5 |
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*/ |
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package jsr166y; |
8 |
< |
import java.io.Serializable; |
9 |
< |
import java.util.*; |
8 |
> |
|
9 |
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import java.util.concurrent.*; |
10 |
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import java.util.concurrent.atomic.*; |
11 |
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import sun.misc.Unsafe; |
12 |
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import java.lang.reflect.*; |
10 |
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|
11 |
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import java.io.Serializable; |
12 |
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import java.util.Collection; |
13 |
> |
import java.util.Collections; |
14 |
> |
import java.util.List; |
15 |
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import java.util.RandomAccess; |
16 |
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import java.util.Map; |
17 |
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import java.util.WeakHashMap; |
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|
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/** |
20 |
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* Abstract base class for tasks that run within a {@link |
21 |
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* ForkJoinPool}. A ForkJoinTask is a thread-like entity that is much |
20 |
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* Abstract base class for tasks that run within a {@link ForkJoinPool}. |
21 |
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* A {@code ForkJoinTask} is a thread-like entity that is much |
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* 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. |
25 |
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* |
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* <p> A "main" ForkJoinTask begins execution when submitted to a |
27 |
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* {@link ForkJoinPool}. Once started, it will usually in turn start |
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* other subtasks. As indicated by the name of this class, many |
29 |
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* programs using ForkJoinTasks employ only methods <code>fork</code> |
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* and <code>join</code>, or derivatives such as |
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* <code>invokeAll</code>. However, this class also provides a number |
32 |
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* of other methods that can come into play in advanced usages, as |
33 |
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* well as extension mechanics that allow support of new forms of |
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* fork/join processing. |
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* <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, |
29 |
> |
* many programs using {@code ForkJoinTask} employ only methods |
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> |
* {@link #fork} and {@link #join}, or derivatives such as {@link |
31 |
> |
* #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 |
33 |
> |
* extension mechanics that allow support of new forms of fork/join |
34 |
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* processing. |
35 |
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* |
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* <p>A ForkJoinTask is a lightweight form of {@link Future}. The |
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* efficiency of ForkJoinTasks stems from a set of restrictions (that |
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* are only partially statically enforceable) reflecting their |
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* intended use as computational tasks calculating pure functions or |
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* operating on purely isolated objects. The primary coordination |
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* mechanisms are {@link #fork}, that arranges asynchronous execution, |
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* and {@link #join}, that doesn't proceed until the task's result has |
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* been computed. Computations should avoid <code>synchronized</code> |
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* methods or blocks, and should minimize other blocking |
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* synchronization apart from joining other tasks or using |
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* synchronizers such as Phasers that are advertised to cooperate with |
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* fork/join scheduling. Tasks should also not perform blocking IO, |
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* and should ideally access variables that are completely independent |
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* of those accessed by other running tasks. Minor breaches of these |
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* restrictions, for example using shared output streams, may be |
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* tolerable in practice, but frequent use may result in poor |
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* performance, and the potential to indefinitely stall if the number |
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* of threads not waiting for IO or other external synchronization |
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* becomes exhausted. This usage restriction is in part enforced by |
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* not permitting checked exceptions such as <code>IOExceptions</code> |
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* to be thrown. However, computations may still encounter unchecked |
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* exceptions, that are rethrown to callers attempting join |
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* them. These exceptions may additionally include |
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* RejectedExecutionExceptions stemming from internal resource |
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* exhaustion such as failure to allocate internal task queues. |
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* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}. |
37 |
> |
* The efficiency of {@code ForkJoinTask}s stems from a set of |
38 |
> |
* restrictions (that are only partially statically enforceable) |
39 |
> |
* reflecting their intended use as computational tasks calculating |
40 |
> |
* pure functions or operating on purely isolated objects. The |
41 |
> |
* primary coordination mechanisms are {@link #fork}, that arranges |
42 |
> |
* asynchronous execution, and {@link #join}, that doesn't proceed |
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> |
* until the task's result has been computed. Computations should |
44 |
> |
* avoid {@code synchronized} methods or blocks, and should minimize |
45 |
> |
* other blocking synchronization apart from joining other tasks or |
46 |
> |
* using synchronizers such as Phasers that are advertised to |
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> |
* cooperate with fork/join scheduling. Tasks should also not perform |
48 |
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* blocking IO, and should ideally access variables that are |
49 |
> |
* completely independent of those accessed by other running |
50 |
> |
* tasks. Minor breaches of these restrictions, for example using |
51 |
> |
* shared output streams, may be tolerable in practice, but frequent |
52 |
> |
* use may result in poor performance, and the potential to |
53 |
> |
* indefinitely stall if the number of threads not waiting for IO or |
54 |
> |
* other external synchronization becomes exhausted. This usage |
55 |
> |
* restriction is in part enforced by not permitting checked |
56 |
> |
* exceptions such as {@code IOExceptions} to be thrown. However, |
57 |
> |
* computations may still encounter unchecked exceptions, that are |
58 |
> |
* rethrown to callers attempting to join them. These exceptions may |
59 |
> |
* additionally include RejectedExecutionExceptions stemming from |
60 |
> |
* internal resource exhaustion such as failure to allocate internal |
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* task queues. |
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* |
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* <p>The primary method for awaiting completion and extracting |
