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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.78 by jsr166, Fri Jun 3 14:20:43 2011 UTC vs.
Revision 1.89 by dl, Mon Apr 9 13:11:44 2012 UTC

#	Line 8 | Line 8 | package jsr166y;
8
9		import java.io.Serializable;
10		import java.util.Collection;
11	–	import java.util.Collections;
11		import java.util.List;
12		import java.util.RandomAccess;
14	–	import java.util.Map;
13		import java.lang.ref.WeakReference;
14		import java.lang.ref.ReferenceQueue;
15		import java.util.concurrent.Callable;
16		import java.util.concurrent.CancellationException;
17		import java.util.concurrent.ExecutionException;
20	–	import java.util.concurrent.Executor;
21	–	import java.util.concurrent.ExecutorService;
18		import java.util.concurrent.Future;
19		import java.util.concurrent.RejectedExecutionException;
20		import java.util.concurrent.RunnableFuture;
#	Line 47 | Line 43 | import java.lang.reflect.Constructor;
43		* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
44		* The efficiency of {@code ForkJoinTask}s stems from a set of
45		* restrictions (that are only partially statically enforceable)
46	<	* reflecting their intended use as computational tasks calculating
47	<	* pure functions or operating on purely isolated objects.  The
48	<	* primary coordination mechanisms are {@link #fork}, that arranges
46	>	* reflecting their main use as computational tasks calculating pure
47	>	* functions or operating on purely isolated objects.  The primary
48	>	* coordination mechanisms are {@link #fork}, that arranges
49		* asynchronous execution, and {@link #join}, that doesn't proceed
50		* until the task's result has been computed.  Computations should
51	<	* avoid {@code synchronized} methods or blocks, and should minimize
52	<	* other blocking synchronization apart from joining other tasks or
53	<	* using synchronizers such as Phasers that are advertised to
54	<	* cooperate with fork/join scheduling. Tasks should also not perform
55	<	* blocking IO, and should ideally access variables that are
56	<	* completely independent of those accessed by other running
57	<	* tasks. Minor breaches of these restrictions, for example using
58	<	* shared output streams, may be tolerable in practice, but frequent
59	<	* use may result in poor performance, and the potential to
60	<	* indefinitely stall if the number of threads not waiting for IO or
61	<	* other external synchronization becomes exhausted. This usage
62	<	* restriction is in part enforced by not permitting checked
63	<	* exceptions such as {@code IOExceptions} to be thrown. However,
64	<	* computations may still encounter unchecked exceptions, that are
65	<	* rethrown to callers attempting to join them. These exceptions may
66	<	* additionally include {@link RejectedExecutionException} stemming
67	<	* from internal resource exhaustion, such as failure to allocate
68	<	* internal task queues. Rethrown exceptions behave in the same way as
69	<	* regular exceptions, but, when possible, contain stack traces (as
70	<	* displayed for example using {@code ex.printStackTrace()}) of both
71	<	* the thread that initiated the computation as well as the thread
72	<	* actually encountering the exception; minimally only the latter.
51	>	* ideally avoid {@code synchronized} methods or blocks, and should
52	>	* minimize other blocking synchronization apart from joining other
53	>	* tasks or using synchronizers such as Phasers that are advertised to
54	>	* cooperate with fork/join scheduling. Subdividable tasks should also
55	>	* not perform blocking IO, and should ideally access variables that
56	>	* are completely independent of those accessed by other running
57	>	* tasks. These guidelines are loosely enforced by not permitting
58	>	* checked exceptions such as {@code IOExceptions} to be
59	>	* thrown. However, computations may still encounter unchecked
60	>	* exceptions, that are rethrown to callers attempting to join
61	>	* them. These exceptions may additionally include {@link
62	>	* RejectedExecutionException} stemming from internal resource
63	>	* exhaustion, such as failure to allocate internal task
64	>	* queues. Rethrown exceptions behave in the same way as regular
65	>	* exceptions, but, when possible, contain stack traces (as displayed
66	>	* for example using {@code ex.printStackTrace()}) of both the thread
67	>	* that initiated the computation as well as the thread actually
68	>	* encountering the exception; minimally only the latter.
69	>	*
70	>	* <p>It is possible to define and use ForkJoinTasks that may block,
71	>	* but doing do requires three further considerations: (1) Completion
72	>	* of few if any <em>other</em> tasks should be dependent on a task
73	>	* that blocks on external synchronization or IO. Event-style async
74	>	* tasks that are never joined often fall into this category.  (2) To
75	>	* minimize resource impact, tasks should be small; ideally performing
76	>	* only the (possibly) blocking action. (3) Unless the {@link
77	>	* ForkJoinPool.ManagedBlocker} API is used, or the number of possibly
78	>	* blocked tasks is known to be less than the pool's {@link
79	>	* ForkJoinPool#getParallelism} level, the pool cannot guarantee that
80	>	* enough threads will be available to ensure progress or good
81	>	* performance.
82		*
83		* <p>The primary method for awaiting completion and extracting
84		* results of a task is {@link #join}, but there are several variants:
#	Line 89 | Line 94 | import java.lang.reflect.Constructor;
94		* performs the most common form of parallel invocation: forking a set
95		* of tasks and joining them all.
96		*
97	+	* <p>In the most typical usages, a fork-join pair act like a call
98	+	* (fork) and return (join) from a parallel recursive function. As is
99	+	* the case with other forms of recursive calls, returns (joins)
100	+	* should be performed innermost-first. For example, {@code a.fork();
101	+	* b.fork(); b.join(); a.join();} is likely to be substantially more
102	+	* efficient than joining {@code a} before {@code b}.
103	+	*
104		* <p>The execution status of tasks may be queried at several levels
105		* of detail: {@link #isDone} is true if a task completed in any way
106		* (including the case where a task was cancelled without executing);
#	Line 104 | Line 116 | import java.lang.reflect.Constructor;
116		* <p>The ForkJoinTask class is not usually directly subclassed.
