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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 #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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* 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 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 |
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* are of this form, consider using a pool in |
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* {@linkplain 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. |
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* |
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* @throws the exception |
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*/ |
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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)); |
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} |
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} |
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|
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/** |
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* Returns result or throws exception using j.u.c.Future conventions. |
393 |
* Only call when {@code isDone} known to be true or thread known |
394 |
* to be interrupted. |
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*/ |
396 |
private V reportFutureResult() |
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throws InterruptedException, ExecutionException { |
398 |
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(); |
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if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
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throw new ExecutionException(ex); |
407 |
} |
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return getRawResult(); |
409 |
} |
410 |
|
411 |
/** |
412 |
* Returns result or throws exception using j.u.c.Future conventions |
413 |
* with timeouts. |
414 |
*/ |
415 |
private V reportTimedFutureResult() |
416 |
throws InterruptedException, ExecutionException, TimeoutException { |
417 |
if (Thread.interrupted()) |
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throw new InterruptedException(); |
419 |
Throwable ex; |
420 |
int s = status & COMPLETION_MASK; |
421 |
if (s == NORMAL) |
422 |
return getRawResult(); |
423 |
else if (s == CANCELLED) |
424 |
throw new CancellationException(); |
425 |
else if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
426 |
throw new ExecutionException(ex); |
427 |
else |
428 |
throw new TimeoutException(); |
429 |
} |
430 |
|
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// internal execution methods |
432 |
|
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/** |
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 |
* Subsequent modifications to the state of this task or any data |
515 |
* it operates on are not necessarily consistently observable by |
516 |
* any thread other than the one executing it unless preceded by a |
517 |
* call to {@link #join} or related methods, or a call to {@link |
518 |
* #isDone} returning {@code true}. |
519 |
* |
520 |
* <p>This method may be invoked only from within {@code |
521 |
* ForkJoinTask} computations (as may be determined using method |
522 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
523 |
* result in exceptions or errors, possibly including {@code |
524 |
* ClassCastException}. |
525 |
* |
526 |
* @return {@code this}, to simplify usage |
527 |
*/ |
528 |
public final ForkJoinTask<V> fork() { |
529 |
((ForkJoinWorkerThread) Thread.currentThread()) |
530 |
.pushTask(this); |
531 |
return this; |
532 |
} |
533 |
|
534 |
/** |
535 |
* Returns the result of the computation when it {@link #isDone is done}. |
536 |
* This method differs from {@link #get()} in that |
537 |
* abnormal completion results in {@code RuntimeException} or |
538 |
* {@code Error}, not {@code ExecutionException}. |
539 |
* |
540 |
* @return the computed result |
541 |
*/ |
542 |
public final V join() { |
543 |
ForkJoinWorkerThread w = getWorker(); |
544 |
if (w == null || status < 0 || !w.unpushTask(this) || !tryExec()) |
545 |
