9 |
|
import java.util.*; |
10 |
|
import java.util.concurrent.*; |
11 |
|
import java.util.concurrent.atomic.*; |
12 |
– |
import sun.misc.Unsafe; |
13 |
– |
import java.lang.reflect.*; |
12 |
|
|
13 |
|
/** |
14 |
< |
* Abstract base class for tasks that run within a ForkJoinPool. A |
15 |
< |
* ForkJoinTask is a thread-like entity that is much lighter weight |
16 |
< |
* than a normal thread. Huge numbers of tasks and subtasks may be |
17 |
< |
* hosted by a small number of actual threads in a ForkJoinPool, |
18 |
< |
* at the price of some usage limitations. |
14 |
> |
* Abstract base class for tasks that run within a {@link |
15 |
> |
* ForkJoinPool}. A ForkJoinTask is a thread-like entity that is much |
16 |
> |
* lighter weight than a normal thread. Huge numbers of tasks and |
17 |
> |
* subtasks may be hosted by a small number of actual threads in a |
18 |
> |
* ForkJoinPool, at the price of some usage limitations. |
19 |
|
* |
20 |
< |
* <p> ForkJoinTasks are forms of <tt>Futures</tt> supporting a |
21 |
< |
* limited range of use. The "lightness" of ForkJoinTasks is due to a |
22 |
< |
* set of restrictions (that are only partially statically |
23 |
< |
* enforceable) reflecting their intended use as computational tasks |
24 |
< |
* calculating pure functions or operating on purely isolated objects. |
25 |
< |
* The primary coordination mechanisms supported for ForkJoinTasks are |
26 |
< |
* <tt>fork</tt>, that arranges asynchronous execution, and |
27 |
< |
* <tt>join</tt>, that doesn't proceed until the task's result has |
28 |
< |
* been computed. (Cancellation is also supported). The computation |
29 |
< |
* defined in the <tt>compute</tt> method should avoid |
30 |
< |
* <tt>synchronized</tt> methods or blocks, and should minimize |
31 |
< |
* blocking synchronization apart from joining other tasks or using |
20 |
> |
* <p> A "main" ForkJoinTask begins execution when submitted to a |
21 |
> |
* {@link ForkJoinPool}. Once started, it will usually in turn start |
22 |
> |
* other subtasks. As indicated by the name of this class, many |
23 |
> |
* programs using ForkJoinTasks employ only methods {@code fork} |
24 |
> |
* and {@code join}, or derivatives such as |
25 |
> |
* {@code invokeAll}. However, this class also provides a number |
26 |
> |
* of other methods that can come into play in advanced usages, as |
27 |
> |
* well as extension mechanics that allow support of new forms of |
28 |
> |
* fork/join processing. |
29 |
> |
* |
30 |
> |
* <p>A ForkJoinTask is a lightweight form of {@link Future}. The |
31 |
> |
* efficiency of ForkJoinTasks stems from a set of restrictions (that |
32 |
> |
* are only partially statically enforceable) reflecting their |
33 |
> |
* intended use as computational tasks calculating pure functions or |
34 |
> |
* operating on purely isolated objects. The primary coordination |
35 |
> |
* mechanisms are {@link #fork}, that arranges asynchronous execution, |
36 |
> |
* and {@link #join}, that doesn't proceed until the task's result has |
37 |
> |
* been computed. Computations should avoid {@code synchronized} |
38 |
> |
* methods or blocks, and should minimize other blocking |
39 |
> |
* synchronization apart from joining other tasks or using |
40 |
|
* synchronizers such as Phasers that are advertised to cooperate with |
41 |
|
* fork/join scheduling. Tasks should also not perform blocking IO, |
42 |
|
* and should ideally access variables that are completely independent |
44 |
|
* restrictions, for example using shared output streams, may be |
45 |
|
* tolerable in practice, but frequent use may result in poor |
46 |
|
* performance, and the potential to indefinitely stall if the number |
47 |
< |
* of threads not waiting for external synchronization becomes |
48 |
< |
* exhausted. This usage restriction is in part enforced by not |
49 |
< |
* permitting checked exceptions such as IOExceptions to be |
50 |
< |
* thrown. However, computations may still encounter unchecked |
47 |
> |
* of threads not waiting for IO or other external synchronization |
48 |
> |
* becomes exhausted. This usage restriction is in part enforced by |
49 |
> |
* not permitting checked exceptions such as {@code IOExceptions} |
50 |
> |
* to be thrown. However, computations may still encounter unchecked |
51 |
|
* exceptions, that are rethrown to callers attempting join |
52 |
|
* them. These exceptions may additionally include |
53 |
|
* RejectedExecutionExceptions stemming from internal resource |
54 |
|
* exhaustion such as failure to allocate internal task queues. |
55 |
|
* |
56 |
< |
* <p> The <tt>ForkJoinTask</tt> class is not usually directly |
57 |
< |
* subclassed. Instead, you subclass one of the abstract classes that |
58 |
< |
* support different styles of fork/join processing. Normally, a |
59 |
< |
* concrete ForkJoinTask subclass declares fields comprising its |
60 |
< |
* parameters, established in a constructor, and then defines a |
61 |
< |
* <tt>compute</tt> method that somehow uses the control methods |
62 |
< |
* supplied by this base class. While these methods have |
63 |
< |
* <tt>public</tt> access, some of them may only be called from within |
64 |
< |
* other ForkJoinTasks. Attempts to invoke them in other contexts |
65 |
< |
* result in exceptions or errors including ClassCastException. The |
66 |
< |
* only way to invoke a "main" driver task is to submit it to a |
67 |
< |
* ForkJoinPool. Once started, this will usually in turn start other |
68 |
< |
* subtasks. |
56 |
> |
* <p>The primary method for awaiting completion and extracting |
57 |
> |
* results of a task is {@link #join}, but there are several variants: |
58 |
> |
* The {@link Future#get} methods support interruptible and/or timed |
59 |
> |
* waits for completion and report results using {@code Future} |
60 |
> |
* conventions. Method {@link #helpJoin} enables callers to actively |
61 |
> |
* execute other tasks while awaiting joins, which is sometimes more |
62 |
> |
* efficient but only applies when all subtasks are known to be |
63 |
> |
* strictly tree-structured. Method {@link #invoke} is semantically |
64 |
> |
* equivalent to {@code fork(); join()} but always attempts to |
65 |
> |
* begin execution in the current thread. The "<em>quiet</em>" forms |
66 |
> |
* of these methods do not extract results or report exceptions. These |
67 |
> |
* may be useful when a set of tasks are being executed, and you need |
68 |
> |
* to delay processing of results or exceptions until all complete. |
69 |
> |
* Method {@code invokeAll} (available in multiple versions) |
70 |
> |
* performs the most common form of parallel invocation: forking a set |
71 |
> |
* of tasks and joining them all. |
72 |
> |
* |
73 |
> |
* <p> The ForkJoinTask class is not usually directly subclassed. |
74 |
> |
* Instead, you subclass one of the abstract classes that support a |
75 |
> |
* particular style of fork/join processing. Normally, a concrete |
76 |
> |
* ForkJoinTask subclass declares fields comprising its parameters, |
77 |
> |
* established in a constructor, and then defines a {@code compute} |
78 |
> |
* method that somehow uses the control methods supplied by this base |
79 |
> |
* class. While these methods have {@code public} access (to allow |
80 |
> |
* instances of different task subclasses to call each others |
81 |
> |
* methods), some of them may only be called from within other |
82 |
> |
* ForkJoinTasks (as may be determined using method {@link |
83 |
> |
* #inForkJoinPool}). Attempts to invoke them in other contexts |
84 |