117		* Instead, you subclass one of the abstract classes that support a
118		* particular style of fork/join processing, typically {@link
119	<	* RecursiveAction} for computations that do not return results, or
120	<	* {@link RecursiveTask} for those that do.  Normally, a concrete
121	<	* ForkJoinTask subclass declares fields comprising its parameters,
122	<	* established in a constructor, and then defines a {@code compute}
123	<	* method that somehow uses the control methods supplied by this base
124	<	* class. While these methods have {@code public} access (to allow
125	<	* instances of different task subclasses to call each other's
126	<	* methods), some of them may only be called from within other
127	<	* ForkJoinTasks (as may be determined using method {@link
128	<	* #inForkJoinPool}).  Attempts to invoke them in other contexts
129	<	* result in exceptions or errors, possibly including
130	<	* {@code ClassCastException}.
119	>	* RecursiveAction} for most computations that do not return results,
120	>	* {@link RecursiveTask} for those that do, and {@link
121	>	* CountedCompleter} for those in which completed actions trigger
122	>	* other actions.  Normally, a concrete ForkJoinTask subclass declares
123	>	* fields comprising its parameters, established in a constructor, and
124	>	* then defines a {@code compute} method that somehow uses the control
125	>	* methods supplied by this base class. While these methods have
126	>	* {@code public} access (to allow instances of different task
127	>	* subclasses to call each other's methods), some of them may only be
128	>	* called from within other ForkJoinTasks (as may be determined using
129	>	* method {@link #inForkJoinPool}).  Attempts to invoke them in other
130	>	* contexts result in exceptions or errors, possibly including {@code
131	>	* ClassCastException}.
132		*
133		* <p>Method {@link #join} and its variants are appropriate for use
134		* only when completion dependencies are acyclic; that is, the
#	Line 125 | Line 138 | import java.lang.reflect.Constructor;
138		* supports other methods and techniques (for example the use of
139		* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that
140		* may be of use in constructing custom subclasses for problems that
141	<	* are not statically structured as DAGs.
141	>	* are not statically structured as DAGs. To support such usages a
142	>	* ForkJoinTask may be atomically <em>tagged</em> with a {@code
143	>	* short} value using {@link #setForkJoinTaskTag} or {@link
144	>	* #compareAndSetForkJoinTaskTag} and checked using {@link
145	>	* #getForkJoinTaskTag}. The ForkJoinTask implementation does not
146	>	* use these {@code protected} methods or tags for any purpose, but
147	>	* they may be of use in the construction of specialized subclasses.
148	>	* For example, parallel graph traversals can use the supplied methods
149	>	* to avoid revisiting nodes/tasks that have already been processed.
150	>	* Also, completion based designs can use them to record that subtasks
151	>	* have completed. (Method names for tagging are bulky in part to
152	>	* encourage definition of methods that reflect their usage patterns.)
153		*
154		* <p>Most base support methods are {@code final}, to prevent
155		* overriding of implementations that are intrinsically tied to the
#	Line 165 | Line 189 | public abstract class ForkJoinTask<V> im
189		* See the internal documentation of class ForkJoinPool for a
190		* general implementation overview.  ForkJoinTasks are mainly
191		* responsible for maintaining their "status" field amidst relays
192	<	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
193	<	* methods of this class are more-or-less layered into (1) basic
194	<	* status maintenance (2) execution and awaiting completion (3)
195	<	* user-level methods that additionally report results. This is
196	<	* sometimes hard to see because this file orders exported methods
197	<	* in a way that flows well in javadocs.
192	>	* to methods in ForkJoinWorkerThread and ForkJoinPool.
193	>	*
194	>	* The methods of this class are more-or-less layered into
195	>	* (1) basic status maintenance
196	>	* (2) execution and awaiting completion
197	>	* (3) user-level methods that additionally report results.
198	>	* This is sometimes hard to see because this file orders exported
199	>	* methods in a way that flows well in javadocs.
200		*/
201
202		/*
203		* The status field holds run control status bits packed into a
204		* single int to minimize footprint and to ensure atomicity (via
205		* CAS).  Status is initially zero, and takes on nonnegative
206	<	* values until completed, upon which status holds value
207	<	* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
208	<	* waits by other threads have the SIGNAL bit set.  Completion of
209	<	* a stolen task with SIGNAL set awakens any waiters via
210	<	* notifyAll. Even though suboptimal for some purposes, we use
211	<	* basic builtin wait/notify to take advantage of "monitor
212	<	* inflation" in JVMs that we would otherwise need to emulate to
213	<	* avoid adding further per-task bookkeeping overhead.  We want
214	<	* these monitors to be "fat", i.e., not use biasing or thin-lock
215	<	* techniques, so use some odd coding idioms that tend to avoid
216	<	* them.
206	>	* values until completed, upon which status (anded with
207	>	* DONE_MASK) holds value NORMAL, CANCELLED, or EXCEPTIONAL. Tasks
208	>	* undergoing blocking waits by other threads have the SIGNAL bit
209	>	* set.  Completion of a stolen task with SIGNAL set awakens any
210	>	* waiters via notifyAll. Even though suboptimal for some
211	>	* purposes, we use basic builtin wait/notify to take advantage of
212	>	* "monitor inflation" in JVMs that we would otherwise need to
213	>	* emulate to avoid adding further per-task bookkeeping overhead.
214	>	* We want these monitors to be "fat", i.e., not use biasing or
215	>	* thin-lock techniques, so use some odd coding idioms that tend
216	>	* to avoid them, mainly by arranging that every synchronized
217	>	* block performs a wait, notifyAll or both.
218	>	*
219	>	* These control bits occupy only (some of) the upper half (16
220	>	* bits) of status field. The lower bits are used for user-defined
221	>	* tags.
