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*/ |
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package jsr166y; |
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import java.util.*; |
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|
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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.concurrent.locks.LockSupport; |
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import java.util.concurrent.locks.ReentrantLock; |
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import java.util.concurrent.atomic.AtomicInteger; |
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import java.util.concurrent.CountDownLatch; |
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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>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 {@code ForkJoinPool} differs from other kinds of {@link |
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* ExecutorService} mainly by virtue of employing |
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* <em>work-stealing</em>: all threads in the pool attempt to find and |
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* execute subtasks created by other active tasks (eventually blocking |
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* waiting for work if none exist). This enables efficient processing |
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* when most tasks spawn other subtasks (as do most {@code |
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* ForkJoinTask}s). When setting <em>asyncMode</em> to true in |
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* constructors, {@code ForkJoinPool}s may also be appropriate for use |
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* with event-style tasks that are never joined. |
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* |
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* <p>A 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>A {@code ForkJoinPool} is constructed with a given target |
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* parallelism level; by default, equal to the number of available |
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* processors. The pool attempts to maintain enough active (or |
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* available) threads by dynamically adding, suspending, or resuming |
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* internal worker threads, even if some tasks are stalled waiting to |
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* join others. However, no such adjustments are guaranteed in the |
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* face of blocked IO or other unmanaged synchronization. The nested |
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* {@link ManagedBlocker} interface enables extension of the kinds of |
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* synchronization accommodated. |
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* |
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* <p>In addition to execution and lifecycle control methods, this |
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* class provides status check methods (for example |
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* {@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 |
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* table. These are designed to be used by clients not already engaged |
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* in fork/join computations in the current pool. The main forms of |
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* these methods accept instances of {@code ForkJoinTask}, but |
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* overloaded forms also allow mixed execution of plain {@code |
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* Runnable}- or {@code Callable}- based activities as well. However, |
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* tasks that are already executing in a pool should normally |
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* <em>NOT</em> use these pool execution methods, but instead use the |
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* within-computation forms listed in the table. |
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* |
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* <table BORDER CELLPADDING=3 CELLSPACING=1> |
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* <tr> |
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* <td></td> |
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* <td ALIGN=CENTER> <b>Call from non-fork/join clients</b></td> |
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* <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td> |
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* </tr> |
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* <tr> |
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* <td> <b>Arange async execution</td> |
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* <td> {@link #execute(ForkJoinTask)}</td> |
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* <td> {@link ForkJoinTask#fork}</td> |
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* </tr> |
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* <tr> |
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* <td> <b>Await and obtain result</td> |
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* <td> {@link #invoke(ForkJoinTask)}</td> |
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* <td> {@link ForkJoinTask#invoke}</td> |
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* </tr> |
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* <tr> |
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* <td> <b>Arrange exec and obtain Future</td> |
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* <td> {@link #submit(ForkJoinTask)}</td> |
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* <td> {@link ForkJoinTask#fork} (ForkJoinTasks <em>are</em> Futures)</td> |
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* </tr> |
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* </table> |
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* |
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* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is |
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* used for all parallel task execution in a program or subsystem. |
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* Otherwise, use would not usually outweigh the construction and |
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* bookkeeping overhead of creating a large set of threads. For |
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* example, a common pool could be used for the {@code SortTasks} |
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* illustrated in {@link RecursiveAction}. Because {@code |
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* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon |
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* daemon} mode, there is typically no need to explicitly {@link |
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* #shutdown} such a pool upon program exit. |
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* |
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* <pre> |
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* static final ForkJoinPool mainPool = new ForkJoinPool(); |
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* ... |
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* public void sort(long[] array) { |
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* mainPool.invoke(new SortTask(array, 0, array.length)); |
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* } |
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* </pre> |
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* |
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* <p><b>Implementation notes</b>: This implementation restricts the |
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* maximum number of running threads to 32767. Attempts to create |
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* pools with greater than the maximum 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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/* |
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* See the extended comments interspersed below for design, |
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* rationale, and walkthroughs. |
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*/ |
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|
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/** Mask for packing and unpacking shorts */ |
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private static final int shortMask = 0xffff; |
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|
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/** Max pool size -- must be a power of two minus 1 */ |
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private static final int MAX_THREADS = 0x7FFF; |
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|
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/** |
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* Factory for creating new ForkJoinWorkerThreads. A |
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* ForkJoinWorkerThreadFactory must be defined and used for |
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* ForkJoinWorkerThread subclasses that extend base functionality |
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* or initialize threads with different contexts. |
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* Implementation Overview |
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* |
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* This class provides the central bookkeeping and control for a |
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* set of worker threads: Submissions from non-FJ threads enter |
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* into a submission queue. Workers take these tasks and typically |
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* split them into subtasks that may be stolen by other workers. |
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* The main work-stealing mechanics implemented in class |
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* ForkJoinWorkerThread give first priority to processing tasks |
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* from their own queues (LIFO or FIFO, depending on mode), then |
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* to randomized FIFO steals of tasks in other worker queues, and |
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* lastly to new submissions. These mechanics do not consider |
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* affinities, loads, cache localities, etc, so rarely provide the |
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* best possible performance on a given machine, but portably |
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* provide good throughput by averaging over these factors. |
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* (Further, even if we did try to use such information, we do not |
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* usually have a basis for exploiting it. For example, some sets |
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* of tasks profit from cache affinities, but others are harmed by |
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* cache pollution effects.) |
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* |
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* Beyond work-stealing support and essential bookkeeping, the |
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* main responsibility of this framework is to take actions when |
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* one worker is waiting to join a task stolen (or always held by) |
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* another. Becauae we are multiplexing many tasks on to a pool |
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* of workers, we can't just let them block (as in Thread.join). |
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* We also cannot just reassign the joiner's run-time stack with |
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* another and replace it later, which would be a form of |
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* "continuation", that even if possible is not necessarily a good |
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* idea. Given that the creation costs of most threads on most |
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* systems mainly surrounds setting up runtime stacks, thread |
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* creation and switching is usually not much more expensive than |
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* stack creation and switching, and is more flexible). Instead we |
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* combine two tactics: |
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* |
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* Helping: Arranging for the joiner to execute some task that it |
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* would be running if the steal had not occurred. Method |
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* ForkJoinWorkerThread.helpJoinTask tracks joining->stealing |
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* links to try to find such a task. |
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* |
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* Compensating: Unless there are already enough live threads, |
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* method helpMaintainParallelism() may create or or |
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* re-activate a spare thread to compensate for blocked |
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* joiners until they unblock. |
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* |
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* Because the determining existence of conservatively safe |
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* helping targets, the availability of already-created spares, |
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* and the apparent need to create new spares are all racy and |
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* require heuristic guidance, we rely on multiple retries of |
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* each. Further, because it is impossible to keep exactly the |
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* target (parallelism) number of threads running at any given |
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* time, we allow compensation during joins to fail, and enlist |
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* all other threads to help out whenever they are not otherwise |
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* occupied (i.e., mainly in method preStep). |
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* |
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* The ManagedBlocker extension API can't use helping so relies |
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* only on compensation in method awaitBlocker. |
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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 steal tasks from each |
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* other. We do not want to negate this by creating bottlenecks |
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* implementing other management responsibilities. So we use a |
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* collection of techniques that avoid, reduce, or cope well with |
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* contention. These entail several instances of bit-packing into |
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* CASable fields to maintain only the minimally required |
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* atomicity. To enable such packing, we restrict maximum |
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* parallelism to (1<<15)-1 (enabling twice this (to accommodate |
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* unbalanced increments and decrements) to fit into a 16 bit |
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* field, which is far in excess of normal operating range. Even |
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* though updates to some of these bookkeeping fields do sometimes |
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* contend with each other, they don't normally cache-contend with |
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* updates to others enough to warrant memory padding or |
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* isolation. So they are all held as fields of ForkJoinPool |
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* objects. The main capabilities are as follows: |
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* |
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* 1. Creating and removing workers. Workers are recorded in the |
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* "workers" array. This is an array as opposed to some other data |
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* structure to support index-based random steals by workers. |
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* Updates to the array recording new workers and unrecording |
