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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.35 by dl, Tue Aug 4 12:41:27 2009 UTC vs.
Revision 1.62 by dl, Fri Sep 17 14:24:56 2010 UTC

#	Line 28 | Line 28 | import java.util.WeakHashMap;
28		* start other subtasks.  As indicated by the name of this class,
29		* many programs using {@code ForkJoinTask} employ only methods
30		* {@link #fork} and {@link #join}, or derivatives such as {@link
31	<	* #invokeAll}.  However, this class also provides a number of other
32	<	* methods that can come into play in advanced usages, as well as
33	<	* extension mechanics that allow support of new forms of fork/join
34	<	* processing.
31	>	* #invokeAll(ForkJoinTask...) invokeAll}.  However, this class also
32	>	* provides a number of other methods that can come into play in
33	>	* advanced usages, as well as extension mechanics that allow
34	>	* support of new forms of fork/join processing.
35		*
36		* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
37		* The efficiency of {@code ForkJoinTask}s stems from a set of
#	Line 56 | Line 56 | import java.util.WeakHashMap;
56		* exceptions such as {@code IOExceptions} to be thrown. However,
57		* computations may still encounter unchecked exceptions, that are
58		* rethrown to callers attempting to join them. These exceptions may
59	<	* additionally include RejectedExecutionExceptions stemming from
60	<	* internal resource exhaustion such as failure to allocate internal
61	<	* task queues.
59	>	* additionally include {@link RejectedExecutionException} stemming
60	>	* from internal resource exhaustion, such as failure to allocate
61	>	* internal task queues.
62		*
63		* <p>The primary method for awaiting completion and extracting
64		* results of a task is {@link #join}, but there are several variants:
65		* The {@link Future#get} methods support interruptible and/or timed
66		* waits for completion and report results using {@code Future}
67	<	* 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
67	>	* conventions. Method {@link #invoke} is semantically
68		* equivalent to {@code fork(); join()} but always attempts to begin
69		* execution in the current thread. The "<em>quiet</em>" forms of
70		* these methods do not extract results or report exceptions. These
#	Line 80 | Line 77 | import java.util.WeakHashMap;
77		* <p>The execution status of tasks may be queried at several levels
78		* of detail: {@link #isDone} is true if a task completed in any way
79		* (including the case where a task was cancelled without executing);
83	–	* {@link #isCancelled} is true if completion was due to cancellation;
80		* {@link #isCompletedNormally} is true if a task completed without
81	<	* cancellation or encountering an exception; {@link
82	<	* #isCompletedExceptionally} is true if if the task encountered an
83	<	* exception (in which case {@link #getException} returns the
84	<	* exception); {@link #isCancelled} is true if the task was cancelled
85	<	* (in which case {@link #getException} returns a {@link
86	<	* java.util.concurrent.CancellationException}; and {@link
87	<	* #isCompletedAbnormally} is true if a task was either cancelled or
92	<	* encountered an exception.
81	>	* cancellation or encountering an exception; {@link #isCancelled} is
82	>	* true if the task was cancelled (in which case {@link #getException}
83	>	* returns a {@link java.util.concurrent.CancellationException}); and
84	>	* {@link #isCompletedAbnormally} is true if a task was either
85	>	* cancelled or encountered an exception, in which case {@link
86	>	* #getException} will return either the encountered exception or
87	>	* {@link java.util.concurrent.CancellationException}.
88		*
89		* <p>The ForkJoinTask class is not usually directly subclassed.
90		* Instead, you subclass one of the abstract classes that support a
#	Line 105 | Line 100 | import java.util.WeakHashMap;
100		* ForkJoinTasks (as may be determined using method {@link
101		* #inForkJoinPool}).  Attempts to invoke them in other contexts
102		* result in exceptions or errors, possibly including
103	<	* ClassCastException.
103	>	* {@code ClassCastException}.
104		*
105		* <p>Most base support methods are {@code final}, to prevent
106		* overriding of implementations that are intrinsically tied to the
#	Line 125 | Line 120 | import java.util.WeakHashMap;
120		* improve throughput. If too small, then memory and internal task
121		* maintenance overhead may overwhelm processing.
122		*
123	<	* <p>This class provides {@code adapt} methods for {@link
124	<	* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
125	<	* may be of use when mixing execution of ForkJoinTasks with other
126	<	* kinds of tasks. When all tasks are of this form, consider using a
132	<	* pool in {@link ForkJoinPool#setAsyncMode async mode}.
