasks in the specified collection, returning when
737	>	* {@code isDone} holds for each task or an (unchecked) exception
738	>	* is encountered, in which case the exception is rethrown. If
739	>	* more than one task encounters an exception, then this method
740	>	* throws any one of these exceptions. If any task encounters an
741	>	* exception, others may be cancelled. However, the execution
742	>	* status of individual tasks is not guaranteed upon exceptional
743	>	* return. The status of each task may be obtained using {@link
744	>	* #getException()} and related methods to check if they have been
745	>	* cancelled, completed normally or exceptionally, or left
746	>	* unprocessed.
747	>	*
748	>	* <p>This method may be invoked only from within {@code
749	>	* ForkJoinPool} computations (as may be determined using method
750	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
751	>	* result in exceptions or errors, possibly including {@code
752	>	* ClassCastException}.
753	>	*
754	>	* @param tasks the collection of tasks
755	>	* @return the tasks argument, to simplify usage
756	>	* @throws NullPointerException if tasks or any element are null
757		*/
758	<	private boolean tryQuietlyInvoke() {
759	<	try {
760	<	if (!exec())
761	<	return false;
762	<	} catch (Throwable rex) {
763	<	setDoneExceptionally(rex);
764	<	return false;
758	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
759	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
760	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
761	>	return tasks;
762	>	}
763	>	@SuppressWarnings("unchecked")
764	>	List<? extends ForkJoinTask<?>> ts =
765	>	(List<? extends ForkJoinTask<?>>) tasks;
766	>	Throwable ex = null;
767	>	int last = ts.size() - 1;
768	>	for (int i = last; i >= 0; --i) {
769	>	ForkJoinTask<?> t = ts.get(i);
770	>	if (t == null) {
771	>	if (ex == null)
772	>	ex = new NullPointerException();
773	>	}
774	>	else if (i != 0)
775	>	t.fork();
776	>	else if (t.doInvoke() < NORMAL && ex == null)
777	>	ex = t.getException();
778	>	}
779	>	for (int i = 1; i <= last; ++i) {
780	>	ForkJoinTask<?> t = ts.get(i);
781	>	if (t != null) {
782	>	if (ex != null)
783	>	t.cancel(false);
784	>	else if (t.doJoin() < NORMAL)
785	>	ex = t.getException();
786	>	}
787		}
788	<	setNormalCompletion();
789	<	return true;
788	>	if (ex != null)
789	>	U.throwException(ex);
790	>	return tasks;
791		}
792
793		/**
794	<	* Cancel, ignoring any exceptions it throws
794	>	* Attempts to cancel execution of this task. This attempt will
795	>	* fail if the task has already completed or could not be
796	>	* cancelled for some other reason. If successful, and this task
797	>	* has not started when {@code cancel} is called, execution of
798	>	* this task is suppressed. After this method returns
799	>	* successfully, unless there is an intervening call to {@link
800	>	* #reinitialize}, subsequent calls to {@link #isCancelled},
801	>	* {@link #isDone}, and {@code cancel} will return {@code true}
802	>	* and calls to {@link #join} and related methods will result in
803	>	* {@code CancellationException}.
804	>	*
805	>	* <p>This method may be overridden in subclasses, but if so, must
806	>	* still ensure that these properties hold. In particular, the
807	>	* {@code cancel} method itself must not throw exceptions.
808	>	*
809	>	* <p>This method is designed to be invoked by <em>other</em>
810	>	* tasks. To terminate the current task, you can just return or
811	>	* throw an unchecked exception from its computation method, or
812	>	* invoke {@link #completeExceptionally}.
813	>	*
814	>	* @param mayInterruptIfRunning this value has no effect in the
815	>	* default implementation because interrupts are not used to
816	>	* control cancellation.
817	>	*
818	>	* @return {@code true} if this task is now cancelled
819		*/
820	<	final void cancelIgnoreExceptions() {
821	<	try {
449	<	cancel(false);
450	<	} catch(Throwable ignore) {
451	<	}
820	>	public boolean cancel(boolean mayInterruptIfRunning) {
821	>	return (setCompletion(CANCELLED) & DONE_MASK) == CANCELLED;
822		}
823
824	<	// public methods
824	>	public final boolean isDone() {
825	>	return status < 0;
826	>	}
827	>
828	>	public final boolean isCancelled() {
829	>	return (status & DONE_MASK) == CANCELLED;
830	>	}
831
832		/**
833	<	* Arranges to asynchronously execute this task.  While it is not
834	<	* necessarily enforced, it is a usage error to fork a task more
835	<	* than once unless it has completed and been reinitialized.  This
460	<	* method may be invoked only from within other ForkJoinTask
461	<	* computations. Attempts to invoke in other contexts result in
462	<	* exceptions or errors including ClassCastException.
833	>	* Returns {@code true} if this task threw an exception or was cancelled.
834	>	*
835	>	* @return {@code true} if this task threw an exception or was cancelled
836		*/
837	<	public final void fork() {
838	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
837	>	public final boolean isCompletedAbnormally() {
838	>	return status < NORMAL;
839		}
840
841		/**
842	<	* Returns the result of the computation when it is ready.
843	<	* This method differs from <tt>get</tt> in that abnormal
471	<	* completion results in RuntimeExceptions or Errors, not
472	<	* ExecutionExceptions.
842	>	* Returns {@code true} if this task completed without throwing an
843	>	* exception and was not cancelled.
