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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.15 by jsr166, Fri Jul 24 22:05:22 2009 UTC vs.
Revision 1.47 by dl, Sun Apr 18 12:51:18 2010 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.io.Serializable;
9	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
11	<	import sun.misc.Unsafe;
12	<	import java.lang.reflect.*;
10	>
11	>	import java.io.Serializable;
12	>	import java.util.Collection;
13	>	import java.util.Collections;
14	>	import java.util.List;
15	>	import java.util.RandomAccess;
16	>	import java.util.Map;
17	>	import java.util.WeakHashMap;
18
19		/**
20	<	* Abstract base class for tasks that run within a {@link
21	<	* ForkJoinPool}.  A ForkJoinTask is a thread-like entity that is much
20	>	* Abstract base class for tasks that run within a {@link ForkJoinPool}.
21	>	* A {@code ForkJoinTask} is a thread-like entity that is much
22		* lighter weight than a normal thread.  Huge numbers of tasks and
23		* subtasks may be hosted by a small number of actual threads in a
24		* ForkJoinPool, at the price of some usage limitations.
25		*
26	<	* <p> A "main" ForkJoinTask begins execution when submitted to a
27	<	* {@link ForkJoinPool}. Once started, it will usually in turn start
28	<	* other subtasks.  As indicated by the name of this class, many
29	<	* programs using ForkJoinTasks employ only methods {@code fork}
30	<	* and {@code join}, or derivatives such as
31	<	* {@code invokeAll}.  However, this class also provides a number
32	<	* of other methods that can come into play in advanced usages, as
33	<	* well as extension mechanics that allow support of new forms of
34	<	* fork/join processing.
26	>	* <p>A "main" {@code ForkJoinTask} begins execution when submitted
27	>	* to a {@link ForkJoinPool}.  Once started, it will usually in turn
28	>	* start other subtasks.  As indicated by the name of this class,
29	>	* many programs using {@code ForkJoinTask} employ only methods
30	>	* {@link #fork} and {@link #join}, or derivatives such as {@link
31	>	* #invokeAll}.  However, this class also provides a number of other
32	>	* methods that can come into play in advanced usages, as well as
33	>	* extension mechanics that allow support of new forms of fork/join
34	>	* processing.
35		*
36	<	* <p>A ForkJoinTask is a lightweight form of {@link Future}.  The
37	<	* efficiency of ForkJoinTasks stems from a set of restrictions (that
38	<	* are only partially statically enforceable) reflecting their
39	<	* intended use as computational tasks calculating pure functions or
40	<	* operating on purely isolated objects.  The primary coordination
41	<	* mechanisms are {@link #fork}, that arranges asynchronous execution,
42	<	* and {@link #join}, that doesn't proceed until the task's result has
43	<	* been computed.  Computations should avoid {@code synchronized}
44	<	* methods or blocks, and should minimize other blocking
45	<	* synchronization apart from joining other tasks or using
46	<	* synchronizers such as Phasers that are advertised to cooperate with
47	<	* fork/join scheduling. Tasks should also not perform blocking IO,
48	<	* and should ideally access variables that are completely independent
49	<	* of those accessed by other running tasks. Minor breaches of these
50	<	* restrictions, for example using shared output streams, may be
51	<	* tolerable in practice, but frequent use may result in poor
52	<	* performance, and the potential to indefinitely stall if the number
53	<	* of threads not waiting for IO or other external synchronization
54	<	* becomes exhausted. This usage restriction is in part enforced by
55	<	* not permitting checked exceptions such as {@code IOExceptions}
56	<	* to be thrown. However, computations may still encounter unchecked
57	<	* exceptions, that are rethrown to callers attempting join
58	<	* them. These exceptions may additionally include
59	<	* RejectedExecutionExceptions stemming from internal resource
60	<	* exhaustion such as failure to allocate internal task queues.
36	>	* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
37	>	* The efficiency of {@code ForkJoinTask}s stems from a set of
38	>	* restrictions (that are only partially statically enforceable)
39	>	* reflecting their intended use as computational tasks calculating
40	>	* pure functions or operating on purely isolated objects.  The
41	>	* primary coordination mechanisms are {@link #fork}, that arranges
42	>	* asynchronous execution, and {@link #join}, that doesn't proceed
43	>	* until the task's result has been computed.  Computations should
44	>	* avoid {@code synchronized} methods or blocks, and should minimize
45	>	* other blocking synchronization apart from joining other tasks or
46	>	* using synchronizers such as Phasers that are advertised to
47	>	* cooperate with fork/join scheduling. Tasks should also not perform
48	>	* blocking IO, and should ideally access variables that are
49	>	* completely independent of those accessed by other running
50	>	* tasks. Minor breaches of these restrictions, for example using
51	>	* shared output streams, may be tolerable in practice, but frequent
52	>	* use may result in poor performance, and the potential to
53	>	* indefinitely stall if the number of threads not waiting for IO or
54	>	* other external synchronization becomes exhausted. This usage
55	>	* restriction is in part enforced by not permitting checked
56	>	* exceptions such as {@code IOExceptions} to be thrown. However,
57	>	* computations may still encounter unchecked exceptions, that are
58	>	* rethrown to callers attempting to join them. These exceptions may
59	>	* additionally include {@link RejectedExecutionException} stemming
60	>	* from internal resource exhaustion, such as failure to allocate
61	>	* internal task queues.
62		*
63		* <p>The primary method for awaiting completion and extracting
64		* results of a task is {@link #join}, but there are several variants:
#	Line 63 | Line 68 | import java.lang.reflect.*;
68		* execute other tasks while awaiting joins, which is sometimes more
69		* efficient but only applies when all subtasks are known to be
70		* strictly tree-structured. Method {@link #invoke} is semantically
71	<	* equivalent to {@code fork(); join()} but always attempts to
72	<	* begin execution in the current thread. The "<em>quiet</em>" forms
73	<	* of these methods do not extract results or report exceptions. These
71	>	* equivalent to {@code fork(); join()} but always attempts to begin
72	>	* execution in the current thread. The "<em>quiet</em>" forms of
73	>	* these methods do not extract results or report exceptions. These
74		* may be useful when a set of tasks are being executed, and you need
75		* to delay processing of results or exceptions until all complete.
76		* Method {@code invokeAll} (available in multiple versions)
77		* performs the most common form of parallel invocation: forking a set
78		* of tasks and joining them all.
79		*
80	<	* <p> The ForkJoinTask class is not usually directly subclassed.
80	>	* <p>The execution status of tasks may be queried at several levels
81	>	* of detail: {@link #isDone} is true if a task completed in any way
82	>	* (including the case where a task was cancelled without executing);
83	>	* {@link #isCompletedNormally} is true if a task completed without
84	>	* cancellation or encountering an exception; {@link #isCancelled} is
85	>	* true if the task was cancelled (in which case {@link #getException}
86	>	* returns a {@link java.util.concurrent.CancellationException}); and
87	>	* {@link #isCompletedAbnormally} is true if a task was either
88	>	* cancelled or encountered an exception, in which case {@link
89	>	* #getException} will return either the encountered exception or
90	>	* {@link java.util.concurrent.CancellationException}.
91	>	*
92	>	* <p>The ForkJoinTask class is not usually directly subclassed.
93		* Instead, you subclass one of the abstract classes that support a
94	<	* particular style of fork/join processing.  Normally, a concrete
94	>	* particular style of fork/join processing, typically {@link
95	>	* RecursiveAction} for computations that do not return results, or
96	>	* {@link RecursiveTask} for those that do.  Normally, a concrete
97		* ForkJoinTask subclass declares fields comprising its parameters,
98		* established in a constructor, and then defines a {@code compute}
99		* method that somehow uses the control methods supplied by this base
100		* class. While these methods have {@code public} access (to allow
101	<	* instances of different task subclasses to call each others
101	>	* instances of different task subclasses to call each other's
102		* methods), some of them may only be called from within other
103		* ForkJoinTasks (as may be determined using method {@link
104		* #inForkJoinPool}).  Attempts to invoke them in other contexts
105		* result in exceptions or errors, possibly including
106		* ClassCastException.
