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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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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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package jsr166y; |
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import java.util.concurrent.*; |
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import java.io.Serializable; |
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import java.util.Collection; |
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import java.util.Collections; |
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import java.util.List; |
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import java.util.RandomAccess; |
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import java.util.Map; |
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import java.util.WeakHashMap; |
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import java.lang.ref.WeakReference; |
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import java.lang.ref.ReferenceQueue; |
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import java.util.concurrent.Callable; |
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import java.util.concurrent.CancellationException; |
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import java.util.concurrent.ExecutionException; |
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import java.util.concurrent.Future; |
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import java.util.concurrent.RejectedExecutionException; |
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import java.util.concurrent.RunnableFuture; |
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import java.util.concurrent.TimeUnit; |
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import java.util.concurrent.TimeoutException; |
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import java.util.concurrent.locks.ReentrantLock; |
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import java.lang.reflect.Constructor; |
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/** |
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* Abstract base class for tasks that run within a {@link ForkJoinPool}. |
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* start other subtasks. As indicated by the name of this class, |
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* many programs using {@code ForkJoinTask} employ only methods |
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* {@link #fork} and {@link #join}, or derivatives such as {@link |
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* #invokeAll}. However, this class also provides a number of other |
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* methods that can come into play in advanced usages, as well as |
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* extension mechanics that allow support of new forms of fork/join |
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* processing. |
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* #invokeAll(ForkJoinTask...) invokeAll}. However, this class also |
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* provides a number of other methods that can come into play in |
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* advanced usages, as well as extension mechanics that allow |
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* support of new forms of fork/join processing. |
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* |
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* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}. |
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* The efficiency of {@code ForkJoinTask}s stems from a set of |
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* 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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* reflecting their main use as computational tasks calculating pure |
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* functions or operating on purely isolated objects. The primary |
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* 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 {@link RejectedExecutionException} stemming |
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* from internal resource exhaustion, such as failure to allocate |
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* internal task queues. |
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* ideally avoid {@code synchronized} methods or blocks, and should |
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* minimize other blocking synchronization apart from joining other |
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* tasks or using synchronizers such as Phasers that are advertised to |
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* cooperate with fork/join scheduling. Subdividable tasks should also |
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* not perform blocking IO, and should ideally access variables that |
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* are completely independent of those accessed by other running |
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* tasks. These guidelines are loosely enforced by not permitting |
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* checked exceptions such as {@code IOExceptions} to be |
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* thrown. However, computations may still encounter unchecked |
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* exceptions, that are rethrown to callers attempting to join |
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* them. These exceptions may additionally include {@link |
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* RejectedExecutionException} stemming from internal resource |
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* exhaustion, such as failure to allocate internal task |
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* queues. Rethrown exceptions behave in the same way as regular |
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* exceptions, but, when possible, contain stack traces (as displayed |
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* for example using {@code ex.printStackTrace()}) of both the thread |
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* that initiated the computation as well as the thread actually |
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* encountering the exception; minimally only the latter. |
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* |
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* <p>It is possible to define and use ForkJoinTasks that may block, |
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* but doing do requires three further considerations: (1) Completion |
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* of few if any <em>other</em> tasks should be dependent on a task |
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* that blocks on external synchronization or IO. Event-style async |
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* tasks that are never joined often fall into this category. (2) To |
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* minimize resource impact, tasks should be small; ideally performing |
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* only the (possibly) blocking action. (3) Unless the {@link |
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* ForkJoinPool.ManagedBlocker} API is used, or the number of possibly |
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* blocked tasks is known to be less than the pool's {@link |
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* ForkJoinPool#getParallelism} level, the pool cannot guarantee that |
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* enough threads will be available to ensure progress or good |
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* performance. |
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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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* 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>In the most typical usages, a fork-join pair act like a a call |
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* (fork) and return (join) from a parallel recursive function. As is |
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* the case with other forms of recursive calls, returns (joins) |
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* should be performed innermost-first. For example, {@code a.fork(); |
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* b.fork(); b.join(); a.join();} is likely to be substantially more |
