5 |
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*/ |
6 |
|
|
7 |
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package jsr166y; |
8 |
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|
8 |
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import java.io.Serializable; |
9 |
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import java.util.Collection; |
11 |
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import java.util.Collections; |
10 |
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import java.util.List; |
11 |
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import java.util.RandomAccess; |
14 |
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import java.util.Map; |
12 |
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import java.lang.ref.WeakReference; |
13 |
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import java.lang.ref.ReferenceQueue; |
14 |
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import java.util.concurrent.Callable; |
15 |
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import java.util.concurrent.CancellationException; |
16 |
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import java.util.concurrent.ExecutionException; |
20 |
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import java.util.concurrent.Executor; |
21 |
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import java.util.concurrent.ExecutorService; |
17 |
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import java.util.concurrent.Future; |
18 |
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import java.util.concurrent.RejectedExecutionException; |
19 |
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import java.util.concurrent.RunnableFuture; |
42 |
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* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}. |
43 |
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* The efficiency of {@code ForkJoinTask}s stems from a set of |
44 |
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* 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 |
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* 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 |
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* <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 |
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* |
96 |
+ |
* <p>In the most typical usages, a fork-join pair act like a call |
97 |
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* (fork) and return (join) from a parallel recursive function. As is |
98 |
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* the case with other forms of recursive calls, returns (joins) |
99 |
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* should be performed innermost-first. For example, {@code a.fork(); |
100 |
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* b.fork(); b.join(); a.join();} is likely to be substantially more |
101 |
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* efficient than joining {@code a} before {@code b}. |
102 |
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* |
103 |
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* <p>The execution status of tasks may be queried at several levels |
104 |
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* 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>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 processed. |
147 |
> |
* Also, completion based designs can use them to record that one |
148 |
> |
* subtask has completed. (Method names for marking are bulky in part |
149 |
> |
* to encourage definition of methods that reflect their usage |
150 |
> |
* patterns.) |
151 |
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* |
152 |
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* <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 |
|
|
218 |
|
/** The run status of this task */ |
219 |
|
volatile int status; // accessed directly by pool and workers |
220 |
< |
private static final int NORMAL = -1; |
221 |
< |
private static final int CANCELLED = -2; |
222 |
< |
private static final int EXCEPTIONAL = -3; |
