5 |
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*/ |
6 |
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package jsr166y; |
8 |
+ |
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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 |
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* ForkJoinPool, at the price of some usage limitations. |
32 |
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* |
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 |
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* #invokeAll(ForkJoinTask...) invokeAll}. However, this class also |
42 |
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* 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 |
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* |
46 |
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* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}. |
47 |
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* The efficiency of {@code ForkJoinTask}s stems from a set of |
55 |
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* minimize other blocking synchronization apart from joining other |
56 |
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* tasks or using synchronizers such as Phasers that are advertised to |
57 |
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* 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 |
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* are completely independent of those accessed by other running |
60 |
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* tasks. These guidelines are loosely enforced by not permitting |
61 |
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* checked exceptions such as {@code IOExceptions} to be |
71 |
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* encountering the exception; minimally only the latter. |
72 |
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* |
73 |
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* <p>It is possible to define and use ForkJoinTasks that may block, |
74 |
< |
* but doing do requires three further considerations: (1) Completion |
74 |
> |
* but doing so 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 |
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* 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 |
98 |
|
* performs the most common form of parallel invocation: forking a set |
99 |
|
* of tasks and joining them all. |
100 |
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* |
101 |
< |
* <p>In the most typical usages, a fork-join pair act like a a call |
101 |
> |
* <p>In the most typical usages, a fork-join pair act like a call |
102 |
|
* (fork) and return (join) from a parallel recursive function. As is |
103 |
|
* the case with other forms of recursive calls, returns (joins) |
104 |
|
* should be performed innermost-first. For example, {@code a.fork(); |
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 |
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* 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>marked</em> using {@link |
141 |
< |
* #markForkJoinTask} and checked for marking using {@link |
142 |
< |
* #isMarkedForkJoinTask}. The ForkJoinTask implementation does not |
143 |
< |
* use these {@code protected} methods or marks for any purpose, but |
144 |
< |
* they may be of use in the construction of specialized subclasses. |
145 |
< |
* For example, parallel graph traversals can use the supplied methods |
146 |
< |
* to avoid revisiting nodes/tasks that have already been |
147 |
< |
* processed. Also, completion based designs can use them to record |
148 |
< |
* that one subtask has completed. (Method names for marking are bulky |
149 |
< |
* in part to encourage definition of methods that reflect their usage |
150 |
< |
* patterns.) |
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 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 |
196 |
|
* methods in a way that flows well in javadocs. |
197 |
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*/ |
198 |
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|
200 |
– |
/** |
201 |
– |
* The number of times to try to help join a task without any |
202 |
– |
* apparent progress before giving up and blocking. The value is |
203 |
– |
* arbitrary but should be large enough to cope with transient |
204 |
