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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/licenses/publicdomain |
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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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package jsr166y; |
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import java.util.*; |
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import java.util.concurrent.*; |
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import java.util.concurrent.locks.*; |
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import java.util.concurrent.atomic.*; |
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import sun.misc.Unsafe; |
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import java.lang.reflect.*; |
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|
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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.atomic.AtomicLong; |
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import java.util.concurrent.locks.AbstractQueuedSynchronizer; |
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import java.util.concurrent.locks.Condition; |
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|
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/** |
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* An {@link ExecutorService} for running {@link ForkJoinTask}s. A |
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* ForkJoinPool provides the entry point for submissions from |
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* non-ForkJoinTasks, as well as management and monitoring operations. |
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* Normally a single ForkJoinPool is used for a large number of |
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* submitted tasks. Otherwise, use would not usually outweigh the |
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* construction and bookkeeping overhead of creating a large set of |
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* threads. |
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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 tasks submitted to the pool and/or created by other active |
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* tasks (eventually blocking waiting for work if none exist). This |
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* enables efficient processing when most tasks spawn other subtasks |
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* (as do most {@code ForkJoinTask}s), as well as when many small |
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* tasks are submitted to the pool from external clients. Especially |
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* when setting <em>asyncMode</em> to true in constructors, {@code |
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* ForkJoinPool}s may also be appropriate for use with event-style |
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* tasks that are never joined. |
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* |
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* <p>ForkJoinPools differ from other kinds of Executors mainly in |
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* that they provide <em>work-stealing</em>: all threads in the pool |
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* attempt to find and execute subtasks created by other active tasks |
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* (eventually blocking if none exist). This makes them efficient when |
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* most tasks spawn other subtasks (as do most ForkJoinTasks), as well |
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* as the mixed execution of some plain Runnable- or Callable- based |
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* activities along with ForkJoinTasks. When setting |
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* {@code setAsyncMode}, a ForkJoinPools may also be appropriate for |
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* use with fine-grained tasks that are never joined. Otherwise, other |
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* ExecutorService implementations are typically more appropriate |
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* choices. |
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* <p>A static {@link #commonPool} is available and appropriate for |
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* most applications. The common pool is used by any ForkJoinTask that |
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* is not explicitly submitted to a specified pool. Using the common |
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* pool normally reduces resource usage (its threads are slowly |
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* reclaimed during periods of non-use, and reinstated upon subsequent |
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* use). The common pool is by default constructed with default |
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* parameters, but these may be controlled by setting any or all of |
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* the three properties {@code |
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* java.util.concurrent.ForkJoinPool.common.{parallelism, |
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* threadFactory, exceptionHandler}}. |
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* |
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* <p>A ForkJoinPool may be constructed with a given parallelism level |
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* (target pool size), which it attempts to maintain by dynamically |
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* adding, suspending, or resuming threads, even if some tasks are |
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* waiting to join others. However, no such adjustments are performed |
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* in the face of blocked IO or other unmanaged synchronization. The |
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* nested {@code ManagedBlocker} interface enables extension of |
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* the kinds of synchronization accommodated. The target parallelism |
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* level may also be changed dynamically ({@code setParallelism}) |
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* and thread construction can be limited using methods |
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* {@code setMaximumPoolSize} and/or |
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* {@code setMaintainsParallelism}. |
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* <p>For applications that require separate or custom pools, a {@code |
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* ForkJoinPool} may be constructed with a given target parallelism |
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* level; by default, equal to the number of available processors. The |
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* pool attempts to maintain enough active (or available) threads by |
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* dynamically adding, suspending, or resuming internal worker |
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* threads, even if some tasks are stalled waiting to join |
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* others. However, no such adjustments are guaranteed in the face of |
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* blocked IO or other unmanaged synchronization. The nested {@link |
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* 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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* {@code getStealCount}) that are intended to aid in developing, |
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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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* {@code toString} returns indications of pool state in a |
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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 table. |
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* These are designed to be used primarily by clients not already |
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* engaged in fork/join computations in the current pool. The main |
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* forms of these methods accept instances of {@code ForkJoinTask}, |
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* but 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 instead |
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* use the within-computation forms listed in the table unless using |
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* async event-style tasks that are not usually joined, in which case |
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* there is little difference among choice of methods. |
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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>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 result in |
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* IllegalArgumentExceptions. |
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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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public class ForkJoinPool extends AbstractExecutorService { |
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/* |
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* See the extended comments interspersed below for design, |
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* rationale, and walkthroughs. |
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* Implementation Overview |
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* |
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* This class and its nested classes provide the main |
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* functionality and control for a set of worker threads: |
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* Submissions from non-FJ threads enter into submission queues. |
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* Workers take these tasks and typically split them into subtasks |
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* that may be stolen by other workers. Preference rules give |
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* first priority to processing tasks from their own queues (LIFO |
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* or FIFO, depending on mode), then to randomized FIFO steals of |
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* tasks in other queues. |
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* |
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* WorkQueues |
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* ========== |
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* |
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* Most operations occur within work-stealing queues (in nested |
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* class WorkQueue). These are special forms of Deques that |
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* support only three of the four possible end-operations -- push, |
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* pop, and poll (aka steal), under the further constraints that |
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* push and pop are called only from the owning thread (or, as |
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* extended here, under a lock), while poll may be called from |
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* other threads. (If you are unfamiliar with them, you probably |
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* want to read Herlihy and Shavit's book "The Art of |
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* Multiprocessor programming", chapter 16 describing these in |
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* more detail before proceeding.) The main work-stealing queue |
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* design is roughly similar to those in the papers "Dynamic |
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* Circular Work-Stealing Deque" by Chase and Lev, SPAA 2005 |
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* (http://research.sun.com/scalable/pubs/index.html) and |
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* "Idempotent work stealing" by Michael, Saraswat, and Vechev, |
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* PPoPP 2009 (http://portal.acm.org/citation.cfm?id=1504186). |
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* The main differences ultimately stem from GC requirements that |
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* we null out taken slots as soon as we can, to maintain as small |
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* a footprint as possible even in programs generating huge |
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* numbers of tasks. To accomplish this, we shift the CAS |
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* arbitrating pop vs poll (steal) from being on the indices |
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* ("base" and "top") to the slots themselves. So, both a |
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* successful pop and poll mainly entail a CAS of a slot from |
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* non-null to null. Because we rely on CASes of references, we |
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* do not need tag bits on base or top. They are simple ints as |
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* used in any circular array-based queue (see for example |
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* ArrayDeque). Updates to the indices must still be ordered in a |
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* way that guarantees that top == base means the queue is empty, |
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* but otherwise may err on the side of possibly making the queue |
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* appear nonempty when a push, pop, or poll have not fully |
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* committed. Note that this means that the poll operation, |
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* considered individually, is not wait-free. One thief cannot |
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* successfully continue until another in-progress one (or, if |
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* previously empty, a push) completes. However, in the |
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* aggregate, we ensure at least probabilistic non-blockingness. |
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* If an attempted steal fails, a thief always chooses a different |
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* random victim target to try next. So, in order for one thief to |
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* progress, it suffices for any in-progress poll or new push on |
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* any empty queue to complete. (This is why we normally use |
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* method pollAt and its variants that try once at the apparent |
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* base index, else consider alternative actions, rather than |
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* method poll.) |
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* |
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* This approach also enables support of a user mode in which local |
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* task processing is in FIFO, not LIFO order, simply by using |
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* poll rather than pop. This can be useful in message-passing |
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* frameworks in which tasks are never joined. However neither |
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* mode considers affinities, loads, cache localities, etc, so |
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* rarely provide the best possible performance on a given |
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* machine, but portably provide good throughput by averaging over |
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* these factors. (Further, even if we did try to use such |
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* information, we do not usually have a basis for exploiting it. |
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* For example, some sets of tasks profit from cache affinities, |
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* but others are harmed by cache pollution effects.) |
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* |
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* WorkQueues are also used in a similar way for tasks submitted |
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* to the pool. We cannot mix these tasks in the same queues used |
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* for work-stealing (this would contaminate lifo/fifo |
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* processing). Instead, we loosely associate submission queues |
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* with submitting threads, using a form of hashing. The |
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* ThreadLocal Submitter class contains a value initially used as |
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* a hash code for choosing existing queues, but may be randomly |
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* repositioned upon contention with other submitters. In |
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* essence, submitters act like workers except that they never |
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* take tasks, and they are multiplexed on to a finite number of |
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* shared work queues. However, classes are set up so that future |
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* extensions could allow submitters to optionally help perform |
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* tasks as well. Insertion of tasks in shared mode requires a |
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* lock (mainly to protect in the case of resizing) but we use |
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* only a simple spinlock (using bits in field runState), because |
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* submitters encountering a busy queue move on to try or create |
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* other queues -- they block only when creating and registering |
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* new queues. |
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* |
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* Management |
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* ========== |
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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 two volatile variables |
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* that are by far most often read (not written) as status and |
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* consistency checks. |
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* |
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* Field "ctl" contains 64 bits holding all the information needed |
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* to atomically decide to add, inactivate, enqueue (on an event |
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* queue), dequeue, and/or re-activate workers. To enable this |
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* packing, we restrict maximum parallelism to (1<<15)-1 (which is |
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* far in excess of normal operating range) to allow ids, counts, |
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* and their negations (used for thresholding) to fit into 16bit |
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* fields. |
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* |
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* Field "runState" contains 32 bits needed to register and |
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* deregister WorkQueues, as well as to enable shutdown. It is |
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* only modified under a lock (normally briefly held, but |
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* occasionally protecting allocations and resizings) but even |
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* when locked remains available to check consistency. |
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* |
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* Recording WorkQueues. WorkQueues are recorded in the |
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* "workQueues" array that is created upon first use and expanded |
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* if necessary. Updates to the array while recording new workers |
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* and unrecording terminated ones are protected from each other |
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* by a lock but the array is otherwise concurrently readable, and |
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* accessed directly. To simplify index-based operations, the |
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* array size is always a power of two, and all readers must |
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* tolerate null slots. Shared (submission) queues are at even |
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* indices, worker queues at odd indices. Grouping them together |
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* in this way simplifies and speeds up task scanning. |
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* |
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* All worker thread creation is on-demand, triggered by task |
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* submissions, replacement of terminated workers, and/or |
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* compensation for blocked workers. However, all other support |
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* code is set up to work with other policies. To ensure that we |
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* do not hold on to worker references that would prevent GC, ALL |
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* accesses to workQueues are via indices into the workQueues |
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* array (which is one source of some of the messy code |
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* constructions here). In essence, the workQueues array serves as |
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* a weak reference mechanism. Thus for example the wait queue |
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* field of ctl stores indices, not references. Access to the |
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* workQueues in associated methods (for example signalWork) must |
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* both index-check and null-check the IDs. All such accesses |
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* ignore bad IDs by returning out early from what they are doing, |
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* since this can only be associated with termination, in which |
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* case it is OK to give up. All uses of the workQueues array |
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* also check that it is non-null (even if previously |
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* non-null). This allows nulling during termination, which is |
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* currently not necessary, but remains an option for |
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* resource-revocation-based shutdown schemes. It also helps |
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* reduce JIT issuance of uncommon-trap code, which tends to |
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* unnecessarily complicate control flow in some methods. |
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* |
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* Event 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. In many usages, ramp-up time to activate workers is |
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* the main limiting factor in overall performance (this is |
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* compounded at program start-up by JIT compilation and |
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* allocation). So we try to streamline this as much as possible. |
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* We park/unpark workers after placing in an event wait queue |
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* when they cannot find work. This "queue" is actually a simple |
