56 |
|
* exceptions such as {@code IOExceptions} to be thrown. However, |
57 |
|
* computations may still encounter unchecked exceptions, that are |
58 |
|
* rethrown to callers attempting to join them. These exceptions may |
59 |
< |
* additionally include RejectedExecutionExceptions stemming from |
60 |
< |
* internal resource exhaustion such as failure to allocate internal |
61 |
< |
* task queues. |
59 |
> |
* additionally include {@link RejectedExecutionException} stemming |
60 |
> |
* from internal resource exhaustion, such as failure to allocate |
61 |
> |
* internal task queues. |
62 |
|
* |
63 |
|
* <p>The primary method for awaiting completion and extracting |
64 |
|
* results of a task is {@link #join}, but there are several variants: |
65 |
|
* The {@link Future#get} methods support interruptible and/or timed |
66 |
|
* waits for completion and report results using {@code Future} |
67 |
< |
* conventions. Method {@link #helpJoin} enables callers to actively |
68 |
< |
* execute other tasks while awaiting joins, which is sometimes more |
69 |
< |
* efficient but only applies when all subtasks are known to be |
70 |
< |
* strictly tree-structured. Method {@link #invoke} is semantically |
67 |
> |
* conventions. Method {@link #invoke} is semantically |
68 |
|
* equivalent to {@code fork(); join()} but always attempts to begin |
69 |
|
* execution in the current thread. The "<em>quiet</em>" forms of |
70 |
|
* these methods do not extract results or report exceptions. These |
77 |
|
* <p>The execution status of tasks may be queried at several levels |
78 |
|
* of detail: {@link #isDone} is true if a task completed in any way |
79 |
|
* (including the case where a task was cancelled without executing); |
83 |
– |
* {@link #isCancelled} is true if completion was due to cancellation; |
80 |
|
* {@link #isCompletedNormally} is true if a task completed without |
81 |
< |
* cancellation or encountering an exception; {@link |
82 |
< |
* #isCompletedExceptionally} is true if if the task encountered an |
83 |
< |
* exception (in which case {@link #getException} returns the |
84 |
< |
* exception); {@link #isCancelled} is true if the task was cancelled |
85 |
< |
* (in which case {@link #getException} returns a {@link |
86 |
< |
* java.util.concurrent.CancellationException}); and {@link |
87 |
< |
* #isCompletedAbnormally} is true if a task was either cancelled or |
92 |
< |
* encountered an exception. |
81 |
> |
* cancellation or encountering an exception; {@link #isCancelled} is |
82 |
> |
* true if the task was cancelled (in which case {@link #getException} |
83 |
> |
* returns a {@link java.util.concurrent.CancellationException}); and |
84 |
> |
* {@link #isCompletedAbnormally} is true if a task was either |
85 |
> |
* cancelled or encountered an exception, in which case {@link |
86 |
> |
* #getException} will return either the encountered exception or |
87 |
> |
* {@link java.util.concurrent.CancellationException}. |
88 |
|
* |
89 |
|
* <p>The ForkJoinTask class is not usually directly subclassed. |
90 |
|
* Instead, you subclass one of the abstract classes that support a |
120 |
|
* improve throughput. If too small, then memory and internal task |
121 |
|
* maintenance overhead may overwhelm processing. |
122 |
|
* |
123 |
< |
* <p>This class provides {@code adapt} methods for {@link |
124 |
< |
* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that |
125 |
< |
* may be of use when mixing execution of ForkJoinTasks with other |
126 |
< |
* kinds of tasks. When all tasks are of this form, consider using a |
132 |
< |
* pool in {@link ForkJoinPool#setAsyncMode async mode}. |
123 |
> |
* <p>This class provides {@code adapt} methods for {@link Runnable} |
124 |
> |
* and {@link Callable}, that may be of use when mixing execution of |
125 |
> |
* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are |
126 |
> |
* of this form, consider using a pool constructed in <em>asyncMode</em>. |
127 |
|
* |
128 |
|
* <p>ForkJoinTasks are {@code Serializable}, which enables them to be |
129 |
|
* used in extensions such as remote execution frameworks. It is |
135 |
|
*/ |
136 |
|
public abstract class ForkJoinTask<V> implements Future<V>, Serializable { |
137 |
|
|
138 |
< |
/** |
139 |
< |
* Run control status bits packed into a single int to minimize |
140 |
< |
* footprint and to ensure atomicity (via CAS). Status is |
141 |
< |
* initially zero, and takes on nonnegative values until |
142 |
< |
* completed, upon which status holds COMPLETED. CANCELLED, or |
143 |
< |
* EXCEPTIONAL, which use the top 3 bits. Tasks undergoing |
144 |
< |
* blocking waits by other threads have SIGNAL_MASK bits set -- |
145 |
< |
* bit 15 for external (nonFJ) waits, and the rest a count of |
146 |
< |
* waiting FJ threads. (This representation relies on |
147 |
< |
