ViewVC Help

View File | Revision Log | Show Annotations | Download File | Root Listing

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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.27 by dl, Sun Aug 2 11:54:31 2009 UTC vs.
Revision 1.90 by dl, Sat Apr 21 11:45:20 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	–
9		import java.io.Serializable;
10		import java.util.Collection;
13	–	import java.util.Collections;
11		import java.util.List;
12	<	import java.util.Map;
13	<	import java.util.WeakHashMap;
12	>	import java.util.RandomAccess;
13	>	import java.lang.ref.WeakReference;
14	>	import java.lang.ref.ReferenceQueue;
15	>	import java.util.concurrent.Callable;
16	>	import java.util.concurrent.CancellationException;
17	>	import java.util.concurrent.ExecutionException;
18	>	import java.util.concurrent.Future;
19	>	import java.util.concurrent.RejectedExecutionException;
20	>	import java.util.concurrent.RunnableFuture;
21	>	import java.util.concurrent.TimeUnit;
22	>	import java.util.concurrent.TimeoutException;
23	>	import java.util.concurrent.locks.ReentrantLock;
24	>	import java.lang.reflect.Constructor;
25
26		/**
27		* Abstract base class for tasks that run within a {@link ForkJoinPool}.
#	Line 22 | Line 30 | import java.util.WeakHashMap;
30		* subtasks may be hosted by a small number of actual threads in a
31		* ForkJoinPool, at the price of some usage limitations.
32		*
33	<	* <p> A "main" ForkJoinTask begins execution when submitted to a
34	<	* {@link ForkJoinPool}. Once started, it will usually in turn start
35	<	* other subtasks.  As indicated by the name of this class, many
36	<	* programs using ForkJoinTasks employ only methods {@code fork} and
37	<	* {@code join}, or derivatives such as {@code invokeAll}.  However,
38	<	* this class also provides a number of other methods that can come
39	<	* into play in advanced usages, as well as extension mechanics that
40	<	* allow support of new forms of fork/join processing.
33	>	* <p>A "main" {@code ForkJoinTask} begins execution when submitted
34	>	* to a {@link ForkJoinPool}.  Once started, it will usually in turn
35	>	* start other subtasks.  As indicated by the name of this class,
36	>	* many programs using {@code ForkJoinTask} employ only methods
37	>	* {@link #fork} and {@link #join}, or derivatives such as {@link
38	>	* #invokeAll(ForkJoinTask...) invokeAll}.  However, this class also
39	>	* provides a number of other methods that can come into play in
40	>	* advanced usages, as well as extension mechanics that allow
41	>	* support of new forms of fork/join processing.
42	>	*
43	>	* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
44	>	* The efficiency of {@code ForkJoinTask}s stems from a set of
45	>	* restrictions (that are only partially statically enforceable)
46	>	* reflecting their main use as computational tasks calculating pure
47	>	* functions or operating on purely isolated objects.  The primary
48	>	* coordination mechanisms are {@link #fork}, that arranges
49	>	* asynchronous execution, and {@link #join}, that doesn't proceed
50	>	* until the task's result has been computed.  Computations should
51	>	* ideally avoid {@code synchronized} methods or blocks, and should
52	>	* minimize other blocking synchronization apart from joining other
53	>	* tasks or using synchronizers such as Phasers that are advertised to
54	>	* cooperate with fork/join scheduling. Subdividable tasks should also
55	>	* not perform blocking IO, and should ideally access variables that
56	>	* are completely independent of those accessed by other running
57	>	* tasks. These guidelines are loosely enforced by not permitting
58	>	* checked exceptions such as {@code IOExceptions} to be
59	>	* thrown. However, computations may still encounter unchecked
60	>	* exceptions, that are rethrown to callers attempting to join
61	>	* them. These exceptions may additionally include {@link
62	>	* RejectedExecutionException} stemming from internal resource
63	>	* exhaustion, such as failure to allocate internal task
64	>	* queues. Rethrown exceptions behave in the same way as regular
65	>	* exceptions, but, when possible, contain stack traces (as displayed
66	>	* for example using {@code ex.printStackTrace()}) of both the thread
67	>	* that initiated the computation as well as the thread actually
68	>	* encountering the exception; minimally only the latter.
69		*
70	<	* <p>A ForkJoinTask is a lightweight form of {@link Future}.  The
71	<	* efficiency of ForkJoinTasks stems from a set of restrictions (that
72	<	* are only partially statically enforceable) reflecting their
73	<	* intended use as computational tasks calculating pure functions or
74	<	* operating on purely isolated objects.  The primary coordination
75	<	* mechanisms are {@link #fork}, that arranges asynchronous execution,
76	<	* and {@link #join}, that doesn't proceed until the task's result has
77	<	* been computed.  Computations should avoid {@code synchronized}
78	<	* methods or blocks, and should minimize other blocking
79	<	* synchronization apart from joining other tasks or using
80	<	* synchronizers such as Phasers that are advertised to cooperate with
81	<	* fork/join scheduling. Tasks should also not perform blocking IO,
82	<	* 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 IO or other external synchronization
52	<	* becomes exhausted. This usage restriction is in part enforced by
53	<	* not permitting checked exceptions such as {@code IOExceptions}
54	<	* to be thrown. However, computations may still encounter unchecked
55	<	* exceptions, that are rethrown to callers attempting join
56	<	* them. These exceptions may additionally include
57	<	* RejectedExecutionExceptions stemming from internal resource
58	<	* exhaustion such as failure to allocate internal task queues.
70	>	* <p>It is possible to define and use ForkJoinTasks that may block,
71	>	* but doing do requires three further considerations: (1) Completion
72	>	* of few if any <em>other</em> tasks should be dependent on a task
73	>	* that blocks on external synchronization or IO. Event-style async
74	>	* tasks that are never joined (for example, those subclassing {@link
75	>	* CountedCompleter}) often fall into this category.  (2) To minimize
76	>	* resource impact, tasks should be small; ideally performing only the
77	>	* (possibly) blocking action. (3) Unless the {@link
78	>	* ForkJoinPool.ManagedBlocker} API is used, or the number of possibly
79	>	* blocked tasks is known to be less than the pool's {@link
80	>	* ForkJoinPool#getParallelism} level, the pool cannot guarantee that
81	>	* enough threads will be available to ensure progress or good
82	>	* performance.
83		*
84		* <p>The primary method for awaiting completion and extracting
85		* results of a task is {@link #join}, but there are several variants:
86		* The {@link Future#get} methods support interruptible and/or timed
87		* waits for completion and report results using {@code Future}
88	<	* conventions. Method {@link #helpJoin} enables callers to actively
89	<	* execute other tasks while awaiting joins, which is sometimes more
90	<	* efficient but only applies when all subtasks are known to be
91	<	* strictly tree-structured. Method {@link #invoke} is semantically
68	<	* equivalent to {@code fork(); join()} but always attempts to
69	<	* begin execution in the current thread. The "<em>quiet</em>" forms
70	<	* of these methods do not extract results or report exceptions. These
88	>	* conventions. Method {@link #invoke} is semantically
89	>	* equivalent to {@code fork(); join()} but always attempts to begin
90	>	* execution in the current thread. The "<em>quiet</em>" forms of
91	>	* these methods do not extract results or report exceptions. These
92		* may be useful when a set of tasks are being executed, and you need
93		* to delay processing of results or exceptions until all complete.
94		* Method {@code invokeAll} (available in multiple versions)
95		* performs the most common form of parallel invocation: forking a set
96		* of tasks and joining them all.
97		*
98	<	* <p> The ForkJoinTask class is not usually directly subclassed.
98	>	* <p>In the most typical usages, a fork-join pair act like a call
99	>	* (fork) and return (join) from a parallel recursive function. As is
100	>	* the case with other forms of recursive calls, returns (joins)
101	>	* should be performed innermost-first. For example, {@code a.fork();
102	>	* b.fork(); b.join(); a.join();} is likely to be substantially more
103	>	* efficient than joining {@code a} before {@code b}.
104	>	*
105	>	* <p>The execution status of tasks may be queried at several levels
106	>	* of detail: {@link #isDone} is true if a task completed in any way
107	>	* (including the case where a task was cancelled without executing);
108	>	* {@link #isCompletedNormally} is true if a task completed without
109	>	* cancellation or encountering an exception; {@link #isCancelled} is
110	>	* true if the task was cancelled (in which case {@link #getException}
111	>	* returns a {@link java.util.concurrent.CancellationException}); and
112	>	* {@link #isCompletedAbnormally} is true if a task was either
113	>	* cancelled or encountered an exception, in which case {@link
114	>	* #getException} will return either the encountered exception or
115	>	* {@link java.util.concurrent.CancellationException}.
116	>	*
117	>	* <p>The ForkJoinTask class is not usually directly subclassed.
118		* Instead, you subclass one of the abstract classes that support a
119		* particular style of fork/join processing, typically {@link
120	<	* RecursiveAction} for computations that do not return results, or
121	<	* {@link RecursiveTask} for those that do.  Normally, a concrete
122	<	* ForkJoinTask subclass declares fields comprising its parameters,
123	<	* established in a constructor, and then defines a {@code compute}
124	<	* method that somehow uses the control methods supplied by this base
125	<	* class. While these methods have {@code public} access (to allow
126	<	* instances of different task subclasses to call each others
127	<	* methods), some of them may only be called from within other
128	<	* ForkJoinTasks (as may be determined using method {@link
129	<	* #inForkJoinPool}).  Attempts to invoke them in other contexts
130	<	* result in exceptions or errors, possibly including
131	<	* ClassCastException.
120	>	* RecursiveAction} for most computations that do not return results,
121	>	* {@link RecursiveTask} for those that do, and {@link
122	>	* CountedCompleter} for those in which completed actions trigger
123	>	* other actions.  Normally, a concrete ForkJoinTask subclass declares
124	>	* fields comprising its parameters, established in a constructor, and
125	>	* then defines a {@code compute} method that somehow uses the control
126	>	* methods supplied by this base class. While these methods have
127	>	* {@code public} access (to allow instances of different task
128	>	* subclasses to call each other's methods), some of them may only be
129	>	* called from within other ForkJoinTasks (as may be determined using
130	>	* method {@link #inForkJoinPool}).  Attempts to invoke them in other
131	>	* contexts result in exceptions or errors, possibly including {@code
132	>	* ClassCastException}.
