30 |
|
* 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 |
|
* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}. |
47 |
|
* The efficiency of {@code ForkJoinTask}s stems from a set of |
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. While these methods have |
127 |
< |
* {@code public} access (to allow instances of different task |
128 |
< |
* subclasses to call each other's methods), some of them may only be |
129 |
< |
* called from within other ForkJoinTasks (as may be determined using |
130 |
< |
* method {@link #inForkJoinPool}). Attempts to invoke them in other |
131 |
< |
* contexts result in exceptions or errors, possibly including {@code |
132 |
< |
* ClassCastException}. |
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 |
284 |
|
* @return status upon completion |
285 |
|
*/ |
286 |
|
private int externalAwaitDone() { |
290 |
– |
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 |
< |
} |
347 |
< |
else |
348 |
< |
s = externalAwaitDone(); |
349 |
< |
} |
350 |
< |
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); |
364 |
< |
else |
365 |
< |
s = externalAwaitDone(); |
366 |
< |
} |
367 |
< |
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 |
598 |
|
} |
599 |
|
|
600 |
|
/** |
601 |
+ |
* A version of "sneaky throw" to relay exceptions |
602 |
+ |
*/ |
603 |
+ |
static void rethrow(final Throwable ex) { |
604 |
+ |
if (ex != null) { |
605 |
+ |
if (ex instanceof Error) |
606 |
+ |
throw (Error)ex; |
607 |
+ |
if (ex instanceof RuntimeException) |
608 |
+ |
throw (RuntimeException)ex; |
609 |
+ |
throw uncheckedThrowable(ex, RuntimeException.class); |
610 |
+ |
} |
611 |
+ |
} |
612 |
+ |
|
613 |
+ |
/** |
614 |
+ |
* The sneaky part of sneaky throw, relying on generics |
615 |
+ |
* limitations to evade compiler complaints about rethrowing |
616 |
+ |
* unchecked exceptions |
617 |
+ |
*/ |
618 |
+ |
@SuppressWarnings("unchecked") static <T extends Throwable> |
619 |
+ |
T uncheckedThrowable(final Throwable t, final Class<T> c) { |
620 |
+ |
return (T)t; // rely on vacuous cast |
621 |
+ |
} |
622 |
+ |
|
623 |
+ |
/** |
624 |
|
* Throws exception, if any, associated with the given status. |
625 |
|
*/ |
626 |
|
private void reportException(int s) { |
627 |
< |
Throwable ex = ((s == CANCELLED) ? new CancellationException() : |
628 |
< |
(s == EXCEPTIONAL) ? getThrowableException() : |
629 |
< |
null); |
630 |
< |
if (ex != null) |
616 |
< |
U.throwException(ex); |
627 |
> |
if (s == CANCELLED) |
628 |
> |
throw new CancellationException(); |
629 |
> |
if (s == EXCEPTIONAL) |
630 |
> |
rethrow(getThrowableException()); |
631 |
|
} |
632 |
|
|
633 |
|
// public methods |
634 |
|
|
635 |
|
/** |
636 |
< |
* Arranges to asynchronously execute this task. While it is not |
637 |
< |
* necessarily enforced, it is a usage error to fork a task more |
638 |
< |
* than once unless it has completed and been reinitialized. |
639 |
< |
* Subsequent modifications to the state of this task or any data |
640 |
< |
* it operates on are not necessarily consistently observable by |
641 |
< |
* any thread other than the one executing it unless preceded by a |
642 |
< |
* call to {@link #join} or related methods, or a call to {@link |
643 |
< |
* #isDone} returning {@code true}. |
644 |
< |
* |
645 |
< |
* <p>This method may be invoked only from within {@code |
646 |
< |
* ForkJoinPool} computations (as may be determined using method |
633 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
634 |
< |
* result in exceptions or errors, possibly including {@code |
635 |
< |
* ClassCastException}. |
636 |
> |
* Arranges to asynchronously execute this task in the pool the |
637 |
> |
* current task is running in, if applicable, or using the {@link |
638 |
> |
* ForkJoinPool#commonPool} if not {@link #inForkJoinPool}. While |
639 |
> |
* it is not necessarily enforced, it is a usage error to fork a |
640 |
> |
* task more than once unless it has completed and been |
641 |
> |
* reinitialized. Subsequent modifications to the state of this |