– |
* stalls (due to GC etc) that can cause helping methods not to be |
205 |
– |
* able to proceed because other workers have not progressed to |
206 |
– |
* the point where subtasks can be found or taken. |
207 |
– |
*/ |
208 |
– |
private static final int HELP_RETRIES = 32; |
209 |
– |
|
199 |
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/* |
200 |
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* The status field holds run control status bits packed into a |
201 |
|
* single int to minimize footprint and to ensure atomicity (via |
202 |
|
* CAS). Status is initially zero, and takes on nonnegative |
203 |
< |
* values until completed, upon which status holds value |
204 |
< |
* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking |
205 |
< |
* waits by other threads have the SIGNAL bit set. Completion of |
206 |
< |
* a stolen task with SIGNAL set awakens any waiters via |
207 |
< |
* notifyAll. Even though suboptimal for some purposes, we use |
208 |
< |
* basic builtin wait/notify to take advantage of "monitor |
209 |
< |
* inflation" in JVMs that we would otherwise need to emulate to |
210 |
< |
* avoid adding further per-task bookkeeping overhead. We want |
211 |
< |
* these monitors to be "fat", i.e., not use biasing or thin-lock |
212 |
< |
* techniques, so use some odd coding idioms that tend to avoid |
213 |
< |
* them. |
203 |
> |
* values until completed, upon which status (anded with |
204 |
> |
* DONE_MASK) holds value NORMAL, CANCELLED, or EXCEPTIONAL. Tasks |
205 |
> |
* undergoing blocking waits by other threads have the SIGNAL bit |
206 |
> |
* set. Completion of a stolen task with SIGNAL set awakens any |
207 |
> |
* waiters via notifyAll. Even though suboptimal for some |
208 |
> |
* purposes, we use basic builtin wait/notify to take advantage of |
209 |
> |
* "monitor inflation" in JVMs that we would otherwise need to |
210 |
> |
* emulate to avoid adding further per-task bookkeeping overhead. |
211 |
> |
* We want these monitors to be "fat", i.e., not use biasing or |
212 |
> |
* thin-lock techniques, so use some odd coding idioms that tend |
213 |
> |
* to avoid them, mainly by arranging that every synchronized |
214 |
> |
* block performs a wait, notifyAll or both. |
215 |
> |
* |
216 |
> |
* These control bits occupy only (some of) the upper half (16 |
217 |
> |
* bits) of status field. The lower bits are used for user-defined |
218 |
> |
* tags. |
219 |
|
*/ |
220 |
|
|
221 |
|
/** The run status of this task */ |
222 |
|
volatile int status; // accessed directly by pool and workers |
223 |
< |
static final int NORMAL = 0xfffffffc; // negative with low 2 bits 0 |
224 |
< |
static final int CANCELLED = 0xfffffff8; // must be < NORMAL |
225 |
< |
static final int EXCEPTIONAL = 0xfffffff4; // must be < CANCELLED |
226 |
< |
static final int SIGNAL = 0x00000001; |
227 |
< |
static final int MARKED = 0x00000002; |
223 |
> |
static final int DONE_MASK = 0xf0000000; // mask out non-completion bits |
224 |
> |
static final int NORMAL = 0xf0000000; // must be negative |
225 |
> |
static final int CANCELLED = 0xc0000000; // must be < NORMAL |
226 |
> |
static final int EXCEPTIONAL = 0x80000000; // must be < CANCELLED |
227 |
> |
static final int SIGNAL = 0x00010000; // must be >= 1 << 16 |
228 |
> |
static final int SMASK = 0x0000ffff; // short bits for tags |
229 |
|
|
230 |
|
/** |
231 |
|
* Marks completion and wakes up threads waiting to join this |
232 |
< |
* task, also clearing signal request bits. A specialization for |
238 |
< |
* NORMAL completion is in method doExec |
232 |
> |
* task. |
233 |
|
* |
234 |
|
* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
235 |
|
* @return completion status on exit |
238 |
|
for (int s;;) { |
239 |
|
if ((s = status) < 0) |
240 |
|
return s; |
241 |
< |
if (U.compareAndSwapInt(this, STATUS, s, (s & ~SIGNAL)|completion)) { |
242 |
< |
if ((s & SIGNAL) != 0) |
241 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | completion)) { |
242 |
> |
if ((s >>> 16) != 0) |
243 |
|
synchronized (this) { notifyAll(); } |
244 |
|
return completion; |
245 |
|
} |
261 |
|
} catch (Throwable rex) { |
262 |
|
return setExceptionalCompletion(rex); |
263 |
|
} |
264 |
< |
while ((s = status) >= 0 && completed) { |
265 |
< |
if (U.compareAndSwapInt(this, STATUS, s, (s & ~SIGNAL)|NORMAL)) { |
272 |
< |