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* results of a task is {@link #join}, but there are several variants: |
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* The {@link Future#get} methods support interruptible and/or timed |
66 |
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* waits for completion and report results using <code>Future</code> |
66 |
> |
* waits for completion and report results using {@code Future} |
67 |
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* conventions. Method {@link #helpJoin} enables callers to actively |
68 |
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* execute other tasks while awaiting joins, which is sometimes more |
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* efficient but only applies when all subtasks are known to be |
70 |
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* strictly tree-structured. Method {@link #invoke} is semantically |
71 |
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* equivalent to <code>fork(); join()</code> but always attempts to |
72 |
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* begin execution in the current thread. The "<em>quiet</em>" forms |
73 |
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* of these methods do not extract results or report exceptions. These |
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* equivalent to {@code fork(); join()} but always attempts to begin |
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* execution in the current thread. The "<em>quiet</em>" forms of |
73 |
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* these methods do not extract results or report exceptions. These |
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* may be useful when a set of tasks are being executed, and you need |
75 |
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* to delay processing of results or exceptions until all complete. |
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* Method <code>invokeAll</code> (available in multiple versions) |
76 |
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* Method {@code invokeAll} (available in multiple versions) |
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* performs the most common form of parallel invocation: forking a set |
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* of tasks and joining them all. |
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* |
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* <p> The ForkJoinTask class is not usually directly subclassed. |
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* <p>The execution status of tasks may be queried at several levels |
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* of detail: {@link #isDone} is true if a task completed in any way |
82 |
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* (including the case where a task was cancelled without executing); |
83 |
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* {@link #isCancelled} is true if completion was due to cancellation; |
84 |
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* {@link #isCompletedNormally} is true if a task completed without |
85 |
> |
* cancellation or encountering an exception; {@link |
86 |
> |
* #isCompletedExceptionally} is true if if the task encountered an |
87 |
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* exception (in which case {@link #getException} returns the |
88 |
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* exception); {@link #isCancelled} is true if the task was cancelled |
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* (in which case {@link #getException} returns a {@link |
90 |
> |
* java.util.concurrent.CancellationException}); and {@link |
91 |
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* #isCompletedAbnormally} is true if a task was either cancelled or |
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* encountered an exception. |
93 |
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* |
94 |
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* <p>The ForkJoinTask class is not usually directly subclassed. |
95 |
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* Instead, you subclass one of the abstract classes that support a |
96 |
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* particular style of fork/join processing. Normally, a concrete |
96 |
> |
* particular style of fork/join processing, typically {@link |
97 |
> |
* RecursiveAction} for computations that do not return results, or |
98 |
> |
* {@link RecursiveTask} for those that do. Normally, a concrete |
99 |
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* ForkJoinTask subclass declares fields comprising its parameters, |
100 |
< |
* established in a constructor, and then defines a <code>compute</code> |
100 |
> |
* established in a constructor, and then defines a {@code compute} |
101 |
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* method that somehow uses the control methods supplied by this base |
102 |
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* class. While these methods have <code>public</code> access (to allow |
103 |
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* instances of different task subclasses to call each others |
102 |
> |
* class. While these methods have {@code public} access (to allow |
103 |
> |
* instances of different task subclasses to call each other's |
104 |
|
* methods), some of them may only be called from within other |
105 |
< |
* ForkJoinTasks. Attempts to invoke them in other contexts result in |
106 |
< |
* exceptions or errors possibly including ClassCastException. |
105 |
> |
* ForkJoinTasks (as may be determined using method {@link |
106 |
> |
* #inForkJoinPool}). Attempts to invoke them in other contexts |
107 |
> |
* result in exceptions or errors, possibly including |
108 |
> |
* ClassCastException. |
109 |
|
* |
110 |
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* <p>Most base support methods are <code>final</code> because their |
111 |
< |
* implementations are intrinsically tied to the underlying |
112 |
< |
* lightweight task scheduling framework, and so cannot be overridden. |
113 |
< |
* Developers creating new basic styles of fork/join processing should |
114 |
< |
* minimally implement <code>protected</code> methods |
115 |
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* <code>exec</code>, <code>setRawResult</code>, and |
116 |
< |
* <code>getRawResult</code>, while also introducing an abstract |
117 |
< |
* computational method that can be implemented in its subclasses, |
118 |
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* possibly relying on other <code>protected</code> methods provided |
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* by this class. |
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* <p>Most base support methods are {@code final}, to prevent |
111 |
> |
* overriding of implementations that are intrinsically tied to the |
112 |
> |
* underlying lightweight task scheduling framework. Developers |
113 |
> |
* creating new basic styles of fork/join processing should minimally |
114 |
> |
* implement {@code protected} methods {@link #exec}, {@link |
115 |
> |
* #setRawResult}, and {@link #getRawResult}, while also introducing |
116 |
> |
* an abstract computational method that can be implemented in its |
117 |
> |
* subclasses, possibly relying on other {@code protected} methods |
118 |
> |
* provided by this class. |
119 |
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* |
120 |
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* <p>ForkJoinTasks should perform relatively small amounts of |
121 |
< |
* computations, othewise splitting into smaller tasks. As a very |
122 |
< |
* rough rule of thumb, a task should perform more than 100 and less |
123 |
< |
* than 10000 basic computational steps. If tasks are too big, then |
124 |
< |
* parellelism cannot improve throughput. If too small, then memory |
125 |
< |
* and internal task maintenance overhead may overwhelm processing. |
121 |
> |
* computation. Large tasks should be split into smaller subtasks, |
122 |
> |
* usually via recursive decomposition. As a very rough rule of thumb, |
123 |
> |
* a task should perform more than 100 and less than 10000 basic |
124 |
> |
* computational steps. If tasks are too big, then parallelism cannot |
125 |
> |
* improve throughput. If too small, then memory and internal task |
126 |
> |
* maintenance overhead may overwhelm processing. |
127 |
|
* |
128 |
< |
* <p>ForkJoinTasks are <code>Serializable</code>, which enables them |
129 |
< |
* to be used in extensions such as remote execution frameworks. It is |
130 |
< |
* in general sensible to serialize tasks only before or after, but |
131 |
< |
