ViewVC Help

View File | Revision Log | Show Annotations | Download File | Root Listing

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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.63 by dl, Sat Sep 18 12:10:21 2010 UTC vs.
Revision 1.81 by dl, Thu Jan 26 00:08:13 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	–
9	–	import java.util.concurrent.*;
8		import java.io.Serializable;
9		import java.util.Collection;
12	–	import java.util.Collections;
10		import java.util.List;
11		import java.util.RandomAccess;
12	<	import java.util.Map;
13	<	import java.util.WeakHashMap;
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;
17	>	import java.util.concurrent.Future;
18	>	import java.util.concurrent.RejectedExecutionException;
19	>	import java.util.concurrent.RunnableFuture;
20	>	import java.util.concurrent.TimeUnit;
21	>	import java.util.concurrent.TimeoutException;
22	>	import java.util.concurrent.locks.ReentrantLock;
23	>	import java.lang.reflect.Constructor;
24
25		/**
26		* Abstract base class for tasks that run within a {@link ForkJoinPool}.
#	Line 35 | Line 42 | import java.util.WeakHashMap;
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.
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 73 | Line 93 | import java.util.WeakHashMap;
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 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 101 | Line 128 | import java.util.WeakHashMap;
128		* result in exceptions or errors, possibly including
129		* {@code ClassCastException}.
130		*
131	+	* <p>Method {@link #join} and its variants are appropriate for use
132	+	* only when completion dependencies are acyclic; that is, the
133	+	* parallel computation can be described as a directed acyclic graph
134	+	* (DAG). Otherwise, executions may encounter a form of deadlock as
135	+	* tasks cyclically wait for each other.  However, this framework
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. To support such usages a
140	+	* ForkJoinTask may be atomically <em>marked</em> using {@link
141	+	* #markForkJoinTask} and checked for marking using {@link
142	+	* #isMarkedForkJoinTask}. The ForkJoinTask implementation does not
143	+	* use these {@code protected} methods or marks for any purpose, but
144	+	* they may be of use in the construction of specialized subclasses.
145	+	* For example, parallel graph traversals can use the supplied methods
146	+	* to avoid revisiting nodes/tasks that have already been
147	+	* processed. Also, completion based designs can use them to record
148	+	* that one subtask has completed. (Method names for marking are bulky
149	+	* in part to encourage definition of methods that reflect their usage
150	+	* patterns.)
151	+	*
152		* <p>Most base support methods are {@code final}, to prevent
153		* overriding of implementations that are intrinsically tied to the
154		* underlying lightweight task scheduling framework.  Developers
#	Line 115 | Line 163 | import java.util.WeakHashMap;
163		* computation. Large tasks should be split into smaller subtasks,
164		* usually via recursive decomposition. As a very rough rule of thumb,
165		* a task should perform more than 100 and less than 10000 basic
166	<	* computational steps. If tasks are too big, then parallelism cannot
167	<	* improve throughput. If too small, then memory and internal task
168	<	* maintenance overhead may overwhelm processing.
166	>	* computational steps, and should avoid indefinite looping. If tasks
167	>	* are too big, then parallelism cannot improve throughput. If too
168	>	* small, then memory and internal task maintenance overhead may
169	>	* overwhelm processing.
170		*
171		* <p>This class provides {@code adapt} methods for {@link Runnable}
172		* and {@link Callable}, that may be of use when mixing execution of
#	Line 138 | 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. In particular, most
196	<	* join mechanics are in method quietlyJoin, below.
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 number of times to try to help join a task without any
202	>	* apparent progress before giving up and blocking. The value is
203	>	* arbitrary but should be large enough to cope with transient
204	>	* stalls (due to GC etc) that can cause helping methods not to be
205	>	* able to proceed because other workers have not progressed to
206	>	* the point where subtasks can be found or taken.
207		*/
208	+	private static final int HELP_RETRIES = 32;
209
210		/*
211		* The status field holds run control status bits packed into a
#	Line 166 | Line 226 | public abstract class ForkJoinTask<V> im
226
227		/** The run status of this task */
228		volatile int status; // accessed directly by pool and workers
229	+	static final int NORMAL      = 0xfffffffc;  // negative with low 2 bits 0
230	+	static final int CANCELLED   = 0xfffffff8;  // must be < NORMAL
231	+	static final int EXCEPTIONAL = 0xfffffff4;  // must be < CANCELLED
232	+	static final int SIGNAL      = 0x00000001;
233	+	static final int MARKED      = 0x00000002;
234
235	<	private static final int NORMAL      = -1;
236	<	private static final int CANCELLED   = -2;
237	<	private static final int EXCEPTIONAL = -3;
238	<	private static final int SIGNAL      =  1;
235	>	/**
236	>	* Marks completion and wakes up threads waiting to join this
237	>	* task, also clearing signal request bits. A specialization for
238	>	* NORMAL completion is in method doExec
239	>	*
240	>	* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
241	>	* @return completion status on exit
242	>	*/
243	>	private int setCompletion(int completion) {
244	>	for (int s;;) {
245	>	if ((s = status) < 0)
246	>	return s;
247	>	if (U.compareAndSwapInt(this, STATUS, s, (s & ~SIGNAL)|completion)) {
248	>	if ((s & SIGNAL) != 0)
249	>	synchronized (this) { notifyAll(); }
250	>	return completion;
251	>	}
252	>	}
253	>	}
254
255		/**
256	<	* Table of exceptions thrown by tasks, to enable reporting by
257	<	* callers. Because exceptions are rare, we don't directly keep
258	<	* them with task objects, but instead use a weak ref table.  Note
259	<	* that cancellation exceptions don't appear in the table, but are
260	<	* instead recorded as status values.
181	<	* TODO: Use ConcurrentReferenceHashMap
256	>	* Primary execution method for stolen tasks. Unless done, calls
257	>	* exec and records status if completed, but doesn't wait for
258	>	* completion otherwise.
259	>	*
260	>	* @return status on exit from this method
261		*/
262	<	static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
263	<	Collections.synchronizedMap
264	<	(new WeakHashMap<ForkJoinTask<?>, Throwable>());
262	>	final int doExec() {
263	>	int s; boolean completed;
264	>	if ((s = status) >= 0) {
265	>	try {
266	>	completed = exec();
267	>	} catch (Throwable rex) {
268	>	return setExceptionalCompletion(rex);
269	>	}
270	>	while ((s = status) >= 0 && completed) {
271	>	if (U.compareAndSwapInt(this, STATUS, s, (s & ~SIGNAL)|NORMAL)) {
272	>	if ((s & SIGNAL) != 0)
273	>	synchronized (this) { notifyAll(); }
274	>	return NORMAL;
275	>	}
276	>	}
277	>	}
278	>	return s;
279	>	}
280	>
281	>	/**
282	>	* Blocks a non-worker-thread until completion.
