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/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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* This file is available under and governed by the GNU General Public
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* License version 2 only, as published by the Free Software Foundation.
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* However, the following notice accompanied the original version of this
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* file:
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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/publicdomain/zero/1.0/
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*/
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package java.util.concurrent;
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import java.util.ArrayList;
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import java.util.Arrays;
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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.Random;
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import java.util.concurrent.AbstractExecutorService;
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import java.util.concurrent.Callable;
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import java.util.concurrent.ExecutorService;
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import java.util.concurrent.Future;
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import java.util.concurrent.RejectedExecutionException;
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import java.util.concurrent.RunnableFuture;
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import java.util.concurrent.TimeUnit;
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import java.util.concurrent.atomic.AtomicInteger;
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import java.util.concurrent.locks.LockSupport;
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import java.util.concurrent.locks.ReentrantLock;
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import java.util.concurrent.locks.Condition;
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/**
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* An {@link ExecutorService} for running {@link ForkJoinTask}s.
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* A {@code ForkJoinPool} provides the entry point for submissions
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* from non-{@code ForkJoinTask} clients, as well as management and
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* monitoring operations.
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*
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* <p>A {@code ForkJoinPool} differs from other kinds of {@link
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* ExecutorService} mainly by virtue of employing
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* <em>work-stealing</em>: all threads in the pool attempt to find and
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* execute subtasks created by other active tasks (eventually blocking
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* waiting for work if none exist). This enables efficient processing
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* when most tasks spawn other subtasks (as do most {@code
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* ForkJoinTask}s). When setting <em>asyncMode</em> to true in
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* constructors, {@code ForkJoinPool}s may also be appropriate for use
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* with event-style tasks that are never joined.
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*
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* <p>A {@code ForkJoinPool} is constructed with a given target
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* parallelism level; by default, equal to the number of available
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* processors. The pool attempts to maintain enough active (or
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* available) threads by dynamically adding, suspending, or resuming
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* internal worker threads, even if some tasks are stalled waiting to
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* join others. However, no such adjustments are guaranteed in the
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* face of blocked IO or other unmanaged synchronization. The nested
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* {@link ManagedBlocker} interface enables extension of the kinds of
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* synchronization accommodated.
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*
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* <p>In addition to execution and lifecycle control methods, this
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* class provides status check methods (for example
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* {@link #getStealCount}) that are intended to aid in developing,
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* tuning, and monitoring fork/join applications. Also, method
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* {@link #toString} returns indications of pool state in a
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* convenient form for informal monitoring.
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*
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* <p> As is the case with other ExecutorServices, there are three
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* main task execution methods summarized in the following
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* table. These are designed to be used by clients not already engaged
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* in fork/join computations in the current pool. The main forms of
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* these methods accept instances of {@code ForkJoinTask}, but
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* overloaded forms also allow mixed execution of plain {@code
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* Runnable}- or {@code Callable}- based activities as well. However,
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* tasks that are already executing in a pool should normally
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* <em>NOT</em> use these pool execution methods, but instead use the
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* within-computation forms listed in the table.
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*
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* <table BORDER CELLPADDING=3 CELLSPACING=1>
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* <tr>
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* <td></td>
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* <td ALIGN=CENTER> <b>Call from non-fork/join clients</b></td>
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* <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td>
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* </tr>
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* <tr>
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* <td> <b>Arrange async execution</td>
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* <td> {@link #execute(ForkJoinTask)}</td>
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* <td> {@link ForkJoinTask#fork}</td>
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* </tr>
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* <tr>
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* <td> <b>Await and obtain result</td>
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* <td> {@link #invoke(ForkJoinTask)}</td>
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* <td> {@link ForkJoinTask#invoke}</td>
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* </tr>
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* <tr>
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* <td> <b>Arrange exec and obtain Future</td>
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* <td> {@link #submit(ForkJoinTask)}</td>
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* <td> {@link ForkJoinTask#fork} (ForkJoinTasks <em>are</em> Futures)</td>
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* </tr>
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* </table>
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*
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* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is
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* used for all parallel task execution in a program or subsystem.
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* Otherwise, use would not usually outweigh the construction and
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* bookkeeping overhead of creating a large set of threads. For
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* example, a common pool could be used for the {@code SortTasks}
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* illustrated in {@link RecursiveAction}. Because {@code
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* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
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* daemon} mode, there is typically no need to explicitly {@link
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* #shutdown} such a pool upon program exit.
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*
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* <pre>
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* static final ForkJoinPool mainPool = new ForkJoinPool();
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* ...
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* public void sort(long[] array) {
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* mainPool.invoke(new SortTask(array, 0, array.length));
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* }
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* </pre>
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*
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* <p><b>Implementation notes</b>: This implementation restricts the
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* maximum number of running threads to 32767. Attempts to create
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* pools with greater than the maximum number result in
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* {@code IllegalArgumentException}.
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*
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* <p>This implementation rejects submitted tasks (that is, by throwing
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* {@link RejectedExecutionException}) only when the pool is shut down
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* or internal resources have been exhausted.
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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 class ForkJoinPool extends AbstractExecutorService {
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/*
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* Implementation Overview
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*
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* This class provides the central bookkeeping and control for a
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* set of worker threads: Submissions from non-FJ threads enter
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* into a submission queue. Workers take these tasks and typically
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* split them into subtasks that may be stolen by other workers.
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* Preference rules give first priority to processing tasks from
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* their own queues (LIFO or FIFO, depending on mode), then to
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* randomized FIFO steals of tasks in other worker queues, and
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* lastly to new submissions.
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*
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* The main throughput advantages of work-stealing stem from
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* decentralized control -- workers mostly take tasks from
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* themselves or each other. We cannot negate this in the
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* implementation of other management responsibilities. The main
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* tactic for avoiding bottlenecks is packing nearly all
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* essentially atomic control state into a single 64bit volatile
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* variable ("ctl"). This variable is read on the order of 10-100
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* times as often as it is modified (always via CAS). (There is
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* some additional control state, for example variable "shutdown"
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* for which we can cope with uncoordinated updates.) This
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* streamlines synchronization and control at the expense of messy
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* constructions needed to repack status bits upon updates.
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* Updates tend not to contend with each other except during
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* bursts while submitted tasks begin or end. In some cases when
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* they do contend, threads can instead do something else
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* (usually, scan for tasks) until contention subsides.
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*
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* To enable packing, we restrict maximum parallelism to (1<<15)-1
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* (which is far in excess of normal operating range) to allow
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* ids, counts, and their negations (used for thresholding) to fit
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* into 16bit fields.
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*
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* Recording Workers. Workers are recorded in the "workers" array
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* that is created upon pool construction and expanded if (rarely)
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* necessary. This is an array as opposed to some other data
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* structure to support index-based random steals by workers.
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* Updates to the array recording new workers and unrecording
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* terminated ones are protected from each other by a seqLock
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* (scanGuard) but the array is otherwise concurrently readable,
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* and accessed directly by workers. To simplify index-based
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* operations, the array size is always a power of two, and all
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* readers must tolerate null slots. To avoid flailing during
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* start-up, the array is presized to hold twice #parallelism
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* workers (which is unlikely to need further resizing during
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* execution). But to avoid dealing with so many null slots,
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* variable scanGuard includes a mask for the nearest power of two
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* that contains all current workers. All worker thread creation
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* is on-demand, triggered by task submissions, replacement of
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* terminated workers, and/or compensation for blocked
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* workers. However, all other support code is set up to work with
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* other policies. To ensure that we do not hold on to worker
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* references that would prevent GC, ALL accesses to workers are
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* via indices into the workers array (which is one source of some
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* of the messy code constructions here). In essence, the workers
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* array serves as a weak reference mechanism. Thus for example
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* the wait queue field of ctl stores worker indices, not worker
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* references. Access to the workers in associated methods (for
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* example signalWork) must both index-check and null-check the
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* IDs. All such accesses ignore bad IDs by returning out early
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* from what they are doing, since this can only be associated
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* with termination, in which case it is OK to give up.
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*
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* All uses of the workers array, as well as queue arrays, check
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* that the array is non-null (even if previously non-null). This
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* allows nulling during termination, which is currently not
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* necessary, but remains an option for resource-revocation-based
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* shutdown schemes.
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*
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* Wait Queuing. Unlike HPC work-stealing frameworks, we cannot
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* let workers spin indefinitely scanning for tasks when none can
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* be found immediately, and we cannot start/resume workers unless
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* there appear to be tasks available. On the other hand, we must
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* quickly prod them into action when new tasks are submitted or
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* generated. We park/unpark workers after placing in an event
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* wait queue when they cannot find work. This "queue" is actually
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* a simple Treiber stack, headed by the "id" field of ctl, plus a
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* 15bit counter value to both wake up waiters (by advancing their
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* count) and avoid ABA effects. Successors are held in worker
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* field "nextWait". Queuing deals with several intrinsic races,
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* mainly that a task-producing thread can miss seeing (and
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* signalling) another thread that gave up looking for work but
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* has not yet entered the wait queue. We solve this by requiring
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* a full sweep of all workers both before (in scan()) and after
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* (in tryAwaitWork()) a newly waiting worker is added to the wait
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* queue. During a rescan, the worker might release some other
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* queued worker rather than itself, which has the same net
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* effect. Because enqueued workers may actually be rescanning
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* rather than waiting, we set and clear the "parked" field of
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* ForkJoinWorkerThread to reduce unnecessary calls to unpark.
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* (Use of the parked field requires a secondary recheck to avoid
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* missed signals.)
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*
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* Signalling. We create or wake up workers only when there
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* appears to be at least one task they might be able to find and
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* execute. When a submission is added or another worker adds a
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* task to a queue that previously had two or fewer tasks, they
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* signal waiting workers (or trigger creation of new ones if
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* fewer than the given parallelism level -- see signalWork).
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* These primary signals are buttressed by signals during rescans
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* as well as those performed when a worker steals a task and
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* notices that there are more tasks too; together these cover the
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* signals needed in cases when more than two tasks are pushed
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* but untaken.
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*
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* Trimming workers. To release resources after periods of lack of
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* use, a worker starting to wait when the pool is quiescent will
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* time out and terminate if the pool has remained quiescent for
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* SHRINK_RATE nanosecs. This will slowly propagate, eventually
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* terminating all workers after long periods of non-use.
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*
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* Submissions. External submissions are maintained in an
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* array-based queue that is structured identically to
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* ForkJoinWorkerThread queues except for the use of
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* submissionLock in method addSubmission. Unlike the case for
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* worker queues, multiple external threads can add new
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* submissions, so adding requires a lock.
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*
|
jaroslav@1890
|
274 |
* Compensation. Beyond work-stealing support and lifecycle
|
jaroslav@1890
|
275 |
* control, the main responsibility of this framework is to take
|
jaroslav@1890
|
276 |
* actions when one worker is waiting to join a task stolen (or
|
jaroslav@1890
|
277 |
* always held by) another. Because we are multiplexing many
|
jaroslav@1890
|
278 |
* tasks on to a pool of workers, we can't just let them block (as
|
jaroslav@1890
|
279 |
* in Thread.join). We also cannot just reassign the joiner's
|
jaroslav@1890
|
280 |
* run-time stack with another and replace it later, which would
|
jaroslav@1890
|
281 |
* be a form of "continuation", that even if possible is not
|
jaroslav@1890
|
282 |
* necessarily a good idea since we sometimes need both an
|
jaroslav@1890
|
283 |
* unblocked task and its continuation to progress. Instead we
|
jaroslav@1890
|
284 |
* combine two tactics:
|
jaroslav@1890
|
285 |
*
|
jaroslav@1890
|
286 |
* Helping: Arranging for the joiner to execute some task that it
|
jaroslav@1890
|
287 |
* would be running if the steal had not occurred. Method
|
jaroslav@1890
|
288 |
* ForkJoinWorkerThread.joinTask tracks joining->stealing
|
jaroslav@1890
|
289 |
* links to try to find such a task.
|
jaroslav@1890
|
290 |
*
|
jaroslav@1890
|
291 |
* Compensating: Unless there are already enough live threads,
|
jaroslav@1890
|
292 |
* method tryPreBlock() may create or re-activate a spare
|
jaroslav@1890
|
293 |
* thread to compensate for blocked joiners until they
|
jaroslav@1890
|
294 |
* unblock.
|
jaroslav@1890
|
295 |
*
|
jaroslav@1890
|
296 |
* The ManagedBlocker extension API can't use helping so relies
|
jaroslav@1890
|
297 |
* only on compensation in method awaitBlocker.
|
jaroslav@1890
|
298 |
*
|
jaroslav@1890
|
299 |
* It is impossible to keep exactly the target parallelism number
|
jaroslav@1890
|
300 |
* of threads running at any given time. Determining the
|
jaroslav@1890
|
301 |
* existence of conservatively safe helping targets, the
|
jaroslav@1890
|
302 |
* availability of already-created spares, and the apparent need
|
jaroslav@1890
|
303 |
* to create new spares are all racy and require heuristic
|
jaroslav@1890
|
304 |
* guidance, so we rely on multiple retries of each. Currently,
|
jaroslav@1890
|
305 |
* in keeping with on-demand signalling policy, we compensate only
|
jaroslav@1890
|
306 |
* if blocking would leave less than one active (non-waiting,
|
jaroslav@1890
|
307 |
* non-blocked) worker. Additionally, to avoid some false alarms
|
jaroslav@1890
|
308 |
* due to GC, lagging counters, system activity, etc, compensated
|
jaroslav@1890
|
309 |
* blocking for joins is only attempted after rechecks stabilize
|
jaroslav@1890
|
310 |
* (retries are interspersed with Thread.yield, for good
|
jaroslav@1890
|
311 |
* citizenship). The variable blockedCount, incremented before
|
jaroslav@1890
|
312 |
* blocking and decremented after, is sometimes needed to
|
jaroslav@1890
|
313 |
* distinguish cases of waiting for work vs blocking on joins or
|
jaroslav@1890
|
314 |
* other managed sync. Both cases are equivalent for most pool
|
jaroslav@1890
|
315 |
* control, so we can update non-atomically. (Additionally,
|
jaroslav@1890
|
316 |
* contention on blockedCount alleviates some contention on ctl).
|
jaroslav@1890
|
317 |
*
|
jaroslav@1890
|
318 |
* Shutdown and Termination. A call to shutdownNow atomically sets
|
jaroslav@1890
|
319 |
* the ctl stop bit and then (non-atomically) sets each workers
|
jaroslav@1890
|
320 |
* "terminate" status, cancels all unprocessed tasks, and wakes up
|
jaroslav@1890
|
321 |
* all waiting workers. Detecting whether termination should
|
jaroslav@1890
|
322 |
* commence after a non-abrupt shutdown() call requires more work
|
jaroslav@1890
|
323 |
* and bookkeeping. We need consensus about quiesence (i.e., that
|
jaroslav@1890
|
324 |
* there is no more work) which is reflected in active counts so
|
jaroslav@1890
|
325 |
* long as there are no current blockers, as well as possible
|
jaroslav@1890
|
326 |
* re-evaluations during independent changes in blocking or
|
jaroslav@1890
|
327 |
* quiescing workers.
|
jaroslav@1890
|
328 |
*
|
jaroslav@1890
|
329 |
* Style notes: There is a lot of representation-level coupling
|
jaroslav@1890
|
330 |
* among classes ForkJoinPool, ForkJoinWorkerThread, and
|
jaroslav@1890
|
331 |
* ForkJoinTask. Most fields of ForkJoinWorkerThread maintain
|
jaroslav@1890
|
332 |
* data structures managed by ForkJoinPool, so are directly
|
jaroslav@1890
|
333 |
* accessed. Conversely we allow access to "workers" array by
|
jaroslav@1890
|
334 |
* workers, and direct access to ForkJoinTask.status by both
|
jaroslav@1890
|
335 |
* ForkJoinPool and ForkJoinWorkerThread. There is little point
|
jaroslav@1890
|
336 |
* trying to reduce this, since any associated future changes in
|
jaroslav@1890
|
337 |
* representations will need to be accompanied by algorithmic
|
jaroslav@1890
|
338 |
* changes anyway. All together, these low-level implementation
|
jaroslav@1890
|
339 |
* choices produce as much as a factor of 4 performance
|
jaroslav@1890
|
340 |
* improvement compared to naive implementations, and enable the
|
jaroslav@1890
|
341 |
* processing of billions of tasks per second, at the expense of
|
jaroslav@1890
|
342 |
* some ugliness.
|
jaroslav@1890
|
343 |
*
|
jaroslav@1890
|
344 |
* Methods signalWork() and scan() are the main bottlenecks so are
|
jaroslav@1890
|
345 |
* especially heavily micro-optimized/mangled. There are lots of
|
jaroslav@1890
|
346 |
* inline assignments (of form "while ((local = field) != 0)")
|
jaroslav@1890
|
347 |
* which are usually the simplest way to ensure the required read
|
jaroslav@1890
|
348 |
* orderings (which are sometimes critical). This leads to a
|
jaroslav@1890
|
349 |
* "C"-like style of listing declarations of these locals at the
|
jaroslav@1890
|
350 |
* heads of methods or blocks. There are several occurrences of
|
jaroslav@1890
|
351 |
* the unusual "do {} while (!cas...)" which is the simplest way
|
jaroslav@1890
|
352 |
* to force an update of a CAS'ed variable. There are also other
|
jaroslav@1890
|
353 |
* coding oddities that help some methods perform reasonably even
|
jaroslav@1890
|
354 |
* when interpreted (not compiled).
|
jaroslav@1890
|
355 |
*
|
jaroslav@1890
|
356 |
* The order of declarations in this file is: (1) declarations of
|
jaroslav@1890
|
357 |
* statics (2) fields (along with constants used when unpacking
|
jaroslav@1890
|
358 |
* some of them), listed in an order that tends to reduce
|
jaroslav@1890
|
359 |
* contention among them a bit under most JVMs. (3) internal
|
jaroslav@1890
|
360 |
* control methods (4) callbacks and other support for
|
jaroslav@1890
|
361 |
* ForkJoinTask and ForkJoinWorkerThread classes, (5) exported
|
jaroslav@1890
|
362 |
* methods (plus a few little helpers). (6) static block
|
jaroslav@1890
|
363 |
* initializing all statics in a minimally dependent order.
|
jaroslav@1890
|
364 |
*/
|
jaroslav@1890
|
365 |
|
jaroslav@1890
|
366 |
/**
|
jaroslav@1890
|
367 |
* Factory for creating new {@link ForkJoinWorkerThread}s.
|
jaroslav@1890
|
368 |
* A {@code ForkJoinWorkerThreadFactory} must be defined and used
|
jaroslav@1890
|
369 |
* for {@code ForkJoinWorkerThread} subclasses that extend base
|
jaroslav@1890
|
370 |
* functionality or initialize threads with different contexts.
