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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.32 by dl, Mon Aug 3 13:01:15 2009 UTC vs.
Revision 1.46 by dl, Mon Apr 5 15:52:26 2010 UTC

#	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:
#	Line 68 | Line 68 | import java.util.WeakHashMap;
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
71	<	* equivalent to {@code fork(); join()} but always attempts to
72	<	* begin execution in the current thread. The "<em>quiet</em>" forms
73	<	* of these methods do not extract results or report exceptions. These
71	>	* equivalent to {@code fork(); join()} but always attempts to begin
72	>	* execution in the current thread. The "<em>quiet</em>" forms of
73	>	* these methods do not extract results or report exceptions. These
74		* may be useful when a set of tasks are being executed, and you need
75		* to delay processing of results or exceptions until all complete.
76		* Method {@code invokeAll} (available in multiple versions)
77		* performs the most common form of parallel invocation: forking a set
78		* of tasks and joining them all.
79		*
80	+	* <p>The execution status of tasks may be queried at several levels
81	+	* of detail: {@link #isDone} is true if a task completed in any way
82	+	* (including the case where a task was cancelled without executing);
83	+	* {@link #isCompletedNormally} is true if a task completed without
84	+	* cancellation or encountering an exception; {@link #isCancelled} is
85	+	* true if the task was cancelled (in which case {@link #getException}
86	+	* returns a {@link java.util.concurrent.CancellationException}); and
87	+	* {@link #isCompletedAbnormally} is true if a task was either
88	+	* cancelled or encountered an exception, in which case {@link
89	+	* #getException} will return either the encountered exception or
90	+	* {@link java.util.concurrent.CancellationException}.
91	+	*
92		* <p>The ForkJoinTask class is not usually directly subclassed.
93		* Instead, you subclass one of the abstract classes that support a
94		* particular style of fork/join processing, typically {@link
#	Line 111 | Line 123 | import java.util.WeakHashMap;
123		* improve throughput. If too small, then memory and internal task
124		* maintenance overhead may overwhelm processing.
125		*
126	<	* <p>This class provides {@code adapt} methods for {@link
127	<	* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
128	<	* may be of use when mixing execution of ForkJoinTasks with other
129	<	* kinds of tasks. When all tasks are of this form, consider using a
130	<	* pool in {@link ForkJoinPool#setAsyncMode}.
126	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
127	>	* and {@link Callable}, that may be of use when mixing execution of
128	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks
129	>	* are of this form, consider using a pool in
130	>	* {@linkplain ForkJoinPool#setAsyncMode async mode}.
131		*
132		* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
133		* used in extensions such as remote execution frameworks. It is
#	Line 127 | Line 139 | import java.util.WeakHashMap;
139		*/
140		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
141
142	+	/*
143	+	* See the internal documentation of class ForkJoinPool for a
144	+	* general implementation overview.  ForkJoinTasks are mainly
145	+	* responsible for maintaining their "status" field amidst relays
146	+	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
147	+	* methods of this class are more-or-less layered into (1) basic
148	+	* status maintenance (2) execution and awaiting completion (3)
149	+	* user-level methods that additionally report results. This is
150	+	* sometimes hard to see because this file orders exported methods
151	+	* in a way that flows well in javadocs.
152	+	*/
153	+
154		/**
155		* Run control status bits packed into a single int to minimize
156		* footprint and to ensure atomicity (via CAS).  Status is
#	Line 136 | Line 160 | public abstract class ForkJoinTask<V> im
160		* blocking waits by other threads have SIGNAL_MASK bits set --
161		* bit 15 for external (nonFJ) waits, and the rest a count of
162		* waiting FJ threads.  (This representation relies on
163	<	* ForkJoinPool max thread limits). Completion of a stolen task
164	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
165	<	* though suboptimal for some purposes, we use basic builtin
166	<	* wait/notify to take advantage of "monitor inflation" in JVMs
167	<	* that we would otherwise need to emulate to avoid adding further
168	<	* per-task bookkeeping overhead. Note that bits 16-28 are
169	<	* currently unused. Also value 0x80000000 is available as spare
170	<	* completion value.
163	>	* ForkJoinPool max thread limits). Signal counts are not directly
164	>	* incremented by ForkJoinTask methods, but instead via a call to
165	>	* requestSignal within ForkJoinPool.preJoin, once their need is
166	>	* established.
167	>	*
168	>	* Completion of a stolen task with SIGNAL_MASK bits set awakens
169	>	* any waiters via notifyAll. Even though suboptimal for some
170	>	* purposes, we use basic builtin wait/notify to take advantage of
171	>	* "monitor inflation" in JVMs that we would otherwise need to
172	>	* emulate to avoid adding further per-task bookkeeping overhead.
173	>	* We want these monitors to be "fat", i.e., not use biasing or
174	>	* thin-lock techniques, so use some odd coding idioms that tend
175	>	* to avoid them.
176	>	*
177	>	* Note that bits 16-28 are currently unused. Also value
178	>	* 0x80000000 is available as spare completion value.
