5 |
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*/ |
6 |
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7 |
|
package jsr166y; |
8 |
– |
|
8 |
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import java.io.Serializable; |
9 |
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import java.util.Collection; |
10 |
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import java.util.List; |
42 |
|
* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}. |
43 |
|
* The efficiency of {@code ForkJoinTask}s stems from a set of |
44 |
|
* restrictions (that are only partially statically enforceable) |
45 |
< |
* reflecting their intended use as computational tasks calculating |
46 |
< |
* pure functions or operating on purely isolated objects. The |
47 |
< |
* primary coordination mechanisms are {@link #fork}, that arranges |
45 |
> |
* reflecting their main use as computational tasks calculating pure |
46 |
> |
* functions or operating on purely isolated objects. The primary |
47 |
> |
* coordination mechanisms are {@link #fork}, that arranges |
48 |
|
* asynchronous execution, and {@link #join}, that doesn't proceed |
49 |
|
* until the task's result has been computed. Computations should |
50 |
< |
* avoid {@code synchronized} methods or blocks, and should minimize |
51 |
< |
* other blocking synchronization apart from joining other tasks or |
52 |
< |
* using synchronizers such as Phasers that are advertised to |
53 |
< |
* cooperate with fork/join scheduling. Tasks should also not perform |
54 |
< |
* blocking IO, and should ideally access variables that are |
55 |
< |
* completely independent of those accessed by other running |
56 |
< |
* tasks. Minor breaches of these restrictions, for example using |
57 |
< |
* shared output streams, may be tolerable in practice, but frequent |
58 |
< |
* use may result in poor performance, and the potential to |
59 |
< |
* indefinitely stall if the number of threads not waiting for IO or |
60 |
< |
* other external synchronization becomes exhausted. This usage |
61 |
< |
* restriction is in part enforced by not permitting checked |
62 |
< |
* exceptions such as {@code IOExceptions} to be thrown. However, |
63 |
< |
* computations may still encounter unchecked exceptions, that are |
64 |
< |
* rethrown to callers attempting to join them. These exceptions may |
65 |
< |
* additionally include {@link RejectedExecutionException} stemming |
66 |
< |
* from internal resource exhaustion, such as failure to allocate |
67 |
< |
* internal task queues. Rethrown exceptions behave in the same way as |
68 |
< |
* regular exceptions, but, when possible, contain stack traces (as |
69 |
< |
* displayed for example using {@code ex.printStackTrace()}) of both |
70 |
< |
* the thread that initiated the computation as well as the thread |
71 |
< |
* actually encountering the exception; minimally only the latter. |
50 |
> |
* ideally avoid {@code synchronized} methods or blocks, and should |
51 |
> |
* minimize other blocking synchronization apart from joining other |
52 |
> |
* tasks or using synchronizers such as Phasers that are advertised to |
53 |
> |
* cooperate with fork/join scheduling. Subdividable tasks should also |
54 |
> |
* not perform blocking IO, and should ideally access variables that |
55 |
> |
* are completely independent of those accessed by other running |
56 |
> |
* tasks. These guidelines are loosely enforced by not permitting |
57 |
> |
* checked exceptions such as {@code IOExceptions} to be |
58 |
> |
* thrown. However, computations may still encounter unchecked |
59 |
> |
* exceptions, that are rethrown to callers attempting to join |
60 |
> |
* them. These exceptions may additionally include {@link |
61 |
> |
* RejectedExecutionException} stemming from internal resource |
62 |
> |
* exhaustion, such as failure to allocate internal task |
63 |
> |
* queues. Rethrown exceptions behave in the same way as regular |
64 |
> |
* exceptions, but, when possible, contain stack traces (as displayed |
65 |
> |
* for example using {@code ex.printStackTrace()}) of both the thread |
66 |
> |
* that initiated the computation as well as the thread actually |
67 |
> |
* encountering the exception; minimally only the latter. |
68 |
> |
* |
69 |
> |
* <p>It is possible to define and use ForkJoinTasks that may block, |
70 |
> |
* but doing do requires three further considerations: (1) Completion |
71 |
> |
* of few if any <em>other</em> tasks should be dependent on a task |
72 |
> |
* that blocks on external synchronization or IO. Event-style async |
73 |
> |
* tasks that are never joined often fall into this category. (2) To |
74 |
> |
* minimize resource impact, tasks should be small; ideally performing |
