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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.73 by jsr166, Sun Nov 28 21:21:03 2010 UTC vs.
Revision 1.103 by jsr166, Tue Oct 13 19:45:34 2015 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Doug Lea with assistance from members of JCP JSR-166
3		* Expert Group and released to the public domain, as explained at
4	<	* http://creativecommons.org/licenses/publicdomain
4	>	* http://creativecommons.org/publicdomain/zero/1.0/
5		*/
6
7		package jsr166y;
8
9		import java.io.Serializable;
10		import java.util.Collection;
11	–	import java.util.Collections;
11		import java.util.List;
12		import java.util.RandomAccess;
13	<	import java.util.Map;
14	<	import java.util.WeakHashMap;
13	>	import java.lang.ref.WeakReference;
14	>	import java.lang.ref.ReferenceQueue;
15		import java.util.concurrent.Callable;
16		import java.util.concurrent.CancellationException;
17		import java.util.concurrent.ExecutionException;
19	–	import java.util.concurrent.Executor;
20	–	import java.util.concurrent.ExecutorService;
18		import java.util.concurrent.Future;
19		import java.util.concurrent.RejectedExecutionException;
20		import java.util.concurrent.RunnableFuture;
21		import java.util.concurrent.TimeUnit;
22		import java.util.concurrent.TimeoutException;
23	+	import java.util.concurrent.locks.ReentrantLock;
24	+	import java.lang.reflect.Constructor;
25
26		/**
27		* Abstract base class for tasks that run within a {@link ForkJoinPool}.
#	Line 31 | Line 30 | import java.util.concurrent.TimeoutExcep
30		* subtasks may be hosted by a small number of actual threads in a
31		* ForkJoinPool, at the price of some usage limitations.
32		*
33	<	* <p>A "main" {@code ForkJoinTask} begins execution when submitted
34	<	* to a {@link ForkJoinPool}.  Once started, it will usually in turn
35	<	* start other subtasks.  As indicated by the name of this class,
36	<	* many programs using {@code ForkJoinTask} employ only methods
37	<	* {@link #fork} and {@link #join}, or derivatives such as {@link
33	>	* <p>A "main" {@code ForkJoinTask} begins execution when it is
34	>	* explicitly submitted to a {@link ForkJoinPool}, or, if not already
35	>	* engaged in a ForkJoin computation, commenced in the {@link
36	>	* ForkJoinPool#commonPool()} via {@link #fork}, {@link #invoke}, or
37	>	* related methods.  Once started, it will usually in turn start other
38	>	* subtasks.  As indicated by the name of this class, many programs
39	>	* using {@code ForkJoinTask} employ only methods {@link #fork} and
40	>	* {@link #join}, or derivatives such as {@link
41		* #invokeAll(ForkJoinTask...) invokeAll}.  However, this class also
42		* provides a number of other methods that can come into play in
43	<	* advanced usages, as well as extension mechanics that allow
44	<	* support of new forms of fork/join processing.
43	>	* advanced usages, as well as extension mechanics that allow support
44	>	* of new forms of fork/join processing.
45		*
46		* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
47		* The efficiency of {@code ForkJoinTask}s stems from a set of
48		* restrictions (that are only partially statically enforceable)
49	<	* reflecting their intended use as computational tasks calculating
50	<	* pure functions or operating on purely isolated objects.  The
51	<	* primary coordination mechanisms are {@link #fork}, that arranges
49	>	* reflecting their main use as computational tasks calculating pure
50	>	* functions or operating on purely isolated objects.  The primary
51	>	* coordination mechanisms are {@link #fork}, that arranges
52		* asynchronous execution, and {@link #join}, that doesn't proceed
53		* until the task's result has been computed.  Computations should
54	<	* avoid {@code synchronized} methods or blocks, and should minimize
55	<	* other blocking synchronization apart from joining other tasks or
56	<	* using synchronizers such as Phasers that are advertised to
57	<	* cooperate with fork/join scheduling. Tasks should also not perform
58	<	* blocking IO, and should ideally access variables that are
59	<	* completely independent of those accessed by other running
60	<	* tasks. Minor breaches of these restrictions, for example using
61	<	* shared output streams, may be tolerable in practice, but frequent
62	<	* use may result in poor performance, and the potential to
63	<	* indefinitely stall if the number of threads not waiting for IO or
64	<	* other external synchronization becomes exhausted. This usage
65	<	* restriction is in part enforced by not permitting checked
66	<	* exceptions such as {@code IOExceptions} to be thrown. However,
67	<	* computations may still encounter unchecked exceptions, that are
68	<	* rethrown to callers attempting to join them. These exceptions may
69	<	* additionally include {@link RejectedExecutionException} stemming
70	<	* from internal resource exhaustion, such as failure to allocate
71	<	* internal task queues.
54	>	* ideally avoid {@code synchronized} methods or blocks, and should
55	>	* minimize other blocking synchronization apart from joining other
56	>	* tasks or using synchronizers such as Phasers that are advertised to
57	>	* cooperate with fork/join scheduling. Subdividable tasks should also
58	>	* not perform blocking I/O, and should ideally access variables that
59	>	* are completely independent of those accessed by other running
60	>	* tasks. These guidelines are loosely enforced by not permitting
61	>	* checked exceptions such as {@code IOExceptions} to be
62	>	* thrown. However, computations may still encounter unchecked
63	>	* exceptions, that are rethrown to callers attempting to join
64	>	* them. These exceptions may additionally include {@link
65	>	* RejectedExecutionException} stemming from internal resource
66	>	* exhaustion, such as failure to allocate internal task
67	>	* queues. Rethrown exceptions behave in the same way as regular
68	>	* exceptions, but, when possible, contain stack traces (as displayed
69	>	* for example using {@code ex.printStackTrace()}) of both the thread
70	>	* that initiated the computation as well as the thread actually
71	>	* encountering the exception; minimally only the latter.
72	>	*
73	>	* <p>It is possible to define and use ForkJoinTasks that may block,
74	>	* but doing do requires three further considerations: (1) Completion
75	>	* of few if any <em>other</em> tasks should be dependent on a task
76	>	* that blocks on external synchronization or I/O. Event-style async
77	>	* tasks that are never joined (for example, those subclassing {@link
78	>	* CountedCompleter}) often fall into this category.  (2) To minimize
79	>	* resource impact, tasks should be small; ideally performing only the
80	>	* (possibly) blocking action. (3) Unless the {@link
81	>	* ForkJoinPool.ManagedBlocker} API is used, or the number of possibly
82	>	* blocked tasks is known to be less than the pool's {@link
83	>	* ForkJoinPool#getParallelism} level, the pool cannot guarantee that
84	>	* enough threads will be available to ensure progress or good
85	>	* performance.
86		*
87		* <p>The primary method for awaiting completion and extracting
88		* results of a task is {@link #join}, but there are several variants:
#	Line 82 | Line 98 | import java.util.concurrent.TimeoutExcep
98		* performs the most common form of parallel invocation: forking a set
99		* of tasks and joining them all.
100		*
101	+	* <p>In the most typical usages, a fork-join pair act like a call
102	+	* (fork) and return (join) from a parallel recursive function. As is
103	+	* the case with other forms of recursive calls, returns (joins)
104	+	* should be performed innermost-first. For example, {@code a.fork();
105	+	* b.fork(); b.join(); a.join();} is likely to be substantially more
106	+	* efficient than joining {@code a} before {@code b}.
107	+	*
108		* <p>The execution status of tasks may be queried at several levels
109		* of detail: {@link #isDone} is true if a task completed in any way
110		* (including the case where a task was cancelled without executing);
#	Line 97 | Line 120 | import java.util.concurrent.TimeoutExcep
120		* <p>The ForkJoinTask class is not usually directly subclassed.
121		* Instead, you subclass one of the abstract classes that support a
122		* particular style of fork/join processing, typically {@link
123	<	* RecursiveAction} for computations that do not return results, or
124	<	* {@link RecursiveTask} for those that do.  Normally, a concrete
125	<	* ForkJoinTask subclass declares fields comprising its parameters,
126	<	* established in a constructor, and then defines a {@code compute}
127	<	* method that somehow uses the control methods supplied by this base
128	<	* class. While these methods have {@code public} access (to allow
129	<	* instances of different task subclasses to call each other's
107	<	* methods), some of them may only be called from within other
108	<	* ForkJoinTasks (as may be determined using method {@link
109	<	* #inForkJoinPool}).  Attempts to invoke them in other contexts
110	<	* result in exceptions or errors, possibly including
111	<	* {@code ClassCastException}.
