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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/licenses/publicdomain |
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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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package jsr166y; |
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import java.util.concurrent.*; |
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import java.io.Serializable; |
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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.RandomAccess; |
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import java.util.Map; |
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import java.util.WeakHashMap; |
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import java.lang.ref.WeakReference; |
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import java.lang.ref.ReferenceQueue; |
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import java.util.concurrent.Callable; |
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import java.util.concurrent.CancellationException; |
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import java.util.concurrent.ExecutionException; |
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import java.util.concurrent.Future; |
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import java.util.concurrent.RejectedExecutionException; |
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import java.util.concurrent.RunnableFuture; |
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import java.util.concurrent.TimeUnit; |
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import java.util.concurrent.TimeoutException; |
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import java.util.concurrent.locks.ReentrantLock; |
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import java.lang.reflect.Constructor; |
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/** |
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* Abstract base class for tasks that run within a {@link ForkJoinPool}. |
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* start other subtasks. As indicated by the name of this class, |
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* many programs using {@code ForkJoinTask} employ only methods |
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* {@link #fork} and {@link #join}, or derivatives such as {@link |
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* #invokeAll}. However, this class also provides a number of other |
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* methods that can come into play in advanced usages, as well as |
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* extension mechanics that allow support of new forms of fork/join |
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* processing. |
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* #invokeAll(ForkJoinTask...) invokeAll}. However, this class also |
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* provides a number of other methods that can come into play in |
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* advanced usages, as well as extension mechanics that allow |
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* support of new forms of fork/join processing. |
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* |
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* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}. |
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* The efficiency of {@code ForkJoinTask}s stems from a set of |
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* restrictions (that are only partially statically enforceable) |
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* reflecting their intended use as computational tasks calculating |
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* pure functions or operating on purely isolated objects. The |
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* primary coordination mechanisms are {@link #fork}, that arranges |
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* reflecting their main use as computational tasks calculating pure |
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* functions or operating on purely isolated objects. The primary |
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* coordination mechanisms are {@link #fork}, that arranges |
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* asynchronous execution, and {@link #join}, that doesn't proceed |
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* until the task's result has been computed. Computations should |
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* avoid {@code synchronized} methods or blocks, and should minimize |
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* other blocking synchronization apart from joining other tasks or |
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* using synchronizers such as Phasers that are advertised to |
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* cooperate with fork/join scheduling. Tasks should also not perform |
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* blocking IO, and should ideally access variables that are |
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* completely independent of those accessed by other running |
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* tasks. Minor breaches of these restrictions, for example using |
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* shared output streams, may be tolerable in practice, but frequent |
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* use may result in poor performance, and the potential to |
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* indefinitely stall if the number of threads not waiting for IO or |
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* other external synchronization becomes exhausted. This usage |
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* restriction is in part enforced by not permitting checked |
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* exceptions such as {@code IOExceptions} to be thrown. However, |
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* computations may still encounter unchecked exceptions, that are |
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* rethrown to callers attempting to join them. These exceptions may |
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* additionally include RejectedExecutionExceptions stemming from |
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* internal resource exhaustion such as failure to allocate internal |
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* task queues. |
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* ideally avoid {@code synchronized} methods or blocks, and should |
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* minimize other blocking synchronization apart from joining other |
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* tasks or using synchronizers such as Phasers that are advertised to |
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* cooperate with fork/join scheduling. Subdividable tasks should also |
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* not perform blocking IO, and should ideally access variables that |
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* are completely independent of those accessed by other running |
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* tasks. These guidelines are loosely enforced by not permitting |
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* checked exceptions such as {@code IOExceptions} to be |
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* thrown. However, computations may still encounter unchecked |
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* exceptions, that are rethrown to callers attempting to join |
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* them. These exceptions may additionally include {@link |
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* RejectedExecutionException} stemming from internal resource |
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* exhaustion, such as failure to allocate internal task |
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* queues. Rethrown exceptions behave in the same way as regular |
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* exceptions, but, when possible, contain stack traces (as displayed |
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* for example using {@code ex.printStackTrace()}) of both the thread |
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* that initiated the computation as well as the thread actually |
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* encountering the exception; minimally only the latter. |
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* |
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* <p>It is possible to define and use ForkJoinTasks that may block, |
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* but doing do requires three further considerations: (1) Completion |
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* of few if any <em>other</em> tasks should be dependent on a task |
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* that blocks on external synchronization or IO. Event-style async |
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* tasks that are never joined often fall into this category. (2) To |
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* minimize resource impact, tasks should be small; ideally performing |
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* only the (possibly) blocking action. (3) Unless the {@link |
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* ForkJoinPool.ManagedBlocker} API is used, or the number of possibly |
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* blocked tasks is known to be less than the pool's {@link |
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* ForkJoinPool#getParallelism} level, the pool cannot guarantee that |
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* enough threads will be available to ensure progress or good |
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* performance. |
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* |
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* <p>The primary method for awaiting completion and extracting |
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* results of a task is {@link #join}, but there are several variants: |
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* The {@link Future#get} methods support interruptible and/or timed |
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* waits for completion and report results using {@code Future} |
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* conventions. Method {@link #helpJoin} enables callers to actively |
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* execute other tasks while awaiting joins, which is sometimes more |
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* efficient but only applies when all subtasks are known to be |
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* strictly tree-structured. Method {@link #invoke} is semantically |
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* conventions. Method {@link #invoke} is semantically |
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* equivalent to {@code fork(); join()} but always attempts to begin |
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* execution in the current thread. The "<em>quiet</em>" forms of |
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* these methods do not extract results or report exceptions. These |
