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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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import java.util.concurrent.*; |
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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 |
1.1 |
|
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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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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 |
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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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dl |
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 |
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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} |
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dl |
1.49 |
* conventions. Method {@link #invoke} is semantically |
68 |
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 |
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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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dl |
1.35 |
* |
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jsr166 |
1.28 |
* <p>The ForkJoinTask class is not usually directly subclassed. |
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dl |
1.2 |
* Instead, you subclass one of the abstract classes that support a |
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dl |
1.27 |
* particular style of fork/join processing, typically {@link |
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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} |
96 |
dl |
1.2 |
* method that somehow uses the control methods supplied by this base |
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jsr166 |
1.8 |
* class. While these methods have {@code public} access (to allow |
98 |
dl |
1.32 |
* instances of different task subclasses to call each other's |
99 |
dl |
1.2 |
* methods), some of them may only be called from within other |
100 |
dl |
1.13 |
* ForkJoinTasks (as may be determined using method {@link |
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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 |
103 |
dl |
1.57 |
* {@code ClassCastException}. |
104 |
dl |
1.1 |
* |
105 |
dl |
1.32 |
* <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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* underlying lightweight task scheduling framework. Developers |
108 |
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* creating new basic styles of fork/join processing should minimally |
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* implement {@code protected} methods {@link #exec}, {@link |
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* #setRawResult}, and {@link #getRawResult}, while also introducing |
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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 |
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* provided by this class. |
114 |
dl |
1.1 |
* |
115 |
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* <p>ForkJoinTasks should perform relatively small amounts of |
116 |
dl |
1.32 |
* computation. Large tasks should be split into smaller subtasks, |
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* usually via recursive decomposition. As a very rough rule of thumb, |
118 |
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* a task should perform more than 100 and less than 10000 basic |
119 |
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* computational steps. If tasks are too big, then parallelism cannot |
120 |
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* improve throughput. If too small, then memory and internal task |
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* maintenance overhead may overwhelm processing. |
122 |
dl |
1.1 |
* |
123 |
jsr166 |
1.37 |
* <p>This class provides {@code adapt} methods for {@link Runnable} |
124 |
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* and {@link Callable}, that may be of use when mixing execution of |
125 |
dl |
1.49 |
* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are |
126 |
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* of this form, consider using a pool constructed in <em>asyncMode</em>. |
127 |
dl |
1.27 |
* |
128 |
dl |
1.32 |
* <p>ForkJoinTasks are {@code Serializable}, which enables them to be |
129 |
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* used in extensions such as remote execution frameworks. It is |
130 |
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* sensible to serialize tasks only before or after, but not during, |
131 |
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* execution. Serialization is not relied on during execution itself. |
132 |
jsr166 |
1.12 |
* |
133 |
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* @since 1.7 |
134 |
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* @author Doug Lea |
135 |
dl |
1.1 |
*/ |
136 |
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public abstract class ForkJoinTask<V> implements Future<V>, Serializable { |
137 |
dl |
1.2 |
|
138 |
dl |
1.46 |
/* |
139 |
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* See the internal documentation of class ForkJoinPool for a |
140 |
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* general implementation overview. ForkJoinTasks are mainly |
141 |
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* responsible for maintaining their "status" field amidst relays |
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* to methods in ForkJoinWorkerThread and ForkJoinPool. The |
143 |
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* methods of this class are more-or-less layered into (1) basic |
144 |
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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 |
146 |
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* sometimes hard to see because this file orders exported methods |
147 |
dl |
1.53 |
* in a way that flows well in javadocs. In particular, most |
148 |
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* join mechanics are in method quietlyJoin, below. |
149 |
dl |
1.46 |
*/ |
150 |
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151 |
dl |
1.50 |
/* |
152 |
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* The status field holds run control status bits packed into a |
153 |
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* single int to minimize footprint and to ensure atomicity (via |
154 |
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* CAS). Status is initially zero, and takes on nonnegative |
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* values until completed, upon which status holds value |
156 |
jsr166 |
1.59 |
* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking |
157 |
dl |
1.50 |
* waits by other threads have the SIGNAL bit set. Completion of |
158 |
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* a stolen task with SIGNAL set awakens any waiters via |
