Phasers ensure lack of starvation when used by ForkJoinTasks.
+ *
*
*
* Sample usages:
@@ -90,18 +92,18 @@ 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();
@@ -110,59 +112,55 @@ 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
@@ -176,6 +174,9 @@ 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 {
/*
@@ -200,24 +201,24 @@ public class Phaser {
* and encoding simple, and keeping race windows short.
*
* Note: there are some cheats in arrive() that rely on unarrived
- * being lowest 16 bits.
+ * count being lowest 16 bits.
*/
private volatile long state;
private static final int ushortBits = 16;
- private static final int ushortMask = (1 << ushortBits) - 1;
- private static final int phaseMask = 0x7fffffff;
+ private static final int ushortMask = 0xffff;
+ 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 & (ushortMask << 16)) >>> 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) {
@@ -225,17 +226,21 @@ public class Phaser {
}
private static long stateFor(int phase, int parties, int unarrived) {
- return (((long)phase) << 32) | ((parties << 16) | unarrived);
+ return ((((long) phase) << 32) | (((long) parties) << 16) |
+ (long) unarrived);
}
private static long trippedStateFor(int phase, int parties) {
- return (((long)phase) << 32) | ((parties << 16) | parties);
+ long lp = (long) parties;
+ return (((long) phase) << 32) | (lp << 16) | lp;
}
- private static IllegalStateException badBounds(int parties, int unarrived) {
- return new IllegalStateException
- ("Attempt to set " + unarrived +
- " unarrived of " + parties + " parties");
+ /**
+ * Returns message string for bad bounds exceptions.
+ */
+ private static String badBounds(int parties, int unarrived) {
+ return ("Attempt to set " + unarrived +
+ " unarrived of " + parties + " parties");
}
/**
@@ -252,7 +257,7 @@ public class Phaser {
// Wait queues
/**
- * Heads of Treiber stacks waiting for nonFJ threads. To eliminate
+ * Heads of Treiber stacks for waiting threads. To eliminate
* contention while releasing some threads while adding others, we
* use two of them, alternating across even and odd phases.
*/
@@ -260,7 +265,7 @@ 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;
}
/**
@@ -268,7 +273,7 @@ public class Phaser {
* root if necessary.
*/
private long getReconciledState() {
- return parent == null? state : reconcileState();
+ return (parent == null) ? state : reconcileState();
}
/**
@@ -296,7 +301,8 @@ public class Phaser {
/**
* Creates a new Phaser without any initially registered parties,
- * initial phase number 0, and no parent.
+ * initial phase number 0, and no parent. Any thread using this
+ * Phaser will need to first register for it.
*/
public Phaser() {
this(null);
@@ -305,9 +311,10 @@ 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);
@@ -318,7 +325,8 @@ 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;
@@ -334,13 +342,14 @@ 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)
@@ -358,9 +367,10 @@ 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);
@@ -368,10 +378,11 @@ 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)
@@ -394,7 +405,7 @@ public class Phaser {
if (phase < 0)
break;
if (parties > ushortMask || unarrived > ushortMask)
- throw badBounds(parties, unarrived);
+ throw new IllegalStateException(badBounds(parties, unarrived));
if (phase == phaseOf(root.state) &&
casState(s, stateFor(phase, parties, unarrived)))
break;
@@ -407,15 +418,17 @@ 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;
for (;;) {
long s = state;
phase = phaseOf(s);
+ if (phase < 0)
+ break;
int parties = partiesOf(s);
int unarrived = unarrivedOf(s) - 1;
if (unarrived > 0) { // Not the last arrival
@@ -427,7 +440,7 @@ 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;
@@ -441,12 +454,10 @@ public class Phaser {
}
}
}
- else if (phase < 0) // Don't throw exception if terminated