> |
* result in exceptions or errors, possibly including |
85 |
> |
* ClassCastException. |
86 |
|
* |
87 |
< |
* <p>Most base support methods are <tt>final</tt> because their |
87 |
> |
* <p>Most base support methods are {@code final} because their |
88 |
|
* implementations are intrinsically tied to the underlying |
89 |
|
* lightweight task scheduling framework, and so cannot be overridden. |
90 |
|
* Developers creating new basic styles of fork/join processing should |
91 |
< |
* minimally implement protected methods <tt>exec</tt>, |
92 |
< |
* <tt>setRawResult</tt>, and <tt>getRawResult</tt>, while also |
93 |
< |
* introducing an abstract computational method that can be |
94 |
< |
* implemented in its subclasses. To support such extensions, |
95 |
< |
* instances of ForkJoinTasks maintain an atomically updated |
96 |
< |
* <tt>short</tt> representing user-defined control state. Control |
74 |
< |
* state is guaranteed initially to be zero, and to be negative upon |
75 |
< |
* completion, but may otherwise be used for any other control |
76 |
< |
* purposes, such as maintaining join counts. The {@link |
77 |
< |
* ForkJoinWorkerThread} class supports additional inspection and |
78 |
< |
* tuning methods that can be useful when developing extensions. |
91 |
> |
* minimally implement {@code protected} methods |
92 |
> |
* {@code exec}, {@code setRawResult}, and |
93 |
> |
* {@code getRawResult}, while also introducing an abstract |
94 |
> |
* computational method that can be implemented in its subclasses, |
95 |
> |
* possibly relying on other {@code protected} methods provided |
96 |
> |
* by this class. |
97 |
|
* |
98 |
|
* <p>ForkJoinTasks should perform relatively small amounts of |
99 |
< |
* computations, othewise splitting into smaller tasks. As a very |
99 |
> |
* computations, otherwise splitting into smaller tasks. As a very |
100 |
|
* rough rule of thumb, a task should perform more than 100 and less |
101 |
|
* than 10000 basic computational steps. If tasks are too big, then |
102 |
< |
* parellelism cannot improve throughput. If too small, then memory |
102 |
> |
* parallelism cannot improve throughput. If too small, then memory |
103 |
|
* and internal task maintenance overhead may overwhelm processing. |
104 |
|
* |
105 |
< |
* <p>ForkJoinTasks are <tt>Serializable</tt>, which enables them to |
106 |
< |
* be used in extensions such as remote execution frameworks. However, |
107 |
< |
* it is in general safe to serialize tasks only before or after, but |
105 |
> |
* <p>ForkJoinTasks are {@code Serializable}, which enables them |
106 |
> |
* to be used in extensions such as remote execution frameworks. It is |
107 |
> |
* in general sensible to serialize tasks only before or after, but |
108 |
|
* not during execution. Serialization is not relied on during |
109 |
|
* execution itself. |
110 |
+ |
* |
111 |
+ |
* @since 1.7 |
112 |
+ |
* @author Doug Lea |
113 |
|
*/ |
114 |
|
public abstract class ForkJoinTask<V> implements Future<V>, Serializable { |
115 |
+ |
|
116 |
|
/** |
117 |
< |
* Status field holding all run status. We pack this into a single |
118 |
< |
* int both to minimize footprint overhead and to ensure atomicity |
119 |
< |
* (updates are via CAS). |
98 |
< |
* |
99 |
< |
* Status is initially zero, and takes on nonnegative values until |
117 |
> |
* Run control status bits packed into a single int to minimize |
118 |
> |
* footprint and to ensure atomicity (via CAS). Status is |
119 |
> |
* initially zero, and takes on nonnegative values until |
120 |
|
* completed, upon which status holds COMPLETED. CANCELLED, or |
121 |
|
* EXCEPTIONAL, which use the top 3 bits. Tasks undergoing |
122 |
|
* blocking waits by other threads have SIGNAL_MASK bits set -- |
131 |
|
* currently unused. Also value 0x80000000 is available as spare |
132 |
|
* completion value. |
133 |
|
*/ |
134 |
< |
volatile int status; // accessed directy by pool and workers |
134 |
> |
volatile int status; // accessed directly by pool and workers |
135 |
|
|
136 |
|
static final int COMPLETION_MASK = 0xe0000000; |
137 |
|
static final int NORMAL = 0xe0000000; // == mask |
144 |
|
/** |
145 |
|
* Table of exceptions thrown by tasks, to enable reporting by |
146 |
|
* callers. Because exceptions are rare, we don't directly keep |
147 |
< |
* them with task objects, but instead us a weak ref table. Note |
147 |
> |
* them with task objects, but instead use a weak ref table. Note |
148 |
|
* that cancellation exceptions don't appear in the table, but are |
149 |
|
* instead recorded as status values. |
150 |
< |
* Todo: Use ConcurrentReferenceHashMap |
150 |
> |
* TODO: Use ConcurrentReferenceHashMap |
151 |
|
*/ |
152 |
|
static final Map<ForkJoinTask<?>, Throwable> exceptionMap = |
153 |
|
Collections.synchronizedMap |
156 |
|
// within-package utilities |
157 |
|
|
158 |
|
/** |
159 |
< |
* Get current worker thread, or null if not a worker thread |
159 |
> |
* Gets current worker thread, or null if not a worker thread. |
160 |
|
*/ |
161 |
|
static ForkJoinWorkerThread getWorker() { |
162 |
|
Thread t = Thread.currentThread(); |
163 |
< |
return ((t instanceof ForkJoinWorkerThread)? |
164 |
< |
(ForkJoinWorkerThread)t : null); |
145 |
< |
} |
146 |
< |
|
147 |
< |
/** |
148 |
< |
* Get pool of current worker thread, or null if not a worker thread |
149 |
< |
*/ |
150 |
< |
static ForkJoinPool getWorkerPool() { |
151 |
< |
Thread t = Thread.currentThread(); |
152 |
< |
return ((t instanceof ForkJoinWorkerThread)? |
153 |
< |
((ForkJoinWorkerThread)t).pool : null); |
163 |
> |
return ((t instanceof ForkJoinWorkerThread) ? |
164 |
> |
(ForkJoinWorkerThread) t : null); |
165 |
|
} |
166 |
|
|
167 |
|
final boolean casStatus(int cmp, int val) { |
168 |
< |
return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val); |
168 |
> |
return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val); |
169 |
|
} |
170 |
|
|
171 |
|
/** |
173 |
|
*/ |
174 |
|
static void rethrowException(Throwable ex) { |
175 |
|
if (ex != null) |
176 |
< |
_unsafe.throwException(ex); |
176 |
> |
UNSAFE.throwException(ex); |
177 |
|
} |
178 |
|
|
179 |
|
// Setting completion status |
180 |
|
|
181 |
|
/** |
182 |
< |
* Mark completion and wake up threads waiting to join this task. |
182 |
> |
* Marks completion and wakes up threads waiting to join this task. |
183 |
> |
* |
184 |
|
* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
185 |
|
*/ |
186 |
|
final void setCompletion(int completion) { |
187 |
< |
ForkJoinPool pool = getWorkerPool(); |
187 |
> |
ForkJoinPool pool = getPool(); |
188 |
|
if (pool != null) { |
189 |
|
int s; // Clear signal bits while setting completion status |
190 |
< |
do;while ((s = status) >= 0 && !casStatus(s, completion)); |
190 |
> |
do {} while ((s = status) >= 0 && !casStatus(s, completion)); |
191 |
|
|
192 |
|
if ((s & SIGNAL_MASK) != 0) { |
193 |
|
if ((s &= INTERNAL_SIGNAL_MASK) != 0) |
194 |
|
pool.updateRunningCount(s); |
195 |
< |
synchronized(this) { notifyAll(); } |
195 |
> |
synchronized (this) { notifyAll(); } |
196 |
|
} |
197 |
|
} |
198 |
|
else |
205 |
|
*/ |
206 |
|
private void externallySetCompletion(int completion) { |
207 |
|
int s; |
208 |
< |
do;while ((s = status) >= 0 && |
209 |
< |
!casStatus(s, (s & SIGNAL_MASK) | completion)); |
210 |
< |
synchronized(this) { notifyAll(); } |
208 |
> |
do {} while ((s = status) >= 0 && |
209 |
> |
!casStatus(s, (s & SIGNAL_MASK) | completion)); |
210 |
> |
synchronized (this) { notifyAll(); } |
211 |
|
} |
212 |
|
|
213 |
|
/** |
214 |
< |
