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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.65 by jsr166, Sat Oct 16 16:37:30 2010 UTC vs.
Revision 1.80 by jsr166, Fri Jul 1 18:30:14 2011 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.*;
9		import java.io.Serializable;
10		import java.util.Collection;
12	–	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 57 | Line 65 | import java.util.WeakHashMap;
65		* rethrown to callers attempting to join them. These exceptions may
66		* additionally include {@link RejectedExecutionException} stemming
67		* from internal resource exhaustion, such as failure to allocate
68	<	* internal task queues.
68	>	* internal task queues. Rethrown exceptions behave in the same way as
69	>	* regular exceptions, but, when possible, contain stack traces (as
70	>	* displayed for example using {@code ex.printStackTrace()}) of both
71	>	* the thread that initiated the computation as well as the thread
72	>	* actually encountering the exception; minimally only the latter.
73		*
74		* <p>The primary method for awaiting completion and extracting
75		* results of a task is {@link #join}, but there are several variants:
#	Line 101 | Line 113 | import java.util.WeakHashMap;
113		* result in exceptions or errors, possibly including
114		* {@code ClassCastException}.
115		*
116	+	* <p>Method {@link #join} and its variants are appropriate for use
117	+	* only when completion dependencies are acyclic; that is, the
118	+	* parallel computation can be described as a directed acyclic graph
119	+	* (DAG). Otherwise, executions may encounter a form of deadlock as
120	+	* tasks cyclically wait for each other.  However, this framework
121	+	* supports other methods and techniques (for example the use of
122	+	* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that
123	+	* may be of use in constructing custom subclasses for problems that
124	+	* are not statically structured as DAGs.
125	+	*
126		* <p>Most base support methods are {@code final}, to prevent
127		* overriding of implementations that are intrinsically tied to the
128		* underlying lightweight task scheduling framework.  Developers
#	Line 115 | Line 137 | import java.util.WeakHashMap;
137		* computation. Large tasks should be split into smaller subtasks,
138		* usually via recursive decomposition. As a very rough rule of thumb,
139		* a task should perform more than 100 and less than 10000 basic
140	<	* computational steps. If tasks are too big, then parallelism cannot
141	<	* improve throughput. If too small, then memory and internal task
142	<	* maintenance overhead may overwhelm processing.
140	>	* computational steps, and should avoid indefinite looping. If tasks
141	>	* are too big, then parallelism cannot improve throughput. If too
142	>	* small, then memory and internal task maintenance overhead may
143	>	* overwhelm processing.
144		*
145		* <p>This class provides {@code adapt} methods for {@link Runnable}
146		* and {@link Callable}, that may be of use when mixing execution of
#	Line 138 | Line 161 | public abstract class ForkJoinTask<V> im
161		* See the internal documentation of class ForkJoinPool for a
162		* general implementation overview.  ForkJoinTasks are mainly
163		* responsible for maintaining their "status" field amidst relays
164	<	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
165	<	* methods of this class are more-or-less layered into (1) basic
166	<	* status maintenance (2) execution and awaiting completion (3)
167	<	* user-level methods that additionally report results. This is
168	<	* sometimes hard to see because this file orders exported methods
169	<	* in a way that flows well in javadocs. In particular, most
170	<	* join mechanics are in method quietlyJoin, below.
164	>	* to methods in ForkJoinWorkerThread and ForkJoinPool.
165	>	*
166	>	* The methods of this class are more-or-less layered into
167	>	* (1) basic status maintenance
168	>	* (2) execution and awaiting completion
169	>	* (3) user-level methods that additionally report results.
170	>	* This is sometimes hard to see because this file orders exported
171	>	* methods in a way that flows well in javadocs.
172		*/
173
174		/*
#	Line 166 | Line 190 | public abstract class ForkJoinTask<V> im
190
191		/** The run status of this task */
192		volatile int status; // accessed directly by pool and workers
169	–
193		private static final int NORMAL      = -1;
194		private static final int CANCELLED   = -2;
195		private static final int EXCEPTIONAL = -3;
196		private static final int SIGNAL      =  1;
197
198		/**
176	–	* Table of exceptions thrown by tasks, to enable reporting by
177	–	* callers. Because exceptions are rare, we don't directly keep
178	–	* them with task objects, but instead use a weak ref table.  Note
179	–	* that cancellation exceptions don't appear in the table, but are
180	–	* instead recorded as status values.
181	–	* TODO: Use ConcurrentReferenceHashMap
182	–	*/
183	–	static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
184	–	Collections.synchronizedMap
185	–	(new WeakHashMap<ForkJoinTask<?>, Throwable>());
186	–
187	–	// Maintaining completion status
188	–
189	–	/**
199		* Marks completion and wakes up threads waiting to join this task,
200		* also clearing signal request bits.
