5 |
|
*/ |
6 |
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|
7 |
|
package jsr166y; |
8 |
+ |
|
9 |
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import java.io.Serializable; |
10 |
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import java.util.Collection; |
11 |
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import java.util.List; |
30 |
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* subtasks may be hosted by a small number of actual threads in a |
31 |
|
* ForkJoinPool, at the price of some usage limitations. |
32 |
|
* |
33 |
< |
* <p>A "main" {@code ForkJoinTask} begins execution when submitted |
34 |
< |
* to a {@link ForkJoinPool}. Once started, it will usually in turn |
35 |
< |
* start other subtasks. As indicated by the name of this class, |
36 |
< |
* many programs using {@code ForkJoinTask} employ only methods |
37 |
< |
* {@link #fork} and {@link #join}, or derivatives such as {@link |
33 |
> |
* <p>A "main" {@code ForkJoinTask} begins execution when it is |
34 |
> |
* explicitly submitted to a {@link ForkJoinPool}, or, if not already |
35 |
> |
* engaged in a ForkJoin computation, commenced in the {@link |
36 |
> |
* ForkJoinPool#commonPool()} via {@link #fork}, {@link #invoke}, or |
37 |
> |
* related methods. Once started, it will usually in turn start other |
38 |
> |
* subtasks. As indicated by the name of this class, many programs |
39 |
> |
* using {@code ForkJoinTask} employ only methods {@link #fork} and |
40 |
> |
* {@link #join}, or derivatives such as {@link |
41 |
|
* #invokeAll(ForkJoinTask...) invokeAll}. However, this class also |
42 |
|
* provides a number of other methods that can come into play in |
43 |
< |
* advanced usages, as well as extension mechanics that allow |
44 |
< |
* support of new forms of fork/join processing. |
43 |
> |
* advanced usages, as well as extension mechanics that allow support |
44 |
> |
* of new forms of fork/join processing. |
45 |
|
* |
46 |
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* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}. |
47 |
|
* The efficiency of {@code ForkJoinTask}s stems from a set of |
55 |
|
* minimize other blocking synchronization apart from joining other |
56 |
|
* tasks or using synchronizers such as Phasers that are advertised to |
57 |
|
* cooperate with fork/join scheduling. Subdividable tasks should also |
58 |
< |
* not perform blocking IO, and should ideally access variables that |
58 |
> |
* not perform blocking I/O, and should ideally access variables that |
59 |
|
* are completely independent of those accessed by other running |
60 |
|
* tasks. These guidelines are loosely enforced by not permitting |
61 |
|
* checked exceptions such as {@code IOExceptions} to be |
73 |
|
* <p>It is possible to define and use ForkJoinTasks that may block, |
74 |
|
* but doing do requires three further considerations: (1) Completion |
75 |
|
* of few if any <em>other</em> tasks should be dependent on a task |
76 |
< |
* that blocks on external synchronization or IO. Event-style async |
77 |
< |
* tasks that are never joined often fall into this category. (2) To |
78 |
< |
* minimize resource impact, tasks should be small; ideally performing |
79 |
< |
* only the (possibly) blocking action. (3) Unless the {@link |
76 |
> |
* that blocks on external synchronization or I/O. Event-style async |
77 |
> |
* tasks that are never joined (for example, those subclassing {@link |
78 |
> |
* CountedCompleter}) often fall into this category. (2) To minimize |
79 |
> |
* resource impact, tasks should be small; ideally performing only the |
80 |
> |
* (possibly) blocking action. (3) Unless the {@link |
81 |
|
* ForkJoinPool.ManagedBlocker} API is used, or the number of possibly |
82 |
|
* blocked tasks is known to be less than the pool's {@link |
83 |
|
* ForkJoinPool#getParallelism} level, the pool cannot guarantee that |
120 |
|
* <p>The ForkJoinTask class is not usually directly subclassed. |
121 |
|
* Instead, you subclass one of the abstract classes that support a |
122 |
|
* particular style of fork/join processing, typically {@link |
123 |
< |
* RecursiveAction} for computations that do not return results, or |
124 |
< |
* {@link RecursiveTask} for those that do. Normally, a concrete |
125 |
< |
* ForkJoinTask subclass declares fields comprising its parameters, |
126 |
< |
* established in a constructor, and then defines a {@code compute} |
127 |
< |
* method that somehow uses the control methods supplied by this base |
128 |
< |
* class. While these methods have {@code public} access (to allow |
129 |
< |
* instances of different task subclasses to call each other's |
125 |
< |
* methods), some of them may only be called from within other |
126 |
< |
* ForkJoinTasks (as may be determined using method {@link |
127 |
< |
* #inForkJoinPool}). Attempts to invoke them in other contexts |
128 |
< |
* result in exceptions or errors, possibly including |
129 |
< |
* {@code ClassCastException}. |