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* terminated ones are protected from each other by a lock |
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* (workerLock) but the array is otherwise concurrently readable, |
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* and accessed directly by workers. To simplify index-based |
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* operations, the array size is always a power of two, and all |
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* readers must tolerate null slots. Currently, all worker thread |
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* creation is on-demand, triggered by task submissions, |
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* replacement of terminated workers, and/or compensation for |
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* blocked workers. However, all other support code is set up to |
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* work with other policies. |
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* |
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* To ensure that we do not hold on to worker references that |
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* would prevent GC, ALL accesses to workers are via indices into |
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* the workers array (which is one source of some of the unusual |
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* code constructions here). In essence, the workers array serves |
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* as a WeakReference mechanism. Thus for example the event queue |
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* stores worker indices, not worker references. Access to the |
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* workers in associated methods (for example releaseEventWaiters) |
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* must 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 shutdown, in which case |
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* it is OK to give up. On termination, we just clobber these |
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* data structures without trying to use them. |
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* |
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* 2. Bookkeeping for dynamically adding and removing workers. We |
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* aim to approximately maintain the given level of parallelism. |
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* When some workers are known to be blocked (on joins or via |
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* ManagedBlocker), we may create or resume others to take their |
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* place until they unblock (see below). Implementing this |
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* requires counts of the number of "running" threads (i.e., those |
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* that are neither blocked nor artifically suspended) as well as |
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* the total number. These two values are packed into one field, |
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* "workerCounts" because we need accurate snapshots when deciding |
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* to create, resume or suspend. Note however that the |
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* correspondance of these counts to reality is not guaranteed. In |
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* particular updates for unblocked threads may lag until they |
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* actually wake up. |
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* |
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* 3. Maintaining global run state. The run state of the pool |
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* consists of a runLevel (SHUTDOWN, TERMINATING, etc) similar to |
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* those in other Executor implementations, as well as a count of |
238 |
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* "active" workers -- those that are, or soon will be, or |
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* recently were executing tasks. The runLevel and active count |
240 |
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* are packed together in order to correctly trigger shutdown and |
241 |
> |
* termination. Without care, active counts can be subject to very |
242 |
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* high contention. We substantially reduce this contention by |
243 |
> |
* relaxing update rules. A worker must claim active status |
244 |
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* prospectively, by activating if it sees that a submitted or |
245 |
> |
* stealable task exists (it may find after activating that the |
246 |
> |
* task no longer exists). It stays active while processing this |
247 |
> |
* task (if it exists) and any other local subtasks it produces, |
248 |
> |
* until it cannot find any other tasks. It then tries |
249 |
> |
* inactivating (see method preStep), but upon update contention |
250 |
> |
* instead scans for more tasks, later retrying inactivation if it |
251 |
> |
* doesn't find any. |
252 |
> |
* |
253 |
> |
* 4. Managing idle workers waiting for tasks. We cannot let |
254 |
> |
* workers spin indefinitely scanning for tasks when none are |
255 |
> |
* available. On the other hand, we must quickly prod them into |
256 |
> |
* action when new tasks are submitted or generated. We |
257 |
> |
* park/unpark these idle workers using an event-count scheme. |
258 |
> |
* Field eventCount is incremented upon events that may enable |
259 |
> |
* workers that previously could not find a task to now find one: |
260 |
> |
* Submission of a new task to the pool, or another worker pushing |
261 |
> |
* a task onto a previously empty queue. (We also use this |
262 |
> |
* mechanism for configuration and termination actions that |
263 |
> |
* require wakeups of idle workers). Each worker maintains its |
264 |
> |
* last known event count, and blocks when a scan for work did not |
265 |
> |
* find a task AND its lastEventCount matches the current |
266 |
> |
* eventCount. Waiting idle workers are recorded in a variant of |
267 |
> |
* Treiber stack headed by field eventWaiters which, when nonzero, |
268 |
> |
* encodes the thread index and count awaited for by the worker |
269 |
> |
* thread most recently calling eventSync. This thread in turn has |
270 |
> |
* a record (field nextEventWaiter) for the next waiting worker. |
271 |
> |
* In addition to allowing simpler decisions about need for |
272 |
> |
* wakeup, the event count bits in eventWaiters serve the role of |
273 |
> |
* tags to avoid ABA errors in Treiber stacks. Upon any wakeup, |
274 |
> |
* released threads also try to release others (but give up upon |
275 |
> |
* contention to reduce useless flailing). The net effect is a |
276 |
> |
* tree-like diffusion of signals, where released threads (and |
277 |
> |
* possibly others) help with unparks. To further reduce |
278 |
> |
* contention effects a bit, failed CASes to increment field |
279 |
> |
* eventCount are tolerated without retries in signalWork. |
280 |
> |
* Conceptually they are merged into the same event, which is OK |
281 |
> |
* when their only purpose is to enable workers to scan for work. |
282 |
> |
* |
283 |
> |
* 5. Managing suspension of extra workers. When a worker is about |
284 |
> |
* to block waiting for a join (or via ManagedBlockers), we may |
285 |
> |
* create a new thread to maintain parallelism level, or at least |
286 |
> |
* avoid starvation. Usually, extra threads are needed for only |
287 |
> |
* very short periods, yet join dependencies are such that we |
288 |
> |
* sometimes need them in bursts. Rather than create new threads |
289 |
> |
* each time this happens, we suspend no-longer-needed extra ones |
290 |
> |
* as "spares". For most purposes, we don't distinguish "extra" |
291 |
> |
* spare threads from normal "core" threads: On each call to |
292 |
> |
* preStep (the only point at which we can do this) a worker |
293 |
> |
* checks to see if there are now too many running workers, and if |
294 |
> |
* so, suspends itself. Method helpMaintainParallelism looks for |
295 |
> |
* suspended threads to resume before considering creating a new |
296 |
> |
* replacement. The spares themselves are encoded on another |
297 |
> |
* variant of a Treiber Stack, headed at field "spareWaiters". |
298 |
> |
* Note that the use of spares is intrinsically racy. One thread |
299 |
> |
* may become a spare at about the same time as another is |
300 |
> |
* needlessly being created. We counteract this and related slop |
301 |
> |
* in part by requiring resumed spares to immediately recheck (in |
302 |
> |
* preStep) to see whether they they should re-suspend. |
303 |
> |
* |
304 |
> |
* 6. Killing off unneeded workers. The Spare and Event queues use |
305 |
> |
* similar mechanisms to shed unused workers: The oldest (first) |
306 |
> |
* waiter uses a timed rather than hard wait. When this wait times |
307 |
> |
* out without a normal wakeup, it tries to shutdown any one (for |
308 |
> |
* convenience the newest) other waiter via tryShutdownSpare or |
309 |
> |
* tryShutdownWaiter, respectively. The wakeup rates for spares |
310 |
> |
* are much shorter than for waiters. Together, they will |
311 |
> |
* eventually reduce the number of worker threads to a minimum of |
312 |
> |
* one after a long enough period without use. |
313 |
> |
* |
314 |
> |
* 7. Deciding when to create new workers. The main dynamic |
315 |
> |
* control in this class is deciding when to create extra threads |
316 |
> |
* in method helpMaintainParallelism. We would like to keep |
317 |
> |
* exactly #parallelism threads running, which is an impossble |
318 |
> |
* task. We always need to create one when the number of running |
319 |
> |
* threads would become zero and all workers are busy. Beyond |
320 |
> |
* this, we must rely on heuristics that work well in the the |
321 |
> |
* presence of transients phenomena such as GC stalls, dynamic |
322 |
> |
* compilation, and wake-up lags. These transients are extremely |
323 |
> |
* common -- we are normally trying to fully saturate the CPUs on |
324 |
> |
* a machine, so almost any activity other than running tasks |
325 |
> |
* impedes accuracy. Our main defense is to allow some slack in |
326 |
> |
* creation thresholds, using rules that reflect the fact that the |
327 |
> |
* more threads we have running, the more likely that we are |
328 |
> |
* underestimating the number running threads. (We also include |
329 |
> |
* some heuristic use of Thread.yield when all workers appear to |
330 |
> |
* be busy, to improve likelihood of counts settling.) The rules |
331 |
> |
* also better cope with the fact that some of the methods in this |
332 |
> |
* class tend to never become compiled (but are interpreted), so |
333 |
> |
* some components of the entire set of controls might execute 100 |
334 |
> |
* times faster than others. And similarly for cases where the |
335 |
> |
* apparent lack of work is just due to GC stalls and other |
336 |
> |
* transient system activity. |
337 |
> |
* |
338 |
> |
* Beware that there is a lot of representation-level coupling |
339 |
> |
* among classes ForkJoinPool, ForkJoinWorkerThread, and |
340 |
> |
* ForkJoinTask. For example, direct access to "workers" array by |
341 |
> |
* workers, and direct access to ForkJoinTask.status by both |
342 |
> |
* ForkJoinPool and ForkJoinWorkerThread. There is little point |
343 |
> |
* trying to reduce this, since any associated future changes in |
344 |
> |
* representations will need to be accompanied by algorithmic |
345 |
> |
* changes anyway. |
346 |
> |
* |
347 |
> |
* Style notes: There are lots of inline assignments (of form |
348 |
> |
* "while ((local = field) != 0)") which are usually the simplest |
349 |
> |
* way to ensure the required read orderings (which are sometimes |
350 |
> |
* critical). Also several occurrences of the unusual "do {} |
351 |
> |
* while(!cas...)" which is the simplest way to force an update of |
352 |
> |
* a CAS'ed variable. There are also other coding oddities that |
353 |
> |
* help some methods perform reasonably even when interpreted (not |
354 |
> |
* compiled), at the expense of some messy constructions that |
355 |
> |
* reduce byte code counts. |
356 |
> |
* |
357 |
> |
* The order of declarations in this file is: (1) statics (2) |
358 |
> |
* fields (along with constants used when unpacking some of them) |
359 |
> |
* (3) internal control methods (4) callbacks and other support |
360 |
> |
* for ForkJoinTask and ForkJoinWorkerThread classes, (5) exported |
361 |
> |
* methods (plus a few little helpers). |
362 |
> |
*/ |
363 |
> |
|
364 |
> |
/** |
365 |
> |
* Factory for creating new {@link ForkJoinWorkerThread}s. |
366 |
> |
* A {@code ForkJoinWorkerThreadFactory} must be defined and used |
367 |
> |
* for {@code ForkJoinWorkerThread} subclasses that extend base |
368 |
> |
* functionality or initialize threads with different contexts. |
369 |
|
*/ |
370 |
|
public static interface ForkJoinWorkerThreadFactory { |
371 |
|
/** |
372 |
|
* Returns a new worker thread operating in the given pool. |
373 |
|
* |
374 |
|
* @param pool the pool this thread works in |
375 |
< |
* @throws NullPointerException if pool is null |
375 |
> |
* @throws NullPointerException if the pool is null |
376 |
|
*/ |
377 |
|
public ForkJoinWorkerThread newThread(ForkJoinPool pool); |
378 |
|
} |
381 |
|
* Default ForkJoinWorkerThreadFactory implementation; creates a |
382 |
|
* new ForkJoinWorkerThread. |
383 |
|
*/ |
384 |
< |
static class DefaultForkJoinWorkerThreadFactory |
384 |
> |
static class DefaultForkJoinWorkerThreadFactory |
385 |
|
implements ForkJoinWorkerThreadFactory { |
386 |
|
public ForkJoinWorkerThread newThread(ForkJoinPool pool) { |
387 |
< |
try { |
100 |
< |
return new ForkJoinWorkerThread(pool); |
101 |
< |
} catch (OutOfMemoryError oom) { |
102 |
< |
return null; |
103 |
< |
} |
387 |
> |
return new ForkJoinWorkerThread(pool); |
388 |
|
} |
389 |
|
} |
390 |
|
|
420 |
|
new AtomicInteger(); |
421 |
|
|
422 |
|
/** |
423 |
< |
* Array holding all worker threads in the pool. Initialized upon |
424 |
< |
* first use. Array size must be a power of two. Updates and |
425 |
< |
* replacements are protected by workerLock, but it is always kept |
426 |
< |
* in a consistent enough state to be randomly accessed without |
427 |
< |
* locking by workers performing work-stealing. |
423 |
> |
* The wakeup interval (in nanoseconds) for the oldest worker |
424 |
> |
* worker waiting for an event invokes tryShutdownWaiter to shrink |
425 |
> |
* the number of workers. The exact value does not matter too |
426 |
> |
* much, but should be long enough to slowly release resources |
427 |
> |
* during long periods without use without disrupting normal use. |
428 |
> |
*/ |
429 |
> |
private static final long SHRINK_RATE_NANOS = |
430 |
> |
60L * 1000L * 1000L * 1000L; // one minute |
431 |
> |
|
432 |
> |
/** |
433 |
> |
* Absolute bound for parallelism level. Twice this number plus |
434 |
> |
* one (i.e., 0xfff) must fit into a 16bit field to enable |
435 |
> |
* word-packing for some counts and indices. |
436 |
> |
*/ |
437 |
> |
private static final int MAX_WORKERS = 0x7fff; |
438 |
> |
|
439 |
> |
/** |
440 |
> |
* Array holding all worker threads in the pool. Array size must |
441 |
> |
* be a power of two. Updates and replacements are protected by |
442 |
> |
* workerLock, but the array is always kept in a consistent enough |
443 |
> |
* state to be randomly accessed without locking by workers |
444 |
> |
* performing work-stealing, as well as other traversal-based |
445 |
> |
* methods in this class. All readers must tolerate that some |
446 |
> |
* array slots may be null. |
447 |
|
*/ |
448 |
|
volatile ForkJoinWorkerThread[] workers; |
449 |
|
|
450 |
|
/** |
451 |
< |
* Lock protecting access to workers. |
451 |
> |
* Queue for external submissions. |
452 |
|
*/ |
453 |
< |
private final ReentrantLock workerLock; |
453 |
> |
private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue; |
454 |
|
|
455 |
|
/** |
456 |
< |
* Condition for awaitTermination. |
456 |
> |
* Lock protecting updates to workers array. |
457 |
|
*/ |
458 |
< |
private final Condition termination; |
458 |
> |
private final ReentrantLock workerLock; |
459 |
|
|
460 |
|
/** |
461 |
< |
* The uncaught exception handler used when any worker |
159 |
< |
* abruptly terminates |
461 |
> |
* Latch released upon termination. |
462 |
|
*/ |
463 |
< |
private Thread.UncaughtExceptionHandler ueh; |
463 |
> |
private final Phaser termination; |
464 |
|
|
465 |
|
/** |
466 |
|
* Creation factory for worker threads. |
468 |
|
private final ForkJoinWorkerThreadFactory factory; |
469 |
|
|
470 |
|
/** |
169 |
– |
* Head of stack of threads that were created to maintain |
170 |
– |
* parallelism when other threads blocked, but have since |
171 |
– |
* suspended when the parallelism level rose. |
172 |
– |
*/ |
173 |
– |
private volatile WaitQueueNode spareStack; |
174 |
– |
|
175 |
– |
/** |
471 |
|
* Sum of per-thread steal counts, updated only when threads are |
472 |
|
* idle or terminating. |
473 |
|
*/ |
474 |
< |
private final AtomicLong stealCount; |
474 |
> |
private volatile long stealCount; |
475 |
|
|
476 |
|
/** |
477 |
< |
* Queue for external submissions. |
477 |
> |
* Encoded record of top of treiber stack of threads waiting for |
478 |
> |
* events. The top 32 bits contain the count being waited for. The |
