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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.12 by jsr166, Wed Jul 22 01:36:51 2009 UTC vs.
Revision 1.52 by dl, Sat Jul 24 20:28:18 2010 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.io.Serializable;
9	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
11	<	import sun.misc.Unsafe;
12	<	import java.lang.reflect.*;
10	>
11	>	import java.io.Serializable;
12	>	import java.util.Collection;
13	>	import java.util.Collections;
14	>	import java.util.List;
15	>	import java.util.RandomAccess;
16	>	import java.util.Map;
17	>	import java.util.WeakHashMap;
18
19		/**
20	<	* Abstract base class for tasks that run within a {@link
21	<	* ForkJoinPool}.  A ForkJoinTask is a thread-like entity that is much
20	>	* Abstract base class for tasks that run within a {@link ForkJoinPool}.
21	>	* A {@code ForkJoinTask} is a thread-like entity that is much
22		* lighter weight than a normal thread.  Huge numbers of tasks and
23		* subtasks may be hosted by a small number of actual threads in a
24		* ForkJoinPool, at the price of some usage limitations.
25		*
26	<	* <p> A "main" ForkJoinTask begins execution when submitted to a
27	<	* {@link ForkJoinPool}. Once started, it will usually in turn start
28	<	* other subtasks.  As indicated by the name of this class, many
29	<	* programs using ForkJoinTasks employ only methods {@code fork}
30	<	* and {@code join}, or derivatives such as
31	<	* {@code invokeAll}.  However, this class also provides a number
32	<	* of other methods that can come into play in advanced usages, as
33	<	* well as extension mechanics that allow support of new forms of
34	<	* fork/join processing.
26	>	* <p>A "main" {@code ForkJoinTask} begins execution when submitted
27	>	* to a {@link ForkJoinPool}.  Once started, it will usually in turn
28	>	* start other subtasks.  As indicated by the name of this class,
29	>	* many programs using {@code ForkJoinTask} employ only methods
30	>	* {@link #fork} and {@link #join}, or derivatives such as {@link
31	>	* #invokeAll}.  However, this class also provides a number of other
32	>	* methods that can come into play in advanced usages, as well as
33	>	* extension mechanics that allow support of new forms of fork/join
34	>	* processing.
35		*
36	<	* <p>A ForkJoinTask is a lightweight form of {@link Future}.  The
37	<	* efficiency of ForkJoinTasks stems from a set of restrictions (that
38	<	* are only partially statically enforceable) reflecting their
39	<	* intended use as computational tasks calculating pure functions or
40	<	* operating on purely isolated objects.  The primary coordination
41	<	* mechanisms are {@link #fork}, that arranges asynchronous execution,
42	<	* and {@link #join}, that doesn't proceed until the task's result has
43	<	* been computed.  Computations should avoid {@code synchronized}
44	<	* methods or blocks, and should minimize other blocking
45	<	* synchronization apart from joining other tasks or using
46	<	* synchronizers such as Phasers that are advertised to cooperate with
47	<	* fork/join scheduling. Tasks should also not perform blocking IO,
48	<	* and should ideally access variables that are completely independent
49	<	* of those accessed by other running tasks. Minor breaches of these
50	<	* restrictions, for example using shared output streams, may be
51	<	* tolerable in practice, but frequent use may result in poor
52	<	* performance, and the potential to indefinitely stall if the number
53	<	* of threads not waiting for IO or other external synchronization
54	<	* becomes exhausted. This usage restriction is in part enforced by
55	<	* not permitting checked exceptions such as {@code IOExceptions}
56	<	* to be thrown. However, computations may still encounter unchecked
57	<	* exceptions, that are rethrown to callers attempting join
58	<	* them. These exceptions may additionally include
59	<	* RejectedExecutionExceptions stemming from internal resource
60	<	* exhaustion such as failure to allocate internal task queues.
36	>	* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
37	>	* The efficiency of {@code ForkJoinTask}s stems from a set of
38	>	* restrictions (that are only partially statically enforceable)
39	>	* reflecting their intended use as computational tasks calculating
40	>	* pure functions or operating on purely isolated objects.  The
41	>	* primary coordination mechanisms are {@link #fork}, that arranges
42	>	* asynchronous execution, and {@link #join}, that doesn't proceed
43	>	* until the task's result has been computed.  Computations should
44	>	* avoid {@code synchronized} methods or blocks, and should minimize
45	>	* other blocking synchronization apart from joining other tasks or
46	>	* using synchronizers such as Phasers that are advertised to
47	>	* cooperate with fork/join scheduling. Tasks should also not perform
48	>	* blocking IO, and should ideally access variables that are
49	>	* completely independent of those accessed by other running
50	>	* tasks. Minor breaches of these restrictions, for example using
51	>	* shared output streams, may be tolerable in practice, but frequent
52	>	* use may result in poor performance, and the potential to
53	>	* indefinitely stall if the number of threads not waiting for IO or
54	>	* other external synchronization becomes exhausted. This usage
55	>	* restriction is in part enforced by not permitting checked
56	>	* exceptions such as {@code IOExceptions} to be thrown. However,
57	>	* computations may still encounter unchecked exceptions, that are
58	>	* rethrown to callers attempting to join them. These exceptions may
59	>	* additionally include {@link RejectedExecutionException} stemming
60	>	* from internal resource exhaustion, such as failure to allocate
61	>	* internal task queues.
62		*
63		* <p>The primary method for awaiting completion and extracting
64		* results of a task is {@link #join}, but there are several variants:
65		* The {@link Future#get} methods support interruptible and/or timed
66		* waits for completion and report results using {@code Future}
67	<	* conventions. Method {@link #helpJoin} enables callers to actively
68	<	* execute other tasks while awaiting joins, which is sometimes more
69	<	* efficient but only applies when all subtasks are known to be
70	<	* strictly tree-structured. Method {@link #invoke} is semantically
66	<	* equivalent to {@code fork(); join()} but always attempts to
67	<	* begin execution in the current thread. The "<em>quiet</em>" forms
68	<	* of these methods do not extract results or report exceptions. These
67	>	* conventions. Method {@link #invoke} is semantically
68	>	* equivalent to {@code fork(); join()} but always attempts to begin
69	>	* execution in the current thread. The "<em>quiet</em>" forms of
70	>	* these methods do not extract results or report exceptions. These
71		* may be useful when a set of tasks are being executed, and you need
72		* to delay processing of results or exceptions until all complete.
73		* Method {@code invokeAll} (available in multiple versions)
74		* performs the most common form of parallel invocation: forking a set
75		* of tasks and joining them all.
76		*
77	<	* <p> The ForkJoinTask class is not usually directly subclassed.
77	>	* <p>The execution status of tasks may be queried at several levels
78	>	* of detail: {@link #isDone} is true if a task completed in any way
79	>	* (including the case where a task was cancelled without executing);
80	>	* {@link #isCompletedNormally} is true if a task completed without
81	>	* cancellation or encountering an exception; {@link #isCancelled} is
82	>	* true if the task was cancelled (in which case {@link #getException}
83	>	* returns a {@link java.util.concurrent.CancellationException}); and
84	>	* {@link #isCompletedAbnormally} is true if a task was either
85	>	* cancelled or encountered an exception, in which case {@link
86	>	* #getException} will return either the encountered exception or
87	>	* {@link java.util.concurrent.CancellationException}.
88	>	*
89	>	* <p>The ForkJoinTask class is not usually directly subclassed.
90		* Instead, you subclass one of the abstract classes that support a
91	<	* particular style of fork/join processing.  Normally, a concrete
91	>	* particular style of fork/join processing, typically {@link
92	>	* RecursiveAction} for computations that do not return results, or
93	>	* {@link RecursiveTask} for those that do.  Normally, a concrete
94		* ForkJoinTask subclass declares fields comprising its parameters,
95		* established in a constructor, and then defines a {@code compute}
96		* method that somehow uses the control methods supplied by this base
97		* class. While these methods have {@code public} access (to allow
98	<	* instances of different task subclasses to call each others
98	>	* instances of different task subclasses to call each other's
99		* methods), some of them may only be called from within other
100	<	* ForkJoinTasks. Attempts to invoke them in other contexts result in
101	<	* exceptions or errors possibly including ClassCastException.
