--- jsr166/src/jsr166y/ForkJoinTask.java 2010/09/04 11:33:53 1.57
+++ jsr166/src/jsr166y/ForkJoinTask.java 2010/09/18 12:10:21 1.63
@@ -7,7 +7,6 @@
package jsr166y;
import java.util.concurrent.*;
-
import java.io.Serializable;
import java.util.Collection;
import java.util.Collections;
@@ -28,10 +27,10 @@ import java.util.WeakHashMap;
* 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}. 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.
+ * #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.
*
*
A {@code ForkJoinTask} is a lightweight form of {@link Future}.
* The efficiency of {@code ForkJoinTask}s stems from a set of
@@ -153,7 +152,7 @@ public abstract class ForkJoinTask im
* single int to minimize footprint and to ensure atomicity (via
* CAS). Status is initially zero, and takes on nonnegative
* values until completed, upon which status holds value
- * NORMAL. CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
+ * NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
* waits by other threads have the SIGNAL bit set. Completion of
* a stolen task with SIGNAL set awakens any waiters via
* notifyAll. Even though suboptimal for some purposes, we use
@@ -206,7 +205,7 @@ public abstract class ForkJoinTask im
/**
* Records exception and sets exceptional completion.
- *
+ *
* @return status on exit
*/
private void setExceptionalCompletion(Throwable rex) {
@@ -223,7 +222,7 @@ public abstract class ForkJoinTask im
int s; // the odd construction reduces lock bias effects
while ((s = status) >= 0) {
try {
- synchronized(this) {
+ synchronized (this) {
if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
wait();
}
@@ -243,7 +242,7 @@ public abstract class ForkJoinTask im
int s;
if ((s = status) >= 0) {
try {
- synchronized(this) {
+ synchronized (this) {
if (UNSAFE.compareAndSwapInt(this, statusOffset, s,SIGNAL))
wait(millis, 0);
}
@@ -261,7 +260,7 @@ public abstract class ForkJoinTask im
private void externalAwaitDone() {
int s;
while ((s = status) >= 0) {
- synchronized(this) {
+ synchronized (this) {
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, SIGNAL)){
boolean interrupted = false;
while (status >= 0) {
@@ -621,13 +620,14 @@ public abstract class ForkJoinTask im
/**
* Completes this task, and if not already aborted or cancelled,
- * returning a {@code null} result upon {@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.
+ * 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
*/
@@ -641,11 +641,34 @@ public abstract class ForkJoinTask im
setCompletion(NORMAL);
}
+ /**
+ * 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 {
- quietlyJoin();
- if (Thread.interrupted())
- throw new InterruptedException();
- int s = status;
+ int s;
+ if (Thread.currentThread() instanceof ForkJoinWorkerThread) {
+ quietlyJoin();
+ s = status;
+ }
+ else {
+ while ((s = status) >= 0) {
+ synchronized (this) { // interruptible form of awaitDone
+ if (UNSAFE.compareAndSwapInt(this, statusOffset,
+ s, SIGNAL)) {
+ while (status >= 0)
+ wait();
+ }
+ }
+ }
+ }
if (s < NORMAL) {
Throwable ex;
if (s == CANCELLED)
@@ -656,6 +679,20 @@ public abstract class ForkJoinTask im
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 {
Thread t = Thread.currentThread();
@@ -679,7 +716,7 @@ public abstract class ForkJoinTask im
boolean dec = false; // true if pool count decremented
long nanos = unit.toNanos(timeout);
for (;;) {
- if (Thread.interrupted() && pool == null) {
+ if (pool == null && Thread.interrupted()) {
interrupted = true;
break;
}
@@ -697,7 +734,7 @@ public abstract class ForkJoinTask im
long ms = nt / 1000000;
int ns = (int) (nt % 1000000);
try {
- synchronized(this) {
+ synchronized (this) {
if (status >= 0)
wait(ms, ns);
}
@@ -764,9 +801,7 @@ public abstract class ForkJoinTask im
/**
* Commences performing this task and awaits its completion if
* necessary, 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.
+ * exception.
*/
public final void quietlyInvoke() {
if (status >= 0) {