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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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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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dl |
1.35 |
* equivalent to {@code fork(); join()} but always attempts to begin |
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* execution in the current thread. The "<em>quiet</em>" forms of |
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* these methods do not extract results or report exceptions. These |
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1.2 |
* may be useful when a set of tasks are being executed, and you need |
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* to delay processing of results or exceptions until all complete. |
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jsr166 |
1.8 |
* Method {@code invokeAll} (available in multiple versions) |
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1.2 |
* performs the most common form of parallel invocation: forking a set |
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* of tasks and joining them all. |
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* |
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dl |
1.35 |
* <p>The execution status of tasks may be queried at several levels |
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* of detail: {@link #isDone} is true if a task completed in any way |
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* (including the case where a task was cancelled without executing); |
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* {@link #isCompletedNormally} is true if a task completed without |
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dl |
1.42 |
* cancellation or encountering an exception; {@link #isCancelled} is |
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* true if the task was cancelled (in which case {@link #getException} |
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* returns a {@link java.util.concurrent.CancellationException}); and |
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* {@link #isCompletedAbnormally} is true if a task was either |
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* cancelled or encountered an exception, in which case {@link |
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* #getException} will return either the encountered exception or |
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* {@link java.util.concurrent.CancellationException}. |
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dl |
1.35 |
* |
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jsr166 |
1.28 |
* <p>The ForkJoinTask class is not usually directly subclassed. |
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dl |
1.2 |
* Instead, you subclass one of the abstract classes that support a |
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dl |
1.27 |
* particular style of fork/join processing, typically {@link |
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* RecursiveAction} for computations that do not return results, or |
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* {@link RecursiveTask} for those that do. Normally, a concrete |
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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 |
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dl |
1.2 |
* methods), some of them may only be called from within other |
103 |
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. |
107 |
dl |
1.1 |
* |
108 |
dl |
1.32 |
* <p>Most base support methods are {@code final}, to prevent |
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* overriding of implementations that are intrinsically tied to the |
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* underlying lightweight task scheduling framework. Developers |
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* creating new basic styles of fork/join processing should minimally |
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* implement {@code protected} methods {@link #exec}, {@link |
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* #setRawResult}, and {@link #getRawResult}, while also introducing |
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* an abstract computational method that can be implemented in its |
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* subclasses, possibly relying on other {@code protected} methods |
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* provided by this class. |
117 |
dl |
1.1 |
* |
118 |
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* <p>ForkJoinTasks should perform relatively small amounts of |
119 |
dl |
1.32 |
* computation. Large tasks should be split into smaller subtasks, |
120 |
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* usually via recursive decomposition. As a very rough rule of thumb, |
121 |
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* a task should perform more than 100 and less than 10000 basic |
122 |
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* computational steps. If tasks are too big, then parallelism cannot |
123 |
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* improve throughput. If too small, then memory and internal task |
124 |
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* maintenance overhead may overwhelm processing. |
125 |
dl |
1.1 |
* |
126 |
jsr166 |
1.37 |
* <p>This class provides {@code adapt} methods for {@link Runnable} |
127 |
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* and {@link Callable}, that may be of use when mixing execution of |
128 |
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* {@code ForkJoinTasks} with other kinds of tasks. When all tasks |
129 |
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* are of this form, consider using a pool in |
130 |
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* {@linkplain ForkJoinPool#setAsyncMode async mode}. |
131 |
dl |
1.27 |
* |
132 |
dl |
1.32 |
* <p>ForkJoinTasks are {@code Serializable}, which enables them to be |
133 |
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* used in extensions such as remote execution frameworks. It is |
134 |
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* sensible to serialize tasks only before or after, but not during, |
135 |
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* execution. Serialization is not relied on during execution itself. |
136 |
jsr166 |
1.12 |
* |
137 |
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* @since 1.7 |
138 |
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* @author Doug Lea |
139 |
dl |
1.1 |
*/ |
140 |
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public abstract class ForkJoinTask<V> implements Future<V>, Serializable { |
141 |
dl |
1.2 |
|
142 |
dl |
1.1 |
/** |
143 |
dl |
1.2 |
* Run control status bits packed into a single int to minimize |
144 |
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* footprint and to ensure atomicity (via CAS). Status is |
145 |
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* initially zero, and takes on nonnegative values until |
146 |
dl |
1.1 |
* completed, upon which status holds COMPLETED. CANCELLED, or |
147 |
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* EXCEPTIONAL, which use the top 3 bits. Tasks undergoing |
148 |
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* blocking waits by other threads have SIGNAL_MASK bits set -- |
149 |
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* bit 15 for external (nonFJ) waits, and the rest a count of |
150 |
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* waiting FJ threads. (This representation relies on |
151 |
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* ForkJoinPool max thread limits). Completion of a stolen task |
