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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.67 by dl, Sun Nov 21 14:43:27 2010 UTC vs.
Revision 1.92 by dl, Wed Oct 31 12:49:24 2012 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Doug Lea with assistance from members of JCP JSR-166
3		* Expert Group and released to the public domain, as explained at
4	<	* http://creativecommons.org/licenses/publicdomain
4	>	* http://creativecommons.org/publicdomain/zero/1.0/
5		*/
6
7		package jsr166y;
8
9		import java.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 IO, 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 IO. 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
130	<	* methods), some of them may only be called from within other
131	<	* ForkJoinTasks (as may be determined using method {@link
132	<	* #inForkJoinPool}).  Attempts to invoke them in other contexts
133	<	* result in exceptions or errors, possibly including
134	<	* {@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
133	>	* parallel computation can be described as a directed acyclic graph
134	>	* (DAG). Otherwise, executions may encounter a form of deadlock as
135	>	* tasks cyclically wait for each other.  However, this framework
136	>	* supports other methods and techniques (for example the use of
137	>	* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that
138	>	* may be of use in constructing custom subclasses for problems that
139	>	* are not statically structured as DAGs. To support such usages a
140	>	* ForkJoinTask may be atomically <em>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 124 | Line 162 | import java.util.concurrent.TimeoutExcep
162		* computation. Large tasks should be split into smaller subtasks,
163		* usually via recursive decomposition. As a very rough rule of thumb,
164		* a task should perform more than 100 and less than 10000 basic
165	<	* computational steps. If tasks are too big, then parallelism cannot
166	<	* improve throughput. If too small, then memory and internal task
167	<	* maintenance overhead may overwhelm processing.
165	>	* computational steps, and should avoid indefinite looping. If tasks
166	>	* are too big, then parallelism cannot improve throughput. If too
167	>	* small, then memory and internal task maintenance overhead may
168	>	* overwhelm processing.
169		*
170		* <p>This class provides {@code adapt} methods for {@link Runnable}
171		* and {@link Callable}, that may be of use when mixing execution of
#	Line 147 | 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	>	boolean interrupted = false;
289	>	if ((s = status) >= 0 && ForkJoinPool.tryUnsubmitFromCommonPool(this))
290	>	s = doExec();
291	>	while (s >= 0) {
292	>	if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
293	>	synchronized (this) {
294	>	if (status >= 0) {
295	>	try {
296	>	wait();
297	>	} catch (InterruptedException ie) {
298	>	interrupted = true;
299	>	}
300	>	}
301	>	else
302	>	notifyAll();
303	>	}
304	>	}
305	>	s = status;
306	>	}
307	>	if (interrupted)
308	>	Thread.currentThread().interrupt();
309	>	return s;
310	>	}
311	>
312	>	/**
313	>	* Blocks a non-worker-thread until completion or interruption.
314	>	*/
315	>	private int externalInterruptibleAwaitDone() throws InterruptedException {
316	>	if (Thread.interrupted())
317	>	throw new InterruptedException();
318	>	int s;
319	>	if ((s = status) >= 0 && ForkJoinPool.tryUnsubmitFromCommonPool(this))
320	>	s = doExec();
321	>	while (s >= 0) {
322	>	if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
323	>	synchronized (this) {
324	>	if (status >= 0)
325	>	wait();
326	>	else
327	>	notifyAll();
328	>	}
329	>	}
330	>	s = status;
331	>	}
332	>	return s;
333	>	}
334	>
335	>	/**
336	>	* Implementation for join, get, quietlyJoin. Directly handles
337	>	* only cases of already-completed, external wait, and
338	>	* unfork+exec.  Others are relayed to ForkJoinPool.awaitJoin.
339	>	*
340	>	* @return status upon completion
341	>	*/
342	>	private int doJoin() {
343	>	int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w;
344	>	return (s = status) < 0 ? s :
345	>	((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
346	>	(w = (wt = (ForkJoinWorkerThread)t).workQueue).
347	>	tryUnpush(this) && (s = doExec()) < 0 ? s :
348	>	wt.pool.awaitJoin(w, this) :
349	>	externalAwaitDone();
350	>	}
351	>
352	>	/**
353	>	* Implementation for invoke, quietlyInvoke.
354	>	*
355	>	* @return status upon completion
356	>	*/
357	>	private int doInvoke() {
358	>	int s; Thread t; ForkJoinWorkerThread wt;
359	>	return (s = doExec()) < 0 ? s :
360	>	((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
361	>	(wt = (ForkJoinWorkerThread)t).pool.awaitJoin(wt.workQueue, this) :
362	>	externalAwaitDone();
363	>	}
364	>
365	>	// Exception table support
366
367		/**
368		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 187 | Line 370 | public abstract class ForkJoinTask<V> im
370		* them with task objects, but instead use a weak ref table.  Note
371		* that cancellation exceptions don't appear in the table, but are
372		* instead recorded as status values.
373	<	* TODO: Use ConcurrentReferenceHashMap
373	>	*
374	>	* Note: These statics are initialized below in static block.
375		*/
376	<	static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
377	<	Collections.synchronizedMap
378	<	(new WeakHashMap<ForkJoinTask<?>, Throwable>());
376	>	private static final ExceptionNode[] exceptionTable;
377	>	private static final ReentrantLock exceptionTableLock;
378	>	private static final ReferenceQueue<Object> exceptionTableRefQueue;
379
380	<	// Maintaining completion status
380	>	/**
381	>	* Fixed capacity for exceptionTable.
382	>	*/
383	>	private static final int EXCEPTION_MAP_CAPACITY = 32;
384
385		/**
386	<	* Marks completion and wakes up threads waiting to join this task,
387	<	* also clearing signal request bits.
386	>	* Key-value nodes for exception table.  The chained hash table
387	>	* uses identity comparisons, full locking, and weak references
388	>	* for keys. The table has a fixed capacity because it only
389	>	* maintains task exceptions long enough for joiners to access
390	>	* them, so should never become very large for sustained
391	>	* periods. However, since we do not know when the last joiner
392	>	* completes, we must use weak references and expunge them. We do
393	>	* so on each operation (hence full locking). Also, some thread in
394	>	* any ForkJoinPool will call helpExpungeStaleExceptions when its
395	>	* pool becomes isQuiescent.