201		*
202		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
203	+	* @return completion status on exit
204		*/
205	<	private void setCompletion(int completion) {
206	<	int s;
207	<	while ((s = status) >= 0) {
205	>	private int setCompletion(int completion) {
206	>	for (int s;;) {
207	>	if ((s = status) < 0)
208	>	return s;
209		if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
210		if (s != 0)
211		synchronized (this) { notifyAll(); }
212	<	break;
212	>	return completion;
213		}
214		}
215		}
216
217		/**
218	<	* Records exception and sets exceptional completion.
218	>	* Tries to block a worker thread until completed or timed out.
219	>	* Uses Object.wait time argument conventions.
220	>	* May fail on contention or interrupt.
221		*
222	<	* @return status on exit
222	>	* @param millis if > 0, wait time.
223		*/
224	<	private void setExceptionalCompletion(Throwable rex) {
225	<	exceptionMap.put(this, rex);
226	<	setCompletion(EXCEPTIONAL);
227	<	}
228	<
229	<	/**
230	<	* Blocks a worker thread until completion. Called only by
218	<	* pool. Currently unused -- pool-based waits use timeout
219	<	* version below.
220	<	*/
221	<	final void internalAwaitDone() {
222	<	int s;         // the odd construction reduces lock bias effects
223	<	while ((s = status) >= 0) {
224	<	try {
224	>	final void tryAwaitDone(long millis) {
225	>	int s;
226	>	try {
227	>	if (((s = status) > 0 ||
228	>	(s == 0 &&
229	>	UNSAFE.compareAndSwapInt(this, statusOffset, 0, SIGNAL))) &&
230	>	status > 0) {
231		synchronized (this) {
232	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
233	<	wait();
232	>	if (status > 0)
233	>	wait(millis);
234		}
229	–	} catch (InterruptedException ie) {
230	–	cancelIfTerminating();
235		}
236	+	} catch (InterruptedException ie) {
237	+	// caller must check termination
238		}
239		}
240
241		/**
242	<	* Blocks a worker thread until completed or timed out.  Called
243	<	* only by pool.
238	<	*
239	<	* @return status on exit
242	>	* Blocks a non-worker-thread until completion.
243	>	* @return status upon completion
244		*/
245	<	final int internalAwaitDone(long millis) {
245	>	private int externalAwaitDone() {
246		int s;
247		if ((s = status) >= 0) {
248	<	try {
249	<	synchronized (this) {
250	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
251	<	wait(millis, 0);
248	>	boolean interrupted = false;
249	>	synchronized (this) {
250	>	while ((s = status) >= 0) {
251	>	if (s == 0)
252	>	UNSAFE.compareAndSwapInt(this, statusOffset,
253	>	0, SIGNAL);
254	>	else {
255	>	try {
256	>	wait();
257	>	} catch (InterruptedException ie) {
258	>	interrupted = true;
259	>	}
260	>	}
261		}
249	–	} catch (InterruptedException ie) {
250	–	cancelIfTerminating();
262		}
263	<	s = status;
263	>	if (interrupted)
264	>	Thread.currentThread().interrupt();
265		}
266		return s;
267		}
268
269		/**
270	<	* Blocks a non-worker-thread until completion.
270	>	* Blocks a non-worker-thread until completion or interruption or timeout.
271		*/
272	<	private void externalAwaitDone() {
272	>	private int externalInterruptibleAwaitDone(long millis)
273	>	throws InterruptedException {
274		int s;
275	<	while ((s = status) >= 0) {
275	>	if (Thread.interrupted())
276	>	throw new InterruptedException();
277	>	if ((s = status) >= 0) {
278		synchronized (this) {
279	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
280	<	boolean interrupted = false;
281	<	while (status >= 0) {
282	<	try {
283	<	wait();
284	<	} catch (InterruptedException ie) {
285	<	interrupted = true;
286	<	}
279	>	while ((s = status) >= 0) {
280	>	if (s == 0)
281	>	UNSAFE.compareAndSwapInt(this, statusOffset,
282	>	0, SIGNAL);
283	>	else {
284	>	wait(millis);
285	>	if (millis > 0L)
286	>	break;
287		}
273	–	if (interrupted)
274	–	Thread.currentThread().interrupt();
275	–	break;
288		}
289		}
290		}
291	+	return s;
292		}
293
294		/**
295	<	* Unless done, calls exec and records status if completed, but
296	<	* doesn't wait for completion otherwise. Primary execution method
297	<	* for ForkJoinWorkerThread.
295	>	* Primary execution method for stolen tasks. Unless done, calls
296	>	* exec and records status if completed, but doesn't wait for
297	>	* completion otherwise.
298		*/
299	<	final void quietlyExec() {
300	<	try {
301	<	if (status < 0 || !exec())
299	>	final void doExec() {
300	>	if (status >= 0) {
301	>	boolean completed;
302	>	try {
303	>	completed = exec();
304	>	} catch (Throwable rex) {
305	>	setExceptionalCompletion(rex);
306		return;
307	+	}
308	+	if (completed)
309	+	setCompletion(NORMAL); // must be outside try block
310	+	}
311	+	}
312	+
313	+	/**
314	+	* Primary mechanics for join, get, quietlyJoin.