* not during execution. Serialization is not relied on during |
132 |
< |
* execution itself. |
128 |
> |
* <p>This class provides {@code adapt} methods for {@link |
129 |
> |
* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that |
130 |
> |
* may be of use when mixing execution of ForkJoinTasks with other |
131 |
> |
* kinds of tasks. When all tasks are of this form, consider using a |
132 |
> |
* pool in {@link ForkJoinPool#setAsyncMode async mode}. |
133 |
> |
* |
134 |
> |
* <p>ForkJoinTasks are {@code Serializable}, which enables them to be |
135 |
> |
* used in extensions such as remote execution frameworks. It is |
136 |
> |
* sensible to serialize tasks only before or after, but not during, |
137 |
> |
* execution. Serialization is not relied on during execution itself. |
138 |
> |
* |
139 |
> |
* @since 1.7 |
140 |
> |
* @author Doug Lea |
141 |
|
*/ |
142 |
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public abstract class ForkJoinTask<V> implements Future<V>, Serializable { |
143 |
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|
159 |
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* currently unused. Also value 0x80000000 is available as spare |
160 |
|
* completion value. |
161 |
|
*/ |
162 |
< |
volatile int status; // accessed directy by pool and workers |
162 |
> |
volatile int status; // accessed directly by pool and workers |
163 |
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|
164 |
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static final int COMPLETION_MASK = 0xe0000000; |
165 |
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static final int NORMAL = 0xe0000000; // == mask |
172 |
|
/** |
173 |
|
* Table of exceptions thrown by tasks, to enable reporting by |
174 |
|
* callers. Because exceptions are rare, we don't directly keep |
175 |
< |
* them with task objects, but instead us a weak ref table. Note |
175 |
> |
* them with task objects, but instead use a weak ref table. Note |
176 |
|
* that cancellation exceptions don't appear in the table, but are |
177 |
|
* instead recorded as status values. |
178 |
< |
* Todo: Use ConcurrentReferenceHashMap |
178 |
> |
* TODO: Use ConcurrentReferenceHashMap |
179 |
|
*/ |
180 |
|
static final Map<ForkJoinTask<?>, Throwable> exceptionMap = |
181 |
|
Collections.synchronizedMap |
184 |
|
// within-package utilities |
185 |
|
|
186 |
|
/** |
187 |
< |
* Get current worker thread, or null if not a worker thread |
187 |
> |
* Gets current worker thread, or null if not a worker thread. |
188 |
|
*/ |
189 |
|
static ForkJoinWorkerThread getWorker() { |
190 |
|
Thread t = Thread.currentThread(); |
191 |
< |
return ((t instanceof ForkJoinWorkerThread)? |
192 |
< |
(ForkJoinWorkerThread)t : null); |
191 |
> |
return ((t instanceof ForkJoinWorkerThread) ? |
192 |
> |
(ForkJoinWorkerThread) t : null); |
193 |
|
} |
194 |
|
|
195 |
|
final boolean casStatus(int cmp, int val) { |
196 |
< |
return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val); |
196 |
> |
return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val); |
197 |
|
} |
198 |
|
|
199 |
|
/** |
201 |
|
*/ |
202 |
|
static void rethrowException(Throwable ex) { |
203 |
|
if (ex != null) |
204 |
< |
_unsafe.throwException(ex); |
204 |
> |
UNSAFE.throwException(ex); |
205 |
|
} |
206 |
|
|
207 |
|
// Setting completion status |
208 |
|
|
209 |
|
/** |
210 |
< |
* Mark completion and wake up threads waiting to join this task. |
210 |
> |
* Marks completion and wakes up threads waiting to join this task. |
211 |
> |
* |
212 |
|
* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
213 |
|
*/ |
214 |
|
final void setCompletion(int completion) { |
215 |
|
ForkJoinPool pool = getPool(); |
216 |
|
if (pool != null) { |
217 |
|
int s; // Clear signal bits while setting completion status |
218 |
< |
do;while ((s = status) >= 0 && !casStatus(s, completion)); |
218 |
> |
do {} while ((s = status) >= 0 && !casStatus(s, completion)); |
219 |
|
|
220 |
|
if ((s & SIGNAL_MASK) != 0) { |
221 |
|
if ((s &= INTERNAL_SIGNAL_MASK) != 0) |
222 |
|
pool.updateRunningCount(s); |
223 |
< |
synchronized(this) { notifyAll(); } |
223 |
> |
synchronized (this) { notifyAll(); } |
224 |
|
} |
225 |
|
} |
226 |
|
else |
233 |
|
*/ |
234 |
|
private void externallySetCompletion(int completion) { |
235 |
|
int s; |
236 |
< |
do;while ((s = status) >= 0 && |
237 |
< |
!casStatus(s, (s & SIGNAL_MASK) | completion)); |
238 |
< |
synchronized(this) { notifyAll(); } |
236 |
> |
do {} while ((s = status) >= 0 && |
237 |
> |
!casStatus(s, (s & SIGNAL_MASK) | completion)); |
238 |
> |
synchronized (this) { notifyAll(); } |
239 |
|
} |
240 |
|
|
241 |
|
/** |
242 |
< |
* Sets status to indicate normal completion |
242 |
> |
* Sets status to indicate normal completion. |
243 |
|
*/ |
244 |
|
final void setNormalCompletion() { |
245 |
|
// Try typical fast case -- single CAS, no signal, not already done. |
246 |
|
// Manually expand casStatus to improve chances of inlining it |
247 |
< |
if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL)) |
247 |
> |
if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL)) |
248 |
|
setCompletion(NORMAL); |
249 |
|
} |
250 |
|
|
251 |
|
// internal waiting and notification |
252 |
|
|
253 |
|
/** |
254 |
< |
* Performs the actual monitor wait for awaitDone |
254 |
> |
* Performs the actual monitor wait for awaitDone. |
255 |
|
*/ |
256 |
|
private void doAwaitDone() { |
257 |
|
// Minimize lock bias and in/de-flation effects by maximizing |
258 |
|
// chances of waiting inside sync |
259 |
|
try { |
260 |
|
while (status >= 0) |
261 |
< |
synchronized(this) { if (status >= 0) wait(); } |
261 |
> |
synchronized (this) { if (status >= 0) wait(); } |
262 |
|
} catch (InterruptedException ie) { |
263 |
|
onInterruptedWait(); |
264 |
|
} |
265 |
|
} |
266 |
|
|
267 |
|
/** |
268 |
< |
* Performs the actual monitor wait for awaitDone |
268 |
> |
* Performs the actual timed monitor wait for awaitDone. |
269 |
|
*/ |
270 |
|
private void doAwaitDone(long startTime, long nanos) { |
271 |
< |
synchronized(this) { |
271 |
> |
synchronized (this) { |
272 |
|
try { |
273 |
|
while (status >= 0) { |
274 |
< |
long nt = nanos - System.nanoTime() - startTime; |
274 |
> |
long nt = nanos - (System.nanoTime() - startTime); |
275 |
|
if (nt <= 0) |
276 |
|
break; |
277 |
< |
wait(nt / 1000000, (int)(nt % 1000000)); |
277 |
> |
wait(nt / 1000000, (int) (nt % 1000000)); |
278 |
|
} |
279 |
|
} catch (InterruptedException ie) { |
280 |
|
onInterruptedWait(); |
287 |
|
/** |
288 |
|
* Sets status to indicate there is joiner, then waits for join, |
289 |
|
* surrounded with pool notifications. |
290 |
+ |
* |
291 |
|
* @return status upon exit |
292 |
|
*/ |
293 |
< |
private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) { |
294 |
< |
ForkJoinPool pool = w == null? null : w.pool; |
293 |
> |
private int awaitDone(ForkJoinWorkerThread w, |
294 |
> |
boolean maintainParallelism) { |
295 |
> |
ForkJoinPool pool = (w == null) ? null : w.pool; |
296 |
|
int s; |
297 |
|
while ((s = status) >= 0) { |
298 |
< |
if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) { |
298 |
> |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
299 |
|
if (pool == null || !pool.preJoin(this, maintainParallelism)) |
300 |
|
doAwaitDone(); |
301 |
|
if (((s = status) & INTERNAL_SIGNAL_MASK) != 0) |
308 |
|
|
309 |
|
/** |
310 |
|
* Timed version of awaitDone |
311 |
+ |
* |
312 |
|
* @return status upon exit |
313 |
|
*/ |
314 |
|
private int awaitDone(ForkJoinWorkerThread w, long nanos) { |
315 |
< |
ForkJoinPool pool = w == null? null : w.pool; |
315 |
> |
ForkJoinPool pool = (w == null) ? null : w.pool; |
316 |
|
int s; |
317 |
|
while ((s = status) >= 0) { |
318 |
< |
if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) { |
318 |
> |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
319 |
|
long startTime = System.nanoTime(); |
320 |
|
if (pool == null || !pool.preJoin(this, false)) |
321 |
|
doAwaitDone(startTime, nanos); |
332 |
|
} |
333 |
|
|
334 |
|
/** |
335 |
< |
* Notify pool that thread is unblocked. Called by signalled |
335 |
> |
* Notifies pool that thread is unblocked. Called by signalled |
336 |
|
* threads when woken by non-FJ threads (which is atypical). |
337 |
|
*/ |
338 |
|
private void adjustPoolCountsOnUnblock(ForkJoinPool pool) { |
339 |
|
int s; |
340 |
< |
do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK)); |
340 |
> |
do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK)); |
341 |
|
if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0) |
342 |
|
pool.updateRunningCount(s); |
343 |
|
} |
344 |
|
|
345 |
|
/** |
346 |
< |
* Notify pool to adjust counts on cancelled or timed out wait |
346 |
> |
* Notifies pool to adjust counts on cancelled or timed out wait. |
347 |
|
*/ |
348 |
|
private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) { |
349 |
|
if (pool != null) { |
358 |
|
