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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.33 by dl, Tue Aug 4 00:36:45 2009 UTC vs.
Revision 1.49 by dl, Wed Jul 7 19:52:31 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:
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
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
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
71		* may be useful when a set of tasks are being executed, and you need
72		* to delay processing of results or exceptions until all complete.
73		* Method {@code invokeAll} (available in multiple versions)
74		* performs the most common form of parallel invocation: forking a set
75		* of tasks and joining them all.
76		*
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);
80	+	* {@link #isCompletedNormally} is true if a task completed without
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
91		* particular style of fork/join processing, typically {@link
#	Line 111 | 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
118	<	* pool in {@link ForkJoinPool#setAsyncMode}.
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 127 | Line 135 | import java.util.WeakHashMap;
135		*/
136		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
137
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.
148	+	*/
149	+
150		/**
151		* Run control status bits packed into a single int to minimize
152		* footprint and to ensure atomicity (via CAS).  Status is
153		* initially zero, and takes on nonnegative values until
154	<	* completed, upon which status holds COMPLETED. CANCELLED, or
155	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
156	<	* blocking waits by other threads have SIGNAL_MASK bits set --
157	<	* bit 15 for external (nonFJ) waits, and the rest a count of
158	<	* waiting FJ threads.  (This representation relies on
159	<	* ForkJoinPool max thread limits). Completion of a stolen task
160	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
161	<	* though suboptimal for some purposes, we use basic builtin
162	<	* wait/notify to take advantage of "monitor inflation" in JVMs
163	<	* that we would otherwise need to emulate to avoid adding further
144	<	* per-task bookkeeping overhead. Note that bits 16-28 are
145	<	* currently unused. Also value 0x80000000 is available as spare
146	<	* completion value.
154	>	* completed, upon which status holds value COMPLETED. CANCELLED,
155	>	* or EXCEPTIONAL. Tasks undergoing blocking waits by other
156	>	* threads have the SIGNAL bit set.  Completion of a stolen task
157	>	* with SIGNAL set awakens any waiters via notifyAll. Even though
158	>	* suboptimal for some purposes, we use basic builtin wait/notify
159	>	* to take advantage of "monitor inflation" in JVMs that we would
160	>	* otherwise need to emulate to avoid adding further per-task
161	>	* bookkeeping overhead.  We want these monitors to be "fat",
162	>	* i.e., not use biasing or thin-lock techniques, so use some odd
163	>	* coding idioms that tend to avoid them.
164		*/
165		volatile int status; // accessed directly by pool and workers
166
167	<	static final int COMPLETION_MASK      = 0xe0000000;
168	<	static final int NORMAL               = 0xe0000000; // == mask
169	<	static final int CANCELLED            = 0xc0000000;
170	<	static final int EXCEPTIONAL          = 0xa0000000;
154	<	static final int SIGNAL_MASK          = 0x0000ffff;
155	<	static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
156	<	static final int EXTERNAL_SIGNAL      = 0x00008000; // top bit of low word
167	>	private static final int NORMAL      = -1;
168	>	private static final int CANCELLED   = -2;
169	>	private static final int EXCEPTIONAL = -3;
170	>	private static final int SIGNAL      =  1;
171
172		/**
173		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 167 | Line 181 | public abstract class ForkJoinTask<V> im
181		Collections.synchronizedMap
182		(new WeakHashMap<ForkJoinTask<?>, Throwable>());
183
184	<	// within-package utilities
171	<
172	<	/**
173	<	* Gets current worker thread, or null if not a worker thread.
174	<	*/
175	<	static ForkJoinWorkerThread getWorker() {
176	<	Thread t = Thread.currentThread();
177	<	return ((t instanceof ForkJoinWorkerThread) ?
178	<	(ForkJoinWorkerThread) t : null);
179	<	}
180	<
181	<	final boolean casStatus(int cmp, int val) {
182	<	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
183	<	}
184	<
185	<	/**
186	<	* Workaround for not being able to rethrow unchecked exceptions.
187	<	*/
188	<	static void rethrowException(Throwable ex) {
189	<	if (ex != null)
190	<	UNSAFE.throwException(ex);
191	<	}
192	<
193	<	// Setting completion status
184	>	// Maintaining completion status
185
186		/**
187	<	* Marks completion and wakes up threads waiting to join this task.