479 |
> |
* bottom 16 bits contains one plus the pool index of waiting |
480 |
> |
* worker thread. (Bits 16-31 are unused.) |
481 |
|
*/ |
482 |
< |
private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue; |
482 |
> |
private volatile long eventWaiters; |
483 |
> |
|
484 |
> |
private static final int EVENT_COUNT_SHIFT = 32; |
485 |
> |
private static final long WAITER_ID_MASK = (1L << 16) - 1L; |
486 |
|
|
487 |
|
/** |
488 |
< |
* Head of Treiber stack for barrier sync. See below for explanation. |
488 |
> |
* A counter for events that may wake up worker threads: |
489 |
> |
* - Submission of a new task to the pool |
490 |
> |
* - A worker pushing a task on an empty queue |
491 |
> |
* - termination |
492 |
|
*/ |
493 |
< |
private volatile WaitQueueNode syncStack; |
493 |
> |
private volatile int eventCount; |
494 |
|
|
495 |
|
/** |
496 |
< |
* The count for event barrier |
496 |
> |
* Encoded record of top of treiber stack of spare threads waiting |
497 |
> |
* for resumption. The top 16 bits contain an arbitrary count to |
498 |
> |
* avoid ABA effects. The bottom 16bits contains one plus the pool |
499 |
> |
* index of waiting worker thread. |
500 |
|
*/ |
501 |
< |
private volatile long eventCount; |
501 |
> |
private volatile int spareWaiters; |
502 |
> |
|
503 |
> |
private static final int SPARE_COUNT_SHIFT = 16; |
504 |
> |
private static final int SPARE_ID_MASK = (1 << 16) - 1; |
505 |
|
|
506 |
|
/** |
507 |
< |
* Pool number, just for assigning useful names to worker threads |
507 |
> |
* Lifecycle control. The low word contains the number of workers |
508 |
> |
* that are (probably) executing tasks. This value is atomically |
509 |
> |
* incremented before a worker gets a task to run, and decremented |
510 |
> |
* when worker has no tasks and cannot find any. Bits 16-18 |
511 |
> |
* contain runLevel value. When all are zero, the pool is |
512 |
> |
* running. Level transitions are monotonic (running -> shutdown |
513 |
> |
* -> terminating -> terminated) so each transition adds a bit. |
514 |
> |
* These are bundled together to ensure consistent read for |
515 |
> |
* termination checks (i.e., that runLevel is at least SHUTDOWN |
516 |
> |
* and active threads is zero). |
517 |
> |
* |
518 |
> |
* Notes: Most direct CASes are dependent on these bitfield |
519 |
> |
* positions. Also, this field is non-private to enable direct |
520 |
> |
* performance-sensitive CASes in ForkJoinWorkerThread. |
521 |
|
*/ |
522 |
< |
private final int poolNumber; |
522 |
> |
volatile int runState; |
523 |
> |
|
524 |
> |
// Note: The order among run level values matters. |
525 |
> |
private static final int RUNLEVEL_SHIFT = 16; |
526 |
> |
private static final int SHUTDOWN = 1 << RUNLEVEL_SHIFT; |
527 |
> |
private static final int TERMINATING = 1 << (RUNLEVEL_SHIFT + 1); |
528 |
> |
private static final int TERMINATED = 1 << (RUNLEVEL_SHIFT + 2); |
529 |
> |
private static final int ACTIVE_COUNT_MASK = (1 << RUNLEVEL_SHIFT) - 1; |
530 |
|
|
531 |
|
/** |
532 |
< |
* The maximum allowed pool size |
532 |
> |
* Holds number of total (i.e., created and not yet terminated) |
533 |
> |
* and running (i.e., not blocked on joins or other managed sync) |
534 |
> |
* threads, packed together to ensure consistent snapshot when |
535 |
> |
* making decisions about creating and suspending spare |
536 |
> |
* threads. Updated only by CAS. Note that adding a new worker |
537 |
> |
* requires incrementing both counts, since workers start off in |
538 |
> |
* running state. |
539 |
|
*/ |
540 |
< |
private volatile int maxPoolSize; |
540 |
> |
private volatile int workerCounts; |
541 |
> |
|
542 |
> |
private static final int TOTAL_COUNT_SHIFT = 16; |
543 |
> |
private static final int RUNNING_COUNT_MASK = (1 << TOTAL_COUNT_SHIFT) - 1; |
544 |
> |
private static final int ONE_RUNNING = 1; |
545 |
> |
private static final int ONE_TOTAL = 1 << TOTAL_COUNT_SHIFT; |
546 |
|
|
547 |
|
/** |
548 |
< |
* The desired parallelism level, updated only under workerLock. |
548 |
> |
* The target parallelism level. |
549 |
> |
* Accessed directly by ForkJoinWorkerThreads. |
550 |
|
*/ |
551 |
< |
private volatile int parallelism; |
551 |
> |
final int parallelism; |
552 |
|
|
553 |
|
/** |
554 |
|
* True if use local fifo, not default lifo, for local polling |
555 |
+ |
* Read by, and replicated by ForkJoinWorkerThreads |
556 |
|
*/ |
557 |
< |
private volatile boolean locallyFifo; |
557 |
> |
final boolean locallyFifo; |
558 |
|
|
559 |
|
/** |
560 |
< |
* Holds number of total (i.e., created and not yet terminated) |
561 |
< |
* and running (i.e., not blocked on joins or other managed sync) |
219 |
< |
* threads, packed into one int to ensure consistent snapshot when |
220 |
< |
* making decisions about creating and suspending spare |
221 |
< |
* threads. Updated only by CAS. Note: CASes in |
222 |
< |
* updateRunningCount and preJoin assume that running active count |
223 |
< |
* is in low word, so need to be modified if this changes. |
560 |
> |
* The uncaught exception handler used when any worker abruptly |
561 |
> |
* terminates. |
562 |
|
*/ |
563 |
< |
private volatile int workerCounts; |
563 |
> |
private final Thread.UncaughtExceptionHandler ueh; |
564 |
> |
|
565 |
> |
/** |
566 |
> |
* Pool number, just for assigning useful names to worker threads |
567 |
> |
*/ |
568 |
> |
private final int poolNumber; |
569 |
|
|
570 |
< |
private static int totalCountOf(int s) { return s >>> 16; } |
571 |
< |
private static int runningCountOf(int s) { return s & shortMask; } |
572 |
< |
private static int workerCountsFor(int t, int r) { return (t << 16) + r; } |
570 |
> |
|
571 |
> |
// Utilities for CASing fields. Note that most of these |
572 |
> |
// are usually manually inlined by callers |
573 |
|
|
574 |
|
/** |
575 |
< |
* 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). |
235 |
< |
* |
236 |
< |
* @param delta the number to add |
575 |
> |
* Increments running count part of workerCounts |
576 |
|
*/ |
577 |
< |
final void updateRunningCount(int delta) { |
578 |
< |
int s; |
579 |
< |
do {} while (!casWorkerCounts(s = workerCounts, s + delta)); |
577 |
> |
final void incrementRunningCount() { |
578 |
> |
int c; |
579 |
> |
do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
580 |
> |
c = workerCounts, |
581 |
> |
c + ONE_RUNNING)); |
582 |
|
} |
583 |
|
|
584 |
|
/** |
585 |
< |
* Adds delta (which may be negative) to both total and running |
245 |
< |
* count. This must be called upon creation and termination of |
246 |
< |
* worker threads. |
247 |
< |
* |
248 |
< |
* @param delta the number to add |
585 |
> |
* Tries to decrement running count unless already zero |
586 |
|
*/ |
587 |
< |
private void updateWorkerCount(int delta) { |
588 |
< |
int d = delta + (delta << 16); // add to both lo and hi parts |
589 |
< |
int s; |
590 |
< |
do {} while (!casWorkerCounts(s = workerCounts, s + d)); |
587 |
> |
final boolean tryDecrementRunningCount() { |
588 |
> |
int wc = workerCounts; |
589 |
> |
if ((wc & RUNNING_COUNT_MASK) == 0) |
590 |
> |
return false; |
591 |
> |
return UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
592 |
> |
wc, wc - ONE_RUNNING); |
593 |
|
} |
594 |
|
|
595 |
|
/** |
596 |
< |
* Lifecycle control. High word contains runState, low word |
597 |
< |
* contains the number of workers that are (probably) executing |
598 |
< |
* tasks. This value is atomically incremented before a worker |
599 |
< |
* gets a task to run, and decremented when worker has no tasks |
600 |
< |
* and cannot find any. These two fields are bundled together to |
262 |
< |
* support correct termination triggering. Note: activeCount |
263 |
< |
* CAS'es cheat by assuming active count is in low word, so need |
264 |
< |
* to be modified if this changes |
596 |
> |
* Forces decrement of encoded workerCounts, awaiting nonzero if |
597 |
> |
* (rarely) necessary when other count updates lag. |
598 |
> |
* |
599 |
> |
* @param dr -- either zero or ONE_RUNNING |
600 |
> |
* @param dt == either zero or ONE_TOTAL |
601 |
|
*/ |
602 |
< |
private volatile int runControl; |
603 |
< |
|
604 |
< |
// RunState values. Order among values matters |
605 |
< |
private static final int RUNNING = 0; |
606 |
< |
private static final int SHUTDOWN = 1; |
607 |
< |
private static final int TERMINATING = 2; |
608 |
< |
private static final int TERMINATED = 3; |
602 |
> |
private void decrementWorkerCounts(int dr, int dt) { |
603 |
> |
for (;;) { |
604 |
> |
int wc = workerCounts; |
605 |
> |
if ((wc & RUNNING_COUNT_MASK) - dr < 0 || |
606 |
> |
(wc >>> TOTAL_COUNT_SHIFT) - dt < 0) { |
607 |
> |
if ((runState & TERMINATED) != 0) |
608 |
> |
return; // lagging termination on a backout |
609 |
> |
Thread.yield(); |
610 |
> |
} |
611 |
> |
if (UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
612 |
> |
wc, wc - (dr + dt))) |
613 |
> |
return; |
614 |
> |
} |
615 |
> |
} |
616 |
|
|
617 |
< |
private static int runStateOf(int c) { return c >>> 16; } |
618 |
< |
private static int activeCountOf(int c) { return c & shortMask; } |
619 |
< |
private static int runControlFor(int r, int a) { return (r << 16) + a; } |
617 |
> |
/** |
618 |
> |
* Increments event count |
619 |
> |
*/ |
620 |
> |
private void advanceEventCount() { |
621 |
> |
int c; |
622 |
> |
do {} while(!UNSAFE.compareAndSwapInt(this, eventCountOffset, |
623 |
> |
c = eventCount, c+1)); |
624 |
> |
} |
625 |
|
|
626 |
|
/** |
627 |
|
* Tries incrementing active count; fails on contention. |
628 |
< |
* Called by workers before/during executing tasks. |
628 |
> |
* Called by workers before executing tasks. |
629 |
|
* |
630 |
|
* @return true on success |
631 |
|
*/ |
632 |
|
final boolean tryIncrementActiveCount() { |
633 |
< |
int c = runControl; |
634 |
< |
return casRunControl(c, c+1); |
633 |
> |
int c; |
634 |
> |
return UNSAFE.compareAndSwapInt(this, runStateOffset, |
635 |
> |
c = runState, c + 1); |
636 |
|
} |
637 |
|
|
638 |
|
/** |
639 |
|
* Tries decrementing active count; fails on contention. |
640 |
< |
* Possibly triggers termination on success. |
292 |
< |
* Called by workers when they can't find tasks. |
293 |
< |
* |
294 |
< |
* @return true on success |
640 |
> |
* Called when workers cannot find tasks to run. |
641 |
|
*/ |
642 |
|
final boolean tryDecrementActiveCount() { |
643 |
< |
int c = runControl; |
644 |
< |
int nextc = c - 1; |
645 |
< |
if (!casRunControl(c, nextc)) |
300 |
< |
return false; |
301 |
< |
if (canTerminateOnShutdown(nextc)) |
302 |
< |
terminateOnShutdown(); |
303 |
< |
return true; |
643 |
> |
int c; |
644 |
> |
return UNSAFE.compareAndSwapInt(this, runStateOffset, |
645 |
> |
c = runState, c - 1); |
646 |
|
} |
647 |
|
|
648 |
|
/** |
649 |
< |
* Returns true if argument represents zero active count and |
650 |
< |
* nonzero runstate, which is the triggering condition for |
309 |
< |
* terminating on shutdown. |
649 |
> |
* Advances to at least the given level. Returns true if not |
650 |
> |
* already in at least the given level. |
651 |
|
*/ |
652 |
< |
private static boolean canTerminateOnShutdown(int c) { |
653 |
< |
// i.e. least bit is nonzero runState bit |
654 |
< |
return ((c & -c) >>> 16) != 0; |
652 |
> |
private boolean advanceRunLevel(int level) { |
653 |
> |
for (;;) { |
654 |
> |
int s = runState; |
655 |
> |
if ((s & level) != 0) |
656 |
> |
return false; |
657 |
> |
if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, s | level)) |
658 |
> |
return true; |
659 |
> |
} |
660 |
|
} |
661 |
|
|
662 |
+ |
// workers array maintenance |
663 |
+ |
|
664 |
|
/** |
665 |
< |
* Transition run state to at least the given state. Return true |
318 |
< |
* if not already at least given state. |
665 |
> |
* Records and returns a workers array index for new worker. |
666 |
|
*/ |
667 |
< |
private boolean transitionRunStateTo(int state) { |
668 |
< |
for (;;) { |
669 |
< |
int c = runControl; |
670 |
< |
if (runStateOf(c) >= state) |
671 |
< |
return false; |
672 |
< |
if (casRunControl(c, runControlFor(state, activeCountOf(c)))) |
673 |
< |
return true; |
667 |
> |
private int recordWorker(ForkJoinWorkerThread w) { |
668 |
> |
// Try using slot totalCount-1. If not available, scan and/or resize |
669 |
> |
int k = (workerCounts >>> TOTAL_COUNT_SHIFT) - 1; |
670 |
> |
final ReentrantLock lock = this.workerLock; |
671 |
> |
lock.lock(); |
672 |
> |
try { |
673 |
> |
ForkJoinWorkerThread[] ws = workers; |
674 |
> |
int n = ws.length; |
675 |
> |
if (k < 0 || k >= n || ws[k] != null) { |
676 |
> |
for (k = 0; k < n && ws[k] != null; ++k) |
677 |
> |
; |
678 |
> |
if (k == n) |
679 |
> |
ws = Arrays.copyOf(ws, n << 1); |
680 |
> |
} |
681 |
> |
ws[k] = w; |
682 |
> |
workers = ws; // volatile array write ensures slot visibility |
683 |
> |
} finally { |
684 |
> |
lock.unlock(); |
685 |
|
} |
686 |
+ |
return k; |
687 |
|
} |
688 |
|
|
689 |
|
/** |
690 |
< |
* Controls whether to add spares to maintain parallelism |
690 |
> |
* Nulls out record of worker in workers array |
691 |
|
*/ |
692 |
< |
private volatile boolean maintainsParallelism; |
692 |
> |
private void forgetWorker(ForkJoinWorkerThread w) { |
693 |
> |
int idx = w.poolIndex; |
694 |
> |
// Locking helps method recordWorker avoid unecessary expansion |
695 |
> |
final ReentrantLock lock = this.workerLock; |
696 |
> |
lock.lock(); |
697 |
> |
try { |
698 |
> |
ForkJoinWorkerThread[] ws = workers; |
699 |
> |
if (idx >= 0 && idx < ws.length && ws[idx] == w) // verify |
700 |
> |
ws[idx] = null; |
701 |
> |
} finally { |
702 |
> |
lock.unlock(); |
703 |
> |
} |
704 |
> |
} |
705 |
|
|
706 |
< |
// Constructors |
706 |
> |
// adding and removing workers |
707 |
|
|
708 |
|
/** |
709 |
< |
* Creates a ForkJoinPool with a pool size equal to the number of |
710 |
< |
* processors available on the system, using the default |
711 |
< |
* ForkJoinWorkerThreadFactory. |
709 |
> |
* Tries to create and add new worker. Assumes that worker counts |
710 |
> |
* are already updated to accommodate the worker, so adjusts on |
711 |
> |
* failure. |
712 |
|
* |
713 |
< |
* @throws SecurityException if a security manager exists and |
343 |
< |
* the caller is not permitted to modify threads |
344 |
< |
* because it does not hold {@link |
345 |
< |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
713 |
> |
* @return the worker, or null on failure |
714 |
|
*/ |
715 |
< |
public ForkJoinPool() { |
716 |
< |
this(Runtime.getRuntime().availableProcessors(), |
717 |
< |
defaultForkJoinWorkerThreadFactory); |
715 |
> |
private ForkJoinWorkerThread addWorker() { |
716 |
> |
ForkJoinWorkerThread w = null; |
717 |
> |
try { |
718 |
> |
w = factory.newThread(this); |
719 |
> |
} finally { // Adjust on either null or exceptional factory return |
720 |
> |
if (w == null) { |
721 |
> |
decrementWorkerCounts(ONE_RUNNING, ONE_TOTAL); |
722 |
> |
tryTerminate(false); // in case of failure during shutdown |
723 |
> |
} |
724 |
> |
} |
725 |
> |
if (w != null) { |
726 |
> |
w.start(recordWorker(w), ueh); |
727 |
> |
advanceEventCount(); |
728 |
> |
} |
729 |
> |
return w; |
730 |
|
} |
731 |
|
|
732 |
|
/** |
733 |
< |
* Creates a ForkJoinPool with the indicated parallelism level |
734 |
< |
* threads and using the default ForkJoinWorkerThreadFactory. |
733 |
> |
* Final callback from terminating worker. Removes record of |
734 |
> |
* worker from array, and adjusts counts. If pool is shutting |
735 |
> |
* down, tries to complete terminatation. |
736 |
|
* |
737 |
< |
* @param parallelism the number of worker threads |
357 |
< |
* @throws IllegalArgumentException if parallelism less than or |
358 |
< |
* equal to zero |
359 |
< |
* @throws SecurityException if a security manager exists and |
360 |
< |
* the caller is not permitted to modify threads |
361 |
< |
* because it does not hold {@link |
362 |
< |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
737 |
> |
* @param w the worker |
738 |
|
*/ |
739 |
< |
public ForkJoinPool(int parallelism) { |
740 |
< |
this(parallelism, defaultForkJoinWorkerThreadFactory); |
739 |
> |
final void workerTerminated(ForkJoinWorkerThread w) { |
740 |
> |
forgetWorker(w); |
741 |
> |
decrementWorkerCounts(w.isTrimmed()? 0 : ONE_RUNNING, ONE_TOTAL); |
742 |
> |
while (w.stealCount != 0) // collect final count |
743 |
> |
tryAccumulateStealCount(w); |
744 |
> |
tryTerminate(false); |
745 |
|
} |
746 |
|
|
747 |
+ |
// Waiting for and signalling events |
748 |
+ |
|
749 |
|
/** |
750 |
< |
* Creates a ForkJoinPool with parallelism equal to the number of |
751 |
< |
* processors available on the system and using the given |
752 |
< |
* ForkJoinWorkerThreadFactory. |
753 |
< |
* |
373 |
< |
* @param factory the factory for creating new threads |
374 |
< |
* @throws NullPointerException if factory is null |
375 |
< |
* @throws SecurityException if a security manager exists and |
376 |
< |
* the caller is not permitted to modify threads |
377 |
< |
* because it does not hold {@link |
378 |
< |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
750 |
> |
* Releases workers blocked on a count not equal to current count. |
751 |
> |
* Normally called after precheck that eventWaiters isn't zero to |
752 |
> |
* avoid wasted array checks. Gives up upon a change in count or |
753 |
> |
* contention, letting other workers take over. |
754 |
|
*/ |
755 |
< |
public ForkJoinPool(ForkJoinWorkerThreadFactory factory) { |
756 |
< |
this(Runtime.getRuntime().availableProcessors(), factory); |
755 |
> |
private void releaseEventWaiters() { |
756 |
> |
ForkJoinWorkerThread[] ws = workers; |
757 |
> |
int n = ws.length; |
758 |
> |
long h = eventWaiters; |
759 |
> |
int ec = eventCount; |
760 |
> |
ForkJoinWorkerThread w; int id; |
761 |
> |
while ((int)(h >>> EVENT_COUNT_SHIFT) != ec && |
762 |
> |
(id = ((int)(h & WAITER_ID_MASK)) - 1) >= 0 && |
763 |
> |
id < n && (w = ws[id]) != null && |
764 |
> |
UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
765 |
> |
h, h = w.nextWaiter)) { |
766 |
> |
