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third-party-mirror/openjdk/jdk25u/HEAD/./src/java.base/share/classes/java/util/concurrent/ForkJoinTask.java
blob: 51b2488264e0339d092ba31e923f2f543d08a47a [file]
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/*
* This file is available under and governed by the GNU General Public
* License version 2 only, as published by the Free Software Foundation.
* However, the following notice accompanied the original version of this
* file:
*
* Written by Doug Lea with assistance from members of JCP JSR-166
* Expert Group and released to the public domain, as explained at
* http://creativecommons.org/publicdomain/zero/1.0/
*/
package java.util.concurrent;
import java.io.Serializable;
import java.lang.reflect.Constructor;
import java.util.Collection;
import java.util.List;
import java.util.Objects;
import java.util.RandomAccess;
import java.util.concurrent.locks.LockSupport;
import jdk.internal.misc.Unsafe;
/**
* Abstract base class for tasks that run within a {@link ForkJoinPool}.
* A {@code ForkJoinTask} is a thread-like entity that is much
* lighter weight than a normal thread. Huge numbers of tasks and
* subtasks may be hosted by a small number of actual threads in a
* ForkJoinPool, at the price of some usage limitations.
*
* <p>A "main" {@code ForkJoinTask} begins execution when it is
* explicitly submitted to a {@link ForkJoinPool}, or, if not already
* engaged in a ForkJoin computation, commenced in the {@link
* ForkJoinPool#commonPool()} via {@link #fork}, {@link #invoke}, or
* related methods. Once started, it will usually in turn start other
* subtasks. As indicated by the name of this class, many programs
* using {@code ForkJoinTask} employ only methods {@link #fork} and
* {@link #join}, or derivatives such as {@link
* #invokeAll(ForkJoinTask...) invokeAll}. However, this class also
* provides a number of other methods that can come into play in
* advanced usages, as well as extension mechanics that allow support
* of new forms of fork/join processing.
*
* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
* The efficiency of {@code ForkJoinTask}s stems from a set of
* restrictions (that are only partially statically enforceable)
* reflecting their main use as computational tasks calculating pure
* functions or operating on purely isolated objects. The primary
* coordination mechanisms are {@link #fork}, that arranges
* asynchronous execution, and {@link #join}, that doesn't proceed
* until the task's result has been computed. Computations should
* ideally avoid {@code synchronized} methods or blocks, and should
* minimize other blocking synchronization apart from joining other
* tasks or using synchronizers such as Phasers that are advertised to
* cooperate with fork/join scheduling. Subdividable tasks should also
* not perform blocking I/O, and should ideally access variables that
* are completely independent of those accessed by other running
* tasks. These guidelines are loosely enforced by not permitting
* checked exceptions such as {@code IOExceptions} to be
* thrown. However, computations may still encounter unchecked
* exceptions, that are rethrown to callers attempting to join
* them. These exceptions may additionally include {@link
* RejectedExecutionException} stemming from internal resource
* exhaustion, such as failure to allocate internal task
* queues. Rethrown exceptions behave in the same way as regular
* exceptions, but, when possible, contain stack traces (as displayed
* for example using {@code ex.printStackTrace()}) of both the thread
* that initiated the computation as well as the thread actually
* encountering the exception; minimally only the latter.
*
* <p>It is possible to define and use ForkJoinTasks that may block,
* but doing so requires three further considerations: (1) Completion
* of few if any <em>other</em> tasks should be dependent on a task
* that blocks on external synchronization or I/O. Event-style async
* tasks that are never joined (for example, those subclassing {@link
* CountedCompleter}) often fall into this category. (2) To minimize
* resource impact, tasks should be small; ideally performing only the
* (possibly) blocking action. (3) Unless the {@link
* ForkJoinPool.ManagedBlocker} API is used, or the number of possibly
* blocked tasks is known to be less than the pool's {@link
* ForkJoinPool#getParallelism} level, the pool cannot guarantee that
* enough threads will be available to ensure progress or good
* performance.
*
* <p>The primary method for awaiting completion and extracting
* results of a task is {@link #join}, but there are several variants:
* The {@link Future#get} methods support interruptible and/or timed
* waits for completion and report results using {@code Future}
* conventions. Method {@link #invoke} is semantically
* equivalent to {@code fork(); join()} but always attempts to begin
* execution in the current thread. The "<em>quiet</em>" forms of
* these methods do not extract results or report exceptions. These
* may be useful when a set of tasks are being executed, and you need
* to delay processing of results or exceptions until all complete.
* Method {@code invokeAll} (available in multiple versions)
* performs the most common form of parallel invocation: forking a set
* of tasks and joining them all.
*
* <p>In the most typical usages, a fork-join pair act like a call
* (fork) and return (join) from a parallel recursive function. As is
* the case with other forms of recursive calls, returns (joins)
* should be performed innermost-first. For example, {@code a.fork();
* b.fork(); b.join(); a.join();} is likely to be substantially more
* efficient than joining {@code a} before {@code b}.
*
* <p>The execution status of tasks may be queried at several levels
* of detail: {@link #isDone} is true if a task completed in any way
* (including the case where a task was cancelled without executing);
* {@link #isCompletedNormally} is true if a task completed without
* cancellation or encountering an exception; {@link #isCancelled} is
* true if the task was cancelled (in which case {@link #getException()}
* returns a {@link CancellationException}); and
* {@link #isCompletedAbnormally} is true if a task was either
* cancelled or encountered an exception, in which case {@link
* #getException()} will return either the encountered exception or
* {@link CancellationException}.
*
* <p>The ForkJoinTask class is not usually directly subclassed.
* Instead, you subclass one of the abstract classes that support a
* particular style of fork/join processing, typically {@link
* RecursiveAction} for most computations that do not return results,
* {@link RecursiveTask} for those that do, and {@link
* CountedCompleter} for those in which completed actions trigger
* other actions. Normally, a concrete ForkJoinTask subclass declares
* fields comprising its parameters, established in a constructor, and
* then defines a {@code compute} method that somehow uses the control
* methods supplied by this base class.
*
* <p>Method {@link #join} and its variants are appropriate for use
* only when completion dependencies are acyclic; that is, the
* parallel computation can be described as a directed acyclic graph
* (DAG). Otherwise, executions may encounter a form of deadlock as
* tasks cyclically wait for each other. However, this framework
* supports other methods and techniques (for example the use of
* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that
* may be of use in constructing custom subclasses for problems that
* are not statically structured as DAGs. To support such usages, a
* ForkJoinTask may be atomically <em>tagged</em> with a {@code short}
* value using {@link #setForkJoinTaskTag} or {@link
* #compareAndSetForkJoinTaskTag} and checked using {@link
* #getForkJoinTaskTag}. The ForkJoinTask implementation does not use
* these {@code protected} methods or tags for any purpose, but they
* may be of use in the construction of specialized subclasses. For
* example, parallel graph traversals can use the supplied methods to
* avoid revisiting nodes/tasks that have already been processed.
* (Method names for tagging are bulky in part to encourage definition
* of methods that reflect their usage patterns.)
*
* <p>Most base support methods are {@code final}, to prevent
* overriding of implementations that are intrinsically tied to the
* underlying lightweight task scheduling framework. Developers
* creating new basic styles of fork/join processing should minimally
* implement {@code protected} methods {@link #exec}, {@link
* #setRawResult}, and {@link #getRawResult}, while also introducing
* an abstract computational method that can be implemented in its
* subclasses, possibly relying on other {@code protected} methods
* provided by this class.
