| 57 |
|
* effect as providing a barrier action to a CyclicBarrier. |
| 58 |
|
* |
| 59 |
|
* <li> Phasers may enter a <em>termination</em> state in which all |
| 60 |
< |
* await actions immediately return, indicating (via a negative phase |
| 61 |
< |
* value) that execution is complete. Termination is triggered by |
| 62 |
< |
* executing the overridable {@code onAdvance} method that is invoked |
| 63 |
< |
* each time the barrier is about to be tripped. When a Phaser is |
| 64 |
< |
* controlling an action with a fixed number of iterations, it is |
| 65 |
< |
* often convenient to override this method to cause termination when |
| 66 |
< |
* the current phase number reaches a threshold. Method |
| 67 |
< |
* {@code forceTermination} is also available to abruptly release |
| 68 |
< |
* waiting threads and allow them to terminate. |
| 60 |
> |
* actions immediately return without updating phaser state or waiting |
| 61 |
> |
* for advance, and indicating (via a negative phase value) that |
| 62 |
> |
* execution is complete. Termination is triggered by executing the |
| 63 |
> |
* overridable {@code onAdvance} method that is invoked each time the |
| 64 |
> |
* barrier is about to be tripped. When a Phaser is controlling an |
| 65 |
> |
* action with a fixed number of iterations, it is often convenient to |
| 66 |
> |
* override this method to cause termination when the current phase |
| 67 |
> |
* number reaches a threshold. Method {@code forceTermination} is also |
| 68 |
> |
* available to abruptly release waiting threads and allow them to |
| 69 |
> |
* terminate. |
| 70 |
|
* |
| 71 |
|
* <li> Phasers may be tiered to reduce contention. Phasers with large |
| 72 |
|
* numbers of parties that would otherwise experience heavy |
| 82 |
|
* within handlers of those exceptions, often after invoking |
| 83 |
|
* {@code forceTermination}. |
| 84 |
|
* |
| 85 |
+ |
* <li>Phasers ensure lack of starvation when used by ForkJoinTasks. |
| 86 |
+ |
* |
| 87 |
|
* </ul> |
| 88 |
|
* |
| 89 |
|
* <p><b>Sample usages:</b> |
| 203 |
|
* and encoding simple, and keeping race windows short. |
| 204 |
|
* |
| 205 |
|
* Note: there are some cheats in arrive() that rely on unarrived |
| 206 |
< |
* being lowest 16 bits. |
| 206 |
> |
* count being lowest 16 bits. |
| 207 |
|
*/ |
| 208 |
|
private volatile long state; |
| 209 |
|
|
| 210 |
|
private static final int ushortBits = 16; |
| 211 |
< |
private static final int ushortMask = (1 << ushortBits) - 1; |
| 212 |
< |
private static final int phaseMask = 0x7fffffff; |
| 211 |
> |
private static final int ushortMask = 0xffff; |
| 212 |
> |
private static final int phaseMask = 0x7fffffff; |
| 213 |
|
|
| 214 |
|
private static int unarrivedOf(long s) { |
| 215 |
|
return (int)(s & ushortMask); |
| 216 |
|
} |
| 217 |
|
|
| 218 |
|
private static int partiesOf(long s) { |
| 219 |
< |
return (int)(s & (ushortMask << 16)) >>> 16; |
| 219 |
> |
return ((int)s) >>> 16; |
| 220 |
|
} |
| 221 |
|
|
