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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.48 by dl, Thu May 27 16:46:48 2010 UTC vs.
Revision 1.88 by dl, Sun Mar 4 19:47:08 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	–
8		import java.io.Serializable;
9		import java.util.Collection;
13	–	import java.util.Collections;
10		import java.util.List;
11		import java.util.RandomAccess;
12	<	import java.util.Map;
13	<	import java.util.WeakHashMap;
12	>	import java.lang.ref.WeakReference;
13	>	import java.lang.ref.ReferenceQueue;
14	>	import java.util.concurrent.Callable;
15	>	import java.util.concurrent.CancellationException;
16	>	import java.util.concurrent.ExecutionException;
17	>	import java.util.concurrent.Future;
18	>	import java.util.concurrent.RejectedExecutionException;
19	>	import java.util.concurrent.RunnableFuture;
20	>	import java.util.concurrent.TimeUnit;
21	>	import java.util.concurrent.TimeoutException;
22	>	import java.util.concurrent.locks.ReentrantLock;
23	>	import java.lang.reflect.Constructor;
24
25		/**
26		* Abstract base class for tasks that run within a {@link ForkJoinPool}.
#	Line 28 | Line 34 | import java.util.WeakHashMap;
34		* start other subtasks.  As indicated by the name of this class,
35		* many programs using {@code ForkJoinTask} employ only methods
36		* {@link #fork} and {@link #join}, or derivatives such as {@link
37	<	* #invokeAll}.  However, this class also provides a number of other
38	<	* methods that can come into play in advanced usages, as well as
39	<	* extension mechanics that allow support of new forms of fork/join
40	<	* processing.
37	>	* #invokeAll(ForkJoinTask...) invokeAll}.  However, this class also
38	>	* provides a number of other methods that can come into play in
39	>	* advanced usages, as well as extension mechanics that allow
40	>	* support of new forms of fork/join processing.
41		*
42		* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
43		* The efficiency of {@code ForkJoinTask}s stems from a set of
44		* restrictions (that are only partially statically enforceable)
45	<	* reflecting their intended use as computational tasks calculating
46	<	* pure functions or operating on purely isolated objects.  The
47	<	* primary coordination mechanisms are {@link #fork}, that arranges
45	>	* reflecting their main use as computational tasks calculating pure
46	>	* functions or operating on purely isolated objects.  The primary
47	>	* coordination mechanisms are {@link #fork}, that arranges
48		* asynchronous execution, and {@link #join}, that doesn't proceed
49		* until the task's result has been computed.  Computations should
50	<	* avoid {@code synchronized} methods or blocks, and should minimize
51	<	* other blocking synchronization apart from joining other tasks or
52	<	* using synchronizers such as Phasers that are advertised to
53	<	* cooperate with fork/join scheduling. Tasks should also not perform
54	<	* blocking IO, and should ideally access variables that are
55	<	* completely independent of those accessed by other running
56	<	* tasks. Minor breaches of these restrictions, for example using
57	<	* shared output streams, may be tolerable in practice, but frequent
58	<	* use may result in poor performance, and the potential to
59	<	* indefinitely stall if the number of threads not waiting for IO or
60	<	* other external synchronization becomes exhausted. This usage
61	<	* restriction is in part enforced by not permitting checked
62	<	* exceptions such as {@code IOExceptions} to be thrown. However,
63	<	* computations may still encounter unchecked exceptions, that are
64	<	* rethrown to callers attempting to join them. These exceptions may
65	<	* additionally include {@link RejectedExecutionException} stemming
66	<	* from internal resource exhaustion, such as failure to allocate
67	<	* internal task queues.
50	>	* ideally avoid {@code synchronized} methods or blocks, and should
51	>	* minimize other blocking synchronization apart from joining other
52	>	* tasks or using synchronizers such as Phasers that are advertised to
53	>	* cooperate with fork/join scheduling. Subdividable tasks should also
54	>	* not perform blocking IO, and should ideally access variables that
55	>	* are completely independent of those accessed by other running
56	>	* tasks. These guidelines are loosely enforced by not permitting
57	>	* checked exceptions such as {@code IOExceptions} to be
58	>	* thrown. However, computations may still encounter unchecked
59	>	* exceptions, that are rethrown to callers attempting to join
60	>	* them. These exceptions may additionally include {@link
61	>	* RejectedExecutionException} stemming from internal resource
62	>	* exhaustion, such as failure to allocate internal task
63	>	* queues. Rethrown exceptions behave in the same way as regular
64	>	* exceptions, but, when possible, contain stack traces (as displayed
65	>	* for example using {@code ex.printStackTrace()}) of both the thread
66	>	* that initiated the computation as well as the thread actually
67	>	* encountering the exception; minimally only the latter.
68	>	*
69	>	* <p>It is possible to define and use ForkJoinTasks that may block,
70	>	* but doing do requires three further considerations: (1) Completion
71	>	* of few if any <em>other</em> tasks should be dependent on a task
72	>	* that blocks on external synchronization or IO. Event-style async
73	>	* tasks that are never joined often fall into this category.  (2) To
74	>	* minimize resource impact, tasks should be small; ideally performing
75	>	* only the (possibly) blocking action. (3) Unless the {@link
76	>	* ForkJoinPool.ManagedBlocker} API is used, or the number of possibly
77	>	* blocked tasks is known to be less than the pool's {@link
78	>	* ForkJoinPool#getParallelism} level, the pool cannot guarantee that
79	>	* enough threads will be available to ensure progress or good
80	>	* performance.
81		*
82		* <p>The primary method for awaiting completion and extracting
83		* results of a task is {@link #join}, but there are several variants:
84		* The {@link Future#get} methods support interruptible and/or timed
85		* waits for completion and report results using {@code Future}
86	<	* conventions. Method {@link #helpJoin} enables callers to actively
68	<	* execute other tasks while awaiting joins, which is sometimes more
69	<	* efficient but only applies when all subtasks are known to be
70	<	* strictly tree-structured. Method {@link #invoke} is semantically
86	>	* conventions. Method {@link #invoke} is semantically
87		* equivalent to {@code fork(); join()} but always attempts to begin
88		* execution in the current thread. The "<em>quiet</em>" forms of
89		* these methods do not extract results or report exceptions. These
#	Line 77 | Line 93 | import java.util.WeakHashMap;
93		* performs the most common form of parallel invocation: forking a set
94		* of tasks and joining them all.
95		*
96	+	* <p>In the most typical usages, a fork-join pair act like a call
97	+	* (fork) and return (join) from a parallel recursive function. As is
98	+	* the case with other forms of recursive calls, returns (joins)
99	+	* should be performed innermost-first. For example, {@code a.fork();
100	+	* b.fork(); b.join(); a.join();} is likely to be substantially more
101	+	* efficient than joining {@code a} before {@code b}.
102	+	*
103		* <p>The execution status of tasks may be queried at several levels
104		* of detail: {@link #isDone} is true if a task completed in any way
105		* (including the case where a task was cancelled without executing);
#	Line 103 | Line 126 | import java.util.WeakHashMap;
126		* ForkJoinTasks (as may be determined using method {@link
127		* #inForkJoinPool}).  Attempts to invoke them in other contexts
128		* result in exceptions or errors, possibly including
129	<	* ClassCastException.
129	>	* {@code ClassCastException}.
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
141	>	* short} value using {@link #setForkJoinTaskTag} or {@link
142	>	* #compareAndSetForkJoinTaskTag} and checked using {@link
143	>	* #getForkJoinTaskTag}. The ForkJoinTask implementation does not
144	>	* use these {@code protected} methods or tags for any purpose, but
145	>	* they may be of use in the construction of specialized subclasses.
146	>	* For example, parallel graph traversals can use the supplied methods
147	>	* to avoid revisiting nodes/tasks that have already been processed.
148	>	* Also, completion based designs can use them to record that subtasks
149	>	* have completed. (Method names for tagging are bulky in part to
150	>	* encourage definition of methods that reflect their usage patterns.)
151		*
152		* <p>Most base support methods are {@code final}, to prevent
153		* overriding of implementations that are intrinsically tied to the
#	Line 119 | Line 163 | import java.util.WeakHashMap;
163		* computation. Large tasks should be split into smaller subtasks,
164		* usually via recursive decomposition. As a very rough rule of thumb,
165		* a task should perform more than 100 and less than 10000 basic
166	<	* computational steps. If tasks are too big, then parallelism cannot
167	<	* improve throughput. If too small, then memory and internal task
168	<	* maintenance overhead may overwhelm processing.
166	>	* computational steps, and should avoid indefinite looping. If tasks
167	>	* are too big, then parallelism cannot improve throughput. If too
168	>	* small, then memory and internal task maintenance overhead may
169	>	* overwhelm processing.
