--- jsr166/src/jsr166y/ForkJoinPool.java	2009/01/12 17:16:18	1.4
+++ jsr166/src/jsr166y/ForkJoinPool.java	2009/07/23 23:23:41	1.18
@@ -27,7 +27,9 @@ import java.lang.reflect.*;
  * (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. Otherwise, other
+ * 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.
  *
@@ -36,24 +38,27 @@ import java.lang.reflect.*;
  * 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</code> interface enables extension of
+ * nested {@code ManagedBlocker} interface enables extension of
  * the kinds of synchronization accommodated.  The target parallelism
- * level may also be changed dynamically (<code>setParallelism</code>)
- * and dynamically thread construction can be limited using methods
- * <code>setMaximumPoolSize</code> and/or
- * <code>setMaintainsParallelism</code>.
+ * level may also be changed dynamically ({@code setParallelism})
+ * and thread construction can be limited using methods
+ * {@code setMaximumPoolSize} and/or
+ * {@code setMaintainsParallelism}.
  *
  * <p>In addition to execution and lifecycle control methods, this
  * class provides status check methods (for example
- * <code>getStealCount</code>) that are intended to aid in developing,
+ * {@code getStealCount}) that are intended to aid in developing,
  * tuning, and monitoring fork/join applications. Also, method
- * <code>toString</code> returns indications of pool state in a
+ * {@code toString} returns indications of pool state in a
  * convenient form for informal monitoring.
  *
  * <p><b>Implementation notes</b>: This implementation restricts the
  * maximum number of running threads to 32767. Attempts to create
  * pools with greater than the maximum result in
  * IllegalArgumentExceptions.
+ *
+ * @since 1.7
+ * @author Doug Lea
  */
 public class ForkJoinPool extends AbstractExecutorService {
 
@@ -79,13 +84,13 @@ public class ForkJoinPool extends Abstra
          * Returns a new worker thread operating in the given pool.
          *
          * @param pool the pool this thread works in
-         * @throws NullPointerException if pool is null;
+         * @throws NullPointerException if pool is null
          */
         public ForkJoinWorkerThread newThread(ForkJoinPool pool);
     }
 
     /**
-     * Default ForkJoinWorkerThreadFactory implementation, creates a
+     * Default ForkJoinWorkerThreadFactory implementation; creates a
      * new ForkJoinWorkerThread.
      */
     static class  DefaultForkJoinWorkerThreadFactory
@@ -131,11 +136,11 @@ public class ForkJoinPool extends Abstra
         new AtomicInteger();
 
     /**
-     * Array holding all worker threads in the pool. Array size must
-     * be a power of two.  Updates and replacements are protected by
-     * workerLock, but it is always kept in a consistent enough state
-     * to be randomly accessed without locking by workers performing
-     * work-stealing.
+     * Array holding all worker threads in the pool. Initialized upon
+     * first use. Array size must be a power of two.  Updates and
+     * replacements are protected by workerLock, but it is always kept
+     * in a consistent enough state to be randomly accessed without
+     * locking by workers performing work-stealing.
      */
     volatile ForkJoinWorkerThread[] workers;
 
@@ -151,7 +156,7 @@ public class ForkJoinPool extends Abstra
 
     /**
      * The uncaught exception handler used when any worker
-     * abrupty terminates
+     * abruptly terminates
      */
     private Thread.UncaughtExceptionHandler ueh;
 
@@ -179,7 +184,7 @@ public class ForkJoinPool extends Abstra
     private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue;
 
     /**
-     * Head of Treiber stack for barrier sync. See below for explanation
+     * Head of Treiber stack for barrier sync. See below for explanation.
      */
     private volatile WaitQueueNode syncStack;
 
@@ -204,13 +209,18 @@ public class ForkJoinPool extends Abstra
     private volatile int parallelism;
 
     /**
+     * True if use local fifo, not default lifo, for local polling
+     */
+    private volatile boolean locallyFifo;
+
+    /**
      * Holds number of total (i.e., created and not yet terminated)
      * and running (i.e., not blocked on joins or other managed sync)
      * threads, packed into one int to ensure consistent snapshot when
      * making decisions about creating and suspending spare
      * threads. Updated only by CAS.  Note: CASes in
-     * updateRunningCount and preJoin running active count is in low
-     * word, so need to be modified if this changes
+     * updateRunningCount and preJoin assume that running active count
+     * is in low word, so need to be modified if this changes.
      */
     private volatile int workerCounts;
 
@@ -219,26 +229,28 @@ public class ForkJoinPool extends Abstra
     private static int workerCountsFor(int t, int r) { return (t << 16) + r; }
 
     /**
-     * Add delta (which may be negative) to running count.  This must
+     * Adds delta (which may be negative) to running count.  This must
      * be called before (with negative arg) and after (with positive)
-     * any managed synchronization (i.e., mainly, joins)
+     * any managed synchronization (i.e., mainly, joins).
+     *
      * @param delta the number to add
      */
     final void updateRunningCount(int delta) {
         int s;
-        do;while (!casWorkerCounts(s = workerCounts, s + delta));
+        do {} while (!casWorkerCounts(s = workerCounts, s + delta));
     }
 
     /**
-     * Add delta (which may be negative) to both total and running
+     * Adds delta (which may be negative) to both total and running
      * count.  This must be called upon creation and termination of
      * worker threads.
+     *
      * @param delta the number to add
      */
     private void updateWorkerCount(int delta) {
         int d = delta + (delta << 16); // add to both lo and hi parts
         int s;
-        do;while (!casWorkerCounts(s = workerCounts, s + d));
+        do {} while (!casWorkerCounts(s = workerCounts, s + d));
     }
 
     /**
@@ -264,9 +276,10 @@ public class ForkJoinPool extends Abstra
     private static int runControlFor(int r, int a)   { return (r << 16) + a; }
 
