18 |
|
* lighter weight than a normal thread. Huge numbers of tasks and |
19 |
|
* subtasks may be hosted by a small number of actual threads in a |
20 |
|
* ForkJoinPool, at the price of some usage limitations. |
21 |
< |
* |
21 |
> |
* |
22 |
|
* <p> A "main" ForkJoinTask begins execution when submitted to a |
23 |
|
* {@link ForkJoinPool}. Once started, it will usually in turn start |
24 |
|
* other subtasks. As indicated by the name of this class, many |
25 |
< |
* programs using ForkJoinTasks employ only methods <code>fork</code> |
26 |
< |
* and <code>join</code>, or derivatives such as |
27 |
< |
* <code>invokeAll</code>. However, this class also provides a number |
25 |
> |
* programs using ForkJoinTasks employ only methods {@code fork} |
26 |
> |
* and {@code join}, or derivatives such as |
27 |
> |
* {@code invokeAll}. However, this class also provides a number |
28 |
|
* of other methods that can come into play in advanced usages, as |
29 |
|
* well as extension mechanics that allow support of new forms of |
30 |
|
* fork/join processing. |
31 |
< |
* |
31 |
> |
* |
32 |
|
* <p>A ForkJoinTask is a lightweight form of {@link Future}. The |
33 |
|
* efficiency of ForkJoinTasks stems from a set of restrictions (that |
34 |
|
* are only partially statically enforceable) reflecting their |
36 |
|
* operating on purely isolated objects. The primary coordination |
37 |
|
* mechanisms are {@link #fork}, that arranges asynchronous execution, |
38 |
|
* and {@link #join}, that doesn't proceed until the task's result has |
39 |
< |
* been computed. Computations should avoid <code>synchronized</code> |
39 |
> |
* been computed. Computations should avoid {@code synchronized} |
40 |
|
* methods or blocks, and should minimize other blocking |
41 |
|
* synchronization apart from joining other tasks or using |
42 |
|
* synchronizers such as Phasers that are advertised to cooperate with |
48 |
|
* performance, and the potential to indefinitely stall if the number |
49 |
|
* of threads not waiting for IO or other external synchronization |
50 |
|
* becomes exhausted. This usage restriction is in part enforced by |
51 |
< |
* not permitting checked exceptions such as <code>IOExceptions</code> |
51 |
> |
* not permitting checked exceptions such as {@code IOExceptions} |
52 |
|
* to be thrown. However, computations may still encounter unchecked |
53 |
|
* exceptions, that are rethrown to callers attempting join |
54 |
|
* them. These exceptions may additionally include |
58 |
|
* <p>The primary method for awaiting completion and extracting |
59 |
|
* results of a task is {@link #join}, but there are several variants: |
60 |
|
* The {@link Future#get} methods support interruptible and/or timed |
61 |
< |
* waits for completion and report results using <code>Future</code> |
61 |
> |
* waits for completion and report results using {@code Future} |
62 |
|
* conventions. Method {@link #helpJoin} enables callers to actively |
63 |
|
* execute other tasks while awaiting joins, which is sometimes more |
64 |
|
* efficient but only applies when all subtasks are known to be |
65 |
|
* strictly tree-structured. Method {@link #invoke} is semantically |
66 |
< |
* equivalent to <code>fork(); join()</code> but always attempts to |
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 |
69 |
|
* may be useful when a set of tasks are being executed, and you need |
70 |
|
* to delay processing of results or exceptions until all complete. |
71 |
< |
* Method <code>invokeAll</code> (available in multiple versions) |
71 |
> |
* Method {@code invokeAll} (available in multiple versions) |
72 |
|
* performs the most common form of parallel invocation: forking a set |
73 |
|
* of tasks and joining them all. |
74 |
|
* |
76 |
|
* Instead, you subclass one of the abstract classes that support a |
77 |
|
* particular style of fork/join processing. Normally, a concrete |
78 |
|
* ForkJoinTask subclass declares fields comprising its parameters, |
79 |
< |
* established in a constructor, and then defines a <code>compute</code> |
79 |
> |
* established in a constructor, and then defines a {@code compute} |
80 |
|
* method that somehow uses the control methods supplied by this base |
81 |
< |
* class. While these methods have <code>public</code> access (to allow |
81 |
> |
* class. While these methods have {@code public} access (to allow |
82 |
|
* instances of different task subclasses to call each others |
83 |