170		*
171		* <p>This class provides {@code adapt} methods for {@link Runnable}
172		* and {@link Callable}, that may be of use when mixing execution of
173	<	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks
174	<	* are of this form, consider using a pool in
130	<	* {@linkplain ForkJoinPool#setAsyncMode async mode}.
173	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
174	>	* of this form, consider using a pool constructed in <em>asyncMode</em>.
175		*
176		* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
177		* used in extensions such as remote execution frameworks. It is
#	Line 143 | Line 187 | public abstract class ForkJoinTask<V> im
187		* See the internal documentation of class ForkJoinPool for a
188		* general implementation overview.  ForkJoinTasks are mainly
189		* responsible for maintaining their "status" field amidst relays
190	<	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
147	<	* methods of this class are more-or-less layered into (1) basic
148	<	* status maintenance (2) execution and awaiting completion (3)
149	<	* user-level methods that additionally report results. This is
150	<	* sometimes hard to see because this file orders exported methods
151	<	* in a way that flows well in javadocs.
152	<	*/
153	<
154	<	/**
155	<	* Run control status bits packed into a single int to minimize
156	<	* footprint and to ensure atomicity (via CAS).  Status is
157	<	* initially zero, and takes on nonnegative values until
158	<	* completed, upon which status holds COMPLETED. CANCELLED, or
159	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
160	<	* blocking waits by other threads have the SIGNAL bit set.
161	<	*
162	<	* Completion of a stolen task with SIGNAL set awakens any waiters
163	<	* via notifyAll. Even though suboptimal for some purposes, we use
164	<	* basic builtin wait/notify to take advantage of "monitor
165	<	* inflation" in JVMs that we would otherwise need to emulate to
166	<	* avoid adding further per-task bookkeeping overhead.  We want
167	<	* these monitors to be "fat", i.e., not use biasing or thin-lock
168	<	* techniques, so use some odd coding idioms that tend to avoid
169	<	* them.
190	>	* to methods in ForkJoinWorkerThread and ForkJoinPool.
191		*
192	<	* Note that bits 1-28 are currently unused. Also value
193	<	* 0x80000000 is available as spare completion value.
192	>	* The methods of this class are more-or-less layered into
193	>	* (1) basic status maintenance
194	>	* (2) execution and awaiting completion
195	>	* (3) user-level methods that additionally report results.
196	>	* This is sometimes hard to see because this file orders exported
197	>	* methods in a way that flows well in javadocs.
198		*/
174	–	volatile int status; // accessed directly by pool and workers
175	–
176	–	private static final int COMPLETION_MASK      = 0xe0000000;
177	–	private static final int NORMAL               = 0xe0000000; // == mask
178	–	private static final int CANCELLED            = 0xc0000000;
179	–	private static final int EXCEPTIONAL          = 0xa0000000;
180	–	private static final int SIGNAL               = 0x00000001;
199
200	<	/**
201	<	* Table of exceptions thrown by tasks, to enable reporting by
202	<	* callers. Because exceptions are rare, we don't directly keep
203	<	* them with task objects, but instead use a weak ref table.  Note
204	<	* that cancellation exceptions don't appear in the table, but are
205	<	* instead recorded as status values.
206	<	* TODO: Use ConcurrentReferenceHashMap
200	>	/*
201	>	* The status field holds run control status bits packed into a
202	>	* single int to minimize footprint and to ensure atomicity (via
203	>	* CAS).  Status is initially zero, and takes on nonnegative
204	>	* values until completed, upon which status (anded with
205	>	* DONE_MASK) holds value NORMAL, CANCELLED, or EXCEPTIONAL. Tasks
206	>	* undergoing blocking waits by other threads have the SIGNAL bit
207	>	* set.  Completion of a stolen task with SIGNAL set awakens any
208	>	* waiters via notifyAll. Even though suboptimal for some
209	>	* purposes, we use basic builtin wait/notify to take advantage of
210	>	* "monitor inflation" in JVMs that we would otherwise need to
211	>	* emulate to avoid adding further per-task bookkeeping overhead.
212	>	* We want these monitors to be "fat", i.e., not use biasing or
213	>	* thin-lock techniques, so use some odd coding idioms that tend
214	>	* to avoid them, mainly by arranging that every synchronized
215	>	* block performs a wait, notifyAll or both.
216	>	*
217	>	* These control bits occupy only (some of) the upper half (16
218	>	* bits) of status field. The lower bits are used for user-defined
219	>	* tags.
220		*/
190	–	static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
191	–	Collections.synchronizedMap
192	–	(new WeakHashMap<ForkJoinTask<?>, Throwable>());
221
222	<	// Maintaining completion status
222	>	/** The run status of this task */
223	>	volatile int status; // accessed directly by pool and workers
224	>	static final int DONE_MASK   = 0xf0000000;  // mask out non-completion bits
225	>	static final int NORMAL      = 0xf0000000;  // must be negative
226	>	static final int CANCELLED   = 0xc0000000;  // must be < NORMAL
227	>	static final int EXCEPTIONAL = 0x80000000;  // must be < CANCELLED
228	>	static final int SIGNAL      = 0x00010000;  // must be >= 1 << 16
229	>	static final int SMASK       = 0x0000ffff;  // short bits for tags
230
231		/**
232	<	* Marks completion and wakes up threads waiting to join this task,
233	<	* also clearing signal request bits.
232	>	* Marks completion and wakes up threads waiting to join this
233	>	* task.
234		*
235		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
236	<	* @return status on exit
236	>	* @return completion status on exit
237		*/
238		private int setCompletion(int completion) {
239	<	int s;
240	<	while ((s = status) >= 0) {
241	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
242	<	if ((s & SIGNAL) != 0)
239	>	for (int s;;) {
240	>	if ((s = status) < 0)
241	>	return s;
242	>	if (U.compareAndSwapInt(this, STATUS, s, s | completion)) {
243	>	if ((s >>> 16) != 0)
244		synchronized (this) { notifyAll(); }
245		return completion;
246		}
247		}
248	+	}
249	+
250	+	/**
251	+	* Primary execution method for stolen tasks. Unless done, calls
252	+	* exec and records status if completed, but doesn't wait for
253	+	* completion otherwise.
254	+	*
255	+	* @return status on exit from this method
256	+	*/
257	+	final int doExec() {
258	+	int s; boolean completed;
259	+	if ((s = status) >= 0) {
260	+	try {
261	+	completed = exec();
262	+	} catch (Throwable rex) {
263	+	return setExceptionalCompletion(rex);
264	+	}
265	+	if (completed)
266	+	s = setCompletion(NORMAL);
267	+	}
268		return s;
269		}
270
271		/**
272	<	* Record exception and set exceptional completion
273	<	* @return status on exit
272	>	* Tries to set SIGNAL status. Used by ForkJoinPool. Other
273	>	* variants are directly incorporated into externalAwaitDone etc.
274	>	*
275	>	* @return true if successful
276		*/
277	<	private int setExceptionalCompletion(Throwable rex) {
278	<	exceptionMap.put(this, rex);
279	<	return setCompletion(EXCEPTIONAL);
277	>	final boolean trySetSignal() {
278	>	int s;
279	>	return U.compareAndSwapInt(this, STATUS, s = status, s | SIGNAL);
280		}
281
282		/**
283	<	* Blocks a worker thread until completion. Called only by pool.
283	>	* Blocks a non-worker-thread until completion.
284	>	* @return status upon completion
285		*/
286	<	final void internalAwaitDone() {
286	>	private int externalAwaitDone() {
287	>	boolean interrupted = false;
288		int s;
289		while ((s = status) >= 0) {
290	<	synchronized(this) {
291	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, s|SIGNAL)){
292	<	do {
290	>	if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
291	>	synchronized (this) {
292	>	if (status >= 0) {
293		try {
294		wait();
295		} catch (InterruptedException ie) {
296	<	cancelIfTerminating();
296	>	interrupted = true;
297		}
298	<	} while (status >= 0);
299	<	break;
298	>	}
299	>	else
300	>	notifyAll();
301		}
302		}
303		}
304	+	if (interrupted)
305	+	Thread.currentThread().interrupt();
306	+	return s;
307		}
308
309		/**
310	<	* Blocks a non-worker-thread until completion.
247	<	* @return status on exit
310	>	* Blocks a non-worker-thread until completion or interruption.
