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提交 381e10cf 编写于 作者: P psandoz
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8019370: Sync j.u.c Fork/Join from 166 to tl 

Reviewed-by: chegar, martin
Contributed-by: NDoug Lea <dl@cs.oswego.edu>
上级 605a051c
隐藏空白更改
内联 并排
Showing with 1052 addition and 1070 deletion
src/share/classes/java/util/concurrent/AbstractExecutorService.java
浏览文件 @ 381e10cf
......@@ -38,19 +38,19 @@ import java.util.*;
/**
* Provides default implementations of {@link ExecutorService}
* execution methods. This class implements the <tt>submit</tt>,
* <tt>invokeAny</tt> and <tt>invokeAll</tt> methods using a
* {@link RunnableFuture} returned by <tt>newTaskFor</tt>, which defaults
* execution methods. This class implements the {@code submit},
* {@code invokeAny} and {@code invokeAll} methods using a
* {@link RunnableFuture} returned by {@code newTaskFor}, which defaults
* to the {@link FutureTask} class provided in this package. For example,
* the implementation of <tt>submit(Runnable)</tt> creates an
* associated <tt>RunnableFuture</tt> that is executed and
* returned. Subclasses may override the <tt>newTaskFor</tt> methods
* to return <tt>RunnableFuture</tt> implementations other than
* <tt>FutureTask</tt>.
* the implementation of {@code submit(Runnable)} creates an
* associated {@code RunnableFuture} that is executed and
* returned. Subclasses may override the {@code newTaskFor} methods
* to return {@code RunnableFuture} implementations other than
* {@code FutureTask}.
*
* <p> <b>Extension example</b>. Here is a sketch of a class
* <p><b>Extension example</b>. Here is a sketch of a class
* that customizes {@link ThreadPoolExecutor} to use
* a <tt>CustomTask</tt> class instead of the default <tt>FutureTask</tt>:
* a {@code CustomTask} class instead of the default {@code FutureTask}:
* <pre> {@code
* public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
*
......@@ -71,15 +71,15 @@ import java.util.*;
public abstract class AbstractExecutorService implements ExecutorService {
/**
* Returns a <tt>RunnableFuture</tt> for the given runnable and default
* Returns a {@code RunnableFuture} for the given runnable and default
* value.
*
* @param runnable the runnable task being wrapped
* @param value the default value for the returned future
* @return a <tt>RunnableFuture</tt> which when run will run the
* underlying runnable and which, as a <tt>Future</tt>, will yield
* @return a {@code RunnableFuture} which, when run, will run the
* underlying runnable and which, as a {@code Future}, will yield
* the given value as its result and provide for cancellation of
* the underlying task.
* the underlying task
* @since 1.6
*/
protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
......@@ -87,13 +87,13 @@ public abstract class AbstractExecutorService implements ExecutorService {
}
/**
* Returns a <tt>RunnableFuture</tt> for the given callable task.
* Returns a {@code RunnableFuture} for the given callable task.
*
* @param callable the callable task being wrapped
* @return a <tt>RunnableFuture</tt> which when run will call the
* underlying callable and which, as a <tt>Future</tt>, will yield
* @return a {@code RunnableFuture} which, when run, will call the
* underlying callable and which, as a {@code Future}, will yield
* the callable's result as its result and provide for
* cancellation of the underlying task.
* cancellation of the underlying task
* @since 1.6
*/
protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
......@@ -144,7 +144,7 @@ public abstract class AbstractExecutorService implements ExecutorService {
int ntasks = tasks.size();
if (ntasks == 0)
throw new IllegalArgumentException();
List<Future<T>> futures= new ArrayList<Future<T>>(ntasks);
ArrayList<Future<T>> futures = new ArrayList<Future<T>>(ntasks);
ExecutorCompletionService<T> ecs =
new ExecutorCompletionService<T>(this);
......@@ -202,8 +202,8 @@ public abstract class AbstractExecutorService implements ExecutorService {
throw ee;
} finally {
for (Future<T> f : futures)
f.cancel(true);
for (int i = 0, size = futures.size(); i < size; i++)
futures.get(i).cancel(true);
}
}
......@@ -227,7 +227,7 @@ public abstract class AbstractExecutorService implements ExecutorService {
throws InterruptedException {
if (tasks == null)
throw new NullPointerException();
List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
ArrayList<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
boolean done = false;
try {
for (Callable<T> t : tasks) {
......@@ -235,7 +235,8 @@ public abstract class AbstractExecutorService implements ExecutorService {
futures.add(f);
execute(f);
}
for (Future<T> f : futures) {
for (int i = 0, size = futures.size(); i < size; i++) {
Future<T> f = futures.get(i);
if (!f.isDone()) {
try {
f.get();
......@@ -248,8 +249,8 @@ public abstract class AbstractExecutorService implements ExecutorService {
return futures;
} finally {
if (!done)
for (Future<T> f : futures)
f.cancel(true);
for (int i = 0, size = futures.size(); i < size; i++)
futures.get(i).cancel(true);
}
}
......@@ -259,25 +260,26 @@ public abstract class AbstractExecutorService implements ExecutorService {
if (tasks == null)
throw new NullPointerException();
long nanos = unit.toNanos(timeout);
List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
ArrayList<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
boolean done = false;
try {
for (Callable<T> t : tasks)
futures.add(newTaskFor(t));
final long deadline = System.nanoTime() + nanos;
final int size = futures.size();
// Interleave time checks and calls to execute in case
// executor doesn't have any/much parallelism.
Iterator<Future<T>> it = futures.iterator();
while (it.hasNext()) {
execute((Runnable)(it.next()));
for (int i = 0; i < size; i++) {
execute((Runnable)futures.get(i));
nanos = deadline - System.nanoTime();
if (nanos <= 0L)
return futures;
}
for (Future<T> f : futures) {
for (int i = 0; i < size; i++) {
Future<T> f = futures.get(i);
if (!f.isDone()) {
if (nanos <= 0L)
return futures;
......@@ -295,8 +297,8 @@ public abstract class AbstractExecutorService implements ExecutorService {
return futures;
} finally {
if (!done)
for (Future<T> f : futures)
f.cancel(true);
for (int i = 0, size = futures.size(); i < size; i++)
futures.get(i).cancel(true);
}
}
......
src/share/classes/java/util/concurrent/Callable.java
浏览文件 @ 381e10cf
......@@ -38,21 +38,21 @@ package java.util.concurrent;
/**
* A task that returns a result and may throw an exception.
* Implementors define a single method with no arguments called
* <tt>call</tt>.
* {@code call}.
*
* <p>The <tt>Callable</tt> interface is similar to {@link
* <p>The {@code Callable} interface is similar to {@link
* java.lang.Runnable}, in that both are designed for classes whose
* instances are potentially executed by another thread. A
* <tt>Runnable</tt>, however, does not return a result and cannot
* {@code Runnable}, however, does not return a result and cannot
* throw a checked exception.
*
* <p> The {@link Executors} class contains utility methods to
* convert from other common forms to <tt>Callable</tt> classes.
* <p>The {@link Executors} class contains utility methods to
* convert from other common forms to {@code Callable} classes.
*
* @see Executor
* @since 1.5
* @author Doug Lea
* @param <V> the result type of method <tt>call</tt>
* @param <V> the result type of method {@code call}
*/
public interface Callable<V> {
/**
......
src/share/classes/java/util/concurrent/CancellationException.java
浏览文件 @ 381e10cf
......@@ -47,12 +47,12 @@ public class CancellationException extends IllegalStateException {
private static final long serialVersionUID = -9202173006928992231L;
/**
* Constructs a <tt>CancellationException</tt> with no detail message.
* Constructs a {@code CancellationException} with no detail message.
*/
public CancellationException() {}
/**
* Constructs a <tt>CancellationException</tt> with the specified detail
* Constructs a {@code CancellationException} with the specified detail
* message.
*
* @param message the detail message
......
src/share/classes/java/util/concurrent/CompletableFuture.java
浏览文件 @ 381e10cf
......@@ -1209,7 +1209,7 @@ public class CompletableFuture<T> implements Future<T> {
(r = a.result) != null &&
compareAndSet(0, 1)) {
if ((r instanceof AltResult) &&
(ex = ((AltResult)r).ex) != null) {
(ex = ((AltResult)r).ex) != null) {
try {
t = fn.apply(ex);
} catch (Throwable rex) {
......@@ -2892,7 +2892,7 @@ public class CompletableFuture<T> implements Future<T> {
if (r != null && (d == null || d.compareAndSet(0, 1))) {
T t = null; Throwable ex, dx = null;
if (r instanceof AltResult) {
if ((ex = ((AltResult)r).ex) != null) {
if ((ex = ((AltResult)r).ex) != null) {
try {
t = fn.apply(ex);
} catch (Throwable rex) {
......
src/share/classes/java/util/concurrent/CompletionService.java
浏览文件 @ 381e10cf
......@@ -38,17 +38,17 @@ package java.util.concurrent;
/**
* A service that decouples the production of new asynchronous tasks
* from the consumption of the results of completed tasks. Producers
* <tt>submit</tt> tasks for execution. Consumers <tt>take</tt>
* {@code submit} tasks for execution. Consumers {@code take}
* completed tasks and process their results in the order they
* complete. A <tt>CompletionService</tt> can for example be used to
* manage asynchronous IO, in which tasks that perform reads are
* complete. A {@code CompletionService} can for example be used to
* manage asynchronous I/O, in which tasks that perform reads are
* submitted in one part of a program or system, and then acted upon
* in a different part of the program when the reads complete,
* possibly in a different order than they were requested.
*
* <p>Typically, a <tt>CompletionService</tt> relies on a separate
* <p>Typically, a {@code CompletionService} relies on a separate
* {@link Executor} to actually execute the tasks, in which case the
* <tt>CompletionService</tt> only manages an internal completion
* {@code CompletionService} only manages an internal completion
* queue. The {@link ExecutorCompletionService} class provides an
* implementation of this approach.
*
......@@ -80,7 +80,7 @@ public interface CompletionService<V> {
* @param task the task to submit
* @param result the result to return upon successful completion
* @return a Future representing pending completion of the task,
* and whose <tt>get()</tt> method will return the given
* and whose {@code get()} method will return the given
* result value upon completion
* @throws RejectedExecutionException if the task cannot be
* scheduled for execution
......@@ -99,10 +99,10 @@ public interface CompletionService<V> {
/**
* Retrieves and removes the Future representing the next
* completed task or <tt>null</tt> if none are present.
* completed task, or {@code null} if none are present.
*
* @return the Future representing the next completed task, or
* <tt>null</tt> if none are present
* {@code null} if none are present
*/
Future<V> poll();
......@@ -112,11 +112,11 @@ public interface CompletionService<V> {
* time if none are yet present.
*
* @param timeout how long to wait before giving up, in units of
* <tt>unit</tt>
* @param unit a <tt>TimeUnit</tt> determining how to interpret the
* <tt>timeout</tt> parameter
* {@code unit}
* @param unit a {@code TimeUnit} determining how to interpret the
* {@code timeout} parameter
* @return the Future representing the next completed task or
* <tt>null</tt> if the specified waiting time elapses
* {@code null} if the specified waiting time elapses
* before one is present
* @throws InterruptedException if interrupted while waiting
*/
......
src/share/classes/java/util/concurrent/CountedCompleter.java
浏览文件 @ 381e10cf
......@@ -37,14 +37,15 @@ package java.util.concurrent;
/**
* A {@link ForkJoinTask} with a completion action performed when
* triggered and there are no remaining pending
* actions. CountedCompleters are in general more robust in the
* triggered and there are no remaining pending actions.
* CountedCompleters are in general more robust in the
* presence of subtask stalls and blockage than are other forms of
* ForkJoinTasks, but are less intuitive to program. Uses of
* CountedCompleter are similar to those of other completion based
* components (such as {@link java.nio.channels.CompletionHandler})
* except that multiple <em>pending</em> completions may be necessary
* to trigger the completion action {@link #onCompletion}, not just one.
* to trigger the completion action {@link #onCompletion(CountedCompleter)},
* not just one.
* Unless initialized otherwise, the {@linkplain #getPendingCount pending
* count} starts at zero, but may be (atomically) changed using
* methods {@link #setPendingCount}, {@link #addToPendingCount}, and
......@@ -69,9 +70,10 @@ package java.util.concurrent;
* <p>A concrete CountedCompleter class must define method {@link
* #compute}, that should in most cases (as illustrated below), invoke
* {@code tryComplete()} once before returning. The class may also
* optionally override method {@link #onCompletion} to perform an
* action upon normal completion, and method {@link
* #onExceptionalCompletion} to perform an action upon any exception.
* optionally override method {@link #onCompletion(CountedCompleter)}
* to perform an action upon normal completion, and method
* {@link #onExceptionalCompletion(Throwable, CountedCompleter)} to
* perform an action upon any exception.
*
* <p>CountedCompleters most often do not bear results, in which case
* they are normally declared as {@code CountedCompleter<Void>}, and
......@@ -92,13 +94,14 @@ package java.util.concurrent;
* only as an internal helper for other computations, so its own task
* status (as reported in methods such as {@link ForkJoinTask#isDone})
* is arbitrary; this status changes only upon explicit invocations of
* {@link #complete}, {@link ForkJoinTask#cancel}, {@link
* ForkJoinTask#completeExceptionally} or upon exceptional completion
* of method {@code compute}. Upon any exceptional completion, the
* exception may be relayed to a task's completer (and its completer,
* and so on), if one exists and it has not otherwise already
* completed. Similarly, cancelling an internal CountedCompleter has
* only a local effect on that completer, so is not often useful.
* {@link #complete}, {@link ForkJoinTask#cancel},
* {@link ForkJoinTask#completeExceptionally(Throwable)} or upon
* exceptional completion of method {@code compute}. Upon any
* exceptional completion, the exception may be relayed to a task's
* completer (and its completer, and so on), if one exists and it has
* not otherwise already completed. Similarly, cancelling an internal
* CountedCompleter has only a local effect on that completer, so is
* not often useful.
*
* <p><b>Sample Usages.</b>
*
......@@ -125,8 +128,8 @@ package java.util.concurrent;
* improve load balancing. In the recursive case, the second of each
* pair of subtasks to finish triggers completion of its parent
* (because no result combination is performed, the default no-op
* implementation of method {@code onCompletion} is not overridden). A
* static utility method sets up the base task and invokes it
* implementation of method {@code onCompletion} is not overridden).
* A static utility method sets up the base task and invokes it
* (here, implicitly using the {@link ForkJoinPool#commonPool()}).
*
* <pre> {@code
......@@ -181,12 +184,11 @@ package java.util.concurrent;
* }
* }</pre>
*
* As a further improvement, notice that the left task need not even
* exist. Instead of creating a new one, we can iterate using the
* original task, and add a pending count for each fork. Additionally,
* because no task in this tree implements an {@link #onCompletion}
* method, {@code tryComplete()} can be replaced with {@link
* #propagateCompletion}.
* As a further improvement, notice that the left task need not even exist.
* Instead of creating a new one, we can iterate using the original task,
* and add a pending count for each fork. Additionally, because no task
* in this tree implements an {@link #onCompletion(CountedCompleter)} method,
* {@code tryComplete()} can be replaced with {@link #propagateCompletion}.
*
* <pre> {@code
* class ForEach<E> ...
......@@ -253,7 +255,7 @@ package java.util.concurrent;
* public static <E> E search(E[] array) {
* return new Searcher<E>(null, array, new AtomicReference<E>(), 0, array.length).invoke();
* }
*}}</pre>
* }}</pre>
*
* In this example, as well as others in which tasks have no other
* effects except to compareAndSet a common result, the trailing
......@@ -264,7 +266,7 @@ package java.util.concurrent;
*
* <p><b>Recording subtasks.</b> CountedCompleter tasks that combine
* results of multiple subtasks usually need to access these results
* in method {@link #onCompletion}. As illustrated in the following
* in method {@link #onCompletion(CountedCompleter)}. As illustrated in the following
* class (that performs a simplified form of map-reduce where mappings
* and reductions are all of type {@code E}), one way to do this in
* divide and conquer designs is to have each subtask record its
......@@ -365,7 +367,7 @@ package java.util.concurrent;
* while (h - l >= 2) {
* int mid = (l + h) >>> 1;
* addToPendingCount(1);
* (forks = new MapReducer(this, array, mapper, reducer, mid, h, forks)).fork;
* (forks = new MapReducer(this, array, mapper, reducer, mid, h, forks)).fork();
* h = mid;
* }
* if (h > l)
......@@ -386,7 +388,7 @@ package java.util.concurrent;
*
* <p><b>Triggers.</b> Some CountedCompleters are themselves never
* forked, but instead serve as bits of plumbing in other designs;
* including those in which the completion of one of more async tasks
* including those in which the completion of one or more async tasks
* triggers another async task. For example:
*
* <pre> {@code
......@@ -460,27 +462,28 @@ public abstract class CountedCompleter<T> extends ForkJoinTask<T> {
* (and/or links to other results) to combine.
*
* @param caller the task invoking this method (which may
* be this task itself).
* be this task itself)
*/
public void onCompletion(CountedCompleter<?> caller) {
}
/**
* Performs an action when method {@link #completeExceptionally}
* is invoked or method {@link #compute} throws an exception, and
* this task has not otherwise already completed normally. On
* entry to this method, this task {@link
* ForkJoinTask#isCompletedAbnormally}. The return value of this
* method controls further propagation: If {@code true} and this
* task has a completer, then this completer is also completed
* exceptionally. The default implementation of this method does
* nothing except return {@code true}.
* Performs an action when method {@link
* #completeExceptionally(Throwable)} is invoked or method {@link
* #compute} throws an exception, and this task has not already
* otherwise completed normally. On entry to this method, this task
* {@link ForkJoinTask#isCompletedAbnormally}. The return value
* of this method controls further propagation: If {@code true}
* and this task has a completer that has not completed, then that
* completer is also completed exceptionally, with the same
* exception as this completer. The default implementation of
* this method does nothing except return {@code true}.
*
* @param ex the exception
* @param caller the task invoking this method (which may
* be this task itself).
* @return true if this exception should be propagated to this
* task's completer, if one exists.
* be this task itself)
* @return {@code true} if this exception should be propagated to this
* task's completer, if one exists
*/
public boolean onExceptionalCompletion(Throwable ex, CountedCompleter<?> caller) {
return true;
......@@ -520,8 +523,7 @@ public abstract class CountedCompleter<T> extends ForkJoinTask<T> {
* @param delta the value to add
*/
public final void addToPendingCount(int delta) {
int c; // note: can replace with intrinsic in jdk8
do {} while (!U.compareAndSwapInt(this, PENDING, c = pending, c+delta));
U.getAndAddInt(this, PENDING, delta);
}
/**
......@@ -530,7 +532,7 @@ public abstract class CountedCompleter<T> extends ForkJoinTask<T> {
*
* @param expected the expected value
* @param count the new value
* @return true if successful
* @return {@code true} if successful
*/
public final boolean compareAndSetPendingCount(int expected, int count) {
return U.compareAndSwapInt(this, PENDING, expected, count);
......@@ -564,9 +566,9 @@ public abstract class CountedCompleter<T> extends ForkJoinTask<T> {
/**
* If the pending count is nonzero, decrements the count;
* otherwise invokes {@link #onCompletion} and then similarly
* tries to complete this task's completer, if one exists,
* else marks this task as complete.
* otherwise invokes {@link #onCompletion(CountedCompleter)}
* and then similarly tries to complete this task's completer,
* if one exists, else marks this task as complete.
