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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.37 by jsr166, Tue Aug 4 20:24:54 2009 UTC vs.
Revision 1.63 by dl, Sat Sep 18 12:10:21 2010 UTC

#	Line 7 | Line 7
7		package jsr166y;
8
9		import java.util.concurrent.*;
10	–
10		import java.io.Serializable;
11		import java.util.Collection;
12		import java.util.Collections;
#	Line 28 | Line 27 | import java.util.WeakHashMap;
27		* start other subtasks.  As indicated by the name of this class,
28		* many programs using {@code ForkJoinTask} employ only methods
29		* {@link #fork} and {@link #join}, or derivatives such as {@link
30	<	* #invokeAll}.  However, this class also provides a number of other
31	<	* methods that can come into play in advanced usages, as well as
32	<	* extension mechanics that allow support of new forms of fork/join
33	<	* processing.
30	>	* #invokeAll(ForkJoinTask...) invokeAll}.  However, this class also
31	>	* provides a number of other methods that can come into play in
32	>	* advanced usages, as well as extension mechanics that allow
33	>	* support of new forms of fork/join processing.
34		*
35		* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
36		* The efficiency of {@code ForkJoinTask}s stems from a set of
#	Line 56 | Line 55 | import java.util.WeakHashMap;
55		* exceptions such as {@code IOExceptions} to be thrown. However,
56		* computations may still encounter unchecked exceptions, that are
57		* rethrown to callers attempting to join them. These exceptions may
58	<	* additionally include RejectedExecutionExceptions stemming from
59	<	* internal resource exhaustion such as failure to allocate internal
60	<	* task queues.
58	>	* additionally include {@link RejectedExecutionException} stemming
59	>	* from internal resource exhaustion, such as failure to allocate
60	>	* internal task queues.
61		*
62		* <p>The primary method for awaiting completion and extracting
63		* results of a task is {@link #join}, but there are several variants:
64		* The {@link Future#get} methods support interruptible and/or timed
65		* waits for completion and report results using {@code Future}
66	<	* 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
66	>	* conventions. Method {@link #invoke} is semantically
67		* equivalent to {@code fork(); join()} but always attempts to begin
68		* execution in the current thread. The "<em>quiet</em>" forms of
69		* these methods do not extract results or report exceptions. These
#	Line 80 | Line 76 | import java.util.WeakHashMap;
76		* <p>The execution status of tasks may be queried at several levels
77		* of detail: {@link #isDone} is true if a task completed in any way
78		* (including the case where a task was cancelled without executing);
83	–	* {@link #isCancelled} is true if completion was due to cancellation;
79		* {@link #isCompletedNormally} is true if a task completed without
80	<	* cancellation or encountering an exception; {@link
81	<	* #isCompletedExceptionally} is true if if the task encountered an
82	<	* exception (in which case {@link #getException} returns the
83	<	* exception); {@link #isCancelled} is true if the task was cancelled
84	<	* (in which case {@link #getException} returns a {@link
85	<	* java.util.concurrent.CancellationException}); and {@link
86	<	* #isCompletedAbnormally} is true if a task was either cancelled or
92	<	* encountered an exception.
80	>	* cancellation or encountering an exception; {@link #isCancelled} is
81	>	* true if the task was cancelled (in which case {@link #getException}
82	>	* returns a {@link java.util.concurrent.CancellationException}); and
83	>	* {@link #isCompletedAbnormally} is true if a task was either
84	>	* cancelled or encountered an exception, in which case {@link
85	>	* #getException} will return either the encountered exception or
86	>	* {@link java.util.concurrent.CancellationException}.
87		*
88		* <p>The ForkJoinTask class is not usually directly subclassed.
89		* Instead, you subclass one of the abstract classes that support a
#	Line 105 | Line 99 | import java.util.WeakHashMap;
99		* ForkJoinTasks (as may be determined using method {@link
100		* #inForkJoinPool}).  Attempts to invoke them in other contexts
101		* result in exceptions or errors, possibly including
102	<	* ClassCastException.
102	>	* {@code ClassCastException}.
103		*
104		* <p>Most base support methods are {@code final}, to prevent
105		* overriding of implementations that are intrinsically tied to the
#	Line 127 | Line 121 | import java.util.WeakHashMap;
121		*
122		* <p>This class provides {@code adapt} methods for {@link Runnable}
123		* and {@link Callable}, that may be of use when mixing execution of
124	<	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks
125	<	* are of this form, consider using a pool in
132	<	* {@linkplain ForkJoinPool#setAsyncMode async mode}.
124	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
125	>	* of this form, consider using a pool constructed in <em>asyncMode</em>.
