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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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volatile int status; // accessed directly by pool and workers |
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|
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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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/** |
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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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/* |
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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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|
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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 (anded with |
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* DONE_MASK) holds value NORMAL, CANCELLED, or EXCEPTIONAL. Tasks |
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* undergoing blocking waits by other threads have the SIGNAL bit |
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* set. Completion of a stolen task with SIGNAL set awakens any |
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* waiters via notifyAll. Even though suboptimal for some |
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* purposes, we use basic builtin wait/notify to take advantage of |
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* "monitor inflation" in JVMs that we would otherwise need to |
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* emulate to avoid adding further per-task bookkeeping overhead. |
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* We want these monitors to be "fat", i.e., not use biasing or |
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* thin-lock techniques, so use some odd coding idioms that tend |
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* to avoid them, mainly by arranging that every synchronized |
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* block performs a wait, notifyAll or both. |
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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 DONE_MASK = 0xf0000000; // mask out non-completion bits |
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static final int NORMAL = 0xf0000000; // must be negative |
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static final int CANCELLED = 0xc0000000; // must be < NORMAL |
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static final int EXCEPTIONAL = 0x80000000; // 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. A specialization for NORMAL completion is in method |
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* 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 | 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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* 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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} |
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while ((s = status) >= 0 && completed) { |
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if (U.compareAndSwapInt(this, STATUS, s, s | NORMAL)) { |
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if ((s & SIGNAL) != 0) |
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synchronized (this) { notifyAll(); } |
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return NORMAL; |
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} |
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} |
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} |
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return s; |
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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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* Tries to set SIGNAL status. Used by ForkJoinPool. Other |
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* variants are directly incorporated into externalAwaitDone etc. |
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* |
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> |
* @return true if successful |
278 |
|
*/ |
279 |
< |
final void setNormalCompletion() { |
280 |
< |
// Try typical fast case -- single CAS, no signal, not already done. |
281 |
< |
// Manually expand casStatus to improve chances of inlining it |
247 |
< |
if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL)) |
248 |
< |
setCompletion(NORMAL); |
279 |
> |
final boolean trySetSignal() { |
280 |
> |
int s; |
281 |
> |
return U.compareAndSwapInt(this, STATUS, s = status, s | SIGNAL); |
282 |
|
} |
283 |
|
|
251 |
– |
// internal waiting and notification |
252 |
– |
|
284 |
|
/** |
285 |
< |
* Performs the actual monitor wait for awaitDone. |
285 |
> |
* Blocks a non-worker-thread until completion. |
286 |
> |
* @return status upon completion |
287 |
|
*/ |
288 |
< |
private void doAwaitDone() { |
289 |
< |
// Minimize lock bias and in/de-flation effects by maximizing |
290 |
< |
// chances of waiting inside sync |
291 |
< |
try { |
292 |
< |
while (status >= 0) |
293 |
< |
synchronized (this) { if (status >= 0) wait(); } |
294 |
< |
} catch (InterruptedException ie) { |
295 |
< |
onInterruptedWait(); |
288 |
> |
private int externalAwaitDone() { |
289 |
> |
boolean interrupted = false; |
290 |
> |
int s; |
291 |
> |
while ((s = status) >= 0) { |
292 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
293 |
> |
synchronized (this) { |
294 |
> |
if (status >= 0) { |
295 |
> |
try { |
296 |
> |
wait(); |
297 |
> |
} catch (InterruptedException ie) { |
298 |
> |
interrupted = true; |
299 |
> |
} |
300 |
> |
} |
301 |
> |
else |
302 |
> |
notifyAll(); |
303 |
> |
} |
304 |
> |
} |
305 |
|
} |
306 |
+ |
if (interrupted) |
307 |
+ |
Thread.currentThread().interrupt(); |
308 |
+ |
return s; |
309 |
|
} |
310 |
|
|
311 |
|
/** |
312 |
< |
* Performs the actual timed monitor wait for awaitDone. |
312 |
> |
* Blocks a non-worker-thread until completion or interruption. |
313 |
|
*/ |
314 |
< |
private void doAwaitDone(long startTime, long nanos) { |
315 |
< |
synchronized (this) { |
316 |
< |
try { |
317 |
< |
while (status >= 0) { |
318 |
< |
long nt = nanos - (System.nanoTime() - startTime); |
319 |
< |
if (nt <= 0) |
320 |
< |
break; |
321 |
< |
wait(nt / 1000000, (int) (nt % 1000000)); |
314 |
> |
private int externalInterruptibleAwaitDone() throws InterruptedException { |
315 |
> |
int s; |
316 |
> |
if (Thread.interrupted()) |
317 |
> |
throw new InterruptedException(); |
318 |
> |
while ((s = status) >= 0) { |
319 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
320 |
> |
synchronized (this) { |
321 |
> |
if (status >= 0) |
322 |
> |
wait(); |
323 |
> |
else |
324 |
> |
notifyAll(); |
325 |
|
} |
279 |
– |
} catch (InterruptedException ie) { |
280 |
– |
onInterruptedWait(); |
326 |
|
} |
327 |
|
} |
328 |
+ |
return s; |
329 |
|
} |
330 |
|
|
285 |
– |
// Awaiting completion |
331 |
|
|
332 |
|
/** |
333 |
< |
* Sets status to indicate there is joiner, then waits for join, |
334 |
< |
* surrounded with pool notifications. |
335 |
< |
* |
336 |
< |
* @return status upon exit |
337 |
< |
*/ |
338 |
< |
private int awaitDone(ForkJoinWorkerThread w, |
339 |
< |
boolean maintainParallelism) { |
340 |
< |
ForkJoinPool pool = (w == null) ? null : w.pool; |
341 |
< |
int s; |
342 |
< |
while ((s = status) >= 0) { |
343 |
< |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
344 |
< |
if (pool == null || !pool.preJoin(this, maintainParallelism)) |
345 |
< |
doAwaitDone(); |
301 |
< |
if (((s = status) & INTERNAL_SIGNAL_MASK) != 0) |
302 |
< |
adjustPoolCountsOnUnblock(pool); |
303 |
< |
break; |
333 |
> |