|
* methods), some of them may only be called from within other |
84 |
< |
* ForkJoinTasks. Attempts to invoke them in other contexts result in |
85 |
< |
* exceptions or errors including ClassCastException. |
84 |
> |
* ForkJoinTasks (as may be determined using method {@link |
85 |
> |
* #inForkJoinPool}). Attempts to invoke them in other contexts |
86 |
> |
* result in exceptions or errors possibly including |
87 |
> |
* ClassCastException. |
88 |
|
* |
89 |
< |
* <p>Most base support methods are <code>final</code> because their |
89 |
> |
* <p>Most base support methods are {@code final} because their |
90 |
|
* implementations are intrinsically tied to the underlying |
91 |
|
* lightweight task scheduling framework, and so cannot be overridden. |
92 |
|
* Developers creating new basic styles of fork/join processing should |
93 |
< |
* minimally implement <code>protected</code> methods |
94 |
< |
* <code>exec</code>, <code>setRawResult</code>, and |
95 |
< |
* <code>getRawResult</code>, while also introducing an abstract |
93 |
> |
* minimally implement {@code protected} methods |
94 |
> |
* {@code exec}, {@code setRawResult}, and |
95 |
> |
* {@code getRawResult}, while also introducing an abstract |
96 |
|
* computational method that can be implemented in its subclasses, |
97 |
< |
* possibly relying on other <code>protected</code> methods provided |
97 |
> |
* possibly relying on other {@code protected} methods provided |
98 |
|
* by this class. |
99 |
|
* |
100 |
|
* <p>ForkJoinTasks should perform relatively small amounts of |
101 |
< |
* computations, othewise splitting into smaller tasks. As a very |
101 |
> |
* computations, otherwise splitting into smaller tasks. As a very |
102 |
|
* rough rule of thumb, a task should perform more than 100 and less |
103 |
|
* than 10000 basic computational steps. If tasks are too big, then |
104 |
< |
* parellelism cannot improve throughput. If too small, then memory |
104 |
> |
* parallelism cannot improve throughput. If too small, then memory |
105 |
|
* and internal task maintenance overhead may overwhelm processing. |
106 |
|
* |
107 |
< |
* <p>ForkJoinTasks are <code>Serializable</code>, which enables them |
107 |
> |
* <p>ForkJoinTasks are {@code Serializable}, which enables them |
108 |
|
* to be used in extensions such as remote execution frameworks. It is |
109 |
|
* in general sensible to serialize tasks only before or after, but |
110 |
|
* not during execution. Serialization is not relied on during |
111 |
|
* execution itself. |
112 |
+ |
* |
113 |
+ |
* @since 1.7 |
114 |
+ |
* @author Doug Lea |
115 |
|
*/ |
116 |
|
public abstract class ForkJoinTask<V> implements Future<V>, Serializable { |
117 |
|
|
133 |
|
* currently unused. Also value 0x80000000 is available as spare |
134 |
|
* completion value. |
135 |
|
*/ |
136 |
< |
volatile int status; // accessed directy by pool and workers |
136 |
> |
volatile int status; // accessed directly by pool and workers |
137 |
|
|
138 |
|
static final int COMPLETION_MASK = 0xe0000000; |
139 |
|
static final int NORMAL = 0xe0000000; // == mask |
146 |
|
/** |
147 |
|
* Table of exceptions thrown by tasks, to enable reporting by |
148 |
|
* callers. Because exceptions are rare, we don't directly keep |
149 |
< |
* them with task objects, but instead us a weak ref table. Note |
149 |
> |
* them with task objects, but instead use a weak ref table. Note |
150 |
|
* that cancellation exceptions don't appear in the table, but are |
151 |
|
* instead recorded as status values. |
152 |
< |
* Todo: Use ConcurrentReferenceHashMap |
152 |
> |
* TODO: Use ConcurrentReferenceHashMap |
153 |
|
*/ |
154 |
|
static final Map<ForkJoinTask<?>, Throwable> exceptionMap = |
155 |
|
Collections.synchronizedMap |
158 |
|
// within-package utilities |
159 |
|
|
160 |
|
/** |
161 |
< |
* Get current worker thread, or null if not a worker thread |
161 |
> |
* Gets current worker thread, or null if not a worker thread. |
162 |
|
*/ |
163 |
|
static ForkJoinWorkerThread getWorker() { |
164 |
|
Thread t = Thread.currentThread(); |
167 |
|
} |
168 |
|
|
169 |
|
final boolean casStatus(int cmp, int val) { |
170 |
< |
return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val); |
170 |
> |
return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val); |
171 |
|
} |
172 |
|
|
173 |
|
/** |
175 |
|
*/ |
176 |
|
static void rethrowException(Throwable ex) { |
177 |
|
if (ex != null) |
178 |
< |