396	>	*/
397	>	static final class ExceptionNode extends WeakReference<ForkJoinTask<?>> {
398	>	final Throwable ex;
399	>	ExceptionNode next;
400	>	final long thrower;  // use id not ref to avoid weak cycles
401	>	ExceptionNode(ForkJoinTask<?> task, Throwable ex, ExceptionNode next) {
402	>	super(task, exceptionTableRefQueue);
403	>	this.ex = ex;
404	>	this.next = next;
405	>	this.thrower = Thread.currentThread().getId();
406	>	}
407	>	}
408	>
409	>	/**
410	>	* Records exception and sets status.
411		*
412	<	* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
412	>	* @return status on exit
413		*/
414	<	private void setCompletion(int completion) {
414	>	final int recordExceptionalCompletion(Throwable ex) {
415		int s;
416	<	while ((s = status) >= 0) {
417	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
418	<	if (s != 0)
419	<	synchronized (this) { notifyAll(); }
420	<	break;
416	>	if ((s = status) >= 0) {
417	>	int h = System.identityHashCode(this);
418	>	final ReentrantLock lock = exceptionTableLock;
419	>	lock.lock();
420	>	try {
421	>	expungeStaleExceptions();
422	>	ExceptionNode[] t = exceptionTable;
423	>	int i = h & (t.length - 1);
424	>	for (ExceptionNode e = t[i]; ; e = e.next) {
425	>	if (e == null) {
426	>	t[i] = new ExceptionNode(this, ex, t[i]);
427	>	break;
428	>	}
429	>	if (e.get() == this) // already present
430	>	break;
431	>	}
432	>	} finally {
433	>	lock.unlock();
434		}
435	+	s = setCompletion(EXCEPTIONAL);
436		}
437	+	return s;
438		}
439
440		/**
441	<	* Records exception and sets exceptional completion.
441	>	* Records exception and possibly propagates
442		*
443		* @return status on exit
444		*/
445	<	private void setExceptionalCompletion(Throwable rex) {
446	<	exceptionMap.put(this, rex);
447	<	setCompletion(EXCEPTIONAL);
445	>	private int setExceptionalCompletion(Throwable ex) {
446	>	int s = recordExceptionalCompletion(ex);
447	>	if ((s & DONE_MASK) == EXCEPTIONAL)
448	>	internalPropagateException(ex);
449	>	return s;
450		}
451
452		/**
453	<	* Blocks a worker thread until completion. Called only by
227	<	* pool. Currently unused -- pool-based waits use timeout
228	<	* version below.
453	>	* Hook for exception propagation support for tasks with completers.
454		*/
455	<	final void internalAwaitDone() {
456	<	int s;         // the odd construction reduces lock bias effects
457	<	while ((s = status) >= 0) {
455	>	void internalPropagateException(Throwable ex) {
456	>	}
457	>
458	>	/**
459	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
460	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
461	>	* exceptions, but if it does anyway, we have no recourse during
462	>	* shutdown, so guard against this case.
463	>	*/
464	>	static final void cancelIgnoringExceptions(ForkJoinTask<?> t) {
465	>	if (t != null && t.status >= 0) {
466		try {
467	<	synchronized (this) {
468	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
236	<	wait();
237	<	}
238	<	} catch (InterruptedException ie) {
239	<	cancelIfTerminating();
467	>	t.cancel(false);
468	>	} catch (Throwable ignore) {
469		}
470		}
471		}
472
473		/**
474	<	* Blocks a worker thread until completed or timed out.  Called
246	<	* only by pool.
247	<	*
248	<	* @return status on exit
474	>	* Removes exception node and clears status
475		*/
476	<	final int internalAwaitDone(long millis, int nanos) {
477	<	int s;
478	<	if ((s = status) >= 0) {
476	>	private void clearExceptionalCompletion() {
477	>	int h = System.identityHashCode(this);
478	>	final ReentrantLock lock = exceptionTableLock;
479	>	lock.lock();
480	>	try {
481	>	ExceptionNode[] t = exceptionTable;
482	>	int i = h & (t.length - 1);
483	>	ExceptionNode e = t[i];
484	>	ExceptionNode pred = null;
485	>	while (e != null) {
486	>	ExceptionNode next = e.next;
487	>	if (e.get() == this) {
488	>	if (pred == null)
489	>	t[i] = next;
490	>	else
491	>	pred.next = next;
492	>	break;
493	>	}
494	>	pred = e;
495	>	e = next;
496	>	}
497	>	expungeStaleExceptions();
498	>	status = 0;
499	>	} finally {
500	>	lock.unlock();
501	>	}
502	>	}
503	>
504	>	/**
505	>	* Returns a rethrowable exception for the given task, if
506	>	* available. To provide accurate stack traces, if the exception
507	>	* was not thrown by the current thread, we try to create a new
508	>	* exception of the same type as the one thrown, but with the
509	>	* recorded exception as its cause. If there is no such
510	>	* constructor, we instead try to use a no-arg constructor,
511	>	* followed by initCause, to the same effect. If none of these
512	>	* apply, or any fail due to other exceptions, we return the
513	>	* recorded exception, which is still correct, although it may
514	>	* contain a misleading stack trace.