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* performs the most common form of parallel invocation: forking a set |
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* of tasks and joining them all. |
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* |
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* <p>In the most typical usages, a fork-join pair act like a call |
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* (fork) and return (join) from a parallel recursive function. As is |
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* the case with other forms of recursive calls, returns (joins) |
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* should be performed innermost-first. For example, {@code a.fork(); |
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* b.fork(); b.join(); a.join();} is likely to be substantially more |
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* efficient than joining {@code a} before {@code b}. |
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* |
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* <p>The execution status of tasks may be queried at several levels |
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* of detail: {@link #isDone} is true if a task completed in any way |
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* (including the case where a task was cancelled without executing); |
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* {@link #isCancelled} is true if completion was due to cancellation; |
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* {@link #isCompletedNormally} is true if a task completed without |
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* cancellation or encountering an exception; {@link |
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* #isCompletedExceptionally} is true if if the task encountered an |
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* exception (in which case {@link #getException} returns the |
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* exception); {@link #isCancelled} is true if the task was cancelled |
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* (in which case {@link #getException} returns a {@link |
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* java.util.concurrent.CancellationException}); and {@link |
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* #isCompletedAbnormally} is true if a task was either cancelled or |
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* encountered an exception. |
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* cancellation or encountering an exception; {@link #isCancelled} is |
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* true if the task was cancelled (in which case {@link #getException} |
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* returns a {@link java.util.concurrent.CancellationException}); and |
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* {@link #isCompletedAbnormally} is true if a task was either |
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* cancelled or encountered an exception, in which case {@link |
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* #getException} will return either the encountered exception or |
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* {@link java.util.concurrent.CancellationException}. |
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* |
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* <p>The ForkJoinTask class is not usually directly subclassed. |
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* Instead, you subclass one of the abstract classes that support a |
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* ForkJoinTasks (as may be determined using method {@link |
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* #inForkJoinPool}). Attempts to invoke them in other contexts |
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* result in exceptions or errors, possibly including |
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* ClassCastException. |
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* {@code ClassCastException}. |
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* |
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* <p>Method {@link #join} and its variants are appropriate for use |
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* only when completion dependencies are acyclic; that is, the |
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* parallel computation can be described as a directed acyclic graph |
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* (DAG). Otherwise, executions may encounter a form of deadlock as |
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* tasks cyclically wait for each other. However, this framework |
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* supports other methods and techniques (for example the use of |
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* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that |
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* may be of use in constructing custom subclasses for problems that |
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* are not statically structured as DAGs. To support such usages a |
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* ForkJoinTask may be atomically <em>marked</em> using {@link |
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* #markForkJoinTask} and checked for marking using {@link |
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* #isMarkedForkJoinTask}. The ForkJoinTask implementation does not |
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* use these {@code protected} methods or marks for any purpose, but |
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* they may be of use in the construction of specialized subclasses. |
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* For example, parallel graph traversals can use the supplied methods |
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* to avoid revisiting nodes/tasks that have already been processed. |
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* Also, completion based designs can use them to record that one |
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* subtask has completed. (Method names for marking are bulky in part |
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* to encourage definition of methods that reflect their usage |
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* patterns.) |
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* |
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* <p>Most base support methods are {@code final}, to prevent |
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* overriding of implementations that are intrinsically tied to the |
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* computation. Large tasks should be split into smaller subtasks, |
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* usually via recursive decomposition. As a very rough rule of thumb, |
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* a task should perform more than 100 and less than 10000 basic |
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* computational steps. If tasks are too big, then parallelism cannot |
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* improve throughput. If too small, then memory and internal task |
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* maintenance overhead may overwhelm processing. |
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* computational steps, and should avoid indefinite looping. If tasks |
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* are too big, then parallelism cannot improve throughput. If too |
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* small, then memory and internal task maintenance overhead may |
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* overwhelm processing. |
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* |
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* <p>This class provides {@code adapt} methods for {@link |
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* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that |
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* may be of use when mixing execution of ForkJoinTasks with other |
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* kinds of tasks. When all tasks are of this form, consider using a |
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* pool in {@link ForkJoinPool#setAsyncMode async mode}. |
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* <p>This class provides {@code adapt} methods for {@link Runnable} |
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* and {@link Callable}, that may be of use when mixing execution of |
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* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are |
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* of this form, consider using a pool constructed in <em>asyncMode</em>. |
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* |
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* <p>ForkJoinTasks are {@code Serializable}, which enables them to be |
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* used in extensions such as remote execution frameworks. It is |
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*/ |
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public abstract class ForkJoinTask<V> implements Future<V>, Serializable { |
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/** |
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* Run control status bits packed into a single int to minimize |
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* footprint and to ensure atomicity (via CAS). Status is |
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* initially zero, and takes on nonnegative values until |
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* completed, upon which status holds COMPLETED. CANCELLED, or |
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* EXCEPTIONAL, which use the top 3 bits. Tasks undergoing |
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* blocking waits by other threads have SIGNAL_MASK bits set -- |
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* bit 15 for external (nonFJ) waits, and the rest a count of |
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* waiting FJ threads. (This representation relies on |
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* ForkJoinPool max thread limits). Completion of a stolen task |
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* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even |
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* though suboptimal for some purposes, we use basic builtin |
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* wait/notify to take advantage of "monitor inflation" in JVMs |
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* that we would otherwise need to emulate to avoid adding further |
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* per-task bookkeeping overhead. Note that bits 16-28 are |
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* currently unused. Also value 0x80000000 is available as spare |
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* completion value. |
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/* |
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* See the internal documentation of class ForkJoinPool for a |
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* general implementation overview. ForkJoinTasks are mainly |
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* responsible for maintaining their "status" field amidst relays |
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* to methods in ForkJoinWorkerThread and ForkJoinPool. |
