--- jsr166/src/jsr166y/ForkJoinPool.java 2009/07/24 23:47:01 1.21
+++ jsr166/src/jsr166y/ForkJoinPool.java 2009/07/27 21:41:53 1.29
@@ -5,14 +5,23 @@
*/
package jsr166y;
-import java.util.*;
+
import java.util.concurrent.*;
-import java.util.concurrent.locks.*;
-import java.util.concurrent.atomic.*;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.LockSupport;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
/**
- * An {@link ExecutorService} for running {@link ForkJoinTask}s. A
- * ForkJoinPool provides the entry point for submissions from
+ * An {@link ExecutorService} for running {@link ForkJoinTask}s.
+ * A ForkJoinPool provides the entry point for submissions from
* non-ForkJoinTasks, as well as management and monitoring operations.
* Normally a single ForkJoinPool is used for a large number of
* submitted tasks. Otherwise, use would not usually outweigh the
@@ -25,29 +34,29 @@ import java.util.concurrent.atomic.*;
* (eventually blocking if none exist). This makes them efficient when
* most tasks spawn other subtasks (as do most ForkJoinTasks), as well
* as the mixed execution of some plain Runnable- or Callable- based
- * activities along with ForkJoinTasks. When setting
- * {@code setAsyncMode}, a ForkJoinPools may also be appropriate for
- * use with fine-grained tasks that are never joined. Otherwise, other
- * ExecutorService implementations are typically more appropriate
- * choices.
+ * activities along with ForkJoinTasks. When setting {@linkplain
+ * #setAsyncMode async mode}, a ForkJoinPool may also be appropriate
+ * for use with fine-grained tasks that are never joined. Otherwise,
+ * other ExecutorService implementations are typically more
+ * appropriate choices.
*
*
A ForkJoinPool may be constructed with a given parallelism level
* (target pool size), which it attempts to maintain by dynamically
* adding, suspending, or resuming threads, even if some tasks are
* waiting to join others. However, no such adjustments are performed
* in the face of blocked IO or other unmanaged synchronization. The
- * nested {@code ManagedBlocker} interface enables extension of
+ * nested {@link ManagedBlocker} interface enables extension of
* the kinds of synchronization accommodated. The target parallelism
- * level may also be changed dynamically ({@code setParallelism})
+ * level may also be changed dynamically ({@link #setParallelism})
* and thread construction can be limited using methods
- * {@code setMaximumPoolSize} and/or
- * {@code setMaintainsParallelism}.
+ * {@link #setMaximumPoolSize} and/or
+ * {@link #setMaintainsParallelism}.
*
*
In addition to execution and lifecycle control methods, this
* class provides status check methods (for example
- * {@code getStealCount}) that are intended to aid in developing,
+ * {@link #getStealCount}) that are intended to aid in developing,
* tuning, and monitoring fork/join applications. Also, method
- * {@code toString} returns indications of pool state in a
+ * {@link #toString} returns indications of pool state in a
* convenient form for informal monitoring.
*
*
Implementation notes: This implementation restricts the
@@ -302,8 +311,8 @@ public class ForkJoinPool extends Abstra
}
/**
- * Returns true if argument represents zero active count and
- * nonzero runstate, which is the triggering condition for
+ * Returns {@code true} if argument represents zero active count
+ * and nonzero runstate, which is the triggering condition for
* terminating on shutdown.
*/
private static boolean canTerminateOnShutdown(int c) {
@@ -539,6 +548,8 @@ public class ForkJoinPool extends Abstra
* Common code for execute, invoke and submit
*/
private void doSubmit(ForkJoinTask task) {
+ if (task == null)
+ throw new NullPointerException();
if (isShutdown())
throw new RejectedExecutionException();
if (workers == null)
@@ -574,7 +585,12 @@ public class ForkJoinPool extends Abstra
// AbstractExecutorService methods
public void execute(Runnable task) {
- doSubmit(new AdaptedRunnable(task, null));
+ ForkJoinTask> job;
+ if (task instanceof ForkJoinTask>) // avoid re-wrap
+ job = (ForkJoinTask>) task;
+ else
+ job = new AdaptedRunnable(task, null);
+ doSubmit(job);
}
public ForkJoinTask submit(Callable task) {
@@ -590,12 +606,30 @@ public class ForkJoinPool extends Abstra
}
public ForkJoinTask> submit(Runnable task) {
- ForkJoinTask job = new AdaptedRunnable(task, null);
+ ForkJoinTask> job;
+ if (task instanceof ForkJoinTask>) // avoid re-wrap
+ job = (ForkJoinTask>) task;
+ else
+ job = new AdaptedRunnable(task, null);
doSubmit(job);
return job;
}
/**
+ * Submits a ForkJoinTask for execution.