179		*/
180		volatile int status; // accessed directly by pool and workers
181
182	<	static final int COMPLETION_MASK      = 0xe0000000;
183	<	static final int NORMAL               = 0xe0000000; // == mask
184	<	static final int CANCELLED            = 0xc0000000;
185	<	static final int EXCEPTIONAL          = 0xa0000000;
186	<	static final int SIGNAL_MASK          = 0x0000ffff;
187	<	static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
188	<	static final int EXTERNAL_SIGNAL      = 0x00008000; // top bit of low word
182	>	private static final int COMPLETION_MASK      = 0xe0000000;
183	>	private static final int NORMAL               = 0xe0000000; // == mask
184	>	private static final int CANCELLED            = 0xc0000000;
185	>	private static final int EXCEPTIONAL          = 0xa0000000;
186	>	private static final int SIGNAL_MASK          = 0x0000ffff;
187	>	private static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
188	>	private static final int EXTERNAL_SIGNAL      = 0x00008000;
189
190		/**
191		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 167 | Line 199 | public abstract class ForkJoinTask<V> im
199		Collections.synchronizedMap
200		(new WeakHashMap<ForkJoinTask<?>, Throwable>());
201
202	<	// within-package utilities
202	>	// Maintaining completion status
203
204		/**
205	<	* Gets current worker thread, or null if not a worker thread.
205	>	* Marks completion and wakes up threads waiting to join this task,
206	>	* also clearing signal request bits.
207	>	*
208	>	* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
209		*/
210	<	static ForkJoinWorkerThread getWorker() {
211	<	Thread t = Thread.currentThread();
212	<	return ((t instanceof ForkJoinWorkerThread) ?
213	<	(ForkJoinWorkerThread) t : null);
214	<	}
215	<
216	<	final boolean casStatus(int cmp, int val) {
217	<	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
210	>	private void setCompletion(int completion) {
211	>	int s;
212	>	while ((s = status) >= 0) {
213	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
214	>	if ((s & SIGNAL_MASK) != 0) {
215	>	Thread t = Thread.currentThread();
216	>	if (t instanceof ForkJoinWorkerThread)
217	>	((ForkJoinWorkerThread) t).pool.updateRunningCount
218	>	(s & INTERNAL_SIGNAL_MASK);
219	>	synchronized (this) { notifyAll(); }
220	>	}
221	>	return;
222	>	}
223	>	}
224		}
225
226		/**
227	<	* Workaround for not being able to rethrow unchecked exceptions.
227	>	* Record exception and set exceptional completion
228		*/
229	<	static void rethrowException(Throwable ex) {
230	<	if (ex != null)
231	<	UNSAFE.throwException(ex);
229	>	private void setDoneExceptionally(Throwable rex) {
230	>	exceptionMap.put(this, rex);
231	>	setCompletion(EXCEPTIONAL);
232		}
233
193	–	// Setting completion status
194	–
234		/**
235	<	* Marks completion and wakes up threads waiting to join this task.
235	>	* Main internal execution method: Unless done, calls exec and
236	>	* records completion.
237		*
238	<	* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
238	>	* @return true if ran and completed normally
239		*/
240	<	final void setCompletion(int completion) {
241	<	ForkJoinPool pool = getPool();
242	<	if (pool != null) {
243	<	int s; // Clear signal bits while setting completion status
244	<	do {} while ((s = status) >= 0 && !casStatus(s, completion));
245	<
246	<	if ((s & SIGNAL_MASK) != 0) {
207	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
208	<	pool.updateRunningCount(s);
209	<	synchronized (this) { notifyAll(); }
210	<	}
240	>	final boolean tryExec() {
241	>	try {
242	>	if (status < 0 || !exec())
243	>	return false;
244	>	} catch (Throwable rex) {
245	>	setDoneExceptionally(rex);
246	>	return false;
247		}
248	<	else
249	<	externallySetCompletion(completion);
248	>	setCompletion(NORMAL); // must be outside try block
249	>	return true;
250		}
251
252		/**
253	<	* Version of setCompletion for non-FJ threads.  Leaves signal
254	<	* bits for unblocked threads to adjust, and always notifies.
253	>	* Increments internal signal count (thus requesting signal upon
254	>	* completion) unless already done.  Call only once per join.
255	>	* Used by ForkJoinPool.preJoin.
256	>	*
257	>	* @return status
258		*/
259	<	private void externallySetCompletion(int completion) {
259	>	final int requestSignal() {
260		int s;
261	<	do {} while ((s = status) >= 0 &&
262	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
263	<	synchronized (this) { notifyAll(); }
261	>	do {} while ((s = status) >= 0 &&
262	>	!UNSAFE.compareAndSwapInt(this, statusOffset, s, s + 1));
263	>	return s;
264		}
265	<
265	>
266		/**
267	<	* Sets status to indicate normal completion.
267	>	* Sets external signal request unless already done.
