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package jsr166y; |
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import java.util.concurrent.*; |
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|
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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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/** |
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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>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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/** |
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* Run control status bits packed into a single int to minimize |
148 |
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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 |
203 |
|
*/ |
204 |
< |
final void setCompletion(int completion) { |
205 |
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ForkJoinPool pool = getPool(); |
206 |
< |
if (pool != null) { |
207 |
< |
int s; // Clear signal bits while setting completion status |
208 |
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do {} while ((s = status) >= 0 && !casStatus(s, completion)); |
209 |
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|
210 |
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if ((s & SIGNAL_MASK) != 0) { |
207 |
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if ((s &= INTERNAL_SIGNAL_MASK) != 0) |
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< |
pool.updateRunningCount(s); |
209 |
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synchronized (this) { notifyAll(); } |
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> |
private void setCompletion(int completion) { |
205 |
> |
int s; |
206 |
> |
while ((s = status) >= 0) { |
207 |
> |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) { |
208 |
> |
if (s != 0) |
209 |
> |
synchronized (this) { notifyAll(); } |
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> |
break; |
211 |
|
} |
212 |
|
} |
212 |
– |
else |
213 |
– |
externallySetCompletion(completion); |
214 |
– |
} |
215 |
– |
|
216 |
– |
/** |
217 |
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* Version of setCompletion for non-FJ threads. Leaves signal |
218 |
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* bits for unblocked threads to adjust, and always notifies. |
219 |
– |
*/ |
220 |
– |
private void externallySetCompletion(int completion) { |
221 |
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int s; |
222 |
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do {} while ((s = status) >= 0 && |
223 |
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!casStatus(s, (s & SIGNAL_MASK) | completion)); |
224 |
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synchronized (this) { notifyAll(); } |
225 |
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} |
226 |
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|
227 |
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/** |
228 |
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* Sets status to indicate normal completion. |
229 |
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*/ |
230 |
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final void setNormalCompletion() { |
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// Try typical fast case -- single CAS, no signal, not already done. |
232 |
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// Manually expand casStatus to improve chances of inlining it |
233 |
– |
if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL)) |
234 |
– |
setCompletion(NORMAL); |
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} |
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|
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// internal waiting and notification |
238 |
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|
215 |
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/** |
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* Performs the actual monitor wait for awaitDone. |
216 |
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* Records exception and sets exceptional completion. |
217 |
> |
* |
218 |
> |
* @return status on exit |
219 |
|
*/ |
220 |
< |
private void doAwaitDone() { |
221 |
< |
// Minimize lock bias and in/de-flation effects by maximizing |
222 |
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// chances of waiting inside sync |
245 |
< |
try { |
246 |
< |
while (status >= 0) |
247 |
< |
synchronized (this) { if (status >= 0) wait(); } |
248 |
< |
} catch (InterruptedException ie) { |
249 |
< |
onInterruptedWait(); |
250 |
< |
} |
220 |
> |
private void setExceptionalCompletion(Throwable rex) { |
221 |
> |
exceptionMap.put(this, rex); |
222 |
> |
setCompletion(EXCEPTIONAL); |
223 |
|
} |
224 |
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|
225 |
|
/** |
226 |
< |
* Performs the actual timed monitor wait for awaitDone. |
226 |
> |
* Blocks a worker thread until completion. Called only by |
227 |
> |
* pool. Currently unused -- pool-based waits use timeout |
228 |
> |
* version below. |
229 |
|
*/ |
230 |
< |
private void doAwaitDone(long startTime, long nanos) { |
231 |
< |
synchronized (this) { |
230 |
> |
final void internalAwaitDone() { |
231 |
> |
int s; // the odd construction reduces lock bias effects |
232 |
> |
while ((s = status) >= 0) { |
233 |
|
try { |
234 |
< |
while (status >= 0) { |
235 |
< |
long nt = nanos - (System.nanoTime() - startTime); |
236 |
< |
if (nt <= 0) |
262 |
< |
break; |
263 |
< |
wait(nt / 1000000, (int) (nt % 1000000)); |
234 |
> |
synchronized (this) { |
235 |
> |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL)) |