126		*
127		* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
128		* used in extensions such as remote execution frameworks. It is
#	Line 141 | Line 134 | import java.util.WeakHashMap;
134		*/
135		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
136
137	<	/**
138	<	* Run control status bits packed into a single int to minimize
139	<	* footprint and to ensure atomicity (via CAS).  Status is
140	<	* initially zero, and takes on nonnegative values until
141	<	* completed, upon which status holds COMPLETED. CANCELLED, or
142	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
143	<	* blocking waits by other threads have SIGNAL_MASK bits set --
144	<	* bit 15 for external (nonFJ) waits, and the rest a count of
145	<	* waiting FJ threads.  (This representation relies on
146	<	* ForkJoinPool max thread limits). Completion of a stolen task
147	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
148	<	* though suboptimal for some purposes, we use basic builtin
149	<	* wait/notify to take advantage of "monitor inflation" in JVMs
150	<	* that we would otherwise need to emulate to avoid adding further
151	<	* per-task bookkeeping overhead. Note that bits 16-28 are
152	<	* currently unused. Also value 0x80000000 is available as spare
153	<	* completion value.
137	>	/*
138	>	* See the internal documentation of class ForkJoinPool for a
139	>	* general implementation overview.  ForkJoinTasks are mainly
140	>	* responsible for maintaining their "status" field amidst relays
141	>	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
142	>	* methods of this class are more-or-less layered into (1) basic
143	>	* status maintenance (2) execution and awaiting completion (3)
144	>	* user-level methods that additionally report results. This is
145	>	* sometimes hard to see because this file orders exported methods
146	>	* in a way that flows well in javadocs. In particular, most
147	>	* join mechanics are in method quietlyJoin, below.
148	>	*/
149	>
150	>	/*
151	>	* The status field holds run control status bits packed into a
152	>	* single int to minimize footprint and to ensure atomicity (via
153	>	* CAS).  Status is initially zero, and takes on nonnegative
154	>	* values until completed, upon which status holds value
155	>	* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
156	>	* waits by other threads have the SIGNAL bit set.  Completion of
157	>	* a stolen task with SIGNAL set awakens any waiters via
158	>	* notifyAll. Even though suboptimal for some purposes, we use
159	>	* basic builtin wait/notify to take advantage of "monitor
160	>	* inflation" in JVMs that we would otherwise need to emulate to
161	>	* avoid adding further per-task bookkeeping overhead.  We want
162	>	* these monitors to be "fat", i.e., not use biasing or thin-lock
163	>	* techniques, so use some odd coding idioms that tend to avoid
164	>	* them.
165		*/
166	+
167	+	/** The run status of this task */
168		volatile int status; // accessed directly by pool and workers
169
170	<	static final int COMPLETION_MASK      = 0xe0000000;
171	<	static final int NORMAL               = 0xe0000000; // == mask
172	<	static final int CANCELLED            = 0xc0000000;
173	<	static final int EXCEPTIONAL          = 0xa0000000;
168	<	static final int SIGNAL_MASK          = 0x0000ffff;
169	<	static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
170	<	static final int EXTERNAL_SIGNAL      = 0x00008000; // top bit of low word
170	>	private static final int NORMAL      = -1;
171	>	private static final int CANCELLED   = -2;
172	>	private static final int EXCEPTIONAL = -3;
173	>	private static final int SIGNAL      =  1;
174
175		/**
176		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 181 | Line 184 | public abstract class ForkJoinTask<V> im
184		Collections.synchronizedMap
185		(new WeakHashMap<ForkJoinTask<?>, Throwable>());
186
187	<	// within-package utilities
185	<
186	<	/**
187	<	* Gets current worker thread, or null if not a worker thread.
188	<	*/
189	<	static ForkJoinWorkerThread getWorker() {
190	<	Thread t = Thread.currentThread();
191	<	return ((t instanceof ForkJoinWorkerThread) ?
192	<	(ForkJoinWorkerThread) t : null);
193	<	}
194	<
195	<	final boolean casStatus(int cmp, int val) {
196	<	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
197	<	}
187	>	// Maintaining completion status
188
189		/**
190	<	* Workaround for not being able to rethrow unchecked exceptions.
191	<	*/
202	<	static void rethrowException(Throwable ex) {
203	<	if (ex != null)
204	<	UNSAFE.throwException(ex);
205	<	}
206	<
207	<	// Setting completion status
208	<
209	<	/**
210	<	* Marks completion and wakes up threads waiting to join this task.
190	>	* Marks completion and wakes up threads waiting to join this task,
191	>	* also clearing signal request bits.
192		*
193		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
194		*/
195	<	final void setCompletion(int completion) {
196	<	ForkJoinPool pool = getPool();
197	<	if (pool != null) {
198	<	int s; // Clear signal bits while setting completion status
199	<	do {} while ((s = status) >= 0 && !casStatus(s, completion));
200	<
201	<	if ((s & SIGNAL_MASK) != 0) {
221	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
222	<	pool.updateRunningCount(s);
223	<	synchronized (this) { notifyAll(); }
195	>	private void setCompletion(int completion) {
196	>	int s;
197	>	while ((s = status) >= 0) {
198	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
199	>	if (s != 0)
200	>	synchronized (this) { notifyAll(); }
201	>	break;
202		}
203		}
226	–	else
227	–	externallySetCompletion(completion);
204		}
205
206		/**
207	<	* Version of setCompletion for non-FJ threads.  Leaves signal
208	<	* bits for unblocked threads to adjust, and always notifies.
