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import java.util.concurrent.atomic.AtomicLong; |
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/** |
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< |
* An {@link ExecutorService} for running {@link ForkJoinTask}s. A |
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< |
* ForkJoinPool provides the entry point for submissions from |
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> |
* An {@link ExecutorService} for running {@link ForkJoinTask}s. |
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> |
* A ForkJoinPool provides the entry point for submissions from |
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* non-ForkJoinTasks, as well as management and monitoring operations. |
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* Normally a single ForkJoinPool is used for a large number of |
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* submitted tasks. Otherwise, use would not usually outweigh the |
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* (eventually blocking if none exist). This makes them efficient when |
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* most tasks spawn other subtasks (as do most ForkJoinTasks), as well |
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* as the mixed execution of some plain Runnable- or Callable- based |
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< |
* activities along with ForkJoinTasks. When setting |
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< |
* {@code setAsyncMode}, a ForkJoinPools may also be appropriate for |
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< |
* use with fine-grained tasks that are never joined. Otherwise, other |
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< |
* ExecutorService implementations are typically more appropriate |
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< |
* choices. |
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> |
* activities along with ForkJoinTasks. When setting {@linkplain |
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> |
* #setAsyncMode async mode}, a ForkJoinPool may also be appropriate |
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> |
* for use with fine-grained tasks that are never joined. Otherwise, |
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> |
* other ExecutorService implementations are typically more |
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> |
* appropriate choices. |
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* |
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* <p>A ForkJoinPool may be constructed with a given parallelism level |
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* (target pool size), which it attempts to maintain by dynamically |
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* adding, suspending, or resuming threads, even if some tasks are |
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* waiting to join others. However, no such adjustments are performed |
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* in the face of blocked IO or other unmanaged synchronization. The |
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< |
* nested {@code ManagedBlocker} interface enables extension of |
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> |
* nested {@link ManagedBlocker} interface enables extension of |
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* the kinds of synchronization accommodated. The target parallelism |
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< |
* level may also be changed dynamically ({@code setParallelism}) |
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> |
* level may also be changed dynamically ({@link #setParallelism}) |
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* and thread construction can be limited using methods |
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< |
* {@code setMaximumPoolSize} and/or |
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< |
* {@code setMaintainsParallelism}. |
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> |
* {@link #setMaximumPoolSize} and/or |
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> |
* {@link #setMaintainsParallelism}. |
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* |
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* <p>In addition to execution and lifecycle control methods, this |
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* class provides status check methods (for example |
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< |
* {@code getStealCount}) that are intended to aid in developing, |
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> |
* {@link #getStealCount}) that are intended to aid in developing, |
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* tuning, and monitoring fork/join applications. Also, method |
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< |
* {@code toString} returns indications of pool state in a |
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> |
* {@link #toString} returns indications of pool state in a |
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* convenient form for informal monitoring. |
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* |
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* <p><b>Implementation notes</b>: This implementation restricts the |
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} |
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|
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/** |
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< |
* Returns true if argument represents zero active count and |