} |
359 |
|
|
360 |
|
/** |
361 |
< |
* Handle interruptions during waits. |
361 |
> |
* Handles interruptions during waits. |
362 |
|
*/ |
363 |
|
private void onInterruptedWait() { |
364 |
|
ForkJoinWorkerThread w = getWorker(); |
377 |
|
} |
378 |
|
|
379 |
|
/** |
380 |
< |
* Throws the exception associated with status s; |
380 |
> |
* Throws the exception associated with status s. |
381 |
> |
* |
382 |
|
* @throws the exception |
383 |
|
*/ |
384 |
|
private void reportException(int s) { |
391 |
|
} |
392 |
|
|
393 |
|
/** |
394 |
< |
* Returns result or throws exception using j.u.c.Future conventions |
395 |
< |
* Only call when isDone known to be true. |
394 |
> |
* Returns result or throws exception using j.u.c.Future conventions. |
395 |
> |
* Only call when {@code isDone} known to be true. |
396 |
|
*/ |
397 |
|
private V reportFutureResult() |
398 |
|
throws ExecutionException, InterruptedException { |
399 |
+ |
if (Thread.interrupted()) |
400 |
+ |
throw new InterruptedException(); |
401 |
|
int s = status & COMPLETION_MASK; |
402 |
|
if (s < NORMAL) { |
403 |
|
Throwable ex; |
405 |
|
throw new CancellationException(); |
406 |
|
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
407 |
|
throw new ExecutionException(ex); |
370 |
– |
if (Thread.interrupted()) |
371 |
– |
throw new InterruptedException(); |
408 |
|
} |
409 |
|
return getRawResult(); |
410 |
|
} |
411 |
|
|
412 |
|
/** |
413 |
|
* Returns result or throws exception using j.u.c.Future conventions |
414 |
< |
* with timeouts |
414 |
> |
* with timeouts. |
415 |
|
*/ |
416 |
|
private V reportTimedFutureResult() |
417 |
|
throws InterruptedException, ExecutionException, TimeoutException { |
418 |
+ |
if (Thread.interrupted()) |
419 |
+ |
throw new InterruptedException(); |
420 |
|
Throwable ex; |
421 |
|
int s = status & COMPLETION_MASK; |
422 |
|
if (s == NORMAL) |
425 |
|
throw new CancellationException(); |
426 |
|
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
427 |
|
throw new ExecutionException(ex); |
390 |
– |
if (Thread.interrupted()) |
391 |
– |
throw new InterruptedException(); |
428 |
|
throw new TimeoutException(); |
429 |
|
} |
430 |
|
|
432 |
|
|
433 |
|
/** |
434 |
|
* Calls exec, recording completion, and rethrowing exception if |
435 |
< |
* encountered. Caller should normally check status before calling |
435 |
> |
* encountered. Caller should normally check status before calling. |
436 |
> |
* |
437 |
|
* @return true if completed normally |
438 |
|
*/ |
439 |
|
private boolean tryExec() { |
451 |
|
|
452 |
|
/** |
453 |
|
* Main execution method used by worker threads. Invokes |
454 |
< |
* base computation unless already complete |
454 |
> |
* base computation unless already complete. |
455 |
|
*/ |
456 |
|
final void quietlyExec() { |
457 |
|
if (status >= 0) { |
458 |
|
try { |
459 |
|
if (!exec()) |
460 |
|
return; |
461 |
< |
} catch(Throwable rex) { |
461 |
> |
} catch (Throwable rex) { |
462 |
|
setDoneExceptionally(rex); |
463 |
|
return; |
464 |
|
} |
467 |
|
} |
468 |
|
|
469 |
|
/** |
470 |
< |
* Calls exec, recording but not rethrowing exception |
471 |
< |
* Caller should normally check status before calling |
470 |
> |
* Calls exec(), recording but not rethrowing exception. |
471 |
> |
* Caller should normally check status before calling. |
472 |
> |
* |
473 |
|
* @return true if completed normally |
474 |
|
*/ |
475 |
|
private boolean tryQuietlyInvoke() { |
485 |
|
} |
486 |
|
|
487 |
|
/** |
488 |
< |
* Cancel, ignoring any exceptions it throws |
488 |
> |
* Cancels, ignoring any exceptions it throws. |
489 |
|
*/ |
490 |
|
final void cancelIgnoringExceptions() { |
491 |
|
try { |
492 |
|
cancel(false); |
493 |
< |
} catch(Throwable ignore) { |
493 |
> |
} catch (Throwable ignore) { |
494 |
|
} |
495 |
|
} |
496 |
|
|
502 |
|
ForkJoinTask<?> t; |
503 |
|
while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null) |
504 |
|
t.quietlyExec(); |
505 |
< |
return (s >= 0)? awaitDone(w, false) : s; // block if no work |
505 |
> |
return (s >= 0) ? awaitDone(w, false) : s; // block if no work |
506 |
|
} |
507 |
|
|
508 |
|
// public methods |
510 |
|
/** |
511 |
|
* Arranges to asynchronously execute this task. While it is not |
512 |
|
* necessarily enforced, it is a usage error to fork a task more |
513 |
< |
* than once unless it has completed and been reinitialized. This |
514 |
< |
* method may be invoked only from within ForkJoinTask |
515 |
< |
* computations. Attempts to invoke in other contexts result in |
516 |
< |
* exceptions or errors possibly including ClassCastException. |
513 |
> |
* than once unless it has completed and been reinitialized. |
514 |
> |
* |
515 |
> |
* <p>This method may be invoked only from within {@code |
516 |
> |
* ForkJoinTask} computations (as may be determined using method |
517 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
518 |
> |
* result in exceptions or errors, possibly including {@code |
519 |
> |
* ClassCastException}. |
520 |
> |
* |
521 |
> |
* @return {@code this}, to simplify usage |
522 |
|
*/ |
523 |
< |
public final void fork() { |
524 |
< |
((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this); |
523 |
> |
public final ForkJoinTask<V> fork() { |
524 |
> |
((ForkJoinWorkerThread) Thread.currentThread()) |
525 |
> |
.pushTask(this); |
526 |
> |
return this; |
527 |
|
} |
528 |
|
|
529 |
|
/** |
530 |
|
* Returns the result of the computation when it is ready. |
531 |
< |
* This method differs from <code>get</code> in that abnormal |
532 |
< |
* completion results in RuntimeExceptions or Errors, not |
533 |
< |
* ExecutionExceptions. |
531 |
> |
* This method differs from {@link #get()} in that |
532 |
> |
* abnormal completion results in {@code RuntimeException} or |
533 |
> |
* {@code Error}, not {@code ExecutionException}. |
534 |
|
* |
535 |
|
* @return the computed result |
536 |
|
*/ |
543 |
|
|
544 |
|
/** |
545 |
|
* Commences performing this task, awaits its completion if |
546 |
< |
* necessary, and return its result. |
547 |
< |
* @throws Throwable (a RuntimeException, Error, or unchecked |
548 |
< |
* exception) if the underlying computation did so. |
546 |
> |
* necessary, and return its result, or throws an (unchecked) |
547 |
> |
* exception if the underlying computation did so. |
548 |
> |
* |
549 |
|
* @return the computed result |
550 |
|
*/ |
551 |
|
public final V invoke() { |
556 |
|
} |
557 |
|
|
558 |
|
/** |
559 |
< |
* Forks both tasks, returning when <code>isDone</code> holds for |
560 |
< |
* both of them or an exception is encountered. This method may be |
561 |
< |
* invoked only from within ForkJoinTask computations. Attempts to |
562 |
< |
* invoke in other contexts result in exceptions or errors |
563 |
< |
* possibly including ClassCastException. |
564 |
< |
* @param t1 one task |
565 |
< |
* @param t2 the other task |
566 |
< |
* @throws NullPointerException if t1 or t2 are null |
567 |
< |
* @throws RuntimeException or Error if either task did so. |
559 |
> |
* Forks the given tasks, returning when {@code isDone} holds for |
560 |
> |
* each task or an (unchecked) exception is encountered, in which |
561 |
> |
* case the exception is rethrown. If more than one task |
562 |
> |
* encounters an exception, then this method throws any one of |
563 |
> |
* these exceptions. The individual status of each task may be |
564 |
> |
* checked using {@link #getException()} and related methods. |
565 |
> |
* |
566 |
> |
* <p>This method may be invoked only from within {@code |
567 |
> |
* ForkJoinTask} computations (as may be determined using method |
568 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
569 |
> |
* result in exceptions or errors, possibly including {@code |
570 |
> |
* ClassCastException}. |
571 |
> |
* |
572 |
> |
* @param t1 the first task |
573 |
> |
* @param t2 the second task |
574 |
> |
* @throws NullPointerException if any task is null |
575 |
|
*/ |
576 |
< |
public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) { |
576 |
> |
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) { |
577 |
|
t2.fork(); |
578 |
|
t1.invoke(); |
579 |
|
t2.join(); |
580 |
|
} |
581 |
|
|
582 |
|
/** |
583 |
< |
* Forks the given tasks, returning when <code>isDone</code> holds |
584 |
< |
* for all of them. If any task encounters an exception, others |
585 |
< |
* may be cancelled. This method may be invoked only from within |
586 |
< |
* ForkJoinTask computations. Attempts to invoke in other contexts |
587 |
< |
* result in exceptions or errors possibly including ClassCastException. |
588 |
< |
* @param tasks the array of tasks |
589 |
< |
* @throws NullPointerException if tasks or any element are null. |
590 |
< |
* @throws RuntimeException or Error if any task did so. |
583 |
> |
* Forks the given tasks, returning when {@code isDone} holds for |
584 |
> |
* each task or an (unchecked) exception is encountered, in which |