* Implementation for join, get, quietlyJoin. Directly handles |
334 |
> |
* only cases of already-completed, external wait, and |
335 |
> |
* unfork+exec. Others are relayed to ForkJoinPool.awaitJoin. |
336 |
> |
* |
337 |
> |
* @return status upon completion |
338 |
> |
*/ |
339 |
> |
private int doJoin() { |
340 |
> |
int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w; |
341 |
> |
if ((s = status) >= 0) { |
342 |
> |
if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) { |
343 |
> |
if (!(w = (wt = (ForkJoinWorkerThread)t).workQueue). |
344 |
> |
tryUnpush(this) || (s = doExec()) >= 0) |
345 |
> |
s = wt.pool.awaitJoin(w, this); |
346 |
|
} |
347 |
+ |
else |
348 |
+ |
s = externalAwaitDone(); |
349 |
|
} |
350 |
|
return s; |
351 |
|
} |
352 |
|
|
353 |
|
/** |
354 |
< |
* Timed version of awaitDone |
354 |
> |
* Implementation for invoke, quietlyInvoke. |
355 |
|
* |
356 |
< |
* @return status upon exit |
356 |
> |
* @return status upon completion |
357 |
|
*/ |
358 |
< |
private int awaitDone(ForkJoinWorkerThread w, long nanos) { |
359 |
< |
ForkJoinPool pool = (w == null) ? null : w.pool; |
360 |
< |
int s; |
361 |
< |
while ((s = status) >= 0) { |
362 |
< |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
363 |
< |
long startTime = System.nanoTime(); |
364 |
< |
if (pool == null || !pool.preJoin(this, false)) |
365 |
< |
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; |
329 |
< |
} |
358 |
> |
private int doInvoke() { |
359 |
> |
int s; Thread t; ForkJoinWorkerThread wt; |
360 |
> |
if ((s = doExec()) >= 0) { |
361 |
> |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) |
362 |
> |
s = (wt = (ForkJoinWorkerThread)t).pool.awaitJoin(wt.workQueue, |
363 |
> |
this); |
364 |
> |
else |
365 |
> |
s = externalAwaitDone(); |
366 |
|
} |
367 |
|
return s; |
368 |
|
} |
369 |
|
|
370 |
+ |
// Exception table support |
371 |
+ |
|
372 |
|
/** |
373 |
< |
* Notifies pool that thread is unblocked. Called by signalled |
374 |
< |
* threads when woken by non-FJ threads (which is atypical). |
373 |
> |
* Table of exceptions thrown by tasks, to enable reporting by |
374 |
> |
* callers. Because exceptions are rare, we don't directly keep |
375 |
> |
* them with task objects, but instead use a weak ref table. Note |
376 |
> |
* that cancellation exceptions don't appear in the table, but are |
377 |
> |
* instead recorded as status values. |
378 |
> |
* |
379 |
> |
* Note: These statics are initialized below in static block. |
380 |
|
*/ |
381 |
< |
private void adjustPoolCountsOnUnblock(ForkJoinPool pool) { |
382 |
< |
int s; |
383 |
< |
do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK)); |
341 |
< |
if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0) |
342 |
< |
pool.updateRunningCount(s); |
343 |
< |
} |
381 |
> |
private static final ExceptionNode[] exceptionTable; |
382 |
> |
private static final ReentrantLock exceptionTableLock; |
383 |
> |
private static final ReferenceQueue<Object> exceptionTableRefQueue; |
384 |
|
|
385 |
|
/** |
386 |
< |
* Notifies pool to adjust counts on cancelled or timed out wait. |
386 |
> |
* Fixed capacity for exceptionTable. |
387 |
|
*/ |
388 |
< |
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 |
< |
} |
388 |
> |
private static final int EXCEPTION_MAP_CAPACITY = 32; |
389 |
|
|
390 |
|
/** |
391 |
< |
* Handles interruptions during waits. |
391 |
> |
* Key-value nodes for exception table. The chained hash table |
392 |
> |
* uses identity comparisons, full locking, and weak references |
393 |
> |
* for keys. The table has a fixed capacity because it only |
394 |
> |
* maintains task exceptions long enough for joiners to access |
395 |
> |
* them, so should never become very large for sustained |
396 |
> |
* periods. However, since we do not know when the last joiner |
397 |
> |
* completes, we must use weak references and expunge them. We do |
398 |
> |
* so on each operation (hence full locking). Also, some thread in |
399 |
> |
* any ForkJoinPool will call helpExpungeStaleExceptions when its |
400 |
> |
* pool becomes isQuiescent. |
401 |
|
*/ |
402 |
< |
private void onInterruptedWait() { |
403 |
< |
ForkJoinWorkerThread w = getWorker(); |
404 |
< |
if (w == null) |
405 |
< |
Thread.currentThread().interrupt(); // re-interrupt |
406 |
< |
else if (w.isTerminating()) |
407 |
< |
cancelIgnoringExceptions(); |
408 |
< |
// else if FJworker, ignore interrupt |
409 |
< |
} |
410 |
< |
|
411 |
< |
// Recording and reporting exceptions |
373 |
< |
|
374 |
< |
private void setDoneExceptionally(Throwable rex) { |
375 |
< |
exceptionMap.put(this, rex); |
376 |
< |
setCompletion(EXCEPTIONAL); |
402 |
> |
static final class ExceptionNode extends WeakReference<ForkJoinTask<?>> { |
403 |
> |
final Throwable ex; |
404 |
> |
ExceptionNode next; |
405 |
> |
final long thrower; // use id not ref to avoid weak cycles |
406 |
> |
ExceptionNode(ForkJoinTask<?> task, Throwable ex, ExceptionNode next) { |
407 |
> |
super(task, exceptionTableRefQueue); |
408 |
> |
this.ex = ex; |
409 |
> |
this.next = next; |
410 |
> |
this.thrower = Thread.currentThread().getId(); |
411 |
> |
} |
412 |
|
} |
413 |
|
|
414 |
|
/** |
415 |
< |
* Throws the exception associated with status s. |
415 |
> |
* Records exception and sets exceptional completion. |
416 |
|
* |
417 |
< |
* @throws the exception |
417 |
> |
* @return status on exit |
418 |
|
*/ |
419 |
< |
private void reportException(int s) { |
420 |
< |
if ((s &= COMPLETION_MASK) < NORMAL) { |
421 |
< |
if (s == CANCELLED) |
422 |
< |
throw new CancellationException(); |
423 |
< |
else |
424 |
< |
rethrowException(exceptionMap.get(this)); |
419 |
> |
private int setExceptionalCompletion(Throwable ex) { |
420 |
> |
int h = System.identityHashCode(this); |
421 |
> |
final ReentrantLock lock = exceptionTableLock; |
422 |
> |
lock.lock(); |
423 |
> |
try { |
424 |
> |
expungeStaleExceptions(); |
425 |
> |
ExceptionNode[] t = exceptionTable; |
426 |
> |
int i = h & (t.length - 1); |
427 |
> |
for (ExceptionNode e = t[i]; ; e = e.next) { |
428 |
> |
if (e == null) { |
429 |
> |
t[i] = new ExceptionNode(this, ex, t[i]); |
430 |
> |
break; |
431 |
> |
} |
432 |
> |
if (e.get() == this) // already present |
433 |
> |
break; |
434 |
> |
} |
435 |
> |
} finally { |
436 |
> |
lock.unlock(); |
437 |
|
} |
438 |
+ |
return setCompletion(EXCEPTIONAL); |
439 |
|
} |
440 |
|
|
441 |
|
/** |
442 |
< |
* Returns result or throws exception using j.u.c.Future conventions. |
443 |
< |
* Only call when {@code isDone} known to be true. |
442 |
> |
* Cancels, ignoring any exceptions thrown by cancel. Used during |
443 |
> |
* worker and pool shutdown. Cancel is spec'ed not to throw any |
444 |
> |
* exceptions, but if it does anyway, we have no recourse during |
445 |
> |
* shutdown, so guard against this case. |
446 |
|
*/ |
447 |
< |
private V reportFutureResult() |
448 |
< |
throws ExecutionException, InterruptedException { |
449 |
< |
if (Thread.interrupted()) |
450 |
< |
throw new InterruptedException(); |
451 |
< |
int s = status & COMPLETION_MASK; |
452 |
< |
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); |
447 |
> |
static final void cancelIgnoringExceptions(ForkJoinTask<?> t) { |
448 |
> |
if (t != null && t.status >= 0) { |
449 |
> |
try { |
450 |
> |
t.cancel(false); |
451 |
> |
} catch (Throwable ignore) { |
452 |
> |
} |
453 |
|
} |
409 |
– |
return getRawResult(); |
454 |
|
} |
455 |
|
|
456 |
|
/** |
457 |
< |
* Returns result or throws exception using j.u.c.Future conventions |
414 |
< |
* with timeouts. |
457 |
> |
* Removes exception node and clears status |
458 |
|
*/ |
459 |
< |
private V reportTimedFutureResult() |
460 |
< |
throws InterruptedException, ExecutionException, TimeoutException { |
461 |
< |
if (Thread.interrupted()) |
462 |
< |
throw new InterruptedException(); |
463 |
< |
Throwable ex; |