reportException(awaitDone(w, true)); |
546 |
return getRawResult(); |
547 |
} |
548 |
|
549 |
/** |
550 |
* Commences performing this task, awaits its completion if |
551 |
* necessary, and return its result, or throws an (unchecked) |
552 |
* exception if the underlying computation did so. |
553 |
* |
554 |
* @return the computed result |
555 |
*/ |
556 |
public final V invoke() { |
557 |
if (status >= 0 && tryExec()) |
558 |
return getRawResult(); |
559 |
else |
560 |
return join(); |
561 |
} |
562 |
|
563 |
/** |
564 |
* Forks the given tasks, returning when {@code isDone} holds for |
565 |
* each task or an (unchecked) exception is encountered, in which |
566 |
* case the exception is rethrown. If either task encounters an |
567 |
* exception, the other one may be, but is not guaranteed to be, |
568 |
* cancelled. If both tasks throw an exception, then this method |
569 |
* throws one of them. The individual status of each task may be |
570 |
* checked using {@link #getException()} and related methods. |
571 |
* |
572 |
* <p>This method may be invoked only from within {@code |
573 |
* ForkJoinTask} computations (as may be determined using method |
574 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
575 |
* result in exceptions or errors, possibly including {@code |
576 |
* ClassCastException}. |
577 |
* |
578 |
* @param t1 the first task |
579 |
* @param t2 the second task |
580 |
* @throws NullPointerException if any task is null |
581 |
*/ |
582 |
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) { |
583 |
t2.fork(); |
584 |
t1.invoke(); |
585 |
t2.join(); |
586 |
} |
587 |
|
588 |
/** |
589 |
* Forks the given tasks, returning when {@code isDone} holds for |
590 |
* each task or an (unchecked) exception is encountered, in which |
591 |
* case the exception is rethrown. If any task encounters an |
592 |
* exception, others may be, but are not guaranteed to be, |
593 |
* cancelled. If more than one task encounters an exception, then |
594 |
* this method throws any one of these exceptions. The individual |
595 |
* status of each task may be checked using {@link #getException()} |
596 |
* and related methods. |
597 |
* |
598 |
* <p>This method may be invoked only from within {@code |
599 |
* ForkJoinTask} computations (as may be determined using method |
600 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
601 |
* result in exceptions or errors, possibly including {@code |
602 |
* ClassCastException}. |
603 |
* |
604 |
* @param tasks the tasks |
605 |
* @throws NullPointerException if any task is null |
606 |
*/ |
607 |
public static void invokeAll(ForkJoinTask<?>... tasks) { |
608 |
Throwable ex = null; |
609 |
int last = tasks.length - 1; |
610 |
for (int i = last; i >= 0; --i) { |
611 |
ForkJoinTask<?> t = tasks[i]; |
612 |
if (t == null) { |
613 |
if (ex == null) |
614 |
ex = new NullPointerException(); |
615 |
} |
616 |
else if (i != 0) |
617 |
t.fork(); |
618 |
else { |
619 |
t.quietlyInvoke(); |
620 |
if (ex == null) |
621 |
ex = t.getException(); |
622 |
} |
623 |
} |
624 |
for (int i = 1; i <= last; ++i) { |
625 |
ForkJoinTask<?> t = tasks[i]; |
626 |
if (t != null) { |
627 |
if (ex != null) |
628 |
t.cancel(false); |
629 |
else { |
630 |
t.quietlyJoin(); |
631 |
if (ex == null) |
632 |
ex = t.getException(); |
633 |
} |
634 |
} |
635 |
} |
636 |
if (ex != null) |
637 |
rethrowException(ex); |
638 |
} |
639 |
|
640 |
/** |
641 |
* Forks all tasks in the specified collection, returning when |
642 |
* {@code isDone} holds for each task or an (unchecked) exception |
643 |
* is encountered. If any task encounters an exception, others |
644 |
* may be, but are not guaranteed to be, cancelled. If more than |
645 |
* one task encounters an exception, then this method throws any |
646 |
* one of these exceptions. The individual status of each task |
647 |
* may be checked using {@link #getException()} and related |
648 |
* methods. The behavior of this operation is undefined if the |
649 |
* specified collection is modified while the operation is in |
650 |
* progress. |
651 |
* |
652 |
* <p>This method may be invoked only from within {@code |
653 |
* ForkJoinTask} computations (as may be determined using method |