*
* <p>ForkJoinTasks should perform relatively small amounts of
* computation. Large tasks should be split into smaller subtasks,
* usually via recursive decomposition. As a very rough rule of thumb,
* a task should perform more than 100 and less than 10000 basic
* computational steps, and should avoid indefinite looping. If tasks
* are too big, then parallelism cannot improve throughput. If too
* small, then memory and internal task maintenance overhead may
* overwhelm processing.
*
* <p>This class provides {@code adapt} methods for {@link Runnable}
* and {@link Callable}, that may be of use when mixing execution of
* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
* of this form, consider using a pool constructed in <em>asyncMode</em>.
*
* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
* used in extensions such as remote execution frameworks. It is
* sensible to serialize tasks only before or after, but not during,
* execution. Serialization is not relied on during execution itself.
*
* @param <V> the type of the result of the task
*
* @since 1.7
* @author Doug Lea
*/
public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
/*
* See the internal documentation of class ForkJoinPool for a
* general implementation overview. ForkJoinTasks are mainly
* responsible for maintaining their "status" field amidst relays
* to methods in ForkJoinWorkerThread and ForkJoinPool, along with
* recording and reporting exceptions. The status field mainly
* holds bits recording completion status. Note that there is no
* status bit representing "running", recording whether incomplete
* tasks are queued vs executing. However these cases can be
* distinguished in subclasses of InterruptibleTask that adds this
* capability by recording the running thread. Cancellation is
* recorded in status bits (ABNORMAL but not THROWN), but reported
* in joining methods by throwing an exception. Other exceptions
* of completed (THROWN) tasks are recorded in the "aux" field,
* but are reconstructed (in getException) to produce more useful
* stack traces when reported. Sentinels for interruptions or
* timeouts while waiting for completion are not recorded as
* status bits but are included in return values of methods in
* which they occur.
*
* The methods of this class are more-or-less layered into
* (1) basic status maintenance
* (2) execution and awaiting completion
* (3) user-level methods that additionally report results.
* (4) Subclasses for adaptors and internal usages
* This is sometimes hard to see because this file orders exported
* methods in a way that flows well in javadocs.
*/
/**
* Nodes for threads waiting for completion, or holding a thrown
* exception (never both). Waiting threads prepend nodes
* Treiber-stack-style. Signallers detach and unpark
* waiters. Cancelled waiters try to unsplice.
*/
static final class Aux {
Thread thread; // thrower or waiter
final Throwable ex;
Aux next; // accessed only via memory-acquire chains
Aux(Thread thread, Throwable ex) {
this.thread = thread;
this.ex = ex;
}
final boolean casNext(Aux c, Aux v) { // used only in cancellation
return U.compareAndSetReference(this, NEXT, c, v);
}
private static final Unsafe U;
private static final long NEXT;
static {
U = Unsafe.getUnsafe();
NEXT = U.objectFieldOffset(Aux.class, "next");
}
}
/*
* The status field holds bits packed into a single int to ensure
* atomicity. Status is initially zero, and takes on nonnegative
* values until completed, upon which it holds (sign bit) DONE,
* possibly with ABNORMAL (cancelled or exceptional) and THROWN
* (in which case an exception has been stored). A value of
* ABNORMAL without DONE signifies an interrupted wait. These
* control bits occupy only (some of) the upper half (16 bits) of
* status field. The lower bits are used for user-defined tags.
*/
static final int DONE = 1 << 31; // must be negative
static final int ABNORMAL = 1 << 16;
static final int THROWN = 1 << 17;
static final int HAVE_EXCEPTION = DONE | ABNORMAL | THROWN;
static final int NUH_BIT = 24; // no external caller helping
static final int NO_USER_HELP = 1 << NUH_BIT;
static final int MARKER = 1 << 30; // utility marker
static final int SMASK = 0xffff; // short bits for tags
static final int UNCOMPENSATE = 1 << 16; // helpJoin sentinel
// Fields
/** @serial */
volatile int status; // accessed directly by pool and workers
private transient volatile Aux aux; // either waiters or thrown Exception
// Support for atomic operations
private static final Unsafe U;
private static final long STATUS;
private static final long AUX;
private int getAndBitwiseOrStatus(int v) {
return U.getAndBitwiseOrInt(this, STATUS, v);
}
private boolean casStatus(int c, int v) {
return U.compareAndSetInt(this, STATUS, c, v);
}
final int noUserHelp() { // nonvolatile read; return 0 or 1
return (U.getInt(this, STATUS) & NO_USER_HELP) >>> NUH_BIT;
}
final void setNoUserHelp() { // for use in constructors only
U.putInt(this, STATUS, NO_USER_HELP);
}
// Support for waiting and signalling
private boolean casAux(Aux c, Aux v) {
return U.compareAndSetReference(this, AUX, c, v);
}
private Aux compareAndExchangeAux(Aux c, Aux v) {
return (Aux)U.compareAndExchangeReference(this, AUX, c, v);
}
/** Removes and unparks waiters */
private void signalWaiters() {
for (Aux a = aux;;) {
if (a == null || a.ex != null)
break;
if (a == (a = compareAndExchangeAux(a, null))) {
do { // detach entire list
LockSupport.unpark(a.thread);
} while ((a = a.next) != null);
break;
}
}
}
/**
* Sets DONE status and wakes up threads waiting to join this task.
*/
private void setDone() {
getAndBitwiseOrStatus(DONE);
signalWaiters();
}
/**
* Sets ABNORMAL DONE status unless already done, and wakes up threads
* waiting to join this task.
* @return previous status
*/
final int trySetCancelled() {
int s;
if ((s = status) >= 0 &&
(s = getAndBitwiseOrStatus(DONE | ABNORMAL)) >= 0)
signalWaiters();
return s;
}
/**
* Records exception and sets ABNORMAL THROWN DONE status unless
* already done, and wakes up threads waiting to join this task.
* If losing a race with setDone or trySetCancelled, the exception
* may be recorded but not reported.
*
* @return true if set
*/
final boolean trySetThrown(Throwable ex) {
int s;
boolean set = false, installed = false;
if ((s = status) >= 0) {
Aux a, p = null, h = new Aux(Thread.currentThread(), ex);
do {
if (!installed && ((a = aux) == null || a.ex == null) &&
(installed = casAux(a, h)))
p = a; // list of waiters replaced by h
if (installed && (set = casStatus(s, s | HAVE_EXCEPTION)))
break;
} while ((s = status) >= 0);
for (; p != null; p = p.next)
LockSupport.unpark(p.thread);
}
return set;
}
/**
* Overridable action on setting exception
*/
void onAuxExceptionSet(Throwable ex) {
}
/**
* Tries to set exception, if so invoking onAuxExceptionSet
*/
final void trySetException(Throwable ex) {
if (trySetThrown(ex))
onAuxExceptionSet(ex);
}
/*
* Waits for signal, interrupt, timeout, or pool termination.