223 |
< |
private static final int SIGNAL = 1; |
220 |
> |
static final int DONE_MASK = 0xf0000000; // mask out non-completion bits |
221 |
> |
static final int NORMAL = 0xf0000000; // must be negative |
222 |
> |
static final int CANCELLED = 0xc0000000; // must be < NORMAL |
223 |
> |
static final int EXCEPTIONAL = 0x80000000; // must be < CANCELLED |
224 |
> |
static final int SIGNAL = 0x00000001; |
225 |
> |
static final int MARKED = 0x00000002; |
226 |
|
|
227 |
|
/** |
228 |
< |
* Marks completion and wakes up threads waiting to join this task, |
229 |
< |
* also clearing signal request bits. |
228 |
> |
* Marks completion and wakes up threads waiting to join this |
229 |
> |
* task. A specialization for NORMAL completion is in method |
230 |
> |
* doExec. |
231 |
|
* |
232 |
|
* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
233 |
|
* @return completion status on exit |
236 |
|
for (int s;;) { |
237 |
|
if ((s = status) < 0) |
238 |
|
return s; |
239 |
< |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) { |
240 |
< |
if (s != 0) |
239 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | completion)) { |
240 |
> |
if ((s & SIGNAL) != 0) |
241 |
|
synchronized (this) { notifyAll(); } |
242 |
|
return completion; |
243 |
|
} |
245 |
|
} |
246 |
|
|
247 |
|
/** |
248 |
< |
* Tries to block a worker thread until completed or timed out. |
249 |
< |
* Uses Object.wait time argument conventions. |
250 |
< |
* May fail on contention or interrupt. |
248 |
> |
* Primary execution method for stolen tasks. Unless done, calls |
249 |
> |
* exec and records status if completed, but doesn't wait for |
250 |
> |
* completion otherwise. |
251 |
|
* |
252 |
< |
* @param millis if > 0, wait time. |
252 |
> |
* @return status on exit from this method |
253 |
|
*/ |
254 |
< |
final void tryAwaitDone(long millis) { |
255 |
< |
int s; |
256 |
< |
try { |
257 |
< |
if (((s = status) > 0 || |
258 |
< |
(s == 0 && |
259 |
< |
UNSAFE.compareAndSwapInt(this, statusOffset, 0, SIGNAL))) && |
260 |
< |
status > 0) { |
261 |
< |
synchronized (this) { |
262 |
< |
if (status > 0) |
263 |
< |
wait(millis); |
254 |
> |
final int doExec() { |
255 |
> |
int s; boolean completed; |
256 |
> |
if ((s = status) >= 0) { |
257 |
> |
try { |
258 |
> |
completed = exec(); |
259 |
> |
} catch (Throwable rex) { |
260 |
> |
return setExceptionalCompletion(rex); |
261 |
> |
} |
262 |
> |
while ((s = status) >= 0 && completed) { |
263 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | NORMAL)) { |
264 |
> |
if ((s & SIGNAL) != 0) |
265 |
> |
synchronized (this) { notifyAll(); } |
266 |
> |
return NORMAL; |
267 |
|
} |
268 |
|
} |
238 |
– |
} catch (InterruptedException ie) { |
239 |
– |
// caller must check termination |
269 |
|
} |
270 |
+ |
return s; |
271 |
+ |
} |
272 |
+ |
|
273 |
+ |
/** |
274 |
+ |
* Tries to set SIGNAL status. Used by ForkJoinPool. Other |
275 |
+ |
* variants are directly incorporated into externalAwaitDone etc. |
276 |
+ |
* |
277 |
+ |
* @return true if successful |
278 |
+ |
*/ |
279 |
+ |
final boolean trySetSignal() { |
280 |
+ |
int s; |
281 |
+ |
return U.compareAndSwapInt(this, STATUS, s = status, s | SIGNAL); |
282 |
|
} |
283 |
|
|
284 |
|
/** |
286 |
|
* @return status upon completion |
287 |
|
*/ |
288 |
|
private int externalAwaitDone() { |
289 |
+ |
boolean interrupted = false; |
290 |
|
int s; |
291 |
< |
if ((s = status) >= 0) { |
292 |
< |
boolean interrupted = false; |
293 |
< |
synchronized (this) { |
294 |
< |
while ((s = status) >= 0) { |
253 |
< |
if (s == 0) |
254 |
< |
UNSAFE.compareAndSwapInt(this, statusOffset, |
255 |
< |
0, SIGNAL); |
256 |
< |
else { |
291 |
> |
while ((s = status) >= 0) { |
292 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
293 |
> |
synchronized (this) { |
294 |
> |
if (status >= 0) { |
295 |
|
try { |
296 |
|
wait(); |
297 |
|
} catch (InterruptedException ie) { |
298 |
|
interrupted = true; |
299 |
|
} |
300 |
|
} |
301 |
+ |
else |
302 |
+ |
notifyAll(); |
303 |
|
} |
304 |
|
} |
265 |
– |
if (interrupted) |
266 |
– |
Thread.currentThread().interrupt(); |
305 |
|
} |
306 |
+ |
if (interrupted) |
307 |
+ |
