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dl |
1.1 |
/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/licenses/publicdomain |
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*/ |
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package jsr166y; |
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jsr166 |
1.17 |
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dl |
1.1 |
import java.io.Serializable; |
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jsr166 |
1.17 |
import java.util.Collection; |
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import java.util.Collections; |
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import java.util.List; |
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dl |
1.32 |
import java.util.RandomAccess; |
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jsr166 |
1.17 |
import java.util.Map; |
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import java.util.WeakHashMap; |
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dl |
1.66 |
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.Executor; |
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import java.util.concurrent.ExecutorService; |
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import java.util.concurrent.Future; |
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import java.util.concurrent.RejectedExecutionException; |
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import java.util.concurrent.RunnableFuture; |
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import java.util.concurrent.TimeUnit; |
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import java.util.concurrent.TimeoutException; |
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dl |
1.1 |
|
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/** |
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jsr166 |
1.26 |
* Abstract base class for tasks that run within a {@link ForkJoinPool}. |
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* A {@code ForkJoinTask} is a thread-like entity that is much |
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dl |
1.2 |
* lighter weight than a normal thread. Huge numbers of tasks and |
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* subtasks may be hosted by a small number of actual threads in a |
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* ForkJoinPool, at the price of some usage limitations. |
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dl |
1.4 |
* |
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jsr166 |
1.28 |
* <p>A "main" {@code ForkJoinTask} begins execution when submitted |
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* to a {@link ForkJoinPool}. Once started, it will usually in turn |
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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 |
39 |
dl |
1.62 |
* #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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1.4 |
* |
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jsr166 |
1.28 |
* <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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* 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 |
66 |
dl |
1.32 |
* rethrown to callers attempting to join them. These exceptions may |
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jsr166 |
1.44 |
* additionally include {@link RejectedExecutionException} stemming |
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* from internal resource exhaustion, such as failure to allocate |
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* internal task queues. |
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dl |
1.1 |
* |
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1.2 |
* <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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jsr166 |
1.8 |
* waits for completion and report results using {@code Future} |
75 |
dl |
1.49 |
* conventions. Method {@link #invoke} is semantically |
76 |
dl |
1.35 |
* 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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1.2 |
* may be useful when a set of tasks are being executed, and you need |
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* to delay processing of results or exceptions until all complete. |
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jsr166 |
1.8 |
* Method {@code invokeAll} (available in multiple versions) |
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1.2 |
* 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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dl |
1.35 |
* <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 #isCompletedNormally} is true if a task completed without |
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dl |
1.42 |
* cancellation or encountering an exception; {@link #isCancelled} is |
90 |
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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 |
94 |
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* #getException} will return either the encountered exception or |
95 |
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* {@link java.util.concurrent.CancellationException}. |
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dl |
1.35 |
* |
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jsr166 |
1.28 |
* <p>The ForkJoinTask class is not usually directly subclassed. |
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1.2 |
* Instead, you subclass one of the abstract classes that support a |
99 |
dl |
1.27 |
* particular style of fork/join processing, typically {@link |
100 |
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* RecursiveAction} for computations that do not return results, or |
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* {@link RecursiveTask} for those that do. Normally, a concrete |
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1.2 |
* ForkJoinTask subclass declares fields comprising its parameters, |
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jsr166 |
1.8 |
* established in a constructor, and then defines a {@code compute} |
104 |
dl |
1.2 |
* method that somehow uses the control methods supplied by this base |
105 |
jsr166 |
1.8 |
* class. While these methods have {@code public} access (to allow |
106 |
dl |
1.32 |
* instances of different task subclasses to call each other's |
107 |
dl |
1.2 |
* methods), some of them may only be called from within other |
108 |
dl |
1.13 |
* ForkJoinTasks (as may be determined using method {@link |
109 |
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* #inForkJoinPool}). Attempts to invoke them in other contexts |
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jsr166 |
1.14 |
* result in exceptions or errors, possibly including |
111 |
dl |
1.57 |
* {@code ClassCastException}. |
112 |
dl |
1.1 |
* |
113 |
dl |
1.69 |
* <p>Method {@link #join} and its variants are appropriate for use |
114 |
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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 |
116 |
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* (DAG). Otherwise, executions may encounter a form of deadlock as |
117 |
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* tasks cyclically wait for each other. However, this framework |
118 |
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* supports other methods and techniques (for example the use of |
119 |
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* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that |
120 |
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* may be of use in constructing custom subclasses for problems that |
121 |
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* are not statically structured as DAGs. |
122 |
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* |
123 |
dl |
1.32 |