123	>	* RecursiveAction} for most computations that do not return results,
124	>	* {@link RecursiveTask} for those that do, and {@link
125	>	* CountedCompleter} for those in which completed actions trigger
126	>	* other actions.  Normally, a concrete ForkJoinTask subclass declares
127	>	* fields comprising its parameters, established in a constructor, and
128	>	* then defines a {@code compute} method that somehow uses the control
129	>	* methods supplied by this base class.
130		*
131		* <p>Method {@link #join} and its variants are appropriate for use
132		* only when completion dependencies are acyclic; that is, the
#	Line 118 | Line 136 | import java.util.concurrent.TimeoutExcep
136		* supports other methods and techniques (for example the use of
137		* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that
138		* may be of use in constructing custom subclasses for problems that
139	<	* are not statically structured as DAGs.
139	>	* are not statically structured as DAGs. To support such usages a
140	>	* ForkJoinTask may be atomically <em>tagged</em> with a {@code short}
141	>	* value using {@link #setForkJoinTaskTag} or {@link
142	>	* #compareAndSetForkJoinTaskTag} and checked using {@link
143	>	* #getForkJoinTaskTag}. The ForkJoinTask implementation does not use
144	>	* these {@code protected} methods or tags for any purpose, but they
145	>	* may be of use in the construction of specialized subclasses.  For
146	>	* example, parallel graph traversals can use the supplied methods to
147	>	* avoid revisiting nodes/tasks that have already been processed.
148	>	* (Method names for tagging are bulky in part to encourage definition
149	>	* of methods that reflect their usage patterns.)
150		*
151		* <p>Most base support methods are {@code final}, to prevent
152		* overriding of implementations that are intrinsically tied to the
#	Line 158 | Line 186 | public abstract class ForkJoinTask<V> im
186		* See the internal documentation of class ForkJoinPool for a
187		* general implementation overview.  ForkJoinTasks are mainly
188		* responsible for maintaining their "status" field amidst relays
189	<	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
190	<	* methods of this class are more-or-less layered into (1) basic
191	<	* status maintenance (2) execution and awaiting completion (3)
192	<	* user-level methods that additionally report results. This is
193	<	* sometimes hard to see because this file orders exported methods
194	<	* in a way that flows well in javadocs. In particular, most
195	<	* join mechanics are in method quietlyJoin, below.
189	>	* to methods in ForkJoinWorkerThread and ForkJoinPool.
190	>	*
191	>	* The methods of this class are more-or-less layered into
192	>	* (1) basic status maintenance
193	>	* (2) execution and awaiting completion
194	>	* (3) user-level methods that additionally report results.
195	>	* This is sometimes hard to see because this file orders exported
196	>	* methods in a way that flows well in javadocs.
197		*/
198
199		/*
200		* The status field holds run control status bits packed into a
201		* single int to minimize footprint and to ensure atomicity (via
202		* CAS).  Status is initially zero, and takes on nonnegative
203	<	* values until completed, upon which status holds value
204	<	* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
205	<	* waits by other threads have the SIGNAL bit set.  Completion of
206	<	* a stolen task with SIGNAL set awakens any waiters via
207	<	* notifyAll. Even though suboptimal for some purposes, we use
208	<	* basic builtin wait/notify to take advantage of "monitor
209	<	* inflation" in JVMs that we would otherwise need to emulate to
210	<	* avoid adding further per-task bookkeeping overhead.  We want
211	<	* these monitors to be "fat", i.e., not use biasing or thin-lock
212	<	* techniques, so use some odd coding idioms that tend to avoid
213	<	* them.
203	>	* values until completed, upon which status (anded with
204	>	* DONE_MASK) holds value NORMAL, CANCELLED, or EXCEPTIONAL. Tasks
205	>	* undergoing blocking waits by other threads have the SIGNAL bit
206	>	* set.  Completion of a stolen task with SIGNAL set awakens any
207	>	* waiters via notifyAll. Even though suboptimal for some
208	>	* purposes, we use basic builtin wait/notify to take advantage of
209	>	* "monitor inflation" in JVMs that we would otherwise need to
210	>	* emulate to avoid adding further per-task bookkeeping overhead.
211	>	* We want these monitors to be "fat", i.e., not use biasing or
212	>	* thin-lock techniques, so use some odd coding idioms that tend
213	>	* to avoid them, mainly by arranging that every synchronized
214	>	* block performs a wait, notifyAll or both.
215	>	*
216	>	* These control bits occupy only (some of) the upper half (16
217	>	* bits) of status field. The lower bits are used for user-defined
218	>	* tags.
219		*/
220
221		/** The run status of this task */
222		volatile int status; // accessed directly by pool and workers
223	+	static final int DONE_MASK   = 0xf0000000;  // mask out non-completion bits
224	+	static final int NORMAL      = 0xf0000000;  // must be negative
225	+	static final int CANCELLED   = 0xc0000000;  // must be < NORMAL
226	+	static final int EXCEPTIONAL = 0x80000000;  // must be < CANCELLED
227	+	static final int SIGNAL      = 0x00010000;  // must be >= 1 << 16
228	+	static final int SMASK       = 0x0000ffff;  // short bits for tags
229
230	<	private static final int NORMAL      = -1;
231	<	private static final int CANCELLED   = -2;
232	<	private static final int EXCEPTIONAL = -3;
233	<	private static final int SIGNAL      =  1;
230	>	/**
231	>	* Marks completion and wakes up threads waiting to join this
232	>	* task.
233	>	*
234	>	* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
235	>	* @return completion status on exit
236	>	*/
237	>	private int setCompletion(int completion) {
238	>	for (int s;;) {
239	>	if ((s = status) < 0)
240	>	return s;
241	>	if (U.compareAndSwapInt(this, STATUS, s, s | completion)) {
242	>	if ((s >>> 16) != 0)
243	>	synchronized (this) { notifyAll(); }
244	>	return completion;
245	>	}
246	>	}
247	>	}
248	>
249	>	/**
250	>	* Primary execution method for stolen tasks. Unless done, calls
251	>	* exec and records status if completed, but doesn't wait for
252	>	* completion otherwise.
253	>	*
254	>	* @return status on exit from this method
255	>	*/
256	>	final int doExec() {
257	>	int s; boolean completed;
258	>	if ((s = status) >= 0) {
259	>	try {
260	>	completed = exec();
261	>	} catch (Throwable rex) {
262	>	return setExceptionalCompletion(rex);
263	>	}
264	>	if (completed)
265	>	s = setCompletion(NORMAL);
266	>	}
267	>	return s;
268	>	}
269	>
270	>	/**
271	>	* Tries to set SIGNAL status unless already completed. Used by
272	>	* ForkJoinPool. Other variants are directly incorporated into
273	>	* externalAwaitDone etc.
274	>	*
275	>	* @return true if successful
276	>	*/
277	>	final boolean trySetSignal() {
278	>	int s = status;
279	>	return s >= 0 && U.compareAndSwapInt(this, STATUS, s, s | SIGNAL);
280	>	}
281	>
282	>	/**
283	>	* Blocks a non-worker-thread until completion.
284	>	* @return status upon completion
285	>	*/
286	>	private int externalAwaitDone() {
287	>	int s;
288	>	ForkJoinPool.externalHelpJoin(this);
289	>	boolean interrupted = false;
290	>	while ((s = status) >= 0) {
291	>	if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
292	>	synchronized (this) {
293	>	if (status >= 0) {
294	>	try {
295	>	wait();
296	>	} catch (InterruptedException ie) {
297	>	interrupted = true;
298	>	}
299	>	}
300	>	else
301	>	notifyAll();
302	>	}
303	>	}
304	>	}
305	>	if (interrupted)
306	>	Thread.currentThread().interrupt();
307	>	return s;
308	>	}
309	>
310	>	/**
311	>	* Blocks a non-worker-thread until completion or interruption.