268	>	*
269	>	* @return status
270		*/
271	<	final void setNormalCompletion() {
272	<	// Try typical fast case -- single CAS, no signal, not already done.
273	<	// Manually expand casStatus to improve chances of inlining it
274	<	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
275	<	setCompletion(NORMAL);
271	>	private int requestExternalSignal() {
272	>	int s;
273	>	do {} while ((s = status) >= 0 &&
274	>	!UNSAFE.compareAndSwapInt(this, statusOffset,
275	>	s, s | EXTERNAL_SIGNAL));
276	>	return s;
277		}
278
279	<	// internal waiting and notification
280	<
281	<	/**
282	<	* Performs the actual monitor wait for awaitDone.
279	>	/*
280	>	* Awaiting completion. The four versions, internal vs external X
281	>	* untimed vs timed, have the same overall structure but differ
282	>	* from each other enough to defy simple integration.
283		*/
242	–	private void doAwaitDone() {
243	–	// Minimize lock bias and in/de-flation effects by maximizing
244	–	// chances of waiting inside sync
245	–	try {
246	–	while (status >= 0)
247	–	synchronized (this) { if (status >= 0) wait(); }
248	–	} catch (InterruptedException ie) {
249	–	onInterruptedWait();
250	–	}
251	–	}
284
285		/**
286	<	* Performs the actual timed monitor wait for awaitDone.
286	>	* Blocks a worker until this task is done, also maintaining pool
287	>	* and signal counts
288		*/
289	<	private void doAwaitDone(long startTime, long nanos) {
290	<	synchronized (this) {
291	<	try {
292	<	while (status >= 0) {
293	<	long nt = nanos - (System.nanoTime() - startTime);
294	<	if (nt <= 0)
295	<	break;
296	<	wait(nt / 1000000, (int) (nt % 1000000));
289	>	private void awaitDone(ForkJoinWorkerThread w) {
290	>	if (status >= 0) {
291	>	w.pool.preJoin(this);
292	>	while (status >= 0) {
293	>	try { // minimize lock scope
294	>	synchronized(this) {
295	>	if (status >= 0)
296	>	wait();
297	>	else { // help release; also helps avoid lock-biasing
298	>	notifyAll();
299	>	break;
300	>	}
301	>	}
302	>	} catch (InterruptedException ie) {
303	>	cancelIfTerminating();
304		}
265	–	} catch (InterruptedException ie) {
266	–	onInterruptedWait();
305		}
306		}
307		}
308
271	–	// Awaiting completion
272	–
309		/**
310	<	* Sets status to indicate there is joiner, then waits for join,
275	<	* surrounded with pool notifications.
276	<	*
277	<	* @return status upon exit
310	>	* Blocks a non-ForkJoin thread until this task is done.
311		*/
312	<	private int awaitDone(ForkJoinWorkerThread w,
313	<	boolean maintainParallelism) {
314	<	ForkJoinPool pool = (w == null) ? null : w.pool;
315	<	int s;
316	<	while ((s = status) >= 0) {
317	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
318	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
319	<	doAwaitDone();
320	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
321	<	adjustPoolCountsOnUnblock(pool);
322	<	break;
312	>	private void externalAwaitDone() {
313	>	if (requestExternalSignal() >= 0) {
314	>	boolean interrupted = false;
315	>	while (status >= 0) {
316	>	try {
317	>	synchronized(this) {
318	>	if (status >= 0)
319	>	wait();
320	>	else {
321	>	notifyAll();
322	>	break;
323	>	}
324	>	}
325	>	} catch (InterruptedException ie) {
326	>	interrupted = true;
327	>	}
328		}
329	+	if (interrupted)
330	+	Thread.currentThread().interrupt();
331		}
292	–	return s;
332		}
333
334		/**
335	<	* Timed version of awaitDone
297	<	*
298	<	* @return status upon exit
335	>	* Blocks a worker until this task is done or timeout elapses
336		*/
337	<	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
338	<	ForkJoinPool pool = (w == null) ? null : w.pool;
339	<	int s;
340	<	while ((s = status) >= 0) {
341	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
342	<	long startTime = System.nanoTime();
343	<	if (pool == null || !pool.preJoin(this, false))
344	<	doAwaitDone(startTime, nanos);
345	<	if ((s = status) >= 0) {
346	<	adjustPoolCountsOnCancelledWait(pool);
347	<	s = status;
337	>	private void timedAwaitDone(ForkJoinWorkerThread w, long nanos) {
338	>	if (status >= 0) {
339	>	long startTime = System.nanoTime();
340	>	ForkJoinPool pool = w.pool;
341	>	pool.preJoin(this);
342	>	while (status >= 0) {
343	>	long nt = nanos - (System.nanoTime() - startTime);
344	>	if (nt > 0) {
345	>	long ms = nt / 1000000;
346	>	int ns = (int) (nt % 1000000);
347	>	try {
348	>	synchronized(this) { if (status >= 0) wait(ms, ns); }
349	>	} catch (InterruptedException ie) {
350	>	cancelIfTerminating();
351	>	}
352	>	}
353	>	else {
354	>	int s; // adjust running count on timeout
355	>	while ((s = status) >= 0 &&
356	>	(s & INTERNAL_SIGNAL_MASK) != 0) {
357	>	if (UNSAFE.compareAndSwapInt(this, statusOffset,
358	>	s, s - 1)) {
359	>	pool.updateRunningCount(1);
360	>	break;
361	>	}
362	>	}
363	>	break;
364		}
312	–	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
313	–	adjustPoolCountsOnUnblock(pool);
314	–	break;
365		}
366		}
317	–	return s;
318	–	}
319	–
320	–	/**
321	–	* Notifies pool that thread is unblocked. Called by signalled
322	–	* threads when woken by non-FJ threads (which is atypical).