283	>	* @return status upon completion
284	>	*/
285	>	private int externalAwaitDone() {
286	>	int s;
287	>	if ((s = status) >= 0) {
288	>	boolean interrupted = false;
289	>	synchronized (this) {
290	>	while ((s = status) >= 0) {
291	>	if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
292	>	try {
293	>	wait();
294	>	} catch (InterruptedException ie) {
295	>	interrupted = true;
296	>	}
297	>	}
298	>	}
299	>	}
300	>	if (interrupted)
301	>	Thread.currentThread().interrupt();
302	>	}
303	>	return s;
304	>	}
305	>
306	>	/**
307	>	* Blocks a non-worker-thread until completion or interruption or timeout.
308	>	*/
309	>	private int externalInterruptibleAwaitDone(long millis)
310	>	throws InterruptedException {
311	>	int s;
312	>	if (Thread.interrupted())
313	>	throw new InterruptedException();
314	>	if ((s = status) >= 0) {
315	>	synchronized (this) {
316	>	while ((s = status) >= 0) {
317	>	if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
318	>	wait(millis);
319	>	if (millis > 0L)
320	>	break;
321	>	}
322	>	}
323	>	}
324	>	}
325	>	return s;
326	>	}
327
187	–	// Maintaining completion status
328
329		/**
330	<	* Marks completion and wakes up threads waiting to join this task,
331	<	* also clearing signal request bits.
330	>	* Implementation for join, get, quietlyJoin. Directly handles
331	>	* only cases of already-completed, external wait, and
332	>	* unfork+exec.  Others are relayed to awaitJoin.
333		*
334	<	* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
334	>	* @return status upon completion
335	>	*/
336	>	private int doJoin() {
337	>	int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w;
338	>	if ((s = status) >= 0) {
339	>	if (!((t = Thread.currentThread()) instanceof ForkJoinWorkerThread))
340	>	s = externalAwaitDone();
341	>	else if (!(w = (wt = (ForkJoinWorkerThread)t).workQueue).
342	>	tryUnpush(this) || (s = doExec()) >= 0)
343	>	s = awaitJoin(w, wt.pool);
344	>	}
345	>	return s;
346	>	}
347	>
348	>	/**
349	>	* Helps and/or blocks until joined.
350	>	*
351	>	* @param w the joiner
352	>	* @param p the pool
353	>	* @return status upon completion
354		*/
355	<	private void setCompletion(int completion) {
355	>	private int awaitJoin(ForkJoinPool.WorkQueue w, ForkJoinPool p) {
356		int s;
357	<	while ((s = status) >= 0) {
358	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
359	<	if (s != 0)
360	<	synchronized (this) { notifyAll(); }
357	>	ForkJoinTask<?> prevJoin = w.currentJoin;
358	>	w.currentJoin = this;
359	>	for (int k = HELP_RETRIES; (s = status) >= 0;) {
360	>	if ((w.queueSize() > 0) ?
361	>	w.tryRemoveAndExec(this) :        // self-help
362	>	p.tryHelpStealer(w, this))        // help process tasks
363	>	k = HELP_RETRIES;                 // reset if made progress
364	>	else if ((s = status) < 0)            // recheck
365		break;
366	+	else if (--k > 0) {
367	+	if ((k & 3) == 1)
368	+	Thread.yield();               // occasionally yield
369	+	}
370	+	else if (k == 0)
371	+	p.tryPollForAndExec(w, this);     // uncommon self-help case
372	+	else if (p.tryCompensate()) {         // true if can block
373	+	try {
374	+	int ss = status;
375	+	if (ss >= 0 &&                // assert need signal
376	+	U.compareAndSwapInt(this, STATUS, ss, ss | SIGNAL)) {
377	+	synchronized (this) {
378	+	if (status >= 0)      // block
379	+	wait();
380	+	}
381	+	}
382	+	} catch (InterruptedException ignore) {
383	+	} finally {
384	+	p.incrementActiveCount();     // re-activate
385	+	}
386		}
387		}
388	+	w.currentJoin = prevJoin;
389	+	return s;
390	+	}
391	+
392	+	/**
393	+	* Implementation for invoke, quietlyInvoke.
394	+	*
395	+	* @return status upon completion
396	+	*/
397	+	private int doInvoke() {
398	+	int s;
399	+	if ((s = doExec()) < 0)
400	+	return s;
401	+	else
402	+	return doJoin();
403	+	}
404	+
405	+	// Exception table support
406	+
407	+	/**
408	+	* Table of exceptions thrown by tasks, to enable reporting by
409	+	* callers. Because exceptions are rare, we don't directly keep
410	+	* them with task objects, but instead use a weak ref table.  Note
411	+	* that cancellation exceptions don't appear in the table, but are
412	+	* instead recorded as status values.
413	+	*
414	+	* Note: These statics are initialized below in static block.
415	+	*/
416	+	private static final ExceptionNode[] exceptionTable;
417	+	private static final ReentrantLock exceptionTableLock;
418	+	private static final ReferenceQueue<Object> exceptionTableRefQueue;
419	+
420	+	/**
421	+	* Fixed capacity for exceptionTable.
422	+	*/
423	+	private static final int EXCEPTION_MAP_CAPACITY = 32;
424	+
425	+	/**
426	+	* Key-value nodes for exception table.  The chained hash table
427	+	* uses identity comparisons, full locking, and weak references
428	+	* for keys. The table has a fixed capacity because it only
429	+	* maintains task exceptions long enough for joiners to access
430	+	* them, so should never become very large for sustained
431	+	* periods. However, since we do not know when the last joiner
432	+	* completes, we must use weak references and expunge them. We do
433	+	* so on each operation (hence full locking). Also, some thread in
434	+	* any ForkJoinPool will call helpExpungeStaleExceptions when its
435	+	* pool becomes isQuiescent.
