[ViewVC] Diff of: jsr166/jsr166/src/jsr166y/ForkJoinTask.java

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.19 by dl, Sat Jul 25 17:49:01 2009 UTC vs.
Revision 1.85 by jsr166, Tue Jan 31 01:51:13 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	–
9	–	import java.util.concurrent.*;
10	–
8		import java.io.Serializable;
9		import java.util.Collection;
13	–	import java.util.Collections;
10		import java.util.List;
11	<	import java.util.Map;
12	<	import java.util.WeakHashMap;
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 {@link
27	<	* ForkJoinPool}. A ForkJoinTask is a thread-like entity that is much
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" ForkJoinTask begins execution when submitted to a
33	<	* {@link ForkJoinPool}. Once started, it will usually in turn start
34	<	* other subtasks. As indicated by the name of this class, many
35	<	* programs using ForkJoinTasks employ only methods {@code fork}
36	<	* and {@code join}, or derivatives such as
37	<	* {@code invokeAll}. However, this class also provides a number
38	<	* of other methods that can come into play in advanced usages, as
39	<	* well as extension mechanics that allow support of new forms of
40	<	* fork/join processing.
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 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>A ForkJoinTask is a lightweight form of {@link Future}. The
70	<	* efficiency of ForkJoinTasks stems from a set of restrictions (that
71	<	* are only partially statically enforceable) reflecting their
72	<	* intended use as computational tasks calculating pure functions or
73	<	* operating on purely isolated objects. The primary coordination
74	<	* mechanisms are {@link #fork}, that arranges asynchronous execution,
75	<	* and {@link #join}, that doesn't proceed until the task's result has
76	<	* been computed. Computations should avoid {@code synchronized}
77	<	* methods or blocks, and should minimize other blocking
78	<	* synchronization apart from joining other tasks or using
79	<	* synchronizers such as Phasers that are advertised to cooperate with
80	<	* fork/join scheduling. Tasks should also not perform blocking IO,
47	<	* and should ideally access variables that are completely independent
48	<	* of those accessed by other running tasks. Minor breaches of these
49	<	* restrictions, for example using shared output streams, may be
50	<	* tolerable in practice, but frequent use may result in poor
51	<	* performance, and the potential to indefinitely stall if the number
52	<	* of threads not waiting for IO or other external synchronization
53	<	* becomes exhausted. This usage restriction is in part enforced by
54	<	* not permitting checked exceptions such as {@code IOExceptions}
55	<	* to be thrown. However, computations may still encounter unchecked
56	<	* exceptions, that are rethrown to callers attempting join
57	<	* them. These exceptions may additionally include
58	<	* RejectedExecutionExceptions stemming from internal resource
59	<	* exhaustion such as failure to allocate internal task queues.
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 #helpJoin} enables callers to actively
87	<	* execute other tasks while awaiting joins, which is sometimes more
88	<	* efficient but only applies when all subtasks are known to be
89	<	* strictly tree-structured. Method {@link #invoke} is semantically
69	<	* equivalent to {@code fork(); join()} but always attempts to
70	<	* begin execution in the current thread. The "<em>quiet</em>" forms
71	<	* of these methods do not extract results or report exceptions. These
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> The ForkJoinTask class is not usually directly subclassed.
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. Normally, a concrete
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 others
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	<	* ClassCastException.
129	>	* {@code ClassCastException}.
130		*
131	<	* <p>Most base support methods are {@code final} because their
132	<	* implementations are intrinsically tied to the underlying
133	<	* lightweight task scheduling framework, and so cannot be overridden.
134	<	* Developers creating new basic styles of fork/join processing should
135	<	* minimally implement {@code protected} methods
136	<	* {@code exec}, {@code setRawResult}, and
137	<	* {@code getRawResult}, while also introducing an abstract
138	<	* computational method that can be implemented in its subclasses,
139	<	* possibly relying on other {@code protected} methods provided
140	<	* by this class.
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, otherwise 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	<	* parallelism cannot improve throughput. If too small, then memory
167	<	* and internal task maintenance overhead may overwhelm processing.
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
177	<	* to be used in extensions such as remote execution frameworks. It is
178	<	* in general sensible to serialize tasks only before or after, but
179	<	* not during execution. Serialization is not relied on during
114	<	* execution itself.
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 {
185
186	<	/**
187	<	* Run control status bits packed into a single int to minimize
188	<	* footprint and to ensure atomicity (via CAS). Status is
189	<	* initially zero, and takes on nonnegative values until
190	<	* completed, upon which status holds COMPLETED. CANCELLED, or
191	<	* EXCEPTIONAL, which use the top 3 bits. Tasks undergoing
192	<	* blocking waits by other threads have SIGNAL_MASK bits set --
193	<	* bit 15 for external (nonFJ) waits, and the rest a count of
194	<	* waiting FJ threads. (This representation relies on
195	<	* ForkJoinPool max thread limits). Completion of a stolen task
196	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
197	<	* though suboptimal for some purposes, we use basic builtin
133	<	* wait/notify to take advantage of "monitor inflation" in JVMs
134	<	* that we would otherwise need to emulate to avoid adding further
135	<	* per-task bookkeeping overhead. Note that bits 16-28 are
136	<	* currently unused. Also value 0x80000000 is available as spare
137	<	* completion value.
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		*/
139	–	volatile int status; // accessed directly by pool and workers
140	–
141	–	static final int COMPLETION_MASK = 0xe0000000;
142	–	static final int NORMAL = 0xe0000000; // == mask
143	–	static final int CANCELLED = 0xc0000000;
144	–	static final int EXCEPTIONAL = 0xa0000000;
145	–	static final int SIGNAL_MASK = 0x0000ffff;
146	–	static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
147	–	static final int EXTERNAL_SIGNAL = 0x00008000; // top bit of low word
199
200		/**
201	<	* Table of exceptions thrown by tasks, to enable reporting by
202	<	* callers. Because exceptions are rare, we don't directly keep
203	<	* them with task objects, but instead use a weak ref table. Note
204	<	* that cancellation exceptions don't appear in the table, but are
205	<	* instead recorded as status values.
206	<	* TODO: Use ConcurrentReferenceHashMap
201	>	* The number of times to try to help join a task without any
202	>	* apparent progress before giving up and blocking. The value is
203	>	* arbitrary but should be large enough to cope with transient
204	>	* stalls (due to GC etc) that can cause helping methods not to be
205	>	* able to proceed because other workers have not progressed to
206	>	* the point where subtasks can be found or taken.
207	>	*/
208	>	private static final int HELP_RETRIES = 32;
209	>
210	>	/*
211	>	* The status field holds run control status bits packed into a
212	>	* single int to minimize footprint and to ensure atomicity (via
213	>	* CAS). Status is initially zero, and takes on nonnegative
214	>	* values until completed, upon which status holds value
215	>	* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
216	>	* waits by other threads have the SIGNAL bit set. Completion of
217	>	* a stolen task with SIGNAL set awakens any waiters via
218	>	* notifyAll. Even though suboptimal for some purposes, we use
219	>	* basic builtin wait/notify to take advantage of "monitor
220	>	* inflation" in JVMs that we would otherwise need to emulate to
221	>	* avoid adding further per-task bookkeeping overhead. We want
222	>	* these monitors to be "fat", i.e., not use biasing or thin-lock
223	>	* techniques, so use some odd coding idioms that tend to avoid
224	>	* them.
225		*/
157	–	static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
158	–	Collections.synchronizedMap
159	–	(new WeakHashMap<ForkJoinTask<?>, Throwable>());
160	–
161	–	// within-package utilities
226
227	<	/**
228	<	* Gets current worker thread, or null if not a worker thread.
229	<	*/
230	<	static ForkJoinWorkerThread getWorker() {
231	<	Thread t = Thread.currentThread();
232	<	return ((t instanceof ForkJoinWorkerThread) ?
233	<	(ForkJoinWorkerThread) t : null);
170	<	}
171	<
172	<	final boolean casStatus(int cmp, int val) {
173	<	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
174	<	}
175	<
176	<	/**
177	<	* Workaround for not being able to rethrow unchecked exceptions.
178	<	*/
179	<	static void rethrowException(Throwable ex) {
180	<	if (ex != null)
181	<	UNSAFE.throwException(ex);
182	<	}
183	<
184	<	// Setting completion status
227	>	/** The run status of this task */
228	>	volatile int status; // accessed directly by pool and workers
229	>	static final int NORMAL = 0xfffffffc; // negative with low 2 bits 0
230	>	static final int CANCELLED = 0xfffffff8; // must be < NORMAL
231	>	static final int EXCEPTIONAL = 0xfffffff4; // must be < CANCELLED
232	>	static final int SIGNAL = 0x00000001;
233	>	static final int MARKED = 0x00000002;
234
235		/**
236	<	* Marks completion and wakes up threads waiting to join this task.
236	>	* Marks completion and wakes up threads waiting to join this
237	>	* task, also clearing signal request bits. A specialization for
238	>	* NORMAL completion is in method doExec.
239		*
240		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
241	+	* @return completion status on exit
242		*/
243	<	final void setCompletion(int completion) {
244	<	ForkJoinPool pool = getPool();
245	<	if (pool != null) {
246	<	int s; // Clear signal bits while setting completion status
247	<	do {} while ((s = status) >= 0 && !casStatus(s, completion));
248	<
249	<	if ((s & SIGNAL_MASK) != 0) {
250	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
199	<	pool.updateRunningCount(s);
200	<	synchronized (this) { notifyAll(); }
243	>	private int setCompletion(int completion) {
244	>	for (int s;;) {
245	>	if ((s = status) < 0)
246	>	return s;
247	>	if (U.compareAndSwapInt(this, STATUS, s, (s & ~SIGNAL)\|completion)) {
248	>	if ((s & SIGNAL) != 0)
249	>	synchronized (this) { notifyAll(); }
250	>	return completion;
251		}
252		}
203	–	else
204	–	externallySetCompletion(completion);
205	–	}
206	–
207	–	/**
208	–	* Version of setCompletion for non-FJ threads. Leaves signal
209	–	* bits for unblocked threads to adjust, and always notifies.
