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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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1.8 |
* equivalent to {@code fork(); join()} but always attempts to |
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* 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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* 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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* ForkJoinTasks. Attempts to invoke them in other contexts result in |
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1.4 |
* exceptions or errors possibly including 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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*/ |
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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 |
/** |
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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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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 -- |
120 |
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* bit 15 for external (nonFJ) waits, and the rest a count of |
121 |
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* waiting FJ threads. (This representation relies on |
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* ForkJoinPool max thread limits). Completion of a stolen task |
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* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even |
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* though suboptimal for some purposes, we use basic builtin |
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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 |
127 |
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* per-task bookkeeping overhead. Note that bits 16-28 are |
128 |
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* currently unused. Also value 0x80000000 is available as spare |
129 |
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* completion value. |
130 |
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*/ |
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jsr166 |
1.9 |
volatile int status; // accessed directly by pool and workers |
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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 |
140 |
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/** |
142 |
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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 |
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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 |
148 |
dl |
1.1 |
*/ |
149 |
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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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/** |
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jsr166 |
1.10 |
* Gets current worker thread, or null if not a worker thread. |
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dl |
1.1 |
*/ |
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static ForkJoinWorkerThread getWorker() { |
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Thread t = Thread.currentThread(); |
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return ((t instanceof ForkJoinWorkerThread)? |
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(ForkJoinWorkerThread)t : null); |
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} |
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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. |
170 |
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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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/** |
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jsr166 |
1.10 |
* Marks completion and wakes up threads waiting to join this task. |
180 |
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* |
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dl |
1.1 |
* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
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*/ |
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final void setCompletion(int completion) { |
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dl |
1.2 |
ForkJoinPool pool = getPool(); |
185 |
dl |
1.1 |
if (pool != null) { |
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int s; // Clear signal bits while setting completion status |
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do;while ((s = status) >= 0 && !casStatus(s, completion)); |
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189 |
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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); |
192 |
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synchronized(this) { notifyAll(); } |
193 |
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} |
194 |
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} |
195 |
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else |
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externallySetCompletion(completion); |
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} |
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/** |
200 |
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* Version of setCompletion for non-FJ threads. Leaves signal |
201 |
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* bits for unblocked threads to adjust, and always notifies. |
202 |
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*/ |
203 |
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private void externallySetCompletion(int completion) { |
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int s; |
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do;while ((s = status) >= 0 && |
206 |
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!casStatus(s, (s & SIGNAL_MASK) | completion)); |
207 |
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synchronized(this) { notifyAll(); } |
208 |
