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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.75 by dl, Tue Feb 22 10:50:51 2011 UTC vs.
Revision 1.87 by dl, Sun Mar 4 15:52:45 2012 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Doug Lea with assistance from members of JCP JSR-166
3		* Expert Group and released to the public domain, as explained at
4	<	* http://creativecommons.org/licenses/publicdomain
4	>	* http://creativecommons.org/publicdomain/zero/1.0/
5		*/
6
7		package jsr166y;
8	–
8		import java.io.Serializable;
9		import java.util.Collection;
11	–	import java.util.Collections;
10		import java.util.List;
11		import java.util.RandomAccess;
14	–	import java.util.Map;
12		import java.lang.ref.WeakReference;
13		import java.lang.ref.ReferenceQueue;
14		import java.util.concurrent.Callable;
15		import java.util.concurrent.CancellationException;
16		import java.util.concurrent.ExecutionException;
20	–	import java.util.concurrent.Executor;
21	–	import java.util.concurrent.ExecutorService;
17		import java.util.concurrent.Future;
18		import java.util.concurrent.RejectedExecutionException;
19		import java.util.concurrent.RunnableFuture;
#	Line 47 | Line 42 | import java.lang.reflect.Constructor;
42		* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
43		* The efficiency of {@code ForkJoinTask}s stems from a set of
44		* restrictions (that are only partially statically enforceable)
45	<	* reflecting their intended use as computational tasks calculating
46	<	* pure functions or operating on purely isolated objects.  The
47	<	* primary coordination mechanisms are {@link #fork}, that arranges
45	>	* reflecting their main use as computational tasks calculating pure
46	>	* functions or operating on purely isolated objects.  The primary
47	>	* coordination mechanisms are {@link #fork}, that arranges
48		* asynchronous execution, and {@link #join}, that doesn't proceed
49		* until the task's result has been computed.  Computations should
50	<	* avoid {@code synchronized} methods or blocks, and should minimize
51	<	* other blocking synchronization apart from joining other tasks or
52	<	* using synchronizers such as Phasers that are advertised to
53	<	* cooperate with fork/join scheduling. Tasks should also not perform
54	<	* blocking IO, and should ideally access variables that are
55	<	* completely independent of those accessed by other running
56	<	* tasks. Minor breaches of these restrictions, for example using
57	<	* shared output streams, may be tolerable in practice, but frequent
58	<	* use may result in poor performance, and the potential to
59	<	* indefinitely stall if the number of threads not waiting for IO or
60	<	* other external synchronization becomes exhausted. This usage
61	<	* restriction is in part enforced by not permitting checked
62	<	* exceptions such as {@code IOExceptions} to be thrown. However,
63	<	* computations may still encounter unchecked exceptions, that are
64	<	* rethrown to callers attempting to join them. These exceptions may
65	<	* additionally include {@link RejectedExecutionException} stemming
66	<	* from internal resource exhaustion, such as failure to allocate
67	<	* internal task queues. Rethrown exceptions behave in the same way as
68	<	* regular exceptions, but, when possible, contain stack traces (as
69	<	* displayed for example using {@code ex.printStackTrace()}) of both
70	<	* the thread that initiated the computation as well as the thread
71	<	* actually encountering the exception; minimally only the latter.
50	>	* ideally avoid {@code synchronized} methods or blocks, and should
51	>	* minimize other blocking synchronization apart from joining other
52	>	* tasks or using synchronizers such as Phasers that are advertised to
53	>	* cooperate with fork/join scheduling. Subdividable tasks should also
54	>	* not perform blocking IO, and should ideally access variables that
55	>	* are completely independent of those accessed by other running
56	>	* tasks. These guidelines are loosely enforced by not permitting
57	>	* checked exceptions such as {@code IOExceptions} to be
58	>	* thrown. However, computations may still encounter unchecked
59	>	* exceptions, that are rethrown to callers attempting to join
60	>	* them. These exceptions may additionally include {@link
61	>	* RejectedExecutionException} stemming from internal resource
62	>	* exhaustion, such as failure to allocate internal task
63	>	* queues. Rethrown exceptions behave in the same way as regular
64	>	* exceptions, but, when possible, contain stack traces (as displayed
65	>	* for example using {@code ex.printStackTrace()}) of both the thread
66	>	* that initiated the computation as well as the thread actually
67	>	* encountering the exception; minimally only the latter.
68	>	*
69	>	* <p>It is possible to define and use ForkJoinTasks that may block,
70	>	* but doing do requires three further considerations: (1) Completion
71	>	* of few if any <em>other</em> tasks should be dependent on a task
72	>	* that blocks on external synchronization or IO. Event-style async
73	>	* tasks that are never joined often fall into this category.  (2) To
74	>	* minimize resource impact, tasks should be small; ideally performing
75	>	* only the (possibly) blocking action. (3) Unless the {@link
76	>	* ForkJoinPool.ManagedBlocker} API is used, or the number of possibly
77	>	* blocked tasks is known to be less than the pool's {@link
78	>	* ForkJoinPool#getParallelism} level, the pool cannot guarantee that
79	>	* enough threads will be available to ensure progress or good
80	>	* performance.
81		*
82		* <p>The primary method for awaiting completion and extracting
83		* results of a task is {@link #join}, but there are several variants:
#	Line 89 | Line 93 | import java.lang.reflect.Constructor;
93		* performs the most common form of parallel invocation: forking a set
94		* of tasks and joining them all.