* ForkJoinPool max thread limits). Completion of a stolen task |
148 |
< |
* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even |
149 |
< |
* though suboptimal for some purposes, we use basic builtin |
150 |
< |
* wait/notify to take advantage of "monitor inflation" in JVMs |
151 |
< |
* that we would otherwise need to emulate to avoid adding further |
152 |
< |
* per-task bookkeeping overhead. Note that bits 16-28 are |
153 |
< |
* currently unused. Also value 0x80000000 is available as spare |
154 |
< |
* completion value. |
138 |
> |
/* |
139 |
> |
* See the internal documentation of class ForkJoinPool for a |
140 |
> |
* general implementation overview. ForkJoinTasks are mainly |
141 |
> |
* responsible for maintaining their "status" field amidst relays |
142 |
> |
* to methods in ForkJoinWorkerThread and ForkJoinPool. The |
143 |
> |
* methods of this class are more-or-less layered into (1) basic |
144 |
> |
* status maintenance (2) execution and awaiting completion (3) |
145 |
> |
* user-level methods that additionally report results. This is |
146 |
> |
* sometimes hard to see because this file orders exported methods |
147 |
> |
* in a way that flows well in javadocs. In particular, most |
148 |
> |
* join mechanics are in method quietlyJoin, below. |
149 |
> |
*/ |
150 |
> |
|
151 |
> |
/* |
152 |
> |
* The status field holds run control status bits packed into a |
153 |
> |
* single int to minimize footprint and to ensure atomicity (via |
154 |
> |
* CAS). Status is initially zero, and takes on nonnegative |
155 |
> |
* values until completed, upon which status holds value |
156 |
> |
* COMPLETED. CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking |
157 |
> |
* waits by other threads have the SIGNAL bit set. Completion of |
158 |
> |
* a stolen task with SIGNAL set awakens any waiters via |
159 |
> |
* notifyAll. Even though suboptimal for some purposes, we use |
160 |
> |
* basic builtin wait/notify to take advantage of "monitor |
161 |
> |
* inflation" in JVMs that we would otherwise need to emulate to |
162 |
> |
* avoid adding further per-task bookkeeping overhead. We want |
163 |
> |
* these monitors to be "fat", i.e., not use biasing or thin-lock |
164 |
> |
* techniques, so use some odd coding idioms that tend to avoid |
165 |
> |
* them. |
166 |
|
*/ |
167 |
+ |
|
168 |
+ |
/** The run status of this task */ |
169 |
|
volatile int status; // accessed directly by pool and workers |
170 |
|
|
171 |
< |
static final int COMPLETION_MASK = 0xe0000000; |
172 |
< |
static final int NORMAL = 0xe0000000; // == mask |
173 |
< |
static final int CANCELLED = 0xc0000000; |
174 |
< |
static final int EXCEPTIONAL = 0xa0000000; |
168 |
< |
static final int SIGNAL_MASK = 0x0000ffff; |
169 |
< |
static final int INTERNAL_SIGNAL_MASK = 0x00007fff; |
170 |
< |
static final int EXTERNAL_SIGNAL = 0x00008000; // top bit of low word |
171 |
> |
private static final int NORMAL = -1; |
172 |
> |
private static final int CANCELLED = -2; |
173 |
> |
private static final int EXCEPTIONAL = -3; |
174 |
> |
private static final int SIGNAL = 1; |
175 |
|
|
176 |
|
/** |
177 |
|
* Table of exceptions thrown by tasks, to enable reporting by |
185 |
|
Collections.synchronizedMap |
186 |
|
(new WeakHashMap<ForkJoinTask<?>, Throwable>()); |
187 |
|
|
188 |
< |
// within-package utilities |
188 |
> |
// Maintaining completion status |
189 |
|
|
190 |
|
/** |
191 |
< |
* Gets current worker thread, or null if not a worker thread. |
192 |
< |
*/ |
189 |
< |
static ForkJoinWorkerThread getWorker() { |
190 |
< |
Thread t = Thread.currentThread(); |
191 |
< |
return ((t instanceof ForkJoinWorkerThread) ? |
192 |
< |
(ForkJoinWorkerThread) t : null); |
193 |
< |
} |
194 |
< |
|
195 |
< |
final boolean casStatus(int cmp, int val) { |
196 |
< |
return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val); |
197 |
< |
} |
198 |
< |
|
199 |
< |
/** |
200 |
< |
* Workaround for not being able to rethrow unchecked exceptions. |
201 |
< |
*/ |
202 |
< |
static void rethrowException(Throwable ex) { |
203 |
< |
if (ex != null) |
204 |
< |
UNSAFE.throwException(ex); |
205 |
< |
} |
206 |
< |
|
207 |
< |
// Setting completion status |
208 |
< |
|
209 |
< |
/** |
210 |
< |
* Marks completion and wakes up threads waiting to join this task. |
191 |
> |
* Marks completion and wakes up threads waiting to join this task, |
192 |
> |
* also clearing signal request bits. |
193 |
|
* |
194 |
|
* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
195 |
|
*/ |
196 |
< |
final void setCompletion(int completion) { |
197 |
< |
ForkJoinPool pool = getPool(); |
198 |
< |
if (pool != null) { |
199 |
< |
int s; // Clear signal bits while setting completion status |
200 |
< |
do {} while ((s = status) >= 0 && !casStatus(s, completion)); |
201 |
< |
|
202 |
< |
if ((s & SIGNAL_MASK) != 0) { |
221 |
< |
if ((s &= INTERNAL_SIGNAL_MASK) != 0) |