107		*
108	<	* <p>Most base support methods are {@code final} because their
109	<	* implementations are intrinsically tied to the underlying
110	<	* lightweight task scheduling framework, and so cannot be overridden.
111	<	* Developers creating new basic styles of fork/join processing should
112	<	* minimally implement {@code protected} methods
113	<	* {@code exec}, {@code setRawResult}, and
114	<	* {@code getRawResult}, while also introducing an abstract
115	<	* computational method that can be implemented in its subclasses,
116	<	* possibly relying on other {@code protected} methods provided
98	<	* by this class.
108	>	* <p>Most base support methods are {@code final}, to prevent
109	>	* overriding of implementations that are intrinsically tied to the
110	>	* underlying lightweight task scheduling framework.  Developers
111	>	* creating new basic styles of fork/join processing should minimally
112	>	* implement {@code protected} methods {@link #exec}, {@link
113	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
114	>	* an abstract computational method that can be implemented in its
115	>	* subclasses, possibly relying on other {@code protected} methods
116	>	* provided by this class.
117		*
118		* <p>ForkJoinTasks should perform relatively small amounts of
119	<	* computations, otherwise splitting into smaller tasks. As a very
120	<	* rough rule of thumb, a task should perform more than 100 and less
121	<	* than 10000 basic computational steps. If tasks are too big, then
122	<	* parallelism cannot improve throughput. If too small, then memory
123	<	* and internal task maintenance overhead may overwhelm processing.
119	>	* computation. Large tasks should be split into smaller subtasks,
120	>	* usually via recursive decomposition. As a very rough rule of thumb,
121	>	* a task should perform more than 100 and less than 10000 basic
122	>	* computational steps. If tasks are too big, then parallelism cannot
123	>	* improve throughput. If too small, then memory and internal task
124	>	* maintenance overhead may overwhelm processing.
125	>	*
126	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
127	>	* and {@link Callable}, that may be of use when mixing execution of
128	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks
129	>	* are of this form, consider using a pool in
130	>	* {@linkplain ForkJoinPool#setAsyncMode async mode}.
131		*
132	<	* <p>ForkJoinTasks are {@code Serializable}, which enables them
133	<	* to be used in extensions such as remote execution frameworks. It is
134	<	* in general sensible to serialize tasks only before or after, but
135	<	* not during execution. Serialization is not relied on during
111	<	* execution itself.
132	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
133	>	* used in extensions such as remote execution frameworks. It is
134	>	* sensible to serialize tasks only before or after, but not during,
135	>	* execution. Serialization is not relied on during execution itself.
136		*
137		* @since 1.7
138		* @author Doug Lea
139		*/
140		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
141
142	+	/*
143	+	* See the internal documentation of class ForkJoinPool for a
144	+	* general implementation overview.  ForkJoinTasks are mainly
145	+	* responsible for maintaining their "status" field amidst relays
146	+	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
147	+	* methods of this class are more-or-less layered into (1) basic
148	+	* status maintenance (2) execution and awaiting completion (3)
149	+	* user-level methods that additionally report results. This is
150	+	* sometimes hard to see because this file orders exported methods
151	+	* in a way that flows well in javadocs.
152	+	*/
153	+
154		/**
155		* Run control status bits packed into a single int to minimize
156		* footprint and to ensure atomicity (via CAS).  Status is
#	Line 124 | Line 160 | public abstract class ForkJoinTask<V> im
160		* blocking waits by other threads have SIGNAL_MASK bits set --
161		* bit 15 for external (nonFJ) waits, and the rest a count of
162		* waiting FJ threads.  (This representation relies on
163	<	* ForkJoinPool max thread limits). Completion of a stolen task
164	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
165	<	* though suboptimal for some purposes, we use basic builtin
166	<	* wait/notify to take advantage of "monitor inflation" in JVMs
167	<	* that we would otherwise need to emulate to avoid adding further
168	<	* per-task bookkeeping overhead. Note that bits 16-28 are
169	<	* currently unused. Also value 0x80000000 is available as spare
170	<	* completion value.
163	>	* ForkJoinPool max thread limits). Signal counts are not directly
164	>	* incremented by ForkJoinTask methods, but instead via a call to
165	>	* requestSignal within ForkJoinPool.preJoin, once their need is
166	>	* established.
167	>	*
168	>	* Completion of a stolen task with SIGNAL_MASK bits set awakens
169	>	* any waiters via notifyAll. Even though suboptimal for some
170	>	* purposes, we use basic builtin wait/notify to take advantage of
171	>	* "monitor inflation" in JVMs that we would otherwise need to
172	>	* emulate to avoid adding further per-task bookkeeping overhead.
173	>	* We want these monitors to be "fat", i.e., not use biasing or
174	>	* thin-lock techniques, so use some odd coding idioms that tend
175	>	* to avoid them.
176	>	*
177	>	* Note that bits 16-28 are currently unused. Also value
178	>	* 0x80000000 is available as spare completion value.
179		*/
180		volatile int status; // accessed directly by pool and workers
181
182	<	static final int COMPLETION_MASK      = 0xe0000000;
183	<	static final int NORMAL               = 0xe0000000; // == mask
184	<	static final int CANCELLED            = 0xc0000000;
185	<	static final int EXCEPTIONAL          = 0xa0000000;
186	<	static final int SIGNAL_MASK          = 0x0000ffff;
187	<	static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
188	<	static final int EXTERNAL_SIGNAL      = 0x00008000; // top bit of low word
182	>	private static final int COMPLETION_MASK      = 0xe0000000;
183	>	private static final int NORMAL               = 0xe0000000; // == mask
184	>	private static final int CANCELLED            = 0xc0000000;
185	>	private static final int EXCEPTIONAL          = 0xa0000000;
186	>	private static final int SIGNAL_MASK          = 0x0000ffff;
187	>	private static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
188	>	private static final int EXTERNAL_SIGNAL      = 0x00008000;
189
190		/**
191		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 155 | Line 199 | public abstract class ForkJoinTask<V> im
199		Collections.synchronizedMap
200		(new WeakHashMap<ForkJoinTask<?>, Throwable>());
201
202	<	// within-package utilities
202	>	// Maintaining completion status
203
204		/**
205	<	* Gets current worker thread, or null if not a worker thread.
205	>	* Marks completion and wakes up threads waiting to join this task,
206	>	* also clearing signal request bits.
207	>	*
208	>	* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
209		*/
210	<	static ForkJoinWorkerThread getWorker() {
211	<	Thread t = Thread.currentThread();
212	<	return ((t instanceof ForkJoinWorkerThread) ?
213	<	(ForkJoinWorkerThread) t : null);
214	<	}
215	<
216	<	final boolean casStatus(int cmp, int val) {
217	<	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
210	>	private void setCompletion(int completion) {
211	>	int s;
212	>	while ((s = status) >= 0) {
213	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
214	>	if ((s & SIGNAL_MASK) != 0) {
215	>	Thread t = Thread.currentThread();
216	>	if (t instanceof ForkJoinWorkerThread)
217	>	((ForkJoinWorkerThread) t).pool.updateRunningCount
218	>	(s & INTERNAL_SIGNAL_MASK);
219	>	synchronized (this) { notifyAll(); }
220	>	}
221	>	return;
222	>	}
223	>	}
224		}
225
226		/**
227	<	* Workaround for not being able to rethrow unchecked exceptions.
227	>	* Record exception and set exceptional completion
228		*/
229	<	static void rethrowException(Throwable ex) {
230	<	if (ex != null)
231	<	UNSAFE.throwException(ex);
229	>	private void setDoneExceptionally(Throwable rex) {
230	>	exceptionMap.put(this, rex);
231	>	setCompletion(EXCEPTIONAL);
232		}
233
181	–	// Setting completion status
182	–
234		/**
235	<	* Marks completion and wakes up threads waiting to join this task.
235	>	* Main internal execution method: Unless done, calls exec and
236	>	* records completion.
