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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/licenses/publicdomain |
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*/ |
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|
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package jsr166y; |
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|
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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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|
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/** |
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* Abstract base class for tasks that run within a {@link ForkJoinPool}. |
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* A {@code ForkJoinTask} is a thread-like entity that is much |
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* lighter weight than a normal thread. Huge numbers of tasks and |
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* subtasks may be hosted by a small number of actual threads in a |
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* ForkJoinPool, at the price of some usage limitations. |
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* |
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* <p>A "main" {@code ForkJoinTask} begins execution when submitted |
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* to a {@link ForkJoinPool}. Once started, it will usually in turn |
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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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* |
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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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* restrictions (that are only partially statically enforceable) |
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* reflecting their intended use as computational tasks calculating |
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* pure functions or operating on purely isolated objects. The |
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* primary coordination mechanisms are {@link #fork}, that arranges |
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* asynchronous execution, and {@link #join}, that doesn't proceed |
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* until the task's result has been computed. Computations should |
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* avoid {@code synchronized} methods or blocks, and should minimize |
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* other blocking synchronization apart from joining other tasks or |
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* using synchronizers such as Phasers that are advertised to |
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* cooperate with fork/join scheduling. Tasks should also not perform |
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* blocking IO, and should ideally access variables that are |
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* completely independent of those accessed by other running |
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* tasks. Minor breaches of these restrictions, for example using |
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* shared output streams, may be tolerable in practice, but frequent |
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* use may result in poor performance, and the potential to |
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* indefinitely stall if the number of threads not waiting for IO or |
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* other external synchronization becomes exhausted. This usage |
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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 to 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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* |
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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 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 #isCancelled} is true if completion was due to cancellation; |
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* {@link #isCompletedNormally} is true if a task completed without |
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* cancellation or encountering an exception; {@link |
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* #isCompletedExceptionally} is true if if the task encountered an |
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* exception (in which case {@link #getException} returns the |
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* exception); {@link #isCancelled} is true if the task was cancelled |
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* (in which case {@link #getException} returns a {@link |
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* java.util.concurrent.CancellationException}; and {@link |
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* #isCompletedAbnormally} is true if a task was either cancelled or |
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* encountered an exception. |
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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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* RecursiveAction} for computations that do not return results, or |
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* {@link RecursiveTask} for those that do. Normally, a concrete |
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* ForkJoinTask subclass declares fields comprising its parameters, |
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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 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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* |
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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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* 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 async mode}. |
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* |
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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 |
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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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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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|
