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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 1.46 by dl, Mon Apr 5 15:52:26 2010 UTC

#	Line 12 | Line 12 | 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
#	Line 22 | Line 23 | import java.util.WeakHashMap;
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} and
30	<	* {@code join}, or derivatives such as {@code invokeAll}.  However,
31	<	* this class also provides a number of other methods that can come
32	<	* into play in advanced usages, as well as extension mechanics that
33	<	* allow support of new forms of 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 65 | Line 68 | import java.util.WeakHashMap;
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, typically {@link
95		* RecursiveAction} for computations that do not return results, or
#	Line 83 | Line 98 | import java.util.WeakHashMap;
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	<	* {@link #exec}, {@link #setRawResult}, and
114	<	* {@link #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
102	<	* 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
127	<	* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
128	<	* may be of use when mixing execution of ForkJoinTasks with other
129	<	* kinds of tasks. When all tasks are of this form, consider using a
130	<	* pool in {@link ForkJoinPool#setAsyncMode}.
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
121	<	* 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 134 | 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 165 | 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
191	–	// Setting completion status
192	–
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) {
205	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
206	<	pool.updateRunningCount(s);
207	<	synchronized (this) { notifyAll(); }
208	<	}
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(); }
261	>	do {} while ((s = status) >= 0 &&
262	>	!UNSAFE.compareAndSwapInt(this, statusOffset, s, s + 1));
263	>	return s;
264		}
265	<
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		*/
240	–	private void doAwaitDone() {
241	–	// Minimize lock bias and in/de-flation effects by maximizing
242	–	// chances of waiting inside sync
243	–	try {
244	–	while (status >= 0)
245	–	synchronized (this) { if (status >= 0) wait(); }
246	–	} catch (InterruptedException ie) {
247	–	onInterruptedWait();
248	–	}
249	–	}
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		}
263	–	} catch (InterruptedException ie) {
264	–	onInterruptedWait();
305		}
306		}
307		}
308
269	–	// Awaiting completion
270	–
309		/**
310	<	* Sets status to indicate there is joiner, then waits for join,
273	<	* surrounded with pool notifications.
274	<	*
275	<	* @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		}
290	–	return s;
332		}
333
334		/**
335	<	* Timed version of awaitDone
295	<	*
296	<	* @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		}
310	–	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
311	–	adjustPoolCountsOnUnblock(pool);
312	–	break;
365		}
366		}
315	–	return s;
367		}
368
369		/**
370	<	* Notifies pool that thread is unblocked. Called by signalled
320	<	* 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	<
329	<	/**
330	<	* Notifies pool to adjust counts on cancelled or timed out wait.
331	<	*/
332	<	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);
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	<	/**
345	<	* Handles interruptions during waits.
346	<	*/
347	<	private void onInterruptedWait() {
348	<	ForkJoinWorkerThread w = getWorker();
349	<	if (w == null)
350	<	Thread.currentThread().interrupt(); // re-interrupt
351	<	else if (w.isTerminating())
352	<	cancelIgnoringExceptions();
353	<	// else if FJworker, ignore interrupt
354	<	}
355	<
356	<	// Recording and reporting exceptions
357	<
358	<	private void setDoneExceptionally(Throwable rex) {
359	<	exceptionMap.put(this, rex);
360	<	setCompletion(EXCEPTIONAL);
361	<	}
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
373	<	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 387 | 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);
390	–	if (Thread.interrupted())
391	–	throw new InterruptedException();
425		}
426		return getRawResult();
427		}
#	Line 399 | 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();
412	<	throw new TimeoutException();
413	<	}
414	<
415	<	// internal execution methods
416	<
417	<	/**
418	<	* Calls exec, recording completion, and rethrowing exception if
419	<	* encountered. Caller should normally check status before calling.
420	<	*
421	<	* @return true if completed normally
422	<	*/
423	<	private boolean tryExec() {
424	<	try { // try block must contain only call to exec
425	<	if (!exec())
426	<	return false;
427	<	} catch (Throwable rex) {
428	<	setDoneExceptionally(rex);
429	<	rethrowException(rex);
430	<	return false; // not reached
431	<	}
432	<	setNormalCompletion();
433	<	return true;
434	<	}
435	<
436	<	/**
437	<	* Main execution method used by worker threads. Invokes
438	<	* base computation unless already complete.