237		*
238	<	* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
238	>	* @return true if ran and completed normally
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) {
195	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
196	<	pool.updateRunningCount(s);
197	<	synchronized (this) { notifyAll(); }
198	<	}
240	>	final boolean tryExec() {
241	>	try {
242	>	if (status < 0 || !exec())
243	>	return false;
244	>	} catch (Throwable rex) {
245	>	setDoneExceptionally(rex);
246	>	return false;
247		}
248	<	else
249	<	externallySetCompletion(completion);
248	>	setCompletion(NORMAL); // must be outside try block
249	>	return true;
250		}
251
252		/**
253	<	* Version of setCompletion for non-FJ threads.  Leaves signal
254	<	* bits for unblocked threads to adjust, and always notifies.
253	>	* Increments internal signal count (thus requesting signal upon
254	>	* completion) unless already done.  Call only once per join.
255	>	* Used by ForkJoinPool.preJoin.
256	>	*
257	>	* @return status
258		*/
259	<	private void externallySetCompletion(int completion) {
259	>	final int requestSignal() {
260		int s;
261		do {} while ((s = status) >= 0 &&
262	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
263	<	synchronized (this) { notifyAll(); }
262	>	!UNSAFE.compareAndSwapInt(this, statusOffset, s, s + 1));
263	>	return s;
264		}
265
266		/**
267	<	* Sets status to indicate normal completion.
267	>	* Sets external signal request unless already done.
268	>	*
269	>	* @return status
270		*/
271	<	final void setNormalCompletion() {
272	<	// Try typical fast case -- single CAS, no signal, not already done.
273	<	// Manually expand casStatus to improve chances of inlining it
274	<	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
275	<	setCompletion(NORMAL);
271	>	private int requestExternalSignal() {
272	>	int s;
273	>	do {} while ((s = status) >= 0 &&
274	>	!UNSAFE.compareAndSwapInt(this, statusOffset,
275	>	s, s | EXTERNAL_SIGNAL));
276	>	return s;
277		}
278
279	<	// internal waiting and notification
280	<
281	<	/**
282	<	* Performs the actual monitor wait for awaitDone.
279	>	/*
280	>	* Awaiting completion. The four versions, internal vs external X
281	>	* untimed vs timed, have the same overall structure but differ
282	>	* from each other enough to defy simple integration.
283		*/
230	–	private void doAwaitDone() {
231	–	// Minimize lock bias and in/de-flation effects by maximizing
232	–	// chances of waiting inside sync
233	–	try {
234	–	while (status >= 0)
235	–	synchronized (this) { if (status >= 0) wait(); }
236	–	} catch (InterruptedException ie) {
237	–	onInterruptedWait();
238	–	}
239	–	}
284
285		/**
286	<	* Performs the actual timed monitor wait for awaitDone.
286	>	* Blocks a worker until this task is done, also maintaining pool
287	>	* and signal counts
288		*/
289	<	private void doAwaitDone(long startTime, long nanos) {
290	<	synchronized (this) {
291	<	try {
292	<	while (status >= 0) {
293	<	long nt = nanos - System.nanoTime() - startTime;
294	<	if (nt <= 0)
295	<	break;
296	<	wait(nt / 1000000, (int) (nt % 1000000));
289	>	private void awaitDone(ForkJoinWorkerThread w) {
290	>	if (status >= 0) {
291	>	w.pool.preJoin(this);
292	>	while (status >= 0) {
293	>	try { // minimize lock scope
294	>	synchronized(this) {
295	>	if (status >= 0)
296	>	wait();
297	>	else { // help release; also helps avoid lock-biasing
298	>	notifyAll();
299	>	break;
300	>	}
301	>	}
302	>	} catch (InterruptedException ie) {
303	>	cancelIfTerminating();
304		}
253	–	} catch (InterruptedException ie) {
254	–	onInterruptedWait();
305		}
306		}
307		}
308
259	–	// Awaiting completion
260	–
309		/**
310	<	* Sets status to indicate there is joiner, then waits for join,
263	<	* surrounded with pool notifications.
264	<	*
265	<	* @return status upon exit
310	>	* Blocks a non-ForkJoin thread until this task is done.
311		*/
312	<	private int awaitDone(ForkJoinWorkerThread w,
313	<	boolean maintainParallelism) {
314	<	ForkJoinPool pool = (w == null) ? null : w.pool;
315	<	int s;
316	<	while ((s = status) >= 0) {
317	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
318	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
319	<	doAwaitDone();
320	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
321	<	adjustPoolCountsOnUnblock(pool);
322	<	break;
312	>	private void externalAwaitDone() {
313	>	if (requestExternalSignal() >= 0) {
314	>	boolean interrupted = false;
315	>	while (status >= 0) {
316	>	try {
317	>	synchronized(this) {
318	>	if (status >= 0)
319	>	wait();
320	>	else {
321	>	notifyAll();
322	>	break;
323	>	}
324	>	}
325	>	} catch (InterruptedException ie) {
326	>	interrupted = true;
327	>	}
328		}
329	+	if (interrupted)
330	+	Thread.currentThread().interrupt();
331		}
280	–	return s;
332		}
333
334		/**
335	<	* Timed version of awaitDone
285	<	*
286	<	* @return status upon exit
335	>	* Blocks a worker until this task is done or timeout elapses
336		*/
337	<	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
338	<	ForkJoinPool pool = (w == null) ? null : w.pool;
339	<	int s;
340	<	while ((s = status) >= 0) {
341	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
342	<	long startTime = System.nanoTime();
343	<	if (pool == null || !pool.preJoin(this, false))
344	<	doAwaitDone(startTime, nanos);
345	<	if ((s = status) >= 0) {
346	<	adjustPoolCountsOnCancelledWait(pool);
347	<	s = status;
337	>	private void timedAwaitDone(ForkJoinWorkerThread w, long nanos) {
338	>	if (status >= 0) {
339	>	long startTime = System.nanoTime();
340	>	ForkJoinPool pool = w.pool;
341	>	pool.preJoin(this);
342	>	while (status >= 0) {
343	>	long nt = nanos - (System.nanoTime() - startTime);
344	>	if (nt > 0) {
345	>	long ms = nt / 1000000;
346	>	int ns = (int) (nt % 1000000);
347	>	try {
348	>	synchronized(this) { if (status >= 0) wait(ms, ns); }
349	>	} catch (InterruptedException ie) {
350	>	cancelIfTerminating();
351	>	}
352	>	}
353	>	else {
354	>	int s; // adjust running count on timeout
355	>	while ((s = status) >= 0 &&
356	>	(s & INTERNAL_SIGNAL_MASK) != 0) {
357	>	if (UNSAFE.compareAndSwapInt(this, statusOffset,
358	>	s, s - 1)) {
359	>	pool.updateRunningCount(1);
360	>	break;
361	>	}
362	>	}
363	>	break;
364		}
300	–	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
301	–	adjustPoolCountsOnUnblock(pool);
302	–	break;
365		}
366		}
305	–	return s;
367		}
368
369		/**
370	<	* Notifies pool that thread is unblocked. Called by signalled
310	<	* threads when woken by non-FJ threads (which is atypical).
370	>	* Blocks a non-ForkJoin thread until this task is done or timeout elapses
371		*/
372	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
373	<	int s;
374	<	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
375	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
376	<	pool.updateRunningCount(s);
377	<	}
378	<
319	<	/**
320	<	* Notifies pool to adjust counts on cancelled or timed out wait.
321	<	*/
322	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
323	<	if (pool != null) {
324	<	int s;
325	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
326	<	if (casStatus(s, s - 1)) {
327	<	pool.updateRunningCount(1);
372	>	private void externalTimedAwaitDone(long nanos) {
373	>	if (requestExternalSignal() >= 0) {
374	>	long startTime = System.nanoTime();
375	>	boolean interrupted = false;
376	>	while (status >= 0) {
377	>	long nt = nanos - (System.nanoTime() - startTime);
378	>	if (nt <= 0)
379		break;
380	+	long ms = nt / 1000000;
381	+	int ns = (int) (nt % 1000000);
382	+	try {
383	+	synchronized(this) { if (status >= 0) wait(ms, ns); }
384	+	} catch (InterruptedException ie) {
385	+	interrupted = true;
386		}
387		}
388	+	if (interrupted)
389	+	Thread.currentThread().interrupt();
390		}
391		}
392
393	<	/**
335	<	* Handles interruptions during waits.