*/
public final void tryComplete() {
CountedCompleter<?> a = this, s = a;
......@@ -585,12 +587,12 @@ public abstract class CountedCompleter<T> extends ForkJoinTask<T> {
/**
* Equivalent to {@link #tryComplete} but does not invoke {@link
* #onCompletion} along the completion path: If the pending count
* is nonzero, decrements the count; otherwise, similarly tries to
* complete this task's completer, if one exists, else marks this
* task as complete. This method may be useful in cases where
* {@code onCompletion} should not, or need not, be invoked for
* each completer in a computation.
* #onCompletion(CountedCompleter)} along the completion path:
* If the pending count is nonzero, decrements the count;
* otherwise, similarly tries to complete this task's completer, if
* one exists, else marks this task as complete. This method may be
* useful in cases where {@code onCompletion} should not, or need
* not, be invoked for each completer in a computation.
*/
public final void propagateCompletion() {
CountedCompleter<?> a = this, s = a;
......@@ -607,13 +609,15 @@ public abstract class CountedCompleter<T> extends ForkJoinTask<T> {
}
/**
* Regardless of pending count, invokes {@link #onCompletion},
* marks this task as complete and further triggers {@link
* #tryComplete} on this task's completer, if one exists. The
* given rawResult is used as an argument to {@link #setRawResult}
* before invoking {@link #onCompletion} or marking this task as
* complete; its value is meaningful only for classes overriding
* {@code setRawResult}.
* Regardless of pending count, invokes
* {@link #onCompletion(CountedCompleter)}, marks this task as
* complete and further triggers {@link #tryComplete} on this
* task's completer, if one exists. The given rawResult is
* used as an argument to {@link #setRawResult} before invoking
* {@link #onCompletion(CountedCompleter)} or marking this task
* as complete; its value is meaningful only for classes
* overriding {@code setRawResult}. This method does not modify
* the pending count.
*
* <p>This method may be useful when forcing completion as soon as
* any one (versus all) of several subtask results are obtained.
......@@ -632,7 +636,6 @@ public abstract class CountedCompleter<T> extends ForkJoinTask<T> {
p.tryComplete();
}
/**
* If this task's pending count is zero, returns this task;
* otherwise decrements its pending count and returns {@code
......@@ -653,8 +656,8 @@ public abstract class CountedCompleter<T> extends ForkJoinTask<T> {
/**
* If this task does not have a completer, invokes {@link
* ForkJoinTask#quietlyComplete} and returns {@code null}. Or, if
* this task's pending count is non-zero, decrements its pending
* count and returns {@code null}. Otherwise, returns the
* the completer's pending count is non-zero, decrements that
* pending count and returns {@code null}. Otherwise, returns the
* completer. This method can be used as part of a completion
* traversal loop for homogeneous task hierarchies:
*
......@@ -690,14 +693,35 @@ public abstract class CountedCompleter<T> extends ForkJoinTask<T> {
}
}
/**
* If this task has not completed, attempts to process at most the
* given number of other unprocessed tasks for which this task is
* on the completion path, if any are known to exist.
*
* @param maxTasks the maximum number of tasks to process. If
* less than or equal to zero, then no tasks are
* processed.
*/
public final void helpComplete(int maxTasks) {
Thread t; ForkJoinWorkerThread wt;
if (maxTasks > 0 && status >= 0) {
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
(wt = (ForkJoinWorkerThread)t).pool.
helpComplete(wt.workQueue, this, maxTasks);
else
ForkJoinPool.common.externalHelpComplete(this, maxTasks);
}
}
/**
* Supports ForkJoinTask exception propagation.
*/
void internalPropagateException(Throwable ex) {
CountedCompleter<?> a = this, s = a;
while (a.onExceptionalCompletion(ex, s) &&
(a = (s = a).completer) != null && a.status >= 0)
a.recordExceptionalCompletion(ex);
(a = (s = a).completer) != null && a.status >= 0 &&
a.recordExceptionalCompletion(ex) == EXCEPTIONAL)
;
}
/**
......
src/share/classes/java/util/concurrent/ExecutionException.java
浏览文件 @ 381e10cf
......@@ -48,14 +48,14 @@ public class ExecutionException extends Exception {
private static final long serialVersionUID = 7830266012832686185L;
/**
* Constructs an <tt>ExecutionException</tt> with no detail message.
* Constructs an {@code ExecutionException} with no detail message.
* The cause is not initialized, and may subsequently be
* initialized by a call to {@link #initCause(Throwable) initCause}.
*/
protected ExecutionException() { }
/**
* Constructs an <tt>ExecutionException</tt> with the specified detail
* Constructs an {@code ExecutionException} with the specified detail
* message. The cause is not initialized, and may subsequently be
* initialized by a call to {@link #initCause(Throwable) initCause}.
*
......@@ -66,7 +66,7 @@ public class ExecutionException extends Exception {
}
/**
* Constructs an <tt>ExecutionException</tt> with the specified detail
* Constructs an {@code ExecutionException} with the specified detail
* message and cause.
*
* @param message the detail message
......@@ -78,7 +78,7 @@ public class ExecutionException extends Exception {
}
/**
* Constructs an <tt>ExecutionException</tt> with the specified cause.
* Constructs an {@code ExecutionException} with the specified cause.
* The detail message is set to {@code (cause == null ? null :
* cause.toString())} (which typically contains the class and
* detail message of {@code cause}).
......
src/share/classes/java/util/concurrent/Executor.java
浏览文件 @ 381e10cf
......@@ -39,9 +39,9 @@ package java.util.concurrent;
* An object that executes submitted {@link Runnable} tasks. This
* interface provides a way of decoupling task submission from the
* mechanics of how each task will be run, including details of thread
* use, scheduling, etc. An <tt>Executor</tt> is normally used
* use, scheduling, etc. An {@code Executor} is normally used
* instead of explicitly creating threads. For example, rather than
* invoking <tt>new Thread(new(RunnableTask())).start()</tt> for each
* invoking {@code new Thread(new(RunnableTask())).start()} for each
* of a set of tasks, you might use:
*
* <pre>
......@@ -51,7 +51,7 @@ package java.util.concurrent;
* ...
* </pre>
*
* However, the <tt>Executor</tt> interface does not strictly
* However, the {@code Executor} interface does not strictly
* require that execution be asynchronous. In the simplest case, an
* executor can run the submitted task immediately in the caller's
* thread:
......@@ -74,7 +74,7 @@ package java.util.concurrent;
* }
* }}</pre>
*
* Many <tt>Executor</tt> implementations impose some sort of
* Many {@code Executor} implementations impose some sort of
* limitation on how and when tasks are scheduled. The executor below
* serializes the submission of tasks to a second executor,
* illustrating a composite executor.
......@@ -111,7 +111,7 @@ package java.util.concurrent;
* }
* }}</pre>
*
* The <tt>Executor</tt> implementations provided in this package
* The {@code Executor} implementations provided in this package
* implement {@link ExecutorService}, which is a more extensive
* interface. The {@link ThreadPoolExecutor} class provides an
* extensible thread pool implementation. The {@link Executors} class
......@@ -130,11 +130,11 @@ public interface Executor {
/**
* Executes the given command at some time in the future. The command
* may execute in a new thread, in a pooled thread, or in the calling
* thread, at the discretion of the <tt>Executor</tt> implementation.
* thread, at the discretion of the {@code Executor} implementation.
*
* @param command the runnable task
* @throws RejectedExecutionException if this task cannot be
* accepted for execution.
* accepted for execution
* @throws NullPointerException if command is null
*/
void execute(Runnable command);
......
src/share/classes/java/util/concurrent/ExecutorService.java
浏览文件 @ 381e10cf
......@@ -42,21 +42,21 @@ import java.util.Collection;
* methods that can produce a {@link Future} for tracking progress of
* one or more asynchronous tasks.
*
* <p> An <tt>ExecutorService</tt> can be shut down, which will cause
* <p>An {@code ExecutorService} can be shut down, which will cause
* it to reject new tasks. Two different methods are provided for
* shutting down an <tt>ExecutorService</tt>. The {@link #shutdown}
* shutting down an {@code ExecutorService}. The {@link #shutdown}
* method will allow previously submitted tasks to execute before
* terminating, while the {@link #shutdownNow} method prevents waiting
* tasks from starting and attempts to stop currently executing tasks.
* Upon termination, an executor has no tasks actively executing, no
* tasks awaiting execution, and no new tasks can be submitted. An
* unused <tt>ExecutorService</tt> should be shut down to allow
* unused {@code ExecutorService} should be shut down to allow
* reclamation of its resources.
*
* <p> Method <tt>submit</tt> extends base method {@link
* Executor#execute} by creating and returning a {@link Future} that
* can be used to cancel execution and/or wait for completion.
* Methods <tt>invokeAny</tt> and <tt>invokeAll</tt> perform the most
* <p>Method {@code submit} extends base method {@link
* Executor#execute(Runnable)} by creating and returning a {@link Future}
* that can be used to cancel execution and/or wait for completion.
* Methods {@code invokeAny} and {@code invokeAll} perform the most
* commonly useful forms of bulk execution, executing a collection of
* tasks and then waiting for at least one, or all, to
* complete. (Class {@link ExecutorCompletionService} can be used to
......@@ -101,9 +101,9 @@ import java.util.Collection;
* }
* }}</pre>
*
* The following method shuts down an <tt>ExecutorService</tt> in two phases,
* first by calling <tt>shutdown</tt> to reject incoming tasks, and then
* calling <tt>shutdownNow</tt>, if necessary, to cancel any lingering tasks:
* The following method shuts down an {@code ExecutorService} in two phases,
* first by calling {@code shutdown} to reject incoming tasks, and then
* calling {@code shutdownNow}, if necessary, to cancel any lingering tasks:
*
* <pre> {@code
* void shutdownAndAwaitTermination(ExecutorService pool) {
......@@ -149,8 +149,8 @@ public interface ExecutorService extends Executor {
* shutting down this ExecutorService may manipulate
* threads that the caller is not permitted to modify
* because it does not hold {@link
* java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
* or the security manager's <tt>checkAccess</tt> method
* java.lang.RuntimePermission}{@code ("modifyThread")},
* or the security manager's {@code checkAccess} method
* denies access.
*/
void shutdown();
......@@ -174,25 +174,25 @@ public interface ExecutorService extends Executor {
* shutting down this ExecutorService may manipulate
* threads that the caller is not permitted to modify
* because it does not hold {@link
* java.lang.RuntimePermission}<tt>("modifyThread")</tt>,
* or the security manager's <tt>checkAccess</tt> method
* java.lang.RuntimePermission}{@code ("modifyThread")},
* or the security manager's {@code checkAccess} method
* denies access.
*/
List<Runnable> shutdownNow();
/**
* Returns <tt>true</tt> if this executor has been shut down.
* Returns {@code true} if this executor has been shut down.
*
* @return <tt>true</tt> if this executor has been shut down
* @return {@code true} if this executor has been shut down
*/
boolean isShutdown();
/**
* Returns <tt>true</tt> if all tasks have completed following shut down.
* Note that <tt>isTerminated</tt> is never <tt>true</tt> unless
* either <tt>shutdown</tt> or <tt>shutdownNow</tt> was called first.
* Returns {@code true} if all tasks have completed following shut down.
* Note that {@code isTerminated} is never {@code true} unless
* either {@code shutdown} or {@code shutdownNow} was called first.
*
* @return <tt>true</tt> if all tasks have completed following shut down
* @return {@code true} if all tasks have completed following shut down
*/
boolean isTerminated();
......@@ -203,8 +203,8 @@ public interface ExecutorService extends Executor {
*
* @param timeout the maximum time to wait
* @param unit the time unit of the timeout argument
* @return <tt>true</tt> if this executor terminated and
* <tt>false</tt> if the timeout elapsed before termination
* @return {@code true} if this executor terminated and
* {@code false} if the timeout elapsed before termination
* @throws InterruptedException if interrupted while waiting
*/
boolean awaitTermination(long timeout, TimeUnit unit)
......@@ -213,15 +213,15 @@ public interface ExecutorService extends Executor {
/**
* Submits a value-returning task for execution and returns a
* Future representing the pending results of the task. The
* Future's <tt>get</tt> method will return the task's result upon
* Future's {@code get} method will return the task's result upon
* successful completion.
*
* <p>
* If you would like to immediately block waiting
* for a task, you can use constructions of the form
* <tt>result = exec.submit(aCallable).get();</tt>
* {@code result = exec.submit(aCallable).get();}
*
* <p> Note: The {@link Executors} class includes a set of methods
* <p>Note: The {@link Executors} class includes a set of methods
* that can convert some other common closure-like objects,
* for example, {@link java.security.PrivilegedAction} to
* {@link Callable} form so they can be submitted.
......@@ -236,7 +236,7 @@ public interface ExecutorService extends Executor {
/**
* Submits a Runnable task for execution and returns a Future
* representing that task. The Future's <tt>get</tt> method will
* representing that task. The Future's {@code get} method will
* return the given result upon successful completion.
*
* @param task the task to submit
......@@ -250,8 +250,8 @@ public interface ExecutorService extends Executor {
/**
* Submits a Runnable task for execution and returns a Future
* representing that task. The Future's <tt>get</tt> method will
* return <tt>null</tt> upon <em>successful</em> completion.
* representing that task. The Future's {@code get} method will
* return {@code null} upon <em>successful</em> completion.
*
* @param task the task to submit
* @return a Future representing pending completion of the task
......@@ -264,7 +264,7 @@ public interface ExecutorService extends Executor {
/**
* Executes the given tasks, returning a list of Futures holding
* their status and results when all complete.
* {@link Future#isDone} is <tt>true</tt> for each
* {@link Future#isDone} is {@code true} for each
* element of the returned list.
* Note that a <em>completed</em> task could have
* terminated either normally or by throwing an exception.
......@@ -272,12 +272,12 @@ public interface ExecutorService extends Executor {
* collection is modified while this operation is in progress.
*
* @param tasks the collection of tasks
* @return A list of Futures representing the tasks, in the same
* @return a list of Futures representing the tasks, in the same
* sequential order as produced by the iterator for the
* given task list, each of which has completed.
* given task list, each of which has completed
* @throws InterruptedException if interrupted while waiting, in
* which case unfinished tasks are cancelled.
* @throws NullPointerException if tasks or any of its elements are <tt>null</tt>
* which case unfinished tasks are cancelled
* @throws NullPointerException if tasks or any of its elements are {@code null}
* @throws RejectedExecutionException if any task cannot be
* scheduled for execution
*/
......@@ -288,7 +288,7 @@ public interface ExecutorService extends Executor {
* Executes the given tasks, returning a list of Futures holding
* their status and results
* when all complete or the timeout expires, whichever happens first.
* {@link Future#isDone} is <tt>true</tt> for each
* {@link Future#isDone} is {@code true} for each
* element of the returned list.
* Upon return, tasks that have not completed are cancelled.
* Note that a <em>completed</em> task could have
......@@ -307,7 +307,7 @@ public interface ExecutorService extends Executor {
* @throws InterruptedException if interrupted while waiting, in
* which case unfinished tasks are cancelled
* @throws NullPointerException if tasks, any of its elements, or
* unit are <tt>null</tt>
* unit are {@code null}
* @throws RejectedExecutionException if any task cannot be scheduled
* for execution
*/
......@@ -327,7 +327,7 @@ public interface ExecutorService extends Executor {
* @return the result returned by one of the tasks
* @throws InterruptedException if interrupted while waiting
* @throws NullPointerException if tasks or any element task
* subject to execution is <tt>null</tt>
* subject to execution is {@code null}
* @throws IllegalArgumentException if tasks is empty
* @throws ExecutionException if no task successfully completes
* @throws RejectedExecutionException if tasks cannot be scheduled
......@@ -348,10 +348,10 @@ public interface ExecutorService extends Executor {
* @param tasks the collection of tasks
* @param timeout the maximum time to wait
* @param unit the time unit of the timeout argument
* @return the result returned by one of the tasks.
* @return the result returned by one of the tasks
* @throws InterruptedException if interrupted while waiting
* @throws NullPointerException if tasks, or unit, or any element
* task subject to execution is <tt>null</tt>
* task subject to execution is {@code null}
* @throws TimeoutException if the given timeout elapses before
* any task successfully completes
* @throws ExecutionException if no task successfully completes
......
src/share/classes/java/util/concurrent/Executors.java
浏览文件 @ 381e10cf
......@@ -62,7 +62,7 @@ import sun.security.util.SecurityConstants;
* that sets newly created threads to a known state.
* <li> Methods that create and return a {@link Callable}
* out of other closure-like forms, so they can be used
* in execution methods requiring <tt>Callable</tt>.
* in execution methods requiring {@code Callable}.
* </ul>
*
* @since 1.5
......@@ -73,7 +73,7 @@ public class Executors {
/**
* Creates a thread pool that reuses a fixed number of threads
* operating off a shared unbounded queue. At any point, at most
* <tt>nThreads</tt> threads will be active processing tasks.
* {@code nThreads} threads will be active processing tasks.
* If additional tasks are submitted when all threads are active,
* they will wait in the queue until a thread is available.
* If any thread terminates due to a failure during execution
......@@ -91,11 +91,48 @@ public class Executors {
new LinkedBlockingQueue<Runnable>());
}
/**
* Creates a thread pool that maintains enough threads to support
* the given parallelism level, and may use multiple queues to
* reduce contention. The parallelism level corresponds to the
* maximum number of threads actively engaged in, or available to
* engage in, task processing. The actual number of threads may
* grow and shrink dynamically. A work-stealing pool makes no
* guarantees about the order in which submitted tasks are
* executed.
*
* @param parallelism the targeted parallelism level
* @return the newly created thread pool
* @throws IllegalArgumentException if {@code parallelism <= 0}
* @since 1.8
*/
public static ExecutorService newWorkStealingPool(int parallelism) {
return new ForkJoinPool
(parallelism,
ForkJoinPool.defaultForkJoinWorkerThreadFactory,
null, true);
}
/**
* Creates a work-stealing thread pool using all
* {@link Runtime#availableProcessors available processors}
* as its target parallelism level.
* @return the newly created thread pool
* @see #newWorkStealingPool(int)
* @since 1.8
*/
public static ExecutorService newWorkStealingPool() {
return new ForkJoinPool
(Runtime.getRuntime().availableProcessors(),
ForkJoinPool.defaultForkJoinWorkerThreadFactory,
null, true);
}
/**
* Creates a thread pool that reuses a fixed number of threads
* operating off a shared unbounded queue, using the provided
* ThreadFactory to create new threads when needed. At any point,
* at most <tt>nThreads</tt> threads will be active processing
* at most {@code nThreads} threads will be active processing
* tasks. If additional tasks are submitted when all threads are
* active, they will wait in the queue until a thread is
* available. If any thread terminates due to a failure during
......@@ -125,7 +162,7 @@ public class Executors {
* subsequent tasks.) Tasks are guaranteed to execute
* sequentially, and no more than one task will be active at any
* given time. Unlike the otherwise equivalent
* <tt>newFixedThreadPool(1)</tt> the returned executor is
* {@code newFixedThreadPool(1)} the returned executor is
* guaranteed not to be reconfigurable to use additional threads.
*
* @return the newly created single-threaded Executor
......@@ -141,7 +178,7 @@ public class Executors {
* Creates an Executor that uses a single worker thread operating
* off an unbounded queue, and uses the provided ThreadFactory to
* create a new thread when needed. Unlike the otherwise
* equivalent <tt>newFixedThreadPool(1, threadFactory)</tt> the
* equivalent {@code newFixedThreadPool(1, threadFactory)} the
* returned executor is guaranteed not to be reconfigurable to use
* additional threads.
*
......@@ -164,7 +201,7 @@ public class Executors {
* will reuse previously constructed threads when they are
* available. These pools will typically improve the performance
* of programs that execute many short-lived asynchronous tasks.