123 |
> |
* RecursiveAction} for most computations that do not return results, |
124 |
> |
* {@link RecursiveTask} for those that do, and {@link |
125 |
> |
* CountedCompleter} for those in which completed actions trigger |
126 |
> |
* other actions. Normally, a concrete ForkJoinTask subclass declares |
127 |
> |
* fields comprising its parameters, established in a constructor, and |
128 |
> |
* then defines a {@code compute} method that somehow uses the control |
129 |
> |
* methods supplied by this base class. |
130 |
|
* |
131 |
|
* <p>Method {@link #join} and its variants are appropriate for use |
132 |
|
* only when completion dependencies are acyclic; that is, the |
137 |
|
* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that |
138 |
|
* may be of use in constructing custom subclasses for problems that |
139 |
|
* are not statically structured as DAGs. To support such usages a |
140 |
< |
* ForkJoinTask may be atomically <em>tagged</em> with a {@code |
141 |
< |
* short} value using {@link #setForkJoinTaskTag} or {@link |
140 |
> |
* ForkJoinTask may be atomically <em>tagged</em> with a {@code short} |
141 |
> |
* value using {@link #setForkJoinTaskTag} or {@link |
142 |
|
* #compareAndSetForkJoinTaskTag} and checked using {@link |
143 |
< |
* #getForkJoinTaskTag}. The ForkJoinTask implementation does not |
144 |
< |
* use these {@code protected} methods or tags for any purpose, but |
145 |
< |
* they may be of use in the construction of specialized subclasses. |
146 |
< |
* For example, parallel graph traversals can use the supplied methods |
147 |
< |
* to avoid revisiting nodes/tasks that have already been processed. |
148 |
< |
* Also, completion based designs can use them to record that subtasks |
149 |
< |
* have completed. (Method names for tagging are bulky in part to |
150 |
< |
* encourage definition of methods that reflect their usage patterns.) |
143 |
> |
* #getForkJoinTaskTag}. The ForkJoinTask implementation does not use |
144 |
> |
* these {@code protected} methods or tags for any purpose, but they |
145 |
> |
* may be of use in the construction of specialized subclasses. For |
146 |
> |
* example, parallel graph traversals can use the supplied methods to |
147 |
> |
* avoid revisiting nodes/tasks that have already been processed. |
148 |
> |
* (Method names for tagging are bulky in part to encourage definition |
149 |
> |
* of methods that reflect their usage patterns.) |
150 |
|
* |
151 |
|
* <p>Most base support methods are {@code final}, to prevent |
152 |
|
* overriding of implementations that are intrinsically tied to the |
268 |
|
} |
269 |
|
|
270 |
|
/** |
271 |
< |
* Tries to set SIGNAL status. Used by ForkJoinPool. Other |
272 |
< |
* variants are directly incorporated into externalAwaitDone etc. |
271 |
> |
* Tries to set SIGNAL status unless already completed. Used by |
272 |
> |
* ForkJoinPool. Other variants are directly incorporated into |
273 |
> |
* externalAwaitDone etc. |
274 |
|
* |
275 |
|
* @return true if successful |
276 |
|
*/ |
277 |
|
final boolean trySetSignal() { |
278 |
< |
int s; |
279 |
< |
return U.compareAndSwapInt(this, STATUS, s = status, s | SIGNAL); |
278 |
> |
int s = status; |
279 |
> |
return s >= 0 && U.compareAndSwapInt(this, STATUS, s, s | SIGNAL); |
280 |
|
} |
281 |
|
|
282 |
|
/** |
284 |
|
* @return status upon completion |
285 |
|
*/ |
286 |
|
private int externalAwaitDone() { |
287 |
– |
boolean interrupted = false; |
287 |
|
int s; |
288 |
+ |
ForkJoinPool.externalHelpJoin(this); |
289 |
+ |
boolean interrupted = false; |
290 |
|
while ((s = status) >= 0) { |
291 |
|
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
292 |
|
synchronized (this) { |
314 |
|
int s; |
315 |
|
if (Thread.interrupted()) |
316 |
|
throw new InterruptedException(); |
317 |
+ |
ForkJoinPool.externalHelpJoin(this); |
318 |
|
while ((s = status) >= 0) { |
319 |
|
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
320 |
|
synchronized (this) { |
328 |
|
return s; |
329 |
|
} |
330 |
|
|
331 |
+ |
|
332 |
|
/** |
333 |
|
* Implementation for join, get, quietlyJoin. Directly handles |
334 |
|
* only cases of already-completed, external wait, and |
338 |
|
*/ |
339 |
|
private int doJoin() { |
340 |
|
int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w; |
341 |
< |
if ((s = status) >= 0) { |
342 |
< |
if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) { |
343 |
< |
if (!(w = (wt = (ForkJoinWorkerThread)t).workQueue). |
344 |
< |
tryUnpush(this) || (s = doExec()) >= 0) |
345 |
< |
s = wt.pool.awaitJoin(w, this); |
346 |
< |
} |
344 |
< |
else |
345 |
< |
s = externalAwaitDone(); |
346 |
< |
} |
347 |
< |
return s; |
341 |
> |
return (s = status) < 0 ? s : |
342 |
> |
((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? |
343 |
> |
(w = (wt = (ForkJoinWorkerThread)t).workQueue). |
344 |
> |
tryUnpush(this) && (s = doExec()) < 0 ? s : |
345 |
> |
wt.pool.awaitJoin(w, this) : |
346 |
> |
externalAwaitDone(); |
347 |
|