222 |
< |
pool.updateRunningCount(s); |
223 |
< |
synchronized (this) { notifyAll(); } |
196 |
> |
private void setCompletion(int completion) { |
197 |
> |
int s; |
198 |
> |
while ((s = status) >= 0) { |
199 |
> |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) { |
200 |
> |
if (s != 0) |
201 |
> |
synchronized (this) { notifyAll(); } |
202 |
> |
break; |
203 |
|
} |
204 |
|
} |
226 |
– |
else |
227 |
– |
externallySetCompletion(completion); |
228 |
– |
} |
229 |
– |
|
230 |
– |
/** |
231 |
– |
* Version of setCompletion for non-FJ threads. Leaves signal |
232 |
– |
* bits for unblocked threads to adjust, and always notifies. |
233 |
– |
*/ |
234 |
– |
private void externallySetCompletion(int completion) { |
235 |
– |
int s; |
236 |
– |
do {} while ((s = status) >= 0 && |
237 |
– |
!casStatus(s, (s & SIGNAL_MASK) | completion)); |
238 |
– |
synchronized (this) { notifyAll(); } |
239 |
– |
} |
240 |
– |
|
241 |
– |
/** |
242 |
– |
* Sets status to indicate normal completion. |
243 |
– |
*/ |
244 |
– |
final void setNormalCompletion() { |
245 |
– |
// Try typical fast case -- single CAS, no signal, not already done. |
246 |
– |
// Manually expand casStatus to improve chances of inlining it |
247 |
– |
if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL)) |
248 |
– |
setCompletion(NORMAL); |
205 |
|
} |
206 |
|
|
251 |
– |
// internal waiting and notification |
252 |
– |
|
207 |
|
/** |
208 |
< |
* Performs the actual monitor wait for awaitDone. |
208 |
> |
* Record exception and set exceptional completion |
209 |
> |
* @return status on exit |
210 |
|
*/ |
211 |
< |
private void doAwaitDone() { |
212 |
< |
// Minimize lock bias and in/de-flation effects by maximizing |
213 |
< |
// chances of waiting inside sync |
259 |
< |
try { |
260 |
< |
while (status >= 0) |
261 |
< |
synchronized (this) { if (status >= 0) wait(); } |
262 |
< |
} catch (InterruptedException ie) { |
263 |
< |
onInterruptedWait(); |
264 |
< |
} |
211 |
> |
private void setExceptionalCompletion(Throwable rex) { |
212 |
> |
exceptionMap.put(this, rex); |
213 |
> |
setCompletion(EXCEPTIONAL); |
214 |
|
} |
215 |
|
|
216 |
|
/** |
217 |
< |
* Performs the actual timed monitor wait for awaitDone. |
217 |
> |
* Blocks a worker thread until completion. Called only by pool. |
218 |
|
*/ |
219 |
< |
private void doAwaitDone(long startTime, long nanos) { |
220 |
< |
synchronized (this) { |
219 |
> |
final void internalAwaitDone() { |
220 |
> |
int s; // the odd construction reduces lock bias effects |
221 |
> |
while ((s = status) >= 0) { |
222 |
|
try { |
223 |
< |
while (status >= 0) { |
224 |
< |
long nt = nanos - (System.nanoTime() - startTime); |
225 |
< |
if (nt <= 0) |
276 |
< |
break; |
277 |
< |
wait(nt / 1000000, (int) (nt % 1000000)); |
223 |
> |
synchronized(this) { |
224 |
> |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL)) |
225 |
> |
wait(); |
226 |
|
} |
227 |
|
} catch (InterruptedException ie) { |
228 |
< |
onInterruptedWait(); |
228 |
> |
cancelIfTerminating(); |
229 |
|
} |
230 |
|
} |
231 |
|
} |
232 |
|
|
285 |
– |
// Awaiting completion |
286 |
– |
|
233 |
|
/** |
234 |
< |
* Sets status to indicate there is joiner, then waits for join, |
289 |
< |
* surrounded with pool notifications. |
290 |
< |
* |
291 |
< |
* @return status upon exit |
234 |
> |
* Blocks a non-worker-thread until completion. |
235 |
|
*/ |
236 |
< |
private int awaitDone(ForkJoinWorkerThread w, |
294 |
< |
boolean maintainParallelism) { |
295 |
< |
ForkJoinPool pool = (w == null) ? null : w.pool; |
236 |
> |
private void externalAwaitDone() { |
237 |
|
int s; |
238 |
|
while ((s = status) >= 0) { |
239 |
< |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
240 |
< |
if (pool == null || !pool.preJoin(this, maintainParallelism)) |
241 |
< |
doAwaitDone(); |
242 |
< |
if (((s = status) & INTERNAL_SIGNAL_MASK) != 0) |
243 |
< |
adjustPoolCountsOnUnblock(pool); |
244 |
< |
break; |
245 |
< |
} |
246 |
< |
} |
247 |
< |
return s; |
248 |
< |
} |
249 |
< |
|
250 |
< |
/** |
310 |
< |
* Timed version of awaitDone |
311 |
< |
* |
312 |
< |
* @return status upon exit |
313 |
< |
*/ |
314 |
< |
private int awaitDone(ForkJoinWorkerThread w, long nanos) { |
315 |
< |
ForkJoinPool pool = (w == null) ? null : w.pool; |
316 |
< |
int s; |
317 |
< |
while ((s = status) >= 0) { |
318 |
< |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
319 |
< |
long startTime = System.nanoTime(); |
320 |
< |
if (pool == null || !pool.preJoin(this, false)) |
321 |
< |
doAwaitDone(startTime, nanos); |
322 |
< |
if ((s = status) >= 0) { |
323 |
< |
adjustPoolCountsOnCancelledWait(pool); |
324 |
< |
s = status; |
325 |
< |
} |
326 |
< |
if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0) |
327 |
< |
adjustPoolCountsOnUnblock(pool); |
328 |
< |
break; |
329 |
< |
} |
330 |
< |
} |
331 |
< |
return s; |
332 |
