--- jsr166/src/jsr166y/ForkJoinTask.java 2009/01/06 14:30:31 1.1
+++ jsr166/src/jsr166y/ForkJoinTask.java 2009/07/25 17:49:01 1.19
@@ -5,32 +5,43 @@
*/
package jsr166y;
-import java.io.Serializable;
-import java.util.*;
+
import java.util.concurrent.*;
-import java.util.concurrent.atomic.*;
-import sun.misc.Unsafe;
-import java.lang.reflect.*;
+
+import java.io.Serializable;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.WeakHashMap;
/**
- * Abstract base class for tasks that run within a ForkJoinPool. A
- * 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.
+ * Abstract base class for tasks that run within a {@link
+ * ForkJoinPool}. A 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.
*
- *
ForkJoinTasks are forms of Futures supporting a
- * limited range of use. The "lightness" of ForkJoinTasks is due to a
- * set of restrictions (that are only partially statically
- * enforceable) reflecting their intended use as computational tasks
- * calculating pure functions or operating on purely isolated objects.
- * The primary coordination mechanisms supported for ForkJoinTasks are
- * fork, that arranges asynchronous execution, and
- * join, that doesn't proceed until the task's result has
- * been computed. (Cancellation is also supported). The computation
- * defined in the compute method should avoid
- * synchronized methods or blocks, and should minimize
- * blocking synchronization apart from joining other tasks or using
+ *
A "main" ForkJoinTask begins execution when submitted to a
+ * {@link ForkJoinPool}. Once started, it will usually in turn start
+ * other subtasks. As indicated by the name of this class, many
+ * programs using ForkJoinTasks employ only methods {@code fork}
+ * and {@code join}, or derivatives such as
+ * {@code 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 ForkJoinTask is a lightweight form of {@link Future}. The
+ * efficiency of ForkJoinTasks stems from a set of restrictions (that
+ * are only partially statically enforceable) reflecting their
+ * intended 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 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. Tasks should also not perform blocking IO,
* and should ideally access variables that are completely independent
@@ -38,65 +49,79 @@ import java.lang.reflect.*;
* restrictions, for example using shared output streams, may be
* tolerable in practice, but frequent use may result in poor
* performance, and the potential to indefinitely stall if the number
- * of threads not waiting for external synchronization becomes
- * exhausted. This usage restriction is in part enforced by not
- * permitting checked exceptions such as IOExceptions to be
- * thrown. However, computations may still encounter unchecked
+ * of threads not waiting for IO or other external synchronization
+ * becomes exhausted. This usage restriction is in part 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 join
* them. These exceptions may additionally include
* RejectedExecutionExceptions stemming from internal resource
* exhaustion such as failure to allocate internal task queues.
*
- *
The ForkJoinTask class is not usually directly
- * subclassed. Instead, you subclass one of the abstract classes that
- * support different styles of fork/join processing. Normally, a
- * concrete ForkJoinTask subclass declares fields comprising its
- * parameters, established in a constructor, and then defines a
- * compute method that somehow uses the control methods
- * supplied by this base class. While these methods have
- * public access, some of them may only be called from within
- * other ForkJoinTasks. Attempts to invoke them in other contexts
- * result in exceptions or errors including ClassCastException. The
- * only way to invoke a "main" driver task is to submit it to a
- * ForkJoinPool. Once started, this will usually in turn start other
- * subtasks.
+ *
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 #helpJoin} enables callers to actively
+ * execute other tasks while awaiting joins, which is sometimes more
+ * efficient but only applies when all subtasks are known to be
+ * strictly tree-structured. Method {@link #invoke} is semantically
+ * equivalent to {@code fork(); join()} but always attempts to
+ * begin execution in the current thread. The "quiet" 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.
+ *
+ *
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. 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. 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 (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 final because their
+ *
Most base support methods are {@code final} because their
* implementations are intrinsically tied to the underlying
* lightweight task scheduling framework, and so cannot be overridden.
