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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.List; |
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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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* restriction is in part enforced by not permitting checked |
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* exceptions such as {@code IOExceptions} to be thrown. However, |
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* computations may still encounter unchecked exceptions, that are |
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* rethrown to callers attempting join them. These exceptions may |
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* additionally include RejectedExecutionExceptions stemming from |
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* internal resource exhaustion such as failure to allocate internal |
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* task queues. |
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* rethrown to callers attempting to join them. These exceptions may |
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* additionally include {@link RejectedExecutionException} stemming |
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* from internal resource exhaustion, such as failure to allocate |
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* internal task queues. |
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* |
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* <p>The primary method for awaiting completion and extracting |
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* results of a task is {@link #join}, but there are several variants: |
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* The {@link Future#get} methods support interruptible and/or timed |
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* waits for completion and report results using {@code Future} |
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* conventions. Method {@link #helpJoin} enables callers to actively |
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* execute other tasks while awaiting joins, which is sometimes more |
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* efficient but only applies when all subtasks are known to be |
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* strictly tree-structured. Method {@link #invoke} is semantically |
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* equivalent to {@code fork(); join()} but always attempts to |
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* begin execution in the current thread. The "<em>quiet</em>" forms |
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* of these methods do not extract results or report exceptions. These |
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* conventions. Method {@link #invoke} is semantically |
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* equivalent to {@code fork(); join()} but always attempts to begin |
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* execution in the current thread. The "<em>quiet</em>" forms of |
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* these methods do not extract results or report exceptions. These |
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* may be useful when a set of tasks are being executed, and you need |
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* to delay processing of results or exceptions until all complete. |
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* Method {@code invokeAll} (available in multiple versions) |
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* performs the most common form of parallel invocation: forking a set |
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* of tasks and joining them all. |
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* |
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* <p>The execution status of tasks may be queried at several levels |
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* of detail: {@link #isDone} is true if a task completed in any way |
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* (including the case where a task was cancelled without executing); |
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* {@link #isCompletedNormally} is true if a task completed without |
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* cancellation or encountering an exception; {@link #isCancelled} is |
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* true if the task was cancelled (in which case {@link #getException} |
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* returns a {@link java.util.concurrent.CancellationException}); and |
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* {@link #isCompletedAbnormally} is true if a task was either |
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* cancelled or encountered an exception, in which case {@link |
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* #getException} will return either the encountered exception or |
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* {@link java.util.concurrent.CancellationException}. |
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* |
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* <p>The ForkJoinTask class is not usually directly subclassed. |
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* Instead, you subclass one of the abstract classes that support a |
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* particular style of fork/join processing, typically {@link |
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* established in a constructor, and then defines a {@code compute} |
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* method that somehow uses the control methods supplied by this base |
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* class. While these methods have {@code public} access (to allow |
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* instances of different task subclasses to call each others |
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* instances of different task subclasses to call each other's |
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* methods), some of them may only be called from within other |
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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>Most base support methods are {@code final} because their |
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* implementations are intrinsically tied to the underlying |
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* lightweight task scheduling framework, and so cannot be overridden. |
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* Developers creating new basic styles of fork/join processing should |
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* minimally implement {@code protected} methods |
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* {@link #exec}, {@link #setRawResult}, and |
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* {@link #getRawResult}, while also introducing an abstract |
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* computational method that can be implemented in its subclasses, |
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* possibly relying on other {@code protected} methods provided |
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* by this class. |
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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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* underlying lightweight task scheduling framework. Developers |
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* creating new basic styles of fork/join processing should minimally |
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* implement {@code protected} methods {@link #exec}, {@link |
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* #setRawResult}, and {@link #getRawResult}, while also introducing |
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* an abstract computational method that can be implemented in its |
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* subclasses, possibly relying on other {@code protected} methods |
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* provided by this class. |
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* |
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* <p>ForkJoinTasks should perform relatively small amounts of |
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* computations, otherwise splitting into smaller tasks. As a very |
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* rough rule of thumb, a task should perform more than 100 and less |
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* than 10000 basic computational steps. If tasks are too big, then |
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* parallelism cannot improve throughput. If too small, then memory |
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* and internal task maintenance overhead may overwhelm processing. |