315	+	* @return status upon completion
316	+	*/
317	+	private int doJoin() {
318	+	Thread t; ForkJoinWorkerThread w; int s; boolean completed;
319	+	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
320	+	if ((s = status) < 0)
321	+	return s;
322	+	if ((w = (ForkJoinWorkerThread)t).unpushTask(this)) {
323	+	try {
324	+	completed = exec();
325	+	} catch (Throwable rex) {
326	+	return setExceptionalCompletion(rex);
327	+	}
328	+	if (completed)
329	+	return setCompletion(NORMAL);
330	+	}
331	+	return w.joinTask(this);
332	+	}
333	+	else
334	+	return externalAwaitDone();
335	+	}
336	+
337	+	/**
338	+	* Primary mechanics for invoke, quietlyInvoke.
339	+	* @return status upon completion
340	+	*/
341	+	private int doInvoke() {
342	+	int s; boolean completed;
343	+	if ((s = status) < 0)
344	+	return s;
345	+	try {
346	+	completed = exec();
347		} catch (Throwable rex) {
348	<	setExceptionalCompletion(rex);
349	<	return;
348	>	return setExceptionalCompletion(rex);
349	>	}
350	>	if (completed)
351	>	return setCompletion(NORMAL);
352	>	else
353	>	return doJoin();
354	>	}
355	>
356	>	// Exception table support
357	>
358	>	/**
359	>	* Table of exceptions thrown by tasks, to enable reporting by
360	>	* callers. Because exceptions are rare, we don't directly keep
361	>	* them with task objects, but instead use a weak ref table.  Note
362	>	* that cancellation exceptions don't appear in the table, but are
363	>	* instead recorded as status values.
364	>	*
365	>	* Note: These statics are initialized below in static block.
366	>	*/
367	>	private static final ExceptionNode[] exceptionTable;
368	>	private static final ReentrantLock exceptionTableLock;
369	>	private static final ReferenceQueue<Object> exceptionTableRefQueue;
370	>
371	>	/**
372	>	* Fixed capacity for exceptionTable.
373	>	*/
374	>	private static final int EXCEPTION_MAP_CAPACITY = 32;
375	>
376	>	/**
377	>	* Key-value nodes for exception table.  The chained hash table
378	>	* uses identity comparisons, full locking, and weak references
379	>	* for keys. The table has a fixed capacity because it only
380	>	* maintains task exceptions long enough for joiners to access
381	>	* them, so should never become very large for sustained
382	>	* periods. However, since we do not know when the last joiner
383	>	* completes, we must use weak references and expunge them. We do
384	>	* so on each operation (hence full locking). Also, some thread in
385	>	* any ForkJoinPool will call helpExpungeStaleExceptions when its
386	>	* pool becomes isQuiescent.
387	>	*/
388	>	static final class ExceptionNode extends WeakReference<ForkJoinTask<?>>{
389	>	final Throwable ex;
390	>	ExceptionNode next;
391	>	final long thrower;  // use id not ref to avoid weak cycles
392	>	ExceptionNode(ForkJoinTask<?> task, Throwable ex, ExceptionNode next) {
393	>	super(task, exceptionTableRefQueue);
394	>	this.ex = ex;
395	>	this.next = next;
396	>	this.thrower = Thread.currentThread().getId();
397	>	}
398	>	}
399	>
400	>	/**
401	>	* Records exception and sets exceptional completion.
402	>	*
403	>	* @return status on exit
404	>	*/
405	>	private int setExceptionalCompletion(Throwable ex) {
406	>	int h = System.identityHashCode(this);
407	>	final ReentrantLock lock = exceptionTableLock;
408	>	lock.lock();
409	>	try {
410	>	expungeStaleExceptions();
411	>	ExceptionNode[] t = exceptionTable;
412	>	int i = h & (t.length - 1);
413	>	for (ExceptionNode e = t[i]; ; e = e.next) {
414	>	if (e == null) {
415	>	t[i] = new ExceptionNode(this, ex, t[i]);
416	>	break;
417	>	}
418	>	if (e.get() == this) // already present
419	>	break;
420	>	}
421	>	} finally {
422	>	lock.unlock();
423	>	}
424	>	return setCompletion(EXCEPTIONAL);
425	>	}
426	>
427	>	/**
428	>	* Removes exception node and clears status
429	>	*/
430	>	private void clearExceptionalCompletion() {
431	>	int h = System.identityHashCode(this);
432	>	final ReentrantLock lock = exceptionTableLock;
433	>	lock.lock();
434	>	try {
435	>	ExceptionNode[] t = exceptionTable;
436	>	int i = h & (t.length - 1);
437	>	ExceptionNode e = t[i];
438	>	ExceptionNode pred = null;
439	>	while (e != null) {
440	>	ExceptionNode next = e.next;
441	>	if (e.get() == this) {
442	>	if (pred == null)
443	>	t[i] = next;
444	>	else
445	>	pred.next = next;
446	>	break;
447	>	}
448	>	pred = e;
449	>	e = next;
450	>	}
451	>	expungeStaleExceptions();
452	>	status = 0;
453	>	} finally {
454	>	lock.unlock();
455	>	}
456	>	}
457	>
458	>	/**
459	>	* Returns a rethrowable exception for the given task, if
460	>	* available. To provide accurate stack traces, if the exception
461	>	* was not thrown by the current thread, we try to create a new
462	>	* exception of the same type as the one thrown, but with the
463	>	* recorded exception as its cause. If there is no such
464	>	* constructor, we instead try to use a no-arg constructor,
465	>	* followed by initCause, to the same effect. If none of these
466	>	* apply, or any fail due to other exceptions, we return the
467	>	* recorded exception, which is still correct, although it may
468	>	* contain a misleading stack trace.