* Sets status to indicate normal completion |
214 |
> |
* Sets status to indicate normal completion. |
215 |
|
*/ |
216 |
|
final void setNormalCompletion() { |
217 |
|
// Try typical fast case -- single CAS, no signal, not already done. |
218 |
|
// Manually expand casStatus to improve chances of inlining it |
219 |
< |
if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL)) |
219 |
> |
if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL)) |
220 |
|
setCompletion(NORMAL); |
221 |
|
} |
222 |
|
|
223 |
|
// internal waiting and notification |
224 |
|
|
225 |
|
/** |
226 |
< |
* Performs the actual monitor wait for awaitDone |
226 |
> |
* Performs the actual monitor wait for awaitDone. |
227 |
|
*/ |
228 |
|
private void doAwaitDone() { |
229 |
|
// Minimize lock bias and in/de-flation effects by maximizing |
230 |
|
// chances of waiting inside sync |
231 |
|
try { |
232 |
|
while (status >= 0) |
233 |
< |
synchronized(this) { if (status >= 0) wait(); } |
233 |
> |
synchronized (this) { if (status >= 0) wait(); } |
234 |
|
} catch (InterruptedException ie) { |
235 |
|
onInterruptedWait(); |
236 |
|
} |
237 |
|
} |
238 |
|
|
239 |
|
/** |
240 |
< |
* Performs the actual monitor wait for awaitDone |
240 |
> |
* Performs the actual timed monitor wait for awaitDone. |
241 |
|
*/ |
242 |
|
private void doAwaitDone(long startTime, long nanos) { |
243 |
< |
synchronized(this) { |
243 |
> |
synchronized (this) { |
244 |
|
try { |
245 |
|
while (status >= 0) { |
246 |
|
long nt = nanos - System.nanoTime() - startTime; |
247 |
|
if (nt <= 0) |
248 |
|
break; |
249 |
< |
wait(nt / 1000000, (int)(nt % 1000000)); |
249 |
> |
wait(nt / 1000000, (int) (nt % 1000000)); |
250 |
|
} |
251 |
|
} catch (InterruptedException ie) { |
252 |
|
onInterruptedWait(); |
259 |
|
/** |
260 |
|
* Sets status to indicate there is joiner, then waits for join, |
261 |
|
* surrounded with pool notifications. |
262 |
+ |
* |
263 |
|
* @return status upon exit |
264 |
|
*/ |
265 |
< |
final int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) { |
266 |
< |
ForkJoinPool pool = w == null? null : w.pool; |
265 |
> |
private int awaitDone(ForkJoinWorkerThread w, |
266 |
> |
boolean maintainParallelism) { |
267 |
> |
ForkJoinPool pool = (w == null) ? null : w.pool; |
268 |
|
int s; |
269 |
|
while ((s = status) >= 0) { |
270 |
< |
if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) { |
270 |
> |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
271 |
|
if (pool == null || !pool.preJoin(this, maintainParallelism)) |
272 |
|
doAwaitDone(); |
273 |
|
if (((s = status) & INTERNAL_SIGNAL_MASK) != 0) |
280 |
|
|
281 |
|
/** |
282 |
|
* Timed version of awaitDone |
283 |
+ |
* |
284 |
|
* @return status upon exit |
285 |
|
*/ |
286 |
< |
final int awaitDone(ForkJoinWorkerThread w, long nanos) { |
287 |
< |
ForkJoinPool pool = w == null? null : w.pool; |
286 |
> |
private int awaitDone(ForkJoinWorkerThread w, long nanos) { |
287 |
> |
ForkJoinPool pool = (w == null) ? null : w.pool; |
288 |
|
int s; |
289 |
|
while ((s = status) >= 0) { |
290 |
< |
if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) { |
290 |
> |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
291 |
|
long startTime = System.nanoTime(); |
292 |
|
if (pool == null || !pool.preJoin(this, false)) |
293 |
|
doAwaitDone(startTime, nanos); |
304 |
|
} |
305 |
|
|
306 |
|
/** |
307 |
< |
* Notify pool that thread is unblocked. Called by signalled |
307 |
> |
* Notifies pool that thread is unblocked. Called by signalled |
308 |
|
* threads when woken by non-FJ threads (which is atypical). |
309 |
|
*/ |
310 |
|
private void adjustPoolCountsOnUnblock(ForkJoinPool pool) { |
311 |
|
int s; |
312 |
< |
do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK)); |
312 |
> |
do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK)); |
313 |
|
if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0) |
314 |
|
pool.updateRunningCount(s); |
315 |
|
} |
316 |
|
|
317 |
|
/** |
318 |
< |
* Notify pool to adjust counts on cancelled or timed out wait |
318 |
> |
* Notifies pool to adjust counts on cancelled or timed out wait. |
319 |
|
*/ |
320 |
|
private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) { |
321 |
|
if (pool != null) { |
329 |
|
} |
330 |
|
} |
331 |
|
|
332 |
+ |
/** |
333 |
+ |
* Handles interruptions during waits. |
334 |
+ |
*/ |
335 |
|
private void onInterruptedWait() { |
336 |
< |
Thread t = Thread.currentThread(); |
337 |
< |
if (t instanceof ForkJoinWorkerThread) { |
338 |
< |
ForkJoinWorkerThread w = (ForkJoinWorkerThread)t; |
339 |
< |
if (w.isTerminating()) |
340 |
< |
cancelIgnoreExceptions(); |
341 |
< |
} |
324 |
< |
else { // re-interrupt |
325 |
< |
try { |
326 |
< |
t.interrupt(); |
327 |
< |
} catch (SecurityException ignore) { |
328 |
< |
} |
329 |
< |
} |
336 |
> |
ForkJoinWorkerThread w = getWorker(); |
337 |
> |
if (w == null) |
338 |
> |
Thread.currentThread().interrupt(); // re-interrupt |
339 |
> |
else if (w.isTerminating()) |
340 |
> |
cancelIgnoringExceptions(); |
341 |
> |
// else if FJworker, ignore interrupt |
342 |
|
} |
343 |
|
|
344 |
|
// Recording and reporting exceptions |
349 |
|
} |
350 |
|
|
351 |
|
/** |
352 |
< |
* Throws the exception associated with status s; |
352 |
> |
* Throws the exception associated with status s. |
353 |
> |
* |
354 |
|
* @throws the exception |
355 |
|
*/ |
356 |
|
private void reportException(int s) { |
363 |
|
} |
364 |
|
|
365 |
|
/** |
366 |
< |
* Returns result or throws exception using j.u.c.Future conventions |
367 |
< |
* Only call when isDone known to be true. |
366 |
> |
* Returns result or throws exception using j.u.c.Future conventions. |
367 |
> |
* Only call when {@code isDone} known to be true. |
368 |
|
*/ |
369 |
|
private V reportFutureResult() |
370 |
|
throws ExecutionException, InterruptedException { |
383 |
|
|
384 |
|
/** |
385 |
|
* Returns result or throws exception using j.u.c.Future conventions |
386 |
< |
* with timeouts |
386 |
> |
* with timeouts. |
387 |
|
*/ |
388 |
|
private V reportTimedFutureResult() |
389 |
|
throws InterruptedException, ExecutionException, TimeoutException { |
404 |
|
|
405 |
|
/** |
406 |
|
* Calls exec, recording completion, and rethrowing exception if |
407 |
< |
* encountered. Caller should normally check status before calling |
407 |
> |
* encountered. Caller should normally check status before calling. |
408 |
> |
* |
409 |
|
* @return true if completed normally |
410 |
|
*/ |
411 |
|
private boolean tryExec() { |
423 |
|
|
424 |
|
/** |
425 |
|
* Main execution method used by worker threads. Invokes |
426 |
< |
* base computation unless already complete |
426 |
> |
* base computation unless already complete. |
427 |
|
*/ |
428 |
|
final void quietlyExec() { |
429 |
|
if (status >= 0) { |
430 |
|
try { |
431 |
|
if (!exec()) |
432 |
|
return; |
433 |
< |
} catch(Throwable rex) { |
433 |
> |
} catch (Throwable rex) { |
434 |
|
setDoneExceptionally(rex); |
435 |
|
return; |
436 |
|
} |
439 |
|
} |
440 |
|
|
441 |
|
/** |
442 |
< |
* Calls exec, recording but not rethrowing exception |
443 |
< |
* Caller should normally check status before calling |
442 |
> |
* Calls exec(), recording but not rethrowing exception. |
443 |
> |
* Caller should normally check status before calling. |
444 |
> |
* |
445 |
|
* @return true if completed normally |
446 |
|
*/ |
447 |
|
private boolean tryQuietlyInvoke() { |
457 |
|
} |
458 |
|
|
459 |
|
/** |
460 |
< |
* Cancel, ignoring any exceptions it throws |
460 |
> |
* Cancels, ignoring any exceptions it throws. |
461 |
|