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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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* |
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* <p>This class provides {@code adapt} methods for {@link |
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* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that |
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* may be of use when mixing execution of ForkJoinTasks with other |
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* kinds of tasks. When all tasks are of this form, consider using a |
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* pool in {@link ForkJoinPool#setAsyncMode}. |
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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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* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are |
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* of this form, consider using a pool constructed in <em>asyncMode</em>. |
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* |
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* <p>ForkJoinTasks are {@code Serializable}, which enables them |
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* to be used in extensions such as remote execution frameworks. It is |
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* in general sensible to serialize tasks only before or after, but |
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* not during execution. Serialization is not relied on during |
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* execution itself. |
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* <p>ForkJoinTasks are {@code Serializable}, which enables them to be |
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* used in extensions such as remote execution frameworks. It is |
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* sensible to serialize tasks only before or after, but not during, |
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* execution. Serialization is not relied on during execution itself. |
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* |
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* @since 1.7 |
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* @author Doug Lea |
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*/ |
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public abstract class ForkJoinTask<V> implements Future<V>, Serializable { |
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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 COMPLETED. CANCELLED, or |
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* EXCEPTIONAL, which use the top 3 bits. Tasks undergoing |
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* blocking waits by other threads have SIGNAL_MASK bits set -- |
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* bit 15 for external (nonFJ) waits, and the rest a count of |
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* waiting FJ threads. (This representation relies on |
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* ForkJoinPool max thread limits). Completion of a stolen task |
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* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even |
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* though suboptimal for some purposes, we use basic builtin |
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* wait/notify to take advantage of "monitor inflation" in JVMs |
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* that we would otherwise need to emulate to avoid adding further |
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* per-task bookkeeping overhead. Note that bits 16-28 are |
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* currently unused. Also value 0x80000000 is available as spare |
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* completion value. |
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/* |
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* See the internal documentation of class ForkJoinPool for a |
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* general implementation overview. ForkJoinTasks are mainly |
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* responsible for maintaining their "status" field amidst relays |
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* to methods in ForkJoinWorkerThread and ForkJoinPool. The |
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* methods of this class are more-or-less layered into (1) basic |
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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. 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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* 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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|
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static final int COMPLETION_MASK = 0xe0000000; |
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static final int NORMAL = 0xe0000000; // == mask |
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static final int CANCELLED = 0xc0000000; |
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static final int EXCEPTIONAL = 0xa0000000; |
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static final int SIGNAL_MASK = 0x0000ffff; |
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static final int INTERNAL_SIGNAL_MASK = 0x00007fff; |
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static final int EXTERNAL_SIGNAL = 0x00008000; // top bit of low word |
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private static final int NORMAL = -1; |
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private static final int CANCELLED = -2; |
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private static final int EXCEPTIONAL = -3; |
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private static final int SIGNAL = 1; |
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|
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/** |
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* Table of exceptions thrown by tasks, to enable reporting by |
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Collections.synchronizedMap |
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(new WeakHashMap<ForkJoinTask<?>, Throwable>()); |
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|
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// within-package utilities |
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|
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/** |
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* Gets current worker thread, or null if not a worker thread. |
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*/ |
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static ForkJoinWorkerThread getWorker() { |
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Thread t = Thread.currentThread(); |
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return ((t instanceof ForkJoinWorkerThread) ? |
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(ForkJoinWorkerThread) t : null); |
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} |
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|
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final boolean casStatus(int cmp, int val) { |
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return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val); |
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} |
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// Maintaining completion status |
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|
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/** |
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* Workaround for not being able to rethrow unchecked exceptions. |
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*/ |
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static void rethrowException(Throwable ex) { |
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if (ex != null) |
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UNSAFE.throwException(ex); |
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} |
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|
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// Setting completion status |
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|
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/** |
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* Marks completion and wakes up threads waiting to join this task. |
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* Marks completion and wakes up threads waiting to join this task, |
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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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*/ |
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final void setCompletion(int completion) { |
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ForkJoinPool pool = getPool(); |
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if (pool != null) { |