* Calls to <tt>execute</tt> will reuse previously constructed
* Calls to {@code execute} will reuse previously constructed
* threads if available. If no existing thread is available, a new
* thread will be created and added to the pool. Threads that have
* not been used for sixty seconds are terminated and removed from
......@@ -206,7 +243,7 @@ public class Executors {
* subsequent tasks.) Tasks are guaranteed to execute
* sequentially, and no more than one task will be active at any
* given time. Unlike the otherwise equivalent
* <tt>newScheduledThreadPool(1)</tt> the returned executor is
* {@code newScheduledThreadPool(1)} the returned executor is
* guaranteed not to be reconfigurable to use additional threads.
* @return the newly created scheduled executor
*/
......@@ -223,7 +260,7 @@ public class Executors {
* place if needed to execute subsequent tasks.) Tasks are
* guaranteed to execute sequentially, and no more than one task
* will be active at any given time. Unlike the otherwise
* equivalent <tt>newScheduledThreadPool(1, threadFactory)</tt>
* equivalent {@code newScheduledThreadPool(1, threadFactory)}
* the returned executor is guaranteed not to be reconfigurable to
* use additional threads.
* @param threadFactory the factory to use when creating new
......@@ -240,7 +277,7 @@ public class Executors {
* Creates a thread pool that can schedule commands to run after a
* given delay, or to execute periodically.
* @param corePoolSize the number of threads to keep in the pool,
* even if they are idle.
* even if they are idle
* @return a newly created scheduled thread pool
* @throws IllegalArgumentException if {@code corePoolSize < 0}
*/
......@@ -252,9 +289,9 @@ public class Executors {
* Creates a thread pool that can schedule commands to run after a
* given delay, or to execute periodically.
* @param corePoolSize the number of threads to keep in the pool,
* even if they are idle.
* even if they are idle
* @param threadFactory the factory to use when the executor
* creates a new thread.
* creates a new thread
* @return a newly created scheduled thread pool
* @throws IllegalArgumentException if {@code corePoolSize < 0}
* @throws NullPointerException if threadFactory is null
......@@ -264,7 +301,6 @@ public class Executors {
return new ScheduledThreadPoolExecutor(corePoolSize, threadFactory);
}
/**
* Returns an object that delegates all defined {@link
* ExecutorService} methods to the given executor, but not any
......@@ -272,7 +308,7 @@ public class Executors {
* casts. This provides a way to safely "freeze" configuration and
* disallow tuning of a given concrete implementation.
* @param executor the underlying implementation
* @return an <tt>ExecutorService</tt> instance
* @return an {@code ExecutorService} instance
* @throws NullPointerException if executor null
*/
public static ExecutorService unconfigurableExecutorService(ExecutorService executor) {
......@@ -288,7 +324,7 @@ public class Executors {
* casts. This provides a way to safely "freeze" configuration and
* disallow tuning of a given concrete implementation.
* @param executor the underlying implementation
* @return a <tt>ScheduledExecutorService</tt> instance
* @return a {@code ScheduledExecutorService} instance
* @throws NullPointerException if executor null
*/
public static ScheduledExecutorService unconfigurableScheduledExecutorService(ScheduledExecutorService executor) {
......@@ -303,9 +339,9 @@ public class Executors {
* same {@link ThreadGroup}. If there is a {@link
* java.lang.SecurityManager}, it uses the group of {@link
* System#getSecurityManager}, else the group of the thread
* invoking this <tt>defaultThreadFactory</tt> method. Each new
* invoking this {@code defaultThreadFactory} method. Each new
* thread is created as a non-daemon thread with priority set to
* the smaller of <tt>Thread.NORM_PRIORITY</tt> and the maximum
* the smaller of {@code Thread.NORM_PRIORITY} and the maximum
* priority permitted in the thread group. New threads have names
* accessible via {@link Thread#getName} of
* <em>pool-N-thread-M</em>, where <em>N</em> is the sequence
......@@ -324,30 +360,31 @@ public class Executors {
* Executors#defaultThreadFactory}, additionally setting the
* AccessControlContext and contextClassLoader of new threads to
* be the same as the thread invoking this
* <tt>privilegedThreadFactory</tt> method. A new
* <tt>privilegedThreadFactory</tt> can be created within an
* {@link AccessController#doPrivileged} action setting the
* current thread's access control context to create threads with
* the selected permission settings holding within that action.
* {@code privilegedThreadFactory} method. A new
* {@code privilegedThreadFactory} can be created within an
* {@link AccessController#doPrivileged AccessController.doPrivileged}
* action setting the current thread's access control context to
* create threads with the selected permission settings holding
* within that action.
*
* <p> Note that while tasks running within such threads will have
* <p>Note that while tasks running within such threads will have
* the same access control and class loader settings as the
* current thread, they need not have the same {@link
* java.lang.ThreadLocal} or {@link
* java.lang.InheritableThreadLocal} values. If necessary,
* particular values of thread locals can be set or reset before
* any task runs in {@link ThreadPoolExecutor} subclasses using
* {@link ThreadPoolExecutor#beforeExecute}. Also, if it is
* necessary to initialize worker threads to have the same
* InheritableThreadLocal settings as some other designated
* thread, you can create a custom ThreadFactory in which that
* thread waits for and services requests to create others that
* will inherit its values.
* {@link ThreadPoolExecutor#beforeExecute(Thread, Runnable)}.
* Also, if it is necessary to initialize worker threads to have
* the same InheritableThreadLocal settings as some other
* designated thread, you can create a custom ThreadFactory in
* which that thread waits for and services requests to create
* others that will inherit its values.
*
* @return a thread factory
* @throws AccessControlException if the current access control
* context does not have permission to both get and set context
* class loader.
* class loader
*/
public static ThreadFactory privilegedThreadFactory() {
return new PrivilegedThreadFactory();
......@@ -357,7 +394,7 @@ public class Executors {
* Returns a {@link Callable} object that, when
* called, runs the given task and returns the given result. This
* can be useful when applying methods requiring a
* <tt>Callable</tt> to an otherwise resultless action.
* {@code Callable} to an otherwise resultless action.
* @param task the task to run
* @param result the result to return
* @return a callable object
......@@ -371,7 +408,7 @@ public class Executors {
/**
* Returns a {@link Callable} object that, when
* called, runs the given task and returns <tt>null</tt>.
* called, runs the given task and returns {@code null}.
* @param task the task to run
* @return a callable object
* @throws NullPointerException if task null
......@@ -412,18 +449,17 @@ public class Executors {
}
/**
* Returns a {@link Callable} object that will, when
* called, execute the given <tt>callable</tt> under the current
* access control context. This method should normally be
* invoked within an {@link AccessController#doPrivileged} action
* to create callables that will, if possible, execute under the
* selected permission settings holding within that action; or if
* not possible, throw an associated {@link
* Returns a {@link Callable} object that will, when called,
* execute the given {@code callable} under the current access
* control context. This method should normally be invoked within
* an {@link AccessController#doPrivileged AccessController.doPrivileged}
* action to create callables that will, if possible, execute
* under the selected permission settings holding within that
* action; or if not possible, throw an associated {@link
* AccessControlException}.
* @param callable the underlying task
* @return a callable object
* @throws NullPointerException if callable null
*
*/
public static <T> Callable<T> privilegedCallable(Callable<T> callable) {
if (callable == null)
......@@ -432,22 +468,23 @@ public class Executors {
}
/**
* Returns a {@link Callable} object that will, when
* called, execute the given <tt>callable</tt> under the current
* access control context, with the current context class loader
* as the context class loader. This method should normally be
* invoked within an {@link AccessController#doPrivileged} action
* to create callables that will, if possible, execute under the
* selected permission settings holding within that action; or if
* not possible, throw an associated {@link
* Returns a {@link Callable} object that will, when called,
* execute the given {@code callable} under the current access
* control context, with the current context class loader as the
* context class loader. This method should normally be invoked
* within an
* {@link AccessController#doPrivileged AccessController.doPrivileged}
* action to create callables that will, if possible, execute
* under the selected permission settings holding within that
* action; or if not possible, throw an associated {@link
* AccessControlException}.
* @param callable the underlying task
*
* @param callable the underlying task
* @return a callable object
* @throws NullPointerException if callable null
* @throws AccessControlException if the current access control
* context does not have permission to both set and get context
* class loader.
* class loader
*/
public static <T> Callable<T> privilegedCallableUsingCurrentClassLoader(Callable<T> callable) {
if (callable == null)
......@@ -699,7 +736,6 @@ public class Executors {
}
}
/** Cannot instantiate. */
private Executors() {}
}
src/share/classes/java/util/concurrent/ForkJoinPool.java
浏览文件 @ 381e10cf
......@@ -47,6 +47,7 @@ import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.RunnableFuture;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.TimeUnit;
/**
......@@ -79,9 +80,9 @@ import java.util.concurrent.TimeUnit;
* level; by default, equal to the number of available processors. The
* pool attempts to maintain enough active (or available) threads by
* dynamically adding, suspending, or resuming internal worker
* threads, even if some tasks are stalled waiting to join
* others. However, no such adjustments are guaranteed in the face of
* blocked I/O or other unmanaged synchronization. The nested {@link
* threads, even if some tasks are stalled waiting to join others.
* However, no such adjustments are guaranteed in the face of blocked
* I/O or other unmanaged synchronization. The nested {@link
* ManagedBlocker} interface enables extension of the kinds of
* synchronization accommodated.
*
......@@ -157,6 +158,7 @@ import java.util.concurrent.TimeUnit;
* @since 1.7
* @author Doug Lea
*/
@sun.misc.Contended
public class ForkJoinPool extends AbstractExecutorService {
/*
......@@ -189,32 +191,35 @@ public class ForkJoinPool extends AbstractExecutorService {
* (http://research.sun.com/scalable/pubs/index.html) and
* "Idempotent work stealing" by Michael, Saraswat, and Vechev,
* PPoPP 2009 (http://portal.acm.org/citation.cfm?id=1504186).
* The main differences ultimately stem from GC requirements that
* we null out taken slots as soon as we can, to maintain as small
* a footprint as possible even in programs generating huge
* numbers of tasks. To accomplish this, we shift the CAS
* arbitrating pop vs poll (steal) from being on the indices
* ("base" and "top") to the slots themselves. So, both a
* successful pop and poll mainly entail a CAS of a slot from
* non-null to null. Because we rely on CASes of references, we
* do not need tag bits on base or top. They are simple ints as
* used in any circular array-based queue (see for example
* ArrayDeque). Updates to the indices must still be ordered in a
* way that guarantees that top == base means the queue is empty,
* but otherwise may err on the side of possibly making the queue
* appear nonempty when a push, pop, or poll have not fully
* committed. Note that this means that the poll operation,
* considered individually, is not wait-free. One thief cannot
* successfully continue until another in-progress one (or, if
* previously empty, a push) completes. However, in the
* aggregate, we ensure at least probabilistic non-blockingness.
* If an attempted steal fails, a thief always chooses a different
* random victim target to try next. So, in order for one thief to
* progress, it suffices for any in-progress poll or new push on
* any empty queue to complete. (This is why we normally use
* method pollAt and its variants that try once at the apparent
* base index, else consider alternative actions, rather than
* method poll.)
* See also "Correct and Efficient Work-Stealing for Weak Memory
* Models" by Le, Pop, Cohen, and Nardelli, PPoPP 2013
* (http://www.di.ens.fr/~zappa/readings/ppopp13.pdf) for an
* analysis of memory ordering (atomic, volatile etc) issues. The
* main differences ultimately stem from GC requirements that we
* null out taken slots as soon as we can, to maintain as small a
* footprint as possible even in programs generating huge numbers
* of tasks. To accomplish this, we shift the CAS arbitrating pop
* vs poll (steal) from being on the indices ("base" and "top") to
* the slots themselves. So, both a successful pop and poll
* mainly entail a CAS of a slot from non-null to null. Because
* we rely on CASes of references, we do not need tag bits on base
* or top. They are simple ints as used in any circular
* array-based queue (see for example ArrayDeque). Updates to the
* indices must still be ordered in a way that guarantees that top
* == base means the queue is empty, but otherwise may err on the
* side of possibly making the queue appear nonempty when a push,
* pop, or poll have not fully committed. Note that this means
* that the poll operation, considered individually, is not
* wait-free. One thief cannot successfully continue until another
* in-progress one (or, if previously empty, a push) completes.
* However, in the aggregate, we ensure at least probabilistic
* non-blockingness. If an attempted steal fails, a thief always
* chooses a different random victim target to try next. So, in
* order for one thief to progress, it suffices for any
* in-progress poll or new push on any empty queue to
* complete. (This is why we normally use method pollAt and its
* variants that try once at the apparent base index, else
* consider alternative actions, rather than method poll.)
*
* This approach also enables support of a user mode in which local
* task processing is in FIFO, not LIFO order, simply by using
......@@ -334,37 +339,35 @@ public class ForkJoinPool extends AbstractExecutorService {
* has not yet entered the wait queue. We solve this by requiring
* a full sweep of all workers (via repeated calls to method
* scan()) both before and after a newly waiting worker is added
* to the wait queue. During a rescan, the worker might release
* some other queued worker rather than itself, which has the same
* net effect. Because enqueued workers may actually be rescanning
* rather than waiting, we set and clear the "parker" field of
* WorkQueues to reduce unnecessary calls to unpark. (This
* requires a secondary recheck to avoid missed signals.) Note
* the unusual conventions about Thread.interrupts surrounding
* parking and other blocking: Because interrupts are used solely
* to alert threads to check termination, which is checked anyway
* upon blocking, we clear status (using Thread.interrupted)
* before any call to park, so that park does not immediately
* return due to status being set via some other unrelated call to
* interrupt in user code.
* to the wait queue. Because enqueued workers may actually be
* rescanning rather than waiting, we set and clear the "parker"
* field of WorkQueues to reduce unnecessary calls to unpark.
* (This requires a secondary recheck to avoid missed signals.)
* Note the unusual conventions about Thread.interrupts
* surrounding parking and other blocking: Because interrupts are
* used solely to alert threads to check termination, which is
* checked anyway upon blocking, we clear status (using
* Thread.interrupted) before any call to park, so that park does
* not immediately return due to status being set via some other
* unrelated call to interrupt in user code.
*
* Signalling. We create or wake up workers only when there
* appears to be at least one task they might be able to find and
* execute. However, many other threads may notice the same task
* and each signal to wake up a thread that might take it. So in
* general, pools will be over-signalled. When a submission is
* added or another worker adds a task to a queue that has fewer
* than two tasks, they signal waiting workers (or trigger
* creation of new ones if fewer than the given parallelism level
* -- signalWork), and may leave a hint to the unparked worker to
* help signal others upon wakeup). These primary signals are
* buttressed by others (see method helpSignal) whenever other
* threads scan for work or do not have a task to process. On
* most platforms, signalling (unpark) overhead time is noticeably
* execute. When a submission is added or another worker adds a
* task to a queue that has fewer than two tasks, they signal
* waiting workers (or trigger creation of new ones if fewer than
* the given parallelism level -- signalWork). These primary
* signals are buttressed by others whenever other threads remove
* a task from a queue and notice that there are other tasks there
* as well. So in general, pools will be over-signalled. On most
* platforms, signalling (unpark) overhead time is noticeably
* long, and the time between signalling a thread and it actually
* making progress can be very noticeably long, so it is worth
* offloading these delays from critical paths as much as
* possible.
* possible. Additionally, workers spin-down gradually, by staying
* alive so long as they see the ctl state changing. Similar
* stability-sensing techniques are also used before blocking in
* awaitJoin and helpComplete.
*
* Trimming workers. To release resources after periods of lack of
* use, a worker starting to wait when the pool is quiescent will
......@@ -477,7 +480,7 @@ public class ForkJoinPool extends AbstractExecutorService {
* Common Pool
* ===========
*
* The static common Pool always exists after static
* The static common pool always exists after static
* initialization. Since it (or any other created pool) need
* never be used, we minimize initial construction overhead and
* footprint to the setup of about a dozen fields, with no nested
......@@ -485,8 +488,11 @@ public class ForkJoinPool extends AbstractExecutorService {
* fullExternalPush during the first submission to the pool.
*
* When external threads submit to the common pool, they can
* perform some subtask processing (see externalHelpJoin and
* related methods). We do not need to record whether these
* perform subtask processing (see externalHelpJoin and related
* methods). This caller-helps policy makes it sensible to set
* common pool parallelism level to one (or more) less than the
* total number of available cores, or even zero for pure
* caller-runs. We do not need to record whether external
* submissions are to the common pool -- if not, externalHelpJoin
* returns quickly (at the most helping to signal some common pool
* workers). These submitters would otherwise be blocked waiting
......@@ -631,18 +637,10 @@ public class ForkJoinPool extends AbstractExecutorService {
* do not want multiple WorkQueue instances or multiple queue
* arrays sharing cache lines. (It would be best for queue objects
* and their arrays to share, but there is nothing available to
* help arrange that). Unfortunately, because they are recorded
* in a common array, WorkQueue instances are often moved to be
* adjacent by garbage collectors. To reduce impact, we use field
* padding that works OK on common platforms; this effectively
* trades off slightly slower average field access for the sake of
* avoiding really bad worst-case access. (Until better JVM
* support is in place, this padding is dependent on transient
* properties of JVM field layout rules.) We also take care in
* allocating, sizing and resizing the array. Non-shared queue
* arrays are initialized by workers before use. Others are
* allocated on first use.
* help arrange that). The @Contended annotation alerts JVMs to
* try to keep instances apart.
*/
@sun.misc.Contended
static final class WorkQueue {
/**
* Capacity of work-stealing queue array upon initialization.
......@@ -664,16 +662,12 @@ public class ForkJoinPool extends AbstractExecutorService {
*/
static final int MAXIMUM_QUEUE_CAPACITY = 1 << 26; // 64M
// Heuristic padding to ameliorate unfortunate memory placements
volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06;
int seed; // for random scanning; initialize nonzero
volatile int eventCount; // encoded inactivation count; < 0 if inactive
int nextWait; // encoded record of next event waiter
int hint; // steal or signal hint (index)
int poolIndex; // index of this queue in pool (or 0)
final int mode; // 0: lifo, > 0: fifo, < 0: shared
int nsteals; // number of steals
int hint; // steal index hint
short poolIndex; // index of this queue in pool
final short mode; // 0: lifo, > 0: fifo, < 0: shared
volatile int qlock; // 1: locked, -1: terminate; else 0
volatile int base; // index of next slot for poll
int top; // index of next slot for push
......@@ -684,15 +678,12 @@ public class ForkJoinPool extends AbstractExecutorService {
volatile ForkJoinTask<?> currentJoin; // task being joined in awaitJoin
ForkJoinTask<?> currentSteal; // current non-local task being executed
volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17;
volatile Object pad18, pad19, pad1a, pad1b, pad1c, pad1d;
WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode,
int seed) {
this.pool = pool;
this.owner = owner;
this.mode = mode;
this.seed = seed;
this.mode = (short)mode;
this.hint = seed; // store initial seed for runWorker
// Place indices in the center of array (that is not yet allocated)
base = top = INITIAL_QUEUE_CAPACITY >>> 1;
}
......@@ -705,7 +696,7 @@ public class ForkJoinPool extends AbstractExecutorService {
return (n >= 0) ? 0 : -n; // ignore transient negative
}
/**
/**
* Provides a more accurate estimate of whether this queue has
* any tasks than does queueSize, by checking whether a
* near-empty queue has at least one unclaimed task.