844		*
845	<	* @return the computed result
845	>	* @return {@code true} if this task completed without throwing an
846	>	* exception and was not cancelled
847		*/
848	<	public final V join() {
849	<	ForkJoinWorkerThread w = getWorker();
478	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
479	<	reportException(awaitDone(w, true));
480	<	return getRawResult();
848	>	public final boolean isCompletedNormally() {
849	>	return (status & DONE_MASK) == NORMAL;
850		}
851
852	<	public final V get() throws InterruptedException, ExecutionException {
853	<	ForkJoinWorkerThread w = getWorker();
854	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
855	<	awaitDone(w, true);
856	<	return reportFutureResult();
852	>	/**
853	>	* Returns the exception thrown by the base computation, or a
854	>	* {@code CancellationException} if cancelled, or {@code null} if
855	>	* none or if the method has not yet completed.
856	>	*
857	>	* @return the exception, or {@code null} if none
858	>	*/
859	>	public final Throwable getException() {
860	>	int s = status & DONE_MASK;
861	>	return ((s >= NORMAL)    ? null :
862	>	(s == CANCELLED) ? new CancellationException() :
863	>	getThrowableException());
864		}
865
866	<	public final V get(long timeout, TimeUnit unit)
867	<	throws InterruptedException, ExecutionException, TimeoutException {
868	<	ForkJoinWorkerThread w = getWorker();
869	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
870	<	awaitDone(w, unit.toNanos(timeout));
871	<	return reportTimedFutureResult();
866	>	/**
867	>	* Completes this task abnormally, and if not already aborted or
868	>	* cancelled, causes it to throw the given exception upon
869	>	* {@code join} and related operations. This method may be used
870	>	* to induce exceptions in asynchronous tasks, or to force
871	>	* completion of tasks that would not otherwise complete.  Its use
872	>	* in other situations is discouraged.  This method is
873	>	* overridable, but overridden versions must invoke {@code super}
874	>	* implementation to maintain guarantees.
875	>	*
876	>	* @param ex the exception to throw. If this exception is not a
877	>	* {@code RuntimeException} or {@code Error}, the actual exception
878	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
879	>	*/
880	>	public void completeExceptionally(Throwable ex) {
881	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
882	>	(ex instanceof Error) ? ex :
883	>	new RuntimeException(ex));
884		}
885
886		/**
887	<	* Possibly executes other tasks until this task is ready, then
888	<	* returns the result of the computation.  This method may be more
889	<	* efficient than <tt>join</tt>, but is only applicable when there
890	<	* are no potemtial dependencies between continuation of the
891	<	* current task and that of any other task that might be executed
892	<	* while helping. (This usually holds for pure divide-and-conquer
893	<	* tasks).
887	>	* Completes this task, and if not already aborted or cancelled,
888	>	* returning the given value as the result of subsequent
889	>	* invocations of {@code join} and related operations. This method
890	>	* may be used to provide results for asynchronous tasks, or to
891	>	* provide alternative handling for tasks that would not otherwise
892	>	* complete normally. Its use in other situations is
893	>	* discouraged. This method is overridable, but overridden
894	>	* versions must invoke {@code super} implementation to maintain
895	>	* guarantees.
896	>	*
897	>	* @param value the result value for this task
898	>	*/
899	>	public void complete(V value) {
900	>	try {
901	>	setRawResult(value);
902	>	} catch (Throwable rex) {
903	>	setExceptionalCompletion(rex);
904	>	return;
905	>	}
906	>	setCompletion(NORMAL);
907	>	}
908	>
909	>	/**
910	>	* Waits if necessary for the computation to complete, and then
911	>	* retrieves its result.
912	>	*
913		* @return the computed result
914	+	* @throws CancellationException if the computation was cancelled
915	+	* @throws ExecutionException if the computation threw an
916	+	* exception
917	+	* @throws InterruptedException if the current thread is not a
918	+	* member of a ForkJoinPool and was interrupted while waiting
919		*/
920	<	public final V helpJoin() {
921	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
922	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
923	<	reportException(w.helpJoinTask(this));
920	>	public final V get() throws InterruptedException, ExecutionException {
921	>	int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ?
922	>	doJoin() : externalInterruptibleAwaitDone();
923	>	Throwable ex;
924	>	if ((s &= DONE_MASK) == CANCELLED)
925	>	throw new CancellationException();
926	>	if (s == EXCEPTIONAL && (ex = getThrowableException()) != null)
927	>	throw new ExecutionException(ex);
928		return getRawResult();
929		}
930
931		/**
932	<	* Performs this task, awaits its completion if necessary, and
933	<	* return its result.
934	<	* @throws Throwable (a RuntimeException, Error, or unchecked
935	<	* exception) if the underlying computation did so.
932	>	* Waits if necessary for at most the given time for the computation
933	>	* to complete, and then retrieves its result, if available.