436	+	*/
437	+	static final class ExceptionNode extends WeakReference<ForkJoinTask<?>>{
438	+	final Throwable ex;
439	+	ExceptionNode next;
440	+	final long thrower;  // use id not ref to avoid weak cycles
441	+	ExceptionNode(ForkJoinTask<?> task, Throwable ex, ExceptionNode next) {
442	+	super(task, exceptionTableRefQueue);
443	+	this.ex = ex;
444	+	this.next = next;
445	+	this.thrower = Thread.currentThread().getId();
446	+	}
447		}
448
449		/**
#	Line 208 | Line 451 | public abstract class ForkJoinTask<V> im
451		*
452		* @return status on exit
453		*/
454	<	private void setExceptionalCompletion(Throwable rex) {
455	<	exceptionMap.put(this, rex);
456	<	setCompletion(EXCEPTIONAL);
454	>	private int setExceptionalCompletion(Throwable ex) {
455	>	int h = System.identityHashCode(this);
456	>	final ReentrantLock lock = exceptionTableLock;
457	>	lock.lock();
458	>	try {
459	>	expungeStaleExceptions();
460	>	ExceptionNode[] t = exceptionTable;
461	>	int i = h & (t.length - 1);
462	>	for (ExceptionNode e = t[i]; ; e = e.next) {
463	>	if (e == null) {
464	>	t[i] = new ExceptionNode(this, ex, t[i]);
465	>	break;
466	>	}
467	>	if (e.get() == this) // already present
468	>	break;
469	>	}
470	>	} finally {
471	>	lock.unlock();
472	>	}
473	>	return setCompletion(EXCEPTIONAL);
474		}
475
476		/**
477	<	* Blocks a worker thread until completion. Called only by
478	<	* pool. Currently unused -- pool-based waits use timeout
479	<	* version below.
477	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
478	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
479	>	* exceptions, but if it does anyway, we have no recourse during
480	>	* shutdown, so guard against this case.
481		*/
482	<	final void internalAwaitDone() {
483	<	int s;         // the odd construction reduces lock bias effects
223	<	while ((s = status) >= 0) {
482	>	static final void cancelIgnoringExceptions(ForkJoinTask<?> t) {
483	>	if (t != null && t.status >= 0) {
484		try {
485	<	synchronized (this) {
486	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
227	<	wait();
228	<	}
229	<	} catch (InterruptedException ie) {
230	<	cancelIfTerminating();
485	>	t.cancel(false);
486	>	} catch (Throwable ignore) {
487		}
488		}
489		}
490
491		/**
492	<	* Blocks a worker thread until completed or timed out.  Called
237	<	* only by pool.
238	<	*
239	<	* @return status on exit
492	>	* Removes exception node and clears status
493		*/
494	<	final int internalAwaitDone(long millis) {
495	<	int s;
496	<	if ((s = status) >= 0) {
494	>	private void clearExceptionalCompletion() {
495	>	int h = System.identityHashCode(this);
496	>	final ReentrantLock lock = exceptionTableLock;
497	>	lock.lock();
498	>	try {
499	>	ExceptionNode[] t = exceptionTable;
500	>	int i = h & (t.length - 1);
501	>	ExceptionNode e = t[i];
502	>	ExceptionNode pred = null;
503	>	while (e != null) {
504	>	ExceptionNode next = e.next;
505	>	if (e.get() == this) {
506	>	if (pred == null)
507	>	t[i] = next;
508	>	else
509	>	pred.next = next;
510	>	break;
511	>	}
512	>	pred = e;
513	>	e = next;
514	>	}
515	>	expungeStaleExceptions();
516	>	status = 0;
517	>	} finally {
518	>	lock.unlock();
519	>	}
520	>	}
521	>
522	>	/**
523	>	* Returns a rethrowable exception for the given task, if
524	>	* available. To provide accurate stack traces, if the exception
525	>	* was not thrown by the current thread, we try to create a new
526	>	* exception of the same type as the one thrown, but with the
527	>	* recorded exception as its cause. If there is no such
528	>	* constructor, we instead try to use a no-arg constructor,
529	>	* followed by initCause, to the same effect. If none of these
530	>	* apply, or any fail due to other exceptions, we return the
531	>	* recorded exception, which is still correct, although it may
532	>	* contain a misleading stack trace.
533	>	*
534	>	* @return the exception, or null if none
535	>	*/
536	>	private Throwable getThrowableException() {
537	>	if (status != EXCEPTIONAL)
538	>	return null;
539	>	int h = System.identityHashCode(this);
540	>	ExceptionNode e;
541	>	final ReentrantLock lock = exceptionTableLock;
542	>	lock.lock();
543	>	try {
544	>	expungeStaleExceptions();
545	>	ExceptionNode[] t = exceptionTable;
546	>	e = t[h & (t.length - 1)];
547	>	while (e != null && e.get() != this)
548	>	e = e.next;
549	>	} finally {
550	>	lock.unlock();
551	>	}
552	>	Throwable ex;
553	>	if (e == null || (ex = e.ex) == null)
554	>	return null;
555	>	if (e.thrower != Thread.currentThread().getId()) {
556	>	Class<? extends Throwable> ec = ex.getClass();
557		try {
558	<	synchronized (this) {
559	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
560	<	wait(millis, 0);
558	>	Constructor<?> noArgCtor = null;
559	>	Constructor<?>[] cs = ec.getConstructors();// public ctors only
560	>	for (int i = 0; i < cs.length; ++i) {
561	>	Constructor<?> c = cs[i];
562	>	Class<?>[] ps = c.getParameterTypes();
563	>	if (ps.length == 0)
564	>	noArgCtor = c;
565	>	else if (ps.length == 1 && ps[0] == Throwable.class)
566	>	return (Throwable)(c.newInstance(ex));
567	>	}
568	>	if (noArgCtor != null) {
569	>	Throwable wx = (Throwable)(noArgCtor.newInstance());
570	>	wx.initCause(ex);
571	>	return wx;
572		}
573	<	} catch (InterruptedException ie) {
250	<	cancelIfTerminating();
573	>	} catch (Exception ignore) {
574		}
252	–	s = status;
575		}
576	<	return s;
576	>	return ex;
577		}
578
579		/**
580	<	* Blocks a non-worker-thread until completion.
580	>	* Poll stale refs and remove them. Call only while holding lock.