*/ |
462 |
< |
final void cancelIgnoreExceptions() { |
462 |
> |
final void cancelIgnoringExceptions() { |
463 |
|
try { |
464 |
|
cancel(false); |
465 |
< |
} catch(Throwable ignore) { |
465 |
> |
} catch (Throwable ignore) { |
466 |
|
} |
467 |
|
} |
468 |
|
|
469 |
+ |
/** |
470 |
+ |
* Main implementation of helpJoin |
471 |
+ |
*/ |
472 |
+ |
private int busyJoin(ForkJoinWorkerThread w) { |
473 |
+ |
int s; |
474 |
+ |
ForkJoinTask<?> t; |
475 |
+ |
while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null) |
476 |
+ |
t.quietlyExec(); |
477 |
+ |
return (s >= 0) ? awaitDone(w, false) : s; // block if no work |
478 |
+ |
} |
479 |
+ |
|
480 |
|
// public methods |
481 |
|
|
482 |
|
/** |
483 |
|
* Arranges to asynchronously execute this task. While it is not |
484 |
|
* necessarily enforced, it is a usage error to fork a task more |
485 |
|
* than once unless it has completed and been reinitialized. This |
486 |
< |
* method may be invoked only from within other ForkJoinTask |
487 |
< |
* computations. Attempts to invoke in other contexts result in |
488 |
< |
* exceptions or errors including ClassCastException. |
486 |
> |
* method may be invoked only from within ForkJoinTask |
487 |
> |
* computations (as may be determined using method {@link |
488 |
> |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
489 |
> |
* in exceptions or errors, possibly including ClassCastException. |
490 |
|
*/ |
491 |
|
public final void fork() { |
492 |
< |
((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this); |
492 |
> |
((ForkJoinWorkerThread) Thread.currentThread()) |
493 |
> |
.pushTask(this); |
494 |
|
} |
495 |
|
|
496 |
|
/** |
497 |
|
* Returns the result of the computation when it is ready. |
498 |
< |
* This method differs from <tt>get</tt> in that abnormal |
498 |
> |
* This method differs from {@code get} in that abnormal |
499 |
|
* completion results in RuntimeExceptions or Errors, not |
500 |
|
* ExecutionExceptions. |
501 |
|
* |
508 |
|
return getRawResult(); |
509 |
|
} |
510 |
|
|
483 |
– |
public final V get() throws InterruptedException, ExecutionException { |
484 |
– |
ForkJoinWorkerThread w = getWorker(); |
485 |
– |
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
486 |
– |
awaitDone(w, true); |
487 |
– |
return reportFutureResult(); |
488 |
– |
} |
489 |
– |
|
490 |
– |
public final V get(long timeout, TimeUnit unit) |
491 |
– |
throws InterruptedException, ExecutionException, TimeoutException { |
492 |
– |
ForkJoinWorkerThread w = getWorker(); |
493 |
– |
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
494 |
– |
awaitDone(w, unit.toNanos(timeout)); |
495 |
– |
return reportTimedFutureResult(); |
496 |
– |
} |
497 |
– |
|
511 |
|
/** |
512 |
< |
* Possibly executes other tasks until this task is ready, then |
513 |
< |
* returns the result of the computation. This method may be more |
514 |
< |
* efficient than <tt>join</tt>, but is only applicable when there |
502 |
< |
* are no potemtial dependencies between continuation of the |
503 |
< |
* current task and that of any other task that might be executed |
504 |
< |
* while helping. (This usually holds for pure divide-and-conquer |
505 |
< |
* tasks). |
506 |
< |
* @return the computed result |
507 |
< |
*/ |
508 |
< |
public final V helpJoin() { |
509 |
< |
ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread()); |
510 |
< |
if (status < 0 || !w.unpushTask(this) || !tryExec()) |
511 |
< |
reportException(w.helpJoinTask(this)); |
512 |
< |
return getRawResult(); |
513 |
< |
} |
514 |
< |
|
515 |
< |
/** |
516 |
< |
* Performs this task, awaits its completion if necessary, and |
517 |
< |
* return its result. |
512 |
> |
* Commences performing this task, awaits its completion if |
513 |
> |
* necessary, and return its result. |
514 |
> |
* |
515 |
|
* @throws Throwable (a RuntimeException, Error, or unchecked |
516 |
< |
* exception) if the underlying computation did so. |
516 |
> |
* exception) if the underlying computation did so |
517 |
|
* @return the computed result |
518 |
|
*/ |
519 |
|
public final V invoke() { |
524 |
|
} |
525 |
|
|
526 |
|
/** |
527 |
< |
* Joins this task, without returning its result or throwing an |
528 |
< |
* exception. This method may be useful when processing |
529 |
< |
* collections of tasks when some have been cancelled or otherwise |
530 |
< |
* known to have aborted. |
527 |
> |
* Forks both tasks, returning when {@code isDone} holds for |
528 |
> |
* both of them or an exception is encountered. This method may be |
529 |
> |
* invoked only from within ForkJoinTask computations (as may be |
530 |
> |
* determined using method {@link #inForkJoinPool}). Attempts to |
531 |
> |
* invoke in other contexts result in exceptions or errors, |
532 |
> |
* possibly including ClassCastException. |
533 |
> |
* |
534 |
> |
* @param t1 one task |
535 |
> |
* @param t2 the other task |
536 |
> |
* @throws NullPointerException if t1 or t2 are null |
537 |
> |
* @throws RuntimeException or Error if either task did so |
538 |
|
*/ |
539 |
< |
public final void quietlyJoin() { |
540 |
< |
if (status >= 0) { |
541 |
< |
ForkJoinWorkerThread w = getWorker(); |
542 |
< |
if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke()) |
539 |
< |
awaitDone(w, true); |
540 |
< |
} |
539 |
> |
public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) { |
540 |
> |
t2.fork(); |
541 |
> |
t1.invoke(); |
542 |
> |
t2.join(); |
543 |
|
} |
544 |
|
|
545 |
|
/** |
546 |
< |
* Possibly executes other tasks until this task is ready. |
546 |
> |
* Forks the given tasks, returning when {@code isDone} holds |
547 |
> |
* for all of them. If any task encounters an exception, others |
548 |
> |
* may be cancelled. This method may be invoked only from within |
549 |
> |
* ForkJoinTask computations (as may be determined using method |
550 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
551 |
> |
* result in exceptions or errors, possibly including |
552 |
> |
* ClassCastException. |
553 |
> |
* |
554 |
> |
* @param tasks the array of tasks |
555 |
> |
* @throws NullPointerException if tasks or any element are null |
556 |
> |
* @throws RuntimeException or Error if any task did so |
557 |
|
*/ |
558 |
< |
public final void quietlyHelpJoin() { |
559 |
< |
if (status >= 0) { |
560 |
< |
ForkJoinWorkerThread w = |
561 |
< |
(ForkJoinWorkerThread)(Thread.currentThread()); |
562 |
< |
if (!w.unpushTask(this) || !tryQuietlyInvoke()) |
563 |
< |
w.helpJoinTask(this); |
558 |
> |
public static void invokeAll(ForkJoinTask<?>... tasks) { |
559 |
> |
Throwable ex = null; |
560 |
> |
int last = tasks.length - 1; |
561 |
> |
for (int i = last; i >= 0; --i) { |
562 |
> |
ForkJoinTask<?> t = tasks[i]; |
563 |
> |
if (t == null) { |
564 |
> |
if (ex == null) |
565 |
> |
ex = new NullPointerException(); |
566 |
> |
} |
567 |
> |
else if (i != 0) |
568 |
> |
t.fork(); |
569 |
> |
else { |
570 |
> |
t.quietlyInvoke(); |
571 |
> |
if (ex == null) |
572 |
> |
ex = t.getException(); |
573 |
> |
} |
574 |
|
} |
575 |
+ |
for (int i = 1; i <= last; ++i) { |
576 |
+ |
ForkJoinTask<?> t = tasks[i]; |
577 |
+ |
if (t != null) { |
578 |
+ |
if (ex != null) |
579 |
+ |
t.cancel(false); |
580 |
+ |
else { |
581 |
+ |
t.quietlyJoin(); |
582 |
+ |
if (ex == null) |
583 |
+ |
ex = t.getException(); |
584 |
+ |
} |
585 |
+ |
} |
586 |
+ |
} |
587 |
+ |
if (ex != null) |
588 |
+ |
rethrowException(ex); |
589 |
|
} |
590 |
|
|
591 |
|
/** |
592 |
< |
* Performs this task and awaits its completion if necessary, |
593 |
< |
* without returning its result or throwing an exception. This |