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int s; // Clear signal bits while setting completion status |
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do {} while ((s = status) >= 0 && !casStatus(s, completion)); |
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|
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if ((s & SIGNAL_MASK) != 0) { |
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if ((s &= INTERNAL_SIGNAL_MASK) != 0) |
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pool.updateRunningCount(s); |
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synchronized (this) { notifyAll(); } |
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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 != 0) |
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synchronized (this) { notifyAll(); } |
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break; |
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} |
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} |
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else |
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externallySetCompletion(completion); |
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} |
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|
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/** |
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* Version of setCompletion for non-FJ threads. Leaves signal |
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* bits for unblocked threads to adjust, and always notifies. |
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*/ |
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private void externallySetCompletion(int completion) { |
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int s; |
222 |
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do {} while ((s = status) >= 0 && |
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!casStatus(s, (s & SIGNAL_MASK) | completion)); |
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synchronized (this) { notifyAll(); } |
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} |
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|
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/** |
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* Sets status to indicate normal completion. |
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*/ |
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final void setNormalCompletion() { |
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// Try typical fast case -- single CAS, no signal, not already done. |
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// Manually expand casStatus to improve chances of inlining it |
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if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL)) |
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setCompletion(NORMAL); |
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} |
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|
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// internal waiting and notification |
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|
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/** |
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* Performs the actual monitor wait for awaitDone. |
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* Records exception and sets exceptional completion. |
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* |
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* @return status on exit |
229 |
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*/ |
230 |
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private void doAwaitDone() { |
231 |
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// Minimize lock bias and in/de-flation effects by maximizing |
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// chances of waiting inside sync |
245 |
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try { |
246 |
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while (status >= 0) |
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synchronized (this) { if (status >= 0) wait(); } |
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} catch (InterruptedException ie) { |
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onInterruptedWait(); |
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} |
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private void setExceptionalCompletion(Throwable rex) { |
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exceptionMap.put(this, rex); |
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setCompletion(EXCEPTIONAL); |
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} |
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|
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/** |
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* Performs the actual timed monitor wait for awaitDone. |
236 |
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* Blocks a worker thread until completion. Called only by |
237 |
> |
* pool. Currently unused -- pool-based waits use timeout |
238 |
> |
* version below. |
239 |
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*/ |
240 |
< |
private void doAwaitDone(long startTime, long nanos) { |
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synchronized (this) { |
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final void internalAwaitDone() { |
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> |
int s; // the odd construction reduces lock bias effects |
242 |
> |
while ((s = status) >= 0) { |
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try { |
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while (status >= 0) { |
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< |
long nt = nanos - (System.nanoTime() - startTime); |
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if (nt <= 0) |
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break; |
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wait(nt / 1000000, (int) (nt % 1000000)); |
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synchronized (this) { |
245 |
> |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL)) |
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wait(); |
247 |
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} |
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} catch (InterruptedException ie) { |
249 |
< |
onInterruptedWait(); |
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> |
cancelIfTerminating(); |
250 |
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} |
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} |
252 |
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} |
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|
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// Awaiting completion |
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|
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/** |
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* Sets status to indicate there is joiner, then waits for join, |
256 |
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* surrounded with pool notifications. |
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* Blocks a worker thread until completed or timed out. Called |
256 |
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* only by pool. |
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* |
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* @return status upon exit |
258 |
> |
* @return status on exit |
259 |
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*/ |
260 |
< |
private int awaitDone(ForkJoinWorkerThread w, |
280 |
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boolean maintainParallelism) { |
281 |
< |
ForkJoinPool pool = (w == null) ? null : w.pool; |
260 |
> |
final int internalAwaitDone(long millis, int nanos) { |
261 |
|
int s; |
262 |
< |
while ((s = status) >= 0) { |
263 |
< |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
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if (pool == null || !pool.preJoin(this, maintainParallelism)) |
265 |
< |
doAwaitDone(); |
266 |
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if (((s = status) & INTERNAL_SIGNAL_MASK) != 0) |
288 |
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adjustPoolCountsOnUnblock(pool); |
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< |
break; |
290 |
< |
} |
291 |
< |
} |
292 |
< |
return s; |
293 |
< |
} |
294 |
< |
|
295 |
< |
/** |
296 |
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* Timed version of awaitDone |
297 |
< |
* |
298 |
< |
* @return status upon exit |
299 |
< |
*/ |
300 |
< |
private int awaitDone(ForkJoinWorkerThread w, long nanos) { |
301 |
< |
ForkJoinPool pool = (w == null) ? null : w.pool; |
302 |
< |
int s; |
303 |
< |
while ((s = status) >= 0) { |
304 |
< |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
305 |
< |
long startTime = System.nanoTime(); |
306 |
< |
if (pool == null || !pool.preJoin(this, false)) |
307 |
< |
doAwaitDone(startTime, nanos); |
308 |
< |
if ((s = status) >= 0) { |
309 |
< |
adjustPoolCountsOnCancelledWait(pool); |