......@@ -730,20 +721,18 @@ public class ForkJoinPool extends AbstractExecutorService {
*/
final void push(ForkJoinTask<?> task) {
ForkJoinTask<?>[] a; ForkJoinPool p;
int s = top, m, n;
int s = top, n;
if ((a = array) != null) { // ignore if queue removed
int j = (((m = a.length - 1) & s) << ASHIFT) + ABASE;
U.putOrderedObject(a, j, task);
if ((n = (top = s + 1) - base) <= 2) {
if ((p = pool) != null)
p.signalWork(this);
}
int m = a.length - 1;
U.putOrderedObject(a, ((m & s) << ASHIFT) + ABASE, task);
if ((n = (top = s + 1) - base) <= 2)
(p = pool).signalWork(p.workQueues, this);
else if (n >= m)
growArray();
}
}
/**
/**
* Initializes or doubles the capacity of array. Call either
* by owner or with lock held -- it is OK for base, but not
* top, to move while resizings are in progress.
......@@ -801,9 +790,8 @@ public class ForkJoinPool extends AbstractExecutorService {
if ((a = array) != null) {
int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
if ((t = (ForkJoinTask<?>)U.getObjectVolatile(a, j)) != null &&
base == b &&
U.compareAndSwapObject(a, j, t, null)) {
base = b + 1;
base == b && U.compareAndSwapObject(a, j, t, null)) {
U.putOrderedInt(this, QBASE, b + 1);
return t;
}
}
......@@ -819,9 +807,8 @@ public class ForkJoinPool extends AbstractExecutorService {
int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
if (t != null) {
if (base == b &&
U.compareAndSwapObject(a, j, t, null)) {
base = b + 1;
if (U.compareAndSwapObject(a, j, t, null)) {
U.putOrderedInt(this, QBASE, b + 1);
return t;
}
}
......@@ -878,46 +865,40 @@ public class ForkJoinPool extends AbstractExecutorService {
ForkJoinTask.cancelIgnoringExceptions(t);
}
/**
* Computes next value for random probes. Scans don't require
* a very high quality generator, but also not a crummy one.
* Marsaglia xor-shift is cheap and works well enough. Note:
* This is manually inlined in its usages in ForkJoinPool to
* avoid writes inside busy scan loops.
*/
final int nextSeed() {
int r = seed;
r ^= r << 13;
r ^= r >>> 17;
return seed = r ^= r << 5;
}
// Specialized execution methods
/**
* Pops and runs tasks until empty.
* Polls and runs tasks until empty.
*/
private void popAndExecAll() {
// A bit faster than repeated pop calls
ForkJoinTask<?>[] a; int m, s; long j; ForkJoinTask<?> t;
while ((a = array) != null && (m = a.length - 1) >= 0 &&
(s = top - 1) - base >= 0 &&
(t = ((ForkJoinTask<?>)
U.getObject(a, j = ((m & s) << ASHIFT) + ABASE)))
!= null) {
if (U.compareAndSwapObject(a, j, t, null)) {
top = s;
t.doExec();
}
}
final void pollAndExecAll() {
for (ForkJoinTask<?> t; (t = poll()) != null;)
t.doExec();
}
/**
* Polls and runs tasks until empty.
* Executes a top-level task and any local tasks remaining
* after execution.
*/
private void pollAndExecAll() {
for (ForkJoinTask<?> t; (t = poll()) != null;)
t.doExec();
final void runTask(ForkJoinTask<?> task) {
if ((currentSteal = task) != null) {
task.doExec();
ForkJoinTask<?>[] a = array;
int md = mode;
++nsteals;
currentSteal = null;
if (md != 0)
pollAndExecAll();
else if (a != null) {
int s, m = a.length - 1;
ForkJoinTask<?> t;
while ((s = top - 1) - base >= 0 &&
(t = (ForkJoinTask<?>)U.getAndSetObject
(a, ((m & s) << ASHIFT) + ABASE, null)) != null) {
top = s;
t.doExec();
}
}
}
}
/**
......@@ -928,13 +909,15 @@ public class ForkJoinPool extends AbstractExecutorService {
* @return false if no progress can be made, else true
*/
final boolean tryRemoveAndExec(ForkJoinTask<?> task) {
boolean stat = true, removed = false, empty = true;
boolean stat;
ForkJoinTask<?>[] a; int m, s, b, n;
if ((a = array) != null && (m = a.length - 1) >= 0 &&
if (task != null && (a = array) != null && (m = a.length - 1) >= 0 &&
(n = (s = top) - (b = base)) > 0) {
boolean removed = false, empty = true;
stat = true;
for (ForkJoinTask<?> t;;) { // traverse from s to b
int j = ((--s & m) << ASHIFT) + ABASE;
t = (ForkJoinTask<?>)U.getObjectVolatile(a, j);
long j = ((--s & m) << ASHIFT) + ABASE;
t = (ForkJoinTask<?>)U.getObject(a, j);
if (t == null) // inconsistent length
break;
else if (t == task) {
......@@ -962,68 +945,95 @@ public class ForkJoinPool extends AbstractExecutorService {
break;
}
}
if (removed)
task.doExec();
}
if (removed)
task.doExec();
else
stat = false;
return stat;
}
/**
* Polls for and executes the given task or any other task in
* its CountedCompleter computation.
* Tries to poll for and execute the given task or any other
* task in its CountedCompleter computation.
*/
final boolean pollAndExecCC(ForkJoinTask<?> root) {
ForkJoinTask<?>[] a; int b; Object o;
outer: while ((b = base) - top < 0 && (a = array) != null) {
final boolean pollAndExecCC(CountedCompleter<?> root) {
ForkJoinTask<?>[] a; int b; Object o; CountedCompleter<?> t, r;
if ((b = base) - top < 0 && (a = array) != null) {
long j = (((a.length - 1) & b) << ASHIFT) + ABASE;
if ((o = U.getObject(a, j)) == null ||
!(o instanceof CountedCompleter))
break;
for (CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;;) {
if (r == root) {
if (base == b &&
U.compareAndSwapObject(a, j, t, null)) {
base = b + 1;
t.doExec();
if ((o = U.getObjectVolatile(a, j)) == null)
return true; // retry
if (o instanceof CountedCompleter) {
for (t = (CountedCompleter<?>)o, r = t;;) {
if (r == root) {
if (base == b &&
U.compareAndSwapObject(a, j, t, null)) {
U.putOrderedInt(this, QBASE, b + 1);
t.doExec();
}
return true;
}
else
break; // restart
else if ((r = r.completer) == null)
break; // not part of root computation
}
if ((r = r.completer) == null)
break outer; // not part of root computation
}
}
return false;
}
/**
* Executes a top-level task and any local tasks remaining
* after execution.
* Tries to pop and execute the given task or any other task
* in its CountedCompleter computation.
*/
final void runTask(ForkJoinTask<?> t) {
if (t != null) {
(currentSteal = t).doExec();
currentSteal = null;
++nsteals;
if (base - top < 0) { // process remaining local tasks
if (mode == 0)
popAndExecAll();
else
pollAndExecAll();
final boolean externalPopAndExecCC(CountedCompleter<?> root) {
ForkJoinTask<?>[] a; int s; Object o; CountedCompleter<?> t, r;
if (base - (s = top) < 0 && (a = array) != null) {
long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE;
if ((o = U.getObject(a, j)) instanceof CountedCompleter) {
for (t = (CountedCompleter<?>)o, r = t;;) {
if (r == root) {
if (U.compareAndSwapInt(this, QLOCK, 0, 1)) {
if (top == s && array == a &&
U.compareAndSwapObject(a, j, t, null)) {
top = s - 1;
qlock = 0;
t.doExec();
}
else
qlock = 0;
}
return true;
}
else if ((r = r.completer) == null)
break;
}
}
}
return false;
}
/**
* Executes a non-top-level (stolen) task.
* Internal version
*/
final void runSubtask(ForkJoinTask<?> t) {
if (t != null) {
ForkJoinTask<?> ps = currentSteal;
(currentSteal = t).doExec();
currentSteal = ps;
final boolean internalPopAndExecCC(CountedCompleter<?> root) {
ForkJoinTask<?>[] a; int s; Object o; CountedCompleter<?> t, r;
if (base - (s = top) < 0 && (a = array) != null) {
long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE;
if ((o = U.getObject(a, j)) instanceof CountedCompleter) {
for (t = (CountedCompleter<?>)o, r = t;;) {
if (r == root) {
if (U.compareAndSwapObject(a, j, t, null)) {
top = s - 1;
t.doExec();
}
return true;
}
else if ((r = r.completer) == null)
break;
}
}
}
return false;
}
/**
......@@ -1040,6 +1050,7 @@ public class ForkJoinPool extends AbstractExecutorService {
// Unsafe mechanics
private static final sun.misc.Unsafe U;
private static final long QBASE;
private static final long QLOCK;
private static final int ABASE;
private static final int ASHIFT;
......@@ -1048,6 +1059,8 @@ public class ForkJoinPool extends AbstractExecutorService {
U = sun.misc.Unsafe.getUnsafe();
Class<?> k = WorkQueue.class;
Class<?> ak = ForkJoinTask[].class;
QBASE = U.objectFieldOffset
(k.getDeclaredField("base"));
QLOCK = U.objectFieldOffset
(k.getDeclaredField("qlock"));
ABASE = U.arrayBaseOffset(ak);
......@@ -1087,7 +1100,7 @@ public class ForkJoinPool extends AbstractExecutorService {
/**
* Common pool parallelism. To allow simpler use and management
* when common pool threads are disabled, we allow the underlying
* common.config field to be zero, but in that case still report
* common.parallelism field to be zero, but in that case still report
* parallelism as 1 to reflect resulting caller-runs mechanics.
*/
static final int commonParallelism;
......@@ -1227,35 +1240,18 @@ public class ForkJoinPool extends AbstractExecutorService {
static final int FIFO_QUEUE = 1;
static final int SHARED_QUEUE = -1;
// bounds for #steps in scan loop -- must be power 2 minus 1
private static final int MIN_SCAN = 0x1ff; // cover estimation slop
private static final int MAX_SCAN = 0x1ffff; // 4 * max workers
// Instance fields
/*
* Field layout of this class tends to matter more than one would
* like. Runtime layout order is only loosely related to
* declaration order and may differ across JVMs, but the following
* empirically works OK on current JVMs.
*/
// Heuristic padding to ameliorate unfortunate memory placements
volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06;
volatile long stealCount; // collects worker counts
volatile long ctl; // main pool control
volatile int plock; // shutdown status and seqLock
volatile int indexSeed; // worker/submitter index seed
final int config; // mode and parallelism level
final short parallelism; // parallelism level
final short mode; // LIFO/FIFO
WorkQueue[] workQueues; // main registry
final ForkJoinWorkerThreadFactory factory;
final UncaughtExceptionHandler ueh; // per-worker UEH
final String workerNamePrefix; // to create worker name string
volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17;
volatile Object pad18, pad19, pad1a, pad1b;
/**
* Acquires the plock lock to protect worker array and related
* updates. This method is called only if an initial CAS on plock
......@@ -1307,11 +1303,11 @@ public class ForkJoinPool extends AbstractExecutorService {
* parallelism level exist. Adjusts counts etc on failure.
*/
private void tryAddWorker() {
long c; int u;
long c; int u, e;
while ((u = (int)((c = ctl) >>> 32)) < 0 &&
(u & SHORT_SIGN) != 0 && (int)c == 0) {
long nc = (long)(((u + UTC_UNIT) & UTC_MASK) |
((u + UAC_UNIT) & UAC_MASK)) << 32;
(u & SHORT_SIGN) != 0 && (e = (int)c) >= 0) {
long nc = ((long)(((u + UTC_UNIT) & UTC_MASK) |
((u + UAC_UNIT) & UAC_MASK)) << 32) | (long)e;
if (U.compareAndSwapLong(this, CTL, c, nc)) {
ForkJoinWorkerThreadFactory fac;
Throwable ex = null;
......@@ -1322,8 +1318,8 @@ public class ForkJoinPool extends AbstractExecutorService {
wt.start();
break;
}
} catch (Throwable e) {
ex = e;
} catch (Throwable rex) {
ex = rex;
}
deregisterWorker(wt, ex);
break;
......@@ -1351,7 +1347,7 @@ public class ForkJoinPool extends AbstractExecutorService {
do {} while (!U.compareAndSwapInt(this, INDEXSEED, s = indexSeed,
s += SEED_INCREMENT) ||
s == 0); // skip 0
WorkQueue w = new WorkQueue(this, wt, config >>> 16, s);
WorkQueue w = new WorkQueue(this, wt, mode, s);
if (((ps = plock) & PL_LOCK) != 0 ||
!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
ps = acquirePlock();
......@@ -1371,14 +1367,15 @@ public class ForkJoinPool extends AbstractExecutorService {
}
}
}
w.eventCount = w.poolIndex = r; // volatile write orders
w.poolIndex = (short)r;
w.eventCount = r; // volatile write orders
ws[r] = w;
}
} finally {
if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
releasePlock(nps);
}
wt.setName(workerNamePrefix.concat(Integer.toString(w.poolIndex)));
wt.setName(workerNamePrefix.concat(Integer.toString(w.poolIndex >>> 1)));
return w;
}
......@@ -1396,9 +1393,7 @@ public class ForkJoinPool extends AbstractExecutorService {
if (wt != null && (w = wt.workQueue) != null) {
int ps;
w.qlock = -1; // ensure set
long ns = w.nsteals, sc; // collect steal count
do {} while (!U.compareAndSwapLong(this, STEALCOUNT,
sc = stealCount, sc + ns));
U.getAndAddLong(this, STEALCOUNT, w.nsteals); // collect steals
if (((ps = plock) & PL_LOCK) != 0 ||
!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
ps = acquirePlock();
......@@ -1464,19 +1459,21 @@ public class ForkJoinPool extends AbstractExecutorService {
* @param task the task. Caller must ensure non-null.
*/
final void externalPush(ForkJoinTask<?> task) {
WorkQueue[] ws; WorkQueue q; int z, m; ForkJoinTask<?>[] a;
if ((z = ThreadLocalRandom.getProbe()) != 0 && plock > 0 &&
(ws = workQueues) != null && (m = (ws.length - 1)) >= 0 &&
(q = ws[m & z & SQMASK]) != null &&
WorkQueue q; int m, s, n, am; ForkJoinTask<?>[] a;
int r = ThreadLocalRandom.getProbe();
int ps = plock;
WorkQueue[] ws = workQueues;
if (ps > 0 && ws != null && (m = (ws.length - 1)) >= 0 &&
(q = ws[m & r & SQMASK]) != null && r != 0 &&
U.compareAndSwapInt(q, QLOCK, 0, 1)) { // lock
int b = q.base, s = q.top, n, an;
if ((a = q.array) != null && (an = a.length) > (n = s + 1 - b)) {
int j = (((an - 1) & s) << ASHIFT) + ABASE;
if ((a = q.array) != null &&
(am = a.length - 1) > (n = (s = q.top) - q.base)) {
int j = ((am & s) << ASHIFT) + ABASE;
U.putOrderedObject(a, j, task);
q.top = s + 1; // push on to deque
q.qlock = 0;
if (n <= 2)
signalWork(q);
if (n <= 1)
signalWork(ws, q);
return;
}
q.qlock = 0;
......@@ -1514,7 +1511,7 @@ public class ForkJoinPool extends AbstractExecutorService {
throw new RejectedExecutionException();
else if (ps == 0 || (ws = workQueues) == null ||
(m = ws.length - 1) < 0) { // initialize workQueues
int p = config & SMASK; // find power of two table size
int p = parallelism; // find power of two table size
int n = (p > 1) ? p - 1 : 1; // ensure at least 2 slots
n |= n >>> 1; n |= n >>> 2; n |= n >>> 4;
n |= n >>> 8; n |= n >>> 16; n = (n + 1) << 1;
......@@ -1546,7 +1543,7 @@ public class ForkJoinPool extends AbstractExecutorService {
q.qlock = 0; // unlock
}
if (submitted) {
signalWork(q);
signalWork(ws, q);
return;
}
}
......@@ -1554,6 +1551,7 @@ public class ForkJoinPool extends AbstractExecutorService {
}
else if (((ps = plock) & PL_LOCK) == 0) { // create new queue
q = new WorkQueue(this, null, SHARED_QUEUE, r);
q.poolIndex = (short)k;
if (((ps = plock) & PL_LOCK) != 0 ||
!U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
ps = acquirePlock();
......@@ -1577,41 +1575,42 @@ public class ForkJoinPool extends AbstractExecutorService {
*/
final void incrementActiveCount() {
long c;
do {} while (!U.compareAndSwapLong(this, CTL, c = ctl, c + AC_UNIT));
do {} while (!U.compareAndSwapLong
(this, CTL, c = ctl, ((c & ~AC_MASK) |
((c & AC_MASK) + AC_UNIT))));
}
/**
* Tries to create or activate a worker if too few are active.
*
* @param q the (non-null) queue holding tasks to be signalled
* @param ws the worker array to use to find signallees
* @param q if non-null, the queue holding tasks to be processed
*/
final void signalWork(WorkQueue q) {
int hint = q.poolIndex;
long c; int e, u, i, n; WorkQueue[] ws; WorkQueue w; Thread p;
while ((u = (int)((c = ctl) >>> 32)) < 0) {
if ((e = (int)c) > 0) {
if ((ws = workQueues) != null && ws.length > (i = e & SMASK) &&
(w = ws[i]) != null && w.eventCount == (e | INT_SIGN)) {
long nc = (((long)(w.nextWait & E_MASK)) |
((long)(u + UAC_UNIT) << 32));
if (U.compareAndSwapLong(this, CTL, c, nc)) {
w.hint = hint;
w.eventCount = (e + E_SEQ) & E_MASK;
if ((p = w.parker) != null)
U.unpark(p);
break;
}
if (q.top - q.base <= 0)
break;
}
else
break;
}
else {
final void signalWork(WorkQueue[] ws, WorkQueue q) {
for (;;) {
long c; int e, u, i; WorkQueue w; Thread p;
if ((u = (int)((c = ctl) >>> 32)) >= 0)
break;
if ((e = (int)c) <= 0) {
if ((short)u < 0)
tryAddWorker();
break;
}
if (ws == null || ws.length <= (i = e & SMASK) ||
(w = ws[i]) == null)
break;
long nc = (((long)(w.nextWait & E_MASK)) |
((long)(u + UAC_UNIT)) << 32);
int ne = (e + E_SEQ) & E_MASK;
if (w.eventCount == (e | INT_SIGN) &&
U.compareAndSwapLong(this, CTL, c, nc)) {
w.eventCount = ne;
if ((p = w.parker) != null)
U.unpark(p);
break;
}
if (q != null && q.base >= q.top)
break;
}
}
......@@ -1622,215 +1621,152 @@ public class ForkJoinPool extends AbstractExecutorService {
*/
final void runWorker(WorkQueue w) {
w.growArray(); // allocate queue
do { w.runTask(scan(w)); } while (w.qlock >= 0);
for (int r = w.hint; scan(w, r) == 0; ) {
r ^= r << 13; r ^= r >>> 17; r ^= r << 5; // xorshift
}
}
/**
* Scans for and, if found, returns one task, else possibly
* Scans for and, if found, runs one task, else possibly
* inactivates the worker. This method operates on single reads of
* volatile state and is designed to be re-invoked continuously,
* in part because it returns upon detecting inconsistencies,
* contention, or state changes that indicate possible success on
* re-invocation.
*
* The scan searches for tasks across queues (starting at a random
* index, and relying on registerWorker to irregularly scatter
* them within array to avoid bias), checking each at least twice.
* The scan terminates upon either finding a non-empty queue, or
* completing the sweep. If the worker is not inactivated, it
* takes and returns a task from this queue. Otherwise, if not
* activated, it signals workers (that may include itself) and
* returns so caller can retry. Also returns for true if the
* worker array may have changed during an empty scan. On failure
* to find a task, we take one of the following actions, after
* which the caller will retry calling this method unless
* terminated.