100	>	* ForkJoinTasks (as may be determined using method {@link
101	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
102	>	* result in exceptions or errors, possibly including
103	>	* ClassCastException.
104		*
105	<	* <p>Most base support methods are {@code final} because their
106	<	* implementations are intrinsically tied to the underlying
107	<	* lightweight task scheduling framework, and so cannot be overridden.
108	<	* Developers creating new basic styles of fork/join processing should
109	<	* minimally implement {@code protected} methods
110	<	* {@code exec}, {@code setRawResult}, and
111	<	* {@code getRawResult}, while also introducing an abstract
112	<	* computational method that can be implemented in its subclasses,
113	<	* possibly relying on other {@code protected} methods provided
96	<	* by this class.
105	>	* <p>Most base support methods are {@code final}, to prevent
106	>	* overriding of implementations that are intrinsically tied to the
107	>	* underlying lightweight task scheduling framework.  Developers
108	>	* creating new basic styles of fork/join processing should minimally
109	>	* implement {@code protected} methods {@link #exec}, {@link
110	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
111	>	* an abstract computational method that can be implemented in its
112	>	* subclasses, possibly relying on other {@code protected} methods
113	>	* provided by this class.
114		*
115		* <p>ForkJoinTasks should perform relatively small amounts of
116	<	* computations, otherwise splitting into smaller tasks. As a very
117	<	* rough rule of thumb, a task should perform more than 100 and less
118	<	* than 10000 basic computational steps. If tasks are too big, then
119	<	* parallelism cannot improve throughput. If too small, then memory
120	<	* and internal task maintenance overhead may overwhelm processing.
116	>	* computation. Large tasks should be split into smaller subtasks,
117	>	* usually via recursive decomposition. As a very rough rule of thumb,
118	>	* a task should perform more than 100 and less than 10000 basic
119	>	* computational steps. If tasks are too big, then parallelism cannot
120	>	* improve throughput. If too small, then memory and internal task
121	>	* maintenance overhead may overwhelm processing.
122		*
123	<	* <p>ForkJoinTasks are {@code Serializable}, which enables them
124	<	* to be used in extensions such as remote execution frameworks. It is
125	<	* in general sensible to serialize tasks only before or after, but
126	<	* not during execution. Serialization is not relied on during
127	<	* execution itself.
123	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
124	>	* and {@link Callable}, that may be of use when mixing execution of
125	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
126	>	* of this form, consider using a pool constructed in <em>asyncMode</em>.
127	>	*
128	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
129	>	* used in extensions such as remote execution frameworks. It is
130	>	* sensible to serialize tasks only before or after, but not during,
131	>	* execution. Serialization is not relied on during execution itself.
132		*
133		* @since 1.7
134		* @author Doug Lea
135		*/
136		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
137
138	<	/**
139	<	* Run control status bits packed into a single int to minimize
140	<	* footprint and to ensure atomicity (via CAS).  Status is
141	<	* initially zero, and takes on nonnegative values until
142	<	* completed, upon which status holds COMPLETED. CANCELLED, or
143	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
144	<	* blocking waits by other threads have SIGNAL_MASK bits set --
145	<	* bit 15 for external (nonFJ) waits, and the rest a count of
146	<	* waiting FJ threads.  (This representation relies on
147	<	* ForkJoinPool max thread limits). Completion of a stolen task
148	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
149	<	* though suboptimal for some purposes, we use basic builtin
150	<	* wait/notify to take advantage of "monitor inflation" in JVMs
151	<	* that we would otherwise need to emulate to avoid adding further
152	<	* per-task bookkeeping overhead. Note that bits 16-28 are
153	<	* currently unused. Also value 0x80000000 is available as spare
154	<	* completion value.
138	>	/*
139	>	* See the internal documentation of class ForkJoinPool for a
140	>	* general implementation overview.  ForkJoinTasks are mainly
141	>	* responsible for maintaining their "status" field amidst relays
142	>	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
143	>	* methods of this class are more-or-less layered into (1) basic
144	>	* status maintenance (2) execution and awaiting completion (3)
145	>	* user-level methods that additionally report results. This is
146	>	* sometimes hard to see because this file orders exported methods
147	>	* in a way that flows well in javadocs.
148	>	*/
149	>
150	>	/*
151	>	* The status field holds run control status bits packed into a
152	>	* single int to minimize footprint and to ensure atomicity (via
153	>	* CAS).  Status is initially zero, and takes on nonnegative
154	>	* values until completed, upon which status holds value
155	>	* COMPLETED. CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
156	>	* waits by other threads have the SIGNAL bit set.  Completion of
157	>	* a stolen task with SIGNAL set awakens any waiters via
158	>	* notifyAll. Even though suboptimal for some purposes, we use
159	>	* basic builtin wait/notify to take advantage of "monitor
160	>	* inflation" in JVMs that we would otherwise need to emulate to
161	>	* avoid adding further per-task bookkeeping overhead.  We want
162	>	* these monitors to be "fat", i.e., not use biasing or thin-lock
163	>	* techniques, so use some odd coding idioms that tend to avoid
164	>	* them.
165		*/
166	+
167	+	/** Run status of this task */
168		volatile int status; // accessed directly by pool and workers
169
170	<	static final int COMPLETION_MASK      = 0xe0000000;
171	<	static final int NORMAL               = 0xe0000000; // == mask
172	<	static final int CANCELLED            = 0xc0000000;
173	<	static final int EXCEPTIONAL          = 0xa0000000;
140	<	static final int SIGNAL_MASK          = 0x0000ffff;
141	<	static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
142	<	static final int EXTERNAL_SIGNAL      = 0x00008000; // top bit of low word
170	>	private static final int NORMAL      = -1;
171	>	private static final int CANCELLED   = -2;
172	>	private static final int EXCEPTIONAL = -3;
173	>	private static final int SIGNAL      =  1;
174
175		/**
176		* Table of exceptions thrown by tasks, to enable reporting by
#	Line 153 | Line 184 | public abstract class ForkJoinTask<V> im
184		Collections.synchronizedMap
185		(new WeakHashMap<ForkJoinTask<?>, Throwable>());
186
187	<	// within-package utilities
157	<
158	<	/**
159	<	* Gets current worker thread, or null if not a worker thread.
160	<	*/
161	<	static ForkJoinWorkerThread getWorker() {
162	<	Thread t = Thread.currentThread();
163	<	return ((t instanceof ForkJoinWorkerThread)?
164	<	(ForkJoinWorkerThread)t : null);
165	<	}
166	<
167	<	final boolean casStatus(int cmp, int val) {
168	<	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
169	<	}
187	>	// Maintaining completion status
188
189		/**
190	<	* Workaround for not being able to rethrow unchecked exceptions.
191	<	*/
174	<	static void rethrowException(Throwable ex) {
175	<	if (ex != null)
176	<	UNSAFE.throwException(ex);
177	<	}
178	<
179	<	// Setting completion status
180	<
181	<	/**
182	<	* Marks completion and wakes up threads waiting to join this task.
190	>	* Marks completion and wakes up threads waiting to join this task,
191	>	* also clearing signal request bits.
192		*
193		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
194	+	* @return status on exit
195		*/
196	<	final void setCompletion(int completion) {
197	<	ForkJoinPool pool = getPool();
198	<	if (pool != null) {
199	<	int s; // Clear signal bits while setting completion status
200	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
201	<
202	<	if ((s & SIGNAL_MASK) != 0) {
193	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
194	<	pool.updateRunningCount(s);
195	<	synchronized(this) { notifyAll(); }
196	>	private int setCompletion(int completion) {
197	>	int s;
198	>	while ((s = status) >= 0) {
199	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
200	>	if (s != 0)
201	>	synchronized (this) { notifyAll(); }
202	>	return completion;
203		}
204		}
205	<	else
199	<	externallySetCompletion(completion);
200	<	}
201	<
202	<	/**
203	<	* Version of setCompletion for non-FJ threads.  Leaves signal
204	<	* bits for unblocked threads to adjust, and always notifies.
205	<	*/
206	<	private void externallySetCompletion(int completion) {
207	<	int s;
208	<	do;while ((s = status) >= 0 &&
209	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
210	<	synchronized(this) { notifyAll(); }
211	<	}
212	<
213	<	/**
214	<	* Sets status to indicate normal completion
215	<	*/
216	<	final void setNormalCompletion() {
217	<	// Try typical fast case -- single CAS, no signal, not already done.