159 |
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* notifyAll. Even though suboptimal for some purposes, we use |
160 |
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* basic builtin wait/notify to take advantage of "monitor |
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* inflation" in JVMs that we would otherwise need to emulate to |
162 |
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* avoid adding further per-task bookkeeping overhead. We want |
163 |
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* these monitors to be "fat", i.e., not use biasing or thin-lock |
164 |
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* techniques, so use some odd coding idioms that tend to avoid |
165 |
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* them. |
166 |
dl |
1.1 |
*/ |
167 |
dl |
1.50 |
|
168 |
dl |
1.53 |
/** The run status of this task */ |
169 |
jsr166 |
1.9 |
volatile int status; // accessed directly by pool and workers |
170 |
dl |
1.1 |
|
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dl |
1.49 |
private static final int NORMAL = -1; |
172 |
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private static final int CANCELLED = -2; |
173 |
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private static final int EXCEPTIONAL = -3; |
174 |
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private static final int SIGNAL = 1; |
175 |
dl |
1.1 |
|
176 |
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/** |
177 |
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* Table of exceptions thrown by tasks, to enable reporting by |
178 |
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* callers. Because exceptions are rare, we don't directly keep |
179 |
jsr166 |
1.10 |
* them with task objects, but instead use a weak ref table. Note |
180 |
dl |
1.1 |
* that cancellation exceptions don't appear in the table, but are |
181 |
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* instead recorded as status values. |
182 |
jsr166 |
1.10 |
* TODO: Use ConcurrentReferenceHashMap |
183 |
dl |
1.1 |
*/ |
184 |
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static final Map<ForkJoinTask<?>, Throwable> exceptionMap = |
185 |
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Collections.synchronizedMap |
186 |
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(new WeakHashMap<ForkJoinTask<?>, Throwable>()); |
187 |
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188 |
dl |
1.46 |
// Maintaining completion status |
189 |
dl |
1.1 |
|
190 |
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/** |
191 |
dl |
1.46 |
* Marks completion and wakes up threads waiting to join this task, |
192 |
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* also clearing signal request bits. |
193 |
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* |
194 |
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* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
195 |
dl |
1.1 |
*/ |
196 |
dl |
1.53 |
private void setCompletion(int completion) { |
197 |
dl |
1.46 |
int s; |
198 |
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while ((s = status) >= 0) { |
199 |
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if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) { |
200 |
dl |
1.51 |
if (s != 0) |
201 |
dl |
1.46 |
synchronized (this) { notifyAll(); } |
202 |
dl |
1.53 |
break; |
203 |
dl |
1.46 |
} |
204 |
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} |
205 |
dl |
1.1 |
} |
206 |
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207 |
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/** |
208 |
jsr166 |
1.56 |
* Records exception and sets exceptional completion. |
209 |
jsr166 |
1.60 |
* |
210 |
dl |
1.48 |
* @return status on exit |
211 |
dl |
1.1 |
*/ |
212 |
dl |
1.53 |
private void setExceptionalCompletion(Throwable rex) { |
213 |
dl |
1.46 |
exceptionMap.put(this, rex); |
214 |
dl |
1.53 |
setCompletion(EXCEPTIONAL); |
215 |
dl |
1.1 |
} |
216 |
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217 |
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/** |
218 |
dl |
1.55 |
* Blocks a worker thread until completion. Called only by |
219 |
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* pool. Currently unused -- pool-based waits use timeout |
220 |
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* version below. |
221 |
dl |
1.1 |
*/ |
222 |
dl |
1.50 |
final void internalAwaitDone() { |
223 |
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int s; // the odd construction reduces lock bias effects |
224 |
dl |
1.48 |
while ((s = status) >= 0) { |
225 |
dl |
1.50 |
try { |
226 |
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synchronized(this) { |
227 |
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if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL)) |
228 |
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wait(); |
229 |
dl |
1.1 |
} |
230 |
dl |
1.50 |
} catch (InterruptedException ie) { |
231 |
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cancelIfTerminating(); |
232 |
dl |
1.1 |
} |
233 |
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} |
234 |
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} |
235 |
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236 |
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/** |
237 |
dl |
1.55 |
* Blocks a worker thread until completed or timed out. Called |
238 |
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* only by pool. |
239 |
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* |
240 |
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* @return status on exit |
241 |
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*/ |
242 |
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final int internalAwaitDone(long millis) { |
243 |
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int s; |
244 |
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if ((s = status) >= 0) { |
245 |
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try { |
246 |
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synchronized(this) { |
247 |
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if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL)) |
248 |
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wait(millis, 0); |
249 |
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} |
250 |
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} catch (InterruptedException ie) { |
251 |
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cancelIfTerminating(); |
252 |
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} |
253 |
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s = status; |
254 |
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} |
255 |
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return s; |
256 |
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} |
257 |
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258 |
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/** |
259 |
dl |
1.48 |
* Blocks a non-worker-thread until completion. |
260 |
