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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.57 by dl, Sat Sep 4 11:33:53 2010 UTC vs.
Revision 1.93 by dl, Wed Nov 14 17:20:37 2012 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Doug Lea with assistance from members of JCP JSR-166
3		* Expert Group and released to the public domain, as explained at
4	<	* http://creativecommons.org/licenses/publicdomain
4	>	* http://creativecommons.org/publicdomain/zero/1.0/
5		*/
6
7		package jsr166y;
8
9	–	import java.util.concurrent.*;
10	–
9		import java.io.Serializable;
10		import java.util.Collection;
13	–	import java.util.Collections;
11		import java.util.List;
12		import java.util.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;
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 23 | Line 30 | import java.util.WeakHashMap;
30		* subtasks may be hosted by a small number of actual threads in a
31		* ForkJoinPool, at the price of some usage limitations.
32		*
33	<	* <p>A "main" {@code ForkJoinTask} begins execution when submitted
34	<	* to a {@link ForkJoinPool}.  Once started, it will usually in turn
35	<	* start other subtasks.  As indicated by the name of this class,
36	<	* many programs using {@code ForkJoinTask} employ only methods
37	<	* {@link #fork} and {@link #join}, or derivatives such as {@link
38	<	* #invokeAll}.  However, this class also provides a number of other
39	<	* methods that can come into play in advanced usages, as well as
40	<	* extension mechanics that allow support of new forms of fork/join
41	<	* processing.
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 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 74 | Line 98 | import java.util.WeakHashMap;
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 89 | Line 120 | import java.util.WeakHashMap;
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 116 | Line 162 | import java.util.WeakHashMap;
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 139 | 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	+	/**
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	<	private static final int NORMAL      = -1;
172	<	private static final int CANCELLED   = -2;
173	<	private static final int EXCEPTIONAL = -3;
174	<	private static final int SIGNAL      =  1;
362	>	// Exception table support
363
364		/**
365		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 179 | 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 =
185	<	Collections.synchronizedMap
186	<	(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	>	ExceptionNode(ForkJoinTask<?> task, Throwable ex, ExceptionNode next) {
399	>	super(task, exceptionTableRefQueue);
400	>	this.ex = ex;
401	>	this.next = next;
402	>	this.thrower = Thread.currentThread().getId();
403	>	}
404	>	}
405
406		/**
407	<	* Marks completion and wakes up threads waiting to join this task,
192	<	* also clearing signal request bits.
407	>	* Records exception and sets status.
408		*
409	<	* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
409	>	* @return status on exit
410		*/
411	<	private void setCompletion(int completion) {
411	>	final int recordExceptionalCompletion(Throwable ex) {
412		int s;
413	<	while ((s = status) >= 0) {
414	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
415	<	if (s != 0)
416	<	synchronized (this) { notifyAll(); }
417	<	break;
413	>	if ((s = status) >= 0) {
414	>	int h = System.identityHashCode(this);
415	>	final ReentrantLock lock = exceptionTableLock;
416	>	lock.lock();
417	>	try {
418	>	expungeStaleExceptions();
419	>	ExceptionNode[] t = exceptionTable;
420	>	int i = h & (t.length - 1);
421	>	for (ExceptionNode e = t[i]; ; e = e.next) {
422	>	if (e == null) {
423	>	t[i] = new ExceptionNode(this, ex, t[i]);
424	>	break;
425	>	}
426	>	if (e.get() == this) // already present
427	>	break;
428	>	}
429	>	} finally {
430	>	lock.unlock();
431		}
432	+	s = setCompletion(EXCEPTIONAL);
433		}
434	+	return s;
435		}
436
437		/**
438	<	* Records exception and sets exceptional completion.
439	<	*
438	>	* Records exception and possibly propagates
439	>	*
440		* @return status on exit
441		*/
442	<	private void setExceptionalCompletion(Throwable rex) {
443	<	exceptionMap.put(this, rex);
444	<	setCompletion(EXCEPTIONAL);
442	>	private int setExceptionalCompletion(Throwable ex) {
443	>	int s = recordExceptionalCompletion(ex);
444	>	if ((s & DONE_MASK) == EXCEPTIONAL)
445	>	internalPropagateException(ex);
446	>	return s;
447		}
448
449		/**
450	<	* Blocks a worker thread until completion. Called only by
219	<	* pool. Currently unused -- pool-based waits use timeout
220	<	* version below.
450	>	* Hook for exception propagation support for tasks with completers.
451		*/
452	<	final void internalAwaitDone() {
453	<	int s;         // the odd construction reduces lock bias effects
454	<	while ((s = status) >= 0) {
452	>	void internalPropagateException(Throwable ex) {
453	>	}
454	>
455	>	/**
456	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
457	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
458	>	* exceptions, but if it does anyway, we have no recourse during
459	>	* shutdown, so guard against this case.
460	>	*/
461	>	static final void cancelIgnoringExceptions(ForkJoinTask<?> t) {
462	>	if (t != null && t.status >= 0) {
463		try {
464	<	synchronized(this) {
465	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
228	<	wait();
229	<	}
230	<	} catch (InterruptedException ie) {
231	<	cancelIfTerminating();
464	>	t.cancel(false);
465	>	} catch (Throwable ignore) {
466		}
467		}
468		}
469
470		/**
471	<	* Blocks a worker thread until completed or timed out.  Called
238	<	* only by pool.
239	<	*
240	<	* @return status on exit
471	>	* Removes exception node and clears status
472		*/
473	<	final int internalAwaitDone(long millis) {
474	<	int s;
475	<	if ((s = status) >= 0) {
473	>	private void clearExceptionalCompletion() {
474	>	int h = System.identityHashCode(this);
475	>	final ReentrantLock lock = exceptionTableLock;
476	>	lock.lock();
477	>	try {
478	>	ExceptionNode[] t = exceptionTable;
479	>	int i = h & (t.length - 1);
480	>	ExceptionNode e = t[i];
481	>	ExceptionNode pred = null;
482	>	while (e != null) {
483	>	ExceptionNode next = e.next;
484	>	if (e.get() == this) {
485	>	if (pred == null)
486	>	t[i] = next;
487	>	else
488	>	pred.next = next;
489	>	break;
490	>	}
491	>	pred = e;
492	>	e = next;
493	>	}
494	>	expungeStaleExceptions();
495	>	status = 0;
496	>	} finally {
497	>	lock.unlock();
498	>	}
499	>	}
500	>
501	>	/**
502	>	* Returns a rethrowable exception for the given task, if
503	>	* available. To provide accurate stack traces, if the exception
504	>	* was not thrown by the current thread, we try to create a new
505	>	* exception of the same type as the one thrown, but with the
506	>	* recorded exception as its cause. If there is no such
507	>	* constructor, we instead try to use a no-arg constructor,
508	>	* followed by initCause, to the same effect. If none of these
509	>	* apply, or any fail due to other exceptions, we return the
510	>	* recorded exception, which is still correct, although it may
511	>	* contain a misleading stack trace.