| 222 |
|
private static int phaseOf(long s) { |
| 228 |
|
} |
| 229 |
|
|
| 230 |
|
private static long stateFor(int phase, int parties, int unarrived) { |
| 231 |
< |
return (((long)phase) << 32) | ((parties << 16) | unarrived); |
| 231 |
> |
return ((((long)phase) << 32) | (((long)parties) << 16) | |
| 232 |
> |
(long)unarrived); |
| 233 |
|
} |
| 234 |
|
|
| 235 |
|
private static long trippedStateFor(int phase, int parties) { |
| 236 |
< |
return (((long)phase) << 32) | ((parties << 16) | parties); |
| 236 |
> |
long lp = (long)parties; |
| 237 |
> |
return (((long)phase) << 32) | (lp << 16) | lp; |
| 238 |
|
} |
| 239 |
|
|
| 240 |
< |
private static IllegalStateException badBounds(int parties, int unarrived) { |
| 241 |
< |
return new IllegalStateException |
| 242 |
< |
("Attempt to set " + unarrived + |
| 243 |
< |
" unarrived of " + parties + " parties"); |
| 240 |
> |
/** |
| 241 |
> |
* Returns message string for bad bounds exceptions |
| 242 |
> |
*/ |
| 243 |
> |
private static String badBounds(int parties, int unarrived) { |
| 244 |
> |
return ("Attempt to set " + unarrived + |
| 245 |
> |
" unarrived of " + parties + " parties"); |
| 246 |
|
} |
| 247 |
|
|
| 248 |
|
/** |
| 259 |
|
// Wait queues |
| 260 |
|
|
| 261 |
|
/** |
| 262 |
< |
* Heads of Treiber stacks waiting for nonFJ threads. To eliminate |
| 262 |
> |
* Heads of Treiber stacks for waiting threads. To eliminate |
| 263 |
|
* contention while releasing some threads while adding others, we |
| 264 |
|
* use two of them, alternating across even and odd phases. |
| 265 |
|
*/ |
| 303 |
|
|
| 304 |
|
/** |
| 305 |
|
* Creates a new Phaser without any initially registered parties, |
| 306 |
< |
* initial phase number 0, and no parent. |
| 306 |
> |
* initial phase number 0, and no parent. Any thread using this |
| 307 |
> |
* Phaser will need to first register for it. |
| 308 |
|
*/ |
| 309 |
|
public Phaser() { |
| 310 |
|
this(null); |
| 399 |
|
phase = phaseOf(s); |
| 400 |
|
int unarrived = unarrivedOf(s) + registrations; |
| 401 |
|
int parties = partiesOf(s) + registrations; |
| 402 |
< |
if (phase < 0) |
| 402 |
> |
if (phase < 0) |
| 403 |
|
break; |
| 404 |
|
if (parties > ushortMask || unarrived > ushortMask) |
| 405 |
< |
throw badBounds(parties, unarrived); |
| 405 |
> |
throw new IllegalStateException(badBounds(parties, unarrived)); |
| 406 |
|
if (phase == phaseOf(root.state) && |
| 407 |
|
casState(s, stateFor(phase, parties, unarrived))) |
| 408 |
|
break; |
| 424 |
|
for (;;) { |
| 425 |
|
long s = state; |
| 426 |
|
phase = phaseOf(s); |
| 427 |
+ |
if (phase < 0) |
| 428 |
+ |
break; |
| 429 |
|
int parties = partiesOf(s); |
| 430 |
|
int unarrived = unarrivedOf(s) - 1; |
| 431 |
|
if (unarrived > 0) { // Not the last arrival |
| 451 |
|
} |
| 452 |
|
} |
| 453 |
|
} |
| 444 |
– |
else if (phase < 0) // Don't throw exception if terminated |
| 445 |
– |
break; |
| 454 |
|
else if (phase != phaseOf(root.state)) // or if unreconciled |
| 455 |
|