95		*
96	+	* <p>In the most typical usages, a fork-join pair act like a call
97	+	* (fork) and return (join) from a parallel recursive function. As is
98	+	* the case with other forms of recursive calls, returns (joins)
99	+	* should be performed innermost-first. For example, {@code a.fork();
100	+	* b.fork(); b.join(); a.join();} is likely to be substantially more
101	+	* efficient than joining {@code a} before {@code b}.
102	+	*
103		* <p>The execution status of tasks may be queried at several levels
104		* of detail: {@link #isDone} is true if a task completed in any way
105		* (including the case where a task was cancelled without executing);
#	Line 125 | Line 136 | import java.lang.reflect.Constructor;
136		* supports other methods and techniques (for example the use of
137		* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that
138		* may be of use in constructing custom subclasses for problems that
139	<	* are not statically structured as DAGs.
139	>	* are not statically structured as DAGs. To support such usages a
140	>	* ForkJoinTask may be atomically <em>tagged</em> with a {@code
141	>	* short} value using {@link #setForkJoinTaskTag} or {@link
142	>	* #compareAndSetForkJoinTaskTag} and checked using {@link
143	>	* #getForkJoinTaskTag}. The ForkJoinTask implementation does not
144	>	* use these {@code protected} methods or tags for any purpose, but
145	>	* they may be of use in the construction of specialized subclasses.
146	>	* For example, parallel graph traversals can use the supplied methods
147	>	* to avoid revisiting nodes/tasks that have already been processed.
148	>	* Also, completion based designs can use them to record that subtasks
149	>	* have completed. (Method names for tagging are bulky in part to
150	>	* encourage definition of methods that reflect their usage patterns.)
151		*
152		* <p>Most base support methods are {@code final}, to prevent
153		* overriding of implementations that are intrinsically tied to the
#	Line 165 | Line 187 | public abstract class ForkJoinTask<V> im
187		* See the internal documentation of class ForkJoinPool for a
188		* general implementation overview.  ForkJoinTasks are mainly
189		* responsible for maintaining their "status" field amidst relays
190	<	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
191	<	* methods of this class are more-or-less layered into (1) basic
192	<	* status maintenance (2) execution and awaiting completion (3)
193	<	* user-level methods that additionally report results. This is
194	<	* sometimes hard to see because this file orders exported methods
195	<	* in a way that flows well in javadocs.
190	>	* to methods in ForkJoinWorkerThread and ForkJoinPool.
191	>	*
192	>	* The methods of this class are more-or-less layered into
193	>	* (1) basic status maintenance
194	>	* (2) execution and awaiting completion
195	>	* (3) user-level methods that additionally report results.
196	>	* This is sometimes hard to see because this file orders exported
197	>	* methods in a way that flows well in javadocs.
198		*/
199
200		/*
201		* The status field holds run control status bits packed into a
202		* single int to minimize footprint and to ensure atomicity (via
203		* CAS).  Status is initially zero, and takes on nonnegative
204	<	* values until completed, upon which status holds value
205	<	* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
206	<	* waits by other threads have the SIGNAL bit set.  Completion of
207	<	* a stolen task with SIGNAL set awakens any waiters via
208	<	* notifyAll. Even though suboptimal for some purposes, we use
209	<	* basic builtin wait/notify to take advantage of "monitor
210	<	* inflation" in JVMs that we would otherwise need to emulate to
211	<	* avoid adding further per-task bookkeeping overhead.  We want
212	<	* these monitors to be "fat", i.e., not use biasing or thin-lock
213	<	* techniques, so use some odd coding idioms that tend to avoid
214	<	* them.
204	>	* values until completed, upon which status (anded with
205	>	* DONE_MASK) holds value NORMAL, CANCELLED, or EXCEPTIONAL. Tasks
206	>	* undergoing blocking waits by other threads have the SIGNAL bit
207	>	* set.  Completion of a stolen task with SIGNAL set awakens any
208	>	* waiters via notifyAll. Even though suboptimal for some
209	>	* purposes, we use basic builtin wait/notify to take advantage of
210	>	* "monitor inflation" in JVMs that we would otherwise need to
211	>	* emulate to avoid adding further per-task bookkeeping overhead.
212	>	* We want these monitors to be "fat", i.e., not use biasing or
213	>	* thin-lock techniques, so use some odd coding idioms that tend
214	>	* to avoid them, mainly by arranging that every synchronized
215	>	* block performs a wait, notifyAll or both.
216	>	*
217	>	* These control bits occupy only (some of) the upper half (16
218	>	* bits) of status field. The lower bits are used for user-defined
219	>	* tags.
220		*/
221
222		/** The run status of this task */
223		volatile int status; // accessed directly by pool and workers
224	<	private static final int NORMAL      = -1;
225	<	private static final int CANCELLED   = -2;
226	<	private static final int EXCEPTIONAL = -3;
227	<	private static final int SIGNAL      =  1;
224	>	static final int DONE_MASK   = 0xf0000000;  // mask out non-completion bits
225	>	static final int NORMAL      = 0xf0000000;  // must be negative
226	>	static final int CANCELLED   = 0xc0000000;  // must be < NORMAL
227	>	static final int EXCEPTIONAL = 0x80000000;  // must be < CANCELLED
228	>	static final int SIGNAL      = 0x00010000;  // must be >= 1 << 16
229	>	static final int SMASK       = 0x0000ffff;  // short bits for tags
230
231		/**
232	<	* Marks completion and wakes up threads waiting to join this task,
233	<	* also clearing signal request bits.