642 |
> |
* task or any data it operates on are not necessarily |
643 |
> |
* consistently observable by any thread other than the one |
644 |
> |
* executing it unless preceded by a call to {@link #join} or |
645 |
> |
* related methods, or a call to {@link #isDone} returning {@code |
646 |
> |
* true}. |
647 |
|
* |
648 |
|
* @return {@code this}, to simplify usage |
649 |
|
*/ |
650 |
|
public final ForkJoinTask<V> fork() { |
651 |
< |
((ForkJoinWorkerThread)Thread.currentThread()).workQueue.push(this); |
651 |
> |
Thread t; |
652 |
> |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) |
653 |
> |
((ForkJoinWorkerThread)t).workQueue.push(this); |
654 |
> |
else |
655 |
> |
ForkJoinPool.commonPool.externalPush(this); |
656 |
|
return this; |
657 |
|
} |
658 |
|
|
702 |
|
* cancelled, completed normally or exceptionally, or left |
703 |
|
* unprocessed. |
704 |
|
* |
690 |
– |
* <p>This method may be invoked only from within {@code |
691 |
– |
* ForkJoinPool} computations (as may be determined using method |
692 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
693 |
– |
* result in exceptions or errors, possibly including {@code |
694 |
– |
* ClassCastException}. |
695 |
– |
* |
705 |
|
* @param t1 the first task |
706 |
|
* @param t2 the second task |
707 |
|
* @throws NullPointerException if any task is null |
727 |
|
* related methods to check if they have been cancelled, completed |
728 |
|
* normally or exceptionally, or left unprocessed. |
729 |
|
* |
721 |
– |
* <p>This method may be invoked only from within {@code |
722 |
– |
* ForkJoinPool} computations (as may be determined using method |
723 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
724 |
– |
* result in exceptions or errors, possibly including {@code |
725 |
– |
* ClassCastException}. |
726 |
– |
* |
730 |
|
* @param tasks the tasks |
731 |
|
* @throws NullPointerException if any task is null |
732 |
|
*/ |
754 |
|
} |
755 |
|
} |
756 |
|
if (ex != null) |
757 |
< |
U.throwException(ex); |
757 |
> |
rethrow(ex); |
758 |
|
} |
759 |
|
|
760 |
|
/** |
770 |
|
* cancelled, completed normally or exceptionally, or left |
771 |
|
* unprocessed. |
772 |
|
* |
770 |
– |
* <p>This method may be invoked only from within {@code |
771 |
– |
* ForkJoinPool} computations (as may be determined using method |
772 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
773 |
– |
* result in exceptions or errors, possibly including {@code |
774 |
– |
* ClassCastException}. |
775 |
– |
* |
773 |
|
* @param tasks the collection of tasks |
774 |
|
* @return the tasks argument, to simplify usage |
775 |
|
* @throws NullPointerException if tasks or any element are null |
805 |
|
} |
806 |
|
} |
807 |
|
if (ex != null) |
808 |
< |
U.throwException(ex); |
808 |
> |
rethrow(ex); |
809 |
|
return tasks; |
810 |
|
} |
811 |
|
|
988 |
|
ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; |
989 |
|
p = wt.pool; |
990 |
|
w = wt.workQueue; |
991 |
< |
s = p.helpJoinOnce(w, this); // no retries on failure |
991 |
> |
p.helpJoinOnce(w, this); // no retries on failure |
992 |
|
} |
993 |
+ |
else |
994 |
+ |
ForkJoinPool.externalHelpJoin(this); |
995 |
|
boolean canBlock = false; |
996 |
|
boolean interrupted = false; |
997 |
|
try { |
998 |
|
while ((s = status) >= 0) { |
999 |
< |
if (w != null && w.runState < 0) |
999 |
> |
if (w != null && w.qlock < 0) |
1000 |
|
cancelIgnoringExceptions(this); |
1001 |
|
else if (!canBlock) { |
1002 |
< |
if (p == null || p.tryCompensate(this, null)) |
1002 |
> |
if (p == null || p.tryCompensate()) |
1003 |
|
canBlock = true; |
1004 |
|
} |
1005 |
|
else { |
1067 |
|
* be of use in designs in which many tasks are forked, but none |
1068 |
|
* are explicitly joined, instead executing them until all are |
1069 |
|
* processed. |
1071 |
– |
* |
1072 |
– |
* <p>This method may be invoked only from within {@code |
1073 |
– |
* ForkJoinPool} computations (as may be determined using method |
1074 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1075 |
– |