reconcileState(); |
| 456 |
|
else |
| 457 |
< |
throw badBounds(parties, unarrived); |
| 457 |
> |
throw new IllegalStateException(badBounds(parties, unarrived)); |
| 458 |
|
} |
| 459 |
|
return phase; |
| 460 |
|
} |
| 478 |
|
for (;;) { |
| 479 |
|
long s = state; |
| 480 |
|
phase = phaseOf(s); |
| 481 |
+ |
if (phase < 0) |
| 482 |
+ |
break; |
| 483 |
|
int parties = partiesOf(s) - 1; |
| 484 |
|
int unarrived = unarrivedOf(s) - 1; |
| 485 |
|
if (parties >= 0) { |
| 505 |
|
} |
| 506 |
|
continue; |
| 507 |
|
} |
| 498 |
– |
if (phase < 0) |
| 499 |
– |
break; |
| 508 |
|
if (par != null && phase != phaseOf(root.state)) { |
| 509 |
|
reconcileState(); |
| 510 |
|
continue; |
| 511 |
|
} |
| 512 |
|
} |
| 513 |
< |
throw badBounds(parties, unarrived); |
| 513 |
> |
throw new IllegalStateException(badBounds(parties, unarrived)); |
| 514 |
|
} |
| 515 |
|
return phase; |
| 516 |
|
} |
| 542 |
|
int p = phaseOf(s); |
| 543 |
|
if (p != phase) |
| 544 |
|
return p; |
| 545 |
< |
if (unarrivedOf(s) == 0) |
| 545 |
> |
if (unarrivedOf(s) == 0 && parent != null) |
| 546 |
|
parent.awaitAdvance(phase); |
| 547 |
|
// Fall here even if parent waited, to reconcile and help release |
| 548 |
|
return untimedWait(phase); |
| 557 |
|
* @return the phase on exit from this method |
| 558 |
|
* @throws InterruptedException if thread interrupted while waiting |
| 559 |
|
*/ |
| 560 |
< |
public int awaitAdvanceInterruptibly(int phase) throws InterruptedException { |
| 560 |
> |
public int awaitAdvanceInterruptibly(int phase) |
| 561 |
> |
throws InterruptedException { |
| 562 |
|
if (phase < 0) |
| 563 |
|
return phase; |
| 564 |
|
long s = getReconciledState(); |
| 565 |
|
int p = phaseOf(s); |
| 566 |
|
if (p != phase) |
| 567 |
|
return p; |
| 568 |
< |
if (unarrivedOf(s) != 0) |
| 568 |
> |
if (unarrivedOf(s) == 0 && parent != null) |
| 569 |
|
parent.awaitAdvanceInterruptibly(phase); |
| 570 |
|
return interruptibleWait(phase); |
| 571 |
|
} |
| 587 |
|
int p = phaseOf(s); |
| 588 |
|
if (p != phase) |
| 589 |
|
return p; |
| 590 |
< |
if (unarrivedOf(s) == 0) |
| 590 |
> |
if (unarrivedOf(s) == 0 && parent != null) |
| 591 |
|
parent.awaitAdvanceInterruptibly(phase, timeout, unit); |
| 592 |
|
return timedWait(phase, unit.toNanos(timeout)); |
| 593 |
|
} |
| 738 |
|
|
| 739 |
|
// methods for waiting |
| 740 |
|
|
| 732 |
– |
/** The number of CPUs, for spin control */ |
| 733 |
– |
static final int NCPUS = Runtime.getRuntime().availableProcessors(); |
| 734 |
– |
|
| 735 |
– |
/** |
| 736 |
– |
* The number of times to spin before blocking in timed waits. |
| 737 |
– |
* The value is empirically derived. |
| 738 |
– |
*/ |
| 739 |
– |
static final int maxTimedSpins = (NCPUS < 2)? 0 : 32; |
| 740 |
– |
|
| 741 |
– |
/** |
| 742 |
– |
* The number of times to spin before blocking in untimed waits. |
| 743 |
– |
* This is greater than timed value because untimed waits spin |
| 744 |
– |
* faster since they don't need to check times on each spin. |