210	–	*/
211	–	private void externallySetCompletion(int completion) {
212	–	int s;
213	–	do {} while ((s = status) >= 0 &&
214	–	!casStatus(s, (s & SIGNAL_MASK) \| completion));
215	–	synchronized (this) { notifyAll(); }
253		}
254
255		/**
256	<	* Sets status to indicate normal completion.
257	<	*/
258	<	final void setNormalCompletion() {
259	<	// Try typical fast case -- single CAS, no signal, not already done.
260	<	// Manually expand casStatus to improve chances of inlining it
261	<	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
262	<	setCompletion(NORMAL);
256	>	* Primary execution method for stolen tasks. Unless done, calls
257	>	* exec and records status if completed, but doesn't wait for
258	>	* completion otherwise.
259	>	*
260	>	* @return status on exit from this method
261	>	*/
262	>	final int doExec() {
263	>	int s; boolean completed;
264	>	if ((s = status) >= 0) {
265	>	try {
266	>	completed = exec();
267	>	} catch (Throwable rex) {
268	>	return setExceptionalCompletion(rex);
269	>	}
270	>	while ((s = status) >= 0 && completed) {
271	>	if (U.compareAndSwapInt(this, STATUS, s, (s & ~SIGNAL)\|NORMAL)) {
272	>	if ((s & SIGNAL) != 0)
273	>	synchronized (this) { notifyAll(); }
274	>	return NORMAL;
275	>	}
276	>	}
277	>	}
278	>	return s;
279		}
280
228	–	// internal waiting and notification
229	–
281		/**
282	<	* Performs the actual monitor wait for awaitDone.
282	>	* Blocks a non-worker-thread until completion.
283	>	* @return status upon completion
284		*/
285	<	private void doAwaitDone() {
286	<	// Minimize lock bias and in/de-flation effects by maximizing
287	<	// chances of waiting inside sync
288	<	try {
289	<	while (status >= 0)
290	<	synchronized (this) { if (status >= 0) wait(); }
291	<	} catch (InterruptedException ie) {
292	<	onInterruptedWait();
285	>	private int externalAwaitDone() {
286	>	int s;
287	>	if ((s = status) >= 0) {
288	>	boolean interrupted = false;
289	>	synchronized (this) {
290	>	while ((s = status) >= 0) {
291	>	if (U.compareAndSwapInt(this, STATUS, s, s \| SIGNAL)) {
292	>	try {
293	>	wait();
294	>	} catch (InterruptedException ie) {
295	>	interrupted = true;
296	>	}
297	>	}
298	>	}
299	>	}
300	>	if (interrupted)
301	>	Thread.currentThread().interrupt();
302		}
303	+	return s;
304		}
305
306		/**
307	<	* Performs the actual timed monitor wait for awaitDone.
307	>	* Blocks a non-worker-thread until completion or interruption or timeout.
308		*/
309	<	private void doAwaitDone(long startTime, long nanos) {
310	<	synchronized (this) {
311	<	try {
312	<	while (status >= 0) {
313	<	long nt = nanos - System.nanoTime() - startTime;
314	<	if (nt <= 0)
315	<	break;
316	<	wait(nt / 1000000, (int) (nt % 1000000));
309	>	private int externalInterruptibleAwaitDone(long millis)
310	>	throws InterruptedException {
311	>	int s;
312	>	if (Thread.interrupted())
313	>	throw new InterruptedException();
314	>	if ((s = status) >= 0) {
315	>	synchronized (this) {
316	>	while ((s = status) >= 0) {
317	>	if (U.compareAndSwapInt(this, STATUS, s, s \| SIGNAL)) {
318	>	wait(millis);
319	>	if (millis > 0L)
320	>	break;
321	>	}
322		}
256	–	} catch (InterruptedException ie) {
257	–	onInterruptedWait();
323		}
324		}
325	+	return s;
326		}
327
262	–	// Awaiting completion
328
329		/**
330	<	* Sets status to indicate there is joiner, then waits for join,
331	<	* surrounded with pool notifications.
330	>	* Implementation for join, get, quietlyJoin. Directly handles
331	>	* only cases of already-completed, external wait, and
332	>	* unfork+exec. Others are relayed to awaitJoin.
333	>	*
334	>	* @return status upon completion
335	>	*/
336	>	private int doJoin() {
337	>	int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w;
338	>	if ((s = status) >= 0) {
339	>	if (!((t = Thread.currentThread()) instanceof ForkJoinWorkerThread))
340	>	s = externalAwaitDone();
341	>	else if (!(w = (wt = (ForkJoinWorkerThread)t).workQueue).
342	>	tryUnpush(this) \|\| (s = doExec()) >= 0)
343	>	s = awaitJoin(w, wt.pool);
344	>	}
345	>	return s;
346	>	}
347	>
348	>	/**
349	>	* Helps and/or blocks until joined.
350		*
351	<	* @return status upon exit
351	>	* @param w the joiner
352	>	* @param p the pool
353	>	* @return status upon completion
354		*/
355	<	private int awaitDone(ForkJoinWorkerThread w,
271	<	boolean maintainParallelism) {
272	<	ForkJoinPool pool = (w == null) ? null : w.pool;
355	>	private int awaitJoin(ForkJoinPool.WorkQueue w, ForkJoinPool p) {
356		int s;
357	<	while ((s = status) >= 0) {
358	<	if (casStatus(s, (pool == null) ? s\|EXTERNAL_SIGNAL : s+1)) {
359	<	if (pool == null \|\| !pool.preJoin(this, maintainParallelism))
360	<	doAwaitDone();
361	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
362	<	adjustPoolCountsOnUnblock(pool);
357	>	ForkJoinTask<?> prevJoin = w.currentJoin;
358	>	w.currentJoin = this;
359	>	for (int k = HELP_RETRIES; (s = status) >= 0;) {
360	>	if ((w.queueSize() > 0) ?
361	>	w.tryRemoveAndExec(this) : // self-help
362	>	p.tryHelpStealer(w, this)) // help process tasks
363	>	k = HELP_RETRIES; // reset if made progress
364	>	else if ((s = status) < 0) // recheck
365		break;
366	+	else if (--k > 0) {
367	+	if ((k & 3) == 1)
368	+	Thread.yield(); // occasionally yield
369	+	}
370	+	else if (k == 0)
371	+	p.tryPollForAndExec(w, this); // uncommon self-help case
372	+	else if (p.tryCompensate()) { // true if can block
373	+	try {
374	+	int ss = status;
375	+	if (ss >= 0 && // assert need signal
376	+	U.compareAndSwapInt(this, STATUS, ss, ss \| SIGNAL)) {
377	+	synchronized (this) {
378	+	if (status >= 0) // block
379	+	wait();
380	+	}
381	+	}
382	+	} catch (InterruptedException ignore) {
383	+	} finally {
384	+	p.incrementActiveCount(); // re-activate
385	+	}
386		}
387		}
388	+	w.currentJoin = prevJoin;
389		return s;
390		}
391
392		/**
393	<	* Timed version of awaitDone
393	>	* Implementation for invoke, quietlyInvoke.
394		*
395	<	* @return status upon exit
395	>	* @return status upon completion
396		*/
397	<	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
398	<	ForkJoinPool pool = (w == null) ? null : w.pool;
399	<	int s;
400	<	while ((s = status) >= 0) {
401	<	if (casStatus(s, (pool == null) ? s\|EXTERNAL_SIGNAL : s+1)) {
402	<	long startTime = System.nanoTime();
403	<	if (pool == null \|\| !pool.preJoin(this, false))
404	<	doAwaitDone(startTime, nanos);
299	<	if ((s = status) >= 0) {
300	<	adjustPoolCountsOnCancelledWait(pool);
301	<	s = status;
302	<	}
303	<	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
304	<	adjustPoolCountsOnUnblock(pool);
305	<	break;
397	>	private int doInvoke() {
398	>	int s; Thread t;
399	>	if ((s = doExec()) >= 0) {
400	>	if (!((t = Thread.currentThread()) instanceof ForkJoinWorkerThread))
401	>	s = externalAwaitDone();
402	>	else {
403	>	ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
404	>	s = awaitJoin(wt.workQueue, wt.pool);
405		}
406		}
407		return s;
408		}
409
410	+	// Exception table support
411	+
412		/**
413	<	* Notifies pool that thread is unblocked. Called by signalled
414	<	* threads when woken by non-FJ threads (which is atypical).
413	>	* Table of exceptions thrown by tasks, to enable reporting by
414	>	* callers. Because exceptions are rare, we don't directly keep
415	>	* them with task objects, but instead use a weak ref table. Note
416	>	* that cancellation exceptions don't appear in the table, but are
417	>	* instead recorded as status values.
418	>	*
419	>	* Note: These statics are initialized below in static block.
420		*/
421	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
422	<	int s;
423	<	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
318	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
319	<	pool.updateRunningCount(s);
320	<	}
421	>	private static final ExceptionNode[] exceptionTable;
422	>	private static final ReentrantLock exceptionTableLock;
423	>	private static final ReferenceQueue<Object> exceptionTableRefQueue;
424
425		/**
426	<	* Notifies pool to adjust counts on cancelled or timed out wait.
426	>	* Fixed capacity for exceptionTable.
427		*/
428	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
326	<	if (pool != null) {
327	<	int s;
328	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
329	<	if (casStatus(s, s - 1)) {
330	<	pool.updateRunningCount(1);
331	<	break;
332	<	}
333	<	}
334	<	}
335	<	}
428	>	private static final int EXCEPTION_MAP_CAPACITY = 32;
429
430		/**
431	<	* Handles interruptions during waits.