* result in exceptions or errors, possibly including {@code |
1076 |
– |
* ClassCastException}. |
1070 |
|
*/ |
1071 |
|
public static void helpQuiesce() { |
1072 |
< |
ForkJoinWorkerThread wt = |
1073 |
< |
(ForkJoinWorkerThread)Thread.currentThread(); |
1074 |
< |
wt.pool.helpQuiescePool(wt.workQueue); |
1072 |
> |
Thread t; |
1073 |
> |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) { |
1074 |
> |
ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; |
1075 |
> |
wt.pool.helpQuiescePool(wt.workQueue); |
1076 |
> |
} |
1077 |
> |
else |
1078 |
> |
ForkJoinPool.externalHelpQuiescePool(); |
1079 |
|
} |
1080 |
|
|
1081 |
|
/** |
1128 |
|
|
1129 |
|
/** |
1130 |
|
* Tries to unschedule this task for execution. This method will |
1131 |
< |
* typically succeed if this task is the most recently forked task |
1132 |
< |
* by the current thread, and has not commenced executing in |
1133 |
< |
* another thread. This method may be useful when arranging |
1134 |
< |
* alternative local processing of tasks that could have been, but |
1135 |
< |
* were not, stolen. |
1139 |
< |
* |
1140 |
< |
* <p>This method may be invoked only from within {@code |
1141 |
< |
* ForkJoinPool} computations (as may be determined using method |
1142 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1143 |
< |
* result in exceptions or errors, possibly including {@code |
1144 |
< |
* ClassCastException}. |
1131 |
> |
* typically (but is not guaranteed to) succeed if this task is |
1132 |
> |
* the most recently forked task by the current thread, and has |
1133 |
> |
* not commenced executing in another thread. This method may be |
1134 |
> |
* useful when arranging alternative local processing of tasks |
1135 |
> |
* that could have been, but were not, stolen. |
1136 |
|
* |
1137 |
|
* @return {@code true} if unforked |
1138 |
|
*/ |
1139 |
|
public boolean tryUnfork() { |
1140 |
< |
return ((ForkJoinWorkerThread)Thread.currentThread()) |
1141 |
< |
.workQueue.tryUnpush(this); |
1140 |
> |
Thread t; |
1141 |
> |
return (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? |
1142 |
> |
((ForkJoinWorkerThread)t).workQueue.tryUnpush(this) : |
1143 |
> |
ForkJoinPool.tryExternalUnpush(this)); |
1144 |
|
} |
1145 |
|
|
1146 |
|
/** |
1149 |
|
* value may be useful for heuristic decisions about whether to |
1150 |
|
* fork other tasks. |
1151 |
|
* |
1159 |
– |
* <p>This method may be invoked only from within {@code |
1160 |
– |
* ForkJoinPool} computations (as may be determined using method |
1161 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1162 |
– |
* result in exceptions or errors, possibly including {@code |
1163 |
– |
* ClassCastException}. |
1164 |
– |
* |
1152 |
|
* @return the number of tasks |
1153 |
|
*/ |
1154 |
|
public static int getQueuedTaskCount() { |
1155 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1156 |
< |
.workQueue.queueSize(); |
1155 |
> |
Thread t; ForkJoinPool.WorkQueue q; |
1156 |
> |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) |
1157 |
> |
q = ((ForkJoinWorkerThread)t).workQueue; |
1158 |
> |
else |
1159 |
> |
q = ForkJoinPool.commonSubmitterQueue(); |
1160 |
> |
return (q == null) ? 0 : q.queueSize(); |
1161 |
|
} |
1162 |
|
|
1163 |
|
/** |
1164 |
|
* Returns an estimate of how many more locally queued tasks are |
1165 |
|
* held by the current worker thread than there are other worker |
1166 |
< |
* threads that might steal them. This value may be useful for |
1166 |
> |
* threads that might steal them, or zero if this thread is not |
1167 |
> |
* operating in a ForkJoinPool. This value may be useful for |
1168 |
|
* heuristic decisions about whether to fork other tasks. In many |
1169 |
|
* usages of ForkJoinTasks, at steady state, each worker should |
1170 |
|
* aim to maintain a small constant surplus (for example, 3) of |
1171 |
|
* tasks, and to process computations locally if this threshold is |
1172 |
|
* exceeded. |
1173 |
|
* |
1182 |
– |
* <p>This method may be invoked only from within {@code |
1183 |
– |
* ForkJoinPool} computations (as may be determined using method |
