--- jsr166/src/jsr166y/ForkJoinTask.java 2009/07/20 22:26:03 1.9 +++ jsr166/src/jsr166y/ForkJoinTask.java 2009/07/22 19:04:11 1.13 @@ -81,8 +81,10 @@ import java.lang.reflect.*; * class. While these methods have {@code public} access (to allow * instances of different task subclasses to call each others * methods), some of them may only be called from within other - * ForkJoinTasks. Attempts to invoke them in other contexts result in - * exceptions or errors possibly including ClassCastException. + * ForkJoinTasks (as may be determined using method {@link + * #inForkJoinPool}). Attempts to invoke them in other contexts + * result in exceptions or errors possibly including + * ClassCastException. * *

Most base support methods are {@code final} because their * implementations are intrinsically tied to the underlying @@ -107,6 +109,9 @@ import java.lang.reflect.*; * in general 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 implements Future, Serializable { @@ -141,10 +146,10 @@ public abstract class ForkJoinTask im /** * Table of exceptions thrown by tasks, to enable reporting by * callers. Because exceptions are rare, we don't directly keep - * them with task objects, but instead us a weak ref table. Note + * them with task objects, but instead use a weak ref table. Note * that cancellation exceptions don't appear in the table, but are * instead recorded as status values. - * Todo: Use ConcurrentReferenceHashMap + * TODO: Use ConcurrentReferenceHashMap */ static final Map, Throwable> exceptionMap = Collections.synchronizedMap @@ -153,7 +158,7 @@ public abstract class ForkJoinTask im // within-package utilities /** - * Get current worker thread, or null if not a worker thread + * Gets current worker thread, or null if not a worker thread. */ static ForkJoinWorkerThread getWorker() { Thread t = Thread.currentThread(); @@ -162,7 +167,7 @@ public abstract class ForkJoinTask im } final boolean casStatus(int cmp, int val) { - return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val); + return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val); } /** @@ -170,13 +175,14 @@ public abstract class ForkJoinTask im */ static void rethrowException(Throwable ex) { if (ex != null) - _unsafe.throwException(ex); + UNSAFE.throwException(ex); } // Setting completion status /** - * Mark completion and wake up threads waiting to join this task. + * Marks completion and wakes up threads waiting to join this task. + * * @param completion one of NORMAL, CANCELLED, EXCEPTIONAL */ final void setCompletion(int completion) { @@ -212,7 +218,7 @@ public abstract class ForkJoinTask im final void setNormalCompletion() { // Try typical fast case -- single CAS, no signal, not already done. // Manually expand casStatus to improve chances of inlining it - if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL)) + if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL)) setCompletion(NORMAL); } @@ -255,6 +261,7 @@ public abstract class ForkJoinTask im /** * Sets status to indicate there is joiner, then waits for join, * surrounded with pool notifications. + * * @return status upon exit */ private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) { @@ -297,7 +304,7 @@ public abstract class ForkJoinTask im } /** - * Notify pool that thread is unblocked. Called by signalled + * Notifies pool that thread is unblocked. Called by signalled * threads when woken by non-FJ threads (which is atypical). */ private void adjustPoolCountsOnUnblock(ForkJoinPool pool) { @@ -308,7 +315,7 @@ public abstract class ForkJoinTask im } /** - * Notify pool to adjust counts on cancelled or timed out wait + * Notifies pool to adjust counts on cancelled or timed out wait. */ private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) { if (pool != null) { @@ -323,7 +330,7 @@ public abstract class ForkJoinTask im } /** - * Handle interruptions during waits. + * Handles interruptions during waits. */ private void onInterruptedWait() { ForkJoinWorkerThread w = getWorker(); @@ -342,7 +349,8 @@ public abstract class ForkJoinTask im } /** - * Throws the exception associated with status s; + * Throws the exception associated with status s. + * * @throws the exception */ private void reportException(int s) { @@ -355,7 +363,7 @@ public abstract class ForkJoinTask im } /** - * Returns result or throws exception using j.u.c.Future conventions + * Returns result or throws exception using j.u.c.Future conventions. * Only call when isDone known to be true. */ private V reportFutureResult() @@ -375,7 +383,7 @@ public abstract class ForkJoinTask im /** * Returns result or throws exception using j.u.c.Future conventions - * with timeouts + * with timeouts. */ private V reportTimedFutureResult() throws InterruptedException, ExecutionException, TimeoutException { @@ -396,7 +404,8 @@ public abstract class ForkJoinTask im /** * Calls exec, recording completion, and rethrowing exception if - * encountered. Caller should normally check status before calling + * encountered. Caller should normally check status before calling. + * * @return true if completed normally */ private boolean tryExec() { @@ -414,7 +423,7 @@ public abstract class ForkJoinTask im /** * Main execution method used by worker threads. Invokes - * base computation unless already complete + * base computation unless already complete. */ final void quietlyExec() { if (status >= 0) { @@ -430,8 +439,9 @@ public abstract class ForkJoinTask im } /** - * Calls exec, recording but not rethrowing exception - * Caller should normally check status before calling + * Calls exec(), recording but not rethrowing exception. + * Caller should normally check status before calling. + * * @return true if completed normally */ private boolean tryQuietlyInvoke() { @@ -447,7 +457,7 @@ public abstract class ForkJoinTask im } /** - * Cancel, ignoring any exceptions it throws + * Cancels, ignoring any exceptions it throws. */ final void cancelIgnoringExceptions() { try { @@ -474,8 +484,9 @@ public abstract class ForkJoinTask im * necessarily enforced, it is a usage error to fork a task more * than once unless it has completed and been reinitialized. This * method may be invoked only from within ForkJoinTask - * computations. Attempts to invoke in other contexts result in - * exceptions or errors possibly including ClassCastException. + * computations (as may be determined using method {@link + * #inForkJoinPool}). Attempts to invoke in other contexts result + * in exceptions or errors possibly including ClassCastException. */ public final void fork() { ((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this); @@ -499,8 +510,9 @@ public abstract class ForkJoinTask im /** * Commences performing this task, awaits its completion if * necessary, and return its result. + * * @throws Throwable (a RuntimeException, Error, or unchecked - * exception) if the underlying computation did so. + * exception) if the underlying computation did so * @return the computed result */ public final V invoke() { @@ -513,13 +525,15 @@ public abstract class ForkJoinTask im /** * Forks both tasks, returning when {@code isDone} holds for * both of them or an exception is encountered. This method may be - * invoked only from within ForkJoinTask computations. Attempts to + * invoked only from within ForkJoinTask computations (as may be + * determined using method {@link #inForkJoinPool}). Attempts to * invoke in other contexts result in exceptions or errors * possibly including ClassCastException. + * * @param t1 one task * @param t2 the other task * @throws NullPointerException if t1 or t2 are null - * @throws RuntimeException or Error if either task did so. + * @throws RuntimeException or Error if either task did so */ public static void invokeAll(ForkJoinTaskt1, ForkJoinTask t2) { t2.fork(); @@ -531,11 +545,13 @@ public abstract class ForkJoinTask im * Forks the given tasks, returning when {@code isDone} holds * for all of them. If any task encounters an exception, others * may be cancelled. This method may be invoked only from within - * ForkJoinTask computations. Attempts to invoke in other contexts - * result in exceptions or errors possibly including ClassCastException. + * ForkJoinTask computations (as may be determined using method + * {@link #inForkJoinPool}). Attempts to invoke in other contexts + * result in exceptions or errors possibly including + * ClassCastException. * @param tasks the array of tasks - * @throws NullPointerException if tasks or any element are null. - * @throws RuntimeException or Error if any task did so. + * @throws NullPointerException if tasks or any element are null + * @throws RuntimeException or Error if any task did so */ public static void invokeAll(ForkJoinTask... tasks) { Throwable ex = null; @@ -574,12 +590,14 @@ public abstract class ForkJoinTask im * Forks all tasks in the collection, returning when * {@code isDone} holds for all of them. If any task * encounters an exception, others may be cancelled. This method - * may be invoked only from within ForkJoinTask - * computations. Attempts to invoke in other contexts result in - * exceptions or errors possibly including ClassCastException. + * may be invoked only from within ForkJoinTask computations (as + * may be determined using method {@link + * #inForkJoinPool}). Attempts to invoke in other contexts resul!t + * in exceptions or errors possibly including ClassCastException. + * * @param tasks the collection of tasks - * @throws NullPointerException if tasks or any element are null. - * @throws RuntimeException or Error if any task did so. + * @throws NullPointerException if tasks or any element are null + * @throws RuntimeException or Error if any task did so */ public static void invokeAll(Collection> tasks) { if (!(tasks instanceof List)) { @@ -623,6 +641,7 @@ public abstract class ForkJoinTask im /** * Returns true if the computation performed by this task has * completed (or has been cancelled). + * * @return true if this computation has completed */ public final boolean isDone() { @@ -631,6 +650,7 @@ public abstract class ForkJoinTask im /** * Returns true if this task was cancelled. + * * @return true if this task was cancelled */ public final boolean isCancelled() { @@ -670,7 +690,8 @@ public abstract class ForkJoinTask im } /** - * Returns true if this task threw an exception or was cancelled + * Returns true if this task threw an exception or was cancelled. + * * @return true if this task threw an exception or was cancelled */ public final boolean isCompletedAbnormally() { @@ -681,6 +702,7 @@ public abstract class ForkJoinTask im * Returns the exception thrown by the base computation, or a * CancellationException if cancelled, or null if none or if the * method has not yet completed. + * * @return the exception, or null if none */ public final Throwable getException() { @@ -722,7 +744,7 @@ public abstract class ForkJoinTask im * overridable, but overridden versions must invoke {@code super} * implementation to maintain guarantees. * - * @param value the result value for this task. + * @param value the result value for this task */ public void complete(V value) { try { @@ -757,8 +779,11 @@ public abstract class ForkJoinTask im * current task and that of any other task that might be executed * while helping. (This usually holds for pure divide-and-conquer * tasks). This method may be invoked only from within - * ForkJoinTask computations. Attempts to invoke in other contexts - * result in exceptions or errors possibly including ClassCastException. + * ForkJoinTask computations (as may be determined using method + * {@link #inForkJoinPool}). Attempts to invoke in other contexts + * resul!t in exceptions or errors possibly including + * ClassCastException. + * * @return the computed result */ public final V helpJoin() { @@ -771,8 +796,9 @@ public abstract class ForkJoinTask im /** * Possibly executes other tasks until this task is ready. This * method may be invoked only from within ForkJoinTask - * computations. Attempts to invoke in other contexts result in - * exceptions or errors possibly including ClassCastException. + * computations (as may be determined using method {@link + * #inForkJoinPool}). Attempts to invoke in other contexts resul!t + * in exceptions or errors possibly including ClassCastException. */ public final void quietlyHelpJoin() { if (status >= 0) { @@ -838,7 +864,8 @@ public abstract class ForkJoinTask im /** * Returns the pool hosting the current task execution, or null - * if this task is executing outside of any pool. + * if this task is executing outside of any ForkJoinPool. + * * @return the pool, or null if none. */ public static ForkJoinPool getPool() { @@ -848,14 +875,27 @@ public abstract class ForkJoinTask im } /** + * Returns true if the current thread is executing as a + * ForkJoinPool computation. + * @return true if the current thread is executing as a + * ForkJoinPool computation, or false otherwise + */ + public static boolean inForkJoinPool() { + return Thread.currentThread() instanceof ForkJoinWorkerThread; + } + + /** * Tries to unschedule this task for execution. This method will * typically 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. This method may be invoked only from within - * ForkJoinTask computations. Attempts to invoke in other contexts - * result in exceptions or errors possibly including ClassCastException. + * ForkJoinTask computations (as may be determined using method + * {@link #inForkJoinPool}). Attempts to invoke in other contexts + * result in exceptions or errors possibly including + * ClassCastException. + * * @return true if unforked */ public boolean tryUnfork() { @@ -867,6 +907,7 @@ public abstract class ForkJoinTask im * 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() { @@ -875,7 +916,7 @@ public abstract class ForkJoinTask im } /** - * Returns a estimate of how many more locally queued tasks are + * 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. This value may be useful for * heuristic decisions about whether to fork other tasks. In many @@ -883,6 +924,7 @@ public abstract class ForkJoinTask im * 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() { @@ -899,7 +941,7 @@ public abstract class ForkJoinTask im * aid debugging, as well as to support extensions. Its use in any * other context is discouraged. * - * @return the result, or null if not completed. + * @return the result, or null if not completed */ public abstract V getRawResult(); @@ -920,6 +962,7 @@ public abstract class ForkJoinTask im * asynchronous actions that require explicit invocations of * {@code complete} to become joinable. It may throw exceptions * to indicate abnormal exit. + * * @return true if completed normally * @throws Error or RuntimeException if encountered during computation */ @@ -932,8 +975,9 @@ public abstract class ForkJoinTask im * be polled or executed next. This method is designed primarily * to support extensions, and is unlikely to be useful otherwise. * This method may be invoked only from within ForkJoinTask - * computations. Attempts to invoke in other contexts result in - * exceptions or errors possibly including ClassCastException. + * computations (as may be determined using method {@link + * #inForkJoinPool}). Attempts to invoke in other contexts result + * in exceptions or errors possibly including ClassCastException. * * @return the next task, or null if none are available */ @@ -946,7 +990,8 @@ public abstract class ForkJoinTask im * queued by the current thread but not yet executed. This method * is designed primarily to support extensions, and is unlikely to * be useful otherwise. This method may be invoked only from - * within ForkJoinTask computations. Attempts to invoke in other + * within ForkJoinTask computations (as may be determined using + * method {@link #inForkJoinPool}). Attempts to invoke in other * contexts result in exceptions or errors possibly including * ClassCastException. * @@ -965,7 +1010,8 @@ public abstract class ForkJoinTask im * of the pool this task is operating in. This method is designed * primarily to support extensions, and is unlikely to be useful * otherwise. This method may be invoked only from within - * ForkJoinTask computations. Attempts to invoke in other contexts + * ForkJoinTask computations (as may be determined using method + * {@link #inForkJoinPool}). Attempts to invoke in other contexts * result in exceptions or errors possibly including * ClassCastException. * @@ -984,7 +1030,7 @@ public abstract class ForkJoinTask im * Save the state to a stream. * * @serialData the current run status and the exception thrown - * during execution, or null if none. + * during execution, or null if none * @param s the stream */ private void writeObject(java.io.ObjectOutputStream s) @@ -995,6 +1041,7 @@ public abstract class ForkJoinTask im /** * Reconstitute the instance from a stream. + * * @param s the stream */ private void readObject(java.io.ObjectInputStream s) @@ -1033,16 +1080,16 @@ public abstract class ForkJoinTask im private static long fieldOffset(String fieldName) throws NoSuchFieldException { - return _unsafe.objectFieldOffset + return UNSAFE.objectFieldOffset (ForkJoinTask.class.getDeclaredField(fieldName)); } - static final Unsafe _unsafe; + static final Unsafe UNSAFE; static final long statusOffset; static { try { - _unsafe = getUnsafe(); + UNSAFE = getUnsafe(); statusOffset = fieldOffset("status"); } catch (Throwable e) { throw new RuntimeException("Could not initialize intrinsics", e);