323	–	*/
324	–	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
325	–	int s;
326	–	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
327	–	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
328	–	pool.updateRunningCount(s);
367		}
368
369		/**
370	<	* Notifies pool to adjust counts on cancelled or timed out wait.
370	>	* Blocks a non-ForkJoin thread until this task is done or timeout elapses
371		*/
372	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
373	<	if (pool != null) {
374	<	int s;
375	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
376	<	if (casStatus(s, s - 1)) {
377	<	pool.updateRunningCount(1);
372	>	private void externalTimedAwaitDone(long nanos) {
373	>	if (requestExternalSignal() >= 0) {
374	>	long startTime = System.nanoTime();
375	>	boolean interrupted = false;
376	>	while (status >= 0) {
377	>	long nt = nanos - (System.nanoTime() - startTime);
378	>	if (nt <= 0)
379		break;
380	+	long ms = nt / 1000000;
381	+	int ns = (int) (nt % 1000000);
382	+	try {
383	+	synchronized(this) { if (status >= 0) wait(ms, ns); }
384	+	} catch (InterruptedException ie) {
385	+	interrupted = true;
386		}
387		}
388	+	if (interrupted)
389	+	Thread.currentThread().interrupt();
390		}
391		}
392
393	<	/**
347	<	* Handles interruptions during waits.
348	<	*/
349	<	private void onInterruptedWait() {
350	<	ForkJoinWorkerThread w = getWorker();
351	<	if (w == null)
352	<	Thread.currentThread().interrupt(); // re-interrupt
353	<	else if (w.isTerminating())
354	<	cancelIgnoringExceptions();
355	<	// else if FJworker, ignore interrupt
356	<	}
357	<
358	<	// Recording and reporting exceptions
359	<
360	<	private void setDoneExceptionally(Throwable rex) {
361	<	exceptionMap.put(this, rex);
362	<	setCompletion(EXCEPTIONAL);
363	<	}
393	>	// reporting results
394
395		/**
396	<	* Throws the exception associated with status s.
397	<	*
398	<	* @throws the exception
396	>	* Returns result or throws the exception associated with status.
397	>	* Uses Unsafe as a workaround for javac not allowing rethrow of
398	>	* unchecked exceptions.
399		*/
400	<	private void reportException(int s) {
401	<	if ((s &= COMPLETION_MASK) < NORMAL) {
402	<	if (s == CANCELLED)
403	<	throw new CancellationException();
404	<	else
375	<	rethrowException(exceptionMap.get(this));
400	>	private V reportResult() {
401	>	if ((status & COMPLETION_MASK) < NORMAL) {
402	>	Throwable ex = getException();
403	>	if (ex != null)
404	>	UNSAFE.throwException(ex);
405		}
406	+	return getRawResult();
407		}
408
409		/**
410		* Returns result or throws exception using j.u.c.Future conventions.
411	<	* Only call when {@code isDone} known to be true.
411	>	* Only call when {@code isDone} known to be true or thread known
412	>	* to be interrupted.
413		*/
414		private V reportFutureResult()
415	<	throws ExecutionException, InterruptedException {
415	>	throws InterruptedException, ExecutionException {
416	>	if (Thread.interrupted())
417	>	throw new InterruptedException();
418		int s = status & COMPLETION_MASK;
419		if (s < NORMAL) {
420		Throwable ex;
#	Line 389 | Line 422 | public abstract class ForkJoinTask<V> im
422		throw new CancellationException();
423		if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
424		throw new ExecutionException(ex);
392	–	if (Thread.interrupted())
393	–	throw new InterruptedException();
425		}
426		return getRawResult();
427		}
#	Line 401 | Line 432 | public abstract class ForkJoinTask<V> im
432		*/
433		private V reportTimedFutureResult()
434		throws InterruptedException, ExecutionException, TimeoutException {
435	+	if (Thread.interrupted())
436	+	throw new InterruptedException();
437		Throwable ex;
438		int s = status & COMPLETION_MASK;
439		if (s == NORMAL)
440		return getRawResult();
441	<	if (s == CANCELLED)
441	>	else if (s == CANCELLED)
442		throw new CancellationException();
443	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
443	>	else if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
444		throw new ExecutionException(ex);
445	<	if (Thread.interrupted())
446	<	throw new InterruptedException();
414	<	throw new TimeoutException();
415	<	}
416	<
417	<	// internal execution methods
418	<
419	<	/**
420	<	* Calls exec, recording completion, and rethrowing exception if
421	<	* encountered. Caller should normally check status before calling.