|
jaroslav@1890
|
371 |
*/
|
jaroslav@1890
|
372 |
public static interface ForkJoinWorkerThreadFactory {
|
jaroslav@1890
|
373 |
/**
|
jaroslav@1890
|
374 |
* Returns a new worker thread operating in the given pool.
|
jaroslav@1890
|
375 |
*
|
jaroslav@1890
|
376 |
* @param pool the pool this thread works in
|
jaroslav@1890
|
377 |
* @throws NullPointerException if the pool is null
|
jaroslav@1890
|
378 |
*/
|
jaroslav@1890
|
379 |
public ForkJoinWorkerThread newThread(ForkJoinPool pool);
|
jaroslav@1890
|
380 |
}
|
jaroslav@1890
|
381 |
|
jaroslav@1890
|
382 |
/**
|
jaroslav@1890
|
383 |
* Default ForkJoinWorkerThreadFactory implementation; creates a
|
jaroslav@1890
|
384 |
* new ForkJoinWorkerThread.
|
jaroslav@1890
|
385 |
*/
|
jaroslav@1890
|
386 |
static class DefaultForkJoinWorkerThreadFactory
|
jaroslav@1890
|
387 |
implements ForkJoinWorkerThreadFactory {
|
jaroslav@1890
|
388 |
public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
|
jaroslav@1890
|
389 |
return new ForkJoinWorkerThread(pool);
|
jaroslav@1890
|
390 |
}
|
jaroslav@1890
|
391 |
}
|
jaroslav@1890
|
392 |
|
jaroslav@1890
|
393 |
/**
|
jaroslav@1890
|
394 |
* Creates a new ForkJoinWorkerThread. This factory is used unless
|
jaroslav@1890
|
395 |
* overridden in ForkJoinPool constructors.
|
jaroslav@1890
|
396 |
*/
|
jaroslav@1890
|
397 |
public static final ForkJoinWorkerThreadFactory
|
jaroslav@1890
|
398 |
defaultForkJoinWorkerThreadFactory;
|
jaroslav@1890
|
399 |
|
jaroslav@1890
|
400 |
/**
|
jaroslav@1890
|
401 |
* If there is a security manager, makes sure caller has
|
jaroslav@1890
|
402 |
* permission to modify threads.
|
jaroslav@1890
|
403 |
*/
|
jaroslav@1890
|
404 |
private static void checkPermission() {
|
jaroslav@1895
|
405 |
throw new SecurityException();
|
jaroslav@1890
|
406 |
}
|
jaroslav@1890
|
407 |
|
jaroslav@1890
|
408 |
/**
|
jaroslav@1890
|
409 |
* Generator for assigning sequence numbers as pool names.
|
jaroslav@1890
|
410 |
*/
|
jaroslav@1890
|
411 |
private static final AtomicInteger poolNumberGenerator;
|
jaroslav@1890
|
412 |
|
jaroslav@1890
|
413 |
/**
|
jaroslav@1890
|
414 |
* Generator for initial random seeds for worker victim
|
jaroslav@1890
|
415 |
* selection. This is used only to create initial seeds. Random
|
jaroslav@1890
|
416 |
* steals use a cheaper xorshift generator per steal attempt. We
|
jaroslav@1890
|
417 |
* don't expect much contention on seedGenerator, so just use a
|
jaroslav@1890
|
418 |
* plain Random.
|
jaroslav@1890
|
419 |
*/
|
jaroslav@1890
|
420 |
static final Random workerSeedGenerator;
|
jaroslav@1890
|
421 |
|
jaroslav@1890
|
422 |
/**
|
jaroslav@1890
|
423 |
* Array holding all worker threads in the pool. Initialized upon
|
jaroslav@1890
|
424 |
* construction. Array size must be a power of two. Updates and
|
jaroslav@1890
|
425 |
* replacements are protected by scanGuard, but the array is
|
jaroslav@1890
|
426 |
* always kept in a consistent enough state to be randomly
|
jaroslav@1890
|
427 |
* accessed without locking by workers performing work-stealing,
|
jaroslav@1890
|
428 |
* as well as other traversal-based methods in this class, so long
|
jaroslav@1890
|
429 |
* as reads memory-acquire by first reading ctl. All readers must
|
jaroslav@1890
|
430 |
* tolerate that some array slots may be null.
|
jaroslav@1890
|
431 |
*/
|
jaroslav@1890
|
432 |
ForkJoinWorkerThread[] workers;
|
jaroslav@1890
|
433 |
|
jaroslav@1890
|
434 |
/**
|
jaroslav@1890
|
435 |
* Initial size for submission queue array. Must be a power of
|
jaroslav@1890
|
436 |
* two. In many applications, these always stay small so we use a
|
jaroslav@1890
|
437 |
* small initial cap.
|
jaroslav@1890
|
438 |
*/
|
jaroslav@1890
|
439 |
private static final int INITIAL_QUEUE_CAPACITY = 8;
|
jaroslav@1890
|
440 |
|
jaroslav@1890
|
441 |
/**
|
jaroslav@1890
|
442 |
* Maximum size for submission queue array. Must be a power of two
|
jaroslav@1890
|
443 |
* less than or equal to 1 << (31 - width of array entry) to
|
jaroslav@1890
|
444 |
* ensure lack of index wraparound, but is capped at a lower
|
jaroslav@1890
|
445 |
* value to help users trap runaway computations.
|
jaroslav@1890
|
446 |
*/
|
jaroslav@1890
|
447 |
private static final int MAXIMUM_QUEUE_CAPACITY = 1 << 24; // 16M
|
jaroslav@1890
|
448 |
|
jaroslav@1890
|
449 |
/**
|
jaroslav@1890
|
450 |
* Array serving as submission queue. Initialized upon construction.
|
jaroslav@1890
|
451 |
*/
|
jaroslav@1890
|
452 |
private ForkJoinTask<?>[] submissionQueue;
|
jaroslav@1890
|
453 |
|
jaroslav@1890
|
454 |
/**
|
jaroslav@1890
|
455 |
* Lock protecting submissions array for addSubmission
|
jaroslav@1890
|
456 |
*/
|
jaroslav@1890
|
457 |
private final ReentrantLock submissionLock;
|
jaroslav@1890
|
458 |
|
jaroslav@1890
|
459 |
/**
|
jaroslav@1890
|
460 |
* Condition for awaitTermination, using submissionLock for
|
jaroslav@1890
|
461 |
* convenience.
|
jaroslav@1890
|
462 |
*/
|
jaroslav@1890
|
463 |
private final Condition termination;
|
jaroslav@1890
|
464 |
|
jaroslav@1890
|
465 |
/**
|
jaroslav@1890
|
466 |
* Creation factory for worker threads.
|
jaroslav@1890
|
467 |
*/
|
jaroslav@1890
|
468 |
private final ForkJoinWorkerThreadFactory factory;
|
jaroslav@1890
|
469 |
|
jaroslav@1890
|
470 |
/**
|
jaroslav@1890
|
471 |
* The uncaught exception handler used when any worker abruptly
|
jaroslav@1890
|
472 |
* terminates.
|
jaroslav@1890
|
473 |
*/
|
jaroslav@1890
|
474 |
final Thread.UncaughtExceptionHandler ueh;
|
jaroslav@1890
|
475 |
|
jaroslav@1890
|
476 |
/**
|
jaroslav@1890
|
477 |
* Prefix for assigning names to worker threads
|
jaroslav@1890
|
478 |
*/
|
jaroslav@1890
|
479 |
private final String workerNamePrefix;
|
jaroslav@1890
|
480 |
|
jaroslav@1890
|
481 |
/**
|
jaroslav@1890
|
482 |
* Sum of per-thread steal counts, updated only when threads are
|
jaroslav@1890
|
483 |
* idle or terminating.
|
jaroslav@1890
|
484 |
*/
|
jaroslav@1890
|
485 |
private volatile long stealCount;
|
jaroslav@1890
|
486 |
|
jaroslav@1890
|
487 |
/**
|
jaroslav@1890
|
488 |
* Main pool control -- a long packed with:
|
jaroslav@1890
|
489 |
* AC: Number of active running workers minus target parallelism (16 bits)
|
jaroslav@1890
|
490 |
* TC: Number of total workers minus target parallelism (16bits)
|
jaroslav@1890
|
491 |
* ST: true if pool is terminating (1 bit)
|
jaroslav@1890
|
492 |
* EC: the wait count of top waiting thread (15 bits)
|
jaroslav@1890
|
493 |
* ID: ~poolIndex of top of Treiber stack of waiting threads (16 bits)
|
jaroslav@1890
|
494 |
*
|
jaroslav@1890
|
495 |
* When convenient, we can extract the upper 32 bits of counts and
|
jaroslav@1890
|
496 |
* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
|
jaroslav@1890
|
497 |
* (int)ctl. The ec field is never accessed alone, but always
|
jaroslav@1890
|
498 |
* together with id and st. The offsets of counts by the target
|
jaroslav@1890
|
499 |
* parallelism and the positionings of fields makes it possible to
|
jaroslav@1890
|
500 |
* perform the most common checks via sign tests of fields: When
|
jaroslav@1890
|
501 |
* ac is negative, there are not enough active workers, when tc is
|
jaroslav@1890
|
502 |
* negative, there are not enough total workers, when id is
|
jaroslav@1890
|
503 |
* negative, there is at least one waiting worker, and when e is
|
jaroslav@1890
|
504 |
* negative, the pool is terminating. To deal with these possibly
|
jaroslav@1890
|
505 |
* negative fields, we use casts in and out of "short" and/or
|
jaroslav@1890
|
506 |
* signed shifts to maintain signedness.
|
jaroslav@1890
|
507 |
*/
|
jaroslav@1890
|
508 |
volatile long ctl;
|
jaroslav@1890
|
509 |
|
jaroslav@1890
|
510 |
// bit positions/shifts for fields
|
jaroslav@1890
|
511 |
private static final int AC_SHIFT = 48;
|
jaroslav@1890
|
512 |
private static final int TC_SHIFT = 32;
|
jaroslav@1890
|
513 |
private static final int ST_SHIFT = 31;
|
jaroslav@1890
|
514 |
private static final int EC_SHIFT = 16;
|
jaroslav@1890
|
515 |
|
jaroslav@1890
|
516 |
// bounds
|
jaroslav@1890
|
517 |
private static final int MAX_ID = 0x7fff; // max poolIndex
|
jaroslav@1890
|
518 |
private static final int SMASK = 0xffff; // mask short bits
|
jaroslav@1890
|
519 |
private static final int SHORT_SIGN = 1 << 15;
|
jaroslav@1890
|
520 |
private static final int INT_SIGN = 1 << 31;
|
jaroslav@1890
|
521 |
|
jaroslav@1890
|
522 |
// masks
|
jaroslav@1890
|
523 |
private static final long STOP_BIT = 0x0001L << ST_SHIFT;
|
jaroslav@1890
|
524 |
private static final long AC_MASK = ((long)SMASK) << AC_SHIFT;
|
jaroslav@1890
|
525 |
private static final long TC_MASK = ((long)SMASK) << TC_SHIFT;
|
jaroslav@1890
|
526 |
|
jaroslav@1890
|
527 |
// units for incrementing and decrementing
|
jaroslav@1890
|
528 |
private static final long TC_UNIT = 1L << TC_SHIFT;
|
jaroslav@1890
|
529 |
private static final long AC_UNIT = 1L << AC_SHIFT;
|
jaroslav@1890
|
530 |
|
jaroslav@1890
|
531 |
// masks and units for dealing with u = (int)(ctl >>> 32)
|
jaroslav@1890
|
532 |
private static final int UAC_SHIFT = AC_SHIFT - 32;
|
jaroslav@1890
|
533 |
private static final int UTC_SHIFT = TC_SHIFT - 32;
|
jaroslav@1890
|
534 |
private static final int UAC_MASK = SMASK << UAC_SHIFT;
|
jaroslav@1890
|
535 |
private static final int UTC_MASK = SMASK << UTC_SHIFT;
|
jaroslav@1890
|
536 |
private static final int UAC_UNIT = 1 << UAC_SHIFT;
|
jaroslav@1890
|
537 |
private static final int UTC_UNIT = 1 << UTC_SHIFT;
|
jaroslav@1890
|
538 |
|
jaroslav@1890
|
539 |
// masks and units for dealing with e = (int)ctl
|
jaroslav@1890
|
540 |
private static final int E_MASK = 0x7fffffff; // no STOP_BIT
|
jaroslav@1890
|
541 |
private static final int EC_UNIT = 1 << EC_SHIFT;
|
jaroslav@1890
|
542 |
|
jaroslav@1890
|
543 |
/**
|
jaroslav@1890
|
544 |
* The target parallelism level.
|
jaroslav@1890
|
545 |
*/
|
jaroslav@1890
|
546 |
final int parallelism;
|
jaroslav@1890
|
547 |
|
jaroslav@1890
|
548 |
/**
|
jaroslav@1890
|
549 |
* Index (mod submission queue length) of next element to take
|
jaroslav@1890
|
550 |
* from submission queue. Usage is identical to that for
|
jaroslav@1890
|
551 |
* per-worker queues -- see ForkJoinWorkerThread internal
|
jaroslav@1890
|
552 |
* documentation.
|
jaroslav@1890
|
553 |
*/
|
jaroslav@1890
|
554 |
volatile int queueBase;
|
jaroslav@1890
|
555 |
|
jaroslav@1890
|
556 |
/**
|
jaroslav@1890
|
557 |
* Index (mod submission queue length) of next element to add
|
jaroslav@1890
|
558 |
* in submission queue. Usage is identical to that for
|
jaroslav@1890
|
559 |
* per-worker queues -- see ForkJoinWorkerThread internal
|
jaroslav@1890
|
560 |
* documentation.
|
jaroslav@1890
|
561 |
*/
|
jaroslav@1890
|
562 |
int queueTop;
|
jaroslav@1890
|
563 |
|
jaroslav@1890
|
564 |
/**
|
jaroslav@1890
|
565 |
* True when shutdown() has been called.
|
jaroslav@1890
|
566 |
*/
|
jaroslav@1890
|
567 |
volatile boolean shutdown;
|
jaroslav@1890
|
568 |
|
jaroslav@1890
|
569 |
/**
|
jaroslav@1890
|
570 |
* True if use local fifo, not default lifo, for local polling
|
jaroslav@1890
|
571 |
* Read by, and replicated by ForkJoinWorkerThreads
|
jaroslav@1890
|
572 |
*/
|
jaroslav@1890
|
573 |
final boolean locallyFifo;
|
jaroslav@1890
|
574 |
|
jaroslav@1890
|
575 |
/**
|
jaroslav@1890
|
576 |
* The number of threads in ForkJoinWorkerThreads.helpQuiescePool.
|
jaroslav@1890
|
577 |
* When non-zero, suppresses automatic shutdown when active
|
jaroslav@1890
|
578 |
* counts become zero.
|
jaroslav@1890
|
579 |
*/
|
jaroslav@1890
|
580 |
volatile int quiescerCount;
|
jaroslav@1890
|
581 |
|
jaroslav@1890
|
582 |
/**
|
jaroslav@1890
|
583 |
* The number of threads blocked in join.
|
jaroslav@1890
|
584 |
*/
|
jaroslav@1890
|
585 |
volatile int blockedCount;
|
jaroslav@1890
|
586 |
|
jaroslav@1890
|
587 |
/**
|
jaroslav@1890
|
588 |
* Counter for worker Thread names (unrelated to their poolIndex)
|
jaroslav@1890
|
589 |
*/
|
jaroslav@1890
|
590 |
private volatile int nextWorkerNumber;
|
jaroslav@1890
|
591 |
|
jaroslav@1890
|
592 |
/**
|
jaroslav@1890
|
593 |
* The index for the next created worker. Accessed under scanGuard.
|
jaroslav@1890
|
594 |
*/
|
jaroslav@1890
|
595 |
private int nextWorkerIndex;
|
jaroslav@1890
|
596 |
|
jaroslav@1890
|
597 |
/**
|
jaroslav@1890
|
598 |
* SeqLock and index masking for updates to workers array. Locked
|
jaroslav@1890
|
599 |
* when SG_UNIT is set. Unlocking clears bit by adding
|
jaroslav@1890
|
600 |
* SG_UNIT. Staleness of read-only operations can be checked by
|
jaroslav@1890
|
601 |
* comparing scanGuard to value before the reads. The low 16 bits
|
jaroslav@1890
|
602 |
* (i.e, anding with SMASK) hold (the smallest power of two
|
jaroslav@1890
|
603 |
* covering all worker indices, minus one, and is used to avoid
|
jaroslav@1890
|
604 |
* dealing with large numbers of null slots when the workers array
|
jaroslav@1890
|
605 |
* is overallocated.
|
jaroslav@1890
|
606 |
*/
|
jaroslav@1890
|
607 |
volatile int scanGuard;
|
jaroslav@1890
|
608 |
|
jaroslav@1890
|
609 |
private static final int SG_UNIT = 1 << 16;
|
jaroslav@1890
|
610 |
|
jaroslav@1890
|
611 |
/**
|
jaroslav@1890
|
612 |
* The wakeup interval (in nanoseconds) for a worker waiting for a
|
jaroslav@1890
|
613 |
* task when the pool is quiescent to instead try to shrink the
|
jaroslav@1890
|
614 |
* number of workers. The exact value does not matter too
|
jaroslav@1890
|
615 |
* much. It must be short enough to release resources during
|
jaroslav@1890
|
616 |
* sustained periods of idleness, but not so short that threads
|
jaroslav@1890
|
617 |
* are continually re-created.
|
jaroslav@1890
|
618 |
*/
|
jaroslav@1890
|
619 |
private static final long SHRINK_RATE =
|
jaroslav@1890
|
620 |
4L * 1000L * 1000L * 1000L; // 4 seconds
|
jaroslav@1890
|
621 |
|
jaroslav@1890
|
622 |
/**
|
jaroslav@1890
|
623 |
* Top-level loop for worker threads: On each step: if the
|
jaroslav@1890
|
624 |
* previous step swept through all queues and found no tasks, or
|
jaroslav@1890
|
625 |
* there are excess threads, then possibly blocks. Otherwise,
|
jaroslav@1890
|
626 |
* scans for and, if found, executes a task. Returns when pool
|
jaroslav@1890
|
627 |
* and/or worker terminate.