654 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
655 |
* result in exceptions or errors, possibly including {@code |
656 |
* ClassCastException}. |
657 |
* |
658 |
* @param tasks the collection of tasks |
659 |
* @return the tasks argument, to simplify usage |
660 |
* @throws NullPointerException if tasks or any element are null |
661 |
*/ |
662 |
public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) { |
663 |
if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) { |
664 |
invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()])); |
665 |
return tasks; |
666 |
} |
667 |
@SuppressWarnings("unchecked") |
668 |
List<? extends ForkJoinTask<?>> ts = |
669 |
(List<? extends ForkJoinTask<?>>) tasks; |
670 |
Throwable ex = null; |
671 |
int last = ts.size() - 1; |
672 |
for (int i = last; i >= 0; --i) { |
673 |
ForkJoinTask<?> t = ts.get(i); |
674 |
if (t == null) { |
675 |
if (ex == null) |
676 |
ex = new NullPointerException(); |
677 |
} |
678 |
else if (i != 0) |
679 |
t.fork(); |
680 |
else { |
681 |
t.quietlyInvoke(); |
682 |
if (ex == null) |
683 |
ex = t.getException(); |
684 |
} |
685 |
} |
686 |
for (int i = 1; i <= last; ++i) { |
687 |
ForkJoinTask<?> t = ts.get(i); |
688 |
if (t != null) { |
689 |
if (ex != null) |
690 |
t.cancel(false); |
691 |
else { |
692 |
t.quietlyJoin(); |
693 |
if (ex == null) |
694 |
ex = t.getException(); |
695 |
} |
696 |
} |
697 |
} |
698 |
if (ex != null) |
699 |
rethrowException(ex); |
700 |
return tasks; |
701 |
} |
702 |
|
703 |
/** |
704 |
* Attempts to cancel execution of this task. This attempt will |
705 |
* fail if the task has already completed, has already been |
706 |
* cancelled, or could not be cancelled for some other reason. If |
707 |
* successful, and this task has not started when cancel is |
708 |
* called, execution of this task is suppressed, {@link |
709 |
* #isCancelled} will report true, and {@link #join} will result |
710 |
* in a {@code CancellationException} being thrown. |
711 |
* |
712 |
* <p>This method may be overridden in subclasses, but if so, must |
713 |
* still ensure that these minimal properties hold. In particular, |
714 |
* the {@code cancel} method itself must not throw exceptions. |
715 |
* |
716 |
* <p>This method is designed to be invoked by <em>other</em> |
717 |
* tasks. To terminate the current task, you can just return or |
718 |
* throw an unchecked exception from its computation method, or |
719 |
* invoke {@link #completeExceptionally}. |
720 |
* |
721 |
* @param mayInterruptIfRunning this value is ignored in the |
722 |
* default implementation because tasks are not |
723 |
* cancelled via interruption |
724 |
* |
725 |
* @return {@code true} if this task is now cancelled |
726 |
*/ |
727 |
public boolean cancel(boolean mayInterruptIfRunning) { |
728 |
setCompletion(CANCELLED); |
729 |
return (status & COMPLETION_MASK) == CANCELLED; |
730 |
} |
731 |
|
732 |
public final boolean isDone() { |
733 |
return status < 0; |
734 |
} |
735 |
|
736 |
public final boolean isCancelled() { |
737 |
return (status & COMPLETION_MASK) == CANCELLED; |
738 |
} |
739 |
|
740 |
/** |
741 |
* Returns {@code true} if this task threw an exception or was cancelled. |
742 |
* |
743 |
* @return {@code true} if this task threw an exception or was cancelled |
744 |
*/ |
745 |
public final boolean isCompletedAbnormally() { |
746 |
return (status & COMPLETION_MASK) < NORMAL; |
747 |
} |
748 |
|
749 |
/** |
750 |
* Returns {@code true} if this task completed without throwing an |
751 |
* exception and was not cancelled. |
752 |
* |
753 |
* @return {@code true} if this task completed without throwing an |
754 |
* exception and was not cancelled |
755 |
*/ |
756 |
public final boolean isCompletedNormally() { |
757 |
return (status & COMPLETION_MASK) == NORMAL; |
758 |
} |
759 |
|
760 |
/** |
761 |
* Returns the exception thrown by the base computation, or a |
762 |
* {@code CancellationException} if cancelled, or {@code null} if |
763 |
* none or if the method has not yet completed. |
764 |
* |
765 |
* @return the exception, or {@code null} if none |
766 |
*/ |
767 |
public final Throwable getException() { |
768 |
int s = status & COMPLETION_MASK; |
769 |
