--- jsr166/src/jsr166y/Phaser.java 2009/03/19 04:49:44 1.11
+++ jsr166/src/jsr166y/Phaser.java 2009/08/23 13:37:08 1.35
@@ -7,10 +7,9 @@
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
@@ -20,53 +19,58 @@ import java.lang.reflect.*;
*
*
*
- * - 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
+ *
- The number of parties registered 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.)
*
*
- 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}).
+ * zero, and advancing when all parties arrive at the barrier
+ * (wrapping around to zero after reaching {@code Integer.MAX_VALUE}).
*
- *
- 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:
+ *
- 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, which may also be invoked independently:
*
*
*
- * - Arriving at a barrier. Methods {@code arrive} and
- * {@code arriveAndDeregister} do not block, but return
- * the phase value current upon entry to the method.
- *
- *
- Awaiting others. Method {@code awaitAdvance} requires an
- * argument indicating the entry phase, and returns when the
- * barrier advances to a new phase.
+ *
- Arriving at a barrier. Methods {@link #arrive} and
+ * {@link #arriveAndDeregister} do not block, but return
+ * an associated arrival phase number;
+ * that is, the phase number of the barrier to which the
+ * arrival applied.
+ *
+ *
- Awaiting others. Method {@link #awaitAdvance} requires an
+ * argument indicating an arrival phase number, and returns
+ * when the barrier advances to a new phase.
*
*
*
* - 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.
+ * 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}.
*
*
- Phasers may enter a termination 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.
+ * 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.
*
*
- Phasers may be tiered to reduce contention. Phasers with large
* numbers of parties that would otherwise experience heavy
@@ -76,96 +80,90 @@ import java.lang.reflect.*;
*
*
- 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
+ * {@code CyclicBarrier}, 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 ensure lack of starvation when used by ForkJoinTasks.
+ *
- 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.
*
*
*
* Sample usages:
*
- *
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:
- *
- *
- * void runTasks(List<Runnable> list) {
- * final Phaser phaser = new Phaser(1); // "1" to register self
- * for (Runnable r : list) {
- * phaser.register();
- * new Thread() {
- * public void run() {
- * phaser.arriveAndAwaitAdvance(); // await all creation
- * r.run();
- * phaser.arriveAndDeregister(); // signal completion
- * }
- * }.start();
+ * 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:
+ *
+ *
{@code
+ * void runTasks(List tasks) {
+ * final Phaser phaser = new Phaser(1); // "1" to register self
+ * // create and start threads
+ * for (Runnable task : tasks) {
+ * phaser.register();
+ * new Thread() {
+ * public void run() {
+ * phaser.arriveAndAwaitAdvance(); // await all creation
+ * 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();
+ * }}
*
* One way to cause a set of threads to repeatedly perform actions
* for a given number of iterations is to override {@code onAdvance}:
*
- *
- * void startTasks(List<Runnable> list, final int iterations) {
- * final Phaser phaser = new Phaser() {
- * public boolean onAdvance(int phase, int registeredParties) {
- * return phase >= iterations || registeredParties == 0;
+ * {@code
+ * void startTasks(List 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 task : tasks) {
+ * phaser.register();
+ * new Thread() {
+ * public void run() {
+ * do {
+ * task.run();
+ * phaser.arriveAndAwaitAdvance();
+ * } while(!phaser.isTerminated();
* }
- * };
- * phaser.register();
- * for (Runnable r : list) {
- * phaser.register();
- * new Thread() {
- * public void run() {
- * do {
- * r.run();
- * phaser.arriveAndAwaitAdvance();
- * } while(!phaser.isTerminated();
- * }
- * }.start();
+ * }.start();
* }
* phaser.arriveAndDeregister(); // deregister self, don't wait
- * }
- *
+ * }}
*
- * To create a set of tasks using a tree of Phasers,
+ *
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:
- *
- * void build(Task[] actions, int lo, int hi, Phaser b) {
- * int step = (hi - lo) / TASKS_PER_PHASER;
- * if (step > 1) {
- * int i = lo;
- * while (i < hi) {
- * int r = Math.min(i + step, hi);
- * build(actions, i, r, new Phaser(b));
- * i = r;
- * }
- * }
- * else {
- * for (int i = lo; i < hi; ++i)
- * actions[i] = new Task(b);
- * // assumes new Task(b) performs b.register()
- * }
- * }
- * // .. initially called, for n tasks via
- * build(new Task[n], 0, n, new Phaser());
- *
+ * {@code
+ * void build(Task[] actions, int lo, int hi, Phaser b) {
+ * int step = (hi - lo) / TASKS_PER_PHASER;
+ * if (step > 1) {
+ * int i = lo;
+ * while (i < hi) {
+ * int r = Math.min(i + step, hi);
+ * build(actions, i, r, new Phaser(b));
+ * i = r;
+ * }
+ * } else {
+ * for (int i = lo; i < hi; ++i)
+ * actions[i] = new Task(b);
+ * // assumes new Task(b) performs b.register()
+ * }
+ * }
+ * // .. initially called, for n tasks via
+ * build(new Task[n], 0, n, new Phaser());}
*
* The best value of {@code TASKS_PER_PHASER} depends mainly on
* expected barrier synchronization rates. A value as low as four may
@@ -176,9 +174,12 @@ import java.lang.reflect.*;
*
* Implementation notes: 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.