LockSupport.unpark(w); |
767 |
> |
if (eventWaiters != h || eventCount != ec) |
768 |
> |
break; |
769 |
> |
} |
770 |
|
} |
771 |
|
|
772 |
|
/** |
773 |
< |
* Creates a ForkJoinPool with the given parallelism and factory. |
773 |
> |
* Tries to advance eventCount and releases waiters. Called only |
774 |
> |
* from workers. |
775 |
> |
*/ |
776 |
> |
final void signalWork() { |
777 |
> |
int c; // try to increment event count -- CAS failure OK |
778 |
> |
UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1); |
779 |
> |
if (eventWaiters != 0L) |
780 |
> |
releaseEventWaiters(); |
781 |
> |
} |
782 |
> |
|
783 |
> |
/** |
784 |
> |
* Adds the given worker to event queue and blocks until |
785 |
> |
* terminating or event count advances from the workers |
786 |
> |
* lastEventCount value |
787 |
|
* |
788 |
< |
* @param parallelism the targeted number of worker threads |
388 |
< |
* @param factory the factory for creating new threads |
389 |
< |
* @throws IllegalArgumentException if parallelism less than or |
390 |
< |
* equal to zero, or greater than implementation limit |
391 |
< |
* @throws NullPointerException if factory is null |
392 |
< |
* @throws SecurityException if a security manager exists and |
393 |
< |
* the caller is not permitted to modify threads |
394 |
< |
* because it does not hold {@link |
395 |
< |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
788 |
> |
* @param w the calling worker thread |
789 |
|
*/ |
790 |
< |
public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) { |
791 |
< |
if (parallelism <= 0 || parallelism > MAX_THREADS) |
792 |
< |
throw new IllegalArgumentException(); |
793 |
< |
if (factory == null) |
794 |
< |
throw new NullPointerException(); |
795 |
< |
checkPermission(); |
796 |
< |
this.factory = factory; |
797 |
< |
this.parallelism = parallelism; |
798 |
< |
this.maxPoolSize = MAX_THREADS; |
799 |
< |
this.maintainsParallelism = true; |
800 |
< |
this.poolNumber = poolNumberGenerator.incrementAndGet(); |
801 |
< |
this.workerLock = new ReentrantLock(); |
802 |
< |
this.termination = workerLock.newCondition(); |
803 |
< |
this.stealCount = new AtomicLong(); |
411 |
< |
this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>(); |
412 |
< |
// worker array and workers are lazily constructed |
790 |
> |
private void eventSync(ForkJoinWorkerThread w) { |
791 |
> |
int ec = w.lastEventCount; |
792 |
> |
long nh = (((long)ec) << EVENT_COUNT_SHIFT) | ((long)(w.poolIndex+1)); |
793 |
> |
long h; |
794 |
> |
while ((runState < SHUTDOWN || !tryTerminate(false)) && |
795 |
> |
(((int)((h = eventWaiters) & WAITER_ID_MASK)) == 0 || |
796 |
> |
(int)(h >>> EVENT_COUNT_SHIFT) == ec) && |
797 |
> |
eventCount == ec) { |
798 |
> |
if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
799 |
> |
w.nextWaiter = h, nh)) { |
800 |
> |
awaitEvent(w, ec); |
801 |
> |
break; |
802 |
> |
} |
803 |
> |
} |
804 |
|
} |
805 |
|
|
806 |
|
/** |
807 |
< |
* Creates a new worker thread using factory. |
807 |
> |
* Blocks the given worker (that has already been entered as an |
808 |
> |
* event waiter) until terminating or event count advances from |
809 |
> |
* the given value. The oldest (first) waiter uses a timed wait to |
810 |
> |
* occasionally one-by-one shrink the number of workers (to a |
811 |
> |
* minumum of one) if the pool has not been used for extended |
812 |
> |
* periods. |
813 |
|
* |
814 |
< |
* @param index the index to assign worker |
815 |
< |
* @return new worker, or null of factory failed |
814 |
> |
* @param w the calling worker thread |
815 |
> |
* @param ec the count |
816 |
|
*/ |
817 |
< |
private ForkJoinWorkerThread createWorker(int index) { |
818 |
< |
Thread.UncaughtExceptionHandler h = ueh; |
819 |
< |
ForkJoinWorkerThread w = factory.newThread(this); |
820 |
< |
if (w != null) { |
821 |
< |
w.poolIndex = index; |
822 |
< |
w.setDaemon(true); |
823 |
< |
w.setAsyncMode(locallyFifo); |
824 |
< |
w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index); |
825 |
< |
if (h != null) |
826 |
< |
w.setUncaughtExceptionHandler(h); |
817 |
> |
private void awaitEvent(ForkJoinWorkerThread w, int ec) { |
818 |
> |
while (eventCount == ec) { |
819 |
> |
if (tryAccumulateStealCount(w)) { // transfer while idle |
820 |
> |
boolean untimed = (w.nextWaiter != 0L || |
821 |
> |
(workerCounts & RUNNING_COUNT_MASK) <= 1); |
822 |
> |
long startTime = untimed? 0 : System.nanoTime(); |
823 |
> |
Thread.interrupted(); // clear/ignore interrupt |
824 |
> |
if (eventCount != ec || !w.isRunning() || |
825 |
> |
runState >= TERMINATING) // recheck after clear |
826 |
> |
break; |
827 |
> |
if (untimed) |
828 |
> |
LockSupport.park(w); |
829 |
> |
else { |
830 |
> |
LockSupport.parkNanos(w, SHRINK_RATE_NANOS); |
831 |
> |
if (eventCount != ec || !w.isRunning() || |
832 |
> |
runState >= TERMINATING) |
833 |
> |
break; |
834 |
> |
if (System.nanoTime() - startTime >= SHRINK_RATE_NANOS) |
835 |
> |
tryShutdownWaiter(ec); |
836 |
> |
} |
837 |
> |
} |
838 |
|
} |
432 |
– |
return w; |
839 |
|
} |
840 |
|
|
841 |
|
/** |
842 |
< |
* Returns a good size for worker array given pool size. |
843 |
< |
* Currently requires size to be a power of two. |
842 |
> |
* Callback from the oldest waiter in awaitEvent waking up after a |
843 |
> |
* period of non-use. Tries (once) to shutdown an event waiter (or |
844 |
> |
* a spare, if one exists). Note that we don't need CAS or locks |
845 |
> |
* here because the method is called only from one thread |
846 |
> |
* occasionally waking (and even misfires are OK). Note that |
847 |
> |
* until the shutdown worker fully terminates, workerCounts |
848 |
> |
* will overestimate total count, which is tolerable. |
849 |
> |
* |
850 |
> |
* @param ec the event count waited on by caller (to abort |
851 |
> |
* attempt if count has since changed). |
852 |
> |
*/ |
853 |
> |
private void tryShutdownWaiter(int ec) { |
854 |
> |
if (spareWaiters != 0) { // prefer killing spares |
855 |
> |
tryShutdownSpare(); |
856 |
> |
return; |
857 |
> |
} |
858 |
> |
ForkJoinWorkerThread[] ws = workers; |
859 |
> |
int n = ws.length; |
860 |
> |
long h = eventWaiters; |
861 |
> |
ForkJoinWorkerThread w; int id; long nh; |
862 |
> |
if (runState == 0 && |
863 |
> |
submissionQueue.isEmpty() && |
864 |
> |
eventCount == ec && |
865 |
> |
(id = ((int)(h & WAITER_ID_MASK)) - 1) >= 0 && |
866 |
> |
id < n && (w = ws[id]) != null && |
867 |
> |
(nh = w.nextWaiter) != 0L && // keep at least one worker |
868 |
> |
UNSAFE.compareAndSwapLong(this, eventWaitersOffset, h, nh)) { |
869 |
> |
w.shutdown(); |
870 |
> |
LockSupport.unpark(w); |
871 |
> |
} |
872 |
> |
releaseEventWaiters(); |
873 |
> |
} |
874 |
> |
|
875 |
> |
// Maintaining spares |
876 |
> |
|
877 |
> |
/** |
878 |
> |
* Pushes worker onto the spare stack |
879 |
|
*/ |
880 |
< |
private static int arraySizeFor(int poolSize) { |
881 |
< |
return (poolSize <= 1) ? 1 : |
882 |
< |
(1 << (32 - Integer.numberOfLeadingZeros(poolSize-1))); |
880 |
> |
final void pushSpare(ForkJoinWorkerThread w) { |
881 |
> |
int ns = (++w.spareCount << SPARE_COUNT_SHIFT) | (w.poolIndex + 1); |
882 |
> |
do {} while (!UNSAFE.compareAndSwapInt(this, spareWaitersOffset, |
883 |
> |
w.nextSpare = spareWaiters,ns)); |
884 |
> |
} |
885 |
> |
|
886 |
> |
/** |
887 |
> |
* Callback from oldest spare occasionally waking up. Tries |
888 |
> |
* (once) to shutdown a spare. Same idea as tryShutdownWaiter. |
889 |
> |
*/ |
890 |
> |
final void tryShutdownSpare() { |
891 |
> |
int sw, id; |
892 |
> |
ForkJoinWorkerThread w; |
893 |
> |
ForkJoinWorkerThread[] ws; |
894 |
> |
if ((id = ((sw = spareWaiters) & SPARE_ID_MASK) - 1) >= 0 && |
895 |
> |
id < (ws = workers).length && (w = ws[id]) != null && |
896 |
> |
(workerCounts & RUNNING_COUNT_MASK) >= parallelism && |
897 |
> |
UNSAFE.compareAndSwapInt(this, spareWaitersOffset, |
898 |
> |
sw, w.nextSpare)) { |
899 |
> |
w.shutdown(); |
900 |
> |
LockSupport.unpark(w); |
901 |
> |
advanceEventCount(); |
902 |
> |
} |
903 |
|
} |
904 |
|
|
905 |
|
/** |
906 |
< |
* Creates or resizes array if necessary to hold newLength. |
907 |
< |
* Call only under exclusion. |
906 |
> |
* Tries (once) to resume a spare if worker counts match |
907 |
> |
* the given count. |
908 |
|
* |
909 |
< |
* @return the array |
909 |
> |
* @param wc workerCounts value on invocation of this method |
910 |
|
*/ |
911 |
< |
private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) { |
911 |
> |
private void tryResumeSpare(int wc) { |
912 |
|
ForkJoinWorkerThread[] ws = workers; |
913 |
< |
if (ws == null) |
914 |
< |
return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)]; |
915 |
< |
else if (newLength > ws.length) |
916 |
< |
return workers = Arrays.copyOf(ws, arraySizeFor(newLength)); |
917 |
< |
else |
918 |
< |
return ws; |
913 |
> |
int n = ws.length; |
914 |
> |
int sw, id, rs; ForkJoinWorkerThread w; |
915 |
> |
if ((id = ((sw = spareWaiters) & SPARE_ID_MASK) - 1) >= 0 && |
916 |
> |
id < n && (w = ws[id]) != null && |
917 |
> |
(rs = runState) < TERMINATING && |
918 |
> |
eventWaiters == 0L && workerCounts == wc) { |
919 |
> |
// In case all workers busy, heuristically back off to let settle |
920 |
> |
Thread.yield(); |
921 |
> |
if (eventWaiters == 0L && runState == rs && // recheck |
922 |
> |
workerCounts == wc && spareWaiters == sw && |
923 |
> |
UNSAFE.compareAndSwapInt(this, spareWaitersOffset, |
924 |
> |
sw, w.nextSpare)) { |
925 |
> |
int c; // increment running count before resume |
926 |
> |
do {} while(!UNSAFE.compareAndSwapInt |
927 |
> |
(this, workerCountsOffset, |
928 |
> |
c = workerCounts, c + ONE_RUNNING)); |
929 |
> |
if (w.tryUnsuspend()) |
930 |
> |
LockSupport.unpark(w); |
931 |
> |
else // back out if w was shutdown |
932 |
> |
decrementWorkerCounts(ONE_RUNNING, 0); |
933 |
> |
} |
934 |
> |
} |
935 |
> |
} |
936 |
> |
|
937 |
> |
// adding workers on demand |
938 |
> |
|
939 |
> |
/** |
940 |
> |
* Adds one or more workers if needed to establish target parallelism. |
941 |
> |
* Retries upon contention. |
942 |
> |
*/ |
943 |
> |
private void addWorkerIfBelowTarget() { |
944 |
> |
int pc = parallelism; |
945 |
> |
int wc; |
946 |
> |
while (((wc = workerCounts) >>> TOTAL_COUNT_SHIFT) < pc && |
947 |
> |
runState < TERMINATING) { |
948 |
> |
if (UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc, |
949 |
> |
wc + (ONE_RUNNING|ONE_TOTAL))) { |
950 |
> |
if (addWorker() == null) |
951 |
> |
break; |
952 |
> |
} |
953 |
> |
} |
954 |
|
} |
955 |
|
|
956 |
|
/** |
957 |
< |
* Tries to shrink workers into smaller array after one or more terminate. |
957 |
> |
* Tries (once) to add a new worker if all existing workers are |
958 |
> |
* busy, and there are either no running workers or the deficit is |
959 |
> |
* at least twice the surplus. |
960 |
> |
* |
961 |
> |
* @param wc workerCounts value on invocation of this method |
962 |
|
*/ |
963 |
< |
private void tryShrinkWorkerArray() { |
964 |
< |
ForkJoinWorkerThread[] ws = workers; |
965 |
< |
if (ws != null) { |
966 |
< |
int len = ws.length; |
967 |
< |
int last = len - 1; |
968 |
< |
while (last >= 0 && ws[last] == null) |
969 |
< |
--last; |
970 |
< |
int newLength = arraySizeFor(last+1); |
971 |
< |
if (newLength < len) |
972 |
< |
workers = Arrays.copyOf(ws, newLength); |
963 |
> |
private void tryAddWorkerIfBusy(int wc) { |
964 |
> |
int tc, rc, rs; |
965 |
> |
int pc = parallelism; |
966 |
> |
if ((tc = wc >>> TOTAL_COUNT_SHIFT) < MAX_WORKERS && |
967 |
> |
((rc = wc & RUNNING_COUNT_MASK) == 0 || |
968 |
> |
rc < pc - ((tc - pc) << 1)) && |
969 |
> |
(rs = runState) < TERMINATING && |
970 |
> |
(rs & ACTIVE_COUNT_MASK) == tc) { |
971 |
> |
// Since all workers busy, heuristically back off to let settle |
972 |
> |
Thread.yield(); |
973 |
> |
if (eventWaiters == 0L && spareWaiters == 0 && // recheck |
974 |
> |
runState == rs && workerCounts == wc && |
975 |
> |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc, |
976 |
> |
wc + (ONE_RUNNING|ONE_TOTAL))) |
977 |
> |
addWorker(); |
978 |
|
} |
979 |
|
} |
980 |
|
|
981 |
|
/** |
982 |
< |
* Initializes workers if necessary. |
982 |
> |
* Does at most one of: |
983 |
> |
* |
984 |
> |
* 1. Help wake up existing workers waiting for work via |
985 |
> |
* releaseEventWaiters. (If any exist, then it doesn't |
986 |
> |
* matter right now if under target parallelism level.) |
987 |
> |
* |
988 |
> |
* 2. If a spare exists, try (once) to resume it via tryResumeSpare. |
989 |
> |
* |
990 |
> |
* 3. If there are not enough total workers, add some |
991 |
> |
* via addWorkerIfBelowTarget; |
992 |
> |
* |
993 |
> |
* 4. Try (once) to add a new worker if all existing workers |
994 |
> |
* are busy, via tryAddWorkerIfBusy |
995 |
|
*/ |
996 |
< |
final void ensureWorkerInitialization() { |
997 |
< |
ForkJoinWorkerThread[] ws = workers; |
998 |
< |
if (ws == null) { |
999 |
< |
final ReentrantLock lock = this.workerLock; |
1000 |
< |
lock.lock(); |
1001 |
< |
try { |
1002 |
< |
ws = workers; |
1003 |
< |
if (ws == null) { |
1004 |
< |
int ps = parallelism; |
1005 |
< |
ws = ensureWorkerArrayCapacity(ps); |
1006 |
< |
for (int i = 0; i < ps; ++i) { |
1007 |
< |
ForkJoinWorkerThread w = createWorker(i); |
1008 |
< |
if (w != null) { |
1009 |
< |
ws[i] = w; |
1010 |
< |
w.start(); |
1011 |
< |
updateWorkerCount(1); |
1012 |
< |
} |
996 |
> |
private void helpMaintainParallelism() { |
997 |
> |
long h; int pc, wc; |
998 |
> |
if (((int)((h = eventWaiters) & WAITER_ID_MASK)) != 0) { |
999 |
> |
if ((int)(h >>> EVENT_COUNT_SHIFT) != eventCount) |
1000 |
> |
releaseEventWaiters(); // avoid useless call |
1001 |
> |
} |
1002 |
> |
else if ((pc = parallelism) > |
1003 |
> |
((wc = workerCounts) & RUNNING_COUNT_MASK)) { |
1004 |
> |
if (spareWaiters != 0) |
1005 |
> |
tryResumeSpare(wc); |
1006 |
> |
else if ((wc >>> TOTAL_COUNT_SHIFT) < pc) |
1007 |
> |
addWorkerIfBelowTarget(); |
1008 |
> |
else |
1009 |
> |
tryAddWorkerIfBusy(wc); |
1010 |
> |
} |
1011 |
> |
} |
1012 |
> |
|
1013 |
> |
/** |
1014 |
> |
* Callback from workers invoked upon each top-level action (i.e., |
1015 |
> |
* stealing a task or taking a submission and running it). |
1016 |
> |
* Performs one or more of the following: |
1017 |
> |
* |
1018 |
> |
* 1. If the worker is active, try to set its active status to |
1019 |
> |
* inactive and update activeCount. On contention, we may try |
1020 |
> |
* again on this or subsequent call. |
1021 |
> |
* |
1022 |
> |
* 2. Release any existing event waiters that are now relesable |
1023 |
> |
* |
1024 |
> |
* 3. If there are too many running threads, suspend this worker |
1025 |
> |
* (first forcing inactive if necessary). If it is not |
1026 |
> |
* needed, it may be killed while suspended via |
1027 |
> |
* tryShutdownSpare. Otherwise, upon resume it rechecks to make |
1028 |
> |
* sure that it is still needed. |
1029 |
> |
* |
1030 |
> |
* 4. If more than 1 miss, await the next task event via |
1031 |
> |
* eventSync (first forcing inactivation if necessary), upon |
1032 |
> |
* which worker may also be killed, via tryShutdownWaiter. |
1033 |
> |
* |
1034 |
> |
* 5. Help reactivate other workers via helpMaintainParallelism |
1035 |
> |
* |
1036 |
> |
* @param w the worker |
1037 |
> |
* @param misses the number of scans by caller failing to find work |
1038 |
> |
* (saturating at 2 to avoid wraparound) |
1039 |
> |
*/ |
1040 |
> |
final void preStep(ForkJoinWorkerThread w, int misses) { |
1041 |
> |
boolean active = w.active; |
1042 |
> |
int pc = parallelism; |
1043 |
> |
for (;;) { |
1044 |
> |
int rs, wc, rc, ec; long h; |
1045 |
> |
if (active && UNSAFE.compareAndSwapInt(this, runStateOffset, |
1046 |
> |
rs = runState, rs - 1)) |
1047 |
> |
active = w.active = false; |
1048 |
> |
if (((int)((h = eventWaiters) & WAITER_ID_MASK)) != 0 && |
1049 |
> |
(int)(h >>> EVENT_COUNT_SHIFT) != eventCount) { |
1050 |
> |
releaseEventWaiters(); |
1051 |
> |
if (misses > 1) |
1052 |
> |
continue; // clear before sync below |
1053 |
> |
} |
1054 |
> |
if ((rc = ((wc = workerCounts) & RUNNING_COUNT_MASK)) > pc) { |
1055 |
> |
if (!active && // must inactivate to suspend |
1056 |
> |
workerCounts == wc && // try to suspend as spare |
1057 |
> |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
1058 |
> |
wc, wc - ONE_RUNNING)) { |
1059 |
> |
w.suspendAsSpare(); |
1060 |
> |
if (!w.isRunning()) |
1061 |
> |
break; // was killed while spare |
1062 |
> |
} |
1063 |
> |
continue; |
1064 |
> |
} |
1065 |
> |
if (misses > 0) { |
1066 |
> |
if ((ec = eventCount) == w.lastEventCount && misses > 1) { |
1067 |
> |
if (!active) { // must inactivate to sync |
1068 |
> |
eventSync(w); |
1069 |
> |
if (w.isRunning()) |
1070 |
> |
misses = 1; // don't re-sync |
1071 |
> |
else |
1072 |
> |
break; // was killed while waiting |
1073 |
|
} |
1074 |
+ |
continue; |
1075 |
|
} |
1076 |
< |
} finally { |
499 |
< |
lock.unlock(); |
1076 |
> |
w.lastEventCount = ec; |
1077 |
|
} |
1078 |
+ |
if (rc < pc) |
1079 |
+ |
helpMaintainParallelism(); |
1080 |
+ |
break; |
1081 |
|
} |
1082 |
|
} |
1083 |
|
|
1084 |
|
/** |
1085 |
< |
* Worker creation and startup for threads added via setParallelism. |
1085 |
> |
* Helps and/or blocks awaiting join of the given task. |
1086 |
> |
* Alternates between helpJoinTask() and helpMaintainParallelism() |
1087 |
> |
* as many times as there is a deficit in running count (or longer |
1088 |
> |
* if running count would become zero), then blocks if task still |
1089 |
> |
* not done. |
1090 |
> |
* |
1091 |
> |
* @param joinMe the task to join |
1092 |
|
*/ |
1093 |
< |
private void createAndStartAddedWorkers() { |
1094 |
< |
resumeAllSpares(); // Allow spares to convert to nonspare |
1095 |
< |
int ps = parallelism; |
1096 |
< |
ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps); |
1097 |
< |
int len = ws.length; |
1098 |
< |
// Sweep through slots, to keep lowest indices most populated |
1099 |
< |
int k = 0; |
1100 |
< |
while (k < len) { |
1101 |
< |
if (ws[k] != null) { |
1102 |
< |
++k; |