594 |
< |
* method may be useful when processing collections of tasks when |
595 |
< |
* some have been cancelled or otherwise known to have aborted. |
592 |
> |
* Forks all tasks in the collection, returning when |
593 |
> |
* {@code isDone} holds for all of them. If any task |
594 |
> |
* encounters an exception, others may be cancelled. This method |
595 |
> |
* may be invoked only from within ForkJoinTask computations (as |
596 |
> |
* may be determined using method {@link |
597 |
> |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
598 |
> |
* in exceptions or errors, possibly including ClassCastException. |
599 |
> |
* |
600 |
> |
* @param tasks the collection of tasks |
601 |
> |
* @throws NullPointerException if tasks or any element are null |
602 |
> |
* @throws RuntimeException or Error if any task did so |
603 |
|
*/ |
604 |
< |
public final void quietlyInvoke() { |
605 |
< |
if (status >= 0 && !tryQuietlyInvoke()) |
606 |
< |
quietlyJoin(); |
604 |
> |
public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) { |
605 |
> |
if (!(tasks instanceof List<?>)) { |
606 |
> |
invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()])); |
607 |
> |
return; |
608 |
> |
} |
609 |
> |
@SuppressWarnings("unchecked") |
610 |
> |
List<? extends ForkJoinTask<?>> ts = |
611 |
> |
(List<? extends ForkJoinTask<?>>) tasks; |
612 |
> |
Throwable ex = null; |
613 |
> |
int last = ts.size() - 1; |
614 |
> |
for (int i = last; i >= 0; --i) { |
615 |
> |
ForkJoinTask<?> t = ts.get(i); |
616 |
> |
if (t == null) { |
617 |
> |
if (ex == null) |
618 |
> |
ex = new NullPointerException(); |
619 |
> |
} |
620 |
> |
else if (i != 0) |
621 |
> |
t.fork(); |
622 |
> |
else { |
623 |
> |
t.quietlyInvoke(); |
624 |
> |
if (ex == null) |
625 |
> |
ex = t.getException(); |
626 |
> |
} |
627 |
> |
} |
628 |
> |
for (int i = 1; i <= last; ++i) { |
629 |
> |
ForkJoinTask<?> t = ts.get(i); |
630 |
> |
if (t != null) { |
631 |
> |
if (ex != null) |
632 |
> |
t.cancel(false); |
633 |
> |
else { |
634 |
> |
t.quietlyJoin(); |
635 |
> |
if (ex == null) |
636 |
> |
ex = t.getException(); |
637 |
> |
} |
638 |
> |
} |
639 |
> |
} |
640 |
> |
if (ex != null) |
641 |
> |
rethrowException(ex); |
642 |
|
} |
643 |
|
|
644 |
|
/** |
645 |
|
* Returns true if the computation performed by this task has |
646 |
|
* completed (or has been cancelled). |
647 |
+ |
* |
648 |
|
* @return true if this computation has completed |
649 |
|
*/ |
650 |
|
public final boolean isDone() { |
653 |
|
|
654 |
|
/** |
655 |
|
* Returns true if this task was cancelled. |
656 |
+ |
* |
657 |
|
* @return true if this task was cancelled |
658 |
|
*/ |
659 |
|
public final boolean isCancelled() { |
661 |
|
} |
662 |
|
|
663 |
|
/** |
584 |
– |
* Returns true if this task threw an exception or was cancelled |
585 |
– |
* @return true if this task threw an exception or was cancelled |
586 |
– |
*/ |
587 |
– |
public final boolean completedAbnormally() { |
588 |
– |
return (status & COMPLETION_MASK) < NORMAL; |
589 |
– |
} |
590 |
– |
|
591 |
– |
/** |
592 |
– |
* Returns the exception thrown by the base computation, or a |
593 |
– |
* CancellationException if cancelled, or null if none or if the |
594 |
– |
* method has not yet completed. |
595 |
– |
* @return the exception, or null if none |
596 |
– |
*/ |
597 |
– |
public final Throwable getException() { |
598 |
– |
int s = status & COMPLETION_MASK; |
599 |
– |
if (s >= NORMAL) |
600 |
– |
return null; |
601 |
– |
if (s == CANCELLED) |
602 |
– |
return new CancellationException(); |
603 |
– |
return exceptionMap.get(this); |
604 |
– |
} |
605 |
– |
|
606 |
– |
/** |
664 |
|
* Asserts that the results of this task's computation will not be |
665 |
< |
* used. If a cancellation occurs before this task is processed, |
666 |
< |
* then its <tt>compute</tt> method will not be executed, |
667 |
< |
* <tt>isCancelled</tt> will report true, and <tt>join</tt> will |
668 |
< |
* result in a CancellationException being thrown. Otherwise, when |
665 |
> |
* used. If a cancellation occurs before attempting to execute this |
666 |
> |
* task, then execution will be suppressed, {@code isCancelled} |
667 |
> |
* will report true, and {@code join} will result in a |
668 |
> |
* {@code CancellationException} being thrown. Otherwise, when |
669 |
|
* cancellation races with completion, there are no guarantees |
670 |
< |
* about whether <tt>isCancelled</tt> will report true, whether |
671 |
< |
* <tt>join</tt> will return normally or via an exception, or |
670 |
> |
* about whether {@code isCancelled} will report true, whether |
671 |
> |
* {@code join} will return normally or via an exception, or |
672 |
|
* whether these behaviors will remain consistent upon repeated |
673 |
|
* invocation. |
674 |
|
* |
679 |
|
* <p> This method is designed to be invoked by <em>other</em> |
680 |
|
* tasks. To terminate the current task, you can just return or |
681 |
|
* throw an unchecked exception from its computation method, or |
682 |
< |
* invoke <tt>completeExceptionally(someException)</tt>. |
682 |
> |
* invoke {@code completeExceptionally}. |
683 |
|
* |
684 |
|
* @param mayInterruptIfRunning this value is ignored in the |
685 |
|
* default implementation because tasks are not in general |
686 |
< |
* cancelled via interruption. |
686 |
> |
* cancelled via interruption |
687 |
|
* |
688 |
|
* @return true if this task is now cancelled |
689 |
|
*/ |
693 |
|
} |
694 |
|
|
695 |
|
/** |
696 |
+ |
* Returns true if this task threw an exception or was cancelled. |
697 |
+ |
* |
698 |
+ |
* @return true if this task threw an exception or was cancelled |
699 |
+ |
*/ |
700 |
+ |
public final boolean isCompletedAbnormally() { |
701 |
+ |
return (status & COMPLETION_MASK) < NORMAL; |
702 |
+ |
} |
703 |
+ |
|
704 |
+ |
/** |
705 |
+ |
* Returns the exception thrown by the base computation, or a |
706 |
+ |
* CancellationException if cancelled, or null if none or if the |
707 |
+ |
* method has not yet completed. |
708 |
+ |
* |
709 |
+ |
* @return the exception, or null if none |
710 |
+ |
*/ |
711 |
+ |
public final Throwable getException() { |
712 |
+ |
int s = status & COMPLETION_MASK; |
713 |
+ |
if (s >= NORMAL) |
714 |
+ |
return null; |
715 |
+ |
if (s == CANCELLED) |
716 |
+ |
return new CancellationException(); |
717 |
+ |
return exceptionMap.get(this); |
718 |
+ |
} |
719 |
+ |
|
720 |
+ |
/** |
721 |
|
* Completes this task abnormally, and if not already aborted or |
722 |
|
* cancelled, causes it to throw the given exception upon |
723 |
< |
* <tt>join</tt> and related operations. This method may be used |
723 |
> |
* {@code join} and related operations. This method may be used |
724 |
|
* to induce exceptions in asynchronous tasks, or to force |
725 |
< |
* completion of tasks that would not otherwise complete. This |
726 |
< |
* method is overridable, but overridden versions must invoke |
727 |
< |
* <tt>super</tt> implementation to maintain guarantees. |
725 |
> |
* completion of tasks that would not otherwise complete. Its use |
726 |
> |
* in other situations is likely to be wrong. This method is |
727 |
> |
* overridable, but overridden versions must invoke {@code super} |
728 |
> |
* implementation to maintain guarantees. |
729 |
> |
* |
730 |
|
* @param ex the exception to throw. If this exception is |
731 |
|
* not a RuntimeException or Error, the actual exception thrown |
732 |
|
* will be a RuntimeException with cause ex. |
733 |
|
*/ |
734 |
|
public void completeExceptionally(Throwable ex) { |
735 |
|