123	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
124	>	* and {@link Callable}, that may be of use when mixing execution of
125	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
126	>	* of this form, consider using a pool constructed in <em>asyncMode</em>.
127		*
128		* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
129		* used in extensions such as remote execution frameworks. It is
#	Line 141 | Line 135 | import java.util.WeakHashMap;
135		*/
136		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
137
138	<	/**
139	<	* Run control status bits packed into a single int to minimize
140	<	* footprint and to ensure atomicity (via CAS).  Status is
141	<	* initially zero, and takes on nonnegative values until
142	<	* completed, upon which status holds COMPLETED. CANCELLED, or
143	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
144	<	* blocking waits by other threads have SIGNAL_MASK bits set --
145	<	* bit 15 for external (nonFJ) waits, and the rest a count of
146	<	* waiting FJ threads.  (This representation relies on
147	<	* ForkJoinPool max thread limits). Completion of a stolen task
148	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
149	<	* though suboptimal for some purposes, we use basic builtin
150	<	* wait/notify to take advantage of "monitor inflation" in JVMs
151	<	* that we would otherwise need to emulate to avoid adding further
152	<	* per-task bookkeeping overhead. Note that bits 16-28 are
153	<	* currently unused. Also value 0x80000000 is available as spare
154	<	* completion value.
138	>	/*
139	>	* See the internal documentation of class ForkJoinPool for a
140	>	* general implementation overview.  ForkJoinTasks are mainly
141	>	* responsible for maintaining their "status" field amidst relays
142	>	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
143	>	* methods of this class are more-or-less layered into (1) basic
144	>	* status maintenance (2) execution and awaiting completion (3)
145	>	* user-level methods that additionally report results. This is
146	>	* sometimes hard to see because this file orders exported methods
147	>	* in a way that flows well in javadocs. In particular, most
148	>	* join mechanics are in method quietlyJoin, below.
149	>	*/
150	>
151	>	/*
152	>	* The status field holds run control status bits packed into a
153	>	* single int to minimize footprint and to ensure atomicity (via
154	>	* CAS).  Status is initially zero, and takes on nonnegative
155	>	* values until completed, upon which status holds value
156	>	* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
157	>	* waits by other threads have the SIGNAL bit set.  Completion of
158	>	* a stolen task with SIGNAL set awakens any waiters via
159	>	* notifyAll. Even though suboptimal for some purposes, we use
160	>	* basic builtin wait/notify to take advantage of "monitor
161	>	* inflation" in JVMs that we would otherwise need to emulate to
162	>	* avoid adding further per-task bookkeeping overhead.  We want
163	>	* these monitors to be "fat", i.e., not use biasing or thin-lock
164	>	* techniques, so use some odd coding idioms that tend to avoid
165	>	* them.
166		*/
167	+
168	+	/** The run status of this task */
169		volatile int status; // accessed directly by pool and workers
170
171	<	static final int COMPLETION_MASK      = 0xe0000000;
172	<	static final int NORMAL               = 0xe0000000; // == mask
173	<	static final int CANCELLED            = 0xc0000000;
174	<	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
171	>	private static final int NORMAL      = -1;
172	>	private static final int CANCELLED   = -2;
173	>	private static final int EXCEPTIONAL = -3;
174	>	private static final int SIGNAL      =  1;
175
176		/**
177		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 181 | Line 185 | public abstract class ForkJoinTask<V> im
185		Collections.synchronizedMap
186		(new WeakHashMap<ForkJoinTask<?>, Throwable>());
187
188	<	// 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	<	}
198	<
199	<	/**
200	<	* Workaround for not being able to rethrow unchecked exceptions.
201	<	*/
202	<	static void rethrowException(Throwable ex) {
203	<	if (ex != null)
204	<	UNSAFE.throwException(ex);
205	<	}
206	<
207	<	// Setting completion status
188	>	// Maintaining completion status
189
190		/**
191	<	* Marks completion and wakes up threads waiting to join this task.
191	>	* Marks completion and wakes up threads waiting to join this task,
192	>	* also clearing signal request bits.