1184 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1185 |
– |
* result in exceptions or errors, possibly including {@code |
1186 |
– |
* ClassCastException}. |
1187 |
– |
* |
1174 |
|
* @return the surplus number of tasks, which may be negative |
1175 |
|
*/ |
1176 |
|
public static int getSurplusQueuedTaskCount() { |
1177 |
< |
/* |
1192 |
< |
* The aim of this method is to return a cheap heuristic guide |
1193 |
< |
* for task partitioning when programmers, frameworks, tools, |
1194 |
< |
* or languages have little or no idea about task granularity. |
1195 |
< |
* In essence by offering this method, we ask users only about |
1196 |
< |
* tradeoffs in overhead vs expected throughput and its |
1197 |
< |
* variance, rather than how finely to partition tasks. |
1198 |
< |
* |
1199 |
< |
* In a steady state strict (tree-structured) computation, |
1200 |
< |
* each thread makes available for stealing enough tasks for |
1201 |
< |
* other threads to remain active. Inductively, if all threads |
1202 |
< |
* play by the same rules, each thread should make available |
1203 |
< |
* only a constant number of tasks. |
1204 |
< |
* |
1205 |
< |
* The minimum useful constant is just 1. But using a value of |
1206 |
< |
* 1 would require immediate replenishment upon each steal to |
1207 |
< |
* maintain enough tasks, which is infeasible. Further, |
1208 |
< |
* partitionings/granularities of offered tasks should |
1209 |
< |
* minimize steal rates, which in general means that threads |
1210 |
< |
* nearer the top of computation tree should generate more |
1211 |
< |
* than those nearer the bottom. In perfect steady state, each |
1212 |
< |
* thread is at approximately the same level of computation |
1213 |
< |
* tree. However, producing extra tasks amortizes the |
1214 |
< |
* uncertainty of progress and diffusion assumptions. |
1215 |
< |
* |
1216 |
< |
* So, users will want to use values larger, but not much |
1217 |
< |
* larger than 1 to both smooth over transient shortages and |
1218 |
< |
* hedge against uneven progress; as traded off against the |
1219 |
< |
* cost of extra task overhead. We leave the user to pick a |
1220 |
< |
* threshold value to compare with the results of this call to |
1221 |
< |
* guide decisions, but recommend values such as 3. |
1222 |
< |
* |
1223 |
< |
* When all threads are active, it is on average OK to |
1224 |
< |
* estimate surplus strictly locally. In steady-state, if one |
1225 |
< |
* thread is maintaining say 2 surplus tasks, then so are |
1226 |
< |
* others. So we can just use estimated queue length. |
1227 |
< |
* However, this strategy alone leads to serious mis-estimates |
1228 |
< |
* in some non-steady-state conditions (ramp-up, ramp-down, |
1229 |
< |
* other stalls). We can detect many of these by further |
1230 |
< |
* considering the number of "idle" threads, that are known to |
1231 |
< |
* have zero queued tasks, so compensate by a factor of |
1232 |
< |
* (#idle/#active) threads. |
1233 |
< |
*/ |
1234 |
< |
ForkJoinWorkerThread wt = |
1235 |
< |
(ForkJoinWorkerThread)Thread.currentThread(); |
1236 |
< |
return wt.workQueue.queueSize() - wt.pool.idlePerActive(); |
1177 |
> |
return ForkJoinPool.getSurplusQueuedTaskCount(); |
1178 |
|
} |
1179 |
|
|
1180 |
|
// Extension methods |
1225 |
|
* primarily to support extensions, and is unlikely to be useful |
1226 |
|
* otherwise. |
1227 |
|
* |
1287 |
– |
* <p>This method may be invoked only from within {@code |
1288 |
– |
* ForkJoinPool} computations (as may be determined using method |
1289 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1290 |
– |
* result in exceptions or errors, possibly including {@code |
1291 |
– |
* ClassCastException}. |
1292 |
– |
* |
1228 |
|
* @return the next task, or {@code null} if none are available |
1229 |
|
*/ |
1230 |
|
protected static ForkJoinTask<?> peekNextLocalTask() { |
1231 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()).workQueue.peek(); |
1231 |
> |
Thread t; ForkJoinPool.WorkQueue q; |
