| /* |
| * 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.invoke.MethodHandles; |
| import java.lang.invoke.VarHandle; |
| import java.lang.reflect.Constructor; |
| import java.util.Collection; |
| import java.util.List; |
| import java.util.RandomAccess; |
| import java.util.concurrent.locks.LockSupport; |
| |
| // BEGIN android-note |
| // removed java 9 code |
| // END android-note |
| |
| /** |
| * 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. |
| * |
| * @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. |
| * |
| * 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. |
| * This is sometimes hard to see because this file orders exported |
| * methods in a way that flows well in javadocs. |
| * |
| * Revision notes: The use of "Aux" field replaces previous |
| * reliance on a table to hold exceptions and synchronized blocks |
| * and monitors to wait for completion. |
| */ |
| |
| /** |
| * 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 { |
| final Thread thread; |
| final Throwable ex; // null if a waiter |
| 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 NEXT.compareAndSet(this, c, v); |
| } |
| private static final VarHandle NEXT; |
| static { |
| try { |
| NEXT = MethodHandles.lookup() |
| .findVarHandle(Aux.class, "next", Aux.class); |
| } catch (ReflectiveOperationException e) { |
| throw new ExceptionInInitializerError(e); |
| } |
| } |
| } |
| |
| /* |
| * 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. |
| */ |
| private static final int DONE = 1 << 31; // must be negative |
| private static final int ABNORMAL = 1 << 16; |
| private static final int THROWN = 1 << 17; |
| private static final int SMASK = 0xffff; // short bits for tags |
| private static final int UNCOMPENSATE = 1 << 16; // helpJoin return sentinel |
| |
| // Fields |
| 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 VarHandle STATUS; |
| private static final VarHandle AUX; |
| private int getAndBitwiseOrStatus(int v) { |
| return (int)STATUS.getAndBitwiseOr(this, v); |
| } |
| private boolean casStatus(int c, int v) { |
| return STATUS.compareAndSet(this, c, v); |
| } |
| private boolean casAux(Aux c, Aux v) { |
| return AUX.compareAndSet(this, c, v); |
| } |
| |
| /** Removes and unparks waiters */ |
| private void signalWaiters() { |
| for (Aux a; (a = aux) != null && a.ex == null; ) { |
| if (casAux(a, null)) { // detach entire list |
| for (Thread t; a != null; a = a.next) { |
| if ((t = a.thread) != Thread.currentThread() && t != null) |
| LockSupport.unpark(t); // don't self-signal |
| } |
| break; |
| } |
| } |
| } |
| |
| /** |
| * Sets DONE status and wakes up threads waiting to join this task. |
| * @return status on exit |
| */ |
| private int setDone() { |
| int s = getAndBitwiseOrStatus(DONE) | DONE; |
| signalWaiters(); |
| return s; |
| } |
| |
| /** |
| * Sets ABNORMAL DONE status unless already done, and wakes up threads |
| * waiting to join this task. |
| * @return status on exit |
| */ |
| private int trySetCancelled() { |
| int s; |
| do {} while ((s = status) >= 0 && !casStatus(s, s |= (DONE | ABNORMAL))); |
| 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 status on exit |
| */ |
| final int trySetThrown(Throwable ex) { |
| Aux h = new Aux(Thread.currentThread(), ex), p = null; |
| boolean installed = false; |
| int s; |
| while ((s = status) >= 0) { |
| Aux a; |
| if (!installed && ((a = aux) == null || a.ex == null) && |
| (installed = casAux(a, h))) |
| p = a; // list of waiters replaced by h |
| if (installed && casStatus(s, s |= (DONE | ABNORMAL | THROWN))) |
| break; |
| } |
| for (; p != null; p = p.next) |
| LockSupport.unpark(p.thread); |
| return s; |
| } |
| |
| /** |
| * Records exception unless already done. Overridable in subclasses. |
| * |
| * @return status on exit |
| */ |
| int trySetException(Throwable ex) { |
| return trySetThrown(ex); |
| } |
| |
| /** |
| * Constructor for subclasses to call. |