236 |
> |
wait(); |
237 |
|
} |
238 |
|
} catch (InterruptedException ie) { |
239 |
< |
onInterruptedWait(); |
239 |
> |
cancelIfTerminating(); |
240 |
|
} |
241 |
|
} |
242 |
|
} |
243 |
|
|
271 |
– |
// Awaiting completion |
272 |
– |
|
244 |
|
/** |
245 |
< |
* Sets status to indicate there is joiner, then waits for join, |
246 |
< |
* surrounded with pool notifications. |
245 |
> |
* Blocks a worker thread until completed or timed out. Called |
246 |
> |
* only by pool. |
247 |
|
* |
248 |
< |
* @return status upon exit |
248 |
> |
* @return status on exit |
249 |
|
*/ |
250 |
< |
private int awaitDone(ForkJoinWorkerThread w, |
280 |
< |
boolean maintainParallelism) { |
281 |
< |
ForkJoinPool pool = (w == null) ? null : w.pool; |
250 |
> |
final int internalAwaitDone(long millis, int nanos) { |
251 |
|
int s; |
252 |
< |
while ((s = status) >= 0) { |
253 |
< |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
254 |
< |
if (pool == null || !pool.preJoin(this, maintainParallelism)) |
255 |
< |
doAwaitDone(); |
256 |
< |
if (((s = status) & INTERNAL_SIGNAL_MASK) != 0) |
288 |
< |
adjustPoolCountsOnUnblock(pool); |
289 |
< |
break; |
290 |
< |
} |
291 |
< |
} |
292 |
< |
return s; |
293 |
< |
} |
294 |
< |
|
295 |
< |
/** |
296 |
< |
* 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; |
252 |
> |
if ((s = status) >= 0) { |
253 |
> |
try { |
254 |
> |
synchronized (this) { |
255 |
> |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL)) |
256 |
> |
wait(millis, nanos); |
257 |
|
} |
258 |
< |
if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0) |
259 |
< |
adjustPoolCountsOnUnblock(pool); |
314 |
< |
break; |
258 |
> |
} catch (InterruptedException ie) { |
259 |
> |
cancelIfTerminating(); |
260 |
|
} |
261 |
+ |
s = status; |
262 |
|
} |
263 |
|
return s; |
264 |
|
} |
265 |
|
|
266 |
|
/** |
267 |
< |
* Notifies pool that thread is unblocked. Called by signalled |
322 |
< |
* threads when woken by non-FJ threads (which is atypical). |
267 |
> |
* Blocks a non-worker-thread until completion. |
268 |
|
*/ |
269 |
< |
private void adjustPoolCountsOnUnblock(ForkJoinPool pool) { |
269 |
> |
private void externalAwaitDone() { |
270 |
|
int s; |
271 |
< |
do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK)); |
272 |
< |
if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0) |
273 |
< |
pool.updateRunningCount(s); |
274 |
< |
} |
275 |
< |
|
276 |
< |
/** |
277 |
< |
* Notifies pool to adjust counts on cancelled or timed out wait. |
278 |
< |
*/ |
279 |
< |
private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) { |
280 |
< |
if (pool != null) { |
281 |
< |
int s; |
282 |
< |
while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) { |
283 |
< |
if (casStatus(s, s - 1)) { |
339 |
< |
pool.updateRunningCount(1); |
271 |
> |
while ((s = status) >= 0) { |
272 |
> |
synchronized (this) { |
273 |
> |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) { |
274 |
> |
boolean interrupted = false; |
275 |
> |
while (status >= 0) { |
276 |
> |
try { |
277 |
> |
wait(); |
278 |
> |
} catch (InterruptedException ie) { |
279 |
> |
interrupted = true; |
280 |
> |
} |
281 |
> |
} |
282 |
> |
if (interrupted) |
283 |
> |
Thread.currentThread().interrupt(); |
284 |
|
break; |
285 |
|
} |
286 |
|
} |
288 |
|
} |
289 |
|
|
290 |
|
/** |
291 |
< |
* Handles interruptions during waits. |
292 |
< |
*/ |
293 |
< |
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. |
291 |
> |
* Unless done, calls exec and records status if completed, but |
292 |
> |
* doesn't wait for completion otherwise. Primary execution method |
293 |
> |
* for ForkJoinWorkerThread. |
294 |
|
*/ |
295 |
|
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() { |
296 |
|
try { |
297 |
< |
if (!exec()) |
298 |
< |
return false; |
297 |
> |
if (status < 0 || !exec()) |
298 |
> |
return; |
299 |
|
} catch (Throwable rex) { |
300 |
< |
setDoneExceptionally(rex); |
301 |
< |
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) { |
300 |
> |
setExceptionalCompletion(rex); |
301 |
> |
return; |
302 |
|
} |
303 |
< |
} |
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 |
303 |
> |
setCompletion(NORMAL); // must be outside try block |
304 |
|
} |
305 |
|
|
306 |
|
// public methods |
308 |
|
/** |
309 |
|
* Arranges to asynchronously execute this task. While it is not |
310 |
|
* necessarily enforced, it is a usage error to fork a task more |
311 |
< |
* than once unless it has completed and been reinitialized. This |
312 |
< |
* method may be invoked only from within ForkJoinTask |
313 |
< |
* computations (as may be determined using method {@link |
314 |
< |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
315 |
< |
* in exceptions or errors, possibly including ClassCastException. |
311 |
> |
* than once unless it has completed and been reinitialized. |
312 |
> |
* Subsequent modifications to the state of this task or any data |
313 |
> |
* it operates on are not necessarily consistently observable by |
314 |
> |
* any thread other than the one executing it unless preceded by a |
315 |
> |
* call to {@link #join} or related methods, or a call to {@link |
316 |
> |
* #isDone} returning {@code true}. |
317 |
> |
* |
318 |
> |
* <p>This method may be invoked only from within {@code |
319 |
> |
* ForkJoinTask} computations (as may be determined using method |
320 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
321 |
> |
* result in exceptions or errors, possibly including {@code |
322 |
> |
* ClassCastException}. |
323 |
|
* |
324 |
< |
* @return {@code this}, to simplify usage. |
324 |
> |
* @return {@code this}, to simplify usage |
325 |
|
*/ |
326 |
|
public final ForkJoinTask<V> fork() { |
327 |
|
((ForkJoinWorkerThread) Thread.currentThread()) |