311		*/
312	<	private int externalAwaitDone() {
312	>	private int externalInterruptibleAwaitDone() throws InterruptedException {
313		int s;
314	+	if (Thread.interrupted())
315	+	throw new InterruptedException();
316		while ((s = status) >= 0) {
317	<	synchronized(this) {
318	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, s|SIGNAL)){
319	<	boolean interrupted = false;
320	<	do {
321	<	try {
322	<	wait();
258	<	} catch (InterruptedException ie) {
259	<	interrupted = true;
260	<	}
261	<	} while ((s = status) >= 0);
262	<	if (interrupted)
263	<	Thread.currentThread().interrupt();
264	<	break;
317	>	if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
318	>	synchronized (this) {
319	>	if (status >= 0)
320	>	wait();
321	>	else
322	>	notifyAll();
323		}
324		}
325		}
#	Line 269 | Line 327 | public abstract class ForkJoinTask<V> im
327		}
328
329		/**
330	<	* Unless done, calls exec and records status if completed, but
331	<	* doesn't wait for completion otherwise.
330	>	* Implementation for join, get, quietlyJoin. Directly handles
331	>	* only cases of already-completed, external wait, and
332	>	* unfork+exec.  Others are relayed to ForkJoinPool.awaitJoin.
333	>	*
334	>	* @return status upon completion
335	>	*/
336	>	private int doJoin() {
337	>	int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w;
338	>	if ((s = status) >= 0) {
339	>	if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) {
340	>	if (!(w = (wt = (ForkJoinWorkerThread)t).workQueue).
341	>	tryUnpush(this) || (s = doExec()) >= 0)
342	>	s = wt.pool.awaitJoin(w, this);
343	>	}
344	>	else
345	>	s = externalAwaitDone();
346	>	}
347	>	return s;
348	>	}
349	>
350	>	/**
351	>	* Implementation for invoke, quietlyInvoke.
352	>	*
353	>	* @return status upon completion
354		*/
355	<	final void tryExec() {
356	<	try {
357	<	if (status < 0 || !exec())
358	<	return;
359	<	} catch (Throwable rex) {
360	<	setExceptionalCompletion(rex);
361	<	return;
355	>	private int doInvoke() {
356	>	int s; Thread t; ForkJoinWorkerThread wt;
357	>	if ((s = doExec()) >= 0) {
358	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
359	>	s = (wt = (ForkJoinWorkerThread)t).pool.awaitJoin(wt.workQueue,
360	>	this);
361	>	else
362	>	s = externalAwaitDone();
363		}
364	<	setCompletion(NORMAL); // must be outside try block
364	>	return s;
365		}
366
367	+	// Exception table support
368	+
369	+	/**
370	+	* Table of exceptions thrown by tasks, to enable reporting by
371	+	* callers. Because exceptions are rare, we don't directly keep
372	+	* them with task objects, but instead use a weak ref table.  Note
373	+	* that cancellation exceptions don't appear in the table, but are
374	+	* instead recorded as status values.
375	+	*
376	+	* Note: These statics are initialized below in static block.
377	+	*/
378	+	private static final ExceptionNode[] exceptionTable;
379	+	private static final ReentrantLock exceptionTableLock;
380	+	private static final ReferenceQueue<Object> exceptionTableRefQueue;
381	+
382	+	/**
383	+	* Fixed capacity for exceptionTable.
384	+	*/
385	+	private static final int EXCEPTION_MAP_CAPACITY = 32;
386	+
387		/**
388	<	* If not done and this task is next in worker queue, runs it,
389	<	* else waits for it.
388	>	* Key-value nodes for exception table.  The chained hash table
389	>	* uses identity comparisons, full locking, and weak references
390	>	* for keys. The table has a fixed capacity because it only
391	>	* maintains task exceptions long enough for joiners to access
392	>	* them, so should never become very large for sustained
393	>	* periods. However, since we do not know when the last joiner
394	>	* completes, we must use weak references and expunge them. We do
395	>	* so on each operation (hence full locking). Also, some thread in
396	>	* any ForkJoinPool will call helpExpungeStaleExceptions when its
397	>	* pool becomes isQuiescent.
398	>	*/
399	>	static final class ExceptionNode extends WeakReference<ForkJoinTask<?>> {
400	>	final Throwable ex;
401	>	ExceptionNode next;
402	>	final long thrower;  // use id not ref to avoid weak cycles
403	>	ExceptionNode(ForkJoinTask<?> task, Throwable ex, ExceptionNode next) {
404	>	super(task, exceptionTableRefQueue);
405	>	this.ex = ex;
406	>	this.next = next;
407	>	this.thrower = Thread.currentThread().getId();
408	>	}
409	>	}
410	>
411	>	/**
412	>	* Records exception and sets exceptional completion.
413	>	*
414		* @return status on exit
415		*/
416	<	private int waitingJoin() {
417	<	int s = status;
418	<	if (s < 0)
419	<	return s;
420	<	Thread t = Thread.currentThread();
421	<	if (t instanceof ForkJoinWorkerThread) {
422	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
423	<	if (w.unpushTask(this)) {
424	<	boolean completed;
425	<	try {
426	<	completed = exec();
427	<	} catch (Throwable rex) {
303	<	return setExceptionalCompletion(rex);
416	>	private int setExceptionalCompletion(Throwable ex) {
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 (completed)
430	<	return setCompletion(NORMAL);
429	>	if (e.get() == this) // already present
430	>	break;
431		}
432	<	return w.pool.awaitJoin(this);
432	>	} finally {
433	>	lock.unlock();
434		}
435	<	else
311	<	return externalAwaitDone();
435	>	return setCompletion(EXCEPTIONAL);
436		}
437
438		/**
439	<	* Unless done, calls exec and records status if completed, or
440	<	* waits for completion otherwise.
441	<	* @return status on exit
439	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
440	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
441	>	* exceptions, but if it does anyway, we have no recourse during
442	>	* shutdown, so guard against this case.
443	>	*/
444	>	static final void cancelIgnoringExceptions(ForkJoinTask<?> t) {
445	>	if (t != null && t.status >= 0) {
446	>	try {
447	>	t.cancel(false);
448	>	} catch (Throwable ignore) {
449	>	}
450	>	}
451	>	}
452	>
453	>	/**
454	>	* Removes exception node and clears status
455		*/
456	<	private int waitingInvoke() {
457	<	int s = status;
458	<	if (s < 0)
459	<	return s;
323	<	boolean completed;
456	>	private void clearExceptionalCompletion() {
457	>	int h = System.identityHashCode(this);
458	>	final ReentrantLock lock = exceptionTableLock;
459	>	lock.lock();
460		try {
461	<	completed = exec();
462	<	} catch (Throwable rex) {
463	<	return setExceptionalCompletion(rex);
461	>	ExceptionNode[] t = exceptionTable;
462	>	int i = h & (t.length - 1);
463	>	ExceptionNode e = t[i];
464	>	ExceptionNode pred = null;
465	>	while (e != null) {
466	>	ExceptionNode next = e.next;
467	>	if (e.get() == this) {
468	>	if (pred == null)
469	>	t[i] = next;
470	>	else
471	>	pred.next = next;
472	>	break;
473	>	}
474	>	pred = e;
475	>	e = next;
476	>	}
477	>	expungeStaleExceptions();
478	>	status = 0;
479	>	} finally {
480	>	lock.unlock();
481		}
329	–	if (completed)
330	–	return setCompletion(NORMAL);
331	–	return waitingJoin();
482		}
483
484		/**
485	<	* If this task is next in worker queue, runs it, else processes other
486	<	* tasks until complete.
487	<	* @return status on exit
485	>	* Returns a rethrowable exception for the given task, if
486	>	* available. To provide accurate stack traces, if the exception
487	>	* was not thrown by the current thread, we try to create a new
488	>	* exception of the same type as the one thrown, but with the
489	>	* recorded exception as its cause. If there is no such
490	>	* constructor, we instead try to use a no-arg constructor,
491	>	* followed by initCause, to the same effect. If none of these
492	>	* apply, or any fail due to other exceptions, we return the
493	>	* recorded exception, which is still correct, although it may
494	>	* contain a misleading stack trace.
