30 |
|
* subtasks may be hosted by a small number of actual threads in a |
31 |
|
* ForkJoinPool, at the price of some usage limitations. |
32 |
|
* |
33 |
< |
* <p>A "main" {@code ForkJoinTask} begins execution when submitted |
34 |
< |
* to a {@link ForkJoinPool}. Once started, it will usually in turn |
35 |
< |
* start other subtasks. As indicated by the name of this class, |
36 |
< |
* many programs using {@code ForkJoinTask} employ only methods |
37 |
< |
* {@link #fork} and {@link #join}, or derivatives such as {@link |
33 |
> |
* <p>A "main" {@code ForkJoinTask} begins execution when it is |
34 |
> |
* explicitly submitted to a {@link ForkJoinPool}, or, if not already |
35 |
> |
* engaged in a ForkJoin computation, commenced in the {@link |
36 |
> |
* ForkJoinPool#commonPool} via {@link #fork}, {@link #invoke}, or |
37 |
> |
* related methods. Once started, it will usually in turn start other |
38 |
> |
* subtasks. As indicated by the name of this class, many programs |
39 |
> |
* using {@code ForkJoinTask} employ only methods {@link #fork} and |
40 |
> |
* {@link #join}, or derivatives such as {@link |
41 |
|
* #invokeAll(ForkJoinTask...) invokeAll}. However, this class also |
42 |
|
* provides a number of other methods that can come into play in |
43 |
< |
* advanced usages, as well as extension mechanics that allow |
44 |
< |
* support of new forms of fork/join processing. |
43 |
> |
* advanced usages, as well as extension mechanics that allow support |
44 |
> |
* of new forms of fork/join processing. |
45 |
|
* |
46 |
|
* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}. |
47 |
|
* The efficiency of {@code ForkJoinTask}s stems from a set of |
48 |
|
* restrictions (that are only partially statically enforceable) |
49 |
< |
* reflecting their intended use as computational tasks calculating |
50 |
< |
* pure functions or operating on purely isolated objects. The |
51 |
< |
* primary coordination mechanisms are {@link #fork}, that arranges |
49 |
> |
* reflecting their main use as computational tasks calculating pure |
50 |
> |
* functions or operating on purely isolated objects. The primary |
51 |
> |
* coordination mechanisms are {@link #fork}, that arranges |
52 |
|
* asynchronous execution, and {@link #join}, that doesn't proceed |
53 |
|
* until the task's result has been computed. Computations should |
54 |
< |
* avoid {@code synchronized} methods or blocks, and should minimize |
55 |
< |
* other blocking synchronization apart from joining other tasks or |
56 |
< |
* using synchronizers such as Phasers that are advertised to |
57 |
< |
* cooperate with fork/join scheduling. Tasks should also not perform |
58 |
< |
* blocking IO, and should ideally access variables that are |
59 |
< |
* completely independent of those accessed by other running |
60 |
< |
* tasks. Minor breaches of these restrictions, for example using |
61 |
< |
* shared output streams, may be tolerable in practice, but frequent |
62 |
< |
* use may result in poor performance, and the potential to |
63 |
< |
* indefinitely stall if the number of threads not waiting for IO or |
64 |
< |
* other external synchronization becomes exhausted. This usage |
65 |
< |
* restriction is in part enforced by not permitting checked |
66 |
< |
* exceptions such as {@code IOExceptions} to be thrown. However, |
67 |
< |
* computations may still encounter unchecked exceptions, that are |
68 |
< |
* rethrown to callers attempting to join them. These exceptions may |
69 |
< |
* additionally include {@link RejectedExecutionException} stemming |
70 |
< |
* from internal resource exhaustion, such as failure to allocate |
71 |
< |
* internal task queues. Rethrown exceptions behave in the same way as |
72 |
< |
* regular exceptions, but, when possible, contain stack traces (as |
73 |
< |
* displayed for example using {@code ex.printStackTrace()}) of both |
74 |
< |
* the thread that initiated the computation as well as the thread |
75 |
< |
* actually encountering the exception; minimally only the latter. |
54 |
> |
* ideally avoid {@code synchronized} methods or blocks, and should |
55 |
> |
* minimize other blocking synchronization apart from joining other |
56 |
> |
* tasks or using synchronizers such as Phasers that are advertised to |
57 |
> |
* cooperate with fork/join scheduling. Subdividable tasks should also |
58 |
> |
* not perform blocking IO, and should ideally access variables that |
59 |
> |
* are completely independent of those accessed by other running |
60 |
> |
* tasks. These guidelines are loosely enforced by not permitting |
61 |
> |
* checked exceptions such as {@code IOExceptions} to be |
62 |
> |
* thrown. However, computations may still encounter unchecked |
63 |
> |
* exceptions, that are rethrown to callers attempting to join |
64 |
> |
* them. These exceptions may additionally include {@link |
65 |
> |
* RejectedExecutionException} stemming from internal resource |
66 |
> |
* exhaustion, such as failure to allocate internal task |
67 |
> |
* queues. Rethrown exceptions behave in the same way as regular |
68 |
> |
* exceptions, but, when possible, contain stack traces (as displayed |
69 |
> |
* for example using {@code ex.printStackTrace()}) of both the thread |
70 |
> |
* that initiated the computation as well as the thread actually |
71 |
> |
* encountering the exception; minimally only the latter. |
72 |
> |
* |
73 |
> |
* <p>It is possible to define and use ForkJoinTasks that may block, |
74 |
> |
* but doing do requires three further considerations: (1) Completion |
75 |
> |
* of few if any <em>other</em> tasks should be dependent on a task |
76 |
> |
* that blocks on external synchronization or IO. Event-style async |
77 |
> |
* tasks that are never joined (for example, those subclassing {@link |
78 |
> |
* CountedCompleter}) often fall into this category. (2) To minimize |
79 |
> |
* resource impact, tasks should be small; ideally performing only the |
80 |
> |
* (possibly) blocking action. (3) Unless the {@link |
81 |
> |
* ForkJoinPool.ManagedBlocker} API is used, or the number of possibly |
82 |
> |
* blocked tasks is known to be less than the pool's {@link |
83 |
> |
* ForkJoinPool#getParallelism} level, the pool cannot guarantee that |
84 |
> |
* enough threads will be available to ensure progress or good |
85 |
> |
* performance. |
86 |
|
* |
87 |
|
* <p>The primary method for awaiting completion and extracting |
88 |
|
* results of a task is {@link #join}, but there are several variants: |
98 |
|
* performs the most common form of parallel invocation: forking a set |
99 |
|
* of tasks and joining them all. |
100 |
|
* |
101 |
+ |
* <p>In the most typical usages, a fork-join pair act like a call |
102 |
+ |
* (fork) and return (join) from a parallel recursive function. As is |
103 |
+ |
* the case with other forms of recursive calls, returns (joins) |
104 |
+ |
* should be performed innermost-first. For example, {@code a.fork(); |
105 |
+ |
* b.fork(); b.join(); a.join();} is likely to be substantially more |
106 |
+ |
* efficient than joining {@code a} before {@code b}. |
107 |
+ |
* |
108 |
|
* <p>The execution status of tasks may be queried at several levels |
109 |
|
* of detail: {@link #isDone} is true if a task completed in any way |
110 |
|
* (including the case where a task was cancelled without executing); |
120 |
|
* <p>The ForkJoinTask class is not usually directly subclassed. |