     /**
-     * Try incrementing active count; fail on contention. Called by
-     * workers before/during executing tasks.
-     * @return true on success;
+     * Tries incrementing active count; fails on contention.
+     * Called by workers before/during executing tasks.
+     *
+     * @return true on success
      */
     final boolean tryIncrementActiveCount() {
         int c = runControl;
@@ -274,9 +287,10 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
-     * Try decrementing active count; fail on contention.
-     * Possibly trigger termination on success
+     * Tries decrementing active count; fails on contention.
+     * Possibly triggers termination on success.
      * Called by workers when they can't find tasks.
+     *
      * @return true on success
      */
     final boolean tryDecrementActiveCount() {
@@ -290,12 +304,13 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
-     * Return true if argument represents zero active count and
+     * Returns 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) {
-        return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit
+        // i.e. least bit is nonzero runState bit
+        return ((c & -c) >>> 16) != 0;
     }
 
     /**
@@ -321,12 +336,13 @@ public class ForkJoinPool extends Abstra
 
     /**
      * Creates a ForkJoinPool with a pool size equal to the number of
-     * processors available on the system and using the default
-     * ForkJoinWorkerThreadFactory,
+     * processors available on the system, using the default
+     * ForkJoinWorkerThreadFactory.
+     *
      * @throws SecurityException if a security manager exists and
      *         the caller is not permitted to modify threads
      *         because it does not hold {@link
-     *         java.lang.RuntimePermission}<code>("modifyThread")</code>,
+     *         java.lang.RuntimePermission}{@code ("modifyThread")}
      */
     public ForkJoinPool() {
         this(Runtime.getRuntime().availableProcessors(),
@@ -334,15 +350,16 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
-     * Creates a ForkJoinPool with the indicated parellelism level
-     * threads, and using the default ForkJoinWorkerThreadFactory,
+     * Creates a ForkJoinPool with the indicated parallelism level
+     * threads and using the default ForkJoinWorkerThreadFactory.
+     *
      * @param parallelism the number of worker threads
      * @throws IllegalArgumentException if parallelism less than or
      * equal to zero
      * @throws SecurityException if a security manager exists and
      *         the caller is not permitted to modify threads
      *         because it does not hold {@link
-     *         java.lang.RuntimePermission}<code>("modifyThread")</code>,
+     *         java.lang.RuntimePermission}{@code ("modifyThread")}
      */
     public ForkJoinPool(int parallelism) {
         this(parallelism, defaultForkJoinWorkerThreadFactory);
@@ -351,13 +368,14 @@ public class ForkJoinPool extends Abstra
     /**
      * Creates a ForkJoinPool with parallelism equal to the number of
      * processors available on the system and using the given
-     * ForkJoinWorkerThreadFactory,
+     * ForkJoinWorkerThreadFactory.
+     *
      * @param factory the factory for creating new threads
      * @throws NullPointerException if factory is null
      * @throws SecurityException if a security manager exists and
      *         the caller is not permitted to modify threads
      *         because it does not hold {@link
-     *         java.lang.RuntimePermission}<code>("modifyThread")</code>,
+     *         java.lang.RuntimePermission}{@code ("modifyThread")}
      */
     public ForkJoinPool(ForkJoinWorkerThreadFactory factory) {
         this(Runtime.getRuntime().availableProcessors(), factory);
@@ -369,12 +387,12 @@ public class ForkJoinPool extends Abstra
      * @param parallelism the targeted number of worker threads
      * @param factory the factory for creating new threads
      * @throws IllegalArgumentException if parallelism less than or
-     * equal to zero, or greater than implementation limit.
+     * equal to zero, or greater than implementation limit
      * @throws NullPointerException if factory is null
      * @throws SecurityException if a security manager exists and
      *         the caller is not permitted to modify threads
      *         because it does not hold {@link
-     *         java.lang.RuntimePermission}<code>("modifyThread")</code>,
+     *         java.lang.RuntimePermission}{@code ("modifyThread")}
      */
     public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) {
         if (parallelism <= 0 || parallelism > MAX_THREADS)
@@ -391,11 +409,12 @@ public class ForkJoinPool extends Abstra
         this.termination = workerLock.newCondition();
         this.stealCount = new AtomicLong();
         this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>();
-        createAndStartInitialWorkers(parallelism);
+        // worker array and workers are lazily constructed
     }
 
     /**
-     * Create new worker using factory.
+     * Creates a new worker thread using factory.
+     *
      * @param index the index to assign worker
      * @return new worker, or null of factory failed
      */
@@ -405,6 +424,7 @@ public class ForkJoinPool extends Abstra
         if (w != null) {
             w.poolIndex = index;
             w.setDaemon(true);
+            w.setAsyncMode(locallyFifo);
             w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index);
             if (h != null)
                 w.setUncaughtExceptionHandler(h);
@@ -413,15 +433,18 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
-     * Return a good size for worker array given pool size.
+     * Returns a good size for worker array given pool size.
      * Currently requires size to be a power of two.
      */
-    private static int arraySizeFor(int ps) {
-        return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1)));
+    private static int arraySizeFor(int poolSize) {
+        return (poolSize <= 1) ? 1 :
+            (1 << (32 - Integer.numberOfLeadingZeros(poolSize-1)));
     }
 
     /**
-     * Create or resize array if necessary to hold newLength
+     * Creates or resizes array if necessary to hold newLength.
+     * Call only under exclusion.
+     *
      * @return the array
      */
     private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) {
@@ -435,39 +458,46 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
-     * Try to shrink workers into smaller array after one or more terminate
+     * Tries to shrink workers into smaller array after one or more terminate.
      */
     private void tryShrinkWorkerArray() {
         ForkJoinWorkerThread[] ws = workers;
-        int len = ws.length;
-        int last = len - 1;
-        while (last >= 0 && ws[last] == null)
-            --last;
-        int newLength = arraySizeFor(last+1);
-        if (newLength < len)
-            workers = Arrays.copyOf(ws, newLength);
+        if (ws != null) {
+            int len = ws.length;
+            int last = len - 1;
+            while (last >= 0 && ws[last] == null)
+                --last;
+            int newLength = arraySizeFor(last+1);
+            if (newLength < len)
+                workers = Arrays.copyOf(ws, newLength);
+        }
     }
 