187	>	* Marks completion and wakes up threads waiting to join this task,
188	>	* also clearing signal request bits.
189		*
190		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
191	+	* @return status on exit
192		*/
193	<	final void setCompletion(int completion) {
201	<	ForkJoinPool pool = getPool();
202	<	if (pool != null) {
203	<	int s; // Clear signal bits while setting completion status
204	<	do {} while ((s = status) >= 0 && !casStatus(s, completion));
205	<
206	<	if ((s & SIGNAL_MASK) != 0) {
207	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
208	<	pool.updateRunningCount(s);
209	<	synchronized (this) { notifyAll(); }
210	<	}
211	<	}
212	<	else
213	<	externallySetCompletion(completion);
214	<	}
215	<
216	<	/**
217	<	* Version of setCompletion for non-FJ threads.  Leaves signal
218	<	* bits for unblocked threads to adjust, and always notifies.
219	<	*/
220	<	private void externallySetCompletion(int completion) {
193	>	private int setCompletion(int completion) {
194		int s;
195	<	do {} while ((s = status) >= 0 &&
196	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
197	<	synchronized (this) { notifyAll(); }
198	<	}
199	<
227	<	/**
228	<	* Sets status to indicate normal completion.
229	<	*/
230	<	final void setNormalCompletion() {
231	<	// Try typical fast case -- single CAS, no signal, not already done.
232	<	// Manually expand casStatus to improve chances of inlining it
233	<	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
234	<	setCompletion(NORMAL);
235	<	}
236	<
237	<	// internal waiting and notification
238	<
239	<	/**
240	<	* Performs the actual monitor wait for awaitDone.
241	<	*/
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	<	}
252	<
253	<	/**
254	<	* Performs the actual timed monitor wait for awaitDone.
255	<	*/
256	<	private void doAwaitDone(long startTime, long nanos) {
257	<	synchronized (this) {
258	<	try {
259	<	while (status >= 0) {
260	<	long nt = nanos - (System.nanoTime() - startTime);
261	<	if (nt <= 0)
262	<	break;
263	<	wait(nt / 1000000, (int) (nt % 1000000));
264	<	}
265	<	} catch (InterruptedException ie) {
266	<	onInterruptedWait();
195	>	while ((s = status) >= 0) {
196	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
197	>	if (s == SIGNAL)
198	>	synchronized (this) { notifyAll(); }
199	>	return completion;
200		}
201		}
202	+	return s;
203		}
204
271	–	// Awaiting completion
272	–
205		/**
206	<	* Sets status to indicate there is joiner, then waits for join,
207	<	* surrounded with pool notifications.
276	<	*
277	<	* @return status upon exit
206	>	* Record exception and set exceptional completion
207	>	* @return status on exit
208		*/
209	<	private int awaitDone(ForkJoinWorkerThread w,
210	<	boolean maintainParallelism) {
211	<	ForkJoinPool pool = (w == null) ? null : w.pool;
282	<	int s;
283	<	while ((s = status) >= 0) {
284	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
285	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
286	<	doAwaitDone();
287	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
288	<	adjustPoolCountsOnUnblock(pool);
289	<	break;
290	<	}
291	<	}
292	<	return s;
209	>	private int setExceptionalCompletion(Throwable rex) {
210	>	exceptionMap.put(this, rex);
211	>	return setCompletion(EXCEPTIONAL);
212		}
213
214		/**
215	<	* Timed version of awaitDone
297	<	*
298	<	* @return status upon exit
215	>	* Blocks a worker thread until completion. Called only by pool.
216		*/
217	<	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
301	<	ForkJoinPool pool = (w == null) ? null : w.pool;
217	>	final int internalAwaitDone() {
218		int s;
219		while ((s = status) >= 0) {
220	<	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
221	<	long startTime = System.nanoTime();
222	<	if (pool == null || !pool.preJoin(this, false))
223	<	doAwaitDone(startTime, nanos);
224	<	if ((s = status) >= 0) {
225	<	adjustPoolCountsOnCancelledWait(pool);
226	<	s = status;
220	>	synchronized(this) {
221	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
222	>	do {
223	>	try {
224	>	wait();
225	>	} catch (InterruptedException ie) {
226	>	cancelIfTerminating();
227	>	}
228	>	} while ((s = status) >= 0);
229	>	break;
230		}
312	–	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
313	–	adjustPoolCountsOnUnblock(pool);
314	–	break;
231		}
232		}
233		return s;
234		}
235
236		/**
237	<	* Notifies pool that thread is unblocked. Called by signalled
238	<	* threads when woken by non-FJ threads (which is atypical).