469	>	*
470	>	* @return the exception, or null if none
471	>	*/
472	>	private Throwable getThrowableException() {
473	>	if (status != EXCEPTIONAL)
474	>	return null;
475	>	int h = System.identityHashCode(this);
476	>	ExceptionNode e;
477	>	final ReentrantLock lock = exceptionTableLock;
478	>	lock.lock();
479	>	try {
480	>	expungeStaleExceptions();
481	>	ExceptionNode[] t = exceptionTable;
482	>	e = t[h & (t.length - 1)];
483	>	while (e != null && e.get() != this)
484	>	e = e.next;
485	>	} finally {
486	>	lock.unlock();
487	>	}
488	>	Throwable ex;
489	>	if (e == null || (ex = e.ex) == null)
490	>	return null;
491	>	if (e.thrower != Thread.currentThread().getId()) {
492	>	Class<? extends Throwable> ec = ex.getClass();
493	>	try {
494	>	Constructor<?> noArgCtor = null;
495	>	Constructor<?>[] cs = ec.getConstructors();// public ctors only
496	>	for (int i = 0; i < cs.length; ++i) {
497	>	Constructor<?> c = cs[i];
498	>	Class<?>[] ps = c.getParameterTypes();
499	>	if (ps.length == 0)
500	>	noArgCtor = c;
501	>	else if (ps.length == 1 && ps[0] == Throwable.class)
502	>	return (Throwable)(c.newInstance(ex));
503	>	}
504	>	if (noArgCtor != null) {
505	>	Throwable wx = (Throwable)(noArgCtor.newInstance());
506	>	wx.initCause(ex);
507	>	return wx;
508	>	}
509	>	} catch (Exception ignore) {
510	>	}
511	>	}
512	>	return ex;
513	>	}
514	>
515	>	/**
516	>	* Poll stale refs and remove them. Call only while holding lock.
517	>	*/
518	>	private static void expungeStaleExceptions() {
519	>	for (Object x; (x = exceptionTableRefQueue.poll()) != null;) {
520	>	if (x instanceof ExceptionNode) {
521	>	ForkJoinTask<?> key = ((ExceptionNode)x).get();
522	>	ExceptionNode[] t = exceptionTable;
523	>	int i = System.identityHashCode(key) & (t.length - 1);
524	>	ExceptionNode e = t[i];
525	>	ExceptionNode pred = null;
526	>	while (e != null) {
527	>	ExceptionNode next = e.next;
528	>	if (e == x) {
529	>	if (pred == null)
530	>	t[i] = next;
531	>	else
532	>	pred.next = next;
533	>	break;
534	>	}
535	>	pred = e;
536	>	e = next;
537	>	}
538	>	}
539		}
540	<	setCompletion(NORMAL); // must be outside try block
540	>	}
541	>
542	>	/**
543	>	* If lock is available, poll stale refs and remove them.
544	>	* Called from ForkJoinPool when pools become quiescent.
545	>	*/
546	>	static final void helpExpungeStaleExceptions() {
547	>	final ReentrantLock lock = exceptionTableLock;
548	>	if (lock.tryLock()) {
549	>	try {
550	>	expungeStaleExceptions();
551	>	} finally {
552	>	lock.unlock();
553	>	}
554	>	}
555	>	}
556	>
557	>	/**
558	>	* Report the result of invoke or join; called only upon
559	>	* non-normal return of internal versions.
560	>	*/
561	>	private V reportResult() {
562	>	int s; Throwable ex;
563	>	if ((s = status) == CANCELLED)
564	>	throw new CancellationException();
565	>	if (s == EXCEPTIONAL && (ex = getThrowableException()) != null)
566	>	UNSAFE.throwException(ex);
567	>	return getRawResult();
568		}
569
570		// public methods
#	Line 307 | Line 580 | public abstract class ForkJoinTask<V> im
580		* #isDone} returning {@code true}.
581		*
582		* <p>This method may be invoked only from within {@code
583	<	* ForkJoinTask} computations (as may be determined using method
583	>	* ForkJoinPool} computations (as may be determined using method
584		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
585		* result in exceptions or errors, possibly including {@code
586		* ClassCastException}.