209	<	*/
234	<	private void externallySetCompletion(int completion) {
235	<	int s;
236	<	do {} while ((s = status) >= 0 &&
237	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
238	<	synchronized (this) { notifyAll(); }
239	<	}
240	<
241	<	/**
242	<	* Sets status to indicate normal completion.
243	<	*/
244	<	final void setNormalCompletion() {
245	<	// Try typical fast case -- single CAS, no signal, not already done.
246	<	// Manually expand casStatus to improve chances of inlining it
247	<	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
248	<	setCompletion(NORMAL);
249	<	}
250	<
251	<	// internal waiting and notification
252	<
253	<	/**
254	<	* Performs the actual monitor wait for awaitDone.
207	>	* Records exception and sets exceptional completion.
208	>	*
209	>	* @return status on exit
210		*/
211	<	private void doAwaitDone() {
212	<	// Minimize lock bias and in/de-flation effects by maximizing
213	<	// chances of waiting inside sync
259	<	try {
260	<	while (status >= 0)
261	<	synchronized (this) { if (status >= 0) wait(); }
262	<	} catch (InterruptedException ie) {
263	<	onInterruptedWait();
264	<	}
211	>	private void setExceptionalCompletion(Throwable rex) {
212	>	exceptionMap.put(this, rex);
213	>	setCompletion(EXCEPTIONAL);
214		}
215
216		/**
217	<	* Performs the actual timed monitor wait for awaitDone.
217	>	* Blocks a worker thread until completion. Called only by
218	>	* pool. Currently unused -- pool-based waits use timeout
219	>	* version below.
220		*/
221	<	private void doAwaitDone(long startTime, long nanos) {
222	<	synchronized (this) {
221	>	final void internalAwaitDone() {
222	>	int s;         // the odd construction reduces lock bias effects
223	>	while ((s = status) >= 0) {
224		try {
225	<	while (status >= 0) {
226	<	long nt = nanos - (System.nanoTime() - startTime);
227	<	if (nt <= 0)
276	<	break;
277	<	wait(nt / 1000000, (int) (nt % 1000000));
225	>	synchronized (this) {
226	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
227	>	wait();
228		}
229		} catch (InterruptedException ie) {
230	<	onInterruptedWait();
281	<	}
282	<	}
283	<	}
284	<
285	<	// Awaiting completion
286	<
287	<	/**
288	<	* Sets status to indicate there is joiner, then waits for join,
289	<	* surrounded with pool notifications.
290	<	*
291	<	* @return status upon exit
292	<	*/
293	<	private int awaitDone(ForkJoinWorkerThread w,
294	<	boolean maintainParallelism) {
295	<	ForkJoinPool pool = (w == null) ? null : w.pool;
296	<	int s;
297	<	while ((s = status) >= 0) {
298	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
299	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
300	<	doAwaitDone();
301	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
302	<	adjustPoolCountsOnUnblock(pool);
303	<	break;
230	>	cancelIfTerminating();
231		}
232		}
306	–	return s;
233		}
234
235		/**
236	<	* Timed version of awaitDone
236	>	* Blocks a worker thread until completed or timed out.  Called
237	>	* only by pool.
238		*
239	<	* @return status upon exit
239	>	* @return status on exit
240		*/
241	<	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
315	<	ForkJoinPool pool = (w == null) ? null : w.pool;
241	>	final int internalAwaitDone(long millis) {
242		int s;
243	<	while ((s = status) >= 0) {
244	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
245	<	long startTime = System.nanoTime();
246	<	if (pool == null || !pool.preJoin(this, false))
247	<	doAwaitDone(startTime, nanos);
322	<	if ((s = status) >= 0) {
323	<	adjustPoolCountsOnCancelledWait(pool);
324	<	s = status;
243	>	if ((s = status) >= 0) {
244	>	try {
245	>	synchronized (this) {
246	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
247	>	wait(millis, 0);
248		}
249	<	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
250	<	adjustPoolCountsOnUnblock(pool);
328	<	break;
249	>	} catch (InterruptedException ie) {
250	>	cancelIfTerminating();
251		}
252	+	s = status;
253		}
254		return s;
255		}
256
257		/**
258	<	* Notifies pool that thread is unblocked. Called by signalled
336	<	* threads when woken by non-FJ threads (which is atypical).
258	>	* Blocks a non-worker-thread until completion.