| 745 |
– |
*/ |
| 746 |
– |
static final int maxUntimedSpins = maxTimedSpins * 32; |
| 747 |
– |
|
| 748 |
– |
/** |
| 749 |
– |
* The number of nanoseconds for which it is faster to spin |
| 750 |
– |
* rather than to use timed park. A rough estimate suffices. |
| 751 |
– |
*/ |
| 752 |
– |
static final long spinForTimeoutThreshold = 1000L; |
| 753 |
– |
|
| 741 |
|
/** |
| 742 |
< |
* Wait nodes for Treiber stack representing wait queue for non-FJ |
| 756 |
< |
* tasks. |
| 742 |
> |
* Wait nodes for Treiber stack representing wait queue |
| 743 |
|
*/ |
| 744 |
< |
static final class QNode { |
| 745 |
< |
QNode next; |
| 744 |
> |
static final class QNode implements ForkJoinPool.ManagedBlocker { |
| 745 |
> |
final Phaser phaser; |
| 746 |
> |
final int phase; |
| 747 |
> |
final long startTime; |
| 748 |
> |
final long nanos; |
| 749 |
> |
final boolean timed; |
| 750 |
> |
final boolean interruptible; |
| 751 |
> |
volatile boolean wasInterrupted = false; |
| 752 |
|
volatile Thread thread; // nulled to cancel wait |
| 753 |
< |
QNode() { |
| 753 |
> |
QNode next; |
| 754 |
> |
QNode(Phaser phaser, int phase, boolean interruptible, |
| 755 |
> |
boolean timed, long startTime, long nanos) { |
| 756 |
> |
this.phaser = phaser; |
| 757 |
> |
this.phase = phase; |
| 758 |
> |
this.timed = timed; |
| 759 |
> |
this.interruptible = interruptible; |
| 760 |
> |
this.startTime = startTime; |
| 761 |
> |
this.nanos = nanos; |
| 762 |
|
thread = Thread.currentThread(); |
| 763 |
|
} |
| 764 |
+ |
public boolean isReleasable() { |
| 765 |
+ |
return (thread == null || |
| 766 |
+ |
phaser.getPhase() != phase || |
| 767 |
+ |
(interruptible && wasInterrupted) || |
| 768 |
+ |
(timed && (nanos - (System.nanoTime() - startTime)) <= 0)); |
| 769 |
+ |
} |
| 770 |
+ |
public boolean block() { |
| 771 |
+ |
if (Thread.interrupted()) { |
| 772 |
+ |
wasInterrupted = true; |
| 773 |
+ |
if (interruptible) |
| 774 |
+ |
return true; |
| 775 |
+ |
} |
| 776 |
+ |
if (!timed) |
| 777 |
+ |
LockSupport.park(this); |
| 778 |
+ |
else { |
| 779 |
+ |
long waitTime = nanos - (System.nanoTime() - startTime); |
| 780 |
+ |
if (waitTime <= 0) |
| 781 |
+ |
return true; |
| 782 |
+ |
LockSupport.parkNanos(this, waitTime); |
| 783 |
+ |
} |
| 784 |
+ |
return isReleasable(); |
| 785 |
+ |
} |
| 786 |
|
void signal() { |
| 787 |
|
Thread t = thread; |
| 788 |
|
if (t != null) { |
| 790 |
|
LockSupport.unpark(t); |
| 791 |
|
} |
| 792 |
|
} |
| 793 |
+ |
boolean doWait() { |
| 794 |
+ |
if (thread != null) { |
| 795 |
+ |
try { |
| 796 |
+ |
ForkJoinPool.managedBlock(this, false); |
| 797 |
+ |
} catch (InterruptedException ie) { |
| 798 |
+ |
} |
| 799 |
+ |
} |
| 800 |
+ |
return wasInterrupted; |
| 801 |
+ |
} |
| 802 |
+ |
|
| 803 |
|
} |
| 804 |
|
|
| 805 |
|
/** |
| 815 |
|
} |
| 816 |
|
|
| 817 |
|
/** |
| 818 |
+ |
* Tries to enqueue given node in the appropriate wait queue |
| 819 |
+ |
* @return true if successful |
| 820 |
+ |
*/ |