422	<	*
423	<	* @return true if completed normally
424	<	*/
425	<	private boolean tryExec() {
426	<	try { // try block must contain only call to exec
427	<	if (!exec())
428	<	return false;
429	<	} catch (Throwable rex) {
430	<	setDoneExceptionally(rex);
431	<	rethrowException(rex);
432	<	return false; // not reached
433	<	}
434	<	setNormalCompletion();
435	<	return true;
436	<	}
437	<
438	<	/**
439	<	* Main execution method used by worker threads. Invokes
440	<	* base computation unless already complete.
441	<	*/
442	<	final void quietlyExec() {
443	<	if (status >= 0) {
444	<	try {
445	<	if (!exec())
446	<	return;
447	<	} catch (Throwable rex) {
448	<	setDoneExceptionally(rex);
449	<	return;
450	<	}
451	<	setNormalCompletion();
452	<	}
453	<	}
454	<
455	<	/**
456	<	* Calls exec(), recording but not rethrowing exception.
457	<	* Caller should normally check status before calling.
458	<	*
459	<	* @return true if completed normally
460	<	*/
461	<	private boolean tryQuietlyInvoke() {
462	<	try {
463	<	if (!exec())
464	<	return false;
465	<	} catch (Throwable rex) {
466	<	setDoneExceptionally(rex);
467	<	return false;
468	<	}
469	<	setNormalCompletion();
470	<	return true;
471	<	}
472	<
473	<	/**
474	<	* Cancels, ignoring any exceptions it throws.
475	<	*/
476	<	final void cancelIgnoringExceptions() {
477	<	try {
478	<	cancel(false);
479	<	} catch (Throwable ignore) {
480	<	}
481	<	}
482	<
483	<	/**
484	<	* Main implementation of helpJoin
485	<	*/
486	<	private int busyJoin(ForkJoinWorkerThread w) {
487	<	int s;
488	<	ForkJoinTask<?> t;
489	<	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
490	<	t.quietlyExec();
491	<	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
445	>	else
446	>	throw new TimeoutException();
447		}
448
449		// public methods
#	Line 497 | Line 452 | public abstract class ForkJoinTask<V> im
452		* Arranges to asynchronously execute this task.  While it is not
453		* necessarily enforced, it is a usage error to fork a task more
454		* than once unless it has completed and been reinitialized.
455	+	* Subsequent modifications to the state of this task or any data
456	+	* it operates on are not necessarily consistently observable by
457	+	* any thread other than the one executing it unless preceded by a
458	+	* call to {@link #join} or related methods, or a call to {@link
459	+	* #isDone} returning {@code true}.
460		*
461		* <p>This method may be invoked only from within {@code
462		* ForkJoinTask} computations (as may be determined using method
#	Line 513 | Line 473 | public abstract class ForkJoinTask<V> im
473		}
474
475		/**
476	<	* Returns the result of the computation when it is ready.
476	>	* Returns the result of the computation when it {@link #isDone is done}.
477		* This method differs from {@link #get()} in that
478		* abnormal completion results in {@code RuntimeException} or
479		* {@code Error}, not {@code ExecutionException}.
#	Line 521 | Line 481 | public abstract class ForkJoinTask<V> im
481		* @return the computed result
482		*/
483		public final V join() {
484	<	ForkJoinWorkerThread w = getWorker();
485	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
526	<	reportException(awaitDone(w, true));
527	<	return getRawResult();
484	>	quietlyJoin();
485	>	return reportResult();
486		}
487
488		/**
489		* Commences performing this task, awaits its completion if
490	<	* necessary, and return its result.
490	>	* necessary, and return its result, or throws an (unchecked)
491	>	* exception if the underlying computation did so.
492		*
534	–	* @throws Throwable (a RuntimeException, Error, or unchecked
535	–	* exception) if the underlying computation did so
493		* @return the computed result
494		*/
495		public final V invoke() {
496	<	if (status >= 0 && tryExec())
497	<	return getRawResult();
498	<	else
542	<	return join();
496	>	if (!tryExec())
497	>	quietlyJoin();
498	>	return reportResult();
499		}
500
501		/**
502	<	* Forks the given tasks, returning when {@code isDone} holds
503	<	* for each task or an exception is encountered.
502	>	* Forks the given tasks, returning when {@code isDone} holds for
503	>	* each task or an (unchecked) exception is encountered, in which
504	>	* case the exception is rethrown.  If either task encounters an
505	>	* exception, the other one may be, but is not guaranteed to be,
506	>	* cancelled.  If both tasks throw an exception, then this method
507	>	* throws one of them.  The individual status of each task may be
508	>	* checked using {@link #getException()} and related methods.