336	<	*/
337	<	private void onInterruptedWait() {
338	<	ForkJoinWorkerThread w = getWorker();
339	<	if (w == null)
340	<	Thread.currentThread().interrupt(); // re-interrupt
341	<	else if (w.isTerminating())
342	<	cancelIgnoringExceptions();
343	<	// else if FJworker, ignore interrupt
344	<	}
345	<
346	<	// Recording and reporting exceptions
347	<
348	<	private void setDoneExceptionally(Throwable rex) {
349	<	exceptionMap.put(this, rex);
350	<	setCompletion(EXCEPTIONAL);
351	<	}
393	>	// reporting results
394
395		/**
396	<	* Throws the exception associated with status s.
397	<	*
398	<	* @throws the exception
396	>	* Returns result or throws the exception associated with status.
397	>	* Uses Unsafe as a workaround for javac not allowing rethrow of
398	>	* unchecked exceptions.
399		*/
400	<	private void reportException(int s) {
401	<	if ((s &= COMPLETION_MASK) < NORMAL) {
402	<	if (s == CANCELLED)
403	<	throw new CancellationException();
404	<	else
363	<	rethrowException(exceptionMap.get(this));
400	>	private V reportResult() {
401	>	if ((status & COMPLETION_MASK) < NORMAL) {
402	>	Throwable ex = getException();
403	>	if (ex != null)
404	>	UNSAFE.throwException(ex);
405		}
406	+	return getRawResult();
407		}
408
409		/**
410		* Returns result or throws exception using j.u.c.Future conventions.
411	<	* Only call when {@code isDone} known to be true.
411	>	* Only call when {@code isDone} known to be true or thread known
412	>	* to be interrupted.
413		*/
414		private V reportFutureResult()
415	<	throws ExecutionException, InterruptedException {
415	>	throws InterruptedException, ExecutionException {
416	>	if (Thread.interrupted())
417	>	throw new InterruptedException();
418		int s = status & COMPLETION_MASK;
419		if (s < NORMAL) {
420		Throwable ex;
#	Line 377 | Line 422 | public abstract class ForkJoinTask<V> im
422		throw new CancellationException();
423		if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
424		throw new ExecutionException(ex);
380	–	if (Thread.interrupted())
381	–	throw new InterruptedException();
425		}
426		return getRawResult();
427		}
#	Line 389 | Line 432 | public abstract class ForkJoinTask<V> im
432		*/
433		private V reportTimedFutureResult()
434		throws InterruptedException, ExecutionException, TimeoutException {
435	+	if (Thread.interrupted())
436	+	throw new InterruptedException();
437		Throwable ex;
438		int s = status & COMPLETION_MASK;
439		if (s == NORMAL)
440		return getRawResult();
441	<	if (s == CANCELLED)
441	>	else if (s == CANCELLED)
442		throw new CancellationException();
443	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
443	>	else if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
444		throw new ExecutionException(ex);
445	<	if (Thread.interrupted())
446	<	throw new InterruptedException();
402	<	throw new TimeoutException();
403	<	}
404	<
405	<	// internal execution methods
406	<
407	<	/**
408	<	* Calls exec, recording completion, and rethrowing exception if
409	<	* encountered. Caller should normally check status before calling.
410	<	*
411	<	* @return true if completed normally
412	<	*/
413	<	private boolean tryExec() {
414	<	try { // try block must contain only call to exec
415	<	if (!exec())
416	<	return false;
417	<	} catch (Throwable rex) {
418	<	setDoneExceptionally(rex);
419	<	rethrowException(rex);
420	<	return false; // not reached
421	<	}
422	<	setNormalCompletion();
423	<	return true;
424	<	}
425	<
426	<	/**
427	<	* Main execution method used by worker threads. Invokes
428	<	* base computation unless already complete.
429	<	*/
430	<	final void quietlyExec() {
431	<	if (status >= 0) {
432	<	try {
433	<	if (!exec())
434	<	return;
435	<	} catch (Throwable rex) {
436	<	setDoneExceptionally(rex);
437	<	return;
438	<	}
439	<	setNormalCompletion();
440	<	}
441	<	}
442	<
443	<	/**
444	<	* Calls exec(), recording but not rethrowing exception.
445	<	* Caller should normally check status before calling.
446	<	*
447	<	* @return true if completed normally
448	<	*/
449	<	private boolean tryQuietlyInvoke() {
450	<	try {
451	<	if (!exec())
452	<	return false;
453	<	} catch (Throwable rex) {
454	<	setDoneExceptionally(rex);
455	<	return false;
456	<	}
457	<	setNormalCompletion();
458	<	return true;
459	<	}
460	<
461	<	/**
462	<	* Cancels, ignoring any exceptions it throws.
463	<	*/
464	<	final void cancelIgnoringExceptions() {
465	<	try {
466	<	cancel(false);
467	<	} catch (Throwable ignore) {
468	<	}
469	<	}
470	<
471	<	/**
472	<	* Main implementation of helpJoin
473	<	*/
474	<	private int busyJoin(ForkJoinWorkerThread w) {
475	<	int s;
476	<	ForkJoinTask<?> t;
477	<	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
478	<	t.quietlyExec();
479	<	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
445	>	else
446	>	throw new TimeoutException();
447		}
448
449		// public methods
#	Line 484 | Line 451 | public abstract class ForkJoinTask<V> im
451		/**
452		* Arranges to asynchronously execute this task.  While it is not
453		* necessarily enforced, it is a usage error to fork a task more
454	<	* than once unless it has completed and been reinitialized.  This
455	<	* method may be invoked only from within ForkJoinTask
456	<	* computations (as may be determined using method {@link
457	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
458	<	* in exceptions or errors, possibly including ClassCastException.
454	>	* than once unless it has completed and been reinitialized.
455	>	* Subsequent modifications to the state of this task or any data
456	>	* it operates on are not necessarily consistently observable by
457	>	* any thread other than the one executing it unless preceded by a
458	>	* call to {@link #join} or related methods, or a call to {@link
459	>	* #isDone} returning {@code true}.
460	>	*
461	>	* <p>This method may be invoked only from within {@code
462	>	* ForkJoinTask} computations (as may be determined using method
463	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
464	>	* result in exceptions or errors, possibly including {@code
465	>	* ClassCastException}.
466	>	*
467	>	* @return {@code this}, to simplify usage
468		*/
469	<	public final void fork() {
469	>	public final ForkJoinTask<V> fork() {
470		((ForkJoinWorkerThread) Thread.currentThread())
471		.pushTask(this);
472	+	return this;
473		}
474
475		/**
476	<	* Returns the result of the computation when it is ready.
477	<	* This method differs from {@code get} in that abnormal
478	<	* completion results in RuntimeExceptions or Errors, not
479	<	* ExecutionExceptions.
476	>	* Returns the result of the computation when it {@link #isDone is done}.
477	>	* This method differs from {@link #get()} in that
478	>	* abnormal completion results in {@code RuntimeException} or
479	>	* {@code Error}, not {@code ExecutionException}.
480		*
481		* @return the computed result
482		*/
483		public final V join() {
484	<	ForkJoinWorkerThread w = getWorker();
485	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
509	<	reportException(awaitDone(w, true));
510	<	return getRawResult();
484	>	quietlyJoin();
485	>	return reportResult();
486		}
487
488		/**
489		* Commences performing this task, awaits its completion if
490	<	* necessary, and return its result.
490	>	* necessary, and return its result, or throws an (unchecked)
491	>	* exception if the underlying computation did so.