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} |
209 |
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210 |
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/** |
211 |
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* Sets status to indicate normal completion |
212 |
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*/ |
213 |
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final void setNormalCompletion() { |
214 |
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// Try typical fast case -- single CAS, no signal, not already done. |
215 |
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// Manually expand casStatus to improve chances of inlining it |
216 |
jsr166 |
1.11 |
if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL)) |
217 |
dl |
1.1 |
setCompletion(NORMAL); |
218 |
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} |
219 |
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220 |
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// internal waiting and notification |
221 |
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222 |
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/** |
223 |
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* Performs the actual monitor wait for awaitDone |
224 |
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*/ |
225 |
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private void doAwaitDone() { |
226 |
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// Minimize lock bias and in/de-flation effects by maximizing |
227 |
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// chances of waiting inside sync |
228 |
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try { |
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while (status >= 0) |
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synchronized(this) { if (status >= 0) wait(); } |
231 |
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} catch (InterruptedException ie) { |
232 |
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onInterruptedWait(); |
233 |
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} |
234 |
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} |
235 |
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236 |
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/** |
237 |
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* Performs the actual monitor wait for awaitDone |
238 |
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*/ |
239 |
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private void doAwaitDone(long startTime, long nanos) { |
240 |
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synchronized(this) { |
241 |
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try { |
242 |
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while (status >= 0) { |
243 |
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long nt = nanos - System.nanoTime() - startTime; |
244 |
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if (nt <= 0) |
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break; |
246 |
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wait(nt / 1000000, (int)(nt % 1000000)); |
247 |
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} |
248 |
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} catch (InterruptedException ie) { |
249 |
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onInterruptedWait(); |
250 |
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} |
251 |
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} |
252 |
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} |
253 |
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254 |
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// Awaiting completion |
255 |
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256 |
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/** |
257 |
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* Sets status to indicate there is joiner, then waits for join, |
258 |
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* surrounded with pool notifications. |
259 |
jsr166 |
1.10 |
* |
260 |
dl |
1.1 |
* @return status upon exit |
261 |
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*/ |
262 |
dl |
1.3 |
private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) { |
263 |
dl |
1.1 |
ForkJoinPool pool = w == null? null : w.pool; |
264 |
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int s; |
265 |
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while ((s = status) >= 0) { |
266 |
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if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) { |
267 |
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if (pool == null || !pool.preJoin(this, maintainParallelism)) |
268 |
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doAwaitDone(); |
269 |
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if (((s = status) & INTERNAL_SIGNAL_MASK) != 0) |
270 |
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adjustPoolCountsOnUnblock(pool); |
271 |
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break; |
272 |
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} |
273 |
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} |
274 |
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return s; |
275 |
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} |
276 |
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277 |
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/** |
278 |
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* Timed version of awaitDone |
279 |
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* @return status upon exit |
280 |
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*/ |
281 |
dl |
1.3 |
private int awaitDone(ForkJoinWorkerThread w, long nanos) { |
282 |
dl |
1.1 |
ForkJoinPool pool = w == null? null : w.pool; |
283 |
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int s; |
284 |
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while ((s = status) >= 0) { |
285 |
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if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) { |