75 |
> |
* only the (possibly) blocking action. (3) Unless the {@link |
76 |
> |
* ForkJoinPool.ManagedBlocker} API is used, or the number of possibly |
77 |
> |
* blocked tasks is known to be less than the pool's {@link |
78 |
> |
* ForkJoinPool#getParallelism} level, the pool cannot guarantee that |
79 |
> |
* enough threads will be available to ensure progress or good |
80 |
> |
* performance. |
81 |
|
* |
82 |
|
* <p>The primary method for awaiting completion and extracting |
83 |
|
* results of a task is {@link #join}, but there are several variants: |
93 |
|
* performs the most common form of parallel invocation: forking a set |
94 |
|
* of tasks and joining them all. |
95 |
|
* |
96 |
+ |
* <p>In the most typical usages, a fork-join pair act like a call |
97 |
+ |
* (fork) and return (join) from a parallel recursive function. As is |
98 |
+ |
* the case with other forms of recursive calls, returns (joins) |
99 |
+ |
* should be performed innermost-first. For example, {@code a.fork(); |
100 |
+ |
* b.fork(); b.join(); a.join();} is likely to be substantially more |
101 |
+ |
* efficient than joining {@code a} before {@code b}. |
102 |
+ |
* |
103 |
|
* <p>The execution status of tasks may be queried at several levels |
104 |
|
* of detail: {@link #isDone} is true if a task completed in any way |
105 |
|
* (including the case where a task was cancelled without executing); |
136 |
|
* supports other methods and techniques (for example the use of |
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. |
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 |
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.) |
151 |
|
* |
152 |
|
* <p>Most base support methods are {@code final}, to prevent |
153 |
|
* overriding of implementations that are intrinsically tied to the |
187 |
|
* See the internal documentation of class ForkJoinPool for a |
188 |
|
* general implementation overview. ForkJoinTasks are mainly |
189 |
|
* responsible for maintaining their "status" field amidst relays |
190 |
< |
* to methods in ForkJoinWorkerThread and ForkJoinPool. The |
191 |
< |
* methods of this class are more-or-less layered into (1) basic |
192 |
< |
* status maintenance (2) execution and awaiting completion (3) |
193 |
< |
* user-level methods that additionally report results. This is |
194 |
< |
* sometimes hard to see because this file orders exported methods |
195 |
< |
* in a way that flows well in javadocs. |
190 |
> |
* to methods in ForkJoinWorkerThread and ForkJoinPool. |
191 |
> |
* |
192 |
> |
* The methods of this class are more-or-less layered into |
193 |
> |
* (1) basic status maintenance |
194 |
> |
* (2) execution and awaiting completion |
195 |
> |
* (3) user-level methods that additionally report results. |
196 |
> |
* This is sometimes hard to see because this file orders exported |
197 |
> |
* methods in a way that flows well in javadocs. |
198 |
|
*/ |
199 |
|
|
200 |
|
/* |
201 |
|
* The status field holds run control status bits packed into a |
202 |
|
* single int to minimize footprint and to ensure atomicity (via |
203 |
|
* CAS). Status is initially zero, and takes on nonnegative |
204 |
< |
* values until completed, upon which status holds value |
205 |
< |
* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking |
206 |
< |
* waits by other threads have the SIGNAL bit set. Completion of |
207 |
< |
* a stolen task with SIGNAL set awakens any waiters via |
208 |
< |
* notifyAll. Even though suboptimal for some purposes, we use |
209 |
< |
* basic builtin wait/notify to take advantage of "monitor |
210 |
< |
* inflation" in JVMs that we would otherwise need to emulate to |
211 |
< |
* avoid adding further per-task bookkeeping overhead. We want |
212 |
< |
* these monitors to be "fat", i.e., not use biasing or thin-lock |
213 |
< |
* techniques, so use some odd coding idioms that tend to avoid |
214 |
< |
* them. |
204 |
> |
* values until completed, upon which status (anded with |
205 |
> |
* DONE_MASK) holds value NORMAL, CANCELLED, or EXCEPTIONAL. Tasks |
206 |
> |
* undergoing blocking waits by other threads have the SIGNAL bit |
207 |
> |
* set. Completion of a stolen task with SIGNAL set awakens any |
208 |
> |
* waiters via notifyAll. Even though suboptimal for some |
209 |
> |
* purposes, we use basic builtin wait/notify to take advantage of |
210 |
> |
* "monitor inflation" in JVMs that we would otherwise need to |
211 |
> |
* emulate to avoid adding further per-task bookkeeping overhead. |
212 |
> |
* We want these monitors to be "fat", i.e., not use biasing or |
213 |
> |
* thin-lock techniques, so use some odd coding idioms that tend |
214 |
> |