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* efficient than joining {@code a} before {@code b}. |
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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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* result in exceptions or errors, possibly including |
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* {@code ClassCastException}. |
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* |
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* <p>Method {@link #join} and its variants are appropriate for use |
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* only when completion dependencies are acyclic; that is, the |
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* parallel computation can be described as a directed acyclic graph |
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* (DAG). Otherwise, executions may encounter a form of deadlock as |
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* tasks cyclically wait for each other. However, this framework |
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* supports other methods and techniques (for example the use of |
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* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that |
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* may be of use in constructing custom subclasses for problems that |
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* are not statically structured as DAGs. To support such usages a |
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* ForkJoinTask may be atomically <em>marked</em> using {@link |
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* #markForkJoinTask} and checked for marking using {@link |
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* #isMarkedForkJoinTask}. The ForkJoinTask implementation does not |
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* use these {@code protected} methods or marks for any purpose, but |
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* they may be of use in the construction of specialized subclasses. |
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* For example, parallel graph traversals can use the supplied methods |
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* to avoid revisiting nodes/tasks that have already been |
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* processed. Also, completion based designs can use them to record |
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* that one subtask has completed. (Method names for marking are bulky |
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* in part to encourage definition of methods that reflect their usage |
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* patterns.) |
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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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* computation. Large tasks should be split into smaller subtasks, |
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* usually via recursive decomposition. As a very rough rule of thumb, |
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* a task should perform more than 100 and less than 10000 basic |
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* computational steps. If tasks are too big, then parallelism cannot |
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* improve throughput. If too small, then memory and internal task |
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* maintenance overhead may overwhelm processing. |
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* computational steps, and should avoid indefinite looping. If tasks |
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* are too big, then parallelism cannot improve throughput. If too |
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* small, then memory and internal task maintenance overhead may |
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* overwhelm processing. |
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* |
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* <p>This class provides {@code adapt} methods for {@link Runnable} |
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* and {@link Callable}, that may be of use when mixing execution of |
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* See the internal documentation of class ForkJoinPool for a |
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* general implementation overview. ForkJoinTasks are mainly |
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* responsible for maintaining their "status" field amidst relays |
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* to methods in ForkJoinWorkerThread and ForkJoinPool. The |
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* methods of this class are more-or-less layered into (1) basic |
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* status maintenance (2) execution and awaiting completion (3) |
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* user-level methods that additionally report results. This is |
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* sometimes hard to see because this file orders exported methods |
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* in a way that flows well in javadocs. In particular, most |
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* join mechanics are in method quietlyJoin, below. |
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* to methods in ForkJoinWorkerThread and ForkJoinPool. |
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* |
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* The methods of this class are more-or-less layered into |
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* (1) basic status maintenance |
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* (2) execution and awaiting completion |
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* (3) user-level methods that additionally report results. |
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* This is sometimes hard to see because this file orders exported |
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* methods in a way that flows well in javadocs. |
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*/ |
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|
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/** |
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* The number of times to try to help join a task without any |
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* apparent progress before giving up and blocking. The value is |
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* arbitrary but should be large enough to cope with transient |
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* stalls (due to GC etc) that can cause helping methods not to be |
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* able to proceed because other workers have not progressed to |
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* the point where subtasks can be found or taken. |
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*/ |
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private static final int HELP_RETRIES = 32; |
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/* |
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* The status field holds run control status bits packed into a |
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* single int to minimize footprint and to ensure atomicity (via |
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* CAS). Status is initially zero, and takes on nonnegative |
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* values until completed, upon which status holds value |
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* NORMAL. CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking |
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* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking |
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* waits by other threads have the SIGNAL bit set. Completion of |
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* a stolen task with SIGNAL set awakens any waiters via |
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* notifyAll. Even though suboptimal for some purposes, we use |
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/** The run status of this task */ |
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volatile int status; // accessed directly by pool and workers |
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static final int NORMAL = 0xfffffffc; // negative with low 2 bits 0 |