+ *
+ * @since 1.7
+ * @author Doug Lea
*/
public class Phaser {
/*
@@ -212,15 +213,15 @@ public class Phaser {
private static final int phaseMask = 0x7fffffff;
private static int unarrivedOf(long s) {
- return (int)(s & ushortMask);
+ return (int) (s & ushortMask);
}
private static int partiesOf(long s) {
- return ((int)s) >>> 16;
+ return ((int) s) >>> 16;
}
private static int phaseOf(long s) {
- return (int)(s >>> 32);
+ return (int) (s >>> 32);
}
private static int arrivedOf(long s) {
@@ -228,17 +229,17 @@ public class Phaser {
}
private static long stateFor(int phase, int parties, int unarrived) {
- return ((((long)phase) << 32) | (((long)parties) << 16) |
- (long)unarrived);
+ return ((((long) phase) << 32) | (((long) parties) << 16) |
+ (long) unarrived);
}
private static long trippedStateFor(int phase, int parties) {
- long lp = (long)parties;
- return (((long)phase) << 32) | (lp << 16) | lp;
+ long lp = (long) parties;
+ return (((long) phase) << 32) | (lp << 16) | lp;
}
/**
- * Returns message string for bad bounds exceptions
+ * Returns message string for bad bounds exceptions.
*/
private static String badBounds(int parties, int unarrived) {
return ("Attempt to set " + unarrived +
@@ -251,7 +252,7 @@ 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;
@@ -267,7 +268,7 @@ public class Phaser {
private final AtomicReference oddQ = new AtomicReference();
private AtomicReference queueFor(int phase) {
- return (phase & 1) == 0? evenQ : oddQ;
+ return ((phase & 1) == 0) ? evenQ : oddQ;
}
/**
@@ -275,7 +276,7 @@ public class Phaser {
* root if necessary.
*/
private long getReconciledState() {
- return parent == null? state : reconcileState();
+ return (parent == null) ? state : reconcileState();
}
/**
@@ -302,31 +303,33 @@ 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.
+ *
+ * @param parties the number of parties required to trip barrier
* @throws IllegalArgumentException if parties less than zero
- * or greater than the maximum number of parties supported.
+ * or greater than the maximum number of parties supported
*/
public Phaser(int parties) {
this(null, parties);
}
/**
- * 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.
- * @param parent the parent phaser.
+ *
+ * @param parent the parent phaser
*/
public Phaser(Phaser parent) {
int phase = 0;
@@ -341,14 +344,15 @@ public class Phaser {
}
/**
- * Creates a new Phaser with the given parent and numbers of
- * registered unarrived parties. If parent is non-null this phaser
+ * 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.
- * @param parent the parent phaser.
- * @param parties the number of parties required to trip barrier.
+ *
+ * @param parent the parent phaser
+ * @param parties the number of parties required to trip barrier
* @throws IllegalArgumentException if parties less than zero
- * or greater than the maximum number of parties supported.
+ * or greater than the maximum number of parties supported
*/
public Phaser(Phaser parent, int parties) {
if (parties < 0 || parties > ushortMask)
@@ -366,9 +370,10 @@ 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.
+ * than the maximum supported number of parties
*/
public int register() {
return doRegister(1);
@@ -376,10 +381,11 @@ 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
+ *
+ * @param parties the number of parties required to trip barrier
+ * @return the arrival phase number to which this registration applied
* @throws IllegalStateException if attempting to register more
- * than the maximum supported number of parties.
+ * than the maximum supported number of parties
*/
public int bulkRegister(int parties) {
if (parties < 0)
@@ -399,7 +405,7 @@ public class Phaser {
phase = phaseOf(s);
int unarrived = unarrivedOf(s) + registrations;
int parties = partiesOf(s) + registrations;
- if (phase < 0)
+ if (phase < 0)
break;
if (parties > ushortMask || unarrived > ushortMask)
throw new IllegalStateException(badBounds(parties, unarrived));
@@ -414,10 +420,9 @@ 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.