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< |
* nonzero runstate, which is the triggering condition for |
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> |
* Returns {@code true} if argument represents zero active count |
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> |
* and nonzero runstate, which is the triggering condition for |
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* terminating on shutdown. |
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*/ |
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private static boolean canTerminateOnShutdown(int c) { |
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* Returns the handler for internal worker threads that terminate |
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* due to unrecoverable errors encountered while executing tasks. |
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* |
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< |
* @return the handler, or null if none |
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> |
* @return the handler, or {@code null} if none |
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*/ |
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public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() { |
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Thread.UncaughtExceptionHandler h; |
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* as handler. |
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* |
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* @param h the new handler |
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< |
* @return the old handler, or null if none |
| 744 |
> |
* @return the old handler, or {@code null} if none |
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* @throws SecurityException if a security manager exists and |
| 746 |
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* the caller is not permitted to modify threads |
| 747 |
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* because it does not hold {@link |
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/** |
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* Returns the number of worker threads that have started but not |
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* yet terminated. This result returned by this method may differ |
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< |
* from {@code getParallelism} when threads are created to |
| 818 |
> |
* from {@link #getParallelism} when threads are created to |
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* maintain parallelism when others are cooperatively blocked. |
| 820 |
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* |
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* @return the number of worker threads |
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|
| 852 |
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|
| 853 |
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/** |
| 854 |
< |
* Returns true if this pool dynamically maintains its target |
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< |
* parallelism level. If false, new threads are added only to |
| 856 |
< |
* avoid possible starvation. |
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< |
* This setting is by default true. |
| 854 |
> |
* Returns {@code true} if this pool dynamically maintains its |
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> |
* target parallelism level. If false, new threads are added only |
| 856 |
> |
* to avoid possible starvation. This setting is by default true. |
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* |
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< |
* @return true if maintains parallelism |
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> |
* @return {@code true} if maintains parallelism |
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*/ |
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public boolean getMaintainsParallelism() { |
| 861 |
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return maintainsParallelism; |
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* parallelism level. If false, new threads are added only to |
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* avoid possible starvation. |
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* |
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< |
* @param enable true to maintains parallelism |
| 869 |
> |
* @param enable {@code true} to maintain parallelism |
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*/ |
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public void setMaintainsParallelism(boolean enable) { |
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maintainsParallelism = enable; |
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* tasks that are never joined. This mode may be more appropriate |
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* than default locally stack-based mode in applications in which |
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* worker threads only process asynchronous tasks. This method is |
| 880 |
< |
* designed to be invoked only when pool is quiescent, and |
| 880 |
> |
* designed to be invoked only when the pool is quiescent, and |
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* typically only before any tasks are submitted. The effects of |
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* invocations at other times may be unpredictable. |
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* |
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< |
* @param async if true, use locally FIFO scheduling |
| 884 |
> |