_unsafe.throwException(ex); |
178 |
> |
UNSAFE.throwException(ex); |
179 |
|
} |
180 |
|
|
181 |
|
// Setting completion status |
182 |
|
|
183 |
|
/** |
184 |
< |
* Mark completion and wake up threads waiting to join this task. |
184 |
> |
* Marks completion and wakes up threads waiting to join this task. |
185 |
> |
* |
186 |
|
* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
187 |
|
*/ |
188 |
|
final void setCompletion(int completion) { |
218 |
|
final void setNormalCompletion() { |
219 |
|
// Try typical fast case -- single CAS, no signal, not already done. |
220 |
|
// Manually expand casStatus to improve chances of inlining it |
221 |
< |
if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL)) |
221 |
> |
if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL)) |
222 |
|
setCompletion(NORMAL); |
223 |
|
} |
224 |
|
|
261 |
|
/** |
262 |
|
* Sets status to indicate there is joiner, then waits for join, |
263 |
|
* surrounded with pool notifications. |
264 |
+ |
* |
265 |
|
* @return status upon exit |
266 |
|
*/ |
267 |
|
private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) { |
304 |
|
} |
305 |
|
|
306 |
|
/** |
307 |
< |
* Notify pool that thread is unblocked. Called by signalled |
307 |
> |
* Notifies pool that thread is unblocked. Called by signalled |
308 |
|
* threads when woken by non-FJ threads (which is atypical). |
309 |
|
*/ |
310 |
|
private void adjustPoolCountsOnUnblock(ForkJoinPool pool) { |
315 |
|
} |
316 |
|
|
317 |
|
/** |
318 |
< |
* Notify pool to adjust counts on cancelled or timed out wait |
318 |
> |
* Notifies pool to adjust counts on cancelled or timed out wait. |
319 |
|
*/ |
320 |
|
private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) { |
321 |
|
if (pool != null) { |
330 |
|
} |
331 |
|
|
332 |
|
/** |
333 |
< |
* Handle interruptions during waits. |
333 |
> |
* Handles interruptions during waits. |
334 |
|
*/ |
335 |
|
private void onInterruptedWait() { |
336 |
|
ForkJoinWorkerThread w = getWorker(); |
349 |
|
} |
350 |
|
|
351 |
|
/** |
352 |
< |
* Throws the exception associated with status s; |
352 |
> |
* Throws the exception associated with status s. |
353 |
> |
* |
354 |
|
* @throws the exception |
355 |
|
*/ |
356 |
|
private void reportException(int s) { |
363 |
|
} |
364 |
|
|
365 |
|
/** |
366 |
< |
* Returns result or throws exception using j.u.c.Future conventions |
366 |
> |
* Returns result or throws exception using j.u.c.Future conventions. |
367 |
|
* Only call when isDone known to be true. |
368 |
|
*/ |
369 |
|
private V reportFutureResult() |
383 |
|
|
384 |
|
/** |
385 |
|
* Returns result or throws exception using j.u.c.Future conventions |
386 |
< |
* with timeouts |
386 |
> |
* with timeouts. |
387 |
|
*/ |
388 |
|
private V reportTimedFutureResult() |
389 |
|
throws InterruptedException, ExecutionException, TimeoutException { |
404 |
|
|
405 |
|
/** |
406 |
|
* Calls exec, recording completion, and rethrowing exception if |
407 |
< |
* encountered. Caller should normally check status before calling |
407 |
> |
* encountered. Caller should normally check status before calling. |
408 |
> |
* |
409 |
|
* @return true if completed normally |
410 |
|
*/ |
411 |
|
private boolean tryExec() { |
423 |
|
|
424 |
|
/** |
425 |
|
* Main execution method used by worker threads. Invokes |
426 |
< |
* base computation unless already complete |
426 |
> |
* base computation unless already complete. |
427 |
|
*/ |
428 |
|
final void quietlyExec() { |
429 |
|
if (status >= 0) { |
439 |
|
} |
440 |
|
|
441 |
|
/** |
442 |
< |
* Calls exec, recording but not rethrowing exception |
443 |
< |
* Caller should normally check status before calling |
442 |
> |
* Calls exec(), recording but not rethrowing exception. |
443 |
> |
* Caller should normally check status before calling. |
444 |
> |
* |
445 |
|
* @return true if completed normally |
446 |
|
*/ |
447 |
|
private boolean tryQuietlyInvoke() { |
457 |
|
} |
458 |
|
|
459 |
|
/** |
460 |
< |
* Cancel, ignoring any exceptions it throws |
460 |
> |
* Cancels, ignoring any exceptions it throws. |
461 |
|
*/ |
462 |
|
final void cancelIgnoringExceptions() { |
463 |
|
try { |
484 |
|
* necessarily enforced, it is a usage error to fork a task more |
485 |
|
* than once unless it has completed and been reinitialized. This |
486 |
|
* method may be invoked only from within ForkJoinTask |
487 |
< |
* computations. Attempts to invoke in other contexts result in |
488 |
< |