232	>	* Marks completion and wakes up threads waiting to join this
233	>	* task.
234		*
235		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
236		* @return completion status on exit
#	Line 208 | Line 239 | public abstract class ForkJoinTask<V> im
239		for (int s;;) {
240		if ((s = status) < 0)
241		return s;
242	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
243	<	if (s != 0)
242	>	if (U.compareAndSwapInt(this, STATUS, s, s | completion)) {
243	>	if ((s >>> 16) != 0)
244		synchronized (this) { notifyAll(); }
245		return completion;
246		}
#	Line 217 | Line 248 | public abstract class ForkJoinTask<V> im
248		}
249
250		/**
251	<	* Tries to block a worker thread until completed or timed out.
252	<	* Uses Object.wait time argument conventions.
253	<	* May fail on contention or interrupt.
251	>	* Primary execution method for stolen tasks. Unless done, calls
252	>	* exec and records status if completed, but doesn't wait for
253	>	* completion otherwise.
254		*
255	<	* @param millis if > 0, wait time.
255	>	* @return status on exit from this method
256		*/
257	<	final void tryAwaitDone(long millis) {
258	<	int s;
259	<	try {
260	<	if (((s = status) > 0 ||
261	<	(s == 0 &&
262	<	UNSAFE.compareAndSwapInt(this, statusOffset, 0, SIGNAL))) &&
263	<	status > 0) {
233	<	synchronized (this) {
234	<	if (status > 0)
235	<	wait(millis);
236	<	}
257	>	final int doExec() {
258	>	int s; boolean completed;
259	>	if ((s = status) >= 0) {
260	>	try {
261	>	completed = exec();
262	>	} catch (Throwable rex) {
263	>	return setExceptionalCompletion(rex);
264		}
265	<	} catch (InterruptedException ie) {
266	<	// caller must check termination
265	>	if (completed)
266	>	s = setCompletion(NORMAL);
267		}
268	+	return s;
269	+	}
270	+
271	+	/**
272	+	* Tries to set SIGNAL status. Used by ForkJoinPool. Other
273	+	* variants are directly incorporated into externalAwaitDone etc.
274	+	*
275	+	* @return true if successful
276	+	*/
277	+	final boolean trySetSignal() {
278	+	int s;
279	+	return U.compareAndSwapInt(this, STATUS, s = status, s | SIGNAL);
280		}
281
282		/**
#	Line 245 | Line 284 | public abstract class ForkJoinTask<V> im
284		* @return status upon completion
285		*/
286		private int externalAwaitDone() {
287	+	boolean interrupted = false;
288		int s;
289	<	if ((s = status) >= 0) {
290	<	boolean interrupted = false;
291	<	synchronized (this) {
292	<	while ((s = status) >= 0) {
253	<	if (s == 0)
254	<	UNSAFE.compareAndSwapInt(this, statusOffset,
255	<	0, SIGNAL);
256	<	else {
289	>	while ((s = status) >= 0) {
290	>	if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
291	>	synchronized (this) {
292	>	if (status >= 0) {
293		try {
294		wait();
295		} catch (InterruptedException ie) {
296		interrupted = true;
297		}
298		}
299	+	else
300	+	notifyAll();
301		}
302		}
265	–	if (interrupted)
266	–	Thread.currentThread().interrupt();
303		}
304	+	if (interrupted)
305	+	Thread.currentThread().interrupt();
306		return s;
307		}
308
309		/**
310	<	* Blocks a non-worker-thread until completion or interruption or timeout.
310	>	* Blocks a non-worker-thread until completion or interruption.
311		*/
312	<	private int externalInterruptibleAwaitDone(long millis)
275	<	throws InterruptedException {
312	>	private int externalInterruptibleAwaitDone() throws InterruptedException {
313		int s;
314		if (Thread.interrupted())
315		throw new InterruptedException();
316	<	if ((s = status) >= 0) {
317	<	synchronized (this) {
318	<	while ((s = status) >= 0) {
319	<	if (s == 0)
320	<	UNSAFE.compareAndSwapInt(this, statusOffset,
321	<	0, SIGNAL);
322	<	else {
286	<	wait(millis);
287	<	if (millis > 0L)
288	<	break;
289	<	}
316	>	while ((s = status) >= 0) {
317	>	if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
318	>	synchronized (this) {
319	>	if (status >= 0)
320	>	wait();
321	>	else
322	>	notifyAll();
323		}
324		}
325		}
#	Line 294 | Line 327 | public abstract class ForkJoinTask<V> im
327		}
328
329		/**
330	<	* Primary execution method for stolen tasks. Unless done, calls
331	<	* exec and records status if completed, but doesn't wait for
332	<	* completion otherwise.
333	<	*/
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.
330	>	* Implementation for join, get, quietlyJoin. Directly handles
331	>	* only cases of already-completed, external wait, and
332	>	* unfork+exec.  Others are relayed to ForkJoinPool.awaitJoin.
333	>	*
334		* @return status upon completion
335		*/
336		private int doJoin() {
337	<	Thread t; ForkJoinWorkerThread w; int s; boolean completed;
338	<	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
339	<	if ((s = status) < 0)
340	<	return s;
341	<	if ((w = (ForkJoinWorkerThread)t).unpushTask(this)) {
342	<	try {
326	<	completed = exec();
327	<	} catch (Throwable rex) {
328	<	return setExceptionalCompletion(rex);
329	<	}
330	<	if (completed)
331	<	return setCompletion(NORMAL);
337	>	int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w;
338	>	if ((s = status) >= 0) {
339	>	if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) {
340	>	if (!(w = (wt = (ForkJoinWorkerThread)t).workQueue).