286 |
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long startTime = System.nanoTime(); |
287 |
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if (pool == null || !pool.preJoin(this, false)) |
288 |
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doAwaitDone(startTime, nanos); |
289 |
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if ((s = status) >= 0) { |
290 |
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adjustPoolCountsOnCancelledWait(pool); |
291 |
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s = status; |
292 |
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} |
293 |
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if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0) |
294 |
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adjustPoolCountsOnUnblock(pool); |
295 |
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break; |
296 |
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} |
297 |
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} |
298 |
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return s; |
299 |
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} |
300 |
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301 |
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/** |
302 |
jsr166 |
1.10 |
* Notifies pool that thread is unblocked. Called by signalled |
303 |
dl |
1.1 |
* threads when woken by non-FJ threads (which is atypical). |
304 |
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*/ |
305 |
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private void adjustPoolCountsOnUnblock(ForkJoinPool pool) { |
306 |
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int s; |
307 |
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do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK)); |
308 |
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if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0) |
309 |
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pool.updateRunningCount(s); |
310 |
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} |
311 |
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312 |
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/** |
313 |
jsr166 |
1.10 |
* Notifies pool to adjust counts on cancelled or timed out wait. |
314 |
dl |
1.1 |
*/ |
315 |
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private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) { |
316 |
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if (pool != null) { |
317 |
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int s; |
318 |
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while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) { |
319 |
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if (casStatus(s, s - 1)) { |
320 |
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pool.updateRunningCount(1); |
321 |
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break; |
322 |
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} |
323 |
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} |
324 |
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} |
325 |
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} |
326 |
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|
327 |
dl |
1.2 |
/** |
328 |
jsr166 |
1.10 |
* Handles interruptions during waits. |
329 |
dl |
1.2 |
*/ |
330 |
dl |
1.1 |
private void onInterruptedWait() { |
331 |
dl |
1.2 |
ForkJoinWorkerThread w = getWorker(); |
332 |
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if (w == null) |
333 |
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Thread.currentThread().interrupt(); // re-interrupt |
334 |
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else if (w.isTerminating()) |
335 |
dl |
1.3 |
cancelIgnoringExceptions(); |
336 |
dl |
1.2 |
// else if FJworker, ignore interrupt |
337 |
dl |
1.1 |
} |
338 |
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|
339 |
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// Recording and reporting exceptions |
340 |
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341 |
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private void setDoneExceptionally(Throwable rex) { |
342 |
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exceptionMap.put(this, rex); |
343 |
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setCompletion(EXCEPTIONAL); |
344 |
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} |
345 |
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|
346 |
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/** |
347 |
jsr166 |
1.10 |
* Throws the exception associated with status s. |
348 |
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* |
349 |
dl |
1.1 |
* @throws the exception |
350 |
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*/ |
351 |
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private void reportException(int s) { |
352 |
|
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if ((s &= COMPLETION_MASK) < NORMAL) { |
353 |
|
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if (s == CANCELLED) |
354 |
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throw new CancellationException(); |
355 |
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else |
356 |
|
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rethrowException(exceptionMap.get(this)); |
357 |
|
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} |
358 |
|
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} |
359 |
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360 |
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/** |
361 |
jsr166 |
1.10 |
* Returns result or throws exception using j.u.c.Future conventions. |
362 |
dl |
1.1 |
* Only call when isDone known to be true. |
363 |
|
|
*/ |
364 |
|
|
private V reportFutureResult() |
365 |
|
|
throws ExecutionException, InterruptedException { |
366 |
|
|
int s = status & COMPLETION_MASK; |
367 |
|
|
if (s < NORMAL) { |
368 |
|
|
Throwable ex; |
369 |
|
|
if (s == CANCELLED) |
370 |
|
|
throw new CancellationException(); |