222		*/
223
224		/** The run status of this task */
225		volatile int status; // accessed directly by pool and workers
226	<	private static final int NORMAL      = -1;
227	<	private static final int CANCELLED   = -2;
228	<	private static final int EXCEPTIONAL = -3;
229	<	private static final int SIGNAL      =  1;
226	>	static final int DONE_MASK   = 0xf0000000;  // mask out non-completion bits
227	>	static final int NORMAL      = 0xf0000000;  // must be negative
228	>	static final int CANCELLED   = 0xc0000000;  // must be < NORMAL
229	>	static final int EXCEPTIONAL = 0x80000000;  // must be < CANCELLED
230	>	static final int SIGNAL      = 0x00010000;  // must be >= 1 << 16
231	>	static final int SMASK       = 0x0000ffff;  // short bits for tags
232
233		/**
234	<	* Marks completion and wakes up threads waiting to join this task,
235	<	* also clearing signal request bits.
234	>	* Marks completion and wakes up threads waiting to join this
235	>	* task.
236		*
237		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
238		* @return completion status on exit
#	Line 208 | Line 241 | public abstract class ForkJoinTask<V> im
241		for (int s;;) {
242		if ((s = status) < 0)
243		return s;
244	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
245	<	if (s != 0)
244	>	if (U.compareAndSwapInt(this, STATUS, s, s | completion)) {
245	>	if ((s >>> 16) != 0)
246		synchronized (this) { notifyAll(); }
247		return completion;
248		}
#	Line 217 | Line 250 | public abstract class ForkJoinTask<V> im
250		}
251
252		/**
253	<	* Tries to block a worker thread until completed or timed out.
254	<	* Uses Object.wait time argument conventions.
255	<	* May fail on contention or interrupt.
253	>	* Primary execution method for stolen tasks. Unless done, calls
254	>	* exec and records status if completed, but doesn't wait for
255	>	* completion otherwise.
256		*
257	<	* @param millis if > 0, wait time.
257	>	* @return status on exit from this method
258		*/
259	<	final void tryAwaitDone(long millis) {
260	<	int s;
261	<	try {
262	<	if (((s = status) > 0 ||
263	<	(s == 0 &&
264	<	UNSAFE.compareAndSwapInt(this, statusOffset, 0, SIGNAL))) &&
265	<	status > 0) {
233	<	synchronized (this) {
234	<	if (status > 0)
235	<	wait(millis);
236	<	}
259	>	final int doExec() {
260	>	int s; boolean completed;
261	>	if ((s = status) >= 0) {
262	>	try {
263	>	completed = exec();
264	>	} catch (Throwable rex) {
265	>	return setExceptionalCompletion(rex);
266		}
267	<	} catch (InterruptedException ie) {
268	<	// caller must check termination
267	>	if (completed)
268	>	s = setCompletion(NORMAL);
269		}
270	+	return s;
271	+	}
272	+
273	+	/**
274	+	* Tries to set SIGNAL status unless already completed. Used by
275	+	* ForkJoinPool. Other variants are directly incorporated into
276	+	* externalAwaitDone etc.
277	+	*
278	+	* @return true if successful
279	+	*/
280	+	final boolean trySetSignal() {
281	+	int s = status;
282	+	return s >= 0 && U.compareAndSwapInt(this, STATUS, s, s | SIGNAL);
283		}
284
285		/**
#	Line 245 | Line 287 | public abstract class ForkJoinTask<V> im
287		* @return status upon completion
288		*/
289		private int externalAwaitDone() {
290	+	boolean interrupted = false;
291		int s;
292	<	if ((s = status) >= 0) {
293	<	boolean interrupted = false;
294	<	synchronized (this) {
295	<	while ((s = status) >= 0) {
253	<	if (s == 0)
254	<	UNSAFE.compareAndSwapInt(this, statusOffset,
255	<	0, SIGNAL);
256	<	else {
292	>	while ((s = status) >= 0) {
293	>	if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
294	>	synchronized (this) {
295	>	if (status >= 0) {
296		try {
297		wait();
298		} catch (InterruptedException ie) {
299		interrupted = true;
300		}
301		}
302	+	else
303	+	notifyAll();
304		}
305		}
265	–	if (interrupted)
266	–	Thread.currentThread().interrupt();
306		}
307	+	if (interrupted)
308	+	Thread.currentThread().interrupt();
309		return s;
310		}
311
312		/**
313	<	* Blocks a non-worker-thread until completion or interruption or timeout.
313	>	* Blocks a non-worker-thread until completion or interruption.
314		*/
315	<	private int externalInterruptibleAwaitDone(long millis)
275	<	throws InterruptedException {
315	>	private int externalInterruptibleAwaitDone() throws InterruptedException {
316		int s;
317		if (Thread.interrupted())
318		throw new InterruptedException();
319	<	if ((s = status) >= 0) {
320	<	synchronized (this) {
321	<	while ((s = status) >= 0) {
322	<	if (s == 0)
323	<	UNSAFE.compareAndSwapInt(this, statusOffset,
324	<	0, SIGNAL);
325	<	else {
286	<	wait(millis);
287	<	if (millis > 0L)
288	<	break;
289	<	}
319	>	while ((s = status) >= 0) {
320	>	if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
321	>	synchronized (this) {
322	>	if (status >= 0)
323	>	wait();
324	>	else
325	>	notifyAll();
326		}
327		}
328		}
#	Line 294 | Line 330 | public abstract class ForkJoinTask<V> im
330		}
331
332		/**
333	<	* Primary execution method for stolen tasks. Unless done, calls
334	<	* exec and records status if completed, but doesn't wait for
335	<	* completion otherwise.
336	<	*/
301	<	final void doExec() {
302	<	if (status >= 0) {
303	<	boolean completed;
304	<	try {
305	<	completed = exec();
306	<	} catch (Throwable rex) {
307	<	setExceptionalCompletion(rex);
308	<	return;
309	<	}
310	<	if (completed)
311	<	setCompletion(NORMAL); // must be outside try block
312	<	}
313	<	}
314	<
315	<	/**
316	<	* Primary mechanics for join, get, quietlyJoin.