312	>	*/
313	>	private int externalInterruptibleAwaitDone() throws InterruptedException {
314	>	int s;
315	>	if (Thread.interrupted())
316	>	throw new InterruptedException();
317	>	ForkJoinPool.externalHelpJoin(this);
318	>	while ((s = status) >= 0) {
319	>	if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
320	>	synchronized (this) {
321	>	if (status >= 0)
322	>	wait();
323	>	else
324	>	notifyAll();
325	>	}
326	>	}
327	>	}
328	>	return s;
329	>	}
330	>
331	>
332	>	/**
333	>	* Implementation for join, get, quietlyJoin. Directly handles
334	>	* only cases of already-completed, external wait, and
335	>	* unfork+exec.  Others are relayed to ForkJoinPool.awaitJoin.
336	>	*
337	>	* @return status upon completion
338	>	*/
339	>	private int doJoin() {
340	>	int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w;
341	>	return (s = status) < 0 ? s :
342	>	((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
343	>	(w = (wt = (ForkJoinWorkerThread)t).workQueue).
344	>	tryUnpush(this) && (s = doExec()) < 0 ? s :
345	>	wt.pool.awaitJoin(w, this) :
346	>	externalAwaitDone();
347	>	}
348	>
349	>	/**
350	>	* Implementation for invoke, quietlyInvoke.
351	>	*
352	>	* @return status upon completion
353	>	*/
354	>	private int doInvoke() {
355	>	int s; Thread t; ForkJoinWorkerThread wt;
356	>	return (s = doExec()) < 0 ? s :
357	>	((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
358	>	(wt = (ForkJoinWorkerThread)t).pool.awaitJoin(wt.workQueue, this) :
359	>	externalAwaitDone();
360	>	}
361	>
362	>	// Exception table support
363
364		/**
365		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 198 | Line 367 | public abstract class ForkJoinTask<V> im
367		* them with task objects, but instead use a weak ref table.  Note
368		* that cancellation exceptions don't appear in the table, but are
369		* instead recorded as status values.
370	<	* TODO: Use ConcurrentReferenceHashMap
370	>	*
371	>	* Note: These statics are initialized below in static block.
372	>	*/
373	>	private static final ExceptionNode[] exceptionTable;
374	>	private static final ReentrantLock exceptionTableLock;
375	>	private static final ReferenceQueue<Object> exceptionTableRefQueue;
376	>
377	>	/**
378	>	* Fixed capacity for exceptionTable.
379		*/
380	<	static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
204	<	Collections.synchronizedMap
205	<	(new WeakHashMap<ForkJoinTask<?>, Throwable>());
380	>	private static final int EXCEPTION_MAP_CAPACITY = 32;
381
382	<	// Maintaining completion status
382	>	/**
383	>	* Key-value nodes for exception table.  The chained hash table
384	>	* uses identity comparisons, full locking, and weak references
385	>	* for keys. The table has a fixed capacity because it only
386	>	* maintains task exceptions long enough for joiners to access
387	>	* them, so should never become very large for sustained
388	>	* periods. However, since we do not know when the last joiner
389	>	* completes, we must use weak references and expunge them. We do
390	>	* so on each operation (hence full locking). Also, some thread in
391	>	* any ForkJoinPool will call helpExpungeStaleExceptions when its
392	>	* pool becomes isQuiescent.
393	>	*/
394	>	static final class ExceptionNode extends WeakReference<ForkJoinTask<?>> {
395	>	final Throwable ex;
396	>	ExceptionNode next;
397	>	final long thrower;  // use id not ref to avoid weak cycles
398	>	final int hashCode;  // store task hashCode before weak ref disappears
399	>	ExceptionNode(ForkJoinTask<?> task, Throwable ex, ExceptionNode next) {
400	>	super(task, exceptionTableRefQueue);
401	>	this.ex = ex;
402	>	this.next = next;
403	>	this.thrower = Thread.currentThread().getId();
404	>	this.hashCode = System.identityHashCode(task);
405	>	}
406	>	}
407
408		/**
409	<	* Marks completion and wakes up threads waiting to join this task,
211	<	* also clearing signal request bits.
409	>	* Records exception and sets status.
410		*
411	<	* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
411	>	* @return status on exit
412		*/
413	<	private void setCompletion(int completion) {
413	>	final int recordExceptionalCompletion(Throwable ex) {
414		int s;
415	<	while ((s = status) >= 0) {
416	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
417	<	if (s != 0)
418	<	synchronized (this) { notifyAll(); }
419	<	break;
415	>	if ((s = status) >= 0) {
416	>	int h = System.identityHashCode(this);
417	>	final ReentrantLock lock = exceptionTableLock;
418	>	lock.lock();
419	>	try {
420	>	expungeStaleExceptions();
421	>	ExceptionNode[] t = exceptionTable;
422	>	int i = h & (t.length - 1);
423	>	for (ExceptionNode e = t[i]; ; e = e.next) {
424	>	if (e == null) {
425	>	t[i] = new ExceptionNode(this, ex, t[i]);
426	>	break;
427	>	}
428	>	if (e.get() == this) // already present
429	>	break;
430	>	}
431	>	} finally {
432	>	lock.unlock();
433		}
434	+	s = setCompletion(EXCEPTIONAL);
435		}
436	+	return s;
437		}
438
439		/**
440	<	* Records exception and sets exceptional completion.
440	>	* Records exception and possibly propagates.
441		*
442		* @return status on exit
443		*/
444	<	private void setExceptionalCompletion(Throwable rex) {
445	<	exceptionMap.put(this, rex);
446	<	setCompletion(EXCEPTIONAL);
444	>	private int setExceptionalCompletion(Throwable ex) {
445	>	int s = recordExceptionalCompletion(ex);
446	>	if ((s & DONE_MASK) == EXCEPTIONAL)
447	>	internalPropagateException(ex);
448	>	return s;
449		}
450
451		/**
452	<	* Blocks a worker thread until completed or timed out.  Called
238	<	* only by pool.
452	>	* Hook for exception propagation support for tasks with completers.
453		*/
454	<	final void internalAwaitDone(long millis, int nanos) {
455	<	int s = status;
456	<	if ((s == 0 &&
457	<	UNSAFE.compareAndSwapInt(this, statusOffset, 0, SIGNAL)) ||
458	<	s > 0)  {
459	<	try {     // the odd construction reduces lock bias effects
460	<	synchronized (this) {
461	<	if (status > 0)
462	<	wait(millis, nanos);
454	>	void internalPropagateException(Throwable ex) {
455	>	}
456	>
457	>	/**
458	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
459	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
460	>	* exceptions, but if it does anyway, we have no recourse during
461	>	* shutdown, so guard against this case.
462	>	*/
463	>	static final void cancelIgnoringExceptions(ForkJoinTask<?> t) {
464	>	if (t != null && t.status >= 0) {
465	>	try {
466	>	t.cancel(false);
467	>	} catch (Throwable ignore) {
468	>	}
469	>	}
470	>	}
471	>
472	>	/**
473	>	* Removes exception node and clears status.
474	>	*/
475	>	private void clearExceptionalCompletion() {
476	>	int h = System.identityHashCode(this);
477	>	final ReentrantLock lock = exceptionTableLock;
478	>	lock.lock();
479	>	try {
480	>	ExceptionNode[] t = exceptionTable;
481	>	int i = h & (t.length - 1);
482	>	ExceptionNode e = t[i];
483	>	ExceptionNode pred = null;
484	>	while (e != null) {
485	>	ExceptionNode next = e.next;
486	>	if (e.get() == this) {
487	>	if (pred == null)
488	>	t[i] = next;
489		else
490	<	notifyAll();
490	>	pred.next = next;
491	>	break;
492		}
493	<	} catch (InterruptedException ie) {
494	<	cancelIfTerminating();
493	>	pred = e;
494	>	e = next;
495		}
496	+	expungeStaleExceptions();
497	+	status = 0;
498	+	} finally {
499	+	lock.unlock();
500		}
501		}
502
503		/**
504	<	* Blocks a non-worker-thread until completion.
