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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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dl |
1.4 |
* |
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jsr166 |
1.28 |
* <p>A "main" {@code ForkJoinTask} begins execution when submitted |
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* to a {@link ForkJoinPool}. Once started, it will usually in turn |
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* start other subtasks. As indicated by the name of this class, |
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* many programs using {@code ForkJoinTask} employ only methods |
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* {@link #fork} and {@link #join}, or derivatives such as {@link |
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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 |
1.28 |
* additionally include RejectedExecutionExceptions stemming from |
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* internal resource exhaustion such as failure to allocate internal |
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* task queues. |
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dl |
1.1 |
* |
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dl |
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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1.2 |
* conventions. Method {@link #helpJoin} enables callers to actively |
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* execute other tasks while awaiting joins, which is sometimes more |
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* efficient but only applies when all subtasks are known to be |
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* strictly tree-structured. Method {@link #invoke} is semantically |
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jsr166 |
1.8 |
* equivalent to {@code fork(); join()} but always attempts to |
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dl |
1.2 |
* begin execution in the current thread. The "<em>quiet</em>" forms |
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* of 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 |
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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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dl |
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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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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dl |
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} |
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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 |
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dl |
1.32 |
* instances of different task subclasses to call each other's |
90 |
dl |
1.2 |
* methods), some of them may only be called from within other |
91 |
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 |
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dl |
1.13 |
* ClassCastException. |
95 |
dl |
1.1 |
* |
96 |
dl |
1.32 |
* <p>Most base support methods are {@code final}, to prevent |
97 |
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* overriding of implementations that are intrinsically tied to the |
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* underlying lightweight task scheduling framework. Developers |
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* creating new basic styles of fork/join processing should minimally |
100 |
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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. |
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dl |
1.1 |
* |
106 |
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* <p>ForkJoinTasks should perform relatively small amounts of |
107 |
dl |
1.32 |
* computation. Large tasks should be split into smaller subtasks, |
108 |
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* usually via recursive decomposition. As a very rough rule of thumb, |
109 |
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* a task should perform more than 100 and less than 10000 basic |
110 |
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* computational steps. If tasks are too big, then parallelism cannot |
111 |
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* improve throughput. If too small, then memory and internal task |
112 |
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* maintenance overhead may overwhelm processing. |
113 |
dl |
1.1 |
* |
114 |
dl |
1.27 |
* <p>This class provides {@code adapt} methods for {@link |
115 |
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* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that |
116 |
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* may be of use when mixing execution of ForkJoinTasks with other |
117 |
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* kinds of tasks. When all tasks are of this form, consider using a |
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* pool in {@link ForkJoinPool#setAsyncMode}. |
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* |
120 |
dl |
1.32 |
* <p>ForkJoinTasks are {@code Serializable}, which enables them to be |
121 |
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* used in extensions such as remote execution frameworks. It is |
122 |
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* sensible to serialize tasks only before or after, but not during, |
123 |
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* execution. Serialization is not relied on during execution itself. |
124 |
jsr166 |
1.12 |
* |
125 |
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* @since 1.7 |
126 |
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* @author Doug Lea |
127 |
dl |
1.1 |
*/ |
128 |
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public abstract class ForkJoinTask<V> implements Future<V>, Serializable { |
129 |
dl |
1.2 |
|
130 |
dl |
1.1 |
/** |
131 |
dl |
1.2 |
* Run control status bits packed into a single int to minimize |
132 |
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* footprint and to ensure atomicity (via CAS). Status is |
133 |
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* initially zero, and takes on nonnegative values until |
134 |
dl |
1.1 |
* completed, upon which status holds COMPLETED. CANCELLED, or |
135 |
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* EXCEPTIONAL, which use the top 3 bits. Tasks undergoing |
136 |
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* blocking waits by other threads have SIGNAL_MASK bits set -- |
137 |
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* bit 15 for external (nonFJ) waits, and the rest a count of |
138 |
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* waiting FJ threads. (This representation relies on |
139 |
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* ForkJoinPool max thread limits). Completion of a stolen task |
140 |
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* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even |
141 |
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* though suboptimal for some purposes, we use basic builtin |
142 |
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* wait/notify to take advantage of "monitor inflation" in JVMs |
143 |
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* that we would otherwise need to emulate to avoid adding further |
144 |
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* per-task bookkeeping overhead. Note that bits 16-28 are |
145 |
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* currently unused. Also value 0x80000000 is available as spare |
146 |
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* completion value. |
147 |
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*/ |