|
jaroslav@1890
|
628 |
*
|
jaroslav@1890
|
629 |
* @param w the worker
|
jaroslav@1890
|
630 |
*/
|
jaroslav@1890
|
631 |
final void work(ForkJoinWorkerThread w) {
|
jaroslav@1890
|
632 |
boolean swept = false; // true on empty scans
|
jaroslav@1890
|
633 |
long c;
|
jaroslav@1890
|
634 |
while (!w.terminate && (int)(c = ctl) >= 0) {
|
jaroslav@1890
|
635 |
int a; // active count
|
jaroslav@1890
|
636 |
if (!swept && (a = (int)(c >> AC_SHIFT)) <= 0)
|
jaroslav@1890
|
637 |
swept = scan(w, a);
|
jaroslav@1890
|
638 |
else if (tryAwaitWork(w, c))
|
jaroslav@1890
|
639 |
swept = false;
|
jaroslav@1890
|
640 |
}
|
jaroslav@1890
|
641 |
}
|
jaroslav@1890
|
642 |
|
jaroslav@1890
|
643 |
// Signalling
|
jaroslav@1890
|
644 |
|
jaroslav@1890
|
645 |
/**
|
jaroslav@1890
|
646 |
* Wakes up or creates a worker.
|
jaroslav@1890
|
647 |
*/
|
jaroslav@1890
|
648 |
final void signalWork() {
|
jaroslav@1890
|
649 |
/*
|
jaroslav@1890
|
650 |
* The while condition is true if: (there is are too few total
|
jaroslav@1890
|
651 |
* workers OR there is at least one waiter) AND (there are too
|
jaroslav@1890
|
652 |
* few active workers OR the pool is terminating). The value
|
jaroslav@1890
|
653 |
* of e distinguishes the remaining cases: zero (no waiters)
|
jaroslav@1890
|
654 |
* for create, negative if terminating (in which case do
|
jaroslav@1890
|
655 |
* nothing), else release a waiter. The secondary checks for
|
jaroslav@1890
|
656 |
* release (non-null array etc) can fail if the pool begins
|
jaroslav@1890
|
657 |
* terminating after the test, and don't impose any added cost
|
jaroslav@1890
|
658 |
* because JVMs must perform null and bounds checks anyway.
|
jaroslav@1890
|
659 |
*/
|
jaroslav@1890
|
660 |
long c; int e, u;
|
jaroslav@1890
|
661 |
while ((((e = (int)(c = ctl)) | (u = (int)(c >>> 32))) &
|
jaroslav@1890
|
662 |
(INT_SIGN|SHORT_SIGN)) == (INT_SIGN|SHORT_SIGN) && e >= 0) {
|
jaroslav@1890
|
663 |
if (e > 0) { // release a waiting worker
|
jaroslav@1890
|
664 |
int i; ForkJoinWorkerThread w; ForkJoinWorkerThread[] ws;
|
jaroslav@1890
|
665 |
if ((ws = workers) == null ||
|
jaroslav@1890
|
666 |
(i = ~e & SMASK) >= ws.length ||
|
jaroslav@1890
|
667 |
(w = ws[i]) == null)
|
jaroslav@1890
|
668 |
break;
|
jaroslav@1890
|
669 |
long nc = (((long)(w.nextWait & E_MASK)) |
|
jaroslav@1890
|
670 |
((long)(u + UAC_UNIT) << 32));
|
jaroslav@1890
|
671 |
if (w.eventCount == e &&
|
jaroslav@1890
|
672 |
UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) {
|
jaroslav@1890
|
673 |
w.eventCount = (e + EC_UNIT) & E_MASK;
|
jaroslav@1890
|
674 |
if (w.parked)
|
jaroslav@1890
|
675 |
UNSAFE.unpark(w);
|
jaroslav@1890
|
676 |
break;
|
jaroslav@1890
|
677 |
}
|
jaroslav@1890
|
678 |
}
|
jaroslav@1890
|
679 |
else if (UNSAFE.compareAndSwapLong
|
jaroslav@1890
|
680 |
(this, ctlOffset, c,
|
jaroslav@1890
|
681 |
(long)(((u + UTC_UNIT) & UTC_MASK) |
|
jaroslav@1890
|
682 |
((u + UAC_UNIT) & UAC_MASK)) << 32)) {
|
jaroslav@1890
|
683 |
addWorker();
|
jaroslav@1890
|
684 |
break;
|
jaroslav@1890
|
685 |
}
|
jaroslav@1890
|
686 |
}
|
jaroslav@1890
|
687 |
}
|
jaroslav@1890
|
688 |
|
jaroslav@1890
|
689 |
/**
|
jaroslav@1890
|
690 |
* Variant of signalWork to help release waiters on rescans.
|
jaroslav@1890
|
691 |
* Tries once to release a waiter if active count < 0.
|
jaroslav@1890
|
692 |
*
|
jaroslav@1890
|
693 |
* @return false if failed due to contention, else true
|
jaroslav@1890
|
694 |
*/
|
jaroslav@1890
|
695 |
private boolean tryReleaseWaiter() {
|
jaroslav@1890
|
696 |
long c; int e, i; ForkJoinWorkerThread w; ForkJoinWorkerThread[] ws;
|
jaroslav@1890
|
697 |
if ((e = (int)(c = ctl)) > 0 &&
|
jaroslav@1890
|
698 |
(int)(c >> AC_SHIFT) < 0 &&
|
jaroslav@1890
|
699 |
(ws = workers) != null &&
|
jaroslav@1890
|
700 |
(i = ~e & SMASK) < ws.length &&
|
jaroslav@1890
|
701 |
(w = ws[i]) != null) {
|
jaroslav@1890
|
702 |
long nc = ((long)(w.nextWait & E_MASK) |
|
jaroslav@1890
|
703 |
((c + AC_UNIT) & (AC_MASK|TC_MASK)));
|
jaroslav@1890
|
704 |
if (w.eventCount != e ||
|
jaroslav@1890
|
705 |
!UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc))
|
jaroslav@1890
|
706 |
return false;
|
jaroslav@1890
|
707 |
w.eventCount = (e + EC_UNIT) & E_MASK;
|
jaroslav@1890
|
708 |
if (w.parked)
|
jaroslav@1890
|
709 |
UNSAFE.unpark(w);
|
jaroslav@1890
|
710 |
}
|
jaroslav@1890
|
711 |
return true;
|
jaroslav@1890
|
712 |
}
|
jaroslav@1890
|
713 |
|
jaroslav@1890
|
714 |
// Scanning for tasks
|
jaroslav@1890
|
715 |
|
jaroslav@1890
|
716 |
/**
|
jaroslav@1890
|
717 |
* Scans for and, if found, executes one task. Scans start at a
|
jaroslav@1890
|
718 |
* random index of workers array, and randomly select the first
|
jaroslav@1890
|
719 |
* (2*#workers)-1 probes, and then, if all empty, resort to 2
|
jaroslav@1890
|
720 |
* circular sweeps, which is necessary to check quiescence. and
|
jaroslav@1890
|
721 |
* taking a submission only if no stealable tasks were found. The
|
jaroslav@1890
|
722 |
* steal code inside the loop is a specialized form of
|
jaroslav@1890
|
723 |
* ForkJoinWorkerThread.deqTask, followed bookkeeping to support
|
jaroslav@1890
|
724 |
* helpJoinTask and signal propagation. The code for submission
|
jaroslav@1890
|
725 |
* queues is almost identical. On each steal, the worker completes
|
jaroslav@1890
|
726 |
* not only the task, but also all local tasks that this task may
|
jaroslav@1890
|
727 |
* have generated. On detecting staleness or contention when
|
jaroslav@1890
|
728 |
* trying to take a task, this method returns without finishing
|
jaroslav@1890
|
729 |
* sweep, which allows global state rechecks before retry.
|
jaroslav@1890
|
730 |
*
|
jaroslav@1890
|
731 |
* @param w the worker
|
jaroslav@1890
|
732 |
* @param a the number of active workers
|
jaroslav@1890
|
733 |
* @return true if swept all queues without finding a task
|
jaroslav@1890
|
734 |
*/
|
jaroslav@1890
|
735 |
private boolean scan(ForkJoinWorkerThread w, int a) {
|
jaroslav@1890
|
736 |
int g = scanGuard; // mask 0 avoids useless scans if only one active
|
jaroslav@1890
|
737 |
int m = (parallelism == 1 - a && blockedCount == 0) ? 0 : g & SMASK;
|
jaroslav@1890
|
738 |
ForkJoinWorkerThread[] ws = workers;
|
jaroslav@1890
|
739 |
if (ws == null || ws.length <= m) // staleness check
|
jaroslav@1890
|
740 |
return false;
|
jaroslav@1890
|
741 |
for (int r = w.seed, k = r, j = -(m + m); j <= m + m; ++j) {
|
jaroslav@1890
|
742 |
ForkJoinTask<?> t; ForkJoinTask<?>[] q; int b, i;
|
jaroslav@1890
|
743 |
ForkJoinWorkerThread v = ws[k & m];
|
jaroslav@1890
|
744 |
if (v != null && (b = v.queueBase) != v.queueTop &&
|
jaroslav@1890
|
745 |
(q = v.queue) != null && (i = (q.length - 1) & b) >= 0) {
|
jaroslav@1890
|
746 |
long u = (i << ASHIFT) + ABASE;
|
jaroslav@1890
|
747 |
if ((t = q[i]) != null && v.queueBase == b &&
|
jaroslav@1890
|
748 |
UNSAFE.compareAndSwapObject(q, u, t, null)) {
|
jaroslav@1890
|
749 |
int d = (v.queueBase = b + 1) - v.queueTop;
|
jaroslav@1890
|
750 |
v.stealHint = w.poolIndex;
|
jaroslav@1890
|
751 |
if (d != 0)
|
jaroslav@1890
|
752 |
signalWork(); // propagate if nonempty
|
jaroslav@1890
|
753 |
w.execTask(t);
|
jaroslav@1890
|
754 |
}
|
jaroslav@1890
|
755 |
r ^= r << 13; r ^= r >>> 17; w.seed = r ^ (r << 5);
|
jaroslav@1890
|
756 |
return false; // store next seed
|
jaroslav@1890
|
757 |
}
|
jaroslav@1890
|
758 |
else if (j < 0) { // xorshift
|
jaroslav@1890
|
759 |
r ^= r << 13; r ^= r >>> 17; k = r ^= r << 5;
|
jaroslav@1890
|
760 |
}
|
jaroslav@1890
|
761 |
else
|
jaroslav@1890
|
762 |
++k;
|
jaroslav@1890
|
763 |
}
|
jaroslav@1890
|
764 |
if (scanGuard != g) // staleness check
|
jaroslav@1890
|
765 |
return false;
|
jaroslav@1890
|
766 |
else { // try to take submission
|
jaroslav@1890
|
767 |
ForkJoinTask<?> t; ForkJoinTask<?>[] q; int b, i;
|
jaroslav@1890
|
768 |
if ((b = queueBase) != queueTop &&
|
jaroslav@1890
|
769 |
(q = submissionQueue) != null &&
|
jaroslav@1890
|
770 |
(i = (q.length - 1) & b) >= 0) {
|
jaroslav@1890
|
771 |
long u = (i << ASHIFT) + ABASE;
|
jaroslav@1890
|
772 |
if ((t = q[i]) != null && queueBase == b &&
|
jaroslav@1890
|
773 |
UNSAFE.compareAndSwapObject(q, u, t, null)) {
|
jaroslav@1890
|
774 |
queueBase = b + 1;
|
jaroslav@1890
|
775 |
w.execTask(t);
|
jaroslav@1890
|
776 |
}
|
jaroslav@1890
|
777 |
return false;
|
jaroslav@1890
|
778 |
}
|
jaroslav@1890
|
779 |
return true; // all queues empty
|
jaroslav@1890
|
780 |
}
|
jaroslav@1890
|
781 |
}
|
jaroslav@1890
|
782 |
|
jaroslav@1890
|
783 |
/**
|
jaroslav@1890
|
784 |
* Tries to enqueue worker w in wait queue and await change in
|
jaroslav@1890
|
785 |
* worker's eventCount. If the pool is quiescent and there is
|
jaroslav@1890
|
786 |
* more than one worker, possibly terminates worker upon exit.
|
jaroslav@1890
|
787 |
* Otherwise, before blocking, rescans queues to avoid missed
|
jaroslav@1890
|
788 |
* signals. Upon finding work, releases at least one worker
|
jaroslav@1890
|
789 |
* (which may be the current worker). Rescans restart upon
|
jaroslav@1890
|
790 |
* detected staleness or failure to release due to
|
jaroslav@1890
|
791 |
* contention. Note the unusual conventions about Thread.interrupt
|
jaroslav@1890
|
792 |
* here and elsewhere: Because interrupts are used solely to alert
|
jaroslav@1890
|
793 |
* threads to check termination, which is checked here anyway, we
|
jaroslav@1890
|
794 |
* clear status (using Thread.interrupted) before any call to
|
jaroslav@1890
|
795 |
* park, so that park does not immediately return due to status
|
jaroslav@1890
|
796 |
* being set via some other unrelated call to interrupt in user
|
jaroslav@1890
|
797 |
* code.
|
jaroslav@1890
|
798 |
*
|
jaroslav@1890
|
799 |
* @param w the calling worker
|
jaroslav@1890
|
800 |
* @param c the ctl value on entry
|
jaroslav@1890
|
801 |
* @return true if waited or another thread was released upon enq
|
jaroslav@1890
|
802 |
*/
|
jaroslav@1890
|
803 |
private boolean tryAwaitWork(ForkJoinWorkerThread w, long c) {
|
jaroslav@1890
|
804 |
int v = w.eventCount;
|
jaroslav@1890
|
805 |
w.nextWait = (int)c; // w's successor record
|
jaroslav@1890
|
806 |
long nc = (long)(v & E_MASK) | ((c - AC_UNIT) & (AC_MASK|TC_MASK));
|
jaroslav@1890
|
807 |
if (ctl != c || !UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) {
|
jaroslav@1890
|
808 |
long d = ctl; // return true if lost to a deq, to force scan
|
jaroslav@1890
|
809 |
return (int)d != (int)c && ((d - c) & AC_MASK) >= 0L;
|
jaroslav@1890
|
810 |
}
|
jaroslav@1890
|
811 |
for (int sc = w.stealCount; sc != 0;) { // accumulate stealCount
|
jaroslav@1890
|
812 |
long s = stealCount;
|
jaroslav@1890
|
813 |
if (UNSAFE.compareAndSwapLong(this, stealCountOffset, s, s + sc))
|
jaroslav@1890
|
814 |
sc = w.stealCount = 0;
|
jaroslav@1890
|
815 |
else if (w.eventCount != v)
|
jaroslav@1890
|
816 |
return true; // update next time
|
jaroslav@1890
|
817 |
}
|
jaroslav@1890
|
818 |
if ((!shutdown || !tryTerminate(false)) &&
|
jaroslav@1890
|
819 |
(int)c != 0 && parallelism + (int)(nc >> AC_SHIFT) == 0 &&
|
jaroslav@1890
|
820 |
blockedCount == 0 && quiescerCount == 0)
|
jaroslav@1890
|
821 |
idleAwaitWork(w, nc, c, v); // quiescent
|
jaroslav@1890
|
822 |
for (boolean rescanned = false;;) {
|
jaroslav@1890
|
823 |
if (w.eventCount != v)
|
jaroslav@1890
|
824 |
return true;
|
jaroslav@1890
|
825 |
if (!rescanned) {
|
jaroslav@1890
|
826 |
int g = scanGuard, m = g & SMASK;
|
jaroslav@1890
|
827 |
ForkJoinWorkerThread[] ws = workers;
|
jaroslav@1890
|
828 |
if (ws != null && m < ws.length) {
|
jaroslav@1890
|
829 |
rescanned = true;
|
jaroslav@1890
|
830 |
for (int i = 0; i <= m; ++i) {
|
jaroslav@1890
|
831 |
ForkJoinWorkerThread u = ws[i];
|
jaroslav@1890
|
832 |
if (u != null) {
|
jaroslav@1890
|
833 |
if (u.queueBase != u.queueTop &&
|
jaroslav@1890
|
834 |
!tryReleaseWaiter())
|
jaroslav@1890
|
835 |
rescanned = false; // contended
|
jaroslav@1890
|
836 |
if (w.eventCount != v)
|
jaroslav@1890
|
837 |
return true;
|
jaroslav@1890
|
838 |
}
|
jaroslav@1890
|
839 |
}
|
jaroslav@1890
|
840 |
}
|
jaroslav@1890
|
841 |
if (scanGuard != g || // stale
|
jaroslav@1890
|
842 |
(queueBase != queueTop && !tryReleaseWaiter()))
|
jaroslav@1890
|
843 |
rescanned = false;
|
jaroslav@1890
|
844 |
if (!rescanned)
|
jaroslav@1890
|
845 |
Thread.yield(); // reduce contention
|
jaroslav@1890
|
846 |
else
|
jaroslav@1890
|
847 |
Thread.interrupted(); // clear before park
|
jaroslav@1890
|
848 |
}
|
jaroslav@1890
|
849 |
else {
|
jaroslav@1890
|
850 |
w.parked = true; // must recheck
|
jaroslav@1890
|
851 |
if (w.eventCount != v) {
|
jaroslav@1890
|
852 |
w.parked = false;
|
jaroslav@1890
|
853 |
return true;
|
jaroslav@1890
|
854 |
}
|
jaroslav@1890
|
855 |
LockSupport.park(this);
|
jaroslav@1890
|
856 |
rescanned = w.parked = false;
|
jaroslav@1890
|
857 |
}
|
jaroslav@1890
|
858 |
}
|
jaroslav@1890
|
859 |
}
|
jaroslav@1890
|
860 |
|
jaroslav@1890
|
861 |
/**
|
jaroslav@1890
|
862 |
* If inactivating worker w has caused pool to become
|
jaroslav@1890
|
863 |
* quiescent, check for pool termination, and wait for event
|
jaroslav@1890
|
864 |
* for up to SHRINK_RATE nanosecs (rescans are unnecessary in
|
jaroslav@1890
|
865 |
* this case because quiescence reflects consensus about lack
|
jaroslav@1890
|
866 |
* of work). On timeout, if ctl has not changed, terminate the
|
jaroslav@1890
|
867 |
* worker. Upon its termination (see deregisterWorker), it may
|
jaroslav@1890
|
868 |
* wake up another worker to possibly repeat this process.
