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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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import java.io.Serializable; |
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import java.util.*; |
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import java.util.concurrent.*; |
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import java.util.concurrent.atomic.*; |
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import sun.misc.Unsafe; |
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import java.lang.reflect.*; |
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/** |
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dl |
1.2 |
* Abstract base class for tasks that run within a {@link |
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* ForkJoinPool}. A ForkJoinTask is a thread-like entity that is much |
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* lighter weight than a normal thread. Huge numbers of tasks and |
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* subtasks may be hosted by a small number of actual threads in a |
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* ForkJoinPool, at the price of some usage limitations. |
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1.4 |
* |
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1.2 |
* <p> A "main" ForkJoinTask begins execution when submitted to a |
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* {@link ForkJoinPool}. Once started, it will usually in turn start |
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* other subtasks. As indicated by the name of this class, many |
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jsr166 |
1.8 |
* programs using ForkJoinTasks employ only methods {@code fork} |
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* and {@code join}, or derivatives such as |
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* {@code invokeAll}. However, this class also provides a number |
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1.2 |
* of other methods that can come into play in advanced usages, as |
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* well as extension mechanics that allow support of new forms of |
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* fork/join processing. |
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1.4 |
* |
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1.2 |
* <p>A ForkJoinTask is a lightweight form of {@link Future}. The |
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* efficiency of ForkJoinTasks stems from a set of restrictions (that |
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* are only partially statically enforceable) reflecting their |
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* intended use as computational tasks calculating pure functions or |
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* operating on purely isolated objects. The primary coordination |
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* mechanisms are {@link #fork}, that arranges asynchronous execution, |
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* and {@link #join}, that doesn't proceed until the task's result has |
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jsr166 |
1.8 |
* been computed. Computations should avoid {@code synchronized} |
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1.2 |
* methods or blocks, and should minimize other blocking |
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* synchronization apart from joining other tasks or using |
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1.1 |
* synchronizers such as Phasers that are advertised to cooperate with |
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* fork/join scheduling. Tasks should also not perform blocking IO, |
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* and should ideally access variables that are completely independent |
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* of those accessed by other running tasks. Minor breaches of these |
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* restrictions, for example using shared output streams, may be |
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* tolerable in practice, but frequent use may result in poor |
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* performance, and the potential to indefinitely stall if the number |
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1.2 |
* of threads not waiting for IO or other external synchronization |
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* becomes exhausted. This usage restriction is in part enforced by |
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jsr166 |
1.8 |
* not permitting checked exceptions such as {@code IOExceptions} |
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1.2 |
* to be thrown. However, computations may still encounter unchecked |
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1.1 |
* exceptions, that are rethrown to callers attempting join |
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* them. These exceptions may additionally include |
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* RejectedExecutionExceptions stemming from internal resource |
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* exhaustion such as failure to allocate internal task queues. |
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* |
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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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jsr166 |
1.8 |
* equivalent to {@code fork(); join()} but always attempts to |
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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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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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* <p> The ForkJoinTask class is not usually directly subclassed. |
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* Instead, you subclass one of the abstract classes that support a |
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* particular style of fork/join processing. Normally, a concrete |
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* 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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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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1.2 |
* instances of different task subclasses to call each others |
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* methods), some of them may only be called from within other |
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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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1.13 |
* ClassCastException. |
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1.1 |
* |
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jsr166 |
1.8 |
* <p>Most base support methods are {@code final} because their |
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1.1 |
* implementations are intrinsically tied to the underlying |
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* lightweight task scheduling framework, and so cannot be overridden. |
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* Developers creating new basic styles of fork/join processing should |
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jsr166 |
1.8 |