333	>	* Implementation for join, get, quietlyJoin. Directly handles
334	>	* only cases of already-completed, external wait, and
335	>	* unfork+exec.  Others are relayed to ForkJoinPool.awaitJoin.
336	>	*
337		* @return status upon completion
338		*/
339		private int doJoin() {
340	<	Thread t; ForkJoinWorkerThread w; int s; boolean completed;
341	<	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
342	<	if ((s = status) < 0)
343	<	return s;
344	<	if ((w = (ForkJoinWorkerThread)t).unpushTask(this)) {
345	<	try {
326	<	completed = exec();
327	<	} catch (Throwable rex) {
328	<	return setExceptionalCompletion(rex);
329	<	}
330	<	if (completed)
331	<	return setCompletion(NORMAL);
340	>	int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w;
341	>	if ((s = status) >= 0) {
342	>	if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) {
343	>	if (!(w = (wt = (ForkJoinWorkerThread)t).workQueue).
344	>	tryUnpush(this) || (s = doExec()) >= 0)
345	>	s = wt.pool.awaitJoin(w, this);
346		}
347	<	return w.joinTask(this);
347	>	else
348	>	s = externalAwaitDone();
349		}
350	<	else
336	<	return externalAwaitDone();
350	>	return s;
351		}
352
353		/**
354	<	* Primary mechanics for invoke, quietlyInvoke.
354	>	* Implementation for invoke, quietlyInvoke.
355	>	*
356		* @return status upon completion
357		*/
358		private int doInvoke() {
359	<	int s; boolean completed;
360	<	if ((s = status) < 0)
361	<	return s;
362	<	try {
363	<	completed = exec();
364	<	} catch (Throwable rex) {
365	<	return setExceptionalCompletion(rex);
359	>	int s; Thread t; ForkJoinWorkerThread wt;
360	>	if ((s = doExec()) >= 0) {
361	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
362	>	s = (wt = (ForkJoinWorkerThread)t).pool.awaitJoin(wt.workQueue,
363	>	this);
364	>	else
365	>	s = externalAwaitDone();
366		}
367	<	if (completed)
353	<	return setCompletion(NORMAL);
354	<	else
355	<	return doJoin();
367	>	return s;
368		}
369
370		// Exception table support
#	Line 387 | Line 399 | public abstract class ForkJoinTask<V> im
399		* any ForkJoinPool will call helpExpungeStaleExceptions when its
400		* pool becomes isQuiescent.
401		*/
402	<	static final class ExceptionNode extends WeakReference<ForkJoinTask<?>>{
402	>	static final class ExceptionNode extends WeakReference<ForkJoinTask<?>> {
403		final Throwable ex;
404		ExceptionNode next;
405		final long thrower;  // use id not ref to avoid weak cycles
#	Line 405 | Line 417 | public abstract class ForkJoinTask<V> im
417		* @return status on exit
418		*/
419		private int setExceptionalCompletion(Throwable ex) {
420	<	int h = System.identityHashCode(this);
421	<	final ReentrantLock lock = exceptionTableLock;
422	<	lock.lock();
423	<	try {
424	<	expungeStaleExceptions();
425	<	ExceptionNode[] t = exceptionTable;
426	<	int i = h & (t.length - 1);
427	<	for (ExceptionNode e = t[i]; ; e = e.next) {
428	<	if (e == null) {
429	<	t[i] = new ExceptionNode(this, ex, t[i]);
430	<	break;
420	>	int s;
421	>	if ((s = status) >= 0) {
422	>	int h = System.identityHashCode(this);
423	>	final ReentrantLock lock = exceptionTableLock;
424	>	lock.lock();
425	>	try {
426	>	expungeStaleExceptions();
427	>	ExceptionNode[] t = exceptionTable;
428	>	int i = h & (t.length - 1);
429	>	for (ExceptionNode e = t[i]; ; e = e.next) {
430	>	if (e == null) {
431	>	t[i] = new ExceptionNode(this, ex, t[i]);
432	>	break;
433	>	}
434	>	if (e.get() == this) // already present
435	>	break;
436		}
437	<	if (e.get() == this) // already present
438	<	break;
437	>	} finally {
438	>	lock.unlock();
439	>	}
440	>	s = setCompletion(EXCEPTIONAL);
441	>	}
442	>	ForkJoinTask<?> p = internalGetCompleter(); // propagate
443	>	if (p != null && p.status >= 0)
444	>	p.setExceptionalCompletion(ex);
445	>	return s;
446	>	}
447	>
448	>	/**
449	>	* Exception propagation support for tasks with completers.
450	>	*/
451	>	ForkJoinTask<?> internalGetCompleter() {
452	>	return null;
453	>	}
454	>
455	>	/**
456	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
457	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
458	>	* exceptions, but if it does anyway, we have no recourse during
459	>	* shutdown, so guard against this case.
460	>	*/
461	>	static final void cancelIgnoringExceptions(ForkJoinTask<?> t) {
462	>	if (t != null && t.status >= 0) {
463	>	try {
464	>	t.cancel(false);
465	>	} catch (Throwable ignore) {
466		}
423	–	} finally {
424	–	lock.unlock();
467		}
426	–	return setCompletion(EXCEPTIONAL);
468		}
469
470		/**
#	Line 472 | Line 513 | public abstract class ForkJoinTask<V> im
513		* @return the exception, or null if none
514		*/
515		private Throwable getThrowableException() {
516	<	if (status != EXCEPTIONAL)
516	>	if ((status & DONE_MASK) != EXCEPTIONAL)
517		return null;
518		int h = System.identityHashCode(this);
519		ExceptionNode e;
#	Line 490 | Line 531 | public abstract class ForkJoinTask<V> im
531		Throwable ex;
532		if (e == null || (ex = e.ex) == null)
533		return null;
534	<	if (e.thrower != Thread.currentThread().getId()) {
534	>	if (false && e.thrower != Thread.currentThread().getId()) {
535		Class<? extends Throwable> ec = ex.getClass();
536		try {
537		Constructor<?> noArgCtor = null;
#	Line 557 | Line 598 | public abstract class ForkJoinTask<V> im
598		}
599
600		/**
601	<	* Report the result of invoke or join; called only upon
561	<	* non-normal return of internal versions.