152 |
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* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even |
153 |
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* though suboptimal for some purposes, we use basic builtin |
154 |
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* wait/notify to take advantage of "monitor inflation" in JVMs |
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* that we would otherwise need to emulate to avoid adding further |
156 |
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* per-task bookkeeping overhead. Note that bits 16-28 are |
157 |
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* currently unused. Also value 0x80000000 is available as spare |
158 |
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* completion value. |
159 |
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*/ |
160 |
jsr166 |
1.9 |
volatile int status; // accessed directly by pool and workers |
161 |
dl |
1.1 |
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162 |
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static final int COMPLETION_MASK = 0xe0000000; |
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static final int NORMAL = 0xe0000000; // == mask |
164 |
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static final int CANCELLED = 0xc0000000; |
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static final int EXCEPTIONAL = 0xa0000000; |
166 |
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static final int SIGNAL_MASK = 0x0000ffff; |
167 |
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static final int INTERNAL_SIGNAL_MASK = 0x00007fff; |
168 |
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static final int EXTERNAL_SIGNAL = 0x00008000; // top bit of low word |
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170 |
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/** |
171 |
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* Table of exceptions thrown by tasks, to enable reporting by |
172 |
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* callers. Because exceptions are rare, we don't directly keep |
173 |
jsr166 |
1.10 |
* them with task objects, but instead use a weak ref table. Note |
174 |
dl |
1.1 |
* that cancellation exceptions don't appear in the table, but are |
175 |
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* instead recorded as status values. |
176 |
jsr166 |
1.10 |
* TODO: Use ConcurrentReferenceHashMap |
177 |
dl |
1.1 |
*/ |
178 |
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static final Map<ForkJoinTask<?>, Throwable> exceptionMap = |
179 |
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Collections.synchronizedMap |
180 |
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(new WeakHashMap<ForkJoinTask<?>, Throwable>()); |
181 |
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182 |
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// within-package utilities |
183 |
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184 |
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/** |
185 |
jsr166 |
1.10 |
* Gets current worker thread, or null if not a worker thread. |
186 |
dl |
1.1 |
*/ |
187 |
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static ForkJoinWorkerThread getWorker() { |
188 |
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Thread t = Thread.currentThread(); |
189 |
jsr166 |
1.14 |
return ((t instanceof ForkJoinWorkerThread) ? |
190 |
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(ForkJoinWorkerThread) t : null); |
191 |
dl |
1.1 |
} |
192 |
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193 |
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final boolean casStatus(int cmp, int val) { |
194 |
jsr166 |
1.11 |
return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val); |
195 |
dl |
1.1 |
} |
196 |
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197 |
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/** |
198 |
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* Workaround for not being able to rethrow unchecked exceptions. |
199 |
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*/ |
200 |
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static void rethrowException(Throwable ex) { |
201 |
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if (ex != null) |
202 |
jsr166 |
1.11 |
UNSAFE.throwException(ex); |
203 |
dl |
1.1 |
} |
204 |
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205 |
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// Setting completion status |
206 |
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207 |
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/** |
208 |
jsr166 |
1.10 |
* Marks completion and wakes up threads waiting to join this task. |
209 |
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* |
210 |
dl |
1.1 |
* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
211 |
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*/ |
212 |
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final void setCompletion(int completion) { |
213 |
dl |
1.2 |
ForkJoinPool pool = getPool(); |
214 |
dl |
1.1 |
if (pool != null) { |
215 |
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int s; // Clear signal bits while setting completion status |
216 |
jsr166 |
1.14 |
do {} while ((s = status) >= 0 && !casStatus(s, completion)); |
217 |
dl |
1.1 |
|
218 |
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if ((s & SIGNAL_MASK) != 0) { |
219 |
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if ((s &= INTERNAL_SIGNAL_MASK) != 0) |
220 |
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pool.updateRunningCount(s); |
221 |
jsr166 |
1.14 |
synchronized (this) { notifyAll(); } |
222 |
dl |
1.1 |
} |
223 |
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} |
224 |
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else |
225 |
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externallySetCompletion(completion); |
226 |
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} |
227 |
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228 |
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/** |
229 |
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* Version of setCompletion for non-FJ threads. Leaves signal |
230 |
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* bits for unblocked threads to adjust, and always notifies. |
231 |
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*/ |
232 |
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private void externallySetCompletion(int completion) { |
233 |
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int s; |
234 |
jsr166 |
1.14 |
do {} while ((s = status) >= 0 && |
235 |
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!casStatus(s, (s & SIGNAL_MASK) | completion)); |
236 |
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synchronized (this) { notifyAll(); } |
237 |
dl |
1.1 |
} |
238 |
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239 |
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/** |
240 |
jsr166 |
1.14 |
* Sets status to indicate normal completion. |
241 |
dl |
1.1 |
*/ |
242 |
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final void setNormalCompletion() { |
243 |
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// Try typical fast case -- single CAS, no signal, not already done. |
244 |
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// Manually expand casStatus to improve chances of inlining it |
245 |
jsr166 |
1.11 |
if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL)) |
246 |
dl |
1.1 |
setCompletion(NORMAL); |
247 |
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} |
248 |
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|
249 |
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// internal waiting and notification |
250 |
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251 |