* minimally implement {@code protected} methods |
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* {@code exec}, {@code setRawResult}, and |
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* {@code getRawResult}, while also introducing an abstract |
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1.2 |
* computational method that can be implemented in its subclasses, |
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jsr166 |
1.8 |
* possibly relying on other {@code protected} methods provided |
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1.2 |
* by this class. |
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1.1 |
* |
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* <p>ForkJoinTasks should perform relatively small amounts of |
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jsr166 |
1.9 |
* computations, otherwise splitting into smaller tasks. As a very |
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1.1 |
* rough rule of thumb, a task should perform more than 100 and less |
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* than 10000 basic computational steps. If tasks are too big, then |
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jsr166 |
1.9 |
* parallelism cannot improve throughput. If too small, then memory |
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1.1 |
* and internal task maintenance overhead may overwhelm processing. |
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* |
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jsr166 |
1.8 |
* <p>ForkJoinTasks are {@code Serializable}, which enables them |
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1.2 |
* to be used in extensions such as remote execution frameworks. It is |
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* in general sensible to serialize tasks only before or after, but |
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1.1 |
* not during execution. Serialization is not relied on during |
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* execution itself. |
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jsr166 |
1.12 |
* |
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* @since 1.7 |
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* @author Doug Lea |
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1.1 |
*/ |
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public abstract class ForkJoinTask<V> implements Future<V>, Serializable { |
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1.2 |
|
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1.1 |
/** |
119 |
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1.2 |
* Run control status bits packed into a single int to minimize |
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* footprint and to ensure atomicity (via CAS). Status is |
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* initially zero, and takes on nonnegative values until |
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dl |
1.1 |
* completed, upon which status holds COMPLETED. CANCELLED, or |
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* EXCEPTIONAL, which use the top 3 bits. Tasks undergoing |
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* blocking waits by other threads have SIGNAL_MASK bits set -- |
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* bit 15 for external (nonFJ) waits, and the rest a count of |
126 |
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* waiting FJ threads. (This representation relies on |
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* ForkJoinPool max thread limits). Completion of a stolen task |
128 |
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* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even |
129 |
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* though suboptimal for some purposes, we use basic builtin |
130 |
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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 |
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* per-task bookkeeping overhead. Note that bits 16-28 are |
133 |
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* currently unused. Also value 0x80000000 is available as spare |
134 |
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* completion value. |
135 |
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*/ |
136 |
jsr166 |
1.9 |
volatile int status; // accessed directly by pool and workers |
137 |
dl |
1.1 |
|
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static final int COMPLETION_MASK = 0xe0000000; |
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static final int NORMAL = 0xe0000000; // == mask |
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static final int CANCELLED = 0xc0000000; |
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static final int EXCEPTIONAL = 0xa0000000; |
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static final int SIGNAL_MASK = 0x0000ffff; |
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static final int INTERNAL_SIGNAL_MASK = 0x00007fff; |
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static final int EXTERNAL_SIGNAL = 0x00008000; // top bit of low word |
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/** |
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* Table of exceptions thrown by tasks, to enable reporting by |
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* callers. Because exceptions are rare, we don't directly keep |
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jsr166 |
1.10 |
* them with task objects, but instead use a weak ref table. Note |
150 |
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1.1 |
* that cancellation exceptions don't appear in the table, but are |
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* instead recorded as status values. |
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jsr166 |
1.10 |
* TODO: Use ConcurrentReferenceHashMap |
153 |
dl |
1.1 |
*/ |
154 |
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static final Map<ForkJoinTask<?>, Throwable> exceptionMap = |
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Collections.synchronizedMap |
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(new WeakHashMap<ForkJoinTask<?>, Throwable>()); |
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// within-package utilities |
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/** |
161 |
jsr166 |
1.10 |
* Gets current worker thread, or null if not a worker thread. |
162 |
dl |
1.1 |
*/ |
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static ForkJoinWorkerThread getWorker() { |
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Thread t = Thread.currentThread(); |
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jsr166 |
1.14 |
return ((t instanceof ForkJoinWorkerThread) ? |
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(ForkJoinWorkerThread) t : null); |
167 |
dl |
1.1 |
} |
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final boolean casStatus(int cmp, int val) { |
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jsr166 |
1.11 |
return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val); |
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dl |
1.1 |
} |
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/** |
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* Workaround for not being able to rethrow unchecked exceptions. |
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*/ |
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static void rethrowException(Throwable ex) { |
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if (ex != null) |