934	>	*
935	>	* @param timeout the maximum time to wait
936	>	* @param unit the time unit of the timeout argument
937		* @return the computed result
938	+	* @throws CancellationException if the computation was cancelled
939	+	* @throws ExecutionException if the computation threw an
940	+	* exception
941	+	* @throws InterruptedException if the current thread is not a
942	+	* member of a ForkJoinPool and was interrupted while waiting
943	+	* @throws TimeoutException if the wait timed out
944		*/
945	<	public final V invoke() {
946	<	if (status >= 0 && tryExec())
947	<	return getRawResult();
948	<	else
949	<	return join();
945	>	public final V get(long timeout, TimeUnit unit)
946	>	throws InterruptedException, ExecutionException, TimeoutException {
947	>	if (Thread.interrupted())
948	>	throw new InterruptedException();
949	>	// Messy in part because we measure in nanosecs, but wait in millisecs
950	>	int s; long ns, ms;
951	>	if ((s = status) >= 0 && (ns = unit.toNanos(timeout)) > 0L) {
952	>	long deadline = System.nanoTime() + ns;
953	>	ForkJoinPool p = null;
954	>	ForkJoinPool.WorkQueue w = null;
955	>	Thread t = Thread.currentThread();
956	>	if (t instanceof ForkJoinWorkerThread) {
957	>	ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
958	>	p = wt.pool;
959	>	w = wt.workQueue;
960	>	s = p.helpJoinOnce(w, this); // no retries on failure
961	>	}
962	>	boolean canBlock = false;
963	>	boolean interrupted = false;
964	>	try {
965	>	while ((s = status) >= 0) {
966	>	if (w != null && w.runState < 0)
967	>	cancelIgnoringExceptions(this);
968	>	else if (!canBlock) {
969	>	if (p == null || p.tryCompensate(this, null))
970	>	canBlock = true;
971	>	}
972	>	else {
973	>	if ((ms = TimeUnit.NANOSECONDS.toMillis(ns)) > 0L &&
974	>	U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
975	>	synchronized (this) {
976	>	if (status >= 0) {
977	>	try {
978	>	wait(ms);
979	>	} catch (InterruptedException ie) {
980	>	if (p == null)
981	>	interrupted = true;
982	>	}
983	>	}
984	>	else
985	>	notifyAll();
986	>	}
987	>	}
988	>	if ((s = status) < 0 || interrupted ||
989	>	(ns = deadline - System.nanoTime()) <= 0L)
990	>	break;
991	>	}
992	>	}
993	>	} finally {
994	>	if (p != null && canBlock)
995	>	p.incrementActiveCount();
996	>	}
997	>	if (interrupted)
998	>	throw new InterruptedException();
999	>	}
1000	>	if ((s &= DONE_MASK) != NORMAL) {
1001	>	Throwable ex;
1002	>	if (s == CANCELLED)
1003	>	throw new CancellationException();
1004	>	if (s != EXCEPTIONAL)
1005	>	throw new TimeoutException();
1006	>	if ((ex = getThrowableException()) != null)
1007	>	throw new ExecutionException(ex);
1008	>	}
1009	>	return getRawResult();
1010		}
1011
1012		/**
1013	<	* Joins this task, without returning its result or throwing an
1013	>	* Joins this task, without returning its result or throwing its
1014		* exception. This method may be useful when processing
1015		* collections of tasks when some have been cancelled or otherwise
1016		* known to have aborted.
1017		*/
1018		public final void quietlyJoin() {
1019	<	if (status >= 0) {
537	<	ForkJoinWorkerThread w = getWorker();
538	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
539	<	awaitDone(w, true);
540	<	}
1019	>	doJoin();
1020		}
1021
1022		/**
1023	<	* Possibly executes other tasks until this task is ready.
1023	>	* Commences performing this task and awaits its completion if
1024	>	* necessary, without returning its result or throwing its
1025	>	* exception.
1026		*/
1027	<	public final void quietlyHelpJoin() {
1028	<	if (status >= 0) {
548	<	ForkJoinWorkerThread w =
549	<	(ForkJoinWorkerThread)(Thread.currentThread());
550	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
551	<	w.helpJoinTask(this);
552	<	}
1027	>	public final void quietlyInvoke() {
1028	>	doInvoke();
1029		}
1030
1031		/**
1032	<	* Performs this task and awaits its completion if necessary,
1033	<	* without returning its result or throwing an exception. This
1034	<	* method may be useful when processing collections of tasks when
1035	<	* some have been cancelled or otherwise known to have aborted.
1032	>	* Possibly executes tasks until the pool hosting the current task
1033	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
1034	>	* be of use in designs in which many tasks are forked, but none
1035	>	* are explicitly joined, instead executing them until all are
1036	>	* processed.
1037	>	*
1038	>	* <p>This method may be invoked only from within {@code
1039	>	* ForkJoinPool} computations (as may be determined using method
1040	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1041	>	* result in exceptions or errors, possibly including {@code
1042	>	* ClassCastException}.
1043		*/
1044	<	public final void quietlyInvoke() {
1045	<	if (status >= 0 && !tryQuietlyInvoke())
1046	<	quietlyJoin();
1044	>	public static void helpQuiesce() {
1045	>	ForkJoinWorkerThread wt =
1046	>	(ForkJoinWorkerThread)Thread.currentThread();
1047	>	wt.pool.helpQuiescePool(wt.workQueue);
1048		}
1049
1050		/**
1051	<	* Returns true if the computation performed by this task has
1052	<	* completed (or has been cancelled).
1053	<	* @return true if this computation has completed
1051	>	* Resets the internal bookkeeping state of this task, allowing a
1052	>	* subsequent {@code fork}. This method allows repeated reuse of
1053	>	* this task, but only if reuse occurs when this task has either
1054	>	* never been forked, or has been forked, then completed and all
1055	>	* outstanding joins of this task have also completed. Effects
1056	>	* under any other usage conditions are not guaranteed.
1057	>	* This method may be useful when executing
1058	>	* pre-constructed trees of subtasks in loops.
1059	>	*
1060	>	* <p>Upon completion of this method, {@code isDone()} reports
1061	>	* {@code false}, and {@code getException()} reports {@code
1062	>	* null}. However, the value returned by {@code getRawResult} is
1063	>	* unaffected. To clear this value, you can invoke {@code
1064	>	* setRawResult(null)}.
1065		*/
1066	<	public final boolean isDone() {
1067	<	return status < 0;
1066	>	public void reinitialize() {
1067	>	if ((status & DONE_MASK) == EXCEPTIONAL)
1068	>	clearExceptionalCompletion();
1069	>	else
1070	>	status = 0;
1071		}
1072
1073		/**
1074	<	* Returns true if this task was cancelled.
1075	<	* @return true if this task was cancelled
1074	>	* Returns the pool hosting the current task execution, or null
1075	>	* if this task is executing outside of any ForkJoinPool.
1076	>	*
1077	>	* @see #inForkJoinPool
1078	>	* @return the pool, or {@code null} if none
1079		*/
1080	<	public final boolean isCancelled() {
1081	<	return (status & COMPLETION_MASK) == CANCELLED;
1080	>	public static ForkJoinPool getPool() {
1081	>	Thread t = Thread.currentThread();
1082	>	return (t instanceof ForkJoinWorkerThread) ?
