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package jsr166y; |
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import java.util.concurrent.*; |
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|
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import java.io.Serializable; |
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import java.util.Collection; |
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import java.util.Collections; |
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import java.util.RandomAccess; |
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import java.util.Map; |
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import java.util.WeakHashMap; |
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import java.util.concurrent.Callable; |
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import java.util.concurrent.CancellationException; |
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import java.util.concurrent.ExecutionException; |
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import java.util.concurrent.Executor; |
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import java.util.concurrent.ExecutorService; |
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import java.util.concurrent.Future; |
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import java.util.concurrent.RejectedExecutionException; |
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import java.util.concurrent.RunnableFuture; |
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import java.util.concurrent.TimeUnit; |
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import java.util.concurrent.TimeoutException; |
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|
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/** |
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* Abstract base class for tasks that run within a {@link ForkJoinPool}. |
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* start other subtasks. As indicated by the name of this class, |
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* many programs using {@code ForkJoinTask} employ only methods |
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* {@link #fork} and {@link #join}, or derivatives such as {@link |
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< |
* #invokeAll}. However, this class also provides a number of other |
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< |
* methods that can come into play in advanced usages, as well as |
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* extension mechanics that allow support of new forms of fork/join |
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< |
* processing. |
39 |
> |
* #invokeAll(ForkJoinTask...) invokeAll}. However, this class also |
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* provides a number of other methods that can come into play in |
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> |
* advanced usages, as well as extension mechanics that allow |
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* support of new forms of fork/join processing. |
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* |
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* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}. |
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* The efficiency of {@code ForkJoinTask}s stems from a set of |
110 |
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* result in exceptions or errors, possibly including |
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* {@code ClassCastException}. |
112 |
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* |
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* <p>Method {@link #join} and its variants are appropriate for use |
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* only when completion dependencies are acyclic; that is, the |
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* parallel computation can be described as a directed acyclic graph |
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* (DAG). Otherwise, executions may encounter a form of deadlock as |
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* tasks cyclically wait for each other. However, this framework |
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* supports other methods and techniques (for example the use of |
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* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that |
120 |
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* may be of use in constructing custom subclasses for problems that |
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* are not statically structured as DAGs. |
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* |
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* <p>Most base support methods are {@code final}, to prevent |
124 |
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* overriding of implementations that are intrinsically tied to the |