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jsr166 |
1.11 |
UNSAFE.throwException(ex); |
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dl |
1.1 |
} |
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// Setting completion status |
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/** |
184 |
jsr166 |
1.10 |
* Marks completion and wakes up threads waiting to join this task. |
185 |
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* |
186 |
dl |
1.1 |
* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
187 |
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*/ |
188 |
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final void setCompletion(int completion) { |
189 |
dl |
1.2 |
ForkJoinPool pool = getPool(); |
190 |
dl |
1.1 |
if (pool != null) { |
191 |
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int s; // Clear signal bits while setting completion status |
192 |
jsr166 |
1.14 |
do {} while ((s = status) >= 0 && !casStatus(s, completion)); |
193 |
dl |
1.1 |
|
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if ((s & SIGNAL_MASK) != 0) { |
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if ((s &= INTERNAL_SIGNAL_MASK) != 0) |
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pool.updateRunningCount(s); |
197 |
jsr166 |
1.14 |
synchronized (this) { notifyAll(); } |
198 |
dl |
1.1 |
} |
199 |
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} |
200 |
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else |
201 |
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externallySetCompletion(completion); |
202 |
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} |
203 |
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204 |
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/** |
205 |
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* Version of setCompletion for non-FJ threads. Leaves signal |
206 |
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* bits for unblocked threads to adjust, and always notifies. |
207 |
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*/ |
208 |
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private void externallySetCompletion(int completion) { |
209 |
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int s; |
210 |
jsr166 |
1.14 |
do {} while ((s = status) >= 0 && |
211 |
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!casStatus(s, (s & SIGNAL_MASK) | completion)); |
212 |
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synchronized (this) { notifyAll(); } |
213 |
dl |
1.1 |
} |
214 |
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215 |
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/** |
216 |
jsr166 |
1.14 |
* Sets status to indicate normal completion. |
217 |
dl |
1.1 |
*/ |
218 |
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final void setNormalCompletion() { |
219 |
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// Try typical fast case -- single CAS, no signal, not already done. |
220 |
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// Manually expand casStatus to improve chances of inlining it |
221 |
jsr166 |
1.11 |
if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL)) |
222 |
dl |
1.1 |
setCompletion(NORMAL); |
223 |
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} |
224 |
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225 |
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// internal waiting and notification |
226 |
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227 |
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/** |
228 |
jsr166 |
1.14 |
* Performs the actual monitor wait for awaitDone. |
229 |
dl |
1.1 |
*/ |
230 |
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private void doAwaitDone() { |
231 |
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// Minimize lock bias and in/de-flation effects by maximizing |
232 |
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// chances of waiting inside sync |
233 |
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try { |
234 |
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while (status >= 0) |
235 |
jsr166 |
1.14 |
synchronized (this) { if (status >= 0) wait(); } |
236 |
dl |
1.1 |
} catch (InterruptedException ie) { |
237 |
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onInterruptedWait(); |
238 |
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} |
239 |
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} |
240 |
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241 |
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/** |
242 |
jsr166 |
1.14 |
* Performs the actual timed monitor wait for awaitDone. |
243 |
dl |
1.1 |
*/ |
244 |
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private void doAwaitDone(long startTime, long nanos) { |
245 |
jsr166 |
1.14 |
synchronized (this) { |
246 |
dl |
1.1 |
try { |
247 |
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while (status >= 0) { |
248 |
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long nt = nanos - System.nanoTime() - startTime; |
249 |
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if (nt <= 0) |
250 |
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break; |
251 |
jsr166 |
1.14 |
wait(nt / 1000000, (int) (nt % 1000000)); |
252 |
dl |
1.1 |
} |
253 |
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} catch (InterruptedException ie) { |
254 |
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onInterruptedWait(); |
255 |
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} |
256 |
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} |
257 |
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} |
258 |
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259 |
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// Awaiting completion |
260 |
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261 |
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/** |
262 |
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* Sets status to indicate there is joiner, then waits for join, |
263 |
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* surrounded with pool notifications. |
264 |
jsr166 |
1.10 |
* |
265 |
dl |
1.1 |
* @return status upon exit |
266 |
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*/ |
267 |
jsr166 |
1.14 |
private int awaitDone(ForkJoinWorkerThread w, |
268 |
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boolean maintainParallelism) { |
269 |
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ForkJoinPool pool = (w == null) ? null : w.pool; |
270 |
dl |
1.1 |
int s; |
271 |
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while ((s = status) >= 0) { |
272 |
jsr166 |
1.14 |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
273 |
dl |
1.1 |
if (pool == null || !pool.preJoin(this, maintainParallelism)) |
274 |
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doAwaitDone(); |
275 |
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if (((s = status) & INTERNAL_SIGNAL_MASK) != 0) |
276 |
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adjustPoolCountsOnUnblock(pool); |
277 |
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break; |
278 |
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} |
279 |
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} |
280 |
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return s; |
281 |
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} |
282 |
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283 |
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/** |
284 |
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* Timed version of awaitDone |