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* Treiber stack, headed by the "id" field of ctl, plus a 15bit |
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* counter value (that reflects the number of times a worker has |
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* been inactivated) to avoid ABA effects (we need only as many |
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* version numbers as worker threads). Successors are held in |
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* field WorkQueue.nextWait. Queuing deals with several intrinsic |
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* races, 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 (via repeated calls to method |
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* scan()) both before and after a newly waiting worker is added |
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* to the wait queue. During a rescan, the worker might release |
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* some other queued worker rather than itself, which has the same |
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* net effect. Because enqueued workers may actually be rescanning |
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* rather than waiting, we set and clear the "parker" field of |
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* WorkQueues to reduce unnecessary calls to unpark. (This |
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* requires a secondary recheck to avoid missed signals.) Note |
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* the unusual conventions about Thread.interrupts surrounding |
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* parking and other blocking: Because interrupts are used solely |
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* to alert threads to check termination, which is checked anyway |
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* upon blocking, we clear status (using Thread.interrupted) |
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* before any call to park, so that park does not immediately |
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* return due to status being set via some other unrelated call to |
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* interrupt in user code. |
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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 fewer than two 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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* together these cover the signals needed in cases when more |
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* tasks are pushed but untaken, and improve performance compared |
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* to having one thread wake up all workers. |
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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 a |
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* given period -- a short period if there are more threads than |
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* parallelism, longer as the number of threads decreases. This |
321 |
> |
* will slowly propagate, eventually terminating all workers after |
322 |
> |
* periods of non-use. |
323 |
> |
* |
324 |
> |
* Shutdown and Termination. A call to shutdownNow atomically sets |
325 |
> |
* a runState bit and then (non-atomically) sets each worker's |
326 |
> |
* runState status, cancels all unprocessed tasks, and wakes up |
327 |
> |
* all waiting workers. Detecting whether termination should |
328 |
> |
* commence after a non-abrupt shutdown() call requires more work |
329 |
> |
* and bookkeeping. We need consensus about quiescence (i.e., that |
330 |
> |
* there is no more work). The active count provides a primary |
331 |
> |
* indication but non-abrupt shutdown still requires a rechecking |
332 |
> |
* scan for any workers that are inactive but not queued. |
333 |
> |
* |
334 |
> |
* Joining Tasks |
335 |
> |
* ============= |
336 |
> |
* |
337 |
> |
* Any of several actions may be taken when one worker is waiting |
338 |
> |
* to join a task stolen (or always held) by another. Because we |
339 |
> |
* are multiplexing many tasks on to a pool of workers, we can't |
340 |
> |
* just let them block (as in Thread.join). We also cannot just |
341 |
> |
* reassign the joiner's run-time stack with another and replace |
342 |
> |
* it later, which would be a form of "continuation", that even if |
343 |
> |
* possible is not necessarily a good idea since we sometimes need |
344 |
> |
* both an unblocked task and its continuation to progress. |
345 |
> |
* Instead we combine two tactics: |
346 |
> |
* |
347 |
> |
* Helping: Arranging for the joiner to execute some task that it |
348 |
> |
* would be running if the steal had not occurred. |
349 |
> |
* |
350 |
> |
* Compensating: Unless there are already enough live threads, |
351 |
> |
* method tryCompensate() may create or re-activate a spare |
352 |
> |
* thread to compensate for blocked joiners until they unblock. |
353 |
> |
* |
354 |
> |
* A third form (implemented in tryRemoveAndExec and |
355 |
> |
* tryPollForAndExec) amounts to helping a hypothetical |
356 |
> |
* compensator: If we can readily tell that a possible action of a |
357 |
> |
* compensator is to steal and execute the task being joined, the |
358 |
> |
* joining thread can do so directly, without the need for a |
359 |
> |
* compensation thread (although at the expense of larger run-time |
360 |
> |
* stacks, but the tradeoff is typically worthwhile). |
361 |
> |
* |
362 |
> |
* The ManagedBlocker extension API can't use helping so relies |
363 |
> |
* only on compensation in method awaitBlocker. |
364 |
> |
* |
365 |
> |
* The algorithm in tryHelpStealer entails a form of "linear" |
366 |
> |
* helping: Each worker records (in field currentSteal) the most |
367 |
> |
* recent task it stole from some other worker. Plus, it records |
368 |
> |
* (in field currentJoin) the task it is currently actively |
369 |
> |
* joining. Method tryHelpStealer uses these markers to try to |
370 |
> |
* find a worker to help (i.e., steal back a task from and execute |
371 |
> |
* it) that could hasten completion of the actively joined task. |
372 |
> |
* In essence, the joiner executes a task that would be on its own |
373 |
> |
* local deque had the to-be-joined task not been stolen. This may |
374 |
> |
* be seen as a conservative variant of the approach in Wagner & |
375 |
> |
* Calder "Leapfrogging: a portable technique for implementing |
376 |
> |
* efficient futures" SIGPLAN Notices, 1993 |
377 |
> |
* (http://portal.acm.org/citation.cfm?id=155354). It differs in |
378 |
> |
* that: (1) We only maintain dependency links across workers upon |
379 |
> |
* steals, rather than use per-task bookkeeping. This sometimes |
380 |
> |
* requires a linear scan of workQueues array to locate stealers, |
381 |
> |
* but often doesn't because stealers leave hints (that may become |
382 |
> |
* stale/wrong) of where to locate them. A stealHint is only a |
383 |
> |
* hint because a worker might have had multiple steals and the |
384 |
> |
* hint records only one of them (usually the most current). |
385 |
> |
* Hinting isolates cost to when it is needed, rather than adding |
386 |
> |
* to per-task overhead. (2) It is "shallow", ignoring nesting |
387 |
> |
* and potentially cyclic mutual steals. (3) It is intentionally |
388 |
> |
* racy: field currentJoin is updated only while actively joining, |
389 |
> |
* which means that we miss links in the chain during long-lived |
390 |
> |
* tasks, GC stalls etc (which is OK since blocking in such cases |
391 |
> |
* is usually a good idea). (4) We bound the number of attempts |
392 |
> |
* to find work (see MAX_HELP) and fall back to suspending the |
393 |
> |
* worker and if necessary replacing it with another. |
394 |
> |
* |
395 |
> |
* It is impossible to keep exactly the target parallelism number |
396 |
> |
* of threads running at any given time. Determining the |
397 |
> |
* existence of conservatively safe helping targets, the |
398 |
> |
* availability of already-created spares, and the apparent need |
399 |
> |
* to create new spares are all racy, so we rely on multiple |
400 |
> |
* retries of each. Compensation in the apparent absence of |
401 |
> |
* helping opportunities is challenging to control on JVMs, where |
402 |
> |
* GC and other activities can stall progress of tasks that in |
403 |
> |
* turn stall out many other dependent tasks, without us being |
404 |
> |
* able to determine whether they will ever require compensation. |
405 |
> |
* Even though work-stealing otherwise encounters little |
406 |
> |
* degradation in the presence of more threads than cores, |
407 |
> |
* aggressively adding new threads in such cases entails risk of |
408 |
> |
* unwanted positive feedback control loops in which more threads |
409 |
> |
* cause more dependent stalls (as well as delayed progress of |
410 |
> |
* unblocked threads to the point that we know they are available) |
411 |
> |
* leading to more situations requiring more threads, and so |
412 |
> |
* on. This aspect of control can be seen as an (analytically |
413 |
> |
* intractable) game with an opponent that may choose the worst |
414 |
> |
* (for us) active thread to stall at any time. We take several |
415 |
> |
* precautions to bound losses (and thus bound gains), mainly in |
416 |
> |
* methods tryCompensate and awaitJoin: (1) We only try |
417 |
> |
* compensation after attempting enough helping steps (measured |
418 |
> |
* via counting and timing) that we have already consumed the |
419 |
> |
* estimated cost of creating and activating a new thread. (2) We |
420 |
> |
* allow up to 50% of threads to be blocked before initially |
421 |
> |
* adding any others, and unless completely saturated, check that |
422 |
> |
* some work is available for a new worker before adding. Also, we |
423 |
> |
* create up to only 50% more threads until entering a mode that |
424 |
> |
* only adds a thread if all others are possibly blocked. All |
425 |
> |
* together, this means that we might be half as fast to react, |
426 |
> |
* and create half as many threads as possible in the ideal case, |
427 |
> |
* but present vastly fewer anomalies in all other cases compared |
428 |
> |
* to both more aggressive and more conservative alternatives. |
429 |
> |
* |
430 |
> |
* Style notes: There is a lot of representation-level coupling |
431 |
> |
* among classes ForkJoinPool, ForkJoinWorkerThread, and |
432 |
> |
* ForkJoinTask. The fields of WorkQueue maintain data structures |
433 |
> |
* managed by ForkJoinPool, so are directly accessed. There is |
434 |
> |
* little point trying to reduce this, since any associated future |
435 |
> |
* changes in representations will need to be accompanied by |
436 |
> |
* algorithmic changes anyway. Several methods intrinsically |
437 |
> |
* sprawl because they must accumulate sets of consistent reads of |
438 |
> |
* volatiles held in local variables. Methods signalWork() and |
439 |
> |
* scan() are the main bottlenecks, so are especially heavily |
440 |
> |
* micro-optimized/mangled. There are lots of inline assignments |
441 |
> |
* (of form "while ((local = field) != 0)") which are usually the |
442 |
> |
* simplest way to ensure the required read orderings (which are |
443 |
> |
* sometimes critical). This leads to a "C"-like style of listing |
444 |
> |
* declarations of these locals at the heads of methods or blocks. |
445 |
> |
* There are several occurrences of the unusual "do {} while |
446 |
> |
* (!cas...)" which is the simplest way to force an update of a |
447 |
> |
* CAS'ed variable. There are also other coding oddities that help |
448 |
> |
* some methods perform reasonably even when interpreted (not |
449 |
> |
* compiled). |
450 |
> |
* |
451 |
> |
* The order of declarations in this file is: |
452 |
> |
* (1) Static utility functions |
453 |
> |
* (2) Nested (static) classes |
454 |
> |
* (3) Static fields |
455 |
> |
* (4) Fields, along with constants used when unpacking some of them |
456 |
> |
* (5) Internal control methods |
457 |
> |
* (6) Callbacks and other support for ForkJoinTask methods |
458 |
> |
* (7) Exported methods |
459 |
> |
* (8) Static block initializing statics in minimally dependent order |
460 |
|
*/ |
461 |
|
|
462 |
< |
/** Mask for packing and unpacking shorts */ |
71 |
< |
private static final int shortMask = 0xffff; |
462 |
> |
// Static utilities |
463 |
|
|
464 |
< |
/** Max pool size -- must be a power of two minus 1 */ |
465 |
< |
private static final int MAX_THREADS = 0x7FFF; |
464 |
> |
/** |
465 |
> |
* If there is a security manager, makes sure caller has |
466 |
> |
* permission to modify threads. |
467 |
> |
*/ |
468 |
> |
private static void checkPermission() { |
469 |
> |
SecurityManager security = System.getSecurityManager(); |
470 |
> |
if (security != null) |
471 |
> |
security.checkPermission(modifyThreadPermission); |
472 |
> |
} |
473 |
> |
|
474 |
> |
// Nested classes |
475 |
|
|
476 |
|
/** |
477 |
< |
* Factory for creating new ForkJoinWorkerThreads. A |
478 |
< |
* ForkJoinWorkerThreadFactory must be defined and used for |
479 |
< |
* ForkJoinWorkerThread subclasses that extend base functionality |
480 |
< |
* or initialize threads with different contexts. |
477 |
> |
* Factory for creating new {@link ForkJoinWorkerThread}s. |
478 |
> |
* A {@code ForkJoinWorkerThreadFactory} must be defined and used |
479 |
> |
* for {@code ForkJoinWorkerThread} subclasses that extend base |
480 |
> |
* functionality or initialize threads with different contexts. |
481 |
|
*/ |
482 |
|
public static interface ForkJoinWorkerThreadFactory { |
483 |
|
/** |
484 |
|
* Returns a new worker thread operating in the given pool. |
485 |
|
* |
486 |
|
* @param pool the pool this thread works in |
487 |
< |
* @throws NullPointerException if pool is null |
487 |
> |
* @throws NullPointerException if the pool is null |
488 |
|
*/ |
489 |
|
public ForkJoinWorkerThread newThread(ForkJoinPool pool); |
490 |
|
} |
493 |
|
* Default ForkJoinWorkerThreadFactory implementation; creates a |
494 |
|
* new ForkJoinWorkerThread. |
495 |
|
*/ |
496 |
< |
static class DefaultForkJoinWorkerThreadFactory |
496 |
> |
static class DefaultForkJoinWorkerThreadFactory |
497 |
|
implements ForkJoinWorkerThreadFactory { |
498 |
|
public ForkJoinWorkerThread newThread(ForkJoinPool pool) { |
499 |
< |
try { |
500 |
< |
return new ForkJoinWorkerThread(pool); |
501 |
< |
} catch (OutOfMemoryError oom) { |
499 |
> |
return new ForkJoinWorkerThread(pool); |
500 |
> |
} |
501 |
> |
} |
502 |
> |
|
503 |
> |
/** |
504 |
> |
* Class for artificial tasks that are used to replace the target |
505 |
> |
* of local joins if they are removed from an interior queue slot |
506 |
> |
* in WorkQueue.tryRemoveAndExec. We don't need the proxy to |
507 |
> |
* actually do anything beyond having a unique identity. |
508 |
> |
*/ |
509 |
> |
static final class EmptyTask extends ForkJoinTask<Void> { |
510 |
> |
EmptyTask() { status = ForkJoinTask.NORMAL; } // force done |
511 |
> |
public final Void getRawResult() { return null; } |
512 |
> |
public final void setRawResult(Void x) {} |
513 |
> |
public final boolean exec() { return true; } |
514 |
> |
} |
515 |
> |
|
516 |
> |
/** |
517 |
> |
* Queues supporting work-stealing as well as external task |
518 |
> |
* submission. See above for main rationale and algorithms. |
519 |
> |
* Implementation relies heavily on "Unsafe" intrinsics |
520 |
> |
* and selective use of "volatile": |
521 |
> |
* |
522 |
> |
* Field "base" is the index (mod array.length) of the least valid |
523 |
> |
* queue slot, which is always the next position to steal (poll) |
524 |
> |
* from if nonempty. Reads and writes require volatile orderings |
525 |
> |
* but not CAS, because updates are only performed after slot |
526 |
> |
* CASes. |
527 |
> |
* |
528 |
> |
* Field "top" is the index (mod array.length) of the next queue |
529 |
> |
* slot to push to or pop from. It is written only by owner thread |
530 |
> |
* for push, or under lock for trySharedPush, and accessed by |
531 |
> |
* other threads only after reading (volatile) base. Both top and |
532 |
> |
* base are allowed to wrap around on overflow, but (top - base) |
533 |
> |
* (or more commonly -(base - top) to force volatile read of base |
534 |
> |
* before top) still estimates size. |
535 |
> |
* |
536 |
> |
* The array slots are read and written using the emulation of |
537 |
> |
* volatiles/atomics provided by Unsafe. Insertions must in |
538 |
> |
* general use putOrderedObject as a form of releasing store to |
539 |
> |
* ensure that all writes to the task object are ordered before |
540 |
> |
* its publication in the queue. (Although we can avoid one case |
541 |
> |
* of this when locked in trySharedPush.) All removals entail a |
542 |
> |
* CAS to null. The array is always a power of two. To ensure |
543 |
> |
* safety of Unsafe array operations, all accesses perform |
544 |
> |
* explicit null checks and implicit bounds checks via |
545 |
> |
* power-of-two masking. |
546 |
> |
* |
547 |
> |
* In addition to basic queuing support, this class contains |
548 |
> |
* fields described elsewhere to control execution. It turns out |
549 |
> |
* to work better memory-layout-wise to include them in this |
550 |
> |
* class rather than a separate class. |
551 |
> |
* |
552 |
> |
* Performance on most platforms is very sensitive to placement of |
553 |
> |
* instances of both WorkQueues and their arrays -- we absolutely |
554 |
> |
* do not want multiple WorkQueue instances or multiple queue |
555 |
> |
* arrays sharing cache lines. (It would be best for queue objects |
556 |
> |
* and their arrays to share, but there is nothing available to |
557 |
> |
* help arrange that). Unfortunately, because they are recorded |
558 |
> |
* in a common array, WorkQueue instances are often moved to be |
559 |
> |
* adjacent by garbage collectors. To reduce impact, we use field |
560 |
> |
* padding that works OK on common platforms; this effectively |
561 |
> |
* trades off slightly slower average field access for the sake of |
562 |
> |
* avoiding really bad worst-case access. (Until better JVM |
563 |
> |
* support is in place, this padding is dependent on transient |
564 |
> |
* properties of JVM field layout rules.) We also take care in |
565 |
> |
* allocating, sizing and resizing the array. Non-shared queue |
566 |
> |
* arrays are initialized (via method growArray) by workers before |
567 |
> |
* use. Others are allocated on first use. |
568 |
> |
*/ |
569 |
> |
static final class WorkQueue { |
570 |
> |
/** |
571 |
> |
* Capacity of work-stealing queue array upon initialization. |
572 |
> |
* Must be a power of two; at least 4, but should be larger to |
573 |
> |
* reduce or eliminate cacheline sharing among queues. |
574 |
> |
* Currently, it is much larger, as a partial workaround for |
575 |
> |
* the fact that JVMs often place arrays in locations that |
576 |
> |
* share GC bookkeeping (especially cardmarks) such that |
577 |
> |
* per-write accesses encounter serious memory contention. |
578 |
> |
*/ |
579 |
> |
static final int INITIAL_QUEUE_CAPACITY = 1 << 13; |
580 |
> |
|
581 |
> |
/** |
582 |
> |
* Maximum size for queue arrays. Must be a power of two less |
583 |
> |
* than or equal to 1 << (31 - width of array entry) to ensure |
584 |
> |
* lack of wraparound of index calculations, but defined to a |
585 |
> |
* value a bit less than this to help users trap runaway |
586 |
> |
* programs before saturating systems. |
587 |
> |
*/ |
588 |
> |
static final int MAXIMUM_QUEUE_CAPACITY = 1 << 26; // 64M |
589 |
> |
|
590 |
> |
volatile long totalSteals; // cumulative number of steals |
591 |
> |
int seed; // for random scanning; initialize nonzero |
592 |
> |
volatile int eventCount; // encoded inactivation count; < 0 if inactive |
593 |
> |
int nextWait; // encoded record of next event waiter |
594 |
> |
int rescans; // remaining scans until block |
595 |
> |
int nsteals; // top-level task executions since last idle |
596 |
> |
final int mode; // lifo, fifo, or shared |
597 |
> |
int poolIndex; // index of this queue in pool (or 0) |
598 |
> |
int stealHint; // index of most recent known stealer |
599 |
> |
volatile int runState; // 1: locked, -1: terminate; else 0 |
600 |
> |
volatile int base; // index of next slot for poll |
601 |
> |
int top; // index of next slot for push |
602 |
> |
ForkJoinTask<?>[] array; // the elements (initially unallocated) |
603 |
> |
final ForkJoinPool pool; // the containing pool (may be null) |
604 |
> |
final ForkJoinWorkerThread owner; // owning thread or null if shared |
605 |
> |
volatile Thread parker; // == owner during call to park; else null |
606 |
> |
volatile ForkJoinTask<?> currentJoin; // task being joined in awaitJoin |
607 |
> |
ForkJoinTask<?> currentSteal; // current non-local task being executed |
608 |
> |
// Heuristic padding to ameliorate unfortunate memory placements |
609 |
> |
Object p00, p01, p02, p03, p04, p05, p06, p07; |
610 |
> |
Object p08, p09, p0a, p0b, p0c, p0d, p0e; |
611 |
> |
|
612 |
> |
WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode) { |
613 |
> |
this.mode = mode; |
614 |
> |
this.pool = pool; |
615 |
> |
this.owner = owner; |
616 |
> |
// Place indices in the center of array (that is not yet allocated) |
617 |
> |
base = top = INITIAL_QUEUE_CAPACITY >>> 1; |
618 |
> |
} |
619 |
> |
|
620 |
> |
/** |
621 |
> |
* Returns the approximate number of tasks in the queue. |
622 |
> |
*/ |
623 |
> |
final int queueSize() { |
624 |
> |
int n = base - top; // non-owner callers must read base first |
625 |
> |
return (n >= 0) ? 0 : -n; // ignore transient negative |
626 |
> |
} |
627 |
> |
|
628 |
> |
/** |
629 |
> |
* Provides a more accurate estimate of whether this queue has |
630 |
> |
* any tasks than does queueSize, by checking whether a |
631 |
> |
* near-empty queue has at least one unclaimed task. |
632 |
> |
*/ |
633 |
> |
final boolean isEmpty() { |
634 |
> |
ForkJoinTask<?>[] a; int m, s; |
635 |
> |
int n = base - (s = top); |
636 |
> |
return (n >= 0 || |
637 |
> |
(n == -1 && |
638 |
> |
((a = array) == null || |
639 |
> |
(m = a.length - 1) < 0 || |
640 |
> |
U.getObjectVolatile |
641 |
> |
(a, ((m & (s - 1)) << ASHIFT) + ABASE) == null))); |
642 |
> |
} |
643 |
> |
|
644 |
> |
/** |
645 |
> |
* Pushes a task. Call only by owner in unshared queues. |
646 |
> |
* |
647 |
> |
* @param task the task. Caller must ensure non-null. |
648 |
> |
* @throw RejectedExecutionException if array cannot be resized |
649 |
> |
*/ |
650 |
> |
final void push(ForkJoinTask<?> task) { |
651 |
> |
ForkJoinTask<?>[] a; ForkJoinPool p; |
652 |
> |
int s = top, m, n; |
653 |
> |
if ((a = array) != null) { // ignore if queue removed |
654 |
> |
U.putOrderedObject |
655 |
> |
(a, (((m = a.length - 1) & s) << ASHIFT) + ABASE, task); |
656 |
> |
if ((n = (top = s + 1) - base) <= 2) { |
657 |
> |
if ((p = pool) != null) |
658 |
> |
p.signalWork(); |
659 |
> |
} |
660 |
> |
else if (n >= m) |
661 |
> |
growArray(true); |
662 |
> |
} |
663 |
> |
} |
664 |
> |
|
665 |
> |
/** |
666 |
> |
* Pushes a task if lock is free and array is either big |
667 |
> |
* enough or can be resized to be big enough. |
668 |
> |
* |
669 |
> |
* @param task the task. Caller must ensure non-null. |
670 |
> |
* @return true if submitted |
671 |
> |
*/ |
672 |
> |
final boolean trySharedPush(ForkJoinTask<?> task) { |
673 |
> |
boolean submitted = false; |
674 |
> |
if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) { |
675 |
> |
ForkJoinTask<?>[] a = array; |
676 |
> |
int s = top; |
677 |
> |
try { |
678 |
> |
if ((a != null && a.length > s + 1 - base) || |
679 |
> |
(a = growArray(false)) != null) { // must presize |
680 |
> |
int j = (((a.length - 1) & s) << ASHIFT) + ABASE; |
681 |
> |
U.putObject(a, (long)j, task); // don't need "ordered" |
682 |
> |
top = s + 1; |
683 |
> |
submitted = true; |
684 |
> |
} |
685 |
> |
} finally { |
686 |
> |
runState = 0; // unlock |
687 |
> |
} |
688 |
> |
} |
689 |
> |
return submitted; |
690 |
> |
} |
691 |
> |
|
692 |
> |
/** |
693 |
> |
* Takes next task, if one exists, in LIFO order. Call only |
694 |
> |
* by owner in unshared queues. |
695 |
> |
*/ |
696 |
> |
final ForkJoinTask<?> pop() { |
697 |
> |
ForkJoinTask<?>[] a; ForkJoinTask<?> t; int m; |
698 |
> |
if ((a = array) != null && (m = a.length - 1) >= 0) { |
699 |
> |
for (int s; (s = top - 1) - base >= 0;) { |
700 |
> |
long j = ((m & s) << ASHIFT) + ABASE; |
701 |
> |
if ((t = (ForkJoinTask<?>)U.getObject(a, j)) == null) |
702 |
> |
break; |
703 |
> |
if (U.compareAndSwapObject(a, j, t, null)) { |
704 |
> |
top = s; |
705 |
> |
return t; |
706 |
> |
} |
707 |
> |
} |
708 |
> |
} |
709 |
> |
return null; |
710 |
> |
} |
711 |
> |
|
712 |
> |
final ForkJoinTask<?> sharedPop() { |
713 |
> |
ForkJoinTask<?> task = null; |
714 |
> |
if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) { |
715 |
> |
try { |
716 |
> |
ForkJoinTask<?>[] a; int m; |
717 |
> |
if ((a = array) != null && (m = a.length - 1) >= 0) { |
718 |
> |
for (int s; (s = top - 1) - base >= 0;) { |
719 |
> |
long j = ((m & s) << ASHIFT) + ABASE; |
720 |
> |
ForkJoinTask<?> t = |
721 |
> |
(ForkJoinTask<?>)U.getObject(a, j); |
722 |
> |
if (t == null) |
723 |
> |
break; |
724 |
> |
if (U.compareAndSwapObject(a, j, t, null)) { |
725 |
> |
top = s; |
726 |
> |
task = t; |
727 |
> |
break; |
728 |
> |
} |
729 |
> |
} |
730 |
> |
} |
731 |
> |
} finally { |
732 |
> |
runState = 0; |
733 |
> |
} |
734 |
> |
} |
735 |
> |
return task; |
736 |
> |
} |
737 |
> |
|
738 |
> |
|
739 |
> |
/** |
740 |
> |
* Takes a task in FIFO order if b is base of queue and a task |
741 |
> |