259		*/
260	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
260	>	private void externalAwaitDone() {
261		int s;
262	<	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
263	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
264	<	pool.updateRunningCount(s);
265	<	}
266	<
267	<	/**
268	<	* Notifies pool to adjust counts on cancelled or timed out wait.
269	<	*/
270	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
271	<	if (pool != null) {
272	<	int s;
273	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
274	<	if (casStatus(s, s - 1)) {
353	<	pool.updateRunningCount(1);
262	>	while ((s = status) >= 0) {
263	>	synchronized (this) {
264	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
265	>	boolean interrupted = false;
266	>	while (status >= 0) {
267	>	try {
268	>	wait();
269	>	} catch (InterruptedException ie) {
270	>	interrupted = true;
271	>	}
272	>	}
273	>	if (interrupted)
274	>	Thread.currentThread().interrupt();
275		break;
276		}
277		}
#	Line 358 | Line 279 | public abstract class ForkJoinTask<V> im
279		}
280
281		/**
282	<	* Handles interruptions during waits.
283	<	*/
284	<	private void onInterruptedWait() {
364	<	ForkJoinWorkerThread w = getWorker();
365	<	if (w == null)
366	<	Thread.currentThread().interrupt(); // re-interrupt
367	<	else if (w.isTerminating())
368	<	cancelIgnoringExceptions();
369	<	// else if FJworker, ignore interrupt
370	<	}
371	<
372	<	// Recording and reporting exceptions
373	<
374	<	private void setDoneExceptionally(Throwable rex) {
375	<	exceptionMap.put(this, rex);
376	<	setCompletion(EXCEPTIONAL);
377	<	}
378	<
379	<	/**
380	<	* Throws the exception associated with status s.
381	<	*
382	<	* @throws the exception
383	<	*/
384	<	private void reportException(int s) {
385	<	if ((s &= COMPLETION_MASK) < NORMAL) {
386	<	if (s == CANCELLED)
387	<	throw new CancellationException();
388	<	else
389	<	rethrowException(exceptionMap.get(this));
390	<	}
391	<	}
392	<
393	<	/**
394	<	* Returns result or throws exception using j.u.c.Future conventions.
395	<	* Only call when {@code isDone} known to be true.
396	<	*/
397	<	private V reportFutureResult()
398	<	throws InterruptedException, ExecutionException {
399	<	if (Thread.interrupted())
400	<	throw new InterruptedException();
401	<	int s = status & COMPLETION_MASK;
402	<	if (s < NORMAL) {
403	<	Throwable ex;
404	<	if (s == CANCELLED)
405	<	throw new CancellationException();
406	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
407	<	throw new ExecutionException(ex);
408	<	}
409	<	return getRawResult();
410	<	}
411	<
412	<	/**
413	<	* Returns result or throws exception using j.u.c.Future conventions
414	<	* with timeouts.
415	<	*/
416	<	private V reportTimedFutureResult()
417	<	throws InterruptedException, ExecutionException, TimeoutException {
418	<	if (Thread.interrupted())
419	<	throw new InterruptedException();
420	<	Throwable ex;
421	<	int s = status & COMPLETION_MASK;
422	<	if (s == NORMAL)
423	<	return getRawResult();
424	<	else if (s == CANCELLED)
425	<	throw new CancellationException();
426	<	else if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
427	<	throw new ExecutionException(ex);
428	<	else
429	<	throw new TimeoutException();
430	<	}
431	<
432	<	// internal execution methods
433	<
434	<	/**
435	<	* Calls exec, recording completion, and rethrowing exception if
436	<	* encountered. Caller should normally check status before calling.
437	<	*
438	<	* @return true if completed normally
439	<	*/
440	<	private boolean tryExec() {
441	<	try { // try block must contain only call to exec
442	<	if (!exec())
443	<	return false;
444	<	} catch (Throwable rex) {
445	<	setDoneExceptionally(rex);
446	<	rethrowException(rex);
447	<	return false; // not reached
448	<	}
449	<	setNormalCompletion();
450	<	return true;
451	<	}
452	<
453	<	/**
454	<	* Main execution method used by worker threads. Invokes
455	<	* base computation unless already complete.
282	>	* Unless done, calls exec and records status if completed, but
283	>	* doesn't wait for completion otherwise. Primary execution method
284	>	* for ForkJoinWorkerThread.
285		*/
286		final void quietlyExec() {
458	–	if (status >= 0) {
459	–	try {
460	–	if (!exec())
461	–	return;
462	–	} catch (Throwable rex) {
463	–	setDoneExceptionally(rex);
464	–	return;
465	–	}
466	–	setNormalCompletion();
467	–	}
468	–	}
469	–
470	–	/**
471	–	* Calls exec(), recording but not rethrowing exception.
472	–	* Caller should normally check status before calling.