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* underlying lightweight task scheduling framework. Developers |
134 |
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* computation. Large tasks should be split into smaller subtasks, |
135 |
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* usually via recursive decomposition. As a very rough rule of thumb, |
136 |
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* a task should perform more than 100 and less than 10000 basic |
137 |
< |
* computational steps. If tasks are too big, then parallelism cannot |
138 |
< |
* improve throughput. If too small, then memory and internal task |
139 |
< |
* maintenance overhead may overwhelm processing. |
137 |
> |
* computational steps, and should avoid indefinite looping. If tasks |
138 |
> |
* are too big, then parallelism cannot improve throughput. If too |
139 |
> |
* small, then memory and internal task maintenance overhead may |
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> |
* overwhelm processing. |
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* |
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* <p>This class provides {@code adapt} methods for {@link Runnable} |
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* and {@link Callable}, that may be of use when mixing execution of |
234 |
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} |
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|
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/** |
237 |
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* Blocks a worker thread until completion. Called only by |
238 |
< |
* pool. Currently unused -- pool-based waits use timeout |
220 |
< |
* version below. |
237 |
> |
* Blocks a worker thread until completed or timed out. Called |
238 |
> |
* only by pool. |
239 |
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*/ |
240 |
< |
final void internalAwaitDone() { |
241 |
< |
int s; // the odd construction reduces lock bias effects |
242 |
< |
while ((s = status) >= 0) { |
243 |
< |
try { |
244 |
< |
synchronized(this) { |
245 |
< |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL)) |
246 |
< |
wait(); |
240 |
> |
final void internalAwaitDone(long millis, int nanos) { |
241 |
> |
if (status >= 0) { |
242 |
> |
try { // the odd construction reduces lock bias effects |
243 |
> |
synchronized (this) { |
244 |
> |
if (status > 0 || |
245 |
> |
UNSAFE.compareAndSwapInt(this, statusOffset, |
246 |
> |
0, SIGNAL)) |
247 |
> |
wait(millis, nanos); |
248 |
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} |
249 |
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} catch (InterruptedException ie) { |
250 |
|
cancelIfTerminating(); |
253 |
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} |
254 |
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|
255 |
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/** |
256 |
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* Blocks a worker thread until completed or timed out. Called |
238 |
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* only by pool. |
239 |
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* |
240 |
< |
* @return status on exit |
256 |
> |
* Blocks a non-worker-thread until completion. |
257 |
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*/ |
258 |
< |
final int internalAwaitDone(long millis) { |
259 |
< |
int s; |
260 |
< |
if ((s = status) >= 0) { |
261 |
< |
try { |
262 |
< |
synchronized(this) { |
263 |
< |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL)) |
264 |
< |
wait(millis, 0); |
258 |
> |
private void externalAwaitDone() { |
259 |
> |
if (status >= 0) { |
260 |
> |
boolean interrupted = false; |
261 |
> |
synchronized(this) { |
262 |
> |
int s; |
263 |
> |
while ((s = status) >= 0) { |
264 |
> |
if (s == 0 && |
265 |
> |
!UNSAFE.compareAndSwapInt(this, statusOffset, |
266 |
> |
0, SIGNAL)) |
267 |
> |
continue; |
268 |
> |
try { |
269 |
> |
wait(); |
270 |
> |
} catch (InterruptedException ie) { |
271 |
> |
interrupted = true; |
272 |
> |
} |
273 |
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} |
250 |
– |
} catch (InterruptedException ie) { |
251 |
– |
cancelIfTerminating(); |
274 |
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} |
275 |
< |
s = status; |
275 |
> |
if (interrupted) |
276 |
> |
Thread.currentThread().interrupt(); |
277 |
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} |
255 |
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return s; |
278 |
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} |
279 |
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|
280 |
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/** |
281 |
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* Blocks a non-worker-thread until completion. |
281 |
> |
* Blocks a non-worker-thread until completion or interruption or timeout |
282 |
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*/ |
283 |
< |
private void externalAwaitDone() { |
284 |
< |
int s; |
285 |
< |
while ((s = status) >= 0) { |
283 |
> |