148 |
jsr166 |
1.9 |
volatile int status; // accessed directly by pool and workers |
149 |
dl |
1.1 |
|
150 |
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static final int COMPLETION_MASK = 0xe0000000; |
151 |
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static final int NORMAL = 0xe0000000; // == mask |
152 |
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static final int CANCELLED = 0xc0000000; |
153 |
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static final int EXCEPTIONAL = 0xa0000000; |
154 |
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static final int SIGNAL_MASK = 0x0000ffff; |
155 |
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static final int INTERNAL_SIGNAL_MASK = 0x00007fff; |
156 |
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static final int EXTERNAL_SIGNAL = 0x00008000; // top bit of low word |
157 |
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158 |
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/** |
159 |
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* Table of exceptions thrown by tasks, to enable reporting by |
160 |
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* callers. Because exceptions are rare, we don't directly keep |
161 |
jsr166 |
1.10 |
* them with task objects, but instead use a weak ref table. Note |
162 |
dl |
1.1 |
* that cancellation exceptions don't appear in the table, but are |
163 |
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* instead recorded as status values. |
164 |
jsr166 |
1.10 |
* TODO: Use ConcurrentReferenceHashMap |
165 |
dl |
1.1 |
*/ |
166 |
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static final Map<ForkJoinTask<?>, Throwable> exceptionMap = |
167 |
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Collections.synchronizedMap |
168 |
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(new WeakHashMap<ForkJoinTask<?>, Throwable>()); |
169 |
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170 |
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// within-package utilities |
171 |
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172 |
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/** |
173 |
jsr166 |
1.10 |
* Gets current worker thread, or null if not a worker thread. |
174 |
dl |
1.1 |
*/ |
175 |
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static ForkJoinWorkerThread getWorker() { |
176 |
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Thread t = Thread.currentThread(); |
177 |
jsr166 |
1.14 |
return ((t instanceof ForkJoinWorkerThread) ? |
178 |
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(ForkJoinWorkerThread) t : null); |
179 |
dl |
1.1 |
} |
180 |
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181 |
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final boolean casStatus(int cmp, int val) { |
182 |
jsr166 |
1.11 |
return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val); |
183 |
dl |
1.1 |
} |
184 |
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185 |
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/** |
186 |
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* Workaround for not being able to rethrow unchecked exceptions. |
187 |
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*/ |
188 |
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static void rethrowException(Throwable ex) { |
189 |
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if (ex != null) |
190 |
jsr166 |
1.11 |
UNSAFE.throwException(ex); |
191 |
dl |
1.1 |
} |
192 |
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193 |
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// Setting completion status |
194 |
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195 |
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/** |
196 |
jsr166 |
1.10 |
* Marks completion and wakes up threads waiting to join this task. |
197 |
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* |
198 |
dl |
1.1 |
* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
199 |
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*/ |
200 |
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final void setCompletion(int completion) { |
201 |
dl |
1.2 |
ForkJoinPool pool = getPool(); |
202 |
dl |
1.1 |
if (pool != null) { |
203 |
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int s; // Clear signal bits while setting completion status |
204 |
jsr166 |
1.14 |
do {} while ((s = status) >= 0 && !casStatus(s, completion)); |
205 |
dl |
1.1 |
|
206 |
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if ((s & SIGNAL_MASK) != 0) { |
207 |
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if ((s &= INTERNAL_SIGNAL_MASK) != 0) |
208 |
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pool.updateRunningCount(s); |
209 |
jsr166 |
1.14 |
synchronized (this) { notifyAll(); } |
210 |
dl |
1.1 |
} |
211 |
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} |
212 |
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else |
213 |
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externallySetCompletion(completion); |
214 |
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} |
215 |
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216 |
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/** |
217 |
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* Version of setCompletion for non-FJ threads. Leaves signal |
218 |
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* bits for unblocked threads to adjust, and always notifies. |
219 |
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*/ |
220 |
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private void externallySetCompletion(int completion) { |
221 |
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int s; |
222 |
jsr166 |
1.14 |
do {} while ((s = status) >= 0 && |
223 |
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!casStatus(s, (s & SIGNAL_MASK) | completion)); |
224 |
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synchronized (this) { notifyAll(); } |
225 |
dl |
1.1 |
} |
226 |
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227 |
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/** |
228 |
jsr166 |
1.14 |
* Sets status to indicate normal completion. |
229 |
dl |
1.1 |
*/ |
230 |
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final void setNormalCompletion() { |
231 |
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// Try typical fast case -- single CAS, no signal, not already done. |
232 |
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// Manually expand casStatus to improve chances of inlining it |
233 |
jsr166 |
1.11 |
if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL)) |
234 |
dl |
1.1 |
setCompletion(NORMAL); |
235 |
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} |
236 |
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237 |
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// internal waiting and notification |
238 |
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239 |
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/** |
240 |
jsr166 |
1.14 |
* Performs the actual monitor wait for awaitDone. |
241 |
dl |
1.1 |
*/ |
242 |
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private void doAwaitDone() { |
243 |
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// Minimize lock bias and in/de-flation effects by maximizing |
244 |
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// chances of waiting inside sync |
245 |
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try { |
246 |
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while (status >= 0) |
247 |
jsr166 |
1.14 |
synchronized (this) { if (status >= 0) wait(); } |
248 |
dl |
1.1 |
} catch (InterruptedException ie) { |
249 |
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onInterruptedWait(); |
250 |
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} |
251 |