133	>	*
134	>	* <p>Method {@link #join} and its variants are appropriate for use
135	>	* only when completion dependencies are acyclic; that is, the
136	>	* parallel computation can be described as a directed acyclic graph
137	>	* (DAG). Otherwise, executions may encounter a form of deadlock as
138	>	* tasks cyclically wait for each other.  However, this framework
139	>	* supports other methods and techniques (for example the use of
140	>	* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that
141	>	* may be of use in constructing custom subclasses for problems that
142	>	* are not statically structured as DAGs. To support such usages a
143	>	* ForkJoinTask may be atomically <em>tagged</em> with a {@code short}
144	>	* value using {@link #setForkJoinTaskTag} or {@link
145	>	* #compareAndSetForkJoinTaskTag} and checked using {@link
146	>	* #getForkJoinTaskTag}. The ForkJoinTask implementation does not use
147	>	* these {@code protected} methods or tags for any purpose, but they
148	>	* may be of use in the construction of specialized subclasses.  For
149	>	* example, parallel graph traversals can use the supplied methods to
150	>	* avoid revisiting nodes/tasks that have already been processed.
151	>	* (Method names for tagging are bulky in part to encourage definition
152	>	* of methods that reflect their usage patterns.)
153		*
154	<	* <p>Most base support methods are {@code final} because their
155	<	* implementations are intrinsically tied to the underlying
156	<	* lightweight task scheduling framework, and so cannot be overridden.
157	<	* Developers creating new basic styles of fork/join processing should
158	<	* minimally implement {@code protected} methods
159	<	* {@link #exec}, {@link #setRawResult}, and
160	<	* {@link #getRawResult}, while also introducing an abstract
161	<	* computational method that can be implemented in its subclasses,
162	<	* possibly relying on other {@code protected} methods provided
102	<	* by this class.
154	>	* <p>Most base support methods are {@code final}, to prevent
155	>	* overriding of implementations that are intrinsically tied to the
156	>	* underlying lightweight task scheduling framework.  Developers
157	>	* creating new basic styles of fork/join processing should minimally
158	>	* implement {@code protected} methods {@link #exec}, {@link
159	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
160	>	* an abstract computational method that can be implemented in its
161	>	* subclasses, possibly relying on other {@code protected} methods
162	>	* provided by this class.
163		*
164		* <p>ForkJoinTasks should perform relatively small amounts of
165	<	* computations, otherwise splitting into smaller tasks. As a very
166	<	* rough rule of thumb, a task should perform more than 100 and less
167	<	* than 10000 basic computational steps. If tasks are too big, then
168	<	* parallelism cannot improve throughput. If too small, then memory
169	<	* and internal task maintenance overhead may overwhelm processing.
165	>	* computation. Large tasks should be split into smaller subtasks,
166	>	* usually via recursive decomposition. As a very rough rule of thumb,
167	>	* a task should perform more than 100 and less than 10000 basic
168	>	* computational steps, and should avoid indefinite looping. If tasks
169	>	* are too big, then parallelism cannot improve throughput. If too
170	>	* small, then memory and internal task maintenance overhead may
171	>	* overwhelm processing.
172		*
173	<	* <p>This class provides {@code adapt} methods for {@link
174	<	* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
175	<	* may be of use when mixing execution of ForkJoinTasks with other
176	<	* kinds of tasks. When all tasks are of this form, consider using a
115	<	* pool in {@link ForkJoinPool#setAsyncMode}.
173	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
174	>	* and {@link Callable}, that may be of use when mixing execution of
175	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
176	>	* of this form, consider using a pool constructed in <em>asyncMode</em>.
177		*
178	<	* <p>ForkJoinTasks are {@code Serializable}, which enables them
179	<	* to be used in extensions such as remote execution frameworks. It is
180	<	* in general sensible to serialize tasks only before or after, but
181	<	* not during execution. Serialization is not relied on during
121	<	* execution itself.
178	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
179	>	* used in extensions such as remote execution frameworks. It is
180	>	* sensible to serialize tasks only before or after, but not during,
181	>	* execution. Serialization is not relied on during execution itself.
182		*
183		* @since 1.7
184		* @author Doug Lea
185		*/
186		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
187
188	<	/**
189	<	* Run control status bits packed into a single int to minimize
190	<	* footprint and to ensure atomicity (via CAS).  Status is
191	<	* initially zero, and takes on nonnegative values until
192	<	* completed, upon which status holds COMPLETED. CANCELLED, or
193	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
194	<	* blocking waits by other threads have SIGNAL_MASK bits set --
195	<	* bit 15 for external (nonFJ) waits, and the rest a count of
196	<	* waiting FJ threads.  (This representation relies on
197	<	* ForkJoinPool max thread limits). Completion of a stolen task
198	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
199	<	* though suboptimal for some purposes, we use basic builtin
200	<	* wait/notify to take advantage of "monitor inflation" in JVMs
201	<	* that we would otherwise need to emulate to avoid adding further
202	<	* per-task bookkeeping overhead. Note that bits 16-28 are
203	<	* currently unused. Also value 0x80000000 is available as spare
204	<	* completion value.
205	<	*/
206	<	volatile int status; // accessed directly by pool and workers
207	<
208	<	static final int COMPLETION_MASK      = 0xe0000000;
209	<	static final int NORMAL               = 0xe0000000; // == mask
210	<	static final int CANCELLED            = 0xc0000000;
211	<	static final int EXCEPTIONAL          = 0xa0000000;
212	<	static final int SIGNAL_MASK          = 0x0000ffff;
213	<	static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
214	<	static final int EXTERNAL_SIGNAL      = 0x00008000; // top bit of low word
215	<
216	<	/**
217	<	* Table of exceptions thrown by tasks, to enable reporting by
218	<	* callers. Because exceptions are rare, we don't directly keep
219	<	* them with task objects, but instead use a weak ref table.  Note
220	<	* that cancellation exceptions don't appear in the table, but are
221	<	* instead recorded as status values.
162	<	* TODO: Use ConcurrentReferenceHashMap
163	<	*/
164	<	static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
165	<	Collections.synchronizedMap
166	<	(new WeakHashMap<ForkJoinTask<?>, Throwable>());
167	<
168	<	// within-package utilities
169	<
170	<	/**
171	<	* Gets current worker thread, or null if not a worker thread.
188	>	/*
189	>	* See the internal documentation of class ForkJoinPool for a
190	>	* general implementation overview.  ForkJoinTasks are mainly
191	>	* responsible for maintaining their "status" field amidst relays
192	>	* to methods in ForkJoinWorkerThread and ForkJoinPool.
193	>	*
194	>	* The methods of this class are more-or-less layered into
195	>	* (1) basic status maintenance
196	>	* (2) execution and awaiting completion
197	>	* (3) user-level methods that additionally report results.
198	>	* This is sometimes hard to see because this file orders exported
199	>	* methods in a way that flows well in javadocs.
200	>	*/
201	>
202	>	/*
203	>	* The status field holds run control status bits packed into a
204	>	* single int to minimize footprint and to ensure atomicity (via
205	>	* CAS).  Status is initially zero, and takes on nonnegative
206	>	* values until completed, upon which status (anded with
207	>	* DONE_MASK) holds value NORMAL, CANCELLED, or EXCEPTIONAL. Tasks
208	>	* undergoing blocking waits by other threads have the SIGNAL bit
209	>	* set.  Completion of a stolen task with SIGNAL set awakens any
210	>	* waiters via notifyAll. Even though suboptimal for some
211	>	* purposes, we use basic builtin wait/notify to take advantage of
212	>	* "monitor inflation" in JVMs that we would otherwise need to
213	>	* emulate to avoid adding further per-task bookkeeping overhead.
214	>	* We want these monitors to be "fat", i.e., not use biasing or
215	>	* thin-lock techniques, so use some odd coding idioms that tend
216	>	* to avoid them, mainly by arranging that every synchronized
217	>	* block performs a wait, notifyAll or both.
218	>	*
219	>	* These control bits occupy only (some of) the upper half (16
220	>	* bits) of status field. The lower bits are used for user-defined
221	>	* tags.
222		*/
173	–	static ForkJoinWorkerThread getWorker() {
174	–	Thread t = Thread.currentThread();
175	–	return ((t instanceof ForkJoinWorkerThread) ?
176	–	(ForkJoinWorkerThread) t : null);
177	–	}
223
224	<	final boolean casStatus(int cmp, int val) {
225	<	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
226	<	}
227	<
228	<	/**
229	<	* Workaround for not being able to rethrow unchecked exceptions.
230	<	*/
231	<	static void rethrowException(Throwable ex) {
187	<	if (ex != null)
188	<	UNSAFE.throwException(ex);
189	<	}
190	<
191	<	// Setting completion status
224	>	/** The run status of this task */
225	>	volatile int status; // accessed directly by pool and workers
226	>	static final int DONE_MASK   = 0xf0000000;  // mask out non-completion bits
227	>	static final int NORMAL      = 0xf0000000;  // must be negative
228	>	static final int CANCELLED   = 0xc0000000;  // must be < NORMAL
229	>	static final int EXCEPTIONAL = 0x80000000;  // must be < CANCELLED
230	>	static final int SIGNAL      = 0x00010000;  // must be >= 1 << 16
231	>	static final int SMASK       = 0x0000ffff;  // short bits for tags
232
233		/**
234	<	* Marks completion and wakes up threads waiting to join this task.
234	>	* Marks completion and wakes up threads waiting to join this
235	>	* task.
236		*
237		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
238	+	* @return completion status on exit
239		*/
240	<	final void setCompletion(int completion) {
241	<	ForkJoinPool pool = getPool();
242	<	if (pool != null) {
243	<	int s; // Clear signal bits while setting completion status
244	<	do {} while ((s = status) >= 0 && !casStatus(s, completion));
245	<
246	<	if ((s & SIGNAL_MASK) != 0) {
247	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
206	<	pool.updateRunningCount(s);
207	<	synchronized (this) { notifyAll(); }
240	>	private int setCompletion(int completion) {
241	>	for (int s;;) {
242	>	if ((s = status) < 0)
243	>	return s;
244	>	if (U.compareAndSwapInt(this, STATUS, s, s | completion)) {
245	>	if ((s >>> 16) != 0)
246	>	synchronized (this) { notifyAll(); }
247	>	return completion;
248		}
249		}
210	–	else
211	–	externallySetCompletion(completion);
250		}
251
252		/**
253	<	* Version of setCompletion for non-FJ threads.  Leaves signal
254	<	* bits for unblocked threads to adjust, and always notifies.