*
* * If pool is terminating, terminate the worker.
*
* * If not already enqueued, try to inactivate and enqueue the
* worker on wait queue. Or, if inactivating has caused the pool
* to be quiescent, relay to idleAwaitWork to possibly shrink
* pool.
*
* * If already enqueued and none of the above apply, possibly
* park awaiting signal, else lingering to help scan and signal.
*
* * If a non-empty queue discovered or left as a hint,
* help wake up other workers before return.
* The scan searches for tasks across queues starting at a random
* index, checking each at least twice. The scan terminates upon
* either finding a non-empty queue, or completing the sweep. If
* the worker is not inactivated, it takes and runs a task from
* this queue. Otherwise, if not activated, it tries to activate
* itself or some other worker by signalling. On failure to find a
* task, returns (for retry) if pool state may have changed during
* an empty scan, or tries to inactivate if active, else possibly
* blocks or terminates via method awaitWork.
*
* @param w the worker (via its WorkQueue)
* @return a task or null if none found
* @param r a random seed
* @return worker qlock status if would have waited, else 0
*/
private final ForkJoinTask<?> scan(WorkQueue w) {
private final int scan(WorkQueue w, int r) {
WorkQueue[] ws; int m;
int ps = plock; // read plock before ws
if (w != null && (ws = workQueues) != null && (m = ws.length - 1) >= 0) {
int ec = w.eventCount; // ec is negative if inactive
int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
w.hint = -1; // update seed and clear hint
int j = ((m + m + 1) | MIN_SCAN) & MAX_SCAN;
do {
WorkQueue q; ForkJoinTask<?>[] a; int b;
if ((q = ws[(r + j) & m]) != null && (b = q.base) - q.top < 0 &&
(a = q.array) != null) { // probably nonempty
int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
ForkJoinTask<?> t = (ForkJoinTask<?>)
U.getObjectVolatile(a, i);
if (q.base == b && ec >= 0 && t != null &&
U.compareAndSwapObject(a, i, t, null)) {
if ((q.base = b + 1) - q.top < 0)
signalWork(q);
return t; // taken
}
else if ((ec < 0 || j < m) && (int)(ctl >> AC_SHIFT) <= 0) {
w.hint = (r + j) & m; // help signal below
break; // cannot take
long c = ctl; // for consistency check
if ((ws = workQueues) != null && (m = ws.length - 1) >= 0 && w != null) {
for (int j = m + m + 1, ec = w.eventCount;;) {
WorkQueue q; int b, e; ForkJoinTask<?>[] a; ForkJoinTask<?> t;
if ((q = ws[(r - j) & m]) != null &&
(b = q.base) - q.top < 0 && (a = q.array) != null) {
long i = (((a.length - 1) & b) << ASHIFT) + ABASE;
if ((t = ((ForkJoinTask<?>)
U.getObjectVolatile(a, i))) != null) {
if (ec < 0)
helpRelease(c, ws, w, q, b);
else if (q.base == b &&
U.compareAndSwapObject(a, i, t, null)) {
U.putOrderedInt(q, QBASE, b + 1);
if ((b + 1) - q.top < 0)
signalWork(ws, q);
w.runTask(t);
}
}
break;
}
} while (--j >= 0);
int h, e, ns; long c, sc; WorkQueue q;
if ((ns = w.nsteals) != 0) {
if (U.compareAndSwapLong(this, STEALCOUNT,
sc = stealCount, sc + ns))
w.nsteals = 0; // collect steals and rescan
}
else if (plock != ps) // consistency check
; // skip
else if ((e = (int)(c = ctl)) < 0)
w.qlock = -1; // pool is terminating
else {
if ((h = w.hint) < 0) {
if (ec >= 0) { // try to enqueue/inactivate
long nc = (((long)ec |
((c - AC_UNIT) & (AC_MASK|TC_MASK))));
w.nextWait = e; // link and mark inactive
else if (--j < 0) {
if ((ec | (e = (int)c)) < 0) // inactive or terminating
return awaitWork(w, c, ec);
else if (ctl == c) { // try to inactivate and enqueue
long nc = (long)ec | ((c - AC_UNIT) & (AC_MASK|TC_MASK));
w.nextWait = e;
w.eventCount = ec | INT_SIGN;
if (ctl != c || !U.compareAndSwapLong(this, CTL, c, nc))
w.eventCount = ec; // unmark on CAS failure
else if ((int)(c >> AC_SHIFT) == 1 - (config & SMASK))
idleAwaitWork(w, nc, c);
}
else if (w.eventCount < 0 && ctl == c) {
Thread wt = Thread.currentThread();
Thread.interrupted(); // clear status
U.putObject(wt, PARKBLOCKER, this);
w.parker = wt; // emulate LockSupport.park
if (w.eventCount < 0) // recheck
U.park(false, 0L); // block
w.parker = null;
U.putObject(wt, PARKBLOCKER, null);
}
}
if ((h >= 0 || (h = w.hint) >= 0) &&
(ws = workQueues) != null && h < ws.length &&
(q = ws[h]) != null) { // signal others before retry
WorkQueue v; Thread p; int u, i, s;
for (int n = (config & SMASK) - 1;;) {
int idleCount = (w.eventCount < 0) ? 0 : -1;
if (((s = idleCount - q.base + q.top) <= n &&
(n = s) <= 0) ||
(u = (int)((c = ctl) >>> 32)) >= 0 ||
(e = (int)c) <= 0 || m < (i = e & SMASK) ||
(v = ws[i]) == null)
break;
long nc = (((long)(v.nextWait & E_MASK)) |
((long)(u + UAC_UNIT) << 32));
if (v.eventCount != (e | INT_SIGN) ||
!U.compareAndSwapLong(this, CTL, c, nc))
break;
v.hint = h;
v.eventCount = (e + E_SEQ) & E_MASK;
if ((p = v.parker) != null)
U.unpark(p);
if (--n <= 0)
break;
if (!U.compareAndSwapLong(this, CTL, c, nc))
w.eventCount = ec; // back out
}
break;
}
}
}
return null;
return 0;
}
/**
* If inactivating worker w has caused the pool to become
* quiescent, checks for pool termination, and, so long as this is
* not the only worker, waits for event for up to a given
* duration. On timeout, if ctl has not changed, terminates the
* worker, which will in turn wake up another worker to possibly
* repeat this process.
* A continuation of scan(), possibly blocking or terminating
* worker w. Returns without blocking if pool state has apparently
* changed since last invocation. Also, if inactivating w has
* caused the pool to become quiescent, checks for pool
* termination, and, so long as this is not the only worker, waits
* for event for up to a given duration. On timeout, if ctl has
* not changed, terminates the worker, which will in turn wake up
* another worker to possibly repeat this process.
*
* @param w the calling worker
* @param currentCtl the ctl value triggering possible quiescence
* @param prevCtl the ctl value to restore if thread is terminated
*/
private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
if (w != null && w.eventCount < 0 &&
!tryTerminate(false, false) && (int)prevCtl != 0 &&
ctl == currentCtl) {
int dc = -(short)(currentCtl >>> TC_SHIFT);
long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
long deadline = System.nanoTime() + parkTime - TIMEOUT_SLOP;
Thread wt = Thread.currentThread();
while (ctl == currentCtl) {
Thread.interrupted(); // timed variant of version in scan()
U.putObject(wt, PARKBLOCKER, this);
w.parker = wt;
if (ctl == currentCtl)
U.park(false, parkTime);
w.parker = null;
U.putObject(wt, PARKBLOCKER, null);
if (ctl != currentCtl)
break;
if (deadline - System.nanoTime() <= 0L &&
U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
w.eventCount = (w.eventCount + E_SEQ) | E_MASK;
w.hint = -1;
w.qlock = -1; // shrink
break;
* @param c the ctl value on entry to scan
* @param ec the worker's eventCount on entry to scan
*/
private final int awaitWork(WorkQueue w, long c, int ec) {
int stat, ns; long parkTime, deadline;
if ((stat = w.qlock) >= 0 && w.eventCount == ec && ctl == c &&
!Thread.interrupted()) {
int e = (int)c;
int u = (int)(c >>> 32);
int d = (u >> UAC_SHIFT) + parallelism; // active count
if (e < 0 || (d <= 0 && tryTerminate(false, false)))
stat = w.qlock = -1; // pool is terminating
else if ((ns = w.nsteals) != 0) { // collect steals and retry
w.nsteals = 0;
U.getAndAddLong(this, STEALCOUNT, (long)ns);
}
else {
long pc = ((d > 0 || ec != (e | INT_SIGN)) ? 0L :
((long)(w.nextWait & E_MASK)) | // ctl to restore
((long)(u + UAC_UNIT)) << 32);
if (pc != 0L) { // timed wait if last waiter
int dc = -(short)(c >>> TC_SHIFT);
parkTime = (dc < 0 ? FAST_IDLE_TIMEOUT:
(dc + 1) * IDLE_TIMEOUT);
deadline = System.nanoTime() + parkTime - TIMEOUT_SLOP;
}
else
parkTime = deadline = 0L;
if (w.eventCount == ec && ctl == c) {
Thread wt = Thread.currentThread();
U.putObject(wt, PARKBLOCKER, this);
w.parker = wt; // emulate LockSupport.park
if (w.eventCount == ec && ctl == c)
U.park(false, parkTime); // must recheck before park
w.parker = null;
U.putObject(wt, PARKBLOCKER, null);
if (parkTime != 0L && ctl == c &&
deadline - System.nanoTime() <= 0L &&
U.compareAndSwapLong(this, CTL, c, pc))
stat = w.qlock = -1; // shrink pool
}
}
}
return stat;
}
/**
* Scans through queues looking for work while joining a task; if
* any present, signals. May return early if more signalling is
* detectably unneeded.
*
* @param task return early if done
* @param origin an index to start scan
*/
private void helpSignal(ForkJoinTask<?> task, int origin) {
WorkQueue[] ws; WorkQueue w; Thread p; long c; int m, u, e, i, s;
if (task != null && task.status >= 0 &&
(u = (int)(ctl >>> 32)) < 0 && (u >> UAC_SHIFT) < 0 &&
(ws = workQueues) != null && (m = ws.length - 1) >= 0) {
outer: for (int k = origin, j = m; j >= 0; --j) {
WorkQueue q = ws[k++ & m];
for (int n = m;;) { // limit to at most m signals
if (task.status < 0)
break outer;
if (q == null ||
((s = -q.base + q.top) <= n && (n = s) <= 0))
break;
if ((u = (int)((c = ctl) >>> 32)) >= 0 ||
(e = (int)c) <= 0 || m < (i = e & SMASK) ||
(w = ws[i]) == null)
break outer;
long nc = (((long)(w.nextWait & E_MASK)) |
((long)(u + UAC_UNIT) << 32));
if (w.eventCount != (e | INT_SIGN))
break outer;
if (U.compareAndSwapLong(this, CTL, c, nc)) {
w.eventCount = (e + E_SEQ) & E_MASK;
if ((p = w.parker) != null)
U.unpark(p);
if (--n <= 0)
break;
}
}
* Possibly releases (signals) a worker. Called only from scan()
* when a worker with apparently inactive status finds a non-empty
* queue. This requires revalidating all of the associated state
* from caller.
*/
private final void helpRelease(long c, WorkQueue[] ws, WorkQueue w,
WorkQueue q, int b) {
WorkQueue v; int e, i; Thread p;
if (w != null && w.eventCount < 0 && (e = (int)c) > 0 &&
ws != null && ws.length > (i = e & SMASK) &&
(v = ws[i]) != null && ctl == c) {
long nc = (((long)(v.nextWait & E_MASK)) |
((long)((int)(c >>> 32) + UAC_UNIT)) << 32);
int ne = (e + E_SEQ) & E_MASK;
if (q != null && q.base == b && w.eventCount < 0 &&
v.eventCount == (e | INT_SIGN) &&
U.compareAndSwapLong(this, CTL, c, nc)) {
v.eventCount = ne;
if ((p = v.parker) != null)
U.unpark(p);
}
}
}
......@@ -1855,7 +1791,8 @@ public class ForkJoinPool extends AbstractExecutorService {
*/
private int tryHelpStealer(WorkQueue joiner, ForkJoinTask<?> task) {
int stat = 0, steps = 0; // bound to avoid cycles
if (joiner != null && task != null) { // hoist null checks
if (task != null && joiner != null &&
joiner.base - joiner.top >= 0) { // hoist checks
restart: for (;;) {
ForkJoinTask<?> subtask = task; // current target
for (WorkQueue j = joiner, v;;) { // v is stealer of subtask
......@@ -1882,7 +1819,7 @@ public class ForkJoinPool extends AbstractExecutorService {
}
}
for (;;) { // help stealer or descend to its stealer
ForkJoinTask[] a; int b;
ForkJoinTask[] a; int b;
if (subtask.status < 0) // surround probes with
continue restart; // consistency checks
if ((b = v.base) - v.top < 0 && (a = v.array) != null) {
......@@ -1893,13 +1830,23 @@ public class ForkJoinPool extends AbstractExecutorService {
v.currentSteal != subtask)
continue restart; // stale
stat = 1; // apparent progress
if (t != null && v.base == b &&
U.compareAndSwapObject(a, i, t, null)) {
v.base = b + 1; // help stealer
joiner.runSubtask(t);
if (v.base == b) {
if (t == null)
break restart;
if (U.compareAndSwapObject(a, i, t, null)) {
U.putOrderedInt(v, QBASE, b + 1);
ForkJoinTask<?> ps = joiner.currentSteal;
int jt = joiner.top;
do {
joiner.currentSteal = t;
t.doExec(); // clear local tasks too
} while (task.status >= 0 &&
joiner.top != jt &&
(t = joiner.pop()) != null);
joiner.currentSteal = ps;
break restart;
}
}
else if (v.base == b && ++steps == MAX_HELP)
break restart; // v apparently stalled
}
else { // empty -- try to descend
ForkJoinTask<?> next = v.currentJoin;
......@@ -1926,27 +1873,45 @@ public class ForkJoinPool extends AbstractExecutorService {
* and run tasks within the target's computation.
*
* @param task the task to join
* @param mode if shared, exit upon completing any task
* if all workers are active
*/
private int helpComplete(ForkJoinTask<?> task, int mode) {
WorkQueue[] ws; WorkQueue q; int m, n, s, u;
if (task != null && (ws = workQueues) != null &&
(m = ws.length - 1) >= 0) {
for (int j = 1, origin = j;;) {
* @param maxTasks the maximum number of other tasks to run
*/
final int helpComplete(WorkQueue joiner, CountedCompleter<?> task,
int maxTasks) {
WorkQueue[] ws; int m;
int s = 0;
if ((ws = workQueues) != null && (m = ws.length - 1) >= 0 &&
joiner != null && task != null) {
int j = joiner.poolIndex;
int scans = m + m + 1;
long c = 0L; // for stability check
for (int k = scans; ; j += 2) {
WorkQueue q;
if ((s = task.status) < 0)
return s;
if ((q = ws[j & m]) != null && q.pollAndExecCC(task)) {
origin = j;
if (mode == SHARED_QUEUE &&
((u = (int)(ctl >>> 32)) >= 0 || (u >> UAC_SHIFT) >= 0))
break;
else if (joiner.internalPopAndExecCC(task)) {
if (--maxTasks <= 0) {
s = task.status;
break;
}
k = scans;
}
else if ((j = (j + 2) & m) == origin)
else if ((s = task.status) < 0)
break;
else if ((q = ws[j & m]) != null && q.pollAndExecCC(task)) {
if (--maxTasks <= 0) {
s = task.status;
break;
}
k = scans;
}
else if (--k < 0) {
if (c == (c = ctl))
break;
k = scans;
}
}
}
return 0;
return s;
}
/**
......@@ -1955,17 +1920,22 @@ public class ForkJoinPool extends AbstractExecutorService {
* for blocking. Fails on contention or termination. Otherwise,
* adds a new thread if no idle workers are available and pool
* may become starved.
*
* @param c the assumed ctl value
*/
final boolean tryCompensate() {
int pc = config & SMASK, e, i, tc; long c;
WorkQueue[] ws; WorkQueue w; Thread p;
if ((ws = workQueues) != null && (e = (int)(c = ctl)) >= 0) {
if (e != 0 && (i = e & SMASK) < ws.length &&
(w = ws[i]) != null && w.eventCount == (e | INT_SIGN)) {
final boolean tryCompensate(long c) {
WorkQueue[] ws = workQueues;
int pc = parallelism, e = (int)c, m, tc;
if (ws != null && (m = ws.length - 1) >= 0 && e >= 0 && ctl == c) {
WorkQueue w = ws[e & m];
if (e != 0 && w != null) {
Thread p;
long nc = ((long)(w.nextWait & E_MASK) |
(c & (AC_MASK|TC_MASK)));
if (U.compareAndSwapLong(this, CTL, c, nc)) {
w.eventCount = (e + E_SEQ) & E_MASK;
int ne = (e + E_SEQ) & E_MASK;
if (w.eventCount == (e | INT_SIGN) &&
U.compareAndSwapLong(this, CTL, c, nc)) {
w.eventCount = ne;
if ((p = w.parker) != null)
U.unpark(p);
return true; // replace with idle worker
......@@ -2008,23 +1978,20 @@ public class ForkJoinPool extends AbstractExecutorService {
*/
final int awaitJoin(WorkQueue joiner, ForkJoinTask<?> task) {
int s = 0;
if (joiner != null && task != null && (s = task.status) >= 0) {
if (task != null && (s = task.status) >= 0 && joiner != null) {
ForkJoinTask<?> prevJoin = joiner.currentJoin;
joiner.currentJoin = task;
do {} while ((s = task.status) >= 0 && !joiner.isEmpty() &&
joiner.tryRemoveAndExec(task)); // process local tasks
if (s >= 0 && (s = task.status) >= 0) {
helpSignal(task, joiner.poolIndex);
if ((s = task.status) >= 0 &&
(task instanceof CountedCompleter))
s = helpComplete(task, LIFO_QUEUE);
}
do {} while (joiner.tryRemoveAndExec(task) && // process local tasks
(s = task.status) >= 0);
if (s >= 0 && (task instanceof CountedCompleter))
s = helpComplete(joiner, (CountedCompleter<?>)task, Integer.MAX_VALUE);
long cc = 0; // for stability checks
while (s >= 0 && (s = task.status) >= 0) {
if ((!joiner.isEmpty() || // try helping
(s = tryHelpStealer(joiner, task)) == 0) &&
if ((s = tryHelpStealer(joiner, task)) == 0 &&
(s = task.status) >= 0) {
helpSignal(task, joiner.poolIndex);
if ((s = task.status) >= 0 && tryCompensate()) {
if (!tryCompensate(cc))
cc = ctl;
else {
if (task.trySetSignal() && (s = task.status) >= 0) {
synchronized (task) {
if (task.status >= 0) {
......@@ -2037,9 +2004,11 @@ public class ForkJoinPool extends AbstractExecutorService {
task.notifyAll();
}
}
long c; // re-activate
long c; // reactivate
do {} while (!U.compareAndSwapLong
(this, CTL, c = ctl, c + AC_UNIT));
(this, CTL, c = ctl,
((c & ~AC_MASK) |
((c & AC_MASK) + AC_UNIT))));
}
}
}
......@@ -2061,15 +2030,11 @@ public class ForkJoinPool extends AbstractExecutorService {
if (joiner != null && task != null && (s = task.status) >= 0) {
ForkJoinTask<?> prevJoin = joiner.currentJoin;
joiner.currentJoin = task;
do {} while ((s = task.status) >= 0 && !joiner.isEmpty() &&
joiner.tryRemoveAndExec(task));
if (s >= 0 && (s = task.status) >= 0) {
helpSignal(task, joiner.poolIndex);
if ((s = task.status) >= 0 &&
(task instanceof CountedCompleter))
s = helpComplete(task, LIFO_QUEUE);
}
if (s >= 0 && joiner.isEmpty()) {
do {} while (joiner.tryRemoveAndExec(task) && // process local tasks
(s = task.status) >= 0);
if (s >= 0) {
if (task instanceof CountedCompleter)
helpComplete(joiner, (CountedCompleter<?>)task, Integer.MAX_VALUE);
do {} while (task.status >= 0 &&
tryHelpStealer(joiner, task) > 0);
}
......@@ -2081,14 +2046,14 @@ public class ForkJoinPool extends AbstractExecutorService {
* Returns a (probably) non-empty steal queue, if one is found
* during a scan, else null. This method must be retried by
* caller if, by the time it tries to use the queue, it is empty.