| */ |
| public ForkJoinTask() {} |
| |
| static boolean isExceptionalStatus(int s) { // needed by subclasses |
| return (s & THROWN) != 0; |
| } |
| |
| /** |
| * Unless done, calls exec and records status if completed, but |
| * doesn't wait for completion otherwise. |
| * |
| * @return status on exit from this method |
| */ |
| final int doExec() { |
| int s; boolean completed; |
| if ((s = status) >= 0) { |
| try { |
| completed = exec(); |
| } catch (Throwable rex) { |
| s = trySetException(rex); |
| completed = false; |
| } |
| if (completed) |
| s = setDone(); |
| } |
| return s; |
| } |
| |
| /** |
| * Helps and/or waits for completion from join, get, or invoke; |
| * called from either internal or external threads. |
| * |
| * @param pool if nonnull, known submitted pool, else assumes current pool |
| * @param ran true if task known to have been exec'd |
| * @param interruptible true if park interruptibly when external |
| * @param timed true if use timed wait |
| * @param nanos if timed, timeout value |
| * @return ABNORMAL if interrupted, else status on exit |
| */ |
| private int awaitDone(ForkJoinPool pool, boolean ran, |
| boolean interruptible, boolean timed, |
| long nanos) { |
| ForkJoinPool p; boolean internal; int s; Thread t; |
| ForkJoinPool.WorkQueue q = null; |
| if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) { |
| ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; |
| p = wt.pool; |
| if (pool == null) |
| pool = p; |
| if (internal = (pool == p)) |
| q = wt.workQueue; |
| } |
| else { |
| internal = false; |
| p = ForkJoinPool.common; |
| if (pool == null) |
| pool = p; |
| if (pool == p && p != null) |
| q = p.externalQueue(); |
| } |
| if (interruptible && Thread.interrupted()) |
| return ABNORMAL; |
| if ((s = status) < 0) |
| return s; |
| long deadline = 0L; |
| if (timed) { |
| if (nanos <= 0L) |
| return 0; |
| else if ((deadline = nanos + System.nanoTime()) == 0L) |
| deadline = 1L; |
| } |
| boolean uncompensate = false; |
| if (q != null && p != null) { // try helping |
| // help even in timed mode if pool has no parallelism |
| boolean canHelp = !timed || (p.mode & SMASK) == 0; |
| if (canHelp) { |
| if ((this instanceof CountedCompleter) && |
| (s = p.helpComplete(this, q, internal)) < 0) |
| return s; |
| if (!ran && ((!internal && q.externalTryUnpush(this)) || |
| q.tryRemove(this, internal)) && (s = doExec()) < 0) |
| return s; |
| } |
| if (internal) { |
| if ((s = p.helpJoin(this, q, canHelp)) < 0) |
| return s; |
| if (s == UNCOMPENSATE) |
| uncompensate = true; |
| } |
| } |
| // block until done or cancelled wait |
| boolean interrupted = false, queued = false; |
| boolean parked = false, fail = false; |
| Aux node = null; |
| while ((s = status) >= 0) { |
| Aux a; long ns; |
| if (fail || (fail = (pool != null && pool.mode < 0))) |
| casStatus(s, s | (DONE | ABNORMAL)); // try to cancel |
| else if (parked && Thread.interrupted()) { |
| if (interruptible) { |
| s = ABNORMAL; |
| break; |
| } |
| interrupted = true; |
| } |
| else if (queued) { |
| if (deadline != 0L) { |
| if ((ns = deadline - System.nanoTime()) <= 0L) |
| break; |
| LockSupport.parkNanos(ns); |
| } |
| else |
| LockSupport.park(); |
| parked = true; |
| } |
| else if (node != null) { |
| if ((a = aux) != null && a.ex != null) |
| Thread.onSpinWait(); // exception in progress |
| else if (queued = casAux(node.next = a, node)) |
| LockSupport.setCurrentBlocker(this); |
| } |
| else { |
| try { |
| node = new Aux(Thread.currentThread(), null); |
| } catch (Throwable ex) { // cannot create |
| fail = true; |
| } |
| } |
| } |
| if (pool != null && uncompensate) |
| pool.uncompensate(); |
| |
| if (queued) { |
| LockSupport.setCurrentBlocker(null); |
| if (s >= 0) { // cancellation similar to AbstractQueuedSynchronizer |
| outer: for (Aux a; (a = aux) != null && a.ex == null; ) { |
| for (Aux trail = null;;) { |
| Aux next = a.next; |