* <p>Most base support methods are {@code final}, to prevent |
124 |
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* overriding of implementations that are intrinsically tied to the |
125 |
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* underlying lightweight task scheduling framework. Developers |
126 |
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* creating new basic styles of fork/join processing should minimally |
127 |
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* implement {@code protected} methods {@link #exec}, {@link |
128 |
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* #setRawResult}, and {@link #getRawResult}, while also introducing |
129 |
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* an abstract computational method that can be implemented in its |
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* subclasses, possibly relying on other {@code protected} methods |
131 |
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* provided by this class. |
132 |
dl |
1.1 |
* |
133 |
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* <p>ForkJoinTasks should perform relatively small amounts of |
134 |
dl |
1.32 |
* computation. Large tasks should be split into smaller subtasks, |
135 |
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* usually via recursive decomposition. As a very rough rule of thumb, |
136 |
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* a task should perform more than 100 and less than 10000 basic |
137 |
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* computational steps. If tasks are too big, then parallelism cannot |
138 |
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* improve throughput. If too small, then memory and internal task |
139 |
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* maintenance overhead may overwhelm processing. |
140 |
dl |
1.1 |
* |
141 |
jsr166 |
1.37 |
* <p>This class provides {@code adapt} methods for {@link Runnable} |
142 |
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* and {@link Callable}, that may be of use when mixing execution of |
143 |
dl |
1.49 |
* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are |
144 |
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* of this form, consider using a pool constructed in <em>asyncMode</em>. |
145 |
dl |
1.27 |
* |
146 |
dl |
1.32 |
* <p>ForkJoinTasks are {@code Serializable}, which enables them to be |
147 |
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* used in extensions such as remote execution frameworks. It is |
148 |
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* sensible to serialize tasks only before or after, but not during, |
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* execution. Serialization is not relied on during execution itself. |
150 |
jsr166 |
1.12 |
* |
151 |
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* @since 1.7 |
152 |
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* @author Doug Lea |
153 |
dl |
1.1 |
*/ |
154 |
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public abstract class ForkJoinTask<V> implements Future<V>, Serializable { |
155 |
dl |
1.2 |
|
156 |
dl |
1.46 |
/* |
157 |
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* See the internal documentation of class ForkJoinPool for a |
158 |
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* general implementation overview. ForkJoinTasks are mainly |
159 |
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* responsible for maintaining their "status" field amidst relays |
160 |
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* to methods in ForkJoinWorkerThread and ForkJoinPool. The |
161 |
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* methods of this class are more-or-less layered into (1) basic |
162 |
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* status maintenance (2) execution and awaiting completion (3) |
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* user-level methods that additionally report results. This is |
164 |
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* sometimes hard to see because this file orders exported methods |
165 |
dl |
1.53 |
* in a way that flows well in javadocs. In particular, most |
166 |
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* join mechanics are in method quietlyJoin, below. |
167 |
dl |
1.46 |
*/ |
168 |
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169 |
dl |
1.50 |
/* |
170 |
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* The status field holds run control status bits packed into a |
171 |
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* single int to minimize footprint and to ensure atomicity (via |
172 |
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* CAS). Status is initially zero, and takes on nonnegative |
173 |
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* values until completed, upon which status holds value |
174 |
jsr166 |
1.59 |
* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking |
175 |
dl |
1.50 |
* waits by other threads have the SIGNAL bit set. Completion of |
176 |
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* a stolen task with SIGNAL set awakens any waiters via |
177 |
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* notifyAll. Even though suboptimal for some purposes, we use |
178 |
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* basic builtin wait/notify to take advantage of "monitor |
179 |
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* inflation" in JVMs that we would otherwise need to emulate to |
180 |
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* avoid adding further per-task bookkeeping overhead. We want |
181 |
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* these monitors to be "fat", i.e., not use biasing or thin-lock |
182 |
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* techniques, so use some odd coding idioms that tend to avoid |
183 |
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* them. |
184 |
dl |
1.1 |
*/ |
185 |
dl |
1.50 |
|
186 |
dl |
1.53 |
/** The run status of this task */ |
187 |
jsr166 |
1.9 |
volatile int status; // accessed directly by pool and workers |
188 |
dl |
1.1 |
|
189 |
dl |
1.49 |
private static final int NORMAL = -1; |
190 |
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private static final int CANCELLED = -2; |
191 |
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private static final int EXCEPTIONAL = -3; |
192 |
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private static final int SIGNAL = 1; |
193 |
dl |
1.1 |
|
194 |
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/** |
195 |
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* Table of exceptions thrown by tasks, to enable reporting by |
196 |
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* callers. Because exceptions are rare, we don't directly keep |
197 |
jsr166 |
1.10 |
* them with task objects, but instead use a weak ref table. Note |
198 |
dl |
1.1 |
* that cancellation exceptions don't appear in the table, but are |
199 |
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* instead recorded as status values. |
200 |
jsr166 |
1.10 |
* TODO: Use ConcurrentReferenceHashMap |
201 |
dl |
1.1 |
*/ |
202 |
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static final Map<ForkJoinTask<?>, Throwable> exceptionMap = |
203 |
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Collections.synchronizedMap |
204 |
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(new WeakHashMap<ForkJoinTask<?>, Throwable>()); |
205 |
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206 |
dl |
1.46 |
// Maintaining completion status |
207 |
dl |
1.1 |
|
208 |
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/** |
209 |
dl |
1.46 |
* Marks completion and wakes up threads waiting to join this task, |
210 |
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* also clearing signal request bits. |