492		*
517	–	* @throws Throwable (a RuntimeException, Error, or unchecked
518	–	* exception) if the underlying computation did so
493		* @return the computed result
494		*/
495		public final V invoke() {
496	<	if (status >= 0 && tryExec())
497	<	return getRawResult();
498	<	else
525	<	return join();
496	>	if (!tryExec())
497	>	quietlyJoin();
498	>	return reportResult();
499		}
500
501		/**
502	<	* Forks both tasks, returning when {@code isDone} holds for
503	<	* both of them or an exception is encountered. This method may be
504	<	* invoked only from within ForkJoinTask computations (as may be
505	<	* determined using method {@link #inForkJoinPool}). Attempts to
506	<	* invoke in other contexts result in exceptions or errors,
507	<	* possibly including ClassCastException.
502	>	* Forks the given tasks, returning when {@code isDone} holds for
503	>	* each task or an (unchecked) exception is encountered, in which
504	>	* case the exception is rethrown.  If either task encounters an
505	>	* exception, the other one may be, but is not guaranteed to be,
506	>	* cancelled.  If both tasks throw an exception, then this method
507	>	* throws one of them.  The individual status of each task may be
508	>	* checked using {@link #getException()} and related methods.
509		*
510	<	* @param t1 one task
511	<	* @param t2 the other task
512	<	* @throws NullPointerException if t1 or t2 are null
513	<	* @throws RuntimeException or Error if either task did so
510	>	* <p>This method may be invoked only from within {@code
511	>	* ForkJoinTask} computations (as may be determined using method
512	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
513	>	* result in exceptions or errors, possibly including {@code
514	>	* ClassCastException}.
515	>	*
516	>	* @param t1 the first task
517	>	* @param t2 the second task
518	>	* @throws NullPointerException if any task is null
519		*/
520	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
520	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
521		t2.fork();
522		t1.invoke();
523		t2.join();
524		}
525
526		/**
527	<	* Forks the given tasks, returning when {@code isDone} holds
528	<	* for all of them. If any task encounters an exception, others
529	<	* may be cancelled.  This method may be invoked only from within
530	<	* ForkJoinTask computations (as may be determined using method
531	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
532	<	* result in exceptions or errors, possibly including
533	<	* ClassCastException.
527	>	* Forks the given tasks, returning when {@code isDone} holds for
528	>	* each task or an (unchecked) exception is encountered, in which
529	>	* case the exception is rethrown. If any task encounters an
530	>	* exception, others may be, but are not guaranteed to be,
531	>	* cancelled.  If more than one task encounters an exception, then
532	>	* this method throws any one of these exceptions.  The individual
533	>	* status of each task may be checked using {@link #getException()}
534	>	* and related methods.
535	>	*
536	>	* <p>This method may be invoked only from within {@code
537	>	* ForkJoinTask} computations (as may be determined using method
538	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
539	>	* result in exceptions or errors, possibly including {@code
540	>	* ClassCastException}.
541		*
542	<	* @param tasks the array of tasks
543	<	* @throws NullPointerException if tasks or any element are null
558	<	* @throws RuntimeException or Error if any task did so
542	>	* @param tasks the tasks
543	>	* @throws NullPointerException if any task is null
544		*/
545		public static void invokeAll(ForkJoinTask<?>... tasks) {
546		Throwable ex = null;
#	Line 587 | Line 572 | public abstract class ForkJoinTask<V> im
572		}
573		}
574		if (ex != null)
575	<	rethrowException(ex);
575	>	UNSAFE.throwException(ex);
576		}
577
578		/**
579	<	* Forks all tasks in the collection, returning when
580	<	* {@code isDone} holds for all of them. If any task
581	<	* encounters an exception, others may be cancelled.  This method
582	<	* may be invoked only from within ForkJoinTask computations (as
583	<	* may be determined using method {@link
584	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
585	<	* in exceptions or errors, possibly including ClassCastException.
579	>	* Forks all tasks in the specified collection, returning when
580	>	* {@code isDone} holds for each task or an (unchecked) exception
581	>	* is encountered.  If any task encounters an exception, others
582	>	* may be, but are not guaranteed to be, cancelled.  If more than
583	>	* one task encounters an exception, then this method throws any
584	>	* one of these exceptions.  The individual status of each task
585	>	* may be checked using {@link #getException()} and related
586	>	* methods.  The behavior of this operation is undefined if the
587	>	* specified collection is modified while the operation is in
588	>	* progress.
589	>	*
590	>	* <p>This method may be invoked only from within {@code
591	>	* ForkJoinTask} computations (as may be determined using method
592	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
593	>	* result in exceptions or errors, possibly including {@code
594	>	* ClassCastException}.
595		*
596		* @param tasks the collection of tasks
597	+	* @return the tasks argument, to simplify usage
598		* @throws NullPointerException if tasks or any element are null
604	–	* @throws RuntimeException or Error if any task did so
599		*/
600	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
601	<	if (!(tasks instanceof List<?>)) {
600	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
601	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
602		invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
603	<	return;
603	>	return tasks;
604		}
605		@SuppressWarnings("unchecked")
606		List<? extends ForkJoinTask<?>> ts =
#	Line 640 | Line 634 | public abstract class ForkJoinTask<V> im
634		}
635		}
636		if (ex != null)
637	<	rethrowException(ex);
638	<	}
645	<
646	<	/**
647	<	* Returns true if the computation performed by this task has
648	<	* completed (or has been cancelled).
649	<	*
650	<	* @return true if this computation has completed
651	<	*/
652	<	public final boolean isDone() {
653	<	return status < 0;
654	<	}
655	<
656	<	/**
657	<	* Returns true if this task was cancelled.
658	<	*
659	<	* @return true if this task was cancelled
660	<	*/
661	<	public final boolean isCancelled() {
662	<	return (status & COMPLETION_MASK) == CANCELLED;
637	>	UNSAFE.throwException(ex);
638	>	return tasks;
639		}
640
641		/**
642	<	* Asserts that the results of this task's computation will not be
643	<	* used. If a cancellation occurs before attempting to execute this
644	<	* task, then execution will be suppressed, {@code isCancelled}
645	<	* will report true, and {@code join} will result in a
646	<	* {@code CancellationException} being thrown. Otherwise, when
647	<	* cancellation races with completion, there are no guarantees
648	<	* about whether {@code isCancelled} will report true, whether
673	<	* {@code join} will return normally or via an exception, or
674	<	* whether these behaviors will remain consistent upon repeated
675	<	* invocation.
642	>	* Attempts to cancel execution of this task. This attempt will
643	>	* fail if the task has already completed, has already been
644	>	* cancelled, or could not be cancelled for some other reason. If
645	>	* successful, and this task has not started when cancel is
646	>	* called, execution of this task is suppressed, {@link
647	>	* #isCancelled} will report true, and {@link #join} will result
648	>	* in a {@code CancellationException} being thrown.
649		*
650		* <p>This method may be overridden in subclasses, but if so, must
651		* still ensure that these minimal properties hold. In particular,
652	<	* the cancel method itself must not throw exceptions.
652	>	* the {@code cancel} method itself must not throw exceptions.
653		*
654	<	* <p> This method is designed to be invoked by <em>other</em>
654	>	* <p>This method is designed to be invoked by <em>other</em>
655		* tasks. To terminate the current task, you can just return or
656		* throw an unchecked exception from its computation method, or
657	<	* invoke {@code completeExceptionally}.
657	>	* invoke {@link #completeExceptionally}.
658		*
659		* @param mayInterruptIfRunning this value is ignored in the
660	<	* default implementation because tasks are not in general
660	>	* default implementation because tasks are not
661		* cancelled via interruption
662		*
663	<	* @return true if this task is now cancelled
663	>	* @return {@code true} if this task is now cancelled
664		*/
665		public boolean cancel(boolean mayInterruptIfRunning) {
666		setCompletion(CANCELLED);
#	Line 695 | Line 668 | public abstract class ForkJoinTask<V> im
668		}
669
670		/**
671	<	* Returns true if this task threw an exception or was cancelled.
671	>	* Cancels, ignoring any exceptions it throws. Used during worker
672	>	* and pool shutdown.