464 |
< |
int s = status & COMPLETION_MASK; |
465 |
< |
if (s == NORMAL) |
466 |
< |
return getRawResult(); |
467 |
< |
if (s == CANCELLED) |
468 |
< |
throw new CancellationException(); |
469 |
< |
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
470 |
< |
throw new ExecutionException(ex); |
471 |
< |
throw new TimeoutException(); |
459 |
> |
private void clearExceptionalCompletion() { |
460 |
> |
int h = System.identityHashCode(this); |
461 |
> |
final ReentrantLock lock = exceptionTableLock; |
462 |
> |
lock.lock(); |
463 |
> |
try { |
464 |
> |
ExceptionNode[] t = exceptionTable; |
465 |
> |
int i = h & (t.length - 1); |
466 |
> |
ExceptionNode e = t[i]; |
467 |
> |
ExceptionNode pred = null; |
468 |
> |
while (e != null) { |
469 |
> |
ExceptionNode next = e.next; |
470 |
> |
if (e.get() == this) { |
471 |
> |
if (pred == null) |
472 |
> |
t[i] = next; |
473 |
> |
else |
474 |
> |
pred.next = next; |
475 |
> |
break; |
476 |
> |
} |
477 |
> |
pred = e; |
478 |
> |
e = next; |
479 |
> |
} |
480 |
> |
expungeStaleExceptions(); |
481 |
> |
status = 0; |
482 |
> |
} finally { |
483 |
> |
lock.unlock(); |
484 |
> |
} |
485 |
|
} |
486 |
|
|
431 |
– |
// internal execution methods |
432 |
– |
|
487 |
|
/** |
488 |
< |
* Calls exec, recording completion, and rethrowing exception if |
489 |
< |
* encountered. Caller should normally check status before calling. |
488 |
> |
* Returns a rethrowable exception for the given task, if |
489 |
> |
* available. To provide accurate stack traces, if the exception |
490 |
> |
* was not thrown by the current thread, we try to create a new |
491 |
> |
* exception of the same type as the one thrown, but with the |
492 |
> |
* recorded exception as its cause. If there is no such |
493 |
> |
* constructor, we instead try to use a no-arg constructor, |
494 |
> |
* followed by initCause, to the same effect. If none of these |
495 |
> |
* apply, or any fail due to other exceptions, we return the |
496 |
> |
* recorded exception, which is still correct, although it may |
497 |
> |
* contain a misleading stack trace. |
498 |
|
* |
499 |
< |
* @return true if completed normally |
499 |
> |
* @return the exception, or null if none |
500 |
|
*/ |
501 |
< |
private boolean tryExec() { |
502 |
< |
try { // try block must contain only call to exec |
503 |
< |
if (!exec()) |
504 |
< |
return false; |
505 |
< |
} catch (Throwable rex) { |
506 |
< |
setDoneExceptionally(rex); |
507 |
< |
rethrowException(rex); |
508 |
< |
return false; // not reached |
501 |
> |
private Throwable getThrowableException() { |
502 |
> |
if ((status & DONE_MASK) != EXCEPTIONAL) |
503 |
> |
return null; |
504 |
> |
int h = System.identityHashCode(this); |
505 |
> |
ExceptionNode e; |
506 |
> |
final ReentrantLock lock = exceptionTableLock; |
507 |
> |
lock.lock(); |
508 |
> |
try { |
509 |
> |
expungeStaleExceptions(); |
510 |
> |
ExceptionNode[] t = exceptionTable; |
511 |
> |
e = t[h & (t.length - 1)]; |
512 |
> |
while (e != null && e.get() != this) |
513 |
> |
e = e.next; |
514 |
> |
} finally { |
515 |
> |
lock.unlock(); |
516 |
|
} |
517 |
< |
setNormalCompletion(); |
518 |
< |
return true; |
519 |
< |
} |
520 |
< |
|
521 |
< |
/** |
453 |
< |
* Main execution method used by worker threads. Invokes |
454 |
< |
* base computation unless already complete. |
455 |
< |
*/ |
456 |
< |
final void quietlyExec() { |
457 |
< |
if (status >= 0) { |
517 |
> |
Throwable ex; |
518 |
> |
if (e == null || (ex = e.ex) == null) |
519 |
> |
return null; |
520 |
> |
if (e.thrower != Thread.currentThread().getId()) { |
521 |
> |
Class<? extends Throwable> ec = ex.getClass(); |
522 |
|
try { |
523 |
< |
if (!exec()) |
524 |
< |
return; |
525 |
< |
} catch (Throwable rex) { |
526 |
< |
setDoneExceptionally(rex); |
527 |
< |
return; |
523 |
> |
Constructor<?> noArgCtor = null; |
524 |
> |
Constructor<?>[] cs = ec.getConstructors();// public ctors only |
525 |
> |
for (int i = 0; i < cs.length; ++i) { |
526 |
> |
Constructor<?> c = cs[i]; |
527 |
> |
Class<?>[] ps = c.getParameterTypes(); |
528 |
> |
if (ps.length == 0) |
529 |
> |
noArgCtor = c; |
530 |
> |
else if (ps.length == 1 && ps[0] == Throwable.class) |
531 |
> |
return (Throwable)(c.newInstance(ex)); |
532 |
> |
} |
533 |
> |
if (noArgCtor != null) { |
534 |
> |
Throwable wx = (Throwable)(noArgCtor.newInstance()); |
535 |
> |
wx.initCause(ex); |
536 |
> |
return wx; |
537 |
> |
} |
538 |
> |
} catch (Exception ignore) { |
539 |
|
} |
465 |
– |
setNormalCompletion(); |
540 |
|
} |
541 |
+ |
return ex; |
542 |
|
} |
543 |
|
|
544 |
|
/** |
545 |
< |
* Calls exec(), recording but not rethrowing exception. |
471 |
< |
* Caller should normally check status before calling. |
472 |
< |
* |
473 |
< |
* @return true if completed normally |
545 |
> |
* Poll stale refs and remove them. Call only while holding lock. |
546 |
|
*/ |
547 |
< |
private boolean tryQuietlyInvoke() { |
548 |
< |
try { |
549 |
< |
if (!exec()) |
550 |
< |
return false; |
551 |
< |
} catch (Throwable rex) { |
552 |
< |
setDoneExceptionally(rex); |
553 |
< |
return false; |
547 |
> |
private static void expungeStaleExceptions() { |
548 |
> |
for (Object x; (x = exceptionTableRefQueue.poll()) != null;) { |
549 |
> |
if (x instanceof ExceptionNode) { |
550 |
> |
ForkJoinTask<?> key = ((ExceptionNode)x).get(); |
551 |
> |
ExceptionNode[] t = exceptionTable; |
552 |
> |
int i = System.identityHashCode(key) & (t.length - 1); |
553 |
> |
ExceptionNode e = t[i]; |
554 |
> |
ExceptionNode pred = null; |
555 |
> |
while (e != null) { |
556 |
> |
ExceptionNode next = e.next; |
557 |
> |
if (e == x) { |
558 |
> |
if (pred == null) |
559 |
> |
t[i] = next; |
560 |
> |
else |
561 |
> |
pred.next = next; |
562 |
> |
break; |
563 |
> |
} |
564 |
> |
pred = e; |
565 |
> |
e = next; |
566 |
> |
} |
567 |
> |
} |
568 |
|
} |
483 |
– |
setNormalCompletion(); |
484 |
– |
return true; |
569 |
|
} |
570 |
|
|
571 |
|
/** |
572 |
< |
* Cancels, ignoring any exceptions it throws. |
572 |
> |
* If lock is available, poll stale refs and remove them. |
573 |
> |
* Called from ForkJoinPool when pools become quiescent. |
574 |
|
*/ |
575 |
< |
final void cancelIgnoringExceptions() { |
576 |
< |
try { |
577 |
< |
cancel(false); |
578 |
< |
} catch (Throwable ignore) { |
575 |
> |
static final void helpExpungeStaleExceptions() { |
576 |
> |
final ReentrantLock lock = exceptionTableLock; |
577 |
> |
if (lock.tryLock()) { |
578 |
> |
try { |
579 |
> |
expungeStaleExceptions(); |
580 |
> |
} finally { |
581 |
> |
lock.unlock(); |
582 |
> |
} |
583 |
|
} |
584 |
|
} |
585 |
|
|
586 |
|
/** |
587 |
< |
* Main implementation of helpJoin |
587 |
> |
* Throws exception, if any, associated with the given status. |
588 |
|
*/ |
589 |
< |
private int busyJoin(ForkJoinWorkerThread w) { |
590 |
< |
int s; |
591 |
< |
ForkJoinTask<?> t; |
592 |
< |
while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null) |
593 |
< |
t.quietlyExec(); |
594 |
< |
return (s >= 0) ? awaitDone(w, false) : s; // block if no work |
589 |
> |
private void reportException(int s) { |
590 |
> |
Throwable ex = ((s == CANCELLED) ? new CancellationException() : |
591 |
> |
(s == EXCEPTIONAL) ? getThrowableException() : |
592 |
> |
null); |
593 |
> |
if (ex != null) |
594 |
> |
U.throwException(ex); |
595 |
|
} |
596 |
|
|
597 |
|
// public methods |
600 |
|
* Arranges to asynchronously execute this task. While it is not |
601 |
|
* necessarily enforced, it is a usage error to fork a task more |
602 |
|
* than once unless it has completed and been reinitialized. |
603 |
+ |
* Subsequent modifications to the state of this task or any data |
604 |
+ |
* it operates on are not necessarily consistently observable by |
605 |
+ |
* any thread other than the one executing it unless preceded by a |
606 |
+ |
* call to {@link #join} or related methods, or a call to {@link |