* can be claimed without contention. Specialized versions |
742 |
> |
* appear in ForkJoinPool methods scan and tryHelpStealer. |
743 |
> |
*/ |
744 |
> |
final ForkJoinTask<?> pollAt(int b) { |
745 |
> |
ForkJoinTask<?> t; ForkJoinTask<?>[] a; |
746 |
> |
if ((a = array) != null) { |
747 |
> |
int j = (((a.length - 1) & b) << ASHIFT) + ABASE; |
748 |
> |
if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) != null && |
749 |
> |
base == b && |
750 |
> |
U.compareAndSwapObject(a, j, t, null)) { |
751 |
> |
base = b + 1; |
752 |
> |
return t; |
753 |
> |
} |
754 |
> |
} |
755 |
> |
return null; |
756 |
> |
} |
757 |
> |
|
758 |
> |
/** |
759 |
> |
* Takes next task, if one exists, in FIFO order. |
760 |
> |
*/ |
761 |
> |
final ForkJoinTask<?> poll() { |
762 |
> |
ForkJoinTask<?>[] a; int b; ForkJoinTask<?> t; |
763 |
> |
while ((b = base) - top < 0 && (a = array) != null) { |
764 |
> |
int j = (((a.length - 1) & b) << ASHIFT) + ABASE; |
765 |
> |
t = (ForkJoinTask<?>)U.getObjectVolatile(a, j); |
766 |
> |
if (t != null) { |
767 |
> |
if (base == b && |
768 |
> |
U.compareAndSwapObject(a, j, t, null)) { |
769 |
> |
base = b + 1; |
770 |
> |
return t; |
771 |
> |
} |
772 |
> |
} |
773 |
> |
else if (base == b) { |
774 |
> |
if (b + 1 == top) |
775 |
> |
break; |
776 |
> |
Thread.yield(); // wait for lagging update |
777 |
> |
} |
778 |
> |
} |
779 |
> |
return null; |
780 |
> |
} |
781 |
> |
|
782 |
> |
/** |
783 |
> |
* Takes next task, if one exists, in order specified by mode. |
784 |
> |
*/ |
785 |
> |
final ForkJoinTask<?> nextLocalTask() { |
786 |
> |
return mode == 0 ? pop() : poll(); |
787 |
> |
} |
788 |
> |
|
789 |
> |
/** |
790 |
> |
* Returns next task, if one exists, in order specified by mode. |
791 |
> |
*/ |
792 |
> |
final ForkJoinTask<?> peek() { |
793 |
> |
ForkJoinTask<?>[] a = array; int m; |
794 |
> |
if (a == null || (m = a.length - 1) < 0) |
795 |
> |
return null; |
796 |
> |
int i = mode == 0 ? top - 1 : base; |
797 |
> |
int j = ((i & m) << ASHIFT) + ABASE; |
798 |
> |
return (ForkJoinTask<?>)U.getObjectVolatile(a, j); |
799 |
> |
} |
800 |
> |
|
801 |
> |
/** |
802 |
> |
* Pops the given task only if it is at the current top. |
803 |
> |
*/ |
804 |
> |
final boolean tryUnpush(ForkJoinTask<?> t) { |
805 |
> |
ForkJoinTask<?>[] a; int s; |
806 |
> |
if ((a = array) != null && (s = top) != base && |
807 |
> |
U.compareAndSwapObject |
808 |
> |
(a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) { |
809 |
> |
top = s; |
810 |
> |
return true; |
811 |
> |
} |
812 |
> |
return false; |
813 |
> |
} |
814 |
> |
|
815 |
> |
/** |
816 |
> |
* Version of tryUnpush for shared queues; called by non-FJ |
817 |
> |
* submitters after prechecking that task probably exists. |
818 |
> |
*/ |
819 |
> |
final boolean trySharedUnpush(ForkJoinTask<?> t) { |
820 |
> |
boolean success = false; |
821 |
> |
if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) { |
822 |
> |
try { |
823 |
> |
ForkJoinTask<?>[] a; int s; |
824 |
> |
if ((a = array) != null && (s = top) != base && |
825 |
> |
U.compareAndSwapObject |
826 |
> |
(a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) { |
827 |
> |
top = s; |
828 |
> |
success = true; |
829 |
> |
} |
830 |
> |
} finally { |
831 |
> |
runState = 0; // unlock |
832 |
> |
} |
833 |
> |
} |
834 |
> |
return success; |
835 |
> |
} |
836 |
> |
|
837 |
> |
/** |
838 |
> |
* Polls the given task only if it is at the current base. |
839 |
> |
*/ |
840 |
> |
final boolean pollFor(ForkJoinTask<?> task) { |
841 |
> |
ForkJoinTask<?>[] a; int b; |
842 |
> |
if ((b = base) - top < 0 && (a = array) != null) { |
843 |
> |
int j = (((a.length - 1) & b) << ASHIFT) + ABASE; |
844 |
> |
if (U.getObjectVolatile(a, j) == task && base == b && |
845 |
> |
U.compareAndSwapObject(a, j, task, null)) { |
846 |
> |
base = b + 1; |
847 |
> |
return true; |
848 |
> |
} |
849 |
> |
} |
850 |
> |
return false; |
851 |
> |
} |
852 |
> |
|
853 |
> |
/** |
854 |
> |
* Initializes or doubles the capacity of array. Call either |
855 |
> |
* by owner or with lock held -- it is OK for base, but not |
856 |
> |
* top, to move while resizings are in progress. |
857 |
> |
* |
858 |
> |
* @param rejectOnFailure if true, throw exception if capacity |
859 |
> |
* exceeded (relayed ultimately to user); else return null. |
860 |
> |
*/ |
861 |
> |
final ForkJoinTask<?>[] growArray(boolean rejectOnFailure) { |
862 |
> |
ForkJoinTask<?>[] oldA = array; |
863 |
> |
int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY; |
864 |
> |
if (size <= MAXIMUM_QUEUE_CAPACITY) { |
865 |
> |
int oldMask, t, b; |
866 |
> |
ForkJoinTask<?>[] a = array = new ForkJoinTask<?>[size]; |
867 |
> |
if (oldA != null && (oldMask = oldA.length - 1) >= 0 && |
868 |
> |
(t = top) - (b = base) > 0) { |
869 |
> |
int mask = size - 1; |
870 |
> |
do { |
871 |
> |
ForkJoinTask<?> x; |
872 |
> |
int oldj = ((b & oldMask) << ASHIFT) + ABASE; |
873 |
> |
int j = ((b & mask) << ASHIFT) + ABASE; |
874 |
> |
x = (ForkJoinTask<?>)U.getObjectVolatile(oldA, oldj); |
875 |
> |
if (x != null && |
876 |
> |
U.compareAndSwapObject(oldA, oldj, x, null)) |
877 |
> |
U.putObjectVolatile(a, j, x); |
878 |
> |
} while (++b != t); |
879 |
> |
} |
880 |
> |
return a; |
881 |
> |
} |
882 |
> |
else if (!rejectOnFailure) |
883 |
|
return null; |
884 |
+ |
else |
885 |
+ |
throw new RejectedExecutionException("Queue capacity exceeded"); |
886 |
+ |
} |
887 |
+ |
|
888 |
+ |
/** |
889 |
+ |
* Removes and cancels all known tasks, ignoring any exceptions. |
890 |
+ |
*/ |
891 |
+ |
final void cancelAll() { |
892 |
+ |
ForkJoinTask.cancelIgnoringExceptions(currentJoin); |
893 |
+ |
ForkJoinTask.cancelIgnoringExceptions(currentSteal); |
894 |
+ |
for (ForkJoinTask<?> t; (t = poll()) != null; ) |
895 |
+ |
ForkJoinTask.cancelIgnoringExceptions(t); |
896 |
+ |
} |
897 |
+ |
|
898 |
+ |
/** |
899 |
+ |
* Computes next value for random probes. Scans don't require |
900 |
+ |
* a very high quality generator, but also not a crummy one. |
901 |
+ |
* Marsaglia xor-shift is cheap and works well enough. Note: |
902 |
+ |
* This is manually inlined in its usages in ForkJoinPool to |
903 |
+ |
* avoid writes inside busy scan loops. |
904 |
+ |
*/ |
905 |
+ |
final int nextSeed() { |
906 |
+ |
int r = seed; |
907 |
+ |
r ^= r << 13; |
908 |
+ |
r ^= r >>> 17; |
909 |
+ |
return seed = r ^= r << 5; |
910 |
+ |
} |
911 |
+ |
|
912 |
+ |
// Specialized execution methods |
913 |
+ |
|
914 |
+ |
/** |
915 |
+ |
* Pops and runs tasks until empty. |
916 |
+ |
*/ |
917 |
+ |
private void popAndExecAll() { |
918 |
+ |
// A bit faster than repeated pop calls |
919 |
+ |
ForkJoinTask<?>[] a; int m, s; long j; ForkJoinTask<?> t; |
920 |
+ |
while ((a = array) != null && (m = a.length - 1) >= 0 && |
921 |
+ |
(s = top - 1) - base >= 0 && |
922 |
+ |
(t = ((ForkJoinTask<?>) |
923 |
+ |
U.getObject(a, j = ((m & s) << ASHIFT) + ABASE))) |
924 |
+ |
!= null) { |
925 |
+ |
if (U.compareAndSwapObject(a, j, t, null)) { |
926 |
+ |
top = s; |
927 |
+ |
t.doExec(); |
928 |
+ |
} |
929 |
+ |
} |
930 |
+ |
} |
931 |
+ |
|
932 |
+ |
/** |
933 |
+ |
* Polls and runs tasks until empty. |
934 |
+ |
*/ |
935 |
+ |
private void pollAndExecAll() { |
936 |
+ |
for (ForkJoinTask<?> t; (t = poll()) != null;) |
937 |
+ |
t.doExec(); |
938 |
+ |
} |
939 |
+ |
|
940 |
+ |
/** |
941 |
+ |
* If present, removes from queue and executes the given task, or |
942 |
+ |
* any other cancelled task. Returns (true) immediately on any CAS |
943 |
+ |
* or consistency check failure so caller can retry. |
944 |
+ |
* |
945 |
+ |
* @return 0 if no progress can be made, else positive |
946 |
+ |
* (this unusual convention simplifies use with tryHelpStealer.) |
947 |
+ |
*/ |
948 |
+ |
final int tryRemoveAndExec(ForkJoinTask<?> task) { |
949 |
+ |
int stat = 1; |
950 |
+ |
boolean removed = false, empty = true; |
951 |
+ |
ForkJoinTask<?>[] a; int m, s, b, n; |
952 |
+ |
if ((a = array) != null && (m = a.length - 1) >= 0 && |
953 |
+ |
(n = (s = top) - (b = base)) > 0) { |
954 |
+ |
for (ForkJoinTask<?> t;;) { // traverse from s to b |
955 |
+ |
int j = ((--s & m) << ASHIFT) + ABASE; |
956 |
+ |
t = (ForkJoinTask<?>)U.getObjectVolatile(a, j); |
957 |
+ |
if (t == null) // inconsistent length |
958 |
+ |
break; |
959 |
+ |
else if (t == task) { |
960 |
+ |
if (s + 1 == top) { // pop |
961 |
+ |
if (!U.compareAndSwapObject(a, j, task, null)) |
962 |
+ |
break; |
963 |
+ |
top = s; |
964 |
+ |
removed = true; |
965 |
+ |
} |
966 |
+ |
else if (base == b) // replace with proxy |
967 |
+ |
removed = U.compareAndSwapObject(a, j, task, |
968 |
+ |
new EmptyTask()); |
969 |
+ |
break; |
970 |
+ |
} |
971 |
+ |
else if (t.status >= 0) |
972 |
+ |
empty = false; |
973 |
+ |
else if (s + 1 == top) { // pop and throw away |
974 |
+ |
if (U.compareAndSwapObject(a, j, t, null)) |
975 |
+ |
top = s; |
976 |
+ |
break; |
977 |
+ |
} |
978 |
+ |
if (--n == 0) { |
979 |
+ |
if (!empty && base == b) |
980 |
+ |
stat = 0; |
981 |
+ |
break; |
982 |
+ |
} |
983 |
+ |
} |
984 |
+ |
} |
985 |
+ |
if (removed) |
986 |
+ |
task.doExec(); |
987 |
+ |
return stat; |
988 |
+ |
} |
989 |
+ |
|
990 |
+ |
/** |
991 |
+ |
* Version of shared pop that takes top element only if it |
992 |
+ |
* its root is the given CountedCompleter. |
993 |
+ |
*/ |
994 |
+ |
final CountedCompleter<?> sharedPopCC(CountedCompleter<?> root) { |
995 |
+ |
CountedCompleter<?> task = null; |
996 |
+ |
if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) { |
997 |
+ |
try { |
998 |
+ |
ForkJoinTask<?>[] a; int m; |
999 |
+ |
if ((a = array) != null && (m = a.length - 1) >= 0) { |
1000 |
+ |
outer:for (int s; (s = top - 1) - base >= 0;) { |
1001 |
+ |
long j = ((m & s) << ASHIFT) + ABASE; |
1002 |
+ |
ForkJoinTask<?> t = |
1003 |
+ |
(ForkJoinTask<?>)U.getObject(a, j); |
1004 |
+ |
if (t == null || !(t instanceof CountedCompleter)) |
1005 |
+ |
break; |
1006 |
+ |
CountedCompleter<?> cc = (CountedCompleter<?>)t; |
1007 |
+ |
for (CountedCompleter<?> q = cc, p;;) { |
1008 |
+ |
if (q == root) { |
1009 |
+ |
if (U.compareAndSwapObject(a, j, cc, null)) { |
1010 |
+ |
top = s; |
1011 |
+ |
task = cc; |
1012 |
+ |
break outer; |
1013 |
+ |
} |
1014 |
+ |
break; |
1015 |
+ |
} |
1016 |
+ |
if ((p = q.completer) == null) |
1017 |
+ |
break outer; |
1018 |
+ |
q = p; |
1019 |
+ |
} |
1020 |
+ |
} |
1021 |
+ |
} |
1022 |
+ |
} finally { |
1023 |
+ |
runState = 0; |
1024 |
+ |
} |
1025 |
+ |
} |
1026 |
+ |
return task; |
1027 |
+ |
} |
1028 |
+ |
|
1029 |
+ |
/** |
1030 |
+ |
* Executes a top-level task and any local tasks remaining |
1031 |
+ |
* after execution. |
1032 |
+ |
*/ |
1033 |
+ |
final void runTask(ForkJoinTask<?> t) { |
1034 |
+ |
if (t != null) { |
1035 |
+ |
currentSteal = t; |
1036 |
+ |
t.doExec(); |
1037 |
+ |
if (top != base) { // process remaining local tasks |
1038 |
+ |
if (mode == 0) |
1039 |
+ |
popAndExecAll(); |
1040 |
+ |
else |
1041 |
+ |
pollAndExecAll(); |
1042 |
+ |
} |
1043 |
+ |
++nsteals; |
1044 |
+ |
currentSteal = null; |
1045 |
+ |
} |
1046 |
+ |
} |
1047 |
+ |
|
1048 |
+ |
/** |
1049 |
+ |
* Executes a non-top-level (stolen) task. |
1050 |
+ |
*/ |
1051 |
+ |
final void runSubtask(ForkJoinTask<?> t) { |
1052 |
+ |
if (t != null) { |
1053 |
+ |
ForkJoinTask<?> ps = currentSteal; |
1054 |
+ |
currentSteal = t; |
1055 |
+ |
t.doExec(); |
1056 |
+ |
currentSteal = ps; |
1057 |
+ |
} |
1058 |
+ |
} |
1059 |
+ |
|
1060 |
+ |
/** |
1061 |
+ |
* Returns true if owned and not known to be blocked. |
1062 |
+ |
*/ |
1063 |
+ |
final boolean isApparentlyUnblocked() { |
1064 |
+ |
Thread wt; Thread.State s; |
1065 |
+ |
return (eventCount >= 0 && |
1066 |
+ |
(wt = owner) != null && |
1067 |
+ |
(s = wt.getState()) != Thread.State.BLOCKED && |
1068 |
+ |
s != Thread.State.WAITING && |
1069 |
+ |
s != Thread.State.TIMED_WAITING); |
1070 |
+ |
} |
1071 |
+ |
|
1072 |
+ |
/** |
1073 |
+ |
* If this owned and is not already interrupted, try to |
1074 |
+ |
* interrupt and/or unpark, ignoring exceptions. |
1075 |
+ |
*/ |
1076 |
+ |
final void interruptOwner() { |
1077 |
+ |
Thread wt, p; |
1078 |
+ |
if ((wt = owner) != null && !wt.isInterrupted()) { |
1079 |
+ |
try { |
1080 |
+ |
wt.interrupt(); |
1081 |
+ |
} catch (SecurityException ignore) { |
1082 |
+ |
} |
1083 |
|
} |
1084 |
+ |
if ((p = parker) != null) |
1085 |
+ |
U.unpark(p); |
1086 |
+ |
} |
1087 |
+ |
|
1088 |
+ |
// Unsafe mechanics |
1089 |
+ |
private static final sun.misc.Unsafe U; |
1090 |
+ |
private static final long RUNSTATE; |
1091 |
+ |
private static final int ABASE; |
1092 |
+ |
private static final int ASHIFT; |
1093 |
+ |
static { |
1094 |
+ |
int s; |
1095 |
+ |
try { |
1096 |
+ |
U = getUnsafe(); |
1097 |
+ |
Class<?> k = WorkQueue.class; |
1098 |
+ |
Class<?> ak = ForkJoinTask[].class; |
1099 |
+ |
RUNSTATE = U.objectFieldOffset |
1100 |
+ |
(k.getDeclaredField("runState")); |
1101 |
+ |
ABASE = U.arrayBaseOffset(ak); |
1102 |
+ |
s = U.arrayIndexScale(ak); |
1103 |
+ |
} catch (Exception e) { |
1104 |
+ |
throw new Error(e); |
1105 |
+ |
} |
1106 |
+ |
if ((s & (s-1)) != 0) |
1107 |
+ |
throw new Error("data type scale not a power of two"); |
1108 |
+ |
ASHIFT = 31 - Integer.numberOfLeadingZeros(s); |
1109 |
|
} |
1110 |
|
} |
1111 |
|
|
1112 |
|
/** |
1113 |
+ |
* Per-thread records for threads that submit to pools. Currently |
1114 |
+ |
* holds only pseudo-random seed / index that is used to choose |
1115 |
+ |
* submission queues in method doSubmit. In the future, this may |
1116 |
+ |
* also incorporate a means to implement different task rejection |
1117 |
+ |
* and resubmission policies. |
1118 |
+ |
* |
1119 |
+ |
* Seeds for submitters and workers/workQueues work in basically |
1120 |
+ |
* the same way but are initialized and updated using slightly |
1121 |
+ |
* different mechanics. Both are initialized using the same |
1122 |
+ |
* approach as in class ThreadLocal, where successive values are |
1123 |
+ |
* unlikely to collide with previous values. This is done during |
1124 |
+ |
* registration for workers, but requires a separate AtomicInteger |
1125 |
+ |
* for submitters. Seeds are then randomly modified upon |
1126 |
+ |
* collisions using xorshifts, which requires a non-zero seed. |
1127 |
+ |
*/ |
1128 |
+ |
static final class Submitter { |
1129 |
+ |
int seed; |
1130 |
+ |
Submitter() { |
1131 |
+ |
int s = nextSubmitterSeed.getAndAdd(SEED_INCREMENT); |
1132 |
+ |
seed = (s == 0) ? 1 : s; // ensure non-zero |
1133 |
+ |
} |
1134 |
+ |
} |
1135 |
+ |
|
1136 |
+ |
/** ThreadLocal class for Submitters */ |
1137 |
+ |
static final class ThreadSubmitter extends ThreadLocal<Submitter> { |
1138 |
+ |
public Submitter initialValue() { return new Submitter(); } |
1139 |
+ |
} |
1140 |
+ |
|
1141 |
+ |
// static fields (initialized in static initializer below) |
1142 |
+ |
|
1143 |
+ |
/** |
1144 |
|
* Creates a new ForkJoinWorkerThread. This factory is used unless |
1145 |
|
* overridden in ForkJoinPool constructors. |
1146 |
|
*/ |
1147 |
|
public static final ForkJoinWorkerThreadFactory |
1148 |
< |
defaultForkJoinWorkerThreadFactory = |
1149 |
< |
new DefaultForkJoinWorkerThreadFactory(); |
1148 |
> |
defaultForkJoinWorkerThreadFactory; |
1149 |
> |
|
1150 |
> |
/** Property prefix for constructing common pool */ |
1151 |
> |
private static final String propPrefix = |
1152 |
> |
"java.util.concurrent.ForkJoinPool.common."; |
1153 |
> |
|
1154 |
> |
/** |
1155 |
> |
* Common (static) pool. Non-null for public use unless a static |
1156 |
> |
* construction exception, but internal usages must null-check on |
1157 |
> |
* use. |
1158 |
> |
*/ |
1159 |
> |
static final ForkJoinPool commonPool; |
1160 |
> |
|
1161 |
> |
/** |
1162 |
> |
* Common pool parallelism. Must equal commonPool.parallelism. |
1163 |
> |
*/ |
1164 |
> |
static final int commonPoolParallelism; |
1165 |
> |
|
1166 |
> |
/** |
1167 |
> |
* Generator for assigning sequence numbers as pool names. |
1168 |
> |
*/ |
1169 |
> |
private static final AtomicInteger poolNumberGenerator; |
1170 |
> |
|
1171 |
> |
/** |
1172 |
> |
* Generator for initial hashes/seeds for submitters. Accessed by |
1173 |
> |
* Submitter class constructor. |
1174 |
> |
*/ |
1175 |
> |
static final AtomicInteger nextSubmitterSeed; |
1176 |
|
|
1177 |
|
/** |
1178 |
|
* Permission required for callers of methods that may start or |
1179 |
|
* kill threads. |
1180 |
|
*/ |
1181 |
< |
private static final RuntimePermission modifyThreadPermission = |
120 |
< |
new RuntimePermission("modifyThread"); |
1181 |
> |
private static final RuntimePermission modifyThreadPermission; |
1182 |
|
|
1183 |
|
/** |
1184 |
< |
* If there is a security manager, makes sure caller has |
1185 |
< |
* permission to modify threads. |
1184 |
> |
* Per-thread submission bookkeeping. Shared across all pools |
1185 |
> |
* to reduce ThreadLocal pollution and because random motion |
1186 |
> |
* to avoid contention in one pool is likely to hold for others. |
1187 |
|
*/ |
1188 |
< |
private static void checkPermission() { |
1189 |
< |
SecurityManager security = System.getSecurityManager(); |
1190 |
< |
if (security != null) |
129 |
< |
security.checkPermission(modifyThreadPermission); |
130 |
< |
} |
1188 |
> |
private static final ThreadSubmitter submitters; |
1189 |
> |
|
1190 |
> |
// static constants |
1191 |
|
|
1192 |
|
/** |
1193 |
< |
* Generator for assigning sequence numbers as pool names. |
1193 |
> |
* Initial timeout value (in nanoseconds) for the thread triggering |
1194 |
> |
* quiescence to park waiting for new work. On timeout, the thread |
1195 |
> |
* will instead try to shrink the number of workers. |
1196 |
> |
*/ |
1197 |
> |
private static final long IDLE_TIMEOUT = 1000L * 1000L * 1000L; // 1sec |
1198 |
> |
|
1199 |
> |
/** |
1200 |
> |
* Timeout value when there are more threads than parallelism level |
1201 |
|
*/ |
1202 |
< |
private static final AtomicInteger poolNumberGenerator = |
136 |
< |
new AtomicInteger(); |
1202 |
> |
private static final long FAST_IDLE_TIMEOUT = 100L * 1000L * 1000L; |
1203 |
|
|
1204 |
|
/** |
1205 |
< |
* Array holding all worker threads in the pool. Initialized upon |
1206 |
< |
* first use. Array size must be a power of two. Updates and |
1207 |
< |
* replacements are protected by workerLock, but it is always kept |
1208 |
< |
* in a consistent enough state to be randomly accessed without |
1209 |
< |
* locking by workers performing work-stealing. |
1205 |
> |
* The maximum stolen->joining link depth allowed in method |
1206 |
> |
* tryHelpStealer. Must be a power of two. This value also |
1207 |
> |
* controls the maximum number of times to try to help join a task |
1208 |
> |
* without any apparent progress or change in pool state before |
1209 |
> |
* giving up and blocking (see awaitJoin). Depths for legitimate |
1210 |
> |
* chains are unbounded, but we use a fixed constant to avoid |
1211 |
> |
* (otherwise unchecked) cycles and to bound staleness of |
1212 |
> |
* traversal parameters at the expense of sometimes blocking when |
1213 |
> |
* we could be helping. |
1214 |
|
*/ |
1215 |
< |
volatile ForkJoinWorkerThread[] workers; |
1215 |
> |
private static final int MAX_HELP = 64; |
1216 |
|
|
1217 |
|
/** |
1218 |
< |
* Lock protecting access to workers. |
1218 |
> |
* Secondary time-based bound (in nanosecs) for helping attempts |
1219 |
> |
* before trying compensated blocking in awaitJoin. Used in |
1220 |
> |
* conjunction with MAX_HELP to reduce variance due to different |
1221 |
> |
* polling rates associated with different helping options. The |
1222 |
> |
* value should roughly approximate the time required to create |
1223 |
> |
* and/or activate a worker thread. |
1224 |
|
*/ |
1225 |
< |
private final ReentrantLock workerLock; |
1225 |
> |
private static final long COMPENSATION_DELAY = 1L << 18; // ~0.25 millisec |
1226 |
|
|
1227 |
|
/** |
1228 |
< |
* Condition for awaitTermination. |
1228 |
> |
* Increment for seed generators. See class ThreadLocal for |
1229 |
> |
* explanation. |
1230 |
|
*/ |
1231 |
< |
private final Condition termination; |
1231 |
> |
private static final int SEED_INCREMENT = 0x61c88647; |
1232 |
|
|
1233 |
|
/** |
1234 |
< |
* The uncaught exception handler used when any worker |
1235 |
< |
* abruptly terminates |
1234 |
> |
* Bits and masks for control variables |
1235 |
> |
* |
1236 |
> |
* Field ctl is a long packed with: |
1237 |
> |
* AC: Number of active running workers minus target parallelism (16 bits) |
1238 |
> |
* TC: Number of total workers minus target parallelism (16 bits) |
1239 |
> |
* ST: true if pool is terminating (1 bit) |
1240 |
> |
* EC: the wait count of top waiting thread (15 bits) |
1241 |
> |
* ID: poolIndex of top of Treiber stack of waiters (16 bits) |
1242 |
> |
* |
1243 |
> |
* When convenient, we can extract the upper 32 bits of counts and |
1244 |
> |
* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e = |
1245 |
> |
* (int)ctl. The ec field is never accessed alone, but always |
1246 |
> |
* together with id and st. The offsets of counts by the target |
1247 |
> |
* parallelism and the positionings of fields makes it possible to |
1248 |
> |
* perform the most common checks via sign tests of fields: When |
1249 |
> |
* ac is negative, there are not enough active workers, when tc is |
1250 |
> |
* negative, there are not enough total workers, and when e is |
1251 |
> |
* negative, the pool is terminating. To deal with these possibly |
1252 |
> |
* negative fields, we use casts in and out of "short" and/or |
1253 |
> |
* signed shifts to maintain signedness. |
1254 |
> |
* |
1255 |
> |
* When a thread is queued (inactivated), its eventCount field is |
1256 |
> |
* set negative, which is the only way to tell if a worker is |
1257 |
> |
* prevented from executing tasks, even though it must continue to |
1258 |
> |
* scan for them to avoid queuing races. Note however that |
1259 |
> |
* eventCount updates lag releases so usage requires care. |
1260 |
> |
* |
1261 |
> |
* Field runState is an int packed with: |
1262 |
> |
* SHUTDOWN: true if shutdown is enabled (1 bit) |
1263 |
> |
* SEQ: a sequence number updated upon (de)registering workers (30 bits) |
1264 |
> |
* INIT: set true after workQueues array construction (1 bit) |
1265 |
> |
* |
1266 |
> |
* The sequence number enables simple consistency checks: |
1267 |
> |
* Staleness of read-only operations on the workQueues array can |
1268 |
> |
* be checked by comparing runState before vs after the reads. |
1269 |
|
*/ |
1270 |
< |
private Thread.UncaughtExceptionHandler ueh; |
1270 |
> |
|
1271 |
> |
// bit positions/shifts for fields |
1272 |
> |
private static final int AC_SHIFT = 48; |
1273 |
> |
private static final int TC_SHIFT = 32; |
1274 |
> |
private static final int ST_SHIFT = 31; |
1275 |
> |
private static final int EC_SHIFT = 16; |
1276 |
> |
|
1277 |
> |
// bounds |
1278 |
> |
private static final int SMASK = 0xffff; // short bits |
1279 |
> |
private static final int MAX_CAP = 0x7fff; // max #workers - 1 |
1280 |
> |
private static final int SQMASK = 0xfffe; // even short bits |
1281 |
> |
private static final int SHORT_SIGN = 1 << 15; |
1282 |
> |
private static final int INT_SIGN = 1 << 31; |
1283 |
> |
|
1284 |
> |
// masks |
1285 |
> |
private static final long STOP_BIT = 0x0001L << ST_SHIFT; |
1286 |
> |
private static final long AC_MASK = ((long)SMASK) << AC_SHIFT; |
1287 |
> |
private static final long TC_MASK = ((long)SMASK) << TC_SHIFT; |
1288 |
> |
|
1289 |
> |
// units for incrementing and decrementing |
1290 |
> |
private static final long TC_UNIT = 1L << TC_SHIFT; |
1291 |
> |
private static final long AC_UNIT = 1L << AC_SHIFT; |
1292 |
> |
|
1293 |
> |
// masks and units for dealing with u = (int)(ctl >>> 32) |
1294 |
> |
private static final int UAC_SHIFT = AC_SHIFT - 32; |
1295 |
> |
private static final int UTC_SHIFT = TC_SHIFT - 32; |
1296 |
> |
private static final int UAC_MASK = SMASK << UAC_SHIFT; |
1297 |
> |
private static final int UTC_MASK = SMASK << UTC_SHIFT; |
1298 |
> |
private static final int UAC_UNIT = 1 << UAC_SHIFT; |
1299 |
> |
private static final int UTC_UNIT = 1 << UTC_SHIFT; |
1300 |
> |
|
1301 |
> |
// masks and units for dealing with e = (int)ctl |
1302 |
> |
private static final int E_MASK = 0x7fffffff; // no STOP_BIT |
1303 |
> |
private static final int E_SEQ = 1 << EC_SHIFT; |
1304 |
> |
|
1305 |
> |
// runState bits |
1306 |
> |
private static final int SHUTDOWN = 1 << 31; |
1307 |
> |
|
1308 |
> |
// access mode for WorkQueue |
1309 |
> |
static final int LIFO_QUEUE = 0; |
1310 |
> |
static final int FIFO_QUEUE = 1; |
1311 |
> |
static final int SHARED_QUEUE = -1; |
1312 |
> |
|
1313 |
> |
// Instance fields |
1314 |
> |
|
1315 |
> |
/* |
1316 |
> |
* Field layout order in this class tends to matter more than one |
1317 |
> |
* would like. Runtime layout order is only loosely related to |
1318 |
> |
* declaration order and may differ across JVMs, but the following |
1319 |
> |
* empirically works OK on current JVMs. |
1320 |
> |
*/ |
1321 |
> |
|
1322 |
> |
volatile long stealCount; // collects worker counts |
1323 |
> |
volatile long ctl; // main pool control |
1324 |
> |
final int parallelism; // parallelism level |
1325 |
> |
final int localMode; // per-worker scheduling mode |
1326 |
> |
volatile int nextWorkerNumber; // to create worker name string |
1327 |
> |
final int submitMask; // submit queue index bound |
1328 |
> |
int nextSeed; // for initializing worker seeds |
1329 |
> |
volatile int mainLock; // spinlock for array updates |
1330 |
> |
volatile int runState; // shutdown status and seq |
1331 |
> |
WorkQueue[] workQueues; // main registry |
1332 |
> |
final ForkJoinWorkerThreadFactory factory; // factory for new workers |
1333 |
> |
final Thread.UncaughtExceptionHandler ueh; // per-worker UEH |
1334 |
> |
final String workerNamePrefix; // to create worker name string |
1335 |
> |
|
1336 |
> |
/* |
1337 |
> |
* Mechanics for main lock protecting worker array updates. Uses |
1338 |
> |