193		*
194		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
195		*/
196	<	final void setCompletion(int completion) {
197	<	ForkJoinPool pool = getPool();
198	<	if (pool != null) {
199	<	int s; // Clear signal bits while setting completion status
200	<	do {} while ((s = status) >= 0 && !casStatus(s, completion));
201	<
202	<	if ((s & SIGNAL_MASK) != 0) {
221	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
222	<	pool.updateRunningCount(s);
223	<	synchronized (this) { notifyAll(); }
196	>	private void setCompletion(int completion) {
197	>	int s;
198	>	while ((s = status) >= 0) {
199	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
200	>	if (s != 0)
201	>	synchronized (this) { notifyAll(); }
202	>	break;
203		}
204		}
226	–	else
227	–	externallySetCompletion(completion);
205		}
206
207		/**
208	<	* Version of setCompletion for non-FJ threads.  Leaves signal
209	<	* bits for unblocked threads to adjust, and always notifies.
210	<	*/
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.
208	>	* Records exception and sets exceptional completion.
209	>	*
210	>	* @return status on exit
211		*/
212	<	private void doAwaitDone() {
213	<	// Minimize lock bias and in/de-flation effects by maximizing
214	<	// 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	<	}
212	>	private void setExceptionalCompletion(Throwable rex) {
213	>	exceptionMap.put(this, rex);
214	>	setCompletion(EXCEPTIONAL);
215		}
216
217		/**
218	<	* Performs the actual timed monitor wait for awaitDone.
218	>	* Blocks a worker thread until completion. Called only by
219	>	* pool. Currently unused -- pool-based waits use timeout
220	>	* version below.
221		*/
222	<	private void doAwaitDone(long startTime, long nanos) {
223	<	synchronized (this) {
222	>	final void internalAwaitDone() {
223	>	int s;         // the odd construction reduces lock bias effects
224	>	while ((s = status) >= 0) {
225		try {
226	<	while (status >= 0) {
227	<	long nt = nanos - (System.nanoTime() - startTime);
228	<	if (nt <= 0)
276	<	break;
277	<	wait(nt / 1000000, (int) (nt % 1000000));
226	>	synchronized (this) {
227	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
228	>	wait();
229		}
230		} catch (InterruptedException ie) {
231	<	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;
231	>	cancelIfTerminating();
232		}
233		}
306	–	return s;
234		}
235
236		/**
237	<	* Timed version of awaitDone
237	>	* Blocks a worker thread until completed or timed out.  Called
238	>	* only by pool.
239		*
240	<	* @return status upon exit
240	>	* @return status on exit
241		*/
242	<	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
315	<	ForkJoinPool pool = (w == null) ? null : w.pool;
242	>	final int internalAwaitDone(long millis) {
243		int s;
244	<	while ((s = status) >= 0) {
245	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
246	<	long startTime = System.nanoTime();
247	<	if (pool == null || !pool.preJoin(this, false))
248	<	doAwaitDone(startTime, nanos);
322	<	if ((s = status) >= 0) {
323	<	adjustPoolCountsOnCancelledWait(pool);
324	<	s = status;
244	>	if ((s = status) >= 0) {
245	>	try {
246	>	synchronized (this) {
247	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
248	>	wait(millis, 0);
249		}
250	<	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
251	<	adjustPoolCountsOnUnblock(pool);
328	<	break;
250	>	} catch (InterruptedException ie) {
251	>	cancelIfTerminating();
252		}
253	+	s = status;
254		}
255		return s;
256		}
257
258		/**
259	<	* Notifies pool that thread is unblocked. Called by signalled
336	<	* threads when woken by non-FJ threads (which is atypical).
259	>	* Blocks a non-worker-thread until completion.
260		*/
261	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
261	>	private void externalAwaitDone() {
262		int s;
263	<	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
264	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
265	<	pool.updateRunningCount(s);
266	<	}
267	<
268	<	/**
269	<	* Notifies pool to adjust counts on cancelled or timed out wait.
270	<	*/
271	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
272	<	if (pool != null) {
273	<	int s;
274	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
275	<	if (casStatus(s, s - 1)) {
353	<	pool.updateRunningCount(1);
263	>	while ((s = status) >= 0) {
264	>	synchronized (this) {
265	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
266	>	boolean interrupted = false;
267	>	while (status >= 0) {
268	>	try {
269	>	wait();
270	>	} catch (InterruptedException ie) {
271	>	interrupted = true;
272	>	}
273	>	}
274	>	if (interrupted)
275	>	Thread.currentThread().interrupt();
276		break;
277		}
278		}
#	Line 358 | Line 280 | public abstract class ForkJoinTask<V> im
280		}
281
282		/**
283	<	* Handles interruptions during waits.