211 |
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* |
212 |
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* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
213 |
dl |
1.1 |
*/ |
214 |
dl |
1.53 |
private void setCompletion(int completion) { |
215 |
dl |
1.46 |
int s; |
216 |
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while ((s = status) >= 0) { |
217 |
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if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) { |
218 |
dl |
1.51 |
if (s != 0) |
219 |
dl |
1.46 |
synchronized (this) { notifyAll(); } |
220 |
dl |
1.53 |
break; |
221 |
dl |
1.46 |
} |
222 |
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} |
223 |
dl |
1.1 |
} |
224 |
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225 |
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/** |
226 |
jsr166 |
1.56 |
* Records exception and sets exceptional completion. |
227 |
jsr166 |
1.60 |
* |
228 |
dl |
1.48 |
* @return status on exit |
229 |
dl |
1.1 |
*/ |
230 |
dl |
1.53 |
private void setExceptionalCompletion(Throwable rex) { |
231 |
dl |
1.46 |
exceptionMap.put(this, rex); |
232 |
dl |
1.53 |
setCompletion(EXCEPTIONAL); |
233 |
dl |
1.1 |
} |
234 |
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235 |
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/** |
236 |
dl |
1.55 |
* Blocks a worker thread until completion. Called only by |
237 |
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* pool. Currently unused -- pool-based waits use timeout |
238 |
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* version below. |
239 |
dl |
1.1 |
*/ |
240 |
dl |
1.50 |
final void internalAwaitDone() { |
241 |
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int s; // the odd construction reduces lock bias effects |
242 |
dl |
1.48 |
while ((s = status) >= 0) { |
243 |
dl |
1.50 |
try { |
244 |
jsr166 |
1.61 |
synchronized (this) { |
245 |
dl |
1.50 |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL)) |
246 |
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wait(); |
247 |
dl |
1.1 |
} |
248 |
dl |
1.50 |
} catch (InterruptedException ie) { |
249 |
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cancelIfTerminating(); |
250 |
dl |
1.1 |
} |
251 |
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} |
252 |
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} |
253 |
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|
254 |
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/** |
255 |
dl |
1.55 |
* Blocks a worker thread until completed or timed out. Called |
256 |
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* only by pool. |
257 |
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* |
258 |
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* @return status on exit |
259 |
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*/ |
260 |
dl |
1.66 |
final int internalAwaitDone(long millis, int nanos) { |
261 |
dl |
1.55 |
int s; |
262 |
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if ((s = status) >= 0) { |
263 |
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try { |
264 |
jsr166 |
1.61 |
synchronized (this) { |
265 |
dl |
1.55 |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL)) |
266 |
dl |
1.66 |
wait(millis, nanos); |
267 |
dl |
1.55 |
} |
268 |
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} catch (InterruptedException ie) { |
269 |
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cancelIfTerminating(); |
270 |
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} |
271 |
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s = status; |
272 |
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} |
273 |
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return s; |
274 |
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} |
275 |
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|
276 |
|
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/** |
277 |
dl |
1.48 |
* Blocks a non-worker-thread until completion. |
278 |
dl |
1.1 |
*/ |
279 |
dl |
1.53 |
private void externalAwaitDone() { |
280 |
dl |
1.48 |
int s; |
281 |
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while ((s = status) >= 0) { |
282 |
jsr166 |
1.61 |
synchronized (this) { |
283 |
jsr166 |
1.65 |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) { |
284 |
dl |
1.48 |
boolean interrupted = false; |
285 |
dl |
1.53 |
while (status >= 0) { |
286 |
dl |
1.48 |
try { |
287 |
dl |
1.47 |
wait(); |
288 |
dl |
1.48 |
} catch (InterruptedException ie) { |
289 |
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interrupted = true; |
290 |
dl |
1.46 |
} |
291 |
dl |
1.50 |
} |
292 |
dl |
1.48 |
if (interrupted) |
293 |
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Thread.currentThread().interrupt(); |
294 |
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break; |
295 |
dl |
1.46 |
} |
296 |
dl |
1.1 |
} |
297 |
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} |
298 |
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} |
299 |
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|
300 |
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/** |
301 |
dl |
1.48 |
* Unless done, calls exec and records status if completed, but |
302 |
dl |
1.49 |
* doesn't wait for completion otherwise. Primary execution method |
303 |
|
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* for ForkJoinWorkerThread. |
304 |
dl |
1.1 |
*/ |
305 |
dl |
1.53 |
final void quietlyExec() { |
306 |
dl |
1.48 |
try { |
307 |
|
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if (status < 0 || !exec()) |
308 |
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return; |
309 |
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} catch (Throwable rex) { |
310 |
|
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setExceptionalCompletion(rex); |
311 |
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return; |
312 |
dl |
1.1 |
} |
313 |
dl |
1.48 |
setCompletion(NORMAL); // must be outside try block |
314 |
dl |
1.1 |
} |
315 |
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|
316 |
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// public methods |
317 |
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|
318 |
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/** |
319 |
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* Arranges to asynchronously execute this task. While it is not |
320 |
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* necessarily enforced, it is a usage error to fork a task more |
321 |
jsr166 |
1.31 |
* than once unless it has completed and been reinitialized. |
322 |
dl |
1.43 |
* Subsequent modifications to the state of this task or any data |
323 |
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* it operates on are not necessarily consistently observable by |
324 |
|
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* any thread other than the one executing it unless preceded by a |
325 |
|
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* call to {@link #join} or related methods, or a call to {@link |
326 |
|
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* #isDone} returning {@code true}. |
327 |
dl |
1.18 |
* |
328 |
jsr166 |
1.31 |
* <p>This method may be invoked only from within {@code |
329 |
|
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* ForkJoinTask} computations (as may be determined using method |
330 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
331 |
|
|
* result in exceptions or errors, possibly including {@code |
332 |
|
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* ClassCastException}. |
333 |
|
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* |
334 |
|
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* @return {@code this}, to simplify usage |
335 |
dl |
1.1 |
*/ |
336 |
dl |
1.18 |
public final ForkJoinTask<V> fork() { |
337 |
jsr166 |
1.14 |
((ForkJoinWorkerThread) Thread.currentThread()) |
338 |
|
|
.pushTask(this); |