* @param async if {@code true}, use locally FIFO scheduling |
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* @return the previous mode |
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+ |
* @see #getAsyncMode |
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*/ |
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public boolean setAsyncMode(boolean async) { |
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boolean oldMode = locallyFifo; |
| 900 |
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} |
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|
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/** |
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< |
* Returns true if this pool uses local first-in-first-out |
| 903 |
> |
* Returns {@code true} if this pool uses local first-in-first-out |
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* scheduling mode for forked tasks that are never joined. |
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* |
| 906 |
< |
* @return true if this pool uses async mode |
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> |
* @return {@code true} if this pool uses async mode |
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> |
* @see #setAsyncMode |
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*/ |
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public boolean getAsyncMode() { |
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return locallyFifo; |
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} |
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|
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/** |
| 948 |
< |
* Returns true if all worker threads are currently idle. An idle |
| 949 |
< |
* worker is one that cannot obtain a task to execute because none |
| 950 |
< |
* are available to steal from other threads, and there are no |
| 951 |
< |
* pending submissions to the pool. This method is conservative; |
| 952 |
< |
* it might not return true immediately upon idleness of all |
| 953 |
< |
* threads, but will eventually become true if threads remain |
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< |
* inactive. |
| 948 |
> |
* Returns {@code true} if all worker threads are currently idle. |
| 949 |
> |
* An idle worker is one that cannot obtain a task to execute |
| 950 |
> |
* because none are available to steal from other threads, and |
| 951 |
> |
* there are no pending submissions to the pool. This method is |
| 952 |
> |
* conservative; it might not return {@code true} immediately upon |
| 953 |
> |
* idleness of all threads, but will eventually become true if |
| 954 |
> |
* threads remain inactive. |
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* |
| 956 |
< |
* @return true if all threads are currently idle |
| 956 |
> |
* @return {@code true} if all threads are currently idle |
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*/ |
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public boolean isQuiescent() { |
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return activeCountOf(runControl) == 0; |
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} |
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|
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/** |
| 1022 |
< |
* Returns true if there are any tasks submitted to this pool |
| 1023 |
< |
* that have not yet begun executing. |
| 1022 |
> |
* Returns {@code true} if there are any tasks submitted to this |
| 1023 |
> |
* pool that have not yet begun executing. |
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* |
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* @return {@code true} if there are any queued submissions |
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*/ |
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* available. This method may be useful in extensions to this |
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* class that re-assign work in systems with multiple pools. |
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* |
| 1036 |
< |
* @return the next submission, or null if none |
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> |
* @return the next submission, or {@code null} if none |
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*/ |
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protected ForkJoinTask<?> pollSubmission() { |
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return submissionQueue.poll(); |
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* @param c the collection to transfer elements into |
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* @return the number of elements transferred |
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*/ |
| 1059 |
< |
protected int drainTasksTo(Collection<ForkJoinTask<?>> c) { |
| 1059 |
> |
protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) { |
| 1060 |
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int n = submissionQueue.drainTo(c); |
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ForkJoinWorkerThread[] ws = workers; |
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if (ws != null) { |
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public void shutdown() { |
| 1123 |
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checkPermission(); |
| 1124 |
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transitionRunStateTo(SHUTDOWN); |
| 1125 |
< |
if (canTerminateOnShutdown(runControl)) |
| 1125 |
> |
if (canTerminateOnShutdown(runControl)) { |
| 1126 |
> |
if (workers == null) { // shutting down before workers created |
| 1127 |
> |
final ReentrantLock lock = this.workerLock; |
| 1128 |
> |
lock.lock(); |
| 1129 |
> |
try { |
| 1130 |
> |
if (workers == null) { |
| 1131 |