284	<	*/
285	<	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 ExecutionException, InterruptedException {
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	<	if (s == CANCELLED)
425	<	throw new CancellationException();
426	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
427	<	throw new ExecutionException(ex);
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.
283	>	* Unless done, calls exec and records status if completed, but
284	>	* doesn't wait for completion otherwise. Primary execution method
285	>	* for ForkJoinWorkerThread.
286		*/
287		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() {
288		try {
289	<	if (!exec())
290	<	return false;
289	>	if (status < 0 || !exec())
290	>	return;
291		} catch (Throwable rex) {
292	<	setDoneExceptionally(rex);
293	<	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) {
292	>	setExceptionalCompletion(rex);
293	>	return;
294		}
295	<	}
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
295	>	setCompletion(NORMAL); // must be outside try block
296		}
297
298		// public methods
#	Line 511 | Line 301 | public abstract class ForkJoinTask<V> im
301		* Arranges to asynchronously execute this task.  While it is not
302		* necessarily enforced, it is a usage error to fork a task more
303		* than once unless it has completed and been reinitialized.
304	+	* Subsequent modifications to the state of this task or any data
305	+	* it operates on are not necessarily consistently observable by
306	+	* any thread other than the one executing it unless preceded by a
307	+	* call to {@link #join} or related methods, or a call to {@link
308	+	* #isDone} returning {@code true}.
309		*
310		* <p>This method may be invoked only from within {@code
311		* ForkJoinTask} computations (as may be determined using method
#	Line 527 | Line 322 | public abstract class ForkJoinTask<V> im
322		}
323
324		/**
325	<	* Returns the result of the computation when it is ready.
325	>	* Returns the result of the computation when it {@link #isDone is done}.
326		* This method differs from {@link #get()} in that
327		* abnormal completion results in {@code RuntimeException} or
328		* {@code Error}, not {@code ExecutionException}.
#	Line 535 | Line 330 | public abstract class ForkJoinTask<V> im
330		* @return the computed result
331		*/
332		public final V join() {
333	<	ForkJoinWorkerThread w = getWorker();
334	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
335	<	reportException(awaitDone(w, true));
333	>	quietlyJoin();
334	>	Throwable ex;
335	>	if (status < NORMAL && (ex = getException()) != null)
336	>	UNSAFE.throwException(ex);
337		return getRawResult();
338		}
339
340		/**
341		* Commences performing this task, awaits its completion if
342	<	* necessary, and return its result, or throws an (unchecked)
343	<	* exception if the underlying computation did so.
342	>	* necessary, and returns its result, or throws an (unchecked)
343	>	* {@code RuntimeException} or {@code Error} if the underlying
344	>	* computation did so.
345		*
346		* @return the computed result
347		*/
348		public final V invoke() {
349	<	if (status >= 0 && tryExec())
350	<	return getRawResult();
351	<	else
352	<	return join();
349	>	quietlyInvoke();
350	>	Throwable ex;
351	>	if (status < NORMAL && (ex = getException()) != null)
352	>	UNSAFE.throwException(ex);
353	>	return getRawResult();
354		}
355
356		/**
357		* Forks the given tasks, returning when {@code isDone} holds for
358		* each task or an (unchecked) exception is encountered, in which
359	<	* case the exception is rethrown.  If more than one task
359	>	* case the exception is rethrown. If more than one task
360		* encounters an exception, then this method throws any one of
361	<	* these exceptions.  The individual status of each task may be
362	<	* checked using {@link #getException()} and related methods.
361	>	* these exceptions. If any task encounters an exception, the
362	>	* other may be cancelled. However, the execution status of
363	>	* individual tasks is not guaranteed upon exceptional return. The
364	>	* status of each task may be obtained using {@link
365	>	* #getException()} and related methods to check if they have been
366	>	* cancelled, completed normally or exceptionally, or left
367	>	* unprocessed.
368		*
369		* <p>This method may be invoked only from within {@code
370		* ForkJoinTask} computations (as may be determined using method
#	Line 582 | Line 385 | public abstract class ForkJoinTask<V> im
385		/**
386		* Forks the given tasks, returning when {@code isDone} holds for
387		* each task or an (unchecked) exception is encountered, in which
388	<	* case the exception is rethrown. If any task encounters an
389	<	* exception, others may be, but are not guaranteed to be,
390	<	* cancelled.  If more than one task encounters an exception, then
391	<	* this method throws any one of these exceptions.  The individual
392	<	* status of each task may be checked using {@link #getException()}
393	<	* and related methods.
