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package jsr166y; |
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import java.util.concurrent.*; |
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import java.io.Serializable; |
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import java.util.Collection; |
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import java.util.Collections; |
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import java.util.RandomAccess; |
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import java.util.Map; |
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import java.util.WeakHashMap; |
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import java.util.concurrent.Callable; |
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import java.util.concurrent.CancellationException; |
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import java.util.concurrent.ExecutionException; |
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import java.util.concurrent.Executor; |
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import java.util.concurrent.ExecutorService; |
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import java.util.concurrent.Future; |
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import java.util.concurrent.RejectedExecutionException; |
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import java.util.concurrent.RunnableFuture; |
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import java.util.concurrent.TimeUnit; |
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import java.util.concurrent.TimeoutException; |
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/** |
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* Abstract base class for tasks that run within a {@link ForkJoinPool}. |
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* start other subtasks. As indicated by the name of this class, |
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* many programs using {@code ForkJoinTask} employ only methods |
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* {@link #fork} and {@link #join}, or derivatives such as {@link |
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* #invokeAll}. However, this class also provides a number of other |
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* methods that can come into play in advanced usages, as well as |
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* extension mechanics that allow support of new forms of fork/join |
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* processing. |
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* #invokeAll(ForkJoinTask...) invokeAll}. However, this class also |
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* provides a number of other methods that can come into play in |
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* advanced usages, as well as extension mechanics that allow |
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* support of new forms of fork/join processing. |
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* |
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* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}. |
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* The efficiency of {@code ForkJoinTask}s stems from a set of |
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* ForkJoinTasks (as may be determined using method {@link |
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* #inForkJoinPool}). Attempts to invoke them in other contexts |
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* result in exceptions or errors, possibly including |
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* ClassCastException. |
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* {@code ClassCastException}. |
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* |
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* <p>Method {@link #join} and its variants are appropriate for use |
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* only when completion dependencies are acyclic; that is, the |
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* parallel computation can be described as a directed acyclic graph |
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* (DAG). Otherwise, executions may encounter a form of deadlock as |
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* tasks cyclically wait for each other. However, this framework |
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* supports other methods and techniques (for example the use of |
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* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that |
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* may be of use in constructing custom subclasses for problems that |
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* are not statically structured as DAGs. |
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* |
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* <p>Most base support methods are {@code final}, to prevent |
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* overriding of implementations that are intrinsically tied to the |
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* computation. Large tasks should be split into smaller subtasks, |
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* usually via recursive decomposition. As a very rough rule of thumb, |
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* a task should perform more than 100 and less than 10000 basic |
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* computational steps. If tasks are too big, then parallelism cannot |
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* improve throughput. If too small, then memory and internal task |
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* maintenance overhead may overwhelm processing. |
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* computational steps, and should avoid indefinite looping. If tasks |
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* are too big, then parallelism cannot improve throughput. If too |