310 |
< |
s = status; |
262 |
> |
if ((s = status) >= 0) { |
263 |
> |
try { |
264 |
> |
synchronized (this) { |
265 |
> |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL)) |
266 |
> |
wait(millis, nanos); |
267 |
|
} |
268 |
< |
if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0) |
269 |
< |
adjustPoolCountsOnUnblock(pool); |
314 |
< |
break; |
268 |
> |
} catch (InterruptedException ie) { |
269 |
> |
cancelIfTerminating(); |
270 |
|
} |
271 |
+ |
s = status; |
272 |
|
} |
273 |
|
return s; |
274 |
|
} |
275 |
|
|
276 |
|
/** |
277 |
< |
* Notifies pool that thread is unblocked. Called by signalled |
322 |
< |
* threads when woken by non-FJ threads (which is atypical). |
277 |
> |
* Blocks a non-worker-thread until completion. |
278 |
|
*/ |
279 |
< |
private void adjustPoolCountsOnUnblock(ForkJoinPool pool) { |
279 |
> |
private void externalAwaitDone() { |
280 |
|
int s; |
281 |
< |
do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK)); |
282 |
< |
if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0) |
283 |
< |
pool.updateRunningCount(s); |
284 |
< |
} |
285 |
< |
|
286 |
< |
/** |
287 |
< |
* Notifies pool to adjust counts on cancelled or timed out wait. |
288 |
< |
*/ |
289 |
< |
private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) { |
290 |
< |
if (pool != null) { |
291 |
< |
int s; |
292 |
< |
while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) { |
293 |
< |
if (casStatus(s, s - 1)) { |
339 |
< |
pool.updateRunningCount(1); |
281 |
> |
while ((s = status) >= 0) { |
282 |
> |
synchronized (this) { |
283 |
> |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) { |
284 |
> |
boolean interrupted = false; |
285 |
> |
while (status >= 0) { |
286 |
> |
try { |
287 |
> |
wait(); |
288 |
> |
} catch (InterruptedException ie) { |
289 |
> |
interrupted = true; |
290 |
> |
} |
291 |
> |
} |
292 |
> |
if (interrupted) |
293 |
> |
Thread.currentThread().interrupt(); |
294 |
|
break; |
295 |
|
} |
296 |
|
} |
298 |
|
} |
299 |
|
|
300 |
|
/** |
301 |
< |
* Handles interruptions during waits. |
302 |
< |
*/ |
303 |
< |
private void onInterruptedWait() { |
350 |
< |
ForkJoinWorkerThread w = getWorker(); |
351 |
< |
if (w == null) |
352 |
< |
Thread.currentThread().interrupt(); // re-interrupt |
353 |
< |
else if (w.isTerminating()) |
354 |
< |
cancelIgnoringExceptions(); |
355 |
< |
// else if FJworker, ignore interrupt |
356 |
< |
} |
357 |
< |
|
358 |
< |
// Recording and reporting exceptions |
359 |
< |
|
360 |
< |
private void setDoneExceptionally(Throwable rex) { |
361 |
< |
exceptionMap.put(this, rex); |
362 |
< |
setCompletion(EXCEPTIONAL); |
363 |
< |
} |
364 |
< |
|
365 |
< |
/** |
366 |
< |
* Throws the exception associated with status s. |
367 |
< |
* |
368 |
< |
* @throws the exception |
369 |
< |
*/ |
370 |
< |
private void reportException(int s) { |
371 |
< |
if ((s &= COMPLETION_MASK) < NORMAL) { |
372 |
< |
if (s == CANCELLED) |
373 |
< |
throw new CancellationException(); |
374 |
< |
else |
375 |
< |
rethrowException(exceptionMap.get(this)); |
376 |
< |
} |
377 |
< |
} |
378 |
< |
|
379 |
< |
/** |
380 |
< |
* Returns result or throws exception using j.u.c.Future conventions. |
381 |
< |
* Only call when {@code isDone} known to be true. |
382 |
< |
*/ |
383 |
< |
private V reportFutureResult() |
384 |
< |
throws ExecutionException, InterruptedException { |
385 |
< |
int s = status & COMPLETION_MASK; |
386 |
< |
if (s < NORMAL) { |
387 |
< |
Throwable ex; |
388 |
< |
if (s == CANCELLED) |
389 |
< |
throw new CancellationException(); |
390 |
< |
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
391 |
< |
throw new ExecutionException(ex); |
392 |
< |
if (Thread.interrupted()) |
393 |
< |
throw new InterruptedException(); |
394 |
< |
} |
395 |
< |
return getRawResult(); |
396 |
< |
} |
397 |
< |
|
398 |
< |
/** |
399 |
< |
* Returns result or throws exception using j.u.c.Future conventions |
400 |
< |
* with timeouts. |
401 |
< |
*/ |
402 |
< |
private V reportTimedFutureResult() |
403 |
< |
throws InterruptedException, ExecutionException, TimeoutException { |
404 |
< |
Throwable ex; |
405 |
< |
int s = status & COMPLETION_MASK; |
406 |
< |
if (s == NORMAL) |
407 |
< |
return getRawResult(); |
408 |
< |
if (s == CANCELLED) |
409 |
< |
throw new CancellationException(); |
410 |
< |
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
411 |
< |
throw new ExecutionException(ex); |
412 |
< |
if (Thread.interrupted()) |
413 |
< |
throw new InterruptedException(); |
414 |
< |
throw new TimeoutException(); |
415 |
< |
} |
416 |
< |
|
417 |
< |
// internal execution methods |
418 |
< |
|
419 |
< |
/** |
420 |
< |
* Calls exec, recording completion, and rethrowing exception if |
421 |
< |
* encountered. Caller should normally check status before calling. |
422 |
< |
* |
423 |
< |
* @return true if completed normally |
424 |
< |
*/ |
425 |
< |
private boolean tryExec() { |
426 |
< |
try { // try block must contain only call to exec |
427 |
< |
if (!exec()) |
428 |
< |
return false; |
429 |
< |
} catch (Throwable rex) { |
430 |
< |
setDoneExceptionally(rex); |
431 |
< |
rethrowException(rex); |
432 |
< |
return false; // not reached |
433 |
< |
} |
434 |
< |
setNormalCompletion(); |
435 |
< |
return true; |
436 |
< |
} |
437 |
< |
|
438 |
< |
/** |
439 |
< |
* Main execution method used by worker threads. Invokes |
440 |
< |
* base computation unless already complete. |
301 |
> |
* Unless done, calls exec and records status if completed, but |
302 |
> |
* doesn't wait for completion otherwise. Primary execution method |
303 |
> |
* for ForkJoinWorkerThread. |
304 |
|
*/ |
305 |
|
final void quietlyExec() { |
443 |
– |
if (status >= 0) { |
444 |
– |
try { |
445 |
– |
if (!exec()) |
446 |
– |
return; |
447 |
– |
} catch (Throwable rex) { |
448 |
– |
setDoneExceptionally(rex); |
449 |
– |
return; |
450 |
– |
} |
451 |
– |
setNormalCompletion(); |
452 |
– |
} |
453 |
– |
} |
454 |
– |
|
455 |
– |
/** |
456 |
– |
* Calls exec(), recording but not rethrowing exception. |
457 |
– |
* Caller should normally check status before calling. |
458 |
– |
* |
459 |
– |
* @return true if completed normally |
460 |
– |
*/ |
461 |
– |
private boolean tryQuietlyInvoke() { |
306 |
|
try { |
307 |
< |
if (!exec()) |
308 |
< |
return false; |
307 |
> |
if (status < 0 || !exec()) |
308 |
> |
return; |
309 |
|
} catch (Throwable rex) { |
310 |
< |
setDoneExceptionally(rex); |
311 |
< |
return false; |
468 |
< |
} |
469 |
< |
setNormalCompletion(); |
470 |
< |
return true; |
471 |
< |
} |
472 |
< |
|
473 |
< |
/** |
474 |
< |
* Cancels, ignoring any exceptions it throws. |
475 |
< |
*/ |
476 |
< |
final void cancelIgnoringExceptions() { |
477 |
< |
try { |
478 |
< |
cancel(false); |
479 |
< |
} catch (Throwable ignore) { |
310 |
> |
setExceptionalCompletion(rex); |
311 |
> |
return; |
312 |
|
} |
313 |
< |
} |
482 |
< |
|
483 |
< |
/** |
484 |
< |
* Main implementation of helpJoin |
485 |
< |
*/ |
486 |
< |
private int busyJoin(ForkJoinWorkerThread w) { |
487 |
< |
int s; |
488 |
< |
ForkJoinTask<?> t; |
489 |
< |
while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null) |
490 |
< |
t.quietlyExec(); |
491 |
< |
return (s >= 0) ? awaitDone(w, false) : s; // block if no work |
313 |
> |
setCompletion(NORMAL); // must be outside try block |
314 |
|
} |
315 |
|
|
316 |
|
// public methods |
318 |
|
/** |
319 |
|
* Arranges to asynchronously execute this task. While it is not |
320 |
|
* necessarily enforced, it is a usage error to fork a task more |
321 |
< |
* than once unless it has completed and been reinitialized. This |
322 |
< |
* method may be invoked only from within ForkJoinTask |
323 |
< |
* computations (as may be determined using method {@link |
324 |
< |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
325 |
< |
* in exceptions or errors, possibly including ClassCastException. |
321 |
> |
* than once unless it has completed and been reinitialized. |
322 |
> |
* Subsequent modifications to the state of this task or any data |
323 |
> |
* it operates on are not necessarily consistently observable by |
324 |
> |
* any thread other than the one executing it unless preceded by a |
325 |
> |
* call to {@link #join} or related methods, or a call to {@link |
326 |
> |
* #isDone} returning {@code true}. |
327 |
> |
* |
328 |
> |
* <p>This method may be invoked only from within {@code |
329 |
> |
* ForkJoinTask} computations (as may be determined using method |
330 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
331 |
> |
* result in exceptions or errors, possibly including {@code |
332 |
> |
* ClassCastException}. |
333 |
|
* |
334 |
< |
* @return {@code this}, to simplify usage. |
334 |
> |
* @return {@code this}, to simplify usage |
335 |
|
*/ |
336 |
|
public final ForkJoinTask<V> fork() { |
337 |
|
((ForkJoinWorkerThread) Thread.currentThread()) |
340 |
|
} |
341 |
|
|
342 |
|
/** |
343 |
< |
* Returns the result of the computation when it is ready. |
344 |
< |
* This method differs from {@code get} in that abnormal |
345 |
< |
* completion results in RuntimeExceptions or Errors, not |
346 |
< |
* ExecutionExceptions. |
343 |
> |
* Returns the result of the computation when it {@link #isDone is |
344 |
> |
* done}. This method differs from {@link #get()} in that |
345 |
> |
