--- jsr166/src/jsr166y/ForkJoinTask.java 2009/08/04 13:16:54 1.36
+++ jsr166/src/jsr166y/ForkJoinTask.java 2010/04/05 15:52:26 1.46
@@ -56,9 +56,9 @@ import java.util.WeakHashMap;
* 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 RejectedExecutionExceptions stemming from
- * internal resource exhaustion such as failure to allocate internal
- * task queues.
+ * additionally include {@link RejectedExecutionException} stemming
+ * from internal resource exhaustion, such as failure to allocate
+ * internal task queues.
*
* The primary method for awaiting completion and extracting
* results of a task is {@link #join}, but there are several variants:
@@ -80,16 +80,14 @@ import java.util.WeakHashMap;
*
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 #isCancelled} is true if completion was due to cancellation;
* {@link #isCompletedNormally} is true if a task completed without
- * cancellation or encountering an exception; {@link
- * #isCompletedExceptionally} is true if if the task encountered an
- * exception (in which case {@link #getException} returns the
- * exception); {@link #isCancelled} is true if the task was cancelled
- * (in which case {@link #getException} returns a {@link
- * java.util.concurrent.CancellationException}); and {@link
- * #isCompletedAbnormally} is true if a task was either cancelled or
- * encountered an exception.
+ * cancellation or encountering an exception; {@link #isCancelled} is
+ * true if the task was cancelled (in which case {@link #getException}
+ * returns a {@link java.util.concurrent.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 java.util.concurrent.CancellationException}.
*
*
The ForkJoinTask class is not usually directly subclassed.
* Instead, you subclass one of the abstract classes that support a
@@ -125,11 +123,11 @@ import java.util.WeakHashMap;
* improve throughput. If too small, then memory and internal task
* maintenance overhead may overwhelm processing.
*
- *
This class provides {@code adapt} methods for {@link
- * java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
- * may be of use when mixing execution of ForkJoinTasks with other
- * kinds of tasks. When all tasks are of this form, consider using a
- * pool in {@link ForkJoinPool#setAsyncMode async mode}.
+ *
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 in
+ * {@linkplain ForkJoinPool#setAsyncMode async mode}.
*
*
ForkJoinTasks are {@code Serializable}, which enables them to be
* used in extensions such as remote execution frameworks. It is
@@ -141,6 +139,18 @@ import java.util.WeakHashMap;
*/
public abstract class ForkJoinTask implements Future, 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.
+ */
+
/**
* Run control status bits packed into a single int to minimize
* footprint and to ensure atomicity (via CAS). Status is
@@ -150,24 +160,32 @@ public abstract class ForkJoinTask im
* blocking waits by other threads have SIGNAL_MASK bits set --
* bit 15 for external (nonFJ) waits, and the rest a count of
* waiting FJ threads. (This representation relies on
- * ForkJoinPool max thread limits). Completion of a stolen task
- * with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
- * though suboptimal for some purposes, we use basic builtin
- * wait/notify to take advantage of "monitor inflation" in JVMs
- * that we would otherwise need to emulate to avoid adding further
- * per-task bookkeeping overhead. Note that bits 16-28 are
- * currently unused. Also value 0x80000000 is available as spare
- * completion value.
+ * ForkJoinPool max thread limits). Signal counts are not directly
+ * incremented by ForkJoinTask methods, but instead via a call to
+ * requestSignal within ForkJoinPool.preJoin, once their need is
+ * established.
+ *
+ * Completion of a stolen task with SIGNAL_MASK bits set awakens
+ * any waiters via notifyAll. Even though suboptimal for some
+ * purposes, we use basic builtin wait/notify to take advantage of
+ * "monitor inflation" in JVMs that we would otherwise need to
+ * emulate to avoid adding further per-task bookkeeping overhead.
+ * We want these monitors to be "fat", i.e., not use biasing or
+ * thin-lock techniques, so use some odd coding idioms that tend
+ * to avoid them.
+ *
+ * Note that bits 16-28 are currently unused. Also value
+ * 0x80000000 is available as spare completion value.