* Developers creating new basic styles of fork/join processing should
- * minimally implement protected methods exec,
- * setRawResult, and getRawResult, while also
- * introducing an abstract computational method that can be
- * implemented in its subclasses. To support such extensions,
- * instances of ForkJoinTasks maintain an atomically updated
- * short representing user-defined control state. Control
- * state is guaranteed initially to be zero, and to be negative upon
- * completion, but may otherwise be used for any other control
- * purposes, such as maintaining join counts. The {@link
- * ForkJoinWorkerThread} class supports additional inspection and
- * tuning methods that can be useful when developing extensions.
+ * minimally implement {@code protected} methods
+ * {@code exec}, {@code setRawResult}, and
+ * {@code 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.
*
*
ForkJoinTasks should perform relatively small amounts of
- * computations, othewise splitting into smaller tasks. As a very
+ * computations, otherwise splitting into smaller tasks. As a very
* rough rule of thumb, a task should perform more than 100 and less
* than 10000 basic computational steps. If tasks are too big, then
- * parellelism cannot improve throughput. If too small, then memory
+ * parallelism cannot improve throughput. If too small, then memory
* and internal task maintenance overhead may overwhelm processing.
*
- *
ForkJoinTasks are Serializable, which enables them to
- * be used in extensions such as remote execution frameworks. However,
- * it is in general safe to serialize tasks only before or after, but
+ *
ForkJoinTasks are {@code Serializable}, which enables them
+ * to be used in extensions such as remote execution frameworks. It is
+ * 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 {
+
/**
- * Status field holding all run status. We pack this into a single
- * int both to minimize footprint overhead and to ensure atomicity
- * (updates are via CAS).
- *
- * Status is initially zero, and takes on nonnegative values until
+ * Run control status bits packed into a 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 COMPLETED. CANCELLED, or
* EXCEPTIONAL, which use the top 3 bits. Tasks undergoing
* blocking waits by other threads have SIGNAL_MASK bits set --
@@ -111,7 +136,7 @@ public abstract class ForkJoinTask im
* currently unused. Also value 0x80000000 is available as spare
* completion value.
*/
- volatile int status; // accessed directy by pool and workers
+ volatile int status; // accessed directly by pool and workers
static final int COMPLETION_MASK = 0xe0000000;
static final int NORMAL = 0xe0000000; // == mask
@@ -124,10 +149,10 @@ 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
@@ -136,25 +161,16 @@ 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();
- return ((t instanceof ForkJoinWorkerThread)?
- (ForkJoinWorkerThread)t : null);
- }
-
- /**
- * Get pool of current worker thread, or null if not a worker thread
- */
- static ForkJoinPool getWorkerPool() {
- Thread t = Thread.currentThread();
- return ((t instanceof ForkJoinWorkerThread)?
- ((ForkJoinWorkerThread)t).pool : null);
+ return ((t instanceof ForkJoinWorkerThread) ?
+ (ForkJoinWorkerThread) t : null);
}
final boolean casStatus(int cmp, int val) {
- return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
+ return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
}
/**
@@ -162,25 +178,26 @@ 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) {
- ForkJoinPool pool = getWorkerPool();
+ ForkJoinPool pool = getPool();
if (pool != null) {
int s; // Clear signal bits while setting completion status
- do;while ((s = status) >= 0 && !casStatus(s, completion));
+ 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(); }
+ synchronized (this) { notifyAll(); }
}
}
else
@@ -193,48 +210,48 @@ public abstract class ForkJoinTask im
*/
private void externallySetCompletion(int completion) {
int s;
- do;while ((s = status) >= 0 &&
- !casStatus(s, (s & SIGNAL_MASK) | completion));
- synchronized(this) { notifyAll(); }
+ do {} while ((s = status) >= 0 &&
+ !casStatus(s, (s & SIGNAL_MASK) | completion));
+ synchronized (this) { notifyAll(); }
}
/**
- * Sets status to indicate normal completion
+ * Sets status to indicate normal completion.
*/
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);
}
// internal waiting and notification
/**
- * Performs the actual monitor wait for awaitDone
+ * Performs the actual monitor wait for awaitDone.