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/** |
252 |
jsr166 |
1.14 |
* Performs the actual monitor wait for awaitDone. |
253 |
dl |
1.1 |
*/ |
254 |
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private void doAwaitDone() { |
255 |
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// Minimize lock bias and in/de-flation effects by maximizing |
256 |
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// chances of waiting inside sync |
257 |
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try { |
258 |
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while (status >= 0) |
259 |
jsr166 |
1.14 |
synchronized (this) { if (status >= 0) wait(); } |
260 |
dl |
1.1 |
} catch (InterruptedException ie) { |
261 |
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onInterruptedWait(); |
262 |
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} |
263 |
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} |
264 |
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265 |
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/** |
266 |
jsr166 |
1.14 |
* Performs the actual timed monitor wait for awaitDone. |
267 |
dl |
1.1 |
*/ |
268 |
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private void doAwaitDone(long startTime, long nanos) { |
269 |
jsr166 |
1.14 |
synchronized (this) { |
270 |
dl |
1.1 |
try { |
271 |
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while (status >= 0) { |
272 |
dl |
1.25 |
long nt = nanos - (System.nanoTime() - startTime); |
273 |
dl |
1.1 |
if (nt <= 0) |
274 |
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break; |
275 |
jsr166 |
1.14 |
wait(nt / 1000000, (int) (nt % 1000000)); |
276 |
dl |
1.1 |
} |
277 |
|
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} catch (InterruptedException ie) { |
278 |
|
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onInterruptedWait(); |
279 |
|
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} |
280 |
|
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} |
281 |
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} |
282 |
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|
283 |
|
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// Awaiting completion |
284 |
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|
285 |
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/** |
286 |
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* Sets status to indicate there is joiner, then waits for join, |
287 |
|
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* surrounded with pool notifications. |
288 |
jsr166 |
1.10 |
* |
289 |
dl |
1.1 |
* @return status upon exit |
290 |
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*/ |
291 |
jsr166 |
1.14 |
private int awaitDone(ForkJoinWorkerThread w, |
292 |
|
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boolean maintainParallelism) { |
293 |
|
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ForkJoinPool pool = (w == null) ? null : w.pool; |
294 |
dl |
1.1 |
int s; |
295 |
|
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while ((s = status) >= 0) { |
296 |
jsr166 |
1.14 |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
297 |
dl |
1.1 |
if (pool == null || !pool.preJoin(this, maintainParallelism)) |
298 |
|
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doAwaitDone(); |
299 |
|
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if (((s = status) & INTERNAL_SIGNAL_MASK) != 0) |
300 |
|
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adjustPoolCountsOnUnblock(pool); |
301 |
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break; |
302 |
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} |
303 |
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} |
304 |
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return s; |
305 |
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} |
306 |
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|
307 |
|
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/** |
308 |
|
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* Timed version of awaitDone |
309 |
jsr166 |
1.14 |
* |
310 |
dl |
1.1 |
* @return status upon exit |
311 |
|
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*/ |
312 |
dl |
1.3 |
private int awaitDone(ForkJoinWorkerThread w, long nanos) { |
313 |
jsr166 |
1.14 |
ForkJoinPool pool = (w == null) ? null : w.pool; |
314 |
dl |
1.1 |
int s; |
315 |
|
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while ((s = status) >= 0) { |
316 |
jsr166 |
1.14 |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
317 |
dl |
1.1 |
long startTime = System.nanoTime(); |
318 |
|
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if (pool == null || !pool.preJoin(this, false)) |
319 |
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doAwaitDone(startTime, nanos); |
320 |
|
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if ((s = status) >= 0) { |
321 |
|
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adjustPoolCountsOnCancelledWait(pool); |
322 |
|
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s = status; |
323 |
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} |
324 |
|
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if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0) |
325 |
|
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adjustPoolCountsOnUnblock(pool); |
326 |
|
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break; |
327 |
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} |
328 |
|
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} |
329 |
|
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return s; |
330 |
|
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} |
331 |
|
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|
332 |
|
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/** |
333 |
jsr166 |
1.10 |
* Notifies pool that thread is unblocked. Called by signalled |
334 |
dl |
1.1 |
* threads when woken by non-FJ threads (which is atypical). |
335 |
|
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*/ |
336 |
|
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private void adjustPoolCountsOnUnblock(ForkJoinPool pool) { |
337 |
|
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int s; |
338 |
jsr166 |
1.14 |
do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK)); |
339 |
dl |
1.1 |
if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0) |
340 |
|
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pool.updateRunningCount(s); |
341 |
|
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} |
342 |
|
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|
343 |
|
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/** |
344 |
jsr166 |
1.10 |
* Notifies pool to adjust counts on cancelled or timed out wait. |
345 |
dl |
1.1 |
*/ |
346 |
|
|
private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) { |
347 |
|
|
if (pool != null) { |
348 |
|
|
int s; |
349 |
|
|
while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) { |
350 |
|
|
if (casStatus(s, s - 1)) { |
351 |
|
|
pool.updateRunningCount(1); |
352 |
|
|
break; |
353 |
|
|
} |
354 |
|
|
} |
355 |
|
|
} |
356 |
|
|
} |
357 |
|
|
|
358 |
dl |
1.2 |
/** |
359 |
jsr166 |
1.10 |
* Handles interruptions during waits. |
360 |
dl |
1.2 |
*/ |
361 |
dl |
1.1 |
private void onInterruptedWait() { |
362 |
dl |
1.2 |
ForkJoinWorkerThread w = getWorker(); |
363 |
|
|
if (w == null) |
364 |
|
|
Thread.currentThread().interrupt(); // re-interrupt |
365 |
|
|
else if (w.isTerminating()) |
366 |
dl |
1.3 |
cancelIgnoringExceptions(); |
367 |
dl |
1.2 |
// else if FJworker, ignore interrupt |
368 |
dl |
1.1 |
} |
369 |
|
|
|
370 |
|
|
// Recording and reporting exceptions |
371 |
|
|
|
372 |
|
|
private void setDoneExceptionally(Throwable rex) { |
373 |
|
|
exceptionMap.put(this, rex); |
374 |
|
|
setCompletion(EXCEPTIONAL); |
375 |
|
|
} |
376 |
|
|
|
377 |