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} |
252 |
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253 |
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/** |
254 |
jsr166 |
1.14 |
* Performs the actual timed monitor wait for awaitDone. |
255 |
dl |
1.1 |
*/ |
256 |
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private void doAwaitDone(long startTime, long nanos) { |
257 |
jsr166 |
1.14 |
synchronized (this) { |
258 |
dl |
1.1 |
try { |
259 |
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while (status >= 0) { |
260 |
dl |
1.25 |
long nt = nanos - (System.nanoTime() - startTime); |
261 |
dl |
1.1 |
if (nt <= 0) |
262 |
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break; |
263 |
jsr166 |
1.14 |
wait(nt / 1000000, (int) (nt % 1000000)); |
264 |
dl |
1.1 |
} |
265 |
|
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} catch (InterruptedException ie) { |
266 |
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onInterruptedWait(); |
267 |
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} |
268 |
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} |
269 |
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} |
270 |
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|
271 |
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// Awaiting completion |
272 |
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273 |
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/** |
274 |
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* Sets status to indicate there is joiner, then waits for join, |
275 |
|
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* surrounded with pool notifications. |
276 |
jsr166 |
1.10 |
* |
277 |
dl |
1.1 |
* @return status upon exit |
278 |
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*/ |
279 |
jsr166 |
1.14 |
private int awaitDone(ForkJoinWorkerThread w, |
280 |
|
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boolean maintainParallelism) { |
281 |
|
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ForkJoinPool pool = (w == null) ? null : w.pool; |
282 |
dl |
1.1 |
int s; |
283 |
|
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while ((s = status) >= 0) { |
284 |
jsr166 |
1.14 |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
285 |
dl |
1.1 |
if (pool == null || !pool.preJoin(this, maintainParallelism)) |
286 |
|
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doAwaitDone(); |
287 |
|
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if (((s = status) & INTERNAL_SIGNAL_MASK) != 0) |
288 |
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adjustPoolCountsOnUnblock(pool); |
289 |
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break; |
290 |
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} |
291 |
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} |
292 |
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return s; |
293 |
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} |
294 |
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|
295 |
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/** |
296 |
|
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* Timed version of awaitDone |
297 |
jsr166 |
1.14 |
* |
298 |
dl |
1.1 |
* @return status upon exit |
299 |
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*/ |
300 |
dl |
1.3 |
private int awaitDone(ForkJoinWorkerThread w, long nanos) { |
301 |
jsr166 |
1.14 |
ForkJoinPool pool = (w == null) ? null : w.pool; |
302 |
dl |
1.1 |
int s; |
303 |
|
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while ((s = status) >= 0) { |
304 |
jsr166 |
1.14 |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
305 |
dl |
1.1 |
long startTime = System.nanoTime(); |
306 |
|
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if (pool == null || !pool.preJoin(this, false)) |
307 |
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doAwaitDone(startTime, nanos); |
308 |
|
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if ((s = status) >= 0) { |
309 |
|
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adjustPoolCountsOnCancelledWait(pool); |
310 |
|
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s = status; |
311 |
|
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} |
312 |
|
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if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0) |
313 |
|
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adjustPoolCountsOnUnblock(pool); |
314 |
|
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break; |
315 |
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} |
316 |
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} |
317 |
|
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return s; |
318 |
|
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} |
319 |
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|
320 |
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/** |
321 |
jsr166 |
1.10 |
* Notifies pool that thread is unblocked. Called by signalled |
322 |
dl |
1.1 |
* threads when woken by non-FJ threads (which is atypical). |
323 |
|
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*/ |
324 |
|
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private void adjustPoolCountsOnUnblock(ForkJoinPool pool) { |
325 |
|
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int s; |
326 |
jsr166 |
1.14 |
do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK)); |
327 |
dl |
1.1 |
if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0) |
328 |
|
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pool.updateRunningCount(s); |
329 |
|
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} |
330 |
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|
331 |
|
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/** |
332 |
jsr166 |
1.10 |
* Notifies pool to adjust counts on cancelled or timed out wait. |
333 |
dl |
1.1 |
*/ |
334 |
|
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private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) { |
335 |
|
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if (pool != null) { |
336 |
|
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int s; |
337 |
|
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while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) { |
338 |
|
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if (casStatus(s, s - 1)) { |
339 |
|
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pool.updateRunningCount(1); |
340 |
|
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break; |
341 |
|
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} |
342 |
|
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} |
343 |
|
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} |
344 |
|
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} |
345 |
|
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|
346 |
dl |
1.2 |
/** |
347 |
jsr166 |
1.10 |
* Handles interruptions during waits. |
348 |
dl |
1.2 |
*/ |
349 |
dl |
1.1 |
private void onInterruptedWait() { |
350 |
dl |
1.2 |
ForkJoinWorkerThread w = getWorker(); |
351 |
|
|
if (w == null) |
352 |
|
|
Thread.currentThread().interrupt(); // re-interrupt |
353 |
|
|
else if (w.isTerminating()) |
354 |
dl |
1.3 |
cancelIgnoringExceptions(); |
355 |
dl |
1.2 |
// else if FJworker, ignore interrupt |
356 |
dl |
1.1 |
} |
357 |
|
|
|
358 |
|
|
// Recording and reporting exceptions |
359 |
|
|
|
360 |
|
|
private void setDoneExceptionally(Throwable rex) { |
361 |
|
|
exceptionMap.put(this, rex); |
362 |
|
|
setCompletion(EXCEPTIONAL); |
363 |
|
|
} |
364 |
|
|
|
365 |
|
|
/** |
366 |
jsr166 |
1.10 |
* Throws the exception associated with status s. |
367 |
|
|
* |
368 |
dl |
1.1 |
* @throws the exception |
369 |
|
|
*/ |
370 |
|
|
private void reportException(int s) { |
371 |
|
|
if ((s &= COMPLETION_MASK) < NORMAL) { |
372 |
|
|
if (s == CANCELLED) |
373 |
|
|
throw new CancellationException(); |