255	<	*/
256	<	private void externallySetCompletion(int completion) {
257	<	int s;
258	<	do {} while ((s = status) >= 0 &&
259	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
260	<	synchronized (this) { notifyAll(); }
253	>	* Primary execution method for stolen tasks. Unless done, calls
254	>	* exec and records status if completed, but doesn't wait for
255	>	* completion otherwise.
256	>	*
257	>	* @return status on exit from this method
258	>	*/
259	>	final int doExec() {
260	>	int s; boolean completed;
261	>	if ((s = status) >= 0) {
262	>	try {
263	>	completed = exec();
264	>	} catch (Throwable rex) {
265	>	return setExceptionalCompletion(rex);
266	>	}
267	>	if (completed)
268	>	s = setCompletion(NORMAL);
269	>	}
270	>	return s;
271		}
272
273		/**
274	<	* Sets status to indicate normal completion.
274	>	* Tries to set SIGNAL status unless already completed. Used by
275	>	* ForkJoinPool. Other variants are directly incorporated into
276	>	* externalAwaitDone etc.
277	>	*
278	>	* @return true if successful
279		*/
280	<	final void setNormalCompletion() {
281	<	// Try typical fast case -- single CAS, no signal, not already done.
282	<	// Manually expand casStatus to improve chances of inlining it
231	<	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
232	<	setCompletion(NORMAL);
280	>	final boolean trySetSignal() {
281	>	int s = status;
282	>	return s >= 0 && U.compareAndSwapInt(this, STATUS, s, s | SIGNAL);
283		}
284
235	–	// internal waiting and notification
236	–
285		/**
286	<	* Performs the actual monitor wait for awaitDone.
286	>	* Blocks a non-worker-thread until completion.
287	>	* @return status upon completion
288		*/
289	<	private void doAwaitDone() {
290	<	// Minimize lock bias and in/de-flation effects by maximizing
291	<	// chances of waiting inside sync
292	<	try {
293	<	while (status >= 0)
294	<	synchronized (this) { if (status >= 0) wait(); }
295	<	} catch (InterruptedException ie) {
296	<	onInterruptedWait();
289	>	private int externalAwaitDone() {
290	>	boolean interrupted = false;
291	>	int s;
292	>	while ((s = status) >= 0) {
293	>	if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
294	>	synchronized (this) {
295	>	if (status >= 0) {
296	>	try {
297	>	wait();
298	>	} catch (InterruptedException ie) {
299	>	interrupted = true;
300	>	}
301	>	}
302	>	else
303	>	notifyAll();
304	>	}
305	>	}
306		}
307	+	if (interrupted)
308	+	Thread.currentThread().interrupt();
309	+	return s;
310		}
311
312		/**
313	<	* Performs the actual timed monitor wait for awaitDone.
313	>	* Blocks a non-worker-thread until completion or interruption.
314		*/
315	<	private void doAwaitDone(long startTime, long nanos) {
316	<	synchronized (this) {
317	<	try {
318	<	while (status >= 0) {
319	<	long nt = nanos - (System.nanoTime() - startTime);
320	<	if (nt <= 0)
321	<	break;
322	<	wait(nt / 1000000, (int) (nt % 1000000));
315	>	private int externalInterruptibleAwaitDone() throws InterruptedException {
316	>	int s;
317	>	if (Thread.interrupted())
318	>	throw new InterruptedException();
319	>	while ((s = status) >= 0) {
320	>	if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
321	>	synchronized (this) {
322	>	if (status >= 0)
323	>	wait();
324	>	else
325	>	notifyAll();
326		}
263	–	} catch (InterruptedException ie) {
264	–	onInterruptedWait();
327		}
328		}
329	+	return s;
330		}
331
269	–	// Awaiting completion
270	–
332		/**
333	<	* Sets status to indicate there is joiner, then waits for join,
334	<	* surrounded with pool notifications.
335	<	*
336	<	* @return status upon exit
337	<	*/
338	<	private int awaitDone(ForkJoinWorkerThread w,
339	<	boolean maintainParallelism) {
340	<	ForkJoinPool pool = (w == null) ? null : w.pool;
341	<	int s;
342	<	while ((s = status) >= 0) {
343	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
344	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
345	<	doAwaitDone();
285	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
286	<	adjustPoolCountsOnUnblock(pool);
287	<	break;
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	>	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		return s;
351		}
352
353		/**
354	<	* Timed version of awaitDone
354	>	* Implementation for invoke, quietlyInvoke.
355		*
356	<	* @return status upon exit
356	>	* @return status upon completion
357		*/
358	<	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
359	<	ForkJoinPool pool = (w == null) ? null : w.pool;
360	<	int s;
361	<	while ((s = status) >= 0) {
362	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
363	<	long startTime = System.nanoTime();
364	<	if (pool == null || !pool.preJoin(this, false))
365	<	doAwaitDone(startTime, nanos);
306	<	if ((s = status) >= 0) {
307	<	adjustPoolCountsOnCancelledWait(pool);
308	<	s = status;
309	<	}
310	<	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
311	<	adjustPoolCountsOnUnblock(pool);
312	<	break;
313	<	}
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	<	* Notifies pool that thread is unblocked. Called by signalled
374	<	* threads when woken by non-FJ threads (which is atypical).
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	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
382	<	int s;
383	<	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
325	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
326	<	pool.updateRunningCount(s);
327	<	}
381	>	private static final ExceptionNode[] exceptionTable;
382	>	private static final ReentrantLock exceptionTableLock;
383	>	private static final ReferenceQueue<Object> exceptionTableRefQueue;
384
385		/**
386	<	* Notifies pool to adjust counts on cancelled or timed out wait.
386	>	* Fixed capacity for exceptionTable.
387		*/
388	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
333	<	if (pool != null) {
334	<	int s;
335	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
336	<	if (casStatus(s, s - 1)) {
337	<	pool.updateRunningCount(1);
338	<	break;
339	<	}
340	<	}
341	<	}
342	<	}
388	>	private static final int EXCEPTION_MAP_CAPACITY = 32;
389
390		/**
391	<	* Handles interruptions during waits.
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 onInterruptedWait() {
403	<	ForkJoinWorkerThread w = getWorker();
404	<	if (w == null)
405	<	Thread.currentThread().interrupt(); // re-interrupt
406	<	else if (w.isTerminating())
407	<	cancelIgnoringExceptions();
408	<	// else if FJworker, ignore interrupt
409	<	}
410	<
411	<	// Recording and reporting exceptions
357	<
358	<	private void setDoneExceptionally(Throwable rex) {
359	<	exceptionMap.put(this, rex);
360	<	setCompletion(EXCEPTIONAL);
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	<	* Throws the exception associated with status s.
415	>	* Records exception and sets status.
416		*
417	<	* @throws the exception
417	>	* @return status on exit
418		*/
419	<	private void reportException(int s) {
420	<	if ((s &= COMPLETION_MASK) < NORMAL) {
421	<	if (s == CANCELLED)
422	<	throw new CancellationException();
423	<	else
424	<	rethrowException(exceptionMap.get(this));
419	>	final int recordExceptionalCompletion(Throwable ex) {
420	>	int s;
421	>	if ((s = status) >= 0) {
422	>	int h = System.identityHashCode(this);
423	>	final ReentrantLock lock = exceptionTableLock;
424	>	lock.lock();
425	>	try {
426	>	expungeStaleExceptions();
427	>	ExceptionNode[] t = exceptionTable;
428	>	int i = h & (t.length - 1);
429	>	for (ExceptionNode e = t[i]; ; e = e.next) {
430	>	if (e == null) {
431	>	t[i] = new ExceptionNode(this, ex, t[i]);
432	>	break;
433	>	}
434	>	if (e.get() == this) // already present
435	>	break;
436	>	}
437	>	} finally {
438	>	lock.unlock();
439	>	}
440	>	s = setCompletion(EXCEPTIONAL);
441		}
442	+	return s;
443		}
444
445		/**
446	<	* Returns result or throws exception using j.u.c.Future conventions.
447	<	* Only call when {@code isDone} known to be true.
446	>	* Records exception and possibly propagates
447	>	*
448	>	* @return status on exit
449		*/
450	<	private V reportFutureResult()
451	<	throws ExecutionException, InterruptedException {
452	<	int s = status & COMPLETION_MASK;
453	<	if (s < NORMAL) {
454	<	Throwable ex;
386	<	if (s == CANCELLED)
387	<	throw new CancellationException();
388	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
389	<	throw new ExecutionException(ex);
390	<	if (Thread.interrupted())
391	<	throw new InterruptedException();
392	<	}
393	<	return getRawResult();
450	>	private int setExceptionalCompletion(Throwable ex) {
451	>	int s = recordExceptionalCompletion(ex);
452	>	if ((s & DONE_MASK) == EXCEPTIONAL)
453	>	internalPropagateException(ex);
454	>	return s;
455		}
456
457		/**
458	<	* Returns result or throws exception using j.u.c.Future conventions
398	<	* with timeouts.
458	>	* Hook for exception propagation support for tasks with completers.
459		*/
460	<	private V reportTimedFutureResult()
401	<	throws InterruptedException, ExecutionException, TimeoutException {
402	<	Throwable ex;
403	<	int s = status & COMPLETION_MASK;
404	<	if (s == NORMAL)
405	<	return getRawResult();
406	<	if (s == CANCELLED)
407	<	throw new CancellationException();
408	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
409	<	throw new ExecutionException(ex);
410	<	if (Thread.interrupted())
411	<	throw new InterruptedException();
412	<	throw new TimeoutException();
460	>	void internalPropagateException(Throwable ex) {
461		}
462
415	–	// internal execution methods
416	–
463		/**
464	<	* Calls exec, recording completion, and rethrowing exception if
465	<	* encountered. Caller should normally check status before calling.
466	<	*
467	<	* @return true if completed normally
464	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
465	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
466	>	* exceptions, but if it does anyway, we have no recourse during
467	>	* shutdown, so guard against this case.