Thread.currentThread().interrupt(); |
308 |
|
return s; |
309 |
|
} |
310 |
|
|
311 |
|
/** |
312 |
< |
* Blocks a non-worker-thread until completion or interruption or timeout. |
312 |
> |
* Blocks a non-worker-thread until completion or interruption. |
313 |
|
*/ |
314 |
< |
private int externalInterruptibleAwaitDone(long millis) |
275 |
< |
throws InterruptedException { |
314 |
> |
private int externalInterruptibleAwaitDone() throws InterruptedException { |
315 |
|
int s; |
316 |
|
if (Thread.interrupted()) |
317 |
|
throw new InterruptedException(); |
318 |
< |
if ((s = status) >= 0) { |
319 |
< |
synchronized (this) { |
320 |
< |
while ((s = status) >= 0) { |
321 |
< |
if (s == 0) |
322 |
< |
UNSAFE.compareAndSwapInt(this, statusOffset, |
323 |
< |
0, SIGNAL); |
324 |
< |
else { |
286 |
< |
wait(millis); |
287 |
< |
if (millis > 0L) |
288 |
< |
break; |
289 |
< |
} |
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 |
|
} |
328 |
|
return s; |
329 |
|
} |
330 |
|
|
296 |
– |
/** |
297 |
– |
* Primary execution method for stolen tasks. Unless done, calls |
298 |
– |
* exec and records status if completed, but doesn't wait for |
299 |
– |
* completion otherwise. |
300 |
– |
*/ |
301 |
– |
final void doExec() { |
302 |
– |
if (status >= 0) { |
303 |
– |
boolean completed; |
304 |
– |
try { |
305 |
– |
completed = exec(); |
306 |
– |
} catch (Throwable rex) { |
307 |
– |
setExceptionalCompletion(rex); |
308 |
– |
return; |
309 |
– |
} |
310 |
– |
if (completed) |
311 |
– |
setCompletion(NORMAL); // must be outside try block |
312 |
– |
} |
313 |
– |
} |
331 |
|
|
332 |
|
/** |
333 |
< |
* Primary mechanics for join, get, quietlyJoin. |
333 |
> |
* Implementation for join, get, quietlyJoin. Directly handles |
334 |
> |
* only cases of already-completed, external wait, and |
335 |
> |
* unfork+exec. Others are relayed to ForkJoinPool.awaitJoin. |
336 |
> |
* |
337 |
|
* @return status upon completion |
338 |
|
*/ |
339 |
|
private int doJoin() { |
340 |
< |
Thread t; ForkJoinWorkerThread w; int s; boolean completed; |
341 |
< |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) { |
342 |
< |
if ((s = status) < 0) |
343 |
< |
return s; |
344 |
< |
if ((w = (ForkJoinWorkerThread)t).unpushTask(this)) { |
345 |
< |
try { |
326 |
< |
completed = exec(); |
327 |
< |
} catch (Throwable rex) { |
328 |
< |
return setExceptionalCompletion(rex); |
329 |
< |
} |
330 |
< |
if (completed) |
331 |
< |
return setCompletion(NORMAL); |
340 |
> |
int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w; |
341 |
> |
if ((s = status) >= 0) { |
342 |
> |
if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) { |
343 |
> |
if (!(w = (wt = (ForkJoinWorkerThread)t).workQueue). |
344 |
> |
tryUnpush(this) || (s = doExec()) >= 0) |
345 |
> |
s = wt.pool.awaitJoin(w, this); |
346 |
|
} |
347 |
< |
return w.joinTask(this); |
347 |
> |
else |
348 |
> |
s = externalAwaitDone(); |
349 |
|
} |
350 |
< |
else |
336 |
< |
return externalAwaitDone(); |
350 |
> |
return s; |
351 |
|
} |
352 |
|
|
353 |
|
/** |
354 |
< |
* Primary mechanics for invoke, quietlyInvoke. |
354 |
> |
* Implementation for invoke, quietlyInvoke. |
355 |
> |
* |
356 |
|
* @return status upon completion |
357 |
|
*/ |
358 |
|
private int doInvoke() { |
359 |
< |
int s; boolean completed; |
360 |
< |
if ((s = status) < 0) |
361 |
< |
return s; |
362 |
< |
try { |
363 |
< |
completed = exec(); |
364 |
< |
} catch (Throwable rex) { |
365 |
< |
return setExceptionalCompletion(rex); |
359 |
> |
int s; Thread t; ForkJoinWorkerThread wt; |
360 |
> |
if ((s = doExec()) >= 0) { |
361 |
> |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) |
362 |
> |
s = (wt = (ForkJoinWorkerThread)t).pool.awaitJoin(wt.workQueue, |
363 |
> |
this); |
364 |
> |
else |
365 |
> |
s = externalAwaitDone(); |
366 |
|
} |
367 |
< |
if (completed) |
353 |
< |
return setCompletion(NORMAL); |
354 |
< |
else |
355 |
< |
return doJoin(); |
367 |
> |
return s; |
368 |
|
} |
369 |
|
|
370 |
|
// Exception table support |
399 |
|
* any ForkJoinPool will call helpExpungeStaleExceptions when its |
400 |
|
* pool becomes isQuiescent. |
401 |
|
*/ |
402 |
< |