* to avoid them, mainly by arranging that every synchronized |
215 |
> |
* block performs a wait, notifyAll or both. |
216 |
> |
* |
217 |
> |
* These control bits occupy only (some of) the upper half (16 |
218 |
> |
* bits) of status field. The lower bits are used for user-defined |
219 |
> |
* tags. |
220 |
|
*/ |
221 |
|
|
222 |
|
/** The run status of this task */ |
223 |
|
volatile int status; // accessed directly by pool and workers |
224 |
< |
private static final int NORMAL = -1; |
225 |
< |
private static final int CANCELLED = -2; |
226 |
< |
private static final int EXCEPTIONAL = -3; |
227 |
< |
private static final int SIGNAL = 1; |
224 |
> |
static final int DONE_MASK = 0xf0000000; // mask out non-completion bits |
225 |
> |
static final int NORMAL = 0xf0000000; // must be negative |
226 |
> |
static final int CANCELLED = 0xc0000000; // must be < NORMAL |
227 |
> |
static final int EXCEPTIONAL = 0x80000000; // must be < CANCELLED |
228 |
> |
static final int SIGNAL = 0x00010000; // must be >= 1 << 16 |
229 |
> |
static final int SMASK = 0x0000ffff; // short bits for tags |
230 |
|
|
231 |
|
/** |
232 |
< |
* Marks completion and wakes up threads waiting to join this task, |
233 |
< |
* also clearing signal request bits. |
232 |
> |
* Marks completion and wakes up threads waiting to join this |
233 |
> |
* task. |
234 |
|
* |
235 |
|
* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
236 |
|
* @return completion status on exit |
239 |
|
for (int s;;) { |
240 |
|
if ((s = status) < 0) |
241 |
|
return s; |
242 |
< |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) { |
243 |
< |
if (s != 0) |
242 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | completion)) { |
243 |
> |
if ((s >>> 16) != 0) |
244 |
|
synchronized (this) { notifyAll(); } |
245 |
|
return completion; |
246 |
|
} |
248 |
|
} |
249 |
|
|
250 |
|
/** |
251 |
< |
* Tries to block a worker thread until completed or timed out. |
252 |
< |
* Uses Object.wait time argument conventions. |
253 |
< |
* May fail on contention or interrupt. |
251 |
> |
* Primary execution method for stolen tasks. Unless done, calls |
252 |
> |
* exec and records status if completed, but doesn't wait for |
253 |
> |
* completion otherwise. |
254 |
|
* |
255 |
< |
* @param millis if > 0, wait time. |
255 |
> |
* @return status on exit from this method |
256 |
|
*/ |
257 |
< |
final void tryAwaitDone(long millis) { |
258 |
< |
int s; |
259 |
< |
try { |
260 |
< |
if (((s = status) > 0 || |
261 |
< |
(s == 0 && |
262 |
< |
UNSAFE.compareAndSwapInt(this, statusOffset, 0, SIGNAL))) && |
263 |
< |
status > 0) { |
229 |
< |
synchronized (this) { |
230 |
< |
if (status > 0) |
231 |
< |
wait(millis); |
232 |
< |
} |
257 |
> |
final int doExec() { |
258 |
> |
int s; boolean completed; |
259 |
> |
if ((s = status) >= 0) { |
260 |
> |
try { |
261 |
> |
completed = exec(); |
262 |
> |
} catch (Throwable rex) { |
263 |
> |
return setExceptionalCompletion(rex); |
264 |
|
} |
265 |
< |
} catch (InterruptedException ie) { |
266 |
< |
// caller must check termination |
265 |
> |
if (completed) |
266 |
> |
s = setCompletion(NORMAL); |
267 |
|
} |
268 |
+ |
return s; |
269 |
+ |
} |
270 |
+ |
|
271 |
+ |
/** |
272 |
+ |
* Tries to set SIGNAL status. Used by ForkJoinPool. Other |
273 |
+ |
* variants are directly incorporated into 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); |
280 |
|
} |
281 |
|
|
282 |
|
/** |
284 |
|
* @return status upon completion |
285 |
|
*/ |
286 |
|
private int externalAwaitDone() { |
287 |
+ |
boolean interrupted = false; |
288 |
|
int s; |
289 |
< |
if ((s = status) >= 0) { |
290 |
< |
boolean interrupted = false; |
291 |
< |
synchronized (this) { |
292 |
< |
while ((s = status) >= 0) { |
249 |
< |
if (s == 0) |
250 |
< |
UNSAFE.compareAndSwapInt(this, statusOffset, |
251 |
< |
0, SIGNAL); |
252 |
< |
else { |
289 |
> |
while ((s = status) >= 0) { |
290 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
291 |
> |
synchronized (this) { |
292 |
> |
if (status >= 0) { |
293 |
|
try { |
294 |
|
wait(); |
295 |
|
} catch (InterruptedException ie) { |
296 |
|
interrupted = true; |
297 |
|
} |
298 |
|
} |
299 |
+ |
else |
300 |
+ |
notifyAll(); |
301 |
|
} |
302 |
|
} |
261 |
– |
if (interrupted) |
262 |
– |
Thread.currentThread().interrupt(); |
303 |
|
} |
304 |
+ |
if (interrupted) |
305 |
+ |
Thread.currentThread().interrupt(); |
306 |
|
return s; |
307 |
|
} |
308 |
|
|
309 |
|
/** |
310 |
< |
* Blocks a non-worker-thread until completion or interruption or timeout. |
310 |
> |
* Blocks a non-worker-thread until completion or interruption. |
311 |
|
*/ |
312 |
< |
private int externalInterruptibleAwaitDone(long millis) |
271 |
< |