285 |
jsr166 |
1.14 |
* |
286 |
dl |
1.1 |
* @return status upon exit |
287 |
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*/ |
288 |
dl |
1.3 |
private int awaitDone(ForkJoinWorkerThread w, long nanos) { |
289 |
jsr166 |
1.14 |
ForkJoinPool pool = (w == null) ? null : w.pool; |
290 |
dl |
1.1 |
int s; |
291 |
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while ((s = status) >= 0) { |
292 |
jsr166 |
1.14 |
if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) { |
293 |
dl |
1.1 |
long startTime = System.nanoTime(); |
294 |
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if (pool == null || !pool.preJoin(this, false)) |
295 |
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doAwaitDone(startTime, nanos); |
296 |
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if ((s = status) >= 0) { |
297 |
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adjustPoolCountsOnCancelledWait(pool); |
298 |
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s = status; |
299 |
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} |
300 |
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if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0) |
301 |
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adjustPoolCountsOnUnblock(pool); |
302 |
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break; |
303 |
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} |
304 |
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} |
305 |
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return s; |
306 |
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} |
307 |
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|
308 |
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/** |
309 |
jsr166 |
1.10 |
* Notifies pool that thread is unblocked. Called by signalled |
310 |
dl |
1.1 |
* threads when woken by non-FJ threads (which is atypical). |
311 |
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*/ |
312 |
|
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private void adjustPoolCountsOnUnblock(ForkJoinPool pool) { |
313 |
|
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int s; |
314 |
jsr166 |
1.14 |
do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK)); |
315 |
dl |
1.1 |
if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0) |
316 |
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pool.updateRunningCount(s); |
317 |
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} |
318 |
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|
319 |
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/** |
320 |
jsr166 |
1.10 |
* Notifies pool to adjust counts on cancelled or timed out wait. |
321 |
dl |
1.1 |
*/ |
322 |
|
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private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) { |
323 |
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if (pool != null) { |
324 |
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int s; |
325 |
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while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) { |
326 |
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if (casStatus(s, s - 1)) { |
327 |
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pool.updateRunningCount(1); |
328 |
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break; |
329 |
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} |
330 |
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} |
331 |
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} |
332 |
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} |
333 |
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|
334 |
dl |
1.2 |
/** |
335 |
jsr166 |
1.10 |
* Handles interruptions during waits. |
336 |
dl |
1.2 |
*/ |
337 |
dl |
1.1 |
private void onInterruptedWait() { |
338 |
dl |
1.2 |
ForkJoinWorkerThread w = getWorker(); |
339 |
|
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if (w == null) |
340 |
|
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Thread.currentThread().interrupt(); // re-interrupt |
341 |
|
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else if (w.isTerminating()) |
342 |
dl |
1.3 |
cancelIgnoringExceptions(); |
343 |
dl |
1.2 |
// else if FJworker, ignore interrupt |
344 |
dl |
1.1 |
} |
345 |
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|
346 |
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// Recording and reporting exceptions |
347 |
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|
348 |
|
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private void setDoneExceptionally(Throwable rex) { |
349 |
|
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exceptionMap.put(this, rex); |
350 |
|
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setCompletion(EXCEPTIONAL); |
351 |
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} |
352 |
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353 |
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/** |
354 |
jsr166 |
1.10 |
* Throws the exception associated with status s. |
355 |
|
|
* |
356 |
dl |
1.1 |
* @throws the exception |
357 |
|
|
*/ |
358 |
|
|
private void reportException(int s) { |
359 |
|
|
if ((s &= COMPLETION_MASK) < NORMAL) { |
360 |
|
|
if (s == CANCELLED) |
361 |
|
|
throw new CancellationException(); |
362 |
|
|
else |
363 |
|
|
rethrowException(exceptionMap.get(this)); |
364 |
|
|
} |
365 |
|
|
} |
366 |
|
|
|
367 |
|
|
/** |
368 |
jsr166 |
1.10 |
* Returns result or throws exception using j.u.c.Future conventions. |
369 |
jsr166 |
1.14 |
* Only call when {@code isDone} known to be true. |
370 |
dl |
1.1 |
*/ |
371 |
|
|
private V reportFutureResult() |
372 |
|
|
throws ExecutionException, InterruptedException { |
373 |
|
|
int s = status & COMPLETION_MASK; |
374 |
|
|
if (s < NORMAL) { |
375 |
|
|
Throwable ex; |
376 |
|
|
if (s == CANCELLED) |
377 |
|
|
throw new CancellationException(); |
378 |
|
|
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
379 |
|
|
throw new ExecutionException(ex); |
380 |
|
|
if (Thread.interrupted()) |
381 |
|
|
throw new InterruptedException(); |
382 |
|
|
} |
383 |
|
|
return getRawResult(); |
384 |
|
|
} |
385 |
|
|
|
386 |
|
|
/** |
387 |
|
|
* Returns result or throws exception using j.u.c.Future conventions |
388 |
jsr166 |
1.10 |
* with timeouts. |
389 |
dl |
1.1 |
*/ |
390 |
|
|
private V reportTimedFutureResult() |
391 |
|
|
throws InterruptedException, ExecutionException, TimeoutException { |
392 |
|
|
Throwable ex; |
393 |
|
|
int s = status & COMPLETION_MASK; |
394 |
|
|
if (s == NORMAL) |
395 |
|
|
return getRawResult(); |
396 |
|
|
if (s == CANCELLED) |
397 |
|
|
throw new CancellationException(); |
398 |
|
|
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
399 |
|
|
throw new ExecutionException(ex); |
400 |
|
|
if (Thread.interrupted()) |
401 |
|
|
throw new InterruptedException(); |
402 |
|
|
throw new TimeoutException(); |
403 |
|
|
} |
404 |
|
|
|
405 |
|
|
// internal execution methods |
406 |
|
|
|
407 |
|
|
/** |
408 |
|
|
* Calls exec, recording completion, and rethrowing exception if |
409 |
jsr166 |
1.10 |
* encountered. Caller should normally check status before calling. |
410 |
|
|
* |
411 |
dl |
1.1 |
* @return true if completed normally |
412 |
|
|
*/ |
413 |
|
|
private boolean tryExec() { |
414 |
|
|
try { // try block must contain only call to exec |
415 |
|
|
if (!exec()) |
416 |
|
|
return false; |
417 |
|
|
} catch (Throwable rex) { |
418 |
|
|
setDoneExceptionally(rex); |
419 |
|
|
rethrowException(rex); |
420 |
|
|
return false; // not reached |
421 |
|
|
} |
422 |
|
|
setNormalCompletion(); |