* the same strategy as ConcurrentHashMap bins -- a spinLock for |
1339 |
> |
* normal cases, but falling back to builtin lock when (rarely) |
1340 |
> |
* needed. See internal ConcurrentHashMap documentation for |
1341 |
> |
* explanation. |
1342 |
> |
*/ |
1343 |
> |
|
1344 |
> |
static final int LOCK_WAITING = 2; // bit to indicate need for signal |
1345 |
> |
static final int MAX_LOCK_SPINS = 1 << 8; |
1346 |
> |
|
1347 |
> |
private void tryAwaitMainLock() { |
1348 |
> |
int spins = MAX_LOCK_SPINS, r = 0, h; |
1349 |
> |
while (((h = mainLock) & 1) != 0) { |
1350 |
> |
if (r == 0) |
1351 |
> |
r = ThreadLocalRandom.current().nextInt(); // randomize spins |
1352 |
> |
else if (spins >= 0) { |
1353 |
> |
r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift |
1354 |
> |
if (r >= 0) |
1355 |
> |
--spins; |
1356 |
> |
} |
1357 |
> |
else if (U.compareAndSwapInt(this, MAINLOCK, h, h | LOCK_WAITING)) { |
1358 |
> |
synchronized (this) { |
1359 |
> |
if ((mainLock & LOCK_WAITING) != 0) { |
1360 |
> |
try { |
1361 |
> |
wait(); |
1362 |
> |
} catch (InterruptedException ie) { |
1363 |
> |
try { |
1364 |
> |
Thread.currentThread().interrupt(); |
1365 |
> |
} catch (SecurityException ignore) { |
1366 |
> |
} |
1367 |
> |
} |
1368 |
> |
} |
1369 |
> |
else |
1370 |
> |
notifyAll(); // possibly won race vs signaller |
1371 |
> |
} |
1372 |
> |
break; |
1373 |
> |
} |
1374 |
> |
} |
1375 |
> |
} |
1376 |
> |
|
1377 |
> |
// Creating, registering, and deregistering workers |
1378 |
|
|
1379 |
|
/** |
1380 |
< |
* Creation factory for worker threads. |
1380 |
> |
* Tries to create and start a worker |
1381 |
|
*/ |
1382 |
< |
private final ForkJoinWorkerThreadFactory factory; |
1382 |
> |
private void addWorker() { |
1383 |
> |
Throwable ex = null; |
1384 |
> |
ForkJoinWorkerThread wt = null; |
1385 |
> |
try { |
1386 |
> |
if ((wt = factory.newThread(this)) != null) { |
1387 |
> |
wt.start(); |
1388 |
> |
return; |
1389 |
> |
} |
1390 |
> |
} catch (Throwable e) { |
1391 |
> |
ex = e; |
1392 |
> |
} |
1393 |
> |
deregisterWorker(wt, ex); // adjust counts etc on failure |
1394 |
> |
} |
1395 |
|
|
1396 |
|
/** |
1397 |
< |
* Head of stack of threads that were created to maintain |
1398 |
< |
* parallelism when other threads blocked, but have since |
1399 |
< |
* suspended when the parallelism level rose. |
1397 |
> |
* Callback from ForkJoinWorkerThread constructor to assign a |
1398 |
> |
* public name. This must be separate from registerWorker because |
1399 |
> |
* it is called during the "super" constructor call in |
1400 |
> |
* ForkJoinWorkerThread. |
1401 |
|
*/ |
1402 |
< |
private volatile WaitQueueNode spareStack; |
1402 |
> |
final String nextWorkerName() { |
1403 |
> |
int n; |
1404 |
> |
do {} while (!U.compareAndSwapInt(this, NEXTWORKERNUMBER, |
1405 |
> |
n = nextWorkerNumber, ++n)); |
1406 |
> |
return workerNamePrefix.concat(Integer.toString(n)); |
1407 |
> |
} |
1408 |
|
|
1409 |
|
/** |
1410 |
< |
* Sum of per-thread steal counts, updated only when threads are |
1411 |
< |
* idle or terminating. |
1410 |
> |
* Callback from ForkJoinWorkerThread constructor to establish its |
1411 |
> |
* poolIndex and record its WorkQueue. To avoid scanning bias due |
1412 |
> |
* to packing entries in front of the workQueues array, we treat |
1413 |
> |
* the array as a simple power-of-two hash table using per-thread |
1414 |
> |
* seed as hash, expanding as needed. |
1415 |
> |
* |
1416 |
> |
* @param w the worker's queue |
1417 |
|
*/ |
1418 |
< |
private final AtomicLong stealCount; |
1418 |
> |
final void registerWorker(WorkQueue w) { |
1419 |
> |
while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1)) |
1420 |
> |
tryAwaitMainLock(); |
1421 |
> |
try { |
1422 |
> |
WorkQueue[] ws; |
1423 |
> |
if ((ws = workQueues) == null) |
1424 |
> |
ws = workQueues = new WorkQueue[submitMask + 1]; |
1425 |
> |
if (w != null) { |
1426 |
> |
int rs, n = ws.length, m = n - 1; |
1427 |
> |
int s = nextSeed += SEED_INCREMENT; // rarely-colliding sequence |
1428 |
> |
w.seed = (s == 0) ? 1 : s; // ensure non-zero seed |
1429 |
> |
int r = (s << 1) | 1; // use odd-numbered indices |
1430 |
> |
if (ws[r &= m] != null) { // collision |
1431 |
> |
int probes = 0; // step by approx half size |
1432 |
> |
int step = (n <= 4) ? 2 : ((n >>> 1) & SQMASK) + 2; |
1433 |
> |
while (ws[r = (r + step) & m] != null) { |
1434 |
> |
if (++probes >= n) { |
1435 |
> |
workQueues = ws = Arrays.copyOf(ws, n <<= 1); |
1436 |
> |
m = n - 1; |
1437 |
> |
probes = 0; |
1438 |
> |
} |
1439 |
> |
} |
1440 |
> |
} |
1441 |
> |
w.eventCount = w.poolIndex = r; // establish before recording |
1442 |
> |
ws[r] = w; // also update seq |
1443 |
> |
runState = ((rs = runState) & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN); |
1444 |
> |
} |
1445 |
> |
} finally { |
1446 |
> |
if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) { |
1447 |
> |
mainLock = 0; |
1448 |
> |
synchronized (this) { notifyAll(); }; |
1449 |
> |
} |
1450 |
> |
} |
1451 |
> |
} |
1452 |
|
|
1453 |
|
/** |
1454 |
< |
* Queue for external submissions. |
1454 |
> |
* Final callback from terminating worker, as well as upon failure |
1455 |
> |
* to construct or start a worker in addWorker. Removes record of |
1456 |
> |
* worker from array, and adjusts counts. If pool is shutting |
1457 |
> |
* down, tries to complete termination. |
1458 |
> |
* |
1459 |
> |
* @param wt the worker thread or null if addWorker failed |
1460 |
> |
* @param ex the exception causing failure, or null if none |
1461 |
|
*/ |
1462 |
< |
private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue; |
1462 |
> |
final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) { |
1463 |
> |
WorkQueue w = null; |
1464 |
> |
if (wt != null && (w = wt.workQueue) != null) { |
1465 |
> |
w.runState = -1; // ensure runState is set |
1466 |
> |
long steals = w.totalSteals + w.nsteals, sc; |
1467 |
> |
do {} while (!U.compareAndSwapLong(this, STEALCOUNT, |
1468 |
> |
sc = stealCount, sc + steals)); |
1469 |
> |
int idx = w.poolIndex; |
1470 |
> |
while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1)) |
1471 |
> |
tryAwaitMainLock(); |
1472 |
> |
try { |
1473 |
> |
WorkQueue[] ws = workQueues; |
1474 |
> |
if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w) |
1475 |
> |
ws[idx] = null; |
1476 |
> |
} finally { |
1477 |
> |
if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) { |
1478 |
> |
mainLock = 0; |
1479 |
> |
synchronized (this) { notifyAll(); }; |
1480 |
> |
} |
1481 |
> |
} |
1482 |
> |
} |
1483 |
> |
|
1484 |
> |
long c; // adjust ctl counts |
1485 |
> |
do {} while (!U.compareAndSwapLong |
1486 |
> |
(this, CTL, c = ctl, (((c - AC_UNIT) & AC_MASK) | |
1487 |
> |
((c - TC_UNIT) & TC_MASK) | |
1488 |
> |
(c & ~(AC_MASK|TC_MASK))))); |
1489 |
> |
|
1490 |
> |
if (!tryTerminate(false, false) && w != null) { |
1491 |
> |
w.cancelAll(); // cancel remaining tasks |
1492 |
> |
if (w.array != null) // suppress signal if never ran |
1493 |
> |
signalWork(); // wake up or create replacement |
1494 |
> |
if (ex == null) // help clean refs on way out |
1495 |
> |
ForkJoinTask.helpExpungeStaleExceptions(); |
1496 |
> |
} |
1497 |
> |
|
1498 |
> |
if (ex != null) // rethrow |
1499 |
> |
ForkJoinTask.rethrow(ex); |
1500 |
> |
} |
1501 |
> |
|
1502 |
> |
// Submissions |
1503 |
> |
|
1504 |
> |
/** |
1505 |
> |
* Unless shutting down, adds the given task to a submission queue |
1506 |
> |
* at submitter's current queue index (modulo submission |
1507 |
> |
* range). If no queue exists at the index, one is created. If |
1508 |
> |
* the queue is busy, another index is randomly chosen. The |
1509 |
> |
* submitMask bounds the effective number of queues to the |
1510 |
> |
* (nearest power of two for) parallelism level. |
1511 |
> |
* |
1512 |
> |
* @param task the task. Caller must ensure non-null. |
1513 |
> |
*/ |
1514 |
> |
private void doSubmit(ForkJoinTask<?> task) { |
1515 |
> |
Submitter s = submitters.get(); |
1516 |
> |
for (int r = s.seed, m = submitMask;;) { |
1517 |
> |
WorkQueue[] ws; WorkQueue q; |
1518 |
> |
int k = r & m & SQMASK; // use only even indices |
1519 |
> |
if (runState < 0) |
1520 |
> |
throw new RejectedExecutionException(); // shutting down |
1521 |
> |
else if ((ws = workQueues) == null || ws.length <= k) { |
1522 |
> |
while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1)) |
1523 |
> |
tryAwaitMainLock(); |
1524 |
> |
try { |
1525 |
> |
if (workQueues == null) |
1526 |
> |
workQueues = new WorkQueue[submitMask + 1]; |
1527 |
> |
} finally { |
1528 |
> |
if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) { |
1529 |
> |
mainLock = 0; |
1530 |
> |
synchronized (this) { notifyAll(); }; |
1531 |
> |
} |
1532 |
> |
} |
1533 |
> |
} |
1534 |
> |
else if ((q = ws[k]) == null) { // create new queue |
1535 |
> |
WorkQueue nq = new WorkQueue(this, null, SHARED_QUEUE); |
1536 |
> |
while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1)) |
1537 |
> |
tryAwaitMainLock(); |
1538 |
> |
try { |
1539 |
> |
int rs = runState; // to update seq |
1540 |
> |
if (ws == workQueues && ws[k] == null) { |
1541 |
> |
ws[k] = nq; |
1542 |
> |
runState = ((rs & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN)); |
1543 |
> |
} |
1544 |
> |
} finally { |
1545 |
> |
if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) { |
1546 |
> |
mainLock = 0; |
1547 |
> |
synchronized (this) { notifyAll(); }; |
1548 |
> |
} |
1549 |
> |
} |
1550 |
> |
} |
1551 |
> |
else if (q.trySharedPush(task)) { |
1552 |
> |
signalWork(); |
1553 |
> |
return; |
1554 |
> |
} |
1555 |
> |
else if (m > 1) { // move to a different index |
1556 |
> |
r ^= r << 13; // same xorshift as WorkQueues |
1557 |
> |
r ^= r >>> 17; |
1558 |
> |
s.seed = r ^= r << 5; |
1559 |
> |
} |
1560 |
> |
else |
1561 |
> |
Thread.yield(); // yield if no alternatives |
1562 |
> |
} |
1563 |
> |
} |
1564 |
|
|
1565 |
|
/** |
1566 |
< |
* Head of Treiber stack for barrier sync. See below for explanation. |
1566 |
> |
* Submits the given (non-null) task to the common pool, if possible. |
1567 |
|
*/ |
1568 |
< |
private volatile WaitQueueNode syncStack; |
1568 |
> |
static void submitToCommonPool(ForkJoinTask<?> task) { |
1569 |
> |
ForkJoinPool p; |
1570 |
> |
if ((p = commonPool) == null) |
1571 |
> |
throw new RejectedExecutionException("Common Pool Unavailable"); |
1572 |
> |
p.doSubmit(task); |
1573 |
> |
} |
1574 |
|
|
1575 |
|
/** |
1576 |
< |
* The count for event barrier |
1576 |
> |
* Returns true if the given task was submitted to common pool |
1577 |
> |
* and has not yet commenced execution, and is available for |
1578 |
> |
* removal according to execution policies; if so removing the |
1579 |
> |
* submission from the pool. |
1580 |
> |
* |
1581 |
> |
* @param task the task |
1582 |
> |
* @return true if successful |
1583 |
|
*/ |
1584 |
< |
private volatile long eventCount; |
1584 |
> |
static boolean tryUnsubmitFromCommonPool(ForkJoinTask<?> task) { |
1585 |
> |
// If not oversaturating platform, peek, looking for task and |
1586 |
> |
// eligibility before using trySharedUnpush to actually take |
1587 |
> |
// it under lock |
1588 |
> |
ForkJoinPool p; WorkQueue[] ws; WorkQueue w, q; |
1589 |
> |
ForkJoinTask<?>[] a; int ac, s, m; |
1590 |
> |
if ((p = commonPool) != null && (ws = p.workQueues) != null) { |
1591 |
> |
int k = submitters.get().seed & p.submitMask & SQMASK; |
1592 |
> |
if ((m = ws.length - 1) >= k && (q = ws[k]) != null && |
1593 |
> |
(ac = (int)(p.ctl >> AC_SHIFT)) <= 0) { |
1594 |
> |
if (ac == 0) { // double check if all workers active |
1595 |
> |
for (int i = 1; i <= m; i += 2) { |
1596 |
> |
if ((w = ws[i]) != null && w.parker != null) { |
1597 |
> |
ac = -1; |
1598 |
> |
break; |
1599 |
> |
} |
1600 |
> |
} |
1601 |
> |
} |
1602 |
> |
return (ac < 0 && (a = q.array) != null && |
1603 |
> |
(s = q.top - 1) - q.base >= 0 && |
1604 |
> |
s >= 0 && s < a.length && |
1605 |
> |
a[s] == task && |
1606 |
> |
q.trySharedUnpush(task)); |
1607 |
> |
} |
1608 |
> |
} |
1609 |
> |
return false; |
1610 |
> |
} |
1611 |
|
|
1612 |
|
/** |
1613 |
< |
* Pool number, just for assigning useful names to worker threads |
1613 |
> |
* Tries to pop and run a task within same computation from common pool |
1614 |
|
*/ |
1615 |
< |
private final int poolNumber; |
1615 |
> |
static void popAndExecCCFromCommonPool(CountedCompleter<?> cc) { |
1616 |
> |
ForkJoinPool p; WorkQueue[] ws; WorkQueue q, w; int m, ac; |
1617 |
> |
CountedCompleter<?> par, task; |
1618 |
> |
if ((p = commonPool) != null && (ws = p.workQueues) != null) { |
1619 |
> |
while ((par = cc.completer) != null) // find root |
1620 |
> |
cc = par; |
1621 |
> |
int k = submitters.get().seed & p.submitMask & SQMASK; |
1622 |
> |
if ((m = ws.length - 1) >= k && (q = ws[k]) != null && |
1623 |
> |
(ac = (int)(p.ctl >> AC_SHIFT)) <= 0) { |
1624 |
> |
if (ac == 0) { |
1625 |
> |
for (int i = 1; i <= m; i += 2) { |
1626 |
> |
if ((w = ws[i]) != null && w.parker != null) { |
1627 |
> |
ac = -1; |
1628 |
> |
break; |
1629 |
> |
} |
1630 |
> |
} |
1631 |
> |
} |
1632 |
> |
if (ac < 0 && q.top - q.base > 0 && |
1633 |
> |
(task = q.sharedPopCC(cc)) != null) |
1634 |
> |
task.exec(); |
1635 |
> |
} |
1636 |
> |
} |
1637 |
> |
} |
1638 |
> |
|
1639 |
> |
// Maintaining ctl counts |
1640 |
|
|
1641 |
|
/** |
1642 |
< |
* The maximum allowed pool size |
1642 |
> |
* Increments active count; mainly called upon return from blocking. |
1643 |
|
*/ |
1644 |
< |
private volatile int maxPoolSize; |
1644 |
> |
final void incrementActiveCount() { |
1645 |
> |
long c; |
1646 |
> |
do {} while (!U.compareAndSwapLong(this, CTL, c = ctl, c + AC_UNIT)); |
1647 |
> |
} |
1648 |
|
|
1649 |
|
/** |
1650 |
< |
* The desired parallelism level, updated only under workerLock. |
1650 |
> |
* Tries to create one or activate one or more workers if too few are active. |
1651 |
|
*/ |
1652 |
< |
private volatile int parallelism; |
1652 |
> |
final void signalWork() { |
1653 |
> |
long c; int u; |
1654 |
> |
while ((u = (int)((c = ctl) >>> 32)) < 0) { // too few active |
1655 |
> |
WorkQueue[] ws = workQueues; int e, i; WorkQueue w; Thread p; |
1656 |
> |
if ((e = (int)c) > 0) { // at least one waiting |
1657 |
> |
if (ws != null && (i = e & SMASK) < ws.length && |
1658 |
> |
(w = ws[i]) != null && w.eventCount == (e | INT_SIGN)) { |
1659 |
> |
long nc = (((long)(w.nextWait & E_MASK)) | |
1660 |
> |
((long)(u + UAC_UNIT) << 32)); |
1661 |
> |
if (U.compareAndSwapLong(this, CTL, c, nc)) { |
1662 |
> |
w.eventCount = (e + E_SEQ) & E_MASK; |
1663 |
> |
if ((p = w.parker) != null) |
1664 |
> |
U.unpark(p); // activate and release |
1665 |
> |
break; |
1666 |
> |
} |
1667 |
> |
} |
1668 |
> |
else |
1669 |
> |
break; |
1670 |
> |
} |
1671 |
> |
else if (e == 0 && (u & SHORT_SIGN) != 0) { // too few total |
1672 |
> |
long nc = (long)(((u + UTC_UNIT) & UTC_MASK) | |
1673 |
> |
((u + UAC_UNIT) & UAC_MASK)) << 32; |
1674 |
> |
if (U.compareAndSwapLong(this, CTL, c, nc)) { |
1675 |
> |
addWorker(); |
1676 |
> |
break; |
1677 |
> |
} |
1678 |
> |
} |
1679 |
> |
else |
1680 |
> |
break; |
1681 |
> |
} |
1682 |
> |
} |
1683 |
> |
|
1684 |
> |
// Scanning for tasks |
1685 |
|
|
1686 |
|
/** |
1687 |
< |
* True if use local fifo, not default lifo, for local polling |
1687 |
> |
* Top-level runloop for workers, called by ForkJoinWorkerThread.run. |
1688 |
|
*/ |
1689 |
< |
private volatile boolean locallyFifo; |
1689 |
> |
final void runWorker(WorkQueue w) { |
1690 |
> |
w.growArray(false); // initialize queue array in this thread |
1691 |
> |
do { w.runTask(scan(w)); } while (w.runState >= 0); |
1692 |
> |
} |
1693 |
> |
|
1694 |
> |
/** |
1695 |
> |
* Scans for and, if found, returns one task, else possibly |
1696 |
> |
* inactivates the worker. This method operates on single reads of |
1697 |
> |
* volatile state and is designed to be re-invoked continuously, |
1698 |
> |
* in part because it returns upon detecting inconsistencies, |
1699 |
> |
* contention, or state changes that indicate possible success on |
1700 |
> |
* re-invocation. |
1701 |
> |
* |
1702 |
> |
* The scan searches for tasks across a random permutation of |
1703 |
> |
* queues (starting at a random index and stepping by a random |
1704 |
> |
* relative prime, checking each at least once). The scan |
1705 |
> |
* terminates upon either finding a non-empty queue, or completing |
1706 |
> |
* the sweep. If the worker is not inactivated, it takes and |
1707 |
> |
* returns a task from this queue. On failure to find a task, we |
1708 |
> |
* take one of the following actions, after which the caller will |
1709 |
> |
* retry calling this method unless terminated. |
1710 |
> |
* |
1711 |
> |
* * If pool is terminating, terminate the worker. |
1712 |
> |
* |
1713 |
> |
* * If not a complete sweep, try to release a waiting worker. If |
1714 |
> |
* the scan terminated because the worker is inactivated, then the |
1715 |
> |
* released worker will often be the calling worker, and it can |
1716 |
> |
* succeed obtaining a task on the next call. Or maybe it is |
1717 |
> |
* another worker, but with same net effect. Releasing in other |
1718 |
> |
* cases as well ensures that we have enough workers running. |
1719 |
> |
* |
1720 |
> |
* * If not already enqueued, try to inactivate and enqueue the |
1721 |
> |
* worker on wait queue. Or, if inactivating has caused the pool |
1722 |
> |
* to be quiescent, relay to idleAwaitWork to check for |
1723 |
> |
* termination and possibly shrink pool. |
1724 |
> |
* |
1725 |
> |
* * If already inactive, and the caller has run a task since the |
1726 |
> |
* last empty scan, return (to allow rescan) unless others are |
1727 |
> |
* also inactivated. Field WorkQueue.rescans counts down on each |
1728 |
> |
* scan to ensure eventual inactivation and blocking. |
1729 |
> |
* |
1730 |
> |
* * If already enqueued and none of the above apply, park |
1731 |
> |
* awaiting signal, |
1732 |
> |
* |
1733 |
> |
* @param w the worker (via its WorkQueue) |
1734 |
> |
* @return a task or null if none found |
1735 |
> |
*/ |
1736 |
> |
private final ForkJoinTask<?> scan(WorkQueue w) { |
1737 |
> |
WorkQueue[] ws; // first update random seed |
1738 |
> |
int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5; |
1739 |
> |
int rs = runState, m; // volatile read order matters |
1740 |
> |
if ((ws = workQueues) != null && (m = ws.length - 1) > 0) { |
1741 |
> |
int ec = w.eventCount; // ec is negative if inactive |
1742 |
> |
int step = (r >>> 16) | 1; // relative prime |
1743 |
> |
for (int j = (m + 1) << 2; ; r += step) { |
1744 |
> |
WorkQueue q; ForkJoinTask<?> t; ForkJoinTask<?>[] a; int b; |
1745 |
> |
if ((q = ws[r & m]) != null && (b = q.base) - q.top < 0 && |
1746 |
> |
(a = q.array) != null) { // probably nonempty |
1747 |
> |
int i = (((a.length - 1) & b) << ASHIFT) + ABASE; |
1748 |
> |
t = (ForkJoinTask<?>)U.getObjectVolatile(a, i); |
1749 |
> |
if (q.base == b && ec >= 0 && t != null && |
1750 |
> |
U.compareAndSwapObject(a, i, t, null)) { |
1751 |
> |
if (q.top - (q.base = b + 1) > 0) |
1752 |
> |
signalWork(); // help pushes signal |
1753 |
> |
return t; |
1754 |
> |
} |
1755 |
> |
else if (ec < 0 || j <= m) { |
1756 |
> |
rs = 0; // mark scan as imcomplete |
1757 |
> |
break; // caller can retry after release |
1758 |
> |
} |
1759 |
> |
} |
1760 |
> |
if (--j < 0) |
1761 |
> |
break; |
1762 |
> |
} |
1763 |
> |
|
1764 |
> |
long c = ctl; int e = (int)c, a = (int)(c >> AC_SHIFT), nr, ns; |
1765 |
> |
if (e < 0) // decode ctl on empty scan |
1766 |
> |
w.runState = -1; // pool is terminating |
1767 |
> |
else if (rs == 0 || rs != runState) { // incomplete scan |
1768 |
> |
WorkQueue v; Thread p; // try to release a waiter |
1769 |
> |
if (e > 0 && a < 0 && w.eventCount == ec && |
1770 |
> |
(v = ws[e & m]) != null && v.eventCount == (e | INT_SIGN)) { |
1771 |
> |
long nc = ((long)(v.nextWait & E_MASK) | |
1772 |
> |
((c + AC_UNIT) & (AC_MASK|TC_MASK))); |
1773 |
> |
if (ctl == c && U.compareAndSwapLong(this, CTL, c, nc)) { |
1774 |
> |
v.eventCount = (e + E_SEQ) & E_MASK; |
1775 |
> |
if ((p = v.parker) != null) |
1776 |
> |
U.unpark(p); |
1777 |
> |
} |
1778 |
> |
} |
1779 |
> |
} |
1780 |
> |
else if (ec >= 0) { // try to enqueue/inactivate |
1781 |
> |
long nc = (long)ec | ((c - AC_UNIT) & (AC_MASK|TC_MASK)); |
1782 |
> |
w.nextWait = e; |
1783 |
> |
w.eventCount = ec | INT_SIGN; // mark as inactive |
1784 |
> |
if (ctl != c || !U.compareAndSwapLong(this, CTL, c, nc)) |
1785 |
> |
w.eventCount = ec; // unmark on CAS failure |
1786 |
> |
else { |
1787 |
> |
if ((ns = w.nsteals) != 0) { |
1788 |
> |
w.nsteals = 0; // set rescans if ran task |
1789 |
> |
w.rescans = (a > 0) ? 0 : a + parallelism; |
1790 |
> |
w.totalSteals += ns; |
1791 |
> |
} |
1792 |
> |
if (a == 1 - parallelism) // quiescent |
1793 |
> |
idleAwaitWork(w, nc, c); |
1794 |
> |
} |
1795 |
> |
} |
1796 |
> |
else if (w.eventCount < 0) { // already queued |
1797 |
> |
int ac = a + parallelism; |
1798 |
> |
if ((nr = w.rescans) > 0) // continue rescanning |
1799 |
> |
w.rescans = (ac < nr) ? ac : nr - 1; |
1800 |
> |
else if (((w.seed >>> 16) & ac) == 0) { // randomize park |
1801 |
> |
Thread.interrupted(); // clear status |
1802 |
> |
Thread wt = Thread.currentThread(); |
1803 |
> |
U.putObject(wt, PARKBLOCKER, this); |
1804 |
> |
w.parker = wt; // emulate LockSupport.park |
1805 |
> |
if (w.eventCount < 0) // recheck |
1806 |
> |
U.park(false, 0L); |
1807 |
> |
w.parker = null; |
1808 |
> |
U.putObject(wt, PARKBLOCKER, null); |
1809 |
> |
} |
1810 |
> |
} |
1811 |
> |
} |
1812 |
> |
return null; |
1813 |
> |
} |
1814 |
> |
|
1815 |
> |
/** |
1816 |
> |
* If inactivating worker w has caused the pool to become |
1817 |
> |
* quiescent, checks for pool termination, and, so long as this is |
1818 |
> |
* not the only worker, waits for event for up to a given |
1819 |
> |
* duration. On timeout, if ctl has not changed, terminates the |
1820 |
> |
* worker, which will in turn wake up another worker to possibly |
1821 |
> |
* repeat this process. |
1822 |
> |
* |
1823 |
> |
* @param w the calling worker |
1824 |
> |
* @param currentCtl the ctl value triggering possible quiescence |
1825 |
> |
* @param prevCtl the ctl value to restore if thread is terminated |
1826 |
> |
*/ |
1827 |
> |
private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) { |
1828 |
> |
if (w.eventCount < 0 && !tryTerminate(false, false) && |
1829 |
> |
(int)prevCtl != 0 && !hasQueuedSubmissions() && ctl == currentCtl) { |
1830 |
> |
int dc = -(short)(currentCtl >>> TC_SHIFT); |
1831 |
> |
long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT; |
1832 |
> |
long deadline = System.nanoTime() + parkTime - 100000L; // 1ms slop |
1833 |
> |
Thread wt = Thread.currentThread(); |
1834 |
> |
while (ctl == currentCtl) { |
1835 |
> |
Thread.interrupted(); // timed variant of version in scan() |
1836 |
> |
U.putObject(wt, PARKBLOCKER, this); |
1837 |
> |
w.parker = wt; |
1838 |
> |
if (ctl == currentCtl) |
1839 |
> |
U.park(false, parkTime); |
1840 |
> |
w.parker = null; |
1841 |
> |
U.putObject(wt, PARKBLOCKER, null); |
1842 |
> |
if (ctl != currentCtl) |
1843 |
> |
break; |
1844 |
> |
if (deadline - System.nanoTime() <= 0L && |
1845 |
> |
U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) { |
1846 |
> |
w.eventCount = (w.eventCount + E_SEQ) | E_MASK; |
1847 |
> |
w.runState = -1; // shrink |
1848 |
> |
break; |
1849 |
> |
} |
1850 |
> |
} |
1851 |
> |
} |
1852 |
> |
} |
1853 |
|
|
1854 |
|
/** |
1855 |
< |
* Holds number of total (i.e., created and not yet terminated) |
1856 |
< |
* and running (i.e., not blocked on joins or other managed sync) |
1857 |
< |
* threads, packed into one int to ensure consistent snapshot when |
1858 |
< |
* making decisions about creating and suspending spare |
1859 |
< |
* threads. Updated only by CAS. Note: CASes in |
1860 |
< |
* updateRunningCount and preJoin assume that running active count |
1861 |
< |
* is in low word, so need to be modified if this changes. |
1855 |
> |
* Tries to locate and execute tasks for a stealer of the given |
1856 |
> |
* task, or in turn one of its stealers, Traces currentSteal -> |
1857 |
> |
* currentJoin links looking for a thread working on a descendant |
1858 |
> |
* of the given task and with a non-empty queue to steal back and |
1859 |
> |
* execute tasks from. The first call to this method upon a |
1860 |
> |
* waiting join will often entail scanning/search, (which is OK |
1861 |
> |
* because the joiner has nothing better to do), but this method |
1862 |
> |
* leaves hints in workers to speed up subsequent calls. The |
1863 |
> |
* implementation is very branchy to cope with potential |
1864 |
> |
* inconsistencies or loops encountering chains that are stale, |
1865 |
> |
* unknown, or so long that they are likely cyclic. |
1866 |
> |
* |
1867 |
> |
* @param joiner the joining worker |
1868 |
> |
* @param task the task to join |
1869 |
> |
* @return 0 if no progress can be made, negative if task |
1870 |
> |
* known complete, else positive |
1871 |
> |
*/ |
1872 |
> |
private int tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) { |
1873 |
> |
int stat = 0, steps = 0; // bound to avoid cycles |
1874 |
> |
if (joiner != null && task != null) { // hoist null checks |
1875 |
> |
restart: for (;;) { |
1876 |
> |
ForkJoinTask<?> subtask = task; // current target |
1877 |
> |
for (WorkQueue j = joiner, v;;) { // v is stealer of subtask |
1878 |
> |
WorkQueue[] ws; int m, s, h; |
1879 |
> |
if ((s = task.status) < 0) { |
1880 |
> |
stat = s; |
1881 |
> |
break restart; |
1882 |
> |
} |
1883 |
> |
if ((ws = workQueues) == null || (m = ws.length - 1) <= 0) |
1884 |
> |
break restart; // shutting down |
1885 |
> |
if ((v = ws[h = (j.stealHint | 1) & m]) == null || |
1886 |
> |
v.currentSteal != subtask) { |
1887 |
> |
for (int origin = h;;) { // find stealer |
1888 |
> |
if (((h = (h + 2) & m) & 15) == 1 && |
1889 |
> |
(subtask.status < 0 || j.currentJoin != subtask)) |
1890 |
> |