581		*/
582	<	private void externalAwaitDone() {
583	<	int s;
584	<	while ((s = status) >= 0) {
585	<	synchronized (this) {
586	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
587	<	boolean interrupted = false;
588	<	while (status >= 0) {
589	<	try {
590	<	wait();
591	<	} catch (InterruptedException ie) {
592	<	interrupted = true;
593	<	}
582	>	private static void expungeStaleExceptions() {
583	>	for (Object x; (x = exceptionTableRefQueue.poll()) != null;) {
584	>	if (x instanceof ExceptionNode) {
585	>	ForkJoinTask<?> key = ((ExceptionNode)x).get();
586	>	ExceptionNode[] t = exceptionTable;
587	>	int i = System.identityHashCode(key) & (t.length - 1);
588	>	ExceptionNode e = t[i];
589	>	ExceptionNode pred = null;
590	>	while (e != null) {
591	>	ExceptionNode next = e.next;
592	>	if (e == x) {
593	>	if (pred == null)
594	>	t[i] = next;
595	>	else
596	>	pred.next = next;
597	>	break;
598		}
599	<	if (interrupted)
600	<	Thread.currentThread().interrupt();
275	<	break;
599	>	pred = e;
600	>	e = next;
601		}
602		}
603		}
604		}
605
606		/**
607	<	* Unless done, calls exec and records status if completed, but
608	<	* doesn't wait for completion otherwise. Primary execution method
284	<	* for ForkJoinWorkerThread.
607	>	* If lock is available, poll stale refs and remove them.
608	>	* Called from ForkJoinPool when pools become quiescent.
609		*/
610	<	final void quietlyExec() {
611	<	try {
612	<	if (status < 0 || !exec())
613	<	return;
614	<	} catch (Throwable rex) {
615	<	setExceptionalCompletion(rex);
616	<	return;
610	>	static final void helpExpungeStaleExceptions() {
611	>	final ReentrantLock lock = exceptionTableLock;
612	>	if (lock.tryLock()) {
613	>	try {
614	>	expungeStaleExceptions();
615	>	} finally {
616	>	lock.unlock();
617	>	}
618		}
619	<	setCompletion(NORMAL); // must be outside try block
619	>	}
620	>
621	>	/**
622	>	* Report the result of invoke or join; called only upon
623	>	* non-normal return of internal versions.
624	>	*/
625	>	private V reportResult() {
626	>	int s; Throwable ex;
627	>	if ((s = status) == CANCELLED)
628	>	throw new CancellationException();
629	>	if (s == EXCEPTIONAL && (ex = getThrowableException()) != null)
630	>	U.throwException(ex);
631	>	return getRawResult();
632		}
633
634		// public methods
#	Line 307 | Line 644 | public abstract class ForkJoinTask<V> im
644		* #isDone} returning {@code true}.
645		*
646		* <p>This method may be invoked only from within {@code
647	<	* ForkJoinTask} computations (as may be determined using method
647	>	* ForkJoinPool} computations (as may be determined using method
648		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
649		* result in exceptions or errors, possibly including {@code
650		* ClassCastException}.
#	Line 315 | Line 652 | public abstract class ForkJoinTask<V> im
652		* @return {@code this}, to simplify usage
653		*/
654		public final ForkJoinTask<V> fork() {
655	<	((ForkJoinWorkerThread) Thread.currentThread())
656	<	.pushTask(this);
655	>	ForkJoinWorkerThread wt;
656	>	(wt = (ForkJoinWorkerThread)Thread.currentThread()).
657	>	workQueue.push(this, wt.pool);
658		return this;
659		}
660
661		/**
662	<	* Returns the result of the computation when it {@link #isDone is done}.
663	<	* This method differs from {@link #get()} in that
662	>	* Returns the result of the computation when it {@link #isDone is
663	>	* done}.  This method differs from {@link #get()} in that
664		* abnormal completion results in {@code RuntimeException} or
665	<	* {@code Error}, not {@code ExecutionException}.
665	>	* {@code Error}, not {@code ExecutionException}, and that
666	>	* interrupts of the calling thread do <em>not</em> cause the
667	>	* method to abruptly return by throwing {@code
668	>	* InterruptedException}.
669		*
670		* @return the computed result
671		*/
672		public final V join() {
673	<	quietlyJoin();
674	<	Throwable ex;
675	<	if (status < NORMAL && (ex = getException()) != null)
676	<	UNSAFE.throwException(ex);
336	<	return getRawResult();
673	>	if (doJoin() != NORMAL)
674	>	return reportResult();
675	>	else
676	>	return getRawResult();
677		}
678
679		/**
#	Line 345 | Line 685 | public abstract class ForkJoinTask<V> im
685		* @return the computed result
686		*/
687		public final V invoke() {
688	<	quietlyInvoke();
689	<	Throwable ex;
690	<	if (status < NORMAL && (ex = getException()) != null)
691	<	UNSAFE.throwException(ex);
352	<	return getRawResult();
688	>	if (doInvoke() != NORMAL)
689	>	return reportResult();
690	>	else
691	>	return getRawResult();
692		}
693
694		/**
#	Line 366 | Line 705 | public abstract class ForkJoinTask<V> im
705		* unprocessed.
706		*
707		* <p>This method may be invoked only from within {@code
708	<	* ForkJoinTask} computations (as may be determined using method
708	>	* ForkJoinPool} computations (as may be determined using method
709		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
710		* result in exceptions or errors, possibly including {@code
711		* ClassCastException}.
#	Line 394 | Line 733 | public abstract class ForkJoinTask<V> im
733		* normally or exceptionally, or left unprocessed.
734		*
735		* <p>This method may be invoked only from within {@code
736	<	* ForkJoinTask} computations (as may be determined using method
736	>	* ForkJoinPool} computations (as may be determined using method
737		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
738		* result in exceptions or errors, possibly including {@code
739		* ClassCastException}.
#	Line 413 | Line 752 | public abstract class ForkJoinTask<V> im
752		}
753		else if (i != 0)
754		t.fork();
755	<	else {
756	<	t.quietlyInvoke();
418	<	if (ex == null && t.status < NORMAL)
419	<	ex = t.getException();
420	<	}
755	>	else if (t.doInvoke() < NORMAL && ex == null)
756	>	ex = t.getException();
757		}
758		for (int i = 1; i <= last; ++i) {
759		ForkJoinTask<?> t = tasks[i];
760		if (t != null) {
761		if (ex != null)
762		t.cancel(false);
763	<	else {
764	<	t.quietlyJoin();
429	<	if (ex == null && t.status < NORMAL)
430	<	ex = t.getException();
431	<	}
763	>	else if (t.doJoin() < NORMAL)
764	>	ex = t.getException();
765		}
766		}
767		if (ex != null)
768	<	UNSAFE.throwException(ex);
768	>	U.throwException(ex);
769		}
770
771		/**
#	Line 449 | Line 782 | public abstract class ForkJoinTask<V> im
782		* unprocessed.