121 |
|
* Instead, you subclass one of the abstract classes that support a |
122 |
|
* particular style of fork/join processing, typically {@link |
123 |
< |
* RecursiveAction} for computations that do not return results, or |
124 |
< |
* {@link RecursiveTask} for those that do. Normally, a concrete |
125 |
< |
* ForkJoinTask subclass declares fields comprising its parameters, |
126 |
< |
* established in a constructor, and then defines a {@code compute} |
127 |
< |
* method that somehow uses the control methods supplied by this base |
128 |
< |
* class. While these methods have {@code public} access (to allow |
129 |
< |
* instances of different task subclasses to call each other's |
110 |
< |
* methods), some of them may only be called from within other |
111 |
< |
* ForkJoinTasks (as may be determined using method {@link |
112 |
< |
* #inForkJoinPool}). Attempts to invoke them in other contexts |
113 |
< |
* result in exceptions or errors, possibly including |
114 |
< |
* {@code ClassCastException}. |
123 |
> |
* RecursiveAction} for most computations that do not return results, |
124 |
> |
* {@link RecursiveTask} for those that do, and {@link |
125 |
> |
* CountedCompleter} for those in which completed actions trigger |
126 |
> |
* other actions. Normally, a concrete ForkJoinTask subclass declares |
127 |
> |
* fields comprising its parameters, established in a constructor, and |
128 |
> |
* then defines a {@code compute} method that somehow uses the control |
129 |
> |
* methods supplied by this base class. |
130 |
|
* |
131 |
|
* <p>Method {@link #join} and its variants are appropriate for use |
132 |
|
* only when completion dependencies are acyclic; that is, the |
136 |
|
* supports other methods and techniques (for example the use of |
137 |
|
* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that |
138 |
|
* may be of use in constructing custom subclasses for problems that |
139 |
< |
* are not statically structured as DAGs. |
139 |
> |
* are not statically structured as DAGs. To support such usages a |
140 |
> |
* ForkJoinTask may be atomically <em>tagged</em> with a {@code short} |
141 |
> |
* value using {@link #setForkJoinTaskTag} or {@link |
142 |
> |
* #compareAndSetForkJoinTaskTag} and checked using {@link |
143 |
> |
* #getForkJoinTaskTag}. The ForkJoinTask implementation does not use |
144 |
> |
* these {@code protected} methods or tags for any purpose, but they |
145 |
> |
* may be of use in the construction of specialized subclasses. For |
146 |
> |
* example, parallel graph traversals can use the supplied methods to |
147 |
> |
* avoid revisiting nodes/tasks that have already been processed. |
148 |
> |
* (Method names for tagging are bulky in part to encourage definition |
149 |
> |
* of methods that reflect their usage patterns.) |
150 |
|
* |
151 |
|
* <p>Most base support methods are {@code final}, to prevent |
152 |
|
* overriding of implementations that are intrinsically tied to the |
186 |
|
* See the internal documentation of class ForkJoinPool for a |
187 |
|
* general implementation overview. ForkJoinTasks are mainly |
188 |
|
* responsible for maintaining their "status" field amidst relays |
189 |
< |
* to methods in ForkJoinWorkerThread and ForkJoinPool. The |
190 |
< |
* methods of this class are more-or-less layered into (1) basic |
191 |
< |
* status maintenance (2) execution and awaiting completion (3) |
192 |
< |
* user-level methods that additionally report results. This is |
193 |
< |
* sometimes hard to see because this file orders exported methods |
194 |
< |
* in a way that flows well in javadocs. |
189 |
> |
* to methods in ForkJoinWorkerThread and ForkJoinPool. |
190 |
> |
* |
191 |
> |
* The methods of this class are more-or-less layered into |
192 |
> |
* (1) basic status maintenance |
193 |
> |
* (2) execution and awaiting completion |
194 |
> |
* (3) user-level methods that additionally report results. |
195 |
> |
* This is sometimes hard to see because this file orders exported |
196 |
> |
* methods in a way that flows well in javadocs. |
197 |
|
*/ |
198 |
|
|
199 |
|
/* |
200 |
|
* The status field holds run control status bits packed into a |
201 |
|
* single int to minimize footprint and to ensure atomicity (via |
202 |
|
* CAS). Status is initially zero, and takes on nonnegative |
203 |
< |
* values until completed, upon which status holds value |
204 |
< |
* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking |
205 |
< |
* waits by other threads have the SIGNAL bit set. Completion of |
206 |
< |
* a stolen task with SIGNAL set awakens any waiters via |
207 |
< |
* notifyAll. Even though suboptimal for some purposes, we use |
208 |
< |
* basic builtin wait/notify to take advantage of "monitor |
209 |
< |
* inflation" in JVMs that we would otherwise need to emulate to |
210 |
< |
* avoid adding further per-task bookkeeping overhead. We want |
211 |
< |
* these monitors to be "fat", i.e., not use biasing or thin-lock |
212 |
< |
* techniques, so use some odd coding idioms that tend to avoid |
213 |
< |
* them. |
203 |
> |
* values until completed, upon which status (anded with |
204 |
> |
* DONE_MASK) holds value NORMAL, CANCELLED, or EXCEPTIONAL. Tasks |
205 |
> |
* undergoing blocking waits by other threads have the SIGNAL bit |
206 |
> |
* set. Completion of a stolen task with SIGNAL set awakens any |
207 |
> |
* waiters via notifyAll. Even though suboptimal for some |
208 |
> |
* purposes, we use basic builtin wait/notify to take advantage of |
209 |
> |
* "monitor inflation" in JVMs that we would otherwise need to |
210 |
> |
* emulate to avoid adding further per-task bookkeeping overhead. |
211 |
> |
* We want these monitors to be "fat", i.e., not use biasing or |
212 |
> |
* thin-lock techniques, so use some odd coding idioms that tend |
213 |
> |
* to avoid them, mainly by arranging that every synchronized |
214 |
> |
* block performs a wait, notifyAll or both. |
215 |
> |
* |
216 |
> |
* These control bits occupy only (some of) the upper half (16 |
217 |
> |
* bits) of status field. The lower bits are used for user-defined |
218 |
> |
* tags. |
219 |
|
*/ |
220 |
|
|
221 |
|
/** The run status of this task */ |
222 |
|
volatile int status; // accessed directly by pool and workers |
223 |
< |
private static final int NORMAL = -1; |
224 |
< |
private static final int CANCELLED = -2; |
225 |
< |
private static final int EXCEPTIONAL = -3; |
226 |
< |
private static final int SIGNAL = 1; |
223 |
> |
static final int DONE_MASK = 0xf0000000; // mask out non-completion bits |
224 |
> |
static final int NORMAL = 0xf0000000; // must be negative |
225 |
> |
static final int CANCELLED = 0xc0000000; // must be < NORMAL |
226 |
> |
static final int EXCEPTIONAL = 0x80000000; // must be < CANCELLED |
227 |
> |
static final int SIGNAL = 0x00010000; // must be >= 1 << 16 |
228 |
> |
static final int SMASK = 0x0000ffff; // short bits for tags |
229 |
|
|
230 |
|
/** |
231 |
< |
* Marks completion and wakes up threads waiting to join this task, |
232 |
< |
* also clearing signal request bits. |
231 |
> |
* Marks completion and wakes up threads waiting to join this |
232 |
> |
* task. |
233 |
|
* |
234 |
|
* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
235 |
|
* @return completion status on exit |
238 |
|
for (int s;;) { |
239 |
|
if ((s = status) < 0) |
240 |
|
return s; |
241 |
< |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) { |