237	>	* Blocks a non-worker-thread until completion.
238	>	* @return status on exit
239		*/
240	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
240	>	private int externalAwaitDone() {
241		int s;
242	<	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
243	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
244	<	pool.updateRunningCount(s);
245	<	}
246	<
247	<	/**
248	<	* Notifies pool to adjust counts on cancelled or timed out wait.
249	<	*/
250	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
251	<	if (pool != null) {
252	<	int s;
253	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
254	<	if (casStatus(s, s - 1)) {
339	<	pool.updateRunningCount(1);
242	>	while ((s = status) >= 0) {
243	>	synchronized(this) {
244	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
245	>	boolean interrupted = false;
246	>	do {
247	>	try {
248	>	wait();
249	>	} catch (InterruptedException ie) {
250	>	interrupted = true;
251	>	}
252	>	} while ((s = status) >= 0);
253	>	if (interrupted)
254	>	Thread.currentThread().interrupt();
255		break;
256		}
257		}
258		}
259	+	return s;
260		}
261
262		/**
263	<	* Handles interruptions during waits.
264	<	*/
265	<	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	<	}
364	<
365	<	/**
366	<	* Throws the exception associated with status s.
367	<	*
368	<	* @throws the exception
263	>	* Unless done, calls exec and records status if completed, but
264	>	* doesn't wait for completion otherwise. Primary execution method
265	>	* for ForkJoinWorkerThread.
266		*/
267	<	private void reportException(int s) {
268	<	if ((s &= COMPLETION_MASK) < NORMAL) {
269	<	if (s == CANCELLED)
270	<	throw new CancellationException();
271	<	else
272	<	rethrowException(exceptionMap.get(this));
267	>	final void tryExec() {
268	>	try {
269	>	if (status < 0 || !exec())
270	>	return;
271	>	} catch (Throwable rex) {
272	>	setExceptionalCompletion(rex);
273	>	return;
274		}
275	+	setCompletion(NORMAL); // must be outside try block
276		}
277
278		/**
279	<	* Returns result or throws exception using j.u.c.Future conventions.
280	<	* Only call when {@code isDone} known to be true.
279	>	* If not done and this task is next in worker queue, runs it,
280	>	* else waits for it.
281	>	* @return status on exit
282		*/
283	<	private V reportFutureResult()
284	<	throws ExecutionException, InterruptedException {
285	<	int s = status & COMPLETION_MASK;
286	<	if (s < NORMAL) {
287	<	Throwable ex;
288	<	if (s == CANCELLED)
289	<	throw new CancellationException();
290	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
291	<	throw new ExecutionException(ex);
292	<	if (Thread.interrupted())
293	<	throw new InterruptedException();
294	<	}
295	<	return getRawResult();
296	<	}
297	<
298	<	/**
299	<	* Returns result or throws exception using j.u.c.Future conventions
300	<	* with timeouts.
301	<	*/
402	<	private V reportTimedFutureResult()
403	<	throws InterruptedException, ExecutionException, TimeoutException {
404	<	Throwable ex;
405	<	int s = status & COMPLETION_MASK;
406	<	if (s == NORMAL)
407	<	return getRawResult();
408	<	if (s == CANCELLED)
409	<	throw new CancellationException();
410	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
411	<	throw new ExecutionException(ex);
412	<	if (Thread.interrupted())
413	<	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
283	>	private int doJoin() {
284	>	int stat;
285	>	if ((stat = status) < 0)
286	>	return stat;
287	>	Thread t = Thread.currentThread();
288	>	ForkJoinWorkerThread w;
289	>	if (t instanceof ForkJoinWorkerThread) {
290	>	if ((w = (ForkJoinWorkerThread) t).unpushTask(this)) {
291	>	boolean completed;
292	>	try {
293	>	completed = exec();
294	>	} catch (Throwable rex) {
295	>	return setExceptionalCompletion(rex);
296	>	}
297	>	if (completed)
298	>	return setCompletion(NORMAL);
299	>	}
300	>	w.joinTask(this);
301	>	return status;
302		}
303	<	setNormalCompletion();
435	<	return true;
303	>	return externalAwaitDone();
304		}
305
306		/**
307	<	* Main execution method used by worker threads. Invokes
308	<	* base computation unless already complete.