607 |
+ |
* #isDone} returning {@code true}. |
608 |
|
* |
609 |
|
* <p>This method may be invoked only from within {@code |
610 |
< |
* ForkJoinTask} computations (as may be determined using method |
610 |
> |
* ForkJoinPool} computations (as may be determined using method |
611 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
612 |
|
* result in exceptions or errors, possibly including {@code |
613 |
|
* ClassCastException}. |
615 |
|
* @return {@code this}, to simplify usage |
616 |
|
*/ |
617 |
|
public final ForkJoinTask<V> fork() { |
618 |
< |
((ForkJoinWorkerThread) Thread.currentThread()) |
525 |
< |
.pushTask(this); |
618 |
> |
((ForkJoinWorkerThread)Thread.currentThread()).workQueue.push(this); |
619 |
|
return this; |
620 |
|
} |
621 |
|
|
622 |
|
/** |
623 |
< |
* Returns the result of the computation when it is ready. |
624 |
< |
* This method differs from {@link #get()} in that |
623 |
> |
* Returns the result of the computation when it {@link #isDone is |
624 |
> |
* done}. This method differs from {@link #get()} in that |
625 |
|
* abnormal completion results in {@code RuntimeException} or |
626 |
< |
* {@code Error}, not {@code ExecutionException}. |
626 |
> |
* {@code Error}, not {@code ExecutionException}, and that |
627 |
> |
* interrupts of the calling thread do <em>not</em> cause the |
628 |
> |
* method to abruptly return by throwing {@code |
629 |
> |
* InterruptedException}. |
630 |
|
* |
631 |
|
* @return the computed result |
632 |
|
*/ |
633 |
|
public final V join() { |
634 |
< |
ForkJoinWorkerThread w = getWorker(); |
635 |
< |
if (w == null || status < 0 || !w.unpushTask(this) || !tryExec()) |
636 |
< |
reportException(awaitDone(w, true)); |
634 |
> |
int s; |
635 |
> |
if ((s = doJoin() & DONE_MASK) != NORMAL) |
636 |
> |
reportException(s); |
637 |
|
return getRawResult(); |
638 |
|
} |
639 |
|
|
640 |
|
/** |
641 |
|
* Commences performing this task, awaits its completion if |
642 |
< |
* necessary, and return its result, or throws an (unchecked) |
643 |
< |
* exception if the underlying computation did so. |
642 |
> |
* necessary, and returns its result, or throws an (unchecked) |
643 |
> |
* {@code RuntimeException} or {@code Error} if the underlying |
644 |
> |
* computation did so. |
645 |
|
* |
646 |
|
* @return the computed result |
647 |
|
*/ |
648 |
|
public final V invoke() { |
649 |
< |
if (status >= 0 && tryExec()) |
650 |
< |
return getRawResult(); |
651 |
< |
else |
652 |
< |
return join(); |
649 |
> |
int s; |
650 |
> |
if ((s = doInvoke() & DONE_MASK) != NORMAL) |
651 |
> |
reportException(s); |
652 |
> |
return getRawResult(); |
653 |
|
} |
654 |
|
|
655 |
|
/** |
656 |
|
* Forks the given tasks, returning when {@code isDone} holds for |
657 |
|
* each task or an (unchecked) exception is encountered, in which |
658 |
< |
* case the exception is rethrown. If more than one task |
658 |
> |
* case the exception is rethrown. If more than one task |
659 |
|
* encounters an exception, then this method throws any one of |
660 |
< |
* these exceptions. The individual status of each task may be |
661 |
< |
* checked using {@link #getException()} and related methods. |
660 |
> |
* these exceptions. If any task encounters an exception, the |
661 |
> |
* other may be cancelled. However, the execution status of |
662 |
> |
* individual tasks is not guaranteed upon exceptional return. The |
663 |
> |
* status of each task may be obtained using {@link |
664 |
> |
* #getException()} and related methods to check if they have been |
665 |
> |
* cancelled, completed normally or exceptionally, or left |
666 |
> |
* unprocessed. |
667 |
|
* |
668 |
|
* <p>This method may be invoked only from within {@code |
669 |
< |
* ForkJoinTask} computations (as may be determined using method |
669 |
> |
* ForkJoinPool} computations (as may be determined using method |
670 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
671 |
|
* result in exceptions or errors, possibly including {@code |
672 |
|
* ClassCastException}. |
676 |
|
* @throws NullPointerException if any task is null |
677 |
|
*/ |
678 |
|
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) { |
679 |
+ |
int s1, s2; |
680 |
|
t2.fork(); |
681 |
< |
t1.invoke(); |
682 |
< |
t2.join(); |
681 |
> |
if ((s1 = t1.doInvoke() & DONE_MASK) != NORMAL) |
682 |
> |
t1.reportException(s1); |
683 |
> |
if ((s2 = t2.doJoin() & DONE_MASK) != NORMAL) |
684 |
> |
t2.reportException(s2); |
685 |
|
} |
686 |
|
|
687 |
|
/** |
688 |
|
* Forks the given tasks, returning when {@code isDone} holds for |
689 |
|
* each task or an (unchecked) exception is encountered, in which |
690 |
< |
* case the exception is rethrown. If any task encounters an |
691 |
< |
* exception, others may be, but are not guaranteed to be, |
692 |
< |
* cancelled. If more than one task encounters an exception, then |
693 |
< |
* this method throws any one of these exceptions. The individual |
694 |
< |
* status of each task may be checked using {@link #getException()} |
695 |
< |
* and related methods. |
690 |
> |
* case the exception is rethrown. If more than one task |
691 |
> |
* encounters an exception, then this method throws any one of |
692 |
> |
* these exceptions. If any task encounters an exception, others |
693 |
> |
* may be cancelled. However, the execution status of individual |
694 |
> |
* tasks is not guaranteed upon exceptional return. The status of |
695 |
> |
* each task may be obtained using {@link #getException()} and |
696 |
> |
* related methods to check if they have been cancelled, completed |
697 |
> |
* normally or exceptionally, or left unprocessed. |
698 |
|
* |
699 |
|
* <p>This method may be invoked only from within {@code |
700 |
< |
* ForkJoinTask} computations (as may be determined using method |
700 |
> |
* ForkJoinPool} computations (as may be determined using method |
701 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
702 |
|
* result in exceptions or errors, possibly including {@code |
703 |
|
* ClassCastException}. |
716 |
|
} |
717 |
|
else if (i != 0) |
718 |
|
t.fork(); |
719 |
< |
else { |
720 |
< |
t.quietlyInvoke(); |
614 |
< |
if (ex == null) |
615 |
< |
ex = t.getException(); |
616 |
< |
} |
719 |
> |
else if (t.doInvoke() < NORMAL && ex == null) |
720 |
> |
ex = t.getException(); |
721 |
|
} |
722 |
|
for (int i = 1; i <= last; ++i) { |
723 |
|
ForkJoinTask<?> t = tasks[i]; |
724 |
|
if (t != null) { |
725 |
|
if (ex != null) |
726 |
|
t.cancel(false); |
727 |
< |
else { |
728 |
< |
t.quietlyJoin(); |
625 |
< |
if (ex == null) |
626 |
< |
ex = t.getException(); |
627 |
< |
} |
727 |
> |
else if (t.doJoin() < NORMAL) |
728 |
> |
ex = t.getException(); |
729 |
|
} |
730 |
|
} |
731 |
|
if (ex != null) |
732 |
< |
rethrowException(ex); |
732 |
> |
U.throwException(ex); |
733 |
|
} |
734 |
|
|
735 |
|
/** |
736 |
|
* Forks all tasks in the specified collection, returning when |
737 |
|
* {@code isDone} holds for each task or an (unchecked) exception |
738 |
< |
* is encountered. If any task encounters an exception, others |
739 |
< |
* may be, but are not guaranteed to be, cancelled. If more than |
740 |
< |
* one task encounters an exception, then this method throws any |
741 |
< |
* one of these exceptions. The individual status of each task |
742 |
< |
* may be checked using {@link #getException()} and related |
743 |
< |
* methods. The behavior of this operation is undefined if the |
744 |
< |
* specified collection is modified while the operation is in |
745 |
< |
* progress. |
738 |
> |
* is encountered, in which case the exception is rethrown. If |
739 |
> |
* more than one task encounters an exception, then this method |
740 |
> |
* throws any one of these exceptions. If any task encounters an |
741 |
> |
* exception, others may be cancelled. However, the execution |