515	>	*
516	>	* @return the exception, or null if none
517	>	*/
518	>	private Throwable getThrowableException() {
519	>	if ((status & DONE_MASK) != EXCEPTIONAL)
520	>	return null;
521	>	int h = System.identityHashCode(this);
522	>	ExceptionNode e;
523	>	final ReentrantLock lock = exceptionTableLock;
524	>	lock.lock();
525	>	try {
526	>	expungeStaleExceptions();
527	>	ExceptionNode[] t = exceptionTable;
528	>	e = t[h & (t.length - 1)];
529	>	while (e != null && e.get() != this)
530	>	e = e.next;
531	>	} finally {
532	>	lock.unlock();
533	>	}
534	>	Throwable ex;
535	>	if (e == null || (ex = e.ex) == null)
536	>	return null;
537	>	if (false && e.thrower != Thread.currentThread().getId()) {
538	>	Class<? extends Throwable> ec = ex.getClass();
539		try {
540	<	synchronized (this) {
541	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
542	<	wait(millis, nanos);
540	>	Constructor<?> noArgCtor = null;
541	>	Constructor<?>[] cs = ec.getConstructors();// public ctors only
542	>	for (int i = 0; i < cs.length; ++i) {
543	>	Constructor<?> c = cs[i];
544	>	Class<?>[] ps = c.getParameterTypes();
545	>	if (ps.length == 0)
546	>	noArgCtor = c;
547	>	else if (ps.length == 1 && ps[0] == Throwable.class)
548	>	return (Throwable)(c.newInstance(ex));
549	>	}
550	>	if (noArgCtor != null) {
551	>	Throwable wx = (Throwable)(noArgCtor.newInstance());
552	>	wx.initCause(ex);
553	>	return wx;
554		}
555	<	} catch (InterruptedException ie) {
259	<	cancelIfTerminating();
555	>	} catch (Exception ignore) {
556		}
261	–	s = status;
557		}
558	<	return s;
558	>	return ex;
559		}
560
561		/**
562	<	* Blocks a non-worker-thread until completion.
562	>	* Poll stale refs and remove them. Call only while holding lock.
563		*/
564	<	private void externalAwaitDone() {
565	<	int s;
566	<	while ((s = status) >= 0) {
567	<	synchronized (this) {
568	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
569	<	boolean interrupted = false;
570	<	while (status >= 0) {
571	<	try {
572	<	wait();
573	<	} catch (InterruptedException ie) {
574	<	interrupted = true;
575	<	}
564	>	private static void expungeStaleExceptions() {
565	>	for (Object x; (x = exceptionTableRefQueue.poll()) != null;) {
566	>	if (x instanceof ExceptionNode) {
567	>	ForkJoinTask<?> key = ((ExceptionNode)x).get();
568	>	ExceptionNode[] t = exceptionTable;
569	>	int i = System.identityHashCode(key) & (t.length - 1);
570	>	ExceptionNode e = t[i];
571	>	ExceptionNode pred = null;
572	>	while (e != null) {
573	>	ExceptionNode next = e.next;
574	>	if (e == x) {
575	>	if (pred == null)
576	>	t[i] = next;
577	>	else
578	>	pred.next = next;
579	>	break;
580		}
581	<	if (interrupted)
582	<	Thread.currentThread().interrupt();
284	<	break;
581	>	pred = e;
582	>	e = next;
583		}
584		}
585		}
586		}
587
588		/**
589	<	* Unless done, calls exec and records status if completed, but
590	<	* doesn't wait for completion otherwise. Primary execution method
293	<	* for ForkJoinWorkerThread.
589	>	* If lock is available, poll stale refs and remove them.
590	>	* Called from ForkJoinPool when pools become quiescent.
591		*/
592	<	final void quietlyExec() {
593	<	try {
594	<	if (status < 0 || !exec())
595	<	return;
596	<	} catch (Throwable rex) {
597	<	setExceptionalCompletion(rex);
598	<	return;
592	>	static final void helpExpungeStaleExceptions() {
593	>	final ReentrantLock lock = exceptionTableLock;
594	>	if (lock.tryLock()) {
595	>	try {
596	>	expungeStaleExceptions();
597	>	} finally {
598	>	lock.unlock();
599	>	}
600	>	}
601	>	}
602	>
603	>	/**
604	>	* A version of "sneaky throw" to relay exceptions
605	>	*/
606	>	static void rethrow(final Throwable ex) {
607	>	if (ex != null) {
608	>	if (ex instanceof Error)
609	>	throw (Error)ex;
610	>	if (ex instanceof RuntimeException)
611	>	throw (RuntimeException)ex;
612	>	throw uncheckedThrowable(ex, RuntimeException.class);
613		}
614	<	setCompletion(NORMAL); // must be outside try block
614	>	}
615	>
616	>	/**
617	>	* The sneaky part of sneaky throw, relying on generics
618	>	* limitations to evade compiler complaints about rethrowing
619	>	* unchecked exceptions
620	>	*/
621	>	@SuppressWarnings("unchecked") static <T extends Throwable>
622	>	T uncheckedThrowable(final Throwable t, final Class<T> c) {
623	>	return (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	<	* ForkJoinTask} computations (as may be determined using method
320	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
321	<	* result in exceptions or errors, possibly including {@code
322	<	* 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.submitToCommonPool(this);
659		return this;
660		}
661
662		/**
663	<	* Returns the result of the computation when it {@link #isDone is done}.
664	<	* This method differs from {@link #get()} in that
663	>	* Returns the result of the computation when it {@link #isDone is
664	>	* done}.  This method differs from {@link #get()} in that
665		* abnormal completion results in {@code RuntimeException} or
666	<	* {@code Error}, not {@code ExecutionException}.
666	>	* {@code Error}, not {@code ExecutionException}, and that
667	>	* interrupts of the calling thread do <em>not</em> cause the
668	>	* method to abruptly return by throwing {@code
669	>	* InterruptedException}.
670		*
671		* @return the computed result
672		*/
673		public final V join() {
674	<	quietlyJoin();
675	<	Throwable ex;
676	<	if (status < NORMAL && (ex = getException()) != null)
344	<	UNSAFE.throwException(ex);
674	>	int s;
675	>	if ((s = doJoin() & DONE_MASK) != NORMAL)
676	>	reportException(s);
677		return getRawResult();
678		}
679
#	Line 354 | 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)
360	<	UNSAFE.throwException(ex);
689	>	int s;
690	>	if ((s = doInvoke() & DONE_MASK) != NORMAL)
691	>	reportException(s);
692		return getRawResult();
693		}
694
#	Line 374 | Line 705 | public abstract class ForkJoinTask<V> im
705		* cancelled, completed normally or exceptionally, or left
706		* unprocessed.
707		*
377	–	* <p>This method may be invoked only from within {@code
378	–	* ForkJoinTask} computations (as may be determined using method
379	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
380	–	* result in exceptions or errors, possibly including {@code
381	–	* ClassCastException}.
382	–	*
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 402 | 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		*
405	–	* <p>This method may be invoked only from within {@code
406	–	* ForkJoinTask} computations (as may be determined using method
407	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
408	–	* result in exceptions or errors, possibly including {@code
409	–	* ClassCastException}.