| if (a == node) { |
| if (trail != null) |
| trail.casNext(trail, next); |
| else if (casAux(a, next)) |
| break outer; // cannot be re-encountered |
| break; // restart |
| } else { |
| trail = a; |
| if ((a = next) == null) |
| break outer; |
| } |
| } |
| } |
| } |
| else { |
| signalWaiters(); // help clean or signal |
| if (interrupted) |
| Thread.currentThread().interrupt(); |
| } |
| } |
| return s; |
| } |
| |
| /** |
| * Cancels, ignoring any exceptions thrown by cancel. Cancel is |
| * spec'ed not to throw any exceptions, but if it does anyway, we |
| * have no recourse, so guard against this case. |
| */ |
| static final void cancelIgnoringExceptions(Future<?> t) { |
| if (t != null) { |
| try { |
| t.cancel(true); |
| } catch (Throwable ignore) { |
| } |
| } |
| } |
| |
| /** |
| * 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. |
| * |
| * @return the exception, or null if none |
| */ |
| private Throwable getThrowableException() { |
| Throwable ex; Aux a; |
| if ((a = aux) == null) |
| ex = null; |
| else if ((ex = a.ex) != null && 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 ex; |
| } |
| |
| /** |
| * Returns exception associated with the given status, or null if none. |
| */ |
| private Throwable getException(int s) { |
| Throwable ex = null; |
| if ((s & ABNORMAL) != 0 && |
| ((s & THROWN) == 0 || (ex = getThrowableException()) == null)) |
| ex = new CancellationException(); |
| return ex; |
| } |
| |
| /** |
| * Throws exception associated with the given status, or |
| * CancellationException if none recorded. |
| */ |
| private void reportException(int s) { |
| ForkJoinTask.<RuntimeException>uncheckedThrow( |
| (s & THROWN) != 0 ? getThrowableException() : null); |
| } |
| |
| /** |
| * Throws exception for (timed or untimed) get, wrapping if |
| * necessary in an ExecutionException. |
| */ |
| private void reportExecutionException(int s) { |
| Throwable ex = null; |
| if (s == ABNORMAL) |
| ex = new InterruptedException(); |
| else if (s >= 0) |
| ex = new TimeoutException(); |
| else if ((s & THROWN) != 0 && (ex = getThrowableException()) != null) |
| ex = new ExecutionException(ex); |
| ForkJoinTask.<RuntimeException>uncheckedThrow(ex); |
| } |
| |
| /** |
| * 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 |
| } |
| |
| // public methods |
| |
| /** |
| * 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 w; |
| if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) |
| (w = (ForkJoinWorkerThread)t).workQueue.push(this, w.pool); |
| else |
| ForkJoinPool.common.externalPush(this); |
| 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(null, false, false, false, 0L); |
| if ((s & ABNORMAL) != 0) |
| reportException(s); |
| 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() { |
| int s; |
| if ((s = doExec()) >= 0) |
| s = awaitDone(null, true, false, false, 0L); |
| if ((s & ABNORMAL) != 0) |
| reportException(s); |
| return getRawResult(); |
| } |
| |
| /** |
| * 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(); |
| if ((s1 = t1.doExec()) >= 0) |
| s1 = t1.awaitDone(null, true, false, false, 0L); |
| if ((s1 & ABNORMAL) != 0) { |
| cancelIgnoringExceptions(t2); |
| t1.reportException(s1); |
| } |
| else if (((s2 = t2.awaitDone(null, false, false, false, 0L)) & ABNORMAL) != 0) |
| t2.reportException(s2); |
| } |
| |
| /** |
| * 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; |
| if ((t = tasks[i]) == null) { |
| ex = new NullPointerException(); |
| break; |
| } |
| if (i == 0) { |
| int s; |
| if ((s = t.doExec()) >= 0) |
| s = t.awaitDone(null, true, false, false, 0L); |
| if ((s & ABNORMAL) != 0) |
| ex = t.getException(s); |
| break; |
| } |
| t.fork(); |
| } |
| if (ex == null) { |
| for (int i = 1; i <= last; ++i) { |
| ForkJoinTask<?> t; |
| if ((t = tasks[i]) != null) { |
| int s; |
| if ((s = t.status) >= 0) |
| s = t.awaitDone(null, false, false, false, 0L); |
| if ((s & ABNORMAL) != 0 && (ex = t.getException(s)) != null) |