|
jaroslav@1890
|
869 |
*
|
jaroslav@1890
|
870 |
* @param w the calling worker
|
jaroslav@1890
|
871 |
* @param currentCtl the ctl value after enqueuing w
|
jaroslav@1890
|
872 |
* @param prevCtl the ctl value if w terminated
|
jaroslav@1890
|
873 |
* @param v the eventCount w awaits change
|
jaroslav@1890
|
874 |
*/
|
jaroslav@1890
|
875 |
private void idleAwaitWork(ForkJoinWorkerThread w, long currentCtl,
|
jaroslav@1890
|
876 |
long prevCtl, int v) {
|
jaroslav@1890
|
877 |
if (w.eventCount == v) {
|
jaroslav@1890
|
878 |
if (shutdown)
|
jaroslav@1890
|
879 |
tryTerminate(false);
|
jaroslav@1890
|
880 |
ForkJoinTask.helpExpungeStaleExceptions(); // help clean weak refs
|
jaroslav@1890
|
881 |
while (ctl == currentCtl) {
|
jaroslav@1890
|
882 |
long startTime = System.nanoTime();
|
jaroslav@1890
|
883 |
w.parked = true;
|
jaroslav@1890
|
884 |
if (w.eventCount == v) // must recheck
|
jaroslav@1890
|
885 |
LockSupport.parkNanos(this, SHRINK_RATE);
|
jaroslav@1890
|
886 |
w.parked = false;
|
jaroslav@1890
|
887 |
if (w.eventCount != v)
|
jaroslav@1890
|
888 |
break;
|
jaroslav@1890
|
889 |
else if (System.nanoTime() - startTime <
|
jaroslav@1890
|
890 |
SHRINK_RATE - (SHRINK_RATE / 10)) // timing slop
|
jaroslav@1890
|
891 |
Thread.interrupted(); // spurious wakeup
|
jaroslav@1890
|
892 |
else if (UNSAFE.compareAndSwapLong(this, ctlOffset,
|
jaroslav@1890
|
893 |
currentCtl, prevCtl)) {
|
jaroslav@1890
|
894 |
w.terminate = true; // restore previous
|
jaroslav@1890
|
895 |
w.eventCount = ((int)currentCtl + EC_UNIT) & E_MASK;
|
jaroslav@1890
|
896 |
break;
|
jaroslav@1890
|
897 |
}
|
jaroslav@1890
|
898 |
}
|
jaroslav@1890
|
899 |
}
|
jaroslav@1890
|
900 |
}
|
jaroslav@1890
|
901 |
|
jaroslav@1890
|
902 |
// Submissions
|
jaroslav@1890
|
903 |
|
jaroslav@1890
|
904 |
/**
|
jaroslav@1890
|
905 |
* Enqueues the given task in the submissionQueue. Same idea as
|
jaroslav@1890
|
906 |
* ForkJoinWorkerThread.pushTask except for use of submissionLock.
|
jaroslav@1890
|
907 |
*
|
jaroslav@1890
|
908 |
* @param t the task
|
jaroslav@1890
|
909 |
*/
|
jaroslav@1890
|
910 |
private void addSubmission(ForkJoinTask<?> t) {
|
jaroslav@1890
|
911 |
final ReentrantLock lock = this.submissionLock;
|
jaroslav@1890
|
912 |
lock.lock();
|
jaroslav@1890
|
913 |
try {
|
jaroslav@1890
|
914 |
ForkJoinTask<?>[] q; int s, m;
|
jaroslav@1890
|
915 |
if ((q = submissionQueue) != null) { // ignore if queue removed
|
jaroslav@1890
|
916 |
long u = (((s = queueTop) & (m = q.length-1)) << ASHIFT)+ABASE;
|
jaroslav@1890
|
917 |
UNSAFE.putOrderedObject(q, u, t);
|
jaroslav@1890
|
918 |
queueTop = s + 1;
|
jaroslav@1890
|
919 |
if (s - queueBase == m)
|
jaroslav@1890
|
920 |
growSubmissionQueue();
|
jaroslav@1890
|
921 |
}
|
jaroslav@1890
|
922 |
} finally {
|
jaroslav@1890
|
923 |
lock.unlock();
|
jaroslav@1890
|
924 |
}
|
jaroslav@1890
|
925 |
signalWork();
|
jaroslav@1890
|
926 |
}
|
jaroslav@1890
|
927 |
|
jaroslav@1890
|
928 |
// (pollSubmission is defined below with exported methods)
|
jaroslav@1890
|
929 |
|
jaroslav@1890
|
930 |
/**
|
jaroslav@1890
|
931 |
* Creates or doubles submissionQueue array.
|
jaroslav@1890
|
932 |
* Basically identical to ForkJoinWorkerThread version.
|
jaroslav@1890
|
933 |
*/
|
jaroslav@1890
|
934 |
private void growSubmissionQueue() {
|
jaroslav@1890
|
935 |
ForkJoinTask<?>[] oldQ = submissionQueue;
|
jaroslav@1890
|
936 |
int size = oldQ != null ? oldQ.length << 1 : INITIAL_QUEUE_CAPACITY;
|
jaroslav@1890
|
937 |
if (size > MAXIMUM_QUEUE_CAPACITY)
|
jaroslav@1890
|
938 |
throw new RejectedExecutionException("Queue capacity exceeded");
|
jaroslav@1890
|
939 |
if (size < INITIAL_QUEUE_CAPACITY)
|
jaroslav@1890
|
940 |
size = INITIAL_QUEUE_CAPACITY;
|
jaroslav@1890
|
941 |
ForkJoinTask<?>[] q = submissionQueue = new ForkJoinTask<?>[size];
|
jaroslav@1890
|
942 |
int mask = size - 1;
|
jaroslav@1890
|
943 |
int top = queueTop;
|
jaroslav@1890
|
944 |
int oldMask;
|
jaroslav@1890
|
945 |
if (oldQ != null && (oldMask = oldQ.length - 1) >= 0) {
|
jaroslav@1890
|
946 |
for (int b = queueBase; b != top; ++b) {
|
jaroslav@1890
|
947 |
long u = ((b & oldMask) << ASHIFT) + ABASE;
|
jaroslav@1890
|
948 |
Object x = UNSAFE.getObjectVolatile(oldQ, u);
|
jaroslav@1890
|
949 |
if (x != null && UNSAFE.compareAndSwapObject(oldQ, u, x, null))
|
jaroslav@1890
|
950 |
UNSAFE.putObjectVolatile
|
jaroslav@1890
|
951 |
(q, ((b & mask) << ASHIFT) + ABASE, x);
|
jaroslav@1890
|
952 |
}
|
jaroslav@1890
|
953 |
}
|
jaroslav@1890
|
954 |
}
|
jaroslav@1890
|
955 |
|
jaroslav@1890
|
956 |
// Blocking support
|
jaroslav@1890
|
957 |
|
jaroslav@1890
|
958 |
/**
|
jaroslav@1890
|
959 |
* Tries to increment blockedCount, decrement active count
|
jaroslav@1890
|
960 |
* (sometimes implicitly) and possibly release or create a
|
jaroslav@1890
|
961 |
* compensating worker in preparation for blocking. Fails
|
jaroslav@1890
|
962 |
* on contention or termination.
|
jaroslav@1890
|
963 |
*
|
jaroslav@1890
|
964 |
* @return true if the caller can block, else should recheck and retry
|
jaroslav@1890
|
965 |
*/
|
jaroslav@1890
|
966 |
private boolean tryPreBlock() {
|
jaroslav@1890
|
967 |
int b = blockedCount;
|
jaroslav@1890
|
968 |
if (UNSAFE.compareAndSwapInt(this, blockedCountOffset, b, b + 1)) {
|
jaroslav@1890
|
969 |
int pc = parallelism;
|
jaroslav@1890
|
970 |
do {
|
jaroslav@1890
|
971 |
ForkJoinWorkerThread[] ws; ForkJoinWorkerThread w;
|
jaroslav@1890
|
972 |
int e, ac, tc, rc, i;
|
jaroslav@1890
|
973 |
long c = ctl;
|
jaroslav@1890
|
974 |
int u = (int)(c >>> 32);
|
jaroslav@1890
|
975 |
if ((e = (int)c) < 0) {
|
jaroslav@1890
|
976 |
// skip -- terminating
|
jaroslav@1890
|
977 |
}
|
jaroslav@1890
|
978 |
else if ((ac = (u >> UAC_SHIFT)) <= 0 && e != 0 &&
|
jaroslav@1890
|
979 |
(ws = workers) != null &&
|
jaroslav@1890
|
980 |
(i = ~e & SMASK) < ws.length &&
|
jaroslav@1890
|
981 |
(w = ws[i]) != null) {
|
jaroslav@1890
|
982 |
long nc = ((long)(w.nextWait & E_MASK) |
|
jaroslav@1890
|
983 |
(c & (AC_MASK|TC_MASK)));
|
jaroslav@1890
|
984 |
if (w.eventCount == e &&
|
jaroslav@1890
|
985 |
UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) {
|
jaroslav@1890
|
986 |
w.eventCount = (e + EC_UNIT) & E_MASK;
|
jaroslav@1890
|
987 |
if (w.parked)
|
jaroslav@1890
|
988 |
UNSAFE.unpark(w);
|
jaroslav@1890
|
989 |
return true; // release an idle worker
|
jaroslav@1890
|
990 |
}
|
jaroslav@1890
|
991 |
}
|
jaroslav@1890
|
992 |
else if ((tc = (short)(u >>> UTC_SHIFT)) >= 0 && ac + pc > 1) {
|
jaroslav@1890
|
993 |
long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK);
|
jaroslav@1890
|
994 |
if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc))
|
jaroslav@1890
|
995 |
return true; // no compensation needed
|
jaroslav@1890
|
996 |
}
|
jaroslav@1890
|
997 |
else if (tc + pc < MAX_ID) {
|
jaroslav@1890
|
998 |
long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK);
|
jaroslav@1890
|
999 |
if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) {
|
jaroslav@1890
|
1000 |
addWorker();
|
jaroslav@1890
|
1001 |
return true; // create a replacement
|
jaroslav@1890
|
1002 |
}
|
jaroslav@1890
|
1003 |
}
|
jaroslav@1890
|
1004 |
// try to back out on any failure and let caller retry
|
jaroslav@1890
|
1005 |
} while (!UNSAFE.compareAndSwapInt(this, blockedCountOffset,
|
jaroslav@1890
|
1006 |
b = blockedCount, b - 1));
|
jaroslav@1890
|
1007 |
}
|
jaroslav@1890
|
1008 |
return false;
|
jaroslav@1890
|
1009 |
}
|
jaroslav@1890
|
1010 |
|
jaroslav@1890
|
1011 |
/**
|
jaroslav@1890
|
1012 |
* Decrements blockedCount and increments active count
|
jaroslav@1890
|
1013 |
*/
|
jaroslav@1890
|
1014 |
private void postBlock() {
|
jaroslav@1890
|
1015 |
long c;
|
jaroslav@1890
|
1016 |
do {} while (!UNSAFE.compareAndSwapLong(this, ctlOffset, // no mask
|
jaroslav@1890
|
1017 |
c = ctl, c + AC_UNIT));
|
jaroslav@1890
|
1018 |
int b;
|
jaroslav@1890
|
1019 |
do {} while (!UNSAFE.compareAndSwapInt(this, blockedCountOffset,
|
jaroslav@1890
|
1020 |
b = blockedCount, b - 1));
|
jaroslav@1890
|
1021 |
}
|
jaroslav@1890
|
1022 |
|
jaroslav@1890
|
1023 |
/**
|
jaroslav@1890
|
1024 |
* Possibly blocks waiting for the given task to complete, or
|
jaroslav@1890
|
1025 |
* cancels the task if terminating. Fails to wait if contended.
|
jaroslav@1890
|
1026 |
*
|
jaroslav@1890
|
1027 |
* @param joinMe the task
|
jaroslav@1890
|
1028 |
*/
|
jaroslav@1890
|
1029 |
final void tryAwaitJoin(ForkJoinTask<?> joinMe) {
|
jaroslav@1890
|
1030 |
int s;
|
jaroslav@1890
|
1031 |
Thread.interrupted(); // clear interrupts before checking termination
|
jaroslav@1890
|
1032 |
if (joinMe.status >= 0) {
|
jaroslav@1890
|
1033 |
if (tryPreBlock()) {
|
jaroslav@1890
|
1034 |
joinMe.tryAwaitDone(0L);
|
jaroslav@1890
|
1035 |
postBlock();
|
jaroslav@1890
|
1036 |
}
|
jaroslav@1890
|
1037 |
else if ((ctl & STOP_BIT) != 0L)
|
jaroslav@1890
|
1038 |
joinMe.cancelIgnoringExceptions();
|
jaroslav@1890
|
1039 |
}
|
jaroslav@1890
|
1040 |
}
|
jaroslav@1890
|
1041 |
|
jaroslav@1890
|
1042 |
/**
|
jaroslav@1890
|
1043 |
* Possibly blocks the given worker waiting for joinMe to
|
jaroslav@1890
|
1044 |
* complete or timeout
|
jaroslav@1890
|
1045 |
*
|
jaroslav@1890
|
1046 |
* @param joinMe the task
|
jaroslav@1890
|
1047 |
* @param millis the wait time for underlying Object.wait
|
jaroslav@1890
|
1048 |
*/
|
jaroslav@1890
|
1049 |
final void timedAwaitJoin(ForkJoinTask<?> joinMe, long nanos) {
|
jaroslav@1890
|
1050 |
while (joinMe.status >= 0) {
|
jaroslav@1890
|
1051 |
Thread.interrupted();
|
jaroslav@1890
|
1052 |
if ((ctl & STOP_BIT) != 0L) {
|
jaroslav@1890
|
1053 |
joinMe.cancelIgnoringExceptions();
|
jaroslav@1890
|
1054 |
break;
|
jaroslav@1890
|
1055 |
}
|
jaroslav@1890
|
1056 |
if (tryPreBlock()) {
|
jaroslav@1890
|
1057 |
long last = System.nanoTime();
|
jaroslav@1890
|
1058 |
while (joinMe.status >= 0) {
|
jaroslav@1890
|
1059 |
long millis = TimeUnit.NANOSECONDS.toMillis(nanos);
|
jaroslav@1890
|
1060 |
if (millis <= 0)
|
jaroslav@1890
|
1061 |
break;
|
jaroslav@1890
|
1062 |
joinMe.tryAwaitDone(millis);
|
jaroslav@1890
|
1063 |
if (joinMe.status < 0)
|
jaroslav@1890
|
1064 |
break;
|
jaroslav@1890
|
1065 |
if ((ctl & STOP_BIT) != 0L) {
|
jaroslav@1890
|
1066 |
joinMe.cancelIgnoringExceptions();
|
jaroslav@1890
|
1067 |
break;
|
jaroslav@1890
|
1068 |
}
|
jaroslav@1890
|
1069 |
long now = System.nanoTime();
|
jaroslav@1890
|
1070 |
nanos -= now - last;
|
jaroslav@1890
|
1071 |
last = now;
|
jaroslav@1890
|
1072 |
}
|
jaroslav@1890
|
1073 |
postBlock();
|
jaroslav@1890
|
1074 |
break;
|
jaroslav@1890
|
1075 |
}
|
jaroslav@1890
|
1076 |
}
|
jaroslav@1890
|
1077 |
}
|
jaroslav@1890
|
1078 |
|
jaroslav@1890
|
1079 |
/**
|
jaroslav@1890
|
1080 |
* If necessary, compensates for blocker, and blocks
|
jaroslav@1890
|
1081 |
*/
|
jaroslav@1890
|
1082 |
private void awaitBlocker(ManagedBlocker blocker)
|
jaroslav@1890
|
1083 |
throws InterruptedException {
|
jaroslav@1890
|
1084 |
while (!blocker.isReleasable()) {
|
jaroslav@1890
|
1085 |
if (tryPreBlock()) {
|
jaroslav@1890
|
1086 |
try {
|
jaroslav@1890
|
1087 |
do {} while (!blocker.isReleasable() && !blocker.block());
|
jaroslav@1890
|
1088 |
} finally {
|
jaroslav@1890
|
1089 |
postBlock();
|
jaroslav@1890
|
1090 |
}
|
jaroslav@1890
|
1091 |
break;
|
jaroslav@1890
|
1092 |
}
|
jaroslav@1890
|
1093 |
}
|
jaroslav@1890
|
1094 |
}
|
jaroslav@1890
|
1095 |
|
jaroslav@1890
|
1096 |
// Creating, registering and deregistring workers
|
jaroslav@1890
|
1097 |
|
jaroslav@1890
|
1098 |
/**
|
jaroslav@1890
|
1099 |
* Tries to create and start a worker; minimally rolls back counts
|
jaroslav@1890
|
1100 |
* on failure.
|
jaroslav@1890
|
1101 |
*/
|
jaroslav@1890
|
1102 |
private void addWorker() {
|
jaroslav@1890
|
1103 |
Throwable ex = null;
|
jaroslav@1890
|
1104 |
ForkJoinWorkerThread t = null;
|
jaroslav@1890
|
1105 |
try {
|
jaroslav@1890
|
1106 |
t = factory.newThread(this);
|
jaroslav@1890
|
1107 |
} catch (Throwable e) {
|
jaroslav@1890
|
1108 |
ex = e;
|
jaroslav@1890
|
1109 |
}
|
jaroslav@1890
|
1110 |
if (t == null) { // null or exceptional factory return
|
jaroslav@1890
|
1111 |
long c; // adjust counts
|
jaroslav@1890
|
1112 |
do {} while (!UNSAFE.compareAndSwapLong
|
jaroslav@1890
|
1113 |
(this, ctlOffset, c = ctl,
|
jaroslav@1890
|
1114 |
(((c - AC_UNIT) & AC_MASK) |
|
jaroslav@1890
|
1115 |
((c - TC_UNIT) & TC_MASK) |
|
jaroslav@1890
|
1116 |
(c & ~(AC_MASK|TC_MASK)))));
|
jaroslav@1890
|
1117 |
// Propagate exception if originating from an external caller
|
jaroslav@1890
|
1118 |
if (!tryTerminate(false) && ex != null &&
|
jaroslav@1890
|
1119 |
!(Thread.currentThread() instanceof ForkJoinWorkerThread))
|
jaroslav@1890
|
1120 |
UNSAFE.throwException(ex);
|
jaroslav@1890
|
1121 |
}
|
jaroslav@1890
|
1122 |
else
|
jaroslav@1890
|
1123 |
t.start();
|
jaroslav@1890
|
1124 |
}
|
jaroslav@1890
|
1125 |
|
jaroslav@1890
|
1126 |
/**
|
jaroslav@1890
|
1127 |
* Callback from ForkJoinWorkerThread constructor to assign a
|
jaroslav@1890
|
1128 |
* public name
|
jaroslav@1890
|
1129 |
*/
|
jaroslav@1890
|
1130 |
final String nextWorkerName() {
|
jaroslav@1890
|
1131 |
for (int n;;) {
|
jaroslav@1890
|
1132 |
if (UNSAFE.compareAndSwapInt(this, nextWorkerNumberOffset,
|
jaroslav@1890
|
1133 |
n = nextWorkerNumber, ++n))
|
jaroslav@1890
|
1134 |
return workerNamePrefix + n;
|
jaroslav@1890
|
1135 |
}
|
jaroslav@1890
|
1136 |
}
|
jaroslav@1890
|
1137 |
|
jaroslav@1890
|
1138 |
/**
|
jaroslav@1890
|
1139 |
* Callback from ForkJoinWorkerThread constructor to
|
jaroslav@1890
|
1140 |
* determine its poolIndex and record in workers array.