218	<	// Manually expand casStatus to improve chances of inlining it
219	<	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
220	<	setCompletion(NORMAL);
205	>	return s;
206		}
207
223	–	// internal waiting and notification
224	–
208		/**
209	<	* Performs the actual monitor wait for awaitDone
209	>	* Record exception and set exceptional completion
210	>	* @return status on exit
211		*/
212	<	private void doAwaitDone() {
213	<	// Minimize lock bias and in/de-flation effects by maximizing
214	<	// chances of waiting inside sync
231	<	try {
232	<	while (status >= 0)
233	<	synchronized(this) { if (status >= 0) wait(); }
234	<	} catch (InterruptedException ie) {
235	<	onInterruptedWait();
236	<	}
212	>	private int setExceptionalCompletion(Throwable rex) {
213	>	exceptionMap.put(this, rex);
214	>	return setCompletion(EXCEPTIONAL);
215		}
216
217		/**
218	<	* Performs the actual monitor wait for awaitDone
218	>	* Blocks a worker thread until completion. Called only by pool.
219		*/
220	<	private void doAwaitDone(long startTime, long nanos) {
221	<	synchronized(this) {
220	>	final void internalAwaitDone() {
221	>	int s;         // the odd construction reduces lock bias effects
222	>	while ((s = status) >= 0) {
223		try {
224	<	while (status >= 0) {
225	<	long nt = nanos - System.nanoTime() - startTime;
226	<	if (nt <= 0)
248	<	break;
249	<	wait(nt / 1000000, (int)(nt % 1000000));
224	>	synchronized(this) {
225	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
226	>	wait();
227		}
228		} catch (InterruptedException ie) {
229	<	onInterruptedWait();
253	<	}
254	<	}
255	<	}
256	<
257	<	// Awaiting completion
258	<
259	<	/**
260	<	* Sets status to indicate there is joiner, then waits for join,
261	<	* surrounded with pool notifications.
262	<	*
263	<	* @return status upon exit
264	<	*/
265	<	private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
266	<	ForkJoinPool pool = w == null? null : w.pool;
267	<	int s;
268	<	while ((s = status) >= 0) {
269	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
270	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
271	<	doAwaitDone();
272	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
273	<	adjustPoolCountsOnUnblock(pool);
274	<	break;
229	>	cancelIfTerminating();
230		}
231		}
277	–	return s;
232		}
233
234		/**
235	<	* Timed version of awaitDone
236	<	* @return status upon exit
235	>	* Blocks a non-worker-thread until completion.
236	>	* @return status on exit
237		*/
238	<	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
285	<	ForkJoinPool pool = w == null? null : w.pool;
238	>	private int externalAwaitDone() {
239		int s;
240		while ((s = status) >= 0) {
241	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
242	<	long startTime = System.nanoTime();
243	<	if (pool == null || !pool.preJoin(this, false))
244	<	doAwaitDone(startTime, nanos);
245	<	if ((s = status) >= 0) {
246	<	adjustPoolCountsOnCancelledWait(pool);
247	<	s = status;
241	>	synchronized(this) {
242	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
243	>	boolean interrupted = false;
244	>	while ((s = status) >= 0) {
245	>	try {
246	>	wait();
247	>	} catch (InterruptedException ie) {
248	>	interrupted = true;
249	>	}
250	>	}
251	>	if (interrupted)
252	>	Thread.currentThread().interrupt();
253	>	break;
254		}
296	–	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
297	–	adjustPoolCountsOnUnblock(pool);
298	–	break;
255		}
256		}
257		return s;
258		}
259
260		/**
261	<	* Notifies pool that thread is unblocked. Called by signalled
262	<	* threads when woken by non-FJ threads (which is atypical).
261	>	* Unless done, calls exec and records status if completed, but
262	>	* doesn't wait for completion otherwise. Primary execution method
263	>	* for ForkJoinWorkerThread.
264		*/
265	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
266	<	int s;
267	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
268	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
269	<	pool.updateRunningCount(s);
265	>	final void tryExec() {
266	>	try {
267	>	if (status < 0 || !exec())
268	>	return;
269	>	} catch (Throwable rex) {
270	>	setExceptionalCompletion(rex);
271	>	return;
272	>	}
273	>	setCompletion(NORMAL); // must be outside try block
274		}
275
276		/**
277	<	* Notifies pool to adjust counts on cancelled or timed out wait.
278	<	*/
279	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
280	<	if (pool != null) {
281	<	int s;
282	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
283	<	if (casStatus(s, s - 1)) {
284	<	pool.updateRunningCount(1);
285	<	break;
277	>	* If not done and this task is next in worker queue, runs it,
278	>	* else waits for it.
279	>	* @return status on exit
280	>	*/
281	>	private int doJoin() {
282	>	int stat;
283	>	Thread t;
284	>	ForkJoinWorkerThread w;
285	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
286	>	if ((stat = status) < 0)
287	>	return stat;
288	>	if ((w = (ForkJoinWorkerThread) t).unpushTask(this)) {
289	>	boolean completed;
290	>	try {
291	>	completed = exec();
292	>	} catch (Throwable rex) {
293	>	return setExceptionalCompletion(rex);
294		}
295	+	if (completed)
296	+	return setCompletion(NORMAL);
297		}
298	+	return w.joinTask(this);
299		}
300	+	return externalAwaitDone();
301		}
302
303		/**
304	<	* Handles interruptions during waits.
305	<	*/
306	<	private void onInterruptedWait() {
334	<	ForkJoinWorkerThread w = getWorker();
335	<	if (w == null)
336	<	Thread.currentThread().interrupt(); // re-interrupt
337	<	else if (w.isTerminating())
338	<	cancelIgnoringExceptions();
339	<	// else if FJworker, ignore interrupt
340	<	}
341	<
342	<	// Recording and reporting exceptions
343	<
344	<	private void setDoneExceptionally(Throwable rex) {
345	<	exceptionMap.put(this, rex);
346	<	setCompletion(EXCEPTIONAL);
347	<	}
348	<
349	<	/**
350	<	* Throws the exception associated with status s.
351	<	*
352	<	* @throws the exception
353	<	*/
354	<	private void reportException(int s) {
355	<	if ((s &= COMPLETION_MASK) < NORMAL) {
356	<	if (s == CANCELLED)
357	<	throw new CancellationException();
358	<	else
359	<	rethrowException(exceptionMap.get(this));
360	<	}
361	<	}
362	<
363	<	/**
364	<	* Returns result or throws exception using j.u.c.Future conventions.
365	<	* Only call when isDone known to be true.
366	<	*/
367	<	private V reportFutureResult()
368	<	throws ExecutionException, InterruptedException {
369	<	int s = status & COMPLETION_MASK;
370	<	if (s < NORMAL) {
371	<	Throwable ex;
372	<	if (s == CANCELLED)
373	<	throw new CancellationException();
374	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
375	<	throw new ExecutionException(ex);
376	<	if (Thread.interrupted())
377	<	throw new InterruptedException();
378	<	}
379	<	return getRawResult();
380	<	}
381	<
382	<	/**
383	<	* Returns result or throws exception using j.u.c.Future conventions
384	<	* with timeouts.
385	<	*/
386	<	private V reportTimedFutureResult()
387	<	throws InterruptedException, ExecutionException, TimeoutException {
388	<	Throwable ex;
389	<	int s = status & COMPLETION_MASK;
390	<	if (s == NORMAL)
391	<	return getRawResult();
392	<	if (s == CANCELLED)
393	<	throw new CancellationException();
394	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
395	<	throw new ExecutionException(ex);
396	<	if (Thread.interrupted())
397	<	throw new InterruptedException();
398	<	throw new TimeoutException();
399	<	}
400	<
401	<	// internal execution methods
402	<
403	<	/**
404	<	* Calls exec, recording completion, and rethrowing exception if
405	<	* encountered. Caller should normally check status before calling.