1083	>	((ForkJoinWorkerThread) t).pool : null;
1084		}
1085
1086		/**
1087	<	* Returns true if this task threw an exception or was cancelled
1088	<	* @return true if this task threw an exception or was cancelled
1087	>	* Returns {@code true} if the current thread is a {@link
1088	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation.
1089	>	*
1090	>	* @return {@code true} if the current thread is a {@link
1091	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation,
1092	>	* or {@code false} otherwise
1093		*/
1094	<	public final boolean completedAbnormally() {
1095	<	return (status & COMPLETION_MASK) < NORMAL;
1094	>	public static boolean inForkJoinPool() {
1095	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
1096		}
1097
1098		/**
1099	<	* Returns the exception thrown by the base computation, or a
1100	<	* CancellationException if cancelled, or null if none or if the
1101	<	* method has not yet completed.
1102	<	* @return the exception, or null if none
1099	>	* Tries to unschedule this task for execution. This method will
1100	>	* typically succeed if this task is the most recently forked task
1101	>	* by the current thread, and has not commenced executing in
1102	>	* another thread.  This method may be useful when arranging
1103	>	* alternative local processing of tasks that could have been, but
1104	>	* were not, stolen.
1105	>	*
1106	>	* <p>This method may be invoked only from within {@code
1107	>	* ForkJoinPool} computations (as may be determined using method
1108	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1109	>	* result in exceptions or errors, possibly including {@code
1110	>	* ClassCastException}.
1111	>	*
1112	>	* @return {@code true} if unforked
1113		*/
1114	<	public final Throwable getException() {
1115	<	int s = status & COMPLETION_MASK;
1116	<	if (s >= NORMAL)
600	<	return null;
601	<	if (s == CANCELLED)
602	<	return new CancellationException();
603	<	return exceptionMap.get(this);
1114	>	public boolean tryUnfork() {
1115	>	return ((ForkJoinWorkerThread)Thread.currentThread())
1116	>	.workQueue.tryUnpush(this);
1117		}
1118
1119		/**
1120	<	* Asserts that the results of this task's computation will not be
1121	<	* used. If a cancellation occurs before this task is processed,
1122	<	* then its <tt>compute</tt> method will not be executed,
1123	<	* <tt>isCancelled</tt> will report true, and <tt>join</tt> will
611	<	* result in a CancellationException being thrown. Otherwise, when
612	<	* cancellation races with completion, there are no guarantees
613	<	* about whether <tt>isCancelled</tt> will report true, whether
614	<	* <tt>join</tt> will return normally or via an exception, or
615	<	* whether these behaviors will remain consistent upon repeated
616	<	* invocation.
1120	>	* Returns an estimate of the number of tasks that have been
1121	>	* forked by the current worker thread but not yet executed. This
1122	>	* value may be useful for heuristic decisions about whether to
1123	>	* fork other tasks.
1124		*
1125	<	* <p>This method may be overridden in subclasses, but if so, must
1126	<	* still ensure that these minimal properties hold. In particular,
1127	<	* the cancel method itself must not throw exceptions.
1125	>	* <p>This method may be invoked only from within {@code
1126	>	* ForkJoinPool} computations (as may be determined using method
1127	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1128	>	* result in exceptions or errors, possibly including {@code
1129	>	* ClassCastException}.
1130		*
1131	<	* <p> This method is designed to be invoked by <em>other</em>
1132	<	* tasks. To terminate the current task, you can just return or
1133	<	* throw an unchecked exception from its computation method, or
1134	<	* invoke <tt>completeExceptionally(someException)</tt>.
1131	>	* @return the number of tasks
1132	>	*/
1133	>	public static int getQueuedTaskCount() {
1134	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1135	>	.workQueue.queueSize();
1136	>	}
1137	>
1138	>	/**
1139	>	* Returns an estimate of how many more locally queued tasks are
1140	>	* held by the current worker thread than there are other worker
1141	>	* threads that might steal them.  This value may be useful for
1142	>	* heuristic decisions about whether to fork other tasks. In many
1143	>	* usages of ForkJoinTasks, at steady state, each worker should
1144	>	* aim to maintain a small constant surplus (for example, 3) of
1145	>	* tasks, and to process computations locally if this threshold is
1146	>	* exceeded.
1147		*
1148	<	* @param mayInterruptIfRunning this value is ignored in the
1149	<	* default implementation because tasks are not in general
1150	<	* cancelled via interruption.
1148	>	* <p>This method may be invoked only from within {@code
1149	>	* ForkJoinPool} computations (as may be determined using method
1150	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1151	>	* result in exceptions or errors, possibly including {@code
1152	>	* ClassCastException}.
1153		*
1154	<	* @return true if this task is now cancelled
1154	>	* @return the surplus number of tasks, which may be negative
1155		*/
1156	<	public boolean cancel(boolean mayInterruptIfRunning) {
1157	<	setCompletion(CANCELLED);
1158	<	return (status & COMPLETION_MASK) == CANCELLED;
1159	<	}
1156	>	public static int getSurplusQueuedTaskCount() {
1157	>	/*
1158	>	* The aim of this method is to return a cheap heuristic guide
1159	>	* for task partitioning when programmers, frameworks, tools,
1160	>	* or languages have little or no idea about task granularity.
1161	>	* In essence by offering this method, we ask users only about
1162	>	* tradeoffs in overhead vs expected throughput and its
1163	>	* variance, rather than how finely to partition tasks.
1164	>	*
1165	>	* In a steady state strict (tree-structured) computation,
1166	>	* each thread makes available for stealing enough tasks for
1167	>	* other threads to remain active. Inductively, if all threads
1168	>	* play by the same rules, each thread should make available
1169	>	* only a constant number of tasks.