783		*
784		* <p>This method may be invoked only from within {@code
785	<	* ForkJoinTask} computations (as may be determined using method
785	>	* ForkJoinPool} computations (as may be determined using method
786		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
787		* result in exceptions or errors, possibly including {@code
788		* ClassCastException}.
#	Line 476 | Line 809 | public abstract class ForkJoinTask<V> im
809		}
810		else if (i != 0)
811		t.fork();
812	<	else {
813	<	t.quietlyInvoke();
481	<	if (ex == null && t.status < NORMAL)
482	<	ex = t.getException();
483	<	}
812	>	else if (t.doInvoke() < NORMAL && ex == null)
813	>	ex = t.getException();
814		}
815		for (int i = 1; i <= last; ++i) {
816		ForkJoinTask<?> t = ts.get(i);
817		if (t != null) {
818		if (ex != null)
819		t.cancel(false);
820	<	else {
821	<	t.quietlyJoin();
492	<	if (ex == null && t.status < NORMAL)
493	<	ex = t.getException();
494	<	}
820	>	else if (t.doJoin() < NORMAL)
821	>	ex = t.getException();
822		}
823		}
824		if (ex != null)
825	<	UNSAFE.throwException(ex);
825	>	U.throwException(ex);
826		return tasks;
827		}
828
829		/**
830		* Attempts to cancel execution of this task. This attempt will
831	<	* fail if the task has already completed, has already been
832	<	* cancelled, or could not be cancelled for some other reason. If
833	<	* successful, and this task has not started when cancel is
834	<	* called, execution of this task is suppressed, {@link
835	<	* #isCancelled} will report true, and {@link #join} will result
836	<	* in a {@code CancellationException} being thrown.
831	>	* fail if the task has already completed or could not be
832	>	* cancelled for some other reason. If successful, and this task
833	>	* has not started when {@code cancel} is called, execution of
834	>	* this task is suppressed. After this method returns
835	>	* successfully, unless there is an intervening call to {@link
836	>	* #reinitialize}, subsequent calls to {@link #isCancelled},
837	>	* {@link #isDone}, and {@code cancel} will return {@code true}
838	>	* and calls to {@link #join} and related methods will result in
839	>	* {@code CancellationException}.
840		*
841		* <p>This method may be overridden in subclasses, but if so, must
842	<	* still ensure that these minimal properties hold. In particular,
843	<	* the {@code cancel} method itself must not throw exceptions.
842	>	* still ensure that these properties hold. In particular, the
843	>	* {@code cancel} method itself must not throw exceptions.
844		*
845		* <p>This method is designed to be invoked by <em>other</em>
846		* tasks. To terminate the current task, you can just return or
847		* throw an unchecked exception from its computation method, or
848		* invoke {@link #completeExceptionally}.
849		*
850	<	* @param mayInterruptIfRunning this value is ignored in the
851	<	* default implementation because tasks are not
852	<	* cancelled via interruption
850	>	* @param mayInterruptIfRunning this value has no effect in the
851	>	* default implementation because interrupts are not used to
852	>	* control cancellation.
853		*
854		* @return {@code true} if this task is now cancelled
855		*/
856		public boolean cancel(boolean mayInterruptIfRunning) {
857	<	setCompletion(CANCELLED);
528	<	return status == CANCELLED;
529	<	}
530	<
531	<	/**
532	<	* Cancels, ignoring any exceptions thrown by cancel. Used during
533	<	* worker and pool shutdown. Cancel is spec'ed not to throw any
534	<	* exceptions, but if it does anyway, we have no recourse during
535	<	* shutdown, so guard against this case.
536	<	*/
537	<	final void cancelIgnoringExceptions() {
538	<	try {
539	<	cancel(false);
540	<	} catch (Throwable ignore) {
541	<	}
542	<	}
543	<
544	<	/**
545	<	* Cancels if current thread is a terminating worker thread,
546	<	* ignoring any exceptions thrown by cancel.
547	<	*/
548	<	final void cancelIfTerminating() {
549	<	Thread t = Thread.currentThread();
550	<	if ((t instanceof ForkJoinWorkerThread) &&
551	<	((ForkJoinWorkerThread) t).isTerminating()) {
552	<	try {
553	<	cancel(false);
554	<	} catch (Throwable ignore) {
555	<	}
556	<	}
857	>	return setCompletion(CANCELLED) == CANCELLED;
858		}
859
860		public final boolean isDone() {
#	Line 595 | Line 896 | public abstract class ForkJoinTask<V> im
896		int s = status;
897		return ((s >= NORMAL)    ? null :
898		(s == CANCELLED) ? new CancellationException() :
899	<	exceptionMap.get(this));
899	>	getThrowableException());
900		}
901
902		/**
#	Line 653 | Line 954 | public abstract class ForkJoinTask<V> im
954		* member of a ForkJoinPool and was interrupted while waiting
955		*/
956		public final V get() throws InterruptedException, ExecutionException {
957	<	int s;
958	<	if (Thread.currentThread() instanceof ForkJoinWorkerThread) {
959	<	quietlyJoin();
960	<	s = status;
961	<	}
962	<	else {
963	<	while ((s = status) >= 0) {
663	<	synchronized (this) { // interruptible form of awaitDone
664	<	if (UNSAFE.compareAndSwapInt(this, statusOffset,
665	<	s, SIGNAL)) {
666	<	while (status >= 0)
667	<	wait();
668	<	}
669	<	}
670	<	}
671	<	}
672	<	if (s < NORMAL) {
673	<	Throwable ex;
674	<	if (s == CANCELLED)
675	<	throw new CancellationException();
676	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
677	<	throw new ExecutionException(ex);
678	<	}
957	>	int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ?