if ((s & SIGNAL) != 0) |
273 |
< |
synchronized (this) { notifyAll(); } |
274 |
< |
return NORMAL; |
275 |
< |
} |
276 |
< |
} |
264 |
> |
if (completed) |
265 |
> |
s = setCompletion(NORMAL); |
266 |
|
} |
267 |
|
return s; |
268 |
|
} |
269 |
|
|
270 |
|
/** |
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 = status; |
279 |
+ |
return s >= 0 && U.compareAndSwapInt(this, STATUS, s, s | SIGNAL); |
280 |
+ |
} |
281 |
+ |
|
282 |
+ |
/** |
283 |
|
* Blocks a non-worker-thread until completion. |
284 |
|
* @return status upon completion |
285 |
|
*/ |
286 |
|
private int externalAwaitDone() { |
287 |
|
int s; |
288 |
< |
if ((s = status) >= 0) { |
289 |
< |
boolean interrupted = false; |
290 |
< |
synchronized (this) { |
291 |
< |
while ((s = status) >= 0) { |
292 |
< |
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
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) { |
293 |
> |
if (status >= 0) { |
294 |
|
try { |
295 |
|
wait(); |
296 |
|
} catch (InterruptedException ie) { |
297 |
|
interrupted = true; |
298 |
|
} |
299 |
|
} |
300 |
+ |
else |
301 |
+ |
notifyAll(); |
302 |
|
} |
303 |
|
} |
300 |
– |
if (interrupted) |
301 |
– |
Thread.currentThread().interrupt(); |
304 |
|
} |
305 |
+ |
if (interrupted) |
306 |
+ |
Thread.currentThread().interrupt(); |
307 |
|
return s; |
308 |
|
} |
309 |
|
|
310 |
|
/** |
311 |
< |
* Blocks a non-worker-thread until completion or interruption or timeout. |
311 |
> |
* Blocks a non-worker-thread until completion or interruption. |
312 |
|
*/ |
313 |
< |
private int externalInterruptibleAwaitDone(long millis) |
310 |
< |
throws InterruptedException { |
313 |
> |
private int externalInterruptibleAwaitDone() throws InterruptedException { |
314 |
|
int s; |
315 |
|
if (Thread.interrupted()) |
316 |
|
throw new InterruptedException(); |
317 |
< |
if ((s = status) >= 0) { |
318 |
< |
synchronized (this) { |
319 |
< |
while ((s = status) >= 0) { |
320 |
< |
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
321 |
< |
wait(millis); |
322 |
< |
if (millis > 0L) |
323 |
< |
break; |
324 |
< |
} |
317 |
> |
ForkJoinPool.externalHelpJoin(this); |
318 |
> |
while ((s = status) >= 0) { |
319 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
320 |
> |
synchronized (this) { |
321 |
> |
if (status >= 0) |
322 |
> |
wait(); |
323 |
> |
else |
324 |
> |
notifyAll(); |
325 |
|
} |
326 |
|
} |
327 |
|
} |
332 |
|
/** |
333 |
|
* Implementation for join, get, quietlyJoin. Directly handles |
334 |
|
* only cases of already-completed, external wait, and |
335 |
< |
* unfork+exec. Others are relayed to awaitJoin. |
335 |
> |
* unfork+exec. Others are relayed to ForkJoinPool.awaitJoin. |
336 |
|
* |
337 |
|
* @return status upon completion |
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 |
< |
s = externalAwaitDone(); |
344 |
< |
else if (!(w = (wt = (ForkJoinWorkerThread)t).workQueue). |
345 |
< |
tryUnpush(this) || (s = doExec()) >= 0) |
346 |
< |
s = awaitJoin(w, wt.pool); |
344 |
< |
} |
345 |
< |
return s; |
346 |
< |
} |
347 |
< |
|
348 |
< |
/** |
349 |
< |
* Helps and/or blocks until joined. |
350 |
< |
* |
351 |
< |
* @param w the joiner |
352 |
< |
* @param p the pool |
353 |
< |
* @return status upon completion |
354 |
< |
*/ |
355 |
< |
private int awaitJoin(ForkJoinPool.WorkQueue w, ForkJoinPool p) { |
356 |
< |
int s; |
357 |
< |
ForkJoinTask<?> prevJoin = w.currentJoin; |
358 |
< |
w.currentJoin = this; |
359 |
< |
for (int k = HELP_RETRIES; (s = status) >= 0;) { |
360 |
< |
if ((w.queueSize() > 0) ? |
361 |
< |
w.tryRemoveAndExec(this) : // self-help |
362 |
< |
p.tryHelpStealer(w, this)) // help process tasks |
363 |
< |
k = HELP_RETRIES; // reset if made progress |
364 |
< |
else if ((s = status) < 0) // recheck |
365 |
< |
break; |
366 |
< |
else if (--k > 0) { |
367 |
< |
if ((k & 3) == 1) |
368 |
< |
Thread.yield(); // occasionally yield |
369 |
< |
} |
370 |
< |
else if (k == 0) |
371 |
< |
p.tryPollForAndExec(w, this); // uncommon self-help case |
372 |
< |
else if (p.tryCompensate()) { // true if can block |
373 |
< |
try { |
374 |
< |
int ss = status; |
375 |
< |
if (ss >= 0 && // assert need signal |
376 |
< |
U.compareAndSwapInt(this, STATUS, ss, ss | SIGNAL)) { |
377 |
< |
synchronized (this) { |
378 |
< |
if (status >= 0) // block |
379 |
< |
wait(); |
380 |
< |
} |
381 |
< |
} |
382 |
< |
} catch (InterruptedException ignore) { |