374 |
|
|
else |
375 |
|
|
rethrowException(exceptionMap.get(this)); |
376 |
|
|
} |
377 |
|
|
} |
378 |
|
|
|
379 |
|
|
/** |
380 |
jsr166 |
1.10 |
* Returns result or throws exception using j.u.c.Future conventions. |
381 |
jsr166 |
1.14 |
* Only call when {@code isDone} known to be true. |
382 |
dl |
1.1 |
*/ |
383 |
|
|
private V reportFutureResult() |
384 |
|
|
throws ExecutionException, InterruptedException { |
385 |
|
|
int s = status & COMPLETION_MASK; |
386 |
|
|
if (s < NORMAL) { |
387 |
|
|
Throwable ex; |
388 |
|
|
if (s == CANCELLED) |
389 |
|
|
throw new CancellationException(); |
390 |
|
|
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
391 |
|
|
throw new ExecutionException(ex); |
392 |
|
|
if (Thread.interrupted()) |
393 |
|
|
throw new InterruptedException(); |
394 |
|
|
} |
395 |
|
|
return getRawResult(); |
396 |
|
|
} |
397 |
|
|
|
398 |
|
|
/** |
399 |
|
|
* Returns result or throws exception using j.u.c.Future conventions |
400 |
jsr166 |
1.10 |
* with timeouts. |
401 |
dl |
1.1 |
*/ |
402 |
|
|
private V reportTimedFutureResult() |
403 |
|
|
throws InterruptedException, ExecutionException, TimeoutException { |
404 |
|
|
Throwable ex; |
405 |
|
|
int s = status & COMPLETION_MASK; |
406 |
|
|
if (s == NORMAL) |
407 |
|
|
return getRawResult(); |
408 |
|
|
if (s == CANCELLED) |
409 |
|
|
throw new CancellationException(); |
410 |
|
|
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
411 |
|
|
throw new ExecutionException(ex); |
412 |
|
|
if (Thread.interrupted()) |
413 |
|
|
throw new InterruptedException(); |
414 |
|
|
throw new TimeoutException(); |
415 |
|
|
} |
416 |
|
|
|
417 |
|
|
// internal execution methods |
418 |
|
|
|
419 |
|
|
/** |
420 |
|
|
* Calls exec, recording completion, and rethrowing exception if |
421 |
jsr166 |
1.10 |
* encountered. Caller should normally check status before calling. |
422 |
|
|
* |
423 |
dl |
1.1 |
* @return true if completed normally |
424 |
|
|
*/ |
425 |
|
|
private boolean tryExec() { |
426 |
|
|
try { // try block must contain only call to exec |
427 |
|
|
if (!exec()) |
428 |
|
|
return false; |
429 |
|
|
} catch (Throwable rex) { |
430 |
|
|
setDoneExceptionally(rex); |
431 |
|
|
rethrowException(rex); |
432 |
|
|
return false; // not reached |
433 |
|
|
} |
434 |
|
|
setNormalCompletion(); |
435 |
|
|
return true; |
436 |
|
|
} |
437 |
|
|
|
438 |
|
|
/** |
439 |
|
|
* Main execution method used by worker threads. Invokes |
440 |
jsr166 |
1.10 |
* base computation unless already complete. |
441 |
dl |
1.1 |
*/ |
442 |
|
|
final void quietlyExec() { |
443 |
|
|
if (status >= 0) { |
444 |
|
|
try { |
445 |
|
|
if (!exec()) |
446 |
|
|
return; |
447 |
jsr166 |
1.14 |
} catch (Throwable rex) { |
448 |
dl |
1.1 |
setDoneExceptionally(rex); |
449 |
|
|
return; |
450 |
|
|
} |
451 |
|
|
setNormalCompletion(); |
452 |
|
|
} |
453 |
|
|
} |
454 |
|
|
|
455 |
|
|
/** |
456 |
jsr166 |
1.10 |
* Calls exec(), recording but not rethrowing exception. |
457 |
|
|
* Caller should normally check status before calling. |
458 |
|
|
* |
459 |
dl |
1.1 |
* @return true if completed normally |
460 |
|
|
*/ |
461 |
|
|
private boolean tryQuietlyInvoke() { |
462 |
|
|
try { |
463 |
|
|
if (!exec()) |
464 |
|
|
return false; |
465 |
|
|
} catch (Throwable rex) { |
466 |
|
|
setDoneExceptionally(rex); |
467 |
|
|
return false; |
468 |
|
|
} |
469 |
|
|
setNormalCompletion(); |
470 |
|
|
return true; |
471 |
|
|
} |
472 |
|
|
|
473 |
|
|
/** |
474 |
jsr166 |
1.10 |
* Cancels, ignoring any exceptions it throws. |
475 |
dl |
1.1 |
*/ |
476 |
dl |
1.3 |
final void cancelIgnoringExceptions() { |
477 |
dl |
1.1 |
try { |
478 |
|
|
cancel(false); |
479 |
jsr166 |
1.14 |
} catch (Throwable ignore) { |
480 |
dl |
1.1 |
} |
481 |
|
|
} |
482 |
|
|
|
483 |
dl |
1.3 |
/** |
484 |
|
|
* Main implementation of helpJoin |
485 |
|
|
*/ |
486 |
|
|
private int busyJoin(ForkJoinWorkerThread w) { |
487 |
|
|
int s; |
488 |
|
|
ForkJoinTask<?> t; |
489 |
|
|
while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null) |
490 |
|
|
t.quietlyExec(); |
491 |
jsr166 |
1.14 |
return (s >= 0) ? awaitDone(w, false) : s; // block if no work |
492 |
dl |
1.3 |
} |
493 |
|
|
|
494 |
dl |
1.1 |
// public methods |
495 |
|
|
|
496 |
|
|
/** |
497 |
|
|
* Arranges to asynchronously execute this task. While it is not |
498 |
|
|
* necessarily enforced, it is a usage error to fork a task more |
499 |
jsr166 |
1.31 |
* than once unless it has completed and been reinitialized. |
500 |
dl |
1.18 |
* |
501 |
jsr166 |
1.31 |
* <p>This method may be invoked only from within {@code |
502 |
|
|
* ForkJoinTask} computations (as may be determined using method |
503 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
504 |
|
|
* result in exceptions or errors, possibly including {@code |
505 |
|
|
* ClassCastException}. |
506 |
|
|
* |
507 |
|
|
* @return {@code this}, to simplify usage |
508 |
dl |
1.1 |
*/ |
509 |
dl |
1.18 |
public final ForkJoinTask<V> fork() { |
510 |
jsr166 |
1.14 |
((ForkJoinWorkerThread) Thread.currentThread()) |
511 |
|
|
.pushTask(this); |
512 |
dl |
1.18 |
return this; |
513 |
dl |
1.1 |
} |
514 |
|
|
|
515 |
|
|
/** |
516 |
|
|
* Returns the result of the computation when it is ready. |
517 |
jsr166 |
1.31 |
* This method differs from {@link #get()} in that |
518 |
|
|
* abnormal completion results in {@code RuntimeException} or |
519 |
|
|
* {@code Error}, not {@code ExecutionException}. |
520 |
dl |
1.1 |
* |
521 |
|
|
* @return the computed result |
522 |
|
|
*/ |
523 |
|
|
public final V join() { |
524 |
|
|
ForkJoinWorkerThread w = getWorker(); |
525 |
|
|
if (w == null || status < 0 || !w.unpushTask(this) || !tryExec()) |
526 |
|
|
reportException(awaitDone(w, true)); |
527 |
|
|
return getRawResult(); |
528 |
|
|
} |
529 |
|
|
|
530 |
|
|
/** |
531 |
dl |
1.2 |
* Commences performing this task, awaits its completion if |
532 |
|
|
* necessary, and return its result. |
533 |
jsr166 |
1.10 |
* |
534 |
dl |
1.1 |
* @throws Throwable (a RuntimeException, Error, or unchecked |
535 |
jsr166 |
1.10 |
* exception) if the underlying computation did so |
536 |
dl |
1.1 |
* @return the computed result |
537 |
|
|
*/ |
538 |
|
|
public final V invoke() { |
539 |
|
|
if (status >= 0 && tryExec()) |
540 |
|
|
return getRawResult(); |
541 |
|
|
else |
542 |
|
|
return join(); |
543 |
|
|
} |
544 |
|
|
|
545 |
|
|
/** |
546 |
jsr166 |
1.31 |
* Forks the given tasks, returning when {@code isDone} holds |
547 |
|
|
* for each task or an exception is encountered. |
548 |
|
|
* |
549 |
|
|
* <p>This method may be invoked only from within {@code |
550 |
|
|
* ForkJoinTask} computations (as may be determined using method |
551 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
552 |
|
|
* result in exceptions or errors, possibly including {@code |
553 |
|
|
* ClassCastException}. |
554 |
jsr166 |
1.10 |
* |
555 |
dl |
1.27 |
* @param t1 the first task |
556 |
|
|
* @param t2 the second task |
557 |
|
|
* @throws NullPointerException if any task is null |
558 |
|
|
* @throws RuntimeException or Error if a task did so |
559 |
dl |
1.1 |
*/ |
560 |
jsr166 |
1.31 |
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) { |
561 |
dl |
1.2 |
t2.fork(); |
562 |
|
|
t1.invoke(); |
563 |
|
|
t2.join(); |
564 |
dl |
1.1 |
} |
565 |
|
|
|
566 |
|
|
/** |
567 |
dl |
1.27 |
* Forks the given tasks, returning when {@code isDone} holds for |
568 |
|
|
* each task or an exception is encountered. If any task |
569 |
|
|
* encounters an exception, others may be, but are not guaranteed |
570 |
jsr166 |
1.31 |
* to be, cancelled. |
571 |
|
|
* |
572 |
|
|
* <p>This method may be invoked only from within {@code |
573 |
|
|
* ForkJoinTask} computations (as may be determined using method |
574 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
575 |
|
|
* result in exceptions or errors, possibly including {@code |
576 |
|
|
* ClassCastException}. |
577 |
jsr166 |
1.14 |
* |
578 |
dl |
1.27 |