#	Line 321 | Line 594 | public abstract class ForkJoinTask<V> im
594		}
595
596		/**
597	<	* Returns the result of the computation when it {@link #isDone is done}.
598	<	* This method differs from {@link #get()} in that
597	>	* Returns the result of the computation when it {@link #isDone is
598	>	* done}.  This method differs from {@link #get()} in that
599		* abnormal completion results in {@code RuntimeException} or
600	<	* {@code Error}, not {@code ExecutionException}.
600	>	* {@code Error}, not {@code ExecutionException}, and that
601	>	* interrupts of the calling thread do <em>not</em> cause the
602	>	* method to abruptly return by throwing {@code
603	>	* InterruptedException}.
604		*
605		* @return the computed result
606		*/
607		public final V join() {
608	<	quietlyJoin();
609	<	Throwable ex;
610	<	if (status < NORMAL && (ex = getException()) != null)
611	<	UNSAFE.throwException(ex);
336	<	return getRawResult();
608	>	if (doJoin() != NORMAL)
609	>	return reportResult();
610	>	else
611	>	return getRawResult();
612		}
613
614		/**
#	Line 345 | Line 620 | public abstract class ForkJoinTask<V> im
620		* @return the computed result
621		*/
622		public final V invoke() {
623	<	quietlyInvoke();
624	<	Throwable ex;
625	<	if (status < NORMAL && (ex = getException()) != null)
626	<	UNSAFE.throwException(ex);
352	<	return getRawResult();
623	>	if (doInvoke() != NORMAL)
624	>	return reportResult();
625	>	else
626	>	return getRawResult();
627		}
628
629		/**
#	Line 366 | Line 640 | public abstract class ForkJoinTask<V> im
640		* unprocessed.
641		*
642		* <p>This method may be invoked only from within {@code
643	<	* ForkJoinTask} computations (as may be determined using method
643	>	* ForkJoinPool} computations (as may be determined using method
644		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
645		* result in exceptions or errors, possibly including {@code
646		* ClassCastException}.
#	Line 394 | Line 668 | public abstract class ForkJoinTask<V> im
668		* normally or exceptionally, or left unprocessed.
669		*
670		* <p>This method may be invoked only from within {@code
671	<	* ForkJoinTask} computations (as may be determined using method
671	>	* ForkJoinPool} computations (as may be determined using method
672		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
673		* result in exceptions or errors, possibly including {@code
674		* ClassCastException}.
#	Line 413 | Line 687 | public abstract class ForkJoinTask<V> im
687		}
688		else if (i != 0)
689		t.fork();
690	<	else {
691	<	t.quietlyInvoke();
418	<	if (ex == null && t.status < NORMAL)
419	<	ex = t.getException();
420	<	}
690	>	else if (t.doInvoke() < NORMAL && ex == null)
691	>	ex = t.getException();
692		}
693		for (int i = 1; i <= last; ++i) {
694		ForkJoinTask<?> t = tasks[i];
695		if (t != null) {
696		if (ex != null)
697		t.cancel(false);
698	<	else {
699	<	t.quietlyJoin();
429	<	if (ex == null && t.status < NORMAL)
430	<	ex = t.getException();
431	<	}
698	>	else if (t.doJoin() < NORMAL)
699	>	ex = t.getException();
700		}
701		}
702		if (ex != null)
#	Line 449 | Line 717 | public abstract class ForkJoinTask<V> im
717		* unprocessed.
718		*
719		* <p>This method may be invoked only from within {@code
720	<	* ForkJoinTask} computations (as may be determined using method
720	>	* ForkJoinPool} computations (as may be determined using method
721		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
722		* result in exceptions or errors, possibly including {@code
723		* ClassCastException}.
#	Line 476 | Line 744 | public abstract class ForkJoinTask<V> im
744		}
745		else if (i != 0)
746		t.fork();
747	<	else {
748	<	t.quietlyInvoke();
481	<	if (ex == null && t.status < NORMAL)
482	<	ex = t.getException();
483	<	}
747	>	else if (t.doInvoke() < NORMAL && ex == null)
748	>	ex = t.getException();
749		}
750		for (int i = 1; i <= last; ++i) {
751		ForkJoinTask<?> t = ts.get(i);
752		if (t != null) {
753		if (ex != null)
754		t.cancel(false);
755	<	else {
756	<	t.quietlyJoin();
492	<	if (ex == null && t.status < NORMAL)
493	<	ex = t.getException();
494	<	}
755	>	else if (t.doJoin() < NORMAL)
756	>	ex = t.getException();
757		}
758		}
759		if (ex != null)
#	Line 501 | Line 763 | public abstract class ForkJoinTask<V> im
763
764		/**
765		* Attempts to cancel execution of this task. This attempt will
766	<	* fail if the task has already completed, has already been
767	<	* cancelled, or could not be cancelled for some other reason. If
768	<	* successful, and this task has not started when cancel is
769	<	* called, execution of this task is suppressed, {@link
770	<	* #isCancelled} will report true, and {@link #join} will result
771	<	* in a {@code CancellationException} being thrown.