} |
348 |
|
|
349 |
|
/** |
353 |
|
*/ |
354 |
|
private int doInvoke() { |
355 |
|
int s; Thread t; ForkJoinWorkerThread wt; |
356 |
< |
if ((s = doExec()) >= 0) { |
357 |
< |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) |
358 |
< |
s = (wt = (ForkJoinWorkerThread)t).pool.awaitJoin(wt.workQueue, |
359 |
< |
this); |
361 |
< |
else |
362 |
< |
s = externalAwaitDone(); |
363 |
< |
} |
364 |
< |
return s; |
356 |
> |
return (s = doExec()) < 0 ? s : |
357 |
> |
((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? |
358 |
> |
(wt = (ForkJoinWorkerThread)t).pool.awaitJoin(wt.workQueue, this) : |
359 |
> |
externalAwaitDone(); |
360 |
|
} |
361 |
|
|
362 |
|
// Exception table support |
395 |
|
final Throwable ex; |
396 |
|
ExceptionNode next; |
397 |
|
final long thrower; // use id not ref to avoid weak cycles |
398 |
+ |
final int hashCode; // store task hashCode before weak ref disappears |
399 |
|
ExceptionNode(ForkJoinTask<?> task, Throwable ex, ExceptionNode next) { |
400 |
|
super(task, exceptionTableRefQueue); |
401 |
|
this.ex = ex; |
402 |
|
this.next = next; |
403 |
|
this.thrower = Thread.currentThread().getId(); |
404 |
+ |
this.hashCode = System.identityHashCode(task); |
405 |
|
} |
406 |
|
} |
407 |
|
|
408 |
|
/** |
409 |
< |
* Records exception and sets exceptional completion. |
409 |
> |
* Records exception and sets status. |
410 |
|
* |
411 |
|
* @return status on exit |
412 |
|
*/ |
413 |
< |
private int setExceptionalCompletion(Throwable ex) { |
414 |
< |
int h = System.identityHashCode(this); |
415 |
< |
final ReentrantLock lock = exceptionTableLock; |
416 |
< |
lock.lock(); |
417 |
< |
try { |
418 |
< |
expungeStaleExceptions(); |
419 |
< |
ExceptionNode[] t = exceptionTable; |
420 |
< |
int i = h & (t.length - 1); |
421 |
< |
for (ExceptionNode e = t[i]; ; e = e.next) { |
422 |
< |
if (e == null) { |
423 |
< |
t[i] = new ExceptionNode(this, ex, t[i]); |
424 |
< |
break; |
413 |
> |
final int recordExceptionalCompletion(Throwable ex) { |
414 |
> |
int s; |
415 |
> |
if ((s = status) >= 0) { |
416 |
> |
int h = System.identityHashCode(this); |
417 |
> |
final ReentrantLock lock = exceptionTableLock; |
418 |
> |
lock.lock(); |
419 |
> |
try { |
420 |
> |
expungeStaleExceptions(); |
421 |
> |
ExceptionNode[] t = exceptionTable; |
422 |
> |
int i = h & (t.length - 1); |
423 |
> |
for (ExceptionNode e = t[i]; ; e = e.next) { |
424 |
> |
if (e == null) { |
425 |
> |
t[i] = new ExceptionNode(this, ex, t[i]); |
426 |
> |
break; |
427 |
> |
} |
428 |
> |
if (e.get() == this) // already present |
429 |
> |
break; |
430 |
|
} |
431 |
< |
if (e.get() == this) // already present |
432 |
< |
break; |
431 |
> |
} finally { |
432 |
> |
lock.unlock(); |
433 |
|
} |
434 |
< |
} finally { |
433 |
< |
lock.unlock(); |
434 |
> |
s = setCompletion(EXCEPTIONAL); |
435 |
|
} |
436 |
< |
return setCompletion(EXCEPTIONAL); |
436 |
> |
return s; |
437 |
> |
} |
438 |
> |
|
439 |
> |
/** |
440 |
> |
* Records exception and possibly propagates. |
441 |
> |
* |
442 |
> |
* @return status on exit |
443 |
> |
*/ |
444 |
> |
private int setExceptionalCompletion(Throwable ex) { |
445 |
> |
int s = recordExceptionalCompletion(ex); |
446 |
> |
if ((s & DONE_MASK) == EXCEPTIONAL) |
447 |
> |
internalPropagateException(ex); |
448 |
> |
return s; |
449 |
> |
} |
450 |
> |
|
451 |
> |
/** |
452 |
> |
* Hook for exception propagation support for tasks with completers. |
453 |
> |
*/ |
454 |
> |
void internalPropagateException(Throwable ex) { |
455 |
|
} |
456 |
|
|
457 |
|
/** |
470 |
|
} |
471 |
|
|
472 |
|
/** |
473 |
< |
* Removes exception node and clears status |
473 |
> |
* Removes exception node and clears status. |
474 |
|
*/ |
475 |
|
private void clearExceptionalCompletion() { |
476 |
|
int h = System.identityHashCode(this); |
533 |
|
Throwable ex; |
534 |
|
if (e == null || (ex = e.ex) == null) |
535 |
|
return null; |
536 |
< |
if (e.thrower != Thread.currentThread().getId()) { |
536 |
> |
if (false && e.thrower != Thread.currentThread().getId()) { |
537 |
|
Class<? extends Throwable> ec = ex.getClass(); |
538 |
|
try { |
539 |
|
Constructor<?> noArgCtor = null; |
563 |
|
private static void expungeStaleExceptions() { |
564 |
|
for (Object x; (x = exceptionTableRefQueue.poll()) != null;) { |
565 |
|
if (x instanceof ExceptionNode) { |
566 |
< |
ForkJoinTask<?> key = ((ExceptionNode)x).get(); |
566 |
> |
int hashCode = ((ExceptionNode)x).hashCode; |
567 |
|
ExceptionNode[] t = exceptionTable; |
568 |
< |
int i = System.identityHashCode(key) & (t.length - 1); |
568 |
> |
int i = hashCode & (t.length - 1); |
569 |
|
ExceptionNode e = t[i]; |
570 |
|
ExceptionNode pred = null; |
571 |
|
while (e != null) { |
600 |
|
} |
601 |
|
|
602 |
|
/** |
603 |
+ |
* A version of "sneaky throw" to relay exceptions |
604 |
+ |
*/ |
605 |
+ |
static void rethrow(final Throwable ex) { |
606 |
+ |
if (ex != null) { |
607 |
+ |
if (ex instanceof Error) |
608 |
+ |
throw (Error)ex; |
609 |
+ |
if (ex instanceof RuntimeException) |