509		*
510		* <p>This method may be invoked only from within {@code
511		* ForkJoinTask} computations (as may be determined using method
#	Line 555 | Line 516 | public abstract class ForkJoinTask<V> im
516		* @param t1 the first task
517		* @param t2 the second task
518		* @throws NullPointerException if any task is null
558	–	* @throws RuntimeException or Error if a task did so
519		*/
520		public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
521		t2.fork();
#	Line 565 | Line 525 | public abstract class ForkJoinTask<V> im
525
526		/**
527		* Forks the given tasks, returning when {@code isDone} holds for
528	<	* each task or an exception is encountered. If any task
529	<	* encounters an exception, others may be, but are not guaranteed
530	<	* to be, cancelled.
528	>	* each task or an (unchecked) exception is encountered, in which
529	>	* case the exception is rethrown. If any task encounters an
530	>	* exception, others may be, but are not guaranteed to be,
531	>	* cancelled.  If more than one task encounters an exception, then
532	>	* this method throws any one of these exceptions.  The individual
533	>	* status of each task may be checked using {@link #getException()}
534	>	* and related methods.
535		*
536		* <p>This method may be invoked only from within {@code
537		* ForkJoinTask} computations (as may be determined using method
#	Line 576 | Line 540 | public abstract class ForkJoinTask<V> im
540		* ClassCastException}.
541		*
542		* @param tasks the tasks
543	<	* @throws NullPointerException if tasks or any element are null
580	<	* @throws RuntimeException or Error if any task did so
543	>	* @throws NullPointerException if any task is null
544		*/
545		public static void invokeAll(ForkJoinTask<?>... tasks) {
546		Throwable ex = null;
#	Line 609 | Line 572 | public abstract class ForkJoinTask<V> im
572		}
573		}
574		if (ex != null)
575	<	rethrowException(ex);
575	>	UNSAFE.throwException(ex);
576		}
577
578		/**
579		* Forks all tasks in the specified collection, returning when
580	<	* {@code isDone} holds for each task or an exception is
581	<	* encountered.  If any task encounters an exception, others may
582	<	* be, but are not guaranteed to be, cancelled. The behavior of
583	<	* this operation is undefined if the specified collection is
584	<	* modified while the operation is in progress.
580	>	* {@code isDone} holds for each task or an (unchecked) exception
581	>	* is encountered.  If any task encounters an exception, others
582	>	* may be, but are not guaranteed to be, cancelled.  If more than
583	>	* one task encounters an exception, then this method throws any
584	>	* one of these exceptions.  The individual status of each task
585	>	* may be checked using {@link #getException()} and related
586	>	* methods.  The behavior of this operation is undefined if the
587	>	* specified collection is modified while the operation is in
588	>	* progress.
589		*
590		* <p>This method may be invoked only from within {@code
591		* ForkJoinTask} computations (as may be determined using method
#	Line 629 | Line 596 | public abstract class ForkJoinTask<V> im
596		* @param tasks the collection of tasks
597		* @return the tasks argument, to simplify usage
598		* @throws NullPointerException if tasks or any element are null
632	–	* @throws RuntimeException or Error if any task did so
599		*/
600		public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
601		if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
#	Line 668 | Line 634 | public abstract class ForkJoinTask<V> im
634		}
635		}
636		if (ex != null)
637	<	rethrowException(ex);
637	>	UNSAFE.throwException(ex);
638		return tasks;
639		}
640
641		/**
642	<	* Returns {@code true} if the computation performed by this task
643	<	* has completed (or has been cancelled).
644	<	*
645	<	* @return {@code true} if this computation has completed
646	<	*/
647	<	public final boolean isDone() {
648	<	return status < 0;
683	<	}
684	<
685	<	/**
686	<	* Returns {@code true} if this task was cancelled.
687	<	*
688	<	* @return {@code true} if this task was cancelled
689	<	*/
690	<	public final boolean isCancelled() {
691	<	return (status & COMPLETION_MASK) == CANCELLED;
692	<	}
693	<
694	<	/**
695	<	* Asserts that the results of this task's computation will not be
696	<	* used. If a cancellation occurs before attempting to execute this
697	<	* task, execution will be suppressed, {@link #isCancelled}
698	<	* will report true, and {@link #join} will result in a
699	<	* {@code CancellationException} being thrown. Otherwise, when
700	<	* cancellation races with completion, there are no guarantees
701	<	* about whether {@code isCancelled} will report {@code true},
702	<	* whether {@code join} will return normally or via an exception,
703	<	* or whether these behaviors will remain consistent upon repeated
704	<	* invocation.
642	>	* Attempts to cancel execution of this task. This attempt will
643	>	* fail if the task has already completed, has already been
644	>	* cancelled, or could not be cancelled for some other reason. If
645	>	* successful, and this task has not started when cancel is
646	>	* called, execution of this task is suppressed, {@link
647	>	* #isCancelled} will report true, and {@link #join} will result
648	>	* in a {@code CancellationException} being thrown.