*
* @param pool if nonnull, the pool of ForkJoinWorkerThread caller
* @param compensation result from a helping method
* @param interruptible if wait is interruptible
* @param deadline if nonzero, timeout deadline
* @return ABNORMAL if interrupted, 0 on timeout, else status on exit
*/
private int awaitDone(ForkJoinPool pool, int compensation,
boolean interruptible, long deadline) {
int s;
if ((s = status) >= 0) {
Aux node = null;
try { // spinwait if out of memory
node = new Aux(Thread.currentThread(), null);
} catch (OutOfMemoryError ex) {
}
boolean queued = false;
for (Aux a;;) { // try to install node
if ((s = status) < 0)
break;
else if (node == null)
Thread.onSpinWait();
else if (((a = aux) == null || a.ex == null) &&
(queued = casAux(node.next = a, node)))
break;
}
if (queued) { // await signal or interrupt
LockSupport.setCurrentBlocker(this);
int interrupts = 0; // < 0 : throw; > 0 : re-interrupt
for (;;) {
if ((s = status) < 0)
break;
else if (interrupts < 0) {
s = ABNORMAL; // interrupted and not done
break;
}
else if (Thread.interrupted()) {
if (!ForkJoinPool.poolIsStopping(pool))
interrupts = interruptible ? -1 : 1;
else {
interrupts = 1; // re-assert if cleared
try {
cancel(true);
} catch (Throwable ignore) {
}
}
}
else if (deadline != 0L) {
long ns;
if ((ns = deadline - System.nanoTime()) <= 0) {
s = 0;
break;
}
LockSupport.parkNanos(ns);
}
else
LockSupport.park();
}
node.thread = null; // help clean aux; raciness OK
clean: for (Aux a;;) { // remove node if still present
if ((a = aux) == null || a.ex != null)
break;
for (Aux prev = null;;) {
Aux next = a.next;
if (a == node) {
if (prev != null)
prev.casNext(prev, next);
else if (casAux(a, next))
break clean;
break; // check for failed or stale CAS
}
prev = a;
if ((a = next) == null)
break clean; // not found
}
}
LockSupport.setCurrentBlocker(null);
if (interrupts > 0)
Thread.currentThread().interrupt();
}
}
if (compensation == UNCOMPENSATE && pool != null)
pool.uncompensate();
return s;
}
/**
* Tries applicable helping steps while joining this task,
* otherwise invokes blocking version of awaitDone. Called only
* when pre-checked not to be done, and pre-screened for
* interrupts and timeouts, if applicable.
*
* @param interruptible if wait is interruptible
* @param deadline if nonzero, timeout deadline
* @return ABNORMAL if interrupted, else status on exit
*/
private int awaitDone(boolean interruptible, long deadline) {
ForkJoinWorkerThread wt; ForkJoinPool p; ForkJoinPool.WorkQueue q;
Thread t; boolean internal; int s, ss;
if (internal =
(t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
p = (wt = (ForkJoinWorkerThread)t).pool;
q = wt.workQueue;
}
else
q = ForkJoinPool.externalQueue(p = ForkJoinPool.common);
return (((s = (p == null) ? 0 :
((this instanceof CountedCompleter) ?
p.helpComplete(this, q, internal) :
!internal && ((ss = status) & NO_USER_HELP) != 0 ? ss :
p.helpJoin(this, q, internal))) < 0)) ? s :
awaitDone(internal ? p : null, s, interruptible, deadline);
}
/**
* Runs a task body: Unless done, calls exec and records status if
* completed, but doesn't wait for completion otherwise.
*/
final void doExec() {
if (status >= 0) {
boolean completed = false;
try {
completed = exec();
} catch (Throwable rex) {
trySetException(rex);
}
if (completed)
setDone();
}
}
// Reporting Exceptions
/**
* Returns a rethrowable exception for this task, if available.
* To provide accurate stack traces, if the exception was not
* thrown by the current thread, we try to create a new exception
* of the same type as the one thrown, but with the recorded
* exception as its cause. If there is no such constructor, we
* instead try to use a no-arg constructor, followed by initCause,
* to the same effect. If none of these apply, or any fail due to
* other exceptions, we return the recorded exception, which is
* still correct, although it may contain a misleading stack
* trace.
*
* @param asExecutionException true if wrap as ExecutionException
* @return the exception, or null if none
*/
private Throwable getException(boolean asExecutionException) {
int s; Throwable ex; Aux a;
if ((s = status) >= 0 || (s & ABNORMAL) == 0)
return null;
else if ((s & THROWN) == 0 || (a = aux) == null || (ex = a.ex) == null) {
ex = new CancellationException();
if (!asExecutionException || !(this instanceof InterruptibleTask))
return ex; // else wrap below
}
else if (a.thread != Thread.currentThread()) {
try {
Constructor<?> noArgCtor = null, oneArgCtor = null;
for (Constructor<?> c : ex.getClass().getConstructors()) {
Class<?>[] ps = c.getParameterTypes();
if (ps.length == 0)
noArgCtor = c;
else if (ps.length == 1 && ps[0] == Throwable.class) {
oneArgCtor = c;
break;
}
}
if (oneArgCtor != null)
ex = (Throwable)oneArgCtor.newInstance(ex);
else if (noArgCtor != null) {
Throwable rx = (Throwable)noArgCtor.newInstance();
rx.initCause(ex);
ex = rx;
}
} catch (Exception ignore) {
}
}
return (asExecutionException) ? new ExecutionException(ex) : ex;
}
/**
* Throws thrown exception, or CancellationException if none
* recorded.
*/
private void reportException(boolean asExecutionException) {
ForkJoinTask.<RuntimeException>
uncheckedThrow(getException(asExecutionException));
}
/**
* A version of "sneaky throw" to relay exceptions in other
* contexts.
*/
static void rethrow(Throwable ex) {
ForkJoinTask.<RuntimeException>uncheckedThrow(ex);
}
/**
* The sneaky part of sneaky throw, relying on generics
* limitations to evade compiler complaints about rethrowing
* unchecked exceptions. If argument null, throws
* CancellationException.
*/
@SuppressWarnings("unchecked") static <T extends Throwable>
void uncheckedThrow(Throwable t) throws T {
if (t == null)
t = new CancellationException();
throw (T)t; // rely on vacuous cast
}
// Utilities shared among ForkJoinTask, ForkJoinPool
/**
* Sets MARKER bit, returning nonzero if previously set
*/
final int setForkJoinTaskStatusMarkerBit() {
return getAndBitwiseOrStatus(MARKER) & MARKER;
}
/**
* Returns nonzero if MARKER bit set.
*/
final int getForkJoinTaskStatusMarkerBit() {
return status & MARKER;
}
// public methods
/**
* Constructor for subclasses to call.
*/
public ForkJoinTask() {}
/**
* Arranges to asynchronously execute this task in the pool the
* current task is running in, if applicable, or using the {@link
* ForkJoinPool#commonPool()} if not {@link #inForkJoinPool}. While
* it is not necessarily enforced, it is a usage error to fork a
* task more than once unless it has completed and been
* reinitialized. Subsequent modifications to the state of this
* task or any data it operates on are not necessarily
* consistently observable by any thread other than the one
* executing it unless preceded by a call to {@link #join} or
* related methods, or a call to {@link #isDone} returning {@code
* true}.
*
* @return {@code this}, to simplify usage
*/
public final ForkJoinTask<V> fork() {
Thread t; ForkJoinWorkerThread wt;
ForkJoinPool p; ForkJoinPool.WorkQueue q; boolean internal;
if (internal =
(t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
q = (wt = (ForkJoinWorkerThread)t).workQueue;
p = wt.pool;
}
else
q = (p = ForkJoinPool.common).externalSubmissionQueue(false);
q.push(this, p, internal);
return this;
}
/**
* Returns the result of the computation when it
* {@linkplain #isDone is done}.
* This method differs from {@link #get()} in that abnormal
* completion results in {@code RuntimeException} or {@code Error},
* not {@code ExecutionException}, and that interrupts of the
* calling thread do <em>not</em> cause the method to abruptly
* return by throwing {@code InterruptedException}.