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* |
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* The methods of this class are more-or-less layered into |
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* (1) basic status maintenance |
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* (2) execution and awaiting completion |
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* (3) user-level methods that additionally report results. |
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* This is sometimes hard to see because this file orders exported |
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* methods in a way that flows well in javadocs. |
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*/ |
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volatile int status; // accessed directly by pool and workers |
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static final int COMPLETION_MASK = 0xe0000000; |
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static final int NORMAL = 0xe0000000; // == mask |
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static final int CANCELLED = 0xc0000000; |
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static final int EXCEPTIONAL = 0xa0000000; |
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static final int SIGNAL_MASK = 0x0000ffff; |
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static final int INTERNAL_SIGNAL_MASK = 0x00007fff; |
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static final int EXTERNAL_SIGNAL = 0x00008000; // top bit of low word |
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/** |
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* Table of exceptions thrown by tasks, to enable reporting by |
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* callers. Because exceptions are rare, we don't directly keep |
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* them with task objects, but instead use a weak ref table. Note |
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* that cancellation exceptions don't appear in the table, but are |
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* instead recorded as status values. |
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* TODO: Use ConcurrentReferenceHashMap |
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* The number of times to try to help join a task without any |
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* apparent progress before giving up and blocking. The value is |
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* arbitrary but should be large enough to cope with transient |
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* stalls (due to GC etc) that can cause helping methods not to be |
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* able to proceed because other workers have not progressed to |
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* the point where subtasks can be found or taken. |
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*/ |
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private static final int HELP_RETRIES = 32; |
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|
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/* |
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* The status field holds run control status bits packed into a |
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* single int to minimize footprint and to ensure atomicity (via |
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* CAS). Status is initially zero, and takes on nonnegative |
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* values until completed, upon which status holds value |
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* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking |
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* waits by other threads have the SIGNAL bit set. Completion of |
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* a stolen task with SIGNAL set awakens any waiters via |
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* notifyAll. Even though suboptimal for some purposes, we use |
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* basic builtin wait/notify to take advantage of "monitor |
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* inflation" in JVMs that we would otherwise need to emulate to |
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* avoid adding further per-task bookkeeping overhead. We want |
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* these monitors to be "fat", i.e., not use biasing or thin-lock |
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* techniques, so use some odd coding idioms that tend to avoid |
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* them. |
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*/ |
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static final Map<ForkJoinTask<?>, Throwable> exceptionMap = |
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Collections.synchronizedMap |
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(new WeakHashMap<ForkJoinTask<?>, Throwable>()); |
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|
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// within-package utilities |
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|
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/** |
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* Gets current worker thread, or null if not a worker thread. |
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*/ |
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static ForkJoinWorkerThread getWorker() { |
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Thread t = Thread.currentThread(); |
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return ((t instanceof ForkJoinWorkerThread) ? |
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(ForkJoinWorkerThread) t : null); |
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} |
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|
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final boolean casStatus(int cmp, int val) { |
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return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val); |
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} |
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|
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/** |
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* Workaround for not being able to rethrow unchecked exceptions. |
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*/ |
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static void rethrowException(Throwable ex) { |
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if (ex != null) |
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UNSAFE.throwException(ex); |
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} |
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|
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// Setting completion status |
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/** The run status of this task */ |
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volatile int status; // accessed directly by pool and workers |
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static final int NORMAL = 0xfffffffc; // negative with low 2 bits 0 |
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static final int CANCELLED = 0xfffffff8; // must be < NORMAL |
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static final int EXCEPTIONAL = 0xfffffff4; // must be < CANCELLED |
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static final int SIGNAL = 0x00000001; |
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static final int MARKED = 0x00000002; |
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|
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/** |
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* Marks completion and wakes up threads waiting to join this task. |
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* Marks completion and wakes up threads waiting to join this |
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* task, also clearing signal request bits. A specialization for |
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* NORMAL completion is in method doExec. |
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* |
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* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
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* @return completion status on exit |
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*/ |
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final void setCompletion(int completion) { |
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ForkJoinPool pool = getPool(); |
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if (pool != null) { |
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int s; // Clear signal bits while setting completion status |
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do {} while ((s = status) >= 0 && !casStatus(s, completion)); |
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|
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if ((s & SIGNAL_MASK) != 0) { |
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if ((s &= INTERNAL_SIGNAL_MASK) != 0) |
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pool.updateRunningCount(s); |
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synchronized (this) { notifyAll(); } |
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private int setCompletion(int completion) { |
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for (int s;;) { |
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if ((s = status) < 0) |
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return s; |
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if (U.compareAndSwapInt(this, STATUS, s, (s & ~SIGNAL)|completion)) { |
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if ((s & SIGNAL) != 0) |
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synchronized (this) { notifyAll(); } |
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return completion; |
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} |
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} |
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else |
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externallySetCompletion(completion); |
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} |
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|
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/** |
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* Version of setCompletion for non-FJ threads. Leaves signal |
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* bits for unblocked threads to adjust, and always notifies. |
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*/ |
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private void externallySetCompletion(int completion) { |
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int s; |
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do {} while ((s = status) >= 0 && |
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!casStatus(s, (s & SIGNAL_MASK) | completion)); |
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synchronized (this) { notifyAll(); } |
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} |
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|
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/** |
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* Sets status to indicate normal completion. |
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*/ |
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final void setNormalCompletion() { |