242 |
< |
if (s != 0) |
241 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | completion)) { |
242 |
> |
if ((s >>> 16) != 0) |
243 |
|
synchronized (this) { notifyAll(); } |
244 |
|
return completion; |
245 |
|
} |
247 |
|
} |
248 |
|
|
249 |
|
/** |
250 |
< |
* Tries to block a worker thread until completed or timed out. |
251 |
< |
* Uses Object.wait time argument conventions. |
252 |
< |
* May fail on contention or interrupt. |
250 |
> |
* Primary execution method for stolen tasks. Unless done, calls |
251 |
> |
* exec and records status if completed, but doesn't wait for |
252 |
> |
* completion otherwise. |
253 |
|
* |
254 |
< |
* @param millis if > 0, wait time. |
254 |
> |
* @return status on exit from this method |
255 |
|
*/ |
256 |
< |
final void tryAwaitDone(long millis) { |
257 |
< |
int s; |
258 |
< |
try { |
259 |
< |
if (((s = status) > 0 || |
260 |
< |
(s == 0 && |
261 |
< |
UNSAFE.compareAndSwapInt(this, statusOffset, 0, SIGNAL))) && |
262 |
< |
status > 0) { |
229 |
< |
synchronized (this) { |
230 |
< |
if (status > 0) |
231 |
< |
wait(millis); |
232 |
< |
} |
256 |
> |
final int doExec() { |
257 |
> |
int s; boolean completed; |
258 |
> |
if ((s = status) >= 0) { |
259 |
> |
try { |
260 |
> |
completed = exec(); |
261 |
> |
} catch (Throwable rex) { |
262 |
> |
return setExceptionalCompletion(rex); |
263 |
|
} |
264 |
< |
} catch (InterruptedException ie) { |
265 |
< |
// caller must check termination |
264 |
> |
if (completed) |
265 |
> |
s = setCompletion(NORMAL); |
266 |
|
} |
267 |
+ |
return s; |
268 |
+ |
} |
269 |
+ |
|
270 |
+ |
/** |
271 |
+ |
* Tries to set SIGNAL status unless already completed. Used by |
272 |
+ |
* ForkJoinPool. Other variants are directly incorporated into |
273 |
+ |
* externalAwaitDone etc. |
274 |
+ |
* |
275 |
+ |
* @return true if successful |
276 |
+ |
*/ |
277 |
+ |
final boolean trySetSignal() { |
278 |
+ |
int s = status; |
279 |
+ |
return s >= 0 && U.compareAndSwapInt(this, STATUS, s, s | SIGNAL); |
280 |
|
} |
281 |
|
|
282 |
|
/** |
285 |
|
*/ |
286 |
|
private int externalAwaitDone() { |
287 |
|
int s; |
288 |
< |
if ((s = status) >= 0) { |
289 |
< |
boolean interrupted = false; |
290 |
< |
synchronized (this) { |
291 |
< |
while ((s = status) >= 0) { |
292 |
< |
if (s == 0) |
293 |
< |
UNSAFE.compareAndSwapInt(this, statusOffset, |
294 |
< |
0, SIGNAL); |
252 |
< |
else { |
288 |
> |
boolean interrupted = false; |
289 |
> |
if ((s = status) >= 0 && ForkJoinPool.tryUnsubmitFromCommonPool(this)) |
290 |
> |
s = doExec(); |
291 |
> |
while (s >= 0) { |
292 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
293 |
> |
synchronized (this) { |
294 |
> |
if (status >= 0) { |
295 |
|
try { |
296 |
|
wait(); |
297 |
|
} catch (InterruptedException ie) { |
298 |
|
interrupted = true; |
299 |
|
} |
300 |
|
} |
301 |
+ |
else |
302 |
+ |
notifyAll(); |
303 |
|
} |
304 |
|
} |
305 |
< |
if (interrupted) |
262 |
< |
Thread.currentThread().interrupt(); |
305 |
> |
s = status; |
306 |
|
} |
307 |
+ |
if (interrupted) |
308 |
+ |
Thread.currentThread().interrupt(); |
309 |
|
return s; |
310 |
|
} |
311 |
|
|
312 |
|
/** |
313 |
< |
* Blocks a non-worker-thread until completion or interruption or timeout. |
313 |
> |
* Blocks a non-worker-thread until completion or interruption. |
314 |
|
*/ |
315 |
< |
private int externalInterruptibleAwaitDone(long millis) |
271 |
< |
throws InterruptedException { |
272 |
< |
int s; |
315 |
> |
private int externalInterruptibleAwaitDone() throws InterruptedException { |
316 |
|
if (Thread.interrupted()) |
317 |
|
throw new InterruptedException(); |
318 |
< |
if ((s = status) >= 0) { |
319 |
< |
synchronized (this) { |
320 |
< |
while ((s = status) >= 0) { |
321 |
< |
if (s == 0) |
322 |
< |
UNSAFE.compareAndSwapInt(this, statusOffset, |
323 |
< |
0, SIGNAL); |
324 |
< |
else { |
325 |
< |
wait(millis); |
326 |
< |
if (millis > 0L) |
327 |
< |
break; |
285 |
< |
} |
318 |
> |
int s; |
319 |
> |
if ((s = status) >= 0 && ForkJoinPool.tryUnsubmitFromCommonPool(this)) |
320 |
> |
s = doExec(); |
321 |
> |
while (s >= 0) { |
322 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
323 |
> |
synchronized (this) { |
324 |
> |
if (status >= 0) |
325 |
> |
wait(); |
326 |
> |
else |
327 |
> |
notifyAll(); |
328 |
|
} |
329 |
|
} |
330 |
+ |
s = status; |
331 |
|
} |
332 |
|
return s; |
333 |
|
} |
334 |
|
|
335 |
|
/** |
336 |
< |
* Primary execution method for stolen tasks. Unless done, calls |
337 |
< |
* exec and records status if completed, but doesn't wait for |
338 |
< |
* completion otherwise. |
339 |
< |
*/ |
297 |
< |
final void doExec() { |
298 |
< |
if (status >= 0) { |
299 |
< |
boolean completed; |
300 |
< |
try { |
301 |
< |
completed = exec(); |
302 |
< |
} catch (Throwable rex) { |
303 |
< |
setExceptionalCompletion(rex); |
304 |
< |
return; |
305 |
< |
} |
306 |
< |
if (completed) |
307 |
< |
setCompletion(NORMAL); // must be outside try block |
308 |
< |
} |
309 |
< |
} |
310 |
< |
|
311 |
< |
/** |
312 |
< |
* Primary mechanics for join, get, quietlyJoin. |
336 |
> |
* Implementation for join, get, quietlyJoin. Directly handles |
337 |
> |
* only cases of already-completed, external wait, and |
338 |
> |
* unfork+exec. Others are relayed to ForkJoinPool.awaitJoin. |
339 |
> |
* |
340 |
|
* @return status upon completion |
341 |
|
*/ |
342 |
|
private int doJoin() { |
343 |
< |
Thread t; ForkJoinWorkerThread w; int s; boolean completed; |
344 |
< |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) { |
345 |
< |
if ((s = status) < 0) |
346 |
< |
return s; |
347 |
< |
if ((w = (ForkJoinWorkerThread)t).unpushTask(this)) { |
348 |
< |
try { |
349 |
< |
completed = exec(); |
323 |
< |
} catch (Throwable rex) { |
324 |
< |
return setExceptionalCompletion(rex); |
325 |
< |
} |
326 |
< |
if (completed) |
327 |
< |
return setCompletion(NORMAL); |
328 |
< |
} |
329 |
< |
return w.joinTask(this); |
330 |
< |
} |
331 |
< |
else |
332 |
< |
return externalAwaitDone(); |
343 |
> |
int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w; |
344 |
> |
return (s = status) < 0 ? s : |
345 |
> |
((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? |
346 |
> |
(w = (wt = (ForkJoinWorkerThread)t).workQueue). |
347 |
> |
tryUnpush(this) && (s = doExec()) < 0 ? s : |
348 |
> |
wt.pool.awaitJoin(w, this) : |
349 |
> |
externalAwaitDone(); |
350 |
|
} |
351 |
|
|
352 |
|
/** |
353 |
< |
* Primary mechanics for invoke, quietlyInvoke. |
353 |
> |
* Implementation for invoke, quietlyInvoke. |
354 |
> |
* |
355 |
|
* @return status upon completion |
356 |
|
*/ |
357 |
|
private int doInvoke() { |
358 |
< |
int s; boolean completed; |
359 |
< |
if ((s = status) < 0) |
360 |
< |
return s; |
361 |
< |
try { |
362 |
< |
completed = exec(); |
345 |
< |
} catch (Throwable rex) { |
346 |
< |
return setExceptionalCompletion(rex); |
347 |
< |
} |
348 |
< |
if (completed) |
349 |
< |
return setCompletion(NORMAL); |
350 |
< |
else |
351 |
< |
return doJoin(); |
358 |
> |
int s; Thread t; ForkJoinWorkerThread wt; |
359 |
> |
return (s = doExec()) < 0 ? s : |
360 |
> |
((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? |
361 |
> |
(wt = (ForkJoinWorkerThread)t).pool.awaitJoin(wt.workQueue, this) : |
362 |
> |
externalAwaitDone(); |
363 |
|
} |
364 |
|
|
365 |
|
// Exception table support |
394 |
|
* any ForkJoinPool will call helpExpungeStaleExceptions when its |
395 |
|