601	>	* Throws exception, if any, associated with the given status.
602		*/
603	<	private V reportResult() {
604	<	int s; Throwable ex;
605	<	if ((s = status) == CANCELLED)
606	<	throw new CancellationException();
607	<	if (s == EXCEPTIONAL && (ex = getThrowableException()) != null)
608	<	UNSAFE.throwException(ex);
569	<	return getRawResult();
603	>	private void reportException(int s) {
604	>	Throwable ex = ((s == CANCELLED) ?  new CancellationException() :
605	>	(s == EXCEPTIONAL) ? getThrowableException() :
606	>	null);
607	>	if (ex != null)
608	>	U.throwException(ex);
609		}
610
611		// public methods
#	Line 590 | Line 629 | public abstract class ForkJoinTask<V> im
629		* @return {@code this}, to simplify usage
630		*/
631		public final ForkJoinTask<V> fork() {
632	<	((ForkJoinWorkerThread) Thread.currentThread())
594	<	.pushTask(this);
632	>	((ForkJoinWorkerThread)Thread.currentThread()).workQueue.push(this);
633		return this;
634		}
635
#	Line 607 | Line 645 | public abstract class ForkJoinTask<V> im
645		* @return the computed result
646		*/
647		public final V join() {
648	<	if (doJoin() != NORMAL)
649	<	return reportResult();
650	<	else
651	<	return getRawResult();
648	>	int s;
649	>	if ((s = doJoin() & DONE_MASK) != NORMAL)
650	>	reportException(s);
651	>	return getRawResult();
652		}
653
654		/**
#	Line 622 | Line 660 | public abstract class ForkJoinTask<V> im
660		* @return the computed result
661		*/
662		public final V invoke() {
663	<	if (doInvoke() != NORMAL)
664	<	return reportResult();
665	<	else
666	<	return getRawResult();
663	>	int s;
664	>	if ((s = doInvoke() & DONE_MASK) != NORMAL)
665	>	reportException(s);
666	>	return getRawResult();
667		}
668
669		/**
#	Line 652 | Line 690 | public abstract class ForkJoinTask<V> im
690		* @throws NullPointerException if any task is null
691		*/
692		public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
693	+	int s1, s2;
694		t2.fork();
695	<	t1.invoke();
696	<	t2.join();
695	>	if ((s1 = t1.doInvoke() & DONE_MASK) != NORMAL)
696	>	t1.reportException(s1);
697	>	if ((s2 = t2.doJoin() & DONE_MASK) != NORMAL)
698	>	t2.reportException(s2);
699		}
700
701		/**
#	Line 697 | Line 738 | public abstract class ForkJoinTask<V> im
738		if (t != null) {
739		if (ex != null)
740		t.cancel(false);
741	<	else if (t.doJoin() < NORMAL && ex == null)
741	>	else if (t.doJoin() < NORMAL)
742		ex = t.getException();
743		}
744		}
745		if (ex != null)
746	<	UNSAFE.throwException(ex);
746	>	U.throwException(ex);
747		}
748
749		/**
#	Line 754 | Line 795 | public abstract class ForkJoinTask<V> im
795		if (t != null) {
796		if (ex != null)
797		t.cancel(false);
798	<	else if (t.doJoin() < NORMAL && ex == null)
798	>	else if (t.doJoin() < NORMAL)
799		ex = t.getException();
800		}
801		}
802		if (ex != null)
803	<	UNSAFE.throwException(ex);
803	>	U.throwException(ex);
804		return tasks;
805		}
806
#	Line 791 | Line 832 | public abstract class ForkJoinTask<V> im
832		* @return {@code true} if this task is now cancelled
833		*/
834		public boolean cancel(boolean mayInterruptIfRunning) {
835	<	return setCompletion(CANCELLED) == CANCELLED;
795	<	}
796	<
797	<	/**
798	<	* Cancels, ignoring any exceptions thrown by cancel. Used during
799	<	* worker and pool shutdown. Cancel is spec'ed not to throw any
800	<	* exceptions, but if it does anyway, we have no recourse during
801	<	* shutdown, so guard against this case.
802	<	*/
803	<	final void cancelIgnoringExceptions() {
804	<	try {
805	<	cancel(false);
806	<	} catch (Throwable ignore) {
807	<	}
835	>	return (setCompletion(CANCELLED) & DONE_MASK) == CANCELLED;
836		}
837
838		public final boolean isDone() {
#	Line 812 | Line 840 | public abstract class ForkJoinTask<V> im
840		}
841
842		public final boolean isCancelled() {
843	<	return status == CANCELLED;
843	>	return (status & DONE_MASK) == CANCELLED;
844		}
845
846		/**
#	Line 832 | Line 860 | public abstract class ForkJoinTask<V> im
860		* exception and was not cancelled
861		*/
862		public final boolean isCompletedNormally() {
863	<	return status == NORMAL;
863	>	return (status & DONE_MASK) == NORMAL;
864		}
865
866		/**
#	Line 843 | Line 871 | public abstract class ForkJoinTask<V> im
871		* @return the exception, or {@code null} if none
872		*/
873		public final Throwable getException() {
874	<	int s = status;
874	>	int s = status & DONE_MASK;
875		return ((s >= NORMAL)    ? null :
876		(s == CANCELLED) ? new CancellationException() :
877		getThrowableException());
#	Line 893 | Line 921 | public abstract class ForkJoinTask<V> im
921		}
922
923		/**
924	+	* Completes this task normally without setting a value. The most
925	+	* recent value established by {@link #setRawResult} (or {@code
926	+	* null} by default) will be returned as the result of subsequent
927	+	* invocations of {@code join} and related operations.
