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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.43 by dl, Wed Aug 19 11:24:58 2009 UTC vs.
Revision 1.67 by dl, Sun Nov 21 14:43:27 2010 UTC

#	Line 6 | Line 6
6
7		package jsr166y;
8
9	–	import java.util.concurrent.*;
10	–
9		import java.io.Serializable;
10		import java.util.Collection;
11		import java.util.Collections;
#	Line 15 | Line 13 | import java.util.List;
13		import java.util.RandomAccess;
14		import java.util.Map;
15		import java.util.WeakHashMap;
16	+	import java.util.concurrent.Callable;
17	+	import java.util.concurrent.CancellationException;
18	+	import java.util.concurrent.ExecutionException;
19	+	import java.util.concurrent.Executor;
20	+	import java.util.concurrent.ExecutorService;
21	+	import java.util.concurrent.Future;
22	+	import java.util.concurrent.RejectedExecutionException;
23	+	import java.util.concurrent.RunnableFuture;
24	+	import java.util.concurrent.TimeUnit;
25	+	import java.util.concurrent.TimeoutException;
26
27		/**
28		* Abstract base class for tasks that run within a {@link ForkJoinPool}.
#	Line 28 | Line 36 | import java.util.WeakHashMap;
36		* start other subtasks.  As indicated by the name of this class,
37		* many programs using {@code ForkJoinTask} employ only methods
38		* {@link #fork} and {@link #join}, or derivatives such as {@link
39	<	* #invokeAll}.  However, this class also provides a number of other
40	<	* methods that can come into play in advanced usages, as well as
41	<	* extension mechanics that allow support of new forms of fork/join
42	<	* processing.
39	>	* #invokeAll(ForkJoinTask...) invokeAll}.  However, this class also
40	>	* provides a number of other methods that can come into play in
41	>	* advanced usages, as well as extension mechanics that allow
42	>	* support of new forms of fork/join processing.
43		*
44		* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
45		* The efficiency of {@code ForkJoinTask}s stems from a set of
#	Line 56 | Line 64 | import java.util.WeakHashMap;
64		* exceptions such as {@code IOExceptions} to be thrown. However,
65		* computations may still encounter unchecked exceptions, that are
66		* rethrown to callers attempting to join them. These exceptions may
67	<	* additionally include RejectedExecutionExceptions stemming from
68	<	* internal resource exhaustion such as failure to allocate internal
69	<	* task queues.
67	>	* additionally include {@link RejectedExecutionException} stemming
68	>	* from internal resource exhaustion, such as failure to allocate
69	>	* internal task queues.
70		*
71		* <p>The primary method for awaiting completion and extracting
72		* results of a task is {@link #join}, but there are several variants:
73		* The {@link Future#get} methods support interruptible and/or timed
74		* waits for completion and report results using {@code Future}
75	<	* 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
75	>	* conventions. Method {@link #invoke} is semantically
76		* equivalent to {@code fork(); join()} but always attempts to begin
77		* execution in the current thread. The "<em>quiet</em>" forms of
78		* these methods do not extract results or report exceptions. These
#	Line 103 | Line 108 | import java.util.WeakHashMap;
108		* ForkJoinTasks (as may be determined using method {@link
109		* #inForkJoinPool}).  Attempts to invoke them in other contexts
110		* result in exceptions or errors, possibly including
111	<	* ClassCastException.
111	>	* {@code ClassCastException}.
112		*
113		* <p>Most base support methods are {@code final}, to prevent
114		* overriding of implementations that are intrinsically tied to the
#	Line 125 | Line 130 | import java.util.WeakHashMap;
130		*
131		* <p>This class provides {@code adapt} methods for {@link Runnable}
132		* and {@link Callable}, that may be of use when mixing execution of
133	<	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks
134	<	* are of this form, consider using a pool in
130	<	* {@linkplain ForkJoinPool#setAsyncMode async mode}.
133	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
134	>	* of this form, consider using a pool constructed in <em>asyncMode</em>.
135		*
136		* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
137		* used in extensions such as remote execution frameworks. It is
#	Line 139 | Line 143 | import java.util.WeakHashMap;
143		*/
144		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
145
146	<	/**
147	<	* Run control status bits packed into a single int to minimize
148	<	* footprint and to ensure atomicity (via CAS).  Status is
149	<	* initially zero, and takes on nonnegative values until
150	<	* completed, upon which status holds COMPLETED. CANCELLED, or
151	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
152	<	* blocking waits by other threads have SIGNAL_MASK bits set --
153	<	* bit 15 for external (nonFJ) waits, and the rest a count of
154	<	* waiting FJ threads.  (This representation relies on
155	<	* ForkJoinPool max thread limits). Completion of a stolen task
156	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
157	<	* though suboptimal for some purposes, we use basic builtin
158	<	* wait/notify to take advantage of "monitor inflation" in JVMs
159	<	* that we would otherwise need to emulate to avoid adding further
160	<	* per-task bookkeeping overhead. Note that bits 16-28 are
161	<	* currently unused. Also value 0x80000000 is available as spare
162	<	* completion value.