512	>	*
513	>	* @return the exception, or null if none
514	>	*/
515	>	private Throwable getThrowableException() {
516	>	if ((status & DONE_MASK) != EXCEPTIONAL)
517	>	return null;
518	>	int h = System.identityHashCode(this);
519	>	ExceptionNode e;
520	>	final ReentrantLock lock = exceptionTableLock;
521	>	lock.lock();
522	>	try {
523	>	expungeStaleExceptions();
524	>	ExceptionNode[] t = exceptionTable;
525	>	e = t[h & (t.length - 1)];
526	>	while (e != null && e.get() != this)
527	>	e = e.next;
528	>	} finally {
529	>	lock.unlock();
530	>	}
531	>	Throwable ex;
532	>	if (e == null || (ex = e.ex) == null)
533	>	return null;
534	>	if (false && e.thrower != Thread.currentThread().getId()) {
535	>	Class<? extends Throwable> ec = ex.getClass();
536		try {
537	<	synchronized(this) {
538	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
539	<	wait(millis, 0);
537	>	Constructor<?> noArgCtor = null;
538	>	Constructor<?>[] cs = ec.getConstructors();// public ctors only
539	>	for (int i = 0; i < cs.length; ++i) {
540	>	Constructor<?> c = cs[i];
541	>	Class<?>[] ps = c.getParameterTypes();
542	>	if (ps.length == 0)
543	>	noArgCtor = c;
544	>	else if (ps.length == 1 && ps[0] == Throwable.class)
545	>	return (Throwable)(c.newInstance(ex));
546	>	}
547	>	if (noArgCtor != null) {
548	>	Throwable wx = (Throwable)(noArgCtor.newInstance());
549	>	wx.initCause(ex);
550	>	return wx;
551		}
552	<	} catch (InterruptedException ie) {
251	<	cancelIfTerminating();
552	>	} catch (Exception ignore) {
553		}
253	–	s = status;
554		}
555	<	return s;
555	>	return ex;
556		}
557
558		/**
559	<	* Blocks a non-worker-thread until completion.
559	>	* Poll stale refs and remove them. Call only while holding lock.
560		*/
561	<	private void externalAwaitDone() {
562	<	int s;
563	<	while ((s = status) >= 0) {
564	<	synchronized(this) {
565	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
566	<	boolean interrupted = false;
567	<	while (status >= 0) {
568	<	try {
569	<	wait();
570	<	} catch (InterruptedException ie) {
571	<	interrupted = true;
572	<	}
561	>	private static void expungeStaleExceptions() {
562	>	for (Object x; (x = exceptionTableRefQueue.poll()) != null;) {
563	>	if (x instanceof ExceptionNode) {
564	>	ForkJoinTask<?> key = ((ExceptionNode)x).get();
565	>	ExceptionNode[] t = exceptionTable;
566	>	int i = System.identityHashCode(key) & (t.length - 1);
567	>	ExceptionNode e = t[i];
568	>	ExceptionNode pred = null;
569	>	while (e != null) {
570	>	ExceptionNode next = e.next;
571	>	if (e == x) {
572	>	if (pred == null)
573	>	t[i] = next;
574	>	else
575	>	pred.next = next;
576	>	break;
577		}
578	<	if (interrupted)
579	<	Thread.currentThread().interrupt();
276	<	break;
578	>	pred = e;
579	>	e = next;
580		}
581		}
582		}
583		}
584
585		/**
586	<	* Unless done, calls exec and records status if completed, but
587	<	* doesn't wait for completion otherwise. Primary execution method
285	<	* for ForkJoinWorkerThread.
586	>	* If lock is available, poll stale refs and remove them.
587	>	* Called from ForkJoinPool when pools become quiescent.
588		*/
589	<	final void quietlyExec() {
590	<	try {
591	<	if (status < 0 || !exec())
592	<	return;
593	<	} catch (Throwable rex) {
594	<	setExceptionalCompletion(rex);
595	<	return;
589	>	static final void helpExpungeStaleExceptions() {
590	>	final ReentrantLock lock = exceptionTableLock;
591	>	if (lock.tryLock()) {
592	>	try {
593	>	expungeStaleExceptions();
594	>	} finally {
595	>	lock.unlock();
596	>	}
597		}
598	<	setCompletion(NORMAL); // must be outside try block
598	>	}
599	>
600	>	/**
601	>	* A version of "sneaky throw" to relay exceptions
602	>	*/
603	>	static void rethrow(final Throwable ex) {
604	>	if (ex != null) {
605	>	if (ex instanceof Error)
606	>	throw (Error)ex;
607	>	if (ex instanceof RuntimeException)
608	>	throw (RuntimeException)ex;
609	>	throw uncheckedThrowable(ex, RuntimeException.class);
610	>	}
611	>	}
612	>
613	>	/**
614	>	* The sneaky part of sneaky throw, relying on generics
615	>	* limitations to evade compiler complaints about rethrowing
616	>	* unchecked exceptions
617	>	*/
618	>	@SuppressWarnings("unchecked") static <T extends Throwable>
619	>	T uncheckedThrowable(final Throwable t, final Class<T> c) {
620	>	return (T)t; // rely on vacuous cast
621	>	}
622	>
623	>	/**
624	>	* Throws exception, if any, associated with the given status.
625	>	*/
626	>	private void reportException(int s) {
627	>	if (s == CANCELLED)
628	>	throw new CancellationException();
629	>	if (s == EXCEPTIONAL)
630	>	rethrow(getThrowableException());
631		}
632
633		// public methods
634
635		/**
636	<	* Arranges to asynchronously execute this task.  While it is not
637	<	* necessarily enforced, it is a usage error to fork a task more
638	<	* than once unless it has completed and been reinitialized.