371 |
|
|
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
372 |
|
|
throw new ExecutionException(ex); |
373 |
|
|
if (Thread.interrupted()) |
374 |
|
|
throw new InterruptedException(); |
375 |
|
|
} |
376 |
|
|
return getRawResult(); |
377 |
|
|
} |
378 |
|
|
|
379 |
|
|
/** |
380 |
|
|
* Returns result or throws exception using j.u.c.Future conventions |
381 |
jsr166 |
1.10 |
* with timeouts. |
382 |
dl |
1.1 |
*/ |
383 |
|
|
private V reportTimedFutureResult() |
384 |
|
|
throws InterruptedException, ExecutionException, TimeoutException { |
385 |
|
|
Throwable ex; |
386 |
|
|
int s = status & COMPLETION_MASK; |
387 |
|
|
if (s == NORMAL) |
388 |
|
|
return getRawResult(); |
389 |
|
|
if (s == CANCELLED) |
390 |
|
|
throw new CancellationException(); |
391 |
|
|
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
392 |
|
|
throw new ExecutionException(ex); |
393 |
|
|
if (Thread.interrupted()) |
394 |
|
|
throw new InterruptedException(); |
395 |
|
|
throw new TimeoutException(); |
396 |
|
|
} |
397 |
|
|
|
398 |
|
|
// internal execution methods |
399 |
|
|
|
400 |
|
|
/** |
401 |
|
|
* Calls exec, recording completion, and rethrowing exception if |
402 |
jsr166 |
1.10 |
* encountered. Caller should normally check status before calling. |
403 |
|
|
* |
404 |
dl |
1.1 |
* @return true if completed normally |
405 |
|
|
*/ |
406 |
|
|
private boolean tryExec() { |
407 |
|
|
try { // try block must contain only call to exec |
408 |
|
|
if (!exec()) |
409 |
|
|
return false; |
410 |
|
|
} catch (Throwable rex) { |
411 |
|
|
setDoneExceptionally(rex); |
412 |
|
|
rethrowException(rex); |
413 |
|
|
return false; // not reached |
414 |
|
|
} |
415 |
|
|
setNormalCompletion(); |
416 |
|
|
return true; |
417 |
|
|
} |
418 |
|
|
|
419 |
|
|
/** |
420 |
|
|
* Main execution method used by worker threads. Invokes |
421 |
jsr166 |
1.10 |
* base computation unless already complete. |
422 |
dl |
1.1 |
*/ |
423 |
|
|
final void quietlyExec() { |
424 |
|
|
if (status >= 0) { |
425 |
|
|
try { |
426 |
|
|
if (!exec()) |
427 |
|
|
return; |
428 |
|
|
} catch(Throwable rex) { |
429 |
|
|
setDoneExceptionally(rex); |
430 |
|
|
return; |
431 |
|
|
} |
432 |
|
|
setNormalCompletion(); |
433 |
|
|
} |
434 |
|
|
} |
435 |
|
|
|
436 |
|
|
/** |
437 |
jsr166 |
1.10 |
* Calls exec(), recording but not rethrowing exception. |
438 |
|
|
* Caller should normally check status before calling. |
439 |
|
|
* |
440 |
dl |
1.1 |
* @return true if completed normally |
441 |
|
|
*/ |
442 |
|
|
private boolean tryQuietlyInvoke() { |
443 |
|
|
try { |
444 |
|
|
if (!exec()) |
445 |
|
|
return false; |
446 |
|
|
} catch (Throwable rex) { |
447 |
|
|
setDoneExceptionally(rex); |
448 |
|
|
return false; |
449 |
|
|
} |
450 |
|
|
setNormalCompletion(); |
451 |
|
|
return true; |
452 |
|
|
} |
453 |
|
|
|
454 |
|
|
/** |
455 |
jsr166 |
1.10 |
* Cancels, ignoring any exceptions it throws. |
456 |
dl |
1.1 |
*/ |
457 |
dl |
1.3 |
final void cancelIgnoringExceptions() { |
458 |
dl |
1.1 |
try { |
459 |
|
|
cancel(false); |
460 |
|
|
} catch(Throwable ignore) { |
461 |
|
|
} |
462 |
|
|
} |
463 |
|
|
|
464 |
dl |
1.3 |
/** |
465 |
|
|
* Main implementation of helpJoin |
466 |
|
|
*/ |
467 |
|
|
private int busyJoin(ForkJoinWorkerThread w) { |
468 |
|
|
int s; |
469 |
|
|
ForkJoinTask<?> t; |
470 |
|
|
while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null) |
471 |
|
|
t.quietlyExec(); |
472 |
|
|
return (s >= 0)? awaitDone(w, false) : s; // block if no work |
473 |
|
|
} |
474 |
|
|
|
475 |
dl |
1.1 |
// public methods |
476 |
|
|
|
477 |
|
|
/** |
478 |
|
|
* Arranges to asynchronously execute this task. While it is not |
479 |
|
|
* necessarily enforced, it is a usage error to fork a task more |
480 |
|
|
* than once unless it has completed and been reinitialized. This |
481 |
dl |
1.2 |
* method may be invoked only from within ForkJoinTask |
482 |
dl |
1.1 |
* computations. Attempts to invoke in other contexts result in |
483 |
dl |
1.4 |
* exceptions or errors possibly including ClassCastException. |
484 |
dl |
1.1 |
*/ |
485 |
|
|
public final void fork() { |
486 |
|
|
((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this); |
487 |
|
|
} |
488 |
|
|
|
489 |
|
|
/** |
490 |
|
|
* Returns the result of the computation when it is ready. |
491 |
jsr166 |
1.8 |
* This method differs from {@code get} in that abnormal |
492 |
dl |
1.1 |
* completion results in RuntimeExceptions or Errors, not |
493 |
|
|
* ExecutionExceptions. |
494 |
|
|
* |
495 |
|
|
* @return the computed result |
496 |
|
|
*/ |
497 |
|
|
public final V join() { |
498 |
|
|
ForkJoinWorkerThread w = getWorker(); |
499 |
|
|
if (w == null || status < 0 || !w.unpushTask(this) || !tryExec()) |
500 |
|
|
reportException(awaitDone(w, true)); |
501 |
|
|
return getRawResult(); |
502 |
|
|
} |
503 |
|
|
|
504 |
|
|
/** |
505 |
dl |
1.2 |
* Commences performing this task, awaits its completion if |
506 |
|
|
* necessary, and return its result. |
507 |
jsr166 |
1.10 |
* |
508 |
dl |
1.1 |
* @throws Throwable (a RuntimeException, Error, or unchecked |
509 |
jsr166 |
1.10 |
* exception) if the underlying computation did so |
510 |
dl |
1.1 |
* @return the computed result |
511 |
|
|
*/ |
512 |
|
|
public final V invoke() { |
513 |
|
|
if (status >= 0 && tryExec()) |
514 |
|
|
return getRawResult(); |
515 |
|
|
else |
516 |
|
|
return join(); |
517 |
|
|
} |
518 |
|
|
|
519 |
|
|
/** |
520 |
jsr166 |
1.8 |
* Forks both tasks, returning when {@code isDone} holds for |
521 |
dl |
1.2 |
* both of them or an exception is encountered. This method may be |
522 |
|
|
* invoked only from within ForkJoinTask computations. Attempts to |
523 |
|
|
* invoke in other contexts result in exceptions or errors |
524 |
dl |
1.4 |
* possibly including ClassCastException. |
525 |
jsr166 |
1.10 |
* |
526 |
dl |
1.2 |
* @param t1 one task |
527 |
|
|
* @param t2 the other task |
528 |
|
|
* @throws NullPointerException if t1 or t2 are null |
529 |
jsr166 |
1.10 |
* @throws RuntimeException or Error if either task did so |
530 |
dl |
1.1 |
*/ |
531 |
dl |
1.2 |
public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) { |
