--- jsr166/src/jsr166y/Phaser.java 2009/03/19 05:10:42 1.12
+++ jsr166/src/jsr166y/Phaser.java 2009/07/23 23:07:57 1.18
@@ -93,18 +93,18 @@ import java.lang.reflect.*;
* 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();
+ * {@code
+ * void runTasks(List 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();
* }
*
* doSomethingOnBehalfOfWorkers();
@@ -113,59 +113,55 @@ import java.lang.reflect.*;
* p = phaser.awaitAdvance(p); // ... and await arrival
* otherActions(); // do other things while tasks execute
* phaser.awaitAdvance(p); // await final completion
- * }
- *
+ * }}
*
* 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 list, 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) {
+ * phaser.register();
+ * new Thread() {
+ * public void run() {
+ * do {
+ * r.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,
* you could use code of the following form, assuming a
* 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
@@ -179,6 +175,9 @@ import java.lang.reflect.*;
* parties result in IllegalStateExceptions. 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 +211,15 @@ 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 +227,17 @@ 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 +
@@ -267,7 +266,7 @@ 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 +274,7 @@ public class Phaser {
* root if necessary.
*/
private long getReconciledState() {
- return parent == null? state : reconcileState();
+ return (parent == null) ? state : reconcileState();
}
/**
@@ -313,9 +312,10 @@ public class Phaser {
/**
* 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);
@@ -326,7 +326,8 @@ public class Phaser {
* 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;
@@ -342,13 +343,14 @@ public class Phaser {
/**
* Creates a new Phaser with the given parent and numbers of
- * registered unarrived parties. If parent is non-null this phaser
+ * 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 +368,10 @@ public class Phaser {
/**
* Adds a new unarrived party to this phaser.
+ *
* @return the current barrier phase number upon registration
* @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 +379,11 @@ public class Phaser {
/**
* Adds the given number of new unarrived parties to this phaser.
- * @param parties the number of parties required to trip barrier.
+ *
+ * @param parties the number of parties required to trip barrier
* @return the current barrier phase number upon registration
* @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)
@@ -415,9 +419,9 @@ public class Phaser {
* in turn wait for others via {@link #awaitAdvance}).
*
* @return the barrier phase number upon entry to this method, or a
- * negative value if terminated;
+ * 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 +441,7 @@ 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;
@@ -467,9 +471,9 @@ public class Phaser {
* zero parties, this phaser is also deregistered from its parent.
*
* @return the current barrier phase number upon entry to
- * this method, or a negative value if terminated;
+ * this method, 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 +502,7 @@ 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;
@@ -520,9 +524,10 @@ public class Phaser {
* 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
* @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());
@@ -532,6 +537,7 @@ 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
*/
@@ -553,6 +559,7 @@ public class Phaser {
* 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
* @throws InterruptedException if thread interrupted while waiting
@@ -574,12 +581,14 @@ 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
* @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 +629,7 @@ 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() {
@@ -628,6 +638,7 @@ 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
*/
@@ -637,6 +648,7 @@ public class Phaser {
/**
* Returns the number of parties registered at this barrier.
+ *
* @return the number of parties
*/
public int getRegisteredParties() {
@@ -646,6 +658,7 @@ 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 +668,7 @@ 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() {
@@ -663,6 +677,7 @@ public class Phaser {
/**
* Returns the parent of this phaser, or null if none.
+ *
* @return the parent of this phaser, or null if none
*/
public Phaser getParent() {
@@ -672,6 +687,7 @@ 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 +696,7 @@ public class Phaser {
/**
* Returns {@code true} if this barrier has been terminated.
+ *
* @return {@code true} if this barrier has been terminated
*/
public boolean isTerminated() {
@@ -803,7 +820,7 @@ 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 +832,8 @@ 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 +843,7 @@ public class Phaser {
/**
* Enqueues node and waits unless aborted or signalled.
+ *
* @return current phase
*/
private int untimedWait(int phase) {
@@ -938,16 +957,16 @@ public class Phaser {
private static long fieldOffset(String fieldName)
throws NoSuchFieldException {
- return _unsafe.objectFieldOffset
+ return UNSAFE.objectFieldOffset
(Phaser.class.getDeclaredField(fieldName));
}
- static final Unsafe _unsafe;
+ static final Unsafe UNSAFE;
static final long stateOffset;
static {
try {
- _unsafe = getUnsafe();
+ UNSAFE = getUnsafe();
stateOffset = fieldOffset("state");
} catch (Throwable e) {
throw new RuntimeException("Could not initialize intrinsics", e);
@@ -955,6 +974,6 @@ public class Phaser {
}
final boolean casState(long cmp, long val) {
- return _unsafe.compareAndSwapLong(this, stateOffset, cmp, val);
+ return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
}
}