* @param r a (random) seed for scanning
*/
private WorkQueue findNonEmptyStealQueue(int r) {
private WorkQueue findNonEmptyStealQueue() {
int r = ThreadLocalRandom.nextSecondarySeed();
for (;;) {
int ps = plock, m; WorkQueue[] ws; WorkQueue q;
if ((ws = workQueues) != null && (m = ws.length - 1) >= 0) {
for (int j = (m + 1) << 2; j >= 0; --j) {
if ((q = ws[(((r + j) << 1) | 1) & m]) != null &&
if ((q = ws[(((r - j) << 1) | 1) & m]) != null &&
q.base - q.top < 0)
return q;
}
......@@ -2105,35 +2070,36 @@ public class ForkJoinPool extends AbstractExecutorService {
* find tasks either.
*/
final void helpQuiescePool(WorkQueue w) {
ForkJoinTask<?> ps = w.currentSteal;
for (boolean active = true;;) {
long c; WorkQueue q; ForkJoinTask<?> t; int b;
while ((t = w.nextLocalTask()) != null) {
if (w.base - w.top < 0)
signalWork(w);
while ((t = w.nextLocalTask()) != null)
t.doExec();
}
if ((q = findNonEmptyStealQueue(w.nextSeed())) != null) {
if ((q = findNonEmptyStealQueue()) != null) {
if (!active) { // re-establish active count
active = true;
do {} while (!U.compareAndSwapLong
(this, CTL, c = ctl, c + AC_UNIT));
(this, CTL, c = ctl,
((c & ~AC_MASK) |
((c & AC_MASK) + AC_UNIT))));
}
if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null) {
if (q.base - q.top < 0)
signalWork(q);
w.runSubtask(t);
(w.currentSteal = t).doExec();
w.currentSteal = ps;
}
}
else if (active) { // decrement active count without queuing
long nc = (c = ctl) - AC_UNIT;
if ((int)(nc >> AC_SHIFT) + (config & SMASK) == 0)
return; // bypass decrement-then-increment
long nc = ((c = ctl) & ~AC_MASK) | ((c & AC_MASK) - AC_UNIT);
if ((int)(nc >> AC_SHIFT) + parallelism == 0)
break; // bypass decrement-then-increment
if (U.compareAndSwapLong(this, CTL, c, nc))
active = false;
}
else if ((int)((c = ctl) >> AC_SHIFT) + (config & SMASK) == 0 &&
U.compareAndSwapLong(this, CTL, c, c + AC_UNIT))
return;
else if ((int)((c = ctl) >> AC_SHIFT) + parallelism <= 0 &&
U.compareAndSwapLong
(this, CTL, c, ((c & ~AC_MASK) |
((c & AC_MASK) + AC_UNIT))))
break;
}
}
......@@ -2147,13 +2113,10 @@ public class ForkJoinPool extends AbstractExecutorService {
WorkQueue q; int b;
if ((t = w.nextLocalTask()) != null)
return t;
if ((q = findNonEmptyStealQueue(w.nextSeed())) == null)
if ((q = findNonEmptyStealQueue()) == null)
return null;
if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null) {
if (q.base - q.top < 0)
signalWork(q);
if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
return t;
}
}
}
......@@ -2206,7 +2169,7 @@ public class ForkJoinPool extends AbstractExecutorService {
static int getSurplusQueuedTaskCount() {
Thread t; ForkJoinWorkerThread wt; ForkJoinPool pool; WorkQueue q;
if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) {
int p = (pool = (wt = (ForkJoinWorkerThread)t).pool).config & SMASK;
int p = (pool = (wt = (ForkJoinWorkerThread)t).pool).parallelism;
int n = (q = wt.workQueue).top - q.base;
int a = (int)(pool.ctl >> AC_SHIFT) + p;
return n - (a > (p >>>= 1) ? 0 :
......@@ -2236,7 +2199,7 @@ public class ForkJoinPool extends AbstractExecutorService {
*/
private boolean tryTerminate(boolean now, boolean enable) {
int ps;
if (this == common) // cannot shut down
if (this == common) // cannot shut down
return false;
if ((ps = plock) >= 0) { // enable by setting plock
if (!enable)
......@@ -2250,7 +2213,7 @@ public class ForkJoinPool extends AbstractExecutorService {
}
for (long c;;) {
if (((c = ctl) & STOP_BIT) != 0) { // already terminating
if ((short)(c >>> TC_SHIFT) == -(config & SMASK)) {
if ((short)(c >>> TC_SHIFT) + parallelism <= 0) {
synchronized (this) {
notifyAll(); // signal when 0 workers
}
......@@ -2259,17 +2222,15 @@ public class ForkJoinPool extends AbstractExecutorService {
}
if (!now) { // check if idle & no tasks
WorkQueue[] ws; WorkQueue w;
if ((int)(c >> AC_SHIFT) != -(config & SMASK))
if ((int)(c >> AC_SHIFT) + parallelism > 0)
return false;
if ((ws = workQueues) != null) {
for (int i = 0; i < ws.length; ++i) {
if ((w = ws[i]) != null) {
if (!w.isEmpty()) { // signal unprocessed tasks
signalWork(w);
return false;
}
if ((i & 1) != 0 && w.eventCount >= 0)
return false; // unqueued inactive worker
if ((w = ws[i]) != null &&
(!w.isEmpty() ||
((i & 1) != 0 && w.eventCount >= 0))) {
signalWork(ws, w);
return false;
}
}
}
......@@ -2336,116 +2297,67 @@ public class ForkJoinPool extends AbstractExecutorService {
/**
* Tries to pop the given task from submitter's queue in common pool.
*/
static boolean tryExternalUnpush(ForkJoinTask<?> t) {
ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
ForkJoinTask<?>[] a; int m, s, z;
if (t != null &&
(z = ThreadLocalRandom.getProbe()) != 0 &&
(p = common) != null &&
(ws = p.workQueues) != null &&
(m = ws.length - 1) >= 0 &&
(q = ws[m & z & SQMASK]) != null &&
(s = q.top) != q.base &&
(a = q.array) != null) {
final boolean tryExternalUnpush(ForkJoinTask<?> task) {
WorkQueue joiner; ForkJoinTask<?>[] a; int m, s;
WorkQueue[] ws = workQueues;
int z = ThreadLocalRandom.getProbe();
boolean popped = false;
if (ws != null && (m = ws.length - 1) >= 0 &&
(joiner = ws[z & m & SQMASK]) != null &&
joiner.base != (s = joiner.top) &&
(a = joiner.array) != null) {
long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE;
if (U.getObject(a, j) == t &&
U.compareAndSwapInt(q, QLOCK, 0, 1)) {
if (q.array == a && q.top == s && // recheck
U.compareAndSwapObject(a, j, t, null)) {
q.top = s - 1;
q.qlock = 0;
return true;
if (U.getObject(a, j) == task &&
U.compareAndSwapInt(joiner, QLOCK, 0, 1)) {
if (joiner.top == s && joiner.array == a &&
U.compareAndSwapObject(a, j, task, null)) {
joiner.top = s - 1;
popped = true;
}
q.qlock = 0;
joiner.qlock = 0;
}
}
return false;
return popped;
}
/**
* Tries to pop and run local tasks within the same computation
* as the given root. On failure, tries to help complete from
* other queues via helpComplete.
*/
private void externalHelpComplete(WorkQueue q, ForkJoinTask<?> root) {
ForkJoinTask<?>[] a; int m;
if (q != null && (a = q.array) != null && (m = (a.length - 1)) >= 0 &&
root != null && root.status >= 0) {
for (;;) {
int s, u; Object o; CountedCompleter<?> task = null;
if ((s = q.top) - q.base > 0) {
long j = ((m & (s - 1)) << ASHIFT) + ABASE;
if ((o = U.getObject(a, j)) != null &&
(o instanceof CountedCompleter)) {
CountedCompleter<?> t = (CountedCompleter<?>)o, r = t;
do {
if (r == root) {
if (U.compareAndSwapInt(q, QLOCK, 0, 1)) {
if (q.array == a && q.top == s &&
U.compareAndSwapObject(a, j, t, null)) {
q.top = s - 1;
task = t;
}
q.qlock = 0;
}
break;
}
} while ((r = r.completer) != null);
final int externalHelpComplete(CountedCompleter<?> task, int maxTasks) {
WorkQueue joiner; int m;
WorkQueue[] ws = workQueues;
int j = ThreadLocalRandom.getProbe();
int s = 0;
if (ws != null && (m = ws.length - 1) >= 0 &&
(joiner = ws[j & m & SQMASK]) != null && task != null) {
int scans = m + m + 1;
long c = 0L; // for stability check
j |= 1; // poll odd queues
for (int k = scans; ; j += 2) {
WorkQueue q;
if ((s = task.status) < 0)
break;
else if (joiner.externalPopAndExecCC(task)) {
if (--maxTasks <= 0) {
s = task.status;
break;
}
k = scans;
}
if (task != null)
task.doExec();
if (root.status < 0 ||
(config != 0 &&
((u = (int)(ctl >>> 32)) >= 0 || (u >> UAC_SHIFT) >= 0)))
break;
if (task == null) {
helpSignal(root, q.poolIndex);
if (root.status >= 0)
helpComplete(root, SHARED_QUEUE);
else if ((s = task.status) < 0)
break;
}
}
}
}
/**
* Tries to help execute or signal availability of the given task
* from submitter's queue in common pool.
*/
static void externalHelpJoin(ForkJoinTask<?> t) {
// Some hard-to-avoid overlap with tryExternalUnpush
ForkJoinPool p; WorkQueue[] ws; WorkQueue q, w;
ForkJoinTask<?>[] a; int m, s, n, z;
if (t != null &&
(z = ThreadLocalRandom.getProbe()) != 0 &&
(p = common) != null &&
(ws = p.workQueues) != null &&
(m = ws.length - 1) >= 0 &&
(q = ws[m & z & SQMASK]) != null &&
(a = q.array) != null) {
int am = a.length - 1;
if ((s = q.top) != q.base) {
long j = ((am & (s - 1)) << ASHIFT) + ABASE;
if (U.getObject(a, j) == t &&
U.compareAndSwapInt(q, QLOCK, 0, 1)) {
if (q.array == a && q.top == s &&
U.compareAndSwapObject(a, j, t, null)) {
q.top = s - 1;
q.qlock = 0;
t.doExec();
else if ((q = ws[j & m]) != null && q.pollAndExecCC(task)) {
if (--maxTasks <= 0) {
s = task.status;
break;
}
else
q.qlock = 0;
k = scans;
}
else if (--k < 0) {
if (c == (c = ctl))
break;
k = scans;
}
}
if (t.status >= 0) {
if (t instanceof CountedCompleter)
p.externalHelpComplete(q, t);
else
p.helpSignal(t, q.poolIndex);
}
}
return s;
}
// Exported methods
......@@ -2517,7 +2429,7 @@ public class ForkJoinPool extends AbstractExecutorService {
this(checkParallelism(parallelism),
checkFactory(factory),
handler,
asyncMode,
(asyncMode ? FIFO_QUEUE : LIFO_QUEUE),
"ForkJoinPool-" + nextPoolId() + "-worker-");
checkPermission();
}
......@@ -2543,12 +2455,13 @@ public class ForkJoinPool extends AbstractExecutorService {
private ForkJoinPool(int parallelism,
ForkJoinWorkerThreadFactory factory,
UncaughtExceptionHandler handler,
boolean asyncMode,
int mode,
String workerNamePrefix) {
this.workerNamePrefix = workerNamePrefix;
this.factory = factory;
this.ueh = handler;
this.config = parallelism | (asyncMode ? (FIFO_QUEUE << 16) : 0);
this.mode = (short)mode;
this.parallelism = (short)parallelism;
long np = (long)(-parallelism); // offset ctl counts
this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
}
......@@ -2736,8 +2649,8 @@ public class ForkJoinPool extends AbstractExecutorService {
* @return the targeted parallelism level of this pool
*/
public int getParallelism() {
int par = (config & SMASK);
return (par > 0) ? par : 1;
int par;
return ((par = parallelism) > 0) ? par : 1;
}
/**
......@@ -2759,7 +2672,7 @@ public class ForkJoinPool extends AbstractExecutorService {
* @return the number of worker threads
*/
public int getPoolSize() {
return (config & SMASK) + (short)(ctl >>> TC_SHIFT);
return parallelism + (short)(ctl >>> TC_SHIFT);
}
/**
......@@ -2769,7 +2682,7 @@ public class ForkJoinPool extends AbstractExecutorService {
* @return {@code true} if this pool uses async mode
*/
public boolean getAsyncMode() {
return (config >>> 16) == FIFO_QUEUE;
return mode == FIFO_QUEUE;
}
/**
......@@ -2800,7 +2713,7 @@ public class ForkJoinPool extends AbstractExecutorService {
* @return the number of active threads
*/
public int getActiveThreadCount() {
int r = (config & SMASK) + (int)(ctl >> AC_SHIFT);
int r = parallelism + (int)(ctl >> AC_SHIFT);
return (r <= 0) ? 0 : r; // suppress momentarily negative values
}
......@@ -2816,7 +2729,7 @@ public class ForkJoinPool extends AbstractExecutorService {
* @return {@code true} if all threads are currently idle
*/
public boolean isQuiescent() {
return (int)(ctl >> AC_SHIFT) + (config & SMASK) == 0;
return parallelism + (int)(ctl >> AC_SHIFT) <= 0;
}
/**
......@@ -2979,7 +2892,7 @@ public class ForkJoinPool extends AbstractExecutorService {
}
}
}
int pc = (config & SMASK);
int pc = parallelism;
int tc = pc + (short)(c >>> TC_SHIFT);
int ac = pc + (int)(c >> AC_SHIFT);
if (ac < 0) // ignore transient negative
......@@ -3052,7 +2965,7 @@ public class ForkJoinPool extends AbstractExecutorService {
public boolean isTerminated() {
long c = ctl;
return ((c & STOP_BIT) != 0L &&
(short)(c >>> TC_SHIFT) == -(config & SMASK));
(short)(c >>> TC_SHIFT) + parallelism <= 0);
}
/**
......@@ -3071,7 +2984,7 @@ public class ForkJoinPool extends AbstractExecutorService {
public boolean isTerminating() {
long c = ctl;
return ((c & STOP_BIT) != 0L &&
(short)(c >>> TC_SHIFT) != -(config & SMASK));
(short)(c >>> TC_SHIFT) + parallelism > 0);
}
/**
......@@ -3108,19 +3021,20 @@ public class ForkJoinPool extends AbstractExecutorService {
long nanos = unit.toNanos(timeout);
if (isTerminated())
return true;
long startTime = System.nanoTime();
boolean terminated = false;
if (nanos <= 0L)
return false;
long deadline = System.nanoTime() + nanos;
synchronized (this) {
for (long waitTime = nanos, millis = 0L;;) {
if (terminated = isTerminated() ||
waitTime <= 0L ||
(millis = unit.toMillis(waitTime)) <= 0L)
break;
wait(millis);
waitTime = nanos - (System.nanoTime() - startTime);
for (;;) {
if (isTerminated())
return true;
if (nanos <= 0L)
return false;
long millis = TimeUnit.NANOSECONDS.toMillis(nanos);
wait(millis > 0L ? millis : 1L);
nanos = deadline - System.nanoTime();
}
}
return terminated;
}
/**
......@@ -3159,11 +3073,8 @@ public class ForkJoinPool extends AbstractExecutorService {
ForkJoinTask<?> t; WorkQueue q; int b;
if ((q = ws[r++ & m]) != null && (b = q.base) - q.top < 0) {
found = true;
if ((t = q.pollAt(b)) != null) {
if (q.base - q.top < 0)
signalWork(q);
if ((t = q.pollAt(b)) != null)
t.doExec();
}
break;
}
}
......@@ -3278,21 +3189,8 @@ public class ForkJoinPool extends AbstractExecutorService {
Thread t = Thread.currentThread();
if (t instanceof ForkJoinWorkerThread) {
ForkJoinPool p = ((ForkJoinWorkerThread)t).pool;
while (!blocker.isReleasable()) { // variant of helpSignal
WorkQueue[] ws; WorkQueue q; int m, u;
if ((ws = p.workQueues) != null && (m = ws.length - 1) >= 0) {
for (int i = 0; i <= m; ++i) {
if (blocker.isReleasable())
return;
if ((q = ws[i]) != null && q.base - q.top < 0) {
p.signalWork(q);
if ((u = (int)(p.ctl >>> 32)) >= 0 ||
(u >> UAC_SHIFT) >= 0)
break;
}
}
}
if (p.tryCompensate()) {
while (!blocker.isReleasable()) {
if (p.tryCompensate(p.ctl)) {
try {
do {} while (!blocker.isReleasable() &&
!blocker.block());
......@@ -3330,6 +3228,7 @@ public class ForkJoinPool extends AbstractExecutorService {
private static final long STEALCOUNT;
private static final long PLOCK;
private static final long INDEXSEED;
private static final long QBASE;
private static final long QLOCK;
static {
......@@ -3349,6 +3248,8 @@ public class ForkJoinPool extends AbstractExecutorService {
PARKBLOCKER = U.objectFieldOffset
(tk.getDeclaredField("parkBlocker"));
Class<?> wk = WorkQueue.class;
QBASE = U.objectFieldOffset
(wk.getDeclaredField("base"));
QLOCK = U.objectFieldOffset
(wk.getDeclaredField("qlock"));
Class<?> ak = ForkJoinTask[].class;
......@@ -3368,7 +3269,7 @@ public class ForkJoinPool extends AbstractExecutorService {
common = java.security.AccessController.doPrivileged
(new java.security.PrivilegedAction<ForkJoinPool>() {
public ForkJoinPool run() { return makeCommonPool(); }});
int par = common.config; // report 1 even if threads disabled
int par = common.parallelism; // report 1 even if threads disabled
commonParallelism = par > 0 ? par : 1;
}
......@@ -3381,7 +3282,7 @@ public class ForkJoinPool extends AbstractExecutorService {
ForkJoinWorkerThreadFactory factory
= defaultForkJoinWorkerThreadFactory;
UncaughtExceptionHandler handler = null;
try { // ignore exceptions in accesing/parsing properties
try { // ignore exceptions in accessing/parsing properties
String pp = System.getProperty
("java.util.concurrent.ForkJoinPool.common.parallelism");
String fp = System.getProperty
......@@ -3399,11 +3300,12 @@ public class ForkJoinPool extends AbstractExecutorService {
} catch (Exception ignore) {
}
if (parallelism < 0)
parallelism = Runtime.getRuntime().availableProcessors();
if (parallelism < 0 && // default 1 less than #cores
(parallelism = Runtime.getRuntime().availableProcessors() - 1) < 0)
parallelism = 0;
if (parallelism > MAX_CAP)
parallelism = MAX_CAP;
return new ForkJoinPool(parallelism, factory, handler, false,
return new ForkJoinPool(parallelism, factory, handler, LIFO_QUEUE,
"ForkJoinPool.commonPool-worker-");
}
......