307	>	* Unless done, calls exec and records status if completed, or
308	>	* waits for completion otherwise.
309	>	* @return status on exit
310		*/
311	<	final void quietlyExec() {
312	<	if (status >= 0) {
311	>	private int doInvoke() {
312	>	int stat;
313	>	if ((stat = status) >= 0) {
314	>	boolean completed;
315		try {
316	<	if (!exec())
446	<	return;
316	>	completed = exec();
317		} catch (Throwable rex) {
318	<	setDoneExceptionally(rex);
449	<	return;
318	>	return setExceptionalCompletion(rex);
319		}
320	<	setNormalCompletion();
321	<	}
322	<	}
323	<
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) {
320	>	if (completed)
321	>	stat = setCompletion(NORMAL);
322	>	else
323	>	stat = doJoin();
324		}
325	+	return stat;
326		}
327
328		/**
329	<	* Main implementation of helpJoin
329	>	* Returns result or throws exception associated with given status.
330	>	* @param s the status
331		*/
332	<	private int busyJoin(ForkJoinWorkerThread w) {
333	<	int s;
334	<	ForkJoinTask<?> t;
335	<	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
336	<	t.quietlyExec();
491	<	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
332	>	private V reportResult(int s) {
333	>	Throwable ex;
334	>	if (s < NORMAL && (ex = getException()) != null)
335	>	UNSAFE.throwException(ex);
336	>	return getRawResult();
337		}
338
339		// public methods
#	Line 497 | Line 342 | public abstract class ForkJoinTask<V> im
342		* Arranges to asynchronously execute this task.  While it is not
343		* necessarily enforced, it is a usage error to fork a task more
344		* than once unless it has completed and been reinitialized.
345	+	* Subsequent modifications to the state of this task or any data
346	+	* it operates on are not necessarily consistently observable by
347	+	* any thread other than the one executing it unless preceded by a
348	+	* call to {@link #join} or related methods, or a call to {@link
349	+	* #isDone} returning {@code true}.
350		*
351		* <p>This method may be invoked only from within {@code
352		* ForkJoinTask} computations (as may be determined using method
#	Line 513 | Line 363 | public abstract class ForkJoinTask<V> im
363		}
364
365		/**
366	<	* Returns the result of the computation when it is ready.
366	>	* Returns the result of the computation when it {@link #isDone is done}.
367		* This method differs from {@link #get()} in that
368		* abnormal completion results in {@code RuntimeException} or
369		* {@code Error}, not {@code ExecutionException}.
#	Line 521 | Line 371 | public abstract class ForkJoinTask<V> im
371		* @return the computed result
372		*/
373		public final V join() {
374	<	ForkJoinWorkerThread w = getWorker();
525	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
526	<	reportException(awaitDone(w, true));
527	<	return getRawResult();
374	>	return reportResult(doJoin());
375		}
376
377		/**
378		* Commences performing this task, awaits its completion if
379	<	* necessary, and return its result.
379	>	* necessary, and return its result, or throws an (unchecked)
380	>	* exception if the underlying computation did so.
381		*
534	–	* @throws Throwable (a RuntimeException, Error, or unchecked
535	–	* exception) if the underlying computation did so
382		* @return the computed result
383		*/
384		public final V invoke() {
385	<	if (status >= 0 && tryExec())
540	<	return getRawResult();
541	<	else
542	<	return join();
385	>	return reportResult(doInvoke());
386		}
387
388		/**
389	<	* Forks the given tasks, returning when {@code isDone} holds
390	<	* for each task or an exception is encountered.
389	>	* Forks the given tasks, returning when {@code isDone} holds for
390	>	* each task or an (unchecked) exception is encountered, in which
391	>	* case the exception is rethrown.  If either task encounters an
392	>	* exception, the other one may be, but is not guaranteed to be,
393	>	* cancelled.  If both tasks throw an exception, then this method
394	>	* throws one of them.  The individual status of each task may be
395	>	* checked using {@link #getException()} and related methods.