532 |
|
|
t2.fork(); |
533 |
|
|
t1.invoke(); |
534 |
|
|
t2.join(); |
535 |
dl |
1.1 |
} |
536 |
|
|
|
537 |
|
|
/** |
538 |
jsr166 |
1.8 |
* Forks the given tasks, returning when {@code isDone} holds |
539 |
dl |
1.2 |
* for all of them. If any task encounters an exception, others |
540 |
|
|
* may be cancelled. This method may be invoked only from within |
541 |
|
|
* ForkJoinTask computations. Attempts to invoke in other contexts |
542 |
dl |
1.4 |
* result in exceptions or errors possibly including ClassCastException. |
543 |
jsr166 |
1.10 |
* |
544 |
dl |
1.2 |
* @param tasks the array of tasks |
545 |
jsr166 |
1.10 |
* @throws NullPointerException if tasks or any element are null |
546 |
|
|
* @throws RuntimeException or Error if any task did so |
547 |
dl |
1.1 |
*/ |
548 |
dl |
1.2 |
public static void invokeAll(ForkJoinTask<?>... tasks) { |
549 |
|
|
Throwable ex = null; |
550 |
|
|
int last = tasks.length - 1; |
551 |
|
|
for (int i = last; i >= 0; --i) { |
552 |
|
|
ForkJoinTask<?> t = tasks[i]; |
553 |
|
|
if (t == null) { |
554 |
|
|
if (ex == null) |
555 |
|
|
ex = new NullPointerException(); |
556 |
|
|
} |
557 |
|
|
else if (i != 0) |
558 |
|
|
t.fork(); |
559 |
|
|
else { |
560 |
|
|
t.quietlyInvoke(); |
561 |
|
|
if (ex == null) |
562 |
|
|
ex = t.getException(); |
563 |
|
|
} |
564 |
|
|
} |
565 |
|
|
for (int i = 1; i <= last; ++i) { |
566 |
|
|
ForkJoinTask<?> t = tasks[i]; |
567 |
|
|
if (t != null) { |
568 |
|
|
if (ex != null) |
569 |
|
|
t.cancel(false); |
570 |
|
|
else { |
571 |
|
|
t.quietlyJoin(); |
572 |
|
|
if (ex == null) |
573 |
|
|
ex = t.getException(); |
574 |
|
|
} |
575 |
|
|
} |
576 |
dl |
1.1 |
} |
577 |
dl |
1.2 |
if (ex != null) |
578 |
|
|
rethrowException(ex); |
579 |
dl |
1.1 |
} |
580 |
|
|
|
581 |
|
|
/** |
582 |
dl |
1.2 |
* Forks all tasks in the collection, returning when |
583 |
jsr166 |
1.8 |
* {@code isDone} holds for all of them. If any task |
584 |
dl |
1.2 |
* encounters an exception, others may be cancelled. This method |
585 |
|
|
* may be invoked only from within ForkJoinTask |
586 |
jsr166 |
1.9 |
* computations. Attempts to invoke in other contexts result in |
587 |
dl |
1.4 |
* exceptions or errors possibly including ClassCastException. |
588 |
jsr166 |
1.10 |
* |
589 |
dl |
1.2 |
* @param tasks the collection of tasks |
590 |
jsr166 |
1.10 |
* @throws NullPointerException if tasks or any element are null |
591 |
|
|
* @throws RuntimeException or Error if any task did so |
592 |
dl |
1.1 |
*/ |
593 |
dl |
1.2 |
public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) { |
594 |
|
|
if (!(tasks instanceof List)) { |
595 |
|
|
invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()])); |
596 |
|
|
return; |
597 |
|
|
} |
598 |
|
|
List<? extends ForkJoinTask<?>> ts = |
599 |
|
|
(List<? extends ForkJoinTask<?>>)tasks; |
600 |
|
|
Throwable ex = null; |
601 |
|
|
int last = ts.size() - 1; |
602 |
|
|
for (int i = last; i >= 0; --i) { |
603 |
|
|
ForkJoinTask<?> t = ts.get(i); |
604 |
|
|
if (t == null) { |
605 |
|
|
if (ex == null) |
606 |
|
|
ex = new NullPointerException(); |
607 |
|
|
} |
608 |
|
|
else if (i != 0) |
609 |
|
|
t.fork(); |
610 |
|
|
else { |
611 |
|
|
t.quietlyInvoke(); |
612 |
|
|
if (ex == null) |
613 |
|
|
ex = t.getException(); |
614 |
|
|
} |
615 |
|
|
} |
616 |
|
|
for (int i = 1; i <= last; ++i) { |
617 |
|
|
ForkJoinTask<?> t = ts.get(i); |
618 |
|
|
if (t != null) { |
619 |
|
|
if (ex != null) |
620 |
|
|
t.cancel(false); |
621 |
|
|
else { |
622 |
|
|
t.quietlyJoin(); |
623 |
|
|
if (ex == null) |
624 |
|
|
ex = t.getException(); |
625 |
|
|
} |
626 |
|
|
} |
627 |
|
|
} |
628 |
|
|
if (ex != null) |
629 |
|
|
rethrowException(ex); |
630 |
dl |
1.1 |
} |
631 |
|
|
|
632 |
|
|
/** |
633 |
|
|
* Returns true if the computation performed by this task has |
634 |
|
|
* completed (or has been cancelled). |
635 |
jsr166 |
1.10 |
* |
636 |
dl |
1.1 |
* @return true if this computation has completed |
637 |
|
|
*/ |
638 |
|
|
public final boolean isDone() { |
639 |
|
|
return status < 0; |
640 |
|
|
} |
641 |
|
|
|
642 |
|
|
/** |
643 |
|
|
* Returns true if this task was cancelled. |
644 |
jsr166 |
1.10 |
* |
645 |
dl |
1.1 |
* @return true if this task was cancelled |
646 |
|
|
*/ |
647 |
|
|
public final boolean isCancelled() { |
648 |
|
|
return (status & COMPLETION_MASK) == CANCELLED; |
649 |
|
|
} |
650 |
|
|
|
651 |
|
|
/** |
652 |
|
|
* Asserts that the results of this task's computation will not be |
653 |
jsr166 |
1.9 |
* used. If a cancellation occurs before attempting to execute this |
654 |
jsr166 |
1.8 |
* task, then execution will be suppressed, {@code isCancelled} |
655 |
|
|
* will report true, and {@code join} will result in a |
656 |
|
|
* {@code CancellationException} being thrown. Otherwise, when |
657 |
dl |
1.1 |
* cancellation races with completion, there are no guarantees |
658 |
jsr166 |
1.8 |
* about whether {@code isCancelled} will report true, whether |
659 |
|
|
* {@code join} will return normally or via an exception, or |
660 |
dl |
1.1 |
* whether these behaviors will remain consistent upon repeated |
661 |
|
|
* invocation. |
662 |
|
|
* |
663 |
|
|
* <p>This method may be overridden in subclasses, but if so, must |
664 |
|
|
* still ensure that these minimal properties hold. In particular, |
665 |
|
|
* the cancel method itself must not throw exceptions. |
666 |
|
|
* |
667 |
|
|
* <p> This method is designed to be invoked by <em>other</em> |
668 |
|
|
* tasks. To terminate the current task, you can just return or |
669 |
|
|
* throw an unchecked exception from its computation method, or |
670 |
jsr166 |
1.8 |
* invoke {@code completeExceptionally}. |
671 |
dl |
1.1 |
* |
672 |
|
|
* @param mayInterruptIfRunning this value is ignored in the |
673 |
|
|
* default implementation because tasks are not in general |
674 |
|
|
* cancelled via interruption. |
675 |
|
|
* |
676 |
|
|
* @return true if this task is now cancelled |
677 |
|
|
*/ |
678 |
|
|
public boolean cancel(boolean mayInterruptIfRunning) { |
679 |
|
|
setCompletion(CANCELLED); |
680 |
|
|
return (status & COMPLETION_MASK) == CANCELLED; |