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static final int CANCELLED = 0xfffffff8; // must be < NORMAL |
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static final int EXCEPTIONAL = 0xfffffff4; // must be < CANCELLED |
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static final int SIGNAL = 0x00000001; |
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static final int MARKED = 0x00000002; |
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private static final int NORMAL = -1; |
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private static final int CANCELLED = -2; |
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private static final int EXCEPTIONAL = -3; |
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private static final int SIGNAL = 1; |
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/** |
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* Marks completion and wakes up threads waiting to join this |
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* task, also clearing signal request bits. A specialization for |
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* NORMAL completion is in method doExec |
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* |
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* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
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* @return completion status on exit |
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*/ |
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private int setCompletion(int completion) { |
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for (int s;;) { |
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if ((s = status) < 0) |
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return s; |
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if (U.compareAndSwapInt(this, STATUS, s, (s & ~SIGNAL)|completion)) { |
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if ((s & SIGNAL) != 0) |
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synchronized (this) { notifyAll(); } |
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return completion; |
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} |
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} |
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} |
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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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* Primary execution method for stolen tasks. Unless done, calls |
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* exec and records status if completed, but doesn't wait for |
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* completion otherwise. |
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* |
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* @return status on exit from this method |
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*/ |
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final int doExec() { |
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int s; boolean completed; |
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if ((s = status) >= 0) { |
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try { |
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completed = exec(); |
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} catch (Throwable rex) { |
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return setExceptionalCompletion(rex); |
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} |
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while ((s = status) >= 0 && completed) { |
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if (U.compareAndSwapInt(this, STATUS, s, (s & ~SIGNAL)|NORMAL)) { |
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if ((s & SIGNAL) != 0) |
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synchronized (this) { notifyAll(); } |
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return NORMAL; |
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} |
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} |
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} |
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return s; |
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} |
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|
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/** |
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* Blocks a non-worker-thread until completion. |
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* @return status upon completion |
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*/ |
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private int externalAwaitDone() { |
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int s; |
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if ((s = status) >= 0) { |
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boolean interrupted = false; |
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synchronized (this) { |
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while ((s = status) >= 0) { |
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if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
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try { |
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wait(); |
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} catch (InterruptedException ie) { |
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interrupted = true; |
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} |
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} |
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} |
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} |
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if (interrupted) |
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Thread.currentThread().interrupt(); |
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} |
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return s; |
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} |
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|
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/** |
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* Blocks a non-worker-thread until completion or interruption or timeout. |
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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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private int externalInterruptibleAwaitDone(long millis) |
310 |
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throws InterruptedException { |
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int s; |
312 |
> |
if (Thread.interrupted()) |
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throw new InterruptedException(); |
314 |
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if ((s = status) >= 0) { |
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synchronized (this) { |
316 |
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while ((s = status) >= 0) { |
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if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
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wait(millis); |
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if (millis > 0L) |
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break; |
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} |
322 |
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} |
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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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// Maintaining 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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* also clearing signal request bits. |
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* Implementation for join, get, quietlyJoin. Directly handles |
331 |
> |
* only cases of already-completed, external wait, and |
332 |
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* unfork+exec. Others are relayed to awaitJoin. |
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* |
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* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
334 |
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* @return status upon completion |
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*/ |
336 |
< |
private void setCompletion(int completion) { |
336 |
> |
private int doJoin() { |
337 |
> |
int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w; |
338 |
> |
if ((s = status) >= 0) { |
339 |
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if (!((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) |
340 |
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s = externalAwaitDone(); |