742 |
> |
* status of individual tasks is not guaranteed upon exceptional |
743 |
> |
* return. The status of each task may be obtained using {@link |
744 |
> |
* #getException()} and related methods to check if they have been |
745 |
> |
* cancelled, completed normally or exceptionally, or left |
746 |
> |
* unprocessed. |
747 |
|
* |
748 |
|
* <p>This method may be invoked only from within {@code |
749 |
< |
* ForkJoinTask} computations (as may be determined using method |
749 |
> |
* ForkJoinPool} computations (as may be determined using method |
750 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
751 |
|
* result in exceptions or errors, possibly including {@code |
752 |
|
* ClassCastException}. |
773 |
|
} |
774 |
|
else if (i != 0) |
775 |
|
t.fork(); |
776 |
< |
else { |
777 |
< |
t.quietlyInvoke(); |
676 |
< |
if (ex == null) |
677 |
< |
ex = t.getException(); |
678 |
< |
} |
776 |
> |
else if (t.doInvoke() < NORMAL && ex == null) |
777 |
> |
ex = t.getException(); |
778 |
|
} |
779 |
|
for (int i = 1; i <= last; ++i) { |
780 |
|
ForkJoinTask<?> t = ts.get(i); |
781 |
|
if (t != null) { |
782 |
|
if (ex != null) |
783 |
|
t.cancel(false); |
784 |
< |
else { |
785 |
< |
t.quietlyJoin(); |
687 |
< |
if (ex == null) |
688 |
< |
ex = t.getException(); |
689 |
< |
} |
784 |
> |
else if (t.doJoin() < NORMAL) |
785 |
> |
ex = t.getException(); |
786 |
|
} |
787 |
|
} |
788 |
|
if (ex != null) |
789 |
< |
rethrowException(ex); |
789 |
> |
U.throwException(ex); |
790 |
|
return tasks; |
791 |
|
} |
792 |
|
|
793 |
|
/** |
794 |
|
* Attempts to cancel execution of this task. This attempt will |
795 |
< |
* fail if the task has already completed, has already been |
796 |
< |
* cancelled, or could not be cancelled for some other reason. If |
797 |
< |
* successful, and this task has not started when cancel is |
798 |
< |
* called, execution of this task is suppressed, {@link |
799 |
< |
* #isCancelled} will report true, and {@link #join} will result |
800 |
< |
* in a {@code CancellationException} being thrown. |
795 |
> |
* fail if the task has already completed or could not be |
796 |
> |
* cancelled for some other reason. If successful, and this task |
797 |
> |
* has not started when {@code cancel} is called, execution of |
798 |
> |
* this task is suppressed. After this method returns |
799 |
> |
* successfully, unless there is an intervening call to {@link |
800 |
> |
* #reinitialize}, subsequent calls to {@link #isCancelled}, |
801 |
> |
* {@link #isDone}, and {@code cancel} will return {@code true} |
802 |
> |
* and calls to {@link #join} and related methods will result in |
803 |
> |
* {@code CancellationException}. |
804 |
|
* |
805 |
|
* <p>This method may be overridden in subclasses, but if so, must |
806 |
< |
* still ensure that these minimal properties hold. In particular, |
807 |
< |
* the {@code cancel} method itself must not throw exceptions. |
806 |
> |
* still ensure that these properties hold. In particular, the |
807 |
> |
* {@code cancel} method itself must not throw exceptions. |
808 |
|
* |
809 |
|
* <p>This method is designed to be invoked by <em>other</em> |
810 |
|
* tasks. To terminate the current task, you can just return or |
811 |
|
* throw an unchecked exception from its computation method, or |
812 |
|
* invoke {@link #completeExceptionally}. |
813 |
|
* |
814 |
< |
* @param mayInterruptIfRunning this value is ignored in the |
815 |
< |
* default implementation because tasks are not |
816 |
< |
* cancelled via interruption |
814 |
> |
* @param mayInterruptIfRunning this value has no effect in the |
815 |
> |
* default implementation because interrupts are not used to |
816 |
> |
* control cancellation. |
817 |
|
* |
818 |
|
* @return {@code true} if this task is now cancelled |
819 |
|
*/ |
820 |
|
public boolean cancel(boolean mayInterruptIfRunning) { |
821 |
< |
setCompletion(CANCELLED); |
723 |
< |
return (status & COMPLETION_MASK) == CANCELLED; |
821 |
> |
return (setCompletion(CANCELLED) & DONE_MASK) == CANCELLED; |
822 |
|
} |
823 |
|
|
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 |
– |
*/ |
824 |
|
public final boolean isDone() { |
825 |
|
return status < 0; |
826 |
|
} |
827 |
|
|
736 |
– |
/** |
737 |
– |
* Returns {@code true} if this task was cancelled. |
738 |
– |
* |
739 |
– |
* @return {@code true} if this task was cancelled |
740 |
– |
*/ |
828 |
|
public final boolean isCancelled() { |
829 |
< |
return (status & COMPLETION_MASK) == CANCELLED; |
829 |
> |
return (status & DONE_MASK) == CANCELLED; |
830 |
|
} |
831 |
|
|
832 |
|
/** |
835 |
|
* @return {@code true} if this task threw an exception or was cancelled |
836 |
|
*/ |
837 |
|
public final boolean isCompletedAbnormally() { |
838 |
< |
return (status & COMPLETION_MASK) < NORMAL; |
838 |
> |
return status < NORMAL; |
839 |
|
} |
840 |
|
|
841 |
|
/** |
846 |
|
* exception and was not cancelled |
847 |
|
*/ |
848 |
|
public final boolean isCompletedNormally() { |
849 |
< |
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; |
849 |
> |
return (status & DONE_MASK) == NORMAL; |
850 |
|
} |
851 |
|
|
852 |
|
/** |
857 |
|
* @return the exception, or {@code null} if none |
858 |
|
*/ |
859 |
|
public final Throwable getException() { |
860 |
< |
int s = status & COMPLETION_MASK; |
861 |
< |
if (s >= NORMAL) |
862 |
< |
return null; |
863 |
< |
if (s == CANCELLED) |
786 |
< |
return new CancellationException(); |
787 |
< |
return exceptionMap.get(this); |
860 |
> |
int s = status & DONE_MASK; |
861 |
> |
return ((s >= NORMAL) ? null : |
862 |
> |
(s == CANCELLED) ? new CancellationException() : |
863 |
> |
getThrowableException()); |
864 |
|
} |
865 |
|
|
866 |
|
/** |
873 |
|
* overridable, but overridden versions must invoke {@code super} |
874 |
|
* implementation to maintain guarantees. |
875 |
|
* |
876 |
< |
* @param ex the exception to throw. If this exception is |
877 |
< |
* not a RuntimeException or Error, the actual exception thrown |
878 |
< |
* will be a RuntimeException with cause ex. |
876 |
> |
* @param ex the exception to throw. If this exception is not a |
877 |
> |
* {@code RuntimeException} or {@code Error}, the actual exception |
878 |
> |
* thrown will be a {@code RuntimeException} with cause {@code ex}. |
879 |
|
*/ |
880 |
|
public void completeExceptionally(Throwable ex) { |
881 |
< |
setDoneExceptionally((ex instanceof RuntimeException) || |
882 |
< |
(ex instanceof Error) ? ex : |
883 |
< |
new RuntimeException(ex)); |
881 |
> |
setExceptionalCompletion((ex instanceof RuntimeException) || |
882 |
> |
(ex instanceof Error) ? ex : |
883 |
> |
new RuntimeException(ex)); |
884 |
|
} |
885 |
|
|
886 |
|
/** |
887 |
|
* Completes this task, and if not already aborted or cancelled, |
888 |
< |
* returning a {@code null} result upon {@code join} and related |
889 |
< |
* operations. This method may be used to provide results for |
890 |
< |
* asynchronous tasks, or to provide alternative handling for |
891 |
< |
* tasks that would not otherwise complete normally. Its use in |
892 |
< |
* other situations is discouraged. This method is |
893 |
< |
* overridable, but overridden versions must invoke {@code super} |
894 |
< |
* implementation to maintain guarantees. |
888 |
> |
* returning the given value as the result of subsequent |
889 |
> |
* invocations of {@code join} and related operations. This method |
890 |
> |
* may be used to provide results for asynchronous tasks, or to |
891 |
> |
* provide alternative handling for tasks that would not otherwise |
892 |
> |
* complete normally. Its use in other situations is |
893 |
> |
* discouraged. This method is overridable, but overridden |
894 |
> |
* versions must invoke {@code super} implementation to maintain |
895 |
> |
* guarantees. |
896 |
|
* |
897 |
|
* @param value the result value for this task |