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* small, then memory and internal task maintenance overhead may |
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* overwhelm processing. |
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* |
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* <p>This class provides {@code adapt} methods for {@link Runnable} |
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* and {@link Callable}, that may be of use when mixing execution of |
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* status maintenance (2) execution and awaiting completion (3) |
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* user-level methods that additionally report results. This is |
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* sometimes hard to see because this file orders exported methods |
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* in a way that flows well in javadocs. |
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* in a way that flows well in javadocs. In particular, most |
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* join mechanics are in method quietlyJoin, below. |
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*/ |
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|
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/** |
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* Run control status bits packed into a single int to minimize |
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* footprint and to ensure atomicity (via CAS). Status is |
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* initially zero, and takes on nonnegative values until |
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* completed, upon which status holds value COMPLETED. CANCELLED, |
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* or EXCEPTIONAL. Tasks undergoing blocking waits by other |
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* threads have the SIGNAL bit set. Completion of a stolen task |
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* with SIGNAL set awakens any waiters via notifyAll. Even though |
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* suboptimal for some purposes, we use basic builtin wait/notify |
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* to take advantage of "monitor inflation" in JVMs that we would |
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* otherwise need to emulate to avoid adding further per-task |
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* bookkeeping overhead. We want these monitors to be "fat", |
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* i.e., not use biasing or thin-lock techniques, so use some odd |
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* coding idioms that tend to avoid them. |
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/* |
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* The status field holds run control status bits packed into a |
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* single int to minimize footprint and to ensure atomicity (via |
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* CAS). Status is initially zero, and takes on nonnegative |
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* values until completed, upon which status holds value |
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* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking |
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* waits by other threads have the SIGNAL bit set. Completion of |
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* a stolen task with SIGNAL set awakens any waiters via |
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* notifyAll. Even though suboptimal for some purposes, we use |
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* basic builtin wait/notify to take advantage of "monitor |
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* inflation" in JVMs that we would otherwise need to emulate to |
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* avoid adding further per-task bookkeeping overhead. We want |
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* these monitors to be "fat", i.e., not use biasing or thin-lock |
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* techniques, so use some odd coding idioms that tend to avoid |
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* them. |
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*/ |
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|
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/** The run status of this task */ |
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volatile int status; // accessed directly by pool and workers |
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private static final int NORMAL = -1; |
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* also clearing signal request bits. |
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* |
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* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
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* @return status on exit |
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*/ |
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private int setCompletion(int completion) { |
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private void setCompletion(int completion) { |
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int s; |
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while ((s = status) >= 0) { |
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if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) { |
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if (s == SIGNAL) |
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if (s != 0) |
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synchronized (this) { notifyAll(); } |
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return completion; |
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break; |
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} |
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} |