958	>	doJoin() : externalInterruptibleAwaitDone(0L);
959	>	Throwable ex;
960	>	if (s == CANCELLED)
961	>	throw new CancellationException();
962	>	if (s == EXCEPTIONAL && (ex = getThrowableException()) != null)
963	>	throw new ExecutionException(ex);
964		return getRawResult();
965		}
966
#	Line 695 | Line 980 | public abstract class ForkJoinTask<V> im
980		*/
981		public final V get(long timeout, TimeUnit unit)
982		throws InterruptedException, ExecutionException, TimeoutException {
983	+	// Messy in part because we measure in nanos, but wait in millis
984	+	int s; long millis, nanos;
985		Thread t = Thread.currentThread();
986	<	ForkJoinPool pool;
987	<	if (t instanceof ForkJoinWorkerThread) {
988	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
989	<	if (status >= 0 && w.unpushTask(this))
990	<	quietlyExec();
704	<	pool = w.pool;
986	>	if (!(t instanceof ForkJoinWorkerThread)) {
987	>	if ((millis = unit.toMillis(timeout)) > 0L)
988	>	s = externalInterruptibleAwaitDone(millis);
989	>	else
990	>	s = status;
991		}
992	<	else
993	<	pool = null;
994	<	/*
995	<	* Timed wait loop intermixes cases for FJ (pool != null) and
996	<	* non FJ threads. For FJ, decrement pool count but don't try
997	<	* for replacement; increment count on completion. For non-FJ,
998	<	* deal with interrupts. This is messy, but a little less so
999	<	* than is splitting the FJ and nonFJ cases.
1000	<	*/
1001	<	boolean interrupted = false;
1002	<	boolean dec = false; // true if pool count decremented
1003	<	long nanos = unit.toNanos(timeout);
1004	<	for (;;) {
1005	<	if (pool == null && Thread.interrupted()) {
720	<	interrupted = true;
721	<	break;
722	<	}
723	<	int s = status;
724	<	if (s < 0)
725	<	break;
726	<	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
727	<	long startTime = System.nanoTime();
728	<	long nt; // wait time
729	<	while (status >= 0 &&
730	<	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
731	<	if (pool != null && !dec)
732	<	dec = pool.tryDecrementRunningCount();
992	>	else if ((s = status) >= 0 && (nanos = unit.toNanos(timeout)) > 0L) {
993	>	long deadline = System.nanoTime() + nanos;
994	>	ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
995	>	ForkJoinPool.WorkQueue w = wt.workQueue;
996	>	ForkJoinPool p = wt.pool;
997	>	if (w.tryUnpush(this))
998	>	doExec();
999	>	boolean blocking = false;
1000	>	try {
1001	>	while ((s = status) >= 0) {
1002	>	if (w.runState < 0)
1003	>	cancelIgnoringExceptions(this);
1004	>	else if (!blocking)
1005	>	blocking = p.tryCompensate();
1006		else {
1007	<	long ms = nt / 1000000;
1008	<	int ns = (int) (nt % 1000000);
1009	<	try {
1010	<	synchronized (this) {
1011	<	if (status >= 0)
1012	<	wait(ms, ns);
1013	<	}
1014	<	} catch (InterruptedException ie) {
1015	<	if (pool != null)
743	<	cancelIfTerminating();
744	<	else {
745	<	interrupted = true;
746	<	break;
1007	>	millis = TimeUnit.NANOSECONDS.toMillis(nanos);
1008	>	if (millis > 0L &&
1009	>	U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
1010	>	try {
1011	>	synchronized (this) {
1012	>	if (status >= 0)
1013	>	wait(millis);
1014	>	}
1015	>	} catch (InterruptedException ie) {
1016		}
1017		}
1018	+	if ((s = status) < 0 ||
1019	+	(nanos = deadline - System.nanoTime()) <= 0L)
1020	+	break;
1021		}
1022		}
1023	<	break;
1023	>	} finally {
1024	>	if (blocking)
1025	>	p.incrementActiveCount();
1026		}
1027		}
1028	<	if (pool != null && dec)
755	<	pool.incrementRunningCount();
756	<	if (interrupted)
757	<	throw new InterruptedException();
758	<	int es = status;
759	<	if (es != NORMAL) {
1028	>	if (s != NORMAL) {
1029		Throwable ex;
1030	<	if (es == CANCELLED)
1030	>	if (s == CANCELLED)
1031		throw new CancellationException();
1032	<	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
1032	>	if (s != EXCEPTIONAL)
1033	>	throw new TimeoutException();
1034	>	if ((ex = getThrowableException()) != null)
1035		throw new ExecutionException(ex);
765	–	throw new TimeoutException();
1036		}
1037		return getRawResult();
1038		}
#	Line 774 | Line 1044 | public abstract class ForkJoinTask<V> im
1044		* known to have aborted.
1045		*/
1046		public final void quietlyJoin() {
1047	<	Thread t;
778	<	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
779	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
780	<	if (status >= 0) {
781	<	if (w.unpushTask(this)) {
782	<	boolean completed;
783	<	try {
784	<	completed = exec();
785	<	} catch (Throwable rex) {
786	<	setExceptionalCompletion(rex);
787	<	return;
788	<	}
789	<	if (completed) {
790	<	setCompletion(NORMAL);
791	<	return;
792	<	}
793	<	}
794	<	w.joinTask(this);
795	<	}
796	<	}
797	<	else
798	<	externalAwaitDone();
1047	>	doJoin();
1048		}
1049
1050		/**
#	Line 804 | Line 1053 | public abstract class ForkJoinTask<V> im
1053		* exception.
1054		*/
1055		public final void quietlyInvoke() {
1056	<	if (status >= 0) {
808	<	boolean completed;
809	<	try {
810	<	completed = exec();
811	<	} catch (Throwable rex) {
812	<	setExceptionalCompletion(rex);
813	<	return;
814	<	}
815	<	if (completed)
816	<	setCompletion(NORMAL);
817	<	else
818	<	quietlyJoin();
819	<	}
1056	>	doInvoke();
1057		}
1058
1059		/**
#	Line 827 | Line 1064 | public abstract class ForkJoinTask<V> im
1064		* processed.
1065		*
1066		* <p>This method may be invoked only from within {@code
1067	<	* ForkJoinTask} computations (as may be determined using method
1067	>	* ForkJoinPool} computations (as may be determined using method
1068		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1069		* result in exceptions or errors, possibly including {@code
1070		* ClassCastException}.
1071		*/
1072		public static void helpQuiesce() {
1073	<	((ForkJoinWorkerThread) Thread.currentThread())
1074	<	.helpQuiescePool();
1073	>	ForkJoinWorkerThread w =
1074	>	(ForkJoinWorkerThread)Thread.currentThread();
1075	>	w.pool.helpQuiescePool(w.workQueue);
1076		}
1077
1078		/**
#	Line 846 | Line 1084 | public abstract class ForkJoinTask<V> im
1084		* under any other usage conditions are not guaranteed.