431	>	* Key-value nodes for exception table. The chained hash table
432	>	* uses identity comparisons, full locking, and weak references
433	>	* for keys. The table has a fixed capacity because it only
434	>	* maintains task exceptions long enough for joiners to access
435	>	* them, so should never become very large for sustained
436	>	* periods. However, since we do not know when the last joiner
437	>	* completes, we must use weak references and expunge them. We do
438	>	* so on each operation (hence full locking). Also, some thread in
439	>	* any ForkJoinPool will call helpExpungeStaleExceptions when its
440	>	* pool becomes isQuiescent.
441		*/
442	<	private void onInterruptedWait() {
443	<	ForkJoinWorkerThread w = getWorker();
444	<	if (w == null)
445	<	Thread.currentThread().interrupt(); // re-interrupt
446	<	else if (w.isTerminating())
447	<	cancelIgnoringExceptions();
448	<	// else if FJworker, ignore interrupt
449	<	}
450	<
451	<	// Recording and reporting exceptions
350	<
351	<	private void setDoneExceptionally(Throwable rex) {
352	<	exceptionMap.put(this, rex);
353	<	setCompletion(EXCEPTIONAL);
442	>	static final class ExceptionNode extends WeakReference<ForkJoinTask<?>> {
443	>	final Throwable ex;
444	>	ExceptionNode next;
445	>	final long thrower; // use id not ref to avoid weak cycles
446	>	ExceptionNode(ForkJoinTask<?> task, Throwable ex, ExceptionNode next) {
447	>	super(task, exceptionTableRefQueue);
448	>	this.ex = ex;
449	>	this.next = next;
450	>	this.thrower = Thread.currentThread().getId();
451	>	}
452		}
453
454		/**
455	<	* Throws the exception associated with status s.
455	>	* Records exception and sets exceptional completion.
456		*
457	<	* @throws the exception
457	>	* @return status on exit
458		*/
459	<	private void reportException(int s) {
460	<	if ((s &= COMPLETION_MASK) < NORMAL) {
461	<	if (s == CANCELLED)
462	<	throw new CancellationException();
463	<	else
464	<	rethrowException(exceptionMap.get(this));
459	>	private int setExceptionalCompletion(Throwable ex) {
460	>	int h = System.identityHashCode(this);
461	>	final ReentrantLock lock = exceptionTableLock;
462	>	lock.lock();
463	>	try {
464	>	expungeStaleExceptions();
465	>	ExceptionNode[] t = exceptionTable;
466	>	int i = h & (t.length - 1);
467	>	for (ExceptionNode e = t[i]; ; e = e.next) {
468	>	if (e == null) {
469	>	t[i] = new ExceptionNode(this, ex, t[i]);
470	>	break;
471	>	}
472	>	if (e.get() == this) // already present
473	>	break;
474	>	}
475	>	} finally {
476	>	lock.unlock();
477		}
478	+	return setCompletion(EXCEPTIONAL);
479		}
480
481		/**
482	<	* Returns result or throws exception using j.u.c.Future conventions.
483	<	* Only call when {@code isDone} known to be true.
482	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
483	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
484	>	* exceptions, but if it does anyway, we have no recourse during
485	>	* shutdown, so guard against this case.
486		*/
487	<	private V reportFutureResult()
488	<	throws ExecutionException, InterruptedException {
489	<	int s = status & COMPLETION_MASK;
490	<	if (s < NORMAL) {
491	<	Throwable ex;
492	<	if (s == CANCELLED)
380	<	throw new CancellationException();
381	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
382	<	throw new ExecutionException(ex);
383	<	if (Thread.interrupted())
384	<	throw new InterruptedException();
487	>	static final void cancelIgnoringExceptions(ForkJoinTask<?> t) {
488	>	if (t != null && t.status >= 0) {
489	>	try {
490	>	t.cancel(false);
491	>	} catch (Throwable ignore) {
492	>	}
493		}
386	–	return getRawResult();
494		}
495
496		/**
497	<	* Returns result or throws exception using j.u.c.Future conventions
391	<	* with timeouts.
497	>	* Removes exception node and clears status
498		*/
499	<	private V reportTimedFutureResult()
500	<	throws InterruptedException, ExecutionException, TimeoutException {
501	<	Throwable ex;
502	<	int s = status & COMPLETION_MASK;
503	<	if (s == NORMAL)
504	<	return getRawResult();
505	<	if (s == CANCELLED)
506	<	throw new CancellationException();
507	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
508	<	throw new ExecutionException(ex);
509	<	if (Thread.interrupted())
510	<	throw new InterruptedException();
511	<	throw new TimeoutException();
499	>	private void clearExceptionalCompletion() {
500	>	int h = System.identityHashCode(this);
501	>	final ReentrantLock lock = exceptionTableLock;
502	>	lock.lock();
503	>	try {
504	>	ExceptionNode[] t = exceptionTable;
505	>	int i = h & (t.length - 1);
506	>	ExceptionNode e = t[i];
507	>	ExceptionNode pred = null;
508	>	while (e != null) {
509	>	ExceptionNode next = e.next;
510	>	if (e.get() == this) {
511	>	if (pred == null)
512	>	t[i] = next;
513	>	else
514	>	pred.next = next;
515	>	break;
516	>	}
517	>	pred = e;
518	>	e = next;
519	>	}
520	>	expungeStaleExceptions();
521	>	status = 0;
522	>	} finally {
523	>	lock.unlock();
524	>	}
525		}
526
408	–	// internal execution methods
409	–
527		/**
528	<	* Calls exec, recording completion, and rethrowing exception if
529	<	* encountered. Caller should normally check status before calling.
528	>	* Returns a rethrowable exception for the given task, if
529	>	* available. To provide accurate stack traces, if the exception
530	>	* was not thrown by the current thread, we try to create a new
531	>	* exception of the same type as the one thrown, but with the
532	>	* recorded exception as its cause. If there is no such
533	>	* constructor, we instead try to use a no-arg constructor,
534	>	* followed by initCause, to the same effect. If none of these
535	>	* apply, or any fail due to other exceptions, we return the
536	>	* recorded exception, which is still correct, although it may
537	>	* contain a misleading stack trace.
538		*
539	<	* @return true if completed normally
539	>	* @return the exception, or null if none
540		*/
541	<	private boolean tryExec() {
542	<	try { // try block must contain only call to exec
543	<	if (!exec())
544	<	return false;
545	<	} catch (Throwable rex) {
546	<	setDoneExceptionally(rex);
547	<	rethrowException(rex);
548	<	return false; // not reached
541	>	private Throwable getThrowableException() {
542	>	if (status != EXCEPTIONAL)
543	>	return null;
544	>	int h = System.identityHashCode(this);
545	>	ExceptionNode e;
546	>	final ReentrantLock lock = exceptionTableLock;
547	>	lock.lock();
548	>	try {
549	>	expungeStaleExceptions();
550	>	ExceptionNode[] t = exceptionTable;
551	>	e = t[h & (t.length - 1)];
552	>	while (e != null && e.get() != this)
553	>	e = e.next;
554	>	} finally {
555	>	lock.unlock();
556		}
557	<	setNormalCompletion();
558	<	return true;
559	<	}
560	<
561	<	/**
430	<	* Main execution method used by worker threads. Invokes
431	<	* base computation unless already complete.
432	<	*/
433	<	final void quietlyExec() {
434	<	if (status >= 0) {
557	>	Throwable ex;
558	>	if (e == null \|\| (ex = e.ex) == null)
559	>	return null;
560	>	if (e.thrower != Thread.currentThread().getId()) {
561	>	Class<? extends Throwable> ec = ex.getClass();
562		try {
563	<	if (!exec())
564	<	return;
565	<	} catch (Throwable rex) {
566	<	setDoneExceptionally(rex);
567	<	return;
563	>	Constructor<?> noArgCtor = null;
564	>	Constructor<?>[] cs = ec.getConstructors();// public ctors only
565	>	for (int i = 0; i < cs.length; ++i) {
566	>	Constructor<?> c = cs[i];
567	>	Class<?>[] ps = c.getParameterTypes();
568	>	if (ps.length == 0)
569	>	noArgCtor = c;
570	>	else if (ps.length == 1 && ps[0] == Throwable.class)
571	>	return (Throwable)(c.newInstance(ex));
572	>	}
573	>	if (noArgCtor != null) {
574	>	Throwable wx = (Throwable)(noArgCtor.newInstance());
575	>	wx.initCause(ex);
576	>	return wx;
577	>	}
578	>	} catch (Exception ignore) {
579		}
442	–	setNormalCompletion();
580		}
581	+	return ex;
582		}
583
584		/**
585	<	* Calls exec(), recording but not rethrowing exception.
448	<	* Caller should normally check status before calling.
449	<	*
450	<	* @return true if completed normally
585	>	* Poll stale refs and remove them. Call only while holding lock.
586		*/
587	<	private boolean tryQuietlyInvoke() {
588	<	try {
589	<	if (!exec())
590	<	return false;
591	<	} catch (Throwable rex) {
592	<	setDoneExceptionally(rex);
593	<	return false;
587	>	private static void expungeStaleExceptions() {
588	>	for (Object x; (x = exceptionTableRefQueue.poll()) != null;) {
589	>	if (x instanceof ExceptionNode) {
590	>	ForkJoinTask<?> key = ((ExceptionNode)x).get();
591	>	ExceptionNode[] t = exceptionTable;
592	>	int i = System.identityHashCode(key) & (t.length - 1);
593	>	ExceptionNode e = t[i];
594	>	ExceptionNode pred = null;
595	>	while (e != null) {
596	>	ExceptionNode next = e.next;
597	>	if (e == x) {
598	>	if (pred == null)
599	>	t[i] = next;
600	>	else
601	>	pred.next = next;
602	>	break;
603	>	}
604	>	pred = e;
605	>	e = next;
606	>	}
607	>	}
608		}
460	–	setNormalCompletion();
461	–	return true;
609		}
610
611		/**
612	<	* Cancels, ignoring any exceptions it throws.