throws InterruptedException { |
312 |
> |
private int externalInterruptibleAwaitDone() throws InterruptedException { |
313 |
|
int s; |
314 |
|
if (Thread.interrupted()) |
315 |
|
throw new InterruptedException(); |
316 |
< |
if ((s = status) >= 0) { |
317 |
< |
synchronized (this) { |
318 |
< |
while ((s = status) >= 0) { |
319 |
< |
if (s == 0) |
320 |
< |
UNSAFE.compareAndSwapInt(this, statusOffset, |
321 |
< |
0, SIGNAL); |
322 |
< |
else { |
282 |
< |
wait(millis); |
283 |
< |
if (millis > 0L) |
284 |
< |
break; |
285 |
< |
} |
316 |
> |
while ((s = status) >= 0) { |
317 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
318 |
> |
synchronized (this) { |
319 |
> |
if (status >= 0) |
320 |
> |
wait(); |
321 |
> |
else |
322 |
> |
notifyAll(); |
323 |
|
} |
324 |
|
} |
325 |
|
} |
327 |
|
} |
328 |
|
|
329 |
|
/** |
330 |
< |
* Primary execution method for stolen tasks. Unless done, calls |
331 |
< |
* exec and records status if completed, but doesn't wait for |
332 |
< |
* completion otherwise. |
333 |
< |
*/ |
297 |
< |
final void doExec() { |
298 |
< |
if (status >= 0) { |
299 |
< |
boolean completed; |
300 |
< |
try { |
301 |
< |
completed = exec(); |
302 |
< |
} catch (Throwable rex) { |
303 |
< |
setExceptionalCompletion(rex); |
304 |
< |
return; |
305 |
< |
} |
306 |
< |
if (completed) |
307 |
< |
setCompletion(NORMAL); // must be outside try block |
308 |
< |
} |
309 |
< |
} |
310 |
< |
|
311 |
< |
/** |
312 |
< |
* Primary mechanics for join, get, quietlyJoin. |
330 |
> |
* Implementation for join, get, quietlyJoin. Directly handles |
331 |
> |
* only cases of already-completed, external wait, and |
332 |
> |
* unfork+exec. Others are relayed to ForkJoinPool.awaitJoin. |
333 |
> |
* |
334 |
|
* @return status upon completion |
335 |
|
*/ |
336 |
|
private int doJoin() { |
337 |
< |
Thread t; ForkJoinWorkerThread w; int s; boolean completed; |
338 |
< |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) { |
339 |
< |
if ((s = status) < 0) |
340 |
< |
return s; |
341 |
< |
if ((w = (ForkJoinWorkerThread)t).unpushTask(this)) { |
342 |
< |
try { |
322 |
< |
completed = exec(); |
323 |
< |
} catch (Throwable rex) { |
324 |
< |
return setExceptionalCompletion(rex); |
325 |
< |
} |
326 |
< |
if (completed) |
327 |
< |
return setCompletion(NORMAL); |
337 |
> |
int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w; |
338 |
> |
if ((s = status) >= 0) { |
339 |
> |
if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) { |
340 |
> |
if (!(w = (wt = (ForkJoinWorkerThread)t).workQueue). |
341 |
> |
tryUnpush(this) || (s = doExec()) >= 0) |
342 |
> |
s = wt.pool.awaitJoin(w, this); |
343 |
|
} |
344 |
< |
return w.joinTask(this); |
344 |
> |
else |
345 |
> |
s = externalAwaitDone(); |
346 |
|
} |
347 |
< |
else |
332 |
< |
return externalAwaitDone(); |
347 |
> |
return s; |
348 |
|
} |
349 |
|
|
350 |
|
/** |
351 |
< |
* Primary mechanics for invoke, quietlyInvoke. |
351 |
> |
* Implementation for invoke, quietlyInvoke. |
352 |
> |
* |
353 |
|
* @return status upon completion |
354 |
|
*/ |
355 |
|
private int doInvoke() { |
356 |
< |
int s; boolean completed; |
357 |
< |
if ((s = status) < 0) |
358 |
< |
return s; |
359 |
< |
try { |
360 |
< |
completed = exec(); |
361 |
< |
} catch (Throwable rex) { |
362 |
< |
return setExceptionalCompletion(rex); |
356 |
> |
int s; Thread t; ForkJoinWorkerThread wt; |
357 |
> |
if ((s = doExec()) >= 0) { |
358 |
> |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) |
359 |
> |
s = (wt = (ForkJoinWorkerThread)t).pool.awaitJoin(wt.workQueue, |
360 |
> |
this); |
361 |
> |
else |
362 |
> |
s = externalAwaitDone(); |
363 |
|
} |
364 |
< |
if (completed) |
349 |
< |
return setCompletion(NORMAL); |
350 |
< |
else |
351 |
< |
return doJoin(); |
364 |
> |
return s; |
365 |
|
} |
366 |
|
|
367 |
|
// Exception table support |
396 |
|
* any ForkJoinPool will call helpExpungeStaleExceptions when its |
397 |
|
* pool becomes isQuiescent. |
398 |
|
*/ |
399 |
< |
static final class ExceptionNode extends WeakReference<ForkJoinTask<?>>{ |
399 |
> |
static final class ExceptionNode extends WeakReference<ForkJoinTask<?>> { |
400 |
|
final Throwable ex; |
401 |
|
ExceptionNode next; |
402 |
|
final long thrower; // use id not ref to avoid weak cycles |
436 |
|
} |
437 |
|
|
438 |
|
/** |
439 |
+ |
* Cancels, ignoring any exceptions thrown by cancel. Used during |
440 |
+ |
* worker and pool shutdown. Cancel is spec'ed not to throw any |
441 |
+ |
* exceptions, but if it does anyway, we have no recourse during |
442 |
+ |
* shutdown, so guard against this case. |
443 |
+ |
*/ |
444 |
+ |
static final void cancelIgnoringExceptions(ForkJoinTask<?> t) { |
445 |
+ |
if (t != null && t.status >= 0) { |