410	–	*
733		* @param tasks the tasks
734		* @throws NullPointerException if any task is null
735		*/
#	Line 422 | Line 744 | public abstract class ForkJoinTask<V> im
744		}
745		else if (i != 0)
746		t.fork();
747	<	else {
748	<	t.quietlyInvoke();
427	<	if (ex == null && t.status < NORMAL)
428	<	ex = t.getException();
429	<	}
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();
438	<	if (ex == null && t.status < NORMAL)
439	<	ex = t.getException();
440	<	}
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 457 | Line 773 | public abstract class ForkJoinTask<V> im
773		* cancelled, completed normally or exceptionally, or left
774		* unprocessed.
775		*
460	–	* <p>This method may be invoked only from within {@code
461	–	* ForkJoinTask} computations (as may be determined using method
462	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
463	–	* result in exceptions or errors, possibly including {@code
464	–	* ClassCastException}.
465	–	*
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 485 | Line 795 | public abstract class ForkJoinTask<V> im
795		}
796		else if (i != 0)
797		t.fork();
798	<	else {
799	<	t.quietlyInvoke();
490	<	if (ex == null && t.status < NORMAL)
491	<	ex = t.getException();
492	<	}
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();
501	<	if (ex == null && t.status < NORMAL)
502	<	ex = t.getException();
503	<	}
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
815		/**
816		* Attempts to cancel execution of this task. This attempt will
817	<	* fail if the task has already completed, has already been
818	<	* cancelled, or could not be cancelled for some other reason. If
819	<	* successful, and this task has not started when cancel is
820	<	* called, execution of this task is suppressed, {@link
821	<	* #isCancelled} will report true, and {@link #join} will result
822	<	* in a {@code CancellationException} being thrown.
817	>	* fail if the task has already completed or could not be
818	>	* cancelled for some other reason. If successful, and this task
819	>	* has not started when {@code cancel} is called, execution of
820	>	* this task is suppressed. After this method returns
821	>	* successfully, unless there is an intervening call to {@link
822	>	* #reinitialize}, subsequent calls to {@link #isCancelled},
823	>	* {@link #isDone}, and {@code cancel} will return {@code true}
824	>	* and calls to {@link #join} and related methods will result in
825	>	* {@code CancellationException}.
826		*
827		* <p>This method may be overridden in subclasses, but if so, must
828	<	* still ensure that these minimal properties hold. In particular,
829	<	* the {@code cancel} method itself must not throw exceptions.
828	>	* still ensure that these properties hold. In particular, the
829	>	* {@code cancel} method itself must not throw exceptions.
830		*
831		* <p>This method is designed to be invoked by <em>other</em>
832		* tasks. To terminate the current task, you can just return or
833		* throw an unchecked exception from its computation method, or
834		* invoke {@link #completeExceptionally}.
835		*
836	<	* @param mayInterruptIfRunning this value is ignored in the
837	<	* default implementation because tasks are not
838	<	* cancelled via interruption
836	>	* @param mayInterruptIfRunning this value has no effect in the
837	>	* default implementation because interrupts are not used to
838	>	* control cancellation.
839		*
840		* @return {@code true} if this task is now cancelled
841		*/
842		public boolean cancel(boolean mayInterruptIfRunning) {
843	<	setCompletion(CANCELLED);
537	<	return status == CANCELLED;
538	<	}
539	<
540	<	/**
541	<	* Cancels, ignoring any exceptions thrown by cancel. Used during
542	<	* worker and pool shutdown. Cancel is spec'ed not to throw any
543	<	* exceptions, but if it does anyway, we have no recourse during
544	<	* shutdown, so guard against this case.
545	<	*/
546	<	final void cancelIgnoringExceptions() {
547	<	try {
548	<	cancel(false);
549	<	} catch (Throwable ignore) {
550	<	}
551	<	}
552	<
553	<	/**
554	<	* Cancels if current thread is a terminating worker thread,
555	<	* ignoring any exceptions thrown by cancel.
556	<	*/
557	<	final void cancelIfTerminating() {
558	<	Thread t = Thread.currentThread();
559	<	if ((t instanceof ForkJoinWorkerThread) &&
560	<	((ForkJoinWorkerThread) t).isTerminating()) {
561	<	try {
562	<	cancel(false);
563	<	} catch (Throwable ignore) {
564	<	}
565	<	}
843	>	return (setCompletion(CANCELLED) & DONE_MASK) == CANCELLED;
844		}
845
846		public final boolean isDone() {
#	Line 570 | 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 590 | 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 601 | 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 651 | 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 662 | 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	<	int s;
956	<	if (Thread.currentThread() instanceof ForkJoinWorkerThread) {
957	<	quietlyJoin();
958	<	s = status;
959	<	}
960	<	else {
961	<	while ((s = status) >= 0) {
672	<	synchronized (this) { // interruptible form of awaitDone
673	<	if (UNSAFE.compareAndSwapInt(this, statusOffset,
674	<	s, SIGNAL)) {
675	<	while (status >= 0)
676	<	wait();
677	<	}
678	<	}
679	<	}
680	<	}
681	<	if (s < NORMAL) {
682	<	Throwable ex;
683	<	if (s == CANCELLED)
684	<	throw new CancellationException();
685	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
686	<	throw new ExecutionException(ex);
687	<	}
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 704 | 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	<	if (status >= 0) {
981	>	if (Thread.interrupted())
982	>	throw new InterruptedException();
983	>	// Messy in part because we measure in nanosecs, but wait in millisecs
984	>	int s; long ns, ms;
985	>	if ((s = status) >= 0 && (ns = unit.toNanos(timeout)) > 0L) {