* abnormal completion results in {@code RuntimeException} or |
346 |
> |
* {@code Error}, not {@code ExecutionException}, and that |
347 |
> |
* interrupts of the calling thread do <em>not</em> cause the |
348 |
> |
* method to abruptly return by throwing {@code |
349 |
> |
* InterruptedException}. |
350 |
|
* |
351 |
|
* @return the computed result |
352 |
|
*/ |
353 |
|
public final V join() { |
354 |
< |
ForkJoinWorkerThread w = getWorker(); |
355 |
< |
if (w == null || status < 0 || !w.unpushTask(this) || !tryExec()) |
356 |
< |
reportException(awaitDone(w, true)); |
354 |
> |
quietlyJoin(); |
355 |
> |
Throwable ex; |
356 |
> |
if (status < NORMAL && (ex = getException()) != null) |
357 |
> |
UNSAFE.throwException(ex); |
358 |
|
return getRawResult(); |
359 |
|
} |
360 |
|
|
361 |
|
/** |
362 |
|
* Commences performing this task, awaits its completion if |
363 |
< |
* necessary, and return its result. |
363 |
> |
* necessary, and returns its result, or throws an (unchecked) |
364 |
> |
* {@code RuntimeException} or {@code Error} if the underlying |
365 |
> |
* computation did so. |
366 |
|
* |
532 |
– |
* @throws Throwable (a RuntimeException, Error, or unchecked |
533 |
– |
* exception) if the underlying computation did so |
367 |
|
* @return the computed result |
368 |
|
*/ |
369 |
|
public final V invoke() { |
370 |
< |
if (status >= 0 && tryExec()) |
371 |
< |
return getRawResult(); |
372 |
< |
else |
373 |
< |
return join(); |
370 |
> |
quietlyInvoke(); |
371 |
> |
Throwable ex; |
372 |
> |
if (status < NORMAL && (ex = getException()) != null) |
373 |
> |
UNSAFE.throwException(ex); |
374 |
> |
return getRawResult(); |
375 |
|
} |
376 |
|
|
377 |
|
/** |
378 |
|
* Forks the given tasks, returning when {@code isDone} holds for |
379 |
< |
* each task or an exception is encountered. This method may be |
380 |
< |
* invoked only from within ForkJoinTask computations (as may be |
381 |
< |
* determined using method {@link #inForkJoinPool}). Attempts to |
382 |
< |
* invoke in other contexts result in exceptions or errors, |
383 |
< |
* possibly including ClassCastException. |
379 |
> |
* each task or an (unchecked) exception is encountered, in which |
380 |
> |
* case the exception is rethrown. If more than one task |
381 |
> |
* encounters an exception, then this method throws any one of |
382 |
> |
* these exceptions. If any task encounters an exception, the |
383 |
> |
* other may be cancelled. However, the execution status of |
384 |
> |
* individual tasks is not guaranteed upon exceptional return. The |
385 |
> |
* status of each task may be obtained using {@link |
386 |
> |
* #getException()} and related methods to check if they have been |
387 |
> |
* cancelled, completed normally or exceptionally, or left |
388 |
> |
* unprocessed. |
389 |
> |
* |
390 |
> |
* <p>This method may be invoked only from within {@code |
391 |
> |
* ForkJoinPool} computations (as may be determined using method |
392 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
393 |
> |
* result in exceptions or errors, possibly including {@code |
394 |
> |
* ClassCastException}. |
395 |
|
* |
396 |
|
* @param t1 the first task |
397 |
|
* @param t2 the second task |
398 |
|
* @throws NullPointerException if any task is null |
554 |
– |
* @throws RuntimeException or Error if a task did so |
399 |
|
*/ |
400 |
< |
public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) { |
400 |
> |
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) { |
401 |
|
t2.fork(); |
402 |
|
t1.invoke(); |
403 |
|
t2.join(); |
405 |
|
|
406 |
|
/** |
407 |
|
* Forks the given tasks, returning when {@code isDone} holds for |
408 |
< |
* each task or an exception is encountered. If any task |
409 |
< |
* encounters an exception, others may be, but are not guaranteed |
410 |
< |
* to be, cancelled. This method may be invoked only from within |
411 |
< |
* ForkJoinTask computations (as may be determined using method |
412 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
413 |
< |
* result in exceptions or errors, possibly including |
414 |
< |
* ClassCastException. |
415 |
< |
* |
416 |
< |
* Overloadings of this method exist for the special cases |
417 |
< |
* of one to four arguments. |
408 |
> |
* each task or an (unchecked) exception is encountered, in which |
409 |
> |
* case the exception is rethrown. If more than one task |
410 |
> |
* encounters an exception, then this method throws any one of |
411 |
> |
* these exceptions. If any task encounters an exception, others |
412 |
> |
* may be cancelled. However, the execution status of individual |
413 |
> |
* tasks is not guaranteed upon exceptional return. The status of |
414 |
> |
* each task may be obtained using {@link #getException()} and |
415 |
> |
* related methods to check if they have been cancelled, completed |
416 |
> |
* normally or exceptionally, or left unprocessed. |
417 |
> |
* |
418 |
> |
* <p>This method may be invoked only from within {@code |
419 |
> |
* ForkJoinPool} computations (as may be determined using method |
420 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
421 |
> |
* result in exceptions or errors, possibly including {@code |
422 |
> |
* ClassCastException}. |
423 |
|
* |
424 |
|
* @param tasks the tasks |
425 |
< |
* @throws NullPointerException if tasks or any element are null |
577 |
< |
* @throws RuntimeException or Error if any task did so |
425 |
> |
* @throws NullPointerException if any task is null |
426 |
|
*/ |
427 |
|
public static void invokeAll(ForkJoinTask<?>... tasks) { |
428 |
|
Throwable ex = null; |
437 |
|
t.fork(); |
438 |
|
else { |
439 |
|
t.quietlyInvoke(); |
440 |
< |
if (ex == null) |
440 |
> |
if (ex == null && t.status < NORMAL) |
441 |
|
ex = t.getException(); |
442 |
|
} |
443 |
|
} |
448 |
|
t.cancel(false); |
449 |
|
else { |
450 |
|
t.quietlyJoin(); |
451 |
< |
if (ex == null) |
451 |
> |
if (ex == null && t.status < NORMAL) |
452 |
|
ex = t.getException(); |
453 |
|
} |
454 |
|
} |
455 |
|
} |
456 |
|
if (ex != null) |
457 |
< |
rethrowException(ex); |
457 |
> |
UNSAFE.throwException(ex); |
458 |
|
} |
459 |
|
|
460 |
|
/** |
461 |
< |
* Forks all tasks in the collection, returning when {@code |
462 |
< |
* isDone} holds for each task or an exception is encountered. If |
463 |
< |
* any task encounters an exception, others may be, but are not |
464 |
< |
* guaranteed to be, cancelled. This method may be invoked only |
465 |
< |
* from within ForkJoinTask computations (as may be determined |
466 |
< |
* using method {@link #inForkJoinPool}). Attempts to invoke in |
467 |
< |
* other contexts result in exceptions or errors, possibly |
468 |
< |
* including ClassCastException. |
461 |
> |
* Forks all tasks in the specified collection, returning when |
462 |
> |
* {@code isDone} holds for each task or an (unchecked) exception |
463 |
> |
* is encountered, in which case the exception is rethrown. If |
464 |
> |
* more than one task encounters an exception, then this method |
465 |
> |
* throws any one of these exceptions. If any task encounters an |
466 |
> |
* exception, others may be cancelled. However, the execution |
467 |
> |
* status of individual tasks is not guaranteed upon exceptional |
468 |
> |
* return. The status of each task may be obtained using {@link |
469 |
> |
* #getException()} and related methods to check if they have been |
470 |
> |
* cancelled, completed normally or exceptionally, or left |
471 |
> |
* unprocessed. |
472 |
> |
* |
473 |
> |
* <p>This method may be invoked only from within {@code |
474 |
> |
* ForkJoinPool} computations (as may be determined using method |
475 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
476 |
> |
* result in exceptions or errors, possibly including {@code |
477 |
> |
* ClassCastException}. |
478 |
|
* |
479 |
|
* @param tasks the collection of tasks |
480 |
|
* @return the tasks argument, to simplify usage |
481 |
|
* @throws NullPointerException if tasks or any element are null |
625 |
– |
* @throws RuntimeException or Error if any task did so |
482 |
|
*/ |
483 |
|
public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) { |
484 |
< |
if (!(tasks instanceof List<?>)) { |
484 |
> |
if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) { |
485 |
|
invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()])); |
486 |
|
return tasks; |
487 |
|
} |
500 |
|
t.fork(); |
501 |
|
else { |
502 |
|
t.quietlyInvoke(); |
503 |
< |
if (ex == null) |
503 |
> |
if (ex == null && t.status < NORMAL) |
504 |
|
ex = t.getException(); |
505 |
|
} |
506 |
|
} |
511 |
|
t.cancel(false); |
512 |
|
else { |
513 |
|
t.quietlyJoin(); |
514 |
< |
if (ex == null) |
514 |
> |
if (ex == null && t.status < NORMAL) |
515 |
|
ex = t.getException(); |
516 |
|
} |
517 |
|
} |
518 |
|
} |
519 |
|
if (ex != null) |
520 |
< |
rethrowException(ex); |
520 |
> |
UNSAFE.throwException(ex); |
521 |
|
return tasks; |
522 |
|
} |
523 |
|
|
524 |
|
/** |
525 |
< |
* Returns {@code true} if the computation performed by this task |
526 |
< |
* has completed (or has been cancelled). |
527 |
< |
* |
528 |
< |
* @return {@code true} if this computation has completed |
529 |
< |
*/ |
530 |
< |
public final boolean isDone() { |
531 |
< |
return status < 0; |
532 |
< |
} |
533 |
< |
|
534 |
< |
/** |
679 |
< |