146	>	/*
147	>	* See the internal documentation of class ForkJoinPool for a
148	>	* general implementation overview.  ForkJoinTasks are mainly
149	>	* responsible for maintaining their "status" field amidst relays
150	>	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
151	>	* methods of this class are more-or-less layered into (1) basic
152	>	* status maintenance (2) execution and awaiting completion (3)
153	>	* user-level methods that additionally report results. This is
154	>	* sometimes hard to see because this file orders exported methods
155	>	* in a way that flows well in javadocs. In particular, most
156	>	* join mechanics are in method quietlyJoin, below.
157	>	*/
158	>
159	>	/*
160	>	* The status field holds run control status bits packed into a
161	>	* single int to minimize footprint and to ensure atomicity (via
162	>	* CAS).  Status is initially zero, and takes on nonnegative
163	>	* values until completed, upon which status holds value
164	>	* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
165	>	* waits by other threads have the SIGNAL bit set.  Completion of
166	>	* a stolen task with SIGNAL set awakens any waiters via
167	>	* notifyAll. Even though suboptimal for some purposes, we use
168	>	* basic builtin wait/notify to take advantage of "monitor
169	>	* inflation" in JVMs that we would otherwise need to emulate to
170	>	* avoid adding further per-task bookkeeping overhead.  We want
171	>	* these monitors to be "fat", i.e., not use biasing or thin-lock
172	>	* techniques, so use some odd coding idioms that tend to avoid
173	>	* them.
174		*/
175	+
176	+	/** The run status of this task */
177		volatile int status; // accessed directly by pool and workers
178
179	<	static final int COMPLETION_MASK      = 0xe0000000;
180	<	static final int NORMAL               = 0xe0000000; // == mask
181	<	static final int CANCELLED            = 0xc0000000;
182	<	static final int EXCEPTIONAL          = 0xa0000000;
166	<	static final int SIGNAL_MASK          = 0x0000ffff;
167	<	static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
168	<	static final int EXTERNAL_SIGNAL      = 0x00008000; // top bit of low word
179	>	private static final int NORMAL      = -1;
180	>	private static final int CANCELLED   = -2;
181	>	private static final int EXCEPTIONAL = -3;
182	>	private static final int SIGNAL      =  1;
183
184		/**
185		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 179 | Line 193 | public abstract class ForkJoinTask<V> im
193		Collections.synchronizedMap
194		(new WeakHashMap<ForkJoinTask<?>, Throwable>());
195
196	<	// within-package utilities
196	>	// Maintaining completion status
197
198		/**
199	<	* Gets current worker thread, or null if not a worker thread.
200	<	*/
187	<	static ForkJoinWorkerThread getWorker() {
188	<	Thread t = Thread.currentThread();
189	<	return ((t instanceof ForkJoinWorkerThread) ?
190	<	(ForkJoinWorkerThread) t : null);
191	<	}
192	<
193	<	final boolean casStatus(int cmp, int val) {
194	<	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
195	<	}
196	<
197	<	/**
198	<	* Workaround for not being able to rethrow unchecked exceptions.
199	<	*/
200	<	static void rethrowException(Throwable ex) {
201	<	if (ex != null)
202	<	UNSAFE.throwException(ex);
203	<	}
204	<
205	<	// Setting completion status
206	<
207	<	/**
208	<	* Marks completion and wakes up threads waiting to join this task.
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		*/
204	<	final void setCompletion(int completion) {
205	<	ForkJoinPool pool = getPool();
206	<	if (pool != null) {
207	<	int s; // Clear signal bits while setting completion status
208	<	do {} while ((s = status) >= 0 && !casStatus(s, completion));
209	<
210	<	if ((s & SIGNAL_MASK) != 0) {
219	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
220	<	pool.updateRunningCount(s);
221	<	synchronized (this) { notifyAll(); }
204	>	private void setCompletion(int completion) {
205	>	int s;
206	>	while ((s = status) >= 0) {
207	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
208	>	if (s != 0)
209	>	synchronized (this) { notifyAll(); }
210	>	break;
211		}
212		}
224	–	else
225	–	externallySetCompletion(completion);
226	–	}
227	–
228	–	/**
229	–	* Version of setCompletion for non-FJ threads.  Leaves signal
230	–	* bits for unblocked threads to adjust, and always notifies.
231	–	*/
232	–	private void externallySetCompletion(int completion) {
233	–	int s;
234	–	do {} while ((s = status) >= 0 &&
235	–	!casStatus(s, (s & SIGNAL_MASK) | completion));
236	–	synchronized (this) { notifyAll(); }
213		}
214
215		/**
216	<	* Sets status to indicate normal completion.
217	<	*/
218	<	final void setNormalCompletion() {
243	<	// Try typical fast case -- single CAS, no signal, not already done.