766	>	* fail if the task has already completed or could not be
767	>	* cancelled for some other reason. If successful, and this task
768	>	* has not started when {@code cancel} is called, execution of
769	>	* this task is suppressed. After this method returns
770	>	* successfully, unless there is an intervening call to {@link
771	>	* #reinitialize}, subsequent calls to {@link #isCancelled},
772	>	* {@link #isDone}, and {@code cancel} will return {@code true}
773	>	* and calls to {@link #join} and related methods will result in
774	>	* {@code CancellationException}.
775		*
776		* <p>This method may be overridden in subclasses, but if so, must
777	<	* still ensure that these minimal properties hold. In particular,
778	<	* the {@code cancel} method itself must not throw exceptions.
777	>	* still ensure that these properties hold. In particular, the
778	>	* {@code cancel} method itself must not throw exceptions.
779		*
780		* <p>This method is designed to be invoked by <em>other</em>
781		* tasks. To terminate the current task, you can just return or
782		* throw an unchecked exception from its computation method, or
783		* invoke {@link #completeExceptionally}.
784		*
785	<	* @param mayInterruptIfRunning this value is ignored in the
786	<	* default implementation because tasks are not
787	<	* cancelled via interruption
785	>	* @param mayInterruptIfRunning this value has no effect in the
786	>	* default implementation because interrupts are not used to
787	>	* control cancellation.
788		*
789		* @return {@code true} if this task is now cancelled
790		*/
791		public boolean cancel(boolean mayInterruptIfRunning) {
792	<	setCompletion(CANCELLED);
528	<	return status == CANCELLED;
792	>	return setCompletion(CANCELLED) == CANCELLED;
793		}
794
795		/**
#	Line 541 | Line 805 | public abstract class ForkJoinTask<V> im
805		}
806		}
807
544	–	/**
545	–	* Cancels if current thread is a terminating worker thread,
546	–	* ignoring any exceptions thrown by cancel.
547	–	*/
548	–	final void cancelIfTerminating() {
549	–	Thread t = Thread.currentThread();
550	–	if ((t instanceof ForkJoinWorkerThread) &&
551	–	((ForkJoinWorkerThread) t).isTerminating()) {
552	–	try {
553	–	cancel(false);
554	–	} catch (Throwable ignore) {
555	–	}
556	–	}
557	–	}
558	–
808		public final boolean isDone() {
809		return status < 0;
810		}
#	Line 595 | Line 844 | public abstract class ForkJoinTask<V> im
844		int s = status;
845		return ((s >= NORMAL)    ? null :
846		(s == CANCELLED) ? new CancellationException() :
847	<	exceptionMap.get(this));
847	>	getThrowableException());
848		}
849
850		/**
#	Line 653 | Line 902 | public abstract class ForkJoinTask<V> im
902		* member of a ForkJoinPool and was interrupted while waiting
903		*/
904		public final V get() throws InterruptedException, ExecutionException {
905	<	int s;
906	<	if (Thread.currentThread() instanceof ForkJoinWorkerThread) {
907	<	quietlyJoin();
908	<	s = status;
909	<	}
910	<	else {
911	<	while ((s = status) >= 0) {
663	<	synchronized (this) { // interruptible form of awaitDone
664	<	if (UNSAFE.compareAndSwapInt(this, statusOffset,
665	<	s, SIGNAL)) {
666	<	while (status >= 0)
667	<	wait();
668	<	}
669	<	}
670	<	}
671	<	}
672	<	if (s < NORMAL) {
673	<	Throwable ex;
674	<	if (s == CANCELLED)
675	<	throw new CancellationException();
676	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
677	<	throw new ExecutionException(ex);
678	<	}
905	>	int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ?
906	>	doJoin() : externalInterruptibleAwaitDone(0L);
907	>	Throwable ex;
908	>	if (s == CANCELLED)
909	>	throw new CancellationException();
910	>	if (s == EXCEPTIONAL && (ex = getThrowableException()) != null)
911	>	throw new ExecutionException(ex);
912		return getRawResult();
913		}
914
#	Line 696 | Line 929 | public abstract class ForkJoinTask<V> im
929		public final V get(long timeout, TimeUnit unit)
930		throws InterruptedException, ExecutionException, TimeoutException {
931		Thread t = Thread.currentThread();
699	–	ForkJoinPool pool;
932		if (t instanceof ForkJoinWorkerThread) {
933		ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
934	<	if (status >= 0 && w.unpushTask(this))
935	<	quietlyExec();
936	<	pool = w.pool;
937	<	}
938	<	else
939	<	pool = null;
940	<	/*
941	<	* Timed wait loop intermixes cases for FJ (pool != null) and
710	<	* non FJ threads. For FJ, decrement pool count but don't try
711	<	* for replacement; increment count on completion. For non-FJ,
712	<	* deal with interrupts. This is messy, but a little less so
713	<	* than is splitting the FJ and nonFJ cases.