dl |
1.1 |
*/ |
261 |
dl |
1.53 |
private void externalAwaitDone() { |
262 |
dl |
1.48 |
int s; |
263 |
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while ((s = status) >= 0) { |
264 |
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synchronized(this) { |
265 |
dl |
1.49 |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){ |
266 |
dl |
1.48 |
boolean interrupted = false; |
267 |
dl |
1.53 |
while (status >= 0) { |
268 |
dl |
1.48 |
try { |
269 |
dl |
1.47 |
wait(); |
270 |
dl |
1.48 |
} catch (InterruptedException ie) { |
271 |
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interrupted = true; |
272 |
dl |
1.46 |
} |
273 |
dl |
1.50 |
} |
274 |
dl |
1.48 |
if (interrupted) |
275 |
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Thread.currentThread().interrupt(); |
276 |
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break; |
277 |
dl |
1.46 |
} |
278 |
dl |
1.1 |
} |
279 |
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} |
280 |
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} |
281 |
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282 |
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/** |
283 |
dl |
1.48 |
* Unless done, calls exec and records status if completed, but |
284 |
dl |
1.49 |
* doesn't wait for completion otherwise. Primary execution method |
285 |
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* for ForkJoinWorkerThread. |
286 |
dl |
1.1 |
*/ |
287 |
dl |
1.53 |
final void quietlyExec() { |
288 |
dl |
1.48 |
try { |
289 |
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if (status < 0 || !exec()) |
290 |
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return; |
291 |
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} catch (Throwable rex) { |
292 |
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setExceptionalCompletion(rex); |
293 |
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return; |
294 |
dl |
1.1 |
} |
295 |
dl |
1.48 |
setCompletion(NORMAL); // must be outside try block |
296 |
dl |
1.1 |
} |
297 |
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|
298 |
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// public methods |
299 |
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|
300 |
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/** |
301 |
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* Arranges to asynchronously execute this task. While it is not |
302 |
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* necessarily enforced, it is a usage error to fork a task more |
303 |
jsr166 |
1.31 |
* than once unless it has completed and been reinitialized. |
304 |
dl |
1.43 |
* Subsequent modifications to the state of this task or any data |
305 |
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* it operates on are not necessarily consistently observable by |
306 |
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* any thread other than the one executing it unless preceded by a |
307 |
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* call to {@link #join} or related methods, or a call to {@link |
308 |
|
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* #isDone} returning {@code true}. |
309 |
dl |
1.18 |
* |
310 |
jsr166 |
1.31 |
* <p>This method may be invoked only from within {@code |
311 |
|
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* ForkJoinTask} computations (as may be determined using method |
312 |
|
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* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
313 |
|
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* result in exceptions or errors, possibly including {@code |
314 |
|
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* ClassCastException}. |
315 |
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* |
316 |
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* @return {@code this}, to simplify usage |
317 |
dl |
1.1 |
*/ |
318 |
dl |
1.18 |
public final ForkJoinTask<V> fork() { |
319 |
jsr166 |
1.14 |
((ForkJoinWorkerThread) Thread.currentThread()) |
320 |
|
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.pushTask(this); |
321 |
dl |
1.18 |
return this; |
322 |
dl |
1.1 |
} |
323 |
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|
324 |
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/** |
325 |
dl |
1.41 |
* Returns the result of the computation when it {@link #isDone is done}. |
326 |
jsr166 |
1.31 |
* This method differs from {@link #get()} in that |
327 |
|
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* abnormal completion results in {@code RuntimeException} or |
328 |
|
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* {@code Error}, not {@code ExecutionException}. |
329 |
dl |
1.1 |
* |
330 |
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* @return the computed result |
331 |
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*/ |
332 |
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public final V join() { |
333 |
dl |
1.53 |
quietlyJoin(); |
334 |
|
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Throwable ex; |
335 |
|
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if (status < NORMAL && (ex = getException()) != null) |
336 |
|
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UNSAFE.throwException(ex); |
337 |
|
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return getRawResult(); |
338 |
dl |
1.1 |
} |
339 |
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|
340 |
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/** |
341 |
dl |
1.2 |
* Commences performing this task, awaits its completion if |
342 |
jsr166 |
1.56 |
* necessary, and returns its result, or throws an (unchecked) |
343 |
dl |
1.57 |
* {@code RuntimeException} or {@code Error} if the underlying |
344 |
|
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* computation did so. |
345 |
jsr166 |
1.10 |
* |
346 |
dl |
1.1 |
* @return the computed result |
347 |
|
|
*/ |
348 |
|
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public final V invoke() { |
349 |
dl |
1.53 |
quietlyInvoke(); |
350 |
|
|
Throwable ex; |
351 |
|
|
if (status < NORMAL && (ex = getException()) != null) |
352 |
|
|
UNSAFE.throwException(ex); |
353 |
|
|
return getRawResult(); |
354 |
dl |
1.1 |
} |
355 |
|
|
|
356 |
|
|
/** |
357 |
dl |
1.34 |
* Forks the given tasks, returning when {@code isDone} holds for |
358 |
|
|
* each task or an (unchecked) exception is encountered, in which |
359 |
dl |
1.57 |
* case the exception is rethrown. If more than one task |
360 |
|
|
* encounters an exception, then this method throws any one of |
361 |
|
|
* these exceptions. If any task encounters an exception, the |
362 |
|
|
* other may be cancelled. However, the execution status of |
363 |
|
|
* individual tasks is not guaranteed upon exceptional return. The |
364 |
|
|
* status of each task may be obtained using {@link |
365 |
|
|
* #getException()} and related methods to check if they have been |
366 |
|
|
* cancelled, completed normally or exceptionally, or left |
367 |
|
|
* unprocessed. |
368 |
jsr166 |
1.31 |
* |
369 |
|
|
* <p>This method may be invoked only from within {@code |