986	>	long deadline = System.nanoTime() + ns;
987	>	ForkJoinPool p = null;
988	>	ForkJoinPool.WorkQueue w = null;
989		Thread t = Thread.currentThread();
990		if (t instanceof ForkJoinWorkerThread) {
991	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
992	<	boolean completed = false; // timed variant of quietlyJoin
993	<	if (w.unpushTask(this)) {
994	<	try {
715	<	completed = exec();
716	<	} catch (Throwable rex) {
717	<	setExceptionalCompletion(rex);
718	<	}
719	<	}
720	<	if (completed)
721	<	setCompletion(NORMAL);
722	<	else if (status >= 0)
723	<	w.joinTask(this, true, nanos);
991	>	ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
992	>	p = wt.pool;
993	>	w = wt.workQueue;
994	>	s = p.helpJoinOnce(w, this); // no retries on failure
995		}
996	<	else if (Thread.interrupted())
997	<	throw new InterruptedException();
998	<	else {
999	<	long startTime = System.nanoTime();
1000	<	int s; long nt;
1001	<	while ((s = status) >= 0 &&
1002	<	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
1003	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,
1004	<	SIGNAL)) {
1005	<	long ms = nt / 1000000;
1006	<	int ns = (int) (nt % 1000000);
1007	<	synchronized (this) {
1008	<	if (status >= 0)
1009	<	wait(ms, ns); // exit on IE throw
996	>	boolean canBlock = false;
997	>	boolean interrupted = false;
998	>	try {
999	>	while ((s = status) >= 0) {
1000	>	if (w != null && w.runState < 0)
1001	>	cancelIgnoringExceptions(this);
1002	>	else if (!canBlock) {
1003	>	if (p == null || p.tryCompensate(this, null))
1004	>	canBlock = true;
1005	>	}
1006	>	else {
1007	>	if ((ms = TimeUnit.NANOSECONDS.toMillis(ns)) > 0L &&
1008	>	U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
1009	>	synchronized (this) {
1010	>	if (status >= 0) {
1011	>	try {
1012	>	wait(ms);
1013	>	} catch (InterruptedException ie) {
1014	>	if (p == null)
1015	>	interrupted = true;
1016	>	}
1017	>	}
1018	>	else
1019	>	notifyAll();
1020	>	}
1021		}
1022	+	if ((s = status) < 0 || interrupted ||
1023	+	(ns = deadline - System.nanoTime()) <= 0L)
1024	+	break;
1025		}
1026		}
1027	+	} finally {
1028	+	if (p != null && canBlock)
1029	+	p.incrementActiveCount();
1030		}
1031	+	if (interrupted)
1032	+	throw new InterruptedException();
1033		}
1034	<	int es = status;
745	<	if (es != NORMAL) {
1034	>	if ((s &= DONE_MASK) != NORMAL) {
1035		Throwable ex;
1036	<	if (es == CANCELLED)
1036	>	if (s == CANCELLED)
1037		throw new CancellationException();
1038	<	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
1038	>	if (s != EXCEPTIONAL)
1039	>	throw new TimeoutException();
1040	>	if ((ex = getThrowableException()) != null)
1041		throw new ExecutionException(ex);
751	–	throw new TimeoutException();
1042		}
1043		return getRawResult();
1044		}
#	Line 760 | Line 1050 | public abstract class ForkJoinTask<V> im
1050		* known to have aborted.
1051		*/
1052		public final void quietlyJoin() {
1053	<	Thread t;
764	<	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
765	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
766	<	if (status >= 0) {
767	<	if (w.unpushTask(this)) {
768	<	boolean completed;
769	<	try {
770	<	completed = exec();
771	<	} catch (Throwable rex) {
772	<	setExceptionalCompletion(rex);
773	<	return;
774	<	}
775	<	if (completed) {
776	<	setCompletion(NORMAL);
777	<	return;
778	<	}
779	<	}
780	<	w.joinTask(this, false, 0L);
781	<	}
782	<	}
783	<	else
784	<	externalAwaitDone();
1053	>	doJoin();
1054		}
1055
1056		/**
#	Line 790 | Line 1059 | public abstract class ForkJoinTask<V> im
1059		* exception.
1060		*/
1061		public final void quietlyInvoke() {
1062	<	if (status >= 0) {
794	<	boolean completed;
795	<	try {
796	<	completed = exec();
797	<	} catch (Throwable rex) {
798	<	setExceptionalCompletion(rex);
799	<	return;
800	<	}
801	<	if (completed)
802	<	setCompletion(NORMAL);
803	<	else
804	<	quietlyJoin();
805	<	}
1062	>	doInvoke();
1063		}
1064
1065		/**
#	Line 811 | Line 1068 | public abstract class ForkJoinTask<V> im
1068		* be of use in designs in which many tasks are forked, but none
1069		* are explicitly joined, instead executing them until all are
1070		* processed.
814	–	*
815	–	* <p>This method may be invoked only from within {@code
816	–	* ForkJoinTask} computations (as may be determined using method
817	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
818	–	* result in exceptions or errors, possibly including {@code
819	–	* ClassCastException}.
1071		*/
1072		public static void helpQuiesce() {
1073	<	((ForkJoinWorkerThread) Thread.currentThread())
1074	<	.helpQuiescePool();
1073	>	Thread t;
1074	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
1075	>	ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
1076	>	wt.pool.helpQuiescePool(wt.workQueue);
1077	>	}
1078	>	else
1079	>	ForkJoinPool.externalHelpQuiescePool();
1080		}
1081
1082		/**
#	Line 832 | Line 1088 | public abstract class ForkJoinTask<V> im
1088		* under any other usage conditions are not guaranteed.
1089		* This method may be useful when executing
1090		* pre-constructed trees of subtasks in loops.
1091	<	*
1091	>	*
1092		* <p>Upon completion of this method, {@code isDone()} reports
1093		* {@code false}, and {@code getException()} reports {@code
1094		* null}. However, the value returned by {@code getRawResult} is
#	Line 840 | Line 1096 | public abstract class ForkJoinTask<V> im
1096		* setRawResult(null)}.
1097		*/
1098		public void reinitialize() {
1099	<	if (status == EXCEPTIONAL)
1100	<	exceptionMap.remove(this);
1101	<	status = 0;
1099	>	if ((status & DONE_MASK) == EXCEPTIONAL)
1100	>	clearExceptionalCompletion();
1101	>	else
1102	>	status = 0;
1103		}
1104
1105		/**
#	Line 859 | Line 1116 | public abstract class ForkJoinTask<V> im
1116		}
1117
1118		/**
1119	<	* Returns {@code true} if the current thread is executing as a
1120	<	* ForkJoinPool computation.