339 |
dl |
1.18 |
return this; |
340 |
dl |
1.1 |
} |
341 |
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|
342 |
|
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/** |
343 |
dl |
1.69 |
* Returns the result of the computation when it {@link #isDone is |
344 |
|
|
* done}. This method differs from {@link #get()} in that |
345 |
jsr166 |
1.31 |
* abnormal completion results in {@code RuntimeException} or |
346 |
dl |
1.69 |
* {@code Error}, not {@code ExecutionException}, and that |
347 |
|
|
* interrupts of the calling thread do <em>not</em> cause the |
348 |
|
|
* method to abruptly return by throwing {@code |
349 |
|
|
* InterruptedException}. |
350 |
dl |
1.1 |
* |
351 |
|
|
* @return the computed result |
352 |
|
|
*/ |
353 |
|
|
public final V join() { |
354 |
dl |
1.53 |
quietlyJoin(); |
355 |
|
|
Throwable ex; |
356 |
|
|
if (status < NORMAL && (ex = getException()) != null) |
357 |
|
|
UNSAFE.throwException(ex); |
358 |
|
|
return getRawResult(); |
359 |
dl |
1.1 |
} |
360 |
|
|
|
361 |
|
|
/** |
362 |
dl |
1.2 |
* Commences performing this task, awaits its completion if |
363 |
jsr166 |
1.56 |
* necessary, and returns its result, or throws an (unchecked) |
364 |
dl |
1.57 |
* {@code RuntimeException} or {@code Error} if the underlying |
365 |
|
|
* computation did so. |
366 |
jsr166 |
1.10 |
* |
367 |
dl |
1.1 |
* @return the computed result |
368 |
|
|
*/ |
369 |
|
|
public final V invoke() { |
370 |
dl |
1.53 |
quietlyInvoke(); |
371 |
|
|
Throwable ex; |
372 |
|
|
if (status < NORMAL && (ex = getException()) != null) |
373 |
|
|
UNSAFE.throwException(ex); |
374 |
|
|
return getRawResult(); |
375 |
dl |
1.1 |
} |
376 |
|
|
|
377 |
|
|
/** |
378 |
dl |
1.34 |
* Forks the given tasks, returning when {@code isDone} holds for |
379 |
|
|
* each task or an (unchecked) exception is encountered, in which |
380 |
dl |
1.57 |
* case the exception is rethrown. If more than one task |
381 |
|
|
* encounters an exception, then this method throws any one of |
382 |
|
|
* these exceptions. If any task encounters an exception, the |
383 |
|
|
* other may be cancelled. However, the execution status of |
384 |
|
|
* individual tasks is not guaranteed upon exceptional return. The |
385 |
|
|
* status of each task may be obtained using {@link |
386 |
|
|
* #getException()} and related methods to check if they have been |
387 |
|
|
* cancelled, completed normally or exceptionally, or left |
388 |
|
|
* unprocessed. |
389 |
jsr166 |
1.31 |
* |
390 |
|
|
* <p>This method may be invoked only from within {@code |
391 |
dl |
1.69 |
* ForkJoinPool} computations (as may be determined using method |
392 |
jsr166 |
1.31 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
393 |
|
|
* result in exceptions or errors, possibly including {@code |
394 |
|
|
* ClassCastException}. |
395 |
jsr166 |
1.10 |
* |
396 |
dl |
1.27 |
* @param t1 the first task |
397 |
|
|
* @param t2 the second task |
398 |
|
|
* @throws NullPointerException if any task is null |
399 |
dl |
1.1 |
*/ |
400 |
jsr166 |
1.31 |
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) { |
401 |
dl |
1.2 |
t2.fork(); |
402 |
|
|
t1.invoke(); |
403 |
|
|
t2.join(); |
404 |
dl |
1.1 |
} |
405 |
|
|
|
406 |
|
|
/** |
407 |
dl |
1.27 |
* Forks the given tasks, returning when {@code isDone} holds for |
408 |
dl |
1.34 |
* each task or an (unchecked) exception is encountered, in which |
409 |
dl |
1.57 |
* case the exception is rethrown. If more than one task |
410 |
|
|
* encounters an exception, then this method throws any one of |
411 |
|
|
* these exceptions. If any task encounters an exception, others |
412 |
|
|
* may be cancelled. However, the execution status of individual |
413 |
|
|
* tasks is not guaranteed upon exceptional return. The status of |
414 |
|
|
* each task may be obtained using {@link #getException()} and |
415 |
|
|
* related methods to check if they have been cancelled, completed |
416 |
|
|
* normally or exceptionally, or left unprocessed. |
417 |
jsr166 |
1.31 |
* |
418 |
|
|
* <p>This method may be invoked only from within {@code |
419 |
dl |
1.69 |
* ForkJoinPool} computations (as may be determined using method |
420 |
jsr166 |
1.31 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
421 |
|
|
* result in exceptions or errors, possibly including {@code |
422 |
|
|
* ClassCastException}. |
423 |
jsr166 |
1.14 |
* |
424 |
dl |
1.27 |
* @param tasks the tasks |
425 |
dl |
1.34 |
* @throws NullPointerException if any task is null |
426 |
dl |
1.1 |
*/ |
427 |
dl |
1.2 |
public static void invokeAll(ForkJoinTask<?>... tasks) { |
428 |
|
|
Throwable ex = null; |
429 |
|
|
int last = tasks.length - 1; |
430 |
|
|
for (int i = last; i >= 0; --i) { |
431 |
|
|
ForkJoinTask<?> t = tasks[i]; |
432 |
|
|
if (t == null) { |
433 |
|
|
if (ex == null) |
434 |
|
|
ex = new NullPointerException(); |
435 |
|
|
} |
436 |
|
|
else if (i != 0) |
437 |
|
|
t.fork(); |
438 |
dl |
1.53 |
else { |
439 |
|
|
t.quietlyInvoke(); |
440 |
|
|
if (ex == null && t.status < NORMAL) |
441 |
|
|
ex = t.getException(); |
442 |
|
|
} |
443 |
dl |
1.2 |
} |
444 |
|
|
for (int i = 1; i <= last; ++i) { |
445 |
|
|
ForkJoinTask<?> t = tasks[i]; |
446 |
|
|
if (t != null) { |
447 |
|
|
if (ex != null) |
448 |
|
|
t.cancel(false); |
449 |
dl |
1.53 |
else { |
450 |
|
|
t.quietlyJoin(); |
451 |
|
|
if (ex == null && t.status < NORMAL) |
452 |
|
|
ex = t.getException(); |
453 |
|
|
} |
454 |
dl |
1.2 |
} |
455 |
dl |
1.1 |
} |
456 |
dl |
1.2 |
if (ex != null) |
457 |
dl |
1.46 |
UNSAFE.throwException(ex); |
458 |
dl |
1.1 |
} |
459 |
|
|
|
460 |
|
|
/** |
461 |
dl |
1.32 |
* Forks all tasks in the specified collection, returning when |
462 |
dl |
1.34 |
* {@code isDone} holds for each task or an (unchecked) exception |
463 |
dl |
1.57 |
* is encountered, in which case the exception is rethrown. If |
464 |
|
|
* more than one task encounters an exception, then this method |
465 |
|
|
* throws any one of these exceptions. If any task encounters an |
466 |
|
|
* exception, others may be cancelled. However, the execution |
467 |
|
|
* status of individual tasks is not guaranteed upon exceptional |
468 |
|
|
* return. The status of each task may be obtained using {@link |
469 |
|
|
* #getException()} and related methods to check if they have been |
470 |
|
|
* cancelled, completed normally or exceptionally, or left |
471 |
|
|
* unprocessed. |
472 |
jsr166 |
1.31 |
* |
473 |
|
|
* <p>This method may be invoked only from within {@code |
474 |
dl |
1.69 |
* ForkJoinPool} computations (as may be determined using method |
475 |
jsr166 |
1.31 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
476 |
|
|
* result in exceptions or errors, possibly including {@code |
477 |
|
|
* ClassCastException}. |
478 |
jsr166 |
1.10 |
* |
479 |
dl |
1.2 |
* @param tasks the collection of tasks |
480 |
dl |
1.19 |
* @return the tasks argument, to simplify usage |
481 |
jsr166 |
1.10 |
* @throws NullPointerException if tasks or any element are null |
482 |
dl |
1.1 |
*/ |
483 |
dl |
1.19 |
public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) { |
484 |
dl |
1.32 |
if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) { |
485 |
jsr166 |
1.14 |
invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()])); |
486 |
dl |
1.19 |
return tasks; |
487 |
dl |
1.2 |
} |
488 |
jsr166 |
1.15 |
@SuppressWarnings("unchecked") |
489 |
dl |
1.2 |
List<? extends ForkJoinTask<?>> ts = |
490 |
jsr166 |
1.14 |
(List<? extends ForkJoinTask<?>>) tasks; |
491 |
dl |
1.2 |
Throwable ex = null; |
492 |
|
|
int last = ts.size() - 1; |
493 |
|
|
for (int i = last; i >= 0; --i) { |
494 |
|
|
ForkJoinTask<?> t = ts.get(i); |
495 |
|
|
if (t == null) { |
496 |
|
|
if (ex == null) |
497 |
|
|
ex = new NullPointerException(); |
498 |
|
|
} |
499 |
|
|
else if (i != 0) |
500 |
|
|
t.fork(); |
501 |
dl |
1.53 |
else { |
502 |
|
|
t.quietlyInvoke(); |
503 |
|
|
if (ex == null && t.status < NORMAL) |
504 |
|
|
ex = t.getException(); |
505 |
|
|
} |
506 |
dl |