1103 |
< |
continue; |
1093 |
> |
final void awaitJoin(ForkJoinTask<?> joinMe, ForkJoinWorkerThread worker) { |
1094 |
> |
int threshold = parallelism; // descend blocking thresholds |
1095 |
> |
while (joinMe.status >= 0) { |
1096 |
> |
boolean block; int wc; |
1097 |
> |
worker.helpJoinTask(joinMe); |
1098 |
> |
if (joinMe.status < 0) |
1099 |
> |
break; |
1100 |
> |
if (((wc = workerCounts) & RUNNING_COUNT_MASK) <= threshold) { |
1101 |
> |
if (threshold > 0) |
1102 |
> |
--threshold; |
1103 |
> |
else |
1104 |
> |
advanceEventCount(); // force release |
1105 |
> |
block = false; |
1106 |
|
} |
1107 |
< |
int s = workerCounts; |
1108 |
< |
int tc = totalCountOf(s); |
1109 |
< |
int rc = runningCountOf(s); |
1110 |
< |
if (rc >= ps || tc >= ps) |
1107 |
> |
else |
1108 |
> |
block = UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
1109 |
> |
wc, wc - ONE_RUNNING); |
1110 |
> |
helpMaintainParallelism(); |
1111 |
> |
if (block) { |
1112 |
> |
int c; |
1113 |
> |
joinMe.internalAwaitDone(); |
1114 |
> |
do {} while (!UNSAFE.compareAndSwapInt |
1115 |
> |
(this, workerCountsOffset, |
1116 |
> |
c = workerCounts, c + ONE_RUNNING)); |
1117 |
|
break; |
1118 |
< |
if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) { |
1119 |
< |
ForkJoinWorkerThread w = createWorker(k); |
1120 |
< |
if (w != null) { |
1121 |
< |
ws[k++] = w; |
1122 |
< |
w.start(); |
1118 |
> |
} |
1119 |
> |
} |
1120 |
> |
} |
1121 |
> |
|
1122 |
> |
/** |
1123 |
> |
* Same idea as awaitJoin, but no helping |
1124 |
> |
*/ |
1125 |
> |
final void awaitBlocker(ManagedBlocker blocker) |
1126 |
> |
throws InterruptedException { |
1127 |
> |
int threshold = parallelism; |
1128 |
> |
while (!blocker.isReleasable()) { |
1129 |
> |
boolean block; int wc; |
1130 |
> |
if (((wc = workerCounts) & RUNNING_COUNT_MASK) <= threshold) { |
1131 |
> |
if (threshold > 0) |
1132 |
> |
--threshold; |
1133 |
> |
else |
1134 |
> |
advanceEventCount(); |
1135 |
> |
block = false; |
1136 |
> |
} |
1137 |
> |
else |
1138 |
> |
block = UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
1139 |
> |
wc, wc - ONE_RUNNING); |
1140 |
> |
helpMaintainParallelism(); |
1141 |
> |
if (block) { |
1142 |
> |
try { |
1143 |
> |
do {} while (!blocker.isReleasable() && !blocker.block()); |
1144 |
> |
} finally { |
1145 |
> |
int c; |
1146 |
> |
do {} while (!UNSAFE.compareAndSwapInt |
1147 |
> |
(this, workerCountsOffset, |
1148 |
> |
c = workerCounts, c + ONE_RUNNING)); |
1149 |
|
} |
1150 |
< |
else { |
1151 |
< |
updateWorkerCount(-1); // back out on failed creation |
1152 |
< |
break; |
1150 |
> |
break; |
1151 |
> |
} |
1152 |
> |
} |
1153 |
> |
} |
1154 |
> |
|
1155 |
> |
/** |
1156 |
> |
* Possibly initiates and/or completes termination. |
1157 |
> |
* |
1158 |
> |
* @param now if true, unconditionally terminate, else only |
1159 |
> |
* if shutdown and empty queue and no active workers |
1160 |
> |
* @return true if now terminating or terminated |
1161 |
> |
*/ |
1162 |
> |
private boolean tryTerminate(boolean now) { |
1163 |
> |
if (now) |
1164 |
> |
advanceRunLevel(SHUTDOWN); // ensure at least SHUTDOWN |
1165 |
> |
else if (runState < SHUTDOWN || |
1166 |
> |
!submissionQueue.isEmpty() || |
1167 |
> |
(runState & ACTIVE_COUNT_MASK) != 0) |
1168 |
> |
return false; |
1169 |
> |
|
1170 |
> |
if (advanceRunLevel(TERMINATING)) |
1171 |
> |
startTerminating(); |
1172 |
> |
|
1173 |
> |
// Finish now if all threads terminated; else in some subsequent call |
1174 |
> |
if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) { |
1175 |
> |
advanceRunLevel(TERMINATED); |
1176 |
> |
termination.arrive(); |
1177 |
> |
} |
1178 |
> |
return true; |
1179 |
> |
} |
1180 |
> |
|
1181 |
> |
/** |
1182 |
> |
* Actions on transition to TERMINATING |
1183 |
> |
* |
1184 |
> |
* Runs up to four passes through workers: (0) shutting down each |
1185 |
> |
* (without waking up if parked) to quickly spread notifications |
1186 |
> |
* without unnecessary bouncing around event queues etc (1) wake |
1187 |
> |
* up and help cancel tasks (2) interrupt (3) mop up races with |
1188 |
> |
* interrupted workers |
1189 |
> |
*/ |
1190 |
> |
private void startTerminating() { |
1191 |
> |
cancelSubmissions(); |
1192 |
> |
for (int passes = 0; passes < 4 && workerCounts != 0; ++passes) { |
1193 |
> |
advanceEventCount(); |
1194 |
> |
eventWaiters = 0L; // clobber lists |
1195 |
> |
spareWaiters = 0; |
1196 |
> |
ForkJoinWorkerThread[] ws = workers; |
1197 |
> |
int n = ws.length; |
1198 |
> |
for (int i = 0; i < n; ++i) { |
1199 |
> |
ForkJoinWorkerThread w = ws[i]; |
1200 |
> |
if (w != null) { |
1201 |
> |
w.shutdown(); |
1202 |
> |
if (passes > 0 && !w.isTerminated()) { |
1203 |
> |
w.cancelTasks(); |
1204 |
> |
LockSupport.unpark(w); |
1205 |
> |
if (passes > 1) { |
1206 |
> |
try { |
1207 |
> |
w.interrupt(); |
1208 |
> |
} catch (SecurityException ignore) { |
1209 |
> |
} |
1210 |
> |
} |
1211 |
> |
} |
1212 |
|
} |
1213 |
|
} |
1214 |
|
} |
1215 |
|
} |
1216 |
|
|
1217 |
+ |
/** |
1218 |
+ |
* Clear out and cancel submissions, ignoring exceptions |
1219 |
+ |
*/ |
1220 |
+ |
private void cancelSubmissions() { |
1221 |
+ |
ForkJoinTask<?> task; |
1222 |
+ |
while ((task = submissionQueue.poll()) != null) { |
1223 |
+ |
try { |
1224 |
+ |
task.cancel(false); |
1225 |
+ |
} catch (Throwable ignore) { |
1226 |
+ |
} |
1227 |
+ |
} |
1228 |
+ |
} |
1229 |
+ |
|
1230 |
+ |
// misc support for ForkJoinWorkerThread |
1231 |
+ |
|
1232 |
+ |
/** |
1233 |
+ |
* Returns pool number |
1234 |
+ |
*/ |
1235 |
+ |
final int getPoolNumber() { |
1236 |
+ |
return poolNumber; |
1237 |
+ |
} |
1238 |
+ |
|
1239 |
+ |
/** |
1240 |
+ |
* Tries to accumulates steal count from a worker, clearing |
1241 |
+ |
* the worker's value. |
1242 |
+ |
* |
1243 |
+ |
* @return true if worker steal count now zero |
1244 |
+ |
*/ |
1245 |
+ |
final boolean tryAccumulateStealCount(ForkJoinWorkerThread w) { |
1246 |
+ |
int sc = w.stealCount; |
1247 |
+ |
long c = stealCount; |
1248 |
+ |
// CAS even if zero, for fence effects |
1249 |
+ |
if (UNSAFE.compareAndSwapLong(this, stealCountOffset, c, c + sc)) { |
1250 |
+ |
if (sc != 0) |
1251 |
+ |
w.stealCount = 0; |
1252 |
+ |
return true; |
1253 |
+ |
} |
1254 |
+ |
return sc == 0; |
1255 |
+ |
} |
1256 |
+ |
|
1257 |
+ |
/** |
1258 |
+ |
* Returns the approximate (non-atomic) number of idle threads per |
1259 |
+ |
* active thread. |
1260 |
+ |
*/ |
1261 |
+ |
final int idlePerActive() { |
1262 |
+ |
int pc = parallelism; // use parallelism, not rc |
1263 |
+ |
int ac = runState; // no mask -- artifically boosts during shutdown |
1264 |
+ |
// Use exact results for small values, saturate past 4 |
1265 |
+ |
return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3; |
1266 |
+ |
} |
1267 |
+ |
|
1268 |
+ |
// Public and protected methods |
1269 |
+ |
|
1270 |
+ |
// Constructors |
1271 |
+ |
|
1272 |
+ |
/** |
1273 |
+ |
* Creates a {@code ForkJoinPool} with parallelism equal to {@link |
1274 |
+ |
* java.lang.Runtime#availableProcessors}, using the {@linkplain |
1275 |
+ |
* #defaultForkJoinWorkerThreadFactory default thread factory}, |
1276 |
+ |
* no UncaughtExceptionHandler, and non-async LIFO processing mode. |
1277 |
+ |
* |
1278 |
+ |
* @throws SecurityException if a security manager exists and |
1279 |
+ |
* the caller is not permitted to modify threads |
1280 |
+ |
* because it does not hold {@link |
1281 |
+ |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1282 |
+ |
*/ |
1283 |
+ |
public ForkJoinPool() { |
1284 |
+ |
this(Runtime.getRuntime().availableProcessors(), |
1285 |
+ |
defaultForkJoinWorkerThreadFactory, null, false); |
1286 |
+ |
} |
1287 |
+ |
|
1288 |
+ |
/** |
1289 |
+ |
* Creates a {@code ForkJoinPool} with the indicated parallelism |
1290 |
+ |
* level, the {@linkplain |
1291 |
+ |
* #defaultForkJoinWorkerThreadFactory default thread factory}, |
1292 |
+ |
* no UncaughtExceptionHandler, and non-async LIFO processing mode. |
1293 |
+ |
* |
1294 |
+ |
* @param parallelism the parallelism level |
1295 |
+ |
* @throws IllegalArgumentException if parallelism less than or |
1296 |
+ |
* equal to zero, or greater than implementation limit |
1297 |
+ |
* @throws SecurityException if a security manager exists and |
1298 |
+ |
* the caller is not permitted to modify threads |
1299 |
+ |
* because it does not hold {@link |
1300 |
+ |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1301 |
+ |
*/ |
1302 |
+ |
public ForkJoinPool(int parallelism) { |
1303 |
+ |
this(parallelism, defaultForkJoinWorkerThreadFactory, null, false); |
1304 |
+ |
} |
1305 |
+ |
|
1306 |
+ |
/** |
1307 |
+ |
* Creates a {@code ForkJoinPool} with the given parameters. |
1308 |
+ |
* |
1309 |
+ |
* @param parallelism the parallelism level. For default value, |
1310 |
+ |
* use {@link java.lang.Runtime#availableProcessors}. |
1311 |
+ |
* @param factory the factory for creating new threads. For default value, |
1312 |
+ |
* use {@link #defaultForkJoinWorkerThreadFactory}. |
1313 |
+ |
* @param handler the handler for internal worker threads that |
1314 |
+ |
* terminate due to unrecoverable errors encountered while executing |
1315 |
+ |
* tasks. For default value, use <code>null</code>. |
1316 |
+ |
* @param asyncMode if true, |
1317 |
+ |
* establishes local first-in-first-out scheduling mode for forked |
1318 |
+ |
* tasks that are never joined. This mode may be more appropriate |
1319 |
+ |
* than default locally stack-based mode in applications in which |
1320 |
+ |
* worker threads only process event-style asynchronous tasks. |
1321 |
+ |
* For default value, use <code>false</code>. |
1322 |
+ |
* @throws IllegalArgumentException if parallelism less than or |
1323 |
+ |
* equal to zero, or greater than implementation limit |
1324 |
+ |
* @throws NullPointerException if the factory is null |
1325 |
+ |
* @throws SecurityException if a security manager exists and |
1326 |
+ |
* the caller is not permitted to modify threads |
1327 |
+ |
* because it does not hold {@link |
1328 |
+ |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1329 |
+ |
*/ |
1330 |
+ |
public ForkJoinPool(int parallelism, |
1331 |
+ |
ForkJoinWorkerThreadFactory factory, |
1332 |
+ |
Thread.UncaughtExceptionHandler handler, |
1333 |
+ |
boolean asyncMode) { |
1334 |
+ |
checkPermission(); |
1335 |
+ |
if (factory == null) |
1336 |
+ |
throw new NullPointerException(); |
1337 |
+ |
if (parallelism <= 0 || parallelism > MAX_WORKERS) |
1338 |
+ |
throw new IllegalArgumentException(); |
1339 |
+ |
this.parallelism = parallelism; |
1340 |
+ |
this.factory = factory; |
1341 |
+ |
this.ueh = handler; |
1342 |
+ |
this.locallyFifo = asyncMode; |
1343 |
+ |
int arraySize = initialArraySizeFor(parallelism); |
1344 |
+ |
this.workers = new ForkJoinWorkerThread[arraySize]; |
1345 |
+ |
this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>(); |
1346 |
+ |
this.workerLock = new ReentrantLock(); |
1347 |
+ |
this.termination = new Phaser(1); |
1348 |
+ |
this.poolNumber = poolNumberGenerator.incrementAndGet(); |
1349 |
+ |
} |
1350 |
+ |
|
1351 |
+ |
/** |
1352 |
+ |
* Returns initial power of two size for workers array. |
1353 |
+ |
* @param pc the initial parallelism level |
1354 |
+ |
*/ |
1355 |
+ |
private static int initialArraySizeFor(int pc) { |
1356 |
+ |
// See Hackers Delight, sec 3.2. We know MAX_WORKERS < (1 >>> 16) |
1357 |
+ |
int size = pc < MAX_WORKERS ? pc + 1 : MAX_WORKERS; |
1358 |
+ |
size |= size >>> 1; |
1359 |
+ |
size |= size >>> 2; |
1360 |
+ |
size |= size >>> 4; |
1361 |
+ |
size |= size >>> 8; |
1362 |
+ |
return size + 1; |
1363 |
+ |
} |
1364 |
+ |
|
1365 |
|
// Execution methods |
1366 |
|
|
1367 |
|
/** |
1368 |
|
* Common code for execute, invoke and submit |
1369 |
|
*/ |
1370 |
|
private <T> void doSubmit(ForkJoinTask<T> task) { |
1371 |
< |
if (isShutdown()) |
1371 |
> |
if (task == null) |
1372 |
> |
throw new NullPointerException(); |
1373 |
> |
if (runState >= SHUTDOWN) |
1374 |
|
throw new RejectedExecutionException(); |
546 |
– |
if (workers == null) |
547 |
– |
ensureWorkerInitialization(); |
1375 |
|
submissionQueue.offer(task); |
1376 |
< |
signalIdleWorkers(); |
1376 |
> |
advanceEventCount(); |
1377 |
> |
if (eventWaiters != 0L) |
1378 |
> |
releaseEventWaiters(); |
1379 |
> |
if ((workerCounts >>> TOTAL_COUNT_SHIFT) < parallelism) |
1380 |
> |
addWorkerIfBelowTarget(); |
1381 |
|
} |
1382 |
|
|
1383 |
|
/** |
1385 |
|
* |
1386 |
|
* @param task the task |
1387 |
|
* @return the task's result |
1388 |
< |
* @throws NullPointerException if task is null |
1389 |
< |
* @throws RejectedExecutionException if pool is shut down |
1388 |
> |
* @throws NullPointerException if the task is null |
1389 |
> |
* @throws RejectedExecutionException if the task cannot be |
1390 |
> |
* scheduled for execution |
1391 |
|
*/ |
1392 |
|
public <T> T invoke(ForkJoinTask<T> task) { |
1393 |
|
doSubmit(task); |
1398 |
|
* Arranges for (asynchronous) execution of the given task. |
1399 |
|
* |
1400 |
|
* @param task the task |
1401 |
< |
* @throws NullPointerException if task is null |
1402 |
< |
* @throws RejectedExecutionException if pool is shut down |
1401 |
> |
* @throws NullPointerException if the task is null |
1402 |
> |
* @throws RejectedExecutionException if the task cannot be |
1403 |
> |
* scheduled for execution |
1404 |
|
*/ |
1405 |
< |
public <T> void execute(ForkJoinTask<T> task) { |
1405 |
> |
public void execute(ForkJoinTask<?> task) { |
1406 |
|
doSubmit(task); |
1407 |
|
} |
1408 |
|
|
1409 |
|
// AbstractExecutorService methods |
1410 |
|
|
1411 |
+ |
/** |
1412 |
+ |
* @throws NullPointerException if the task is null |
1413 |
+ |
* @throws RejectedExecutionException if the task cannot be |
1414 |
+ |
* scheduled for execution |
1415 |
+ |
*/ |
1416 |
|
public void execute(Runnable task) { |
1417 |
< |
doSubmit(new AdaptedRunnable<Void>(task, null)); |
1417 |
> |
ForkJoinTask<?> job; |
1418 |
> |
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
1419 |
> |
job = (ForkJoinTask<?>) task; |
1420 |
> |
else |
1421 |
> |
job = ForkJoinTask.adapt(task, null); |
1422 |
> |
doSubmit(job); |
1423 |
> |
} |
1424 |
> |
|
1425 |
> |
/** |
1426 |
> |
* Submits a ForkJoinTask for execution. |
1427 |
> |
* |
1428 |
> |
* @param task the task to submit |
1429 |
> |
* @return the task |
1430 |
> |
* @throws NullPointerException if the task is null |
1431 |
> |
* @throws RejectedExecutionException if the task cannot be |
1432 |
> |
* scheduled for execution |
1433 |
> |
*/ |
1434 |
> |
public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) { |
1435 |
> |
doSubmit(task); |
1436 |
> |
return task; |
1437 |
|
} |
1438 |
|
|
1439 |
+ |
/** |
1440 |
+ |
* @throws NullPointerException if the task is null |
1441 |
+ |
* @throws RejectedExecutionException if the task cannot be |
1442 |
+ |
* scheduled for execution |
1443 |
+ |
*/ |
1444 |
|
public <T> ForkJoinTask<T> submit(Callable<T> task) { |
1445 |
< |
ForkJoinTask<T> job = new AdaptedCallable<T>(task); |
1445 |
> |
ForkJoinTask<T> job = ForkJoinTask.adapt(task); |
1446 |
|
doSubmit(job); |
1447 |
|
return job; |
1448 |
|
} |
1449 |
|
|
1450 |
+ |
/** |
1451 |
+ |
* @throws NullPointerException if the task is null |
1452 |
+ |
* @throws RejectedExecutionException if the task cannot be |
1453 |
+ |
* scheduled for execution |
1454 |
+ |
*/ |
1455 |
|
public <T> ForkJoinTask<T> submit(Runnable task, T result) { |
1456 |
< |
ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result); |
1456 |
> |
ForkJoinTask<T> job = ForkJoinTask.adapt(task, result); |
1457 |
|
doSubmit(job); |
1458 |
|
return job; |
1459 |
|
} |
1460 |
|
|
1461 |
+ |
/** |
1462 |
+ |
* @throws NullPointerException if the task is null |
1463 |
+ |
* @throws RejectedExecutionException if the task cannot be |
1464 |
+ |
* scheduled for execution |
1465 |
+ |
*/ |
1466 |
|
public ForkJoinTask<?> submit(Runnable task) { |
1467 |
< |
ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null); |
1467 |
> |
ForkJoinTask<?> job; |
1468 |
> |
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
1469 |
> |
job = (ForkJoinTask<?>) task; |
1470 |
> |
else |
1471 |
> |
job = ForkJoinTask.adapt(task, null); |
1472 |
|
doSubmit(job); |
1473 |
|
return job; |
1474 |
|
} |
1475 |
|
|
1476 |
|
/** |
1477 |
< |
* Adaptor for Runnables. This implements RunnableFuture |
1478 |
< |
* to be compliant with AbstractExecutorService constraints. |
1477 |
> |
* @throws NullPointerException {@inheritDoc} |
1478 |
> |
* @throws RejectedExecutionException {@inheritDoc} |
1479 |
|
*/ |
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 |
627 |
– |
*/ |
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 |
– |
|
1480 |
|
public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) { |
1481 |
|
ArrayList<ForkJoinTask<T>> forkJoinTasks = |
1482 |
|
new ArrayList<ForkJoinTask<T>>(tasks.size()); |
1483 |
|
for (Callable<T> task : tasks) |
1484 |
< |
forkJoinTasks.add(new AdaptedCallable<T>(task)); |
1484 |
> |
forkJoinTasks.add(ForkJoinTask.adapt(task)); |
1485 |
|
invoke(new InvokeAll<T>(forkJoinTasks)); |
1486 |
|
|
1487 |
|
@SuppressWarnings({"unchecked", "rawtypes"}) |
1488 |
< |
List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks; |
1488 |
> |
List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks; |
1489 |
|
return futures; |
1490 |
|
} |
1491 |
|
|
1499 |
|
private static final long serialVersionUID = -7914297376763021607L; |
1500 |
|
} |
1501 |
|
|
676 |
– |
// Configuration and status settings and queries |
677 |
– |
|
1502 |
|
/** |
1503 |
|
* Returns the factory used for constructing new workers. |
1504 |
|
* |
1512 |
|
* Returns the handler for internal worker threads that terminate |
1513 |
|
* due to unrecoverable errors encountered while executing tasks. |
1514 |
|
* |
1515 |
< |
* @return the handler, or null if none |
1515 |
> |
* @return the handler, or {@code null} if none |
1516 |
|
*/ |
1517 |
|
public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() { |
1518 |
< |