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/** |
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* Table of exceptions thrown by tasks, to enable reporting by |
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* callers. Because exceptions are rare, we don't directly keep |
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* them with task objects, but instead use a weak ref table. Note |
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* that cancellation exceptions don't appear in the table, but are |
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* instead recorded as status values. |
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* TODO: Use ConcurrentReferenceHashMap |
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*/ |
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static final Map<ForkJoinTask<?>, Throwable> exceptionMap = |
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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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|
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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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* |
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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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} |
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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; |
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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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*/ |
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private void doAwaitDone() { |
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// Minimize lock bias and in/de-flation effects by maximizing |
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// chances of waiting inside sync |
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try { |
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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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} |
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|
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/** |
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* Performs the actual timed monitor wait for awaitDone. |
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*/ |
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private void doAwaitDone(long startTime, long nanos) { |
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synchronized (this) { |
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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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} |
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} catch (InterruptedException ie) { |
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onInterruptedWait(); |
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} |
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} |
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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, |
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* surrounded with pool notifications. |
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* |
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* @return status upon exit |
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*/ |
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private int awaitDone(ForkJoinWorkerThread w, |
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boolean maintainParallelism) { |
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ForkJoinPool pool = (w == null) ? null : w.pool; |
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int s; |
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while ((s = status) >= 0) { |
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if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
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if (pool == null || !pool.preJoin(this, maintainParallelism)) |
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doAwaitDone(); |
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if (((s = status) & INTERNAL_SIGNAL_MASK) != 0) |
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adjustPoolCountsOnUnblock(pool); |
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break; |
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} |
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} |
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return s; |
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} |
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|
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/** |
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* Timed version of awaitDone |
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* |
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* @return status upon exit |
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*/ |
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private int awaitDone(ForkJoinWorkerThread w, long nanos) { |
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ForkJoinPool pool = (w == null) ? null : w.pool; |
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int s; |
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while ((s = status) >= 0) { |
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if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
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long startTime = System.nanoTime(); |
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if (pool == null || !pool.preJoin(this, false)) |
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doAwaitDone(startTime, nanos); |
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if ((s = status) >= 0) { |
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adjustPoolCountsOnCancelledWait(pool); |
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s = status; |
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} |
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if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0) |
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adjustPoolCountsOnUnblock(pool); |
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break; |
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} |
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} |
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return s; |