639	<	* Subsequent modifications to the state of this task or any data
640	<	* it operates on are not necessarily consistently observable by
641	<	* any thread other than the one executing it unless preceded by a
642	<	* call to {@link #join} or related methods, or a call to {@link
643	<	* #isDone} returning {@code true}.
644	<	*
645	<	* <p>This method may be invoked only from within {@code
646	<	* ForkJoinTask} computations (as may be determined using method
312	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
313	<	* result in exceptions or errors, possibly including {@code
314	<	* ClassCastException}.
636	>	* Arranges to asynchronously execute this task in the pool the
637	>	* current task is running in, if applicable, or using the {@link
638	>	* ForkJoinPool#commonPool} if not {@link #inForkJoinPool}.  While
639	>	* it is not necessarily enforced, it is a usage error to fork a
640	>	* task more than once unless it has completed and been
641	>	* reinitialized.  Subsequent modifications to the state of this
642	>	* task or any data it operates on are not necessarily
643	>	* consistently observable by any thread other than the one
644	>	* executing it unless preceded by a call to {@link #join} or
645	>	* related methods, or a call to {@link #isDone} returning {@code
646	>	* true}.
647		*
648		* @return {@code this}, to simplify usage
649		*/
650		public final ForkJoinTask<V> fork() {
651	<	((ForkJoinWorkerThread) Thread.currentThread())
652	<	.pushTask(this);
651	>	Thread t;
652	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
653	>	((ForkJoinWorkerThread)t).workQueue.push(this);
654	>	else
655	>	ForkJoinPool.commonPool.externalPush(this);
656		return this;
657		}
658
659		/**
660	<	* Returns the result of the computation when it {@link #isDone is done}.
661	<	* This method differs from {@link #get()} in that
660	>	* Returns the result of the computation when it {@link #isDone is
661	>	* done}.  This method differs from {@link #get()} in that
662		* abnormal completion results in {@code RuntimeException} or
663	<	* {@code Error}, not {@code ExecutionException}.
663	>	* {@code Error}, not {@code ExecutionException}, and that
664	>	* interrupts of the calling thread do <em>not</em> cause the
665	>	* method to abruptly return by throwing {@code
666	>	* InterruptedException}.
667		*
668		* @return the computed result
669		*/
670		public final V join() {
671	<	quietlyJoin();
672	<	Throwable ex;
673	<	if (status < NORMAL && (ex = getException()) != null)
336	<	UNSAFE.throwException(ex);
671	>	int s;
672	>	if ((s = doJoin() & DONE_MASK) != NORMAL)
673	>	reportException(s);
674		return getRawResult();
675		}
676
#	Line 346 | Line 683 | public abstract class ForkJoinTask<V> im
683		* @return the computed result
684		*/
685		public final V invoke() {
686	<	quietlyInvoke();
687	<	Throwable ex;
688	<	if (status < NORMAL && (ex = getException()) != null)
352	<	UNSAFE.throwException(ex);
686	>	int s;
687	>	if ((s = doInvoke() & DONE_MASK) != NORMAL)
688	>	reportException(s);
689		return getRawResult();
690		}
691
#	Line 366 | Line 702 | public abstract class ForkJoinTask<V> im
702		* cancelled, completed normally or exceptionally, or left
703		* unprocessed.
704		*
369	–	* <p>This method may be invoked only from within {@code
370	–	* ForkJoinTask} computations (as may be determined using method
371	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
372	–	* result in exceptions or errors, possibly including {@code
373	–	* ClassCastException}.
374	–	*
705		* @param t1 the first task
706		* @param t2 the second task
707		* @throws NullPointerException if any task is null
708		*/
709		public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
710	+	int s1, s2;
711		t2.fork();
712	<	t1.invoke();
713	<	t2.join();
712	>	if ((s1 = t1.doInvoke() & DONE_MASK) != NORMAL)
713	>	t1.reportException(s1);
714	>	if ((s2 = t2.doJoin() & DONE_MASK) != NORMAL)
715	>	t2.reportException(s2);
716		}
717
718		/**
#	Line 394 | Line 727 | public abstract class ForkJoinTask<V> im
727		* related methods to check if they have been cancelled, completed
728		* normally or exceptionally, or left unprocessed.
729		*
397	–	* <p>This method may be invoked only from within {@code
398	–	* ForkJoinTask} computations (as may be determined using method
399	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
400	–	* result in exceptions or errors, possibly including {@code
401	–	* ClassCastException}.
402	–	*
730		* @param tasks the tasks
731		* @throws NullPointerException if any task is null
732		*/
#	Line 414 | Line 741 | public abstract class ForkJoinTask<V> im
741		}
742		else if (i != 0)
743		t.fork();
744	<	else {
745	<	t.quietlyInvoke();
419	<	if (ex == null && t.status < NORMAL)
420	<	ex = t.getException();
421	<	}
744	>	else if (t.doInvoke() < NORMAL && ex == null)
745	>	ex = t.getException();
746		}
747		for (int i = 1; i <= last; ++i) {
748		ForkJoinTask<?> t = tasks[i];
749		if (t != null) {
750		if (ex != null)
751		t.cancel(false);
752	<	else {
753	<	t.quietlyJoin();
430	<	if (ex == null && t.status < NORMAL)
431	<	ex = t.getException();
432	<	}
752	>	else if (t.doJoin() < NORMAL)
753	>	ex = t.getException();
754		}
755		}
756		if (ex != null)
757	<	UNSAFE.throwException(ex);
757	>	rethrow(ex);
758		}
759
760		/**
#	Line 449 | Line 770 | public abstract class ForkJoinTask<V> im
770		* cancelled, completed normally or exceptionally, or left
771		* unprocessed.
772		*
452	–	* <p>This method may be invoked only from within {@code
453	–	* ForkJoinTask} computations (as may be determined using method
454	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
455	–	* result in exceptions or errors, possibly including {@code
456	–	* ClassCastException}.