1085		* This method may be useful when executing
1086		* pre-constructed trees of subtasks in loops.
1087	+	*
1088	+	* <p>Upon completion of this method, {@code isDone()} reports
1089	+	* {@code false}, and {@code getException()} reports {@code
1090	+	* null}. However, the value returned by {@code getRawResult} is
1091	+	* unaffected. To clear this value, you can invoke {@code
1092	+	* setRawResult(null)}.
1093		*/
1094		public void reinitialize() {
1095		if (status == EXCEPTIONAL)
1096	<	exceptionMap.remove(this);
1097	<	status = 0;
1096	>	clearExceptionalCompletion();
1097	>	else
1098	>	status = 0;
1099		}
1100
1101		/**
#	Line 867 | Line 1112 | public abstract class ForkJoinTask<V> im
1112		}
1113
1114		/**
1115	<	* Returns {@code true} if the current thread is executing as a
1116	<	* ForkJoinPool computation.
1115	>	* Returns {@code true} if the current thread is a {@link
1116	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation.
1117		*
1118	<	* @return {@code true} if the current thread is executing as a
1119	<	* ForkJoinPool computation, or false otherwise
1118	>	* @return {@code true} if the current thread is a {@link
1119	>	* ForkJoinWorkerThread} executing as a ForkJoinPool computation,
1120	>	* or {@code false} otherwise
1121		*/
1122		public static boolean inForkJoinPool() {
1123		return Thread.currentThread() instanceof ForkJoinWorkerThread;
#	Line 886 | Line 1132 | public abstract class ForkJoinTask<V> im
1132		* were not, stolen.
1133		*
1134		* <p>This method may be invoked only from within {@code
1135	<	* ForkJoinTask} computations (as may be determined using method
1135	>	* ForkJoinPool} computations (as may be determined using method
1136		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1137		* result in exceptions or errors, possibly including {@code
1138		* ClassCastException}.
#	Line 894 | Line 1140 | public abstract class ForkJoinTask<V> im
1140		* @return {@code true} if unforked
1141		*/
1142		public boolean tryUnfork() {
1143	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1144	<	.unpushTask(this);
1143	>	return ((ForkJoinWorkerThread)Thread.currentThread())
1144	>	.workQueue.tryUnpush(this);
1145		}
1146
1147		/**
#	Line 905 | Line 1151 | public abstract class ForkJoinTask<V> im
1151		* fork other tasks.
1152		*
1153		* <p>This method may be invoked only from within {@code
1154	<	* ForkJoinTask} computations (as may be determined using method
1154	>	* ForkJoinPool} computations (as may be determined using method
1155		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1156		* result in exceptions or errors, possibly including {@code
1157		* ClassCastException}.
#	Line 914 | Line 1160 | public abstract class ForkJoinTask<V> im
1160		*/
1161		public static int getQueuedTaskCount() {
1162		return ((ForkJoinWorkerThread) Thread.currentThread())
1163	<	.getQueueSize();
1163	>	.workQueue.queueSize();
1164		}
1165
1166		/**
#	Line 928 | Line 1174 | public abstract class ForkJoinTask<V> im
1174		* exceeded.
1175		*
1176		* <p>This method may be invoked only from within {@code
1177	<	* ForkJoinTask} computations (as may be determined using method
1177	>	* ForkJoinPool} computations (as may be determined using method
1178		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1179		* result in exceptions or errors, possibly including {@code
1180		* ClassCastException}.
#	Line 936 | Line 1182 | public abstract class ForkJoinTask<V> im
1182		* @return the surplus number of tasks, which may be negative
1183		*/
1184		public static int getSurplusQueuedTaskCount() {
1185	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1186	<	.getEstimatedSurplusTaskCount();
1185	>	/*
1186	>	* The aim of this method is to return a cheap heuristic guide
1187	>	* for task partitioning when programmers, frameworks, tools,
1188	>	* or languages have little or no idea about task granularity.
1189	>	* In essence by offering this method, we ask users only about
1190	>	* tradeoffs in overhead vs expected throughput and its
1191	>	* variance, rather than how finely to partition tasks.
1192	>	*
1193	>	* In a steady state strict (tree-structured) computation,
1194	>	* each thread makes available for stealing enough tasks for
1195	>	* other threads to remain active. Inductively, if all threads
1196	>	* play by the same rules, each thread should make available
1197	>	* only a constant number of tasks.
1198	>	*
1199	>	* The minimum useful constant is just 1. But using a value of
1200	>	* 1 would require immediate replenishment upon each steal to
1201	>	* maintain enough tasks, which is infeasible.  Further,
1202	>	* partitionings/granularities of offered tasks should
1203	>	* minimize steal rates, which in general means that threads
1204	>	* nearer the top of computation tree should generate more
1205	>	* than those nearer the bottom. In perfect steady state, each
1206	>	* thread is at approximately the same level of computation
1207	>	* tree. However, producing extra tasks amortizes the
1208	>	* uncertainty of progress and diffusion assumptions.
1209	>	*
1210	>	* So, users will want to use values larger, but not much
1211	>	* larger than 1 to both smooth over transient shortages and
1212	>	* hedge against uneven progress; as traded off against the
1213	>	* cost of extra task overhead. We leave the user to pick a
1214	>	* threshold value to compare with the results of this call to
1215	>	* guide decisions, but recommend values such as 3.
1216	>	*
1217	>	* When all threads are active, it is on average OK to
1218	>	* estimate surplus strictly locally. In steady-state, if one
1219	>	* thread is maintaining say 2 surplus tasks, then so are
1220	>	* others. So we can just use estimated queue length.
1221	>	* However, this strategy alone leads to serious mis-estimates
1222	>	* in some non-steady-state conditions (ramp-up, ramp-down,
1223	>	* other stalls). We can detect many of these by further
1224	>	* considering the number of "idle" threads, that are known to
1225	>	* have zero queued tasks, so compensate by a factor of
1226	>	* (#idle/#active) threads.
1227	>	*/
1228	>	ForkJoinWorkerThread w =
1229	>	(ForkJoinWorkerThread)Thread.currentThread();
1230	>	return w.workQueue.queueSize() - w.pool.idlePerActive();
1231		}
1232
1233		// Extension methods
#	Line 986 | Line 1276 | public abstract class ForkJoinTask<V> im
1276		* otherwise.