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else if (!(w = (wt = (ForkJoinWorkerThread)t).workQueue). |
342 |
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tryUnpush(this) || (s = doExec()) >= 0) |
343 |
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s = awaitJoin(w, wt.pool); |
344 |
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} |
345 |
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return s; |
346 |
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} |
347 |
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|
348 |
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/** |
349 |
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* Helps and/or blocks until joined. |
350 |
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* |
351 |
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* @param w the joiner |
352 |
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* @param p the pool |
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* @return status upon completion |
354 |
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*/ |
355 |
> |
private int awaitJoin(ForkJoinPool.WorkQueue w, ForkJoinPool p) { |
356 |
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int s; |
357 |
< |
while ((s = status) >= 0) { |
358 |
< |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) { |
359 |
< |
if (s != 0) |
360 |
< |
synchronized (this) { notifyAll(); } |
357 |
> |
ForkJoinTask<?> prevJoin = w.currentJoin; |
358 |
> |
w.currentJoin = this; |
359 |
> |
for (int k = HELP_RETRIES; (s = status) >= 0;) { |
360 |
> |
if ((w.queueSize() > 0) ? |
361 |
> |
w.tryRemoveAndExec(this) : // self-help |
362 |
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p.tryHelpStealer(w, this)) // help process tasks |
363 |
> |
k = HELP_RETRIES; // reset if made progress |
364 |
> |
else if ((s = status) < 0) // recheck |
365 |
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break; |
366 |
+ |
else if (--k > 0) { |
367 |
+ |
if ((k & 3) == 1) |
368 |
+ |
Thread.yield(); // occasionally yield |
369 |
+ |
} |
370 |
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else if (k == 0) |
371 |
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p.tryPollForAndExec(w, this); // uncommon self-help case |
372 |
+ |
else if (p.tryCompensate()) { // true if can block |
373 |
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try { |
374 |
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int ss = status; |
375 |
+ |
if (ss >= 0 && // assert need signal |
376 |
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U.compareAndSwapInt(this, STATUS, ss, ss | SIGNAL)) { |
377 |
+ |
synchronized (this) { |
378 |
+ |
if (status >= 0) // block |
379 |
+ |
wait(); |
380 |
+ |
} |
381 |
+ |
} |
382 |
+ |
} catch (InterruptedException ignore) { |
383 |
+ |
} finally { |
384 |
+ |
p.incrementActiveCount(); // re-activate |
385 |
+ |
} |
386 |
|
} |
387 |
|
} |
388 |
+ |
w.currentJoin = prevJoin; |
389 |
+ |
return s; |
390 |
+ |
} |
391 |
+ |
|
392 |
+ |
/** |
393 |
+ |
* Implementation for invoke, quietlyInvoke. |
394 |
+ |
* |
395 |
+ |
* @return status upon completion |
396 |
+ |
*/ |
397 |
+ |
private int doInvoke() { |
398 |
+ |
int s; |
399 |
+ |
if ((s = doExec()) < 0) |
400 |
+ |
return s; |
401 |
+ |
else |
402 |
+ |
return doJoin(); |
403 |
+ |
} |
404 |
+ |
|
405 |
+ |
// Exception table support |
406 |
+ |
|
407 |
+ |
/** |
408 |
+ |
* Table of exceptions thrown by tasks, to enable reporting by |
409 |
+ |
* callers. Because exceptions are rare, we don't directly keep |
410 |
+ |
* them with task objects, but instead use a weak ref table. Note |
411 |
+ |
* that cancellation exceptions don't appear in the table, but are |
412 |
+ |
* instead recorded as status values. |
413 |
+ |
* |
414 |
+ |
* Note: These statics are initialized below in static block. |
415 |
+ |
*/ |
416 |
+ |
private static final ExceptionNode[] exceptionTable; |
417 |
+ |
private static final ReentrantLock exceptionTableLock; |
418 |
+ |
private static final ReferenceQueue<Object> exceptionTableRefQueue; |
419 |
+ |
|
420 |
+ |
/** |
421 |
+ |
* Fixed capacity for exceptionTable. |
422 |
+ |
*/ |
423 |
+ |
private static final int EXCEPTION_MAP_CAPACITY = 32; |
424 |
+ |
|
425 |
+ |
/** |
426 |
+ |
* Key-value nodes for exception table. The chained hash table |
427 |
+ |
* uses identity comparisons, full locking, and weak references |
428 |
+ |
* for keys. The table has a fixed capacity because it only |
429 |
+ |
* maintains task exceptions long enough for joiners to access |
430 |
+ |
* them, so should never become very large for sustained |
431 |
+ |
* periods. However, since we do not know when the last joiner |
432 |
+ |
* completes, we must use weak references and expunge them. We do |
433 |
+ |
* so on each operation (hence full locking). Also, some thread in |
434 |
+ |
* any ForkJoinPool will call helpExpungeStaleExceptions when its |
435 |
+ |
* pool becomes isQuiescent. |
436 |
+ |
*/ |
437 |
+ |
static final class ExceptionNode extends WeakReference<ForkJoinTask<?>>{ |
438 |
+ |
final Throwable ex; |
439 |
+ |
ExceptionNode next; |
440 |
+ |
final long thrower; // use id not ref to avoid weak cycles |
441 |
+ |
ExceptionNode(ForkJoinTask<?> task, Throwable ex, ExceptionNode next) { |
442 |
+ |
super(task, exceptionTableRefQueue); |
443 |
+ |
this.ex = ex; |
444 |
+ |
this.next = next; |
445 |
+ |
this.thrower = Thread.currentThread().getId(); |
446 |
+ |
} |
447 |
|
} |
448 |
|
|
449 |
|
/** |
450 |
|
* Records exception and sets exceptional completion. |
451 |
< |
* |
451 |
> |
* |
452 |
|
* @return status on exit |
453 |
|
*/ |
454 |
< |
private void setExceptionalCompletion(Throwable rex) { |
455 |
< |
exceptionMap.put(this, rex); |
456 |
< |
setCompletion(EXCEPTIONAL); |
454 |
> |
private int setExceptionalCompletion(Throwable ex) { |
455 |
> |
int h = System.identityHashCode(this); |
456 |
> |
final ReentrantLock lock = exceptionTableLock; |
457 |
> |
lock.lock(); |
458 |
> |
try { |
459 |
> |
expungeStaleExceptions(); |
460 |
> |
ExceptionNode[] t = exceptionTable; |
461 |
> |
int i = h & (t.length - 1); |
462 |
> |
for (ExceptionNode e = t[i]; ; e = e.next) { |
463 |
> |
if (e == null) { |
464 |
> |
t[i] = new ExceptionNode(this, ex, t[i]); |
465 |
> |
break; |
466 |
> |
} |
467 |
> |
if (e.get() == this) // already present |
468 |
> |
break; |
469 |
> |
} |
470 |
> |
} finally { |
471 |
> |
lock.unlock(); |
472 |
> |
} |
473 |
> |
return setCompletion(EXCEPTIONAL); |
474 |
|
} |
475 |
|
|
476 |
|
/** |
477 |
< |
* Blocks a worker thread until completion. Called only by |
478 |
< |
* pool. Currently unused -- pool-based waits use timeout |
479 |
< |
* version below. |
477 |
> |
* Cancels, ignoring any exceptions thrown by cancel. Used during |
478 |
> |
* worker and pool shutdown. Cancel is spec'ed not to throw any |
479 |
> |
* exceptions, but if it does anyway, we have no recourse during |
480 |
> |
* shutdown, so guard against this case. |
481 |
|
*/ |
482 |
< |
final void internalAwaitDone() { |
483 |
< |
int s; // the odd construction reduces lock bias effects |
224 |
< |
while ((s = status) >= 0) { |
482 |
> |
static final void cancelIgnoringExceptions(ForkJoinTask<?> t) { |
483 |
> |
if (t != null && t.status >= 0) { |
484 |
|
try { |
485 |
< |
synchronized(this) { |
486 |
< |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL)) |
228 |
< |
wait(); |
229 |
< |
} |
230 |
< |
} catch (InterruptedException ie) { |
231 |
< |
cancelIfTerminating(); |
485 |
> |
t.cancel(false); |
486 |
> |
} catch (Throwable ignore) { |
487 |
|
} |
488 |
|
} |
489 |
|
} |
490 |
|
|
491 |
|
/** |
492 |
< |
* Blocks a worker thread until completed or timed out. Called |
238 |
< |
* only by pool. |
239 |
< |
* |
240 |
< |
* @return status on exit |
492 |
> |
* Removes exception node and clears status |
493 |
|
*/ |
494 |
< |
final int internalAwaitDone(long millis) { |
495 |
< |
int s; |
496 |
< |
if ((s = status) >= 0) { |
494 |
> |
private void clearExceptionalCompletion() { |
495 |
> |
int h = System.identityHashCode(this); |
496 |
> |
final ReentrantLock lock = exceptionTableLock; |
497 |
> |
lock.lock(); |
498 |
> |
try { |
499 |
> |
ExceptionNode[] t = exceptionTable; |
500 |
> |
int i = h & (t.length - 1); |
501 |
> |
ExceptionNode e = t[i]; |
502 |
> |
ExceptionNode pred = null; |
503 |
> |
while (e != null) { |
504 |
> |
ExceptionNode next = e.next; |
505 |
> |
if (e.get() == this) { |
506 |
> |
if (pred == null) |
507 |
> |
t[i] = next; |
508 |
> |
else |
509 |
> |
pred.next = next; |
510 |
> |
break; |
511 |
> |
} |
512 |
> |
pred = e; |
513 |
> |
e = next; |
514 |
> |
} |
515 |
> |
expungeStaleExceptions(); |
516 |
> |
status = 0; |
517 |
> |
} finally { |
518 |
> |
lock.unlock(); |
519 |
> |
} |
520 |
> |
} |
521 |
> |
|
522 |
> |
/** |
523 |
> |
* Returns a rethrowable exception for the given task, if |