649		*
650		* <p>This method may be overridden in subclasses, but if so, must
651		* still ensure that these minimal properties hold. In particular,
#	Line 713 | Line 657 | public abstract class ForkJoinTask<V> im
657		* invoke {@link #completeExceptionally}.
658		*
659		* @param mayInterruptIfRunning this value is ignored in the
660	<	* default implementation because tasks are not in general
660	>	* default implementation because tasks are not
661		* cancelled via interruption
662		*
663		* @return {@code true} if this task is now cancelled
#	Line 724 | Line 668 | public abstract class ForkJoinTask<V> im
668		}
669
670		/**
671	+	* Cancels, ignoring any exceptions it throws. Used during worker
672	+	* and pool shutdown.
673	+	*/
674	+	final void cancelIgnoringExceptions() {
675	+	try {
676	+	cancel(false);
677	+	} catch (Throwable ignore) {
678	+	}
679	+	}
680	+
681	+	/**
682	+	* Cancels ignoring exceptions if worker is terminating
683	+	*/
684	+	private void cancelIfTerminating() {
685	+	Thread t = Thread.currentThread();
686	+	if ((t instanceof ForkJoinWorkerThread) &&
687	+	((ForkJoinWorkerThread) t).isTerminating()) {
688	+	try {
689	+	cancel(false);
690	+	} catch (Throwable ignore) {
691	+	}
692	+	}
693	+	}
694	+
695	+	public final boolean isDone() {
696	+	return status < 0;
697	+	}
698	+
699	+	public final boolean isCancelled() {
700	+	return (status & COMPLETION_MASK) == CANCELLED;
701	+	}
702	+
703	+	/**
704		* Returns {@code true} if this task threw an exception or was cancelled.
705		*
706		* @return {@code true} if this task threw an exception or was cancelled
#	Line 733 | Line 710 | public abstract class ForkJoinTask<V> im
710		}
711
712		/**
713	+	* Returns {@code true} if this task completed without throwing an
714	+	* exception and was not cancelled.
715	+	*
716	+	* @return {@code true} if this task completed without throwing an
717	+	* exception and was not cancelled
718	+	*/
719	+	public final boolean isCompletedNormally() {
720	+	return (status & COMPLETION_MASK) == NORMAL;
721	+	}
722	+
723	+	/**
724		* Returns the exception thrown by the base computation, or a
725		* {@code CancellationException} if cancelled, or {@code null} if
726		* none or if the method has not yet completed.
#	Line 741 | Line 729 | public abstract class ForkJoinTask<V> im
729		*/
730		public final Throwable getException() {
731		int s = status & COMPLETION_MASK;
732	<	if (s >= NORMAL)
733	<	return null;
734	<	if (s == CANCELLED)
747	<	return new CancellationException();
748	<	return exceptionMap.get(this);
732	>	return ((s >= NORMAL)    ? null :
733	>	(s == CANCELLED) ? new CancellationException() :
734	>	exceptionMap.get(this));
735		}
736
737		/**
#	Line 758 | Line 744 | public abstract class ForkJoinTask<V> im
744		* overridable, but overridden versions must invoke {@code super}
745		* implementation to maintain guarantees.
746		*
747	<	* @param ex the exception to throw. If this exception is
748	<	* not a RuntimeException or Error, the actual exception thrown
749	<	* will be a RuntimeException with cause ex.
747	>	* @param ex the exception to throw. If this exception is not a
748	>	* {@code RuntimeException} or {@code Error}, the actual exception
749	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
750		*/
751		public void completeExceptionally(Throwable ex) {
752		setDoneExceptionally((ex instanceof RuntimeException) ||
#	Line 787 | Line 773 | public abstract class ForkJoinTask<V> im
773		setDoneExceptionally(rex);
774		return;
775		}
776	<	setNormalCompletion();
776	>	setCompletion(NORMAL);
777		}
778
779		public final V get() throws InterruptedException, ExecutionException {
780	<	ForkJoinWorkerThread w = getWorker();
795	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
796	<	awaitDone(w, true);
780	>	quietlyJoin();
781		return reportFutureResult();
782		}
783	<
783	>
784		public final V get(long timeout, TimeUnit unit)
785		throws InterruptedException, ExecutionException, TimeoutException {
786		long nanos = unit.toNanos(timeout);
787	<	ForkJoinWorkerThread w = getWorker();
788	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
789	<	awaitDone(w, nanos);
787	>	Thread t = Thread.currentThread();
788	>	if (t instanceof ForkJoinWorkerThread) {
789	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
790	>	if (!w.unpushTask(this) || !tryExec())
791	>	timedAwaitDone(w, nanos);
792	>	}
793	>	else
794	>	externalTimedAwaitDone(nanos);
795		return reportTimedFutureResult();
796		}
797
798		/**
799	<	* Possibly executes other tasks until this task is ready, then
800	<	* returns the result of the computation.  This method may be more
801	<	* efficient than {@code join}, but is only applicable when
802	<	* there are no potential dependencies between continuation of the
803	<	* current task and that of any other task that might be executed
804	<	* while helping. (This usually holds for pure divide-and-conquer
805	<	* tasks).