457	–	*
773		* @param tasks the collection of tasks
774		* @return the tasks argument, to simplify usage
775		* @throws NullPointerException if tasks or any element are null
#	Line 477 | Line 792 | public abstract class ForkJoinTask<V> im
792		}
793		else if (i != 0)
794		t.fork();
795	<	else {
796	<	t.quietlyInvoke();
482	<	if (ex == null && t.status < NORMAL)
483	<	ex = t.getException();
484	<	}
795	>	else if (t.doInvoke() < NORMAL && ex == null)
796	>	ex = t.getException();
797		}
798		for (int i = 1; i <= last; ++i) {
799		ForkJoinTask<?> t = ts.get(i);
800		if (t != null) {
801		if (ex != null)
802		t.cancel(false);
803	<	else {
804	<	t.quietlyJoin();
493	<	if (ex == null && t.status < NORMAL)
494	<	ex = t.getException();
495	<	}
803	>	else if (t.doJoin() < NORMAL)
804	>	ex = t.getException();
805		}
806		}
807		if (ex != null)
808	<	UNSAFE.throwException(ex);
808	>	rethrow(ex);
809		return tasks;
810		}
811
812		/**
813		* Attempts to cancel execution of this task. This attempt will
814	<	* fail if the task has already completed, has already been
815	<	* cancelled, or could not be cancelled for some other reason. If
816	<	* successful, and this task has not started when cancel is
817	<	* called, execution of this task is suppressed, {@link
818	<	* #isCancelled} will report true, and {@link #join} will result
819	<	* in a {@code CancellationException} being thrown.
814	>	* fail if the task has already completed or could not be
815	>	* cancelled for some other reason. If successful, and this task
816	>	* has not started when {@code cancel} is called, execution of
817	>	* this task is suppressed. After this method returns
818	>	* successfully, unless there is an intervening call to {@link
819	>	* #reinitialize}, subsequent calls to {@link #isCancelled},
820	>	* {@link #isDone}, and {@code cancel} will return {@code true}
821	>	* and calls to {@link #join} and related methods will result in
822	>	* {@code CancellationException}.
823		*
824		* <p>This method may be overridden in subclasses, but if so, must
825	<	* still ensure that these minimal properties hold. In particular,
826	<	* the {@code cancel} method itself must not throw exceptions.
825	>	* still ensure that these properties hold. In particular, the
826	>	* {@code cancel} method itself must not throw exceptions.
827		*
828		* <p>This method is designed to be invoked by <em>other</em>
829		* tasks. To terminate the current task, you can just return or
830		* throw an unchecked exception from its computation method, or
831		* invoke {@link #completeExceptionally}.
832		*
833	<	* @param mayInterruptIfRunning this value is ignored in the
834	<	* default implementation because tasks are not
835	<	* cancelled via interruption
833	>	* @param mayInterruptIfRunning this value has no effect in the
834	>	* default implementation because interrupts are not used to
835	>	* control cancellation.
836		*
837		* @return {@code true} if this task is now cancelled
838		*/
839		public boolean cancel(boolean mayInterruptIfRunning) {
840	<	setCompletion(CANCELLED);
529	<	return status == CANCELLED;
530	<	}
531	<
532	<	/**
533	<	* Cancels, ignoring any exceptions thrown by cancel. Used during
534	<	* worker and pool shutdown. Cancel is spec'ed not to throw any
535	<	* exceptions, but if it does anyway, we have no recourse during
536	<	* shutdown, so guard against this case.
537	<	*/
538	<	final void cancelIgnoringExceptions() {
539	<	try {
540	<	cancel(false);
541	<	} catch (Throwable ignore) {
542	<	}
543	<	}
544	<
545	<	/**
546	<	* Cancels if current thread is a terminating worker thread,
547	<	* ignoring any exceptions thrown by cancel.
548	<	*/
549	<	final void cancelIfTerminating() {
550	<	Thread t = Thread.currentThread();
551	<	if ((t instanceof ForkJoinWorkerThread) &&
552	<	((ForkJoinWorkerThread) t).isTerminating()) {
553	<	try {
554	<	cancel(false);
555	<	} catch (Throwable ignore) {
556	<	}
557	<	}
840	>	return (setCompletion(CANCELLED) & DONE_MASK) == CANCELLED;
841		}
842
843		public final boolean isDone() {
#	Line 562 | Line 845 | public abstract class ForkJoinTask<V> im
845		}
846
847		public final boolean isCancelled() {
848	<	return status == CANCELLED;
848	>	return (status & DONE_MASK) == CANCELLED;
849		}
850
851		/**
#	Line 582 | Line 865 | public abstract class ForkJoinTask<V> im
865		* exception and was not cancelled
866		*/
867		public final boolean isCompletedNormally() {
868	<	return status == NORMAL;
868	>	return (status & DONE_MASK) == NORMAL;
869		}
870
871		/**
#	Line 593 | Line 876 | public abstract class ForkJoinTask<V> im
876		* @return the exception, or {@code null} if none
877		*/
878		public final Throwable getException() {
879	<	int s = status;
879	>	int s = status & DONE_MASK;
880		return ((s >= NORMAL)    ? null :
881		(s == CANCELLED) ? new CancellationException() :
882	<	exceptionMap.get(this));
882	>	getThrowableException());
883		}
884
885		/**
#	Line 621 | Line 904 | public abstract class ForkJoinTask<V> im
904
905		/**
906		* Completes this task, and if not already aborted or cancelled,
907	<	* returning a {@code null} result upon {@code join} and related
908	<	* operations. This method may be used to provide results for
909	<	* asynchronous tasks, or to provide alternative handling for
910	<	* tasks that would not otherwise complete normally. Its use in
911	<	* other situations is discouraged. This method is
912	<	* overridable, but overridden versions must invoke {@code super}
913	<	* implementation to maintain guarantees.
907	>	* returning the given value as the result of subsequent
908	>	* invocations of {@code join} and related operations. This method
909	>	* may be used to provide results for asynchronous tasks, or to
910	>	* provide alternative handling for tasks that would not otherwise
911	>	* complete normally. Its use in other situations is
912	>	* discouraged. This method is overridable, but overridden
913	>	* versions must invoke {@code super} implementation to maintain
914	>	* guarantees.
915		*
916		* @param value the result value for this task
917		*/
#	Line 641 | Line 925 | public abstract class ForkJoinTask<V> im
925		setCompletion(NORMAL);
926		}
927
928	+	/**
929	+	* Completes this task normally without setting a value. The most
930	+	* recent value established by {@link #setRawResult} (or {@code
931	+	* null} by default) will be returned as the result of subsequent
932	+	* invocations of {@code join} and related operations.
933	+	*
934	+	* @since 1.8
935	+	*/
936	+	public final void quietlyComplete() {
937	+	setCompletion(NORMAL);
938	+	}
939	+
940	+	/**
941	+	* Waits if necessary for the computation to complete, and then
942	+	* retrieves its result.