612	>	* If lock is available, poll stale refs and remove them.
613	>	* Called from ForkJoinPool when pools become quiescent.
614		*/
615	<	final void cancelIgnoringExceptions() {
616	<	try {
617	<	cancel(false);
618	<	} catch (Throwable ignore) {
615	>	static final void helpExpungeStaleExceptions() {
616	>	final ReentrantLock lock = exceptionTableLock;
617	>	if (lock.tryLock()) {
618	>	try {
619	>	expungeStaleExceptions();
620	>	} finally {
621	>	lock.unlock();
622	>	}
623		}
624		}
625
626		/**
627	<	* Main implementation of helpJoin
627	>	* Report the result of invoke or join; called only upon
628	>	* non-normal return of internal versions.
629		*/
630	<	private int busyJoin(ForkJoinWorkerThread w) {
631	<	int s;
632	<	ForkJoinTask<?> t;
633	<	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
634	<	t.quietlyExec();
635	<	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
630	>	private V reportResult() {
631	>	int s; Throwable ex;
632	>	if ((s = status) == CANCELLED)
633	>	throw new CancellationException();
634	>	if (s == EXCEPTIONAL && (ex = getThrowableException()) != null)
635	>	U.throwException(ex);
636	>	return getRawResult();
637		}
638
639		// public methods
#	Line 487 \| Line 641 \| public abstract class ForkJoinTask<V> im
641		/**
642		* Arranges to asynchronously execute this task. While it is not
643		* necessarily enforced, it is a usage error to fork a task more
644	<	* than once unless it has completed and been reinitialized. This
645	<	* method may be invoked only from within ForkJoinTask
646	<	* computations (as may be determined using method {@link
647	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
648	<	* in exceptions or errors, possibly including ClassCastException.
644	>	* than once unless it has completed and been reinitialized.
645	>	* Subsequent modifications to the state of this task or any data
646	>	* it operates on are not necessarily consistently observable by
647	>	* any thread other than the one executing it unless preceded by a
648	>	* call to {@link #join} or related methods, or a call to {@link
649	>	* #isDone} returning {@code true}.
650	>	*
651	>	* <p>This method may be invoked only from within {@code
652	>	* ForkJoinPool} computations (as may be determined using method
653	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
654	>	* result in exceptions or errors, possibly including {@code
655	>	* ClassCastException}.
656		*
657	<	* @return <code>this</code>, to simplify usage.
657	>	* @return {@code this}, to simplify usage
658		*/
659		public final ForkJoinTask<V> fork() {
660	<	((ForkJoinWorkerThread) Thread.currentThread())
661	<	.pushTask(this);
660	>	ForkJoinWorkerThread wt;
661	>	(wt = (ForkJoinWorkerThread)Thread.currentThread()).
662	>	workQueue.push(this, wt.pool);
663		return this;
664		}
665
666		/**
667	<	* Returns the result of the computation when it is ready.
668	<	* This method differs from {@code get} in that abnormal
669	<	* completion results in RuntimeExceptions or Errors, not
670	<	* ExecutionExceptions.
667	>	* Returns the result of the computation when it {@link #isDone is
668	>	* done}. This method differs from {@link #get()} in that
669	>	* abnormal completion results in {@code RuntimeException} or
670	>	* {@code Error}, not {@code ExecutionException}, and that
671	>	* interrupts of the calling thread do <em>not</em> cause the
672	>	* method to abruptly return by throwing {@code
673	>	* InterruptedException}.
674		*
675		* @return the computed result
676		*/
677		public final V join() {
678	<	ForkJoinWorkerThread w = getWorker();
679	<	if (w == null \|\| status < 0 \|\| !w.unpushTask(this) \|\| !tryExec())
680	<	reportException(awaitDone(w, true));
681	<	return getRawResult();
678	>	if (doJoin() != NORMAL)
679	>	return reportResult();
680	>	else
681	>	return getRawResult();
682		}
683
684		/**
685		* Commences performing this task, awaits its completion if
686	<	* necessary, and return its result.
686	>	* necessary, and returns its result, or throws an (unchecked)
687	>	* {@code RuntimeException} or {@code Error} if the underlying
688	>	* computation did so.
689		*
523	–	* @throws Throwable (a RuntimeException, Error, or unchecked
524	–	* exception) if the underlying computation did so
690		* @return the computed result
691		*/
692		public final V invoke() {
693	<	if (status >= 0 && tryExec())
694	<	return getRawResult();
693	>	if (doInvoke() != NORMAL)
694	>	return reportResult();
695		else
696	<	return join();
696	>	return getRawResult();
697		}
698
699		/**
700	<	* Forks both tasks, returning when {@code isDone} holds for
701	<	* both of them or an exception is encountered. This method may be
702	<	* invoked only from within ForkJoinTask computations (as may be
703	<	* determined using method {@link #inForkJoinPool}). Attempts to
704	<	* invoke in other contexts result in exceptions or errors,
705	<	* possibly including ClassCastException.
706	<	*
707	<	* @param t1 one task
708	<	* @param t2 the other task
709	<	* @throws NullPointerException if t1 or t2 are null
710	<	* @throws RuntimeException or Error if either task did so
700	>	* Forks the given tasks, returning when {@code isDone} holds for
701	>	* each task or an (unchecked) exception is encountered, in which
702	>	* case the exception is rethrown. If more than one task
703	>	* encounters an exception, then this method throws any one of
704	>	* these exceptions. If any task encounters an exception, the
705	>	* other may be cancelled. However, the execution status of
706	>	* individual tasks is not guaranteed upon exceptional return. The
707	>	* status of each task may be obtained using {@link
708	>	* #getException()} and related methods to check if they have been
709	>	* cancelled, completed normally or exceptionally, or left
710	>	* unprocessed.
711	>	*
712	>	* <p>This method may be invoked only from within {@code
713	>	* ForkJoinPool} computations (as may be determined using method
714	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
715	>	* result in exceptions or errors, possibly including {@code
716	>	* ClassCastException}.
717	>	*
718	>	* @param t1 the first task
719	>	* @param t2 the second task
720	>	* @throws NullPointerException if any task is null
721		*/
722	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
722	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
723		t2.fork();
724		t1.invoke();
725		t2.join();
726		}
727
728		/**
729	<	* Forks the given tasks, returning when {@code isDone} holds
730	<	* for all of them. If any task encounters an exception, others
731	<	* may be cancelled. This method may be invoked only from within
732	<	* ForkJoinTask computations (as may be determined using method
733	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
734	<	* result in exceptions or errors, possibly including
735	<	* ClassCastException.
729	>	* Forks the given tasks, returning when {@code isDone} holds for
730	>	* each task or an (unchecked) exception is encountered, in which
731	>	* case the exception is rethrown. If more than one task
732	>	* encounters an exception, then this method throws any one of
733	>	* these exceptions. If any task encounters an exception, others
734	>	* may be cancelled. However, the execution status of individual
735	>	* tasks is not guaranteed upon exceptional return. The status of
736	>	* each task may be obtained using {@link #getException()} and
737	>	* related methods to check if they have been cancelled, completed
738	>	* normally or exceptionally, or left unprocessed.
739	>	*
740	>	* <p>This method may be invoked only from within {@code
741	>	* ForkJoinPool} computations (as may be determined using method
742	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
743	>	* result in exceptions or errors, possibly including {@code
744	>	* ClassCastException}.
745		*
746	<	* @param tasks the array of tasks
747	<	* @throws NullPointerException if tasks or any element are null
564	<	* @throws RuntimeException or Error if any task did so
746	>	* @param tasks the tasks
747	>	* @throws NullPointerException if any task is null
748		*/
749		public static void invokeAll(ForkJoinTask<?>... tasks) {
750		Throwable ex = null;
#	Line 574 \| Line 757 \| public abstract class ForkJoinTask<V> im
757		}
758		else if (i != 0)
759		t.fork();
760	<	else {
761	<	t.quietlyInvoke();
579	<	if (ex == null)
580	<	ex = t.getException();
581	<	}
760	>	else if (t.doInvoke() < NORMAL && ex == null)
761	>	ex = t.getException();
762		}
763		for (int i = 1; i <= last; ++i) {
764		ForkJoinTask<?> t = tasks[i];
765		if (t != null) {
766		if (ex != null)
767		t.cancel(false);
768	<	else {
769	<	t.quietlyJoin();
590	<	if (ex == null)
591	<	ex = t.getException();
592	<	}
768	>	else if (t.doJoin() < NORMAL)
769	>	ex = t.getException();
770		}
771		}
772		if (ex != null)
773	<	rethrowException(ex);
773	>	U.throwException(ex);
774		}
775
776		/**
777	<	* Forks all tasks in the collection, returning when
778	<	* {@code isDone} holds for all of them. If any task
779	<	* encounters an exception, others may be cancelled. This method
780	<	* may be invoked only from within ForkJoinTask computations (as
781	<	* may be determined using method {@link
782	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
783	<	* in exceptions or errors, possibly including ClassCastException.
777	>	* Forks all tasks in the specified collection, returning when
778	>	* {@code isDone} holds for each task or an (unchecked) exception
779	>	* is encountered, in which case the exception is rethrown. If
780	>	* more than one task encounters an exception, then this method
781	>	* throws any one of these exceptions. If any task encounters an
782	>	* exception, others may be cancelled. However, the execution
783	>	* status of individual tasks is not guaranteed upon exceptional
784	>	* return. The status of each task may be obtained using {@link
785	>	* #getException()} and related methods to check if they have been
786	>	* cancelled, completed normally or exceptionally, or left
787	>	* unprocessed.