- break;
else if (phase != phaseOf(root.state)) // or if unreconciled
reconcileState();
else
- throw badBounds(parties, unarrived);
+ throw new IllegalStateException(badBounds(parties, unarrived));
}
return phase;
}
@@ -459,9 +470,9 @@ 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
@@ -470,6 +481,8 @@ public class Phaser {
for (;;) {
long s = state;
phase = phaseOf(s);
+ if (phase < 0)
+ break;
int parties = partiesOf(s) - 1;
int unarrived = unarrivedOf(s) - 1;
if (parties >= 0) {
@@ -488,21 +501,19 @@ 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;
}
continue;
}
- if (phase < 0)
- break;
if (par != null && phase != phaseOf(root.state)) {
reconcileState();
continue;
}
}
- throw badBounds(parties, unarrived);
+ throw new IllegalStateException(badBounds(parties, unarrived));
}
return phase;
}
@@ -512,9 +523,10 @@ 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());
@@ -524,6 +536,7 @@ 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
*/
@@ -534,7 +547,7 @@ public class Phaser {
int p = phaseOf(s);
if (p != phase)
return p;
- if (unarrivedOf(s) == 0)
+ if (unarrivedOf(s) == 0 && parent != null)
parent.awaitAdvance(phase);
// Fall here even if parent waited, to reconcile and help release
return untimedWait(phase);
@@ -545,18 +558,20 @@ 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
*/
- public int awaitAdvanceInterruptibly(int phase) throws InterruptedException {
+ public int awaitAdvanceInterruptibly(int phase)
+ throws InterruptedException {
if (phase < 0)
return phase;
long s = getReconciledState();
int p = phaseOf(s);
if (p != phase)
return p;
- if (unarrivedOf(s) != 0)
+ if (unarrivedOf(s) == 0 && parent != null)
parent.awaitAdvanceInterruptibly(phase);
return interruptibleWait(phase);
}
@@ -565,12 +580,14 @@ 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;
@@ -578,7 +595,7 @@ public class Phaser {
int p = phaseOf(s);
if (p != phase)
return p;
- if (unarrivedOf(s) == 0)
+ if (unarrivedOf(s) == 0 && parent != null)
parent.awaitAdvanceInterruptibly(phase, timeout, unit);
return timedWait(phase, unit.toNanos(timeout));
}
@@ -611,6 +628,7 @@ 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() {
@@ -619,6 +637,7 @@ 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
*/
@@ -628,6 +647,7 @@ public class Phaser {
/**
* Returns the number of parties registered at this barrier.
+ *
* @return the number of parties
*/
public int getRegisteredParties() {
@@ -637,6 +657,7 @@ 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() {
@@ -646,6 +667,7 @@ 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() {
@@ -654,6 +676,7 @@ 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() {
@@ -663,6 +686,7 @@ 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() {
@@ -671,6 +695,7 @@ public class Phaser {
/**
* Returns {@code true} if this barrier has been terminated.
+ *
* @return {@code true} if this barrier has been terminated
*/
public boolean isTerminated() {
@@ -729,38 +754,51 @@ public class Phaser {
// methods for waiting
- /** The number of CPUs, for spin control */
- static final int NCPUS = Runtime.getRuntime().availableProcessors();
-
- /**
- * The number of times to spin before blocking in timed waits.
- * The value is empirically derived.
- */
- static final int maxTimedSpins = (NCPUS < 2)? 0 : 32;
-
- /**
- * The number of times to spin before blocking in untimed waits.
- * This is greater than timed value because untimed waits spin
- * faster since they don't need to check times on each spin.
- */
- static final int maxUntimedSpins = maxTimedSpins * 32;
-
- /**
- * The number of nanoseconds for which it is faster to spin
- * rather than to use timed park. A rough estimate suffices.
- */
- static final long spinForTimeoutThreshold = 1000L;
-
/**
- * Wait nodes for Treiber stack representing wait queue for non-FJ
- * tasks.