*
* @return the computed result
*/
public final V join() {
int s;
if ((((s = status) < 0 ? s : awaitDone(false, 0L)) & ABNORMAL) != 0)
reportException(false);
return getRawResult();
}
/**
* Commences performing this task, awaits its completion if
* necessary, and returns its result, or throws an (unchecked)
* {@code RuntimeException} or {@code Error} if the underlying
* computation did so.
*
* @return the computed result
*/
public final V invoke() {
doExec();
return join();
}
/**
* Forks the given tasks, returning when {@code isDone} holds for
* each task or an (unchecked) exception is encountered, in which
* case the exception is rethrown. If more than one task
* encounters an exception, then this method throws any one of
* these exceptions. If any task encounters an exception, the
* other may be cancelled. However, the execution status of
* individual tasks is not guaranteed upon exceptional return. The
* status of each task may be obtained using {@link
* #getException()} and related methods to check if they have been
* cancelled, completed normally or exceptionally, or left
* unprocessed.
*
* @param t1 the first task
* @param t2 the second task
* @throws NullPointerException if any task is null
*/
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
int s1, s2;
if (t1 == null || t2 == null)
throw new NullPointerException();
t2.fork();
t1.doExec();
if ((((s1 = t1.status) < 0 ? s1 :
t1.awaitDone(false, 0L)) & ABNORMAL) != 0) {
t2.cancel(false);
t1.reportException(false);
}
else if ((((s2 = t2.status) < 0 ? s2 :
t2.awaitDone(false, 0L)) & ABNORMAL) != 0)
t2.reportException(false);
}
/**
* Forks the given tasks, returning when {@code isDone} holds for
* each task or an (unchecked) exception is encountered, in which
* case the exception is rethrown. If more than one task
* encounters an exception, then this method throws any one of
* these exceptions. If any task encounters an exception, others
* may be cancelled. However, the execution status of individual
* tasks is not guaranteed upon exceptional return. The status of
* each task may be obtained using {@link #getException()} and
* related methods to check if they have been cancelled, completed
* normally or exceptionally, or left unprocessed.
*
* @param tasks the tasks
* @throws NullPointerException if any task is null
*/
public static void invokeAll(ForkJoinTask<?>... tasks) {
Throwable ex = null;
int last = tasks.length - 1;
for (int i = last; i >= 0; --i) {
ForkJoinTask<?> t; int s;
if ((t = tasks[i]) == null) {
ex = new NullPointerException();
break;
}
if (i == 0) {
t.doExec();
if ((((s = t.status) < 0 ? s :
t.awaitDone(false, 0L)) & ABNORMAL) != 0)
ex = t.getException(false);
break;
}
t.fork();
}
if (ex == null) {
for (int i = 1; i <= last; ++i) {
ForkJoinTask<?> t; int s;
if ((t = tasks[i]) != null &&
((((s = t.status) < 0 ? s :
t.awaitDone(false, 0L)) & ABNORMAL) != 0) &&
(ex = t.getException(false)) != null)
break;
}
}
if (ex != null) {
for (int i = 1; i <= last; ++i) {
ForkJoinTask<?> t;
if ((t = tasks[i]) != null)
t.cancel(false);
}
rethrow(ex);
}
}
/**
* Forks all tasks in the specified collection, returning when
* {@code isDone} holds for each task or an (unchecked) exception
* is encountered, in which case the exception is rethrown. If
* more than one task encounters an exception, then this method
* throws any one of these exceptions. If any task encounters an
* exception, others may be cancelled. However, the execution
* status of individual tasks is not guaranteed upon exceptional
* return. The status of each task may be obtained using {@link
* #getException()} and related methods to check if they have been
* cancelled, completed normally or exceptionally, or left
* unprocessed.
*
* @param tasks the collection of tasks
* @param <T> the type of the values returned from the tasks
* @return the tasks argument, to simplify usage
* @throws NullPointerException if tasks or any element are null
*/
public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
invokeAll(tasks.toArray(new ForkJoinTask<?>[0]));
return tasks;
}
List<? extends ForkJoinTask<?>> ts =
(List<? extends ForkJoinTask<?>>) tasks;
Throwable ex = null;
int last = ts.size() - 1; // nearly same as array version
for (int i = last; i >= 0; --i) {
ForkJoinTask<?> t; int s;
if ((t = ts.get(i)) == null) {
ex = new NullPointerException();
break;
}
if (i == 0) {
t.doExec();
if ((((s = t.status) < 0 ? s :
t.awaitDone(false, 0L)) & ABNORMAL) != 0)
ex = t.getException(false);
break;
}
t.fork();
}
if (ex == null) {
for (int i = 1; i <= last; ++i) {
ForkJoinTask<?> t; int s;
if ((t = ts.get(i)) != null &&
((((s = t.status) < 0 ? s :
t.awaitDone(false, 0L)) & ABNORMAL) != 0) &&
(ex = t.getException(false)) != null)
break;
}
}
if (ex != null) {
for (int i = 1; i <= last; ++i) {
ForkJoinTask<?> t;
if ((t = ts.get(i)) != null)
t.cancel(false);
}
rethrow(ex);
}
return tasks;
}
/**
* Attempts to cancel execution of this task. This attempt will
* fail if the task has already completed or could not be
* cancelled for some other reason. If successful, and this task
* has not started when {@code cancel} is called, execution of
* this task is suppressed. After this method returns
* successfully, unless there is an intervening call to {@link
* #reinitialize}, subsequent calls to {@link #isCancelled},
* {@link #isDone}, and {@code cancel} will return {@code true}
* and calls to {@link #join} and related methods will result in
* {@code CancellationException}.
*
* <p>This method may be overridden in subclasses, but if so, must
* still ensure that these properties hold. In particular, the
* {@code cancel} method itself must not throw exceptions.
*
* <p>This method is designed to be invoked by <em>other</em>
* tasks. To terminate the current task, you can just return or
* throw an unchecked exception from its computation method, or
* invoke {@link #completeExceptionally(Throwable)}.
*
* @param mayInterruptIfRunning this value has no effect in the
* default implementation because interrupts are not used to
* control cancellation.
*
* @return {@code true} if this task is now cancelled
*/
public boolean cancel(boolean mayInterruptIfRunning) {
int s = trySetCancelled();
return (s >= 0 || (s & (ABNORMAL | THROWN)) == ABNORMAL);
}
public final boolean isDone() {
return status < 0;
}
public final boolean isCancelled() {
return (status & (ABNORMAL | THROWN)) == ABNORMAL;
}
/**
* Returns {@code true} if this task threw an exception or was cancelled.
*
* @return {@code true} if this task threw an exception or was cancelled
*/
public final boolean isCompletedAbnormally() {
return (status & ABNORMAL) != 0;
}
/**
* Returns {@code true} if this task completed without throwing an
* exception and was not cancelled.