244	<	// Manually expand casStatus to improve chances of inlining it
245	<	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
246	<	setCompletion(NORMAL);
247	<	}
248	<
249	<	// internal waiting and notification
250	<
251	<	/**
252	<	* Performs the actual monitor wait for awaitDone.
216	>	* Records exception and sets exceptional completion.
217	>	*
218	>	* @return status on exit
219		*/
220	<	private void doAwaitDone() {
221	<	// Minimize lock bias and in/de-flation effects by maximizing
222	<	// chances of waiting inside sync
257	<	try {
258	<	while (status >= 0)
259	<	synchronized (this) { if (status >= 0) wait(); }
260	<	} catch (InterruptedException ie) {
261	<	onInterruptedWait();
262	<	}
220	>	private void setExceptionalCompletion(Throwable rex) {
221	>	exceptionMap.put(this, rex);
222	>	setCompletion(EXCEPTIONAL);
223		}
224
225		/**
226	<	* Performs the actual timed monitor wait for awaitDone.
226	>	* Blocks a worker thread until completion. Called only by
227	>	* pool. Currently unused -- pool-based waits use timeout
228	>	* version below.
229		*/
230	<	private void doAwaitDone(long startTime, long nanos) {
231	<	synchronized (this) {
230	>	final void internalAwaitDone() {
231	>	int s;         // the odd construction reduces lock bias effects
232	>	while ((s = status) >= 0) {
233		try {
234	<	while (status >= 0) {
235	<	long nt = nanos - (System.nanoTime() - startTime);
236	<	if (nt <= 0)
274	<	break;
275	<	wait(nt / 1000000, (int) (nt % 1000000));
234	>	synchronized (this) {
235	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
236	>	wait();
237		}
238		} catch (InterruptedException ie) {
239	<	onInterruptedWait();
279	<	}
280	<	}
281	<	}
282	<
283	<	// Awaiting completion
284	<
285	<	/**
286	<	* Sets status to indicate there is joiner, then waits for join,
287	<	* surrounded with pool notifications.
288	<	*
289	<	* @return status upon exit
290	<	*/
291	<	private int awaitDone(ForkJoinWorkerThread w,
292	<	boolean maintainParallelism) {
293	<	ForkJoinPool pool = (w == null) ? null : w.pool;
294	<	int s;
295	<	while ((s = status) >= 0) {
296	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
297	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
298	<	doAwaitDone();
299	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
300	<	adjustPoolCountsOnUnblock(pool);
301	<	break;
239	>	cancelIfTerminating();
240		}
241		}
304	–	return s;
242		}
243
244		/**
245	<	* Timed version of awaitDone
245	>	* Blocks a worker thread until completed or timed out.  Called
246	>	* only by pool.
247		*
248	<	* @return status upon exit
248	>	* @return status on exit
249		*/
250	<	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
313	<	ForkJoinPool pool = (w == null) ? null : w.pool;
250	>	final int internalAwaitDone(long millis, int nanos) {
251		int s;
252	<	while ((s = status) >= 0) {
253	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
254	<	long startTime = System.nanoTime();
255	<	if (pool == null || !pool.preJoin(this, false))
256	<	doAwaitDone(startTime, nanos);
320	<	if ((s = status) >= 0) {
321	<	adjustPoolCountsOnCancelledWait(pool);
322	<	s = status;
252	>	if ((s = status) >= 0) {
253	>	try {
254	>	synchronized (this) {
255	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
256	>	wait(millis, nanos);
257		}
258	<	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
259	<	adjustPoolCountsOnUnblock(pool);
326	<	break;
258	>	} catch (InterruptedException ie) {
259	>	cancelIfTerminating();
260		}
261	+	s = status;
262		}
263		return s;
264		}
265
266		/**
267	<	* Notifies pool that thread is unblocked. Called by signalled
334	<	* threads when woken by non-FJ threads (which is atypical).
267	>	* Blocks a non-worker-thread until completion.
268		*/
269	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
269	>	private void externalAwaitDone() {
270		int s;
271	<	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
272	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
273	<	pool.updateRunningCount(s);
274	<	}
275	<
276	<	/**
277	<	* Notifies pool to adjust counts on cancelled or timed out wait.
278	<	*/
279	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
280	<	if (pool != null) {
281	<	int s;
282	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
283	<	if (casStatus(s, s - 1)) {
351	<	pool.updateRunningCount(1);
271	>	while ((s = status) >= 0) {
272	>	synchronized (this) {
273	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
274	>	boolean interrupted = false;
275	>	while (status >= 0) {
276	>	try {
277	>	wait();
278	>	} catch (InterruptedException ie) {
279	>	interrupted = true;
280	>	}
281	>	}
282	>	if (interrupted)
283	>	Thread.currentThread().interrupt();
284		break;
285		}
286		}
#	Line 356 | Line 288 | public abstract class ForkJoinTask<V> im
288		}
289
290		/**
291	<	* Handles interruptions during waits.