+ * Wait nodes for Treiber stack representing wait queue
*/
- static final class QNode {
- QNode next;
+ static final class QNode implements ForkJoinPool.ManagedBlocker {
+ final Phaser phaser;
+ final int phase;
+ final long startTime;
+ final long nanos;
+ final boolean timed;
+ final boolean interruptible;
+ volatile boolean wasInterrupted = false;
volatile Thread thread; // nulled to cancel wait
- QNode() {
+ QNode next;
+ QNode(Phaser phaser, int phase, boolean interruptible,
+ boolean timed, long startTime, long nanos) {
+ this.phaser = phaser;
+ this.phase = phase;
+ this.timed = timed;
+ this.interruptible = interruptible;
+ this.startTime = startTime;
+ this.nanos = nanos;
thread = Thread.currentThread();
}
+ public boolean isReleasable() {
+ return (thread == null ||
+ phaser.getPhase() != phase ||
+ (interruptible && wasInterrupted) ||
+ (timed && (nanos - (System.nanoTime() - startTime)) <= 0));
+ }
+ public boolean block() {
+ if (Thread.interrupted()) {
+ wasInterrupted = true;
+ if (interruptible)
+ return true;
+ }
+ if (!timed)
+ LockSupport.park(this);
+ else {
+ long waitTime = nanos - (System.nanoTime() - startTime);
+ if (waitTime <= 0)
+ return true;
+ LockSupport.parkNanos(this, waitTime);
+ }
+ return isReleasable();
+ }
void signal() {
Thread t = thread;
if (t != null) {
@@ -768,10 +806,20 @@ public class Phaser {
LockSupport.unpark(t);
}
}
+ boolean doWait() {
+ if (thread != null) {
+ try {
+ ForkJoinPool.managedBlock(this, false);
+ } catch (InterruptedException ie) {
+ }
+ }
+ return wasInterrupted;
+ }
+
}
/**
- * 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);
@@ -783,137 +831,147 @@ public class Phaser {
}
/**
+ * Tries to enqueue given node in the appropriate wait queue.
+ *
+ * @return true if successful
+ */
+ private boolean tryEnqueue(QNode node) {
+ AtomicReference head = queueFor(node.phase);
+ return head.compareAndSet(node.next = head.get(), node);
+ }
+
+ /**
* Enqueues node and waits unless aborted or signalled.
+ *
+ * @return current phase
*/
private int untimedWait(int phase) {
- int spins = maxUntimedSpins;
QNode node = null;
- boolean interrupted = false;
boolean queued = false;
+ boolean interrupted = false;
int p;
while ((p = getPhase()) == phase) {
- interrupted = Thread.interrupted();
- if (node != null) {
- if (!queued) {
- AtomicReference head = queueFor(phase);
- queued = head.compareAndSet(node.next = head.get(), node);
- }
- else if (node.thread != null)
- LockSupport.park(this);
- }
- else if (spins <= 0)
- node = new QNode();
+ if (Thread.interrupted())
+ interrupted = true;
+ else if (node == null)
+ node = new QNode(this, phase, false, false, 0, 0);
+ else if (!queued)
+ queued = tryEnqueue(node);
else
- --spins;
+ interrupted = node.doWait();
}
if (node != null)
node.thread = null;
+ releaseWaiters(phase);
if (interrupted)
Thread.currentThread().interrupt();
- releaseWaiters(phase);
return p;
}
/**
- * Messier interruptible version
+ * Interruptible version
+ * @return current phase
*/
private int interruptibleWait(int phase) throws InterruptedException {
- int spins = maxUntimedSpins;
QNode node = null;
boolean queued = false;
boolean interrupted = false;
int p;
- while ((p = getPhase()) == phase) {
- if (interrupted = Thread.interrupted())
- break;
- if (node != null) {
- if (!queued) {
- AtomicReference head = queueFor(phase);
- queued = head.compareAndSet(node.next = head.get(), node);
- }
- else if (node.thread != null)
- LockSupport.park(this);
- }
- else if (spins <= 0)
- node = new QNode();
+ while ((p = getPhase()) == phase && !interrupted) {
+ if (Thread.interrupted())
+ interrupted = true;
+ else if (node == null)
+ node = new QNode(this, phase, true, false, 0, 0);
+ else if (!queued)
+ queued = tryEnqueue(node);
else
- --spins;
+ interrupted = node.doWait();
}
if (node != null)
node.thread = null;
+ if (p != phase || (p = getPhase()) != phase)
+ releaseWaiters(phase);
if (interrupted)
throw new InterruptedException();
- releaseWaiters(phase);
return p;
}
/**
- * Even messier timeout version.