*
* @return {@code true} if this task completed without throwing an
* exception and was not cancelled
*/
public final boolean isCompletedNormally() {
return (status & (DONE | ABNORMAL)) == DONE;
}
/**
* @since 19
*/
@Override
public State state() {
int s = status;
return (s >= 0) ? State.RUNNING :
((s & (DONE | ABNORMAL)) == DONE) ? State.SUCCESS:
((s & (ABNORMAL | THROWN)) == (ABNORMAL | THROWN)) ? State.FAILED :
State.CANCELLED;
}
/**
* @since 19
*/
@Override
public V resultNow() {
int s = status;
if ((s & DONE) == 0)
throw new IllegalStateException("Task has not completed");
if ((s & ABNORMAL) != 0) {
if ((s & THROWN) != 0)
throw new IllegalStateException("Task completed with exception");
else
throw new IllegalStateException("Task was cancelled");
}
return getRawResult();
}
/**
* @since 19
*/
@Override
public Throwable exceptionNow() {
Throwable ex;
if ((status & HAVE_EXCEPTION) != HAVE_EXCEPTION ||
(ex = getException(false)) == null)
throw new IllegalStateException();
return ex;
}
/**
* Returns the exception thrown by the base computation, or a
* {@code CancellationException} if cancelled, or {@code null} if
* none or if the method has not yet completed.
*
* @return the exception, or {@code null} if none
*/
public final Throwable getException() {
return getException(false);
}
/**
* Completes this task abnormally, and if not already aborted or
* cancelled, causes it to throw the given exception upon
* {@code join} and related operations. This method may be used
* to induce exceptions in asynchronous tasks, or to force
* completion of tasks that would not otherwise complete. Its use
* in other situations is discouraged. This method is
* overridable, but overridden versions must invoke {@code super}
* implementation to maintain guarantees.
*
* @param ex the exception to throw. If this exception is not a
* {@code RuntimeException} or {@code Error}, the actual exception
* thrown will be a {@code RuntimeException} with cause {@code ex}.
*/
public void completeExceptionally(Throwable ex) {
trySetException((ex instanceof RuntimeException) ||
(ex instanceof Error) ? ex :
new RuntimeException(ex));
}
/**
* Completes this task, and if not already aborted or cancelled,
* returning the given value as the result of subsequent
* invocations of {@code join} and related operations. This method
* may be used to provide results for asynchronous tasks, or to
* provide alternative handling for tasks that would not otherwise
* complete normally. Its use in other situations is
* discouraged. This method is overridable, but overridden
* versions must invoke {@code super} implementation to maintain
* guarantees.
*
* @param value the result value for this task
*/
public void complete(V value) {
try {
setRawResult(value);
} catch (Throwable rex) {
trySetException(rex);
return;
}
setDone();
}
/**
* Completes this task normally without setting a value. The most
* recent value established by {@link #setRawResult} (or {@code
* null} by default) will be returned as the result of subsequent
* invocations of {@code join} and related operations.
*
* @since 1.8
*/
public final void quietlyComplete() {
setDone();
}
/**
* Waits if necessary for the computation to complete, and then
* retrieves its result.
*
* @return the computed result
* @throws CancellationException if the computation was cancelled
* @throws ExecutionException if the computation threw an
* exception
* @throws InterruptedException if the current thread is not a
* member of a ForkJoinPool and was interrupted while waiting
*/
public final V get() throws InterruptedException, ExecutionException {
int stat = status;
int s = ((stat < 0) ? stat :
(Thread.interrupted()) ? ABNORMAL :
awaitDone(true, 0L));
if (s == ABNORMAL)
throw new InterruptedException();
else if ((s & ABNORMAL) != 0)
reportException(true);
return getRawResult();
}
/**
* Waits if necessary for at most the given time for the computation
* to complete, and then retrieves its result, if available.
*
* @param timeout the maximum time to wait
* @param unit the time unit of the timeout argument
* @return the computed result
* @throws CancellationException if the computation was cancelled
* @throws ExecutionException if the computation threw an
* exception
* @throws InterruptedException if the current thread is not a
* member of a ForkJoinPool and was interrupted while waiting
* @throws TimeoutException if the wait timed out
*/
public final V get(long timeout, TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException {
long nanos = unit.toNanos(timeout);
int stat = status;
int s = ((stat < 0) ? stat :
(Thread.interrupted()) ? ABNORMAL :
(nanos <= 0L) ? 0 :
awaitDone(true, (System.nanoTime() + nanos) | 1L));
if (s == ABNORMAL)
throw new InterruptedException();
else if (s >= 0)
throw new TimeoutException();
else if ((s & ABNORMAL) != 0)
reportException(true);
return getRawResult();
}
/**
* Joins this task, without returning its result or throwing its
* exception. This method may be useful when processing
* collections of tasks when some have been cancelled or otherwise
* known to have aborted.
*/
public final void quietlyJoin() {
if (status >= 0)
awaitDone(false, 0L);
}
/**
* Commences performing this task and awaits its completion if
* necessary, without returning its result or throwing its
* exception.
*/
public final void quietlyInvoke() {
doExec();
if (status >= 0)
awaitDone(false, 0L);
}
/**
* Tries to join this task, returning true if it completed
* (possibly exceptionally) before the given timeout elapsed and
* the current thread has not been interrupted.
*
* @param timeout the maximum time to wait
* @param unit the time unit of the timeout argument
* @return true if this task completed
* @throws InterruptedException if the current thread was
* interrupted while waiting
* @since 19
*/
public final boolean quietlyJoin(long timeout, TimeUnit unit)
throws InterruptedException {
long nanos = unit.toNanos(timeout);
int stat = status;
int s = ((stat < 0) ? stat :
(Thread.interrupted()) ? ABNORMAL :
(nanos <= 0L) ? 0 :
awaitDone(true, (System.nanoTime() + nanos) | 1L));
if (s == ABNORMAL)
throw new InterruptedException();
return (s < 0);
}
/**
* Tries to join this task, returning true if it completed
* (possibly exceptionally) before the given timeout elapsed.
*
* @param timeout the maximum time to wait
* @param unit the time unit of the timeout argument
* @return true if this task completed
* @since 19
*/
public final boolean quietlyJoinUninterruptibly(long timeout,
TimeUnit unit) {
int s;
long nanos = unit.toNanos(timeout);
if ((s = status) >= 0 && nanos > 0L)
s = awaitDone(false, (System.nanoTime() + nanos) | 1L);
return (s < 0);
}
/**
* Utility for possibly-timed ForkJoinPool.invokeAll
*/
final void quietlyJoinPoolInvokeAllTask(long deadline)
throws InterruptedException {
int s;
if ((s = status) >= 0) {
if (Thread.interrupted())
s = ABNORMAL;
else if (deadline == 0L || deadline - System.nanoTime() > 0L)
s = awaitDone(true, deadline);
if (s == ABNORMAL)
throw new InterruptedException();
else if (s >= 0)
cancel(true);
}
}
/**
* Possibly executes tasks until the pool hosting the current task
* {@linkplain ForkJoinPool#isQuiescent is quiescent}. This
* method may be of use in designs in which many tasks are forked,
* but none are explicitly joined, instead executing them until
* all are processed.
*/
public static void helpQuiesce() {
ForkJoinPool.helpQuiescePool(null, Long.MAX_VALUE, false);
}
/**
* Resets the internal bookkeeping state of this task, allowing a
* subsequent {@code fork}. This method allows repeated reuse of
* this task, but only if reuse occurs when this task has either
* never been forked, or has been forked, then completed and all
* outstanding joins of this task have also completed. Effects
* under any other usage conditions are not guaranteed.
* This method may be useful when executing
* pre-constructed trees of subtasks in loops.
*
* <p>Upon completion of this method, {@code isDone()} reports
* {@code false}, and {@code getException()} reports {@code
* null}. However, the value returned by {@code getRawResult} is
* unaffected. To clear this value, you can invoke {@code
* setRawResult(null)}.