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return s; |
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} |
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/** |
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* Record exception and set exceptional completion |
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* Records exception and sets exceptional completion. |
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* |
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* @return status on exit |
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*/ |
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private int setExceptionalCompletion(Throwable rex) { |
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private void setExceptionalCompletion(Throwable rex) { |
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exceptionMap.put(this, rex); |
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return setCompletion(EXCEPTIONAL); |
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setCompletion(EXCEPTIONAL); |
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} |
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/** |
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* Blocks a worker thread until completion. Called only by pool. |
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* Blocks a worker thread until completed or timed out. Called |
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* only by pool. |
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*/ |
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final int internalAwaitDone() { |
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int s; |
242 |
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while ((s = status) >= 0) { |
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synchronized(this) { |
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if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) { |
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do { |
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try { |
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wait(); |
225 |
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} catch (InterruptedException ie) { |
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cancelIfTerminating(); |
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} |
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} while ((s = status) >= 0); |
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break; |
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final void internalAwaitDone(long millis, int nanos) { |
241 |
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if (status >= 0) { |
242 |
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try { // the odd construction reduces lock bias effects |
243 |
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synchronized (this) { |
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if (status > 0 || |
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UNSAFE.compareAndSwapInt(this, statusOffset, |
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0, SIGNAL)) |
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wait(millis, nanos); |
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} |
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} catch (InterruptedException ie) { |
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cancelIfTerminating(); |
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} |
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} |
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return s; |
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} |
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|
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/** |
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* Blocks a non-worker-thread until completion. |
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* @return status on exit |
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*/ |
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private int externalAwaitDone() { |
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int s; |
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while ((s = status) >= 0) { |
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private void externalAwaitDone() { |
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if (status >= 0) { |
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boolean interrupted = false; |
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synchronized(this) { |
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int s; |
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while ((s = status) >= 0) { |
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if (s == 0 && |
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!UNSAFE.compareAndSwapInt(this, statusOffset, |
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0, SIGNAL)) |
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continue; |
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try { |
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wait(); |
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} catch (InterruptedException ie) { |
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interrupted = true; |
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} |
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} |
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} |
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if (interrupted) |
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Thread.currentThread().interrupt(); |
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} |
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} |
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|
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/** |
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* Blocks a non-worker-thread until completion or interruption or timeout. |
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*/ |
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private void externalInterruptibleAwaitDone(boolean timed, long nanos) |