370 |
|
|
* ForkJoinTask} computations (as may be determined using method |
371 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
372 |
|
|
* result in exceptions or errors, possibly including {@code |
373 |
|
|
* ClassCastException}. |
374 |
jsr166 |
1.10 |
* |
375 |
dl |
1.27 |
* @param t1 the first task |
376 |
|
|
* @param t2 the second task |
377 |
|
|
* @throws NullPointerException if any task is null |
378 |
dl |
1.1 |
*/ |
379 |
jsr166 |
1.31 |
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) { |
380 |
dl |
1.2 |
t2.fork(); |
381 |
|
|
t1.invoke(); |
382 |
|
|
t2.join(); |
383 |
dl |
1.1 |
} |
384 |
|
|
|
385 |
|
|
/** |
386 |
dl |
1.27 |
* Forks the given tasks, returning when {@code isDone} holds for |
387 |
dl |
1.34 |
* each task or an (unchecked) exception is encountered, in which |
388 |
dl |
1.57 |
* case the exception is rethrown. If more than one task |
389 |
|
|
* encounters an exception, then this method throws any one of |
390 |
|
|
* these exceptions. If any task encounters an exception, others |
391 |
|
|
* may be cancelled. However, the execution status of individual |
392 |
|
|
* tasks is not guaranteed upon exceptional return. The status of |
393 |
|
|
* each task may be obtained using {@link #getException()} and |
394 |
|
|
* related methods to check if they have been cancelled, completed |
395 |
|
|
* normally or exceptionally, or left unprocessed. |
396 |
jsr166 |
1.31 |
* |
397 |
|
|
* <p>This method may be invoked only from within {@code |
398 |
|
|
* ForkJoinTask} computations (as may be determined using method |
399 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
400 |
|
|
* result in exceptions or errors, possibly including {@code |
401 |
|
|
* ClassCastException}. |
402 |
jsr166 |
1.14 |
* |
403 |
dl |
1.27 |
* @param tasks the tasks |
404 |
dl |
1.34 |
* @throws NullPointerException if any task is null |
405 |
dl |
1.1 |
*/ |
406 |
dl |
1.2 |
public static void invokeAll(ForkJoinTask<?>... tasks) { |
407 |
|
|
Throwable ex = null; |
408 |
|
|
int last = tasks.length - 1; |
409 |
|
|
for (int i = last; i >= 0; --i) { |
410 |
|
|
ForkJoinTask<?> t = tasks[i]; |
411 |
|
|
if (t == null) { |
412 |
|
|
if (ex == null) |
413 |
|
|
ex = new NullPointerException(); |
414 |
|
|
} |
415 |
|
|
else if (i != 0) |
416 |
|
|
t.fork(); |
417 |
dl |
1.53 |
else { |
418 |
|
|
t.quietlyInvoke(); |
419 |
|
|
if (ex == null && t.status < NORMAL) |
420 |
|
|
ex = t.getException(); |
421 |
|
|
} |
422 |
dl |
1.2 |
} |
423 |
|
|
for (int i = 1; i <= last; ++i) { |
424 |
|
|
ForkJoinTask<?> t = tasks[i]; |
425 |
|
|
if (t != null) { |
426 |
|
|
if (ex != null) |
427 |
|
|
t.cancel(false); |
428 |
dl |
1.53 |
else { |
429 |
|
|
t.quietlyJoin(); |
430 |
|
|
if (ex == null && t.status < NORMAL) |
431 |
|
|
ex = t.getException(); |
432 |
|
|
} |
433 |
dl |
1.2 |
} |
434 |
dl |
1.1 |
} |
435 |
dl |
1.2 |
if (ex != null) |
436 |
dl |
1.46 |
UNSAFE.throwException(ex); |
437 |
dl |
1.1 |
} |
438 |
|
|
|
439 |
|
|
/** |
440 |
dl |
1.32 |
* Forks all tasks in the specified collection, returning when |
441 |
dl |
1.34 |
* {@code isDone} holds for each task or an (unchecked) exception |
442 |
dl |
1.57 |
* is encountered, in which case the exception is rethrown. If |
443 |
|
|
* more than one task encounters an exception, then this method |
444 |
|
|
* throws any one of these exceptions. If any task encounters an |
445 |
|
|
* exception, others may be cancelled. However, the execution |
446 |
|
|
* status of individual tasks is not guaranteed upon exceptional |
447 |
|
|
* return. The status of each task may be obtained using {@link |
448 |
|
|
* #getException()} and related methods to check if they have been |
449 |
|
|
* cancelled, completed normally or exceptionally, or left |
450 |
|
|
* unprocessed. |
451 |
jsr166 |
1.31 |
* |
452 |
|
|
* <p>This method may be invoked only from within {@code |
453 |
|
|
* ForkJoinTask} computations (as may be determined using method |
454 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
455 |
|
|
* result in exceptions or errors, possibly including {@code |
456 |
|
|
* ClassCastException}. |
457 |
jsr166 |
1.10 |
* |
458 |
dl |
1.2 |
* @param tasks the collection of tasks |
459 |
dl |
1.19 |
* @return the tasks argument, to simplify usage |
460 |
jsr166 |
1.10 |
* @throws NullPointerException if tasks or any element are null |
461 |
dl |
1.1 |
*/ |
462 |
dl |
1.19 |
public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) { |
463 |
dl |
1.32 |
if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) { |
464 |
jsr166 |
1.14 |
invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()])); |
465 |
dl |
1.19 |
return tasks; |
466 |
dl |
1.2 |
} |
467 |
jsr166 |
1.15 |
@SuppressWarnings("unchecked") |
468 |
dl |
1.2 |
List<? extends ForkJoinTask<?>> ts = |
469 |
jsr166 |
1.14 |
(List<? extends ForkJoinTask<?>>) tasks; |
470 |
dl |
1.2 |
Throwable ex = null; |
471 |
|
|
int last = ts.size() - 1; |
472 |
|
|
for (int i = last; i >= 0; --i) { |
473 |
|
|
ForkJoinTask<?> t = ts.get(i); |
474 |
|
|
if (t == null) { |
475 |
|
|
if (ex == null) |
476 |
|
|
ex = new NullPointerException(); |
477 |
|
|
} |
478 |
|
|
else if (i != 0) |
479 |
|
|
t.fork(); |
480 |
dl |
1.53 |
else { |
481 |
|
|
t.quietlyInvoke(); |
482 |
|
|
if (ex == null && t.status < NORMAL) |
483 |
|
|
ex = t.getException(); |
484 |
|
|
} |
485 |
dl |
1.2 |
} |
486 |
|
|
for (int i = 1; i <= last; ++i) { |
487 |
|
|
ForkJoinTask<?> t = ts.get(i); |
488 |
|
|
if (t != null) { |
489 |
|
|
if (ex != null) |
490 |
|
|
t.cancel(false); |
491 |
dl |
1.53 |
else { |
492 |
|
|
t.quietlyJoin(); |
493 |
|
|
if (ex == null && t.status < NORMAL) |
494 |
|
|
ex = t.getException(); |
495 |
|
|
} |
496 |
dl |
1.2 |
} |
497 |
|
|
} |
498 |
|
|
if (ex != null) |
499 |
dl |
1.46 |
UNSAFE.throwException(ex); |
500 |
dl |
1.19 |
return tasks; |
501 |
dl |
1.1 |
} |
502 |
|
|
|
503 |
|
|
/** |
504 |
dl |
1.33 |
* Attempts to cancel execution of this task. This attempt will |
505 |
|
|
* fail if the task has already completed, has already been |
506 |
|
|
* cancelled, or could not be cancelled for some other reason. If |
507 |
|
|
* successful, and this task has not started when cancel is |
508 |
|
|
* called, execution of this task is suppressed, {@link |
509 |
|
|
* #isCancelled} will report true, and {@link #join} will result |
510 |
|
|
* in a {@code CancellationException} being thrown. |
511 |
dl |
1.1 |
* |
512 |
|
|
* <p>This method may be overridden in subclasses, but if so, must |
513 |
|
|
* still ensure that these minimal properties hold. In particular, |
514 |
jsr166 |
1.29 |
* the {@code cancel} method itself must not throw exceptions. |
515 |
dl |
1.1 |
* |
516 |
jsr166 |
1.28 |
* <p>This method is designed to be invoked by <em>other</em> |
517 |
dl |
1.1 |
* tasks. To terminate the current task, you can just return or |
518 |
|
|
* throw an unchecked exception from its computation method, or |
519 |
jsr166 |
1.24 |
* invoke {@link #completeExceptionally}. |
520 |
dl |
1.1 |
* |
521 |
|
|
* @param mayInterruptIfRunning this value is ignored in the |
522 |
dl |
1.33 |
* default implementation because tasks are not |