static final class ExceptionNode extends WeakReference<ForkJoinTask<?>>{ |
402 |
> |
static final class ExceptionNode extends WeakReference<ForkJoinTask<?>> { |
403 |
|
final Throwable ex; |
404 |
|
ExceptionNode next; |
405 |
|
final long thrower; // use id not ref to avoid weak cycles |
439 |
|
} |
440 |
|
|
441 |
|
/** |
442 |
+ |
* Cancels, ignoring any exceptions thrown by cancel. Used during |
443 |
+ |
* worker and pool shutdown. Cancel is spec'ed not to throw any |
444 |
+ |
* exceptions, but if it does anyway, we have no recourse during |
445 |
+ |
* shutdown, so guard against this case. |
446 |
+ |
*/ |
447 |
+ |
static final void cancelIgnoringExceptions(ForkJoinTask<?> t) { |
448 |
+ |
if (t != null && t.status >= 0) { |
449 |
+ |
try { |
450 |
+ |
t.cancel(false); |
451 |
+ |
} catch (Throwable ignore) { |
452 |
+ |
} |
453 |
+ |
} |
454 |
+ |
} |
455 |
+ |
|
456 |
+ |
/** |
457 |
|
* Removes exception node and clears status |
458 |
|
*/ |
459 |
|
private void clearExceptionalCompletion() { |
499 |
|
* @return the exception, or null if none |
500 |
|
*/ |
501 |
|
private Throwable getThrowableException() { |
502 |
< |
if (status != EXCEPTIONAL) |
502 |
> |
if ((status & DONE_MASK) != EXCEPTIONAL) |
503 |
|
return null; |
504 |
|
int h = System.identityHashCode(this); |
505 |
|
ExceptionNode e; |
584 |
|
} |
585 |
|
|
586 |
|
/** |
587 |
< |
* Report the result of invoke or join; called only upon |
561 |
< |
* non-normal return of internal versions. |
587 |
> |
* Throws exception, if any, associated with the given status. |
588 |
|
*/ |
589 |
< |
private V reportResult() { |
590 |
< |
int s; Throwable ex; |
591 |
< |
if ((s = status) == CANCELLED) |
592 |
< |
throw new CancellationException(); |
593 |
< |
if (s == EXCEPTIONAL && (ex = getThrowableException()) != null) |
594 |
< |
UNSAFE.throwException(ex); |
569 |
< |
return getRawResult(); |
589 |
> |
private void reportException(int s) { |
590 |
> |
Throwable ex = ((s == CANCELLED) ? new CancellationException() : |
591 |
> |
(s == EXCEPTIONAL) ? getThrowableException() : |
592 |
> |
null); |
593 |
> |
if (ex != null) |
594 |
> |
U.throwException(ex); |
595 |
|
} |
596 |
|
|
597 |
|
// public methods |
615 |
|
* @return {@code this}, to simplify usage |
616 |
|
*/ |
617 |
|
public final ForkJoinTask<V> fork() { |
618 |
< |
((ForkJoinWorkerThread) Thread.currentThread()) |
594 |
< |
.pushTask(this); |
618 |
> |
((ForkJoinWorkerThread)Thread.currentThread()).workQueue.push(this); |
619 |
|
return this; |
620 |
|
} |
621 |
|
|
631 |
|
* @return the computed result |
632 |
|
*/ |
633 |
|
public final V join() { |
634 |
< |
if (doJoin() != NORMAL) |
635 |
< |
return reportResult(); |
636 |
< |
else |
637 |
< |
return getRawResult(); |
634 |
> |
int s; |
635 |
> |
if ((s = doJoin() & DONE_MASK) != NORMAL) |
636 |
> |
reportException(s); |
637 |
> |
return getRawResult(); |
638 |
|
} |
639 |
|
|
640 |
|
/** |
646 |
|
* @return the computed result |
647 |
|
*/ |
648 |
|
public final V invoke() { |
649 |
< |
if (doInvoke() != NORMAL) |
650 |
< |
return reportResult(); |
651 |
< |
else |
652 |
< |
return getRawResult(); |
649 |
> |
int s; |
650 |
> |
if ((s = doInvoke() & DONE_MASK) != NORMAL) |
651 |
> |
reportException(s); |
652 |
> |
return getRawResult(); |
653 |
|
} |
654 |
|
|
655 |
|
/** |
676 |
|
* @throws NullPointerException if any task is null |
677 |
|
*/ |
678 |
|
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) { |
679 |
+ |
int s1, s2; |
680 |
|
t2.fork(); |
681 |
< |
t1.invoke(); |
682 |
< |
t2.join(); |
681 |
> |
if ((s1 = t1.doInvoke() & DONE_MASK) != NORMAL) |
682 |
> |
t1.reportException(s1); |
683 |
> |
if ((s2 = t2.doJoin() & DONE_MASK) != NORMAL) |
684 |
> |
t2.reportException(s2); |
685 |
|
} |
686 |
|
|
687 |
|
/** |
724 |
|
if (t != null) { |
725 |
|
if (ex != null) |
726 |
|
t.cancel(false); |
727 |
< |
else if (t.doJoin() < NORMAL && ex == null) |
727 |
> |
else if (t.doJoin() < NORMAL) |
728 |
|
ex = t.getException(); |
729 |
|
} |
730 |
|
} |
731 |
|
if (ex != null) |
732 |
< |
UNSAFE.throwException(ex); |
732 |
> |
U.throwException(ex); |
733 |
|
} |
734 |
|
|
735 |
|
/** |
781 |
|
if (t != null) { |
782 |
|
if (ex != null) |