1170	>	*
1171	>	* The minimum useful constant is just 1. But using a value of
1172	>	* 1 would require immediate replenishment upon each steal to
1173	>	* maintain enough tasks, which is infeasible.  Further,
1174	>	* partitionings/granularities of offered tasks should
1175	>	* minimize steal rates, which in general means that threads
1176	>	* nearer the top of computation tree should generate more
1177	>	* than those nearer the bottom. In perfect steady state, each
1178	>	* thread is at approximately the same level of computation
1179	>	* tree. However, producing extra tasks amortizes the
1180	>	* uncertainty of progress and diffusion assumptions.
1181	>	*
1182	>	* So, users will want to use values larger, but not much
1183	>	* larger than 1 to both smooth over transient shortages and
1184	>	* hedge against uneven progress; as traded off against the
1185	>	* cost of extra task overhead. We leave the user to pick a
1186	>	* threshold value to compare with the results of this call to
1187	>	* guide decisions, but recommend values such as 3.
1188	>	*
1189	>	* When all threads are active, it is on average OK to
1190	>	* estimate surplus strictly locally. In steady-state, if one
1191	>	* thread is maintaining say 2 surplus tasks, then so are
1192	>	* others. So we can just use estimated queue length.
1193	>	* However, this strategy alone leads to serious mis-estimates
1194	>	* in some non-steady-state conditions (ramp-up, ramp-down,
1195	>	* other stalls). We can detect many of these by further
1196	>	* considering the number of "idle" threads, that are known to
1197	>	* have zero queued tasks, so compensate by a factor of
1198	>	* (#idle/#active) threads.
1199	>	*/
1200	>	ForkJoinWorkerThread wt =
1201	>	(ForkJoinWorkerThread)Thread.currentThread();
1202	>	return wt.workQueue.queueSize() - wt.pool.idlePerActive();
1203	>	}
1204	>
1205	>	// Extension methods
1206	>
1207	>	/**
1208	>	* Returns the result that would be returned by {@link #join}, even
1209	>	* if this task completed abnormally, or {@code null} if this task
1210	>	* is not known to have been completed.  This method is designed
1211	>	* to aid debugging, as well as to support extensions. Its use in
1212	>	* any other context is discouraged.
1213	>	*
1214	>	* @return the result, or {@code null} if not completed
1215	>	*/
1216	>	public abstract V getRawResult();
1217
1218		/**
1219	<	* Completes this task abnormally, and if not already aborted or
1220	<	* cancelled, causes it to throw the given exception upon
1221	<	* <tt>join</tt> and related operations. This method may be used
1222	<	* to induce exceptions in asynchronous tasks, or to force
1223	<	* completion of tasks that would not otherwise complete.  This
644	<	* method is overridable, but overridden versions must invoke
645	<	* <tt>super</tt> implementation to maintain guarantees.
646	<	* @param ex the exception to throw. If this exception is
647	<	* not a RuntimeException or Error, the actual exception thrown
648	<	* will be a RuntimeException with cause ex.
1219	>	* Forces the given value to be returned as a result.  This method
1220	>	* is designed to support extensions, and should not in general be
1221	>	* called otherwise.
1222	>	*
1223	>	* @param value the value
1224		*/
1225	<	public void completeExceptionally(Throwable ex) {
651	<	setDoneExceptionally((ex instanceof RuntimeException) ||
652	<	(ex instanceof Error)? ex :
653	<	new RuntimeException(ex));
654	<	}
1225	>	protected abstract void setRawResult(V value);
1226
1227		/**
1228	<	* Completes this task, and if not already aborted or cancelled,
1229	<	* returning a <tt>null</tt> result upon <tt>join</tt> and related
1230	<	* operations. This method may be used to provide results for
1231	<	* asynchronous tasks, or to provide alternative handling for
1232	<	* tasks that would not otherwise complete normally.
1228	>	* Immediately performs the base action of this task.  This method
1229	>	* is designed to support extensions, and should not in general be
1230	>	* called otherwise. The return value controls whether this task
1231	>	* is considered to be done normally. It may return false in
1232	>	* asynchronous actions that require explicit invocations of
1233	>	* {@link #complete} to become joinable. It may also throw an
1234	>	* (unchecked) exception to indicate abnormal exit.
1235		*
1236	<	* @param value the result value for this task.
1236	>	* @return {@code true} if completed normally
1237		*/
1238	<	public void complete(V value) {
1239	<	try {
1240	<	setRawResult(value);
1241	<	} catch(Throwable rex) {
1242	<	setDoneExceptionally(rex);
1243	<	return;
1244	<	}
1245	<	setNormalCompletion();
1238	>	protected abstract boolean exec();
1239	>
1240	>	/**
1241	>	* Returns, but does not unschedule or execute, a task queued by
1242	>	* the current thread but not yet executed, if one is immediately
1243	>	* available. There is no guarantee that this task will actually
1244	>	* be polled or executed next. Conversely, this method may return
1245	>	* null even if a task exists but cannot be accessed without
1246	>	* contention with other threads.  This method is designed
1247	>	* primarily to support extensions, and is unlikely to be useful
1248	>	* otherwise.
1249	>	*
1250	>	* <p>This method may be invoked only from within {@code
1251	>	* ForkJoinPool} computations (as may be determined using method
1252	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1253	>	* result in exceptions or errors, possibly including {@code
1254	>	* ClassCastException}.