292	<	*/
293	<	private void onInterruptedWait() {
362	<	ForkJoinWorkerThread w = getWorker();
363	<	if (w == null)
364	<	Thread.currentThread().interrupt(); // re-interrupt
365	<	else if (w.isTerminating())
366	<	cancelIgnoringExceptions();
367	<	// else if FJworker, ignore interrupt
368	<	}
369	<
370	<	// Recording and reporting exceptions
371	<
372	<	private void setDoneExceptionally(Throwable rex) {
373	<	exceptionMap.put(this, rex);
374	<	setCompletion(EXCEPTIONAL);
375	<	}
376	<
377	<	/**
378	<	* Throws the exception associated with status s.
379	<	*
380	<	* @throws the exception
381	<	*/
382	<	private void reportException(int s) {
383	<	if ((s &= COMPLETION_MASK) < NORMAL) {
384	<	if (s == CANCELLED)
385	<	throw new CancellationException();
386	<	else
387	<	rethrowException(exceptionMap.get(this));
388	<	}
389	<	}
390	<
391	<	/**
392	<	* Returns result or throws exception using j.u.c.Future conventions.
393	<	* Only call when {@code isDone} known to be true or thread known
394	<	* to be interrupted.
395	<	*/
396	<	private V reportFutureResult()
397	<	throws InterruptedException, ExecutionException {
398	<	if (Thread.interrupted())
399	<	throw new InterruptedException();
400	<	int s = status & COMPLETION_MASK;
401	<	if (s < NORMAL) {
402	<	Throwable ex;
403	<	if (s == CANCELLED)
404	<	throw new CancellationException();
405	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
406	<	throw new ExecutionException(ex);
407	<	}
408	<	return getRawResult();
409	<	}
410	<
411	<	/**
412	<	* Returns result or throws exception using j.u.c.Future conventions
413	<	* with timeouts.
414	<	*/
415	<	private V reportTimedFutureResult()
416	<	throws InterruptedException, ExecutionException, TimeoutException {
417	<	if (Thread.interrupted())
418	<	throw new InterruptedException();
419	<	Throwable ex;
420	<	int s = status & COMPLETION_MASK;
421	<	if (s == NORMAL)
422	<	return getRawResult();
423	<	else if (s == CANCELLED)
424	<	throw new CancellationException();
425	<	else if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
426	<	throw new ExecutionException(ex);
427	<	else
428	<	throw new TimeoutException();
429	<	}
430	<
431	<	// internal execution methods
432	<
433	<	/**
434	<	* Calls exec, recording completion, and rethrowing exception if
435	<	* encountered. Caller should normally check status before calling.
436	<	*
437	<	* @return true if completed normally
438	<	*/
439	<	private boolean tryExec() {
440	<	try { // try block must contain only call to exec
441	<	if (!exec())
442	<	return false;
443	<	} catch (Throwable rex) {
444	<	setDoneExceptionally(rex);
445	<	rethrowException(rex);
446	<	return false; // not reached
447	<	}
448	<	setNormalCompletion();
449	<	return true;
450	<	}
451	<
452	<	/**
453	<	* Main execution method used by worker threads. Invokes
454	<	* base computation unless already complete.
291	>	* Unless done, calls exec and records status if completed, but
292	>	* doesn't wait for completion otherwise. Primary execution method
293	>	* for ForkJoinWorkerThread.
294		*/
295		final void quietlyExec() {
457	–	if (status >= 0) {
458	–	try {
459	–	if (!exec())
460	–	return;
461	–	} catch (Throwable rex) {
462	–	setDoneExceptionally(rex);
463	–	return;
464	–	}
465	–	setNormalCompletion();
466	–	}
467	–	}
468	–
469	–	/**
470	–	* Calls exec(), recording but not rethrowing exception.
471	–	* Caller should normally check status before calling.
472	–	*
473	–	* @return true if completed normally
474	–	*/
475	–	private boolean tryQuietlyInvoke() {
296		try {
297	<	if (!exec())
298	<	return false;
297	>	if (status < 0 || !exec())
298	>	return;
299		} catch (Throwable rex) {
300	<	setDoneExceptionally(rex);
301	<	return false;
482	<	}
483	<	setNormalCompletion();
484	<	return true;
485	<	}
486	<
487	<	/**
488	<	* Cancels, ignoring any exceptions it throws.
489	<	*/
490	<	final void cancelIgnoringExceptions() {
491	<	try {
492	<	cancel(false);
493	<	} catch (Throwable ignore) {
300	>	setExceptionalCompletion(rex);
301	>	return;
302		}
303	<	}
496	<
497	<	/**
498	<	* Main implementation of helpJoin
499	<	*/
500	<	private int busyJoin(ForkJoinWorkerThread w) {
501	<	int s;
502	<	ForkJoinTask<?> t;
503	<	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
504	<	t.quietlyExec();
505	<	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
303	>	setCompletion(NORMAL); // must be outside try block
304		}
305
306		// public methods
#	Line 540 | Line 338 | public abstract class ForkJoinTask<V> im
338		* @return the computed result
339		*/
340		public final V join() {
341	<	ForkJoinWorkerThread w = getWorker();
342	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
343	<	reportException(awaitDone(w, true));
341	>	quietlyJoin();
342	>	Throwable ex;
343	>	if (status < NORMAL && (ex = getException()) != null)
344	>	UNSAFE.throwException(ex);
345		return getRawResult();
346		}
347
348		/**
349		* Commences performing this task, awaits its completion if
350	<	* necessary, and return its result, or throws an (unchecked)
351	<	* exception if the underlying computation did so.
