--- jsr166/src/jsr166y/Phaser.java	2009/07/23 23:07:57	1.18
+++ jsr166/src/jsr166y/Phaser.java	2009/08/24 12:49:39	1.40
@@ -7,131 +7,148 @@
 package jsr166y;
 
 import java.util.concurrent.*;
-import java.util.concurrent.atomic.*;
+
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.concurrent.locks.LockSupport;
-import sun.misc.Unsafe;
-import java.lang.reflect.*;
 
 /**
- * A reusable synchronization barrier, similar in functionality to a
+ * A reusable synchronization barrier, similar in functionality to
  * {@link java.util.concurrent.CyclicBarrier CyclicBarrier} and
  * {@link java.util.concurrent.CountDownLatch CountDownLatch}
  * but supporting more flexible usage.
  *
- * <ul>
- *
- * <li> The number of parties synchronizing on a phaser may vary over
- * time.  A task may register to be a party at any time, and may
- * deregister upon arriving at the barrier.  As is the case with most
- * basic synchronization constructs, registration and deregistration
- * affect only internal counts; they do not establish any further
- * internal bookkeeping, so tasks cannot query whether they are
- * registered. (However, you can introduce such bookkeeping by
- * subclassing this class.)
- *
- * <li> Each generation has an associated phase value, starting at
- * zero, and advancing when all parties reach the barrier (wrapping
- * around to zero after reaching {@code Integer.MAX_VALUE}).
- *
- * <li> Like a CyclicBarrier, a Phaser may be repeatedly awaited.
- * Method {@code arriveAndAwaitAdvance} has effect analogous to
- * {@code CyclicBarrier.await}.  However, Phasers separate two
- * aspects of coordination, that may also be invoked independently:
+ * <p> <b>Registration.</b> Unlike the case for other barriers, the
+ * number of parties <em>registered</em> to synchronize on a phaser
+ * may vary over time.  Tasks may be registered at any time (using
+ * methods {@link #register}, {@link #bulkRegister}, or forms of
+ * constructors establishing initial numbers of parties), and
+ * optionally deregistered upon any arrival (using {@link
+ * #arriveAndDeregister}).  As is the case with most basic
+ * synchronization constructs, registration and deregistration affect
+ * only internal counts; they do not establish any further internal
+ * bookkeeping, so tasks cannot query whether they are registered.
+ * (However, you can introduce such bookkeeping by subclassing this
+ * class.)
+ *
+ * <p> <b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code
+ * Phaser} may be repeatedly awaited.  Method {@link
+ * #arriveAndAwaitAdvance} has effect analogous to {@link
+ * java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each
+ * generation of a {@code Phaser} has an associated phase number. The
+ * phase number starts at zero, and advances when all parties arrive
+ * at the barrier, wrapping around to zero after reaching {@code
+ * Integer.MAX_VALUE}. The use of phase numbers enables independent
+ * control of actions upon arrival at a barrier and upon awaiting
+ * others, via two kinds of methods that may be invoked by any
+ * registered party:
  *
  * <ul>
  *
- *   <li> Arriving at a barrier. Methods {@code arrive} and
- *       {@code arriveAndDeregister} do not block, but return
- *       the phase value current upon entry to the method.
- *
- *   <li> Awaiting others. Method {@code awaitAdvance} requires an
- *       argument indicating the entry phase, and returns when the
- *       barrier advances to a new phase.
- * </ul>
+ *   <li> <b>Arrival.</b> Methods {@link #arrive} and
+ *       {@link #arriveAndDeregister} record arrival at a
+ *       barrier. These methods do not block, but return an associated
+ *       <em>arrival phase number</em>; that is, the phase number of
+ *       the barrier to which the arrival applied. When the final
+ *       party for a given phase arrives, an optional barrier action
+ *       is performed and the phase advances.  Barrier actions,
+ *       performed by the party triggering a phase advance, are
+ *       arranged by overriding method {@link #onAdvance(int, int)},
+ *       which also controls termination. Overriding this method is
+ *       similar to, but more flexible than, providing a barrier
+ *       action to a {@code CyclicBarrier}.
+ *
+ *   <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an
+ *       argument indicating an arrival phase number, and returns when
+ *       the barrier advances to (or is already at) a different phase.