|
|
/** |
378 |
jsr166 |
1.10 |
* Throws the exception associated with status s. |
379 |
|
|
* |
380 |
dl |
1.1 |
* @throws the exception |
381 |
|
|
*/ |
382 |
|
|
private void reportException(int s) { |
383 |
|
|
if ((s &= COMPLETION_MASK) < NORMAL) { |
384 |
|
|
if (s == CANCELLED) |
385 |
|
|
throw new CancellationException(); |
386 |
|
|
else |
387 |
|
|
rethrowException(exceptionMap.get(this)); |
388 |
|
|
} |
389 |
|
|
} |
390 |
|
|
|
391 |
|
|
/** |
392 |
jsr166 |
1.10 |
* Returns result or throws exception using j.u.c.Future conventions. |
393 |
dl |
1.38 |
* Only call when {@code isDone} known to be true or thread known |
394 |
|
|
* to be interrupted. |
395 |
dl |
1.1 |
*/ |
396 |
|
|
private V reportFutureResult() |
397 |
jsr166 |
1.37 |
throws InterruptedException, ExecutionException { |
398 |
dl |
1.34 |
if (Thread.interrupted()) |
399 |
|
|
throw new InterruptedException(); |
400 |
dl |
1.1 |
int s = status & COMPLETION_MASK; |
401 |
|
|
if (s < NORMAL) { |
402 |
|
|
Throwable ex; |
403 |
|
|
if (s == CANCELLED) |
404 |
|
|
throw new CancellationException(); |
405 |
|
|
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
406 |
|
|
throw new ExecutionException(ex); |
407 |
|
|
} |
408 |
|
|
return getRawResult(); |
409 |
|
|
} |
410 |
|
|
|
411 |
|
|
/** |
412 |
|
|
* Returns result or throws exception using j.u.c.Future conventions |
413 |
jsr166 |
1.10 |
* with timeouts. |
414 |
dl |
1.1 |
*/ |
415 |
|
|
private V reportTimedFutureResult() |
416 |
|
|
throws InterruptedException, ExecutionException, TimeoutException { |
417 |
dl |
1.34 |
if (Thread.interrupted()) |
418 |
|
|
throw new InterruptedException(); |
419 |
dl |
1.1 |
Throwable ex; |
420 |
|
|
int s = status & COMPLETION_MASK; |
421 |
|
|
if (s == NORMAL) |
422 |
|
|
return getRawResult(); |
423 |
jsr166 |
1.37 |
else if (s == CANCELLED) |
424 |
dl |
1.1 |
throw new CancellationException(); |
425 |
jsr166 |
1.37 |
else if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
426 |
dl |
1.1 |
throw new ExecutionException(ex); |
427 |
jsr166 |
1.37 |
else |
428 |
|
|
throw new TimeoutException(); |
429 |
dl |
1.1 |
} |
430 |
|
|
|
431 |
|
|
// internal execution methods |
432 |
|
|
|
433 |
|
|
/** |
434 |
|
|
* Calls exec, recording completion, and rethrowing exception if |
435 |
jsr166 |
1.10 |
* encountered. Caller should normally check status before calling. |
436 |
|
|
* |
437 |
dl |
1.1 |
* @return true if completed normally |
438 |
|
|
*/ |
439 |
|
|
private boolean tryExec() { |
440 |
|
|
try { // try block must contain only call to exec |
441 |
|
|
if (!exec()) |
442 |
|
|
return false; |
443 |
|
|
} catch (Throwable rex) { |
444 |
|
|
setDoneExceptionally(rex); |
445 |
|
|
rethrowException(rex); |
446 |
|
|
return false; // not reached |
447 |
|
|
} |
448 |
|
|
setNormalCompletion(); |
449 |
|
|
return true; |
450 |
|
|
} |
451 |
|
|
|
452 |
|
|
/** |
453 |
|
|
* Main execution method used by worker threads. Invokes |
454 |
jsr166 |
1.10 |
* base computation unless already complete. |
455 |
dl |
1.1 |
*/ |
456 |
|
|
final void quietlyExec() { |
457 |
|
|
if (status >= 0) { |
458 |
|
|
try { |
459 |
|
|
if (!exec()) |
460 |
|
|
return; |
461 |
jsr166 |
1.14 |
} catch (Throwable rex) { |
462 |
dl |
1.1 |
setDoneExceptionally(rex); |
463 |
|
|
return; |
464 |
|
|
} |
465 |
|
|
setNormalCompletion(); |
466 |
|
|
} |
467 |
|
|
} |
468 |
|
|
|
469 |
|
|
/** |
470 |
jsr166 |
1.10 |
* Calls exec(), recording but not rethrowing exception. |
471 |
|
|
* Caller should normally check status before calling. |
472 |
|
|
* |
473 |
dl |
1.1 |
* @return true if completed normally |
474 |
|
|
*/ |
475 |
|
|
private boolean tryQuietlyInvoke() { |
476 |
|
|
try { |
477 |
|
|
if (!exec()) |
478 |
|
|
return false; |
479 |
|
|
} catch (Throwable rex) { |
480 |
|
|
setDoneExceptionally(rex); |
481 |
|
|
return false; |
482 |
|
|
} |
483 |
|
|
setNormalCompletion(); |
484 |
|
|
return true; |
485 |
|
|
} |
486 |
|
|
|
487 |
|
|
/** |
488 |
jsr166 |
1.10 |
* Cancels, ignoring any exceptions it throws. |
489 |
dl |
1.1 |
*/ |
490 |
dl |
1.3 |
final void cancelIgnoringExceptions() { |
491 |
dl |
1.1 |
try { |
492 |
|
|
cancel(false); |
493 |
jsr166 |
1.14 |
} catch (Throwable ignore) { |
494 |
dl |
1.1 |
} |
495 |
|
|
} |
496 |
|
|
|
497 |
dl |
1.3 |
/** |
498 |
|
|
* Main implementation of helpJoin |
499 |
|
|
*/ |
500 |
|
|
private int busyJoin(ForkJoinWorkerThread w) { |
501 |
|
|
int s; |
502 |
|
|
ForkJoinTask<?> t; |
503 |
|
|
while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null) |
504 |
|
|
t.quietlyExec(); |
505 |
jsr166 |
1.14 |
return (s >= 0) ? awaitDone(w, false) : s; // block if no work |
506 |
dl |
1.3 |
} |
507 |
|
|
|
508 |
dl |
1.1 |
// public methods |
509 |
|
|
|
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 |
jsr166 |
1.31 |
* than once unless it has completed and been reinitialized. |
514 |
dl |
1.18 |
* |
515 |
jsr166 |
1.31 |
* <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 |
dl |
1.1 |
*/ |
523 |
dl |
1.18 |
public final ForkJoinTask<V> fork() { |
524 |
jsr166 |
1.14 |
((ForkJoinWorkerThread) Thread.currentThread()) |
525 |
|
|
.pushTask(this); |
526 |
dl |
1.18 |
return this; |
527 |
dl |
1.1 |
} |
528 |
|
|
|
529 |
|
|
/** |
530 |
dl |
1.41 |
* Returns the result of the computation when it {@link #isDone is done}. |
531 |
jsr166 |
1.31 |
* This method differs from {@link #get()} in that |
532 |
|
|
* abnormal completion results in {@code RuntimeException} or |
533 |
|
|
* {@code Error}, not {@code ExecutionException}. |
534 |
dl |
1.1 |
* |
535 |
|
|
* @return the computed result |
536 |
|
|
*/ |
537 |
|
|
public final V join() { |
538 |
|
|
ForkJoinWorkerThread w = getWorker(); |
539 |
|
|
if (w == null || status < 0 || !w.unpushTask(this) || !tryExec()) |
540 |
|
|
reportException(awaitDone(w, true)); |
541 |
|
|
return getRawResult(); |
542 |
|
|
} |
543 |
|
|
|
544 |
|
|
/** |
545 |
dl |
1.2 |
* Commences performing this task, awaits its completion if |
546 |
dl |
1.34 |
* necessary, and return its result, or throws an (unchecked) |
547 |
|
|
* exception if the underlying computation did so. |
548 |
jsr166 |
1.10 |
* |
549 |
dl |
1.1 |
* @return the computed result |
550 |
|
|
*/ |
551 |
|
|
public final V invoke() { |
552 |
|
|
if (status >= 0 && tryExec()) |
553 |
|
|
return getRawResult(); |
554 |
|
|
else |
555 |
|
|
return join(); |
556 |
|
|
} |
557 |
|
|
|
558 |
|
|
/** |
559 |
dl |
1.34 |
* Forks the given tasks, returning when {@code isDone} holds for |
560 |
|
|
* each task or an (unchecked) exception is encountered, in which |
561 |
jsr166 |
1.39 |
* case the exception is rethrown. If either task encounters an |
562 |
|
|
* exception, the other one may be, but is not guaranteed to be, |
563 |
|
|
* cancelled. If both tasks throw an exception, then this method |
564 |
|
|
* throws one of them. The individual status of each task may be |
565 |
dl |
1.34 |
* checked using {@link #getException()} and related methods. |
566 |
jsr166 |
1.31 |
* |
567 |
|
|
* <p>This method may be invoked only from within {@code |
568 |
|
|
* ForkJoinTask} computations (as may be determined using method |
569 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
570 |
|
|
* result in exceptions or errors, possibly including {@code |
571 |
|
|
* ClassCastException}. |
572 |
jsr166 |
1.10 |
* |
573 |
dl |
1.27 |
* @param t1 the first task |
574 |
|
|
* @param t2 the second task |
575 |
|
|
* @throws NullPointerException if any task is null |
576 |
dl |
1.1 |
*/ |
577 |
jsr166 |
1.31 |
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) { |
578 |
dl |
1.2 |
t2.fork(); |
579 |
|
|
t1.invoke(); |
580 |
|
|
t2.join(); |
581 |
dl |
1.1 |
} |
582 |
|
|
|
583 |
|
|
/** |
584 |
dl |
1.27 |
* Forks the given tasks, returning when {@code isDone} holds for |
585 |
dl |
1.34 |
* each task or an (unchecked) exception is encountered, in which |
586 |
|
|
* case the exception is rethrown. If any task encounters an |