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} |
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|
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/** |
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* Notifies pool that thread is unblocked. Called by signalled |
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* threads when woken by non-FJ threads (which is atypical). |
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*/ |
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private void adjustPoolCountsOnUnblock(ForkJoinPool pool) { |
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int s; |
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do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK)); |
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if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0) |
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pool.updateRunningCount(s); |
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} |
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|
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/** |
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* Notifies pool to adjust counts on cancelled or timed out wait. |
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*/ |
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private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) { |
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if (pool != null) { |
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int s; |
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while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) { |
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if (casStatus(s, s - 1)) { |
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pool.updateRunningCount(1); |
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break; |
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} |
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} |
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} |
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} |
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|
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/** |
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* Handles interruptions during waits. |
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*/ |
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private void onInterruptedWait() { |
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ForkJoinWorkerThread w = getWorker(); |
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if (w == null) |
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Thread.currentThread().interrupt(); // re-interrupt |
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else if (w.isTerminating()) |
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cancelIgnoringExceptions(); |
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// else if FJworker, ignore interrupt |
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} |
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|
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// Recording and reporting exceptions |
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|
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private void setDoneExceptionally(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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* Throws the exception associated with status s. |
381 |
* |
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* @throws the exception |
383 |
*/ |
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private void reportException(int s) { |
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if ((s &= COMPLETION_MASK) < NORMAL) { |
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if (s == CANCELLED) |
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throw new CancellationException(); |
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else |
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rethrowException(exceptionMap.get(this)); |
390 |
} |
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} |
392 |
|
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/** |
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* Returns result or throws exception using j.u.c.Future conventions. |
395 |
* Only call when {@code isDone} known to be true. |
396 |
*/ |
397 |
private V reportFutureResult() |
398 |
throws ExecutionException, InterruptedException { |
399 |
if (Thread.interrupted()) |
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throw new InterruptedException(); |
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int s = status & COMPLETION_MASK; |
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if (s < NORMAL) { |
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Throwable ex; |
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if (s == CANCELLED) |
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throw new CancellationException(); |
406 |
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
407 |
throw new ExecutionException(ex); |
408 |
} |
409 |
return getRawResult(); |
410 |
} |
411 |
|
412 |
/** |
413 |
* Returns result or throws exception using j.u.c.Future conventions |
414 |
* with timeouts. |
415 |
*/ |
416 |
private V reportTimedFutureResult() |
417 |
throws InterruptedException, ExecutionException, TimeoutException { |
418 |
if (Thread.interrupted()) |
419 |
throw new InterruptedException(); |
420 |
Throwable ex; |
421 |
int s = status & COMPLETION_MASK; |
422 |
if (s == NORMAL) |
423 |
return getRawResult(); |
424 |
if (s == CANCELLED) |
425 |
throw new CancellationException(); |
426 |
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
427 |
throw new ExecutionException(ex); |
428 |
throw new TimeoutException(); |
429 |
} |
430 |
|
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// internal execution methods |
432 |
|
433 |
/** |
434 |
* Calls exec, recording completion, and rethrowing exception if |
435 |
* encountered. Caller should normally check status before calling. |
436 |
* |
437 |
* @return true if completed normally |
438 |
*/ |
439 |
private boolean tryExec() { |
440 |
try { // try block must contain only call to exec |
441 |
if (!exec()) |
442 |
return false; |
443 |
} catch (Throwable rex) { |
444 |
setDoneExceptionally(rex); |
445 |
rethrowException(rex); |
446 |
return false; // not reached |
447 |
} |
448 |
setNormalCompletion(); |
449 |
return true; |
450 |
} |
451 |
|
452 |
/** |