* pool becomes isQuiescent. |
396 |
|
*/ |
397 |
< |
static final class ExceptionNode extends WeakReference<ForkJoinTask<?>>{ |
397 |
> |
static final class ExceptionNode extends WeakReference<ForkJoinTask<?>> { |
398 |
|
final Throwable ex; |
399 |
|
ExceptionNode next; |
400 |
|
final long thrower; // use id not ref to avoid weak cycles |
407 |
|
} |
408 |
|
|
409 |
|
/** |
410 |
< |
* Records exception and sets exceptional completion. |
410 |
> |
* Records exception and sets status. |
411 |
|
* |
412 |
|
* @return status on exit |
413 |
|
*/ |
414 |
< |
private int setExceptionalCompletion(Throwable ex) { |
415 |
< |
int h = System.identityHashCode(this); |
416 |
< |
final ReentrantLock lock = exceptionTableLock; |
417 |
< |
lock.lock(); |
418 |
< |
try { |
419 |
< |
expungeStaleExceptions(); |
420 |
< |
ExceptionNode[] t = exceptionTable; |
421 |
< |
int i = h & (t.length - 1); |
422 |
< |
for (ExceptionNode e = t[i]; ; e = e.next) { |
423 |
< |
if (e == null) { |
424 |
< |
t[i] = new ExceptionNode(this, ex, t[i]); |
425 |
< |
break; |
414 |
> |
final int recordExceptionalCompletion(Throwable ex) { |
415 |
> |
int s; |
416 |
> |
if ((s = status) >= 0) { |
417 |
> |
int h = System.identityHashCode(this); |
418 |
> |
final ReentrantLock lock = exceptionTableLock; |
419 |
> |
lock.lock(); |
420 |
> |
try { |
421 |
> |
expungeStaleExceptions(); |
422 |
> |
ExceptionNode[] t = exceptionTable; |
423 |
> |
int i = h & (t.length - 1); |
424 |
> |
for (ExceptionNode e = t[i]; ; e = e.next) { |
425 |
> |
if (e == null) { |
426 |
> |
t[i] = new ExceptionNode(this, ex, t[i]); |
427 |
> |
break; |
428 |
> |
} |
429 |
> |
if (e.get() == this) // already present |
430 |
> |
break; |
431 |
|
} |
432 |
< |
if (e.get() == this) // already present |
433 |
< |
break; |
432 |
> |
} finally { |
433 |
> |
lock.unlock(); |
434 |
> |
} |
435 |
> |
s = setCompletion(EXCEPTIONAL); |
436 |
> |
} |
437 |
> |
return s; |
438 |
> |
} |
439 |
> |
|
440 |
> |
/** |
441 |
> |
* Records exception and possibly propagates |
442 |
> |
* |
443 |
> |
* @return status on exit |
444 |
> |
*/ |
445 |
> |
private int setExceptionalCompletion(Throwable ex) { |
446 |
> |
int s = recordExceptionalCompletion(ex); |
447 |
> |
if ((s & DONE_MASK) == EXCEPTIONAL) |
448 |
> |
internalPropagateException(ex); |
449 |
> |
return s; |
450 |
> |
} |
451 |
> |
|
452 |
> |
/** |
453 |
> |
* Hook for exception propagation support for tasks with completers. |
454 |
> |
*/ |
455 |
> |
void internalPropagateException(Throwable ex) { |
456 |
> |
} |
457 |
> |
|
458 |
> |
/** |
459 |
> |
* Cancels, ignoring any exceptions thrown by cancel. Used during |
460 |
> |
* worker and pool shutdown. Cancel is spec'ed not to throw any |
461 |
> |
* exceptions, but if it does anyway, we have no recourse during |
462 |
> |
* shutdown, so guard against this case. |
463 |
> |
*/ |
464 |
> |
static final void cancelIgnoringExceptions(ForkJoinTask<?> t) { |
465 |
> |
if (t != null && t.status >= 0) { |
466 |
> |
try { |
467 |
> |
t.cancel(false); |
468 |
> |
} catch (Throwable ignore) { |
469 |
|
} |
419 |
– |
} finally { |
420 |
– |
lock.unlock(); |
470 |
|
} |
422 |
– |
return setCompletion(EXCEPTIONAL); |
471 |
|
} |
472 |
|
|
473 |
|
/** |
516 |
|
* @return the exception, or null if none |
517 |
|
*/ |
518 |
|
private Throwable getThrowableException() { |
519 |
< |
if (status != EXCEPTIONAL) |
519 |
> |
if ((status & DONE_MASK) != EXCEPTIONAL) |
520 |
|
return null; |
521 |
|
int h = System.identityHashCode(this); |
522 |
|
ExceptionNode e; |
534 |
|
Throwable ex; |
535 |
|
if (e == null || (ex = e.ex) == null) |
536 |
|
return null; |
537 |
< |
if (e.thrower != Thread.currentThread().getId()) { |
537 |
> |
if (false && e.thrower != Thread.currentThread().getId()) { |
538 |
|
Class<? extends Throwable> ec = ex.getClass(); |
539 |
|
try { |
540 |
|
Constructor<?> noArgCtor = null; |
601 |
|
} |
602 |
|
|
603 |
|
/** |
604 |
< |
* Report the result of invoke or join; called only upon |
557 |
< |
* non-normal return of internal versions. |
604 |
> |
* Throws exception, if any, associated with the given status. |
605 |
|
*/ |
606 |
< |
private V reportResult() { |
607 |
< |
int s; Throwable ex; |
608 |
< |
if ((s = status) == CANCELLED) |
609 |
< |
throw new CancellationException(); |
610 |
< |
if (s == EXCEPTIONAL && (ex = getThrowableException()) != null) |
611 |
< |
UNSAFE.throwException(ex); |
565 |
< |
return getRawResult(); |
606 |
> |
private void reportException(int s) { |
607 |
> |
Throwable ex = ((s == CANCELLED) ? new CancellationException() : |
608 |
> |
(s == EXCEPTIONAL) ? getThrowableException() : |
609 |
> |
null); |
610 |
> |
if (ex != null) |
611 |
> |
U.throwException(ex); |
612 |
|
} |
613 |
|
|
614 |
|
// public methods |
615 |
|
|
616 |
|
/** |
617 |
< |
* Arranges to asynchronously execute this task. While it is not |
618 |
< |
* necessarily enforced, it is a usage error to fork a task more |
619 |
< |
* than once unless it has completed and been reinitialized. |
620 |
< |
* Subsequent modifications to the state of this task or any data |
621 |
< |
* it operates on are not necessarily consistently observable by |
622 |
< |
* any thread other than the one executing it unless preceded by a |
623 |
< |
* call to {@link #join} or related methods, or a call to {@link |
624 |
< |
* #isDone} returning {@code true}. |
625 |
< |
* |
626 |
< |
* <p>This method may be invoked only from within {@code |
627 |
< |
* ForkJoinPool} computations (as may be determined using method |
582 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
583 |
< |
* result in exceptions or errors, possibly including {@code |
584 |
< |
* ClassCastException}. |
617 |
> |
* Arranges to asynchronously execute this task in the pool the |
618 |
> |
* current task is running in, if applicable, or using the {@link |
619 |
> |
* ForkJoinPool#commonPool} if not {@link #inForkJoinPool}. While |
620 |
> |
* it is not necessarily enforced, it is a usage error to fork a |
621 |
> |
* task more than once unless it has completed and been |
622 |
> |
* reinitialized. Subsequent modifications to the state of this |
623 |
> |
* task or any data it operates on are not necessarily |
624 |
> |
* consistently observable by any thread other than the one |
625 |
> |
* executing it unless preceded by a call to {@link #join} or |
626 |
> |
* related methods, or a call to {@link #isDone} returning {@code |
627 |
> |
* true}. |
628 |
|
* |
629 |
|
* @return {@code this}, to simplify usage |
630 |
|
*/ |
631 |
|
public final ForkJoinTask<V> fork() { |
632 |
< |
((ForkJoinWorkerThread) Thread.currentThread()) |
633 |
< |
.pushTask(this); |
632 |
> |
Thread t; |
633 |
> |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) |
634 |
> |
((ForkJoinWorkerThread)t).workQueue.push(this); |
635 |
> |
else |
636 |
> |
ForkJoinPool.submitToCommonPool(this); |
637 |
|
return this; |
638 |
|
} |
639 |
|
|
649 |
|
* @return the computed result |
650 |
|
*/ |
651 |
|
public final V join() { |
652 |
< |
if (doJoin() != NORMAL) |
653 |
< |
return reportResult(); |
654 |
< |
else |
655 |
< |
return getRawResult(); |
652 |
> |
int s; |
653 |
> |
if ((s = doJoin() & DONE_MASK) != NORMAL) |
654 |
> |
reportException(s); |
655 |
> |
return getRawResult(); |
656 |
|
} |
657 |
|
|
658 |
|
/** |
664 |
|
* @return the computed result |
665 |
|
*/ |
666 |
|
public final V invoke() { |
667 |
< |
if (doInvoke() != NORMAL) |