|
jaroslav@1890
|
1141 |
*
|
jaroslav@1890
|
1142 |
* @param w the worker
|
jaroslav@1890
|
1143 |
* @return the worker's pool index
|
jaroslav@1890
|
1144 |
*/
|
jaroslav@1890
|
1145 |
final int registerWorker(ForkJoinWorkerThread w) {
|
jaroslav@1890
|
1146 |
/*
|
jaroslav@1890
|
1147 |
* In the typical case, a new worker acquires the lock, uses
|
jaroslav@1890
|
1148 |
* next available index and returns quickly. Since we should
|
jaroslav@1890
|
1149 |
* not block callers (ultimately from signalWork or
|
jaroslav@1890
|
1150 |
* tryPreBlock) waiting for the lock needed to do this, we
|
jaroslav@1890
|
1151 |
* instead help release other workers while waiting for the
|
jaroslav@1890
|
1152 |
* lock.
|
jaroslav@1890
|
1153 |
*/
|
jaroslav@1890
|
1154 |
for (int g;;) {
|
jaroslav@1890
|
1155 |
ForkJoinWorkerThread[] ws;
|
jaroslav@1890
|
1156 |
if (((g = scanGuard) & SG_UNIT) == 0 &&
|
jaroslav@1890
|
1157 |
UNSAFE.compareAndSwapInt(this, scanGuardOffset,
|
jaroslav@1890
|
1158 |
g, g | SG_UNIT)) {
|
jaroslav@1890
|
1159 |
int k = nextWorkerIndex;
|
jaroslav@1890
|
1160 |
try {
|
jaroslav@1890
|
1161 |
if ((ws = workers) != null) { // ignore on shutdown
|
jaroslav@1890
|
1162 |
int n = ws.length;
|
jaroslav@1890
|
1163 |
if (k < 0 || k >= n || ws[k] != null) {
|
jaroslav@1890
|
1164 |
for (k = 0; k < n && ws[k] != null; ++k)
|
jaroslav@1890
|
1165 |
;
|
jaroslav@1890
|
1166 |
if (k == n)
|
jaroslav@1890
|
1167 |
ws = workers = Arrays.copyOf(ws, n << 1);
|
jaroslav@1890
|
1168 |
}
|
jaroslav@1890
|
1169 |
ws[k] = w;
|
jaroslav@1890
|
1170 |
nextWorkerIndex = k + 1;
|
jaroslav@1890
|
1171 |
int m = g & SMASK;
|
jaroslav@1890
|
1172 |
g = (k > m) ? ((m << 1) + 1) & SMASK : g + (SG_UNIT<<1);
|
jaroslav@1890
|
1173 |
}
|
jaroslav@1890
|
1174 |
} finally {
|
jaroslav@1890
|
1175 |
scanGuard = g;
|
jaroslav@1890
|
1176 |
}
|
jaroslav@1890
|
1177 |
return k;
|
jaroslav@1890
|
1178 |
}
|
jaroslav@1890
|
1179 |
else if ((ws = workers) != null) { // help release others
|
jaroslav@1890
|
1180 |
for (ForkJoinWorkerThread u : ws) {
|
jaroslav@1890
|
1181 |
if (u != null && u.queueBase != u.queueTop) {
|
jaroslav@1890
|
1182 |
if (tryReleaseWaiter())
|
jaroslav@1890
|
1183 |
break;
|
jaroslav@1890
|
1184 |
}
|
jaroslav@1890
|
1185 |
}
|
jaroslav@1890
|
1186 |
}
|
jaroslav@1890
|
1187 |
}
|
jaroslav@1890
|
1188 |
}
|
jaroslav@1890
|
1189 |
|
jaroslav@1890
|
1190 |
/**
|
jaroslav@1890
|
1191 |
* Final callback from terminating worker. Removes record of
|
jaroslav@1890
|
1192 |
* worker from array, and adjusts counts. If pool is shutting
|
jaroslav@1890
|
1193 |
* down, tries to complete termination.
|
jaroslav@1890
|
1194 |
*
|
jaroslav@1890
|
1195 |
* @param w the worker
|
jaroslav@1890
|
1196 |
*/
|
jaroslav@1890
|
1197 |
final void deregisterWorker(ForkJoinWorkerThread w, Throwable ex) {
|
jaroslav@1890
|
1198 |
int idx = w.poolIndex;
|
jaroslav@1890
|
1199 |
int sc = w.stealCount;
|
jaroslav@1890
|
1200 |
int steps = 0;
|
jaroslav@1890
|
1201 |
// Remove from array, adjust worker counts and collect steal count.
|
jaroslav@1890
|
1202 |
// We can intermix failed removes or adjusts with steal updates
|
jaroslav@1890
|
1203 |
do {
|
jaroslav@1890
|
1204 |
long s, c;
|
jaroslav@1890
|
1205 |
int g;
|
jaroslav@1890
|
1206 |
if (steps == 0 && ((g = scanGuard) & SG_UNIT) == 0 &&
|
jaroslav@1890
|
1207 |
UNSAFE.compareAndSwapInt(this, scanGuardOffset,
|
jaroslav@1890
|
1208 |
g, g |= SG_UNIT)) {
|
jaroslav@1890
|
1209 |
ForkJoinWorkerThread[] ws = workers;
|
jaroslav@1890
|
1210 |
if (ws != null && idx >= 0 &&
|
jaroslav@1890
|
1211 |
idx < ws.length && ws[idx] == w)
|
jaroslav@1890
|
1212 |
ws[idx] = null; // verify
|
jaroslav@1890
|
1213 |
nextWorkerIndex = idx;
|
jaroslav@1890
|
1214 |
scanGuard = g + SG_UNIT;
|
jaroslav@1890
|
1215 |
steps = 1;
|
jaroslav@1890
|
1216 |
}
|
jaroslav@1890
|
1217 |
if (steps == 1 &&
|
jaroslav@1890
|
1218 |
UNSAFE.compareAndSwapLong(this, ctlOffset, c = ctl,
|
jaroslav@1890
|
1219 |
(((c - AC_UNIT) & AC_MASK) |
|
jaroslav@1890
|
1220 |
((c - TC_UNIT) & TC_MASK) |
|
jaroslav@1890
|
1221 |
(c & ~(AC_MASK|TC_MASK)))))
|
jaroslav@1890
|
1222 |
steps = 2;
|
jaroslav@1890
|
1223 |
if (sc != 0 &&
|
jaroslav@1890
|
1224 |
UNSAFE.compareAndSwapLong(this, stealCountOffset,
|
jaroslav@1890
|
1225 |
s = stealCount, s + sc))
|
jaroslav@1890
|
1226 |
sc = 0;
|
jaroslav@1890
|
1227 |
} while (steps != 2 || sc != 0);
|
jaroslav@1890
|
1228 |
if (!tryTerminate(false)) {
|
jaroslav@1890
|
1229 |
if (ex != null) // possibly replace if died abnormally
|
jaroslav@1890
|
1230 |
signalWork();
|
jaroslav@1890
|
1231 |
else
|
jaroslav@1890
|
1232 |
tryReleaseWaiter();
|
jaroslav@1890
|
1233 |
}
|
jaroslav@1890
|
1234 |
}
|
jaroslav@1890
|
1235 |
|
jaroslav@1890
|
1236 |
// Shutdown and termination
|
jaroslav@1890
|
1237 |
|
jaroslav@1890
|
1238 |
/**
|
jaroslav@1890
|
1239 |
* Possibly initiates and/or completes termination.
|
jaroslav@1890
|
1240 |
*
|
jaroslav@1890
|
1241 |
* @param now if true, unconditionally terminate, else only
|
jaroslav@1890
|
1242 |
* if shutdown and empty queue and no active workers
|
jaroslav@1890
|
1243 |
* @return true if now terminating or terminated
|
jaroslav@1890
|
1244 |
*/
|
jaroslav@1890
|
1245 |
private boolean tryTerminate(boolean now) {
|
jaroslav@1890
|
1246 |
long c;
|
jaroslav@1890
|
1247 |
while (((c = ctl) & STOP_BIT) == 0) {
|
jaroslav@1890
|
1248 |
if (!now) {
|
jaroslav@1890
|
1249 |
if ((int)(c >> AC_SHIFT) != -parallelism)
|
jaroslav@1890
|
1250 |
return false;
|
jaroslav@1890
|
1251 |
if (!shutdown || blockedCount != 0 || quiescerCount != 0 ||
|
jaroslav@1890
|
1252 |
queueBase != queueTop) {
|
jaroslav@1890
|
1253 |
if (ctl == c) // staleness check
|
jaroslav@1890
|
1254 |
return false;
|
jaroslav@1890
|
1255 |
continue;
|
jaroslav@1890
|
1256 |
}
|
jaroslav@1890
|
1257 |
}
|
jaroslav@1890
|
1258 |
if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, c | STOP_BIT))
|
jaroslav@1890
|
1259 |
startTerminating();
|
jaroslav@1890
|
1260 |
}
|
jaroslav@1890
|
1261 |
if ((short)(c >>> TC_SHIFT) == -parallelism) { // signal when 0 workers
|
jaroslav@1890
|
1262 |
final ReentrantLock lock = this.submissionLock;
|
jaroslav@1890
|
1263 |
lock.lock();
|
jaroslav@1890
|
1264 |
try {
|
jaroslav@1890
|
1265 |
termination.signalAll();
|
jaroslav@1890
|
1266 |
} finally {
|
jaroslav@1890
|
1267 |
lock.unlock();
|
jaroslav@1890
|
1268 |
}
|
jaroslav@1890
|
1269 |
}
|
jaroslav@1890
|
1270 |
return true;
|
jaroslav@1890
|
1271 |
}
|
jaroslav@1890
|
1272 |
|
jaroslav@1890
|
1273 |
/**
|
jaroslav@1890
|
1274 |
* Runs up to three passes through workers: (0) Setting
|
jaroslav@1890
|
1275 |
* termination status for each worker, followed by wakeups up to
|
jaroslav@1890
|
1276 |
* queued workers; (1) helping cancel tasks; (2) interrupting
|
jaroslav@1890
|
1277 |
* lagging threads (likely in external tasks, but possibly also
|
jaroslav@1890
|
1278 |
* blocked in joins). Each pass repeats previous steps because of
|
jaroslav@1890
|
1279 |
* potential lagging thread creation.
|
jaroslav@1890
|
1280 |
*/
|
jaroslav@1890
|
1281 |
private void startTerminating() {
|
jaroslav@1890
|
1282 |
cancelSubmissions();
|
jaroslav@1890
|
1283 |
for (int pass = 0; pass < 3; ++pass) {
|
jaroslav@1890
|
1284 |
ForkJoinWorkerThread[] ws = workers;
|
jaroslav@1890
|
1285 |
if (ws != null) {
|
jaroslav@1890
|
1286 |
for (ForkJoinWorkerThread w : ws) {
|
jaroslav@1890
|
1287 |
if (w != null) {
|
jaroslav@1890
|
1288 |
w.terminate = true;
|
jaroslav@1890
|
1289 |
if (pass > 0) {
|
jaroslav@1890
|
1290 |
w.cancelTasks();
|
jaroslav@1890
|
1291 |
if (pass > 1 && !w.isInterrupted()) {
|
jaroslav@1890
|
1292 |
try {
|
jaroslav@1890
|
1293 |
w.interrupt();
|
jaroslav@1890
|
1294 |
} catch (SecurityException ignore) {
|
jaroslav@1890
|
1295 |
}
|
jaroslav@1890
|
1296 |
}
|
jaroslav@1890
|
1297 |
}
|
jaroslav@1890
|
1298 |
}
|
jaroslav@1890
|
1299 |
}
|
jaroslav@1890
|
1300 |
terminateWaiters();
|
jaroslav@1890
|
1301 |
}
|
jaroslav@1890
|
1302 |
}
|
jaroslav@1890
|
1303 |
}
|
jaroslav@1890
|
1304 |
|
jaroslav@1890
|
1305 |
/**
|
jaroslav@1890
|
1306 |
* Polls and cancels all submissions. Called only during termination.
|
jaroslav@1890
|
1307 |
*/
|
jaroslav@1890
|
1308 |
private void cancelSubmissions() {
|
jaroslav@1890
|
1309 |
while (queueBase != queueTop) {
|
jaroslav@1890
|
1310 |
ForkJoinTask<?> task = pollSubmission();
|
jaroslav@1890
|
1311 |
if (task != null) {
|
jaroslav@1890
|
1312 |
try {
|
jaroslav@1890
|
1313 |
task.cancel(false);
|
jaroslav@1890
|
1314 |
} catch (Throwable ignore) {
|
jaroslav@1890
|
1315 |
}
|
jaroslav@1890
|
1316 |
}
|
jaroslav@1890
|
1317 |
}
|
jaroslav@1890
|
1318 |
}
|
jaroslav@1890
|
1319 |
|
jaroslav@1890
|
1320 |
/**
|
jaroslav@1890
|
1321 |
* Tries to set the termination status of waiting workers, and
|
jaroslav@1890
|
1322 |
* then wakes them up (after which they will terminate).
|
jaroslav@1890
|
1323 |
*/
|
jaroslav@1890
|
1324 |
private void terminateWaiters() {
|
jaroslav@1890
|
1325 |
ForkJoinWorkerThread[] ws = workers;
|
jaroslav@1890
|
1326 |
if (ws != null) {
|
jaroslav@1890
|
1327 |
ForkJoinWorkerThread w; long c; int i, e;
|
jaroslav@1890
|
1328 |
int n = ws.length;
|
jaroslav@1890
|
1329 |
while ((i = ~(e = (int)(c = ctl)) & SMASK) < n &&
|
jaroslav@1890
|
1330 |
(w = ws[i]) != null && w.eventCount == (e & E_MASK)) {
|
jaroslav@1890
|
1331 |
if (UNSAFE.compareAndSwapLong(this, ctlOffset, c,
|
jaroslav@1890
|
1332 |
(long)(w.nextWait & E_MASK) |
|
jaroslav@1890
|
1333 |
((c + AC_UNIT) & AC_MASK) |
|
jaroslav@1890
|
1334 |
(c & (TC_MASK|STOP_BIT)))) {
|
jaroslav@1890
|
1335 |
w.terminate = true;
|
jaroslav@1890
|
1336 |
w.eventCount = e + EC_UNIT;
|
jaroslav@1890
|
1337 |
if (w.parked)
|
jaroslav@1890
|
1338 |
UNSAFE.unpark(w);
|
jaroslav@1890
|
1339 |
}
|
jaroslav@1890
|
1340 |
}
|
jaroslav@1890
|
1341 |
}
|
jaroslav@1890
|
1342 |
}
|
jaroslav@1890
|
1343 |
|
jaroslav@1890
|
1344 |
// misc ForkJoinWorkerThread support
|
jaroslav@1890
|
1345 |
|
jaroslav@1890
|
1346 |
/**
|
jaroslav@1890
|
1347 |
* Increment or decrement quiescerCount. Needed only to prevent
|
jaroslav@1890
|
1348 |
* triggering shutdown if a worker is transiently inactive while
|
jaroslav@1890
|
1349 |
* checking quiescence.
|
jaroslav@1890
|
1350 |
*
|
jaroslav@1890
|
1351 |
* @param delta 1 for increment, -1 for decrement
|
jaroslav@1890
|
1352 |
*/
|
jaroslav@1890
|
1353 |
final void addQuiescerCount(int delta) {
|
jaroslav@1890
|
1354 |
int c;
|
jaroslav@1890
|
1355 |
do {} while (!UNSAFE.compareAndSwapInt(this, quiescerCountOffset,
|
jaroslav@1890
|
1356 |
c = quiescerCount, c + delta));
|
jaroslav@1890
|
1357 |
}
|
jaroslav@1890
|
1358 |
|
jaroslav@1890
|
1359 |
/**
|
jaroslav@1890
|
1360 |
* Directly increment or decrement active count without
|
jaroslav@1890
|
1361 |
* queuing. This method is used to transiently assert inactivation
|
jaroslav@1890
|
1362 |
* while checking quiescence.
|
jaroslav@1890
|
1363 |
*
|
jaroslav@1890
|
1364 |
* @param delta 1 for increment, -1 for decrement
|
jaroslav@1890
|
1365 |
*/
|
jaroslav@1890
|
1366 |
final void addActiveCount(int delta) {
|
jaroslav@1890
|
1367 |
long d = delta < 0 ? -AC_UNIT : AC_UNIT;
|
jaroslav@1890
|
1368 |
long c;
|
jaroslav@1890
|
1369 |
do {} while (!UNSAFE.compareAndSwapLong(this, ctlOffset, c = ctl,
|
jaroslav@1890
|
1370 |
((c + d) & AC_MASK) |
|
jaroslav@1890
|
1371 |
(c & ~AC_MASK)));
|
jaroslav@1890
|
1372 |
}
|
jaroslav@1890
|
1373 |
|
jaroslav@1890
|
1374 |
/**
|
jaroslav@1890
|
1375 |
* Returns the approximate (non-atomic) number of idle threads per
|
jaroslav@1890
|
1376 |
* active thread.
|
jaroslav@1890
|
1377 |
*/
|
jaroslav@1890
|
1378 |
final int idlePerActive() {
|
jaroslav@1890
|
1379 |
// Approximate at powers of two for small values, saturate past 4
|
jaroslav@1890
|
1380 |
int p = parallelism;
|
jaroslav@1890
|
1381 |
int a = p + (int)(ctl >> AC_SHIFT);
|
jaroslav@1890
|
1382 |
return (a > (p >>>= 1) ? 0 :
|
jaroslav@1890
|
1383 |
a > (p >>>= 1) ? 1 :
|
jaroslav@1890
|
1384 |
a > (p >>>= 1) ? 2 :
|
jaroslav@1890
|
1385 |
a > (p >>>= 1) ? 4 :
|
jaroslav@1890
|
1386 |
8);
|
jaroslav@1890
|
1387 |
}
|
jaroslav@1890
|
1388 |
|
jaroslav@1890
|
1389 |
// Exported methods
|
jaroslav@1890
|
1390 |
|
jaroslav@1890
|
1391 |
// Constructors
|
jaroslav@1890
|
1392 |
|
jaroslav@1890
|
1393 |
/**
|
jaroslav@1890
|
1394 |
* Creates a {@code ForkJoinPool} with parallelism equal to {@link
|
jaroslav@1890
|
1395 |
* java.lang.Runtime#availableProcessors}, using the {@linkplain
|
jaroslav@1890
|
1396 |
* #defaultForkJoinWorkerThreadFactory default thread factory},
|
jaroslav@1890
|
1397 |
* no UncaughtExceptionHandler, and non-async LIFO processing mode.