423 |
|
|
return true; |
424 |
|
|
} |
425 |
|
|
|
426 |
|
|
/** |
427 |
|
|
* Main execution method used by worker threads. Invokes |
428 |
jsr166 |
1.10 |
* base computation unless already complete. |
429 |
dl |
1.1 |
*/ |
430 |
|
|
final void quietlyExec() { |
431 |
|
|
if (status >= 0) { |
432 |
|
|
try { |
433 |
|
|
if (!exec()) |
434 |
|
|
return; |
435 |
jsr166 |
1.14 |
} catch (Throwable rex) { |
436 |
dl |
1.1 |
setDoneExceptionally(rex); |
437 |
|
|
return; |
438 |
|
|
} |
439 |
|
|
setNormalCompletion(); |
440 |
|
|
} |
441 |
|
|
} |
442 |
|
|
|
443 |
|
|
/** |
444 |
jsr166 |
1.10 |
* Calls exec(), recording but not rethrowing exception. |
445 |
|
|
* Caller should normally check status before calling. |
446 |
|
|
* |
447 |
dl |
1.1 |
* @return true if completed normally |
448 |
|
|
*/ |
449 |
|
|
private boolean tryQuietlyInvoke() { |
450 |
|
|
try { |
451 |
|
|
if (!exec()) |
452 |
|
|
return false; |
453 |
|
|
} catch (Throwable rex) { |
454 |
|
|
setDoneExceptionally(rex); |
455 |
|
|
return false; |
456 |
|
|
} |
457 |
|
|
setNormalCompletion(); |
458 |
|
|
return true; |
459 |
|
|
} |
460 |
|
|
|
461 |
|
|
/** |
462 |
jsr166 |
1.10 |
* Cancels, ignoring any exceptions it throws. |
463 |
dl |
1.1 |
*/ |
464 |
dl |
1.3 |
final void cancelIgnoringExceptions() { |
465 |
dl |
1.1 |
try { |
466 |
|
|
cancel(false); |
467 |
jsr166 |
1.14 |
} catch (Throwable ignore) { |
468 |
dl |
1.1 |
} |
469 |
|
|
} |
470 |
|
|
|
471 |
dl |
1.3 |
/** |
472 |
|
|
* Main implementation of helpJoin |
473 |
|
|
*/ |
474 |
|
|
private int busyJoin(ForkJoinWorkerThread w) { |
475 |
|
|
int s; |
476 |
|
|
ForkJoinTask<?> t; |
477 |
|
|
while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null) |
478 |
|
|
t.quietlyExec(); |
479 |
jsr166 |
1.14 |
return (s >= 0) ? awaitDone(w, false) : s; // block if no work |
480 |
dl |
1.3 |
} |
481 |
|
|
|
482 |
dl |
1.1 |
// public methods |
483 |
|
|
|
484 |
|
|
/** |
485 |
|
|
* Arranges to asynchronously execute this task. While it is not |
486 |
|
|
* necessarily enforced, it is a usage error to fork a task more |
487 |
|
|
* than once unless it has completed and been reinitialized. This |
488 |
dl |
1.2 |
* method may be invoked only from within ForkJoinTask |
489 |
dl |
1.13 |
* computations (as may be determined using method {@link |
490 |
|
|
* #inForkJoinPool}). Attempts to invoke in other contexts result |
491 |
jsr166 |
1.14 |
* in exceptions or errors, possibly including ClassCastException. |
492 |
dl |
1.1 |
*/ |
493 |
|
|
public final void fork() { |
494 |
jsr166 |
1.14 |
((ForkJoinWorkerThread) Thread.currentThread()) |
495 |
|
|
.pushTask(this); |
496 |
dl |
1.1 |
} |
497 |
|
|
|
498 |
|
|
/** |
499 |
|
|
* Returns the result of the computation when it is ready. |
500 |
jsr166 |
1.8 |
* This method differs from {@code get} in that abnormal |
501 |
dl |
1.1 |
* completion results in RuntimeExceptions or Errors, not |
502 |
|
|
* ExecutionExceptions. |
503 |
|
|
* |
504 |
|
|
* @return the computed result |
505 |
|
|
*/ |
506 |
|
|
public final V join() { |
507 |
|
|
ForkJoinWorkerThread w = getWorker(); |
508 |
|
|
if (w == null || status < 0 || !w.unpushTask(this) || !tryExec()) |
509 |
|
|
reportException(awaitDone(w, true)); |
510 |
|
|
return getRawResult(); |
511 |
|
|
} |
512 |
|
|
|
513 |
|
|
/** |
514 |
dl |
1.2 |
* Commences performing this task, awaits its completion if |
515 |
|
|
* necessary, and return its result. |
516 |
jsr166 |
1.10 |
* |
517 |
dl |
1.1 |
* @throws Throwable (a RuntimeException, Error, or unchecked |
518 |
jsr166 |
1.10 |
* exception) if the underlying computation did so |
519 |
dl |
1.1 |
* @return the computed result |
520 |
|
|
*/ |
521 |
|
|
public final V invoke() { |
522 |
|
|
if (status >= 0 && tryExec()) |
523 |
|
|
return getRawResult(); |
524 |
|
|
else |
525 |
|
|
return join(); |
526 |
|
|
} |
527 |
|
|
|
528 |
|
|
/** |
529 |
jsr166 |
1.8 |
* Forks both tasks, returning when {@code isDone} holds for |
530 |
dl |
1.2 |
* both of them or an exception is encountered. This method may be |
531 |
dl |
1.13 |
* invoked only from within ForkJoinTask computations (as may be |
532 |
|
|
* determined using method {@link #inForkJoinPool}). Attempts to |
533 |
jsr166 |
1.14 |
* invoke in other contexts result in exceptions or errors, |
534 |
dl |
1.4 |
* possibly including ClassCastException. |
535 |
jsr166 |
1.10 |
* |
536 |
dl |
1.2 |
* @param t1 one task |
537 |
|
|
* @param t2 the other task |
538 |
|
|
* @throws NullPointerException if t1 or t2 are null |
539 |
jsr166 |
1.10 |
* @throws RuntimeException or Error if either task did so |
540 |
dl |
1.1 |
*/ |
541 |
dl |
1.2 |
public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) { |
542 |
|
|
t2.fork(); |
543 |
|
|
t1.invoke(); |
544 |
|
|
t2.join(); |
545 |
dl |
1.1 |
} |
546 |
|
|
|
547 |
|
|
/** |
548 |
jsr166 |
1.8 |
* Forks the given tasks, returning when {@code isDone} holds |
549 |
dl |
1.2 |
* for all of them. If any task encounters an exception, others |
550 |
|
|
* may be cancelled. This method may be invoked only from within |
551 |
dl |
1.13 |
* ForkJoinTask computations (as may be determined using method |
552 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
553 |
jsr166 |
1.14 |
* result in exceptions or errors, possibly including |
554 |
dl |
1.13 |
* ClassCastException. |
555 |
jsr166 |
1.14 |
* |
556 |
dl |
1.2 |
* @param tasks the array of tasks |
557 |
jsr166 |
1.10 |
* @throws NullPointerException if tasks or any element are null |
558 |
|
|
* @throws RuntimeException or Error if any task did so |
559 |
dl |
1.1 |
*/ |
560 |
dl |
1.2 |
public static void invokeAll(ForkJoinTask<?>... tasks) { |
561 |
|
|
Throwable ex = null; |
562 |
|
|
int last = tasks.length - 1; |
563 |
|
|
for (int i = last; i >= 0; --i) { |
564 |
|
|
ForkJoinTask<?> t = tasks[i]; |
565 |
|
|
if (t == null) { |
566 |
|
|
if (ex == null) |
567 |
|
|
ex = new NullPointerException(); |
568 |
|
|
} |
569 |
|
|
else if (i != 0) |
570 |
|
|
t.fork(); |
571 |
|
|
else { |
572 |
|
|
t.quietlyInvoke(); |
573 |
|
|
if (ex == null) |
574 |
|
|
ex = t.getException(); |
575 |
|
|
} |
576 |
|
|
} |
577 |
|
|
for (int i = 1; i <= last; ++i) { |
578 |
|
|
ForkJoinTask<?> t = tasks[i]; |
579 |
|
|
if (t != null) { |
580 |
|
|
if (ex != null) |
581 |
|
|
t.cancel(false); |
582 |
|
|
else { |
583 |
|
|
t.quietlyJoin(); |
584 |
|
|
if (ex == null) |
585 |
|
|
ex = t.getException(); |
586 |
|
|
} |
587 |
|
|
} |
588 |
dl |
1.1 |
} |
589 |
dl |
1.2 |
if (ex != null) |
590 |
|
|
rethrowException(ex); |
591 |
dl |
1.1 |
} |
592 |
|
|
|
593 |
|
|
/** |
594 |
dl |
1.2 |
* Forks all tasks in the collection, returning when |
595 |
jsr166 |
1.8 |
* {@code isDone} holds for all of them. If any task |
596 |
dl |
1.2 |
* encounters an exception, others may be cancelled. This method |
597 |
dl |
1.13 |
* may be invoked only from within ForkJoinTask computations (as |
598 |
|
|
* may be determined using method {@link |
599 |
jsr166 |
1.14 |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
600 |
|
|
* in exceptions or errors, possibly including ClassCastException. |
601 |
jsr166 |
1.10 |
* |
602 |
dl |
1.2 |
* @param tasks the collection of tasks |
603 |
jsr166 |
1.10 |
* @throws NullPointerException if tasks or any element are null |
604 |
|
|
* @throws RuntimeException or Error if any task did so |
605 |
dl |
1.1 |
*/ |
606 |
dl |
1.2 |
public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) { |
607 |
|
|
if (!(tasks instanceof List)) { |
608 |
jsr166 |
1.14 |
invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()])); |
609 |
dl |
1.2 |
return; |
610 |
|
|
} |
611 |
|
|
List<? extends ForkJoinTask<?>> ts = |