505	<	*/
506	<	private void externalAwaitDone() {
507	<	if (status >= 0) {
508	<	boolean interrupted = false;
509	<	synchronized (this) {
510	<	for (;;) {
511	<	int s = status;
512	<	if (s == 0)
513	<	UNSAFE.compareAndSwapInt(this, statusOffset,
514	<	0, SIGNAL);
515	<	else if (s < 0) {
516	<	notifyAll();
517	<	break;
518	<	}
519	<	else {
520	<	try {
521	<	wait();
522	<	} catch (InterruptedException ie) {
523	<	interrupted = true;
524	<	}
525	<	}
504	>	* Returns a rethrowable exception for the given task, if
505	>	* available. To provide accurate stack traces, if the exception
506	>	* was not thrown by the current thread, we try to create a new
507	>	* exception of the same type as the one thrown, but with the
508	>	* recorded exception as its cause. If there is no such
509	>	* constructor, we instead try to use a no-arg constructor,
510	>	* followed by initCause, to the same effect. If none of these
511	>	* apply, or any fail due to other exceptions, we return the
512	>	* recorded exception, which is still correct, although it may
513	>	* contain a misleading stack trace.
514	>	*
515	>	* @return the exception, or null if none
516	>	*/
517	>	private Throwable getThrowableException() {
518	>	if ((status & DONE_MASK) != EXCEPTIONAL)
519	>	return null;
520	>	int h = System.identityHashCode(this);
521	>	ExceptionNode e;
522	>	final ReentrantLock lock = exceptionTableLock;
523	>	lock.lock();
524	>	try {
525	>	expungeStaleExceptions();
526	>	ExceptionNode[] t = exceptionTable;
527	>	e = t[h & (t.length - 1)];
528	>	while (e != null && e.get() != this)
529	>	e = e.next;
530	>	} finally {
531	>	lock.unlock();
532	>	}
533	>	Throwable ex;
534	>	if (e == null || (ex = e.ex) == null)
535	>	return null;
536	>	if (false && e.thrower != Thread.currentThread().getId()) {
537	>	Class<? extends Throwable> ec = ex.getClass();
538	>	try {
539	>	Constructor<?> noArgCtor = null;
540	>	Constructor<?>[] cs = ec.getConstructors();// public ctors only
541	>	for (int i = 0; i < cs.length; ++i) {
542	>	Constructor<?> c = cs[i];
543	>	Class<?>[] ps = c.getParameterTypes();
544	>	if (ps.length == 0)
545	>	noArgCtor = c;
546	>	else if (ps.length == 1 && ps[0] == Throwable.class)
547	>	return (Throwable)(c.newInstance(ex));
548	>	}
549	>	if (noArgCtor != null) {
550	>	Throwable wx = (Throwable)(noArgCtor.newInstance());
551	>	wx.initCause(ex);
552	>	return wx;
553		}
554	+	} catch (Exception ignore) {
555		}
283	–	if (interrupted)
284	–	Thread.currentThread().interrupt();
556		}
557	+	return ex;
558		}
559
560		/**
561	<	* Blocks a non-worker-thread until completion or interruption or timeout.
561	>	* Poll stale refs and remove them. Call only while holding lock.
562		*/
563	<	private void externalInterruptibleAwaitDone(boolean timed, long nanos)
564	<	throws InterruptedException {
565	<	if (Thread.interrupted())
566	<	throw new InterruptedException();
567	<	if (status >= 0) {
568	<	long startTime = timed ? System.nanoTime() : 0L;
569	<	synchronized (this) {
570	<	for (;;) {
571	<	long nt;
572	<	int s = status;
573	<	if (s == 0)
574	<	UNSAFE.compareAndSwapInt(this, statusOffset,
575	<	0, SIGNAL);
576	<	else if (s < 0) {
577	<	notifyAll();
563	>	private static void expungeStaleExceptions() {
564	>	for (Object x; (x = exceptionTableRefQueue.poll()) != null;) {
565	>	if (x instanceof ExceptionNode) {
566	>	int hashCode = ((ExceptionNode)x).hashCode;
567	>	ExceptionNode[] t = exceptionTable;
568	>	int i = hashCode & (t.length - 1);
569	>	ExceptionNode e = t[i];
570	>	ExceptionNode pred = null;
571	>	while (e != null) {
572	>	ExceptionNode next = e.next;
573	>	if (e == x) {
574	>	if (pred == null)
575	>	t[i] = next;
576	>	else
577	>	pred.next = next;
578		break;
579		}
580	<	else if (!timed)
581	<	wait();
310	<	else if ((nt = nanos - (System.nanoTime()-startTime)) > 0L)
311	<	wait(nt / 1000000, (int)(nt % 1000000));
312	<	else
313	<	break;
580	>	pred = e;
581	>	e = next;
582		}
583		}
584		}
585		}
586
587		/**
588	<	* Unless done, calls exec and records status if completed, but
589	<	* doesn't wait for completion otherwise. Primary execution method
322	<	* for ForkJoinWorkerThread.
588	>	* If lock is available, poll stale refs and remove them.
589	>	* Called from ForkJoinPool when pools become quiescent.
590		*/
591	<	final void quietlyExec() {
592	<	try {
593	<	if (status < 0 || !exec())
594	<	return;
595	<	} catch (Throwable rex) {
596	<	setExceptionalCompletion(rex);
597	<	return;
591	>	static final void helpExpungeStaleExceptions() {
592	>	final ReentrantLock lock = exceptionTableLock;
593	>	if (lock.tryLock()) {
594	>	try {
595	>	expungeStaleExceptions();
596	>	} finally {
597	>	lock.unlock();
598	>	}
599		}
600	<	setCompletion(NORMAL); // must be outside try block
600	>	}
601	>
602	>	/**
603	>	* A version of "sneaky throw" to relay exceptions
604	>	*/
605	>	static void rethrow(final Throwable ex) {
606	>	if (ex != null) {
607	>	if (ex instanceof Error)
608	>	throw (Error)ex;
609	>	if (ex instanceof RuntimeException)
610	>	throw (RuntimeException)ex;
611	>	ForkJoinTask.<RuntimeException>uncheckedThrow(ex);
612	>	}
613	>	}
614	>
615	>	/**
616	>	* The sneaky part of sneaky throw, relying on generics
617	>	* limitations to evade compiler complaints about rethrowing
618	>	* unchecked exceptions
619	>	*/
620	>	@SuppressWarnings("unchecked") static <T extends Throwable>
621	>	void uncheckedThrow(Throwable t) throws T {
622	>	if (t != null)
623	>	throw (T)t; // rely on vacuous cast
624	>	}
625	>
626	>	/**
627	>	* Throws exception, if any, associated with the given status.
628	>	*/
629	>	private void reportException(int s) {
630	>	if (s == CANCELLED)
631	>	throw new CancellationException();
632	>	if (s == EXCEPTIONAL)
633	>	rethrow(getThrowableException());
634		}
635
636		// public methods
637
638		/**
639	<	* Arranges to asynchronously execute this task.  While it is not
640	<	* necessarily enforced, it is a usage error to fork a task more
641	<	* than once unless it has completed and been reinitialized.
642	<	* Subsequent modifications to the state of this task or any data
643	<	* it operates on are not necessarily consistently observable by
644	<	* any thread other than the one executing it unless preceded by a
645	<	* call to {@link #join} or related methods, or a call to {@link
646	<	* #isDone} returning {@code true}.
647	<	*
648	<	* <p>This method may be invoked only from within {@code
649	<	* ForkJoinPool} computations (as may be determined using method
349	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
350	<	* result in exceptions or errors, possibly including {@code
351	<	* ClassCastException}.
639	>	* Arranges to asynchronously execute this task in the pool the
640	>	* current task is running in, if applicable, or using the {@link
641	>	* ForkJoinPool#commonPool()} if not {@link #inForkJoinPool}.  While
642	>	* it is not necessarily enforced, it is a usage error to fork a
643	>	* task more than once unless it has completed and been
644	>	* reinitialized.  Subsequent modifications to the state of this
645	>	* task or any data it operates on are not necessarily
646	>	* consistently observable by any thread other than the one
647	>	* executing it unless preceded by a call to {@link #join} or
648	>	* related methods, or a call to {@link #isDone} returning {@code
649	>	* true}.