continue restart; // occasional staleness check |
1891 |
> |
if ((v = ws[h]) != null && |
1892 |
> |
v.currentSteal == subtask) { |
1893 |
> |
j.stealHint = h; // save hint |
1894 |
> |
break; |
1895 |
> |
} |
1896 |
> |
if (h == origin) |
1897 |
> |
break restart; // cannot find stealer |
1898 |
> |
} |
1899 |
> |
} |
1900 |
> |
for (;;) { // help stealer or descend to its stealer |
1901 |
> |
ForkJoinTask[] a; int b; |
1902 |
> |
if (subtask.status < 0) // surround probes with |
1903 |
> |
continue restart; // consistency checks |
1904 |
> |
if ((b = v.base) - v.top < 0 && (a = v.array) != null) { |
1905 |
> |
int i = (((a.length - 1) & b) << ASHIFT) + ABASE; |
1906 |
> |
ForkJoinTask<?> t = |
1907 |
> |
(ForkJoinTask<?>)U.getObjectVolatile(a, i); |
1908 |
> |
if (subtask.status < 0 || j.currentJoin != subtask || |
1909 |
> |
v.currentSteal != subtask) |
1910 |
> |
continue restart; // stale |
1911 |
> |
stat = 1; // apparent progress |
1912 |
> |
if (t != null && v.base == b && |
1913 |
> |
U.compareAndSwapObject(a, i, t, null)) { |
1914 |
> |
v.base = b + 1; // help stealer |
1915 |
> |
joiner.runSubtask(t); |
1916 |
> |
} |
1917 |
> |
else if (v.base == b && ++steps == MAX_HELP) |
1918 |
> |
break restart; // v apparently stalled |
1919 |
> |
} |
1920 |
> |
else { // empty -- try to descend |
1921 |
> |
ForkJoinTask<?> next = v.currentJoin; |
1922 |
> |
if (subtask.status < 0 || j.currentJoin != subtask || |
1923 |
> |
v.currentSteal != subtask) |
1924 |
> |
continue restart; // stale |
1925 |
> |
else if (next == null || ++steps == MAX_HELP) |
1926 |
> |
break restart; // dead-end or maybe cyclic |
1927 |
> |
else { |
1928 |
> |
subtask = next; |
1929 |
> |
j = v; |
1930 |
> |
break; |
1931 |
> |
} |
1932 |
> |
} |
1933 |
> |
} |
1934 |
> |
} |
1935 |
> |
} |
1936 |
> |
} |
1937 |
> |
return stat; |
1938 |
> |
} |
1939 |
> |
|
1940 |
> |
/** |
1941 |
> |
* If task is at base of some steal queue, steals and executes it. |
1942 |
> |
* |
1943 |
> |
* @param joiner the joining worker |
1944 |
> |
* @param task the task |
1945 |
|
*/ |
1946 |
< |
private volatile int workerCounts; |
1946 |
> |
private void tryPollForAndExec(WorkQueue joiner, ForkJoinTask<?> task) { |
1947 |
> |
WorkQueue[] ws; |
1948 |
> |
if ((ws = workQueues) != null) { |
1949 |
> |
for (int j = 1; j < ws.length && task.status >= 0; j += 2) { |
1950 |
> |
WorkQueue q = ws[j]; |
1951 |
> |
if (q != null && q.pollFor(task)) { |
1952 |
> |
joiner.runSubtask(task); |
1953 |
> |
break; |
1954 |
> |
} |
1955 |
> |
} |
1956 |
> |
} |
1957 |
> |
} |
1958 |
|
|
1959 |
< |
private static int totalCountOf(int s) { return s >>> 16; } |
1960 |
< |
private static int runningCountOf(int s) { return s & shortMask; } |
1961 |
< |
private static int workerCountsFor(int t, int r) { return (t << 16) + r; } |
1959 |
> |
/** |
1960 |
> |
* Tries to decrement active count (sometimes implicitly) and |
1961 |
> |
* possibly release or create a compensating worker in preparation |
1962 |
> |
* for blocking. Fails on contention or termination. Otherwise, |
1963 |
> |
* adds a new thread if no idle workers are available and either |
1964 |
> |
* pool would become completely starved or: (at least half |
1965 |
> |
* starved, and fewer than 50% spares exist, and there is at least |
1966 |
> |
* one task apparently available). Even though the availability |
1967 |
> |
* check requires a full scan, it is worthwhile in reducing false |
1968 |
> |
* alarms. |
1969 |
> |
* |
1970 |
> |
* @param task if non-null, a task being waited for |
1971 |
> |
* @param blocker if non-null, a blocker being waited for |
1972 |
> |
* @return true if the caller can block, else should recheck and retry |
1973 |
> |
*/ |
1974 |
> |
final boolean tryCompensate(ForkJoinTask<?> task, ManagedBlocker blocker) { |
1975 |
> |
int pc = parallelism, e; |
1976 |
> |
long c = ctl; |
1977 |
> |
WorkQueue[] ws = workQueues; |
1978 |
> |
if ((e = (int)c) >= 0 && ws != null) { |
1979 |
> |
int u, a, ac, hc; |
1980 |
> |
int tc = (short)((u = (int)(c >>> 32)) >>> UTC_SHIFT) + pc; |
1981 |
> |
boolean replace = false; |
1982 |
> |
if ((a = u >> UAC_SHIFT) <= 0) { |
1983 |
> |
if ((ac = a + pc) <= 1) |
1984 |
> |
replace = true; |
1985 |
> |
else if ((e > 0 || (task != null && |
1986 |
> |
ac <= (hc = pc >>> 1) && tc < pc + hc))) { |
1987 |
> |
WorkQueue w; |
1988 |
> |
for (int j = 0; j < ws.length; ++j) { |
1989 |
> |
if ((w = ws[j]) != null && !w.isEmpty()) { |
1990 |
> |
replace = true; |
1991 |
> |
break; // in compensation range and tasks available |
1992 |
> |
} |
1993 |
> |
} |
1994 |
> |
} |
1995 |
> |
} |
1996 |
> |
if ((task == null || task.status >= 0) && // recheck need to block |
1997 |
> |
(blocker == null || !blocker.isReleasable()) && ctl == c) { |
1998 |
> |
if (!replace) { // no compensation |
1999 |
> |
long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK); |
2000 |
> |
if (U.compareAndSwapLong(this, CTL, c, nc)) |
2001 |
> |
return true; |
2002 |
> |
} |
2003 |
> |
else if (e != 0) { // release an idle worker |
2004 |
> |
WorkQueue w; Thread p; int i; |
2005 |
> |
if ((i = e & SMASK) < ws.length && (w = ws[i]) != null) { |
2006 |
> |
long nc = ((long)(w.nextWait & E_MASK) | |
2007 |
> |
(c & (AC_MASK|TC_MASK))); |
2008 |
> |
if (w.eventCount == (e | INT_SIGN) && |
2009 |
> |
U.compareAndSwapLong(this, CTL, c, nc)) { |
2010 |
> |
w.eventCount = (e + E_SEQ) & E_MASK; |
2011 |
> |
if ((p = w.parker) != null) |
2012 |
> |
U.unpark(p); |
2013 |
> |
return true; |
2014 |
> |
} |
2015 |
> |
} |
2016 |
> |
} |
2017 |
> |
else if (tc < MAX_CAP) { // create replacement |
2018 |
> |
long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK); |
2019 |
> |
if (U.compareAndSwapLong(this, CTL, c, nc)) { |
2020 |
> |
addWorker(); |
2021 |
> |
return true; |
2022 |
> |
} |
2023 |
> |
} |
2024 |
> |
} |
2025 |
> |
} |
2026 |
> |
return false; |
2027 |
> |
} |
2028 |
|
|
2029 |
|
/** |
2030 |
< |
* Adds delta (which may be negative) to running count. This must |
233 |
< |
* be called before (with negative arg) and after (with positive) |
234 |
< |
* any managed synchronization (i.e., mainly, joins). |
2030 |
> |
* Helps and/or blocks until the given task is done. |
2031 |
|
* |
2032 |
< |
* @param delta the number to add |
2032 |
> |
* @param joiner the joining worker |
2033 |
> |
* @param task the task |
2034 |
> |
* @return task status on exit |
2035 |
|
*/ |
2036 |
< |
final void updateRunningCount(int delta) { |
2036 |
> |
final int awaitJoin(WorkQueue joiner, ForkJoinTask<?> task) { |
2037 |
|
int s; |
2038 |
< |
do {} while (!casWorkerCounts(s = workerCounts, s + delta)); |
2038 |
> |
if ((s = task.status) >= 0) { |
2039 |
> |
ForkJoinTask<?> prevJoin = joiner.currentJoin; |
2040 |
> |
joiner.currentJoin = task; |
2041 |
> |
long startTime = 0L; |
2042 |
> |
for (int k = 0;;) { |
2043 |
> |
if ((s = (joiner.isEmpty() ? // try to help |
2044 |
> |
tryHelpStealer(joiner, task) : |
2045 |
> |
joiner.tryRemoveAndExec(task))) == 0 && |
2046 |
> |
(s = task.status) >= 0) { |
2047 |
> |
if (k == 0) { |
2048 |
> |
startTime = System.nanoTime(); |
2049 |
> |
tryPollForAndExec(joiner, task); // check uncommon case |
2050 |
> |
} |
2051 |
> |
else if ((k & (MAX_HELP - 1)) == 0 && |
2052 |
> |
System.nanoTime() - startTime >= |
2053 |
> |
COMPENSATION_DELAY && |
2054 |
> |
tryCompensate(task, null)) { |
2055 |
> |
if (task.trySetSignal()) { |
2056 |
> |
synchronized (task) { |
2057 |
> |
if (task.status >= 0) { |
2058 |
> |
try { // see ForkJoinTask |
2059 |
> |
task.wait(); // for explanation |
2060 |
> |
} catch (InterruptedException ie) { |
2061 |
> |
} |
2062 |
> |
} |
2063 |
> |
else |
2064 |
> |
task.notifyAll(); |
2065 |
> |
} |
2066 |
> |
} |
2067 |
> |
long c; // re-activate |
2068 |
> |
do {} while (!U.compareAndSwapLong |
2069 |
> |
(this, CTL, c = ctl, c + AC_UNIT)); |
2070 |
> |
} |
2071 |
> |
} |
2072 |
> |
if (s < 0 || (s = task.status) < 0) { |
2073 |
> |
joiner.currentJoin = prevJoin; |
2074 |
> |
break; |
2075 |
> |
} |
2076 |
> |
else if ((k++ & (MAX_HELP - 1)) == MAX_HELP >>> 1) |
2077 |
> |
Thread.yield(); // for politeness |
2078 |
> |
} |
2079 |
> |
} |
2080 |
> |
return s; |
2081 |
|
} |
2082 |
|
|
2083 |
|
/** |
2084 |
< |
* Adds delta (which may be negative) to both total and running |
2085 |
< |
* count. This must be called upon creation and termination of |
2086 |
< |
* worker threads. |
2084 |
> |
* Stripped-down variant of awaitJoin used by timed joins. Tries |
2085 |
> |
* to help join only while there is continuous progress. (Caller |
2086 |
> |
* will then enter a timed wait.) |
2087 |
|
* |
2088 |
< |
* @param delta the number to add |
2088 |
> |
* @param joiner the joining worker |
2089 |
> |
* @param task the task |
2090 |
> |
* @return task status on exit |
2091 |
|
*/ |
2092 |
< |
private void updateWorkerCount(int delta) { |
251 |
< |
int d = delta + (delta << 16); // add to both lo and hi parts |
2092 |
> |
final int helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) { |
2093 |
|
int s; |
2094 |
< |
do {} while (!casWorkerCounts(s = workerCounts, s + d)); |
2094 |
> |
while ((s = task.status) >= 0 && |
2095 |
> |
(joiner.isEmpty() ? |
2096 |
> |
tryHelpStealer(joiner, task) : |
2097 |
> |
joiner.tryRemoveAndExec(task)) != 0) |
2098 |
> |
; |
2099 |
> |
return s; |
2100 |
|
} |
2101 |
|
|
2102 |
|
/** |
2103 |
< |
* Lifecycle control. High word contains runState, low word |
2104 |
< |
* contains the number of workers that are (probably) executing |
2105 |
< |
* tasks. This value is atomically incremented before a worker |
2106 |
< |
* gets a task to run, and decremented when worker has no tasks |
2107 |
< |
* and cannot find any. These two fields are bundled together to |
2108 |
< |
* support correct termination triggering. Note: activeCount |
2109 |
< |
* CAS'es cheat by assuming active count is in low word, so need |
2110 |
< |
* to be modified if this changes |
2111 |
< |
*/ |
2112 |
< |
private volatile int runControl; |
2103 |
> |
* Returns a (probably) non-empty steal queue, if one is found |
2104 |
> |
* during a random, then cyclic scan, else null. This method must |
2105 |
> |
* be retried by caller if, by the time it tries to use the queue, |
2106 |
> |
* it is empty. |
2107 |
> |
*/ |
2108 |
> |
private WorkQueue findNonEmptyStealQueue(WorkQueue w) { |
2109 |
> |
// Similar to loop in scan(), but ignoring submissions |
2110 |
> |
int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5; |
2111 |
> |
int step = (r >>> 16) | 1; |
2112 |
> |
for (WorkQueue[] ws;;) { |
2113 |
> |
int rs = runState, m; |
2114 |
> |
if ((ws = workQueues) == null || (m = ws.length - 1) < 1) |
2115 |
> |
return null; |
2116 |
> |
for (int j = (m + 1) << 2; ; r += step) { |
2117 |
> |
WorkQueue q = ws[((r << 1) | 1) & m]; |
2118 |
> |
if (q != null && !q.isEmpty()) |
2119 |
> |
return q; |
2120 |
> |
else if (--j < 0) { |
2121 |
> |
if (runState == rs) |
2122 |
> |
return null; |
2123 |
> |
break; |
2124 |
> |
} |
2125 |
> |
} |
2126 |
> |
} |
2127 |
> |
} |
2128 |
|
|
2129 |
< |
// RunState values. Order among values matters |
2130 |
< |
private static final int RUNNING = 0; |
2131 |
< |
private static final int SHUTDOWN = 1; |
2132 |
< |
private static final int TERMINATING = 2; |
2133 |
< |
private static final int TERMINATED = 3; |
2129 |
> |
/** |
2130 |
> |
* Runs tasks until {@code isQuiescent()}. We piggyback on |
2131 |
> |
* active count ctl maintenance, but rather than blocking |
2132 |
> |
* when tasks cannot be found, we rescan until all others cannot |
2133 |
> |
* find tasks either. |
2134 |
> |
*/ |
2135 |
> |
final void helpQuiescePool(WorkQueue w) { |
2136 |
> |
for (boolean active = true;;) { |
2137 |
> |
ForkJoinTask<?> localTask; // exhaust local queue |
2138 |
> |
while ((localTask = w.nextLocalTask()) != null) |
2139 |
> |
localTask.doExec(); |
2140 |
> |
WorkQueue q = findNonEmptyStealQueue(w); |
2141 |
> |
if (q != null) { |
2142 |
> |
ForkJoinTask<?> t; int b; |
2143 |
> |
if (!active) { // re-establish active count |
2144 |
> |
long c; |
2145 |
> |
active = true; |
2146 |
> |
do {} while (!U.compareAndSwapLong |
2147 |
> |
(this, CTL, c = ctl, c + AC_UNIT)); |
2148 |
> |
} |
2149 |
> |
if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null) |
2150 |
> |
w.runSubtask(t); |
2151 |
> |
} |
2152 |
> |
else { |
2153 |
> |
long c; |
2154 |
> |
if (active) { // decrement active count without queuing |
2155 |
> |
active = false; |
2156 |
> |
do {} while (!U.compareAndSwapLong |
2157 |
> |
(this, CTL, c = ctl, c -= AC_UNIT)); |
2158 |
> |
} |
2159 |
> |
else |
2160 |
> |
c = ctl; // re-increment on exit |
2161 |
> |
if ((int)(c >> AC_SHIFT) + parallelism == 0) { |
2162 |
> |
do {} while (!U.compareAndSwapLong |
2163 |
> |
(this, CTL, c = ctl, c + AC_UNIT)); |
2164 |
> |
break; |
2165 |
> |
} |
2166 |
> |
} |
2167 |
> |
} |
2168 |
> |
} |
2169 |
|
|
2170 |
< |
private static int runStateOf(int c) { return c >>> 16; } |
2171 |
< |
private static int activeCountOf(int c) { return c & shortMask; } |
2172 |
< |
private static int runControlFor(int r, int a) { return (r << 16) + a; } |
2170 |
> |
/** |
2171 |
> |
* Restricted version of helpQuiescePool for non-FJ callers |
2172 |
> |
*/ |
2173 |
> |
static void externalHelpQuiescePool() { |
2174 |
> |
ForkJoinPool p; WorkQueue[] ws; WorkQueue q, sq; |
2175 |
> |
ForkJoinTask<?>[] a; int b; |
2176 |
> |
ForkJoinTask<?> t = null; |
2177 |
> |
int k = submitters.get().seed & SQMASK; |
2178 |
> |
if ((p = commonPool) != null && |
2179 |
> |
(ws = p.workQueues) != null && |
2180 |
> |
ws.length > (k &= p.submitMask) && |
2181 |
> |
(q = ws[k]) != null) { |
2182 |
> |
while (q.top - q.base > 0) { |
2183 |
> |
if ((t = q.sharedPop()) != null) |
2184 |
> |
break; |
2185 |
> |
} |
2186 |
> |
if (t == null && (sq = p.findNonEmptyStealQueue(q)) != null && |
2187 |
> |
(b = sq.base) - sq.top < 0) |
2188 |
> |
t = sq.pollAt(b); |
2189 |
> |
if (t != null) |
2190 |
> |
t.doExec(); |
2191 |
> |
} |
2192 |
> |
} |
2193 |
|
|
2194 |
|
/** |
2195 |
< |
* Tries incrementing active count; fails on contention. |
280 |
< |
* Called by workers before/during executing tasks. |
2195 |
> |
* Gets and removes a local or stolen task for the given worker. |
2196 |
|
* |
2197 |
< |
* @return true on success |
2197 |
> |
* @return a task, if available |
2198 |
|
*/ |
2199 |
< |
final boolean tryIncrementActiveCount() { |
2200 |
< |
int c = runControl; |
2201 |
< |
return casRunControl(c, c+1); |
2199 |
> |
final ForkJoinTask<?> nextTaskFor(WorkQueue w) { |
2200 |
> |
for (ForkJoinTask<?> t;;) { |
2201 |
> |
WorkQueue q; int b; |
2202 |
> |
if ((t = w.nextLocalTask()) != null) |
2203 |
> |
return t; |
2204 |
> |
if ((q = findNonEmptyStealQueue(w)) == null) |
2205 |
> |
return null; |
2206 |
> |
if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null) |
2207 |
> |
return t; |
2208 |
> |
} |
2209 |
|
} |
2210 |
|
|
2211 |
|
/** |
2212 |
< |
* Tries decrementing active count; fails on contention. |
2213 |
< |
* Possibly triggers termination on success. |
2214 |
< |
* Called by workers when they can't find tasks. |
293 |
< |
* |
294 |
< |
* @return true on success |
2212 |
> |
* Returns the approximate (non-atomic) number of idle threads per |
2213 |
> |
* active thread to offset steal queue size for method |
2214 |
> |
* ForkJoinTask.getSurplusQueuedTaskCount(). |
2215 |
|
*/ |
2216 |
< |
final boolean tryDecrementActiveCount() { |
2217 |
< |
int c = runControl; |
2218 |
< |
int nextc = c - 1; |
2219 |
< |
if (!casRunControl(c, nextc)) |
2220 |
< |
return false; |
2221 |
< |
if (canTerminateOnShutdown(nextc)) |
2222 |
< |
terminateOnShutdown(); |
2223 |
< |
return true; |
2216 |
> |
final int idlePerActive() { |
2217 |
> |
// Approximate at powers of two for small values, saturate past 4 |
2218 |
> |
int p = parallelism; |
2219 |
> |
int a = p + (int)(ctl >> AC_SHIFT); |
2220 |
> |
return (a > (p >>>= 1) ? 0 : |
2221 |
> |
a > (p >>>= 1) ? 1 : |
2222 |
> |
a > (p >>>= 1) ? 2 : |
2223 |
> |
a > (p >>>= 1) ? 4 : |
2224 |
> |
8); |
2225 |
|
} |
2226 |
|
|
2227 |
|
/** |
2228 |
< |
* Returns true if argument represents zero active count and |
308 |
< |
* nonzero runstate, which is the triggering condition for |
309 |
< |
* terminating on shutdown. |
2228 |
> |
* Returns approximate submission queue length for the given caller |
2229 |
|
*/ |
2230 |
< |
private static boolean canTerminateOnShutdown(int c) { |
2231 |
< |
// i.e. least bit is nonzero runState bit |
2232 |
< |
return ((c & -c) >>> 16) != 0; |
2230 |
> |
static int getEstimatedSubmitterQueueLength() { |
2231 |
> |
ForkJoinPool p; WorkQueue[] ws; WorkQueue q; |
2232 |
> |
int k = submitters.get().seed & SQMASK; |
2233 |
> |
return ((p = commonPool) != null && (ws = p.workQueues) != null && |
2234 |
> |
ws.length > (k &= p.submitMask) && |
2235 |
> |
(q = ws[k]) != null) ? |
2236 |
> |
q.queueSize() : 0; |
2237 |
|
} |
2238 |
|
|
2239 |
+ |
// Termination |
2240 |
+ |
|
2241 |
|
/** |
2242 |
< |
* Transition run state to at least the given state. Return true |
2243 |
< |
* if not already at least given state. |
2242 |
> |
* Possibly initiates and/or completes termination. The caller |
2243 |
> |
* triggering termination runs three passes through workQueues: |
2244 |
> |
* (0) Setting termination status, followed by wakeups of queued |
2245 |
> |
* workers; (1) cancelling all tasks; (2) interrupting lagging |
2246 |
> |
* threads (likely in external tasks, but possibly also blocked in |
2247 |
> |
* joins). Each pass repeats previous steps because of potential |
2248 |
> |
* lagging thread creation. |
2249 |
> |
* |
2250 |
> |
* @param now if true, unconditionally terminate, else only |
2251 |
> |
* if no work and no active workers |
2252 |
> |
* @param enable if true, enable shutdown when next possible |
2253 |
> |
* @return true if now terminating or terminated |
2254 |
|
*/ |
2255 |
< |
private boolean transitionRunStateTo(int state) { |
2256 |
< |
for (;;) { |
2257 |
< |
int c = runControl; |
2258 |
< |
if (runStateOf(c) >= state) |
2259 |
< |
return false; |
2260 |
< |
if (casRunControl(c, runControlFor(state, activeCountOf(c)))) |
2255 |
> |
private boolean tryTerminate(boolean now, boolean enable) { |
2256 |
> |
for (long c;;) { |
2257 |
> |
if (((c = ctl) & STOP_BIT) != 0) { // already terminating |
2258 |
> |
if ((short)(c >>> TC_SHIFT) == -parallelism) { |
2259 |
> |
synchronized (this) { |
2260 |
> |
notifyAll(); // signal when 0 workers |
2261 |
> |
} |
2262 |
> |
} |
2263 |
|
return true; |
2264 |
+ |
} |
2265 |
+ |
if (runState >= 0) { // not yet enabled |
2266 |
+ |
if (!enable) |
2267 |
+ |
return false; |
2268 |
+ |
while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1)) |
2269 |
+ |
tryAwaitMainLock(); |
2270 |
+ |
try { |
2271 |
+ |
runState |= SHUTDOWN; |
2272 |
+ |
} finally { |
2273 |
+ |
if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) { |
2274 |
+ |
mainLock = 0; |
2275 |
+ |
synchronized (this) { notifyAll(); }; |
2276 |
+ |
} |
2277 |
+ |
} |
2278 |
+ |
} |
2279 |
+ |
if (!now) { // check if idle & no tasks |
2280 |
+ |
if ((int)(c >> AC_SHIFT) != -parallelism || |
2281 |
+ |
hasQueuedSubmissions()) |
2282 |
+ |
return false; |
2283 |
+ |
// Check for unqueued inactive workers. One pass suffices. |
2284 |
+ |
WorkQueue[] ws = workQueues; WorkQueue w; |
2285 |
+ |
if (ws != null) { |
2286 |
+ |
for (int i = 1; i < ws.length; i += 2) { |
2287 |
+ |
if ((w = ws[i]) != null && w.eventCount >= 0) |
2288 |
+ |
return false; |
2289 |
+ |
} |
2290 |
+ |
} |
2291 |
+ |
} |
2292 |
+ |
if (U.compareAndSwapLong(this, CTL, c, c | STOP_BIT)) { |
2293 |
+ |
for (int pass = 0; pass < 3; ++pass) { |
2294 |
+ |
WorkQueue[] ws = workQueues; |
2295 |
+ |
if (ws != null) { |
2296 |
+ |
WorkQueue w; |
2297 |
+ |
int n = ws.length; |
2298 |
+ |
for (int i = 0; i < n; ++i) { |
2299 |
+ |
if ((w = ws[i]) != null) { |
2300 |
+ |
w.runState = -1; |
2301 |
+ |
if (pass > 0) { |
2302 |
+ |
w.cancelAll(); |
2303 |
+ |
if (pass > 1) |
2304 |
+ |
w.interruptOwner(); |
2305 |
+ |
} |
2306 |
+ |
} |
2307 |
+ |
} |
2308 |
+ |
// Wake up workers parked on event queue |
2309 |
+ |
int i, e; long cc; Thread p; |
2310 |
+ |
while ((e = (int)(cc = ctl) & E_MASK) != 0 && |
2311 |
+ |
(i = e & SMASK) < n && |
2312 |
+ |
(w = ws[i]) != null) { |
2313 |
+ |
long nc = ((long)(w.nextWait & E_MASK) | |
2314 |
+ |
((cc + AC_UNIT) & AC_MASK) | |
2315 |
+ |
(cc & (TC_MASK|STOP_BIT))); |
2316 |
+ |
if (w.eventCount == (e | INT_SIGN) && |
2317 |
+ |
U.compareAndSwapLong(this, CTL, cc, nc)) { |
2318 |
+ |
w.eventCount = (e + E_SEQ) & E_MASK; |
2319 |
+ |
w.runState = -1; |
2320 |
+ |
if ((p = w.parker) != null) |
2321 |
+ |
U.unpark(p); |
2322 |
+ |
} |
2323 |
+ |
} |
2324 |
+ |
} |
2325 |
+ |
} |
2326 |
+ |
} |
2327 |
|
} |
2328 |
|
} |
2329 |
|
|
2330 |
< |
/** |
331 |
< |
* Controls whether to add spares to maintain parallelism |
332 |
< |
*/ |
333 |
< |
private volatile boolean maintainsParallelism; |
2330 |
> |
// Exported methods |
2331 |
|
|
2332 |
|
// Constructors |
2333 |
|
|
2334 |
|
/** |
2335 |
< |
* Creates a ForkJoinPool with a pool size equal to the number of |
2336 |
< |
* processors available on the system, using the default |
2337 |
< |
* ForkJoinWorkerThreadFactory. |
2335 |
> |
* Creates a {@code ForkJoinPool} with parallelism equal to {@link |
2336 |
> |
* java.lang.Runtime#availableProcessors}, using the {@linkplain |
2337 |
> |
* #defaultForkJoinWorkerThreadFactory default thread factory}, |
2338 |
> |
* no UncaughtExceptionHandler, and non-async LIFO processing mode. |
2339 |
|
* |
2340 |
|
* @throws SecurityException if a security manager exists and |
2341 |
|
* the caller is not permitted to modify threads |
2344 |
|
*/ |
2345 |
|
public ForkJoinPool() { |
2346 |
|
this(Runtime.getRuntime().availableProcessors(), |
2347 |
< |
defaultForkJoinWorkerThreadFactory); |
2347 |
> |
defaultForkJoinWorkerThreadFactory, null, false); |
2348 |
|
} |
2349 |
|
|
2350 |
|
/** |
2351 |
< |
* Creates a ForkJoinPool with the indicated parallelism level |
2352 |
< |
* threads and using the default ForkJoinWorkerThreadFactory. |
2351 |
> |
* Creates a {@code ForkJoinPool} with the indicated parallelism |
2352 |
> |
* level, the {@linkplain |
2353 |
> |
* #defaultForkJoinWorkerThreadFactory default thread factory}, |
2354 |
> |
* no UncaughtExceptionHandler, and non-async LIFO processing mode. |
2355 |
|
* |
2356 |
< |
* @param parallelism the number of worker threads |
2356 |
> |
* @param parallelism the parallelism level |
2357 |
|
* @throws IllegalArgumentException if parallelism less than or |
2358 |
< |
* equal to zero |
2358 |
> |
* equal to zero, or greater than implementation limit |
2359 |
|
* @throws SecurityException if a security manager exists and |
2360 |
|
* the caller is not permitted to modify threads |
2361 |
|
* because it does not hold {@link |
2362 |
|
* java.lang.RuntimePermission}{@code ("modifyThread")} |
2363 |
|
*/ |
2364 |
|
public ForkJoinPool(int parallelism) { |
2365 |
< |
this(parallelism, defaultForkJoinWorkerThreadFactory); |
2365 |
> |
this(parallelism, defaultForkJoinWorkerThreadFactory, null, false); |
2366 |
|
} |
2367 |
|
|
2368 |
|
/** |
2369 |
< |
* Creates a ForkJoinPool with parallelism equal to the number of |
370 |
< |
* processors available on the system and using the given |
371 |
< |
* ForkJoinWorkerThreadFactory. |
2369 |
> |
* Creates a {@code ForkJoinPool} with the given parameters. |
2370 |
|
* |
2371 |
< |
* @param factory the factory for creating new threads |
2372 |
< |
* @throws NullPointerException if factory is null |
2373 |
< |
* @throws SecurityException if a security manager exists and |
2374 |
< |
* the caller is not permitted to modify threads |
2375 |
< |
* because it does not hold {@link |
2376 |
< |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
2377 |
< |
*/ |
2378 |
< |
public ForkJoinPool(ForkJoinWorkerThreadFactory factory) { |
2379 |
< |
this(Runtime.getRuntime().availableProcessors(), factory); |
2380 |
< |
} |
2381 |
< |
|
2382 |
< |
/** |
2383 |
< |
* Creates a ForkJoinPool with the given parallelism and factory. |
386 |
< |
* |
387 |
< |
* @param parallelism the targeted number of worker threads |
388 |
< |
* @param factory the factory for creating new threads |
2371 |
> |
* @param parallelism the parallelism level. For default value, |
2372 |
> |
* use {@link java.lang.Runtime#availableProcessors}. |
2373 |
> |
* @param factory the factory for creating new threads. For default value, |
2374 |
> |
* use {@link #defaultForkJoinWorkerThreadFactory}. |
2375 |
> |
* @param handler the handler for internal worker threads that |
2376 |
> |
* terminate due to unrecoverable errors encountered while executing |
2377 |
> |
* tasks. For default value, use {@code null}. |
2378 |
> |
* @param asyncMode if true, |
2379 |
> |
* establishes local first-in-first-out scheduling mode for forked |
2380 |
> |
* tasks that are never joined. This mode may be more appropriate |
2381 |
> |
* than default locally stack-based mode in applications in which |
2382 |
> |
* worker threads only process event-style asynchronous tasks. |
2383 |
> |
* For default value, use {@code false}. |
2384 |
|
* @throws IllegalArgumentException if parallelism less than or |
2385 |
< |
* equal to zero, or greater than implementation limit |
2386 |
< |
* @throws NullPointerException if factory is null |
2385 |
> |
* equal to zero, or greater than implementation limit |
2386 |
> |
* @throws NullPointerException if the factory is null |
2387 |
|
* @throws SecurityException if a security manager exists and |
2388 |
|
* the caller is not permitted to modify threads |
2389 |
|
* because it does not hold {@link |
2390 |
|
* java.lang.RuntimePermission}{@code ("modifyThread")} |
2391 |
|
*/ |
2392 |
< |
public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) { |
2393 |
< |
if (parallelism <= 0 || parallelism > MAX_THREADS) |
2394 |
< |
throw new IllegalArgumentException(); |
2392 |
> |
public ForkJoinPool(int parallelism, |
2393 |
> |