383 |
< |
} finally { |
384 |
< |
p.incrementActiveCount(); // re-activate |
385 |
< |
} |
386 |
< |
} |
387 |
< |
} |
388 |
< |
w.currentJoin = prevJoin; |
389 |
< |
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 |
|
/** |
352 |
|
* @return status upon completion |
353 |
|
*/ |
354 |
|
private int doInvoke() { |
355 |
< |
int s; |
356 |
< |
if ((s = doExec()) < 0) |
357 |
< |
return s; |
358 |
< |
else |
359 |
< |
return doJoin(); |
355 |
> |
int s; Thread t; ForkJoinWorkerThread wt; |
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 |
391 |
|
* any ForkJoinPool will call helpExpungeStaleExceptions when its |
392 |
|
* pool becomes isQuiescent. |
393 |
|
*/ |
394 |
< |
static final class ExceptionNode extends WeakReference<ForkJoinTask<?>>{ |
394 |
> |
static final class ExceptionNode extends WeakReference<ForkJoinTask<?>> { |
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 { |
471 |
< |
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); |
515 |
|
* @return the exception, or null if none |
516 |
|
*/ |
517 |
|
private Throwable getThrowableException() { |
518 |
< |
if (status != EXCEPTIONAL) |
518 |
> |
if ((status & DONE_MASK) != EXCEPTIONAL) |
519 |
|
return null; |
520 |
|
int h = System.identityHashCode(this); |
521 |
|
ExceptionNode e; |
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 |
< |
* Report the result of invoke or join; called only upon |
604 |
< |
* non-normal return of internal versions. |
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 |
< |
private V reportResult() { |
621 |
< |
int s; Throwable ex; |
622 |
< |
if ((s = status) == CANCELLED) |
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 |
> |
if (s == CANCELLED) |
631 |
|
throw new CancellationException(); |
632 |
< |
if (s == EXCEPTIONAL && (ex = getThrowableException()) != null) |
633 |
< |
U.throwException(ex); |
631 |
< |
return getRawResult(); |
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 |
648 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
649 |
< |
* result in exceptions or errors, possibly including {@code |
650 |
< |
* 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 wt; |
655 |
< |
(wt = (ForkJoinWorkerThread)Thread.currentThread()). |
656 |
< |
workQueue.push(this, wt.pool); |
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 |
|
|
671 |
|
* @return the computed result |
672 |
|
*/ |
673 |
|
public final V join() { |
674 |
< |
if (doJoin() != NORMAL) |
675 |
< |
return reportResult(); |
676 |
< |
else |
677 |
< |
return getRawResult(); |
674 |
> |
int s; |
675 |
> |
if ((s = doJoin() & DONE_MASK) != NORMAL) |
676 |
> |
reportException(s); |
677 |
> |
return getRawResult(); |
678 |
|
} |
679 |
|
|
680 |
|
/** |
686 |
|
* @return the computed result |
687 |
|
*/ |
688 |
|
public final V invoke() { |
689 |
< |
if (doInvoke() != NORMAL) |
690 |
< |
return reportResult(); |
691 |
< |
else |
692 |
< |
return getRawResult(); |
689 |
> |
int s; |
690 |
> |
if ((s = doInvoke() & DONE_MASK) != NORMAL) |
691 |
> |
reportException(s); |
692 |
> |
return getRawResult(); |
693 |
|
} |
694 |
|
|
695 |
|
/** |
705 |
|
* cancelled, completed normally or exceptionally, or left |
706 |
|
* unprocessed. |
707 |
|
* |
707 |
– |
* <p>This method may be invoked only from within {@code |
708 |
– |
* ForkJoinPool} computations (as may be determined using method |
709 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
710 |
– |
* result in exceptions or errors, possibly including {@code |
711 |
– |
* ClassCastException}. |
712 |
– |
* |
708 |
|
* @param t1 the first task |
709 |
|
* @param t2 the second task |
710 |
|
* @throws NullPointerException if any task is null |
711 |
|
*/ |
712 |
|
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) { |
713 |
+ |
int s1, s2; |
714 |
|
t2.fork(); |
715 |
< |
t1.invoke(); |
716 |
< |
t2.join(); |
715 |
> |
if ((s1 = t1.doInvoke() & DONE_MASK) != NORMAL) |
716 |
> |
t1.reportException(s1); |
717 |
> |
if ((s2 = t2.doJoin() & DONE_MASK) != NORMAL) |
718 |
> |
t2.reportException(s2); |
719 |
|
} |
720 |
|
|
721 |
|
/** |
730 |
|
* related methods to check if they have been cancelled, completed |
731 |
|
* normally or exceptionally, or left unprocessed. |
732 |
|
* |
735 |
– |
* <p>This method may be invoked only from within {@code |
736 |
– |
* ForkJoinPool} computations (as may be determined using method |