341	>	tryUnpush(this) || (s = doExec()) >= 0)
342	>	s = wt.pool.awaitJoin(w, this);
343		}
344	<	return w.joinTask(this);
344	>	else
345	>	s = externalAwaitDone();
346		}
347	<	else
336	<	return externalAwaitDone();
347	>	return s;
348		}
349
350		/**
351	<	* Primary mechanics for invoke, quietlyInvoke.
351	>	* Implementation for invoke, quietlyInvoke.
352	>	*
353		* @return status upon completion
354		*/
355		private int doInvoke() {
356	<	int s; boolean completed;
357	<	if ((s = status) < 0)
358	<	return s;
359	<	try {
360	<	completed = exec();
361	<	} catch (Throwable rex) {
362	<	return setExceptionalCompletion(rex);
356	>	int s; Thread t; ForkJoinWorkerThread wt;
357	>	if ((s = doExec()) >= 0) {
358	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
359	>	s = (wt = (ForkJoinWorkerThread)t).pool.awaitJoin(wt.workQueue,
360	>	this);
361	>	else
362	>	s = externalAwaitDone();
363		}
364	<	if (completed)
353	<	return setCompletion(NORMAL);
354	<	else
355	<	return doJoin();
364	>	return s;
365		}
366
367		// Exception table support
#	Line 384 | Line 393 | public abstract class ForkJoinTask<V> im
393		* periods. However, since we do not know when the last joiner
394		* completes, we must use weak references and expunge them. We do
395		* so on each operation (hence full locking). Also, some thread in
396	<	* any ForkJoinPool will call helpExpunge when its pool becomes
397	<	* isQuiescent.
396	>	* any ForkJoinPool will call helpExpungeStaleExceptions when its
397	>	* pool becomes isQuiescent.
398		*/
399	<	static final class ExceptionNode extends WeakReference<ForkJoinTask<?>>{
399	>	static final class ExceptionNode extends WeakReference<ForkJoinTask<?>> {
400		final Throwable ex;
401		ExceptionNode next;
402	<	final long thrower;
402	>	final long thrower;  // use id not ref to avoid weak cycles
403		ExceptionNode(ForkJoinTask<?> task, Throwable ex, ExceptionNode next) {
404		super(task, exceptionTableRefQueue);
405		this.ex = ex;
#	Line 406 | Line 415 | public abstract class ForkJoinTask<V> im
415		*/
416		private int setExceptionalCompletion(Throwable ex) {
417		int h = System.identityHashCode(this);
418	<	ReentrantLock lock = exceptionTableLock;
418	>	final ReentrantLock lock = exceptionTableLock;
419		lock.lock();
420		try {
421		expungeStaleExceptions();
#	Line 427 | Line 436 | public abstract class ForkJoinTask<V> im
436		}
437
438		/**
439	+	* Cancels, ignoring any exceptions thrown by cancel. Used during
440	+	* worker and pool shutdown. Cancel is spec'ed not to throw any
441	+	* exceptions, but if it does anyway, we have no recourse during
442	+	* shutdown, so guard against this case.
443	+	*/
444	+	static final void cancelIgnoringExceptions(ForkJoinTask<?> t) {
445	+	if (t != null && t.status >= 0) {
446	+	try {
447	+	t.cancel(false);
448	+	} catch (Throwable ignore) {
449	+	}
450	+	}
451	+	}
452	+
453	+	/**
454		* Removes exception node and clears status
455		*/
456		private void clearExceptionalCompletion() {
457		int h = System.identityHashCode(this);
458	<	ReentrantLock lock = exceptionTableLock;
458	>	final ReentrantLock lock = exceptionTableLock;
459		lock.lock();
460		try {
461		ExceptionNode[] t = exceptionTable;
#	Line 472 | Line 496 | public abstract class ForkJoinTask<V> im
496		* @return the exception, or null if none
497		*/
498		private Throwable getThrowableException() {
499	<	if (status != EXCEPTIONAL)
499	>	if ((status & DONE_MASK) != EXCEPTIONAL)
500		return null;
501		int h = System.identityHashCode(this);
502		ExceptionNode e;
503	<	ReentrantLock lock = exceptionTableLock;
503	>	final ReentrantLock lock = exceptionTableLock;
504		lock.lock();
505		try {
506		expungeStaleExceptions();
#	Line 491 | Line 515 | public abstract class ForkJoinTask<V> im
515		if (e == null || (ex = e.ex) == null)
516		return null;
517		if (e.thrower != Thread.currentThread().getId()) {
518	<	Class ec = ex.getClass();
518	>	Class<? extends Throwable> ec = ex.getClass();
519		try {
520		Constructor<?> noArgCtor = null;
521		Constructor<?>[] cs = ec.getConstructors();// public ctors only
#	Line 542 | Line 566 | public abstract class ForkJoinTask<V> im
566		}
567
568		/**
569	<	* If lock is available, poll any stale refs and remove them.
569	>	* If lock is available, poll stale refs and remove them.
570		* Called from ForkJoinPool when pools become quiescent.
571		*/
572		static final void helpExpungeStaleExceptions() {
573	<	ReentrantLock lock = exceptionTableLock;
573	>	final ReentrantLock lock = exceptionTableLock;
574		if (lock.tryLock()) {
575		try {
576		expungeStaleExceptions();
#	Line 557 | Line 581 | public abstract class ForkJoinTask<V> im
581		}
582
583		/**
584	<	* Report the result of invoke or join; called only upon
561	<	* non-normal return of internal versions.