446 |
+ |
try { |
447 |
+ |
t.cancel(false); |
448 |
+ |
} catch (Throwable ignore) { |
449 |
+ |
} |
450 |
+ |
} |
451 |
+ |
} |
452 |
+ |
|
453 |
+ |
/** |
454 |
|
* Removes exception node and clears status |
455 |
|
*/ |
456 |
|
private void clearExceptionalCompletion() { |
496 |
|
* @return the exception, or null if none |
497 |
|
*/ |
498 |
|
private Throwable getThrowableException() { |
499 |
< |
if (status != EXCEPTIONAL) |
499 |
> |
if ((status & DONE_MASK) != EXCEPTIONAL) |
500 |
|
return null; |
501 |
|
int h = System.identityHashCode(this); |
502 |
|
ExceptionNode e; |
581 |
|
} |
582 |
|
|
583 |
|
/** |
584 |
< |
* Report the result of invoke or join; called only upon |
557 |
< |
* non-normal return of internal versions. |
584 |
> |
* Throws exception, if any, associated with the given status. |
585 |
|
*/ |
586 |
< |
private V reportResult() { |
587 |
< |
int s; Throwable ex; |
588 |
< |
if ((s = status) == CANCELLED) |
589 |
< |
throw new CancellationException(); |
590 |
< |
if (s == EXCEPTIONAL && (ex = getThrowableException()) != null) |
591 |
< |
UNSAFE.throwException(ex); |
565 |
< |
return getRawResult(); |
586 |
> |
private void reportException(int s) { |
587 |
> |
Throwable ex = ((s == CANCELLED) ? new CancellationException() : |
588 |
> |
(s == EXCEPTIONAL) ? getThrowableException() : |
589 |
> |
null); |
590 |
> |
if (ex != null) |
591 |
> |
U.throwException(ex); |
592 |
|
} |
593 |
|
|
594 |
|
// public methods |
612 |
|
* @return {@code this}, to simplify usage |
613 |
|
*/ |
614 |
|
public final ForkJoinTask<V> fork() { |
615 |
< |
((ForkJoinWorkerThread) Thread.currentThread()) |
590 |
< |
.pushTask(this); |
615 |
> |
((ForkJoinWorkerThread)Thread.currentThread()).workQueue.push(this); |
616 |
|
return this; |
617 |
|
} |
618 |
|
|
628 |
|
* @return the computed result |
629 |
|
*/ |
630 |
|
public final V join() { |
631 |
< |
if (doJoin() != NORMAL) |
632 |
< |
return reportResult(); |
633 |
< |
else |
634 |
< |
return getRawResult(); |
631 |
> |
int s; |
632 |
> |
if ((s = doJoin() & DONE_MASK) != NORMAL) |
633 |
> |
reportException(s); |
634 |
> |
return getRawResult(); |
635 |
|
} |
636 |
|
|
637 |
|
/** |
643 |
|
* @return the computed result |
644 |
|
*/ |
645 |
|
public final V invoke() { |
646 |
< |
if (doInvoke() != NORMAL) |
647 |
< |
return reportResult(); |
648 |
< |
else |
649 |
< |
return getRawResult(); |
646 |
> |
int s; |
647 |
> |
if ((s = doInvoke() & DONE_MASK) != NORMAL) |
648 |
> |
reportException(s); |
649 |
> |
return getRawResult(); |
650 |
|
} |
651 |
|
|
652 |
|
/** |
673 |
|
* @throws NullPointerException if any task is null |
674 |
|
*/ |
675 |
|
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) { |
676 |
+ |
int s1, s2; |
677 |
|
t2.fork(); |
678 |
< |
t1.invoke(); |
679 |
< |
t2.join(); |
678 |
> |
if ((s1 = t1.doInvoke() & DONE_MASK) != NORMAL) |
679 |
> |
t1.reportException(s1); |
680 |
> |
if ((s2 = t2.doJoin() & DONE_MASK) != NORMAL) |
681 |
> |
t2.reportException(s2); |
682 |
|
} |
683 |
|
|
684 |
|
/** |
721 |
|
if (t != null) { |
722 |
|
if (ex != null) |
723 |
|
t.cancel(false); |
724 |
< |
else if (t.doJoin() < NORMAL && ex == null) |
724 |
> |
else if (t.doJoin() < NORMAL) |
725 |
|
ex = t.getException(); |
726 |
|
} |
727 |
|
} |
728 |
|
if (ex != null) |
729 |
< |
UNSAFE.throwException(ex); |
729 |
> |
U.throwException(ex); |
730 |
|
} |
731 |
|
|
732 |
|
/** |
778 |
|
if (t != null) { |
779 |
|
if (ex != null) |
780 |
|
t.cancel(false); |
781 |
< |
else if (t.doJoin() < NORMAL && ex == null) |
781 |
> |
else if (t.doJoin() < NORMAL) |
782 |
|
ex = t.getException(); |
783 |
|
} |
784 |
|
} |
785 |
|
if (ex != null) |
786 |
< |
UNSAFE.throwException(ex); |
786 |
> |
U.throwException(ex); |
787 |
|
return tasks; |
788 |
|
} |
789 |
|
|
815 |
|
* @return {@code true} if this task is now cancelled |
816 |
|
*/ |
817 |
|
public boolean cancel(boolean mayInterruptIfRunning) { |
818 |
< |
return setCompletion(CANCELLED) == CANCELLED; |
791 |
< |
} |
792 |
< |
|
793 |
< |
/** |
794 |
< |
* Cancels, ignoring any exceptions thrown by cancel. Used during |
795 |
< |
* worker and pool shutdown. Cancel is spec'ed not to throw any |
796 |
< |
* exceptions, but if it does anyway, we have no recourse during |
797 |
< |
* shutdown, so guard against this case. |
798 |
< |
*/ |
799 |
< |
final void cancelIgnoringExceptions() { |
800 |
< |
try { |
801 |
< |
cancel(false); |
802 |
< |
} catch (Throwable ignore) { |
803 |
< |
} |
818 |
> |
return (setCompletion(CANCELLED) & DONE_MASK) == CANCELLED; |
819 |
|
} |
820 |
|
|
821 |
|
public final boolean isDone() { |
823 |
|
} |
824 |
|
|
825 |
|
public final boolean isCancelled() { |
826 |
< |
return status == CANCELLED; |