     /**
-     * Initial worker array and worker creation and startup. (This
-     * must be done under lock to avoid interference by some of the
-     * newly started threads while creating others.)
+     * Initializes workers if necessary.
      */
-    private void createAndStartInitialWorkers(int ps) {
-        final ReentrantLock lock = this.workerLock;
-        lock.lock();
-        try {
-            ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps);
-            for (int i = 0; i < ps; ++i) {
-                ForkJoinWorkerThread w = createWorker(i);
-                if (w != null) {
-                    ws[i] = w;
-                    w.start();
-                    updateWorkerCount(1);
+    final void ensureWorkerInitialization() {
+        ForkJoinWorkerThread[] ws = workers;
+        if (ws == null) {
+            final ReentrantLock lock = this.workerLock;
+            lock.lock();
+            try {
+                ws = workers;
+                if (ws == null) {
+                    int ps = parallelism;
+                    ws = ensureWorkerArrayCapacity(ps);
+                    for (int i = 0; i < ps; ++i) {
+                        ForkJoinWorkerThread w = createWorker(i);
+                        if (w != null) {
+                            ws[i] = w;
+                            w.start();
+                            updateWorkerCount(1);
+                        }
+                    }
                 }
+            } finally {
+                lock.unlock();
             }
-        } finally {
-            lock.unlock();
         }
     }
 
@@ -513,12 +543,15 @@ public class ForkJoinPool extends Abstra
     private <T> void doSubmit(ForkJoinTask<T> task) {
         if (isShutdown())
             throw new RejectedExecutionException();
+        if (workers == null)
+            ensureWorkerInitialization();
         submissionQueue.offer(task);
         signalIdleWorkers();
     }
 
     /**
-     * Performs the given task; returning its result upon completion
+     * Performs the given task, returning its result upon completion.
+     *
      * @param task the task
      * @return the task's result
      * @throws NullPointerException if task is null
@@ -531,6 +564,7 @@ public class ForkJoinPool extends Abstra
 
     /**
      * Arranges for (asynchronous) execution of the given task.
+     *
      * @param task the task
      * @throws NullPointerException if task is null
      * @throws RejectedExecutionException if pool is shut down
@@ -565,7 +599,7 @@ public class ForkJoinPool extends Abstra
 
     /**
      * Adaptor for Runnables. This implements RunnableFuture
-     * to be compliant with AbstractExecutorService constraints
+     * to be compliant with AbstractExecutorService constraints.
      */
     static final class AdaptedRunnable<T> extends ForkJoinTask<T>
         implements RunnableFuture<T> {
@@ -585,6 +619,7 @@ public class ForkJoinPool extends Abstra
             return true;
         }
         public void run() { invoke(); }
+        private static final long serialVersionUID = 5232453952276885070L;
     }
 
     /**
@@ -613,6 +648,7 @@ public class ForkJoinPool extends Abstra
             }
         }
         public void run() { invoke(); }
+        private static final long serialVersionUID = 2838392045355241008L;
     }
 
     public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) {
@@ -621,21 +657,23 @@ public class ForkJoinPool extends Abstra
         for (Callable<T> c : tasks)
             ts.add(new AdaptedCallable<T>(c));
         invoke(new InvokeAll<T>(ts));
-        return (List<Future<T>>)(List)ts;
+        return (List<Future<T>>) (List) ts;
     }
 
     static final class InvokeAll<T> extends RecursiveAction {
         final ArrayList<ForkJoinTask<T>> tasks;
         InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; }
         public void compute() {
-            try { invokeAll(tasks); } catch(Exception ignore) {}
+            try { invokeAll(tasks); }
+            catch (Exception ignore) {}
         }
+        private static final long serialVersionUID = -7914297376763021607L;
     }
 
     // Configuration and status settings and queries
 
     /**
-     * Returns the factory used for constructing new workers
+     * Returns the factory used for constructing new workers.
      *
      * @return the factory used for constructing new workers
      */
@@ -646,6 +684,7 @@ 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
      */
     public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
@@ -671,7 +710,7 @@ public class ForkJoinPool extends Abstra
      * @throws SecurityException if a security manager exists and
      *         the caller is not permitted to modify threads
      *         because it does not hold {@link
-     *         java.lang.RuntimePermission}<code>("modifyThread")</code>,
+     *         java.lang.RuntimePermission}{@code ("modifyThread")}
      */
     public Thread.UncaughtExceptionHandler
         setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) {
@@ -683,10 +722,12 @@ public class ForkJoinPool extends Abstra
             old = ueh;
             ueh = h;
             ForkJoinWorkerThread[] ws = workers;
-            for (int i = 0; i < ws.length; ++i) {
-                ForkJoinWorkerThread w = ws[i];
-                if (w != null)
-                    w.setUncaughtExceptionHandler(h);
+            if (ws != null) {
+                for (int i = 0; i < ws.length; ++i) {
+                    ForkJoinWorkerThread w = ws[i];
+                    if (w != null)
+                        w.setUncaughtExceptionHandler(h);
+                }
             }
         } finally {
             lock.unlock();
@@ -696,14 +737,15 @@ public class ForkJoinPool extends Abstra
 