350	>	* necessary, and returns its result, or throws an (unchecked)
351	>	* {@code RuntimeException} or {@code Error} if the underlying
352	>	* computation did so.
353		*
354		* @return the computed result
355		*/
356		public final V invoke() {
357	<	if (status >= 0 && tryExec())
358	<	return getRawResult();
359	<	else
360	<	return join();
357	>	quietlyInvoke();
358	>	Throwable ex;
359	>	if (status < NORMAL && (ex = getException()) != null)
360	>	UNSAFE.throwException(ex);
361	>	return getRawResult();
362		}
363
364		/**
365		* Forks the given tasks, returning when {@code isDone} holds for
366		* each task or an (unchecked) exception is encountered, in which
367	<	* case the exception is rethrown.  If either task encounters an
368	<	* exception, the other one may be, but is not guaranteed to be,
369	<	* cancelled.  If both tasks throw an exception, then this method
370	<	* throws one of them.  The individual status of each task may be
371	<	* checked using {@link #getException()} and related methods.
367	>	* case the exception is rethrown. If more than one task
368	>	* encounters an exception, then this method throws any one of
369	>	* these exceptions. If any task encounters an exception, the
370	>	* other may be cancelled. However, the execution status of
371	>	* individual tasks is not guaranteed upon exceptional return. The
372	>	* status of each task may be obtained using {@link
373	>	* #getException()} and related methods to check if they have been
374	>	* cancelled, completed normally or exceptionally, or left
375	>	* unprocessed.
376		*
377		* <p>This method may be invoked only from within {@code
378		* ForkJoinTask} computations (as may be determined using method
#	Line 588 | Line 393 | public abstract class ForkJoinTask<V> im
393		/**
394		* Forks the given tasks, returning when {@code isDone} holds for
395		* each task or an (unchecked) exception is encountered, in which
396	<	* case the exception is rethrown. If any task encounters an
397	<	* exception, others may be, but are not guaranteed to be,
398	<	* cancelled.  If more than one task encounters an exception, then
399	<	* this method throws any one of these exceptions.  The individual
400	<	* status of each task may be checked using {@link #getException()}
401	<	* and related methods.
396	>	* case the exception is rethrown. If more than one task
397	>	* encounters an exception, then this method throws any one of
398	>	* these exceptions. If any task encounters an exception, others
399	>	* may be cancelled. However, the execution status of individual
400	>	* tasks is not guaranteed upon exceptional return. The status of
401	>	* each task may be obtained using {@link #getException()} and
402	>	* related methods to check if they have been cancelled, completed
403	>	* normally or exceptionally, or left unprocessed.
404		*
405		* <p>This method may be invoked only from within {@code
406		* ForkJoinTask} computations (as may be determined using method
#	Line 617 | Line 424 | public abstract class ForkJoinTask<V> im
424		t.fork();
425		else {
426		t.quietlyInvoke();
427	<	if (ex == null)
427	>	if (ex == null && t.status < NORMAL)
428		ex = t.getException();
429		}
430		}
#	Line 628 | Line 435 | public abstract class ForkJoinTask<V> im
435		t.cancel(false);
436		else {
437		t.quietlyJoin();
438	<	if (ex == null)
438	>	if (ex == null && t.status < NORMAL)
439		ex = t.getException();
440		}
441		}
442		}
443		if (ex != null)
444	<	rethrowException(ex);
444	>	UNSAFE.throwException(ex);
445		}
446
447		/**
448		* Forks all tasks in the specified collection, returning when
449		* {@code isDone} holds for each task or an (unchecked) exception
450	<	* is encountered.  If any task encounters an exception, others
451	<	* may be, but are not guaranteed to be, cancelled.  If more than
452	<	* one task encounters an exception, then this method throws any
453	<	* one of these exceptions.  The individual status of each task
454	<	* may be checked using {@link #getException()} and related
455	<	* methods.  The behavior of this operation is undefined if the
456	<	* specified collection is modified while the operation is in
457	<	* progress.
450	>	* is encountered, in which case the exception is rethrown. If
451	>	* more than one task encounters an exception, then this method
452	>	* throws any one of these exceptions. If any task encounters an
453	>	* exception, others may be cancelled. However, the execution
454	>	* status of individual tasks is not guaranteed upon exceptional
455	>	* return. The status of each task may be obtained using {@link
456	>	* #getException()} and related methods to check if they have been
457	>	* cancelled, completed normally or exceptionally, or left
458	>	* unprocessed.