714	<	*/
715	<	boolean interrupted = false;
716	<	boolean dec = false; // true if pool count decremented
717	<	long nanos = unit.toNanos(timeout);
718	<	for (;;) {
719	<	if (pool == null && Thread.interrupted()) {
720	<	interrupted = true;
721	<	break;
722	<	}
723	<	int s = status;
724	<	if (s < 0)
725	<	break;
726	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
727	<	long startTime = System.nanoTime();
728	<	long nt; // wait time
729	<	while (status >= 0 &&
730	<	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
731	<	if (pool != null && !dec)
732	<	dec = pool.tryDecrementRunningCount();
733	<	else {
734	<	long ms = nt / 1000000;
735	<	int ns = (int) (nt % 1000000);
736	<	try {
737	<	synchronized (this) {
738	<	if (status >= 0)
739	<	wait(ms, ns);
740	<	}
741	<	} catch (InterruptedException ie) {
742	<	if (pool != null)
743	<	cancelIfTerminating();
744	<	else {
745	<	interrupted = true;
746	<	break;
747	<	}
748	<	}
934	>	long nanos = unit.toNanos(timeout);
935	>	if (status >= 0) {
936	>	boolean completed = false;
937	>	if (w.unpushTask(this)) {
938	>	try {
939	>	completed = exec();
940	>	} catch (Throwable rex) {
941	>	setExceptionalCompletion(rex);
942		}
943		}
944	<	break;
944	>	if (completed)
945	>	setCompletion(NORMAL);
946	>	else if (status >= 0 && nanos > 0)
947	>	w.pool.timedAwaitJoin(this, nanos);
948		}
949		}
950	<	if (pool != null && dec)
951	<	pool.incrementRunningCount();
952	<	if (interrupted)
953	<	throw new InterruptedException();
954	<	int es = status;
955	<	if (es != NORMAL) {
950	>	else {
951	>	long millis = unit.toMillis(timeout);
952	>	if (millis > 0)
953	>	externalInterruptibleAwaitDone(millis);
954	>	}
955	>	int s = status;
956	>	if (s != NORMAL) {
957		Throwable ex;
958	<	if (es == CANCELLED)
958	>	if (s == CANCELLED)
959		throw new CancellationException();
960	<	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
960	>	if (s != EXCEPTIONAL)
961	>	throw new TimeoutException();
962	>	if ((ex = getThrowableException()) != null)
963		throw new ExecutionException(ex);
765	–	throw new TimeoutException();
964		}
965		return getRawResult();
966		}
#	Line 774 | Line 972 | public abstract class ForkJoinTask<V> im
972		* known to have aborted.
973		*/
974		public final void quietlyJoin() {
975	<	Thread t;
778	<	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
779	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
780	<	if (status >= 0) {
781	<	if (w.unpushTask(this)) {
782	<	boolean completed;
783	<	try {
784	<	completed = exec();
785	<	} catch (Throwable rex) {
786	<	setExceptionalCompletion(rex);
787	<	return;
788	<	}
789	<	if (completed) {
790	<	setCompletion(NORMAL);
791	<	return;
792	<	}
793	<	}
794	<	w.joinTask(this);
795	<	}
796	<	}
797	<	else
798	<	externalAwaitDone();
975	>	doJoin();
976		}
977
978		/**
#	Line 804 | Line 981 | public abstract class ForkJoinTask<V> im
981		* exception.
982		*/
983		public final void quietlyInvoke() {
984	<	if (status >= 0) {
808	<	boolean completed;
809	<	try {
810	<	completed = exec();
811	<	} catch (Throwable rex) {
812	<	setExceptionalCompletion(rex);
813	<	return;
814	<	}
815	<	if (completed)
816	<	setCompletion(NORMAL);
817	<	else
818	<	quietlyJoin();
819	<	}
984	>	doInvoke();
985		}
986
987		/**
#	Line 827 | Line 992 | public abstract class ForkJoinTask<V> im
992		* processed.
993		*
994		* <p>This method may be invoked only from within {@code
995	<	* ForkJoinTask} computations (as may be determined using method
995	>	* ForkJoinPool} computations (as may be determined using method
996		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
997		* result in exceptions or errors, possibly including {@code
998		* ClassCastException}.
#	Line 846 | Line 1011 | public abstract class ForkJoinTask<V> im
1011		* under any other usage conditions are not guaranteed.
1012		* This method may be useful when executing
1013		* pre-constructed trees of subtasks in loops.
1014	+	*
1015	+	* <p>Upon completion of this method, {@code isDone()} reports
1016	+	* {@code false}, and {@code getException()} reports {@code
1017	+	* null}. However, the value returned by {@code getRawResult} is
1018	+	* unaffected. To clear this value, you can invoke {@code
1019	+	* setRawResult(null)}.