587 |
|
|
* exception, others may be, but are not guaranteed to be, |
588 |
|
|
* cancelled. If more than one task encounters an exception, then |
589 |
|
|
* this method throws any one of these exceptions. The individual |
590 |
|
|
* status of each task may be checked using {@link #getException()} |
591 |
|
|
* and related methods. |
592 |
jsr166 |
1.31 |
* |
593 |
|
|
* <p>This method may be invoked only from within {@code |
594 |
|
|
* ForkJoinTask} computations (as may be determined using method |
595 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
596 |
|
|
* result in exceptions or errors, possibly including {@code |
597 |
|
|
* ClassCastException}. |
598 |
jsr166 |
1.14 |
* |
599 |
dl |
1.27 |
* @param tasks the tasks |
600 |
dl |
1.34 |
* @throws NullPointerException if any task is null |
601 |
dl |
1.1 |
*/ |
602 |
dl |
1.2 |
public static void invokeAll(ForkJoinTask<?>... tasks) { |
603 |
|
|
Throwable ex = null; |
604 |
|
|
int last = tasks.length - 1; |
605 |
|
|
for (int i = last; i >= 0; --i) { |
606 |
|
|
ForkJoinTask<?> t = tasks[i]; |
607 |
|
|
if (t == null) { |
608 |
|
|
if (ex == null) |
609 |
|
|
ex = new NullPointerException(); |
610 |
|
|
} |
611 |
|
|
else if (i != 0) |
612 |
|
|
t.fork(); |
613 |
|
|
else { |
614 |
|
|
t.quietlyInvoke(); |
615 |
|
|
if (ex == null) |
616 |
|
|
ex = t.getException(); |
617 |
|
|
} |
618 |
|
|
} |
619 |
|
|
for (int i = 1; i <= last; ++i) { |
620 |
|
|
ForkJoinTask<?> t = tasks[i]; |
621 |
|
|
if (t != null) { |
622 |
|
|
if (ex != null) |
623 |
|
|
t.cancel(false); |
624 |
|
|
else { |
625 |
|
|
t.quietlyJoin(); |
626 |
|
|
if (ex == null) |
627 |
|
|
ex = t.getException(); |
628 |
|
|
} |
629 |
|
|
} |
630 |
dl |
1.1 |
} |
631 |
dl |
1.2 |
if (ex != null) |
632 |
|
|
rethrowException(ex); |
633 |
dl |
1.1 |
} |
634 |
|
|
|
635 |
|
|
/** |
636 |
dl |
1.32 |
* Forks all tasks in the specified collection, returning when |
637 |
dl |
1.34 |
* {@code isDone} holds for each task or an (unchecked) exception |
638 |
|
|
* is encountered. If any task encounters an exception, others |
639 |
|
|
* may be, but are not guaranteed to be, cancelled. If more than |
640 |
|
|
* one task encounters an exception, then this method throws any |
641 |
|
|
* one of these exceptions. The individual status of each task |
642 |
|
|
* may be checked using {@link #getException()} and related |
643 |
|
|
* methods. The behavior of this operation is undefined if the |
644 |
|
|
* specified collection is modified while the operation is in |
645 |
|
|
* progress. |
646 |
jsr166 |
1.31 |
* |
647 |
|
|
* <p>This method may be invoked only from within {@code |
648 |
|
|
* ForkJoinTask} computations (as may be determined using method |
649 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
650 |
|
|
* result in exceptions or errors, possibly including {@code |
651 |
|
|
* ClassCastException}. |
652 |
jsr166 |
1.10 |
* |
653 |
dl |
1.2 |
* @param tasks the collection of tasks |
654 |
dl |
1.19 |
* @return the tasks argument, to simplify usage |
655 |
jsr166 |
1.10 |
* @throws NullPointerException if tasks or any element are null |
656 |
dl |
1.1 |
*/ |
657 |
dl |
1.19 |
public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) { |
658 |
dl |
1.32 |
if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) { |
659 |
jsr166 |
1.14 |
invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()])); |
660 |
dl |
1.19 |
return tasks; |
661 |
dl |
1.2 |
} |
662 |
jsr166 |
1.15 |
@SuppressWarnings("unchecked") |
663 |
dl |
1.2 |
List<? extends ForkJoinTask<?>> ts = |
664 |
jsr166 |
1.14 |
(List<? extends ForkJoinTask<?>>) tasks; |
665 |
dl |
1.2 |
Throwable ex = null; |
666 |
|
|
int last = ts.size() - 1; |
667 |
|
|
for (int i = last; i >= 0; --i) { |
668 |
|
|
ForkJoinTask<?> t = ts.get(i); |
669 |
|
|
if (t == null) { |
670 |
|
|
if (ex == null) |
671 |
|
|
ex = new NullPointerException(); |
672 |
|
|
} |
673 |
|
|
else if (i != 0) |
674 |
|
|
t.fork(); |
675 |
|
|
else { |
676 |
|
|
t.quietlyInvoke(); |
677 |
|
|
if (ex == null) |
678 |
|
|
ex = t.getException(); |
679 |
|
|
} |
680 |
|
|
} |
681 |
|
|
for (int i = 1; i <= last; ++i) { |
682 |
|
|
ForkJoinTask<?> t = ts.get(i); |
683 |
|
|
if (t != null) { |
684 |
|
|
if (ex != null) |
685 |
|
|
t.cancel(false); |
686 |
|
|
else { |
687 |
|
|
t.quietlyJoin(); |
688 |
|
|
if (ex == null) |
689 |
|
|
ex = t.getException(); |
690 |
|
|
} |
691 |
|
|
} |
692 |
|
|
} |
693 |
|
|
if (ex != null) |
694 |
|
|
rethrowException(ex); |
695 |
dl |
1.19 |
return tasks; |
696 |
dl |
1.1 |
} |
697 |
|
|
|
698 |
|
|
/** |
699 |
dl |
1.33 |
* Attempts to cancel execution of this task. This attempt will |
700 |
|
|
* fail if the task has already completed, has already been |
701 |
|
|
* cancelled, or could not be cancelled for some other reason. If |
702 |
|
|
* successful, and this task has not started when cancel is |
703 |
|
|
* called, execution of this task is suppressed, {@link |
704 |
|
|
* #isCancelled} will report true, and {@link #join} will result |
705 |
|
|
* in a {@code CancellationException} being thrown. |
706 |
dl |
1.1 |
* |
707 |
|
|
* <p>This method may be overridden in subclasses, but if so, must |
708 |
|
|
* still ensure that these minimal properties hold. In particular, |
709 |
jsr166 |
1.29 |
* the {@code cancel} method itself must not throw exceptions. |
710 |
dl |
1.1 |
* |
711 |
jsr166 |
1.28 |
* <p>This method is designed to be invoked by <em>other</em> |
712 |
dl |
1.1 |
* tasks. To terminate the current task, you can just return or |
713 |
|
|
* throw an unchecked exception from its computation method, or |
714 |
jsr166 |
1.24 |
* invoke {@link #completeExceptionally}. |
715 |
dl |
1.1 |
* |
716 |
|
|
* @param mayInterruptIfRunning this value is ignored in the |
717 |
dl |
1.33 |
* default implementation because tasks are not |
718 |
jsr166 |
1.14 |
* cancelled via interruption |
719 |
dl |
1.1 |
* |
720 |
jsr166 |
1.23 |
* @return {@code true} if this task is now cancelled |
721 |
dl |
1.1 |
*/ |
722 |
|
|
public boolean cancel(boolean mayInterruptIfRunning) { |
723 |
|
|
setCompletion(CANCELLED); |
724 |
|
|
return (status & COMPLETION_MASK) == CANCELLED; |
725 |
|
|
} |
726 |
|
|
|
727 |
dl |
1.34 |
public final boolean isDone() { |
728 |
|
|
return status < 0; |
729 |
|
|
} |
730 |
|
|
|
731 |
|
|
public final boolean isCancelled() { |
732 |
|
|
return (status & COMPLETION_MASK) == CANCELLED; |
733 |
|
|
} |
734 |
|
|
|
735 |
|
|
/** |
736 |
jsr166 |
1.23 |
* Returns {@code true} if this task threw an exception or was cancelled. |
737 |
jsr166 |
1.10 |
* |
738 |
jsr166 |
1.23 |
* @return {@code true} if this task threw an exception or was cancelled |
739 |
dl |
1.3 |
*/ |
740 |
|
|
public final boolean isCompletedAbnormally() { |
741 |
|
|
return (status & COMPLETION_MASK) < NORMAL; |
742 |
|
|
} |
743 |
|
|
|
744 |
|
|
/** |
745 |
dl |
1.34 |
* Returns {@code true} if this task completed without throwing an |
746 |
|
|
* exception and was not cancelled. |
747 |
|
|
* |
748 |
|
|
* @return {@code true} if this task completed without throwing an |
749 |
|
|
* exception and was not cancelled |
750 |
|
|
*/ |
751 |
|
|
public final boolean isCompletedNormally() { |
752 |
|
|
return (status & COMPLETION_MASK) == NORMAL; |
753 |
|
|
} |
754 |
|
|
|
755 |
|
|
/** |
756 |
dl |
1.3 |
* Returns the exception thrown by the base computation, or a |
757 |
jsr166 |
1.29 |
* {@code CancellationException} if cancelled, or {@code null} if |
758 |
|
|
* none or if the method has not yet completed. |
759 |
jsr166 |
1.10 |
* |
760 |
jsr166 |
1.23 |
* @return the exception, or {@code null} if none |
761 |
dl |
1.3 |
*/ |
762 |
|
|
public final Throwable getException() { |
763 |
|
|
int s = status & COMPLETION_MASK; |
764 |
jsr166 |
1.37 |
return ((s >= NORMAL) ? null : |
765 |
|
|
(s == CANCELLED) ? new CancellationException() : |
766 |
|
|
exceptionMap.get(this)); |
767 |
dl |
1.3 |
} |
768 |
|
|
|