|
jaroslav@1890
|
1398 |
*
|
jaroslav@1890
|
1399 |
* @throws SecurityException if a security manager exists and
|
jaroslav@1890
|
1400 |
* the caller is not permitted to modify threads
|
jaroslav@1890
|
1401 |
* because it does not hold {@link
|
jaroslav@1890
|
1402 |
* java.lang.RuntimePermission}{@code ("modifyThread")}
|
jaroslav@1890
|
1403 |
*/
|
jaroslav@1890
|
1404 |
public ForkJoinPool() {
|
jaroslav@1895
|
1405 |
this(1,
|
jaroslav@1890
|
1406 |
defaultForkJoinWorkerThreadFactory, null, false);
|
jaroslav@1890
|
1407 |
}
|
jaroslav@1890
|
1408 |
|
jaroslav@1890
|
1409 |
/**
|
jaroslav@1890
|
1410 |
* Creates a {@code ForkJoinPool} with the indicated parallelism
|
jaroslav@1890
|
1411 |
* level, the {@linkplain
|
jaroslav@1890
|
1412 |
* #defaultForkJoinWorkerThreadFactory default thread factory},
|
jaroslav@1890
|
1413 |
* no UncaughtExceptionHandler, and non-async LIFO processing mode.
|
jaroslav@1890
|
1414 |
*
|
jaroslav@1890
|
1415 |
* @param parallelism the parallelism level
|
jaroslav@1890
|
1416 |
* @throws IllegalArgumentException if parallelism less than or
|
jaroslav@1890
|
1417 |
* equal to zero, or greater than implementation limit
|
jaroslav@1890
|
1418 |
* @throws SecurityException if a security manager exists and
|
jaroslav@1890
|
1419 |
* the caller is not permitted to modify threads
|
jaroslav@1890
|
1420 |
* because it does not hold {@link
|
jaroslav@1890
|
1421 |
* java.lang.RuntimePermission}{@code ("modifyThread")}
|
jaroslav@1890
|
1422 |
*/
|
jaroslav@1890
|
1423 |
public ForkJoinPool(int parallelism) {
|
jaroslav@1890
|
1424 |
this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
|
jaroslav@1890
|
1425 |
}
|
jaroslav@1890
|
1426 |
|
jaroslav@1890
|
1427 |
/**
|
jaroslav@1890
|
1428 |
* Creates a {@code ForkJoinPool} with the given parameters.
|
jaroslav@1890
|
1429 |
*
|
jaroslav@1890
|
1430 |
* @param parallelism the parallelism level. For default value,
|
jaroslav@1890
|
1431 |
* use {@link java.lang.Runtime#availableProcessors}.
|
jaroslav@1890
|
1432 |
* @param factory the factory for creating new threads. For default value,
|
jaroslav@1890
|
1433 |
* use {@link #defaultForkJoinWorkerThreadFactory}.
|
jaroslav@1890
|
1434 |
* @param handler the handler for internal worker threads that
|
jaroslav@1890
|
1435 |
* terminate due to unrecoverable errors encountered while executing
|
jaroslav@1890
|
1436 |
* tasks. For default value, use {@code null}.
|
jaroslav@1890
|
1437 |
* @param asyncMode if true,
|
jaroslav@1890
|
1438 |
* establishes local first-in-first-out scheduling mode for forked
|
jaroslav@1890
|
1439 |
* tasks that are never joined. This mode may be more appropriate
|
jaroslav@1890
|
1440 |
* than default locally stack-based mode in applications in which
|
jaroslav@1890
|
1441 |
* worker threads only process event-style asynchronous tasks.
|
jaroslav@1890
|
1442 |
* For default value, use {@code false}.
|
jaroslav@1890
|
1443 |
* @throws IllegalArgumentException if parallelism less than or
|
jaroslav@1890
|
1444 |
* equal to zero, or greater than implementation limit
|
jaroslav@1890
|
1445 |
* @throws NullPointerException if the factory is null
|
jaroslav@1890
|
1446 |
* @throws SecurityException if a security manager exists and
|
jaroslav@1890
|
1447 |
* the caller is not permitted to modify threads
|
jaroslav@1890
|
1448 |
* because it does not hold {@link
|
jaroslav@1890
|
1449 |
* java.lang.RuntimePermission}{@code ("modifyThread")}
|
jaroslav@1890
|
1450 |
*/
|
jaroslav@1890
|
1451 |
public ForkJoinPool(int parallelism,
|
jaroslav@1890
|
1452 |
ForkJoinWorkerThreadFactory factory,
|
jaroslav@1890
|
1453 |
Thread.UncaughtExceptionHandler handler,
|
jaroslav@1890
|
1454 |
boolean asyncMode) {
|
jaroslav@1890
|
1455 |
checkPermission();
|
jaroslav@1890
|
1456 |
if (factory == null)
|
jaroslav@1890
|
1457 |
throw new NullPointerException();
|
jaroslav@1890
|
1458 |
if (parallelism <= 0 || parallelism > MAX_ID)
|
jaroslav@1890
|
1459 |
throw new IllegalArgumentException();
|
jaroslav@1890
|
1460 |
this.parallelism = parallelism;
|
jaroslav@1890
|
1461 |
this.factory = factory;
|
jaroslav@1890
|
1462 |
this.ueh = handler;
|
jaroslav@1890
|
1463 |
this.locallyFifo = asyncMode;
|
jaroslav@1890
|
1464 |
long np = (long)(-parallelism); // offset ctl counts
|
jaroslav@1890
|
1465 |
this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
|
jaroslav@1890
|
1466 |
this.submissionQueue = new ForkJoinTask<?>[INITIAL_QUEUE_CAPACITY];
|
jaroslav@1890
|
1467 |
// initialize workers array with room for 2*parallelism if possible
|
jaroslav@1890
|
1468 |
int n = parallelism << 1;
|
jaroslav@1890
|
1469 |
if (n >= MAX_ID)
|
jaroslav@1890
|
1470 |
n = MAX_ID;
|
jaroslav@1890
|
1471 |
else { // See Hackers Delight, sec 3.2, where n < (1 << 16)
|
jaroslav@1890
|
1472 |
n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8;
|
jaroslav@1890
|
1473 |
}
|
jaroslav@1890
|
1474 |
workers = new ForkJoinWorkerThread[n + 1];
|
jaroslav@1890
|
1475 |
this.submissionLock = new ReentrantLock();
|
jaroslav@1890
|
1476 |
this.termination = submissionLock.newCondition();
|
jaroslav@1890
|
1477 |
StringBuilder sb = new StringBuilder("ForkJoinPool-");
|
jaroslav@1890
|
1478 |
sb.append(poolNumberGenerator.incrementAndGet());
|
jaroslav@1890
|
1479 |
sb.append("-worker-");
|
jaroslav@1890
|
1480 |
this.workerNamePrefix = sb.toString();
|
jaroslav@1890
|
1481 |
}
|
jaroslav@1890
|
1482 |
|
jaroslav@1890
|
1483 |
// Execution methods
|
jaroslav@1890
|
1484 |
|
jaroslav@1890
|
1485 |
/**
|
jaroslav@1890
|
1486 |
* Performs the given task, returning its result upon completion.
|
jaroslav@1890
|
1487 |
* If the computation encounters an unchecked Exception or Error,
|
jaroslav@1890
|
1488 |
* it is rethrown as the outcome of this invocation. Rethrown
|
jaroslav@1890
|
1489 |
* exceptions behave in the same way as regular exceptions, but,
|
jaroslav@1890
|
1490 |
* when possible, contain stack traces (as displayed for example
|
jaroslav@1890
|
1491 |
* using {@code ex.printStackTrace()}) of both the current thread
|
jaroslav@1890
|
1492 |
* as well as the thread actually encountering the exception;
|
jaroslav@1890
|
1493 |
* minimally only the latter.
|
jaroslav@1890
|
1494 |
*
|
jaroslav@1890
|
1495 |
* @param task the task
|
jaroslav@1890
|
1496 |
* @return the task's result
|
jaroslav@1890
|
1497 |
* @throws NullPointerException if the task is null
|
jaroslav@1890
|
1498 |
* @throws RejectedExecutionException if the task cannot be
|
jaroslav@1890
|
1499 |
* scheduled for execution
|
jaroslav@1890
|
1500 |
*/
|
jaroslav@1890
|
1501 |
public <T> T invoke(ForkJoinTask<T> task) {
|
jaroslav@1890
|
1502 |
Thread t = Thread.currentThread();
|
jaroslav@1890
|
1503 |
if (task == null)
|
jaroslav@1890
|
1504 |
throw new NullPointerException();
|
jaroslav@1890
|
1505 |
if (shutdown)
|
jaroslav@1890
|
1506 |
throw new RejectedExecutionException();
|
jaroslav@1890
|
1507 |
if ((t instanceof ForkJoinWorkerThread) &&
|
jaroslav@1890
|
1508 |
((ForkJoinWorkerThread)t).pool == this)
|
jaroslav@1890
|
1509 |
return task.invoke(); // bypass submit if in same pool
|
jaroslav@1890
|
1510 |
else {
|
jaroslav@1890
|
1511 |
addSubmission(task);
|
jaroslav@1890
|
1512 |
return task.join();
|
jaroslav@1890
|
1513 |
}
|
jaroslav@1890
|
1514 |
}
|
jaroslav@1890
|
1515 |
|
jaroslav@1890
|
1516 |
/**
|
jaroslav@1890
|
1517 |
* Unless terminating, forks task if within an ongoing FJ
|
jaroslav@1890
|
1518 |
* computation in the current pool, else submits as external task.
|
jaroslav@1890
|
1519 |
*/
|
jaroslav@1890
|
1520 |
private <T> void forkOrSubmit(ForkJoinTask<T> task) {
|
jaroslav@1890
|
1521 |
ForkJoinWorkerThread w;
|
jaroslav@1890
|
1522 |
Thread t = Thread.currentThread();
|
jaroslav@1890
|
1523 |
if (shutdown)
|
jaroslav@1890
|
1524 |
throw new RejectedExecutionException();
|
jaroslav@1890
|
1525 |
if ((t instanceof ForkJoinWorkerThread) &&
|
jaroslav@1890
|
1526 |
(w = (ForkJoinWorkerThread)t).pool == this)
|
jaroslav@1890
|
1527 |
w.pushTask(task);
|
jaroslav@1890
|
1528 |
else
|
jaroslav@1890
|
1529 |
addSubmission(task);
|
jaroslav@1890
|
1530 |
}
|
jaroslav@1890
|
1531 |
|
jaroslav@1890
|
1532 |
/**
|
jaroslav@1890
|
1533 |
* Arranges for (asynchronous) execution of the given task.
|
jaroslav@1890
|
1534 |
*
|
jaroslav@1890
|
1535 |
* @param task the task
|
jaroslav@1890
|
1536 |
* @throws NullPointerException if the task is null
|
jaroslav@1890
|
1537 |
* @throws RejectedExecutionException if the task cannot be
|
jaroslav@1890
|
1538 |
* scheduled for execution
|
jaroslav@1890
|
1539 |
*/
|
jaroslav@1890
|
1540 |
public void execute(ForkJoinTask<?> task) {
|
jaroslav@1890
|
1541 |
if (task == null)
|
jaroslav@1890
|
1542 |
throw new NullPointerException();
|
jaroslav@1890
|
1543 |
forkOrSubmit(task);
|
jaroslav@1890
|
1544 |
}
|
jaroslav@1890
|
1545 |
|
jaroslav@1890
|
1546 |
// AbstractExecutorService methods
|
jaroslav@1890
|
1547 |
|
jaroslav@1890
|
1548 |
/**
|
jaroslav@1890
|
1549 |
* @throws NullPointerException if the task is null
|
jaroslav@1890
|
1550 |
* @throws RejectedExecutionException if the task cannot be
|
jaroslav@1890
|
1551 |
* scheduled for execution
|
jaroslav@1890
|
1552 |
*/
|
jaroslav@1890
|
1553 |
public void execute(Runnable task) {
|
jaroslav@1890
|
1554 |
if (task == null)
|
jaroslav@1890
|
1555 |
throw new NullPointerException();
|
jaroslav@1890
|
1556 |
ForkJoinTask<?> job;
|
jaroslav@1890
|
1557 |
if (task instanceof ForkJoinTask<?>) // avoid re-wrap
|
jaroslav@1890
|
1558 |
job = (ForkJoinTask<?>) task;
|
jaroslav@1890
|
1559 |
else
|
jaroslav@1890
|
1560 |
job = ForkJoinTask.adapt(task, null);
|
jaroslav@1890
|
1561 |
forkOrSubmit(job);
|
jaroslav@1890
|
1562 |
}
|
jaroslav@1890
|
1563 |
|
jaroslav@1890
|
1564 |
/**
|
jaroslav@1890
|
1565 |
* Submits a ForkJoinTask for execution.
|
jaroslav@1890
|
1566 |
*
|
jaroslav@1890
|
1567 |
* @param task the task to submit
|
jaroslav@1890
|
1568 |
* @return the task
|
jaroslav@1890
|
1569 |
* @throws NullPointerException if the task is null
|
jaroslav@1890
|
1570 |
* @throws RejectedExecutionException if the task cannot be
|
jaroslav@1890
|
1571 |
* scheduled for execution
|
jaroslav@1890
|
1572 |
*/
|
jaroslav@1890
|
1573 |
public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) {
|
jaroslav@1890
|
1574 |
if (task == null)
|
jaroslav@1890
|
1575 |
throw new NullPointerException();
|
jaroslav@1890
|
1576 |
forkOrSubmit(task);
|
jaroslav@1890
|
1577 |
return task;
|
jaroslav@1890
|
1578 |
}
|
jaroslav@1890
|
1579 |
|
jaroslav@1890
|
1580 |
/**
|
jaroslav@1890
|
1581 |
* @throws NullPointerException if the task is null
|
jaroslav@1890
|
1582 |
* @throws RejectedExecutionException if the task cannot be
|
jaroslav@1890
|
1583 |
* scheduled for execution
|
jaroslav@1890
|
1584 |
*/
|
jaroslav@1890
|
1585 |
public <T> ForkJoinTask<T> submit(Callable<T> task) {
|
jaroslav@1890
|
1586 |
if (task == null)
|
jaroslav@1890
|
1587 |
throw new NullPointerException();
|
jaroslav@1890
|
1588 |
ForkJoinTask<T> job = ForkJoinTask.adapt(task);
|
jaroslav@1890
|
1589 |
forkOrSubmit(job);
|
jaroslav@1890
|
1590 |
return job;
|
jaroslav@1890
|
1591 |
}
|
jaroslav@1890
|
1592 |
|
jaroslav@1890
|
1593 |
/**
|
jaroslav@1890
|
1594 |
* @throws NullPointerException if the task is null
|
jaroslav@1890
|
1595 |
* @throws RejectedExecutionException if the task cannot be
|
jaroslav@1890
|
1596 |
* scheduled for execution
|
jaroslav@1890
|
1597 |
*/
|
jaroslav@1890
|
1598 |
public <T> ForkJoinTask<T> submit(Runnable task, T result) {
|
jaroslav@1890
|
1599 |
if (task == null)
|
jaroslav@1890
|
1600 |
throw new NullPointerException();
|
jaroslav@1890
|
1601 |
ForkJoinTask<T> job = ForkJoinTask.adapt(task, result);
|
jaroslav@1890
|
1602 |
forkOrSubmit(job);
|
jaroslav@1890
|
1603 |
return job;
|
jaroslav@1890
|
1604 |
}
|
jaroslav@1890
|
1605 |
|
jaroslav@1890
|
1606 |
/**
|
jaroslav@1890
|
1607 |
* @throws NullPointerException if the task is null
|
jaroslav@1890
|
1608 |
* @throws RejectedExecutionException if the task cannot be
|
jaroslav@1890
|
1609 |
* scheduled for execution
|
jaroslav@1890
|
1610 |
*/
|
jaroslav@1890
|
1611 |
public ForkJoinTask<?> submit(Runnable task) {
|
jaroslav@1890
|
1612 |
if (task == null)
|
jaroslav@1890
|
1613 |
throw new NullPointerException();
|
jaroslav@1890
|
1614 |
ForkJoinTask<?> job;
|
jaroslav@1890
|
1615 |
if (task instanceof ForkJoinTask<?>) // avoid re-wrap
|
jaroslav@1890
|
1616 |
job = (ForkJoinTask<?>) task;
|
jaroslav@1890
|
1617 |
else
|
jaroslav@1890
|
1618 |
job = ForkJoinTask.adapt(task, null);
|
jaroslav@1890
|
1619 |
forkOrSubmit(job);
|
jaroslav@1890
|
1620 |
return job;
|
jaroslav@1890
|
1621 |
}
|
jaroslav@1890
|
1622 |
|
jaroslav@1890
|
1623 |
/**
|
jaroslav@1890
|
1624 |
* @throws NullPointerException {@inheritDoc}
|
jaroslav@1890
|
1625 |
* @throws RejectedExecutionException {@inheritDoc}
|
jaroslav@1890
|
1626 |
*/
|
jaroslav@1890
|
1627 |
public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
|
jaroslav@1890
|
1628 |
ArrayList<ForkJoinTask<T>> forkJoinTasks =
|
jaroslav@1890
|
1629 |
new ArrayList<ForkJoinTask<T>>(tasks.size());
|
jaroslav@1890
|
1630 |
for (Callable<T> task : tasks)
|
jaroslav@1890
|
1631 |
forkJoinTasks.add(ForkJoinTask.adapt(task));
|
jaroslav@1890
|
1632 |
invoke(new InvokeAll<T>(forkJoinTasks));
|
jaroslav@1890
|
1633 |
|
jaroslav@1890
|
1634 |
@SuppressWarnings({"unchecked", "rawtypes"})
|
jaroslav@1890
|
1635 |
List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks;
|
jaroslav@1890
|
1636 |
return futures;
|
jaroslav@1890
|
1637 |
}
|
jaroslav@1890
|
1638 |
|
jaroslav@1890
|
1639 |
static final class InvokeAll<T> extends RecursiveAction {
|
jaroslav@1890
|
1640 |
final ArrayList<ForkJoinTask<T>> tasks;
|
jaroslav@1890
|
1641 |
InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
|
jaroslav@1890
|
1642 |
public void compute() {
|
jaroslav@1890
|
1643 |
try { invokeAll(tasks); }
|
jaroslav@1890
|
1644 |
catch (Exception ignore) {}
|
jaroslav@1890
|
1645 |
}
|
jaroslav@1890
|
1646 |
private static final long serialVersionUID = -7914297376763021607L;
|
jaroslav@1890
|
1647 |
}
|
jaroslav@1890
|
1648 |
|
jaroslav@1890
|
1649 |
/**
|
jaroslav@1890
|
1650 |
* Returns the factory used for constructing new workers.