396		*
397		* <p>This method may be invoked only from within {@code
398		* ForkJoinTask} computations (as may be determined using method
#	Line 555 | Line 403 | public abstract class ForkJoinTask<V> im
403		* @param t1 the first task
404		* @param t2 the second task
405		* @throws NullPointerException if any task is null
558	–	* @throws RuntimeException or Error if a task did so
406		*/
407		public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
408		t2.fork();
#	Line 565 | Line 412 | public abstract class ForkJoinTask<V> im
412
413		/**
414		* Forks the given tasks, returning when {@code isDone} holds for
415	<	* each task or an exception is encountered. If any task
416	<	* encounters an exception, others may be, but are not guaranteed
417	<	* to be, cancelled.
415	>	* each task or an (unchecked) exception is encountered, in which
416	>	* case the exception is rethrown. If any task encounters an
417	>	* exception, others may be, but are not guaranteed to be,
418	>	* cancelled.  If more than one task encounters an exception, then
419	>	* this method throws any one of these exceptions.  The individual
420	>	* status of each task may be checked using {@link #getException()}
421	>	* and related methods.
422		*
423		* <p>This method may be invoked only from within {@code
424		* ForkJoinTask} computations (as may be determined using method
#	Line 576 | Line 427 | public abstract class ForkJoinTask<V> im
427		* ClassCastException}.
428		*
429		* @param tasks the tasks
430	<	* @throws NullPointerException if tasks or any element are null
580	<	* @throws RuntimeException or Error if any task did so
430	>	* @throws NullPointerException if any task is null
431		*/
432		public static void invokeAll(ForkJoinTask<?>... tasks) {
433		Throwable ex = null;
#	Line 590 | Line 440 | public abstract class ForkJoinTask<V> im
440		}
441		else if (i != 0)
442		t.fork();
443	<	else {
444	<	t.quietlyInvoke();
595	<	if (ex == null)
596	<	ex = t.getException();
597	<	}
443	>	else if (t.doInvoke() < NORMAL && ex == null)
444	>	ex = t.getException();
445		}
446		for (int i = 1; i <= last; ++i) {
447		ForkJoinTask<?> t = tasks[i];
448		if (t != null) {
449		if (ex != null)
450		t.cancel(false);
451	<	else {
452	<	t.quietlyJoin();
606	<	if (ex == null)
607	<	ex = t.getException();
608	<	}
451	>	else if (t.doJoin() < NORMAL && ex == null)
452	>	ex = t.getException();
453		}
454		}
455		if (ex != null)
456	<	rethrowException(ex);
456	>	UNSAFE.throwException(ex);
457		}
458
459		/**
460		* Forks all tasks in the specified collection, returning when
461	<	* {@code isDone} holds for each task or an exception is
462	<	* encountered.  If any task encounters an exception, others may
463	<	* be, but are not guaranteed to be, cancelled. The behavior of
464	<	* this operation is undefined if the specified collection is
465	<	* modified while the operation is in progress.
461	>	* {@code isDone} holds for each task or an (unchecked) exception
462	>	* is encountered.  If any task encounters an exception, others
463	>	* may be, but are not guaranteed to be, cancelled.  If more than
464	>	* one task encounters an exception, then this method throws any
465	>	* one of these exceptions.  The individual status of each task
466	>	* may be checked using {@link #getException()} and related
467	>	* methods.  The behavior of this operation is undefined if the
468	>	* specified collection is modified while the operation is in
469	>	* progress.