650		*
651		* @return {@code this}, to simplify usage
652		*/
653		public final ForkJoinTask<V> fork() {
654	<	((ForkJoinWorkerThread) Thread.currentThread())
655	<	.pushTask(this);
654	>	Thread t;
655	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
656	>	((ForkJoinWorkerThread)t).workQueue.push(this);
657	>	else
658	>	ForkJoinPool.common.externalPush(this);
659		return this;
660		}
661
#	Line 370 | Line 671 | public abstract class ForkJoinTask<V> im
671		* @return the computed result
672		*/
673		public final V join() {
674	<	quietlyJoin();
675	<	Throwable ex;
676	<	if (status < NORMAL && (ex = getException()) != null)
376	<	UNSAFE.throwException(ex);
674	>	int s;
675	>	if ((s = doJoin() & DONE_MASK) != NORMAL)
676	>	reportException(s);
677		return getRawResult();
678		}
679
#	Line 386 | Line 686 | public abstract class ForkJoinTask<V> im
686		* @return the computed result
687		*/
688		public final V invoke() {
689	<	quietlyInvoke();
690	<	Throwable ex;
691	<	if (status < NORMAL && (ex = getException()) != null)
392	<	UNSAFE.throwException(ex);
689	>	int s;
690	>	if ((s = doInvoke() & DONE_MASK) != NORMAL)
691	>	reportException(s);
692		return getRawResult();
693		}
694
#	Line 406 | Line 705 | public abstract class ForkJoinTask<V> im
705		* cancelled, completed normally or exceptionally, or left
706		* unprocessed.
707		*
409	–	* <p>This method may be invoked only from within {@code
410	–	* ForkJoinPool} computations (as may be determined using method
411	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
412	–	* result in exceptions or errors, possibly including {@code
413	–	* ClassCastException}.
414	–	*
708		* @param t1 the first task
709		* @param t2 the second task
710		* @throws NullPointerException if any task is null
711		*/
712		public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
713	+	int s1, s2;
714		t2.fork();
715	<	t1.invoke();
716	<	t2.join();
715	>	if ((s1 = t1.doInvoke() & DONE_MASK) != NORMAL)
716	>	t1.reportException(s1);
717	>	if ((s2 = t2.doJoin() & DONE_MASK) != NORMAL)
718	>	t2.reportException(s2);
719		}
720
721		/**
#	Line 434 | Line 730 | public abstract class ForkJoinTask<V> im
730		* related methods to check if they have been cancelled, completed
731		* normally or exceptionally, or left unprocessed.
732		*
437	–	* <p>This method may be invoked only from within {@code
438	–	* ForkJoinPool} computations (as may be determined using method
439	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
440	–	* result in exceptions or errors, possibly including {@code
441	–	* ClassCastException}.
442	–	*
733		* @param tasks the tasks
734		* @throws NullPointerException if any task is null
735		*/
#	Line 454 | Line 744 | public abstract class ForkJoinTask<V> im
744		}
745		else if (i != 0)
746		t.fork();
747	<	else {
748	<	t.quietlyInvoke();
459	<	if (ex == null && t.status < NORMAL)
460	<	ex = t.getException();
461	<	}
747	>	else if (t.doInvoke() < NORMAL && ex == null)
748	>	ex = t.getException();
749		}
750		for (int i = 1; i <= last; ++i) {
751		ForkJoinTask<?> t = tasks[i];
752		if (t != null) {
753		if (ex != null)
754		t.cancel(false);
755	<	else {
756	<	t.quietlyJoin();
470	<	if (ex == null && t.status < NORMAL)
471	<	ex = t.getException();
472	<	}
755	>	else if (t.doJoin() < NORMAL)
756	>	ex = t.getException();
757		}
758		}
759		if (ex != null)
760	<	UNSAFE.throwException(ex);
760	>	rethrow(ex);
761		}
762
763		/**
#	Line 489 | Line 773 | public abstract class ForkJoinTask<V> im
773		* cancelled, completed normally or exceptionally, or left
774		* unprocessed.
775		*
492	–	* <p>This method may be invoked only from within {@code
493	–	* ForkJoinPool} computations (as may be determined using method
494	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
495	–	* result in exceptions or errors, possibly including {@code
496	–	* ClassCastException}.
497	–	*
776		* @param tasks the collection of tasks
777		* @return the tasks argument, to simplify usage
778		* @throws NullPointerException if tasks or any element are null
#	Line 517 | Line 795 | public abstract class ForkJoinTask<V> im
795		}
796		else if (i != 0)
797		t.fork();
798	<	else {
799	<	t.quietlyInvoke();
522	<	if (ex == null && t.status < NORMAL)
523	<	ex = t.getException();
524	<	}
798	>	else if (t.doInvoke() < NORMAL && ex == null)
799	>	ex = t.getException();
800		}
801		for (int i = 1; i <= last; ++i) {
802		ForkJoinTask<?> t = ts.get(i);
803		if (t != null) {
804		if (ex != null)
805		t.cancel(false);
806	<	else {
807	<	t.quietlyJoin();
533	<	if (ex == null && t.status < NORMAL)
534	<	ex = t.getException();
535	<	}
806	>	else if (t.doJoin() < NORMAL)
807	>	ex = t.getException();
808		}
809		}
810		if (ex != null)
811	<	UNSAFE.throwException(ex);
811	>	rethrow(ex);
812		return tasks;
813		}
814
#	Line 568 | Line 840 | public abstract class ForkJoinTask<V> im
840		* @return {@code true} if this task is now cancelled
841		*/
842		public boolean cancel(boolean mayInterruptIfRunning) {
843	<	setCompletion(CANCELLED);
572	<	return status == CANCELLED;
573	<	}
574	<
575	<	/**
576	<	* Cancels, ignoring any exceptions thrown by cancel. Used during
577	<	* worker and pool shutdown. Cancel is spec'ed not to throw any
578	<	* exceptions, but if it does anyway, we have no recourse during
579	<	* shutdown, so guard against this case.
580	<	*/
581	<	final void cancelIgnoringExceptions() {
582	<	try {
583	<	cancel(false);
584	<	} catch (Throwable ignore) {
585	<	}
586	<	}
587	<
588	<	/**
589	<	* Cancels if current thread is a terminating worker thread,
590	<	* ignoring any exceptions thrown by cancel.
591	<	*/
592	<	final void cancelIfTerminating() {
593	<	Thread t = Thread.currentThread();
594	<	if ((t instanceof ForkJoinWorkerThread) &&
595	<	((ForkJoinWorkerThread) t).isTerminating()) {
596	<	try {
597	<	cancel(false);
598	<	} catch (Throwable ignore) {
599	<	}
600	<	}
843	>	return (setCompletion(CANCELLED) & DONE_MASK) == CANCELLED;
844		}
845
846		public final boolean isDone() {
#	Line 605 | Line 848 | public abstract class ForkJoinTask<V> im
848		}
849
850		public final boolean isCancelled() {
851	<	return status == CANCELLED;
851	>	return (status & DONE_MASK) == CANCELLED;
852		}
853
854		/**
#	Line 625 | Line 868 | public abstract class ForkJoinTask<V> im
868		* exception and was not cancelled
869		*/
870		public final boolean isCompletedNormally() {
871	<	return status == NORMAL;
871	>	return (status & DONE_MASK) == NORMAL;
872		}
873
874		/**
#	Line 636 | Line 879 | public abstract class ForkJoinTask<V> im
879		* @return the exception, or {@code null} if none
880		*/
881		public final Throwable getException() {
882	<	int s = status;
882	>	int s = status & DONE_MASK;
883		return ((s >= NORMAL)    ? null :
884		(s == CANCELLED) ? new CancellationException() :
885	<	exceptionMap.get(this));
885	>	getThrowableException());
886		}
887
888		/**
#	Line 686 | Line 929 | public abstract class ForkJoinTask<V> im
929		}
930
931		/**
932	+	* Completes this task normally without setting a value. The most
933	+	* recent value established by {@link #setRawResult} (or {@code
934	+	* null} by default) will be returned as the result of subsequent
935	+	* invocations of {@code join} and related operations.
936	+	*
937	+	* @since 1.8
938	+	*/
939	+	public final void quietlyComplete() {
940	+	setCompletion(NORMAL);
941	+	}
942	+
943	+	/**
944		* Waits if necessary for the computation to complete, and then
945		* retrieves its result.