495	>	*
496	>	* @return the exception, or null if none
497	>	*/
498	>	private Throwable getThrowableException() {
499	>	if ((status & DONE_MASK) != EXCEPTIONAL)
500	>	return null;
501	>	int h = System.identityHashCode(this);
502	>	ExceptionNode e;
503	>	final ReentrantLock lock = exceptionTableLock;
504	>	lock.lock();
505	>	try {
506	>	expungeStaleExceptions();
507	>	ExceptionNode[] t = exceptionTable;
508	>	e = t[h & (t.length - 1)];
509	>	while (e != null && e.get() != this)
510	>	e = e.next;
511	>	} finally {
512	>	lock.unlock();
513	>	}
514	>	Throwable ex;
515	>	if (e == null || (ex = e.ex) == null)
516	>	return null;
517	>	if (e.thrower != Thread.currentThread().getId()) {
518	>	Class<? extends Throwable> ec = ex.getClass();
519	>	try {
520	>	Constructor<?> noArgCtor = null;
521	>	Constructor<?>[] cs = ec.getConstructors();// public ctors only
522	>	for (int i = 0; i < cs.length; ++i) {
523	>	Constructor<?> c = cs[i];
524	>	Class<?>[] ps = c.getParameterTypes();
525	>	if (ps.length == 0)
526	>	noArgCtor = c;
527	>	else if (ps.length == 1 && ps[0] == Throwable.class)
528	>	return (Throwable)(c.newInstance(ex));
529	>	}
530	>	if (noArgCtor != null) {
531	>	Throwable wx = (Throwable)(noArgCtor.newInstance());
532	>	wx.initCause(ex);
533	>	return wx;
534	>	}
535	>	} catch (Exception ignore) {
536	>	}
537	>	}
538	>	return ex;
539	>	}
540	>
541	>	/**
542	>	* Poll stale refs and remove them. Call only while holding lock.
543		*/
544	<	private int busyJoin() {
545	<	int s = status;
546	<	if (s < 0)
547	<	return s;
548	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
549	<	if (w.unpushTask(this)) {
550	<	boolean completed;
544	>	private static void expungeStaleExceptions() {
545	>	for (Object x; (x = exceptionTableRefQueue.poll()) != null;) {
546	>	if (x instanceof ExceptionNode) {
547	>	ForkJoinTask<?> key = ((ExceptionNode)x).get();
548	>	ExceptionNode[] t = exceptionTable;
549	>	int i = System.identityHashCode(key) & (t.length - 1);
550	>	ExceptionNode e = t[i];
551	>	ExceptionNode pred = null;
552	>	while (e != null) {
553	>	ExceptionNode next = e.next;
554	>	if (e == x) {
555	>	if (pred == null)
556	>	t[i] = next;
557	>	else
558	>	pred.next = next;
559	>	break;
560	>	}
561	>	pred = e;
562	>	e = next;
563	>	}
564	>	}
565	>	}
566	>	}
567	>
568	>	/**
569	>	* If lock is available, poll stale refs and remove them.
570	>	* Called from ForkJoinPool when pools become quiescent.
571	>	*/
572	>	static final void helpExpungeStaleExceptions() {
573	>	final ReentrantLock lock = exceptionTableLock;
574	>	if (lock.tryLock()) {
575		try {
576	<	completed = exec();
577	<	} catch (Throwable rex) {
578	<	return setExceptionalCompletion(rex);
576	>	expungeStaleExceptions();
577	>	} finally {
578	>	lock.unlock();
579		}
351	–	if (completed)
352	–	return setCompletion(NORMAL);
580		}
354	–	return w.execWhileJoining(this);
581		}
582
583		/**
584	<	* Returns result or throws exception associated with given status.
359	<	* @param s the status
584	>	* Throws exception, if any, associated with the given status.
585		*/
586	<	private V reportResult(int s) {
587	<	Throwable ex;
588	<	if (s < NORMAL && (ex = getException()) != null)
589	<	UNSAFE.throwException(ex);
590	<	return getRawResult();
586	>	private void reportException(int s) {
587	>	Throwable ex = ((s == CANCELLED) ?  new CancellationException() :
588	>	(s == EXCEPTIONAL) ? getThrowableException() :
589	>	null);
590	>	if (ex != null)
591	>	U.throwException(ex);
592		}
593
594		// public methods
#	Line 378 | Line 604 | public abstract class ForkJoinTask<V> im
604		* #isDone} returning {@code true}.
605		*
606		* <p>This method may be invoked only from within {@code
607	<	* ForkJoinTask} computations (as may be determined using method
607	>	* ForkJoinPool} computations (as may be determined using method
608		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
609		* result in exceptions or errors, possibly including {@code
610		* ClassCastException}.
#	Line 386 | Line 612 | public abstract class ForkJoinTask<V> im
612		* @return {@code this}, to simplify usage
613		*/
614		public final ForkJoinTask<V> fork() {
615	<	((ForkJoinWorkerThread) Thread.currentThread())
390	<	.pushTask(this);
615	>	((ForkJoinWorkerThread)Thread.currentThread()).workQueue.push(this);
616		return this;
617		}
618
619		/**
620	<	* Returns the result of the computation when it {@link #isDone is done}.
621	<	* This method differs from {@link #get()} in that
620	>	* Returns the result of the computation when it {@link #isDone is
621	>	* done}.  This method differs from {@link #get()} in that
622		* abnormal completion results in {@code RuntimeException} or
623	<	* {@code Error}, not {@code ExecutionException}.
623	>	* {@code Error}, not {@code ExecutionException}, and that
624	>	* interrupts of the calling thread do <em>not</em> cause the
625	>	* method to abruptly return by throwing {@code
626	>	* InterruptedException}.
627		*
628		* @return the computed result
629		*/
630		public final V join() {
631	<	return reportResult(waitingJoin());
631	>	int s;
632	>	if ((s = doJoin() & DONE_MASK) != NORMAL)
633	>	reportException(s);
634	>	return getRawResult();
635		}
636
637		/**
638		* Commences performing this task, awaits its completion if
639	<	* necessary, and return its result, or throws an (unchecked)
640	<	* exception if the underlying computation did so.
639	>	* necessary, and returns its result, or throws an (unchecked)
640	>	* {@code RuntimeException} or {@code Error} if the underlying
641	>	* computation did so.
642		*
643		* @return the computed result
644		*/
645		public final V invoke() {
646	<	return reportResult(waitingInvoke());
646	>	int s;
647	>	if ((s = doInvoke() & DONE_MASK) != NORMAL)
648	>	reportException(s);
649	>	return getRawResult();
650		}
651
652		/**
653		* Forks the given tasks, returning when {@code isDone} holds for
654		* each task or an (unchecked) exception is encountered, in which
655	<	* case the exception is rethrown.  If either task encounters an
656	<	* exception, the other one may be, but is not guaranteed to be,
657	<	* cancelled.  If both tasks throw an exception, then this method
658	<	* throws one of them.  The individual status of each task may be
659	<	* checked using {@link #getException()} and related methods.
655	>	* case the exception is rethrown. If more than one task
656	>	* encounters an exception, then this method throws any one of
657	>	* these exceptions. If any task encounters an exception, the
658	>	* other may be cancelled. However, the execution status of
659	>	* individual tasks is not guaranteed upon exceptional return. The
660	>	* status of each task may be obtained using {@link
661	>	* #getException()} and related methods to check if they have been
662	>	* cancelled, completed normally or exceptionally, or left
663	>	* unprocessed.
664		*
665		* <p>This method may be invoked only from within {@code
666	<	* ForkJoinTask} computations (as may be determined using method
666	>	* ForkJoinPool} computations (as may be determined using method
667		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
668		* result in exceptions or errors, possibly including {@code
669		* ClassCastException}.
#	Line 434 | Line 673 | public abstract class ForkJoinTask<V> im
673		* @throws NullPointerException if any task is null
674		*/
675		public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
676	+	int s1, s2;
677		t2.fork();
678	<	t1.invoke();
679	<	t2.join();
678	>	if ((s1 = t1.doInvoke() & DONE_MASK) != NORMAL)
679	>	t1.reportException(s1);
680	>	if ((s2 = t2.doJoin() & DONE_MASK) != NORMAL)
681	>	t2.reportException(s2);
682		}
683
684		/**
685		* Forks the given tasks, returning when {@code isDone} holds for
686		* each task or an (unchecked) exception is encountered, in which
687	<	* case the exception is rethrown. If any task encounters an
688	<	* exception, others may be, but are not guaranteed to be,
689	<	* cancelled.  If more than one task encounters an exception, then
690	<	* this method throws any one of these exceptions.  The individual
691	<	* status of each task may be checked using {@link #getException()}
692	<	* and related methods.
687	>	* case the exception is rethrown. If more than one task
688	>	* encounters an exception, then this method throws any one of
689	>	* these exceptions. If any task encounters an exception, others
690	>	* may be cancelled. However, the execution status of individual
691	>	* tasks is not guaranteed upon exceptional return. The status of
692	>	* each task may be obtained using {@link #getException()} and
693	>	* related methods to check if they have been cancelled, completed
694	>	* normally or exceptionally, or left unprocessed.
695		*
696		* <p>This method may be invoked only from within {@code
697	<	* ForkJoinTask} computations (as may be determined using method
697	>	* ForkJoinPool} computations (as may be determined using method
698		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
699		* result in exceptions or errors, possibly including {@code
700		* ClassCastException}.