* @param tasks the tasks |
579 |
jsr166 |
1.10 |
* @throws NullPointerException if tasks or any element are null |
580 |
|
|
* @throws RuntimeException or Error if any task did so |
581 |
dl |
1.1 |
*/ |
582 |
dl |
1.2 |
public static void invokeAll(ForkJoinTask<?>... tasks) { |
583 |
|
|
Throwable ex = null; |
584 |
|
|
int last = tasks.length - 1; |
585 |
|
|
for (int i = last; i >= 0; --i) { |
586 |
|
|
ForkJoinTask<?> t = tasks[i]; |
587 |
|
|
if (t == null) { |
588 |
|
|
if (ex == null) |
589 |
|
|
ex = new NullPointerException(); |
590 |
|
|
} |
591 |
|
|
else if (i != 0) |
592 |
|
|
t.fork(); |
593 |
|
|
else { |
594 |
|
|
t.quietlyInvoke(); |
595 |
|
|
if (ex == null) |
596 |
|
|
ex = t.getException(); |
597 |
|
|
} |
598 |
|
|
} |
599 |
|
|
for (int i = 1; i <= last; ++i) { |
600 |
|
|
ForkJoinTask<?> t = tasks[i]; |
601 |
|
|
if (t != null) { |
602 |
|
|
if (ex != null) |
603 |
|
|
t.cancel(false); |
604 |
|
|
else { |
605 |
|
|
t.quietlyJoin(); |
606 |
|
|
if (ex == null) |
607 |
|
|
ex = t.getException(); |
608 |
|
|
} |
609 |
|
|
} |
610 |
dl |
1.1 |
} |
611 |
dl |
1.2 |
if (ex != null) |
612 |
|
|
rethrowException(ex); |
613 |
dl |
1.1 |
} |
614 |
|
|
|
615 |
|
|
/** |
616 |
dl |
1.32 |
* Forks all tasks in the specified collection, returning when |
617 |
|
|
* {@code isDone} holds for each task or an exception is |
618 |
|
|
* encountered. If any task encounters an exception, others may |
619 |
|
|
* be, but are not guaranteed to be, cancelled. The behavior of |
620 |
|
|
* this operation is undefined if the specified collection is |
621 |
|
|
* modified while the operation is in progress. |
622 |
jsr166 |
1.31 |
* |
623 |
|
|
* <p>This method may be invoked only from within {@code |
624 |
|
|
* ForkJoinTask} computations (as may be determined using method |
625 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
626 |
|
|
* result in exceptions or errors, possibly including {@code |
627 |
|
|
* ClassCastException}. |
628 |
jsr166 |
1.10 |
* |
629 |
dl |
1.2 |
* @param tasks the collection of tasks |
630 |
dl |
1.19 |
* @return the tasks argument, to simplify usage |
631 |
jsr166 |
1.10 |
* @throws NullPointerException if tasks or any element are null |
632 |
|
|
* @throws RuntimeException or Error if any task did so |
633 |
dl |
1.1 |
*/ |
634 |
dl |
1.19 |
public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) { |
635 |
dl |
1.32 |
if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) { |
636 |
jsr166 |
1.14 |
invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()])); |
637 |
dl |
1.19 |
return tasks; |
638 |
dl |
1.2 |
} |
639 |
jsr166 |
1.15 |
@SuppressWarnings("unchecked") |
640 |
dl |
1.2 |
List<? extends ForkJoinTask<?>> ts = |
641 |
jsr166 |
1.14 |
(List<? extends ForkJoinTask<?>>) tasks; |
642 |
dl |
1.2 |
Throwable ex = null; |
643 |
|
|
int last = ts.size() - 1; |
644 |
|
|
for (int i = last; i >= 0; --i) { |
645 |
|
|
ForkJoinTask<?> t = ts.get(i); |
646 |
|
|
if (t == null) { |
647 |
|
|
if (ex == null) |
648 |
|
|
ex = new NullPointerException(); |
649 |
|
|
} |
650 |
|
|
else if (i != 0) |
651 |
|
|
t.fork(); |
652 |
|
|
else { |
653 |
|
|
t.quietlyInvoke(); |
654 |
|
|
if (ex == null) |
655 |
|
|
ex = t.getException(); |
656 |
|
|
} |
657 |
|
|
} |
658 |
|
|
for (int i = 1; i <= last; ++i) { |
659 |
|
|
ForkJoinTask<?> t = ts.get(i); |
660 |
|
|
if (t != null) { |
661 |
|
|
if (ex != null) |
662 |
|
|
t.cancel(false); |
663 |
|
|
else { |
664 |
|
|
t.quietlyJoin(); |
665 |
|
|
if (ex == null) |
666 |
|
|
ex = t.getException(); |
667 |
|
|
} |
668 |
|
|
} |
669 |
|
|
} |
670 |
|
|
if (ex != null) |
671 |
|
|
rethrowException(ex); |
672 |
dl |
1.19 |
return tasks; |
673 |
dl |
1.1 |
} |
674 |
|
|
|
675 |
|
|
/** |
676 |
jsr166 |
1.23 |
* Returns {@code true} if the computation performed by this task |
677 |
|
|
* has completed (or has been cancelled). |
678 |
jsr166 |
1.10 |
* |
679 |
jsr166 |
1.23 |
* @return {@code true} if this computation has completed |
680 |
dl |
1.1 |
*/ |
681 |
|
|
public final boolean isDone() { |
682 |
|
|
return status < 0; |
683 |
|
|
} |
684 |
|
|
|
685 |
|
|
/** |
686 |
jsr166 |
1.23 |
* Returns {@code true} if this task was cancelled. |
687 |
jsr166 |
1.10 |
* |
688 |
jsr166 |
1.23 |
* @return {@code true} if this task was cancelled |
689 |
dl |
1.1 |
*/ |
690 |
|
|
public final boolean isCancelled() { |
691 |
|
|
return (status & COMPLETION_MASK) == CANCELLED; |
692 |
|
|
} |
693 |
|
|
|
694 |
|
|
/** |
695 |
|
|
* Asserts that the results of this task's computation will not be |
696 |
jsr166 |
1.9 |
* used. If a cancellation occurs before attempting to execute this |
697 |
jsr166 |
1.24 |
* task, execution will be suppressed, {@link #isCancelled} |
698 |
|
|
* will report true, and {@link #join} will result in a |
699 |
jsr166 |
1.8 |
* {@code CancellationException} being thrown. Otherwise, when |
700 |
dl |
1.1 |
* cancellation races with completion, there are no guarantees |
701 |
jsr166 |
1.24 |
* about whether {@code isCancelled} will report {@code true}, |
702 |
|
|
* whether {@code join} will return normally or via an exception, |
703 |
|
|
* or whether these behaviors will remain consistent upon repeated |
704 |
dl |
1.1 |
* invocation. |
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 |
jsr166 |
1.29 |
* the {@code cancel} method itself must not throw exceptions. |
709 |
dl |
1.1 |
* |
710 |
jsr166 |
1.28 |
* <p>This method is designed to be invoked by <em>other</em> |
711 |
dl |
1.1 |
* tasks. To terminate the current task, you can just return or |
712 |
|
|
* throw an unchecked exception from its computation method, or |
713 |
jsr166 |
1.24 |
* invoke {@link #completeExceptionally}. |
714 |
dl |
1.1 |
* |
715 |
|
|
* @param mayInterruptIfRunning this value is ignored in the |
716 |
|
|
* default implementation because tasks are not in general |
717 |
jsr166 |
1.14 |
* cancelled via interruption |
718 |
dl |
1.1 |
* |
719 |
jsr166 |
1.23 |
* @return {@code true} if this task is now cancelled |
720 |
dl |
1.1 |
*/ |
721 |
|
|
public boolean cancel(boolean mayInterruptIfRunning) { |
722 |
|
|
setCompletion(CANCELLED); |
723 |
|
|
return (status & COMPLETION_MASK) == CANCELLED; |
724 |
|
|
} |
725 |
|
|
|
726 |
|
|
/** |
727 |
jsr166 |
1.23 |
* Returns {@code true} if this task threw an exception or was cancelled. |
728 |
jsr166 |
1.10 |
* |
729 |
jsr166 |
1.23 |
* @return {@code true} if this task threw an exception or was cancelled |
730 |
dl |
1.3 |
*/ |
731 |
|
|
public final boolean isCompletedAbnormally() { |
732 |
|
|
return (status & COMPLETION_MASK) < NORMAL; |
733 |
|
|
} |
734 |
|
|
|
735 |
|
|
/** |
736 |
|
|
* Returns the exception thrown by the base computation, or a |
737 |
jsr166 |
1.29 |
* {@code CancellationException} if cancelled, or {@code null} if |
738 |
|
|
* none or if the method has not yet completed. |
739 |
jsr166 |
1.10 |
* |
740 |
jsr166 |
1.23 |
* @return the exception, or {@code null} if none |
741 |
dl |
1.3 |
*/ |
742 |
|
|
public final Throwable getException() { |
743 |
|
|
int s = status & COMPLETION_MASK; |
744 |
|
|
if (s >= NORMAL) |
745 |
|
|
return null; |
746 |
|
|
if (s == CANCELLED) |
747 |
|
|
return new CancellationException(); |
748 |
|
|
return exceptionMap.get(this); |
749 |
|
|
} |
750 |
|
|
|
751 |
|
|
/** |
752 |
dl |
1.1 |
* Completes this task abnormally, and if not already aborted or |
753 |
|
|
* cancelled, causes it to throw the given exception upon |
754 |
jsr166 |
1.8 |
* {@code join} and related operations. This method may be used |
755 |
dl |
1.1 |
* to induce exceptions in asynchronous tasks, or to force |
756 |
dl |
1.2 |
* completion of tasks that would not otherwise complete. Its use |
757 |
dl |
1.27 |
* in other situations is discouraged. This method is |
758 |
jsr166 |
1.8 |
* overridable, but overridden versions must invoke {@code super} |
759 |
dl |
1.2 |
* implementation to maintain guarantees. |
760 |
|
|
* |
761 |
dl |
1.1 |