946		*
#	Line 697 | Line 952 | public abstract class ForkJoinTask<V> im
952		* member of a ForkJoinPool and was interrupted while waiting
953		*/
954		public final V get() throws InterruptedException, ExecutionException {
955	<	Thread t = Thread.currentThread();
956	<	if (t instanceof ForkJoinWorkerThread)
957	<	quietlyJoin();
958	<	else
959	<	externalInterruptibleAwaitDone(false, 0L);
960	<	int s = status;
961	<	if (s != NORMAL) {
707	<	Throwable ex;
708	<	if (s == CANCELLED)
709	<	throw new CancellationException();
710	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
711	<	throw new ExecutionException(ex);
712	<	}
955	>	int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ?
956	>	doJoin() : externalInterruptibleAwaitDone();
957	>	Throwable ex;
958	>	if ((s &= DONE_MASK) == CANCELLED)
959	>	throw new CancellationException();
960	>	if (s == EXCEPTIONAL && (ex = getThrowableException()) != null)
961	>	throw new ExecutionException(ex);
962		return getRawResult();
963		}
964
#	Line 729 | Line 978 | public abstract class ForkJoinTask<V> im
978		*/
979		public final V get(long timeout, TimeUnit unit)
980		throws InterruptedException, ExecutionException, TimeoutException {
981	<	long nanos = unit.toNanos(timeout);
982	<	Thread t = Thread.currentThread();
983	<	if (t instanceof ForkJoinWorkerThread)
984	<	((ForkJoinWorkerThread)t).joinTask(this, true, nanos);
985	<	else
986	<	externalInterruptibleAwaitDone(true, nanos);
987	<	int s = status;
988	<	if (s != NORMAL) {
981	>	if (Thread.interrupted())
982	>	throw new InterruptedException();
983	>	// Messy in part because we measure in nanosecs, but wait in millisecs
984	>	int s; long ms;
985	>	long ns = unit.toNanos(timeout);
986	>	if ((s = status) >= 0 && ns > 0L) {
987	>	long deadline = System.nanoTime() + ns;
988	>	ForkJoinPool p = null;
989	>	ForkJoinPool.WorkQueue w = null;
990	>	Thread t = Thread.currentThread();
991	>	if (t instanceof ForkJoinWorkerThread) {
992	>	ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
993	>	p = wt.pool;
994	>	w = wt.workQueue;
995	>	p.helpJoinOnce(w, this); // no retries on failure
996	>	}
997	>	else
998	>	ForkJoinPool.externalHelpJoin(this);
999	>	boolean canBlock = false;
1000	>	boolean interrupted = false;
1001	>	try {
1002	>	while ((s = status) >= 0) {
1003	>	if (w != null && w.qlock < 0)
1004	>	cancelIgnoringExceptions(this);
1005	>	else if (!canBlock) {
1006	>	if (p == null || p.tryCompensate())
1007	>	canBlock = true;
1008	>	}
1009	>	else {
1010	>	if ((ms = TimeUnit.NANOSECONDS.toMillis(ns)) > 0L &&
1011	>	U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
1012	>	synchronized (this) {
1013	>	if (status >= 0) {
1014	>	try {
1015	>	wait(ms);
1016	>	} catch (InterruptedException ie) {
1017	>	if (p == null)
1018	>	interrupted = true;
1019	>	}
1020	>	}
1021	>	else
1022	>	notifyAll();
1023	>	}
1024	>	}
1025	>	if ((s = status) < 0 || interrupted ||
1026	>	(ns = deadline - System.nanoTime()) <= 0L)
1027	>	break;
1028	>	}
1029	>	}
1030	>	} finally {
1031	>	if (p != null && canBlock)
1032	>	p.incrementActiveCount();
1033	>	}
1034	>	if (interrupted)
1035	>	throw new InterruptedException();
1036	>	}
1037	>	if ((s &= DONE_MASK) != NORMAL) {
1038		Throwable ex;
1039		if (s == CANCELLED)
1040		throw new CancellationException();
1041	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
1041	>	if (s != EXCEPTIONAL)
1042	>	throw new TimeoutException();
1043	>	if ((ex = getThrowableException()) != null)
1044		throw new ExecutionException(ex);
745	–	throw new TimeoutException();
1045		}
1046		return getRawResult();
1047		}
#	Line 754 | Line 1053 | public abstract class ForkJoinTask<V> im
1053		* known to have aborted.
1054		*/
1055		public final void quietlyJoin() {
1056	<	Thread t;
758	<	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
759	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
760	<	if (status >= 0) {
761	<	if (w.unpushTask(this)) {
762	<	boolean completed;
763	<	try {
764	<	completed = exec();
765	<	} catch (Throwable rex) {
766	<	setExceptionalCompletion(rex);
767	<	return;
768	<	}
769	<	if (completed) {
770	<	setCompletion(NORMAL);
771	<	return;
772	<	}
773	<	}
774	<	w.joinTask(this, false, 0L);
775	<	}
776	<	}
777	<	else
778	<	externalAwaitDone();
1056	>	doJoin();
1057		}
1058
1059		/**
#	Line 784 | Line 1062 | public abstract class ForkJoinTask<V> im
1062		* exception.
1063		*/
1064		public final void quietlyInvoke() {
1065	<	if (status >= 0) {
788	<	boolean completed;
789	<	try {
790	<	completed = exec();
791	<	} catch (Throwable rex) {
792	<	setExceptionalCompletion(rex);
793	<	return;
794	<	}
795	<	if (completed)
796	<	setCompletion(NORMAL);
797	<	else
798	<	quietlyJoin();
799	<	}
1065	>	doInvoke();
1066		}
1067
1068		/**
1069		* Possibly executes tasks until the pool hosting the current task
1070	<	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
1071	<	* be of use in designs in which many tasks are forked, but none
1072	<	* are explicitly joined, instead executing them until all are
1073	<	* processed.
808	<	*
809	<	* <p>This method may be invoked only from within {@code
810	<	* ForkJoinPool} computations (as may be determined using method
811	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
812	<	* result in exceptions or errors, possibly including {@code
813	<	* ClassCastException}.
1070	>	* {@linkplain ForkJoinPool#isQuiescent is quiescent}.  This
1071	>	* method may be of use in designs in which many tasks are forked,
1072	>	* but none are explicitly joined, instead executing them until
1073	>	* all are processed.
1074		*/
1075		public static void helpQuiesce() {
1076	<	((ForkJoinWorkerThread) Thread.currentThread())
1077	<	.helpQuiescePool();
1076	>	Thread t;
1077	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
1078	>	ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
1079	>	wt.pool.helpQuiescePool(wt.workQueue);
1080	>	}
1081	>	else
1082	>	ForkJoinPool.quiesceCommonPool();
1083		}
1084
1085		/**
#	Line 834 | Line 1099 | public abstract class ForkJoinTask<V> im
1099		* setRawResult(null)}.
1100		*/
1101		public void reinitialize() {
1102	<	if (status == EXCEPTIONAL)
1103	<	exceptionMap.remove(this);
1104	<	status = 0;
1102	>	if ((status & DONE_MASK) == EXCEPTIONAL)
1103	>	clearExceptionalCompletion();
1104	>	else
1105	>	status = 0;
1106		}
1107
1108		/**
#	Line 866 | Line 1132 | public abstract class ForkJoinTask<V> im
1132
1133		/**
1134		* Tries to unschedule this task for execution. This method will
1135	<	* typically succeed if this task is the most recently forked task
1136	<	* by the current thread, and has not commenced executing in
1137	<	* another thread.  This method may be useful when arranging
1138	<	* alternative local processing of tasks that could have been, but
1139	<	* were not, stolen.
874	<	*
875	<	* <p>This method may be invoked only from within {@code
876	<	* ForkJoinPool} computations (as may be determined using method
877	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
878	<	* result in exceptions or errors, possibly including {@code
879	<	* ClassCastException}.
1135	>	* typically (but is not guaranteed to) succeed if this task is
1136	>	* the most recently forked task by the current thread, and has
1137	>	* not commenced executing in another thread.  This method may be
1138	>	* useful when arranging alternative local processing of tasks
1139	>	* that could have been, but were not, stolen.