+ * Timeout version.
+ * @return current phase
*/
private int timedWait(int phase, long nanos)
throws InterruptedException, TimeoutException {
+ long startTime = System.nanoTime();
+ QNode node = null;
+ boolean queued = false;
+ boolean interrupted = false;
int p;
- if ((p = getPhase()) == phase) {
- long lastTime = System.nanoTime();
- int spins = maxTimedSpins;
- QNode node = null;
- boolean queued = false;
- boolean interrupted = false;
- while ((p = getPhase()) == phase) {
- if (interrupted = Thread.interrupted())
- break;
- long now = System.nanoTime();
- if ((nanos -= now - lastTime) <= 0)
- break;
- lastTime = now;
- if (node != null) {
- if (!queued) {
- AtomicReference head = queueFor(phase);
- queued = head.compareAndSet(node.next = head.get(), node);
- }
- else if (node.thread != null &&
- nanos > spinForTimeoutThreshold) {
- LockSupport.parkNanos(this, nanos);
- }
- }
- else if (spins <= 0)
- node = new QNode();
- else
- --spins;
- }
- if (node != null)
- node.thread = null;
- if (interrupted)
- throw new InterruptedException();
- if (p == phase && (p = getPhase()) == phase)
- throw new TimeoutException();
+ while ((p = getPhase()) == phase && !interrupted) {
+ if (Thread.interrupted())
+ interrupted = true;
+ else if (nanos - (System.nanoTime() - startTime) <= 0)
+ break;
+ else if (node == null)
+ node = new QNode(this, phase, true, true, startTime, nanos);
+ else if (!queued)
+ queued = tryEnqueue(node);
+ else
+ interrupted = node.doWait();
}
- releaseWaiters(phase);
+ if (node != null)
+ node.thread = null;
+ if (p != phase || (p = getPhase()) != phase)
+ releaseWaiters(phase);
+ if (interrupted)
+ throw new InterruptedException();
+ if (p == phase)
+ throw new TimeoutException();
return p;
}
- // Temporary Unsafe mechanics for preliminary release
+ // Unsafe mechanics for jsr166y 3rd party package.
+ 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 {
+ return getUnsafeByReflection();
+ }});
+ } catch (java.security.PrivilegedActionException e) {
+ throw new RuntimeException("Could not initialize intrinsics",
+ e.getCause());
+ }
+ }
+ }
- static final Unsafe _unsafe;
- static final long stateOffset;
+ private static sun.misc.Unsafe getUnsafeByReflection()
+ throws NoSuchFieldException, IllegalAccessException {
+ java.lang.reflect.Field f =
+ sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
+ f.setAccessible(true);
+ return (sun.misc.Unsafe) f.get(null);
+ }
- static {
+ private static long fieldOffset(String fieldName, Class klazz) {
try {
- if (Phaser.class.getClassLoader() != null) {
- Field f = Unsafe.class.getDeclaredField("theUnsafe");
- f.setAccessible(true);
- _unsafe = (Unsafe)f.get(null);
- }
- else
- _unsafe = Unsafe.getUnsafe();
- stateOffset = _unsafe.objectFieldOffset
- (Phaser.class.getDeclaredField("state"));
- } catch (Exception e) {
- throw new RuntimeException("Could not initialize intrinsics", e);
+ return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
+ } catch (NoSuchFieldException e) {
+ // Convert Exception to Error
+ NoSuchFieldError error = new NoSuchFieldError(fieldName);
+ error.initCause(e);
+ throw error;
}
}
+ private static final sun.misc.Unsafe UNSAFE = getUnsafe();
+ static final long stateOffset =
+ fieldOffset("state", Phaser.class);
+
final boolean casState(long cmp, long val) {
- return _unsafe.compareAndSwapLong(this, stateOffset, cmp, val);
+ return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
}
}