*/
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(); }
+ synchronized (this) { if (status >= 0) wait(); }
} catch (InterruptedException ie) {
onInterruptedWait();
}
}
/**
- * Performs the actual monitor wait for awaitDone
+ * Performs the actual timed monitor wait for awaitDone.
*/
private void doAwaitDone(long startTime, long nanos) {
- synchronized(this) {
+ synchronized (this) {
try {
while (status >= 0) {
long nt = nanos - System.nanoTime() - startTime;
if (nt <= 0)
break;
- wait(nt / 1000000, (int)(nt % 1000000));
+ wait(nt / 1000000, (int) (nt % 1000000));
}
} catch (InterruptedException ie) {
onInterruptedWait();
@@ -247,13 +264,15 @@ public abstract class ForkJoinTask im
/**
* Sets status to indicate there is joiner, then waits for join,
* surrounded with pool notifications.
+ *
* @return status upon exit
*/
- final int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
- ForkJoinPool pool = w == null? null : w.pool;
+ 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 (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
if (pool == null || !pool.preJoin(this, maintainParallelism))
doAwaitDone();
if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
@@ -266,13 +285,14 @@ public abstract class ForkJoinTask im
/**
* Timed version of awaitDone
+ *
* @return status upon exit
*/
- final int awaitDone(ForkJoinWorkerThread w, long nanos) {
- ForkJoinPool pool = w == null? null : w.pool;
+ 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)) {
+ if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
long startTime = System.nanoTime();
if (pool == null || !pool.preJoin(this, false))
doAwaitDone(startTime, nanos);
@@ -289,18 +309,18 @@ 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) {
int s;
- do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
+ do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
pool.updateRunningCount(s);
}
/**
- * 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) {
@@ -314,19 +334,16 @@ public abstract class ForkJoinTask im
}
}
+ /**
+ * Handles interruptions during waits.
+ */
private void onInterruptedWait() {
- Thread t = Thread.currentThread();
- if (t instanceof ForkJoinWorkerThread) {
- ForkJoinWorkerThread w = (ForkJoinWorkerThread)t;
- if (w.isTerminating())
- cancelIgnoreExceptions();
- }
- else { // re-interrupt
- try {
- t.interrupt();
- } catch (SecurityException ignore) {
- }
- }
+ 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
@@ -337,7 +354,8 @@ 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) {
@@ -350,8 +368,8 @@ public abstract class ForkJoinTask im
}
/**
- * Returns result or throws exception using j.u.c.Future conventions
- * Only call when isDone known to be true.
+ * Returns result or throws exception using j.u.c.Future conventions.
+ * Only call when {@code isDone} known to be true.
*/
private V reportFutureResult()
throws ExecutionException, InterruptedException {
@@ -370,7 +388,7 @@ 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 {
@@ -391,7 +409,8 @@ 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() {
@@ -409,14 +428,14 @@ 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) {
try {
if (!exec())
return;
- } catch(Throwable rex) {
+ } catch (Throwable rex) {
setDoneExceptionally(rex);
return;
}
@@ -425,8 +444,9 @@ 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() {
@@ -442,32 +462,48 @@ public abstract class ForkJoinTask im
}
/**
- * Cancel, ignoring any exceptions it throws
+ * Cancels, ignoring any exceptions it throws.
*/
- final void cancelIgnoreExceptions() {
+ final void cancelIgnoringExceptions() {
try {
cancel(false);
- } catch(Throwable ignore) {
+ } 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
+ }
+
// public methods
/**
* 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. This
- * method may be invoked only from within other ForkJoinTask
- * computations. Attempts to invoke in other contexts result in
- * exceptions or errors including ClassCastException.
+ * method may be 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.
+ *
+ * @return this
, to simplify usage.
*/
- public final void fork() {
- ((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
+ public final ForkJoinTask fork() {
+ ((ForkJoinWorkerThread) Thread.currentThread())
+ .pushTask(this);
+ return this;
}
/**
* Returns the result of the computation when it is ready.