#	Line 469 | Line 713 | public abstract class ForkJoinTask<V> im
713		}
714		else if (i != 0)
715		t.fork();
716	<	else if (t.waitingInvoke() < NORMAL && ex == null)
716	>	else if (t.doInvoke() < NORMAL && ex == null)
717		ex = t.getException();
718		}
719		for (int i = 1; i <= last; ++i) {
#	Line 477 | Line 721 | public abstract class ForkJoinTask<V> im
721		if (t != null) {
722		if (ex != null)
723		t.cancel(false);
724	<	else if (t.waitingJoin() < NORMAL && ex == null)
724	>	else if (t.doJoin() < NORMAL)
725		ex = t.getException();
726		}
727		}
728		if (ex != null)
729	<	UNSAFE.throwException(ex);
729	>	U.throwException(ex);
730		}
731
732		/**
733		* Forks all tasks in the specified collection, returning when
734		* {@code isDone} holds for each task or an (unchecked) exception
735	<	* is encountered.  If any task encounters an exception, others
736	<	* may be, but are not guaranteed to be, cancelled.  If more than
737	<	* one task encounters an exception, then this method throws any
738	<	* one of these exceptions.  The individual status of each task
739	<	* may be checked using {@link #getException()} and related
740	<	* methods.  The behavior of this operation is undefined if the
741	<	* specified collection is modified while the operation is in
742	<	* progress.
735	>	* is encountered, in which case the exception is rethrown. If
736	>	* more than one task encounters an exception, then this method
737	>	* throws any one of these exceptions. If any task encounters an
738	>	* exception, others may be cancelled. However, the execution
739	>	* status of individual tasks is not guaranteed upon exceptional
740	>	* return. The status of each task may be obtained using {@link
741	>	* #getException()} and related methods to check if they have been
742	>	* cancelled, completed normally or exceptionally, or left
743	>	* unprocessed.
744		*
745		* <p>This method may be invoked only from within {@code
746	<	* ForkJoinTask} computations (as may be determined using method
746	>	* ForkJoinPool} computations (as may be determined using method
747		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
748		* result in exceptions or errors, possibly including {@code
749		* ClassCastException}.
#	Line 525 | Line 770 | public abstract class ForkJoinTask<V> im
770		}
771		else if (i != 0)
772		t.fork();
773	<	else if (t.waitingInvoke() < NORMAL && ex == null)
773	>	else if (t.doInvoke() < NORMAL && ex == null)
774		ex = t.getException();
775		}
776		for (int i = 1; i <= last; ++i) {
#	Line 533 | Line 778 | public abstract class ForkJoinTask<V> im
778		if (t != null) {
779		if (ex != null)
780		t.cancel(false);
781	<	else if (t.waitingJoin() < NORMAL && ex == null)
781	>	else if (t.doJoin() < NORMAL)
782		ex = t.getException();
783		}
784		}
785		if (ex != null)
786	<	UNSAFE.throwException(ex);
786	>	U.throwException(ex);
787		return tasks;
788		}
789
790		/**
791		* Attempts to cancel execution of this task. This attempt will
792	<	* fail if the task has already completed, has already been
793	<	* cancelled, or could not be cancelled for some other reason. If
794	<	* successful, and this task has not started when cancel is
795	<	* called, execution of this task is suppressed, {@link
796	<	* #isCancelled} will report true, and {@link #join} will result
797	<	* in a {@code CancellationException} being thrown.
792	>	* fail if the task has already completed or could not be
793	>	* cancelled for some other reason. If successful, and this task
794	>	* has not started when {@code cancel} is called, execution of
795	>	* this task is suppressed. After this method returns
796	>	* successfully, unless there is an intervening call to {@link
797	>	* #reinitialize}, subsequent calls to {@link #isCancelled},
798	>	* {@link #isDone}, and {@code cancel} will return {@code true}
799	>	* and calls to {@link #join} and related methods will result in
800	>	* {@code CancellationException}.
801		*
802		* <p>This method may be overridden in subclasses, but if so, must
803	<	* still ensure that these minimal properties hold. In particular,
804	<	* the {@code cancel} method itself must not throw exceptions.
803	>	* still ensure that these properties hold. In particular, the
804	>	* {@code cancel} method itself must not throw exceptions.
805		*
806		* <p>This method is designed to be invoked by <em>other</em>
807		* tasks. To terminate the current task, you can just return or
808		* throw an unchecked exception from its computation method, or
809		* invoke {@link #completeExceptionally}.
810		*
811	<	* @param mayInterruptIfRunning this value is ignored in the
812	<	* default implementation because tasks are not
813	<	* cancelled via interruption
811	>	* @param mayInterruptIfRunning this value has no effect in the
812	>	* default implementation because interrupts are not used to
813	>	* control cancellation.
814		*
815		* @return {@code true} if this task is now cancelled
816		*/
817		public boolean cancel(boolean mayInterruptIfRunning) {
818	<	setCompletion(CANCELLED);
571	<	return (status & COMPLETION_MASK) == CANCELLED;
572	<	}
573	<
574	<	/**
575	<	* Cancels, ignoring any exceptions it throws. Used during worker
576	<	* and pool shutdown.
577	<	*/
578	<	final void cancelIgnoringExceptions() {
579	<	try {
580	<	cancel(false);
581	<	} catch (Throwable ignore) {
582	<	}
583	<	}
584	<
585	<	/**
586	<	* Cancels ignoring exceptions if worker is terminating
587	<	*/
588	<	private void cancelIfTerminating() {
589	<	Thread t = Thread.currentThread();
590	<	if ((t instanceof ForkJoinWorkerThread) &&
591	<	((ForkJoinWorkerThread) t).isTerminating()) {
592	<	try {
593	<	cancel(false);
594	<	} catch (Throwable ignore) {
595	<	}
596	<	}
818	>	return (setCompletion(CANCELLED) & DONE_MASK) == CANCELLED;
819		}
820
821		public final boolean isDone() {
#	Line 601 | Line 823 | public abstract class ForkJoinTask<V> im
823		}
824
825		public final boolean isCancelled() {
826	<	return (status & COMPLETION_MASK) == CANCELLED;
826	>	return (status & DONE_MASK) == CANCELLED;
827		}
828
829		/**
#	Line 610 | Line 832 | public abstract class ForkJoinTask<V> im
832		* @return {@code true} if this task threw an exception or was cancelled
833		*/
834		public final boolean isCompletedAbnormally() {
835	<	return (status & COMPLETION_MASK) < NORMAL;
835	>	return status < NORMAL;
836		}
837
838		/**
#	Line 621 | Line 843 | public abstract class ForkJoinTask<V> im
843		* exception and was not cancelled
844		*/
845		public final boolean isCompletedNormally() {
846	<	return (status & COMPLETION_MASK) == NORMAL;
846	>	return (status & DONE_MASK) == NORMAL;
847		}
848
849		/**
#	Line 632 | Line 854 | public abstract class ForkJoinTask<V> im
854		* @return the exception, or {@code null} if none
855		*/
856		public final Throwable getException() {
857	<	int s = status & COMPLETION_MASK;
857	>	int s = status & DONE_MASK;
858		return ((s >= NORMAL)    ? null :
859		(s == CANCELLED) ? new CancellationException() :
860	<	exceptionMap.get(this));
860	>	getThrowableException());
861		}
862
863		/**
#	Line 660 | Line 882 | public abstract class ForkJoinTask<V> im
882
883		/**
884		* Completes this task, and if not already aborted or cancelled,
885	<	* returning a {@code null} result upon {@code join} and related
886	<	* operations. This method may be used to provide results for
887	<	* asynchronous tasks, or to provide alternative handling for
888	<	* tasks that would not otherwise complete normally. Its use in
889	<	* other situations is discouraged. This method is
890	<	* overridable, but overridden versions must invoke {@code super}
891	<	* implementation to maintain guarantees.
885	>	* returning the given value as the result of subsequent
886	>	* invocations of {@code join} and related operations. This method
887	>	* may be used to provide results for asynchronous tasks, or to
888	>	* provide alternative handling for tasks that would not otherwise
889	>	* complete normally. Its use in other situations is
890	>	* discouraged. This method is overridable, but overridden
891	>	* versions must invoke {@code super} implementation to maintain
892	>	* guarantees.