610 |
+ |
throw (RuntimeException)ex; |
611 |
+ |
ForkJoinTask.<RuntimeException>uncheckedThrow(ex); |
612 |
+ |
} |
613 |
+ |
} |
614 |
+ |
|
615 |
+ |
/** |
616 |
+ |
* The sneaky part of sneaky throw, relying on generics |
617 |
+ |
* limitations to evade compiler complaints about rethrowing |
618 |
+ |
* unchecked exceptions |
619 |
+ |
*/ |
620 |
+ |
@SuppressWarnings("unchecked") static <T extends Throwable> |
621 |
+ |
void uncheckedThrow(Throwable t) throws T { |
622 |
+ |
if (t != null) |
623 |
+ |
throw (T)t; // rely on vacuous cast |
624 |
+ |
} |
625 |
+ |
|
626 |
+ |
/** |
627 |
|
* Throws exception, if any, associated with the given status. |
628 |
|
*/ |
629 |
|
private void reportException(int s) { |
630 |
< |
Throwable ex = ((s == CANCELLED) ? new CancellationException() : |
631 |
< |
(s == EXCEPTIONAL) ? getThrowableException() : |
632 |
< |
null); |
633 |
< |
if (ex != null) |
591 |
< |
U.throwException(ex); |
630 |
> |
if (s == CANCELLED) |
631 |
> |
throw new CancellationException(); |
632 |
> |
if (s == EXCEPTIONAL) |
633 |
> |
rethrow(getThrowableException()); |
634 |
|
} |
635 |
|
|
636 |
|
// public methods |
637 |
|
|
638 |
|
/** |
639 |
< |
* Arranges to asynchronously execute this task. While it is not |
640 |
< |
* necessarily enforced, it is a usage error to fork a task more |
641 |
< |
* than once unless it has completed and been reinitialized. |
642 |
< |
* Subsequent modifications to the state of this task or any data |
643 |
< |
* it operates on are not necessarily consistently observable by |
644 |
< |
* any thread other than the one executing it unless preceded by a |
645 |
< |
* call to {@link #join} or related methods, or a call to {@link |
646 |
< |
* #isDone} returning {@code true}. |
647 |
< |
* |
648 |
< |
* <p>This method may be invoked only from within {@code |
649 |
< |
* ForkJoinPool} computations (as may be determined using method |
608 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
609 |
< |
* result in exceptions or errors, possibly including {@code |
610 |
< |
* ClassCastException}. |
639 |
> |
* Arranges to asynchronously execute this task in the pool the |
640 |
> |
* current task is running in, if applicable, or using the {@link |
641 |
> |
* ForkJoinPool#commonPool()} if not {@link #inForkJoinPool}. While |
642 |
> |
* it is not necessarily enforced, it is a usage error to fork a |
643 |
> |
* task more than once unless it has completed and been |
644 |
> |
* reinitialized. Subsequent modifications to the state of this |
645 |
> |
* task or any data it operates on are not necessarily |
646 |
> |
* consistently observable by any thread other than the one |
647 |
> |
* executing it unless preceded by a call to {@link #join} or |
648 |
> |
* related methods, or a call to {@link #isDone} returning {@code |
649 |
> |
* true}. |
650 |
|
* |
651 |
|
* @return {@code this}, to simplify usage |
652 |
|
*/ |
653 |
|
public final ForkJoinTask<V> fork() { |
654 |
< |
((ForkJoinWorkerThread)Thread.currentThread()).workQueue.push(this); |
654 |
> |
Thread t; |
655 |
> |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) |
656 |
> |
((ForkJoinWorkerThread)t).workQueue.push(this); |
657 |
> |
else |
658 |
> |
ForkJoinPool.common.externalPush(this); |
659 |
|
return this; |
660 |
|
} |
661 |
|
|
705 |
|
* cancelled, completed normally or exceptionally, or left |
706 |
|
* unprocessed. |
707 |
|
* |
665 |
– |
* <p>This method may be invoked only from within {@code |
666 |
– |
* ForkJoinPool} computations (as may be determined using method |
667 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
668 |
– |
* result in exceptions or errors, possibly including {@code |
669 |
– |
* ClassCastException}. |
670 |
– |
* |
708 |
|
* @param t1 the first task |
709 |
|
* @param t2 the second task |
710 |
|
* @throws NullPointerException if any task is null |
730 |
|
* related methods to check if they have been cancelled, completed |
731 |
|
* normally or exceptionally, or left unprocessed. |
732 |
|
* |
696 |
– |
* <p>This method may be invoked only from within {@code |
697 |
– |
* ForkJoinPool} computations (as may be determined using method |
698 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
699 |
– |
* result in exceptions or errors, possibly including {@code |
700 |
– |
* ClassCastException}. |
701 |
– |
* |
733 |
|
* @param tasks the tasks |
734 |
|
* @throws NullPointerException if any task is null |
735 |
|
*/ |
757 |
|
} |
758 |
|
} |
759 |
|
if (ex != null) |
760 |
< |
U.throwException(ex); |
760 |
> |
rethrow(ex); |
761 |
|
} |
762 |
|
|
763 |
|
/** |
773 |
|
* cancelled, completed normally or exceptionally, or left |
774 |
|
* unprocessed. |
775 |
|
* |
745 |
– |
* <p>This method may be invoked only from within {@code |
746 |
– |
* ForkJoinPool} computations (as may be determined using method |
747 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
748 |
– |
* result in exceptions or errors, possibly including {@code |
749 |