612 |
jsr166 |
1.14 |
(List<? extends ForkJoinTask<?>>) tasks; |
613 |
dl |
1.2 |
Throwable ex = null; |
614 |
|
|
int last = ts.size() - 1; |
615 |
|
|
for (int i = last; i >= 0; --i) { |
616 |
|
|
ForkJoinTask<?> t = ts.get(i); |
617 |
|
|
if (t == null) { |
618 |
|
|
if (ex == null) |
619 |
|
|
ex = new NullPointerException(); |
620 |
|
|
} |
621 |
|
|
else if (i != 0) |
622 |
|
|
t.fork(); |
623 |
|
|
else { |
624 |
|
|
t.quietlyInvoke(); |
625 |
|
|
if (ex == null) |
626 |
|
|
ex = t.getException(); |
627 |
|
|
} |
628 |
|
|
} |
629 |
|
|
for (int i = 1; i <= last; ++i) { |
630 |
|
|
ForkJoinTask<?> t = ts.get(i); |
631 |
|
|
if (t != null) { |
632 |
|
|
if (ex != null) |
633 |
|
|
t.cancel(false); |
634 |
|
|
else { |
635 |
|
|
t.quietlyJoin(); |
636 |
|
|
if (ex == null) |
637 |
|
|
ex = t.getException(); |
638 |
|
|
} |
639 |
|
|
} |
640 |
|
|
} |
641 |
|
|
if (ex != null) |
642 |
|
|
rethrowException(ex); |
643 |
dl |
1.1 |
} |
644 |
|
|
|
645 |
|
|
/** |
646 |
|
|
* Returns true if the computation performed by this task has |
647 |
|
|
* completed (or has been cancelled). |
648 |
jsr166 |
1.10 |
* |
649 |
dl |
1.1 |
* @return true if this computation has completed |
650 |
|
|
*/ |
651 |
|
|
public final boolean isDone() { |
652 |
|
|
return status < 0; |
653 |
|
|
} |
654 |
|
|
|
655 |
|
|
/** |
656 |
|
|
* Returns true if this task was cancelled. |
657 |
jsr166 |
1.10 |
* |
658 |
dl |
1.1 |
* @return true if this task was cancelled |
659 |
|
|
*/ |
660 |
|
|
public final boolean isCancelled() { |
661 |
|
|
return (status & COMPLETION_MASK) == CANCELLED; |
662 |
|
|
} |
663 |
|
|
|
664 |
|
|
/** |
665 |
|
|
* Asserts that the results of this task's computation will not be |
666 |
jsr166 |
1.9 |
* used. If a cancellation occurs before attempting to execute this |
667 |
jsr166 |
1.8 |
* task, then execution will be suppressed, {@code isCancelled} |
668 |
|
|
* will report true, and {@code join} will result in a |
669 |
|
|
* {@code CancellationException} being thrown. Otherwise, when |
670 |
dl |
1.1 |
* cancellation races with completion, there are no guarantees |
671 |
jsr166 |
1.8 |
* about whether {@code isCancelled} will report true, whether |
672 |
|
|
* {@code join} will return normally or via an exception, or |
673 |
dl |
1.1 |
* whether these behaviors will remain consistent upon repeated |
674 |
|
|
* invocation. |
675 |
|
|
* |
676 |
|
|
* <p>This method may be overridden in subclasses, but if so, must |
677 |
|
|
* still ensure that these minimal properties hold. In particular, |
678 |
|
|
* the cancel method itself must not throw exceptions. |
679 |
|
|
* |
680 |
|
|
* <p> This method is designed to be invoked by <em>other</em> |
681 |
|
|
* tasks. To terminate the current task, you can just return or |
682 |
|
|
* throw an unchecked exception from its computation method, or |
683 |
jsr166 |
1.8 |
* invoke {@code completeExceptionally}. |
684 |
dl |
1.1 |
* |
685 |
|
|
* @param mayInterruptIfRunning this value is ignored in the |
686 |
|
|
* default implementation because tasks are not in general |
687 |
jsr166 |
1.14 |
* cancelled via interruption |
688 |
dl |
1.1 |
* |
689 |
|
|
* @return true if this task is now cancelled |
690 |
|
|
*/ |
691 |
|
|
public boolean cancel(boolean mayInterruptIfRunning) { |
692 |
|
|
setCompletion(CANCELLED); |
693 |
|
|
return (status & COMPLETION_MASK) == CANCELLED; |
694 |
|
|
} |
695 |
|
|
|
696 |
|
|
/** |
697 |
jsr166 |
1.10 |
* Returns true if this task threw an exception or was cancelled. |
698 |
|
|
* |
699 |
dl |
1.3 |
* @return true if this task threw an exception or was cancelled |
700 |
|
|
*/ |
701 |
|
|
public final boolean isCompletedAbnormally() { |
702 |
|
|
return (status & COMPLETION_MASK) < NORMAL; |
703 |
|
|
} |
704 |
|
|
|
705 |
|
|
/** |
706 |
|
|
* Returns the exception thrown by the base computation, or a |
707 |
|
|
* CancellationException if cancelled, or null if none or if the |
708 |
|
|
* method has not yet completed. |
709 |
jsr166 |
1.10 |
* |
710 |
dl |
1.3 |
* @return the exception, or null if none |
711 |
|
|
*/ |
712 |
|
|
public final Throwable getException() { |
713 |
|
|
int s = status & COMPLETION_MASK; |
714 |
|
|
if (s >= NORMAL) |
715 |
|
|
return null; |
716 |
|
|
if (s == CANCELLED) |
717 |
|
|
return new CancellationException(); |
718 |
|
|
return exceptionMap.get(this); |
719 |
|
|
} |
720 |
|
|
|
721 |
|
|
/** |
722 |
dl |
1.1 |
* Completes this task abnormally, and if not already aborted or |
723 |
|
|
* cancelled, causes it to throw the given exception upon |
724 |
jsr166 |
1.8 |
* {@code join} and related operations. This method may be used |
725 |
dl |
1.1 |
* to induce exceptions in asynchronous tasks, or to force |
726 |
dl |
1.2 |
* completion of tasks that would not otherwise complete. Its use |
727 |
|
|
* in other situations is likely to be wrong. This method is |
728 |
jsr166 |
1.8 |
* overridable, but overridden versions must invoke {@code super} |
729 |
dl |
1.2 |
* implementation to maintain guarantees. |
730 |
|
|
* |
731 |
dl |
1.1 |
* @param ex the exception to throw. If this exception is |
732 |
|
|
* not a RuntimeException or Error, the actual exception thrown |
733 |
|
|
* will be a RuntimeException with cause ex. |
734 |
|
|
*/ |
735 |
|
|
public void completeExceptionally(Throwable ex) { |
736 |
|
|
setDoneExceptionally((ex instanceof RuntimeException) || |
737 |
jsr166 |
1.14 |
(ex instanceof Error) ? ex : |
738 |
dl |
1.1 |
new RuntimeException(ex)); |
739 |
|
|
} |
740 |
|
|
|
741 |
|
|
/** |
742 |
|
|
* Completes this task, and if not already aborted or cancelled, |
743 |
jsr166 |
1.8 |
* returning a {@code null} result upon {@code join} and related |
744 |
dl |
1.1 |
* operations. This method may be used to provide results for |
745 |
|
|
* asynchronous tasks, or to provide alternative handling for |
746 |
dl |
1.2 |
* tasks that would not otherwise complete normally. Its use in |
747 |
|
|
* other situations is likely to be wrong. This method is |
748 |
jsr166 |
1.8 |
* overridable, but overridden versions must invoke {@code super} |
749 |
dl |
1.2 |
* implementation to maintain guarantees. |
750 |
dl |
1.1 |
* |
751 |
jsr166 |
1.10 |
* @param value the result value for this task |
752 |
dl |
1.1 |
*/ |
753 |
|
|
public void complete(V value) { |
754 |
|
|
try { |
755 |
|
|
setRawResult(value); |
756 |
jsr166 |
1.14 |
} catch (Throwable rex) { |
757 |
dl |
1.1 |
setDoneExceptionally(rex); |
758 |
|
|
return; |
759 |
|
|
} |
760 |
|
|
setNormalCompletion(); |
761 |
|
|
} |
762 |
|
|
|
763 |
dl |
1.3 |
public final V get() throws InterruptedException, ExecutionException { |
764 |
|
|
ForkJoinWorkerThread w = getWorker(); |
765 |
|
|
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
766 |
|
|
awaitDone(w, true); |
767 |
|
|
return reportFutureResult(); |
768 |
|
|
} |
769 |
|
|
|
770 |
|
|
public final V get(long timeout, TimeUnit unit) |
771 |
|
|
throws InterruptedException, ExecutionException, TimeoutException { |
772 |
|
|
ForkJoinWorkerThread w = getWorker(); |
773 |
|
|
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
774 |
|
|
awaitDone(w, unit.toNanos(timeout)); |
775 |
|
|
return reportTimedFutureResult(); |
776 |
|
|
} |
777 |
|
|
|
778 |
dl |
1.1 |
/** |
779 |
dl |
1.2 |
* Possibly executes other tasks until this task is ready, then |
780 |
|
|
* returns the result of the computation. This method may be more |
781 |
jsr166 |
1.8 |
* efficient than {@code join}, but is only applicable when |
782 |
jsr166 |
1.9 |
* there are no potential dependencies between continuation of the |
783 |
dl |
1.2 |
* current task and that of any other task that might be executed |