src/share/classes/java/util/concurrent/ForkJoinTask.java
浏览文件 @ 381e10cf
......@@ -165,7 +165,7 @@ import java.lang.reflect.Constructor;
* supports other methods and techniques (for example the use of
* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that
* may be of use in constructing custom subclasses for problems that
* are not statically structured as DAGs. To support such usages a
* are not statically structured as DAGs. To support such usages, a
* ForkJoinTask may be atomically <em>tagged</em> with a {@code short}
* value using {@link #setForkJoinTaskTag} or {@link
* #compareAndSetForkJoinTaskTag} and checked using {@link
......@@ -314,25 +314,35 @@ public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
*/
private int externalAwaitDone() {
int s;
ForkJoinPool.externalHelpJoin(this);
boolean interrupted = false;
while ((s = status) >= 0) {
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
synchronized (this) {
if (status >= 0) {
try {
wait();
} catch (InterruptedException ie) {
interrupted = true;
ForkJoinPool cp = ForkJoinPool.common;
if ((s = status) >= 0) {
if (cp != null) {
if (this instanceof CountedCompleter)
s = cp.externalHelpComplete((CountedCompleter<?>)this, Integer.MAX_VALUE);
else if (cp.tryExternalUnpush(this))
s = doExec();
}
if (s >= 0 && (s = status) >= 0) {
boolean interrupted = false;
do {
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
synchronized (this) {
if (status >= 0) {
try {
wait();
} catch (InterruptedException ie) {
interrupted = true;
}
}
else
notifyAll();
}
}
else
notifyAll();
}
} while ((s = status) >= 0);
if (interrupted)
Thread.currentThread().interrupt();
}
}
if (interrupted)
Thread.currentThread().interrupt();
return s;
}
......@@ -341,9 +351,15 @@ public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
*/
private int externalInterruptibleAwaitDone() throws InterruptedException {
int s;
ForkJoinPool cp = ForkJoinPool.common;
if (Thread.interrupted())
throw new InterruptedException();
ForkJoinPool.externalHelpJoin(this);
if ((s = status) >= 0 && cp != null) {
if (this instanceof CountedCompleter)
cp.externalHelpComplete((CountedCompleter<?>)this, Integer.MAX_VALUE);
else if (cp.tryExternalUnpush(this))
doExec();
}
while ((s = status) >= 0) {
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
synchronized (this) {
......@@ -357,7 +373,6 @@ public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
return s;
}
/**
* Implementation for join, get, quietlyJoin. Directly handles
* only cases of already-completed, external wait, and
......@@ -629,14 +644,9 @@ public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
/**
* A version of "sneaky throw" to relay exceptions
*/
static void rethrow(final Throwable ex) {
if (ex != null) {
if (ex instanceof Error)
throw (Error)ex;
if (ex instanceof RuntimeException)
throw (RuntimeException)ex;
static void rethrow(Throwable ex) {
if (ex != null)
ForkJoinTask.<RuntimeException>uncheckedThrow(ex);
}
}
/**
......@@ -646,8 +656,7 @@ public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
*/
@SuppressWarnings("unchecked") static <T extends Throwable>
void uncheckedThrow(Throwable t) throws T {
if (t != null)
throw (T)t; // rely on vacuous cast
throw (T)t; // rely on vacuous cast
}
/**
......@@ -1010,6 +1019,7 @@ public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
// Messy in part because we measure in nanosecs, but wait in millisecs
int s; long ms;
long ns = unit.toNanos(timeout);
ForkJoinPool cp;
if ((s = status) >= 0 && ns > 0L) {
long deadline = System.nanoTime() + ns;
ForkJoinPool p = null;
......@@ -1021,8 +1031,12 @@ public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
w = wt.workQueue;
p.helpJoinOnce(w, this); // no retries on failure
}
else
ForkJoinPool.externalHelpJoin(this);
else if ((cp = ForkJoinPool.common) != null) {
if (this instanceof CountedCompleter)
cp.externalHelpComplete((CountedCompleter<?>)this, Integer.MAX_VALUE);
else if (cp.tryExternalUnpush(this))
doExec();
}
boolean canBlock = false;
boolean interrupted = false;
try {
......@@ -1030,7 +1044,7 @@ public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
if (w != null && w.qlock < 0)
cancelIgnoringExceptions(this);
else if (!canBlock) {
if (p == null || p.tryCompensate())
if (p == null || p.tryCompensate(p.ctl))
canBlock = true;
}
else {
......@@ -1171,7 +1185,7 @@ public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
Thread t;
return (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
((ForkJoinWorkerThread)t).workQueue.tryUnpush(this) :
ForkJoinPool.tryExternalUnpush(this));
ForkJoinPool.common.tryExternalUnpush(this));
}
/**
......@@ -1340,7 +1354,7 @@ public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
*
* @param e the expected tag value
* @param tag the new tag value
* @return true if successful; i.e., the current value was
* @return {@code true} if successful; i.e., the current value was
* equal to e and is now tag.
* @since 1.8
*/
......
src/share/classes/java/util/concurrent/ForkJoinWorkerThread.java
浏览文件 @ 381e10cf
......@@ -43,8 +43,8 @@ package java.util.concurrent;
* scheduling or execution. However, you can override initialization
* and termination methods surrounding the main task processing loop.
* If you do create such a subclass, you will also need to supply a
* custom {@link ForkJoinPool.ForkJoinWorkerThreadFactory} to use it
* in a {@code ForkJoinPool}.
* custom {@link ForkJoinPool.ForkJoinWorkerThreadFactory} to
* {@linkplain ForkJoinPool#ForkJoinPool use it} in a {@code ForkJoinPool}.
*
* @since 1.7
* @author Doug Lea
......@@ -89,16 +89,17 @@ public class ForkJoinWorkerThread extends Thread {
}
/**
* Returns the index number of this thread in its pool. The
* returned value ranges from zero to the maximum number of
* threads (minus one) that have ever been created in the pool.
* This method may be useful for applications that track status or
* collect results per-worker rather than per-task.
* Returns the unique index number of this thread in its pool.
* The returned value ranges from zero to the maximum number of
* threads (minus one) that may exist in the pool, and does not
* change during the lifetime of the thread. This method may be
* useful for applications that track status or collect results
* per-worker-thread rather than per-task.
*
* @return the index number
*/
public int getPoolIndex() {
return workQueue.poolIndex;
return workQueue.poolIndex >>> 1; // ignore odd/even tag bit
}
/**
......
src/share/classes/java/util/concurrent/Future.java
浏览文件 @ 381e10cf
......@@ -36,19 +36,19 @@
package java.util.concurrent;
/**
* A <tt>Future</tt> represents the result of an asynchronous
* A {@code Future} represents the result of an asynchronous
* computation. Methods are provided to check if the computation is
* complete, to wait for its completion, and to retrieve the result of
* the computation. The result can only be retrieved using method
* <tt>get</tt> when the computation has completed, blocking if
* {@code get} when the computation has completed, blocking if
* necessary until it is ready. Cancellation is performed by the
* <tt>cancel</tt> method. Additional methods are provided to
* {@code cancel} method. Additional methods are provided to
* determine if the task completed normally or was cancelled. Once a
* computation has completed, the computation cannot be cancelled.
* If you would like to use a <tt>Future</tt> for the sake
* If you would like to use a {@code Future} for the sake
* of cancellability but not provide a usable result, you can
* declare types of the form {@code Future<?>} and
* return <tt>null</tt> as a result of the underlying task.
* return {@code null} as a result of the underlying task.
*
* <p>
* <b>Sample Usage</b> (Note that the following classes are all
......@@ -72,9 +72,9 @@ package java.util.concurrent;
* }
* }}</pre>
*
* The {@link FutureTask} class is an implementation of <tt>Future</tt> that
* implements <tt>Runnable</tt>, and so may be executed by an <tt>Executor</tt>.
* For example, the above construction with <tt>submit</tt> could be replaced by:
* The {@link FutureTask} class is an implementation of {@code Future} that
* implements {@code Runnable}, and so may be executed by an {@code Executor}.
* For example, the above construction with {@code submit} could be replaced by:
* <pre> {@code
* FutureTask<String> future =
* new FutureTask<String>(new Callable<String>() {
......@@ -91,7 +91,7 @@ package java.util.concurrent;
* @see Executor
* @since 1.5
* @author Doug Lea
* @param <V> The result type returned by this Future's <tt>get</tt> method
* @param <V> The result type returned by this Future's {@code get} method
*/
public interface Future<V> {
......@@ -99,41 +99,41 @@ public interface Future<V> {
* Attempts to cancel execution of this task. This attempt will
* fail if the task has already completed, has already been cancelled,
* or could not be cancelled for some other reason. If successful,
* and this task has not started when <tt>cancel</tt> is called,
* and this task has not started when {@code cancel} is called,
* this task should never run. If the task has already started,
* then the <tt>mayInterruptIfRunning</tt> parameter determines
* then the {@code mayInterruptIfRunning} parameter determines
* whether the thread executing this task should be interrupted in
* an attempt to stop the task.
*
* <p>After this method returns, subsequent calls to {@link #isDone} will
* always return <tt>true</tt>. Subsequent calls to {@link #isCancelled}
* will always return <tt>true</tt> if this method returned <tt>true</tt>.
* always return {@code true}. Subsequent calls to {@link #isCancelled}
* will always return {@code true} if this method returned {@code true}.
*
* @param mayInterruptIfRunning <tt>true</tt> if the thread executing this
* @param mayInterruptIfRunning {@code true} if the thread executing this
* task should be interrupted; otherwise, in-progress tasks are allowed
* to complete
* @return <tt>false</tt> if the task could not be cancelled,
* @return {@code false} if the task could not be cancelled,
* typically because it has already completed normally;
* <tt>true</tt> otherwise
* {@code true} otherwise
*/
boolean cancel(boolean mayInterruptIfRunning);
/**
* Returns <tt>true</tt> if this task was cancelled before it completed
* Returns {@code true} if this task was cancelled before it completed
* normally.
*
* @return <tt>true</tt> if this task was cancelled before it completed
* @return {@code true} if this task was cancelled before it completed
*/
boolean isCancelled();
/**
* Returns <tt>true</tt> if this task completed.
* Returns {@code true} if this task completed.
*
* Completion may be due to normal termination, an exception, or
* cancellation -- in all of these cases, this method will return
* <tt>true</tt>.
* {@code true}.
*
* @return <tt>true</tt> if this task completed
* @return {@code true} if this task completed
*/
boolean isDone();
......
src/share/classes/java/util/concurrent/FutureTask.java
浏览文件 @ 381e10cf
......@@ -162,19 +162,23 @@ public class FutureTask<V> implements RunnableFuture<V> {
}
public boolean cancel(boolean mayInterruptIfRunning) {
if (state != NEW)
if (!(state == NEW &&
UNSAFE.compareAndSwapInt(this, stateOffset, NEW,
mayInterruptIfRunning ? INTERRUPTING : CANCELLED)))
return false;
if (mayInterruptIfRunning) {
if (!UNSAFE.compareAndSwapInt(this, stateOffset, NEW, INTERRUPTING))
return false;
Thread t = runner;
if (t != null)
t.interrupt();
UNSAFE.putOrderedInt(this, stateOffset, INTERRUPTED); // final state
try { // in case call to interrupt throws exception
if (mayInterruptIfRunning) {
try {
Thread t = runner;
if (t != null)
t.interrupt();
} finally { // final state
UNSAFE.putOrderedInt(this, stateOffset, INTERRUPTED);
}
}
} finally {
finishCompletion();
}
else if (!UNSAFE.compareAndSwapInt(this, stateOffset, NEW, CANCELLED))
return false;
finishCompletion();
return true;
}
......@@ -288,7 +292,7 @@ public class FutureTask<V> implements RunnableFuture<V> {
* designed for use with tasks that intrinsically execute more
* than once.
*
* @return true if successfully run and reset
* @return {@code true} if successfully run and reset
*/
protected boolean runAndReset() {
if (state != NEW ||
......
src/share/classes/java/util/concurrent/RecursiveAction.java
浏览文件 @ 381e10cf
......@@ -63,7 +63,7 @@ package java.util.concurrent;
* }
* }
* // implementation details follow:
* final static int THRESHOLD = 1000;
* static final int THRESHOLD = 1000;
* void sortSequentially(int lo, int hi) {
* Arrays.sort(array, lo, hi);
* }
......@@ -140,21 +140,21 @@ package java.util.concurrent;
* int h = hi;
* Applyer right = null;
* while (h - l > 1 && getSurplusQueuedTaskCount() <= 3) {
* int mid = (l + h) >>> 1;
* right = new Applyer(array, mid, h, right);
* right.fork();
* h = mid;
* int mid = (l + h) >>> 1;
* right = new Applyer(array, mid, h, right);
* right.fork();
* h = mid;
* }
* double sum = atLeaf(l, h);
* while (right != null) {
* if (right.tryUnfork()) // directly calculate if not stolen
* sum += right.atLeaf(right.lo, right.hi);
* if (right.tryUnfork()) // directly calculate if not stolen
* sum += right.atLeaf(right.lo, right.hi);
* else {
* right.join();
* sum += right.result;
* }
* right = right.next;
* }
* right.join();
* sum += right.result;
* }
* right = right.next;
* }
* result = sum;
* }
* }}</pre>
......
src/share/classes/java/util/concurrent/RecursiveTask.java
浏览文件 @ 381e10cf
......@@ -46,7 +46,7 @@ package java.util.concurrent;
* Fibonacci(int n) { this.n = n; }
* Integer compute() {
* if (n <= 1)
* return n;
* return n;
* Fibonacci f1 = new Fibonacci(n - 1);
* f1.fork();
* Fibonacci f2 = new Fibonacci(n - 2);
......@@ -75,6 +75,7 @@ public abstract class RecursiveTask<V> extends ForkJoinTask<V> {
/**
* The main computation performed by this task.
* @return the result of the computation
*/
protected abstract V compute();
......
src/share/classes/java/util/concurrent/RejectedExecutionException.java
浏览文件 @ 381e10cf
......@@ -46,14 +46,14 @@ public class RejectedExecutionException extends RuntimeException {
private static final long serialVersionUID = -375805702767069545L;
/**
* Constructs a <tt>RejectedExecutionException</tt> with no detail message.
* Constructs a {@code RejectedExecutionException} with no detail message.
* The cause is not initialized, and may subsequently be
* initialized by a call to {@link #initCause(Throwable) initCause}.
*/
public RejectedExecutionException() { }
/**
* Constructs a <tt>RejectedExecutionException</tt> with the
* Constructs a {@code RejectedExecutionException} with the
* specified detail message. The cause is not initialized, and may
* subsequently be initialized by a call to {@link
* #initCause(Throwable) initCause}.
......@@ -65,7 +65,7 @@ public class RejectedExecutionException extends RuntimeException {
}
/**
* Constructs a <tt>RejectedExecutionException</tt> with the
* Constructs a {@code RejectedExecutionException} with the
* specified detail message and cause.
*
* @param message the detail message
......@@ -77,10 +77,10 @@ public class RejectedExecutionException extends RuntimeException {
}
/**
* Constructs a <tt>RejectedExecutionException</tt> with the
* Constructs a {@code RejectedExecutionException} with the
* specified cause. The detail message is set to {@code (cause ==
* null ? null : cause.toString())} (which typically contains
* the class and detail message of <tt>cause</tt>).
* the class and detail message of {@code cause}).
*
* @param cause the cause (which is saved for later retrieval by the
* {@link #getCause()} method)
......
src/share/classes/java/util/concurrent/RunnableFuture.java
浏览文件 @ 381e10cf
......@@ -37,13 +37,13 @@ package java.util.concurrent;
/**
* A {@link Future} that is {@link Runnable}. Successful execution of
* the <tt>run</tt> method causes completion of the <tt>Future</tt>
* the {@code run} method causes completion of the {@code Future}
* and allows access to its results.
* @see FutureTask
* @see Executor
* @since 1.6
* @author Doug Lea
* @param <V> The result type returned by this Future's <tt>get</tt> method
* @param <V> The result type returned by this Future's {@code get} method
*/
public interface RunnableFuture<V> extends Runnable, Future<V> {
/**
......
src/share/classes/java/util/concurrent/RunnableScheduledFuture.java
浏览文件 @ 381e10cf
......@@ -37,22 +37,22 @@ package java.util.concurrent;
/**
* A {@link ScheduledFuture} that is {@link Runnable}. Successful
* execution of the <tt>run</tt> method causes completion of the
* <tt>Future</tt> and allows access to its results.
* execution of the {@code run} method causes completion of the
* {@code Future} and allows access to its results.
* @see FutureTask
* @see Executor
* @since 1.6
* @author Doug Lea
* @param <V> The result type returned by this Future's <tt>get</tt> method
* @param <V> The result type returned by this Future's {@code get} method
*/
public interface RunnableScheduledFuture<V> extends RunnableFuture<V>, ScheduledFuture<V> {
/**
* Returns true if this is a periodic task. A periodic task may
* Returns {@code true} if this task is periodic. A periodic task may
* re-run according to some schedule. A non-periodic task can be
* run only once.
*
* @return true if this task is periodic
* @return {@code true} if this task is periodic
*/
boolean isPeriodic();
}
src/share/classes/java/util/concurrent/ScheduledExecutorService.java
浏览文件 @ 381e10cf
......@@ -39,30 +39,30 @@ package java.util.concurrent;
* An {@link ExecutorService} that can schedule commands to run after a given
* delay, or to execute periodically.
*
* <p> The <tt>schedule</tt> methods create tasks with various delays
* <p>The {@code schedule} methods create tasks with various delays
* and return a task object that can be used to cancel or check
* execution. The <tt>scheduleAtFixedRate</tt> and
* <tt>scheduleWithFixedDelay</tt> methods create and execute tasks
* execution. The {@code scheduleAtFixedRate} and
* {@code scheduleWithFixedDelay} methods create and execute tasks
* that run periodically until cancelled.
*
* <p> Commands submitted using the {@link Executor#execute} and
* {@link ExecutorService} <tt>submit</tt> methods are scheduled with
* a requested delay of zero. Zero and negative delays (but not
* periods) are also allowed in <tt>schedule</tt> methods, and are
* <p>Commands submitted using the {@link Executor#execute(Runnable)}
* and {@link ExecutorService} {@code submit} methods are scheduled
* with a requested delay of zero. Zero and negative delays (but not
* periods) are also allowed in {@code schedule} methods, and are
* treated as requests for immediate execution.
*
* <p>All <tt>schedule</tt> methods accept <em>relative</em> delays and
* <p>All {@code schedule} methods accept <em>relative</em> delays and
* periods as arguments, not absolute times or dates. It is a simple
* matter to transform an absolute time represented as a {@link
* java.util.Date} to the required form. For example, to schedule at
* a certain future <tt>date</tt>, you can use: <tt>schedule(task,
* a certain future {@code date}, you can use: {@code schedule(task,
* date.getTime() - System.currentTimeMillis(),
* TimeUnit.MILLISECONDS)</tt>. Beware however that expiration of a
* relative delay need not coincide with the current <tt>Date</tt> at
* TimeUnit.MILLISECONDS)}. Beware however that expiration of a
* relative delay need not coincide with the current {@code Date} at
* which the task is enabled due to network time synchronization
* protocols, clock drift, or other factors.
*
* The {@link Executors} class provides convenient factory methods for
* <p>The {@link Executors} class provides convenient factory methods for
* the ScheduledExecutorService implementations provided in this package.