+ *       Unlike similar constructions using {@code CyclicBarrier},
+ *       method {@code awaitAdvance} continues to wait even if the
+ *       waiting thread is interrupted. Interruptible and timeout
+ *       versions are also available, but exceptions encountered while
+ *       tasks wait interruptibly or with timeout do not change the
+ *       state of the barrier. If necessary, you can perform any
+ *       associated recovery within handlers of those exceptions,
+ *       often after invoking {@code forceTermination}.  Phasers may
+ *       also be used by tasks executing in a {@link ForkJoinPool},
+ *       which will ensure sufficient parallelism to execute tasks
+ *       when others are blocked waiting for a phase to advance.
  *
+ * </ul>
  *
- * <li> Barrier actions, performed by the task triggering a phase
- * advance while others may be waiting, are arranged by overriding
- * method {@code onAdvance}, that also controls termination.
- * Overriding this method may be used to similar but more flexible
- * effect as providing a barrier action to a CyclicBarrier.
- *
- * <li> Phasers may enter a <em>termination</em> state in which all
- * actions immediately return without updating phaser state or waiting
- * for advance, and indicating (via a negative phase value) that
- * execution is complete.  Termination is triggered by executing the
- * overridable {@code onAdvance} method that is invoked each time the
- * barrier is about to be tripped. When a Phaser is controlling an
- * action with a fixed number of iterations, it is often convenient to
- * override this method to cause termination when the current phase
- * number reaches a threshold. Method {@code forceTermination} is also
- * available to abruptly release waiting threads and allow them to
- * terminate.
+ * <p> <b>Termination.</b> A {@code Phaser} may enter a
+ * <em>termination</em> state in which all synchronization methods
+ * immediately return without updating phaser state or waiting for
+ * advance, and indicating (via a negative phase value) that execution
+ * is complete.  Termination is triggered when an invocation of {@code
+ * onAdvance} returns {@code true}.  As illustrated below, when
+ * phasers control actions with a fixed number of iterations, it is
+ * often convenient to override this method to cause termination when
+ * the current phase number reaches a threshold. Method {@link
+ * #forceTermination} is also available to abruptly release waiting
+ * threads and allow them to terminate.
  *
- * <li> Phasers may be tiered to reduce contention. Phasers with large
+ * <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged
+ * in tree structures) to reduce contention. Phasers with large
  * numbers of parties that would otherwise experience heavy
- * synchronization contention costs may instead be arranged in trees.
- * This will typically greatly increase throughput even though it
- * incurs somewhat greater per-operation overhead.
- *
- * <li> By default, {@code awaitAdvance} continues to wait even if
- * the waiting thread is interrupted. And unlike the case in
- * CyclicBarriers, exceptions encountered while tasks wait
- * interruptibly or with timeout do not change the state of the
- * barrier. If necessary, you can perform any associated recovery
- * within handlers of those exceptions, often after invoking
- * {@code forceTermination}.
- *
- * <li>Phasers ensure lack of starvation when used by ForkJoinTasks.
- *
- * </ul>
+ * synchronization contention costs may instead be set up so that
+ * groups of sub-phasers share a common parent.  This may greatly
+ * increase throughput even though it incurs greater per-operation
+ * overhead.
+ *
+ * <p><b>Monitoring.</b> While synchronization methods may be invoked
+ * only by registered parties, the current state of a phaser may be
+ * monitored by any caller.  At any given moment there are {@link
+ * #getRegisteredParties} parties in total, of which {@link
+ * #getArrivedParties} have arrived at the current phase ({@link
+ * #getPhase}).  When the remaining ({@link #getUnarrivedParties})
+ * parties arrive, the phase advances; thus, this value is always
+ * greater than zero if there are any registered parties.  The values
+ * returned by these methods may reflect transient states and so are
+ * not in general useful for synchronization control.  Method {@link