1119	>	* Returns {@code true} if the current thread is a {@link
1120	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation.
1121		*
1122	<	* @return {@code true} if the current thread is executing as a
1123	<	* ForkJoinPool computation, or false otherwise
1122	>	* @return {@code true} if the current thread is a {@link
1123	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation,
1124	>	* or {@code false} otherwise
1125		*/
1126		public static boolean inForkJoinPool() {
1127		return Thread.currentThread() instanceof ForkJoinWorkerThread;
#	Line 871 | Line 1129 | public abstract class ForkJoinTask<V> im
1129
1130		/**
1131		* Tries to unschedule this task for execution. This method will
1132	<	* typically succeed if this task is the most recently forked task
1133	<	* by the current thread, and has not commenced executing in
1134	<	* another thread.  This method may be useful when arranging
1135	<	* alternative local processing of tasks that could have been, but
1136	<	* were not, stolen.
879	<	*
880	<	* <p>This method may be invoked only from within {@code
881	<	* ForkJoinTask} computations (as may be determined using method
882	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
883	<	* result in exceptions or errors, possibly including {@code
884	<	* ClassCastException}.
1132	>	* typically (but is not guaranteed to) succeed if this task is
1133	>	* the most recently forked task by the current thread, and has
1134	>	* not commenced executing in another thread.  This method may be
1135	>	* useful when arranging alternative local processing of tasks
1136	>	* that could have been, but were not, stolen.
1137		*
1138		* @return {@code true} if unforked
1139		*/
1140		public boolean tryUnfork() {
1141	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1142	<	.unpushTask(this);
1141	>	Thread t;
1142	>	return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
1143	>	((ForkJoinWorkerThread)t).workQueue.tryUnpush(this) :
1144	>	ForkJoinPool.tryUnsubmitFromCommonPool(this);
1145		}
1146
1147		/**
#	Line 896 | Line 1150 | public abstract class ForkJoinTask<V> im
1150		* value may be useful for heuristic decisions about whether to
1151		* fork other tasks.
1152		*
899	–	* <p>This method may be invoked only from within {@code
900	–	* ForkJoinTask} computations (as may be determined using method
901	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
902	–	* result in exceptions or errors, possibly including {@code
903	–	* ClassCastException}.
904	–	*
1153		* @return the number of tasks
1154		*/
1155		public static int getQueuedTaskCount() {
1156	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1157	<	.getQueueSize();
1156	>	Thread t;
1157	>	return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
1158	>	((ForkJoinWorkerThread)t).workQueue.queueSize() :
1159	>	ForkJoinPool.getEstimatedSubmitterQueueLength();
1160		}
1161
1162		/**
1163		* Returns an estimate of how many more locally queued tasks are
1164		* held by the current worker thread than there are other worker
1165	<	* threads that might steal them.  This value may be useful for
1165	>	* threads that might steal them, or zero if this thread is not
1166	>	* operating in a ForkJoinPool. This value may be useful for
1167		* heuristic decisions about whether to fork other tasks. In many
1168		* usages of ForkJoinTasks, at steady state, each worker should
1169		* aim to maintain a small constant surplus (for example, 3) of
1170		* tasks, and to process computations locally if this threshold is
1171		* exceeded.
1172		*
922	–	* <p>This method may be invoked only from within {@code
923	–	* ForkJoinTask} computations (as may be determined using method
924	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
925	–	* result in exceptions or errors, possibly including {@code
926	–	* ClassCastException}.
927	–	*
1173		* @return the surplus number of tasks, which may be negative
1174		*/
1175		public static int getSurplusQueuedTaskCount() {
1176	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1177	<	.getEstimatedSurplusTaskCount();
1176	>	/*
1177	>	* The aim of this method is to return a cheap heuristic guide
1178	>	* for task partitioning when programmers, frameworks, tools,
1179	>	* or languages have little or no idea about task granularity.
1180	>	* In essence by offering this method, we ask users only about
1181	>	* tradeoffs in overhead vs expected throughput and its
1182	>	* variance, rather than how finely to partition tasks.
1183	>	*
1184	>	* In a steady state strict (tree-structured) computation,
1185	>	* each thread makes available for stealing enough tasks for
1186	>	* other threads to remain active. Inductively, if all threads
1187	>	* play by the same rules, each thread should make available
1188	>	* only a constant number of tasks.
1189	>	*
1190	>	* The minimum useful constant is just 1. But using a value of
1191	>	* 1 would require immediate replenishment upon each steal to
1192	>	* maintain enough tasks, which is infeasible.  Further,
1193	>	* partitionings/granularities of offered tasks should
1194	>	* minimize steal rates, which in general means that threads
1195	>	* nearer the top of computation tree should generate more
1196	>	* than those nearer the bottom. In perfect steady state, each
1197	>	* thread is at approximately the same level of computation
1198	>	* tree. However, producing extra tasks amortizes the
1199	>	* uncertainty of progress and diffusion assumptions.
1200	>	*
1201	>	* So, users will want to use values larger, but not much
1202	>	* larger than 1 to both smooth over transient shortages and
1203	>	* hedge against uneven progress; as traded off against the
1204	>	* cost of extra task overhead. We leave the user to pick a
1205	>	* threshold value to compare with the results of this call to
1206	>	* guide decisions, but recommend values such as 3.
1207	>	*
1208	>	* When all threads are active, it is on average OK to
1209	>	* estimate surplus strictly locally. In steady-state, if one
1210	>	* thread is maintaining say 2 surplus tasks, then so are
1211	>	* others. So we can just use estimated queue length.
1212	>	* However, this strategy alone leads to serious mis-estimates
1213	>	* in some non-steady-state conditions (ramp-up, ramp-down,
1214	>	* other stalls). We can detect many of these by further
1215	>	* considering the number of "idle" threads, that are known to
1216	>	* have zero queued tasks, so compensate by a factor of
1217	>	* (#idle/#active) threads.