1255	>	*
1256	>	* @return the next task, or {@code null} if none are available
1257	>	*/
1258	>	protected static ForkJoinTask<?> peekNextLocalTask() {
1259	>	return ((ForkJoinWorkerThread) Thread.currentThread()).workQueue.peek();
1260		}
1261
1262		/**
1263	<	* Resets the internal bookkeeping state of this task, allowing a
1264	<	* subsequent <tt>fork</tt>. This method allows repeated reuse of
1265	<	* this task, but only if reuse occurs when this task has either
1266	<	* never been forked, or has been forked, then completed and all
1267	<	* outstanding joins of this task have also completed. Effects
1268	<	* under any other usage conditions are not guaranteed, and are
1269	<	* almost surely wrong. This method may be useful when executing
1270	<	* pre-constructed trees of subtasks in loops.
1263	>	* Unschedules and returns, without executing, the next task
1264	>	* queued by the current thread but not yet executed.  This method
1265	>	* is designed primarily to support extensions, and is unlikely to
1266	>	* be useful otherwise.
1267	>	*
1268	>	* <p>This method may be invoked only from within {@code
1269	>	* ForkJoinPool} computations (as may be determined using method
1270	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1271	>	* result in exceptions or errors, possibly including {@code
1272	>	* ClassCastException}.
1273	>	*
1274	>	* @return the next task, or {@code null} if none are available
1275		*/
1276	<	public void reinitialize() {
1277	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
1278	<	exceptionMap.remove(this);
688	<	status = 0;
1276	>	protected static ForkJoinTask<?> pollNextLocalTask() {
1277	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1278	>	.workQueue.nextLocalTask();
1279		}
1280
1281		/**
1282	<	* Tries to unschedule this task for execution. This method will
1283	<	* typically succeed if this task is the next task that would be
1284	<	* executed by the current thread, and will typically fail (return
1285	<	* false) otherwise. This method may be useful when arranging
1286	<	* faster local processing of tasks that could have been, but were
1287	<	* not, stolen.
1288	<	* @return true if unforked
1282	>	* Unschedules and returns, without executing, the next task
1283	>	* queued by the current thread but not yet executed, if one is
1284	>	* available, or if not available, a task that was forked by some
1285	>	* other thread, if available. Availability may be transient, so a
1286	>	* {@code null} result does not necessarily imply quiescence
1287	>	* of the pool this task is operating in.  This method is designed
1288	>	* primarily to support extensions, and is unlikely to be useful
1289	>	* otherwise.
1290	>	*
1291	>	* <p>This method may be invoked only from within {@code
1292	>	* ForkJoinPool} computations (as may be determined using method
1293	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1294	>	* result in exceptions or errors, possibly including {@code
1295	>	* ClassCastException}.
1296	>	*
1297	>	* @return a task, or {@code null} if none are available
1298		*/
1299	<	public boolean tryUnfork() {
1300	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
1299	>	protected static ForkJoinTask<?> pollTask() {
1300	>	ForkJoinWorkerThread wt =
1301	>	(ForkJoinWorkerThread)Thread.currentThread();
1302	>	return wt.pool.nextTaskFor(wt.workQueue);
1303		}
1304
1305	+	// Mark-bit operations
1306	+
1307		/**
1308	<	* Forks both tasks, returning when <tt>isDone</tt> holds for both
1309	<	* of them or an exception is encountered. This method may be
1310	<	* invoked only from within other ForkJoinTask
1311	<	* computations. Attempts to invoke in other contexts result in
709	<	* exceptions or errors including ClassCastException.
710	<	* @param t1 one task
711	<	* @param t2 the other task
712	<	* @throws NullPointerException if t1 or t2 are null
713	<	* @throws RuntimeException or Error if either task did so.
1308	>	* Returns true if this task is marked.
1309	>	*
1310	>	* @return true if this task is marked
1311	>	* @since 1.8
1312		*/
1313	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
1314	<	t2.fork();
717	<	t1.invoke();
718	<	t2.join();
1313	>	public final boolean isMarkedForkJoinTask() {
1314	>	return (status & MARKED) != 0;
1315		}
1316
1317		/**
1318	<	* Forks the given tasks, returning when <tt>isDone</tt> holds for
1319	<	* all of them. If any task encounters an exception, others may be
1320	<	* cancelled.  This method may be invoked only from within other
1321	<	* ForkJoinTask computations. Attempts to invoke in other contexts
726	<	* result in exceptions or errors including ClassCastException.
727	<	* @param tasks the array of tasks
728	<	* @throws NullPointerException if tasks or any element are null.
729	<	* @throws RuntimeException or Error if any task did so.
1318	>	* Atomically sets the mark on this task.
1319	>	*
1320	>	* @return true if this task was previously unmarked
1321	>	* @since 1.8
1322		*/
1323	<	public static void invokeAll(ForkJoinTask<?>... tasks) {
1324	<	Throwable ex = null;
1325	<	int last = tasks.length - 1;
1326	<	for (int i = last; i >= 0; --i) {
1327	<	ForkJoinTask<?> t = tasks[i];
1328	<	if (t == null) {
737	<	if (ex == null)
738	<	ex = new NullPointerException();
739	<	}
740	<	else if (i != 0)
741	<	t.fork();
742	<	else {
743	<	t.quietlyInvoke();
744	<	if (ex == null)
745	<	ex = t.getException();
746	<	}
747	<	}
748	<	for (int i = 1; i <= last; ++i) {
749	<	ForkJoinTask<?> t = tasks[i];
750	<	if (t != null) {
751	<	if (ex != null)
752	<	t.cancel(false);
753	<	else {
754	<	t.quietlyJoin();
755	<	if (ex == null)
756	<	ex = t.getException();
757	<	}
758	<	}
1323	>	public final boolean markForkJoinTask() {
1324	>	for (int s;;) {
1325	>	if (((s = status) & MARKED) != 0)
1326	>	return false;
1327	>	if (U.compareAndSwapInt(this, STATUS, s, s | MARKED))
1328	>	return true;
1329		}
760	–	if (ex != null)
761	–	rethrowException(ex);
1330		}
1331
1332		/**
1333	<	* Forks all tasks in the collection, returning when
1334	<	* <tt>isDone</tt> holds for all of them. If any task encounters
1335	<	* an exception, others may be cancelled.  This method may be
1336	<	* invoked only from within other ForkJoinTask
769	<	* computations. Attempts to invoke in other contexts result in
770	<	* exceptions or errors including ClassCastException.