return ((s >= NORMAL) ? null : |
770 |
(s == CANCELLED) ? new CancellationException() : |
771 |
exceptionMap.get(this)); |
772 |
} |
773 |
|
774 |
/** |
775 |
* Completes this task abnormally, and if not already aborted or |
776 |
* cancelled, causes it to throw the given exception upon |
777 |
* {@code join} and related operations. This method may be used |
778 |
* to induce exceptions in asynchronous tasks, or to force |
779 |
* completion of tasks that would not otherwise complete. Its use |
780 |
* in other situations is discouraged. This method is |
781 |
* overridable, but overridden versions must invoke {@code super} |
782 |
* implementation to maintain guarantees. |
783 |
* |
784 |
* @param ex the exception to throw. If this exception is |
785 |
* not a RuntimeException or Error, the actual exception thrown |
786 |
* will be a RuntimeException with cause ex. |
787 |
*/ |
788 |
public void completeExceptionally(Throwable ex) { |
789 |
setDoneExceptionally((ex instanceof RuntimeException) || |
790 |
(ex instanceof Error) ? ex : |
791 |
new RuntimeException(ex)); |
792 |
} |
793 |
|
794 |
/** |
795 |
* Completes this task, and if not already aborted or cancelled, |
796 |
* returning a {@code null} result upon {@code join} and related |
797 |
* operations. This method may be used to provide results for |
798 |
* asynchronous tasks, or to provide alternative handling for |
799 |
* tasks that would not otherwise complete normally. Its use in |
800 |
* other situations is discouraged. This method is |
801 |
* overridable, but overridden versions must invoke {@code super} |
802 |
* implementation to maintain guarantees. |
803 |
* |
804 |
* @param value the result value for this task |
805 |
*/ |
806 |
public void complete(V value) { |
807 |
try { |
808 |
setRawResult(value); |
809 |
} catch (Throwable rex) { |
810 |
setDoneExceptionally(rex); |
811 |
return; |
812 |
} |
813 |
setNormalCompletion(); |
814 |
} |
815 |
|
816 |
public final V get() throws InterruptedException, ExecutionException { |
817 |
ForkJoinWorkerThread w = getWorker(); |
818 |
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
819 |
awaitDone(w, true); |
820 |
return reportFutureResult(); |
821 |
} |
822 |
|
823 |
public final V get(long timeout, TimeUnit unit) |
824 |
throws InterruptedException, ExecutionException, TimeoutException { |
825 |
long nanos = unit.toNanos(timeout); |
826 |
ForkJoinWorkerThread w = getWorker(); |
827 |
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
828 |
awaitDone(w, nanos); |
829 |
return reportTimedFutureResult(); |
830 |
} |
831 |
|
832 |
/** |
833 |
* Possibly executes other tasks until this task {@link #isDone is |
834 |
* done}, then returns the result of the computation. This method |
835 |
* may be more efficient than {@code join}, but is only applicable |
836 |
* when there are no potential dependencies between continuation |
837 |
* of the current task and that of any other task that might be |
838 |
* executed while helping. (This usually holds for pure |
839 |
* divide-and-conquer tasks). |
840 |
* |
841 |
* <p>This method may be invoked only from within {@code |
842 |
* ForkJoinTask} computations (as may be determined using method |
843 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
844 |
* result in exceptions or errors, possibly including {@code |
845 |
* ClassCastException}. |
846 |
* |
847 |
* @return the computed result |
848 |
*/ |
849 |
public final V helpJoin() { |
850 |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread(); |
851 |
if (status < 0 || !w.unpushTask(this) || !tryExec()) |
852 |
reportException(busyJoin(w)); |
853 |
return getRawResult(); |
854 |
} |
855 |
|
856 |
/** |
857 |
* Possibly executes other tasks until this task {@link #isDone is |
858 |
* done}. This method may be useful when processing collections |
859 |
* of tasks when some have been cancelled or otherwise known to |
860 |
* have aborted. |
861 |
* |
862 |
* <p>This method may be invoked only from within {@code |
863 |
* ForkJoinTask} computations (as may be determined using method |
864 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
865 |
* result in exceptions or errors, possibly including {@code |
866 |