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throws InterruptedException { |
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if (Thread.interrupted()) |
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throw new InterruptedException(); |
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if (status >= 0) { |
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long startTime = timed ? System.nanoTime() : 0L; |
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synchronized(this) { |
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if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){ |
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boolean interrupted = false; |
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do { |
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try { |
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wait(); |
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} catch (InterruptedException ie) { |
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interrupted = true; |
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} |
298 |
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} while ((s = status) >= 0); |
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if (interrupted) |
300 |
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Thread.currentThread().interrupt(); |
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break; |
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> |
int s; |
291 |
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while ((s = status) >= 0) { |
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> |
long nt; |
293 |
> |
if (s == 0 && |
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!UNSAFE.compareAndSwapInt(this, statusOffset, |
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0, SIGNAL)) |
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continue; |
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> |
else if (!timed) |
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wait(); |
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else if ((nt = nanos - (System.nanoTime()-startTime)) > 0L) |
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wait(nt / 1000000, (int)(nt % 1000000)); |
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> |
else |
302 |
> |
break; |
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} |
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} |
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} |
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return s; |
306 |
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} |
307 |
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|
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/** |
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* doesn't wait for completion otherwise. Primary execution method |
311 |
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* for ForkJoinWorkerThread. |
312 |
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*/ |
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< |
final void tryExec() { |
313 |
> |
final void quietlyExec() { |
314 |
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try { |
315 |
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if (status < 0 || !exec()) |
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return; |
321 |
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setCompletion(NORMAL); // must be outside try block |
322 |
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} |
323 |
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|
278 |
– |
/** |
279 |
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* If not done and this task is next in worker queue, runs it, |
280 |
– |
* else waits for it. |
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* @return status on exit |
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*/ |
283 |
– |
private int doJoin() { |
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– |
int stat; |
285 |
– |
if ((stat = status) < 0) |
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– |
return stat; |
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– |
Thread t = Thread.currentThread(); |
288 |
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ForkJoinWorkerThread w; |
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if (t instanceof ForkJoinWorkerThread) { |
290 |
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if ((w = (ForkJoinWorkerThread) t).unpushTask(this)) { |
291 |
– |
boolean completed; |
292 |
– |
try { |
293 |
– |
completed = exec(); |
294 |
– |
} catch (Throwable rex) { |
295 |
– |
return setExceptionalCompletion(rex); |
296 |
– |
} |
297 |
– |
if (completed) |
298 |
– |
return setCompletion(NORMAL); |
299 |
– |
} |
300 |
– |
w.joinTask(this); |
301 |
– |
return status; |
302 |
– |
} |
303 |
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return externalAwaitDone(); |
304 |
– |
} |
305 |
– |
|
306 |
– |
/** |
307 |
– |
* Unless done, calls exec and records status if completed, or |
308 |
– |
* waits for completion otherwise. |
309 |
– |
* @return status on exit |
310 |
– |
*/ |
311 |
– |
private int doInvoke() { |
312 |
– |
int stat; |
313 |
– |
if ((stat = status) >= 0) { |
314 |
– |
boolean completed; |
315 |
– |
try { |
316 |
– |
completed = exec(); |
317 |
– |
} catch (Throwable rex) { |
318 |
– |
return setExceptionalCompletion(rex); |
319 |
– |
} |
320 |
– |
if (completed) |
321 |
– |
stat = setCompletion(NORMAL); |
322 |
– |
else |
323 |
– |
stat = doJoin(); |
324 |
– |
} |
325 |
– |
return stat; |
326 |
– |
} |
327 |
– |
|
328 |
– |
/** |
329 |
– |
* Returns result or throws exception associated with given status. |
330 |
– |
* @param s the status |
331 |
– |
*/ |
332 |
– |
private V reportResult(int s) { |
333 |
– |
Throwable ex; |
334 |
– |
if (s < NORMAL && (ex = getException()) != null) |
335 |
– |
UNSAFE.throwException(ex); |
336 |
– |
return getRawResult(); |
337 |
– |
} |
338 |
– |
|
324 |
|
// public methods |
325 |
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|
326 |
|
/** |
334 |
|
* #isDone} returning {@code true}. |
335 |
|
* |
336 |
|
* <p>This method may be invoked only from within {@code |
337 |
< |