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// Try typical fast case -- single CAS, no signal, not already done. |
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// Manually expand casStatus to improve chances of inlining it |
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if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL)) |
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setCompletion(NORMAL); |
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* Primary execution method for stolen tasks. Unless done, calls |
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* exec and records status if completed, but doesn't wait for |
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* completion otherwise. |
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* |
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* @return status on exit from this method |
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*/ |
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final int doExec() { |
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int s; boolean completed; |
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if ((s = status) >= 0) { |
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try { |
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completed = exec(); |
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} catch (Throwable rex) { |
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return setExceptionalCompletion(rex); |
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> |
} |
270 |
> |
while ((s = status) >= 0 && completed) { |
271 |
> |
if (U.compareAndSwapInt(this, STATUS, s, (s & ~SIGNAL)|NORMAL)) { |
272 |
> |
if ((s & SIGNAL) != 0) |
273 |
> |
synchronized (this) { notifyAll(); } |
274 |
> |
return NORMAL; |
275 |
> |
} |
276 |
> |
} |
277 |
> |
} |
278 |
> |
return s; |
279 |
|
} |
280 |
|
|
251 |
– |
// internal waiting and notification |
252 |
– |
|
281 |
|
/** |
282 |
< |
* Performs the actual monitor wait for awaitDone. |
282 |
> |
* Blocks a non-worker-thread until completion. |
283 |
> |
* @return status upon completion |
284 |
|
*/ |
285 |
< |
private void doAwaitDone() { |
286 |
< |
// Minimize lock bias and in/de-flation effects by maximizing |
287 |
< |
// chances of waiting inside sync |
288 |
< |
try { |
289 |
< |
while (status >= 0) |
290 |
< |
synchronized (this) { if (status >= 0) wait(); } |
291 |
< |
} catch (InterruptedException ie) { |
292 |
< |
onInterruptedWait(); |
285 |
> |
private int externalAwaitDone() { |
286 |
> |
int s; |
287 |
> |
if ((s = status) >= 0) { |
288 |
> |
boolean interrupted = false; |
289 |
> |
synchronized (this) { |
290 |
> |
while ((s = status) >= 0) { |
291 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
292 |
> |
try { |
293 |
> |
wait(); |
294 |
> |
} catch (InterruptedException ie) { |
295 |
> |
interrupted = true; |
296 |
> |
} |
297 |
> |
} |
298 |
> |
} |
299 |
> |
} |
300 |
> |
if (interrupted) |
301 |
> |
Thread.currentThread().interrupt(); |
302 |
|
} |
303 |
+ |
return s; |
304 |
|
} |
305 |
|
|
306 |
|
/** |
307 |
< |
* Performs the actual timed monitor wait for awaitDone. |
307 |
> |
* Blocks a non-worker-thread until completion or interruption or timeout. |
308 |
|
*/ |
309 |
< |
private void doAwaitDone(long startTime, long nanos) { |
310 |
< |
synchronized (this) { |
311 |
< |
try { |
312 |
< |
while (status >= 0) { |
313 |
< |
long nt = nanos - (System.nanoTime() - startTime); |
314 |
< |
if (nt <= 0) |
315 |
< |
break; |
316 |
< |
wait(nt / 1000000, (int) (nt % 1000000)); |
309 |
> |
private int externalInterruptibleAwaitDone(long millis) |
310 |
> |
throws InterruptedException { |
311 |
> |
int s; |
312 |
> |
if (Thread.interrupted()) |
313 |
> |
throw new InterruptedException(); |
314 |
> |
if ((s = status) >= 0) { |
315 |
> |
synchronized (this) { |
316 |
> |
while ((s = status) >= 0) { |
317 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
318 |
> |
wait(millis); |
319 |
> |
if (millis > 0L) |
320 |
> |
break; |
321 |
> |
} |
322 |
|
} |
279 |
– |
} catch (InterruptedException ie) { |
280 |
– |
onInterruptedWait(); |
323 |
|
} |
324 |
|
} |
325 |
+ |
return s; |
326 |
|
} |
327 |
|
|
285 |
– |
// Awaiting completion |
328 |
|
|
329 |
|
/** |
330 |
< |
* Sets status to indicate there is joiner, then waits for join, |
331 |
< |
* surrounded with pool notifications. |
330 |
> |
* Implementation for join, get, quietlyJoin. Directly handles |
331 |
> |
* only cases of already-completed, external wait, and |
332 |
> |
* unfork+exec. Others are relayed to awaitJoin. |
333 |
> |
* |
334 |
> |
* @return status upon completion |
335 |
> |
*/ |
336 |
> |
private int doJoin() { |
337 |
> |
int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w; |
338 |
> |
if ((s = status) >= 0) { |
339 |
> |
if (!((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) |
340 |
> |
s = externalAwaitDone(); |
341 |
> |
else if (!(w = (wt = (ForkJoinWorkerThread)t).workQueue). |
342 |
> |
tryUnpush(this) || (s = doExec()) >= 0) |
343 |
> |
s = awaitJoin(w, wt.pool); |
344 |
> |
} |
345 |
> |
return s; |
346 |
> |
} |
347 |
> |
|
348 |
> |
/** |
349 |
> |
* Helps and/or blocks until joined. |
350 |
|
* |
351 |
< |
* @return status upon exit |
351 |
> |
* @param w the joiner |
352 |
> |
* @param p the pool |
353 |
> |
* @return status upon completion |
354 |
|
*/ |
355 |
< |
private int awaitDone(ForkJoinWorkerThread w, |
294 |
< |
boolean maintainParallelism) { |
295 |
< |
ForkJoinPool pool = (w == null) ? null : w.pool; |
355 |
> |
private int awaitJoin(ForkJoinPool.WorkQueue w, ForkJoinPool p) { |
356 |
|
int s; |
357 |
< |
while ((s = status) >= 0) { |
358 |
< |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
359 |
< |
if (pool == null || !pool.preJoin(this, maintainParallelism)) |
360 |
< |
doAwaitDone(); |
361 |
< |
if (((s = status) & INTERNAL_SIGNAL_MASK) != 0) |
362 |
< |
adjustPoolCountsOnUnblock(pool); |
357 |
> |
ForkJoinTask<?> prevJoin = w.currentJoin; |
358 |
> |
w.currentJoin = this; |
359 |
> |
for (int k = HELP_RETRIES; (s = status) >= 0;) { |
360 |
> |
if ((w.queueSize() > 0) ? |
361 |
> |
w.tryRemoveAndExec(this) : // self-help |
362 |
> |
p.tryHelpStealer(w, this)) // help process tasks |
363 |
> |
k = HELP_RETRIES; // reset if made progress |
364 |
> |
else if ((s = status) < 0) // recheck |
365 |
|
break; |
366 |
+ |
else if (--k > 0) { |
367 |
+ |
if ((k & 3) == 1) |
368 |
+ |
Thread.yield(); // occasionally yield |
369 |
+ |
} |
370 |
+ |
else if (k == 0) |
371 |
+ |
p.tryPollForAndExec(w, this); // uncommon self-help case |
372 |
+ |
else if (p.tryCompensate()) { // true if can block |
373 |
+ |
try { |
374 |
+ |
int ss = status; |
375 |
+ |
if (ss >= 0 && // assert need signal |
376 |
+ |
U.compareAndSwapInt(this, STATUS, ss, ss | SIGNAL)) { |
377 |
+ |
synchronized (this) { |
378 |
+ |
if (status >= 0) // block |
379 |
+ |
wait(); |
380 |
+ |
} |
381 |
+ |
} |
382 |
+ |
} catch (InterruptedException ignore) { |
383 |
+ |
} finally { |
384 |
+ |
p.incrementActiveCount(); // re-activate |
385 |
+ |
} |
386 |
|
} |
387 |
|
} |
388 |
+ |
w.currentJoin = prevJoin; |
389 |
|
return s; |
390 |
|
} |
391 |
|
|
392 |
|
/** |
393 |
< |
* Timed version of awaitDone |
393 |
> |
* Implementation for invoke, quietlyInvoke. |
394 |
|
* |
395 |
< |
* @return status upon exit |
395 |
> |
* @return status upon completion |
396 |
|
*/ |
397 |
< |
private int awaitDone(ForkJoinWorkerThread w, long nanos) { |
398 |
< |
ForkJoinPool pool = (w == null) ? null : w.pool; |
399 |
< |
int s; |
400 |
< |
while ((s = status) >= 0) { |
401 |
< |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
402 |
< |
long startTime = System.nanoTime(); |
403 |
< |
if (pool == null || !pool.preJoin(this, false)) |
404 |
< |
doAwaitDone(startTime, nanos); |
322 |
< |
if ((s = status) >= 0) { |
323 |
< |
adjustPoolCountsOnCancelledWait(pool); |
324 |
< |
s = status; |
325 |
< |
} |
326 |
< |
if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0) |
327 |
< |
adjustPoolCountsOnUnblock(pool); |
328 |
< |
break; |
397 |
> |
private int doInvoke() { |
398 |
> |
int s; Thread t; |
399 |
> |
if ((s = doExec()) >= 0) { |
400 |
> |
if (!((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) |
401 |
> |
s = externalAwaitDone(); |
402 |
> |
else { |
403 |
> |
ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; |
404 |
> |
s = awaitJoin(wt.workQueue, wt.pool); |
405 |
|
} |
406 |
|
} |
407 |
|
return s; |
408 |
|
} |
409 |
|
|
410 |
+ |
// Exception table support |
411 |
+ |
|
412 |
|
/** |
413 |
< |
* Notifies pool that thread is unblocked. Called by signalled |
414 |
< |
* threads when woken by non-FJ threads (which is atypical). |
413 |
> |
* Table of exceptions thrown by tasks, to enable reporting by |
414 |
> |
* callers. Because exceptions are rare, we don't directly keep |
415 |
> |
* them with task objects, but instead use a weak ref table. Note |
416 |
> |
* that cancellation exceptions don't appear in the table, but are |
417 |
> |
* instead recorded as status values. |
418 |
> |
* |
419 |
> |
* Note: These statics are initialized below in static block. |
420 |
|
*/ |
421 |
< |
private void adjustPoolCountsOnUnblock(ForkJoinPool pool) { |
422 |
< |
int s; |
423 |
< |
do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK)); |
341 |
< |
if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0) |
342 |
< |
pool.updateRunningCount(s); |
343 |
< |
} |
421 |
> |
private static final ExceptionNode[] exceptionTable; |
422 |
> |
private static final ReentrantLock exceptionTableLock; |
423 |
> |
private static final ReferenceQueue<Object> exceptionTableRefQueue; |
424 |
|
|
425 |
|
/** |
426 |
< |
* Notifies pool to adjust counts on cancelled or timed out wait. |
426 |
> |
* Fixed capacity for exceptionTable. |
427 |
|
*/ |
428 |
< |
private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) { |
349 |
< |
if (pool != null) { |
350 |
< |
int s; |
351 |
< |
while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) { |
352 |
< |
if (casStatus(s, s - 1)) { |
353 |
< |
pool.updateRunningCount(1); |
354 |
< |
break; |
355 |
< |
} |
356 |
< |
} |
357 |
< |
} |
358 |
< |
} |
428 |
> |
private static final int EXCEPTION_MAP_CAPACITY = 32; |
429 |
|
|
430 |
|
/** |
431 |
< |
* Handles interruptions during waits. |
431 |
> |
* Key-value nodes for exception table. The chained hash table |
432 |
> |
* uses identity comparisons, full locking, and weak references |
433 |
> |
* for keys. The table has a fixed capacity because it only |
434 |
> |
* maintains task exceptions long enough for joiners to access |
435 |
> |
* them, so should never become very large for sustained |
436 |
> |
* periods. However, since we do not know when the last joiner |
437 |
> |
* completes, we must use weak references and expunge them. We do |
438 |
> |
* so on each operation (hence full locking). Also, some thread in |
439 |
> |
* any ForkJoinPool will call helpExpungeStaleExceptions when its |
440 |
> |
* pool becomes isQuiescent. |
441 |
|
*/ |
442 |
< |
private void onInterruptedWait() { |
443 |
< |
ForkJoinWorkerThread w = getWorker(); |
444 |
< |
if (w == null) |
445 |
< |
Thread.currentThread().interrupt(); // re-interrupt |
446 |
< |
else if (w.isTerminating()) |
447 |
< |
cancelIgnoringExceptions(); |
448 |
< |
// else if FJworker, ignore interrupt |
449 |
< |
} |
450 |
< |
|
451 |
< |
// Recording and reporting exceptions |
373 |
< |
|
374 |
< |
private void setDoneExceptionally(Throwable rex) { |
375 |
< |
exceptionMap.put(this, rex); |
376 |
< |
setCompletion(EXCEPTIONAL); |
442 |
> |
static final class ExceptionNode extends WeakReference<ForkJoinTask<?>>{ |
443 |
> |
final Throwable ex; |
444 |
> |
ExceptionNode next; |
445 |
> |
final long thrower; // use id not ref to avoid weak cycles |
446 |
> |
ExceptionNode(ForkJoinTask<?> task, Throwable ex, ExceptionNode next) { |
447 |
> |
super(task, exceptionTableRefQueue); |
448 |
> |
this.ex = ex; |
449 |
> |
this.next = next; |
450 |
> |
this.thrower = Thread.currentThread().getId(); |
451 |
> |
} |