| break; |
| } |
| } |
| } |
| if (ex != null) { |
| for (int i = 1; i <= last; ++i) |
| cancelIgnoringExceptions(tasks[i]); |
| 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; |
| } |
| @SuppressWarnings("unchecked") |
| 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; |
| if ((t = ts.get(i)) == null) { |
| ex = new NullPointerException(); |
| break; |
| } |
| if (i == 0) { |
| int s; |
| if ((s = t.doExec()) >= 0) |
| s = t.awaitDone(null, true, false, false, 0L); |
| if ((s & ABNORMAL) != 0) |
| ex = t.getException(s); |
| break; |
| } |
| t.fork(); |
| } |
| if (ex == null) { |
| for (int i = 1; i <= last; ++i) { |
| ForkJoinTask<?> t; |
| if ((t = ts.get(i)) != null) { |
| int s; |
| if ((s = t.status) >= 0) |
| s = t.awaitDone(null, false, false, false, 0L); |
| if ((s & ABNORMAL) != 0 && (ex = t.getException(s)) != null) |
| break; |
| } |
| } |
| } |
| if (ex != null) { |
| for (int i = 1; i <= last; ++i) |
| cancelIgnoringExceptions(ts.get(i)); |
| 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) { |
| return (trySetCancelled() & (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; |
| } |
| |
| /** |
| * 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(status); |
| } |
| |
| /** |
| * 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 s = awaitDone(null, false, true, false, 0L); |
| if ((s & ABNORMAL) != 0) |
| reportExecutionException(s); |
| 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 s = awaitDone(null, false, true, true, nanos); |
| if (s >= 0 || (s & ABNORMAL) != 0) |
| reportExecutionException(s); |
| 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(null, false, false, false, 0L); |
| } |
| |
| |
| /** |
| * Commences performing this task and awaits its completion if |
| * necessary, without returning its result or throwing its |
| * exception. |
| */ |
| public final void quietlyInvoke() { |
| if (doExec() >= 0) |
| awaitDone(null, true, false, false, 0L); |
| } |
| |
| // Versions of join/get for pool.invoke* methods that use external, |
| // possibly-non-commonPool submits |
| |
| final void awaitPoolInvoke(ForkJoinPool pool) { |
| awaitDone(pool, false, false, false, 0L); |
| } |
| final void awaitPoolInvoke(ForkJoinPool pool, long nanos) { |
| awaitDone(pool, false, true, true, nanos); |
| } |
| final V joinForPoolInvoke(ForkJoinPool pool) { |
| int s = awaitDone(pool, false, false, false, 0L); |
| if ((s & ABNORMAL) != 0) |
| reportException(s); |
| return getRawResult(); |
| } |
| final V getForPoolInvoke(ForkJoinPool pool) |
| throws InterruptedException, ExecutionException { |
| int s = awaitDone(pool, false, true, false, 0L); |
| if ((s & ABNORMAL) != 0) |
| reportExecutionException(s); |
| return getRawResult(); |
| } |
| final V getForPoolInvoke(ForkJoinPool pool, long nanos) |
| throws InterruptedException, ExecutionException, TimeoutException { |
| int s = awaitDone(pool, false, true, true, nanos); |
| if (s >= 0 || (s & ABNORMAL) != 0) |
| reportExecutionException(s); |
| return getRawResult(); |
| } |
| |
| /** |
| * 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() { |
| Thread t; ForkJoinWorkerThread w; ForkJoinPool p; |
| if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread && |
| (p = (w = (ForkJoinWorkerThread)t).pool) != null) |
| p.helpQuiescePool(w.workQueue, Long.MAX_VALUE, false); |
| else |
| ForkJoinPool.common.externalHelpQuiescePool(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 = 0; |
| } |
| |
| /** |
| * 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; |
| return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) |
| ? (q = ((ForkJoinWorkerThread)t).workQueue) != null |
| && q.tryUnpush(this) |
| : (q = ForkJoinPool.commonQueue()) != null |
| && q.externalTryUnpush(this); |
| } |
| |
| /** |
| * 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 |
| * @hide API from OpenJDK 9, not yet exposed on Android. |
| */ |