524 |
> |
* available. To provide accurate stack traces, if the exception |
525 |
> |
* was not thrown by the current thread, we try to create a new |
526 |
> |
* exception of the same type as the one thrown, but with the |
527 |
> |
* recorded exception as its cause. If there is no such |
528 |
> |
* constructor, we instead try to use a no-arg constructor, |
529 |
> |
* followed by initCause, to the same effect. If none of these |
530 |
> |
* apply, or any fail due to other exceptions, we return the |
531 |
> |
* recorded exception, which is still correct, although it may |
532 |
> |
* contain a misleading stack trace. |
533 |
> |
* |
534 |
> |
* @return the exception, or null if none |
535 |
> |
*/ |
536 |
> |
private Throwable getThrowableException() { |
537 |
> |
if (status != EXCEPTIONAL) |
538 |
> |
return null; |
539 |
> |
int h = System.identityHashCode(this); |
540 |
> |
ExceptionNode e; |
541 |
> |
final ReentrantLock lock = exceptionTableLock; |
542 |
> |
lock.lock(); |
543 |
> |
try { |
544 |
> |
expungeStaleExceptions(); |
545 |
> |
ExceptionNode[] t = exceptionTable; |
546 |
> |
e = t[h & (t.length - 1)]; |
547 |
> |
while (e != null && e.get() != this) |
548 |
> |
e = e.next; |
549 |
> |
} finally { |
550 |
> |
lock.unlock(); |
551 |
> |
} |
552 |
> |
Throwable ex; |
553 |
> |
if (e == null || (ex = e.ex) == null) |
554 |
> |
return null; |
555 |
> |
if (e.thrower != Thread.currentThread().getId()) { |
556 |
> |
Class<? extends Throwable> ec = ex.getClass(); |
557 |
|
try { |
558 |
< |
synchronized(this) { |
559 |
< |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL)) |
560 |
< |
wait(millis, 0); |
558 |
> |
Constructor<?> noArgCtor = null; |
559 |
> |
Constructor<?>[] cs = ec.getConstructors();// public ctors only |
560 |
> |
for (int i = 0; i < cs.length; ++i) { |
561 |
> |
Constructor<?> c = cs[i]; |
562 |
> |
Class<?>[] ps = c.getParameterTypes(); |
563 |
> |
if (ps.length == 0) |
564 |
> |
noArgCtor = c; |
565 |
> |
else if (ps.length == 1 && ps[0] == Throwable.class) |
566 |
> |
return (Throwable)(c.newInstance(ex)); |
567 |
> |
} |
568 |
> |
if (noArgCtor != null) { |
569 |
> |
Throwable wx = (Throwable)(noArgCtor.newInstance()); |
570 |
> |
wx.initCause(ex); |
571 |
> |
return wx; |
572 |
|
} |
573 |
< |
} catch (InterruptedException ie) { |
251 |
< |
cancelIfTerminating(); |
573 |
> |
} catch (Exception ignore) { |
574 |
|
} |
253 |
– |
s = status; |
575 |
|
} |
576 |
< |
return s; |
576 |
> |
return ex; |
577 |
|
} |
578 |
|
|
579 |
|
/** |
580 |
< |
* Blocks a non-worker-thread until completion. |
580 |
> |
* Poll stale refs and remove them. Call only while holding lock. |
581 |
|
*/ |
582 |
< |
private void externalAwaitDone() { |
583 |
< |
int s; |
584 |
< |
while ((s = status) >= 0) { |
585 |
< |
synchronized(this) { |
586 |
< |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){ |
587 |
< |
boolean interrupted = false; |
588 |
< |
while (status >= 0) { |
589 |
< |
try { |
590 |
< |
wait(); |
591 |
< |
} catch (InterruptedException ie) { |
592 |
< |
interrupted = true; |
593 |
< |
} |
582 |
> |
private static void expungeStaleExceptions() { |
583 |
> |
for (Object x; (x = exceptionTableRefQueue.poll()) != null;) { |
584 |
> |
if (x instanceof ExceptionNode) { |
585 |
> |
ForkJoinTask<?> key = ((ExceptionNode)x).get(); |
586 |
> |
ExceptionNode[] t = exceptionTable; |
587 |
> |
int i = System.identityHashCode(key) & (t.length - 1); |
588 |
> |
ExceptionNode e = t[i]; |
589 |
> |
ExceptionNode pred = null; |
590 |
> |
while (e != null) { |
591 |
> |
ExceptionNode next = e.next; |
592 |
> |
if (e == x) { |
593 |
> |
if (pred == null) |
594 |
> |
t[i] = next; |
595 |
> |
else |
596 |
> |
pred.next = next; |
597 |
> |
break; |
598 |
|
} |
599 |
< |
if (interrupted) |
600 |
< |
Thread.currentThread().interrupt(); |
276 |
< |
break; |
599 |
> |
pred = e; |
600 |
> |
e = next; |
601 |
|
} |
602 |
|
} |
603 |
|
} |
604 |
|
} |
605 |
|
|
606 |
|
/** |
607 |
< |
* Unless done, calls exec and records status if completed, but |
608 |
< |
* doesn't wait for completion otherwise. Primary execution method |
285 |
< |
* for ForkJoinWorkerThread. |
607 |
> |
* If lock is available, poll stale refs and remove them. |
608 |
> |
* Called from ForkJoinPool when pools become quiescent. |
609 |
|
*/ |
610 |
< |
final void quietlyExec() { |
611 |
< |
try { |
612 |
< |
if (status < 0 || !exec()) |
613 |
< |
return; |
614 |
< |
} catch (Throwable rex) { |
615 |
< |
setExceptionalCompletion(rex); |
616 |
< |
return; |
610 |
> |
static final void helpExpungeStaleExceptions() { |
611 |
> |
final ReentrantLock lock = exceptionTableLock; |
612 |
> |
if (lock.tryLock()) { |
613 |
> |
try { |
614 |
> |
expungeStaleExceptions(); |
615 |
> |
} finally { |
616 |
> |
lock.unlock(); |
617 |
> |
} |
618 |
|
} |
619 |
< |
setCompletion(NORMAL); // must be outside try block |
619 |
> |
} |
620 |
> |
|
621 |
> |
/** |
622 |
> |
* Report the result of invoke or join; called only upon |
623 |
> |
* non-normal return of internal versions. |
624 |
> |
*/ |
625 |
> |
private V reportResult() { |
626 |
> |
int s; Throwable ex; |
627 |
> |
if ((s = status) == CANCELLED) |
628 |
> |
throw new CancellationException(); |
629 |
> |
if (s == EXCEPTIONAL && (ex = getThrowableException()) != null) |
630 |
> |
U.throwException(ex); |
631 |
> |
return getRawResult(); |
632 |
|
} |
633 |
|
|
634 |
|
// public methods |
644 |
|
* #isDone} returning {@code true}. |
645 |
|
* |
646 |
|
* <p>This method may be invoked only from within {@code |
647 |
< |
* ForkJoinTask} computations (as may be determined using method |
647 |
> |
* ForkJoinPool} 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}. |
652 |
|
* @return {@code this}, to simplify usage |
653 |
|
*/ |
654 |
|
public final ForkJoinTask<V> fork() { |
655 |
< |
((ForkJoinWorkerThread) Thread.currentThread()) |
656 |
< |
.pushTask(this); |
655 |
> |
ForkJoinWorkerThread wt; |
656 |
> |
(wt = (ForkJoinWorkerThread)Thread.currentThread()). |
657 |
> |
workQueue.push(this, wt.pool); |
658 |
|
return this; |
659 |
|
} |
660 |
|
|
661 |
|
/** |
662 |
< |
* Returns the result of the computation when it {@link #isDone is done}. |
663 |
< |
* This method differs from {@link #get()} in that |
662 |
> |
* Returns the result of the computation when it {@link #isDone is |
663 |
> |
* done}. This method differs from {@link #get()} in that |
664 |
|
* abnormal completion results in {@code RuntimeException} or |
665 |
< |
* {@code Error}, not {@code ExecutionException}. |
665 |
> |
* {@code Error}, not {@code ExecutionException}, and that |
666 |
> |
* interrupts of the calling thread do <em>not</em> cause the |
667 |
> |
* method to abruptly return by throwing {@code |
668 |
> |
* InterruptedException}. |
669 |
|
* |
670 |
|
* @return the computed result |
671 |
|
*/ |
672 |
|
public final V join() { |
673 |
< |
quietlyJoin(); |
674 |
< |
Throwable ex; |
675 |
< |
if (status < NORMAL && (ex = getException()) != null) |
676 |
< |
UNSAFE.throwException(ex); |
337 |
< |
return getRawResult(); |
673 |
> |
if (doJoin() != NORMAL) |
674 |
> |
return reportResult(); |
675 |
> |
else |
676 |
> |
return getRawResult(); |
677 |
|
} |
678 |
|
|
679 |
|
/** |
685 |
|
* @return the computed result |
686 |
|
*/ |
687 |
|
public final V invoke() { |
688 |
< |
quietlyInvoke(); |
689 |
< |
Throwable ex; |
690 |
< |
if (status < NORMAL && (ex = getException()) != null) |
691 |
< |
UNSAFE.throwException(ex); |
353 |
< |
return getRawResult(); |
688 |
> |
if (doInvoke() != NORMAL) |
689 |
> |
return reportResult(); |
690 |
> |
else |
691 |
> |
return getRawResult(); |
692 |
|
} |
693 |
|
|
694 |
|
/** |
705 |
|
* unprocessed. |
706 |
|
* |
707 |
|
* <p>This method may be invoked only from within {@code |
708 |
< |
* ForkJoinTask} computations (as may be determined using method |
708 |
> |
* ForkJoinPool} computations (as may be determined using method |
709 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
710 |
|
* result in exceptions or errors, possibly including {@code |
711 |
|
* ClassCastException}. |
733 |
|
* normally or exceptionally, or left unprocessed. |
734 |
|
* |
735 |
|
* <p>This method may be invoked only from within {@code |
736 |
< |
* ForkJoinTask} computations (as may be determined using method |
736 |
> |
* ForkJoinPool} computations (as may be determined using method |
737 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
738 |
|
* result in exceptions or errors, possibly including {@code |
739 |
|
* ClassCastException}. |
752 |
|
} |
753 |
|
else if (i != 0) |
754 |
|
t.fork(); |
755 |
< |
else { |
756 |
< |
t.quietlyInvoke(); |
419 |
< |
if (ex == null && t.status < NORMAL) |
420 |
< |
ex = t.getException(); |
421 |
< |
} |
755 |
> |
else if (t.doInvoke() < NORMAL && ex == null) |
756 |
> |
ex = t.getException(); |
757 |
|
} |
758 |
|
for (int i = 1; i <= last; ++i) { |
759 |