- * This method differs from get in that abnormal
+ * This method differs from {@code get} in that abnormal
* completion results in RuntimeExceptions or Errors, not
* ExecutionExceptions.
*
@@ -480,43 +516,12 @@ public abstract class ForkJoinTask im
return getRawResult();
}
- public final V get() throws InterruptedException, ExecutionException {
- ForkJoinWorkerThread w = getWorker();
- if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
- awaitDone(w, true);
- return reportFutureResult();
- }
-
- public final V get(long timeout, TimeUnit unit)
- throws InterruptedException, ExecutionException, TimeoutException {
- ForkJoinWorkerThread w = getWorker();
- if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
- awaitDone(w, unit.toNanos(timeout));
- 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 join, but is only applicable when there
- * are no potemtial 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).
- * @return the computed result
- */
- public final V helpJoin() {
- ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
- if (status < 0 || !w.unpushTask(this) || !tryExec())
- reportException(w.helpJoinTask(this));
- return getRawResult();
- }
-
- /**
- * Performs this task, awaits its completion if necessary, and
- * return its result.
+ * 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() {
@@ -527,45 +532,129 @@ public abstract class ForkJoinTask im
}
/**
- * Joins this task, without returning its result or throwing an
- * exception. This method may be useful when processing
- * collections of tasks when some have been cancelled or otherwise
- * known to have aborted.
+ * 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 (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
*/
- public final void quietlyJoin() {
- if (status >= 0) {
- ForkJoinWorkerThread w = getWorker();
- if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
- awaitDone(w, true);
- }
+ public static void invokeAll(ForkJoinTask>t1, ForkJoinTask> t2) {
+ t2.fork();
+ t1.invoke();
+ t2.join();
}
/**
- * Possibly executes other tasks until this task is ready.
+ * 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 (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
*/
- public final void quietlyHelpJoin() {
- if (status >= 0) {
- ForkJoinWorkerThread w =
- (ForkJoinWorkerThread)(Thread.currentThread());
- if (!w.unpushTask(this) || !tryQuietlyInvoke())
- w.helpJoinTask(this);
+ public static void invokeAll(ForkJoinTask>... tasks) {
+ Throwable ex = null;
+ int last = tasks.length - 1;
+ for (int i = last; i >= 0; --i) {
+ ForkJoinTask> t = tasks[i];
+ if (t == null) {
+ if (ex == null)
+ ex = new NullPointerException();
+ }
+ else if (i != 0)
+ t.fork();
+ else {
+ t.quietlyInvoke();
+ if (ex == null)
+ ex = t.getException();
+ }
}
+ for (int i = 1; i <= last; ++i) {
+ ForkJoinTask> t = tasks[i];
+ if (t != null) {
+ if (ex != null)
+ t.cancel(false);
+ else {
+ t.quietlyJoin();
+ if (ex == null)
+ ex = t.getException();
+ }
+ }
+ }
+ if (ex != null)
+ rethrowException(ex);
}
/**
- * Performs this task and awaits its completion if necessary,
- * without returning its result or throwing an 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 quietlyInvoke() {
- if (status >= 0 && !tryQuietlyInvoke())
- quietlyJoin();
+ * 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 (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 collection of tasks
+ * @return the tasks argument, to simplify usage
+ * @throws NullPointerException if tasks or any element are null
+ * @throws RuntimeException or Error if any task did so
+ */
+ public static > Collection invokeAll(Collection tasks) {
+ if (!(tasks instanceof List>)) {
+ invokeAll(tasks.toArray(new ForkJoinTask>[tasks.size()]));
+ return tasks;
+ }
+ @SuppressWarnings("unchecked")
+ List extends ForkJoinTask>> ts =
+ (List extends ForkJoinTask>>) tasks;
+ Throwable ex = null;
+ int last = ts.size() - 1;
+ for (int i = last; i >= 0; --i) {
+ ForkJoinTask> t = ts.get(i);
+ if (t == null) {
+ if (ex == null)
+ ex = new NullPointerException();
+ }
+ else if (i != 0)
+ t.fork();
+ else {
+ t.quietlyInvoke();
+ if (ex == null)
+ ex = t.getException();
+ }
+ }
+ for (int i = 1; i <= last; ++i) {
+ ForkJoinTask> t = ts.get(i);
+ if (t != null) {
+ if (ex != null)
+ t.cancel(false);
+ else {
+ t.quietlyJoin();
+ if (ex == null)
+ ex = t.getException();
+ }
+ }
+ }
+ if (ex != null)
+ rethrowException(ex);
+ return tasks;
}
/**
* 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() {
@@ -574,6 +663,7 @@ public abstract class ForkJoinTask im
/**
* Returns true if this task was cancelled.