783 |
|
t.cancel(false); |
784 |
< |
else if (t.doJoin() < NORMAL && ex == null) |
784 |
> |
else if (t.doJoin() < NORMAL) |
785 |
|
ex = t.getException(); |
786 |
|
} |
787 |
|
} |
788 |
|
if (ex != null) |
789 |
< |
UNSAFE.throwException(ex); |
789 |
> |
U.throwException(ex); |
790 |
|
return tasks; |
791 |
|
} |
792 |
|
|
818 |
|
* @return {@code true} if this task is now cancelled |
819 |
|
*/ |
820 |
|
public boolean cancel(boolean mayInterruptIfRunning) { |
821 |
< |
return setCompletion(CANCELLED) == CANCELLED; |
795 |
< |
} |
796 |
< |
|
797 |
< |
/** |
798 |
< |
* Cancels, ignoring any exceptions thrown by cancel. Used during |
799 |
< |
* worker and pool shutdown. Cancel is spec'ed not to throw any |
800 |
< |
* exceptions, but if it does anyway, we have no recourse during |
801 |
< |
* shutdown, so guard against this case. |
802 |
< |
*/ |
803 |
< |
final void cancelIgnoringExceptions() { |
804 |
< |
try { |
805 |
< |
cancel(false); |
806 |
< |
} catch (Throwable ignore) { |
807 |
< |
} |
821 |
> |
return (setCompletion(CANCELLED) & DONE_MASK) == CANCELLED; |
822 |
|
} |
823 |
|
|
824 |
|
public final boolean isDone() { |
826 |
|
} |
827 |
|
|
828 |
|
public final boolean isCancelled() { |
829 |
< |
return status == CANCELLED; |
829 |
> |
return (status & DONE_MASK) == CANCELLED; |
830 |
|
} |
831 |
|
|
832 |
|
/** |
846 |
|
* exception and was not cancelled |
847 |
|
*/ |
848 |
|
public final boolean isCompletedNormally() { |
849 |
< |
return status == NORMAL; |
849 |
> |
return (status & DONE_MASK) == NORMAL; |
850 |
|
} |
851 |
|
|
852 |
|
/** |
857 |
|
* @return the exception, or {@code null} if none |
858 |
|
*/ |
859 |
|
public final Throwable getException() { |
860 |
< |
int s = status; |
860 |
> |
int s = status & DONE_MASK; |
861 |
|
return ((s >= NORMAL) ? null : |
862 |
|
(s == CANCELLED) ? new CancellationException() : |
863 |
|
getThrowableException()); |
919 |
|
*/ |
920 |
|
public final V get() throws InterruptedException, ExecutionException { |
921 |
|
int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ? |
922 |
< |
doJoin() : externalInterruptibleAwaitDone(0L); |
922 |
> |
doJoin() : externalInterruptibleAwaitDone(); |
923 |
|
Throwable ex; |
924 |
< |
if (s == CANCELLED) |
924 |
> |
if ((s &= DONE_MASK) == CANCELLED) |
925 |
|
throw new CancellationException(); |
926 |
|
if (s == EXCEPTIONAL && (ex = getThrowableException()) != null) |
927 |
|
throw new ExecutionException(ex); |
944 |
|
*/ |
945 |
|
public final V get(long timeout, TimeUnit unit) |
946 |
|
throws InterruptedException, ExecutionException, TimeoutException { |
947 |
< |
Thread t = Thread.currentThread(); |
948 |
< |
if (t instanceof ForkJoinWorkerThread) { |
949 |
< |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
950 |
< |
long nanos = unit.toNanos(timeout); |
951 |
< |
if (status >= 0) { |
952 |
< |
boolean completed = false; |
953 |
< |
if (w.unpushTask(this)) { |
954 |
< |
try { |
955 |
< |
completed = exec(); |
956 |
< |
} catch (Throwable rex) { |
957 |
< |
setExceptionalCompletion(rex); |
947 |
> |
if (Thread.interrupted()) |
948 |
> |
throw new InterruptedException(); |
949 |
> |
// Messy in part because we measure in nanosecs, but wait in millisecs |
950 |
> |
int s; long ns, ms; |
951 |
> |
if ((s = status) >= 0 && (ns = unit.toNanos(timeout)) > 0L) { |
952 |
> |
long deadline = System.nanoTime() + ns; |
953 |
> |
ForkJoinPool p = null; |
954 |
> |
ForkJoinPool.WorkQueue w = null; |
955 |
> |
Thread t = Thread.currentThread(); |
956 |
> |
if (t instanceof ForkJoinWorkerThread) { |
957 |
> |
ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; |
958 |
> |
p = wt.pool; |
959 |
> |
w = wt.workQueue; |
960 |
> |
s = p.helpJoinOnce(w, this); // no retries on failure |
961 |
> |
} |
962 |
> |
boolean canBlock = false; |
963 |
> |
boolean interrupted = false; |
964 |
> |
try { |
965 |
> |
while ((s = status) >= 0) { |
966 |
> |
if (w != null && w.runState < 0) |
967 |
> |
cancelIgnoringExceptions(this); |
968 |
> |
else if (!canBlock) { |
969 |
> |
if (p == null || p.tryCompensate(this, null)) |
970 |
> |
canBlock = true; |
971 |
> |
} |
972 |
> |
else { |
973 |
> |