1.2 |
} |
507 |
|
|
for (int i = 1; i <= last; ++i) { |
508 |
|
|
ForkJoinTask<?> t = ts.get(i); |
509 |
|
|
if (t != null) { |
510 |
|
|
if (ex != null) |
511 |
|
|
t.cancel(false); |
512 |
dl |
1.53 |
else { |
513 |
|
|
t.quietlyJoin(); |
514 |
|
|
if (ex == null && t.status < NORMAL) |
515 |
|
|
ex = t.getException(); |
516 |
|
|
} |
517 |
dl |
1.2 |
} |
518 |
|
|
} |
519 |
|
|
if (ex != null) |
520 |
dl |
1.46 |
UNSAFE.throwException(ex); |
521 |
dl |
1.19 |
return tasks; |
522 |
dl |
1.1 |
} |
523 |
|
|
|
524 |
|
|
/** |
525 |
dl |
1.33 |
* Attempts to cancel execution of this task. This attempt will |
526 |
dl |
1.69 |
* fail if the task has already completed or could not be |
527 |
|
|
* cancelled for some other reason. If successful, and this task |
528 |
|
|
* has not started when {@code cancel} is called, execution of |
529 |
|
|
* this task is suppressed. After this method returns |
530 |
|
|
* successfully, unless there is an intervening call to {@link |
531 |
|
|
* #reinitialize}, subsequent calls to {@link #isCancelled}, |
532 |
|
|
* {@link #isDone}, and {@code cancel} will return {@code true} |
533 |
|
|
* and calls to {@link #join} and related methods will result in |
534 |
|
|
* {@code CancellationException}. |
535 |
dl |
1.1 |
* |
536 |
|
|
* <p>This method may be overridden in subclasses, but if so, must |
537 |
dl |
1.69 |
* still ensure that these properties hold. In particular, the |
538 |
|
|
* {@code cancel} method itself must not throw exceptions. |
539 |
dl |
1.1 |
* |
540 |
jsr166 |
1.28 |
* <p>This method is designed to be invoked by <em>other</em> |
541 |
dl |
1.1 |
* tasks. To terminate the current task, you can just return or |
542 |
|
|
* throw an unchecked exception from its computation method, or |
543 |
jsr166 |
1.24 |
* invoke {@link #completeExceptionally}. |
544 |
dl |
1.1 |
* |
545 |
dl |
1.69 |
* @param mayInterruptIfRunning this value has no effect in the |
546 |
|
|
* default implementation because interrupts are not used to |
547 |
|
|
* control cancellation. |
548 |
dl |
1.1 |
* |
549 |
jsr166 |
1.23 |
* @return {@code true} if this task is now cancelled |
550 |
dl |
1.1 |
*/ |
551 |
|
|
public boolean cancel(boolean mayInterruptIfRunning) { |
552 |
dl |
1.53 |
setCompletion(CANCELLED); |
553 |
|
|
return status == CANCELLED; |
554 |
dl |
1.1 |
} |
555 |
|
|
|
556 |
dl |
1.46 |
/** |
557 |
dl |
1.52 |
* Cancels, ignoring any exceptions thrown by cancel. Used during |
558 |
|
|
* worker and pool shutdown. Cancel is spec'ed not to throw any |
559 |
|
|
* exceptions, but if it does anyway, we have no recourse during |
560 |
|
|
* shutdown, so guard against this case. |
561 |
dl |
1.46 |
*/ |
562 |
|
|
final void cancelIgnoringExceptions() { |
563 |
|
|
try { |
564 |
|
|
cancel(false); |
565 |
|
|
} catch (Throwable ignore) { |
566 |
|
|
} |
567 |
|
|
} |
568 |
|
|
|
569 |
|
|
/** |
570 |
jsr166 |
1.56 |
* Cancels if current thread is a terminating worker thread, |
571 |
|
|
* ignoring any exceptions thrown by cancel. |
572 |
dl |
1.46 |
*/ |
573 |
dl |
1.50 |
final void cancelIfTerminating() { |
574 |
dl |
1.46 |
Thread t = Thread.currentThread(); |
575 |
|
|
if ((t instanceof ForkJoinWorkerThread) && |
576 |
dl |
1.47 |
((ForkJoinWorkerThread) t).isTerminating()) { |
577 |
dl |
1.46 |
try { |
578 |
|
|
cancel(false); |
579 |
|
|
} catch (Throwable ignore) { |
580 |
|
|
} |
581 |
|
|
} |
582 |
|
|
} |
583 |
|
|
|
584 |
dl |
1.34 |
public final boolean isDone() { |
585 |
|
|
return status < 0; |
586 |
|
|
} |
587 |
|
|
|
588 |
|
|
public final boolean isCancelled() { |
589 |
dl |
1.49 |
return status == CANCELLED; |
590 |
dl |
1.34 |
} |
591 |
|
|
|
592 |
|
|
/** |
593 |
jsr166 |
1.23 |
* Returns {@code true} if this task threw an exception or was cancelled. |
594 |
jsr166 |
1.10 |
* |
595 |
jsr166 |
1.23 |
* @return {@code true} if this task threw an exception or was cancelled |
596 |
dl |
1.3 |
*/ |
597 |
|
|
public final boolean isCompletedAbnormally() { |
598 |
dl |
1.49 |
return status < NORMAL; |
599 |
dl |
1.3 |
} |
600 |
|
|
|
601 |
|
|
/** |
602 |
dl |
1.34 |
* Returns {@code true} if this task completed without throwing an |
603 |
|
|
* exception and was not cancelled. |
604 |
|
|
* |
605 |
|
|
* @return {@code true} if this task completed without throwing an |
606 |
|
|
* exception and was not cancelled |
607 |
|
|
*/ |
608 |
|
|
public final boolean isCompletedNormally() { |
609 |
dl |
1.49 |
return status == NORMAL; |
610 |
dl |
1.34 |
} |
611 |
|
|
|
612 |
|
|
/** |
613 |
dl |
1.3 |
* Returns the exception thrown by the base computation, or a |
614 |
jsr166 |
1.29 |
* {@code CancellationException} if cancelled, or {@code null} if |
615 |
|
|
* none or if the method has not yet completed. |
616 |
jsr166 |
1.10 |
* |
617 |
jsr166 |
1.23 |
* @return the exception, or {@code null} if none |
618 |
dl |
1.3 |
*/ |
619 |
|
|
public final Throwable getException() { |
620 |
dl |
1.49 |
int s = status; |
621 |
jsr166 |
1.37 |
return ((s >= NORMAL) ? null : |
622 |
|
|
(s == CANCELLED) ? new CancellationException() : |
623 |
|
|
exceptionMap.get(this)); |
624 |
dl |
1.3 |
} |
625 |
|
|
|
626 |
|
|
/** |
627 |
dl |
1.1 |
* Completes this task abnormally, and if not already aborted or |
628 |
|
|
* cancelled, causes it to throw the given exception upon |
629 |
jsr166 |
1.8 |
* {@code join} and related operations. This method may be used |
630 |
dl |
1.1 |
* to induce exceptions in asynchronous tasks, or to force |
631 |
dl |
1.2 |
* completion of tasks that would not otherwise complete. Its use |
632 |
dl |
1.27 |
* in other situations is discouraged. This method is |
633 |
jsr166 |
1.8 |
* overridable, but overridden versions must invoke {@code super} |
634 |
dl |
1.2 |
* implementation to maintain guarantees. |
635 |
|
|
* |
636 |
jsr166 |
1.44 |
* @param ex the exception to throw. If this exception is not a |
637 |
|
|
* {@code RuntimeException} or {@code Error}, the actual exception |
638 |
|
|
* thrown will be a {@code RuntimeException} with cause {@code ex}. |
639 |
dl |
1.1 |
*/ |
640 |
|
|
public void completeExceptionally(Throwable ex) { |
641 |
dl |
1.48 |
setExceptionalCompletion((ex instanceof RuntimeException) || |
642 |
|
|
(ex instanceof Error) ? ex : |
643 |
|
|
new RuntimeException(ex)); |
644 |
dl |
1.1 |
} |
645 |
|
|
|
646 |
|
|
/** |
647 |
|
|
* Completes this task, and if not already aborted or cancelled, |
648 |
dl |
1.58 |
* returning the given value as the result of subsequent |
649 |
|
|
* invocations of {@code join} and related operations. This method |
650 |
|
|
* may be used to provide results for asynchronous tasks, or to |
651 |
|
|
* provide alternative handling for tasks that would not otherwise |
652 |
|
|
* complete normally. Its use in other situations is |
653 |
|
|
* discouraged. This method is overridable, but overridden |
654 |
|
|
* versions must invoke {@code super} implementation to maintain |
655 |
|
|
* guarantees. |
656 |
dl |
1.1 |
* |
657 |
jsr166 |
1.10 |
* @param value the result value for this task |
658 |
dl |
1.1 |
*/ |
659 |
|
|
public void complete(V value) { |
660 |
|
|
try { |
661 |
|
|
setRawResult(value); |
662 |
jsr166 |
1.14 |
} catch (Throwable rex) { |
663 |
dl |
1.48 |
setExceptionalCompletion(rex); |
664 |
dl |
1.1 |
return; |
665 |
|
|
} |
666 |
dl |
1.46 |
setCompletion(NORMAL); |
667 |
dl |
1.1 |
} |
668 |
|
|
|
669 |
dl |
1.62 |
/** |
670 |
dl |
1.63 |
* Waits if necessary for the computation to complete, and then |
671 |
|
|
* retrieves its result. |
672 |
|
|
* |
673 |
|
|
* @return the computed result |
674 |
|
|
* @throws CancellationException if the computation was cancelled |
675 |
|
|
* @throws ExecutionException if the computation threw an |
676 |
|
|
* exception |
677 |
|
|
* @throws InterruptedException if the current thread is not a |
678 |
|
|
* member of a ForkJoinPool and was interrupted while waiting |
679 |
dl |
1.62 |
*/ |
680 |
dl |
1.3 |
public final V get() throws InterruptedException, ExecutionException { |
681 |
dl |