+ *
* @return true if this task was cancelled
*/
public final boolean isCancelled() {
@@ -581,37 +671,14 @@ public abstract class ForkJoinTask im
}
/**
- * 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 completedAbnormally() {
- return (status & COMPLETION_MASK) < NORMAL;
- }
-
- /**
- * 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() {
- int s = status & COMPLETION_MASK;
- if (s >= NORMAL)
- return null;
- if (s == CANCELLED)
- return new CancellationException();
- return exceptionMap.get(this);
- }
-
- /**
* Asserts that the results of this task's computation will not be
- * used. If a cancellation occurs before this task is processed,
- * then its compute method will not be executed,
- * isCancelled will report true, and join will
- * result in a CancellationException being thrown. Otherwise, when
+ * used. If a cancellation occurs before attempting to execute this
+ * task, then execution will be suppressed, {@code isCancelled}
+ * will report true, and {@code join} will result in a
+ * {@code CancellationException} being thrown. Otherwise, when
* cancellation races with completion, there are no guarantees
- * about whether isCancelled will report true, whether
- * join will return normally or via an exception, or
+ * about whether {@code isCancelled} will report true, whether
+ * {@code join} will return normally or via an exception, or
* whether these behaviors will remain consistent upon repeated
* invocation.
*
@@ -622,11 +689,11 @@ public abstract class ForkJoinTask im
* This method is designed to be invoked by other
* tasks. To terminate the current task, you can just return or
* throw an unchecked exception from its computation method, or
- * invoke completeExceptionally(someException).
+ * invoke {@code completeExceptionally}.
*
* @param mayInterruptIfRunning this value is ignored in the
* default implementation because tasks are not in general
- * cancelled via interruption.
+ * cancelled via interruption
*
* @return true if this task is now cancelled
*/
@@ -636,45 +703,165 @@ public abstract class ForkJoinTask im
}
/**
+ * 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() {
+ return (status & COMPLETION_MASK) < NORMAL;
+ }
+
+ /**
+ * 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() {
+ int s = status & COMPLETION_MASK;
+ if (s >= NORMAL)
+ return null;
+ if (s == CANCELLED)
+ return new CancellationException();
+ return exceptionMap.get(this);
+ }
+
+ /**
* Completes this task abnormally, and if not already aborted or
* cancelled, causes it to throw the given exception upon
- * join and related operations. This method may be used
+ * {@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. This
- * method is overridable, but overridden versions must invoke
- * super implementation to maintain guarantees.
+ * completion of tasks that would not otherwise complete. Its use
+ * in other situations is likely to be wrong. 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 RuntimeException or Error, the actual exception thrown
* will be a RuntimeException with cause ex.
*/
public void completeExceptionally(Throwable ex) {
setDoneExceptionally((ex instanceof RuntimeException) ||
- (ex instanceof Error)? ex :
+ (ex instanceof Error) ? ex :
new RuntimeException(ex));
}
/**
* Completes this task, and if not already aborted or cancelled,
- * returning a null result upon join and related
+ * 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.