ForkJoinWorkerThreadFactory factory, |
2394 |
> |
Thread.UncaughtExceptionHandler handler, |
2395 |
> |
boolean asyncMode) { |
2396 |
> |
checkPermission(); |
2397 |
|
if (factory == null) |
2398 |
|
throw new NullPointerException(); |
2399 |
< |
checkPermission(); |
2400 |
< |
this.factory = factory; |
2399 |
> |
if (parallelism <= 0 || parallelism > MAX_CAP) |
2400 |
> |
throw new IllegalArgumentException(); |
2401 |
|
this.parallelism = parallelism; |
2402 |
< |
this.maxPoolSize = MAX_THREADS; |
2403 |
< |
this.maintainsParallelism = true; |
2404 |
< |
this.poolNumber = poolNumberGenerator.incrementAndGet(); |
2405 |
< |
this.workerLock = new ReentrantLock(); |
2406 |
< |
this.termination = workerLock.newCondition(); |
2407 |
< |
this.stealCount = new AtomicLong(); |
2408 |
< |
this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>(); |
2409 |
< |
// worker array and workers are lazily constructed |
2410 |
< |
} |
2411 |
< |
|
2412 |
< |
/** |
2413 |
< |
* Creates a new worker thread using factory. |
2414 |
< |
* |
2415 |
< |
* @param index the index to assign worker |
2416 |
< |
* @return new worker, or null of factory failed |
420 |
< |
*/ |
421 |
< |
private ForkJoinWorkerThread createWorker(int index) { |
422 |
< |
Thread.UncaughtExceptionHandler h = ueh; |
423 |
< |
ForkJoinWorkerThread w = factory.newThread(this); |
424 |
< |
if (w != null) { |
425 |
< |
w.poolIndex = index; |
426 |
< |
w.setDaemon(true); |
427 |
< |
w.setAsyncMode(locallyFifo); |
428 |
< |
w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index); |
429 |
< |
if (h != null) |
430 |
< |
w.setUncaughtExceptionHandler(h); |
431 |
< |
} |
432 |
< |
return w; |
2402 |
> |
this.factory = factory; |
2403 |
> |
this.ueh = handler; |
2404 |
> |
this.localMode = asyncMode ? FIFO_QUEUE : LIFO_QUEUE; |
2405 |
> |
long np = (long)(-parallelism); // offset ctl counts |
2406 |
> |
this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK); |
2407 |
> |
// Use nearest power 2 for workQueues size. See Hackers Delight sec 3.2. |
2408 |
> |
int n = parallelism - 1; |
2409 |
> |
n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8; n |= n >>> 16; |
2410 |
> |
this.submitMask = ((n + 1) << 1) - 1; |
2411 |
> |
int pn = poolNumberGenerator.incrementAndGet(); |
2412 |
> |
StringBuilder sb = new StringBuilder("ForkJoinPool-"); |
2413 |
> |
sb.append(Integer.toString(pn)); |
2414 |
> |
sb.append("-worker-"); |
2415 |
> |
this.workerNamePrefix = sb.toString(); |
2416 |
> |
this.runState = 1; // set init flag |
2417 |
|
} |
2418 |
|
|
2419 |
|
/** |
2420 |
< |
* Returns a good size for worker array given pool size. |
2421 |
< |
* Currently requires size to be a power of two. |
2422 |
< |
*/ |
2423 |
< |
private static int arraySizeFor(int poolSize) { |
2424 |
< |
return (poolSize <= 1) ? 1 : |
2425 |
< |
(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1))); |
2420 |
> |
* Constructor for common pool, suitable only for static initialization. |
2421 |
> |
* Basically the same as above, but uses smallest possible initial footprint. |
2422 |
> |
*/ |
2423 |
> |
ForkJoinPool(int parallelism, int submitMask, |
2424 |
> |
ForkJoinWorkerThreadFactory factory, |
2425 |
> |
Thread.UncaughtExceptionHandler handler) { |
2426 |
> |
this.factory = factory; |
2427 |
> |
this.ueh = handler; |
2428 |
> |
this.submitMask = submitMask; |
2429 |
> |
this.parallelism = parallelism; |
2430 |
> |
long np = (long)(-parallelism); |
2431 |
> |
this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK); |
2432 |
> |
this.localMode = LIFO_QUEUE; |
2433 |
> |
this.workerNamePrefix = "ForkJoinPool.commonPool-worker-"; |
2434 |
> |
this.runState = 1; |
2435 |
|
} |
2436 |
|
|
2437 |
|
/** |
2438 |
< |
* Creates or resizes array if necessary to hold newLength. |
446 |
< |
* Call only under exclusion. |
2438 |
> |
* Returns the common pool instance. |
2439 |
|
* |
2440 |
< |
* @return the array |
449 |
< |
*/ |
450 |
< |
private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) { |
451 |
< |
ForkJoinWorkerThread[] ws = workers; |
452 |
< |
if (ws == null) |
453 |
< |
return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)]; |
454 |
< |
else if (newLength > ws.length) |
455 |
< |
return workers = Arrays.copyOf(ws, arraySizeFor(newLength)); |
456 |
< |
else |
457 |
< |
return ws; |
458 |
< |
} |
459 |
< |
|
460 |
< |
/** |
461 |
< |
* Tries to shrink workers into smaller array after one or more terminate. |
462 |
< |
*/ |
463 |
< |
private void tryShrinkWorkerArray() { |
464 |
< |
ForkJoinWorkerThread[] ws = workers; |
465 |
< |
if (ws != null) { |
466 |
< |
int len = ws.length; |
467 |
< |
int last = len - 1; |
468 |
< |
while (last >= 0 && ws[last] == null) |
469 |
< |
--last; |
470 |
< |
int newLength = arraySizeFor(last+1); |
471 |
< |
if (newLength < len) |
472 |
< |
workers = Arrays.copyOf(ws, newLength); |
473 |
< |
} |
474 |
< |
} |
475 |
< |
|
476 |
< |
/** |
477 |
< |
* Initializes workers if necessary. |
2440 |
> |
* @return the common pool instance |
2441 |
|
*/ |
2442 |
< |
final void ensureWorkerInitialization() { |
2443 |
< |
ForkJoinWorkerThread[] ws = workers; |
2444 |
< |
if (ws == null) { |
2445 |
< |
final ReentrantLock lock = this.workerLock; |
2446 |
< |
lock.lock(); |
484 |
< |
try { |
485 |
< |
ws = workers; |
486 |
< |
if (ws == null) { |
487 |
< |
int ps = parallelism; |
488 |
< |
ws = ensureWorkerArrayCapacity(ps); |
489 |
< |
for (int i = 0; i < ps; ++i) { |
490 |
< |
ForkJoinWorkerThread w = createWorker(i); |
491 |
< |
if (w != null) { |
492 |
< |
ws[i] = w; |
493 |
< |
w.start(); |
494 |
< |
updateWorkerCount(1); |
495 |
< |
} |
496 |
< |
} |
497 |
< |
} |
498 |
< |
} finally { |
499 |
< |
lock.unlock(); |
500 |
< |
} |
501 |
< |
} |
502 |
< |
} |
503 |
< |
|
504 |
< |
/** |
505 |
< |
* Worker creation and startup for threads added via setParallelism. |
506 |
< |
*/ |
507 |
< |
private void createAndStartAddedWorkers() { |
508 |
< |
resumeAllSpares(); // Allow spares to convert to nonspare |
509 |
< |
int ps = parallelism; |
510 |
< |
ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps); |
511 |
< |
int len = ws.length; |
512 |
< |
// Sweep through slots, to keep lowest indices most populated |
513 |
< |
int k = 0; |
514 |
< |
while (k < len) { |
515 |
< |
if (ws[k] != null) { |
516 |
< |
++k; |
517 |
< |
continue; |
518 |
< |
} |
519 |
< |
int s = workerCounts; |
520 |
< |
int tc = totalCountOf(s); |
521 |
< |
int rc = runningCountOf(s); |
522 |
< |
if (rc >= ps || tc >= ps) |
523 |
< |
break; |
524 |
< |
if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) { |
525 |
< |
ForkJoinWorkerThread w = createWorker(k); |
526 |
< |
if (w != null) { |
527 |
< |
ws[k++] = w; |
528 |
< |
w.start(); |
529 |
< |
} |
530 |
< |
else { |
531 |
< |
updateWorkerCount(-1); // back out on failed creation |
532 |
< |
break; |
533 |
< |
} |
534 |
< |
} |
535 |
< |
} |
2442 |
> |
public static ForkJoinPool commonPool() { |
2443 |
> |
ForkJoinPool p; |
2444 |
> |
if ((p = commonPool) == null) |
2445 |
> |
throw new Error("Common Pool Unavailable"); |
2446 |
> |
return p; |
2447 |
|
} |
2448 |
|
|
2449 |
|
// Execution methods |
2450 |
|
|
2451 |
|
/** |
541 |
– |
* Common code for execute, invoke and submit |
542 |
– |
*/ |
543 |
– |
private <T> void doSubmit(ForkJoinTask<T> task) { |
544 |
– |
if (isShutdown()) |
545 |
– |
throw new RejectedExecutionException(); |
546 |
– |
if (workers == null) |
547 |
– |
ensureWorkerInitialization(); |
548 |
– |
submissionQueue.offer(task); |
549 |
– |
signalIdleWorkers(); |
550 |
– |
} |
551 |
– |
|
552 |
– |
/** |
2452 |
|
* Performs the given task, returning its result upon completion. |
2453 |
+ |
* If the computation encounters an unchecked Exception or Error, |
2454 |
+ |
* it is rethrown as the outcome of this invocation. Rethrown |
2455 |
+ |
* exceptions behave in the same way as regular exceptions, but, |
2456 |
+ |
* when possible, contain stack traces (as displayed for example |
2457 |
+ |
* using {@code ex.printStackTrace()}) of both the current thread |
2458 |
+ |
* as well as the thread actually encountering the exception; |
2459 |
+ |
* minimally only the latter. |
2460 |
|
* |
2461 |
|
* @param task the task |
2462 |
|
* @return the task's result |
2463 |
< |
* @throws NullPointerException if task is null |
2464 |
< |
* @throws RejectedExecutionException if pool is shut down |
2463 |
> |
* @throws NullPointerException if the task is null |
2464 |
> |
* @throws RejectedExecutionException if the task cannot be |
2465 |
> |
* scheduled for execution |
2466 |
|
*/ |
2467 |
|
public <T> T invoke(ForkJoinTask<T> task) { |
2468 |
+ |
if (task == null) |
2469 |
+ |
throw new NullPointerException(); |
2470 |
|
doSubmit(task); |
2471 |
|
return task.join(); |
2472 |
|
} |
2475 |
|
* Arranges for (asynchronous) execution of the given task. |
2476 |
|
* |
2477 |
|
* @param task the task |
2478 |
< |
* @throws NullPointerException if task is null |
2479 |
< |
* @throws RejectedExecutionException if pool is shut down |
2478 |
> |
* @throws NullPointerException if the task is null |
2479 |
> |
* @throws RejectedExecutionException if the task cannot be |
2480 |
> |
* scheduled for execution |
2481 |
|
*/ |
2482 |
< |
public <T> void execute(ForkJoinTask<T> task) { |
2482 |
> |
public void execute(ForkJoinTask<?> task) { |
2483 |
> |
if (task == null) |
2484 |
> |
throw new NullPointerException(); |
2485 |
|
doSubmit(task); |
2486 |
|
} |
2487 |
|
|
2488 |
|
// AbstractExecutorService methods |
2489 |
|
|
2490 |
+ |
/** |
2491 |
+ |
* @throws NullPointerException if the task is null |
2492 |
+ |
* @throws RejectedExecutionException if the task cannot be |
2493 |
+ |
* scheduled for execution |
2494 |
+ |
*/ |
2495 |
|
public void execute(Runnable task) { |
2496 |
< |
doSubmit(new AdaptedRunnable<Void>(task, null)); |
2496 |
> |
if (task == null) |
2497 |
> |
throw new NullPointerException(); |
2498 |
> |
ForkJoinTask<?> job; |
2499 |
> |
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
2500 |
> |
job = (ForkJoinTask<?>) task; |
2501 |
> |
else |
2502 |
> |
job = new ForkJoinTask.AdaptedRunnableAction(task); |
2503 |
> |
doSubmit(job); |
2504 |
> |
} |
2505 |
> |
|
2506 |
> |
/** |
2507 |
> |
* Submits a ForkJoinTask for execution. |
2508 |
> |
* |
2509 |
> |
* @param task the task to submit |
2510 |
> |
* @return the task |
2511 |
> |
* @throws NullPointerException if the task is null |
2512 |
> |
* @throws RejectedExecutionException if the task cannot be |
2513 |
> |
* scheduled for execution |
2514 |
> |
*/ |
2515 |
> |
public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) { |
2516 |
> |
if (task == null) |
2517 |
> |
throw new NullPointerException(); |
2518 |
> |
doSubmit(task); |
2519 |
> |
return task; |
2520 |
|
} |
2521 |
|
|
2522 |
+ |
/** |
2523 |
+ |
* @throws NullPointerException if the task is null |
2524 |
+ |
* @throws RejectedExecutionException if the task cannot be |
2525 |
+ |
* scheduled for execution |
2526 |
+ |
*/ |
2527 |
|
public <T> ForkJoinTask<T> submit(Callable<T> task) { |
2528 |
< |
ForkJoinTask<T> job = new AdaptedCallable<T>(task); |
2528 |
> |
ForkJoinTask<T> job = new ForkJoinTask.AdaptedCallable<T>(task); |
2529 |
|
doSubmit(job); |
2530 |
|
return job; |
2531 |
|
} |
2532 |
|
|
2533 |
+ |
/** |
2534 |
+ |
* @throws NullPointerException if the task is null |
2535 |
+ |
* @throws RejectedExecutionException if the task cannot be |
2536 |
+ |
* scheduled for execution |
2537 |
+ |
*/ |
2538 |
|
public <T> ForkJoinTask<T> submit(Runnable task, T result) { |
2539 |
< |
ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result); |
2539 |
> |
ForkJoinTask<T> job = new ForkJoinTask.AdaptedRunnable<T>(task, result); |
2540 |
|
doSubmit(job); |
2541 |
|
return job; |
2542 |
|
} |
2543 |
|
|
2544 |
+ |
/** |
2545 |
+ |
* @throws NullPointerException if the task is null |
2546 |
+ |
* @throws RejectedExecutionException if the task cannot be |
2547 |
+ |
* scheduled for execution |
2548 |
+ |
*/ |
2549 |
|
public ForkJoinTask<?> submit(Runnable task) { |
2550 |
< |
ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null); |
2550 |
> |
if (task == null) |
2551 |
> |
throw new NullPointerException(); |
2552 |
> |
ForkJoinTask<?> job; |
2553 |
> |
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
2554 |
> |
job = (ForkJoinTask<?>) task; |
2555 |
> |
else |
2556 |
> |
job = new ForkJoinTask.AdaptedRunnableAction(task); |
2557 |
|
doSubmit(job); |
2558 |
|
return job; |
2559 |
|
} |
2560 |
|
|
2561 |
|
/** |
2562 |
< |
* Adaptor for Runnables. This implements RunnableFuture |
2563 |
< |
* to be compliant with AbstractExecutorService constraints. |
603 |
< |
*/ |
604 |
< |
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
605 |
< |
implements RunnableFuture<T> { |
606 |
< |
final Runnable runnable; |
607 |
< |
final T resultOnCompletion; |
608 |
< |
T result; |
609 |
< |
AdaptedRunnable(Runnable runnable, T result) { |
610 |
< |
if (runnable == null) throw new NullPointerException(); |
611 |
< |
this.runnable = runnable; |
612 |
< |
this.resultOnCompletion = result; |
613 |
< |
} |
614 |
< |
public T getRawResult() { return result; } |
615 |
< |
public void setRawResult(T v) { result = v; } |
616 |
< |
public boolean exec() { |
617 |
< |
runnable.run(); |
618 |
< |
result = resultOnCompletion; |
619 |
< |
return true; |
620 |
< |
} |
621 |
< |
public void run() { invoke(); } |
622 |
< |
private static final long serialVersionUID = 5232453952276885070L; |
623 |
< |
} |
624 |
< |
|
625 |
< |
/** |
626 |
< |
* Adaptor for Callables |
2562 |
> |
* @throws NullPointerException {@inheritDoc} |
2563 |
> |
* @throws RejectedExecutionException {@inheritDoc} |
2564 |
|
*/ |
628 |
– |
static final class AdaptedCallable<T> extends ForkJoinTask<T> |
629 |
– |
implements RunnableFuture<T> { |
630 |
– |
final Callable<T> callable; |
631 |
– |
T result; |
632 |
– |
AdaptedCallable(Callable<T> callable) { |
633 |
– |
if (callable == null) throw new NullPointerException(); |
634 |
– |
this.callable = callable; |
635 |
– |
} |
636 |
– |
public T getRawResult() { return result; } |
637 |
– |
public void setRawResult(T v) { result = v; } |
638 |
– |
public boolean exec() { |
639 |
– |
try { |
640 |
– |
result = callable.call(); |
641 |
– |
return true; |
642 |
– |
} catch (Error err) { |
643 |
– |
throw err; |
644 |
– |
} catch (RuntimeException rex) { |
645 |
– |
throw rex; |
646 |
– |
} catch (Exception ex) { |
647 |
– |
throw new RuntimeException(ex); |
648 |
– |
} |
649 |
– |
} |
650 |
– |
public void run() { invoke(); } |
651 |
– |
private static final long serialVersionUID = 2838392045355241008L; |
652 |
– |
} |
653 |
– |
|
2565 |
|
public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) { |
2566 |
< |
ArrayList<ForkJoinTask<T>> ts = |
2567 |
< |
new ArrayList<ForkJoinTask<T>>(tasks.size()); |
2568 |
< |
for (Callable<T> c : tasks) |
2569 |
< |
ts.add(new AdaptedCallable<T>(c)); |
2570 |
< |
invoke(new InvokeAll<T>(ts)); |
2571 |
< |
return (List<Future<T>>) (List) ts; |
2572 |
< |
} |
2566 |
> |
// In previous versions of this class, this method constructed |
2567 |
> |
// a task to run ForkJoinTask.invokeAll, but now external |
2568 |
> |
// invocation of multiple tasks is at least as efficient. |
2569 |
> |
List<ForkJoinTask<T>> fs = new ArrayList<ForkJoinTask<T>>(tasks.size()); |
2570 |
> |
// Workaround needed because method wasn't declared with |
2571 |
> |
// wildcards in return type but should have been. |
2572 |
> |
@SuppressWarnings({"unchecked", "rawtypes"}) |
2573 |
> |
List<Future<T>> futures = (List<Future<T>>) (List) fs; |
2574 |
|
|
2575 |
< |
static final class InvokeAll<T> extends RecursiveAction { |
2576 |
< |
final ArrayList<ForkJoinTask<T>> tasks; |
2577 |
< |
InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; } |
2578 |
< |
public void compute() { |
2579 |
< |
try { invokeAll(tasks); } |
2580 |
< |
catch (Exception ignore) {} |
2575 |
> |
boolean done = false; |
2576 |
> |
try { |
2577 |
> |
for (Callable<T> t : tasks) { |
2578 |
> |
ForkJoinTask<T> f = new ForkJoinTask.AdaptedCallable<T>(t); |
2579 |
> |
doSubmit(f); |
2580 |
> |
fs.add(f); |
2581 |
> |
} |
2582 |
> |
for (ForkJoinTask<T> f : fs) |
2583 |
> |
f.quietlyJoin(); |
2584 |
> |
done = true; |
2585 |
> |
return futures; |
2586 |
> |
} finally { |
2587 |
> |
if (!done) |
2588 |
> |
for (ForkJoinTask<T> f : fs) |
2589 |
> |
f.cancel(false); |
2590 |
|
} |
670 |
– |
private static final long serialVersionUID = -7914297376763021607L; |
2591 |
|
} |
2592 |
|
|
673 |
– |
// Configuration and status settings and queries |
674 |
– |
|
2593 |
|
/** |
2594 |
|
* Returns the factory used for constructing new workers. |
2595 |
|
* |
2603 |
|
* Returns the handler for internal worker threads that terminate |
2604 |
|
* due to unrecoverable errors encountered while executing tasks. |
2605 |
|
* |
2606 |
< |
* @return the handler, or null if none |
2606 |
> |
* @return the handler, or {@code null} if none |
2607 |
|
*/ |
2608 |
|
public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() { |
2609 |
< |
Thread.UncaughtExceptionHandler h; |
692 |
< |
final ReentrantLock lock = this.workerLock; |
693 |
< |
lock.lock(); |
694 |
< |
try { |
695 |
< |
h = ueh; |
696 |
< |
} finally { |
697 |
< |
lock.unlock(); |
698 |
< |
} |
699 |
< |
return h; |
700 |
< |
} |
701 |
< |
|
702 |
< |
/** |
703 |
< |
* Sets the handler for internal worker threads that terminate due |
704 |
< |
* to unrecoverable errors encountered while executing tasks. |
705 |
< |
* Unless set, the current default or ThreadGroup handler is used |
706 |
< |
* as handler. |
707 |
< |
* |
708 |
< |
* @param h the new handler |
709 |
< |
* @return the old handler, or null if none |
710 |
< |
* @throws SecurityException if a security manager exists and |
711 |
< |
* the caller is not permitted to modify threads |
712 |
< |
* because it does not hold {@link |
713 |
< |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
714 |
< |
*/ |
715 |
< |
public Thread.UncaughtExceptionHandler |
716 |
< |
setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) { |
717 |
< |
checkPermission(); |
718 |
< |
Thread.UncaughtExceptionHandler old = null; |
719 |
< |
final ReentrantLock lock = this.workerLock; |
720 |
< |
lock.lock(); |
721 |
< |
try { |
722 |
< |
old = ueh; |
723 |
< |
ueh = h; |
724 |
< |
ForkJoinWorkerThread[] ws = workers; |
725 |
< |
if (ws != null) { |
726 |
< |
for (int i = 0; i < ws.length; ++i) { |
727 |
< |
ForkJoinWorkerThread w = ws[i]; |
728 |
< |
if (w != null) |
729 |
< |
w.setUncaughtExceptionHandler(h); |
730 |
< |
} |
731 |
< |
} |
732 |
< |
} finally { |
733 |
< |
lock.unlock(); |
734 |
< |
} |
735 |
< |
return old; |
2609 |
> |
return ueh; |
2610 |
|
} |
2611 |
|
|
738 |
– |
|
2612 |
|
/** |
2613 |
< |
* Sets the target parallelism level of this pool. |
2613 |
> |
* Returns the targeted parallelism level of this pool. |
2614 |
|
* |
2615 |
< |
* @param parallelism the target parallelism |
743 |
< |
* @throws IllegalArgumentException if parallelism less than or |
744 |
< |
* equal to zero or greater than maximum size bounds |
745 |
< |
* @throws SecurityException if a security manager exists and |
746 |
< |
* the caller is not permitted to modify threads |
747 |
< |
* because it does not hold {@link |
748 |
< |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
2615 |
> |
* @return the targeted parallelism level of this pool |
2616 |
|
*/ |
2617 |
< |
public void setParallelism(int parallelism) { |
2618 |
< |
checkPermission(); |
752 |
< |
if (parallelism <= 0 || parallelism > maxPoolSize) |
753 |
< |
throw new IllegalArgumentException(); |
754 |
< |
final ReentrantLock lock = this.workerLock; |
755 |
< |
lock.lock(); |
756 |
< |
try { |
757 |
< |
if (!isTerminating()) { |
758 |
< |
int p = this.parallelism; |
759 |
< |
this.parallelism = parallelism; |
760 |
< |
if (parallelism > p) |
761 |
< |
createAndStartAddedWorkers(); |
762 |
< |
else |
763 |
< |
trimSpares(); |
764 |
< |
} |
765 |
< |
} finally { |
766 |
< |
lock.unlock(); |
767 |
< |
} |
768 |
< |
signalIdleWorkers(); |
2617 |
> |
public int getParallelism() { |
2618 |
> |
return parallelism; |
2619 |
|
} |
2620 |
|
|
2621 |
|
/** |
2622 |
< |
* Returns the targeted number of worker threads in this pool. |
2622 |
> |
* Returns the targeted parallelism level of the common pool. |
2623 |
|
* |
2624 |
< |
* @return the targeted number of worker threads in this pool |
2624 |
> |
* @return the targeted parallelism level of the common pool |
2625 |
|
*/ |
2626 |
< |
public int getParallelism() { |
2627 |
< |
return parallelism; |
2626 |
> |
public static int getCommonPoolParallelism() { |
2627 |
> |
return commonPoolParallelism; |
2628 |
|
} |
2629 |
|
|
2630 |
|
/** |
2631 |
|
* Returns the number of worker threads that have started but not |
2632 |
< |
* yet terminated. This result returned by this method may differ |
2633 |
< |
* from {@code getParallelism} when threads are created to |
2632 |
> |
* yet terminated. The result returned by this method may differ |
2633 |
> |
* from {@link #getParallelism} when threads are created to |
2634 |
|
* maintain parallelism when others are cooperatively blocked. |
2635 |
|
* |
2636 |
|
* @return the number of worker threads |
2637 |
|
*/ |
2638 |
|
public int getPoolSize() { |
2639 |
< |
return totalCountOf(workerCounts); |
790 |
< |
} |
791 |
< |
|
792 |
< |
/** |
793 |
< |
* Returns the maximum number of threads allowed to exist in the |
794 |
< |
* pool, even if there are insufficient unblocked running threads. |
795 |
< |
* |
796 |
< |
* @return the maximum |
797 |
< |
*/ |
798 |
< |
public int getMaximumPoolSize() { |
799 |
< |
return maxPoolSize; |
800 |
< |
} |
801 |
< |
|
802 |
< |
/** |
803 |
< |
* Sets the maximum number of threads allowed to exist in the |
804 |
< |
* pool, even if there are insufficient unblocked running threads. |
805 |
< |
* Setting this value has no effect on current pool size. It |
806 |
< |
* controls construction of new threads. |
807 |
< |
* |
808 |
< |
* @throws IllegalArgumentException if negative or greater then |
809 |
< |
* internal implementation limit |
810 |
< |
*/ |
811 |
< |
public void setMaximumPoolSize(int newMax) { |
812 |
< |
if (newMax < 0 || newMax > MAX_THREADS) |
813 |
< |
throw new IllegalArgumentException(); |
814 |
< |
maxPoolSize = newMax; |
815 |
< |
} |
816 |
< |
|
817 |
< |
|
818 |
< |
/** |
819 |
< |
* Returns true if this pool dynamically maintains its target |
820 |
< |
* parallelism level. If false, new threads are added only to |
821 |
< |
* avoid possible starvation. |
822 |
< |
* This setting is by default true. |
823 |
< |
* |
824 |
< |
* @return true if maintains parallelism |
825 |
< |
*/ |
826 |
< |
public boolean getMaintainsParallelism() { |
827 |
< |
return maintainsParallelism; |
828 |
< |
} |
829 |
< |
|
830 |
< |
/** |
831 |
< |
* Sets whether this pool dynamically maintains its target |
832 |
< |
* parallelism level. If false, new threads are added only to |
833 |
< |
* avoid possible starvation. |
834 |
< |
* |
835 |
< |
* @param enable true to maintains parallelism |
836 |
< |
*/ |
837 |
< |
public void setMaintainsParallelism(boolean enable) { |
838 |
< |
maintainsParallelism = enable; |
2639 |
> |
return parallelism + (short)(ctl >>> TC_SHIFT); |
2640 |
|
} |
2641 |
|
|
2642 |
|
/** |
2643 |
< |
* Establishes local first-in-first-out scheduling mode for forked |
843 |
< |
* tasks that are never joined. This mode may be more appropriate |
844 |
< |
* than default locally stack-based mode in applications in which |
845 |
< |
* worker threads only process asynchronous tasks. This method is |
846 |
< |
* designed to be invoked only when pool is quiescent, and |
847 |
< |
* typically only before any tasks are submitted. The effects of |
848 |
< |
* invocations at other times may be unpredictable. |
849 |
< |
* |
850 |
< |
* @param async if true, use locally FIFO scheduling |
851 |
< |
* @return the previous mode |
852 |
< |
*/ |
853 |
< |
public boolean setAsyncMode(boolean async) { |
854 |
< |
boolean oldMode = locallyFifo; |
855 |
< |
locallyFifo = async; |
856 |
< |
ForkJoinWorkerThread[] ws = workers; |
857 |
< |
if (ws != null) { |
858 |
< |
for (int i = 0; i < ws.length; ++i) { |
859 |
< |
ForkJoinWorkerThread t = ws[i]; |
860 |
< |
if (t != null) |
861 |
< |
t.setAsyncMode(async); |
862 |
< |
} |
863 |
< |
} |
864 |
< |
return oldMode; |
865 |
< |
} |
866 |
< |
|
867 |
< |
/** |
868 |
< |
* Returns true if this pool uses local first-in-first-out |
2643 |
> |
* Returns {@code true} if this pool uses local first-in-first-out |
2644 |
|
* scheduling mode for forked tasks that are never joined. |
2645 |
|
* |
2646 |
< |
* @return true if this pool uses async mode |
2646 |
> |
* @return {@code true} if this pool uses async mode |
2647 |
|
*/ |
2648 |
|
public boolean getAsyncMode() { |
2649 |
< |
return locallyFifo; |
2649 |
> |
return localMode != 0; |
2650 |
|
} |
2651 |
|
|
2652 |
|
/** |
2653 |
|
* Returns an estimate of the number of worker threads that are |
2654 |
|
* not blocked waiting to join tasks or for other managed |
2655 |
< |
* synchronization. |
2655 |
> |
* synchronization. This method may overestimate the |
2656 |
> |
* number of running threads. |
2657 |
|
* |
2658 |
|
* @return the number of worker threads |
2659 |
|
*/ |
2660 |
|
public int getRunningThreadCount() { |
2661 |
< |
return runningCountOf(workerCounts); |
2661 |
> |
int rc = 0; |
2662 |
> |
WorkQueue[] ws; WorkQueue w; |
2663 |
> |
if ((ws = workQueues) != null) { |
2664 |
> |
for (int i = 1; i < ws.length; i += 2) { |
2665 |
> |
if ((w = ws[i]) != null && w.isApparentlyUnblocked()) |
2666 |
> |
++rc; |
2667 |
> |
} |
2668 |
> |
} |
2669 |
> |
return rc; |
2670 |
|
} |
2671 |
|
|
2672 |
|
/** |
2677 |
|
* @return the number of active threads |
2678 |
|
*/ |
2679 |
|
public int getActiveThreadCount() { |
2680 |
< |
return activeCountOf(runControl); |
2681 |
< |
} |
898 |
< |
|
899 |
< |
/** |
900 |
< |
* Returns an estimate of the number of threads that are currently |