| 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; |
| } |
| } |
| |
| /** |
| * 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) { |
| if (runnable == null) throw new NullPointerException(); |
| 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) { |
| if (runnable == null) throw new NullPointerException(); |
| 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 Runnables in which failure forces worker exception. |
| */ |
| static final class RunnableExecuteAction extends ForkJoinTask<Void> { |
| @SuppressWarnings("serial") // Conditionally serializable |
| final Runnable runnable; |
| RunnableExecuteAction(Runnable runnable) { |
| if (runnable == null) throw new NullPointerException(); |
| this.runnable = runnable; |
| } |
| public final Void getRawResult() { return null; } |
| public final void setRawResult(Void v) { } |
| public final boolean exec() { runnable.run(); return true; } |
| int trySetException(Throwable ex) { // if a handler, invoke it |
| int s; Thread t; java.lang.Thread.UncaughtExceptionHandler h; |
| if (isExceptionalStatus(s = trySetThrown(ex)) && |
| (h = ((t = Thread.currentThread()). |
| getUncaughtExceptionHandler())) != null) { |
| try { |
| h.uncaughtException(t, ex); |
| } catch (Throwable ignore) { |
| } |
| } |
| return s; |
| } |
| 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) { |
| if (callable == null) throw new NullPointerException(); |
| 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; |
| } |
| |
| static final class AdaptedInterruptibleCallable<T> extends ForkJoinTask<T> |
| implements RunnableFuture<T> { |
| @SuppressWarnings("serial") // Conditionally serializable |
| final Callable<? extends T> callable; |
| @SuppressWarnings("serial") // Conditionally serializable |
| transient volatile Thread runner; |
| T result; |
| AdaptedInterruptibleCallable(Callable<? extends T> callable) { |
| if (callable == null) throw new NullPointerException(); |
| this.callable = callable; |
| } |
| public final T getRawResult() { return result; } |
| public final void setRawResult(T v) { result = v; } |
| public final boolean exec() { |
| Thread.interrupted(); |
| runner = Thread.currentThread(); |
| try { |
| if (!isDone()) // recheck |
| result = callable.call(); |
| return true; |
| } catch (RuntimeException rex) { |
| throw rex; |
| } catch (Exception ex) { |
| throw new RuntimeException(ex); |
| } finally { |
| runner = null; |
| Thread.interrupted(); |
| } |
| } |
| public final void run() { invoke(); } |
| public final boolean cancel(boolean mayInterruptIfRunning) { |
| Thread t; |
| boolean stat = super.cancel(false); |
| if (mayInterruptIfRunning && (t = runner) != null) { |
| try { |
| t.interrupt(); |
| } catch (Throwable ignore) { |
| } |
| } |
| return stat; |
| } |
| public String toString() { |
| return super.toString() + "[Wrapped task = " + callable + "]"; |
| } |
| private static final long serialVersionUID = 2838392045355241008L; |
| } |
| |
| /** |
| * 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(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>(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>(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 17 |
| */ |
| // adaptInterruptible deferred to its own independent change |
| // https://bugs.openjdk.java.net/browse/JDK-8246587 |
| /* TODO: public */ private static <T> ForkJoinTask<T> adaptInterruptible(Callable<? extends T> callable) { |
| return new AdaptedInterruptibleCallable<T>(callable); |
| } |
| |
| // 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) |
| trySetThrown((Throwable)ex); |
| } |
| |
| static { |
| try { |
| MethodHandles.Lookup l = MethodHandles.lookup(); |
| STATUS = l.findVarHandle(ForkJoinTask.class, "status", int.class); |
| AUX = l.findVarHandle(ForkJoinTask.class, "aux", Aux.class); |
| } catch (ReflectiveOperationException e) { |
| throw new ExceptionInInitializerError(e); |
| } |
| } |
| |
| } |