943	+	*
944	+	* @return the computed result
945	+	* @throws CancellationException if the computation was cancelled
946	+	* @throws ExecutionException if the computation threw an
947	+	* exception
948	+	* @throws InterruptedException if the current thread is not a
949	+	* member of a ForkJoinPool and was interrupted while waiting
950	+	*/
951		public final V get() throws InterruptedException, ExecutionException {
952	<	quietlyJoin();
953	<	if (Thread.interrupted())
954	<	throw new InterruptedException();
955	<	int s = status;
956	<	if (s < NORMAL) {
957	<	Throwable ex;
958	<	if (s == CANCELLED)
652	<	throw new CancellationException();
653	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
654	<	throw new ExecutionException(ex);
655	<	}
952	>	int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ?
953	>	doJoin() : externalInterruptibleAwaitDone();
954	>	Throwable ex;
955	>	if ((s &= DONE_MASK) == CANCELLED)
956	>	throw new CancellationException();
957	>	if (s == EXCEPTIONAL && (ex = getThrowableException()) != null)
958	>	throw new ExecutionException(ex);
959		return getRawResult();
960		}
961
962	+	/**
963	+	* Waits if necessary for at most the given time for the computation
964	+	* to complete, and then retrieves its result, if available.
965	+	*
966	+	* @param timeout the maximum time to wait
967	+	* @param unit the time unit of the timeout argument
968	+	* @return the computed result
969	+	* @throws CancellationException if the computation was cancelled
970	+	* @throws ExecutionException if the computation threw an
971	+	* exception
972	+	* @throws InterruptedException if the current thread is not a
973	+	* member of a ForkJoinPool and was interrupted while waiting
974	+	* @throws TimeoutException if the wait timed out
975	+	*/
976		public final V get(long timeout, TimeUnit unit)
977		throws InterruptedException, ExecutionException, TimeoutException {
978	<	Thread t = Thread.currentThread();
979	<	ForkJoinPool pool;
980	<	if (t instanceof ForkJoinWorkerThread) {
981	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
982	<	if (status >= 0 && w.unpushTask(this))
983	<	quietlyExec();
984	<	pool = w.pool;
985	<	}
986	<	else
987	<	pool = null;
988	<	/*
989	<	* Timed wait loop intermixes cases for FJ (pool != null) and
990	<	* non FJ threads. For FJ, decrement pool count but don't try
991	<	* for replacement; increment count on completion. For non-FJ,
675	<	* deal with interrupts. This is messy, but a little less so
676	<	* than is splitting the FJ and nonFJ cases.
677	<	*/
678	<	boolean interrupted = false;
679	<	boolean dec = false; // true if pool count decremented
680	<	long nanos = unit.toNanos(timeout);
681	<	for (;;) {
682	<	if (Thread.interrupted() && pool == null) {
683	<	interrupted = true;
684	<	break;
978	>	if (Thread.interrupted())
979	>	throw new InterruptedException();
980	>	// Messy in part because we measure in nanosecs, but wait in millisecs
981	>	int s; long ns, ms;
982	>	if ((s = status) >= 0 && (ns = unit.toNanos(timeout)) > 0L) {
983	>	long deadline = System.nanoTime() + ns;
984	>	ForkJoinPool p = null;
985	>	ForkJoinPool.WorkQueue w = null;
986	>	Thread t = Thread.currentThread();
987	>	if (t instanceof ForkJoinWorkerThread) {
988	>	ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
989	>	p = wt.pool;
990	>	w = wt.workQueue;
991	>	p.helpJoinOnce(w, this); // no retries on failure
992		}
993	<	int s = status;
994	<	if (s < 0)
995	<	break;
996	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
997	<	long startTime = System.nanoTime();
998	<	long nt; // wait time
999	<	while (status >= 0 &&
1000	<	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
1001	<	if (pool != null && !dec)
1002	<	dec = pool.tryDecrementRunningCount();
993	>	else
994	>	ForkJoinPool.externalHelpJoin(this);
995	>	boolean canBlock = false;
996	>	boolean interrupted = false;
997	>	try {
998	>	while ((s = status) >= 0) {
999	>	if (w != null && w.qlock < 0)
1000	>	cancelIgnoringExceptions(this);
1001	>	else if (!canBlock) {
1002	>	if (p == null || p.tryCompensate())
1003	>	canBlock = true;
1004	>	}
1005		else {
1006	<	long ms = nt / 1000000;
1007	<	int ns = (int) (nt % 1000000);
1008	<	try {
1009	<	synchronized(this) {
1010	<	if (status >= 0)
1011	<	wait(ms, ns);
1012	<	}
1013	<	} catch (InterruptedException ie) {
1014	<	if (pool != null)
1015	<	cancelIfTerminating();
1016	<	else {
1017	<	interrupted = true;
1018	<	break;
1006	>	if ((ms = TimeUnit.NANOSECONDS.toMillis(ns)) > 0L &&
1007	>	U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
1008	>	synchronized (this) {
1009	>	if (status >= 0) {
1010	>	try {
1011	>	wait(ms);
1012	>	} catch (InterruptedException ie) {
1013	>	if (p == null)
1014	>	interrupted = true;
1015	>	}
1016	>	}
1017	>	else
1018	>	notifyAll();
1019		}
1020		}
1021	+	if ((s = status) < 0 || interrupted ||
1022	+	(ns = deadline - System.nanoTime()) <= 0L)
1023	+	break;
1024		}
1025		}
1026	<	break;
1026	>	} finally {
1027	>	if (p != null && canBlock)
1028	>	p.incrementActiveCount();
1029		}
1030	+	if (interrupted)
1031	+	throw new InterruptedException();
1032		}
1033	<	if (pool != null && dec)
718	<	pool.incrementRunningCount();
719	<	if (interrupted)
720	<	throw new InterruptedException();
721	<	int es = status;
722	<	if (es != NORMAL) {
1033	>	if ((s &= DONE_MASK) != NORMAL) {
1034		Throwable ex;
1035	<	if (es == CANCELLED)
1035	>	if (s == CANCELLED)
1036		throw new CancellationException();
1037	<	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
1037	>	if (s != EXCEPTIONAL)
1038	>	throw new TimeoutException();
1039	>	if ((ex = getThrowableException()) != null)
1040		throw new ExecutionException(ex);
728	–	throw new TimeoutException();
1041		}
1042		return getRawResult();
1043		}
#	Line 737 | Line 1049 | public abstract class ForkJoinTask<V> im
1049		* known to have aborted.