388	>	* case the exception is rethrown. If more than one task
389	>	* encounters an exception, then this method throws any one of
390	>	* these exceptions. If any task encounters an exception, others
391	>	* may be cancelled. However, the execution status of individual
392	>	* tasks is not guaranteed upon exceptional return. The status of
393	>	* each task may be obtained using {@link #getException()} and
394	>	* related methods to check if they have been cancelled, completed
395	>	* normally or exceptionally, or left unprocessed.
396		*
397		* <p>This method may be invoked only from within {@code
398		* ForkJoinTask} computations (as may be determined using method
#	Line 611 | Line 416 | public abstract class ForkJoinTask<V> im
416		t.fork();
417		else {
418		t.quietlyInvoke();
419	<	if (ex == null)
419	>	if (ex == null && t.status < NORMAL)
420		ex = t.getException();
421		}
422		}
#	Line 622 | Line 427 | public abstract class ForkJoinTask<V> im
427		t.cancel(false);
428		else {
429		t.quietlyJoin();
430	<	if (ex == null)
430	>	if (ex == null && t.status < NORMAL)
431		ex = t.getException();
432		}
433		}
434		}
435		if (ex != null)
436	<	rethrowException(ex);
436	>	UNSAFE.throwException(ex);
437		}
438
439		/**
440		* Forks all tasks in the specified collection, returning when
441		* {@code isDone} holds for each task or an (unchecked) exception
442	<	* is encountered.  If any task encounters an exception, others
443	<	* may be, but are not guaranteed to be, cancelled.  If more than
444	<	* one task encounters an exception, then this method throws any
445	<	* one of these exceptions.  The individual status of each task
446	<	* may be checked using {@link #getException()} and related
447	<	* methods.  The behavior of this operation is undefined if the
448	<	* specified collection is modified while the operation is in
449	<	* progress.
442	>	* is encountered, in which case the exception is rethrown. If
443	>	* more than one task encounters an exception, then this method
444	>	* throws any one of these exceptions. If any task encounters an
445	>	* exception, others may be cancelled. However, the execution
446	>	* status of individual tasks is not guaranteed upon exceptional
447	>	* return. The status of each task may be obtained using {@link
448	>	* #getException()} and related methods to check if they have been
449	>	* cancelled, completed normally or exceptionally, or left
450	>	* unprocessed.
451		*
452		* <p>This method may be invoked only from within {@code
453		* ForkJoinTask} computations (as may be determined using method
#	Line 673 | Line 479 | public abstract class ForkJoinTask<V> im
479		t.fork();
480		else {
481		t.quietlyInvoke();
482	<	if (ex == null)
482	>	if (ex == null && t.status < NORMAL)
483		ex = t.getException();
484		}
485		}
#	Line 684 | Line 490 | public abstract class ForkJoinTask<V> im
490		t.cancel(false);
491		else {
492		t.quietlyJoin();
493	<	if (ex == null)
493	>	if (ex == null && t.status < NORMAL)
494		ex = t.getException();
495		}
496		}
497		}
498		if (ex != null)
499	<	rethrowException(ex);
499	>	UNSAFE.throwException(ex);
500		return tasks;
501		}
502
#	Line 720 | Line 526 | public abstract class ForkJoinTask<V> im
526		*/
527		public boolean cancel(boolean mayInterruptIfRunning) {
528		setCompletion(CANCELLED);
529	<	return (status & COMPLETION_MASK) == CANCELLED;
529	>	return status == CANCELLED;
530		}
531
532		/**
533	<	* Returns {@code true} if the computation performed by this task
534	<	* has completed (or has been cancelled).
535	<	*
536	<	* @return {@code true} if this computation has completed
533	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
534	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
535	>	* exceptions, but if it does anyway, we have no recourse during
536	>	* shutdown, so guard against this case.
537		*/
538	<	public final boolean isDone() {
539	<	return status < 0;
538	>	final void cancelIgnoringExceptions() {
539	>	try {
540	>	cancel(false);
541	>	} catch (Throwable ignore) {
542	>	}
543		}
544
545		/**
546	<	* Returns {@code true} if this task was cancelled.
547	<	*
739	<	* @return {@code true} if this task was cancelled
546	>	* Cancels if current thread is a terminating worker thread,
547	>	* ignoring any exceptions thrown by cancel.