*/
volatile int status; // accessed directly by pool and workers
- static final int COMPLETION_MASK = 0xe0000000;
- static final int NORMAL = 0xe0000000; // == mask
- static final int CANCELLED = 0xc0000000;
- static final int EXCEPTIONAL = 0xa0000000;
- static final int SIGNAL_MASK = 0x0000ffff;
- static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
- static final int EXTERNAL_SIGNAL = 0x00008000; // top bit of low word
+ private static final int COMPLETION_MASK = 0xe0000000;
+ private static final int NORMAL = 0xe0000000; // == mask
+ private static final int CANCELLED = 0xc0000000;
+ private static final int EXCEPTIONAL = 0xa0000000;
+ private static final int SIGNAL_MASK = 0x0000ffff;
+ private static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
+ private static final int EXTERNAL_SIGNAL = 0x00008000;
/**
* Table of exceptions thrown by tasks, to enable reporting by
@@ -181,221 +199,220 @@ public abstract class ForkJoinTask im
Collections.synchronizedMap
(new WeakHashMap, Throwable>());
- // within-package utilities
+ // Maintaining completion status
/**
- * Gets current worker thread, or null if not a worker thread.
+ * Marks completion and wakes up threads waiting to join this task,
+ * also clearing signal request bits.
+ *
+ * @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
*/
- static ForkJoinWorkerThread getWorker() {
- Thread t = Thread.currentThread();
- return ((t instanceof ForkJoinWorkerThread) ?
- (ForkJoinWorkerThread) t : null);
- }
-
- final boolean casStatus(int cmp, int val) {
- return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
+ private void setCompletion(int completion) {
+ int s;
+ while ((s = status) >= 0) {
+ if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
+ if ((s & SIGNAL_MASK) != 0) {
+ Thread t = Thread.currentThread();
+ if (t instanceof ForkJoinWorkerThread)
+ ((ForkJoinWorkerThread) t).pool.updateRunningCount
+ (s & INTERNAL_SIGNAL_MASK);
+ synchronized (this) { notifyAll(); }
+ }
+ return;
+ }
+ }
}
/**
- * Workaround for not being able to rethrow unchecked exceptions.
+ * Record exception and set exceptional completion
*/
- static void rethrowException(Throwable ex) {
- if (ex != null)
- UNSAFE.throwException(ex);
+ private void setDoneExceptionally(Throwable rex) {
+ exceptionMap.put(this, rex);
+ setCompletion(EXCEPTIONAL);
}
- // Setting completion status
-
/**
- * Marks completion and wakes up threads waiting to join this task.
+ * Main internal execution method: Unless done, calls exec and
+ * records completion.
*
- * @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
+ * @return true if ran and completed normally
*/
- final void setCompletion(int completion) {
- ForkJoinPool pool = getPool();
- if (pool != null) {
- int s; // Clear signal bits while setting completion status
- do {} while ((s = status) >= 0 && !casStatus(s, completion));
-
- if ((s & SIGNAL_MASK) != 0) {
- if ((s &= INTERNAL_SIGNAL_MASK) != 0)
- pool.updateRunningCount(s);
- synchronized (this) { notifyAll(); }
- }
+ final boolean tryExec() {
+ try {
+ if (status < 0 || !exec())
+ return false;
+ } catch (Throwable rex) {
+ setDoneExceptionally(rex);
+ return false;
}
- else
- externallySetCompletion(completion);
+ setCompletion(NORMAL); // must be outside try block
+ return true;
}
/**
- * Version of setCompletion for non-FJ threads. Leaves signal
- * bits for unblocked threads to adjust, and always notifies.
+ * Increments internal signal count (thus requesting signal upon
+ * completion) unless already done. Call only once per join.
+ * Used by ForkJoinPool.preJoin.
+ *
+ * @return status
*/
- private void externallySetCompletion(int completion) {
+ final int requestSignal() {
int s;
- do {} while ((s = status) >= 0 &&
- !casStatus(s, (s & SIGNAL_MASK) | completion));
- synchronized (this) { notifyAll(); }
+ do {} while ((s = status) >= 0 &&
+ !UNSAFE.compareAndSwapInt(this, statusOffset, s, s + 1));
+ return s;
}
-
+
/**
- * Sets status to indicate normal completion.
+ * Sets external signal request unless already done.
+ *
+ * @return status
*/
- 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))
- setCompletion(NORMAL);
+ private int requestExternalSignal() {
+ int s;
+ do {} while ((s = status) >= 0 &&
+ !UNSAFE.compareAndSwapInt(this, statusOffset,
+ s, s | EXTERNAL_SIGNAL));
+ return s;
}
- // internal waiting and notification
-
- /**
- * Performs the actual monitor wait for awaitDone.