private void externalInterruptibleAwaitDone(boolean timed, long nanos) |
284 |
> |
throws InterruptedException { |
285 |
> |
if (Thread.interrupted()) |
286 |
> |
throw new InterruptedException(); |
287 |
> |
if (status >= 0) { |
288 |
> |
long startTime = timed ? System.nanoTime() : 0L; |
289 |
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synchronized(this) { |
290 |
< |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){ |
291 |
< |
boolean interrupted = false; |
292 |
< |
while (status >= 0) { |
293 |
< |
try { |
294 |
< |
wait(); |
295 |
< |
} catch (InterruptedException ie) { |
296 |
< |
interrupted = true; |
297 |
< |
} |
298 |
< |
} |
299 |
< |
if (interrupted) |
300 |
< |
Thread.currentThread().interrupt(); |
301 |
< |
break; |
290 |
> |
int s; |
291 |
> |
while ((s = status) >= 0) { |
292 |
> |
long nt; |
293 |
> |
if (s == 0 && |
294 |
> |
!UNSAFE.compareAndSwapInt(this, statusOffset, |
295 |
> |
0, SIGNAL)) |
296 |
> |
continue; |
297 |
> |
else if (!timed) |
298 |
> |
wait(); |
299 |
> |
else if ((nt = nanos - (System.nanoTime()-startTime)) > 0L) |
300 |
> |
wait(nt / 1000000, (int)(nt % 1000000)); |
301 |
> |
else |
302 |
> |
break; |
303 |
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} |
304 |
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} |
305 |
|
} |
334 |
|
* #isDone} returning {@code true}. |
335 |
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* |
336 |
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* <p>This method may be invoked only from within {@code |
337 |
< |
* ForkJoinTask} computations (as may be determined using method |
337 |
> |
* ForkJoinPool} computations (as may be determined using method |
338 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
339 |
|
* result in exceptions or errors, possibly including {@code |
340 |
|
* ClassCastException}. |
348 |
|
} |
349 |
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|
350 |
|
/** |
351 |
< |
* Returns the result of the computation when it {@link #isDone is done}. |
352 |
< |
* This method differs from {@link #get()} in that |
351 |
> |
* Returns the result of the computation when it {@link #isDone is |
352 |
> |
* done}. This method differs from {@link #get()} in that |
353 |
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* abnormal completion results in {@code RuntimeException} or |
354 |
< |
* {@code Error}, not {@code ExecutionException}. |
354 |
> |
* {@code Error}, not {@code ExecutionException}, and that |
355 |
> |
* interrupts of the calling thread do <em>not</em> cause the |
356 |
> |
* method to abruptly return by throwing {@code |
357 |
> |
* InterruptedException}. |
358 |
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* |
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* @return the computed result |
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*/ |
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* unprocessed. |
397 |
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* |
398 |
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* <p>This method may be invoked only from within {@code |
399 |
< |
* ForkJoinTask} computations (as may be determined using method |
399 |
> |
* ForkJoinPool} computations (as may be determined using method |
400 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
401 |
|
* result in exceptions or errors, possibly including {@code |
402 |
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* ClassCastException}. |
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* normally or exceptionally, or left unprocessed. |
425 |
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* |
426 |
|
* <p>This method may be invoked only from within {@code |
427 |
< |
* ForkJoinTask} computations (as may be determined using method |
427 |
> |
* ForkJoinPool} computations (as may be determined using method |
428 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
429 |
|
* result in exceptions or errors, possibly including {@code |
430 |
|
* ClassCastException}. |
479 |
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* unprocessed. |
480 |
|
* |
481 |
|
* <p>This method may be invoked only from within {@code |
482 |
< |
* ForkJoinTask} computations (as may be determined using method |
482 |
> |
* ForkJoinPool} computations (as may be determined using method |
483 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
484 |
|
* result in exceptions or errors, possibly including {@code |
485 |
|
* ClassCastException}. |
531 |
|
|
532 |
|
/** |
533 |
|
* Attempts to cancel execution of this task. This attempt will |
534 |
< |
* fail if the task has already completed, has already been |
535 |
< |
* cancelled, or could not be cancelled for some other reason. If |
536 |
< |
* successful, and this task has not started when cancel is |
537 |
< |
* called, execution of this task is suppressed, {@link |
538 |
< |
* #isCancelled} will report true, and {@link #join} will result |
539 |
< |
* in a {@code CancellationException} being thrown. |
534 |
> |
* fail if the task has already completed or could not be |
535 |
> |