673	>	*/
674	>	final void cancelIgnoringExceptions() {
675	>	try {
676	>	cancel(false);
677	>	} catch (Throwable ignore) {
678	>	}
679	>	}
680	>
681	>	/**
682	>	* Cancels ignoring exceptions if worker is terminating
683	>	*/
684	>	private void cancelIfTerminating() {
685	>	Thread t = Thread.currentThread();
686	>	if ((t instanceof ForkJoinWorkerThread) &&
687	>	((ForkJoinWorkerThread) t).isTerminating()) {
688	>	try {
689	>	cancel(false);
690	>	} catch (Throwable ignore) {
691	>	}
692	>	}
693	>	}
694	>
695	>	public final boolean isDone() {
696	>	return status < 0;
697	>	}
698	>
699	>	public final boolean isCancelled() {
700	>	return (status & COMPLETION_MASK) == CANCELLED;
701	>	}
702	>
703	>	/**
704	>	* Returns {@code true} if this task threw an exception or was cancelled.
705		*
706	<	* @return true if this task threw an exception or was cancelled
706	>	* @return {@code true} if this task threw an exception or was cancelled
707		*/
708		public final boolean isCompletedAbnormally() {
709		return (status & COMPLETION_MASK) < NORMAL;
710		}
711
712		/**
713	+	* Returns {@code true} if this task completed without throwing an
714	+	* exception and was not cancelled.
715	+	*
716	+	* @return {@code true} if this task completed without throwing an
717	+	* exception and was not cancelled
718	+	*/
719	+	public final boolean isCompletedNormally() {
720	+	return (status & COMPLETION_MASK) == NORMAL;
721	+	}
722	+
723	+	/**
724		* Returns the exception thrown by the base computation, or a
725	<	* CancellationException if cancelled, or null if none or if the
726	<	* method has not yet completed.
725	>	* {@code CancellationException} if cancelled, or {@code null} if
726	>	* none or if the method has not yet completed.
727		*
728	<	* @return the exception, or null if none
728	>	* @return the exception, or {@code null} if none
729		*/
730		public final Throwable getException() {
731		int s = status & COMPLETION_MASK;
732	<	if (s >= NORMAL)
733	<	return null;
734	<	if (s == CANCELLED)
718	<	return new CancellationException();
719	<	return exceptionMap.get(this);
732	>	return ((s >= NORMAL)    ? null :
733	>	(s == CANCELLED) ? new CancellationException() :
734	>	exceptionMap.get(this));
735		}
736
737		/**
#	Line 725 | Line 740 | public abstract class ForkJoinTask<V> im
740		* {@code join} and related operations. This method may be used
741		* to induce exceptions in asynchronous tasks, or to force
742		* completion of tasks that would not otherwise complete.  Its use
743	<	* in other situations is likely to be wrong.  This method is
743	>	* in other situations is discouraged.  This method is
744		* overridable, but overridden versions must invoke {@code super}
745		* implementation to maintain guarantees.
746		*
747	<	* @param ex the exception to throw. If this exception is
748	<	* not a RuntimeException or Error, the actual exception thrown
749	<	* will be a RuntimeException with cause ex.
747	>	* @param ex the exception to throw. If this exception is not a
748	>	* {@code RuntimeException} or {@code Error}, the actual exception
749	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
750		*/
751		public void completeExceptionally(Throwable ex) {
752		setDoneExceptionally((ex instanceof RuntimeException) ||
#	Line 745 | Line 760 | public abstract class ForkJoinTask<V> im
760		* operations. This method may be used to provide results for
761		* asynchronous tasks, or to provide alternative handling for
762		* tasks that would not otherwise complete normally. Its use in
763	<	* other situations is likely to be wrong. This method is
763	>	* other situations is discouraged. This method is
764		* overridable, but overridden versions must invoke {@code super}
765		* implementation to maintain guarantees.
766		*
#	Line 758 | Line 773 | public abstract class ForkJoinTask<V> im
773		setDoneExceptionally(rex);
774		return;
775		}
776	<	setNormalCompletion();
776	>	setCompletion(NORMAL);
777		}
778
779		public final V get() throws InterruptedException, ExecutionException {
780	<	ForkJoinWorkerThread w = getWorker();
766	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
767	<	awaitDone(w, true);
780	>	quietlyJoin();
781		return reportFutureResult();
782		}
783
784		public final V get(long timeout, TimeUnit unit)
785		throws InterruptedException, ExecutionException, TimeoutException {
786	<	ForkJoinWorkerThread w = getWorker();
787	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
788	<	awaitDone(w, unit.toNanos(timeout));
786	>	long nanos = unit.toNanos(timeout);
787	>	Thread t = Thread.currentThread();
788	>	if (t instanceof ForkJoinWorkerThread) {
789	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
790	>	if (!w.unpushTask(this) || !tryExec())
791	>	timedAwaitDone(w, nanos);
792	>	}
793	>	else
794	>	externalTimedAwaitDone(nanos);
795		return reportTimedFutureResult();
796		}
797
798		/**
799	<	* Possibly executes other tasks until this task is ready, then
800	<	* returns the result of the computation.  This method may be more
801	<	* efficient than {@code join}, but is only applicable when
802	<	* there are no potential dependencies between continuation of the
803	<	* current task and that of any other task that might be executed
804	<	* while helping. (This usually holds for pure divide-and-conquer
805	<	* tasks). This method may be invoked only from within
806	<	* ForkJoinTask computations (as may be determined using method
807	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
808	<	* result in exceptions or errors, possibly including
809	<	* ClassCastException.
799	>	* Possibly executes other tasks until this task {@link #isDone is
800	>	* done}, then returns the result of the computation.  This method
801	>	* may be more efficient than {@code join}, but is only applicable
802	>	* when there are no potential dependencies between continuation
803	>	* of the current task and that of any other task that might be
804	>	* executed while helping. (This usually holds for pure
805	>	* divide-and-conquer tasks).
806	>	*
807	>	* <p>This method may be invoked only from within {@code
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 {@code
811	>	* ClassCastException}.
812		*
813		* @return the computed result
814		*/
815		public final V helpJoin() {
816	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
817	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
797	<	reportException(busyJoin(w));
798	<	return getRawResult();
816	>	quietlyHelpJoin();
817	>	return reportResult();
818		}
819
820		/**
821	<	* Possibly executes other tasks until this task is ready.  This
822	<	* method may be invoked only from within ForkJoinTask
823	<	* computations (as may be determined using method {@link
824	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
825	<	* in exceptions or errors, possibly including ClassCastException.
821	>	* Possibly executes other tasks until this task {@link #isDone is
822	>	* done}.  This method may be useful when processing collections
823	>	* of tasks when some have been cancelled or otherwise known to
824	>	* have aborted.
825	>	*
826	>	* <p>This method may be invoked only from within {@code
827	>	* ForkJoinTask} computations (as may be determined using method
828	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
829	>	* result in exceptions or errors, possibly including {@code
830	>	* ClassCastException}.
831		*/
832		public final void quietlyHelpJoin() {
833	<	if (status >= 0) {
834	<	ForkJoinWorkerThread w =
835	<	(ForkJoinWorkerThread) Thread.currentThread();
836	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
837	<	busyJoin(w);
833	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
834	>	if (!w.unpushTask(this) || !tryExec()) {
835	>	for (;;) {
836	>	ForkJoinTask<?> t;
837	>	if (status < 0)
838	>	return;
839	>	else if ((t = w.scanWhileJoining(this)) != null)
840	>	t.tryExec();
841	>	else if (status < 0)
842	>	return;
843	>	else if (w.pool.preBlockHelpingJoin(this)) {
844	>	while (status >= 0) { // variant of awaitDone
845	>	try {
846	>	synchronized(this) {
847	>	if (status >= 0)
848	>	wait();
849	>	else {
850	>	notifyAll();
851	>	break;
852	>	}
853	>	}
854	>	} catch (InterruptedException ie) {
855	>	cancelIfTerminating();
856	>	}
857	>	}
858	>	return;
859	>	}
860	>	}
861		}
862		}
863
#	Line 821 | Line 868 | public abstract class ForkJoinTask<V> im
868		* known to have aborted.