| 821 |
+ |
private boolean tryEnqueue(QNode node) { |
| 822 |
+ |
AtomicReference<QNode> head = queueFor(node.phase); |
| 823 |
+ |
return head.compareAndSet(node.next = head.get(), node); |
| 824 |
+ |
} |
| 825 |
+ |
|
| 826 |
+ |
/** |
| 827 |
|
* Enqueues node and waits unless aborted or signalled. |
| 828 |
+ |
* @return current phase |
| 829 |
|
*/ |
| 830 |
|
private int untimedWait(int phase) { |
| 789 |
– |
int spins = maxUntimedSpins; |
| 831 |
|
QNode node = null; |
| 791 |
– |
boolean interrupted = false; |
| 832 |
|
boolean queued = false; |
| 833 |
+ |
boolean interrupted = false; |
| 834 |
|
int p; |
| 835 |
|
while ((p = getPhase()) == phase) { |
| 836 |
< |
interrupted = Thread.interrupted(); |
| 837 |
< |
if (node != null) { |
| 838 |
< |
if (!queued) { |
| 839 |
< |
AtomicReference<QNode> head = queueFor(phase); |
| 840 |
< |
queued = head.compareAndSet(node.next = head.get(), node); |
| 841 |
< |
} |
| 801 |
< |
else if (node.thread != null) |
| 802 |
< |
LockSupport.park(this); |
| 803 |
< |
} |
| 804 |
< |
else if (spins <= 0) |
| 805 |
< |
node = new QNode(); |
| 836 |
> |
if (Thread.interrupted()) |
| 837 |
> |
interrupted = true; |
| 838 |
> |
else if (node == null) |
| 839 |
> |
node = new QNode(this, phase, false, false, 0, 0); |
| 840 |
> |
else if (!queued) |
| 841 |
> |
queued = tryEnqueue(node); |
| 842 |
|
else |
| 843 |
< |
--spins; |
| 843 |
> |
interrupted = node.doWait(); |
| 844 |
|
} |
| 845 |
|
if (node != null) |
| 846 |
|
node.thread = null; |
| 847 |
+ |
releaseWaiters(phase); |
| 848 |
|
if (interrupted) |
| 849 |
|
Thread.currentThread().interrupt(); |
| 813 |
– |
releaseWaiters(phase); |
| 850 |
|
return p; |
| 851 |
|
} |
| 852 |
|
|
| 853 |
|
/** |
| 854 |
< |
* Messier interruptible version |
| 854 |
> |
* Interruptible version |
| 855 |
> |
* @return current phase |
| 856 |
|
*/ |
| 857 |
|
private int interruptibleWait(int phase) throws InterruptedException { |
| 821 |
– |
int spins = maxUntimedSpins; |
| 858 |
|
QNode node = null; |
| 859 |
|
boolean queued = false; |
| 860 |
|
boolean interrupted = false; |
| 861 |
|
int p; |
| 862 |
< |
while ((p = getPhase()) == phase) { |
| 863 |
< |
if (interrupted = Thread.interrupted()) |
| 864 |
< |
break; |
| 865 |
< |
if (node != null) { |
| 866 |
< |
if (!queued) { |
| 867 |
< |
AtomicReference<QNode> head = queueFor(phase); |
| 868 |
< |
queued = head.compareAndSet(node.next = head.get(), node); |
| 833 |
< |
} |
| 834 |
< |
else if (node.thread != null) |
| 835 |
< |
LockSupport.park(this); |
| 836 |
< |
} |
| 837 |
< |
else if (spins <= 0) |
| 838 |
< |
node = new QNode(); |
| 862 |
> |
while ((p = getPhase()) == phase && !interrupted) { |
| 863 |
> |
if (Thread.interrupted()) |
| 864 |
> |
interrupted = true; |
| 865 |
> |
else if (node == null) |
| 866 |
> |
node = new QNode(this, phase, true, false, 0, 0); |
| 867 |
> |
else if (!queued) |
| 868 |
> |
queued = tryEnqueue(node); |
| 869 |
|
else |
| 870 |
< |
--spins; |
| 870 |
> |