459		*
460		* <p>This method may be invoked only from within {@code
461		* ForkJoinTask} computations (as may be determined using method
#	Line 679 | Line 487 | public abstract class ForkJoinTask<V> im
487		t.fork();
488		else {
489		t.quietlyInvoke();
490	<	if (ex == null)
490	>	if (ex == null && t.status < NORMAL)
491		ex = t.getException();
492		}
493		}
#	Line 690 | Line 498 | public abstract class ForkJoinTask<V> im
498		t.cancel(false);
499		else {
500		t.quietlyJoin();
501	<	if (ex == null)
501	>	if (ex == null && t.status < NORMAL)
502		ex = t.getException();
503		}
504		}
505		}
506		if (ex != null)
507	<	rethrowException(ex);
507	>	UNSAFE.throwException(ex);
508		return tasks;
509		}
510
#	Line 726 | Line 534 | public abstract class ForkJoinTask<V> im
534		*/
535		public boolean cancel(boolean mayInterruptIfRunning) {
536		setCompletion(CANCELLED);
537	<	return (status & COMPLETION_MASK) == CANCELLED;
537	>	return status == CANCELLED;
538	>	}
539	>
540	>	/**
541	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
542	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
543	>	* exceptions, but if it does anyway, we have no recourse during
544	>	* shutdown, so guard against this case.
545	>	*/
546	>	final void cancelIgnoringExceptions() {
547	>	try {
548	>	cancel(false);
549	>	} catch (Throwable ignore) {
550	>	}
551	>	}
552	>
553	>	/**
554	>	* Cancels if current thread is a terminating worker thread,
555	>	* ignoring any exceptions thrown by cancel.
556	>	*/
557	>	final void cancelIfTerminating() {
558	>	Thread t = Thread.currentThread();
559	>	if ((t instanceof ForkJoinWorkerThread) &&
560	>	((ForkJoinWorkerThread) t).isTerminating()) {
561	>	try {
562	>	cancel(false);
563	>	} catch (Throwable ignore) {
564	>	}
565	>	}
566		}
567
568		public final boolean isDone() {
#	Line 734 | Line 570 | public abstract class ForkJoinTask<V> im
570		}
571
572		public final boolean isCancelled() {
573	<	return (status & COMPLETION_MASK) == CANCELLED;
573	>	return status == CANCELLED;
574		}
575
576		/**
#	Line 743 | Line 579 | public abstract class ForkJoinTask<V> im
579		* @return {@code true} if this task threw an exception or was cancelled
580		*/
581		public final boolean isCompletedAbnormally() {
582	<	return (status & COMPLETION_MASK) < NORMAL;
582	>	return status < NORMAL;
583		}
584
585		/**
#	Line 754 | Line 590 | public abstract class ForkJoinTask<V> im
590		* exception and was not cancelled
591		*/
592		public final boolean isCompletedNormally() {
593	<	return (status & COMPLETION_MASK) == NORMAL;
593	>	return status == NORMAL;
594		}
595
596		/**
#	Line 765 | Line 601 | public abstract class ForkJoinTask<V> im
601		* @return the exception, or {@code null} if none
602		*/
603		public final Throwable getException() {
604	<	int s = status & COMPLETION_MASK;
604	>	int s = status;
605		return ((s >= NORMAL)    ? null :
606		(s == CANCELLED) ? new CancellationException() :
607		exceptionMap.get(this));
#	Line 781 | Line 617 | public abstract class ForkJoinTask<V> im
617		* overridable, but overridden versions must invoke {@code super}
618		* implementation to maintain guarantees.
619		*
620	<	* @param ex the exception to throw. If this exception is
621	<	* not a RuntimeException or Error, the actual exception thrown
622	<	* will be a RuntimeException with cause ex.
620	>	* @param ex the exception to throw. If this exception is not a
621	>	* {@code RuntimeException} or {@code Error}, the actual exception
622	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
623		*/
624		public void completeExceptionally(Throwable ex) {
625	<	setDoneExceptionally((ex instanceof RuntimeException) ||
626	<	(ex instanceof Error) ? ex :
627	<	new RuntimeException(ex));
625	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
626	>	(ex instanceof Error) ? ex :
627	>	new RuntimeException(ex));
628		}
629
630		/**
631		* Completes this task, and if not already aborted or cancelled,
632	<	* returning a {@code null} result upon {@code join} and related
633	<	* operations. This method may be used to provide results for
634	<	* asynchronous tasks, or to provide alternative handling for
635	<	* tasks that would not otherwise complete normally. Its use in
636	<	* other situations is discouraged. This method is
637	<	* overridable, but overridden versions must invoke {@code super}
638	<	* implementation to maintain guarantees.