788	>	*
789	>	* <p>This method may be invoked only from within {@code
790	>	* ForkJoinPool} computations (as may be determined using method
791	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
792	>	* result in exceptions or errors, possibly including {@code
793	>	* ClassCastException}.
794		*
795		* @param tasks the collection of tasks
796		* @return the tasks argument, to simplify usage
797		* @throws NullPointerException if tasks or any element are null
611	–	* @throws RuntimeException or Error if any task did so
798		*/
799		public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
800	<	if (!(tasks instanceof List<?>)) {
800	>	if (!(tasks instanceof RandomAccess) \|\| !(tasks instanceof List<?>)) {
801		invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
802		return tasks;
803		}
#	Line 628 \| Line 814 \| public abstract class ForkJoinTask<V> im
814		}
815		else if (i != 0)
816		t.fork();
817	<	else {
818	<	t.quietlyInvoke();
633	<	if (ex == null)
634	<	ex = t.getException();
635	<	}
817	>	else if (t.doInvoke() < NORMAL && ex == null)
818	>	ex = t.getException();
819		}
820		for (int i = 1; i <= last; ++i) {
821		ForkJoinTask<?> t = ts.get(i);
822		if (t != null) {
823		if (ex != null)
824		t.cancel(false);
825	<	else {
826	<	t.quietlyJoin();
644	<	if (ex == null)
645	<	ex = t.getException();
646	<	}
825	>	else if (t.doJoin() < NORMAL)
826	>	ex = t.getException();
827		}
828		}
829		if (ex != null)
830	<	rethrowException(ex);
830	>	U.throwException(ex);
831		return tasks;
832		}
833
834		/**
835	<	* Returns true if the computation performed by this task has
836	<	* completed (or has been cancelled).
835	>	* Attempts to cancel execution of this task. This attempt will
836	>	* fail if the task has already completed or could not be
837	>	* cancelled for some other reason. If successful, and this task
838	>	* has not started when {@code cancel} is called, execution of
839	>	* this task is suppressed. After this method returns
840	>	* successfully, unless there is an intervening call to {@link
841	>	* #reinitialize}, subsequent calls to {@link #isCancelled},
842	>	* {@link #isDone}, and {@code cancel} will return {@code true}
843	>	* and calls to {@link #join} and related methods will result in
844	>	* {@code CancellationException}.
845	>	*
846	>	* <p>This method may be overridden in subclasses, but if so, must
847	>	* still ensure that these properties hold. In particular, the
848	>	* {@code cancel} method itself must not throw exceptions.
849		*
850	<	* @return true if this computation has completed
850	>	* <p>This method is designed to be invoked by <em>other</em>
851	>	* tasks. To terminate the current task, you can just return or
852	>	* throw an unchecked exception from its computation method, or
853	>	* invoke {@link #completeExceptionally}.
854	>	*
855	>	* @param mayInterruptIfRunning this value has no effect in the
856	>	* default implementation because interrupts are not used to
857	>	* control cancellation.
858	>	*
859	>	* @return {@code true} if this task is now cancelled
860		*/
861	+	public boolean cancel(boolean mayInterruptIfRunning) {
862	+	return setCompletion(CANCELLED) == CANCELLED;
863	+	}
864	+
865		public final boolean isDone() {
866		return status < 0;
867		}
868
664	–	/**
665	–	* Returns true if this task was cancelled.
666	–	*
667	–	* @return true if this task was cancelled
668	–	*/
869		public final boolean isCancelled() {
870	<	return (status & COMPLETION_MASK) == CANCELLED;
870	>	return status == CANCELLED;
871		}
872
873		/**
874	<	* Asserts that the results of this task's computation will not be
675	<	* used. If a cancellation occurs before attempting to execute this
676	<	* task, then execution will be suppressed, {@code isCancelled}
677	<	* will report true, and {@code join} will result in a
678	<	* {@code CancellationException} being thrown. Otherwise, when
679	<	* cancellation races with completion, there are no guarantees
680	<	* about whether {@code isCancelled} will report true, whether
681	<	* {@code join} will return normally or via an exception, or
682	<	* whether these behaviors will remain consistent upon repeated
683	<	* invocation.
684	<	*
685	<	* <p>This method may be overridden in subclasses, but if so, must
686	<	* still ensure that these minimal properties hold. In particular,
687	<	* the cancel method itself must not throw exceptions.
688	<	*
689	<	* <p> This method is designed to be invoked by <em>other</em>
690	<	* tasks. To terminate the current task, you can just return or
691	<	* throw an unchecked exception from its computation method, or
692	<	* invoke {@code completeExceptionally}.
693	<	*
694	<	* @param mayInterruptIfRunning this value is ignored in the
695	<	* default implementation because tasks are not in general
696	<	* cancelled via interruption
874	>	* Returns {@code true} if this task threw an exception or was cancelled.
875		*
876	<	* @return true if this task is now cancelled
876	>	* @return {@code true} if this task threw an exception or was cancelled
877		*/
878	<	public boolean cancel(boolean mayInterruptIfRunning) {
879	<	setCompletion(CANCELLED);
702	<	return (status & COMPLETION_MASK) == CANCELLED;
878	>	public final boolean isCompletedAbnormally() {
879	>	return status < NORMAL;
880		}
881
882		/**
883	<	* Returns true if this task threw an exception or was cancelled.
883	>	* Returns {@code true} if this task completed without throwing an
884	>	* exception and was not cancelled.
885		*
886	<	* @return true if this task threw an exception or was cancelled
886	>	* @return {@code true} if this task completed without throwing an
887	>	* exception and was not cancelled
888		*/
889	<	public final boolean isCompletedAbnormally() {
890	<	return (status & COMPLETION_MASK) < NORMAL;
889	>	public final boolean isCompletedNormally() {
890	>	return status == NORMAL;
891		}
892
893		/**
894		* Returns the exception thrown by the base computation, or a
895	<	* CancellationException if cancelled, or null if none or if the
896	<	* method has not yet completed.
895	>	* {@code CancellationException} if cancelled, or {@code null} if
896	>	* none or if the method has not yet completed.
897		*
898	<	* @return the exception, or null if none
898	>	* @return the exception, or {@code null} if none
899		*/
900		public final Throwable getException() {
901	<	int s = status & COMPLETION_MASK;
902	<	if (s >= NORMAL)
903	<	return null;
904	<	if (s == CANCELLED)
726	<	return new CancellationException();
727	<	return exceptionMap.get(this);
901	>	int s = status;
902	>	return ((s >= NORMAL) ? null :
903	>	(s == CANCELLED) ? new CancellationException() :
904	>	getThrowableException());
905		}
906
907		/**
#	Line 733 \| Line 910 \| public abstract class ForkJoinTask<V> im
910		* {@code join} and related operations. This method may be used
911		* to induce exceptions in asynchronous tasks, or to force
912		* completion of tasks that would not otherwise complete. Its use
913	<	* in other situations is likely to be wrong. This method is
913	>	* in other situations is discouraged. This method is
914		* overridable, but overridden versions must invoke {@code super}
915		* implementation to maintain guarantees.
916		*
917	<	* @param ex the exception to throw. If this exception is
918	<	* not a RuntimeException or Error, the actual exception thrown
919	<	* will be a RuntimeException with cause ex.
917	>	* @param ex the exception to throw. If this exception is not a
918	>	* {@code RuntimeException} or {@code Error}, the actual exception
919	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
920		*/
921		public void completeExceptionally(Throwable ex) {
922	<	setDoneExceptionally((ex instanceof RuntimeException) \|\|
923	<	(ex instanceof Error) ? ex :
924	<	new RuntimeException(ex));
922	>	setExceptionalCompletion((ex instanceof RuntimeException) \|\|
923	>	(ex instanceof Error) ? ex :
924	>	new RuntimeException(ex));
925		}
926
927		/**
928		* Completes this task, and if not already aborted or cancelled,
929	<	* returning a {@code null} result upon {@code join} and related
930	<	* operations. This method may be used to provide results for
931	<	* asynchronous tasks, or to provide alternative handling for
932	<	* tasks that would not otherwise complete normally. Its use in
933	<	* other situations is likely to be wrong. This method is
934	<	* overridable, but overridden versions must invoke {@code super}
935	<	* implementation to maintain guarantees.
929	>	* returning the given value as the result of subsequent
930	>	* invocations of {@code join} and related operations. This method
931	>	* may be used to provide results for asynchronous tasks, or to
932	>	* provide alternative handling for tasks that would not otherwise
933	>	* complete normally. Its use in other situations is
934	>	* discouraged. This method is overridable, but overridden
935	>	* versions must invoke {@code super} implementation to maintain
936	>	* guarantees.
937		*
938		* @param value the result value for this task
939		*/
#	Line 763 \| Line 941 \| public abstract class ForkJoinTask<V> im
941		try {
942		setRawResult(value);
943		} catch (Throwable rex) {
944	<	setDoneExceptionally(rex);
944	>	setExceptionalCompletion(rex);
945		return;
946		}
947	<	setNormalCompletion();
770	<	}
771	<
772	<	public final V get() throws InterruptedException, ExecutionException {
773	<	ForkJoinWorkerThread w = getWorker();
774	<	if (w == null \|\| status < 0 \|\| !w.unpushTask(this) \|\| !tryQuietlyInvoke())
775	<	awaitDone(w, true);
776	<	return reportFutureResult();
777	<	}
778	<
779	<	public final V get(long timeout, TimeUnit unit)
780	<	throws InterruptedException, ExecutionException, TimeoutException {
781	<	ForkJoinWorkerThread w = getWorker();
782	<	if (w == null \|\| status < 0 \|\| !w.unpushTask(this) \|\| !tryQuietlyInvoke())
783	<	awaitDone(w, unit.toNanos(timeout));
784	<	return reportTimedFutureResult();
947	>	setCompletion(NORMAL);
948		}
949
950		/**
951	<	* Possibly executes other tasks until this task is ready, then
952	<	* returns the result of the computation. This method may be more
790	<	* efficient than {@code join}, but is only applicable when
791	<	* there are no potential dependencies between continuation of the
792	<	* current task and that of any other task that might be executed
793	<	* while helping. (This usually holds for pure divide-and-conquer
794	<	* tasks). This method may be invoked only from within
795	<	* ForkJoinTask computations (as may be determined using method
796	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
797	<	* result in exceptions or errors, possibly including
798	<	* ClassCastException.