* @param ex the exception to throw. If this exception is |
762 |
|
|
* not a RuntimeException or Error, the actual exception thrown |
763 |
|
|
* will be a RuntimeException with cause ex. |
764 |
|
|
*/ |
765 |
|
|
public void completeExceptionally(Throwable ex) { |
766 |
|
|
setDoneExceptionally((ex instanceof RuntimeException) || |
767 |
jsr166 |
1.14 |
(ex instanceof Error) ? ex : |
768 |
dl |
1.1 |
new RuntimeException(ex)); |
769 |
|
|
} |
770 |
|
|
|
771 |
|
|
/** |
772 |
|
|
* Completes this task, and if not already aborted or cancelled, |
773 |
jsr166 |
1.8 |
* returning a {@code null} result upon {@code join} and related |
774 |
dl |
1.1 |
* operations. This method may be used to provide results for |
775 |
|
|
* asynchronous tasks, or to provide alternative handling for |
776 |
dl |
1.2 |
* tasks that would not otherwise complete normally. Its use in |
777 |
dl |
1.27 |
* other situations is discouraged. This method is |
778 |
jsr166 |
1.8 |
* overridable, but overridden versions must invoke {@code super} |
779 |
dl |
1.2 |
* implementation to maintain guarantees. |
780 |
dl |
1.1 |
* |
781 |
jsr166 |
1.10 |
* @param value the result value for this task |
782 |
dl |
1.1 |
*/ |
783 |
|
|
public void complete(V value) { |
784 |
|
|
try { |
785 |
|
|
setRawResult(value); |
786 |
jsr166 |
1.14 |
} catch (Throwable rex) { |
787 |
dl |
1.1 |
setDoneExceptionally(rex); |
788 |
|
|
return; |
789 |
|
|
} |
790 |
|
|
setNormalCompletion(); |
791 |
|
|
} |
792 |
|
|
|
793 |
dl |
1.3 |
public final V get() throws InterruptedException, ExecutionException { |
794 |
|
|
ForkJoinWorkerThread w = getWorker(); |
795 |
|
|
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
796 |
|
|
awaitDone(w, true); |
797 |
|
|
return reportFutureResult(); |
798 |
|
|
} |
799 |
|
|
|
800 |
|
|
public final V get(long timeout, TimeUnit unit) |
801 |
|
|
throws InterruptedException, ExecutionException, TimeoutException { |
802 |
dl |
1.25 |
long nanos = unit.toNanos(timeout); |
803 |
dl |
1.3 |
ForkJoinWorkerThread w = getWorker(); |
804 |
|
|
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
805 |
dl |
1.25 |
awaitDone(w, nanos); |
806 |
dl |
1.3 |
return reportTimedFutureResult(); |
807 |
|
|
} |
808 |
|
|
|
809 |
dl |
1.1 |
/** |
810 |
dl |
1.2 |
* Possibly executes other tasks until this task is ready, then |
811 |
|
|
* returns the result of the computation. This method may be more |
812 |
jsr166 |
1.8 |
* efficient than {@code join}, but is only applicable when |
813 |
jsr166 |
1.9 |
* there are no potential dependencies between continuation of the |
814 |
dl |
1.2 |
* current task and that of any other task that might be executed |
815 |
|
|
* while helping. (This usually holds for pure divide-and-conquer |
816 |
jsr166 |
1.31 |
* tasks). |
817 |
|
|
* |
818 |
|
|
* <p>This method may be invoked only from within {@code |
819 |
|
|
* ForkJoinTask} computations (as may be determined using method |
820 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
821 |
|
|
* result in exceptions or errors, possibly including {@code |
822 |
|
|
* ClassCastException}. |
823 |
jsr166 |
1.10 |
* |
824 |
dl |
1.2 |
* @return the computed result |
825 |
|
|
*/ |
826 |
|
|
public final V helpJoin() { |
827 |
jsr166 |
1.14 |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread(); |
828 |
dl |
1.2 |
if (status < 0 || !w.unpushTask(this) || !tryExec()) |
829 |
dl |
1.3 |
reportException(busyJoin(w)); |
830 |
dl |
1.2 |
return getRawResult(); |
831 |
|
|
} |
832 |
|
|
|
833 |
|
|
/** |
834 |
dl |
1.32 |
* Possibly executes other tasks until this task is ready. This |
835 |
|
|
* method may be useful when processing collections of tasks when |
836 |
|
|
* some have been cancelled or otherwise known to have aborted. |
837 |
jsr166 |
1.31 |
* |
838 |
|
|
* <p>This method may be invoked only from within {@code |
839 |
|
|
* ForkJoinTask} computations (as may be determined using method |
840 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
841 |
|
|
* result in exceptions or errors, possibly including {@code |
842 |
|
|
* ClassCastException}. |
843 |
dl |
1.2 |
*/ |
844 |
|
|
public final void quietlyHelpJoin() { |
845 |
|
|
if (status >= 0) { |
846 |
|
|
ForkJoinWorkerThread w = |
847 |
jsr166 |
1.14 |
(ForkJoinWorkerThread) Thread.currentThread(); |
848 |
dl |
1.2 |
if (!w.unpushTask(this) || !tryQuietlyInvoke()) |
849 |
dl |
1.3 |
busyJoin(w); |
850 |
dl |
1.2 |
} |
851 |
|
|
} |
852 |
|
|
|
853 |
|
|
/** |
854 |
|
|
* Joins this task, without returning its result or throwing an |
855 |
|
|
* exception. This method may be useful when processing |
856 |
|
|
* collections of tasks when some have been cancelled or otherwise |
857 |
|
|
* known to have aborted. |
858 |
|
|
*/ |
859 |
|
|
public final void quietlyJoin() { |
860 |
|
|
if (status >= 0) { |
861 |
|
|
ForkJoinWorkerThread w = getWorker(); |
862 |
|
|
if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke()) |
863 |
|
|
awaitDone(w, true); |
864 |
|
|
} |
865 |
|
|
} |
866 |
|
|
|
867 |
|
|
/** |
868 |
|
|
* Commences performing this task and awaits its completion if |
869 |
|
|
* necessary, without returning its result or throwing an |
870 |
|
|
* exception. This method may be useful when processing |
871 |
|
|
* collections of tasks when some have been cancelled or otherwise |
872 |
|
|
* known to have aborted. |
873 |
|
|
*/ |
874 |
|
|
public final void quietlyInvoke() { |
875 |
|
|
if (status >= 0 && !tryQuietlyInvoke()) |
876 |
|
|
quietlyJoin(); |
877 |
|
|
} |
878 |
|
|
|
879 |
|
|
/** |
880 |
dl |
1.3 |
* Possibly executes tasks until the pool hosting the current task |
881 |
|
|
* {@link ForkJoinPool#isQuiescent}. This method may be of use in |
882 |
|
|
* designs in which many tasks are forked, but none are explicitly |
883 |
jsr166 |
1.31 |
* joined, instead executing them until all are processed. |
884 |
|
|
* |
885 |
|
|
* <p>This method may be invoked only from within {@code |
886 |
|
|
* ForkJoinTask} computations (as may be determined using method |
887 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
888 |
|
|
* result in exceptions or errors, possibly including {@code |
889 |
|
|
* ClassCastException}. |
890 |
dl |
1.3 |
*/ |
891 |
|
|
public static void helpQuiesce() { |
892 |
jsr166 |
1.14 |
((ForkJoinWorkerThread) Thread.currentThread()) |
893 |
|
|
.helpQuiescePool(); |
894 |
dl |
1.3 |
} |
895 |
|
|
|
896 |
|
|
/** |
897 |
dl |
1.1 |
* Resets the internal bookkeeping state of this task, allowing a |
898 |
jsr166 |
1.8 |
* subsequent {@code fork}. This method allows repeated reuse of |
899 |
dl |
1.1 |
* this task, but only if reuse occurs when this task has either |
900 |
|
|
* never been forked, or has been forked, then completed and all |
901 |
|
|
* outstanding joins of this task have also completed. Effects |
902 |
dl |
1.30 |
* under any other usage conditions are not guaranteed. |
903 |
|
|
* This method may be useful when executing |
904 |
dl |
1.1 |
* pre-constructed trees of subtasks in loops. |
905 |
|
|
*/ |
906 |
|
|
public void reinitialize() { |
907 |
|
|
if ((status & COMPLETION_MASK) == EXCEPTIONAL) |
908 |
|
|
exceptionMap.remove(this); |
909 |
|
|
status = 0; |
910 |
|
|
} |
911 |
|
|
|
912 |
|
|
/** |
913 |
dl |
1.2 |
* Returns the pool hosting the current task execution, or null |
914 |
dl |
1.13 |
* if this task is executing outside of any ForkJoinPool. |
915 |
jsr166 |
1.10 |
* |
916 |
dl |
1.27 |
* @see #inForkJoinPool |
917 |
jsr166 |
1.23 |
* @return the pool, or {@code null} if none |
918 |
dl |
1.1 |
*/ |
919 |
dl |
1.2 |
public static ForkJoinPool getPool() { |
920 |
|
|
Thread t = Thread.currentThread(); |
921 |
jsr166 |
1.15 |
return (t instanceof ForkJoinWorkerThread) ? |
922 |
|
|
((ForkJoinWorkerThread) t).pool : null; |
923 |
dl |
1.1 |
} |
924 |
|
|
|
925 |
|
|
/** |
926 |
jsr166 |
1.14 |
* Returns {@code true} if the current thread is executing as a |
927 |
dl |
1.13 |
* ForkJoinPool computation. |
928 |
jsr166 |
1.14 |