* exceptions or errors including ClassCastException. |
487 |
> |
* computations (as may be determined using method {@link |
488 |
> |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
489 |
> |
* in exceptions or errors possibly including ClassCastException. |
490 |
|
*/ |
491 |
|
public final void fork() { |
492 |
|
((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this); |
494 |
|
|
495 |
|
/** |
496 |
|
* Returns the result of the computation when it is ready. |
497 |
< |
* This method differs from <code>get</code> in that abnormal |
497 |
> |
* This method differs from {@code get} in that abnormal |
498 |
|
* completion results in RuntimeExceptions or Errors, not |
499 |
|
* ExecutionExceptions. |
500 |
|
* |
510 |
|
/** |
511 |
|
* Commences performing this task, awaits its completion if |
512 |
|
* necessary, and return its result. |
513 |
+ |
* |
514 |
|
* @throws Throwable (a RuntimeException, Error, or unchecked |
515 |
< |
* exception) if the underlying computation did so. |
515 |
> |
* exception) if the underlying computation did so |
516 |
|
* @return the computed result |
517 |
|
*/ |
518 |
|
public final V invoke() { |
523 |
|
} |
524 |
|
|
525 |
|
/** |
526 |
< |
* Forks both tasks, returning when <code>isDone</code> holds for |
526 |
> |
* Forks both tasks, returning when {@code isDone} holds for |
527 |
|
* both of them or an exception is encountered. This method may be |
528 |
< |
* invoked only from within ForkJoinTask computations. Attempts to |
528 |
> |
* invoked only from within ForkJoinTask computations (as may be |
529 |
> |
* determined using method {@link #inForkJoinPool}). Attempts to |
530 |
|
* invoke in other contexts result in exceptions or errors |
531 |
< |
* including ClassCastException. |
531 |
> |
* possibly including ClassCastException. |
532 |
> |
* |
533 |
|
* @param t1 one task |
534 |
|
* @param t2 the other task |
535 |
|
* @throws NullPointerException if t1 or t2 are null |
536 |
< |
* @throws RuntimeException or Error if either task did so. |
536 |
> |
* @throws RuntimeException or Error if either task did so |
537 |
|
*/ |
538 |
|
public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) { |
539 |
|
t2.fork(); |
542 |
|
} |
543 |
|
|
544 |
|
/** |
545 |
< |
* Forks the given tasks, returning when <code>isDone</code> holds |
545 |
> |
* Forks the given tasks, returning when {@code isDone} holds |
546 |
|
* for all of them. If any task encounters an exception, others |
547 |
|
* may be cancelled. This method may be invoked only from within |
548 |
< |
* ForkJoinTask computations. Attempts to invoke in other contexts |
549 |
< |
* result in exceptions or errors including ClassCastException. |
548 |
> |
* ForkJoinTask computations (as may be determined using method |
549 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
550 |
> |
* result in exceptions or errors possibly including |
551 |
> |
* ClassCastException. |
552 |
|
* @param tasks the array of tasks |
553 |
< |
* @throws NullPointerException if tasks or any element are null. |
554 |
< |
* @throws RuntimeException or Error if any task did so. |
553 |
> |
* @throws NullPointerException if tasks or any element are null |
554 |
> |
* @throws RuntimeException or Error if any task did so |
555 |
|
*/ |
556 |
|
public static void invokeAll(ForkJoinTask<?>... tasks) { |
557 |
|
Throwable ex = null; |
588 |
|
|
589 |
|
/** |
590 |
|
* Forks all tasks in the collection, returning when |
591 |
< |
* <code>isDone</code> holds for all of them. If any task |
591 |
> |
* {@code isDone} holds for all of them. If any task |
592 |
|
* encounters an exception, others may be cancelled. This method |
593 |
< |
* may be invoked only from within ForkJoinTask |
594 |
< |
* computations. Attempts to invoke in other contexts resul!t in |
595 |
< |
* exceptions or errors including ClassCastException. |
593 |
> |
* may be invoked only from within ForkJoinTask computations (as |
594 |
> |
* may be determined using method {@link |
595 |
> |
* #inForkJoinPool}). Attempts to invoke in other contexts resul!t |
596 |
> |
* in exceptions or errors possibly including ClassCastException. |
597 |
> |
* |
598 |
|
* @param tasks the collection of tasks |
599 |
< |
* @throws NullPointerException if tasks or any element are null. |
600 |
< |
* @throws RuntimeException or Error if any task did so. |
599 |
> |
* @throws NullPointerException if tasks or any element are null |
600 |
> |