468		*/
469	<	private boolean tryExec() {
470	<	try { // try block must contain only call to exec
471	<	if (!exec())
472	<	return false;
473	<	} catch (Throwable rex) {
474	<	setDoneExceptionally(rex);
429	<	rethrowException(rex);
430	<	return false; // not reached
469	>	static final void cancelIgnoringExceptions(ForkJoinTask<?> t) {
470	>	if (t != null && t.status >= 0) {
471	>	try {
472	>	t.cancel(false);
473	>	} catch (Throwable ignore) {
474	>	}
475		}
432	–	setNormalCompletion();
433	–	return true;
476		}
477
478		/**
479	<	* Main execution method used by worker threads. Invokes
438	<	* base computation unless already complete.
479	>	* Removes exception node and clears status
480		*/
481	<	final void quietlyExec() {
482	<	if (status >= 0) {
483	<	try {
484	<	if (!exec())
485	<	return;
486	<	} catch (Throwable rex) {
487	<	setDoneExceptionally(rex);
488	<	return;
481	>	private void clearExceptionalCompletion() {
482	>	int h = System.identityHashCode(this);
483	>	final ReentrantLock lock = exceptionTableLock;
484	>	lock.lock();
485	>	try {
486	>	ExceptionNode[] t = exceptionTable;
487	>	int i = h & (t.length - 1);
488	>	ExceptionNode e = t[i];
489	>	ExceptionNode pred = null;
490	>	while (e != null) {
491	>	ExceptionNode next = e.next;
492	>	if (e.get() == this) {
493	>	if (pred == null)
494	>	t[i] = next;
495	>	else
496	>	pred.next = next;
497	>	break;
498	>	}
499	>	pred = e;
500	>	e = next;
501		}
502	<	setNormalCompletion();
502	>	expungeStaleExceptions();
503	>	status = 0;
504	>	} finally {
505	>	lock.unlock();
506		}
507		}
508
509		/**
510	<	* Calls exec(), recording but not rethrowing exception.
511	<	* Caller should normally check status before calling.
510	>	* Returns a rethrowable exception for the given task, if
511	>	* available. To provide accurate stack traces, if the exception
512	>	* was not thrown by the current thread, we try to create a new
513	>	* exception of the same type as the one thrown, but with the
514	>	* recorded exception as its cause. If there is no such
515	>	* constructor, we instead try to use a no-arg constructor,
516	>	* followed by initCause, to the same effect. If none of these
517	>	* apply, or any fail due to other exceptions, we return the
518	>	* recorded exception, which is still correct, although it may
519	>	* contain a misleading stack trace.
520		*
521	<	* @return true if completed normally
521	>	* @return the exception, or null if none
522		*/
523	<	private boolean tryQuietlyInvoke() {
523	>	private Throwable getThrowableException() {
524	>	if ((status & DONE_MASK) != EXCEPTIONAL)
525	>	return null;
526	>	int h = System.identityHashCode(this);
527	>	ExceptionNode e;
528	>	final ReentrantLock lock = exceptionTableLock;
529	>	lock.lock();
530		try {
531	<	if (!exec())
532	<	return false;
533	<	} catch (Throwable rex) {
534	<	setDoneExceptionally(rex);
535	<	return false;
531	>	expungeStaleExceptions();
532	>	ExceptionNode[] t = exceptionTable;
533	>	e = t[h & (t.length - 1)];
534	>	while (e != null && e.get() != this)
535	>	e = e.next;
536	>	} finally {
537	>	lock.unlock();
538	>	}
539	>	Throwable ex;
540	>	if (e == null || (ex = e.ex) == null)
541	>	return null;
542	>	if (false && e.thrower != Thread.currentThread().getId()) {
543	>	Class<? extends Throwable> ec = ex.getClass();
544	>	try {
545	>	Constructor<?> noArgCtor = null;
546	>	Constructor<?>[] cs = ec.getConstructors();// public ctors only
547	>	for (int i = 0; i < cs.length; ++i) {
548	>	Constructor<?> c = cs[i];
549	>	Class<?>[] ps = c.getParameterTypes();
550	>	if (ps.length == 0)
551	>	noArgCtor = c;
552	>	else if (ps.length == 1 && ps[0] == Throwable.class)
553	>	return (Throwable)(c.newInstance(ex));
554	>	}
555	>	if (noArgCtor != null) {
556	>	Throwable wx = (Throwable)(noArgCtor.newInstance());
557	>	wx.initCause(ex);
558	>	return wx;
559	>	}
560	>	} catch (Exception ignore) {
561	>	}
562		}
563	<	setNormalCompletion();
468	<	return true;
563	>	return ex;
564		}
565
566		/**
567	<	* Cancels, ignoring any exceptions it throws.
567	>	* Poll stale refs and remove them. Call only while holding lock.
568		*/
569	<	final void cancelIgnoringExceptions() {
570	<	try {
571	<	cancel(false);
572	<	} catch (Throwable ignore) {
569	>	private static void expungeStaleExceptions() {
570	>	for (Object x; (x = exceptionTableRefQueue.poll()) != null;) {
571	>	if (x instanceof ExceptionNode) {
572	>	ForkJoinTask<?> key = ((ExceptionNode)x).get();
573	>	ExceptionNode[] t = exceptionTable;
574	>	int i = System.identityHashCode(key) & (t.length - 1);
575	>	ExceptionNode e = t[i];
576	>	ExceptionNode pred = null;
577	>	while (e != null) {
578	>	ExceptionNode next = e.next;
579	>	if (e == x) {
580	>	if (pred == null)
581	>	t[i] = next;
582	>	else
583	>	pred.next = next;
584	>	break;
585	>	}
586	>	pred = e;
587	>	e = next;
588	>	}
589	>	}
590		}
591		}
592
593		/**
594	<	* Main implementation of helpJoin
594	>	* If lock is available, poll stale refs and remove them.
595	>	* Called from ForkJoinPool when pools become quiescent.
596		*/
597	<	private int busyJoin(ForkJoinWorkerThread w) {
598	<	int s;
599	<	ForkJoinTask<?> t;
600	<	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
601	<	t.quietlyExec();
602	<	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
597	>	static final void helpExpungeStaleExceptions() {
598	>	final ReentrantLock lock = exceptionTableLock;
599	>	if (lock.tryLock()) {
600	>	try {
601	>	expungeStaleExceptions();
602	>	} finally {
603	>	lock.unlock();
604	>	}
605	>	}
606	>	}
607	>
608	>	/**
609	>	* Throws exception, if any, associated with the given status.
610	>	*/
611	>	private void reportException(int s) {
612	>	Throwable ex = ((s == CANCELLED) ?  new CancellationException() :
613	>	(s == EXCEPTIONAL) ? getThrowableException() :
614	>	null);
615	>	if (ex != null)
616	>	U.throwException(ex);
617		}
618
619		// public methods
#	Line 494 | Line 621 | public abstract class ForkJoinTask<V> im
621		/**
622		* Arranges to asynchronously execute this task.  While it is not
623		* necessarily enforced, it is a usage error to fork a task more
624	<	* than once unless it has completed and been reinitialized.  This
625	<	* method may be invoked only from within ForkJoinTask
626	<	* computations (as may be determined using method {@link
627	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
628	<	* in exceptions or errors, possibly including ClassCastException.
624	>	* than once unless it has completed and been reinitialized.
625	>	* Subsequent modifications to the state of this task or any data
626	>	* it operates on are not necessarily consistently observable by
627	>	* any thread other than the one executing it unless preceded by a
628	>	* call to {@link #join} or related methods, or a call to {@link
629	>	* #isDone} returning {@code true}.
630	>	*
631	>	* <p>This method may be invoked only from within {@code
632	>	* ForkJoinPool} computations (as may be determined using method
633	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
634	>	* result in exceptions or errors, possibly including {@code
635	>	* ClassCastException}.
636		*
637	<	* @return {@code this}, to simplify usage.
637	>	* @return {@code this}, to simplify usage
638		*/
639		public final ForkJoinTask<V> fork() {
640	<	((ForkJoinWorkerThread) Thread.currentThread())
507	<	.pushTask(this);
640	>	((ForkJoinWorkerThread)Thread.currentThread()).workQueue.push(this);
641		return this;
642		}
643
644		/**
645	<	* Returns the result of the computation when it is ready.
646	<	* This method differs from {@code get} in that abnormal
647	<	* completion results in RuntimeExceptions or Errors, not
648	<	* ExecutionExceptions.
645	>	* Returns the result of the computation when it {@link #isDone is
646	>	* done}.  This method differs from {@link #get()} in that
647	>	* abnormal completion results in {@code RuntimeException} or
648	>	* {@code Error}, not {@code ExecutionException}, and that
649	>	* interrupts of the calling thread do <em>not</em> cause the
650	>	* method to abruptly return by throwing {@code
651	>	* InterruptedException}.
652		*
653		* @return the computed result
654		*/
655		public final V join() {
656	<	ForkJoinWorkerThread w = getWorker();
657	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
658	<	reportException(awaitDone(w, true));
656	>	int s;
657	>	if ((s = doJoin() & DONE_MASK) != NORMAL)
658	>	reportException(s);
659		return getRawResult();
660		}
661
662		/**
663		* Commences performing this task, awaits its completion if
664	<	* necessary, and return its result.
664	>	* necessary, and returns its result, or throws an (unchecked)
665	>	* {@code RuntimeException} or {@code Error} if the underlying
666	>	* computation did so.
667		*
530	–	* @throws Throwable (a RuntimeException, Error, or unchecked
531	–	* exception) if the underlying computation did so
668		* @return the computed result
669		*/
670		public final V invoke() {
671	<	if (status >= 0 && tryExec())
672	<	return getRawResult();
673	<	else
674	<	return join();
671	>	int s;
672	>	if ((s = doInvoke() & DONE_MASK) != NORMAL)
673	>	reportException(s);
674	>	return getRawResult();
675		}
676
677		/**
678		* Forks the given tasks, returning when {@code isDone} holds for
679	<	* each task or an exception is encountered. This method may be
680	<	* invoked only from within ForkJoinTask computations (as may be
681	<	* determined using method {@link #inForkJoinPool}). Attempts to
682	<	* invoke in other contexts result in exceptions or errors,
683	<	* possibly including ClassCastException.
679	>	* each task or an (unchecked) exception is encountered, in which
680	>	* case the exception is rethrown. If more than one task
681	>	* encounters an exception, then this method throws any one of
682	>	* these exceptions. If any task encounters an exception, the
683	>	* other may be cancelled. However, the execution status of
684	>	* individual tasks is not guaranteed upon exceptional return. The
685	>	* status of each task may be obtained using {@link
686	>	* #getException()} and related methods to check if they have been
687	>	* cancelled, completed normally or exceptionally, or left
688	>	* unprocessed.