330 |
|
} |
331 |
|
|
332 |
|
/** |
333 |
< |
* Returns the result of the computation when it is ready. |
334 |
< |
* This method differs from {@code get} in that abnormal |
335 |
< |
* completion results in RuntimeExceptions or Errors, not |
336 |
< |
* ExecutionExceptions. |
333 |
> |
* Returns the result of the computation when it {@link #isDone is done}. |
334 |
> |
* This method differs from {@link #get()} in that |
335 |
> |
* abnormal completion results in {@code RuntimeException} or |
336 |
> |
* {@code Error}, not {@code ExecutionException}. |
337 |
|
* |
338 |
|
* @return the computed result |
339 |
|
*/ |
340 |
|
public final V join() { |
341 |
< |
ForkJoinWorkerThread w = getWorker(); |
342 |
< |
if (w == null || status < 0 || !w.unpushTask(this) || !tryExec()) |
343 |
< |
reportException(awaitDone(w, true)); |
341 |
> |
quietlyJoin(); |
342 |
> |
Throwable ex; |
343 |
> |
if (status < NORMAL && (ex = getException()) != null) |
344 |
> |
UNSAFE.throwException(ex); |
345 |
|
return getRawResult(); |
346 |
|
} |
347 |
|
|
348 |
|
/** |
349 |
|
* Commences performing this task, awaits its completion if |
350 |
< |
* necessary, and return its result. |
350 |
> |
* necessary, and returns its result, or throws an (unchecked) |
351 |
> |
* {@code RuntimeException} or {@code Error} if the underlying |
352 |
> |
* computation did so. |
353 |
|
* |
532 |
– |
* @throws Throwable (a RuntimeException, Error, or unchecked |
533 |
– |
* exception) if the underlying computation did so |
354 |
|
* @return the computed result |
355 |
|
*/ |
356 |
|
public final V invoke() { |
357 |
< |
if (status >= 0 && tryExec()) |
358 |
< |
return getRawResult(); |
359 |
< |
else |
360 |
< |
return join(); |
357 |
> |
quietlyInvoke(); |
358 |
> |
Throwable ex; |
359 |
> |
if (status < NORMAL && (ex = getException()) != null) |
360 |
> |
UNSAFE.throwException(ex); |
361 |
> |
return getRawResult(); |
362 |
|
} |
363 |
|
|
364 |
|
/** |
365 |
|
* Forks the given tasks, returning when {@code isDone} holds for |
366 |
< |
* each task or an exception is encountered. This method may be |
367 |
< |
* invoked only from within ForkJoinTask computations (as may be |
368 |
< |
* determined using method {@link #inForkJoinPool}). Attempts to |
369 |
< |
* invoke in other contexts result in exceptions or errors, |
370 |
< |
* possibly including ClassCastException. |
366 |
> |
* each task or an (unchecked) exception is encountered, in which |
367 |
> |
* case the exception is rethrown. If more than one task |
368 |
> |
* encounters an exception, then this method throws any one of |
369 |
> |
* these exceptions. If any task encounters an exception, the |
370 |
> |
* other may be cancelled. However, the execution status of |
371 |
> |
* individual tasks is not guaranteed upon exceptional return. The |
372 |
> |
* status of each task may be obtained using {@link |
373 |
> |
* #getException()} and related methods to check if they have been |
374 |
> |
* cancelled, completed normally or exceptionally, or left |
375 |
> |
* unprocessed. |
376 |
> |
* |
377 |
> |
* <p>This method may be invoked only from within {@code |
378 |
> |
* ForkJoinTask} computations (as may be determined using method |
379 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
380 |
> |
* result in exceptions or errors, possibly including {@code |
381 |
> |
* ClassCastException}. |
382 |
|
* |
383 |
|
* @param t1 the first task |
384 |
|
* @param t2 the second task |
385 |
|
* @throws NullPointerException if any task is null |
554 |
– |
* @throws RuntimeException or Error if a task did so |
386 |
|
*/ |
387 |
< |
public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) { |
387 |
> |
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) { |
388 |
|
t2.fork(); |
389 |
|
t1.invoke(); |
390 |
|
t2.join(); |
392 |
|
|
393 |
|
/** |
394 |
|
* Forks the given tasks, returning when {@code isDone} holds for |
395 |
< |
* each task or an exception is encountered. If any task |
396 |
< |
* encounters an exception, others may be, but are not guaranteed |
397 |
< |
* to be, cancelled. This method may be invoked only from within |
398 |
< |
* ForkJoinTask computations (as may be determined using method |
399 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
400 |
< |
* result in exceptions or errors, possibly including |
401 |
< |
* ClassCastException. |
402 |
< |
* |
403 |
< |
* Overloadings of this method exist for the special cases |
404 |
< |
* of one to four arguments. |
395 |
> |
* each task or an (unchecked) exception is encountered, in which |
396 |
> |
* case the exception is rethrown. If more than one task |
397 |
> |
* encounters an exception, then this method throws any one of |
398 |
> |
* these exceptions. If any task encounters an exception, others |
399 |
> |
* may be cancelled. However, the execution status of individual |
400 |
> |
* tasks is not guaranteed upon exceptional return. The status of |
401 |
> |
* each task may be obtained using {@link #getException()} and |
402 |
> |
* related methods to check if they have been cancelled, completed |
403 |
> |
* normally or exceptionally, or left unprocessed. |
404 |
> |
* |
405 |
> |
* <p>This method may be invoked only from within {@code |
406 |
> |
* ForkJoinTask} computations (as may be determined using method |
407 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
408 |
> |
* result in exceptions or errors, possibly including {@code |
409 |
> |
* ClassCastException}. |
410 |
|
* |
411 |
|
* @param tasks the tasks |
412 |
< |
* @throws NullPointerException if tasks or any element are null |
577 |
< |
* @throws RuntimeException or Error if any task did so |
412 |
> |
* @throws NullPointerException if any task is null |
413 |
|