928	+	*
929	+	* @since 1.8
930	+	*/
931	+	public final void quietlyComplete() {
932	+	setCompletion(NORMAL);
933	+	}
934	+
935	+	/**
936		* Waits if necessary for the computation to complete, and then
937		* retrieves its result.
938		*
#	Line 905 | Line 945 | public abstract class ForkJoinTask<V> im
945		*/
946		public final V get() throws InterruptedException, ExecutionException {
947		int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ?
948	<	doJoin() : externalInterruptibleAwaitDone(0L);
948	>	doJoin() : externalInterruptibleAwaitDone();
949		Throwable ex;
950	<	if (s == CANCELLED)
950	>	if ((s &= DONE_MASK) == CANCELLED)
951		throw new CancellationException();
952		if (s == EXCEPTIONAL && (ex = getThrowableException()) != null)
953		throw new ExecutionException(ex);
#	Line 930 | Line 970 | public abstract class ForkJoinTask<V> im
970		*/
971		public final V get(long timeout, TimeUnit unit)
972		throws InterruptedException, ExecutionException, TimeoutException {
973	<	Thread t = Thread.currentThread();
974	<	if (t instanceof ForkJoinWorkerThread) {
975	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
976	<	long nanos = unit.toNanos(timeout);
977	<	if (status >= 0) {
978	<	boolean completed = false;
979	<	if (w.unpushTask(this)) {
980	<	try {
981	<	completed = exec();
982	<	} catch (Throwable rex) {
983	<	setExceptionalCompletion(rex);
973	>	if (Thread.interrupted())
974	>	throw new InterruptedException();
975	>	// Messy in part because we measure in nanosecs, but wait in millisecs
976	>	int s; long ns, ms;
977	>	if ((s = status) >= 0 && (ns = unit.toNanos(timeout)) > 0L) {
978	>	long deadline = System.nanoTime() + ns;
979	>	ForkJoinPool p = null;
980	>	ForkJoinPool.WorkQueue w = null;
981	>	Thread t = Thread.currentThread();
982	>	if (t instanceof ForkJoinWorkerThread) {
983	>	ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
984	>	p = wt.pool;
985	>	w = wt.workQueue;
986	>	s = p.helpJoinOnce(w, this); // no retries on failure
987	>	}
988	>	boolean canBlock = false;
989	>	boolean interrupted = false;
990	>	try {
991	>	while ((s = status) >= 0) {
992	>	if (w != null && w.runState < 0)
993	>	cancelIgnoringExceptions(this);
994	>	else if (!canBlock) {
995	>	if (p == null || p.tryCompensate(this, null))
996	>	canBlock = true;
997	>	}
998	>	else {
999	>	if ((ms = TimeUnit.NANOSECONDS.toMillis(ns)) > 0L &&
1000	>	U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
1001	>	synchronized (this) {
1002	>	if (status >= 0) {
1003	>	try {
1004	>	wait(ms);
1005	>	} catch (InterruptedException ie) {
1006	>	if (p == null)
1007	>	interrupted = true;
1008	>	}
1009	>	}
1010	>	else
1011	>	notifyAll();
1012	>	}
1013	>	}
1014	>	if ((s = status) < 0 || interrupted ||
1015	>	(ns = deadline - System.nanoTime()) <= 0L)
1016	>	break;
1017		}
1018		}
1019	<	if (completed)
1020	<	setCompletion(NORMAL);
1021	<	else if (status >= 0 && nanos > 0)
949	<	w.pool.timedAwaitJoin(this, nanos);
1019	>	} finally {
1020	>	if (p != null && canBlock)
1021	>	p.incrementActiveCount();
1022		}
1023	+	if (interrupted)
1024	+	throw new InterruptedException();
1025		}
1026	<	else {
953	<	long millis = unit.toMillis(timeout);
954	<	if (millis > 0)
955	<	externalInterruptibleAwaitDone(millis);
956	<	}
957	<	int s = status;
958	<	if (s != NORMAL) {
1026	>	if ((s &= DONE_MASK) != NORMAL) {
1027		Throwable ex;
1028		if (s == CANCELLED)
1029		throw new CancellationException();
#	Line 1000 | Line 1068 | public abstract class ForkJoinTask<V> im
1068		* ClassCastException}.
1069		*/
1070		public static void helpQuiesce() {
1071	<	((ForkJoinWorkerThread) Thread.currentThread())
1072	<	.helpQuiescePool();
1071	>	ForkJoinWorkerThread wt =
1072	>	(ForkJoinWorkerThread)Thread.currentThread();
1073	>	wt.pool.helpQuiescePool(wt.workQueue);
1074		}
1075
1076		/**
#	Line 1021 | Line 1090 | public abstract class ForkJoinTask<V> im
1090		* setRawResult(null)}.
1091		*/
1092		public void reinitialize() {
1093	<	if (status == EXCEPTIONAL)
1093	>	if ((status & DONE_MASK) == EXCEPTIONAL)
1094		clearExceptionalCompletion();
1095		else
1096		status = 0;
#	Line 1069 | Line 1138 | public abstract class ForkJoinTask<V> im
1138		* @return {@code true} if unforked
1139		*/
1140		public boolean tryUnfork() {
1141	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1142	<	.unpushTask(this);
1141	>	return ((ForkJoinWorkerThread)Thread.currentThread())
1142	>	.workQueue.tryUnpush(this);
1143		}
1144
1145		/**
#	Line 1089 | Line 1158 | public abstract class ForkJoinTask<V> im
1158		*/
1159		public static int getQueuedTaskCount() {
1160		return ((ForkJoinWorkerThread) Thread.currentThread())
1161	<	.getQueueSize();
1161	>	.workQueue.queueSize();
1162		}
1163
1164		/**
#	Line 1111 | Line 1180 | public abstract class ForkJoinTask<V> im
1180		* @return the surplus number of tasks, which may be negative
1181		*/
1182		public static int getSurplusQueuedTaskCount() {
1183	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1184	<	.getEstimatedSurplusTaskCount();
1183	>	/*
1184	>	* The aim of this method is to return a cheap heuristic guide
1185	>	* for task partitioning when programmers, frameworks, tools,
1186	>	* or languages have little or no idea about task granularity.