668 |
< |
return reportResult(); |
669 |
< |
else |
670 |
< |
return getRawResult(); |
667 |
> |
int s; |
668 |
> |
if ((s = doInvoke() & DONE_MASK) != NORMAL) |
669 |
> |
reportException(s); |
670 |
> |
return getRawResult(); |
671 |
|
} |
672 |
|
|
673 |
|
/** |
683 |
|
* cancelled, completed normally or exceptionally, or left |
684 |
|
* unprocessed. |
685 |
|
* |
640 |
– |
* <p>This method may be invoked only from within {@code |
641 |
– |
* ForkJoinPool} computations (as may be determined using method |
642 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
643 |
– |
* result in exceptions or errors, possibly including {@code |
644 |
– |
* ClassCastException}. |
645 |
– |
* |
686 |
|
* @param t1 the first task |
687 |
|
* @param t2 the second task |
688 |
|
* @throws NullPointerException if any task is null |
689 |
|
*/ |
690 |
|
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) { |
691 |
+ |
int s1, s2; |
692 |
|
t2.fork(); |
693 |
< |
t1.invoke(); |
694 |
< |
t2.join(); |
693 |
> |
if ((s1 = t1.doInvoke() & DONE_MASK) != NORMAL) |
694 |
> |
t1.reportException(s1); |
695 |
> |
if ((s2 = t2.doJoin() & DONE_MASK) != NORMAL) |
696 |
> |
t2.reportException(s2); |
697 |
|
} |
698 |
|
|
699 |
|
/** |
708 |
|
* related methods to check if they have been cancelled, completed |
709 |
|
* normally or exceptionally, or left unprocessed. |
710 |
|
* |
668 |
– |
* <p>This method may be invoked only from within {@code |
669 |
– |
* ForkJoinPool} computations (as may be determined using method |
670 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
671 |
– |
* result in exceptions or errors, possibly including {@code |
672 |
– |
* ClassCastException}. |
673 |
– |
* |
711 |
|
* @param tasks the tasks |
712 |
|
* @throws NullPointerException if any task is null |
713 |
|
*/ |
730 |
|
if (t != null) { |
731 |
|
if (ex != null) |
732 |
|
t.cancel(false); |
733 |
< |
else if (t.doJoin() < NORMAL && ex == null) |
733 |
> |
else if (t.doJoin() < NORMAL) |
734 |
|
ex = t.getException(); |
735 |
|
} |
736 |
|
} |
737 |
|
if (ex != null) |
738 |
< |
UNSAFE.throwException(ex); |
738 |
> |
U.throwException(ex); |
739 |
|
} |
740 |
|
|
741 |
|
/** |
751 |
|
* cancelled, completed normally or exceptionally, or left |
752 |
|
* unprocessed. |
753 |
|
* |
717 |
– |
* <p>This method may be invoked only from within {@code |
718 |
– |
* ForkJoinPool} computations (as may be determined using method |
719 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
720 |
– |
* result in exceptions or errors, possibly including {@code |
721 |
– |
* ClassCastException}. |
722 |
– |
* |
754 |
|
* @param tasks the collection of tasks |
755 |
|
* @return the tasks argument, to simplify usage |
756 |
|
* @throws NullPointerException if tasks or any element are null |
781 |
|
if (t != null) { |
782 |
|
if (ex != null) |
783 |
|
t.cancel(false); |
784 |
< |
else if (t.doJoin() < NORMAL && ex == null) |
784 |
> |
else if (t.doJoin() < NORMAL) |
785 |
|
ex = t.getException(); |
786 |
|
} |
787 |
|
} |
788 |
|
if (ex != null) |
789 |
< |
UNSAFE.throwException(ex); |
789 |
> |
U.throwException(ex); |
790 |
|
return tasks; |
791 |
|
} |
792 |
|
|
818 |
|
* @return {@code true} if this task is now cancelled |
819 |
|
*/ |
820 |
|
public boolean cancel(boolean mayInterruptIfRunning) { |
821 |
< |
return setCompletion(CANCELLED) == CANCELLED; |
791 |
< |
} |
792 |
< |
|
793 |
< |
/** |
794 |
< |
* Cancels, ignoring any exceptions thrown by cancel. Used during |
795 |
< |
* worker and pool shutdown. Cancel is spec'ed not to throw any |
796 |
< |
* exceptions, but if it does anyway, we have no recourse during |
797 |
< |
* shutdown, so guard against this case. |
798 |
< |
*/ |
799 |
< |
final void cancelIgnoringExceptions() { |
800 |
< |
try { |
801 |
< |
cancel(false); |
802 |
< |
} catch (Throwable ignore) { |
803 |
< |
} |
821 |
> |
return (setCompletion(CANCELLED) & DONE_MASK) == CANCELLED; |
822 |
|
} |
823 |
|
|
824 |
|
public final boolean isDone() { |
826 |
|
} |
827 |
|
|
828 |
|
public final boolean isCancelled() { |
829 |
< |
return status == CANCELLED; |
829 |
> |
return (status & DONE_MASK) == CANCELLED; |
830 |
|
} |
831 |
|
|
832 |
|
/** |
846 |
|
* exception and was not cancelled |
847 |
|
*/ |
848 |
|
public final boolean isCompletedNormally() { |
849 |
< |
return status == NORMAL; |
849 |
> |
return (status & DONE_MASK) == NORMAL; |
850 |
|
} |
851 |
|
|
852 |
|
/** |
857 |
|
* @return the exception, or {@code null} if none |
858 |
|
*/ |
859 |
|
public final Throwable getException() { |
860 |
< |
int s = status; |
860 |
> |
int s = status & DONE_MASK; |
861 |
|
return ((s >= NORMAL) ? null : |
862 |
|
(s == CANCELLED) ? new CancellationException() : |
863 |
|
getThrowableException()); |
907 |
|
} |
908 |
|
|
909 |
|
/** |
910 |
+ |
* Completes this task normally without setting a value. The most |
911 |
+ |
* recent value established by {@link #setRawResult} (or {@code |
912 |
+ |
* null} by default) will be returned as the result of subsequent |
913 |
+ |
* invocations of {@code join} and related operations. |
914 |
+ |
* |
915 |
+ |
* @since 1.8 |
916 |
+ |
*/ |
917 |
+ |
public final void quietlyComplete() { |
918 |
+ |
setCompletion(NORMAL); |
919 |
+ |
} |
920 |
+ |
|
921 |
+ |
/** |
922 |
|
* Waits if necessary for the computation to complete, and then |
923 |
|
* retrieves its result. |
924 |
|
* |
931 |
|
*/ |
932 |
|
public final V get() throws InterruptedException, ExecutionException { |
933 |
|
int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ? |
934 |
< |
doJoin() : externalInterruptibleAwaitDone(0L); |
934 |
> |
doJoin() : externalInterruptibleAwaitDone(); |
935 |
|
Throwable ex; |
936 |
< |
if (s == CANCELLED) |
936 |
> |
if ((s &= DONE_MASK) == CANCELLED) |
937 |
|
throw new CancellationException(); |
938 |
|
if (s == EXCEPTIONAL && (ex = getThrowableException()) != null) |
939 |
|
throw new ExecutionException(ex); |
956 |
|
*/ |
957 |
|
public final V get(long timeout, TimeUnit unit) |
958 |
|
throws InterruptedException, ExecutionException, TimeoutException { |
959 |
< |
Thread t = Thread.currentThread(); |
960 |
< |
if (t instanceof ForkJoinWorkerThread) { |
961 |
< |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
962 |
< |
long nanos = unit.toNanos(timeout); |
963 |
< |
if (status >= 0) { |
964 |
< |
boolean completed = false; |
965 |
< |
if (w.unpushTask(this)) { |
966 |
< |
try { |
967 |
< |
completed = exec(); |
968 |
< |
} catch (Throwable rex) { |
969 |
< |
setExceptionalCompletion(rex); |
959 |
> |
if (Thread.interrupted()) |
960 |
> |
throw new InterruptedException(); |
961 |
> |
// Messy in part because we measure in nanosecs, but wait in millisecs |
962 |
> |
int s; long ns, ms; |
963 |
> |
if ((s = status) >= 0 && (ns = unit.toNanos(timeout)) > 0L) { |
964 |
> |
long deadline = System.nanoTime() + ns; |
965 |
> |
ForkJoinPool p = null; |
966 |
> |
ForkJoinPool.WorkQueue w = null; |
967 |
> |
Thread t = Thread.currentThread(); |
968 |
> |
if (t instanceof ForkJoinWorkerThread) { |
969 |
> |
ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; |
970 |
> |
p = wt.pool; |
971 |
> |
w = wt.workQueue; |
972 |
> |
s = p.helpJoinOnce(w, this); // no retries on failure |
973 |
> |
} |
974 |
> |
boolean canBlock = false; |
975 |
> |
boolean interrupted = false; |
976 |
> |
try { |
977 |
> |
while ((s = status) >= 0) { |
978 |
> |
if (w != null && w.runState < 0) |
979 |