1050		*/
1051		public final void quietlyJoin() {
1052	<	Thread t;
741	<	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
742	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
743	<	if (status >= 0) {
744	<	if (w.unpushTask(this)) {
745	<	boolean completed;
746	<	try {
747	<	completed = exec();
748	<	} catch (Throwable rex) {
749	<	setExceptionalCompletion(rex);
750	<	return;
751	<	}
752	<	if (completed) {
753	<	setCompletion(NORMAL);
754	<	return;
755	<	}
756	<	}
757	<	w.joinTask(this);
758	<	}
759	<	}
760	<	else
761	<	externalAwaitDone();
1052	>	doJoin();
1053		}
1054
1055		/**
1056		* Commences performing this task and awaits its completion if
1057		* necessary, without returning its result or throwing its
1058	<	* exception. This method may be useful when processing
768	<	* collections of tasks when some have been cancelled or otherwise
769	<	* known to have aborted.
1058	>	* exception.
1059		*/
1060		public final void quietlyInvoke() {
1061	<	if (status >= 0) {
773	<	boolean completed;
774	<	try {
775	<	completed = exec();
776	<	} catch (Throwable rex) {
777	<	setExceptionalCompletion(rex);
778	<	return;
779	<	}
780	<	if (completed)
781	<	setCompletion(NORMAL);
782	<	else
783	<	quietlyJoin();
784	<	}
1061	>	doInvoke();
1062		}
1063
1064		/**
#	Line 790 | Line 1067 | public abstract class ForkJoinTask<V> im
1067		* be of use in designs in which many tasks are forked, but none
1068		* are explicitly joined, instead executing them until all are
1069		* processed.
793	–	*
794	–	* <p>This method may be invoked only from within {@code
795	–	* ForkJoinTask} computations (as may be determined using method
796	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
797	–	* result in exceptions or errors, possibly including {@code
798	–	* ClassCastException}.
1070		*/
1071		public static void helpQuiesce() {
1072	<	((ForkJoinWorkerThread) Thread.currentThread())
1073	<	.helpQuiescePool();
1072	>	Thread t;
1073	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
1074	>	ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
1075	>	wt.pool.helpQuiescePool(wt.workQueue);
1076	>	}
1077	>	else
1078	>	ForkJoinPool.externalHelpQuiescePool();
1079		}
1080
1081		/**
#	Line 811 | Line 1087 | public abstract class ForkJoinTask<V> im
1087		* under any other usage conditions are not guaranteed.
1088		* This method may be useful when executing
1089		* pre-constructed trees of subtasks in loops.
1090	+	*
1091	+	* <p>Upon completion of this method, {@code isDone()} reports
1092	+	* {@code false}, and {@code getException()} reports {@code
1093	+	* null}. However, the value returned by {@code getRawResult} is
1094	+	* unaffected. To clear this value, you can invoke {@code
1095	+	* setRawResult(null)}.
1096		*/
1097		public void reinitialize() {
1098	<	if (status == EXCEPTIONAL)
1099	<	exceptionMap.remove(this);
1100	<	status = 0;
1098	>	if ((status & DONE_MASK) == EXCEPTIONAL)
1099	>	clearExceptionalCompletion();
1100	>	else
1101	>	status = 0;
1102		}
1103
1104		/**
#	Line 832 | Line 1115 | public abstract class ForkJoinTask<V> im
1115		}
1116
1117		/**
1118	<	* Returns {@code true} if the current thread is executing as a
1119	<	* ForkJoinPool computation.
1118	>	* Returns {@code true} if the current thread is a {@link
1119	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation.
1120		*
1121	<	* @return {@code true} if the current thread is executing as a
1122	<	* ForkJoinPool computation, or false otherwise
1121	>	* @return {@code true} if the current thread is a {@link
1122	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation,
1123	>	* or {@code false} otherwise
1124		*/
1125		public static boolean inForkJoinPool() {
1126		return Thread.currentThread() instanceof ForkJoinWorkerThread;
#	Line 844 | Line 1128 | public abstract class ForkJoinTask<V> im
1128
1129		/**
1130		* Tries to unschedule this task for execution. This method will
1131	<	* typically succeed if this task is the most recently forked task
1132	<	* by the current thread, and has not commenced executing in
1133	<	* another thread.  This method may be useful when arranging
1134	<	* alternative local processing of tasks that could have been, but
1135	<	* were not, stolen.
852	<	*
853	<	* <p>This method may be invoked only from within {@code
854	<	* ForkJoinTask} computations (as may be determined using method
855	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
856	<	* result in exceptions or errors, possibly including {@code
857	<	* ClassCastException}.
1131	>	* typically (but is not guaranteed to) succeed if this task is
1132	>	* the most recently forked task by the current thread, and has
1133	>	* not commenced executing in another thread.  This method may be
1134	>	* useful when arranging alternative local processing of tasks
1135	>	* that could have been, but were not, stolen.
1136		*
1137		* @return {@code true} if unforked
1138		*/
1139		public boolean tryUnfork() {
1140	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1141	<	.unpushTask(this);
1140	>	Thread t;
1141	>	return (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
1142	>	((ForkJoinWorkerThread)t).workQueue.tryUnpush(this) :
1143	>	ForkJoinPool.tryExternalUnpush(this));
1144		}
1145
1146		/**
#	Line 869 | Line 1149 | public abstract class ForkJoinTask<V> im
1149		* value may be useful for heuristic decisions about whether to
1150		* fork other tasks.
1151		*
872	–	* <p>This method may be invoked only from within {@code
873	–	* ForkJoinTask} computations (as may be determined using method
874	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
875	–	* result in exceptions or errors, possibly including {@code
876	–	* ClassCastException}.
877	–	*
1152		* @return the number of tasks
1153		*/
1154		public static int getQueuedTaskCount() {
1155	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1156	<	.getQueueSize();
1155	>	Thread t; ForkJoinPool.WorkQueue q;
1156	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
1157	>	q = ((ForkJoinWorkerThread)t).workQueue;
1158	>	else
1159	>	q = ForkJoinPool.commonSubmitterQueue();
1160	>	return (q == null) ? 0 : q.queueSize();
1161		}
1162
1163		/**
1164		* Returns an estimate of how many more locally queued tasks are
1165		* held by the current worker thread than there are other worker
1166	<	* threads that might steal them.  This value may be useful for
1166	>	* threads that might steal them, or zero if this thread is not
1167	>	* operating in a ForkJoinPool. This value may be useful for
1168		* heuristic decisions about whether to fork other tasks. In many
1169		* usages of ForkJoinTasks, at steady state, each worker should
1170		* aim to maintain a small constant surplus (for example, 3) of
1171		* tasks, and to process computations locally if this threshold is
1172		* exceeded.