* Returns {@code true} if this task was cancelled. |
680 |
< |
* |
681 |
< |
* @return {@code true} if this task was cancelled |
682 |
< |
*/ |
683 |
< |
public final boolean isCancelled() { |
684 |
< |
return (status & COMPLETION_MASK) == CANCELLED; |
685 |
< |
} |
686 |
< |
|
687 |
< |
/** |
688 |
< |
* Asserts that the results of this task's computation will not be |
689 |
< |
* used. If a cancellation occurs before attempting to execute this |
690 |
< |
* task, execution will be suppressed, {@link #isCancelled} |
691 |
< |
* will report true, and {@link #join} will result in a |
692 |
< |
* {@code CancellationException} being thrown. Otherwise, when |
693 |
< |
* cancellation races with completion, there are no guarantees |
694 |
< |
* about whether {@code isCancelled} will report {@code true}, |
695 |
< |
* whether {@code join} will return normally or via an exception, |
696 |
< |
* or whether these behaviors will remain consistent upon repeated |
697 |
< |
* invocation. |
525 |
> |
* Attempts to cancel execution of this task. This attempt will |
526 |
> |
* fail if the task has already completed or could not be |
527 |
> |
* cancelled for some other reason. If successful, and this task |
528 |
> |
* has not started when {@code cancel} is called, execution of |
529 |
> |
* this task is suppressed. After this method returns |
530 |
> |
* successfully, unless there is an intervening call to {@link |
531 |
> |
* #reinitialize}, subsequent calls to {@link #isCancelled}, |
532 |
> |
* {@link #isDone}, and {@code cancel} will return {@code true} |
533 |
> |
* and calls to {@link #join} and related methods will result in |
534 |
> |
* {@code CancellationException}. |
535 |
|
* |
536 |
|
* <p>This method may be overridden in subclasses, but if so, must |
537 |
< |
* still ensure that these minimal properties hold. In particular, |
538 |
< |
* the {@code cancel} method itself must not throw exceptions. |
537 |
> |
* still ensure that these properties hold. In particular, the |
538 |
> |
* {@code cancel} method itself must not throw exceptions. |
539 |
|
* |
540 |
|
* <p>This method is designed to be invoked by <em>other</em> |
541 |
|
* tasks. To terminate the current task, you can just return or |
542 |
|
* throw an unchecked exception from its computation method, or |
543 |
|
* invoke {@link #completeExceptionally}. |
544 |
|
* |
545 |
< |
* @param mayInterruptIfRunning this value is ignored in the |
546 |
< |
* default implementation because tasks are not in general |
547 |
< |
* cancelled via interruption |
545 |
> |
* @param mayInterruptIfRunning this value has no effect in the |
546 |
> |
* default implementation because interrupts are not used to |
547 |
> |
* control cancellation. |
548 |
|
* |
549 |
|
* @return {@code true} if this task is now cancelled |
550 |
|
*/ |
551 |
|
public boolean cancel(boolean mayInterruptIfRunning) { |
552 |
|
setCompletion(CANCELLED); |
553 |
< |
return (status & COMPLETION_MASK) == CANCELLED; |
553 |
> |
return status == CANCELLED; |
554 |
> |
} |
555 |
> |
|
556 |
> |
/** |
557 |
> |
* Cancels, ignoring any exceptions thrown by cancel. Used during |
558 |
> |
* worker and pool shutdown. Cancel is spec'ed not to throw any |
559 |
> |
* exceptions, but if it does anyway, we have no recourse during |
560 |
> |
* shutdown, so guard against this case. |
561 |
> |
*/ |
562 |
> |
final void cancelIgnoringExceptions() { |
563 |
> |
try { |
564 |
> |
cancel(false); |
565 |
> |
} catch (Throwable ignore) { |
566 |
> |
} |
567 |
> |
} |
568 |
> |
|
569 |
> |
/** |
570 |
> |
* Cancels if current thread is a terminating worker thread, |
571 |
> |
* ignoring any exceptions thrown by cancel. |
572 |
> |
*/ |
573 |
> |
final void cancelIfTerminating() { |
574 |
> |
Thread t = Thread.currentThread(); |
575 |
> |
if ((t instanceof ForkJoinWorkerThread) && |
576 |
> |
((ForkJoinWorkerThread) t).isTerminating()) { |
577 |
> |
try { |
578 |
> |
cancel(false); |
579 |
> |
} catch (Throwable ignore) { |
580 |
> |
} |
581 |
> |
} |
582 |
> |
} |
583 |
> |
|
584 |
> |
public final boolean isDone() { |
585 |
> |
return status < 0; |
586 |
> |
} |
587 |
> |
|
588 |
> |
public final boolean isCancelled() { |
589 |
> |
return status == CANCELLED; |
590 |
|
} |
591 |
|
|
592 |
|
/** |
595 |
|
* @return {@code true} if this task threw an exception or was cancelled |
596 |
|
*/ |
597 |
|
public final boolean isCompletedAbnormally() { |
598 |
< |
return (status & COMPLETION_MASK) < NORMAL; |
598 |
> |
return status < NORMAL; |
599 |
> |
} |
600 |
> |
|
601 |
> |
/** |
602 |
> |
* Returns {@code true} if this task completed without throwing an |
603 |
> |
* exception and was not cancelled. |
604 |
> |
* |
605 |
> |
* @return {@code true} if this task completed without throwing an |
606 |
> |
* exception and was not cancelled |
607 |
> |
*/ |
608 |
> |
public final boolean isCompletedNormally() { |
609 |
> |
return status == NORMAL; |
610 |
|
} |
611 |
|
|
612 |
|
/** |
617 |
|
* @return the exception, or {@code null} if none |
618 |
|
*/ |
619 |
|
public final Throwable getException() { |
620 |
< |
int s = status & COMPLETION_MASK; |
621 |
< |
if (s >= NORMAL) |
622 |
< |
return null; |
623 |
< |
if (s == CANCELLED) |
740 |
< |
return new CancellationException(); |
741 |
< |
return exceptionMap.get(this); |
620 |
> |
int s = status; |
621 |
> |
return ((s >= NORMAL) ? null : |
622 |
> |
(s == CANCELLED) ? new CancellationException() : |
623 |
> |
exceptionMap.get(this)); |
624 |
|
} |
625 |
|
|
626 |
|
/** |
633 |
|
* overridable, but overridden versions must invoke {@code super} |
634 |
|
* implementation to maintain guarantees. |
635 |
|
* |
636 |
< |
* @param ex the exception to throw. If this exception is |
637 |
< |
* not a RuntimeException or Error, the actual exception thrown |
638 |
< |
* will be a RuntimeException with cause ex. |
636 |
> |
* @param ex the exception to throw. If this exception is not a |
637 |
> |
* {@code RuntimeException} or {@code Error}, the actual exception |
638 |
> |
* thrown will be a {@code RuntimeException} with cause {@code ex}. |
639 |
|
*/ |
640 |
|
public void completeExceptionally(Throwable ex) { |
641 |
< |
setDoneExceptionally((ex instanceof RuntimeException) || |
642 |
< |
(ex instanceof Error) ? ex : |
643 |
< |
new RuntimeException(ex)); |
641 |
> |
setExceptionalCompletion((ex instanceof RuntimeException) || |
642 |
> |
(ex instanceof Error) ? ex : |
643 |
> |
new RuntimeException(ex)); |
644 |
|
} |
645 |
|
|
646 |
|
/** |
647 |
|
* Completes this task, and if not already aborted or cancelled, |
648 |
< |
* returning a {@code null} result upon {@code join} and related |
649 |
< |
* operations. This method may be used to provide results for |
650 |
< |
* asynchronous tasks, or to provide alternative handling for |
651 |
< |
* tasks that would not otherwise complete normally. Its use in |
652 |
< |
* other situations is discouraged. This method is |
653 |
< |
* overridable, but overridden versions must invoke {@code super} |
654 |
< |
* implementation to maintain guarantees. |
648 |
> |
* returning the given value as the result of subsequent |
649 |
> |
* invocations of {@code join} and related operations. This method |
650 |
> |
* may be used to provide results for asynchronous tasks, or to |
651 |
> |
* provide alternative handling for tasks that would not otherwise |
652 |
> |
* complete normally. Its use in other situations is |
653 |
> |
* discouraged. This method is overridable, but overridden |
654 |
> |
* versions must invoke {@code super} implementation to maintain |
655 |
> |
* guarantees. |
656 |
|
* |
657 |
|
* @param value the result value for this task |
658 |
|
*/ |
660 |
|
try { |
661 |
|
setRawResult(value); |
662 |
|
} catch (Throwable rex) { |
663 |
< |
setDoneExceptionally(rex); |
663 |
> |
setExceptionalCompletion(rex); |
664 |
|
return; |
665 |
|
} |
666 |
< |
setNormalCompletion(); |
784 |
< |
} |
785 |
< |
|
786 |
< |
public final V get() throws InterruptedException, ExecutionException { |
787 |
< |
ForkJoinWorkerThread w = getWorker(); |
788 |
< |
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
789 |
< |
awaitDone(w, true); |
790 |
< |
return reportFutureResult(); |
791 |
< |
} |
792 |
< |
|
793 |
< |
public final V get(long timeout, TimeUnit unit) |
794 |
< |
throws InterruptedException, ExecutionException, TimeoutException { |
795 |
< |
long nanos = unit.toNanos(timeout); |
796 |
< |
ForkJoinWorkerThread w = getWorker(); |
797 |
< |
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
798 |
< |
awaitDone(w, nanos); |
799 |
< |
return reportTimedFutureResult(); |
666 |
> |
setCompletion(NORMAL); |
667 |
|
} |
668 |
|
|
669 |
|
/** |
670 |
< |
* Possibly executes other tasks until this task is ready, then |
671 |
< |
* returns the result of the computation. This method may be more |
805 |
< |
* efficient than {@code join}, but is only applicable when |
806 |
< |
* there are no potential dependencies between continuation of the |
807 |
< |
* current task and that of any other task that might be executed |
808 |
< |
* while helping. (This usually holds for pure divide-and-conquer |
809 |
< |
* tasks). This method may be invoked only from within |
810 |
< |
* ForkJoinTask computations (as may be determined using method |
811 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