737 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
738 |
– |
* result in exceptions or errors, possibly including {@code |
739 |
– |
* ClassCastException}. |
740 |
– |
* |
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 |
|
* |
784 |
– |
* <p>This method may be invoked only from within {@code |
785 |
– |
* ForkJoinPool} computations (as may be determined using method |
786 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
787 |
– |
* result in exceptions or errors, possibly including {@code |
788 |
– |
* ClassCastException}. |
789 |
– |
* |
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 |
|
|
840 |
|
* @return {@code true} if this task is now cancelled |
841 |
|
*/ |
842 |
|
public boolean cancel(boolean mayInterruptIfRunning) { |
843 |
< |
return setCompletion(CANCELLED) == CANCELLED; |
843 |
> |
return (setCompletion(CANCELLED) & DONE_MASK) == CANCELLED; |
844 |
|
} |
845 |
|
|
846 |
|
public final boolean isDone() { |
848 |
|
} |
849 |
|
|
850 |
|
public final boolean isCancelled() { |
851 |
< |
return status == CANCELLED; |
851 |
> |
return (status & DONE_MASK) == CANCELLED; |
852 |
|
} |
853 |
|
|
854 |
|
/** |
868 |
|
* exception and was not cancelled |
869 |
|
*/ |
870 |
|
public final boolean isCompletedNormally() { |
871 |
< |
return status == NORMAL; |
871 |
> |
return (status & DONE_MASK) == NORMAL; |
872 |
|
} |
873 |
|
|
874 |
|
/** |
879 |
|
* @return the exception, or {@code null} if none |
880 |
|
*/ |
881 |
|
public final Throwable getException() { |
882 |
< |
int s = status; |
882 |
> |
int s = status & DONE_MASK; |
883 |
|
return ((s >= NORMAL) ? null : |
884 |
|
(s == CANCELLED) ? new CancellationException() : |
885 |
|
getThrowableException()); |
929 |
|
} |
930 |
|
|
931 |
|
/** |
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); |
941 |
+ |
} |
942 |
+ |
|
943 |
+ |
/** |
944 |
|
* Waits if necessary for the computation to complete, and then |
945 |
|
* retrieves its result. |
946 |
|
* |
953 |
|
*/ |
954 |
|
public final V get() throws InterruptedException, ExecutionException { |
955 |
|
int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ? |
956 |
< |
doJoin() : externalInterruptibleAwaitDone(0L); |
956 |
> |
doJoin() : externalInterruptibleAwaitDone(); |
957 |
|
Throwable ex; |
958 |
< |
if (s == CANCELLED) |
958 |
> |
if ((s &= DONE_MASK) == CANCELLED) |
959 |
|
throw new CancellationException(); |
960 |
|
if (s == EXCEPTIONAL && (ex = getThrowableException()) != null) |
961 |
|
throw new ExecutionException(ex); |
978 |
|
*/ |
979 |
|
public final V get(long timeout, TimeUnit unit) |
980 |
|
throws InterruptedException, ExecutionException, TimeoutException { |
981 |
< |
// Messy in part because we measure in nanos, but wait in millis |
982 |
< |
int s; long millis, nanos; |
983 |
< |
Thread t = Thread.currentThread(); |
984 |
< |
if (!(t instanceof ForkJoinWorkerThread)) { |
985 |
< |
if ((millis = unit.toMillis(timeout)) > 0L) |
986 |
< |
s = externalInterruptibleAwaitDone(millis); |
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 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; |
990 |
> |
Thread t = Thread.currentThread(); |
991 |
> |
if (t instanceof ForkJoinWorkerThread) { |
992 |
> |
ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; |
993 |
> |
p = wt.pool; |
994 |
> |
w = wt.workQueue; |
995 |
> |
p.helpJoinOnce(w, this); // no retries on failure |
996 |
> |
} |
997 |
|
else |
998 |
< |
s = status; |
999 |
< |
} |
1000 |
< |
else if ((s = status) >= 0 && (nanos = unit.toNanos(timeout)) > 0L) { |
993 |
< |
long deadline = System.nanoTime() + nanos; |
994 |
< |
ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; |
995 |
< |
ForkJoinPool.WorkQueue w = wt.workQueue; |
996 |
< |
ForkJoinPool p = wt.pool; |
997 |
< |
if (w.tryUnpush(this)) |
998 |
< |
doExec(); |
999 |
< |
boolean blocking = false; |
998 |
> |
ForkJoinPool.externalHelpJoin(this); |
999 |
> |
boolean canBlock = false; |
1000 |
> |
boolean interrupted = false; |
1001 |
|
try { |
1002 |
|
while ((s = status) >= 0) { |
1003 |
< |
if (w.runState < 0) |
1003 |
> |
if (w != null && w.qlock < 0) |
1004 |
|
cancelIgnoringExceptions(this); |
1005 |
< |
else if (!blocking) |
1006 |
< |
blocking = p.tryCompensate(); |
1005 |
> |
else if (!canBlock) { |
1006 |
> |
if (p == null || p.tryCompensate()) |
1007 |
> |
canBlock = true; |