*/ |
414 |
|
public static void invokeAll(ForkJoinTask<?>... tasks) { |
415 |
|
Throwable ex = null; |
424 |
|
t.fork(); |
425 |
|
else { |
426 |
|
t.quietlyInvoke(); |
427 |
< |
if (ex == null) |
427 |
> |
if (ex == null && t.status < NORMAL) |
428 |
|
ex = t.getException(); |
429 |
|
} |
430 |
|
} |
435 |
|
t.cancel(false); |
436 |
|
else { |
437 |
|
t.quietlyJoin(); |
438 |
< |
if (ex == null) |
438 |
> |
if (ex == null && t.status < NORMAL) |
439 |
|
ex = t.getException(); |
440 |
|
} |
441 |
|
} |
442 |
|
} |
443 |
|
if (ex != null) |
444 |
< |
rethrowException(ex); |
444 |
> |
UNSAFE.throwException(ex); |
445 |
|
} |
446 |
|
|
447 |
|
/** |
448 |
< |
* Forks all tasks in the collection, returning when {@code |
449 |
< |
* isDone} holds for each task or an exception is encountered. If |
450 |
< |
* any task encounters an exception, others may be, but are not |
451 |
< |
* guaranteed to be, cancelled. This method may be invoked only |
452 |
< |
* from within ForkJoinTask computations (as may be determined |
453 |
< |
* using method {@link #inForkJoinPool}). Attempts to invoke in |
454 |
< |
* other contexts result in exceptions or errors, possibly |
455 |
< |
* including ClassCastException. |
448 |
> |
* Forks all tasks in the specified collection, returning when |
449 |
> |
* {@code isDone} holds for each task or an (unchecked) exception |
450 |
> |
* is encountered, in which case the exception is rethrown. If |
451 |
> |
* more than one task encounters an exception, then this method |
452 |
> |
* throws any one of these exceptions. If any task encounters an |
453 |
> |
* exception, others may be cancelled. However, the execution |
454 |
> |
* status of individual tasks is not guaranteed upon exceptional |
455 |
> |
* return. The status of each task may be obtained using {@link |
456 |
> |
* #getException()} and related methods to check if they have been |
457 |
> |
* cancelled, completed normally or exceptionally, or left |
458 |
> |
* unprocessed. |
459 |
> |
* |
460 |
> |
* <p>This method may be invoked only from within {@code |
461 |
> |
* ForkJoinTask} computations (as may be determined using method |
462 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
463 |
> |
* result in exceptions or errors, possibly including {@code |
464 |
> |
* ClassCastException}. |
465 |
|
* |
466 |
|
* @param tasks the collection of tasks |
467 |
|
* @return the tasks argument, to simplify usage |
468 |
|
* @throws NullPointerException if tasks or any element are null |
625 |
– |
* @throws RuntimeException or Error if any task did so |
469 |
|
*/ |
470 |
|
public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) { |
471 |
< |
if (!(tasks instanceof List<?>)) { |
471 |
> |
if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) { |
472 |
|
invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()])); |
473 |
|
return tasks; |
474 |
|
} |
487 |
|
t.fork(); |
488 |
|
else { |
489 |
|
t.quietlyInvoke(); |
490 |
< |
if (ex == null) |
490 |
> |
if (ex == null && t.status < NORMAL) |
491 |
|
ex = t.getException(); |
492 |
|
} |
493 |
|
} |
498 |
|
t.cancel(false); |
499 |
|
else { |
500 |
|
t.quietlyJoin(); |
501 |
< |
if (ex == null) |
501 |
> |
if (ex == null && t.status < NORMAL) |
502 |
|
ex = t.getException(); |
503 |
|
} |
504 |
|
} |
505 |
|
} |
506 |
|
if (ex != null) |
507 |
< |
rethrowException(ex); |
507 |
> |
UNSAFE.throwException(ex); |
508 |
|
return tasks; |
509 |
|
} |
510 |
|
|
511 |
|
/** |
512 |
< |
* Returns {@code true} if the computation performed by this task |
513 |
< |
* has completed (or has been cancelled). |
514 |
< |
* |
515 |
< |
* @return {@code true} if this computation has completed |
516 |
< |
*/ |
517 |
< |
public final boolean isDone() { |
518 |
< |
return status < 0; |
676 |
< |
} |
677 |
< |
|
678 |
< |
/** |
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. |
512 |
> |
* Attempts to cancel execution of this task. This attempt will |
513 |
> |
* fail if the task has already completed, has already been |
514 |
> |
* cancelled, or could not be cancelled for some other reason. If |
515 |
> |
* successful, and this task has not started when cancel is |
516 |
> |
* called, execution of this task is suppressed, {@link |
517 |
> |
* #isCancelled} will report true, and {@link #join} will result |
518 |
> |
* in a {@code CancellationException} being thrown. |
519 |
|
* |
520 |
|
* <p>This method may be overridden in subclasses, but if so, must |
521 |
|
* still ensure that these minimal properties hold. In particular, |
527 |
|
* invoke {@link #completeExceptionally}. |
528 |
|
* |
529 |
|
* @param mayInterruptIfRunning this value is ignored in the |
530 |
< |
* default implementation because tasks are not in general |
530 |
> |
* default implementation because tasks are not |
531 |
|
* cancelled via interruption |
532 |
|
* |
533 |
|
* @return {@code true} if this task is now cancelled |
534 |
|
*/ |
535 |
|
public boolean cancel(boolean mayInterruptIfRunning) { |
536 |
|
setCompletion(CANCELLED); |
537 |
< |
return (status & COMPLETION_MASK) == CANCELLED; |
537 |
> |
return status == CANCELLED; |
538 |
> |
} |
539 |
> |
|
540 |
> |
/** |
541 |
> |
* Cancels, ignoring any exceptions thrown by cancel. Used during |
542 |
> |
* worker and pool shutdown. Cancel is spec'ed not to throw any |
543 |
> |
* exceptions, but if it does anyway, we have no recourse during |
544 |
> |
* shutdown, so guard against this case. |
545 |
> |
*/ |
546 |
> |
final void cancelIgnoringExceptions() { |
547 |
> |
try { |
548 |
> |
cancel(false); |
549 |
> |
} catch (Throwable ignore) { |
550 |
> |
} |
551 |
> |
} |
552 |
> |
|
553 |
> |
/** |
554 |
> |
* Cancels if current thread is a terminating worker thread, |
555 |
> |