*/
public void reinitialize() {
aux = null;
status &= NO_USER_HELP;
}
/**
* Returns the pool hosting the current thread, or {@code null}
* if the current thread is executing outside of any ForkJoinPool.
*
* <p>This method returns {@code null} if and only if {@link
* #inForkJoinPool} returns {@code false}.
*
* @return the pool, or {@code null} if none
*/
public static ForkJoinPool getPool() {
Thread t;
return (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
((ForkJoinWorkerThread) t).pool : null);
}
/**
* Returns {@code true} if the current thread is a {@link
* ForkJoinWorkerThread} executing as a ForkJoinPool computation.
*
* @return {@code true} if the current thread is a {@link
* ForkJoinWorkerThread} executing as a ForkJoinPool computation,
* or {@code false} otherwise
*/
public static boolean inForkJoinPool() {
return Thread.currentThread() instanceof ForkJoinWorkerThread;
}
/**
* Tries to unschedule this task for execution. This method will
* typically (but is not guaranteed to) succeed if this task is
* the most recently forked task by the current thread, and has
* not commenced executing in another thread. This method may be
* useful when arranging alternative local processing of tasks
* that could have been, but were not, stolen.
*
* @return {@code true} if unforked
*/
public boolean tryUnfork() {
Thread t; ForkJoinPool.WorkQueue q; boolean internal;
if (internal =
(t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
q = ((ForkJoinWorkerThread)t).workQueue;
else
q = ForkJoinPool.commonQueue();
return (q != null && q.tryUnpush(this, internal));
}
/**
* Returns an estimate of the number of tasks that have been
* forked by the current worker thread but not yet executed. This
* value may be useful for heuristic decisions about whether to
* fork other tasks.
*
* @return the number of tasks
*/
public static int getQueuedTaskCount() {
Thread t; ForkJoinPool.WorkQueue q;
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
q = ((ForkJoinWorkerThread)t).workQueue;
else
q = ForkJoinPool.commonQueue();
return (q == null) ? 0 : q.queueSize();
}
/**
* Returns an estimate of how many more locally queued tasks are
* held by the current worker thread than there are other worker
* threads that might steal them, or zero if this thread is not
* operating in a ForkJoinPool. This value may be useful for
* heuristic decisions about whether to fork other tasks. In many
* usages of ForkJoinTasks, at steady state, each worker should
* aim to maintain a small constant surplus (for example, 3) of
* tasks, and to process computations locally if this threshold is
* exceeded.
*
* @return the surplus number of tasks, which may be negative
*/
public static int getSurplusQueuedTaskCount() {
return ForkJoinPool.getSurplusQueuedTaskCount();
}
// Extension methods
/**
* Returns the result that would be returned by {@link #join}, even
* if this task completed abnormally, or {@code null} if this task
* is not known to have been completed. This method is designed
* to aid debugging, as well as to support extensions. Its use in
* any other context is discouraged.
*
* @return the result, or {@code null} if not completed
*/
public abstract V getRawResult();
/**
* Forces the given value to be returned as a result. This method
* is designed to support extensions, and should not in general be
* called otherwise.
*
* @param value the value
*/
protected abstract void setRawResult(V value);
/**
* Immediately performs the base action of this task and returns
* true if, upon return from this method, this task is guaranteed
* to have completed. This method may return false otherwise, to
* indicate that this task is not necessarily complete (or is not
* known to be complete), for example in asynchronous actions that
* require explicit invocations of completion methods. This method
* may also throw an (unchecked) exception to indicate abnormal
* exit. This method is designed to support extensions, and should
* not in general be called otherwise.
*
* @return {@code true} if this task is known to have completed normally
*/
protected abstract boolean exec();
/**
* Returns, but does not unschedule or execute, a task queued by
* the current thread but not yet executed, if one is immediately
* available. There is no guarantee that this task will actually
* be polled or executed next. Conversely, this method may return
* null even if a task exists but cannot be accessed without
* contention with other threads. This method is designed
* primarily to support extensions, and is unlikely to be useful
* otherwise.
*
* @return the next task, or {@code null} if none are available
*/
protected static ForkJoinTask<?> peekNextLocalTask() {
Thread t; ForkJoinPool.WorkQueue q;
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
q = ((ForkJoinWorkerThread)t).workQueue;
else
q = ForkJoinPool.commonQueue();
return (q == null) ? null : q.peek();
}
/**
* Unschedules and returns, without executing, the next task
* queued by the current thread but not yet executed, if the
* current thread is operating in a ForkJoinPool. This method is
* designed primarily to support extensions, and is unlikely to be
* useful otherwise.
*
* @return the next task, or {@code null} if none are available
*/
protected static ForkJoinTask<?> pollNextLocalTask() {
Thread t;
return (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
((ForkJoinWorkerThread)t).workQueue.nextLocalTask() : null);
}
/**
* If the current thread is operating in a ForkJoinPool,
* unschedules and returns, without executing, the next task
* queued by the current thread but not yet executed, if one is
* available, or if not available, a task that was forked by some
* other thread, if available. Availability may be transient, so a
* {@code null} result does not necessarily imply quiescence of
* the pool this task is operating in. This method is designed
* primarily to support extensions, and is unlikely to be useful
* otherwise.
*
* @return a task, or {@code null} if none are available
*/
protected static ForkJoinTask<?> pollTask() {
Thread t; ForkJoinWorkerThread w;
return (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
(w = (ForkJoinWorkerThread)t).pool.nextTaskFor(w.workQueue) :
null);
}
/**
* If the current thread is operating in a ForkJoinPool,
* unschedules and returns, without executing, a task externally
* submitted to the pool, if one is available. Availability may be
* transient, so a {@code null} result does not necessarily imply
* quiescence of the pool. This method is designed primarily to
* support extensions, and is unlikely to be useful otherwise.
*
* @return a task, or {@code null} if none are available
* @since 9
*/
protected static ForkJoinTask<?> pollSubmission() {
Thread t;
return (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
((ForkJoinWorkerThread)t).pool.pollSubmission() : null);
}
// tag operations
/**
* Returns the tag for this task.
*
* @return the tag for this task
* @since 1.8
*/
public final short getForkJoinTaskTag() {
return (short)status;
}
/**
* Atomically sets the tag value for this task and returns the old value.
*
* @param newValue the new tag value
* @return the previous value of the tag
* @since 1.8
*/
public final short setForkJoinTaskTag(short newValue) {
for (int s;;) {
if (casStatus(s = status, (s & ~SMASK) | (newValue & SMASK)))
return (short)s;
}
}
/**
* Atomically conditionally sets the tag value for this task.
* Among other applications, tags can be used as visit markers
* in tasks operating on graphs, as in methods that check: {@code
* if (task.compareAndSetForkJoinTaskTag((short)0, (short)1))}
* before processing, otherwise exiting because the node has
* already been visited.
*
* @param expect the expected tag value
* @param update the new tag value
* @return {@code true} if successful; i.e., the current value was
* equal to {@code expect} and was changed to {@code update}.
* @since 1.8
*/
public final boolean compareAndSetForkJoinTaskTag(short expect, short update) {
for (int s;;) {
if ((short)(s = status) != expect)
return false;
if (casStatus(s, (s & ~SMASK) | (update & SMASK)))
return true;
}
}
// Factory methods for adaptors below
/**
* Returns a new {@code ForkJoinTask} that performs the {@code run}
* method of the given {@code Runnable} as its action, and returns
* a null result upon {@link #join}.