901 |
< |
* idle waiting for tasks. This method may underestimate the |
902 |
< |
* number of idle threads. |
903 |
< |
* |
904 |
< |
* @return the number of idle threads |
905 |
< |
*/ |
906 |
< |
final int getIdleThreadCount() { |
907 |
< |
int c = runningCountOf(workerCounts) - activeCountOf(runControl); |
908 |
< |
return (c <= 0) ? 0 : c; |
2680 |
> |
int r = parallelism + (int)(ctl >> AC_SHIFT); |
2681 |
> |
return (r <= 0) ? 0 : r; // suppress momentarily negative values |
2682 |
|
} |
2683 |
|
|
2684 |
|
/** |
2685 |
< |
* Returns true if all worker threads are currently idle. An idle |
2686 |
< |
* worker is one that cannot obtain a task to execute because none |
2687 |
< |
* are available to steal from other threads, and there are no |
2688 |
< |
* pending submissions to the pool. This method is conservative; |
2689 |
< |
* it might not return true immediately upon idleness of all |
2690 |
< |
* threads, but will eventually become true if threads remain |
2691 |
< |
* inactive. |
2685 |
> |
* Returns {@code true} if all worker threads are currently idle. |
2686 |
> |
* An idle worker is one that cannot obtain a task to execute |
2687 |
> |
* because none are available to steal from other threads, and |
2688 |
> |
* there are no pending submissions to the pool. This method is |
2689 |
> |
* conservative; it might not return {@code true} immediately upon |
2690 |
> |
* idleness of all threads, but will eventually become true if |
2691 |
> |
* threads remain inactive. |
2692 |
|
* |
2693 |
< |
* @return true if all threads are currently idle |
2693 |
> |
* @return {@code true} if all threads are currently idle |
2694 |
|
*/ |
2695 |
|
public boolean isQuiescent() { |
2696 |
< |
return activeCountOf(runControl) == 0; |
2696 |
> |
return (int)(ctl >> AC_SHIFT) + parallelism == 0; |
2697 |
|
} |
2698 |
|
|
2699 |
|
/** |
2708 |
|
* @return the number of steals |
2709 |
|
*/ |
2710 |
|
public long getStealCount() { |
2711 |
< |
return stealCount.get(); |
2712 |
< |
} |
2713 |
< |
|
2714 |
< |
/** |
2715 |
< |
* Accumulates steal count from a worker. |
2716 |
< |
* Call only when worker known to be idle. |
2717 |
< |
*/ |
2718 |
< |
private void updateStealCount(ForkJoinWorkerThread w) { |
2719 |
< |
int sc = w.getAndClearStealCount(); |
947 |
< |
if (sc != 0) |
948 |
< |
stealCount.addAndGet(sc); |
2711 |
> |
long count = stealCount; |
2712 |
> |
WorkQueue[] ws; WorkQueue w; |
2713 |
> |
if ((ws = workQueues) != null) { |
2714 |
> |
for (int i = 1; i < ws.length; i += 2) { |
2715 |
> |
if ((w = ws[i]) != null) |
2716 |
> |
count += w.totalSteals; |
2717 |
> |
} |
2718 |
> |
} |
2719 |
> |
return count; |
2720 |
|
} |
2721 |
|
|
2722 |
|
/** |
2731 |
|
*/ |
2732 |
|
public long getQueuedTaskCount() { |
2733 |
|
long count = 0; |
2734 |
< |
ForkJoinWorkerThread[] ws = workers; |
2735 |
< |
if (ws != null) { |
2736 |
< |
for (int i = 0; i < ws.length; ++i) { |
2737 |
< |
ForkJoinWorkerThread t = ws[i]; |
2738 |
< |
if (t != null) |
968 |
< |
count += t.getQueueSize(); |
2734 |
> |
WorkQueue[] ws; WorkQueue w; |
2735 |
> |
if ((ws = workQueues) != null) { |
2736 |
> |
for (int i = 1; i < ws.length; i += 2) { |
2737 |
> |
if ((w = ws[i]) != null) |
2738 |
> |
count += w.queueSize(); |
2739 |
|
} |
2740 |
|
} |
2741 |
|
return count; |
2742 |
|
} |
2743 |
|
|
2744 |
|
/** |
2745 |
< |
* Returns an estimate of the number tasks submitted to this pool |
2746 |
< |
* that have not yet begun executing. This method takes time |
2747 |
< |
* proportional to the number of submissions. |
2745 |
> |
* Returns an estimate of the number of tasks submitted to this |
2746 |
> |
* pool that have not yet begun executing. This method may take |
2747 |
> |
* time proportional to the number of submissions. |
2748 |
|
* |
2749 |
|
* @return the number of queued submissions |
2750 |
|
*/ |
2751 |
|
public int getQueuedSubmissionCount() { |
2752 |
< |
return submissionQueue.size(); |
2752 |
> |
int count = 0; |
2753 |
> |
WorkQueue[] ws; WorkQueue w; |
2754 |
> |
if ((ws = workQueues) != null) { |
2755 |
> |
for (int i = 0; i < ws.length; i += 2) { |
2756 |
> |
if ((w = ws[i]) != null) |
2757 |
> |
count += w.queueSize(); |
2758 |
> |
} |
2759 |
> |
} |
2760 |
> |
return count; |
2761 |
|
} |
2762 |
|
|
2763 |
|
/** |
2764 |
< |
* Returns true if there are any tasks submitted to this pool |
2765 |
< |
* that have not yet begun executing. |
2764 |
> |
* Returns {@code true} if there are any tasks submitted to this |
2765 |
> |
* pool that have not yet begun executing. |
2766 |
|
* |
2767 |
|
* @return {@code true} if there are any queued submissions |
2768 |
|
*/ |
2769 |
|
public boolean hasQueuedSubmissions() { |
2770 |
< |
return !submissionQueue.isEmpty(); |
2770 |
> |
WorkQueue[] ws; WorkQueue w; |
2771 |
> |
if ((ws = workQueues) != null) { |
2772 |
> |
for (int i = 0; i < ws.length; i += 2) { |
2773 |
> |
if ((w = ws[i]) != null && !w.isEmpty()) |
2774 |
> |
return true; |
2775 |
> |
} |
2776 |
> |
} |
2777 |
> |
return false; |
2778 |
|
} |
2779 |
|
|
2780 |
|
/** |
2782 |
|
* available. This method may be useful in extensions to this |
2783 |
|
* class that re-assign work in systems with multiple pools. |
2784 |
|
* |
2785 |
< |
* @return the next submission, or null if none |
2785 |
> |
* @return the next submission, or {@code null} if none |
2786 |
|
*/ |
2787 |
|
protected ForkJoinTask<?> pollSubmission() { |
2788 |
< |
return submissionQueue.poll(); |
2788 |
> |
WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t; |
2789 |
> |
if ((ws = workQueues) != null) { |
2790 |
> |
for (int i = 0; i < ws.length; i += 2) { |
2791 |
> |
if ((w = ws[i]) != null && (t = w.poll()) != null) |
2792 |
> |
return t; |
2793 |
> |
} |
2794 |
> |
} |
2795 |
> |
return null; |
2796 |
|
} |
2797 |
|
|
2798 |
|
/** |
2799 |
|
* Removes all available unexecuted submitted and forked tasks |
2800 |
|
* from scheduling queues and adds them to the given collection, |
2801 |
|
* without altering their execution status. These may include |
2802 |
< |
* artificially generated or wrapped tasks. This method is designed |
2803 |
< |
* to be invoked only when the pool is known to be |
2802 |
> |
* artificially generated or wrapped tasks. This method is |
2803 |
> |
* designed to be invoked only when the pool is known to be |
2804 |
|
* quiescent. Invocations at other times may not remove all |
2805 |
|
* tasks. A failure encountered while attempting to add elements |
2806 |
|
* to collection {@code c} may result in elements being in |
2812 |
|
* @param c the collection to transfer elements into |
2813 |
|
* @return the number of elements transferred |
2814 |
|
*/ |
2815 |
< |
protected int drainTasksTo(Collection<ForkJoinTask<?>> c) { |
2816 |
< |
int n = submissionQueue.drainTo(c); |
2817 |
< |
ForkJoinWorkerThread[] ws = workers; |
2818 |
< |
if (ws != null) { |
2815 |
> |
protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) { |
2816 |
> |
int count = 0; |
2817 |
> |
WorkQueue[] ws; WorkQueue w; ForkJoinTask<?> t; |
2818 |
> |
if ((ws = workQueues) != null) { |
2819 |
|
for (int i = 0; i < ws.length; ++i) { |
2820 |
< |
ForkJoinWorkerThread w = ws[i]; |
2821 |
< |
if (w != null) |
2822 |
< |
n += w.drainTasksTo(c); |
2820 |
> |
if ((w = ws[i]) != null) { |
2821 |
> |
while ((t = w.poll()) != null) { |
2822 |
> |
c.add(t); |
2823 |
> |
++count; |
2824 |
> |
} |
2825 |
> |
} |
2826 |
|
} |
2827 |
|
} |
2828 |
< |
return n; |
2828 |
> |
return count; |
2829 |
|
} |
2830 |
|
|
2831 |
|
/** |
2836 |
|
* @return a string identifying this pool, as well as its state |
2837 |
|
*/ |
2838 |
|
public String toString() { |
2839 |
< |
int ps = parallelism; |
2840 |
< |
int wc = workerCounts; |
2841 |
< |
int rc = runControl; |
2842 |
< |
long st = getStealCount(); |
2843 |
< |
long qt = getQueuedTaskCount(); |
2844 |
< |
long qs = getQueuedSubmissionCount(); |
2839 |
> |
// Use a single pass through workQueues to collect counts |
2840 |
> |
long qt = 0L, qs = 0L; int rc = 0; |
2841 |
> |
long st = stealCount; |
2842 |
> |
long c = ctl; |
2843 |
> |
WorkQueue[] ws; WorkQueue w; |
2844 |
> |
if ((ws = workQueues) != null) { |
2845 |
> |
for (int i = 0; i < ws.length; ++i) { |
2846 |
> |
if ((w = ws[i]) != null) { |
2847 |
> |
int size = w.queueSize(); |
2848 |
> |
if ((i & 1) == 0) |
2849 |
> |
qs += size; |
2850 |
> |
else { |
2851 |
> |
qt += size; |
2852 |
> |
st += w.totalSteals; |
2853 |
> |
if (w.isApparentlyUnblocked()) |
2854 |
> |
++rc; |
2855 |
> |
} |
2856 |
> |
} |
2857 |
> |
} |
2858 |
> |
} |
2859 |
> |
int pc = parallelism; |
2860 |
> |
int tc = pc + (short)(c >>> TC_SHIFT); |
2861 |
> |
int ac = pc + (int)(c >> AC_SHIFT); |
2862 |
> |
if (ac < 0) // ignore transient negative |
2863 |
> |
ac = 0; |
2864 |
> |
String level; |
2865 |
> |
if ((c & STOP_BIT) != 0) |
2866 |
> |
level = (tc == 0) ? "Terminated" : "Terminating"; |
2867 |
> |
else |
2868 |
> |
level = runState < 0 ? "Shutting down" : "Running"; |
2869 |
|
return super.toString() + |
2870 |
< |
"[" + runStateToString(runStateOf(rc)) + |
2871 |
< |
", parallelism = " + ps + |
2872 |
< |
", size = " + totalCountOf(wc) + |
2873 |
< |
", active = " + activeCountOf(rc) + |
2874 |
< |
", running = " + runningCountOf(wc) + |
2870 |
> |
"[" + level + |
2871 |
> |
", parallelism = " + pc + |
2872 |
> |
", size = " + tc + |
2873 |
> |
", active = " + ac + |
2874 |
> |
", running = " + rc + |
2875 |
|
", steals = " + st + |
2876 |
|
", tasks = " + qt + |
2877 |
|
", submissions = " + qs + |
2878 |
|
"]"; |
2879 |
|
} |
2880 |
|
|
1062 |
– |
private static String runStateToString(int rs) { |
1063 |
– |
switch(rs) { |
1064 |
– |
case RUNNING: return "Running"; |
1065 |
– |
case SHUTDOWN: return "Shutting down"; |
1066 |
– |
case TERMINATING: return "Terminating"; |
1067 |
– |
case TERMINATED: return "Terminated"; |
1068 |
– |
default: throw new Error("Unknown run state"); |
1069 |
– |
} |
1070 |
– |
} |
1071 |
– |
|
1072 |
– |
// lifecycle control |
1073 |
– |
|
2881 |
|
/** |
2882 |
< |
* Initiates an orderly shutdown in which previously submitted |
2883 |
< |
* tasks are executed, but no new tasks will be accepted. |
2884 |
< |
* Invocation has no additional effect if already shut down. |
2885 |
< |
* Tasks that are in the process of being submitted concurrently |
2886 |
< |
* during the course of this method may or may not be rejected. |
2882 |
> |
* Possibly initiates an orderly shutdown in which previously |
2883 |
> |
* submitted tasks are executed, but no new tasks will be |
2884 |
> |
* accepted. Invocation has no effect on execution state if this |
2885 |
> |
* is the {@link #commonPool}, and no additional effect if |
2886 |
> |
* already shut down. Tasks that are in the process of being |
2887 |
> |
* submitted concurrently during the course of this method may or |
2888 |
> |
* may not be rejected. |
2889 |
|
* |
2890 |
|
* @throws SecurityException if a security manager exists and |
2891 |
|
* the caller is not permitted to modify threads |
2894 |
|
*/ |
2895 |
|
public void shutdown() { |
2896 |
|
checkPermission(); |
2897 |
< |
transitionRunStateTo(SHUTDOWN); |
2898 |
< |
if (canTerminateOnShutdown(runControl)) |
1090 |
< |
terminateOnShutdown(); |
2897 |
> |
if (this != commonPool) |
2898 |
> |
tryTerminate(false, true); |
2899 |
|
} |
2900 |
|
|
2901 |
|
/** |
2902 |
< |
* Attempts to stop all actively executing tasks, and cancels all |
2903 |
< |
* waiting tasks. Tasks that are in the process of being |
2904 |
< |
* submitted or executed concurrently during the course of this |
2905 |
< |
* method may or may not be rejected. Unlike some other executors, |
2906 |
< |
* this method cancels rather than collects non-executed tasks |
2907 |
< |
* upon termination, so always returns an empty list. However, you |
2908 |
< |
* can use method {@code drainTasksTo} before invoking this |
2909 |
< |
* method to transfer unexecuted tasks to another collection. |
2902 |
> |
* Possibly attempts to cancel and/or stop all tasks, and reject |
2903 |
> |
* all subsequently submitted tasks. Invocation has no effect on |
2904 |
> |
* execution state if this is the {@link #commonPool}, and no |
2905 |
> |
* additional effect if already shut down. Otherwise, tasks that |
2906 |
> |
* are in the process of being submitted or executed concurrently |
2907 |
> |
* during the course of this method may or may not be |
2908 |
> |
* rejected. This method cancels both existing and unexecuted |
2909 |
> |
* tasks, in order to permit termination in the presence of task |
2910 |
> |
* dependencies. So the method always returns an empty list |
2911 |
> |
* (unlike the case for some other Executors). |
2912 |
|
* |
2913 |
|
* @return an empty list |
2914 |
|
* @throws SecurityException if a security manager exists and |
2918 |
|
*/ |
2919 |
|
public List<Runnable> shutdownNow() { |
2920 |
|
checkPermission(); |
2921 |
< |
terminate(); |
2921 |
> |
if (this != commonPool) |
2922 |
> |
tryTerminate(true, true); |
2923 |
|
return Collections.emptyList(); |
2924 |
|
} |
2925 |
|
|
2929 |
|
* @return {@code true} if all tasks have completed following shut down |
2930 |
|
*/ |
2931 |
|
public boolean isTerminated() { |
2932 |
< |
return runStateOf(runControl) == TERMINATED; |
2932 |
> |
long c = ctl; |
2933 |
> |
return ((c & STOP_BIT) != 0L && |
2934 |
> |
(short)(c >>> TC_SHIFT) == -parallelism); |
2935 |
|
} |
2936 |
|
|
2937 |
|
/** |
2938 |
|
* Returns {@code true} if the process of termination has |
2939 |
< |
* commenced but possibly not yet completed. |
2939 |
> |
* commenced but not yet completed. This method may be useful for |
2940 |
> |
* debugging. A return of {@code true} reported a sufficient |
2941 |
> |
* period after shutdown may indicate that submitted tasks have |
2942 |
> |
* ignored or suppressed interruption, or are waiting for IO, |
2943 |
> |
* causing this executor not to properly terminate. (See the |
2944 |
> |
* advisory notes for class {@link ForkJoinTask} stating that |
2945 |
> |
* tasks should not normally entail blocking operations. But if |
2946 |
> |
* they do, they must abort them on interrupt.) |
2947 |
|
* |
2948 |
< |
* @return {@code true} if terminating |
2948 |
> |
* @return {@code true} if terminating but not yet terminated |
2949 |
|
*/ |
2950 |
|
public boolean isTerminating() { |
2951 |
< |
return runStateOf(runControl) >= TERMINATING; |
2951 |
> |
long c = ctl; |
2952 |
> |
return ((c & STOP_BIT) != 0L && |
2953 |
> |
(short)(c >>> TC_SHIFT) != -parallelism); |
2954 |
|
} |
2955 |
|
|
2956 |
|
/** |
2959 |
|
* @return {@code true} if this pool has been shut down |
2960 |
|
*/ |
2961 |
|
public boolean isShutdown() { |
2962 |
< |
return runStateOf(runControl) >= SHUTDOWN; |
2962 |
> |
return runState < 0; |
2963 |
|
} |
2964 |
|
|
2965 |
|
/** |
2976 |
|
public boolean awaitTermination(long timeout, TimeUnit unit) |
2977 |
|
throws InterruptedException { |
2978 |
|
long nanos = unit.toNanos(timeout); |
2979 |
< |
final ReentrantLock lock = this.workerLock; |
1158 |
< |
lock.lock(); |
1159 |
< |
try { |
1160 |
< |
for (;;) { |
1161 |
< |
if (isTerminated()) |
1162 |
< |
return true; |
1163 |
< |
if (nanos <= 0) |
1164 |
< |
return false; |
1165 |
< |
nanos = termination.awaitNanos(nanos); |
1166 |
< |
} |
1167 |
< |
} finally { |
1168 |
< |
lock.unlock(); |
1169 |
< |
} |
1170 |
< |
} |
1171 |
< |
|
1172 |
< |
// Shutdown and termination support |
1173 |
< |
|
1174 |
< |
/** |
1175 |
< |
* Callback from terminating worker. Nulls out the corresponding |
1176 |
< |
* workers slot, and if terminating, tries to terminate; else |
1177 |
< |
* tries to shrink workers array. |
1178 |
< |
* |
1179 |
< |
* @param w the worker |
1180 |
< |
*/ |
1181 |
< |
final void workerTerminated(ForkJoinWorkerThread w) { |
1182 |
< |
updateStealCount(w); |
1183 |
< |
updateWorkerCount(-1); |
1184 |
< |
final ReentrantLock lock = this.workerLock; |
1185 |
< |
lock.lock(); |
1186 |
< |
try { |
1187 |
< |
ForkJoinWorkerThread[] ws = workers; |
1188 |
< |
if (ws != null) { |
1189 |
< |
int idx = w.poolIndex; |
1190 |
< |
if (idx >= 0 && idx < ws.length && ws[idx] == w) |
1191 |
< |
ws[idx] = null; |
1192 |
< |
if (totalCountOf(workerCounts) == 0) { |
1193 |
< |
terminate(); // no-op if already terminating |
1194 |
< |
transitionRunStateTo(TERMINATED); |
1195 |
< |
termination.signalAll(); |
1196 |
< |
} |
1197 |
< |
else if (!isTerminating()) { |
1198 |
< |
tryShrinkWorkerArray(); |
1199 |
< |
tryResumeSpare(true); // allow replacement |
1200 |
< |
} |
1201 |
< |
} |
1202 |
< |
} finally { |
1203 |
< |
lock.unlock(); |
1204 |
< |
} |
1205 |
< |
signalIdleWorkers(); |
1206 |
< |
} |
1207 |
< |
|
1208 |
< |
/** |
1209 |
< |
* Initiates termination. |
1210 |
< |
*/ |
1211 |
< |
private void terminate() { |
1212 |
< |
if (transitionRunStateTo(TERMINATING)) { |
1213 |
< |
stopAllWorkers(); |
1214 |
< |
resumeAllSpares(); |
1215 |
< |
signalIdleWorkers(); |
1216 |
< |
cancelQueuedSubmissions(); |
1217 |
< |
cancelQueuedWorkerTasks(); |
1218 |
< |
interruptUnterminatedWorkers(); |
1219 |
< |
signalIdleWorkers(); // resignal after interrupt |
1220 |
< |
} |
1221 |
< |
} |
1222 |
< |
|
1223 |
< |
/** |
1224 |
< |
* Possibly terminates when on shutdown state. |
1225 |
< |
*/ |
1226 |
< |
private void terminateOnShutdown() { |
1227 |
< |
if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl)) |
1228 |
< |
terminate(); |
1229 |
< |
} |
1230 |
< |
|
1231 |
< |
/** |
1232 |
< |
* Clears out and cancels submissions. |
1233 |
< |
*/ |
1234 |
< |
private void cancelQueuedSubmissions() { |
1235 |
< |
ForkJoinTask<?> task; |
1236 |
< |
while ((task = pollSubmission()) != null) |
1237 |
< |
task.cancel(false); |
1238 |
< |
} |
1239 |
< |
|
1240 |
< |
/** |
1241 |
< |
* Cleans out worker queues. |
1242 |
< |
*/ |
1243 |
< |
private void cancelQueuedWorkerTasks() { |
1244 |
< |
final ReentrantLock lock = this.workerLock; |
1245 |
< |
lock.lock(); |
1246 |
< |
try { |
1247 |
< |
ForkJoinWorkerThread[] ws = workers; |
1248 |
< |
if (ws != null) { |
1249 |
< |
for (int i = 0; i < ws.length; ++i) { |
1250 |
< |
ForkJoinWorkerThread t = ws[i]; |
1251 |
< |
if (t != null) |
1252 |
< |
t.cancelTasks(); |
1253 |
< |
} |
1254 |
< |
} |
1255 |
< |
} finally { |
1256 |
< |
lock.unlock(); |
1257 |
< |
} |
1258 |
< |
} |
1259 |
< |
|
1260 |
< |
/** |
1261 |
< |
* Sets each worker's status to terminating. Requires lock to avoid |
1262 |
< |
* conflicts with add/remove. |
1263 |
< |
*/ |
1264 |
< |
private void stopAllWorkers() { |
1265 |
< |
final ReentrantLock lock = this.workerLock; |
1266 |
< |
lock.lock(); |
1267 |
< |
try { |
1268 |
< |
ForkJoinWorkerThread[] ws = workers; |
1269 |
< |
if (ws != null) { |
1270 |
< |
for (int i = 0; i < ws.length; ++i) { |
1271 |
< |
ForkJoinWorkerThread t = ws[i]; |
1272 |
< |
if (t != null) |
1273 |
< |
t.shutdownNow(); |
1274 |
< |
} |
1275 |
< |
} |
1276 |
< |
} finally { |
1277 |
< |
lock.unlock(); |
1278 |
< |
} |
1279 |
< |
} |
1280 |
< |
|
1281 |
< |
/** |
1282 |
< |
* Interrupts all unterminated workers. This is not required for |
1283 |
< |
* sake of internal control, but may help unstick user code during |
1284 |
< |
* shutdown. |
1285 |
< |
*/ |
1286 |
< |
private void interruptUnterminatedWorkers() { |
1287 |
< |
final ReentrantLock lock = this.workerLock; |
1288 |
< |
lock.lock(); |
1289 |
< |
try { |
1290 |
< |
ForkJoinWorkerThread[] ws = workers; |
1291 |
< |
if (ws != null) { |
1292 |
< |
for (int i = 0; i < ws.length; ++i) { |
1293 |
< |
ForkJoinWorkerThread t = ws[i]; |
1294 |
< |
if (t != null && !t.isTerminated()) { |
1295 |
< |
try { |
1296 |
< |
t.interrupt(); |
1297 |
< |
} catch (SecurityException ignore) { |
1298 |
< |
} |
1299 |
< |
} |
1300 |
< |
} |
1301 |
< |
} |
1302 |
< |
} finally { |
1303 |
< |
lock.unlock(); |
1304 |
< |
} |
1305 |
< |
} |
1306 |
< |
|
1307 |
< |
|
1308 |
< |
/* |
1309 |
< |
* Nodes for event barrier to manage idle threads. Queue nodes |
1310 |
< |
* are basic Treiber stack nodes, also used for spare stack. |
1311 |
< |
* |
1312 |
< |
* The event barrier has an event count and a wait queue (actually |
1313 |
< |
* a Treiber stack). Workers are enabled to look for work when |
1314 |
< |
* the eventCount is incremented. If they fail to find work, they |
1315 |
< |
* may wait for next count. Upon release, threads help others wake |
1316 |
< |
* up. |
1317 |
< |
* |
1318 |
< |
* Synchronization events occur only in enough contexts to |
1319 |
< |
* maintain overall liveness: |
1320 |
< |
* |
1321 |
< |
* - Submission of a new task to the pool |
1322 |
< |
* - Resizes or other changes to the workers array |
1323 |
< |
* - pool termination |
1324 |
< |
* - A worker pushing a task on an empty queue |
1325 |
< |
* |
1326 |
< |
* The case of pushing a task occurs often enough, and is heavy |
1327 |
< |
* enough compared to simple stack pushes, to require special |
1328 |
< |
* handling: Method signalWork returns without advancing count if |
1329 |
< |
* the queue appears to be empty. This would ordinarily result in |
1330 |
< |
* races causing some queued waiters not to be woken up. To avoid |
1331 |
< |
* this, the first worker enqueued in method sync (see |
1332 |
< |
* syncIsReleasable) rescans for tasks after being enqueued, and |
1333 |
< |
* helps signal if any are found. This works well because the |
1334 |
< |
* worker has nothing better to do, and so might as well help |
1335 |
< |
* alleviate the overhead and contention on the threads actually |
1336 |
< |
* doing work. Also, since event counts increments on task |
1337 |
< |
* availability exist to maintain liveness (rather than to force |
1338 |
< |
* refreshes etc), it is OK for callers to exit early if |
1339 |
< |
* contending with another signaller. |
1340 |
< |
*/ |
1341 |
< |
static final class WaitQueueNode { |
1342 |
< |
WaitQueueNode next; // only written before enqueued |
1343 |
< |
volatile ForkJoinWorkerThread thread; // nulled to cancel wait |
1344 |
< |
final long count; // unused for spare stack |
1345 |
< |
|
1346 |
< |
WaitQueueNode(long c, ForkJoinWorkerThread w) { |
1347 |
< |
count = c; |
1348 |
< |
thread = w; |
1349 |
< |
} |
1350 |
< |
|
1351 |
< |
/** |
1352 |
< |
* Wakes up waiter, returning false if known to already |
1353 |
< |
*/ |
1354 |
< |
boolean signal() { |
1355 |
< |
ForkJoinWorkerThread t = thread; |
1356 |
< |
if (t == null) |
1357 |
< |
return false; |
1358 |
< |
thread = null; |
1359 |
< |
LockSupport.unpark(t); |
2979 |
> |
if (isTerminated()) |
2980 |
|
return true; |
2981 |
< |
} |
2982 |
< |
|
2983 |
< |
/** |
2984 |
< |
* Awaits release on sync. |
2985 |
< |
*/ |
2986 |
< |
void awaitSyncRelease(ForkJoinPool p) { |
2987 |
< |
while (thread != null && !p.syncIsReleasable(this)) |
1368 |
< |
LockSupport.park(this); |
1369 |
< |
} |
1370 |
< |
|
1371 |
< |
/** |
1372 |
< |
* Awaits resumption as spare. |
1373 |
< |
*/ |
1374 |
< |
void awaitSpareRelease() { |
1375 |
< |
while (thread != null) { |
1376 |
< |
if (!Thread.interrupted()) |
1377 |
< |
LockSupport.park(this); |
1378 |
< |
} |
1379 |
< |
} |
1380 |
< |
} |
1381 |
< |
|
1382 |
< |
/** |
1383 |
< |
* Ensures that no thread is waiting for count to advance from the |
1384 |
< |
* current value of eventCount read on entry to this method, by |
1385 |
< |
* releasing waiting threads if necessary. |
1386 |
< |
* |
1387 |
< |
* @return the count |
1388 |
< |
*/ |
1389 |
< |
final long ensureSync() { |
1390 |
< |
long c = eventCount; |
1391 |
< |
WaitQueueNode q; |
1392 |
< |
while ((q = syncStack) != null && q.count < c) { |
1393 |
< |
if (casBarrierStack(q, null)) { |
1394 |
< |
do { |
1395 |
< |
q.signal(); |
1396 |
< |
} while ((q = q.next) != null); |
1397 |
< |
break; |
1398 |
< |
} |
1399 |
< |
} |
1400 |
< |
return c; |
1401 |
< |
} |
1402 |
< |
|
1403 |
< |
/** |
1404 |
< |
* Increments event count and releases waiting threads. |
1405 |
< |
*/ |
1406 |
< |
private void signalIdleWorkers() { |
1407 |
< |
long c; |
1408 |
< |
do {} while (!casEventCount(c = eventCount, c+1)); |
1409 |
< |
ensureSync(); |
1410 |
< |
} |
1411 |
< |
|
1412 |
< |
/** |
1413 |
< |
* Signals threads waiting to poll a task. Because method sync |
1414 |
< |
* rechecks availability, it is OK to only proceed if queue |
1415 |
< |
* appears to be non-empty, and OK to skip under contention to |
1416 |
< |
* increment count (since some other thread succeeded). |
1417 |
< |
*/ |
1418 |
< |
final void signalWork() { |
1419 |
< |
long c; |
1420 |
< |
WaitQueueNode q; |
1421 |
< |
if (syncStack != null && |
1422 |
< |
casEventCount(c = eventCount, c+1) && |
1423 |
< |
(((q = syncStack) != null && q.count <= c) && |
1424 |
< |
(!casBarrierStack(q, q.next) || !q.signal()))) |
1425 |
< |
ensureSync(); |
1426 |
< |
} |
1427 |
< |
|
1428 |
< |
/** |
1429 |
< |
* Waits until event count advances from last value held by |
1430 |
< |
* caller, or if excess threads, caller is resumed as spare, or |
1431 |
< |
* caller or pool is terminating. Updates caller's event on exit. |
1432 |
< |
* |
1433 |
< |
* @param w the calling worker thread |
1434 |
< |
*/ |
1435 |
< |
final void sync(ForkJoinWorkerThread w) { |
1436 |
< |
updateStealCount(w); // Transfer w's count while it is idle |
1437 |
< |
|
1438 |
< |
while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) { |
1439 |
< |
long prev = w.lastEventCount; |
1440 |
< |
WaitQueueNode node = null; |
1441 |
< |
WaitQueueNode h; |
1442 |
< |
while (eventCount == prev && |
1443 |
< |
((h = syncStack) == null || h.count == prev)) { |
1444 |
< |
if (node == null) |
1445 |
< |
node = new WaitQueueNode(prev, w); |
1446 |
< |
if (casBarrierStack(node.next = h, node)) { |
1447 |
< |
node.awaitSyncRelease(this); |
1448 |
< |
break; |
1449 |
< |
} |
1450 |
< |
} |
1451 |
< |
long ec = ensureSync(); |
1452 |
< |
if (ec != prev) { |
1453 |
< |
w.lastEventCount = ec; |
1454 |
< |
break; |
1455 |
< |
} |
1456 |
< |
} |
1457 |
< |
} |
1458 |
< |
|
1459 |
< |
/** |
1460 |
< |
* Returns true if worker waiting on sync can proceed: |
1461 |
< |
* - on signal (thread == null) |