1.62 |
int s; |
682 |
|
|
if (Thread.currentThread() instanceof ForkJoinWorkerThread) { |
683 |
|
|
quietlyJoin(); |
684 |
|
|
s = status; |
685 |
|
|
} |
686 |
|
|
else { |
687 |
|
|
while ((s = status) >= 0) { |
688 |
|
|
synchronized (this) { // interruptible form of awaitDone |
689 |
jsr166 |
1.64 |
if (UNSAFE.compareAndSwapInt(this, statusOffset, |
690 |
dl |
1.62 |
s, SIGNAL)) { |
691 |
|
|
while (status >= 0) |
692 |
|
|
wait(); |
693 |
|
|
} |
694 |
|
|
} |
695 |
|
|
} |
696 |
|
|
} |
697 |
dl |
1.48 |
if (s < NORMAL) { |
698 |
|
|
Throwable ex; |
699 |
|
|
if (s == CANCELLED) |
700 |
|
|
throw new CancellationException(); |
701 |
|
|
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
702 |
|
|
throw new ExecutionException(ex); |
703 |
|
|
} |
704 |
|
|
return getRawResult(); |
705 |
dl |
1.3 |
} |
706 |
dl |
1.47 |
|
707 |
dl |
1.62 |
/** |
708 |
dl |
1.63 |
* Waits if necessary for at most the given time for the computation |
709 |
|
|
* to complete, and then retrieves its result, if available. |
710 |
|
|
* |
711 |
|
|
* @param timeout the maximum time to wait |
712 |
|
|
* @param unit the time unit of the timeout argument |
713 |
|
|
* @return the computed result |
714 |
|
|
* @throws CancellationException if the computation was cancelled |
715 |
|
|
* @throws ExecutionException if the computation threw an |
716 |
|
|
* exception |
717 |
|
|
* @throws InterruptedException if the current thread is not a |
718 |
|
|
* member of a ForkJoinPool and was interrupted while waiting |
719 |
|
|
* @throws TimeoutException if the wait timed out |
720 |
dl |
1.62 |
*/ |
721 |
dl |
1.3 |
public final V get(long timeout, TimeUnit unit) |
722 |
|
|
throws InterruptedException, ExecutionException, TimeoutException { |
723 |
dl |
1.54 |
long nanos = unit.toNanos(timeout); |
724 |
dl |
1.66 |
if (status >= 0) { |
725 |
|
|
Thread t = Thread.currentThread(); |
726 |
|
|
if (t instanceof ForkJoinWorkerThread) { |
727 |
|
|
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
728 |
|
|
boolean completed = false; // timed variant of quietlyJoin |
729 |
|
|
if (w.unpushTask(this)) { |
730 |
|
|
try { |
731 |
|
|
completed = exec(); |
732 |
|
|
} catch (Throwable rex) { |
733 |
|
|
setExceptionalCompletion(rex); |
734 |
|
|
} |
735 |
|
|
} |
736 |
|
|
if (completed) |
737 |
|
|
setCompletion(NORMAL); |
738 |
|
|
else if (status >= 0) |
739 |
|
|
w.joinTask(this, true, nanos); |
740 |
dl |
1.48 |
} |
741 |
dl |
1.66 |
else if (Thread.interrupted()) |
742 |
|
|
throw new InterruptedException(); |
743 |
|
|
else { |
744 |
dl |
1.48 |
long startTime = System.nanoTime(); |
745 |
dl |
1.66 |
int s; long nt; |
746 |
|
|
while ((s = status) >= 0 && |
747 |
dl |
1.48 |
(nt = nanos - (System.nanoTime() - startTime)) > 0) { |
748 |
dl |
1.66 |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, |
749 |
|
|
SIGNAL)) { |
750 |
dl |
1.48 |
long ms = nt / 1000000; |
751 |
|
|
int ns = (int) (nt % 1000000); |
752 |
dl |
1.66 |
synchronized (this) { |
753 |
|
|
if (status >= 0) |
754 |
|
|
wait(ms, ns); // exit on IE throw |
755 |
dl |
1.48 |
} |
756 |
|
|
} |
757 |
|
|
} |
758 |
|
|
} |
759 |
|
|
} |
760 |
dl |
1.49 |
int es = status; |
761 |
dl |
1.48 |
if (es != NORMAL) { |
762 |
|
|
Throwable ex; |
763 |
|
|
if (es == CANCELLED) |
764 |
|
|
throw new CancellationException(); |
765 |
|
|
if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
766 |
|
|
throw new ExecutionException(ex); |
767 |
|
|
throw new TimeoutException(); |
768 |
|
|
} |
769 |
|
|
return getRawResult(); |
770 |
dl |
1.3 |
} |
771 |
|
|
|
772 |
dl |
1.1 |
/** |
773 |
dl |
1.53 |
* Joins this task, without returning its result or throwing its |
774 |
dl |
1.2 |
* exception. This method may be useful when processing |
775 |
|
|
* collections of tasks when some have been cancelled or otherwise |
776 |
|
|
* known to have aborted. |
777 |
|
|
*/ |
778 |
|
|
public final void quietlyJoin() { |
779 |
dl |
1.53 |
Thread t; |
780 |
|
|
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) { |
781 |
|
|
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
782 |
|
|
if (status >= 0) { |
783 |
|
|
if (w.unpushTask(this)) { |
784 |
|
|
boolean completed; |
785 |
|
|
try { |
786 |
|
|
completed = exec(); |
787 |
|
|
} catch (Throwable rex) { |
788 |
|
|
setExceptionalCompletion(rex); |
789 |
|
|
return; |
790 |
|
|
} |
791 |
|
|
if (completed) { |
792 |
|
|
setCompletion(NORMAL); |
793 |
|
|
return; |
794 |
|
|
} |
795 |
|
|
} |
796 |
dl |
1.66 |
w.joinTask(this, false, 0L); |
797 |
dl |
1.53 |
} |
798 |
|
|
} |
799 |
|
|
else |
800 |
|
|
externalAwaitDone(); |
801 |
dl |
1.2 |
} |
802 |
|
|
|
803 |
|
|
/** |
804 |
|
|
* Commences performing this task and awaits its completion if |
805 |
dl |
1.53 |
* necessary, without returning its result or throwing its |
806 |
dl |
1.58 |
* exception. |
807 |
dl |
1.2 |
*/ |
808 |
|
|
public final void quietlyInvoke() { |
809 |
dl |
1.53 |
if (status >= 0) { |
810 |
|
|
boolean completed; |
811 |
|
|
try { |
812 |
|
|
completed = exec(); |
813 |
|
|
} catch (Throwable rex) { |
814 |
|
|
setExceptionalCompletion(rex); |
815 |
|
|
return; |
816 |
|
|
} |
817 |
|
|
if (completed) |
818 |
|
|
setCompletion(NORMAL); |
819 |
|
|
else |
820 |
|
|
quietlyJoin(); |
821 |
|
|
} |
822 |
dl |
1.2 |
} |
823 |
|
|
|
824 |
|
|
/** |
825 |
dl |
1.3 |
* Possibly executes tasks until the pool hosting the current task |
826 |
dl |
1.33 |
* {@link ForkJoinPool#isQuiescent is quiescent}. This method may |
827 |
|
|
* be of use in designs in which many tasks are forked, but none |
828 |
|
|
* are explicitly joined, instead executing them until all are |
829 |
|
|
* processed. |
830 |
jsr166 |
1.31 |
* |
831 |
|
|
* <p>This method may be invoked only from within {@code |
832 |
dl |
1.69 |
* ForkJoinPool} computations (as may be determined using method |
833 |
jsr166 |
1.31 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
834 |
|
|
* result in exceptions or errors, possibly including {@code |
835 |
|
|
* ClassCastException}. |
836 |
dl |
1.3 |
*/ |
837 |
|
|
public static void helpQuiesce() { |
838 |
jsr166 |
1.14 |
((ForkJoinWorkerThread) Thread.currentThread()) |
839 |
|
|
.helpQuiescePool(); |
840 |
dl |
1.3 |
} |
841 |
|
|
|
842 |
|
|
/** |
843 |
dl |
1.1 |
* Resets the internal bookkeeping state of this task, allowing a |
844 |
jsr166 |
1.8 |
* subsequent {@code fork}. This method allows repeated reuse of |
845 |
dl |
1.1 |
* this task, but only if reuse occurs when this task has either |
846 |
|
|
* never been forked, or has been forked, then completed and all |
847 |
|
|
* outstanding joins of this task have also completed. Effects |
848 |
dl |
1.30 |
* under any other usage conditions are not guaranteed. |
849 |
|
|
* This method may be useful when executing |
850 |
dl |
1.1 |
* pre-constructed trees of subtasks in loops. |
851 |
jsr166 |
1.68 |
* |
852 |
dl |
1.67 |
* <p>Upon completion of this method, {@code isDone()} reports |
853 |
|
|
* {@code false}, and {@code getException()} reports {@code |
854 |
|
|
* null}. However, the value returned by {@code getRawResult} is |
855 |
|
|
* unaffected. To clear this value, you can invoke {@code |
856 |
|
|
* setRawResult(null)}. |
857 |
dl |
1.1 |
*/ |
858 |
|
|
public void reinitialize() { |
859 |
dl |
1.49 |
if (status == EXCEPTIONAL) |
860 |
dl |
1.1 |
exceptionMap.remove(this); |
861 |
|
|
status = 0; |
862 |
|
|
} |
863 |
|
|
|
864 |
|
|
/** |
865 |
dl |
1.2 |
* Returns the pool hosting the current task execution, or null |
866 |
dl |
1.13 |
* if this task is executing outside of any ForkJoinPool. |
867 |
jsr166 |
1.10 |
* |
868 |
dl |
1.27 |
* @see #inForkJoinPool |
869 |
jsr166 |
1.23 |
* @return the pool, or {@code null} if none |
870 |
dl |
1.1 |
*/ |
871 |
dl |
1.2 |
public static ForkJoinPool getPool() { |
872 |
|
|
Thread t = Thread.currentThread(); |
873 |
jsr166 |
1.15 |
return (t instanceof ForkJoinWorkerThread) ? |
874 |
|
|
((ForkJoinWorkerThread) t).pool : null; |
875 |
dl |
1.1 |
} |
876 |
|
|
|
877 |
|
|
/** |
878 |