470		*
471		* <p>This method may be invoked only from within {@code
472		* ForkJoinTask} computations (as may be determined using method
#	Line 629 | Line 477 | public abstract class ForkJoinTask<V> im
477		* @param tasks the collection of tasks
478		* @return the tasks argument, to simplify usage
479		* @throws NullPointerException if tasks or any element are null
632	–	* @throws RuntimeException or Error if any task did so
480		*/
481		public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
482		if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
#	Line 649 | Line 496 | public abstract class ForkJoinTask<V> im
496		}
497		else if (i != 0)
498		t.fork();
499	<	else {
500	<	t.quietlyInvoke();
654	<	if (ex == null)
655	<	ex = t.getException();
656	<	}
499	>	else if (t.doInvoke() < NORMAL && ex == null)
500	>	ex = t.getException();
501		}
502		for (int i = 1; i <= last; ++i) {
503		ForkJoinTask<?> t = ts.get(i);
504		if (t != null) {
505		if (ex != null)
506		t.cancel(false);
507	<	else {
508	<	t.quietlyJoin();
665	<	if (ex == null)
666	<	ex = t.getException();
667	<	}
507	>	else if (t.doJoin() < NORMAL && ex == null)
508	>	ex = t.getException();
509		}
510		}
511		if (ex != null)
512	<	rethrowException(ex);
512	>	UNSAFE.throwException(ex);
513		return tasks;
514		}
515
516		/**
676	–	* Returns {@code true} if the computation performed by this task
677	–	* has completed (or has been cancelled).
678	–	*
679	–	* @return {@code true} if this computation has completed
680	–	*/
681	–	public final boolean isDone() {
682	–	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	–	/**
517		* Attempts to cancel execution of this task. This attempt will
518		* fail if the task has already completed, has already been
519		* cancelled, or could not be cancelled for some other reason. If
#	Line 717 | Line 539 | public abstract class ForkJoinTask<V> im
539		*/
540		public boolean cancel(boolean mayInterruptIfRunning) {
541		setCompletion(CANCELLED);
542	<	return (status & COMPLETION_MASK) == CANCELLED;
542	>	return status == CANCELLED;
543	>	}
544	>
545	>	/**
546	>	* Cancels, ignoring any exceptions it throws. Used during worker
547	>	* and pool shutdown.
548	>	*/
549	>	final void cancelIgnoringExceptions() {
550	>	try {
551	>	cancel(false);
552	>	} catch (Throwable ignore) {
553	>	}
554	>	}
555	>
556	>	/**
557	>	* Cancels ignoring exceptions if worker is terminating
558	>	*/
559	>	private void cancelIfTerminating() {
560	>	Thread t = Thread.currentThread();
561	>	if ((t instanceof ForkJoinWorkerThread) &&
562	>	((ForkJoinWorkerThread) t).isTerminating()) {
563	>	try {
564	>	cancel(false);
565	>	} catch (Throwable ignore) {
566	>	}
567	>	}
568	>	}
569	>
570	>	public final boolean isDone() {
571	>	return status < 0;
572	>	}
573	>
574	>	public final boolean isCancelled() {
575	>	return status == CANCELLED;
576		}
577
578		/**
#	Line 726 | Line 581 | public abstract class ForkJoinTask<V> im
581		* @return {@code true} if this task threw an exception or was cancelled
582		*/
583		public final boolean isCompletedAbnormally() {
584	<	return (status & COMPLETION_MASK) < NORMAL;
584	>	return status < NORMAL;
585	>	}
586	>
587	>	/**
588	>	* Returns {@code true} if this task completed without throwing an
589	>	* exception and was not cancelled.
590	>	*
591	>	* @return {@code true} if this task completed without throwing an
592	>	* exception and was not cancelled
593	>	*/
594	>	public final boolean isCompletedNormally() {
595	>	return status == NORMAL;
596		}
597
598		/**
#	Line 737 | Line 603 | public abstract class ForkJoinTask<V> im
603		* @return the exception, or {@code null} if none
604		*/
605		public final Throwable getException() {
606	<	int s = status & COMPLETION_MASK;
607	<	if (s >= NORMAL)
608	<	return null;
609	<	if (s == CANCELLED)
744	<	return new CancellationException();
745	<	return exceptionMap.get(this);
606	>	int s = status;
607	>	return ((s >= NORMAL)    ? null :
608	>	(s == CANCELLED) ? new CancellationException() :
609	>	exceptionMap.get(this));
610		}
611
612		/**
#	Line 755 | Line 619 | public abstract class ForkJoinTask<V> im
619		* overridable, but overridden versions must invoke {@code super}
620		* implementation to maintain guarantees.
621		*
622	<	* @param ex the exception to throw. If this exception is
623	<	* not a RuntimeException or Error, the actual exception thrown
624	<	* will be a RuntimeException with cause ex.