473	–	*
474	–	* @return true if completed normally
475	–	*/
476	–	private boolean tryQuietlyInvoke() {
287		try {
288	<	if (!exec())
289	<	return false;
288	>	if (status < 0 || !exec())
289	>	return;
290		} catch (Throwable rex) {
291	<	setDoneExceptionally(rex);
292	<	return false;
483	<	}
484	<	setNormalCompletion();
485	<	return true;
486	<	}
487	<
488	<	/**
489	<	* Cancels, ignoring any exceptions it throws.
490	<	*/
491	<	final void cancelIgnoringExceptions() {
492	<	try {
493	<	cancel(false);
494	<	} catch (Throwable ignore) {
291	>	setExceptionalCompletion(rex);
292	>	return;
293		}
294	<	}
497	<
498	<	/**
499	<	* Main implementation of helpJoin
500	<	*/
501	<	private int busyJoin(ForkJoinWorkerThread w) {
502	<	int s;
503	<	ForkJoinTask<?> t;
504	<	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
505	<	t.quietlyExec();
506	<	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
294	>	setCompletion(NORMAL); // must be outside try block
295		}
296
297		// public methods
#	Line 512 | Line 300 | public abstract class ForkJoinTask<V> im
300		* Arranges to asynchronously execute this task.  While it is not
301		* necessarily enforced, it is a usage error to fork a task more
302		* than once unless it has completed and been reinitialized.
303	+	* Subsequent modifications to the state of this task or any data
304	+	* it operates on are not necessarily consistently observable by
305	+	* any thread other than the one executing it unless preceded by a
306	+	* call to {@link #join} or related methods, or a call to {@link
307	+	* #isDone} returning {@code true}.
308		*
309		* <p>This method may be invoked only from within {@code
310		* ForkJoinTask} computations (as may be determined using method
#	Line 528 | Line 321 | public abstract class ForkJoinTask<V> im
321		}
322
323		/**
324	<	* Returns the result of the computation when it is ready.
324	>	* Returns the result of the computation when it {@link #isDone is done}.
325		* This method differs from {@link #get()} in that
326		* abnormal completion results in {@code RuntimeException} or
327		* {@code Error}, not {@code ExecutionException}.
#	Line 536 | Line 329 | public abstract class ForkJoinTask<V> im
329		* @return the computed result
330		*/
331		public final V join() {
332	<	ForkJoinWorkerThread w = getWorker();
333	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
334	<	reportException(awaitDone(w, true));
332	>	quietlyJoin();
333	>	Throwable ex;
334	>	if (status < NORMAL && (ex = getException()) != null)
335	>	UNSAFE.throwException(ex);
336		return getRawResult();
337		}
338
339		/**
340		* Commences performing this task, awaits its completion if
341	<	* necessary, and return its result, or throws an (unchecked)
342	<	* exception if the underlying computation did so.
341	>	* necessary, and returns its result, or throws an (unchecked)
342	>	* {@code RuntimeException} or {@code Error} if the underlying
343	>	* computation did so.
344		*
345		* @return the computed result
346		*/
347		public final V invoke() {
348	<	if (status >= 0 && tryExec())
349	<	return getRawResult();
350	<	else
351	<	return join();
348	>	quietlyInvoke();
349	>	Throwable ex;
350	>	if (status < NORMAL && (ex = getException()) != null)
351	>	UNSAFE.throwException(ex);
352	>	return getRawResult();
353		}
354
355		/**
356		* Forks the given tasks, returning when {@code isDone} holds for
357		* each task or an (unchecked) exception is encountered, in which
358	<	* case the exception is rethrown.  If more than one task
358	>	* case the exception is rethrown. If more than one task
359		* encounters an exception, then this method throws any one of
360	<	* these exceptions.  The individual status of each task may be
361	<	* checked using {@link #getException()} and related methods.
360	>	* these exceptions. If any task encounters an exception, the
361	>	* other may be cancelled. However, the execution status of
362	>	* individual tasks is not guaranteed upon exceptional return. The
363	>	* status of each task may be obtained using {@link
364	>	* #getException()} and related methods to check if they have been
365	>	* cancelled, completed normally or exceptionally, or left
366	>	* unprocessed.
367		*
368		* <p>This method may be invoked only from within {@code
369		* ForkJoinTask} computations (as may be determined using method
#	Line 583 | Line 384 | public abstract class ForkJoinTask<V> im
384		/**
385		* Forks the given tasks, returning when {@code isDone} holds for
386		* each task or an (unchecked) exception is encountered, in which
387	<	* case the exception is rethrown. If any task encounters an
388	<	* exception, others may be, but are not guaranteed to be,
389	<	* cancelled.  If more than one task encounters an exception, then
390	<	* this method throws any one of these exceptions.  The individual
391	<	* status of each task may be checked using {@link #getException()}
392	<	* and related methods.