jsr166 |
1.14 |
* Returns {@code true} if the current thread is executing as a |
879 |
dl |
1.13 |
* ForkJoinPool computation. |
880 |
jsr166 |
1.14 |
* |
881 |
|
|
* @return {@code true} if the current thread is executing as a |
882 |
dl |
1.13 |
* ForkJoinPool computation, or false otherwise |
883 |
|
|
*/ |
884 |
|
|
public static boolean inForkJoinPool() { |
885 |
|
|
return Thread.currentThread() instanceof ForkJoinWorkerThread; |
886 |
|
|
} |
887 |
|
|
|
888 |
|
|
/** |
889 |
dl |
1.2 |
* Tries to unschedule this task for execution. This method will |
890 |
|
|
* typically succeed if this task is the most recently forked task |
891 |
|
|
* by the current thread, and has not commenced executing in |
892 |
|
|
* another thread. This method may be useful when arranging |
893 |
|
|
* alternative local processing of tasks that could have been, but |
894 |
jsr166 |
1.31 |
* were not, stolen. |
895 |
|
|
* |
896 |
|
|
* <p>This method may be invoked only from within {@code |
897 |
dl |
1.69 |
* ForkJoinPool} computations (as may be determined using method |
898 |
jsr166 |
1.31 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
899 |
|
|
* result in exceptions or errors, possibly including {@code |
900 |
|
|
* ClassCastException}. |
901 |
jsr166 |
1.10 |
* |
902 |
jsr166 |
1.23 |
* @return {@code true} if unforked |
903 |
dl |
1.1 |
*/ |
904 |
dl |
1.2 |
public boolean tryUnfork() { |
905 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
906 |
|
|
.unpushTask(this); |
907 |
dl |
1.1 |
} |
908 |
|
|
|
909 |
|
|
/** |
910 |
dl |
1.2 |
* Returns an estimate of the number of tasks that have been |
911 |
|
|
* forked by the current worker thread but not yet executed. This |
912 |
|
|
* value may be useful for heuristic decisions about whether to |
913 |
jsr166 |
1.31 |
* fork other tasks. |
914 |
|
|
* |
915 |
|
|
* <p>This method may be invoked only from within {@code |
916 |
dl |
1.69 |
* ForkJoinPool} computations (as may be determined using method |
917 |
jsr166 |
1.31 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
918 |
|
|
* result in exceptions or errors, possibly including {@code |
919 |
|
|
* ClassCastException}. |
920 |
|
|
* |
921 |
dl |
1.2 |
* @return the number of tasks |
922 |
|
|
*/ |
923 |
|
|
public static int getQueuedTaskCount() { |
924 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
925 |
|
|
.getQueueSize(); |
926 |
dl |
1.2 |
} |
927 |
|
|
|
928 |
|
|
/** |
929 |
jsr166 |
1.10 |
* Returns an estimate of how many more locally queued tasks are |
930 |
dl |
1.1 |
* held by the current worker thread than there are other worker |
931 |
dl |
1.2 |
* threads that might steal them. This value may be useful for |
932 |
|
|
* heuristic decisions about whether to fork other tasks. In many |
933 |
|
|
* usages of ForkJoinTasks, at steady state, each worker should |
934 |
|
|
* aim to maintain a small constant surplus (for example, 3) of |
935 |
|
|
* tasks, and to process computations locally if this threshold is |
936 |
jsr166 |
1.31 |
* exceeded. |
937 |
|
|
* |
938 |
|
|
* <p>This method may be invoked only from within {@code |
939 |
dl |
1.69 |
* ForkJoinPool} computations (as may be determined using method |
940 |
jsr166 |
1.31 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
941 |
|
|
* result in exceptions or errors, possibly including {@code |
942 |
|
|
* ClassCastException}. |
943 |
|
|
* |
944 |
dl |
1.1 |
* @return the surplus number of tasks, which may be negative |
945 |
|
|
*/ |
946 |
dl |
1.2 |
public static int getSurplusQueuedTaskCount() { |
947 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
948 |
dl |
1.1 |
.getEstimatedSurplusTaskCount(); |
949 |
|
|
} |
950 |
|
|
|
951 |
dl |
1.2 |
// Extension methods |
952 |
dl |
1.1 |
|
953 |
|
|
/** |
954 |
jsr166 |
1.23 |
* Returns the result that would be returned by {@link #join}, even |
955 |
|
|
* if this task completed abnormally, or {@code null} if this task |
956 |
|
|
* is not known to have been completed. This method is designed |
957 |
|
|
* to aid debugging, as well as to support extensions. Its use in |
958 |
|
|
* any other context is discouraged. |
959 |
dl |
1.1 |
* |
960 |
jsr166 |
1.23 |
* @return the result, or {@code null} if not completed |
961 |
dl |
1.1 |
*/ |
962 |
|
|
public abstract V getRawResult(); |
963 |
|
|
|
964 |
|
|
/** |
965 |
|
|
* Forces the given value to be returned as a result. This method |
966 |
|
|
* is designed to support extensions, and should not in general be |
967 |
|
|
* called otherwise. |
968 |
|
|
* |
969 |
|
|
* @param value the value |
970 |
|
|
*/ |
971 |
|
|
protected abstract void setRawResult(V value); |
972 |
|
|
|
973 |
|
|
/** |
974 |
|
|
* Immediately performs the base action of this task. This method |
975 |
|
|
* is designed to support extensions, and should not in general be |
976 |
|
|
* called otherwise. The return value controls whether this task |
977 |
|
|
* is considered to be done normally. It may return false in |
978 |
|
|
* asynchronous actions that require explicit invocations of |
979 |
dl |
1.34 |
* {@link #complete} to become joinable. It may also throw an |
980 |
|
|
* (unchecked) exception to indicate abnormal exit. |
981 |
jsr166 |
1.10 |
* |
982 |
jsr166 |
1.23 |
* @return {@code true} if completed normally |
983 |
dl |
1.1 |
*/ |
984 |
|
|
protected abstract boolean exec(); |
985 |
|
|
|
986 |
dl |
1.2 |
/** |
987 |
dl |
1.25 |
* Returns, but does not unschedule or execute, a task queued by |
988 |
|
|
* the current thread but not yet executed, if one is immediately |
989 |
dl |
1.6 |
* available. There is no guarantee that this task will actually |
990 |
dl |
1.25 |
* be polled or executed next. Conversely, this method may return |
991 |
|
|
* null even if a task exists but cannot be accessed without |
992 |
|
|
* contention with other threads. This method is designed |
993 |
|
|
* primarily to support extensions, and is unlikely to be useful |
994 |
jsr166 |
1.31 |
* otherwise. |
995 |
|
|
* |
996 |
|
|
* <p>This method may be invoked only from within {@code |
997 |
dl |
1.69 |
* ForkJoinPool} computations (as may be determined using method |
998 |
jsr166 |
1.31 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
999 |
|
|
* result in exceptions or errors, possibly including {@code |
1000 |
|
|
* ClassCastException}. |
1001 |
dl |
1.2 |
* |
1002 |
jsr166 |
1.23 |
* @return the next task, or {@code null} if none are available |
1003 |
dl |
1.2 |
*/ |
1004 |
|
|
protected static ForkJoinTask<?> peekNextLocalTask() { |
1005 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1006 |
|
|
.peekTask(); |
1007 |
dl |
1.2 |
} |
1008 |
|
|
|
1009 |
|
|
/** |
1010 |
dl |
1.6 |
* Unschedules and returns, without executing, the next task |
1011 |
|
|
* queued by the current thread but not yet executed. This method |
1012 |
|
|
* is designed primarily to support extensions, and is unlikely to |
1013 |
jsr166 |
1.31 |
* be useful otherwise. |
1014 |
|
|
* |
1015 |
|
|
* <p>This method may be invoked only from within {@code |
1016 |
dl |
1.69 |
* ForkJoinPool} computations (as may be determined using method |
1017 |
jsr166 |
1.31 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1018 |
|
|
* result in exceptions or errors, possibly including {@code |
1019 |
|
|
* ClassCastException}. |
1020 |
dl |
1.2 |
* |
1021 |
jsr166 |
1.23 |
* @return the next task, or {@code null} if none are available |
1022 |
dl |
1.2 |
*/ |
1023 |
|
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
1024 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1025 |
|
|
.pollLocalTask(); |
1026 |
dl |
1.2 |
} |
1027 |
jsr166 |
1.7 |
|
1028 |
dl |
1.2 |
/** |
1029 |
dl |
1.6 |
* Unschedules and returns, without executing, the next task |
1030 |
|
|
* queued by the current thread but not yet executed, if one is |
1031 |
|
|
* available, or if not available, a task that was forked by some |
1032 |
|
|
* other thread, if available. Availability may be transient, so a |
1033 |
jsr166 |
1.9 |