if ((ms = TimeUnit.NANOSECONDS.toMillis(ns)) > 0L && |
974 |
> |
U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
975 |
> |
synchronized (this) { |
976 |
> |
if (status >= 0) { |
977 |
> |
try { |
978 |
> |
wait(ms); |
979 |
> |
} catch (InterruptedException ie) { |
980 |
> |
if (p == null) |
981 |
> |
interrupted = true; |
982 |
> |
} |
983 |
> |
} |
984 |
> |
else |
985 |
> |
notifyAll(); |
986 |
> |
} |
987 |
> |
} |
988 |
> |
if ((s = status) < 0 || interrupted || |
989 |
> |
(ns = deadline - System.nanoTime()) <= 0L) |
990 |
> |
break; |
991 |
|
} |
992 |
|
} |
993 |
< |
if (completed) |
994 |
< |
setCompletion(NORMAL); |
995 |
< |
else if (status >= 0 && nanos > 0) |
949 |
< |
w.pool.timedAwaitJoin(this, nanos); |
993 |
> |
} finally { |
994 |
> |
if (p != null && canBlock) |
995 |
> |
p.incrementActiveCount(); |
996 |
|
} |
997 |
+ |
if (interrupted) |
998 |
+ |
throw new InterruptedException(); |
999 |
|
} |
1000 |
< |
else { |
953 |
< |
long millis = unit.toMillis(timeout); |
954 |
< |
if (millis > 0) |
955 |
< |
externalInterruptibleAwaitDone(millis); |
956 |
< |
} |
957 |
< |
int s = status; |
958 |
< |
if (s != NORMAL) { |
1000 |
> |
if ((s &= DONE_MASK) != NORMAL) { |
1001 |
|
Throwable ex; |
1002 |
|
if (s == CANCELLED) |
1003 |
|
throw new CancellationException(); |
1042 |
|
* ClassCastException}. |
1043 |
|
*/ |
1044 |
|
public static void helpQuiesce() { |
1045 |
< |
((ForkJoinWorkerThread) Thread.currentThread()) |
1046 |
< |
.helpQuiescePool(); |
1045 |
> |
ForkJoinWorkerThread wt = |
1046 |
> |
(ForkJoinWorkerThread)Thread.currentThread(); |
1047 |
> |
wt.pool.helpQuiescePool(wt.workQueue); |
1048 |
|
} |
1049 |
|
|
1050 |
|
/** |
1064 |
|
* setRawResult(null)}. |
1065 |
|
*/ |
1066 |
|
public void reinitialize() { |
1067 |
< |
if (status == EXCEPTIONAL) |
1067 |
> |
if ((status & DONE_MASK) == EXCEPTIONAL) |
1068 |
|
clearExceptionalCompletion(); |
1069 |
|
else |
1070 |
|
status = 0; |
1112 |
|
* @return {@code true} if unforked |
1113 |
|
*/ |
1114 |
|
public boolean tryUnfork() { |
1115 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1116 |
< |
.unpushTask(this); |
1115 |
> |
return ((ForkJoinWorkerThread)Thread.currentThread()) |
1116 |
> |
.workQueue.tryUnpush(this); |
1117 |
|
} |
1118 |
|
|
1119 |
|
/** |
1132 |
|
*/ |
1133 |
|
public static int getQueuedTaskCount() { |
1134 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1135 |
< |
.getQueueSize(); |
1135 |
> |
.workQueue.queueSize(); |
1136 |
|
} |
1137 |
|
|
1138 |
|
/** |
1154 |
|
* @return the surplus number of tasks, which may be negative |
1155 |
|
*/ |
1156 |
|
public static int getSurplusQueuedTaskCount() { |
1157 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1158 |
< |
.getEstimatedSurplusTaskCount(); |
1157 |
> |
/* |
1158 |
> |
* The aim of this method is to return a cheap heuristic guide |
1159 |
> |
* for task partitioning when programmers, frameworks, tools, |
1160 |
> |
* or languages have little or no idea about task granularity. |
1161 |
> |
* In essence by offering this method, we ask users only about |
1162 |
> |
* tradeoffs in overhead vs expected throughput and its |
1163 |
> |
* variance, rather than how finely to partition tasks. |
1164 |
> |
* |
1165 |
> |
* In a steady state strict (tree-structured) computation, |
1166 |
> |
* each thread makes available for stealing enough tasks for |
1167 |
> |
* other threads to remain active. Inductively, if all threads |
1168 |
> |
* play by the same rules, each thread should make available |
1169 |
> |
* only a constant number of tasks. |
1170 |
> |
* |
1171 |
> |
* The minimum useful constant is just 1. But using a value of |
1172 |
> |
* 1 would require immediate replenishment upon each steal to |
1173 |
> |
* maintain enough tasks, which is infeasible. Further, |
1174 |
> |
* partitionings/granularities of offered tasks should |
1175 |
> |
* minimize steal rates, which in general means that threads |
1176 |
> |
* nearer the top of computation tree should generate more |
1177 |
> |
* than those nearer the bottom. In perfect steady state, each |
1178 |
> |
* thread is at approximately the same level of computation |
1179 |
> |