+ *
+ * @param task the task to submit
+ * @return the task
+ * @throws RejectedExecutionException if the task cannot be
+ * scheduled for execution
+ * @throws NullPointerException if the task is null
+ */
+ public ForkJoinTask submit(ForkJoinTask task) {
+ doSubmit(task);
+ return task;
+ }
+
+ /**
* Adaptor for Runnables. This implements RunnableFuture
* to be compliant with AbstractExecutorService constraints.
*/
@@ -686,7 +720,7 @@ public class ForkJoinPool extends Abstra
* Returns the handler for internal worker threads that terminate
* due to unrecoverable errors encountered while executing tasks.
*
- * @return the handler, or null if none
+ * @return the handler, or {@code null} if none
*/
public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
Thread.UncaughtExceptionHandler h;
@@ -707,7 +741,7 @@ public class ForkJoinPool extends Abstra
* as handler.
*
* @param h the new handler
- * @return the old handler, or null if none
+ * @return the old handler, or {@code null} if none
* @throws SecurityException if a security manager exists and
* the caller is not permitted to modify threads
* because it does not hold {@link
@@ -781,7 +815,7 @@ public class ForkJoinPool extends Abstra
/**
* Returns the number of worker threads that have started but not
* yet terminated. This result returned by this method may differ
- * from {@code getParallelism} when threads are created to
+ * from {@link #getParallelism} when threads are created to
* maintain parallelism when others are cooperatively blocked.
*
* @return the number of worker threads
@@ -817,12 +851,11 @@ public class ForkJoinPool extends Abstra
/**
- * Returns true if this pool dynamically maintains its target
- * parallelism level. If false, new threads are added only to
- * avoid possible starvation.
- * This setting is by default true.
+ * Returns {@code true} if this pool dynamically maintains its
+ * target parallelism level. If false, new threads are added only
+ * to avoid possible starvation. This setting is by default true.
*
- * @return true if maintains parallelism
+ * @return {@code true} if maintains parallelism
*/
public boolean getMaintainsParallelism() {
return maintainsParallelism;
@@ -833,7 +866,7 @@ public class ForkJoinPool extends Abstra
* parallelism level. If false, new threads are added only to
* avoid possible starvation.
*
- * @param enable true to maintains parallelism
+ * @param enable {@code true} to maintain parallelism
*/
public void setMaintainsParallelism(boolean enable) {
maintainsParallelism = enable;
@@ -844,12 +877,13 @@ public class ForkJoinPool extends Abstra
* tasks that are never joined. This mode may be more appropriate
* than default locally stack-based mode in applications in which
* worker threads only process asynchronous tasks. This method is
- * designed to be invoked only when pool is quiescent, and
+ * designed to be invoked only when the pool is quiescent, and
* typically only before any tasks are submitted. The effects of
* invocations at other times may be unpredictable.
*
- * @param async if true, use locally FIFO scheduling
+ * @param async if {@code true}, use locally FIFO scheduling
* @return the previous mode
+ * @see #getAsyncMode
*/
public boolean setAsyncMode(boolean async) {
boolean oldMode = locallyFifo;
@@ -866,10 +900,11 @@ public class ForkJoinPool extends Abstra
}
/**
- * Returns true if this pool uses local first-in-first-out
+ * Returns {@code true} if this pool uses local first-in-first-out
* scheduling mode for forked tasks that are never joined.
*
- * @return true if this pool uses async mode
+ * @return {@code true} if this pool uses async mode
+ * @see #setAsyncMode
*/
public boolean getAsyncMode() {
return locallyFifo;
@@ -910,15 +945,15 @@ public class ForkJoinPool extends Abstra
}
/**
- * Returns true if all worker threads are currently idle. An idle
- * worker is one that cannot obtain a task to execute because none
- * are available to steal from other threads, and there are no
- * pending submissions to the pool. This method is conservative;
- * it might not return true immediately upon idleness of all
- * threads, but will eventually become true if threads remain
- * inactive.
+ * Returns {@code true} if all worker threads are currently idle.
+ * An idle worker is one that cannot obtain a task to execute
+ * because none are available to steal from other threads, and
+ * there are no pending submissions to the pool. This method is
+ * conservative; it might not return {@code true} immediately upon
+ * idleness of all threads, but will eventually become true if
+ * threads remain inactive.