439	<	*/
440	<	final void quietlyExec() {
441	<	if (status >= 0) {
442	<	try {
443	<	if (!exec())
444	<	return;
445	<	} catch (Throwable rex) {
446	<	setDoneExceptionally(rex);
447	<	return;
448	<	}
449	<	setNormalCompletion();
450	<	}
451	<	}
452	<
453	<	/**
454	<	* Calls exec(), recording but not rethrowing exception.
455	<	* Caller should normally check status before calling.
456	<	*
457	<	* @return true if completed normally
458	<	*/
459	<	private boolean tryQuietlyInvoke() {
460	<	try {
461	<	if (!exec())
462	<	return false;
463	<	} catch (Throwable rex) {
464	<	setDoneExceptionally(rex);
465	<	return false;
466	<	}
467	<	setNormalCompletion();
468	<	return true;
469	<	}
470	<
471	<	/**
472	<	* Cancels, ignoring any exceptions it throws.
473	<	*/
474	<	final void cancelIgnoringExceptions() {
475	<	try {
476	<	cancel(false);
477	<	} catch (Throwable ignore) {
478	<	}
479	<	}
480	<
481	<	/**
482	<	* Main implementation of helpJoin
483	<	*/
484	<	private int busyJoin(ForkJoinWorkerThread w) {
485	<	int s;
486	<	ForkJoinTask<?> t;
487	<	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
488	<	t.quietlyExec();
489	<	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
445	>	else
446	>	throw new TimeoutException();
447		}
448
449		// public methods
#	Line 494 | 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.
467	>	* @return {@code this}, to simplify usage
468		*/
469		public final ForkJoinTask<V> fork() {
470		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 509 | Line 473 | public abstract class ForkJoinTask<V> im
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())
522	<	reportException(awaitDone(w, true));
523	<	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		*
530	–	* @throws Throwable (a RuntimeException, Error, or unchecked
531	–	* 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
538	<	return join();
496	>	if (!tryExec())
497	>	quietlyJoin();
498	>	return reportResult();
499		}
500
501		/**
502		* Forks the given tasks, returning when {@code isDone} holds for
503	<	* each task 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.
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	>	* <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
552	–	* @throws RuntimeException or Error if a task did so
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();
#	Line 559 | Line 525 | public abstract class ForkJoinTask<V> im
525
526		/**
527		* Forks the given tasks, returning when {@code isDone} holds for
528	<	* each task or an exception is encountered. If any task
529	<	* encounters an exception, others may be, but are not guaranteed
530	<	* to be, cancelled.  This method may be invoked only from within
531	<	* ForkJoinTask computations (as may be determined using method
532	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
533	<	* result in exceptions or errors, possibly including
534	<	* ClassCastException.
535	<	*
536	<	* Overloadings of this method exist for the special cases
537	<	* of one to four arguments.
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 tasks
543	<	* @throws NullPointerException if tasks or any element are null
575	<	* @throws RuntimeException or Error if any task did so
543	>	* @throws NullPointerException if any task is null
544		*/
545		public static void invokeAll(ForkJoinTask<?>... tasks) {
546		Throwable ex = null;
#	Line 604 | 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 {@code
580	<	* isDone} holds for each task or an exception is encountered. If
581	<	* any task encounters an exception, others may be, but are not
582	<	* guaranteed to be, cancelled.  This method may be invoked only
583	<	* from within ForkJoinTask computations (as may be determined
584	<	* using method {@link #inForkJoinPool}). Attempts to invoke in
585	<	* other contexts result in exceptions or errors, possibly
586	<	* 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
623	–	* @throws RuntimeException or Error if any task did so
599		*/
600		public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
601	<	if (!(tasks instanceof List<?>)) {
601	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
602		invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
603		return tasks;
604		}
#	Line 659 | Line 634 | public abstract class ForkJoinTask<V> im
634		}
635		}
636		if (ex != null)
637	<	rethrowException(ex);
637	>	UNSAFE.throwException(ex);
638		return tasks;
639		}
640
641		/**
642	<	* Returns {@code true} if the computation performed by this task
643	<	* has completed (or has been cancelled).