689	>	*
690	>	* <p>This method may be invoked only from within {@code
691	>	* ForkJoinPool} computations (as may be determined using method
692	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
693	>	* result in exceptions or errors, possibly including {@code
694	>	* ClassCastException}.
695		*
696		* @param t1 the first task
697		* @param t2 the second task
698		* @throws NullPointerException if any task is null
552	–	* @throws RuntimeException or Error if a task did so
699		*/
700	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
700	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
701	>	int s1, s2;
702		t2.fork();
703	<	t1.invoke();
704	<	t2.join();
703	>	if ((s1 = t1.doInvoke() & DONE_MASK) != NORMAL)
704	>	t1.reportException(s1);
705	>	if ((s2 = t2.doJoin() & DONE_MASK) != NORMAL)
706	>	t2.reportException(s2);
707		}
708
709		/**
710		* Forks the given tasks, returning when {@code isDone} holds for
711	<	* each task or an exception is encountered. If any task
712	<	* encounters an exception, others may be, but are not guaranteed
713	<	* to be, cancelled.  This method may be invoked only from within
714	<	* ForkJoinTask computations (as may be determined using method
715	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
716	<	* result in exceptions or errors, possibly including
717	<	* ClassCastException.
718	<	*
719	<	* Overloadings of this method exist for the special cases
720	<	* of one to four arguments.
711	>	* each task or an (unchecked) exception is encountered, in which
712	>	* case the exception is rethrown. If more than one task
713	>	* encounters an exception, then this method throws any one of
714	>	* these exceptions. If any task encounters an exception, others
715	>	* may be cancelled. However, the execution status of individual
716	>	* tasks is not guaranteed upon exceptional return. The status of
717	>	* each task may be obtained using {@link #getException()} and
718	>	* related methods to check if they have been cancelled, completed
719	>	* normally or exceptionally, or left unprocessed.
720	>	*
721	>	* <p>This method may be invoked only from within {@code
722	>	* ForkJoinPool} computations (as may be determined using method
723	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
724	>	* result in exceptions or errors, possibly including {@code
725	>	* ClassCastException}.
726		*
727		* @param tasks the tasks
728	<	* @throws NullPointerException if tasks or any element are null
575	<	* @throws RuntimeException or Error if any task did so
728	>	* @throws NullPointerException if any task is null
729		*/
730		public static void invokeAll(ForkJoinTask<?>... tasks) {
731		Throwable ex = null;
#	Line 585 | Line 738 | public abstract class ForkJoinTask<V> im
738		}
739		else if (i != 0)
740		t.fork();
741	<	else {
742	<	t.quietlyInvoke();
590	<	if (ex == null)
591	<	ex = t.getException();
592	<	}
741	>	else if (t.doInvoke() < NORMAL && ex == null)
742	>	ex = t.getException();
743		}
744		for (int i = 1; i <= last; ++i) {
745		ForkJoinTask<?> t = tasks[i];
746		if (t != null) {
747		if (ex != null)
748		t.cancel(false);
749	<	else {
750	<	t.quietlyJoin();
601	<	if (ex == null)
602	<	ex = t.getException();
603	<	}
749	>	else if (t.doJoin() < NORMAL)
750	>	ex = t.getException();
751		}
752		}
753		if (ex != null)
754	<	rethrowException(ex);
754	>	U.throwException(ex);
755		}
756
757		/**
758	<	* Forks all tasks in the collection, returning when {@code
759	<	* isDone} holds for each task or an exception is encountered. If
760	<	* any task encounters an exception, others may be, but are not
761	<	* guaranteed to be, cancelled.  This method may be invoked only
762	<	* from within ForkJoinTask computations (as may be determined
763	<	* using method {@link #inForkJoinPool}). Attempts to invoke in
764	<	* other contexts result in exceptions or errors, possibly
765	<	* including ClassCastException.
758	>	* Forks all tasks in the specified collection, returning when
759	>	* {@code isDone} holds for each task or an (unchecked) exception
760	>	* is encountered, in which case the exception is rethrown. If
761	>	* more than one task encounters an exception, then this method
762	>	* throws any one of these exceptions. If any task encounters an
763	>	* exception, others may be cancelled. However, the execution
764	>	* status of individual tasks is not guaranteed upon exceptional
765	>	* return. The status of each task may be obtained using {@link
766	>	* #getException()} and related methods to check if they have been
767	>	* cancelled, completed normally or exceptionally, or left
768	>	* unprocessed.
769	>	*
770	>	* <p>This method may be invoked only from within {@code
771	>	* ForkJoinPool} computations (as may be determined using method
772	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
773	>	* result in exceptions or errors, possibly including {@code
774	>	* ClassCastException}.
775		*
776		* @param tasks the collection of tasks
777		* @return the tasks argument, to simplify usage
778		* @throws NullPointerException if tasks or any element are null
623	–	* @throws RuntimeException or Error if any task did so
779		*/
780		public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
781	<	if (!(tasks instanceof List<?>)) {
781	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
782		invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
783		return tasks;
784		}
#	Line 640 | Line 795 | public abstract class ForkJoinTask<V> im
795		}
796		else if (i != 0)
797		t.fork();
798	<	else {
799	<	t.quietlyInvoke();
645	<	if (ex == null)
646	<	ex = t.getException();
647	<	}
798	>	else if (t.doInvoke() < NORMAL && ex == null)
799	>	ex = t.getException();
800		}
801		for (int i = 1; i <= last; ++i) {
802		ForkJoinTask<?> t = ts.get(i);
803		if (t != null) {
804		if (ex != null)
805		t.cancel(false);
806	<	else {
807	<	t.quietlyJoin();
656	<	if (ex == null)
657	<	ex = t.getException();
658	<	}
806	>	else if (t.doJoin() < NORMAL)
807	>	ex = t.getException();
808		}
809		}
810		if (ex != null)
811	<	rethrowException(ex);
811	>	U.throwException(ex);
812		return tasks;
813		}
814
815		/**
816	<	* Returns {@code true} if the computation performed by this task
817	<	* has completed (or has been cancelled).
818	<	*
819	<	* @return {@code true} if this computation has completed
820	<	*/
821	<	public final boolean isDone() {
822	<	return status < 0;
823	<	}
824	<
825	<	/**
677	<	* Returns {@code true} if this task was cancelled.
678	<	*
679	<	* @return {@code true} if this task was cancelled
680	<	*/
681	<	public final boolean isCancelled() {
682	<	return (status & COMPLETION_MASK) == CANCELLED;
683	<	}
684	<
685	<	/**
686	<	* Asserts that the results of this task's computation will not be
687	<	* used. If a cancellation occurs before attempting to execute this
688	<	* task, execution will be suppressed, {@link #isCancelled}
689	<	* will report true, and {@link #join} will result in a
690	<	* {@code CancellationException} being thrown. Otherwise, when
691	<	* cancellation races with completion, there are no guarantees
692	<	* about whether {@code isCancelled} will report {@code true},
693	<	* whether {@code join} will return normally or via an exception,
694	<	* or whether these behaviors will remain consistent upon repeated
695	<	* invocation.
816	>	* Attempts to cancel execution of this task. This attempt will
817	>	* fail if the task has already completed or could not be
818	>	* cancelled for some other reason. If successful, and this task
819	>	* has not started when {@code cancel} is called, execution of
820	>	* this task is suppressed. After this method returns
821	>	* successfully, unless there is an intervening call to {@link
822	>	* #reinitialize}, subsequent calls to {@link #isCancelled},
823	>	* {@link #isDone}, and {@code cancel} will return {@code true}
824	>	* and calls to {@link #join} and related methods will result in
825	>	* {@code CancellationException}.
826		*
827		* <p>This method may be overridden in subclasses, but if so, must
828	<	* still ensure that these minimal properties hold. In particular,
829	<	* the cancel method itself must not throw exceptions.
828	>	* still ensure that these properties hold. In particular, the
829	>	* {@code cancel} method itself must not throw exceptions.
830		*
831	<	* <p> This method is designed to be invoked by <em>other</em>
831	>	* <p>This method is designed to be invoked by <em>other</em>
832		* tasks. To terminate the current task, you can just return or
833		* throw an unchecked exception from its computation method, or
834		* invoke {@link #completeExceptionally}.
835		*
836	<	* @param mayInterruptIfRunning this value is ignored in the
837	<	* default implementation because tasks are not in general
838	<	* cancelled via interruption
836	>	* @param mayInterruptIfRunning this value has no effect in the
837	>	* default implementation because interrupts are not used to
838	>	* control cancellation.
839		*
840		* @return {@code true} if this task is now cancelled
841		*/
842		public boolean cancel(boolean mayInterruptIfRunning) {
843	<	setCompletion(CANCELLED);
844	<	return (status & COMPLETION_MASK) == CANCELLED;
843	>	return (setCompletion(CANCELLED) & DONE_MASK) == CANCELLED;
844	>	}
845	>
846	>	public final boolean isDone() {
847	>	return status < 0;
848	>	}
849	>
850	>	public final boolean isCancelled() {
851	>	return (status & DONE_MASK) == CANCELLED;
852		}
853
854		/**
#	Line 720 | Line 857 | public abstract class ForkJoinTask<V> im
857		* @return {@code true} if this task threw an exception or was cancelled
858		*/
859		public final boolean isCompletedAbnormally() {
860	<	return (status & COMPLETION_MASK) < NORMAL;
860	>	return status < NORMAL;
861	>	}
862	>
863	>	/**
864	>	* Returns {@code true} if this task completed without throwing an
865	>	* exception and was not cancelled.
866	>	*
867	>	* @return {@code true} if this task completed without throwing an
868	>	* exception and was not cancelled
869	>	*/
870	>	public final boolean isCompletedNormally() {
871	>	return (status & DONE_MASK) == NORMAL;
872		}
873
874		/**
875		* Returns the exception thrown by the base computation, or a
876	<	* CancellationException if cancelled, or null if none or if the
877	<	* method has not yet completed.
876	>	* {@code CancellationException} if cancelled, or {@code null} if
877	>	* none or if the method has not yet completed.