585 |
> |
* case the exception is rethrown. If any task encounters an |
586 |
> |
* exception, others may be, but are not guaranteed to be, |
587 |
> |
* cancelled. If more than one task encounters an exception, then |
588 |
> |
* this method throws any one of these exceptions. The individual |
589 |
> |
* status of each task may be checked using {@link #getException()} |
590 |
> |
* and related methods. |
591 |
> |
* |
592 |
> |
* <p>This method may be invoked only from within {@code |
593 |
> |
* ForkJoinTask} computations (as may be determined using method |
594 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
595 |
> |
* result in exceptions or errors, possibly including {@code |
596 |
> |
* ClassCastException}. |
597 |
> |
* |
598 |
> |
* @param tasks the tasks |
599 |
> |
* @throws NullPointerException if any task is null |
600 |
|
*/ |
601 |
|
public static void invokeAll(ForkJoinTask<?>... tasks) { |
602 |
|
Throwable ex = null; |
632 |
|
} |
633 |
|
|
634 |
|
/** |
635 |
< |
* Forks all tasks in the collection, returning when |
636 |
< |
* <code>isDone</code> holds for all of them. If any task |
637 |
< |
* encounters an exception, others may be cancelled. This method |
638 |
< |
* may be invoked only from within ForkJoinTask |
639 |
< |
* computations. Attempts to invoke in other contexts resul!t in |
640 |
< |
* exceptions or errors possibly including ClassCastException. |
635 |
> |
* Forks all tasks in the specified collection, returning when |
636 |
> |
* {@code isDone} holds for each task or an (unchecked) exception |
637 |
> |
* is encountered. If any task encounters an exception, others |
638 |
> |
* may be, but are not guaranteed to be, cancelled. If more than |
639 |
> |
* one task encounters an exception, then this method throws any |
640 |
> |
* one of these exceptions. The individual status of each task |
641 |
> |
* may be checked using {@link #getException()} and related |
642 |
> |
* methods. The behavior of this operation is undefined if the |
643 |
> |
* specified collection is modified while the operation is in |
644 |
> |
* progress. |
645 |
> |
* |
646 |
> |
* <p>This method may be invoked only from within {@code |
647 |
> |
* ForkJoinTask} computations (as may be determined using method |
648 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
649 |
> |
* result in exceptions or errors, possibly including {@code |
650 |
> |
* ClassCastException}. |
651 |
> |
* |
652 |
|
* @param tasks the collection of tasks |
653 |
< |
* @throws NullPointerException if tasks or any element are null. |
654 |
< |
* @throws RuntimeException or Error if any task did so. |
653 |
> |
* @return the tasks argument, to simplify usage |
654 |
> |
* @throws NullPointerException if tasks or any element are null |
655 |
|
*/ |
656 |
< |
public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) { |
657 |
< |
if (!(tasks instanceof List)) { |
658 |
< |
invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()])); |
659 |
< |
return; |
656 |
> |
public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) { |
657 |
> |
if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) { |
658 |
> |
invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()])); |
659 |
> |
return tasks; |
660 |
|
} |
661 |
+ |
@SuppressWarnings("unchecked") |
662 |
|
List<? extends ForkJoinTask<?>> ts = |
663 |
< |
(List<? extends ForkJoinTask<?>>)tasks; |
663 |
> |
(List<? extends ForkJoinTask<?>>) tasks; |
664 |
|
Throwable ex = null; |
665 |
|
int last = ts.size() - 1; |
666 |
|
for (int i = last; i >= 0; --i) { |
691 |
|
} |
692 |
|
if (ex != null) |
693 |
|
rethrowException(ex); |
694 |
+ |
return tasks; |
695 |
|
} |
696 |
|
|
697 |
|
/** |
698 |
< |
* Returns true if the computation performed by this task has |
699 |
< |
* completed (or has been cancelled). |
700 |
< |
* @return true if this computation has completed |
701 |
< |
*/ |
702 |
< |
public final boolean isDone() { |
703 |
< |
return status < 0; |
704 |
< |
} |
631 |
< |
|
632 |
< |
/** |
633 |
< |
* Returns true if this task was cancelled. |
634 |
< |
* @return true if this task was cancelled |
635 |
< |
*/ |
636 |
< |
public final boolean isCancelled() { |
637 |
< |
return (status & COMPLETION_MASK) == CANCELLED; |
638 |
< |
} |
639 |
< |
|
640 |
< |
/** |
641 |
< |
* Asserts that the results of this task's computation will not be |
642 |
< |
* used. If a cancellation occurs before atempting to execute this |
643 |
< |
* task, then execution will be suppressed, <code>isCancelled</code> |
644 |
< |
* will report true, and <code>join</code> will result in a |
645 |
< |
* <code>CancellationException</code> being thrown. Otherwise, when |
646 |
< |
* cancellation races with completion, there are no guarantees |
647 |
< |
* about whether <code>isCancelled</code> will report true, whether |
648 |
< |
* <code>join</code> will return normally or via an exception, or |
649 |
< |
* whether these behaviors will remain consistent upon repeated |
650 |
< |
* invocation. |
698 |
> |
* Attempts to cancel execution of this task. This attempt will |
699 |
> |
* fail if the task has already completed, has already been |
700 |
> |
* cancelled, or could not be cancelled for some other reason. If |
701 |
> |
* successful, and this task has not started when cancel is |
702 |
> |
* called, execution of this task is suppressed, {@link |
703 |
> |
* #isCancelled} will report true, and {@link #join} will result |
704 |
> |
* in a {@code CancellationException} being thrown. |
705 |
|
* |
706 |
|
* <p>This method may be overridden in subclasses, but if so, must |
707 |
|
* still ensure that these minimal properties hold. In particular, |
708 |
< |
* the cancel method itself must not throw exceptions. |
708 |
> |
* the {@code cancel} method itself must not throw exceptions. |
709 |
|
* |
710 |
< |
* <p> This method is designed to be invoked by <em>other</em> |
710 |
> |
* <p>This method is designed to be invoked by <em>other</em> |
711 |
|
* tasks. To terminate the current task, you can just return or |
712 |
|
* throw an unchecked exception from its computation method, or |
713 |
< |
* invoke <code>completeExceptionally</code>. |
713 |
> |
* invoke {@link #completeExceptionally}. |
714 |
|
* |
715 |
|
* @param mayInterruptIfRunning this value is ignored in the |
716 |
< |
* default implementation because tasks are not in general |
717 |
< |
* cancelled via interruption. |
716 |
> |
* default implementation because tasks are not |
717 |
> |
* cancelled via interruption |
718 |
|
* |
719 |
< |
* @return true if this task is now cancelled |
719 |
> |
* @return {@code true} if this task is now cancelled |
720 |
|
*/ |
721 |
|
public boolean cancel(boolean mayInterruptIfRunning) { |
722 |
|
setCompletion(CANCELLED); |
724 |
|
} |
725 |
|
|
726 |
|
/** |
727 |
< |
* Returns true if this task threw an exception or was cancelled |
728 |
< |
* @return true if this task threw an exception or was cancelled |
727 |
> |
* Returns {@code true} if the computation performed by this task |
728 |
> |
* has completed (or has been cancelled). |
729 |
> |
* |
730 |
> |
* @return {@code true} if this computation has completed |
731 |
> |
*/ |
732 |
> |
public final boolean isDone() { |
733 |
> |
return status < 0; |
734 |
> |
} |
735 |
> |
|
736 |
> |
/** |
737 |
> |
* Returns {@code true} if this task was cancelled. |
738 |
> |
* |
739 |
> |
* @return {@code true} if this task was cancelled |
740 |
> |
*/ |
741 |
> |
public final boolean isCancelled() { |
742 |
> |
return (status & COMPLETION_MASK) == CANCELLED; |
743 |
> |
} |
744 |
> |
|
745 |
> |
/** |
746 |
> |
* Returns {@code true} if this task threw an exception or was cancelled. |
747 |
> |
* |
748 |
> |
* @return {@code true} if this task threw an exception or was cancelled |
749 |
|
*/ |
750 |
|
public final boolean isCompletedAbnormally() { |
751 |
|
return (status & COMPLETION_MASK) < NORMAL; |
752 |
|
} |
753 |
|
|
754 |
|
/** |
755 |
+ |
* Returns {@code true} if this task completed without throwing an |
756 |
+ |
* exception and was not cancelled. |
757 |
+ |
* |
758 |
+ |
* @return {@code true} if this task completed without throwing an |
759 |
+ |
* exception and was not cancelled |
760 |
+ |
*/ |
761 |
+ |
public final boolean isCompletedNormally() { |
762 |
+ |
return (status & COMPLETION_MASK) == NORMAL; |
763 |
+ |
} |
764 |
+ |
|
765 |
+ |
/** |
766 |
+ |
* Returns {@code true} if this task threw an exception. |
767 |
+ |
* |
768 |
+ |
* @return {@code true} if this task threw an exception |
769 |
+ |
*/ |
770 |
+ |
public final boolean isCompletedExceptionally() { |
771 |
+ |
return (status & COMPLETION_MASK) == EXCEPTIONAL; |
772 |
+ |
} |
773 |
+ |
|
774 |
+ |
/** |
775 |
|
* Returns the exception thrown by the base computation, or a |
776 |
< |
* CancellationException if cancelled, or null if none or if the |
777 |
< |
* method has not yet completed. |