406	<	*
407	<	* @return true if completed normally
408	<	*/
409	<	private boolean tryExec() {
410	<	try { // try block must contain only call to exec
411	<	if (!exec())
412	<	return false;
413	<	} catch (Throwable rex) {
414	<	setDoneExceptionally(rex);
415	<	rethrowException(rex);
416	<	return false; // not reached
417	<	}
418	<	setNormalCompletion();
419	<	return true;
420	<	}
421	<
422	<	/**
423	<	* Main execution method used by worker threads. Invokes
424	<	* base computation unless already complete.
304	>	* Unless done, calls exec and records status if completed, or
305	>	* waits for completion otherwise.
306	>	* @return status on exit
307		*/
308	<	final void quietlyExec() {
309	<	if (status >= 0) {
308	>	private int doInvoke() {
309	>	int stat;
310	>	if ((stat = status) >= 0) {
311	>	boolean completed;
312		try {
313	<	if (!exec())
314	<	return;
315	<	} catch(Throwable rex) {
432	<	setDoneExceptionally(rex);
433	<	return;
313	>	completed = exec();
314	>	} catch (Throwable rex) {
315	>	return setExceptionalCompletion(rex);
316		}
317	<	setNormalCompletion();
436	<	}
437	<	}
438	<
439	<	/**
440	<	* Calls exec(), recording but not rethrowing exception.
441	<	* Caller should normally check status before calling.
442	<	*
443	<	* @return true if completed normally
444	<	*/
445	<	private boolean tryQuietlyInvoke() {
446	<	try {
447	<	if (!exec())
448	<	return false;
449	<	} catch (Throwable rex) {
450	<	setDoneExceptionally(rex);
451	<	return false;
317	>	stat = completed ? setCompletion(NORMAL) : doJoin();
318		}
319	<	setNormalCompletion();
454	<	return true;
319	>	return stat;
320		}
321
322		/**
323	<	* Cancels, ignoring any exceptions it throws.
323	>	* Returns result or throws exception associated with given status.
324	>	* @param s the status
325		*/
326	<	final void cancelIgnoringExceptions() {
327	<	try {
328	<	cancel(false);
329	<	} catch(Throwable ignore) {
330	<	}
465	<	}
466	<
467	<	/**
468	<	* Main implementation of helpJoin
469	<	*/
470	<	private int busyJoin(ForkJoinWorkerThread w) {
471	<	int s;
472	<	ForkJoinTask<?> t;
473	<	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
474	<	t.quietlyExec();
475	<	return (s >= 0)? awaitDone(w, false) : s; // block if no work
326	>	private V reportResult(int s) {
327	>	Throwable ex;
328	>	if (s < NORMAL && (ex = getException()) != null)
329	>	UNSAFE.throwException(ex);
330	>	return getRawResult();
331		}
332
333		// public methods
#	Line 480 | Line 335 | public abstract class ForkJoinTask<V> im
335		/**
336		* Arranges to asynchronously execute this task.  While it is not
337		* necessarily enforced, it is a usage error to fork a task more
338	<	* than once unless it has completed and been reinitialized.  This
339	<	* method may be invoked only from within ForkJoinTask
340	<	* computations. Attempts to invoke in other contexts result in
341	<	* exceptions or errors possibly including ClassCastException.
342	<	*/
343	<	public final void fork() {
344	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
338	>	* than once unless it has completed and been reinitialized.
339	>	* Subsequent modifications to the state of this task or any data
340	>	* it operates on are not necessarily consistently observable by
341	>	* any thread other than the one executing it unless preceded by a
342	>	* call to {@link #join} or related methods, or a call to {@link
343	>	* #isDone} returning {@code true}.
344	>	*
345	>	* <p>This method may be invoked only from within {@code
346	>	* ForkJoinTask} computations (as may be determined using method
347	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
348	>	* result in exceptions or errors, possibly including {@code
349	>	* ClassCastException}.
350	>	*
351	>	* @return {@code this}, to simplify usage
352	>	*/
353	>	public final ForkJoinTask<V> fork() {
354	>	((ForkJoinWorkerThread) Thread.currentThread())
355	>	.pushTask(this);
356	>	return this;
357		}
358
359		/**
360	<	* Returns the result of the computation when it is ready.
361	<	* This method differs from {@code get} in that abnormal
362	<	* completion results in RuntimeExceptions or Errors, not
363	<	* ExecutionExceptions.
360	>	* Returns the result of the computation when it {@link #isDone is done}.
361	>	* This method differs from {@link #get()} in that
362	>	* abnormal completion results in {@code RuntimeException} or
363	>	* {@code Error}, not {@code ExecutionException}.
364		*
365		* @return the computed result
366		*/
367		public final V join() {
368	<	ForkJoinWorkerThread w = getWorker();
502	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
503	<	reportException(awaitDone(w, true));
504	<	return getRawResult();
368	>	return reportResult(doJoin());
369		}
370
371		/**
372		* Commences performing this task, awaits its completion if
373	<	* necessary, and return its result.
373	>	* necessary, and return its result, or throws an (unchecked)
374	>	* exception if the underlying computation did so.
375		*
511	–	* @throws Throwable (a RuntimeException, Error, or unchecked
512	–	* exception) if the underlying computation did so
376		* @return the computed result
377		*/
378		public final V invoke() {
379	<	if (status >= 0 && tryExec())
517	<	return getRawResult();
518	<	else
519	<	return join();
379	>	return reportResult(doInvoke());
380		}
381
382		/**
383	<	* Forks both tasks, returning when {@code isDone} holds for
384	<	* both of them or an exception is encountered. This method may be
385	<	* invoked only from within ForkJoinTask computations. Attempts to
386	<	* invoke in other contexts result in exceptions or errors
387	<	* possibly including ClassCastException.
383	>	* Forks the given tasks, returning when {@code isDone} holds for
384	>	* each task or an (unchecked) exception is encountered, in which
385	>	* case the exception is rethrown.  If either task encounters an
386	>	* exception, the other one may be, but is not guaranteed to be,
387	>	* cancelled.  If both tasks throw an exception, then this method
388	>	* throws one of them.  The individual status of each task may be
389	>	* checked using {@link #getException()} and related methods.
390	>	*
391	>	* <p>This method may be invoked only from within {@code
392	>	* ForkJoinTask} computations (as may be determined using method
393	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
394	>	* result in exceptions or errors, possibly including {@code
395	>	* ClassCastException}.
396		*
397	<	* @param t1 one task
398	<	* @param t2 the other task
399	<	* @throws NullPointerException if t1 or t2 are null
532	<	* @throws RuntimeException or Error if either task did so
397	>	* @param t1 the first task
398	>	* @param t2 the second task
399	>	* @throws NullPointerException if any task is null
400		*/
401	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
401	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
402		t2.fork();
403		t1.invoke();
404		t2.join();
405		}
406
407		/**
408	<	* Forks the given tasks, returning when {@code isDone} holds
409	<	* for all of them. If any task encounters an exception, others
410	<	* may be cancelled.  This method may be invoked only from within
411	<	* ForkJoinTask computations. Attempts to invoke in other contexts
412	<	* result in exceptions or errors possibly including ClassCastException.
408	>	* Forks the given tasks, returning when {@code isDone} holds for
409	>	* each task or an (unchecked) exception is encountered, in which
410	>	* case the exception is rethrown. If any task encounters an
411	>	* exception, others may be, but are not guaranteed to be,
412	>	* cancelled.  If more than one task encounters an exception, then
413	>	* this method throws any one of these exceptions.  The individual
414	>	* status of each task may be checked using {@link #getException()}
415	>	* and related methods.
416	>	*
417	>	* <p>This method may be invoked only from within {@code
418	>	* ForkJoinTask} computations (as may be determined using method
419	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
420	>	* result in exceptions or errors, possibly including {@code
421	>	* ClassCastException}.