*
- * @return true if all threads are currently idle
+ * @return {@code true} if all threads are currently idle
*/
public boolean isQuiescent() {
return activeCountOf(runControl) == 0;
@@ -984,8 +1019,8 @@ public class ForkJoinPool extends Abstra
}
/**
- * Returns true if there are any tasks submitted to this pool
- * that have not yet begun executing.
+ * Returns {@code true} if there are any tasks submitted to this
+ * pool that have not yet begun executing.
*
* @return {@code true} if there are any queued submissions
*/
@@ -998,7 +1033,7 @@ public class ForkJoinPool extends Abstra
* available. This method may be useful in extensions to this
* class that re-assign work in systems with multiple pools.
*
- * @return the next submission, or null if none
+ * @return the next submission, or {@code null} if none
*/
protected ForkJoinTask> pollSubmission() {
return submissionQueue.poll();
@@ -1098,7 +1133,7 @@ public class ForkJoinPool extends Abstra
* method may or may not be rejected. Unlike some other executors,
* this method cancels rather than collects non-executed tasks
* upon termination, so always returns an empty list. However, you
- * can use method {@code drainTasksTo} before invoking this
+ * can use method {@link #drainTasksTo} before invoking this
* method to transfer unexecuted tasks to another collection.
*
* @return an empty list
@@ -1458,7 +1493,7 @@ public class ForkJoinPool extends Abstra
}
/**
- * Returns true if worker waiting on sync can proceed:
+ * Returns {@code true} if worker waiting on sync can proceed:
* - on signal (thread == null)
* - on event count advance (winning race to notify vs signaller)
* - on interrupt
@@ -1466,7 +1501,7 @@ public class ForkJoinPool extends Abstra
* If node was not signalled and event count not advanced on exit,
* then we also help advance event count.
*
- * @return true if node can be released
+ * @return {@code true} if node can be released
*/
final boolean syncIsReleasable(WaitQueueNode node) {
long prev = node.count;
@@ -1485,8 +1520,8 @@ public class ForkJoinPool extends Abstra
}
/**
- * Returns true if a new sync event occurred since last call to
- * sync or this method, if so, updating caller's count.
+ * Returns {@code true} if a new sync event occurred since last
+ * call to sync or this method, if so, updating caller's count.
*/
final boolean hasNewSyncEvent(ForkJoinWorkerThread w) {
long lc = w.lastEventCount;
@@ -1570,8 +1605,8 @@ public class ForkJoinPool extends Abstra
}
/**
- * Returns true if a spare thread appears to be needed. If
- * maintaining parallelism, returns true when the deficit in
+ * Returns {@code true} if a spare thread appears to be needed.
+ * If maintaining parallelism, returns true when the deficit in
* running threads is more than the surplus of total threads, and
* there is apparently some work to do. This self-limiting rule
* means that the more threads that have already been added, the
@@ -1740,10 +1775,10 @@ public class ForkJoinPool extends Abstra
/**
* Interface for extending managed parallelism for tasks running
* in ForkJoinPools. A ManagedBlocker provides two methods.
- * Method {@code isReleasable} must return true if blocking is not
- * necessary. Method {@code block} blocks the current thread if
- * necessary (perhaps internally invoking {@code isReleasable}
- * before actually blocking.).
+ * Method {@code isReleasable} must return {@code true} if
+ * blocking is not necessary. Method {@code block} blocks the
+ * current thread if necessary (perhaps internally invoking
+ * {@code isReleasable} before actually blocking.).
*
* For example, here is a ManagedBlocker based on a
* ReentrantLock:
@@ -1767,15 +1802,15 @@ public class ForkJoinPool extends Abstra
* Possibly blocks the current thread, for example waiting for
* a lock or condition.
*
- * @return true if no additional blocking is necessary (i.e.,
- * if isReleasable would return true)
+ * @return {@code true} if no additional blocking is necessary
+ * (i.e., if isReleasable would return true)
* @throws InterruptedException if interrupted while waiting
* (the method is not required to do so, but is allowed to)
*/
boolean block() throws InterruptedException;
/**
- * Returns true if blocking is unnecessary.
+ * Returns {@code true} if blocking is unnecessary.
*/
boolean isReleasable();
}
@@ -1785,7 +1820,7 @@ public class ForkJoinPool extends Abstra
* is a ForkJoinWorkerThread, this method possibly arranges for a
* spare thread to be activated if necessary to ensure parallelism
* while the current thread is blocked. If
- * {@code maintainParallelism} is true and the pool supports
+ * {@code maintainParallelism} is {@code true} and the pool supports
* it ({@link #getMaintainsParallelism}), this method attempts to
* maintain the pool's nominal parallelism. Otherwise it activates
* a thread only if necessary to avoid complete starvation. This
@@ -1803,10 +1838,10 @@ public class ForkJoinPool extends Abstra
* be expanded to ensure parallelism, and later adjusted.