771	<	* @param tasks the collection of tasks
772	<	* @throws NullPointerException if tasks or any element are null.
773	<	* @throws RuntimeException or Error if any task did so.
1333	>	* Atomically clears the mark on this task.
1334	>	*
1335	>	* @return true if this task was previously marked
1336	>	* @since 1.8
1337		*/
1338	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
1339	<	if (!(tasks instanceof List)) {
1340	<	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
1341	<	return;
1342	<	}
1343	<	List<? extends ForkJoinTask<?>> ts =
781	<	(List<? extends ForkJoinTask<?>>)tasks;
782	<	Throwable ex = null;
783	<	int last = ts.size() - 1;
784	<	for (int i = last; i >= 0; --i) {
785	<	ForkJoinTask<?> t = ts.get(i);
786	<	if (t == null) {
787	<	if (ex == null)
788	<	ex = new NullPointerException();
789	<	}
790	<	else if (i != 0)
791	<	t.fork();
792	<	else {
793	<	t.quietlyInvoke();
794	<	if (ex == null)
795	<	ex = t.getException();
796	<	}
797	<	}
798	<	for (int i = 1; i <= last; ++i) {
799	<	ForkJoinTask<?> t = ts.get(i);
800	<	if (t != null) {
801	<	if (ex != null)
802	<	t.cancel(false);
803	<	else {
804	<	t.quietlyJoin();
805	<	if (ex == null)
806	<	ex = t.getException();
807	<	}
808	<	}
1338	>	public final boolean unmarkForkJoinTask() {
1339	>	for (int s;;) {
1340	>	if (((s = status) & MARKED) == 0)
1341	>	return false;
1342	>	if (U.compareAndSwapInt(this, STATUS, s, s & ~MARKED))
1343	>	return true;
1344		}
810	–	if (ex != null)
811	–	rethrowException(ex);
1345		}
1346
1347		/**
1348	<	* Possibly executes tasks until the pool hosting the current task
1349	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
1350	<	* designs in which many tasks are forked, but none are explicitly
818	<	* joined, instead executing them until all are processed.
1348	>	* Adaptor for Runnables. This implements RunnableFuture
1349	>	* to be compliant with AbstractExecutorService constraints
1350	>	* when used in ForkJoinPool.
1351		*/
1352	<	public static void helpQuiesce() {
1353	<	((ForkJoinWorkerThread)(Thread.currentThread())).
1354	<	helpQuiescePool();
1352	>	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1353	>	implements RunnableFuture<T> {
1354	>	final Runnable runnable;
1355	>	T result;
1356	>	AdaptedRunnable(Runnable runnable, T result) {
1357	>	if (runnable == null) throw new NullPointerException();
1358	>	this.runnable = runnable;
1359	>	this.result = result; // OK to set this even before completion
1360	>	}
1361	>	public final T getRawResult() { return result; }
1362	>	public final void setRawResult(T v) { result = v; }
1363	>	public final boolean exec() { runnable.run(); return true; }
1364	>	public final void run() { invoke(); }
1365	>	private static final long serialVersionUID = 5232453952276885070L;
1366		}
1367
1368		/**
1369	<	* Returns a estimate of how many more locally queued tasks are
827	<	* held by the current worker thread than there are other worker
828	<	* threads that might want to steal them.  This value may be
829	<	* useful for heuristic decisions about whether to fork other
830	<	* tasks. In many usages of ForkJoinTasks, at steady state, each
831	<	* worker should aim to maintain a small constant surplus (for
832	<	* example, 3) of tasks, and to process computations locally if
833	<	* this threshold is exceeded.
834	<	* @return the surplus number of tasks, which may be negative
1369	>	* Adaptor for Runnables without results
1370		*/
1371	<	public static int surplus() {
1372	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
1373	<	.getEstimatedSurplusTaskCount();
1371	>	static final class AdaptedRunnableAction extends ForkJoinTask<Void>
1372	>	implements RunnableFuture<Void> {
1373	>	final Runnable runnable;
1374	>	AdaptedRunnableAction(Runnable runnable) {
1375	>	if (runnable == null) throw new NullPointerException();
1376	>	this.runnable = runnable;
1377	>	}
1378	>	public final Void getRawResult() { return null; }
1379	>	public final void setRawResult(Void v) { }
1380	>	public final boolean exec() { runnable.run(); return true; }
1381	>	public final void run() { invoke(); }
1382	>	private static final long serialVersionUID = 5232453952276885070L;
1383		}
1384
1385	<	// Extension kit
1385	>	/**
1386	>	* Adaptor for Callables
1387	>	*/
1388	>	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1389	>	implements RunnableFuture<T> {
1390	>	final Callable<? extends T> callable;
1391	>	T result;
1392	>	AdaptedCallable(Callable<? extends T> callable) {
1393	>	if (callable == null) throw new NullPointerException();
1394	>	this.callable = callable;
1395	>	}
1396	>	public final T getRawResult() { return result; }
1397	>	public final void setRawResult(T v) { result = v; }
1398	>	public final boolean exec() {
1399	>	try {
1400	>	result = callable.call();
1401	>	return true;
1402	>	} catch (Error err) {
1403	>	throw err;
1404	>	} catch (RuntimeException rex) {
1405	>	throw rex;
1406	>	} catch (Exception ex) {
1407	>	throw new RuntimeException(ex);
1408	>	}
1409	>	}
1410	>	public final void run() { invoke(); }
1411	>	private static final long serialVersionUID = 2838392045355241008L;
1412	>	}
1413
1414		/**
1415	<	* Returns the result that would be returned by <tt>join</tt>, or
1416	<	* null if this task is not known to have been completed.  This
1417	<	* method is designed to aid debugging, as well as to support
847	<	* extensions. Its use in any other context is discouraged.