869		*/
870		public final void quietlyJoin() {
871	<	if (status >= 0) {
872	<	ForkJoinWorkerThread w = getWorker();
873	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
874	<	awaitDone(w, true);
871	>	Thread t = Thread.currentThread();
872	>	if (t instanceof ForkJoinWorkerThread) {
873	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
874	>	if (!w.unpushTask(this) || !tryExec())
875	>	awaitDone(w);
876		}
877	+	else
878	+	externalAwaitDone();
879		}
880
881		/**
#	Line 836 | Line 886 | public abstract class ForkJoinTask<V> im
886		* known to have aborted.
887		*/
888		public final void quietlyInvoke() {
889	<	if (status >= 0 && !tryQuietlyInvoke())
889	>	if (!tryExec())
890		quietlyJoin();
891		}
892
893		/**
894		* Possibly executes tasks until the pool hosting the current task
895	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
896	<	* designs in which many tasks are forked, but none are explicitly
897	<	* joined, instead executing them until all are processed.
895	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
896	>	* be of use in designs in which many tasks are forked, but none
897	>	* are explicitly joined, instead executing them until all are
898	>	* processed.
899	>	*
900	>	* <p>This method may be invoked only from within {@code
901	>	* ForkJoinTask} computations (as may be determined using method
902	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
903	>	* result in exceptions or errors, possibly including {@code
904	>	* ClassCastException}.
905		*/
906		public static void helpQuiesce() {
907		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 857 | Line 914 | public abstract class ForkJoinTask<V> im
914		* this task, but only if reuse occurs when this task has either
915		* never been forked, or has been forked, then completed and all
916		* outstanding joins of this task have also completed. Effects
917	<	* under any other usage conditions are not guaranteed, and are
918	<	* almost surely wrong. This method may be useful when executing
917	>	* under any other usage conditions are not guaranteed.
918	>	* This method may be useful when executing
919		* pre-constructed trees of subtasks in loops.
920		*/
921		public void reinitialize() {
#	Line 871 | Line 928 | public abstract class ForkJoinTask<V> im
928		* Returns the pool hosting the current task execution, or null
929		* if this task is executing outside of any ForkJoinPool.
930		*
931	<	* @return the pool, or null if none
931	>	* @see #inForkJoinPool
932	>	* @return the pool, or {@code null} if none
933		*/
934		public static ForkJoinPool getPool() {
935		Thread t = Thread.currentThread();
#	Line 896 | Line 954 | public abstract class ForkJoinTask<V> im
954		* by the current thread, and has not commenced executing in
955		* another thread.  This method may be useful when arranging
956		* alternative local processing of tasks that could have been, but
957	<	* were not, stolen. This method may be invoked only from within
958	<	* ForkJoinTask computations (as may be determined using method
959	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
960	<	* result in exceptions or errors, possibly including
961	<	* ClassCastException.
957	>	* were not, stolen.
958	>	*
959	>	* <p>This method may be invoked only from within {@code
960	>	* ForkJoinTask} computations (as may be determined using method
961	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
962	>	* result in exceptions or errors, possibly including {@code
963	>	* ClassCastException}.
964		*
965	<	* @return true if unforked
965	>	* @return {@code true} if unforked
966		*/
967		public boolean tryUnfork() {
968		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 915 | Line 975 | public abstract class ForkJoinTask<V> im
975		* value may be useful for heuristic decisions about whether to
976		* fork other tasks.
977		*
978	+	* <p>This method may be invoked only from within {@code
979	+	* ForkJoinTask} computations (as may be determined using method
980	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
981	+	* result in exceptions or errors, possibly including {@code
982	+	* ClassCastException}.
983	+	*
984		* @return the number of tasks
985		*/
986		public static int getQueuedTaskCount() {
#	Line 932 | Line 998 | public abstract class ForkJoinTask<V> im
998		* tasks, and to process computations locally if this threshold is
999		* exceeded.
1000		*
1001	+	* <p>This method may be invoked only from within {@code
1002	+	* ForkJoinTask} computations (as may be determined using method
1003	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1004	+	* result in exceptions or errors, possibly including {@code
1005	+	* ClassCastException}.
1006	+	*
1007		* @return the surplus number of tasks, which may be negative
1008		*/
1009		public static int getSurplusQueuedTaskCount() {
#	Line 942 | Line 1014 | public abstract class ForkJoinTask<V> im
1014		// Extension methods
1015
1016		/**
1017	<	* Returns the result that would be returned by {@code join},
1018	<	* even if this task completed abnormally, or null if this task is
1019	<	* not known to have been completed.  This method is designed to
1020	<	* aid debugging, as well as to support extensions. Its use in any
1021	<	* other context is discouraged.
1017	>	* Returns the result that would be returned by {@link #join}, even
1018	>	* if this task completed abnormally, or {@code null} if this task
1019	>	* is not known to have been completed.  This method is designed
1020	>	* to aid debugging, as well as to support extensions. Its use in
1021	>	* any other context is discouraged.
1022		*
1023	<	* @return the result, or null if not completed
1023	>	* @return the result, or {@code null} if not completed
1024		*/
1025		public abstract V getRawResult();
1026
#	Line 967 | Line 1039 | public abstract class ForkJoinTask<V> im
1039		* called otherwise. The return value controls whether this task
1040		* is considered to be done normally. It may return false in
1041		* asynchronous actions that require explicit invocations of
1042	<	* {@code complete} to become joinable. It may throw exceptions
1043	<	* to indicate abnormal exit.
1042	>	* {@link #complete} to become joinable. It may also throw an
1043	>	* (unchecked) exception to indicate abnormal exit.
1044		*
1045	<	* @return true if completed normally
974	<	* @throws Error or RuntimeException if encountered during computation
1045	>	* @return {@code true} if completed normally
1046		*/
1047		protected abstract boolean exec();
1048
1049		/**
1050	<	* Returns, but does not unschedule or execute, the task queued by
1051	<	* the current thread but not yet executed, if one is
1050	>	* Returns, but does not unschedule or execute, a task queued by
1051	>	* the current thread but not yet executed, if one is immediately
1052		* available. There is no guarantee that this task will actually
1053	<	* be polled or executed next.  This method is designed primarily
1054	<	* to support extensions, and is unlikely to be useful otherwise.
1055	<	* This method may be invoked only from within ForkJoinTask
1056	<	* computations (as may be determined using method {@link
1057	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
1058	<	* in exceptions or errors, possibly including ClassCastException.
1053	>	* be polled or executed next. Conversely, this method may return
1054	>	* null even if a task exists but cannot be accessed without
1055	>	* contention with other threads.  This method is designed
1056	>	* primarily to support extensions, and is unlikely to be useful
1057	>	* otherwise.
1058	>	*
1059	>	* <p>This method may be invoked only from within {@code
1060	>	* ForkJoinTask} computations (as may be determined using method
1061	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1062	>	* result in exceptions or errors, possibly including {@code
1063	>	* ClassCastException}.
1064		*
1065	<	* @return the next task, or null if none are available
1065	>	* @return the next task, or {@code null} if none are available
1066		*/
1067		protected static ForkJoinTask<?> peekNextLocalTask() {
1068		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 997 | Line 1073 | public abstract class ForkJoinTask<V> im
1073		* Unschedules and returns, without executing, the next task
1074		* queued by the current thread but not yet executed.  This method
1075		* is designed primarily to support extensions, and is unlikely to
1076	<	* be useful otherwise.  This method may be invoked only from
1001	<	* within ForkJoinTask computations (as may be determined using
1002	<	* method {@link #inForkJoinPool}). Attempts to invoke in other
1003	<	* contexts result in exceptions or errors, possibly including
1004	<	* ClassCastException.
1076	>	* be useful otherwise.
1077		*
1078	<	* @return the next task, or null if none are available
1078	>	* <p>This method may be invoked only from within {@code
1079	>	* ForkJoinTask} computations (as may be determined using method
1080	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1081	>	* result in exceptions or errors, possibly including {@code
1082	>	* ClassCastException}.