644	<	*
645	<	* @return {@code true} if this computation has completed
646	<	*/
647	<	public final boolean isDone() {
648	<	return status < 0;
674	<	}
675	<
676	<	/**
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.
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 {@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 {@code true} if this task is now cancelled
#	Line 715 | Line 668 | public abstract class ForkJoinTask<V> im
668		}
669
670		/**
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 {@code true} if this task threw an exception or was cancelled
#	Line 724 | Line 710 | public abstract class ForkJoinTask<V> im
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 {@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)
738	<	return new CancellationException();
739	<	return exceptionMap.get(this);
732	>	return ((s >= NORMAL)    ? null :
733	>	(s == CANCELLED) ? new CancellationException() :
734	>	exceptionMap.get(this));
735		}
736
737		/**
#	Line 749 | Line 744 | public abstract class ForkJoinTask<V> im
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 778 | 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();
786	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
787	<	awaitDone(w, true);
780	>	quietlyJoin();
781		return reportFutureResult();
782		}
783	<
783	>
784		public final V get(long timeout, TimeUnit unit)
785		throws InterruptedException, ExecutionException, TimeoutException {
786		long nanos = unit.toNanos(timeout);
787	<	ForkJoinWorkerThread w = getWorker();
788	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
789	<	awaitDone(w, nanos);
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())
818	<	reportException(busyJoin(w));
819	<	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	>	while (status >= 0) {
836	>	ForkJoinTask<?> t = w.scanWhileJoining(this);
837	>	if (t == null) {
838	>	if (status >= 0)
839	>	awaitDone(w);
840	>	break;
841	>	}
842	>	t.tryExec();
843	>	}
844		}
845		}
846
#	Line 842 | Line 851 | public abstract class ForkJoinTask<V> im
851		* known to have aborted.
852		*/
853		public final void quietlyJoin() {
854	<	if (status >= 0) {
855	<	ForkJoinWorkerThread w = getWorker();
856	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
857	<	awaitDone(w, true);
854	>	Thread t = Thread.currentThread();
855	>	if (t instanceof ForkJoinWorkerThread) {
856	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
857	>	if (!w.unpushTask(this) || !tryExec())
858	>	awaitDone(w);
859		}
860	+	else
861	+	externalAwaitDone();
862		}
863
864		/**
#	Line 857 | Line 869 | public abstract class ForkJoinTask<V> im
869		* known to have aborted.
870		*/
871		public final void quietlyInvoke() {
872	<	if (status >= 0 && !tryQuietlyInvoke())
872	>	if (!tryExec())
873		quietlyJoin();
874		}
875
876		/**
877		* Possibly executes tasks until the pool hosting the current task
878	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
879	<	* designs in which many tasks are forked, but none are explicitly
880	<	* joined, instead executing them until all are processed.  This
881	<	* method may be invoked only from within ForkJoinTask
882	<	* computations (as may be determined using method {@link
883	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
884	<	* in exceptions or errors, possibly including ClassCastException.
878	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
879	>	* be of use in designs in which many tasks are forked, but none
880	>	* are explicitly joined, instead executing them until all are
881	>	* processed.
882	>	*
883	>	* <p>This method may be invoked only from within {@code
884	>	* ForkJoinTask} computations (as may be determined using method
885	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
886	>	* result in exceptions or errors, possibly including {@code
887	>	* ClassCastException}.
888		*/
889		public static void helpQuiesce() {
890		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 882 | Line 897 | public abstract class ForkJoinTask<V> im
897		* this task, but only if reuse occurs when this task has either
898		* never been forked, or has been forked, then completed and all
899		* outstanding joins of this task have also completed. Effects
900	<	* under any other usage conditions are not guaranteed, and are
901	<	* discouraged. This method may be useful when executing
900	>	* under any other usage conditions are not guaranteed.