 
     /**
-     * Sets the target paralleism level of this pool.
+     * Sets the target parallelism level of this pool.
+     *
      * @param parallelism the target parallelism
      * @throws IllegalArgumentException if parallelism less than or
-     * equal to zero or greater than maximum size bounds.
+     * equal to zero or greater than maximum size bounds
      * @throws SecurityException if a security manager exists and
      *         the caller is not permitted to modify threads
      *         because it does not hold {@link
-     *         java.lang.RuntimePermission}<code>("modifyThread")</code>,
+     *         java.lang.RuntimePermission}{@code ("modifyThread")}
      */
     public void setParallelism(int parallelism) {
         checkPermission();
@@ -738,7 +780,7 @@ 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</code> when threads are created to
+     * from {@code getParallelism} when threads are created to
      * maintain parallelism when others are cooperatively blocked.
      *
      * @return the number of worker threads
@@ -750,6 +792,7 @@ public class ForkJoinPool extends Abstra
     /**
      * Returns the maximum number of threads allowed to exist in the
      * pool, even if there are insufficient unblocked running threads.
+     *
      * @return the maximum
      */
     public int getMaximumPoolSize() {
@@ -761,8 +804,9 @@ public class ForkJoinPool extends Abstra
      * pool, even if there are insufficient unblocked running threads.
      * Setting this value has no effect on current pool size. It
      * controls construction of new threads.
+     *
      * @throws IllegalArgumentException if negative or greater then
-     * internal implementation limit.
+     * internal implementation limit
      */
     public void setMaximumPoolSize(int newMax) {
         if (newMax < 0 || newMax > MAX_THREADS)
@@ -775,7 +819,8 @@ 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;
+     * This setting is by default true.
+     *
      * @return true if maintains parallelism
      */
     public boolean getMaintainsParallelism() {
@@ -786,6 +831,7 @@ public class ForkJoinPool extends Abstra
      * Sets whether this pool dynamically maintains its target
      * parallelism level. If false, new threads are added only to
      * avoid possible starvation.
+     *
      * @param enable true to maintains parallelism
      */
     public void setMaintainsParallelism(boolean enable) {
@@ -793,6 +839,42 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
+     * Establishes local first-in-first-out scheduling mode for forked
+     * 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
+     * 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
+     * @return the previous mode
+     */
+    public boolean setAsyncMode(boolean async) {
+        boolean oldMode = locallyFifo;
+        locallyFifo = async;
+        ForkJoinWorkerThread[] ws = workers;
+        if (ws != null) {
+            for (int i = 0; i < ws.length; ++i) {
+                ForkJoinWorkerThread t = ws[i];
+                if (t != null)
+                    t.setAsyncMode(async);
+            }
+        }
+        return oldMode;
+    }
+
+    /**
+     * Returns 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
+     */
+    public boolean getAsyncMode() {
+        return locallyFifo;
+    }
+
+    /**
      * Returns an estimate of the number of worker threads that are
      * not blocked waiting to join tasks or for other managed
      * synchronization.
@@ -807,7 +889,8 @@ public class ForkJoinPool extends Abstra
      * Returns an estimate of the number of threads that are currently
      * stealing or executing tasks. This method may overestimate the
      * number of active threads.
-     * @return the number of active threads.
+     *
+     * @return the number of active threads
      */
     public int getActiveThreadCount() {
         return activeCountOf(runControl);
@@ -817,21 +900,23 @@ public class ForkJoinPool extends Abstra
      * Returns an estimate of the number of threads that are currently
      * idle waiting for tasks. This method may underestimate the
      * number of idle threads.
-     * @return the number of idle threads.
+     *
+     * @return the number of idle threads
      */
     final int getIdleThreadCount() {
         int c = runningCountOf(workerCounts) - activeCountOf(runControl);
-        return (c <= 0)? 0 : c;
+        return (c <= 0) ? 0 : c;
     }
 
     /**
      * 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
+     * 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.
+     *
      * @return true if all threads are currently idle
      */
     public boolean isQuiescent() {
@@ -843,18 +928,19 @@ public class ForkJoinPool extends Abstra
      * one thread's work queue by another. The reported value
      * underestimates the actual total number of steals when the pool
      * is not quiescent. This value may be useful for monitoring and
-     * tuning fork/join programs: In general, steal counts should be
+     * tuning fork/join programs: in general, steal counts should be
      * high enough to keep threads busy, but low enough to avoid
      * overhead and contention across threads.
-     * @return the number of steals.
+     *
+     * @return the number of steals
      */
     public long getStealCount() {
         return stealCount.get();
     }
 