+ * #toString} returns snapshots of these state queries in a form
+ * convenient for informal monitoring.
  *
  * <p><b>Sample usages:</b>
  *
- * <p>A Phaser may be used instead of a {@code CountDownLatch} to control
- * a one-shot action serving a variable number of parties. The typical
- * idiom is for the method setting this up to first register, then
- * start the actions, then deregister, as in:
+ * <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
+ * to control a one-shot action serving a variable number of
+ * parties. The typical idiom is for the method setting this up to
+ * first register, then start the actions, then deregister, as in:
  *
  *  <pre> {@code
- * void runTasks(List<Runnable> list) {
+ * void runTasks(List<Runnable> tasks) {
  *   final Phaser phaser = new Phaser(1); // "1" to register self
- *   for (Runnable r : list) {
+ *   // create and start threads
+ *   for (Runnable task : tasks) {
  *     phaser.register();
  *     new Thread() {
  *       public void run() {
  *         phaser.arriveAndAwaitAdvance(); // await all creation
- *         r.run();
- *         phaser.arriveAndDeregister();   // signal completion
+ *         task.run();
  *       }
  *     }.start();
  *   }
  *
- *   doSomethingOnBehalfOfWorkers();
- *   phaser.arrive(); // allow threads to start
- *   int p = phaser.arriveAndDeregister(); // deregister self  ...
- *   p = phaser.awaitAdvance(p); // ... and await arrival
- *   otherActions(); // do other things while tasks execute
- *   phaser.awaitAdvance(p); // await final completion
+ *   // allow threads to start and deregister self
+ *   phaser.arriveAndDeregister();
  * }}</pre>
  *
  * <p>One way to cause a set of threads to repeatedly perform actions
  * for a given number of iterations is to override {@code onAdvance}:
  *
  *  <pre> {@code
- * void startTasks(List<Runnable> list, final int iterations) {
+ * void startTasks(List<Runnable> tasks, final int iterations) {
  *   final Phaser phaser = new Phaser() {
- *     public boolean onAdvance(int phase, int registeredParties) {
+ *     protected boolean onAdvance(int phase, int registeredParties) {
  *       return phase >= iterations || registeredParties == 0;
  *     }
  *   };
  *   phaser.register();
- *   for (Runnable r : list) {
+ *   for (Runnable task : tasks) {
  *     phaser.register();
  *     new Thread() {
  *       public void run() {
  *         do {
- *           r.run();
+ *           task.run();
  *           phaser.arriveAndAwaitAdvance();
  *         } while(!phaser.isTerminated();
  *       }
@@ -140,9 +157,36 @@ import java.lang.reflect.*;
  *   phaser.arriveAndDeregister(); // deregister self, don't wait
  * }}</pre>
  *
- * <p> To create a set of tasks using a tree of Phasers,
+ * If the main task must later await termination, it
+ * may re-register and then execute a similar loop:
+ * <pre> {@code
+ *   // ...
+ *   phaser.register();
+ *   while (!phaser.isTerminated())
+ *     phaser.arriveAndAwaitAdvance();
+ * }</pre>
+ *
+ * Related constructions may be used to await particular phase numbers
+ * in contexts where you are sure that the phase will never wrap around
+ * {@code Integer.MAX_VALUE}. For example:
+ *
+ * <pre> {@code
+ *   void awaitPhase(Phaser phaser, int phase) {
+ *     int p = phaser.register(); // assumes caller not already registered
+ *     while (p < phase) {
+ *       if (phaser.isTerminated())
+ *         // ... deal with unexpected termination
+ *       else
+ *         p = phaser.arriveAndAwaitAdvance();
+ *     }
+ *     phaser.arriveAndDeregister();
+ *   }
+ * }</pre>
+ *
+ *
+ * <p>To create a set of tasks using a tree of phasers,
  * you could use code of the following form, assuming a
- * Task class with a constructor accepting a Phaser that
+ * Task class with a constructor accepting a phaser that
  * it registers for upon construction:
  *  <pre> {@code
  * void build(Task[] actions, int lo, int hi, Phaser b) {
@@ -172,7 +216,7 @@ import java.lang.reflect.*;
  *
  * <p><b>Implementation notes</b>: This implementation restricts the
  * maximum number of parties to 65535. Attempts to register additional
- * parties result in IllegalStateExceptions. However, you can and
+ * parties result in {@code IllegalStateException}. However, you can and
  * should create tiered phasers to accommodate arbitrarily large sets
  * of participants.
  *
@@ -250,7 +294,7 @@ public class Phaser {
     private final Phaser parent;
 