< |
} |
333 |
< |
|
334 |
< |
/** |
335 |
< |
* Notifies pool that thread is unblocked. Called by signalled |
336 |
< |
* threads when woken by non-FJ threads (which is atypical). |
337 |
< |
*/ |
338 |
< |
private void adjustPoolCountsOnUnblock(ForkJoinPool pool) { |
339 |
< |
int s; |
340 |
< |
do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK)); |
341 |
< |
if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0) |
342 |
< |
pool.updateRunningCount(s); |
343 |
< |
} |
344 |
< |
|
345 |
< |
/** |
346 |
< |
* Notifies pool to adjust counts on cancelled or timed out wait. |
347 |
< |
*/ |
348 |
< |
private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) { |
349 |
< |
if (pool != null) { |
350 |
< |
int s; |
351 |
< |
while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) { |
352 |
< |
if (casStatus(s, s - 1)) { |
353 |
< |
pool.updateRunningCount(1); |
239 |
> |
synchronized(this) { |
240 |
> |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){ |
241 |
> |
boolean interrupted = false; |
242 |
> |
while (status >= 0) { |
243 |
> |
try { |
244 |
> |
wait(); |
245 |
> |
} catch (InterruptedException ie) { |
246 |
> |
interrupted = true; |
247 |
> |
} |
248 |
> |
} |
249 |
> |
if (interrupted) |
250 |
> |
Thread.currentThread().interrupt(); |
251 |
|
break; |
252 |
|
} |
253 |
|
} |
255 |
|
} |
256 |
|
|
257 |
|
/** |
258 |
< |
* Handles interruptions during waits. |
259 |
< |
*/ |
260 |
< |
private void onInterruptedWait() { |
364 |
< |
ForkJoinWorkerThread w = getWorker(); |
365 |
< |
if (w == null) |
366 |
< |
Thread.currentThread().interrupt(); // re-interrupt |
367 |
< |
else if (w.isTerminating()) |
368 |
< |
cancelIgnoringExceptions(); |
369 |
< |
// else if FJworker, ignore interrupt |
370 |
< |
} |
371 |
< |
|
372 |
< |
// Recording and reporting exceptions |
373 |
< |
|
374 |
< |
private void setDoneExceptionally(Throwable rex) { |
375 |
< |
exceptionMap.put(this, rex); |
376 |
< |
setCompletion(EXCEPTIONAL); |
377 |
< |
} |
378 |
< |
|
379 |
< |
/** |
380 |
< |
* Throws the exception associated with status s. |
381 |
< |
* |
382 |
< |
* @throws the exception |
383 |
< |
*/ |
384 |
< |
private void reportException(int s) { |
385 |
< |
if ((s &= COMPLETION_MASK) < NORMAL) { |
386 |
< |
if (s == CANCELLED) |
387 |
< |
throw new CancellationException(); |
388 |
< |
else |
389 |
< |
rethrowException(exceptionMap.get(this)); |
390 |
< |
} |
391 |
< |
} |
392 |
< |
|
393 |
< |
/** |
394 |
< |
* Returns result or throws exception using j.u.c.Future conventions. |
395 |
< |
* Only call when {@code isDone} known to be true. |
396 |
< |
*/ |
397 |
< |
private V reportFutureResult() |
398 |
< |
throws ExecutionException, InterruptedException { |
399 |
< |
if (Thread.interrupted()) |
400 |
< |
throw new InterruptedException(); |
401 |
< |
int s = status & COMPLETION_MASK; |
402 |
< |
if (s < NORMAL) { |
403 |
< |
Throwable ex; |
404 |
< |
if (s == CANCELLED) |
405 |
< |
throw new CancellationException(); |
406 |
< |
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
407 |
< |
throw new ExecutionException(ex); |
408 |
< |
} |
409 |
< |
return getRawResult(); |
410 |
< |
} |
411 |
< |
|
412 |
< |
/** |
413 |
< |
* Returns result or throws exception using j.u.c.Future conventions |
414 |
< |
* with timeouts. |
415 |
< |
*/ |
416 |
< |
private V reportTimedFutureResult() |
417 |
< |
throws InterruptedException, ExecutionException, TimeoutException { |
418 |
< |
if (Thread.interrupted()) |
419 |
< |
throw new InterruptedException(); |
420 |
< |
Throwable ex; |
421 |
< |
int s = status & COMPLETION_MASK; |
422 |
< |
if (s == NORMAL) |
423 |
< |
return getRawResult(); |
424 |
< |
if (s == CANCELLED) |
425 |
< |
throw new CancellationException(); |
426 |
< |
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
427 |
< |
throw new ExecutionException(ex); |
428 |
< |
throw new TimeoutException(); |
429 |
< |
} |
430 |
< |
|
431 |
< |
// internal execution methods |
432 |
< |
|
433 |
< |
/** |
434 |
< |
* Calls exec, recording completion, and rethrowing exception if |
435 |
< |
* encountered. Caller should normally check status before calling. |
436 |
< |
* |
437 |
< |
* @return true if completed normally |
438 |
< |
*/ |
439 |
< |
private boolean tryExec() { |
440 |
< |
try { // try block must contain only call to exec |
441 |
< |
if (!exec()) |
442 |
< |
return false; |
443 |
< |
} catch (Throwable rex) { |
444 |
< |
setDoneExceptionally(rex); |
445 |
< |
rethrowException(rex); |
446 |
< |
return false; // not reached |
447 |
< |
} |
448 |
< |
setNormalCompletion(); |
449 |
< |
return true; |
450 |
< |
} |
451 |
< |
|
452 |
< |
/** |
453 |
< |
* Main execution method used by worker threads. Invokes |
454 |
< |
* base computation unless already complete. |
258 |
> |
* Unless done, calls exec and records status if completed, but |
259 |
> |