826 |
> |
return (status & DONE_MASK) == CANCELLED; |
827 |
|
} |
828 |
|
|
829 |
|
/** |
843 |
|
* exception and was not cancelled |
844 |
|
*/ |
845 |
|
public final boolean isCompletedNormally() { |
846 |
< |
return status == NORMAL; |
846 |
> |
return (status & DONE_MASK) == NORMAL; |
847 |
|
} |
848 |
|
|
849 |
|
/** |
854 |
|
* @return the exception, or {@code null} if none |
855 |
|
*/ |
856 |
|
public final Throwable getException() { |
857 |
< |
int s = status; |
857 |
> |
int s = status & DONE_MASK; |
858 |
|
return ((s >= NORMAL) ? null : |
859 |
|
(s == CANCELLED) ? new CancellationException() : |
860 |
|
getThrowableException()); |
904 |
|
} |
905 |
|
|
906 |
|
/** |
907 |
+ |
* Completes this task. The most recent value established by |
908 |
+ |
* {@link #setRawResult} (or {@code null}) will be returned as the |
909 |
+ |
* result of subsequent invocations of {@code join} and related |
910 |
+ |
* operations. This method may be useful when processing sets of |
911 |
+ |
* tasks when some do not otherwise complete normally. Its use in |
912 |
+ |
* other situations is discouraged. |
913 |
+ |
*/ |
914 |
+ |
public final void quietlyComplete() { |
915 |
+ |
setCompletion(NORMAL); |
916 |
+ |
} |
917 |
+ |
|
918 |
+ |
/** |
919 |
|
* Waits if necessary for the computation to complete, and then |
920 |
|
* retrieves its result. |
921 |
|
* |
928 |
|
*/ |
929 |
|
public final V get() throws InterruptedException, ExecutionException { |
930 |
|
int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ? |
931 |
< |
doJoin() : externalInterruptibleAwaitDone(0L); |
931 |
> |
doJoin() : externalInterruptibleAwaitDone(); |
932 |
|
Throwable ex; |
933 |
< |
if (s == CANCELLED) |
933 |
> |
if ((s &= DONE_MASK) == CANCELLED) |
934 |
|
throw new CancellationException(); |
935 |
|
if (s == EXCEPTIONAL && (ex = getThrowableException()) != null) |
936 |
|
throw new ExecutionException(ex); |
953 |
|
*/ |
954 |
|
public final V get(long timeout, TimeUnit unit) |
955 |
|
throws InterruptedException, ExecutionException, TimeoutException { |
956 |
< |
Thread t = Thread.currentThread(); |
957 |
< |
if (t instanceof ForkJoinWorkerThread) { |
958 |
< |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
959 |
< |
long nanos = unit.toNanos(timeout); |
960 |
< |
if (status >= 0) { |
961 |
< |
boolean completed = false; |
962 |
< |
if (w.unpushTask(this)) { |
963 |
< |
try { |
964 |
< |
completed = exec(); |
965 |
< |
} catch (Throwable rex) { |
966 |
< |
setExceptionalCompletion(rex); |
956 |
> |
if (Thread.interrupted()) |
957 |
> |
throw new InterruptedException(); |
958 |
> |
// Messy in part because we measure in nanosecs, but wait in millisecs |
959 |
> |
int s; long ns, ms; |
960 |
> |
if ((s = status) >= 0 && (ns = unit.toNanos(timeout)) > 0L) { |
961 |
> |
long deadline = System.nanoTime() + ns; |
962 |
> |
ForkJoinPool p = null; |
963 |
> |
ForkJoinPool.WorkQueue w = null; |
964 |
> |
Thread t = Thread.currentThread(); |
965 |
> |
if (t instanceof ForkJoinWorkerThread) { |
966 |
> |
ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; |
967 |
> |
p = wt.pool; |
968 |
> |
w = wt.workQueue; |
969 |
> |
s = p.helpJoinOnce(w, this); // no retries on failure |
970 |
> |
} |
971 |
> |
boolean canBlock = false; |
972 |
> |
boolean interrupted = false; |
973 |
> |
try { |
974 |
> |
while ((s = status) >= 0) { |
975 |
> |
if (w != null && w.runState < 0) |
976 |
> |
cancelIgnoringExceptions(this); |
977 |
> |
else if (!canBlock) { |
978 |
> |
if (p == null || p.tryCompensate(this, null)) |
979 |
> |
canBlock = true; |
980 |
> |
} |
981 |
> |
else { |
982 |
> |
if ((ms = TimeUnit.NANOSECONDS.toMillis(ns)) > 0L && |
983 |
> |
U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
984 |
> |
synchronized (this) { |
985 |
> |
if (status >= 0) { |
986 |
> |
try { |
987 |
> |
wait(ms); |
988 |
> |
} catch (InterruptedException ie) { |
989 |
> |
if (p == null) |
990 |
> |
interrupted = true; |
991 |
> |
} |
992 |
> |
} |
993 |
> |
else |
994 |
> |
notifyAll(); |
995 |
> |
} |
996 |
> |
} |
997 |
> |
if ((s = status) < 0 || interrupted || |
998 |
> |
(ns = deadline - System.nanoTime()) <= 0L) |
999 |
> |
break; |
1000 |
|
} |
1001 |
|
} |
1002 |
< |
if (completed) |
1003 |
< |
setCompletion(NORMAL); |
1004 |
< |
else if (status >= 0 && nanos > 0) |
945 |
< |
w.pool.timedAwaitJoin(this, nanos); |
1002 |
> |
} finally { |
1003 |
> |
if (p != null && canBlock) |
1004 |
> |
p.incrementActiveCount(); |
1005 |
|
} |
1006 |
+ |
if (interrupted) |
1007 |
+ |
throw new InterruptedException(); |
1008 |
|
} |
1009 |
< |
else { |
949 |
< |
long millis = unit.toMillis(timeout); |
950 |
< |
if (millis > 0) |
951 |
< |
externalInterruptibleAwaitDone(millis); |