1462 |
< |
* - on event count advance (winning race to notify vs signaller) |
1463 |
< |
* - on interrupt |
1464 |
< |
* - if the first queued node, we find work available |
1465 |
< |
* If node was not signalled and event count not advanced on exit, |
1466 |
< |
* then we also help advance event count. |
1467 |
< |
* |
1468 |
< |
* @return true if node can be released |
1469 |
< |
*/ |
1470 |
< |
final boolean syncIsReleasable(WaitQueueNode node) { |
1471 |
< |
long prev = node.count; |
1472 |
< |
if (!Thread.interrupted() && node.thread != null && |
1473 |
< |
(node.next != null || |
1474 |
< |
!ForkJoinWorkerThread.hasQueuedTasks(workers)) && |
1475 |
< |
eventCount == prev) |
1476 |
< |
return false; |
1477 |
< |
if (node.thread != null) { |
1478 |
< |
node.thread = null; |
1479 |
< |
long ec = eventCount; |
1480 |
< |
if (prev <= ec) // help signal |
1481 |
< |
casEventCount(ec, ec+1); |
1482 |
< |
} |
1483 |
< |
return true; |
1484 |
< |
} |
1485 |
< |
|
1486 |
< |
/** |
1487 |
< |
* Returns true if a new sync event occurred since last call to |
1488 |
< |
* sync or this method, if so, updating caller's count. |
1489 |
< |
*/ |
1490 |
< |
final boolean hasNewSyncEvent(ForkJoinWorkerThread w) { |
1491 |
< |
long lc = w.lastEventCount; |
1492 |
< |
long ec = ensureSync(); |
1493 |
< |
if (ec == lc) |
1494 |
< |
return false; |
1495 |
< |
w.lastEventCount = ec; |
1496 |
< |
return true; |
1497 |
< |
} |
1498 |
< |
|
1499 |
< |
// Parallelism maintenance |
1500 |
< |
|
1501 |
< |
/** |
1502 |
< |
* Decrements running count; if too low, adds spare. |
1503 |
< |
* |
1504 |
< |
* Conceptually, all we need to do here is add or resume a |
1505 |
< |
* spare thread when one is about to block (and remove or |
1506 |
< |
* suspend it later when unblocked -- see suspendIfSpare). |
1507 |
< |
* However, implementing this idea requires coping with |
1508 |
< |
* several problems: we have imperfect information about the |
1509 |
< |
* states of threads. Some count updates can and usually do |
1510 |
< |
* lag run state changes, despite arrangements to keep them |
1511 |
< |
* accurate (for example, when possible, updating counts |
1512 |
< |
* before signalling or resuming), especially when running on |
1513 |
< |
* dynamic JVMs that don't optimize the infrequent paths that |
1514 |
< |
* update counts. Generating too many threads can make these |
1515 |
< |
* problems become worse, because excess threads are more |
1516 |
< |
* likely to be context-switched with others, slowing them all |
1517 |
< |
* down, especially if there is no work available, so all are |
1518 |
< |
* busy scanning or idling. Also, excess spare threads can |
1519 |
< |
* only be suspended or removed when they are idle, not |
1520 |
< |
* immediately when they aren't needed. So adding threads will |
1521 |
< |
* raise parallelism level for longer than necessary. Also, |
1522 |
< |
* FJ applications often encounter highly transient peaks when |
1523 |
< |
* many threads are blocked joining, but for less time than it |
1524 |
< |
* takes to create or resume spares. |
1525 |
< |
* |
1526 |
< |
* @param joinMe if non-null, return early if done |
1527 |
< |
* @param maintainParallelism if true, try to stay within |
1528 |
< |
* target counts, else create only to avoid starvation |
1529 |
< |
* @return true if joinMe known to be done |
1530 |
< |
*/ |
1531 |
< |
final boolean preJoin(ForkJoinTask<?> joinMe, |
1532 |
< |
boolean maintainParallelism) { |
1533 |
< |
maintainParallelism &= maintainsParallelism; // overrride |
1534 |
< |
boolean dec = false; // true when running count decremented |
1535 |
< |
while (spareStack == null || !tryResumeSpare(dec)) { |
1536 |
< |
int counts = workerCounts; |
1537 |
< |
if (dec || (dec = casWorkerCounts(counts, --counts))) { |
1538 |
< |
// CAS cheat |
1539 |
< |
if (!needSpare(counts, maintainParallelism)) |
1540 |
< |
break; |
1541 |
< |
if (joinMe.status < 0) |
1542 |
< |
return true; |
1543 |
< |
if (tryAddSpare(counts)) |
2981 |
> |
long startTime = System.nanoTime(); |
2982 |
> |
boolean terminated = false; |
2983 |
> |
synchronized (this) { |
2984 |
> |
for (long waitTime = nanos, millis = 0L;;) { |
2985 |
> |
if (terminated = isTerminated() || |
2986 |
> |
waitTime <= 0L || |
2987 |
> |
(millis = unit.toMillis(waitTime)) <= 0L) |
2988 |
|
break; |
2989 |
+ |
wait(millis); |
2990 |
+ |
waitTime = nanos - (System.nanoTime() - startTime); |
2991 |
|
} |
2992 |
|
} |
2993 |
< |
return false; |
1548 |
< |
} |
1549 |
< |
|
1550 |
< |
/** |
1551 |
< |
* Same idea as preJoin |
1552 |
< |
*/ |
1553 |
< |
final boolean preBlock(ManagedBlocker blocker, |
1554 |
< |
boolean maintainParallelism) { |
1555 |
< |
maintainParallelism &= maintainsParallelism; |
1556 |
< |
boolean dec = false; |
1557 |
< |
while (spareStack == null || !tryResumeSpare(dec)) { |
1558 |
< |
int counts = workerCounts; |
1559 |
< |
if (dec || (dec = casWorkerCounts(counts, --counts))) { |
1560 |
< |
if (!needSpare(counts, maintainParallelism)) |
1561 |
< |
break; |
1562 |
< |
if (blocker.isReleasable()) |
1563 |
< |
return true; |
1564 |
< |
if (tryAddSpare(counts)) |
1565 |
< |
break; |
1566 |
< |
} |
1567 |
< |
} |
1568 |
< |
return false; |
1569 |
< |
} |
1570 |
< |
|
1571 |
< |
/** |
1572 |
< |
* Returns true if a spare thread appears to be needed. If |
1573 |
< |
* maintaining parallelism, returns true when the deficit in |
1574 |
< |
* running threads is more than the surplus of total threads, and |
1575 |
< |
* there is apparently some work to do. This self-limiting rule |
1576 |
< |
* means that the more threads that have already been added, the |
1577 |
< |
* less parallelism we will tolerate before adding another. |
1578 |
< |
* |
1579 |
< |
* @param counts current worker counts |
1580 |
< |
* @param maintainParallelism try to maintain parallelism |
1581 |
< |
*/ |
1582 |
< |
private boolean needSpare(int counts, boolean maintainParallelism) { |
1583 |
< |
int ps = parallelism; |
1584 |
< |
int rc = runningCountOf(counts); |
1585 |
< |
int tc = totalCountOf(counts); |
1586 |
< |
int runningDeficit = ps - rc; |
1587 |
< |
int totalSurplus = tc - ps; |
1588 |
< |
return (tc < maxPoolSize && |
1589 |
< |
(rc == 0 || totalSurplus < 0 || |
1590 |
< |
(maintainParallelism && |
1591 |
< |
runningDeficit > totalSurplus && |
1592 |
< |
ForkJoinWorkerThread.hasQueuedTasks(workers)))); |
1593 |
< |
} |
1594 |
< |
|
1595 |
< |
/** |
1596 |
< |
* Adds a spare worker if lock available and no more than the |
1597 |
< |
* expected numbers of threads exist. |
1598 |
< |
* |
1599 |
< |
* @return true if successful |
1600 |
< |
*/ |
1601 |
< |
private boolean tryAddSpare(int expectedCounts) { |
1602 |
< |
final ReentrantLock lock = this.workerLock; |
1603 |
< |
int expectedRunning = runningCountOf(expectedCounts); |
1604 |
< |
int expectedTotal = totalCountOf(expectedCounts); |
1605 |
< |
boolean success = false; |
1606 |
< |
boolean locked = false; |
1607 |
< |
// confirm counts while locking; CAS after obtaining lock |
1608 |
< |
try { |
1609 |
< |
for (;;) { |
1610 |
< |
int s = workerCounts; |
1611 |
< |
int tc = totalCountOf(s); |
1612 |
< |
int rc = runningCountOf(s); |
1613 |
< |
if (rc > expectedRunning || tc > expectedTotal) |
1614 |
< |
break; |
1615 |
< |
if (!locked && !(locked = lock.tryLock())) |
1616 |
< |
break; |
1617 |
< |
if (casWorkerCounts(s, workerCountsFor(tc+1, rc+1))) { |
1618 |
< |
createAndStartSpare(tc); |
1619 |
< |
success = true; |
1620 |
< |
break; |
1621 |
< |
} |
1622 |
< |
} |
1623 |
< |
} finally { |
1624 |
< |
if (locked) |
1625 |
< |
lock.unlock(); |
1626 |
< |
} |
1627 |
< |
return success; |
1628 |
< |
} |
1629 |
< |
|
1630 |
< |
/** |
1631 |
< |
* Adds the kth spare worker. On entry, pool counts are already |
1632 |
< |
* adjusted to reflect addition. |
1633 |
< |
*/ |
1634 |
< |
private void createAndStartSpare(int k) { |
1635 |
< |
ForkJoinWorkerThread w = null; |
1636 |
< |
ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(k + 1); |
1637 |
< |
int len = ws.length; |
1638 |
< |
// Probably, we can place at slot k. If not, find empty slot |
1639 |
< |
if (k < len && ws[k] != null) { |
1640 |
< |
for (k = 0; k < len && ws[k] != null; ++k) |
1641 |
< |
; |
1642 |
< |
} |
1643 |
< |
if (k < len && !isTerminating() && (w = createWorker(k)) != null) { |
1644 |
< |
ws[k] = w; |
1645 |
< |
w.start(); |
1646 |
< |
} |
1647 |
< |
else |
1648 |
< |
updateWorkerCount(-1); // adjust on failure |
1649 |
< |
signalIdleWorkers(); |
1650 |
< |
} |
1651 |
< |
|
1652 |
< |
/** |
1653 |
< |
* Suspends calling thread w if there are excess threads. Called |
1654 |
< |
* only from sync. Spares are enqueued in a Treiber stack using |
1655 |
< |
* the same WaitQueueNodes as barriers. They are resumed mainly |
1656 |
< |
* in preJoin, but are also woken on pool events that require all |
1657 |
< |
* threads to check run state. |
1658 |
< |
* |
1659 |
< |
* @param w the caller |
1660 |
< |
*/ |
1661 |
< |
private boolean suspendIfSpare(ForkJoinWorkerThread w) { |
1662 |
< |
WaitQueueNode node = null; |
1663 |
< |
int s; |
1664 |
< |
while (parallelism < runningCountOf(s = workerCounts)) { |
1665 |
< |
if (node == null) |
1666 |
< |
node = new WaitQueueNode(0, w); |
1667 |
< |
if (casWorkerCounts(s, s-1)) { // representation-dependent |
1668 |
< |
// push onto stack |
1669 |
< |
do {} while (!casSpareStack(node.next = spareStack, node)); |
1670 |
< |
// block until released by resumeSpare |
1671 |
< |
node.awaitSpareRelease(); |
1672 |
< |
return true; |
1673 |
< |
} |
1674 |
< |
} |
1675 |
< |
return false; |
1676 |
< |
} |
1677 |
< |
|
1678 |
< |
/** |
1679 |
< |
* Tries to pop and resume a spare thread. |
1680 |
< |
* |
1681 |
< |
* @param updateCount if true, increment running count on success |
1682 |
< |
* @return true if successful |
1683 |
< |
*/ |
1684 |
< |
private boolean tryResumeSpare(boolean updateCount) { |
1685 |
< |
WaitQueueNode q; |
1686 |
< |
while ((q = spareStack) != null) { |
1687 |
< |
if (casSpareStack(q, q.next)) { |
1688 |
< |
if (updateCount) |
1689 |
< |
updateRunningCount(1); |
1690 |
< |
q.signal(); |
1691 |
< |
return true; |
1692 |
< |
} |
1693 |
< |
} |
1694 |
< |
return false; |
1695 |
< |
} |
1696 |
< |
|
1697 |
< |
/** |
1698 |
< |
* Pops and resumes all spare threads. Same idea as ensureSync. |
1699 |
< |
* |
1700 |
< |
* @return true if any spares released |
1701 |
< |
*/ |
1702 |
< |
private boolean resumeAllSpares() { |
1703 |
< |
WaitQueueNode q; |
1704 |
< |
while ( (q = spareStack) != null) { |
1705 |
< |
if (casSpareStack(q, null)) { |
1706 |
< |
do { |
1707 |
< |
updateRunningCount(1); |
1708 |
< |
q.signal(); |
1709 |
< |
} while ((q = q.next) != null); |
1710 |
< |
return true; |
1711 |
< |
} |
1712 |
< |
} |
1713 |
< |
return false; |
1714 |
< |
} |
1715 |
< |
|
1716 |
< |
/** |
1717 |
< |
* Pops and shuts down excessive spare threads. Call only while |
1718 |
< |
* holding lock. This is not guaranteed to eliminate all excess |
1719 |
< |
* threads, only those suspended as spares, which are the ones |
1720 |
< |
* unlikely to be needed in the future. |
1721 |
< |
*/ |
1722 |
< |
private void trimSpares() { |
1723 |
< |
int surplus = totalCountOf(workerCounts) - parallelism; |
1724 |
< |
WaitQueueNode q; |
1725 |
< |
while (surplus > 0 && (q = spareStack) != null) { |
1726 |
< |
if (casSpareStack(q, null)) { |
1727 |
< |
do { |
1728 |
< |
updateRunningCount(1); |
1729 |
< |
ForkJoinWorkerThread w = q.thread; |
1730 |
< |
if (w != null && surplus > 0 && |
1731 |
< |
runningCountOf(workerCounts) > 0 && w.shutdown()) |
1732 |
< |
--surplus; |
1733 |
< |
q.signal(); |
1734 |
< |
} while ((q = q.next) != null); |
1735 |
< |
} |
1736 |
< |
} |
2993 |
> |
return terminated; |
2994 |
|
} |
2995 |
|
|
2996 |
|
/** |
2997 |
|
* Interface for extending managed parallelism for tasks running |
2998 |
< |
* in ForkJoinPools. A ManagedBlocker provides two methods. |
2999 |
< |
* Method {@code isReleasable} must return true if blocking is not |
3000 |
< |
* necessary. Method {@code block} blocks the current thread if |
3001 |
< |
* necessary (perhaps internally invoking {@code isReleasable} |
3002 |
< |
* before actually blocking.). |
2998 |
> |
* in {@link ForkJoinPool}s. |
2999 |
> |
* |
3000 |
> |
* <p>A {@code ManagedBlocker} provides two methods. Method |
3001 |
> |
* {@code isReleasable} must return {@code true} if blocking is |
3002 |
> |
* not necessary. Method {@code block} blocks the current thread |
3003 |
> |
* if necessary (perhaps internally invoking {@code isReleasable} |
3004 |
> |
* before actually blocking). These actions are performed by any |
3005 |
> |
* thread invoking {@link ForkJoinPool#managedBlock}. The |
3006 |
> |
* unusual methods in this API accommodate synchronizers that may, |
3007 |
> |
* but don't usually, block for long periods. Similarly, they |
3008 |
> |
* allow more efficient internal handling of cases in which |
3009 |
> |
* additional workers may be, but usually are not, needed to |
3010 |
> |
* ensure sufficient parallelism. Toward this end, |
3011 |
> |
* implementations of method {@code isReleasable} must be amenable |
3012 |
> |
* to repeated invocation. |
3013 |
|
* |
3014 |
|
* <p>For example, here is a ManagedBlocker based on a |
3015 |
|
* ReentrantLock: |
3027 |
|
* return hasLock || (hasLock = lock.tryLock()); |
3028 |
|
* } |
3029 |
|
* }}</pre> |
3030 |
+ |
* |
3031 |
+ |
* <p>Here is a class that possibly blocks waiting for an |
3032 |
+ |
* item on a given queue: |
3033 |
+ |
* <pre> {@code |
3034 |
+ |
* class QueueTaker<E> implements ManagedBlocker { |
3035 |
+ |
* final BlockingQueue<E> queue; |
3036 |
+ |
* volatile E item = null; |
3037 |
+ |
* QueueTaker(BlockingQueue<E> q) { this.queue = q; } |
3038 |
+ |
* public boolean block() throws InterruptedException { |
3039 |
+ |
* if (item == null) |
3040 |
+ |
* item = queue.take(); |
3041 |
+ |
* return true; |
3042 |
+ |
* } |
3043 |
+ |
* public boolean isReleasable() { |
3044 |
+ |
* return item != null || (item = queue.poll()) != null; |
3045 |
+ |
* } |
3046 |
+ |
* public E getItem() { // call after pool.managedBlock completes |
3047 |
+ |
* return item; |
3048 |
+ |
* } |
3049 |
+ |
* }}</pre> |
3050 |
|
*/ |
3051 |
|
public static interface ManagedBlocker { |
3052 |
|
/** |
3053 |
|
* Possibly blocks the current thread, for example waiting for |
3054 |
|
* a lock or condition. |
3055 |
|
* |
3056 |
< |
* @return true if no additional blocking is necessary (i.e., |
3057 |
< |
* if isReleasable would return true) |
3056 |
> |
* @return {@code true} if no additional blocking is necessary |
3057 |
> |
* (i.e., if isReleasable would return true) |
3058 |
|
* @throws InterruptedException if interrupted while waiting |
3059 |
|
* (the method is not required to do so, but is allowed to) |
3060 |
|
*/ |
3061 |
|
boolean block() throws InterruptedException; |
3062 |
|
|
3063 |
|
/** |
3064 |
< |
* Returns true if blocking is unnecessary. |
3064 |
> |
* Returns {@code true} if blocking is unnecessary. |
3065 |
|
*/ |
3066 |
|
boolean isReleasable(); |
3067 |
|
} |
3068 |
|
|
3069 |
|
/** |
3070 |
|
* Blocks in accord with the given blocker. If the current thread |
3071 |
< |
* is a ForkJoinWorkerThread, this method possibly arranges for a |
3072 |
< |
* spare thread to be activated if necessary to ensure parallelism |
3073 |
< |
* while the current thread is blocked. If |
1787 |
< |
* {@code maintainParallelism} is true and the pool supports |
1788 |
< |
* it ({@link #getMaintainsParallelism}), this method attempts to |
1789 |
< |
* maintain the pool's nominal parallelism. Otherwise it activates |
1790 |
< |
* a thread only if necessary to avoid complete starvation. This |
1791 |
< |
* option may be preferable when blockages use timeouts, or are |
1792 |
< |
* almost always brief. |
3071 |
> |
* is a {@link ForkJoinWorkerThread}, this method possibly |
3072 |
> |
* arranges for a spare thread to be activated if necessary to |
3073 |
> |
* ensure sufficient parallelism while the current thread is blocked. |
3074 |
|
* |
3075 |
< |
* <p> If the caller is not a ForkJoinTask, this method is behaviorally |
3076 |
< |
* equivalent to |
3075 |
> |
* <p>If the caller is not a {@link ForkJoinTask}, this method is |
3076 |
> |
* behaviorally equivalent to |
3077 |
|
* <pre> {@code |
3078 |
|
* while (!blocker.isReleasable()) |
3079 |
|
* if (blocker.block()) |
3080 |
|
* return; |
3081 |
|
* }</pre> |
3082 |
< |
* If the caller is a ForkJoinTask, then the pool may first |
3083 |
< |
* be expanded to ensure parallelism, and later adjusted. |
3082 |
> |
* |
3083 |
> |
* If the caller is a {@code ForkJoinTask}, then the pool may |
3084 |
> |
* first be expanded to ensure parallelism, and later adjusted. |
3085 |
|
* |
3086 |
|
* @param blocker the blocker |
1805 |
– |
* @param maintainParallelism if true and supported by this pool, |
1806 |
– |
* attempt to maintain the pool's nominal parallelism; otherwise |
1807 |
– |
* activate a thread only if necessary to avoid complete |
1808 |
– |
* starvation. |
3087 |
|
* @throws InterruptedException if blocker.block did so |
3088 |
|
*/ |
3089 |
< |
public static void managedBlock(ManagedBlocker blocker, |
1812 |
< |
boolean maintainParallelism) |
3089 |
> |
public static void managedBlock(ManagedBlocker blocker) |
3090 |
|
throws InterruptedException { |
3091 |
|
Thread t = Thread.currentThread(); |
3092 |
< |
ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ? |
3093 |
< |
((ForkJoinWorkerThread) t).pool : null); |
3094 |
< |
if (!blocker.isReleasable()) { |
3095 |
< |
try { |
3096 |
< |
if (pool == null || |
3097 |
< |
!pool.preBlock(blocker, maintainParallelism)) |
3098 |
< |
awaitBlocker(blocker); |
3099 |
< |
} finally { |
3100 |
< |
if (pool != null) |
3101 |
< |
pool.updateRunningCount(1); |
3092 |
> |
ForkJoinPool p = ((t instanceof ForkJoinWorkerThread) ? |
3093 |
> |
((ForkJoinWorkerThread)t).pool : null); |
3094 |
> |
while (!blocker.isReleasable()) { |
3095 |
> |
if (p == null || p.tryCompensate(null, blocker)) { |
3096 |
> |
try { |
3097 |
> |
do {} while (!blocker.isReleasable() && !blocker.block()); |
3098 |
> |
} finally { |
3099 |
> |
if (p != null) |
3100 |
> |
p.incrementActiveCount(); |
3101 |
> |
} |
3102 |
> |
break; |
3103 |
|
} |
3104 |
|
} |
3105 |
|
} |
3106 |
|
|
3107 |
< |
private static void awaitBlocker(ManagedBlocker blocker) |
3108 |
< |
throws InterruptedException { |
3109 |
< |
do {} while (!blocker.isReleasable() && !blocker.block()); |
1832 |
< |
} |
1833 |
< |
|
1834 |
< |
// AbstractExecutorService overrides |
3107 |
> |
// AbstractExecutorService overrides. These rely on undocumented |
3108 |
> |
// fact that ForkJoinTask.adapt returns ForkJoinTasks that also |
3109 |
> |
// implement RunnableFuture. |
3110 |
|
|
3111 |
|
protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) { |
3112 |
< |
return new AdaptedRunnable(runnable, value); |
3112 |
> |
return new ForkJoinTask.AdaptedRunnable<T>(runnable, value); |
3113 |
|
} |
3114 |
|
|
3115 |
|
protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) { |
3116 |
< |
return new AdaptedCallable(callable); |
3116 |
> |
return new ForkJoinTask.AdaptedCallable<T>(callable); |
3117 |
|
} |
3118 |
|
|
3119 |
+ |
// Unsafe mechanics |
3120 |
+ |
private static final sun.misc.Unsafe U; |
3121 |
+ |
private static final long CTL; |
3122 |
+ |
private static final long PARKBLOCKER; |
3123 |
+ |
private static final int ABASE; |
3124 |
+ |
private static final int ASHIFT; |
3125 |
+ |
private static final long NEXTWORKERNUMBER; |
3126 |
+ |
private static final long STEALCOUNT; |
3127 |
+ |
private static final long MAINLOCK; |
3128 |
|
|
3129 |
< |
// Temporary Unsafe mechanics for preliminary release |
3130 |
< |
private static Unsafe getUnsafe() throws Throwable { |
3129 |
> |
static { |
3130 |
> |
poolNumberGenerator = new AtomicInteger(); |
3131 |
> |
nextSubmitterSeed = new AtomicInteger(0x55555555); |
3132 |
> |
modifyThreadPermission = new RuntimePermission("modifyThread"); |
3133 |
> |
defaultForkJoinWorkerThreadFactory = |
3134 |
> |
new DefaultForkJoinWorkerThreadFactory(); |
3135 |
> |
submitters = new ThreadSubmitter(); |
3136 |
> |
int s; |
3137 |
|
try { |
3138 |
< |
return Unsafe.getUnsafe(); |
3138 |
> |
U = getUnsafe(); |
3139 |
> |
Class<?> k = ForkJoinPool.class; |
3140 |
> |
Class<?> ak = ForkJoinTask[].class; |
3141 |
> |
CTL = U.objectFieldOffset |
3142 |
> |
(k.getDeclaredField("ctl")); |
3143 |
> |
NEXTWORKERNUMBER = U.objectFieldOffset |
3144 |
> |
(k.getDeclaredField("nextWorkerNumber")); |
3145 |
> |
STEALCOUNT = U.objectFieldOffset |
3146 |
> |
(k.getDeclaredField("stealCount")); |
3147 |
> |
MAINLOCK = U.objectFieldOffset |
3148 |
> |
(k.getDeclaredField("mainLock")); |
3149 |
> |
Class<?> tk = Thread.class; |
3150 |
> |
PARKBLOCKER = U.objectFieldOffset |
3151 |
> |
(tk.getDeclaredField("parkBlocker")); |
3152 |
> |
ABASE = U.arrayBaseOffset(ak); |
3153 |
> |
s = U.arrayIndexScale(ak); |
3154 |
> |
ASHIFT = 31 - Integer.numberOfLeadingZeros(s); |
3155 |
> |
} catch (Exception e) { |
3156 |
> |
throw new Error(e); |
3157 |
> |
} |
3158 |
> |
if ((s & (s-1)) != 0) |
3159 |
> |
throw new Error("data type scale not a power of two"); |
3160 |
> |
try { // Establish common pool |
3161 |
> |
String pp = System.getProperty(propPrefix + "parallelism"); |
3162 |
> |
String fp = System.getProperty(propPrefix + "threadFactory"); |
3163 |
> |
String up = System.getProperty(propPrefix + "exceptionHandler"); |
3164 |
> |
ForkJoinWorkerThreadFactory fac = (fp == null) ? |
3165 |
> |
defaultForkJoinWorkerThreadFactory : |
3166 |
> |
((ForkJoinWorkerThreadFactory)ClassLoader. |
3167 |
> |
getSystemClassLoader().loadClass(fp).newInstance()); |
3168 |
> |
Thread.UncaughtExceptionHandler ueh = (up == null) ? null : |
3169 |
> |
((Thread.UncaughtExceptionHandler)ClassLoader. |
3170 |
> |
getSystemClassLoader().loadClass(up).newInstance()); |
3171 |
> |
int par; |
3172 |
> |
if ((pp == null || (par = Integer.parseInt(pp)) <= 0)) |
3173 |
> |
par = Runtime.getRuntime().availableProcessors(); |
3174 |
> |
if (par > MAX_CAP) |
3175 |
> |
par = MAX_CAP; |
3176 |
> |
commonPoolParallelism = par; |
3177 |
> |
int n = par - 1; // precompute submit mask |
3178 |
> |
n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; |
3179 |
> |
n |= n >>> 8; n |= n >>> 16; |
3180 |
> |
int mask = ((n + 1) << 1) - 1; |
3181 |
> |
commonPool = new ForkJoinPool(par, mask, fac, ueh); |
3182 |
> |
} catch (Exception e) { |
3183 |
> |
throw new Error(e); |
3184 |
> |
} |
3185 |
> |
} |
3186 |
> |
|
3187 |
> |
/** |
3188 |
> |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
3189 |
> |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
3190 |
> |
* into a jdk. |
3191 |
> |
* |
3192 |
> |
* @return a sun.misc.Unsafe |
3193 |
> |
*/ |
3194 |
> |
private static sun.misc.Unsafe getUnsafe() { |
3195 |
> |
try { |
3196 |
> |
return sun.misc.Unsafe.getUnsafe(); |
3197 |
|
} catch (SecurityException se) { |
3198 |
|
try { |
3199 |
|
return java.security.AccessController.doPrivileged |
3200 |
< |
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
3201 |
< |
public Unsafe run() throws Exception { |
3202 |
< |
return getUnsafePrivileged(); |
3200 |
> |
(new java.security |
3201 |
> |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
3202 |
> |
public sun.misc.Unsafe run() throws Exception { |
3203 |
> |
java.lang.reflect.Field f = sun.misc |
3204 |
> |
.Unsafe.class.getDeclaredField("theUnsafe"); |
3205 |
> |
f.setAccessible(true); |
3206 |
> |
return (sun.misc.Unsafe) f.get(null); |
3207 |
|
}}); |
3208 |
|
} catch (java.security.PrivilegedActionException e) { |
3209 |
< |
throw e.getCause(); |
3209 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
3210 |
> |
e.getCause()); |
3211 |
|
} |
3212 |
|
} |
3213 |
|
} |
3214 |
|
|
1862 |
– |
private static Unsafe getUnsafePrivileged() |
1863 |
– |
throws NoSuchFieldException, IllegalAccessException { |
1864 |
– |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
1865 |
– |
f.setAccessible(true); |
1866 |
– |
return (Unsafe) f.get(null); |
1867 |
– |
} |
1868 |
– |
|
1869 |
– |
private static long fieldOffset(String fieldName) |
1870 |
– |
throws NoSuchFieldException { |
1871 |
– |
return UNSAFE.objectFieldOffset |
1872 |
– |
(ForkJoinPool.class.getDeclaredField(fieldName)); |
1873 |
– |
} |
1874 |
– |
|
1875 |
– |
static final Unsafe UNSAFE; |
1876 |
– |
static final long eventCountOffset; |
1877 |
– |
static final long workerCountsOffset; |
1878 |
– |
static final long runControlOffset; |
1879 |
– |
static final long syncStackOffset; |
1880 |
– |
static final long spareStackOffset; |
1881 |
– |
|
1882 |
– |
static { |
1883 |
– |
try { |
1884 |
– |
UNSAFE = getUnsafe(); |
1885 |
– |
eventCountOffset = fieldOffset("eventCount"); |
1886 |
– |
workerCountsOffset = fieldOffset("workerCounts"); |
1887 |
– |
runControlOffset = fieldOffset("runControl"); |
1888 |
– |
syncStackOffset = fieldOffset("syncStack"); |
1889 |
– |
spareStackOffset = fieldOffset("spareStack"); |
1890 |
– |
} catch (Throwable e) { |
1891 |
– |
throw new RuntimeException("Could not initialize intrinsics", e); |
1892 |
– |
} |
1893 |
– |
} |
1894 |
– |
|
1895 |
– |
private boolean casEventCount(long cmp, long val) { |
1896 |
– |
return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val); |
1897 |
– |
} |
1898 |
– |
private boolean casWorkerCounts(int cmp, int val) { |
1899 |
– |
return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val); |
1900 |
– |
} |
1901 |
– |
private boolean casRunControl(int cmp, int val) { |
1902 |
– |
return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val); |
1903 |
– |
} |
1904 |
– |
private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) { |
1905 |
– |
return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val); |
1906 |
– |
} |
1907 |
– |
private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) { |
1908 |
– |
return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val); |
1909 |
– |
} |
3215 |
|
} |