778 |
< |
* @return the exception, or null if none |
776 |
> |
* {@code CancellationException} if cancelled, or {@code null} if |
777 |
> |
* none or if the method has not yet completed. |
778 |
> |
* |
779 |
> |
* @return the exception, or {@code null} if none |
780 |
|
*/ |
781 |
|
public final Throwable getException() { |
782 |
|
int s = status & COMPLETION_MASK; |
790 |
|
/** |
791 |
|
* Completes this task abnormally, and if not already aborted or |
792 |
|
* cancelled, causes it to throw the given exception upon |
793 |
< |
* <code>join</code> and related operations. This method may be used |
793 |
> |
* {@code join} and related operations. This method may be used |
794 |
|
* to induce exceptions in asynchronous tasks, or to force |
795 |
|
* completion of tasks that would not otherwise complete. Its use |
796 |
< |
* in other situations is likely to be wrong. This method is |
797 |
< |
* overridable, but overridden versions must invoke <code>super</code> |
796 |
> |
* in other situations is discouraged. This method is |
797 |
> |
* overridable, but overridden versions must invoke {@code super} |
798 |
|
* implementation to maintain guarantees. |
799 |
|
* |
800 |
|
* @param ex the exception to throw. If this exception is |
803 |
|
*/ |
804 |
|
public void completeExceptionally(Throwable ex) { |
805 |
|
setDoneExceptionally((ex instanceof RuntimeException) || |
806 |
< |
(ex instanceof Error)? ex : |
806 |
> |
(ex instanceof Error) ? ex : |
807 |
|
new RuntimeException(ex)); |
808 |
|
} |
809 |
|
|
810 |
|
/** |
811 |
|
* Completes this task, and if not already aborted or cancelled, |
812 |
< |
* returning a <code>null</code> result upon <code>join</code> and related |
812 |
> |
* returning a {@code null} result upon {@code join} and related |
813 |
|
* operations. This method may be used to provide results for |
814 |
|
* asynchronous tasks, or to provide alternative handling for |
815 |
|
* tasks that would not otherwise complete normally. Its use in |
816 |
< |
* other situations is likely to be wrong. This method is |
817 |
< |
* overridable, but overridden versions must invoke <code>super</code> |
816 |
> |
* other situations is discouraged. This method is |
817 |
> |
* overridable, but overridden versions must invoke {@code super} |
818 |
|
* implementation to maintain guarantees. |
819 |
|
* |
820 |
< |
* @param value the result value for this task. |
820 |
> |
* @param value the result value for this task |
821 |
|
*/ |
822 |
|
public void complete(V value) { |
823 |
|
try { |
824 |
|
setRawResult(value); |
825 |
< |
} catch(Throwable rex) { |
825 |
> |
} catch (Throwable rex) { |
826 |
|
setDoneExceptionally(rex); |
827 |
|
return; |
828 |
|
} |
838 |
|
|
839 |
|
public final V get(long timeout, TimeUnit unit) |
840 |
|
throws InterruptedException, ExecutionException, TimeoutException { |
841 |
+ |
long nanos = unit.toNanos(timeout); |
842 |
|
ForkJoinWorkerThread w = getWorker(); |
843 |
|
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
844 |
< |
awaitDone(w, unit.toNanos(timeout)); |
844 |
> |
awaitDone(w, nanos); |
845 |
|
return reportTimedFutureResult(); |
846 |
|
} |
847 |
|
|
848 |
|
/** |
849 |
|
* Possibly executes other tasks until this task is ready, then |
850 |
|
* returns the result of the computation. This method may be more |
851 |
< |
* efficient than <code>join</code>, but is only applicable when |
852 |
< |
* there are no potemtial dependencies between continuation of the |
851 |
> |
* efficient than {@code join}, but is only applicable when |
852 |
> |
* there are no potential dependencies between continuation of the |
853 |
|
* current task and that of any other task that might be executed |
854 |
|
* while helping. (This usually holds for pure divide-and-conquer |
855 |
< |
* tasks). This method may be invoked only from within |
856 |
< |
* ForkJoinTask computations. Attempts to invoke in other contexts |
857 |
< |
* resul!t in exceptions or errors possibly including ClassCastException. |
855 |
> |
* tasks). |
856 |
> |
* |
857 |
> |
* <p>This method may be invoked only from within {@code |
858 |
> |
* ForkJoinTask} computations (as may be determined using method |
859 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
860 |
> |
* result in exceptions or errors, possibly including {@code |
861 |
> |
* ClassCastException}. |
862 |
> |
* |
863 |
|
* @return the computed result |
864 |
|
*/ |
865 |
|
public final V helpJoin() { |
866 |
< |
ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread()); |
866 |
> |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread(); |
867 |
|
if (status < 0 || !w.unpushTask(this) || !tryExec()) |
868 |
|
reportException(busyJoin(w)); |
869 |
|
return getRawResult(); |
871 |
|
|
872 |
|
/** |
873 |
|
* Possibly executes other tasks until this task is ready. This |
874 |
< |
* method may be invoked only from within ForkJoinTask |
875 |
< |
* computations. Attempts to invoke in other contexts resul!t in |
876 |
< |
* exceptions or errors possibly including ClassCastException. |
874 |
> |
* method may be useful when processing collections of tasks when |
875 |
> |
* some have been cancelled or otherwise known to have aborted. |
876 |
> |
* |
877 |
> |
* <p>This method may be invoked only from within {@code |
878 |
> |
* ForkJoinTask} computations (as may be determined using method |
879 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
880 |
> |
* result in exceptions or errors, possibly including {@code |
881 |
> |
* ClassCastException}. |
882 |
|
*/ |
883 |
|
public final void quietlyHelpJoin() { |
884 |
|
if (status >= 0) { |
885 |
|
ForkJoinWorkerThread w = |
886 |
< |
(ForkJoinWorkerThread)(Thread.currentThread()); |
886 |
> |
(ForkJoinWorkerThread) Thread.currentThread(); |
887 |
|
if (!w.unpushTask(this) || !tryQuietlyInvoke()) |
888 |
|
busyJoin(w); |
889 |
|
} |
917 |
|
|
918 |
|
/** |
919 |
|
* Possibly executes tasks until the pool hosting the current task |
920 |
< |
* {@link ForkJoinPool#isQuiescent}. This method may be of use in |
921 |
< |
* designs in which many tasks are forked, but none are explicitly |
922 |
< |
* joined, instead executing them until all are processed. |
920 |
> |
* {@link ForkJoinPool#isQuiescent is quiescent}. This method may |
921 |
> |
* be of use in designs in which many tasks are forked, but none |
922 |
> |
* are explicitly joined, instead executing them until all are |
923 |
> |
* processed. |
924 |
> |
* |
925 |
> |
* <p>This method may be invoked only from within {@code |
926 |
> |
* ForkJoinTask} computations (as may be determined using method |
927 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
928 |
> |
* result in exceptions or errors, possibly including {@code |
929 |
> |
* ClassCastException}. |
930 |
|
*/ |
931 |
|
public static void helpQuiesce() { |
932 |
< |
((ForkJoinWorkerThread)(Thread.currentThread())). |
933 |
< |
helpQuiescePool(); |
932 |
> |
((ForkJoinWorkerThread) Thread.currentThread()) |
933 |
> |
.helpQuiescePool(); |
934 |
|
} |
935 |
|
|
936 |
|
/** |
937 |
|
* Resets the internal bookkeeping state of this task, allowing a |
938 |
< |
* subsequent <code>fork</code>. This method allows repeated reuse of |
938 |
> |
* subsequent {@code fork}. This method allows repeated reuse of |
939 |
|
* this task, but only if reuse occurs when this task has either |
940 |
|
* never been forked, or has been forked, then completed and all |
941 |
|
* outstanding joins of this task have also completed. Effects |
942 |
< |
* under any other usage conditions are not guaranteed, and are |
943 |
< |
* almost surely wrong. This method may be useful when executing |
942 |
> |
* under any other usage conditions are not guaranteed. |
943 |
> |
* This method may be useful when executing |
944 |
|
* pre-constructed trees of subtasks in loops. |
945 |
|
*/ |
946 |
|
public void reinitialize() { |
951 |
|
|
952 |
|
/** |
953 |
|
* Returns the pool hosting the current task execution, or null |
954 |
< |
* if this task is executing outside of any pool. |
955 |
< |
* @return the pool, or null if none. |
954 |
> |
* if this task is executing outside of any ForkJoinPool. |
955 |
> |
* |
956 |
> |
* @see #inForkJoinPool |
957 |
> |
* @return the pool, or {@code null} if none |
958 |
|
*/ |
959 |
|
public static ForkJoinPool getPool() { |
960 |
|
Thread t = Thread.currentThread(); |
961 |
< |
return ((t instanceof ForkJoinWorkerThread)? |
962 |
< |
((ForkJoinWorkerThread)t).pool : null); |
961 |
> |
return (t instanceof ForkJoinWorkerThread) ? |
962 |
> |
((ForkJoinWorkerThread) t).pool : null; |
963 |
> |
} |
964 |
> |
|
965 |
> |
/** |
966 |
> |
* Returns {@code true} if the current thread is executing as a |
967 |
> |
* ForkJoinPool computation. |
968 |
> |
* |
969 |
> |
* @return {@code true} if the current thread is executing as a |
970 |
> |
* ForkJoinPool computation, or false otherwise |