548		*/
549	+	final void cancelIfTerminating() {
550	+	Thread t = Thread.currentThread();
551	+	if ((t instanceof ForkJoinWorkerThread) &&
552	+	((ForkJoinWorkerThread) t).isTerminating()) {
553	+	try {
554	+	cancel(false);
555	+	} catch (Throwable ignore) {
556	+	}
557	+	}
558	+	}
559	+
560	+	public final boolean isDone() {
561	+	return status < 0;
562	+	}
563	+
564		public final boolean isCancelled() {
565	<	return (status & COMPLETION_MASK) == CANCELLED;
565	>	return status == CANCELLED;
566		}
567
568		/**
#	Line 748 | Line 571 | public abstract class ForkJoinTask<V> im
571		* @return {@code true} if this task threw an exception or was cancelled
572		*/
573		public final boolean isCompletedAbnormally() {
574	<	return (status & COMPLETION_MASK) < NORMAL;
574	>	return status < NORMAL;
575		}
576
577		/**
#	Line 759 | Line 582 | public abstract class ForkJoinTask<V> im
582		* exception and was not cancelled
583		*/
584		public final boolean isCompletedNormally() {
585	<	return (status & COMPLETION_MASK) == NORMAL;
763	<	}
764	<
765	<	/**
766	<	* Returns {@code true} if this task threw an exception.
767	<	*
768	<	* @return {@code true} if this task threw an exception
769	<	*/
770	<	public final boolean isCompletedExceptionally() {
771	<	return (status & COMPLETION_MASK) == EXCEPTIONAL;
585	>	return status == NORMAL;
586		}
587
588		/**
#	Line 779 | Line 593 | public abstract class ForkJoinTask<V> im
593		* @return the exception, or {@code null} if none
594		*/
595		public final Throwable getException() {
596	<	int s = status & COMPLETION_MASK;
597	<	if (s >= NORMAL)
598	<	return null;
599	<	if (s == CANCELLED)
786	<	return new CancellationException();
787	<	return exceptionMap.get(this);
596	>	int s = status;
597	>	return ((s >= NORMAL)    ? null :
598	>	(s == CANCELLED) ? new CancellationException() :
599	>	exceptionMap.get(this));
600		}
601
602		/**
#	Line 797 | Line 609 | public abstract class ForkJoinTask<V> im
609		* overridable, but overridden versions must invoke {@code super}
610		* implementation to maintain guarantees.
611		*
612	<	* @param ex the exception to throw. If this exception is
613	<	* not a RuntimeException or Error, the actual exception thrown
614	<	* will be a RuntimeException with cause ex.
612	>	* @param ex the exception to throw. If this exception is not a
613	>	* {@code RuntimeException} or {@code Error}, the actual exception
614	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
615		*/
616		public void completeExceptionally(Throwable ex) {
617	<	setDoneExceptionally((ex instanceof RuntimeException) ||
618	<	(ex instanceof Error) ? ex :
619	<	new RuntimeException(ex));
617	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
618	>	(ex instanceof Error) ? ex :
619	>	new RuntimeException(ex));
620		}
621
622		/**
623		* Completes this task, and if not already aborted or cancelled,
624	<	* returning a {@code null} result upon {@code join} and related
625	<	* operations. This method may be used to provide results for
626	<	* asynchronous tasks, or to provide alternative handling for
627	<	* tasks that would not otherwise complete normally. Its use in
628	<	* other situations is discouraged. This method is
629	<	* overridable, but overridden versions must invoke {@code super}
630	<	* implementation to maintain guarantees.
624	>	* returning the given value as the result of subsequent
625	>	* invocations of {@code join} and related operations. This method
626	>	* may be used to provide results for asynchronous tasks, or to
627	>	* provide alternative handling for tasks that would not otherwise
628	>	* complete normally. Its use in other situations is
629	>	* discouraged. This method is overridable, but overridden
630	>	* versions must invoke {@code super} implementation to maintain
631	>	* guarantees.