*
* @param blocker the blocker
- * @param maintainParallelism if true and supported by this pool,
- * attempt to maintain the pool's nominal parallelism; otherwise
- * activate a thread only if necessary to avoid complete
- * starvation.
+ * @param maintainParallelism if {@code true} and supported by
+ * this pool, attempt to maintain the pool's nominal parallelism;
+ * otherwise activate a thread only if necessary to avoid
+ * complete starvation.
* @throws InterruptedException if blocker.block did so
*/
public static void managedBlock(ManagedBlocker blocker,
@@ -1842,55 +1877,19 @@ public class ForkJoinPool extends Abstra
return new AdaptedCallable(callable);
}
-
- // Unsafe mechanics for jsr166y 3rd party package.
- private static sun.misc.Unsafe getUnsafe() {
- try {
- return sun.misc.Unsafe.getUnsafe();
- } catch (SecurityException se) {
- try {
- return java.security.AccessController.doPrivileged
- (new java.security.PrivilegedExceptionAction() {
- public sun.misc.Unsafe run() throws Exception {
- return getUnsafeByReflection();
- }});
- } catch (java.security.PrivilegedActionException e) {
- throw new RuntimeException("Could not initialize intrinsics",
- e.getCause());
- }
- }
- }
-
- private static sun.misc.Unsafe getUnsafeByReflection()
- throws NoSuchFieldException, IllegalAccessException {
- java.lang.reflect.Field f =
- sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
- f.setAccessible(true);
- return (sun.misc.Unsafe) f.get(null);
- }
-
- private static long fieldOffset(String fieldName, Class> klazz) {
- try {
- return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
- } catch (NoSuchFieldException e) {
- // Convert Exception to Error
- NoSuchFieldError error = new NoSuchFieldError(fieldName);
- error.initCause(e);
- throw error;
- }
- }
+ // Unsafe mechanics
private static final sun.misc.Unsafe UNSAFE = getUnsafe();
- static final long eventCountOffset =
- fieldOffset("eventCount", ForkJoinPool.class);
- static final long workerCountsOffset =
- fieldOffset("workerCounts", ForkJoinPool.class);
- static final long runControlOffset =
- fieldOffset("runControl", ForkJoinPool.class);
- static final long syncStackOffset =
- fieldOffset("syncStack",ForkJoinPool.class);
- static final long spareStackOffset =
- fieldOffset("spareStack", ForkJoinPool.class);
+ private static final long eventCountOffset =
+ objectFieldOffset("eventCount", ForkJoinPool.class);
+ private static final long workerCountsOffset =
+ objectFieldOffset("workerCounts", ForkJoinPool.class);
+ private static final long runControlOffset =
+ objectFieldOffset("runControl", ForkJoinPool.class);
+ private static final long syncStackOffset =
+ objectFieldOffset("syncStack",ForkJoinPool.class);
+ private static final long spareStackOffset =
+ objectFieldOffset("spareStack", ForkJoinPool.class);
private boolean casEventCount(long cmp, long val) {
return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
@@ -1907,4 +1906,43 @@ public class ForkJoinPool extends Abstra
private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
}
+
+ private static long objectFieldOffset(String field, Class> klazz) {
+ try {
+ return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
+ } catch (NoSuchFieldException e) {
+ // Convert Exception to corresponding Error
+ NoSuchFieldError error = new NoSuchFieldError(field);
+ error.initCause(e);
+ throw error;
+ }
+ }
+
+ /**
+ * Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package.
+ * Replace with a simple call to Unsafe.getUnsafe when integrating
+ * into a jdk.
+ *
+ * @return a sun.misc.Unsafe
+ */
+ private static sun.misc.Unsafe getUnsafe() {
+ try {
+ return sun.misc.Unsafe.getUnsafe();
+ } catch (SecurityException se) {
+ try {
+ return java.security.AccessController.doPrivileged
+ (new java.security
+ .PrivilegedExceptionAction() {
+ public sun.misc.Unsafe run() throws Exception {
+ java.lang.reflect.Field f = sun.misc
+ .Unsafe.class.getDeclaredField("theUnsafe");
+ f.setAccessible(true);
+ return (sun.misc.Unsafe) f.get(null);
+ }});
+ } catch (java.security.PrivilegedActionException e) {
+ throw new RuntimeException("Could not initialize intrinsics",
+ e.getCause());
+ }
+ }
+ }
}