1173		*
895	–	* <p>This method may be invoked only from within {@code
896	–	* ForkJoinTask} computations (as may be determined using method
897	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
898	–	* result in exceptions or errors, possibly including {@code
899	–	* ClassCastException}.
900	–	*
1174		* @return the surplus number of tasks, which may be negative
1175		*/
1176		public static int getSurplusQueuedTaskCount() {
1177	<	return ((ForkJoinWorkerThread) Thread.currentThread())
905	<	.getEstimatedSurplusTaskCount();
1177	>	return ForkJoinPool.getSurplusQueuedTaskCount();
1178		}
1179
1180		// Extension methods
#	Line 928 | Line 1200 | public abstract class ForkJoinTask<V> im
1200		protected abstract void setRawResult(V value);
1201
1202		/**
1203	<	* Immediately performs the base action of this task.  This method
1204	<	* is designed to support extensions, and should not in general be
1205	<	* called otherwise. The return value controls whether this task
1206	<	* is considered to be done normally. It may return false in
1203	>	* Immediately performs the base action of this task and returns
1204	>	* true if, upon return from this method, this task is guaranteed
1205	>	* to have completed normally. This method may return false
1206	>	* otherwise, to indicate that this task is not necessarily
1207	>	* complete (or is not known to be complete), for example in
1208		* asynchronous actions that require explicit invocations of
1209	<	* {@link #complete} to become joinable. It may also throw an
1210	<	* (unchecked) exception to indicate abnormal exit.
1209	>	* completion methods. This method may also throw an (unchecked)
1210	>	* exception to indicate abnormal exit. This method is designed to
1211	>	* support extensions, and should not in general be called
1212	>	* otherwise.
1213		*
1214	<	* @return {@code true} if completed normally
1214	>	* @return {@code true} if this task is known to have completed normally
1215		*/
1216		protected abstract boolean exec();
1217
#	Line 950 | Line 1225 | public abstract class ForkJoinTask<V> im
1225		* primarily to support extensions, and is unlikely to be useful
1226		* otherwise.
1227		*
953	–	* <p>This method may be invoked only from within {@code
954	–	* ForkJoinTask} computations (as may be determined using method
955	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
956	–	* result in exceptions or errors, possibly including {@code
957	–	* ClassCastException}.
958	–	*
1228		* @return the next task, or {@code null} if none are available
1229		*/
1230		protected static ForkJoinTask<?> peekNextLocalTask() {
1231	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1232	<	.peekTask();
1231	>	Thread t; ForkJoinPool.WorkQueue q;
1232	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
1233	>	q = ((ForkJoinWorkerThread)t).workQueue;
1234	>	else
1235	>	q = ForkJoinPool.commonSubmitterQueue();
1236	>	return (q == null) ? null : q.peek();
1237		}
1238
1239		/**
1240		* Unschedules and returns, without executing, the next task
1241	<	* queued by the current thread but not yet executed.  This method
1242	<	* is designed primarily to support extensions, and is unlikely to
1243	<	* be useful otherwise.
1244	<	*
972	<	* <p>This method may be invoked only from within {@code
973	<	* ForkJoinTask} computations (as may be determined using method
974	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
975	<	* result in exceptions or errors, possibly including {@code
976	<	* ClassCastException}.
1241	>	* queued by the current thread but not yet executed, if the
1242	>	* current thread is operating in a ForkJoinPool.  This method is
1243	>	* designed primarily to support extensions, and is unlikely to be
1244	>	* useful otherwise.
1245		*
1246		* @return the next task, or {@code null} if none are available
1247		*/
1248		protected static ForkJoinTask<?> pollNextLocalTask() {
1249	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1250	<	.pollLocalTask();
1249	>	Thread t;
1250	>	return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
1251	>	((ForkJoinWorkerThread)t).workQueue.nextLocalTask() :
1252	>	null;
1253		}
1254
1255		/**
1256	<	* Unschedules and returns, without executing, the next task
1256	>	* If the current thread is operating in a ForkJoinPool,
1257	>	* unschedules and returns, without executing, the next task
1258		* queued by the current thread but not yet executed, if one is
1259		* available, or if not available, a task that was forked by some
1260		* other thread, if available. Availability may be transient, so a
1261	<	* {@code null} result does not necessarily imply quiescence
1262	<	* of the pool this task is operating in.  This method is designed
1261	>	* {@code null} result does not necessarily imply quiescence of
1262	>	* the pool this task is operating in.  This method is designed
1263		* primarily to support extensions, and is unlikely to be useful
1264		* otherwise.
1265		*
995	–	* <p>This method may be invoked only from within {@code
996	–	* ForkJoinTask} computations (as may be determined using method
997	–	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
998	–	* result in exceptions or errors, possibly including {@code
999	–	* ClassCastException}.
1000	–	*
1266		* @return a task, or {@code null} if none are available
1267		*/
1268		protected static ForkJoinTask<?> pollTask() {
1269	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1270	<	.pollTask();
1269	>	Thread t; ForkJoinWorkerThread wt;
1270	>	return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
1271	>	(wt = (ForkJoinWorkerThread)t).pool.nextTaskFor(wt.workQueue) :
1272	>	null;
1273	>	}
1274	>
1275	>	// tag operations
1276	>
1277	>	/**
1278	>	* Returns the tag for this task.
1279	>	*
1280	>	* @return the tag for this task
1281	>	* @since 1.8
1282	>	*/
1283	>	public final short getForkJoinTaskTag() {
1284	>	return (short)status;
1285	>	}
1286	>
1287	>	/**
1288	>	* Atomically sets the tag value for this task.
1289	>	*
1290	>	* @param tag the tag value
1291	>	* @return the previous value of the tag
1292	>	* @since 1.8
1293	>	*/
1294	>	public final short setForkJoinTaskTag(short tag) {
1295	>	for (int s;;) {
1296	>	if (U.compareAndSwapInt(this, STATUS, s = status,
1297	>	(s & ~SMASK) | (tag & SMASK)))
1298	>	return (short)s;
1299	>	}
1300	>	}
1301	>
1302	>	/**
1303	>	* Atomically conditionally sets the tag value for this task.