* ForkJoinTask} computations (as may be determined using method |
337 |
> |
* ForkJoinPool} computations (as may be determined using method |
338 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
339 |
|
* result in exceptions or errors, possibly including {@code |
340 |
|
* ClassCastException}. |
348 |
|
} |
349 |
|
|
350 |
|
/** |
351 |
< |
* Returns the result of the computation when it {@link #isDone is done}. |
352 |
< |
* This method differs from {@link #get()} in that |
351 |
> |
* Returns the result of the computation when it {@link #isDone is |
352 |
> |
* done}. This method differs from {@link #get()} in that |
353 |
|
* abnormal completion results in {@code RuntimeException} or |
354 |
< |
* {@code Error}, not {@code ExecutionException}. |
354 |
> |
* {@code Error}, not {@code ExecutionException}, and that |
355 |
> |
* interrupts of the calling thread do <em>not</em> cause the |
356 |
> |
* method to abruptly return by throwing {@code |
357 |
> |
* InterruptedException}. |
358 |
|
* |
359 |
|
* @return the computed result |
360 |
|
*/ |
361 |
|
public final V join() { |
362 |
< |
return reportResult(doJoin()); |
362 |
> |
quietlyJoin(); |
363 |
> |
Throwable ex; |
364 |
> |
if (status < NORMAL && (ex = getException()) != null) |
365 |
> |
UNSAFE.throwException(ex); |
366 |
> |
return getRawResult(); |
367 |
|
} |
368 |
|
|
369 |
|
/** |
370 |
|
* Commences performing this task, awaits its completion if |
371 |
< |
* necessary, and return its result, or throws an (unchecked) |
372 |
< |
* exception if the underlying computation did so. |
371 |
> |
* necessary, and returns its result, or throws an (unchecked) |
372 |
> |
* {@code RuntimeException} or {@code Error} if the underlying |
373 |
> |
* computation did so. |
374 |
|
* |
375 |
|
* @return the computed result |
376 |
|
*/ |
377 |
|
public final V invoke() { |
378 |
< |
return reportResult(doInvoke()); |
378 |
> |
quietlyInvoke(); |
379 |
> |
Throwable ex; |
380 |
> |
if (status < NORMAL && (ex = getException()) != null) |
381 |
> |
UNSAFE.throwException(ex); |
382 |
> |
return getRawResult(); |
383 |
|
} |
384 |
|
|
385 |
|
/** |
386 |
|
* Forks the given tasks, returning when {@code isDone} holds for |
387 |
|
* each task or an (unchecked) exception is encountered, in which |
388 |
< |
* case the exception is rethrown. If either task encounters an |
389 |
< |
* exception, the other one may be, but is not guaranteed to be, |
390 |
< |
* cancelled. If both tasks throw an exception, then this method |
391 |
< |
* throws one of them. The individual status of each task may be |
392 |
< |
* checked using {@link #getException()} and related methods. |
388 |
> |
* case the exception is rethrown. If more than one task |
389 |
> |
* encounters an exception, then this method throws any one of |
390 |
> |
* these exceptions. If any task encounters an exception, the |
391 |
> |
* other may be cancelled. However, the execution status of |
392 |
> |
* individual tasks is not guaranteed upon exceptional return. The |
393 |
> |
* status of each task may be obtained using {@link |
394 |
> |
* #getException()} and related methods to check if they have been |
395 |
> |
* cancelled, completed normally or exceptionally, or left |
396 |
> |
* unprocessed. |
397 |
|
* |
398 |
|
* <p>This method may be invoked only from within {@code |
399 |
< |
* ForkJoinTask} computations (as may be determined using method |
399 |
> |
* ForkJoinPool} computations (as may be determined using method |
400 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
401 |
|
* result in exceptions or errors, possibly including {@code |
402 |
|
* ClassCastException}. |
414 |
|
/** |
415 |
|
* Forks the given tasks, returning when {@code isDone} holds for |
416 |
|
* each task or an (unchecked) exception is encountered, in which |
417 |
< |
* case the exception is rethrown. If any task encounters an |
418 |
< |
* exception, others may be, but are not guaranteed to be, |
419 |
< |
* cancelled. If more than one task encounters an exception, then |
420 |
< |
* this method throws any one of these exceptions. The individual |
421 |
< |
* status of each task may be checked using {@link #getException()} |
422 |
< |
* and related methods. |
417 |
> |
* case the exception is rethrown. If more than one task |
418 |
> |
* encounters an exception, then this method throws any one of |
419 |
> |
* these exceptions. If any task encounters an exception, others |
420 |
> |
* may be cancelled. However, the execution status of individual |
421 |
> |
* tasks is not guaranteed upon exceptional return. The status of |
422 |
> |
* each task may be obtained using {@link #getException()} and |
423 |
> |
* related methods to check if they have been cancelled, completed |
424 |
> |
* normally or exceptionally, or left unprocessed. |
425 |
|
* |
426 |
|
* <p>This method may be invoked only from within {@code |
427 |
< |
* ForkJoinTask} computations (as may be determined using method |
427 |
> |
* ForkJoinPool} computations (as may be determined using method |
428 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
429 |
|
* result in exceptions or errors, possibly including {@code |
430 |
|
* ClassCastException}. |
443 |
|
} |
444 |
|
else if (i != 0) |
445 |
|
t.fork(); |
446 |
< |
else if (t.doInvoke() < NORMAL && ex == null) |
447 |
< |
ex = t.getException(); |
446 |
> |
else { |
447 |
> |
t.quietlyInvoke(); |
448 |
> |
if (ex == null && t.status < NORMAL) |
449 |
> |
ex = t.getException(); |
450 |
> |
} |
451 |
|
} |
452 |
|
for (int i = 1; i <= last; ++i) { |
453 |
|
ForkJoinTask<?> t = tasks[i]; |
454 |
|
if (t != null) { |
455 |
|
if (ex != null) |
456 |
|
t.cancel(false); |
457 |
< |
else if (t.doJoin() < NORMAL && ex == null) |
458 |
< |
ex = t.getException(); |
457 |
> |
else { |
458 |
> |
t.quietlyJoin(); |
459 |
> |
if (ex == null && t.status < NORMAL) |
460 |
> |
ex = t.getException(); |
461 |
> |
} |
462 |
|
} |
463 |
|
} |
464 |
|
if (ex != null) |
468 |
|
/** |
469 |
|
* Forks all tasks in the specified collection, returning when |
470 |
|
* {@code isDone} holds for each task or an (unchecked) exception |
471 |
< |
* is encountered. If any task encounters an exception, others |
472 |
< |
* may be, but are not guaranteed to be, cancelled. If more than |