|
jaroslav@1890
|
1651 |
*
|
jaroslav@1890
|
1652 |
* @return the factory used for constructing new workers
|
jaroslav@1890
|
1653 |
*/
|
jaroslav@1890
|
1654 |
public ForkJoinWorkerThreadFactory getFactory() {
|
jaroslav@1890
|
1655 |
return factory;
|
jaroslav@1890
|
1656 |
}
|
jaroslav@1890
|
1657 |
|
jaroslav@1890
|
1658 |
/**
|
jaroslav@1890
|
1659 |
* Returns the handler for internal worker threads that terminate
|
jaroslav@1890
|
1660 |
* due to unrecoverable errors encountered while executing tasks.
|
jaroslav@1890
|
1661 |
*
|
jaroslav@1890
|
1662 |
* @return the handler, or {@code null} if none
|
jaroslav@1890
|
1663 |
*/
|
jaroslav@1890
|
1664 |
public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
|
jaroslav@1890
|
1665 |
return ueh;
|
jaroslav@1890
|
1666 |
}
|
jaroslav@1890
|
1667 |
|
jaroslav@1890
|
1668 |
/**
|
jaroslav@1890
|
1669 |
* Returns the targeted parallelism level of this pool.
|
jaroslav@1890
|
1670 |
*
|
jaroslav@1890
|
1671 |
* @return the targeted parallelism level of this pool
|
jaroslav@1890
|
1672 |
*/
|
jaroslav@1890
|
1673 |
public int getParallelism() {
|
jaroslav@1890
|
1674 |
return parallelism;
|
jaroslav@1890
|
1675 |
}
|
jaroslav@1890
|
1676 |
|
jaroslav@1890
|
1677 |
/**
|
jaroslav@1890
|
1678 |
* Returns the number of worker threads that have started but not
|
jaroslav@1890
|
1679 |
* yet terminated. The result returned by this method may differ
|
jaroslav@1890
|
1680 |
* from {@link #getParallelism} when threads are created to
|
jaroslav@1890
|
1681 |
* maintain parallelism when others are cooperatively blocked.
|
jaroslav@1890
|
1682 |
*
|
jaroslav@1890
|
1683 |
* @return the number of worker threads
|
jaroslav@1890
|
1684 |
*/
|
jaroslav@1890
|
1685 |
public int getPoolSize() {
|
jaroslav@1890
|
1686 |
return parallelism + (short)(ctl >>> TC_SHIFT);
|
jaroslav@1890
|
1687 |
}
|
jaroslav@1890
|
1688 |
|
jaroslav@1890
|
1689 |
/**
|
jaroslav@1890
|
1690 |
* Returns {@code true} if this pool uses local first-in-first-out
|
jaroslav@1890
|
1691 |
* scheduling mode for forked tasks that are never joined.
|
jaroslav@1890
|
1692 |
*
|
jaroslav@1890
|
1693 |
* @return {@code true} if this pool uses async mode
|
jaroslav@1890
|
1694 |
*/
|
jaroslav@1890
|
1695 |
public boolean getAsyncMode() {
|
jaroslav@1890
|
1696 |
return locallyFifo;
|
jaroslav@1890
|
1697 |
}
|
jaroslav@1890
|
1698 |
|
jaroslav@1890
|
1699 |
/**
|
jaroslav@1890
|
1700 |
* Returns an estimate of the number of worker threads that are
|
jaroslav@1890
|
1701 |
* not blocked waiting to join tasks or for other managed
|
jaroslav@1890
|
1702 |
* synchronization. This method may overestimate the
|
jaroslav@1890
|
1703 |
* number of running threads.
|
jaroslav@1890
|
1704 |
*
|
jaroslav@1890
|
1705 |
* @return the number of worker threads
|
jaroslav@1890
|
1706 |
*/
|
jaroslav@1890
|
1707 |
public int getRunningThreadCount() {
|
jaroslav@1890
|
1708 |
int r = parallelism + (int)(ctl >> AC_SHIFT);
|
jaroslav@1890
|
1709 |
return (r <= 0) ? 0 : r; // suppress momentarily negative values
|
jaroslav@1890
|
1710 |
}
|
jaroslav@1890
|
1711 |
|
jaroslav@1890
|
1712 |
/**
|
jaroslav@1890
|
1713 |
* Returns an estimate of the number of threads that are currently
|
jaroslav@1890
|
1714 |
* stealing or executing tasks. This method may overestimate the
|
jaroslav@1890
|
1715 |
* number of active threads.
|
jaroslav@1890
|
1716 |
*
|
jaroslav@1890
|
1717 |
* @return the number of active threads
|
jaroslav@1890
|
1718 |
*/
|
jaroslav@1890
|
1719 |
public int getActiveThreadCount() {
|
jaroslav@1890
|
1720 |
int r = parallelism + (int)(ctl >> AC_SHIFT) + blockedCount;
|
jaroslav@1890
|
1721 |
return (r <= 0) ? 0 : r; // suppress momentarily negative values
|
jaroslav@1890
|
1722 |
}
|
jaroslav@1890
|
1723 |
|
jaroslav@1890
|
1724 |
/**
|
jaroslav@1890
|
1725 |
* Returns {@code true} if all worker threads are currently idle.
|
jaroslav@1890
|
1726 |
* An idle worker is one that cannot obtain a task to execute
|
jaroslav@1890
|
1727 |
* because none are available to steal from other threads, and
|
jaroslav@1890
|
1728 |
* there are no pending submissions to the pool. This method is
|
jaroslav@1890
|
1729 |
* conservative; it might not return {@code true} immediately upon
|
jaroslav@1890
|
1730 |
* idleness of all threads, but will eventually become true if
|
jaroslav@1890
|
1731 |
* threads remain inactive.
|
jaroslav@1890
|
1732 |
*
|
jaroslav@1890
|
1733 |
* @return {@code true} if all threads are currently idle
|
jaroslav@1890
|
1734 |
*/
|
jaroslav@1890
|
1735 |
public boolean isQuiescent() {
|
jaroslav@1890
|
1736 |
return parallelism + (int)(ctl >> AC_SHIFT) + blockedCount == 0;
|
jaroslav@1890
|
1737 |
}
|
jaroslav@1890
|
1738 |
|
jaroslav@1890
|
1739 |
/**
|
jaroslav@1890
|
1740 |
* Returns an estimate of the total number of tasks stolen from
|
jaroslav@1890
|
1741 |
* one thread's work queue by another. The reported value
|
jaroslav@1890
|
1742 |
* underestimates the actual total number of steals when the pool
|
jaroslav@1890
|
1743 |
* is not quiescent. This value may be useful for monitoring and
|
jaroslav@1890
|
1744 |
* tuning fork/join programs: in general, steal counts should be
|
jaroslav@1890
|
1745 |
* high enough to keep threads busy, but low enough to avoid
|
jaroslav@1890
|
1746 |
* overhead and contention across threads.
|
jaroslav@1890
|
1747 |
*
|
jaroslav@1890
|
1748 |
* @return the number of steals
|
jaroslav@1890
|
1749 |
*/
|
jaroslav@1890
|
1750 |
public long getStealCount() {
|
jaroslav@1890
|
1751 |
return stealCount;
|
jaroslav@1890
|
1752 |
}
|
jaroslav@1890
|
1753 |
|
jaroslav@1890
|
1754 |
/**
|
jaroslav@1890
|
1755 |
* Returns an estimate of the total number of tasks currently held
|
jaroslav@1890
|
1756 |
* in queues by worker threads (but not including tasks submitted
|
jaroslav@1890
|
1757 |
* to the pool that have not begun executing). This value is only
|
jaroslav@1890
|
1758 |
* an approximation, obtained by iterating across all threads in
|
jaroslav@1890
|
1759 |
* the pool. This method may be useful for tuning task
|
jaroslav@1890
|
1760 |
* granularities.
|
jaroslav@1890
|
1761 |
*
|
jaroslav@1890
|
1762 |
* @return the number of queued tasks
|
jaroslav@1890
|
1763 |
*/
|
jaroslav@1890
|
1764 |
public long getQueuedTaskCount() {
|
jaroslav@1890
|
1765 |
long count = 0;
|
jaroslav@1890
|
1766 |
ForkJoinWorkerThread[] ws;
|
jaroslav@1890
|
1767 |
if ((short)(ctl >>> TC_SHIFT) > -parallelism &&
|
jaroslav@1890
|
1768 |
(ws = workers) != null) {
|
jaroslav@1890
|
1769 |
for (ForkJoinWorkerThread w : ws)
|
jaroslav@1890
|
1770 |
if (w != null)
|
jaroslav@1890
|
1771 |
count -= w.queueBase - w.queueTop; // must read base first
|
jaroslav@1890
|
1772 |
}
|
jaroslav@1890
|
1773 |
return count;
|
jaroslav@1890
|
1774 |
}
|
jaroslav@1890
|
1775 |
|
jaroslav@1890
|
1776 |
/**
|
jaroslav@1890
|
1777 |
* Returns an estimate of the number of tasks submitted to this
|
jaroslav@1890
|
1778 |
* pool that have not yet begun executing. This method may take
|
jaroslav@1890
|
1779 |
* time proportional to the number of submissions.
|
jaroslav@1890
|
1780 |
*
|
jaroslav@1890
|
1781 |
* @return the number of queued submissions
|
jaroslav@1890
|
1782 |
*/
|
jaroslav@1890
|
1783 |
public int getQueuedSubmissionCount() {
|
jaroslav@1890
|
1784 |
return -queueBase + queueTop;
|
jaroslav@1890
|
1785 |
}
|
jaroslav@1890
|
1786 |
|
jaroslav@1890
|
1787 |
/**
|
jaroslav@1890
|
1788 |
* Returns {@code true} if there are any tasks submitted to this
|
jaroslav@1890
|
1789 |
* pool that have not yet begun executing.
|
jaroslav@1890
|
1790 |
*
|
jaroslav@1890
|
1791 |
* @return {@code true} if there are any queued submissions
|
jaroslav@1890
|
1792 |
*/
|
jaroslav@1890
|
1793 |
public boolean hasQueuedSubmissions() {
|
jaroslav@1890
|
1794 |
return queueBase != queueTop;
|
jaroslav@1890
|
1795 |
}
|
jaroslav@1890
|
1796 |
|
jaroslav@1890
|
1797 |
/**
|
jaroslav@1890
|
1798 |
* Removes and returns the next unexecuted submission if one is
|
jaroslav@1890
|
1799 |
* available. This method may be useful in extensions to this
|
jaroslav@1890
|
1800 |
* class that re-assign work in systems with multiple pools.
|
jaroslav@1890
|
1801 |
*
|
jaroslav@1890
|
1802 |
* @return the next submission, or {@code null} if none
|
jaroslav@1890
|
1803 |
*/
|
jaroslav@1890
|
1804 |
protected ForkJoinTask<?> pollSubmission() {
|
jaroslav@1890
|
1805 |
ForkJoinTask<?> t; ForkJoinTask<?>[] q; int b, i;
|
jaroslav@1890
|
1806 |
while ((b = queueBase) != queueTop &&
|
jaroslav@1890
|
1807 |
(q = submissionQueue) != null &&
|
jaroslav@1890
|
1808 |
(i = (q.length - 1) & b) >= 0) {
|
jaroslav@1890
|
1809 |
long u = (i << ASHIFT) + ABASE;
|
jaroslav@1890
|
1810 |
if ((t = q[i]) != null &&
|
jaroslav@1890
|
1811 |
queueBase == b &&
|
jaroslav@1890
|
1812 |
UNSAFE.compareAndSwapObject(q, u, t, null)) {
|
jaroslav@1890
|
1813 |
queueBase = b + 1;
|
jaroslav@1890
|
1814 |
return t;
|
jaroslav@1890
|
1815 |
}
|
jaroslav@1890
|
1816 |
}
|
jaroslav@1890
|
1817 |
return null;
|
jaroslav@1890
|
1818 |
}
|
jaroslav@1890
|
1819 |
|
jaroslav@1890
|
1820 |
/**
|
jaroslav@1890
|
1821 |
* Removes all available unexecuted submitted and forked tasks
|
jaroslav@1890
|
1822 |
* from scheduling queues and adds them to the given collection,
|
jaroslav@1890
|
1823 |
* without altering their execution status. These may include
|
jaroslav@1890
|
1824 |
* artificially generated or wrapped tasks. This method is
|
jaroslav@1890
|
1825 |
* designed to be invoked only when the pool is known to be
|
jaroslav@1890
|
1826 |
* quiescent. Invocations at other times may not remove all
|
jaroslav@1890
|
1827 |
* tasks. A failure encountered while attempting to add elements
|
jaroslav@1890
|
1828 |
* to collection {@code c} may result in elements being in
|
jaroslav@1890
|
1829 |
* neither, either or both collections when the associated
|
jaroslav@1890
|
1830 |
* exception is thrown. The behavior of this operation is
|
jaroslav@1890
|
1831 |
* undefined if the specified collection is modified while the
|
jaroslav@1890
|
1832 |
* operation is in progress.
|
jaroslav@1890
|
1833 |
*
|
jaroslav@1890
|
1834 |
* @param c the collection to transfer elements into
|
jaroslav@1890
|
1835 |
* @return the number of elements transferred
|
jaroslav@1890
|
1836 |
*/
|
jaroslav@1890
|
1837 |
protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
|
jaroslav@1890
|
1838 |
int count = 0;
|
jaroslav@1890
|
1839 |
while (queueBase != queueTop) {
|
jaroslav@1890
|
1840 |
ForkJoinTask<?> t = pollSubmission();
|
jaroslav@1890
|
1841 |
if (t != null) {
|
jaroslav@1890
|
1842 |
c.add(t);
|
jaroslav@1890
|
1843 |
++count;
|
jaroslav@1890
|
1844 |
}
|
jaroslav@1890
|
1845 |
}
|
jaroslav@1890
|
1846 |
ForkJoinWorkerThread[] ws;
|
jaroslav@1890
|
1847 |
if ((short)(ctl >>> TC_SHIFT) > -parallelism &&
|
jaroslav@1890
|
1848 |
(ws = workers) != null) {
|
jaroslav@1890
|
1849 |
for (ForkJoinWorkerThread w : ws)
|
jaroslav@1890
|
1850 |
if (w != null)
|
jaroslav@1890
|
1851 |
count += w.drainTasksTo(c);
|
jaroslav@1890
|
1852 |
}
|
jaroslav@1890
|
1853 |
return count;
|
jaroslav@1890
|
1854 |
}
|
jaroslav@1890
|
1855 |
|
jaroslav@1890
|
1856 |
/**
|
jaroslav@1890
|
1857 |
* Returns a string identifying this pool, as well as its state,
|
jaroslav@1890
|
1858 |
* including indications of run state, parallelism level, and
|
jaroslav@1890
|
1859 |
* worker and task counts.
|
jaroslav@1890
|
1860 |
*
|
jaroslav@1890
|
1861 |
* @return a string identifying this pool, as well as its state
|
jaroslav@1890
|
1862 |
*/
|
jaroslav@1890
|
1863 |
public String toString() {
|
jaroslav@1890
|
1864 |
long st = getStealCount();
|
jaroslav@1890
|
1865 |
long qt = getQueuedTaskCount();
|
jaroslav@1890
|
1866 |
long qs = getQueuedSubmissionCount();
|
jaroslav@1890
|
1867 |
int pc = parallelism;
|
jaroslav@1890
|
1868 |
long c = ctl;
|
jaroslav@1890
|
1869 |
int tc = pc + (short)(c >>> TC_SHIFT);
|
jaroslav@1890
|
1870 |
int rc = pc + (int)(c >> AC_SHIFT);
|
jaroslav@1890
|
1871 |
if (rc < 0) // ignore transient negative
|
jaroslav@1890
|
1872 |
rc = 0;
|
jaroslav@1890
|
1873 |
int ac = rc + blockedCount;
|
jaroslav@1890
|
1874 |
String level;
|
jaroslav@1890
|
1875 |
if ((c & STOP_BIT) != 0)
|
jaroslav@1890
|
1876 |
level = (tc == 0) ? "Terminated" : "Terminating";
|
jaroslav@1890
|
1877 |
else
|
jaroslav@1890
|
1878 |
level = shutdown ? "Shutting down" : "Running";
|
jaroslav@1890
|
1879 |
return super.toString() +
|
jaroslav@1890
|
1880 |
"[" + level +
|
jaroslav@1890
|
1881 |
", parallelism = " + pc +
|
jaroslav@1890
|
1882 |
", size = " + tc +
|
jaroslav@1890
|
1883 |
", active = " + ac +
|
jaroslav@1890
|
1884 |
", running = " + rc +
|
jaroslav@1890
|
1885 |
", steals = " + st +
|
jaroslav@1890
|
1886 |
", tasks = " + qt +
|
jaroslav@1890
|
1887 |
", submissions = " + qs +
|
jaroslav@1890
|
1888 |
"]";
|
jaroslav@1890
|
1889 |
}
|
jaroslav@1890
|
1890 |
|
jaroslav@1890
|
1891 |
/**
|
jaroslav@1890
|
1892 |
* Initiates an orderly shutdown in which previously submitted
|
jaroslav@1890
|
1893 |
* tasks are executed, but no new tasks will be accepted.
|
jaroslav@1890
|
1894 |
* Invocation has no additional effect if already shut down.
|
jaroslav@1890
|
1895 |
* Tasks that are in the process of being submitted concurrently
|
jaroslav@1890
|
1896 |
* during the course of this method may or may not be rejected.
|
jaroslav@1890
|
1897 |
*
|
jaroslav@1890
|
1898 |
* @throws SecurityException if a security manager exists and
|
jaroslav@1890
|
1899 |
* the caller is not permitted to modify threads
|
jaroslav@1890
|
1900 |
* because it does not hold {@link
|
jaroslav@1890
|
1901 |
* java.lang.RuntimePermission}{@code ("modifyThread")}
|
jaroslav@1890
|
1902 |
*/
|
jaroslav@1890
|
1903 |
public void shutdown() {
|
jaroslav@1890
|
1904 |
checkPermission();
|
jaroslav@1890
|
1905 |
shutdown = true;
|
jaroslav@1890
|
1906 |
tryTerminate(false);
|
jaroslav@1890
|
1907 |
}
|
jaroslav@1890
|
1908 |
|
jaroslav@1890
|
1909 |
/**
|
jaroslav@1890
|
1910 |
* Attempts to cancel and/or stop all tasks, and reject all
|
jaroslav@1890
|
1911 |
* subsequently submitted tasks. Tasks that are in the process of
|
jaroslav@1890
|
1912 |
* being submitted or executed concurrently during the course of
|
jaroslav@1890
|
1913 |
* this method may or may not be rejected. This method cancels
|
jaroslav@1890
|
1914 |
* both existing and unexecuted tasks, in order to permit
|
jaroslav@1890
|
1915 |
* termination in the presence of task dependencies. So the method
|
jaroslav@1890
|
1916 |
* always returns an empty list (unlike the case for some other
|
jaroslav@1890
|
1917 |
* Executors).