799	>	* Possibly executes other tasks until this task {@link #isDone is
800	>	* done}, then returns the result of the computation.  This method
801	>	* may be more efficient than {@code join}, but is only applicable
802	>	* when there are no potential dependencies between continuation
803	>	* of the current task and that of any other task that might be
804	>	* executed while helping. (This usually holds for pure
805	>	* divide-and-conquer tasks).
806		*
807		* <p>This method may be invoked only from within {@code
808		* ForkJoinTask} computations (as may be determined using method
#	Line 824 | Line 813 | public abstract class ForkJoinTask<V> im
813		* @return the computed result
814		*/
815		public final V helpJoin() {
816	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
817	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
829	<	reportException(busyJoin(w));
830	<	return getRawResult();
816	>	quietlyHelpJoin();
817	>	return reportResult();
818		}
819
820		/**
821	<	* Possibly executes other tasks until this task is ready.  This
822	<	* method may be useful when processing collections of tasks when
823	<	* some have been cancelled or otherwise known to have aborted.
821	>	* Possibly executes other tasks until this task {@link #isDone is
822	>	* done}.  This method may be useful when processing collections
823	>	* of tasks when some have been cancelled or otherwise known to
824	>	* have aborted.
825		*
826		* <p>This method may be invoked only from within {@code
827		* ForkJoinTask} computations (as may be determined using method
#	Line 842 | Line 830 | public abstract class ForkJoinTask<V> im
830		* ClassCastException}.
831		*/
832		public final void quietlyHelpJoin() {
833	<	if (status >= 0) {
834	<	ForkJoinWorkerThread w =
835	<	(ForkJoinWorkerThread) Thread.currentThread();
836	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
837	<	busyJoin(w);
833	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
834	>	if (!w.unpushTask(this) || !tryExec()) {
835	>	while (status >= 0) {
836	>	ForkJoinTask<?> t = w.scanWhileJoining(this);
837	>	if (t == null) {
838	>	if (status >= 0)
839	>	awaitDone(w);
840	>	break;
841	>	}
842	>	t.tryExec();
843	>	}
844		}
845		}
846
#	Line 857 | Line 851 | public abstract class ForkJoinTask<V> im
851		* known to have aborted.
852		*/
853		public final void quietlyJoin() {
854	<	if (status >= 0) {
855	<	ForkJoinWorkerThread w = getWorker();
856	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
857	<	awaitDone(w, true);
854	>	Thread t = Thread.currentThread();
855	>	if (t instanceof ForkJoinWorkerThread) {
856	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
857	>	if (!w.unpushTask(this) || !tryExec())
858	>	awaitDone(w);
859		}
860	+	else
861	+	externalAwaitDone();
862		}
863
864		/**
#	Line 872 | Line 869 | public abstract class ForkJoinTask<V> im
869		* known to have aborted.
870		*/
871		public final void quietlyInvoke() {
872	<	if (status >= 0 && !tryQuietlyInvoke())
872	>	if (!tryExec())
873		quietlyJoin();
874		}
875
876		/**
877		* Possibly executes tasks until the pool hosting the current task
878	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
879	<	* designs in which many tasks are forked, but none are explicitly
880	<	* joined, instead executing them until all are processed.
878	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
879	>	* be of use in designs in which many tasks are forked, but none
880	>	* are explicitly joined, instead executing them until all are
881	>	* processed.
882		*
883		* <p>This method may be invoked only from within {@code
884		* ForkJoinTask} computations (as may be determined using method
#	Line 1024 | Line 1022 | public abstract class ForkJoinTask<V> im
1022		* called otherwise. The return value controls whether this task
1023		* is considered to be done normally. It may return false in
1024		* asynchronous actions that require explicit invocations of
1025	<	* {@link #complete} to become joinable. It may throw exceptions
1026	<	* to indicate abnormal exit.
1025	>	* {@link #complete} to become joinable. It may also throw an
1026	>	* (unchecked) exception to indicate abnormal exit.
1027		*
1028		* @return {@code true} if completed normally
1031	–	* @throws Error or RuntimeException if encountered during computation
1029		*/
1030		protected abstract boolean exec();
1031
#	Line 1195 | Line 1192 | public abstract class ForkJoinTask<V> im
1192		private static final long serialVersionUID = -7721805057305804111L;
1193
1194		/**
1195	<	* Save the state to a stream.
1195	>	* Saves the state to a stream.
1196		*
1197		* @serialData the current run status and the exception thrown
1198		* during execution, or {@code null} if none
#	Line 1208 | Line 1205 | public abstract class ForkJoinTask<V> im
1205		}
1206
1207		/**
1208	<	* Reconstitute the instance from a stream.
1208	>	* Reconstitutes the instance from a stream.
1209		*
1210		* @param s the stream
1211		*/

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