632		*
633		* @param value the result value for this task
634		*/
#	Line 823 | Line 636 | public abstract class ForkJoinTask<V> im
636		try {
637		setRawResult(value);
638		} catch (Throwable rex) {
639	<	setDoneExceptionally(rex);
639	>	setExceptionalCompletion(rex);
640		return;
641		}
642	<	setNormalCompletion();
830	<	}
831	<
832	<	public final V get() throws InterruptedException, ExecutionException {
833	<	ForkJoinWorkerThread w = getWorker();
834	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
835	<	awaitDone(w, true);
836	<	return reportFutureResult();
837	<	}
838	<
839	<	public final V get(long timeout, TimeUnit unit)
840	<	throws InterruptedException, ExecutionException, TimeoutException {
841	<	long nanos = unit.toNanos(timeout);
842	<	ForkJoinWorkerThread w = getWorker();
843	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
844	<	awaitDone(w, nanos);
845	<	return reportTimedFutureResult();
642	>	setCompletion(NORMAL);
643		}
644
645		/**
646	<	* Possibly executes other tasks until this task is ready, then
850	<	* returns the result of the computation.  This method may be more
851	<	* efficient than {@code join}, but is only applicable when
852	<	* there are no potential dependencies between continuation of the
853	<	* current task and that of any other task that might be executed
854	<	* while helping. (This usually holds for pure divide-and-conquer
855	<	* tasks).
856	<	*
857	<	* <p>This method may be invoked only from within {@code
858	<	* ForkJoinTask} computations (as may be determined using method
859	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
860	<	* result in exceptions or errors, possibly including {@code
861	<	* ClassCastException}.
862	<	*
863	<	* @return the computed result
646	>	* @throws CancellationException {@inheritDoc}
647		*/
648	<	public final V helpJoin() {
649	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
650	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
651	<	reportException(busyJoin(w));
648	>	public final V get() throws InterruptedException, ExecutionException {
649	>	int s;
650	>	if (Thread.currentThread() instanceof ForkJoinWorkerThread) {
651	>	quietlyJoin();
652	>	s = status;
653	>	}
654	>	else {
655	>	while ((s = status) >= 0) {
656	>	synchronized (this) { // interruptible form of awaitDone
657	>	if (UNSAFE.compareAndSwapInt(this, statusOffset,
658	>	s, SIGNAL)) {
659	>	while (status >= 0)
660	>	wait();
661	>	}
662	>	}
663	>	}
664	>	}
665	>	if (s < NORMAL) {
666	>	Throwable ex;
667	>	if (s == CANCELLED)
668	>	throw new CancellationException();
669	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
670	>	throw new ExecutionException(ex);
671	>	}
672		return getRawResult();
673		}
674
675		/**
676	<	* Possibly executes other tasks until this task is ready.  This
874	<	* method may be useful when processing collections of tasks when
875	<	* some have been cancelled or otherwise known to have aborted.
876	<	*
877	<	* <p>This method may be invoked only from within {@code
878	<	* ForkJoinTask} computations (as may be determined using method
879	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
880	<	* result in exceptions or errors, possibly including {@code
881	<	* ClassCastException}.
676	>	* @throws CancellationException {@inheritDoc}
677		*/
678	<	public final void quietlyHelpJoin() {
679	<	if (status >= 0) {
680	<	ForkJoinWorkerThread w =
681	<	(ForkJoinWorkerThread) Thread.currentThread();
682	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
683	<	busyJoin(w);
678	>	public final V get(long timeout, TimeUnit unit)
679	>	throws InterruptedException, ExecutionException, TimeoutException {
680	>	Thread t = Thread.currentThread();
681	>	ForkJoinPool pool;
682	>	if (t instanceof ForkJoinWorkerThread) {
683	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
684	>	if (status >= 0 && w.unpushTask(this))
685	>	quietlyExec();
686	>	pool = w.pool;
687		}
688	+	else
689	+	pool = null;
690	+	/*
691	+	* Timed wait loop intermixes cases for FJ (pool != null) and
692	+	* non FJ threads. For FJ, decrement pool count but don't try
693	+	* for replacement; increment count on completion. For non-FJ,
694	+	* deal with interrupts. This is messy, but a little less so
695	+	* than is splitting the FJ and nonFJ cases.