387	>	* case the exception is rethrown. If more than one task
388	>	* encounters an exception, then this method throws any one of
389	>	* these exceptions. If any task encounters an exception, others
390	>	* may be cancelled. However, the execution status of individual
391	>	* tasks is not guaranteed upon exceptional return. The status of
392	>	* each task may be obtained using {@link #getException()} and
393	>	* related methods to check if they have been cancelled, completed
394	>	* normally or exceptionally, or left unprocessed.
395		*
396		* <p>This method may be invoked only from within {@code
397		* ForkJoinTask} computations (as may be determined using method
#	Line 612 | Line 415 | public abstract class ForkJoinTask<V> im
415		t.fork();
416		else {
417		t.quietlyInvoke();
418	<	if (ex == null)
418	>	if (ex == null && t.status < NORMAL)
419		ex = t.getException();
420		}
421		}
#	Line 623 | Line 426 | public abstract class ForkJoinTask<V> im
426		t.cancel(false);
427		else {
428		t.quietlyJoin();
429	<	if (ex == null)
429	>	if (ex == null && t.status < NORMAL)
430		ex = t.getException();
431		}
432		}
433		}
434		if (ex != null)
435	<	rethrowException(ex);
435	>	UNSAFE.throwException(ex);
436		}
437
438		/**
439		* Forks all tasks in the specified collection, returning when
440		* {@code isDone} holds for each task or an (unchecked) exception
441	<	* is encountered.  If any task encounters an exception, others
442	<	* may be, but are not guaranteed to be, cancelled.  If more than
443	<	* one task encounters an exception, then this method throws any
444	<	* one of these exceptions.  The individual status of each task
445	<	* may be checked using {@link #getException()} and related
446	<	* methods.  The behavior of this operation is undefined if the
447	<	* specified collection is modified while the operation is in
448	<	* progress.
441	>	* is encountered, in which case the exception is rethrown. If
442	>	* more than one task encounters an exception, then this method
443	>	* throws any one of these exceptions. If any task encounters an
444	>	* exception, others may be cancelled. However, the execution
445	>	* status of individual tasks is not guaranteed upon exceptional
446	>	* return. The status of each task may be obtained using {@link
447	>	* #getException()} and related methods to check if they have been
448	>	* cancelled, completed normally or exceptionally, or left
449	>	* unprocessed.
450		*
451		* <p>This method may be invoked only from within {@code
452		* ForkJoinTask} computations (as may be determined using method
#	Line 674 | Line 478 | public abstract class ForkJoinTask<V> im
478		t.fork();
479		else {
480		t.quietlyInvoke();
481	<	if (ex == null)
481	>	if (ex == null && t.status < NORMAL)
482		ex = t.getException();
483		}
484		}
#	Line 685 | Line 489 | public abstract class ForkJoinTask<V> im
489		t.cancel(false);
490		else {
491		t.quietlyJoin();
492	<	if (ex == null)
492	>	if (ex == null && t.status < NORMAL)
493		ex = t.getException();
494		}
495		}
496		}
497		if (ex != null)
498	<	rethrowException(ex);
498	>	UNSAFE.throwException(ex);
499		return tasks;
500		}
501
#	Line 721 | Line 525 | public abstract class ForkJoinTask<V> im
525		*/
526		public boolean cancel(boolean mayInterruptIfRunning) {
527		setCompletion(CANCELLED);
528	<	return (status & COMPLETION_MASK) == CANCELLED;
528	>	return status == CANCELLED;
529		}
530
531		/**
532	<	* Returns {@code true} if the computation performed by this task
533	<	* has completed (or has been cancelled).
534	<	*
535	<	* @return {@code true} if this computation has completed
532	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
533	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
534	>	* exceptions, but if it does anyway, we have no recourse during
535	>	* shutdown, so guard against this case.
536		*/
537	<	public final boolean isDone() {
538	<	return status < 0;
537	>	final void cancelIgnoringExceptions() {
538	>	try {
539	>	cancel(false);
540	>	} catch (Throwable ignore) {
541	>	}
542		}
543
544		/**
545	<	* Returns {@code true} if this task was cancelled.
546	<	*
740	<	* @return {@code true} if this task was cancelled
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	+
559	+	public final boolean isDone() {
560	+	return status < 0;
561	+	}
562	+
563		public final boolean isCancelled() {
564	<	return (status & COMPLETION_MASK) == CANCELLED;
564	>	return status == CANCELLED;
565		}
566
567		/**
#	Line 749 | Line 570 | public abstract class ForkJoinTask<V> im
570		* @return {@code true} if this task threw an exception or was cancelled
571		*/
572		public final boolean isCompletedAbnormally() {
573	<	return (status & COMPLETION_MASK) < NORMAL;
573	>	return status < NORMAL;
574		}
575
576		/**
#	Line 760 | Line 581 | public abstract class ForkJoinTask<V> im
581		* exception and was not cancelled
582		*/
583		public final boolean isCompletedNormally() {
584	<	return (status & COMPLETION_MASK) == NORMAL;
764	<	}
765	<
766	<	/**
767	<	* Returns {@code true} if this task threw an exception.