|
ForkJoinTask<?> t = tasks[i]; |
760 |
|
if (t != null) { |
761 |
|
if (ex != null) |
762 |
|
t.cancel(false); |
763 |
< |
else { |
764 |
< |
t.quietlyJoin(); |
430 |
< |
if (ex == null && t.status < NORMAL) |
431 |
< |
ex = t.getException(); |
432 |
< |
} |
763 |
> |
else if (t.doJoin() < NORMAL) |
764 |
> |
ex = t.getException(); |
765 |
|
} |
766 |
|
} |
767 |
|
if (ex != null) |
768 |
< |
UNSAFE.throwException(ex); |
768 |
> |
U.throwException(ex); |
769 |
|
} |
770 |
|
|
771 |
|
/** |
782 |
|
* unprocessed. |
783 |
|
* |
784 |
|
* <p>This method may be invoked only from within {@code |
785 |
< |
* ForkJoinTask} computations (as may be determined using method |
785 |
> |
* ForkJoinPool} computations (as may be determined using method |
786 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
787 |
|
* result in exceptions or errors, possibly including {@code |
788 |
|
* ClassCastException}. |
809 |
|
} |
810 |
|
else if (i != 0) |
811 |
|
t.fork(); |
812 |
< |
else { |
813 |
< |
t.quietlyInvoke(); |
482 |
< |
if (ex == null && t.status < NORMAL) |
483 |
< |
ex = t.getException(); |
484 |
< |
} |
812 |
> |
else if (t.doInvoke() < NORMAL && ex == null) |
813 |
> |
ex = t.getException(); |
814 |
|
} |
815 |
|
for (int i = 1; i <= last; ++i) { |
816 |
|
ForkJoinTask<?> t = ts.get(i); |
817 |
|
if (t != null) { |
818 |
|
if (ex != null) |
819 |
|
t.cancel(false); |
820 |
< |
else { |
821 |
< |
t.quietlyJoin(); |
493 |
< |
if (ex == null && t.status < NORMAL) |
494 |
< |
ex = t.getException(); |
495 |
< |
} |
820 |
> |
else if (t.doJoin() < NORMAL) |
821 |
> |
ex = t.getException(); |
822 |
|
} |
823 |
|
} |
824 |
|
if (ex != null) |
825 |
< |
UNSAFE.throwException(ex); |
825 |
> |
U.throwException(ex); |
826 |
|
return tasks; |
827 |
|
} |
828 |
|
|
829 |
|
/** |
830 |
|
* Attempts to cancel execution of this task. This attempt will |
831 |
< |
* fail if the task has already completed, has already been |
832 |
< |
* cancelled, or could not be cancelled for some other reason. If |
833 |
< |
* successful, and this task has not started when cancel is |
834 |
< |
* called, execution of this task is suppressed, {@link |
835 |
< |
* #isCancelled} will report true, and {@link #join} will result |
836 |
< |
* in a {@code CancellationException} being thrown. |
831 |
> |
* fail if the task has already completed or could not be |
832 |
> |
* cancelled for some other reason. If successful, and this task |
833 |
> |
* has not started when {@code cancel} is called, execution of |
834 |
> |
* this task is suppressed. After this method returns |
835 |
> |
* successfully, unless there is an intervening call to {@link |
836 |
> |
* #reinitialize}, subsequent calls to {@link #isCancelled}, |
837 |
> |
* {@link #isDone}, and {@code cancel} will return {@code true} |
838 |
> |
* and calls to {@link #join} and related methods will result in |
839 |
> |
* {@code CancellationException}. |
840 |
|
* |
841 |
|
* <p>This method may be overridden in subclasses, but if so, must |
842 |
< |
* still ensure that these minimal properties hold. In particular, |
843 |
< |
* the {@code cancel} method itself must not throw exceptions. |
842 |
> |
* still ensure that these properties hold. In particular, the |
843 |
> |
* {@code cancel} method itself must not throw exceptions. |
844 |
|
* |
845 |
|
* <p>This method is designed to be invoked by <em>other</em> |
846 |
|
* tasks. To terminate the current task, you can just return or |
847 |
|
* throw an unchecked exception from its computation method, or |
848 |
|
* invoke {@link #completeExceptionally}. |
849 |
|
* |
850 |
< |
* @param mayInterruptIfRunning this value is ignored in the |
851 |
< |
* default implementation because tasks are not |
852 |
< |
* cancelled via interruption |
850 |
> |
* @param mayInterruptIfRunning this value has no effect in the |
851 |
> |
* default implementation because interrupts are not used to |
852 |
> |
* control cancellation. |
853 |
|
* |
854 |
|
* @return {@code true} if this task is now cancelled |
855 |
|
*/ |
856 |
|
public boolean cancel(boolean mayInterruptIfRunning) { |
857 |
< |
setCompletion(CANCELLED); |
529 |
< |
return status == CANCELLED; |
530 |
< |
} |
531 |
< |
|
532 |
< |
/** |
533 |
< |
* Cancels, ignoring any exceptions thrown by cancel. Used during |
534 |
< |
* worker and pool shutdown. Cancel is spec'ed not to throw any |
535 |
< |
* exceptions, but if it does anyway, we have no recourse during |
536 |
< |
* shutdown, so guard against this case. |
537 |
< |
*/ |
538 |
< |
final void cancelIgnoringExceptions() { |
539 |
< |
try { |
540 |
< |
cancel(false); |
541 |
< |
} catch (Throwable ignore) { |
542 |
< |
} |
543 |
< |
} |
544 |
< |
|
545 |
< |
/** |
546 |
< |
* Cancels if current thread is a terminating worker thread, |
547 |
< |
* ignoring any exceptions thrown by cancel. |
548 |
< |
*/ |
549 |
< |
final void cancelIfTerminating() { |
550 |
< |
Thread t = Thread.currentThread(); |
551 |
< |
if ((t instanceof ForkJoinWorkerThread) && |
552 |
< |
((ForkJoinWorkerThread) t).isTerminating()) { |
553 |
< |
try { |
554 |
< |
cancel(false); |
555 |
< |
} catch (Throwable ignore) { |
556 |
< |
} |
557 |
< |
} |
857 |
> |
return setCompletion(CANCELLED) == CANCELLED; |
858 |
|
} |
859 |
|
|
860 |
|
public final boolean isDone() { |
896 |
|
int s = status; |
897 |
|
return ((s >= NORMAL) ? null : |
898 |
|
(s == CANCELLED) ? new CancellationException() : |
899 |
< |
exceptionMap.get(this)); |
899 |
> |
getThrowableException()); |
900 |
|
} |
901 |
|
|
902 |
|
/** |
942 |
|
setCompletion(NORMAL); |
943 |
|
} |
944 |
|
|
945 |
+ |
/** |
946 |
+ |
* Waits if necessary for the computation to complete, and then |
947 |
+ |
* retrieves its result. |
948 |
+ |
* |
949 |
+ |
* @return the computed result |
950 |
+ |
* @throws CancellationException if the computation was cancelled |
951 |
+ |
* @throws ExecutionException if the computation threw an |
952 |
+ |
* exception |
953 |
+ |
* @throws InterruptedException if the current thread is not a |
954 |
+ |
* member of a ForkJoinPool and was interrupted while waiting |
955 |
+ |
*/ |
956 |
|
public final V get() throws InterruptedException, ExecutionException { |
957 |
< |
quietlyJoin(); |
958 |
< |
if (Thread.interrupted()) |
959 |
< |
throw new InterruptedException(); |
960 |
< |
int s = status; |
961 |
< |
if (s < NORMAL) { |
962 |
< |
Throwable ex; |
963 |
< |
if (s == CANCELLED) |
653 |
< |
throw new CancellationException(); |
654 |
< |
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
655 |
< |
throw new ExecutionException(ex); |
656 |
< |
} |
957 |
> |
int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ? |
958 |
> |
doJoin() : externalInterruptibleAwaitDone(0L); |
959 |
> |
Throwable ex; |
960 |
> |
if (s == CANCELLED) |
961 |
> |
throw new CancellationException(); |
962 |
> |
if (s == EXCEPTIONAL && (ex = getThrowableException()) != null) |
963 |
> |
throw new ExecutionException(ex); |
964 |
|
return getRawResult(); |
965 |
|
} |
966 |
|
|
967 |
+ |
/** |
968 |
+ |
* Waits if necessary for at most the given time for the computation |
969 |
+ |
* to complete, and then retrieves its result, if available. |
970 |
+ |
* |
971 |
+ |
* @param timeout the maximum time to wait |
972 |
+ |
* @param unit the time unit of the timeout argument |
973 |
+ |
* @return the computed result |
974 |
+ |
* @throws CancellationException if the computation was cancelled |
975 |
+ |
* @throws ExecutionException if the computation threw an |
976 |
+ |
* exception |
977 |
+ |
* @throws InterruptedException if the current thread is not a |
978 |
+ |
* member of a ForkJoinPool and was interrupted while waiting |
979 |
+ |
* @throws TimeoutException if the wait timed out |
980 |
+ |
*/ |
981 |
|
public final V get(long timeout, TimeUnit unit) |
982 |
|
throws InterruptedException, ExecutionException, TimeoutException { |
983 |
+ |
// Messy in part because we measure in nanos, but wait in millis |
984 |
+ |
int s; long millis, nanos; |
985 |
|
Thread t = Thread.currentThread(); |
986 |
< |
ForkJoinPool pool; |
987 |
< |
if (t instanceof ForkJoinWorkerThread) { |
988 |
< |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
989 |
< |
if (status >= 0 && w.unpushTask(this)) |
990 |
< |
quietlyExec(); |
668 |
< |
pool = w.pool; |
986 |
> |
if (!(t instanceof ForkJoinWorkerThread)) { |
987 |
> |
if ((millis = unit.toMillis(timeout)) > 0L) |
988 |
> |
s = externalInterruptibleAwaitDone(millis); |
989 |
> |
else |
990 |
> |
s = status; |
991 |
|
} |
992 |
< |
else |
993 |
< |
pool = null; |
994 |
< |
/* |
995 |
< |
* Timed wait loop intermixes cases for FJ (pool != null) and |
996 |
< |
* non FJ threads. For FJ, decrement pool count but don't try |
997 |
< |
* for replacement; increment count on completion. For non-FJ, |
998 |
< |
* deal with interrupts. This is messy, but a little less so |
999 |
< |