878		*
879		* @return the exception, or {@code null} if none
880		*/
881		public final Throwable getException() {
882	<	int s = status & COMPLETION_MASK;
883	<	if (s >= NORMAL)
884	<	return null;
885	<	if (s == CANCELLED)
738	<	return new CancellationException();
739	<	return exceptionMap.get(this);
882	>	int s = status & DONE_MASK;
883	>	return ((s >= NORMAL)    ? null :
884	>	(s == CANCELLED) ? new CancellationException() :
885	>	getThrowableException());
886		}
887
888		/**
#	Line 749 | Line 895 | public abstract class ForkJoinTask<V> im
895		* overridable, but overridden versions must invoke {@code super}
896		* implementation to maintain guarantees.
897		*
898	<	* @param ex the exception to throw. If this exception is
899	<	* not a RuntimeException or Error, the actual exception thrown
900	<	* will be a RuntimeException with cause ex.
898	>	* @param ex the exception to throw. If this exception is not a
899	>	* {@code RuntimeException} or {@code Error}, the actual exception
900	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
901		*/
902		public void completeExceptionally(Throwable ex) {
903	<	setDoneExceptionally((ex instanceof RuntimeException) ||
904	<	(ex instanceof Error) ? ex :
905	<	new RuntimeException(ex));
903	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
904	>	(ex instanceof Error) ? ex :
905	>	new RuntimeException(ex));
906		}
907
908		/**
909		* Completes this task, and if not already aborted or cancelled,
910	<	* returning a {@code null} result upon {@code join} and related
911	<	* operations. This method may be used to provide results for
912	<	* asynchronous tasks, or to provide alternative handling for
913	<	* tasks that would not otherwise complete normally. Its use in
914	<	* other situations is discouraged. This method is
915	<	* overridable, but overridden versions must invoke {@code super}
916	<	* implementation to maintain guarantees.
910	>	* returning the given value as the result of subsequent
911	>	* invocations of {@code join} and related operations. This method
912	>	* may be used to provide results for asynchronous tasks, or to
913	>	* provide alternative handling for tasks that would not otherwise
914	>	* complete normally. Its use in other situations is
915	>	* discouraged. This method is overridable, but overridden
916	>	* versions must invoke {@code super} implementation to maintain
917	>	* guarantees.
918		*
919		* @param value the result value for this task
920		*/
#	Line 775 | Line 922 | public abstract class ForkJoinTask<V> im
922		try {
923		setRawResult(value);
924		} catch (Throwable rex) {
925	<	setDoneExceptionally(rex);
925	>	setExceptionalCompletion(rex);
926		return;
927		}
928	<	setNormalCompletion();
782	<	}
783	<
784	<	public final V get() throws InterruptedException, ExecutionException {
785	<	ForkJoinWorkerThread w = getWorker();
786	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
787	<	awaitDone(w, true);
788	<	return reportFutureResult();
928	>	setCompletion(NORMAL);
929		}
930
931	<	public final V get(long timeout, TimeUnit unit)
932	<	throws InterruptedException, ExecutionException, TimeoutException {
933	<	long nanos = unit.toNanos(timeout);
934	<	ForkJoinWorkerThread w = getWorker();
935	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
936	<	awaitDone(w, nanos);
937	<	return reportTimedFutureResult();
931	>	/**
932	>	* Completes this task normally without setting a value. The most
933	>	* recent value established by {@link #setRawResult} (or {@code
934	>	* null} by default) will be returned as the result of subsequent
935	>	* invocations of {@code join} and related operations.
936	>	*
937	>	* @since 1.8
938	>	*/
939	>	public final void quietlyComplete() {
940	>	setCompletion(NORMAL);
941		}
942
943		/**
944	<	* Possibly executes other tasks until this task is ready, then
945	<	* returns the result of the computation.  This method may be more
803	<	* efficient than {@code join}, but is only applicable when
804	<	* there are no potential dependencies between continuation of the
805	<	* current task and that of any other task that might be executed
806	<	* while helping. (This usually holds for pure divide-and-conquer
807	<	* tasks). This method may be invoked only from within
808	<	* ForkJoinTask computations (as may be determined using method
809	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
810	<	* result in exceptions or errors, possibly including
811	<	* ClassCastException.
944	>	* Waits if necessary for the computation to complete, and then
945	>	* retrieves its result.
946		*
947		* @return the computed result
948	+	* @throws CancellationException if the computation was cancelled
949	+	* @throws ExecutionException if the computation threw an
950	+	* exception
951	+	* @throws InterruptedException if the current thread is not a
952	+	* member of a ForkJoinPool and was interrupted while waiting
953		*/
954	<	public final V helpJoin() {
955	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
956	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
957	<	reportException(busyJoin(w));
954	>	public final V get() throws InterruptedException, ExecutionException {
955	>	int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ?
956	>	doJoin() : externalInterruptibleAwaitDone();
957	>	Throwable ex;
958	>	if ((s &= DONE_MASK) == CANCELLED)
959	>	throw new CancellationException();
960	>	if (s == EXCEPTIONAL && (ex = getThrowableException()) != null)
961	>	throw new ExecutionException(ex);
962		return getRawResult();
963		}
964
965		/**
966	<	* Possibly executes other tasks until this task is ready.  This
967	<	* method may be invoked only from within ForkJoinTask
968	<	* computations (as may be determined using method {@link
969	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
970	<	* in exceptions or errors, possibly including ClassCastException.
966	>	* Waits if necessary for at most the given time for the computation
967	>	* to complete, and then retrieves its result, if available.
968	>	*
969	>	* @param timeout the maximum time to wait
970	>	* @param unit the time unit of the timeout argument
971	>	* @return the computed result
972	>	* @throws CancellationException if the computation was cancelled
973	>	* @throws ExecutionException if the computation threw an
974	>	* exception
975	>	* @throws InterruptedException if the current thread is not a
976	>	* member of a ForkJoinPool and was interrupted while waiting
977	>	* @throws TimeoutException if the wait timed out
978		*/
979	<	public final void quietlyHelpJoin() {
980	<	if (status >= 0) {
981	<	ForkJoinWorkerThread w =
982	<	(ForkJoinWorkerThread) Thread.currentThread();
983	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
984	<	busyJoin(w);
979	>	public final V get(long timeout, TimeUnit unit)
980	>	throws InterruptedException, ExecutionException, TimeoutException {
981	>	if (Thread.interrupted())
982	>	throw new InterruptedException();
983	>	// Messy in part because we measure in nanosecs, but wait in millisecs
984	>	int s; long ns, ms;
985	>	if ((s = status) >= 0 && (ns = unit.toNanos(timeout)) > 0L) {
986	>	long deadline = System.nanoTime() + ns;
987	>	ForkJoinPool p = null;
988	>	ForkJoinPool.WorkQueue w = null;
989	>	Thread t = Thread.currentThread();
990	>	if (t instanceof ForkJoinWorkerThread) {
991	>	ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
992	>	p = wt.pool;
993	>	w = wt.workQueue;
994	>	s = p.helpJoinOnce(w, this); // no retries on failure
995	>	}
996	>	boolean canBlock = false;
997	>	boolean interrupted = false;
998	>	try {
999	>	while ((s = status) >= 0) {
1000	>	if (w != null && w.runState < 0)
1001	>	cancelIgnoringExceptions(this);
1002	>	else if (!canBlock) {
1003	>	if (p == null || p.tryCompensate(this, null))
1004	>	canBlock = true;
1005	>	}
1006	>	else {
1007	>	if ((ms = TimeUnit.NANOSECONDS.toMillis(ns)) > 0L &&
1008	>	U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
1009	>	synchronized (this) {
1010	>	if (status >= 0) {
1011	>	try {
1012	>	wait(ms);
1013	>	} catch (InterruptedException ie) {
1014	>	if (p == null)
1015	>	interrupted = true;
1016	>	}
1017	>	}
1018	>	else
1019	>	notifyAll();
1020	>	}
1021	>	}
1022	>	if ((s = status) < 0 || interrupted ||
1023	>	(ns = deadline - System.nanoTime()) <= 0L)
1024	>	break;
1025	>	}
1026	>	}
1027	>	} finally {
1028	>	if (p != null && canBlock)
1029	>	p.incrementActiveCount();
1030	>	}
1031	>	if (interrupted)
1032	>	throw new InterruptedException();
1033	>	}
1034	>	if ((s &= DONE_MASK) != NORMAL) {
1035	>	Throwable ex;
1036	>	if (s == CANCELLED)
1037	>	throw new CancellationException();
1038	>	if (s != EXCEPTIONAL)
1039	>	throw new TimeoutException();
1040	>	if ((ex = getThrowableException()) != null)
1041	>	throw new ExecutionException(ex);
1042		}
1043	+	return getRawResult();
1044		}
1045
1046		/**
1047	<	* Joins this task, without returning its result or throwing an
1047	>	* Joins this task, without returning its result or throwing its
1048		* exception. This method may be useful when processing
1049		* collections of tasks when some have been cancelled or otherwise
1050		* known to have aborted.
1051		*/
1052		public final void quietlyJoin() {
1053	<	if (status >= 0) {
846	<	ForkJoinWorkerThread w = getWorker();
847	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
848	<	awaitDone(w, true);
849	<	}
1053	>	doJoin();
1054		}
1055
1056		/**
1057		* Commences performing this task and awaits its completion if
1058	<	* necessary, without returning its result or throwing an
1059	<	* exception. This method may be useful when processing
856	<	* collections of tasks when some have been cancelled or otherwise
857	<	* known to have aborted.
1058	>	* necessary, without returning its result or throwing its
1059	>	* exception.
1060		*/
1061		public final void quietlyInvoke() {
1062	<	if (status >= 0 && !tryQuietlyInvoke())
861	<	quietlyJoin();
1062	>	doInvoke();
1063		}
1064
1065		/**
1066		* Possibly executes tasks until the pool hosting the current task
1067	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
1068	<	* designs in which many tasks are forked, but none are explicitly
1069	<	* joined, instead executing them until all are processed.  This
1070	<	* method may be invoked only from within ForkJoinTask
1071	<	* computations (as may be determined using method {@link
1072	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
1073	<	* in exceptions or errors, possibly including ClassCastException.
1067	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
1068	>	* be of use in designs in which many tasks are forked, but none
1069	>	* are explicitly joined, instead executing them until all are
1070	>	* processed.
1071	>	*
1072	>	* <p>This method may be invoked only from within {@code
1073	>	* ForkJoinPool} computations (as may be determined using method
1074	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1075	>	* result in exceptions or errors, possibly including {@code
1076	>	* ClassCastException}.
