| 137 |
|
* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that |
| 138 |
|
* may be of use in constructing custom subclasses for problems that |
| 139 |
|
* are not statically structured as DAGs. To support such usages a |
| 140 |
< |
* ForkJoinTask may be atomically <em>marked</em> using {@link |
| 141 |
< |
* #markForkJoinTask} and checked for marking using {@link |
| 142 |
< |
* #isMarkedForkJoinTask}. The ForkJoinTask implementation does not |
| 143 |
< |
* use these {@code protected} methods or marks for any purpose, but |
| 140 |
> |
* ForkJoinTask may be atomically <em>tagged</em> with a {@code |
| 141 |
> |
* short} value using {@link #setForkJoinTaskTag} or {@link |
| 142 |
> |
* #compareAndSetForkJoinTaskTag} and checked using {@link |
| 143 |
> |
* #getForkJoinTaskTag}. The ForkJoinTask implementation does not |
| 144 |
> |
* use these {@code protected} methods or tags for any purpose, but |
| 145 |
|
* they may be of use in the construction of specialized subclasses. |
| 146 |
|
* For example, parallel graph traversals can use the supplied methods |
| 147 |
|
* to avoid revisiting nodes/tasks that have already been processed. |
| 148 |
< |
* Also, completion based designs can use them to record that one |
| 149 |
< |
* subtask has completed. (Method names for marking are bulky in part |
| 150 |
< |
* to encourage definition of methods that reflect their usage |
| 150 |
< |
* patterns.) |
| 148 |
> |
* Also, completion based designs can use them to record that subtasks |
| 149 |
> |
* have completed. (Method names for tagging are bulky in part to |
| 150 |
> |
* encourage definition of methods that reflect their usage patterns.) |
| 151 |
|
* |
| 152 |
|
* <p>Most base support methods are {@code final}, to prevent |
| 153 |
|
* overriding of implementations that are intrinsically tied to the |
| 213 |
|
* thin-lock techniques, so use some odd coding idioms that tend |
| 214 |
|
* to avoid them, mainly by arranging that every synchronized |
| 215 |
|
* block performs a wait, notifyAll or both. |
| 216 |
+ |
* |
| 217 |
+ |
* These control bits occupy only (some of) the upper half (16 |
| 218 |
+ |
* bits) of status field. The lower bits are used for user-defined |
| 219 |
+ |
* tags. |
| 220 |
|
*/ |
| 221 |
|
|
| 222 |
|
/** The run status of this task */ |
| 225 |
|
static final int NORMAL = 0xf0000000; // must be negative |
| 226 |
|
static final int CANCELLED = 0xc0000000; // must be < NORMAL |
| 227 |
|
static final int EXCEPTIONAL = 0x80000000; // must be < CANCELLED |
| 228 |
< |
static final int SIGNAL = 0x00000001; |
| 229 |
< |
static final int MARKED = 0x00000002; |
| 228 |
> |
static final int SIGNAL = 0x00010000; // must be >= 1 << 16 |
| 229 |
> |
static final int SMASK = 0x0000ffff; // short bits for tags |
| 230 |
|
|
| 231 |
|
/** |
| 232 |
|
* Marks completion and wakes up threads waiting to join this |
| 233 |
< |
* task. A specialization for NORMAL completion is in method |
| 230 |
< |
* doExec. |
| 233 |
> |
* task. |
| 234 |
|
* |
| 235 |
|
* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
| 236 |
|
* @return completion status on exit |
| 240 |
|
if ((s = status) < 0) |
| 241 |
|
return s; |
| 242 |
|
if (U.compareAndSwapInt(this, STATUS, s, s | completion)) { |
| 243 |
< |
if ((s & SIGNAL) != 0) |
| 243 |
> |
if ((s >>> 16) != 0) |
| 244 |
|
synchronized (this) { notifyAll(); } |
| 245 |
|
return completion; |
| 246 |
|
} |
| 262 |
|
} catch (Throwable rex) { |
| 263 |
|
return setExceptionalCompletion(rex); |
| 264 |
|
} |
| 265 |
< |
while ((s = status) >= 0 && completed) { |
| 266 |
< |
if (U.compareAndSwapInt(this, STATUS, s, s | NORMAL)) { |
| 264 |
< |
if ((s & SIGNAL) != 0) |
| 265 |
< |
synchronized (this) { notifyAll(); } |
| 266 |
< |
return NORMAL; |
| 267 |
< |
} |
| 268 |
< |
} |
| 265 |
> |
if (completed) |
| 266 |
> |
s = setCompletion(NORMAL); |
| 267 |
|
} |
| 268 |
|