* than is splitting the FJ and nonFJ cases. |
1000 |
< |
*/ |
1001 |
< |
boolean interrupted = false; |
1002 |
< |
boolean dec = false; // true if pool count decremented |
1003 |
< |
long nanos = unit.toNanos(timeout); |
1004 |
< |
for (;;) { |
1005 |
< |
if (pool == null && Thread.interrupted()) { |
684 |
< |
interrupted = true; |
685 |
< |
break; |
686 |
< |
} |
687 |
< |
int s = status; |
688 |
< |
if (s < 0) |
689 |
< |
break; |
690 |
< |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) { |
691 |
< |
long startTime = System.nanoTime(); |
692 |
< |
long nt; // wait time |
693 |
< |
while (status >= 0 && |
694 |
< |
(nt = nanos - (System.nanoTime() - startTime)) > 0) { |
695 |
< |
if (pool != null && !dec) |
696 |
< |
dec = pool.tryDecrementRunningCount(); |
992 |
> |
else if ((s = status) >= 0 && (nanos = unit.toNanos(timeout)) > 0L) { |
993 |
> |
long deadline = System.nanoTime() + nanos; |
994 |
> |
ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; |
995 |
> |
ForkJoinPool.WorkQueue w = wt.workQueue; |
996 |
> |
ForkJoinPool p = wt.pool; |
997 |
> |
if (w.tryUnpush(this)) |
998 |
> |
doExec(); |
999 |
> |
boolean blocking = false; |
1000 |
> |
try { |
1001 |
> |
while ((s = status) >= 0) { |
1002 |
> |
if (w.runState < 0) |
1003 |
> |
cancelIgnoringExceptions(this); |
1004 |
> |
else if (!blocking) |
1005 |
> |
blocking = p.tryCompensate(); |
1006 |
|
else { |
1007 |
< |
long ms = nt / 1000000; |
1008 |
< |
int ns = (int) (nt % 1000000); |
1009 |
< |
try { |
1010 |
< |
synchronized(this) { |
1011 |
< |
if (status >= 0) |
1012 |
< |
wait(ms, ns); |
1013 |
< |
} |
1014 |
< |
} catch (InterruptedException ie) { |
1015 |
< |
if (pool != null) |
707 |
< |
cancelIfTerminating(); |
708 |
< |
else { |
709 |
< |
interrupted = true; |
710 |
< |
break; |
1007 |
> |
millis = TimeUnit.NANOSECONDS.toMillis(nanos); |
1008 |
> |
if (millis > 0L && |
1009 |
> |
U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
1010 |
> |
try { |
1011 |
> |
synchronized (this) { |
1012 |
> |
if (status >= 0) |
1013 |
> |
wait(millis); |
1014 |
> |
} |
1015 |
> |
} catch (InterruptedException ie) { |
1016 |
|
} |
1017 |
|
} |
1018 |
+ |
if ((s = status) < 0 || |
1019 |
+ |
(nanos = deadline - System.nanoTime()) <= 0L) |
1020 |
+ |
break; |
1021 |
|
} |
1022 |
|
} |
1023 |
< |
break; |
1023 |
> |
} finally { |
1024 |
> |
if (blocking) |
1025 |
> |
p.incrementActiveCount(); |
1026 |
|
} |
1027 |
|
} |
1028 |
< |
if (pool != null && dec) |
719 |
< |
pool.incrementRunningCount(); |
720 |
< |
if (interrupted) |
721 |
< |
throw new InterruptedException(); |
722 |
< |
int es = status; |
723 |
< |
if (es != NORMAL) { |
1028 |
> |
if (s != NORMAL) { |
1029 |
|
Throwable ex; |
1030 |
< |
if (es == CANCELLED) |
1030 |
> |
if (s == CANCELLED) |
1031 |
|
throw new CancellationException(); |
1032 |
< |
if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
1032 |
> |
if (s != EXCEPTIONAL) |
1033 |
> |
throw new TimeoutException(); |
1034 |
> |
if ((ex = getThrowableException()) != null) |
1035 |
|
throw new ExecutionException(ex); |
729 |
– |
throw new TimeoutException(); |
1036 |
|
} |
1037 |
|
return getRawResult(); |
1038 |
|
} |
1044 |
|
* known to have aborted. |
1045 |
|
*/ |
1046 |
|
public final void quietlyJoin() { |
1047 |
< |
Thread t; |
742 |
< |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) { |
743 |
< |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
744 |
< |
if (status >= 0) { |
745 |
< |
if (w.unpushTask(this)) { |
746 |
< |
boolean completed; |
747 |
< |
try { |
748 |
< |
completed = exec(); |
749 |
< |
} catch (Throwable rex) { |
750 |
< |
setExceptionalCompletion(rex); |
751 |
< |
return; |
752 |
< |
} |
753 |
< |
if (completed) { |
754 |
< |
setCompletion(NORMAL); |
755 |
< |
return; |
756 |
< |
} |
757 |
< |
} |
758 |
< |
w.joinTask(this); |
759 |
< |
} |
760 |
< |
} |
761 |
< |
else |
762 |
< |
externalAwaitDone(); |
1047 |
> |
doJoin(); |
1048 |
|
} |
1049 |
|
|
1050 |
|
/** |
1053 |
|
* exception. |
1054 |
|
*/ |
1055 |
|
public final void quietlyInvoke() { |
1056 |
< |
if (status >= 0) { |
772 |
< |
boolean completed; |
773 |
< |
try { |
774 |
< |
completed = exec(); |
775 |
< |
} catch (Throwable rex) { |
776 |
< |
setExceptionalCompletion(rex); |
777 |
< |
return; |
778 |
< |
} |
779 |
< |
if (completed) |
780 |
< |
setCompletion(NORMAL); |
781 |
< |
else |
782 |
< |
quietlyJoin(); |
783 |
< |
} |
1056 |
> |
doInvoke(); |
1057 |
|
} |
1058 |
|
|
1059 |
|
/** |
1064 |
|
* processed. |
1065 |
|
* |
1066 |
|
* <p>This method may be invoked only from within {@code |
1067 |
< |
* ForkJoinTask} computations (as may be determined using method |
1067 |
> |
* ForkJoinPool} computations (as may be determined using method |
1068 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1069 |
|
* result in exceptions or errors, possibly including {@code |
1070 |
|
* ClassCastException}. |
1071 |
|
*/ |
1072 |
|
public static void helpQuiesce() { |
1073 |
< |
((ForkJoinWorkerThread) Thread.currentThread()) |
1074 |
< |
.helpQuiescePool(); |
1073 |
> |
ForkJoinWorkerThread w = |
1074 |
> |
(ForkJoinWorkerThread)Thread.currentThread(); |
1075 |
> |
w.pool.helpQuiescePool(w.workQueue); |
1076 |
|
} |
1077 |
|
|
1078 |
|
/** |
1084 |
|
* under any other usage conditions are not guaranteed. |
1085 |
|
* This method may be useful when executing |
1086 |
|
* pre-constructed trees of subtasks in loops. |
1087 |
+ |
* |
1088 |
+ |
* <p>Upon completion of this method, {@code isDone()} reports |
1089 |
+ |
* {@code false}, and {@code getException()} reports {@code |
1090 |
+ |
* null}. However, the value returned by {@code getRawResult} is |
1091 |
+ |
* unaffected. To clear this value, you can invoke {@code |
1092 |
+ |
* setRawResult(null)}. |
1093 |
|
*/ |
1094 |
|
public void reinitialize() { |
1095 |
|
if (status == EXCEPTIONAL) |
1096 |
< |
exceptionMap.remove(this); |
1097 |
< |
status = 0; |
1096 |
> |
clearExceptionalCompletion(); |
1097 |
> |
else |
1098 |
> |
status = 0; |
1099 |
|
} |
1100 |
|
|
1101 |
|
/** |
1112 |
|
} |
1113 |
|
|
1114 |
|
/** |
1115 |
< |
* Returns {@code true} if the current thread is executing as a |
1116 |
< |
* ForkJoinPool computation. |
1115 |
> |
* Returns {@code true} if the current thread is a {@link |
1116 |
> |
* ForkJoinWorkerThread} executing as a ForkJoinPool computation. |
1117 |
|
* |
1118 |
< |
* @return {@code true} if the current thread is executing as a |
1119 |
< |
* ForkJoinPool computation, or false otherwise |
1118 |
> |
* @return {@code true} if the current thread is a {@link |
1119 |
> |
* ForkJoinWorkerThread} executing as a ForkJoinPool computation, |
1120 |
> |
* or {@code false} otherwise |
1121 |
|
*/ |
1122 |
|
public static boolean inForkJoinPool() { |
1123 |
|
return Thread.currentThread() instanceof ForkJoinWorkerThread; |
1132 |
|
* were not, stolen. |
1133 |
|
* |
1134 |
|
* <p>This method may be invoked only from within {@code |
1135 |
< |
* ForkJoinTask} computations (as may be determined using method |
1135 |
> |
* ForkJoinPool} computations (as may be determined using method |
1136 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1137 |
|
* result in exceptions or errors, possibly including {@code |
1138 |
|
* ClassCastException}. |
1140 |
|
* @return {@code true} if unforked |
1141 |
|
*/ |
1142 |
|
public boolean tryUnfork() { |
1143 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1144 |
< |
.unpushTask(this); |
1143 |
> |
return ((ForkJoinWorkerThread)Thread.currentThread()) |
1144 |
> |
.workQueue.tryUnpush(this); |
1145 |
|
} |
1146 |
|
|
1147 |
|
/** |
1151 |
|
* fork other tasks. |
1152 |
|
* |
1153 |
|
* <p>This method may be invoked only from within {@code |
1154 |
< |
* ForkJoinTask} computations (as may be determined using method |
1154 |
> |
* ForkJoinPool} computations (as may be determined using method |
1155 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1156 |
|
* result in exceptions or errors, possibly including {@code |
1157 |
|
* ClassCastException}. |
1160 |
|
*/ |
1161 |
|
public static int getQueuedTaskCount() { |
1162 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1163 |
< |
.getQueueSize(); |
1163 |
> |
.workQueue.queueSize(); |
1164 |
|
} |
1165 |
|
|
1166 |
|
/** |
1174 |
|
* exceeded. |
1175 |
|
* |
1176 |
|
* <p>This method may be invoked only from within {@code |
1177 |
< |
* ForkJoinTask} computations (as may be determined using method |
1177 |
> |
* ForkJoinPool} computations (as may be determined using method |
1178 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1179 |
|
* result in exceptions or errors, possibly including {@code |
1180 |
|
* ClassCastException}. |
1182 |
|
* @return the surplus number of tasks, which may be negative |
1183 |
|
*/ |
1184 |
|
public static int getSurplusQueuedTaskCount() { |
1185 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1186 |
< |
.getEstimatedSurplusTaskCount(); |
1185 |