422		*
423	<	* @param tasks the array of tasks
424	<	* @throws NullPointerException if tasks or any element are null
549	<	* @throws RuntimeException or Error if any task did so
423	>	* @param tasks the tasks
424	>	* @throws NullPointerException if any task is null
425		*/
426		public static void invokeAll(ForkJoinTask<?>... tasks) {
427		Throwable ex = null;
#	Line 559 | Line 434 | public abstract class ForkJoinTask<V> im
434		}
435		else if (i != 0)
436		t.fork();
437	<	else {
438	<	t.quietlyInvoke();
564	<	if (ex == null)
565	<	ex = t.getException();
566	<	}
437	>	else if (t.doInvoke() < NORMAL && ex == null)
438	>	ex = t.getException();
439		}
440		for (int i = 1; i <= last; ++i) {
441		ForkJoinTask<?> t = tasks[i];
442		if (t != null) {
443		if (ex != null)
444		t.cancel(false);
445	<	else {
446	<	t.quietlyJoin();
575	<	if (ex == null)
576	<	ex = t.getException();
577	<	}
445	>	else if (t.doJoin() < NORMAL && ex == null)
446	>	ex = t.getException();
447		}
448		}
449		if (ex != null)
450	<	rethrowException(ex);
450	>	UNSAFE.throwException(ex);
451		}
452
453		/**
454	<	* Forks all tasks in the collection, returning when
455	<	* {@code isDone} holds for all of them. If any task
456	<	* encounters an exception, others may be cancelled.  This method
457	<	* may be invoked only from within ForkJoinTask
458	<	* computations. Attempts to invoke in other contexts result in
459	<	* exceptions or errors possibly including ClassCastException.
454	>	* Forks all tasks in the specified collection, returning when
455	>	* {@code isDone} holds for each task or an (unchecked) exception
456	>	* is encountered.  If any task encounters an exception, others
457	>	* may be, but are not guaranteed to be, cancelled.  If more than
458	>	* one task encounters an exception, then this method throws any
459	>	* one of these exceptions.  The individual status of each task
460	>	* may be checked using {@link #getException()} and related
461	>	* methods.  The behavior of this operation is undefined if the
462	>	* specified collection is modified while the operation is in
463	>	* progress.
464	>	*
465	>	* <p>This method may be invoked only from within {@code
466	>	* ForkJoinTask} computations (as may be determined using method
467	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
468	>	* result in exceptions or errors, possibly including {@code
469	>	* ClassCastException}.
470		*
471		* @param tasks the collection of tasks
472	+	* @return the tasks argument, to simplify usage
473		* @throws NullPointerException if tasks or any element are null
594	–	* @throws RuntimeException or Error if any task did so
474		*/
475	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
476	<	if (!(tasks instanceof List)) {
477	<	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
478	<	return;
475	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
476	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
477	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
478	>	return tasks;
479		}
480	+	@SuppressWarnings("unchecked")
481		List<? extends ForkJoinTask<?>> ts =
482	<	(List<? extends ForkJoinTask<?>>)tasks;
482	>	(List<? extends ForkJoinTask<?>>) tasks;
483		Throwable ex = null;
484		int last = ts.size() - 1;
485		for (int i = last; i >= 0; --i) {
#	Line 610 | Line 490 | public abstract class ForkJoinTask<V> im
490		}
491		else if (i != 0)
492		t.fork();
493	<	else {
494	<	t.quietlyInvoke();
615	<	if (ex == null)
616	<	ex = t.getException();
617	<	}
493	>	else if (t.doInvoke() < NORMAL && ex == null)
494	>	ex = t.getException();
495		}
496		for (int i = 1; i <= last; ++i) {
497		ForkJoinTask<?> t = ts.get(i);
498		if (t != null) {
499		if (ex != null)
500		t.cancel(false);
501	<	else {
502	<	t.quietlyJoin();
626	<	if (ex == null)
627	<	ex = t.getException();
628	<	}
501	>	else if (t.doJoin() < NORMAL && ex == null)
502	>	ex = t.getException();
503		}
504		}
505		if (ex != null)
506	<	rethrowException(ex);
507	<	}
634	<
635	<	/**
636	<	* Returns true if the computation performed by this task has
637	<	* completed (or has been cancelled).
638	<	*
639	<	* @return true if this computation has completed
640	<	*/
641	<	public final boolean isDone() {
642	<	return status < 0;
643	<	}
644	<
645	<	/**
646	<	* Returns true if this task was cancelled.
647	<	*
648	<	* @return true if this task was cancelled
649	<	*/
650	<	public final boolean isCancelled() {
651	<	return (status & COMPLETION_MASK) == CANCELLED;
506	>	UNSAFE.throwException(ex);
507	>	return tasks;
508		}
509
510		/**
511	<	* Asserts that the results of this task's computation will not be
512	<	* used. If a cancellation occurs before attempting to execute this
513	<	* task, then execution will be suppressed, {@code isCancelled}
514	<	* will report true, and {@code join} will result in a
515	<	* {@code CancellationException} being thrown. Otherwise, when
516	<	* cancellation races with completion, there are no guarantees
517	<	* about whether {@code isCancelled} will report true, whether
662	<	* {@code join} will return normally or via an exception, or
663	<	* whether these behaviors will remain consistent upon repeated
664	<	* invocation.
511	>	* Attempts to cancel execution of this task. This attempt will
512	>	* fail if the task has already completed, has already been
513	>	* cancelled, or could not be cancelled for some other reason. If
514	>	* successful, and this task has not started when cancel is
515	>	* called, execution of this task is suppressed, {@link
516	>	* #isCancelled} will report true, and {@link #join} will result
517	>	* in a {@code CancellationException} being thrown.
518		*
519		* <p>This method may be overridden in subclasses, but if so, must
520		* still ensure that these minimal properties hold. In particular,
521	<	* the cancel method itself must not throw exceptions.
521	>	* the {@code cancel} method itself must not throw exceptions.
522		*
523	<	* <p> This method is designed to be invoked by <em>other</em>
523	>	* <p>This method is designed to be invoked by <em>other</em>
524		* tasks. To terminate the current task, you can just return or
525		* throw an unchecked exception from its computation method, or
526	<	* invoke {@code completeExceptionally}.
526	>	* invoke {@link #completeExceptionally}.
527		*
528		* @param mayInterruptIfRunning this value is ignored in the
529	<	* default implementation because tasks are not in general
530	<	* cancelled via interruption.
529	>	* default implementation because tasks are not
530	>	* cancelled via interruption
531		*
532	<	* @return true if this task is now cancelled
532	>	* @return {@code true} if this task is now cancelled
533		*/
534		public boolean cancel(boolean mayInterruptIfRunning) {
535	<	setCompletion(CANCELLED);
536	<	return (status & COMPLETION_MASK) == CANCELLED;
535	>	return setCompletion(CANCELLED) == CANCELLED;
536	>	}
537	>
538	>	/**
539	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
540	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
541	>	* exceptions, but if it does anyway, we have no recourse during
542	>	* shutdown, so guard against this case.
543	>	*/
544	>	final void cancelIgnoringExceptions() {
545	>	try {
546	>	cancel(false);
547	>	} catch (Throwable ignore) {
548	>	}
549	>	}
550	>
551	>	/**
552	>	* Cancels ignoring exceptions if worker is terminating
553	>	*/
554	>	final void cancelIfTerminating() {
555	>	Thread t = Thread.currentThread();
556	>	if ((t instanceof ForkJoinWorkerThread) &&
557	>	((ForkJoinWorkerThread) t).isTerminating()) {
558	>	try {
559	>	cancel(false);
560	>	} catch (Throwable ignore) {
561	>	}
562	>	}
563	>	}
564	>
565	>	public final boolean isDone() {
566	>	return status < 0;
567	>	}
568	>
569	>	public final boolean isCancelled() {
570	>	return status == CANCELLED;
571		}
572
573		/**
574	<	* Returns true if this task threw an exception or was cancelled.
574	>	* Returns {@code true} if this task threw an exception or was cancelled.
575		*
576	<	* @return true if this task threw an exception or was cancelled
576	>	* @return {@code true} if this task threw an exception or was cancelled
577		*/
578		public final boolean isCompletedAbnormally() {
579	<	return (status & COMPLETION_MASK) < NORMAL;
579	>	return status < NORMAL;
580	>	}
581	>
582	>	/**
583	>	* Returns {@code true} if this task completed without throwing an
584	>	* exception and was not cancelled.
585	>	*
586	>	* @return {@code true} if this task completed without throwing an
587	>	* exception and was not cancelled
588	>	*/
589	>	public final boolean isCompletedNormally() {
590	>	return status == NORMAL;
591		}
592
593		/**
594		* Returns the exception thrown by the base computation, or a
595	<	* CancellationException if cancelled, or null if none or if the
596	<	* method has not yet completed.