784 |
|
|
* while helping. (This usually holds for pure divide-and-conquer |
785 |
|
|
* tasks). This method may be invoked only from within |
786 |
dl |
1.13 |
* ForkJoinTask computations (as may be determined using method |
787 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
788 |
jsr166 |
1.14 |
* result in exceptions or errors, possibly including |
789 |
dl |
1.13 |
* ClassCastException. |
790 |
jsr166 |
1.10 |
* |
791 |
dl |
1.2 |
* @return the computed result |
792 |
|
|
*/ |
793 |
|
|
public final V helpJoin() { |
794 |
jsr166 |
1.14 |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread(); |
795 |
dl |
1.2 |
if (status < 0 || !w.unpushTask(this) || !tryExec()) |
796 |
dl |
1.3 |
reportException(busyJoin(w)); |
797 |
dl |
1.2 |
return getRawResult(); |
798 |
|
|
} |
799 |
|
|
|
800 |
|
|
/** |
801 |
|
|
* Possibly executes other tasks until this task is ready. This |
802 |
|
|
* method may be invoked only from within ForkJoinTask |
803 |
dl |
1.13 |
* computations (as may be determined using method {@link |
804 |
jsr166 |
1.14 |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
805 |
|
|
* in exceptions or errors, possibly including ClassCastException. |
806 |
dl |
1.2 |
*/ |
807 |
|
|
public final void quietlyHelpJoin() { |
808 |
|
|
if (status >= 0) { |
809 |
|
|
ForkJoinWorkerThread w = |
810 |
jsr166 |
1.14 |
(ForkJoinWorkerThread) Thread.currentThread(); |
811 |
dl |
1.2 |
if (!w.unpushTask(this) || !tryQuietlyInvoke()) |
812 |
dl |
1.3 |
busyJoin(w); |
813 |
dl |
1.2 |
} |
814 |
|
|
} |
815 |
|
|
|
816 |
|
|
/** |
817 |
|
|
* Joins this task, without returning its result or throwing an |
818 |
|
|
* exception. This method may be useful when processing |
819 |
|
|
* collections of tasks when some have been cancelled or otherwise |
820 |
|
|
* known to have aborted. |
821 |
|
|
*/ |
822 |
|
|
public final void quietlyJoin() { |
823 |
|
|
if (status >= 0) { |
824 |
|
|
ForkJoinWorkerThread w = getWorker(); |
825 |
|
|
if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke()) |
826 |
|
|
awaitDone(w, true); |
827 |
|
|
} |
828 |
|
|
} |
829 |
|
|
|
830 |
|
|
/** |
831 |
|
|
* Commences performing this task and awaits its completion if |
832 |
|
|
* necessary, without returning its result or throwing an |
833 |
|
|
* exception. This method may be useful when processing |
834 |
|
|
* collections of tasks when some have been cancelled or otherwise |
835 |
|
|
* known to have aborted. |
836 |
|
|
*/ |
837 |
|
|
public final void quietlyInvoke() { |
838 |
|
|
if (status >= 0 && !tryQuietlyInvoke()) |
839 |
|
|
quietlyJoin(); |
840 |
|
|
} |
841 |
|
|
|
842 |
|
|
/** |
843 |
dl |
1.3 |
* Possibly executes tasks until the pool hosting the current task |
844 |
|
|
* {@link ForkJoinPool#isQuiescent}. This method may be of use in |
845 |
|
|
* designs in which many tasks are forked, but none are explicitly |
846 |
|
|
* joined, instead executing them until all are processed. |
847 |
|
|
*/ |
848 |
|
|
public static void helpQuiesce() { |
849 |
jsr166 |
1.14 |
((ForkJoinWorkerThread) Thread.currentThread()) |
850 |
|
|
.helpQuiescePool(); |
851 |
dl |
1.3 |
} |
852 |
|
|
|
853 |
|
|
/** |
854 |
dl |
1.1 |
* Resets the internal bookkeeping state of this task, allowing a |
855 |
jsr166 |
1.8 |
* subsequent {@code fork}. This method allows repeated reuse of |
856 |
dl |
1.1 |
* this task, but only if reuse occurs when this task has either |
857 |
|
|
* never been forked, or has been forked, then completed and all |
858 |
|
|
* outstanding joins of this task have also completed. Effects |
859 |
|
|
* under any other usage conditions are not guaranteed, and are |
860 |
|
|
* almost surely wrong. This method may be useful when executing |
861 |
|
|
* pre-constructed trees of subtasks in loops. |
862 |
|
|
*/ |
863 |
|
|
public void reinitialize() { |
864 |
|
|
if ((status & COMPLETION_MASK) == EXCEPTIONAL) |
865 |
|
|
exceptionMap.remove(this); |
866 |
|
|
status = 0; |
867 |
|
|
} |
868 |
|
|
|
869 |
|
|
/** |
870 |
dl |
1.2 |
* Returns the pool hosting the current task execution, or null |
871 |
dl |
1.13 |
* if this task is executing outside of any ForkJoinPool. |
872 |
jsr166 |
1.10 |
* |
873 |
jsr166 |
1.14 |
* @return the pool, or null if none |
874 |
dl |
1.1 |
*/ |
875 |
dl |
1.2 |
public static ForkJoinPool getPool() { |
876 |
|
|
Thread t = Thread.currentThread(); |
877 |
jsr166 |
1.14 |
return ((t instanceof ForkJoinWorkerThread) ? |
878 |
|
|
((ForkJoinWorkerThread) t).pool : null); |
879 |
dl |
1.1 |
} |
880 |
|
|
|
881 |
|
|
/** |
882 |
jsr166 |
1.14 |
* Returns {@code true} if the current thread is executing as a |
883 |
dl |
1.13 |
* ForkJoinPool computation. |
884 |
jsr166 |
1.14 |
* |
885 |
|
|
* @return {@code true} if the current thread is executing as a |
886 |
dl |
1.13 |
* ForkJoinPool computation, or false otherwise |
887 |
|
|
*/ |
888 |
|
|
public static boolean inForkJoinPool() { |
889 |
|
|
return Thread.currentThread() instanceof ForkJoinWorkerThread; |
890 |
|
|
} |
891 |
|
|
|
892 |
|
|
/** |
893 |
dl |
1.2 |
* Tries to unschedule this task for execution. This method will |
894 |
|
|
* typically succeed if this task is the most recently forked task |
895 |
|
|
* by the current thread, and has not commenced executing in |
896 |
|
|
* another thread. This method may be useful when arranging |
897 |
|
|
* alternative local processing of tasks that could have been, but |
898 |
|
|
* were not, stolen. This method may be invoked only from within |
899 |
dl |
1.13 |
* ForkJoinTask computations (as may be determined using method |
900 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
901 |
jsr166 |
1.14 |
* result in exceptions or errors, possibly including |
902 |
dl |
1.13 |
* ClassCastException. |
903 |
jsr166 |
1.10 |
* |
904 |
dl |
1.2 |
* @return true if unforked |
905 |
dl |
1.1 |
*/ |
906 |
dl |
1.2 |
public boolean tryUnfork() { |
907 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
908 |
|
|
.unpushTask(this); |
909 |
dl |
1.1 |
} |
910 |
|
|
|
911 |
|
|
/** |
912 |
dl |
1.2 |
* Returns an estimate of the number of tasks that have been |
913 |
|
|
* forked by the current worker thread but not yet executed. This |
914 |
|
|
* value may be useful for heuristic decisions about whether to |
915 |
|
|
* fork other tasks. |
916 |
jsr166 |
1.10 |
* |
917 |
dl |
1.2 |
* @return the number of tasks |
918 |
|
|
*/ |
919 |
|
|
public static int getQueuedTaskCount() { |
920 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
921 |
|
|
.getQueueSize(); |
922 |
dl |
1.2 |
} |
923 |
|
|
|
924 |
|
|
/** |
925 |
jsr166 |
1.10 |
* Returns an estimate of how many more locally queued tasks are |
926 |
dl |
1.1 |
* held by the current worker thread than there are other worker |
927 |
dl |
1.2 |
* threads that might steal them. This value may be useful for |
928 |
|
|
* heuristic decisions about whether to fork other tasks. In many |
929 |
|
|
* usages of ForkJoinTasks, at steady state, each worker should |
930 |
|
|
* aim to maintain a small constant surplus (for example, 3) of |
931 |
|
|
* tasks, and to process computations locally if this threshold is |
932 |
|
|
* exceeded. |
933 |
jsr166 |
1.10 |
* |
934 |
dl |
1.1 |
* @return the surplus number of tasks, which may be negative |
935 |
|
|
*/ |
936 |
dl |
1.2 |
public static int getSurplusQueuedTaskCount() { |
937 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
938 |
dl |
1.1 |
.getEstimatedSurplusTaskCount(); |
939 |
|
|
} |
940 |
|
|
|
941 |
dl |
1.2 |
// Extension methods |
942 |
dl |
1.1 |
|
943 |
|
|
/** |
944 |
jsr166 |
1.8 |
* Returns the result that would be returned by {@code join}, |
945 |
dl |
1.2 |