898 |
|
*/ |
900 |
|
try { |
901 |
|
setRawResult(value); |
902 |
|
} catch (Throwable rex) { |
903 |
< |
setDoneExceptionally(rex); |
903 |
> |
setExceptionalCompletion(rex); |
904 |
|
return; |
905 |
|
} |
906 |
< |
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(); |
906 |
> |
setCompletion(NORMAL); |
907 |
|
} |
908 |
|
|
909 |
|
/** |
910 |
< |
* Possibly executes other tasks until this task is ready, then |
911 |
< |
* 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}. |
910 |
> |
* Waits if necessary for the computation to complete, and then |
911 |
> |
* retrieves its result. |
912 |
|
* |
913 |
|
* @return the computed result |
914 |
+ |
* @throws CancellationException if the computation was cancelled |
915 |
+ |
* @throws ExecutionException if the computation threw an |
916 |
+ |
* exception |
917 |
+ |
* @throws InterruptedException if the current thread is not a |
918 |
+ |
* member of a ForkJoinPool and was interrupted while waiting |
919 |
|
*/ |
920 |
< |
public final V helpJoin() { |
921 |
< |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread(); |
922 |
< |
if (status < 0 || !w.unpushTask(this) || !tryExec()) |
923 |
< |
reportException(busyJoin(w)); |
920 |
> |
public final V get() throws InterruptedException, ExecutionException { |
921 |
> |
int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ? |
922 |
> |
doJoin() : externalInterruptibleAwaitDone(); |
923 |
> |
Throwable ex; |
924 |
> |
if ((s &= DONE_MASK) == CANCELLED) |
925 |
> |
throw new CancellationException(); |
926 |
> |
if (s == EXCEPTIONAL && (ex = getThrowableException()) != null) |
927 |
> |
throw new ExecutionException(ex); |
928 |
|
return getRawResult(); |
929 |
|
} |
930 |
|
|
931 |
|
/** |
932 |
< |
* Possibly executes other tasks until this task is ready. This |
933 |
< |
* method may be useful when processing collections of tasks when |
875 |
< |
* some have been cancelled or otherwise known to have aborted. |
932 |
> |
* Waits if necessary for at most the given time for the computation |
933 |
> |
* to complete, and then retrieves its result, if available. |
934 |
|
* |
935 |
< |
* <p>This method may be invoked only from within {@code |
936 |
< |
* ForkJoinTask} computations (as may be determined using method |
937 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
938 |
< |
* result in exceptions or errors, possibly including {@code |
939 |
< |
* ClassCastException}. |
935 |
> |
* @param timeout the maximum time to wait |
936 |
> |
* @param unit the time unit of the timeout argument |
937 |
> |
* @return the computed result |
938 |
> |
* @throws CancellationException if the computation was cancelled |
939 |
> |
* @throws ExecutionException if the computation threw an |
940 |
> |
* exception |
941 |
> |
* @throws InterruptedException if the current thread is not a |
942 |
> |
* member of a ForkJoinPool and was interrupted while waiting |
943 |
> |
* @throws TimeoutException if the wait timed out |
944 |
|
*/ |
945 |
< |
public final void quietlyHelpJoin() { |
946 |
< |
if (status >= 0) { |
947 |
< |
ForkJoinWorkerThread w = |
948 |
< |
(ForkJoinWorkerThread) Thread.currentThread(); |
949 |
< |
if (!w.unpushTask(this) || !tryQuietlyInvoke()) |
950 |
< |
busyJoin(w); |
945 |
> |
public final V get(long timeout, TimeUnit unit) |
946 |
> |
throws InterruptedException, ExecutionException, TimeoutException { |
947 |
> |
if (Thread.interrupted()) |
948 |
> |
throw new InterruptedException(); |
949 |
> |
// Messy in part because we measure in nanosecs, but wait in millisecs |
950 |
> |
int s; long ns, ms; |
951 |
> |
if ((s = status) >= 0 && (ns = unit.toNanos(timeout)) > 0L) { |
952 |
> |
long deadline = System.nanoTime() + ns; |
953 |
> |
ForkJoinPool p = null; |
954 |
> |
ForkJoinPool.WorkQueue w = null; |
955 |
> |
Thread t = Thread.currentThread(); |
956 |
> |
if (t instanceof ForkJoinWorkerThread) { |
957 |
> |
ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; |
958 |
> |
p = wt.pool; |
959 |
> |
w = wt.workQueue; |
960 |
> |
s = p.helpJoinOnce(w, this); // no retries on failure |
961 |
> |
} |
962 |
> |
boolean canBlock = false; |
963 |
> |
boolean interrupted = false; |
964 |
> |
try { |
965 |
> |
while ((s = status) >= 0) { |
966 |
> |
if (w != null && w.runState < 0) |
967 |
> |
cancelIgnoringExceptions(this); |
968 |
> |
else if (!canBlock) { |
969 |
> |
if (p == null || p.tryCompensate(this, null)) |
970 |
> |
canBlock = true; |
971 |
> |
} |
972 |
> |
else { |
973 |
> |
if ((ms = TimeUnit.NANOSECONDS.toMillis(ns)) > 0L && |
974 |
> |
U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
975 |
> |
synchronized (this) { |
976 |
> |
if (status >= 0) { |
977 |
> |
try { |
978 |
> |
wait(ms); |
979 |
> |
} catch (InterruptedException ie) { |
980 |
> |
if (p == null) |
981 |
> |
interrupted = true; |
982 |
> |
} |
983 |
> |
} |
984 |
> |
else |
985 |
> |
notifyAll(); |
986 |
> |
} |
987 |
> |
} |
988 |
> |
if ((s = status) < 0 || interrupted || |
989 |
> |
(ns = deadline - System.nanoTime()) <= 0L) |
990 |
> |
break; |
991 |
> |
} |
992 |
> |
} |
993 |
> |
} finally { |
994 |
> |
if (p != null && canBlock) |
995 |
> |
p.incrementActiveCount(); |
996 |
> |
} |
997 |
> |
if (interrupted) |
998 |
> |
throw new InterruptedException(); |
999 |
|
} |
1000 |
+ |
if ((s &= DONE_MASK) != NORMAL) { |
1001 |
+ |
Throwable ex; |
1002 |
+ |
if (s == CANCELLED) |
1003 |
+ |
throw new CancellationException(); |
1004 |
+ |
if (s != EXCEPTIONAL) |
1005 |
+ |
throw new TimeoutException(); |
1006 |
+ |
if ((ex = getThrowableException()) != null) |
1007 |
+ |
throw new ExecutionException(ex); |
1008 |
+ |
} |
1009 |
+ |
return getRawResult(); |
1010 |
|
} |
1011 |
|
|
1012 |
|
/** |
1013 |
< |
* Joins this task, without returning its result or throwing an |
1013 |
> |
* Joins this task, without returning its result or throwing its |
1014 |
|
* exception. This method may be useful when processing |
1015 |
|
* collections of tasks when some have been cancelled or otherwise |
1016 |
|
* known to have aborted. |
1017 |
|
*/ |
1018 |
|
public final void quietlyJoin() { |
1019 |
< |
if (status >= 0) { |
900 |
< |
ForkJoinWorkerThread w = getWorker(); |
901 |
< |
if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke()) |
902 |
< |
awaitDone(w, true); |
903 |
< |
} |
1019 |
> |
doJoin(); |
1020 |
|
} |
1021 |
|
|
1022 |
|
/** |
1023 |
|
* Commences performing this task and awaits its completion if |
1024 |
< |
* necessary, without returning its result or throwing an |
1025 |
< |
* exception. This method may be useful when processing |
910 |
< |
* collections of tasks when some have been cancelled or otherwise |
911 |
< |
* known to have aborted. |
1024 |
> |
* necessary, without returning its result or throwing its |
1025 |
> |
* exception. |
1026 |
|
*/ |
1027 |
|
public final void quietlyInvoke() { |
1028 |
< |
if (status >= 0 && !tryQuietlyInvoke()) |
915 |
< |
quietlyJoin(); |
1028 |
> |
doInvoke(); |
1029 |
|
} |
1030 |
|
|
1031 |
|
/** |
1036 |
|
* processed. |
1037 |
|
* |
1038 |
|
* <p>This method may be invoked only from within {@code |
1039 |
< |
* ForkJoinTask} computations (as may be determined using method |
1039 |
> |
* ForkJoinPool} computations (as may be determined using method |
1040 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1041 |
|
* result in exceptions or errors, possibly including {@code |
1042 |
|
* ClassCastException}. |
1043 |
|
*/ |
1044 |
|
public static void helpQuiesce() { |
1045 |
< |
((ForkJoinWorkerThread) Thread.currentThread()) |
1046 |
< |
.helpQuiescePool(); |
1045 |
> |
ForkJoinWorkerThread wt = |
1046 |
> |
(ForkJoinWorkerThread)Thread.currentThread(); |
1047 |
> |
wt.pool.helpQuiescePool(wt.workQueue); |
1048 |
|
} |
1049 |
|
|
1050 |
|
/** |
1056 |
|
* under any other usage conditions are not guaranteed. |
1057 |
|