952 |
< |
} |
953 |
< |
int s = status; |
954 |
< |
if (s != NORMAL) { |
1009 |
> |
if ((s &= DONE_MASK) != NORMAL) { |
1010 |
|
Throwable ex; |
1011 |
|
if (s == CANCELLED) |
1012 |
|
throw new CancellationException(); |
1051 |
|
* ClassCastException}. |
1052 |
|
*/ |
1053 |
|
public static void helpQuiesce() { |
1054 |
< |
((ForkJoinWorkerThread) Thread.currentThread()) |
1055 |
< |
.helpQuiescePool(); |
1054 |
> |
ForkJoinWorkerThread wt = |
1055 |
> |
(ForkJoinWorkerThread)Thread.currentThread(); |
1056 |
> |
wt.pool.helpQuiescePool(wt.workQueue); |
1057 |
|
} |
1058 |
|
|
1059 |
|
/** |
1073 |
|
* setRawResult(null)}. |
1074 |
|
*/ |
1075 |
|
public void reinitialize() { |
1076 |
< |
if (status == EXCEPTIONAL) |
1076 |
> |
if ((status & DONE_MASK) == EXCEPTIONAL) |
1077 |
|
clearExceptionalCompletion(); |
1078 |
|
else |
1079 |
|
status = 0; |
1121 |
|
* @return {@code true} if unforked |
1122 |
|
*/ |
1123 |
|
public boolean tryUnfork() { |
1124 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1125 |
< |
.unpushTask(this); |
1124 |
> |
return ((ForkJoinWorkerThread)Thread.currentThread()) |
1125 |
> |
.workQueue.tryUnpush(this); |
1126 |
|
} |
1127 |
|
|
1128 |
|
/** |
1141 |
|
*/ |
1142 |
|
public static int getQueuedTaskCount() { |
1143 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1144 |
< |
.getQueueSize(); |
1144 |
> |
.workQueue.queueSize(); |
1145 |
|
} |
1146 |
|
|
1147 |
|
/** |
1163 |
|
* @return the surplus number of tasks, which may be negative |
1164 |
|
*/ |
1165 |
|
public static int getSurplusQueuedTaskCount() { |
1166 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1167 |
< |
.getEstimatedSurplusTaskCount(); |
1166 |
> |
/* |
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(); |
1212 |
|
} |
1213 |
|
|
1214 |
|
// Extension methods |
1265 |
|
* @return the next task, or {@code null} if none are available |
1266 |
|
*/ |
1267 |
|
protected static ForkJoinTask<?> peekNextLocalTask() { |
1268 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1169 |
< |
.peekTask(); |
1268 |
> |
return ((ForkJoinWorkerThread) Thread.currentThread()).workQueue.peek(); |
1269 |
|
} |
1270 |
|
|
1271 |
|
/** |
1284 |
|
*/ |
1285 |
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
1286 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1287 |
< |
.pollLocalTask(); |
1287 |
> |
.workQueue.nextLocalTask(); |
1288 |
|
} |
1289 |
|
|
1290 |
|
/** |
1306 |
|
* @return a task, or {@code null} if none are available |
1307 |
|
*/ |
1308 |
|
protected static ForkJoinTask<?> pollTask() { |
1309 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1310 |
< |
.pollTask(); |
1309 |
> |
ForkJoinWorkerThread wt = |
1310 |
> |
(ForkJoinWorkerThread)Thread.currentThread(); |
1311 |
> |
return wt.pool.nextTaskFor(wt.workQueue); |
1312 |
> |
} |
1313 |
> |
|
1314 |
> |
// tag operations |
1315 |
> |
|
1316 |
> |
/** |
1317 |
> |
* Returns the tag for this task. |
1318 |
> |
* |
1319 |
> |
* @return the tag for this task |
1320 |
> |
* @since 1.8 |
1321 |
> |
*/ |
1322 |
> |
public final short getForkJoinTaskTag() { |
1323 |
> |
return (short)status; |
1324 |
> |
} |
1325 |
> |
|
1326 |
> |
/** |
1327 |
> |
* Atomically sets the tag value for this task. |
1328 |
> |
* |
1329 |
> |
* @param tag the tag value |
1330 |
> |
* @return the previous value of the tag |
1331 |
> |
* @since 1.8 |
1332 |
> |
*/ |
1333 |
> |
public final short setForkJoinTaskTag(short tag) { |
1334 |
> |
for (int s;;) { |
1335 |
> |
if (U.compareAndSwapInt(this, STATUS, s = status, |
1336 |
> |
(s & ~SMASK) | (tag & SMASK))) |
1337 |
> |
return (short)s; |
1338 |
> |
} |
1339 |
> |
} |
1340 |
> |
|
1341 |
> |
/** |
1342 |
> |
* Atomically conditionally sets the tag value for this task. |
1343 |
> |
* Among other applications, tags can be used as visit markers |
1344 |
> |
* in tasks operating on graphs, as in mathods that check: {@code |
1345 |
> |
* if (task.compareAndSetForkJoinTaskTag((short)0, (short)1))} |
1346 |
> |
* before processing, otherwise exiting because the node has |
1347 |
> |
* already been visited. |
1348 |
> |
* |
1349 |
> |
* @param e the expected tag value |
1350 |
> |
* @param tag the new tag value |
1351 |
> |
* @return true if successful; i.e., the current value was |
1352 |
> |
* equal to e and is now tag. |
1353 |
> |
* @since 1.8 |
1354 |
> |
*/ |
1355 |
> |
public final boolean compareAndSetForkJoinTaskTag(short e, short tag) { |
1356 |
> |
for (int s;;) { |
1357 |
> |
if ((short)(s = status) != e) |
1358 |
> |
return false; |
1359 |
> |
if (U.compareAndSwapInt(this, STATUS, s, |
1360 |
> |
(s & ~SMASK) | (tag & SMASK))) |
1361 |
> |
return true; |
1362 |
> |
} |
1363 |
|
} |
1364 |
|
|
1365 |
|