* tree. However, producing extra tasks amortizes the |
1180 |
> |
* uncertainty of progress and diffusion assumptions. |
1181 |
> |
* |
1182 |
> |
* So, users will want to use values larger, but not much |
1183 |
> |
* larger than 1 to both smooth over transient shortages and |
1184 |
> |
* hedge against uneven progress; as traded off against the |
1185 |
> |
* cost of extra task overhead. We leave the user to pick a |
1186 |
> |
* threshold value to compare with the results of this call to |
1187 |
> |
* guide decisions, but recommend values such as 3. |
1188 |
> |
* |
1189 |
> |
* When all threads are active, it is on average OK to |
1190 |
> |
* estimate surplus strictly locally. In steady-state, if one |
1191 |
> |
* thread is maintaining say 2 surplus tasks, then so are |
1192 |
> |
* others. So we can just use estimated queue length. |
1193 |
> |
* However, this strategy alone leads to serious mis-estimates |
1194 |
> |
* in some non-steady-state conditions (ramp-up, ramp-down, |
1195 |
> |
* other stalls). We can detect many of these by further |
1196 |
> |
* considering the number of "idle" threads, that are known to |
1197 |
> |
* have zero queued tasks, so compensate by a factor of |
1198 |
> |
* (#idle/#active) threads. |
1199 |
> |
*/ |
1200 |
> |
ForkJoinWorkerThread wt = |
1201 |
> |
(ForkJoinWorkerThread)Thread.currentThread(); |
1202 |
> |
return wt.workQueue.queueSize() - wt.pool.idlePerActive(); |
1203 |
|
} |
1204 |
|
|
1205 |
|
// Extension methods |
1256 |
|
* @return the next task, or {@code null} if none are available |
1257 |
|
*/ |
1258 |
|
protected static ForkJoinTask<?> peekNextLocalTask() { |
1259 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1173 |
< |
.peekTask(); |
1259 |
> |
return ((ForkJoinWorkerThread) Thread.currentThread()).workQueue.peek(); |
1260 |
|
} |
1261 |
|
|
1262 |
|
/** |
1275 |
|
*/ |
1276 |
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
1277 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1278 |
< |
.pollLocalTask(); |
1278 |
> |
.workQueue.nextLocalTask(); |
1279 |
|
} |
1280 |
|
|
1281 |
|
/** |
1297 |
|
* @return a task, or {@code null} if none are available |
1298 |
|
*/ |
1299 |
|
protected static ForkJoinTask<?> pollTask() { |
1300 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1301 |
< |
.pollTask(); |
1300 |
> |
ForkJoinWorkerThread wt = |
1301 |
> |
(ForkJoinWorkerThread)Thread.currentThread(); |
1302 |
> |
return wt.pool.nextTaskFor(wt.workQueue); |
1303 |
> |
} |
1304 |
> |
|
1305 |
> |
// Mark-bit operations |
1306 |
> |
|
1307 |
> |
/** |
1308 |
> |
* Returns true if this task is marked. |
1309 |
> |
* |
1310 |
> |
* @return true if this task is marked |
1311 |
> |
* @since 1.8 |
1312 |
> |
*/ |
1313 |
> |
public final boolean isMarkedForkJoinTask() { |
1314 |
> |
return (status & MARKED) != 0; |
1315 |
> |
} |
1316 |
> |
|
1317 |
> |
/** |
1318 |
> |
* Atomically sets the mark on this task. |
1319 |
> |
* |
1320 |
> |
* @return true if this task was previously unmarked |
1321 |
> |
* @since 1.8 |
1322 |
> |
*/ |
1323 |
> |
public final boolean markForkJoinTask() { |
1324 |
> |
for (int s;;) { |
1325 |
> |
if (((s = status) & MARKED) != 0) |
1326 |
> |
return false; |
1327 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | MARKED)) |
1328 |
> |
return true; |
1329 |
> |
} |
1330 |
> |
} |
1331 |
> |
|
1332 |
> |
/** |
1333 |
> |
* Atomically clears the mark on this task. |
1334 |
> |
* |
1335 |
> |
* @return true if this task was previously marked |
1336 |
> |
* @since 1.8 |
1337 |
> |
*/ |
1338 |
> |
public final boolean unmarkForkJoinTask() { |
1339 |
> |
for (int s;;) { |
1340 |
> |
if (((s = status) & MARKED) == 0) |
1341 |
> |
return false; |
1342 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s & ~MARKED)) |
1343 |
> |
return true; |
1344 |
> |
} |
1345 |
|
} |
1346 |
|
|
1347 |
|
/** |
1352 |
|
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
1353 |
|
implements RunnableFuture<T> { |
1354 |
|
final Runnable runnable; |
1226 |
– |
final T resultOnCompletion; |
1355 |
|
T result; |
1356 |
|
AdaptedRunnable(Runnable runnable, T result) { |
1357 |
|
if (runnable == null) throw new NullPointerException(); |