* This method may be useful when executing |
1058 |
|
* pre-constructed trees of subtasks in loops. |
1059 |
+ |
* |
1060 |
+ |
* <p>Upon completion of this method, {@code isDone()} reports |
1061 |
+ |
* {@code false}, and {@code getException()} reports {@code |
1062 |
+ |
* null}. However, the value returned by {@code getRawResult} is |
1063 |
+ |
* unaffected. To clear this value, you can invoke {@code |
1064 |
+ |
* setRawResult(null)}. |
1065 |
|
*/ |
1066 |
|
public void reinitialize() { |
1067 |
< |
if ((status & COMPLETION_MASK) == EXCEPTIONAL) |
1068 |
< |
exceptionMap.remove(this); |
1069 |
< |
status = 0; |
1067 |
> |
if ((status & DONE_MASK) == EXCEPTIONAL) |
1068 |
> |
clearExceptionalCompletion(); |
1069 |
> |
else |
1070 |
> |
status = 0; |
1071 |
|
} |
1072 |
|
|
1073 |
|
/** |
1084 |
|
} |
1085 |
|
|
1086 |
|
/** |
1087 |
< |
* Returns {@code true} if the current thread is executing as a |
1088 |
< |
* ForkJoinPool computation. |
1087 |
> |
* Returns {@code true} if the current thread is a {@link |
1088 |
> |
* ForkJoinWorkerThread} executing as a ForkJoinPool computation. |
1089 |
|
* |
1090 |
< |
* @return {@code true} if the current thread is executing as a |
1091 |
< |
* ForkJoinPool computation, or false otherwise |
1090 |
> |
* @return {@code true} if the current thread is a {@link |
1091 |
> |
* ForkJoinWorkerThread} executing as a ForkJoinPool computation, |
1092 |
> |
* or {@code false} otherwise |
1093 |
|
*/ |
1094 |
|
public static boolean inForkJoinPool() { |
1095 |
|
return Thread.currentThread() instanceof ForkJoinWorkerThread; |
1104 |
|
* were not, stolen. |
1105 |
|
* |
1106 |
|
* <p>This method may be invoked only from within {@code |
1107 |
< |
* ForkJoinTask} computations (as may be determined using method |
1107 |
> |
* ForkJoinPool} computations (as may be determined using method |
1108 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1109 |
|
* result in exceptions or errors, possibly including {@code |
1110 |
|
* ClassCastException}. |
1112 |
|
* @return {@code true} if unforked |
1113 |
|
*/ |
1114 |
|
public boolean tryUnfork() { |
1115 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1116 |
< |
.unpushTask(this); |
1115 |
> |
return ((ForkJoinWorkerThread)Thread.currentThread()) |
1116 |
> |
.workQueue.tryUnpush(this); |
1117 |
|
} |
1118 |
|
|
1119 |
|
/** |
1123 |
|
* fork other tasks. |
1124 |
|
* |
1125 |
|
* <p>This method may be invoked only from within {@code |
1126 |
< |
* ForkJoinTask} computations (as may be determined using method |
1126 |
> |
* ForkJoinPool} computations (as may be determined using method |
1127 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1128 |
|
* result in exceptions or errors, possibly including {@code |
1129 |
|
* ClassCastException}. |
1132 |
|
*/ |
1133 |
|
public static int getQueuedTaskCount() { |
1134 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1135 |
< |
.getQueueSize(); |
1135 |
> |
.workQueue.queueSize(); |
1136 |
|
} |
1137 |
|
|
1138 |
|
/** |
1146 |
|
* exceeded. |
1147 |
|
* |
1148 |
|
* <p>This method may be invoked only from within {@code |
1149 |
< |
* ForkJoinTask} computations (as may be determined using method |
1149 |
> |
* ForkJoinPool} computations (as may be determined using method |
1150 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1151 |
|
* result in exceptions or errors, possibly including {@code |
1152 |
|
* ClassCastException}. |
1154 |
|
* @return the surplus number of tasks, which may be negative |
1155 |
|
*/ |
1156 |
|
public static int getSurplusQueuedTaskCount() { |
1157 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1158 |
< |
.getEstimatedSurplusTaskCount(); |
1157 |
> |
/* |
1158 |
> |
* The aim of this method is to return a cheap heuristic guide |
1159 |
> |
* for task partitioning when programmers, frameworks, tools, |
1160 |
> |
* or languages have little or no idea about task granularity. |
1161 |
> |
* In essence by offering this method, we ask users only about |
1162 |
> |
* tradeoffs in overhead vs expected throughput and its |
1163 |
> |
* variance, rather than how finely to partition tasks. |
1164 |
> |
* |
1165 |
> |
* In a steady state strict (tree-structured) computation, |
1166 |
> |
* each thread makes available for stealing enough tasks for |
1167 |
> |
* other threads to remain active. Inductively, if all threads |
1168 |
> |
* play by the same rules, each thread should make available |
1169 |
> |
* only a constant number of tasks. |
1170 |
> |
* |
1171 |
> |
* The minimum useful constant is just 1. But using a value of |
1172 |
> |
* 1 would require immediate replenishment upon each steal to |
1173 |
> |
* maintain enough tasks, which is infeasible. Further, |
1174 |
> |
* partitionings/granularities of offered tasks should |
1175 |
> |
* minimize steal rates, which in general means that threads |
1176 |
> |
* nearer the top of computation tree should generate more |
1177 |
> |
* than those nearer the bottom. In perfect steady state, each |
1178 |
> |
* thread is at approximately the same level of computation |
1179 |
> |
* tree. However, producing extra tasks amortizes the |
1180 |
> |
* uncertainty of progress and diffusion assumptions. |
1181 |
> |
* |
1182 |
> |
* So, users will want to use values larger, but not much |
1183 |
> |
* larger than 1 to both smooth over transient shortages and |
1184 |
> |
* hedge against uneven progress; as traded off against the |
1185 |
> |
* cost of extra task overhead. We leave the user to pick a |
1186 |
> |
* threshold value to compare with the results of this call to |
1187 |
> |
* guide decisions, but recommend values such as 3. |
1188 |
> |
* |
1189 |
> |
* When all threads are active, it is on average OK to |
1190 |
> |
* estimate surplus strictly locally. In steady-state, if one |
1191 |
> |
* thread is maintaining say 2 surplus tasks, then so are |
1192 |
> |
* others. So we can just use estimated queue length. |
1193 |
> |
* However, this strategy alone leads to serious mis-estimates |
1194 |
> |
* in some non-steady-state conditions (ramp-up, ramp-down, |
1195 |
> |
* other stalls). We can detect many of these by further |
1196 |
> |
* considering the number of "idle" threads, that are known to |
1197 |
> |
* have zero queued tasks, so compensate by a factor of |
1198 |
> |
* (#idle/#active) threads. |
1199 |
> |
*/ |
1200 |
> |
ForkJoinWorkerThread wt = |
1201 |
> |
(ForkJoinWorkerThread)Thread.currentThread(); |
1202 |
> |
return wt.workQueue.queueSize() - wt.pool.idlePerActive(); |
1203 |
|
} |
1204 |
|
|
1205 |
|
// Extension methods |
1248 |
|
* otherwise. |
1249 |
|
* |
1250 |
|
* <p>This method may be invoked only from within {@code |
1251 |
< |
* ForkJoinTask} computations (as may be determined using method |
1251 |
> |
* ForkJoinPool} computations (as may be determined using method |
1252 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1253 |
|
* result in exceptions or errors, possibly including {@code |
1254 |
|
* ClassCastException}. |
1256 |
|
* @return the next task, or {@code null} if none are available |
1257 |
|
*/ |
1258 |
|
protected static ForkJoinTask<?> peekNextLocalTask() { |
1259 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1094 |
< |
.peekTask(); |
1259 |
> |
return ((ForkJoinWorkerThread) Thread.currentThread()).workQueue.peek(); |
1260 |
|
} |
1261 |
|
|
1262 |
|
/** |
1266 |
|
* be useful otherwise. |
1267 |
|
* |
1268 |
|
* <p>This method may be invoked only from within {@code |
1269 |
< |
* ForkJoinTask} computations (as may be determined using method |
1269 |
> |
* ForkJoinPool} computations (as may be determined using method |
1270 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1271 |
|
* result in exceptions or errors, possibly including {@code |
1272 |
|
* ClassCastException}. |
1275 |
|
*/ |
1276 |