584	>	* Throws exception, if any, associated with the given status.
585		*/
586	<	private V reportResult() {
587	<	int s; Throwable ex;
588	<	if ((s = status) == CANCELLED)
589	<	throw new CancellationException();
590	<	if (s == EXCEPTIONAL && (ex = getThrowableException()) != null)
591	<	UNSAFE.throwException(ex);
569	<	return getRawResult();
586	>	private void reportException(int s) {
587	>	Throwable ex = ((s == CANCELLED) ?  new CancellationException() :
588	>	(s == EXCEPTIONAL) ? getThrowableException() :
589	>	null);
590	>	if (ex != null)
591	>	U.throwException(ex);
592		}
593
594		// public methods
#	Line 590 | Line 612 | public abstract class ForkJoinTask<V> im
612		* @return {@code this}, to simplify usage
613		*/
614		public final ForkJoinTask<V> fork() {
615	<	((ForkJoinWorkerThread) Thread.currentThread())
594	<	.pushTask(this);
615	>	((ForkJoinWorkerThread)Thread.currentThread()).workQueue.push(this);
616		return this;
617		}
618
#	Line 607 | Line 628 | public abstract class ForkJoinTask<V> im
628		* @return the computed result
629		*/
630		public final V join() {
631	<	if (doJoin() != NORMAL)
632	<	return reportResult();
633	<	else
634	<	return getRawResult();
631	>	int s;
632	>	if ((s = doJoin() & DONE_MASK) != NORMAL)
633	>	reportException(s);
634	>	return getRawResult();
635		}
636
637		/**
#	Line 622 | Line 643 | public abstract class ForkJoinTask<V> im
643		* @return the computed result
644		*/
645		public final V invoke() {
646	<	if (doInvoke() != NORMAL)
647	<	return reportResult();
648	<	else
649	<	return getRawResult();
646	>	int s;
647	>	if ((s = doInvoke() & DONE_MASK) != NORMAL)
648	>	reportException(s);
649	>	return getRawResult();
650		}
651
652		/**
#	Line 652 | Line 673 | public abstract class ForkJoinTask<V> im
673		* @throws NullPointerException if any task is null
674		*/
675		public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
676	+	int s1, s2;
677		t2.fork();
678	<	t1.invoke();
679	<	t2.join();
678	>	if ((s1 = t1.doInvoke() & DONE_MASK) != NORMAL)
679	>	t1.reportException(s1);
680	>	if ((s2 = t2.doJoin() & DONE_MASK) != NORMAL)
681	>	t2.reportException(s2);
682		}
683
684		/**
#	Line 697 | Line 721 | public abstract class ForkJoinTask<V> im
721		if (t != null) {
722		if (ex != null)
723		t.cancel(false);
724	<	else if (t.doJoin() < NORMAL && ex == null)
724	>	else if (t.doJoin() < NORMAL)
725		ex = t.getException();
726		}
727		}
728		if (ex != null)
729	<	UNSAFE.throwException(ex);
729	>	U.throwException(ex);
730		}
731
732		/**
#	Line 754 | Line 778 | public abstract class ForkJoinTask<V> im
778		if (t != null) {
779		if (ex != null)
780		t.cancel(false);
781	<	else if (t.doJoin() < NORMAL && ex == null)
781	>	else if (t.doJoin() < NORMAL)
782		ex = t.getException();
783		}
784		}
785		if (ex != null)
786	<	UNSAFE.throwException(ex);
786	>	U.throwException(ex);
787		return tasks;
788		}
789
#	Line 791 | Line 815 | public abstract class ForkJoinTask<V> im
815		* @return {@code true} if this task is now cancelled
816		*/
817		public boolean cancel(boolean mayInterruptIfRunning) {
818	<	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	<	}
818	>	return (setCompletion(CANCELLED) & DONE_MASK) == CANCELLED;
819		}
820
821		public final boolean isDone() {
#	Line 812 | Line 823 | public abstract class ForkJoinTask<V> im
823		}
824
825		public final boolean isCancelled() {
826	<	return status == CANCELLED;
826	>	return (status & DONE_MASK) == CANCELLED;
827		}
828
829		/**
#	Line 832 | Line 843 | public abstract class ForkJoinTask<V> im
843		* exception and was not cancelled
844		*/
845		public final boolean isCompletedNormally() {
846	<	return status == NORMAL;
846	>	return (status & DONE_MASK) == NORMAL;
847		}
848
849		/**
#	Line 843 | Line 854 | public abstract class ForkJoinTask<V> im
854		* @return the exception, or {@code null} if none
855		*/
856		public final Throwable getException() {
857	<	int s = status;
857	>	int s = status & DONE_MASK;
858		return ((s >= NORMAL)    ? null :
859		(s == CANCELLED) ? new CancellationException() :
860		getThrowableException());
#	Line 893 | Line 904 | public abstract class ForkJoinTask<V> im
904		}
905
906		/**
907	+	* Completes this task. The most recent value established by
908	+	* {@link #setRawResult} (or {@code null}) will be returned as the
909	+	* result of subsequent invocations of {@code join} and related
910	+	* operations. This method may be useful when processing sets of
911	+	* tasks when some do not otherwise complete normally. Its use in
912	+	* other situations is discouraged.