* @throws RuntimeException or Error if any task did so |
601 |
|
*/ |
602 |
|
public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) { |
603 |
|
if (!(tasks instanceof List)) { |
641 |
|
/** |
642 |
|
* Returns true if the computation performed by this task has |
643 |
|
* completed (or has been cancelled). |
644 |
+ |
* |
645 |
|
* @return true if this computation has completed |
646 |
|
*/ |
647 |
|
public final boolean isDone() { |
650 |
|
|
651 |
|
/** |
652 |
|
* Returns true if this task was cancelled. |
653 |
+ |
* |
654 |
|
* @return true if this task was cancelled |
655 |
|
*/ |
656 |
|
public final boolean isCancelled() { |
659 |
|
|
660 |
|
/** |
661 |
|
* Asserts that the results of this task's computation will not be |
662 |
< |
* used. If a cancellation occurs before atempting to execute this |
663 |
< |
* task, then execution will be suppressed, <code>isCancelled</code> |
664 |
< |
* will report true, and <code>join</code> will result in a |
665 |
< |
* <code>CancellationException</code> being thrown. Otherwise, when |
662 |
> |
* used. If a cancellation occurs before attempting to execute this |
663 |
> |
* task, then execution will be suppressed, {@code isCancelled} |
664 |
> |
* will report true, and {@code join} will result in a |
665 |
> |
* {@code CancellationException} being thrown. Otherwise, when |
666 |
|
* cancellation races with completion, there are no guarantees |
667 |
< |
* about whether <code>isCancelled</code> will report true, whether |
668 |
< |
* <code>join</code> will return normally or via an exception, or |
667 |
> |
* about whether {@code isCancelled} will report true, whether |
668 |
> |
* {@code join} will return normally or via an exception, or |
669 |
|
* whether these behaviors will remain consistent upon repeated |
670 |
|
* invocation. |
671 |
|
* |
676 |
|
* <p> This method is designed to be invoked by <em>other</em> |
677 |
|
* tasks. To terminate the current task, you can just return or |
678 |
|
* throw an unchecked exception from its computation method, or |
679 |
< |
* invoke <code>completeExceptionally</code>. |
679 |
> |
* invoke {@code completeExceptionally}. |
680 |
|
* |
681 |
|
* @param mayInterruptIfRunning this value is ignored in the |
682 |
|
* default implementation because tasks are not in general |
690 |
|
} |
691 |
|
|
692 |
|
/** |
693 |
< |
* Returns true if this task threw an exception or was cancelled |
693 |
> |
* Returns true if this task threw an exception or was cancelled. |
694 |
> |
* |
695 |
|
* @return true if this task threw an exception or was cancelled |
696 |
|
*/ |
697 |
|
public final boolean isCompletedAbnormally() { |
702 |
|
* Returns the exception thrown by the base computation, or a |
703 |
|
* CancellationException if cancelled, or null if none or if the |
704 |
|
* method has not yet completed. |
705 |
+ |
* |
706 |
|
* @return the exception, or null if none |
707 |
|
*/ |
708 |
|
public final Throwable getException() { |
717 |
|
/** |
718 |
|
* Completes this task abnormally, and if not already aborted or |
719 |
|
* cancelled, causes it to throw the given exception upon |
720 |
< |
* <code>join</code> and related operations. This method may be used |
720 |
> |
* {@code join} and related operations. This method may be used |
721 |
|
* to induce exceptions in asynchronous tasks, or to force |
722 |
|
* completion of tasks that would not otherwise complete. Its use |
723 |
|
* in other situations is likely to be wrong. This method is |
724 |
< |
* overridable, but overridden versions must invoke <code>super</code> |
724 |
> |
* overridable, but overridden versions must invoke {@code super} |
725 |
|
* implementation to maintain guarantees. |
726 |
|
* |
727 |
|
* @param ex the exception to throw. If this exception is |
736 |
|
|
737 |
|
/** |
738 |
|
* Completes this task, and if not already aborted or cancelled, |
739 |
< |
* returning a <code>null</code> result upon <code>join</code> and related |
739 |
> |
* returning a {@code null} result upon {@code join} and related |
740 |
|
* operations. This method may be used to provide results for |
741 |
|
* asynchronous tasks, or to provide alternative handling for |
742 |
|
* tasks that would not otherwise complete normally. Its use in |
743 |
|
* other situations is likely to be wrong. This method is |
744 |
< |
* overridable, but overridden versions must invoke <code>super</code> |
744 |
> |
* overridable, but overridden versions must invoke {@code super} |