* ignoring any exceptions thrown by cancel. |
556 |
> |
*/ |
557 |
> |
final void cancelIfTerminating() { |
558 |
> |
Thread t = Thread.currentThread(); |
559 |
> |
if ((t instanceof ForkJoinWorkerThread) && |
560 |
> |
((ForkJoinWorkerThread) t).isTerminating()) { |
561 |
> |
try { |
562 |
> |
cancel(false); |
563 |
> |
} catch (Throwable ignore) { |
564 |
> |
} |
565 |
> |
} |
566 |
> |
} |
567 |
> |
|
568 |
> |
public final boolean isDone() { |
569 |
> |
return status < 0; |
570 |
> |
} |
571 |
> |
|
572 |
> |
public final boolean isCancelled() { |
573 |
> |
return status == CANCELLED; |
574 |
|
} |
575 |
|
|
576 |
|
/** |
579 |
|
* @return {@code true} if this task threw an exception or was cancelled |
580 |
|
*/ |
581 |
|
public final boolean isCompletedAbnormally() { |
582 |
< |
return (status & COMPLETION_MASK) < NORMAL; |
582 |
> |
return status < NORMAL; |
583 |
> |
} |
584 |
> |
|
585 |
> |
/** |
586 |
> |
* Returns {@code true} if this task completed without throwing an |
587 |
> |
* exception and was not cancelled. |
588 |
> |
* |
589 |
> |
* @return {@code true} if this task completed without throwing an |
590 |
> |
* exception and was not cancelled |
591 |
> |
*/ |
592 |
> |
public final boolean isCompletedNormally() { |
593 |
> |
return status == NORMAL; |
594 |
|
} |
595 |
|
|
596 |
|
/** |
601 |
|
* @return the exception, or {@code null} if none |
602 |
|
*/ |
603 |
|
public final Throwable getException() { |
604 |
< |
int s = status & COMPLETION_MASK; |
605 |
< |
if (s >= NORMAL) |
606 |
< |
return null; |
607 |
< |
if (s == CANCELLED) |
740 |
< |
return new CancellationException(); |
741 |
< |
return exceptionMap.get(this); |
604 |
> |
int s = status; |
605 |
> |
return ((s >= NORMAL) ? null : |
606 |
> |
(s == CANCELLED) ? new CancellationException() : |
607 |
> |
exceptionMap.get(this)); |
608 |
|
} |
609 |
|
|
610 |
|
/** |
617 |
|
* overridable, but overridden versions must invoke {@code super} |
618 |
|
* implementation to maintain guarantees. |
619 |
|
* |
620 |
< |
* @param ex the exception to throw. If this exception is |
621 |
< |
* not a RuntimeException or Error, the actual exception thrown |
622 |
< |
* will be a RuntimeException with cause ex. |
620 |
> |
* @param ex the exception to throw. If this exception is not a |
621 |
> |
* {@code RuntimeException} or {@code Error}, the actual exception |
622 |
> |
* thrown will be a {@code RuntimeException} with cause {@code ex}. |
623 |
|
*/ |
624 |
|
public void completeExceptionally(Throwable ex) { |
625 |
< |
setDoneExceptionally((ex instanceof RuntimeException) || |
626 |
< |
(ex instanceof Error) ? ex : |
627 |
< |
new RuntimeException(ex)); |
625 |
> |
setExceptionalCompletion((ex instanceof RuntimeException) || |
626 |
> |
(ex instanceof Error) ? ex : |
627 |
> |
new RuntimeException(ex)); |
628 |
|
} |
629 |
|
|
630 |
|
/** |
631 |
|
* Completes this task, and if not already aborted or cancelled, |
632 |
< |
* returning a {@code null} result upon {@code join} and related |
633 |
< |
* operations. This method may be used to provide results for |
634 |
< |
* asynchronous tasks, or to provide alternative handling for |
635 |
< |
* tasks that would not otherwise complete normally. Its use in |
636 |
< |
* other situations is discouraged. This method is |
637 |
< |
* overridable, but overridden versions must invoke {@code super} |
638 |
< |
* implementation to maintain guarantees. |
632 |
> |
* returning the given value as the result of subsequent |
633 |
> |
* invocations of {@code join} and related operations. This method |
634 |
> |
* may be used to provide results for asynchronous tasks, or to |
635 |
> |
* provide alternative handling for tasks that would not otherwise |
636 |
> |
* complete normally. Its use in other situations is |
637 |
> |
* discouraged. This method is overridable, but overridden |
638 |
> |
* versions must invoke {@code super} implementation to maintain |
639 |
> |
* guarantees. |
640 |
|
* |
641 |
|
* @param value the result value for this task |
642 |
|
*/ |
644 |
|
try { |
645 |
|
setRawResult(value); |
646 |
|
} catch (Throwable rex) { |
647 |
< |
setDoneExceptionally(rex); |
647 |
> |
setExceptionalCompletion(rex); |
648 |
|
return; |
649 |
|
} |
650 |
< |
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(); |
650 |
> |
setCompletion(NORMAL); |
651 |
|
} |
652 |
|
|
653 |
|
/** |
654 |
< |
* Possibly executes other tasks until this task is ready, then |
655 |
< |
* 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. |
654 |
> |
* Waits if necessary for the computation to complete, and then |
655 |
> |
* retrieves its result. |
656 |
|
* |
657 |
|
* @return the computed result |
658 |
+ |
* @throws CancellationException if the computation was cancelled |
659 |
+ |
* @throws ExecutionException if the computation threw an |
660 |
+ |
* exception |
661 |
+ |
* @throws InterruptedException if the current thread is not a |
662 |
+ |
* member of a ForkJoinPool and was interrupted while waiting |
663 |
|
*/ |
664 |
< |
public final V helpJoin() { |
665 |
< |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread(); |
666 |
< |
if (status < 0 || !w.unpushTask(this) || !tryExec()) |
667 |
< |
reportException(busyJoin(w)); |
664 |
> |
public final V get() throws InterruptedException, ExecutionException { |
665 |
> |
int s; |
666 |
> |
if (Thread.currentThread() instanceof ForkJoinWorkerThread) { |
667 |
> |
quietlyJoin(); |
668 |
> |
s = status; |
669 |
> |
} |
670 |
> |
else { |
671 |
> |
while ((s = status) >= 0) { |
672 |
> |
synchronized (this) { // interruptible form of awaitDone |
673 |
> |
if (UNSAFE.compareAndSwapInt(this, statusOffset, |
674 |
> |
s, SIGNAL)) { |
675 |
> |
while (status >= 0) |
676 |
> |
wait(); |
677 |
> |
} |