> |
cancelIgnoringExceptions(this); |
980 |
> |
else if (!canBlock) { |
981 |
> |
if (p == null || p.tryCompensate(this, null)) |
982 |
> |
canBlock = true; |
983 |
> |
} |
984 |
> |
else { |
985 |
> |
if ((ms = TimeUnit.NANOSECONDS.toMillis(ns)) > 0L && |
986 |
> |
U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
987 |
> |
synchronized (this) { |
988 |
> |
if (status >= 0) { |
989 |
> |
try { |
990 |
> |
wait(ms); |
991 |
> |
} catch (InterruptedException ie) { |
992 |
> |
if (p == null) |
993 |
> |
interrupted = true; |
994 |
> |
} |
995 |
> |
} |
996 |
> |
else |
997 |
> |
notifyAll(); |
998 |
> |
} |
999 |
> |
} |
1000 |
> |
if ((s = status) < 0 || interrupted || |
1001 |
> |
(ns = deadline - System.nanoTime()) <= 0L) |
1002 |
> |
break; |
1003 |
|
} |
1004 |
|
} |
1005 |
< |
if (completed) |
1006 |
< |
setCompletion(NORMAL); |
1007 |
< |
else if (status >= 0 && nanos > 0) |
945 |
< |
w.pool.timedAwaitJoin(this, nanos); |
1005 |
> |
} finally { |
1006 |
> |
if (p != null && canBlock) |
1007 |
> |
p.incrementActiveCount(); |
1008 |
|
} |
1009 |
+ |
if (interrupted) |
1010 |
+ |
throw new InterruptedException(); |
1011 |
|
} |
1012 |
< |
else { |
949 |
< |
long millis = unit.toMillis(timeout); |
950 |
< |
if (millis > 0) |
951 |
< |
externalInterruptibleAwaitDone(millis); |
952 |
< |
} |
953 |
< |
int s = status; |
954 |
< |
if (s != NORMAL) { |
1012 |
> |
if ((s &= DONE_MASK) != NORMAL) { |
1013 |
|
Throwable ex; |
1014 |
|
if (s == CANCELLED) |
1015 |
|
throw new CancellationException(); |
1046 |
|
* be of use in designs in which many tasks are forked, but none |
1047 |
|
* are explicitly joined, instead executing them until all are |
1048 |
|
* processed. |
991 |
– |
* |
992 |
– |
* <p>This method may be invoked only from within {@code |
993 |
– |
* ForkJoinPool} computations (as may be determined using method |
994 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
995 |
– |
* result in exceptions or errors, possibly including {@code |
996 |
– |
* ClassCastException}. |
1049 |
|
*/ |
1050 |
|
public static void helpQuiesce() { |
1051 |
< |
((ForkJoinWorkerThread) Thread.currentThread()) |
1052 |
< |
.helpQuiescePool(); |
1051 |
> |
Thread t; |
1052 |
> |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) { |
1053 |
> |
ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; |
1054 |
> |
wt.pool.helpQuiescePool(wt.workQueue); |
1055 |
> |
} |
1056 |
> |
else |
1057 |
> |
ForkJoinPool.externalHelpQuiescePool(); |
1058 |
|
} |
1059 |
|
|
1060 |
|
/** |
1074 |
|
* setRawResult(null)}. |
1075 |
|
*/ |
1076 |
|
public void reinitialize() { |
1077 |
< |
if (status == EXCEPTIONAL) |
1077 |
> |
if ((status & DONE_MASK) == EXCEPTIONAL) |
1078 |
|
clearExceptionalCompletion(); |
1079 |
|
else |
1080 |
|
status = 0; |
1107 |
|
|
1108 |
|
/** |
1109 |
|
* Tries to unschedule this task for execution. This method will |
1110 |
< |
* typically succeed if this task is the most recently forked task |
1111 |
< |
* by the current thread, and has not commenced executing in |
1112 |
< |
* another thread. This method may be useful when arranging |
1113 |
< |
* alternative local processing of tasks that could have been, but |
1114 |
< |
* were not, stolen. |
1058 |
< |
* |
1059 |
< |
* <p>This method may be invoked only from within {@code |
1060 |
< |
* ForkJoinPool} computations (as may be determined using method |
1061 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1062 |
< |
* result in exceptions or errors, possibly including {@code |
1063 |
< |
* ClassCastException}. |
1110 |
> |
* typically (but is not guaranteed to) succeed if this task is |
1111 |
> |
* the most recently forked task by the current thread, and has |
1112 |
> |
* not commenced executing in another thread. This method may be |
1113 |
> |
* useful when arranging alternative local processing of tasks |
1114 |
> |
* that could have been, but were not, stolen. |
1115 |
|
* |
1116 |
|
* @return {@code true} if unforked |
1117 |
|
*/ |
1118 |
|
public boolean tryUnfork() { |
1119 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1120 |
< |
.unpushTask(this); |
1119 |
> |
Thread t; |
1120 |
> |
return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? |
1121 |
> |
((ForkJoinWorkerThread)t).workQueue.tryUnpush(this) : |
1122 |
> |
ForkJoinPool.tryUnsubmitFromCommonPool(this); |
1123 |
|
} |
1124 |
|
|
1125 |
|
/** |
1128 |
|
* value may be useful for heuristic decisions about whether to |
1129 |
|
* fork other tasks. |
1130 |
|
* |
1078 |
– |
* <p>This method may be invoked only from within {@code |
1079 |
– |
* ForkJoinPool} computations (as may be determined using method |
1080 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1081 |
– |
* result in exceptions or errors, possibly including {@code |
1082 |
– |
* ClassCastException}. |
1083 |
– |
* |
1131 |
|
* @return the number of tasks |
1132 |
|
*/ |
1133 |
|
public static int getQueuedTaskCount() { |
1134 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1135 |
< |
.getQueueSize(); |
1134 |
> |
Thread t; |
1135 |
> |
return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? |
1136 |
> |
((ForkJoinWorkerThread)t).workQueue.queueSize() : |
1137 |
> |
ForkJoinPool.getEstimatedSubmitterQueueLength(); |
1138 |
|
} |
1139 |
|
|
1140 |
|
/** |
1141 |
|
* Returns an estimate of how many more locally queued tasks are |
1142 |
|
* held by the current worker thread than there are other worker |
1143 |
< |
* threads that might steal them. This value may be useful for |
1143 |
> |
* threads that might steal them, or zero if this thread is not |
1144 |
> |
* operating in a ForkJoinPool. This value may be useful for |
1145 |
|
* heuristic decisions about whether to fork other tasks. In many |
1146 |
|
* usages of ForkJoinTasks, at steady state, each worker should |
1147 |
|
* aim to maintain a small constant surplus (for example, 3) of |
1148 |
|
* tasks, and to process computations locally if this threshold is |
1149 |
|
* exceeded. |
1150 |
|
* |
1101 |
– |
* <p>This method may be invoked only from within {@code |
1102 |
– |
* ForkJoinPool} computations (as may be determined using method |
1103 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1104 |
– |
* result in exceptions or errors, possibly including {@code |
1105 |
– |
* ClassCastException}. |
1106 |
– |
* |
1151 |
|
* @return the surplus number of tasks, which may be negative |
1152 |
|
*/ |
1153 |
|
public static int getSurplusQueuedTaskCount() { |
1154 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1155 |
< |
.getEstimatedSurplusTaskCount(); |
1154 |
> |
/* |
1155 |
> |
* The aim of this method is to return a cheap heuristic guide |
1156 |
> |
* for task partitioning when programmers, frameworks, tools, |
1157 |
> |
* or languages have little or no idea about task granularity. |
1158 |
> |
* In essence by offering this method, we ask users only about |
1159 |
> |
* tradeoffs in overhead vs expected throughput and its |
1160 |
> |
* variance, rather than how finely to partition tasks. |
1161 |
> |
* |
1162 |
> |
* In a steady state strict (tree-structured) computation, |
1163 |
> |
* each thread makes available for stealing enough tasks for |
1164 |
> |
* other threads to remain active. Inductively, if all threads |
1165 |
> |
* play by the same rules, each thread should make available |
1166 |
> |
* only a constant number of tasks. |
1167 |
> |
* |
1168 |
> |