971 |
> |
*/ |
972 |
> |
public static boolean inForkJoinPool() { |
973 |
> |
return Thread.currentThread() instanceof ForkJoinWorkerThread; |
974 |
|
} |
975 |
|
|
976 |
|
/** |
979 |
|
* by the current thread, and has not commenced executing in |
980 |
|
* another thread. This method may be useful when arranging |
981 |
|
* alternative local processing of tasks that could have been, but |
982 |
< |
* were not, stolen. This method may be invoked only from within |
983 |
< |
* ForkJoinTask computations. Attempts to invoke in other contexts |
984 |
< |
* result in exceptions or errors possibly including ClassCastException. |
985 |
< |
* @return true if unforked |
982 |
> |
* were not, stolen. |
983 |
> |
* |
984 |
> |
* <p>This method may be invoked only from within {@code |
985 |
> |
* ForkJoinTask} computations (as may be determined using method |
986 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
987 |
> |
* result in exceptions or errors, possibly including {@code |
988 |
> |
* ClassCastException}. |
989 |
> |
* |
990 |
> |
* @return {@code true} if unforked |
991 |
|
*/ |
992 |
|
public boolean tryUnfork() { |
993 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this); |
993 |
> |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
994 |
> |
.unpushTask(this); |
995 |
|
} |
996 |
|
|
997 |
|
/** |
999 |
|
* forked by the current worker thread but not yet executed. This |
1000 |
|
* value may be useful for heuristic decisions about whether to |
1001 |
|
* fork other tasks. |
1002 |
+ |
* |
1003 |
+ |
* <p>This method may be invoked only from within {@code |
1004 |
+ |
* ForkJoinTask} computations (as may be determined using method |
1005 |
+ |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1006 |
+ |
* result in exceptions or errors, possibly including {@code |
1007 |
+ |
* ClassCastException}. |
1008 |
+ |
* |
1009 |
|
* @return the number of tasks |
1010 |
|
*/ |
1011 |
|
public static int getQueuedTaskCount() { |
1012 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())). |
1013 |
< |
getQueueSize(); |
1012 |
> |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1013 |
> |
.getQueueSize(); |
1014 |
|
} |
1015 |
|
|
1016 |
|
/** |
1017 |
< |
* Returns a estimate of how many more locally queued tasks are |
1017 |
> |
* Returns an estimate of how many more locally queued tasks are |
1018 |
|
* held by the current worker thread than there are other worker |
1019 |
|
* threads that might steal them. This value may be useful for |
1020 |
|
* heuristic decisions about whether to fork other tasks. In many |
1022 |
|
* aim to maintain a small constant surplus (for example, 3) of |
1023 |
|
* tasks, and to process computations locally if this threshold is |
1024 |
|
* exceeded. |
1025 |
+ |
* |
1026 |
+ |
* <p>This method may be invoked only from within {@code |
1027 |
+ |
* ForkJoinTask} computations (as may be determined using method |
1028 |
+ |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1029 |
+ |
* result in exceptions or errors, possibly including {@code |
1030 |
+ |
* ClassCastException}. |
1031 |
+ |
* |
1032 |
|
* @return the surplus number of tasks, which may be negative |
1033 |
|
*/ |
1034 |
|
public static int getSurplusQueuedTaskCount() { |
1035 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())) |
1035 |
> |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1036 |
|
.getEstimatedSurplusTaskCount(); |
1037 |
|
} |
1038 |
|
|
1039 |
|
// Extension methods |
1040 |
|
|
1041 |
|
/** |
1042 |
< |
* Returns the result that would be returned by <code>join</code>, |
1043 |
< |
* even if this task completed abnormally, or null if this task is |
1044 |
< |
* not known to have been completed. This method is designed to |
1045 |
< |
* aid debugging, as well as to support extensions. Its use in any |
1046 |
< |
* other context is discouraged. |
1042 |
> |
* Returns the result that would be returned by {@link #join}, even |
1043 |
> |
* if this task completed abnormally, or {@code null} if this task |
1044 |
> |
* is not known to have been completed. This method is designed |
1045 |
> |
* to aid debugging, as well as to support extensions. Its use in |
1046 |
> |
* any other context is discouraged. |
1047 |
|
* |
1048 |
< |
* @return the result, or null if not completed. |
1048 |
> |
* @return the result, or {@code null} if not completed |
1049 |
|
*/ |
1050 |
|
public abstract V getRawResult(); |
1051 |
|
|
1064 |
|
* called otherwise. The return value controls whether this task |
1065 |
|
* is considered to be done normally. It may return false in |
1066 |
|
* asynchronous actions that require explicit invocations of |
1067 |
< |
* <code>complete</code> to become joinable. It may throw exceptions |
1068 |
< |
* to indicate abnormal exit. |
1069 |
< |
* @return true if completed normally |
1070 |
< |
* @throws Error or RuntimeException if encountered during computation |
1067 |
> |
* {@link #complete} to become joinable. It may also throw an |
1068 |
> |
* (unchecked) exception to indicate abnormal exit. |
1069 |
> |
* |
1070 |
> |
* @return {@code true} if completed normally |
1071 |
|
*/ |
1072 |
|
protected abstract boolean exec(); |
1073 |
|
|
1074 |
|
/** |
1075 |
< |
* Returns, but does not unschedule or execute, the task most |
1076 |
< |
* recently forked by the current thread but not yet executed, if |
1077 |
< |
* one is available. There is no guarantee that this task will |
1078 |
< |
* actually be polled or executed next. |
1079 |
< |
* This method is designed primarily to support extensions, |
1080 |
< |
* and is unlikely to be useful otherwise. |
1081 |
< |
* This method may be invoked only from within |
1082 |
< |
* ForkJoinTask computations. Attempts to invoke in other contexts |
1083 |
< |
* result in exceptions or errors possibly including ClassCastException. |
1075 |
> |
* Returns, but does not unschedule or execute, a task queued by |
1076 |
> |
* the current thread but not yet executed, if one is immediately |
1077 |
> |
* available. There is no guarantee that this task will actually |
1078 |
> |
* be polled or executed next. Conversely, this method may return |
1079 |
> |
* null even if a task exists but cannot be accessed without |
1080 |
> |
* contention with other threads. This method is designed |
1081 |
> |
* primarily to support extensions, and is unlikely to be useful |
1082 |
> |
* otherwise. |
1083 |
> |
* |
1084 |
> |
* <p>This method may be invoked only from within {@code |
1085 |
> |
* ForkJoinTask} computations (as may be determined using method |
1086 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1087 |
> |
* result in exceptions or errors, possibly including {@code |
1088 |
> |
* ClassCastException}. |
1089 |
|
* |
1090 |
< |
* @return the next task, or null if none are available |
1090 |
> |
* @return the next task, or {@code null} if none are available |
1091 |
|
*/ |
1092 |
|
protected static ForkJoinTask<?> peekNextLocalTask() { |
1093 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask(); |
1093 |
> |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1094 |
> |
.peekTask(); |
1095 |
|
} |
1096 |
|
|
1097 |
|
/** |
1098 |
< |
* Unschedules and returns, without executing, the task most |
1099 |
< |
* recently forked by the current thread but not yet executed. |
1100 |
< |
* This method is designed primarily to support extensions, |
1101 |
< |
* and is unlikely to be useful otherwise. |
950 |
< |
* This method may be invoked only from within |
951 |
< |
* ForkJoinTask computations. Attempts to invoke in other contexts |
952 |
< |
* result in exceptions or errors possibly including ClassCastException. |
1098 |
> |
* Unschedules and returns, without executing, the next task |
1099 |
> |
* queued by the current thread but not yet executed. This method |
1100 |
> |
* is designed primarily to support extensions, and is unlikely to |
1101 |
> |
* be useful otherwise. |
1102 |
|
* |
1103 |
< |
* @return the next task, or null if none are available |
1103 |
> |
* <p>This method may be invoked only from within {@code |
1104 |
> |
* ForkJoinTask} computations (as may be determined using method |
1105 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1106 |
> |
* result in exceptions or errors, possibly including {@code |
1107 |
> |
* ClassCastException}. |
1108 |
> |
* |
1109 |
> |
* @return the next task, or {@code null} if none are available |
1110 |
|
*/ |
1111 |
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
1112 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())).popTask(); |
1112 |
> |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1113 |
> |
.pollLocalTask(); |
1114 |
|
} |
1115 |
|
|
1116 |
|
/** |
1117 |
< |
* Unschedules and returns, without executing, the task most |
1118 |
< |
* recently forked by the current thread but not yet executed, if |
1119 |
< |
* one is available, or if not available, a task that was forked |