> |
/* |
1186 |
> |
* The aim of this method is to return a cheap heuristic guide |
1187 |
> |
* for task partitioning when programmers, frameworks, tools, |
1188 |
> |
* or languages have little or no idea about task granularity. |
1189 |
> |
* In essence by offering this method, we ask users only about |
1190 |
> |
* tradeoffs in overhead vs expected throughput and its |
1191 |
> |
* variance, rather than how finely to partition tasks. |
1192 |
> |
* |
1193 |
> |
* In a steady state strict (tree-structured) computation, |
1194 |
> |
* each thread makes available for stealing enough tasks for |
1195 |
> |
* other threads to remain active. Inductively, if all threads |
1196 |
> |
* play by the same rules, each thread should make available |
1197 |
> |
* only a constant number of tasks. |
1198 |
> |
* |
1199 |
> |
* The minimum useful constant is just 1. But using a value of |
1200 |
> |
* 1 would require immediate replenishment upon each steal to |
1201 |
> |
* maintain enough tasks, which is infeasible. Further, |
1202 |
> |
* partitionings/granularities of offered tasks should |
1203 |
> |
* minimize steal rates, which in general means that threads |
1204 |
> |
* nearer the top of computation tree should generate more |
1205 |
> |
* than those nearer the bottom. In perfect steady state, each |
1206 |
> |
* thread is at approximately the same level of computation |
1207 |
> |
* tree. However, producing extra tasks amortizes the |
1208 |
> |
* uncertainty of progress and diffusion assumptions. |
1209 |
> |
* |
1210 |
> |
* So, users will want to use values larger, but not much |
1211 |
> |
* larger than 1 to both smooth over transient shortages and |
1212 |
> |
* hedge against uneven progress; as traded off against the |
1213 |
> |
* cost of extra task overhead. We leave the user to pick a |
1214 |
> |
* threshold value to compare with the results of this call to |
1215 |
> |
* guide decisions, but recommend values such as 3. |
1216 |
> |
* |
1217 |
> |
* When all threads are active, it is on average OK to |
1218 |
> |
* estimate surplus strictly locally. In steady-state, if one |
1219 |
> |
* thread is maintaining say 2 surplus tasks, then so are |
1220 |
> |
* others. So we can just use estimated queue length. |
1221 |
> |
* However, this strategy alone leads to serious mis-estimates |
1222 |
> |
* in some non-steady-state conditions (ramp-up, ramp-down, |
1223 |
> |
* other stalls). We can detect many of these by further |
1224 |
> |
* considering the number of "idle" threads, that are known to |
1225 |
> |
* have zero queued tasks, so compensate by a factor of |
1226 |
> |
* (#idle/#active) threads. |
1227 |
> |
*/ |
1228 |
> |
ForkJoinWorkerThread w = |
1229 |
> |
(ForkJoinWorkerThread)Thread.currentThread(); |
1230 |
> |
return w.workQueue.queueSize() - w.pool.idlePerActive(); |
1231 |
|
} |
1232 |
|
|
1233 |
|
// Extension methods |
1276 |
|
* otherwise. |
1277 |
|
* |
1278 |
|
* <p>This method may be invoked only from within {@code |
1279 |
< |
* ForkJoinTask} computations (as may be determined using method |
1279 |
> |
* ForkJoinPool} computations (as may be determined using method |
1280 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1281 |
|
* result in exceptions or errors, possibly including {@code |
1282 |
|
* ClassCastException}. |
1284 |
|
* @return the next task, or {@code null} if none are available |
1285 |
|
*/ |
1286 |
|
protected static ForkJoinTask<?> peekNextLocalTask() { |
1287 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
962 |
< |
.peekTask(); |
1287 |
> |
return ((ForkJoinWorkerThread) Thread.currentThread()).workQueue.peek(); |
1288 |
|
} |
1289 |
|
|
1290 |
|
/** |
1294 |
|
* be useful otherwise. |
1295 |
|
* |
1296 |
|
* <p>This method may be invoked only from within {@code |
1297 |
< |
* ForkJoinTask} computations (as may be determined using method |
1297 |
> |
* ForkJoinPool} computations (as may be determined using method |
1298 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1299 |
|
* result in exceptions or errors, possibly including {@code |
1300 |
|
* ClassCastException}. |
1303 |
|
*/ |
1304 |
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
1305 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1306 |
< |
.pollLocalTask(); |
1306 |
> |
.workQueue.nextLocalTask(); |
1307 |
|
} |
1308 |
|
|
1309 |
|
/** |
1317 |
|
* otherwise. |
1318 |
|
* |
1319 |
|
* <p>This method may be invoked only from within {@code |
1320 |
< |
* ForkJoinTask} computations (as may be determined using method |
1320 |
> |
* ForkJoinPool} computations (as may be determined using method |
1321 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1322 |
|
* result in exceptions or errors, possibly including {@code |
1323 |
|
* ClassCastException}. |
1325 |
|
* @return a task, or {@code null} if none are available |
1326 |
|
*/ |
1327 |
|
protected static ForkJoinTask<?> pollTask() { |
1328 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1329 |
< |
.pollTask(); |
1328 |
> |
ForkJoinWorkerThread w = |
1329 |
> |
(ForkJoinWorkerThread)Thread.currentThread(); |
1330 |
> |
return w.pool.nextTaskFor(w.workQueue); |
1331 |
> |
} |
1332 |
> |
|
1333 |
> |
// Mark-bit operations |
1334 |
> |
|
1335 |
> |
/** |
1336 |
> |
* Returns true if this task is marked. |
1337 |
> |
* |
1338 |
> |
* @return true if this task is marked |
1339 |
> |
* @since 1.8 |
1340 |
> |
*/ |
1341 |
> |
public final boolean isMarkedForkJoinTask() { |
1342 |
> |
return (status & MARKED) != 0; |
1343 |
> |
} |
1344 |
> |
|
1345 |
> |
/** |
1346 |
> |
* Atomically sets the mark on this task. |
1347 |
> |
* |
1348 |
> |
* @return true if this task was previously unmarked |
1349 |
> |
* @since 1.8 |
1350 |
> |
*/ |
1351 |
> |
public final boolean markForkJoinTask() { |
1352 |
> |
for (int s;;) { |
1353 |
> |
if (((s = status) & MARKED) != 0) |
1354 |
> |
return false; |
1355 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | MARKED)) |
1356 |
> |
return true; |
1357 |
> |
} |
1358 |
> |
} |
1359 |
> |
|
1360 |
> |
/** |
1361 |
> |
* Atomically clears the mark on this task. |
1362 |
> |
* |
1363 |
> |
* @return true if this task was previously marked |
1364 |
> |
* @since 1.8 |
1365 |
> |
*/ |
1366 |
> |
public final boolean unmarkForkJoinTask() { |
1367 |
> |
for (int s;;) { |
1368 |
> |
if (((s = status) & MARKED) == 0) |
1369 |
> |
return false; |
1370 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s & ~MARKED)) |
1371 |
> |
return true; |
1372 |
> |
} |
1373 |
|
} |
1374 |
|
|
1375 |
|
/** |
1470 |
|
private static final long serialVersionUID = -7721805057305804111L; |
1471 |
|
|
1472 |
|
/** |
1473 |
< |
* Saves the state to a stream (that is, serializes it). |
1473 |
> |
* Saves this task to a stream (that is, serializes it). |
1474 |
|
* |
1475 |
|
* @serialData the current run status and the exception thrown |
1476 |
|
* during execution, or {@code null} if none |
1109 |
– |
* @param s the stream |
1477 |
|
*/ |
1478 |
|
private void writeObject(java.io.ObjectOutputStream s) |
1479 |
|
throws java.io.IOException { |
1482 |
|
} |
1483 |
|
|
1484 |
|
/** |
1485 |
< |
* Reconstitutes the instance from a stream (that is, deserializes it). |
1119 |
< |
* |
1120 |
< |
* @param s the stream |
1485 |
> |
* Reconstitutes this task from a stream (that is, deserializes it). |
1486 |
|
*/ |
1487 |
|
private void readObject(java.io.ObjectInputStream s) |
1488 |
|
throws java.io.IOException, ClassNotFoundException { |
1489 |
|
s.defaultReadObject(); |
1490 |
|
Object ex = s.readObject(); |
1491 |
|
if (ex != null) |
1492 |
< |
setExceptionalCompletion((Throwable) ex); |
1492 |
> |
setExceptionalCompletion((Throwable)ex); |
1493 |
|
} |
1494 |
|
|
1495 |
|
// Unsafe mechanics |
1496 |
< |
|
1497 |
< |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1498 |
< |
private static final long statusOffset = |
1499 |
< |
objectFieldOffset("status", ForkJoinTask.class); |
1500 |
< |
|
1501 |
< |
private static long objectFieldOffset(String field, Class<?> klazz) { |
1496 |
> |
private static final sun.misc.Unsafe U; |
1497 |
> |
private static final long STATUS; |
1498 |
> |
static { |
1499 |
> |
exceptionTableLock = new ReentrantLock(); |
1500 |
> |
exceptionTableRefQueue = new ReferenceQueue<Object>(); |
1501 |
> |
exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY]; |
1502 |
|
try { |
1503 |
< |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1504 |
< |
} catch (NoSuchFieldException e) { |
1505 |
< |
// Convert Exception to corresponding Error |
1506 |
< |
NoSuchFieldError error = new NoSuchFieldError(field); |
1507 |
< |
error.initCause(e); |
1143 |
< |
throw error; |
1503 |
> |
U = getUnsafe(); |
1504 |
> |
STATUS = U.objectFieldOffset |
1505 |
> |
(ForkJoinTask.class.getDeclaredField("status")); |
1506 |
> |
} catch (Exception e) { |
1507 |
> |
throw new Error(e); |
1508 |
|
} |
1509 |
|
} |
1510 |
|
|