678 |
> |
} |
679 |
> |
} |
680 |
> |
} |
681 |
> |
if (s < NORMAL) { |
682 |
> |
Throwable ex; |
683 |
> |
if (s == CANCELLED) |
684 |
> |
throw new CancellationException(); |
685 |
> |
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
686 |
> |
throw new ExecutionException(ex); |
687 |
> |
} |
688 |
|
return getRawResult(); |
689 |
|
} |
690 |
|
|
691 |
|
/** |
692 |
< |
* Possibly executes other tasks until this task is ready. This |
693 |
< |
* method may be invoked only from within ForkJoinTask |
694 |
< |
* computations (as may be determined using method {@link |
695 |
< |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
696 |
< |
* in exceptions or errors, possibly including ClassCastException. |
692 |
> |
* Waits if necessary for at most the given time for the computation |
693 |
> |
* to complete, and then retrieves its result, if available. |
694 |
> |
* |
695 |
> |
* @param timeout the maximum time to wait |
696 |
> |
* @param unit the time unit of the timeout argument |
697 |
> |
* @return the computed result |
698 |
> |
* @throws CancellationException if the computation was cancelled |
699 |
> |
* @throws ExecutionException if the computation threw an |
700 |
> |
* exception |
701 |
> |
* @throws InterruptedException if the current thread is not a |
702 |
> |
* member of a ForkJoinPool and was interrupted while waiting |
703 |
> |
* @throws TimeoutException if the wait timed out |
704 |
|
*/ |
705 |
< |
public final void quietlyHelpJoin() { |
705 |
> |
public final V get(long timeout, TimeUnit unit) |
706 |
> |
throws InterruptedException, ExecutionException, TimeoutException { |
707 |
> |
long nanos = unit.toNanos(timeout); |
708 |
|
if (status >= 0) { |
709 |
< |
ForkJoinWorkerThread w = |
710 |
< |
(ForkJoinWorkerThread) Thread.currentThread(); |
711 |
< |
if (!w.unpushTask(this) || !tryQuietlyInvoke()) |
712 |
< |
busyJoin(w); |
709 |
> |
Thread t = Thread.currentThread(); |
710 |
> |
if (t instanceof ForkJoinWorkerThread) { |
711 |
> |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
712 |
> |
boolean completed = false; // timed variant of quietlyJoin |
713 |
> |
if (w.unpushTask(this)) { |
714 |
> |
try { |
715 |
> |
completed = exec(); |
716 |
> |
} catch (Throwable rex) { |
717 |
> |
setExceptionalCompletion(rex); |
718 |
> |
} |
719 |
> |
} |
720 |
> |
if (completed) |
721 |
> |
setCompletion(NORMAL); |
722 |
> |
else if (status >= 0) |
723 |
> |
w.joinTask(this, true, nanos); |
724 |
> |
} |
725 |
> |
else if (Thread.interrupted()) |
726 |
> |
throw new InterruptedException(); |
727 |
> |
else { |
728 |
> |
long startTime = System.nanoTime(); |
729 |
> |
int s; long nt; |
730 |
> |
while ((s = status) >= 0 && |
731 |
> |
(nt = nanos - (System.nanoTime() - startTime)) > 0) { |
732 |
> |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, |
733 |
> |
SIGNAL)) { |
734 |
> |
long ms = nt / 1000000; |
735 |
> |
int ns = (int) (nt % 1000000); |
736 |
> |
synchronized (this) { |
737 |
> |
if (status >= 0) |
738 |
> |
wait(ms, ns); // exit on IE throw |
739 |
> |
} |
740 |
> |
} |
741 |
> |
} |
742 |
> |
} |
743 |
> |
} |
744 |
> |
int es = status; |
745 |
> |
if (es != NORMAL) { |
746 |
> |
Throwable ex; |
747 |
> |
if (es == CANCELLED) |
748 |
> |
throw new CancellationException(); |
749 |
> |
if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
750 |
> |
throw new ExecutionException(ex); |
751 |
> |
throw new TimeoutException(); |
752 |
|
} |
753 |
+ |
return getRawResult(); |
754 |
|
} |
755 |
|
|
756 |
|
/** |
757 |
< |
* Joins this task, without returning its result or throwing an |
757 |
> |
* Joins this task, without returning its result or throwing its |
758 |
|
* exception. This method may be useful when processing |
759 |
|
* collections of tasks when some have been cancelled or otherwise |
760 |
|
* known to have aborted. |
761 |
|
*/ |
762 |
|
public final void quietlyJoin() { |
763 |
< |
if (status >= 0) { |
764 |
< |
ForkJoinWorkerThread w = getWorker(); |
765 |
< |
if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke()) |
766 |
< |
awaitDone(w, true); |
763 |
> |
Thread t; |
764 |
> |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) { |
765 |
> |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
766 |
> |
if (status >= 0) { |
767 |
> |
if (w.unpushTask(this)) { |
768 |
> |
boolean completed; |
769 |
> |
try { |
770 |
> |
completed = exec(); |
771 |
> |
} catch (Throwable rex) { |
772 |
> |
setExceptionalCompletion(rex); |
773 |
> |
return; |
774 |
> |
} |
775 |
> |
if (completed) { |
776 |
> |
setCompletion(NORMAL); |
777 |
> |
return; |
778 |
> |
} |
779 |
> |
} |
780 |
> |
w.joinTask(this, false, 0L); |
781 |
> |
} |
782 |
|
} |
783 |
+ |
else |
784 |
+ |
externalAwaitDone(); |
785 |
|
} |
786 |
|
|
787 |
|
/** |
788 |
|
* Commences performing this task and awaits its completion if |
789 |
< |
* necessary, without returning its result or throwing an |
790 |
< |
* exception. This method may be useful when processing |
858 |
< |
* collections of tasks when some have been cancelled or otherwise |
859 |
< |
* known to have aborted. |
789 |
> |
* necessary, without returning its result or throwing its |
790 |
> |
* exception. |
791 |
|
*/ |
792 |
|
public final void quietlyInvoke() { |
793 |
< |
if (status >= 0 && !tryQuietlyInvoke()) |
794 |
< |
quietlyJoin(); |
793 |
> |
if (status >= 0) { |
794 |
> |
boolean completed; |
795 |
> |
try { |
796 |
> |
completed = exec(); |
797 |
> |
} catch (Throwable rex) { |
798 |
> |
setExceptionalCompletion(rex); |
799 |
> |
return; |
800 |
> |
} |
801 |
> |
if (completed) |
802 |
> |
setCompletion(NORMAL); |
803 |
> |
else |
804 |
> |
quietlyJoin(); |
805 |
> |
} |
806 |
|
} |
807 |
|
|
808 |
|
/** |
809 |
|