769 |
|
|
/** |
770 |
dl |
1.1 |
* Completes this task abnormally, and if not already aborted or |
771 |
|
|
* cancelled, causes it to throw the given exception upon |
772 |
jsr166 |
1.8 |
* {@code join} and related operations. This method may be used |
773 |
dl |
1.1 |
* to induce exceptions in asynchronous tasks, or to force |
774 |
dl |
1.2 |
* completion of tasks that would not otherwise complete. Its use |
775 |
dl |
1.27 |
* in other situations is discouraged. This method is |
776 |
jsr166 |
1.8 |
* overridable, but overridden versions must invoke {@code super} |
777 |
dl |
1.2 |
* implementation to maintain guarantees. |
778 |
|
|
* |
779 |
dl |
1.1 |
* @param ex the exception to throw. If this exception is |
780 |
|
|
* not a RuntimeException or Error, the actual exception thrown |
781 |
|
|
* will be a RuntimeException with cause ex. |
782 |
|
|
*/ |
783 |
|
|
public void completeExceptionally(Throwable ex) { |
784 |
|
|
setDoneExceptionally((ex instanceof RuntimeException) || |
785 |
jsr166 |
1.14 |
(ex instanceof Error) ? ex : |
786 |
dl |
1.1 |
new RuntimeException(ex)); |
787 |
|
|
} |
788 |
|
|
|
789 |
|
|
/** |
790 |
|
|
* Completes this task, and if not already aborted or cancelled, |
791 |
jsr166 |
1.8 |
* returning a {@code null} result upon {@code join} and related |
792 |
dl |
1.1 |
* operations. This method may be used to provide results for |
793 |
|
|
* asynchronous tasks, or to provide alternative handling for |
794 |
dl |
1.2 |
* tasks that would not otherwise complete normally. Its use in |
795 |
dl |
1.27 |
* other situations is discouraged. This method is |
796 |
jsr166 |
1.8 |
* overridable, but overridden versions must invoke {@code super} |
797 |
dl |
1.2 |
* implementation to maintain guarantees. |
798 |
dl |
1.1 |
* |
799 |
jsr166 |
1.10 |
* @param value the result value for this task |
800 |
dl |
1.1 |
*/ |
801 |
|
|
public void complete(V value) { |
802 |
|
|
try { |
803 |
|
|
setRawResult(value); |
804 |
jsr166 |
1.14 |
} catch (Throwable rex) { |
805 |
dl |
1.1 |
setDoneExceptionally(rex); |
806 |
|
|
return; |
807 |
|
|
} |
808 |
|
|
setNormalCompletion(); |
809 |
|
|
} |
810 |
|
|
|
811 |
dl |
1.3 |
public final V get() throws InterruptedException, ExecutionException { |
812 |
|
|
ForkJoinWorkerThread w = getWorker(); |
813 |
|
|
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
814 |
|
|
awaitDone(w, true); |
815 |
|
|
return reportFutureResult(); |
816 |
|
|
} |
817 |
|
|
|
818 |
|
|
public final V get(long timeout, TimeUnit unit) |
819 |
|
|
throws InterruptedException, ExecutionException, TimeoutException { |
820 |
dl |
1.25 |
long nanos = unit.toNanos(timeout); |
821 |
dl |
1.3 |
ForkJoinWorkerThread w = getWorker(); |
822 |
|
|
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
823 |
dl |
1.25 |
awaitDone(w, nanos); |
824 |
dl |
1.3 |
return reportTimedFutureResult(); |
825 |
|
|
} |
826 |
|
|
|
827 |
dl |
1.1 |
/** |
828 |
dl |
1.41 |
* Possibly executes other tasks until this task {@link #isDone is |
829 |
|
|
* done}, then returns the result of the computation. This method |
830 |
|
|
* may be more efficient than {@code join}, but is only applicable |
831 |
|
|
* when there are no potential dependencies between continuation |
832 |
|
|
* of the current task and that of any other task that might be |
833 |
|
|
* executed while helping. (This usually holds for pure |
834 |
|
|
* divide-and-conquer tasks). |
835 |
jsr166 |
1.31 |
* |
836 |
|
|
* <p>This method may be invoked only from within {@code |
837 |
|
|
* ForkJoinTask} computations (as may be determined using method |
838 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
839 |
|
|
* result in exceptions or errors, possibly including {@code |
840 |
|
|
* ClassCastException}. |
841 |
jsr166 |
1.10 |
* |
842 |
dl |
1.2 |
* @return the computed result |
843 |
|
|
*/ |
844 |
|
|
public final V helpJoin() { |
845 |
jsr166 |
1.14 |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread(); |
846 |
dl |
1.2 |
if (status < 0 || !w.unpushTask(this) || !tryExec()) |
847 |
dl |
1.3 |
reportException(busyJoin(w)); |
848 |
dl |
1.2 |
return getRawResult(); |
849 |
|
|
} |
850 |
|
|
|
851 |
|
|
/** |
852 |
dl |
1.41 |
* Possibly executes other tasks until this task {@link #isDone is |
853 |
|
|
* done}. This method may be useful when processing collections |
854 |
|
|
* of tasks when some have been cancelled or otherwise known to |
855 |
|
|
* have aborted. |
856 |
jsr166 |
1.31 |
* |
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 |
dl |
1.2 |
*/ |
863 |
|
|
public final void quietlyHelpJoin() { |
864 |
|
|
if (status >= 0) { |
865 |
|
|
ForkJoinWorkerThread w = |
866 |
jsr166 |
1.14 |
(ForkJoinWorkerThread) Thread.currentThread(); |
867 |
dl |
1.2 |
if (!w.unpushTask(this) || !tryQuietlyInvoke()) |
868 |
dl |
1.3 |
busyJoin(w); |
869 |
dl |
1.2 |
} |
870 |
|
|
} |
871 |
|
|
|
872 |
|
|
/** |
873 |
|
|
* Joins this task, without returning its result or throwing an |
874 |
|
|
* exception. This method may be useful when processing |
875 |
|
|
* collections of tasks when some have been cancelled or otherwise |
876 |
|
|
* known to have aborted. |
877 |
|
|
*/ |
878 |
|
|
public final void quietlyJoin() { |
879 |
|
|
if (status >= 0) { |
880 |
|
|
ForkJoinWorkerThread w = getWorker(); |
881 |
|
|
if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke()) |
882 |
|
|
awaitDone(w, true); |
883 |
|
|
} |
884 |
|
|
} |
885 |
|
|
|
886 |
|
|
/** |
887 |
|
|
* Commences performing this task and awaits its completion if |
888 |
|
|
* necessary, without returning its result or throwing an |
889 |
|
|
* exception. This method may be useful when processing |
890 |
|
|
* collections of tasks when some have been cancelled or otherwise |
891 |
|
|
* known to have aborted. |
892 |
|
|
*/ |
893 |
|
|
public final void quietlyInvoke() { |
894 |
|
|
if (status >= 0 && !tryQuietlyInvoke()) |
895 |
|
|
quietlyJoin(); |
896 |
|
|
} |
897 |
|
|
|
898 |
|
|
/** |
899 |
dl |
1.3 |
* Possibly executes tasks until the pool hosting the current task |
900 |
dl |
1.33 |
* {@link ForkJoinPool#isQuiescent is quiescent}. This method may |
901 |
|
|
* be of use in designs in which many tasks are forked, but none |
902 |
|
|
* are explicitly joined, instead executing them until all are |
903 |
|
|
* processed. |
904 |
jsr166 |
1.31 |
* |
905 |
|
|
* <p>This method may be invoked only from within {@code |
906 |
|
|
* ForkJoinTask} computations (as may be determined using method |
907 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
908 |
|
|
* result in exceptions or errors, possibly including {@code |
909 |
|
|
* ClassCastException}. |
910 |
dl |
1.3 |
*/ |
911 |
|
|
public static void helpQuiesce() { |
912 |
jsr166 |
1.14 |
((ForkJoinWorkerThread) Thread.currentThread()) |
913 |
|
|
.helpQuiescePool(); |
914 |
dl |
1.3 |
} |
915 |
|
|
|
916 |
|
|
/** |
917 |
dl |
1.1 |
* Resets the internal bookkeeping state of this task, allowing a |
918 |
jsr166 |
1.8 |
* subsequent {@code fork}. This method allows repeated reuse of |
919 |
dl |
1.1 |
* this task, but only if reuse occurs when this task has either |
920 |
|
|
* never been forked, or has been forked, then completed and all |
921 |
|
|
* outstanding joins of this task have also completed. Effects |
922 |
dl |
1.30 |
* under any other usage conditions are not guaranteed. |
923 |
|
|
* This method may be useful when executing |
924 |
dl |
1.1 |
* pre-constructed trees of subtasks in loops. |
925 |
|
|
*/ |
926 |
|
|
public void reinitialize() { |
927 |
|
|
if ((status & COMPLETION_MASK) == EXCEPTIONAL) |
928 |
|
|
exceptionMap.remove(this); |
929 |
|
|
status = 0; |
930 |
|
|
} |
931 |
|
|
|
932 |
|
|
/** |
933 |
dl |
1.2 |
* Returns the pool hosting the current task execution, or null |
934 |
dl |
1.13 |
* if this task is executing outside of any ForkJoinPool. |
935 |
jsr166 |
1.10 |
* |
936 |
dl |
1.27 |
* @see #inForkJoinPool |
937 |
jsr166 |
1.23 |