523 |
jsr166 |
1.14 |
* cancelled via interruption |
524 |
dl |
1.1 |
* |
525 |
jsr166 |
1.23 |
* @return {@code true} if this task is now cancelled |
526 |
dl |
1.1 |
*/ |
527 |
|
|
public boolean cancel(boolean mayInterruptIfRunning) { |
528 |
dl |
1.53 |
setCompletion(CANCELLED); |
529 |
|
|
return status == CANCELLED; |
530 |
dl |
1.1 |
} |
531 |
|
|
|
532 |
dl |
1.46 |
/** |
533 |
dl |
1.52 |
* Cancels, ignoring any exceptions thrown by cancel. Used during |
534 |
|
|
* worker and pool shutdown. Cancel is spec'ed not to throw any |
535 |
|
|
* exceptions, but if it does anyway, we have no recourse during |
536 |
|
|
* shutdown, so guard against this case. |
537 |
dl |
1.46 |
*/ |
538 |
|
|
final void cancelIgnoringExceptions() { |
539 |
|
|
try { |
540 |
|
|
cancel(false); |
541 |
|
|
} catch (Throwable ignore) { |
542 |
|
|
} |
543 |
|
|
} |
544 |
|
|
|
545 |
|
|
/** |
546 |
jsr166 |
1.56 |
* Cancels if current thread is a terminating worker thread, |
547 |
|
|
* ignoring any exceptions thrown by cancel. |
548 |
dl |
1.46 |
*/ |
549 |
dl |
1.50 |
final void cancelIfTerminating() { |
550 |
dl |
1.46 |
Thread t = Thread.currentThread(); |
551 |
|
|
if ((t instanceof ForkJoinWorkerThread) && |
552 |
dl |
1.47 |
((ForkJoinWorkerThread) t).isTerminating()) { |
553 |
dl |
1.46 |
try { |
554 |
|
|
cancel(false); |
555 |
|
|
} catch (Throwable ignore) { |
556 |
|
|
} |
557 |
|
|
} |
558 |
|
|
} |
559 |
|
|
|
560 |
dl |
1.34 |
public final boolean isDone() { |
561 |
|
|
return status < 0; |
562 |
|
|
} |
563 |
|
|
|
564 |
|
|
public final boolean isCancelled() { |
565 |
dl |
1.49 |
return status == CANCELLED; |
566 |
dl |
1.34 |
} |
567 |
|
|
|
568 |
|
|
/** |
569 |
jsr166 |
1.23 |
* Returns {@code true} if this task threw an exception or was cancelled. |
570 |
jsr166 |
1.10 |
* |
571 |
jsr166 |
1.23 |
* @return {@code true} if this task threw an exception or was cancelled |
572 |
dl |
1.3 |
*/ |
573 |
|
|
public final boolean isCompletedAbnormally() { |
574 |
dl |
1.49 |
return status < NORMAL; |
575 |
dl |
1.3 |
} |
576 |
|
|
|
577 |
|
|
/** |
578 |
dl |
1.34 |
* Returns {@code true} if this task completed without throwing an |
579 |
|
|
* exception and was not cancelled. |
580 |
|
|
* |
581 |
|
|
* @return {@code true} if this task completed without throwing an |
582 |
|
|
* exception and was not cancelled |
583 |
|
|
*/ |
584 |
|
|
public final boolean isCompletedNormally() { |
585 |
dl |
1.49 |
return status == NORMAL; |
586 |
dl |
1.34 |
} |
587 |
|
|
|
588 |
|
|
/** |
589 |
dl |
1.3 |
* Returns the exception thrown by the base computation, or a |
590 |
jsr166 |
1.29 |
* {@code CancellationException} if cancelled, or {@code null} if |
591 |
|
|
* none or if the method has not yet completed. |
592 |
jsr166 |
1.10 |
* |
593 |
jsr166 |
1.23 |
* @return the exception, or {@code null} if none |
594 |
dl |
1.3 |
*/ |
595 |
|
|
public final Throwable getException() { |
596 |
dl |
1.49 |
int s = status; |
597 |
jsr166 |
1.37 |
return ((s >= NORMAL) ? null : |
598 |
|
|
(s == CANCELLED) ? new CancellationException() : |
599 |
|
|
exceptionMap.get(this)); |
600 |
dl |
1.3 |
} |
601 |
|
|
|
602 |
|
|
/** |
603 |
dl |
1.1 |
* Completes this task abnormally, and if not already aborted or |
604 |
|
|
* cancelled, causes it to throw the given exception upon |
605 |
jsr166 |
1.8 |
* {@code join} and related operations. This method may be used |
606 |
dl |
1.1 |
* to induce exceptions in asynchronous tasks, or to force |
607 |
dl |
1.2 |
* completion of tasks that would not otherwise complete. Its use |
608 |
dl |
1.27 |
* in other situations is discouraged. This method is |
609 |
jsr166 |
1.8 |
* overridable, but overridden versions must invoke {@code super} |
610 |
dl |
1.2 |
* implementation to maintain guarantees. |
611 |
|
|
* |
612 |
jsr166 |
1.44 |
* @param ex the exception to throw. If this exception is not a |
613 |
|
|
* {@code RuntimeException} or {@code Error}, the actual exception |
614 |
|
|
* thrown will be a {@code RuntimeException} with cause {@code ex}. |
615 |
dl |
1.1 |
*/ |
616 |
|
|
public void completeExceptionally(Throwable ex) { |
617 |
dl |
1.48 |
setExceptionalCompletion((ex instanceof RuntimeException) || |
618 |
|
|
(ex instanceof Error) ? ex : |
619 |
|
|
new RuntimeException(ex)); |
620 |
dl |
1.1 |
} |
621 |
|
|
|
622 |
|
|
/** |
623 |
|
|
* Completes this task, and if not already aborted or cancelled, |
624 |
dl |
1.58 |
* returning the given value as the result of subsequent |
625 |
|
|
* invocations of {@code join} and related operations. This method |
626 |
|
|
* may be used to provide results for asynchronous tasks, or to |
627 |
|
|
* provide alternative handling for tasks that would not otherwise |
628 |
|
|
* complete normally. Its use in other situations is |
629 |
|
|
* discouraged. This method is overridable, but overridden |
630 |
|
|
* versions must invoke {@code super} implementation to maintain |
631 |
|
|
* guarantees. |
632 |
dl |
1.1 |
* |
633 |
jsr166 |
1.10 |
* @param value the result value for this task |
634 |
dl |
1.1 |
*/ |
635 |
|
|
public void complete(V value) { |
636 |
|
|
try { |
637 |
|
|
setRawResult(value); |
638 |
jsr166 |
1.14 |
} catch (Throwable rex) { |
639 |
dl |
1.48 |
setExceptionalCompletion(rex); |
640 |
dl |
1.1 |
return; |
641 |
|
|
} |
642 |
dl |
1.46 |
setCompletion(NORMAL); |
643 |
dl |
1.1 |
} |
644 |
|
|
|
645 |
dl |
1.3 |
public final V get() throws InterruptedException, ExecutionException { |
646 |
dl |
1.53 |
quietlyJoin(); |
647 |
dl |
1.48 |
if (Thread.interrupted()) |
648 |
|
|
throw new InterruptedException(); |
649 |
dl |
1.53 |
int s = status; |
650 |
dl |
1.48 |
if (s < NORMAL) { |
651 |
|
|
Throwable ex; |
652 |
|
|
if (s == CANCELLED) |
653 |
|
|
throw new CancellationException(); |
654 |
|
|
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
655 |
|
|
throw new ExecutionException(ex); |
656 |
|
|
} |
657 |
|
|
return getRawResult(); |
658 |
dl |
1.3 |
} |
659 |
dl |
1.47 |
|
660 |
dl |
1.3 |
public final V get(long timeout, TimeUnit unit) |
661 |
|
|
throws InterruptedException, ExecutionException, TimeoutException { |
662 |
dl |
1.46 |
Thread t = Thread.currentThread(); |
663 |
dl |
1.48 |
ForkJoinPool pool; |
664 |
dl |
1.46 |
if (t instanceof ForkJoinWorkerThread) { |
665 |
|
|
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
666 |
dl |
1.48 |
if (status >= 0 && w.unpushTask(this)) |
667 |
dl |
1.53 |
quietlyExec(); |
668 |
dl |
1.48 |
pool = w.pool; |
669 |
dl |
1.46 |
} |
670 |
|
|
else |
671 |
dl |
1.48 |
pool = null; |
672 |
|
|
/* |
673 |
dl |
1.52 |
* Timed wait loop intermixes cases for FJ (pool != null) and |
674 |
dl |
1.48 |
* non FJ threads. For FJ, decrement pool count but don't try |
675 |
|
|
* for replacement; increment count on completion. For non-FJ, |
676 |
|
|
* deal with interrupts. This is messy, but a little less so |
677 |
|
|
* than is splitting the FJ and nonFJ cases. |
678 |
|
|
*/ |
679 |
|
|
boolean interrupted = false; |
680 |
|
|
boolean dec = false; // true if pool count decremented |
681 |
dl |
1.54 |
long nanos = unit.toNanos(timeout); |
682 |
dl |
1.48 |
for (;;) { |
683 |
dl |
1.58 |