1140		*
1141		* @return {@code true} if unforked
1142		*/
1143		public boolean tryUnfork() {
1144	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1145	<	.unpushTask(this);
1144	>	Thread t;
1145	>	return (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
1146	>	((ForkJoinWorkerThread)t).workQueue.tryUnpush(this) :
1147	>	ForkJoinPool.tryExternalUnpush(this));
1148		}
1149
1150		/**
#	Line 891 | Line 1153 | public abstract class ForkJoinTask<V> im
1153		* value may be useful for heuristic decisions about whether to
1154		* fork other tasks.
1155		*
894	–	* <p>This method may be invoked only from within {@code
895	–	* ForkJoinPool} computations (as may be determined using method
896	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
897	–	* result in exceptions or errors, possibly including {@code
898	–	* ClassCastException}.
899	–	*
1156		* @return the number of tasks
1157		*/
1158		public static int getQueuedTaskCount() {
1159	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1160	<	.getQueueSize();
1159	>	Thread t; ForkJoinPool.WorkQueue q;
1160	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
1161	>	q = ((ForkJoinWorkerThread)t).workQueue;
1162	>	else
1163	>	q = ForkJoinPool.commonSubmitterQueue();
1164	>	return (q == null) ? 0 : q.queueSize();
1165		}
1166
1167		/**
1168		* Returns an estimate of how many more locally queued tasks are
1169		* held by the current worker thread than there are other worker
1170	<	* threads that might steal them.  This value may be useful for
1170	>	* threads that might steal them, or zero if this thread is not
1171	>	* operating in a ForkJoinPool. This value may be useful for
1172		* heuristic decisions about whether to fork other tasks. In many
1173		* usages of ForkJoinTasks, at steady state, each worker should
1174		* aim to maintain a small constant surplus (for example, 3) of
1175		* tasks, and to process computations locally if this threshold is
1176		* exceeded.
1177		*
917	–	* <p>This method may be invoked only from within {@code
918	–	* ForkJoinPool} computations (as may be determined using method
919	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
920	–	* result in exceptions or errors, possibly including {@code
921	–	* ClassCastException}.
922	–	*
1178		* @return the surplus number of tasks, which may be negative
1179		*/
1180		public static int getSurplusQueuedTaskCount() {
1181	<	return ((ForkJoinWorkerThread) Thread.currentThread())
927	<	.getEstimatedSurplusTaskCount();
1181	>	return ForkJoinPool.getSurplusQueuedTaskCount();
1182		}
1183
1184		// Extension methods
#	Line 950 | Line 1204 | public abstract class ForkJoinTask<V> im
1204		protected abstract void setRawResult(V value);
1205
1206		/**
1207	<	* Immediately performs the base action of this task.  This method
1208	<	* is designed to support extensions, and should not in general be
1209	<	* called otherwise. The return value controls whether this task
1210	<	* is considered to be done normally. It may return false in
1207	>	* Immediately performs the base action of this task and returns
1208	>	* true if, upon return from this method, this task is guaranteed
1209	>	* to have completed normally. This method may return false
1210	>	* otherwise, to indicate that this task is not necessarily
1211	>	* complete (or is not known to be complete), for example in
1212		* asynchronous actions that require explicit invocations of
1213	<	* {@link #complete} to become joinable. It may also throw an
1214	<	* (unchecked) exception to indicate abnormal exit.
1213	>	* completion methods. This method may also throw an (unchecked)
1214	>	* exception to indicate abnormal exit. This method is designed to
1215	>	* support extensions, and should not in general be called
1216	>	* otherwise.
1217		*
1218	<	* @return {@code true} if completed normally
1218	>	* @return {@code true} if this task is known to have completed normally
1219		*/
1220		protected abstract boolean exec();
1221
#	Line 972 | Line 1229 | public abstract class ForkJoinTask<V> im
1229		* primarily to support extensions, and is unlikely to be useful
1230		* otherwise.
1231		*
975	–	* <p>This method may be invoked only from within {@code
976	–	* ForkJoinPool} computations (as may be determined using method
977	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
978	–	* result in exceptions or errors, possibly including {@code
979	–	* ClassCastException}.
980	–	*
1232		* @return the next task, or {@code null} if none are available
1233		*/
1234		protected static ForkJoinTask<?> peekNextLocalTask() {
1235	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1236	<	.peekTask();
1235	>	Thread t; ForkJoinPool.WorkQueue q;
1236	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
1237	>	q = ((ForkJoinWorkerThread)t).workQueue;
1238	>	else
1239	>	q = ForkJoinPool.commonSubmitterQueue();
1240	>	return (q == null) ? null : q.peek();
1241		}
1242
1243		/**
1244		* Unschedules and returns, without executing, the next task
1245	<	* queued by the current thread but not yet executed.  This method
1246	<	* is designed primarily to support extensions, and is unlikely to
1247	<	* be useful otherwise.
1248	<	*
994	<	* <p>This method may be invoked only from within {@code
995	<	* ForkJoinPool} computations (as may be determined using method
996	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
997	<	* result in exceptions or errors, possibly including {@code
998	<	* ClassCastException}.
1245	>	* queued by the current thread but not yet executed, if the
1246	>	* current thread is operating in a ForkJoinPool.  This method is
1247	>	* designed primarily to support extensions, and is unlikely to be
1248	>	* useful otherwise.
1249		*
1250		* @return the next task, or {@code null} if none are available
1251		*/
1252		protected static ForkJoinTask<?> pollNextLocalTask() {
1253	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1254	<	.pollLocalTask();
1253	>	Thread t;
1254	>	return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
1255	>	((ForkJoinWorkerThread)t).workQueue.nextLocalTask() :
1256	>	null;
1257		}
1258
1259		/**
1260	<	* Unschedules and returns, without executing, the next task
1260	>	* If the current thread is operating in a ForkJoinPool,
1261	>	* unschedules and returns, without executing, the next task
1262		* queued by the current thread but not yet executed, if one is
1263		* available, or if not available, a task that was forked by some
1264		* other thread, if available. Availability may be transient, so a
1265	<	* {@code null} result does not necessarily imply quiescence
1266	<	* of the pool this task is operating in.  This method is designed
1265	>	* {@code null} result does not necessarily imply quiescence of
1266	>	* the pool this task is operating in.  This method is designed
1267		* primarily to support extensions, and is unlikely to be useful
1268		* otherwise.
1269		*
1017	–	* <p>This method may be invoked only from within {@code
1018	–	* ForkJoinPool} computations (as may be determined using method
1019	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1020	–	* result in exceptions or errors, possibly including {@code
1021	–	* ClassCastException}.
1022	–	*
1270		* @return a task, or {@code null} if none are available
1271		*/
1272		protected static ForkJoinTask<?> pollTask() {
1273	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1274	<	.pollTask();
1273	>	Thread t; ForkJoinWorkerThread wt;
1274	>	return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
1275	>	(wt = (ForkJoinWorkerThread)t).pool.nextTaskFor(wt.workQueue) :
1276	>	null;
1277	>	}
1278	>
1279	>	// tag operations
1280	>
1281	>	/**
1282	>	* Returns the tag for this task.
1283	>	*
1284	>	* @return the tag for this task
1285	>	* @since 1.8
1286	>	*/
1287	>	public final short getForkJoinTaskTag() {
1288	>	return (short)status;
1289	>	}
1290	>
1291	>	/**
1292	>	* Atomically sets the tag value for this task.
1293	>	*
1294	>	* @param tag the tag value
1295	>	* @return the previous value of the tag
1296	>	* @since 1.8
1297	>	*/
1298	>	public final short setForkJoinTaskTag(short tag) {
1299	>	for (int s;;) {
1300	>	if (U.compareAndSwapInt(this, STATUS, s = status,
1301	>	(s & ~SMASK) | (tag & SMASK)))
1302	>	return (short)s;
1303	>	}
1304	>	}
1305	>
1306	>	/**
1307	>	* Atomically conditionally sets the tag value for this task.
1308	>	* Among other applications, tags can be used as visit markers
1309	>	* in tasks operating on graphs, as in methods that check: {@code
1310	>	* if (task.compareAndSetForkJoinTaskTag((short)0, (short)1))}
1311	>	* before processing, otherwise exiting because the node has
1312	>	* already been visited.