1187	>	* In essence by offering this method, we ask users only about
1188	>	* tradeoffs in overhead vs expected throughput and its
1189	>	* variance, rather than how finely to partition tasks.
1190	>	*
1191	>	* In a steady state strict (tree-structured) computation,
1192	>	* each thread makes available for stealing enough tasks for
1193	>	* other threads to remain active. Inductively, if all threads
1194	>	* play by the same rules, each thread should make available
1195	>	* only a constant number of tasks.
1196	>	*
1197	>	* The minimum useful constant is just 1. But using a value of
1198	>	* 1 would require immediate replenishment upon each steal to
1199	>	* maintain enough tasks, which is infeasible.  Further,
1200	>	* partitionings/granularities of offered tasks should
1201	>	* minimize steal rates, which in general means that threads
1202	>	* nearer the top of computation tree should generate more
1203	>	* than those nearer the bottom. In perfect steady state, each
1204	>	* thread is at approximately the same level of computation
1205	>	* tree. However, producing extra tasks amortizes the
1206	>	* uncertainty of progress and diffusion assumptions.
1207	>	*
1208	>	* So, users will want to use values larger, but not much
1209	>	* larger than 1 to both smooth over transient shortages and
1210	>	* hedge against uneven progress; as traded off against the
1211	>	* cost of extra task overhead. We leave the user to pick a
1212	>	* threshold value to compare with the results of this call to
1213	>	* guide decisions, but recommend values such as 3.
1214	>	*
1215	>	* When all threads are active, it is on average OK to
1216	>	* estimate surplus strictly locally. In steady-state, if one
1217	>	* thread is maintaining say 2 surplus tasks, then so are
1218	>	* others. So we can just use estimated queue length.
1219	>	* However, this strategy alone leads to serious mis-estimates
1220	>	* in some non-steady-state conditions (ramp-up, ramp-down,
1221	>	* other stalls). We can detect many of these by further
1222	>	* considering the number of "idle" threads, that are known to
1223	>	* have zero queued tasks, so compensate by a factor of
1224	>	* (#idle/#active) threads.
1225	>	*/
1226	>	ForkJoinWorkerThread wt =
1227	>	(ForkJoinWorkerThread)Thread.currentThread();
1228	>	return wt.workQueue.queueSize() - wt.pool.idlePerActive();
1229		}
1230
1231		// Extension methods
#	Line 1138 | Line 1251 | public abstract class ForkJoinTask<V> im
1251		protected abstract void setRawResult(V value);
1252
1253		/**
1254	<	* Immediately performs the base action of this task.  This method
1255	<	* is designed to support extensions, and should not in general be
1256	<	* called otherwise. The return value controls whether this task
1257	<	* is considered to be done normally. It may return false in
1254	>	* Immediately performs the base action of this task and returns
1255	>	* true if, upon return from this method, this task is guaranteed
1256	>	* to have completed normally. This method may return false
1257	>	* otherwise, to indicate that this task is not necessarily
1258	>	* complete (or is not known to be complete), for example in
1259		* asynchronous actions that require explicit invocations of
1260	<	* {@link #complete} to become joinable. It may also throw an
1261	<	* (unchecked) exception to indicate abnormal exit.
1260	>	* completion methods. This method may also throw an (unchecked)
1261	>	* exception to indicate abnormal exit. This method is designed to
1262	>	* support extensions, and should not in general be called
1263	>	* otherwise.
1264		*
1265	<	* @return {@code true} if completed normally
1265	>	* @return {@code true} if this task is known to have completed normally
1266		*/
1267		protected abstract boolean exec();
1268
#	Line 1169 | Line 1285 | public abstract class ForkJoinTask<V> im
1285		* @return the next task, or {@code null} if none are available
1286		*/
1287		protected static ForkJoinTask<?> peekNextLocalTask() {
1288	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1173	<	.peekTask();
1288	>	return ((ForkJoinWorkerThread) Thread.currentThread()).workQueue.peek();
1289		}
1290
1291		/**
#	Line 1189 | Line 1304 | public abstract class ForkJoinTask<V> im
1304		*/
1305		protected static ForkJoinTask<?> pollNextLocalTask() {
1306		return ((ForkJoinWorkerThread) Thread.currentThread())
1307	<	.pollLocalTask();
1307	>	.workQueue.nextLocalTask();
1308		}
1309
1310		/**
#	Line 1211 | Line 1326 | public abstract class ForkJoinTask<V> im
1326		* @return a task, or {@code null} if none are available
1327		*/
1328		protected static ForkJoinTask<?> pollTask() {
1329	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1330	<	.pollTask();
1329	>	ForkJoinWorkerThread wt =
1330	>	(ForkJoinWorkerThread)Thread.currentThread();
1331	>	return wt.pool.nextTaskFor(wt.workQueue);
1332	>	}
1333	>
1334	>	// tag operations
1335	>
1336	>	/**
1337	>	* Returns the tag for this task.
1338	>	*
1339	>	* @return the tag for this task
1340	>	* @since 1.8
1341	>	*/
1342	>	public final short getForkJoinTaskTag() {
1343	>	return (short)status;
1344	>	}
1345	>
1346	>	/**
1347	>	* Atomically sets the tag value for this task.
1348	>	*
1349	>	* @param tag the tag value
1350	>	* @return the previous value of the tag
1351	>	* @since 1.8
1352	>	*/
1353	>	public final short setForkJoinTaskTag(short tag) {
1354	>	for (int s;;) {
1355	>	if (U.compareAndSwapInt(this, STATUS, s = status,
1356	>	(s & ~SMASK) | (tag & SMASK)))
1357	>	return (short)s;
1358	>	}
1359	>	}
1360	>
1361	>	/**
1362	>	* Atomically conditionally sets the tag value for this task.