*
* @param runnable the runnable action
* @return the task
*/
public static ForkJoinTask<?> adapt(Runnable runnable) {
return new AdaptedRunnableAction(
Objects.requireNonNull(runnable));
}
/**
* Returns a new {@code ForkJoinTask} that performs the {@code run}
* method of the given {@code Runnable} as its action, and returns
* the given result upon {@link #join}.
*
* @param runnable the runnable action
* @param result the result upon completion
* @param <T> the type of the result
* @return the task
*/
public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
return new AdaptedRunnable<T>(
Objects.requireNonNull(runnable), result);
}
/**
* Returns a new {@code ForkJoinTask} that performs the {@code call}
* method of the given {@code Callable} as its action, and returns
* its result upon {@link #join}, translating any checked exceptions
* encountered into {@code RuntimeException}.
*
* @param callable the callable action
* @param <T> the type of the callable's result
* @return the task
*/
public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
return new AdaptedCallable<T>(
Objects.requireNonNull(callable));
}
/**
* Returns a new {@code ForkJoinTask} that performs the {@code call}
* method of the given {@code Callable} as its action, and returns
* its result upon {@link #join}, translating any checked exceptions
* encountered into {@code RuntimeException}. Additionally,
* invocations of {@code cancel} with {@code mayInterruptIfRunning
* true} will attempt to interrupt the thread performing the task.
*
* @param callable the callable action
* @param <T> the type of the callable's result
* @return the task
*
* @since 19
*/
public static <T> ForkJoinTask<T> adaptInterruptible(Callable<? extends T> callable) {
return new AdaptedInterruptibleCallable<T>(
Objects.requireNonNull(callable));
}
/**
* Returns a new {@code ForkJoinTask} that performs the {@code run}
* method of the given {@code Runnable} as its action, and returns
* the given result upon {@link #join}, translating any checked exceptions
* encountered into {@code RuntimeException}. Additionally,
* invocations of {@code cancel} with {@code mayInterruptIfRunning
* true} will attempt to interrupt the thread performing the task.
*
* @param runnable the runnable action
* @param result the result upon completion
* @param <T> the type of the result
* @return the task
*
* @since 22
*/
public static <T> ForkJoinTask<T> adaptInterruptible(Runnable runnable, T result) {
return new AdaptedInterruptibleRunnable<T>(
Objects.requireNonNull(runnable), result);
}
/**
* Returns a new {@code ForkJoinTask} that performs the {@code
* run} method of the given {@code Runnable} as its action, and
* returns null upon {@link #join}, translating any checked
* exceptions encountered into {@code RuntimeException}.
* Additionally, invocations of {@code cancel} with {@code
* mayInterruptIfRunning true} will attempt to interrupt the
* thread performing the task.
*
* @param runnable the runnable action
* @return the task
*
* @since 22
*/
public static ForkJoinTask<?> adaptInterruptible(Runnable runnable) {
return new AdaptedInterruptibleRunnable<Void>(
Objects.requireNonNull(runnable), null);
}
// Serialization support
private static final long serialVersionUID = -7721805057305804111L;
/**
* Saves this task to a stream (that is, serializes it).
*
* @param s the stream
* @throws java.io.IOException if an I/O error occurs
* @serialData the current run status and the exception thrown
* during execution, or {@code null} if none
*/
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
Aux a;
s.defaultWriteObject();
s.writeObject((a = aux) == null ? null : a.ex);
}
/**
* Reconstitutes this task from a stream (that is, deserializes it).
* @param s the stream
* @throws ClassNotFoundException if the class of a serialized object
* could not be found
* @throws java.io.IOException if an I/O error occurs
*/
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject();
Object ex = s.readObject();
if (ex != null)
aux = new Aux(Thread.currentThread(), (Throwable)ex);
}
static {
U = Unsafe.getUnsafe();
STATUS = U.objectFieldOffset(ForkJoinTask.class, "status");
AUX = U.objectFieldOffset(ForkJoinTask.class, "aux");
Class<?> dep1 = LockSupport.class; // ensure loaded
Class<?> dep2 = Aux.class;
}
// Special subclasses for adaptors and internal tasks
/**
* Adapter for Runnables. This implements RunnableFuture
* to be compliant with AbstractExecutorService constraints
* when used in ForkJoinPool.
*/
static final class AdaptedRunnable<T> extends ForkJoinTask<T>
implements RunnableFuture<T> {
@SuppressWarnings("serial") // Conditionally serializable
final Runnable runnable;
@SuppressWarnings("serial") // Conditionally serializable
T result;
AdaptedRunnable(Runnable runnable, T result) {
this.runnable = runnable;
this.result = result; // OK to set this even before completion
}
public final T getRawResult() { return result; }
public final void setRawResult(T v) { result = v; }
public final boolean exec() { runnable.run(); return true; }
public final void run() { invoke(); }
public String toString() {
return super.toString() + "[Wrapped task = " + runnable + "]";
}
private static final long serialVersionUID = 5232453952276885070L;
}
/**
* Adapter for Runnables without results.
*/
static final class AdaptedRunnableAction extends ForkJoinTask<Void>
implements RunnableFuture<Void> {
@SuppressWarnings("serial") // Conditionally serializable
final Runnable runnable;
AdaptedRunnableAction(Runnable runnable) {
this.runnable = runnable;
}
public final Void getRawResult() { return null; }
public final void setRawResult(Void v) { }
public final boolean exec() { runnable.run(); return true; }
public final void run() { invoke(); }
public String toString() {
return super.toString() + "[Wrapped task = " + runnable + "]";
}
private static final long serialVersionUID = 5232453952276885070L;
}
/**
* Adapter for Callables.
*/
static final class AdaptedCallable<T> extends ForkJoinTask<T>
implements RunnableFuture<T> {
@SuppressWarnings("serial") // Conditionally serializable
final Callable<? extends T> callable;
@SuppressWarnings("serial") // Conditionally serializable
T result;
AdaptedCallable(Callable<? extends T> callable) {
this.callable = callable;
}
public final T getRawResult() { return result; }
public final void setRawResult(T v) { result = v; }
public final boolean exec() {
try {
result = callable.call();
return true;
} catch (RuntimeException rex) {
throw rex;
} catch (Exception ex) {
throw new RuntimeException(ex);
}
}
public final void run() { invoke(); }
public String toString() {
return super.toString() + "[Wrapped task = " + callable + "]";
}
private static final long serialVersionUID = 2838392045355241008L;
}
/**
* Tasks with semantics conforming to ExecutorService conventions.
* Tasks are interruptible when cancelled, including cases of
* cancellation upon pool termination. In addition to recording
* the running thread to enable interrupt in cancel(true), the
* task checks for termination before executing the compute
* method, to cover shutdown races in which the task has not yet
* been cancelled on entry and might not otherwise be cancelled by
* others.