473 |
< |
* one task encounters an exception, then this method throws any |
474 |
< |
* one of these exceptions. The individual status of each task |
475 |
< |
* may be checked using {@link #getException()} and related |
476 |
< |
* methods. The behavior of this operation is undefined if the |
477 |
< |
* specified collection is modified while the operation is in |
478 |
< |
* progress. |
471 |
> |
* is encountered, in which case the exception is rethrown. If |
472 |
> |
* more than one task encounters an exception, then this method |
473 |
> |
* throws any one of these exceptions. If any task encounters an |
474 |
> |
* exception, others may be cancelled. However, the execution |
475 |
> |
* status of individual tasks is not guaranteed upon exceptional |
476 |
> |
* return. The status of each task may be obtained using {@link |
477 |
> |
* #getException()} and related methods to check if they have been |
478 |
> |
* cancelled, completed normally or exceptionally, or left |
479 |
> |
* unprocessed. |
480 |
|
* |
481 |
|
* <p>This method may be invoked only from within {@code |
482 |
< |
* ForkJoinTask} computations (as may be determined using method |
482 |
> |
* ForkJoinPool} computations (as may be determined using method |
483 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
484 |
|
* result in exceptions or errors, possibly including {@code |
485 |
|
* ClassCastException}. |
506 |
|
} |
507 |
|
else if (i != 0) |
508 |
|
t.fork(); |
509 |
< |
else if (t.doInvoke() < NORMAL && ex == null) |
510 |
< |
ex = t.getException(); |
509 |
> |
else { |
510 |
> |
t.quietlyInvoke(); |
511 |
> |
if (ex == null && t.status < NORMAL) |
512 |
> |
ex = t.getException(); |
513 |
> |
} |
514 |
|
} |
515 |
|
for (int i = 1; i <= last; ++i) { |
516 |
|
ForkJoinTask<?> t = ts.get(i); |
517 |
|
if (t != null) { |
518 |
|
if (ex != null) |
519 |
|
t.cancel(false); |
520 |
< |
else if (t.doJoin() < NORMAL && ex == null) |
521 |
< |
ex = t.getException(); |
520 |
> |
else { |
521 |
> |
t.quietlyJoin(); |
522 |
> |
if (ex == null && t.status < NORMAL) |
523 |
> |
ex = t.getException(); |
524 |
> |
} |
525 |
|
} |
526 |
|
} |
527 |
|
if (ex != null) |
531 |
|
|
532 |
|
/** |
533 |
|
* Attempts to cancel execution of this task. This attempt will |
534 |
< |
* fail if the task has already completed, has already been |
535 |
< |
* cancelled, or could not be cancelled for some other reason. If |
536 |
< |
* successful, and this task has not started when cancel is |
537 |
< |
* called, execution of this task is suppressed, {@link |
538 |
< |
* #isCancelled} will report true, and {@link #join} will result |
539 |
< |
* in a {@code CancellationException} being thrown. |
534 |
> |
* fail if the task has already completed or could not be |
535 |
> |
* cancelled for some other reason. If successful, and this task |
536 |
> |
* has not started when {@code cancel} is called, execution of |
537 |
> |
* this task is suppressed. After this method returns |
538 |
> |
* successfully, unless there is an intervening call to {@link |
539 |
> |
* #reinitialize}, subsequent calls to {@link #isCancelled}, |
540 |
> |
* {@link #isDone}, and {@code cancel} will return {@code true} |
541 |
> |
* and calls to {@link #join} and related methods will result in |
542 |
> |
* {@code CancellationException}. |
543 |
|
* |
544 |
|
* <p>This method may be overridden in subclasses, but if so, must |
545 |
< |
* still ensure that these minimal properties hold. In particular, |
546 |
< |
* the {@code cancel} method itself must not throw exceptions. |
545 |
> |
* still ensure that these properties hold. In particular, the |
546 |
> |
* {@code cancel} method itself must not throw exceptions. |
547 |
|
* |
548 |
|
* <p>This method is designed to be invoked by <em>other</em> |
549 |
|
* tasks. To terminate the current task, you can just return or |
550 |
|
* throw an unchecked exception from its computation method, or |
551 |
|
* invoke {@link #completeExceptionally}. |
552 |
|
* |
553 |
< |
* @param mayInterruptIfRunning this value is ignored in the |
554 |
< |
* default implementation because tasks are not |
555 |
< |
* cancelled via interruption |
553 |
> |
* @param mayInterruptIfRunning this value has no effect in the |
554 |
> |
* default implementation because interrupts are not used to |
555 |
> |
* control cancellation. |
556 |
|
* |
557 |
|
* @return {@code true} if this task is now cancelled |
558 |
|
*/ |
562 |
|
} |
563 |
|
|
564 |
|
/** |
565 |
< |
* Cancels, ignoring any exceptions it throws. Used during worker |
566 |
< |
* and pool shutdown. |
565 |
> |
* Cancels, ignoring any exceptions thrown by cancel. Used during |
566 |
> |
* worker and pool shutdown. Cancel is spec'ed not to throw any |
567 |
> |
* exceptions, but if it does anyway, we have no recourse during |
568 |
> |
* shutdown, so guard against this case. |
569 |
|
*/ |
570 |
|
final void cancelIgnoringExceptions() { |
571 |
|
try { |
575 |
|
} |
576 |
|
|
577 |
|
/** |
578 |
< |
* Cancels ignoring exceptions if worker is terminating |
578 |
> |
* Cancels if current thread is a terminating worker thread, |
579 |
> |
* ignoring any exceptions thrown by cancel. |
580 |
|
*/ |
581 |
< |
private void cancelIfTerminating() { |
581 |
> |
final void cancelIfTerminating() { |
582 |
|
Thread t = Thread.currentThread(); |
583 |
|
if ((t instanceof ForkJoinWorkerThread) && |
584 |
|
((ForkJoinWorkerThread) t).isTerminating()) { |
653 |
|
|
654 |
|
/** |
655 |
|
* Completes this task, and if not already aborted or cancelled, |
656 |
< |
* returning a {@code null} result upon {@code join} and related |
657 |
< |
* operations. This method may be used to provide results for |
658 |
< |
* asynchronous tasks, or to provide alternative handling for |
659 |
< |
* tasks that would not otherwise complete normally. Its use in |
660 |
< |
* other situations is discouraged. This method is |
661 |
< |
* overridable, but overridden versions must invoke {@code super} |
662 |
< |
* implementation to maintain guarantees. |
656 |
> |
* returning the given value as the result of subsequent |
657 |
> |
* invocations of {@code join} and related operations. This method |
658 |
> |
* may be used to provide results for asynchronous tasks, or to |