+ * tasks that would not otherwise complete normally. Its use in
+ * other situations is likely to be wrong. This method is
+ * 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 {
setRawResult(value);
- } catch(Throwable rex) {
+ } catch (Throwable rex) {
setDoneExceptionally(rex);
return;
}
setNormalCompletion();
}
+ public final V get() throws InterruptedException, ExecutionException {
+ ForkJoinWorkerThread w = getWorker();
+ if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
+ awaitDone(w, true);
+ return reportFutureResult();
+ }
+
+ public final V get(long timeout, TimeUnit unit)
+ throws InterruptedException, ExecutionException, TimeoutException {
+ ForkJoinWorkerThread w = getWorker();
+ if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
+ awaitDone(w, unit.toNanos(timeout));
+ 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). This method may be 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.
+ *
+ * @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();
+ }
+
+ /**
+ * Possibly executes other tasks until this task is ready. This
+ * method may be 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.
+ */
+ public final void quietlyHelpJoin() {
+ if (status >= 0) {
+ ForkJoinWorkerThread w =
+ (ForkJoinWorkerThread) Thread.currentThread();
+ if (!w.unpushTask(this) || !tryQuietlyInvoke())
+ busyJoin(w);
+ }
+ }
+
+ /**
+ * Joins this task, without returning its result or throwing an
+ * 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) {
+ ForkJoinWorkerThread w = getWorker();
+ if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
+ awaitDone(w, true);
+ }
+ }
+
+ /**
+ * Commences performing this task and awaits its completion if
+ * necessary, without returning its result or throwing an
+ * 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 quietlyInvoke() {
+ if (status >= 0 && !tryQuietlyInvoke())
+ quietlyJoin();
+ }
+
+ /**
+ * Possibly executes tasks until the pool hosting the current task
+ * {@link ForkJoinPool#isQuiescent}. 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() {
+ ((ForkJoinWorkerThread) Thread.currentThread())
+ .helpQuiescePool();
+ }
+
/**
* Resets the internal bookkeeping state of this task, allowing a
- * subsequent fork. This method allows repeated reuse of
+ * 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
@@ -689,164 +876,87 @@ public abstract class ForkJoinTask im
}
/**
- * Tries to unschedule this task for execution. This method will
- * typically succeed if this task is the next task that would be
- * executed by the current thread, and will typically fail (return
- * false) otherwise. This method may be useful when arranging
- * faster local processing of tasks that could have been, but were
- * not, stolen.
- * @return true if unforked
- */
- public boolean tryUnfork() {
- return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
- }
-
- /**
- * Forks both tasks, returning when isDone holds for both
- * of them or an exception is encountered. This method may be
- * invoked only from within other ForkJoinTask
- * computations. Attempts to invoke in other contexts result in
- * exceptions or errors 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.
+ * Returns the pool hosting the current task execution, or null
+ * if this task is executing outside of any ForkJoinPool.
+ *
+ * @return the pool, or null if none
*/
- public static void invokeAll(ForkJoinTask>t1, ForkJoinTask> t2) {
- t2.fork();
- t1.invoke();
- t2.join();
+ public static ForkJoinPool getPool() {
+ Thread t = Thread.currentThread();
+ return (t instanceof ForkJoinWorkerThread) ?
+ ((ForkJoinWorkerThread) t).pool : null;
}
/**
- * Forks the given tasks, returning when isDone holds for
- * all of them. If any task encounters an exception, others may be
- * cancelled. This method may be invoked only from within other
- * ForkJoinTask computations. Attempts to invoke in other contexts
- * result in exceptions or errors 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.
+ * Returns {@code true} if the current thread is executing as a
+ * ForkJoinPool computation.