* doesn't wait for completion otherwise. Primary execution method |
260 |
> |
* for ForkJoinWorkerThread. |
261 |
|
*/ |
262 |
|
final void quietlyExec() { |
457 |
– |
if (status >= 0) { |
458 |
– |
try { |
459 |
– |
if (!exec()) |
460 |
– |
return; |
461 |
– |
} catch (Throwable rex) { |
462 |
– |
setDoneExceptionally(rex); |
463 |
– |
return; |
464 |
– |
} |
465 |
– |
setNormalCompletion(); |
466 |
– |
} |
467 |
– |
} |
468 |
– |
|
469 |
– |
/** |
470 |
– |
* Calls exec(), recording but not rethrowing exception. |
471 |
– |
* Caller should normally check status before calling. |
472 |
– |
* |
473 |
– |
* @return true if completed normally |
474 |
– |
*/ |
475 |
– |
private boolean tryQuietlyInvoke() { |
263 |
|
try { |
264 |
< |
if (!exec()) |
265 |
< |
return false; |
264 |
> |
if (status < 0 || !exec()) |
265 |
> |
return; |
266 |
|
} catch (Throwable rex) { |
267 |
< |
setDoneExceptionally(rex); |
268 |
< |
return false; |
482 |
< |
} |
483 |
< |
setNormalCompletion(); |
484 |
< |
return true; |
485 |
< |
} |
486 |
< |
|
487 |
< |
/** |
488 |
< |
* Cancels, ignoring any exceptions it throws. |
489 |
< |
*/ |
490 |
< |
final void cancelIgnoringExceptions() { |
491 |
< |
try { |
492 |
< |
cancel(false); |
493 |
< |
} catch (Throwable ignore) { |
267 |
> |
setExceptionalCompletion(rex); |
268 |
> |
return; |
269 |
|
} |
270 |
< |
} |
496 |
< |
|
497 |
< |
/** |
498 |
< |
* Main implementation of helpJoin |
499 |
< |
*/ |
500 |
< |
private int busyJoin(ForkJoinWorkerThread w) { |
501 |
< |
int s; |
502 |
< |
ForkJoinTask<?> t; |
503 |
< |
while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null) |
504 |
< |
t.quietlyExec(); |
505 |
< |
return (s >= 0) ? awaitDone(w, false) : s; // block if no work |
270 |
> |
setCompletion(NORMAL); // must be outside try block |
271 |
|
} |
272 |
|
|
273 |
|
// public methods |
276 |
|
* Arranges to asynchronously execute this task. While it is not |
277 |
|
* necessarily enforced, it is a usage error to fork a task more |
278 |
|
* than once unless it has completed and been reinitialized. |
279 |
+ |
* Subsequent modifications to the state of this task or any data |
280 |
+ |
* it operates on are not necessarily consistently observable by |
281 |
+ |
* any thread other than the one executing it unless preceded by a |
282 |
+ |
* call to {@link #join} or related methods, or a call to {@link |
283 |
+ |
* #isDone} returning {@code true}. |
284 |
|
* |
285 |
|
* <p>This method may be invoked only from within {@code |
286 |
|
* ForkJoinTask} computations (as may be determined using method |
297 |
|
} |
298 |
|
|
299 |
|
/** |
300 |
< |
* Returns the result of the computation when it is ready. |
300 |
> |
* Returns the result of the computation when it {@link #isDone is done}. |
301 |
|
* This method differs from {@link #get()} in that |
302 |
|
* abnormal completion results in {@code RuntimeException} or |
303 |
|
* {@code Error}, not {@code ExecutionException}. |
305 |
|
* @return the computed result |
306 |
|
*/ |
307 |
|
public final V join() { |
308 |
< |
ForkJoinWorkerThread w = getWorker(); |
309 |
< |
if (w == null || status < 0 || !w.unpushTask(this) || !tryExec()) |
310 |
< |
reportException(awaitDone(w, true)); |
308 |
> |
quietlyJoin(); |
309 |
> |
Throwable ex; |
310 |
> |
if (status < NORMAL && (ex = getException()) != null) |
311 |
> |
UNSAFE.throwException(ex); |
312 |
|
return getRawResult(); |
313 |
|
} |
314 |
|
|
320 |
|
* @return the computed result |
321 |
|
*/ |
322 |
|
public final V invoke() { |
323 |
< |
if (status >= 0 && tryExec()) |
324 |
< |
return getRawResult(); |
325 |
< |
else |
326 |
< |
return join(); |
323 |
> |
quietlyInvoke(); |
324 |
> |
Throwable ex; |
325 |
> |
if (status < NORMAL && (ex = getException()) != null) |
326 |
> |
UNSAFE.throwException(ex); |
327 |
> |
return getRawResult(); |
328 |
|
} |
329 |
|
|
330 |
|
/** |
331 |
|
* Forks the given tasks, returning when {@code isDone} holds for |
332 |
|
* each task or an (unchecked) exception is encountered, in which |
333 |
< |
* case the exception is rethrown. If more than one task |
334 |
< |
* encounters an exception, then this method throws any one of |
335 |
< |
* these exceptions. The individual status of each task may be |
333 |
> |
* case the exception is rethrown. If either task encounters an |
334 |
> |
* exception, the other one may be, but is not guaranteed to be, |
335 |
> |
* cancelled. If both tasks throw an exception, then this method |
336 |
> |
* throws one of them. The individual status of each task may be |
337 |
|
* checked using {@link #getException()} and related methods. |
338 |
|
* |
339 |
|
* <p>This method may be invoked only from within {@code |
384 |
|
t.fork(); |
385 |
|
else { |
386 |
|
t.quietlyInvoke(); |
387 |
< |
if (ex == null) |
387 |
> |
if (ex == null && t.status < NORMAL) |
388 |
|
ex = t.getException(); |
389 |
