--- jsr166/src/jsr166y/Phaser.java	2009/08/02 17:02:06	1.25
+++ jsr166/src/jsr166y/Phaser.java	2009/08/23 20:12:24	1.36
@@ -19,54 +19,58 @@ import java.util.concurrent.locks.LockSu
  *
  * <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
+ * <li> 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 may
+ * optionally be 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.)
  *
- * <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> Each generation has an associated phase number. The phase
+ * number starts at zero, amd advances when all parties arrive at the
+ * barrier, wrapping around to zero after reaching {@code
+ * Integer.MAX_VALUE}.
  *
- * <li> Like a {@code CyclicBarrier}, a Phaser may be repeatedly
+ * <li> Like a {@code CyclicBarrier}, a phaser may be repeatedly
  * awaited.  Method {@link #arriveAndAwaitAdvance} has effect
  * analogous to {@link java.util.concurrent.CyclicBarrier#await
  * CyclicBarrier.await}.  However, phasers separate two aspects of
- * coordination, that may also be invoked independently:
+ * coordination, which may also be invoked independently:
  *
  * <ul>
  *
  *   <li> Arriving at a barrier. Methods {@link #arrive} and
  *       {@link #arriveAndDeregister} do not block, but return
- *       the phase value current upon entry to the method.
+ *       an associated <em>arrival phase number</em>;
+ *       that is, the phase number of the barrier to which the
+ *       arrival applied.
  *
  *   <li> Awaiting others. Method {@link #awaitAdvance} requires an
- *       argument indicating the entry phase, and returns when the
- *       barrier advances to a new phase.
+ *       argument indicating an arrival phase number, and returns
+ *       when the barrier advances to a new phase.
  * </ul>
  *
- *
  * <li> Barrier actions, performed by the task triggering a phase
- * advance while others may be waiting, are arranged by overriding
- * method {@link #onAdvance}, that also controls termination.
- * Overriding this method may be used to similar but more flexible
- * effect as providing a barrier action to a {@code CyclicBarrier}.
+ * 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> 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 {@link #forceTermination} is also
- * available to abruptly release waiting threads and allow them to
- * terminate.
+ * execution is complete.  Termination is triggered when an invocation
+ * of {@code onAdvance} returns {@code true}.  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 {@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
  * numbers of parties that would otherwise experience heavy
@@ -82,7 +86,17 @@ import java.util.concurrent.locks.LockSu
  * within handlers of those exceptions, often after invoking
  * {@code forceTermination}.
  *
- * <li>Phasers ensure lack of starvation when used by ForkJoinTasks.
+ * <li>Phasers may be used to coordinate tasks executing in a {@link
+ * ForkJoinPool}, which will ensure sufficient parallelism to execute
+ * tasks when others are blocked waiting for a phase to advance.
+ *
+ * <li>The current state of a phaser may be monitored.  At any given
+ * moment there are {@link #getRegisteredParties}, where {@link
+ * #getArrivedParties} have arrived at the current phase ({@link
+ * #getPhase}). When the remaining {@link #getUnarrivedParties})
+ * arrive, the phase advances. Method {@link #toString} returns
+ * snapshots of these state queries in a form convenient for
+ * informal monitoring.
  *
  * </ul>
  *
@@ -94,44 +108,40 @@ import java.util.concurrent.locks.LockSu
  * 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) {
  *       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();
  *       }
@@ -172,7 +182,7 @@ import java.util.concurrent.locks.LockSu
  *
  * <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.
  *
@@ -369,7 +379,7 @@ 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 +391,7 @@ 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
      */
@@ -418,8 +428,7 @@ public class Phaser {
      * Arrives at the barrier, but does not wait for others.  (You can
      * in turn wait for others via {@link #awaitAdvance}).
      *
-     * @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 +473,14 @@ 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.
      *
-     * @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 +530,13 @@ 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}.
      *
-     * @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 +545,16 @@ 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.
+     *
+     * @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 +570,17 @@ 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, 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.
+     *
+     * @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 +597,21 @@ 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.
+     *
+     * @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 +665,6 @@ 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 +674,8 @@ 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
      */
@@ -721,12 +739,8 @@ public class Phaser {
      * 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 {@link #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.
+     * 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