+ *
+ * @return {@code true} if the current thread is executing as a
+ * ForkJoinPool computation, or false otherwise
*/
- public static void invokeAll(ForkJoinTask>... tasks) {
- Throwable ex = null;
- int last = tasks.length - 1;
- for (int i = last; i >= 0; --i) {
- ForkJoinTask> t = tasks[i];
- if (t == null) {
- if (ex == null)
- ex = new NullPointerException();
- }
- else if (i != 0)
- t.fork();
- else {
- t.quietlyInvoke();
- if (ex == null)
- ex = t.getException();
- }
- }
- for (int i = 1; i <= last; ++i) {
- ForkJoinTask> t = tasks[i];
- if (t != null) {
- if (ex != null)
- t.cancel(false);
- else {
- t.quietlyJoin();
- if (ex == null)
- ex = t.getException();
- }
- }
- }
- if (ex != null)
- rethrowException(ex);
+ public static boolean inForkJoinPool() {
+ return Thread.currentThread() instanceof ForkJoinWorkerThread;
}
/**
- * Forks all tasks in the collection, returning when
- * isDone holds for all of them. If any task encounters
- * an exception, others may be cancelled. This method may be
- * invoked only from within other ForkJoinTask
- * computations. Attempts to invoke in other contexts result in
- * exceptions or errors 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.
+ * 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 (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 static void invokeAll(Collection extends ForkJoinTask>> tasks) {
- if (!(tasks instanceof List)) {
- invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
- return;
- }
- List extends ForkJoinTask>> ts =
- (List extends ForkJoinTask>>)tasks;
- Throwable ex = null;
- int last = ts.size() - 1;
- for (int i = last; i >= 0; --i) {
- ForkJoinTask> t = ts.get(i);
- if (t == null) {
- if (ex == null)
- ex = new NullPointerException();
- }
- else if (i != 0)
- t.fork();
- else {
- t.quietlyInvoke();
- if (ex == null)
- ex = t.getException();
- }
- }
- for (int i = 1; i <= last; ++i) {
- ForkJoinTask> t = ts.get(i);
- if (t != null) {
- if (ex != null)
- t.cancel(false);
- else {
- t.quietlyJoin();
- if (ex == null)
- ex = t.getException();
- }
- }
- }
- if (ex != null)
- rethrowException(ex);
+ public boolean tryUnfork() {
+ return ((ForkJoinWorkerThread) Thread.currentThread())
+ .unpushTask(this);
}
/**
- * Possibly executes tasks until the pool hosting the current task
- * {@link ForkJoinPool#isQuiescent}. 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.
+ * 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 void helpQuiesce() {
- ((ForkJoinWorkerThread)(Thread.currentThread())).
- helpQuiescePool();
+ public static int getQueuedTaskCount() {
+ return ((ForkJoinWorkerThread) Thread.currentThread())
+ .getQueueSize();
}
/**
- * 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 want to steal them. 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.
+ * threads that might steal them. 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 surplus() {
- return ((ForkJoinWorkerThread)(Thread.currentThread()))
+ public static int getSurplusQueuedTaskCount() {
+ return ((ForkJoinWorkerThread) Thread.currentThread())
.getEstimatedSurplusTaskCount();
}
- // Extension kit
+ // Extension methods
/**
- * Returns the result that would be returned by join, or
- * 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.
+ * Returns the result that would be returned by {@code join},
+ * even if this task completed abnormally, or 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 null if not completed.
+ * @return the result, or null if not completed
*/
public abstract V getRawResult();
@@ -865,13 +975,110 @@ public abstract class ForkJoinTask im
* called otherwise. The return value controls whether this task
* is considered to be done normally. It may return false in
* asynchronous actions that require explicit invocations of
- * complete to become joinable. It may throw exceptions
+ * {@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
*/
protected abstract boolean exec();
+ /**
+ * Returns, but does not unschedule or execute, the task queued by
+ * the current thread but not yet executed, if one is
+ * available. There is no guarantee that this task will actually
+ * 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 (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
+ */
+ protected static ForkJoinTask> peekNextLocalTask() {
+ return ((ForkJoinWorkerThread) Thread.currentThread())
+ .peekTask();
+ }
+
+ /**
+ * Unschedules and returns, without executing, the next task
+ * 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 (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
+ */
+ protected static ForkJoinTask> pollNextLocalTask() {
+ return ((ForkJoinWorkerThread) Thread.currentThread())
+ .pollLocalTask();
+ }
+
+ /**
+ * 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. This method may be 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.