1120 |
< |
* by some other thread, if available. Availability may be |
1121 |
< |
* transient, so a <code>null</code> result does not necessarily |
1122 |
< |
* imply quiecence of the pool this task is operating in. |
1123 |
< |
* This method is designed primarily to support extensions, |
1124 |
< |
* and is unlikely to be useful otherwise. |
1125 |
< |
* This method may be invoked only from within |
1126 |
< |
* ForkJoinTask computations. Attempts to invoke in other contexts |
1127 |
< |
* result in exceptions or errors possibly including ClassCastException. |
1117 |
> |
* Unschedules and returns, without executing, the next task |
1118 |
> |
* queued by the current thread but not yet executed, if one is |
1119 |
> |
* available, or if not available, a task that was forked by some |
1120 |
> |
* other thread, if available. Availability may be transient, so a |
1121 |
> |
* {@code null} result does not necessarily imply quiescence |
1122 |
> |
* of the pool this task is operating in. This method is designed |
1123 |
> |
* primarily to support extensions, and is unlikely to be useful |
1124 |
> |
* otherwise. |
1125 |
> |
* |
1126 |
> |
* <p>This method may be invoked only from within {@code |
1127 |
> |
* ForkJoinTask} computations (as may be determined using method |
1128 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1129 |
> |
* result in exceptions or errors, possibly including {@code |
1130 |
> |
* ClassCastException}. |
1131 |
|
* |
1132 |
< |
* @return a task, or null if none are available |
1132 |
> |
* @return a task, or {@code null} if none are available |
1133 |
|
*/ |
1134 |
|
protected static ForkJoinTask<?> pollTask() { |
1135 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())). |
1136 |
< |
pollTask(); |
1135 |
> |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1136 |
> |
.pollTask(); |
1137 |
> |
} |
1138 |
> |
|
1139 |
> |
/** |
1140 |
> |
* Adaptor for Runnables. This implements RunnableFuture |
1141 |
> |
* to be compliant with AbstractExecutorService constraints |
1142 |
> |
* when used in ForkJoinPool. |
1143 |
> |
*/ |
1144 |
> |
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
1145 |
> |
implements RunnableFuture<T> { |
1146 |
> |
final Runnable runnable; |
1147 |
> |
final T resultOnCompletion; |
1148 |
> |
T result; |
1149 |
> |
AdaptedRunnable(Runnable runnable, T result) { |
1150 |
> |
if (runnable == null) throw new NullPointerException(); |
1151 |
> |
this.runnable = runnable; |
1152 |
> |
this.resultOnCompletion = result; |
1153 |
> |
} |
1154 |
> |
public T getRawResult() { return result; } |
1155 |
> |
public void setRawResult(T v) { result = v; } |
1156 |
> |
public boolean exec() { |
1157 |
> |
runnable.run(); |
1158 |
> |
result = resultOnCompletion; |
1159 |
> |
return true; |
1160 |
> |
} |
1161 |
> |
public void run() { invoke(); } |
1162 |
> |
private static final long serialVersionUID = 5232453952276885070L; |
1163 |
> |
} |
1164 |
> |
|
1165 |
> |
/** |
1166 |
> |
* Adaptor for Callables |
1167 |
> |
*/ |
1168 |
> |
static final class AdaptedCallable<T> extends ForkJoinTask<T> |
1169 |
> |
implements RunnableFuture<T> { |
1170 |
> |
final Callable<? extends T> callable; |
1171 |
> |
T result; |
1172 |
> |
AdaptedCallable(Callable<? extends T> callable) { |
1173 |
> |
if (callable == null) throw new NullPointerException(); |
1174 |
> |
this.callable = callable; |
1175 |
> |
} |
1176 |
> |
public T getRawResult() { return result; } |
1177 |
> |
public void setRawResult(T v) { result = v; } |
1178 |
> |
public boolean exec() { |
1179 |
> |
try { |
1180 |
> |
result = callable.call(); |
1181 |
> |
return true; |
1182 |
> |
} catch (Error err) { |
1183 |
> |
throw err; |
1184 |
> |
} catch (RuntimeException rex) { |
1185 |
> |
throw rex; |
1186 |
> |
} catch (Exception ex) { |
1187 |
> |
throw new RuntimeException(ex); |
1188 |
> |
} |
1189 |
> |
} |
1190 |
> |
public void run() { invoke(); } |
1191 |
> |
private static final long serialVersionUID = 2838392045355241008L; |
1192 |
> |
} |
1193 |
> |
|
1194 |
> |
/** |
1195 |
> |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1196 |
> |
* method of the given {@code Runnable} as its action, and returns |
1197 |
> |
* a null result upon {@link #join}. |
1198 |
> |
* |
1199 |
> |
* @param runnable the runnable action |
1200 |
> |
* @return the task |
1201 |
> |
*/ |
1202 |
> |
public static ForkJoinTask<?> adapt(Runnable runnable) { |
1203 |
> |
return new AdaptedRunnable<Void>(runnable, null); |
1204 |
> |
} |
1205 |
> |
|
1206 |
> |
/** |
1207 |
> |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1208 |
> |
* method of the given {@code Runnable} as its action, and returns |
1209 |
> |
* the given result upon {@link #join}. |
1210 |
> |
* |
1211 |
> |
* @param runnable the runnable action |
1212 |
> |
* @param result the result upon completion |
1213 |
> |
* @return the task |
1214 |
> |
*/ |
1215 |
> |
public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) { |
1216 |
> |
return new AdaptedRunnable<T>(runnable, result); |
1217 |
> |
} |
1218 |
> |
|
1219 |
> |
/** |
1220 |
> |
* Returns a new {@code ForkJoinTask} that performs the {@code call} |
1221 |
> |
* method of the given {@code Callable} as its action, and returns |
1222 |
> |
* its result upon {@link #join}, translating any checked exceptions |
1223 |
> |
* encountered into {@code RuntimeException}. |
1224 |
> |
* |
1225 |
> |
* @param callable the callable action |
1226 |
> |
* @return the task |
1227 |
> |
*/ |
1228 |
> |
public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) { |
1229 |
> |
return new AdaptedCallable<T>(callable); |
1230 |
|
} |
1231 |
|
|
1232 |
|
// Serialization support |
1237 |
|
* Save the state to a stream. |
1238 |
|
* |
1239 |
|
* @serialData the current run status and the exception thrown |
1240 |
< |
* during execution, or null if none. |
1240 |
> |
* during execution, or {@code null} if none |
1241 |
|
* @param s the stream |
1242 |
|
*/ |
1243 |
|
private void writeObject(java.io.ObjectOutputStream s) |
1248 |
|
|
1249 |
|
/** |
1250 |
|
* Reconstitute the instance from a stream. |
1251 |
+ |
* |
1252 |
|
* @param s the stream |
1253 |
|
*/ |
1254 |
|
private void readObject(java.io.ObjectInputStream s) |
1258 |
|
status |= EXTERNAL_SIGNAL; // conservatively set external signal |
1259 |
|
Object ex = s.readObject(); |
1260 |
|
if (ex != null) |
1261 |
< |
setDoneExceptionally((Throwable)ex); |
1261 |
> |
setDoneExceptionally((Throwable) ex); |
1262 |
|
} |
1263 |
|
|
1264 |
< |
// Temporary Unsafe mechanics for preliminary release |
1264 |
> |
// Unsafe mechanics |
1265 |
|
|
1266 |
< |
static final Unsafe _unsafe; |
1267 |
< |
static final long statusOffset; |
1266 |
> |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1267 |
> |
private static final long statusOffset = |
1268 |
> |
objectFieldOffset("status", ForkJoinTask.class); |
1269 |
|
|
1270 |
< |
static { |
1270 |
> |
private static long objectFieldOffset(String field, Class<?> klazz) { |
1271 |
|
try { |
1272 |
< |
if (ForkJoinTask.class.getClassLoader() != null) { |
1273 |
< |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
1274 |
< |
f.setAccessible(true); |
1275 |
< |
_unsafe = (Unsafe)f.get(null); |
1276 |
< |
} |
1277 |
< |
else |
1278 |
< |
_unsafe = Unsafe.getUnsafe(); |
1025 |
< |
statusOffset = _unsafe.objectFieldOffset |
1026 |
< |
(ForkJoinTask.class.getDeclaredField("status")); |
1027 |
< |
} catch (Exception ex) { throw new Error(ex); } |
1272 |
> |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1273 |
> |
} catch (NoSuchFieldException e) { |
1274 |
> |
// Convert Exception to corresponding Error |
1275 |
> |
NoSuchFieldError error = new NoSuchFieldError(field); |
1276 |
> |
error.initCause(e); |
1277 |
> |
throw error; |
1278 |
> |
} |
1279 |
|
} |
1280 |
|
|
1281 |
+ |
/** |
1282 |
+ |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
1283 |
+ |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
1284 |
+ |
* into a jdk. |
1285 |
+ |
* |
1286 |
+ |
* @return a sun.misc.Unsafe |
1287 |
+ |
*/ |
1288 |
+ |
private static sun.misc.Unsafe getUnsafe() { |
1289 |
+ |
try { |
1290 |
+ |
return sun.misc.Unsafe.getUnsafe(); |
1291 |
+ |
} catch (SecurityException se) { |
1292 |
+ |
try { |
1293 |
+ |
return java.security.AccessController.doPrivileged |
1294 |
+ |
(new java.security |
1295 |
+ |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1296 |
+ |
public sun.misc.Unsafe run() throws Exception { |
1297 |
+ |
java.lang.reflect.Field f = sun.misc |
1298 |
+ |
.Unsafe.class.getDeclaredField("theUnsafe"); |
1299 |
+ |
f.setAccessible(true); |
1300 |
+ |
return (sun.misc.Unsafe) f.get(null); |
1301 |
+ |
}}); |
1302 |
+ |
} catch (java.security.PrivilegedActionException e) { |
1303 |
+ |
throw new RuntimeException("Could not initialize intrinsics", |
1304 |
+ |
e.getCause()); |
1305 |
+ |
} |
1306 |
+ |
} |
1307 |
+ |
} |
1308 |
|
} |