* |
929 |
|
|
* @return {@code true} if the current thread is executing as a |
930 |
dl |
1.13 |
* ForkJoinPool computation, or false otherwise |
931 |
|
|
*/ |
932 |
|
|
public static boolean inForkJoinPool() { |
933 |
|
|
return Thread.currentThread() instanceof ForkJoinWorkerThread; |
934 |
|
|
} |
935 |
|
|
|
936 |
|
|
/** |
937 |
dl |
1.2 |
* Tries to unschedule this task for execution. This method will |
938 |
|
|
* typically succeed if this task is the most recently forked task |
939 |
|
|
* by the current thread, and has not commenced executing in |
940 |
|
|
* another thread. This method may be useful when arranging |
941 |
|
|
* alternative local processing of tasks that could have been, but |
942 |
jsr166 |
1.31 |
* were not, stolen. |
943 |
|
|
* |
944 |
|
|
* <p>This method may be invoked only from within {@code |
945 |
|
|
* ForkJoinTask} computations (as may be determined using method |
946 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
947 |
|
|
* result in exceptions or errors, possibly including {@code |
948 |
|
|
* ClassCastException}. |
949 |
jsr166 |
1.10 |
* |
950 |
jsr166 |
1.23 |
* @return {@code true} if unforked |
951 |
dl |
1.1 |
*/ |
952 |
dl |
1.2 |
public boolean tryUnfork() { |
953 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
954 |
|
|
.unpushTask(this); |
955 |
dl |
1.1 |
} |
956 |
|
|
|
957 |
|
|
/** |
958 |
dl |
1.2 |
* Returns an estimate of the number of tasks that have been |
959 |
|
|
* forked by the current worker thread but not yet executed. This |
960 |
|
|
* value may be useful for heuristic decisions about whether to |
961 |
jsr166 |
1.31 |
* fork other tasks. |
962 |
|
|
* |
963 |
|
|
* <p>This method may be invoked only from within {@code |
964 |
|
|
* ForkJoinTask} computations (as may be determined using method |
965 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
966 |
|
|
* result in exceptions or errors, possibly including {@code |
967 |
|
|
* ClassCastException}. |
968 |
|
|
* |
969 |
dl |
1.2 |
* @return the number of tasks |
970 |
|
|
*/ |
971 |
|
|
public static int getQueuedTaskCount() { |
972 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
973 |
|
|
.getQueueSize(); |
974 |
dl |
1.2 |
} |
975 |
|
|
|
976 |
|
|
/** |
977 |
jsr166 |
1.10 |
* Returns an estimate of how many more locally queued tasks are |
978 |
dl |
1.1 |
* held by the current worker thread than there are other worker |
979 |
dl |
1.2 |
* threads that might steal them. This value may be useful for |
980 |
|
|
* heuristic decisions about whether to fork other tasks. In many |
981 |
|
|
* usages of ForkJoinTasks, at steady state, each worker should |
982 |
|
|
* aim to maintain a small constant surplus (for example, 3) of |
983 |
|
|
* tasks, and to process computations locally if this threshold is |
984 |
jsr166 |
1.31 |
* exceeded. |
985 |
|
|
* |
986 |
|
|
* <p>This method may be invoked only from within {@code |
987 |
|
|
* ForkJoinTask} computations (as may be determined using method |
988 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
989 |
|
|
* result in exceptions or errors, possibly including {@code |
990 |
|
|
* ClassCastException}. |
991 |
|
|
* |
992 |
dl |
1.1 |
* @return the surplus number of tasks, which may be negative |
993 |
|
|
*/ |
994 |
dl |
1.2 |
public static int getSurplusQueuedTaskCount() { |
995 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
996 |
dl |
1.1 |
.getEstimatedSurplusTaskCount(); |
997 |
|
|
} |
998 |
|
|
|
999 |
dl |
1.2 |
// Extension methods |
1000 |
dl |
1.1 |
|
1001 |
|
|
/** |
1002 |
jsr166 |
1.23 |
* Returns the result that would be returned by {@link #join}, even |
1003 |
|
|
* if this task completed abnormally, or {@code null} if this task |
1004 |
|
|
* is not known to have been completed. This method is designed |
1005 |
|
|
* to aid debugging, as well as to support extensions. Its use in |
1006 |
|
|
* any other context is discouraged. |
1007 |
dl |
1.1 |
* |
1008 |
jsr166 |
1.23 |
* @return the result, or {@code null} if not completed |
1009 |
dl |
1.1 |
*/ |
1010 |
|
|
public abstract V getRawResult(); |
1011 |
|
|
|
1012 |
|
|
/** |
1013 |
|
|
* Forces the given value to be returned as a result. This method |
1014 |
|
|
* is designed to support extensions, and should not in general be |
1015 |
|
|
* called otherwise. |
1016 |
|
|
* |
1017 |
|
|
* @param value the value |
1018 |
|
|
*/ |
1019 |
|
|
protected abstract void setRawResult(V value); |
1020 |
|
|
|
1021 |
|
|
/** |
1022 |
|
|
* Immediately performs the base action of this task. This method |
1023 |
|
|
* is designed to support extensions, and should not in general be |
1024 |
|
|
* called otherwise. The return value controls whether this task |
1025 |
|
|
* is considered to be done normally. It may return false in |
1026 |
|
|
* asynchronous actions that require explicit invocations of |
1027 |
jsr166 |
1.23 |
* {@link #complete} to become joinable. It may throw exceptions |
1028 |
dl |
1.1 |
* to indicate abnormal exit. |
1029 |
jsr166 |
1.10 |
* |
1030 |
jsr166 |
1.23 |
* @return {@code true} if completed normally |
1031 |
dl |
1.1 |
* @throws Error or RuntimeException if encountered during computation |
1032 |
|
|
*/ |
1033 |
|
|
protected abstract boolean exec(); |
1034 |
|
|
|
1035 |
dl |
1.2 |
/** |
1036 |
dl |
1.25 |
* Returns, but does not unschedule or execute, a task queued by |
1037 |
|
|
* the current thread but not yet executed, if one is immediately |
1038 |
dl |
1.6 |
* available. There is no guarantee that this task will actually |
1039 |
dl |
1.25 |
* be polled or executed next. Conversely, this method may return |
1040 |
|
|
* null even if a task exists but cannot be accessed without |
1041 |
|
|
* contention with other threads. This method is designed |
1042 |
|
|
* primarily to support extensions, and is unlikely to be useful |
1043 |
jsr166 |
1.31 |
* otherwise. |
1044 |
|
|
* |
1045 |
|
|
* <p>This method may be invoked only from within {@code |
1046 |
|
|
* ForkJoinTask} computations (as may be determined using method |
1047 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1048 |
|
|
* result in exceptions or errors, possibly including {@code |
1049 |
|
|
* ClassCastException}. |
1050 |
dl |
1.2 |
* |
1051 |
jsr166 |
1.23 |
* @return the next task, or {@code null} if none are available |
1052 |
dl |
1.2 |
*/ |
1053 |
|
|
protected static ForkJoinTask<?> peekNextLocalTask() { |
1054 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1055 |
|
|
.peekTask(); |
1056 |
dl |
1.2 |
} |
1057 |
|
|
|
1058 |
|
|
/** |
1059 |
dl |
1.6 |
* Unschedules and returns, without executing, the next task |
1060 |
|
|
* queued by the current thread but not yet executed. This method |
1061 |
|
|
* is designed primarily to support extensions, and is unlikely to |
1062 |
jsr166 |
1.31 |
* be useful otherwise. |
1063 |
|
|
* |
1064 |
|
|
* <p>This method may be invoked only from within {@code |
1065 |
|
|
* ForkJoinTask} computations (as may be determined using method |
1066 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1067 |
|
|
* result in exceptions or errors, possibly including {@code |
1068 |
|
|
* ClassCastException}. |
1069 |
dl |
1.2 |
* |
1070 |
jsr166 |
1.23 |
* @return the next task, or {@code null} if none are available |
1071 |
dl |
1.2 |
*/ |
1072 |
|
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
1073 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1074 |
|
|
.pollLocalTask(); |
1075 |
dl |
1.2 |
} |
1076 |
jsr166 |
1.7 |
|
1077 |
dl |
1.2 |
/** |
1078 |
dl |
1.6 |
* Unschedules and returns, without executing, the next task |
1079 |
|
|
* queued by the current thread but not yet executed, if one is |
1080 |
|
|
* available, or if not available, a task that was forked by some |
1081 |
|
|
* other thread, if available. Availability may be transient, so a |
1082 |
jsr166 |
1.9 |
* {@code null} result does not necessarily imply quiescence |
1083 |
dl |
1.6 |
* of the pool this task is operating in. This method is designed |