632	>	* returning the given value as the result of subsequent
633	>	* invocations of {@code join} and related operations. This method
634	>	* may be used to provide results for asynchronous tasks, or to
635	>	* provide alternative handling for tasks that would not otherwise
636	>	* complete normally. Its use in other situations is
637	>	* discouraged. This method is overridable, but overridden
638	>	* versions must invoke {@code super} implementation to maintain
639	>	* guarantees.
640		*
641		* @param value the result value for this task
642		*/
#	Line 807 | Line 644 | public abstract class ForkJoinTask<V> im
644		try {
645		setRawResult(value);
646		} catch (Throwable rex) {
647	<	setDoneExceptionally(rex);
647	>	setExceptionalCompletion(rex);
648		return;
649		}
650	<	setNormalCompletion();
814	<	}
815	<
816	<	public final V get() throws InterruptedException, ExecutionException {
817	<	ForkJoinWorkerThread w = getWorker();
818	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
819	<	awaitDone(w, true);
820	<	return reportFutureResult();
821	<	}
822	<
823	<	public final V get(long timeout, TimeUnit unit)
824	<	throws InterruptedException, ExecutionException, TimeoutException {
825	<	long nanos = unit.toNanos(timeout);
826	<	ForkJoinWorkerThread w = getWorker();
827	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
828	<	awaitDone(w, nanos);
829	<	return reportTimedFutureResult();
650	>	setCompletion(NORMAL);
651		}
652
653		/**
654	<	* Possibly executes other tasks until this task {@link #isDone is
655	<	* done}, then returns the result of the computation.  This method
835	<	* may be more efficient than {@code join}, but is only applicable
836	<	* when there are no potential dependencies between continuation
837	<	* of the current task and that of any other task that might be
838	<	* executed while helping. (This usually holds for pure
839	<	* divide-and-conquer tasks).
840	<	*
841	<	* <p>This method may be invoked only from within {@code
842	<	* ForkJoinTask} computations (as may be determined using method
843	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
844	<	* result in exceptions or errors, possibly including {@code
845	<	* ClassCastException}.
654	>	* Waits if necessary for the computation to complete, and then
655	>	* retrieves its result.
656		*
657		* @return the computed result
658	+	* @throws CancellationException if the computation was cancelled
659	+	* @throws ExecutionException if the computation threw an
660	+	* exception
661	+	* @throws InterruptedException if the current thread is not a
662	+	* member of a ForkJoinPool and was interrupted while waiting
663		*/
664	<	public final V helpJoin() {
665	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
666	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
667	<	reportException(busyJoin(w));
664	>	public final V get() throws InterruptedException, ExecutionException {
665	>	int s;
666	>	if (Thread.currentThread() instanceof ForkJoinWorkerThread) {
667	>	quietlyJoin();
668	>	s = status;
669	>	}
670	>	else {
671	>	while ((s = status) >= 0) {
672	>	synchronized (this) { // interruptible form of awaitDone
673	>	if (UNSAFE.compareAndSwapInt(this, statusOffset,
674	>	s, SIGNAL)) {
675	>	while (status >= 0)
676	>	wait();
677	>	}
678	>	}
679	>	}
680	>	}
681	>	if (s < NORMAL) {
682	>	Throwable ex;
683	>	if (s == CANCELLED)
684	>	throw new CancellationException();
685	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
686	>	throw new ExecutionException(ex);
687	>	}
688		return getRawResult();
689		}
690
691		/**
692	<	* Possibly executes other tasks until this task {@link #isDone is
693	<	* done}.  This method may be useful when processing collections
859	<	* of tasks when some have been cancelled or otherwise known to
860	<	* have aborted.
692	>	* Waits if necessary for at most the given time for the computation
693	>	* to complete, and then retrieves its result, if available.
694		*
695	<	* <p>This method may be invoked only from within {@code
696	<	* ForkJoinTask} computations (as may be determined using method
697	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
698	<	* result in exceptions or errors, possibly including {@code
699	<	* ClassCastException}.