768	<	*
769	<	* @return {@code true} if this task threw an exception
770	<	*/
771	<	public final boolean isCompletedExceptionally() {
772	<	return (status & COMPLETION_MASK) == EXCEPTIONAL;
584	>	return status == NORMAL;
585		}
586
587		/**
#	Line 780 | Line 592 | public abstract class ForkJoinTask<V> im
592		* @return the exception, or {@code null} if none
593		*/
594		public final Throwable getException() {
595	<	int s = status & COMPLETION_MASK;
595	>	int s = status;
596		return ((s >= NORMAL)    ? null :
597		(s == CANCELLED) ? new CancellationException() :
598		exceptionMap.get(this));
#	Line 796 | Line 608 | public abstract class ForkJoinTask<V> im
608		* overridable, but overridden versions must invoke {@code super}
609		* implementation to maintain guarantees.
610		*
611	<	* @param ex the exception to throw. If this exception is
612	<	* not a RuntimeException or Error, the actual exception thrown
613	<	* will be a RuntimeException with cause ex.
611	>	* @param ex the exception to throw. If this exception is not a
612	>	* {@code RuntimeException} or {@code Error}, the actual exception
613	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
614		*/
615		public void completeExceptionally(Throwable ex) {
616	<	setDoneExceptionally((ex instanceof RuntimeException) ||
617	<	(ex instanceof Error) ? ex :
618	<	new RuntimeException(ex));
616	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
617	>	(ex instanceof Error) ? ex :
618	>	new RuntimeException(ex));
619		}
620
621		/**
622		* Completes this task, and if not already aborted or cancelled,
623	<	* returning a {@code null} result upon {@code join} and related
624	<	* operations. This method may be used to provide results for
625	<	* asynchronous tasks, or to provide alternative handling for
626	<	* tasks that would not otherwise complete normally. Its use in
627	<	* other situations is discouraged. This method is
628	<	* overridable, but overridden versions must invoke {@code super}
629	<	* implementation to maintain guarantees.
623	>	* returning the given value as the result of subsequent
624	>	* invocations of {@code join} and related operations. This method
625	>	* may be used to provide results for asynchronous tasks, or to
626	>	* provide alternative handling for tasks that would not otherwise
627	>	* complete normally. Its use in other situations is
628	>	* discouraged. This method is overridable, but overridden
629	>	* versions must invoke {@code super} implementation to maintain
630	>	* guarantees.
631		*
632		* @param value the result value for this task
633		*/
#	Line 822 | Line 635 | public abstract class ForkJoinTask<V> im
635		try {
636		setRawResult(value);
637		} catch (Throwable rex) {
638	<	setDoneExceptionally(rex);
638	>	setExceptionalCompletion(rex);
639		return;
640		}
641	<	setNormalCompletion();
829	<	}
830	<
831	<	public final V get() throws InterruptedException, ExecutionException {
832	<	ForkJoinWorkerThread w = getWorker();
833	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
834	<	awaitDone(w, true);
835	<	return reportFutureResult();
836	<	}
837	<
838	<	public final V get(long timeout, TimeUnit unit)
839	<	throws InterruptedException, ExecutionException, TimeoutException {
840	<	long nanos = unit.toNanos(timeout);
841	<	ForkJoinWorkerThread w = getWorker();
842	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
843	<	awaitDone(w, nanos);
844	<	return reportTimedFutureResult();
641	>	setCompletion(NORMAL);
642		}
643
644		/**
645	<	* Possibly executes other tasks until this task is ready, then
646	<	* returns the result of the computation.  This method may be more
850	<	* efficient than {@code join}, but is only applicable when
851	<	* there are no potential dependencies between continuation of the
852	<	* current task and that of any other task that might be executed
853	<	* while helping. (This usually holds for pure divide-and-conquer
854	<	* tasks).
855	<	*
856	<	* <p>This method may be invoked only from within {@code
857	<	* ForkJoinTask} computations (as may be determined using method
858	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
859	<	* result in exceptions or errors, possibly including {@code
860	<	* ClassCastException}.
645	>	* Waits if necessary for the computation to complete, and then
646	>	* retrieves its result.
647		*
648		* @return the computed result
649	+	* @throws CancellationException if the computation was cancelled
650	+	* @throws ExecutionException if the computation threw an
651	+	* exception
652	+	* @throws InterruptedException if the current thread is not a
653	+	* member of a ForkJoinPool and was interrupted while waiting
654		*/
655	<	public final V helpJoin() {
656	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
657	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
658	<	reportException(busyJoin(w));
655	>	public final V get() throws InterruptedException, ExecutionException {
656	>	int s;
657	>	if (Thread.currentThread() instanceof ForkJoinWorkerThread) {
658	>	quietlyJoin();
659	>	s = status;
660	>	}
661	>	else {
662	>	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	>	}
679		return getRawResult();
680		}
681
682		/**
683	<	* Possibly executes other tasks until this task is ready.  This
684	<	* method may be useful when processing collections of tasks when
874	<	* some have been cancelled or otherwise known to have aborted.