453 |
* Main execution method used by worker threads. Invokes |
454 |
* base computation unless already complete. |
455 |
*/ |
456 |
final void quietlyExec() { |
457 |
if (status >= 0) { |
458 |
try { |
459 |
if (!exec()) |
460 |
return; |
461 |
} catch (Throwable rex) { |
462 |
setDoneExceptionally(rex); |
463 |
return; |
464 |
} |
465 |
setNormalCompletion(); |
466 |
} |
467 |
} |
468 |
|
469 |
/** |
470 |
* Calls exec(), recording but not rethrowing exception. |
471 |
* Caller should normally check status before calling. |
472 |
* |
473 |
* @return true if completed normally |
474 |
*/ |
475 |
private boolean tryQuietlyInvoke() { |
476 |
try { |
477 |
if (!exec()) |
478 |
return false; |
479 |
} catch (Throwable rex) { |
480 |
setDoneExceptionally(rex); |
481 |
return false; |
482 |
} |
483 |
setNormalCompletion(); |
484 |
return true; |
485 |
} |
486 |
|
487 |
/** |
488 |
* Cancels, ignoring any exceptions it throws. |
489 |
*/ |
490 |
final void cancelIgnoringExceptions() { |
491 |
try { |
492 |
cancel(false); |
493 |
} catch (Throwable ignore) { |
494 |
} |
495 |
} |
496 |
|
497 |
/** |
498 |
* Main implementation of helpJoin |
499 |
*/ |
500 |
private int busyJoin(ForkJoinWorkerThread w) { |
501 |
int s; |
502 |
ForkJoinTask<?> t; |
503 |
while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null) |
504 |
t.quietlyExec(); |
505 |
return (s >= 0) ? awaitDone(w, false) : s; // block if no work |
506 |
} |
507 |
|
508 |
// public methods |
509 |
|
510 |
/** |
511 |
* Arranges to asynchronously execute this task. While it is not |
512 |
* necessarily enforced, it is a usage error to fork a task more |
513 |
* than once unless it has completed and been reinitialized. |
514 |
* |
515 |
* <p>This method may be invoked only from within {@code |
516 |
* ForkJoinTask} computations (as may be determined using method |
517 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
518 |
* result in exceptions or errors, possibly including {@code |
519 |
* ClassCastException}. |
520 |
* |
521 |
* @return {@code this}, to simplify usage |
522 |
*/ |
523 |
public final ForkJoinTask<V> fork() { |
524 |
((ForkJoinWorkerThread) Thread.currentThread()) |
525 |
.pushTask(this); |
526 |
return this; |
527 |
} |
528 |
|
529 |
/** |
530 |
* Returns the result of the computation when it is ready. |
531 |
* This method differs from {@link #get()} in that |
532 |
* abnormal completion results in {@code RuntimeException} or |
533 |
* {@code Error}, not {@code ExecutionException}. |
534 |
* |
535 |
* @return the computed result |
536 |
*/ |
537 |
public final V join() { |
538 |
ForkJoinWorkerThread w = getWorker(); |
539 |
if (w == null || status < 0 || !w.unpushTask(this) || !tryExec()) |
540 |
reportException(awaitDone(w, true)); |
541 |
return getRawResult(); |
542 |
} |
543 |
|
544 |
/** |
545 |
* Commences performing this task, awaits its completion if |
546 |
* necessary, and return its result, or throws an (unchecked) |
547 |
* exception if the underlying computation did so. |
548 |
* |
549 |
* @return the computed result |
550 |
*/ |
551 |
public final V invoke() { |
552 |
if (status >= 0 && tryExec()) |
553 |
return getRawResult(); |
554 |
else |
555 |
return join(); |
556 |
} |
557 |
|
558 |
/** |
559 |
* Forks the given tasks, returning when {@code isDone} holds for |
560 |
* each task or an (unchecked) exception is encountered, in which |
561 |
* case the exception is rethrown. If more than one task |
562 |
* encounters an exception, then this method throws any one of |
563 |
* these exceptions. The individual status of each task may be |
564 |
* checked using {@link #getException()} and related methods. |
565 |
* |
566 |
* <p>This method may be invoked only from within {@code |
567 |
* ForkJoinTask} computations (as may be determined using method |
568 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
569 |
* result in exceptions or errors, possibly including {@code |
570 |
* ClassCastException}. |
571 |
* |
572 |
* @param t1 the first task |
573 |
* @param t2 the second task |
574 |
* @throws NullPointerException if any task is null |
575 |
*/ |
576 |
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) { |
577 |
t2.fork(); |
578 |
t1.invoke(); |
579 |
t2.join(); |
580 |
} |
581 |
|
582 |
/** |
583 |
* Forks the given tasks, returning when {@code isDone} holds for |
584 |
* each task or an (unchecked) exception is encountered, in which |
585 |
* case the exception is rethrown. If any task encounters an |
586 |
* exception, others may be, but are not guaranteed to be, |
587 |
* cancelled. If more than one task encounters an exception, then |
588 |
* this method throws any one of these exceptions. The individual |
589 |
* status of each task may be checked using {@link #getException()} |
590 |
* and related methods. |
591 |
* |
592 |
* <p>This method may be invoked only from within {@code |
593 |
* ForkJoinTask} computations (as may be determined using method |
594 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
595 |
* result in exceptions or errors, possibly including {@code |
596 |
* ClassCastException}. |
597 |
* |
598 |
* @param tasks the tasks |
599 |
* @throws NullPointerException if any task is null |
600 |
*/ |
601 |
public static void invokeAll(ForkJoinTask<?>... tasks) { |
602 |
Throwable ex = null; |
603 |
int last = tasks.length - 1; |
604 |
for (int i = last; i >= 0; --i) { |
605 |
ForkJoinTask<?> t = tasks[i]; |
606 |
if (t == null) { |
607 |
if (ex == null) |
608 |
ex = new NullPointerException(); |
609 |
} |
610 |
else if (i != 0) |
611 |
t.fork(); |
612 |
else { |
613 |
t.quietlyInvoke(); |
614 |
if (ex == null) |
615 |
ex = t.getException(); |
616 |
} |
617 |
} |
618 |
for (int i = 1; i <= last; ++i) { |
619 |
ForkJoinTask<?> t = tasks[i]; |
620 |
if (t != null) { |
621 |
if (ex != null) |
622 |
t.cancel(false); |
623 |
else { |
624 |
t.quietlyJoin(); |
625 |
if (ex == null) |
626 |
ex = t.getException(); |
627 |
} |
628 |
} |
629 |
} |
630 |
if (ex != null) |
631 |
rethrowException(ex); |
632 |
} |
633 |
|
634 |
/** |
635 |
* Forks all tasks in the specified collection, returning when |
636 |
* {@code isDone} holds for each task or an (unchecked) exception |
637 |
* is encountered. If any task encounters an exception, others |
638 |
* may be, but are not guaranteed to be, cancelled. If more than |
639 |
* one task encounters an exception, then this method throws any |
640 |
* one of these exceptions. The individual status of each task |
641 |
* may be checked using {@link #getException()} and related |
642 |
* methods. The behavior of this operation is undefined if the |