1415	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1416	>	* method of the given {@code Runnable} as its action, and returns
1417	>	* a null result upon {@link #join}.
1418		*
1419	<	* @return the result, or null if not completed.
1419	>	* @param runnable the runnable action
1420	>	* @return the task
1421		*/
1422	<	public abstract V getRawResult();
1422	>	public static ForkJoinTask<?> adapt(Runnable runnable) {
1423	>	return new AdaptedRunnableAction(runnable);
1424	>	}
1425
1426		/**
1427	<	* Forces the given value to be returned as a result.  This method
1428	<	* is designed to support extensions, and should not in general be
1429	<	* called otherwise.
1427	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1428	>	* method of the given {@code Runnable} as its action, and returns
1429	>	* the given result upon {@link #join}.
1430		*
1431	<	* @param value the value
1431	>	* @param runnable the runnable action
1432	>	* @param result the result upon completion
1433	>	* @return the task
1434		*/
1435	<	protected abstract void setRawResult(V value);
1435	>	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1436	>	return new AdaptedRunnable<T>(runnable, result);
1437	>	}
1438
1439		/**
1440	<	* Immediately performs the base action of this task.  This method
1441	<	* is designed to support extensions, and should not in general be
1442	<	* called otherwise. The return value controls whether this task
1443	<	* is considered to be done normally. It may return false in
1444	<	* asynchronous actions that require explicit invocations of
1445	<	* <tt>complete</tt> to become joinable. It may throw exceptions
1446	<	* to indicate abnormal exit.
870	<	* @return true if completed normally
871	<	* @throws Error or RuntimeException if encountered during computation
1440	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1441	>	* method of the given {@code Callable} as its action, and returns
1442	>	* its result upon {@link #join}, translating any checked exceptions
1443	>	* encountered into {@code RuntimeException}.
1444	>	*
1445	>	* @param callable the callable action
1446	>	* @return the task
1447		*/
1448	<	protected abstract boolean exec();
1448	>	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1449	>	return new AdaptedCallable<T>(callable);
1450	>	}
1451
1452		// Serialization support
1453
1454		private static final long serialVersionUID = -7721805057305804111L;
1455
1456		/**
1457	<	* Save the state to a stream.
1457	>	* Saves this task to a stream (that is, serializes it).
1458		*
1459		* @serialData the current run status and the exception thrown
1460	<	* during execution, or null if none.
884	<	* @param s the stream
1460	>	* during execution, or {@code null} if none
1461		*/
1462		private void writeObject(java.io.ObjectOutputStream s)
1463		throws java.io.IOException {
#	Line 890 | Line 1466 | public abstract class ForkJoinTask<V> im
1466		}
1467
1468		/**
1469	<	* Reconstitute the instance from a stream.
894	<	* @param s the stream
1469	>	* Reconstitutes this task from a stream (that is, deserializes it).
1470		*/
1471		private void readObject(java.io.ObjectInputStream s)
1472		throws java.io.IOException, ClassNotFoundException {
1473		s.defaultReadObject();
899	–	//        status &= ~INTERNAL_SIGNAL_MASK; //  todo: define policy
1474		Object ex = s.readObject();
1475		if (ex != null)
1476	<	setDoneExceptionally((Throwable)ex);
1476	>	setExceptionalCompletion((Throwable)ex);
1477		}
1478
1479	<	// Temporary Unsafe mechanics for preliminary release
1480	<
1481	<	static final Unsafe _unsafe;
908	<	static final long statusOffset;
909	<
1479	>	// Unsafe mechanics
1480	>	private static final sun.misc.Unsafe U;
1481	>	private static final long STATUS;
1482		static {
1483	+	exceptionTableLock = new ReentrantLock();
1484	+	exceptionTableRefQueue = new ReferenceQueue<Object>();
1485	+	exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY];
1486		try {
1487	<	if (ForkJoinTask.class.getClassLoader() != null) {
1488	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
914	<	f.setAccessible(true);
915	<	_unsafe = (Unsafe)f.get(null);
916	<	}
917	<	else
918	<	_unsafe = Unsafe.getUnsafe();
919	<	statusOffset = _unsafe.objectFieldOffset
1487	>	U = getUnsafe();
1488	>	STATUS = U.objectFieldOffset
1489		(ForkJoinTask.class.getDeclaredField("status"));
1490	<	} catch (Exception ex) { throw new Error(ex); }
1490	>	} catch (Exception e) {
1491	>	throw new Error(e);
1492	>	}
1493		}
1494
1495	+	/**
1496	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1497	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1498	+	* into a jdk.
1499	+	*
1500	+	* @return a sun.misc.Unsafe
1501	+	*/
1502	+	private static sun.misc.Unsafe getUnsafe() {
1503	+	try {
1504	+	return sun.misc.Unsafe.getUnsafe();
1505	+	} catch (SecurityException se) {
1506	+	try {
1507	+	return java.security.AccessController.doPrivileged
1508	+	(new java.security
1509	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1510	+	public sun.misc.Unsafe run() throws Exception {
1511	+	java.lang.reflect.Field f = sun.misc
1512	+	.Unsafe.class.getDeclaredField("theUnsafe");
1513	+	f.setAccessible(true);
1514	+	return (sun.misc.Unsafe) f.get(null);
1515	+	}});
1516	+	} catch (java.security.PrivilegedActionException e) {
1517	+	throw new RuntimeException("Could not initialize intrinsics",
1518	+	e.getCause());
1519	+	}
1520	+	}
1521	+	}
1522		}

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