     /**
-     * Accumulate steal count from a worker. Call only
-     * when worker known to be idle.
+     * Accumulates steal count from a worker.
+     * Call only when worker known to be idle.
      */
     private void updateStealCount(ForkJoinWorkerThread w) {
         int sc = w.getAndClearStealCount();
@@ -869,15 +955,18 @@ public class ForkJoinPool extends Abstra
      * an approximation, obtained by iterating across all threads in
      * the pool. This method may be useful for tuning task
      * granularities.
-     * @return the number of queued tasks.
+     *
+     * @return the number of queued tasks
      */
     public long getQueuedTaskCount() {
         long count = 0;
         ForkJoinWorkerThread[] ws = workers;
-        for (int i = 0; i < ws.length; ++i) {
-            ForkJoinWorkerThread t = ws[i];
-            if (t != null)
-                count += t.getQueueSize();
+        if (ws != null) {
+            for (int i = 0; i < ws.length; ++i) {
+                ForkJoinWorkerThread t = ws[i];
+                if (t != null)
+                    count += t.getQueueSize();
+            }
         }
         return count;
     }
@@ -886,7 +975,8 @@ public class ForkJoinPool extends Abstra
      * Returns an estimate of the number tasks submitted to this pool
      * that have not yet begun executing. This method takes time
      * proportional to the number of submissions.
-     * @return the number of queued submissions.
+     *
+     * @return the number of queued submissions
      */
     public int getQueuedSubmissionCount() {
         return submissionQueue.size();
@@ -895,7 +985,8 @@ public class ForkJoinPool extends Abstra
     /**
      * Returns true if there are any tasks submitted to this pool
      * that have not yet begun executing.
-     * @return <code>true</code> if there are any queued submissions.
+     *
+     * @return {@code true} if there are any queued submissions
      */
     public boolean hasQueuedSubmissions() {
         return !submissionQueue.isEmpty();
@@ -905,6 +996,7 @@ public class ForkJoinPool extends Abstra
      * Removes and returns the next unexecuted submission if one is
      * 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
      */
     protected ForkJoinTask<?> pollSubmission() {
@@ -912,6 +1004,36 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
+     * Removes all available unexecuted submitted and forked tasks
+     * from scheduling queues and adds them to the given collection,
+     * without altering their execution status. These may include
+     * artificially generated or wrapped tasks. This method is designed
+     * to be invoked only when the pool is known to be
+     * quiescent. Invocations at other times may not remove all
+     * tasks. A failure encountered while attempting to add elements
+     * to collection {@code c} may result in elements being in
+     * neither, either or both collections when the associated
+     * exception is thrown.  The behavior of this operation is
+     * undefined if the specified collection is modified while the
+     * operation is in progress.
+     *
+     * @param c the collection to transfer elements into
+     * @return the number of elements transferred
+     */
+    protected int drainTasksTo(Collection<ForkJoinTask<?>> c) {
+        int n = submissionQueue.drainTo(c);
+        ForkJoinWorkerThread[] ws = workers;
+        if (ws != null) {
+            for (int i = 0; i < ws.length; ++i) {
+                ForkJoinWorkerThread w = ws[i];
+                if (w != null)
+                    n += w.drainTasksTo(c);
+            }
+        }
+        return n;
+    }
+
+    /**
      * Returns a string identifying this pool, as well as its state,
      * including indications of run state, parallelism level, and
      * worker and task counts.
@@ -955,10 +1077,11 @@ public class ForkJoinPool extends Abstra
      * Invocation has no additional effect if already shut down.
      * Tasks that are in the process of being submitted concurrently
      * during the course of this method may or may not be rejected.
+     *
      * @throws SecurityException if a security manager exists and
      *         the caller is not permitted to modify threads
      *         because it does not hold {@link
-     *         java.lang.RuntimePermission}<code>("modifyThread")</code>,
+     *         java.lang.RuntimePermission}{@code ("modifyThread")}
      */
     public void shutdown() {
         checkPermission();
@@ -972,13 +1095,16 @@ public class ForkJoinPool extends Abstra
      * waiting tasks.  Tasks that are in the process of being
      * submitted or executed concurrently during the course of this
      * method may or may not be rejected. Unlike some other executors,
-     * this method cancels rather than collects non-executed tasks,
-     * so always returns an empty list.
+     * 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
+     * method to transfer unexecuted tasks to another collection.
+     *
      * @return an empty list
      * @throws SecurityException if a security manager exists and
      *         the caller is not permitted to modify threads
      *         because it does not hold {@link
-     *         java.lang.RuntimePermission}<code>("modifyThread")</code>,
+     *         java.lang.RuntimePermission}{@code ("modifyThread")}
      */
     public List<Runnable> shutdownNow() {
         checkPermission();
@@ -987,28 +1113,28 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
-     * Returns <code>true</code> if all tasks have completed following shut down.
+     * Returns {@code true} if all tasks have completed following shut down.
      *
-     * @return <code>true</code> if all tasks have completed following shut down
+     * @return {@code true} if all tasks have completed following shut down
      */
     public boolean isTerminated() {
         return runStateOf(runControl) == TERMINATED;
     }
 
     /**
-     * Returns <code>true</code> if the process of termination has
+     * Returns {@code true} if the process of termination has
      * commenced but possibly not yet completed.
      *
-     * @return <code>true</code> if terminating
+     * @return {@code true} if terminating
      */
     public boolean isTerminating() {
         return runStateOf(runControl) >= TERMINATING;
     }
 
     /**
-     * Returns <code>true</code> if this pool has been shut down.
+     * Returns {@code true} if this pool has been shut down.
      *
-     * @return <code>true</code> if this pool has been shut down
+     * @return {@code true} if this pool has been shut down
      */
     public boolean isShutdown() {
         return runStateOf(runControl) >= SHUTDOWN;
@@ -1021,8 +1147,8 @@ public class ForkJoinPool extends Abstra
      *
      * @param timeout the maximum time to wait
      * @param unit the time unit of the timeout argument
-     * @return <code>true</code> if this executor terminated and
-     *         <code>false</code> 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
      */
     public boolean awaitTermination(long timeout, TimeUnit unit)
@@ -1046,9 +1172,10 @@ public class ForkJoinPool extends Abstra
     // Shutdown and termination support
 