643 |
* specified collection is modified while the operation is in |
644 |
* progress. |
645 |
* |
646 |
* <p>This method may be invoked only from within {@code |
647 |
* ForkJoinTask} computations (as may be determined using method |
648 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
649 |
* result in exceptions or errors, possibly including {@code |
650 |
* ClassCastException}. |
651 |
* |
652 |
* @param tasks the collection of tasks |
653 |
* @return the tasks argument, to simplify usage |
654 |
* @throws NullPointerException if tasks or any element are null |
655 |
*/ |
656 |
public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) { |
657 |
if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) { |
658 |
invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()])); |
659 |
return tasks; |
660 |
} |
661 |
@SuppressWarnings("unchecked") |
662 |
List<? extends ForkJoinTask<?>> ts = |
663 |
(List<? extends ForkJoinTask<?>>) tasks; |
664 |
Throwable ex = null; |
665 |
int last = ts.size() - 1; |
666 |
for (int i = last; i >= 0; --i) { |
667 |
ForkJoinTask<?> t = ts.get(i); |
668 |
if (t == null) { |
669 |
if (ex == null) |
670 |
ex = new NullPointerException(); |
671 |
} |
672 |
else if (i != 0) |
673 |
t.fork(); |
674 |
else { |
675 |
t.quietlyInvoke(); |
676 |
if (ex == null) |
677 |
ex = t.getException(); |
678 |
} |
679 |
} |
680 |
for (int i = 1; i <= last; ++i) { |
681 |
ForkJoinTask<?> t = ts.get(i); |
682 |
if (t != null) { |
683 |
if (ex != null) |
684 |
t.cancel(false); |
685 |
else { |
686 |
t.quietlyJoin(); |
687 |
if (ex == null) |
688 |
ex = t.getException(); |
689 |
} |
690 |
} |
691 |
} |
692 |
if (ex != null) |
693 |
rethrowException(ex); |
694 |
return tasks; |
695 |
} |
696 |
|
697 |
/** |
698 |
* Attempts to cancel execution of this task. This attempt will |
699 |
* fail if the task has already completed, has already been |
700 |
* cancelled, or could not be cancelled for some other reason. If |
701 |
* successful, and this task has not started when cancel is |
702 |
* called, execution of this task is suppressed, {@link |
703 |
* #isCancelled} will report true, and {@link #join} will result |
704 |
* in a {@code CancellationException} being thrown. |
705 |
* |
706 |
* <p>This method may be overridden in subclasses, but if so, must |
707 |
* still ensure that these minimal properties hold. In particular, |
708 |
* the {@code cancel} method itself must not throw exceptions. |
709 |
* |
710 |
* <p>This method is designed to be invoked by <em>other</em> |
711 |
* tasks. To terminate the current task, you can just return or |
712 |
* throw an unchecked exception from its computation method, or |
713 |
* invoke {@link #completeExceptionally}. |
714 |
* |
715 |
* @param mayInterruptIfRunning this value is ignored in the |
716 |
* default implementation because tasks are not |
717 |
* cancelled via interruption |
718 |
* |
719 |
* @return {@code true} if this task is now cancelled |
720 |
*/ |
721 |
public boolean cancel(boolean mayInterruptIfRunning) { |
722 |
setCompletion(CANCELLED); |
723 |
return (status & COMPLETION_MASK) == CANCELLED; |
724 |
} |
725 |
|
726 |
/** |
727 |
* Returns {@code true} if the computation performed by this task |
728 |
* has completed (or has been cancelled). |
729 |
* |
730 |
* @return {@code true} if this computation has completed |
731 |
*/ |
732 |
public final boolean isDone() { |
733 |
return status < 0; |
734 |
} |
735 |
|
736 |
/** |
737 |
* Returns {@code true} if this task was cancelled. |
738 |
* |
739 |
* @return {@code true} if this task was cancelled |
740 |
*/ |
741 |
public final boolean isCancelled() { |
742 |
return (status & COMPLETION_MASK) == CANCELLED; |
743 |
} |
744 |
|
745 |
/** |
746 |
* Returns {@code true} if this task threw an exception or was cancelled. |
747 |
* |
748 |
* @return {@code true} if this task threw an exception or was cancelled |
749 |
*/ |
750 |
public final boolean isCompletedAbnormally() { |
751 |
return (status & COMPLETION_MASK) < NORMAL; |
752 |
} |
753 |
|
754 |
/** |
755 |
* Returns {@code true} if this task completed without throwing an |
756 |
* exception and was not cancelled. |
757 |
* |
758 |
* @return {@code true} if this task completed without throwing an |
759 |
* exception and was not cancelled |
760 |
*/ |
761 |
public final boolean isCompletedNormally() { |
762 |
return (status & COMPLETION_MASK) == NORMAL; |
763 |
} |
764 |
|
765 |
/** |
766 |
* Returns {@code true} if this task threw an exception. |
767 |
* |
768 |
* @return {@code true} if this task threw an exception |
769 |
*/ |
770 |
public final boolean isCompletedExceptionally() { |
771 |
return (status & COMPLETION_MASK) == EXCEPTIONAL; |
772 |
} |
773 |
|
774 |
/** |
775 |
* Returns the exception thrown by the base computation, or a |
776 |
* {@code CancellationException} if cancelled, or {@code null} if |
777 |
* none or if the method has not yet completed. |
778 |
* |
779 |
* @return the exception, or {@code null} if none |
780 |
*/ |
781 |
public final Throwable getException() { |
782 |
int s = status & COMPLETION_MASK; |
783 |
if (s >= NORMAL) |
784 |
return null; |
785 |
if (s == CANCELLED) |
786 |
return new CancellationException(); |
787 |
return exceptionMap.get(this); |
788 |
} |
789 |
|
790 |
/** |
791 |
* Completes this task abnormally, and if not already aborted or |
792 |
* cancelled, causes it to throw the given exception upon |
793 |
* {@code join} and related operations. This method may be used |
794 |
* to induce exceptions in asynchronous tasks, or to force |
795 |
* completion of tasks that would not otherwise complete. Its use |
796 |
* in other situations is discouraged. This method is |
797 |
* overridable, but overridden versions must invoke {@code super} |
798 |
* implementation to maintain guarantees. |
799 |
* |
800 |
* @param ex the exception to throw. If this exception is |
801 |
* not a RuntimeException or Error, the actual exception thrown |
802 |
* will be a RuntimeException with cause ex. |
803 |
*/ |
804 |
public void completeExceptionally(Throwable ex) { |
805 |
setDoneExceptionally((ex instanceof RuntimeException) || |
806 |
(ex instanceof Error) ? ex : |
807 |
new RuntimeException(ex)); |
808 |
} |
809 |
|
810 |
/** |
811 |
* Completes this task, and if not already aborted or cancelled, |
812 |
* returning a {@code null} result upon {@code join} and related |
813 |
* operations. This method may be used to provide results for |
814 |
* asynchronous tasks, or to provide alternative handling for |
815 |