+ * of unarrived parties would become negative
*/
public int arrive() {
int phase;
@@ -437,7 +442,7 @@ public class Phaser {
if (par == null) { // directly trip
if (casState
(s,
- trippedStateFor(onAdvance(phase, parties)? -1 :
+ trippedStateFor(onAdvance(phase, parties) ? -1 :
((phase + 1) & phaseMask), parties))) {
releaseWaiters(phase);
break;
@@ -460,16 +465,16 @@ 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.
+ * of registered or unarrived parties would become negative
*/
public int arriveAndDeregister() {
// similar code to arrive, but too different to merge
@@ -498,7 +503,7 @@ public class Phaser {
if (unarrived == 0) {
if (casState
(s,
- trippedStateFor(onAdvance(phase, parties)? -1 :
+ trippedStateFor(onAdvance(phase, parties) ? -1 :
((phase + 1) & phaseMask), parties))) {
releaseWaiters(phase);
break;
@@ -517,23 +522,31 @@ 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.
- * @return the phase on entry to this method
+ * 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 arrival phase number, or a negative number if terminated
* @throws IllegalStateException if not terminated and the number
- * of unarrived parties would become negative.
+ * of unarrived parties would become negative
*/
public int arriveAndAwaitAdvance() {
return awaitAdvance(arrive());
}
/**
- * 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)
@@ -549,15 +562,20 @@ 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)
+ public int awaitAdvanceInterruptibly(int phase)
throws InterruptedException {
if (phase < 0)
return phase;
@@ -571,15 +589,26 @@ 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
*/
- public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
+ public int awaitAdvanceInterruptibly(int phase,
+ long timeout, TimeUnit unit)
throws InterruptedException, TimeoutException {
if (phase < 0)
return phase;
@@ -620,6 +649,7 @@ public class Phaser {
* Returns the current phase number. The maximum phase number is
* {@code Integer.MAX_VALUE}, after which it restarts at
* zero. Upon termination, the phase number is negative.
+ *
* @return the phase number, or a negative value if terminated
*/
public final int getPhase() {
@@ -627,16 +657,8 @@ 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
*/
public int getRegisteredParties() {
@@ -646,6 +668,7 @@ public class Phaser {
/**
* Returns the number of parties that have arrived at the current
* phase of this barrier.
+ *
* @return the number of arrived parties
*/
public int getArrivedParties() {
@@ -655,6 +678,7 @@ public class Phaser {
/**
* Returns the number of registered parties that have not yet
* arrived at the current phase of this barrier.
+ *
* @return the number of unarrived parties
*/
public int getUnarrivedParties() {
@@ -662,8 +686,9 @@ public class Phaser {
}
/**
- * Returns the parent of this phaser, or null if none.
- * @return 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 {@code null} if none
*/
public Phaser getParent() {
return parent;
@@ -672,6 +697,7 @@ public class Phaser {
/**
* Returns the root ancestor of this phaser, which is the same as
* this phaser if it has no parent.
+ *
* @return the root ancestor of this phaser
*/
public Phaser getRoot() {
@@ -680,6 +706,7 @@ public class Phaser {
/**
* Returns {@code true} if this barrier has been terminated.
+ *
* @return {@code true} if this barrier has been terminated
*/
public boolean isTerminated() {
@@ -690,26 +717,22 @@ 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.
*
- * The default version returns true when the number of
+ *
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.
*
- *
You may override this method to perform an action with side
+ *
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
@@ -795,7 +818,7 @@ public class Phaser {
try {
ForkJoinPool.managedBlock(this, false);
} catch (InterruptedException ie) {
- }
+ }
}
return wasInterrupted;
}
@@ -803,7 +826,7 @@ public class Phaser {
}
/**
- * Removes and signals waiting threads from wait queue
+ * Removes and signals waiting threads from wait queue.
*/
private void releaseWaiters(int phase) {
AtomicReference head = queueFor(phase);
@@ -815,7 +838,8 @@ public class Phaser {
}
/**
- * Tries to enqueue given node in the appropriate wait queue
+ * Tries to enqueue given node in the appropriate wait queue.
+ *
* @return true if successful
*/
private boolean tryEnqueue(QNode node) {
@@ -825,6 +849,7 @@ public class Phaser {
/**
* Enqueues node and waits unless aborted or signalled.
+ *
* @return current phase
*/
private int untimedWait(int phase) {
@@ -912,49 +937,52 @@ 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() {
- 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 (Exception 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() {
+ 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());
+ }
+ }
}
}