|
} |
390 |
|
} |
395 |
|
t.cancel(false); |
396 |
|
else { |
397 |
|
t.quietlyJoin(); |
398 |
< |
if (ex == null) |
398 |
> |
if (ex == null && t.status < NORMAL) |
399 |
|
ex = t.getException(); |
400 |
|
} |
401 |
|
} |
402 |
|
} |
403 |
|
if (ex != null) |
404 |
< |
rethrowException(ex); |
404 |
> |
UNSAFE.throwException(ex); |
405 |
|
} |
406 |
|
|
407 |
|
/** |
446 |
|
t.fork(); |
447 |
|
else { |
448 |
|
t.quietlyInvoke(); |
449 |
< |
if (ex == null) |
449 |
> |
if (ex == null && t.status < NORMAL) |
450 |
|
ex = t.getException(); |
451 |
|
} |
452 |
|
} |
457 |
|
t.cancel(false); |
458 |
|
else { |
459 |
|
t.quietlyJoin(); |
460 |
< |
if (ex == null) |
460 |
> |
if (ex == null && t.status < NORMAL) |
461 |
|
ex = t.getException(); |
462 |
|
} |
463 |
|
} |
464 |
|
} |
465 |
|
if (ex != null) |
466 |
< |
rethrowException(ex); |
466 |
> |
UNSAFE.throwException(ex); |
467 |
|
return tasks; |
468 |
|
} |
469 |
|
|
493 |
|
*/ |
494 |
|
public boolean cancel(boolean mayInterruptIfRunning) { |
495 |
|
setCompletion(CANCELLED); |
496 |
< |
return (status & COMPLETION_MASK) == CANCELLED; |
496 |
> |
return status == CANCELLED; |
497 |
|
} |
498 |
|
|
499 |
|
/** |
500 |
< |
* Returns {@code true} if the computation performed by this task |
501 |
< |
* has completed (or has been cancelled). |
502 |
< |
* |
503 |
< |
* @return {@code true} if this computation has completed |
500 |
> |
* Cancels, ignoring any exceptions thrown by cancel. Used during |
501 |
> |
* worker and pool shutdown. Cancel is spec'ed not to throw any |
502 |
> |
* exceptions, but if it does anyway, we have no recourse during |
503 |
> |
* shutdown, so guard against this case. |
504 |
|
*/ |
505 |
< |
public final boolean isDone() { |
506 |
< |
return status < 0; |
505 |
> |
final void cancelIgnoringExceptions() { |
506 |
> |
try { |
507 |
> |
cancel(false); |
508 |
> |
} catch (Throwable ignore) { |
509 |
> |
} |
510 |
|
} |
511 |
|
|
512 |
|
/** |
513 |
< |
* Returns {@code true} if this task was cancelled. |
738 |
< |
* |
739 |
< |
* @return {@code true} if this task was cancelled |
513 |
> |
* Cancels ignoring exceptions if worker is terminating |
514 |
|
*/ |
515 |
+ |
final void cancelIfTerminating() { |
516 |
+ |
Thread t = Thread.currentThread(); |
517 |
+ |
if ((t instanceof ForkJoinWorkerThread) && |
518 |
+ |
((ForkJoinWorkerThread) t).isTerminating()) { |
519 |
+ |
try { |
520 |
+ |
cancel(false); |
521 |
+ |
} catch (Throwable ignore) { |
522 |
+ |
} |
523 |
+ |
} |
524 |
+ |
} |
525 |
+ |
|
526 |
+ |
public final boolean isDone() { |
527 |
+ |
return status < 0; |
528 |
+ |
} |
529 |
+ |
|
530 |
|
public final boolean isCancelled() { |
531 |
< |
return (status & COMPLETION_MASK) == CANCELLED; |
531 |
> |
return status == CANCELLED; |
532 |
|
} |
533 |
|
|
534 |
|
/** |
537 |
|
* @return {@code true} if this task threw an exception or was cancelled |
538 |
|
*/ |
539 |
|
public final boolean isCompletedAbnormally() { |
540 |
< |
return (status & COMPLETION_MASK) < NORMAL; |
540 |
> |
return status < NORMAL; |
541 |
|
} |
542 |
|
|
543 |
|
/** |
548 |
|
* exception and was not cancelled |
549 |
|
*/ |
550 |
|
public final boolean isCompletedNormally() { |
551 |
< |
return (status & COMPLETION_MASK) == NORMAL; |
763 |
< |
} |
764 |
< |
|
765 |
< |
/** |
766 |
< |
* Returns {@code true} if this task threw an exception. |
767 |
< |
* |
768 |
< |
* @return {@code true} if this task threw an exception |
769 |
< |
*/ |
770 |
< |
public final boolean isCompletedExceptionally() { |
771 |
< |
return (status & COMPLETION_MASK) == EXCEPTIONAL; |
551 |
> |
return status == NORMAL; |
552 |
|
} |
553 |
|
|
554 |
|
/** |
559 |
|
* @return the exception, or {@code null} if none |
560 |
|
*/ |
561 |
|
public final Throwable getException() { |
562 |
< |
int s = status & COMPLETION_MASK; |
563 |
< |
if (s >= NORMAL) |
564 |
< |
return null; |
565 |
< |
if (s == CANCELLED) |
786 |
< |
return new CancellationException(); |
787 |
< |
return exceptionMap.get(this); |
562 |
> |
int s = status; |
563 |
> |
return ((s >= NORMAL) ? null : |
564 |
> |
(s == CANCELLED) ? new CancellationException() : |
565 |
> |
exceptionMap.get(this)); |
566 |
|
} |
567 |
|
|
568 |
|
/** |
575 |
|
* overridable, but overridden versions must invoke {@code super} |
576 |
|
* implementation to maintain guarantees. |
577 |
|
* |
578 |
< |
* @param ex the exception to throw. If this exception is |
579 |
< |
* not a RuntimeException or Error, the actual exception thrown |
580 |
< |
* will be a RuntimeException with cause ex. |
578 |
> |
* @param ex the exception to throw. If this exception is not a |
579 |
> |
* {@code RuntimeException} or {@code Error}, the actual exception |
580 |
> |
* thrown will be a {@code RuntimeException} with cause {@code ex}. |
581 |
|
*/ |
582 |
|
public void completeExceptionally(Throwable ex) { |
583 |
< |