901	>	* This method may be useful when executing
902		* pre-constructed trees of subtasks in loops.
903		*/
904		public void reinitialize() {
#	Line 922 | Line 937 | public abstract class ForkJoinTask<V> im
937		* by the current thread, and has not commenced executing in
938		* another thread.  This method may be useful when arranging
939		* alternative local processing of tasks that could have been, but
940	<	* were not, stolen. This method may be invoked only from within
941	<	* ForkJoinTask computations (as may be determined using method
942	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
943	<	* result in exceptions or errors, possibly including
944	<	* ClassCastException.
940	>	* were not, stolen.
941	>	*
942	>	* <p>This method may be invoked only from within {@code
943	>	* ForkJoinTask} computations (as may be determined using method
944	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
945	>	* result in exceptions or errors, possibly including {@code
946	>	* ClassCastException}.
947		*
948		* @return {@code true} if unforked
949		*/
#	Line 939 | Line 956 | public abstract class ForkJoinTask<V> im
956		* Returns an estimate of the number of tasks that have been
957		* forked by the current worker thread but not yet executed. This
958		* value may be useful for heuristic decisions about whether to
959	<	* fork other tasks.  This method may be invoked only from within
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
963	<	* ClassCastException.
959	>	* fork other tasks.
960	>	*
961	>	* <p>This method may be invoked only from within {@code
962	>	* ForkJoinTask} computations (as may be determined using method
963	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
964	>	* result in exceptions or errors, possibly including {@code
965	>	* ClassCastException}.
966	>	*
967		* @return the number of tasks
968		*/
969		public static int getQueuedTaskCount() {
#	Line 959 | Line 979 | public abstract class ForkJoinTask<V> im
979		* usages of ForkJoinTasks, at steady state, each worker should
980		* aim to maintain a small constant surplus (for example, 3) of
981		* tasks, and to process computations locally if this threshold is
982	<	* exceeded.  This method may be invoked only from within
983	<	* ForkJoinTask computations (as may be determined using method
984	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
985	<	* result in exceptions or errors, possibly including
986	<	* ClassCastException.  *
982	>	* exceeded.
983	>	*
984	>	* <p>This method may be invoked only from within {@code
985	>	* ForkJoinTask} computations (as may be determined using method
986	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
987	>	* result in exceptions or errors, possibly including {@code
988	>	* ClassCastException}.
989	>	*
990		* @return the surplus number of tasks, which may be negative
991		*/
992		public static int getSurplusQueuedTaskCount() {
#	Line 999 | Line 1022 | public abstract class ForkJoinTask<V> im
1022		* called otherwise. The return value controls whether this task
1023		* is considered to be done normally. It may return false in
1024		* asynchronous actions that require explicit invocations of
1025	<	* {@link #complete} to become joinable. It may throw exceptions
1026	<	* to indicate abnormal exit.
1025	>	* {@link #complete} to become joinable. It may also throw an
1026	>	* (unchecked) exception to indicate abnormal exit.
1027		*
1028		* @return {@code true} if completed normally
1006	–	* @throws Error or RuntimeException if encountered during computation
1029		*/
1030		protected abstract boolean exec();
1031
#	Line 1015 | Line 1037 | public abstract class ForkJoinTask<V> im
1037		* null even if a task exists but cannot be accessed without
1038		* contention with other threads.  This method is designed
1039		* primarily to support extensions, and is unlikely to be useful
1040	<	* otherwise.  This method may be invoked only from within
1041	<	* ForkJoinTask computations (as may be determined using method
1042	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1043	<	* result in exceptions or errors, possibly including
1044	<	* ClassCastException.
1040	>	* otherwise.
1041	>	*
1042	>	* <p>This method may be invoked only from within {@code
1043	>	* ForkJoinTask} computations (as may be determined using method
1044	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1045	>	* result in exceptions or errors, possibly including {@code
1046	>	* ClassCastException}.