* The minimum useful constant is just 1. But using a value of |
1169 |
> |
* 1 would require immediate replenishment upon each steal to |
1170 |
> |
* maintain enough tasks, which is infeasible. Further, |
1171 |
> |
* partitionings/granularities of offered tasks should |
1172 |
> |
* minimize steal rates, which in general means that threads |
1173 |
> |
* nearer the top of computation tree should generate more |
1174 |
> |
* than those nearer the bottom. In perfect steady state, each |
1175 |
> |
* thread is at approximately the same level of computation |
1176 |
> |
* tree. However, producing extra tasks amortizes the |
1177 |
> |
* uncertainty of progress and diffusion assumptions. |
1178 |
> |
* |
1179 |
> |
* So, users will want to use values larger, but not much |
1180 |
> |
* larger than 1 to both smooth over transient shortages and |
1181 |
> |
* hedge against uneven progress; as traded off against the |
1182 |
> |
* cost of extra task overhead. We leave the user to pick a |
1183 |
> |
* threshold value to compare with the results of this call to |
1184 |
> |
* guide decisions, but recommend values such as 3. |
1185 |
> |
* |
1186 |
> |
* When all threads are active, it is on average OK to |
1187 |
> |
* estimate surplus strictly locally. In steady-state, if one |
1188 |
> |
* thread is maintaining say 2 surplus tasks, then so are |
1189 |
> |
* others. So we can just use estimated queue length. |
1190 |
> |
* However, this strategy alone leads to serious mis-estimates |
1191 |
> |
* in some non-steady-state conditions (ramp-up, ramp-down, |
1192 |
> |
* other stalls). We can detect many of these by further |
1193 |
> |
* considering the number of "idle" threads, that are known to |
1194 |
> |
* have zero queued tasks, so compensate by a factor of |
1195 |
> |
* (#idle/#active) threads. |
1196 |
> |
*/ |
1197 |
> |
Thread t; ForkJoinWorkerThread wt; |
1198 |
> |
return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? |
1199 |
> |
(wt = (ForkJoinWorkerThread)t).workQueue.queueSize() - wt.pool.idlePerActive() : |
1200 |
> |
0; |
1201 |
|
} |
1202 |
|
|
1203 |
|
// Extension methods |
1223 |
|
protected abstract void setRawResult(V value); |
1224 |
|
|
1225 |
|
/** |
1226 |
< |
* Immediately performs the base action of this task. This method |
1227 |
< |
* is designed to support extensions, and should not in general be |
1228 |
< |
* called otherwise. The return value controls whether this task |
1229 |
< |
* is considered to be done normally. It may return false in |
1226 |
> |
* Immediately performs the base action of this task and returns |
1227 |
> |
* true if, upon return from this method, this task is guaranteed |
1228 |
> |
* to have completed normally. This method may return false |
1229 |
> |
* otherwise, to indicate that this task is not necessarily |
1230 |
> |
* complete (or is not known to be complete), for example in |
1231 |
|
* asynchronous actions that require explicit invocations of |
1232 |
< |
* {@link #complete} to become joinable. It may also throw an |
1233 |
< |
* (unchecked) exception to indicate abnormal exit. |
1232 |
> |
* completion methods. This method may also throw an (unchecked) |
1233 |
> |
* exception to indicate abnormal exit. This method is designed to |
1234 |
> |
* support extensions, and should not in general be called |
1235 |
> |
* otherwise. |
1236 |
|
* |
1237 |
< |
* @return {@code true} if completed normally |
1237 |
> |
* @return {@code true} if this task is known to have completed normally |
1238 |
|
*/ |
1239 |
|
protected abstract boolean exec(); |
1240 |
|
|
1241 |
|
/** |
1242 |
|
* Returns, but does not unschedule or execute, a task queued by |
1243 |
|
* the current thread but not yet executed, if one is immediately |
1244 |
< |
* available. There is no guarantee that this task will actually |
1245 |
< |
* be polled or executed next. Conversely, this method may return |
1246 |
< |
* null even if a task exists but cannot be accessed without |
1247 |
< |
* contention with other threads. This method is designed |
1244 |
> |
* available and the current thread is operating in a |
1245 |
> |
* ForkJoinPool. There is no guarantee that this task will |
1246 |
> |
* actually be polled or executed next. Conversely, this method |
1247 |
> |
* may return null even if a task exists but cannot be accessed |
1248 |
> |
* without contention with other threads. This method is designed |
1249 |
|
* primarily to support extensions, and is unlikely to be useful |
1250 |
|
* otherwise. |
1251 |
|
* |
1159 |
– |
* <p>This method may be invoked only from within {@code |
1160 |
– |
* ForkJoinPool} computations (as may be determined using method |
1161 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1162 |
– |
* result in exceptions or errors, possibly including {@code |
1163 |
– |
* ClassCastException}. |
1164 |
– |
* |
1252 |
|
* @return the next task, or {@code null} if none are available |
1253 |
|
*/ |
1254 |
|
protected static ForkJoinTask<?> peekNextLocalTask() { |
1255 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1256 |
< |
.peekTask(); |
1255 |
> |
Thread t; |
1256 |
> |
return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? |
1257 |
> |
((ForkJoinWorkerThread)t).workQueue.peek() : |
1258 |
> |
null; |
1259 |
|
} |
1260 |
|
|
1261 |
|
/** |
1262 |
|
* Unschedules and returns, without executing, the next task |
1263 |
< |
* queued by the current thread but not yet executed. This method |
1264 |
< |
* is designed primarily to support extensions, and is unlikely to |
1265 |
< |
* be useful otherwise. |
1266 |
< |
* |
1178 |
< |
* <p>This method may be invoked only from within {@code |
1179 |
< |
* ForkJoinPool} computations (as may be determined using method |
1180 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1181 |
< |
* result in exceptions or errors, possibly including {@code |
1182 |
< |
* ClassCastException}. |
1263 |
> |
* queued by the current thread but not yet executed, if the |
1264 |
> |
* current thread is operating in a ForkJoinPool. This method is |
1265 |
> |
* designed primarily to support extensions, and is unlikely to be |
1266 |
> |
* useful otherwise. |
1267 |
|
* |
1268 |
|
* @return the next task, or {@code null} if none are available |
1269 |
|
*/ |
1270 |
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
1271 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1272 |
< |
.pollLocalTask(); |
1271 |
> |
Thread t; |
1272 |
> |
return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? |
1273 |
> |
((ForkJoinWorkerThread)t).workQueue.nextLocalTask() : |
1274 |
> |
null; |
1275 |
|
} |
1276 |
|
|
1277 |
|
/** |
1278 |
< |
* Unschedules and returns, without executing, the next task |
1278 |
> |
* If the current thread is operating in a ForkJoinPool, |
1279 |
> |
* unschedules and returns, without executing, the next task |
1280 |
|
* queued by the current thread but not yet executed, if one is |
1281 |
|
* available, or if not available, a task that was forked by some |
1282 |
|
* other thread, if available. Availability may be transient, so a |
1283 |
< |
* {@code null} result does not necessarily imply quiescence |
1284 |
< |
* of the pool this task is operating in. This method is designed |
1283 |
> |
* {@code null} result does not necessarily imply quiescence of |
1284 |
> |
* the pool this task is operating in. This method is designed |
1285 |
|
* primarily to support extensions, and is unlikely to be useful |