622	>	* @param ex the exception to throw. If this exception is not a
623	>	* {@code RuntimeException} or {@code Error}, the actual exception
624	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
625		*/
626		public void completeExceptionally(Throwable ex) {
627	<	setDoneExceptionally((ex instanceof RuntimeException) ||
628	<	(ex instanceof Error) ? ex :
629	<	new RuntimeException(ex));
627	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
628	>	(ex instanceof Error) ? ex :
629	>	new RuntimeException(ex));
630		}
631
632		/**
#	Line 781 | Line 645 | public abstract class ForkJoinTask<V> im
645		try {
646		setRawResult(value);
647		} catch (Throwable rex) {
648	<	setDoneExceptionally(rex);
648	>	setExceptionalCompletion(rex);
649		return;
650		}
651	<	setNormalCompletion();
651	>	setCompletion(NORMAL);
652		}
653
654		public final V get() throws InterruptedException, ExecutionException {
655	<	ForkJoinWorkerThread w = getWorker();
656	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
657	<	awaitDone(w, true);
658	<	return reportFutureResult();
655	>	int s = doJoin();
656	>	if (Thread.interrupted())
657	>	throw new InterruptedException();
658	>	if (s < NORMAL) {
659	>	Throwable ex;
660	>	if (s == CANCELLED)
661	>	throw new CancellationException();
662	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
663	>	throw new ExecutionException(ex);
664	>	}
665	>	return getRawResult();
666		}
667
668		public final V get(long timeout, TimeUnit unit)
669		throws InterruptedException, ExecutionException, TimeoutException {
670	<	long nanos = unit.toNanos(timeout);
671	<	ForkJoinWorkerThread w = getWorker();
672	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
673	<	awaitDone(w, nanos);
674	<	return reportTimedFutureResult();
675	<	}
676	<
806	<	/**
807	<	* Possibly executes other tasks until this task is ready, then
808	<	* returns the result of the computation.  This method may be more
809	<	* efficient than {@code join}, but is only applicable when
810	<	* there are no potential dependencies between continuation of the
811	<	* current task and that of any other task that might be executed
812	<	* while helping. (This usually holds for pure divide-and-conquer
813	<	* tasks).
814	<	*
815	<	* <p>This method may be invoked only from within {@code
816	<	* ForkJoinTask} computations (as may be determined using method
817	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
818	<	* result in exceptions or errors, possibly including {@code
819	<	* ClassCastException}.
820	<	*
821	<	* @return the computed result
822	<	*/
823	<	public final V helpJoin() {
824	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
825	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
826	<	reportException(busyJoin(w));
827	<	return getRawResult();
828	<	}
829	<
830	<	/**
831	<	* Possibly executes other tasks until this task is ready.  This
832	<	* method may be useful when processing collections of tasks when
833	<	* some have been cancelled or otherwise known to have aborted.
834	<	*
835	<	* <p>This method may be invoked only from within {@code
836	<	* ForkJoinTask} computations (as may be determined using method
837	<	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
838	<	* result in exceptions or errors, possibly including {@code
839	<	* ClassCastException}.
840	<	*/
841	<	public final void quietlyHelpJoin() {
842	<	if (status >= 0) {
843	<	ForkJoinWorkerThread w =
844	<	(ForkJoinWorkerThread) Thread.currentThread();
845	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
846	<	busyJoin(w);
670	>	Thread t = Thread.currentThread();
671	>	ForkJoinPool pool;
672	>	if (t instanceof ForkJoinWorkerThread) {
673	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
674	>	if (status >= 0 && w.unpushTask(this))
675	>	tryExec();
676	>	pool = w.pool;
677		}
678	+	else
679	+	pool = null;
680	+	/*
681	+	* Timed wait loop intermixes cases for fj (pool != null) and
682	+	* non FJ threads. For FJ, decrement pool count but don't try
683	+	* for replacement; increment count on completion. For non-FJ,
684	+	* deal with interrupts. This is messy, but a little less so
685	+	* than is splitting the FJ and nonFJ cases.