1020		*/
1021		public void reinitialize() {
1022		if (status == EXCEPTIONAL)
1023	<	exceptionMap.remove(this);
1024	<	status = 0;
1023	>	clearExceptionalCompletion();
1024	>	else
1025	>	status = 0;
1026		}
1027
1028		/**
#	Line 867 | Line 1039 | public abstract class ForkJoinTask<V> im
1039		}
1040
1041		/**
1042	<	* Returns {@code true} if the current thread is executing as a
1043	<	* ForkJoinPool computation.
1042	>	* Returns {@code true} if the current thread is a {@link
1043	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation.
1044		*
1045	<	* @return {@code true} if the current thread is executing as a
1046	<	* ForkJoinPool computation, or false otherwise
1045	>	* @return {@code true} if the current thread is a {@link
1046	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation,
1047	>	* or {@code false} otherwise
1048		*/
1049		public static boolean inForkJoinPool() {
1050		return Thread.currentThread() instanceof ForkJoinWorkerThread;
#	Line 886 | Line 1059 | public abstract class ForkJoinTask<V> im
1059		* were not, stolen.
1060		*
1061		* <p>This method may be invoked only from within {@code
1062	<	* ForkJoinTask} computations (as may be determined using method
1062	>	* ForkJoinPool} computations (as may be determined using method
1063		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1064		* result in exceptions or errors, possibly including {@code
1065		* ClassCastException}.
#	Line 905 | Line 1078 | public abstract class ForkJoinTask<V> im
1078		* fork other tasks.
1079		*
1080		* <p>This method may be invoked only from within {@code
1081	<	* ForkJoinTask} computations (as may be determined using method
1081	>	* ForkJoinPool} computations (as may be determined using method
1082		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1083		* result in exceptions or errors, possibly including {@code
1084		* ClassCastException}.
#	Line 928 | Line 1101 | public abstract class ForkJoinTask<V> im
1101		* exceeded.
1102		*
1103		* <p>This method may be invoked only from within {@code
1104	<	* ForkJoinTask} computations (as may be determined using method
1104	>	* ForkJoinPool} computations (as may be determined using method
1105		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1106		* result in exceptions or errors, possibly including {@code
1107		* ClassCastException}.
#	Line 986 | Line 1159 | public abstract class ForkJoinTask<V> im
1159		* otherwise.
1160		*
1161		* <p>This method may be invoked only from within {@code
1162	<	* ForkJoinTask} computations (as may be determined using method
1162	>	* ForkJoinPool} computations (as may be determined using method
1163		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1164		* result in exceptions or errors, possibly including {@code
1165		* ClassCastException}.
#	Line 1005 | Line 1178 | public abstract class ForkJoinTask<V> im
1178		* be useful otherwise.
1179		*
1180		* <p>This method may be invoked only from within {@code
1181	<	* ForkJoinTask} computations (as may be determined using method
1181	>	* ForkJoinPool} computations (as may be determined using method
1182		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1183		* result in exceptions or errors, possibly including {@code
1184		* ClassCastException}.
#	Line 1028 | Line 1201 | public abstract class ForkJoinTask<V> im
1201		* otherwise.
1202		*
1203		* <p>This method may be invoked only from within {@code
1204	<	* ForkJoinTask} computations (as may be determined using method
1204	>	* ForkJoinPool} computations (as may be determined using method
1205		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1206		* result in exceptions or errors, possibly including {@code
1207		* ClassCastException}.
#	Line 1160 | Line 1333 | public abstract class ForkJoinTask<V> im
1333		s.defaultReadObject();
1334		Object ex = s.readObject();
1335		if (ex != null)
1336	<	setExceptionalCompletion((Throwable) ex);
1336	>	setExceptionalCompletion((Throwable)ex);
1337		}
1338
1339		// Unsafe mechanics
1340	<
1341	<	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1342	<	private static final long statusOffset =
1343	<	objectFieldOffset("status", ForkJoinTask.class);
1344	<
1345	<	private static long objectFieldOffset(String field, Class<?> klazz) {
1340	>	private static final sun.misc.Unsafe UNSAFE;
1341	>	private static final long statusOffset;
1342	>	static {
1343	>	exceptionTableLock = new ReentrantLock();
1344	>	exceptionTableRefQueue = new ReferenceQueue<Object>();
1345	>	exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY];
1346		try {
1347	<	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1348	<	} catch (NoSuchFieldException e) {
1349	<	// Convert Exception to corresponding Error
1350	<	NoSuchFieldError error = new NoSuchFieldError(field);
1351	<	error.initCause(e);
1179	<	throw error;
1347	>	UNSAFE = getUnsafe();
1348	>	statusOffset = UNSAFE.objectFieldOffset
1349	>	(ForkJoinTask.class.getDeclaredField("status"));
1350	>	} catch (Exception e) {
1351	>	throw new Error(e);
1352		}
1353		}
1354

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