setDoneExceptionally((ex instanceof RuntimeException) || |
736 |
< |
(ex instanceof Error)? ex : |
736 |
> |
(ex instanceof Error) ? ex : |
737 |
|
new RuntimeException(ex)); |
738 |
|
} |
739 |
|
|
740 |
|
/** |
741 |
|
* Completes this task, and if not already aborted or cancelled, |
742 |
< |
* returning a <tt>null</tt> result upon <tt>join</tt> and related |
742 |
> |
* returning a {@code null} result upon {@code join} and related |
743 |
|
* operations. This method may be used to provide results for |
744 |
|
* asynchronous tasks, or to provide alternative handling for |
745 |
< |
* tasks that would not otherwise complete normally. |
745 |
> |
* tasks that would not otherwise complete normally. Its use in |
746 |
> |
* other situations is likely to be wrong. This method is |
747 |
> |
* overridable, but overridden versions must invoke {@code super} |
748 |
> |
* implementation to maintain guarantees. |
749 |
|
* |
750 |
< |
* @param value the result value for this task. |
750 |
> |
* @param value the result value for this task |
751 |
|
*/ |
752 |
|
public void complete(V value) { |
753 |
|
try { |
754 |
|
setRawResult(value); |
755 |
< |
} catch(Throwable rex) { |
755 |
> |
} catch (Throwable rex) { |
756 |
|
setDoneExceptionally(rex); |
757 |
|
return; |
758 |
|
} |
759 |
|
setNormalCompletion(); |
760 |
|
} |
761 |
|
|
762 |
+ |
public final V get() throws InterruptedException, ExecutionException { |
763 |
+ |
ForkJoinWorkerThread w = getWorker(); |
764 |
+ |
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
765 |
+ |
awaitDone(w, true); |
766 |
+ |
return reportFutureResult(); |
767 |
+ |
} |
768 |
+ |
|
769 |
+ |
public final V get(long timeout, TimeUnit unit) |
770 |
+ |
throws InterruptedException, ExecutionException, TimeoutException { |
771 |
+ |
ForkJoinWorkerThread w = getWorker(); |
772 |
+ |
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
773 |
+ |
awaitDone(w, unit.toNanos(timeout)); |
774 |
+ |
return reportTimedFutureResult(); |
775 |
+ |
} |
776 |
+ |
|
777 |
+ |
/** |
778 |
+ |
* Possibly executes other tasks until this task is ready, then |
779 |
+ |
* returns the result of the computation. This method may be more |
780 |
+ |
* efficient than {@code join}, but is only applicable when |
781 |
+ |
* there are no potential dependencies between continuation of the |
782 |
+ |
* current task and that of any other task that might be executed |
783 |
+ |
* while helping. (This usually holds for pure divide-and-conquer |
784 |
+ |
* tasks). This method may be invoked only from within |
785 |
+ |
* ForkJoinTask computations (as may be determined using method |
786 |
+ |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
787 |
+ |
* result in exceptions or errors, possibly including |
788 |
+ |
* ClassCastException. |
789 |
+ |
* |
790 |
+ |
* @return the computed result |
791 |
+ |
*/ |
792 |
+ |
public final V helpJoin() { |
793 |
+ |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread(); |
794 |
+ |
if (status < 0 || !w.unpushTask(this) || !tryExec()) |
795 |
+ |
reportException(busyJoin(w)); |
796 |
+ |
return getRawResult(); |
797 |
+ |
} |
798 |
+ |
|
799 |
+ |
/** |
800 |
+ |
* Possibly executes other tasks until this task is ready. This |
801 |
+ |
* method may be invoked only from within ForkJoinTask |
802 |
+ |
* computations (as may be determined using method {@link |
803 |
+ |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
804 |
+ |
* in exceptions or errors, possibly including ClassCastException. |
805 |
+ |
*/ |
806 |
+ |
public final void quietlyHelpJoin() { |
807 |
+ |
if (status >= 0) { |
808 |
+ |
ForkJoinWorkerThread w = |
809 |
+ |
(ForkJoinWorkerThread) Thread.currentThread(); |
810 |
+ |
if (!w.unpushTask(this) || !tryQuietlyInvoke()) |
811 |
+ |
busyJoin(w); |
812 |
+ |
} |
813 |
+ |
} |
814 |
+ |
|
815 |
+ |
/** |
816 |
+ |
* Joins this task, without returning its result or throwing an |
817 |
+ |
* exception. This method may be useful when processing |
818 |
+ |
* collections of tasks when some have been cancelled or otherwise |
819 |
+ |
* known to have aborted. |
820 |
+ |
*/ |
821 |
+ |
public final void quietlyJoin() { |
822 |
+ |
if (status >= 0) { |
823 |
+ |
ForkJoinWorkerThread w = getWorker(); |
824 |
+ |
if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke()) |
825 |
+ |
awaitDone(w, true); |
826 |
+ |
} |
827 |
+ |
} |
828 |
+ |
|
829 |
+ |
/** |
830 |
+ |
* Commences performing this task and awaits its completion if |
831 |
+ |
* necessary, without returning its result or throwing an |
832 |
+ |
* exception. This method may be useful when processing |
833 |
+ |
* collections of tasks when some have been cancelled or otherwise |
834 |
+ |
* known to have aborted. |
835 |
+ |
*/ |
836 |
+ |
public final void quietlyInvoke() { |
837 |
+ |
if (status >= 0 && !tryQuietlyInvoke()) |
838 |
+ |
quietlyJoin(); |
839 |
+ |
} |
840 |
+ |
|
841 |
+ |
/** |
842 |
+ |
* Possibly executes tasks until the pool hosting the current task |
843 |
+ |
* {@link ForkJoinPool#isQuiescent}. This method may be of use in |
844 |
+ |
* designs in which many tasks are forked, but none are explicitly |
845 |
+ |
* joined, instead executing them until all are processed. |
846 |
+ |
*/ |
847 |
+ |
public static void helpQuiesce() { |
848 |
+ |
((ForkJoinWorkerThread) Thread.currentThread()) |
849 |
+ |
.helpQuiescePool(); |
850 |
+ |
} |
851 |
+ |
|
852 |
|
/** |
853 |
|
* Resets the internal bookkeeping state of this task, allowing a |
854 |
< |
* subsequent <tt>fork</tt>. This method allows repeated reuse of |
854 |
> |
* subsequent {@code fork}. This method allows repeated reuse of |
855 |
|
* this task, but only if reuse occurs when this task has either |
856 |
|
* never been forked, or has been forked, then completed and all |
857 |
|
* outstanding joins of this task have also completed. Effects |
866 |
|
} |
867 |
|
|
868 |
|
/** |
869 |
< |
* Tries to unschedule this task for execution. This method will |
870 |
< |
* typically succeed if this task is the next task that would be |
871 |
< |
* executed by the current thread, and will typically fail (return |
872 |
< |
* false) otherwise. This method may be useful when arranging |
696 |
< |
* faster local processing of tasks that could have been, but were |
697 |
< |
* not, stolen. |
698 |
< |
* @return true if unforked |
699 |
< |
*/ |
700 |
< |
public boolean tryUnfork() { |
701 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this); |
702 |
< |
} |
703 |
< |
|
704 |
< |
/** |
705 |
< |
* Forks both tasks, returning when <tt>isDone</tt> holds for both |
706 |
< |
* of them or an exception is encountered. This method may be |
707 |
< |
* invoked only from within other ForkJoinTask |
708 |
< |
* computations. Attempts to invoke in other contexts result in |
709 |
< |
* exceptions or errors including ClassCastException. |
710 |
< |
* @param t1 one task |
711 |
< |
* @param t2 the other task |
712 |
< |
* @throws NullPointerException if t1 or t2 are null |
713 |
< |
* @throws RuntimeException or Error if either task did so. |
869 |
> |
* Returns the pool hosting the current task execution, or null |
870 |
> |
* if this task is executing outside of any ForkJoinPool. |
871 |
> |
* |
872 |
> |
* @return the pool, or null if none |
873 |
|
*/ |
874 |
< |
public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) { |
875 |
< |
t2.fork(); |
876 |
< |
t1.invoke(); |
877 |
< |
t2.join(); |
874 |
> |
public static ForkJoinPool getPool() { |
875 |
> |
Thread t = Thread.currentThread(); |
876 |
> |
return (t instanceof ForkJoinWorkerThread) ? |