1077		*/
1078		public static void helpQuiesce() {
1079	<	((ForkJoinWorkerThread) Thread.currentThread())
1080	<	.helpQuiescePool();
1079	>	ForkJoinWorkerThread wt =
1080	>	(ForkJoinWorkerThread)Thread.currentThread();
1081	>	wt.pool.helpQuiescePool(wt.workQueue);
1082		}
1083
1084		/**
#	Line 882 | Line 1087 | public abstract class ForkJoinTask<V> im
1087		* this task, but only if reuse occurs when this task has either
1088		* never been forked, or has been forked, then completed and all
1089		* outstanding joins of this task have also completed. Effects
1090	<	* under any other usage conditions are not guaranteed, and are
1091	<	* discouraged. This method may be useful when executing
1090	>	* under any other usage conditions are not guaranteed.
1091	>	* This method may be useful when executing
1092		* pre-constructed trees of subtasks in loops.
1093	+	*
1094	+	* <p>Upon completion of this method, {@code isDone()} reports
1095	+	* {@code false}, and {@code getException()} reports {@code
1096	+	* null}. However, the value returned by {@code getRawResult} is
1097	+	* unaffected. To clear this value, you can invoke {@code
1098	+	* setRawResult(null)}.
1099		*/
1100		public void reinitialize() {
1101	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
1102	<	exceptionMap.remove(this);
1103	<	status = 0;
1101	>	if ((status & DONE_MASK) == EXCEPTIONAL)
1102	>	clearExceptionalCompletion();
1103	>	else
1104	>	status = 0;
1105		}
1106
1107		/**
#	Line 906 | Line 1118 | public abstract class ForkJoinTask<V> im
1118		}
1119
1120		/**
1121	<	* Returns {@code true} if the current thread is executing as a
1122	<	* ForkJoinPool computation.
1121	>	* Returns {@code true} if the current thread is a {@link
1122	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation.
1123		*
1124	<	* @return {@code true} if the current thread is executing as a
1125	<	* ForkJoinPool computation, or false otherwise
1124	>	* @return {@code true} if the current thread is a {@link
1125	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation,
1126	>	* or {@code false} otherwise
1127		*/
1128		public static boolean inForkJoinPool() {
1129		return Thread.currentThread() instanceof ForkJoinWorkerThread;
#	Line 922 | Line 1135 | public abstract class ForkJoinTask<V> im
1135		* by the current thread, and has not commenced executing in
1136		* another thread.  This method may be useful when arranging
1137		* alternative local processing of tasks that could have been, but
1138	<	* were not, stolen. This method may be invoked only from within
1139	<	* ForkJoinTask computations (as may be determined using method
1140	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1141	<	* result in exceptions or errors, possibly including
1142	<	* ClassCastException.
1138	>	* were not, stolen.
1139	>	*
1140	>	* <p>This method may be invoked only from within {@code
1141	>	* ForkJoinPool} computations (as may be determined using method
1142	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1143	>	* result in exceptions or errors, possibly including {@code
1144	>	* ClassCastException}.
1145		*
1146		* @return {@code true} if unforked
1147		*/
1148		public boolean tryUnfork() {
1149	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1150	<	.unpushTask(this);
1149	>	return ((ForkJoinWorkerThread)Thread.currentThread())
1150	>	.workQueue.tryUnpush(this);
1151		}
1152
1153		/**
1154		* Returns an estimate of the number of tasks that have been
1155		* forked by the current worker thread but not yet executed. This
1156		* value may be useful for heuristic decisions about whether to
1157	<	* fork other tasks.  This method may be invoked only from within
1158	<	* ForkJoinTask computations (as may be determined using method
1159	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1160	<	* result in exceptions or errors, possibly including
1161	<	* ClassCastException.
1157	>	* fork other tasks.
1158	>	*
1159	>	* <p>This method may be invoked only from within {@code
1160	>	* ForkJoinPool} computations (as may be determined using method
1161	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1162	>	* result in exceptions or errors, possibly including {@code
1163	>	* ClassCastException}.
1164	>	*
1165		* @return the number of tasks
1166		*/
1167		public static int getQueuedTaskCount() {
1168		return ((ForkJoinWorkerThread) Thread.currentThread())
1169	<	.getQueueSize();
1169	>	.workQueue.queueSize();
1170		}
1171
1172		/**
#	Line 959 | Line 1177 | public abstract class ForkJoinTask<V> im
1177		* usages of ForkJoinTasks, at steady state, each worker should
1178		* aim to maintain a small constant surplus (for example, 3) of
1179		* tasks, and to process computations locally if this threshold is
1180	<	* exceeded.  This method may be invoked only from within
1181	<	* ForkJoinTask computations (as may be determined using method
1182	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1183	<	* result in exceptions or errors, possibly including
1184	<	* ClassCastException.  *
1180	>	* exceeded.
1181	>	*
1182	>	* <p>This method may be invoked only from within {@code
1183	>	* ForkJoinPool} computations (as may be determined using method
1184	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1185	>	* result in exceptions or errors, possibly including {@code
1186	>	* ClassCastException}.
1187	>	*
1188		* @return the surplus number of tasks, which may be negative
1189		*/
1190		public static int getSurplusQueuedTaskCount() {
1191	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1192	<	.getEstimatedSurplusTaskCount();
1191	>	/*
1192	>	* The aim of this method is to return a cheap heuristic guide
1193	>	* for task partitioning when programmers, frameworks, tools,
1194	>	* or languages have little or no idea about task granularity.
1195	>	* In essence by offering this method, we ask users only about
1196	>	* tradeoffs in overhead vs expected throughput and its
1197	>	* variance, rather than how finely to partition tasks.
1198	>	*
1199	>	* In a steady state strict (tree-structured) computation,
1200	>	* each thread makes available for stealing enough tasks for
1201	>	* other threads to remain active. Inductively, if all threads
1202	>	* play by the same rules, each thread should make available
1203	>	* only a constant number of tasks.
1204	>	*
1205	>	* The minimum useful constant is just 1. But using a value of
1206	>	* 1 would require immediate replenishment upon each steal to
1207	>	* maintain enough tasks, which is infeasible.  Further,
1208	>	* partitionings/granularities of offered tasks should
1209	>	* minimize steal rates, which in general means that threads
1210	>	* nearer the top of computation tree should generate more
1211	>	* than those nearer the bottom. In perfect steady state, each
1212	>	* thread is at approximately the same level of computation
1213	>	* tree. However, producing extra tasks amortizes the
1214	>	* uncertainty of progress and diffusion assumptions.
1215	>	*
1216	>	* So, users will want to use values larger, but not much
1217	>	* larger than 1 to both smooth over transient shortages and
1218	>	* hedge against uneven progress; as traded off against the
1219	>	* cost of extra task overhead. We leave the user to pick a
1220	>	* threshold value to compare with the results of this call to
1221	>	* guide decisions, but recommend values such as 3.
1222	>	*
1223	>	* When all threads are active, it is on average OK to
1224	>	* estimate surplus strictly locally. In steady-state, if one
1225	>	* thread is maintaining say 2 surplus tasks, then so are
1226	>	* others. So we can just use estimated queue length.
1227	>	* However, this strategy alone leads to serious mis-estimates
1228	>	* in some non-steady-state conditions (ramp-up, ramp-down,
1229	>	* other stalls). We can detect many of these by further
1230	>	* considering the number of "idle" threads, that are known to
1231	>	* have zero queued tasks, so compensate by a factor of
1232	>	* (#idle/#active) threads.
1233	>	*/
1234	>	ForkJoinWorkerThread wt =
1235	>	(ForkJoinWorkerThread)Thread.currentThread();
1236	>	return wt.workQueue.queueSize() - wt.pool.idlePerActive();
1237		}
1238
1239		// Extension methods
#	Line 994 | Line 1259 | public abstract class ForkJoinTask<V> im
1259		protected abstract void setRawResult(V value);
1260
1261		/**
1262	<	* Immediately performs the base action of this task.  This method
1263	<	* is designed to support extensions, and should not in general be
1264	<	* called otherwise. The return value controls whether this task
1265	<	* is considered to be done normally. It may return false in
1262	>	* Immediately performs the base action of this task and returns
1263	>	* true if, upon return from this method, this task is guaranteed
1264	>	* to have completed normally. This method may return false
1265	>	* otherwise, to indicate that this task is not necessarily
1266	>	* complete (or is not known to be complete), for example in
1267		* asynchronous actions that require explicit invocations of
1268	<	* {@link #complete} to become joinable. It may throw exceptions
1269	<	* to indicate abnormal exit.
1268	>	* completion methods. This method may also throw an (unchecked)
1269	>	* exception to indicate abnormal exit. This method is designed to
1270	>	* support extensions, and should not in general be called
1271	>	* otherwise.
1272		*
1273	<	* @return {@code true} if completed normally
1006	<	* @throws Error or RuntimeException if encountered during computation
1273	>	* @return {@code true} if this task is known to have completed normally
1274		*/
1275		protected abstract boolean exec();
1276
#	Line 1015 | Line 1282 | public abstract class ForkJoinTask<V> im
1282		* null even if a task exists but cannot be accessed without
1283		* contention with other threads.  This method is designed
1284		* primarily to support extensions, and is unlikely to be useful
1285	<	* otherwise.  This method may be invoked only from within
1286	<	* ForkJoinTask computations (as may be determined using method
1287	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1288	<	* result in exceptions or errors, possibly including
1289	<	* ClassCastException.
1285	>	* otherwise.
1286	>	*
1287	>	* <p>This method may be invoked only from within {@code
1288	>	* ForkJoinPool} computations (as may be determined using method
1289	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1290	>	* result in exceptions or errors, possibly including {@code
1291	>	* ClassCastException}.
1292		*
1293		* @return the next task, or {@code null} if none are available
1294		*/
1295		protected static ForkJoinTask<?> peekNextLocalTask() {
1296	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1028	<	.peekTask();
1296	>	return ((ForkJoinWorkerThread) Thread.currentThread()).workQueue.peek();
1297		}
1298
1299		/**
1300		* Unschedules and returns, without executing, the next task
1301		* queued by the current thread but not yet executed.  This method
1302		* is designed primarily to support extensions, and is unlikely to
1303	<	* be useful otherwise.  This method may be invoked only from
1304	<	* within ForkJoinTask computations (as may be determined using
1305	<	* method {@link #inForkJoinPool}). Attempts to invoke in other
1306	<	* contexts result in exceptions or errors, possibly including
1307	<	* ClassCastException.