1083	>	*
1084	>	* @return the next task, or {@code null} if none are available
1085		*/
1086		protected static ForkJoinTask<?> pollNextLocalTask() {
1087		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 1018 | Line 1096 | public abstract class ForkJoinTask<V> im
1096		* {@code null} result does not necessarily imply quiescence
1097		* of the pool this task is operating in.  This method is designed
1098		* primarily to support extensions, and is unlikely to be useful
1099	<	* otherwise.  This method may be invoked only from within
1100	<	* ForkJoinTask computations (as may be determined using method
1101	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1102	<	* result in exceptions or errors, possibly including
1103	<	* ClassCastException.
1099	>	* otherwise.
1100	>	*
1101	>	* <p>This method may be invoked only from within {@code
1102	>	* ForkJoinTask} computations (as may be determined using method
1103	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1104	>	* result in exceptions or errors, possibly including {@code
1105	>	* ClassCastException}.
1106		*
1107	<	* @return a task, or null if none are available
1107	>	* @return a task, or {@code null} if none are available
1108		*/
1109		protected static ForkJoinTask<?> pollTask() {
1110		return ((ForkJoinWorkerThread) Thread.currentThread())
1111		.pollTask();
1112		}
1113
1114	+	/**
1115	+	* Adaptor for Runnables. This implements RunnableFuture
1116	+	* to be compliant with AbstractExecutorService constraints
1117	+	* when used in ForkJoinPool.
1118	+	*/
1119	+	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1120	+	implements RunnableFuture<T> {
1121	+	final Runnable runnable;
1122	+	final T resultOnCompletion;
1123	+	T result;
1124	+	AdaptedRunnable(Runnable runnable, T result) {
1125	+	if (runnable == null) throw new NullPointerException();
1126	+	this.runnable = runnable;
1127	+	this.resultOnCompletion = result;
1128	+	}
1129	+	public T getRawResult() { return result; }
1130	+	public void setRawResult(T v) { result = v; }
1131	+	public boolean exec() {
1132	+	runnable.run();
1133	+	result = resultOnCompletion;
1134	+	return true;
1135	+	}
1136	+	public void run() { invoke(); }
1137	+	private static final long serialVersionUID = 5232453952276885070L;
1138	+	}
1139	+
1140	+	/**
1141	+	* Adaptor for Callables
1142	+	*/
1143	+	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1144	+	implements RunnableFuture<T> {
1145	+	final Callable<? extends T> callable;
1146	+	T result;
1147	+	AdaptedCallable(Callable<? extends T> callable) {
1148	+	if (callable == null) throw new NullPointerException();
1149	+	this.callable = callable;
1150	+	}
1151	+	public T getRawResult() { return result; }
1152	+	public void setRawResult(T v) { result = v; }
1153	+	public boolean exec() {
1154	+	try {
1155	+	result = callable.call();
1156	+	return true;
1157	+	} catch (Error err) {
1158	+	throw err;
1159	+	} catch (RuntimeException rex) {
1160	+	throw rex;
1161	+	} catch (Exception ex) {
1162	+	throw new RuntimeException(ex);
1163	+	}
1164	+	}
1165	+	public void run() { invoke(); }
1166	+	private static final long serialVersionUID = 2838392045355241008L;
1167	+	}
1168	+
1169	+	/**
1170	+	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1171	+	* method of the given {@code Runnable} as its action, and returns
1172	+	* a null result upon {@link #join}.
1173	+	*
1174	+	* @param runnable the runnable action
1175	+	* @return the task
1176	+	*/
1177	+	public static ForkJoinTask<?> adapt(Runnable runnable) {
1178	+	return new AdaptedRunnable<Void>(runnable, null);
1179	+	}
1180	+
1181	+	/**
1182	+	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1183	+	* method of the given {@code Runnable} as its action, and returns
1184	+	* the given result upon {@link #join}.
1185	+	*
1186	+	* @param runnable the runnable action
1187	+	* @param result the result upon completion
1188	+	* @return the task
1189	+	*/
1190	+	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1191	+	return new AdaptedRunnable<T>(runnable, result);
1192	+	}
1193	+
1194	+	/**
1195	+	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1196	+	* method of the given {@code Callable} as its action, and returns
1197	+	* its result upon {@link #join}, translating any checked exceptions
1198	+	* encountered into {@code RuntimeException}.
1199	+	*
1200	+	* @param callable the callable action
1201	+	* @return the task
1202	+	*/
1203	+	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1204	+	return new AdaptedCallable<T>(callable);
1205	+	}
1206	+
1207		// Serialization support
1208
1209		private static final long serialVersionUID = -7721805057305804111L;
1210
1211		/**
1212	<	* Save the state to a stream.
1212	>	* Saves the state to a stream.
1213		*
1214		* @serialData the current run status and the exception thrown
1215	<	* during execution, or null if none
1215	>	* during execution, or {@code null} if none
1216		* @param s the stream
1217		*/
1218		private void writeObject(java.io.ObjectOutputStream s)
#	Line 1049 | Line 1222 | public abstract class ForkJoinTask<V> im
1222		}
1223
1224		/**
1225	<	* Reconstitute the instance from a stream.
1225	>	* Reconstitutes the instance from a stream.
1226		*
1227		* @param s the stream
1228		*/
#	Line 1063 | Line 1236 | public abstract class ForkJoinTask<V> im
1236		setDoneExceptionally((Throwable) ex);
1237		}
1238
1239	<	// Temporary Unsafe mechanics for preliminary release
1240	<	private static Unsafe getUnsafe() throws Throwable {
1239	>	// Unsafe mechanics
1240	>
1241	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1242	>	private static final long statusOffset =
1243	>	objectFieldOffset("status", ForkJoinTask.class);
1244	>
1245	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1246		try {
1247	<	return Unsafe.getUnsafe();
1247	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1248	>	} catch (NoSuchFieldException e) {
1249	>	// Convert Exception to corresponding Error
1250	>	NoSuchFieldError error = new NoSuchFieldError(field);
1251	>	error.initCause(e);
1252	>	throw error;
1253	>	}
1254	>	}
1255	>
1256	>	/**
1257	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1258	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1259	>	* into a jdk.
1260	>	*
1261	>	* @return a sun.misc.Unsafe
1262	>	*/
1263	>	private static sun.misc.Unsafe getUnsafe() {
1264	>	try {
1265	>	return sun.misc.Unsafe.getUnsafe();
1266		} catch (SecurityException se) {
1267		try {
1268		return java.security.AccessController.doPrivileged
1269	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1270	<	public Unsafe run() throws Exception {
1271	<	return getUnsafePrivileged();
1269	>	(new java.security
1270	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1271	>	public sun.misc.Unsafe run() throws Exception {
1272	>	java.lang.reflect.Field f = sun.misc
1273	>	.Unsafe.class.getDeclaredField("theUnsafe");
1274	>	f.setAccessible(true);
1275	>	return (sun.misc.Unsafe) f.get(null);
1276		}});
1277		} catch (java.security.PrivilegedActionException e) {
1278	<	throw e.getCause();
1278	>	throw new RuntimeException("Could not initialize intrinsics",
1279	>	e.getCause());
1280		}
1281		}
1282		}
1082	–
1083	–	private static Unsafe getUnsafePrivileged()
1084	–	throws NoSuchFieldException, IllegalAccessException {
1085	–	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1086	–	f.setAccessible(true);
1087	–	return (Unsafe) f.get(null);
1088	–	}
1089	–
1090	–	private static long fieldOffset(String fieldName)
1091	–	throws NoSuchFieldException {
1092	–	return UNSAFE.objectFieldOffset
1093	–	(ForkJoinTask.class.getDeclaredField(fieldName));
1094	–	}
1095	–
1096	–	static final Unsafe UNSAFE;
1097	–	static final long statusOffset;
1098	–
1099	–	static {
1100	–	try {
1101	–	UNSAFE = getUnsafe();
1102	–	statusOffset = fieldOffset("status");
1103	–	} catch (Throwable e) {
1104	–	throw new RuntimeException("Could not initialize intrinsics", e);
1105	–	}
1106	–	}
1107	–
1283		}

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