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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/licenses/publicdomain |
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*/ |
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|
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package jsr166y; |
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|
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import java.util.concurrent.*; |
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|
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import java.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. |
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* A {@code ForkJoinPool} provides the entry point for submissions |
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* from non-{@code ForkJoinTask} clients, as well as management and |
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* monitoring operations. |
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* |
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* <p>A {@code ForkJoinPool} differs from other kinds of {@link |
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* ExecutorService} mainly by virtue of employing |
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* <em>work-stealing</em>: all threads in the pool attempt to find and |
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* execute subtasks created by other active tasks (eventually blocking |
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* waiting for work if none exist). This enables efficient processing |
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* when most tasks spawn other subtasks (as do most {@code |
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* ForkJoinTask}s). When setting <em>asyncMode</em> to true in |
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* constructors, {@code ForkJoinPool}s may also be appropriate for use |
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* with event-style tasks that are never joined. |
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* |
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* <p>A {@code ForkJoinPool} is constructed with a given target |
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* parallelism level; by default, equal to the number of available |
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* processors. The pool attempts to maintain enough active (or |
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* available) threads by dynamically adding, suspending, or resuming |
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* internal worker threads, even if some tasks are stalled waiting to |
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* join others. However, no such adjustments are guaranteed in the |
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* face of blocked IO or other unmanaged synchronization. The nested |
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* {@link ManagedBlocker} interface enables extension of the kinds of |
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* synchronization accommodated. |
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* |
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* <p>In addition to execution and lifecycle control methods, this |
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* class provides status check methods (for example |
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* {@link #getStealCount}) that are intended to aid in developing, |
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* tuning, and monitoring fork/join applications. Also, method |
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* {@link #toString} returns indications of pool state in a |
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* convenient form for informal monitoring. |
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* |
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* <p> As is the case with other ExecutorServices, there are three |
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* main task execution methods summarized in the follwoing |
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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. To avoid inadvertant |
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* cyclic task dependencies and to improve performance, task |
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* submissions to the current pool by an ongoing fork/join |
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* computations may be implicitly translated to the corresponding |
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* ForkJoinTask forms. |
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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 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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* |
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* @since 1.7 |
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* @author Doug Lea |
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*/ |
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public class ForkJoinPool extends AbstractExecutorService { |
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|
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/* |
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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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* 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 the management responsibilities of this class. So |
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* we use a collection of techniques that avoid, reduce, or cope |
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* well with contention. These entail several instances of |
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* bit-packing into CASable fields to maintain only the minimally |
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* required atomicity. To enable such packing, we restrict maximum |
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* parallelism to (1<<15)-1 (enabling twice this to fit into a 16 |
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* bit field), which is far in excess of normal operating range. |
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* Even though updates to some of these bookkeeping fields do |
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* sometimes contend with each other, they don't normally |
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* cache-contend with updates to others enough to warrant memory |
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* padding or isolation. So they are all held as fields of |
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* ForkJoinPool 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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* 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. To support these decisions, |
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* updates to spare counts must be prospective (not |
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* retrospective). For example, the running count is decremented |
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* before blocking by a thread about to block as a spare, but |
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* incremented by the thread about to unblock it. Updates upon |
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* resumption ofr threads blocking in awaitJoin or awaitBlocker |
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* cannot usually be prospective, so the running count is in |
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* general an upper bound of the number of productively running |
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* threads Updates to the workerCounts field sometimes transiently |
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* encounter a fair amount of contention when join dependencies |
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* are such that many threads block or unblock at about the same |
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* time. We alleviate this by sometimes performing an alternative |
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* action on contention like releasing waiters or locating spares. |
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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 |
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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 |
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* are packed together in order to correctly trigger shutdown and |
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* termination. Without care, active counts can be subject to very |
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* high contention. We substantially reduce this contention by |
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* relaxing update rules. A worker must claim active status |
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* prospectively, by activating if it sees that a submitted or |
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* stealable task exists (it may find after activating that the |
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* task no longer exists). It stays active while processing this |
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* task (if it exists) and any other local subtasks it produces, |
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* until it cannot find any other tasks. It then tries |
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* inactivating (see method preStep), but upon update contention |
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* instead scans for more tasks, later retrying inactivation if it |
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* doesn't find any. |
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* |
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* 4. Managing idle workers waiting for tasks. We cannot let |
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* workers spin indefinitely scanning for tasks when none are |
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* available. On the other hand, we must quickly prod them into |
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* action when new tasks are submitted or generated. We |
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* park/unpark these idle workers using an event-count scheme. |
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* Field eventCount is incremented upon events that may enable |
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* workers that previously could not find a task to now find one: |
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* Submission of a new task to the pool, or another worker pushing |
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* a task onto a previously empty queue. (We also use this |
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* mechanism for termination and reconfiguration actions that |
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* require wakeups of idle workers). Each worker maintains its |
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* last known event count, and blocks when a scan for work did not |
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* find a task AND its lastEventCount matches the current |
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* eventCount. Waiting idle workers are recorded in a variant of |
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* Treiber stack headed by field eventWaiters which, when nonzero, |
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* encodes the thread index and count awaited for by the worker |
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* thread most recently calling eventSync. This thread in turn has |
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* a record (field nextEventWaiter) for the next waiting worker. |
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* In addition to allowing simpler decisions about need for |
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* wakeup, the event count bits in eventWaiters serve the role of |
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* tags to avoid ABA errors in Treiber stacks. To reduce delays |
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* in task diffusion, workers not otherwise occupied may invoke |
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* method releaseWaiters, that removes and signals (unparks) |
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* workers not waiting on current count. To minimize task |
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* production stalls associate with signalling, any worker pushing |
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* a task on an empty queue invokes the weaker method signalWork, |
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* that only releases idle workers until it detects interference |
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* by other threads trying to release, and lets them take |
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* over. The net effect is a tree-like diffusion of signals, where |
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* released threads (and possibly others) help with unparks. To |
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* further reduce contention effects a bit, failed CASes to |
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* increment field eventCount are tolerated without retries. |
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* Conceptually they are merged into the same event, which is OK |
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* when their only purpose is to enable workers to scan for work. |
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* |
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* 5. Managing suspension of extra workers. When a worker is about |
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* to block waiting for a join (or via ManagedBlockers), we may |
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* create a new thread to maintain parallelism level, or at least |
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* avoid starvation (see below). Usually, extra threads are needed |
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* for only very short periods, yet join dependencies are such |
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* that we sometimes need them in bursts. Rather than create new |
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* threads each time this happens, we suspend no-longer-needed |
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* extra ones as "spares". For most purposes, we don't distinguish |
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* "extra" spare threads from normal "core" threads: On each call |
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* to preStep (the only point at which we can do this) a worker |
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* checks to see if there are now too many running workers, and if |
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* so, suspends itself. Methods awaitJoin and awaitBlocker look |
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* for suspended threads to resume before considering creating a |
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* new replacement. We don't need a special data structure to |
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* maintain spares; simply scanning the workers array looking for |
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* worker.isSuspended() is fine because the calling thread is |
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* otherwise not doing anything useful anyway; we are at least as |
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* happy if after locating a spare, the caller doesn't actually |
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* block because the join is ready before we try to adjust and |
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* compensate. Note that this is intrinsically racy. One thread |
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* may become a spare at about the same time as another is |
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* needlessly being created. We counteract this and related slop |
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* in part by requiring resumed spares to immediately recheck (in |
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* preStep) to see whether they they should re-suspend. The only |
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* effective difference between "extra" and "core" threads is that |
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* we allow the "extra" ones to time out and die if they are not |
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* resumed within a keep-alive interval of a few seconds. This is |
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* implemented mainly within ForkJoinWorkerThread, but requires |
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* some coordination (isTrimmed() -- meaning killed while |
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* suspended) to correctly maintain pool counts. |
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* |
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* 6. Deciding when to create new workers. The main dynamic |
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* control in this class is deciding when to create extra threads, |
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* in methods awaitJoin and awaitBlocker. We always need to create |
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* one when the number of running threads becomes zero. But |
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* because blocked joins are typically dependent, we don't |
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* necessarily need or want one-to-one replacement. Instead, we |
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* use a combination of heuristics that adds threads only when the |
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* pool appears to be approaching starvation. These effectively |
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* reduce churn at the price of systematically undershooting |
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* target parallelism when many threads are blocked. However, |
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* biasing toward undeshooting partially compensates for the above |
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* mechanics to suspend extra threads, that normally lead to |
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* overshoot because we can only suspend workers in-between |
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* top-level actions. It also better copes with the fact that some |
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* of the methods in this class tend to never become compiled (but |
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* are interpreted), so some components of the entire set of |
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* controls might execute many times faster than others. And |
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* similarly for cases where the apparent lack of work is just due |
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* to GC stalls and other transient system activity. |
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* |
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* Beware that there is a lot of representation-level coupling |
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* among classes ForkJoinPool, ForkJoinWorkerThread, and |
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* ForkJoinTask. For example, direct access to "workers" array by |
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* workers, and direct access to ForkJoinTask.status by both |
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* ForkJoinPool and ForkJoinWorkerThread. There is little point |
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* trying to reduce this, since any associated future changes in |
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* representations will need to be accompanied by algorithmic |
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* changes anyway. |
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* |
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* Style notes: There are lots of inline assignments (of form |
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* "while ((local = field) != 0)") which are usually the simplest |
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* way to ensure read orderings. Also several occurrences of the |
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* unusual "do {} while(!cas...)" which is the simplest way to |
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* force an update of a CAS'ed variable. There are also a few |
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* other coding oddities that help some methods perform reasonably |
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* even when interpreted (not compiled). |
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* |
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* The order of declarations in this file is: (1) statics (2) |
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* fields (along with constants used when unpacking some of them) |
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* (3) internal control methods (4) callbacks and other support |
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* for ForkJoinTask and ForkJoinWorkerThread classes, (5) exported |
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* methods (plus a few little helpers). |
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*/ |
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|
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/** |
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* Factory for creating new {@link ForkJoinWorkerThread}s. |
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* A {@code ForkJoinWorkerThreadFactory} must be defined and used |
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* for {@code ForkJoinWorkerThread} subclasses that extend base |
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* functionality or initialize threads with different contexts. |
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*/ |
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public static interface ForkJoinWorkerThreadFactory { |
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/** |
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* Returns a new worker thread operating in the given pool. |
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* |
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* @param pool the pool this thread works in |
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* @throws NullPointerException if the pool is null |
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*/ |
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public ForkJoinWorkerThread newThread(ForkJoinPool pool); |
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} |
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|
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/** |
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* Default ForkJoinWorkerThreadFactory implementation; creates a |
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* new ForkJoinWorkerThread. |
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*/ |
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static class DefaultForkJoinWorkerThreadFactory |
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implements ForkJoinWorkerThreadFactory { |
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public ForkJoinWorkerThread newThread(ForkJoinPool pool) { |
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return new ForkJoinWorkerThread(pool); |
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} |
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} |
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|
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/** |
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* Creates a new ForkJoinWorkerThread. This factory is used unless |
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* overridden in ForkJoinPool constructors. |
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*/ |
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public static final ForkJoinWorkerThreadFactory |
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defaultForkJoinWorkerThreadFactory = |
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new DefaultForkJoinWorkerThreadFactory(); |
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|
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/** |
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* Permission required for callers of methods that may start or |
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* kill threads. |
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*/ |
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private static final RuntimePermission modifyThreadPermission = |
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new RuntimePermission("modifyThread"); |
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|
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/** |
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* If there is a security manager, makes sure caller has |
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* permission to modify threads. |
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*/ |
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private static void checkPermission() { |
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SecurityManager security = System.getSecurityManager(); |
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if (security != null) |
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security.checkPermission(modifyThreadPermission); |
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} |
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|
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/** |
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* Generator for assigning sequence numbers as pool names. |
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*/ |
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private static final AtomicInteger poolNumberGenerator = |
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new AtomicInteger(); |
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|
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/** |
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* Absolute bound for parallelism level. Twice this number must |
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* fit into a 16bit field to enable word-packing for some counts. |
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*/ |
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private static final int MAX_THREADS = 0x7fff; |
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|
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/** |
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* Array holding all worker threads in the pool. Array size must |
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* be a power of two. Updates and replacements are protected by |
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* workerLock, but the array is always kept in a consistent enough |
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* state to be randomly accessed without locking by workers |
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* performing work-stealing, as well as other traversal-based |
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* methods in this class. All readers must tolerate that some |
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* array slots may be null. |
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*/ |
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volatile ForkJoinWorkerThread[] workers; |
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|
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/** |
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* Queue for external submissions. |
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*/ |
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private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue; |
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|
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/** |
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* Lock protecting updates to workers array. |
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*/ |
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private final ReentrantLock workerLock; |
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|
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/** |
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* Latch released upon termination. |
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*/ |
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private final Phaser termination; |
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|
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/** |
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* Creation factory for worker threads. |
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*/ |
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private final ForkJoinWorkerThreadFactory factory; |
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|
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/** |
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* Sum of per-thread steal counts, updated only when threads are |
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* idle or terminating. |
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*/ |
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private volatile long stealCount; |
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|
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/** |
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* Encoded record of top of treiber stack of threads waiting for |
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* events. The top 32 bits contain the count being waited for. The |
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* bottom word contains one plus the pool index of waiting worker |
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* thread. |
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*/ |
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private volatile long eventWaiters; |
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|
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private static final int EVENT_COUNT_SHIFT = 32; |
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private static final long WAITER_INDEX_MASK = (1L << EVENT_COUNT_SHIFT)-1L; |
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|
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/** |
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* A counter for events that may wake up worker threads: |
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* - Submission of a new task to the pool |
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* - A worker pushing a task on an empty queue |
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* - termination and reconfiguration |
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*/ |
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private volatile int eventCount; |
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|
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/** |
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* Lifecycle control. The low word contains the number of workers |
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* that are (probably) executing tasks. This value is atomically |
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* incremented before a worker gets a task to run, and decremented |
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* when worker has no tasks and cannot find any. Bits 16-18 |
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* contain runLevel value. When all are zero, the pool is |
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* running. Level transitions are monotonic (running -> shutdown |
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* -> terminating -> terminated) so each transition adds a bit. |
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* These are bundled together to ensure consistent read for |
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* termination checks (i.e., that runLevel is at least SHUTDOWN |
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* and active threads is zero). |
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*/ |
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private volatile int runState; |
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|
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// Note: The order among run level values matters. |
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private static final int RUNLEVEL_SHIFT = 16; |
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private static final int SHUTDOWN = 1 << RUNLEVEL_SHIFT; |
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private static final int TERMINATING = 1 << (RUNLEVEL_SHIFT + 1); |
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private static final int TERMINATED = 1 << (RUNLEVEL_SHIFT + 2); |
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private static final int ACTIVE_COUNT_MASK = (1 << RUNLEVEL_SHIFT) - 1; |
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private static final int ONE_ACTIVE = 1; // active update delta |
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|
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/** |
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* Holds number of total (i.e., created and not yet terminated) |
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* and running (i.e., not blocked on joins or other managed sync) |
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* threads, packed together to ensure consistent snapshot when |
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* making decisions about creating and suspending spare |
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* threads. Updated only by CAS. Note that adding a new worker |
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* requires incrementing both counts, since workers start off in |
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* running state. This field is also used for memory-fencing |
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* configuration parameters. |
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*/ |
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private volatile int workerCounts; |
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|
478 |
private static final int TOTAL_COUNT_SHIFT = 16; |
479 |
private static final int RUNNING_COUNT_MASK = (1 << TOTAL_COUNT_SHIFT) - 1; |
480 |
private static final int ONE_RUNNING = 1; |
481 |
private static final int ONE_TOTAL = 1 << TOTAL_COUNT_SHIFT; |
482 |
|
483 |
/** |
484 |
* The target parallelism level. |
485 |
* Accessed directly by ForkJoinWorkerThreads. |
486 |
*/ |
487 |
final int parallelism; |
488 |
|
489 |
/** |
490 |
* True if use local fifo, not default lifo, for local polling |
491 |
* Read by, and replicated by ForkJoinWorkerThreads |
492 |
*/ |
493 |
final boolean locallyFifo; |
494 |
|
495 |
/** |
496 |
* The uncaught exception handler used when any worker abruptly |
497 |
* terminates. |
498 |
*/ |
499 |
private final Thread.UncaughtExceptionHandler ueh; |
500 |
|
501 |
/** |
502 |
* Pool number, just for assigning useful names to worker threads |
503 |
*/ |
504 |
private final int poolNumber; |
505 |
|
506 |
// utilities for updating fields |
507 |
|
508 |
/** |
509 |
* Increments running count. Also used by ForkJoinTask. |
510 |
*/ |
511 |
final void incrementRunningCount() { |
512 |
int c; |
513 |
do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
514 |
c = workerCounts, |
515 |
c + ONE_RUNNING)); |
516 |
} |
517 |
|
518 |
/** |
519 |
* Tries to decrement running count unless already zero |
520 |
*/ |
521 |
final boolean tryDecrementRunningCount() { |
522 |
int wc = workerCounts; |
523 |
if ((wc & RUNNING_COUNT_MASK) == 0) |
524 |
return false; |
525 |
return UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
526 |
wc, wc - ONE_RUNNING); |
527 |
} |
528 |
|
529 |
/** |
530 |
* Tries incrementing active count; fails on contention. |
531 |
* Called by workers before executing tasks. |
532 |
* |
533 |
* @return true on success |
534 |
*/ |
535 |
final boolean tryIncrementActiveCount() { |
536 |
int c; |
537 |
return UNSAFE.compareAndSwapInt(this, runStateOffset, |
538 |
c = runState, c + ONE_ACTIVE); |
539 |
} |
540 |
|
541 |
/** |
542 |
* Tries decrementing active count; fails on contention. |
543 |
* Called when workers cannot find tasks to run. |
544 |
*/ |
545 |
final boolean tryDecrementActiveCount() { |
546 |
int c; |
547 |
return UNSAFE.compareAndSwapInt(this, runStateOffset, |
548 |
c = runState, c - ONE_ACTIVE); |
549 |
} |
550 |
|
551 |
/** |
552 |
* Advances to at least the given level. Returns true if not |
553 |
* already in at least the given level. |
554 |
*/ |
555 |
private boolean advanceRunLevel(int level) { |
556 |
for (;;) { |
557 |
int s = runState; |
558 |
if ((s & level) != 0) |
559 |
return false; |
560 |
if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, s | level)) |
561 |
return true; |
562 |
} |
563 |
} |
564 |
|
565 |
// workers array maintenance |
566 |
|
567 |
/** |
568 |
* Records and returns a workers array index for new worker. |
569 |
*/ |
570 |
private int recordWorker(ForkJoinWorkerThread w) { |
571 |
// Try using slot totalCount-1. If not available, scan and/or resize |
572 |
int k = (workerCounts >>> TOTAL_COUNT_SHIFT) - 1; |
573 |
final ReentrantLock lock = this.workerLock; |
574 |
lock.lock(); |
575 |
try { |
576 |
ForkJoinWorkerThread[] ws = workers; |
577 |
int nws = ws.length; |
578 |
if (k < 0 || k >= nws || ws[k] != null) { |
579 |
for (k = 0; k < nws && ws[k] != null; ++k) |
580 |
; |
581 |
if (k == nws) |
582 |
ws = Arrays.copyOf(ws, nws << 1); |
583 |
} |
584 |
ws[k] = w; |
585 |
workers = ws; // volatile array write ensures slot visibility |
586 |
} finally { |
587 |
lock.unlock(); |
588 |
} |
589 |
return k; |
590 |
} |
591 |
|
592 |
/** |
593 |
* Nulls out record of worker in workers array |
594 |
*/ |
595 |
private void forgetWorker(ForkJoinWorkerThread w) { |
596 |
int idx = w.poolIndex; |
597 |
// Locking helps method recordWorker avoid unecessary expansion |
598 |
final ReentrantLock lock = this.workerLock; |
599 |
lock.lock(); |
600 |
try { |
601 |
ForkJoinWorkerThread[] ws = workers; |
602 |
if (idx >= 0 && idx < ws.length && ws[idx] == w) // verify |
603 |
ws[idx] = null; |
604 |
} finally { |
605 |
lock.unlock(); |
606 |
} |
607 |
} |
608 |
|
609 |
// adding and removing workers |
610 |
|
611 |
/** |
612 |
* Tries to create and add new worker. Assumes that worker counts |
613 |
* are already updated to accommodate the worker, so adjusts on |
614 |
* failure. |
615 |
* |
616 |
* @return new worker or null if creation failed |
617 |
*/ |
618 |
private ForkJoinWorkerThread addWorker() { |
619 |
ForkJoinWorkerThread w = null; |
620 |
try { |
621 |
w = factory.newThread(this); |
622 |
} finally { // Adjust on either null or exceptional factory return |
623 |
if (w == null) { |
624 |
onWorkerCreationFailure(); |
625 |
return null; |
626 |
} |
627 |
} |
628 |
w.start(recordWorker(w), ueh); |
629 |
return w; |
630 |
} |
631 |
|
632 |
/** |
633 |
* Adjusts counts upon failure to create worker |
634 |
*/ |
635 |
private void onWorkerCreationFailure() { |
636 |
for (;;) { |
637 |
int wc = workerCounts; |
638 |
if ((wc >>> TOTAL_COUNT_SHIFT) > 0 && |
639 |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
640 |
wc, wc - (ONE_RUNNING|ONE_TOTAL))) |
641 |
break; |
642 |
} |
643 |
tryTerminate(false); // in case of failure during shutdown |
644 |
} |
645 |
|
646 |
/** |
647 |
* Create enough total workers to establish target parallelism, |
648 |
* giving up if terminating or addWorker fails |
649 |
*/ |
650 |
private void ensureEnoughTotalWorkers() { |
651 |
int wc; |
652 |
while (((wc = workerCounts) >>> TOTAL_COUNT_SHIFT) < parallelism && |
653 |
runState < TERMINATING) { |
654 |
if ((UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
655 |
wc, wc + (ONE_RUNNING|ONE_TOTAL)) && |
656 |
addWorker() == null)) |
657 |
break; |
658 |
} |
659 |
} |
660 |
|
661 |
/** |
662 |
* Final callback from terminating worker. Removes record of |
663 |
* worker from array, and adjusts counts. If pool is shutting |
664 |
* down, tries to complete terminatation, else possibly replaces |
665 |
* the worker. |
666 |
* |
667 |
* @param w the worker |
668 |
*/ |
669 |
final void workerTerminated(ForkJoinWorkerThread w) { |
670 |
if (w.active) { // force inactive |
671 |
w.active = false; |
672 |
do {} while (!tryDecrementActiveCount()); |
673 |
} |
674 |
forgetWorker(w); |
675 |
|
676 |
// Decrement total count, and if was running, running count |
677 |
// Spin (waiting for other updates) if either would be negative |
678 |
int nr = w.isTrimmed() ? 0 : ONE_RUNNING; |
679 |
int unit = ONE_TOTAL + nr; |
680 |
for (;;) { |
681 |
int wc = workerCounts; |
682 |
int rc = wc & RUNNING_COUNT_MASK; |
683 |
if (rc - nr < 0 || (wc >>> TOTAL_COUNT_SHIFT) == 0) |
684 |
Thread.yield(); // back off if waiting for other updates |
685 |
else if (UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
686 |
wc, wc - unit)) |
687 |
break; |
688 |
} |
689 |
|
690 |
accumulateStealCount(w); // collect final count |
691 |
if (!tryTerminate(false)) |
692 |
ensureEnoughTotalWorkers(); |
693 |
} |
694 |
|
695 |
// Waiting for and signalling events |
696 |
|
697 |
/** |
698 |
* Releases workers blocked on a count not equal to current count. |
699 |
*/ |
700 |
private void releaseWaiters() { |
701 |
long top; |
702 |
int id; |
703 |
while ((id = (int)((top = eventWaiters) & WAITER_INDEX_MASK)) > 0 && |
704 |
(int)(top >>> EVENT_COUNT_SHIFT) != eventCount) { |
705 |
ForkJoinWorkerThread[] ws = workers; |
706 |
ForkJoinWorkerThread w; |
707 |
if (ws.length >= id && (w = ws[id - 1]) != null && |
708 |
UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
709 |
top, w.nextWaiter)) |
710 |
LockSupport.unpark(w); |
711 |
} |
712 |
} |
713 |
|
714 |
/** |
715 |
* Ensures eventCount on exit is different (mod 2^32) than on |
716 |
* entry and wakes up all waiters |
717 |
*/ |
718 |
private void signalEvent() { |
719 |
int c; |
720 |
do {} while (!UNSAFE.compareAndSwapInt(this, eventCountOffset, |
721 |
c = eventCount, c+1)); |
722 |
releaseWaiters(); |
723 |
} |
724 |
|
725 |
/** |
726 |
* Advances eventCount and releases waiters until interference by |
727 |
* other releasing threads is detected. |
728 |
*/ |
729 |
final void signalWork() { |
730 |
// EventCount CAS failures are OK -- any change in count suffices. |
731 |
int ec; |
732 |
UNSAFE.compareAndSwapInt(this, eventCountOffset, ec=eventCount, ec+1); |
733 |
outer:for (;;) { |
734 |
long top = eventWaiters; |
735 |
ec = eventCount; |
736 |
for (;;) { |
737 |
ForkJoinWorkerThread[] ws; ForkJoinWorkerThread w; |
738 |
int id = (int)(top & WAITER_INDEX_MASK); |
739 |
if (id <= 0 || (int)(top >>> EVENT_COUNT_SHIFT) == ec) |
740 |
return; |
741 |
if ((ws = workers).length < id || (w = ws[id - 1]) == null || |
742 |
!UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
743 |
top, top = w.nextWaiter)) |
744 |
continue outer; // possibly stale; reread |
745 |
LockSupport.unpark(w); |
746 |
if (top != eventWaiters) // let someone else take over |
747 |
return; |
748 |
} |
749 |
} |
750 |
} |
751 |
|
752 |
/** |
753 |
* If worker is inactive, blocks until terminating or event count |
754 |
* advances from last value held by worker; in any case helps |
755 |
* release others. |
756 |
* |
757 |
* @param w the calling worker thread |
758 |
*/ |
759 |
private void eventSync(ForkJoinWorkerThread w) { |
760 |
if (!w.active) { |
761 |
int prev = w.lastEventCount; |
762 |
long nextTop = (((long)prev << EVENT_COUNT_SHIFT) | |
763 |
((long)(w.poolIndex + 1))); |
764 |
long top; |
765 |
while ((runState < SHUTDOWN || !tryTerminate(false)) && |
766 |
(((int)(top = eventWaiters) & WAITER_INDEX_MASK) == 0 || |
767 |
(int)(top >>> EVENT_COUNT_SHIFT) == prev) && |
768 |
eventCount == prev) { |
769 |
if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
770 |
w.nextWaiter = top, nextTop)) { |
771 |
accumulateStealCount(w); // transfer steals while idle |
772 |
Thread.interrupted(); // clear/ignore interrupt |
773 |
while (eventCount == prev) |
774 |
w.doPark(); |
775 |
break; |
776 |
} |
777 |
} |
778 |
w.lastEventCount = eventCount; |
779 |
} |
780 |
releaseWaiters(); |
781 |
} |
782 |
|
783 |
/** |
784 |
* Callback from workers invoked upon each top-level action (i.e., |
785 |
* stealing a task or taking a submission and running |
786 |
* it). Performs one or both of the following: |
787 |
* |
788 |
* * If the worker cannot find work, updates its active status to |
789 |
* inactive and updates activeCount unless there is contention, in |
790 |
* which case it may try again (either in this or a subsequent |
791 |
* call). Additionally, awaits the next task event and/or helps |
792 |
* wake up other releasable waiters. |
793 |
* |
794 |
* * If there are too many running threads, suspends this worker |
795 |
* (first forcing inactivation if necessary). If it is not |
796 |
* resumed before a keepAlive elapses, the worker may be "trimmed" |
797 |
* -- killed while suspended within suspendAsSpare. Otherwise, |
798 |
* upon resume it rechecks to make sure that it is still needed. |
799 |
* |
800 |
* @param w the worker |
801 |
* @param worked false if the worker scanned for work but didn't |
802 |
* find any (in which case it may block waiting for work). |
803 |
*/ |
804 |
final void preStep(ForkJoinWorkerThread w, boolean worked) { |
805 |
boolean active = w.active; |
806 |
boolean inactivate = !worked & active; |
807 |
for (;;) { |
808 |
if (inactivate) { |
809 |
int rs = runState; |
810 |
if (UNSAFE.compareAndSwapInt(this, runStateOffset, |
811 |
rs, rs - ONE_ACTIVE)) |
812 |
inactivate = active = w.active = false; |
813 |
} |
814 |
int wc = workerCounts; |
815 |
if ((wc & RUNNING_COUNT_MASK) <= parallelism) { |
816 |
if (!worked) |
817 |
eventSync(w); |
818 |
return; |
819 |
} |
820 |
if (!(inactivate |= active) && // must inactivate to suspend |
821 |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
822 |
wc, wc - ONE_RUNNING) && |
823 |
!w.suspendAsSpare()) // false if trimmed |
824 |
return; |
825 |
} |
826 |
} |
827 |
|
828 |
/** |
829 |
* Tries to decrement running count, and if so, possibly creates |
830 |
* or resumes compensating threads before blocking on task joinMe. |
831 |
* This code is sprawled out with manual inlining to evade some |
832 |
* JIT oddities. |
833 |
* |
834 |
* @param joinMe the task to join |
835 |
* @return task status on exit |
836 |
*/ |
837 |
final int tryAwaitJoin(ForkJoinTask<?> joinMe) { |
838 |
int cw = workerCounts; // read now to spoil CAS if counts change as ... |
839 |
releaseWaiters(); // ... a byproduct of releaseWaiters |
840 |
int stat = joinMe.status; |
841 |
if (stat >= 0 && // inline variant of tryDecrementRunningCount |
842 |
(cw & RUNNING_COUNT_MASK) > 0 && |
843 |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
844 |
cw, cw - ONE_RUNNING)) { |
845 |
int pc = parallelism; |
846 |
int scans = 0; // to require confirming passes to add threads |
847 |
outer: while ((workerCounts & RUNNING_COUNT_MASK) < pc) { |
848 |
if ((stat = joinMe.status) < 0) |
849 |
break; |
850 |
ForkJoinWorkerThread spare = null; |
851 |
ForkJoinWorkerThread[] ws = workers; |
852 |
int nws = ws.length; |
853 |
for (int i = 0; i < nws; ++i) { |
854 |
ForkJoinWorkerThread w = ws[i]; |
855 |
if (w != null && w.isSuspended()) { |
856 |
spare = w; |
857 |
break; |
858 |
} |
859 |
} |
860 |
if ((stat = joinMe.status) < 0) // recheck to narrow race |
861 |
break; |
862 |
int wc = workerCounts; |
863 |
int rc = wc & RUNNING_COUNT_MASK; |
864 |
if (rc >= pc) |
865 |
break; |
866 |
if (spare != null) { |
867 |
if (spare.tryUnsuspend()) { |
868 |
int c; // inline incrementRunningCount |
869 |
do {} while (!UNSAFE.compareAndSwapInt |
870 |
(this, workerCountsOffset, |
871 |
c = workerCounts, c + ONE_RUNNING)); |
872 |
LockSupport.unpark(spare); |
873 |
break; |
874 |
} |
875 |
continue; |
876 |
} |
877 |
int tc = wc >>> TOTAL_COUNT_SHIFT; |
878 |
int sc = tc - pc; |
879 |
if (rc > 0) { |
880 |
int p = pc; |
881 |
int s = sc; |
882 |
while (s-- >= 0) { // try keeping 3/4 live |
883 |
if (rc > (p -= (p >>> 2) + 1)) |
884 |
break outer; |
885 |
} |
886 |
} |
887 |
if (scans++ > sc && tc < MAX_THREADS && |
888 |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc, |
889 |
wc + (ONE_RUNNING|ONE_TOTAL))) { |
890 |
addWorker(); |
891 |
break; |
892 |
} |
893 |
} |
894 |
if (stat >= 0) |
895 |
stat = joinMe.internalAwaitDone(); |
896 |
int c; // inline incrementRunningCount |
897 |
do {} while (!UNSAFE.compareAndSwapInt |
898 |
(this, workerCountsOffset, |
899 |
c = workerCounts, c + ONE_RUNNING)); |
900 |
} |
901 |
return stat; |
902 |
} |
903 |
|
904 |
/** |
905 |
* Same idea as (and mostly pasted from) tryAwaitJoin, but |
906 |
* self-contained |
907 |
*/ |
908 |
final void awaitBlocker(ManagedBlocker blocker) |
909 |
throws InterruptedException { |
910 |
for (;;) { |
911 |
if (blocker.isReleasable()) |
912 |
return; |
913 |
int cw = workerCounts; |
914 |
releaseWaiters(); |
915 |
if ((cw & RUNNING_COUNT_MASK) > 0 && |
916 |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
917 |
cw, cw - ONE_RUNNING)) |
918 |
break; |
919 |
} |
920 |
boolean done = false; |
921 |
int pc = parallelism; |
922 |
int scans = 0; |
923 |
outer: while ((workerCounts & RUNNING_COUNT_MASK) < pc) { |
924 |
if (done = blocker.isReleasable()) |
925 |
break; |
926 |
ForkJoinWorkerThread spare = null; |
927 |
ForkJoinWorkerThread[] ws = workers; |
928 |
int nws = ws.length; |
929 |
for (int i = 0; i < nws; ++i) { |
930 |
ForkJoinWorkerThread w = ws[i]; |
931 |
if (w != null && w.isSuspended()) { |
932 |
spare = w; |
933 |
break; |
934 |
} |
935 |
} |
936 |
if (done = blocker.isReleasable()) |
937 |
break; |
938 |
int wc = workerCounts; |
939 |
int rc = wc & RUNNING_COUNT_MASK; |
940 |
if (rc >= pc) |
941 |
break; |
942 |
if (spare != null) { |
943 |
if (spare.tryUnsuspend()) { |
944 |
int c; |
945 |
do {} while (!UNSAFE.compareAndSwapInt |
946 |
(this, workerCountsOffset, |
947 |
c = workerCounts, c + ONE_RUNNING)); |
948 |
LockSupport.unpark(spare); |
949 |
break; |
950 |
} |
951 |
continue; |
952 |
} |
953 |
int tc = wc >>> TOTAL_COUNT_SHIFT; |
954 |
int sc = tc - pc; |
955 |
if (rc > 0) { |
956 |
int p = pc; |
957 |
int s = sc; |
958 |
while (s-- >= 0) { |
959 |
if (rc > (p -= (p >>> 2) + 1)) |
960 |
break outer; |
961 |
} |
962 |
} |
963 |
if (scans++ > sc && tc < MAX_THREADS && |
964 |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc, |
965 |
wc + (ONE_RUNNING|ONE_TOTAL))) { |
966 |
addWorker(); |
967 |
break; |
968 |
} |
969 |
} |
970 |
try { |
971 |
if (!done) |
972 |
do {} while (!blocker.isReleasable() && |
973 |
!blocker.block()); |
974 |
} finally { |
975 |
int c; |
976 |
do {} while (!UNSAFE.compareAndSwapInt |
977 |
(this, workerCountsOffset, |
978 |
c = workerCounts, c + ONE_RUNNING)); |
979 |
} |
980 |
} |
981 |
|
982 |
/** |
983 |
* Possibly initiates and/or completes termination. |
984 |
* |
985 |
* @param now if true, unconditionally terminate, else only |
986 |
* if shutdown and empty queue and no active workers |
987 |
* @return true if now terminating or terminated |
988 |
*/ |
989 |
private boolean tryTerminate(boolean now) { |
990 |
if (now) |
991 |
advanceRunLevel(SHUTDOWN); // ensure at least SHUTDOWN |
992 |
else if (runState < SHUTDOWN || |
993 |
!submissionQueue.isEmpty() || |
994 |
(runState & ACTIVE_COUNT_MASK) != 0) |
995 |
return false; |
996 |
|
997 |
if (advanceRunLevel(TERMINATING)) |
998 |
startTerminating(); |
999 |
|
1000 |
// Finish now if all threads terminated; else in some subsequent call |
1001 |
if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) { |
1002 |
advanceRunLevel(TERMINATED); |
1003 |
termination.arrive(); |
1004 |
} |
1005 |
return true; |
1006 |
} |
1007 |
|
1008 |
/** |
1009 |
* Actions on transition to TERMINATING |
1010 |
*/ |
1011 |
private void startTerminating() { |
1012 |
for (int i = 0; i < 2; ++i) { // twice to mop up newly created workers |
1013 |
cancelSubmissions(); |
1014 |
shutdownWorkers(); |
1015 |
cancelWorkerTasks(); |
1016 |
signalEvent(); |
1017 |
interruptWorkers(); |
1018 |
} |
1019 |
} |
1020 |
|
1021 |
/** |
1022 |
* Clear out and cancel submissions, ignoring exceptions |
1023 |
*/ |
1024 |
private void cancelSubmissions() { |
1025 |
ForkJoinTask<?> task; |
1026 |
while ((task = submissionQueue.poll()) != null) { |
1027 |
try { |
1028 |
task.cancel(false); |
1029 |
} catch (Throwable ignore) { |
1030 |
} |
1031 |
} |
1032 |
} |
1033 |
|
1034 |
/** |
1035 |
* Sets all worker run states to at least shutdown, |
1036 |
* also resuming suspended workers |
1037 |
*/ |
1038 |
private void shutdownWorkers() { |
1039 |
ForkJoinWorkerThread[] ws = workers; |
1040 |
int nws = ws.length; |
1041 |
for (int i = 0; i < nws; ++i) { |
1042 |
ForkJoinWorkerThread w = ws[i]; |
1043 |
if (w != null) |
1044 |
w.shutdown(); |
1045 |
} |
1046 |
} |
1047 |
|
1048 |
/** |
1049 |
* Clears out and cancels all locally queued tasks |
1050 |
*/ |
1051 |
private void cancelWorkerTasks() { |
1052 |
ForkJoinWorkerThread[] ws = workers; |
1053 |
int nws = ws.length; |
1054 |
for (int i = 0; i < nws; ++i) { |
1055 |
ForkJoinWorkerThread w = ws[i]; |
1056 |
if (w != null) |
1057 |
w.cancelTasks(); |
1058 |
} |
1059 |
} |
1060 |
|
1061 |
/** |
1062 |
* Unsticks all workers blocked on joins etc |
1063 |
*/ |
1064 |
private void interruptWorkers() { |
1065 |
ForkJoinWorkerThread[] ws = workers; |
1066 |
int nws = ws.length; |
1067 |
for (int i = 0; i < nws; ++i) { |
1068 |
ForkJoinWorkerThread w = ws[i]; |
1069 |
if (w != null && !w.isTerminated()) { |
1070 |
try { |
1071 |
w.interrupt(); |
1072 |
} catch (SecurityException ignore) { |
1073 |
} |
1074 |
} |
1075 |
} |
1076 |
} |
1077 |
|
1078 |
// misc support for ForkJoinWorkerThread |
1079 |
|
1080 |
/** |
1081 |
* Returns pool number |
1082 |
*/ |
1083 |
final int getPoolNumber() { |
1084 |
return poolNumber; |
1085 |
} |
1086 |
|
1087 |
/** |
1088 |
* Accumulates steal count from a worker, clearing |
1089 |
* the worker's value |
1090 |
*/ |
1091 |
final void accumulateStealCount(ForkJoinWorkerThread w) { |
1092 |
int sc = w.stealCount; |
1093 |
if (sc != 0) { |
1094 |
long c; |
1095 |
w.stealCount = 0; |
1096 |
do {} while (!UNSAFE.compareAndSwapLong(this, stealCountOffset, |
1097 |
c = stealCount, c + sc)); |
1098 |
} |
1099 |
} |
1100 |
|
1101 |
/** |
1102 |
* Returns the approximate (non-atomic) number of idle threads per |
1103 |
* active thread. |
1104 |
*/ |
1105 |
final int idlePerActive() { |
1106 |
int pc = parallelism; // use targeted parallelism, not rc |
1107 |
int ac = runState; // no mask -- artifically boosts during shutdown |
1108 |
// Use exact results for small values, saturate past 4 |
1109 |
return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3; |
1110 |
} |
1111 |
|
1112 |
// Public and protected methods |
1113 |
|
1114 |
// Constructors |
1115 |
|
1116 |
/** |
1117 |
* Creates a {@code ForkJoinPool} with parallelism equal to {@link |
1118 |
* java.lang.Runtime#availableProcessors}, using the {@linkplain |
1119 |
* #defaultForkJoinWorkerThreadFactory default thread factory}, |
1120 |
* no UncaughtExceptionHandler, and non-async LIFO processing mode. |
1121 |
* |
1122 |
* @throws SecurityException if a security manager exists and |
1123 |
* the caller is not permitted to modify threads |
1124 |
* because it does not hold {@link |
1125 |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1126 |
*/ |
1127 |
public ForkJoinPool() { |
1128 |
this(Runtime.getRuntime().availableProcessors(), |
1129 |
defaultForkJoinWorkerThreadFactory, null, false); |
1130 |
} |
1131 |
|
1132 |
/** |
1133 |
* Creates a {@code ForkJoinPool} with the indicated parallelism |
1134 |
* level, the {@linkplain |
1135 |
* #defaultForkJoinWorkerThreadFactory default thread factory}, |
1136 |
* no UncaughtExceptionHandler, and non-async LIFO processing mode. |
1137 |
* |
1138 |
* @param parallelism the parallelism level |
1139 |
* @throws IllegalArgumentException if parallelism less than or |
1140 |
* equal to zero, or greater than implementation limit |
1141 |
* @throws SecurityException if a security manager exists and |
1142 |
* the caller is not permitted to modify threads |
1143 |
* because it does not hold {@link |
1144 |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1145 |
*/ |
1146 |
public ForkJoinPool(int parallelism) { |
1147 |
this(parallelism, defaultForkJoinWorkerThreadFactory, null, false); |
1148 |
} |
1149 |
|
1150 |
/** |
1151 |
* Creates a {@code ForkJoinPool} with the given parameters. |
1152 |
* |
1153 |
* @param parallelism the parallelism level. For default value, |
1154 |
* use {@link java.lang.Runtime#availableProcessors}. |
1155 |
* @param factory the factory for creating new threads. For default value, |
1156 |
* use {@link #defaultForkJoinWorkerThreadFactory}. |
1157 |
* @param handler the handler for internal worker threads that |
1158 |
* terminate due to unrecoverable errors encountered while executing |
1159 |
* tasks. For default value, use <code>null</code>. |
1160 |
* @param asyncMode if true, |
1161 |
* establishes local first-in-first-out scheduling mode for forked |
1162 |
* tasks that are never joined. This mode may be more appropriate |
1163 |
* than default locally stack-based mode in applications in which |
1164 |
* worker threads only process event-style asynchronous tasks. |
1165 |
* For default value, use <code>false</code>. |
1166 |
* @throws IllegalArgumentException if parallelism less than or |
1167 |
* equal to zero, or greater than implementation limit |
1168 |
* @throws NullPointerException if the factory is null |
1169 |
* @throws SecurityException if a security manager exists and |
1170 |
* the caller is not permitted to modify threads |
1171 |
* because it does not hold {@link |
1172 |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1173 |
*/ |
1174 |
public ForkJoinPool(int parallelism, |
1175 |
ForkJoinWorkerThreadFactory factory, |
1176 |
Thread.UncaughtExceptionHandler handler, |
1177 |
boolean asyncMode) { |
1178 |
checkPermission(); |
1179 |
if (factory == null) |
1180 |
throw new NullPointerException(); |
1181 |
if (parallelism <= 0 || parallelism > MAX_THREADS) |
1182 |
throw new IllegalArgumentException(); |
1183 |
this.parallelism = parallelism; |
1184 |
this.factory = factory; |
1185 |
this.ueh = handler; |
1186 |
this.locallyFifo = asyncMode; |
1187 |
int arraySize = initialArraySizeFor(parallelism); |
1188 |
this.workers = new ForkJoinWorkerThread[arraySize]; |
1189 |
this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>(); |
1190 |
this.workerLock = new ReentrantLock(); |
1191 |
this.termination = new Phaser(1); |
1192 |
this.poolNumber = poolNumberGenerator.incrementAndGet(); |
1193 |
} |
1194 |
|
1195 |
/** |
1196 |
* Returns initial power of two size for workers array. |
1197 |
* @param pc the initial parallelism level |
1198 |
*/ |
1199 |
private static int initialArraySizeFor(int pc) { |
1200 |
// See Hackers Delight, sec 3.2. We know MAX_THREADS < (1 >>> 16) |
1201 |
int size = pc < MAX_THREADS ? pc + 1 : MAX_THREADS; |
1202 |
size |= size >>> 1; |
1203 |
size |= size >>> 2; |
1204 |
size |= size >>> 4; |
1205 |
size |= size >>> 8; |
1206 |
return size + 1; |
1207 |
} |
1208 |
|
1209 |
// Execution methods |
1210 |
|
1211 |
/** |
1212 |
* Common code for execute, invoke and submit |
1213 |
*/ |
1214 |
private <T> void doSubmit(ForkJoinTask<T> task) { |
1215 |
if (task == null) |
1216 |
throw new NullPointerException(); |
1217 |
if (runState >= SHUTDOWN) |
1218 |
throw new RejectedExecutionException(); |
1219 |
// Convert submissions to current pool into forks |
1220 |
Thread t = Thread.currentThread(); |
1221 |
ForkJoinWorkerThread w; |
1222 |
if ((t instanceof ForkJoinWorkerThread) && |
1223 |
(w = (ForkJoinWorkerThread) t).pool == this) |
1224 |
w.pushTask(task); |
1225 |
else { |
1226 |
submissionQueue.offer(task); |
1227 |
signalEvent(); |
1228 |
ensureEnoughTotalWorkers(); |
1229 |
} |
1230 |
} |
1231 |
|
1232 |
/** |
1233 |
* Performs the given task, returning its result upon completion. |
1234 |
* If the caller is already engaged in a fork/join computation in |
1235 |
* the current pool, this method is equivalent in effect to |
1236 |
* {@link ForkJoinTask#invoke}. |
1237 |
* |
1238 |
* @param task the task |
1239 |
* @return the task's result |
1240 |
* @throws NullPointerException if the task is null |
1241 |
* @throws RejectedExecutionException if the task cannot be |
1242 |
* scheduled for execution |
1243 |
*/ |
1244 |
public <T> T invoke(ForkJoinTask<T> task) { |
1245 |
doSubmit(task); |
1246 |
return task.join(); |
1247 |
} |
1248 |
|
1249 |
/** |
1250 |
* Arranges for (asynchronous) execution of the given task. |
1251 |
* If the caller is already engaged in a fork/join computation in |
1252 |
* the current pool, this method is equivalent in effect to |
1253 |
* {@link ForkJoinTask#fork}. |
1254 |
* |
1255 |
* @param task the task |
1256 |
* @throws NullPointerException if the task is null |
1257 |
* @throws RejectedExecutionException if the task cannot be |
1258 |
* scheduled for execution |
1259 |
*/ |
1260 |
public void execute(ForkJoinTask<?> task) { |
1261 |
doSubmit(task); |
1262 |
} |
1263 |
|
1264 |
// AbstractExecutorService methods |
1265 |
|
1266 |
/** |
1267 |
* @throws NullPointerException if the task is null |
1268 |
* @throws RejectedExecutionException if the task cannot be |
1269 |
* scheduled for execution |
1270 |
*/ |
1271 |
public void execute(Runnable task) { |
1272 |
ForkJoinTask<?> job; |
1273 |
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
1274 |
job = (ForkJoinTask<?>) task; |
1275 |
else |
1276 |
job = ForkJoinTask.adapt(task, null); |
1277 |
doSubmit(job); |
1278 |
} |
1279 |
|
1280 |
/** |
1281 |
* Submits a ForkJoinTask for execution. |
1282 |
* If the caller is already engaged in a fork/join computation in |
1283 |
* the current pool, this method is equivalent in effect to |
1284 |
* {@link ForkJoinTask#fork}. |
1285 |
* |
1286 |
* @param task the task to submit |
1287 |
* @return the task |
1288 |
* @throws NullPointerException if the task is null |
1289 |
* @throws RejectedExecutionException if the task cannot be |
1290 |
* scheduled for execution |
1291 |
*/ |
1292 |
public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) { |
1293 |
doSubmit(task); |
1294 |
return task; |
1295 |
} |
1296 |
|
1297 |
/** |
1298 |
* @throws NullPointerException if the task is null |
1299 |
* @throws RejectedExecutionException if the task cannot be |
1300 |
* scheduled for execution |
1301 |
*/ |
1302 |
public <T> ForkJoinTask<T> submit(Callable<T> task) { |
1303 |
ForkJoinTask<T> job = ForkJoinTask.adapt(task); |
1304 |
doSubmit(job); |
1305 |
return job; |
1306 |
} |
1307 |
|
1308 |
/** |
1309 |
* @throws NullPointerException if the task is null |
1310 |
* @throws RejectedExecutionException if the task cannot be |
1311 |
* scheduled for execution |
1312 |
*/ |
1313 |
public <T> ForkJoinTask<T> submit(Runnable task, T result) { |
1314 |
ForkJoinTask<T> job = ForkJoinTask.adapt(task, result); |
1315 |
doSubmit(job); |
1316 |
return job; |
1317 |
} |
1318 |
|
1319 |
/** |
1320 |
* @throws NullPointerException if the task is null |
1321 |
* @throws RejectedExecutionException if the task cannot be |
1322 |
* scheduled for execution |
1323 |
*/ |
1324 |
public ForkJoinTask<?> submit(Runnable task) { |
1325 |
ForkJoinTask<?> job; |
1326 |
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
1327 |
job = (ForkJoinTask<?>) task; |
1328 |
else |
1329 |
job = ForkJoinTask.adapt(task, null); |
1330 |
doSubmit(job); |
1331 |
return job; |
1332 |
} |
1333 |
|
1334 |
/** |
1335 |
* @throws NullPointerException {@inheritDoc} |
1336 |
* @throws RejectedExecutionException {@inheritDoc} |
1337 |
*/ |
1338 |
public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) { |
1339 |
ArrayList<ForkJoinTask<T>> forkJoinTasks = |
1340 |
new ArrayList<ForkJoinTask<T>>(tasks.size()); |
1341 |
for (Callable<T> task : tasks) |
1342 |
forkJoinTasks.add(ForkJoinTask.adapt(task)); |
1343 |
invoke(new InvokeAll<T>(forkJoinTasks)); |
1344 |
|
1345 |
@SuppressWarnings({"unchecked", "rawtypes"}) |
1346 |
List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks; |
1347 |
return futures; |
1348 |
} |
1349 |
|
1350 |
static final class InvokeAll<T> extends RecursiveAction { |
1351 |
final ArrayList<ForkJoinTask<T>> tasks; |
1352 |
InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; } |
1353 |
public void compute() { |
1354 |
try { invokeAll(tasks); } |
1355 |
catch (Exception ignore) {} |
1356 |
} |
1357 |
private static final long serialVersionUID = -7914297376763021607L; |
1358 |
} |
1359 |
|
1360 |
/** |
1361 |
* Returns the factory used for constructing new workers. |
1362 |
* |
1363 |
* @return the factory used for constructing new workers |
1364 |
*/ |
1365 |
public ForkJoinWorkerThreadFactory getFactory() { |
1366 |
return factory; |
1367 |
} |
1368 |
|
1369 |
/** |
1370 |
* Returns the handler for internal worker threads that terminate |
1371 |
* due to unrecoverable errors encountered while executing tasks. |
1372 |
* |
1373 |
* @return the handler, or {@code null} if none |
1374 |
*/ |
1375 |
public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() { |
1376 |
return ueh; |
1377 |
} |
1378 |
|
1379 |
/** |
1380 |
* Returns the targeted parallelism level of this pool. |
1381 |
* |
1382 |
* @return the targeted parallelism level of this pool |
1383 |
*/ |
1384 |
public int getParallelism() { |
1385 |
return parallelism; |
1386 |
} |
1387 |
|
1388 |
/** |
1389 |
* Returns the number of worker threads that have started but not |
1390 |
* yet terminated. This result returned by this method may differ |
1391 |
* from {@link #getParallelism} when threads are created to |
1392 |
* maintain parallelism when others are cooperatively blocked. |
1393 |
* |
1394 |
* @return the number of worker threads |
1395 |
*/ |
1396 |
public int getPoolSize() { |
1397 |
return workerCounts >>> TOTAL_COUNT_SHIFT; |
1398 |
} |
1399 |
|
1400 |
/** |
1401 |
* Returns {@code true} if this pool uses local first-in-first-out |
1402 |
* scheduling mode for forked tasks that are never joined. |
1403 |
* |
1404 |
* @return {@code true} if this pool uses async mode |
1405 |
*/ |
1406 |
public boolean getAsyncMode() { |
1407 |
return locallyFifo; |
1408 |
} |
1409 |
|
1410 |
/** |
1411 |
* Returns an estimate of the number of worker threads that are |
1412 |
* not blocked waiting to join tasks or for other managed |
1413 |
* synchronization. This method may overestimate the |
1414 |
* number of running threads. |
1415 |
* |
1416 |
* @return the number of worker threads |
1417 |
*/ |
1418 |
public int getRunningThreadCount() { |
1419 |
return workerCounts & RUNNING_COUNT_MASK; |
1420 |
} |
1421 |
|
1422 |
/** |
1423 |
* Returns an estimate of the number of threads that are currently |
1424 |
* stealing or executing tasks. This method may overestimate the |
1425 |
* number of active threads. |
1426 |
* |
1427 |
* @return the number of active threads |
1428 |
*/ |
1429 |
public int getActiveThreadCount() { |
1430 |
return runState & ACTIVE_COUNT_MASK; |
1431 |
} |
1432 |
|
1433 |
/** |
1434 |
* Returns {@code true} if all worker threads are currently idle. |
1435 |
* An idle worker is one that cannot obtain a task to execute |
1436 |
* because none are available to steal from other threads, and |
1437 |
* there are no pending submissions to the pool. This method is |
1438 |
* conservative; it might not return {@code true} immediately upon |
1439 |
* idleness of all threads, but will eventually become true if |
1440 |
* threads remain inactive. |
1441 |
* |
1442 |
* @return {@code true} if all threads are currently idle |
1443 |
*/ |
1444 |
public boolean isQuiescent() { |
1445 |
return (runState & ACTIVE_COUNT_MASK) == 0; |
1446 |
} |
1447 |
|
1448 |
/** |
1449 |
* Returns an estimate of the total number of tasks stolen from |
1450 |
* one thread's work queue by another. The reported value |
1451 |
* underestimates the actual total number of steals when the pool |
1452 |
* is not quiescent. This value may be useful for monitoring and |
1453 |
* tuning fork/join programs: in general, steal counts should be |
1454 |
* high enough to keep threads busy, but low enough to avoid |
1455 |
* overhead and contention across threads. |
1456 |
* |
1457 |
* @return the number of steals |
1458 |
*/ |
1459 |
public long getStealCount() { |
1460 |
return stealCount; |
1461 |
} |
1462 |
|
1463 |
/** |
1464 |
* Returns an estimate of the total number of tasks currently held |
1465 |
* in queues by worker threads (but not including tasks submitted |
1466 |
* to the pool that have not begun executing). This value is only |
1467 |
* an approximation, obtained by iterating across all threads in |
1468 |
* the pool. This method may be useful for tuning task |
1469 |
* granularities. |
1470 |
* |
1471 |
* @return the number of queued tasks |
1472 |
*/ |
1473 |
public long getQueuedTaskCount() { |
1474 |
long count = 0; |
1475 |
ForkJoinWorkerThread[] ws = workers; |
1476 |
int nws = ws.length; |
1477 |
for (int i = 0; i < nws; ++i) { |
1478 |
ForkJoinWorkerThread w = ws[i]; |
1479 |
if (w != null) |
1480 |
count += w.getQueueSize(); |
1481 |
} |
1482 |
return count; |
1483 |
} |
1484 |
|
1485 |
/** |
1486 |
* Returns an estimate of the number of tasks submitted to this |
1487 |
* pool that have not yet begun executing. This method takes time |
1488 |
* proportional to the number of submissions. |
1489 |
* |
1490 |
* @return the number of queued submissions |
1491 |
*/ |
1492 |
public int getQueuedSubmissionCount() { |
1493 |
return submissionQueue.size(); |
1494 |
} |
1495 |
|
1496 |
/** |
1497 |
* Returns {@code true} if there are any tasks submitted to this |
1498 |
* pool that have not yet begun executing. |
1499 |
* |
1500 |
* @return {@code true} if there are any queued submissions |
1501 |
*/ |
1502 |
public boolean hasQueuedSubmissions() { |
1503 |
return !submissionQueue.isEmpty(); |
1504 |
} |
1505 |
|
1506 |
/** |
1507 |
* Removes and returns the next unexecuted submission if one is |
1508 |
* available. This method may be useful in extensions to this |
1509 |
* class that re-assign work in systems with multiple pools. |
1510 |
* |
1511 |
* @return the next submission, or {@code null} if none |
1512 |
*/ |
1513 |
protected ForkJoinTask<?> pollSubmission() { |
1514 |
return submissionQueue.poll(); |
1515 |
} |
1516 |
|
1517 |
/** |
1518 |
* Removes all available unexecuted submitted and forked tasks |
1519 |
* from scheduling queues and adds them to the given collection, |
1520 |
* without altering their execution status. These may include |
1521 |
* artificially generated or wrapped tasks. This method is |
1522 |
* designed to be invoked only when the pool is known to be |
1523 |
* quiescent. Invocations at other times may not remove all |
1524 |
* tasks. A failure encountered while attempting to add elements |
1525 |
* to collection {@code c} may result in elements being in |
1526 |
* neither, either or both collections when the associated |
1527 |
* exception is thrown. The behavior of this operation is |
1528 |
* undefined if the specified collection is modified while the |
1529 |
* operation is in progress. |
1530 |
* |
1531 |
* @param c the collection to transfer elements into |
1532 |
* @return the number of elements transferred |
1533 |
*/ |
1534 |
protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) { |
1535 |
int n = submissionQueue.drainTo(c); |
1536 |
ForkJoinWorkerThread[] ws = workers; |
1537 |
int nws = ws.length; |
1538 |
for (int i = 0; i < nws; ++i) { |
1539 |
ForkJoinWorkerThread w = ws[i]; |
1540 |
if (w != null) |
1541 |
n += w.drainTasksTo(c); |
1542 |
} |
1543 |
return n; |
1544 |
} |
1545 |
|
1546 |
/** |
1547 |
* Returns count of total parks by existing workers. |
1548 |
* Used during development only since not meaningful to users. |
1549 |
*/ |
1550 |
private int collectParkCount() { |
1551 |
int count = 0; |
1552 |
ForkJoinWorkerThread[] ws = workers; |
1553 |
int nws = ws.length; |
1554 |
for (int i = 0; i < nws; ++i) { |
1555 |
ForkJoinWorkerThread w = ws[i]; |
1556 |
if (w != null) |
1557 |
count += w.parkCount; |
1558 |
} |
1559 |
return count; |
1560 |
} |
1561 |
|
1562 |
/** |
1563 |
* Returns a string identifying this pool, as well as its state, |
1564 |
* including indications of run state, parallelism level, and |
1565 |
* worker and task counts. |
1566 |
* |
1567 |
* @return a string identifying this pool, as well as its state |
1568 |
*/ |
1569 |
public String toString() { |
1570 |
long st = getStealCount(); |
1571 |
long qt = getQueuedTaskCount(); |
1572 |
long qs = getQueuedSubmissionCount(); |
1573 |
int wc = workerCounts; |
1574 |
int tc = wc >>> TOTAL_COUNT_SHIFT; |
1575 |
int rc = wc & RUNNING_COUNT_MASK; |
1576 |
int pc = parallelism; |
1577 |
int rs = runState; |
1578 |
int ac = rs & ACTIVE_COUNT_MASK; |
1579 |
// int pk = collectParkCount(); |
1580 |
return super.toString() + |
1581 |
"[" + runLevelToString(rs) + |
1582 |
", parallelism = " + pc + |
1583 |
", size = " + tc + |
1584 |
", active = " + ac + |
1585 |
", running = " + rc + |
1586 |
", steals = " + st + |
1587 |
", tasks = " + qt + |
1588 |
", submissions = " + qs + |
1589 |
// ", parks = " + pk + |
1590 |
"]"; |
1591 |
} |
1592 |
|
1593 |
private static String runLevelToString(int s) { |
1594 |
return ((s & TERMINATED) != 0 ? "Terminated" : |
1595 |
((s & TERMINATING) != 0 ? "Terminating" : |
1596 |
((s & SHUTDOWN) != 0 ? "Shutting down" : |
1597 |
"Running"))); |
1598 |
} |
1599 |
|
1600 |
/** |
1601 |
* Initiates an orderly shutdown in which previously submitted |
1602 |
* tasks are executed, but no new tasks will be accepted. |
1603 |
* Invocation has no additional effect if already shut down. |
1604 |
* Tasks that are in the process of being submitted concurrently |
1605 |
* during the course of this method may or may not be rejected. |
1606 |
* |
1607 |
* @throws SecurityException if a security manager exists and |
1608 |
* the caller is not permitted to modify threads |
1609 |
* because it does not hold {@link |
1610 |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1611 |
*/ |
1612 |
public void shutdown() { |
1613 |
checkPermission(); |
1614 |
advanceRunLevel(SHUTDOWN); |
1615 |
tryTerminate(false); |
1616 |
} |
1617 |
|
1618 |
/** |
1619 |
* Attempts to cancel and/or stop all tasks, and reject all |
1620 |
* subsequently submitted tasks. Tasks that are in the process of |
1621 |
* being submitted or executed concurrently during the course of |
1622 |
* this method may or may not be rejected. This method cancels |
1623 |
* both existing and unexecuted tasks, in order to permit |
1624 |
* termination in the presence of task dependencies. So the method |
1625 |
* always returns an empty list (unlike the case for some other |
1626 |
* Executors). |
1627 |
* |
1628 |
* @return an empty list |
1629 |
* @throws SecurityException if a security manager exists and |
1630 |
* the caller is not permitted to modify threads |
1631 |
* because it does not hold {@link |
1632 |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1633 |
*/ |
1634 |
public List<Runnable> shutdownNow() { |
1635 |
checkPermission(); |
1636 |
tryTerminate(true); |
1637 |
return Collections.emptyList(); |
1638 |
} |
1639 |
|
1640 |
/** |
1641 |
* Returns {@code true} if all tasks have completed following shut down. |
1642 |
* |
1643 |
* @return {@code true} if all tasks have completed following shut down |
1644 |
*/ |
1645 |
public boolean isTerminated() { |
1646 |
return runState >= TERMINATED; |
1647 |
} |
1648 |
|
1649 |
/** |
1650 |
* Returns {@code true} if the process of termination has |
1651 |
* commenced but not yet completed. This method may be useful for |
1652 |
* debugging. A return of {@code true} reported a sufficient |
1653 |
* period after shutdown may indicate that submitted tasks have |
1654 |
* ignored or suppressed interruption, causing this executor not |
1655 |
* to properly terminate. |
1656 |
* |
1657 |
* @return {@code true} if terminating but not yet terminated |
1658 |
*/ |
1659 |
public boolean isTerminating() { |
1660 |
return (runState & (TERMINATING|TERMINATED)) == TERMINATING; |
1661 |
} |
1662 |
|
1663 |
/** |
1664 |
* Returns {@code true} if this pool has been shut down. |
1665 |
* |
1666 |
* @return {@code true} if this pool has been shut down |
1667 |
*/ |
1668 |
public boolean isShutdown() { |
1669 |
return runState >= SHUTDOWN; |
1670 |
} |
1671 |
|
1672 |
/** |
1673 |
* Blocks until all tasks have completed execution after a shutdown |
1674 |
* request, or the timeout occurs, or the current thread is |
1675 |
* interrupted, whichever happens first. |
1676 |
* |
1677 |
* @param timeout the maximum time to wait |
1678 |
* @param unit the time unit of the timeout argument |
1679 |
* @return {@code true} if this executor terminated and |
1680 |
* {@code false} if the timeout elapsed before termination |
1681 |
* @throws InterruptedException if interrupted while waiting |
1682 |
*/ |
1683 |
public boolean awaitTermination(long timeout, TimeUnit unit) |
1684 |
throws InterruptedException { |
1685 |
try { |
1686 |
return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0; |
1687 |
} catch(TimeoutException ex) { |
1688 |
return false; |
1689 |
} |
1690 |
} |
1691 |
|
1692 |
/** |
1693 |
* Interface for extending managed parallelism for tasks running |
1694 |
* in {@link ForkJoinPool}s. |
1695 |
* |
1696 |
* <p>A {@code ManagedBlocker} provides two methods. |
1697 |
* Method {@code isReleasable} must return {@code true} if |
1698 |
* blocking is not necessary. Method {@code block} blocks the |
1699 |
* current thread if necessary (perhaps internally invoking |
1700 |
* {@code isReleasable} before actually blocking). |
1701 |
* |
1702 |
* <p>For example, here is a ManagedBlocker based on a |
1703 |
* ReentrantLock: |
1704 |
* <pre> {@code |
1705 |
* class ManagedLocker implements ManagedBlocker { |
1706 |
* final ReentrantLock lock; |
1707 |
* boolean hasLock = false; |
1708 |
* ManagedLocker(ReentrantLock lock) { this.lock = lock; } |
1709 |
* public boolean block() { |
1710 |
* if (!hasLock) |
1711 |
* lock.lock(); |
1712 |
* return true; |
1713 |
* } |
1714 |
* public boolean isReleasable() { |
1715 |
* return hasLock || (hasLock = lock.tryLock()); |
1716 |
* } |
1717 |
* }}</pre> |
1718 |
*/ |
1719 |
public static interface ManagedBlocker { |
1720 |
/** |
1721 |
* Possibly blocks the current thread, for example waiting for |
1722 |
* a lock or condition. |
1723 |
* |
1724 |
* @return {@code true} if no additional blocking is necessary |
1725 |
* (i.e., if isReleasable would return true) |
1726 |
* @throws InterruptedException if interrupted while waiting |
1727 |
* (the method is not required to do so, but is allowed to) |
1728 |
*/ |
1729 |
boolean block() throws InterruptedException; |
1730 |
|
1731 |
/** |
1732 |
* Returns {@code true} if blocking is unnecessary. |
1733 |
*/ |
1734 |
boolean isReleasable(); |
1735 |
} |
1736 |
|
1737 |
/** |
1738 |
* Blocks in accord with the given blocker. If the current thread |
1739 |
* is a {@link ForkJoinWorkerThread}, this method possibly |
1740 |
* arranges for a spare thread to be activated if necessary to |
1741 |
* ensure sufficient parallelism while the current thread is blocked. |
1742 |
* |
1743 |
* <p>If the caller is not a {@link ForkJoinTask}, this method is |
1744 |
* behaviorally equivalent to |
1745 |
* <pre> {@code |
1746 |
* while (!blocker.isReleasable()) |
1747 |
* if (blocker.block()) |
1748 |
* return; |
1749 |
* }</pre> |
1750 |
* |
1751 |
* If the caller is a {@code ForkJoinTask}, then the pool may |
1752 |
* first be expanded to ensure parallelism, and later adjusted. |
1753 |
* |
1754 |
* @param blocker the blocker |
1755 |
* @throws InterruptedException if blocker.block did so |
1756 |
*/ |
1757 |
public static void managedBlock(ManagedBlocker blocker) |
1758 |
throws InterruptedException { |
1759 |
Thread t = Thread.currentThread(); |
1760 |
if (t instanceof ForkJoinWorkerThread) |
1761 |
((ForkJoinWorkerThread) t).pool.awaitBlocker(blocker); |
1762 |
else { |
1763 |
do {} while (!blocker.isReleasable() && !blocker.block()); |
1764 |
} |
1765 |
} |
1766 |
|
1767 |
// AbstractExecutorService overrides. These rely on undocumented |
1768 |
// fact that ForkJoinTask.adapt returns ForkJoinTasks that also |
1769 |
// implement RunnableFuture. |
1770 |
|
1771 |
protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) { |
1772 |
return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value); |
1773 |
} |
1774 |
|
1775 |
protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) { |
1776 |
return (RunnableFuture<T>) ForkJoinTask.adapt(callable); |
1777 |
} |
1778 |
|
1779 |
// Unsafe mechanics |
1780 |
|
1781 |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1782 |
private static final long workerCountsOffset = |
1783 |
objectFieldOffset("workerCounts", ForkJoinPool.class); |
1784 |
private static final long runStateOffset = |
1785 |
objectFieldOffset("runState", ForkJoinPool.class); |
1786 |
private static final long eventCountOffset = |
1787 |
objectFieldOffset("eventCount", ForkJoinPool.class); |
1788 |
private static final long eventWaitersOffset = |
1789 |
objectFieldOffset("eventWaiters",ForkJoinPool.class); |
1790 |
private static final long stealCountOffset = |
1791 |
objectFieldOffset("stealCount",ForkJoinPool.class); |
1792 |
|
1793 |
private static long objectFieldOffset(String field, Class<?> klazz) { |
1794 |
try { |
1795 |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1796 |
} catch (NoSuchFieldException e) { |
1797 |
// Convert Exception to corresponding Error |
1798 |
NoSuchFieldError error = new NoSuchFieldError(field); |
1799 |
error.initCause(e); |
1800 |
throw error; |
1801 |
} |
1802 |
} |
1803 |
|
1804 |
/** |
1805 |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
1806 |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
1807 |
* into a jdk. |
1808 |
* |
1809 |
* @return a sun.misc.Unsafe |
1810 |
*/ |
1811 |
private static sun.misc.Unsafe getUnsafe() { |
1812 |
try { |
1813 |
return sun.misc.Unsafe.getUnsafe(); |
1814 |
} catch (SecurityException se) { |
1815 |
try { |
1816 |
return java.security.AccessController.doPrivileged |
1817 |
(new java.security |
1818 |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1819 |
public sun.misc.Unsafe run() throws Exception { |
1820 |
java.lang.reflect.Field f = sun.misc |
1821 |
.Unsafe.class.getDeclaredField("theUnsafe"); |
1822 |
f.setAccessible(true); |
1823 |
return (sun.misc.Unsafe) f.get(null); |
1824 |
}}); |
1825 |
} catch (java.security.PrivilegedActionException e) { |
1826 |
throw new RuntimeException("Could not initialize intrinsics", |
1827 |
e.getCause()); |
1828 |
} |
1829 |
} |
1830 |
} |
1831 |
} |