1084 |
|
|
* primarily to support extensions, and is unlikely to be useful |
1085 |
jsr166 |
1.31 |
* otherwise. |
1086 |
|
|
* |
1087 |
|
|
* <p>This method may be invoked only from within {@code |
1088 |
|
|
* ForkJoinTask} computations (as may be determined using method |
1089 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1090 |
|
|
* result in exceptions or errors, possibly including {@code |
1091 |
|
|
* ClassCastException}. |
1092 |
dl |
1.4 |
* |
1093 |
jsr166 |
1.23 |
* @return a task, or {@code null} if none are available |
1094 |
dl |
1.2 |
*/ |
1095 |
|
|
protected static ForkJoinTask<?> pollTask() { |
1096 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1097 |
|
|
.pollTask(); |
1098 |
dl |
1.2 |
} |
1099 |
|
|
|
1100 |
dl |
1.25 |
/** |
1101 |
|
|
* Adaptor for Runnables. This implements RunnableFuture |
1102 |
|
|
* to be compliant with AbstractExecutorService constraints |
1103 |
|
|
* when used in ForkJoinPool. |
1104 |
|
|
*/ |
1105 |
|
|
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
1106 |
|
|
implements RunnableFuture<T> { |
1107 |
|
|
final Runnable runnable; |
1108 |
|
|
final T resultOnCompletion; |
1109 |
|
|
T result; |
1110 |
|
|
AdaptedRunnable(Runnable runnable, T result) { |
1111 |
|
|
if (runnable == null) throw new NullPointerException(); |
1112 |
|
|
this.runnable = runnable; |
1113 |
|
|
this.resultOnCompletion = result; |
1114 |
|
|
} |
1115 |
|
|
public T getRawResult() { return result; } |
1116 |
|
|
public void setRawResult(T v) { result = v; } |
1117 |
|
|
public boolean exec() { |
1118 |
|
|
runnable.run(); |
1119 |
|
|
result = resultOnCompletion; |
1120 |
|
|
return true; |
1121 |
|
|
} |
1122 |
|
|
public void run() { invoke(); } |
1123 |
|
|
private static final long serialVersionUID = 5232453952276885070L; |
1124 |
|
|
} |
1125 |
|
|
|
1126 |
|
|
/** |
1127 |
|
|
* Adaptor for Callables |
1128 |
|
|
*/ |
1129 |
|
|
static final class AdaptedCallable<T> extends ForkJoinTask<T> |
1130 |
|
|
implements RunnableFuture<T> { |
1131 |
dl |
1.27 |
final Callable<? extends T> callable; |
1132 |
dl |
1.25 |
T result; |
1133 |
dl |
1.27 |
AdaptedCallable(Callable<? extends T> callable) { |
1134 |
dl |
1.25 |
if (callable == null) throw new NullPointerException(); |
1135 |
|
|
this.callable = callable; |
1136 |
|
|
} |
1137 |
|
|
public T getRawResult() { return result; } |
1138 |
|
|
public void setRawResult(T v) { result = v; } |
1139 |
|
|
public boolean exec() { |
1140 |
|
|
try { |
1141 |
|
|
result = callable.call(); |
1142 |
|
|
return true; |
1143 |
|
|
} catch (Error err) { |
1144 |
|
|
throw err; |
1145 |
|
|
} catch (RuntimeException rex) { |
1146 |
|
|
throw rex; |
1147 |
|
|
} catch (Exception ex) { |
1148 |
|
|
throw new RuntimeException(ex); |
1149 |
|
|
} |
1150 |
|
|
} |
1151 |
|
|
public void run() { invoke(); } |
1152 |
|
|
private static final long serialVersionUID = 2838392045355241008L; |
1153 |
|
|
} |
1154 |
dl |
1.18 |
|
1155 |
|
|
/** |
1156 |
jsr166 |
1.31 |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1157 |
|
|
* method of the given {@code Runnable} as its action, and returns |
1158 |
|
|
* a null result upon {@link #join}. |
1159 |
dl |
1.18 |
* |
1160 |
|
|
* @param runnable the runnable action |
1161 |
|
|
* @return the task |
1162 |
|
|
*/ |
1163 |
dl |
1.27 |
public static ForkJoinTask<?> adapt(Runnable runnable) { |
1164 |
dl |
1.25 |
return new AdaptedRunnable<Void>(runnable, null); |
1165 |
dl |
1.18 |
} |
1166 |
|
|
|
1167 |
|
|
/** |
1168 |
jsr166 |
1.31 |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1169 |
|
|
* method of the given {@code Runnable} as its action, and returns |
1170 |
|
|
* the given result upon {@link #join}. |
1171 |
dl |
1.18 |
* |
1172 |
|
|
* @param runnable the runnable action |
1173 |
|
|
* @param result the result upon completion |
1174 |
|
|
* @return the task |
1175 |
|
|
*/ |
1176 |
|
|
public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) { |
1177 |
dl |
1.25 |
return new AdaptedRunnable<T>(runnable, result); |
1178 |
dl |
1.18 |
} |
1179 |
|
|
|
1180 |
|
|
/** |
1181 |
jsr166 |
1.31 |
* Returns a new {@code ForkJoinTask} that performs the {@code call} |
1182 |
|
|
* method of the given {@code Callable} as its action, and returns |
1183 |
|
|
* its result upon {@link #join}, translating any checked exceptions |
1184 |
|
|
* encountered into {@code RuntimeException}. |
1185 |
dl |
1.18 |
* |
1186 |
|
|
* @param callable the callable action |
1187 |
|
|
* @return the task |
1188 |
|
|
*/ |
1189 |
dl |
1.27 |
public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) { |
1190 |
dl |
1.25 |
return new AdaptedCallable<T>(callable); |
1191 |
dl |
1.18 |
} |
1192 |
|
|
|
1193 |
dl |
1.1 |
// Serialization support |
1194 |
|
|
|
1195 |
|
|
private static final long serialVersionUID = -7721805057305804111L; |
1196 |
|
|
|
1197 |
|
|
/** |
1198 |
|
|
* Save the state to a stream. |
1199 |
|
|
* |
1200 |
|
|
* @serialData the current run status and the exception thrown |
1201 |
jsr166 |
1.23 |
* during execution, or {@code null} if none |
1202 |
dl |
1.1 |
* @param s the stream |
1203 |
|
|
*/ |
1204 |
|
|
private void writeObject(java.io.ObjectOutputStream s) |
1205 |
|
|
throws java.io.IOException { |
1206 |
|
|
s.defaultWriteObject(); |
1207 |
|
|
s.writeObject(getException()); |
1208 |
|
|
} |
1209 |
|
|
|
1210 |
|
|
/** |
1211 |
|
|
* Reconstitute the instance from a stream. |
1212 |
jsr166 |
1.10 |
* |
1213 |
dl |
1.1 |
* @param s the stream |
1214 |
|
|
*/ |
1215 |
|
|
private void readObject(java.io.ObjectInputStream s) |
1216 |
|
|
throws java.io.IOException, ClassNotFoundException { |
1217 |
|
|
s.defaultReadObject(); |
1218 |
dl |
1.2 |
status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts |
1219 |
|
|
status |= EXTERNAL_SIGNAL; // conservatively set external signal |
1220 |
dl |
1.1 |
Object ex = s.readObject(); |
1221 |
|
|
if (ex != null) |
1222 |
jsr166 |
1.14 |
setDoneExceptionally((Throwable) ex); |
1223 |
dl |
1.1 |
} |
1224 |
|
|
|
1225 |
jsr166 |
1.22 |
// Unsafe mechanics |
1226 |
|
|
|
1227 |
|
|
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1228 |
|
|
private static final long statusOffset = |
1229 |
|
|
objectFieldOffset("status", ForkJoinTask.class); |
1230 |
|
|
|
1231 |
|
|
private static long objectFieldOffset(String field, Class<?> klazz) { |
1232 |
|
|
try { |
1233 |
|
|
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1234 |
|
|
} catch (NoSuchFieldException e) { |
1235 |
|
|
// Convert Exception to corresponding Error |
1236 |
|
|
NoSuchFieldError error = new NoSuchFieldError(field); |
1237 |
|
|
error.initCause(e); |
1238 |
|
|
throw error; |
1239 |
|
|
} |
1240 |
|
|
} |
1241 |
|
|
|
1242 |
|
|
/** |
1243 |
|
|
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
1244 |
|
|
* Replace with a simple call to Unsafe.getUnsafe when integrating |
1245 |
|
|
* into a jdk. |
1246 |
|
|
* |
1247 |
|
|
* @return a sun.misc.Unsafe |
1248 |
|
|
*/ |
1249 |
jsr166 |
1.16 |
private static sun.misc.Unsafe getUnsafe() { |
1250 |
jsr166 |
1.5 |
try { |
1251 |
jsr166 |
1.16 |
return sun.misc.Unsafe.getUnsafe(); |
1252 |
jsr166 |
1.5 |
} catch (SecurityException se) { |
1253 |
|
|
try { |
1254 |
|
|
return java.security.AccessController.doPrivileged |
1255 |
jsr166 |
1.22 |
(new java.security |
1256 |
|
|
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1257 |
jsr166 |
1.16 |
public sun.misc.Unsafe run() throws Exception { |
1258 |
jsr166 |
1.22 |
java.lang.reflect.Field f = sun.misc |
1259 |
|
|
.Unsafe.class.getDeclaredField("theUnsafe"); |
1260 |
|
|
f.setAccessible(true); |
1261 |
|
|
return (sun.misc.Unsafe) f.get(null); |
1262 |
jsr166 |
1.5 |
}}); |
1263 |
|
|
} catch (java.security.PrivilegedActionException e) { |
1264 |
jsr166 |
1.16 |
throw new RuntimeException("Could not initialize intrinsics", |
1265 |
|
|
e.getCause()); |
1266 |
jsr166 |
1.5 |
} |
1267 |
|
|
} |
1268 |
|
|
} |
1269 |
dl |
1.1 |
} |