*
* <h3>Usage Example</h3>
......@@ -101,8 +101,8 @@ public interface ScheduledExecutorService extends ExecutorService {
* @param delay the time from now to delay execution
* @param unit the time unit of the delay parameter
* @return a ScheduledFuture representing pending completion of
* the task and whose <tt>get()</tt> method will return
* <tt>null</tt> upon completion
* the task and whose {@code get()} method will return
* {@code null} upon completion
* @throws RejectedExecutionException if the task cannot be
* scheduled for execution
* @throws NullPointerException if command is null
......@@ -129,8 +129,8 @@ public interface ScheduledExecutorService extends ExecutorService {
* Creates and executes a periodic action that becomes enabled first
* after the given initial delay, and subsequently with the given
* period; that is executions will commence after
* <tt>initialDelay</tt> then <tt>initialDelay+period</tt>, then
* <tt>initialDelay + 2 * period</tt>, and so on.
* {@code initialDelay} then {@code initialDelay+period}, then
* {@code initialDelay + 2 * period}, and so on.
* If any execution of the task
* encounters an exception, subsequent executions are suppressed.
* Otherwise, the task will only terminate via cancellation or
......@@ -143,7 +143,7 @@ public interface ScheduledExecutorService extends ExecutorService {
* @param period the period between successive executions
* @param unit the time unit of the initialDelay and period parameters
* @return a ScheduledFuture representing pending completion of
* the task, and whose <tt>get()</tt> method will throw an
* the task, and whose {@code get()} method will throw an
* exception upon cancellation
* @throws RejectedExecutionException if the task cannot be
* scheduled for execution
......@@ -170,7 +170,7 @@ public interface ScheduledExecutorService extends ExecutorService {
* execution and the commencement of the next
* @param unit the time unit of the initialDelay and delay parameters
* @return a ScheduledFuture representing pending completion of
* the task, and whose <tt>get()</tt> method will throw an
* the task, and whose {@code get()} method will throw an
* exception upon cancellation
* @throws RejectedExecutionException if the task cannot be
* scheduled for execution
......
src/share/classes/java/util/concurrent/ScheduledThreadPoolExecutor.java
浏览文件 @ 381e10cf
......@@ -81,7 +81,7 @@ import java.util.*;
* without threads to handle tasks once they become eligible to run.
*
* <p><b>Extension notes:</b> This class overrides the
* {@link ThreadPoolExecutor#execute execute} and
* {@link ThreadPoolExecutor#execute(Runnable) execute} and
* {@link AbstractExecutorService#submit(Runnable) submit}
* methods to generate internal {@link ScheduledFuture} objects to
* control per-task delays and scheduling. To preserve
......@@ -256,9 +256,9 @@ public class ScheduledThreadPoolExecutor
}
/**
* Returns true if this is a periodic (not a one-shot) action.
* Returns {@code true} if this is a periodic (not a one-shot) action.
*
* @return true if periodic
* @return {@code true} if periodic
*/
public boolean isPeriodic() {
return period != 0;
......@@ -315,7 +315,7 @@ public class ScheduledThreadPoolExecutor
* is shut down, rejects the task. Otherwise adds task to queue
* and starts a thread, if necessary, to run it. (We cannot
* prestart the thread to run the task because the task (probably)
* shouldn't be run yet,) If the pool is shut down while the task
* shouldn't be run yet.) If the pool is shut down while the task
* is being added, cancel and remove it if required by state and
* run-after-shutdown parameters.
*
......@@ -654,7 +654,7 @@ public class ScheduledThreadPoolExecutor
* {@code false} when already shutdown.
* This value is by default {@code false}.
*
* @param value if {@code true}, continue after shutdown, else don't.
* @param value if {@code true}, continue after shutdown, else don't
* @see #getContinueExistingPeriodicTasksAfterShutdownPolicy
*/
public void setContinueExistingPeriodicTasksAfterShutdownPolicy(boolean value) {
......@@ -686,7 +686,7 @@ public class ScheduledThreadPoolExecutor
* {@code false} when already shutdown.
* This value is by default {@code true}.
*
* @param value if {@code true}, execute after shutdown, else don't.
* @param value if {@code true}, execute after shutdown, else don't
* @see #getExecuteExistingDelayedTasksAfterShutdownPolicy
*/
public void setExecuteExistingDelayedTasksAfterShutdownPolicy(boolean value) {
......@@ -1081,7 +1081,8 @@ public class ScheduledThreadPoolExecutor
long delay = first.getDelay(NANOSECONDS);
if (delay <= 0)
return finishPoll(first);
else if (leader != null)
first = null; // don't retain ref while waiting
if (leader != null)
available.await();
else {
Thread thisThread = Thread.currentThread();
......@@ -1121,6 +1122,7 @@ public class ScheduledThreadPoolExecutor
return finishPoll(first);
if (nanos <= 0)
return null;
first = null; // don't retain ref while waiting
if (nanos < delay || leader != null)
nanos = available.awaitNanos(nanos);
else {
......
src/share/classes/java/util/concurrent/ThreadPoolExecutor.java
浏览文件 @ 381e10cf
......@@ -75,22 +75,23 @@ import java.util.*;
* corePoolSize (see {@link #getCorePoolSize}) and
* maximumPoolSize (see {@link #getMaximumPoolSize}).
*
* When a new task is submitted in method {@link #execute}, and fewer
* than corePoolSize threads are running, a new thread is created to
* handle the request, even if other worker threads are idle. If
* there are more than corePoolSize but less than maximumPoolSize
* threads running, a new thread will be created only if the queue is
* full. By setting corePoolSize and maximumPoolSize the same, you
* create a fixed-size thread pool. By setting maximumPoolSize to an
* essentially unbounded value such as {@code Integer.MAX_VALUE}, you
* allow the pool to accommodate an arbitrary number of concurrent
* tasks. Most typically, core and maximum pool sizes are set only
* upon construction, but they may also be changed dynamically using
* {@link #setCorePoolSize} and {@link #setMaximumPoolSize}. </dd>
* When a new task is submitted in method {@link #execute(Runnable)},
* and fewer than corePoolSize threads are running, a new thread is
* created to handle the request, even if other worker threads are
* idle. If there are more than corePoolSize but less than
* maximumPoolSize threads running, a new thread will be created only
* if the queue is full. By setting corePoolSize and maximumPoolSize
* the same, you create a fixed-size thread pool. By setting
* maximumPoolSize to an essentially unbounded value such as {@code
* Integer.MAX_VALUE}, you allow the pool to accommodate an arbitrary
* number of concurrent tasks. Most typically, core and maximum pool
* sizes are set only upon construction, but they may also be changed
* dynamically using {@link #setCorePoolSize} and {@link
* #setMaximumPoolSize}. </dd>
*
* <dt>On-demand construction</dt>
*
* <dd> By default, even core threads are initially created and
* <dd>By default, even core threads are initially created and
* started only when new tasks arrive, but this can be overridden
* dynamically using method {@link #prestartCoreThread} or {@link
* #prestartAllCoreThreads}. You probably want to prestart threads if
......@@ -117,17 +118,17 @@ import java.util.*;
*
* <dd>If the pool currently has more than corePoolSize threads,
* excess threads will be terminated if they have been idle for more
* than the keepAliveTime (see {@link #getKeepAliveTime}). This
* provides a means of reducing resource consumption when the pool is
* not being actively used. If the pool becomes more active later, new
* threads will be constructed. This parameter can also be changed
* dynamically using method {@link #setKeepAliveTime}. Using a value
* of {@code Long.MAX_VALUE} {@link TimeUnit#NANOSECONDS} effectively
* disables idle threads from ever terminating prior to shut down. By
* default, the keep-alive policy applies only when there are more
* than corePoolSizeThreads. But method {@link
* #allowCoreThreadTimeOut(boolean)} can be used to apply this
* time-out policy to core threads as well, so long as the
* than the keepAliveTime (see {@link #getKeepAliveTime(TimeUnit)}).
* This provides a means of reducing resource consumption when the
* pool is not being actively used. If the pool becomes more active
* later, new threads will be constructed. This parameter can also be
* changed dynamically using method {@link #setKeepAliveTime(long,
* TimeUnit)}. Using a value of {@code Long.MAX_VALUE} {@link
* TimeUnit#NANOSECONDS} effectively disables idle threads from ever
* terminating prior to shut down. By default, the keep-alive policy
* applies only when there are more than corePoolSize threads. But
* method {@link #allowCoreThreadTimeOut(boolean)} can be used to
* apply this time-out policy to core threads as well, so long as the
* keepAliveTime value is non-zero. </dd>
*
* <dt>Queuing</dt>
......@@ -197,14 +198,14 @@ import java.util.*;
*
* <dt>Rejected tasks</dt>
*
* <dd> New tasks submitted in method {@link #execute} will be
* <em>rejected</em> when the Executor has been shut down, and also
* when the Executor uses finite bounds for both maximum threads and
* work queue capacity, and is saturated. In either case, the {@code
* execute} method invokes the {@link
* RejectedExecutionHandler#rejectedExecution} method of its {@link
* RejectedExecutionHandler}. Four predefined handler policies are
* provided:
* <dd>New tasks submitted in method {@link #execute(Runnable)} will be
* <em>rejected</em> when the Executor has been shut down, and also when
* the Executor uses finite bounds for both maximum threads and work queue
* capacity, and is saturated. In either case, the {@code execute} method
* invokes the {@link
* RejectedExecutionHandler#rejectedExecution(Runnable, ThreadPoolExecutor)}
* method of its {@link RejectedExecutionHandler}. Four predefined handler
* policies are provided:
*
* <ol>
*
......@@ -234,30 +235,31 @@ import java.util.*;
*
* <dt>Hook methods</dt>
*
* <dd>This class provides {@code protected} overridable {@link
* #beforeExecute} and {@link #afterExecute} methods that are called
* <dd>This class provides {@code protected} overridable
* {@link #beforeExecute(Thread, Runnable)} and
* {@link #afterExecute(Runnable, Throwable)} methods that are called
* before and after execution of each task. These can be used to
* manipulate the execution environment; for example, reinitializing
* ThreadLocals, gathering statistics, or adding log
* entries. Additionally, method {@link #terminated} can be overridden
* to perform any special processing that needs to be done once the
* Executor has fully terminated.
* ThreadLocals, gathering statistics, or adding log entries.
* Additionally, method {@link #terminated} can be overridden to perform
* any special processing that needs to be done once the Executor has
* fully terminated.
*
* <p>If hook or callback methods throw exceptions, internal worker
* threads may in turn fail and abruptly terminate.</dd>
*
* <dt>Queue maintenance</dt>
*
* <dd> Method {@link #getQueue} allows access to the work queue for
* purposes of monitoring and debugging. Use of this method for any
* other purpose is strongly discouraged. Two supplied methods,
* {@link #remove} and {@link #purge} are available to assist in
* storage reclamation when large numbers of queued tasks become
* cancelled.</dd>
* <dd>Method {@link #getQueue()} allows access to the work queue
* for purposes of monitoring and debugging. Use of this method for
* any other purpose is strongly discouraged. Two supplied methods,
* {@link #remove(Runnable)} and {@link #purge} are available to
* assist in storage reclamation when large numbers of queued tasks
* become cancelled.</dd>
*
* <dt>Finalization</dt>
*
* <dd> A pool that is no longer referenced in a program <em>AND</em>
* <dd>A pool that is no longer referenced in a program <em>AND</em>
* has no remaining threads will be {@code shutdown} automatically. If
* you would like to ensure that unreferenced pools are reclaimed even
* if users forget to call {@link #shutdown}, then you must arrange
......@@ -267,7 +269,7 @@ import java.util.*;
*
* </dl>
*
* <p> <b>Extension example</b>. Most extensions of this class
* <p><b>Extension example</b>. Most extensions of this class
* override one or more of the protected hook methods. For example,
* here is a subclass that adds a simple pause/resume feature:
*
......@@ -336,7 +338,7 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
* bookkeeping before terminating. The user-visible pool size is
* reported as the current size of the workers set.
*
* The runState provides the main lifecyle control, taking on values:
* The runState provides the main lifecycle control, taking on values:
*
* RUNNING: Accept new tasks and process queued tasks
* SHUTDOWN: Don't accept new tasks, but process queued tasks
......@@ -406,14 +408,14 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
}
/**
* Attempt to CAS-increment the workerCount field of ctl.
* Attempts to CAS-increment the workerCount field of ctl.
*/
private boolean compareAndIncrementWorkerCount(int expect) {
return ctl.compareAndSet(expect, expect + 1);
}
/**
* Attempt to CAS-decrement the workerCount field of ctl.
* Attempts to CAS-decrement the workerCount field of ctl.
*/
private boolean compareAndDecrementWorkerCount(int expect) {
return ctl.compareAndSet(expect, expect - 1);
......@@ -498,7 +500,7 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
* We go further and preserve pool invariants even in the face of
* errors such as OutOfMemoryError, that might be thrown while
* trying to create threads. Such errors are rather common due to
* the need to allocate a native stack in Thread#start, and users
* the need to allocate a native stack in Thread.start, and users
* will want to perform clean pool shutdown to clean up. There
* will likely be enough memory available for the cleanup code to
* complete without encountering yet another OutOfMemoryError.
......@@ -848,7 +850,7 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
*/
private List<Runnable> drainQueue() {
BlockingQueue<Runnable> q = workQueue;
List<Runnable> taskList = new ArrayList<Runnable>();
ArrayList<Runnable> taskList = new ArrayList<Runnable>();
q.drainTo(taskList);
if (!q.isEmpty()) {
for (Runnable r : q.toArray(new Runnable[0])) {
......@@ -873,7 +875,7 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
* factory fails to create a thread when asked. If the thread
* creation fails, either due to the thread factory returning
* null, or due to an exception (typically OutOfMemoryError in
* Thread#start), we roll back cleanly.
* Thread.start()), we roll back cleanly.
*
* @param firstTask the task the new thread should run first (or
* null if none). Workers are created with an initial first task
......@@ -920,17 +922,16 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
boolean workerAdded = false;
Worker w = null;
try {
final ReentrantLock mainLock = this.mainLock;
w = new Worker(firstTask);
final Thread t = w.thread;
if (t != null) {
final ReentrantLock mainLock = this.mainLock;
mainLock.lock();
try {
// Recheck while holding lock.
// Back out on ThreadFactory failure or if
// shut down before lock acquired.
int c = ctl.get();
int rs = runStateOf(c);
int rs = runStateOf(ctl.get());
if (rs < SHUTDOWN ||
(rs == SHUTDOWN && firstTask == null)) {
......@@ -1029,7 +1030,8 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
* 4. This worker timed out waiting for a task, and timed-out
* workers are subject to termination (that is,
* {@code allowCoreThreadTimeOut || workerCount > corePoolSize})
* both before and after the timed wait.
* both before and after the timed wait, and if the queue is
* non-empty, this worker is not the last thread in the pool.
*
* @return task, or null if the worker must exit, in which case
* workerCount is decremented
......@@ -1037,7 +1039,6 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
private Runnable getTask() {
boolean timedOut = false; // Did the last poll() time out?
retry:
for (;;) {
int c = ctl.get();
int rs = runStateOf(c);
......@@ -1048,20 +1049,16 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
return null;
}
boolean timed; // Are workers subject to culling?
int wc = workerCountOf(c);
for (;;) {
int wc = workerCountOf(c);
timed = allowCoreThreadTimeOut || wc > corePoolSize;
// Are workers subject to culling?
boolean timed = allowCoreThreadTimeOut || wc > corePoolSize;
if (wc <= maximumPoolSize && ! (timedOut && timed))
break;
if ((wc > maximumPoolSize || (timed && timedOut))
&& (wc > 1 || workQueue.isEmpty())) {
if (compareAndDecrementWorkerCount(c))
return null;
c = ctl.get(); // Re-read ctl
if (runStateOf(c) != rs)
continue retry;
// else CAS failed due to workerCount change; retry inner loop
continue;
}
try {
......@@ -1090,9 +1087,9 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
* usually leads processWorkerExit to replace this thread.
*
* 2. Before running any task, the lock is acquired to prevent
* other pool interrupts while the task is executing, and
* clearInterruptsForTaskRun called to ensure that unless pool is
* stopping, this thread does not have its interrupt set.
* other pool interrupts while the task is executing, and then we
* ensure that unless pool is stopping, this thread does not have
* its interrupt set.
*
* 3. Each task run is preceded by a call to beforeExecute, which
* might throw an exception, in which case we cause thread to die
......@@ -1100,12 +1097,12 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
* the task.
*
* 4. Assuming beforeExecute completes normally, we run the task,
* gathering any of its thrown exceptions to send to
* afterExecute. We separately handle RuntimeException, Error
* (both of which the specs guarantee that we trap) and arbitrary
* Throwables. Because we cannot rethrow Throwables within
* Runnable.run, we wrap them within Errors on the way out (to the
* thread's UncaughtExceptionHandler). Any thrown exception also
* gathering any of its thrown exceptions to send to afterExecute.
* We separately handle RuntimeException, Error (both of which the
* specs guarantee that we trap) and arbitrary Throwables.
* Because we cannot rethrow Throwables within Runnable.run, we
* wrap them within Errors on the way out (to the thread's
* UncaughtExceptionHandler). Any thrown exception also
* conservatively causes thread to die.
*
* 5. After task.run completes, we call afterExecute, which may
......@@ -1443,7 +1440,7 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
* ignored or suppressed interruption, causing this executor not
* to properly terminate.
*
* @return true if terminating but not yet terminated
* @return {@code true} if terminating but not yet terminated
*/
public boolean isTerminating() {
int c = ctl.get();
......@@ -1497,7 +1494,7 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
* Returns the thread factory used to create new threads.
*
* @return the current thread factory
* @see #setThreadFactory
* @see #setThreadFactory(ThreadFactory)
*/
public ThreadFactory getThreadFactory() {
return threadFactory;
......@@ -1520,7 +1517,7 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
* Returns the current handler for unexecutable tasks.
*
* @return the current handler
* @see #setRejectedExecutionHandler
* @see #setRejectedExecutionHandler(RejectedExecutionHandler)
*/
public RejectedExecutionHandler getRejectedExecutionHandler() {
return handler;
......@@ -1692,7 +1689,7 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
* @param unit the time unit of the {@code time} argument
* @throws IllegalArgumentException if {@code time} less than zero or
* if {@code time} is zero and {@code allowsCoreThreadTimeOut}
* @see #getKeepAliveTime
* @see #getKeepAliveTime(TimeUnit)
*/
public void setKeepAliveTime(long time, TimeUnit unit) {
if (time < 0)
......@@ -1713,7 +1710,7 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
*
* @param unit the desired time unit of the result
* @return the time limit
* @see #setKeepAliveTime
* @see #setKeepAliveTime(long, TimeUnit)
*/
public long getKeepAliveTime(TimeUnit unit) {
return unit.convert(keepAliveTime, TimeUnit.NANOSECONDS);
......@@ -1738,7 +1735,7 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
* present, thus causing it not to be run if it has not already
* started.
*
* <p> This method may be useful as one part of a cancellation
* <p>This method may be useful as one part of a cancellation
* scheme. It may fail to remove tasks that have been converted
* into other forms before being placed on the internal queue. For
* example, a task entered using {@code submit} might be
......@@ -1747,7 +1744,7 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
* remove those Futures that have been cancelled.
*
* @param task the task to remove
* @return true if the task was removed
* @return {@code true} if the task was removed
*/
public boolean remove(Runnable task) {
boolean removed = workQueue.remove(task);
......@@ -2042,7 +2039,7 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
*
* @param r the runnable task requested to be executed
* @param e the executor attempting to execute this task
* @throws RejectedExecutionException always.
* @throws RejectedExecutionException always
*/
public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
throw new RejectedExecutionException("Task " + r.toString() +
......@@ -2099,4 +2096,3 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
}
}
}
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