1363	>	* Among other applications, tags can be used as visit markers
1364	>	* in tasks operating on graphs, as in methods that check: {@code
1365	>	* if (task.compareAndSetForkJoinTaskTag((short)0, (short)1))}
1366	>	* before processing, otherwise exiting because the node has
1367	>	* already been visited.
1368	>	*
1369	>	* @param e the expected tag value
1370	>	* @param tag the new tag value
1371	>	* @return true if successful; i.e., the current value was
1372	>	* equal to e and is now tag.
1373	>	* @since 1.8
1374	>	*/
1375	>	public final boolean compareAndSetForkJoinTaskTag(short e, short tag) {
1376	>	for (int s;;) {
1377	>	if ((short)(s = status) != e)
1378	>	return false;
1379	>	if (U.compareAndSwapInt(this, STATUS, s,
1380	>	(s & ~SMASK) | (tag & SMASK)))
1381	>	return true;
1382	>	}
1383		}
1384
1385		/**
#	Line 1223 | Line 1390 | public abstract class ForkJoinTask<V> im
1390		static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1391		implements RunnableFuture<T> {
1392		final Runnable runnable;
1226	–	final T resultOnCompletion;
1393		T result;
1394		AdaptedRunnable(Runnable runnable, T result) {
1395		if (runnable == null) throw new NullPointerException();
1396		this.runnable = runnable;
1397	<	this.resultOnCompletion = result;
1397	>	this.result = result; // OK to set this even before completion
1398		}
1399	<	public T getRawResult() { return result; }
1400	<	public void setRawResult(T v) { result = v; }
1401	<	public boolean exec() {
1402	<	runnable.run();
1403	<	result = resultOnCompletion;
1404	<	return true;
1399	>	public final T getRawResult() { return result; }
1400	>	public final void setRawResult(T v) { result = v; }
1401	>	public final boolean exec() { runnable.run(); return true; }
1402	>	public final void run() { invoke(); }
1403	>	private static final long serialVersionUID = 5232453952276885070L;
1404	>	}
1405	>
1406	>	/**
1407	>	* Adaptor for Runnables without results
1408	>	*/
1409	>	static final class AdaptedRunnableAction extends ForkJoinTask<Void>
1410	>	implements RunnableFuture<Void> {
1411	>	final Runnable runnable;
1412	>	AdaptedRunnableAction(Runnable runnable) {
1413	>	if (runnable == null) throw new NullPointerException();
1414	>	this.runnable = runnable;
1415		}
1416	<	public void run() { invoke(); }
1416	>	public final Void getRawResult() { return null; }
1417	>	public final void setRawResult(Void v) { }
1418	>	public final boolean exec() { runnable.run(); return true; }
1419	>	public final void run() { invoke(); }
1420		private static final long serialVersionUID = 5232453952276885070L;
1421		}
1422
#	Line 1252 | Line 1431 | public abstract class ForkJoinTask<V> im
1431		if (callable == null) throw new NullPointerException();
1432		this.callable = callable;
1433		}
1434	<	public T getRawResult() { return result; }
1435	<	public void setRawResult(T v) { result = v; }
1436	<	public boolean exec() {
1434	>	public final T getRawResult() { return result; }
1435	>	public final void setRawResult(T v) { result = v; }
1436	>	public final boolean exec() {
1437		try {
1438		result = callable.call();
1439		return true;
#	Line 1266 | Line 1445 | public abstract class ForkJoinTask<V> im
1445		throw new RuntimeException(ex);
1446		}
1447		}
1448	<	public void run() { invoke(); }
1448	>	public final void run() { invoke(); }
1449		private static final long serialVersionUID = 2838392045355241008L;
1450		}
1451
#	Line 1279 | Line 1458 | public abstract class ForkJoinTask<V> im
1458		* @return the task
1459		*/
1460		public static ForkJoinTask<?> adapt(Runnable runnable) {
1461	<	return new AdaptedRunnable<Void>(runnable, null);
1461	>	return new AdaptedRunnableAction(runnable);
1462		}
1463
1464		/**
#	Line 1313 | Line 1492 | public abstract class ForkJoinTask<V> im
1492		private static final long serialVersionUID = -7721805057305804111L;
1493
1494		/**
1495	<	* Saves the state to a stream (that is, serializes it).
1495	>	* Saves this task to a stream (that is, serializes it).
1496		*
1497		* @serialData the current run status and the exception thrown
1498		* during execution, or {@code null} if none
1320	–	* @param s the stream
1499		*/
1500		private void writeObject(java.io.ObjectOutputStream s)
1501		throws java.io.IOException {
#	Line 1326 | Line 1504 | public abstract class ForkJoinTask<V> im
1504		}
1505
1506		/**
1507	<	* Reconstitutes the instance from a stream (that is, deserializes it).
1330	<	*
1331	<	* @param s the stream
1507	>	* Reconstitutes this task from a stream (that is, deserializes it).
1508		*/
1509		private void readObject(java.io.ObjectInputStream s)
1510		throws java.io.IOException, ClassNotFoundException {
#	Line 1339 | Line 1515 | public abstract class ForkJoinTask<V> im
1515		}
1516
1517		// Unsafe mechanics
1518	<	private static final sun.misc.Unsafe UNSAFE;
1519	<	private static final long statusOffset;
1518	>	private static final sun.misc.Unsafe U;
1519	>	private static final long STATUS;
1520		static {
1521		exceptionTableLock = new ReentrantLock();
1522		exceptionTableRefQueue = new ReferenceQueue<Object>();
1523		exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY];
1524		try {
1525	<	UNSAFE = getUnsafe();
1526	<	statusOffset = UNSAFE.objectFieldOffset
1525	>	U = getUnsafe();
1526	>	STATUS = U.objectFieldOffset
1527		(ForkJoinTask.class.getDeclaredField("status"));
1528		} catch (Exception e) {
1529		throw new Error(e);

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