893		*
894		* @param value the result value for this task
895		*/
#	Line 680 | Line 903 | public abstract class ForkJoinTask<V> im
903		setCompletion(NORMAL);
904		}
905
906	+	/**
907	+	* Completes this task. The most recent value established by
908	+	* {@link #setRawResult} (or {@code null}) will be returned as the
909	+	* result of subsequent invocations of {@code join} and related
910	+	* operations. This method may be useful when processing sets of
911	+	* tasks when some do not otherwise complete normally. Its use in
912	+	* other situations is discouraged.
913	+	*/
914	+	public final void quietlyComplete() {
915	+	setCompletion(NORMAL);
916	+	}
917	+
918	+	/**
919	+	* Waits if necessary for the computation to complete, and then
920	+	* retrieves its result.
921	+	*
922	+	* @return the computed result
923	+	* @throws CancellationException if the computation was cancelled
924	+	* @throws ExecutionException if the computation threw an
925	+	* exception
926	+	* @throws InterruptedException if the current thread is not a
927	+	* member of a ForkJoinPool and was interrupted while waiting
928	+	*/
929		public final V get() throws InterruptedException, ExecutionException {
930	<	int s = waitingJoin() & COMPLETION_MASK;
931	<	if (Thread.interrupted())
932	<	throw new InterruptedException();
933	<	if (s < NORMAL) {
934	<	Throwable ex;
935	<	if (s == CANCELLED)
936	<	throw new CancellationException();
691	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
692	<	throw new ExecutionException(ex);
693	<	}
930	>	int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ?
931	>	doJoin() : externalInterruptibleAwaitDone();
932	>	Throwable ex;
933	>	if ((s &= DONE_MASK) == CANCELLED)
934	>	throw new CancellationException();
935	>	if (s == EXCEPTIONAL && (ex = getThrowableException()) != null)
936	>	throw new ExecutionException(ex);
937		return getRawResult();
938		}
939
940	+	/**
941	+	* Waits if necessary for at most the given time for the computation
942	+	* to complete, and then retrieves its result, if available.
943	+	*
944	+	* @param timeout the maximum time to wait
945	+	* @param unit the time unit of the timeout argument
946	+	* @return the computed result
947	+	* @throws CancellationException if the computation was cancelled
948	+	* @throws ExecutionException if the computation threw an
949	+	* exception
950	+	* @throws InterruptedException if the current thread is not a
951	+	* member of a ForkJoinPool and was interrupted while waiting
952	+	* @throws TimeoutException if the wait timed out
953	+	*/
954		public final V get(long timeout, TimeUnit unit)
955		throws InterruptedException, ExecutionException, TimeoutException {
956	<	Thread t = Thread.currentThread();
957	<	ForkJoinPool pool;
958	<	if (t instanceof ForkJoinWorkerThread) {
959	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
960	<	if (status >= 0 && w.unpushTask(this))
961	<	tryExec();
962	<	pool = w.pool;
963	<	}
964	<	else
965	<	pool = null;
966	<	/*
967	<	* Timed wait loop intermixes cases for fj (pool != null) and
968	<	* non FJ threads. For FJ, decrement pool count but don't try
969	<	* for replacement; increment count on completion. For non-FJ,
713	<	* deal with interrupts. This is messy, but a little less so
714	<	* than is splitting the FJ and nonFJ cases.
715	<	*/
716	<	boolean interrupted = false;
717	<	boolean dec = false; // true if pool count decremented
718	<	for (;;) {
719	<	if (Thread.interrupted() && pool == null) {
720	<	interrupted = true;
721	<	break;
956	>	if (Thread.interrupted())
957	>	throw new InterruptedException();
958	>	// Messy in part because we measure in nanosecs, but wait in millisecs
959	>	int s; long ns, ms;
960	>	if ((s = status) >= 0 && (ns = unit.toNanos(timeout)) > 0L) {
961	>	long deadline = System.nanoTime() + ns;
962	>	ForkJoinPool p = null;
963	>	ForkJoinPool.WorkQueue w = null;
964	>	Thread t = Thread.currentThread();
965	>	if (t instanceof ForkJoinWorkerThread) {
966	>	ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
967	>	p = wt.pool;
968	>	w = wt.workQueue;
969	>	s = p.helpJoinOnce(w, this); // no retries on failure
970		}
971	<	int s = status;
972	<	if (s < 0)
973	<	break;
974	<	if (UNSAFE.compareAndSwapInt(this, statusOffset,
975	<	s, s | SIGNAL)) {
976	<	long startTime = System.nanoTime();
977	<	long nanos = unit.toNanos(timeout);
978	<	long nt; // wait time
979	<	while (status >= 0 &&
980	<	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
733	<	if (pool != null && !dec)
734	<	dec = pool.tryDecrementRunningCount();
971	>	boolean canBlock = false;
972	>	boolean interrupted = false;
973	>	try {
974	>	while ((s = status) >= 0) {
975	>	if (w != null && w.runState < 0)
976	>	cancelIgnoringExceptions(this);
977	>	else if (!canBlock) {
978	>	if (p == null || p.tryCompensate(this, null))
979	>	canBlock = true;
980	>	}
981		else {
982	<	long ms = nt / 1000000;
983	<	int ns = (int) (nt % 1000000);
984	<	try {
985	<	synchronized(this) {
986	<	if (status >= 0)
987	<	wait(ms, ns);
988	<	}
989	<	} catch (InterruptedException ie) {
990	<	if (pool != null)
991	<	cancelIfTerminating();
992	<	else {
993	<	interrupted = true;
994	<	break;
982	>	if ((ms = TimeUnit.NANOSECONDS.toMillis(ns)) > 0L &&
983	>	U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
984	>	synchronized (this) {
985	>	if (status >= 0) {
986	>	try {
987	>	wait(ms);
988	>	} catch (InterruptedException ie) {
989	>	if (p == null)
990	>	interrupted = true;
991	>	}
992	>	}
993	>	else
994	>	notifyAll();
995		}
996		}
997	+	if ((s = status) < 0 || interrupted ||
998	+	(ns = deadline - System.nanoTime()) <= 0L)
999	+	break;
1000		}
1001		}
1002	<	break;
1002	>	} finally {
1003	>	if (p != null && canBlock)
1004	>	p.incrementActiveCount();
1005		}
1006	+	if (interrupted)
1007	+	throw new InterruptedException();
1008		}
1009	<	if (pool != null && dec)
757	<	pool.updateRunningCount(1);
758	<	if (interrupted)
759	<	throw new InterruptedException();
760	<	int es = status & COMPLETION_MASK;
761	<	if (es != NORMAL) {
1009	>	if ((s &= DONE_MASK) != NORMAL) {
1010		Throwable ex;
1011	<	if (es == CANCELLED)
1011	>	if (s == CANCELLED)
1012		throw new CancellationException();
1013	<	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
1013	>	if (s != EXCEPTIONAL)
1014	>	throw new TimeoutException();
1015	>	if ((ex = getThrowableException()) != null)
1016		throw new ExecutionException(ex);
767	–	throw new TimeoutException();
1017		}
1018		return getRawResult();
1019		}
1020
1021		/**
1022	<	* Possibly executes other tasks until this task {@link #isDone is
774	<	* done}, then returns the result of the computation.  This method
775	<	* may be more efficient than {@code join}, but is only applicable
776	<	* when there are no potential dependencies between continuation
777	<	* of the current task and that of any other task that might be
778	<	* executed while helping. (This usually holds for pure
779	<	* divide-and-conquer tasks).
780	<	*
781	<	* <p>This method may be invoked only from within {@code
782	<	* ForkJoinTask} computations (as may be determined using method
783	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
784	<	* result in exceptions or errors, possibly including {@code
785	<	* ClassCastException}.
786	<	*
787	<	* @return the computed result
788	<	*/
789	<	public final V helpJoin() {
790	<	return reportResult(busyJoin());
791	<	}
792	<
793	<	/**
794	<	* Possibly executes other tasks until this task {@link #isDone is
795	<	* done}.  This method may be useful when processing collections
796	<	* of tasks when some have been cancelled or otherwise known to
797	<	* have aborted.
798	<	*
799	<	* <p>This method may be invoked only from within {@code
800	<	* ForkJoinTask} computations (as may be determined using method
801	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
802	<	* result in exceptions or errors, possibly including {@code
803	<	* ClassCastException}.
804	<	*/
805	<	public final void quietlyHelpJoin() {
806	<	busyJoin();
807	<	}
808	<
809	<	/**
810	<	* Joins this task, without returning its result or throwing an
1022	>	* Joins this task, without returning its result or throwing its
1023		* exception. This method may be useful when processing
1024		* collections of tasks when some have been cancelled or otherwise
1025		* known to have aborted.