1313	>	*
1314	>	* @param e the expected tag value
1315	>	* @param tag the new tag value
1316	>	* @return true if successful; i.e., the current value was
1317	>	* equal to e and is now tag.
1318	>	* @since 1.8
1319	>	*/
1320	>	public final boolean compareAndSetForkJoinTaskTag(short e, short tag) {
1321	>	for (int s;;) {
1322	>	if ((short)(s = status) != e)
1323	>	return false;
1324	>	if (U.compareAndSwapInt(this, STATUS, s,
1325	>	(s & ~SMASK) | (tag & SMASK)))
1326	>	return true;
1327	>	}
1328		}
1329
1330		/**
1331	<	* Adaptor for Runnables. This implements RunnableFuture
1331	>	* Adapter for Runnables. This implements RunnableFuture
1332		* to be compliant with AbstractExecutorService constraints
1333		* when used in ForkJoinPool.
1334		*/
1335		static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1336		implements RunnableFuture<T> {
1337		final Runnable runnable;
1038	–	final T resultOnCompletion;
1338		T result;
1339		AdaptedRunnable(Runnable runnable, T result) {
1340		if (runnable == null) throw new NullPointerException();
1341		this.runnable = runnable;
1342	<	this.resultOnCompletion = result;
1342	>	this.result = result; // OK to set this even before completion
1343		}
1344	<	public T getRawResult() { return result; }
1345	<	public void setRawResult(T v) { result = v; }
1346	<	public boolean exec() {
1347	<	runnable.run();
1348	<	result = resultOnCompletion;
1349	<	return true;
1344	>	public final T getRawResult() { return result; }
1345	>	public final void setRawResult(T v) { result = v; }
1346	>	public final boolean exec() { runnable.run(); return true; }
1347	>	public final void run() { invoke(); }
1348	>	private static final long serialVersionUID = 5232453952276885070L;
1349	>	}
1350	>
1351	>	/**
1352	>	* Adapter for Runnables without results
1353	>	*/
1354	>	static final class AdaptedRunnableAction extends ForkJoinTask<Void>
1355	>	implements RunnableFuture<Void> {
1356	>	final Runnable runnable;
1357	>	AdaptedRunnableAction(Runnable runnable) {
1358	>	if (runnable == null) throw new NullPointerException();
1359	>	this.runnable = runnable;
1360		}
1361	<	public void run() { invoke(); }
1361	>	public final Void getRawResult() { return null; }
1362	>	public final void setRawResult(Void v) { }
1363	>	public final boolean exec() { runnable.run(); return true; }
1364	>	public final void run() { invoke(); }
1365		private static final long serialVersionUID = 5232453952276885070L;
1366		}
1367
1368		/**
1369	<	* Adaptor for Callables
1369	>	* Adapter for Callables
1370		*/
1371		static final class AdaptedCallable<T> extends ForkJoinTask<T>
1372		implements RunnableFuture<T> {
#	Line 1064 | Line 1376 | public abstract class ForkJoinTask<V> im
1376		if (callable == null) throw new NullPointerException();
1377		this.callable = callable;
1378		}
1379	<	public T getRawResult() { return result; }
1380	<	public void setRawResult(T v) { result = v; }
1381	<	public boolean exec() {
1379	>	public final T getRawResult() { return result; }
1380	>	public final void setRawResult(T v) { result = v; }
1381	>	public final boolean exec() {
1382		try {
1383		result = callable.call();
1384		return true;
#	Line 1078 | Line 1390 | public abstract class ForkJoinTask<V> im
1390		throw new RuntimeException(ex);
1391		}
1392		}
1393	<	public void run() { invoke(); }
1393	>	public final void run() { invoke(); }
1394		private static final long serialVersionUID = 2838392045355241008L;
1395		}
1396
#	Line 1091 | Line 1403 | public abstract class ForkJoinTask<V> im
1403		* @return the task
1404		*/
1405		public static ForkJoinTask<?> adapt(Runnable runnable) {
1406	<	return new AdaptedRunnable<Void>(runnable, null);
1406	>	return new AdaptedRunnableAction(runnable);
1407		}
1408
1409		/**
#	Line 1125 | Line 1437 | public abstract class ForkJoinTask<V> im
1437		private static final long serialVersionUID = -7721805057305804111L;
1438
1439		/**
1440	<	* Saves the state to a stream (that is, serializes it).
1440	>	* Saves this task to a stream (that is, serializes it).
1441		*
1442		* @serialData the current run status and the exception thrown
1443		* during execution, or {@code null} if none
1132	–	* @param s the stream
1444		*/
1445		private void writeObject(java.io.ObjectOutputStream s)
1446		throws java.io.IOException {
#	Line 1138 | Line 1449 | public abstract class ForkJoinTask<V> im
1449		}
1450
1451		/**
1452	<	* Reconstitutes the instance from a stream (that is, deserializes it).
1142	<	*
1143	<	* @param s the stream
1452	>	* Reconstitutes this task from a stream (that is, deserializes it).
1453		*/
1454		private void readObject(java.io.ObjectInputStream s)
1455		throws java.io.IOException, ClassNotFoundException {
1456		s.defaultReadObject();
1457		Object ex = s.readObject();
1458		if (ex != null)
1459	<	setExceptionalCompletion((Throwable) ex);
1459	>	setExceptionalCompletion((Throwable)ex);
1460		}
1461
1462		// Unsafe mechanics
1463	+	private static final sun.misc.Unsafe U;
1464	+	private static final long STATUS;
1465
1466	<	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1467	<	private static final long statusOffset =
1468	<	objectFieldOffset("status", ForkJoinTask.class);
1469	<
1159	<	private static long objectFieldOffset(String field, Class<?> klazz) {
1466	>	static {
1467	>	exceptionTableLock = new ReentrantLock();
1468	>	exceptionTableRefQueue = new ReferenceQueue<Object>();
1469	>	exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY];
1470		try {
1471	<	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1472	<	} catch (NoSuchFieldException e) {
1473	<	// Convert Exception to corresponding Error
1474	<	NoSuchFieldError error = new NoSuchFieldError(field);
1475	<	error.initCause(e);
1476	<	throw error;
1471	>	U = getUnsafe();
1472	>	Class<?> k = ForkJoinTask.class;
1473	>	STATUS = U.objectFieldOffset
1474	>	(k.getDeclaredField("status"));
1475	>	} catch (Exception e) {
1476	>	throw new Error(e);
1477		}
1478		}
1479
#	Line 1177 | Line 1487 | public abstract class ForkJoinTask<V> im
1487		private static sun.misc.Unsafe getUnsafe() {
1488		try {
1489		return sun.misc.Unsafe.getUnsafe();
1490	<	} catch (SecurityException se) {
1491	<	try {
1492	<	return java.security.AccessController.doPrivileged
1493	<	(new java.security
1494	<	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1495	<	public sun.misc.Unsafe run() throws Exception {
1496	<	java.lang.reflect.Field f = sun.misc
1497	<	.Unsafe.class.getDeclaredField("theUnsafe");
1498	<	f.setAccessible(true);
1499	<	return (sun.misc.Unsafe) f.get(null);
1500	<	}});
1501	<	} catch (java.security.PrivilegedActionException e) {
1502	<	throw new RuntimeException("Could not initialize intrinsics",
1503	<	e.getCause());
1504	<	}
1490	>	} catch (SecurityException tryReflectionInstead) {}
1491	>	try {
1492	>	return java.security.AccessController.doPrivileged
1493	>	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1494	>	public sun.misc.Unsafe run() throws Exception {
1495	>	Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class;
1496	>	for (java.lang.reflect.Field f : k.getDeclaredFields()) {
1497	>	f.setAccessible(true);
1498	>	Object x = f.get(null);
1499	>	if (k.isInstance(x))
1500	>	return k.cast(x);
1501	>	}
1502	>	throw new NoSuchFieldError("the Unsafe");
1503	>	}});
1504	>	} catch (java.security.PrivilegedActionException e) {
1505	>	throw new RuntimeException("Could not initialize intrinsics",
1506	>	e.getCause());
1507		}
1508		}
1509		}

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