1232 |
> |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) |
1233 |
> |
q = ((ForkJoinWorkerThread)t).workQueue; |
1234 |
> |
else |
1235 |
> |
q = ForkJoinPool.commonSubmitterQueue(); |
1236 |
> |
return (q == null) ? null : q.peek(); |
1237 |
|
} |
1238 |
|
|
1239 |
|
/** |
1240 |
|
* Unschedules and returns, without executing, the next task |
1241 |
< |
* queued by the current thread but not yet executed. This method |
1242 |
< |
* is designed primarily to support extensions, and is unlikely to |
1243 |
< |
* be useful otherwise. |
1244 |
< |
* |
1305 |
< |
* <p>This method may be invoked only from within {@code |
1306 |
< |
* ForkJoinPool} computations (as may be determined using method |
1307 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1308 |
< |
* result in exceptions or errors, possibly including {@code |
1309 |
< |
* ClassCastException}. |
1241 |
> |
* queued by the current thread but not yet executed, if the |
1242 |
> |
* current thread is operating in a ForkJoinPool. This method is |
1243 |
> |
* designed primarily to support extensions, and is unlikely to be |
1244 |
> |
* useful otherwise. |
1245 |
|
* |
1246 |
|
* @return the next task, or {@code null} if none are available |
1247 |
|
*/ |
1248 |
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
1249 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1250 |
< |
.workQueue.nextLocalTask(); |
1249 |
> |
Thread t; |
1250 |
> |
return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? |
1251 |
> |
((ForkJoinWorkerThread)t).workQueue.nextLocalTask() : |
1252 |
> |
null; |
1253 |
|
} |
1254 |
|
|
1255 |
|
/** |
1256 |
< |
* Unschedules and returns, without executing, the next task |
1256 |
> |
* If the current thread is operating in a ForkJoinPool, |
1257 |
> |
* unschedules and returns, without executing, the next task |
1258 |
|
* queued by the current thread but not yet executed, if one is |
1259 |
|
* available, or if not available, a task that was forked by some |
1260 |
|
* other thread, if available. Availability may be transient, so a |
1261 |
< |
* {@code null} result does not necessarily imply quiescence |
1262 |
< |
* of the pool this task is operating in. This method is designed |
1261 |
> |
* {@code null} result does not necessarily imply quiescence of |
1262 |
> |
* the pool this task is operating in. This method is designed |
1263 |
|
* primarily to support extensions, and is unlikely to be useful |
1264 |
|
* otherwise. |
1265 |
|
* |
1328 |
– |
* <p>This method may be invoked only from within {@code |
1329 |
– |
* ForkJoinPool} computations (as may be determined using method |
1330 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1331 |
– |
* result in exceptions or errors, possibly including {@code |
1332 |
– |
* ClassCastException}. |
1333 |
– |
* |
1266 |
|
* @return a task, or {@code null} if none are available |
1267 |
|
*/ |
1268 |
|
protected static ForkJoinTask<?> pollTask() { |
1269 |
< |
ForkJoinWorkerThread wt = |
1270 |
< |
(ForkJoinWorkerThread)Thread.currentThread(); |
1271 |
< |
return wt.pool.nextTaskFor(wt.workQueue); |
1269 |
> |
Thread t; ForkJoinWorkerThread wt; |
1270 |
> |
return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? |
1271 |
> |
(wt = (ForkJoinWorkerThread)t).pool.nextTaskFor(wt.workQueue) : |
1272 |
> |
null; |
1273 |
|
} |
1274 |
|
|
1275 |
|
// tag operations |
1458 |
|
// Unsafe mechanics |
1459 |
|
private static final sun.misc.Unsafe U; |
1460 |
|
private static final long STATUS; |
1461 |
+ |
|
1462 |
|
static { |
1463 |
|
exceptionTableLock = new ReentrantLock(); |
1464 |
|
exceptionTableRefQueue = new ReferenceQueue<Object>(); |
1465 |
|
exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY]; |
1466 |
|
try { |
1467 |
|
U = getUnsafe(); |
1468 |
+ |
Class<?> k = ForkJoinTask.class; |
1469 |
|
STATUS = U.objectFieldOffset |
1470 |
< |
(ForkJoinTask.class.getDeclaredField("status")); |
1470 |
> |
(k.getDeclaredField("status")); |
1471 |
|
} catch (Exception e) { |
1472 |
|
throw new Error(e); |
1473 |
|
} |