452 |
|
} |
453 |
|
|
454 |
|
/** |
455 |
< |
* Throws the exception associated with status s. |
455 |
> |
* Records exception and sets exceptional completion. |
456 |
|
* |
457 |
< |
* @throws the exception |
457 |
> |
* @return status on exit |
458 |
|
*/ |
459 |
< |
private void reportException(int s) { |
460 |
< |
if ((s &= COMPLETION_MASK) < NORMAL) { |
461 |
< |
if (s == CANCELLED) |
462 |
< |
throw new CancellationException(); |
463 |
< |
else |
464 |
< |
rethrowException(exceptionMap.get(this)); |
459 |
> |
private int setExceptionalCompletion(Throwable ex) { |
460 |
> |
int h = System.identityHashCode(this); |
461 |
> |
final ReentrantLock lock = exceptionTableLock; |
462 |
> |
lock.lock(); |
463 |
> |
try { |
464 |
> |
expungeStaleExceptions(); |
465 |
> |
ExceptionNode[] t = exceptionTable; |
466 |
> |
int i = h & (t.length - 1); |
467 |
> |
for (ExceptionNode e = t[i]; ; e = e.next) { |
468 |
> |
if (e == null) { |
469 |
> |
t[i] = new ExceptionNode(this, ex, t[i]); |
470 |
> |
break; |
471 |
> |
} |
472 |
> |
if (e.get() == this) // already present |
473 |
> |
break; |
474 |
> |
} |
475 |
> |
} finally { |
476 |
> |
lock.unlock(); |
477 |
|
} |
478 |
+ |
return setCompletion(EXCEPTIONAL); |
479 |
|
} |
480 |
|
|
481 |
|
/** |
482 |
< |
* Returns result or throws exception using j.u.c.Future conventions. |
483 |
< |
* Only call when {@code isDone} known to be true. |
482 |
> |
* Cancels, ignoring any exceptions thrown by cancel. Used during |
483 |
> |
* worker and pool shutdown. Cancel is spec'ed not to throw any |
484 |
> |
* exceptions, but if it does anyway, we have no recourse during |
485 |
> |
* shutdown, so guard against this case. |
486 |
|
*/ |
487 |
< |
private V reportFutureResult() |
488 |
< |
throws ExecutionException, InterruptedException { |
489 |
< |
if (Thread.interrupted()) |
490 |
< |
throw new InterruptedException(); |
491 |
< |
int s = status & COMPLETION_MASK; |
492 |
< |
if (s < NORMAL) { |
403 |
< |
Throwable ex; |
404 |
< |
if (s == CANCELLED) |
405 |
< |
throw new CancellationException(); |
406 |
< |
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
407 |
< |
throw new ExecutionException(ex); |
487 |
> |
static final void cancelIgnoringExceptions(ForkJoinTask<?> t) { |
488 |
> |
if (t != null && t.status >= 0) { |
489 |
> |
try { |
490 |
> |
t.cancel(false); |
491 |
> |
} catch (Throwable ignore) { |
492 |
> |
} |
493 |
|
} |
409 |
– |
return getRawResult(); |
494 |
|
} |
495 |
|
|
496 |
|
/** |
497 |
< |
* Returns result or throws exception using j.u.c.Future conventions |
414 |
< |
* with timeouts. |
497 |
> |
* Removes exception node and clears status |
498 |
|
*/ |
499 |
< |
private V reportTimedFutureResult() |
500 |
< |
throws InterruptedException, ExecutionException, TimeoutException { |
501 |
< |
if (Thread.interrupted()) |
502 |
< |
throw new InterruptedException(); |
503 |
< |
Throwable ex; |
504 |
< |
int s = status & COMPLETION_MASK; |
505 |
< |
if (s == NORMAL) |
506 |
< |
return getRawResult(); |
507 |
< |
if (s == CANCELLED) |
508 |
< |
throw new CancellationException(); |
509 |
< |
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
510 |
< |
throw new ExecutionException(ex); |
511 |
< |
throw new TimeoutException(); |
499 |
> |
private void clearExceptionalCompletion() { |
500 |
> |
int h = System.identityHashCode(this); |
501 |
> |
final ReentrantLock lock = exceptionTableLock; |
502 |
> |
lock.lock(); |
503 |
> |
try { |
504 |
> |
ExceptionNode[] t = exceptionTable; |
505 |
> |
int i = h & (t.length - 1); |
506 |
> |
ExceptionNode e = t[i]; |
507 |
> |
ExceptionNode pred = null; |
508 |
> |
while (e != null) { |
509 |
> |
ExceptionNode next = e.next; |
510 |
> |
if (e.get() == this) { |
511 |
> |
if (pred == null) |
512 |
> |
t[i] = next; |
513 |
> |
else |
514 |
> |
pred.next = next; |
515 |
> |
break; |
516 |
> |
} |
517 |
> |
pred = e; |
518 |
> |
e = next; |
519 |
> |
} |
520 |
> |
expungeStaleExceptions(); |
521 |
> |
status = 0; |
522 |
> |
} finally { |
523 |
> |
lock.unlock(); |
524 |
> |
} |
525 |
|
} |
526 |
|
|
431 |
– |
// internal execution methods |
432 |
– |
|
527 |
|
/** |
528 |
< |
* Calls exec, recording completion, and rethrowing exception if |
529 |
< |
* encountered. Caller should normally check status before calling. |
528 |
> |
* Returns a rethrowable exception for the given task, if |
529 |
> |
* available. To provide accurate stack traces, if the exception |
530 |
> |
* was not thrown by the current thread, we try to create a new |
531 |
> |
* exception of the same type as the one thrown, but with the |
532 |
> |
* recorded exception as its cause. If there is no such |
533 |
> |
* constructor, we instead try to use a no-arg constructor, |
534 |
> |
* followed by initCause, to the same effect. If none of these |
535 |
> |
* apply, or any fail due to other exceptions, we return the |
536 |
> |
* recorded exception, which is still correct, although it may |
537 |
> |
* contain a misleading stack trace. |
538 |
|
* |
539 |
< |
* @return true if completed normally |
539 |
> |
* @return the exception, or null if none |
540 |
|
*/ |
541 |
< |
private boolean tryExec() { |
542 |
< |
try { // try block must contain only call to exec |
543 |
< |
if (!exec()) |
544 |
< |
return false; |
545 |
< |
} catch (Throwable rex) { |
546 |
< |
setDoneExceptionally(rex); |
547 |
< |
rethrowException(rex); |
548 |
< |
return false; // not reached |
541 |
> |
private Throwable getThrowableException() { |
542 |
> |
if (status != EXCEPTIONAL) |
543 |
> |
return null; |
544 |
> |
int h = System.identityHashCode(this); |
545 |
> |
ExceptionNode e; |
546 |
> |
final ReentrantLock lock = exceptionTableLock; |
547 |
> |
lock.lock(); |
548 |
> |
try { |
549 |
> |
expungeStaleExceptions(); |
550 |
> |
ExceptionNode[] t = exceptionTable; |
551 |
> |
e = t[h & (t.length - 1)]; |
552 |
> |
while (e != null && e.get() != this) |
553 |
> |
e = e.next; |
554 |
> |
} finally { |
555 |
> |
lock.unlock(); |
556 |
|
} |
557 |
< |
setNormalCompletion(); |
558 |
< |
return true; |
559 |
< |
} |
560 |
< |
|
561 |
< |
/** |
453 |
< |
* Main execution method used by worker threads. Invokes |
454 |
< |
* base computation unless already complete. |
455 |
< |
*/ |
456 |
< |
final void quietlyExec() { |
457 |
< |
if (status >= 0) { |
557 |
> |
Throwable ex; |
558 |
> |
if (e == null || (ex = e.ex) == null) |
559 |
> |
return null; |
560 |
> |
if (e.thrower != Thread.currentThread().getId()) { |
561 |
> |
Class<? extends Throwable> ec = ex.getClass(); |
562 |
|
try { |
563 |
< |
if (!exec()) |
564 |
< |
return; |
565 |
< |
} catch (Throwable rex) { |
566 |
< |
setDoneExceptionally(rex); |
567 |
< |
return; |
563 |
> |
Constructor<?> noArgCtor = null; |
564 |
> |
Constructor<?>[] cs = ec.getConstructors();// public ctors only |
565 |
> |
for (int i = 0; i < cs.length; ++i) { |
566 |
> |
Constructor<?> c = cs[i]; |
567 |
> |
Class<?>[] ps = c.getParameterTypes(); |
568 |
> |
if (ps.length == 0) |
569 |
> |
noArgCtor = c; |
570 |
> |
else if (ps.length == 1 && ps[0] == Throwable.class) |
571 |
> |
return (Throwable)(c.newInstance(ex)); |
572 |
> |
} |
573 |
> |
if (noArgCtor != null) { |
574 |
> |
Throwable wx = (Throwable)(noArgCtor.newInstance()); |
575 |
> |
wx.initCause(ex); |
576 |
> |
return wx; |
577 |
> |
} |
578 |
> |
} catch (Exception ignore) { |
579 |
|
} |
465 |
– |
setNormalCompletion(); |
580 |
|
} |
581 |
+ |
return ex; |
582 |
|
} |
583 |
|
|
584 |
|
/** |
585 |
< |
* Calls exec(), recording but not rethrowing exception. |
471 |
< |
* Caller should normally check status before calling. |
472 |
< |
* |
473 |
< |
* @return true if completed normally |
585 |
> |
* Poll stale refs and remove them. Call only while holding lock. |
586 |
|
*/ |
587 |
< |
private boolean tryQuietlyInvoke() { |
588 |
< |
try { |
589 |
< |
if (!exec()) |
590 |
< |
return false; |
591 |
< |
} catch (Throwable rex) { |
592 |
< |
setDoneExceptionally(rex); |
593 |
< |
return false; |
587 |
> |
private static void expungeStaleExceptions() { |
588 |
> |
for (Object x; (x = exceptionTableRefQueue.poll()) != null;) { |
589 |
> |
if (x instanceof ExceptionNode) { |
590 |
> |
ForkJoinTask<?> key = ((ExceptionNode)x).get(); |
591 |
> |
ExceptionNode[] t = exceptionTable; |
592 |
> |
int i = System.identityHashCode(key) & (t.length - 1); |
593 |
> |
ExceptionNode e = t[i]; |
594 |
> |
ExceptionNode pred = null; |
595 |
> |
while (e != null) { |
596 |
> |
ExceptionNode next = e.next; |
597 |
> |
if (e == x) { |
598 |
> |
if (pred == null) |
599 |
> |
t[i] = next; |
600 |
> |
else |
601 |
> |
pred.next = next; |
602 |
> |
break; |
603 |
> |
} |
604 |
> |
pred = e; |
605 |
> |
e = next; |
606 |
> |
} |
607 |
> |
} |
608 |
|
} |
483 |
– |
setNormalCompletion(); |
484 |
– |
return true; |
609 |
|
} |
610 |
|
|
611 |
|
/** |
612 |
< |
* Cancels, ignoring any exceptions it throws. |
612 |
> |
* If lock is available, poll stale refs and remove them. |
613 |
> |
* Called from ForkJoinPool when pools become quiescent. |
614 |
|
*/ |
615 |
< |
final void cancelIgnoringExceptions() { |
616 |
< |
try { |
617 |
< |
cancel(false); |
618 |
< |
} catch (Throwable ignore) { |
615 |
> |
static final void helpExpungeStaleExceptions() { |
616 |
> |
final ReentrantLock lock = exceptionTableLock; |
617 |
> |
if (lock.tryLock()) { |
618 |
> |
try { |
619 |
> |
expungeStaleExceptions(); |
620 |
> |
} finally { |
621 |
> |
lock.unlock(); |
622 |
> |
} |
623 |
|
} |
624 |
|
} |
625 |
|
|
626 |
|
/** |
627 |
< |
* Main implementation of helpJoin |
627 |
> |
* Report the result of invoke or join; called only upon |
628 |
> |
* non-normal return of internal versions. |
629 |
|
*/ |
630 |
< |
private int busyJoin(ForkJoinWorkerThread w) { |
631 |
< |
int s; |
632 |
< |
ForkJoinTask<?> t; |
633 |
< |
while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null) |
634 |
< |
t.quietlyExec(); |
635 |
< |
return (s >= 0) ? awaitDone(w, false) : s; // block if no work |
630 |
> |
private V reportResult() { |
631 |
> |
int s; Throwable ex; |
632 |
> |
if ((s = status) == CANCELLED) |
633 |
> |
throw new CancellationException(); |
634 |
> |
if (s == EXCEPTIONAL && (ex = getThrowableException()) != null) |
635 |
> |
U.throwException(ex); |
636 |
> |
return getRawResult(); |
637 |
|
} |
638 |
|
|
639 |
|
// public methods |
642 |
|
* Arranges to asynchronously execute this task. While it is not |
643 |
|
* necessarily enforced, it is a usage error to fork a task more |
644 |
|
* than once unless it has completed and been reinitialized. |
645 |
+ |
* Subsequent modifications to the state of this task or any data |
646 |
+ |
* it operates on are not necessarily consistently observable by |
647 |
+ |
* any thread other than the one executing it unless preceded by a |
648 |
+ |
* call to {@link #join} or related methods, or a call to {@link |
649 |
+ |
* #isDone} returning {@code true}. |
650 |
|
* |
651 |
|
* <p>This method may be invoked only from within {@code |
652 |
< |
* ForkJoinTask} computations (as may be determined using method |
652 |
> |
* ForkJoinPool} computations (as may be determined using method |
653 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
654 |
|
* result in exceptions or errors, possibly including {@code |
655 |
|
* ClassCastException}. |
657 |
|
* @return {@code this}, to simplify usage |
658 |
|
*/ |
659 |
|
public final ForkJoinTask<V> fork() { |
660 |
< |
((ForkJoinWorkerThread) Thread.currentThread()) |
661 |
< |
.pushTask(this); |
660 |
> |
ForkJoinWorkerThread wt; |
661 |
> |
(wt = (ForkJoinWorkerThread)Thread.currentThread()). |
662 |
> |
workQueue.push(this, wt.pool); |
663 |
|
return this; |
664 |
|
} |
665 |
|
|
666 |
|
/** |
667 |
< |
* Returns the result of the computation when it is ready. |
668 |
< |
* This method differs from {@link #get()} in that |
667 |
> |
* Returns the result of the computation when it {@link #isDone is |
668 |
> |
* done}. This method differs from {@link #get()} in that |
669 |
|
* abnormal completion results in {@code RuntimeException} or |