745 |
|
* implementation to maintain guarantees. |
746 |
|
* |
747 |
< |
* @param value the result value for this task. |
747 |
> |
* @param value the result value for this task |
748 |
|
*/ |
749 |
|
public void complete(V value) { |
750 |
|
try { |
774 |
|
/** |
775 |
|
* Possibly executes other tasks until this task is ready, then |
776 |
|
* returns the result of the computation. This method may be more |
777 |
< |
* efficient than <code>join</code>, but is only applicable when |
778 |
< |
* there are no potemtial dependencies between continuation of the |
777 |
> |
* efficient than {@code join}, but is only applicable when |
778 |
> |
* there are no potential dependencies between continuation of the |
779 |
|
* current task and that of any other task that might be executed |
780 |
|
* while helping. (This usually holds for pure divide-and-conquer |
781 |
|
* tasks). This method may be invoked only from within |
782 |
< |
* ForkJoinTask computations. Attempts to invoke in other contexts |
783 |
< |
* resul!t in exceptions or errors including ClassCastException. |
782 |
> |
* ForkJoinTask computations (as may be determined using method |
783 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
784 |
> |
* resul!t in exceptions or errors possibly including |
785 |
> |
* ClassCastException. |
786 |
> |
* |
787 |
|
* @return the computed result |
788 |
|
*/ |
789 |
|
public final V helpJoin() { |
796 |
|
/** |
797 |
|
* Possibly executes other tasks until this task is ready. This |
798 |
|
* method may be invoked only from within ForkJoinTask |
799 |
< |
* computations. Attempts to invoke in other contexts resul!t in |
800 |
< |
* exceptions or errors including ClassCastException. |
799 |
> |
* computations (as may be determined using method {@link |
800 |
> |
* #inForkJoinPool}). Attempts to invoke in other contexts resul!t |
801 |
> |
* in exceptions or errors possibly including ClassCastException. |
802 |
|
*/ |
803 |
|
public final void quietlyHelpJoin() { |
804 |
|
if (status >= 0) { |
848 |
|
|
849 |
|
/** |
850 |
|
* Resets the internal bookkeeping state of this task, allowing a |
851 |
< |
* subsequent <code>fork</code>. This method allows repeated reuse of |
851 |
> |
* subsequent {@code fork}. This method allows repeated reuse of |
852 |
|
* this task, but only if reuse occurs when this task has either |
853 |
|
* never been forked, or has been forked, then completed and all |
854 |
|
* outstanding joins of this task have also completed. Effects |
864 |
|
|
865 |
|
/** |
866 |
|
* Returns the pool hosting the current task execution, or null |
867 |
< |
* if this task is executing outside of any pool. |
867 |
> |
* if this task is executing outside of any ForkJoinPool. |
868 |
> |
* |
869 |
|
* @return the pool, or null if none. |
870 |
|
*/ |
871 |
|
public static ForkJoinPool getPool() { |
875 |
|
} |
876 |
|
|
877 |
|
/** |
878 |
+ |
* Returns true if the current thread is executing as a |
879 |
+ |
* ForkJoinPool computation. |
880 |
+ |
* @return <code>true</code> if the current thread is executing as a |
881 |
+ |
* ForkJoinPool computation, or false otherwise |
882 |
+ |
*/ |
883 |
+ |
public static boolean inForkJoinPool() { |
884 |
+ |
return Thread.currentThread() instanceof ForkJoinWorkerThread; |
885 |
+ |
} |
886 |
+ |
|
887 |
+ |
/** |
888 |
|
* Tries to unschedule this task for execution. This method will |
889 |
|
* typically succeed if this task is the most recently forked task |
890 |
|
* by the current thread, and has not commenced executing in |
891 |
|
* another thread. This method may be useful when arranging |
892 |
|
* alternative local processing of tasks that could have been, but |
893 |
|
* were not, stolen. This method may be invoked only from within |
894 |
< |
* ForkJoinTask computations. Attempts to invoke in other contexts |
895 |
< |
* result in exceptions or errors including ClassCastException. |
894 |
> |
* ForkJoinTask computations (as may be determined using method |
895 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
896 |
> |
* result in exceptions or errors possibly including |
897 |
> |
* ClassCastException. |
898 |
> |
* |
899 |
|
* @return true if unforked |
900 |
|
*/ |
901 |
|
public boolean tryUnfork() { |
907 |
|
* forked by the current worker thread but not yet executed. This |
908 |
|
* value may be useful for heuristic decisions about whether to |
909 |
|
* fork other tasks. |
910 |
+ |
* |