* ClassCastException}. |
867 |
*/ |
868 |
public final void quietlyHelpJoin() { |
869 |
if (status >= 0) { |
870 |
ForkJoinWorkerThread w = |
871 |
(ForkJoinWorkerThread) Thread.currentThread(); |
872 |
if (!w.unpushTask(this) || !tryQuietlyInvoke()) |
873 |
busyJoin(w); |
874 |
} |
875 |
} |
876 |
|
877 |
/** |
878 |
* Joins this task, without returning its result or throwing an |
879 |
* exception. This method may be useful when processing |
880 |
* collections of tasks when some have been cancelled or otherwise |
881 |
* known to have aborted. |
882 |
*/ |
883 |
public final void quietlyJoin() { |
884 |
if (status >= 0) { |
885 |
ForkJoinWorkerThread w = getWorker(); |
886 |
if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke()) |
887 |
awaitDone(w, true); |
888 |
} |
889 |
} |
890 |
|
891 |
/** |
892 |
* Commences performing this task and awaits its completion if |
893 |
* necessary, 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 quietlyInvoke() { |
899 |
if (status >= 0 && !tryQuietlyInvoke()) |
900 |
quietlyJoin(); |
901 |
} |
902 |
|
903 |
/** |
904 |
* Possibly executes tasks until the pool hosting the current task |
905 |
* {@link ForkJoinPool#isQuiescent is quiescent}. This method may |
906 |
* be of use in designs in which many tasks are forked, but none |
907 |
* are explicitly joined, instead executing them until all are |
908 |
* processed. |
909 |
* |
910 |
* <p>This method may be invoked only from within {@code |
911 |
* ForkJoinTask} computations (as may be determined using method |
912 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
913 |
* result in exceptions or errors, possibly including {@code |
914 |
* ClassCastException}. |
915 |
*/ |
916 |
public static void helpQuiesce() { |
917 |
((ForkJoinWorkerThread) Thread.currentThread()) |
918 |
.helpQuiescePool(); |
919 |
} |
920 |
|
921 |
/** |
922 |
* Resets the internal bookkeeping state of this task, allowing a |
923 |
* subsequent {@code fork}. This method allows repeated reuse of |
924 |
* this task, but only if reuse occurs when this task has either |
925 |
* never been forked, or has been forked, then completed and all |
926 |
* outstanding joins of this task have also completed. Effects |
927 |
* under any other usage conditions are not guaranteed. |
928 |
* This method may be useful when executing |
929 |
* pre-constructed trees of subtasks in loops. |
930 |
*/ |
931 |
public void reinitialize() { |
932 |
if ((status & COMPLETION_MASK) == EXCEPTIONAL) |
933 |
exceptionMap.remove(this); |
934 |
status = 0; |
935 |
} |
936 |
|
937 |
/** |
938 |
* Returns the pool hosting the current task execution, or null |
939 |
* if this task is executing outside of any ForkJoinPool. |
940 |
* |
941 |
* @see #inForkJoinPool |
942 |
* @return the pool, or {@code null} if none |
943 |
*/ |
944 |
public static ForkJoinPool getPool() { |
945 |
Thread t = Thread.currentThread(); |
946 |
return (t instanceof ForkJoinWorkerThread) ? |
947 |
((ForkJoinWorkerThread) t).pool : null; |
948 |
} |
949 |
|
950 |
/** |
951 |
* Returns {@code true} if the current thread is executing as a |
952 |
* ForkJoinPool computation. |
953 |
* |
954 |
* @return {@code true} if the current thread is executing as a |
955 |
* ForkJoinPool computation, or false otherwise |
956 |
*/ |
957 |
public static boolean inForkJoinPool() { |
958 |
return Thread.currentThread() instanceof ForkJoinWorkerThread; |
959 |
} |
960 |
|
961 |
/** |
962 |
* Tries to unschedule this task for execution. This method will |
963 |
* typically succeed if this task is the most recently forked task |
964 |
* by the current thread, and has not commenced executing in |
965 |
* another thread. This method may be useful when arranging |
966 |
* alternative local processing of tasks that could have been, but |
967 |
* were not, stolen. |
968 |
* |
969 |
* <p>This method may be invoked only from within {@code |
970 |
* ForkJoinTask} computations (as may be determined using method |
971 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
972 |
* result in exceptions or errors, possibly including {@code |
973 |
* ClassCastException}. |
974 |
* |
975 |
* @return {@code true} if unforked |
976 |
*/ |
977 |