681 |
|
|
} |
682 |
|
|
|
683 |
|
|
/** |
684 |
jsr166 |
1.10 |
* Returns true if this task threw an exception or was cancelled. |
685 |
|
|
* |
686 |
dl |
1.3 |
* @return true if this task threw an exception or was cancelled |
687 |
|
|
*/ |
688 |
|
|
public final boolean isCompletedAbnormally() { |
689 |
|
|
return (status & COMPLETION_MASK) < NORMAL; |
690 |
|
|
} |
691 |
|
|
|
692 |
|
|
/** |
693 |
|
|
* Returns the exception thrown by the base computation, or a |
694 |
|
|
* CancellationException if cancelled, or null if none or if the |
695 |
|
|
* method has not yet completed. |
696 |
jsr166 |
1.10 |
* |
697 |
dl |
1.3 |
* @return the exception, or null if none |
698 |
|
|
*/ |
699 |
|
|
public final Throwable getException() { |
700 |
|
|
int s = status & COMPLETION_MASK; |
701 |
|
|
if (s >= NORMAL) |
702 |
|
|
return null; |
703 |
|
|
if (s == CANCELLED) |
704 |
|
|
return new CancellationException(); |
705 |
|
|
return exceptionMap.get(this); |
706 |
|
|
} |
707 |
|
|
|
708 |
|
|
/** |
709 |
dl |
1.1 |
* Completes this task abnormally, and if not already aborted or |
710 |
|
|
* cancelled, causes it to throw the given exception upon |
711 |
jsr166 |
1.8 |
* {@code join} and related operations. This method may be used |
712 |
dl |
1.1 |
* to induce exceptions in asynchronous tasks, or to force |
713 |
dl |
1.2 |
* completion of tasks that would not otherwise complete. Its use |
714 |
|
|
* in other situations is likely to be wrong. This method is |
715 |
jsr166 |
1.8 |
* overridable, but overridden versions must invoke {@code super} |
716 |
dl |
1.2 |
* implementation to maintain guarantees. |
717 |
|
|
* |
718 |
dl |
1.1 |
* @param ex the exception to throw. If this exception is |
719 |
|
|
* not a RuntimeException or Error, the actual exception thrown |
720 |
|
|
* will be a RuntimeException with cause ex. |
721 |
|
|
*/ |
722 |
|
|
public void completeExceptionally(Throwable ex) { |
723 |
|
|
setDoneExceptionally((ex instanceof RuntimeException) || |
724 |
|
|
(ex instanceof Error)? ex : |
725 |
|
|
new RuntimeException(ex)); |
726 |
|
|
} |
727 |
|
|
|
728 |
|
|
/** |
729 |
|
|
* Completes this task, and if not already aborted or cancelled, |
730 |
jsr166 |
1.8 |
* returning a {@code null} result upon {@code join} and related |
731 |
dl |
1.1 |
* operations. This method may be used to provide results for |
732 |
|
|
* asynchronous tasks, or to provide alternative handling for |
733 |
dl |
1.2 |
* tasks that would not otherwise complete normally. Its use in |
734 |
|
|
* other situations is likely to be wrong. This method is |
735 |
jsr166 |
1.8 |
* overridable, but overridden versions must invoke {@code super} |
736 |
dl |
1.2 |
* implementation to maintain guarantees. |
737 |
dl |
1.1 |
* |
738 |
jsr166 |
1.10 |
* @param value the result value for this task |
739 |
dl |
1.1 |
*/ |
740 |
|
|
public void complete(V value) { |
741 |
|
|
try { |
742 |
|
|
setRawResult(value); |
743 |
|
|
} catch(Throwable rex) { |
744 |
|
|
setDoneExceptionally(rex); |
745 |
|
|
return; |
746 |
|
|
} |
747 |
|
|
setNormalCompletion(); |
748 |
|
|
} |
749 |
|
|
|
750 |
dl |
1.3 |
public final V get() throws InterruptedException, ExecutionException { |
751 |
|
|
ForkJoinWorkerThread w = getWorker(); |
752 |
|
|
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
753 |
|
|
awaitDone(w, true); |
754 |
|
|
return reportFutureResult(); |
755 |
|
|
} |
756 |
|
|
|
757 |
|
|
public final V get(long timeout, TimeUnit unit) |
758 |
|
|
throws InterruptedException, ExecutionException, TimeoutException { |
759 |
|
|
ForkJoinWorkerThread w = getWorker(); |
760 |
|
|
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
761 |
|
|
awaitDone(w, unit.toNanos(timeout)); |
762 |
|
|
return reportTimedFutureResult(); |
763 |
|
|
} |
764 |
|
|
|
765 |
dl |
1.1 |
/** |
766 |
dl |
1.2 |
* Possibly executes other tasks until this task is ready, then |
767 |
|
|
* returns the result of the computation. This method may be more |
768 |
jsr166 |
1.8 |
* efficient than {@code join}, but is only applicable when |
769 |
jsr166 |
1.9 |
* there are no potential dependencies between continuation of the |
770 |
dl |
1.2 |
* current task and that of any other task that might be executed |
771 |
|
|
* while helping. (This usually holds for pure divide-and-conquer |
772 |
|
|
* tasks). This method may be invoked only from within |
773 |
|
|
* ForkJoinTask computations. Attempts to invoke in other contexts |
774 |
jsr166 |
1.9 |
* result in exceptions or errors possibly including ClassCastException. |
775 |
jsr166 |
1.10 |
* |
776 |
dl |
1.2 |
* @return the computed result |
777 |
|
|
*/ |
778 |
|
|
public final V helpJoin() { |
779 |
|
|
ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread()); |
780 |
|
|
if (status < 0 || !w.unpushTask(this) || !tryExec()) |
781 |
dl |
1.3 |
reportException(busyJoin(w)); |
782 |
dl |
1.2 |
return getRawResult(); |
783 |
|
|
} |
784 |
|
|
|
785 |
|
|
/** |
786 |
|
|
* Possibly executes other tasks until this task is ready. This |
787 |
|
|
* method may be invoked only from within ForkJoinTask |
788 |
jsr166 |
1.9 |
* computations. Attempts to invoke in other contexts result in |
789 |
dl |
1.4 |
* exceptions or errors possibly including ClassCastException. |
790 |
dl |
1.2 |
*/ |
791 |
|
|
public final void quietlyHelpJoin() { |
792 |
|
|
if (status >= 0) { |
793 |
|
|
ForkJoinWorkerThread w = |
794 |
|
|
(ForkJoinWorkerThread)(Thread.currentThread()); |
795 |
|
|
if (!w.unpushTask(this) || !tryQuietlyInvoke()) |
796 |
dl |
1.3 |
busyJoin(w); |
797 |
dl |
1.2 |
} |
798 |
|
|
} |
799 |
|
|
|
800 |
|
|
/** |
801 |
|
|
* Joins this task, without returning its result or throwing an |
802 |
|
|
* exception. This method may be useful when processing |
803 |
|
|
* collections of tasks when some have been cancelled or otherwise |
804 |
|
|
* known to have aborted. |
805 |
|
|
*/ |
806 |
|
|
public final void quietlyJoin() { |
807 |
|
|
if (status >= 0) { |
808 |
|
|
ForkJoinWorkerThread w = getWorker(); |
809 |
|
|
if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke()) |
810 |
|
|
awaitDone(w, true); |
811 |