911 |
|
* @return the number of tasks |
912 |
|
*/ |
913 |
|
public static int getQueuedTaskCount() { |
916 |
|
} |
917 |
|
|
918 |
|
/** |
919 |
< |
* Returns a estimate of how many more locally queued tasks are |
919 |
> |
* Returns an estimate of how many more locally queued tasks are |
920 |
|
* held by the current worker thread than there are other worker |
921 |
|
* threads that might steal them. This value may be useful for |
922 |
|
* heuristic decisions about whether to fork other tasks. In many |
924 |
|
* aim to maintain a small constant surplus (for example, 3) of |
925 |
|
* tasks, and to process computations locally if this threshold is |
926 |
|
* exceeded. |
927 |
+ |
* |
928 |
|
* @return the surplus number of tasks, which may be negative |
929 |
|
*/ |
930 |
|
public static int getSurplusQueuedTaskCount() { |
935 |
|
// Extension methods |
936 |
|
|
937 |
|
/** |
938 |
< |
* Returns the result that would be returned by <code>join</code>, |
938 |
> |
* Returns the result that would be returned by {@code join}, |
939 |
|
* even if this task completed abnormally, or null if this task is |
940 |
|
* not known to have been completed. This method is designed to |
941 |
|
* aid debugging, as well as to support extensions. Its use in any |
942 |
|
* other context is discouraged. |
943 |
|
* |
944 |
< |
* @return the result, or null if not completed. |
944 |
> |
* @return the result, or null if not completed |
945 |
|
*/ |
946 |
|
public abstract V getRawResult(); |
947 |
|
|
960 |
|
* called otherwise. The return value controls whether this task |
961 |
|
* is considered to be done normally. It may return false in |
962 |
|
* asynchronous actions that require explicit invocations of |
963 |
< |
* <code>complete</code> to become joinable. It may throw exceptions |
963 |
> |
* {@code complete} to become joinable. It may throw exceptions |
964 |
|
* to indicate abnormal exit. |
965 |
+ |
* |
966 |
|
* @return true if completed normally |
967 |
|
* @throws Error or RuntimeException if encountered during computation |
968 |
|
*/ |
969 |
|
protected abstract boolean exec(); |
970 |
|
|
971 |
|
/** |
972 |
< |
* Returns, but does not unschedule or execute, the task most |
973 |
< |
* recently forked by the current thread but not yet executed, if |
974 |
< |
* one is available. There is no guarantee that this task will |
975 |
< |
* actually be polled or executed next. |
976 |
< |
* This method is designed primarily to support extensions, |
977 |
< |
* and is unlikely to be useful otherwise. |
972 |
> |
* Returns, but does not unschedule or execute, the task queued by |
973 |
> |
* the current thread but not yet executed, if one is |
974 |
> |
* available. There is no guarantee that this task will actually |
975 |
> |
* be polled or executed next. This method is designed primarily |
976 |
> |
* to support extensions, and is unlikely to be useful otherwise. |
977 |
> |
* This method may be invoked only from within ForkJoinTask |
978 |
> |
* computations (as may be determined using method {@link |
979 |
> |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
980 |
> |
* in exceptions or errors possibly including ClassCastException. |
981 |
|
* |
982 |
|
* @return the next task, or null if none are available |
983 |
|
*/ |
986 |
|
} |
987 |
|
|
988 |
|
/** |
989 |
< |
* Unschedules and returns, without executing, the task most |
990 |
< |
* recently forked by the current thread but not yet executed. |
991 |
< |
* This method is designed primarily to support extensions, |
992 |
< |
* and is unlikely to be useful otherwise. |
989 |
> |
* Unschedules and returns, without executing, the next task |
990 |
> |
* queued by the current thread but not yet executed. This method |
991 |
> |
* is designed primarily to support extensions, and is unlikely to |
992 |
> |
* be useful otherwise. This method may be invoked only from |
993 |
> |
* within ForkJoinTask computations (as may be determined using |
994 |
> |
* method {@link #inForkJoinPool}). Attempts to invoke in other |
995 |
> |
* contexts result in exceptions or errors possibly including |
996 |
> |
* ClassCastException. |
997 |
|
* |
998 |
|
* @return the next task, or null if none are available |
999 |
|
*/ |
1000 |
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
1001 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())).popTask(); |
1001 |
> |
return ((ForkJoinWorkerThread)(Thread.currentThread())).pollLocalTask(); |