setDoneExceptionally((ex instanceof RuntimeException) || |
584 |
< |
(ex instanceof Error) ? ex : |
585 |
< |
new RuntimeException(ex)); |
583 |
> |
setExceptionalCompletion((ex instanceof RuntimeException) || |
584 |
> |
(ex instanceof Error) ? ex : |
585 |
> |
new RuntimeException(ex)); |
586 |
|
} |
587 |
|
|
588 |
|
/** |
601 |
|
try { |
602 |
|
setRawResult(value); |
603 |
|
} catch (Throwable rex) { |
604 |
< |
setDoneExceptionally(rex); |
604 |
> |
setExceptionalCompletion(rex); |
605 |
|
return; |
606 |
|
} |
607 |
< |
setNormalCompletion(); |
607 |
> |
setCompletion(NORMAL); |
608 |
|
} |
609 |
|
|
610 |
|
public final V get() throws InterruptedException, ExecutionException { |
611 |
< |
ForkJoinWorkerThread w = getWorker(); |
612 |
< |
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
613 |
< |
awaitDone(w, true); |
614 |
< |
return reportFutureResult(); |
611 |
> |
quietlyJoin(); |
612 |
> |
if (Thread.interrupted()) |
613 |
> |
throw new InterruptedException(); |
614 |
> |
int s = status; |
615 |
> |
if (s < NORMAL) { |
616 |
> |
Throwable ex; |
617 |
> |
if (s == CANCELLED) |
618 |
> |
throw new CancellationException(); |
619 |
> |
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
620 |
> |
throw new ExecutionException(ex); |
621 |
> |
} |
622 |
> |
return getRawResult(); |
623 |
|
} |
624 |
|
|
625 |
|
public final V get(long timeout, TimeUnit unit) |
626 |
|
throws InterruptedException, ExecutionException, TimeoutException { |
627 |
+ |
Thread t = Thread.currentThread(); |
628 |
+ |
ForkJoinPool pool; |
629 |
+ |
if (t instanceof ForkJoinWorkerThread) { |
630 |
+ |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
631 |
+ |
if (status >= 0 && w.unpushTask(this)) |
632 |
+ |
quietlyExec(); |
633 |
+ |
pool = w.pool; |
634 |
+ |
} |
635 |
+ |
else |
636 |
+ |
pool = null; |
637 |
+ |
/* |
638 |
+ |
* Timed wait loop intermixes cases for FJ (pool != null) and |
639 |
+ |
* non FJ threads. For FJ, decrement pool count but don't try |
640 |
+ |
* for replacement; increment count on completion. For non-FJ, |
641 |
+ |
* deal with interrupts. This is messy, but a little less so |
642 |
+ |
* than is splitting the FJ and nonFJ cases. |
643 |
+ |
*/ |
644 |
+ |
boolean interrupted = false; |
645 |
+ |
boolean dec = false; // true if pool count decremented |
646 |
|
long nanos = unit.toNanos(timeout); |
647 |
< |
ForkJoinWorkerThread w = getWorker(); |
648 |
< |
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
649 |
< |
awaitDone(w, nanos); |
650 |
< |
return reportTimedFutureResult(); |
651 |
< |
} |
652 |
< |
|
653 |
< |
/** |
654 |
< |
* Possibly executes other tasks until this task is ready, then |
655 |
< |
* returns the result of the computation. This method may be more |
656 |
< |
* efficient than {@code join}, but is only applicable when |
657 |
< |
* there are no potential dependencies between continuation of the |
658 |
< |
* current task and that of any other task that might be executed |
659 |
< |
* while helping. (This usually holds for pure divide-and-conquer |
660 |
< |
* tasks). |
661 |
< |
* |
662 |
< |
* <p>This method may be invoked only from within {@code |
663 |
< |
* ForkJoinTask} computations (as may be determined using method |
664 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
665 |
< |
* result in exceptions or errors, possibly including {@code |
666 |
< |
* ClassCastException}. |
667 |
< |
* |
668 |
< |
* @return the computed result |
669 |
< |
*/ |
670 |
< |
public final V helpJoin() { |
671 |
< |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread(); |
672 |
< |
if (status < 0 || !w.unpushTask(this) || !tryExec()) |
673 |
< |
reportException(busyJoin(w)); |
674 |
< |
return getRawResult(); |
675 |
< |
} |
676 |
< |
|
677 |
< |
/** |
678 |
< |
* Possibly executes other tasks until this task is ready. This |
679 |
< |
* method may be useful when processing collections of tasks when |
680 |
< |
* some have been cancelled or otherwise known to have aborted. |
681 |
< |
* |
682 |
< |
* <p>This method may be invoked only from within {@code |
683 |
< |
* ForkJoinTask} computations (as may be determined using method |
684 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
685 |
< |
* result in exceptions or errors, possibly including {@code |
686 |
< |
* ClassCastException}. |
687 |
< |
*/ |
688 |
< |
public final void quietlyHelpJoin() { |
689 |
< |
if (status >= 0) { |
690 |
< |
ForkJoinWorkerThread w = |
691 |
< |
(ForkJoinWorkerThread) Thread.currentThread(); |
692 |
< |
if (!w.unpushTask(this) || !tryQuietlyInvoke()) |
693 |
< |
busyJoin(w); |
647 |
> |
for (;;) { |
648 |
> |
if (Thread.interrupted() && pool == null) { |
649 |
> |
interrupted = true; |
650 |
> |
break; |
651 |
> |
} |
652 |
> |
int s = status; |
653 |
> |
if (s < 0) |
654 |
> |
break; |
655 |
> |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) { |