670 |
< |
* {@code Error}, not {@code ExecutionException}. |
670 |
> |
* {@code Error}, not {@code ExecutionException}, and that |
671 |
> |
* interrupts of the calling thread do <em>not</em> cause the |
672 |
> |
* method to abruptly return by throwing {@code |
673 |
> |
* InterruptedException}. |
674 |
|
* |
675 |
|
* @return the computed result |
676 |
|
*/ |
677 |
|
public final V join() { |
678 |
< |
ForkJoinWorkerThread w = getWorker(); |
679 |
< |
if (w == null || status < 0 || !w.unpushTask(this) || !tryExec()) |
680 |
< |
reportException(awaitDone(w, true)); |
681 |
< |
return getRawResult(); |
678 |
> |
if (doJoin() != NORMAL) |
679 |
> |
return reportResult(); |
680 |
> |
else |
681 |
> |
return getRawResult(); |
682 |
|
} |
683 |
|
|
684 |
|
/** |
685 |
|
* Commences performing this task, awaits its completion if |
686 |
< |
* necessary, and return its result, or throws an (unchecked) |
687 |
< |
* exception if the underlying computation did so. |
686 |
> |
* necessary, and returns its result, or throws an (unchecked) |
687 |
> |
* {@code RuntimeException} or {@code Error} if the underlying |
688 |
> |
* computation did so. |
689 |
|
* |
690 |
|
* @return the computed result |
691 |
|
*/ |
692 |
|
public final V invoke() { |
693 |
< |
if (status >= 0 && tryExec()) |
694 |
< |
return getRawResult(); |
693 |
> |
if (doInvoke() != NORMAL) |
694 |
> |
return reportResult(); |
695 |
|
else |
696 |
< |
return join(); |
696 |
> |
return getRawResult(); |
697 |
|
} |
698 |
|
|
699 |
|
/** |
700 |
|
* Forks the given tasks, returning when {@code isDone} holds for |
701 |
|
* each task or an (unchecked) exception is encountered, in which |
702 |
< |
* case the exception is rethrown. If more than one task |
702 |
> |
* case the exception is rethrown. If more than one task |
703 |
|
* encounters an exception, then this method throws any one of |
704 |
< |
* these exceptions. The individual status of each task may be |
705 |
< |
* checked using {@link #getException()} and related methods. |
704 |
> |
* these exceptions. If any task encounters an exception, the |
705 |
> |
* other may be cancelled. However, the execution status of |
706 |
> |
* individual tasks is not guaranteed upon exceptional return. The |
707 |
> |
* status of each task may be obtained using {@link |
708 |
> |
* #getException()} and related methods to check if they have been |
709 |
> |
* cancelled, completed normally or exceptionally, or left |
710 |
> |
* unprocessed. |
711 |
|
* |
712 |
|
* <p>This method may be invoked only from within {@code |
713 |
< |
* ForkJoinTask} computations (as may be determined using method |
713 |
> |
* ForkJoinPool} computations (as may be determined using method |
714 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
715 |
|
* result in exceptions or errors, possibly including {@code |
716 |
|
* ClassCastException}. |
728 |
|
/** |
729 |
|
* Forks the given tasks, returning when {@code isDone} holds for |
730 |
|
* each task or an (unchecked) exception is encountered, in which |
731 |
< |
* case the exception is rethrown. If any task encounters an |
732 |
< |
* exception, others may be, but are not guaranteed to be, |
733 |
< |
* cancelled. If more than one task encounters an exception, then |
734 |
< |
* this method throws any one of these exceptions. The individual |
735 |
< |
* status of each task may be checked using {@link #getException()} |
736 |
< |
* and related methods. |
731 |
> |
* case the exception is rethrown. If more than one task |
732 |
> |
* encounters an exception, then this method throws any one of |
733 |
> |
* these exceptions. If any task encounters an exception, others |
734 |
> |
* may be cancelled. However, the execution status of individual |
735 |
> |
* tasks is not guaranteed upon exceptional return. The status of |
736 |
> |
* each task may be obtained using {@link #getException()} and |
737 |
> |
* related methods to check if they have been cancelled, completed |
738 |
> |
* normally or exceptionally, or left unprocessed. |
739 |
|
* |
740 |
|
* <p>This method may be invoked only from within {@code |
741 |
< |
* ForkJoinTask} computations (as may be determined using method |
741 |
> |
* ForkJoinPool} computations (as may be determined using method |
742 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
743 |
|
* result in exceptions or errors, possibly including {@code |
744 |
|
* ClassCastException}. |
757 |
|
} |
758 |
|
else if (i != 0) |
759 |
|
t.fork(); |
760 |
< |
else { |
761 |
< |
t.quietlyInvoke(); |
614 |
< |
if (ex == null) |
615 |
< |
ex = t.getException(); |
616 |
< |
} |
760 |
> |
else if (t.doInvoke() < NORMAL && ex == null) |
761 |
> |
ex = t.getException(); |
762 |
|
} |
763 |
|
for (int i = 1; i <= last; ++i) { |
764 |
|
ForkJoinTask<?> t = tasks[i]; |
765 |
|
if (t != null) { |
766 |
|
if (ex != null) |
767 |
|
t.cancel(false); |
768 |
< |
else { |
769 |
< |
t.quietlyJoin(); |
625 |
< |
if (ex == null) |
626 |
< |
ex = t.getException(); |
627 |
< |
} |
768 |
> |
else if (t.doJoin() < NORMAL) |
769 |
> |
ex = t.getException(); |
770 |
|
} |
771 |
|
} |
772 |
|
if (ex != null) |
773 |
< |
rethrowException(ex); |
773 |
> |
U.throwException(ex); |
774 |
|
} |
775 |
|
|
776 |
|
/** |
777 |
|
* Forks all tasks in the specified collection, returning when |
778 |
|
* {@code isDone} holds for each task or an (unchecked) exception |
779 |
< |
* is encountered. If any task encounters an exception, others |
780 |
< |
* may be, but are not guaranteed to be, cancelled. If more than |
781 |
< |
* one task encounters an exception, then this method throws any |
782 |
< |
* one of these exceptions. The individual status of each task |
783 |
< |
* may be checked using {@link #getException()} and related |
784 |
< |
* methods. The behavior of this operation is undefined if the |
785 |
< |
* specified collection is modified while the operation is in |
786 |
< |
* progress. |
779 |
> |
* is encountered, in which case the exception is rethrown. If |
780 |
> |
* more than one task encounters an exception, then this method |
781 |
> |
* throws any one of these exceptions. If any task encounters an |
782 |
> |
* exception, others may be cancelled. However, the execution |
783 |
> |
* status of individual tasks is not guaranteed upon exceptional |
784 |
> |
* return. The status of each task may be obtained using {@link |
785 |
> |
* #getException()} and related methods to check if they have been |
786 |
> |
* cancelled, completed normally or exceptionally, or left |
787 |
> |
* unprocessed. |
788 |
|
* |
789 |
|
* <p>This method may be invoked only from within {@code |
790 |
< |
* ForkJoinTask} computations (as may be determined using method |
790 |
> |
* ForkJoinPool} computations (as may be determined using method |
791 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
792 |
|
* result in exceptions or errors, possibly including {@code |
793 |
|
* ClassCastException}. |
814 |
|
} |
815 |
|
else if (i != 0) |
816 |
|
t.fork(); |
817 |
< |
else { |
818 |
< |
t.quietlyInvoke(); |
676 |
< |
if (ex == null) |
677 |
< |
ex = t.getException(); |
678 |
< |
} |
817 |
> |
else if (t.doInvoke() < NORMAL && ex == null) |
818 |
> |
ex = t.getException(); |
819 |
|
} |
820 |
|
for (int i = 1; i <= last; ++i) { |
821 |
|
ForkJoinTask<?> t = ts.get(i); |
822 |
|
if (t != null) { |
823 |
|
if (ex != null) |
824 |
|
t.cancel(false); |
825 |
< |
else { |
826 |
< |
t.quietlyJoin(); |
687 |
< |
if (ex == null) |
688 |
< |
ex = t.getException(); |
689 |
< |
} |
825 |
> |
else if (t.doJoin() < NORMAL) |
826 |
> |
ex = t.getException(); |
827 |
|
} |
828 |
|
} |
829 |
|
if (ex != null) |
830 |
< |
rethrowException(ex); |
830 |
> |
U.throwException(ex); |
831 |
|
return tasks; |
832 |
|
} |
833 |
|
|
834 |
|
/** |
835 |
|
* Attempts to cancel execution of this task. This attempt will |
836 |
< |
* fail if the task has already completed, has already been |
837 |
< |
* cancelled, or could not be cancelled for some other reason. If |
838 |
< |
* successful, and this task has not started when cancel is |
839 |
< |
* called, execution of this task is suppressed, {@link |
840 |
< |
* #isCancelled} will report true, and {@link #join} will result |
841 |
< |
* in a {@code CancellationException} being thrown. |
836 |
> |
* fail if the task has already completed or could not be |
837 |
> |
* cancelled for some other reason. If successful, and this task |
838 |
> |
* has not started when {@code cancel} is called, execution of |
839 |
> |
* this task is suppressed. After this method returns |
840 |
> |
* successfully, unless there is an intervening call to {@link |
841 |
> |
* #reinitialize}, subsequent calls to {@link #isCancelled}, |
842 |
> |
* {@link #isDone}, and {@code cancel} will return {@code true} |
843 |
> |
* and calls to {@link #join} and related methods will result in |
844 |
> |
* {@code CancellationException}. |
845 |
|
* |
846 |
|
* <p>This method may be overridden in subclasses, but if so, must |
847 |
< |
* still ensure that these minimal properties hold. In particular, |
848 |
< |
* the {@code cancel} method itself must not throw exceptions. |
847 |
> |
* still ensure that these properties hold. In particular, the |
848 |
> |
* {@code cancel} method itself must not throw exceptions. |
849 |
|
* |
850 |
|
* <p>This method is designed to be invoked by <em>other</em> |
851 |
|
* tasks. To terminate the current task, you can just return or |
852 |
|
* throw an unchecked exception from its computation method, or |
853 |
|
* invoke {@link #completeExceptionally}. |
854 |
|
* |
855 |
< |
* @param mayInterruptIfRunning this value is ignored in the |
856 |
< |
* default implementation because tasks are not |
857 |
< |
* cancelled via interruption |
855 |
> |
* @param mayInterruptIfRunning this value has no effect in the |
856 |
> |
* default implementation because interrupts are not used to |
857 |
> |
* control cancellation. |
858 |
|
* |
859 |
|
* @return {@code true} if this task is now cancelled |
860 |
|
*/ |
861 |
|
public boolean cancel(boolean mayInterruptIfRunning) { |
862 |
< |
setCompletion(CANCELLED); |
723 |
< |
return (status & COMPLETION_MASK) == CANCELLED; |
862 |
> |
return setCompletion(CANCELLED) == CANCELLED; |
863 |
|
} |
864 |
|
|
726 |
– |
/** |
727 |
– |
* Returns {@code true} if the computation performed by this task |
728 |
– |
* has completed (or has been cancelled). |
729 |
– |
* |
730 |
– |
* @return {@code true} if this computation has completed |
731 |
– |
*/ |
865 |
|
public final boolean isDone() { |
866 |
|
return status < 0; |
867 |
|
} |
868 |
|
|
736 |
– |
/** |
737 |
– |
* Returns {@code true} if this task was cancelled. |
738 |
– |
* |
739 |
– |
* @return {@code true} if this task was cancelled |
740 |
– |
*/ |
869 |
|
public final boolean isCancelled() { |
870 |
< |
return (status & COMPLETION_MASK) == CANCELLED; |
870 |
> |
return status == CANCELLED; |
871 |
|
} |
872 |
|
|
873 |
|
/** |
876 |
|
* @return {@code true} if this task threw an exception or was cancelled |
877 |
|
*/ |
878 |
|
public final boolean isCompletedAbnormally() { |
879 |
< |
return (status & COMPLETION_MASK) < NORMAL; |
879 |
> |
return status < NORMAL; |
880 |
|
} |
881 |
|
|
882 |
|
/** |
887 |
|
* exception and was not cancelled |
888 |
|
*/ |
889 |
|
public final boolean isCompletedNormally() { |
890 |
< |
return (status & COMPLETION_MASK) == NORMAL; |
763 |
< |
} |
764 |
< |
|
765 |
< |
/** |
766 |
< |
* Returns {@code true} if this task threw an exception. |
767 |
< |
* |
768 |
< |
* @return {@code true} if this task threw an exception |
769 |
< |
*/ |
770 |
< |
public final boolean isCompletedExceptionally() { |
771 |
< |
return (status & COMPLETION_MASK) == EXCEPTIONAL; |
890 |
> |
return status == NORMAL; |
891 |
|
} |
892 |
|
|
893 |
|
/** |
898 |
|
* @return the exception, or {@code null} if none |
899 |
|
*/ |
900 |
|
public final Throwable getException() { |
901 |
< |
int s = status & COMPLETION_MASK; |
902 |
< |
if (s >= NORMAL) |