595	>	* {@code CancellationException} if cancelled, or {@code null} if
596	>	* none or if the method has not yet completed.
597		*
598	<	* @return the exception, or null if none
598	>	* @return the exception, or {@code null} if none
599		*/
600		public final Throwable getException() {
601	<	int s = status & COMPLETION_MASK;
602	<	if (s >= NORMAL)
603	<	return null;
604	<	if (s == CANCELLED)
707	<	return new CancellationException();
708	<	return exceptionMap.get(this);
601	>	int s = status;
602	>	return ((s >= NORMAL)    ? null :
603	>	(s == CANCELLED) ? new CancellationException() :
604	>	exceptionMap.get(this));
605		}
606
607		/**
#	Line 714 | Line 610 | public abstract class ForkJoinTask<V> im
610		* {@code join} and related operations. This method may be used
611		* to induce exceptions in asynchronous tasks, or to force
612		* completion of tasks that would not otherwise complete.  Its use
613	<	* in other situations is likely to be wrong.  This method is
613	>	* in other situations is discouraged.  This method is
614		* overridable, but overridden versions must invoke {@code super}
615		* implementation to maintain guarantees.
616		*
617	<	* @param ex the exception to throw. If this exception is
618	<	* not a RuntimeException or Error, the actual exception thrown
619	<	* will be a RuntimeException with cause ex.
617	>	* @param ex the exception to throw. If this exception is not a
618	>	* {@code RuntimeException} or {@code Error}, the actual exception
619	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
620		*/
621		public void completeExceptionally(Throwable ex) {
622	<	setDoneExceptionally((ex instanceof RuntimeException) ||
623	<	(ex instanceof Error)? ex :
624	<	new RuntimeException(ex));
622	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
623	>	(ex instanceof Error) ? ex :
624	>	new RuntimeException(ex));
625		}
626
627		/**
#	Line 734 | Line 630 | public abstract class ForkJoinTask<V> im
630		* operations. This method may be used to provide results for
631		* asynchronous tasks, or to provide alternative handling for
632		* tasks that would not otherwise complete normally. Its use in
633	<	* other situations is likely to be wrong. This method is
633	>	* other situations is discouraged. This method is
634		* overridable, but overridden versions must invoke {@code super}
635		* implementation to maintain guarantees.
636		*
#	Line 743 | Line 639 | public abstract class ForkJoinTask<V> im
639		public void complete(V value) {
640		try {
641		setRawResult(value);
642	<	} catch(Throwable rex) {
643	<	setDoneExceptionally(rex);
642	>	} catch (Throwable rex) {
643	>	setExceptionalCompletion(rex);
644		return;
645		}
646	<	setNormalCompletion();
646	>	setCompletion(NORMAL);
647		}
648
649		public final V get() throws InterruptedException, ExecutionException {
650	<	ForkJoinWorkerThread w = getWorker();
651	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
652	<	awaitDone(w, true);
653	<	return reportFutureResult();
650	>	int s = doJoin();
651	>	if (Thread.interrupted())
652	>	throw new InterruptedException();
653	>	if (s < NORMAL) {
654	>	Throwable ex;
655	>	if (s == CANCELLED)
656	>	throw new CancellationException();
657	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
658	>	throw new ExecutionException(ex);
659	>	}
660	>	return getRawResult();
661		}
662
663		public final V get(long timeout, TimeUnit unit)
664		throws InterruptedException, ExecutionException, TimeoutException {
665	<	ForkJoinWorkerThread w = getWorker();
666	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
667	<	awaitDone(w, unit.toNanos(timeout));
668	<	return reportTimedFutureResult();
669	<	}
670	<
671	<	/**
672	<	* Possibly executes other tasks until this task is ready, then
673	<	* returns the result of the computation.  This method may be more
674	<	* efficient than {@code join}, but is only applicable when
675	<	* there are no potential dependencies between continuation of the
676	<	* current task and that of any other task that might be executed
677	<	* while helping. (This usually holds for pure divide-and-conquer
678	<	* tasks). This method may be invoked only from within
679	<	* ForkJoinTask computations. Attempts to invoke in other contexts
680	<	* result in exceptions or errors possibly including ClassCastException.
681	<	*
682	<	* @return the computed result
683	<	*/
684	<	public final V helpJoin() {
685	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
686	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
687	<	reportException(busyJoin(w));
688	<	return getRawResult();
689	<	}
690	<
691	<	/**
692	<	* Possibly executes other tasks until this task is ready.  This
693	<	* method may be invoked only from within ForkJoinTask
694	<	* computations. Attempts to invoke in other contexts result in
695	<	* exceptions or errors possibly including ClassCastException.
696	<	*/
697	<	public final void quietlyHelpJoin() {
698	<	if (status >= 0) {
699	<	ForkJoinWorkerThread w =
700	<	(ForkJoinWorkerThread)(Thread.currentThread());
701	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
702	<	busyJoin(w);
665	>	Thread t = Thread.currentThread();
666	>	ForkJoinPool pool;
667	>	if (t instanceof ForkJoinWorkerThread) {
668	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
669	>	if (status >= 0 && w.unpushTask(this))
670	>	tryExec();
671	>	pool = w.pool;
672	>	}
673	>	else
674	>	pool = null;
675	>	/*
676	>	* Timed wait loop intermixes cases for FJ (pool != null) and
677	>	* non FJ threads. For FJ, decrement pool count but don't try
678	>	* for replacement; increment count on completion. For non-FJ,
679	>	* deal with interrupts. This is messy, but a little less so
680	>	* than is splitting the FJ and nonFJ cases.
681	>	*/
682	>	boolean interrupted = false;
683	>	boolean dec = false; // true if pool count decremented
684	>	for (;;) {
685	>	if (Thread.interrupted() && pool == null) {
686	>	interrupted = true;
687	>	break;
688	>	}
689	>	int s = status;
690	>	if (s < 0)
691	>	break;
692	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) {
693	>	long startTime = System.nanoTime();
694	>	long nanos = unit.toNanos(timeout);
695	>	long nt; // wait time
696	>	while (status >= 0 &&
697	>	(nt = nanos - (System.nanoTime() - startTime)) > 0) {
698	>	if (pool != null && !dec)
699	>	dec = pool.tryDecrementRunningCount();
700	>	else {
701	>	long ms = nt / 1000000;
702	>	int ns = (int) (nt % 1000000);
703	>	try {
704	>	synchronized(this) {
705	>	if (status >= 0)
706	>	wait(ms, ns);
707	>	}
708	>	} catch (InterruptedException ie) {
709	>	if (pool != null)
710	>	cancelIfTerminating();
711	>	else {
712	>	interrupted = true;
713	>	break;
714	>	}
715	>	}
716	>	}
717	>	}
718	>	break;
719	>	}
720	>	}
721	>	if (pool != null && dec)
722	>	pool.incrementRunningCount();
723	>	if (interrupted)
724	>	throw new InterruptedException();
725	>	int es = status;
726	>	if (es != NORMAL) {
727	>	Throwable ex;
728	>	if (es == CANCELLED)
729	>	throw new CancellationException();
730	>	if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
731	>	throw new ExecutionException(ex);
732	>	throw new TimeoutException();
733		}
734	+	return getRawResult();
735		}
736
737		/**
#	Line 807 | Line 741 | public abstract class ForkJoinTask<V> im
741		* known to have aborted.
742		*/
743		public final void quietlyJoin() {
744	<	if (status >= 0) {
811	<	ForkJoinWorkerThread w = getWorker();
812	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
813	<	awaitDone(w, true);
814	<	}
744	>	doJoin();
745		}
746
747		/**
#	Line 822 | Line 752 | public abstract class ForkJoinTask<V> im
752		* known to have aborted.
753		*/
754		public final void quietlyInvoke() {
755	<	if (status >= 0 && !tryQuietlyInvoke())
826	<	quietlyJoin();
755	>	doInvoke();
756		}
757
758		/**
759		* Possibly executes tasks until the pool hosting the current task
760	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
761	<	* designs in which many tasks are forked, but none are explicitly
762	<	* joined, instead executing them until all are processed.
760	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
761	>	* be of use in designs in which many tasks are forked, but none
762	>	* are explicitly joined, instead executing them until all are
763	>	* processed.