+ *
+ * @return a task, or null if none are available
+ */
+ protected static ForkJoinTask> pollTask() {
+ return ((ForkJoinWorkerThread) Thread.currentThread())
+ .pollTask();
+ }
+
+ // adaptors
+
+ /**
+ * Returns a new ForkJoinTask that performs the run
+ * method of the given Runnable as its action, and returns a null
+ * result upon join
.
+ *
+ * @param runnable the runnable action
+ * @return the task
+ */
+ public static ForkJoinTask adapt(Runnable runnable) {
+ return new ForkJoinPool.AdaptedRunnable(runnable, null);
+ }
+
+ /**
+ * Returns a new ForkJoinTask that performs the run
+ * method of the given Runnable as its action, and returns the
+ * given result upon join
.
+ *
+ * @param runnable the runnable action
+ * @param result the result upon completion
+ * @return the task
+ */
+ public static ForkJoinTask adapt(Runnable runnable, T result) {
+ return new ForkJoinPool.AdaptedRunnable(runnable, result);
+ }
+
+ /**
+ * Returns a new ForkJoinTask that performs the call
+ * method of the given Callable as its action, and returns its
+ * result upon join
, translating any checked
+ * exceptions encountered into RuntimeException.
+ *
+ * @param callable the callable action
+ * @return the task
+ */
+ public static ForkJoinTask adapt(Callable callable) {
+ return new ForkJoinPool.AdaptedCallable(callable);
+ }
+
// Serialization support
private static final long serialVersionUID = -7721805057305804111L;
@@ -880,7 +1087,7 @@ 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)
@@ -891,34 +1098,58 @@ public abstract class ForkJoinTask im
/**
* Reconstitute the instance from a stream.
+ *
* @param s the stream
*/
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject();
- // status &= ~INTERNAL_SIGNAL_MASK; // todo: define policy
+ status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
+ status |= EXTERNAL_SIGNAL; // conservatively set external signal
Object ex = s.readObject();
if (ex != null)
- setDoneExceptionally((Throwable)ex);
+ setDoneExceptionally((Throwable) ex);
}
- // Temporary Unsafe mechanics for preliminary release
+ // Unsafe mechanics for jsr166y 3rd party package.
+ private static sun.misc.Unsafe getUnsafe() {
+ try {
+ return sun.misc.Unsafe.getUnsafe();
+ } catch (SecurityException se) {
+ try {
+ return java.security.AccessController.doPrivileged
+ (new java.security.PrivilegedExceptionAction() {
+ public sun.misc.Unsafe run() throws Exception {
+ return getUnsafeByReflection();
+ }});
+ } catch (java.security.PrivilegedActionException e) {
+ throw new RuntimeException("Could not initialize intrinsics",
+ e.getCause());
+ }
+ }
+ }
- static final Unsafe _unsafe;
- static final long statusOffset;
+ private static sun.misc.Unsafe getUnsafeByReflection()
+ throws NoSuchFieldException, IllegalAccessException {
+ java.lang.reflect.Field f =
+ sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
+ f.setAccessible(true);
+ return (sun.misc.Unsafe) f.get(null);
+ }
- static {
+ private static long fieldOffset(String fieldName, Class> klazz) {
try {
- if (ForkJoinTask.class.getClassLoader() != null) {
- Field f = Unsafe.class.getDeclaredField("theUnsafe");
- f.setAccessible(true);
- _unsafe = (Unsafe)f.get(null);
- }
- else
- _unsafe = Unsafe.getUnsafe();
- statusOffset = _unsafe.objectFieldOffset
- (ForkJoinTask.class.getDeclaredField("status"));
- } catch (Exception ex) { throw new Error(ex); }
+ return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
+ } catch (NoSuchFieldException e) {
+ // Convert Exception to Error
+ NoSuchFieldError error = new NoSuchFieldError(fieldName);
+ error.initCause(e);
+ throw error;
+ }
}
+ private static final sun.misc.Unsafe UNSAFE = getUnsafe();
+ static final long statusOffset =
+ fieldOffset("status", ForkJoinTask.class);
+
}