913	+	*/
914	+	public final void quietlyComplete() {
915	+	setCompletion(NORMAL);
916	+	}
917	+
918	+	/**
919		* Waits if necessary for the computation to complete, and then
920		* retrieves its result.
921		*
#	Line 905 | Line 928 | public abstract class ForkJoinTask<V> im
928		*/
929		public final V get() throws InterruptedException, ExecutionException {
930		int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ?
931	<	doJoin() : externalInterruptibleAwaitDone(0L);
931	>	doJoin() : externalInterruptibleAwaitDone();
932		Throwable ex;
933	<	if (s == CANCELLED)
933	>	if ((s &= DONE_MASK) == CANCELLED)
934		throw new CancellationException();
935		if (s == EXCEPTIONAL && (ex = getThrowableException()) != null)
936		throw new ExecutionException(ex);
#	Line 930 | Line 953 | public abstract class ForkJoinTask<V> im
953		*/
954		public final V get(long timeout, TimeUnit unit)
955		throws InterruptedException, ExecutionException, TimeoutException {
956	<	Thread t = Thread.currentThread();
957	<	if (t instanceof ForkJoinWorkerThread) {
958	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
959	<	long nanos = unit.toNanos(timeout);
960	<	if (status >= 0) {
961	<	boolean completed = false;
962	<	if (w.unpushTask(this)) {
963	<	try {
964	<	completed = exec();
965	<	} catch (Throwable rex) {
966	<	setExceptionalCompletion(rex);
956	>	if (Thread.interrupted())
957	>	throw new InterruptedException();
958	>	// Messy in part because we measure in nanosecs, but wait in millisecs
959	>	int s; long ns, ms;
960	>	if ((s = status) >= 0 && (ns = unit.toNanos(timeout)) > 0L) {
961	>	long deadline = System.nanoTime() + ns;
962	>	ForkJoinPool p = null;
963	>	ForkJoinPool.WorkQueue w = null;
964	>	Thread t = Thread.currentThread();
965	>	if (t instanceof ForkJoinWorkerThread) {
966	>	ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
967	>	p = wt.pool;
968	>	w = wt.workQueue;
969	>	s = p.helpJoinOnce(w, this); // no retries on failure
970	>	}
971	>	boolean canBlock = false;
972	>	boolean interrupted = false;
973	>	try {
974	>	while ((s = status) >= 0) {
975	>	if (w != null && w.runState < 0)
976	>	cancelIgnoringExceptions(this);
977	>	else if (!canBlock) {
978	>	if (p == null || p.tryCompensate(this, null))
979	>	canBlock = true;
980	>	}
981	>	else {
982	>	if ((ms = TimeUnit.NANOSECONDS.toMillis(ns)) > 0L &&
983	>	U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
984	>	synchronized (this) {
985	>	if (status >= 0) {
986	>	try {
987	>	wait(ms);
988	>	} catch (InterruptedException ie) {
989	>	if (p == null)
990	>	interrupted = true;
991	>	}
992	>	}
993	>	else
994	>	notifyAll();
995	>	}
996	>	}
997	>	if ((s = status) < 0 || interrupted ||
998	>	(ns = deadline - System.nanoTime()) <= 0L)
999	>	break;
1000		}
1001		}
1002	<	if (completed)
1003	<	setCompletion(NORMAL);
1004	<	else if (status >= 0 && nanos > 0)
949	<	w.pool.timedAwaitJoin(this, nanos);
1002	>	} finally {
1003	>	if (p != null && canBlock)
1004	>	p.incrementActiveCount();
1005		}
1006	+	if (interrupted)
1007	+	throw new InterruptedException();
1008		}
1009	<	else {
953	<	long millis = unit.toMillis(timeout);
954	<	if (millis > 0)
955	<	externalInterruptibleAwaitDone(millis);
956	<	}
957	<	int s = status;
958	<	if (s != NORMAL) {
1009	>	if ((s &= DONE_MASK) != NORMAL) {
1010		Throwable ex;
1011		if (s == CANCELLED)
1012		throw new CancellationException();
#	Line 1000 | Line 1051 | public abstract class ForkJoinTask<V> im
1051		* ClassCastException}.
1052		*/
1053		public static void helpQuiesce() {
1054	<	((ForkJoinWorkerThread) Thread.currentThread())
1055	<	.helpQuiescePool();
1054	>	ForkJoinWorkerThread wt =
1055	>	(ForkJoinWorkerThread)Thread.currentThread();
1056	>	wt.pool.helpQuiescePool(wt.workQueue);
1057		}
1058
1059		/**
#	Line 1021 | Line 1073 | public abstract class ForkJoinTask<V> im
1073		* setRawResult(null)}.
1074		*/
1075		public void reinitialize() {
1076	<	if (status == EXCEPTIONAL)
1076	>	if ((status & DONE_MASK) == EXCEPTIONAL)
1077		clearExceptionalCompletion();
1078		else
1079		status = 0;
#	Line 1069 | Line 1121 | public abstract class ForkJoinTask<V> im
1121		* @return {@code true} if unforked
1122		*/
1123		public boolean tryUnfork() {
1124	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1125	<	.unpushTask(this);
1124	>	return ((ForkJoinWorkerThread)Thread.currentThread())
1125	>	.workQueue.tryUnpush(this);
1126		}
1127
1128		/**
#	Line 1089 | Line 1141 | public abstract class ForkJoinTask<V> im
1141		*/
1142		public static int getQueuedTaskCount() {
1143		return ((ForkJoinWorkerThread) Thread.currentThread())
1144	<	.getQueueSize();
1144	>	.workQueue.queueSize();
1145		}
1146
1147		/**
#	Line 1111 | Line 1163 | public abstract class ForkJoinTask<V> im
1163		* @return the surplus number of tasks, which may be negative
1164		*/
1165		public static int getSurplusQueuedTaskCount() {
1166	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1167	<	.getEstimatedSurplusTaskCount();
1166	>	/*
1167	>	* The aim of this method is to return a cheap heuristic guide
1168	>	* for task partitioning when programmers, frameworks, tools,
1169	>	* or languages have little or no idea about task granularity.