764	>	*
765	>	* <p>This method may be invoked only from within {@code
766	>	* ForkJoinTask} computations (as may be determined using method
767	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
768	>	* result in exceptions or errors, possibly including {@code
769	>	* ClassCastException}.
770		*/
771		public static void helpQuiesce() {
772	<	((ForkJoinWorkerThread)(Thread.currentThread())).
773	<	helpQuiescePool();
772	>	((ForkJoinWorkerThread) Thread.currentThread())
773	>	.helpQuiescePool();
774		}
775
776		/**
#	Line 843 | Line 779 | public abstract class ForkJoinTask<V> im
779		* this task, but only if reuse occurs when this task has either
780		* never been forked, or has been forked, then completed and all
781		* outstanding joins of this task have also completed. Effects
782	<	* under any other usage conditions are not guaranteed, and are
783	<	* almost surely wrong. This method may be useful when executing
782	>	* under any other usage conditions are not guaranteed.
783	>	* This method may be useful when executing
784		* pre-constructed trees of subtasks in loops.
785		*/
786		public void reinitialize() {
787	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
787	>	if (status == EXCEPTIONAL)
788		exceptionMap.remove(this);
789		status = 0;
790		}
791
792		/**
793		* Returns the pool hosting the current task execution, or null
794	<	* if this task is executing outside of any pool.
794	>	* if this task is executing outside of any ForkJoinPool.
795		*
796	<	* @return the pool, or null if none
796	>	* @see #inForkJoinPool
797	>	* @return the pool, or {@code null} if none
798		*/
799		public static ForkJoinPool getPool() {
800		Thread t = Thread.currentThread();
801	<	return ((t instanceof ForkJoinWorkerThread)?
802	<	((ForkJoinWorkerThread)t).pool : null);
801	>	return (t instanceof ForkJoinWorkerThread) ?
802	>	((ForkJoinWorkerThread) t).pool : null;
803	>	}
804	>
805	>	/**
806	>	* Returns {@code true} if the current thread is executing as a
807	>	* ForkJoinPool computation.
808	>	*
809	>	* @return {@code true} if the current thread is executing as a
810	>	* ForkJoinPool computation, or false otherwise
811	>	*/
812	>	public static boolean inForkJoinPool() {
813	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
814		}
815
816		/**
#	Line 871 | Line 819 | public abstract class ForkJoinTask<V> im
819		* by the current thread, and has not commenced executing in
820		* another thread.  This method may be useful when arranging
821		* alternative local processing of tasks that could have been, but
822	<	* were not, stolen. This method may be invoked only from within
823	<	* ForkJoinTask computations. Attempts to invoke in other contexts
824	<	* result in exceptions or errors possibly including ClassCastException.
822	>	* were not, stolen.
823	>	*
824	>	* <p>This method may be invoked only from within {@code
825	>	* ForkJoinTask} computations (as may be determined using method
826	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
827	>	* result in exceptions or errors, possibly including {@code
828	>	* ClassCastException}.
829		*
830	<	* @return true if unforked
830	>	* @return {@code true} if unforked
831		*/
832		public boolean tryUnfork() {
833	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
833	>	return ((ForkJoinWorkerThread) Thread.currentThread())
834	>	.unpushTask(this);
835		}
836
837		/**
#	Line 887 | Line 840 | public abstract class ForkJoinTask<V> im
840		* value may be useful for heuristic decisions about whether to
841		* fork other tasks.
842		*
843	+	* <p>This method may be invoked only from within {@code
844	+	* ForkJoinTask} computations (as may be determined using method
845	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
846	+	* result in exceptions or errors, possibly including {@code
847	+	* ClassCastException}.
848	+	*
849		* @return the number of tasks
850		*/
851		public static int getQueuedTaskCount() {
852	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
853	<	getQueueSize();
852	>	return ((ForkJoinWorkerThread) Thread.currentThread())
853	>	.getQueueSize();
854		}
855
856		/**
#	Line 904 | Line 863 | public abstract class ForkJoinTask<V> im
863		* tasks, and to process computations locally if this threshold is
864		* exceeded.
865		*
866	+	* <p>This method may be invoked only from within {@code
867	+	* ForkJoinTask} computations (as may be determined using method
868	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
869	+	* result in exceptions or errors, possibly including {@code
870	+	* ClassCastException}.
871	+	*
872		* @return the surplus number of tasks, which may be negative
873		*/
874		public static int getSurplusQueuedTaskCount() {
875	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
875	>	return ((ForkJoinWorkerThread) Thread.currentThread())
876		.getEstimatedSurplusTaskCount();
877		}
878
879		// Extension methods
880
881		/**
882	<	* Returns the result that would be returned by {@code join},
883	<	* even if this task completed abnormally, or null if this task is
884	<	* not known to have been completed.  This method is designed to
885	<	* aid debugging, as well as to support extensions. Its use in any
886	<	* other context is discouraged.
882	>	* Returns the result that would be returned by {@link #join}, even
883	>	* if this task completed abnormally, or {@code null} if this task
884	>	* is not known to have been completed.  This method is designed
885	>	* to aid debugging, as well as to support extensions. Its use in
886	>	* any other context is discouraged.
887		*
888	<	* @return the result, or null if not completed
888	>	* @return the result, or {@code null} if not completed
889		*/
890		public abstract V getRawResult();
891
#	Line 939 | Line 904 | public abstract class ForkJoinTask<V> im
904		* called otherwise. The return value controls whether this task
905		* is considered to be done normally. It may return false in
906		* asynchronous actions that require explicit invocations of
907	<	* {@code complete} to become joinable. It may throw exceptions
908	<	* to indicate abnormal exit.
907	>	* {@link #complete} to become joinable. It may also throw an
908	>	* (unchecked) exception to indicate abnormal exit.
909		*
910	<	* @return true if completed normally
946	<	* @throws Error or RuntimeException if encountered during computation
910	>	* @return {@code true} if completed normally
911		*/
912		protected abstract boolean exec();
913
914		/**
915	<	* Returns, but does not unschedule or execute, the task queued by
916	<	* the current thread but not yet executed, if one is
915	>	* Returns, but does not unschedule or execute, a task queued by
916	>	* the current thread but not yet executed, if one is immediately
917		* available. There is no guarantee that this task will actually
918	<	* be polled or executed next.  This method is designed primarily
919	<	* to support extensions, and is unlikely to be useful otherwise.
920	<	* This method may be invoked only from within ForkJoinTask
921	<	* computations. Attempts to invoke in other contexts result in
922	<	* exceptions or errors possibly including ClassCastException.
918	>	* be polled or executed next. Conversely, this method may return
919	>	* null even if a task exists but cannot be accessed without
920	>	* contention with other threads.  This method is designed
921	>	* primarily to support extensions, and is unlikely to be useful
922	>	* otherwise.
923	>	*
924	>	* <p>This method may be invoked only from within {@code
925	>	* ForkJoinTask} computations (as may be determined using method
926	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
927	>	* result in exceptions or errors, possibly including {@code
928	>	* ClassCastException}.
929		*
930	<	* @return the next task, or null if none are available
930	>	* @return the next task, or {@code null} if none are available
931		*/
932		protected static ForkJoinTask<?> peekNextLocalTask() {
933	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask();
933	>	return ((ForkJoinWorkerThread) Thread.currentThread())
934	>	.peekTask();
935		}
936
937		/**
938		* Unschedules and returns, without executing, the next task
939		* queued by the current thread but not yet executed.  This method
940		* is designed primarily to support extensions, and is unlikely to
941	<	* be useful otherwise.  This method may be invoked only from
971	<	* within ForkJoinTask computations. Attempts to invoke in other
972	<	* contexts result in exceptions or errors possibly including
973	<	* ClassCastException.
941	>	* be useful otherwise.
942		*
943	<	* @return the next task, or null if none are available
943	>	* <p>This method may be invoked only from within {@code
944	>	* ForkJoinTask} computations (as may be determined using method
945	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
946	>	* result in exceptions or errors, possibly including {@code
947	>	* ClassCastException}.