* cancelled for some other reason. If successful, and this task |
536 |
> |
* has not started when {@code cancel} is called, execution of |
537 |
> |
* this task is suppressed. After this method returns |
538 |
> |
* successfully, unless there is an intervening call to {@link |
539 |
> |
* #reinitialize}, subsequent calls to {@link #isCancelled}, |
540 |
> |
* {@link #isDone}, and {@code cancel} will return {@code true} |
541 |
> |
* and calls to {@link #join} and related methods will result in |
542 |
> |
* {@code CancellationException}. |
543 |
|
* |
544 |
|
* <p>This method may be overridden in subclasses, but if so, must |
545 |
< |
* still ensure that these minimal properties hold. In particular, |
546 |
< |
* the {@code cancel} method itself must not throw exceptions. |
545 |
> |
* still ensure that these properties hold. In particular, the |
546 |
> |
* {@code cancel} method itself must not throw exceptions. |
547 |
|
* |
548 |
|
* <p>This method is designed to be invoked by <em>other</em> |
549 |
|
* tasks. To terminate the current task, you can just return or |
550 |
|
* throw an unchecked exception from its computation method, or |
551 |
|
* invoke {@link #completeExceptionally}. |
552 |
|
* |
553 |
< |
* @param mayInterruptIfRunning this value is ignored in the |
554 |
< |
* default implementation because tasks are not |
555 |
< |
* cancelled via interruption |
553 |
> |
* @param mayInterruptIfRunning this value has no effect in the |
554 |
> |
* default implementation because interrupts are not used to |
555 |
> |
* control cancellation. |
556 |
|
* |
557 |
|
* @return {@code true} if this task is now cancelled |
558 |
|
*/ |
674 |
|
setCompletion(NORMAL); |
675 |
|
} |
676 |
|
|
677 |
+ |
/** |
678 |
+ |
* Waits if necessary for the computation to complete, and then |
679 |
+ |
* retrieves its result. |
680 |
+ |
* |
681 |
+ |
* @return the computed result |
682 |
+ |
* @throws CancellationException if the computation was cancelled |
683 |
+ |
* @throws ExecutionException if the computation threw an |
684 |
+ |
* exception |
685 |
+ |
* @throws InterruptedException if the current thread is not a |
686 |
+ |
* member of a ForkJoinPool and was interrupted while waiting |
687 |
+ |
*/ |
688 |
|
public final V get() throws InterruptedException, ExecutionException { |
689 |
< |
quietlyJoin(); |
690 |
< |
if (Thread.interrupted()) |
691 |
< |
throw new InterruptedException(); |
689 |
> |
Thread t = Thread.currentThread(); |
690 |
> |
if (t instanceof ForkJoinWorkerThread) |
691 |
> |
quietlyJoin(); |
692 |
> |
else |
693 |
> |
externalInterruptibleAwaitDone(false, 0L); |
694 |
|
int s = status; |
695 |
< |
if (s < NORMAL) { |
695 |
> |
if (s != NORMAL) { |
696 |
|
Throwable ex; |
697 |
|
if (s == CANCELLED) |
698 |
|
throw new CancellationException(); |
702 |
|
return getRawResult(); |
703 |
|
} |
704 |
|
|
705 |
+ |
/** |
706 |
+ |
* Waits if necessary for at most the given time for the computation |
707 |
+ |
* to complete, and then retrieves its result, if available. |
708 |
+ |
* |
709 |
+ |
* @param timeout the maximum time to wait |
710 |
+ |
* @param unit the time unit of the timeout argument |
711 |
+ |
* @return the computed result |
712 |
+ |
* @throws CancellationException if the computation was cancelled |
713 |
+ |
* @throws ExecutionException if the computation threw an |
714 |
+ |
* exception |
715 |
+ |
* @throws InterruptedException if the current thread is not a |
716 |
+ |
* member of a ForkJoinPool and was interrupted while waiting |
717 |
+ |
* @throws TimeoutException if the wait timed out |
718 |
+ |
*/ |
719 |
|
public final V get(long timeout, TimeUnit unit) |
720 |
|
throws InterruptedException, ExecutionException, TimeoutException { |
721 |
+ |
long nanos = unit.toNanos(timeout); |
722 |
|
Thread t = Thread.currentThread(); |
723 |
< |
ForkJoinPool pool; |
724 |
< |
if (t instanceof ForkJoinWorkerThread) { |
665 |
< |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
666 |
< |
if (status >= 0 && w.unpushTask(this)) |
667 |
< |
quietlyExec(); |
668 |
< |
pool = w.pool; |
669 |
< |
} |
723 |
> |
if (t instanceof ForkJoinWorkerThread) |
724 |
> |
((ForkJoinWorkerThread)t).joinTask(this, true, nanos); |
725 |
|
else |
726 |
< |
pool = null; |
727 |
< |
/* |
728 |
< |
* Timed wait loop intermixes cases for FJ (pool != null) and |
674 |
< |
* non FJ threads. For FJ, decrement pool count but don't try |
675 |
< |
* for replacement; increment count on completion. For non-FJ, |
676 |
< |
* deal with interrupts. This is messy, but a little less so |
677 |
< |
* than is splitting the FJ and nonFJ cases. |
678 |
< |
*/ |
679 |
< |
boolean interrupted = false; |
680 |
< |
boolean dec = false; // true if pool count decremented |
681 |
< |
long nanos = unit.toNanos(timeout); |
682 |
< |
for (;;) { |
683 |
< |
if (pool == null && Thread.interrupted()) { |
684 |
< |
interrupted = true; |
685 |
< |
break; |
686 |
< |
} |
687 |
< |
int s = status; |
688 |
< |
if (s < 0) |
689 |
< |
break; |
690 |
< |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) { |
691 |
< |
long startTime = System.nanoTime(); |
692 |