812 |
< |
* result in exceptions or errors, possibly including |
813 |
< |
* ClassCastException. |
670 |
> |
* Waits if necessary for the computation to complete, and then |
671 |
> |
* retrieves its result. |
672 |
|
* |
673 |
|
* @return the computed result |
674 |
+ |
* @throws CancellationException if the computation was cancelled |
675 |
+ |
* @throws ExecutionException if the computation threw an |
676 |
+ |
* exception |
677 |
+ |
* @throws InterruptedException if the current thread is not a |
678 |
+ |
* member of a ForkJoinPool and was interrupted while waiting |
679 |
|
*/ |
680 |
< |
public final V helpJoin() { |
681 |
< |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread(); |
682 |
< |
if (status < 0 || !w.unpushTask(this) || !tryExec()) |
683 |
< |
reportException(busyJoin(w)); |
680 |
> |
public final V get() throws InterruptedException, ExecutionException { |
681 |
> |
int s; |
682 |
> |
if (Thread.currentThread() instanceof ForkJoinWorkerThread) { |
683 |
> |
quietlyJoin(); |
684 |
> |
s = status; |
685 |
> |
} |
686 |
> |
else { |
687 |
> |
while ((s = status) >= 0) { |
688 |
> |
synchronized (this) { // interruptible form of awaitDone |
689 |
> |
if (UNSAFE.compareAndSwapInt(this, statusOffset, |
690 |
> |
s, SIGNAL)) { |
691 |
> |
while (status >= 0) |
692 |
> |
wait(); |
693 |
> |
} |
694 |
> |
} |
695 |
> |
} |
696 |
> |
} |
697 |
> |
if (s < NORMAL) { |
698 |
> |
Throwable ex; |
699 |
> |
if (s == CANCELLED) |
700 |
> |
throw new CancellationException(); |
701 |
> |
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
702 |
> |
throw new ExecutionException(ex); |
703 |
> |
} |
704 |
|
return getRawResult(); |
705 |
|
} |
706 |
|
|
707 |
|
/** |
708 |
< |
* Possibly executes other tasks until this task is ready. This |
709 |
< |
* method may be invoked only from within ForkJoinTask |
710 |
< |
* computations (as may be determined using method {@link |
711 |
< |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
712 |
< |
* in exceptions or errors, possibly including ClassCastException. |
708 |
> |
* Waits if necessary for at most the given time for the computation |
709 |
> |
* to complete, and then retrieves its result, if available. |
710 |
> |
* |
711 |
> |
* @param timeout the maximum time to wait |
712 |
> |
* @param unit the time unit of the timeout argument |
713 |
> |
* @return the computed result |
714 |
> |
* @throws CancellationException if the computation was cancelled |
715 |
> |
* @throws ExecutionException if the computation threw an |
716 |
> |
* exception |
717 |
> |
* @throws InterruptedException if the current thread is not a |
718 |
> |
* member of a ForkJoinPool and was interrupted while waiting |
719 |
> |
* @throws TimeoutException if the wait timed out |
720 |
|
*/ |
721 |
< |
public final void quietlyHelpJoin() { |
721 |
> |
public final V get(long timeout, TimeUnit unit) |
722 |
> |
throws InterruptedException, ExecutionException, TimeoutException { |
723 |
> |
long nanos = unit.toNanos(timeout); |
724 |
|
if (status >= 0) { |
725 |
< |
ForkJoinWorkerThread w = |
726 |
< |
(ForkJoinWorkerThread) Thread.currentThread(); |
727 |
< |
if (!w.unpushTask(this) || !tryQuietlyInvoke()) |
728 |
< |
busyJoin(w); |
725 |
> |
Thread t = Thread.currentThread(); |
726 |
> |
if (t instanceof ForkJoinWorkerThread) { |
727 |
> |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
728 |
> |
boolean completed = false; // timed variant of quietlyJoin |
729 |
> |
if (w.unpushTask(this)) { |
730 |
> |
try { |
731 |
> |
completed = exec(); |
732 |
> |
} catch (Throwable rex) { |
733 |
> |
setExceptionalCompletion(rex); |
734 |
> |
} |
735 |
> |
} |
736 |
> |
if (completed) |
737 |
> |
setCompletion(NORMAL); |
738 |
> |
else if (status >= 0) |
739 |
> |
w.joinTask(this, true, nanos); |
740 |
> |
} |
741 |
> |
else if (Thread.interrupted()) |
742 |
> |
throw new InterruptedException(); |
743 |
> |
else { |
744 |
> |
long startTime = System.nanoTime(); |
745 |
> |
int s; long nt; |
746 |
> |
while ((s = status) >= 0 && |
747 |
> |
(nt = nanos - (System.nanoTime() - startTime)) > 0) { |
748 |
> |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, |
749 |
> |
SIGNAL)) { |
750 |
> |
long ms = nt / 1000000; |
751 |
> |
int ns = (int) (nt % 1000000); |
752 |
> |
synchronized (this) { |
753 |
> |
if (status >= 0) |
754 |
> |
wait(ms, ns); // exit on IE throw |
755 |
> |
} |
756 |
> |
} |
757 |
> |
} |
758 |
> |
} |
759 |
> |
} |
760 |
> |
int es = status; |
761 |
> |
if (es != NORMAL) { |
762 |
> |
Throwable ex; |
763 |
> |
if (es == CANCELLED) |
764 |
> |
throw new CancellationException(); |
765 |
> |
if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
766 |
> |
throw new ExecutionException(ex); |
767 |
> |
throw new TimeoutException(); |
768 |
|
} |
769 |
+ |
return getRawResult(); |
770 |
|
} |
771 |
|
|
772 |
|
/** |
773 |
< |
* Joins this task, without returning its result or throwing an |
773 |
> |
* Joins this task, without returning its result or throwing its |
774 |
|
* exception. This method may be useful when processing |
775 |
|
* collections of tasks when some have been cancelled or otherwise |
776 |
|
* known to have aborted. |
777 |
|
*/ |
778 |
|
public final void quietlyJoin() { |
779 |
< |
if (status >= 0) { |
780 |
< |
ForkJoinWorkerThread w = getWorker(); |
781 |
< |
if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke()) |
782 |
< |
awaitDone(w, true); |
779 |
> |
Thread t; |
780 |
> |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) { |
781 |
> |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
782 |
> |
if (status >= 0) { |
783 |
> |
if (w.unpushTask(this)) { |
784 |
> |
boolean completed; |
785 |
> |
try { |
786 |
> |
completed = exec(); |
787 |
> |
} catch (Throwable rex) { |
788 |
> |
setExceptionalCompletion(rex); |
789 |
> |
return; |
790 |
> |
} |
791 |
> |
if (completed) { |
792 |
> |
setCompletion(NORMAL); |
793 |
> |
return; |
794 |
> |
} |
795 |
> |
} |
796 |
> |
w.joinTask(this, false, 0L); |
797 |
> |
} |
798 |
|
} |
799 |
+ |
else |
800 |
+ |
externalAwaitDone(); |
801 |
|
} |
802 |
|
|
803 |
|
/** |
804 |
|
* Commences performing this task and awaits its completion if |
805 |
< |
* necessary, without returning its result or throwing an |
806 |
< |
* exception. This method may be useful when processing |
858 |
< |
* collections of tasks when some have been cancelled or otherwise |
859 |
< |
* known to have aborted. |
805 |
> |
* necessary, without returning its result or throwing its |
806 |
> |
* exception. |
807 |
|
*/ |
808 |
|
public final void quietlyInvoke() { |
809 |
< |
if (status >= 0 && !tryQuietlyInvoke()) |
810 |
< |
quietlyJoin(); |
809 |
> |
if (status >= 0) { |
810 |
> |
boolean completed; |
811 |
> |
try { |
812 |
> |
completed = exec(); |
813 |
> |
} catch (Throwable rex) { |
814 |
> |
setExceptionalCompletion(rex); |
815 |
> |
return; |
816 |
> |
} |
817 |
> |
if (completed) |
818 |
> |
setCompletion(NORMAL); |
819 |
> |
else |
820 |
> |
quietlyJoin(); |
821 |
> |
} |
822 |
|
} |
823 |
|
|
824 |
|
/** |
825 |
|
* Possibly executes tasks until the pool hosting the current task |
826 |
< |
* {@link ForkJoinPool#isQuiescent}. This method may be of use in |
827 |
< |
* designs in which many tasks are forked, but none are explicitly |
828 |
< |
* joined, instead executing them until all are processed. This |
829 |
< |
* method may be invoked only from within ForkJoinTask |
830 |
< |
* computations (as may be determined using method {@link |
831 |
< |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
832 |
< |
* in exceptions or errors, possibly including ClassCastException. |
826 |
> |
* {@link ForkJoinPool#isQuiescent is quiescent}. This method may |
827 |
> |
* be of use in designs in which many tasks are forked, but none |
828 |
> |
* are explicitly joined, instead executing them until all are |
829 |
> |
* processed. |
830 |
> |
* |
831 |
> |
* <p>This method may be invoked only from within {@code |
832 |
> |
* ForkJoinPool} computations (as may be determined using method |
833 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
834 |
> |
* result in exceptions or errors, possibly including {@code |
835 |
> |
* ClassCastException}. |
836 |
|
*/ |
837 |
|
public static void helpQuiesce() { |
838 |
|
((ForkJoinWorkerThread) Thread.currentThread()) |
848 |
|
* under any other usage conditions are not guaranteed. |
849 |
|
* This method may be useful when executing |
850 |
|
* pre-constructed trees of subtasks in loops. |
851 |
+ |
* |
852 |
+ |
* <p>Upon completion of this method, {@code isDone()} reports |
853 |
+ |
* {@code false}, and {@code getException()} reports {@code |
854 |
+ |
* null}. However, the value returned by {@code getRawResult} is |
855 |
+ |
* unaffected. To clear this value, you can invoke {@code |
856 |
+ |
* setRawResult(null)}. |
857 |
|
*/ |
858 |
|
public void reinitialize() { |
859 |
< |
if ((status & COMPLETION_MASK) == EXCEPTIONAL) |
859 |
> |
if (status == EXCEPTIONAL) |
860 |
|
exceptionMap.remove(this); |
861 |
|
status = 0; |
862 |
|
} |
891 |
|
* by the current thread, and has not commenced executing in |
892 |
|
* another thread. This method may be useful when arranging |
893 |
|
* alternative local processing of tasks that could have been, but |
894 |
< |