* tasks that would not otherwise complete normally. Its use in |
816 |
* other situations is discouraged. This method is |
817 |
* overridable, but overridden versions must invoke {@code super} |
818 |
* implementation to maintain guarantees. |
819 |
* |
820 |
* @param value the result value for this task |
821 |
*/ |
822 |
public void complete(V value) { |
823 |
try { |
824 |
setRawResult(value); |
825 |
} catch (Throwable rex) { |
826 |
setDoneExceptionally(rex); |
827 |
return; |
828 |
} |
829 |
setNormalCompletion(); |
830 |
} |
831 |
|
832 |
public final V get() throws InterruptedException, ExecutionException { |
833 |
ForkJoinWorkerThread w = getWorker(); |
834 |
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
835 |
awaitDone(w, true); |
836 |
return reportFutureResult(); |
837 |
} |
838 |
|
839 |
public final V get(long timeout, TimeUnit unit) |
840 |
throws InterruptedException, ExecutionException, TimeoutException { |
841 |
long nanos = unit.toNanos(timeout); |
842 |
ForkJoinWorkerThread w = getWorker(); |
843 |
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
844 |
awaitDone(w, nanos); |
845 |
return reportTimedFutureResult(); |
846 |
} |
847 |
|
848 |
/** |
849 |
* Possibly executes other tasks until this task is ready, then |
850 |
* returns the result of the computation. This method may be more |
851 |
* efficient than {@code join}, but is only applicable when |
852 |
* there are no potential dependencies between continuation of the |
853 |
* current task and that of any other task that might be executed |
854 |
* while helping. (This usually holds for pure divide-and-conquer |
855 |
* tasks). |
856 |
* |
857 |
* <p>This method may be invoked only from within {@code |
858 |
* ForkJoinTask} computations (as may be determined using method |
859 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
860 |
* result in exceptions or errors, possibly including {@code |
861 |
* ClassCastException}. |
862 |
* |
863 |
* @return the computed result |
864 |
*/ |
865 |
public final V helpJoin() { |
866 |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread(); |
867 |
if (status < 0 || !w.unpushTask(this) || !tryExec()) |
868 |
reportException(busyJoin(w)); |
869 |
return getRawResult(); |
870 |
} |
871 |
|
872 |
/** |
873 |
* Possibly executes other tasks until this task is ready. This |
874 |
* method may be useful when processing collections of tasks when |
875 |
* some have been cancelled or otherwise known to have aborted. |
876 |
* |
877 |
* <p>This method may be invoked only from within {@code |
878 |
* ForkJoinTask} computations (as may be determined using method |
879 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
880 |
* result in exceptions or errors, possibly including {@code |
881 |
* ClassCastException}. |
882 |
*/ |
883 |
public final void quietlyHelpJoin() { |
884 |
if (status >= 0) { |
885 |
ForkJoinWorkerThread w = |
886 |
(ForkJoinWorkerThread) Thread.currentThread(); |
887 |
if (!w.unpushTask(this) || !tryQuietlyInvoke()) |
888 |
busyJoin(w); |
889 |
} |
890 |
} |
891 |
|
892 |
/** |
893 |
* Joins this task, without returning its result or throwing an |
894 |
* exception. This method may be useful when processing |
895 |
* collections of tasks when some have been cancelled or otherwise |
896 |
* known to have aborted. |
897 |
*/ |
898 |
public final void quietlyJoin() { |
899 |
if (status >= 0) { |
900 |
ForkJoinWorkerThread w = getWorker(); |
901 |
if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke()) |
902 |
awaitDone(w, true); |
903 |
} |
904 |
} |
905 |
|
906 |
/** |
907 |
* Commences performing this task and awaits its completion if |
908 |
* necessary, without returning its result or throwing an |
909 |
* exception. This method may be useful when processing |
910 |
* collections of tasks when some have been cancelled or otherwise |
911 |
* known to have aborted. |
912 |
*/ |
913 |
public final void quietlyInvoke() { |
914 |
if (status >= 0 && !tryQuietlyInvoke()) |
915 |
quietlyJoin(); |
916 |
} |
917 |
|
918 |
/** |
919 |
* Possibly executes tasks until the pool hosting the current task |
920 |
* {@link ForkJoinPool#isQuiescent is quiescent}. This method may |
921 |
* be of use in designs in which many tasks are forked, but none |
922 |
* are explicitly joined, instead executing them until all are |
923 |
* processed. |
924 |
* |
925 |
* <p>This method may be invoked only from within {@code |
926 |
* ForkJoinTask} computations (as may be determined using method |
927 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
928 |
* result in exceptions or errors, possibly including {@code |
929 |
* ClassCastException}. |
930 |
*/ |
931 |
public static void helpQuiesce() { |
932 |
((ForkJoinWorkerThread) Thread.currentThread()) |
933 |
.helpQuiescePool(); |
934 |
} |
935 |
|
936 |
/** |
937 |
* Resets the internal bookkeeping state of this task, allowing a |
938 |
* subsequent {@code fork}. This method allows repeated reuse of |
939 |
* this task, but only if reuse occurs when this task has either |
940 |
* never been forked, or has been forked, then completed and all |
941 |
* outstanding joins of this task have also completed. Effects |
942 |
* under any other usage conditions are not guaranteed. |
943 |
* This method may be useful when executing |
944 |
* pre-constructed trees of subtasks in loops. |
945 |
*/ |
946 |
public void reinitialize() { |
947 |
if ((status & COMPLETION_MASK) == EXCEPTIONAL) |
948 |
exceptionMap.remove(this); |
949 |
status = 0; |
950 |
} |
951 |
|
952 |
/** |
953 |
* Returns the pool hosting the current task execution, or null |
954 |
* if this task is executing outside of any ForkJoinPool. |
955 |
* |
956 |
* @see #inForkJoinPool |
957 |
* @return the pool, or {@code null} if none |
958 |
*/ |
959 |
public static ForkJoinPool getPool() { |
960 |
Thread t = Thread.currentThread(); |
961 |
return (t instanceof ForkJoinWorkerThread) ? |
962 |
((ForkJoinWorkerThread) t).pool : null; |
963 |
} |
964 |
|
965 |
/** |
966 |
* Returns {@code true} if the current thread is executing as a |
967 |
* ForkJoinPool computation. |
968 |
* |
969 |
* @return {@code true} if the current thread is executing as a |
970 |
* ForkJoinPool computation, or false otherwise |
971 |
*/ |
972 |
public static boolean inForkJoinPool() { |
973 |
return Thread.currentThread() instanceof ForkJoinWorkerThread; |
974 |
} |
975 |
|
976 |
/** |
977 |
* Tries to unschedule this task for execution. This method will |
978 |
* typically succeed if this task is the most recently forked task |
979 |
* by the current thread, and has not commenced executing in |