1218	>	*/
1219	>	Thread t; ForkJoinWorkerThread wt;
1220	>	return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
1221	>	(wt = (ForkJoinWorkerThread)t).workQueue.queueSize() - wt.pool.idlePerActive() :
1222	>	0;
1223		}
1224
1225		// Extension methods
#	Line 955 | Line 1245 | public abstract class ForkJoinTask<V> im
1245		protected abstract void setRawResult(V value);
1246
1247		/**
1248	<	* Immediately performs the base action of this task.  This method
1249	<	* is designed to support extensions, and should not in general be
1250	<	* called otherwise. The return value controls whether this task
1251	<	* is considered to be done normally. It may return false in
1248	>	* Immediately performs the base action of this task and returns
1249	>	* true if, upon return from this method, this task is guaranteed
1250	>	* to have completed normally. This method may return false
1251	>	* otherwise, to indicate that this task is not necessarily
1252	>	* complete (or is not known to be complete), for example in
1253		* asynchronous actions that require explicit invocations of
1254	<	* {@link #complete} to become joinable. It may also throw an
1255	<	* (unchecked) exception to indicate abnormal exit.
1254	>	* completion methods. This method may also throw an (unchecked)
1255	>	* exception to indicate abnormal exit. This method is designed to
1256	>	* support extensions, and should not in general be called
1257	>	* otherwise.
1258		*
1259	<	* @return {@code true} if completed normally
1259	>	* @return {@code true} if this task is known to have completed normally
1260		*/
1261		protected abstract boolean exec();
1262
1263		/**
1264		* Returns, but does not unschedule or execute, a task queued by
1265		* the current thread but not yet executed, if one is immediately
1266	<	* available. There is no guarantee that this task will actually
1267	<	* be polled or executed next. Conversely, this method may return
1268	<	* null even if a task exists but cannot be accessed without
1269	<	* contention with other threads.  This method is designed
1266	>	* available and the current thread is operating in a
1267	>	* ForkJoinPool. There is no guarantee that this task will
1268	>	* actually be polled or executed next. Conversely, this method
1269	>	* may return null even if a task exists but cannot be accessed
1270	>	* without contention with other threads.  This method is designed
1271		* primarily to support extensions, and is unlikely to be useful
1272		* otherwise.
1273		*
980	–	* <p>This method may be invoked only from within {@code
981	–	* ForkJoinTask} computations (as may be determined using method
982	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
983	–	* result in exceptions or errors, possibly including {@code
984	–	* ClassCastException}.
985	–	*
1274		* @return the next task, or {@code null} if none are available
1275		*/
1276		protected static ForkJoinTask<?> peekNextLocalTask() {
1277	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1278	<	.peekTask();
1277	>	Thread t;
1278	>	return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
1279	>	((ForkJoinWorkerThread)t).workQueue.peek() :
1280	>	null;
1281		}
1282
1283		/**
1284		* Unschedules and returns, without executing, the next task
1285	<	* queued by the current thread but not yet executed.  This method
1286	<	* is designed primarily to support extensions, and is unlikely to
1287	<	* be useful otherwise.
1288	<	*
999	<	* <p>This method may be invoked only from within {@code
1000	<	* ForkJoinTask} computations (as may be determined using method
1001	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1002	<	* result in exceptions or errors, possibly including {@code
1003	<	* ClassCastException}.
1285	>	* queued by the current thread but not yet executed, if the
1286	>	* current thread is operating in a ForkJoinPool.  This method is
1287	>	* designed primarily to support extensions, and is unlikely to be
1288	>	* useful otherwise.
1289		*
1290		* @return the next task, or {@code null} if none are available
1291		*/
1292		protected static ForkJoinTask<?> pollNextLocalTask() {
1293	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1294	<	.pollLocalTask();
1293	>	Thread t;
1294	>	return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
1295	>	((ForkJoinWorkerThread)t).workQueue.nextLocalTask() :
1296	>	null;
1297		}
1298
1299		/**
1300	<	* Unschedules and returns, without executing, the next task
1300	>	* If the current thread is operating in a ForkJoinPool,
1301	>	* unschedules and returns, without executing, the next task
1302		* queued by the current thread but not yet executed, if one is
1303		* available, or if not available, a task that was forked by some
1304		* other thread, if available. Availability may be transient, so a
1305	<	* {@code null} result does not necessarily imply quiescence
1306	<	* of the pool this task is operating in.  This method is designed
1305	>	* {@code null} result does not necessarily imply quiescence of
1306	>	* the pool this task is operating in.  This method is designed
1307		* primarily to support extensions, and is unlikely to be useful
1308		* otherwise.
1309		*
1022	–	* <p>This method may be invoked only from within {@code
1023	–	* ForkJoinTask} computations (as may be determined using method
1024	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1025	–	* result in exceptions or errors, possibly including {@code
1026	–	* ClassCastException}.
1027	–	*
1310		* @return a task, or {@code null} if none are available
1311		*/
1312		protected static ForkJoinTask<?> pollTask() {
1313	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1314	<	.pollTask();
1313	>	Thread t; ForkJoinWorkerThread wt;
1314	>	return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
1315	>	(wt = (ForkJoinWorkerThread)t).pool.nextTaskFor(wt.workQueue) :
1316	>	null;
1317	>	}
1318	>
1319	>	// tag operations
1320	>
1321	>	/**
1322	>	* Returns the tag for this task.
1323	>	*
1324	>	* @return the tag for this task
1325	>	* @since 1.8
1326	>	*/
1327	>	public final short getForkJoinTaskTag() {
1328	>	return (short)status;
1329	>	}
1330	>
1331	>	/**
1332	>	* Atomically sets the tag value for this task.
1333	>	*
1334	>	* @param tag the tag value
1335	>	* @return the previous value of the tag
1336	>	* @since 1.8
1337	>	*/
1338	>	public final short setForkJoinTaskTag(short tag) {
1339	>	for (int s;;) {
1340	>	if (U.compareAndSwapInt(this, STATUS, s = status,
1341	>	(s & ~SMASK) | (tag & SMASK)))
1342	>	return (short)s;
1343	>	}
1344	>	}
1345	>
1346	>	/**
1347	>	* Atomically conditionally sets the tag value for this task.
1348	>	* Among other applications, tags can be used as visit markers
1349	>	* in tasks operating on graphs, as in methods that check: {@code
1350	>	* if (task.compareAndSetForkJoinTaskTag((short)0, (short)1))}
1351	>	* before processing, otherwise exiting because the node has
1352	>	* already been visited.