696	+	*/
697	+	boolean interrupted = false;
698	+	boolean dec = false; // true if pool count decremented
699	+	long nanos = unit.toNanos(timeout);
700	+	for (;;) {
701	+	if (pool == null && Thread.interrupted()) {
702	+	interrupted = true;
703	+	break;
704	+	}
705	+	int s = status;
706	+	if (s < 0)
707	+	break;
708	+	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
709	+	long startTime = System.nanoTime();
710	+	long nt; // wait time
711	+	while (status >= 0 &&
712	+	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
713	+	if (pool != null && !dec)
714	+	dec = pool.tryDecrementRunningCount();
715	+	else {
716	+	long ms = nt / 1000000;
717	+	int ns = (int) (nt % 1000000);
718	+	try {
719	+	synchronized (this) {
720	+	if (status >= 0)
721	+	wait(ms, ns);
722	+	}
723	+	} catch (InterruptedException ie) {
724	+	if (pool != null)
725	+	cancelIfTerminating();
726	+	else {
727	+	interrupted = true;
728	+	break;
729	+	}
730	+	}
731	+	}
732	+	}
733	+	break;
734	+	}
735	+	}
736	+	if (pool != null && dec)
737	+	pool.incrementRunningCount();
738	+	if (interrupted)
739	+	throw new InterruptedException();
740	+	int es = status;
741	+	if (es != NORMAL) {
742	+	Throwable ex;
743	+	if (es == CANCELLED)
744	+	throw new CancellationException();
745	+	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
746	+	throw new ExecutionException(ex);
747	+	throw new TimeoutException();
748	+	}
749	+	return getRawResult();
750		}
751
752		/**
753	<	* Joins this task, without returning its result or throwing an
753	>	* Joins this task, without returning its result or throwing its
754		* exception. This method may be useful when processing
755		* collections of tasks when some have been cancelled or otherwise
756		* known to have aborted.
757		*/
758		public final void quietlyJoin() {
759	<	if (status >= 0) {
760	<	ForkJoinWorkerThread w = getWorker();
761	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
762	<	awaitDone(w, true);
759	>	Thread t;
760	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
761	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
762	>	if (status >= 0) {
763	>	if (w.unpushTask(this)) {
764	>	boolean completed;
765	>	try {
766	>	completed = exec();
767	>	} catch (Throwable rex) {
768	>	setExceptionalCompletion(rex);
769	>	return;
770	>	}
771	>	if (completed) {
772	>	setCompletion(NORMAL);
773	>	return;
774	>	}
775	>	}
776	>	w.joinTask(this);
777	>	}
778		}
779	+	else
780	+	externalAwaitDone();
781		}
782
783		/**
784		* Commences performing this task and awaits its completion if
785	<	* necessary, without returning its result or throwing an
786	<	* exception. This method may be useful when processing
910	<	* collections of tasks when some have been cancelled or otherwise
911	<	* known to have aborted.
785	>	* necessary, without returning its result or throwing its
786	>	* exception.
787		*/
788		public final void quietlyInvoke() {
789	<	if (status >= 0 && !tryQuietlyInvoke())
790	<	quietlyJoin();
789	>	if (status >= 0) {
790	>	boolean completed;
791	>	try {
792	>	completed = exec();
793	>	} catch (Throwable rex) {
794	>	setExceptionalCompletion(rex);
795	>	return;
796	>	}
797	>	if (completed)
798	>	setCompletion(NORMAL);
799	>	else
800	>	quietlyJoin();
801	>	}
802		}
803
804		/**
#	Line 944 | Line 830 | public abstract class ForkJoinTask<V> im
830		* pre-constructed trees of subtasks in loops.
831		*/
832		public void reinitialize() {
833	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
833	>	if (status == EXCEPTIONAL)
834		exceptionMap.remove(this);
835		status = 0;
836		}
#	Line 1234 | Line 1120 | public abstract class ForkJoinTask<V> im
1120		private static final long serialVersionUID = -7721805057305804111L;
1121
1122		/**
1123	<	* Save the state to a stream.
1123	>	* Saves the state to a stream (that is, serializes it).
1124		*
1125		* @serialData the current run status and the exception thrown
1126		* during execution, or {@code null} if none
#	Line 1247 | Line 1133 | public abstract class ForkJoinTask<V> im
1133		}
1134
1135		/**
1136	<	* Reconstitute the instance from a stream.
1136	>	* Reconstitutes the instance from a stream (that is, deserializes it).
1137		*
1138		* @param s the stream
1139		*/
1140		private void readObject(java.io.ObjectInputStream s)
1141		throws java.io.IOException, ClassNotFoundException {
1142		s.defaultReadObject();
1257	–	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1258	–	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1143		Object ex = s.readObject();
1144		if (ex != null)
1145	<	setDoneExceptionally((Throwable) ex);
1145	>	setExceptionalCompletion((Throwable) ex);
1146		}
1147
1148		// Unsafe mechanics

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