980 |
* another thread. This method may be useful when arranging |
981 |
* alternative local processing of tasks that could have been, but |
982 |
* were not, stolen. |
983 |
* |
984 |
* <p>This method may be invoked only from within {@code |
985 |
* ForkJoinTask} computations (as may be determined using method |
986 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
987 |
* result in exceptions or errors, possibly including {@code |
988 |
* ClassCastException}. |
989 |
* |
990 |
* @return {@code true} if unforked |
991 |
*/ |
992 |
public boolean tryUnfork() { |
993 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
994 |
.unpushTask(this); |
995 |
} |
996 |
|
997 |
/** |
998 |
* Returns an estimate of the number of tasks that have been |
999 |
* forked by the current worker thread but not yet executed. This |
1000 |
* value may be useful for heuristic decisions about whether to |
1001 |
* fork other tasks. |
1002 |
* |
1003 |
* <p>This method may be invoked only from within {@code |
1004 |
* ForkJoinTask} computations (as may be determined using method |
1005 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1006 |
* result in exceptions or errors, possibly including {@code |
1007 |
* ClassCastException}. |
1008 |
* |
1009 |
* @return the number of tasks |
1010 |
*/ |
1011 |
public static int getQueuedTaskCount() { |
1012 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1013 |
.getQueueSize(); |
1014 |
} |
1015 |
|
1016 |
/** |
1017 |
* Returns an estimate of how many more locally queued tasks are |
1018 |
* held by the current worker thread than there are other worker |
1019 |
* threads that might steal them. This value may be useful for |
1020 |
* heuristic decisions about whether to fork other tasks. In many |
1021 |
* usages of ForkJoinTasks, at steady state, each worker should |
1022 |
* aim to maintain a small constant surplus (for example, 3) of |
1023 |
* tasks, and to process computations locally if this threshold is |
1024 |
* exceeded. |
1025 |
* |
1026 |
* <p>This method may be invoked only from within {@code |
1027 |
* ForkJoinTask} computations (as may be determined using method |
1028 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1029 |
* result in exceptions or errors, possibly including {@code |
1030 |
* ClassCastException}. |
1031 |
* |
1032 |
* @return the surplus number of tasks, which may be negative |
1033 |
*/ |
1034 |
public static int getSurplusQueuedTaskCount() { |
1035 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1036 |
.getEstimatedSurplusTaskCount(); |
1037 |
} |
1038 |
|
1039 |
// Extension methods |
1040 |
|
1041 |
/** |
1042 |
* Returns the result that would be returned by {@link #join}, even |
1043 |
* if this task completed abnormally, or {@code null} if this task |
1044 |
* is not known to have been completed. This method is designed |
1045 |
* to aid debugging, as well as to support extensions. Its use in |
1046 |
* any other context is discouraged. |
1047 |
* |
1048 |
* @return the result, or {@code null} if not completed |
1049 |
*/ |
1050 |
public abstract V getRawResult(); |
1051 |
|
1052 |
/** |
1053 |
* Forces the given value to be returned as a result. This method |
1054 |
* is designed to support extensions, and should not in general be |
1055 |
* called otherwise. |
1056 |
* |
1057 |
* @param value the value |
1058 |
*/ |
1059 |
protected abstract void setRawResult(V value); |
1060 |
|
1061 |
/** |
1062 |
* Immediately performs the base action of this task. This method |
1063 |
* is designed to support extensions, and should not in general be |
1064 |
* called otherwise. The return value controls whether this task |
1065 |
* is considered to be done normally. It may return false in |
1066 |
* asynchronous actions that require explicit invocations of |
1067 |
* {@link #complete} to become joinable. It may also throw an |
1068 |
* (unchecked) exception to indicate abnormal exit. |
1069 |
* |
1070 |
* @return {@code true} if completed normally |
1071 |
*/ |
1072 |
protected abstract boolean exec(); |
1073 |
|
1074 |
/** |
1075 |
* Returns, but does not unschedule or execute, a task queued by |
1076 |
* the current thread but not yet executed, if one is immediately |
1077 |
* available. There is no guarantee that this task will actually |
1078 |
* be polled or executed next. Conversely, this method may return |
1079 |
* null even if a task exists but cannot be accessed without |
1080 |
* contention with other threads. This method is designed |
1081 |
* primarily to support extensions, and is unlikely to be useful |
1082 |
* otherwise. |
1083 |
* |
1084 |
* <p>This method may be invoked only from within {@code |
1085 |
* ForkJoinTask} computations (as may be determined using method |
1086 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1087 |
* result in exceptions or errors, possibly including {@code |
1088 |
* ClassCastException}. |
1089 |
* |
1090 |
* @return the next task, or {@code null} if none are available |
1091 |
*/ |
1092 |
protected static ForkJoinTask<?> peekNextLocalTask() { |
1093 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1094 |
.peekTask(); |
1095 |
} |
1096 |
|
1097 |
/** |
1098 |
* Unschedules and returns, without executing, the next task |
1099 |
* queued by the current thread but not yet executed. This method |
1100 |
* is designed primarily to support extensions, and is unlikely to |
1101 |
* be useful otherwise. |
1102 |
* |
1103 |
* <p>This method may be invoked only from within {@code |
1104 |
* ForkJoinTask} computations (as may be determined using method |
1105 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1106 |
* result in exceptions or errors, possibly including {@code |
1107 |
* ClassCastException}. |
1108 |
* |
1109 |
* @return the next task, or {@code null} if none are available |
1110 |
*/ |
1111 |
protected static ForkJoinTask<?> pollNextLocalTask() { |
1112 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1113 |
.pollLocalTask(); |
1114 |
} |
1115 |
|
1116 |
/** |
1117 |
* Unschedules and returns, without executing, the next task |
1118 |
* queued by the current thread but not yet executed, if one is |
1119 |
* available, or if not available, a task that was forked by some |
1120 |
* other thread, if available. Availability may be transient, so a |
1121 |
* {@code null} result does not necessarily imply quiescence |
1122 |
* of the pool this task is operating in. This method is designed |
1123 |
* primarily to support extensions, and is unlikely to be useful |
1124 |
* otherwise. |
1125 |
* |
1126 |
* <p>This method may be invoked only from within {@code |