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
1277 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1278 |
< |
.pollLocalTask(); |
1278 |
> |
.workQueue.nextLocalTask(); |
1279 |
|
} |
1280 |
|
|
1281 |
|
/** |
1289 |
|
* otherwise. |
1290 |
|
* |
1291 |
|
* <p>This method may be invoked only from within {@code |
1292 |
< |
* ForkJoinTask} computations (as may be determined using method |
1292 |
> |
* ForkJoinPool} computations (as may be determined using method |
1293 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1294 |
|
* result in exceptions or errors, possibly including {@code |
1295 |
|
* ClassCastException}. |
1297 |
|
* @return a task, or {@code null} if none are available |
1298 |
|
*/ |
1299 |
|
protected static ForkJoinTask<?> pollTask() { |
1300 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1301 |
< |
.pollTask(); |
1300 |
> |
ForkJoinWorkerThread wt = |
1301 |
> |
(ForkJoinWorkerThread)Thread.currentThread(); |
1302 |
> |
return wt.pool.nextTaskFor(wt.workQueue); |
1303 |
> |
} |
1304 |
> |
|
1305 |
> |
// Mark-bit operations |
1306 |
> |
|
1307 |
> |
/** |
1308 |
> |
* Returns true if this task is marked. |
1309 |
> |
* |
1310 |
> |
* @return true if this task is marked |
1311 |
> |
* @since 1.8 |
1312 |
> |
*/ |
1313 |
> |
public final boolean isMarkedForkJoinTask() { |
1314 |
> |
return (status & MARKED) != 0; |
1315 |
> |
} |
1316 |
> |
|
1317 |
> |
/** |
1318 |
> |
* Atomically sets the mark on this task. |
1319 |
> |
* |
1320 |
> |
* @return true if this task was previously unmarked |
1321 |
> |
* @since 1.8 |
1322 |
> |
*/ |
1323 |
> |
public final boolean markForkJoinTask() { |
1324 |
> |
for (int s;;) { |
1325 |
> |
if (((s = status) & MARKED) != 0) |
1326 |
> |
return false; |
1327 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | MARKED)) |
1328 |
> |
return true; |
1329 |
> |
} |
1330 |
> |
} |
1331 |
> |
|
1332 |
> |
/** |
1333 |
> |
* Atomically clears the mark on this task. |
1334 |
> |
* |
1335 |
> |
* @return true if this task was previously marked |
1336 |
> |
* @since 1.8 |
1337 |
> |
*/ |
1338 |
> |
public final boolean unmarkForkJoinTask() { |
1339 |
> |
for (int s;;) { |
1340 |
> |
if (((s = status) & MARKED) == 0) |
1341 |
> |
return false; |
1342 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s & ~MARKED)) |
1343 |
> |
return true; |
1344 |
> |
} |
1345 |
|
} |
1346 |
|
|
1347 |
|
/** |
1352 |
|
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
1353 |
|
implements RunnableFuture<T> { |
1354 |
|
final Runnable runnable; |
1147 |
– |
final T resultOnCompletion; |
1355 |
|
T result; |
1356 |
|
AdaptedRunnable(Runnable runnable, T result) { |
1357 |
|
if (runnable == null) throw new NullPointerException(); |
1358 |
|
this.runnable = runnable; |
1359 |
< |
this.resultOnCompletion = result; |
1359 |
> |
this.result = result; // OK to set this even before completion |
1360 |
|
} |
1361 |
< |
public T getRawResult() { return result; } |
1362 |
< |
public void setRawResult(T v) { result = v; } |
1363 |
< |
public boolean exec() { |
1364 |
< |
runnable.run(); |
1365 |
< |
result = resultOnCompletion; |
1366 |
< |
return true; |
1361 |
> |
public final T getRawResult() { return result; } |
1362 |
> |
public final void setRawResult(T v) { result = v; } |
1363 |
> |
public final boolean exec() { runnable.run(); return true; } |
1364 |
> |
public final void run() { invoke(); } |
1365 |
> |
private static final long serialVersionUID = 5232453952276885070L; |
1366 |
> |
} |
1367 |
> |
|
1368 |
> |
/** |
1369 |
> |
* Adaptor for Runnables without results |
1370 |
> |
*/ |
1371 |
> |
static final class AdaptedRunnableAction extends ForkJoinTask<Void> |
1372 |
> |
implements RunnableFuture<Void> { |
1373 |
> |
final Runnable runnable; |
1374 |
> |
AdaptedRunnableAction(Runnable runnable) { |
1375 |
> |
if (runnable == null) throw new NullPointerException(); |
1376 |
> |
this.runnable = runnable; |
1377 |
|
} |
1378 |
< |
public void run() { invoke(); } |
1378 |
> |
public final Void getRawResult() { return null; } |
1379 |
> |
public final void setRawResult(Void v) { } |
1380 |
> |
public final boolean exec() { runnable.run(); return true; } |
1381 |
> |
public final void run() { invoke(); } |
1382 |
|
private static final long serialVersionUID = 5232453952276885070L; |
1383 |
|
} |
1384 |
|
|
1393 |
|
if (callable == null) throw new NullPointerException(); |
1394 |
|
this.callable = callable; |
1395 |
|
} |
1396 |
< |
public T getRawResult() { return result; } |
1397 |
< |
public void setRawResult(T v) { result = v; } |
1398 |
< |
public boolean exec() { |
1396 |
> |
public final T getRawResult() { return result; } |
1397 |
> |
public final void setRawResult(T v) { result = v; } |
1398 |
> |
public final boolean exec() { |
1399 |
|
try { |
1400 |
|
result = callable.call(); |
1401 |
|
return true; |
1407 |
|
throw new RuntimeException(ex); |
1408 |
|
} |
1409 |
|
} |
1410 |
< |
public void run() { invoke(); } |
1410 |
> |
public final void run() { invoke(); } |
1411 |
|
private static final long serialVersionUID = 2838392045355241008L; |
1412 |
|
} |
1413 |
|
|
1420 |
|
* @return the task |
1421 |
|
*/ |
1422 |
|
public static ForkJoinTask<?> adapt(Runnable runnable) { |
1423 |
< |
return new AdaptedRunnable<Void>(runnable, null); |
1423 |
> |
return new AdaptedRunnableAction(runnable); |
1424 |
|
} |
1425 |
|
|
1426 |
|
/** |
1454 |
|
private static final long serialVersionUID = -7721805057305804111L; |
1455 |
|
|
1456 |
|
/** |
1457 |
< |
* Save the state to a stream. |
1457 |
> |
* Saves this task to a stream (that is, serializes it). |
1458 |
|
* |
1459 |
|
* @serialData the current run status and the exception thrown |
1460 |
|
* during execution, or {@code null} if none |
1241 |
– |
* @param s the stream |
1461 |
|
*/ |
1462 |
|
private void writeObject(java.io.ObjectOutputStream s) |
1463 |
|
throws java.io.IOException { |
1466 |
|
} |
1467 |
|
|
1468 |
|
/** |
1469 |
< |
* Reconstitute the instance from a stream. |
1251 |
< |
* |
1252 |
< |
* @param s the stream |
1469 |
> |
* Reconstitutes this task from a stream (that is, deserializes it). |
1470 |
|
*/ |
1471 |
|
private void readObject(java.io.ObjectInputStream s) |
1472 |
|
throws java.io.IOException, ClassNotFoundException { |
1473 |
|
s.defaultReadObject(); |
1257 |
– |
status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts |
1258 |
– |
status |= EXTERNAL_SIGNAL; // conservatively set external signal |
1474 |
|
Object ex = s.readObject(); |
1475 |
|
if (ex != null) |
1476 |
< |
setDoneExceptionally((Throwable) ex); |
1476 |
> |
setExceptionalCompletion((Throwable)ex); |
1477 |
|
} |
1478 |
|
|
1479 |
|
// Unsafe mechanics |
1480 |
< |
|
1481 |
< |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1482 |
< |
private static final long statusOffset = |
1483 |
< |
objectFieldOffset("status", ForkJoinTask.class); |
1484 |
< |
|
1485 |
< |
private static long objectFieldOffset(String field, Class<?> klazz) { |
1480 |
> |
private static final sun.misc.Unsafe U; |
1481 |
> |
private static final long STATUS; |
1482 |
> |
static { |
1483 |
> |
exceptionTableLock = new ReentrantLock(); |
1484 |
> |
exceptionTableRefQueue = new ReferenceQueue<Object>(); |
1485 |
> |
exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY]; |
1486 |
|
try { |
1487 |
< |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1488 |
< |
} catch (NoSuchFieldException e) { |
1489 |
< |
// Convert Exception to corresponding Error |
1490 |
< |
NoSuchFieldError error = new NoSuchFieldError(field); |
1491 |
< |
error.initCause(e); |
1277 |
< |
throw error; |
1487 |
> |
U = getUnsafe(); |
1488 |
> |
STATUS = U.objectFieldOffset |
1489 |
> |
(ForkJoinTask.class.getDeclaredField("status")); |
1490 |
> |
} catch (Exception e) { |
1491 |
> |
throw new Error(e); |
1492 |
|
} |
1493 |
|
} |
1494 |
|
|