* @return the pool, or {@code null} if none |
938 |
dl |
1.1 |
*/ |
939 |
dl |
1.2 |
public static ForkJoinPool getPool() { |
940 |
|
|
Thread t = Thread.currentThread(); |
941 |
jsr166 |
1.15 |
return (t instanceof ForkJoinWorkerThread) ? |
942 |
|
|
((ForkJoinWorkerThread) t).pool : null; |
943 |
dl |
1.1 |
} |
944 |
|
|
|
945 |
|
|
/** |
946 |
jsr166 |
1.14 |
* Returns {@code true} if the current thread is executing as a |
947 |
dl |
1.13 |
* ForkJoinPool computation. |
948 |
jsr166 |
1.14 |
* |
949 |
|
|
* @return {@code true} if the current thread is executing as a |
950 |
dl |
1.13 |
* ForkJoinPool computation, or false otherwise |
951 |
|
|
*/ |
952 |
|
|
public static boolean inForkJoinPool() { |
953 |
|
|
return Thread.currentThread() instanceof ForkJoinWorkerThread; |
954 |
|
|
} |
955 |
|
|
|
956 |
|
|
/** |
957 |
dl |
1.2 |
* Tries to unschedule this task for execution. This method will |
958 |
|
|
* typically succeed if this task is the most recently forked task |
959 |
|
|
* by the current thread, and has not commenced executing in |
960 |
|
|
* another thread. This method may be useful when arranging |
961 |
|
|
* alternative local processing of tasks that could have been, but |
962 |
jsr166 |
1.31 |
* were not, stolen. |
963 |
|
|
* |
964 |
|
|
* <p>This method may be invoked only from within {@code |
965 |
|
|
* ForkJoinTask} computations (as may be determined using method |
966 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
967 |
|
|
* result in exceptions or errors, possibly including {@code |
968 |
|
|
* ClassCastException}. |
969 |
jsr166 |
1.10 |
* |
970 |
jsr166 |
1.23 |
* @return {@code true} if unforked |
971 |
dl |
1.1 |
*/ |
972 |
dl |
1.2 |
public boolean tryUnfork() { |
973 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
974 |
|
|
.unpushTask(this); |
975 |
dl |
1.1 |
} |
976 |
|
|
|
977 |
|
|
/** |
978 |
dl |
1.2 |
* Returns an estimate of the number of tasks that have been |
979 |
|
|
* forked by the current worker thread but not yet executed. This |
980 |
|
|
* value may be useful for heuristic decisions about whether to |
981 |
jsr166 |
1.31 |
* fork other tasks. |
982 |
|
|
* |
983 |
|
|
* <p>This method may be invoked only from within {@code |
984 |
|
|
* ForkJoinTask} computations (as may be determined using method |
985 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
986 |
|
|
* result in exceptions or errors, possibly including {@code |
987 |
|
|
* ClassCastException}. |
988 |
|
|
* |
989 |
dl |
1.2 |
* @return the number of tasks |
990 |
|
|
*/ |
991 |
|
|
public static int getQueuedTaskCount() { |
992 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
993 |
|
|
.getQueueSize(); |
994 |
dl |
1.2 |
} |
995 |
|
|
|
996 |
|
|
/** |
997 |
jsr166 |
1.10 |
* Returns an estimate of how many more locally queued tasks are |
998 |
dl |
1.1 |
* held by the current worker thread than there are other worker |
999 |
dl |
1.2 |
* threads that might steal them. This value may be useful for |
1000 |
|
|
* heuristic decisions about whether to fork other tasks. In many |
1001 |
|
|
* usages of ForkJoinTasks, at steady state, each worker should |
1002 |
|
|
* aim to maintain a small constant surplus (for example, 3) of |
1003 |
|
|
* tasks, and to process computations locally if this threshold is |
1004 |
jsr166 |
1.31 |
* exceeded. |
1005 |
|
|
* |
1006 |
|
|
* <p>This method may be invoked only from within {@code |
1007 |
|
|
* ForkJoinTask} computations (as may be determined using method |
1008 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1009 |
|
|
* result in exceptions or errors, possibly including {@code |
1010 |
|
|
* ClassCastException}. |
1011 |
|
|
* |
1012 |
dl |
1.1 |
* @return the surplus number of tasks, which may be negative |
1013 |
|
|
*/ |
1014 |
dl |
1.2 |
public static int getSurplusQueuedTaskCount() { |
1015 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1016 |
dl |
1.1 |
.getEstimatedSurplusTaskCount(); |
1017 |
|
|
} |
1018 |
|
|
|
1019 |
dl |
1.2 |
// Extension methods |
1020 |
dl |
1.1 |
|
1021 |
|
|
/** |
1022 |
jsr166 |
1.23 |
* Returns the result that would be returned by {@link #join}, even |
1023 |
|
|
* if this task completed abnormally, or {@code null} if this task |
1024 |
|
|
* is not known to have been completed. This method is designed |
1025 |
|
|
* to aid debugging, as well as to support extensions. Its use in |
1026 |
|
|
* any other context is discouraged. |
1027 |
dl |
1.1 |
* |
1028 |
jsr166 |
1.23 |
* @return the result, or {@code null} if not completed |
1029 |
dl |
1.1 |
*/ |
1030 |
|
|
public abstract V getRawResult(); |
1031 |
|
|
|
1032 |
|
|
/** |
1033 |
|
|
* Forces the given value to be returned as a result. This method |
1034 |
|
|
* is designed to support extensions, and should not in general be |
1035 |
|
|
* called otherwise. |
1036 |
|
|
* |
1037 |
|
|
* @param value the value |
1038 |
|
|
*/ |
1039 |
|
|
protected abstract void setRawResult(V value); |
1040 |
|
|
|
1041 |
|
|
/** |
1042 |
|
|
* Immediately performs the base action of this task. This method |
1043 |
|
|
* is designed to support extensions, and should not in general be |
1044 |
|
|
* called otherwise. The return value controls whether this task |
1045 |
|
|
* is considered to be done normally. It may return false in |
1046 |
|
|
* asynchronous actions that require explicit invocations of |
1047 |
dl |
1.34 |
* {@link #complete} to become joinable. It may also throw an |
1048 |
|
|
* (unchecked) exception to indicate abnormal exit. |
1049 |
jsr166 |
1.10 |
* |
1050 |
jsr166 |
1.23 |
* @return {@code true} if completed normally |
1051 |
dl |
1.1 |
*/ |
1052 |
|
|
protected abstract boolean exec(); |
1053 |
|
|
|
1054 |
dl |
1.2 |
/** |
1055 |
dl |
1.25 |
* Returns, but does not unschedule or execute, a task queued by |
1056 |
|
|
* the current thread but not yet executed, if one is immediately |
1057 |
dl |
1.6 |
* available. There is no guarantee that this task will actually |
1058 |
dl |
1.25 |
* be polled or executed next. Conversely, this method may return |
1059 |
|
|
* null even if a task exists but cannot be accessed without |
1060 |
|
|
* contention with other threads. This method is designed |
1061 |
|
|
* primarily to support extensions, and is unlikely to be useful |
1062 |
jsr166 |
1.31 |
* 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<?> peekNextLocalTask() { |
1073 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1074 |
|
|
.peekTask(); |
1075 |
dl |
1.2 |
} |
1076 |
|
|
|
1077 |
|
|
/** |
1078 |
dl |
1.6 |
* Unschedules and returns, without executing, the next task |
1079 |
|
|
* queued by the current thread but not yet executed. This method |
1080 |
|
|
* is designed primarily to support extensions, and is unlikely to |
1081 |
jsr166 |
1.31 |
* be useful otherwise. |
1082 |
|
|
* |
1083 |
|
|
* <p>This method may be invoked only from within {@code |
1084 |
|
|
* ForkJoinTask} computations (as may be determined using method |
1085 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1086 |
|
|
* result in exceptions or errors, possibly including {@code |
1087 |
|
|
* ClassCastException}. |
1088 |
dl |
1.2 |
* |
1089 |
jsr166 |
1.23 |
* @return the next task, or {@code null} if none are available |
1090 |
dl |
1.2 |
*/ |
1091 |
|
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
1092 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1093 |
|
|
.pollLocalTask(); |
1094 |
dl |
1.2 |
} |
1095 |
jsr166 |
1.7 |
|
1096 |
dl |
1.2 |
/** |
1097 |
dl |
1.6 |
* Unschedules and returns, without executing, the next task |
1098 |
|
|
* queued by the current thread but not yet executed, if one is |
1099 |
|
|
* available, or if not available, a task that was forked by some |
1100 |
|
|
* other thread, if available. Availability may be transient, so a |
1101 |
jsr166 |
1.9 |
* {@code null} result does not necessarily imply quiescence |
1102 |
dl |
1.6 |
* of the pool this task is operating in. This method is designed |