659 |
> |
* provide alternative handling for tasks that would not otherwise |
660 |
> |
* complete normally. Its use in other situations is |
661 |
> |
* discouraged. This method is overridable, but overridden |
662 |
> |
* versions must invoke {@code super} implementation to maintain |
663 |
> |
* guarantees. |
664 |
|
* |
665 |
|
* @param value the result value for this task |
666 |
|
*/ |
674 |
|
setCompletion(NORMAL); |
675 |
|
} |
676 |
|
|
677 |
+ |
/** |
678 |
+ |
* Waits if necessary for the computation to complete, and then |
679 |
+ |
* retrieves its result. |
680 |
+ |
* |
681 |
+ |
* @return the computed result |
682 |
+ |
* @throws CancellationException if the computation was cancelled |
683 |
+ |
* @throws ExecutionException if the computation threw an |
684 |
+ |
* exception |
685 |
+ |
* @throws InterruptedException if the current thread is not a |
686 |
+ |
* member of a ForkJoinPool and was interrupted while waiting |
687 |
+ |
*/ |
688 |
|
public final V get() throws InterruptedException, ExecutionException { |
689 |
< |
int s = doJoin(); |
690 |
< |
if (Thread.interrupted()) |
691 |
< |
throw new InterruptedException(); |
692 |
< |
if (s < NORMAL) { |
689 |
> |
Thread t = Thread.currentThread(); |
690 |
> |
if (t instanceof ForkJoinWorkerThread) |
691 |
> |
quietlyJoin(); |
692 |
> |
else |
693 |
> |
externalInterruptibleAwaitDone(false, 0L); |
694 |
> |
int s = status; |
695 |
> |
if (s != NORMAL) { |
696 |
|
Throwable ex; |
697 |
|
if (s == CANCELLED) |
698 |
|
throw new CancellationException(); |
702 |
|
return getRawResult(); |
703 |
|
} |
704 |
|
|
705 |
+ |
/** |
706 |
+ |
* Waits if necessary for at most the given time for the computation |
707 |
+ |
* to complete, and then retrieves its result, if available. |
708 |
+ |
* |
709 |
+ |
* @param timeout the maximum time to wait |
710 |
+ |
* @param unit the time unit of the timeout argument |
711 |
+ |
* @return the computed result |
712 |
+ |
* @throws CancellationException if the computation was cancelled |
713 |
+ |
* @throws ExecutionException if the computation threw an |
714 |
+ |
* exception |
715 |
+ |
* @throws InterruptedException if the current thread is not a |
716 |
+ |
* member of a ForkJoinPool and was interrupted while waiting |
717 |
+ |
* @throws TimeoutException if the wait timed out |
718 |
+ |
*/ |
719 |
|
public final V get(long timeout, TimeUnit unit) |
720 |
|
throws InterruptedException, ExecutionException, TimeoutException { |
721 |
+ |
long nanos = unit.toNanos(timeout); |
722 |
|
Thread t = Thread.currentThread(); |
723 |
< |
ForkJoinPool pool; |
724 |
< |
if (t instanceof ForkJoinWorkerThread) { |
673 |
< |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
674 |
< |
if (status >= 0 && w.unpushTask(this)) |
675 |
< |
tryExec(); |
676 |
< |
pool = w.pool; |
677 |
< |
} |
723 |
> |
if (t instanceof ForkJoinWorkerThread) |
724 |
> |
((ForkJoinWorkerThread)t).joinTask(this, true, nanos); |
725 |
|
else |
726 |
< |
pool = null; |
727 |
< |
/* |
728 |
< |
* Timed wait loop intermixes cases for fj (pool != null) and |
682 |
< |
* non FJ threads. For FJ, decrement pool count but don't try |
683 |
< |
* for replacement; increment count on completion. For non-FJ, |
684 |
< |
* deal with interrupts. This is messy, but a little less so |
685 |
< |
* than is splitting the FJ and nonFJ cases. |
686 |
< |
*/ |
687 |
< |
boolean interrupted = false; |
688 |
< |
boolean dec = false; // true if pool count decremented |
689 |
< |
for (;;) { |
690 |
< |
if (Thread.interrupted() && pool == null) { |
691 |
< |
interrupted = true; |
692 |
< |
break; |
693 |
< |
} |
694 |
< |
int s = status; |
695 |
< |
if (s < 0) |
696 |
< |
break; |
697 |
< |
if (UNSAFE.compareAndSwapInt(this, statusOffset, |
698 |
< |
s, s | SIGNAL)) { |
699 |
< |
long startTime = System.nanoTime(); |
700 |
< |
long nanos = unit.toNanos(timeout); |
701 |
< |
long nt; // wait time |
702 |
< |
while (status >= 0 && |
703 |
< |
(nt = nanos - (System.nanoTime() - startTime)) > 0) { |
704 |
< |
if (pool != null && !dec) |
705 |
< |
dec = pool.tryDecrementRunningCount(); |
706 |
< |
else { |
707 |
< |
long ms = nt / 1000000; |
708 |
< |
int ns = (int) (nt % 1000000); |
709 |
< |
try { |
710 |
< |
synchronized(this) { |
711 |
< |
if (status >= 0) |
712 |
< |
wait(ms, ns); |
713 |
< |
} |
714 |
< |
} catch (InterruptedException ie) { |
715 |
< |
if (pool != null) |
716 |
< |
cancelIfTerminating(); |
717 |
< |
else { |
718 |
< |
interrupted = true; |
719 |
< |
break; |
720 |
< |
} |
721 |
< |
} |
722 |
< |
} |
723 |
< |
} |
724 |
< |
break; |
725 |
< |
} |
726 |
< |
} |
727 |
< |
if (pool != null && dec) |
728 |
< |
pool.incrementRunningCount(); |
729 |
< |
if (interrupted) |
730 |
< |
throw new InterruptedException(); |
731 |
< |
int es = status; |
732 |
< |
if (es != NORMAL) { |
726 |
> |
externalInterruptibleAwaitDone(true, nanos); |
727 |
> |
int s = status; |
728 |
> |
if (s != NORMAL) { |
729 |
|
Throwable ex; |
730 |
< |
if (es == CANCELLED) |
730 |
> |
if (s == CANCELLED) |
731 |
|
throw new CancellationException(); |
732 |
< |
if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
732 |
> |
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
733 |
|
throw new ExecutionException(ex); |
734 |
|
throw new TimeoutException(); |
735 |
|
} |
737 |
|
} |
738 |
|
|
739 |
|
/** |
740 |
< |
* Joins this task, without returning its result or throwing an |
740 |
> |
* Joins this task, without returning its result or throwing its |
741 |
|
* exception. This method may be useful when processing |
742 |
|
* collections of tasks when some have been cancelled or otherwise |
743 |
|
* known to have aborted. |
744 |
|
*/ |
745 |
|
public final void quietlyJoin() { |
746 |
< |
doJoin(); |
746 |
> |
Thread t; |
747 |
> |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) { |
748 |
> |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
749 |
> |
if (status >= 0) { |
750 |
> |
if (w.unpushTask(this)) { |
751 |
> |
boolean completed; |
752 |
> |
try { |
753 |
> |
completed = exec(); |
754 |
> |
} catch (Throwable rex) { |
755 |
> |
setExceptionalCompletion(rex); |
756 |
> |
return; |
757 |
> |
} |
758 |
> |
if (completed) { |
759 |
> |
setCompletion(NORMAL); |