951	>	* Waits if necessary for the computation to complete, and then
952	>	* retrieves its result.
953		*
954		* @return the computed result
955	+	* @throws CancellationException if the computation was cancelled
956	+	* @throws ExecutionException if the computation threw an
957	+	* exception
958	+	* @throws InterruptedException if the current thread is not a
959	+	* member of a ForkJoinPool and was interrupted while waiting
960		*/
961	<	public final V helpJoin() {
962	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
963	<	if (status < 0 \|\| !w.unpushTask(this) \|\| !tryExec())
964	<	reportException(busyJoin(w));
961	>	public final V get() throws InterruptedException, ExecutionException {
962	>	int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ?
963	>	doJoin() : externalInterruptibleAwaitDone(0L);
964	>	Throwable ex;
965	>	if (s == CANCELLED)
966	>	throw new CancellationException();
967	>	if (s == EXCEPTIONAL && (ex = getThrowableException()) != null)
968	>	throw new ExecutionException(ex);
969		return getRawResult();
970		}
971
972		/**
973	<	* Possibly executes other tasks until this task is ready. This
974	<	* method may be invoked only from within ForkJoinTask
975	<	* computations (as may be determined using method {@link
976	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
977	<	* in exceptions or errors, possibly including ClassCastException.
973	>	* Waits if necessary for at most the given time for the computation
974	>	* to complete, and then retrieves its result, if available.
975	>	*
976	>	* @param timeout the maximum time to wait
977	>	* @param unit the time unit of the timeout argument
978	>	* @return the computed result
979	>	* @throws CancellationException if the computation was cancelled
980	>	* @throws ExecutionException if the computation threw an
981	>	* exception
982	>	* @throws InterruptedException if the current thread is not a
983	>	* member of a ForkJoinPool and was interrupted while waiting
984	>	* @throws TimeoutException if the wait timed out
985		*/
986	<	public final void quietlyHelpJoin() {
987	<	if (status >= 0) {
988	<	ForkJoinWorkerThread w =
989	<	(ForkJoinWorkerThread) Thread.currentThread();
990	<	if (!w.unpushTask(this) \|\| !tryQuietlyInvoke())
991	<	busyJoin(w);
986	>	public final V get(long timeout, TimeUnit unit)
987	>	throws InterruptedException, ExecutionException, TimeoutException {
988	>	// Messy in part because we measure in nanos, but wait in millis
989	>	int s; long millis, nanos;
990	>	Thread t = Thread.currentThread();
991	>	if (!(t instanceof ForkJoinWorkerThread)) {
992	>	if ((millis = unit.toMillis(timeout)) > 0L)
993	>	s = externalInterruptibleAwaitDone(millis);
994	>	else
995	>	s = status;
996	>	}
997	>	else if ((s = status) >= 0 && (nanos = unit.toNanos(timeout)) > 0L) {
998	>	long deadline = System.nanoTime() + nanos;
999	>	ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
1000	>	ForkJoinPool.WorkQueue w = wt.workQueue;
1001	>	ForkJoinPool p = wt.pool;
1002	>	if (w.tryUnpush(this))
1003	>	doExec();
1004	>	boolean blocking = false;
1005	>	try {
1006	>	while ((s = status) >= 0) {
1007	>	if (w.runState < 0)
1008	>	cancelIgnoringExceptions(this);
1009	>	else if (!blocking)
1010	>	blocking = p.tryCompensate();
1011	>	else {
1012	>	millis = TimeUnit.NANOSECONDS.toMillis(nanos);
1013	>	if (millis > 0L &&
1014	>	U.compareAndSwapInt(this, STATUS, s, s \| SIGNAL)) {
1015	>	try {
1016	>	synchronized (this) {
1017	>	if (status >= 0)
1018	>	wait(millis);
1019	>	}
1020	>	} catch (InterruptedException ie) {
1021	>	}
1022	>	}
1023	>	if ((s = status) < 0 \|\|
1024	>	(nanos = deadline - System.nanoTime()) <= 0L)
1025	>	break;
1026	>	}
1027	>	}
1028	>	} finally {
1029	>	if (blocking)
1030	>	p.incrementActiveCount();
1031	>	}
1032		}
1033	+	if (s != NORMAL) {
1034	+	Throwable ex;
1035	+	if (s == CANCELLED)
1036	+	throw new CancellationException();
1037	+	if (s != EXCEPTIONAL)
1038	+	throw new TimeoutException();
1039	+	if ((ex = getThrowableException()) != null)
1040	+	throw new ExecutionException(ex);
1041	+	}
1042	+	return getRawResult();
1043		}
1044
1045		/**
1046	<	* Joins this task, without returning its result or throwing an
1046	>	* Joins this task, without returning its result or throwing its
1047		* exception. This method may be useful when processing
1048		* collections of tasks when some have been cancelled or otherwise
1049		* known to have aborted.
1050		*/
1051		public final void quietlyJoin() {
1052	<	if (status >= 0) {
833	<	ForkJoinWorkerThread w = getWorker();
834	<	if (w == null \|\| !w.unpushTask(this) \|\| !tryQuietlyInvoke())
835	<	awaitDone(w, true);
836	<	}
1052	>	doJoin();
1053		}
1054
1055		/**
1056		* Commences performing this task and awaits its completion if
1057	<	* necessary, without returning its result or throwing an
1058	<	* exception. This method may be useful when processing
843	<	* collections of tasks when some have been cancelled or otherwise
844	<	* known to have aborted.
1057	>	* necessary, without returning its result or throwing its
1058	>	* exception.
1059		*/
1060		public final void quietlyInvoke() {
1061	<	if (status >= 0 && !tryQuietlyInvoke())
848	<	quietlyJoin();
1061	>	doInvoke();
1062		}
1063
1064		/**
1065		* Possibly executes tasks until the pool hosting the current task
1066	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
1067	<	* designs in which many tasks are forked, but none are explicitly
1068	<	* joined, instead executing them until all are processed.
1066	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
1067	>	* be of use in designs in which many tasks are forked, but none
1068	>	* are explicitly joined, instead executing them until all are
1069	>	* processed.
1070	>	*
1071	>	* <p>This method may be invoked only from within {@code
1072	>	* ForkJoinPool} computations (as may be determined using method
1073	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1074	>	* result in exceptions or errors, possibly including {@code
1075	>	* ClassCastException}.
1076		*/
1077		public static void helpQuiesce() {
1078	<	((ForkJoinWorkerThread) Thread.currentThread())
1079	<	.helpQuiescePool();
1078	>	ForkJoinWorkerThread wt =
1079	>	(ForkJoinWorkerThread)Thread.currentThread();
1080	>	wt.pool.helpQuiescePool(wt.workQueue);
1081		}
1082
1083		/**
#	Line 865 \| Line 1086 \| public abstract class ForkJoinTask<V> im
1086		* this task, but only if reuse occurs when this task has either
1087		* never been forked, or has been forked, then completed and all
1088		* outstanding joins of this task have also completed. Effects
1089	<	* under any other usage conditions are not guaranteed, and are
1090	<	* almost surely wrong. This method may be useful when executing
1089	>	* under any other usage conditions are not guaranteed.
1090	>	* This method may be useful when executing
1091		* pre-constructed trees of subtasks in loops.
1092	+	*
1093	+	* <p>Upon completion of this method, {@code isDone()} reports
1094	+	* {@code false}, and {@code getException()} reports {@code
1095	+	* null}. However, the value returned by {@code getRawResult} is
1096	+	* unaffected. To clear this value, you can invoke {@code
1097	+	* setRawResult(null)}.
1098		*/
1099		public void reinitialize() {
1100	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
1101	<	exceptionMap.remove(this);
1102	<	status = 0;
1100	>	if (status == EXCEPTIONAL)
1101	>	clearExceptionalCompletion();
1102	>	else
1103	>	status = 0;
1104		}
1105
1106		/**
1107		* Returns the pool hosting the current task execution, or null
1108		* if this task is executing outside of any ForkJoinPool.
1109		*
1110	<	* @return the pool, or null if none
1110	>	* @see #inForkJoinPool
1111	>	* @return the pool, or {@code null} if none
1112		*/
1113		public static ForkJoinPool getPool() {
1114		Thread t = Thread.currentThread();
#	Line 888 \| Line 1117 \| public abstract class ForkJoinTask<V> im
1117		}
1118
1119		/**
1120	<	* Returns {@code true} if the current thread is executing as a
1121	<	* ForkJoinPool computation.
1120	>	* Returns {@code true} if the current thread is a {@link
1121	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation.
1122		*
1123	<	* @return {@code true} if the current thread is executing as a
1124	<	* ForkJoinPool computation, or false otherwise
1123	>	* @return {@code true} if the current thread is a {@link
1124	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation,
1125	>	* or {@code false} otherwise
1126		*/
1127		public static boolean inForkJoinPool() {
1128		return Thread.currentThread() instanceof ForkJoinWorkerThread;
#	Line 904 \| Line 1134 \| public abstract class ForkJoinTask<V> im
1134		* by the current thread, and has not commenced executing in
1135		* another thread. This method may be useful when arranging
1136		* alternative local processing of tasks that could have been, but
1137	<	* were not, stolen. This method may be invoked only from within
908	<	* ForkJoinTask computations (as may be determined using method
909	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
910	<	* result in exceptions or errors, possibly including
911	<	* ClassCastException.
1137	>	* were not, stolen.