+ /*
+ * Awaiting completion. The four versions, internal vs external X
+ * untimed vs timed, have the same overall structure but differ
+ * from each other enough to defy simple integration.
*/
- private void doAwaitDone() {
- // Minimize lock bias and in/de-flation effects by maximizing
- // chances of waiting inside sync
- try {
- while (status >= 0)
- synchronized (this) { if (status >= 0) wait(); }
- } catch (InterruptedException ie) {
- onInterruptedWait();
- }
- }
/**
- * Performs the actual timed monitor wait for awaitDone.
+ * Blocks a worker until this task is done, also maintaining pool
+ * and signal counts
*/
- private void doAwaitDone(long startTime, long nanos) {
- synchronized (this) {
- try {
- while (status >= 0) {
- long nt = nanos - (System.nanoTime() - startTime);
- if (nt <= 0)
- break;
- wait(nt / 1000000, (int) (nt % 1000000));
+ private void awaitDone(ForkJoinWorkerThread w) {
+ if (status >= 0) {
+ w.pool.preJoin(this);
+ while (status >= 0) {
+ try { // minimize lock scope
+ synchronized(this) {
+ if (status >= 0)
+ wait();
+ else { // help release; also helps avoid lock-biasing
+ notifyAll();
+ break;
+ }
+ }
+ } catch (InterruptedException ie) {
+ cancelIfTerminating();
}
- } catch (InterruptedException ie) {
- onInterruptedWait();
}
}
}
- // Awaiting completion
-
/**
- * Sets status to indicate there is joiner, then waits for join,
- * surrounded with pool notifications.
- *
- * @return status upon exit
+ * Blocks a non-ForkJoin thread until this task is done.
*/
- private int awaitDone(ForkJoinWorkerThread w,
- boolean maintainParallelism) {
- ForkJoinPool pool = (w == null) ? null : w.pool;
- int s;
- while ((s = status) >= 0) {
- if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
- if (pool == null || !pool.preJoin(this, maintainParallelism))
- doAwaitDone();
- if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
- adjustPoolCountsOnUnblock(pool);
- break;
+ private void externalAwaitDone() {
+ if (requestExternalSignal() >= 0) {
+ boolean interrupted = false;
+ while (status >= 0) {
+ try {
+ synchronized(this) {
+ if (status >= 0)
+ wait();
+ else {
+ notifyAll();
+ break;
+ }
+ }
+ } catch (InterruptedException ie) {
+ interrupted = true;
+ }
}
+ if (interrupted)
+ Thread.currentThread().interrupt();
}
- return s;
}
/**
- * Timed version of awaitDone
- *
- * @return status upon exit
+ * Blocks a worker until this task is done or timeout elapses
*/
- private int awaitDone(ForkJoinWorkerThread w, long nanos) {
- ForkJoinPool pool = (w == null) ? null : w.pool;
- int s;
- while ((s = status) >= 0) {
- if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
- long startTime = System.nanoTime();
- if (pool == null || !pool.preJoin(this, false))
- doAwaitDone(startTime, nanos);
- if ((s = status) >= 0) {
- adjustPoolCountsOnCancelledWait(pool);
- s = status;
+ private void timedAwaitDone(ForkJoinWorkerThread w, long nanos) {
+ if (status >= 0) {
+ long startTime = System.nanoTime();
+ ForkJoinPool pool = w.pool;
+ pool.preJoin(this);
+ while (status >= 0) {
+ long nt = nanos - (System.nanoTime() - startTime);
+ if (nt > 0) {
+ long ms = nt / 1000000;
+ int ns = (int) (nt % 1000000);
+ try {
+ synchronized(this) { if (status >= 0) wait(ms, ns); }
+ } catch (InterruptedException ie) {
+ cancelIfTerminating();
+ }
+ }
+ else {
+ int s; // adjust running count on timeout
+ while ((s = status) >= 0 &&
+ (s & INTERNAL_SIGNAL_MASK) != 0) {
+ if (UNSAFE.compareAndSwapInt(this, statusOffset,
+ s, s - 1)) {
+ pool.updateRunningCount(1);
+ break;
+ }
+ }
+ break;
}
- if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
- adjustPoolCountsOnUnblock(pool);
- break;
}
}
- return s;
- }
-
- /**
- * Notifies pool that thread is unblocked. Called by signalled
- * threads when woken by non-FJ threads (which is atypical).
- */
- private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
- int s;
- do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
- if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
- pool.updateRunningCount(s);
}
/**
- * Notifies pool to adjust counts on cancelled or timed out wait.