interrupted = node.doWait(); |
| 871 |
|
} |
| 872 |
|
if (node != null) |
| 873 |
|
node.thread = null; |
| 874 |
+ |
if (p != phase || (p = getPhase()) != phase) |
| 875 |
+ |
releaseWaiters(phase); |
| 876 |
|
if (interrupted) |
| 877 |
|
throw new InterruptedException(); |
| 846 |
– |
releaseWaiters(phase); |
| 878 |
|
return p; |
| 879 |
|
} |
| 880 |
|
|
| 881 |
|
/** |
| 882 |
< |
* Even messier timeout version. |
| 882 |
> |
* Timeout version. |
| 883 |
> |
* @return current phase |
| 884 |
|
*/ |
| 885 |
|
private int timedWait(int phase, long nanos) |
| 886 |
|
throws InterruptedException, TimeoutException { |
| 887 |
+ |
long startTime = System.nanoTime(); |
| 888 |
+ |
QNode node = null; |
| 889 |
+ |
boolean queued = false; |
| 890 |
+ |
boolean interrupted = false; |
| 891 |
|
int p; |
| 892 |
< |
if ((p = getPhase()) == phase) { |
| 893 |
< |
long lastTime = System.nanoTime(); |
| 894 |
< |
int spins = maxTimedSpins; |
| 895 |
< |
QNode node = null; |
| 896 |
< |
boolean queued = false; |
| 897 |
< |
boolean interrupted = false; |
| 898 |
< |
while ((p = getPhase()) == phase) { |
| 899 |
< |
if (interrupted = Thread.interrupted()) |
| 900 |
< |
break; |
| 901 |
< |
long now = System.nanoTime(); |
| 902 |
< |
if ((nanos -= now - lastTime) <= 0) |
| 867 |
< |
break; |
| 868 |
< |
lastTime = now; |
| 869 |
< |
if (node != null) { |
| 870 |
< |
if (!queued) { |
| 871 |
< |
AtomicReference<QNode> head = queueFor(phase); |
| 872 |
< |
queued = head.compareAndSet(node.next = head.get(), node); |
| 873 |
< |
} |
| 874 |
< |
else if (node.thread != null && |
| 875 |
< |
nanos > spinForTimeoutThreshold) { |
| 876 |
< |
LockSupport.parkNanos(this, nanos); |
| 877 |
< |
} |
| 878 |
< |
} |
| 879 |
< |
else if (spins <= 0) |
| 880 |
< |
node = new QNode(); |
| 881 |
< |
else |
| 882 |
< |
--spins; |
| 883 |
< |
} |
| 884 |
< |
if (node != null) |
| 885 |
< |
node.thread = null; |
| 886 |
< |
if (interrupted) |
| 887 |
< |
throw new InterruptedException(); |
| 888 |
< |
if (p == phase && (p = getPhase()) == phase) |
| 889 |
< |
throw new TimeoutException(); |
| 892 |
> |
while ((p = getPhase()) == phase && !interrupted) { |
| 893 |
> |
if (Thread.interrupted()) |
| 894 |
> |
interrupted = true; |
| 895 |
> |
else if (nanos - (System.nanoTime() - startTime) <= 0) |
| 896 |
> |
break; |
| 897 |
> |
else if (node == null) |
| 898 |
> |
node = new QNode(this, phase, true, true, startTime, nanos); |
| 899 |
> |
else if (!queued) |
| 900 |
> |
queued = tryEnqueue(node); |
| 901 |
> |
else |
| 902 |
> |
interrupted = node.doWait(); |
| 903 |
|
} |
| 904 |
< |
releaseWaiters(phase); |
| 904 |
> |
if (node != null) |
| 905 |
> |
node.thread = null; |
| 906 |
> |
if (p != phase || (p = getPhase()) != phase) |
| 907 |
> |
releaseWaiters(phase); |
| 908 |
> |
if (interrupted) |
| 909 |
> |
throw new InterruptedException(); |
| 910 |
> |
if (p == phase) |
| 911 |
> |
throw new TimeoutException(); |
| 912 |
|
return p; |
| 913 |
|
} |
| 914 |
|
|