1127 |
* ForkJoinTask} computations (as may be determined using method |
1128 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1129 |
* result in exceptions or errors, possibly including {@code |
1130 |
* ClassCastException}. |
1131 |
* |
1132 |
* @return a task, or {@code null} if none are available |
1133 |
*/ |
1134 |
protected static ForkJoinTask<?> pollTask() { |
1135 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1136 |
.pollTask(); |
1137 |
} |
1138 |
|
1139 |
/** |
1140 |
* Adaptor for Runnables. This implements RunnableFuture |
1141 |
* to be compliant with AbstractExecutorService constraints |
1142 |
* when used in ForkJoinPool. |
1143 |
*/ |
1144 |
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
1145 |
implements RunnableFuture<T> { |
1146 |
final Runnable runnable; |
1147 |
final T resultOnCompletion; |
1148 |
T result; |
1149 |
AdaptedRunnable(Runnable runnable, T result) { |
1150 |
if (runnable == null) throw new NullPointerException(); |
1151 |
this.runnable = runnable; |
1152 |
this.resultOnCompletion = result; |
1153 |
} |
1154 |
public T getRawResult() { return result; } |
1155 |
public void setRawResult(T v) { result = v; } |
1156 |
public boolean exec() { |
1157 |
runnable.run(); |
1158 |
result = resultOnCompletion; |
1159 |
return true; |
1160 |
} |
1161 |
public void run() { invoke(); } |
1162 |
private static final long serialVersionUID = 5232453952276885070L; |
1163 |
} |
1164 |
|
1165 |
/** |
1166 |
* Adaptor for Callables |
1167 |
*/ |
1168 |
static final class AdaptedCallable<T> extends ForkJoinTask<T> |
1169 |
implements RunnableFuture<T> { |
1170 |
final Callable<? extends T> callable; |
1171 |
T result; |
1172 |
AdaptedCallable(Callable<? extends T> callable) { |
1173 |
if (callable == null) throw new NullPointerException(); |
1174 |
this.callable = callable; |
1175 |
} |
1176 |
public T getRawResult() { return result; } |
1177 |
public void setRawResult(T v) { result = v; } |
1178 |
public boolean exec() { |
1179 |
try { |
1180 |
result = callable.call(); |
1181 |
return true; |
1182 |
} catch (Error err) { |
1183 |
throw err; |
1184 |
} catch (RuntimeException rex) { |
1185 |
throw rex; |
1186 |
} catch (Exception ex) { |
1187 |
throw new RuntimeException(ex); |
1188 |
} |
1189 |
} |
1190 |
public void run() { invoke(); } |
1191 |
private static final long serialVersionUID = 2838392045355241008L; |
1192 |
} |
1193 |
|
1194 |
/** |
1195 |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1196 |
* method of the given {@code Runnable} as its action, and returns |
1197 |
* a null result upon {@link #join}. |
1198 |
* |
1199 |
* @param runnable the runnable action |
1200 |
* @return the task |
1201 |
*/ |
1202 |
public static ForkJoinTask<?> adapt(Runnable runnable) { |
1203 |
return new AdaptedRunnable<Void>(runnable, null); |
1204 |
} |
1205 |
|
1206 |
/** |
1207 |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1208 |
* method of the given {@code Runnable} as its action, and returns |
1209 |
* the given result upon {@link #join}. |
1210 |
* |
1211 |
* @param runnable the runnable action |
1212 |
* @param result the result upon completion |
1213 |
* @return the task |
1214 |
*/ |
1215 |
public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) { |
1216 |
return new AdaptedRunnable<T>(runnable, result); |
1217 |
} |
1218 |
|
1219 |
/** |
1220 |
* Returns a new {@code ForkJoinTask} that performs the {@code call} |
1221 |
* method of the given {@code Callable} as its action, and returns |
1222 |
* its result upon {@link #join}, translating any checked exceptions |
1223 |
* encountered into {@code RuntimeException}. |
1224 |
* |
1225 |
* @param callable the callable action |
1226 |
* @return the task |
1227 |
*/ |
1228 |
public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) { |
1229 |
return new AdaptedCallable<T>(callable); |
1230 |
} |
1231 |
|
1232 |
// Serialization support |
1233 |
|
1234 |
private static final long serialVersionUID = -7721805057305804111L; |
1235 |
|
1236 |
/** |
1237 |
* Save the state to a stream. |
1238 |
* |
1239 |
* @serialData the current run status and the exception thrown |
1240 |
* during execution, or {@code null} if none |
1241 |
* @param s the stream |
1242 |
*/ |
1243 |
private void writeObject(java.io.ObjectOutputStream s) |
1244 |
throws java.io.IOException { |
1245 |
s.defaultWriteObject(); |
1246 |
s.writeObject(getException()); |
1247 |
} |
1248 |
|
1249 |
/** |
1250 |
* Reconstitute the instance from a stream. |
1251 |
* |
1252 |
* @param s the stream |
1253 |
*/ |
1254 |
private void readObject(java.io.ObjectInputStream s) |
1255 |
throws java.io.IOException, ClassNotFoundException { |
1256 |
s.defaultReadObject(); |
1257 |
status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts |
1258 |
status |= EXTERNAL_SIGNAL; // conservatively set external signal |
1259 |
Object ex = s.readObject(); |
1260 |
if (ex != null) |
1261 |
setDoneExceptionally((Throwable) ex); |
1262 |
} |
1263 |
|
1264 |
// Unsafe mechanics |
1265 |
|
1266 |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1267 |
private static final long statusOffset = |
1268 |
objectFieldOffset("status", ForkJoinTask.class); |
1269 |
|
1270 |
private static long objectFieldOffset(String field, Class<?> klazz) { |
1271 |
try { |
1272 |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1273 |
} catch (NoSuchFieldException e) { |
1274 |
// Convert Exception to corresponding Error |
1275 |
NoSuchFieldError error = new NoSuchFieldError(field); |
1276 |
error.initCause(e); |
1277 |
throw error; |
1278 |
} |
1279 |
} |
1280 |
|
1281 |
/** |
1282 |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
1283 |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
1284 |
* into a jdk. |
1285 |
* |
1286 |
* @return a sun.misc.Unsafe |
1287 |
*/ |
1288 |
private static sun.misc.Unsafe getUnsafe() { |
1289 |
try { |
1290 |
return sun.misc.Unsafe.getUnsafe(); |
1291 |
} catch (SecurityException se) { |
1292 |
try { |
1293 |
return java.security.AccessController.doPrivileged |
1294 |
(new java.security |
1295 |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1296 |
public sun.misc.Unsafe run() throws Exception { |
1297 |
java.lang.reflect.Field f = sun.misc |
1298 |
.Unsafe.class.getDeclaredField("theUnsafe"); |
1299 |
f.setAccessible(true); |
1300 |
return (sun.misc.Unsafe) f.get(null); |
1301 |
}}); |
1302 |
} catch (java.security.PrivilegedActionException e) { |
1303 |
throw new RuntimeException("Could not initialize intrinsics", |
1304 |
e.getCause()); |
1305 |
} |
1306 |
} |
1307 |
} |
1308 |
} |