|
|
} |
812 |
|
|
} |
813 |
|
|
|
814 |
|
|
/** |
815 |
|
|
* Commences performing this task and awaits its completion if |
816 |
|
|
* necessary, without returning its result or throwing an |
817 |
|
|
* exception. This method may be useful when processing |
818 |
|
|
* collections of tasks when some have been cancelled or otherwise |
819 |
|
|
* known to have aborted. |
820 |
|
|
*/ |
821 |
|
|
public final void quietlyInvoke() { |
822 |
|
|
if (status >= 0 && !tryQuietlyInvoke()) |
823 |
|
|
quietlyJoin(); |
824 |
|
|
} |
825 |
|
|
|
826 |
|
|
/** |
827 |
dl |
1.3 |
* Possibly executes tasks until the pool hosting the current task |
828 |
|
|
* {@link ForkJoinPool#isQuiescent}. This method may be of use in |
829 |
|
|
* designs in which many tasks are forked, but none are explicitly |
830 |
|
|
* joined, instead executing them until all are processed. |
831 |
|
|
*/ |
832 |
|
|
public static void helpQuiesce() { |
833 |
|
|
((ForkJoinWorkerThread)(Thread.currentThread())). |
834 |
|
|
helpQuiescePool(); |
835 |
|
|
} |
836 |
|
|
|
837 |
|
|
/** |
838 |
dl |
1.1 |
* Resets the internal bookkeeping state of this task, allowing a |
839 |
jsr166 |
1.8 |
* subsequent {@code fork}. This method allows repeated reuse of |
840 |
dl |
1.1 |
* this task, but only if reuse occurs when this task has either |
841 |
|
|
* never been forked, or has been forked, then completed and all |
842 |
|
|
* outstanding joins of this task have also completed. Effects |
843 |
|
|
* under any other usage conditions are not guaranteed, and are |
844 |
|
|
* almost surely wrong. This method may be useful when executing |
845 |
|
|
* pre-constructed trees of subtasks in loops. |
846 |
|
|
*/ |
847 |
|
|
public void reinitialize() { |
848 |
|
|
if ((status & COMPLETION_MASK) == EXCEPTIONAL) |
849 |
|
|
exceptionMap.remove(this); |
850 |
|
|
status = 0; |
851 |
|
|
} |
852 |
|
|
|
853 |
|
|
/** |
854 |
dl |
1.2 |
* Returns the pool hosting the current task execution, or null |
855 |
|
|
* if this task is executing outside of any pool. |
856 |
jsr166 |
1.10 |
* |
857 |
|
|
* @return the pool, or null if none |
858 |
dl |
1.1 |
*/ |
859 |
dl |
1.2 |
public static ForkJoinPool getPool() { |
860 |
|
|
Thread t = Thread.currentThread(); |
861 |
|
|
return ((t instanceof ForkJoinWorkerThread)? |
862 |
|
|
((ForkJoinWorkerThread)t).pool : null); |
863 |
dl |
1.1 |
} |
864 |
|
|
|
865 |
|
|
/** |
866 |
dl |
1.2 |
* Tries to unschedule this task for execution. This method will |
867 |
|
|
* typically succeed if this task is the most recently forked task |
868 |
|
|
* by the current thread, and has not commenced executing in |
869 |
|
|
* another thread. This method may be useful when arranging |
870 |
|
|
* alternative local processing of tasks that could have been, but |
871 |
|
|
* were not, stolen. This method may be invoked only from within |
872 |
dl |
1.1 |
* ForkJoinTask computations. Attempts to invoke in other contexts |
873 |
dl |
1.4 |
* result in exceptions or errors possibly including ClassCastException. |
874 |
jsr166 |
1.10 |
* |
875 |
dl |
1.2 |
* @return true if unforked |
876 |
dl |
1.1 |
*/ |
877 |
dl |
1.2 |
public boolean tryUnfork() { |
878 |
|
|
return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this); |
879 |
dl |
1.1 |
} |
880 |
|
|
|
881 |
|
|
/** |
882 |
dl |
1.2 |
* Returns an estimate of the number of tasks that have been |
883 |
|
|
* forked by the current worker thread but not yet executed. This |
884 |
|
|
* value may be useful for heuristic decisions about whether to |
885 |
|
|
* fork other tasks. |
886 |
jsr166 |
1.10 |
* |
887 |
dl |
1.2 |
* @return the number of tasks |
888 |
|
|
*/ |
889 |
|
|
public static int getQueuedTaskCount() { |
890 |
|
|
return ((ForkJoinWorkerThread)(Thread.currentThread())). |
891 |
|
|
getQueueSize(); |
892 |
|
|
} |
893 |
|
|
|
894 |
|
|
/** |
895 |
jsr166 |
1.10 |
* Returns an estimate of how many more locally queued tasks are |
896 |
dl |
1.1 |
* held by the current worker thread than there are other worker |
897 |
dl |
1.2 |
* threads that might steal them. This value may be useful for |
898 |
|
|
* heuristic decisions about whether to fork other tasks. In many |
899 |
|
|
* usages of ForkJoinTasks, at steady state, each worker should |
900 |
|
|
* aim to maintain a small constant surplus (for example, 3) of |
901 |
|
|
* tasks, and to process computations locally if this threshold is |
902 |
|
|
* exceeded. |
903 |
jsr166 |
1.10 |
* |
904 |
dl |
1.1 |
* @return the surplus number of tasks, which may be negative |
905 |
|
|
*/ |
906 |
dl |
1.2 |
public static int getSurplusQueuedTaskCount() { |
907 |
dl |
1.1 |
return ((ForkJoinWorkerThread)(Thread.currentThread())) |
908 |
|
|
.getEstimatedSurplusTaskCount(); |
909 |
|
|
} |
910 |
|
|
|
911 |
dl |
1.2 |
// Extension methods |
912 |
dl |
1.1 |
|
913 |
|
|
/** |
914 |
jsr166 |
1.8 |
* Returns the result that would be returned by {@code join}, |
915 |
dl |
1.2 |
* even if this task completed abnormally, or null if this task is |
916 |
|
|
* not known to have been completed. This method is designed to |
917 |
|
|
* aid debugging, as well as to support extensions. Its use in any |
918 |
|
|
* other context is discouraged. |
919 |
dl |
1.1 |
* |
920 |
jsr166 |
1.10 |
* @return the result, or null if not completed |
921 |
dl |
1.1 |
*/ |
922 |
|
|
public abstract V getRawResult(); |
923 |
|
|
|
924 |
|
|
/** |
925 |
|
|
* Forces the given value to be returned as a result. This method |
926 |
|
|
* is designed to support extensions, and should not in general be |
927 |
|
|
* called otherwise. |
928 |
|
|
* |
929 |
|
|
* @param value the value |
930 |
|
|
*/ |
931 |
|
|
protected abstract void setRawResult(V value); |
932 |
|
|
|
933 |
|
|
/** |
934 |
|
|
* Immediately performs the base action of this task. This method |
935 |
|
|
* is designed to support extensions, and should not in general be |
936 |
|
|
* called otherwise. The return value controls whether this task |
937 |
|
|
* is considered to be done normally. It may return false in |
938 |
|
|
* asynchronous actions that require explicit invocations of |
939 |
jsr166 |
1.8 |