* Possibly executes tasks until the pool hosting the current task |
810 |
< |
* {@link ForkJoinPool#isQuiescent}. This method may be of use in |
811 |
< |
* designs in which many tasks are forked, but none are explicitly |
812 |
< |
* joined, instead executing them until all are processed. This |
813 |
< |
* method may be invoked only from within ForkJoinTask |
814 |
< |
* computations (as may be determined using method {@link |
815 |
< |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
816 |
< |
* in exceptions or errors, possibly including ClassCastException. |
810 |
> |
* {@link ForkJoinPool#isQuiescent is quiescent}. This method may |
811 |
> |
* be of use in designs in which many tasks are forked, but none |
812 |
> |
* are explicitly joined, instead executing them until all are |
813 |
> |
* processed. |
814 |
> |
* |
815 |
> |
* <p>This method may be invoked only from within {@code |
816 |
> |
* ForkJoinTask} computations (as may be determined using method |
817 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
818 |
> |
* result in exceptions or errors, possibly including {@code |
819 |
> |
* ClassCastException}. |
820 |
|
*/ |
821 |
|
public static void helpQuiesce() { |
822 |
|
((ForkJoinWorkerThread) Thread.currentThread()) |
832 |
|
* under any other usage conditions are not guaranteed. |
833 |
|
* This method may be useful when executing |
834 |
|
* pre-constructed trees of subtasks in loops. |
835 |
+ |
* |
836 |
+ |
* <p>Upon completion of this method, {@code isDone()} reports |
837 |
+ |
* {@code false}, and {@code getException()} reports {@code |
838 |
+ |
* null}. However, the value returned by {@code getRawResult} is |
839 |
+ |
* unaffected. To clear this value, you can invoke {@code |
840 |
+ |
* setRawResult(null)}. |
841 |
|
*/ |
842 |
|
public void reinitialize() { |
843 |
< |
if ((status & COMPLETION_MASK) == EXCEPTIONAL) |
843 |
> |
if (status == EXCEPTIONAL) |
844 |
|
exceptionMap.remove(this); |
845 |
|
status = 0; |
846 |
|
} |
875 |
|
* by the current thread, and has not commenced executing in |
876 |
|
* another thread. This method may be useful when arranging |
877 |
|
* alternative local processing of tasks that could have been, but |
878 |
< |
* were not, stolen. This method may be invoked only from within |
879 |
< |
* ForkJoinTask computations (as may be determined using method |
880 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
881 |
< |
* result in exceptions or errors, possibly including |
882 |
< |
* ClassCastException. |
878 |
> |
* were not, stolen. |
879 |
> |
* |
880 |
> |
* <p>This method may be invoked only from within {@code |
881 |
> |
* ForkJoinTask} computations (as may be determined using method |
882 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
883 |
> |
* result in exceptions or errors, possibly including {@code |
884 |
> |
* ClassCastException}. |
885 |
|
* |
886 |
|
* @return {@code true} if unforked |
887 |
|
*/ |
894 |
|
* Returns an estimate of the number of tasks that have been |
895 |
|
* forked by the current worker thread but not yet executed. This |
896 |
|
* value may be useful for heuristic decisions about whether to |
897 |
< |
* fork other tasks. This method may be invoked only from within |
898 |
< |
* ForkJoinTask computations (as may be determined using method |
899 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
900 |
< |
* result in exceptions or errors, possibly including |
901 |
< |
* ClassCastException. |
897 |
> |
* fork other tasks. |
898 |
> |
* |
899 |
> |
* <p>This method may be invoked only from within {@code |
900 |
> |
* ForkJoinTask} computations (as may be determined using method |
901 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
902 |
> |
* result in exceptions or errors, possibly including {@code |
903 |
> |
* ClassCastException}. |
904 |
> |
* |
905 |
|
* @return the number of tasks |
906 |
|
*/ |
907 |
|
public static int getQueuedTaskCount() { |
917 |
|
* usages of ForkJoinTasks, at steady state, each worker should |
918 |
|
* aim to maintain a small constant surplus (for example, 3) of |
919 |
|
* tasks, and to process computations locally if this threshold is |
920 |
< |
* exceeded. This method may be invoked only from within |
921 |
< |
* ForkJoinTask computations (as may be determined using method |
922 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
923 |
< |
* result in exceptions or errors, possibly including |
924 |
< |
* ClassCastException. |
920 |
> |
* exceeded. |
921 |
> |
* |
922 |
> |
* <p>This method may be invoked only from within {@code |
923 |
> |
* ForkJoinTask} computations (as may be determined using method |
924 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
925 |
> |
* result in exceptions or errors, possibly including {@code |
926 |
> |
* ClassCastException}. |
927 |
> |
* |
928 |
|
* @return the surplus number of tasks, which may be negative |
929 |
|
*/ |
930 |
|
public static int getSurplusQueuedTaskCount() { |
960 |
|
* called otherwise. The return value controls whether this task |
961 |
|
* is considered to be done normally. It may return false in |
962 |
|
* asynchronous actions that require explicit invocations of |
963 |
< |
* {@link #complete} to become joinable. It may throw exceptions |
964 |
< |
* to indicate abnormal exit. |
963 |
> |
* {@link #complete} to become joinable. It may also throw an |
964 |
> |
* (unchecked) exception to indicate abnormal exit. |
965 |
|
* |
966 |
|
* @return {@code true} if completed normally |
1008 |
– |
* @throws Error or RuntimeException if encountered during computation |
967 |
|
*/ |
968 |
|
protected abstract boolean exec(); |
969 |
|
|
975 |
|
* null even if a task exists but cannot be accessed without |
976 |
|
* contention with other threads. This method is designed |