– |
* ClassCastException}. |
750 |
– |
* |
776 |
|
* @param tasks the collection of tasks |
777 |
|
* @return the tasks argument, to simplify usage |
778 |
|
* @throws NullPointerException if tasks or any element are null |
808 |
|
} |
809 |
|
} |
810 |
|
if (ex != null) |
811 |
< |
U.throwException(ex); |
811 |
> |
rethrow(ex); |
812 |
|
return tasks; |
813 |
|
} |
814 |
|
|
929 |
|
} |
930 |
|
|
931 |
|
/** |
932 |
< |
* Completes this task. The most recent value established by |
933 |
< |
* {@link #setRawResult} (or {@code null}) will be returned as the |
934 |
< |
* result of subsequent invocations of {@code join} and related |
935 |
< |
* operations. This method may be useful when processing sets of |
936 |
< |
* tasks when some do not otherwise complete normally. Its use in |
937 |
< |
* other situations is discouraged. |
932 |
> |
* Completes this task normally without setting a value. The most |
933 |
> |
* recent value established by {@link #setRawResult} (or {@code |
934 |
> |
* null} by default) will be returned as the result of subsequent |
935 |
> |
* invocations of {@code join} and related operations. |
936 |
> |
* |
937 |
> |
* @since 1.8 |
938 |
|
*/ |
939 |
|
public final void quietlyComplete() { |
940 |
|
setCompletion(NORMAL); |
981 |
|
if (Thread.interrupted()) |
982 |
|
throw new InterruptedException(); |
983 |
|
// Messy in part because we measure in nanosecs, but wait in millisecs |
984 |
< |
int s; long ns, ms; |
985 |
< |
if ((s = status) >= 0 && (ns = unit.toNanos(timeout)) > 0L) { |
984 |
> |
int s; long ms; |
985 |
> |
long ns = unit.toNanos(timeout); |
986 |
> |
if ((s = status) >= 0 && ns > 0L) { |
987 |
|
long deadline = System.nanoTime() + ns; |
988 |
|
ForkJoinPool p = null; |
989 |
|
ForkJoinPool.WorkQueue w = null; |
992 |
|
ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; |
993 |
|
p = wt.pool; |
994 |
|
w = wt.workQueue; |
995 |
< |
s = p.helpJoinOnce(w, this); // no retries on failure |
995 |
> |
p.helpJoinOnce(w, this); // no retries on failure |
996 |
|
} |
997 |
+ |
else |
998 |
+ |
ForkJoinPool.externalHelpJoin(this); |
999 |
|
boolean canBlock = false; |
1000 |
|
boolean interrupted = false; |
1001 |
|
try { |
1002 |
|
while ((s = status) >= 0) { |
1003 |
< |
if (w != null && w.runState < 0) |
1003 |
> |
if (w != null && w.qlock < 0) |
1004 |
|
cancelIgnoringExceptions(this); |
1005 |
|
else if (!canBlock) { |
1006 |
< |
if (p == null || p.tryCompensate(this, null)) |
1006 |
> |
if (p == null || p.tryCompensate()) |
1007 |
|
canBlock = true; |
1008 |
|
} |
1009 |
|
else { |
1067 |
|
|
1068 |
|
/** |
1069 |
|
* Possibly executes tasks until the pool hosting the current task |
1070 |
< |
* {@link ForkJoinPool#isQuiescent is quiescent}. This method may |
1071 |
< |
* be of use in designs in which many tasks are forked, but none |
1072 |
< |
* are explicitly joined, instead executing them until all are |
1073 |
< |
* processed. |
1046 |
< |
* |
1047 |
< |
* <p>This method may be invoked only from within {@code |
1048 |
< |
* ForkJoinPool} computations (as may be determined using method |
1049 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1050 |
< |
* result in exceptions or errors, possibly including {@code |
1051 |
< |
* ClassCastException}. |
1070 |
> |
* {@linkplain ForkJoinPool#isQuiescent is quiescent}. This |
1071 |
> |
* method may be of use in designs in which many tasks are forked, |
1072 |
> |
* but none are explicitly joined, instead executing them until |
1073 |
> |
* all are processed. |
1074 |
|
*/ |
1075 |
|
public static void helpQuiesce() { |
1076 |
< |
ForkJoinWorkerThread wt = |
1077 |
< |
(ForkJoinWorkerThread)Thread.currentThread(); |
1078 |
< |
wt.pool.helpQuiescePool(wt.workQueue); |
1076 |
> |
Thread t; |
1077 |
> |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) { |
1078 |
> |
ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; |
1079 |
> |
wt.pool.helpQuiescePool(wt.workQueue); |
1080 |
> |
} |
1081 |
> |
else |
1082 |
> |
ForkJoinPool.quiesceCommonPool(); |
1083 |
|
} |
1084 |
|
|
1085 |
|
/** |
1132 |
|
|
1133 |
|
/** |
1134 |
|
* Tries to unschedule this task for execution. This method will |
1135 |
< |
* typically succeed if this task is the most recently forked task |
1136 |
< |
* by the current thread, and has not commenced executing in |
1137 |
< |
* another thread. This method may be useful when arranging |
1138 |
< |
* alternative local processing of tasks that could have been, but |
1139 |
< |
* were not, stolen. |
1114 |
< |
* |
1115 |
< |
* <p>This method may be invoked only from within {@code |
1116 |
< |
* ForkJoinPool} computations (as may be determined using method |
1117 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1118 |
< |
* result in exceptions or errors, possibly including {@code |
1119 |
< |
* ClassCastException}. |
1135 |
> |
* typically (but is not guaranteed to) succeed if this task is |
1136 |
> |
* the most recently forked task by the current thread, and has |
1137 |
> |