< |
long nt; // wait time |
693 |
< |
while (status >= 0 && |
694 |
< |
(nt = nanos - (System.nanoTime() - startTime)) > 0) { |
695 |
< |
if (pool != null && !dec) |
696 |
< |
dec = pool.tryDecrementRunningCount(); |
697 |
< |
else { |
698 |
< |
long ms = nt / 1000000; |
699 |
< |
int ns = (int) (nt % 1000000); |
700 |
< |
try { |
701 |
< |
synchronized(this) { |
702 |
< |
if (status >= 0) |
703 |
< |
wait(ms, ns); |
704 |
< |
} |
705 |
< |
} catch (InterruptedException ie) { |
706 |
< |
if (pool != null) |
707 |
< |
cancelIfTerminating(); |
708 |
< |
else { |
709 |
< |
interrupted = true; |
710 |
< |
break; |
711 |
< |
} |
712 |
< |
} |
713 |
< |
} |
714 |
< |
} |
715 |
< |
break; |
716 |
< |
} |
717 |
< |
} |
718 |
< |
if (pool != null && dec) |
719 |
< |
pool.incrementRunningCount(); |
720 |
< |
if (interrupted) |
721 |
< |
throw new InterruptedException(); |
722 |
< |
int es = status; |
723 |
< |
if (es != NORMAL) { |
726 |
> |
externalInterruptibleAwaitDone(true, nanos); |
727 |
> |
int s = status; |
728 |
> |
if (s != NORMAL) { |
729 |
|
Throwable ex; |
730 |
< |
if (es == CANCELLED) |
730 |
> |
if (s == CANCELLED) |
731 |
|
throw new CancellationException(); |
732 |
< |
if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
732 |
> |
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
733 |
|
throw new ExecutionException(ex); |
734 |
|
throw new TimeoutException(); |
735 |
|
} |
760 |
|
return; |
761 |
|
} |
762 |
|
} |
763 |
< |
w.joinTask(this); |
763 |
> |
w.joinTask(this, false, 0L); |
764 |
|
} |
765 |
|
} |
766 |
|
else |
796 |
|
* processed. |
797 |
|
* |
798 |
|
* <p>This method may be invoked only from within {@code |
799 |
< |
* ForkJoinTask} computations (as may be determined using method |
799 |
> |
* ForkJoinPool} computations (as may be determined using method |
800 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
801 |
|
* result in exceptions or errors, possibly including {@code |
802 |
|
* ClassCastException}. |
815 |
|
* under any other usage conditions are not guaranteed. |
816 |
|
* This method may be useful when executing |
817 |
|
* pre-constructed trees of subtasks in loops. |
818 |
+ |
* |
819 |
+ |
* <p>Upon completion of this method, {@code isDone()} reports |
820 |
+ |
* {@code false}, and {@code getException()} reports {@code |
821 |
+ |
* null}. However, the value returned by {@code getRawResult} is |
822 |
+ |
* unaffected. To clear this value, you can invoke {@code |
823 |
+ |
* setRawResult(null)}. |
824 |
|
*/ |
825 |
|
public void reinitialize() { |
826 |
|
if (status == EXCEPTIONAL) |
861 |
|
* were not, stolen. |
862 |
|
* |
863 |
|
* <p>This method may be invoked only from within {@code |
864 |
< |
* ForkJoinTask} computations (as may be determined using method |
864 |
> |
* ForkJoinPool} computations (as may be determined using method |
865 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
866 |
|
* result in exceptions or errors, possibly including {@code |
867 |
|
* ClassCastException}. |
880 |
|
* fork other tasks. |
881 |
|
* |
882 |
|
* <p>This method may be invoked only from within {@code |
883 |
< |
* ForkJoinTask} computations (as may be determined using method |
883 |
> |
* ForkJoinPool} computations (as may be determined using method |
884 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
885 |
|
* result in exceptions or errors, possibly including {@code |
886 |
|
* ClassCastException}. |
903 |
|
* exceeded. |
904 |
|
* |
905 |
|
* <p>This method may be invoked only from within {@code |
906 |
< |
* ForkJoinTask} computations (as may be determined using method |
906 |
> |
* ForkJoinPool} computations (as may be determined using method |
907 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
908 |
|
* result in exceptions or errors, possibly including {@code |
909 |
|
* ClassCastException}. |
961 |
|
* otherwise. |
962 |
|
* |
963 |
|
* <p>This method may be invoked only from within {@code |
964 |
< |
* ForkJoinTask} computations (as may be determined using method |
964 |
> |
* ForkJoinPool} computations (as may be determined using method |
965 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
966 |
|
* result in exceptions or errors, possibly including {@code |
967 |
|
* ClassCastException}. |
980 |
|
* be useful otherwise. |
981 |
|
* |
982 |
|
* <p>This method may be invoked only from within {@code |
983 |
< |
* ForkJoinTask} computations (as may be determined using method |
983 |
> |
* ForkJoinPool} computations (as may be determined using method |
984 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
985 |
|
* result in exceptions or errors, possibly including {@code |
986 |
|
* ClassCastException}. |
1003 |
|
* otherwise. |
1004 |
|
* |
1005 |
|
* <p>This method may be invoked only from within {@code |
1006 |
< |
* ForkJoinTask} computations (as may be determined using method |
1006 |
> |
* ForkJoinPool} computations (as may be determined using method |
1007 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1008 |
|
* result in exceptions or errors, possibly including {@code |
1009 |
|
* ClassCastException}. |