695	>	* @param timeout the maximum time to wait
696	>	* @param unit the time unit of the timeout argument
697	>	* @return the computed result
698	>	* @throws CancellationException if the computation was cancelled
699	>	* @throws ExecutionException if the computation threw an
700	>	* exception
701	>	* @throws InterruptedException if the current thread is not a
702	>	* member of a ForkJoinPool and was interrupted while waiting
703	>	* @throws TimeoutException if the wait timed out
704		*/
705	<	public final void quietlyHelpJoin() {
705	>	public final V get(long timeout, TimeUnit unit)
706	>	throws InterruptedException, ExecutionException, TimeoutException {
707	>	long nanos = unit.toNanos(timeout);
708		if (status >= 0) {
709	<	ForkJoinWorkerThread w =
710	<	(ForkJoinWorkerThread) Thread.currentThread();
711	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
712	<	busyJoin(w);
709	>	Thread t = Thread.currentThread();
710	>	if (t instanceof ForkJoinWorkerThread) {
711	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
712	>	boolean completed = false; // timed variant of quietlyJoin
713	>	if (w.unpushTask(this)) {
714	>	try {
715	>	completed = exec();
716	>	} catch (Throwable rex) {
717	>	setExceptionalCompletion(rex);
718	>	}
719	>	}
720	>	if (completed)
721	>	setCompletion(NORMAL);
722	>	else if (status >= 0)
723	>	w.joinTask(this, true, nanos);
724	>	}
725	>	else if (Thread.interrupted())
726	>	throw new InterruptedException();
727	>	else {
728	>	long startTime = System.nanoTime();
729	>	int s; long nt;
730	>	while ((s = status) >= 0 &&
731	>	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
732	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,
733	>	SIGNAL)) {
734	>	long ms = nt / 1000000;
735	>	int ns = (int) (nt % 1000000);
736	>	synchronized (this) {
737	>	if (status >= 0)
738	>	wait(ms, ns); // exit on IE throw
739	>	}
740	>	}
741	>	}
742	>	}
743		}
744	+	int es = status;
745	+	if (es != NORMAL) {
746	+	Throwable ex;
747	+	if (es == CANCELLED)
748	+	throw new CancellationException();
749	+	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
750	+	throw new ExecutionException(ex);
751	+	throw new TimeoutException();
752	+	}
753	+	return getRawResult();
754		}
755
756		/**
757	<	* Joins this task, without returning its result or throwing an
757	>	* Joins this task, without returning its result or throwing its
758		* exception. This method may be useful when processing
759		* collections of tasks when some have been cancelled or otherwise
760		* known to have aborted.
761		*/
762		public final void quietlyJoin() {
763	<	if (status >= 0) {
764	<	ForkJoinWorkerThread w = getWorker();
765	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
766	<	awaitDone(w, true);
763	>	Thread t;
764	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
765	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
766	>	if (status >= 0) {
767	>	if (w.unpushTask(this)) {
768	>	boolean completed;
769	>	try {
770	>	completed = exec();
771	>	} catch (Throwable rex) {
772	>	setExceptionalCompletion(rex);
773	>	return;
774	>	}
775	>	if (completed) {
776	>	setCompletion(NORMAL);
777	>	return;
778	>	}
779	>	}
780	>	w.joinTask(this, false, 0L);
781	>	}
782		}
783	+	else
784	+	externalAwaitDone();
785		}
786
787		/**
788		* Commences performing this task and awaits its completion if
789	<	* necessary, without returning its result or throwing an
790	<	* exception. This method may be useful when processing
895	<	* collections of tasks when some have been cancelled or otherwise
896	<	* known to have aborted.
789	>	* necessary, without returning its result or throwing its
790	>	* exception.
791		*/
792		public final void quietlyInvoke() {
793	<	if (status >= 0 && !tryQuietlyInvoke())
794	<	quietlyJoin();
793	>	if (status >= 0) {
794	>	boolean completed;
795	>	try {
796	>	completed = exec();
797	>	} catch (Throwable rex) {
798	>	setExceptionalCompletion(rex);
799	>	return;
800	>	}
801	>	if (completed)
802	>	setCompletion(NORMAL);
803	>	else
804	>	quietlyJoin();
805	>	}
806		}
807
808		/**
#	Line 927 | Line 832 | public abstract class ForkJoinTask<V> im
832		* under any other usage conditions are not guaranteed.
833		* This method may be useful when executing
834		* pre-constructed trees of subtasks in loops.
835	+	*
836	+	* <p>Upon completion of this method, {@code isDone()} reports
837	+	* {@code false}, and {@code getException()} reports {@code
838	+	* null}. However, the value returned by {@code getRawResult} is
839	+	* unaffected. To clear this value, you can invoke {@code
840	+	* setRawResult(null)}.
841		*/
842		public void reinitialize() {
843	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
843	>	if (status == EXCEPTIONAL)
844		exceptionMap.remove(this);
845		status = 0;
846		}
#	Line 1219 | Line 1130 | public abstract class ForkJoinTask<V> im
1130		private static final long serialVersionUID = -7721805057305804111L;
1131
1132		/**
1133	<	* Save the state to a stream.
1133	>	* Saves the state to a stream (that is, serializes it).
1134		*
1135		* @serialData the current run status and the exception thrown
1136		* during execution, or {@code null} if none
#	Line 1232 | Line 1143 | public abstract class ForkJoinTask<V> im
1143		}
1144
1145		/**
1146	<	* Reconstitute the instance from a stream.
1146	>	* Reconstitutes the instance from a stream (that is, deserializes it).
1147		*
1148		* @param s the stream
1149		*/
1150		private void readObject(java.io.ObjectInputStream s)
1151		throws java.io.IOException, ClassNotFoundException {
1152		s.defaultReadObject();
1242	–	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1243	–	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1153		Object ex = s.readObject();
1154		if (ex != null)
1155	<	setDoneExceptionally((Throwable) ex);
1155	>	setExceptionalCompletion((Throwable) ex);
1156		}
1157
1158		// Unsafe mechanics

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