if (pool == null && Thread.interrupted()) { |
684 |
dl |
1.48 |
interrupted = true; |
685 |
|
|
break; |
686 |
|
|
} |
687 |
|
|
int s = status; |
688 |
|
|
if (s < 0) |
689 |
|
|
break; |
690 |
dl |
1.52 |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)) { |
691 |
dl |
1.48 |
long startTime = System.nanoTime(); |
692 |
|
|
long nt; // wait time |
693 |
|
|
while (status >= 0 && |
694 |
|
|
(nt = nanos - (System.nanoTime() - startTime)) > 0) { |
695 |
|
|
if (pool != null && !dec) |
696 |
|
|
dec = pool.tryDecrementRunningCount(); |
697 |
|
|
else { |
698 |
|
|
long ms = nt / 1000000; |
699 |
|
|
int ns = (int) (nt % 1000000); |
700 |
|
|
try { |
701 |
|
|
synchronized(this) { |
702 |
|
|
if (status >= 0) |
703 |
|
|
wait(ms, ns); |
704 |
|
|
} |
705 |
|
|
} catch (InterruptedException ie) { |
706 |
|
|
if (pool != null) |
707 |
|
|
cancelIfTerminating(); |
708 |
|
|
else { |
709 |
|
|
interrupted = true; |
710 |
|
|
break; |
711 |
|
|
} |
712 |
|
|
} |
713 |
|
|
} |
714 |
|
|
} |
715 |
|
|
break; |
716 |
|
|
} |
717 |
|
|
} |
718 |
|
|
if (pool != null && dec) |
719 |
dl |
1.49 |
pool.incrementRunningCount(); |
720 |
dl |
1.48 |
if (interrupted) |
721 |
|
|
throw new InterruptedException(); |
722 |
dl |
1.49 |
int es = status; |
723 |
dl |
1.48 |
if (es != NORMAL) { |
724 |
|
|
Throwable ex; |
725 |
|
|
if (es == CANCELLED) |
726 |
|
|
throw new CancellationException(); |
727 |
|
|
if (es == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
728 |
|
|
throw new ExecutionException(ex); |
729 |
|
|
throw new TimeoutException(); |
730 |
|
|
} |
731 |
|
|
return getRawResult(); |
732 |
dl |
1.3 |
} |
733 |
|
|
|
734 |
dl |
1.1 |
/** |
735 |
dl |
1.53 |
* Joins this task, without returning its result or throwing its |
736 |
dl |
1.2 |
* exception. This method may be useful when processing |
737 |
|
|
* collections of tasks when some have been cancelled or otherwise |
738 |
|
|
* known to have aborted. |
739 |
|
|
*/ |
740 |
|
|
public final void quietlyJoin() { |
741 |
dl |
1.53 |
Thread t; |
742 |
|
|
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) { |
743 |
|
|
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
744 |
|
|
if (status >= 0) { |
745 |
|
|
if (w.unpushTask(this)) { |
746 |
|
|
boolean completed; |
747 |
|
|
try { |
748 |
|
|
completed = exec(); |
749 |
|
|
} catch (Throwable rex) { |
750 |
|
|
setExceptionalCompletion(rex); |
751 |
|
|
return; |
752 |
|
|
} |
753 |
|
|
if (completed) { |
754 |
|
|
setCompletion(NORMAL); |
755 |
|
|
return; |
756 |
|
|
} |
757 |
|
|
} |
758 |
|
|
w.joinTask(this); |
759 |
|
|
} |
760 |
|
|
} |
761 |
|
|
else |
762 |
|
|
externalAwaitDone(); |
763 |
dl |
1.2 |
} |
764 |
|
|
|
765 |
|
|
/** |
766 |
|
|
* Commences performing this task and awaits its completion if |
767 |
dl |
1.53 |
* necessary, without returning its result or throwing its |
768 |
dl |
1.58 |
* exception. |
769 |
dl |
1.2 |
*/ |
770 |
|
|
public final void quietlyInvoke() { |
771 |
dl |
1.53 |
if (status >= 0) { |
772 |
|
|
boolean completed; |
773 |
|
|
try { |
774 |
|
|
completed = exec(); |
775 |
|
|
} catch (Throwable rex) { |
776 |
|
|
setExceptionalCompletion(rex); |
777 |
|
|
return; |
778 |
|
|
} |
779 |
|
|
if (completed) |
780 |
|
|
setCompletion(NORMAL); |
781 |
|
|
else |
782 |
|
|
quietlyJoin(); |
783 |
|
|
} |
784 |
dl |
1.2 |
} |
785 |
|
|
|
786 |
|
|
/** |
787 |
dl |
1.3 |
* Possibly executes tasks until the pool hosting the current task |
788 |
dl |
1.33 |
* {@link ForkJoinPool#isQuiescent is quiescent}. This method may |
789 |
|
|
* be of use in designs in which many tasks are forked, but none |
790 |
|
|
* are explicitly joined, instead executing them until all are |
791 |
|
|
* processed. |
792 |
jsr166 |
1.31 |
* |
793 |
|
|
* <p>This method may be invoked only from within {@code |
794 |
|
|
* ForkJoinTask} computations (as may be determined using method |
795 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
796 |
|
|
* result in exceptions or errors, possibly including {@code |
797 |
|
|
* ClassCastException}. |
798 |
dl |
1.3 |
*/ |
799 |
|
|
public static void helpQuiesce() { |
800 |
jsr166 |
1.14 |
((ForkJoinWorkerThread) Thread.currentThread()) |
801 |
|
|
.helpQuiescePool(); |
802 |
dl |
1.3 |
} |
803 |
|
|
|
804 |
|
|
/** |
805 |
dl |
1.1 |
* Resets the internal bookkeeping state of this task, allowing a |
806 |
jsr166 |
1.8 |
* subsequent {@code fork}. This method allows repeated reuse of |
807 |
dl |
1.1 |
* this task, but only if reuse occurs when this task has either |
808 |
|
|
* never been forked, or has been forked, then completed and all |
809 |
|
|
* outstanding joins of this task have also completed. Effects |
810 |
dl |
1.30 |
* under any other usage conditions are not guaranteed. |
811 |
|
|
* This method may be useful when executing |
812 |
dl |
1.1 |
* pre-constructed trees of subtasks in loops. |
813 |
|
|
*/ |
814 |
|
|
public void reinitialize() { |
815 |
dl |
1.49 |
if (status == EXCEPTIONAL) |
816 |
dl |
1.1 |
exceptionMap.remove(this); |
817 |
|
|
status = 0; |
818 |
|
|
} |
819 |
|
|
|
820 |
|
|
/** |
821 |
dl |
1.2 |
* Returns the pool hosting the current task execution, or null |
822 |
dl |
1.13 |
* if this task is executing outside of any ForkJoinPool. |
823 |
jsr166 |
1.10 |
* |
824 |
dl |
1.27 |
* @see #inForkJoinPool |
825 |
jsr166 |
1.23 |
* @return the pool, or {@code null} if none |
826 |
dl |
1.1 |
*/ |
827 |
dl |
1.2 |
public static ForkJoinPool getPool() { |
828 |
|
|
Thread t = Thread.currentThread(); |
829 |
jsr166 |
1.15 |
return (t instanceof ForkJoinWorkerThread) ? |
830 |
|
|
((ForkJoinWorkerThread) t).pool : null; |
831 |
dl |
1.1 |
} |
832 |
|
|
|
833 |
|
|
/** |
834 |
jsr166 |
1.14 |
* Returns {@code true} if the current thread is executing as a |
835 |
dl |
1.13 |
* ForkJoinPool computation. |
836 |
jsr166 |
1.14 |
* |
837 |
|
|
* @return {@code true} if the current thread is executing as a |
838 |
dl |
1.13 |
* ForkJoinPool computation, or false otherwise |
839 |
|
|
*/ |
840 |
|
|
public static boolean inForkJoinPool() { |
841 |
|
|
return Thread.currentThread() instanceof ForkJoinWorkerThread; |
842 |
|
|
} |
843 |
|
|
|
844 |
|
|
/** |
845 |
dl |
1.2 |
* Tries to unschedule this task for execution. This method will |
846 |
|
|
* typically succeed if this task is the most recently forked task |
847 |
|
|
* by the current thread, and has not commenced executing in |
848 |
|
|
* another thread. This method may be useful when arranging |
849 |
|
|
* alternative local processing of tasks that could have been, but |
850 |
jsr166 |
1.31 |
* were not, stolen. |
851 |
|
|
* |
852 |
|
|
* <p>This method may be invoked only from within {@code |
853 |
|
|
* ForkJoinTask} computations (as may be determined using method |
854 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
855 |
|
|
* result in exceptions or errors, possibly including {@code |
856 |
|
|
* ClassCastException}. |
857 |
jsr166 |
1.10 |
* |
858 |
jsr166 |
1.23 |
* @return {@code true} if unforked |
859 |
dl |
1.1 |
*/ |
860 |
dl |
1.2 |
public boolean tryUnfork() { |
861 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
862 |
|
|
.unpushTask(this); |
863 |
dl |
1.1 |