903 |
< |
return null; |
904 |
< |
if (s == CANCELLED) |
786 |
< |
return new CancellationException(); |
787 |
< |
return exceptionMap.get(this); |
901 |
> |
int s = status; |
902 |
> |
return ((s >= NORMAL) ? null : |
903 |
> |
(s == CANCELLED) ? new CancellationException() : |
904 |
> |
getThrowableException()); |
905 |
|
} |
906 |
|
|
907 |
|
/** |
914 |
|
* overridable, but overridden versions must invoke {@code super} |
915 |
|
* implementation to maintain guarantees. |
916 |
|
* |
917 |
< |
* @param ex the exception to throw. If this exception is |
918 |
< |
* not a RuntimeException or Error, the actual exception thrown |
919 |
< |
* will be a RuntimeException with cause ex. |
917 |
> |
* @param ex the exception to throw. If this exception is not a |
918 |
> |
* {@code RuntimeException} or {@code Error}, the actual exception |
919 |
> |
* thrown will be a {@code RuntimeException} with cause {@code ex}. |
920 |
|
*/ |
921 |
|
public void completeExceptionally(Throwable ex) { |
922 |
< |
setDoneExceptionally((ex instanceof RuntimeException) || |
923 |
< |
(ex instanceof Error) ? ex : |
924 |
< |
new RuntimeException(ex)); |
922 |
> |
setExceptionalCompletion((ex instanceof RuntimeException) || |
923 |
> |
(ex instanceof Error) ? ex : |
924 |
> |
new RuntimeException(ex)); |
925 |
|
} |
926 |
|
|
927 |
|
/** |
928 |
|
* Completes this task, and if not already aborted or cancelled, |
929 |
< |
* returning a {@code null} result upon {@code join} and related |
930 |
< |
* operations. This method may be used to provide results for |
931 |
< |
* asynchronous tasks, or to provide alternative handling for |
932 |
< |
* tasks that would not otherwise complete normally. Its use in |
933 |
< |
* other situations is discouraged. This method is |
934 |
< |
* overridable, but overridden versions must invoke {@code super} |
935 |
< |
* implementation to maintain guarantees. |
929 |
> |
* returning the given value as the result of subsequent |
930 |
> |
* invocations of {@code join} and related operations. This method |
931 |
> |
* may be used to provide results for asynchronous tasks, or to |
932 |
> |
* provide alternative handling for tasks that would not otherwise |
933 |
> |
* complete normally. Its use in other situations is |
934 |
> |
* discouraged. This method is overridable, but overridden |
935 |
> |
* versions must invoke {@code super} implementation to maintain |
936 |
> |
* guarantees. |
937 |
|
* |
938 |
|
* @param value the result value for this task |
939 |
|
*/ |
941 |
|
try { |
942 |
|
setRawResult(value); |
943 |
|
} catch (Throwable rex) { |
944 |
< |
setDoneExceptionally(rex); |
944 |
> |
setExceptionalCompletion(rex); |
945 |
|
return; |
946 |
|
} |
947 |
< |
setNormalCompletion(); |
830 |
< |
} |
831 |
< |
|
832 |
< |
public final V get() throws InterruptedException, ExecutionException { |
833 |
< |
ForkJoinWorkerThread w = getWorker(); |
834 |
< |
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
835 |
< |
awaitDone(w, true); |
836 |
< |
return reportFutureResult(); |
837 |
< |
} |
838 |
< |
|
839 |
< |
public final V get(long timeout, TimeUnit unit) |
840 |
< |
throws InterruptedException, ExecutionException, TimeoutException { |
841 |
< |
long nanos = unit.toNanos(timeout); |
842 |
< |
ForkJoinWorkerThread w = getWorker(); |
843 |
< |
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
844 |
< |
awaitDone(w, nanos); |
845 |
< |
return reportTimedFutureResult(); |
947 |
> |
setCompletion(NORMAL); |
948 |
|
} |
949 |
|
|
950 |
|
/** |
951 |
< |
* Possibly executes other tasks until this task is ready, then |
952 |
< |
* returns the result of the computation. This method may be more |
851 |
< |
* efficient than {@code join}, but is only applicable when |
852 |
< |
* there are no potential dependencies between continuation of the |
853 |
< |
* current task and that of any other task that might be executed |
854 |
< |
* while helping. (This usually holds for pure divide-and-conquer |
855 |
< |
* tasks). |
856 |
< |
* |
857 |
< |
* <p>This method may be invoked only from within {@code |
858 |
< |
* ForkJoinTask} computations (as may be determined using method |
859 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
860 |
< |
* result in exceptions or errors, possibly including {@code |
861 |
< |
* ClassCastException}. |
951 |
> |
* Waits if necessary for the computation to complete, and then |
952 |
> |
* retrieves its result. |
953 |
|
* |
954 |
|
* @return the computed result |
955 |
+ |
* @throws CancellationException if the computation was cancelled |
956 |
+ |
* @throws ExecutionException if the computation threw an |
957 |
+ |
* exception |
958 |
+ |
* @throws InterruptedException if the current thread is not a |
959 |
+ |
* member of a ForkJoinPool and was interrupted while waiting |
960 |
|
*/ |
961 |
< |
public final V helpJoin() { |
962 |
< |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread(); |
963 |
< |
if (status < 0 || !w.unpushTask(this) || !tryExec()) |
964 |
< |
reportException(busyJoin(w)); |
961 |
> |
public final V get() throws InterruptedException, ExecutionException { |
962 |
> |
int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ? |
963 |
> |
doJoin() : externalInterruptibleAwaitDone(0L); |
964 |
> |
Throwable ex; |
965 |
> |
if (s == CANCELLED) |
966 |
> |
throw new CancellationException(); |
967 |
> |
if (s == EXCEPTIONAL && (ex = getThrowableException()) != null) |
968 |
> |
throw new ExecutionException(ex); |
969 |
|
return getRawResult(); |
970 |
|
} |
971 |
|
|
972 |
|
/** |
973 |
< |
* Possibly executes other tasks until this task is ready. This |
974 |
< |
* method may be useful when processing collections of tasks when |
875 |
< |
* some have been cancelled or otherwise known to have aborted. |
973 |
> |
* Waits if necessary for at most the given time for the computation |
974 |
> |
* to complete, and then retrieves its result, if available. |
975 |
|
* |
976 |
< |
* <p>This method may be invoked only from within {@code |
977 |
< |
* ForkJoinTask} computations (as may be determined using method |
978 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
979 |
< |
* result in exceptions or errors, possibly including {@code |
980 |
< |
* ClassCastException}. |
976 |
> |
* @param timeout the maximum time to wait |
977 |
> |
* @param unit the time unit of the timeout argument |
978 |
> |
* @return the computed result |
979 |
> |
* @throws CancellationException if the computation was cancelled |
980 |
> |
* @throws ExecutionException if the computation threw an |
981 |
> |
* exception |
982 |
> |
* @throws InterruptedException if the current thread is not a |
983 |
> |
* member of a ForkJoinPool and was interrupted while waiting |
984 |
> |
* @throws TimeoutException if the wait timed out |
985 |
|
*/ |
986 |
< |
public final void quietlyHelpJoin() { |
987 |
< |
if (status >= 0) { |
988 |
< |
ForkJoinWorkerThread w = |
989 |
< |
(ForkJoinWorkerThread) Thread.currentThread(); |
990 |
< |
if (!w.unpushTask(this) || !tryQuietlyInvoke()) |
991 |
< |
busyJoin(w); |
986 |
> |
public final V get(long timeout, TimeUnit unit) |
987 |
> |
throws InterruptedException, ExecutionException, TimeoutException { |
988 |
> |
// Messy in part because we measure in nanos, but wait in millis |
989 |
> |
int s; long millis, nanos; |
990 |
> |
Thread t = Thread.currentThread(); |
991 |
> |
if (!(t instanceof ForkJoinWorkerThread)) { |
992 |
> |
if ((millis = unit.toMillis(timeout)) > 0L) |
993 |
> |
s = externalInterruptibleAwaitDone(millis); |
994 |
> |
else |
995 |
> |
s = status; |
996 |
|
} |
997 |
+ |
else if ((s = status) >= 0 && (nanos = unit.toNanos(timeout)) > 0L) { |
998 |
+ |
long deadline = System.nanoTime() + nanos; |
999 |
+ |
ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; |
1000 |
+ |
ForkJoinPool.WorkQueue w = wt.workQueue; |
1001 |
+ |
ForkJoinPool p = wt.pool; |
1002 |
+ |
if (w.tryUnpush(this)) |
1003 |
+ |
doExec(); |
1004 |
+ |
boolean blocking = false; |
1005 |
+ |
try { |
1006 |
+ |
while ((s = status) >= 0) { |
1007 |
+ |
if (w.runState < 0) |
1008 |
+ |
cancelIgnoringExceptions(this); |
1009 |
+ |
else if (!blocking) |
1010 |
+ |
blocking = p.tryCompensate(); |
1011 |
+ |
else { |
1012 |
+ |
millis = TimeUnit.NANOSECONDS.toMillis(nanos); |
1013 |
+ |
if (millis > 0L && |
1014 |
+ |
U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
1015 |
+ |
try { |
1016 |
+ |
synchronized (this) { |
1017 |
+ |
if (status >= 0) |
1018 |
+ |
wait(millis); |
1019 |
+ |
} |
1020 |
+ |
} catch (InterruptedException ie) { |
1021 |
+ |
} |
1022 |
+ |
} |
1023 |
+ |
if ((s = status) < 0 || |
1024 |
+ |
(nanos = deadline - System.nanoTime()) <= 0L) |
1025 |
+ |
break; |
1026 |
+ |
} |
1027 |
+ |
} |
1028 |
+ |
} finally { |
1029 |
+ |
if (blocking) |
1030 |
+ |
p.incrementActiveCount(); |
1031 |
+ |
} |
1032 |
+ |
} |
1033 |
+ |
if (s != NORMAL) { |
1034 |
+ |
Throwable ex; |
1035 |
+ |
if (s == CANCELLED) |
1036 |
+ |
throw new CancellationException(); |
1037 |
+ |
if (s != EXCEPTIONAL) |
1038 |
+ |
throw new TimeoutException(); |
1039 |
+ |
if ((ex = getThrowableException()) != null) |
1040 |
+ |
throw new ExecutionException(ex); |
1041 |
+ |
} |
1042 |
+ |
return getRawResult(); |
1043 |
|
} |
1044 |
|
|
1045 |
|
/** |
1046 |
< |
* Joins this task, without returning its result or throwing an |
1046 |
> |
* Joins this task, without returning its result or throwing its |
1047 |
|
* exception. This method may be useful when processing |
1048 |
|
* collections of tasks when some have been cancelled or otherwise |
1049 |
|
* known to have aborted. |
1050 |
|
*/ |
1051 |
|
public final void quietlyJoin() { |
1052 |
< |
if (status >= 0) { |
900 |
< |
ForkJoinWorkerThread w = getWorker(); |
901 |
< |
if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke()) |
902 |
< |
awaitDone(w, true); |
903 |
< |
} |
1052 |
> |
doJoin(); |
1053 |
|
} |
1054 |
|
|
1055 |
|
/** |
1056 |
|
* Commences performing this task and awaits its completion if |
1057 |
< |
* necessary, without returning its result or throwing an |
1058 |
< |
* exception. This method may be useful when processing |
910 |
< |
* collections of tasks when some have been cancelled or otherwise |
911 |
< |
* known to have aborted. |
1057 |
> |
* necessary, without returning its result or throwing its |
1058 |
> |
* exception. |
1059 |
|
*/ |
1060 |
|
public final void quietlyInvoke() { |
1061 |
< |
if (status >= 0 && !tryQuietlyInvoke()) |
915 |
< |
quietlyJoin(); |
1061 |
> |
doInvoke(); |
1062 |
|
} |
1063 |
|
|
1064 |
|
/** |
1069 |
|
* processed. |
1070 |
|
* |
1071 |
|
* <p>This method may be invoked only from within {@code |
1072 |
< |
* ForkJoinTask} computations (as may be determined using method |
1072 |
> |
* ForkJoinPool} computations (as may be determined using method |
1073 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1074 |
|
* result in exceptions or errors, possibly including {@code |
1075 |
|
* ClassCastException}. |
1076 |
|
*/ |
1077 |
|
public static void helpQuiesce() { |
1078 |
< |
((ForkJoinWorkerThread) Thread.currentThread()) |
1079 |
< |
.helpQuiescePool(); |
1078 |
> |
ForkJoinWorkerThread wt = |
1079 |
> |
(ForkJoinWorkerThread)Thread.currentThread(); |
1080 |
> |
wt.pool.helpQuiescePool(wt.workQueue); |
1081 |
|
} |
1082 |
|
|
1083 |
|
/** |
1089 |
|
* under any other usage conditions are not guaranteed. |
1090 |
|
* This method may be useful when executing |
1091 |
|
* pre-constructed trees of subtasks in loops. |
1092 |
+ |
* |
1093 |
+ |
* <p>Upon completion of this method, {@code isDone()} reports |
1094 |
+ |
* {@code false}, and {@code getException()} reports {@code |
1095 |
+ |
* null}. However, the value returned by {@code getRawResult} is |
1096 |
+ |
* unaffected. To clear this value, you can invoke {@code |
1097 |
+ |
* setRawResult(null)}. |
1098 |
|
*/ |
1099 |
|
public void reinitialize() { |
1100 |
< |
if ((status & COMPLETION_MASK) == EXCEPTIONAL) |
1101 |
< |
exceptionMap.remove(this); |
1102 |
< |
status = 0; |
1100 |
> |