* not commenced executing in another thread. This method may be |
1138 |
> |
* useful when arranging alternative local processing of tasks |
1139 |
> |
* that could have been, but were not, stolen. |
1140 |
|
* |
1141 |
|
* @return {@code true} if unforked |
1142 |
|
*/ |
1143 |
|
public boolean tryUnfork() { |
1144 |
< |
return ((ForkJoinWorkerThread)Thread.currentThread()) |
1145 |
< |
.workQueue.tryUnpush(this); |
1144 |
> |
Thread t; |
1145 |
> |
return (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? |
1146 |
> |
((ForkJoinWorkerThread)t).workQueue.tryUnpush(this) : |
1147 |
> |
ForkJoinPool.tryExternalUnpush(this)); |
1148 |
|
} |
1149 |
|
|
1150 |
|
/** |
1153 |
|
* value may be useful for heuristic decisions about whether to |
1154 |
|
* fork other tasks. |
1155 |
|
* |
1134 |
– |
* <p>This method may be invoked only from within {@code |
1135 |
– |
* ForkJoinPool} computations (as may be determined using method |
1136 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1137 |
– |
* result in exceptions or errors, possibly including {@code |
1138 |
– |
* ClassCastException}. |
1139 |
– |
* |
1156 |
|
* @return the number of tasks |
1157 |
|
*/ |
1158 |
|
public static int getQueuedTaskCount() { |
1159 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1160 |
< |
.workQueue.queueSize(); |
1159 |
> |
Thread t; ForkJoinPool.WorkQueue q; |
1160 |
> |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) |
1161 |
> |
q = ((ForkJoinWorkerThread)t).workQueue; |
1162 |
> |
else |
1163 |
> |
q = ForkJoinPool.commonSubmitterQueue(); |
1164 |
> |
return (q == null) ? 0 : q.queueSize(); |
1165 |
|
} |
1166 |
|
|
1167 |
|
/** |
1168 |
|
* Returns an estimate of how many more locally queued tasks are |
1169 |
|
* held by the current worker thread than there are other worker |
1170 |
< |
* threads that might steal them. This value may be useful for |
1170 |
> |
* threads that might steal them, or zero if this thread is not |
1171 |
> |
* operating in a ForkJoinPool. This value may be useful for |
1172 |
|
* heuristic decisions about whether to fork other tasks. In many |
1173 |
|
* usages of ForkJoinTasks, at steady state, each worker should |
1174 |
|
* aim to maintain a small constant surplus (for example, 3) of |
1175 |
|
* tasks, and to process computations locally if this threshold is |
1176 |
|
* exceeded. |
1177 |
|
* |
1157 |
– |
* <p>This method may be invoked only from within {@code |
1158 |
– |
* ForkJoinPool} computations (as may be determined using method |
1159 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1160 |
– |
* result in exceptions or errors, possibly including {@code |
1161 |
– |
* ClassCastException}. |
1162 |
– |
* |
1178 |
|
* @return the surplus number of tasks, which may be negative |
1179 |
|
*/ |
1180 |
|
public static int getSurplusQueuedTaskCount() { |
1181 |
< |
/* |
1167 |
< |
* The aim of this method is to return a cheap heuristic guide |
1168 |
< |
* for task partitioning when programmers, frameworks, tools, |
1169 |
< |
* or languages have little or no idea about task granularity. |
1170 |
< |
* In essence by offering this method, we ask users only about |
1171 |
< |
* tradeoffs in overhead vs expected throughput and its |
1172 |
< |
* variance, rather than how finely to partition tasks. |
1173 |
< |
* |
1174 |
< |
* In a steady state strict (tree-structured) computation, |
1175 |
< |
* each thread makes available for stealing enough tasks for |
1176 |
< |
* other threads to remain active. Inductively, if all threads |
1177 |
< |
* play by the same rules, each thread should make available |
1178 |
< |
* only a constant number of tasks. |
1179 |
< |
* |
1180 |
< |
* The minimum useful constant is just 1. But using a value of |
1181 |
< |
* 1 would require immediate replenishment upon each steal to |
1182 |
< |
* maintain enough tasks, which is infeasible. Further, |
1183 |
< |
* partitionings/granularities of offered tasks should |
1184 |
< |
* minimize steal rates, which in general means that threads |
1185 |
< |
* nearer the top of computation tree should generate more |
1186 |
< |
* than those nearer the bottom. In perfect steady state, each |
1187 |
< |
* thread is at approximately the same level of computation |
1188 |
< |
* tree. However, producing extra tasks amortizes the |
1189 |
< |
* uncertainty of progress and diffusion assumptions. |
1190 |
< |
* |
1191 |
< |
* So, users will want to use values larger, but not much |
1192 |
< |
* larger than 1 to both smooth over transient shortages and |
1193 |
< |
* hedge against uneven progress; as traded off against the |
1194 |
< |
* cost of extra task overhead. We leave the user to pick a |
1195 |
< |
* threshold value to compare with the results of this call to |
1196 |
< |
* guide decisions, but recommend values such as 3. |
1197 |
< |
* |
1198 |
< |
* When all threads are active, it is on average OK to |
1199 |
< |
* estimate surplus strictly locally. In steady-state, if one |
1200 |
< |