public boolean tryUnfork() { |
978 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
979 |
.unpushTask(this); |
980 |
} |
981 |
|
982 |
/** |
983 |
* Returns an estimate of the number of tasks that have been |
984 |
* forked by the current worker thread but not yet executed. This |
985 |
* value may be useful for heuristic decisions about whether to |
986 |
* fork other tasks. |
987 |
* |
988 |
* <p>This method may be invoked only from within {@code |
989 |
* ForkJoinTask} computations (as may be determined using method |
990 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
991 |
* result in exceptions or errors, possibly including {@code |
992 |
* ClassCastException}. |
993 |
* |
994 |
* @return the number of tasks |
995 |
*/ |
996 |
public static int getQueuedTaskCount() { |
997 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
998 |
.getQueueSize(); |
999 |
} |
1000 |
|
1001 |
/** |
1002 |
* Returns an estimate of how many more locally queued tasks are |
1003 |
* held by the current worker thread than there are other worker |
1004 |
* threads that might steal them. This value may be useful for |
1005 |
* heuristic decisions about whether to fork other tasks. In many |
1006 |
* usages of ForkJoinTasks, at steady state, each worker should |
1007 |
* aim to maintain a small constant surplus (for example, 3) of |
1008 |
* tasks, and to process computations locally if this threshold is |
1009 |
* exceeded. |
1010 |
* |
1011 |
* <p>This method may be invoked only from within {@code |
1012 |
* ForkJoinTask} computations (as may be determined using method |
1013 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1014 |
* result in exceptions or errors, possibly including {@code |
1015 |
* ClassCastException}. |
1016 |
* |
1017 |
* @return the surplus number of tasks, which may be negative |
1018 |
*/ |
1019 |
public static int getSurplusQueuedTaskCount() { |
1020 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1021 |
.getEstimatedSurplusTaskCount(); |
1022 |
} |
1023 |
|
1024 |
// Extension methods |
1025 |
|
1026 |
/** |
1027 |
* Returns the result that would be returned by {@link #join}, even |
1028 |
* if this task completed abnormally, or {@code null} if this task |
1029 |
* is not known to have been completed. This method is designed |
1030 |
* to aid debugging, as well as to support extensions. Its use in |
1031 |
* any other context is discouraged. |
1032 |
* |
1033 |
* @return the result, or {@code null} if not completed |
1034 |
*/ |
1035 |
public abstract V getRawResult(); |
1036 |
|
1037 |
/** |
1038 |
* Forces the given value to be returned as a result. This method |
1039 |
* is designed to support extensions, and should not in general be |
1040 |
* called otherwise. |
1041 |
* |
1042 |
* @param value the value |
1043 |
*/ |
1044 |
protected abstract void setRawResult(V value); |
1045 |
|
1046 |
/** |
1047 |
* Immediately performs the base action of this task. This method |
1048 |
* is designed to support extensions, and should not in general be |
1049 |
* called otherwise. The return value controls whether this task |
1050 |
* is considered to be done normally. It may return false in |
1051 |
* asynchronous actions that require explicit invocations of |
1052 |
* {@link #complete} to become joinable. It may also throw an |
1053 |
* (unchecked) exception to indicate abnormal exit. |
1054 |
* |
1055 |
* @return {@code true} if completed normally |
1056 |
*/ |
1057 |
protected abstract boolean exec(); |
1058 |
|
1059 |
/** |
1060 |
* Returns, but does not unschedule or execute, a task queued by |
1061 |
* the current thread but not yet executed, if one is immediately |
1062 |
* available. There is no guarantee that this task will actually |
1063 |
* be polled or executed next. Conversely, this method may return |
1064 |
* null even if a task exists but cannot be accessed without |
1065 |
* contention with other threads. This method is designed |
1066 |
* primarily to support extensions, and is unlikely to be useful |
1067 |
* otherwise. |
1068 |
* |
1069 |
* <p>This method may be invoked only from within {@code |
1070 |
* ForkJoinTask} computations (as may be determined using method |