*/
abstract static class InterruptibleTask<T> extends ForkJoinTask<T>
implements RunnableFuture<T> {
transient volatile Thread runner;
InterruptibleTask() {
setNoUserHelp();
}
abstract T compute() throws Exception;
public final boolean exec() {
Thread.interrupted();
Thread t = runner = Thread.currentThread();
try {
if ((t instanceof ForkJoinWorkerThread) &&
ForkJoinPool.poolIsStopping(((ForkJoinWorkerThread)t).pool))
cancel(true);
else {
try {
if (status >= 0)
setRawResult(compute());
} catch (Exception ex) {
trySetException(ex);
}
}
} finally {
runner = null;
}
return postExec();
}
boolean postExec() { // cleanup and return completion status to doExec
return true;
}
final boolean interruptIfRunning(boolean enabled) {
Thread t;
if ((t = runner) == null) // return false if not running
return false;
if (enabled) {
try {
t.interrupt();
} catch (Throwable ignore) {
}
}
return true;
}
public boolean cancel(boolean mayInterruptIfRunning) {
int s;
if ((s = trySetCancelled()) < 0)
return ((s & (ABNORMAL | THROWN)) == ABNORMAL);
interruptIfRunning(mayInterruptIfRunning);
return true;
}
public final void run() { quietlyInvoke(); }
Object adaptee() { return null; } // for printing and diagnostics
public String toString() {
Object a = adaptee();
String s = super.toString();
return ((a == null) ? s :
(s + "[Wrapped task = " + a.toString() + "]"));
}
private static final long serialVersionUID = 2838392045355241008L;
}
/**
* Adapter for Callable-based interruptible tasks.
*/
static final class AdaptedInterruptibleCallable<T> extends InterruptibleTask<T> {
@SuppressWarnings("serial") // Conditionally serializable
final Callable<? extends T> callable;
@SuppressWarnings("serial") // Conditionally serializable
T result;
AdaptedInterruptibleCallable(Callable<? extends T> callable) {
this.callable = callable;
}
public final T getRawResult() { return result; }
public final void setRawResult(T v) { result = v; }
final T compute() throws Exception { return callable.call(); }
final Object adaptee() { return callable; }
private static final long serialVersionUID = 2838392045355241008L;
}
/**
* Adapter for Runnable-based interruptible tasks.
*/
static final class AdaptedInterruptibleRunnable<T> extends InterruptibleTask<T> {
@SuppressWarnings("serial") // Conditionally serializable
final Runnable runnable;
@SuppressWarnings("serial") // Conditionally serializable
final T result;
AdaptedInterruptibleRunnable(Runnable runnable, T result) {
this.runnable = runnable;
this.result = result;
}
public final T getRawResult() { return result; }
public final void setRawResult(T v) { }
final T compute() { runnable.run(); return result; }
final Object adaptee() { return runnable; }
private static final long serialVersionUID = 2838392045355241008L;
}
/**
* Adapter for Runnables in which failure forces worker exception.
*/
static final class RunnableExecuteAction extends InterruptibleTask<Void> {
@SuppressWarnings("serial") // Conditionally serializable
final Runnable runnable;
RunnableExecuteAction(Runnable runnable) {
this.runnable = runnable;
}
public final Void getRawResult() { return null; }
public final void setRawResult(Void v) { }
final Void compute() { runnable.run(); return null; }
final Object adaptee() { return runnable; }
void onAuxExceptionSet(Throwable ex) { // if a handler, invoke it
Thread t; java.lang.Thread.UncaughtExceptionHandler h;
if ((h = ((t = Thread.currentThread()).
getUncaughtExceptionHandler())) != null) {
try {
h.uncaughtException(t, ex);
} catch (Throwable ignore) {
}
}
}
private static final long serialVersionUID = 5232453952276885070L;
}
/**
* Task (that is never forked) to hold results for
* ForkJoinPool.invokeAny, or to report exception if all subtasks
* fail or are cancelled or the pool is terminating. Both
* InvokeAnyRoot and InvokeAnyTask objects exist only transiently
* during invokeAny invocations, so serialization support would be
* nonsensical and is omitted.
*/
@SuppressWarnings("serial")
static final class InvokeAnyRoot<T> extends InterruptibleTask<T> {
volatile T result;
volatile int count; // number of tasks; decremented in case all tasks fail
InvokeAnyRoot() { }
final void tryComplete(InvokeAnyTask<T> f, T v, Throwable ex,
boolean completed) {
if (f != null && !isDone()) {
if (ForkJoinPool.poolIsStopping(getPool()))
trySetCancelled();
else if (f.setForkJoinTaskStatusMarkerBit() == 0) {
if (completed) {
result = v;
quietlyComplete();
}
else if (U.getAndAddInt(this, COUNT, -1) <= 1) {
if (ex == null)
trySetCancelled();
else
trySetException(ex);
}
}
}
}
public final T compute() { return null; } // never forked
public final T getRawResult() { return result; }
public final void setRawResult(T v) { }
// Common support for timed and untimed versions of invokeAny
final T invokeAny(Collection<? extends Callable<T>> tasks,
ForkJoinPool pool, boolean timed, long nanos)
throws InterruptedException, ExecutionException, TimeoutException {
if ((count = tasks.size()) <= 0)
throw new IllegalArgumentException();
if (pool == null)
throw new NullPointerException();
InvokeAnyTask<T> t = null; // list of submitted tasks
try {
for (Callable<T> c : tasks) {
Objects.requireNonNull(c);
pool.execute((ForkJoinTask<?>)
(t = new InvokeAnyTask<T>(c, this, t)));
}
return timed ? get(nanos, TimeUnit.NANOSECONDS) : get();
} finally {
for (; t != null; t = t.pred)
t.onRootCompletion();
}
}
private static final Unsafe U;
private static final long COUNT;
static {
U = Unsafe.getUnsafe();
COUNT = U.objectFieldOffset(InvokeAnyRoot.class, "count");
}
}
/**
* Task with results in InvokeAnyRoot (and never independently
* joined).
*/
@SuppressWarnings("serial")
static final class InvokeAnyTask<T> extends InterruptibleTask<Void> {
final Callable<? extends T> callable;
final InvokeAnyRoot<T> root;
final InvokeAnyTask<T> pred; // to traverse on cancellation
InvokeAnyTask(Callable<T> callable, InvokeAnyRoot<T> root,
InvokeAnyTask<T> pred) {
this.callable = callable;
this.root = root;
this.pred = pred;
}
final Void compute() throws Exception {
InvokeAnyRoot<T> r = root;
T v = null; Throwable ex = null; boolean completed = false;
if (r != null && !r.isDone()) {
try {
v = callable.call();
completed = true;
} catch (Exception rex) {
ex = rex;
} finally {
r.tryComplete(this, v, ex, completed);
}
}
return null;
}
public final boolean cancel(boolean mayInterruptIfRunning) {
InvokeAnyRoot<T> r;
boolean stat = super.cancel(mayInterruptIfRunning);
if ((r = root) != null)
r.tryComplete(this, null, null, false);
return stat;
}
final void onRootCompletion() {
if (!isDone())
super.cancel(true); // no need for tryComplete
}
public final Void getRawResult() { return null; }
public final void setRawResult(Void v) { }
final Object adaptee() { return callable; }
}
/**
* Adapter for Callable-based interruptible tasks with timeout actions.
*/
@SuppressWarnings("serial") // Conditionally serializable
static final class CallableWithTimeout<T> extends InterruptibleTask<T> {
Callable<? extends T> callable; // nulled out after use
ForkJoinTask<?> timeoutAction;
T result;
CallableWithTimeout(Callable<? extends T> callable,
ForkJoinTask<?> timeoutAction) {
this.callable = callable;
this.timeoutAction = timeoutAction;
}
public final T getRawResult() { return result; }
public final void setRawResult(T v) { result = v; }
final Object adaptee() { return callable; }
final T compute() throws Exception {
Callable<? extends T> c;
return ((c = callable) != null) ? c.call() : null;
}
final boolean postExec() { // cancel timeout action
ForkJoinTask<?> t;
callable = null;
if ((t = timeoutAction) != null) {
timeoutAction = null;
try {
t.cancel(false);
} catch (Error | RuntimeException ex) {
}
}
return true;
}
}
}