+ * Blocks a non-ForkJoin thread until this task is done or timeout elapses
*/
- private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
- if (pool != null) {
- int s;
- while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
- if (casStatus(s, s - 1)) {
- pool.updateRunningCount(1);
+ private void externalTimedAwaitDone(long nanos) {
+ if (requestExternalSignal() >= 0) {
+ long startTime = System.nanoTime();
+ boolean interrupted = false;
+ while (status >= 0) {
+ long nt = nanos - (System.nanoTime() - startTime);
+ if (nt <= 0)
break;
+ long ms = nt / 1000000;
+ int ns = (int) (nt % 1000000);
+ try {
+ synchronized(this) { if (status >= 0) wait(ms, ns); }
+ } catch (InterruptedException ie) {
+ interrupted = true;
}
}
+ if (interrupted)
+ Thread.currentThread().interrupt();
}
}
- /**
- * Handles interruptions during waits.
- */
- private void onInterruptedWait() {
- ForkJoinWorkerThread w = getWorker();
- if (w == null)
- Thread.currentThread().interrupt(); // re-interrupt
- else if (w.isTerminating())
- cancelIgnoringExceptions();
- // else if FJworker, ignore interrupt
- }
-
- // Recording and reporting exceptions
-
- private void setDoneExceptionally(Throwable rex) {
- exceptionMap.put(this, rex);
- setCompletion(EXCEPTIONAL);
- }
+ // reporting results
/**
- * Throws the exception associated with status s.
- *
- * @throws the exception
+ * Returns result or throws the exception associated with status.
+ * Uses Unsafe as a workaround for javac not allowing rethrow of
+ * unchecked exceptions.
*/
- private void reportException(int s) {
- if ((s &= COMPLETION_MASK) < NORMAL) {
- if (s == CANCELLED)
- throw new CancellationException();
- else
- rethrowException(exceptionMap.get(this));
+ private V reportResult() {
+ if ((status & COMPLETION_MASK) < NORMAL) {
+ Throwable ex = getException();
+ if (ex != null)
+ UNSAFE.throwException(ex);
}
+ return getRawResult();
}
/**
* Returns result or throws exception using j.u.c.Future conventions.
- * Only call when {@code isDone} known to be true.
+ * Only call when {@code isDone} known to be true or thread known
+ * to be interrupted.
*/
private V reportFutureResult()
- throws ExecutionException, InterruptedException {
+ throws InterruptedException, ExecutionException {
if (Thread.interrupted())
throw new InterruptedException();
int s = status & COMPLETION_MASK;
@@ -421,88 +438,12 @@ public abstract class ForkJoinTask im
int s = status & COMPLETION_MASK;
if (s == NORMAL)
return getRawResult();
- if (s == CANCELLED)
+ else if (s == CANCELLED)
throw new CancellationException();
- if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
+ else if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
throw new ExecutionException(ex);
- throw new TimeoutException();
- }
-
- // internal execution methods
-
- /**
- * Calls exec, recording completion, and rethrowing exception if
- * encountered. Caller should normally check status before calling.
- *
- * @return true if completed normally
- */
- private boolean tryExec() {
- try { // try block must contain only call to exec
- if (!exec())
- return false;
- } catch (Throwable rex) {
- setDoneExceptionally(rex);
- rethrowException(rex);
- return false; // not reached
- }
- setNormalCompletion();
- return true;
- }
-
- /**
- * Main execution method used by worker threads. Invokes
- * base computation unless already complete.
- */
- final void quietlyExec() {
- if (status >= 0) {
- try {
- if (!exec())
- return;
- } catch (Throwable rex) {
- setDoneExceptionally(rex);
- return;
- }
- setNormalCompletion();
- }
- }
-
- /**
- * Calls exec(), recording but not rethrowing exception.
- * Caller should normally check status before calling.
- *
- * @return true if completed normally
- */
- private boolean tryQuietlyInvoke() {
- try {
- if (!exec())
- return false;
- } catch (Throwable rex) {
- setDoneExceptionally(rex);
- return false;
- }
- setNormalCompletion();
- return true;
- }
-
- /**
- * Cancels, ignoring any exceptions it throws.