     /**
-     * The root of Phaser tree. Equals this if not in a tree.  Used to
+     * The root of phaser tree. Equals this if not in a tree.  Used to
      * support faster state push-down.
      */
     private final Phaser root;
@@ -301,16 +345,16 @@ public class Phaser {
     }
 
     /**
-     * Creates a new Phaser without any initially registered parties,
+     * Creates a new phaser without any initially registered parties,
      * initial phase number 0, and no parent. Any thread using this
-     * Phaser will need to first register for it.
+     * phaser will need to first register for it.
      */
     public Phaser() {
         this(null);
     }
 
     /**
-     * Creates a new Phaser with the given numbers of registered
+     * Creates a new phaser with the given numbers of registered
      * unarrived parties, initial phase number 0, and no parent.
      *
      * @param parties the number of parties required to trip barrier
@@ -322,7 +366,7 @@ public class Phaser {
     }
 
     /**
-     * Creates a new Phaser with the given parent, without any
+     * Creates a new phaser with the given parent, without any
      * initially registered parties. If parent is non-null this phaser
      * is registered with the parent and its initial phase number is
      * the same as that of parent phaser.
@@ -342,7 +386,7 @@ public class Phaser {
     }
 
     /**
-     * Creates a new Phaser with the given parent and numbers of
+     * Creates a new phaser with the given parent and numbers of
      * registered unarrived parties. If parent is non-null, this phaser
      * is registered with the parent and its initial phase number is
      * the same as that of parent phaser.
@@ -369,7 +413,7 @@ public class Phaser {
     /**
      * Adds a new unarrived party to this phaser.
      *
-     * @return the current barrier phase number upon registration
+     * @return the arrival phase number to which this registration applied
      * @throws IllegalStateException if attempting to register more
      * than the maximum supported number of parties
      */
@@ -381,7 +425,7 @@ public class Phaser {
      * Adds the given number of new unarrived parties to this phaser.
      *
      * @param parties the number of parties required to trip barrier
-     * @return the current barrier phase number upon registration
+     * @return the arrival phase number to which this registration applied
      * @throws IllegalStateException if attempting to register more
      * than the maximum supported number of parties
      */
@@ -416,10 +460,11 @@ public class Phaser {
 
     /**
      * Arrives at the barrier, but does not wait for others.  (You can
-     * in turn wait for others via {@link #awaitAdvance}).
+     * in turn wait for others via {@link #awaitAdvance}).  It is an
+     * unenforced usage error for an unregistered party to invoke this
+     * method.
      *
-     * @return the barrier phase number upon entry to this method, or a
-     * negative value if terminated
+     * @return the arrival phase number, or a negative value if terminated
      * @throws IllegalStateException if not terminated and the number
      * of unarrived parties would become negative
      */
@@ -464,14 +509,15 @@ public class Phaser {
     }
 
     /**
-     * Arrives at the barrier, and deregisters from it, without
-     * waiting for others. Deregistration reduces number of parties
+     * Arrives at the barrier and deregisters from it without waiting
+     * for others. Deregistration reduces the number of parties
      * required to trip the barrier in future phases.  If this phaser
      * has a parent, and deregistration causes this phaser to have
-     * zero parties, this phaser is also deregistered from its parent.
+     * zero parties, this phaser also arrives at and is deregistered
+     * from its parent.  It is an unenforced usage error for an
+     * unregistered party to invoke this method.
      *
-     * @return the current barrier phase number upon entry to
-     * this method, or a negative value if terminated
+     * @return the arrival phase number, or a negative value if terminated
      * @throws IllegalStateException if not terminated and the number
      * of registered or unarrived parties would become negative
      */
@@ -521,11 +567,14 @@ public class Phaser {
 