656 |
> |
long startTime = System.nanoTime(); |
657 |
> |
long nt; // wait time |
658 |
> |
while (status >= 0 && |
659 |
> |
(nt = nanos - (System.nanoTime() - startTime)) > 0) { |
660 |
> |
if (pool != null && !dec) |
661 |
> |
dec = pool.tryDecrementRunningCount(); |
662 |
> |
else { |
663 |
> |
long ms = nt / 1000000; |
664 |
> |
int ns = (int) (nt % 1000000); |
665 |
> |
try { |
666 |
> |
synchronized(this) { |
667 |
> |
if (status >= 0) |
668 |
> |
wait(ms, ns); |
669 |
> |
} |
670 |
> |
} catch (InterruptedException ie) { |
671 |
> |
if (pool != null) |
672 |
> |
cancelIfTerminating(); |
673 |
> |
else { |
674 |
> |
interrupted = true; |
675 |
> |
break; |
676 |
> |
} |
677 |
> |
} |
678 |
> |
} |
679 |
> |
} |
680 |
> |
break; |
681 |
> |
} |
682 |
> |
} |
683 |
> |
if (pool != null && dec) |
684 |
> |
pool.incrementRunningCount(); |
685 |
> |
if (interrupted) |
686 |
> |
throw new InterruptedException(); |
687 |
> |
int es = status; |
688 |
> |
if (es != NORMAL) { |
689 |
> |
Throwable ex; |
690 |
> |
if (es == CANCELLED) |
691 |
> |
throw new CancellationException(); |
692 |
> |
if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
693 |
> |
throw new ExecutionException(ex); |
694 |
> |
throw new TimeoutException(); |
695 |
|
} |
696 |
+ |
return getRawResult(); |
697 |
|
} |
698 |
|
|
699 |
|
/** |
700 |
< |
* Joins this task, without returning its result or throwing an |
700 |
> |
* Joins this task, without returning its result or throwing its |
701 |
|
* exception. This method may be useful when processing |
702 |
|
* collections of tasks when some have been cancelled or otherwise |
703 |
|
* known to have aborted. |
704 |
|
*/ |
705 |
|
public final void quietlyJoin() { |
706 |
< |
if (status >= 0) { |
707 |
< |
ForkJoinWorkerThread w = getWorker(); |
708 |
< |
if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke()) |
709 |
< |
awaitDone(w, true); |
706 |
> |
Thread t; |
707 |
> |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) { |
708 |
> |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
709 |
> |
if (status >= 0) { |
710 |
> |
if (w.unpushTask(this)) { |
711 |
> |
boolean completed; |
712 |
> |
try { |
713 |
> |
completed = exec(); |
714 |
> |
} catch (Throwable rex) { |
715 |
> |
setExceptionalCompletion(rex); |
716 |
> |
return; |
717 |
> |
} |
718 |
> |
if (completed) { |
719 |
> |
setCompletion(NORMAL); |
720 |
> |
return; |
721 |
> |
} |
722 |
> |
} |
723 |
> |
w.joinTask(this); |
724 |
> |
} |
725 |
|
} |
726 |
+ |
else |
727 |
+ |
externalAwaitDone(); |
728 |
|
} |
729 |
|
|
730 |
|
/** |
731 |
|
* Commences performing this task and awaits its completion if |
732 |
< |
* necessary, without returning its result or throwing an |
732 |
> |
* necessary, without returning its result or throwing its |
733 |
|
* exception. This method may be useful when processing |
734 |
|
* collections of tasks when some have been cancelled or otherwise |
735 |
|
* known to have aborted. |
736 |
|
*/ |
737 |
|
public final void quietlyInvoke() { |
738 |
< |
if (status >= 0 && !tryQuietlyInvoke()) |
739 |
< |
quietlyJoin(); |
738 |
> |
if (status >= 0) { |
739 |
> |
boolean completed; |
740 |
> |
try { |
741 |
> |
completed = exec(); |
742 |
> |
} catch (Throwable rex) { |
743 |
> |
setExceptionalCompletion(rex); |
744 |
> |
return; |
745 |
> |
} |
746 |
> |
if (completed) |
747 |
> |
setCompletion(NORMAL); |
748 |
> |
else |
749 |
> |
quietlyJoin(); |
750 |
> |
} |
751 |
|
} |
752 |
|
|
753 |
|
/** |
779 |
|
* pre-constructed trees of subtasks in loops. |
780 |
|
*/ |
781 |
|
public void reinitialize() { |
782 |
< |
if ((status & COMPLETION_MASK) == EXCEPTIONAL) |
782 |
> |
if (status == EXCEPTIONAL) |
783 |
|
exceptionMap.remove(this); |
784 |
|
status = 0; |
785 |
|
} |
1069 |
|
private static final long serialVersionUID = -7721805057305804111L; |
1070 |
|
|
1071 |
|
/** |
1072 |
< |
* Save the state to a stream. |
1072 |
> |
* Saves the state to a stream. |
1073 |
|
* |
1074 |
|
* @serialData the current run status and the exception thrown |
1075 |
|
* during execution, or {@code null} if none |
1082 |
|
} |
1083 |
|
|
1084 |
|
/** |
1085 |
< |
* Reconstitute the instance from a stream. |
1085 |
> |
* Reconstitutes the instance from a stream. |
1086 |
|
* |
1087 |
|
* @param s the stream |
1088 |
|
*/ |
1089 |
|
private void readObject(java.io.ObjectInputStream s) |
1090 |
|
throws java.io.IOException, ClassNotFoundException { |
1091 |
|
s.defaultReadObject(); |
1257 |
– |
status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts |
1258 |
– |
status |= EXTERNAL_SIGNAL; // conservatively set external signal |
1092 |
|
Object ex = s.readObject(); |
1093 |
|
if (ex != null) |
1094 |
< |
setDoneExceptionally((Throwable) ex); |
1094 |
> |
setExceptionalCompletion((Throwable) ex); |
1095 |
|
} |
1096 |
|
|
1097 |
|
// Unsafe mechanics |