} |
864 |
|
|
|
865 |
|
|
/** |
866 |
dl |
1.2 |
* Returns an estimate of the number of tasks that have been |
867 |
|
|
* forked by the current worker thread but not yet executed. This |
868 |
|
|
* value may be useful for heuristic decisions about whether to |
869 |
jsr166 |
1.31 |
* fork other tasks. |
870 |
|
|
* |
871 |
|
|
* <p>This method may be invoked only from within {@code |
872 |
|
|
* ForkJoinTask} computations (as may be determined using method |
873 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
874 |
|
|
* result in exceptions or errors, possibly including {@code |
875 |
|
|
* ClassCastException}. |
876 |
|
|
* |
877 |
dl |
1.2 |
* @return the number of tasks |
878 |
|
|
*/ |
879 |
|
|
public static int getQueuedTaskCount() { |
880 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
881 |
|
|
.getQueueSize(); |
882 |
dl |
1.2 |
} |
883 |
|
|
|
884 |
|
|
/** |
885 |
jsr166 |
1.10 |
* Returns an estimate of how many more locally queued tasks are |
886 |
dl |
1.1 |
* held by the current worker thread than there are other worker |
887 |
dl |
1.2 |
* threads that might steal them. This value may be useful for |
888 |
|
|
* heuristic decisions about whether to fork other tasks. In many |
889 |
|
|
* usages of ForkJoinTasks, at steady state, each worker should |
890 |
|
|
* aim to maintain a small constant surplus (for example, 3) of |
891 |
|
|
* tasks, and to process computations locally if this threshold is |
892 |
jsr166 |
1.31 |
* exceeded. |
893 |
|
|
* |
894 |
|
|
* <p>This method may be invoked only from within {@code |
895 |
|
|
* ForkJoinTask} computations (as may be determined using method |
896 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
897 |
|
|
* result in exceptions or errors, possibly including {@code |
898 |
|
|
* ClassCastException}. |
899 |
|
|
* |
900 |
dl |
1.1 |
* @return the surplus number of tasks, which may be negative |
901 |
|
|
*/ |
902 |
dl |
1.2 |
public static int getSurplusQueuedTaskCount() { |
903 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
904 |
dl |
1.1 |
.getEstimatedSurplusTaskCount(); |
905 |
|
|
} |
906 |
|
|
|
907 |
dl |
1.2 |
// Extension methods |
908 |
dl |
1.1 |
|
909 |
|
|
/** |
910 |
jsr166 |
1.23 |
* Returns the result that would be returned by {@link #join}, even |
911 |
|
|
* if this task completed abnormally, or {@code null} if this task |
912 |
|
|
* is not known to have been completed. This method is designed |
913 |
|
|
* to aid debugging, as well as to support extensions. Its use in |
914 |
|
|
* any other context is discouraged. |
915 |
dl |
1.1 |
* |
916 |
jsr166 |
1.23 |
* @return the result, or {@code null} if not completed |
917 |
dl |
1.1 |
*/ |
918 |
|
|
public abstract V getRawResult(); |
919 |
|
|
|
920 |
|
|
/** |
921 |
|
|
* Forces the given value to be returned as a result. This method |
922 |
|
|
* is designed to support extensions, and should not in general be |
923 |
|
|
* called otherwise. |
924 |
|
|
* |
925 |
|
|
* @param value the value |
926 |
|
|
*/ |
927 |
|
|
protected abstract void setRawResult(V value); |
928 |
|
|
|
929 |
|
|
/** |
930 |
|
|
* Immediately performs the base action of this task. This method |
931 |
|
|
* is designed to support extensions, and should not in general be |
932 |
|
|
* called otherwise. The return value controls whether this task |
933 |
|
|
* is considered to be done normally. It may return false in |
934 |
|
|
* asynchronous actions that require explicit invocations of |
935 |
dl |
1.34 |
* {@link #complete} to become joinable. It may also throw an |
936 |
|
|
* (unchecked) exception to indicate abnormal exit. |
937 |
jsr166 |
1.10 |
* |
938 |
jsr166 |
1.23 |
* @return {@code true} if completed normally |
939 |
dl |
1.1 |
*/ |
940 |
|
|
protected abstract boolean exec(); |
941 |
|
|
|
942 |
dl |
1.2 |
/** |
943 |
dl |
1.25 |
* Returns, but does not unschedule or execute, a task queued by |
944 |
|
|
* the current thread but not yet executed, if one is immediately |
945 |
dl |
1.6 |
* available. There is no guarantee that this task will actually |
946 |
dl |
1.25 |
* be polled or executed next. Conversely, this method may return |
947 |
|
|
* null even if a task exists but cannot be accessed without |
948 |
|
|
* contention with other threads. This method is designed |
949 |
|
|
* primarily to support extensions, and is unlikely to be useful |
950 |
jsr166 |
1.31 |
* otherwise. |
951 |
|
|
* |
952 |
|
|
* <p>This method may be invoked only from within {@code |
953 |
|
|
* ForkJoinTask} computations (as may be determined using method |
954 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
955 |
|
|
* result in exceptions or errors, possibly including {@code |
956 |
|
|
* ClassCastException}. |
957 |
dl |
1.2 |
* |
958 |
jsr166 |
1.23 |
* @return the next task, or {@code null} if none are available |
959 |
dl |
1.2 |
*/ |
960 |
|
|
protected static ForkJoinTask<?> peekNextLocalTask() { |
961 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
962 |
|
|
.peekTask(); |
963 |
dl |
1.2 |
} |
964 |
|
|
|
965 |
|
|
/** |
966 |
dl |
1.6 |
* Unschedules and returns, without executing, the next task |
967 |
|
|
* queued by the current thread but not yet executed. This method |
968 |
|
|
* is designed primarily to support extensions, and is unlikely to |
969 |
jsr166 |
1.31 |
* be useful otherwise. |
970 |
|
|
* |
971 |
|
|
* <p>This method may be invoked only from within {@code |
972 |
|
|
* ForkJoinTask} computations (as may be determined using method |
973 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
974 |
|
|
* result in exceptions or errors, possibly including {@code |
975 |
|
|
* ClassCastException}. |
976 |
dl |
1.2 |
* |
977 |
jsr166 |
1.23 |
* @return the next task, or {@code null} if none are available |
978 |
dl |
1.2 |
*/ |
979 |
|
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
980 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
981 |
|
|
.pollLocalTask(); |
982 |
dl |
1.2 |
} |
983 |
jsr166 |
1.7 |
|
984 |
dl |
1.2 |
/** |
985 |
dl |
1.6 |
* Unschedules and returns, without executing, the next task |
986 |
|
|
* queued by the current thread but not yet executed, if one is |
987 |
|
|
* available, or if not available, a task that was forked by some |
988 |
|
|
* other thread, if available. Availability may be transient, so a |
989 |
jsr166 |
1.9 |
* {@code null} result does not necessarily imply quiescence |
990 |
dl |
1.6 |
* of the pool this task is operating in. This method is designed |
991 |
|
|
* primarily to support extensions, and is unlikely to be useful |
992 |
jsr166 |
1.31 |
* otherwise. |
993 |
|
|
* |
994 |
|
|
* <p>This method may be invoked only from within {@code |
995 |
|
|
* ForkJoinTask} computations (as may be determined using method |
996 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
997 |
|
|
* result in exceptions or errors, possibly including {@code |
998 |
|
|
* ClassCastException}. |
999 |
dl |
1.4 |
* |
1000 |
jsr166 |
1.23 |
* @return a task, or {@code null} if none are available |
1001 |
dl |
1.2 |
*/ |
1002 |
|
|
protected static ForkJoinTask<?> pollTask() { |
1003 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1004 |