1008 |
> |
} |
1009 |
|
else { |
1010 |
< |
millis = TimeUnit.NANOSECONDS.toMillis(nanos); |
1008 |
< |
if (millis > 0L && |
1010 |
> |
if ((ms = TimeUnit.NANOSECONDS.toMillis(ns)) > 0L && |
1011 |
|
U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
1012 |
< |
try { |
1013 |
< |
synchronized (this) { |
1014 |
< |
if (status >= 0) |
1015 |
< |
wait(millis); |
1012 |
> |
synchronized (this) { |
1013 |
> |
if (status >= 0) { |
1014 |
> |
try { |
1015 |
> |
wait(ms); |
1016 |
> |
} catch (InterruptedException ie) { |
1017 |
> |
if (p == null) |
1018 |
> |
interrupted = true; |
1019 |
> |
} |
1020 |
|
} |
1021 |
< |
} catch (InterruptedException ie) { |
1021 |
> |
else |
1022 |
> |
notifyAll(); |
1023 |
|
} |
1024 |
|
} |
1025 |
< |
if ((s = status) < 0 || |
1026 |
< |
(nanos = deadline - System.nanoTime()) <= 0L) |
1025 |
> |
if ((s = status) < 0 || interrupted || |
1026 |
> |
(ns = deadline - System.nanoTime()) <= 0L) |
1027 |
|
break; |
1028 |
|
} |
1029 |
|
} |
1030 |
|
} finally { |
1031 |
< |
if (blocking) |
1031 |
> |
if (p != null && canBlock) |
1032 |
|
p.incrementActiveCount(); |
1033 |
|
} |
1034 |
+ |
if (interrupted) |
1035 |
+ |
throw new InterruptedException(); |
1036 |
|
} |
1037 |
< |
if (s != NORMAL) { |
1037 |
> |
if ((s &= DONE_MASK) != NORMAL) { |
1038 |
|
Throwable ex; |
1039 |
|
if (s == CANCELLED) |
1040 |
|
throw new CancellationException(); |
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. |
1065 |
< |
* |
1066 |
< |
* <p>This method may be invoked only from within {@code |
1067 |
< |
* ForkJoinPool} computations (as may be determined using method |
1068 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1069 |
< |
* result in exceptions or errors, possibly including {@code |
1070 |
< |
* 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 w = |
1077 |
< |
(ForkJoinWorkerThread)Thread.currentThread(); |
1078 |
< |
w.pool.helpQuiescePool(w.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 |
|
/** |
1099 |
|
* setRawResult(null)}. |
1100 |
|
*/ |
1101 |
|
public void reinitialize() { |
1102 |
< |
if (status == EXCEPTIONAL) |
1102 |
> |
if ((status & DONE_MASK) == EXCEPTIONAL) |
1103 |
|
clearExceptionalCompletion(); |
1104 |
|
else |
1105 |
|
status = 0; |
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. |
1133 |
< |
* |
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}. |
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 |
|
* |
1153 |
– |
* <p>This method may be invoked only from within {@code |
1154 |
– |
* ForkJoinPool} computations (as may be determined using method |
1155 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1156 |
– |
* result in exceptions or errors, possibly including {@code |
1157 |
– |
* ClassCastException}. |
1158 |
– |
* |
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 |
|
* |
1176 |
– |
* <p>This method may be invoked only from within {@code |
1177 |
– |
* ForkJoinPool} computations (as may be determined using method |
1178 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1179 |
– |
* result in exceptions or errors, possibly including {@code |
1180 |
– |
* ClassCastException}. |
1181 |
– |
* |
1178 |
|
* @return the surplus number of tasks, which may be negative |
1179 |
|
*/ |
1180 |
|
public static int getSurplusQueuedTaskCount() { |
1181 |
< |
/* |
1186 |
< |
* The aim of this method is to return a cheap heuristic guide |
1187 |
< |
* for task partitioning when programmers, frameworks, tools, |
1188 |
< |
* or languages have little or no idea about task granularity. |
1189 |
< |
* In essence by offering this method, we ask users only about |
1190 |
< |
* tradeoffs in overhead vs expected throughput and its |
1191 |
< |
* variance, rather than how finely to partition tasks. |
1192 |
< |
* |
1193 |
< |
* In a steady state strict (tree-structured) computation, |
1194 |
< |
* each thread makes available for stealing enough tasks for |
1195 |
< |
* other threads to remain active. Inductively, if all threads |
1196 |
< |
* play by the same rules, each thread should make available |
1197 |
< |
* only a constant number of tasks. |
1198 |
< |
* |
1199 |
< |
* The minimum useful constant is just 1. But using a value of |
1200 |
< |
* 1 would require immediate replenishment upon each steal to |
1201 |
< |
* maintain enough tasks, which is infeasible. Further, |
1202 |
< |