1358 |
|
this.runnable = runnable; |
1359 |
< |
this.resultOnCompletion = result; |
1359 |
> |
this.result = result; // OK to set this even before completion |
1360 |
|
} |
1361 |
< |
public T getRawResult() { return result; } |
1362 |
< |
public void setRawResult(T v) { result = v; } |
1363 |
< |
public boolean exec() { |
1364 |
< |
runnable.run(); |
1365 |
< |
result = resultOnCompletion; |
1366 |
< |
return true; |
1361 |
> |
public final T getRawResult() { return result; } |
1362 |
> |
public final void setRawResult(T v) { result = 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 Runnables without results |
1370 |
> |
*/ |
1371 |
> |
static final class AdaptedRunnableAction extends ForkJoinTask<Void> |
1372 |
> |
implements RunnableFuture<Void> { |
1373 |
> |
final Runnable runnable; |
1374 |
> |
AdaptedRunnableAction(Runnable runnable) { |
1375 |
> |
if (runnable == null) throw new NullPointerException(); |
1376 |
> |
this.runnable = runnable; |
1377 |
|
} |
1378 |
< |
public void run() { invoke(); } |
1378 |
> |
public final Void getRawResult() { return null; } |
1379 |
> |
public final void setRawResult(Void v) { } |
1380 |
> |
public final boolean exec() { runnable.run(); return true; } |
1381 |
> |
public final void run() { invoke(); } |
1382 |
|
private static final long serialVersionUID = 5232453952276885070L; |
1383 |
|
} |
1384 |
|
|
1393 |
|
if (callable == null) throw new NullPointerException(); |
1394 |
|
this.callable = callable; |
1395 |
|
} |
1396 |
< |
public T getRawResult() { return result; } |
1397 |
< |
public void setRawResult(T v) { result = v; } |
1398 |
< |
public boolean exec() { |
1396 |
> |
public final T getRawResult() { return result; } |
1397 |
> |
public final void setRawResult(T v) { result = v; } |
1398 |
> |
public final boolean exec() { |
1399 |
|
try { |
1400 |
|
result = callable.call(); |
1401 |
|
return true; |
1407 |
|
throw new RuntimeException(ex); |
1408 |
|
} |
1409 |
|
} |
1410 |
< |
public void run() { invoke(); } |
1410 |
> |
public final void run() { invoke(); } |
1411 |
|
private static final long serialVersionUID = 2838392045355241008L; |
1412 |
|
} |
1413 |
|
|
1420 |
|
* @return the task |
1421 |
|
*/ |
1422 |
|
public static ForkJoinTask<?> adapt(Runnable runnable) { |
1423 |
< |
return new AdaptedRunnable<Void>(runnable, null); |
1423 |
> |
return new AdaptedRunnableAction(runnable); |
1424 |
|
} |
1425 |
|
|
1426 |
|
/** |
1454 |
|
private static final long serialVersionUID = -7721805057305804111L; |
1455 |
|
|
1456 |
|
/** |
1457 |
< |
* Saves the state to a stream (that is, serializes it). |
1457 |
> |
* Saves this task to a stream (that is, serializes it). |
1458 |
|
* |
1459 |
|
* @serialData the current run status and the exception thrown |
1460 |
|
* during execution, or {@code null} if none |
1320 |
– |
* @param s the stream |
1461 |
|
*/ |
1462 |
|
private void writeObject(java.io.ObjectOutputStream s) |
1463 |
|
throws java.io.IOException { |
1466 |
|
} |
1467 |
|
|
1468 |
|
/** |
1469 |
< |
* Reconstitutes the instance from a stream (that is, deserializes it). |
1330 |
< |
* |
1331 |
< |
* @param s the stream |
1469 |
> |
* Reconstitutes this task from a stream (that is, deserializes it). |
1470 |
|
*/ |
1471 |
|
private void readObject(java.io.ObjectInputStream s) |
1472 |
|
throws java.io.IOException, ClassNotFoundException { |
1477 |
|
} |
1478 |
|
|
1479 |
|
// Unsafe mechanics |
1480 |
< |
private static final sun.misc.Unsafe UNSAFE; |
1481 |
< |
private static final long statusOffset; |
1480 |
> |
private static final sun.misc.Unsafe U; |
1481 |
> |
private static final long STATUS; |
1482 |
|
static { |
1483 |
|
exceptionTableLock = new ReentrantLock(); |
1484 |
|
exceptionTableRefQueue = new ReferenceQueue<Object>(); |
1485 |
|
exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY]; |
1486 |
|
try { |
1487 |
< |
UNSAFE = getUnsafe(); |
1488 |
< |
statusOffset = UNSAFE.objectFieldOffset |
1487 |
> |
U = getUnsafe(); |
1488 |
> |
STATUS = U.objectFieldOffset |
1489 |
|
(ForkJoinTask.class.getDeclaredField("status")); |
1490 |
|
} catch (Exception e) { |
1491 |
|
throw new Error(e); |