683	>	* Waits if necessary for at most the given time for the computation
684	>	* to complete, and then retrieves its result, if available.
685		*
686	<	* <p>This method may be invoked only from within {@code
687	<	* ForkJoinTask} computations (as may be determined using method
688	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
689	<	* result in exceptions or errors, possibly including {@code
690	<	* ClassCastException}.
686	>	* @param timeout the maximum time to wait
687	>	* @param unit the time unit of the timeout argument
688	>	* @return the computed result
689	>	* @throws CancellationException if the computation was cancelled
690	>	* @throws ExecutionException if the computation threw an
691	>	* exception
692	>	* @throws InterruptedException if the current thread is not a
693	>	* member of a ForkJoinPool and was interrupted while waiting
694	>	* @throws TimeoutException if the wait timed out
695		*/
696	<	public final void quietlyHelpJoin() {
697	<	if (status >= 0) {
698	<	ForkJoinWorkerThread w =
699	<	(ForkJoinWorkerThread) Thread.currentThread();
700	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
701	<	busyJoin(w);
696	>	public final V get(long timeout, TimeUnit unit)
697	>	throws InterruptedException, ExecutionException, TimeoutException {
698	>	Thread t = Thread.currentThread();
699	>	ForkJoinPool pool;
700	>	if (t instanceof ForkJoinWorkerThread) {
701	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
702	>	if (status >= 0 && w.unpushTask(this))
703	>	quietlyExec();
704	>	pool = w.pool;
705	>	}
706	>	else
707	>	pool = null;
708	>	/*
709	>	* 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	>	}
749	>	}
750	>	}
751	>	break;
752	>	}
753		}
754	+	if (pool != null && dec)
755	+	pool.incrementRunningCount();
756	+	if (interrupted)
757	+	throw new InterruptedException();
758	+	int es = status;
759	+	if (es != NORMAL) {
760	+	Throwable ex;
761	+	if (es == CANCELLED)
762	+	throw new CancellationException();
763	+	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
764	+	throw new ExecutionException(ex);
765	+	throw new TimeoutException();
766	+	}
767	+	return getRawResult();
768		}
769
770		/**
771	<	* Joins this task, without returning its result or throwing an
771	>	* Joins this task, without returning its result or throwing its
772		* exception. This method may be useful when processing
773		* collections of tasks when some have been cancelled or otherwise
774		* known to have aborted.
775		*/
776		public final void quietlyJoin() {
777	<	if (status >= 0) {
778	<	ForkJoinWorkerThread w = getWorker();
779	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
780	<	awaitDone(w, true);
777	>	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();
799		}
800
801		/**
802		* Commences performing this task and awaits its completion if
803	<	* necessary, without returning its result or throwing an
804	<	* exception. This method may be useful when processing
909	<	* collections of tasks when some have been cancelled or otherwise
910	<	* known to have aborted.
803	>	* necessary, without returning its result or throwing its
804	>	* exception.
805		*/
806		public final void quietlyInvoke() {
807	<	if (status >= 0 && !tryQuietlyInvoke())
808	<	quietlyJoin();
807	>	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	>	}
820		}
821
822		/**
#	Line 943 | Line 848 | public abstract class ForkJoinTask<V> im
848		* pre-constructed trees of subtasks in loops.
849		*/
850		public void reinitialize() {
851	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
851	>	if (status == EXCEPTIONAL)
852		exceptionMap.remove(this);
853		status = 0;
854		}
#	Line 1233 | Line 1138 | public abstract class ForkJoinTask<V> im
1138		private static final long serialVersionUID = -7721805057305804111L;
1139
1140		/**
1141	<	* Save the state to a stream.
1141	>	* Saves the state to a stream (that is, serializes it).
1142		*
1143		* @serialData the current run status and the exception thrown
1144		* during execution, or {@code null} if none
#	Line 1246 | Line 1151 | public abstract class ForkJoinTask<V> im
1151		}
1152
1153		/**
1154	<	* Reconstitute the instance from a stream.
1154	>	* Reconstitutes the instance from a stream (that is, deserializes it).
1155		*
1156		* @param s the stream
1157		*/
1158		private void readObject(java.io.ObjectInputStream s)
1159		throws java.io.IOException, ClassNotFoundException {
1160		s.defaultReadObject();
1256	–	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1257	–	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1161		Object ex = s.readObject();
1162		if (ex != null)
1163	<	setDoneExceptionally((Throwable) ex);
1163	>	setExceptionalCompletion((Throwable) ex);
1164		}
1165
1166		// Unsafe mechanics

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