|
|
.pollTask(); |
1005 |
dl |
1.2 |
} |
1006 |
|
|
|
1007 |
dl |
1.25 |
/** |
1008 |
|
|
* Adaptor for Runnables. This implements RunnableFuture |
1009 |
|
|
* to be compliant with AbstractExecutorService constraints |
1010 |
|
|
* when used in ForkJoinPool. |
1011 |
|
|
*/ |
1012 |
|
|
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
1013 |
|
|
implements RunnableFuture<T> { |
1014 |
|
|
final Runnable runnable; |
1015 |
|
|
final T resultOnCompletion; |
1016 |
|
|
T result; |
1017 |
|
|
AdaptedRunnable(Runnable runnable, T result) { |
1018 |
|
|
if (runnable == null) throw new NullPointerException(); |
1019 |
|
|
this.runnable = runnable; |
1020 |
|
|
this.resultOnCompletion = result; |
1021 |
|
|
} |
1022 |
|
|
public T getRawResult() { return result; } |
1023 |
|
|
public void setRawResult(T v) { result = v; } |
1024 |
|
|
public boolean exec() { |
1025 |
|
|
runnable.run(); |
1026 |
|
|
result = resultOnCompletion; |
1027 |
|
|
return true; |
1028 |
|
|
} |
1029 |
|
|
public void run() { invoke(); } |
1030 |
|
|
private static final long serialVersionUID = 5232453952276885070L; |
1031 |
|
|
} |
1032 |
|
|
|
1033 |
|
|
/** |
1034 |
|
|
* Adaptor for Callables |
1035 |
|
|
*/ |
1036 |
|
|
static final class AdaptedCallable<T> extends ForkJoinTask<T> |
1037 |
|
|
implements RunnableFuture<T> { |
1038 |
dl |
1.27 |
final Callable<? extends T> callable; |
1039 |
dl |
1.25 |
T result; |
1040 |
dl |
1.27 |
AdaptedCallable(Callable<? extends T> callable) { |
1041 |
dl |
1.25 |
if (callable == null) throw new NullPointerException(); |
1042 |
|
|
this.callable = callable; |
1043 |
|
|
} |
1044 |
|
|
public T getRawResult() { return result; } |
1045 |
|
|
public void setRawResult(T v) { result = v; } |
1046 |
|
|
public boolean exec() { |
1047 |
|
|
try { |
1048 |
|
|
result = callable.call(); |
1049 |
|
|
return true; |
1050 |
|
|
} catch (Error err) { |
1051 |
|
|
throw err; |
1052 |
|
|
} catch (RuntimeException rex) { |
1053 |
|
|
throw rex; |
1054 |
|
|
} catch (Exception ex) { |
1055 |
|
|
throw new RuntimeException(ex); |
1056 |
|
|
} |
1057 |
|
|
} |
1058 |
|
|
public void run() { invoke(); } |
1059 |
|
|
private static final long serialVersionUID = 2838392045355241008L; |
1060 |
|
|
} |
1061 |
dl |
1.18 |
|
1062 |
|
|
/** |
1063 |
jsr166 |
1.31 |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1064 |
|
|
* method of the given {@code Runnable} as its action, and returns |
1065 |
|
|
* a null result upon {@link #join}. |
1066 |
dl |
1.18 |
* |
1067 |
|
|
* @param runnable the runnable action |
1068 |
|
|
* @return the task |
1069 |
|
|
*/ |
1070 |
dl |
1.27 |
public static ForkJoinTask<?> adapt(Runnable runnable) { |
1071 |
dl |
1.25 |
return new AdaptedRunnable<Void>(runnable, null); |
1072 |
dl |
1.18 |
} |
1073 |
|
|
|
1074 |
|
|
/** |
1075 |
jsr166 |
1.31 |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1076 |
|
|
* method of the given {@code Runnable} as its action, and returns |
1077 |
|
|
* the given result upon {@link #join}. |
1078 |
dl |
1.18 |
* |
1079 |
|
|
* @param runnable the runnable action |
1080 |
|
|
* @param result the result upon completion |
1081 |
|
|
* @return the task |
1082 |
|
|
*/ |
1083 |
|
|
public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) { |
1084 |
dl |
1.25 |
return new AdaptedRunnable<T>(runnable, result); |
1085 |
dl |
1.18 |
} |
1086 |
|
|
|
1087 |
|
|
/** |
1088 |
jsr166 |
1.31 |
* Returns a new {@code ForkJoinTask} that performs the {@code call} |
1089 |
|
|
* method of the given {@code Callable} as its action, and returns |
1090 |
|
|
* its result upon {@link #join}, translating any checked exceptions |
1091 |
|
|
* encountered into {@code RuntimeException}. |
1092 |
dl |
1.18 |
* |
1093 |
|
|
* @param callable the callable action |
1094 |
|
|
* @return the task |
1095 |
|
|
*/ |
1096 |
dl |
1.27 |
public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) { |
1097 |
dl |
1.25 |
return new AdaptedCallable<T>(callable); |
1098 |
dl |
1.18 |
} |
1099 |
|
|
|
1100 |
dl |
1.1 |
// Serialization support |
1101 |
|
|
|
1102 |
|
|
private static final long serialVersionUID = -7721805057305804111L; |
1103 |
|
|
|
1104 |
|
|
/** |
1105 |
jsr166 |
1.56 |
* Saves the state to a stream (that is, serializes it). |
1106 |
dl |
1.1 |
* |
1107 |
|
|
* @serialData the current run status and the exception thrown |
1108 |
jsr166 |
1.23 |
* during execution, or {@code null} if none |
1109 |
dl |
1.1 |
* @param s the stream |
1110 |
|
|
*/ |
1111 |
|
|
private void writeObject(java.io.ObjectOutputStream s) |
1112 |
|
|
throws java.io.IOException { |
1113 |
|
|
s.defaultWriteObject(); |
1114 |
|
|
s.writeObject(getException()); |
1115 |
|
|
} |
1116 |
|
|
|
1117 |
|
|
/** |
1118 |
jsr166 |
1.56 |
* Reconstitutes the instance from a stream (that is, deserializes it). |
1119 |
jsr166 |
1.10 |
* |
1120 |
dl |
1.1 |
* @param s the stream |
1121 |
|
|
*/ |
1122 |
|
|
private void readObject(java.io.ObjectInputStream s) |
1123 |
|
|
throws java.io.IOException, ClassNotFoundException { |
1124 |
|
|
s.defaultReadObject(); |
1125 |
|
|
Object ex = s.readObject(); |
1126 |
|
|
if (ex != null) |
1127 |
dl |
1.48 |
setExceptionalCompletion((Throwable) ex); |
1128 |
dl |
1.1 |
} |
1129 |
|
|
|
1130 |
jsr166 |
1.22 |
// Unsafe mechanics |
1131 |
|
|
|
1132 |
|
|
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1133 |
|
|
private static final long statusOffset = |
1134 |
|
|
objectFieldOffset("status", ForkJoinTask.class); |
1135 |
|
|
|
1136 |
|
|
private static long objectFieldOffset(String field, Class<?> klazz) { |
1137 |
|
|
try { |
1138 |
|
|
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1139 |
|
|
} catch (NoSuchFieldException e) { |
1140 |
|
|
// Convert Exception to corresponding Error |
1141 |
|
|
NoSuchFieldError error = new NoSuchFieldError(field); |
1142 |
|
|
error.initCause(e); |
1143 |
|
|
throw error; |
1144 |
|
|
} |
1145 |
|
|
} |
1146 |
|
|
|
1147 |
|
|
/** |
1148 |
|
|
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
1149 |
|
|
* Replace with a simple call to Unsafe.getUnsafe when integrating |
1150 |
|
|
* into a jdk. |
1151 |
|
|
* |
1152 |
|
|
* @return a sun.misc.Unsafe |
1153 |
|
|
*/ |
1154 |
jsr166 |
1.16 |
private static sun.misc.Unsafe getUnsafe() { |
1155 |
jsr166 |
1.5 |
try { |
1156 |
jsr166 |
1.16 |
return sun.misc.Unsafe.getUnsafe(); |
1157 |
jsr166 |
1.5 |
} catch (SecurityException se) { |
1158 |
|
|
try { |
1159 |
|
|
return java.security.AccessController.doPrivileged |
1160 |
jsr166 |
1.22 |
(new java.security |
1161 |
|
|
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1162 |
jsr166 |
1.16 |
public sun.misc.Unsafe run() throws Exception { |
1163 |
jsr166 |
1.22 |
java.lang.reflect.Field f = sun.misc |
1164 |
|
|
.Unsafe.class.getDeclaredField("theUnsafe"); |
1165 |
|
|
f.setAccessible(true); |
1166 |
|
|
return (sun.misc.Unsafe) f.get(null); |
1167 |
jsr166 |
1.5 |
}}); |
1168 |
|
|
} catch (java.security.PrivilegedActionException e) { |
1169 |
jsr166 |
1.16 |
throw new RuntimeException("Could not initialize intrinsics", |
1170 |
|
|
e.getCause()); |
1171 |
jsr166 |
1.5 |
} |
1172 |
|
|
} |
1173 |
|
|
} |
1174 |
dl |
1.1 |
} |