* {@code complete} to become joinable. It may throw exceptions |
940 |
dl |
1.1 |
* to indicate abnormal exit. |
941 |
jsr166 |
1.10 |
* |
942 |
dl |
1.1 |
* @return true if completed normally |
943 |
|
|
* @throws Error or RuntimeException if encountered during computation |
944 |
|
|
*/ |
945 |
|
|
protected abstract boolean exec(); |
946 |
|
|
|
947 |
dl |
1.2 |
/** |
948 |
dl |
1.6 |
* Returns, but does not unschedule or execute, the task queued by |
949 |
|
|
* the current thread but not yet executed, if one is |
950 |
|
|
* available. There is no guarantee that this task will actually |
951 |
|
|
* be polled or executed next. This method is designed primarily |
952 |
|
|
* to support extensions, and is unlikely to be useful otherwise. |
953 |
|
|
* This method may be invoked only from within ForkJoinTask |
954 |
|
|
* computations. Attempts to invoke in other contexts result in |
955 |
|
|
* exceptions or errors possibly including ClassCastException. |
956 |
dl |
1.2 |
* |
957 |
|
|
* @return the next task, or null if none are available |
958 |
|
|
*/ |
959 |
|
|
protected static ForkJoinTask<?> peekNextLocalTask() { |
960 |
|
|
return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask(); |
961 |
|
|
} |
962 |
|
|
|
963 |
|
|
/** |
964 |
dl |
1.6 |
* Unschedules and returns, without executing, the next task |
965 |
|
|
* queued by the current thread but not yet executed. This method |
966 |
|
|
* is designed primarily to support extensions, and is unlikely to |
967 |
|
|
* be useful otherwise. This method may be invoked only from |
968 |
|
|
* within ForkJoinTask computations. Attempts to invoke in other |
969 |
|
|
* contexts result in exceptions or errors possibly including |
970 |
|
|
* ClassCastException. |
971 |
dl |
1.2 |
* |
972 |
|
|
* @return the next task, or null if none are available |
973 |
|
|
*/ |
974 |
|
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
975 |
dl |
1.6 |
return ((ForkJoinWorkerThread)(Thread.currentThread())).pollLocalTask(); |
976 |
dl |
1.2 |
} |
977 |
jsr166 |
1.7 |
|
978 |
dl |
1.2 |
/** |
979 |
dl |
1.6 |
* Unschedules and returns, without executing, the next task |
980 |
|
|
* queued by the current thread but not yet executed, if one is |
981 |
|
|
* available, or if not available, a task that was forked by some |
982 |
|
|
* other thread, if available. Availability may be transient, so a |
983 |
jsr166 |
1.9 |
* {@code null} result does not necessarily imply quiescence |
984 |
dl |
1.6 |
* of the pool this task is operating in. This method is designed |
985 |
|
|
* primarily to support extensions, and is unlikely to be useful |
986 |
|
|
* otherwise. This method may be invoked only from within |
987 |
dl |
1.4 |
* ForkJoinTask computations. Attempts to invoke in other contexts |
988 |
dl |
1.6 |
* result in exceptions or errors possibly including |
989 |
|
|
* ClassCastException. |
990 |
dl |
1.4 |
* |
991 |
dl |
1.2 |
* @return a task, or null if none are available |
992 |
|
|
*/ |
993 |
|
|
protected static ForkJoinTask<?> pollTask() { |
994 |
|
|
return ((ForkJoinWorkerThread)(Thread.currentThread())). |
995 |
dl |
1.4 |
pollTask(); |
996 |
dl |
1.2 |
} |
997 |
|
|
|
998 |
dl |
1.1 |
// Serialization support |
999 |
|
|
|
1000 |
|
|
private static final long serialVersionUID = -7721805057305804111L; |
1001 |
|
|
|
1002 |
|
|
/** |
1003 |
|
|
* Save the state to a stream. |
1004 |
|
|
* |
1005 |
|
|
* @serialData the current run status and the exception thrown |
1006 |
jsr166 |
1.10 |
* during execution, or null if none |
1007 |
dl |
1.1 |
* @param s the stream |
1008 |
|
|
*/ |
1009 |
|
|
private void writeObject(java.io.ObjectOutputStream s) |
1010 |
|
|
throws java.io.IOException { |
1011 |
|
|
s.defaultWriteObject(); |
1012 |
|
|
s.writeObject(getException()); |
1013 |
|
|
} |
1014 |
|
|
|
1015 |
|
|
/** |
1016 |
|
|
* Reconstitute the instance from a stream. |
1017 |
jsr166 |
1.10 |
* |
1018 |
dl |
1.1 |
* @param s the stream |
1019 |
|
|
*/ |
1020 |
|
|
private void readObject(java.io.ObjectInputStream s) |
1021 |
|
|
throws java.io.IOException, ClassNotFoundException { |
1022 |
|
|
s.defaultReadObject(); |
1023 |
dl |
1.2 |
status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts |
1024 |
|
|
status |= EXTERNAL_SIGNAL; // conservatively set external signal |
1025 |
dl |
1.1 |
Object ex = s.readObject(); |
1026 |
|
|
if (ex != null) |
1027 |
|
|
setDoneExceptionally((Throwable)ex); |
1028 |
|
|
} |
1029 |
|
|
|
1030 |
|
|
// Temporary Unsafe mechanics for preliminary release |
1031 |
jsr166 |
1.5 |
private static Unsafe getUnsafe() throws Throwable { |
1032 |
|
|
try { |
1033 |
|
|
return Unsafe.getUnsafe(); |
1034 |
|
|
} catch (SecurityException se) { |
1035 |
|
|
try { |
1036 |
|
|
return java.security.AccessController.doPrivileged |
1037 |
|
|
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
1038 |
|
|
public Unsafe run() throws Exception { |
1039 |
|
|
return getUnsafePrivileged(); |
1040 |
|
|
}}); |
1041 |
|
|
} catch (java.security.PrivilegedActionException e) { |
1042 |
|
|
throw e.getCause(); |
1043 |
|
|
} |
1044 |
|
|
} |
1045 |
|
|
} |
1046 |
|
|
|
1047 |
|
|
private static Unsafe getUnsafePrivileged() |
1048 |
|
|
throws NoSuchFieldException, IllegalAccessException { |
1049 |
|
|
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
1050 |
|
|
f.setAccessible(true); |
1051 |
|
|
return (Unsafe) f.get(null); |
1052 |
|
|
} |
1053 |
|
|
|
1054 |
|
|
private static long fieldOffset(String fieldName) |
1055 |
|
|
throws NoSuchFieldException { |
1056 |
jsr166 |
1.11 |
return UNSAFE.objectFieldOffset |
1057 |
jsr166 |
1.5 |
(ForkJoinTask.class.getDeclaredField(fieldName)); |
1058 |
|
|
} |
1059 |
dl |
1.1 |
|
1060 |
jsr166 |
1.11 |
static final Unsafe UNSAFE; |
1061 |
dl |
1.1 |
static final long statusOffset; |
1062 |
|
|
|
1063 |
|
|
static { |
1064 |
|
|
try { |
1065 |
jsr166 |
1.11 |
UNSAFE = getUnsafe(); |
1066 |
jsr166 |
1.5 |
statusOffset = fieldOffset("status"); |
1067 |
|
|
} catch (Throwable e) { |
1068 |
|
|
throw new RuntimeException("Could not initialize intrinsics", e); |
1069 |
|
|
} |
1070 |
dl |
1.1 |
} |
1071 |
|
|
|
1072 |
|
|
} |