     /**
-     * Callback from terminating worker. Null out the corresponding
-     * workers slot, and if terminating, try to terminate, else try to
-     * shrink workers array.
+     * Callback from terminating worker. Nulls out the corresponding
+     * workers slot, and if terminating, tries to terminate; else
+     * tries to shrink workers array.
+     *
      * @param w the worker
      */
     final void workerTerminated(ForkJoinWorkerThread w) {
@@ -1058,17 +1185,19 @@ public class ForkJoinPool extends Abstra
         lock.lock();
         try {
             ForkJoinWorkerThread[] ws = workers;
-            int idx = w.poolIndex;
-            if (idx >= 0 && idx < ws.length && ws[idx] == w)
-                ws[idx] = null;
-            if (totalCountOf(workerCounts) == 0) {
-                terminate(); // no-op if already terminating
-                transitionRunStateTo(TERMINATED);
-                termination.signalAll();
-            }
-            else if (!isTerminating()) {
-                tryShrinkWorkerArray();
-                tryResumeSpare(true); // allow replacement
+            if (ws != null) {
+                int idx = w.poolIndex;
+                if (idx >= 0 && idx < ws.length && ws[idx] == w)
+                    ws[idx] = null;
+                if (totalCountOf(workerCounts) == 0) {
+                    terminate(); // no-op if already terminating
+                    transitionRunStateTo(TERMINATED);
+                    termination.signalAll();
+                }
+                else if (!isTerminating()) {
+                    tryShrinkWorkerArray();
+                    tryResumeSpare(true); // allow replacement
+                }
             }
         } finally {
             lock.unlock();
@@ -1077,7 +1206,7 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
-     * Initiate termination.
+     * Initiates termination.
      */
     private void terminate() {
         if (transitionRunStateTo(TERMINATING)) {
@@ -1092,7 +1221,7 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
-     * Possibly terminate when on shutdown state
+     * Possibly terminates when on shutdown state.
      */
     private void terminateOnShutdown() {
         if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl))
@@ -1100,7 +1229,7 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
-     * Clear out and cancel submissions
+     * Clears out and cancels submissions.
      */
     private void cancelQueuedSubmissions() {
         ForkJoinTask<?> task;
@@ -1109,17 +1238,19 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
-     * Clean out worker queues.
+     * Cleans out worker queues.
      */
     private void cancelQueuedWorkerTasks() {
         final ReentrantLock lock = this.workerLock;
         lock.lock();
         try {
             ForkJoinWorkerThread[] ws = workers;
-            for (int i = 0; i < ws.length; ++i) {
-                ForkJoinWorkerThread t = ws[i];
-                if (t != null)
-                    t.cancelTasks();
+            if (ws != null) {
+                for (int i = 0; i < ws.length; ++i) {
+                    ForkJoinWorkerThread t = ws[i];
+                    if (t != null)
+                        t.cancelTasks();
+                }
             }
         } finally {
             lock.unlock();
@@ -1127,18 +1258,20 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
-     * Set each worker's status to terminating. Requires lock to avoid
-     * conflicts with add/remove
+     * Sets each worker's status to terminating. Requires lock to avoid
+     * conflicts with add/remove.
      */
     private void stopAllWorkers() {
         final ReentrantLock lock = this.workerLock;
         lock.lock();
         try {
             ForkJoinWorkerThread[] ws = workers;
-            for (int i = 0; i < ws.length; ++i) {
-                ForkJoinWorkerThread t = ws[i];
-                if (t != null)
-                    t.shutdownNow();
+            if (ws != null) {
+                for (int i = 0; i < ws.length; ++i) {
+                    ForkJoinWorkerThread t = ws[i];
+                    if (t != null)
+                        t.shutdownNow();
+                }
             }
         } finally {
             lock.unlock();
@@ -1146,7 +1279,7 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
-     * Interrupt all unterminated workers.  This is not required for
+     * Interrupts all unterminated workers.  This is not required for
      * sake of internal control, but may help unstick user code during
      * shutdown.
      */
@@ -1155,12 +1288,14 @@ public class ForkJoinPool extends Abstra
         lock.lock();
         try {
             ForkJoinWorkerThread[] ws = workers;
-            for (int i = 0; i < ws.length; ++i) {
-                ForkJoinWorkerThread t = ws[i];
-                if (t != null && !t.isTerminated()) {
-                    try {
-                        t.interrupt();
-                    } catch (SecurityException ignore) {
+            if (ws != null) {
+                for (int i = 0; i < ws.length; ++i) {
+                    ForkJoinWorkerThread t = ws[i];
+                    if (t != null && !t.isTerminated()) {
+                        try {
+                            t.interrupt();
+                        } catch (SecurityException ignore) {
+                        }
                     }
                 }
             }
@@ -1214,7 +1349,7 @@ public class ForkJoinPool extends Abstra
         }
 
         /**
-         * Wake up waiter, returning false if known to already
+         * Wakes up waiter, returning false if known to already
          */
         boolean signal() {
             ForkJoinWorkerThread t = thread;
@@ -1226,7 +1361,7 @@ public class ForkJoinPool extends Abstra
         }
 
         /**
-         * Await release on sync
+         * Awaits release on sync.
          */
         void awaitSyncRelease(ForkJoinPool p) {
             while (thread != null && !p.syncIsReleasable(this))
@@ -1234,7 +1369,7 @@ public class ForkJoinPool extends Abstra
         }
 
         /**
-         * Await resumption as spare
+         * Awaits resumption as spare.
          */
         void awaitSpareRelease() {
             while (thread != null) {
@@ -1248,6 +1383,7 @@ public class ForkJoinPool extends Abstra
      * Ensures that no thread is waiting for count to advance from the
      * current value of eventCount read on entry to this method, by
      * releasing waiting threads if necessary.
+     *
      * @return the count
      */
     final long ensureSync() {
@@ -1269,12 +1405,12 @@ public class ForkJoinPool extends Abstra
      */
     private void signalIdleWorkers() {
         long c;
-        do;while (!casEventCount(c = eventCount, c+1));
+        do {} while (!casEventCount(c = eventCount, c+1));
         ensureSync();
     }
 
     /**
-     * Signal threads waiting to poll a task. Because method sync
+     * Signals threads waiting to poll a task. Because method sync
      * rechecks availability, it is OK to only proceed if queue
      * appears to be non-empty, and OK to skip under contention to
      * increment count (since some other thread succeeded).
@@ -1293,6 +1429,7 @@ public class ForkJoinPool extends Abstra
      * Waits until event count advances from last value held by
      * caller, or if excess threads, caller is resumed as spare, or
      * caller or pool is terminating. Updates caller's event on exit.
+     *
      * @param w the calling worker thread
      */
     final void sync(ForkJoinWorkerThread w) {
@@ -1302,7 +1439,7 @@ public class ForkJoinPool extends Abstra
             long prev = w.lastEventCount;
             WaitQueueNode node = null;
             WaitQueueNode h;
-            while (eventCount == prev && 
+            while (eventCount == prev &&
                    ((h = syncStack) == null || h.count == prev)) {
                 if (node == null)
                     node = new WaitQueueNode(prev, w);
@@ -1323,10 +1460,11 @@ public class ForkJoinPool extends Abstra
      * Returns true if worker waiting on sync can proceed:
      *  - on signal (thread == null)
      *  - on event count advance (winning race to notify vs signaller)
-     *  - on Interrupt
-     *  - if the first queued node, we find work available 
-     * If node was not signalled and event count not advanced on exit, 
+     *  - on interrupt
+     *  - if the first queued node, we find work available
+     * 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
      */
     final boolean syncIsReleasable(WaitQueueNode node) {
@@ -1361,13 +1499,13 @@ public class ForkJoinPool extends Abstra
     //  Parallelism maintenance
 