1071 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1072 |
* result in exceptions or errors, possibly including {@code |
1073 |
* ClassCastException}. |
1074 |
* |
1075 |
* @return the next task, or {@code null} if none are available |
1076 |
*/ |
1077 |
protected static ForkJoinTask<?> peekNextLocalTask() { |
1078 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1079 |
.peekTask(); |
1080 |
} |
1081 |
|
1082 |
/** |
1083 |
* Unschedules and returns, without executing, the next task |
1084 |
* queued by the current thread but not yet executed. This method |
1085 |
* is designed primarily to support extensions, and is unlikely to |
1086 |
* be useful otherwise. |
1087 |
* |
1088 |
* <p>This method may be invoked only from within {@code |
1089 |
* ForkJoinTask} computations (as may be determined using method |
1090 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1091 |
* result in exceptions or errors, possibly including {@code |
1092 |
* ClassCastException}. |
1093 |
* |
1094 |
* @return the next task, or {@code null} if none are available |
1095 |
*/ |
1096 |
protected static ForkJoinTask<?> pollNextLocalTask() { |
1097 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1098 |
.pollLocalTask(); |
1099 |
} |
1100 |
|
1101 |
/** |
1102 |
* Unschedules and returns, without executing, the next task |
1103 |
* queued by the current thread but not yet executed, if one is |
1104 |
* available, or if not available, a task that was forked by some |
1105 |
* other thread, if available. Availability may be transient, so a |
1106 |
* {@code null} result does not necessarily imply quiescence |
1107 |
* of the pool this task is operating in. This method is designed |
1108 |
* primarily to support extensions, and is unlikely to be useful |
1109 |
* otherwise. |
1110 |
* |
1111 |
* <p>This method may be invoked only from within {@code |
1112 |
* ForkJoinTask} computations (as may be determined using method |
1113 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1114 |
* result in exceptions or errors, possibly including {@code |
1115 |
* ClassCastException}. |
1116 |
* |
1117 |
* @return a task, or {@code null} if none are available |
1118 |
*/ |
1119 |
protected static ForkJoinTask<?> pollTask() { |
1120 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1121 |
.pollTask(); |
1122 |
} |
1123 |
|
1124 |
/** |
1125 |
* Adaptor for Runnables. This implements RunnableFuture |
1126 |
* to be compliant with AbstractExecutorService constraints |
1127 |
* when used in ForkJoinPool. |
1128 |
*/ |
1129 |
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
1130 |
implements RunnableFuture<T> { |
1131 |
final Runnable runnable; |
1132 |
final T resultOnCompletion; |
1133 |
T result; |
1134 |
AdaptedRunnable(Runnable runnable, T result) { |
1135 |
if (runnable == null) throw new NullPointerException(); |
1136 |
this.runnable = runnable; |
1137 |
this.resultOnCompletion = result; |
1138 |
} |
1139 |
public T getRawResult() { return result; } |
1140 |
public void setRawResult(T v) { result = v; } |
1141 |
public boolean exec() { |
1142 |
runnable.run(); |
1143 |
result = resultOnCompletion; |
1144 |
return true; |
1145 |
} |
1146 |
public void run() { invoke(); } |
1147 |
private static final long serialVersionUID = 5232453952276885070L; |
1148 |
} |
1149 |
|
1150 |
/** |
1151 |
* Adaptor for Callables |
1152 |
*/ |
1153 |
static final class AdaptedCallable<T> extends ForkJoinTask<T> |
1154 |
implements RunnableFuture<T> { |
1155 |
final Callable<? extends T> callable; |
1156 |
T result; |
1157 |
AdaptedCallable(Callable<? extends T> callable) { |
1158 |
if (callable == null) throw new NullPointerException(); |
1159 |
this.callable = callable; |
1160 |
} |
1161 |
public T getRawResult() { return result; } |
1162 |
public void setRawResult(T v) { result = v; } |
1163 |
public boolean exec() { |
1164 |
try { |
1165 |
result = callable.call(); |
1166 |
return true; |
1167 |
} catch (Error err) { |
1168 |
throw err; |
1169 |
} catch (RuntimeException rex) { |
1170 |
throw rex; |
1171 |
} catch (Exception ex) { |
1172 |
throw new RuntimeException(ex); |
1173 |
} |
1174 |
} |
1175 |
public void run() { invoke(); } |
1176 |
private static final long serialVersionUID = 2838392045355241008L; |