1138		*
1139	<	* @return true if unforked
1139	>	* <p>This method may be invoked only from within {@code
1140	>	* ForkJoinPool} computations (as may be determined using method
1141	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1142	>	* result in exceptions or errors, possibly including {@code
1143	>	* ClassCastException}.
1144	>	*
1145	>	* @return {@code true} if unforked
1146		*/
1147		public boolean tryUnfork() {
1148	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1149	<	.unpushTask(this);
1148	>	return ((ForkJoinWorkerThread)Thread.currentThread())
1149	>	.workQueue.tryUnpush(this);
1150		}
1151
1152		/**
#	Line 923 \| Line 1155 \| public abstract class ForkJoinTask<V> im
1155		* value may be useful for heuristic decisions about whether to
1156		* fork other tasks.
1157		*
1158	+	* <p>This method may be invoked only from within {@code
1159	+	* ForkJoinPool} computations (as may be determined using method
1160	+	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1161	+	* result in exceptions or errors, possibly including {@code
1162	+	* ClassCastException}.
1163	+	*
1164		* @return the number of tasks
1165		*/
1166		public static int getQueuedTaskCount() {
1167		return ((ForkJoinWorkerThread) Thread.currentThread())
1168	<	.getQueueSize();
1168	>	.workQueue.queueSize();
1169		}
1170
1171		/**
#	Line 940 \| Line 1178 \| public abstract class ForkJoinTask<V> im
1178		* tasks, and to process computations locally if this threshold is
1179		* exceeded.
1180		*
1181	+	* <p>This method may be invoked only from within {@code
1182	+	* ForkJoinPool} computations (as may be determined using method
1183	+	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1184	+	* result in exceptions or errors, possibly including {@code
1185	+	* ClassCastException}.
1186	+	*
1187		* @return the surplus number of tasks, which may be negative
1188		*/
1189		public static int getSurplusQueuedTaskCount() {
1190	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1191	<	.getEstimatedSurplusTaskCount();
1190	>	/*
1191	>	* The aim of this method is to return a cheap heuristic guide
1192	>	* for task partitioning when programmers, frameworks, tools,
1193	>	* or languages have little or no idea about task granularity.
1194	>	* In essence by offering this method, we ask users only about
1195	>	* tradeoffs in overhead vs expected throughput and its
1196	>	* variance, rather than how finely to partition tasks.
1197	>	*
1198	>	* In a steady state strict (tree-structured) computation,
1199	>	* each thread makes available for stealing enough tasks for
1200	>	* other threads to remain active. Inductively, if all threads
1201	>	* play by the same rules, each thread should make available
1202	>	* only a constant number of tasks.
1203	>	*
1204	>	* The minimum useful constant is just 1. But using a value of
1205	>	* 1 would require immediate replenishment upon each steal to
1206	>	* maintain enough tasks, which is infeasible. Further,
1207	>	* partitionings/granularities of offered tasks should
1208	>	* minimize steal rates, which in general means that threads
1209	>	* nearer the top of computation tree should generate more
1210	>	* than those nearer the bottom. In perfect steady state, each
1211	>	* thread is at approximately the same level of computation
1212	>	* tree. However, producing extra tasks amortizes the
1213	>	* uncertainty of progress and diffusion assumptions.
1214	>	*
1215	>	* So, users will want to use values larger, but not much
1216	>	* larger than 1 to both smooth over transient shortages and
1217	>	* hedge against uneven progress; as traded off against the
1218	>	* cost of extra task overhead. We leave the user to pick a
1219	>	* threshold value to compare with the results of this call to
1220	>	* guide decisions, but recommend values such as 3.
1221	>	*
1222	>	* When all threads are active, it is on average OK to
1223	>	* estimate surplus strictly locally. In steady-state, if one
1224	>	* thread is maintaining say 2 surplus tasks, then so are
1225	>	* others. So we can just use estimated queue length.
1226	>	* However, this strategy alone leads to serious mis-estimates
1227	>	* in some non-steady-state conditions (ramp-up, ramp-down,
1228	>	* other stalls). We can detect many of these by further
1229	>	* considering the number of "idle" threads, that are known to
1230	>	* have zero queued tasks, so compensate by a factor of
1231	>	* (#idle/#active) threads.
1232	>	*/
1233	>	ForkJoinWorkerThread wt =
1234	>	(ForkJoinWorkerThread)Thread.currentThread();
1235	>	return wt.workQueue.queueSize() - wt.pool.idlePerActive();
1236		}
1237
1238		// Extension methods
1239
1240		/**
1241	<	* Returns the result that would be returned by {@code join},
1242	<	* even if this task completed abnormally, or null if this task is
1243	<	* not known to have been completed. This method is designed to
1244	<	* aid debugging, as well as to support extensions. Its use in any
1245	<	* other context is discouraged.
1241	>	* Returns the result that would be returned by {@link #join}, even
1242	>	* if this task completed abnormally, or {@code null} if this task
1243	>	* is not known to have been completed. This method is designed
1244	>	* to aid debugging, as well as to support extensions. Its use in
1245	>	* any other context is discouraged.
1246		*
1247	<	* @return the result, or null if not completed
1247	>	* @return the result, or {@code null} if not completed
1248		*/
1249		public abstract V getRawResult();
1250
#	Line 975 \| Line 1263 \| public abstract class ForkJoinTask<V> im
1263		* called otherwise. The return value controls whether this task
1264		* is considered to be done normally. It may return false in
1265		* asynchronous actions that require explicit invocations of
1266	<	* {@code complete} to become joinable. It may throw exceptions
1267	<	* to indicate abnormal exit.
1266	>	* {@link #complete} to become joinable. It may also throw an
1267	>	* (unchecked) exception to indicate abnormal exit.
1268		*
1269	<	* @return true if completed normally
982	<	* @throws Error or RuntimeException if encountered during computation
1269	>	* @return {@code true} if completed normally
1270		*/
1271		protected abstract boolean exec();
1272
1273		/**
1274	<	* Returns, but does not unschedule or execute, the task queued by
1275	<	* the current thread but not yet executed, if one is
1274	>	* Returns, but does not unschedule or execute, a task queued by
1275	>	* the current thread but not yet executed, if one is immediately
1276		* available. There is no guarantee that this task will actually
1277	<	* be polled or executed next. This method is designed primarily
1278	<	* to support extensions, and is unlikely to be useful otherwise.
1279	<	* This method may be invoked only from within ForkJoinTask
1280	<	* computations (as may be determined using method {@link
1281	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
1282	<	* in exceptions or errors, possibly including ClassCastException.
1277	>	* be polled or executed next. Conversely, this method may return
1278	>	* null even if a task exists but cannot be accessed without
1279	>	* contention with other threads. This method is designed
1280	>	* primarily to support extensions, and is unlikely to be useful
1281	>	* otherwise.
1282	>	*
1283	>	* <p>This method may be invoked only from within {@code
1284	>	* ForkJoinPool} computations (as may be determined using method
1285	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1286	>	* result in exceptions or errors, possibly including {@code
1287	>	* ClassCastException}.
1288		*
1289	<	* @return the next task, or null if none are available
1289	>	* @return the next task, or {@code null} if none are available
1290		*/
1291		protected static ForkJoinTask<?> peekNextLocalTask() {
1292	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1001	<	.peekTask();
1292	>	return ((ForkJoinWorkerThread) Thread.currentThread()).workQueue.peek();
1293		}
1294
1295		/**
1296		* Unschedules and returns, without executing, the next task
1297		* queued by the current thread but not yet executed. This method
1298		* is designed primarily to support extensions, and is unlikely to
1299	<	* be useful otherwise. This method may be invoked only from
1300	<	* within ForkJoinTask computations (as may be determined using
1301	<	* method {@link #inForkJoinPool}). Attempts to invoke in other
1302	<	* contexts result in exceptions or errors, possibly including
1303	<	* ClassCastException.
1299	>	* be useful otherwise.
1300	>	*
1301	>	* <p>This method may be invoked only from within {@code
1302	>	* ForkJoinPool} computations (as may be determined using method
1303	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1304	>	* result in exceptions or errors, possibly including {@code
1305	>	* ClassCastException}.
1306		*
1307	<	* @return the next task, or null if none are available
1307	>	* @return the next task, or {@code null} if none are available
1308		*/
1309		protected static ForkJoinTask<?> pollNextLocalTask() {
1310		return ((ForkJoinWorkerThread) Thread.currentThread())
1311	<	.pollLocalTask();
1311	>	.workQueue.nextLocalTask();
1312		}
1313
1314		/**
#	Line 1026 \| Line 1319 \| public abstract class ForkJoinTask<V> im
1319		* {@code null} result does not necessarily imply quiescence
1320		* of the pool this task is operating in. This method is designed
1321		* primarily to support extensions, and is unlikely to be useful
1322	<	* otherwise. This method may be invoked only from within
1030	<	* ForkJoinTask computations (as may be determined using method
1031	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1032	<	* result in exceptions or errors, possibly including
1033	<	* ClassCastException.
1322	>	* otherwise.
1323		*
1324	<	* @return a task, or null if none are available
1324	>	* <p>This method may be invoked only from within {@code
1325	>	* ForkJoinPool} computations (as may be determined using method
1326	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1327	>	* result in exceptions or errors, possibly including {@code
1328	>	* ClassCastException}.
1329	>	*
1330	>	* @return a task, or {@code null} if none are available
1331		*/
1332		protected static ForkJoinTask<?> pollTask() {
1333	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1334	<	.pollTask();
1333	>	ForkJoinWorkerThread wt =
1334	>	(ForkJoinWorkerThread)Thread.currentThread();
1335	>	return wt.pool.nextTaskFor(wt.workQueue);
1336		}
1337
1338	<	// adaptors
1338	>	// Mark-bit operations
1339
1340		/**
1341	<	* Returns a new ForkJoinTask that performs the <code>run</code>
1342	<	* method of the given Runnable as its action, and returns a null
1343	<	* result upon <code>join</code>.