760 |
> |
return; |
761 |
> |
} |
762 |
> |
} |
763 |
> |
w.joinTask(this, false, 0L); |
764 |
> |
} |
765 |
> |
} |
766 |
> |
else |
767 |
> |
externalAwaitDone(); |
768 |
|
} |
769 |
|
|
770 |
|
/** |
771 |
|
* Commences performing this task and awaits its completion if |
772 |
< |
* necessary, without returning its result or throwing an |
773 |
< |
* exception. This method may be useful when processing |
757 |
< |
* collections of tasks when some have been cancelled or otherwise |
758 |
< |
* known to have aborted. |
772 |
> |
* necessary, without returning its result or throwing its |
773 |
> |
* exception. |
774 |
|
*/ |
775 |
|
public final void quietlyInvoke() { |
776 |
< |
doInvoke(); |
776 |
> |
if (status >= 0) { |
777 |
> |
boolean completed; |
778 |
> |
try { |
779 |
> |
completed = exec(); |
780 |
> |
} catch (Throwable rex) { |
781 |
> |
setExceptionalCompletion(rex); |
782 |
> |
return; |
783 |
> |
} |
784 |
> |
if (completed) |
785 |
> |
setCompletion(NORMAL); |
786 |
> |
else |
787 |
> |
quietlyJoin(); |
788 |
> |
} |
789 |
|
} |
790 |
|
|
791 |
|
/** |
796 |
|
* processed. |
797 |
|
* |
798 |
|
* <p>This method may be invoked only from within {@code |
799 |
< |
* ForkJoinTask} computations (as may be determined using method |
799 |
> |
* ForkJoinPool} computations (as may be determined using method |
800 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
801 |
|
* result in exceptions or errors, possibly including {@code |
802 |
|
* ClassCastException}. |
815 |
|
* under any other usage conditions are not guaranteed. |
816 |
|
* This method may be useful when executing |
817 |
|
* pre-constructed trees of subtasks in loops. |
818 |
+ |
* |
819 |
+ |
* <p>Upon completion of this method, {@code isDone()} reports |
820 |
+ |
* {@code false}, and {@code getException()} reports {@code |
821 |
+ |
* null}. However, the value returned by {@code getRawResult} is |
822 |
+ |
* unaffected. To clear this value, you can invoke {@code |
823 |
+ |
* setRawResult(null)}. |
824 |
|
*/ |
825 |
|
public void reinitialize() { |
826 |
|
if (status == EXCEPTIONAL) |
842 |
|
} |
843 |
|
|
844 |
|
/** |
845 |
< |
* Returns {@code true} if the current thread is executing as a |
846 |
< |
* ForkJoinPool computation. |
845 |
> |
* Returns {@code true} if the current thread is a {@link |
846 |
> |
* ForkJoinWorkerThread} executing as a ForkJoinPool computation. |
847 |
|
* |
848 |
< |
* @return {@code true} if the current thread is executing as a |
849 |
< |
* ForkJoinPool computation, or false otherwise |
848 |
> |
* @return {@code true} if the current thread is a {@link |
849 |
> |
* ForkJoinWorkerThread} executing as a ForkJoinPool computation, |
850 |
> |
* or {@code false} otherwise |
851 |
|
*/ |
852 |
|
public static boolean inForkJoinPool() { |
853 |
|
return Thread.currentThread() instanceof ForkJoinWorkerThread; |
862 |
|
* were not, stolen. |
863 |
|
* |
864 |
|
* <p>This method may be invoked only from within {@code |
865 |
< |
* ForkJoinTask} computations (as may be determined using method |
865 |
> |
* ForkJoinPool} computations (as may be determined using method |
866 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
867 |
|
* result in exceptions or errors, possibly including {@code |
868 |
|
* ClassCastException}. |
881 |
|
* fork other tasks. |
882 |
|
* |
883 |
|
* <p>This method may be invoked only from within {@code |
884 |
< |
* ForkJoinTask} computations (as may be determined using method |
884 |
> |
* ForkJoinPool} computations (as may be determined using method |
885 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
886 |
|
* result in exceptions or errors, possibly including {@code |
887 |
|
* ClassCastException}. |
904 |
|
* exceeded. |
905 |
|
* |
906 |
|
* <p>This method may be invoked only from within {@code |
907 |
< |
* ForkJoinTask} computations (as may be determined using method |
907 |
> |
* ForkJoinPool} computations (as may be determined using method |
908 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
909 |
|
* result in exceptions or errors, possibly including {@code |
910 |
|
* ClassCastException}. |
962 |
|
* otherwise. |
963 |
|
* |
964 |
|
* <p>This method may be invoked only from within {@code |
965 |
< |
* ForkJoinTask} computations (as may be determined using method |
965 |
> |
* ForkJoinPool} computations (as may be determined using method |
966 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
967 |
|
* result in exceptions or errors, possibly including {@code |
968 |
|
* ClassCastException}. |
981 |
|
* be useful otherwise. |
982 |
|
* |
983 |
|
* <p>This method may be invoked only from within {@code |
984 |
< |
* ForkJoinTask} computations (as may be determined using method |
984 |
> |
* ForkJoinPool} computations (as may be determined using method |
985 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
986 |
|
* result in exceptions or errors, possibly including {@code |
987 |
|
* ClassCastException}. |
1004 |
|
* otherwise. |
1005 |
|
* |
1006 |
|
* <p>This method may be invoked only from within {@code |
1007 |
< |
* ForkJoinTask} computations (as may be determined using method |
1007 |
> |
* ForkJoinPool} computations (as may be determined using method |
1008 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1009 |
|
* result in exceptions or errors, possibly including {@code |
1010 |
|
* ClassCastException}. |
1114 |
|
private static final long serialVersionUID = -7721805057305804111L; |
1115 |
|
|
1116 |
|
/** |
1117 |
< |
* Saves the state to a stream. |
1117 |
> |
* Saves the state to a stream (that is, serializes it). |
1118 |
|
* |
1119 |
|
* @serialData the current run status and the exception thrown |
1120 |
|
* during execution, or {@code null} if none |
1127 |
|
} |
1128 |
|
|
1129 |
|
/** |
1130 |
< |
* Reconstitutes the instance from a stream. |
1130 |
> |
* Reconstitutes the instance from a stream (that is, deserializes it). |
1131 |
|
* |
1132 |
|
* @param s the stream |
1133 |
|
*/ |
1137 |
|
Object ex = s.readObject(); |
1138 |
|
if (ex != null) |
1139 |
|
setExceptionalCompletion((Throwable) ex); |
1106 |
– |
if (status < 0) |
1107 |
– |
synchronized (this) { notifyAll(); } |
1140 |
|
} |
1141 |
|
|
1142 |
|
// Unsafe mechanics |