1286 |
|
* otherwise. |
1287 |
|
* |
1201 |
– |
* <p>This method may be invoked only from within {@code |
1202 |
– |
* ForkJoinPool} computations (as may be determined using method |
1203 |
– |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1204 |
– |
* result in exceptions or errors, possibly including {@code |
1205 |
– |
* ClassCastException}. |
1206 |
– |
* |
1288 |
|
* @return a task, or {@code null} if none are available |
1289 |
|
*/ |
1290 |
|
protected static ForkJoinTask<?> pollTask() { |
1291 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1292 |
< |
.pollTask(); |
1291 |
> |
Thread t; ForkJoinWorkerThread wt; |
1292 |
> |
return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ? |
1293 |
> |
(wt = (ForkJoinWorkerThread)t).pool.nextTaskFor(wt.workQueue) : |
1294 |
> |
null; |
1295 |
> |
} |
1296 |
> |
|
1297 |
> |
// tag operations |
1298 |
> |
|
1299 |
> |
/** |
1300 |
> |
* Returns the tag for this task. |
1301 |
> |
* |
1302 |
> |
* @return the tag for this task |
1303 |
> |
* @since 1.8 |
1304 |
> |
*/ |
1305 |
> |
public final short getForkJoinTaskTag() { |
1306 |
> |
return (short)status; |
1307 |
> |
} |
1308 |
> |
|
1309 |
> |
/** |
1310 |
> |
* Atomically sets the tag value for this task. |
1311 |
> |
* |
1312 |
> |
* @param tag the tag value |
1313 |
> |
* @return the previous value of the tag |
1314 |
> |
* @since 1.8 |
1315 |
> |
*/ |
1316 |
> |
public final short setForkJoinTaskTag(short tag) { |
1317 |
> |
for (int s;;) { |
1318 |
> |
if (U.compareAndSwapInt(this, STATUS, s = status, |
1319 |
> |
(s & ~SMASK) | (tag & SMASK))) |
1320 |
> |
return (short)s; |
1321 |
> |
} |
1322 |
> |
} |
1323 |
> |
|
1324 |
> |
/** |
1325 |
> |
* Atomically conditionally sets the tag value for this task. |
1326 |
> |
* Among other applications, tags can be used as visit markers |
1327 |
> |
* in tasks operating on graphs, as in methods that check: {@code |
1328 |
> |
* if (task.compareAndSetForkJoinTaskTag((short)0, (short)1))} |
1329 |
> |
* before processing, otherwise exiting because the node has |
1330 |
> |
* already been visited. |
1331 |
> |
* |
1332 |
> |
* @param e the expected tag value |
1333 |
> |
* @param tag the new tag value |
1334 |
> |
* @return true if successful; i.e., the current value was |
1335 |
> |
* equal to e and is now tag. |
1336 |
> |
* @since 1.8 |
1337 |
> |
*/ |
1338 |
> |
public final boolean compareAndSetForkJoinTaskTag(short e, short tag) { |
1339 |
> |
for (int s;;) { |
1340 |
> |
if ((short)(s = status) != e) |
1341 |
> |
return false; |
1342 |
> |
if (U.compareAndSwapInt(this, STATUS, s, |
1343 |
> |
(s & ~SMASK) | (tag & SMASK))) |
1344 |
> |
return true; |
1345 |
> |
} |
1346 |
|
} |
1347 |
|
|
1348 |
|
/** |
1353 |
|
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
1354 |
|
implements RunnableFuture<T> { |
1355 |
|
final Runnable runnable; |
1222 |
– |
final T resultOnCompletion; |
1356 |
|
T result; |
1357 |
|
AdaptedRunnable(Runnable runnable, T result) { |
1358 |
|
if (runnable == null) throw new NullPointerException(); |
1359 |
|
this.runnable = runnable; |
1360 |
< |
this.resultOnCompletion = result; |
1360 |
> |
this.result = result; // OK to set this even before completion |
1361 |
|
} |
1362 |
< |
public T getRawResult() { return result; } |
1363 |
< |
public void setRawResult(T v) { result = v; } |
1364 |
< |
public boolean exec() { |
1365 |
< |
runnable.run(); |
1366 |
< |
result = resultOnCompletion; |
1367 |
< |
return true; |
1362 |
> |
public final T getRawResult() { return result; } |
1363 |
> |
public final void setRawResult(T v) { result = v; } |
1364 |
> |
public final boolean exec() { runnable.run(); return true; } |
1365 |
> |
public final void run() { invoke(); } |
1366 |
> |
private static final long serialVersionUID = 5232453952276885070L; |
1367 |
> |
} |
1368 |
> |
|
1369 |
> |
/** |
1370 |
> |
* Adaptor for Runnables without results |
1371 |
> |
*/ |
1372 |
> |
static final class AdaptedRunnableAction extends ForkJoinTask<Void> |
1373 |
> |
implements RunnableFuture<Void> { |
1374 |
> |
final Runnable runnable; |
1375 |
> |
AdaptedRunnableAction(Runnable runnable) { |
1376 |
> |
if (runnable == null) throw new NullPointerException(); |
1377 |
> |
this.runnable = runnable; |
1378 |
|
} |
1379 |
< |
public void run() { invoke(); } |
1379 |
> |
public final Void getRawResult() { return null; } |
1380 |
> |
public final void setRawResult(Void v) { } |
1381 |
> |
public final boolean exec() { runnable.run(); return true; } |
1382 |
> |
public final void run() { invoke(); } |
1383 |
|
private static final long serialVersionUID = 5232453952276885070L; |
1384 |
|
} |
1385 |
|
|
1394 |
|
if (callable == null) throw new NullPointerException(); |
1395 |
|
this.callable = callable; |
1396 |
|
} |
1397 |
< |
public T getRawResult() { return result; } |
1398 |
< |
public void setRawResult(T v) { result = v; } |
1399 |
< |
public boolean exec() { |
1397 |
> |
public final T getRawResult() { return result; } |
1398 |
> |
public final void setRawResult(T v) { result = v; } |
1399 |
> |
public final boolean exec() { |
1400 |
|
try { |
1401 |
|
result = callable.call(); |
1402 |
|
return true; |
1408 |
|
throw new RuntimeException(ex); |
1409 |
|
} |
1410 |
|
} |
1411 |
< |
public void run() { invoke(); } |
1411 |
> |
public final void run() { invoke(); } |
1412 |
|
private static final long serialVersionUID = 2838392045355241008L; |
1413 |
|
} |
1414 |
|
|
1421 |
|
* @return the task |
1422 |
|
*/ |
1423 |
|
public static ForkJoinTask<?> adapt(Runnable runnable) { |
1424 |
< |
return new AdaptedRunnable<Void>(runnable, null); |
1424 |
> |
return new AdaptedRunnableAction(runnable); |
1425 |
|
} |
1426 |
|
|
1427 |
|
/** |
1455 |
|
private static final long serialVersionUID = -7721805057305804111L; |
1456 |
|
|
1457 |
|
/** |
1458 |
< |
* Saves the state to a stream (that is, serializes it). |
1458 |
> |
* Saves this task to a stream (that is, serializes it). |
1459 |
|
* |
1460 |
|
* @serialData the current run status and the exception thrown |
1461 |
|
* during execution, or {@code null} if none |
1316 |
– |
* @param s the stream |
1462 |
|
*/ |
1463 |
|
private void writeObject(java.io.ObjectOutputStream s) |
1464 |
|
throws java.io.IOException { |
1467 |
|
} |
1468 |
|
|
1469 |
|
/** |
1470 |
< |
* Reconstitutes the instance from a stream (that is, deserializes it). |
1326 |
< |
* |
1327 |
< |
* @param s the stream |
1470 |
> |
* Reconstitutes this task from a stream (that is, deserializes it). |
1471 |
|
*/ |
1472 |
|
private void readObject(java.io.ObjectInputStream s) |
1473 |
|
throws java.io.IOException, ClassNotFoundException { |
1478 |
|
} |
1479 |
|
|
1480 |
|
// Unsafe mechanics |
1481 |
< |
private static final sun.misc.Unsafe UNSAFE; |
1482 |
< |
private static final long statusOffset; |
1481 |
> |
private static final sun.misc.Unsafe U; |
1482 |
> |
private static final long STATUS; |
1483 |
|
static { |
1484 |
|
exceptionTableLock = new ReentrantLock(); |
1485 |
|
exceptionTableRefQueue = new ReferenceQueue<Object>(); |
1486 |
|
exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY]; |
1487 |
|
try { |
1488 |
< |
UNSAFE = getUnsafe(); |
1489 |
< |
statusOffset = UNSAFE.objectFieldOffset |
1488 |
> |
U = getUnsafe(); |
1489 |
> |
STATUS = U.objectFieldOffset |
1490 |
|
(ForkJoinTask.class.getDeclaredField("status")); |
1491 |
|
} catch (Exception e) { |
1492 |
|
throw new Error(e); |