686	+	*/
687	+	boolean interrupted = false;
688	+	boolean dec = false; // true if pool count decremented
689	+	for (;;) {
690	+	if (Thread.interrupted() && pool == null) {
691	+	interrupted = true;
692	+	break;
693	+	}
694	+	int s = status;
695	+	if (s < 0)
696	+	break;
697	+	if (UNSAFE.compareAndSwapInt(this, statusOffset,
698	+	s, s | SIGNAL)) {
699	+	long startTime = System.nanoTime();
700	+	long nanos = unit.toNanos(timeout);
701	+	long nt; // wait time
702	+	while (status >= 0 &&
703	+	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
704	+	if (pool != null && !dec)
705	+	dec = pool.tryDecrementRunningCount();
706	+	else {
707	+	long ms = nt / 1000000;
708	+	int ns = (int) (nt % 1000000);
709	+	try {
710	+	synchronized(this) {
711	+	if (status >= 0)
712	+	wait(ms, ns);
713	+	}
714	+	} catch (InterruptedException ie) {
715	+	if (pool != null)
716	+	cancelIfTerminating();
717	+	else {
718	+	interrupted = true;
719	+	break;
720	+	}
721	+	}
722	+	}
723	+	}
724	+	break;
725	+	}
726	+	}
727	+	if (pool != null && dec)
728	+	pool.incrementRunningCount();
729	+	if (interrupted)
730	+	throw new InterruptedException();
731	+	int es = status;
732	+	if (es != NORMAL) {
733	+	Throwable ex;
734	+	if (es == CANCELLED)
735	+	throw new CancellationException();
736	+	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
737	+	throw new ExecutionException(ex);
738	+	throw new TimeoutException();
739	+	}
740	+	return getRawResult();
741		}
742
743		/**
#	Line 854 | Line 747 | public abstract class ForkJoinTask<V> im
747		* known to have aborted.
748		*/
749		public final void quietlyJoin() {
750	<	if (status >= 0) {
858	<	ForkJoinWorkerThread w = getWorker();
859	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
860	<	awaitDone(w, true);
861	<	}
750	>	doJoin();
751		}
752
753		/**
#	Line 869 | Line 758 | public abstract class ForkJoinTask<V> im
758		* known to have aborted.
759		*/
760		public final void quietlyInvoke() {
761	<	if (status >= 0 && !tryQuietlyInvoke())
873	<	quietlyJoin();
761	>	doInvoke();
762		}
763
764		/**
#	Line 902 | Line 790 | public abstract class ForkJoinTask<V> im
790		* pre-constructed trees of subtasks in loops.
791		*/
792		public void reinitialize() {
793	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
793	>	if (status == EXCEPTIONAL)
794		exceptionMap.remove(this);
795		status = 0;
796		}
#	Line 1022 | Line 910 | public abstract class ForkJoinTask<V> im
910		* called otherwise. The return value controls whether this task
911		* is considered to be done normally. It may return false in
912		* asynchronous actions that require explicit invocations of
913	<	* {@link #complete} to become joinable. It may throw exceptions
914	<	* to indicate abnormal exit.
913	>	* {@link #complete} to become joinable. It may also throw an
914	>	* (unchecked) exception to indicate abnormal exit.
915		*
916		* @return {@code true} if completed normally
1029	–	* @throws Error or RuntimeException if encountered during computation
917		*/
918		protected abstract boolean exec();
919
#	Line 1193 | Line 1080 | public abstract class ForkJoinTask<V> im
1080		private static final long serialVersionUID = -7721805057305804111L;
1081
1082		/**
1083	<	* Save the state to a stream.
1083	>	* Saves the state to a stream.
1084		*
1085		* @serialData the current run status and the exception thrown
1086		* during execution, or {@code null} if none
#	Line 1206 | Line 1093 | public abstract class ForkJoinTask<V> im
1093		}
1094
1095		/**
1096	<	* Reconstitute the instance from a stream.
1096	>	* Reconstitutes the instance from a stream.
1097		*
1098		* @param s the stream
1099		*/
1100		private void readObject(java.io.ObjectInputStream s)
1101		throws java.io.IOException, ClassNotFoundException {
1102		s.defaultReadObject();
1216	–	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1217	–	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1103		Object ex = s.readObject();
1104		if (ex != null)
1105	<	setDoneExceptionally((Throwable) ex);
1105	>	setExceptionalCompletion((Throwable) ex);
1106	>	if (status < 0)
1107	>	synchronized (this) { notifyAll(); }
1108		}
1109
1110		// Unsafe mechanics

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