1047		*
1048		* @return the next task, or {@code null} if none are available
1049		*/
#	Line 1032 | Line 1056 | public abstract class ForkJoinTask<V> im
1056		* Unschedules and returns, without executing, the next task
1057		* queued by the current thread but not yet executed.  This method
1058		* is designed primarily to support extensions, and is unlikely to
1059	<	* be useful otherwise.  This method may be invoked only from
1060	<	* within ForkJoinTask computations (as may be determined using
1061	<	* method {@link #inForkJoinPool}). Attempts to invoke in other
1062	<	* contexts result in exceptions or errors, possibly including
1063	<	* ClassCastException.
1059	>	* be useful otherwise.
1060	>	*
1061	>	* <p>This method may be invoked only from within {@code
1062	>	* ForkJoinTask} computations (as may be determined using method
1063	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1064	>	* result in exceptions or errors, possibly including {@code
1065	>	* ClassCastException}.
1066		*
1067		* @return the next task, or {@code null} if none are available
1068		*/
#	Line 1053 | Line 1079 | public abstract class ForkJoinTask<V> im
1079		* {@code null} result does not necessarily imply quiescence
1080		* of the pool this task is operating in.  This method is designed
1081		* primarily to support extensions, and is unlikely to be useful
1082	<	* otherwise.  This method may be invoked only from within
1083	<	* ForkJoinTask computations (as may be determined using method
1084	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1085	<	* result in exceptions or errors, possibly including
1086	<	* ClassCastException.
1082	>	* otherwise.
1083	>	*
1084	>	* <p>This method may be invoked only from within {@code
1085	>	* ForkJoinTask} computations (as may be determined using method
1086	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1087	>	* result in exceptions or errors, possibly including {@code
1088	>	* ClassCastException}.
1089		*
1090		* @return a task, or {@code null} if none are available
1091		*/
#	Line 1122 | Line 1150 | public abstract class ForkJoinTask<V> im
1150		}
1151
1152		/**
1153	<	* Returns a new ForkJoinTask that performs the {@code run}
1154	<	* method of the given Runnable as its action, and returns a null
1155	<	* result upon {@code join}.
1153	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1154	>	* method of the given {@code Runnable} as its action, and returns
1155	>	* a null result upon {@link #join}.
1156		*
1157		* @param runnable the runnable action
1158		* @return the task
#	Line 1134 | Line 1162 | public abstract class ForkJoinTask<V> im
1162		}
1163
1164		/**
1165	<	* Returns a new ForkJoinTask that performs the {@code run}
1166	<	* method of the given Runnable as its action, and returns the
1167	<	* given result upon {@code join}.
1165	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1166	>	* method of the given {@code Runnable} as its action, and returns
1167	>	* the given result upon {@link #join}.
1168		*
1169		* @param runnable the runnable action
1170		* @param result the result upon completion
#	Line 1147 | Line 1175 | public abstract class ForkJoinTask<V> im
1175		}
1176
1177		/**
1178	<	* Returns a new ForkJoinTask that performs the {@code call}
1179	<	* method of the given Callable as its action, and returns its
1180	<	* result upon {@code join}, translating any checked
1181	<	* exceptions encountered into {@code RuntimeException}.
1178	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1179	>	* method of the given {@code Callable} as its action, and returns
1180	>	* its result upon {@link #join}, translating any checked exceptions
1181	>	* encountered into {@code RuntimeException}.
1182		*
1183		* @param callable the callable action
1184		* @return the task
#	Line 1164 | Line 1192 | public abstract class ForkJoinTask<V> im
1192		private static final long serialVersionUID = -7721805057305804111L;
1193
1194		/**
1195	<	* Save the state to a stream.
1195	>	* Saves the state to a stream.
1196		*
1197		* @serialData the current run status and the exception thrown
1198		* during execution, or {@code null} if none
#	Line 1177 | Line 1205 | public abstract class ForkJoinTask<V> im
1205		}
1206
1207		/**
1208	<	* Reconstitute the instance from a stream.
1208	>	* Reconstitutes the instance from a stream.
1209		*
1210		* @param s the stream
1211		*/

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