1026		*/
1027		public final void quietlyJoin() {
1028	<	waitingJoin();
1028	>	doJoin();
1029		}
1030
1031		/**
1032		* Commences performing this task and awaits its completion if
1033	<	* necessary, without returning its result or throwing an
1034	<	* exception. This method may be useful when processing
823	<	* collections of tasks when some have been cancelled or otherwise
824	<	* known to have aborted.
1033	>	* necessary, without returning its result or throwing its
1034	>	* exception.
1035		*/
1036		public final void quietlyInvoke() {
1037	<	waitingInvoke();
1037	>	doInvoke();
1038		}
1039
1040		/**
#	Line 835 | Line 1045 | public abstract class ForkJoinTask<V> im
1045		* processed.
1046		*
1047		* <p>This method may be invoked only from within {@code
1048	<	* ForkJoinTask} computations (as may be determined using method
1048	>	* ForkJoinPool} computations (as may be determined using method
1049		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1050		* result in exceptions or errors, possibly including {@code
1051		* ClassCastException}.
1052		*/
1053		public static void helpQuiesce() {
1054	<	((ForkJoinWorkerThread) Thread.currentThread())
1055	<	.helpQuiescePool();
1054	>	ForkJoinWorkerThread wt =
1055	>	(ForkJoinWorkerThread)Thread.currentThread();
1056	>	wt.pool.helpQuiescePool(wt.workQueue);
1057		}
1058
1059		/**
#	Line 854 | Line 1065 | public abstract class ForkJoinTask<V> im
1065		* under any other usage conditions are not guaranteed.
1066		* This method may be useful when executing
1067		* pre-constructed trees of subtasks in loops.
1068	+	*
1069	+	* <p>Upon completion of this method, {@code isDone()} reports
1070	+	* {@code false}, and {@code getException()} reports {@code
1071	+	* null}. However, the value returned by {@code getRawResult} is
1072	+	* unaffected. To clear this value, you can invoke {@code
1073	+	* setRawResult(null)}.
1074		*/
1075		public void reinitialize() {
1076	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
1077	<	exceptionMap.remove(this);
1078	<	status = 0;
1076	>	if ((status & DONE_MASK) == EXCEPTIONAL)
1077	>	clearExceptionalCompletion();
1078	>	else
1079	>	status = 0;
1080		}
1081
1082		/**
#	Line 875 | Line 1093 | public abstract class ForkJoinTask<V> im
1093		}
1094
1095		/**
1096	<	* Returns {@code true} if the current thread is executing as a
1097	<	* ForkJoinPool computation.
1096	>	* Returns {@code true} if the current thread is a {@link
1097	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation.
1098		*
1099	<	* @return {@code true} if the current thread is executing as a
1100	<	* ForkJoinPool computation, or false otherwise
1099	>	* @return {@code true} if the current thread is a {@link
1100	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation,
1101	>	* or {@code false} otherwise
1102		*/
1103		public static boolean inForkJoinPool() {
1104		return Thread.currentThread() instanceof ForkJoinWorkerThread;
#	Line 894 | Line 1113 | public abstract class ForkJoinTask<V> im
1113		* were not, stolen.
1114		*
1115		* <p>This method may be invoked only from within {@code
1116	<	* ForkJoinTask} computations (as may be determined using method
1116	>	* ForkJoinPool} computations (as may be determined using method
1117		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1118		* result in exceptions or errors, possibly including {@code
1119		* ClassCastException}.
#	Line 902 | Line 1121 | public abstract class ForkJoinTask<V> im
1121		* @return {@code true} if unforked
1122		*/
1123		public boolean tryUnfork() {
1124	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1125	<	.unpushTask(this);
1124	>	return ((ForkJoinWorkerThread)Thread.currentThread())
1125	>	.workQueue.tryUnpush(this);
1126		}
1127
1128		/**
#	Line 913 | Line 1132 | public abstract class ForkJoinTask<V> im
1132		* fork other tasks.
1133		*
1134		* <p>This method may be invoked only from within {@code
1135	<	* ForkJoinTask} computations (as may be determined using method
1135	>	* ForkJoinPool} computations (as may be determined using method
1136		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1137		* result in exceptions or errors, possibly including {@code
1138		* ClassCastException}.
#	Line 922 | Line 1141 | public abstract class ForkJoinTask<V> im
1141		*/
1142		public static int getQueuedTaskCount() {
1143		return ((ForkJoinWorkerThread) Thread.currentThread())
1144	<	.getQueueSize();
1144	>	.workQueue.queueSize();
1145		}
1146
1147		/**
#	Line 936 | Line 1155 | public abstract class ForkJoinTask<V> im
1155		* exceeded.
1156		*
1157		* <p>This method may be invoked only from within {@code
1158	<	* ForkJoinTask} computations (as may be determined using method
1158	>	* ForkJoinPool} computations (as may be determined using method
1159		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1160		* result in exceptions or errors, possibly including {@code
1161		* ClassCastException}.
#	Line 944 | Line 1163 | public abstract class ForkJoinTask<V> im
1163		* @return the surplus number of tasks, which may be negative
1164		*/
1165		public static int getSurplusQueuedTaskCount() {
1166	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1167	<	.getEstimatedSurplusTaskCount();
1166	>	/*
1167	>	* The aim of this method is to return a cheap heuristic guide
1168	>	* for task partitioning when programmers, frameworks, tools,
1169	>	* or languages have little or no idea about task granularity.
1170	>	* In essence by offering this method, we ask users only about
1171	>	* tradeoffs in overhead vs expected throughput and its
1172	>	* variance, rather than how finely to partition tasks.
1173	>	*
1174	>	* In a steady state strict (tree-structured) computation,
1175	>	* each thread makes available for stealing enough tasks for
1176	>	* other threads to remain active. Inductively, if all threads
1177	>	* play by the same rules, each thread should make available
1178	>	* only a constant number of tasks.
1179	>	*
1180	>	* The minimum useful constant is just 1. But using a value of
1181	>	* 1 would require immediate replenishment upon each steal to
1182	>	* maintain enough tasks, which is infeasible.  Further,
1183	>	* partitionings/granularities of offered tasks should
1184	>	* minimize steal rates, which in general means that threads
1185	>	* nearer the top of computation tree should generate more
1186	>	* than those nearer the bottom. In perfect steady state, each
1187	>	* thread is at approximately the same level of computation
1188	>	* tree. However, producing extra tasks amortizes the
1189	>	* uncertainty of progress and diffusion assumptions.
1190	>	*
1191	>	* So, users will want to use values larger, but not much
1192	>	* larger than 1 to both smooth over transient shortages and
1193	>	* hedge against uneven progress; as traded off against the
1194	>	* cost of extra task overhead. We leave the user to pick a
1195	>	* threshold value to compare with the results of this call to
1196	>	* guide decisions, but recommend values such as 3.
1197	>	*
1198	>	* When all threads are active, it is on average OK to
1199	>	* estimate surplus strictly locally. In steady-state, if one
1200	>	* thread is maintaining say 2 surplus tasks, then so are
1201	>	* others. So we can just use estimated queue length.
1202	>	* However, this strategy alone leads to serious mis-estimates
1203	>	* in some non-steady-state conditions (ramp-up, ramp-down,
1204	>	* other stalls). We can detect many of these by further
1205	>	* considering the number of "idle" threads, that are known to
1206	>	* have zero queued tasks, so compensate by a factor of
1207	>	* (#idle/#active) threads.
1208	>	*/
1209	>	ForkJoinWorkerThread wt =
1210	>	(ForkJoinWorkerThread)Thread.currentThread();
1211	>	return wt.workQueue.queueSize() - wt.pool.idlePerActive();
1212		}
1213
1214		// Extension methods
#	Line 994 | Line 1257 | public abstract class ForkJoinTask<V> im
1257		* otherwise.
1258		*
1259		* <p>This method may be invoked only from within {@code
1260	<	* ForkJoinTask} computations (as may be determined using method
1260	>	* ForkJoinPool} computations (as may be determined using method
1261		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1262		* result in exceptions or errors, possibly including {@code
1263		* ClassCastException}.
#	Line 1002 | Line 1265 | public abstract class ForkJoinTask<V> im
1265		* @return the next task, or {@code null} if none are available
1266		*/
1267		protected static ForkJoinTask<?> peekNextLocalTask() {
1268	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1006	<	.peekTask();
1268	>	return ((ForkJoinWorkerThread) Thread.currentThread()).workQueue.peek();
1269		}
1270
1271		/**
#	Line 1013 | Line 1275 | public abstract class ForkJoinTask<V> im
1275		* be useful otherwise.
1276		*
1277		* <p>This method may be invoked only from within {@code
1278	<	* ForkJoinTask} computations (as may be determined using method
1278	>	* ForkJoinPool} computations (as may be determined using method
1279		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1280		* result in exceptions or errors, possibly including {@code
1281		* ClassCastException}.