> |
terminate(); |
| 1132 |
> |
transitionRunStateTo(TERMINATED); |
| 1133 |
> |
termination.signalAll(); |
| 1134 |
> |
} |
| 1135 |
> |
|
| 1136 |
> |
} finally { |
| 1137 |
> |
lock.unlock(); |
| 1138 |
> |
} |
| 1139 |
> |
} |
| 1140 |
|
terminateOnShutdown(); |
| 1141 |
+ |
} |
| 1142 |
|
} |
| 1143 |
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|
| 1144 |
|
/** |
| 1148 |
|
* method may or may not be rejected. Unlike some other executors, |
| 1149 |
|
* this method cancels rather than collects non-executed tasks |
| 1150 |
|
* upon termination, so always returns an empty list. However, you |
| 1151 |
< |
* can use method {@code drainTasksTo} before invoking this |
| 1151 |
> |
* can use method {@link #drainTasksTo} before invoking this |
| 1152 |
|
* method to transfer unexecuted tasks to another collection. |
| 1153 |
|
* |
| 1154 |
|
* @return an empty list |
| 1508 |
|
} |
| 1509 |
|
|
| 1510 |
|
/** |
| 1511 |
< |
* Returns true if worker waiting on sync can proceed: |
| 1511 |
> |
* Returns {@code true} if worker waiting on sync can proceed: |
| 1512 |
|
* - on signal (thread == null) |
| 1513 |
|
* - on event count advance (winning race to notify vs signaller) |
| 1514 |
|
* - on interrupt |
| 1516 |
|
* If node was not signalled and event count not advanced on exit, |
| 1517 |
|
* then we also help advance event count. |
| 1518 |
|
* |
| 1519 |
< |
* @return true if node can be released |
| 1519 |
> |
* @return {@code true} if node can be released |
| 1520 |
|
*/ |
| 1521 |
|
final boolean syncIsReleasable(WaitQueueNode node) { |
| 1522 |
|
long prev = node.count; |
| 1535 |
|
} |
| 1536 |
|
|
| 1537 |
|
/** |
| 1538 |
< |
* Returns true if a new sync event occurred since last call to |
| 1539 |
< |
* sync or this method, if so, updating caller's count. |
| 1538 |
> |
* Returns {@code true} if a new sync event occurred since last |
| 1539 |
> |
* call to sync or this method, if so, updating caller's count. |
| 1540 |
|
*/ |
| 1541 |
|
final boolean hasNewSyncEvent(ForkJoinWorkerThread w) { |
| 1542 |
|
long lc = w.lastEventCount; |
| 1620 |
|
} |
| 1621 |
|
|
| 1622 |
|
/** |
| 1623 |
< |
* Returns true if a spare thread appears to be needed. If |
| 1624 |
< |
* maintaining parallelism, returns true when the deficit in |
| 1623 |
> |
* Returns {@code true} if a spare thread appears to be needed. |
| 1624 |
> |
* If maintaining parallelism, returns true when the deficit in |
| 1625 |
|
* running threads is more than the surplus of total threads, and |
| 1626 |
|
* there is apparently some work to do. This self-limiting rule |
| 1627 |
|
* means that the more threads that have already been added, the |
| 1790 |
|
/** |
| 1791 |
|
* Interface for extending managed parallelism for tasks running |
| 1792 |
|
* in ForkJoinPools. A ManagedBlocker provides two methods. |
| 1793 |
< |
* Method {@code isReleasable} must return true if blocking is not |
| 1794 |
< |
* necessary. Method {@code block} blocks the current thread if |
| 1795 |
< |
* necessary (perhaps internally invoking {@code isReleasable} |
| 1796 |
< |
* before actually blocking.). |
| 1793 |
> |
* Method {@code isReleasable} must return {@code true} if |
| 1794 |
> |
* blocking is not necessary. Method {@code block} blocks the |
| 1795 |
> |
* current thread if necessary (perhaps internally invoking |
| 1796 |
> |
* {@code isReleasable} before actually blocking.). |
| 1797 |
|
* |
| 1798 |
|
* <p>For example, here is a ManagedBlocker based on a |
| 1799 |
|
* ReentrantLock: |
| 1817 |
|
* Possibly blocks the current thread, for example waiting for |
| 1818 |
|
* a lock or condition. |
| 1819 |
|
* |
| 1820 |
< |
* @return true if no additional blocking is necessary (i.e., |
| 1821 |
< |
* if isReleasable would return true) |
| 1820 |
> |
* @return {@code true} if no additional blocking is necessary |
| 1821 |
> |
* (i.e., if isReleasable would return true) |
| 1822 |
|
* @throws InterruptedException if interrupted while waiting |
| 1823 |
|
* (the method is not required to do so, but is allowed to) |
| 1824 |
|
*/ |
| 1825 |
|
boolean block() throws InterruptedException; |
| 1826 |
|
|
| 1827 |
|
/** |
| 1828 |
< |
* Returns true if blocking is unnecessary. |
| 1828 |
> |
* Returns {@code true} if blocking is unnecessary. |
| 1829 |
|
*/ |
| 1830 |
|
boolean isReleasable(); |
| 1831 |
|
} |
| 1835 |
|
* is a ForkJoinWorkerThread, this method possibly arranges for a |
| 1836 |
|
* spare thread to be activated if necessary to ensure parallelism |
| 1837 |
|
* while the current thread is blocked. If |
| 1838 |
< |
* {@code maintainParallelism} is true and the pool supports |
| 1838 |
> |
* {@code maintainParallelism} is {@code true} and the pool supports |
| 1839 |
|
* it ({@link #getMaintainsParallelism}), this method attempts to |
| 1840 |
|
* maintain the pool's nominal parallelism. Otherwise it activates |
| 1841 |
|
* a thread only if necessary to avoid complete starvation. This |
| 1853 |
|
* be expanded to ensure parallelism, and later adjusted. |
| 1854 |
|
* |
| 1855 |
|
* @param blocker the blocker |
| 1856 |
< |
* @param maintainParallelism if true and supported by this pool, |
| 1857 |
< |
* attempt to maintain the pool's nominal parallelism; otherwise |
| 1858 |
< |
* activate a thread only if necessary to avoid complete |
| 1859 |
< |
* starvation. |
| 1856 |
> |
* @param maintainParallelism if {@code true} and supported by |
| 1857 |
> |
* this pool, attempt to maintain the pool's nominal parallelism; |
| 1858 |
> |
* otherwise activate a thread only if necessary to avoid |
| 1859 |
> |
* complete starvation. |
| 1860 |
|
* @throws InterruptedException if blocker.block did so |
| 1861 |
|
*/ |
| 1862 |
|
public static void managedBlock(ManagedBlocker blocker, |