1177 |
} |
1178 |
|
1179 |
/** |
1180 |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1181 |
* method of the given {@code Runnable} as its action, and returns |
1182 |
* a null result upon {@link #join}. |
1183 |
* |
1184 |
* @param runnable the runnable action |
1185 |
* @return the task |
1186 |
*/ |
1187 |
public static ForkJoinTask<?> adapt(Runnable runnable) { |
1188 |
return new AdaptedRunnable<Void>(runnable, null); |
1189 |
} |
1190 |
|
1191 |
/** |
1192 |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1193 |
* method of the given {@code Runnable} as its action, and returns |
1194 |
* the given result upon {@link #join}. |
1195 |
* |
1196 |
* @param runnable the runnable action |
1197 |
* @param result the result upon completion |
1198 |
* @return the task |
1199 |
*/ |
1200 |
public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) { |
1201 |
return new AdaptedRunnable<T>(runnable, result); |
1202 |
} |
1203 |
|
1204 |
/** |
1205 |
* Returns a new {@code ForkJoinTask} that performs the {@code call} |
1206 |
* method of the given {@code Callable} as its action, and returns |
1207 |
* its result upon {@link #join}, translating any checked exceptions |
1208 |
* encountered into {@code RuntimeException}. |
1209 |
* |
1210 |
* @param callable the callable action |
1211 |
* @return the task |
1212 |
*/ |
1213 |
public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) { |
1214 |
return new AdaptedCallable<T>(callable); |
1215 |
} |
1216 |
|
1217 |
// Serialization support |
1218 |
|
1219 |
private static final long serialVersionUID = -7721805057305804111L; |
1220 |
|
1221 |
/** |
1222 |
* Save the state to a stream. |
1223 |
* |
1224 |
* @serialData the current run status and the exception thrown |
1225 |
* during execution, or {@code null} if none |
1226 |
* @param s the stream |
1227 |
*/ |
1228 |
private void writeObject(java.io.ObjectOutputStream s) |
1229 |
throws java.io.IOException { |
1230 |
s.defaultWriteObject(); |
1231 |
s.writeObject(getException()); |
1232 |
} |
1233 |
|
1234 |
/** |
1235 |
* Reconstitute the instance from a stream. |
1236 |
* |
1237 |
* @param s the stream |
1238 |
*/ |
1239 |
private void readObject(java.io.ObjectInputStream s) |
1240 |
throws java.io.IOException, ClassNotFoundException { |
1241 |
s.defaultReadObject(); |
1242 |
status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts |
1243 |
status |= EXTERNAL_SIGNAL; // conservatively set external signal |
1244 |
Object ex = s.readObject(); |
1245 |
if (ex != null) |
1246 |
setDoneExceptionally((Throwable) ex); |
1247 |
} |
1248 |
|
1249 |
// Unsafe mechanics |
1250 |
|
1251 |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1252 |
private static final long statusOffset = |
1253 |
objectFieldOffset("status", ForkJoinTask.class); |
1254 |
|
1255 |
private static long objectFieldOffset(String field, Class<?> klazz) { |
1256 |
try { |
1257 |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1258 |
} catch (NoSuchFieldException e) { |
1259 |
// Convert Exception to corresponding Error |
1260 |
NoSuchFieldError error = new NoSuchFieldError(field); |
1261 |
error.initCause(e); |
1262 |
throw error; |
1263 |
} |
1264 |
} |
1265 |
|
1266 |
/** |
1267 |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
1268 |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
1269 |
* into a jdk. |
1270 |
* |
1271 |
* @return a sun.misc.Unsafe |
1272 |
*/ |
1273 |
private static sun.misc.Unsafe getUnsafe() { |
1274 |
try { |
1275 |
return sun.misc.Unsafe.getUnsafe(); |
1276 |
} catch (SecurityException se) { |
1277 |
try { |
1278 |
return java.security.AccessController.doPrivileged |
1279 |
(new java.security |
1280 |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1281 |
public sun.misc.Unsafe run() throws Exception { |
1282 |
java.lang.reflect.Field f = sun.misc |
1283 |
.Unsafe.class.getDeclaredField("theUnsafe"); |
1284 |
f.setAccessible(true); |
1285 |
return (sun.misc.Unsafe) f.get(null); |
1286 |
}}); |
1287 |
} catch (java.security.PrivilegedActionException e) { |
1288 |
throw new RuntimeException("Could not initialize intrinsics", |
1289 |
e.getCause()); |
1290 |
} |
1291 |
} |
1292 |
} |
1293 |
} |