1170	>	* In essence by offering this method, we ask users only about
1171	>	* tradeoffs in overhead vs expected throughput and its
1172	>	* variance, rather than how finely to partition tasks.
1173	>	*
1174	>	* In a steady state strict (tree-structured) computation,
1175	>	* each thread makes available for stealing enough tasks for
1176	>	* other threads to remain active. Inductively, if all threads
1177	>	* play by the same rules, each thread should make available
1178	>	* only a constant number of tasks.
1179	>	*
1180	>	* The minimum useful constant is just 1. But using a value of
1181	>	* 1 would require immediate replenishment upon each steal to
1182	>	* maintain enough tasks, which is infeasible.  Further,
1183	>	* partitionings/granularities of offered tasks should
1184	>	* minimize steal rates, which in general means that threads
1185	>	* nearer the top of computation tree should generate more
1186	>	* than those nearer the bottom. In perfect steady state, each
1187	>	* thread is at approximately the same level of computation
1188	>	* tree. However, producing extra tasks amortizes the
1189	>	* uncertainty of progress and diffusion assumptions.
1190	>	*
1191	>	* So, users will want to use values larger, but not much
1192	>	* larger than 1 to both smooth over transient shortages and
1193	>	* hedge against uneven progress; as traded off against the
1194	>	* cost of extra task overhead. We leave the user to pick a
1195	>	* threshold value to compare with the results of this call to
1196	>	* guide decisions, but recommend values such as 3.
1197	>	*
1198	>	* When all threads are active, it is on average OK to
1199	>	* estimate surplus strictly locally. In steady-state, if one
1200	>	* thread is maintaining say 2 surplus tasks, then so are
1201	>	* others. So we can just use estimated queue length.
1202	>	* However, this strategy alone leads to serious mis-estimates
1203	>	* in some non-steady-state conditions (ramp-up, ramp-down,
1204	>	* other stalls). We can detect many of these by further
1205	>	* considering the number of "idle" threads, that are known to
1206	>	* have zero queued tasks, so compensate by a factor of
1207	>	* (#idle/#active) threads.
1208	>	*/
1209	>	ForkJoinWorkerThread wt =
1210	>	(ForkJoinWorkerThread)Thread.currentThread();
1211	>	return wt.workQueue.queueSize() - wt.pool.idlePerActive();
1212		}
1213
1214		// Extension methods
#	Line 1169 | Line 1265 | public abstract class ForkJoinTask<V> im
1265		* @return the next task, or {@code null} if none are available
1266		*/
1267		protected static ForkJoinTask<?> peekNextLocalTask() {
1268	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1173	<	.peekTask();
1268	>	return ((ForkJoinWorkerThread) Thread.currentThread()).workQueue.peek();
1269		}
1270
1271		/**
#	Line 1189 | Line 1284 | public abstract class ForkJoinTask<V> im
1284		*/
1285		protected static ForkJoinTask<?> pollNextLocalTask() {
1286		return ((ForkJoinWorkerThread) Thread.currentThread())
1287	<	.pollLocalTask();
1287	>	.workQueue.nextLocalTask();
1288		}
1289
1290		/**
#	Line 1211 | Line 1306 | public abstract class ForkJoinTask<V> im
1306		* @return a task, or {@code null} if none are available
1307		*/
1308		protected static ForkJoinTask<?> pollTask() {
1309	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1310	<	.pollTask();
1309	>	ForkJoinWorkerThread wt =
1310	>	(ForkJoinWorkerThread)Thread.currentThread();
1311	>	return wt.pool.nextTaskFor(wt.workQueue);
1312	>	}
1313	>
1314	>	// tag operations
1315	>
1316	>	/**
1317	>	* Returns the tag for this task.
1318	>	*
1319	>	* @return the tag for this task
1320	>	* @since 1.8
1321	>	*/
1322	>	public final short getForkJoinTaskTag() {
1323	>	return (short)status;
1324	>	}
1325	>
1326	>	/**
1327	>	* Atomically sets the tag value for this task.
1328	>	*
1329	>	* @param tag the tag value
1330	>	* @return the previous value of the tag
1331	>	* @since 1.8
1332	>	*/
1333	>	public final short setForkJoinTaskTag(short tag) {
1334	>	for (int s;;) {
1335	>	if (U.compareAndSwapInt(this, STATUS, s = status,
1336	>	(s & ~SMASK) | (tag & SMASK)))
1337	>	return (short)s;
1338	>	}
1339	>	}
1340	>
1341	>	/**
1342	>	* Atomically conditionally sets the tag value for this task.
1343	>	* Among other applications, tags can be used as visit markers
1344	>	* in tasks operating on graphs, as in mathods that check: {@code
1345	>	* if (task.compareAndSetForkJoinTaskTag((short)0, (short)1))}
1346	>	* before processing, otherwise exiting because the node has
1347	>	* already been visited.
1348	>	*
1349	>	* @param e the expected tag value
1350	>	* @param tag the new tag value
1351	>	* @return true if successful; i.e., the current value was
1352	>	* equal to e and is now tag.