     /**
      * Arrives at the barrier and awaits others. Equivalent in effect
-     * to {@code awaitAdvance(arrive())}.  If you instead need to
-     * await with interruption of timeout, and/or deregister upon
-     * arrival, you can arrange them using analogous constructions.
+     * to {@code awaitAdvance(arrive())}.  If you need to await with
+     * interruption or timeout, you can arrange this with an analogous
+     * construction using one of the other forms of the awaitAdvance
+     * method.  If instead you need to deregister upon arrival use
+     * {@code arriveAndDeregister}. It is an unenforced usage error
+     * for an unregistered party to invoke this method.
      *
-     * @return the phase on entry to this method
+     * @return the arrival phase number, or a negative number if terminated
      * @throws IllegalStateException if not terminated and the number
      * of unarrived parties would become negative
      */
@@ -534,12 +583,17 @@ public class Phaser {
     }
 
     /**
-     * Awaits the phase of the barrier to advance from the given
-     * value, or returns immediately if argument is negative or this
-     * barrier is terminated.
-     *
-     * @param phase the phase on entry to this method
-     * @return the phase on exit from this method
+     * Awaits the phase of the barrier to advance from the given phase
+     * value, returning immediately if the current phase of the
+     * barrier is not equal to the given phase value or this barrier
+     * is terminated.  It is an unenforced usage error for an
+     * unregistered party to invoke this method.
+     *
+     * @param phase an arrival phase number, or negative value if
+     * terminated; this argument is normally the value returned by a
+     * previous call to {@code arrive} or its variants
+     * @return the next arrival phase number, or a negative value
+     * if terminated or argument is negative
      */
     public int awaitAdvance(int phase) {
         if (phase < 0)
@@ -555,13 +609,18 @@ public class Phaser {
     }
 
     /**
-     * Awaits the phase of the barrier to advance from the given
-     * value, or returns immediately if argument is negative or this
-     * barrier is terminated, or throws InterruptedException if
-     * interrupted while waiting.
-     *
-     * @param phase the phase on entry to this method
-     * @return the phase on exit from this method
+     * Awaits the phase of the barrier to advance from the given phase
+     * value, throwing {@code InterruptedException} if interrupted
+     * while waiting, or returning immediately if the current phase of
+     * the barrier is not equal to the given phase value or this
+     * barrier is terminated. It is an unenforced usage error for an
+     * unregistered party to invoke this method.
+     *
+     * @param phase an arrival phase number, or negative value if
+     * terminated; this argument is normally the value returned by a
+     * previous call to {@code arrive} or its variants
+     * @return the next arrival phase number, or a negative value
+     * if terminated or argument is negative
      * @throws InterruptedException if thread interrupted while waiting
      */
     public int awaitAdvanceInterruptibly(int phase)
@@ -578,12 +637,23 @@ public class Phaser {
     }
 
     /**
-     * Awaits the phase of the barrier to advance from the given value
-     * or the given timeout elapses, or returns immediately if
-     * argument is negative or this barrier is terminated.
-     *
-     * @param phase the phase on entry to this method
-     * @return the phase on exit from this method
+     * Awaits the phase of the barrier to advance from the given phase
+     * value or the given timeout to elapse, throwing {@code
+     * InterruptedException} if interrupted while waiting, or
+     * returning immediately if the current phase of the barrier is
+     * not equal to the given phase value or this barrier is
+     * terminated.  It is an unenforced usage error for an
+     * unregistered party to invoke this method.
+     *
+     * @param phase an arrival phase number, or negative value if
+     * terminated; this argument is normally the value returned by a
+     * previous call to {@code arrive} or its variants
+     * @param timeout how long to wait before giving up, in units of
+     *        {@code unit}
+     * @param unit a {@code TimeUnit} determining how to interpret the
+     *        {@code timeout} parameter
+     * @return the next arrival phase number, or a negative value
+     * if terminated or argument is negative
      * @throws InterruptedException if thread interrupted while waiting
      * @throws TimeoutException if timed out while waiting
      */
@@ -637,16 +707,6 @@ public class Phaser {
     }
 