* thread is maintaining say 2 surplus tasks, then so are |
1201 |
< |
* others. So we can just use estimated queue length. |
1202 |
< |
* However, this strategy alone leads to serious mis-estimates |
1203 |
< |
* in some non-steady-state conditions (ramp-up, ramp-down, |
1204 |
< |
* other stalls). We can detect many of these by further |
1205 |
< |
* considering the number of "idle" threads, that are known to |
1206 |
< |
* have zero queued tasks, so compensate by a factor of |
1207 |
< |
* (#idle/#active) threads. |
1208 |
< |
*/ |
1209 |
< |
ForkJoinWorkerThread wt = |
1210 |
< |
(ForkJoinWorkerThread)Thread.currentThread(); |
1211 |
< |
return wt.workQueue.queueSize() - wt.pool.idlePerActive(); |
1181 |
> |
return ForkJoinPool.getSurplusQueuedTaskCount(); |
1182 |
|
} |
1183 |
|
|
1184 |
|
// Extension methods |
1204 |
|
protected abstract void setRawResult(V value); |
1205 |
|
|
1206 |
|
/** |
1207 |
< |
* Immediately performs the base action of this task. This method |
1208 |
< |
* is designed to support extensions, and should not in general be |
1209 |
< |
* called otherwise. The return value controls whether this task |
1210 |
< |
* is considered to be done normally. It may return false in |
1207 |
> |
* Immediately performs the base action of this task and returns |
1208 |
> |
* true if, upon return from this method, this task is guaranteed |
1209 |
> |
* to have completed normally. This method may return false |
1210 |
> |
* otherwise, to indicate that this task is not necessarily |
1211 |
> |
* complete (or is not known to be complete), for example in |
1212 |
|
* asynchronous actions that require explicit invocations of |
1213 |
< |
* {@link #complete} to become joinable. It may also throw an |
1214 |
< |
* (unchecked) exception to indicate abnormal exit. |
1213 |
> |
* completion methods. This method may also throw an (unchecked) |
1214 |
> |
* exception to indicate abnormal exit. This method is designed to |
1215 |
> |
* support extensions, and should not in general be called |
1216 |
> |
* otherwise. |
1217 |
|
* |
1218 |
< |
* @return {@code true} if completed normally |
1218 |
> |
* @return {@code true} if this task is known to have completed normally |
1219 |
|
*/ |
1220 |
|
protected abstract boolean exec(); |
1221 |
|
|
1229 |
|
* primarily to support extensions, and is unlikely to be useful |
1230 |
|
* otherwise. |
1231 |
|
* |
1259 |
– |
* <p>This method may be invoked only from within {@code |
1260 |
– |
* ForkJoinPool} computations (as may be determined using method |
1261 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1262 |
– |
* result in exceptions or errors, possibly including {@code |
1263 |
– |
* ClassCastException}. |
1264 |
– |
* |
1232 |
|
* @return the next task, or {@code null} if none are available |
1233 |
|
*/ |
1234 |
|
protected static ForkJoinTask<?> peekNextLocalTask() { |
1235 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()).workQueue.peek(); |
1235 |
> |
Thread t; ForkJoinPool.WorkQueue q; |
1236 |
> |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) |
1237 |
> |
q = ((ForkJoinWorkerThread)t).workQueue; |
1238 |
> |
else |
1239 |
> |
q = ForkJoinPool.commonSubmitterQueue(); |
1240 |
> |
return (q == null) ? null : q.peek(); |
1241 |
|
} |
1242 |
|
|
1243 |
|
/** |
1244 |
|
* Unschedules and returns, without executing, the next task |
1245 |
< |
* queued by the current thread but not yet executed. This method |
1246 |
< |
* is designed primarily to support extensions, and is unlikely to |
1247 |
< |
* be useful otherwise. |
1248 |
< |
* |
1277 |
< |
* <p>This method may be invoked only from within {@code |
1278 |
< |
* ForkJoinPool} computations (as may be determined using method |
1279 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1280 |
< |
* result in exceptions or errors, possibly including {@code |
1281 |
< |
* ClassCastException}. |
1245 |
> |
* queued by the current thread but not yet executed, if the |
1246 |
> |
* current thread is operating in a ForkJoinPool. This method is |
1247 |
> |
* designed primarily to support extensions, and is unlikely to be |
1248 |
> |
* useful otherwise. |
1249 |
|
* |
1250 |
|
* @return the next task, or {@code null} if none are available |
1251 |
|
*/ |
1252 |
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
1253 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1254 |
< |
.workQueue.nextLocalTask(); |
1253 |
> |
Thread t; |
1254 |
> |
return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? |
1255 |
> |
((ForkJoinWorkerThread)t).workQueue.nextLocalTask() : |
1256 |
> |
null; |
1257 |
|
} |
1258 |
|
|
1259 |
|
/** |
1260 |
< |
* Unschedules and returns, without executing, the next task |
1260 |
> |
* If the current thread is operating in a ForkJoinPool, |
1261 |
> |
* unschedules and returns, without executing, the next task |
1262 |
|
* queued by the current thread but not yet executed, if one is |
1263 |
|
* available, or if not available, a task that was forked by some |
1264 |
|