return s; |
| 269 |
|
} |
| 326 |
|
return s; |
| 327 |
|
} |
| 328 |
|
|
| 331 |
– |
|
| 329 |
|
/** |
| 330 |
|
* Implementation for join, get, quietlyJoin. Directly handles |
| 331 |
|
* only cases of already-completed, external wait, and |
| 904 |
|
} |
| 905 |
|
|
| 906 |
|
/** |
| 907 |
+ |
* Completes this task. The most recent value established by |
| 908 |
+ |
* {@link #setRawResult} (or {@code null}) will be returned as the |
| 909 |
+ |
* result of subsequent invocations of {@code join} and related |
| 910 |
+ |
* operations. This method may be useful when processing sets of |
| 911 |
+ |
* tasks when some do not otherwise complete normally. Its use in |
| 912 |
+ |
* other situations is discouraged. |
| 913 |
+ |
*/ |
| 914 |
+ |
public final void quietlyComplete() { |
| 915 |
+ |
setCompletion(NORMAL); |
| 916 |
+ |
} |
| 917 |
+ |
|
| 918 |
+ |
/** |
| 919 |
|
* Waits if necessary for the computation to complete, and then |
| 920 |
|
* retrieves its result. |
| 921 |
|
* |
| 1311 |
|
return wt.pool.nextTaskFor(wt.workQueue); |
| 1312 |
|
} |
| 1313 |
|
|
| 1314 |
< |
// Mark-bit operations |
| 1314 |
> |
// tag operations |
| 1315 |
|
|
| 1316 |
|
/** |
| 1317 |
< |
* Returns true if this task is marked. |
| 1317 |
> |
* Returns the tag for this task. |
| 1318 |
|
* |
| 1319 |
< |
* @return true if this task is marked |
| 1319 |
> |
* @return the tag for this task |
| 1320 |
|
* @since 1.8 |
| 1321 |
|
*/ |
| 1322 |
< |
public final boolean isMarkedForkJoinTask() { |
| 1323 |
< |
return (status & MARKED) != 0; |
| 1322 |
> |
public final short getForkJoinTaskTag() { |
| 1323 |
> |
return (short)status; |
| 1324 |
|
} |
| 1325 |
|
|
| 1326 |
|
/** |
| 1327 |
< |
* Atomically sets the mark on this task. |
| 1327 |
> |
* Atomically sets the tag value for this task. |
| 1328 |
|
* |
| 1329 |
< |
* @return true if this task was previously unmarked |
| 1329 |
> |
* @param tag the tag value |
| 1330 |
> |
* @return the previous value of the tag |
| 1331 |
|
* @since 1.8 |
| 1332 |
|
*/ |
| 1333 |
< |
public final boolean markForkJoinTask() { |
| 1333 |
> |
public final short setForkJoinTaskTag(short tag) { |
| 1334 |
|
for (int s;;) { |
| 1335 |
< |
if (((s = status) & MARKED) != 0) |
| 1336 |
< |
return false; |
| 1337 |
< |
if (U.compareAndSwapInt(this, STATUS, s, s | MARKED)) |
| 1328 |
< |
return true; |
| 1335 |
> |
if (U.compareAndSwapInt(this, STATUS, s = status, |
| 1336 |
> |
(s & ~SMASK) | (tag & SMASK))) |
| 1337 |
> |
return (short)s; |
| 1338 |
|
} |
| 1339 |
|
} |
| 1340 |
|
|
| 1341 |
|
/** |
| 1342 |
< |
* Atomically clears the mark on this task. |
| 1342 |
> |
* Atomically conditionally sets the tag value for this task. |
| 1343 |
> |
* Among other applications, tags can be used as visit markers |
| 1344 |
> |
* in tasks operating on graphs, as in mathods that check: {@code |
| 1345 |
> |
* if (task.compareAndSetForkJoinTaskTag((short)0, (short)1))} |
| 1346 |
> |
* before processing, otherwise exiting because the node has |
| 1347 |
> |
* already been visited. |
| 1348 |
|
* |
| 1349 |
< |
* @return true if this task was previously marked |
| 1349 |
> |
* @param e the expected tag value |
| 1350 |
> |
* @param tag the new tag value |
| 1351 |
> |
* @return true if successful; i.e., the current value was |
| 1352 |
> |
* equal to e and is now tag. |
| 1353 |
|
* @since 1.8 |
| 1354 |
|
*/ |
| 1355 |
< |
public final boolean unmarkForkJoinTask() { |
| 1355 |
> |
public final boolean compareAndSetForkJoinTaskTag(short e, short tag) { |
| 1356 |
|
for (int s;;) { |
| 1357 |
< |
if (((s = status) & MARKED) == 0) |
| 1357 |
> |
if ((short)(s = status) != e) |
| 1358 |
|
return false; |
| 1359 |
< |
if (U.compareAndSwapInt(this, STATUS, s, s & ~MARKED)) |
| 1359 |
> |
if (U.compareAndSwapInt(this, STATUS, s, |
| 1360 |
> |
(s & ~SMASK) | (tag & SMASK))) |
| 1361 |
|
return true; |
| 1362 |
|
} |
| 1363 |
|
} |