1341	>	* Returns true if this task is marked.
1342	>	*
1343	>	* @return true if this task is marked
1344	>	* @since 1.8
1345	>	*/
1346	>	public final boolean isMarkedForkJoinTask() {
1347	>	return (status & MARKED) != 0;
1348	>	}
1349	>
1350	>	/**
1351	>	* Atomically sets the mark on this task.
1352	>	*
1353	>	* @return true if this task was previously unmarked
1354	>	* @since 1.8
1355	>	*/
1356	>	public final boolean markForkJoinTask() {
1357	>	for (int s;;) {
1358	>	if (((s = status) & MARKED) != 0)
1359	>	return false;
1360	>	if (U.compareAndSwapInt(this, STATUS, s, s \| MARKED))
1361	>	return true;
1362	>	}
1363	>	}
1364	>
1365	>	/**
1366	>	* Atomically clears the mark on this task.
1367	>	*
1368	>	* @return true if this task was previously marked
1369	>	* @since 1.8
1370	>	*/
1371	>	public final boolean unmarkForkJoinTask() {
1372	>	for (int s;;) {
1373	>	if (((s = status) & MARKED) == 0)
1374	>	return false;
1375	>	if (U.compareAndSwapInt(this, STATUS, s, s & ~MARKED))
1376	>	return true;
1377	>	}
1378	>	}
1379	>
1380	>	/**
1381	>	* Adaptor for Runnables. This implements RunnableFuture
1382	>	* to be compliant with AbstractExecutorService constraints
1383	>	* when used in ForkJoinPool.
1384	>	*/
1385	>	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1386	>	implements RunnableFuture<T> {
1387	>	final Runnable runnable;
1388	>	final T resultOnCompletion;
1389	>	T result;
1390	>	AdaptedRunnable(Runnable runnable, T result) {
1391	>	if (runnable == null) throw new NullPointerException();
1392	>	this.runnable = runnable;
1393	>	this.resultOnCompletion = result;
1394	>	}
1395	>	public T getRawResult() { return result; }
1396	>	public void setRawResult(T v) { result = v; }
1397	>	public boolean exec() {
1398	>	runnable.run();
1399	>	result = resultOnCompletion;
1400	>	return true;
1401	>	}
1402	>	public void run() { invoke(); }
1403	>	private static final long serialVersionUID = 5232453952276885070L;
1404	>	}
1405	>
1406	>	/**
1407	>	* Adaptor for Callables
1408	>	*/
1409	>	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1410	>	implements RunnableFuture<T> {
1411	>	final Callable<? extends T> callable;
1412	>	T result;
1413	>	AdaptedCallable(Callable<? extends T> callable) {
1414	>	if (callable == null) throw new NullPointerException();
1415	>	this.callable = callable;
1416	>	}
1417	>	public T getRawResult() { return result; }
1418	>	public void setRawResult(T v) { result = v; }
1419	>	public boolean exec() {
1420	>	try {
1421	>	result = callable.call();
1422	>	return true;
1423	>	} catch (Error err) {
1424	>	throw err;
1425	>	} catch (RuntimeException rex) {
1426	>	throw rex;
1427	>	} catch (Exception ex) {
1428	>	throw new RuntimeException(ex);
1429	>	}
1430	>	}
1431	>	public void run() { invoke(); }
1432	>	private static final long serialVersionUID = 2838392045355241008L;
1433	>	}
1434	>
1435	>	/**
1436	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1437	>	* method of the given {@code Runnable} as its action, and returns
1438	>	* a null result upon {@link #join}.
1439		*
1440		* @param runnable the runnable action
1441		* @return the task
1442		*/
1443	<	public static ForkJoinTask<Void> adapt(Runnable runnable) {
1444	<	return new ForkJoinPool.AdaptedRunnable<Void>(runnable, null);
1443	>	public static ForkJoinTask<?> adapt(Runnable runnable) {
1444	>	return new AdaptedRunnable<Void>(runnable, null);
1445		}
1446
1447		/**
1448	<	* Returns a new ForkJoinTask that performs the <code>run</code>
1449	<	* method of the given Runnable as its action, and returns the
1450	<	* given result upon <code>join</code>.
1448	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1449	>	* method of the given {@code Runnable} as its action, and returns
1450	>	* the given result upon {@link #join}.
1451		*
1452		* @param runnable the runnable action
1453		* @param result the result upon completion
1454		* @return the task
1455		*/
1456		public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1457	<	return new ForkJoinPool.AdaptedRunnable<T>(runnable, result);
1457	>	return new AdaptedRunnable<T>(runnable, result);
1458		}
1459
1460		/**
1461	<	* Returns a new ForkJoinTask that performs the <code>call</code>
1462	<	* method of the given Callable as its action, and returns its
1463	<	* result upon <code>join</code>, translating any checked
1464	<	* exceptions encountered into <code>RuntimeException<code>.
1461	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1462	>	* method of the given {@code Callable} as its action, and returns
1463	>	* its result upon {@link #join}, translating any checked exceptions
1464	>	* encountered into {@code RuntimeException}.
1465		*
1466		* @param callable the callable action
1467		* @return the task
1468		*/
1469	<	public static <T> ForkJoinTask<T> adapt(Callable<T> callable) {
1470	<	return new ForkJoinPool.AdaptedCallable<T>(callable);
1469	>	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1470	>	return new AdaptedCallable<T>(callable);
1471		}
1472
1473		// Serialization support
#	Line 1084 \| Line 1475 \| public abstract class ForkJoinTask<V> im
1475		private static final long serialVersionUID = -7721805057305804111L;
1476
1477		/**
1478	<	* Save the state to a stream.
1478	>	* Saves this task to a stream (that is, serializes it).
1479		*
1480		* @serialData the current run status and the exception thrown
1481	<	* during execution, or null if none
1091	<	* @param s the stream
1481	>	* during execution, or {@code null} if none
1482		*/
1483		private void writeObject(java.io.ObjectOutputStream s)
1484		throws java.io.IOException {
#	Line 1097 \| Line 1487 \| public abstract class ForkJoinTask<V> im
1487		}
1488
1489		/**
1490	<	* Reconstitute the instance from a stream.
1101	<	*
1102	<	* @param s the stream
1490	>	* Reconstitutes this task from a stream (that is, deserializes it).
1491		*/
1492		private void readObject(java.io.ObjectInputStream s)
1493		throws java.io.IOException, ClassNotFoundException {
1494		s.defaultReadObject();
1107	–	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1108	–	status \|= EXTERNAL_SIGNAL; // conservatively set external signal
1495		Object ex = s.readObject();
1496		if (ex != null)
1497	<	setDoneExceptionally((Throwable) ex);
1497	>	setExceptionalCompletion((Throwable)ex);
1498		}
1499
1500	<	// Unsafe mechanics for jsr166y 3rd party package.
1500	>	// Unsafe mechanics
1501	>	private static final sun.misc.Unsafe U;
1502	>	private static final long STATUS;
1503	>	static {
1504	>	exceptionTableLock = new ReentrantLock();
1505	>	exceptionTableRefQueue = new ReferenceQueue<Object>();
1506	>	exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY];
1507	>	try {
1508	>	U = getUnsafe();
1509	>	STATUS = U.objectFieldOffset
1510	>	(ForkJoinTask.class.getDeclaredField("status"));
1511	>	} catch (Exception e) {
1512	>	throw new Error(e);
1513	>	}
1514	>	}
1515	>
1516	>	/**
1517	>	* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package.
1518	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1519	>	* into a jdk.
1520	>	*
1521	>	* @return a sun.misc.Unsafe
1522	>	*/
1523		private static sun.misc.Unsafe getUnsafe() {
1524		try {
1525		return sun.misc.Unsafe.getUnsafe();
1526		} catch (SecurityException se) {
1527		try {
1528		return java.security.AccessController.doPrivileged
1529	<	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1529	>	(new java.security
1530	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1531		public sun.misc.Unsafe run() throws Exception {
1532	<	return getUnsafeByReflection();
1532	>	java.lang.reflect.Field f = sun.misc
1533	>	.Unsafe.class.getDeclaredField("theUnsafe");
1534	>	f.setAccessible(true);
1535	>	return (sun.misc.Unsafe) f.get(null);
1536		}});
1537		} catch (java.security.PrivilegedActionException e) {
1538		throw new RuntimeException("Could not initialize intrinsics",
#	Line 1128 \| Line 1540 \| public abstract class ForkJoinTask<V> im
1540		}
1541		}
1542		}
1131	–
1132	–	private static sun.misc.Unsafe getUnsafeByReflection()
1133	–	throws NoSuchFieldException, IllegalAccessException {
1134	–	java.lang.reflect.Field f =
1135	–	sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
1136	–	f.setAccessible(true);
1137	–	return (sun.misc.Unsafe) f.get(null);
1138	–	}
1139	–
1140	–	private static long fieldOffset(String fieldName, Class<?> klazz) {
1141	–	try {
1142	–	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
1143	–	} catch (NoSuchFieldException e) {
1144	–	// Convert Exception to Error
1145	–	NoSuchFieldError error = new NoSuchFieldError(fieldName);
1146	–	error.initCause(e);
1147	–	throw error;
1148	–	}
1149	–	}
1150	–
1151	–	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1152	–	static final long statusOffset =
1153	–	fieldOffset("status", ForkJoinTask.class);
1154	–
1543		}

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents): Revision 1.19 by dl, Sat Jul 25 17:49:01 2009 UTC vs. Revision 1.85 by jsr166, Tue Jan 31 01:51:13 2012 UTC

Diff Legend

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.19 by dl, Sat Jul 25 17:49:01 2009 UTC vs.
Revision 1.85 by jsr166, Tue Jan 31 01:51:13 2012 UTC