1002 |
|
} |
1003 |
|
|
1004 |
|
/** |
1005 |
< |
* Unschedules and returns, without executing, the task most |
1006 |
< |
* recently forked by the current thread but not yet executed, if |
1007 |
< |
* one is available, or if not available, a task that was forked |
1008 |
< |
* by some other thread, if available. Availability may be |
1009 |
< |
* transient, so a <code>null</code> result does not necessarily |
1010 |
< |
* imply quiecence of the pool this task is operating in. |
1011 |
< |
* This method is designed primarily to support extensions, |
1012 |
< |
* and is unlikely to be useful otherwise. |
1013 |
< |
* |
1005 |
> |
* Unschedules and returns, without executing, the next task |
1006 |
> |
* queued by the current thread but not yet executed, if one is |
1007 |
> |
* available, or if not available, a task that was forked by some |
1008 |
> |
* other thread, if available. Availability may be transient, so a |
1009 |
> |
* {@code null} result does not necessarily imply quiescence |
1010 |
> |
* of the pool this task is operating in. This method is designed |
1011 |
> |
* primarily to support extensions, and is unlikely to be useful |
1012 |
> |
* otherwise. This method may be invoked only from within |
1013 |
> |
* ForkJoinTask computations (as may be determined using method |
1014 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1015 |
> |
* result in exceptions or errors possibly including |
1016 |
> |
* ClassCastException. |
1017 |
> |
* |
1018 |
|
* @return a task, or null if none are available |
1019 |
|
*/ |
1020 |
|
protected static ForkJoinTask<?> pollTask() { |
1021 |
|
return ((ForkJoinWorkerThread)(Thread.currentThread())). |
1022 |
< |
pollLocalOrStolenTask(); |
1022 |
> |
pollTask(); |
1023 |
|
} |
1024 |
|
|
1025 |
|
// Serialization support |
1030 |
|
* Save the state to a stream. |
1031 |
|
* |
1032 |
|
* @serialData the current run status and the exception thrown |
1033 |
< |
* during execution, or null if none. |
1033 |
> |
* during execution, or null if none |
1034 |
|
* @param s the stream |
1035 |
|
*/ |
1036 |
|
private void writeObject(java.io.ObjectOutputStream s) |
1041 |
|
|
1042 |
|
/** |
1043 |
|
* Reconstitute the instance from a stream. |
1044 |
+ |
* |
1045 |
|
* @param s the stream |
1046 |
|
*/ |
1047 |
|
private void readObject(java.io.ObjectInputStream s) |
1055 |
|
} |
1056 |
|
|
1057 |
|
// Temporary Unsafe mechanics for preliminary release |
1058 |
+ |
private static Unsafe getUnsafe() throws Throwable { |
1059 |
+ |
try { |
1060 |
+ |
return Unsafe.getUnsafe(); |
1061 |
+ |
} catch (SecurityException se) { |
1062 |
+ |
try { |
1063 |
+ |
return java.security.AccessController.doPrivileged |
1064 |
+ |
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
1065 |
+ |
public Unsafe run() throws Exception { |
1066 |
+ |
return getUnsafePrivileged(); |
1067 |
+ |
}}); |
1068 |
+ |
} catch (java.security.PrivilegedActionException e) { |
1069 |
+ |
throw e.getCause(); |
1070 |
+ |
} |
1071 |
+ |
} |
1072 |
+ |
} |
1073 |
+ |
|
1074 |
+ |
private static Unsafe getUnsafePrivileged() |
1075 |
+ |
throws NoSuchFieldException, IllegalAccessException { |
1076 |
+ |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
1077 |
+ |
f.setAccessible(true); |
1078 |
+ |
return (Unsafe) f.get(null); |
1079 |
+ |
} |
1080 |
|
|
1081 |
< |
static final Unsafe _unsafe; |
1081 |
> |
private static long fieldOffset(String fieldName) |
1082 |
> |
throws NoSuchFieldException { |
1083 |
> |
return UNSAFE.objectFieldOffset |
1084 |
> |
(ForkJoinTask.class.getDeclaredField(fieldName)); |
1085 |
> |
} |
1086 |
> |
|
1087 |
> |
static final Unsafe UNSAFE; |
1088 |
|
static final long statusOffset; |
1089 |
|
|
1090 |
|
static { |
1091 |
|
try { |
1092 |
< |
if (ForkJoinTask.class.getClassLoader() != null) { |
1093 |
< |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
1094 |
< |
f.setAccessible(true); |
1095 |
< |
_unsafe = (Unsafe)f.get(null); |
1096 |
< |
} |
1014 |
< |
else |
1015 |
< |
_unsafe = Unsafe.getUnsafe(); |
1016 |
< |
statusOffset = _unsafe.objectFieldOffset |
1017 |
< |
(ForkJoinTask.class.getDeclaredField("status")); |
1018 |
< |
} catch (Exception ex) { throw new Error(ex); } |
1092 |
> |
UNSAFE = getUnsafe(); |
1093 |
> |
statusOffset = fieldOffset("status"); |
1094 |
> |
} catch (Throwable e) { |
1095 |
> |
throw new RuntimeException("Could not initialize intrinsics", e); |
1096 |
> |
} |
1097 |
|
} |
1098 |
|
|
1099 |
|
} |