1303	>	* be useful otherwise.
1304	>	*
1305	>	* <p>This method may be invoked only from within {@code
1306	>	* ForkJoinPool} computations (as may be determined using method
1307	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1308	>	* result in exceptions or errors, possibly including {@code
1309	>	* ClassCastException}.
1310		*
1311		* @return the next task, or {@code null} if none are available
1312		*/
1313		protected static ForkJoinTask<?> pollNextLocalTask() {
1314		return ((ForkJoinWorkerThread) Thread.currentThread())
1315	<	.pollLocalTask();
1315	>	.workQueue.nextLocalTask();
1316		}
1317
1318		/**
#	Line 1053 | Line 1323 | public abstract class ForkJoinTask<V> im
1323		* {@code null} result does not necessarily imply quiescence
1324		* of the pool this task is operating in.  This method is designed
1325		* primarily to support extensions, and is unlikely to be useful
1326	<	* otherwise.  This method may be invoked only from within
1327	<	* ForkJoinTask computations (as may be determined using method
1328	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1329	<	* result in exceptions or errors, possibly including
1330	<	* ClassCastException.
1326	>	* otherwise.
1327	>	*
1328	>	* <p>This method may be invoked only from within {@code
1329	>	* ForkJoinPool} computations (as may be determined using method
1330	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1331	>	* result in exceptions or errors, possibly including {@code
1332	>	* ClassCastException}.
1333		*
1334		* @return a task, or {@code null} if none are available
1335		*/
1336		protected static ForkJoinTask<?> pollTask() {
1337	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1338	<	.pollTask();
1337	>	ForkJoinWorkerThread wt =
1338	>	(ForkJoinWorkerThread)Thread.currentThread();
1339	>	return wt.pool.nextTaskFor(wt.workQueue);
1340	>	}
1341	>
1342	>	// tag operations
1343	>
1344	>	/**
1345	>	* Returns the tag for this task.
1346	>	*
1347	>	* @return the tag for this task
1348	>	* @since 1.8
1349	>	*/
1350	>	public final short getForkJoinTaskTag() {
1351	>	return (short)status;
1352	>	}
1353	>
1354	>	/**
1355	>	* Atomically sets the tag value for this task.
1356	>	*
1357	>	* @param tag the tag value
1358	>	* @return the previous value of the tag
1359	>	* @since 1.8
1360	>	*/
1361	>	public final short setForkJoinTaskTag(short tag) {
1362	>	for (int s;;) {
1363	>	if (U.compareAndSwapInt(this, STATUS, s = status,
1364	>	(s & ~SMASK) | (tag & SMASK)))
1365	>	return (short)s;
1366	>	}
1367	>	}
1368	>
1369	>	/**
1370	>	* Atomically conditionally sets the tag value for this task.
1371	>	* Among other applications, tags can be used as visit markers
1372	>	* in tasks operating on graphs, as in methods that check: {@code
1373	>	* if (task.compareAndSetForkJoinTaskTag((short)0, (short)1))}
1374	>	* before processing, otherwise exiting because the node has
1375	>	* already been visited.
1376	>	*
1377	>	* @param e the expected tag value
1378	>	* @param tag the new tag value
1379	>	* @return true if successful; i.e., the current value was
1380	>	* equal to e and is now tag.
1381	>	* @since 1.8
1382	>	*/
1383	>	public final boolean compareAndSetForkJoinTaskTag(short e, short tag) {
1384	>	for (int s;;) {
1385	>	if ((short)(s = status) != e)
1386	>	return false;
1387	>	if (U.compareAndSwapInt(this, STATUS, s,
1388	>	(s & ~SMASK) | (tag & SMASK)))
1389	>	return true;
1390	>	}
1391		}
1392
1393		/**
#	Line 1074 | Line 1398 | public abstract class ForkJoinTask<V> im
1398		static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1399		implements RunnableFuture<T> {
1400		final Runnable runnable;
1077	–	final T resultOnCompletion;
1401		T result;
1402		AdaptedRunnable(Runnable runnable, T result) {
1403		if (runnable == null) throw new NullPointerException();
1404		this.runnable = runnable;
1405	<	this.resultOnCompletion = result;
1405	>	this.result = result; // OK to set this even before completion
1406		}
1407	<	public T getRawResult() { return result; }
1408	<	public void setRawResult(T v) { result = v; }
1409	<	public boolean exec() {
1410	<	runnable.run();
1411	<	result = resultOnCompletion;
1412	<	return true;
1407	>	public final T getRawResult() { return result; }
1408	>	public final void setRawResult(T v) { result = v; }
1409	>	public final boolean exec() { runnable.run(); return true; }
1410	>	public final void run() { invoke(); }
1411	>	private static final long serialVersionUID = 5232453952276885070L;
1412	>	}
1413	>
1414	>	/**
1415	>	* Adaptor for Runnables without results
1416	>	*/
1417	>	static final class AdaptedRunnableAction extends ForkJoinTask<Void>
1418	>	implements RunnableFuture<Void> {
1419	>	final Runnable runnable;
1420	>	AdaptedRunnableAction(Runnable runnable) {
1421	>	if (runnable == null) throw new NullPointerException();
1422	>	this.runnable = runnable;
1423		}
1424	<	public void run() { invoke(); }
1424	>	public final Void getRawResult() { return null; }
1425	>	public final void setRawResult(Void v) { }
1426	>	public final boolean exec() { runnable.run(); return true; }
1427	>	public final void run() { invoke(); }
1428		private static final long serialVersionUID = 5232453952276885070L;
1429		}
1430
#	Line 1103 | Line 1439 | public abstract class ForkJoinTask<V> im
1439		if (callable == null) throw new NullPointerException();
1440		this.callable = callable;
1441		}
1442	<	public T getRawResult() { return result; }
1443	<	public void setRawResult(T v) { result = v; }
1444	<	public boolean exec() {
1442	>	public final T getRawResult() { return result; }
1443	>	public final void setRawResult(T v) { result = v; }
1444	>	public final boolean exec() {
1445		try {
1446		result = callable.call();
1447		return true;
#	Line 1117 | Line 1453 | public abstract class ForkJoinTask<V> im
1453		throw new RuntimeException(ex);
1454		}
1455		}
1456	<	public void run() { invoke(); }
1456	>	public final void run() { invoke(); }
1457		private static final long serialVersionUID = 2838392045355241008L;
1458		}
1459
1460		/**
1461	<	* Returns a new ForkJoinTask that performs the {@code run}
1462	<	* method of the given Runnable as its action, and returns a null
1463	<	* result upon {@code join}.
1461	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1462	>	* method of the given {@code Runnable} as its action, and returns
1463	>	* a null result upon {@link #join}.
1464		*
1465		* @param runnable the runnable action
1466		* @return the task
1467		*/
1468		public static ForkJoinTask<?> adapt(Runnable runnable) {
1469	<	return new AdaptedRunnable<Void>(runnable, null);
1469	>	return new AdaptedRunnableAction(runnable);
1470		}
1471
1472		/**
1473	<	* Returns a new ForkJoinTask that performs the {@code run}
1474	<	* method of the given Runnable as its action, and returns the
1475	<	* given result upon {@code join}.
1473	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1474	>	* method of the given {@code Runnable} as its action, and returns
1475	>	* the given result upon {@link #join}.
1476		*
1477		* @param runnable the runnable action
1478		* @param result the result upon completion
#	Line 1147 | Line 1483 | public abstract class ForkJoinTask<V> im
1483		}
1484
1485		/**
1486	<	* Returns a new ForkJoinTask that performs the {@code call}
1487	<	* method of the given Callable as its action, and returns its
1488	<	* result upon {@code join}, translating any checked
1489	<	* exceptions encountered into {@code RuntimeException}.
1486	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1487	>	* method of the given {@code Callable} as its action, and returns
1488	>	* its result upon {@link #join}, translating any checked exceptions
1489	>	* encountered into {@code RuntimeException}.
1490		*
1491		* @param callable the callable action
1492		* @return the task
#	Line 1164 | Line 1500 | public abstract class ForkJoinTask<V> im
1500		private static final long serialVersionUID = -7721805057305804111L;
1501
1502		/**
1503	<	* Save the state to a stream.
1503	>	* Saves this task to a stream (that is, serializes it).
1504		*
1505		* @serialData the current run status and the exception thrown
1506		* during execution, or {@code null} if none
1171	–	* @param s the stream
1507		*/
1508		private void writeObject(java.io.ObjectOutputStream s)
1509		throws java.io.IOException {
#	Line 1177 | Line 1512 | public abstract class ForkJoinTask<V> im
1512		}
1513
1514		/**
1515	<	* Reconstitute the instance from a stream.
1181	<	*
1182	<	* @param s the stream
1515	>	* Reconstitutes this task from a stream (that is, deserializes it).
1516		*/
1517		private void readObject(java.io.ObjectInputStream s)
1518		throws java.io.IOException, ClassNotFoundException {
1519		s.defaultReadObject();
1187	–	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1188	–	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1520		Object ex = s.readObject();
1521		if (ex != null)
1522	<	setDoneExceptionally((Throwable) ex);
1522	>	setExceptionalCompletion((Throwable)ex);
1523		}
1524
1525		// Unsafe mechanics
1526	<
1527	<	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1528	<	private static final long statusOffset =
1529	<	objectFieldOffset("status", ForkJoinTask.class);
1530	<
1531	<	private static long objectFieldOffset(String field, Class<?> klazz) {
1526	>	private static final sun.misc.Unsafe U;
1527	>	private static final long STATUS;
1528	>	static {
1529	>	exceptionTableLock = new ReentrantLock();
1530	>	exceptionTableRefQueue = new ReferenceQueue<Object>();
1531	>	exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY];
1532		try {
1533	<	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1534	<	} catch (NoSuchFieldException e) {
1535	<	// Convert Exception to corresponding Error
1536	<	NoSuchFieldError error = new NoSuchFieldError(field);
1537	<	error.initCause(e);
1207	<	throw error;
1533	>	U = getUnsafe();
1534	>	STATUS = U.objectFieldOffset
1535	>	(ForkJoinTask.class.getDeclaredField("status"));
1536	>	} catch (Exception e) {
1537	>	throw new Error(e);
1538		}
1539		}
1540

Diff Legend

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