     /**
-     * Decrement running count; if too low, add spare.
+     * Decrements running count; if too low, adds spare.
      *
      * Conceptually, all we need to do here is add or resume a
      * spare thread when one is about to block (and remove or
      * suspend it later when unblocked -- see suspendIfSpare).
      * However, implementing this idea requires coping with
-     * several problems: We have imperfect information about the
+     * several problems: we have imperfect information about the
      * states of threads. Some count updates can and usually do
      * lag run state changes, despite arrangements to keep them
      * accurate (for example, when possible, updating counts
@@ -1381,7 +1519,7 @@ public class ForkJoinPool extends Abstra
      * only be suspended or removed when they are idle, not
      * immediately when they aren't needed. So adding threads will
      * raise parallelism level for longer than necessary.  Also,
-     * FJ applications often enounter highly transient peaks when
+     * FJ applications often encounter highly transient peaks when
      * many threads are blocked joining, but for less time than it
      * takes to create or resume spares.
      *
@@ -1390,12 +1528,14 @@ public class ForkJoinPool extends Abstra
      * target counts, else create only to avoid starvation
      * @return true if joinMe known to be done
      */
-    final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) {
+    final boolean preJoin(ForkJoinTask<?> joinMe,
+                          boolean maintainParallelism) {
         maintainParallelism &= maintainsParallelism; // overrride
         boolean dec = false;  // true when running count decremented
         while (spareStack == null || !tryResumeSpare(dec)) {
             int counts = workerCounts;
-            if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat
+            if (dec || (dec = casWorkerCounts(counts, --counts))) {
+                // CAS cheat
                 if (!needSpare(counts, maintainParallelism))
                     break;
                 if (joinMe.status < 0)
@@ -1410,7 +1550,8 @@ public class ForkJoinPool extends Abstra
     /**
      * Same idea as preJoin
      */
-    final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){
+    final boolean preBlock(ManagedBlocker blocker,
+                           boolean maintainParallelism) {
         maintainParallelism &= maintainsParallelism;
         boolean dec = false;
         while (spareStack == null || !tryResumeSpare(dec)) {
@@ -1434,6 +1575,7 @@ public class ForkJoinPool extends Abstra
      * there is apparently some work to do.  This self-limiting rule
      * means that the more threads that have already been added, the
      * less parallelism we will tolerate before adding another.
+     *
      * @param counts current worker counts
      * @param maintainParallelism try to maintain parallelism
      */
@@ -1446,13 +1588,14 @@ public class ForkJoinPool extends Abstra
         return (tc < maxPoolSize &&
                 (rc == 0 || totalSurplus < 0 ||
                  (maintainParallelism &&
-                  runningDeficit > totalSurplus && 
+                  runningDeficit > totalSurplus &&
                   ForkJoinWorkerThread.hasQueuedTasks(workers))));
     }
-    
+
     /**
-     * Add a spare worker if lock available and no more than the
-     * expected numbers of threads exist
+     * Adds a spare worker if lock available and no more than the
+     * expected numbers of threads exist.
+     *
      * @return true if successful
      */
     private boolean tryAddSpare(int expectedCounts) {
@@ -1485,7 +1628,7 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
-     * Add the kth spare worker. On entry, pool coounts are already
+     * Adds the kth spare worker. On entry, pool counts are already
      * adjusted to reflect addition.
      */
     private void createAndStartSpare(int k) {
@@ -1507,11 +1650,12 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
-     * Suspend calling thread w if there are excess threads.  Called
-     * only from sync.  Spares are enqueued in a Treiber stack
-     * using the same WaitQueueNodes as barriers.  They are resumed
-     * mainly in preJoin, but are also woken on pool events that
-     * require all threads to check run state.
+     * Suspends calling thread w if there are excess threads.  Called
+     * only from sync.  Spares are enqueued in a Treiber stack using
+     * the same WaitQueueNodes as barriers.  They are resumed mainly
+     * in preJoin, but are also woken on pool events that require all
+     * threads to check run state.
+     *
      * @param w the caller
      */
     private boolean suspendIfSpare(ForkJoinWorkerThread w) {
@@ -1522,7 +1666,7 @@ public class ForkJoinPool extends Abstra
                 node = new WaitQueueNode(0, w);
             if (casWorkerCounts(s, s-1)) { // representation-dependent
                 // push onto stack
-                do;while (!casSpareStack(node.next = spareStack, node));
+                do {} while (!casSpareStack(node.next = spareStack, node));
                 // block until released by resumeSpare
                 node.awaitSpareRelease();
                 return true;
@@ -1532,7 +1676,8 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
-     * Try to pop and resume a spare thread.
+     * Tries to pop and resume a spare thread.
+     *
      * @param updateCount if true, increment running count on success
      * @return true if successful
      */
@@ -1550,7 +1695,8 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
-     * Pop and resume all spare threads. Same idea as ensureSync.
+     * Pops and resumes all spare threads. Same idea as ensureSync.
+     *
      * @return true if any spares released
      */
     private boolean resumeAllSpares() {
@@ -1568,7 +1714,7 @@ public class ForkJoinPool extends Abstra
     }
 
     /**
-     * Pop and shutdown excessive spare threads. Call only while
+     * Pops and shuts down excessive spare threads. Call only while
      * holding lock. This is not guaranteed to eliminate all excess
      * threads, only those suspended as spares, which are the ones
      * unlikely to be needed in the future.
@@ -1593,36 +1739,37 @@ public class ForkJoinPool extends Abstra
     /**
      * Interface for extending managed parallelism for tasks running
      * in ForkJoinPools. A ManagedBlocker provides two methods.
-     * Method <code>isReleasable</code> must return true if blocking is not
-     * necessary. Method <code>block</code> blocks the current thread
-     * if necessary (perhaps internally invoking isReleasable before
-     * actually blocking.).
+     * 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.).
+     *
      * <p>For example, here is a ManagedBlocker based on a
      * ReentrantLock:
-     * <pre>
-     *   class ManagedLocker implements ManagedBlocker {
-     *     final ReentrantLock lock;
-     *     boolean hasLock = false;
-     *     ManagedLocker(ReentrantLock lock) { this.lock = lock; }
-     *     public boolean block() {
-     *        if (!hasLock)
-     *           lock.lock();
-     *        return true;
-     *     }
-     *     public boolean isReleasable() {
-     *        return hasLock || (hasLock = lock.tryLock());
-     *     }
+     *  <pre> {@code
+     * class ManagedLocker implements ManagedBlocker {
+     *   final ReentrantLock lock;
+     *   boolean hasLock = false;
+     *   ManagedLocker(ReentrantLock lock) { this.lock = lock; }
+     *   public boolean block() {
+     *     if (!hasLock)
+     *       lock.lock();
+     *     return true;
+     *   }
+     *   public boolean isReleasable() {
+     *     return hasLock || (hasLock = lock.tryLock());
      *   }
-     * </pre>
+     * }}</pre>
      */
     public static interface ManagedBlocker {
         /**
          * 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).
+         * if isReleasable would return true)
          * @throws InterruptedException if interrupted while waiting
-         * (the method is not required to do so, but is allowe to).
+         * (the method is not required to do so, but is allowed to)
          */
         boolean block() throws InterruptedException;
 