877 |
> |
((ForkJoinWorkerThread) t).pool : null; |
878 |
|
} |
879 |
|
|
880 |
|
/** |
881 |
< |
* Forks the given tasks, returning when <tt>isDone</tt> holds for |
882 |
< |
* all of them. If any task encounters an exception, others may be |
883 |
< |
* cancelled. This method may be invoked only from within other |
884 |
< |
* ForkJoinTask computations. Attempts to invoke in other contexts |
885 |
< |
* result in exceptions or errors including ClassCastException. |
727 |
< |
* @param tasks the array of tasks |
728 |
< |
* @throws NullPointerException if tasks or any element are null. |
729 |
< |
* @throws RuntimeException or Error if any task did so. |
881 |
> |
* Returns {@code true} if the current thread is executing as a |
882 |
> |
* ForkJoinPool computation. |
883 |
> |
* |
884 |
> |
* @return {@code true} if the current thread is executing as a |
885 |
> |
* ForkJoinPool computation, or false otherwise |
886 |
|
*/ |
887 |
< |
public static void invokeAll(ForkJoinTask<?>... tasks) { |
888 |
< |
Throwable ex = null; |
733 |
< |
int last = tasks.length - 1; |
734 |
< |
for (int i = last; i >= 0; --i) { |
735 |
< |
ForkJoinTask<?> t = tasks[i]; |
736 |
< |
if (t == null) { |
737 |
< |
if (ex == null) |
738 |
< |
ex = new NullPointerException(); |
739 |
< |
} |
740 |
< |
else if (i != 0) |
741 |
< |
t.fork(); |
742 |
< |
else { |
743 |
< |
t.quietlyInvoke(); |
744 |
< |
if (ex == null) |
745 |
< |
ex = t.getException(); |
746 |
< |
} |
747 |
< |
} |
748 |
< |
for (int i = 1; i <= last; ++i) { |
749 |
< |
ForkJoinTask<?> t = tasks[i]; |
750 |
< |
if (t != null) { |
751 |
< |
if (ex != null) |
752 |
< |
t.cancel(false); |
753 |
< |
else { |
754 |
< |
t.quietlyJoin(); |
755 |
< |
if (ex == null) |
756 |
< |
ex = t.getException(); |
757 |
< |
} |
758 |
< |
} |
759 |
< |
} |
760 |
< |
if (ex != null) |
761 |
< |
rethrowException(ex); |
887 |
> |
public static boolean inForkJoinPool() { |
888 |
> |
return Thread.currentThread() instanceof ForkJoinWorkerThread; |
889 |
|
} |
890 |
|
|
891 |
|
/** |
892 |
< |
* Forks all tasks in the collection, returning when |
893 |
< |
* <tt>isDone</tt> holds for all of them. If any task encounters |
894 |
< |
* an exception, others may be cancelled. This method may be |
895 |
< |
* invoked only from within other ForkJoinTask |
896 |
< |
* computations. Attempts to invoke in other contexts result in |
897 |
< |
* exceptions or errors including ClassCastException. |
898 |
< |
* @param tasks the collection of tasks |
899 |
< |
* @throws NullPointerException if tasks or any element are null. |
900 |
< |
* @throws RuntimeException or Error if any task did so. |
892 |
> |
* Tries to unschedule this task for execution. This method will |
893 |
> |
* typically succeed if this task is the most recently forked task |
894 |
> |
* by the current thread, and has not commenced executing in |
895 |
> |
* another thread. This method may be useful when arranging |
896 |
> |
* alternative local processing of tasks that could have been, but |
897 |
> |
* were not, stolen. This method may be invoked only from within |
898 |
> |
* ForkJoinTask computations (as may be determined using method |
899 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
900 |
> |
* result in exceptions or errors, possibly including |
901 |
> |
* ClassCastException. |
902 |
> |
* |
903 |
> |
* @return true if unforked |
904 |
|
*/ |
905 |
< |
public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) { |
906 |
< |
if (!(tasks instanceof List)) { |
907 |
< |
invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()])); |
778 |
< |
return; |
779 |
< |
} |
780 |
< |
List<? extends ForkJoinTask<?>> ts = |
781 |
< |
(List<? extends ForkJoinTask<?>>)tasks; |
782 |
< |
Throwable ex = null; |
783 |
< |
int last = ts.size() - 1; |
784 |
< |
for (int i = last; i >= 0; --i) { |
785 |
< |
ForkJoinTask<?> t = ts.get(i); |
786 |
< |
if (t == null) { |
787 |
< |
if (ex == null) |
788 |
< |
ex = new NullPointerException(); |
789 |
< |
} |
790 |
< |
else if (i != 0) |
791 |
< |
t.fork(); |
792 |
< |
else { |
793 |
< |
t.quietlyInvoke(); |
794 |
< |
if (ex == null) |
795 |
< |
ex = t.getException(); |
796 |
< |
} |
797 |
< |
} |
798 |
< |
for (int i = 1; i <= last; ++i) { |
799 |
< |
ForkJoinTask<?> t = ts.get(i); |
800 |
< |
if (t != null) { |
801 |
< |
if (ex != null) |
802 |
< |
t.cancel(false); |
803 |
< |
else { |
804 |
< |
t.quietlyJoin(); |
805 |
< |
if (ex == null) |
806 |
< |
ex = t.getException(); |
807 |
< |
} |
808 |
< |
} |
809 |
< |
} |
810 |
< |
if (ex != null) |
811 |
< |
rethrowException(ex); |
905 |
> |
public boolean tryUnfork() { |
906 |
> |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
907 |
> |
.unpushTask(this); |
908 |
|
} |
909 |
|
|
910 |
|
/** |
911 |
< |
* Possibly executes tasks until the pool hosting the current task |
912 |
< |
* {@link ForkJoinPool#isQuiescent}. This method may be of use in |
913 |
< |
* designs in which many tasks are forked, but none are explicitly |
914 |
< |
* joined, instead executing them until all are processed. |
911 |
> |
* Returns an estimate of the number of tasks that have been |
912 |
> |
* forked by the current worker thread but not yet executed. This |
913 |
> |
* value may be useful for heuristic decisions about whether to |
914 |
> |
* fork other tasks. |
915 |
> |
* |
916 |
> |
* @return the number of tasks |
917 |
|
*/ |
918 |
< |
public static void helpQuiesce() { |
919 |
< |
((ForkJoinWorkerThread)(Thread.currentThread())). |
920 |
< |
helpQuiescePool(); |
918 |
> |
public static int getQueuedTaskCount() { |
919 |
> |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
920 |
> |
.getQueueSize(); |
921 |
|
} |
922 |
|
|
923 |
|
/** |
924 |
< |
* Returns a estimate of how many more locally queued tasks are |
924 |
> |
* Returns an estimate of how many more locally queued tasks are |
925 |
|
* held by the current worker thread than there are other worker |
926 |
< |
* threads that might want to steal them. This value may be |
927 |
< |
* useful for heuristic decisions about whether to fork other |
928 |
< |
* tasks. In many usages of ForkJoinTasks, at steady state, each |
929 |
< |
* worker should aim to maintain a small constant surplus (for |
930 |
< |
* example, 3) of tasks, and to process computations locally if |
931 |
< |
* this threshold is exceeded. |
926 |
> |
* threads that might steal them. This value may be useful for |
927 |
> |
* heuristic decisions about whether to fork other tasks. In many |
928 |
> |
* usages of ForkJoinTasks, at steady state, each worker should |
929 |
> |
* aim to maintain a small constant surplus (for example, 3) of |
930 |
> |
* tasks, and to process computations locally if this threshold is |
931 |
> |
* exceeded. |
932 |
> |
* |
933 |
|
* @return the surplus number of tasks, which may be negative |
934 |
|
*/ |
935 |
< |
public static int surplus() { |
936 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())) |
935 |
> |
public static int getSurplusQueuedTaskCount() { |
936 |
> |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
937 |
|
.getEstimatedSurplusTaskCount(); |
938 |
|
} |
939 |
|
|
940 |
< |
// Extension kit |
940 |
> |
// Extension methods |
941 |
|
|
942 |
|
/** |
943 |
< |
* Returns the result that would be returned by <tt>join</tt>, or |
944 |
< |
* null if this task is not known to have been completed. This |
945 |
< |
* method is designed to aid debugging, as well as to support |
946 |
< |
* extensions. Its use in any other context is discouraged. |
943 |
> |
* Returns the result that would be returned by {@code join}, |