Thread.UncaughtExceptionHandler h; |
695 |
< |
final ReentrantLock lock = this.workerLock; |
696 |
< |
lock.lock(); |
697 |
< |
try { |
698 |
< |
h = ueh; |
699 |
< |
} finally { |
700 |
< |
lock.unlock(); |
701 |
< |
} |
702 |
< |
return h; |
703 |
< |
} |
704 |
< |
|
705 |
< |
/** |
706 |
< |
* Sets the handler for internal worker threads that terminate due |
707 |
< |
* to unrecoverable errors encountered while executing tasks. |
708 |
< |
* Unless set, the current default or ThreadGroup handler is used |
709 |
< |
* as handler. |
710 |
< |
* |
711 |
< |
* @param h the new handler |
712 |
< |
* @return the old handler, or null if none |
713 |
< |
* @throws SecurityException if a security manager exists and |
714 |
< |
* the caller is not permitted to modify threads |
715 |
< |
* because it does not hold {@link |
716 |
< |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
717 |
< |
*/ |
718 |
< |
public Thread.UncaughtExceptionHandler |
719 |
< |
setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) { |
720 |
< |
checkPermission(); |
721 |
< |
Thread.UncaughtExceptionHandler old = null; |
722 |
< |
final ReentrantLock lock = this.workerLock; |
723 |
< |
lock.lock(); |
724 |
< |
try { |
725 |
< |
old = ueh; |
726 |
< |
ueh = h; |
727 |
< |
ForkJoinWorkerThread[] ws = workers; |
728 |
< |
if (ws != null) { |
729 |
< |
for (int i = 0; i < ws.length; ++i) { |
730 |
< |
ForkJoinWorkerThread w = ws[i]; |
731 |
< |
if (w != null) |
732 |
< |
w.setUncaughtExceptionHandler(h); |
733 |
< |
} |
734 |
< |
} |
735 |
< |
} finally { |
736 |
< |
lock.unlock(); |
737 |
< |
} |
738 |
< |
return old; |
739 |
< |
} |
740 |
< |
|
741 |
< |
|
742 |
< |
/** |
743 |
< |
* Sets the target parallelism level of this pool. |
744 |
< |
* |
745 |
< |
* @param parallelism the target parallelism |
746 |
< |
* @throws IllegalArgumentException if parallelism less than or |
747 |
< |
* equal to zero or greater than maximum size bounds |
748 |
< |
* @throws SecurityException if a security manager exists and |
749 |
< |
* the caller is not permitted to modify threads |
750 |
< |
* because it does not hold {@link |
751 |
< |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
752 |
< |
*/ |
753 |
< |
public void setParallelism(int parallelism) { |
754 |
< |
checkPermission(); |
755 |
< |
if (parallelism <= 0 || parallelism > maxPoolSize) |
756 |
< |
throw new IllegalArgumentException(); |
757 |
< |
final ReentrantLock lock = this.workerLock; |
758 |
< |
lock.lock(); |
759 |
< |
try { |
760 |
< |
if (!isTerminating()) { |
761 |
< |
int p = this.parallelism; |
762 |
< |
this.parallelism = parallelism; |
763 |
< |
if (parallelism > p) |
764 |
< |
createAndStartAddedWorkers(); |
765 |
< |
else |
766 |
< |
trimSpares(); |
767 |
< |
} |
768 |
< |
} finally { |
769 |
< |
lock.unlock(); |
770 |
< |
} |
771 |
< |
signalIdleWorkers(); |
1518 |
> |
return ueh; |
1519 |
|
} |
1520 |
|
|
1521 |
|
/** |
1522 |
< |
* Returns the targeted number of worker threads in this pool. |
1522 |
> |
* Returns the targeted parallelism level of this pool. |
1523 |
|
* |
1524 |
< |
* @return the targeted number of worker threads in this pool |
1524 |
> |
* @return the targeted parallelism level of this pool |
1525 |
|
*/ |
1526 |
|
public int getParallelism() { |
1527 |
|
return parallelism; |
1530 |
|
/** |
1531 |
|
* Returns the number of worker threads that have started but not |
1532 |
|
* yet terminated. This result returned by this method may differ |
1533 |
< |
* from {@code getParallelism} when threads are created to |
1533 |
> |
* from {@link #getParallelism} when threads are created to |
1534 |
|
* maintain parallelism when others are cooperatively blocked. |
1535 |
|
* |
1536 |
|
* @return the number of worker threads |
1537 |
|
*/ |
1538 |
|
public int getPoolSize() { |
1539 |
< |
return totalCountOf(workerCounts); |
1539 |
> |
return workerCounts >>> TOTAL_COUNT_SHIFT; |
1540 |
|
} |
1541 |
|
|
1542 |
|
/** |
1543 |
< |
* Returns the maximum number of threads allowed to exist in the |
797 |
< |
* pool, even if there are insufficient unblocked running threads. |
798 |
< |
* |
799 |
< |
* @return the maximum |
800 |
< |
*/ |
801 |
< |
public int getMaximumPoolSize() { |
802 |
< |
return maxPoolSize; |
803 |
< |
} |
804 |
< |
|
805 |
< |
/** |
806 |
< |
* Sets the maximum number of threads allowed to exist in the |
807 |
< |
* pool, even if there are insufficient unblocked running threads. |
808 |
< |
* Setting this value has no effect on current pool size. It |
809 |
< |
* controls construction of new threads. |
810 |
< |
* |
811 |
< |
* @throws IllegalArgumentException if negative or greater then |
812 |
< |
* internal implementation limit |
813 |
< |
*/ |
814 |
< |
public void setMaximumPoolSize(int newMax) { |
815 |
< |
if (newMax < 0 || newMax > MAX_THREADS) |
816 |
< |
throw new IllegalArgumentException(); |
817 |
< |
maxPoolSize = newMax; |
818 |
< |
} |
819 |
< |
|
820 |
< |
|
821 |
< |
/** |
822 |
< |
* Returns true if this pool dynamically maintains its target |
823 |
< |
* parallelism level. If false, new threads are added only to |
824 |
< |
* avoid possible starvation. |
825 |
< |
* This setting is by default true. |
826 |
< |
* |
827 |
< |
* @return true if maintains parallelism |
828 |
< |
*/ |
829 |
< |
public boolean getMaintainsParallelism() { |
830 |
< |
return maintainsParallelism; |
831 |
< |
} |
832 |
< |
|
833 |
< |
/** |
834 |
< |
* Sets whether this pool dynamically maintains its target |
835 |
< |
* parallelism level. If false, new threads are added only to |
836 |
< |
* avoid possible starvation. |
837 |
< |
* |
838 |
< |
* @param enable true to maintains parallelism |
839 |
< |
*/ |
840 |
< |
public void setMaintainsParallelism(boolean enable) { |
841 |
< |
maintainsParallelism = enable; |
842 |
< |
} |
843 |
< |
|
844 |
< |
/** |
845 |
< |
* Establishes local first-in-first-out scheduling mode for forked |
846 |
< |
* tasks that are never joined. This mode may be more appropriate |
847 |
< |
* than default locally stack-based mode in applications in which |
848 |
< |
* worker threads only process asynchronous tasks. This method is |
849 |
< |
* designed to be invoked only when pool is quiescent, and |
850 |
< |
* typically only before any tasks are submitted. The effects of |
851 |
< |
* invocations at other times may be unpredictable. |
852 |
< |
* |
853 |
< |
* @param async if true, use locally FIFO scheduling |
854 |
< |
* @return the previous mode |
855 |
< |
*/ |
856 |
< |
public boolean setAsyncMode(boolean async) { |
857 |
< |
boolean oldMode = locallyFifo; |
858 |
< |
locallyFifo = async; |
859 |
< |
ForkJoinWorkerThread[] ws = workers; |
860 |
< |
if (ws != null) { |
861 |
< |
for (int i = 0; i < ws.length; ++i) { |
862 |
< |
ForkJoinWorkerThread t = ws[i]; |
863 |
< |
if (t != null) |
864 |
< |
t.setAsyncMode(async); |
865 |
< |
} |
866 |
< |
} |
867 |
< |
return oldMode; |
868 |
< |
} |
869 |
< |
|
870 |
< |
/** |
871 |
< |
* Returns true if this pool uses local first-in-first-out |
1543 |
> |
* Returns {@code true} if this pool uses local first-in-first-out |
1544 |
|
* scheduling mode for forked tasks that are never joined. |
1545 |
|
* |
1546 |
< |
* @return true if this pool uses async mode |
1546 |
> |
* @return {@code true} if this pool uses async mode |
1547 |
|
*/ |
1548 |
|
public boolean getAsyncMode() { |
1549 |
|
return locallyFifo; |
1552 |
|
/** |
1553 |
|
* Returns an estimate of the number of worker threads that are |
1554 |
|
* not blocked waiting to join tasks or for other managed |
1555 |
< |
* synchronization. |
1555 |
> |
* synchronization. This method may overestimate the |
1556 |
> |
* number of running threads. |
1557 |
|
* |
1558 |
|
* @return the number of worker threads |
1559 |
|
*/ |
1560 |
|
public int getRunningThreadCount() { |
1561 |
< |
return runningCountOf(workerCounts); |
1561 |
> |
return workerCounts & RUNNING_COUNT_MASK; |
1562 |
|
} |
1563 |
|
|
1564 |
|
/** |
1569 |
|
* @return the number of active threads |
1570 |
|
*/ |
1571 |
|
public int getActiveThreadCount() { |
1572 |
< |
return activeCountOf(runControl); |
1572 |
> |
return runState & ACTIVE_COUNT_MASK; |
1573 |
|
} |
1574 |
|
|
1575 |
|
/** |
1576 |
< |
* Returns an estimate of the number of threads that are currently |
1577 |
< |
* idle waiting for tasks. This method may underestimate the |
1578 |
< |
* number of idle threads. |
1576 |
> |
* Returns {@code true} if all worker threads are currently idle. |
1577 |
> |
* An idle worker is one that cannot obtain a task to execute |
1578 |
> |
* because none are available to steal from other threads, and |
1579 |
> |
* there are no pending submissions to the pool. This method is |
1580 |
> |
* conservative; it might not return {@code true} immediately upon |
1581 |
> |
* idleness of all threads, but will eventually become true if |
1582 |
> |
* threads remain inactive. |
1583 |
|
* |
1584 |
< |
* @return the number of idle threads |
908 |
< |
*/ |
909 |
< |
final int getIdleThreadCount() { |
910 |
< |
int c = runningCountOf(workerCounts) - activeCountOf(runControl); |
911 |
< |
return (c <= 0) ? 0 : c; |
912 |
< |
} |
913 |
< |
|
914 |
< |
/** |
915 |
< |
* Returns true if all worker threads are currently idle. An idle |
916 |
< |
* worker is one that cannot obtain a task to execute because none |
917 |
< |
* are available to steal from other threads, and there are no |
918 |
< |
* pending submissions to the pool. This method is conservative; |
919 |
< |
* it might not return true immediately upon idleness of all |
920 |
< |
* threads, but will eventually become true if threads remain |
921 |
< |
* inactive. |
922 |
< |
* |
923 |
< |
* @return true if all threads are currently idle |
1584 |
> |
* @return {@code true} if all threads are currently idle |
1585 |
|
*/ |
1586 |
|
public boolean isQuiescent() { |
1587 |
< |
return activeCountOf(runControl) == 0; |
1587 |
> |
return (runState & ACTIVE_COUNT_MASK) == 0; |
1588 |
|
} |
1589 |
|
|
1590 |
|
/** |
1599 |
|
* @return the number of steals |
1600 |
|
*/ |
1601 |
|
public long getStealCount() { |
1602 |
< |
return stealCount.get(); |
942 |
< |
} |
943 |
< |
|
944 |
< |
/** |
945 |
< |
* Accumulates steal count from a worker. |
946 |
< |
* Call only when worker known to be idle. |
947 |
< |
*/ |
948 |
< |
private void updateStealCount(ForkJoinWorkerThread w) { |
949 |
< |
int sc = w.getAndClearStealCount(); |
950 |
< |
if (sc != 0) |
951 |
< |
stealCount.addAndGet(sc); |
1602 |
> |
return stealCount; |
1603 |
|
} |
1604 |
|
|
1605 |
|
/** |
1615 |
|
public long getQueuedTaskCount() { |
1616 |
|
long count = 0; |
1617 |
|
ForkJoinWorkerThread[] ws = workers; |
1618 |
< |
if (ws != null) { |
1619 |
< |
for (int i = 0; i < ws.length; ++i) { |
1620 |
< |
ForkJoinWorkerThread t = ws[i]; |
1621 |
< |
if (t != null) |
1622 |
< |
count += t.getQueueSize(); |
972 |
< |
} |
1618 |
> |
int n = ws.length; |
1619 |
> |
for (int i = 0; i < n; ++i) { |
1620 |
> |
ForkJoinWorkerThread w = ws[i]; |
1621 |
> |
if (w != null) |
1622 |
> |
count += w.getQueueSize(); |
1623 |
|
} |
1624 |
|
return count; |
1625 |
|
} |
1626 |
|
|
1627 |
|
/** |
1628 |
< |
* Returns an estimate of the number tasks submitted to this pool |
1629 |
< |
* that have not yet begun executing. This method takes time |
1628 |
> |
* Returns an estimate of the number of tasks submitted to this |
1629 |
> |
* pool that have not yet begun executing. This method takes time |
1630 |
|
* proportional to the number of submissions. |
1631 |
|
* |
1632 |
|
* @return the number of queued submissions |
1636 |
|
} |
1637 |
|
|
1638 |
|
/** |
1639 |
< |
* Returns true if there are any tasks submitted to this pool |
1640 |
< |
* that have not yet begun executing. |
1639 |
> |
* Returns {@code true} if there are any tasks submitted to this |
1640 |
> |
* pool that have not yet begun executing. |
1641 |
|
* |
1642 |
|
* @return {@code true} if there are any queued submissions |
1643 |
|
*/ |
1650 |
|
* available. This method may be useful in extensions to this |
1651 |
|
* class that re-assign work in systems with multiple pools. |
1652 |
|
* |
1653 |
< |
* @return the next submission, or null if none |
1653 |
> |
* @return the next submission, or {@code null} if none |
1654 |
|
*/ |
1655 |
|
protected ForkJoinTask<?> pollSubmission() { |
1656 |
|
return submissionQueue.poll(); |
1660 |
|
* Removes all available unexecuted submitted and forked tasks |
1661 |
|
* from scheduling queues and adds them to the given collection, |
1662 |
|
* without altering their execution status. These may include |
1663 |
< |
* artificially generated or wrapped tasks. This method is designed |
1664 |
< |
* to be invoked only when the pool is known to be |
1663 |
> |
* artificially generated or wrapped tasks. This method is |
1664 |
> |
* designed to be invoked only when the pool is known to be |
1665 |
|
* quiescent. Invocations at other times may not remove all |
1666 |
|
* tasks. A failure encountered while attempting to add elements |
1667 |
|
* to collection {@code c} may result in elements being in |
1673 |
|
* @param c the collection to transfer elements into |
1674 |
|
* @return the number of elements transferred |
1675 |
|
*/ |
1676 |
< |
protected int drainTasksTo(Collection<ForkJoinTask<?>> c) { |
1677 |
< |
int n = submissionQueue.drainTo(c); |
1676 |
> |
protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) { |
1677 |
> |
int count = submissionQueue.drainTo(c); |
1678 |
|
ForkJoinWorkerThread[] ws = workers; |
1679 |
< |
if (ws != null) { |
1680 |
< |
for (int i = 0; i < ws.length; ++i) { |
1681 |
< |
ForkJoinWorkerThread w = ws[i]; |
1682 |
< |
if (w != null) |
1683 |
< |
n += w.drainTasksTo(c); |
1034 |
< |
} |
1679 |
> |
int n = ws.length; |
1680 |
> |
for (int i = 0; i < n; ++i) { |
1681 |
> |
ForkJoinWorkerThread w = ws[i]; |
1682 |
> |
if (w != null) |
1683 |
> |
count += w.drainTasksTo(c); |
1684 |
|
} |
1685 |
< |
return n; |
1685 |
> |
return count; |
1686 |
|
} |
1687 |
|
|
1688 |
|
/** |
1693 |
|
* @return a string identifying this pool, as well as its state |
1694 |
|
*/ |
1695 |
|
public String toString() { |
1047 |
– |
int ps = parallelism; |
1048 |
– |
int wc = workerCounts; |
1049 |
– |
int rc = runControl; |
1696 |
|
long st = getStealCount(); |
1697 |
|
long qt = getQueuedTaskCount(); |
1698 |
|
long qs = getQueuedSubmissionCount(); |
1699 |
+ |
int wc = workerCounts; |
1700 |
+ |
int tc = wc >>> TOTAL_COUNT_SHIFT; |
1701 |
+ |
int rc = wc & RUNNING_COUNT_MASK; |
1702 |
+ |
int pc = parallelism; |
1703 |
+ |
int rs = runState; |
1704 |
+ |
int ac = rs & ACTIVE_COUNT_MASK; |
1705 |
|
return super.toString() + |
1706 |
< |
"[" + runStateToString(runStateOf(rc)) + |
1707 |
< |
", parallelism = " + ps + |
1708 |
< |
", size = " + totalCountOf(wc) + |
1709 |
< |
", active = " + activeCountOf(rc) + |
1710 |
< |
", running = " + runningCountOf(wc) + |
1706 |
> |
"[" + runLevelToString(rs) + |
1707 |
> |
", parallelism = " + pc + |
1708 |
> |
", size = " + tc + |
1709 |
> |
", active = " + ac + |
1710 |
> |
", running = " + rc + |
1711 |
|
", steals = " + st + |
1712 |
|
", tasks = " + qt + |
1713 |
|
", submissions = " + qs + |
1714 |
|
"]"; |
1715 |
|
} |
1716 |
|
|
1717 |
< |
private static String runStateToString(int rs) { |
1718 |
< |
switch(rs) { |
1719 |
< |
case RUNNING: return "Running"; |
1720 |
< |
case SHUTDOWN: return "Shutting down"; |
1721 |
< |
case TERMINATING: return "Terminating"; |
1070 |
< |
case TERMINATED: return "Terminated"; |
1071 |
< |
default: throw new Error("Unknown run state"); |
1072 |
< |
} |
1717 |
> |
private static String runLevelToString(int s) { |
1718 |
> |
return ((s & TERMINATED) != 0 ? "Terminated" : |
1719 |
> |
((s & TERMINATING) != 0 ? "Terminating" : |
1720 |
> |
((s & SHUTDOWN) != 0 ? "Shutting down" : |
1721 |
> |
"Running"))); |
1722 |
|
} |
1723 |
|
|
1075 |
– |
// lifecycle control |
1076 |
– |
|
1724 |
|
/** |
1725 |
|
* Initiates an orderly shutdown in which previously submitted |
1726 |
|
* tasks are executed, but no new tasks will be accepted. |
1735 |
|
*/ |
1736 |
|
public void shutdown() { |
1737 |
|
checkPermission(); |
1738 |
< |
transitionRunStateTo(SHUTDOWN); |
1739 |
< |
if (canTerminateOnShutdown(runControl)) |
1093 |
< |
terminateOnShutdown(); |
1738 |
> |
advanceRunLevel(SHUTDOWN); |
1739 |
> |
tryTerminate(false); |
1740 |
|
} |
1741 |
|
|
1742 |
|
/** |
1743 |
< |
* Attempts to stop all actively executing tasks, and cancels all |
1744 |
< |
* waiting tasks. Tasks that are in the process of being |
1745 |
< |
* submitted or executed concurrently during the course of this |
1746 |
< |
* method may or may not be rejected. Unlike some other executors, |
1747 |
< |
* this method cancels rather than collects non-executed tasks |
1748 |
< |
* upon termination, so always returns an empty list. However, you |
1749 |
< |
* can use method {@code drainTasksTo} before invoking this |
1750 |
< |
* method to transfer unexecuted tasks to another collection. |
1743 |
> |
* Attempts to cancel and/or stop all tasks, and reject all |
1744 |
> |
* subsequently submitted tasks. Tasks that are in the process of |
1745 |
> |
* being submitted or executed concurrently during the course of |
1746 |
> |
* this method may or may not be rejected. This method cancels |
1747 |
> |
* both existing and unexecuted tasks, in order to permit |
1748 |
> |
* termination in the presence of task dependencies. So the method |
1749 |
> |
* always returns an empty list (unlike the case for some other |
1750 |
> |
* Executors). |
1751 |
|
* |
1752 |
|
* @return an empty list |
1753 |
|
* @throws SecurityException if a security manager exists and |
1757 |
|
*/ |
1758 |
|
public List<Runnable> shutdownNow() { |
1759 |
|
checkPermission(); |
1760 |
< |
terminate(); |
1760 |
> |
tryTerminate(true); |
1761 |
|
return Collections.emptyList(); |
1762 |
|
} |
1763 |
|
|
1767 |
|
* @return {@code true} if all tasks have completed following shut down |
1768 |
|
*/ |
1769 |
|
public boolean isTerminated() { |