977 |
|
* primarily to support extensions, and is unlikely to be useful |
978 |
< |
* otherwise. This method may be invoked only from within |
979 |
< |
* ForkJoinTask computations (as may be determined using method |
980 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
981 |
< |
* result in exceptions or errors, possibly including |
982 |
< |
* ClassCastException. |
978 |
> |
* otherwise. |
979 |
> |
* |
980 |
> |
* <p>This method may be invoked only from within {@code |
981 |
> |
* ForkJoinTask} computations (as may be determined using method |
982 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
983 |
> |
* result in exceptions or errors, possibly including {@code |
984 |
> |
* ClassCastException}. |
985 |
|
* |
986 |
|
* @return the next task, or {@code null} if none are available |
987 |
|
*/ |
994 |
|
* Unschedules and returns, without executing, the next task |
995 |
|
* queued by the current thread but not yet executed. This method |
996 |
|
* is designed primarily to support extensions, and is unlikely to |
997 |
< |
* be useful otherwise. This method may be invoked only from |
998 |
< |
* within ForkJoinTask computations (as may be determined using |
999 |
< |
* method {@link #inForkJoinPool}). Attempts to invoke in other |
1000 |
< |
* contexts result in exceptions or errors, possibly including |
1001 |
< |
* ClassCastException. |
997 |
> |
* be useful otherwise. |
998 |
> |
* |
999 |
> |
* <p>This method may be invoked only from within {@code |
1000 |
> |
* ForkJoinTask} computations (as may be determined using method |
1001 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1002 |
> |
* result in exceptions or errors, possibly including {@code |
1003 |
> |
* ClassCastException}. |
1004 |
|
* |
1005 |
|
* @return the next task, or {@code null} if none are available |
1006 |
|
*/ |
1017 |
|
* {@code null} result does not necessarily imply quiescence |
1018 |
|
* of the pool this task is operating in. This method is designed |
1019 |
|
* primarily to support extensions, and is unlikely to be useful |
1020 |
< |
* otherwise. This method may be invoked only from within |
1021 |
< |
* ForkJoinTask computations (as may be determined using method |
1022 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1023 |
< |
* result in exceptions or errors, possibly including |
1024 |
< |
* ClassCastException. |
1020 |
> |
* otherwise. |
1021 |
> |
* |
1022 |
> |
* <p>This method may be invoked only from within {@code |
1023 |
> |
* ForkJoinTask} computations (as may be determined using method |
1024 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1025 |
> |
* result in exceptions or errors, possibly including {@code |
1026 |
> |
* ClassCastException}. |
1027 |
|
* |
1028 |
|
* @return a task, or {@code null} if none are available |
1029 |
|
*/ |
1088 |
|
} |
1089 |
|
|
1090 |
|
/** |
1091 |
< |
* Returns a new ForkJoinTask that performs the {@code run} |
1092 |
< |
* method of the given Runnable as its action, and returns a null |
1093 |
< |
* result upon {@code join}. |
1091 |
> |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1092 |
> |
* method of the given {@code Runnable} as its action, and returns |
1093 |
> |
* a null result upon {@link #join}. |
1094 |
|
* |
1095 |
|
* @param runnable the runnable action |
1096 |
|
* @return the task |
1100 |
|
} |
1101 |
|
|
1102 |
|
/** |
1103 |
< |
* Returns a new ForkJoinTask that performs the {@code run} |
1104 |
< |
* method of the given Runnable as its action, and returns the |
1105 |
< |
* given result upon {@code join}. |
1103 |
> |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1104 |
> |
* method of the given {@code Runnable} as its action, and returns |
1105 |
> |
* the given result upon {@link #join}. |
1106 |
|
* |
1107 |
|
* @param runnable the runnable action |
1108 |
|
* @param result the result upon completion |
1113 |
|
} |
1114 |
|
|
1115 |
|
/** |
1116 |
< |
* Returns a new ForkJoinTask that performs the {@code call} |
1117 |
< |
* method of the given Callable as its action, and returns its |
1118 |
< |
* result upon {@code join}, translating any checked |
1119 |
< |
* exceptions encountered into {@code RuntimeException}. |
1116 |
> |
* Returns a new {@code ForkJoinTask} that performs the {@code call} |
1117 |
> |
* method of the given {@code Callable} as its action, and returns |
1118 |
> |
* its result upon {@link #join}, translating any checked exceptions |
1119 |
> |
* encountered into {@code RuntimeException}. |
1120 |
|
* |
1121 |
|
* @param callable the callable action |
1122 |
|
* @return the task |
1130 |
|
private static final long serialVersionUID = -7721805057305804111L; |
1131 |
|
|
1132 |
|
/** |
1133 |
< |
* Save the state to a stream. |
1133 |
> |
* Saves the state to a stream (that is, serializes it). |
1134 |
|
* |
1135 |
|
* @serialData the current run status and the exception thrown |
1136 |
|
* during execution, or {@code null} if none |
1143 |
|
} |
1144 |
|
|
1145 |
|
/** |
1146 |
< |
* Reconstitute the instance from a stream. |
1146 |
> |
* Reconstitutes the instance from a stream (that is, deserializes it). |
1147 |
|
* |
1148 |
|
* @param s the stream |
1149 |
|
*/ |
1150 |
|
private void readObject(java.io.ObjectInputStream s) |
1151 |
|
throws java.io.IOException, ClassNotFoundException { |
1152 |
|
s.defaultReadObject(); |
1189 |
– |
status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts |
1190 |
– |
status |= EXTERNAL_SIGNAL; // conservatively set external signal |
1153 |
|
Object ex = s.readObject(); |
1154 |
|
if (ex != null) |
1155 |
< |
setDoneExceptionally((Throwable) ex); |
1155 |
> |
setExceptionalCompletion((Throwable) ex); |
1156 |
|
} |
1157 |
|
|
1158 |
|
// Unsafe mechanics |