1353	>	* @since 1.8
1354	>	*/
1355	>	public final boolean compareAndSetForkJoinTaskTag(short e, short tag) {
1356	>	for (int s;;) {
1357	>	if ((short)(s = status) != e)
1358	>	return false;
1359	>	if (U.compareAndSwapInt(this, STATUS, s,
1360	>	(s & ~SMASK) | (tag & SMASK)))
1361	>	return true;
1362	>	}
1363		}
1364
1365		/**
#	Line 1223 | Line 1370 | public abstract class ForkJoinTask<V> im
1370		static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1371		implements RunnableFuture<T> {
1372		final Runnable runnable;
1226	–	final T resultOnCompletion;
1373		T result;
1374		AdaptedRunnable(Runnable runnable, T result) {
1375		if (runnable == null) throw new NullPointerException();
1376		this.runnable = runnable;
1377	<	this.resultOnCompletion = result;
1377	>	this.result = result; // OK to set this even before completion
1378		}
1379	<	public T getRawResult() { return result; }
1380	<	public void setRawResult(T v) { result = v; }
1381	<	public boolean exec() {
1382	<	runnable.run();
1383	<	result = resultOnCompletion;
1384	<	return true;
1379	>	public final T getRawResult() { return result; }
1380	>	public final void setRawResult(T v) { result = v; }
1381	>	public final boolean exec() { runnable.run(); return true; }
1382	>	public final void run() { invoke(); }
1383	>	private static final long serialVersionUID = 5232453952276885070L;
1384	>	}
1385	>
1386	>	/**
1387	>	* Adaptor for Runnables without results
1388	>	*/
1389	>	static final class AdaptedRunnableAction extends ForkJoinTask<Void>
1390	>	implements RunnableFuture<Void> {
1391	>	final Runnable runnable;
1392	>	AdaptedRunnableAction(Runnable runnable) {
1393	>	if (runnable == null) throw new NullPointerException();
1394	>	this.runnable = runnable;
1395		}
1396	<	public void run() { invoke(); }
1396	>	public final Void getRawResult() { return null; }
1397	>	public final void setRawResult(Void v) { }
1398	>	public final boolean exec() { runnable.run(); return true; }
1399	>	public final void run() { invoke(); }
1400		private static final long serialVersionUID = 5232453952276885070L;
1401		}
1402
#	Line 1252 | Line 1411 | public abstract class ForkJoinTask<V> im
1411		if (callable == null) throw new NullPointerException();
1412		this.callable = callable;
1413		}
1414	<	public T getRawResult() { return result; }
1415	<	public void setRawResult(T v) { result = v; }
1416	<	public boolean exec() {
1414	>	public final T getRawResult() { return result; }
1415	>	public final void setRawResult(T v) { result = v; }
1416	>	public final boolean exec() {
1417		try {
1418		result = callable.call();
1419		return true;
#	Line 1266 | Line 1425 | public abstract class ForkJoinTask<V> im
1425		throw new RuntimeException(ex);
1426		}
1427		}
1428	<	public void run() { invoke(); }
1428	>	public final void run() { invoke(); }
1429		private static final long serialVersionUID = 2838392045355241008L;
1430		}
1431
#	Line 1279 | Line 1438 | public abstract class ForkJoinTask<V> im
1438		* @return the task
1439		*/
1440		public static ForkJoinTask<?> adapt(Runnable runnable) {
1441	<	return new AdaptedRunnable<Void>(runnable, null);
1441	>	return new AdaptedRunnableAction(runnable);
1442		}
1443
1444		/**
#	Line 1313 | Line 1472 | public abstract class ForkJoinTask<V> im
1472		private static final long serialVersionUID = -7721805057305804111L;
1473
1474		/**
1475	<	* Saves the state to a stream (that is, serializes it).
1475	>	* Saves this task to a stream (that is, serializes it).
1476		*
1477		* @serialData the current run status and the exception thrown
1478		* during execution, or {@code null} if none
1320	–	* @param s the stream
1479		*/
1480		private void writeObject(java.io.ObjectOutputStream s)
1481		throws java.io.IOException {
#	Line 1326 | Line 1484 | public abstract class ForkJoinTask<V> im
1484		}
1485
1486		/**
1487	<	* Reconstitutes the instance from a stream (that is, deserializes it).
1330	<	*
1331	<	* @param s the stream
1487	>	* Reconstitutes this task from a stream (that is, deserializes it).
1488		*/
1489		private void readObject(java.io.ObjectInputStream s)
1490		throws java.io.IOException, ClassNotFoundException {
#	Line 1339 | Line 1495 | public abstract class ForkJoinTask<V> im
1495		}
1496
1497		// Unsafe mechanics
1498	<	private static final sun.misc.Unsafe UNSAFE;
1499	<	private static final long statusOffset;
1498	>	private static final sun.misc.Unsafe U;
1499	>	private static final long STATUS;
1500		static {
1501		exceptionTableLock = new ReentrantLock();
1502		exceptionTableRefQueue = new ReferenceQueue<Object>();
1503		exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY];
1504		try {
1505	<	UNSAFE = getUnsafe();
1506	<	statusOffset = UNSAFE.objectFieldOffset
1505	>	U = getUnsafe();
1506	>	STATUS = U.objectFieldOffset
1507		(ForkJoinTask.class.getDeclaredField("status"));
1508		} catch (Exception e) {
1509		throw new Error(e);

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