* {@code null} result does not necessarily imply quiescence |
1034 |
dl |
1.6 |
* of the pool this task is operating in. This method is designed |
1035 |
|
|
* primarily to support extensions, and is unlikely to be useful |
1036 |
jsr166 |
1.31 |
* otherwise. |
1037 |
|
|
* |
1038 |
|
|
* <p>This method may be invoked only from within {@code |
1039 |
dl |
1.69 |
* ForkJoinPool} computations (as may be determined using method |
1040 |
jsr166 |
1.31 |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1041 |
|
|
* result in exceptions or errors, possibly including {@code |
1042 |
|
|
* ClassCastException}. |
1043 |
dl |
1.4 |
* |
1044 |
jsr166 |
1.23 |
* @return a task, or {@code null} if none are available |
1045 |
dl |
1.2 |
*/ |
1046 |
|
|
protected static ForkJoinTask<?> pollTask() { |
1047 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1048 |
|
|
.pollTask(); |
1049 |
dl |
1.2 |
} |
1050 |
|
|
|
1051 |
dl |
1.25 |
/** |
1052 |
|
|
* Adaptor for Runnables. This implements RunnableFuture |
1053 |
|
|
* to be compliant with AbstractExecutorService constraints |
1054 |
|
|
* when used in ForkJoinPool. |
1055 |
|
|
*/ |
1056 |
|
|
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
1057 |
|
|
implements RunnableFuture<T> { |
1058 |
|
|
final Runnable runnable; |
1059 |
|
|
final T resultOnCompletion; |
1060 |
|
|
T result; |
1061 |
|
|
AdaptedRunnable(Runnable runnable, T result) { |
1062 |
|
|
if (runnable == null) throw new NullPointerException(); |
1063 |
|
|
this.runnable = runnable; |
1064 |
|
|
this.resultOnCompletion = result; |
1065 |
|
|
} |
1066 |
|
|
public T getRawResult() { return result; } |
1067 |
|
|
public void setRawResult(T v) { result = v; } |
1068 |
|
|
public boolean exec() { |
1069 |
|
|
runnable.run(); |
1070 |
|
|
result = resultOnCompletion; |
1071 |
|
|
return true; |
1072 |
|
|
} |
1073 |
|
|
public void run() { invoke(); } |
1074 |
|
|
private static final long serialVersionUID = 5232453952276885070L; |
1075 |
|
|
} |
1076 |
|
|
|
1077 |
|
|
/** |
1078 |
|
|
* Adaptor for Callables |
1079 |
|
|
*/ |
1080 |
|
|
static final class AdaptedCallable<T> extends ForkJoinTask<T> |
1081 |
|
|
implements RunnableFuture<T> { |
1082 |
dl |
1.27 |
final Callable<? extends T> callable; |
1083 |
dl |
1.25 |
T result; |
1084 |
dl |
1.27 |
AdaptedCallable(Callable<? extends T> callable) { |
1085 |
dl |
1.25 |
if (callable == null) throw new NullPointerException(); |
1086 |
|
|
this.callable = callable; |
1087 |
|
|
} |
1088 |
|
|
public T getRawResult() { return result; } |
1089 |
|
|
public void setRawResult(T v) { result = v; } |
1090 |
|
|
public boolean exec() { |
1091 |
|
|
try { |
1092 |
|
|
result = callable.call(); |
1093 |
|
|
return true; |
1094 |
|
|
} catch (Error err) { |
1095 |
|
|
throw err; |
1096 |
|
|
} catch (RuntimeException rex) { |
1097 |
|
|
throw rex; |
1098 |
|
|
} catch (Exception ex) { |
1099 |
|
|
throw new RuntimeException(ex); |
1100 |
|
|
} |
1101 |
|
|
} |
1102 |
|
|
public void run() { invoke(); } |
1103 |
|
|
private static final long serialVersionUID = 2838392045355241008L; |
1104 |
|
|
} |
1105 |
dl |
1.18 |
|
1106 |
|
|
/** |
1107 |
jsr166 |
1.31 |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1108 |
|
|
* method of the given {@code Runnable} as its action, and returns |
1109 |
|
|
* a null result upon {@link #join}. |
1110 |
dl |
1.18 |
* |
1111 |
|
|
* @param runnable the runnable action |
1112 |
|
|
* @return the task |
1113 |
|
|
*/ |
1114 |
dl |
1.27 |
public static ForkJoinTask<?> adapt(Runnable runnable) { |
1115 |
dl |
1.25 |
return new AdaptedRunnable<Void>(runnable, null); |
1116 |
dl |
1.18 |
} |
1117 |
|
|
|
1118 |
|
|
/** |
1119 |
jsr166 |
1.31 |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1120 |
|
|
* method of the given {@code Runnable} as its action, and returns |
1121 |
|
|
* the given result upon {@link #join}. |
1122 |
dl |
1.18 |
* |
1123 |
|
|
* @param runnable the runnable action |
1124 |
|
|
* @param result the result upon completion |
1125 |
|
|
* @return the task |
1126 |
|
|
*/ |
1127 |
|
|
public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) { |
1128 |
dl |
1.25 |
return new AdaptedRunnable<T>(runnable, result); |
1129 |
dl |
1.18 |
} |
1130 |
|
|
|
1131 |
|
|
/** |
1132 |
jsr166 |
1.31 |
* Returns a new {@code ForkJoinTask} that performs the {@code call} |
1133 |
|
|
* method of the given {@code Callable} as its action, and returns |
1134 |
|
|
* its result upon {@link #join}, translating any checked exceptions |
1135 |
|
|
* encountered into {@code RuntimeException}. |
1136 |
dl |
1.18 |
* |
1137 |
|
|
* @param callable the callable action |
1138 |
|
|
* @return the task |
1139 |
|
|
*/ |
1140 |
dl |
1.27 |
public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) { |
1141 |
dl |
1.25 |
return new AdaptedCallable<T>(callable); |
1142 |
dl |
1.18 |
} |
1143 |
|
|
|
1144 |
dl |
1.1 |
// Serialization support |
1145 |
|
|
|
1146 |
|
|
private static final long serialVersionUID = -7721805057305804111L; |
1147 |
|
|
|
1148 |
|
|
/** |
1149 |
jsr166 |
1.56 |
* Saves the state to a stream (that is, serializes it). |
1150 |
dl |
1.1 |
* |
1151 |
|
|
* @serialData the current run status and the exception thrown |
1152 |
jsr166 |
1.23 |
* during execution, or {@code null} if none |
1153 |
dl |
1.1 |
* @param s the stream |
1154 |
|
|
*/ |
1155 |
|
|
private void writeObject(java.io.ObjectOutputStream s) |
1156 |
|
|
throws java.io.IOException { |
1157 |
|
|
s.defaultWriteObject(); |
1158 |
|
|
s.writeObject(getException()); |
1159 |
|
|
} |
1160 |
|
|
|
1161 |
|
|
/** |
1162 |
jsr166 |
1.56 |
* Reconstitutes the instance from a stream (that is, deserializes it). |
1163 |
jsr166 |
1.10 |
* |
1164 |
dl |
1.1 |
* @param s the stream |
1165 |
|
|
*/ |
1166 |
|
|
private void readObject(java.io.ObjectInputStream s) |
1167 |
|
|
throws java.io.IOException, ClassNotFoundException { |
1168 |
|
|
s.defaultReadObject(); |
1169 |
|
|
Object ex = s.readObject(); |
1170 |
|
|
if (ex != null) |
1171 |
dl |
1.48 |
setExceptionalCompletion((Throwable) ex); |
1172 |
dl |
1.1 |
} |
1173 |
|
|
|
1174 |
jsr166 |
1.22 |
// Unsafe mechanics |
1175 |
|
|
|
1176 |
|
|
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1177 |
|
|
private static final long statusOffset = |
1178 |
|
|
objectFieldOffset("status", ForkJoinTask.class); |
1179 |
|
|
|
1180 |
|
|
private static long objectFieldOffset(String field, Class<?> klazz) { |
1181 |
|
|
try { |
1182 |
|
|
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1183 |
|
|
} catch (NoSuchFieldException e) { |
1184 |
|
|
// Convert Exception to corresponding Error |
1185 |
|
|
NoSuchFieldError error = new NoSuchFieldError(field); |
1186 |
|
|
error.initCause(e); |
1187 |
|
|
throw error; |
1188 |
|
|
} |
1189 |
|
|
} |
1190 |
|
|
|
1191 |
|
|
/** |
1192 |
|
|
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
1193 |
|
|
* Replace with a simple call to Unsafe.getUnsafe when integrating |
1194 |
|
|
* into a jdk. |
1195 |
|
|
* |
1196 |
|
|
* @return a sun.misc.Unsafe |
1197 |
|
|
*/ |
1198 |
jsr166 |
1.16 |
private static sun.misc.Unsafe getUnsafe() { |
1199 |
jsr166 |
1.5 |
try { |
1200 |
jsr166 |
1.16 |
return sun.misc.Unsafe.getUnsafe(); |
1201 |
jsr166 |
1.5 |
} catch (SecurityException se) { |
1202 |
|
|
try { |
1203 |
|
|
return java.security.AccessController.doPrivileged |
1204 |
jsr166 |
1.22 |
(new java.security |
1205 |
|
|
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1206 |
jsr166 |
1.16 |
public sun.misc.Unsafe run() throws Exception { |
1207 |
jsr166 |
1.22 |
java.lang.reflect.Field f = sun.misc |
1208 |
|
|
.Unsafe.class.getDeclaredField("theUnsafe"); |
1209 |
|
|
f.setAccessible(true); |
1210 |
|
|
return (sun.misc.Unsafe) f.get(null); |
1211 |
jsr166 |
1.5 |
}}); |
1212 |
|
|
} catch (java.security.PrivilegedActionException e) { |
1213 |
jsr166 |
1.16 |
throw new RuntimeException("Could not initialize intrinsics", |
1214 |
|
|
e.getCause()); |
1215 |
jsr166 |
1.5 |
} |
1216 |
|
|
} |
1217 |
|
|
} |
1218 |
dl |
1.1 |
} |