/** |
1370 |
|
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
1371 |
|
implements RunnableFuture<T> { |
1372 |
|
final Runnable runnable; |
1222 |
– |
final T resultOnCompletion; |
1373 |
|
T result; |
1374 |
|
AdaptedRunnable(Runnable runnable, T result) { |
1375 |
|
if (runnable == null) throw new NullPointerException(); |
1376 |
|
this.runnable = runnable; |
1377 |
< |
this.resultOnCompletion = result; |
1377 |
> |
this.result = result; // OK to set this even before completion |
1378 |
|
} |
1379 |
< |
public T getRawResult() { return result; } |
1380 |
< |
public void setRawResult(T v) { result = v; } |
1381 |
< |
public boolean exec() { |
1382 |
< |
runnable.run(); |
1383 |
< |
result = resultOnCompletion; |
1384 |
< |
return true; |
1379 |
> |
public final T getRawResult() { return result; } |
1380 |
> |
public final void setRawResult(T v) { result = v; } |
1381 |
> |
public final boolean exec() { runnable.run(); return true; } |
1382 |
> |
public final void run() { invoke(); } |
1383 |
> |
private static final long serialVersionUID = 5232453952276885070L; |
1384 |
> |
} |
1385 |
> |
|
1386 |
> |
/** |
1387 |
> |
* Adaptor for Runnables without results |
1388 |
> |
*/ |
1389 |
> |
static final class AdaptedRunnableAction extends ForkJoinTask<Void> |
1390 |
> |
implements RunnableFuture<Void> { |
1391 |
> |
final Runnable runnable; |
1392 |
> |
AdaptedRunnableAction(Runnable runnable) { |
1393 |
> |
if (runnable == null) throw new NullPointerException(); |
1394 |
> |
this.runnable = runnable; |
1395 |
|
} |
1396 |
< |
public void run() { invoke(); } |
1396 |
> |
public final Void getRawResult() { return null; } |
1397 |
> |
public final void setRawResult(Void v) { } |
1398 |
> |
public final boolean exec() { runnable.run(); return true; } |
1399 |
> |
public final void run() { invoke(); } |
1400 |
|
private static final long serialVersionUID = 5232453952276885070L; |
1401 |
|
} |
1402 |
|
|
1411 |
|
if (callable == null) throw new NullPointerException(); |
1412 |
|
this.callable = callable; |
1413 |
|
} |
1414 |
< |
public T getRawResult() { return result; } |
1415 |
< |
public void setRawResult(T v) { result = v; } |
1416 |
< |
public boolean exec() { |
1414 |
> |
public final T getRawResult() { return result; } |
1415 |
> |
public final void setRawResult(T v) { result = v; } |
1416 |
> |
public final boolean exec() { |
1417 |
|
try { |
1418 |
|
result = callable.call(); |
1419 |
|
return true; |
1425 |
|
throw new RuntimeException(ex); |
1426 |
|
} |
1427 |
|
} |
1428 |
< |
public void run() { invoke(); } |
1428 |
> |
public final void run() { invoke(); } |
1429 |
|
private static final long serialVersionUID = 2838392045355241008L; |
1430 |
|
} |
1431 |
|
|
1438 |
|
* @return the task |
1439 |
|
*/ |
1440 |
|
public static ForkJoinTask<?> adapt(Runnable runnable) { |
1441 |
< |
return new AdaptedRunnable<Void>(runnable, null); |
1441 |
> |
return new AdaptedRunnableAction(runnable); |
1442 |
|
} |
1443 |
|
|
1444 |
|
/** |
1472 |
|
private static final long serialVersionUID = -7721805057305804111L; |
1473 |
|
|
1474 |
|
/** |
1475 |
< |
* Saves the state to a stream (that is, serializes it). |
1475 |
> |
* Saves this task to a stream (that is, serializes it). |
1476 |
|
* |
1477 |
|
* @serialData the current run status and the exception thrown |
1478 |
|
* during execution, or {@code null} if none |
1316 |
– |
* @param s the stream |
1479 |
|
*/ |
1480 |
|
private void writeObject(java.io.ObjectOutputStream s) |
1481 |
|
throws java.io.IOException { |
1484 |
|
} |
1485 |
|
|
1486 |
|
/** |
1487 |
< |
* Reconstitutes the instance from a stream (that is, deserializes it). |
1326 |
< |
* |
1327 |
< |
* @param s the stream |
1487 |
> |
* Reconstitutes this task from a stream (that is, deserializes it). |
1488 |
|
*/ |
1489 |
|
private void readObject(java.io.ObjectInputStream s) |
1490 |
|
throws java.io.IOException, ClassNotFoundException { |
1495 |
|
} |
1496 |
|
|
1497 |
|
// Unsafe mechanics |
1498 |
< |
private static final sun.misc.Unsafe UNSAFE; |
1499 |
< |
private static final long statusOffset; |
1498 |
> |
private static final sun.misc.Unsafe U; |
1499 |
> |
private static final long STATUS; |
1500 |
|
static { |
1501 |
|
exceptionTableLock = new ReentrantLock(); |
1502 |
|
exceptionTableRefQueue = new ReferenceQueue<Object>(); |
1503 |
|
exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY]; |
1504 |
|
try { |
1505 |
< |
UNSAFE = getUnsafe(); |
1506 |
< |
statusOffset = UNSAFE.objectFieldOffset |
1505 |
> |
U = getUnsafe(); |
1506 |
> |
STATUS = U.objectFieldOffset |
1507 |
|
(ForkJoinTask.class.getDeclaredField("status")); |
1508 |
|
} catch (Exception e) { |
1509 |
|
throw new Error(e); |