@@ -1637,20 +1784,20 @@ 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</code> is true and the pool supports
+     * {@code maintainParallelism} is true and the pool supports
      * it ({@link #getMaintainsParallelism}), this method attempts to
-     * maintain the pool's nominal parallelism. Otherwise if activates
+     * maintain the pool's nominal parallelism. Otherwise it activates
      * a thread only if necessary to avoid complete starvation. This
      * option may be preferable when blockages use timeouts, or are
      * almost always brief.
      *
      * <p> If the caller is not a ForkJoinTask, this method is behaviorally
      * equivalent to
-     * <pre>
-     *   while (!blocker.isReleasable())
-     *      if (blocker.block())
-     *         return;
-     * </pre>
+     *  <pre> {@code
+     * while (!blocker.isReleasable())
+     *   if (blocker.block())
+     *     return;
+     * }</pre>
      * If the caller is a ForkJoinTask, then the pool may first
      * be expanded to ensure parallelism, and later adjusted.
      *
@@ -1659,14 +1806,14 @@ public class ForkJoinPool extends Abstra
      * 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.
+     * @throws InterruptedException if blocker.block did so
      */
     public static void managedBlock(ManagedBlocker blocker,
                                     boolean maintainParallelism)
         throws InterruptedException {
         Thread t = Thread.currentThread();
-        ForkJoinPool pool = (t instanceof ForkJoinWorkerThread?
-                             ((ForkJoinWorkerThread)t).pool : null);
+        ForkJoinPool pool = ((t instanceof ForkJoinWorkerThread) ?
+                             ((ForkJoinWorkerThread) t).pool : null);
         if (!blocker.isReleasable()) {
             try {
                 if (pool == null ||
@@ -1681,7 +1828,7 @@ public class ForkJoinPool extends Abstra
 
     private static void awaitBlocker(ManagedBlocker blocker)
         throws InterruptedException {
-        do;while (!blocker.isReleasable() && !blocker.block());
+        do {} while (!blocker.isReleasable() && !blocker.block());
     }
 
     // AbstractExecutorService overrides
@@ -1696,8 +1843,36 @@ public class ForkJoinPool extends Abstra
 
 
     // Temporary Unsafe mechanics for preliminary release
+    private static Unsafe getUnsafe() throws Throwable {
+        try {
+            return Unsafe.getUnsafe();
+        } catch (SecurityException se) {
+            try {
+                return java.security.AccessController.doPrivileged
+                    (new java.security.PrivilegedExceptionAction<Unsafe>() {
+                        public Unsafe run() throws Exception {
+                            return getUnsafePrivileged();
+                        }});
+            } catch (java.security.PrivilegedActionException e) {
+                throw e.getCause();
+            }
+        }
+    }
+
+    private static Unsafe getUnsafePrivileged()
+            throws NoSuchFieldException, IllegalAccessException {
+        Field f = Unsafe.class.getDeclaredField("theUnsafe");
+        f.setAccessible(true);
+        return (Unsafe) f.get(null);
+    }
+
+    private static long fieldOffset(String fieldName)
+            throws NoSuchFieldException {
+        return UNSAFE.objectFieldOffset
+            (ForkJoinPool.class.getDeclaredField(fieldName));
+    }
 
-    static final Unsafe _unsafe;
+    static final Unsafe UNSAFE;
     static final long eventCountOffset;
     static final long workerCountsOffset;
     static final long runControlOffset;
@@ -1706,41 +1881,30 @@ public class ForkJoinPool extends Abstra
 
     static {
         try {
-            if (ForkJoinPool.class.getClassLoader() != null) {
-                Field f = Unsafe.class.getDeclaredField("theUnsafe");
-                f.setAccessible(true);
-                _unsafe = (Unsafe)f.get(null);
-            }
-            else
-                _unsafe = Unsafe.getUnsafe();
-            eventCountOffset = _unsafe.objectFieldOffset
-                (ForkJoinPool.class.getDeclaredField("eventCount"));
-            workerCountsOffset = _unsafe.objectFieldOffset
-                (ForkJoinPool.class.getDeclaredField("workerCounts"));
-            runControlOffset = _unsafe.objectFieldOffset
-                (ForkJoinPool.class.getDeclaredField("runControl"));
-            syncStackOffset = _unsafe.objectFieldOffset
-                (ForkJoinPool.class.getDeclaredField("syncStack"));
-            spareStackOffset = _unsafe.objectFieldOffset
-                (ForkJoinPool.class.getDeclaredField("spareStack"));
-        } catch (Exception e) {
+            UNSAFE = getUnsafe();
+            eventCountOffset = fieldOffset("eventCount");
+            workerCountsOffset = fieldOffset("workerCounts");
+            runControlOffset = fieldOffset("runControl");
+            syncStackOffset = fieldOffset("syncStack");
+            spareStackOffset = fieldOffset("spareStack");
+        } catch (Throwable e) {
             throw new RuntimeException("Could not initialize intrinsics", e);
         }
     }
 
     private boolean casEventCount(long cmp, long val) {
-        return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val);
+        return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val);
     }
     private boolean casWorkerCounts(int cmp, int val) {
-        return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val);
+        return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val);
     }
     private boolean casRunControl(int cmp, int val) {
-        return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val);
+        return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val);
     }
     private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) {
-        return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val);
+        return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val);
     }
     private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) {
-        return _unsafe.compareAndSwapObject(this, syncStackOffset, cmp, val);
+        return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val);
     }
 }