* even if this task completed abnormally, or null if this task is |
946 |
|
|
* not known to have been completed. This method is designed to |
947 |
|
|
* aid debugging, as well as to support extensions. Its use in any |
948 |
|
|
* other context is discouraged. |
949 |
dl |
1.1 |
* |
950 |
jsr166 |
1.10 |
* @return the result, or null if not completed |
951 |
dl |
1.1 |
*/ |
952 |
|
|
public abstract V getRawResult(); |
953 |
|
|
|
954 |
|
|
/** |
955 |
|
|
* Forces the given value to be returned as a result. This method |
956 |
|
|
* is designed to support extensions, and should not in general be |
957 |
|
|
* called otherwise. |
958 |
|
|
* |
959 |
|
|
* @param value the value |
960 |
|
|
*/ |
961 |
|
|
protected abstract void setRawResult(V value); |
962 |
|
|
|
963 |
|
|
/** |
964 |
|
|
* Immediately performs the base action of this task. This method |
965 |
|
|
* is designed to support extensions, and should not in general be |
966 |
|
|
* called otherwise. The return value controls whether this task |
967 |
|
|
* is considered to be done normally. It may return false in |
968 |
|
|
* asynchronous actions that require explicit invocations of |
969 |
jsr166 |
1.8 |
* {@code complete} to become joinable. It may throw exceptions |
970 |
dl |
1.1 |
* to indicate abnormal exit. |
971 |
jsr166 |
1.10 |
* |
972 |
dl |
1.1 |
* @return true if completed normally |
973 |
|
|
* @throws Error or RuntimeException if encountered during computation |
974 |
|
|
*/ |
975 |
|
|
protected abstract boolean exec(); |
976 |
|
|
|
977 |
dl |
1.2 |
/** |
978 |
dl |
1.6 |
* Returns, but does not unschedule or execute, the task queued by |
979 |
|
|
* the current thread but not yet executed, if one is |
980 |
|
|
* available. There is no guarantee that this task will actually |
981 |
|
|
* be polled or executed next. This method is designed primarily |
982 |
|
|
* to support extensions, and is unlikely to be useful otherwise. |
983 |
|
|
* This method may be invoked only from within ForkJoinTask |
984 |
dl |
1.13 |
* computations (as may be determined using method {@link |
985 |
|
|
* #inForkJoinPool}). Attempts to invoke in other contexts result |
986 |
jsr166 |
1.14 |
* in exceptions or errors, possibly including ClassCastException. |
987 |
dl |
1.2 |
* |
988 |
|
|
* @return the next task, or null if none are available |
989 |
|
|
*/ |
990 |
|
|
protected static ForkJoinTask<?> peekNextLocalTask() { |
991 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
992 |
|
|
.peekTask(); |
993 |
dl |
1.2 |
} |
994 |
|
|
|
995 |
|
|
/** |
996 |
dl |
1.6 |
* Unschedules and returns, without executing, the next task |
997 |
|
|
* queued by the current thread but not yet executed. This method |
998 |
|
|
* is designed primarily to support extensions, and is unlikely to |
999 |
|
|
* be useful otherwise. This method may be invoked only from |
1000 |
dl |
1.13 |
* within ForkJoinTask computations (as may be determined using |
1001 |
|
|
* method {@link #inForkJoinPool}). Attempts to invoke in other |
1002 |
jsr166 |
1.14 |
* contexts result in exceptions or errors, possibly including |
1003 |
dl |
1.6 |
* ClassCastException. |
1004 |
dl |
1.2 |
* |
1005 |
|
|
* @return the next task, or null if none are available |
1006 |
|
|
*/ |
1007 |
|
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
1008 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1009 |
|
|
.pollLocalTask(); |
1010 |
dl |
1.2 |
} |
1011 |
jsr166 |
1.7 |
|
1012 |
dl |
1.2 |
/** |
1013 |
dl |
1.6 |
* Unschedules and returns, without executing, the next task |
1014 |
|
|
* queued by the current thread but not yet executed, if one is |
1015 |
|
|
* available, or if not available, a task that was forked by some |
1016 |
|
|
* other thread, if available. Availability may be transient, so a |
1017 |
jsr166 |
1.9 |
* {@code null} result does not necessarily imply quiescence |
1018 |
dl |
1.6 |
* of the pool this task is operating in. This method is designed |
1019 |
|
|
* primarily to support extensions, and is unlikely to be useful |
1020 |
|
|
* otherwise. This method may be invoked only from within |
1021 |
dl |
1.13 |
* ForkJoinTask computations (as may be determined using method |
1022 |
|
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1023 |
jsr166 |
1.14 |
* result in exceptions or errors, possibly including |
1024 |
dl |
1.6 |
* ClassCastException. |
1025 |
dl |
1.4 |
* |
1026 |
dl |
1.2 |
* @return a task, or null if none are available |
1027 |
|
|
*/ |
1028 |
|
|
protected static ForkJoinTask<?> pollTask() { |
1029 |
jsr166 |
1.14 |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1030 |
|
|
.pollTask(); |
1031 |
dl |
1.2 |
} |
1032 |
|
|
|
1033 |
dl |
1.1 |
// Serialization support |
1034 |
|
|
|
1035 |
|
|
private static final long serialVersionUID = -7721805057305804111L; |
1036 |
|
|
|
1037 |
|
|
/** |
1038 |
|
|
* Save the state to a stream. |
1039 |
|
|
* |
1040 |
|
|
* @serialData the current run status and the exception thrown |
1041 |
jsr166 |
1.10 |
* during execution, or null if none |
1042 |
dl |
1.1 |
* @param s the stream |
1043 |
|
|
*/ |
1044 |
|
|
private void writeObject(java.io.ObjectOutputStream s) |
1045 |
|
|
throws java.io.IOException { |
1046 |
|
|
s.defaultWriteObject(); |
1047 |
|
|
s.writeObject(getException()); |
1048 |
|
|
} |
1049 |
|
|
|
1050 |
|
|
/** |
1051 |
|
|
* Reconstitute the instance from a stream. |
1052 |
jsr166 |
1.10 |
* |
1053 |
dl |
1.1 |
* @param s the stream |
1054 |
|
|
*/ |
1055 |
|
|
private void readObject(java.io.ObjectInputStream s) |
1056 |
|
|
throws java.io.IOException, ClassNotFoundException { |
1057 |
|
|
s.defaultReadObject(); |
1058 |
dl |
1.2 |
status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts |
1059 |
|
|
status |= EXTERNAL_SIGNAL; // conservatively set external signal |
1060 |
dl |
1.1 |
Object ex = s.readObject(); |
1061 |
|
|
if (ex != null) |
1062 |
jsr166 |
1.14 |
setDoneExceptionally((Throwable) ex); |
1063 |
dl |
1.1 |
} |
1064 |
|
|
|
1065 |
|
|
// Temporary Unsafe mechanics for preliminary release |
1066 |
jsr166 |
1.5 |
private static Unsafe getUnsafe() throws Throwable { |
1067 |
|
|
try { |
1068 |
|
|
return Unsafe.getUnsafe(); |
1069 |
|
|
} catch (SecurityException se) { |
1070 |
|
|
try { |
1071 |
|
|
return java.security.AccessController.doPrivileged |
1072 |
|
|
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
1073 |
|
|
public Unsafe run() throws Exception { |
1074 |
|
|
return getUnsafePrivileged(); |
1075 |
|
|
}}); |
1076 |
|
|
} catch (java.security.PrivilegedActionException e) { |
1077 |
|
|
throw e.getCause(); |
1078 |
|
|
} |
1079 |
|
|
} |
1080 |
|
|
} |
1081 |
|
|
|
1082 |
|
|
private static Unsafe getUnsafePrivileged() |
1083 |
|
|
throws NoSuchFieldException, IllegalAccessException { |
1084 |
|
|
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
1085 |
|
|
f.setAccessible(true); |
1086 |
|
|
return (Unsafe) f.get(null); |
1087 |
|
|
} |
1088 |
|
|
|
1089 |
|
|
private static long fieldOffset(String fieldName) |
1090 |
|
|
throws NoSuchFieldException { |
1091 |
jsr166 |
1.11 |
return UNSAFE.objectFieldOffset |
1092 |
jsr166 |
1.5 |
(ForkJoinTask.class.getDeclaredField(fieldName)); |
1093 |
|
|
} |
1094 |
dl |
1.1 |
|
1095 |
jsr166 |
1.11 |
static final Unsafe UNSAFE; |
1096 |
dl |
1.1 |
static final long statusOffset; |
1097 |
|
|
|
1098 |
|
|
static { |
1099 |
|
|
try { |
1100 |
jsr166 |
1.11 |
UNSAFE = getUnsafe(); |
1101 |
jsr166 |
1.5 |
statusOffset = fieldOffset("status"); |
1102 |
|
|
} catch (Throwable e) { |
1103 |
|
|
throw new RuntimeException("Could not initialize intrinsics", e); |
1104 |
|
|
} |
1105 |
dl |
1.1 |
} |
1106 |
|
|
|
1107 |
|
|
} |