|
jaroslav@1890
|
1918 |
*
|
jaroslav@1890
|
1919 |
* @return an empty list
|
jaroslav@1890
|
1920 |
* @throws SecurityException if a security manager exists and
|
jaroslav@1890
|
1921 |
* the caller is not permitted to modify threads
|
jaroslav@1890
|
1922 |
* because it does not hold {@link
|
jaroslav@1890
|
1923 |
* java.lang.RuntimePermission}{@code ("modifyThread")}
|
jaroslav@1890
|
1924 |
*/
|
jaroslav@1890
|
1925 |
public List<Runnable> shutdownNow() {
|
jaroslav@1890
|
1926 |
checkPermission();
|
jaroslav@1890
|
1927 |
shutdown = true;
|
jaroslav@1890
|
1928 |
tryTerminate(true);
|
jaroslav@1890
|
1929 |
return Collections.emptyList();
|
jaroslav@1890
|
1930 |
}
|
jaroslav@1890
|
1931 |
|
jaroslav@1890
|
1932 |
/**
|
jaroslav@1890
|
1933 |
* Returns {@code true} if all tasks have completed following shut down.
|
jaroslav@1890
|
1934 |
*
|
jaroslav@1890
|
1935 |
* @return {@code true} if all tasks have completed following shut down
|
jaroslav@1890
|
1936 |
*/
|
jaroslav@1890
|
1937 |
public boolean isTerminated() {
|
jaroslav@1890
|
1938 |
long c = ctl;
|
jaroslav@1890
|
1939 |
return ((c & STOP_BIT) != 0L &&
|
jaroslav@1890
|
1940 |
(short)(c >>> TC_SHIFT) == -parallelism);
|
jaroslav@1890
|
1941 |
}
|
jaroslav@1890
|
1942 |
|
jaroslav@1890
|
1943 |
/**
|
jaroslav@1890
|
1944 |
* Returns {@code true} if the process of termination has
|
jaroslav@1890
|
1945 |
* commenced but not yet completed. This method may be useful for
|
jaroslav@1890
|
1946 |
* debugging. A return of {@code true} reported a sufficient
|
jaroslav@1890
|
1947 |
* period after shutdown may indicate that submitted tasks have
|
jaroslav@1890
|
1948 |
* ignored or suppressed interruption, or are waiting for IO,
|
jaroslav@1890
|
1949 |
* causing this executor not to properly terminate. (See the
|
jaroslav@1890
|
1950 |
* advisory notes for class {@link ForkJoinTask} stating that
|
jaroslav@1890
|
1951 |
* tasks should not normally entail blocking operations. But if
|
jaroslav@1890
|
1952 |
* they do, they must abort them on interrupt.)
|
jaroslav@1890
|
1953 |
*
|
jaroslav@1890
|
1954 |
* @return {@code true} if terminating but not yet terminated
|
jaroslav@1890
|
1955 |
*/
|
jaroslav@1890
|
1956 |
public boolean isTerminating() {
|
jaroslav@1890
|
1957 |
long c = ctl;
|
jaroslav@1890
|
1958 |
return ((c & STOP_BIT) != 0L &&
|
jaroslav@1890
|
1959 |
(short)(c >>> TC_SHIFT) != -parallelism);
|
jaroslav@1890
|
1960 |
}
|
jaroslav@1890
|
1961 |
|
jaroslav@1890
|
1962 |
/**
|
jaroslav@1890
|
1963 |
* Returns true if terminating or terminated. Used by ForkJoinWorkerThread.
|
jaroslav@1890
|
1964 |
*/
|
jaroslav@1890
|
1965 |
final boolean isAtLeastTerminating() {
|
jaroslav@1890
|
1966 |
return (ctl & STOP_BIT) != 0L;
|
jaroslav@1890
|
1967 |
}
|
jaroslav@1890
|
1968 |
|
jaroslav@1890
|
1969 |
/**
|
jaroslav@1890
|
1970 |
* Returns {@code true} if this pool has been shut down.
|
jaroslav@1890
|
1971 |
*
|
jaroslav@1890
|
1972 |
* @return {@code true} if this pool has been shut down
|
jaroslav@1890
|
1973 |
*/
|
jaroslav@1890
|
1974 |
public boolean isShutdown() {
|
jaroslav@1890
|
1975 |
return shutdown;
|
jaroslav@1890
|
1976 |
}
|
jaroslav@1890
|
1977 |
|
jaroslav@1890
|
1978 |
/**
|
jaroslav@1890
|
1979 |
* Blocks until all tasks have completed execution after a shutdown
|
jaroslav@1890
|
1980 |
* request, or the timeout occurs, or the current thread is
|
jaroslav@1890
|
1981 |
* interrupted, whichever happens first.
|
jaroslav@1890
|
1982 |
*
|
jaroslav@1890
|
1983 |
* @param timeout the maximum time to wait
|
jaroslav@1890
|
1984 |
* @param unit the time unit of the timeout argument
|
jaroslav@1890
|
1985 |
* @return {@code true} if this executor terminated and
|
jaroslav@1890
|
1986 |
* {@code false} if the timeout elapsed before termination
|
jaroslav@1890
|
1987 |
* @throws InterruptedException if interrupted while waiting
|
jaroslav@1890
|
1988 |
*/
|
jaroslav@1890
|
1989 |
public boolean awaitTermination(long timeout, TimeUnit unit)
|
jaroslav@1890
|
1990 |
throws InterruptedException {
|
jaroslav@1890
|
1991 |
long nanos = unit.toNanos(timeout);
|
jaroslav@1890
|
1992 |
final ReentrantLock lock = this.submissionLock;
|
jaroslav@1890
|
1993 |
lock.lock();
|
jaroslav@1890
|
1994 |
try {
|
jaroslav@1890
|
1995 |
for (;;) {
|
jaroslav@1890
|
1996 |
if (isTerminated())
|
jaroslav@1890
|
1997 |
return true;
|
jaroslav@1890
|
1998 |
if (nanos <= 0)
|
jaroslav@1890
|
1999 |
return false;
|
jaroslav@1890
|
2000 |
nanos = termination.awaitNanos(nanos);
|
jaroslav@1890
|
2001 |
}
|
jaroslav@1890
|
2002 |
} finally {
|
jaroslav@1890
|
2003 |
lock.unlock();
|
jaroslav@1890
|
2004 |
}
|
jaroslav@1890
|
2005 |
}
|
jaroslav@1890
|
2006 |
|
jaroslav@1890
|
2007 |
/**
|
jaroslav@1890
|
2008 |
* Interface for extending managed parallelism for tasks running
|
jaroslav@1890
|
2009 |
* in {@link ForkJoinPool}s.
|
jaroslav@1890
|
2010 |
*
|
jaroslav@1890
|
2011 |
* <p>A {@code ManagedBlocker} provides two methods. Method
|
jaroslav@1890
|
2012 |
* {@code isReleasable} must return {@code true} if blocking is
|
jaroslav@1890
|
2013 |
* not necessary. Method {@code block} blocks the current thread
|
jaroslav@1890
|
2014 |
* if necessary (perhaps internally invoking {@code isReleasable}
|
jaroslav@1890
|
2015 |
* before actually blocking). These actions are performed by any
|
jaroslav@1890
|
2016 |
* thread invoking {@link ForkJoinPool#managedBlock}. The
|
jaroslav@1890
|
2017 |
* unusual methods in this API accommodate synchronizers that may,
|
jaroslav@1890
|
2018 |
* but don't usually, block for long periods. Similarly, they
|
jaroslav@1890
|
2019 |
* allow more efficient internal handling of cases in which
|
jaroslav@1890
|
2020 |
* additional workers may be, but usually are not, needed to
|
jaroslav@1890
|
2021 |
* ensure sufficient parallelism. Toward this end,
|
jaroslav@1890
|
2022 |
* implementations of method {@code isReleasable} must be amenable
|
jaroslav@1890
|
2023 |
* to repeated invocation.
|
jaroslav@1890
|
2024 |
*
|
jaroslav@1890
|
2025 |
* <p>For example, here is a ManagedBlocker based on a
|
jaroslav@1890
|
2026 |
* ReentrantLock:
|
jaroslav@1890
|
2027 |
* <pre> {@code
|
jaroslav@1890
|
2028 |
* class ManagedLocker implements ManagedBlocker {
|
jaroslav@1890
|
2029 |
* final ReentrantLock lock;
|
jaroslav@1890
|
2030 |
* boolean hasLock = false;
|
jaroslav@1890
|
2031 |
* ManagedLocker(ReentrantLock lock) { this.lock = lock; }
|
jaroslav@1890
|
2032 |
* public boolean block() {
|
jaroslav@1890
|
2033 |
* if (!hasLock)
|
jaroslav@1890
|
2034 |
* lock.lock();
|
jaroslav@1890
|
2035 |
* return true;
|
jaroslav@1890
|
2036 |
* }
|
jaroslav@1890
|
2037 |
* public boolean isReleasable() {
|
jaroslav@1890
|
2038 |
* return hasLock || (hasLock = lock.tryLock());
|
jaroslav@1890
|
2039 |
* }
|
jaroslav@1890
|
2040 |
* }}</pre>
|
jaroslav@1890
|
2041 |
*
|
jaroslav@1890
|
2042 |
* <p>Here is a class that possibly blocks waiting for an
|
jaroslav@1890
|
2043 |
* item on a given queue:
|
jaroslav@1890
|
2044 |
* <pre> {@code
|
jaroslav@1890
|
2045 |
* class QueueTaker<E> implements ManagedBlocker {
|
jaroslav@1890
|
2046 |
* final BlockingQueue<E> queue;
|
jaroslav@1890
|
2047 |
* volatile E item = null;
|
jaroslav@1890
|
2048 |
* QueueTaker(BlockingQueue<E> q) { this.queue = q; }
|
jaroslav@1890
|
2049 |
* public boolean block() throws InterruptedException {
|
jaroslav@1890
|
2050 |
* if (item == null)
|
jaroslav@1890
|
2051 |
* item = queue.take();
|
jaroslav@1890
|
2052 |
* return true;
|
jaroslav@1890
|
2053 |
* }
|
jaroslav@1890
|
2054 |
* public boolean isReleasable() {
|
jaroslav@1890
|
2055 |
* return item != null || (item = queue.poll()) != null;
|
jaroslav@1890
|
2056 |
* }
|
jaroslav@1890
|
2057 |
* public E getItem() { // call after pool.managedBlock completes
|
jaroslav@1890
|
2058 |
* return item;
|
jaroslav@1890
|
2059 |
* }
|
jaroslav@1890
|
2060 |
* }}</pre>
|
jaroslav@1890
|
2061 |
*/
|
jaroslav@1890
|
2062 |
public static interface ManagedBlocker {
|
jaroslav@1890
|
2063 |
/**
|
jaroslav@1890
|
2064 |
* Possibly blocks the current thread, for example waiting for
|
jaroslav@1890
|
2065 |
* a lock or condition.
|
jaroslav@1890
|
2066 |
*
|
jaroslav@1890
|
2067 |
* @return {@code true} if no additional blocking is necessary
|
jaroslav@1890
|
2068 |
* (i.e., if isReleasable would return true)
|
jaroslav@1890
|
2069 |
* @throws InterruptedException if interrupted while waiting
|
jaroslav@1890
|
2070 |
* (the method is not required to do so, but is allowed to)
|
jaroslav@1890
|
2071 |
*/
|
jaroslav@1890
|
2072 |
boolean block() throws InterruptedException;
|
jaroslav@1890
|
2073 |
|
jaroslav@1890
|
2074 |
/**
|
jaroslav@1890
|
2075 |
* Returns {@code true} if blocking is unnecessary.
|
jaroslav@1890
|
2076 |
*/
|
jaroslav@1890
|
2077 |
boolean isReleasable();
|
jaroslav@1890
|
2078 |
}
|
jaroslav@1890
|
2079 |
|
jaroslav@1890
|
2080 |
/**
|
jaroslav@1890
|
2081 |
* Blocks in accord with the given blocker. If the current thread
|
jaroslav@1890
|
2082 |
* is a {@link ForkJoinWorkerThread}, this method possibly
|
jaroslav@1890
|
2083 |
* arranges for a spare thread to be activated if necessary to
|
jaroslav@1890
|
2084 |
* ensure sufficient parallelism while the current thread is blocked.
|
jaroslav@1890
|
2085 |
*
|
jaroslav@1890
|
2086 |
* <p>If the caller is not a {@link ForkJoinTask}, this method is
|
jaroslav@1890
|
2087 |
* behaviorally equivalent to
|
jaroslav@1890
|
2088 |
* <pre> {@code
|
jaroslav@1890
|
2089 |
* while (!blocker.isReleasable())
|
jaroslav@1890
|
2090 |
* if (blocker.block())
|
jaroslav@1890
|
2091 |
* return;
|
jaroslav@1890
|
2092 |
* }</pre>
|
jaroslav@1890
|
2093 |
*
|
jaroslav@1890
|
2094 |
* If the caller is a {@code ForkJoinTask}, then the pool may
|
jaroslav@1890
|
2095 |
* first be expanded to ensure parallelism, and later adjusted.
|
jaroslav@1890
|
2096 |
*
|
jaroslav@1890
|
2097 |
* @param blocker the blocker
|
jaroslav@1890
|
2098 |
* @throws InterruptedException if blocker.block did so
|
jaroslav@1890
|
2099 |
*/
|
jaroslav@1890
|
2100 |
public static void managedBlock(ManagedBlocker blocker)
|
jaroslav@1890
|
2101 |
throws InterruptedException {
|
jaroslav@1890
|
2102 |
Thread t = Thread.currentThread();
|
jaroslav@1890
|
2103 |
if (t instanceof ForkJoinWorkerThread) {
|
jaroslav@1890
|
2104 |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
|
jaroslav@1890
|
2105 |
w.pool.awaitBlocker(blocker);
|
jaroslav@1890
|
2106 |
}
|
jaroslav@1890
|
2107 |
else {
|
jaroslav@1890
|
2108 |
do {} while (!blocker.isReleasable() && !blocker.block());
|
jaroslav@1890
|
2109 |
}
|
jaroslav@1890
|
2110 |
}
|
jaroslav@1890
|
2111 |
|
jaroslav@1890
|
2112 |
// AbstractExecutorService overrides. These rely on undocumented
|
jaroslav@1890
|
2113 |
// fact that ForkJoinTask.adapt returns ForkJoinTasks that also
|
jaroslav@1890
|
2114 |
// implement RunnableFuture.
|
jaroslav@1890
|
2115 |
|
jaroslav@1890
|
2116 |
protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
|
jaroslav@1890
|
2117 |
return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value);
|
jaroslav@1890
|
2118 |
}
|
jaroslav@1890
|
2119 |
|
jaroslav@1890
|
2120 |
protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
|
jaroslav@1890
|
2121 |
return (RunnableFuture<T>) ForkJoinTask.adapt(callable);
|
jaroslav@1890
|
2122 |
}
|
jaroslav@1890
|
2123 |
|
jaroslav@1890
|
2124 |
// Unsafe mechanics
|
jaroslav@1890
|
2125 |
private static final long ctlOffset;
|
jaroslav@1890
|
2126 |
private static final long stealCountOffset;
|
jaroslav@1890
|
2127 |
private static final long blockedCountOffset;
|
jaroslav@1890
|
2128 |
private static final long quiescerCountOffset;
|
jaroslav@1890
|
2129 |
private static final long scanGuardOffset;
|
jaroslav@1890
|
2130 |
private static final long nextWorkerNumberOffset;
|
jaroslav@1890
|
2131 |
private static final long ABASE;
|
jaroslav@1890
|
2132 |
private static final int ASHIFT;
|
jaroslav@1890
|
2133 |
|
jaroslav@1890
|
2134 |
static {
|
jaroslav@1890
|
2135 |
poolNumberGenerator = new AtomicInteger();
|
jaroslav@1890
|
2136 |
workerSeedGenerator = new Random();
|
jaroslav@1890
|
2137 |
modifyThreadPermission = new RuntimePermission("modifyThread");
|
jaroslav@1890
|
2138 |
defaultForkJoinWorkerThreadFactory =
|
jaroslav@1890
|
2139 |
new DefaultForkJoinWorkerThreadFactory();
|
jaroslav@1890
|
2140 |
int s;
|
jaroslav@1890
|
2141 |
try {
|
jaroslav@1890
|
2142 |
UNSAFE = sun.misc.Unsafe.getUnsafe();
|
jaroslav@1890
|
2143 |
Class k = ForkJoinPool.class;
|
jaroslav@1890
|
2144 |
ctlOffset = UNSAFE.objectFieldOffset
|
jaroslav@1890
|
2145 |
(k.getDeclaredField("ctl"));
|
jaroslav@1890
|
2146 |
stealCountOffset = UNSAFE.objectFieldOffset
|
jaroslav@1890
|
2147 |
(k.getDeclaredField("stealCount"));
|
jaroslav@1890
|
2148 |
blockedCountOffset = UNSAFE.objectFieldOffset
|
jaroslav@1890
|
2149 |
(k.getDeclaredField("blockedCount"));
|
jaroslav@1890
|
2150 |
quiescerCountOffset = UNSAFE.objectFieldOffset
|
jaroslav@1890
|
2151 |
(k.getDeclaredField("quiescerCount"));
|
jaroslav@1890
|
2152 |
scanGuardOffset = UNSAFE.objectFieldOffset
|
jaroslav@1890
|
2153 |
(k.getDeclaredField("scanGuard"));
|
jaroslav@1890
|
2154 |
nextWorkerNumberOffset = UNSAFE.objectFieldOffset
|
jaroslav@1890
|
2155 |
(k.getDeclaredField("nextWorkerNumber"));
|
jaroslav@1890
|
2156 |
Class a = ForkJoinTask[].class;
|
jaroslav@1890
|
2157 |
ABASE = UNSAFE.arrayBaseOffset(a);
|
jaroslav@1890
|
2158 |
s = UNSAFE.arrayIndexScale(a);
|
jaroslav@1890
|
2159 |
} catch (Exception e) {
|
jaroslav@1890
|
2160 |
throw new Error(e);
|
jaroslav@1890
|
2161 |
}
|
jaroslav@1890
|
2162 |
if ((s & (s-1)) != 0)
|
jaroslav@1890
|
2163 |
throw new Error("data type scale not a power of two");
|
jaroslav@1890
|
2164 |
ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
|
jaroslav@1890
|
2165 |
}
|
jaroslav@1890
|
2166 |
|
jaroslav@1890
|
2167 |
}
|