948	>	*
949	>	* @return the next task, or {@code null} if none are available
950		*/
951		protected static ForkJoinTask<?> pollNextLocalTask() {
952	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).pollLocalTask();
952	>	return ((ForkJoinWorkerThread) Thread.currentThread())
953	>	.pollLocalTask();
954		}
955
956		/**
#	Line 986 | Line 961 | public abstract class ForkJoinTask<V> im
961		* {@code null} result does not necessarily imply quiescence
962		* of the pool this task is operating in.  This method is designed
963		* primarily to support extensions, and is unlikely to be useful
964	<	* otherwise.  This method may be invoked only from within
965	<	* ForkJoinTask computations. Attempts to invoke in other contexts
966	<	* result in exceptions or errors possibly including
967	<	* ClassCastException.
964	>	* otherwise.
965	>	*
966	>	* <p>This method may be invoked only from within {@code
967	>	* ForkJoinTask} computations (as may be determined using method
968	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
969	>	* result in exceptions or errors, possibly including {@code
970	>	* ClassCastException}.
971		*
972	<	* @return a task, or null if none are available
972	>	* @return a task, or {@code null} if none are available
973		*/
974		protected static ForkJoinTask<?> pollTask() {
975	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
976	<	pollTask();
975	>	return ((ForkJoinWorkerThread) Thread.currentThread())
976	>	.pollTask();
977	>	}
978	>
979	>	/**
980	>	* Adaptor for Runnables. This implements RunnableFuture
981	>	* to be compliant with AbstractExecutorService constraints
982	>	* when used in ForkJoinPool.
983	>	*/
984	>	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
985	>	implements RunnableFuture<T> {
986	>	final Runnable runnable;
987	>	final T resultOnCompletion;
988	>	T result;
989	>	AdaptedRunnable(Runnable runnable, T result) {
990	>	if (runnable == null) throw new NullPointerException();
991	>	this.runnable = runnable;
992	>	this.resultOnCompletion = result;
993	>	}
994	>	public T getRawResult() { return result; }
995	>	public void setRawResult(T v) { result = v; }
996	>	public boolean exec() {
997	>	runnable.run();
998	>	result = resultOnCompletion;
999	>	return true;
1000	>	}
1001	>	public void run() { invoke(); }
1002	>	private static final long serialVersionUID = 5232453952276885070L;
1003	>	}
1004	>
1005	>	/**
1006	>	* Adaptor for Callables
1007	>	*/
1008	>	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1009	>	implements RunnableFuture<T> {
1010	>	final Callable<? extends T> callable;
1011	>	T result;
1012	>	AdaptedCallable(Callable<? extends T> callable) {
1013	>	if (callable == null) throw new NullPointerException();
1014	>	this.callable = callable;
1015	>	}
1016	>	public T getRawResult() { return result; }
1017	>	public void setRawResult(T v) { result = v; }
1018	>	public boolean exec() {
1019	>	try {
1020	>	result = callable.call();
1021	>	return true;
1022	>	} catch (Error err) {
1023	>	throw err;
1024	>	} catch (RuntimeException rex) {
1025	>	throw rex;
1026	>	} catch (Exception ex) {
1027	>	throw new RuntimeException(ex);
1028	>	}
1029	>	}
1030	>	public void run() { invoke(); }
1031	>	private static final long serialVersionUID = 2838392045355241008L;
1032	>	}
1033	>
1034	>	/**
1035	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1036	>	* method of the given {@code Runnable} as its action, and returns
1037	>	* a null result upon {@link #join}.
1038	>	*
1039	>	* @param runnable the runnable action
1040	>	* @return the task
1041	>	*/
1042	>	public static ForkJoinTask<?> adapt(Runnable runnable) {
1043	>	return new AdaptedRunnable<Void>(runnable, null);
1044	>	}
1045	>
1046	>	/**
1047	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1048	>	* method of the given {@code Runnable} as its action, and returns
1049	>	* the given result upon {@link #join}.
1050	>	*
1051	>	* @param runnable the runnable action
1052	>	* @param result the result upon completion
1053	>	* @return the task
1054	>	*/
1055	>	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1056	>	return new AdaptedRunnable<T>(runnable, result);
1057	>	}
1058	>
1059	>	/**
1060	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1061	>	* method of the given {@code Callable} as its action, and returns
1062	>	* its result upon {@link #join}, translating any checked exceptions
1063	>	* encountered into {@code RuntimeException}.
1064	>	*
1065	>	* @param callable the callable action
1066	>	* @return the task
1067	>	*/
1068	>	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1069	>	return new AdaptedCallable<T>(callable);
1070		}
1071
1072		// Serialization support
#	Line 1003 | Line 1074 | public abstract class ForkJoinTask<V> im
1074		private static final long serialVersionUID = -7721805057305804111L;
1075
1076		/**
1077	<	* Save the state to a stream.
1077	>	* Saves the state to a stream.
1078		*
1079		* @serialData the current run status and the exception thrown
1080	<	* during execution, or null if none
1080	>	* during execution, or {@code null} if none
1081		* @param s the stream
1082		*/
1083		private void writeObject(java.io.ObjectOutputStream s)
#	Line 1016 | Line 1087 | public abstract class ForkJoinTask<V> im
1087		}
1088
1089		/**
1090	<	* Reconstitute the instance from a stream.
1090	>	* Reconstitutes the instance from a stream.
1091		*
1092		* @param s the stream
1093		*/
1094		private void readObject(java.io.ObjectInputStream s)
1095		throws java.io.IOException, ClassNotFoundException {
1096		s.defaultReadObject();
1026	–	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1027	–	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1097		Object ex = s.readObject();
1098		if (ex != null)
1099	<	setDoneExceptionally((Throwable)ex);
1099	>	setExceptionalCompletion((Throwable) ex);
1100		}
1101
1102	<	// Temporary Unsafe mechanics for preliminary release
1103	<	private static Unsafe getUnsafe() throws Throwable {
1102	>	// Unsafe mechanics
1103	>
1104	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1105	>	private static final long statusOffset =
1106	>	objectFieldOffset("status", ForkJoinTask.class);
1107	>
1108	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1109		try {
1110	<	return Unsafe.getUnsafe();
1110	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1111	>	} catch (NoSuchFieldException e) {
1112	>	// Convert Exception to corresponding Error
1113	>	NoSuchFieldError error = new NoSuchFieldError(field);
1114	>	error.initCause(e);
1115	>	throw error;
1116	>	}
1117	>	}
1118	>
1119	>	/**
1120	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1121	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1122	>	* into a jdk.
1123	>	*
1124	>	* @return a sun.misc.Unsafe
1125	>	*/
1126	>	private static sun.misc.Unsafe getUnsafe() {
1127	>	try {
1128	>	return sun.misc.Unsafe.getUnsafe();
1129		} catch (SecurityException se) {
1130		try {
1131		return java.security.AccessController.doPrivileged
1132	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1133	<	public Unsafe run() throws Exception {
1134	<	return getUnsafePrivileged();
1132	>	(new java.security
1133	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1134	>	public sun.misc.Unsafe run() throws Exception {
1135	>	java.lang.reflect.Field f = sun.misc
1136	>	.Unsafe.class.getDeclaredField("theUnsafe");
1137	>	f.setAccessible(true);
1138	>	return (sun.misc.Unsafe) f.get(null);
1139		}});
1140		} catch (java.security.PrivilegedActionException e) {
1141	<	throw e.getCause();
1141	>	throw new RuntimeException("Could not initialize intrinsics",
1142	>	e.getCause());
1143		}
1144		}
1145		}
1049	–
1050	–	private static Unsafe getUnsafePrivileged()
1051	–	throws NoSuchFieldException, IllegalAccessException {
1052	–	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1053	–	f.setAccessible(true);
1054	–	return (Unsafe) f.get(null);
1055	–	}
1056	–
1057	–	private static long fieldOffset(String fieldName)
1058	–	throws NoSuchFieldException {
1059	–	return UNSAFE.objectFieldOffset
1060	–	(ForkJoinTask.class.getDeclaredField(fieldName));
1061	–	}
1062	–
1063	–	static final Unsafe UNSAFE;
1064	–	static final long statusOffset;
1065	–
1066	–	static {
1067	–	try {
1068	–	UNSAFE = getUnsafe();
1069	–	statusOffset = fieldOffset("status");
1070	–	} catch (Throwable e) {
1071	–	throw new RuntimeException("Could not initialize intrinsics", e);
1072	–	}
1073	–	}
1074	–
1146		}

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