* partitionings/granularities of offered tasks should |
1203 |
< |
* minimize steal rates, which in general means that threads |
1204 |
< |
* nearer the top of computation tree should generate more |
1205 |
< |
* than those nearer the bottom. In perfect steady state, each |
1206 |
< |
* thread is at approximately the same level of computation |
1207 |
< |
* tree. However, producing extra tasks amortizes the |
1208 |
< |
* uncertainty of progress and diffusion assumptions. |
1209 |
< |
* |
1210 |
< |
* So, users will want to use values larger, but not much |
1211 |
< |
* larger than 1 to both smooth over transient shortages and |
1212 |
< |
* hedge against uneven progress; as traded off against the |
1213 |
< |
* cost of extra task overhead. We leave the user to pick a |
1214 |
< |
* threshold value to compare with the results of this call to |
1215 |
< |
* guide decisions, but recommend values such as 3. |
1216 |
< |
* |
1217 |
< |
* When all threads are active, it is on average OK to |
1218 |
< |
* estimate surplus strictly locally. In steady-state, if one |
1219 |
< |
* thread is maintaining say 2 surplus tasks, then so are |
1220 |
< |
* others. So we can just use estimated queue length. |
1221 |
< |
* However, this strategy alone leads to serious mis-estimates |
1222 |
< |
* in some non-steady-state conditions (ramp-up, ramp-down, |
1223 |
< |
* other stalls). We can detect many of these by further |
1224 |
< |
* considering the number of "idle" threads, that are known to |
1225 |
< |
* have zero queued tasks, so compensate by a factor of |
1226 |
< |
* (#idle/#active) threads. |
1227 |
< |
*/ |
1228 |
< |
ForkJoinWorkerThread w = |
1229 |
< |
(ForkJoinWorkerThread)Thread.currentThread(); |
1230 |
< |
return w.workQueue.queueSize() - w.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 |
|
* |
1278 |
– |
* <p>This method may be invoked only from within {@code |
1279 |
– |
* ForkJoinPool} computations (as may be determined using method |
1280 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1281 |
– |
* result in exceptions or errors, possibly including {@code |
1282 |
– |
* ClassCastException}. |
1283 |
– |
* |
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 |
< |
* |
1296 |
< |
* <p>This method may be invoked only from within {@code |
1297 |
< |
* ForkJoinPool} computations (as may be determined using method |
1298 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1299 |
< |
* result in exceptions or errors, possibly including {@code |
1300 |
< |
* 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 |
|
* |
1319 |
– |
* <p>This method may be invoked only from within {@code |
1320 |
– |
* ForkJoinPool} computations (as may be determined using method |
1321 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1322 |
– |
* result in exceptions or errors, possibly including {@code |
1323 |
– |
* ClassCastException}. |
1324 |
– |
* |
1270 |
|
* @return a task, or {@code null} if none are available |
1271 |
|
*/ |
1272 |
|
protected static ForkJoinTask<?> pollTask() { |
1273 |
< |
ForkJoinWorkerThread w = |
1274 |
< |
(ForkJoinWorkerThread)Thread.currentThread(); |
1275 |
< |
return w.pool.nextTaskFor(w.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 |
< |
// Mark-bit operations |
1279 |
> |
// tag operations |
1280 |
|
|
1281 |
|
/** |
1282 |
< |
* Returns true if this task is marked. |
1282 |
> |
* Returns the tag for this task. |
1283 |
|
* |
1284 |
< |
* @return true if this task is marked |
1284 |
> |
* @return the tag for this task |
1285 |
|
* @since 1.8 |
1286 |
|
*/ |
1287 |
< |
public final boolean isMarkedForkJoinTask() { |
1288 |
< |
return (status & MARKED) != 0; |
1287 |
> |
public final short getForkJoinTaskTag() { |
1288 |
> |
return (short)status; |
1289 |
|
} |
1290 |
|
|
1291 |
|
/** |
1292 |
< |
* Atomically sets the mark on this task. |
1292 |
> |
* Atomically sets the tag value for this task. |
1293 |
|
* |
1294 |
< |
* @return true if this task was previously unmarked |
1294 |
> |
* @param tag the tag value |
1295 |
> |
* @return the previous value of the tag |
1296 |
|
* @since 1.8 |
1297 |
|
*/ |
1298 |
< |
public final boolean markForkJoinTask() { |
1298 |
> |
public final short setForkJoinTaskTag(short tag) { |
1299 |
|
for (int s;;) { |
1300 |
< |
if (((s = status) & MARKED) != 0) |
1301 |
< |
return false; |
1302 |
< |