1304	>	* Among other applications, tags can be used as visit markers
1305	>	* in tasks operating on graphs, as in methods that check: {@code
1306	>	* if (task.compareAndSetForkJoinTaskTag((short)0, (short)1))}
1307	>	* before processing, otherwise exiting because the node has
1308	>	* already been visited.
1309	>	*
1310	>	* @param e the expected tag value
1311	>	* @param tag the new tag value
1312	>	* @return true if successful; i.e., the current value was
1313	>	* equal to e and is now tag.
1314	>	* @since 1.8
1315	>	*/
1316	>	public final boolean compareAndSetForkJoinTaskTag(short e, short tag) {
1317	>	for (int s;;) {
1318	>	if ((short)(s = status) != e)
1319	>	return false;
1320	>	if (U.compareAndSwapInt(this, STATUS, s,
1321	>	(s & ~SMASK) | (tag & SMASK)))
1322	>	return true;
1323	>	}
1324		}
1325
1326		/**
#	Line 1013 | Line 1331 | public abstract class ForkJoinTask<V> im
1331		static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1332		implements RunnableFuture<T> {
1333		final Runnable runnable;
1016	–	final T resultOnCompletion;
1334		T result;
1335		AdaptedRunnable(Runnable runnable, T result) {
1336		if (runnable == null) throw new NullPointerException();
1337		this.runnable = runnable;
1338	<	this.resultOnCompletion = result;
1338	>	this.result = result; // OK to set this even before completion
1339		}
1340	<	public T getRawResult() { return result; }
1341	<	public void setRawResult(T v) { result = v; }
1342	<	public boolean exec() {
1343	<	runnable.run();
1344	<	result = resultOnCompletion;
1345	<	return true;
1340	>	public final T getRawResult() { return result; }
1341	>	public final void setRawResult(T v) { result = v; }
1342	>	public final boolean exec() { runnable.run(); return true; }
1343	>	public final void run() { invoke(); }
1344	>	private static final long serialVersionUID = 5232453952276885070L;
1345	>	}
1346	>
1347	>	/**
1348	>	* Adaptor for Runnables without results
1349	>	*/
1350	>	static final class AdaptedRunnableAction extends ForkJoinTask<Void>
1351	>	implements RunnableFuture<Void> {
1352	>	final Runnable runnable;
1353	>	AdaptedRunnableAction(Runnable runnable) {
1354	>	if (runnable == null) throw new NullPointerException();
1355	>	this.runnable = runnable;
1356		}
1357	<	public void run() { invoke(); }
1357	>	public final Void getRawResult() { return null; }
1358	>	public final void setRawResult(Void v) { }
1359	>	public final boolean exec() { runnable.run(); return true; }
1360	>	public final void run() { invoke(); }
1361		private static final long serialVersionUID = 5232453952276885070L;
1362		}
1363
#	Line 1042 | Line 1372 | public abstract class ForkJoinTask<V> im
1372		if (callable == null) throw new NullPointerException();
1373		this.callable = callable;
1374		}
1375	<	public T getRawResult() { return result; }
1376	<	public void setRawResult(T v) { result = v; }
1377	<	public boolean exec() {
1375	>	public final T getRawResult() { return result; }
1376	>	public final void setRawResult(T v) { result = v; }
1377	>	public final boolean exec() {
1378		try {
1379		result = callable.call();
1380		return true;
#	Line 1056 | Line 1386 | public abstract class ForkJoinTask<V> im
1386		throw new RuntimeException(ex);
1387		}
1388		}
1389	<	public void run() { invoke(); }
1389	>	public final void run() { invoke(); }
1390		private static final long serialVersionUID = 2838392045355241008L;
1391		}
1392
#	Line 1069 | Line 1399 | public abstract class ForkJoinTask<V> im
1399		* @return the task
1400		*/
1401		public static ForkJoinTask<?> adapt(Runnable runnable) {
1402	<	return new AdaptedRunnable<Void>(runnable, null);
1402	>	return new AdaptedRunnableAction(runnable);
1403		}
1404
1405		/**
#	Line 1103 | Line 1433 | public abstract class ForkJoinTask<V> im
1433		private static final long serialVersionUID = -7721805057305804111L;
1434
1435		/**
1436	<	* Saves the state to a stream (that is, serializes it).
1436	>	* Saves this task to a stream (that is, serializes it).
1437		*
1438		* @serialData the current run status and the exception thrown
1439		* during execution, or {@code null} if none
1110	–	* @param s the stream
1440		*/
1441		private void writeObject(java.io.ObjectOutputStream s)
1442		throws java.io.IOException {
#	Line 1116 | Line 1445 | public abstract class ForkJoinTask<V> im
1445		}
1446
1447		/**
1448	<	* Reconstitutes the instance from a stream (that is, deserializes it).
1120	<	*
1121	<	* @param s the stream
1448	>	* Reconstitutes this task from a stream (that is, deserializes it).
1449		*/
1450		private void readObject(java.io.ObjectInputStream s)
1451		throws java.io.IOException, ClassNotFoundException {
1452		s.defaultReadObject();
1453		Object ex = s.readObject();
1454		if (ex != null)
1455	<	setExceptionalCompletion((Throwable) ex);
1455	>	setExceptionalCompletion((Throwable)ex);
1456		}
1457
1458		// Unsafe mechanics
1459	+	private static final sun.misc.Unsafe U;
1460	+	private static final long STATUS;
1461
1462	<	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1463	<	private static final long statusOffset =
1464	<	objectFieldOffset("status", ForkJoinTask.class);
1465	<
1137	<	private static long objectFieldOffset(String field, Class<?> klazz) {
1462	>	static {
1463	>	exceptionTableLock = new ReentrantLock();
1464	>	exceptionTableRefQueue = new ReferenceQueue<Object>();
1465	>	exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY];
1466		try {
1467	<	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1468	<	} catch (NoSuchFieldException e) {
1469	<	// Convert Exception to corresponding Error
1470	<	NoSuchFieldError error = new NoSuchFieldError(field);
1471	<	error.initCause(e);
1472	<	throw error;
1467	>	U = getUnsafe();
1468	>	Class<?> k = ForkJoinTask.class;
1469	>	STATUS = U.objectFieldOffset
1470	>	(k.getDeclaredField("status"));
1471	>	} catch (Exception e) {
1472	>	throw new Error(e);
1473		}
1474		}
1475

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