* were not, stolen. This method may be invoked only from within |
895 |
< |
* ForkJoinTask computations (as may be determined using method |
896 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
897 |
< |
* result in exceptions or errors, possibly including |
898 |
< |
* ClassCastException. |
894 |
> |
* were not, stolen. |
895 |
> |
* |
896 |
> |
* <p>This method may be invoked only from within {@code |
897 |
> |
* ForkJoinPool} computations (as may be determined using method |
898 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
899 |
> |
* result in exceptions or errors, possibly including {@code |
900 |
> |
* ClassCastException}. |
901 |
|
* |
902 |
|
* @return {@code true} if unforked |
903 |
|
*/ |
910 |
|
* Returns an estimate of the number of tasks that have been |
911 |
|
* forked by the current worker thread but not yet executed. This |
912 |
|
* value may be useful for heuristic decisions about whether to |
913 |
< |
* fork other tasks. This method may be invoked only from within |
914 |
< |
* ForkJoinTask computations (as may be determined using method |
915 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
916 |
< |
* result in exceptions or errors, possibly including |
917 |
< |
* ClassCastException. |
913 |
> |
* fork other tasks. |
914 |
> |
* |
915 |
> |
* <p>This method may be invoked only from within {@code |
916 |
> |
* ForkJoinPool} computations (as may be determined using method |
917 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
918 |
> |
* result in exceptions or errors, possibly including {@code |
919 |
> |
* ClassCastException}. |
920 |
> |
* |
921 |
|
* @return the number of tasks |
922 |
|
*/ |
923 |
|
public static int getQueuedTaskCount() { |
933 |
|
* usages of ForkJoinTasks, at steady state, each worker should |
934 |
|
* aim to maintain a small constant surplus (for example, 3) of |
935 |
|
* tasks, and to process computations locally if this threshold is |
936 |
< |
* exceeded. This method may be invoked only from within |
937 |
< |
* ForkJoinTask computations (as may be determined using method |
938 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
939 |
< |
* result in exceptions or errors, possibly including |
940 |
< |
* ClassCastException. |
936 |
> |
* exceeded. |
937 |
> |
* |
938 |
> |
* <p>This method may be invoked only from within {@code |
939 |
> |
* ForkJoinPool} computations (as may be determined using method |
940 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
941 |
> |
* result in exceptions or errors, possibly including {@code |
942 |
> |
* ClassCastException}. |
943 |
> |
* |
944 |
|
* @return the surplus number of tasks, which may be negative |
945 |
|
*/ |
946 |
|
public static int getSurplusQueuedTaskCount() { |
976 |
|
* called otherwise. The return value controls whether this task |
977 |
|
* is considered to be done normally. It may return false in |
978 |
|
* asynchronous actions that require explicit invocations of |
979 |
< |
* {@link #complete} to become joinable. It may throw exceptions |
980 |
< |
* to indicate abnormal exit. |
979 |
> |
* {@link #complete} to become joinable. It may also throw an |
980 |
> |
* (unchecked) exception to indicate abnormal exit. |
981 |
|
* |
982 |
|
* @return {@code true} if completed normally |
1008 |
– |
* @throws Error or RuntimeException if encountered during computation |
983 |
|
*/ |
984 |
|
protected abstract boolean exec(); |
985 |
|
|
991 |
|
* null even if a task exists but cannot be accessed without |
992 |
|
* contention with other threads. This method is designed |
993 |
|
* primarily to support extensions, and is unlikely to be useful |
994 |
< |
* otherwise. This method may be invoked only from within |
995 |
< |
* ForkJoinTask computations (as may be determined using method |
996 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
997 |
< |
* result in exceptions or errors, possibly including |
998 |
< |
* ClassCastException. |
994 |
> |
* otherwise. |
995 |
> |
* |
996 |
> |
* <p>This method may be invoked only from within {@code |
997 |
> |
* ForkJoinPool} computations (as may be determined using method |
998 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
999 |
> |
* result in exceptions or errors, possibly including {@code |
1000 |
> |
* ClassCastException}. |
1001 |
|
* |
1002 |
|
* @return the next task, or {@code null} if none are available |
1003 |
|
*/ |
1010 |
|
* Unschedules and returns, without executing, the next task |
1011 |
|
* queued by the current thread but not yet executed. This method |
1012 |
|
* is designed primarily to support extensions, and is unlikely to |
1013 |
< |
* be useful otherwise. This method may be invoked only from |
1014 |
< |
* within ForkJoinTask computations (as may be determined using |
1015 |
< |
* method {@link #inForkJoinPool}). Attempts to invoke in other |
1016 |
< |
* contexts result in exceptions or errors, possibly including |
1017 |
< |
* ClassCastException. |
1013 |
> |
* be useful otherwise. |
1014 |
> |
* |
1015 |
> |
* <p>This method may be invoked only from within {@code |
1016 |
> |
* ForkJoinPool} computations (as may be determined using method |
1017 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1018 |
> |
* result in exceptions or errors, possibly including {@code |
1019 |
> |
* ClassCastException}. |
1020 |
|
* |
1021 |
|
* @return the next task, or {@code null} if none are available |
1022 |
|
*/ |
1033 |
|
* {@code null} result does not necessarily imply quiescence |
1034 |
|
* of the pool this task is operating in. This method is designed |
1035 |
|
* primarily to support extensions, and is unlikely to be useful |
1036 |
< |
* otherwise. This method may be invoked only from within |
1037 |
< |
* ForkJoinTask computations (as may be determined using method |
1038 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1039 |
< |
* result in exceptions or errors, possibly including |
1040 |
< |
* ClassCastException. |
1036 |
> |
* otherwise. |
1037 |
> |
* |
1038 |
> |
* <p>This method may be invoked only from within {@code |
1039 |
> |
* ForkJoinPool} computations (as may be determined using method |
1040 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1041 |
> |
* result in exceptions or errors, possibly including {@code |
1042 |
> |
* ClassCastException}. |
1043 |
|
* |
1044 |
|
* @return a task, or {@code null} if none are available |
1045 |
|
*/ |
1104 |
|
} |
1105 |
|
|
1106 |
|
/** |
1107 |
< |
* Returns a new ForkJoinTask that performs the {@code run} |
1108 |
< |
* method of the given Runnable as its action, and returns a null |
1109 |
< |
* result upon {@code join}. |
1107 |
> |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1108 |
> |
* method of the given {@code Runnable} as its action, and returns |
1109 |
> |
* a null result upon {@link #join}. |
1110 |
|
* |
1111 |
|
* @param runnable the runnable action |
1112 |
|
* @return the task |
1116 |
|
} |
1117 |
|
|
1118 |
|
/** |
1119 |
< |
* Returns a new ForkJoinTask that performs the {@code run} |
1120 |
< |
* method of the given Runnable as its action, and returns the |
1121 |
< |
* given result upon {@code join}. |
1119 |
> |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1120 |
> |
* method of the given {@code Runnable} as its action, and returns |
1121 |
> |
* the given result upon {@link #join}. |
1122 |
|
* |
1123 |
|
* @param runnable the runnable action |
1124 |
|
* @param result the result upon completion |
1129 |
|
} |
1130 |
|
|
1131 |
|
/** |
1132 |
< |
* Returns a new ForkJoinTask that performs the {@code call} |
1133 |
< |
* method of the given Callable as its action, and returns its |
1134 |
< |
* result upon {@code join}, translating any checked |
1135 |
< |
* exceptions encountered into {@code RuntimeException}. |
1132 |
> |
* Returns a new {@code ForkJoinTask} that performs the {@code call} |
1133 |
> |
* method of the given {@code Callable} as its action, and returns |
1134 |
> |
* its result upon {@link #join}, translating any checked exceptions |
1135 |
> |
* encountered into {@code RuntimeException}. |
1136 |
|
* |
1137 |
|
* @param callable the callable action |
1138 |
|
* @return the task |
1146 |
|
private static final long serialVersionUID = -7721805057305804111L; |
1147 |
|
|
1148 |
|
/** |
1149 |
< |
* Save the state to a stream. |
1149 |
> |
* Saves the state to a stream (that is, serializes it). |
1150 |
|
* |
1151 |
|
* @serialData the current run status and the exception thrown |
1152 |
|
* during execution, or {@code null} if none |
1159 |
|
} |
1160 |
|
|
1161 |
|
/** |
1162 |
< |
* Reconstitute the instance from a stream. |
1162 |
> |
* Reconstitutes the instance from a stream (that is, deserializes it). |
1163 |
|
* |
1164 |
|
* @param s the stream |
1165 |
|
*/ |
1166 |
|
private void readObject(java.io.ObjectInputStream s) |
1167 |
|
throws java.io.IOException, ClassNotFoundException { |
1168 |
|
s.defaultReadObject(); |
1189 |
– |
status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts |
1190 |
– |
status |= EXTERNAL_SIGNAL; // conservatively set external signal |
1169 |
|
Object ex = s.readObject(); |
1170 |
|
if (ex != null) |
1171 |
< |
setDoneExceptionally((Throwable) ex); |
1171 |
> |
setExceptionalCompletion((Throwable) ex); |
1172 |
|
} |
1173 |
|
|
1174 |
|
// Unsafe mechanics |