1353	>	*
1354	>	* @param e the expected tag value
1355	>	* @param tag the new tag value
1356	>	* @return true if successful; i.e., the current value was
1357	>	* equal to e and is now tag.
1358	>	* @since 1.8
1359	>	*/
1360	>	public final boolean compareAndSetForkJoinTaskTag(short e, short tag) {
1361	>	for (int s;;) {
1362	>	if ((short)(s = status) != e)
1363	>	return false;
1364	>	if (U.compareAndSwapInt(this, STATUS, s,
1365	>	(s & ~SMASK) | (tag & SMASK)))
1366	>	return true;
1367	>	}
1368		}
1369
1370		/**
#	Line 1040 | Line 1375 | public abstract class ForkJoinTask<V> im
1375		static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1376		implements RunnableFuture<T> {
1377		final Runnable runnable;
1043	–	final T resultOnCompletion;
1378		T result;
1379		AdaptedRunnable(Runnable runnable, T result) {
1380		if (runnable == null) throw new NullPointerException();
1381		this.runnable = runnable;
1382	<	this.resultOnCompletion = result;
1382	>	this.result = result; // OK to set this even before completion
1383		}
1384	<	public T getRawResult() { return result; }
1385	<	public void setRawResult(T v) { result = v; }
1386	<	public boolean exec() {
1387	<	runnable.run();
1388	<	result = resultOnCompletion;
1389	<	return true;
1384	>	public final T getRawResult() { return result; }
1385	>	public final void setRawResult(T v) { result = v; }
1386	>	public final boolean exec() { runnable.run(); return true; }
1387	>	public final void run() { invoke(); }
1388	>	private static final long serialVersionUID = 5232453952276885070L;
1389	>	}
1390	>
1391	>	/**
1392	>	* Adaptor for Runnables without results
1393	>	*/
1394	>	static final class AdaptedRunnableAction extends ForkJoinTask<Void>
1395	>	implements RunnableFuture<Void> {
1396	>	final Runnable runnable;
1397	>	AdaptedRunnableAction(Runnable runnable) {
1398	>	if (runnable == null) throw new NullPointerException();
1399	>	this.runnable = runnable;
1400		}
1401	<	public void run() { invoke(); }
1401	>	public final Void getRawResult() { return null; }
1402	>	public final void setRawResult(Void v) { }
1403	>	public final boolean exec() { runnable.run(); return true; }
1404	>	public final void run() { invoke(); }
1405		private static final long serialVersionUID = 5232453952276885070L;
1406		}
1407
#	Line 1069 | Line 1416 | public abstract class ForkJoinTask<V> im
1416		if (callable == null) throw new NullPointerException();
1417		this.callable = callable;
1418		}
1419	<	public T getRawResult() { return result; }
1420	<	public void setRawResult(T v) { result = v; }
1421	<	public boolean exec() {
1419	>	public final T getRawResult() { return result; }
1420	>	public final void setRawResult(T v) { result = v; }
1421	>	public final boolean exec() {
1422		try {
1423		result = callable.call();
1424		return true;
#	Line 1083 | Line 1430 | public abstract class ForkJoinTask<V> im
1430		throw new RuntimeException(ex);
1431		}
1432		}
1433	<	public void run() { invoke(); }
1433	>	public final void run() { invoke(); }
1434		private static final long serialVersionUID = 2838392045355241008L;
1435		}
1436
#	Line 1096 | Line 1443 | public abstract class ForkJoinTask<V> im
1443		* @return the task
1444		*/
1445		public static ForkJoinTask<?> adapt(Runnable runnable) {
1446	<	return new AdaptedRunnable<Void>(runnable, null);
1446	>	return new AdaptedRunnableAction(runnable);
1447		}
1448
1449		/**
#	Line 1130 | Line 1477 | public abstract class ForkJoinTask<V> im
1477		private static final long serialVersionUID = -7721805057305804111L;
1478
1479		/**
1480	<	* Saves the state to a stream (that is, serializes it).
1480	>	* Saves this task to a stream (that is, serializes it).
1481		*
1482		* @serialData the current run status and the exception thrown
1483		* during execution, or {@code null} if none
1137	–	* @param s the stream
1484		*/
1485		private void writeObject(java.io.ObjectOutputStream s)
1486		throws java.io.IOException {
#	Line 1143 | Line 1489 | public abstract class ForkJoinTask<V> im
1489		}
1490
1491		/**
1492	<	* Reconstitutes the instance from a stream (that is, deserializes it).
1147	<	*
1148	<	* @param s the stream
1492	>	* Reconstitutes this task from a stream (that is, deserializes it).
1493		*/
1494		private void readObject(java.io.ObjectInputStream s)
1495		throws java.io.IOException, ClassNotFoundException {
1496		s.defaultReadObject();
1497		Object ex = s.readObject();
1498		if (ex != null)
1499	<	setExceptionalCompletion((Throwable) ex);
1499	>	setExceptionalCompletion((Throwable)ex);
1500		}
1501
1502		// Unsafe mechanics
1503	<
1504	<	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1505	<	private static final long statusOffset =
1506	<	objectFieldOffset("status", ForkJoinTask.class);
1507	<
1508	<	private static long objectFieldOffset(String field, Class<?> klazz) {
1503	>	private static final sun.misc.Unsafe U;
1504	>	private static final long STATUS;
1505	>	static {
1506	>	exceptionTableLock = new ReentrantLock();
1507	>	exceptionTableRefQueue = new ReferenceQueue<Object>();
1508	>	exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY];
1509		try {
1510	<	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1511	<	} catch (NoSuchFieldException e) {
1512	<	// Convert Exception to corresponding Error
1513	<	NoSuchFieldError error = new NoSuchFieldError(field);
1514	<	error.initCause(e);
1171	<	throw error;
1510	>	U = getUnsafe();
1511	>	STATUS = U.objectFieldOffset
1512	>	(ForkJoinTask.class.getDeclaredField("status"));
1513	>	} catch (Exception e) {
1514	>	throw new Error(e);
1515		}
1516		}
1517

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