1770 |
< |
return runStateOf(runControl) == TERMINATED; |
1770 |
> |
return runState >= TERMINATED; |
1771 |
|
} |
1772 |
|
|
1773 |
|
/** |
1774 |
|
* Returns {@code true} if the process of termination has |
1775 |
< |
* commenced but possibly not yet completed. |
1775 |
> |
* commenced but not yet completed. This method may be useful for |
1776 |
> |
* debugging. A return of {@code true} reported a sufficient |
1777 |
> |
* period after shutdown may indicate that submitted tasks have |
1778 |
> |
* ignored or suppressed interruption, causing this executor not |
1779 |
> |
* to properly terminate. |
1780 |
|
* |
1781 |
< |
* @return {@code true} if terminating |
1781 |
> |
* @return {@code true} if terminating but not yet terminated |
1782 |
|
*/ |
1783 |
|
public boolean isTerminating() { |
1784 |
< |
return runStateOf(runControl) >= TERMINATING; |
1784 |
> |
return (runState & (TERMINATING|TERMINATED)) == TERMINATING; |
1785 |
|
} |
1786 |
|
|
1787 |
|
/** |
1790 |
|
* @return {@code true} if this pool has been shut down |
1791 |
|
*/ |
1792 |
|
public boolean isShutdown() { |
1793 |
< |
return runStateOf(runControl) >= SHUTDOWN; |
1793 |
> |
return runState >= SHUTDOWN; |
1794 |
|
} |
1795 |
|
|
1796 |
|
/** |
1806 |
|
*/ |
1807 |
|
public boolean awaitTermination(long timeout, TimeUnit unit) |
1808 |
|
throws InterruptedException { |
1159 |
– |
long nanos = unit.toNanos(timeout); |
1160 |
– |
final ReentrantLock lock = this.workerLock; |
1161 |
– |
lock.lock(); |
1162 |
– |
try { |
1163 |
– |
for (;;) { |
1164 |
– |
if (isTerminated()) |
1165 |
– |
return true; |
1166 |
– |
if (nanos <= 0) |
1167 |
– |
return false; |
1168 |
– |
nanos = termination.awaitNanos(nanos); |
1169 |
– |
} |
1170 |
– |
} finally { |
1171 |
– |
lock.unlock(); |
1172 |
– |
} |
1173 |
– |
} |
1174 |
– |
|
1175 |
– |
// Shutdown and termination support |
1176 |
– |
|
1177 |
– |
/** |
1178 |
– |
* Callback from terminating worker. Nulls out the corresponding |
1179 |
– |
* workers slot, and if terminating, tries to terminate; else |
1180 |
– |
* tries to shrink workers array. |
1181 |
– |
* |
1182 |
– |
* @param w the worker |
1183 |
– |
*/ |
1184 |
– |
final void workerTerminated(ForkJoinWorkerThread w) { |
1185 |
– |
updateStealCount(w); |
1186 |
– |
updateWorkerCount(-1); |
1187 |
– |
final ReentrantLock lock = this.workerLock; |
1188 |
– |
lock.lock(); |
1809 |
|
try { |
1810 |
< |
ForkJoinWorkerThread[] ws = workers; |
1811 |
< |
if (ws != null) { |
1192 |
< |
int idx = w.poolIndex; |
1193 |
< |
if (idx >= 0 && idx < ws.length && ws[idx] == w) |
1194 |
< |
ws[idx] = null; |
1195 |
< |
if (totalCountOf(workerCounts) == 0) { |
1196 |
< |
terminate(); // no-op if already terminating |
1197 |
< |
transitionRunStateTo(TERMINATED); |
1198 |
< |
termination.signalAll(); |
1199 |
< |
} |
1200 |
< |
else if (!isTerminating()) { |
1201 |
< |
tryShrinkWorkerArray(); |
1202 |
< |
tryResumeSpare(true); // allow replacement |
1203 |
< |
} |
1204 |
< |
} |
1205 |
< |
} finally { |
1206 |
< |
lock.unlock(); |
1207 |
< |
} |
1208 |
< |
signalIdleWorkers(); |
1209 |
< |
} |
1210 |
< |
|
1211 |
< |
/** |
1212 |
< |
* Initiates termination. |
1213 |
< |
*/ |
1214 |
< |
private void terminate() { |
1215 |
< |
if (transitionRunStateTo(TERMINATING)) { |
1216 |
< |
stopAllWorkers(); |
1217 |
< |
resumeAllSpares(); |
1218 |
< |
signalIdleWorkers(); |
1219 |
< |
cancelQueuedSubmissions(); |
1220 |
< |
cancelQueuedWorkerTasks(); |
1221 |
< |
interruptUnterminatedWorkers(); |
1222 |
< |
signalIdleWorkers(); // resignal after interrupt |
1223 |
< |
} |
1224 |
< |
} |
1225 |
< |
|
1226 |
< |
/** |
1227 |
< |
* Possibly terminates when on shutdown state. |
1228 |
< |
*/ |
1229 |
< |
private void terminateOnShutdown() { |
1230 |
< |
if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl)) |
1231 |
< |
terminate(); |
1232 |
< |
} |
1233 |
< |
|
1234 |
< |
/** |
1235 |
< |
* Clears out and cancels submissions. |
1236 |
< |
*/ |
1237 |
< |
private void cancelQueuedSubmissions() { |
1238 |
< |
ForkJoinTask<?> task; |
1239 |
< |
while ((task = pollSubmission()) != null) |
1240 |
< |
task.cancel(false); |
1241 |
< |
} |
1242 |
< |
|
1243 |
< |
/** |
1244 |
< |
* Cleans out worker queues. |
1245 |
< |
*/ |
1246 |
< |
private void cancelQueuedWorkerTasks() { |
1247 |
< |
final ReentrantLock lock = this.workerLock; |
1248 |
< |
lock.lock(); |
1249 |
< |
try { |
1250 |
< |
ForkJoinWorkerThread[] ws = workers; |
1251 |
< |
if (ws != null) { |
1252 |
< |
for (int i = 0; i < ws.length; ++i) { |
1253 |
< |
ForkJoinWorkerThread t = ws[i]; |
1254 |
< |
if (t != null) |
1255 |
< |
t.cancelTasks(); |
1256 |
< |
} |
1257 |
< |
} |
1258 |
< |
} finally { |
1259 |
< |
lock.unlock(); |
1260 |
< |
} |
1261 |
< |
} |
1262 |
< |
|
1263 |
< |
/** |
1264 |
< |
* Sets each worker's status to terminating. Requires lock to avoid |
1265 |
< |
* conflicts with add/remove. |
1266 |
< |
*/ |
1267 |
< |
private void stopAllWorkers() { |
1268 |
< |
final ReentrantLock lock = this.workerLock; |
1269 |
< |
lock.lock(); |
1270 |
< |
try { |
1271 |
< |
ForkJoinWorkerThread[] ws = workers; |
1272 |
< |
if (ws != null) { |
1273 |
< |
for (int i = 0; i < ws.length; ++i) { |
1274 |
< |
ForkJoinWorkerThread t = ws[i]; |
1275 |
< |
if (t != null) |
1276 |
< |
t.shutdownNow(); |
1277 |
< |
} |
1278 |
< |
} |
1279 |
< |
} finally { |
1280 |
< |
lock.unlock(); |
1281 |
< |
} |
1282 |
< |
} |
1283 |
< |
|
1284 |
< |
/** |
1285 |
< |
* Interrupts all unterminated workers. This is not required for |
1286 |
< |
* sake of internal control, but may help unstick user code during |
1287 |
< |
* shutdown. |
1288 |
< |
*/ |
1289 |
< |
private void interruptUnterminatedWorkers() { |
1290 |
< |
final ReentrantLock lock = this.workerLock; |
1291 |
< |
lock.lock(); |
1292 |
< |
try { |
1293 |
< |
ForkJoinWorkerThread[] ws = workers; |
1294 |
< |
if (ws != null) { |
1295 |
< |
for (int i = 0; i < ws.length; ++i) { |
1296 |
< |
ForkJoinWorkerThread t = ws[i]; |
1297 |
< |
if (t != null && !t.isTerminated()) { |
1298 |
< |
try { |
1299 |
< |
t.interrupt(); |
1300 |
< |
} catch (SecurityException ignore) { |
1301 |
< |
} |
1302 |
< |
} |
1303 |
< |
} |
1304 |
< |
} |
1305 |
< |
} finally { |
1306 |
< |
lock.unlock(); |
1307 |
< |
} |
1308 |
< |
} |
1309 |
< |
|
1310 |
< |
|
1311 |
< |
/* |
1312 |
< |
* Nodes for event barrier to manage idle threads. Queue nodes |
1313 |
< |
* are basic Treiber stack nodes, also used for spare stack. |
1314 |
< |
* |
1315 |
< |
* The event barrier has an event count and a wait queue (actually |
1316 |
< |
* a Treiber stack). Workers are enabled to look for work when |
1317 |
< |
* the eventCount is incremented. If they fail to find work, they |
1318 |
< |
* may wait for next count. Upon release, threads help others wake |
1319 |
< |
* up. |
1320 |
< |
* |
1321 |
< |
* Synchronization events occur only in enough contexts to |
1322 |
< |
* maintain overall liveness: |
1323 |
< |
* |
1324 |
< |
* - Submission of a new task to the pool |
1325 |
< |
* - Resizes or other changes to the workers array |
1326 |
< |
* - pool termination |
1327 |
< |
* - A worker pushing a task on an empty queue |
1328 |
< |
* |
1329 |
< |
* The case of pushing a task occurs often enough, and is heavy |
1330 |
< |
* enough compared to simple stack pushes, to require special |
1331 |
< |
* handling: Method signalWork returns without advancing count if |
1332 |
< |
* the queue appears to be empty. This would ordinarily result in |
1333 |
< |
* races causing some queued waiters not to be woken up. To avoid |
1334 |
< |
* this, the first worker enqueued in method sync (see |
1335 |
< |
* syncIsReleasable) rescans for tasks after being enqueued, and |
1336 |
< |
* helps signal if any are found. This works well because the |
1337 |
< |
* worker has nothing better to do, and so might as well help |
1338 |
< |
* alleviate the overhead and contention on the threads actually |
1339 |
< |
* doing work. Also, since event counts increments on task |
1340 |
< |
* availability exist to maintain liveness (rather than to force |
1341 |
< |
* refreshes etc), it is OK for callers to exit early if |
1342 |
< |
* contending with another signaller. |
1343 |
< |
*/ |
1344 |
< |
static final class WaitQueueNode { |
1345 |
< |
WaitQueueNode next; // only written before enqueued |
1346 |
< |
volatile ForkJoinWorkerThread thread; // nulled to cancel wait |
1347 |
< |
final long count; // unused for spare stack |
1348 |
< |
|
1349 |
< |
WaitQueueNode(long c, ForkJoinWorkerThread w) { |
1350 |
< |
count = c; |
1351 |
< |
thread = w; |
1352 |
< |
} |
1353 |
< |
|
1354 |
< |
/** |
1355 |
< |
* Wakes up waiter, returning false if known to already |
1356 |
< |
*/ |
1357 |
< |
boolean signal() { |
1358 |
< |
ForkJoinWorkerThread t = thread; |
1359 |
< |
if (t == null) |
1360 |
< |
return false; |
1361 |
< |
thread = null; |
1362 |
< |
LockSupport.unpark(t); |
1363 |
< |
return true; |
1364 |
< |
} |
1365 |
< |
|
1366 |
< |
/** |
1367 |
< |
* Awaits release on sync. |
1368 |
< |
*/ |
1369 |
< |
void awaitSyncRelease(ForkJoinPool p) { |
1370 |
< |
while (thread != null && !p.syncIsReleasable(this)) |
1371 |
< |
LockSupport.park(this); |
1372 |
< |
} |
1373 |
< |
|
1374 |
< |
/** |
1375 |
< |
* Awaits resumption as spare. |
1376 |
< |
*/ |
1377 |
< |
void awaitSpareRelease() { |
1378 |
< |
while (thread != null) { |
1379 |
< |
if (!Thread.interrupted()) |
1380 |
< |
LockSupport.park(this); |
1381 |
< |
} |
1382 |
< |
} |
1383 |
< |
} |
1384 |
< |
|
1385 |
< |
/** |
1386 |
< |
* Ensures that no thread is waiting for count to advance from the |
1387 |
< |
* current value of eventCount read on entry to this method, by |
1388 |
< |
* releasing waiting threads if necessary. |
1389 |
< |
* |
1390 |
< |
* @return the count |
1391 |
< |
*/ |
1392 |
< |
final long ensureSync() { |
1393 |
< |
long c = eventCount; |
1394 |
< |
WaitQueueNode q; |
1395 |
< |
while ((q = syncStack) != null && q.count < c) { |
1396 |
< |
if (casBarrierStack(q, null)) { |
1397 |
< |
do { |
1398 |
< |
q.signal(); |
1399 |
< |
} while ((q = q.next) != null); |
1400 |
< |
break; |
1401 |
< |
} |
1402 |
< |
} |
1403 |
< |
return c; |
1404 |
< |
} |
1405 |
< |
|
1406 |
< |
/** |
1407 |
< |
* Increments event count and releases waiting threads. |
1408 |
< |
*/ |
1409 |
< |
private void signalIdleWorkers() { |
1410 |
< |
long c; |
1411 |
< |
do {} while (!casEventCount(c = eventCount, c+1)); |
1412 |
< |
ensureSync(); |
1413 |
< |
} |
1414 |
< |
|
1415 |
< |
/** |
1416 |
< |
* Signals threads waiting to poll a task. Because method sync |
1417 |
< |
* rechecks availability, it is OK to only proceed if queue |
1418 |
< |
* appears to be non-empty, and OK to skip under contention to |
1419 |
< |
* increment count (since some other thread succeeded). |
1420 |
< |
*/ |
1421 |
< |
final void signalWork() { |
1422 |
< |
long c; |
1423 |
< |
WaitQueueNode q; |
1424 |
< |
if (syncStack != null && |
1425 |
< |
casEventCount(c = eventCount, c+1) && |
1426 |
< |
(((q = syncStack) != null && q.count <= c) && |
1427 |
< |
(!casBarrierStack(q, q.next) || !q.signal()))) |
1428 |
< |
ensureSync(); |
1429 |
< |
} |
1430 |
< |
|
1431 |
< |
/** |
1432 |
< |
* Waits until event count advances from last value held by |
1433 |
< |
* caller, or if excess threads, caller is resumed as spare, or |
1434 |
< |
* caller or pool is terminating. Updates caller's event on exit. |
1435 |
< |
* |
1436 |
< |
* @param w the calling worker thread |
1437 |
< |
*/ |
1438 |
< |
final void sync(ForkJoinWorkerThread w) { |
1439 |
< |
updateStealCount(w); // Transfer w's count while it is idle |
1440 |
< |
|
1441 |
< |
while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) { |
1442 |
< |
long prev = w.lastEventCount; |
1443 |
< |
WaitQueueNode node = null; |
1444 |
< |
WaitQueueNode h; |
1445 |
< |
while (eventCount == prev && |
1446 |
< |
((h = syncStack) == null || h.count == prev)) { |
1447 |
< |
if (node == null) |
1448 |
< |
node = new WaitQueueNode(prev, w); |
1449 |
< |
if (casBarrierStack(node.next = h, node)) { |
1450 |
< |
node.awaitSyncRelease(this); |
1451 |
< |
break; |
1452 |
< |
} |
1453 |
< |
} |
1454 |
< |
long ec = ensureSync(); |
1455 |
< |
if (ec != prev) { |
1456 |
< |
w.lastEventCount = ec; |
1457 |
< |
break; |
1458 |
< |
} |
1459 |
< |
} |
1460 |
< |
} |
1461 |
< |
|
1462 |
< |
/** |
1463 |
< |
* Returns true if worker waiting on sync can proceed: |
1464 |
< |
* - on signal (thread == null) |
1465 |
< |
* - on event count advance (winning race to notify vs signaller) |
1466 |
< |
* - on interrupt |
1467 |
< |
* - if the first queued node, we find work available |
1468 |
< |
* If node was not signalled and event count not advanced on exit, |
1469 |
< |
* then we also help advance event count. |
1470 |
< |
* |
1471 |
< |
* @return true if node can be released |
1472 |
< |
*/ |
1473 |
< |
final boolean syncIsReleasable(WaitQueueNode node) { |
1474 |
< |
long prev = node.count; |
1475 |
< |
if (!Thread.interrupted() && node.thread != null && |
1476 |
< |
(node.next != null || |
1477 |
< |
!ForkJoinWorkerThread.hasQueuedTasks(workers)) && |
1478 |
< |
eventCount == prev) |
1810 |
> |
return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0; |
1811 |
> |
} catch(TimeoutException ex) { |
1812 |
|
return false; |
1480 |
– |
if (node.thread != null) { |
1481 |
– |
node.thread = null; |
1482 |
– |
long ec = eventCount; |
1483 |
– |
if (prev <= ec) // help signal |
1484 |
– |
casEventCount(ec, ec+1); |
1485 |
– |
} |
1486 |
– |
return true; |
1487 |
– |
} |
1488 |
– |
|
1489 |
– |
/** |
1490 |
– |
* Returns true if a new sync event occurred since last call to |
1491 |
– |
* sync or this method, if so, updating caller's count. |
1492 |
– |
*/ |
1493 |
– |
final boolean hasNewSyncEvent(ForkJoinWorkerThread w) { |
1494 |
– |
long lc = w.lastEventCount; |
1495 |
– |
long ec = ensureSync(); |
1496 |
– |
if (ec == lc) |
1497 |
– |
return false; |
1498 |
– |
w.lastEventCount = ec; |
1499 |
– |
return true; |
1500 |
– |
} |
1501 |
– |
|
1502 |
– |
// Parallelism maintenance |
1503 |
– |
|
1504 |
– |
/** |
1505 |
– |
* Decrements running count; if too low, adds spare. |
1506 |
– |
* |
1507 |
– |
* Conceptually, all we need to do here is add or resume a |
1508 |
– |
* spare thread when one is about to block (and remove or |
1509 |
– |
* suspend it later when unblocked -- see suspendIfSpare). |
1510 |
– |
* However, implementing this idea requires coping with |
1511 |
– |
* several problems: we have imperfect information about the |
1512 |
– |
* states of threads. Some count updates can and usually do |
1513 |
– |
* lag run state changes, despite arrangements to keep them |
1514 |
– |
* accurate (for example, when possible, updating counts |
1515 |
– |
* before signalling or resuming), especially when running on |
1516 |
– |
* dynamic JVMs that don't optimize the infrequent paths that |
1517 |
– |
* update counts. Generating too many threads can make these |
1518 |
– |
* problems become worse, because excess threads are more |
1519 |
– |
* likely to be context-switched with others, slowing them all |
1520 |
– |
* down, especially if there is no work available, so all are |
1521 |
– |
* busy scanning or idling. Also, excess spare threads can |
1522 |
– |
* only be suspended or removed when they are idle, not |
1523 |
– |
* immediately when they aren't needed. So adding threads will |
1524 |
– |
* raise parallelism level for longer than necessary. Also, |
1525 |
– |
* FJ applications often encounter highly transient peaks when |
1526 |
– |
* many threads are blocked joining, but for less time than it |
1527 |
– |
* takes to create or resume spares. |
1528 |
– |
* |
1529 |
– |
* @param joinMe if non-null, return early if done |
1530 |
– |
* @param maintainParallelism if true, try to stay within |
1531 |
– |
* target counts, else create only to avoid starvation |
1532 |
– |
* @return true if joinMe known to be done |
1533 |
– |
*/ |
1534 |
– |
final boolean preJoin(ForkJoinTask<?> joinMe, |
1535 |
– |
boolean maintainParallelism) { |
1536 |
– |
maintainParallelism &= maintainsParallelism; // overrride |
1537 |
– |
boolean dec = false; // true when running count decremented |
1538 |
– |
while (spareStack == null || !tryResumeSpare(dec)) { |
1539 |
– |
int counts = workerCounts; |
1540 |
– |
if (dec || (dec = casWorkerCounts(counts, --counts))) { |
1541 |
– |
// CAS cheat |
1542 |
– |
if (!needSpare(counts, maintainParallelism)) |
1543 |
– |
break; |
1544 |
– |
if (joinMe.status < 0) |
1545 |
– |
return true; |
1546 |
– |
if (tryAddSpare(counts)) |
1547 |
– |
break; |
1548 |
– |
} |
1549 |
– |
} |
1550 |
– |
return false; |
1551 |
– |
} |
1552 |
– |
|
1553 |
– |
/** |
1554 |
– |
* Same idea as preJoin |
1555 |
– |
*/ |
1556 |
– |
final boolean preBlock(ManagedBlocker blocker, |
1557 |
– |
boolean maintainParallelism) { |
1558 |
– |
maintainParallelism &= maintainsParallelism; |
1559 |
– |
boolean dec = false; |
1560 |
– |
while (spareStack == null || !tryResumeSpare(dec)) { |
1561 |
– |
int counts = workerCounts; |
1562 |
– |
if (dec || (dec = casWorkerCounts(counts, --counts))) { |
1563 |
– |
if (!needSpare(counts, maintainParallelism)) |
1564 |
– |
break; |
1565 |
– |
if (blocker.isReleasable()) |
1566 |
– |
return true; |
1567 |
– |
if (tryAddSpare(counts)) |
1568 |
– |
break; |
1569 |
– |
} |
1570 |
– |
} |
1571 |
– |
return false; |
1572 |
– |
} |
1573 |
– |
|
1574 |
– |
/** |
1575 |
– |
* Returns true if a spare thread appears to be needed. If |
1576 |
– |
* maintaining parallelism, returns true when the deficit in |
1577 |
– |
* running threads is more than the surplus of total threads, and |
1578 |
– |
* there is apparently some work to do. This self-limiting rule |
1579 |
– |
* means that the more threads that have already been added, the |
1580 |
– |
* less parallelism we will tolerate before adding another. |
1581 |
– |
* |
1582 |
– |
* @param counts current worker counts |
1583 |
– |
* @param maintainParallelism try to maintain parallelism |