1103 |
|
|
* primarily to support extensions, and is unlikely to be useful |
1104 |
jsr166 |
1.31 |
* otherwise. |
1105 |
|
|
* |
1106 |
|
|
* <p>This method may be invoked only from within {@code |
1107 |
|
|
* ForkJoinTask} computations (as may be determined using method |
1108 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1109 |
|
|
* result in exceptions or errors, possibly including {@code |
1110 |
|
|
* ClassCastException}. |
1111 |
dl |
1.4 |
* |
1112 |
jsr166 |
1.23 |
* @return a task, or {@code null} if none are available |
1113 |
dl |
1.2 |
*/ |
1114 |
|
|
protected static ForkJoinTask<?> pollTask() { |
1115 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1116 |
|
|
.pollTask(); |
1117 |
dl |
1.2 |
} |
1118 |
|
|
|
1119 |
dl |
1.25 |
/** |
1120 |
|
|
* Adaptor for Runnables. This implements RunnableFuture |
1121 |
|
|
* to be compliant with AbstractExecutorService constraints |
1122 |
|
|
* when used in ForkJoinPool. |
1123 |
|
|
*/ |
1124 |
|
|
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
1125 |
|
|
implements RunnableFuture<T> { |
1126 |
|
|
final Runnable runnable; |
1127 |
|
|
final T resultOnCompletion; |
1128 |
|
|
T result; |
1129 |
|
|
AdaptedRunnable(Runnable runnable, T result) { |
1130 |
|
|
if (runnable == null) throw new NullPointerException(); |
1131 |
|
|
this.runnable = runnable; |
1132 |
|
|
this.resultOnCompletion = result; |
1133 |
|
|
} |
1134 |
|
|
public T getRawResult() { return result; } |
1135 |
|
|
public void setRawResult(T v) { result = v; } |
1136 |
|
|
public boolean exec() { |
1137 |
|
|
runnable.run(); |
1138 |
|
|
result = resultOnCompletion; |
1139 |
|
|
return true; |
1140 |
|
|
} |
1141 |
|
|
public void run() { invoke(); } |
1142 |
|
|
private static final long serialVersionUID = 5232453952276885070L; |
1143 |
|
|
} |
1144 |
|
|
|
1145 |
|
|
/** |
1146 |
|
|
* Adaptor for Callables |
1147 |
|
|
*/ |
1148 |
|
|
static final class AdaptedCallable<T> extends ForkJoinTask<T> |
1149 |
|
|
implements RunnableFuture<T> { |
1150 |
dl |
1.27 |
final Callable<? extends T> callable; |
1151 |
dl |
1.25 |
T result; |
1152 |
dl |
1.27 |
AdaptedCallable(Callable<? extends T> callable) { |
1153 |
dl |
1.25 |
if (callable == null) throw new NullPointerException(); |
1154 |
|
|
this.callable = callable; |
1155 |
|
|
} |
1156 |
|
|
public T getRawResult() { return result; } |
1157 |
|
|
public void setRawResult(T v) { result = v; } |
1158 |
|
|
public boolean exec() { |
1159 |
|
|
try { |
1160 |
|
|
result = callable.call(); |
1161 |
|
|
return true; |
1162 |
|
|
} catch (Error err) { |
1163 |
|
|
throw err; |
1164 |
|
|
} catch (RuntimeException rex) { |
1165 |
|
|
throw rex; |
1166 |
|
|
} catch (Exception ex) { |
1167 |
|
|
throw new RuntimeException(ex); |
1168 |
|
|
} |
1169 |
|
|
} |
1170 |
|
|
public void run() { invoke(); } |
1171 |
|
|
private static final long serialVersionUID = 2838392045355241008L; |
1172 |
|
|
} |
1173 |
dl |
1.18 |
|
1174 |
|
|
/** |
1175 |
jsr166 |
1.31 |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1176 |
|
|
* method of the given {@code Runnable} as its action, and returns |
1177 |
|
|
* a null result upon {@link #join}. |
1178 |
dl |
1.18 |
* |
1179 |
|
|
* @param runnable the runnable action |
1180 |
|
|
* @return the task |
1181 |
|
|
*/ |
1182 |
dl |
1.27 |
public static ForkJoinTask<?> adapt(Runnable runnable) { |
1183 |
dl |
1.25 |
return new AdaptedRunnable<Void>(runnable, null); |
1184 |
dl |
1.18 |
} |
1185 |
|
|
|
1186 |
|
|
/** |
1187 |
jsr166 |
1.31 |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1188 |
|
|
* method of the given {@code Runnable} as its action, and returns |
1189 |
|
|
* the given result upon {@link #join}. |
1190 |
dl |
1.18 |
* |
1191 |
|
|
* @param runnable the runnable action |
1192 |
|
|
* @param result the result upon completion |
1193 |
|
|
* @return the task |
1194 |
|
|
*/ |
1195 |
|
|
public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) { |
1196 |
dl |
1.25 |
return new AdaptedRunnable<T>(runnable, result); |
1197 |
dl |
1.18 |
} |
1198 |
|
|
|
1199 |
|
|
/** |
1200 |
jsr166 |
1.31 |
* Returns a new {@code ForkJoinTask} that performs the {@code call} |
1201 |
|
|
* method of the given {@code Callable} as its action, and returns |
1202 |
|
|
* its result upon {@link #join}, translating any checked exceptions |
1203 |
|
|
* encountered into {@code RuntimeException}. |
1204 |
dl |
1.18 |
* |
1205 |
|
|
* @param callable the callable action |
1206 |
|
|
* @return the task |
1207 |
|
|
*/ |
1208 |
dl |
1.27 |
public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) { |
1209 |
dl |
1.25 |
return new AdaptedCallable<T>(callable); |
1210 |
dl |
1.18 |
} |
1211 |
|
|
|
1212 |
dl |
1.1 |
// Serialization support |
1213 |
|
|
|
1214 |
|
|
private static final long serialVersionUID = -7721805057305804111L; |
1215 |
|
|
|
1216 |
|
|
/** |
1217 |
|
|
* Save the state to a stream. |
1218 |
|
|
* |
1219 |
|
|
* @serialData the current run status and the exception thrown |
1220 |
jsr166 |
1.23 |
* during execution, or {@code null} if none |
1221 |
dl |
1.1 |
* @param s the stream |
1222 |
|
|
*/ |
1223 |
|
|
private void writeObject(java.io.ObjectOutputStream s) |
1224 |
|
|
throws java.io.IOException { |
1225 |
|
|
s.defaultWriteObject(); |
1226 |
|
|
s.writeObject(getException()); |
1227 |
|
|
} |
1228 |
|
|
|
1229 |
|
|
/** |
1230 |
|
|
* Reconstitute the instance from a stream. |
1231 |
jsr166 |
1.10 |
* |
1232 |
dl |
1.1 |
* @param s the stream |
1233 |
|
|
*/ |
1234 |
|
|
private void readObject(java.io.ObjectInputStream s) |
1235 |
|
|
throws java.io.IOException, ClassNotFoundException { |
1236 |
|
|
s.defaultReadObject(); |
1237 |
dl |
1.2 |
status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts |
1238 |
|
|
status |= EXTERNAL_SIGNAL; // conservatively set external signal |
1239 |
dl |
1.1 |
Object ex = s.readObject(); |
1240 |
|
|
if (ex != null) |
1241 |
jsr166 |
1.14 |
setDoneExceptionally((Throwable) ex); |
1242 |
dl |
1.1 |
} |
1243 |
|
|
|
1244 |
jsr166 |
1.22 |
// Unsafe mechanics |
1245 |
|
|
|
1246 |
|
|
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1247 |
|
|
private static final long statusOffset = |
1248 |
|
|
objectFieldOffset("status", ForkJoinTask.class); |
1249 |
|
|
|
1250 |
|
|
private static long objectFieldOffset(String field, Class<?> klazz) { |
1251 |
|
|
try { |
1252 |
|
|
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1253 |
|
|
} catch (NoSuchFieldException e) { |
1254 |
|
|
// Convert Exception to corresponding Error |
1255 |
|
|
NoSuchFieldError error = new NoSuchFieldError(field); |
1256 |
|
|
error.initCause(e); |
1257 |
|
|
throw error; |
1258 |
|
|
} |
1259 |
|
|
} |
1260 |
|
|
|
1261 |
|
|
/** |
1262 |
|
|
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
1263 |
|
|
* Replace with a simple call to Unsafe.getUnsafe when integrating |
1264 |
|
|
* into a jdk. |
1265 |
|
|
* |
1266 |
|
|
* @return a sun.misc.Unsafe |
1267 |
|
|
*/ |
1268 |
jsr166 |
1.16 |
private static sun.misc.Unsafe getUnsafe() { |
1269 |
jsr166 |
1.5 |
try { |
1270 |
jsr166 |
1.16 |
return sun.misc.Unsafe.getUnsafe(); |
1271 |
jsr166 |
1.5 |
} catch (SecurityException se) { |
1272 |
|
|
try { |
1273 |
|
|
return java.security.AccessController.doPrivileged |
1274 |
jsr166 |
1.22 |
(new java.security |
1275 |
|
|
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1276 |
jsr166 |
1.16 |
public sun.misc.Unsafe run() throws Exception { |
1277 |
jsr166 |
1.22 |
java.lang.reflect.Field f = sun.misc |
1278 |
|
|
.Unsafe.class.getDeclaredField("theUnsafe"); |
1279 |
|
|
f.setAccessible(true); |
1280 |
|
|
return (sun.misc.Unsafe) f.get(null); |
1281 |
jsr166 |
1.5 |
}}); |
1282 |
|
|
} catch (java.security.PrivilegedActionException e) { |
1283 |
jsr166 |
1.16 |
throw new RuntimeException("Could not initialize intrinsics", |
1284 |
|
|
e.getCause()); |
1285 |
jsr166 |
1.5 |
} |
1286 |
|
|
} |
1287 |
|
|
} |
1288 |
dl |
1.1 |
} |