- */
- final void cancelIgnoringExceptions() {
- try {
- cancel(false);
- } catch (Throwable ignore) {
- }
- }
-
- /**
- * Main implementation of helpJoin
- */
- private int busyJoin(ForkJoinWorkerThread w) {
- int s;
- ForkJoinTask t;
- while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
- t.quietlyExec();
- return (s >= 0) ? awaitDone(w, false) : s; // block if no work
+ else
+ throw new TimeoutException();
}
// public methods
@@ -511,6 +452,11 @@ public abstract class ForkJoinTask im
* Arranges to asynchronously execute this task. 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}.
*
* This method may be invoked only from within {@code
* ForkJoinTask} computations (as may be determined using method
@@ -527,7 +473,7 @@ public abstract class ForkJoinTask im
}
/**
- * Returns the result of the computation when it is ready.
+ * Returns the result of the computation when it {@link #isDone is done}.
* This method differs from {@link #get()} in that
* abnormal completion results in {@code RuntimeException} or
* {@code Error}, not {@code ExecutionException}.
@@ -535,10 +481,8 @@ public abstract class ForkJoinTask im
* @return the computed result
*/
public final V join() {
- ForkJoinWorkerThread w = getWorker();
- if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
- reportException(awaitDone(w, true));
- return getRawResult();
+ quietlyJoin();
+ return reportResult();
}
/**
@@ -549,18 +493,18 @@ public abstract class ForkJoinTask im
* @return the computed result
*/
public final V invoke() {
- if (status >= 0 && tryExec())
- return getRawResult();
- else
- return join();
+ if (!tryExec())
+ quietlyJoin();
+ return reportResult();
}
/**
* 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. The individual status of each task may be
+ * case the exception is rethrown. If either task encounters an
+ * exception, the other one may be, but is not guaranteed to be,
+ * cancelled. If both tasks throw an exception, then this method
+ * throws one of them. The individual status of each task may be
* checked using {@link #getException()} and related methods.
*
* This method may be invoked only from within {@code
@@ -628,7 +572,7 @@ public abstract class ForkJoinTask im
}
}
if (ex != null)
- rethrowException(ex);
+ UNSAFE.throwException(ex);
}
/**
@@ -690,7 +634,7 @@ public abstract class ForkJoinTask im
}
}
if (ex != null)
- rethrowException(ex);
+ UNSAFE.throwException(ex);
return tasks;
}
@@ -724,20 +668,34 @@ public abstract class ForkJoinTask im
}
/**
- * Returns {@code true} if the computation performed by this task
- * has completed (or has been cancelled).
- *
- * @return {@code true} if this computation has completed
+ * Cancels, ignoring any exceptions it throws. Used during worker
+ * and pool shutdown.
*/
- public final boolean isDone() {
- return status < 0;
+ final void cancelIgnoringExceptions() {
+ try {
+ cancel(false);
+ } catch (Throwable ignore) {
+ }
}
/**
- * Returns {@code true} if this task was cancelled.
- *
- * @return {@code true} if this task was cancelled
+ * Cancels ignoring exceptions if worker is terminating
*/
+ private void cancelIfTerminating() {
+ Thread t = Thread.currentThread();
+ if ((t instanceof ForkJoinWorkerThread) &&
+ ((ForkJoinWorkerThread) t).isTerminating()) {
+ try {
+ cancel(false);
+ } catch (Throwable ignore) {
+ }
+ }
+ }
+
+ public final boolean isDone() {
+ return status < 0;
+ }
+
public final boolean isCancelled() {
return (status & COMPLETION_MASK) == CANCELLED;
}
@@ -763,15 +721,6 @@ public abstract class ForkJoinTask im
}
/**
- * Returns {@code true} if this task threw an exception.
- *
- * @return {@code true} if this task threw an exception
- */
- public final boolean isCompletedExceptionally() {
- return (status & COMPLETION_MASK) == EXCEPTIONAL;
- }
-
- /**
* 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.
@@ -780,11 +729,9 @@ public abstract class ForkJoinTask im
*/
public final Throwable getException() {
int s = status & COMPLETION_MASK;
- if (s >= NORMAL)
- return null;
- if (s == CANCELLED)
- return new CancellationException();
- return exceptionMap.get(this);
+ return ((s >= NORMAL) ? null :
+ (s == CANCELLED) ? new CancellationException() :
+ exceptionMap.get(this));
}
/**
@@ -797,9 +744,9 @@ public abstract class ForkJoinTask im
* overridable, but overridden versions must invoke {@code super}
* implementation to maintain guarantees.
*
- * @param ex the exception to throw. If this exception is
- * not a RuntimeException or Error, the actual exception thrown
- * will be a RuntimeException with cause ex.