if (status == EXCEPTIONAL) |
1101 |
> |
clearExceptionalCompletion(); |
1102 |
> |
else |
1103 |
> |
status = 0; |
1104 |
|
} |
1105 |
|
|
1106 |
|
/** |
1117 |
|
} |
1118 |
|
|
1119 |
|
/** |
1120 |
< |
* Returns {@code true} if the current thread is executing as a |
1121 |
< |
* ForkJoinPool computation. |
1120 |
> |
* Returns {@code true} if the current thread is a {@link |
1121 |
> |
* ForkJoinWorkerThread} executing as a ForkJoinPool computation. |
1122 |
|
* |
1123 |
< |
* @return {@code true} if the current thread is executing as a |
1124 |
< |
* ForkJoinPool computation, or false otherwise |
1123 |
> |
* @return {@code true} if the current thread is a {@link |
1124 |
> |
* ForkJoinWorkerThread} executing as a ForkJoinPool computation, |
1125 |
> |
* or {@code false} otherwise |
1126 |
|
*/ |
1127 |
|
public static boolean inForkJoinPool() { |
1128 |
|
return Thread.currentThread() instanceof ForkJoinWorkerThread; |
1137 |
|
* were not, stolen. |
1138 |
|
* |
1139 |
|
* <p>This method may be invoked only from within {@code |
1140 |
< |
* ForkJoinTask} computations (as may be determined using method |
1140 |
> |
* ForkJoinPool} computations (as may be determined using method |
1141 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1142 |
|
* result in exceptions or errors, possibly including {@code |
1143 |
|
* ClassCastException}. |
1145 |
|
* @return {@code true} if unforked |
1146 |
|
*/ |
1147 |
|
public boolean tryUnfork() { |
1148 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1149 |
< |
.unpushTask(this); |
1148 |
> |
return ((ForkJoinWorkerThread)Thread.currentThread()) |
1149 |
> |
.workQueue.tryUnpush(this); |
1150 |
|
} |
1151 |
|
|
1152 |
|
/** |
1156 |
|
* fork other tasks. |
1157 |
|
* |
1158 |
|
* <p>This method may be invoked only from within {@code |
1159 |
< |
* ForkJoinTask} computations (as may be determined using method |
1159 |
> |
* ForkJoinPool} computations (as may be determined using method |
1160 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1161 |
|
* result in exceptions or errors, possibly including {@code |
1162 |
|
* ClassCastException}. |
1165 |
|
*/ |
1166 |
|
public static int getQueuedTaskCount() { |
1167 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1168 |
< |
.getQueueSize(); |
1168 |
> |
.workQueue.queueSize(); |
1169 |
|
} |
1170 |
|
|
1171 |
|
/** |
1179 |
|
* exceeded. |
1180 |
|
* |
1181 |
|
* <p>This method may be invoked only from within {@code |
1182 |
< |
* ForkJoinTask} computations (as may be determined using method |
1182 |
> |
* ForkJoinPool} computations (as may be determined using method |
1183 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1184 |
|
* result in exceptions or errors, possibly including {@code |
1185 |
|
* ClassCastException}. |
1187 |
|
* @return the surplus number of tasks, which may be negative |
1188 |
|
*/ |
1189 |
|
public static int getSurplusQueuedTaskCount() { |
1190 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1191 |
< |
.getEstimatedSurplusTaskCount(); |
1190 |
> |
/* |
1191 |
> |
* The aim of this method is to return a cheap heuristic guide |
1192 |
> |
* for task partitioning when programmers, frameworks, tools, |
1193 |
> |
* or languages have little or no idea about task granularity. |
1194 |
> |
* In essence by offering this method, we ask users only about |
1195 |
> |
* tradeoffs in overhead vs expected throughput and its |
1196 |
> |
* variance, rather than how finely to partition tasks. |
1197 |
> |
* |
1198 |
> |
* In a steady state strict (tree-structured) computation, |
1199 |
> |
* each thread makes available for stealing enough tasks for |
1200 |
> |
* other threads to remain active. Inductively, if all threads |
1201 |
> |
* play by the same rules, each thread should make available |
1202 |
> |
* only a constant number of tasks. |
1203 |
> |
* |
1204 |
> |
* The minimum useful constant is just 1. But using a value of |
1205 |
> |
* 1 would require immediate replenishment upon each steal to |
1206 |
> |
* maintain enough tasks, which is infeasible. Further, |
1207 |
> |
* partitionings/granularities of offered tasks should |
1208 |
> |
* minimize steal rates, which in general means that threads |
1209 |
> |
* nearer the top of computation tree should generate more |
1210 |
> |
* than those nearer the bottom. In perfect steady state, each |
1211 |
> |
* thread is at approximately the same level of computation |
1212 |
> |
* tree. However, producing extra tasks amortizes the |
1213 |
> |
* uncertainty of progress and diffusion assumptions. |
1214 |
> |
* |
1215 |
> |
* So, users will want to use values larger, but not much |
1216 |
> |
* larger than 1 to both smooth over transient shortages and |
1217 |
> |
* hedge against uneven progress; as traded off against the |
1218 |
> |
* cost of extra task overhead. We leave the user to pick a |
1219 |
> |
* threshold value to compare with the results of this call to |
1220 |
> |
* guide decisions, but recommend values such as 3. |
1221 |
> |
* |
1222 |
> |
* When all threads are active, it is on average OK to |
1223 |
> |
* estimate surplus strictly locally. In steady-state, if one |
1224 |
> |
* thread is maintaining say 2 surplus tasks, then so are |
1225 |
> |
* others. So we can just use estimated queue length. |
1226 |
> |
* However, this strategy alone leads to serious mis-estimates |
1227 |
> |
* in some non-steady-state conditions (ramp-up, ramp-down, |
1228 |
> |
* other stalls). We can detect many of these by further |
1229 |
> |
* considering the number of "idle" threads, that are known to |
1230 |
> |
* have zero queued tasks, so compensate by a factor of |
1231 |
> |
* (#idle/#active) threads. |
1232 |
> |
*/ |
1233 |
> |
ForkJoinWorkerThread wt = |
1234 |
> |
(ForkJoinWorkerThread)Thread.currentThread(); |
1235 |
> |
return wt.workQueue.queueSize() - wt.pool.idlePerActive(); |
1236 |
|
} |
1237 |
|
|
1238 |
|
// Extension methods |
1281 |
|
* otherwise. |
1282 |
|
* |
1283 |
|
* <p>This method may be invoked only from within {@code |
1284 |
< |
* ForkJoinTask} computations (as may be determined using method |
1284 |
> |
* ForkJoinPool} computations (as may be determined using method |
1285 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1286 |
|
* result in exceptions or errors, possibly including {@code |
1287 |
|
* ClassCastException}. |
1289 |
|
* @return the next task, or {@code null} if none are available |
1290 |
|
*/ |
1291 |
|
protected static ForkJoinTask<?> peekNextLocalTask() { |
1292 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1094 |
< |
.peekTask(); |
1292 |
> |
return ((ForkJoinWorkerThread) Thread.currentThread()).workQueue.peek(); |
1293 |
|
} |
1294 |
|
|
1295 |
|
/** |
1299 |
|
* be useful otherwise. |
1300 |
|
* |
1301 |
|
* <p>This method may be invoked only from within {@code |
1302 |
< |
* ForkJoinTask} computations (as may be determined using method |
1302 |
> |
* ForkJoinPool} computations (as may be determined using method |
1303 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1304 |
|
* result in exceptions or errors, possibly including {@code |
1305 |
|
* ClassCastException}. |
1308 |
|
*/ |
1309 |
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
1310 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1311 |
< |
.pollLocalTask(); |
1311 |
> |
.workQueue.nextLocalTask(); |
1312 |
|
} |
1313 |
|
|
1314 |
|
/** |
1322 |
|
* otherwise. |
1323 |
|
* |
1324 |
|
* <p>This method may be invoked only from within {@code |
1325 |
< |
* ForkJoinTask} computations (as may be determined using method |
1325 |
> |
* ForkJoinPool} computations (as may be determined using method |
1326 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1327 |
|
* result in exceptions or errors, possibly including {@code |
1328 |
|
* ClassCastException}. |
1330 |
|
* @return a task, or {@code null} if none are available |
1331 |
|
*/ |
1332 |
|
protected static ForkJoinTask<?> pollTask() { |
1333 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1334 |
< |
.pollTask(); |
1333 |
> |
ForkJoinWorkerThread wt = |
1334 |
> |
(ForkJoinWorkerThread)Thread.currentThread(); |
1335 |
> |
return wt.pool.nextTaskFor(wt.workQueue); |
1336 |
> |
} |
1337 |
> |
|
1338 |
> |
// Mark-bit operations |
1339 |
> |
|
1340 |
> |
/** |
1341 |
> |
* Returns true if this task is marked. |
1342 |
> |
* |
1343 |
> |
* @return true if this task is marked |
1344 |
> |
* @since 1.8 |
1345 |
> |
*/ |
1346 |
> |
public final boolean isMarkedForkJoinTask() { |
1347 |
> |
return (status & MARKED) != 0; |
1348 |
> |
} |
1349 |
> |
|
1350 |
> |
/** |
1351 |
> |
* Atomically sets the mark on this task. |
1352 |
> |
* |
1353 |
> |
* @return true if this task was previously unmarked |
1354 |
> |
* @since 1.8 |
1355 |
> |
*/ |
1356 |
> |
public final boolean markForkJoinTask() { |
1357 |
> |
for (int s;;) { |
1358 |
> |
if (((s = status) & MARKED) != 0) |
1359 |
> |
return false; |
1360 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | MARKED)) |
1361 |
> |
return true; |
1362 |
> |
} |
1363 |
> |
} |
1364 |
> |
|
1365 |
> |
/** |
1366 |
> |
* Atomically clears the mark on this task. |
1367 |
> |
* |
1368 |
> |
* @return true if this task was previously marked |
1369 |
> |
* @since 1.8 |
1370 |
> |
*/ |
1371 |
> |
public final boolean unmarkForkJoinTask() { |
1372 |
> |
for (int s;;) { |
1373 |
> |
if (((s = status) & MARKED) == 0) |
1374 |
> |
return false; |
1375 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s & ~MARKED)) |
1376 |
> |
return true; |
1377 |
> |
} |
1378 |
|
} |
1379 |
|
|
1380 |
|
/** |
1475 |
|
private static final long serialVersionUID = -7721805057305804111L; |
1476 |
|
|
1477 |
|
/** |
1478 |
< |
* Save the state to a stream. |
1478 |
> |
* Saves this task to a stream (that is, serializes it). |
1479 |
|
* |
1480 |
|
* @serialData the current run status and the exception thrown |
1481 |
|
* during execution, or {@code null} if none |
1241 |
– |
* @param s the stream |
1482 |
|
*/ |
1483 |
|
private void writeObject(java.io.ObjectOutputStream s) |
1484 |
|
throws java.io.IOException { |
1487 |
|
} |
1488 |
|
|
1489 |
|
/** |
1490 |
< |
* Reconstitute the instance from a stream. |
1251 |
< |
* |
1252 |
< |
* @param s the stream |
1490 |
> |
* Reconstitutes this task from a stream (that is, deserializes it). |
1491 |
|
*/ |
1492 |
|
private void readObject(java.io.ObjectInputStream s) |
1493 |
|
throws java.io.IOException, ClassNotFoundException { |
1494 |
|
s.defaultReadObject(); |
1257 |
– |
status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts |
1258 |
– |
status |= EXTERNAL_SIGNAL; // conservatively set external signal |
1495 |
|
Object ex = s.readObject(); |
1496 |
|
if (ex != null) |
1497 |
< |
setDoneExceptionally((Throwable) ex); |
1497 |
> |
setExceptionalCompletion((Throwable)ex); |
1498 |
|
} |
1499 |
|
|
1500 |
|
// Unsafe mechanics |
1501 |
< |
|
1502 |
< |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1503 |
< |
private static final long statusOffset = |
1504 |
< |
objectFieldOffset("status", ForkJoinTask.class); |
1505 |
< |
|
1506 |
< |
private static long objectFieldOffset(String field, Class<?> klazz) { |
1501 |
> |
private static final sun.misc.Unsafe U; |
1502 |
> |
private static final long STATUS; |
1503 |
> |
static { |
1504 |
> |
exceptionTableLock = new ReentrantLock(); |
1505 |
> |
exceptionTableRefQueue = new ReferenceQueue<Object>(); |
1506 |
> |
exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY]; |
1507 |
|
try { |
1508 |
< |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1509 |
< |
} catch (NoSuchFieldException e) { |
1510 |
< |
// Convert Exception to corresponding Error |
1511 |
< |
NoSuchFieldError error = new NoSuchFieldError(field); |
1512 |
< |
error.initCause(e); |
1277 |
< |
throw error; |
1508 |
> |
U = getUnsafe(); |
1509 |
> |
STATUS = U.objectFieldOffset |
1510 |
> |
(ForkJoinTask.class.getDeclaredField("status")); |
1511 |
> |
} catch (Exception e) { |
1512 |
> |
throw new Error(e); |
1513 |
|
} |
1514 |
|
} |
1515 |
|
|