1584 |
– |
*/ |
1585 |
– |
private boolean needSpare(int counts, boolean maintainParallelism) { |
1586 |
– |
int ps = parallelism; |
1587 |
– |
int rc = runningCountOf(counts); |
1588 |
– |
int tc = totalCountOf(counts); |
1589 |
– |
int runningDeficit = ps - rc; |
1590 |
– |
int totalSurplus = tc - ps; |
1591 |
– |
return (tc < maxPoolSize && |
1592 |
– |
(rc == 0 || totalSurplus < 0 || |
1593 |
– |
(maintainParallelism && |
1594 |
– |
runningDeficit > totalSurplus && |
1595 |
– |
ForkJoinWorkerThread.hasQueuedTasks(workers)))); |
1596 |
– |
} |
1597 |
– |
|
1598 |
– |
/** |
1599 |
– |
* Adds a spare worker if lock available and no more than the |
1600 |
– |
* expected numbers of threads exist. |
1601 |
– |
* |
1602 |
– |
* @return true if successful |
1603 |
– |
*/ |
1604 |
– |
private boolean tryAddSpare(int expectedCounts) { |
1605 |
– |
final ReentrantLock lock = this.workerLock; |
1606 |
– |
int expectedRunning = runningCountOf(expectedCounts); |
1607 |
– |
int expectedTotal = totalCountOf(expectedCounts); |
1608 |
– |
boolean success = false; |
1609 |
– |
boolean locked = false; |
1610 |
– |
// confirm counts while locking; CAS after obtaining lock |
1611 |
– |
try { |
1612 |
– |
for (;;) { |
1613 |
– |
int s = workerCounts; |
1614 |
– |
int tc = totalCountOf(s); |
1615 |
– |
int rc = runningCountOf(s); |
1616 |
– |
if (rc > expectedRunning || tc > expectedTotal) |
1617 |
– |
break; |
1618 |
– |
if (!locked && !(locked = lock.tryLock())) |
1619 |
– |
break; |
1620 |
– |
if (casWorkerCounts(s, workerCountsFor(tc+1, rc+1))) { |
1621 |
– |
createAndStartSpare(tc); |
1622 |
– |
success = true; |
1623 |
– |
break; |
1624 |
– |
} |
1625 |
– |
} |
1626 |
– |
} finally { |
1627 |
– |
if (locked) |
1628 |
– |
lock.unlock(); |
1629 |
– |
} |
1630 |
– |
return success; |
1631 |
– |
} |
1632 |
– |
|
1633 |
– |
/** |
1634 |
– |
* Adds the kth spare worker. On entry, pool counts are already |
1635 |
– |
* adjusted to reflect addition. |
1636 |
– |
*/ |
1637 |
– |
private void createAndStartSpare(int k) { |
1638 |
– |
ForkJoinWorkerThread w = null; |
1639 |
– |
ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(k + 1); |
1640 |
– |
int len = ws.length; |
1641 |
– |
// Probably, we can place at slot k. If not, find empty slot |
1642 |
– |
if (k < len && ws[k] != null) { |
1643 |
– |
for (k = 0; k < len && ws[k] != null; ++k) |
1644 |
– |
; |
1645 |
– |
} |
1646 |
– |
if (k < len && !isTerminating() && (w = createWorker(k)) != null) { |
1647 |
– |
ws[k] = w; |
1648 |
– |
w.start(); |
1649 |
– |
} |
1650 |
– |
else |
1651 |
– |
updateWorkerCount(-1); // adjust on failure |
1652 |
– |
signalIdleWorkers(); |
1653 |
– |
} |
1654 |
– |
|
1655 |
– |
/** |
1656 |
– |
* Suspends calling thread w if there are excess threads. Called |
1657 |
– |
* only from sync. Spares are enqueued in a Treiber stack using |
1658 |
– |
* the same WaitQueueNodes as barriers. They are resumed mainly |
1659 |
– |
* in preJoin, but are also woken on pool events that require all |
1660 |
– |
* threads to check run state. |
1661 |
– |
* |
1662 |
– |
* @param w the caller |
1663 |
– |
*/ |
1664 |
– |
private boolean suspendIfSpare(ForkJoinWorkerThread w) { |
1665 |
– |
WaitQueueNode node = null; |
1666 |
– |
int s; |
1667 |
– |
while (parallelism < runningCountOf(s = workerCounts)) { |
1668 |
– |
if (node == null) |
1669 |
– |
node = new WaitQueueNode(0, w); |
1670 |
– |
if (casWorkerCounts(s, s-1)) { // representation-dependent |
1671 |
– |
// push onto stack |
1672 |
– |
do {} while (!casSpareStack(node.next = spareStack, node)); |
1673 |
– |
// block until released by resumeSpare |
1674 |
– |
node.awaitSpareRelease(); |
1675 |
– |
return true; |
1676 |
– |
} |
1677 |
– |
} |
1678 |
– |
return false; |
1679 |
– |
} |
1680 |
– |
|
1681 |
– |
/** |
1682 |
– |
* Tries to pop and resume a spare thread. |
1683 |
– |
* |
1684 |
– |
* @param updateCount if true, increment running count on success |
1685 |
– |
* @return true if successful |
1686 |
– |
*/ |
1687 |
– |
private boolean tryResumeSpare(boolean updateCount) { |
1688 |
– |
WaitQueueNode q; |
1689 |
– |
while ((q = spareStack) != null) { |
1690 |
– |
if (casSpareStack(q, q.next)) { |
1691 |
– |
if (updateCount) |
1692 |
– |
updateRunningCount(1); |
1693 |
– |
q.signal(); |
1694 |
– |
return true; |
1695 |
– |
} |
1696 |
– |
} |
1697 |
– |
return false; |
1698 |
– |
} |
1699 |
– |
|
1700 |
– |
/** |
1701 |
– |
* Pops and resumes all spare threads. Same idea as ensureSync. |
1702 |
– |
* |
1703 |
– |
* @return true if any spares released |
1704 |
– |
*/ |
1705 |
– |
private boolean resumeAllSpares() { |
1706 |
– |
WaitQueueNode q; |
1707 |
– |
while ( (q = spareStack) != null) { |
1708 |
– |
if (casSpareStack(q, null)) { |
1709 |
– |
do { |
1710 |
– |
updateRunningCount(1); |
1711 |
– |
q.signal(); |
1712 |
– |
} while ((q = q.next) != null); |
1713 |
– |
return true; |
1714 |
– |
} |
1715 |
– |
} |
1716 |
– |
return false; |
1717 |
– |
} |
1718 |
– |
|
1719 |
– |
/** |
1720 |
– |
* Pops and shuts down excessive spare threads. Call only while |
1721 |
– |
* holding lock. This is not guaranteed to eliminate all excess |
1722 |
– |
* threads, only those suspended as spares, which are the ones |
1723 |
– |
* unlikely to be needed in the future. |
1724 |
– |
*/ |
1725 |
– |
private void trimSpares() { |
1726 |
– |
int surplus = totalCountOf(workerCounts) - parallelism; |
1727 |
– |
WaitQueueNode q; |
1728 |
– |
while (surplus > 0 && (q = spareStack) != null) { |
1729 |
– |
if (casSpareStack(q, null)) { |
1730 |
– |
do { |
1731 |
– |
updateRunningCount(1); |
1732 |
– |
ForkJoinWorkerThread w = q.thread; |
1733 |
– |
if (w != null && surplus > 0 && |
1734 |
– |
runningCountOf(workerCounts) > 0 && w.shutdown()) |
1735 |
– |
--surplus; |
1736 |
– |
q.signal(); |
1737 |
– |
} while ((q = q.next) != null); |
1738 |
– |
} |
1813 |
|
} |
1814 |
|
} |
1815 |
|
|
1816 |
|
/** |
1817 |
|
* Interface for extending managed parallelism for tasks running |
1818 |
< |
* in ForkJoinPools. A ManagedBlocker provides two methods. |
1819 |
< |
* Method {@code isReleasable} must return true if blocking is not |
1820 |
< |
* necessary. Method {@code block} blocks the current thread if |
1821 |
< |
* necessary (perhaps internally invoking {@code isReleasable} |
1822 |
< |
* before actually blocking.). |
1818 |
> |
* in {@link ForkJoinPool}s. |
1819 |
> |
* |
1820 |
> |
* <p>A {@code ManagedBlocker} provides two methods. Method |
1821 |
> |
* {@code isReleasable} must return {@code true} if blocking is |
1822 |
> |
* not necessary. Method {@code block} blocks the current thread |
1823 |
> |
* if necessary (perhaps internally invoking {@code isReleasable} |
1824 |
> |
* before actually blocking). The unusual methods in this API |
1825 |
> |
* accommodate synchronizers that may, but don't usually, block |
1826 |
> |
* for long periods. Similarly, they allow more efficient internal |
1827 |
> |
* handling of cases in which additional workers may be, but |
1828 |
> |
* usually are not, needed to ensure sufficient parallelism. |
1829 |
> |
* Toward this end, implementations of method {@code isReleasable} |
1830 |
> |
* must be amenable to repeated invocation. |
1831 |
|
* |
1832 |
|
* <p>For example, here is a ManagedBlocker based on a |
1833 |
|
* ReentrantLock: |
1845 |
|
* return hasLock || (hasLock = lock.tryLock()); |
1846 |
|
* } |
1847 |
|
* }}</pre> |
1848 |
+ |
* |
1849 |
+ |
* <p>Here is a class that possibly blocks waiting for an |
1850 |
+ |
* item on a given queue: |
1851 |
+ |
* <pre> {@code |
1852 |
+ |
* class QueueTaker<E> implements ManagedBlocker { |
1853 |
+ |
* final BlockingQueue<E> queue; |
1854 |
+ |
* volatile E item = null; |
1855 |
+ |
* QueueTaker(BlockingQueue<E> q) { this.queue = q; } |
1856 |
+ |
* public boolean block() throws InterruptedException { |
1857 |
+ |
* if (item == null) |
1858 |
+ |
* item = queue.take |
1859 |
+ |
* return true; |
1860 |
+ |
* } |
1861 |
+ |
* public boolean isReleasable() { |
1862 |
+ |
* return item != null || (item = queue.poll) != null; |
1863 |
+ |
* } |
1864 |
+ |
* public E getItem() { // call after pool.managedBlock completes |
1865 |
+ |
* return item; |
1866 |
+ |
* } |
1867 |
+ |
* }}</pre> |
1868 |
|
*/ |
1869 |
|
public static interface ManagedBlocker { |
1870 |
|
/** |
1871 |
|
* Possibly blocks the current thread, for example waiting for |
1872 |
|
* a lock or condition. |
1873 |
|
* |
1874 |
< |
* @return true if no additional blocking is necessary (i.e., |
1875 |
< |
* if isReleasable would return true) |
1874 |
> |
* @return {@code true} if no additional blocking is necessary |
1875 |
> |
* (i.e., if isReleasable would return true) |
1876 |
|
* @throws InterruptedException if interrupted while waiting |
1877 |
|
* (the method is not required to do so, but is allowed to) |
1878 |
|
*/ |
1879 |
|
boolean block() throws InterruptedException; |
1880 |
|
|
1881 |
|
/** |
1882 |
< |
* Returns true if blocking is unnecessary. |
1882 |
> |
* Returns {@code true} if blocking is unnecessary. |
1883 |
|
*/ |
1884 |
|
boolean isReleasable(); |
1885 |
|
} |
1886 |
|
|
1887 |
|
/** |
1888 |
|
* Blocks in accord with the given blocker. If the current thread |
1889 |
< |
* is a ForkJoinWorkerThread, this method possibly arranges for a |
1890 |
< |
* spare thread to be activated if necessary to ensure parallelism |
1891 |
< |
* while the current thread is blocked. If |
1790 |
< |
* {@code maintainParallelism} is true and the pool supports |
1791 |
< |
* it ({@link #getMaintainsParallelism}), this method attempts to |
1792 |
< |
* maintain the pool's nominal parallelism. Otherwise it activates |
1793 |
< |
* a thread only if necessary to avoid complete starvation. This |
1794 |
< |
* option may be preferable when blockages use timeouts, or are |
1795 |
< |
* almost always brief. |
1889 |
> |
* is a {@link ForkJoinWorkerThread}, this method possibly |
1890 |
> |
* arranges for a spare thread to be activated if necessary to |
1891 |
> |
* ensure sufficient parallelism while the current thread is blocked. |
1892 |
|
* |
1893 |
< |
* <p> If the caller is not a ForkJoinTask, this method is behaviorally |
1894 |
< |
* equivalent to |
1893 |
> |
* <p>If the caller is not a {@link ForkJoinTask}, this method is |
1894 |
> |
* behaviorally equivalent to |
1895 |
|
* <pre> {@code |
1896 |
|
* while (!blocker.isReleasable()) |
1897 |
|
* if (blocker.block()) |
1898 |
|
* return; |
1899 |
|
* }</pre> |
1900 |
< |
* If the caller is a ForkJoinTask, then the pool may first |
1901 |
< |
* be expanded to ensure parallelism, and later adjusted. |
1900 |
> |
* |
1901 |
> |
* If the caller is a {@code ForkJoinTask}, then the pool may |
1902 |
> |
* first be expanded to ensure parallelism, and later adjusted. |
1903 |
|
* |
1904 |
|
* @param blocker the blocker |
1808 |
– |
* @param maintainParallelism if true and supported by this pool, |
1809 |
– |
* attempt to maintain the pool's nominal parallelism; otherwise |
1810 |
– |
* activate a thread only if necessary to avoid complete |
1811 |
– |
* starvation. |
1905 |
|
* @throws InterruptedException if blocker.block did so |
1906 |
|
*/ |
1907 |
< |
public static void managedBlock(ManagedBlocker blocker, |
1815 |
< |
boolean maintainParallelism) |
1907 |
> |
public static void managedBlock(ManagedBlocker blocker) |
1908 |
|
throws InterruptedException { |
1909 |
|
Thread t = Thread.currentThread(); |
1910 |
< |
ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ? |
1911 |
< |
((ForkJoinWorkerThread) t).pool : null); |
1912 |
< |
if (!blocker.isReleasable()) { |
1913 |
< |
try { |
1914 |
< |
if (pool == null || |
1915 |
< |
!pool.preBlock(blocker, maintainParallelism)) |
1824 |
< |
awaitBlocker(blocker); |
1825 |
< |
} finally { |
1826 |
< |
if (pool != null) |
1827 |
< |
pool.updateRunningCount(1); |
1828 |
< |
} |
1910 |
> |
if (t instanceof ForkJoinWorkerThread) { |
1911 |
> |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
1912 |
> |
w.pool.awaitBlocker(blocker); |
1913 |
> |
} |
1914 |
> |
else { |
1915 |
> |
do {} while (!blocker.isReleasable() && !blocker.block()); |
1916 |
|
} |
1917 |
|
} |
1918 |
|
|
1919 |
< |
private static void awaitBlocker(ManagedBlocker blocker) |
1920 |
< |
throws InterruptedException { |
1921 |
< |
do {} while (!blocker.isReleasable() && !blocker.block()); |
1835 |
< |
} |
1836 |
< |
|
1837 |
< |
// AbstractExecutorService overrides |
1919 |
> |
// AbstractExecutorService overrides. These rely on undocumented |
1920 |
> |
// fact that ForkJoinTask.adapt returns ForkJoinTasks that also |
1921 |
> |
// implement RunnableFuture. |
1922 |
|
|
1923 |
|
protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) { |
1924 |
< |
return new AdaptedRunnable<T>(runnable, value); |
1924 |
> |
return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value); |
1925 |
|
} |
1926 |
|
|
1927 |
|
protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) { |
1928 |
< |
return new AdaptedCallable<T>(callable); |
1928 |
> |
return (RunnableFuture<T>) ForkJoinTask.adapt(callable); |
1929 |
|
} |
1930 |
|
|
1931 |
+ |
// Unsafe mechanics |
1932 |
+ |
|
1933 |
+ |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1934 |
+ |
private static final long workerCountsOffset = |
1935 |
+ |
objectFieldOffset("workerCounts", ForkJoinPool.class); |
1936 |
+ |
private static final long runStateOffset = |
1937 |
+ |
objectFieldOffset("runState", ForkJoinPool.class); |
1938 |
+ |
private static final long eventCountOffset = |
1939 |
+ |
objectFieldOffset("eventCount", ForkJoinPool.class); |
1940 |
+ |
private static final long eventWaitersOffset = |
1941 |
+ |
objectFieldOffset("eventWaiters",ForkJoinPool.class); |
1942 |
+ |
private static final long stealCountOffset = |
1943 |
+ |
objectFieldOffset("stealCount",ForkJoinPool.class); |
1944 |
+ |
private static final long spareWaitersOffset = |
1945 |
+ |
objectFieldOffset("spareWaiters",ForkJoinPool.class); |
1946 |
|
|
1947 |
< |
// Temporary Unsafe mechanics for preliminary release |
1849 |
< |
private static Unsafe getUnsafe() throws Throwable { |
1947 |
> |
private static long objectFieldOffset(String field, Class<?> klazz) { |
1948 |
|
try { |
1949 |
< |
return Unsafe.getUnsafe(); |
1949 |
> |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1950 |
> |
} catch (NoSuchFieldException e) { |
1951 |
> |
// Convert Exception to corresponding Error |
1952 |
> |
NoSuchFieldError error = new NoSuchFieldError(field); |
1953 |
> |
error.initCause(e); |
1954 |
> |
throw error; |
1955 |
> |
} |
1956 |
> |
} |
1957 |
> |
|
1958 |
> |
/** |
1959 |
> |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
1960 |
> |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
1961 |
> |
* into a jdk. |
1962 |
> |
* |
1963 |
> |
* @return a sun.misc.Unsafe |
1964 |
> |
*/ |
1965 |
> |
private static sun.misc.Unsafe getUnsafe() { |
1966 |
> |
try { |
1967 |
> |
return sun.misc.Unsafe.getUnsafe(); |
1968 |
|
} catch (SecurityException se) { |
1969 |
|
try { |
1970 |
|
return java.security.AccessController.doPrivileged |
1971 |
< |
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
1972 |
< |
public Unsafe run() throws Exception { |
1973 |
< |
return getUnsafePrivileged(); |
1971 |
> |
(new java.security |
1972 |
> |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1973 |
> |
public sun.misc.Unsafe run() throws Exception { |
1974 |
> |
java.lang.reflect.Field f = sun.misc |
1975 |
> |
.Unsafe.class.getDeclaredField("theUnsafe"); |
1976 |
> |
f.setAccessible(true); |
1977 |
> |
return (sun.misc.Unsafe) f.get(null); |
1978 |
|
}}); |
1979 |
|
} catch (java.security.PrivilegedActionException e) { |
1980 |
< |
throw e.getCause(); |
1980 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
1981 |
> |
e.getCause()); |
1982 |
|
} |
1983 |
|
} |
1984 |
|
} |
1864 |
– |
|
1865 |
– |
private static Unsafe getUnsafePrivileged() |
1866 |
– |
throws NoSuchFieldException, IllegalAccessException { |
1867 |
– |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
1868 |
– |
f.setAccessible(true); |
1869 |
– |
return (Unsafe) f.get(null); |
1870 |
– |
} |
1871 |
– |
|
1872 |
– |
private static long fieldOffset(String fieldName) |
1873 |
– |
throws NoSuchFieldException { |
1874 |
– |
return UNSAFE.objectFieldOffset |
1875 |
– |
(ForkJoinPool.class.getDeclaredField(fieldName)); |
1876 |
– |
} |
1877 |
– |
|
1878 |
– |
static final Unsafe UNSAFE; |
1879 |
– |
static final long eventCountOffset; |
1880 |
– |
static final long workerCountsOffset; |
1881 |
– |
static final long runControlOffset; |
1882 |
– |
static final long syncStackOffset; |
1883 |
– |
static final long spareStackOffset; |
1884 |
– |
|
1885 |
– |
static { |
1886 |
– |
try { |
1887 |
– |
UNSAFE = getUnsafe(); |
1888 |
– |
eventCountOffset = fieldOffset("eventCount"); |
1889 |
– |
workerCountsOffset = fieldOffset("workerCounts"); |
1890 |
– |
runControlOffset = fieldOffset("runControl"); |
1891 |
– |
syncStackOffset = fieldOffset("syncStack"); |
1892 |
– |
spareStackOffset = fieldOffset("spareStack"); |
1893 |
– |
} catch (Throwable e) { |
1894 |
– |
throw new RuntimeException("Could not initialize intrinsics", e); |
1895 |
– |
} |
1896 |
– |
} |
1897 |
– |
|
1898 |
– |
private boolean casEventCount(long cmp, long val) { |
1899 |
– |
return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val); |
1900 |
– |
} |
1901 |
– |
private boolean casWorkerCounts(int cmp, int val) { |
1902 |
– |
return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val); |
1903 |
– |
} |
1904 |
– |
private boolean casRunControl(int cmp, int val) { |
1905 |
– |
return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val); |
1906 |
– |
} |
1907 |
– |
private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) { |
1908 |
– |
return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val); |
1909 |
– |
} |
1910 |
– |
private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) { |
1911 |
– |
return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val); |
1912 |
– |
} |
1985 |
|
} |