+ * @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) {
setDoneExceptionally((ex instanceof RuntimeException) ||
@@ -826,33 +773,36 @@ public abstract class ForkJoinTask im
setDoneExceptionally(rex);
return;
}
- setNormalCompletion();
+ setCompletion(NORMAL);
}
public final V get() throws InterruptedException, ExecutionException {
- ForkJoinWorkerThread w = getWorker();
- if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
- awaitDone(w, true);
+ quietlyJoin();
return reportFutureResult();
}
-
+
public final V get(long timeout, TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException {
long nanos = unit.toNanos(timeout);
- ForkJoinWorkerThread w = getWorker();
- if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
- awaitDone(w, nanos);
+ Thread t = Thread.currentThread();
+ if (t instanceof ForkJoinWorkerThread) {
+ ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
+ if (!w.unpushTask(this) || !tryExec())
+ timedAwaitDone(w, nanos);
+ }
+ else
+ externalTimedAwaitDone(nanos);
return reportTimedFutureResult();
}
/**
- * Possibly executes other tasks until this task is ready, then
- * returns the result of the computation. This method may be more
- * efficient than {@code join}, but is only applicable when
- * there are no potential dependencies between continuation of the
- * current task and that of any other task that might be executed
- * while helping. (This usually holds for pure divide-and-conquer
- * tasks).
+ * Possibly executes other tasks until this task {@link #isDone is
+ * done}, then returns the result of the computation. This method
+ * may be more efficient than {@code join}, but is only applicable
+ * when there are no potential dependencies between continuation
+ * of the 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 {@code
* ForkJoinTask} computations (as may be determined using method
@@ -863,16 +813,15 @@ public abstract class ForkJoinTask im
* @return the computed result
*/
public final V helpJoin() {
- ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
- if (status < 0 || !w.unpushTask(this) || !tryExec())
- reportException(busyJoin(w));
- return getRawResult();
+ quietlyHelpJoin();
+ return reportResult();
}
/**
- * Possibly executes other tasks until this task is ready. This
- * method may be useful when processing collections of tasks when
- * some have been cancelled or otherwise known to have aborted.
+ * Possibly executes other tasks until this task {@link #isDone is
+ * done}. This method may be useful when processing collections
+ * of tasks when some have been cancelled or otherwise known to
+ * have aborted.
*
* This method may be invoked only from within {@code
* ForkJoinTask} computations (as may be determined using method
@@ -881,11 +830,17 @@ public abstract class ForkJoinTask im
* ClassCastException}.
*/
public final void quietlyHelpJoin() {
- if (status >= 0) {
- ForkJoinWorkerThread w =
- (ForkJoinWorkerThread) Thread.currentThread();
- if (!w.unpushTask(this) || !tryQuietlyInvoke())
- busyJoin(w);
+ ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
+ if (!w.unpushTask(this) || !tryExec()) {
+ while (status >= 0) {
+ ForkJoinTask t = w.scanWhileJoining(this);
+ if (t == null) {
+ if (status >= 0)
+ awaitDone(w);
+ break;
+ }
+ t.tryExec();
+ }
}
}
@@ -896,11 +851,14 @@ public abstract class ForkJoinTask im
* known to have aborted.
*/
public final void quietlyJoin() {
- if (status >= 0) {
- ForkJoinWorkerThread w = getWorker();
- if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
- awaitDone(w, true);
+ Thread t = Thread.currentThread();
+ if (t instanceof ForkJoinWorkerThread) {
+ ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
+ if (!w.unpushTask(this) || !tryExec())
+ awaitDone(w);
}
+ else
+ externalAwaitDone();
}
/**
@@ -911,7 +869,7 @@ public abstract class ForkJoinTask im
* known to have aborted.
*/
public final void quietlyInvoke() {
- if (status >= 0 && !tryQuietlyInvoke())
+ if (!tryExec())
quietlyJoin();
}
@@ -1234,7 +1192,7 @@ public abstract class ForkJoinTask im
private static final long serialVersionUID = -7721805057305804111L;
/**
- * Save the state to a stream.
+ * Saves the state to a stream.
*
* @serialData the current run status and the exception thrown
* during execution, or {@code null} if none
@@ -1247,7 +1205,7 @@ public abstract class ForkJoinTask im
}
/**
- * Reconstitute the instance from a stream.
+ * Reconstitutes the instance from a stream.
*
* @param s the stream
*/