#	Line 1022 | Line 1284 | public abstract class ForkJoinTask<V> im
1284		*/
1285		protected static ForkJoinTask<?> pollNextLocalTask() {
1286		return ((ForkJoinWorkerThread) Thread.currentThread())
1287	<	.pollLocalTask();
1287	>	.workQueue.nextLocalTask();
1288		}
1289
1290		/**
#	Line 1036 | Line 1298 | public abstract class ForkJoinTask<V> im
1298		* otherwise.
1299		*
1300		* <p>This method may be invoked only from within {@code
1301	<	* ForkJoinTask} computations (as may be determined using method
1301	>	* ForkJoinPool} computations (as may be determined using method
1302		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1303		* result in exceptions or errors, possibly including {@code
1304		* ClassCastException}.
#	Line 1044 | Line 1306 | public abstract class ForkJoinTask<V> im
1306		* @return a task, or {@code null} if none are available
1307		*/
1308		protected static ForkJoinTask<?> pollTask() {
1309	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1310	<	.pollTask();
1309	>	ForkJoinWorkerThread wt =
1310	>	(ForkJoinWorkerThread)Thread.currentThread();
1311	>	return wt.pool.nextTaskFor(wt.workQueue);
1312	>	}
1313	>
1314	>	// tag operations
1315	>
1316	>	/**
1317	>	* Returns the tag for this task.
1318	>	*
1319	>	* @return the tag for this task
1320	>	* @since 1.8
1321	>	*/
1322	>	public final short getForkJoinTaskTag() {
1323	>	return (short)status;
1324	>	}
1325	>
1326	>	/**
1327	>	* Atomically sets the tag value for this task.
1328	>	*
1329	>	* @param tag the tag value
1330	>	* @return the previous value of the tag
1331	>	* @since 1.8
1332	>	*/
1333	>	public final short setForkJoinTaskTag(short tag) {
1334	>	for (int s;;) {
1335	>	if (U.compareAndSwapInt(this, STATUS, s = status,
1336	>	(s & ~SMASK) | (tag & SMASK)))
1337	>	return (short)s;
1338	>	}
1339	>	}
1340	>
1341	>	/**
1342	>	* Atomically conditionally sets the tag value for this task.
1343	>	* Among other applications, tags can be used as visit markers
1344	>	* in tasks operating on graphs, as in methods that check: {@code
1345	>	* if (task.compareAndSetForkJoinTaskTag((short)0, (short)1))}
1346	>	* before processing, otherwise exiting because the node has
1347	>	* already been visited.
1348	>	*
1349	>	* @param e the expected tag value
1350	>	* @param tag the new tag value
1351	>	* @return true if successful; i.e., the current value was
1352	>	* equal to e and is now tag.
1353	>	* @since 1.8
1354	>	*/
1355	>	public final boolean compareAndSetForkJoinTaskTag(short e, short tag) {
1356	>	for (int s;;) {
1357	>	if ((short)(s = status) != e)
1358	>	return false;
1359	>	if (U.compareAndSwapInt(this, STATUS, s,
1360	>	(s & ~SMASK) | (tag & SMASK)))
1361	>	return true;
1362	>	}
1363		}
1364
1365		/**
#	Line 1056 | Line 1370 | public abstract class ForkJoinTask<V> im
1370		static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1371		implements RunnableFuture<T> {
1372		final Runnable runnable;
1059	–	final T resultOnCompletion;
1373		T result;
1374		AdaptedRunnable(Runnable runnable, T result) {
1375		if (runnable == null) throw new NullPointerException();
1376		this.runnable = runnable;
1377	<	this.resultOnCompletion = result;
1377	>	this.result = result; // OK to set this even before completion
1378		}
1379	<	public T getRawResult() { return result; }
1380	<	public void setRawResult(T v) { result = v; }
1381	<	public boolean exec() {
1382	<	runnable.run();
1383	<	result = resultOnCompletion;
1384	<	return true;
1379	>	public final T getRawResult() { return result; }
1380	>	public final void setRawResult(T v) { result = v; }
1381	>	public final boolean exec() { runnable.run(); return true; }
1382	>	public final void run() { invoke(); }
1383	>	private static final long serialVersionUID = 5232453952276885070L;
1384	>	}
1385	>
1386	>	/**
1387	>	* Adaptor for Runnables without results
1388	>	*/
1389	>	static final class AdaptedRunnableAction extends ForkJoinTask<Void>
1390	>	implements RunnableFuture<Void> {
1391	>	final Runnable runnable;
1392	>	AdaptedRunnableAction(Runnable runnable) {
1393	>	if (runnable == null) throw new NullPointerException();
1394	>	this.runnable = runnable;
1395		}
1396	<	public void run() { invoke(); }
1396	>	public final Void getRawResult() { return null; }
1397	>	public final void setRawResult(Void v) { }
1398	>	public final boolean exec() { runnable.run(); return true; }
1399	>	public final void run() { invoke(); }
1400		private static final long serialVersionUID = 5232453952276885070L;
1401		}
1402
#	Line 1085 | Line 1411 | public abstract class ForkJoinTask<V> im
1411		if (callable == null) throw new NullPointerException();
1412		this.callable = callable;
1413		}
1414	<	public T getRawResult() { return result; }
1415	<	public void setRawResult(T v) { result = v; }
1416	<	public boolean exec() {
1414	>	public final T getRawResult() { return result; }
1415	>	public final void setRawResult(T v) { result = v; }
1416	>	public final boolean exec() {
1417		try {
1418		result = callable.call();
1419		return true;
#	Line 1099 | Line 1425 | public abstract class ForkJoinTask<V> im
1425		throw new RuntimeException(ex);
1426		}
1427		}
1428	<	public void run() { invoke(); }
1428	>	public final void run() { invoke(); }
1429		private static final long serialVersionUID = 2838392045355241008L;
1430		}
1431
#	Line 1112 | Line 1438 | public abstract class ForkJoinTask<V> im
1438		* @return the task
1439		*/
1440		public static ForkJoinTask<?> adapt(Runnable runnable) {
1441	<	return new AdaptedRunnable<Void>(runnable, null);
1441	>	return new AdaptedRunnableAction(runnable);
1442		}
1443
1444		/**
#	Line 1146 | Line 1472 | public abstract class ForkJoinTask<V> im
1472		private static final long serialVersionUID = -7721805057305804111L;
1473
1474		/**
1475	<	* Saves the state to a stream.
1475	>	* Saves this task to a stream (that is, serializes it).
1476		*
1477		* @serialData the current run status and the exception thrown
1478		* during execution, or {@code null} if none
1153	–	* @param s the stream
1479		*/
1480		private void writeObject(java.io.ObjectOutputStream s)
1481		throws java.io.IOException {
#	Line 1159 | Line 1484 | public abstract class ForkJoinTask<V> im
1484		}
1485
1486		/**
1487	<	* Reconstitutes the instance from a stream.
1163	<	*
1164	<	* @param s the stream
1487	>	* Reconstitutes this task from a stream (that is, deserializes it).
1488		*/
1489		private void readObject(java.io.ObjectInputStream s)
1490		throws java.io.IOException, ClassNotFoundException {
1491		s.defaultReadObject();
1169	–	status |= SIGNAL; // conservatively set external signal
1492		Object ex = s.readObject();
1493		if (ex != null)
1494	<	setExceptionalCompletion((Throwable) ex);
1494	>	setExceptionalCompletion((Throwable)ex);
1495		}
1496
1497		// Unsafe mechanics
1498	<
1499	<	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1500	<	private static final long statusOffset =
1501	<	objectFieldOffset("status", ForkJoinTask.class);
1502	<
1503	<	private static long objectFieldOffset(String field, Class<?> klazz) {
1498	>	private static final sun.misc.Unsafe U;
1499	>	private static final long STATUS;
1500	>	static {
1501	>	exceptionTableLock = new ReentrantLock();
1502	>	exceptionTableRefQueue = new ReferenceQueue<Object>();
1503	>	exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY];
1504		try {
1505	<	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1506	<	} catch (NoSuchFieldException e) {
1507	<	// Convert Exception to corresponding Error
1508	<	NoSuchFieldError error = new NoSuchFieldError(field);
1509	<	error.initCause(e);
1188	<	throw error;
1505	>	U = getUnsafe();
1506	>	STATUS = U.objectFieldOffset
1507	>	(ForkJoinTask.class.getDeclaredField("status"));
1508	>	} catch (Exception e) {
1509	>	throw new Error(e);
1510		}
1511		}
1512

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