944 |
> |
* even if this task completed abnormally, or null if this task is |
945 |
> |
* not known to have been completed. This method is designed to |
946 |
> |
* aid debugging, as well as to support extensions. Its use in any |
947 |
> |
* other context is discouraged. |
948 |
|
* |
949 |
< |
* @return the result, or null if not completed. |
949 |
> |
* @return the result, or null if not completed |
950 |
|
*/ |
951 |
|
public abstract V getRawResult(); |
952 |
|
|
965 |
|
* called otherwise. The return value controls whether this task |
966 |
|
* is considered to be done normally. It may return false in |
967 |
|
* asynchronous actions that require explicit invocations of |
968 |
< |
* <tt>complete</tt> to become joinable. It may throw exceptions |
968 |
> |
* {@code complete} to become joinable. It may throw exceptions |
969 |
|
* to indicate abnormal exit. |
970 |
+ |
* |
971 |
|
* @return true if completed normally |
972 |
|
* @throws Error or RuntimeException if encountered during computation |
973 |
|
*/ |
974 |
|
protected abstract boolean exec(); |
975 |
|
|
976 |
+ |
/** |
977 |
+ |
* Returns, but does not unschedule or execute, the task queued by |
978 |
+ |
* the current thread but not yet executed, if one is |
979 |
+ |
* available. There is no guarantee that this task will actually |
980 |
+ |
* be polled or executed next. This method is designed primarily |
981 |
+ |
* to support extensions, and is unlikely to be useful otherwise. |
982 |
+ |
* This method may be invoked only from within ForkJoinTask |
983 |
+ |
* computations (as may be determined using method {@link |
984 |
+ |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
985 |
+ |
* in exceptions or errors, possibly including ClassCastException. |
986 |
+ |
* |
987 |
+ |
* @return the next task, or null if none are available |
988 |
+ |
*/ |
989 |
+ |
protected static ForkJoinTask<?> peekNextLocalTask() { |
990 |
+ |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
991 |
+ |
.peekTask(); |
992 |
+ |
} |
993 |
+ |
|
994 |
+ |
/** |
995 |
+ |
* Unschedules and returns, without executing, the next task |
996 |
+ |
* queued by the current thread but not yet executed. This method |
997 |
+ |
* is designed primarily to support extensions, and is unlikely to |
998 |
+ |
* be useful otherwise. This method may be invoked only from |
999 |
+ |
* within ForkJoinTask computations (as may be determined using |
1000 |
+ |
* method {@link #inForkJoinPool}). Attempts to invoke in other |
1001 |
+ |
* contexts result in exceptions or errors, possibly including |
1002 |
+ |
* ClassCastException. |
1003 |
+ |
* |
1004 |
+ |
* @return the next task, or null if none are available |
1005 |
+ |
*/ |
1006 |
+ |
protected static ForkJoinTask<?> pollNextLocalTask() { |
1007 |
+ |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1008 |
+ |
.pollLocalTask(); |
1009 |
+ |
} |
1010 |
+ |
|
1011 |
+ |
/** |
1012 |
+ |
* Unschedules and returns, without executing, the next task |
1013 |
+ |
* queued by the current thread but not yet executed, if one is |
1014 |
+ |
* available, or if not available, a task that was forked by some |
1015 |
+ |
* other thread, if available. Availability may be transient, so a |
1016 |
+ |
* {@code null} result does not necessarily imply quiescence |
1017 |
+ |
* of the pool this task is operating in. This method is designed |
1018 |
+ |
* primarily to support extensions, and is unlikely to be useful |
1019 |
+ |
* otherwise. This method may be invoked only from within |
1020 |
+ |
* ForkJoinTask computations (as may be determined using method |
1021 |
+ |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1022 |
+ |
* result in exceptions or errors, possibly including |
1023 |
+ |
* ClassCastException. |
1024 |
+ |
* |
1025 |
+ |
* @return a task, or null if none are available |
1026 |
+ |
*/ |
1027 |
+ |
protected static ForkJoinTask<?> pollTask() { |
1028 |
+ |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1029 |
+ |
.pollTask(); |
1030 |
+ |
} |
1031 |
+ |
|
1032 |
|
// Serialization support |
1033 |
|
|
1034 |
|
private static final long serialVersionUID = -7721805057305804111L; |
1037 |
|
* Save the state to a stream. |
1038 |
|
* |
1039 |
|
* @serialData the current run status and the exception thrown |
1040 |
< |
* during execution, or null if none. |
1040 |
> |
* during execution, or null if none |
1041 |
|
* @param s the stream |
1042 |
|
*/ |
1043 |
|
private void writeObject(java.io.ObjectOutputStream s) |
1048 |
|
|
1049 |
|
/** |
1050 |
|
* Reconstitute the instance from a stream. |
1051 |
+ |
* |
1052 |
|
* @param s the stream |
1053 |
|
*/ |
1054 |
|
private void readObject(java.io.ObjectInputStream s) |
1055 |
|
throws java.io.IOException, ClassNotFoundException { |
1056 |
|
s.defaultReadObject(); |
1057 |
< |
// status &= ~INTERNAL_SIGNAL_MASK; // todo: define policy |
1057 |
> |
status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts |
1058 |
> |
status |= EXTERNAL_SIGNAL; // conservatively set external signal |
1059 |
|
Object ex = s.readObject(); |
1060 |
|
if (ex != null) |
1061 |
< |
setDoneExceptionally((Throwable)ex); |
1061 |
> |
setDoneExceptionally((Throwable) ex); |
1062 |
|
} |
1063 |
|
|
1064 |
< |
// Temporary Unsafe mechanics for preliminary release |
1064 |
> |
// Unsafe mechanics for jsr166y 3rd party package. |
1065 |
> |
private static sun.misc.Unsafe getUnsafe() { |
1066 |
> |
try { |
1067 |
> |
return sun.misc.Unsafe.getUnsafe(); |
1068 |
> |
} catch (SecurityException se) { |
1069 |
> |
try { |
1070 |
> |
return java.security.AccessController.doPrivileged |
1071 |
> |
(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1072 |
> |
public sun.misc.Unsafe run() throws Exception { |
1073 |
> |
return getUnsafeByReflection(); |
1074 |
> |
}}); |
1075 |
> |
} catch (java.security.PrivilegedActionException e) { |
1076 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
1077 |
> |
e.getCause()); |
1078 |
> |
} |
1079 |
> |
} |
1080 |
> |
} |
1081 |
|
|
1082 |
< |
static final Unsafe _unsafe; |
1083 |
< |
static final long statusOffset; |
1082 |
> |
private static sun.misc.Unsafe getUnsafeByReflection() |
1083 |
> |
throws NoSuchFieldException, IllegalAccessException { |
1084 |
> |
java.lang.reflect.Field f = |
1085 |
> |
sun.misc.Unsafe.class.getDeclaredField("theUnsafe"); |
1086 |
> |
f.setAccessible(true); |
1087 |
> |
return (sun.misc.Unsafe) f.get(null); |
1088 |
> |
} |
1089 |
|
|
1090 |
< |
static { |
1090 |
> |
private static long fieldOffset(String fieldName, Class<?> klazz) { |
1091 |
|
try { |
1092 |
< |
if (ForkJoinTask.class.getClassLoader() != null) { |
1093 |
< |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
1094 |
< |
f.setAccessible(true); |
1095 |
< |
_unsafe = (Unsafe)f.get(null); |
1096 |
< |
} |
1097 |
< |
else |
1098 |
< |
_unsafe = Unsafe.getUnsafe(); |
919 |
< |
statusOffset = _unsafe.objectFieldOffset |
920 |
< |
(ForkJoinTask.class.getDeclaredField("status")); |
921 |
< |
} catch (Exception ex) { throw new Error(ex); } |
1092 |
> |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName)); |
1093 |
> |
} catch (NoSuchFieldException e) { |
1094 |
> |
// Convert Exception to Error |
1095 |
> |
NoSuchFieldError error = new NoSuchFieldError(fieldName); |
1096 |
> |
error.initCause(e); |
1097 |
> |
throw error; |
1098 |
> |
} |
1099 |
|
} |
1100 |
|
|
1101 |
+ |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1102 |
+ |
static final long statusOffset = |
1103 |
+ |
fieldOffset("status", ForkJoinTask.class); |
1104 |
+ |
|
1105 |
|
} |