     /**
-     * Returns {@code true} if the current phase number equals the given phase.
-     *
-     * @param phase the phase
-     * @return {@code true} if the current phase number equals the given phase
-     */
-    public final boolean hasPhase(int phase) {
-        return phaseOf(getReconciledState()) == phase;
-    }
-
-    /**
      * Returns the number of parties registered at this barrier.
      *
      * @return the number of parties
@@ -656,8 +716,8 @@ public class Phaser {
     }
 
     /**
-     * Returns the number of parties that have arrived at the current
-     * phase of this barrier.
+     * Returns the number of registered parties that have arrived at
+     * the current phase of this barrier.
      *
      * @return the number of arrived parties
      */
@@ -676,9 +736,9 @@ public class Phaser {
     }
 
     /**
-     * Returns the parent of this phaser, or null if none.
+     * Returns the parent of this phaser, or {@code null} if none.
      *
-     * @return the parent of this phaser, or null if none
+     * @return the parent of this phaser, or {@code null} if none
      */
     public Phaser getParent() {
         return parent;
@@ -707,26 +767,22 @@ public class Phaser {
      * Overridable method to perform an action upon phase advance, and
      * to control termination. This method is invoked whenever the
      * barrier is tripped (and thus all other waiting parties are
-     * dormant). If it returns true, then, rather than advance the
-     * phase number, this barrier will be set to a final termination
-     * state, and subsequent calls to {@code isTerminated} will
-     * return true.
+     * dormant). If it returns {@code true}, then, rather than advance
+     * the phase number, this barrier will be set to a final
+     * termination state, and subsequent calls to {@link #isTerminated}
+     * will return true.
      *
-     * <p> The default version returns true when the number of
+     * <p>The default version returns {@code true} when the number of
      * registered parties is zero. Normally, overrides that arrange
      * termination for other reasons should also preserve this
      * property.
      *
-     * <p> You may override this method to perform an action with side
+     * <p>You may override this method to perform an action with side
      * effects visible to participating tasks, but it is in general
      * only sensible to do so in designs where all parties register
-     * before any arrive, and all {@code awaitAdvance} at each phase.
-     * Otherwise, you cannot ensure lack of interference. In
-     * particular, this method may be invoked more than once per
-     * transition if other parties successfully register while the
-     * invocation of this method is in progress, thus postponing the
-     * transition until those parties also arrive, re-triggering this
-     * method.
+     * before any arrive, and all {@link #awaitAdvance} at each phase.
+     * Otherwise, you cannot ensure lack of interference from other
+     * parties during the invocation of this method.
      *
      * @param phase the phase number on entering the barrier
      * @param registeredParties the current number of registered parties
@@ -931,49 +987,52 @@ public class Phaser {
         return p;
     }
 
-    // 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();
-            }
-        }
-    }
+    // Unsafe mechanics
 
-    private static Unsafe getUnsafePrivileged()
-            throws NoSuchFieldException, IllegalAccessException {
-        Field f = Unsafe.class.getDeclaredField("theUnsafe");
-        f.setAccessible(true);
-        return (Unsafe) f.get(null);
-    }
+    private static final sun.misc.Unsafe UNSAFE = getUnsafe();
+    private static final long stateOffset =
+        objectFieldOffset("state", Phaser.class);
 
-    private static long fieldOffset(String fieldName)
-            throws NoSuchFieldException {
-        return UNSAFE.objectFieldOffset
-            (Phaser.class.getDeclaredField(fieldName));
+    private final boolean casState(long cmp, long val) {
+        return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
     }
 
-    static final Unsafe UNSAFE;
-    static final long stateOffset;
-
-    static {
+    private static long objectFieldOffset(String field, Class<?> klazz) {
         try {
-            UNSAFE = getUnsafe();
-            stateOffset = fieldOffset("state");
-        } catch (Throwable e) {
-            throw new RuntimeException("Could not initialize intrinsics", e);
+            return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
+        } catch (NoSuchFieldException e) {
+            // Convert Exception to corresponding Error
+            NoSuchFieldError error = new NoSuchFieldError(field);
+            error.initCause(e);
+            throw error;
         }
     }
 
-    final boolean casState(long cmp, long val) {
-        return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
+    /**
+     * 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<sun.misc.Unsafe>() {
+                        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());
+            }
+        }
     }
 }