1277		*
1278		* <p>This method may be invoked only from within {@code
1279	<	* ForkJoinTask} computations (as may be determined using method
1279	>	* ForkJoinPool} computations (as may be determined using method
1280		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1281		* result in exceptions or errors, possibly including {@code
1282		* ClassCastException}.
#	Line 994 | Line 1284 | public abstract class ForkJoinTask<V> im
1284		* @return the next task, or {@code null} if none are available
1285		*/
1286		protected static ForkJoinTask<?> peekNextLocalTask() {
1287	<	return ((ForkJoinWorkerThread) Thread.currentThread())
998	<	.peekTask();
1287	>	return ((ForkJoinWorkerThread) Thread.currentThread()).workQueue.peek();
1288		}
1289
1290		/**
#	Line 1005 | Line 1294 | public abstract class ForkJoinTask<V> im
1294		* be useful otherwise.
1295		*
1296		* <p>This method may be invoked only from within {@code
1297	<	* ForkJoinTask} computations (as may be determined using method
1297	>	* ForkJoinPool} computations (as may be determined using method
1298		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1299		* result in exceptions or errors, possibly including {@code
1300		* ClassCastException}.
#	Line 1014 | Line 1303 | public abstract class ForkJoinTask<V> im
1303		*/
1304		protected static ForkJoinTask<?> pollNextLocalTask() {
1305		return ((ForkJoinWorkerThread) Thread.currentThread())
1306	<	.pollLocalTask();
1306	>	.workQueue.nextLocalTask();
1307		}
1308
1309		/**
#	Line 1028 | Line 1317 | public abstract class ForkJoinTask<V> im
1317		* otherwise.
1318		*
1319		* <p>This method may be invoked only from within {@code
1320	<	* ForkJoinTask} computations (as may be determined using method
1320	>	* ForkJoinPool} computations (as may be determined using method
1321		* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1322		* result in exceptions or errors, possibly including {@code
1323		* ClassCastException}.
#	Line 1036 | Line 1325 | public abstract class ForkJoinTask<V> im
1325		* @return a task, or {@code null} if none are available
1326		*/
1327		protected static ForkJoinTask<?> pollTask() {
1328	<	return ((ForkJoinWorkerThread) Thread.currentThread())
1329	<	.pollTask();
1328	>	ForkJoinWorkerThread w =
1329	>	(ForkJoinWorkerThread)Thread.currentThread();
1330	>	return w.pool.nextTaskFor(w.workQueue);
1331	>	}
1332	>
1333	>	// Mark-bit operations
1334	>
1335	>	/**
1336	>	* Returns true if this task is marked.
1337	>	*
1338	>	* @return true if this task is marked
1339	>	* @since 1.8
1340	>	*/
1341	>	public final boolean isMarkedForkJoinTask() {
1342	>	return (status & MARKED) != 0;
1343	>	}
1344	>
1345	>	/**
1346	>	* Atomically sets the mark on this task.
1347	>	*
1348	>	* @return true if this task was previously unmarked
1349	>	* @since 1.8
1350	>	*/
1351	>	public final boolean markForkJoinTask() {
1352	>	for (int s;;) {
1353	>	if (((s = status) & MARKED) != 0)
1354	>	return false;
1355	>	if (U.compareAndSwapInt(this, STATUS, s, s | MARKED))
1356	>	return true;
1357	>	}
1358	>	}
1359	>
1360	>	/**
1361	>	* Atomically clears the mark on this task.
1362	>	*
1363	>	* @return true if this task was previously marked
1364	>	* @since 1.8
1365	>	*/
1366	>	public final boolean unmarkForkJoinTask() {
1367	>	for (int s;;) {
1368	>	if (((s = status) & MARKED) == 0)
1369	>	return false;
1370	>	if (U.compareAndSwapInt(this, STATUS, s, s & ~MARKED))
1371	>	return true;
1372	>	}
1373		}
1374
1375		/**
#	Line 1138 | Line 1470 | public abstract class ForkJoinTask<V> im
1470		private static final long serialVersionUID = -7721805057305804111L;
1471
1472		/**
1473	<	* Saves the state to a stream (that is, serializes it).
1473	>	* Saves this task to a stream (that is, serializes it).
1474		*
1475		* @serialData the current run status and the exception thrown
1476		* during execution, or {@code null} if none
1145	–	* @param s the stream
1477		*/
1478		private void writeObject(java.io.ObjectOutputStream s)
1479		throws java.io.IOException {
#	Line 1151 | Line 1482 | public abstract class ForkJoinTask<V> im
1482		}
1483
1484		/**
1485	<	* Reconstitutes the instance from a stream (that is, deserializes it).
1155	<	*
1156	<	* @param s the stream
1485	>	* Reconstitutes this task from a stream (that is, deserializes it).
1486		*/
1487		private void readObject(java.io.ObjectInputStream s)
1488		throws java.io.IOException, ClassNotFoundException {
1489		s.defaultReadObject();
1490		Object ex = s.readObject();
1491		if (ex != null)
1492	<	setExceptionalCompletion((Throwable) ex);
1492	>	setExceptionalCompletion((Throwable)ex);
1493		}
1494
1495		// Unsafe mechanics
1496	<
1497	<	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1498	<	private static final long statusOffset =
1499	<	objectFieldOffset("status", ForkJoinTask.class);
1500	<
1501	<	private static long objectFieldOffset(String field, Class<?> klazz) {
1496	>	private static final sun.misc.Unsafe U;
1497	>	private static final long STATUS;
1498	>	static {
1499	>	exceptionTableLock = new ReentrantLock();
1500	>	exceptionTableRefQueue = new ReferenceQueue<Object>();
1501	>	exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY];
1502		try {
1503	<	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1504	<	} catch (NoSuchFieldException e) {
1505	<	// Convert Exception to corresponding Error
1506	<	NoSuchFieldError error = new NoSuchFieldError(field);
1507	<	error.initCause(e);
1179	<	throw error;
1503	>	U = getUnsafe();
1504	>	STATUS = U.objectFieldOffset
1505	>	(ForkJoinTask.class.getDeclaredField("status"));
1506	>	} catch (Exception e) {
1507	>	throw new Error(e);
1508		}
1509		}
1510

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines