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package jsr166e; |
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import java.lang.Thread.UncaughtExceptionHandler; |
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import java.util.ArrayList; |
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import java.util.Arrays; |
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import java.util.Collection; |
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import java.util.Collections; |
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import java.util.List; |
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import java.util.Random; |
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import java.util.concurrent.AbstractExecutorService; |
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import java.util.concurrent.Callable; |
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import java.util.concurrent.ExecutorService; |
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import java.util.concurrent.Future; |
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import java.util.concurrent.RejectedExecutionException; |
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import java.util.concurrent.RunnableFuture; |
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import java.util.concurrent.ThreadLocalRandom; |
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import java.util.concurrent.TimeUnit; |
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import java.util.concurrent.atomic.AtomicInteger; |
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import java.util.concurrent.atomic.AtomicLong; |
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import java.util.concurrent.locks.AbstractQueuedSynchronizer; |
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import java.util.concurrent.locks.Condition; |
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/** |
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* An {@link ExecutorService} for running {@link ForkJoinTask}s. |
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* ForkJoinPool}s may also be appropriate for use with event-style |
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* tasks that are never joined. |
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* |
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* <p>A static {@link #commonPool} is available and appropriate for |
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* most applications. The common pool is constructed upon first |
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* access, or upon usage by any ForkJoinTask that is not explictly |
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* submitted to a specified pool. Using the common pool normally |
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* reduces resource usage (its threads are slowly reclaimed during |
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* periods of non-use, and reinstated upon subsequent use). The |
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* common pool is by default constructed with default parameters, but |
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* these may be controlled by setting any or all of the three |
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* properties {@code |
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* java.util.concurrent.ForkJoinPool.common.{parallelism, |
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* threadFactory, exceptionHandler}}. |
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* <p>A static {@link #commonPool()} is available and appropriate for |
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* most applications. The common pool is used by any ForkJoinTask that |
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* is not explicitly submitted to a specified pool. Using the common |
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* pool normally reduces resource usage (its threads are slowly |
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* reclaimed during periods of non-use, and reinstated upon subsequent |
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* use). |
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* |
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* <p>For applications that require separate or custom pools, a {@code |
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* ForkJoinPool} may be constructed with a given target parallelism |
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* level; by default, equal to the number of available processors. The |
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* pool attempts to maintain enough active (or available) threads by |
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* dynamically adding, suspending, or resuming internal worker |
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* threads, even if some tasks are stalled waiting to join |
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* others. However, no such adjustments are guaranteed in the face of |
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* blocked IO or other unmanaged synchronization. The nested {@link |
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* threads, even if some tasks are stalled waiting to join others. |
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* However, no such adjustments are guaranteed in the face of blocked |
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* I/O or other unmanaged synchronization. The nested {@link |
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* ManagedBlocker} interface enables extension of the kinds of |
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* synchronization accommodated. |
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* |
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* {@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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* <p>As is the case with other ExecutorServices, there are three |
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* main task execution methods summarized in the following table. |
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* These are designed to be used primarily by clients not already |
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* engaged in fork/join computations in the current pool. The main |
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* there is little difference among choice of methods. |
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* |
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* <table BORDER CELLPADDING=3 CELLSPACING=1> |
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* <caption>Summary of task execution methods</caption> |
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* <tr> |
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* <td></td> |
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* <td ALIGN=CENTER> <b>Call from non-fork/join clients</b></td> |
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* <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td> |
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* </tr> |
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* <tr> |
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* <td> <b>Arrange async execution</td> |
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* <td> <b>Arrange async execution</b></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> <b>Await and obtain result</b></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> <b>Arrange exec and obtain Future</b></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>The common pool is by default constructed with default |
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* parameters, but these may be controlled by setting three |
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* {@linkplain System#getProperty system properties}: |
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* <ul> |
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* <li>{@code java.util.concurrent.ForkJoinPool.common.parallelism} |
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* - the parallelism level, a non-negative integer |
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* <li>{@code java.util.concurrent.ForkJoinPool.common.threadFactory} |
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* - the class name of a {@link ForkJoinWorkerThreadFactory} |
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* <li>{@code java.util.concurrent.ForkJoinPool.common.exceptionHandler} |
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* - the class name of a {@link UncaughtExceptionHandler} |
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* </ul> |
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* The system class loader is used to load these classes. |
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* Upon any error in establishing these settings, default parameters |
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* are used. It is possible to disable or limit the use of threads in |
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* the common pool by setting the parallelism property to zero, and/or |
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* using a factory that may return {@code null}. |
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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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* (http://research.sun.com/scalable/pubs/index.html) and |
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* "Idempotent work stealing" by Michael, Saraswat, and Vechev, |
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* PPoPP 2009 (http://portal.acm.org/citation.cfm?id=1504186). |
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* The main differences ultimately stem from GC requirements that |
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* we null out taken slots as soon as we can, to maintain as small |
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* a footprint as possible even in programs generating huge |
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* numbers of tasks. To accomplish this, we shift the CAS |
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* arbitrating pop vs poll (steal) from being on the indices |
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* ("base" and "top") to the slots themselves. So, both a |
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* successful pop and poll mainly entail a CAS of a slot from |
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* non-null to null. Because we rely on CASes of references, we |
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* do not need tag bits on base or top. They are simple ints as |
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* used in any circular array-based queue (see for example |
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* ArrayDeque). Updates to the indices must still be ordered in a |
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* way that guarantees that top == base means the queue is empty, |
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* but otherwise may err on the side of possibly making the queue |
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* appear nonempty when a push, pop, or poll have not fully |
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* committed. Note that this means that the poll operation, |
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* considered individually, is not wait-free. One thief cannot |
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* successfully continue until another in-progress one (or, if |
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* previously empty, a push) completes. However, in the |
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* aggregate, we ensure at least probabilistic non-blockingness. |
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* If an attempted steal fails, a thief always chooses a different |
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* random victim target to try next. So, in order for one thief to |
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* progress, it suffices for any in-progress poll or new push on |
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* any empty queue to complete. (This is why we normally use |
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* method pollAt and its variants that try once at the apparent |
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* base index, else consider alternative actions, rather than |
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* method poll.) |
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* See also "Correct and Efficient Work-Stealing for Weak Memory |
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* Models" by Le, Pop, Cohen, and Nardelli, PPoPP 2013 |
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* (http://www.di.ens.fr/~zappa/readings/ppopp13.pdf) for an |
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* analysis of memory ordering (atomic, volatile etc) issues. The |
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* main differences ultimately stem from GC requirements that we |
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* null out taken slots as soon as we can, to maintain as small a |
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* footprint as possible even in programs generating huge numbers |
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* of tasks. To accomplish this, we shift the CAS arbitrating pop |
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* vs poll (steal) from being on the indices ("base" and "top") to |
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* the slots themselves. So, both a successful pop and poll |
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* mainly entail a CAS of a slot from non-null to null. Because |
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* we rely on CASes of references, we do not need tag bits on base |
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* or top. They are simple ints as used in any circular |
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* array-based queue (see for example ArrayDeque). Updates to the |
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* indices must still be ordered in a way that guarantees that top |
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* == base means the queue is empty, but otherwise may err on the |
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* side of possibly making the queue appear nonempty when a push, |
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* pop, or poll have not fully committed. Note that this means |
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* that the poll operation, considered individually, is not |
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* wait-free. One thief cannot successfully continue until another |
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* in-progress one (or, if previously empty, a push) completes. |
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* However, in the aggregate, we ensure at least probabilistic |
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* non-blockingness. If an attempted steal fails, a thief always |
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* chooses a different random victim target to try next. So, in |
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* order for one thief to progress, it suffices for any |
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* in-progress poll or new push on any empty queue to |
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* complete. (This is why we normally use method pollAt and its |
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* variants that try once at the apparent base index, else |
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* consider alternative actions, rather than method poll.) |
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* |
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* This approach also enables support of a user mode in which local |
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* task processing is in FIFO, not LIFO order, simply by using |
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* WorkQueues are also used in a similar way for tasks submitted |
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* to the pool. We cannot mix these tasks in the same queues used |
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* for work-stealing (this would contaminate lifo/fifo |
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* processing). Instead, we loosely associate submission queues |
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* processing). Instead, we randomly associate submission queues |
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* with submitting threads, using a form of hashing. The |
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* ThreadLocal Submitter class contains a value initially used as |
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* a hash code for choosing existing queues, but may be randomly |
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* repositioned upon contention with other submitters. In |
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* essence, submitters act like workers except that they never |
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* take tasks, and they are multiplexed on to a finite number of |
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* shared work queues. However, classes are set up so that future |
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* extensions could allow submitters to optionally help perform |
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* tasks as well. Insertion of tasks in shared mode requires a |
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* lock (mainly to protect in the case of resizing) but we use |
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* only a simple spinlock (using bits in field runState), because |
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* submitters encountering a busy queue move on to try or create |
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* other queues -- they block only when creating and registering |
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* new queues. |
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* Submitter probe value serves as a hash code for |
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* choosing existing queues, and may be randomly repositioned upon |
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* contention with other submitters. In essence, submitters act |
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* like workers except that they are restricted to executing local |
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* tasks that they submitted (or in the case of CountedCompleters, |
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* others with the same root task). However, because most |
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* shared/external queue operations are more expensive than |
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* internal, and because, at steady state, external submitters |
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* will compete for CPU with workers, ForkJoinTask.join and |
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* related methods disable them from repeatedly helping to process |
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* tasks if all workers are active. Insertion of tasks in shared |
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* mode requires a lock (mainly to protect in the case of |
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* resizing) but we use only a simple spinlock (using bits in |
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* field qlock), because submitters encountering a busy queue move |
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* on to try or create other queues -- they block only when |
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* creating and registering new queues. |
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* |
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* Management |
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* ========== |
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* and their negations (used for thresholding) to fit into 16bit |
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* fields. |
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* |
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* Field "runState" contains 32 bits needed to register and |
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* deregister WorkQueues, as well as to enable shutdown. It is |
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* only modified under a lock (normally briefly held, but |
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* occasionally protecting allocations and resizings) but even |
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* when locked remains available to check consistency. |
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* Field "plock" is a form of sequence lock with a saturating |
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* shutdown bit (similarly for per-queue "qlocks"), mainly |
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* protecting updates to the workQueues array, as well as to |
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* enable shutdown. When used as a lock, it is normally only very |
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* briefly held, so is nearly always available after at most a |
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* brief spin, but we use a monitor-based backup strategy to |
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* block when needed. |
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* |
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* Recording WorkQueues. WorkQueues are recorded in the |
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* "workQueues" array that is created upon pool construction and |
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* expanded if necessary. Updates to the array while recording |
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* new workers and unrecording terminated ones are protected from |
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* each other by a lock but the array is otherwise concurrently |
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* readable, and accessed directly. 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. Shared (submission) queues |
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* are at even indices, worker queues at odd indices. Grouping |
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* them together in this way simplifies and speeds up task |
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* scanning. |
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* "workQueues" array that is created upon first use and expanded |
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* if necessary. Updates to the array while recording new workers |
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* and unrecording terminated ones are protected from each other |
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* by a lock but the array is otherwise concurrently readable, and |
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* accessed directly. To simplify index-based operations, the |
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* array size is always a power of two, and all readers must |
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* tolerate null slots. Worker queues are at odd indices. Shared |
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* (submission) queues are at even indices, up to a maximum of 64 |
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* slots, to limit growth even if array needs to expand to add |
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* more workers. Grouping them together in this way simplifies and |
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* speeds up task scanning. |
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* |
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* All worker thread creation is on-demand, triggered by task |
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* submissions, replacement of terminated workers, and/or |
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* has not yet entered the wait queue. We solve this by requiring |
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* a full sweep of all workers (via repeated calls to method |
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* scan()) both before and after a newly waiting worker is added |
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* to the wait queue. During a rescan, the worker might release |
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* some other queued worker rather than itself, which has the same |
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* net effect. Because enqueued workers may actually be rescanning |
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* rather than waiting, we set and clear the "parker" field of |
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* WorkQueues to reduce unnecessary calls to unpark. (This |
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* requires a secondary recheck to avoid missed signals.) Note |
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* the unusual conventions about Thread.interrupts surrounding |
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* parking and other blocking: Because interrupts are used solely |
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* to alert threads to check termination, which is checked anyway |
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* upon blocking, we clear status (using Thread.interrupted) |
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* before any call to park, so that park does not immediately |
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* return due to status being set via some other unrelated call to |
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* interrupt in user code. |
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* to the wait queue. Because enqueued workers may actually be |
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* rescanning rather than waiting, we set and clear the "parker" |
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* field of WorkQueues to reduce unnecessary calls to unpark. |
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* (This requires a secondary recheck to avoid missed signals.) |
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* Note the unusual conventions about Thread.interrupts |
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* surrounding parking and other blocking: Because interrupts are |
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* used solely to alert threads to check termination, which is |
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* checked anyway upon blocking, we clear status (using |
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* Thread.interrupted) before any call to park, so that park does |
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* not immediately return due to status being set via some other |
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* unrelated call to interrupt in user code. |
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* |
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* Signalling. We create or wake up workers only when there |
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* appears to be at least one task they might be able to find and |
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* execute. When a submission is added or another worker adds a |
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* task to a queue that previously had fewer than two tasks, they |
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* signal waiting workers (or trigger creation of new ones if |
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* fewer than the given parallelism level -- see signalWork). |
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* These primary signals are buttressed by signals during rescans; |
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* together these cover the signals needed in cases when more |
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* tasks are pushed but untaken, and improve performance compared |
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* to having one thread wake up all workers. |
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* task to a queue that has fewer than two tasks, they signal |
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* waiting workers (or trigger creation of new ones if fewer than |
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* the given parallelism level -- signalWork). These primary |
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* signals are buttressed by others whenever other threads remove |
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* a task from a queue and notice that there are other tasks there |
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* as well. So in general, pools will be over-signalled. On most |
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* platforms, signalling (unpark) overhead time is noticeably |
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* long, and the time between signalling a thread and it actually |
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* making progress can be very noticeably long, so it is worth |
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* offloading these delays from critical paths as much as |
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* possible. Additionally, workers spin-down gradually, by staying |
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* alive so long as they see the ctl state changing. Similar |
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* stability-sensing techniques are also used before blocking in |
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* awaitJoin and helpComplete. |
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* |
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* Trimming workers. To release resources after periods of lack of |
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* use, a worker starting to wait when the pool is quiescent will |
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* periods of non-use. |
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* |
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* Shutdown and Termination. A call to shutdownNow atomically sets |
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* a runState bit and then (non-atomically) sets each worker's |
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* runState status, cancels all unprocessed tasks, and wakes up |
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* a plock bit and then (non-atomically) sets each worker's |
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* qlock status, cancels all unprocessed tasks, and wakes up |
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* all waiting workers. Detecting whether termination should |
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* commence after a non-abrupt shutdown() call requires more work |
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* and bookkeeping. We need consensus about quiescence (i.e., that |
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* method tryCompensate() may create or re-activate a spare |
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* thread to compensate for blocked joiners until they unblock. |
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* |
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* A third form (implemented in tryRemoveAndExec and |
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* tryPollForAndExec) amounts to helping a hypothetical |
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* compensator: If we can readily tell that a possible action of a |
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* compensator is to steal and execute the task being joined, the |
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* joining thread can do so directly, without the need for a |
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* compensation thread (although at the expense of larger run-time |
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* stacks, but the tradeoff is typically worthwhile). |
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* A third form (implemented in tryRemoveAndExec) amounts to |
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* helping a hypothetical compensator: If we can readily tell that |
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* a possible action of a compensator is to steal and execute the |
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* task being joined, the joining thread can do so directly, |
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* without the need for a compensation thread (although at the |
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* expense of larger run-time stacks, but the tradeoff is |
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* typically worthwhile). |
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* |
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* The ManagedBlocker extension API can't use helping so relies |
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* only on compensation in method awaitBlocker. |
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* steals, rather than use per-task bookkeeping. This sometimes |
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* requires a linear scan of workQueues array to locate stealers, |
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* but often doesn't because stealers leave hints (that may become |
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* stale/wrong) of where to locate them. A stealHint is only a |
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* hint because a worker might have had multiple steals and the |
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* hint records only one of them (usually the most current). |
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* Hinting isolates cost to when it is needed, rather than adding |
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* to per-task overhead. (2) It is "shallow", ignoring nesting |
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* and potentially cyclic mutual steals. (3) It is intentionally |
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* stale/wrong) of where to locate them. It is only a hint |
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* because a worker might have had multiple steals and the hint |
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* records only one of them (usually the most current). Hinting |
410 |
> |
* isolates cost to when it is needed, rather than adding to |
411 |
> |
* per-task overhead. (2) It is "shallow", ignoring nesting and |
412 |
> |
* potentially cyclic mutual steals. (3) It is intentionally |
413 |
|
* racy: field currentJoin is updated only while actively joining, |
414 |
|
* which means that we miss links in the chain during long-lived |
415 |
|
* tasks, GC stalls etc (which is OK since blocking in such cases |
417 |
|
* to find work (see MAX_HELP) and fall back to suspending the |
418 |
|
* worker and if necessary replacing it with another. |
419 |
|
* |
420 |
+ |
* Helping actions for CountedCompleters are much simpler: Method |
421 |
+ |
* helpComplete can take and execute any task with the same root |
422 |
+ |
* as the task being waited on. However, this still entails some |
423 |
+ |
* traversal of completer chains, so is less efficient than using |
424 |
+ |
* CountedCompleters without explicit joins. |
425 |
+ |
* |
426 |
|
* It is impossible to keep exactly the target parallelism number |
427 |
|
* of threads running at any given time. Determining the |
428 |
|
* existence of conservatively safe helping targets, the |
444 |
|
* intractable) game with an opponent that may choose the worst |
445 |
|
* (for us) active thread to stall at any time. We take several |
446 |
|
* precautions to bound losses (and thus bound gains), mainly in |
447 |
< |
* methods tryCompensate and awaitJoin: (1) We only try |
448 |
< |
* compensation after attempting enough helping steps (measured |
449 |
< |
* via counting and timing) that we have already consumed the |
450 |
< |
* estimated cost of creating and activating a new thread. (2) We |
451 |
< |
* allow up to 50% of threads to be blocked before initially |
452 |
< |
* adding any others, and unless completely saturated, check that |
453 |
< |
* some work is available for a new worker before adding. Also, we |
454 |
< |
* create up to only 50% more threads until entering a mode that |
455 |
< |
* only adds a thread if all others are possibly blocked. All |
456 |
< |
* together, this means that we might be half as fast to react, |
457 |
< |
* and create half as many threads as possible in the ideal case, |
458 |
< |
* but present vastly fewer anomalies in all other cases compared |
459 |
< |
* to both more aggressive and more conservative alternatives. |
460 |
< |
* |
461 |
< |
* Style notes: There is a lot of representation-level coupling |
462 |
< |
* among classes ForkJoinPool, ForkJoinWorkerThread, and |
463 |
< |
* ForkJoinTask. The fields of WorkQueue maintain data structures |
464 |
< |
* managed by ForkJoinPool, so are directly accessed. There is |
465 |
< |
* little point trying to reduce this, since any associated future |
466 |
< |
* changes in representations will need to be accompanied by |
467 |
< |
* algorithmic changes anyway. Several methods intrinsically |
468 |
< |
* sprawl because they must accumulate sets of consistent reads of |
469 |
< |
* volatiles held in local variables. Methods signalWork() and |
470 |
< |
* scan() are the main bottlenecks, so are especially heavily |
447 |
> |
* methods tryCompensate and awaitJoin. |
448 |
> |
* |
449 |
> |
* Common Pool |
450 |
> |
* =========== |
451 |
> |
* |
452 |
> |
* The static common pool always exists after static |
453 |
> |
* initialization. Since it (or any other created pool) need |
454 |
> |
* never be used, we minimize initial construction overhead and |
455 |
> |
* footprint to the setup of about a dozen fields, with no nested |
456 |
> |
* allocation. Most bootstrapping occurs within method |
457 |
> |
* fullExternalPush during the first submission to the pool. |
458 |
> |
* |
459 |
> |
* When external threads submit to the common pool, they can |
460 |
> |
* perform subtask processing (see externalHelpJoin and related |
461 |
> |
* methods). This caller-helps policy makes it sensible to set |
462 |
> |
* common pool parallelism level to one (or more) less than the |
463 |
> |
* total number of available cores, or even zero for pure |
464 |
> |
* caller-runs. We do not need to record whether external |
465 |
> |
* submissions are to the common pool -- if not, externalHelpJoin |
466 |
> |
* returns quickly (at the most helping to signal some common pool |
467 |
> |
* workers). These submitters would otherwise be blocked waiting |
468 |
> |
* for completion, so the extra effort (with liberally sprinkled |
469 |
> |
* task status checks) in inapplicable cases amounts to an odd |
470 |
> |
* form of limited spin-wait before blocking in ForkJoinTask.join. |
471 |
> |
* |
472 |
> |
* Style notes |
473 |
> |
* =========== |
474 |
> |
* |
475 |
> |
* There is a lot of representation-level coupling among classes |
476 |
> |
* ForkJoinPool, ForkJoinWorkerThread, and ForkJoinTask. The |
477 |
> |
* fields of WorkQueue maintain data structures managed by |
478 |
> |
* ForkJoinPool, so are directly accessed. There is little point |
479 |
> |
* trying to reduce this, since any associated future changes in |
480 |
> |
* representations will need to be accompanied by algorithmic |
481 |
> |
* changes anyway. Several methods intrinsically sprawl because |
482 |
> |
* they must accumulate sets of consistent reads of volatiles held |
483 |
> |
* in local variables. Methods signalWork() and scan() are the |
484 |
> |
* main bottlenecks, so are especially heavily |
485 |
|
* micro-optimized/mangled. There are lots of inline assignments |
486 |
|
* (of form "while ((local = field) != 0)") which are usually the |
487 |
|
* simplest way to ensure the required read orderings (which are |
489 |
|
* declarations of these locals at the heads of methods or blocks. |
490 |
|
* There are several occurrences of the unusual "do {} while |
491 |
|
* (!cas...)" which is the simplest way to force an update of a |
492 |
< |
* CAS'ed variable. There are also other coding oddities that help |
492 |
> |
* CAS'ed variable. There are also other coding oddities (including |
493 |
> |
* several unnecessary-looking hoisted null checks) that help |
494 |
|
* some methods perform reasonably even when interpreted (not |
495 |
|
* compiled). |
496 |
|
* |
530 |
|
* Returns a new worker thread operating in the given pool. |
531 |
|
* |
532 |
|
* @param pool the pool this thread works in |
533 |
+ |
* @return the new worker thread |
534 |
|
* @throws NullPointerException if the pool is null |
535 |
|
*/ |
536 |
|
public ForkJoinWorkerThread newThread(ForkJoinPool pool); |
540 |
|
* Default ForkJoinWorkerThreadFactory implementation; creates a |
541 |
|
* new ForkJoinWorkerThread. |
542 |
|
*/ |
543 |
< |
static class DefaultForkJoinWorkerThreadFactory |
543 |
> |
static final class DefaultForkJoinWorkerThreadFactory |
544 |
|
implements ForkJoinWorkerThreadFactory { |
545 |
< |
public ForkJoinWorkerThread newThread(ForkJoinPool pool) { |
545 |
> |
public final ForkJoinWorkerThread newThread(ForkJoinPool pool) { |
546 |
|
return new ForkJoinWorkerThread(pool); |
547 |
|
} |
548 |
|
} |
549 |
|
|
550 |
|
/** |
507 |
– |
* A simple non-reentrant lock used for exclusion when managing |
508 |
– |
* queues and workers. We use a custom lock so that we can readily |
509 |
– |
* probe lock state in constructions that check among alternative |
510 |
– |
* actions. The lock is normally only very briefly held, and |
511 |
– |
* sometimes treated as a spinlock, but other usages block to |
512 |
– |
* reduce overall contention in those cases where locked code |
513 |
– |
* bodies perform allocation/resizing. |
514 |
– |
*/ |
515 |
– |
static final class Mutex extends AbstractQueuedSynchronizer { |
516 |
– |
public final boolean tryAcquire(int ignore) { |
517 |
– |
return compareAndSetState(0, 1); |
518 |
– |
} |
519 |
– |
public final boolean tryRelease(int ignore) { |
520 |
– |
setState(0); |
521 |
– |
return true; |
522 |
– |
} |
523 |
– |
public final void lock() { acquire(0); } |
524 |
– |
public final void unlock() { release(0); } |
525 |
– |
public final boolean isHeldExclusively() { return getState() == 1; } |
526 |
– |
public final Condition newCondition() { return new ConditionObject(); } |
527 |
– |
} |
528 |
– |
|
529 |
– |
/** |
551 |
|
* Class for artificial tasks that are used to replace the target |
552 |
|
* of local joins if they are removed from an interior queue slot |
553 |
|
* in WorkQueue.tryRemoveAndExec. We don't need the proxy to |
554 |
|
* actually do anything beyond having a unique identity. |
555 |
|
*/ |
556 |
|
static final class EmptyTask extends ForkJoinTask<Void> { |
557 |
+ |
private static final long serialVersionUID = -7721805057305804111L; |
558 |
|
EmptyTask() { status = ForkJoinTask.NORMAL; } // force done |
559 |
|
public final Void getRawResult() { return null; } |
560 |
|
public final void setRawResult(Void x) {} |
575 |
|
* |
576 |
|
* Field "top" is the index (mod array.length) of the next queue |
577 |
|
* slot to push to or pop from. It is written only by owner thread |
578 |
< |
* for push, or under lock for trySharedPush, and accessed by |
579 |
< |
* other threads only after reading (volatile) base. Both top and |
580 |
< |
* base are allowed to wrap around on overflow, but (top - base) |
581 |
< |
* (or more commonly -(base - top) to force volatile read of base |
582 |
< |
* before top) still estimates size. |
578 |
> |
* for push, or under lock for external/shared push, and accessed |
579 |
> |
* by other threads only after reading (volatile) base. Both top |
580 |
> |
* and base are allowed to wrap around on overflow, but (top - |
581 |
> |
* base) (or more commonly -(base - top) to force volatile read of |
582 |
> |
* base before top) still estimates size. The lock ("qlock") is |
583 |
> |
* forced to -1 on termination, causing all further lock attempts |
584 |
> |
* to fail. (Note: we don't need CAS for termination state because |
585 |
> |
* upon pool shutdown, all shared-queues will stop being used |
586 |
> |
* anyway.) Nearly all lock bodies are set up so that exceptions |
587 |
> |
* within lock bodies are "impossible" (modulo JVM errors that |
588 |
> |
* would cause failure anyway.) |
589 |
|
* |
590 |
|
* The array slots are read and written using the emulation of |
591 |
|
* volatiles/atomics provided by Unsafe. Insertions must in |
592 |
|
* general use putOrderedObject as a form of releasing store to |
593 |
|
* ensure that all writes to the task object are ordered before |
594 |
< |
* its publication in the queue. (Although we can avoid one case |
595 |
< |
* of this when locked in trySharedPush.) All removals entail a |
596 |
< |
* CAS to null. The array is always a power of two. To ensure |
597 |
< |
* safety of Unsafe array operations, all accesses perform |
570 |
< |
* explicit null checks and implicit bounds checks via |
571 |
< |
* power-of-two masking. |
594 |
> |
* its publication in the queue. All removals entail a CAS to |
595 |
> |
* null. The array is always a power of two. To ensure safety of |
596 |
> |
* Unsafe array operations, all accesses perform explicit null |
597 |
> |
* checks and implicit bounds checks via power-of-two masking. |
598 |
|
* |
599 |
|
* In addition to basic queuing support, this class contains |
600 |
|
* fields described elsewhere to control execution. It turns out |
601 |
< |
* to work better memory-layout-wise to include them in this |
602 |
< |
* class rather than a separate class. |
601 |
> |
* to work better memory-layout-wise to include them in this class |
602 |
> |
* rather than a separate class. |
603 |
|
* |
604 |
|
* Performance on most platforms is very sensitive to placement of |
605 |
|
* instances of both WorkQueues and their arrays -- we absolutely |
606 |
|
* do not want multiple WorkQueue instances or multiple queue |
607 |
|
* arrays sharing cache lines. (It would be best for queue objects |
608 |
|
* and their arrays to share, but there is nothing available to |
609 |
< |
* help arrange that). Unfortunately, because they are recorded |
610 |
< |
* in a common array, WorkQueue instances are often moved to be |
585 |
< |
* adjacent by garbage collectors. To reduce impact, we use field |
586 |
< |
* padding that works OK on common platforms; this effectively |
587 |
< |
* trades off slightly slower average field access for the sake of |
588 |
< |
* avoiding really bad worst-case access. (Until better JVM |
589 |
< |
* support is in place, this padding is dependent on transient |
590 |
< |
* properties of JVM field layout rules.) We also take care in |
591 |
< |
* allocating, sizing and resizing the array. Non-shared queue |
592 |
< |
* arrays are initialized (via method growArray) by workers before |
593 |
< |
* use. Others are allocated on first use. |
609 |
> |
* help arrange that). The @Contended annotation alerts JVMs to |
610 |
> |
* try to keep instances apart. |
611 |
|
*/ |
612 |
|
static final class WorkQueue { |
613 |
|
/** |
630 |
|
*/ |
631 |
|
static final int MAXIMUM_QUEUE_CAPACITY = 1 << 26; // 64M |
632 |
|
|
633 |
< |
volatile long totalSteals; // cumulative number of steals |
634 |
< |
int seed; // for random scanning; initialize nonzero |
633 |
> |
// Heuristic padding to ameliorate unfortunate memory placements |
634 |
> |
volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06; |
635 |
> |
|
636 |
|
volatile int eventCount; // encoded inactivation count; < 0 if inactive |
637 |
|
int nextWait; // encoded record of next event waiter |
638 |
< |
int rescans; // remaining scans until block |
639 |
< |
int nsteals; // top-level task executions since last idle |
640 |
< |
final int mode; // lifo, fifo, or shared |
641 |
< |
int poolIndex; // index of this queue in pool (or 0) |
642 |
< |
int stealHint; // index of most recent known stealer |
625 |
< |
volatile int runState; // 1: locked, -1: terminate; else 0 |
638 |
> |
int nsteals; // number of steals |
639 |
> |
int hint; // steal index hint |
640 |
> |
short poolIndex; // index of this queue in pool |
641 |
> |
final short mode; // 0: lifo, > 0: fifo, < 0: shared |
642 |
> |
volatile int qlock; // 1: locked, -1: terminate; else 0 |
643 |
|
volatile int base; // index of next slot for poll |
644 |
|
int top; // index of next slot for push |
645 |
|
ForkJoinTask<?>[] array; // the elements (initially unallocated) |
648 |
|
volatile Thread parker; // == owner during call to park; else null |
649 |
|
volatile ForkJoinTask<?> currentJoin; // task being joined in awaitJoin |
650 |
|
ForkJoinTask<?> currentSteal; // current non-local task being executed |
634 |
– |
// Heuristic padding to ameliorate unfortunate memory placements |
635 |
– |
Object p00, p01, p02, p03, p04, p05, p06, p07; |
636 |
– |
Object p08, p09, p0a, p0b, p0c, p0d, p0e; |
651 |
|
|
652 |
< |
WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode) { |
653 |
< |
this.mode = mode; |
652 |
> |
volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17; |
653 |
> |
volatile Object pad18, pad19, pad1a, pad1b, pad1c, pad1d; |
654 |
> |
|
655 |
> |
WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode, |
656 |
> |
int seed) { |
657 |
|
this.pool = pool; |
658 |
|
this.owner = owner; |
659 |
+ |
this.mode = (short)mode; |
660 |
+ |
this.hint = seed; // store initial seed for runWorker |
661 |
|
// Place indices in the center of array (that is not yet allocated) |
662 |
|
base = top = INITIAL_QUEUE_CAPACITY >>> 1; |
663 |
|
} |
682 |
|
(n == -1 && |
683 |
|
((a = array) == null || |
684 |
|
(m = a.length - 1) < 0 || |
685 |
< |
U.getObjectVolatile |
686 |
< |
(a, ((m & (s - 1)) << ASHIFT) + ABASE) == null))); |
685 |
> |
U.getObject |
686 |
> |
(a, (long)((m & (s - 1)) << ASHIFT) + ABASE) == null))); |
687 |
|
} |
688 |
|
|
689 |
|
/** |
690 |
< |
* Pushes a task. Call only by owner in unshared queues. |
690 |
> |
* Pushes a task. Call only by owner in unshared queues. (The |
691 |
> |
* shared-queue version is embedded in method externalPush.) |
692 |
|
* |
693 |
|
* @param task the task. Caller must ensure non-null. |
694 |
< |
* @throw RejectedExecutionException if array cannot be resized |
694 |
> |
* @throws RejectedExecutionException if array cannot be resized |
695 |
|
*/ |
696 |
|
final void push(ForkJoinTask<?> task) { |
697 |
|
ForkJoinTask<?>[] a; ForkJoinPool p; |
698 |
< |
int s = top, m, n; |
698 |
> |
int s = top, n; |
699 |
|
if ((a = array) != null) { // ignore if queue removed |
700 |
< |
U.putOrderedObject |
701 |
< |
(a, (((m = a.length - 1) & s) << ASHIFT) + ABASE, task); |
702 |
< |
if ((n = (top = s + 1) - base) <= 2) { |
703 |
< |
if ((p = pool) != null) |
684 |
< |
p.signalWork(); |
685 |
< |
} |
700 |
> |
int m = a.length - 1; |
701 |
> |
U.putOrderedObject(a, ((m & s) << ASHIFT) + ABASE, task); |
702 |
> |
if ((n = (top = s + 1) - base) <= 2) |
703 |
> |
(p = pool).signalWork(p.workQueues, this); |
704 |
|
else if (n >= m) |
705 |
< |
growArray(true); |
705 |
> |
growArray(); |
706 |
|
} |
707 |
|
} |
708 |
|
|
709 |
|
/** |
710 |
< |
* Pushes a task if lock is free and array is either big |
711 |
< |
* enough or can be resized to be big enough. |
712 |
< |
* |
695 |
< |
* @param task the task. Caller must ensure non-null. |
696 |
< |
* @return true if submitted |
710 |
> |
* Initializes or doubles the capacity of array. Call either |
711 |
> |
* by owner or with lock held -- it is OK for base, but not |
712 |
> |
* top, to move while resizings are in progress. |
713 |
|
*/ |
714 |
< |
final boolean trySharedPush(ForkJoinTask<?> task) { |
715 |
< |
boolean submitted = false; |
716 |
< |
if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) { |
717 |
< |
ForkJoinTask<?>[] a = array; |
718 |
< |
int s = top; |
719 |
< |
try { |
720 |
< |
if ((a != null && a.length > s + 1 - base) || |
721 |
< |
(a = growArray(false)) != null) { // must presize |
722 |
< |
int j = (((a.length - 1) & s) << ASHIFT) + ABASE; |
723 |
< |
U.putObject(a, (long)j, task); // don't need "ordered" |
724 |
< |
top = s + 1; |
725 |
< |
submitted = true; |
726 |
< |
} |
727 |
< |
} finally { |
728 |
< |
runState = 0; // unlock |
729 |
< |
} |
714 |
> |
final ForkJoinTask<?>[] growArray() { |
715 |
> |
ForkJoinTask<?>[] oldA = array; |
716 |
> |
int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY; |
717 |
> |
if (size > MAXIMUM_QUEUE_CAPACITY) |
718 |
> |
throw new RejectedExecutionException("Queue capacity exceeded"); |
719 |
> |
int oldMask, t, b; |
720 |
> |
ForkJoinTask<?>[] a = array = new ForkJoinTask<?>[size]; |
721 |
> |
if (oldA != null && (oldMask = oldA.length - 1) >= 0 && |
722 |
> |
(t = top) - (b = base) > 0) { |
723 |
> |
int mask = size - 1; |
724 |
> |
do { |
725 |
> |
ForkJoinTask<?> x; |
726 |
> |
int oldj = ((b & oldMask) << ASHIFT) + ABASE; |
727 |
> |
int j = ((b & mask) << ASHIFT) + ABASE; |
728 |
> |
x = (ForkJoinTask<?>)U.getObjectVolatile(oldA, oldj); |
729 |
> |
if (x != null && |
730 |
> |
U.compareAndSwapObject(oldA, oldj, x, null)) |
731 |
> |
U.putObjectVolatile(a, j, x); |
732 |
> |
} while (++b != t); |
733 |
|
} |
734 |
< |
return submitted; |
734 |
> |
return a; |
735 |
|
} |
736 |
|
|
737 |
|
/** |
738 |
|
* Takes next task, if one exists, in LIFO order. Call only |
739 |
< |
* by owner in unshared queues. (We do not have a shared |
721 |
< |
* version of this method because it is never needed.) |
739 |
> |
* by owner in unshared queues. |
740 |
|
*/ |
741 |
|
final ForkJoinTask<?> pop() { |
742 |
|
ForkJoinTask<?>[] a; ForkJoinTask<?> t; int m; |
764 |
|
if ((a = array) != null) { |
765 |
|
int j = (((a.length - 1) & b) << ASHIFT) + ABASE; |
766 |
|
if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) != null && |
767 |
< |
base == b && |
768 |
< |
U.compareAndSwapObject(a, j, t, null)) { |
751 |
< |
base = b + 1; |
767 |
> |
base == b && U.compareAndSwapObject(a, j, t, null)) { |
768 |
> |
U.putOrderedInt(this, QBASE, b + 1); |
769 |
|
return t; |
770 |
|
} |
771 |
|
} |
781 |
|
int j = (((a.length - 1) & b) << ASHIFT) + ABASE; |
782 |
|
t = (ForkJoinTask<?>)U.getObjectVolatile(a, j); |
783 |
|
if (t != null) { |
784 |
< |
if (base == b && |
785 |
< |
U.compareAndSwapObject(a, j, t, null)) { |
769 |
< |
base = b + 1; |
784 |
> |
if (U.compareAndSwapObject(a, j, t, null)) { |
785 |
> |
U.putOrderedInt(this, QBASE, b + 1); |
786 |
|
return t; |
787 |
|
} |
788 |
|
} |
789 |
|
else if (base == b) { |
790 |
|
if (b + 1 == top) |
791 |
|
break; |
792 |
< |
Thread.yield(); // wait for lagging update |
792 |
> |
Thread.yield(); // wait for lagging update (very rare) |
793 |
|
} |
794 |
|
} |
795 |
|
return null; |
816 |
|
|
817 |
|
/** |
818 |
|
* Pops the given task only if it is at the current top. |
819 |
+ |
* (A shared version is available only via FJP.tryExternalUnpush) |
820 |
|
*/ |
821 |
|
final boolean tryUnpush(ForkJoinTask<?> t) { |
822 |
|
ForkJoinTask<?>[] a; int s; |
830 |
|
} |
831 |
|
|
832 |
|
/** |
816 |
– |
* Version of tryUnpush for shared queues; called by non-FJ |
817 |
– |
* submitters. Conservatively fails to unpush if all workers |
818 |
– |
* are active unless there are multiple tasks in queue. |
819 |
– |
*/ |
820 |
– |
final boolean trySharedUnpush(ForkJoinTask<?> task, ForkJoinPool p) { |
821 |
– |
boolean success = false; |
822 |
– |
if (task != null && top != base && runState == 0 && |
823 |
– |
U.compareAndSwapInt(this, RUNSTATE, 0, 1)) { |
824 |
– |
try { |
825 |
– |
ForkJoinTask<?>[] a; int n, s; |
826 |
– |
if ((a = array) != null && (n = (s = top) - base) > 0 && |
827 |
– |
(n > 1 || p == null || (int)(p.ctl >> AC_SHIFT) < 0)) { |
828 |
– |
int j = (((a.length - 1) & --s) << ASHIFT) + ABASE; |
829 |
– |
if (U.getObjectVolatile(a, j) == task && |
830 |
– |
U.compareAndSwapObject(a, j, task, null)) { |
831 |
– |
top = s; |
832 |
– |
success = true; |
833 |
– |
} |
834 |
– |
} |
835 |
– |
} finally { |
836 |
– |
runState = 0; // unlock |
837 |
– |
} |
838 |
– |
} |
839 |
– |
return success; |
840 |
– |
} |
841 |
– |
|
842 |
– |
/** |
843 |
– |
* Polls the given task only if it is at the current base. |
844 |
– |
*/ |
845 |
– |
final boolean pollFor(ForkJoinTask<?> task) { |
846 |
– |
ForkJoinTask<?>[] a; int b; |
847 |
– |
if ((b = base) - top < 0 && (a = array) != null) { |
848 |
– |
int j = (((a.length - 1) & b) << ASHIFT) + ABASE; |
849 |
– |
if (U.getObjectVolatile(a, j) == task && base == b && |
850 |
– |
U.compareAndSwapObject(a, j, task, null)) { |
851 |
– |
base = b + 1; |
852 |
– |
return true; |
853 |
– |
} |
854 |
– |
} |
855 |
– |
return false; |
856 |
– |
} |
857 |
– |
|
858 |
– |
/** |
859 |
– |
* Initializes or doubles the capacity of array. Call either |
860 |
– |
* by owner or with lock held -- it is OK for base, but not |
861 |
– |
* top, to move while resizings are in progress. |
862 |
– |
* |
863 |
– |
* @param rejectOnFailure if true, throw exception if capacity |
864 |
– |
* exceeded (relayed ultimately to user); else return null. |
865 |
– |
*/ |
866 |
– |
final ForkJoinTask<?>[] growArray(boolean rejectOnFailure) { |
867 |
– |
ForkJoinTask<?>[] oldA = array; |
868 |
– |
int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY; |
869 |
– |
if (size <= MAXIMUM_QUEUE_CAPACITY) { |
870 |
– |
int oldMask, t, b; |
871 |
– |
ForkJoinTask<?>[] a = array = new ForkJoinTask<?>[size]; |
872 |
– |
if (oldA != null && (oldMask = oldA.length - 1) >= 0 && |
873 |
– |
(t = top) - (b = base) > 0) { |
874 |
– |
int mask = size - 1; |
875 |
– |
do { |
876 |
– |
ForkJoinTask<?> x; |
877 |
– |
int oldj = ((b & oldMask) << ASHIFT) + ABASE; |
878 |
– |
int j = ((b & mask) << ASHIFT) + ABASE; |
879 |
– |
x = (ForkJoinTask<?>)U.getObjectVolatile(oldA, oldj); |
880 |
– |
if (x != null && |
881 |
– |
U.compareAndSwapObject(oldA, oldj, x, null)) |
882 |
– |
U.putObjectVolatile(a, j, x); |
883 |
– |
} while (++b != t); |
884 |
– |
} |
885 |
– |
return a; |
886 |
– |
} |
887 |
– |
else if (!rejectOnFailure) |
888 |
– |
return null; |
889 |
– |
else |
890 |
– |
throw new RejectedExecutionException("Queue capacity exceeded"); |
891 |
– |
} |
892 |
– |
|
893 |
– |
/** |
833 |
|
* Removes and cancels all known tasks, ignoring any exceptions. |
834 |
|
*/ |
835 |
|
final void cancelAll() { |
839 |
|
ForkJoinTask.cancelIgnoringExceptions(t); |
840 |
|
} |
841 |
|
|
842 |
< |
/** |
904 |
< |
* Computes next value for random probes. Scans don't require |
905 |
< |
* a very high quality generator, but also not a crummy one. |
906 |
< |
* Marsaglia xor-shift is cheap and works well enough. Note: |
907 |
< |
* This is manually inlined in its usages in ForkJoinPool to |
908 |
< |
* avoid writes inside busy scan loops. |
909 |
< |
*/ |
910 |
< |
final int nextSeed() { |
911 |
< |
int r = seed; |
912 |
< |
r ^= r << 13; |
913 |
< |
r ^= r >>> 17; |
914 |
< |
return seed = r ^= r << 5; |
915 |
< |
} |
916 |
< |
|
917 |
< |
// Execution methods |
918 |
< |
|
919 |
< |
/** |
920 |
< |
* Pops and runs tasks until empty. |
921 |
< |
*/ |
922 |
< |
private void popAndExecAll() { |
923 |
< |
// A bit faster than repeated pop calls |
924 |
< |
ForkJoinTask<?>[] a; int m, s; long j; ForkJoinTask<?> t; |
925 |
< |
while ((a = array) != null && (m = a.length - 1) >= 0 && |
926 |
< |
(s = top - 1) - base >= 0 && |
927 |
< |
(t = ((ForkJoinTask<?>) |
928 |
< |
U.getObject(a, j = ((m & s) << ASHIFT) + ABASE))) |
929 |
< |
!= null) { |
930 |
< |
if (U.compareAndSwapObject(a, j, t, null)) { |
931 |
< |
top = s; |
932 |
< |
t.doExec(); |
933 |
< |
} |
934 |
< |
} |
935 |
< |
} |
842 |
> |
// Specialized execution methods |
843 |
|
|
844 |
|
/** |
845 |
|
* Polls and runs tasks until empty. |
846 |
|
*/ |
847 |
< |
private void pollAndExecAll() { |
847 |
> |
final void pollAndExecAll() { |
848 |
|
for (ForkJoinTask<?> t; (t = poll()) != null;) |
849 |
|
t.doExec(); |
850 |
|
} |
851 |
|
|
852 |
|
/** |
853 |
< |
* If present, removes from queue and executes the given task, or |
854 |
< |
* any other cancelled task. Returns (true) immediately on any CAS |
853 |
> |
* Executes a top-level task and any local tasks remaining |
854 |
> |
* after execution. |
855 |
> |
*/ |
856 |
> |
final void runTask(ForkJoinTask<?> task) { |
857 |
> |
if ((currentSteal = task) != null) { |
858 |
> |
task.doExec(); |
859 |
> |
ForkJoinTask<?>[] a = array; |
860 |
> |
int md = mode; |
861 |
> |
++nsteals; |
862 |
> |
currentSteal = null; |
863 |
> |
if (md != 0) |
864 |
> |
pollAndExecAll(); |
865 |
> |
else if (a != null) { |
866 |
> |
int s, m = a.length - 1; |
867 |
> |
while ((s = top - 1) - base >= 0) { |
868 |
> |
long i = ((m & s) << ASHIFT) + ABASE; |
869 |
> |
ForkJoinTask<?> t = (ForkJoinTask<?>)U.getObject(a, i); |
870 |
> |
if (t == null) |
871 |
> |
break; |
872 |
> |
if (U.compareAndSwapObject(a, i, t, null)) { |
873 |
> |
top = s; |
874 |
> |
t.doExec(); |
875 |
> |
} |
876 |
> |
} |
877 |
> |
} |
878 |
> |
} |
879 |
> |
} |
880 |
> |
|
881 |
> |
/** |
882 |
> |
* If present, removes from queue and executes the given task, |
883 |
> |
* or any other cancelled task. Returns (true) on any CAS |
884 |
|
* or consistency check failure so caller can retry. |
885 |
|
* |
886 |
< |
* @return 0 if no progress can be made, else positive |
951 |
< |
* (this unusual convention simplifies use with tryHelpStealer.) |
886 |
> |
* @return false if no progress can be made, else true |
887 |
|
*/ |
888 |
< |
final int tryRemoveAndExec(ForkJoinTask<?> task) { |
889 |
< |
int stat = 1; |
955 |
< |
boolean removed = false, empty = true; |
888 |
> |
final boolean tryRemoveAndExec(ForkJoinTask<?> task) { |
889 |
> |
boolean stat; |
890 |
|
ForkJoinTask<?>[] a; int m, s, b, n; |
891 |
< |
if ((a = array) != null && (m = a.length - 1) >= 0 && |
891 |
> |
if (task != null && (a = array) != null && (m = a.length - 1) >= 0 && |
892 |
|
(n = (s = top) - (b = base)) > 0) { |
893 |
+ |
boolean removed = false, empty = true; |
894 |
+ |
stat = true; |
895 |
|
for (ForkJoinTask<?> t;;) { // traverse from s to b |
896 |
< |
int j = ((--s & m) << ASHIFT) + ABASE; |
897 |
< |
t = (ForkJoinTask<?>)U.getObjectVolatile(a, j); |
896 |
> |
long j = ((--s & m) << ASHIFT) + ABASE; |
897 |
> |
t = (ForkJoinTask<?>)U.getObject(a, j); |
898 |
|
if (t == null) // inconsistent length |
899 |
|
break; |
900 |
|
else if (t == task) { |
918 |
|
} |
919 |
|
if (--n == 0) { |
920 |
|
if (!empty && base == b) |
921 |
< |
stat = 0; |
921 |
> |
stat = false; |
922 |
|
break; |
923 |
|
} |
924 |
|
} |
925 |
+ |
if (removed) |
926 |
+ |
task.doExec(); |
927 |
|
} |
928 |
< |
if (removed) |
929 |
< |
task.doExec(); |
928 |
> |
else |
929 |
> |
stat = false; |
930 |
|
return stat; |
931 |
|
} |
932 |
|
|
933 |
|
/** |
934 |
< |
* Executes a top-level task and any local tasks remaining |
935 |
< |
* after execution. |
934 |
> |
* Tries to poll for and execute the given task or any other |
935 |
> |
* task in its CountedCompleter computation. |
936 |
|
*/ |
937 |
< |
final void runTask(ForkJoinTask<?> t) { |
938 |
< |
if (t != null) { |
939 |
< |
currentSteal = t; |
940 |
< |
t.doExec(); |
941 |
< |
if (top != base) { // process remaining local tasks |
942 |
< |
if (mode == 0) |
943 |
< |
popAndExecAll(); |
944 |
< |
else |
945 |
< |
pollAndExecAll(); |
937 |
> |
final boolean pollAndExecCC(CountedCompleter<?> root) { |
938 |
> |
ForkJoinTask<?>[] a; int b; Object o; CountedCompleter<?> t, r; |
939 |
> |
if ((b = base) - top < 0 && (a = array) != null) { |
940 |
> |
long j = (((a.length - 1) & b) << ASHIFT) + ABASE; |
941 |
> |
if ((o = U.getObjectVolatile(a, j)) == null) |
942 |
> |
return true; // retry |
943 |
> |
if (o instanceof CountedCompleter) { |
944 |
> |
for (t = (CountedCompleter<?>)o, r = t;;) { |
945 |
> |
if (r == root) { |
946 |
> |
if (base == b && |
947 |
> |
U.compareAndSwapObject(a, j, t, null)) { |
948 |
> |
U.putOrderedInt(this, QBASE, b + 1); |
949 |
> |
t.doExec(); |
950 |
> |
} |
951 |
> |
return true; |
952 |
> |
} |
953 |
> |
else if ((r = r.completer) == null) |
954 |
> |
break; // not part of root computation |
955 |
> |
} |
956 |
|
} |
1009 |
– |
++nsteals; |
1010 |
– |
currentSteal = null; |
957 |
|
} |
958 |
+ |
return false; |
959 |
|
} |
960 |
|
|
961 |
|
/** |
962 |
< |
* Executes a non-top-level (stolen) task. |
962 |
> |
* Tries to pop and execute the given task or any other task |
963 |
> |
* in its CountedCompleter computation. |
964 |
|
*/ |
965 |
< |
final void runSubtask(ForkJoinTask<?> t) { |
966 |
< |
if (t != null) { |
967 |
< |
ForkJoinTask<?> ps = currentSteal; |
968 |
< |
currentSteal = t; |
969 |
< |
t.doExec(); |
970 |
< |
currentSteal = ps; |
965 |
> |
final boolean externalPopAndExecCC(CountedCompleter<?> root) { |
966 |
> |
ForkJoinTask<?>[] a; int s; Object o; CountedCompleter<?> t, r; |
967 |
> |
if (base - (s = top) < 0 && (a = array) != null) { |
968 |
> |
long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE; |
969 |
> |
if ((o = U.getObject(a, j)) instanceof CountedCompleter) { |
970 |
> |
for (t = (CountedCompleter<?>)o, r = t;;) { |
971 |
> |
if (r == root) { |
972 |
> |
if (U.compareAndSwapInt(this, QLOCK, 0, 1)) { |
973 |
> |
if (top == s && array == a && |
974 |
> |
U.compareAndSwapObject(a, j, t, null)) { |
975 |
> |
top = s - 1; |
976 |
> |
qlock = 0; |
977 |
> |
t.doExec(); |
978 |
> |
} |
979 |
> |
else |
980 |
> |
qlock = 0; |
981 |
> |
} |
982 |
> |
return true; |
983 |
> |
} |
984 |
> |
else if ((r = r.completer) == null) |
985 |
> |
break; |
986 |
> |
} |
987 |
> |
} |
988 |
|
} |
989 |
+ |
return false; |
990 |
+ |
} |
991 |
+ |
|
992 |
+ |
/** |
993 |
+ |
* Internal version |
994 |
+ |
*/ |
995 |
+ |
final boolean internalPopAndExecCC(CountedCompleter<?> root) { |
996 |
+ |
ForkJoinTask<?>[] a; int s; Object o; CountedCompleter<?> t, r; |
997 |
+ |
if (base - (s = top) < 0 && (a = array) != null) { |
998 |
+ |
long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE; |
999 |
+ |
if ((o = U.getObject(a, j)) instanceof CountedCompleter) { |
1000 |
+ |
for (t = (CountedCompleter<?>)o, r = t;;) { |
1001 |
+ |
if (r == root) { |
1002 |
+ |
if (U.compareAndSwapObject(a, j, t, null)) { |
1003 |
+ |
top = s - 1; |
1004 |
+ |
t.doExec(); |
1005 |
+ |
} |
1006 |
+ |
return true; |
1007 |
+ |
} |
1008 |
+ |
else if ((r = r.completer) == null) |
1009 |
+ |
break; |
1010 |
+ |
} |
1011 |
+ |
} |
1012 |
+ |
} |
1013 |
+ |
return false; |
1014 |
|
} |
1015 |
|
|
1016 |
|
/** |
1025 |
|
s != Thread.State.TIMED_WAITING); |
1026 |
|
} |
1027 |
|
|
1038 |
– |
/** |
1039 |
– |
* If this owned and is not already interrupted, try to |
1040 |
– |
* interrupt and/or unpark, ignoring exceptions. |
1041 |
– |
*/ |
1042 |
– |
final void interruptOwner() { |
1043 |
– |
Thread wt, p; |
1044 |
– |
if ((wt = owner) != null && !wt.isInterrupted()) { |
1045 |
– |
try { |
1046 |
– |
wt.interrupt(); |
1047 |
– |
} catch (SecurityException ignore) { |
1048 |
– |
} |
1049 |
– |
} |
1050 |
– |
if ((p = parker) != null) |
1051 |
– |
U.unpark(p); |
1052 |
– |
} |
1053 |
– |
|
1028 |
|
// Unsafe mechanics |
1029 |
|
private static final sun.misc.Unsafe U; |
1030 |
< |
private static final long RUNSTATE; |
1030 |
> |
private static final long QBASE; |
1031 |
> |
private static final long QLOCK; |
1032 |
|
private static final int ABASE; |
1033 |
|
private static final int ASHIFT; |
1034 |
|
static { |
1060 |
– |
int s; |
1035 |
|
try { |
1036 |
|
U = getUnsafe(); |
1037 |
|
Class<?> k = WorkQueue.class; |
1038 |
|
Class<?> ak = ForkJoinTask[].class; |
1039 |
< |
RUNSTATE = U.objectFieldOffset |
1040 |
< |
(k.getDeclaredField("runState")); |
1039 |
> |
QBASE = U.objectFieldOffset |
1040 |
> |
(k.getDeclaredField("base")); |
1041 |
> |
QLOCK = U.objectFieldOffset |
1042 |
> |
(k.getDeclaredField("qlock")); |
1043 |
|
ABASE = U.arrayBaseOffset(ak); |
1044 |
< |
s = U.arrayIndexScale(ak); |
1044 |
> |
int scale = U.arrayIndexScale(ak); |
1045 |
> |
if ((scale & (scale - 1)) != 0) |
1046 |
> |
throw new Error("data type scale not a power of two"); |
1047 |
> |
ASHIFT = 31 - Integer.numberOfLeadingZeros(scale); |
1048 |
|
} catch (Exception e) { |
1049 |
|
throw new Error(e); |
1050 |
|
} |
1072 |
– |
if ((s & (s-1)) != 0) |
1073 |
– |
throw new Error("data type scale not a power of two"); |
1074 |
– |
ASHIFT = 31 - Integer.numberOfLeadingZeros(s); |
1051 |
|
} |
1052 |
|
} |
1053 |
|
|
1054 |
+ |
// static fields (initialized in static initializer below) |
1055 |
+ |
|
1056 |
|
/** |
1057 |
< |
* Per-thread records for threads that submit to pools. Currently |
1058 |
< |
* holds only pseudo-random seed / index that is used to choose |
1059 |
< |
* submission queues in method doSubmit. In the future, this may |
1060 |
< |
* also incorporate a means to implement different task rejection |
1061 |
< |
* and resubmission policies. |
1084 |
< |
* |
1085 |
< |
* Seeds for submitters and workers/workQueues work in basically |
1086 |
< |
* the same way but are initialized and updated using slightly |
1087 |
< |
* different mechanics. Both are initialized using the same |
1088 |
< |
* approach as in class ThreadLocal, where successive values are |
1089 |
< |
* unlikely to collide with previous values. This is done during |
1090 |
< |
* registration for workers, but requires a separate AtomicInteger |
1091 |
< |
* for submitters. Seeds are then randomly modified upon |
1092 |
< |
* collisions using xorshifts, which requires a non-zero seed. |
1057 |
> |
* Per-thread submission bookkeeping. Shared across all pools |
1058 |
> |
* to reduce ThreadLocal pollution and because random motion |
1059 |
> |
* to avoid contention in one pool is likely to hold for others. |
1060 |
> |
* Lazily initialized on first submission (but null-checked |
1061 |
> |
* in other contexts to avoid unnecessary initialization). |
1062 |
|
*/ |
1063 |
< |
static final class Submitter { |
1095 |
< |
int seed; |
1096 |
< |
Submitter() { |
1097 |
< |
int s = nextSubmitterSeed.getAndAdd(SEED_INCREMENT); |
1098 |
< |
seed = (s == 0) ? 1 : s; // ensure non-zero |
1099 |
< |
} |
1100 |
< |
} |
1101 |
< |
|
1102 |
< |
/** ThreadLocal class for Submitters */ |
1103 |
< |
static final class ThreadSubmitter extends ThreadLocal<Submitter> { |
1104 |
< |
public Submitter initialValue() { return new Submitter(); } |
1105 |
< |
} |
1106 |
< |
|
1107 |
< |
// static fields (initialized in static initializer below) |
1063 |
> |
static final ThreadLocal<Submitter> submitters; |
1064 |
|
|
1065 |
|
/** |
1066 |
|
* Creates a new ForkJoinWorkerThread. This factory is used unless |
1070 |
|
defaultForkJoinWorkerThreadFactory; |
1071 |
|
|
1072 |
|
/** |
1073 |
< |
* Generator for assigning sequence numbers as pool names. |
1073 |
> |
* Permission required for callers of methods that may start or |
1074 |
> |
* kill threads. |
1075 |
|
*/ |
1076 |
< |
private static final AtomicInteger poolNumberGenerator; |
1076 |
> |
private static final RuntimePermission modifyThreadPermission; |
1077 |
|
|
1078 |
|
/** |
1079 |
< |
* Generator for initial hashes/seeds for submitters. Accessed by |
1080 |
< |
* Submitter class constructor. |
1079 |
> |
* Common (static) pool. Non-null for public use unless a static |
1080 |
> |
* construction exception, but internal usages null-check on use |
1081 |
> |
* to paranoically avoid potential initialization circularities |
1082 |
> |
* as well as to simplify generated code. |
1083 |
|
*/ |
1084 |
< |
static final AtomicInteger nextSubmitterSeed; |
1084 |
> |
static final ForkJoinPool common; |
1085 |
|
|
1086 |
|
/** |
1087 |
< |
* Permission required for callers of methods that may start or |
1088 |
< |
* kill threads. |
1087 |
> |
* Common pool parallelism. To allow simpler use and management |
1088 |
> |
* when common pool threads are disabled, we allow the underlying |
1089 |
> |
* common.parallelism field to be zero, but in that case still report |
1090 |
> |
* parallelism as 1 to reflect resulting caller-runs mechanics. |
1091 |
|
*/ |
1092 |
< |
private static final RuntimePermission modifyThreadPermission; |
1092 |
> |
static final int commonParallelism; |
1093 |
|
|
1094 |
|
/** |
1095 |
< |
* Per-thread submission bookkeeping. Shared across all pools |
1135 |
< |
* to reduce ThreadLocal pollution and because random motion |
1136 |
< |
* to avoid contention in one pool is likely to hold for others. |
1095 |
> |
* Sequence number for creating workerNamePrefix. |
1096 |
|
*/ |
1097 |
< |
private static final ThreadSubmitter submitters; |
1097 |
> |
private static int poolNumberSequence; |
1098 |
|
|
1099 |
< |
/** Common default pool */ |
1100 |
< |
static volatile ForkJoinPool commonPool; |
1101 |
< |
|
1102 |
< |
// commonPool construction parameters |
1103 |
< |
private static final String propPrefix = |
1104 |
< |
"java.util.concurrent.ForkJoinPool.common."; |
1105 |
< |
private static final Thread.UncaughtExceptionHandler commonPoolUEH; |
1147 |
< |
private static final ForkJoinWorkerThreadFactory commonPoolFactory; |
1148 |
< |
static final int commonPoolParallelism; |
1149 |
< |
|
1150 |
< |
/** Static initialization lock */ |
1151 |
< |
private static final Mutex initializationLock; |
1099 |
> |
/** |
1100 |
> |
* Returns the next sequence number. We don't expect this to |
1101 |
> |
* ever contend, so use simple builtin sync. |
1102 |
> |
*/ |
1103 |
> |
private static final synchronized int nextPoolId() { |
1104 |
> |
return ++poolNumberSequence; |
1105 |
> |
} |
1106 |
|
|
1107 |
|
// static constants |
1108 |
|
|
1109 |
|
/** |
1110 |
< |
* Initial timeout value (in nanoseconds) for the tread triggering |
1111 |
< |
* quiescence to park waiting for new work. On timeout, the thread |
1112 |
< |
* will instead try to shrink the number of workers. |
1110 |
> |
* Initial timeout value (in nanoseconds) for the thread |
1111 |
> |
* triggering quiescence to park waiting for new work. On timeout, |
1112 |
> |
* the thread will instead try to shrink the number of |
1113 |
> |
* workers. The value should be large enough to avoid overly |
1114 |
> |
* aggressive shrinkage during most transient stalls (long GCs |
1115 |
> |
* etc). |
1116 |
|
*/ |
1117 |
< |
private static final long IDLE_TIMEOUT = 1000L * 1000L * 1000L; // 1sec |
1117 |
> |
private static final long IDLE_TIMEOUT = 2000L * 1000L * 1000L; // 2sec |
1118 |
|
|
1119 |
|
/** |
1120 |
|
* Timeout value when there are more threads than parallelism level |
1121 |
|
*/ |
1122 |
< |
private static final long FAST_IDLE_TIMEOUT = 100L * 1000L * 1000L; |
1122 |
> |
private static final long FAST_IDLE_TIMEOUT = 200L * 1000L * 1000L; |
1123 |
> |
|
1124 |
> |
/** |
1125 |
> |
* Tolerance for idle timeouts, to cope with timer undershoots |
1126 |
> |
*/ |
1127 |
> |
private static final long TIMEOUT_SLOP = 2000000L; |
1128 |
|
|
1129 |
|
/** |
1130 |
|
* The maximum stolen->joining link depth allowed in method |
1131 |
< |
* tryHelpStealer. Must be a power of two. This value also |
1170 |
< |
* controls the maximum number of times to try to help join a task |
1171 |
< |
* without any apparent progress or change in pool state before |
1172 |
< |
* giving up and blocking (see awaitJoin). Depths for legitimate |
1131 |
> |
* tryHelpStealer. Must be a power of two. Depths for legitimate |
1132 |
|
* chains are unbounded, but we use a fixed constant to avoid |
1133 |
|
* (otherwise unchecked) cycles and to bound staleness of |
1134 |
|
* traversal parameters at the expense of sometimes blocking when |
1137 |
|
private static final int MAX_HELP = 64; |
1138 |
|
|
1139 |
|
/** |
1181 |
– |
* Secondary time-based bound (in nanosecs) for helping attempts |
1182 |
– |
* before trying compensated blocking in awaitJoin. Used in |
1183 |
– |
* conjunction with MAX_HELP to reduce variance due to different |
1184 |
– |
* polling rates associated with different helping options. The |
1185 |
– |
* value should roughly approximate the time required to create |
1186 |
– |
* and/or activate a worker thread. |
1187 |
– |
*/ |
1188 |
– |
private static final long COMPENSATION_DELAY = 1L << 18; // ~0.25 millisec |
1189 |
– |
|
1190 |
– |
/** |
1140 |
|
* Increment for seed generators. See class ThreadLocal for |
1141 |
|
* explanation. |
1142 |
|
*/ |
1143 |
|
private static final int SEED_INCREMENT = 0x61c88647; |
1144 |
|
|
1145 |
< |
/** |
1145 |
> |
/* |
1146 |
|
* Bits and masks for control variables |
1147 |
|
* |
1148 |
|
* Field ctl is a long packed with: |
1170 |
|
* scan for them to avoid queuing races. Note however that |
1171 |
|
* eventCount updates lag releases so usage requires care. |
1172 |
|
* |
1173 |
< |
* Field runState is an int packed with: |
1173 |
> |
* Field plock is an int packed with: |
1174 |
|
* SHUTDOWN: true if shutdown is enabled (1 bit) |
1175 |
< |
* SEQ: a sequence number updated upon (de)registering workers (30 bits) |
1176 |
< |
* INIT: set true after workQueues array construction (1 bit) |
1175 |
> |
* SEQ: a sequence lock, with PL_LOCK bit set if locked (30 bits) |
1176 |
> |
* SIGNAL: set when threads may be waiting on the lock (1 bit) |
1177 |
|
* |
1178 |
|
* The sequence number enables simple consistency checks: |
1179 |
|
* Staleness of read-only operations on the workQueues array can |
1180 |
< |
* be checked by comparing runState before vs after the reads. |
1180 |
> |
* be checked by comparing plock before vs after the reads. |
1181 |
|
*/ |
1182 |
|
|
1183 |
|
// bit positions/shifts for fields |
1189 |
|
// bounds |
1190 |
|
private static final int SMASK = 0xffff; // short bits |
1191 |
|
private static final int MAX_CAP = 0x7fff; // max #workers - 1 |
1192 |
< |
private static final int SQMASK = 0xfffe; // even short bits |
1192 |
> |
private static final int EVENMASK = 0xfffe; // even short bits |
1193 |
> |
private static final int SQMASK = 0x007e; // max 64 (even) slots |
1194 |
|
private static final int SHORT_SIGN = 1 << 15; |
1195 |
|
private static final int INT_SIGN = 1 << 31; |
1196 |
|
|
1215 |
|
private static final int E_MASK = 0x7fffffff; // no STOP_BIT |
1216 |
|
private static final int E_SEQ = 1 << EC_SHIFT; |
1217 |
|
|
1218 |
< |
// runState bits |
1218 |
> |
// plock bits |
1219 |
|
private static final int SHUTDOWN = 1 << 31; |
1220 |
+ |
private static final int PL_LOCK = 2; |
1221 |
+ |
private static final int PL_SIGNAL = 1; |
1222 |
+ |
private static final int PL_SPINS = 1 << 8; |
1223 |
|
|
1224 |
|
// access mode for WorkQueue |
1225 |
|
static final int LIFO_QUEUE = 0; |
1226 |
|
static final int FIFO_QUEUE = 1; |
1227 |
|
static final int SHARED_QUEUE = -1; |
1228 |
|
|
1229 |
< |
// Instance fields |
1230 |
< |
|
1278 |
< |
/* |
1279 |
< |
* Field layout order in this class tends to matter more than one |
1280 |
< |
* would like. Runtime layout order is only loosely related to |
1281 |
< |
* declaration order and may differ across JVMs, but the following |
1282 |
< |
* empirically works OK on current JVMs. |
1283 |
< |
*/ |
1229 |
> |
// Heuristic padding to ameliorate unfortunate memory placements |
1230 |
> |
volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06; |
1231 |
|
|
1232 |
+ |
// Instance fields |
1233 |
+ |
volatile long stealCount; // collects worker counts |
1234 |
|
volatile long ctl; // main pool control |
1235 |
< |
final int parallelism; // parallelism level |
1236 |
< |
final int localMode; // per-worker scheduling mode |
1237 |
< |
final int submitMask; // submit queue index bound |
1238 |
< |
int nextSeed; // for initializing worker seeds |
1290 |
< |
volatile int runState; // shutdown status and seq |
1235 |
> |
volatile int plock; // shutdown status and seqLock |
1236 |
> |
volatile int indexSeed; // worker/submitter index seed |
1237 |
> |
final short parallelism; // parallelism level |
1238 |
> |
final short mode; // LIFO/FIFO |
1239 |
|
WorkQueue[] workQueues; // main registry |
1240 |
< |
final Mutex lock; // for registration |
1241 |
< |
final Condition termination; // for awaitTermination |
1242 |
< |
final ForkJoinWorkerThreadFactory factory; // factory for new workers |
1243 |
< |
final Thread.UncaughtExceptionHandler ueh; // per-worker UEH |
1244 |
< |
final AtomicLong stealCount; // collect counts when terminated |
1245 |
< |
final AtomicInteger nextWorkerNumber; // to create worker name string |
1246 |
< |
String workerNamePrefix; // to create worker name string |
1247 |
< |
|
1248 |
< |
// Creating, registering, and deregistering workers |
1249 |
< |
|
1250 |
< |
/** |
1251 |
< |
* Tries to create and start a worker |
1252 |
< |
*/ |
1253 |
< |
private void addWorker() { |
1254 |
< |
Throwable ex = null; |
1255 |
< |
ForkJoinWorkerThread wt = null; |
1256 |
< |
try { |
1257 |
< |
if ((wt = factory.newThread(this)) != null) { |
1258 |
< |
wt.start(); |
1259 |
< |
return; |
1240 |
> |
final ForkJoinWorkerThreadFactory factory; |
1241 |
> |
final UncaughtExceptionHandler ueh; // per-worker UEH |
1242 |
> |
final String workerNamePrefix; // to create worker name string |
1243 |
> |
|
1244 |
> |
volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17; |
1245 |
> |
volatile Object pad18, pad19, pad1a, pad1b; |
1246 |
> |
|
1247 |
> |
/** |
1248 |
> |
* Acquires the plock lock to protect worker array and related |
1249 |
> |
* updates. This method is called only if an initial CAS on plock |
1250 |
> |
* fails. This acts as a spinlock for normal cases, but falls back |
1251 |
> |
* to builtin monitor to block when (rarely) needed. This would be |
1252 |
> |
* a terrible idea for a highly contended lock, but works fine as |
1253 |
> |
* a more conservative alternative to a pure spinlock. |
1254 |
> |
*/ |
1255 |
> |
private int acquirePlock() { |
1256 |
> |
int spins = PL_SPINS, ps, nps; |
1257 |
> |
for (;;) { |
1258 |
> |
if (((ps = plock) & PL_LOCK) == 0 && |
1259 |
> |
U.compareAndSwapInt(this, PLOCK, ps, nps = ps + PL_LOCK)) |
1260 |
> |
return nps; |
1261 |
> |
else if (spins >= 0) { |
1262 |
> |
if (ThreadLocalRandom.current().nextInt() >= 0) |
1263 |
> |
--spins; |
1264 |
> |
} |
1265 |
> |
else if (U.compareAndSwapInt(this, PLOCK, ps, ps | PL_SIGNAL)) { |
1266 |
> |
synchronized (this) { |
1267 |
> |
if ((plock & PL_SIGNAL) != 0) { |
1268 |
> |
try { |
1269 |
> |
wait(); |
1270 |
> |
} catch (InterruptedException ie) { |
1271 |
> |
try { |
1272 |
> |
Thread.currentThread().interrupt(); |
1273 |
> |
} catch (SecurityException ignore) { |
1274 |
> |
} |
1275 |
> |
} |
1276 |
> |
} |
1277 |
> |
else |
1278 |
> |
notifyAll(); |
1279 |
> |
} |
1280 |
|
} |
1313 |
– |
} catch (Throwable e) { |
1314 |
– |
ex = e; |
1281 |
|
} |
1316 |
– |
deregisterWorker(wt, ex); // adjust counts etc on failure |
1282 |
|
} |
1283 |
|
|
1284 |
|
/** |
1285 |
< |
* Callback from ForkJoinWorkerThread constructor to assign a |
1286 |
< |
* public name. This must be separate from registerWorker because |
1322 |
< |
* it is called during the "super" constructor call in |
1323 |
< |
* ForkJoinWorkerThread. |
1285 |
> |
* Unlocks and signals any thread waiting for plock. Called only |
1286 |
> |
* when CAS of seq value for unlock fails. |
1287 |
|
*/ |
1288 |
< |
final String nextWorkerName() { |
1289 |
< |
return workerNamePrefix.concat |
1290 |
< |
(Integer.toString(nextWorkerNumber.addAndGet(1))); |
1288 |
> |
private void releasePlock(int ps) { |
1289 |
> |
plock = ps; |
1290 |
> |
synchronized (this) { notifyAll(); } |
1291 |
|
} |
1292 |
|
|
1293 |
|
/** |
1294 |
< |
* Callback from ForkJoinWorkerThread constructor to establish its |
1295 |
< |
* poolIndex and record its WorkQueue. To avoid scanning bias due |
1333 |
< |
* to packing entries in front of the workQueues array, we treat |
1334 |
< |
* the array as a simple power-of-two hash table using per-thread |
1335 |
< |
* seed as hash, expanding as needed. |
1336 |
< |
* |
1337 |
< |
* @param w the worker's queue |
1294 |
> |
* Tries to create and start one worker if fewer than target |
1295 |
> |
* parallelism level exist. Adjusts counts etc on failure. |
1296 |
|
*/ |
1297 |
< |
final void registerWorker(WorkQueue w) { |
1298 |
< |
Mutex lock = this.lock; |
1299 |
< |
lock.lock(); |
1297 |
> |
private void tryAddWorker() { |
1298 |
> |
long c; int u, e; |
1299 |
> |
while ((u = (int)((c = ctl) >>> 32)) < 0 && |
1300 |
> |
(u & SHORT_SIGN) != 0 && (e = (int)c) >= 0) { |
1301 |
> |
long nc = ((long)(((u + UTC_UNIT) & UTC_MASK) | |
1302 |
> |
((u + UAC_UNIT) & UAC_MASK)) << 32) | (long)e; |
1303 |
> |
if (U.compareAndSwapLong(this, CTL, c, nc)) { |
1304 |
> |
ForkJoinWorkerThreadFactory fac; |
1305 |
> |
Throwable ex = null; |
1306 |
> |
ForkJoinWorkerThread wt = null; |
1307 |
> |
try { |
1308 |
> |
if ((fac = factory) != null && |
1309 |
> |
(wt = fac.newThread(this)) != null) { |
1310 |
> |
wt.start(); |
1311 |
> |
break; |
1312 |
> |
} |
1313 |
> |
} catch (Throwable rex) { |
1314 |
> |
ex = rex; |
1315 |
> |
} |
1316 |
> |
deregisterWorker(wt, ex); |
1317 |
> |
break; |
1318 |
> |
} |
1319 |
> |
} |
1320 |
> |
} |
1321 |
> |
|
1322 |
> |
// Registering and deregistering workers |
1323 |
> |
|
1324 |
> |
/** |
1325 |
> |
* Callback from ForkJoinWorkerThread to establish and record its |
1326 |
> |
* WorkQueue. To avoid scanning bias due to packing entries in |
1327 |
> |
* front of the workQueues array, we treat the array as a simple |
1328 |
> |
* power-of-two hash table using per-thread seed as hash, |
1329 |
> |
* expanding as needed. |
1330 |
> |
* |
1331 |
> |
* @param wt the worker thread |
1332 |
> |
* @return the worker's queue |
1333 |
> |
*/ |
1334 |
> |
final WorkQueue registerWorker(ForkJoinWorkerThread wt) { |
1335 |
> |
UncaughtExceptionHandler handler; WorkQueue[] ws; int s, ps; |
1336 |
> |
wt.setDaemon(true); |
1337 |
> |
if ((handler = ueh) != null) |
1338 |
> |
wt.setUncaughtExceptionHandler(handler); |
1339 |
> |
do {} while (!U.compareAndSwapInt(this, INDEXSEED, s = indexSeed, |
1340 |
> |
s += SEED_INCREMENT) || |
1341 |
> |
s == 0); // skip 0 |
1342 |
> |
WorkQueue w = new WorkQueue(this, wt, mode, s); |
1343 |
> |
if (((ps = plock) & PL_LOCK) != 0 || |
1344 |
> |
!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK)) |
1345 |
> |
ps = acquirePlock(); |
1346 |
> |
int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN); |
1347 |
|
try { |
1348 |
< |
WorkQueue[] ws = workQueues; |
1349 |
< |
if (w != null && ws != null) { // skip on shutdown/failure |
1350 |
< |
int rs, n = ws.length, m = n - 1; |
1351 |
< |
int s = nextSeed += SEED_INCREMENT; // rarely-colliding sequence |
1352 |
< |
w.seed = (s == 0) ? 1 : s; // ensure non-zero seed |
1353 |
< |
int r = (s << 1) | 1; // use odd-numbered indices |
1349 |
< |
if (ws[r &= m] != null) { // collision |
1350 |
< |
int probes = 0; // step by approx half size |
1351 |
< |
int step = (n <= 4) ? 2 : ((n >>> 1) & SQMASK) + 2; |
1348 |
> |
if ((ws = workQueues) != null) { // skip if shutting down |
1349 |
> |
int n = ws.length, m = n - 1; |
1350 |
> |
int r = (s << 1) | 1; // use odd-numbered indices |
1351 |
> |
if (ws[r &= m] != null) { // collision |
1352 |
> |
int probes = 0; // step by approx half size |
1353 |
> |
int step = (n <= 4) ? 2 : ((n >>> 1) & EVENMASK) + 2; |
1354 |
|
while (ws[r = (r + step) & m] != null) { |
1355 |
|
if (++probes >= n) { |
1356 |
|
workQueues = ws = Arrays.copyOf(ws, n <<= 1); |
1359 |
|
} |
1360 |
|
} |
1361 |
|
} |
1362 |
< |
w.eventCount = w.poolIndex = r; // establish before recording |
1363 |
< |
ws[r] = w; // also update seq |
1364 |
< |
runState = ((rs = runState) & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN); |
1362 |
> |
w.poolIndex = (short)r; |
1363 |
> |
w.eventCount = r; // volatile write orders |
1364 |
> |
ws[r] = w; |
1365 |
|
} |
1366 |
|
} finally { |
1367 |
< |
lock.unlock(); |
1367 |
> |
if (!U.compareAndSwapInt(this, PLOCK, ps, nps)) |
1368 |
> |
releasePlock(nps); |
1369 |
|
} |
1370 |
+ |
wt.setName(workerNamePrefix.concat(Integer.toString(w.poolIndex >>> 1))); |
1371 |
+ |
return w; |
1372 |
|
} |
1373 |
|
|
1374 |
|
/** |
1375 |
|
* Final callback from terminating worker, as well as upon failure |
1376 |
< |
* to construct or start a worker in addWorker. Removes record of |
1377 |
< |
* worker from array, and adjusts counts. If pool is shutting |
1378 |
< |
* down, tries to complete termination. |
1376 |
> |
* to construct or start a worker. Removes record of worker from |
1377 |
> |
* array, and adjusts counts. If pool is shutting down, tries to |
1378 |
> |
* complete termination. |
1379 |
|
* |
1380 |
< |
* @param wt the worker thread or null if addWorker failed |
1380 |
> |
* @param wt the worker thread, or null if construction failed |
1381 |
|
* @param ex the exception causing failure, or null if none |
1382 |
|
*/ |
1383 |
|
final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) { |
1379 |
– |
Mutex lock = this.lock; |
1384 |
|
WorkQueue w = null; |
1385 |
|
if (wt != null && (w = wt.workQueue) != null) { |
1386 |
< |
w.runState = -1; // ensure runState is set |
1387 |
< |
stealCount.getAndAdd(w.totalSteals + w.nsteals); |
1388 |
< |
int idx = w.poolIndex; |
1389 |
< |
lock.lock(); |
1390 |
< |
try { // remove record from array |
1386 |
> |
int ps; long sc; |
1387 |
> |
w.qlock = -1; // ensure set |
1388 |
> |
do {} while (!U.compareAndSwapLong(this, STEALCOUNT, |
1389 |
> |
sc = stealCount, |
1390 |
> |
sc + w.nsteals)); |
1391 |
> |
if (((ps = plock) & PL_LOCK) != 0 || |
1392 |
> |
!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK)) |
1393 |
> |
ps = acquirePlock(); |
1394 |
> |
int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN); |
1395 |
> |
try { |
1396 |
> |
int idx = w.poolIndex; |
1397 |
|
WorkQueue[] ws = workQueues; |
1398 |
|
if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w) |
1399 |
|
ws[idx] = null; |
1400 |
|
} finally { |
1401 |
< |
lock.unlock(); |
1401 |
> |
if (!U.compareAndSwapInt(this, PLOCK, ps, nps)) |
1402 |
> |
releasePlock(nps); |
1403 |
|
} |
1404 |
|
} |
1405 |
|
|
1406 |
< |
long c; // adjust ctl counts |
1406 |
> |
long c; // adjust ctl counts |
1407 |
|
do {} while (!U.compareAndSwapLong |
1408 |
|
(this, CTL, c = ctl, (((c - AC_UNIT) & AC_MASK) | |
1409 |
|
((c - TC_UNIT) & TC_MASK) | |
1410 |
|
(c & ~(AC_MASK|TC_MASK))))); |
1411 |
|
|
1412 |
< |
if (!tryTerminate(false, false) && w != null) { |
1413 |
< |
w.cancelAll(); // cancel remaining tasks |
1414 |
< |
if (w.array != null) // suppress signal if never ran |
1415 |
< |
signalWork(); // wake up or create replacement |
1416 |
< |
if (ex == null) // help clean refs on way out |
1417 |
< |
ForkJoinTask.helpExpungeStaleExceptions(); |
1412 |
> |
if (!tryTerminate(false, false) && w != null && w.array != null) { |
1413 |
> |
w.cancelAll(); // cancel remaining tasks |
1414 |
> |
WorkQueue[] ws; WorkQueue v; Thread p; int u, i, e; |
1415 |
> |
while ((u = (int)((c = ctl) >>> 32)) < 0 && (e = (int)c) >= 0) { |
1416 |
> |
if (e > 0) { // activate or create replacement |
1417 |
> |
if ((ws = workQueues) == null || |
1418 |
> |
(i = e & SMASK) >= ws.length || |
1419 |
> |
(v = ws[i]) == null) |
1420 |
> |
break; |
1421 |
> |
long nc = (((long)(v.nextWait & E_MASK)) | |
1422 |
> |
((long)(u + UAC_UNIT) << 32)); |
1423 |
> |
if (v.eventCount != (e | INT_SIGN)) |
1424 |
> |
break; |
1425 |
> |
if (U.compareAndSwapLong(this, CTL, c, nc)) { |
1426 |
> |
v.eventCount = (e + E_SEQ) & E_MASK; |
1427 |
> |
if ((p = v.parker) != null) |
1428 |
> |
U.unpark(p); |
1429 |
> |
break; |
1430 |
> |
} |
1431 |
> |
} |
1432 |
> |
else { |
1433 |
> |
if ((short)u < 0) |
1434 |
> |
tryAddWorker(); |
1435 |
> |
break; |
1436 |
> |
} |
1437 |
> |
} |
1438 |
|
} |
1439 |
< |
|
1440 |
< |
if (ex != null) // rethrow |
1441 |
< |
U.throwException(ex); |
1439 |
> |
if (ex == null) // help clean refs on way out |
1440 |
> |
ForkJoinTask.helpExpungeStaleExceptions(); |
1441 |
> |
else // rethrow |
1442 |
> |
ForkJoinTask.rethrow(ex); |
1443 |
|
} |
1444 |
|
|
1445 |
|
// Submissions |
1446 |
|
|
1447 |
|
/** |
1448 |
+ |
* Per-thread records for threads that submit to pools. Currently |
1449 |
+ |
* holds only pseudo-random seed / index that is used to choose |
1450 |
+ |
* submission queues in method externalPush. In the future, this may |
1451 |
+ |
* also incorporate a means to implement different task rejection |
1452 |
+ |
* and resubmission policies. |
1453 |
+ |
* |
1454 |
+ |
* Seeds for submitters and workers/workQueues work in basically |
1455 |
+ |
* the same way but are initialized and updated using slightly |
1456 |
+ |
* different mechanics. Both are initialized using the same |
1457 |
+ |
* approach as in class ThreadLocal, where successive values are |
1458 |
+ |
* unlikely to collide with previous values. Seeds are then |
1459 |
+ |
* randomly modified upon collisions using xorshifts, which |
1460 |
+ |
* requires a non-zero seed. |
1461 |
+ |
*/ |
1462 |
+ |
static final class Submitter { |
1463 |
+ |
int seed; |
1464 |
+ |
Submitter(int s) { seed = s; } |
1465 |
+ |
} |
1466 |
+ |
|
1467 |
+ |
/** |
1468 |
|
* Unless shutting down, adds the given task to a submission queue |
1469 |
|
* at submitter's current queue index (modulo submission |
1470 |
< |
* range). If no queue exists at the index, one is created. If |
1471 |
< |
* the queue is busy, another index is randomly chosen. The |
1420 |
< |
* submitMask bounds the effective number of queues to the |
1421 |
< |
* (nearest power of two for) parallelism level. |
1470 |
> |
* range). Only the most common path is directly handled in this |
1471 |
> |
* method. All others are relayed to fullExternalPush. |
1472 |
|
* |
1473 |
|
* @param task the task. Caller must ensure non-null. |
1474 |
|
*/ |
1475 |
< |
private void doSubmit(ForkJoinTask<?> task) { |
1476 |
< |
Submitter s = submitters.get(); |
1477 |
< |
for (int r = s.seed, m = submitMask;;) { |
1478 |
< |
WorkQueue[] ws; WorkQueue q; |
1479 |
< |
int k = r & m & SQMASK; // use only even indices |
1480 |
< |
if (runState < 0 || (ws = workQueues) == null || ws.length <= k) |
1481 |
< |
throw new RejectedExecutionException(); // shutting down |
1482 |
< |
else if ((q = ws[k]) == null) { // create new queue |
1483 |
< |
WorkQueue nq = new WorkQueue(this, null, SHARED_QUEUE); |
1484 |
< |
Mutex lock = this.lock; // construct outside lock |
1485 |
< |
lock.lock(); |
1486 |
< |
try { // recheck under lock |
1487 |
< |
int rs = runState; // to update seq |
1488 |
< |
if (ws == workQueues && ws[k] == null) { |
1489 |
< |
ws[k] = nq; |
1490 |
< |
runState = ((rs & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN)); |
1441 |
< |
} |
1442 |
< |
} finally { |
1443 |
< |
lock.unlock(); |
1444 |
< |
} |
1445 |
< |
} |
1446 |
< |
else if (q.trySharedPush(task)) { |
1447 |
< |
signalWork(); |
1475 |
> |
final void externalPush(ForkJoinTask<?> task) { |
1476 |
> |
Submitter z = submitters.get(); |
1477 |
> |
WorkQueue q; int r, m, s, n, am; ForkJoinTask<?>[] a; |
1478 |
> |
int ps = plock; |
1479 |
> |
WorkQueue[] ws = workQueues; |
1480 |
> |
if (z != null && ps > 0 && ws != null && (m = (ws.length - 1)) >= 0 && |
1481 |
> |
(q = ws[m & (r = z.seed) & SQMASK]) != null && r != 0 && |
1482 |
> |
U.compareAndSwapInt(q, QLOCK, 0, 1)) { // lock |
1483 |
> |
if ((a = q.array) != null && |
1484 |
> |
(am = a.length - 1) > (n = (s = q.top) - q.base)) { |
1485 |
> |
int j = ((am & s) << ASHIFT) + ABASE; |
1486 |
> |
U.putOrderedObject(a, j, task); |
1487 |
> |
q.top = s + 1; // push on to deque |
1488 |
> |
q.qlock = 0; |
1489 |
> |
if (n <= 1) |
1490 |
> |
signalWork(ws, q); |
1491 |
|
return; |
1492 |
|
} |
1493 |
< |
else if (m > 1) { // move to a different index |
1451 |
< |
r ^= r << 13; // same xorshift as WorkQueues |
1452 |
< |
r ^= r >>> 17; |
1453 |
< |
s.seed = r ^= r << 5; |
1454 |
< |
} |
1455 |
< |
else |
1456 |
< |
Thread.yield(); // yield if no alternatives |
1493 |
> |
q.qlock = 0; |
1494 |
|
} |
1495 |
+ |
fullExternalPush(task); |
1496 |
|
} |
1497 |
|
|
1498 |
|
/** |
1499 |
< |
* Submits the given (non-null) task to the common pool, if possible. |
1500 |
< |
*/ |
1501 |
< |
static void submitToCommonPool(ForkJoinTask<?> task) { |
1502 |
< |
ForkJoinPool p; |
1503 |
< |
if ((p = commonPool) == null) |
1504 |
< |
p = ensureCommonPool(); |
1505 |
< |
p.doSubmit(task); |
1506 |
< |
} |
1507 |
< |
|
1508 |
< |
/** |
1509 |
< |
* Returns true if the given task was submitted to common pool |
1510 |
< |
* and has not yet commenced execution, and is available for |
1511 |
< |
* removal according to execution policies; if so removing the |
1512 |
< |
* submission from the pool. |
1513 |
< |
* |
1514 |
< |
* @param task the task |
1515 |
< |
* @return true if successful |
1516 |
< |
*/ |
1517 |
< |
static boolean tryUnsubmitFromCommonPool(ForkJoinTask<?> task) { |
1518 |
< |
ForkJoinPool p; WorkQueue[] ws; WorkQueue q; |
1519 |
< |
int k = submitters.get().seed & SQMASK; |
1520 |
< |
return ((p = commonPool) != null && |
1521 |
< |
(ws = p.workQueues) != null && |
1522 |
< |
ws.length > (k &= p.submitMask) && |
1523 |
< |
(q = ws[k]) != null && |
1524 |
< |
q.trySharedUnpush(task, p)); |
1499 |
> |
* Full version of externalPush. This method is called, among |
1500 |
> |
* other times, upon the first submission of the first task to the |
1501 |
> |
* pool, so must perform secondary initialization. It also |
1502 |
> |
* detects first submission by an external thread by looking up |
1503 |
> |
* its ThreadLocal, and creates a new shared queue if the one at |
1504 |
> |
* index if empty or contended. The plock lock body must be |
1505 |
> |
* exception-free (so no try/finally) so we optimistically |
1506 |
> |
* allocate new queues outside the lock and throw them away if |
1507 |
> |
* (very rarely) not needed. |
1508 |
> |
* |
1509 |
> |
* Secondary initialization occurs when plock is zero, to create |
1510 |
> |
* workQueue array and set plock to a valid value. This lock body |
1511 |
> |
* must also be exception-free. Because the plock seq value can |
1512 |
> |
* eventually wrap around zero, this method harmlessly fails to |
1513 |
> |
* reinitialize if workQueues exists, while still advancing plock. |
1514 |
> |
*/ |
1515 |
> |
private void fullExternalPush(ForkJoinTask<?> task) { |
1516 |
> |
int r = 0; // random index seed |
1517 |
> |
for (Submitter z = submitters.get();;) { |
1518 |
> |
WorkQueue[] ws; WorkQueue q; int ps, m, k; |
1519 |
> |
if (z == null) { |
1520 |
> |
if (U.compareAndSwapInt(this, INDEXSEED, r = indexSeed, |
1521 |
> |
r += SEED_INCREMENT) && r != 0) |
1522 |
> |
submitters.set(z = new Submitter(r)); |
1523 |
> |
} |
1524 |
> |
else if (r == 0) { // move to a different index |
1525 |
> |
r = z.seed; |
1526 |
> |
r ^= r << 13; // same xorshift as WorkQueues |
1527 |
> |
r ^= r >>> 17; |
1528 |
> |
z.seed = r ^= (r << 5); |
1529 |
> |
} |
1530 |
> |
if ((ps = plock) < 0) |
1531 |
> |
throw new RejectedExecutionException(); |
1532 |
> |
else if (ps == 0 || (ws = workQueues) == null || |
1533 |
> |
(m = ws.length - 1) < 0) { // initialize workQueues |
1534 |
> |
int p = parallelism; // find power of two table size |
1535 |
> |
int n = (p > 1) ? p - 1 : 1; // ensure at least 2 slots |
1536 |
> |
n |= n >>> 1; |
1537 |
> |
n |= n >>> 2; |
1538 |
> |
n |= n >>> 4; |
1539 |
> |
n |= n >>> 8; |
1540 |
> |
n |= n >>> 16; |
1541 |
> |
n = (n + 1) << 1; |
1542 |
> |
WorkQueue[] nws = ((ws = workQueues) == null || ws.length == 0 ? |
1543 |
> |
new WorkQueue[n] : null); |
1544 |
> |
if (((ps = plock) & PL_LOCK) != 0 || |
1545 |
> |
!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK)) |
1546 |
> |
ps = acquirePlock(); |
1547 |
> |
if (((ws = workQueues) == null || ws.length == 0) && nws != null) |
1548 |
> |
workQueues = nws; |
1549 |
> |
int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN); |
1550 |
> |
if (!U.compareAndSwapInt(this, PLOCK, ps, nps)) |
1551 |
> |
releasePlock(nps); |
1552 |
> |
} |
1553 |
> |
else if ((q = ws[k = r & m & SQMASK]) != null) { |
1554 |
> |
if (q.qlock == 0 && U.compareAndSwapInt(q, QLOCK, 0, 1)) { |
1555 |
> |
ForkJoinTask<?>[] a = q.array; |
1556 |
> |
int s = q.top; |
1557 |
> |
boolean submitted = false; |
1558 |
> |
try { // locked version of push |
1559 |
> |
if ((a != null && a.length > s + 1 - q.base) || |
1560 |
> |
(a = q.growArray()) != null) { // must presize |
1561 |
> |
int j = (((a.length - 1) & s) << ASHIFT) + ABASE; |
1562 |
> |
U.putOrderedObject(a, j, task); |
1563 |
> |
q.top = s + 1; |
1564 |
> |
submitted = true; |
1565 |
> |
} |
1566 |
> |
} finally { |
1567 |
> |
q.qlock = 0; // unlock |
1568 |
> |
} |
1569 |
> |
if (submitted) { |
1570 |
> |
signalWork(ws, q); |
1571 |
> |
return; |
1572 |
> |
} |
1573 |
> |
} |
1574 |
> |
r = 0; // move on failure |
1575 |
> |
} |
1576 |
> |
else if (((ps = plock) & PL_LOCK) == 0) { // create new queue |
1577 |
> |
q = new WorkQueue(this, null, SHARED_QUEUE, r); |
1578 |
> |
q.poolIndex = (short)k; |
1579 |
> |
if (((ps = plock) & PL_LOCK) != 0 || |
1580 |
> |
!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK)) |
1581 |
> |
ps = acquirePlock(); |
1582 |
> |
if ((ws = workQueues) != null && k < ws.length && ws[k] == null) |
1583 |
> |
ws[k] = q; |
1584 |
> |
int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN); |
1585 |
> |
if (!U.compareAndSwapInt(this, PLOCK, ps, nps)) |
1586 |
> |
releasePlock(nps); |
1587 |
> |
} |
1588 |
> |
else |
1589 |
> |
r = 0; |
1590 |
> |
} |
1591 |
|
} |
1592 |
|
|
1593 |
|
// Maintaining ctl counts |
1597 |
|
*/ |
1598 |
|
final void incrementActiveCount() { |
1599 |
|
long c; |
1600 |
< |
do {} while (!U.compareAndSwapLong(this, CTL, c = ctl, c + AC_UNIT)); |
1600 |
> |
do {} while (!U.compareAndSwapLong |
1601 |
> |
(this, CTL, c = ctl, ((c & ~AC_MASK) | |
1602 |
> |
((c & AC_MASK) + AC_UNIT)))); |
1603 |
|
} |
1604 |
|
|
1605 |
|
/** |
1606 |
< |
* Tries to create one or activate one or more workers if too few are active. |
1606 |
> |
* Tries to create or activate a worker if too few are active. |
1607 |
> |
* |
1608 |
> |
* @param ws the worker array to use to find signallees |
1609 |
> |
* @param q if non-null, the queue holding tasks to be processed |
1610 |
|
*/ |
1611 |
< |
final void signalWork() { |
1612 |
< |
long c; int u; |
1613 |
< |
while ((u = (int)((c = ctl) >>> 32)) < 0) { // too few active |
1614 |
< |
WorkQueue[] ws = workQueues; int e, i; WorkQueue w; Thread p; |
1615 |
< |
if ((e = (int)c) > 0) { // at least one waiting |
1616 |
< |
if (ws != null && (i = e & SMASK) < ws.length && |
1617 |
< |
(w = ws[i]) != null && w.eventCount == (e | INT_SIGN)) { |
1618 |
< |
long nc = (((long)(w.nextWait & E_MASK)) | |
1619 |
< |
((long)(u + UAC_UNIT) << 32)); |
1511 |
< |
if (U.compareAndSwapLong(this, CTL, c, nc)) { |
1512 |
< |
w.eventCount = (e + E_SEQ) & E_MASK; |
1513 |
< |
if ((p = w.parker) != null) |
1514 |
< |
U.unpark(p); // activate and release |
1515 |
< |
break; |
1516 |
< |
} |
1517 |
< |
} |
1518 |
< |
else |
1519 |
< |
break; |
1611 |
> |
final void signalWork(WorkQueue[] ws, WorkQueue q) { |
1612 |
> |
for (;;) { |
1613 |
> |
long c; int e, u, i; WorkQueue w; Thread p; |
1614 |
> |
if ((u = (int)((c = ctl) >>> 32)) >= 0) |
1615 |
> |
break; |
1616 |
> |
if ((e = (int)c) <= 0) { |
1617 |
> |
if ((short)u < 0) |
1618 |
> |
tryAddWorker(); |
1619 |
> |
break; |
1620 |
|
} |
1621 |
< |
else if (e == 0 && (u & SHORT_SIGN) != 0) { // too few total |
1622 |
< |
long nc = (long)(((u + UTC_UNIT) & UTC_MASK) | |
1623 |
< |
((u + UAC_UNIT) & UAC_MASK)) << 32; |
1624 |
< |
if (U.compareAndSwapLong(this, CTL, c, nc)) { |
1625 |
< |
addWorker(); |
1626 |
< |
break; |
1627 |
< |
} |
1621 |
> |
if (ws == null || ws.length <= (i = e & SMASK) || |
1622 |
> |
(w = ws[i]) == null) |
1623 |
> |
break; |
1624 |
> |
long nc = (((long)(w.nextWait & E_MASK)) | |
1625 |
> |
((long)(u + UAC_UNIT)) << 32); |
1626 |
> |
int ne = (e + E_SEQ) & E_MASK; |
1627 |
> |
if (w.eventCount == (e | INT_SIGN) && |
1628 |
> |
U.compareAndSwapLong(this, CTL, c, nc)) { |
1629 |
> |
w.eventCount = ne; |
1630 |
> |
if ((p = w.parker) != null) |
1631 |
> |
U.unpark(p); |
1632 |
> |
break; |
1633 |
|
} |
1634 |
< |
else |
1634 |
> |
if (q != null && q.base >= q.top) |
1635 |
|
break; |
1636 |
|
} |
1637 |
|
} |
1642 |
|
* Top-level runloop for workers, called by ForkJoinWorkerThread.run. |
1643 |
|
*/ |
1644 |
|
final void runWorker(WorkQueue w) { |
1645 |
< |
w.growArray(false); // initialize queue array in this thread |
1646 |
< |
do { w.runTask(scan(w)); } while (w.runState >= 0); |
1645 |
> |
w.growArray(); // allocate queue |
1646 |
> |
for (int r = w.hint; scan(w, r) == 0; ) { |
1647 |
> |
r ^= r << 13; r ^= r >>> 17; r ^= r << 5; // xorshift |
1648 |
> |
} |
1649 |
|
} |
1650 |
|
|
1651 |
|
/** |
1652 |
< |
* Scans for and, if found, returns one task, else possibly |
1652 |
> |
* Scans for and, if found, runs one task, else possibly |
1653 |
|
* inactivates the worker. This method operates on single reads of |
1654 |
|
* volatile state and is designed to be re-invoked continuously, |
1655 |
|
* in part because it returns upon detecting inconsistencies, |
1656 |
|
* contention, or state changes that indicate possible success on |
1657 |
|
* re-invocation. |
1658 |
|
* |
1659 |
< |
* The scan searches for tasks across a random permutation of |
1660 |
< |
* queues (starting at a random index and stepping by a random |
1661 |
< |
* relative prime, checking each at least once). The scan |
1662 |
< |
* terminates upon either finding a non-empty queue, or completing |
1663 |
< |
* the sweep. If the worker is not inactivated, it takes and |
1664 |
< |
* returns a task from this queue. On failure to find a task, we |
1665 |
< |
* take one of the following actions, after which the caller will |
1666 |
< |
* retry calling this method unless terminated. |
1667 |
< |
* |
1561 |
< |
* * If pool is terminating, terminate the worker. |
1562 |
< |
* |
1563 |
< |
* * If not a complete sweep, try to release a waiting worker. If |
1564 |
< |
* the scan terminated because the worker is inactivated, then the |
1565 |
< |
* released worker will often be the calling worker, and it can |
1566 |
< |
* succeed obtaining a task on the next call. Or maybe it is |
1567 |
< |
* another worker, but with same net effect. Releasing in other |
1568 |
< |
* cases as well ensures that we have enough workers running. |
1569 |
< |
* |
1570 |
< |
* * If not already enqueued, try to inactivate and enqueue the |
1571 |
< |
* worker on wait queue. Or, if inactivating has caused the pool |
1572 |
< |
* to be quiescent, relay to idleAwaitWork to check for |
1573 |
< |
* termination and possibly shrink pool. |
1574 |
< |
* |
1575 |
< |
* * If already inactive, and the caller has run a task since the |
1576 |
< |
* last empty scan, return (to allow rescan) unless others are |
1577 |
< |
* also inactivated. Field WorkQueue.rescans counts down on each |
1578 |
< |
* scan to ensure eventual inactivation and blocking. |
1579 |
< |
* |
1580 |
< |
* * If already enqueued and none of the above apply, park |
1581 |
< |
* awaiting signal, |
1659 |
> |
* The scan searches for tasks across queues starting at a random |
1660 |
> |
* index, checking each at least twice. The scan terminates upon |
1661 |
> |
* either finding a non-empty queue, or completing the sweep. If |
1662 |
> |
* the worker is not inactivated, it takes and runs a task from |
1663 |
> |
* this queue. Otherwise, if not activated, it tries to activate |
1664 |
> |
* itself or some other worker by signalling. On failure to find a |
1665 |
> |
* task, returns (for retry) if pool state may have changed during |
1666 |
> |
* an empty scan, or tries to inactivate if active, else possibly |
1667 |
> |
* blocks or terminates via method awaitWork. |
1668 |
|
* |
1669 |
|
* @param w the worker (via its WorkQueue) |
1670 |
< |
* @return a task or null if none found |
1670 |
> |
* @param r a random seed |
1671 |
> |
* @return worker qlock status if would have waited, else 0 |
1672 |
|
*/ |
1673 |
< |
private final ForkJoinTask<?> scan(WorkQueue w) { |
1674 |
< |
WorkQueue[] ws; // first update random seed |
1675 |
< |
int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5; |
1676 |
< |
int rs = runState, m; // volatile read order matters |
1677 |
< |
if ((ws = workQueues) != null && (m = ws.length - 1) > 0) { |
1678 |
< |
int ec = w.eventCount; // ec is negative if inactive |
1679 |
< |
int step = (r >>> 16) | 1; // relative prime |
1680 |
< |
for (int j = (m + 1) << 2; ; r += step) { |
1681 |
< |
WorkQueue q; ForkJoinTask<?> t; ForkJoinTask<?>[] a; int b; |
1682 |
< |
if ((q = ws[r & m]) != null && (b = q.base) - q.top < 0 && |
1683 |
< |
(a = q.array) != null) { // probably nonempty |
1684 |
< |
int i = (((a.length - 1) & b) << ASHIFT) + ABASE; |
1685 |
< |
t = (ForkJoinTask<?>)U.getObjectVolatile(a, i); |
1686 |
< |
if (q.base == b && ec >= 0 && t != null && |
1687 |
< |
U.compareAndSwapObject(a, i, t, null)) { |
1688 |
< |
if (q.top - (q.base = b + 1) > 0) |
1689 |
< |
signalWork(); // help pushes signal |
1690 |
< |
return t; |
1691 |
< |
} |
1692 |
< |
else if (ec < 0 || j <= m) { |
1606 |
< |
rs = 0; // mark scan as imcomplete |
1607 |
< |
break; // caller can retry after release |
1673 |
> |
private final int scan(WorkQueue w, int r) { |
1674 |
> |
WorkQueue[] ws; int m; |
1675 |
> |
long c = ctl; // for consistency check |
1676 |
> |
if ((ws = workQueues) != null && (m = ws.length - 1) >= 0 && w != null) { |
1677 |
> |
for (int j = m + m + 1, ec = w.eventCount;;) { |
1678 |
> |
WorkQueue q; int b, e; ForkJoinTask<?>[] a; ForkJoinTask<?> t; |
1679 |
> |
if ((q = ws[(r - j) & m]) != null && |
1680 |
> |
(b = q.base) - q.top < 0 && (a = q.array) != null) { |
1681 |
> |
long i = (((a.length - 1) & b) << ASHIFT) + ABASE; |
1682 |
> |
if ((t = ((ForkJoinTask<?>) |
1683 |
> |
U.getObjectVolatile(a, i))) != null) { |
1684 |
> |
if (ec < 0) |
1685 |
> |
helpRelease(c, ws, w, q, b); |
1686 |
> |
else if (q.base == b && |
1687 |
> |
U.compareAndSwapObject(a, i, t, null)) { |
1688 |
> |
U.putOrderedInt(q, QBASE, b + 1); |
1689 |
> |
if ((b + 1) - q.top < 0) |
1690 |
> |
signalWork(ws, q); |
1691 |
> |
w.runTask(t); |
1692 |
> |
} |
1693 |
|
} |
1694 |
+ |
break; |
1695 |
|
} |
1696 |
< |
if (--j < 0) |
1696 |
> |
else if (--j < 0) { |
1697 |
> |
if ((ec | (e = (int)c)) < 0) // inactive or terminating |
1698 |
> |
return awaitWork(w, c, ec); |
1699 |
> |
else if (ctl == c) { // try to inactivate and enqueue |
1700 |
> |
long nc = (long)ec | ((c - AC_UNIT) & (AC_MASK|TC_MASK)); |
1701 |
> |
w.nextWait = e; |
1702 |
> |
w.eventCount = ec | INT_SIGN; |
1703 |
> |
if (!U.compareAndSwapLong(this, CTL, c, nc)) |
1704 |
> |
w.eventCount = ec; // back out |
1705 |
> |
} |
1706 |
|
break; |
1707 |
+ |
} |
1708 |
|
} |
1709 |
+ |
} |
1710 |
+ |
return 0; |
1711 |
+ |
} |
1712 |
|
|
1713 |
< |
long c = ctl; int e = (int)c, a = (int)(c >> AC_SHIFT), nr, ns; |
1714 |
< |
if (e < 0) // decode ctl on empty scan |
1715 |
< |
w.runState = -1; // pool is terminating |
1716 |
< |
else if (rs == 0 || rs != runState) { // incomplete scan |
1717 |
< |
WorkQueue v; Thread p; // try to release a waiter |
1718 |
< |
if (e > 0 && a < 0 && w.eventCount == ec && |
1719 |
< |
(v = ws[e & m]) != null && v.eventCount == (e | INT_SIGN)) { |
1720 |
< |
long nc = ((long)(v.nextWait & E_MASK) | |
1721 |
< |
((c + AC_UNIT) & (AC_MASK|TC_MASK))); |
1722 |
< |
if (ctl == c && U.compareAndSwapLong(this, CTL, c, nc)) { |
1723 |
< |
v.eventCount = (e + E_SEQ) & E_MASK; |
1724 |
< |
if ((p = v.parker) != null) |
1725 |
< |
U.unpark(p); |
1726 |
< |
} |
1727 |
< |
} |
1713 |
> |
/** |
1714 |
> |
* A continuation of scan(), possibly blocking or terminating |
1715 |
> |
* worker w. Returns without blocking if pool state has apparently |
1716 |
> |
* changed since last invocation. Also, if inactivating w has |
1717 |
> |
* caused the pool to become quiescent, checks for pool |
1718 |
> |
* termination, and, so long as this is not the only worker, waits |
1719 |
> |
* for event for up to a given duration. On timeout, if ctl has |
1720 |
> |
* not changed, terminates the worker, which will in turn wake up |
1721 |
> |
* another worker to possibly repeat this process. |
1722 |
> |
* |
1723 |
> |
* @param w the calling worker |
1724 |
> |
* @param c the ctl value on entry to scan |
1725 |
> |
* @param ec the worker's eventCount on entry to scan |
1726 |
> |
*/ |
1727 |
> |
private final int awaitWork(WorkQueue w, long c, int ec) { |
1728 |
> |
int stat, ns; long parkTime, deadline; |
1729 |
> |
if ((stat = w.qlock) >= 0 && w.eventCount == ec && ctl == c && |
1730 |
> |
!Thread.interrupted()) { |
1731 |
> |
int e = (int)c; |
1732 |
> |
int u = (int)(c >>> 32); |
1733 |
> |
int d = (u >> UAC_SHIFT) + parallelism; // active count |
1734 |
> |
|
1735 |
> |
if (e < 0 || (d <= 0 && tryTerminate(false, false))) |
1736 |
> |
stat = w.qlock = -1; // pool is terminating |
1737 |
> |
else if ((ns = w.nsteals) != 0) { // collect steals and retry |
1738 |
> |
long sc; |
1739 |
> |
w.nsteals = 0; |
1740 |
> |
do {} while (!U.compareAndSwapLong(this, STEALCOUNT, |
1741 |
> |
sc = stealCount, sc + ns)); |
1742 |
|
} |
1743 |
< |
else if (ec >= 0) { // try to enqueue/inactivate |
1744 |
< |
long nc = (long)ec | ((c - AC_UNIT) & (AC_MASK|TC_MASK)); |
1745 |
< |
w.nextWait = e; |
1746 |
< |
w.eventCount = ec | INT_SIGN; // mark as inactive |
1747 |
< |
if (ctl != c || !U.compareAndSwapLong(this, CTL, c, nc)) |
1748 |
< |
w.eventCount = ec; // unmark on CAS failure |
1749 |
< |
else { |
1750 |
< |
if ((ns = w.nsteals) != 0) { |
1751 |
< |
w.nsteals = 0; // set rescans if ran task |
1639 |
< |
w.rescans = (a > 0) ? 0 : a + parallelism; |
1640 |
< |
w.totalSteals += ns; |
1641 |
< |
} |
1642 |
< |
if (a == 1 - parallelism) // quiescent |
1643 |
< |
idleAwaitWork(w, nc, c); |
1743 |
> |
else { |
1744 |
> |
long pc = ((d > 0 || ec != (e | INT_SIGN)) ? 0L : |
1745 |
> |
((long)(w.nextWait & E_MASK)) | // ctl to restore |
1746 |
> |
((long)(u + UAC_UNIT)) << 32); |
1747 |
> |
if (pc != 0L) { // timed wait if last waiter |
1748 |
> |
int dc = -(short)(c >>> TC_SHIFT); |
1749 |
> |
parkTime = (dc < 0 ? FAST_IDLE_TIMEOUT: |
1750 |
> |
(dc + 1) * IDLE_TIMEOUT); |
1751 |
> |
deadline = System.nanoTime() + parkTime - TIMEOUT_SLOP; |
1752 |
|
} |
1753 |
< |
} |
1754 |
< |
else if (w.eventCount < 0) { // already queued |
1755 |
< |
int ac = a + parallelism; |
1648 |
< |
if ((nr = w.rescans) > 0) // continue rescanning |
1649 |
< |
w.rescans = (ac < nr) ? ac : nr - 1; |
1650 |
< |
else if (((w.seed >>> 16) & ac) == 0) { // randomize park |
1651 |
< |
Thread.interrupted(); // clear status |
1753 |
> |
else |
1754 |
> |
parkTime = deadline = 0L; |
1755 |
> |
if (w.eventCount == ec && ctl == c) { |
1756 |
|
Thread wt = Thread.currentThread(); |
1757 |
|
U.putObject(wt, PARKBLOCKER, this); |
1758 |
|
w.parker = wt; // emulate LockSupport.park |
1759 |
< |
if (w.eventCount < 0) // recheck |
1760 |
< |
U.park(false, 0L); |
1759 |
> |
if (w.eventCount == ec && ctl == c) |
1760 |
> |
U.park(false, parkTime); // must recheck before park |
1761 |
|
w.parker = null; |
1762 |
|
U.putObject(wt, PARKBLOCKER, null); |
1763 |
+ |
if (parkTime != 0L && ctl == c && |
1764 |
+ |
deadline - System.nanoTime() <= 0L && |
1765 |
+ |
U.compareAndSwapLong(this, CTL, c, pc)) |
1766 |
+ |
stat = w.qlock = -1; // shrink pool |
1767 |
|
} |
1768 |
|
} |
1769 |
|
} |
1770 |
< |
return null; |
1770 |
> |
return stat; |
1771 |
|
} |
1772 |
|
|
1773 |
|
/** |
1774 |
< |
* If inactivating worker w has caused the pool to become |
1775 |
< |
* quiescent, checks for pool termination, and, so long as this is |
1776 |
< |
* not the only worker, waits for event for up to a given |
1777 |
< |
* duration. On timeout, if ctl has not changed, terminates the |
1778 |
< |
* worker, which will in turn wake up another worker to possibly |
1779 |
< |
* repeat this process. |
1780 |
< |
* |
1781 |
< |
* @param w the calling worker |
1782 |
< |
* @param currentCtl the ctl value triggering possible quiescence |
1783 |
< |
* @param prevCtl the ctl value to restore if thread is terminated |
1784 |
< |
*/ |
1785 |
< |
private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) { |
1786 |
< |
if (w.eventCount < 0 && !tryTerminate(false, false) && |
1787 |
< |
(int)prevCtl != 0 && !hasQueuedSubmissions() && ctl == currentCtl) { |
1788 |
< |
int dc = -(short)(currentCtl >>> TC_SHIFT); |
1789 |
< |
long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT; |
1790 |
< |
long deadline = System.nanoTime() + parkTime - 100000L; // 1ms slop |
1791 |
< |
Thread wt = Thread.currentThread(); |
1792 |
< |
while (ctl == currentCtl) { |
1793 |
< |
Thread.interrupted(); // timed variant of version in scan() |
1686 |
< |
U.putObject(wt, PARKBLOCKER, this); |
1687 |
< |
w.parker = wt; |
1688 |
< |
if (ctl == currentCtl) |
1689 |
< |
U.park(false, parkTime); |
1690 |
< |
w.parker = null; |
1691 |
< |
U.putObject(wt, PARKBLOCKER, null); |
1692 |
< |
if (ctl != currentCtl) |
1693 |
< |
break; |
1694 |
< |
if (deadline - System.nanoTime() <= 0L && |
1695 |
< |
U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) { |
1696 |
< |
w.eventCount = (w.eventCount + E_SEQ) | E_MASK; |
1697 |
< |
w.runState = -1; // shrink |
1698 |
< |
break; |
1699 |
< |
} |
1774 |
> |
* Possibly releases (signals) a worker. Called only from scan() |
1775 |
> |
* when a worker with apparently inactive status finds a non-empty |
1776 |
> |
* queue. This requires revalidating all of the associated state |
1777 |
> |
* from caller. |
1778 |
> |
*/ |
1779 |
> |
private final void helpRelease(long c, WorkQueue[] ws, WorkQueue w, |
1780 |
> |
WorkQueue q, int b) { |
1781 |
> |
WorkQueue v; int e, i; Thread p; |
1782 |
> |
if (w != null && w.eventCount < 0 && (e = (int)c) > 0 && |
1783 |
> |
ws != null && ws.length > (i = e & SMASK) && |
1784 |
> |
(v = ws[i]) != null && ctl == c) { |
1785 |
> |
long nc = (((long)(v.nextWait & E_MASK)) | |
1786 |
> |
((long)((int)(c >>> 32) + UAC_UNIT)) << 32); |
1787 |
> |
int ne = (e + E_SEQ) & E_MASK; |
1788 |
> |
if (q != null && q.base == b && w.eventCount < 0 && |
1789 |
> |
v.eventCount == (e | INT_SIGN) && |
1790 |
> |
U.compareAndSwapLong(this, CTL, c, nc)) { |
1791 |
> |
v.eventCount = ne; |
1792 |
> |
if ((p = v.parker) != null) |
1793 |
> |
U.unpark(p); |
1794 |
|
} |
1795 |
|
} |
1796 |
|
} |
1815 |
|
*/ |
1816 |
|
private int tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) { |
1817 |
|
int stat = 0, steps = 0; // bound to avoid cycles |
1818 |
< |
if (joiner != null && task != null) { // hoist null checks |
1818 |
> |
if (task != null && joiner != null && |
1819 |
> |
joiner.base - joiner.top >= 0) { // hoist checks |
1820 |
|
restart: for (;;) { |
1821 |
|
ForkJoinTask<?> subtask = task; // current target |
1822 |
|
for (WorkQueue j = joiner, v;;) { // v is stealer of subtask |
1827 |
|
} |
1828 |
|
if ((ws = workQueues) == null || (m = ws.length - 1) <= 0) |
1829 |
|
break restart; // shutting down |
1830 |
< |
if ((v = ws[h = (j.stealHint | 1) & m]) == null || |
1830 |
> |
if ((v = ws[h = (j.hint | 1) & m]) == null || |
1831 |
|
v.currentSteal != subtask) { |
1832 |
|
for (int origin = h;;) { // find stealer |
1833 |
|
if (((h = (h + 2) & m) & 15) == 1 && |
1835 |
|
continue restart; // occasional staleness check |
1836 |
|
if ((v = ws[h]) != null && |
1837 |
|
v.currentSteal == subtask) { |
1838 |
< |
j.stealHint = h; // save hint |
1838 |
> |
j.hint = h; // save hint |
1839 |
|
break; |
1840 |
|
} |
1841 |
|
if (h == origin) |
1843 |
|
} |
1844 |
|
} |
1845 |
|
for (;;) { // help stealer or descend to its stealer |
1846 |
< |
ForkJoinTask[] a; int b; |
1846 |
> |
ForkJoinTask<?>[] a; int b; |
1847 |
|
if (subtask.status < 0) // surround probes with |
1848 |
|
continue restart; // consistency checks |
1849 |
|
if ((b = v.base) - v.top < 0 && (a = v.array) != null) { |
1854 |
|
v.currentSteal != subtask) |
1855 |
|
continue restart; // stale |
1856 |
|
stat = 1; // apparent progress |
1857 |
< |
if (t != null && v.base == b && |
1858 |
< |
U.compareAndSwapObject(a, i, t, null)) { |
1859 |
< |
v.base = b + 1; // help stealer |
1860 |
< |
joiner.runSubtask(t); |
1857 |
> |
if (v.base == b) { |
1858 |
> |
if (t == null) |
1859 |
> |
break restart; |
1860 |
> |
if (U.compareAndSwapObject(a, i, t, null)) { |
1861 |
> |
U.putOrderedInt(v, QBASE, b + 1); |
1862 |
> |
ForkJoinTask<?> ps = joiner.currentSteal; |
1863 |
> |
int jt = joiner.top; |
1864 |
> |
do { |
1865 |
> |
joiner.currentSteal = t; |
1866 |
> |
t.doExec(); // clear local tasks too |
1867 |
> |
} while (task.status >= 0 && |
1868 |
> |
joiner.top != jt && |
1869 |
> |
(t = joiner.pop()) != null); |
1870 |
> |
joiner.currentSteal = ps; |
1871 |
> |
break restart; |
1872 |
> |
} |
1873 |
|
} |
1767 |
– |
else if (v.base == b && ++steps == MAX_HELP) |
1768 |
– |
break restart; // v apparently stalled |
1874 |
|
} |
1875 |
|
else { // empty -- try to descend |
1876 |
|
ForkJoinTask<?> next = v.currentJoin; |
1893 |
|
} |
1894 |
|
|
1895 |
|
/** |
1896 |
< |
* If task is at base of some steal queue, steals and executes it. |
1896 |
> |
* Analog of tryHelpStealer for CountedCompleters. Tries to steal |
1897 |
> |
* and run tasks within the target's computation. |
1898 |
|
* |
1899 |
< |
* @param joiner the joining worker |
1794 |
< |
* @param task the task |
1899 |
> |
* @param task the task to join |
1900 |
|
*/ |
1901 |
< |
private void tryPollForAndExec(WorkQueue joiner, ForkJoinTask<?> task) { |
1902 |
< |
WorkQueue[] ws; |
1903 |
< |
if ((ws = workQueues) != null) { |
1904 |
< |
for (int j = 1; j < ws.length && task.status >= 0; j += 2) { |
1905 |
< |
WorkQueue q = ws[j]; |
1906 |
< |
if (q != null && q.pollFor(task)) { |
1907 |
< |
joiner.runSubtask(task); |
1901 |
> |
private int helpComplete(WorkQueue joiner, CountedCompleter<?> task) { |
1902 |
> |
WorkQueue[] ws; int m; |
1903 |
> |
int s = 0; |
1904 |
> |
if ((ws = workQueues) != null && (m = ws.length - 1) >= 0 && |
1905 |
> |
joiner != null && task != null) { |
1906 |
> |
int j = joiner.poolIndex; |
1907 |
> |
int scans = m + m + 1; |
1908 |
> |
long c = 0L; // for stability check |
1909 |
> |
for (int k = scans; ; j += 2) { |
1910 |
> |
WorkQueue q; |
1911 |
> |
if ((s = task.status) < 0) |
1912 |
> |
break; |
1913 |
> |
else if (joiner.internalPopAndExecCC(task)) |
1914 |
> |
k = scans; |
1915 |
> |
else if ((s = task.status) < 0) |
1916 |
|
break; |
1917 |
+ |
else if ((q = ws[j & m]) != null && q.pollAndExecCC(task)) |
1918 |
+ |
k = scans; |
1919 |
+ |
else if (--k < 0) { |
1920 |
+ |
if (c == (c = ctl)) |
1921 |
+ |
break; |
1922 |
+ |
k = scans; |
1923 |
|
} |
1924 |
|
} |
1925 |
|
} |
1926 |
+ |
return s; |
1927 |
|
} |
1928 |
|
|
1929 |
|
/** |
1930 |
|
* Tries to decrement active count (sometimes implicitly) and |
1931 |
|
* possibly release or create a compensating worker in preparation |
1932 |
|
* for blocking. Fails on contention or termination. Otherwise, |
1933 |
< |
* adds a new thread if no idle workers are available and either |
1934 |
< |
* pool would become completely starved or: (at least half |
1935 |
< |
* starved, and fewer than 50% spares exist, and there is at least |
1936 |
< |
* one task apparently available). Even though the availability |
1817 |
< |
* check requires a full scan, it is worthwhile in reducing false |
1818 |
< |
* alarms. |
1819 |
< |
* |
1820 |
< |
* @param task if non-null, a task being waited for |
1821 |
< |
* @param blocker if non-null, a blocker being waited for |
1822 |
< |
* @return true if the caller can block, else should recheck and retry |
1933 |
> |
* adds a new thread if no idle workers are available and pool |
1934 |
> |
* may become starved. |
1935 |
> |
* |
1936 |
> |
* @param c the assumed ctl value |
1937 |
|
*/ |
1938 |
< |
final boolean tryCompensate(ForkJoinTask<?> task, ManagedBlocker blocker) { |
1825 |
< |
int pc = parallelism, e; |
1826 |
< |
long c = ctl; |
1938 |
> |
final boolean tryCompensate(long c) { |
1939 |
|
WorkQueue[] ws = workQueues; |
1940 |
< |
if ((e = (int)c) >= 0 && ws != null) { |
1941 |
< |
int u, a, ac, hc; |
1942 |
< |
int tc = (short)((u = (int)(c >>> 32)) >>> UTC_SHIFT) + pc; |
1943 |
< |
boolean replace = false; |
1944 |
< |
if ((a = u >> UAC_SHIFT) <= 0) { |
1945 |
< |
if ((ac = a + pc) <= 1) |
1946 |
< |
replace = true; |
1947 |
< |
else if ((e > 0 || (task != null && |
1948 |
< |
ac <= (hc = pc >>> 1) && tc < pc + hc))) { |
1949 |
< |
WorkQueue w; |
1950 |
< |
for (int j = 0; j < ws.length; ++j) { |
1951 |
< |
if ((w = ws[j]) != null && !w.isEmpty()) { |
1952 |
< |
replace = true; |
1953 |
< |
break; // in compensation range and tasks available |
1954 |
< |
} |
1955 |
< |
} |
1956 |
< |
} |
1940 |
> |
int pc = parallelism, e = (int)c, m, tc; |
1941 |
> |
if (ws != null && (m = ws.length - 1) >= 0 && e >= 0 && ctl == c) { |
1942 |
> |
WorkQueue w = ws[e & m]; |
1943 |
> |
if (e != 0 && w != null) { |
1944 |
> |
Thread p; |
1945 |
> |
long nc = ((long)(w.nextWait & E_MASK) | |
1946 |
> |
(c & (AC_MASK|TC_MASK))); |
1947 |
> |
int ne = (e + E_SEQ) & E_MASK; |
1948 |
> |
if (w.eventCount == (e | INT_SIGN) && |
1949 |
> |
U.compareAndSwapLong(this, CTL, c, nc)) { |
1950 |
> |
w.eventCount = ne; |
1951 |
> |
if ((p = w.parker) != null) |
1952 |
> |
U.unpark(p); |
1953 |
> |
return true; // replace with idle worker |
1954 |
> |
} |
1955 |
> |
} |
1956 |
> |
else if ((tc = (short)(c >>> TC_SHIFT)) >= 0 && |
1957 |
> |
(int)(c >> AC_SHIFT) + pc > 1) { |
1958 |
> |
long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK); |
1959 |
> |
if (U.compareAndSwapLong(this, CTL, c, nc)) |
1960 |
> |
return true; // no compensation |
1961 |
|
} |
1962 |
< |
if ((task == null || task.status >= 0) && // recheck need to block |
1963 |
< |
(blocker == null || !blocker.isReleasable()) && ctl == c) { |
1964 |
< |
if (!replace) { // no compensation |
1965 |
< |
long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK); |
1966 |
< |
if (U.compareAndSwapLong(this, CTL, c, nc)) |
1967 |
< |
return true; |
1968 |
< |
} |
1969 |
< |
else if (e != 0) { // release an idle worker |
1970 |
< |
WorkQueue w; Thread p; int i; |
1971 |
< |
if ((i = e & SMASK) < ws.length && (w = ws[i]) != null) { |
1856 |
< |
long nc = ((long)(w.nextWait & E_MASK) | |
1857 |
< |
(c & (AC_MASK|TC_MASK))); |
1858 |
< |
if (w.eventCount == (e | INT_SIGN) && |
1859 |
< |
U.compareAndSwapLong(this, CTL, c, nc)) { |
1860 |
< |
w.eventCount = (e + E_SEQ) & E_MASK; |
1861 |
< |
if ((p = w.parker) != null) |
1862 |
< |
U.unpark(p); |
1962 |
> |
else if (tc + pc < MAX_CAP) { |
1963 |
> |
long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK); |
1964 |
> |
if (U.compareAndSwapLong(this, CTL, c, nc)) { |
1965 |
> |
ForkJoinWorkerThreadFactory fac; |
1966 |
> |
Throwable ex = null; |
1967 |
> |
ForkJoinWorkerThread wt = null; |
1968 |
> |
try { |
1969 |
> |
if ((fac = factory) != null && |
1970 |
> |
(wt = fac.newThread(this)) != null) { |
1971 |
> |
wt.start(); |
1972 |
|
return true; |
1973 |
|
} |
1974 |
+ |
} catch (Throwable rex) { |
1975 |
+ |
ex = rex; |
1976 |
|
} |
1977 |
< |
} |
1867 |
< |
else if (tc < MAX_CAP) { // create replacement |
1868 |
< |
long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK); |
1869 |
< |
if (U.compareAndSwapLong(this, CTL, c, nc)) { |
1870 |
< |
addWorker(); |
1871 |
< |
return true; |
1872 |
< |
} |
1977 |
> |
deregisterWorker(wt, ex); // clean up and return false |
1978 |
|
} |
1979 |
|
} |
1980 |
|
} |
1989 |
|
* @return task status on exit |
1990 |
|
*/ |
1991 |
|
final int awaitJoin(WorkQueue joiner, ForkJoinTask<?> task) { |
1992 |
< |
int s; |
1993 |
< |
if ((s = task.status) >= 0) { |
1992 |
> |
int s = 0; |
1993 |
> |
if (task != null && (s = task.status) >= 0 && joiner != null) { |
1994 |
|
ForkJoinTask<?> prevJoin = joiner.currentJoin; |
1995 |
|
joiner.currentJoin = task; |
1996 |
< |
long startTime = 0L; |
1997 |
< |
for (int k = 0;;) { |
1998 |
< |
if ((s = (joiner.isEmpty() ? // try to help |
1999 |
< |
tryHelpStealer(joiner, task) : |
2000 |
< |
joiner.tryRemoveAndExec(task))) == 0 && |
1996 |
> |
do {} while (joiner.tryRemoveAndExec(task) && // process local tasks |
1997 |
> |
(s = task.status) >= 0); |
1998 |
> |
if (s >= 0 && (task instanceof CountedCompleter)) |
1999 |
> |
s = helpComplete(joiner, (CountedCompleter<?>)task); |
2000 |
> |
long cc = 0; // for stability checks |
2001 |
> |
while (s >= 0 && (s = task.status) >= 0) { |
2002 |
> |
if ((s = tryHelpStealer(joiner, task)) == 0 && |
2003 |
|
(s = task.status) >= 0) { |
2004 |
< |
if (k == 0) { |
2005 |
< |
startTime = System.nanoTime(); |
2006 |
< |
tryPollForAndExec(joiner, task); // check uncommon case |
2007 |
< |
} |
1901 |
< |
else if ((k & (MAX_HELP - 1)) == 0 && |
1902 |
< |
System.nanoTime() - startTime >= |
1903 |
< |
COMPENSATION_DELAY && |
1904 |
< |
tryCompensate(task, null)) { |
1905 |
< |
if (task.trySetSignal()) { |
2004 |
> |
if (!tryCompensate(cc)) |
2005 |
> |
cc = ctl; |
2006 |
> |
else { |
2007 |
> |
if (task.trySetSignal() && (s = task.status) >= 0) { |
2008 |
|
synchronized (task) { |
2009 |
|
if (task.status >= 0) { |
2010 |
|
try { // see ForkJoinTask |
2016 |
|
task.notifyAll(); |
2017 |
|
} |
2018 |
|
} |
2019 |
< |
long c; // re-activate |
2019 |
> |
long c; // reactivate |
2020 |
|
do {} while (!U.compareAndSwapLong |
2021 |
< |
(this, CTL, c = ctl, c + AC_UNIT)); |
2021 |
> |
(this, CTL, c = ctl, |
2022 |
> |
((c & ~AC_MASK) | |
2023 |
> |
((c & AC_MASK) + AC_UNIT)))); |
2024 |
|
} |
2025 |
|
} |
1922 |
– |
if (s < 0 || (s = task.status) < 0) { |
1923 |
– |
joiner.currentJoin = prevJoin; |
1924 |
– |
break; |
1925 |
– |
} |
1926 |
– |
else if ((k++ & (MAX_HELP - 1)) == MAX_HELP >>> 1) |
1927 |
– |
Thread.yield(); // for politeness |
2026 |
|
} |
2027 |
+ |
joiner.currentJoin = prevJoin; |
2028 |
|
} |
2029 |
|
return s; |
2030 |
|
} |
2036 |
|
* |
2037 |
|
* @param joiner the joining worker |
2038 |
|
* @param task the task |
1940 |
– |
* @return task status on exit |
2039 |
|
*/ |
2040 |
< |
final int helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) { |
2040 |
> |
final void helpJoinOnce(WorkQueue joiner, ForkJoinTask<?> task) { |
2041 |
|
int s; |
2042 |
< |
while ((s = task.status) >= 0 && |
2043 |
< |
(joiner.isEmpty() ? |
2044 |
< |
tryHelpStealer(joiner, task) : |
2045 |
< |
joiner.tryRemoveAndExec(task)) != 0) |
2046 |
< |
; |
2047 |
< |
return s; |
2042 |
> |
if (joiner != null && task != null && (s = task.status) >= 0) { |
2043 |
> |
ForkJoinTask<?> prevJoin = joiner.currentJoin; |
2044 |
> |
joiner.currentJoin = task; |
2045 |
> |
do {} while (joiner.tryRemoveAndExec(task) && // process local tasks |
2046 |
> |
(s = task.status) >= 0); |
2047 |
> |
if (s >= 0) { |
2048 |
> |
if (task instanceof CountedCompleter) |
2049 |
> |
helpComplete(joiner, (CountedCompleter<?>)task); |
2050 |
> |
do {} while (task.status >= 0 && |
2051 |
> |
tryHelpStealer(joiner, task) > 0); |
2052 |
> |
} |
2053 |
> |
joiner.currentJoin = prevJoin; |
2054 |
> |
} |
2055 |
|
} |
2056 |
|
|
2057 |
|
/** |
2058 |
|
* Returns a (probably) non-empty steal queue, if one is found |
2059 |
< |
* during a random, then cyclic scan, else null. This method must |
2060 |
< |
* be retried by caller if, by the time it tries to use the queue, |
2061 |
< |
* it is empty. |
2062 |
< |
*/ |
2063 |
< |
private WorkQueue findNonEmptyStealQueue(WorkQueue w) { |
2064 |
< |
// Similar to loop in scan(), but ignoring submissions |
2065 |
< |
int r; |
2066 |
< |
if (w == null) // allow external callers |
2067 |
< |
r = ThreadLocalRandom.current().nextInt(); |
2068 |
< |
else { |
2069 |
< |
r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5; |
2070 |
< |
} |
1966 |
< |
int step = (r >>> 16) | 1; |
1967 |
< |
for (WorkQueue[] ws;;) { |
1968 |
< |
int rs = runState, m; |
1969 |
< |
if ((ws = workQueues) == null || (m = ws.length - 1) < 1) |
1970 |
< |
return null; |
1971 |
< |
for (int j = (m + 1) << 2; ; r += step) { |
1972 |
< |
WorkQueue q = ws[((r << 1) | 1) & m]; |
1973 |
< |
if (q != null && !q.isEmpty()) |
1974 |
< |
return q; |
1975 |
< |
else if (--j < 0) { |
1976 |
< |
if (runState == rs) |
1977 |
< |
return null; |
1978 |
< |
break; |
2059 |
> |
* during a scan, else null. This method must be retried by |
2060 |
> |
* caller if, by the time it tries to use the queue, it is empty. |
2061 |
> |
*/ |
2062 |
> |
private WorkQueue findNonEmptyStealQueue() { |
2063 |
> |
int r = ThreadLocalRandom.current().nextInt(); |
2064 |
> |
for (;;) { |
2065 |
> |
int ps = plock, m; WorkQueue[] ws; WorkQueue q; |
2066 |
> |
if ((ws = workQueues) != null && (m = ws.length - 1) >= 0) { |
2067 |
> |
for (int j = (m + 1) << 2; j >= 0; --j) { |
2068 |
> |
if ((q = ws[(((r - j) << 1) | 1) & m]) != null && |
2069 |
> |
q.base - q.top < 0) |
2070 |
> |
return q; |
2071 |
|
} |
2072 |
|
} |
2073 |
+ |
if (plock == ps) |
2074 |
+ |
return null; |
2075 |
|
} |
2076 |
|
} |
2077 |
|
|
2082 |
|
* find tasks either. |
2083 |
|
*/ |
2084 |
|
final void helpQuiescePool(WorkQueue w) { |
2085 |
+ |
ForkJoinTask<?> ps = w.currentSteal; |
2086 |
|
for (boolean active = true;;) { |
2087 |
< |
ForkJoinTask<?> localTask; // exhaust local queue |
2088 |
< |
while ((localTask = w.nextLocalTask()) != null) |
2089 |
< |
localTask.doExec(); |
2090 |
< |
WorkQueue q = findNonEmptyStealQueue(w); |
1996 |
< |
if (q != null) { |
1997 |
< |
ForkJoinTask<?> t; int b; |
2087 |
> |
long c; WorkQueue q; ForkJoinTask<?> t; int b; |
2088 |
> |
while ((t = w.nextLocalTask()) != null) |
2089 |
> |
t.doExec(); |
2090 |
> |
if ((q = findNonEmptyStealQueue()) != null) { |
2091 |
|
if (!active) { // re-establish active count |
1999 |
– |
long c; |
2092 |
|
active = true; |
2093 |
|
do {} while (!U.compareAndSwapLong |
2094 |
< |
(this, CTL, c = ctl, c + AC_UNIT)); |
2094 |
> |
(this, CTL, c = ctl, |
2095 |
> |
((c & ~AC_MASK) | |
2096 |
> |
((c & AC_MASK) + AC_UNIT)))); |
2097 |
> |
} |
2098 |
> |
if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null) { |
2099 |
> |
(w.currentSteal = t).doExec(); |
2100 |
> |
w.currentSteal = ps; |
2101 |
|
} |
2004 |
– |
if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null) |
2005 |
– |
w.runSubtask(t); |
2102 |
|
} |
2103 |
< |
else { |
2104 |
< |
long c; |
2105 |
< |
if (active) { // decrement active count without queuing |
2103 |
> |
else if (active) { // decrement active count without queuing |
2104 |
> |
long nc = ((c = ctl) & ~AC_MASK) | ((c & AC_MASK) - AC_UNIT); |
2105 |
> |
if ((int)(nc >> AC_SHIFT) + parallelism == 0) |
2106 |
> |
break; // bypass decrement-then-increment |
2107 |
> |
if (U.compareAndSwapLong(this, CTL, c, nc)) |
2108 |
|
active = false; |
2011 |
– |
do {} while (!U.compareAndSwapLong |
2012 |
– |
(this, CTL, c = ctl, c -= AC_UNIT)); |
2013 |
– |
} |
2014 |
– |
else |
2015 |
– |
c = ctl; // re-increment on exit |
2016 |
– |
if ((int)(c >> AC_SHIFT) + parallelism == 0) { |
2017 |
– |
do {} while (!U.compareAndSwapLong |
2018 |
– |
(this, CTL, c = ctl, c + AC_UNIT)); |
2019 |
– |
break; |
2020 |
– |
} |
2109 |
|
} |
2110 |
+ |
else if ((int)((c = ctl) >> AC_SHIFT) + parallelism <= 0 && |
2111 |
+ |
U.compareAndSwapLong |
2112 |
+ |
(this, CTL, c, ((c & ~AC_MASK) | |
2113 |
+ |
((c & AC_MASK) + AC_UNIT)))) |
2114 |
+ |
break; |
2115 |
|
} |
2116 |
|
} |
2117 |
|
|
2118 |
|
/** |
2026 |
– |
* Restricted version of helpQuiescePool for non-FJ callers |
2027 |
– |
*/ |
2028 |
– |
static void externalHelpQuiescePool() { |
2029 |
– |
ForkJoinPool p; WorkQueue[] ws; WorkQueue w, q; |
2030 |
– |
ForkJoinTask<?> t; int b; |
2031 |
– |
int k = submitters.get().seed & SQMASK; |
2032 |
– |
if ((p = commonPool) != null && |
2033 |
– |
(ws = p.workQueues) != null && |
2034 |
– |
ws.length > (k &= p.submitMask) && |
2035 |
– |
(w = ws[k]) != null && |
2036 |
– |
(q = p.findNonEmptyStealQueue(w)) != null && |
2037 |
– |
(b = q.base) - q.top < 0 && |
2038 |
– |
(t = q.pollAt(b)) != null) |
2039 |
– |
t.doExec(); |
2040 |
– |
} |
2041 |
– |
|
2042 |
– |
/** |
2119 |
|
* Gets and removes a local or stolen task for the given worker. |
2120 |
|
* |
2121 |
|
* @return a task, if available |
2125 |
|
WorkQueue q; int b; |
2126 |
|
if ((t = w.nextLocalTask()) != null) |
2127 |
|
return t; |
2128 |
< |
if ((q = findNonEmptyStealQueue(w)) == null) |
2128 |
> |
if ((q = findNonEmptyStealQueue()) == null) |
2129 |
|
return null; |
2130 |
|
if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null) |
2131 |
|
return t; |
2133 |
|
} |
2134 |
|
|
2135 |
|
/** |
2136 |
< |
* Returns the approximate (non-atomic) number of idle threads per |
2137 |
< |
* active thread to offset steal queue size for method |
2138 |
< |
* ForkJoinTask.getSurplusQueuedTaskCount(). |
2139 |
< |
*/ |
2140 |
< |
final int idlePerActive() { |
2141 |
< |
// Approximate at powers of two for small values, saturate past 4 |
2142 |
< |
int p = parallelism; |
2143 |
< |
int a = p + (int)(ctl >> AC_SHIFT); |
2144 |
< |
return (a > (p >>>= 1) ? 0 : |
2145 |
< |
a > (p >>>= 1) ? 1 : |
2146 |
< |
a > (p >>>= 1) ? 2 : |
2147 |
< |
a > (p >>>= 1) ? 4 : |
2148 |
< |
8); |
2149 |
< |
} |
2150 |
< |
|
2151 |
< |
/** |
2152 |
< |
* Returns approximate submission queue length for the given caller |
2153 |
< |
*/ |
2154 |
< |
static int getEstimatedSubmitterQueueLength() { |
2155 |
< |
ForkJoinPool p; WorkQueue[] ws; WorkQueue q; |
2156 |
< |
int k = submitters.get().seed & SQMASK; |
2157 |
< |
return ((p = commonPool) != null && |
2158 |
< |
p.runState >= 0 && |
2159 |
< |
(ws = p.workQueues) != null && |
2160 |
< |
ws.length > (k &= p.submitMask) && |
2161 |
< |
(q = ws[k]) != null) ? |
2162 |
< |
q.queueSize() : 0; |
2136 |
> |
* Returns a cheap heuristic guide for task partitioning when |
2137 |
> |
* programmers, frameworks, tools, or languages have little or no |
2138 |
> |
* idea about task granularity. In essence by offering this |
2139 |
> |
* method, we ask users only about tradeoffs in overhead vs |
2140 |
> |
* expected throughput and its variance, rather than how finely to |
2141 |
> |
* partition tasks. |
2142 |
> |
* |
2143 |
> |
* In a steady state strict (tree-structured) computation, each |
2144 |
> |
* thread makes available for stealing enough tasks for other |
2145 |
> |
* threads to remain active. Inductively, if all threads play by |
2146 |
> |
* the same rules, each thread should make available only a |
2147 |
> |
* constant number of tasks. |
2148 |
> |
* |
2149 |
> |
* The minimum useful constant is just 1. But using a value of 1 |
2150 |
> |
* would require immediate replenishment upon each steal to |
2151 |
> |
* maintain enough tasks, which is infeasible. Further, |
2152 |
> |
* partitionings/granularities of offered tasks should minimize |
2153 |
> |
* steal rates, which in general means that threads nearer the top |
2154 |
> |
* of computation tree should generate more than those nearer the |
2155 |
> |
* bottom. In perfect steady state, each thread is at |
2156 |
> |
* approximately the same level of computation tree. However, |
2157 |
> |
* producing extra tasks amortizes the uncertainty of progress and |
2158 |
> |
* diffusion assumptions. |
2159 |
> |
* |
2160 |
> |
* So, users will want to use values larger (but not much larger) |
2161 |
> |
* than 1 to both smooth over transient shortages and hedge |
2162 |
> |
* against uneven progress; as traded off against the cost of |
2163 |
> |
* extra task overhead. We leave the user to pick a threshold |
2164 |
> |
* value to compare with the results of this call to guide |
2165 |
> |
* decisions, but recommend values such as 3. |
2166 |
> |
* |
2167 |
> |
* When all threads are active, it is on average OK to estimate |
2168 |
> |
* surplus strictly locally. In steady-state, if one thread is |
2169 |
> |
* maintaining say 2 surplus tasks, then so are others. So we can |
2170 |
> |
* just use estimated queue length. However, this strategy alone |
2171 |
> |
* leads to serious mis-estimates in some non-steady-state |
2172 |
> |
* conditions (ramp-up, ramp-down, other stalls). We can detect |
2173 |
> |
* many of these by further considering the number of "idle" |
2174 |
> |
* threads, that are known to have zero queued tasks, so |
2175 |
> |
* compensate by a factor of (#idle/#active) threads. |
2176 |
> |
* |
2177 |
> |
* Note: The approximation of #busy workers as #active workers is |
2178 |
> |
* not very good under current signalling scheme, and should be |
2179 |
> |
* improved. |
2180 |
> |
*/ |
2181 |
> |
static int getSurplusQueuedTaskCount() { |
2182 |
> |
Thread t; ForkJoinWorkerThread wt; ForkJoinPool pool; WorkQueue q; |
2183 |
> |
if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) { |
2184 |
> |
int p = (pool = (wt = (ForkJoinWorkerThread)t).pool).parallelism; |
2185 |
> |
int n = (q = wt.workQueue).top - q.base; |
2186 |
> |
int a = (int)(pool.ctl >> AC_SHIFT) + p; |
2187 |
> |
return n - (a > (p >>>= 1) ? 0 : |
2188 |
> |
a > (p >>>= 1) ? 1 : |
2189 |
> |
a > (p >>>= 1) ? 2 : |
2190 |
> |
a > (p >>>= 1) ? 4 : |
2191 |
> |
8); |
2192 |
> |
} |
2193 |
> |
return 0; |
2194 |
|
} |
2195 |
|
|
2196 |
|
// Termination |
2210 |
|
* @return true if now terminating or terminated |
2211 |
|
*/ |
2212 |
|
private boolean tryTerminate(boolean now, boolean enable) { |
2213 |
< |
Mutex lock = this.lock; |
2213 |
> |
int ps; |
2214 |
> |
if (this == common) // cannot shut down |
2215 |
> |
return false; |
2216 |
> |
if ((ps = plock) >= 0) { // enable by setting plock |
2217 |
> |
if (!enable) |
2218 |
> |
return false; |
2219 |
> |
if ((ps & PL_LOCK) != 0 || |
2220 |
> |
!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK)) |
2221 |
> |
ps = acquirePlock(); |
2222 |
> |
int nps = ((ps + PL_LOCK) & ~SHUTDOWN) | SHUTDOWN; |
2223 |
> |
if (!U.compareAndSwapInt(this, PLOCK, ps, nps)) |
2224 |
> |
releasePlock(nps); |
2225 |
> |
} |
2226 |
|
for (long c;;) { |
2227 |
< |
if (((c = ctl) & STOP_BIT) != 0) { // already terminating |
2228 |
< |
if ((short)(c >>> TC_SHIFT) == -parallelism) { |
2229 |
< |
lock.lock(); // don't need try/finally |
2230 |
< |
termination.signalAll(); // signal when 0 workers |
2231 |
< |
lock.unlock(); |
2227 |
> |
if (((c = ctl) & STOP_BIT) != 0) { // already terminating |
2228 |
> |
if ((short)(c >>> TC_SHIFT) + parallelism <= 0) { |
2229 |
> |
synchronized (this) { |
2230 |
> |
notifyAll(); // signal when 0 workers |
2231 |
> |
} |
2232 |
|
} |
2233 |
|
return true; |
2234 |
|
} |
2235 |
< |
if (runState >= 0) { // not yet enabled |
2236 |
< |
if (!enable) |
2237 |
< |
return false; |
2119 |
< |
lock.lock(); |
2120 |
< |
runState |= SHUTDOWN; |
2121 |
< |
lock.unlock(); |
2122 |
< |
} |
2123 |
< |
if (!now) { // check if idle & no tasks |
2124 |
< |
if ((int)(c >> AC_SHIFT) != -parallelism || |
2125 |
< |
hasQueuedSubmissions()) |
2235 |
> |
if (!now) { // check if idle & no tasks |
2236 |
> |
WorkQueue[] ws; WorkQueue w; |
2237 |
> |
if ((int)(c >> AC_SHIFT) + parallelism > 0) |
2238 |
|
return false; |
2239 |
< |
// Check for unqueued inactive workers. One pass suffices. |
2240 |
< |
WorkQueue[] ws = workQueues; WorkQueue w; |
2241 |
< |
if (ws != null) { |
2242 |
< |
for (int i = 1; i < ws.length; i += 2) { |
2243 |
< |
if ((w = ws[i]) != null && w.eventCount >= 0) |
2239 |
> |
if ((ws = workQueues) != null) { |
2240 |
> |
for (int i = 0; i < ws.length; ++i) { |
2241 |
> |
if ((w = ws[i]) != null && |
2242 |
> |
(!w.isEmpty() || |
2243 |
> |
((i & 1) != 0 && w.eventCount >= 0))) { |
2244 |
> |
signalWork(ws, w); |
2245 |
|
return false; |
2246 |
+ |
} |
2247 |
|
} |
2248 |
|
} |
2249 |
|
} |
2250 |
|
if (U.compareAndSwapLong(this, CTL, c, c | STOP_BIT)) { |
2251 |
|
for (int pass = 0; pass < 3; ++pass) { |
2252 |
< |
WorkQueue[] ws = workQueues; |
2253 |
< |
if (ws != null) { |
2140 |
< |
WorkQueue w; |
2252 |
> |
WorkQueue[] ws; WorkQueue w; Thread wt; |
2253 |
> |
if ((ws = workQueues) != null) { |
2254 |
|
int n = ws.length; |
2255 |
|
for (int i = 0; i < n; ++i) { |
2256 |
|
if ((w = ws[i]) != null) { |
2257 |
< |
w.runState = -1; |
2257 |
> |
w.qlock = -1; |
2258 |
|
if (pass > 0) { |
2259 |
|
w.cancelAll(); |
2260 |
< |
if (pass > 1) |
2261 |
< |
w.interruptOwner(); |
2260 |
> |
if (pass > 1 && (wt = w.owner) != null) { |
2261 |
> |
if (!wt.isInterrupted()) { |
2262 |
> |
try { |
2263 |
> |
wt.interrupt(); |
2264 |
> |
} catch (Throwable ignore) { |
2265 |
> |
} |
2266 |
> |
} |
2267 |
> |
U.unpark(wt); |
2268 |
> |
} |
2269 |
|
} |
2270 |
|
} |
2271 |
|
} |
2272 |
|
// Wake up workers parked on event queue |
2273 |
|
int i, e; long cc; Thread p; |
2274 |
|
while ((e = (int)(cc = ctl) & E_MASK) != 0 && |
2275 |
< |
(i = e & SMASK) < n && |
2275 |
> |
(i = e & SMASK) < n && i >= 0 && |
2276 |
|
(w = ws[i]) != null) { |
2277 |
|
long nc = ((long)(w.nextWait & E_MASK) | |
2278 |
|
((cc + AC_UNIT) & AC_MASK) | |
2280 |
|
if (w.eventCount == (e | INT_SIGN) && |
2281 |
|
U.compareAndSwapLong(this, CTL, cc, nc)) { |
2282 |
|
w.eventCount = (e + E_SEQ) & E_MASK; |
2283 |
< |
w.runState = -1; |
2283 |
> |
w.qlock = -1; |
2284 |
|
if ((p = w.parker) != null) |
2285 |
|
U.unpark(p); |
2286 |
|
} |
2291 |
|
} |
2292 |
|
} |
2293 |
|
|
2294 |
+ |
// external operations on common pool |
2295 |
+ |
|
2296 |
+ |
/** |
2297 |
+ |
* Returns common pool queue for a thread that has submitted at |
2298 |
+ |
* least one task. |
2299 |
+ |
*/ |
2300 |
+ |
static WorkQueue commonSubmitterQueue() { |
2301 |
+ |
Submitter z; ForkJoinPool p; WorkQueue[] ws; int m, r; |
2302 |
+ |
return ((z = submitters.get()) != null && |
2303 |
+ |
(p = common) != null && |
2304 |
+ |
(ws = p.workQueues) != null && |
2305 |
+ |
(m = ws.length - 1) >= 0) ? |
2306 |
+ |
ws[m & z.seed & SQMASK] : null; |
2307 |
+ |
} |
2308 |
+ |
|
2309 |
+ |
/** |
2310 |
+ |
* Tries to pop the given task from submitter's queue in common pool. |
2311 |
+ |
*/ |
2312 |
+ |
final boolean tryExternalUnpush(ForkJoinTask<?> task) { |
2313 |
+ |
WorkQueue joiner; ForkJoinTask<?>[] a; int m, s; |
2314 |
+ |
Submitter z = submitters.get(); |
2315 |
+ |
WorkQueue[] ws = workQueues; |
2316 |
+ |
boolean popped = false; |
2317 |
+ |
if (z != null && ws != null && (m = ws.length - 1) >= 0 && |
2318 |
+ |
(joiner = ws[z.seed & m & SQMASK]) != null && |
2319 |
+ |
joiner.base != (s = joiner.top) && |
2320 |
+ |
(a = joiner.array) != null) { |
2321 |
+ |
long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE; |
2322 |
+ |
if (U.getObject(a, j) == task && |
2323 |
+ |
U.compareAndSwapInt(joiner, QLOCK, 0, 1)) { |
2324 |
+ |
if (joiner.top == s && joiner.array == a && |
2325 |
+ |
U.compareAndSwapObject(a, j, task, null)) { |
2326 |
+ |
joiner.top = s - 1; |
2327 |
+ |
popped = true; |
2328 |
+ |
} |
2329 |
+ |
joiner.qlock = 0; |
2330 |
+ |
} |
2331 |
+ |
} |
2332 |
+ |
return popped; |
2333 |
+ |
} |
2334 |
+ |
|
2335 |
+ |
final int externalHelpComplete(CountedCompleter<?> task) { |
2336 |
+ |
WorkQueue joiner; int m, j; |
2337 |
+ |
Submitter z = submitters.get(); |
2338 |
+ |
WorkQueue[] ws = workQueues; |
2339 |
+ |
int s = 0; |
2340 |
+ |
if (z != null && ws != null && (m = ws.length - 1) >= 0 && |
2341 |
+ |
(joiner = ws[(j = z.seed) & m & SQMASK]) != null && task != null) { |
2342 |
+ |
int scans = m + m + 1; |
2343 |
+ |
long c = 0L; // for stability check |
2344 |
+ |
j |= 1; // poll odd queues |
2345 |
+ |
for (int k = scans; ; j += 2) { |
2346 |
+ |
WorkQueue q; |
2347 |
+ |
if ((s = task.status) < 0) |
2348 |
+ |
break; |
2349 |
+ |
else if (joiner.externalPopAndExecCC(task)) |
2350 |
+ |
k = scans; |
2351 |
+ |
else if ((s = task.status) < 0) |
2352 |
+ |
break; |
2353 |
+ |
else if ((q = ws[j & m]) != null && q.pollAndExecCC(task)) |
2354 |
+ |
k = scans; |
2355 |
+ |
else if (--k < 0) { |
2356 |
+ |
if (c == (c = ctl)) |
2357 |
+ |
break; |
2358 |
+ |
k = scans; |
2359 |
+ |
} |
2360 |
+ |
} |
2361 |
+ |
} |
2362 |
+ |
return s; |
2363 |
+ |
} |
2364 |
+ |
|
2365 |
|
// Exported methods |
2366 |
|
|
2367 |
|
// Constructors |
2378 |
|
* java.lang.RuntimePermission}{@code ("modifyThread")} |
2379 |
|
*/ |
2380 |
|
public ForkJoinPool() { |
2381 |
< |
this(Runtime.getRuntime().availableProcessors(), |
2381 |
> |
this(Math.min(MAX_CAP, Runtime.getRuntime().availableProcessors()), |
2382 |
|
defaultForkJoinWorkerThreadFactory, null, false); |
2383 |
|
} |
2384 |
|
|
2426 |
|
*/ |
2427 |
|
public ForkJoinPool(int parallelism, |
2428 |
|
ForkJoinWorkerThreadFactory factory, |
2429 |
< |
Thread.UncaughtExceptionHandler handler, |
2429 |
> |
UncaughtExceptionHandler handler, |
2430 |
|
boolean asyncMode) { |
2431 |
+ |
this(checkParallelism(parallelism), |
2432 |
+ |
checkFactory(factory), |
2433 |
+ |
handler, |
2434 |
+ |
(asyncMode ? FIFO_QUEUE : LIFO_QUEUE), |
2435 |
+ |
"ForkJoinPool-" + nextPoolId() + "-worker-"); |
2436 |
|
checkPermission(); |
2437 |
< |
if (factory == null) |
2438 |
< |
throw new NullPointerException(); |
2437 |
> |
} |
2438 |
> |
|
2439 |
> |
private static int checkParallelism(int parallelism) { |
2440 |
|
if (parallelism <= 0 || parallelism > MAX_CAP) |
2441 |
|
throw new IllegalArgumentException(); |
2442 |
< |
this.parallelism = parallelism; |
2442 |
> |
return parallelism; |
2443 |
> |
} |
2444 |
> |
|
2445 |
> |
private static ForkJoinWorkerThreadFactory checkFactory |
2446 |
> |
(ForkJoinWorkerThreadFactory factory) { |
2447 |
> |
if (factory == null) |
2448 |
> |
throw new NullPointerException(); |
2449 |
> |
return factory; |
2450 |
> |
} |
2451 |
> |
|
2452 |
> |
/** |
2453 |
> |
* Creates a {@code ForkJoinPool} with the given parameters, without |
2454 |
> |
* any security checks or parameter validation. Invoked directly by |
2455 |
> |
* makeCommonPool. |
2456 |
> |
*/ |
2457 |
> |
private ForkJoinPool(int parallelism, |
2458 |
> |
ForkJoinWorkerThreadFactory factory, |
2459 |
> |
UncaughtExceptionHandler handler, |
2460 |
> |
int mode, |
2461 |
> |
String workerNamePrefix) { |
2462 |
> |
this.workerNamePrefix = workerNamePrefix; |
2463 |
|
this.factory = factory; |
2464 |
|
this.ueh = handler; |
2465 |
< |
this.localMode = asyncMode ? FIFO_QUEUE : LIFO_QUEUE; |
2465 |
> |
this.mode = (short)mode; |
2466 |
> |
this.parallelism = (short)parallelism; |
2467 |
|
long np = (long)(-parallelism); // offset ctl counts |
2468 |
|
this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK); |
2251 |
– |
// Use nearest power 2 for workQueues size. See Hackers Delight sec 3.2. |
2252 |
– |
int n = parallelism - 1; |
2253 |
– |
n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8; n |= n >>> 16; |
2254 |
– |
int size = (n + 1) << 1; // #slots = 2*#workers |
2255 |
– |
this.submitMask = size - 1; // room for max # of submit queues |
2256 |
– |
this.workQueues = new WorkQueue[size]; |
2257 |
– |
this.termination = (this.lock = new Mutex()).newCondition(); |
2258 |
– |
this.stealCount = new AtomicLong(); |
2259 |
– |
this.nextWorkerNumber = new AtomicInteger(); |
2260 |
– |
int pn = poolNumberGenerator.incrementAndGet(); |
2261 |
– |
StringBuilder sb = new StringBuilder("ForkJoinPool-"); |
2262 |
– |
sb.append(Integer.toString(pn)); |
2263 |
– |
sb.append("-worker-"); |
2264 |
– |
this.workerNamePrefix = sb.toString(); |
2265 |
– |
lock.lock(); |
2266 |
– |
this.runState = 1; // set init flag |
2267 |
– |
lock.unlock(); |
2469 |
|
} |
2470 |
|
|
2471 |
|
/** |
2472 |
< |
* Returns the common pool instance |
2472 |
> |
* Returns the common pool instance. This pool is statically |
2473 |
> |
* constructed; its run state is unaffected by attempts to {@link |
2474 |
> |
* #shutdown} or {@link #shutdownNow}. However this pool and any |
2475 |
> |
* ongoing processing are automatically terminated upon program |
2476 |
> |
* {@link System#exit}. Any program that relies on asynchronous |
2477 |
> |
* task processing to complete before program termination should |
2478 |
> |
* invoke {@code commonPool().}{@link #awaitQuiescence awaitQuiescence}, |
2479 |
> |
* before exit. |
2480 |
|
* |
2481 |
|
* @return the common pool instance |
2482 |
+ |
* @since 1.8 |
2483 |
|
*/ |
2484 |
|
public static ForkJoinPool commonPool() { |
2485 |
< |
ForkJoinPool p; |
2486 |
< |
return (p = commonPool) != null? p : ensureCommonPool(); |
2278 |
< |
} |
2279 |
< |
|
2280 |
< |
private static ForkJoinPool ensureCommonPool() { |
2281 |
< |
ForkJoinPool p; |
2282 |
< |
if ((p = commonPool) == null) { |
2283 |
< |
final Mutex lock = initializationLock; |
2284 |
< |
lock.lock(); |
2285 |
< |
try { |
2286 |
< |
if ((p = commonPool) == null) { |
2287 |
< |
p = commonPool = new ForkJoinPool(commonPoolParallelism, |
2288 |
< |
commonPoolFactory, |
2289 |
< |
commonPoolUEH, false); |
2290 |
< |
// use a more informative name string for workers |
2291 |
< |
p.workerNamePrefix = "ForkJoinPool.commonPool-worker-"; |
2292 |
< |
} |
2293 |
< |
} finally { |
2294 |
< |
lock.unlock(); |
2295 |
< |
} |
2296 |
< |
} |
2297 |
< |
return p; |
2485 |
> |
// assert common != null : "static init error"; |
2486 |
> |
return common; |
2487 |
|
} |
2488 |
|
|
2489 |
|
// Execution methods |
2499 |
|
* minimally only the latter. |
2500 |
|
* |
2501 |
|
* @param task the task |
2502 |
+ |
* @param <T> the type of the task's result |
2503 |
|
* @return the task's result |
2504 |
|
* @throws NullPointerException if the task is null |
2505 |
|
* @throws RejectedExecutionException if the task cannot be |
2508 |
|
public <T> T invoke(ForkJoinTask<T> task) { |
2509 |
|
if (task == null) |
2510 |
|
throw new NullPointerException(); |
2511 |
< |
doSubmit(task); |
2511 |
> |
externalPush(task); |
2512 |
|
return task.join(); |
2513 |
|
} |
2514 |
|
|
2523 |
|
public void execute(ForkJoinTask<?> task) { |
2524 |
|
if (task == null) |
2525 |
|
throw new NullPointerException(); |
2526 |
< |
doSubmit(task); |
2526 |
> |
externalPush(task); |
2527 |
|
} |
2528 |
|
|
2529 |
|
// AbstractExecutorService methods |
2540 |
|
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
2541 |
|
job = (ForkJoinTask<?>) task; |
2542 |
|
else |
2543 |
< |
job = new ForkJoinTask.AdaptedRunnableAction(task); |
2544 |
< |
doSubmit(job); |
2543 |
> |
job = new ForkJoinTask.RunnableExecuteAction(task); |
2544 |
> |
externalPush(job); |
2545 |
|
} |
2546 |
|
|
2547 |
|
/** |
2548 |
|
* Submits a ForkJoinTask for execution. |
2549 |
|
* |
2550 |
|
* @param task the task to submit |
2551 |
+ |
* @param <T> the type of the task's result |
2552 |
|
* @return the task |
2553 |
|
* @throws NullPointerException if the task is null |
2554 |
|
* @throws RejectedExecutionException if the task cannot be |
2557 |
|
public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) { |
2558 |
|
if (task == null) |
2559 |
|
throw new NullPointerException(); |
2560 |
< |
doSubmit(task); |
2560 |
> |
externalPush(task); |
2561 |
|
return task; |
2562 |
|
} |
2563 |
|
|
2568 |
|
*/ |
2569 |
|
public <T> ForkJoinTask<T> submit(Callable<T> task) { |
2570 |
|
ForkJoinTask<T> job = new ForkJoinTask.AdaptedCallable<T>(task); |
2571 |
< |
doSubmit(job); |
2571 |
> |
externalPush(job); |
2572 |
|
return job; |
2573 |
|
} |
2574 |
|
|
2579 |
|
*/ |
2580 |
|
public <T> ForkJoinTask<T> submit(Runnable task, T result) { |
2581 |
|
ForkJoinTask<T> job = new ForkJoinTask.AdaptedRunnable<T>(task, result); |
2582 |
< |
doSubmit(job); |
2582 |
> |
externalPush(job); |
2583 |
|
return job; |
2584 |
|
} |
2585 |
|
|
2596 |
|
job = (ForkJoinTask<?>) task; |
2597 |
|
else |
2598 |
|
job = new ForkJoinTask.AdaptedRunnableAction(task); |
2599 |
< |
doSubmit(job); |
2599 |
> |
externalPush(job); |
2600 |
|
return job; |
2601 |
|
} |
2602 |
|
|
2608 |
|
// In previous versions of this class, this method constructed |
2609 |
|
// a task to run ForkJoinTask.invokeAll, but now external |
2610 |
|
// invocation of multiple tasks is at least as efficient. |
2611 |
< |
List<ForkJoinTask<T>> fs = new ArrayList<ForkJoinTask<T>>(tasks.size()); |
2421 |
< |
// Workaround needed because method wasn't declared with |
2422 |
< |
// wildcards in return type but should have been. |
2423 |
< |
@SuppressWarnings({"unchecked", "rawtypes"}) |
2424 |
< |
List<Future<T>> futures = (List<Future<T>>) (List) fs; |
2611 |
> |
ArrayList<Future<T>> futures = new ArrayList<Future<T>>(tasks.size()); |
2612 |
|
|
2613 |
|
boolean done = false; |
2614 |
|
try { |
2615 |
|
for (Callable<T> t : tasks) { |
2616 |
|
ForkJoinTask<T> f = new ForkJoinTask.AdaptedCallable<T>(t); |
2617 |
< |
doSubmit(f); |
2618 |
< |
fs.add(f); |
2617 |
> |
futures.add(f); |
2618 |
> |
externalPush(f); |
2619 |
|
} |
2620 |
< |
for (ForkJoinTask<T> f : fs) |
2621 |
< |
f.quietlyJoin(); |
2620 |
> |
for (int i = 0, size = futures.size(); i < size; i++) |
2621 |
> |
((ForkJoinTask<?>)futures.get(i)).quietlyJoin(); |
2622 |
|
done = true; |
2623 |
|
return futures; |
2624 |
|
} finally { |
2625 |
|
if (!done) |
2626 |
< |
for (ForkJoinTask<T> f : fs) |
2627 |
< |
f.cancel(false); |
2626 |
> |
for (int i = 0, size = futures.size(); i < size; i++) |
2627 |
> |
futures.get(i).cancel(false); |
2628 |
|
} |
2629 |
|
} |
2630 |
|
|
2643 |
|
* |
2644 |
|
* @return the handler, or {@code null} if none |
2645 |
|
*/ |
2646 |
< |
public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() { |
2646 |
> |
public UncaughtExceptionHandler getUncaughtExceptionHandler() { |
2647 |
|
return ueh; |
2648 |
|
} |
2649 |
|
|
2653 |
|
* @return the targeted parallelism level of this pool |
2654 |
|
*/ |
2655 |
|
public int getParallelism() { |
2656 |
< |
return parallelism; |
2656 |
> |
int par; |
2657 |
> |
return ((par = parallelism) > 0) ? par : 1; |
2658 |
|
} |
2659 |
|
|
2660 |
|
/** |
2661 |
|
* Returns the targeted parallelism level of the common pool. |
2662 |
|
* |
2663 |
|
* @return the targeted parallelism level of the common pool |
2664 |
+ |
* @since 1.8 |
2665 |
|
*/ |
2666 |
|
public static int getCommonPoolParallelism() { |
2667 |
< |
return commonPoolParallelism; |
2667 |
> |
return commonParallelism; |
2668 |
|
} |
2669 |
|
|
2670 |
|
/** |
2686 |
|
* @return {@code true} if this pool uses async mode |
2687 |
|
*/ |
2688 |
|
public boolean getAsyncMode() { |
2689 |
< |
return localMode != 0; |
2689 |
> |
return mode == FIFO_QUEUE; |
2690 |
|
} |
2691 |
|
|
2692 |
|
/** |
2733 |
|
* @return {@code true} if all threads are currently idle |
2734 |
|
*/ |
2735 |
|
public boolean isQuiescent() { |
2736 |
< |
return (int)(ctl >> AC_SHIFT) + parallelism == 0; |
2736 |
> |
return parallelism + (int)(ctl >> AC_SHIFT) <= 0; |
2737 |
|
} |
2738 |
|
|
2739 |
|
/** |
2748 |
|
* @return the number of steals |
2749 |
|
*/ |
2750 |
|
public long getStealCount() { |
2751 |
< |
long count = stealCount.get(); |
2751 |
> |
long count = stealCount; |
2752 |
|
WorkQueue[] ws; WorkQueue w; |
2753 |
|
if ((ws = workQueues) != null) { |
2754 |
|
for (int i = 1; i < ws.length; i += 2) { |
2755 |
|
if ((w = ws[i]) != null) |
2756 |
< |
count += w.totalSteals; |
2756 |
> |
count += w.nsteals; |
2757 |
|
} |
2758 |
|
} |
2759 |
|
return count; |
2878 |
|
public String toString() { |
2879 |
|
// Use a single pass through workQueues to collect counts |
2880 |
|
long qt = 0L, qs = 0L; int rc = 0; |
2881 |
< |
long st = stealCount.get(); |
2881 |
> |
long st = stealCount; |
2882 |
|
long c = ctl; |
2883 |
|
WorkQueue[] ws; WorkQueue w; |
2884 |
|
if ((ws = workQueues) != null) { |
2889 |
|
qs += size; |
2890 |
|
else { |
2891 |
|
qt += size; |
2892 |
< |
st += w.totalSteals; |
2892 |
> |
st += w.nsteals; |
2893 |
|
if (w.isApparentlyUnblocked()) |
2894 |
|
++rc; |
2895 |
|
} |
2905 |
|
if ((c & STOP_BIT) != 0) |
2906 |
|
level = (tc == 0) ? "Terminated" : "Terminating"; |
2907 |
|
else |
2908 |
< |
level = runState < 0 ? "Shutting down" : "Running"; |
2908 |
> |
level = plock < 0 ? "Shutting down" : "Running"; |
2909 |
|
return super.toString() + |
2910 |
|
"[" + level + |
2911 |
|
", parallelism = " + pc + |
2922 |
|
* Possibly initiates an orderly shutdown in which previously |
2923 |
|
* submitted tasks are executed, but no new tasks will be |
2924 |
|
* accepted. Invocation has no effect on execution state if this |
2925 |
< |
* is the {@link #commonPool}, and no additional effect if |
2925 |
> |
* is the {@link #commonPool()}, and no additional effect if |
2926 |
|
* already shut down. Tasks that are in the process of being |
2927 |
|
* submitted concurrently during the course of this method may or |
2928 |
|
* may not be rejected. |
2934 |
|
*/ |
2935 |
|
public void shutdown() { |
2936 |
|
checkPermission(); |
2937 |
< |
if (this != commonPool) |
2749 |
< |
tryTerminate(false, true); |
2937 |
> |
tryTerminate(false, true); |
2938 |
|
} |
2939 |
|
|
2940 |
|
/** |
2941 |
|
* Possibly attempts to cancel and/or stop all tasks, and reject |
2942 |
|
* all subsequently submitted tasks. Invocation has no effect on |
2943 |
< |
* execution state if this is the {@link #commonPool}, and no |
2943 |
> |
* execution state if this is the {@link #commonPool()}, and no |
2944 |
|
* additional effect if already shut down. Otherwise, tasks that |
2945 |
|
* are in the process of being submitted or executed concurrently |
2946 |
|
* during the course of this method may or may not be |
2957 |
|
*/ |
2958 |
|
public List<Runnable> shutdownNow() { |
2959 |
|
checkPermission(); |
2960 |
< |
if (this != commonPool) |
2773 |
< |
tryTerminate(true, true); |
2960 |
> |
tryTerminate(true, true); |
2961 |
|
return Collections.emptyList(); |
2962 |
|
} |
2963 |
|
|
2969 |
|
public boolean isTerminated() { |
2970 |
|
long c = ctl; |
2971 |
|
return ((c & STOP_BIT) != 0L && |
2972 |
< |
(short)(c >>> TC_SHIFT) == -parallelism); |
2972 |
> |
(short)(c >>> TC_SHIFT) + parallelism <= 0); |
2973 |
|
} |
2974 |
|
|
2975 |
|
/** |
2977 |
|
* commenced but not yet completed. This method may be useful for |
2978 |
|
* debugging. A return of {@code true} reported a sufficient |
2979 |
|
* period after shutdown may indicate that submitted tasks have |
2980 |
< |
* ignored or suppressed interruption, or are waiting for IO, |
2980 |
> |
* ignored or suppressed interruption, or are waiting for I/O, |
2981 |
|
* causing this executor not to properly terminate. (See the |
2982 |
|
* advisory notes for class {@link ForkJoinTask} stating that |
2983 |
|
* tasks should not normally entail blocking operations. But if |
2988 |
|
public boolean isTerminating() { |
2989 |
|
long c = ctl; |
2990 |
|
return ((c & STOP_BIT) != 0L && |
2991 |
< |
(short)(c >>> TC_SHIFT) != -parallelism); |
2991 |
> |
(short)(c >>> TC_SHIFT) + parallelism > 0); |
2992 |
|
} |
2993 |
|
|
2994 |
|
/** |
2997 |
|
* @return {@code true} if this pool has been shut down |
2998 |
|
*/ |
2999 |
|
public boolean isShutdown() { |
3000 |
< |
return runState < 0; |
3000 |
> |
return plock < 0; |
3001 |
|
} |
3002 |
|
|
3003 |
|
/** |
3004 |
< |
* Blocks until all tasks have completed execution after a shutdown |
3005 |
< |
* request, or the timeout occurs, or the current thread is |
3006 |
< |
* interrupted, whichever happens first. |
3004 |
> |
* Blocks until all tasks have completed execution after a |
3005 |
> |
* shutdown request, or the timeout occurs, or the current thread |
3006 |
> |
* is interrupted, whichever happens first. Because the {@link |
3007 |
> |
* #commonPool()} never terminates until program shutdown, when |
3008 |
> |
* applied to the common pool, this method is equivalent to {@link |
3009 |
> |
* #awaitQuiescence(long, TimeUnit)} but always returns {@code false}. |
3010 |
|
* |
3011 |
|
* @param timeout the maximum time to wait |
3012 |
|
* @param unit the time unit of the timeout argument |
3016 |
|
*/ |
3017 |
|
public boolean awaitTermination(long timeout, TimeUnit unit) |
3018 |
|
throws InterruptedException { |
3019 |
+ |
if (Thread.interrupted()) |
3020 |
+ |
throw new InterruptedException(); |
3021 |
+ |
if (this == common) { |
3022 |
+ |
awaitQuiescence(timeout, unit); |
3023 |
+ |
return false; |
3024 |
+ |
} |
3025 |
|
long nanos = unit.toNanos(timeout); |
3026 |
< |
final Mutex lock = this.lock; |
3027 |
< |
lock.lock(); |
3028 |
< |
try { |
3026 |
> |
if (isTerminated()) |
3027 |
> |
return true; |
3028 |
> |
if (nanos <= 0L) |
3029 |
> |
return false; |
3030 |
> |
long deadline = System.nanoTime() + nanos; |
3031 |
> |
synchronized (this) { |
3032 |
|
for (;;) { |
3033 |
|
if (isTerminated()) |
3034 |
|
return true; |
3035 |
< |
if (nanos <= 0) |
3035 |
> |
if (nanos <= 0L) |
3036 |
|
return false; |
3037 |
< |
nanos = termination.awaitNanos(nanos); |
3037 |
> |
long millis = TimeUnit.NANOSECONDS.toMillis(nanos); |
3038 |
> |
wait(millis > 0L ? millis : 1L); |
3039 |
> |
nanos = deadline - System.nanoTime(); |
3040 |
|
} |
2840 |
– |
} finally { |
2841 |
– |
lock.unlock(); |
3041 |
|
} |
3042 |
|
} |
3043 |
|
|
3044 |
|
/** |
3045 |
+ |
* If called by a ForkJoinTask operating in this pool, equivalent |
3046 |
+ |
* in effect to {@link ForkJoinTask#helpQuiesce}. Otherwise, |
3047 |
+ |
* waits and/or attempts to assist performing tasks until this |
3048 |
+ |
* pool {@link #isQuiescent} or the indicated timeout elapses. |
3049 |
+ |
* |
3050 |
+ |
* @param timeout the maximum time to wait |
3051 |
+ |
* @param unit the time unit of the timeout argument |
3052 |
+ |
* @return {@code true} if quiescent; {@code false} if the |
3053 |
+ |
* timeout elapsed. |
3054 |
+ |
*/ |
3055 |
+ |
public boolean awaitQuiescence(long timeout, TimeUnit unit) { |
3056 |
+ |
long nanos = unit.toNanos(timeout); |
3057 |
+ |
ForkJoinWorkerThread wt; |
3058 |
+ |
Thread thread = Thread.currentThread(); |
3059 |
+ |
if ((thread instanceof ForkJoinWorkerThread) && |
3060 |
+ |
(wt = (ForkJoinWorkerThread)thread).pool == this) { |
3061 |
+ |
helpQuiescePool(wt.workQueue); |
3062 |
+ |
return true; |
3063 |
+ |
} |
3064 |
+ |
long startTime = System.nanoTime(); |
3065 |
+ |
WorkQueue[] ws; |
3066 |
+ |
int r = 0, m; |
3067 |
+ |
boolean found = true; |
3068 |
+ |
while (!isQuiescent() && (ws = workQueues) != null && |
3069 |
+ |
(m = ws.length - 1) >= 0) { |
3070 |
+ |
if (!found) { |
3071 |
+ |
if ((System.nanoTime() - startTime) > nanos) |
3072 |
+ |
return false; |
3073 |
+ |
Thread.yield(); // cannot block |
3074 |
+ |
} |
3075 |
+ |
found = false; |
3076 |
+ |
for (int j = (m + 1) << 2; j >= 0; --j) { |
3077 |
+ |
ForkJoinTask<?> t; WorkQueue q; int b; |
3078 |
+ |
if ((q = ws[r++ & m]) != null && (b = q.base) - q.top < 0) { |
3079 |
+ |
found = true; |
3080 |
+ |
if ((t = q.pollAt(b)) != null) |
3081 |
+ |
t.doExec(); |
3082 |
+ |
break; |
3083 |
+ |
} |
3084 |
+ |
} |
3085 |
+ |
} |
3086 |
+ |
return true; |
3087 |
+ |
} |
3088 |
+ |
|
3089 |
+ |
/** |
3090 |
+ |
* Waits and/or attempts to assist performing tasks indefinitely |
3091 |
+ |
* until the {@link #commonPool()} {@link #isQuiescent}. |
3092 |
+ |
*/ |
3093 |
+ |
static void quiesceCommonPool() { |
3094 |
+ |
common.awaitQuiescence(Long.MAX_VALUE, TimeUnit.NANOSECONDS); |
3095 |
+ |
} |
3096 |
+ |
|
3097 |
+ |
/** |
3098 |
|
* Interface for extending managed parallelism for tasks running |
3099 |
|
* in {@link ForkJoinPool}s. |
3100 |
|
* |
3103 |
|
* not necessary. Method {@code block} blocks the current thread |
3104 |
|
* if necessary (perhaps internally invoking {@code isReleasable} |
3105 |
|
* before actually blocking). These actions are performed by any |
3106 |
< |
* thread invoking {@link ForkJoinPool#managedBlock}. The |
3107 |
< |
* unusual methods in this API accommodate synchronizers that may, |
3108 |
< |
* but don't usually, block for long periods. Similarly, they |
3106 |
> |
* thread invoking {@link ForkJoinPool#managedBlock(ManagedBlocker)}. |
3107 |
> |
* The unusual methods in this API accommodate synchronizers that |
3108 |
> |
* may, but don't usually, block for long periods. Similarly, they |
3109 |
|
* allow more efficient internal handling of cases in which |
3110 |
|
* additional workers may be, but usually are not, needed to |
3111 |
|
* ensure sufficient parallelism. Toward this end, |
3163 |
|
|
3164 |
|
/** |
3165 |
|
* Returns {@code true} if blocking is unnecessary. |
3166 |
+ |
* @return {@code true} if blocking is unnecessary |
3167 |
|
*/ |
3168 |
|
boolean isReleasable(); |
3169 |
|
} |
3191 |
|
public static void managedBlock(ManagedBlocker blocker) |
3192 |
|
throws InterruptedException { |
3193 |
|
Thread t = Thread.currentThread(); |
3194 |
< |
ForkJoinPool p = ((t instanceof ForkJoinWorkerThread) ? |
3195 |
< |
((ForkJoinWorkerThread)t).pool : null); |
3196 |
< |
while (!blocker.isReleasable()) { |
3197 |
< |
if (p == null || p.tryCompensate(null, blocker)) { |
3198 |
< |
try { |
3199 |
< |
do {} while (!blocker.isReleasable() && !blocker.block()); |
3200 |
< |
} finally { |
3201 |
< |
if (p != null) |
3194 |
> |
if (t instanceof ForkJoinWorkerThread) { |
3195 |
> |
ForkJoinPool p = ((ForkJoinWorkerThread)t).pool; |
3196 |
> |
while (!blocker.isReleasable()) { |
3197 |
> |
if (p.tryCompensate(p.ctl)) { |
3198 |
> |
try { |
3199 |
> |
do {} while (!blocker.isReleasable() && |
3200 |
> |
!blocker.block()); |
3201 |
> |
} finally { |
3202 |
|
p.incrementActiveCount(); |
3203 |
+ |
} |
3204 |
+ |
break; |
3205 |
|
} |
2951 |
– |
break; |
3206 |
|
} |
3207 |
|
} |
3208 |
+ |
else { |
3209 |
+ |
do {} while (!blocker.isReleasable() && |
3210 |
+ |
!blocker.block()); |
3211 |
+ |
} |
3212 |
|
} |
3213 |
|
|
3214 |
|
// AbstractExecutorService overrides. These rely on undocumented |
3229 |
|
private static final long PARKBLOCKER; |
3230 |
|
private static final int ABASE; |
3231 |
|
private static final int ASHIFT; |
3232 |
+ |
private static final long STEALCOUNT; |
3233 |
+ |
private static final long PLOCK; |
3234 |
+ |
private static final long INDEXSEED; |
3235 |
+ |
private static final long QBASE; |
3236 |
+ |
private static final long QLOCK; |
3237 |
|
|
3238 |
|
static { |
3239 |
< |
poolNumberGenerator = new AtomicInteger(); |
2977 |
< |
nextSubmitterSeed = new AtomicInteger(0x55555555); |
2978 |
< |
modifyThreadPermission = new RuntimePermission("modifyThread"); |
2979 |
< |
defaultForkJoinWorkerThreadFactory = |
2980 |
< |
new DefaultForkJoinWorkerThreadFactory(); |
2981 |
< |
submitters = new ThreadSubmitter(); |
2982 |
< |
initializationLock = new Mutex(); |
2983 |
< |
int s; |
3239 |
> |
// initialize field offsets for CAS etc |
3240 |
|
try { |
3241 |
|
U = getUnsafe(); |
3242 |
|
Class<?> k = ForkJoinPool.class; |
2987 |
– |
Class<?> ak = ForkJoinTask[].class; |
3243 |
|
CTL = U.objectFieldOffset |
3244 |
|
(k.getDeclaredField("ctl")); |
3245 |
+ |
STEALCOUNT = U.objectFieldOffset |
3246 |
+ |
(k.getDeclaredField("stealCount")); |
3247 |
+ |
PLOCK = U.objectFieldOffset |
3248 |
+ |
(k.getDeclaredField("plock")); |
3249 |
+ |
INDEXSEED = U.objectFieldOffset |
3250 |
+ |
(k.getDeclaredField("indexSeed")); |
3251 |
|
Class<?> tk = Thread.class; |
3252 |
|
PARKBLOCKER = U.objectFieldOffset |
3253 |
|
(tk.getDeclaredField("parkBlocker")); |
3254 |
+ |
Class<?> wk = WorkQueue.class; |
3255 |
+ |
QBASE = U.objectFieldOffset |
3256 |
+ |
(wk.getDeclaredField("base")); |
3257 |
+ |
QLOCK = U.objectFieldOffset |
3258 |
+ |
(wk.getDeclaredField("qlock")); |
3259 |
+ |
Class<?> ak = ForkJoinTask[].class; |
3260 |
|
ABASE = U.arrayBaseOffset(ak); |
3261 |
< |
s = U.arrayIndexScale(ak); |
3261 |
> |
int scale = U.arrayIndexScale(ak); |
3262 |
> |
if ((scale & (scale - 1)) != 0) |
3263 |
> |
throw new Error("data type scale not a power of two"); |
3264 |
> |
ASHIFT = 31 - Integer.numberOfLeadingZeros(scale); |
3265 |
|
} catch (Exception e) { |
3266 |
|
throw new Error(e); |
3267 |
|
} |
2998 |
– |
if ((s & (s-1)) != 0) |
2999 |
– |
throw new Error("data type scale not a power of two"); |
3000 |
– |
ASHIFT = 31 - Integer.numberOfLeadingZeros(s); |
3268 |
|
|
3269 |
< |
// Establish configuration for default pool |
3270 |
< |
try { |
3271 |
< |
String pp = System.getProperty(propPrefix + "parallelism"); |
3272 |
< |
String fp = System.getProperty(propPrefix + "threadFactory"); |
3273 |
< |
String up = System.getProperty(propPrefix + "exceptionHandler"); |
3274 |
< |
int par; |
3275 |
< |
if ((pp == null || (par = Integer.parseInt(pp)) <= 0)) |
3276 |
< |
par = Runtime.getRuntime().availableProcessors(); |
3277 |
< |
commonPoolParallelism = par; |
3269 |
> |
submitters = new ThreadLocal<Submitter>(); |
3270 |
> |
defaultForkJoinWorkerThreadFactory = |
3271 |
> |
new DefaultForkJoinWorkerThreadFactory(); |
3272 |
> |
modifyThreadPermission = new RuntimePermission("modifyThread"); |
3273 |
> |
|
3274 |
> |
common = java.security.AccessController.doPrivileged |
3275 |
> |
(new java.security.PrivilegedAction<ForkJoinPool>() { |
3276 |
> |
public ForkJoinPool run() { return makeCommonPool(); }}); |
3277 |
> |
int par = common.parallelism; // report 1 even if threads disabled |
3278 |
> |
commonParallelism = par > 0 ? par : 1; |
3279 |
> |
} |
3280 |
> |
|
3281 |
> |
/** |
3282 |
> |
* Creates and returns the common pool, respecting user settings |
3283 |
> |
* specified via system properties. |
3284 |
> |
*/ |
3285 |
> |
private static ForkJoinPool makeCommonPool() { |
3286 |
> |
int parallelism = -1; |
3287 |
> |
ForkJoinWorkerThreadFactory factory |
3288 |
> |
= defaultForkJoinWorkerThreadFactory; |
3289 |
> |
UncaughtExceptionHandler handler = null; |
3290 |
> |
try { // ignore exceptions in accessing/parsing properties |
3291 |
> |
String pp = System.getProperty |
3292 |
> |
("java.util.concurrent.ForkJoinPool.common.parallelism"); |
3293 |
> |
String fp = System.getProperty |
3294 |
> |
("java.util.concurrent.ForkJoinPool.common.threadFactory"); |
3295 |
> |
String hp = System.getProperty |
3296 |
> |
("java.util.concurrent.ForkJoinPool.common.exceptionHandler"); |
3297 |
> |
if (pp != null) |
3298 |
> |
parallelism = Integer.parseInt(pp); |
3299 |
|
if (fp != null) |
3300 |
< |
commonPoolFactory = (ForkJoinWorkerThreadFactory) |
3301 |
< |
ClassLoader.getSystemClassLoader().loadClass(fp).newInstance(); |
3302 |
< |
else |
3303 |
< |
commonPoolFactory = defaultForkJoinWorkerThreadFactory; |
3304 |
< |
if (up != null) |
3305 |
< |
commonPoolUEH = (Thread.UncaughtExceptionHandler) |
3018 |
< |
ClassLoader.getSystemClassLoader().loadClass(up).newInstance(); |
3019 |
< |
else |
3020 |
< |
commonPoolUEH = null; |
3021 |
< |
} catch (Exception e) { |
3022 |
< |
throw new Error(e); |
3300 |
> |
factory = ((ForkJoinWorkerThreadFactory)ClassLoader. |
3301 |
> |
getSystemClassLoader().loadClass(fp).newInstance()); |
3302 |
> |
if (hp != null) |
3303 |
> |
handler = ((UncaughtExceptionHandler)ClassLoader. |
3304 |
> |
getSystemClassLoader().loadClass(hp).newInstance()); |
3305 |
> |
} catch (Exception ignore) { |
3306 |
|
} |
3307 |
+ |
|
3308 |
+ |
if (parallelism < 0 && // default 1 less than #cores |
3309 |
+ |
(parallelism = Runtime.getRuntime().availableProcessors() - 1) < 0) |
3310 |
+ |
parallelism = 0; |
3311 |
+ |
if (parallelism > MAX_CAP) |
3312 |
+ |
parallelism = MAX_CAP; |
3313 |
+ |
return new ForkJoinPool(parallelism, factory, handler, LIFO_QUEUE, |
3314 |
+ |
"ForkJoinPool.commonPool-worker-"); |
3315 |
|
} |
3316 |
|
|
3317 |
|
/** |
3324 |
|
private static sun.misc.Unsafe getUnsafe() { |
3325 |
|
try { |
3326 |
|
return sun.misc.Unsafe.getUnsafe(); |
3327 |
< |
} catch (SecurityException se) { |
3328 |
< |
try { |
3329 |
< |
return java.security.AccessController.doPrivileged |
3330 |
< |
(new java.security |
3331 |
< |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
3332 |
< |
public sun.misc.Unsafe run() throws Exception { |
3333 |
< |
java.lang.reflect.Field f = sun.misc |
3334 |
< |
.Unsafe.class.getDeclaredField("theUnsafe"); |
3335 |
< |
f.setAccessible(true); |
3336 |
< |
return (sun.misc.Unsafe) f.get(null); |
3337 |
< |
}}); |
3338 |
< |
} catch (java.security.PrivilegedActionException e) { |
3339 |
< |
throw new RuntimeException("Could not initialize intrinsics", |
3340 |
< |
e.getCause()); |
3341 |
< |
} |
3327 |
> |
} catch (SecurityException tryReflectionInstead) {} |
3328 |
> |
try { |
3329 |
> |
return java.security.AccessController.doPrivileged |
3330 |
> |
(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
3331 |
> |
public sun.misc.Unsafe run() throws Exception { |
3332 |
> |
Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class; |
3333 |
> |
for (java.lang.reflect.Field f : k.getDeclaredFields()) { |
3334 |
> |
f.setAccessible(true); |
3335 |
> |
Object x = f.get(null); |
3336 |
> |
if (k.isInstance(x)) |
3337 |
> |
return k.cast(x); |
3338 |
> |
} |
3339 |
> |
throw new NoSuchFieldError("the Unsafe"); |
3340 |
> |
}}); |
3341 |
> |
} catch (java.security.PrivilegedActionException e) { |
3342 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
3343 |
> |
e.getCause()); |
3344 |
|
} |
3345 |
|
} |
3053 |
– |
|
3346 |
|
} |