if (U.compareAndSwapInt(this, STATUS, s, s | MARKED)) |
1356 |
< |
return true; |
1300 |
> |
if (U.compareAndSwapInt(this, STATUS, s = status, |
1301 |
> |
(s & ~SMASK) | (tag & SMASK))) |
1302 |
> |
return (short)s; |
1303 |
|
} |
1304 |
|
} |
1305 |
|
|
1306 |
|
/** |
1307 |
< |
* Atomically clears the mark on this task. |
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 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. |
1313 |
|
* |
1314 |
< |
* @return true if this task was previously marked |
1314 |
> |
* @param e the expected tag value |
1315 |
> |
* @param tag the new tag value |
1316 |
> |
* @return true if successful; i.e., the current value was |
1317 |
> |
* equal to e and is now tag. |
1318 |
|
* @since 1.8 |
1319 |
|
*/ |
1320 |
< |
public final boolean unmarkForkJoinTask() { |
1320 |
> |
public final boolean compareAndSetForkJoinTaskTag(short e, short tag) { |
1321 |
|
for (int s;;) { |
1322 |
< |
if (((s = status) & MARKED) == 0) |
1322 |
> |
if ((short)(s = status) != e) |
1323 |
|
return false; |
1324 |
< |
if (U.compareAndSwapInt(this, STATUS, s, s & ~MARKED)) |
1324 |
> |
if (U.compareAndSwapInt(this, STATUS, s, |
1325 |
> |
(s & ~SMASK) | (tag & SMASK))) |
1326 |
|
return true; |
1327 |
|
} |
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 |
|
*/ |
1335 |
|
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
1336 |
|
implements RunnableFuture<T> { |
1337 |
|
final Runnable runnable; |
1383 |
– |
final T resultOnCompletion; |
1338 |
|
T result; |
1339 |
|
AdaptedRunnable(Runnable runnable, T result) { |
1340 |
|
if (runnable == null) throw new NullPointerException(); |
1341 |
|
this.runnable = runnable; |
1342 |
< |
this.resultOnCompletion = result; |
1342 |
> |
this.result = result; // OK to set this even before completion |
1343 |
|
} |
1344 |
< |
public T getRawResult() { return result; } |
1345 |
< |
public void setRawResult(T v) { result = v; } |
1346 |
< |
public boolean exec() { |
1347 |
< |
runnable.run(); |
1348 |
< |
result = resultOnCompletion; |
1349 |
< |
return true; |
1344 |
> |
public final T getRawResult() { return result; } |
1345 |
> |
public final void setRawResult(T v) { result = v; } |
1346 |
> |
public final boolean exec() { runnable.run(); return true; } |
1347 |
> |
public final void run() { invoke(); } |
1348 |
> |
private static final long serialVersionUID = 5232453952276885070L; |
1349 |
> |
} |
1350 |
> |
|
1351 |
> |
/** |
1352 |
> |
* Adapter for Runnables without results |
1353 |
> |
*/ |
1354 |
> |
static final class AdaptedRunnableAction extends ForkJoinTask<Void> |
1355 |
> |
implements RunnableFuture<Void> { |
1356 |
> |
final Runnable runnable; |
1357 |
> |
AdaptedRunnableAction(Runnable runnable) { |
1358 |
> |
if (runnable == null) throw new NullPointerException(); |
1359 |
> |
this.runnable = runnable; |
1360 |
|
} |
1361 |
< |
public void run() { invoke(); } |
1361 |
> |
public final Void getRawResult() { return null; } |
1362 |
> |
public final void setRawResult(Void v) { } |
1363 |
> |
public final boolean exec() { runnable.run(); return true; } |
1364 |
> |
public final void run() { invoke(); } |
1365 |
|
private static final long serialVersionUID = 5232453952276885070L; |
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> { |
1376 |
|
if (callable == null) throw new NullPointerException(); |
1377 |
|
this.callable = callable; |
1378 |
|
} |
1379 |
< |
public T getRawResult() { return result; } |
1380 |
< |
public void setRawResult(T v) { result = v; } |
1381 |
< |
public boolean exec() { |
1379 |
> |
public final T getRawResult() { return result; } |
1380 |
> |
public final void setRawResult(T v) { result = v; } |
1381 |
> |
public final boolean exec() { |
1382 |
|
try { |
1383 |
|
result = callable.call(); |
1384 |
|
return true; |
1390 |
|
throw new RuntimeException(ex); |
1391 |
|
} |
1392 |
|
} |
1393 |
< |
public void run() { invoke(); } |
1393 |
> |
public final void run() { invoke(); } |
1394 |
|
private static final long serialVersionUID = 2838392045355241008L; |
1395 |
|
} |
1396 |
|
|
1403 |
|
* @return the task |
1404 |
|
*/ |
1405 |
|
public static ForkJoinTask<?> adapt(Runnable runnable) { |
1406 |
< |
return new AdaptedRunnable<Void>(runnable, null); |
1406 |
> |
return new AdaptedRunnableAction(runnable); |
1407 |
|
} |
1408 |
|
|
1409 |
|
/** |
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 |
|
} |