* other thread, if available. Availability may be transient, so a |
1265 |
< |
* {@code null} result does not necessarily imply quiescence |
1266 |
< |
* of the pool this task is operating in. This method is designed |
1265 |
> |
* {@code null} result does not necessarily imply quiescence of |
1266 |
> |
* the pool this task is operating in. This method is designed |
1267 |
|
* primarily to support extensions, and is unlikely to be useful |
1268 |
|
* otherwise. |
1269 |
|
* |
1300 |
– |
* <p>This method may be invoked only from within {@code |
1301 |
– |
* ForkJoinPool} computations (as may be determined using method |
1302 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1303 |
– |
* result in exceptions or errors, possibly including {@code |
1304 |
– |
* ClassCastException}. |
1305 |
– |
* |
1270 |
|
* @return a task, or {@code null} if none are available |
1271 |
|
*/ |
1272 |
|
protected static ForkJoinTask<?> pollTask() { |
1273 |
< |
ForkJoinWorkerThread wt = |
1274 |
< |
(ForkJoinWorkerThread)Thread.currentThread(); |
1275 |
< |
return wt.pool.nextTaskFor(wt.workQueue); |
1273 |
> |
Thread t; ForkJoinWorkerThread wt; |
1274 |
> |
return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? |
1275 |
> |
(wt = (ForkJoinWorkerThread)t).pool.nextTaskFor(wt.workQueue) : |
1276 |
> |
null; |
1277 |
|
} |
1278 |
|
|
1279 |
|
// tag operations |
1306 |
|
/** |
1307 |
|
* Atomically conditionally sets the tag value for this task. |
1308 |
|
* Among other applications, tags can be used as visit markers |
1309 |
< |
* in tasks operating on graphs, as in mathods that check: {@code |
1309 |
> |
* in tasks operating on graphs, as in methods that check: {@code |
1310 |
|
* if (task.compareAndSetForkJoinTaskTag((short)0, (short)1))} |
1311 |
|
* before processing, otherwise exiting because the node has |
1312 |
|
* already been visited. |
1328 |
|
} |
1329 |
|
|
1330 |
|
/** |
1331 |
< |
* Adaptor for Runnables. This implements RunnableFuture |
1331 |
> |
* Adapter for Runnables. This implements RunnableFuture |
1332 |
|
* to be compliant with AbstractExecutorService constraints |
1333 |
|
* when used in ForkJoinPool. |
1334 |
|
*/ |
1349 |
|
} |
1350 |
|
|
1351 |
|
/** |
1352 |
< |
* Adaptor for Runnables without results |
1352 |
> |
* Adapter for Runnables without results |
1353 |
|
*/ |
1354 |
|
static final class AdaptedRunnableAction extends ForkJoinTask<Void> |
1355 |
|
implements RunnableFuture<Void> { |
1366 |
|
} |
1367 |
|
|
1368 |
|
/** |
1369 |
< |
* Adaptor for Callables |
1369 |
> |
* Adapter for Callables |
1370 |
|
*/ |
1371 |
|
static final class AdaptedCallable<T> extends ForkJoinTask<T> |
1372 |
|
implements RunnableFuture<T> { |
1462 |
|
// Unsafe mechanics |
1463 |
|
private static final sun.misc.Unsafe U; |
1464 |
|
private static final long STATUS; |
1465 |
+ |
|
1466 |
|
static { |
1467 |
|
exceptionTableLock = new ReentrantLock(); |
1468 |
|
exceptionTableRefQueue = new ReferenceQueue<Object>(); |
1469 |
|
exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY]; |
1470 |
|
try { |
1471 |
|
U = getUnsafe(); |
1472 |
+ |
Class<?> k = ForkJoinTask.class; |
1473 |
|
STATUS = U.objectFieldOffset |
1474 |
< |
(ForkJoinTask.class.getDeclaredField("status")); |
1474 |
> |
(k.getDeclaredField("status")); |
1475 |
|
} catch (Exception e) { |
1476 |
|
throw new Error(e); |
1477 |
|
} |
1487 |
|
private static sun.misc.Unsafe getUnsafe() { |
1488 |
|
try { |
1489 |
|
return sun.misc.Unsafe.getUnsafe(); |
1490 |
< |
} catch (SecurityException se) { |
1491 |
< |
try { |
1492 |
< |
return java.security.AccessController.doPrivileged |
1493 |
< |
(new java.security |
1494 |
< |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1495 |
< |
public sun.misc.Unsafe run() throws Exception { |
1496 |
< |
java.lang.reflect.Field f = sun.misc |
1497 |
< |
.Unsafe.class.getDeclaredField("theUnsafe"); |
1498 |
< |
f.setAccessible(true); |
1499 |
< |
return (sun.misc.Unsafe) f.get(null); |
1500 |
< |
}}); |
1501 |
< |
} catch (java.security.PrivilegedActionException e) { |
1502 |
< |
throw new RuntimeException("Could not initialize intrinsics", |
1503 |
< |
e.getCause()); |
1504 |
< |
} |
1490 |
> |
} catch (SecurityException tryReflectionInstead) {} |
1491 |
> |
try { |
1492 |
> |
return java.security.AccessController.doPrivileged |
1493 |
> |
(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1494 |
> |
public sun.misc.Unsafe run() throws Exception { |
1495 |
> |
Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class; |
1496 |
> |
for (java.lang.reflect.Field f : k.getDeclaredFields()) { |
1497 |
> |
f.setAccessible(true); |
1498 |
> |
Object x = f.get(null); |
1499 |
> |
if (k.isInstance(x)) |
1500 |
> |
return k.cast(x); |
1501 |
> |
} |
1502 |
> |
throw new NoSuchFieldError("the Unsafe"); |
1503 |
> |
}}); |
1504 |
> |
} catch (java.security.PrivilegedActionException e) { |
1505 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
1506 |
> |
e.getCause()); |
1507 |
|
} |
1508 |
|
} |
1509 |
|
} |