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*/ |
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package jsr166y; |
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< |
import java.util.*; |
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> |
|
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import java.util.concurrent.*; |
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< |
import java.util.concurrent.atomic.*; |
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< |
import java.util.concurrent.locks.*; |
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< |
import sun.misc.Unsafe; |
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< |
import java.lang.reflect.*; |
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> |
|
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> |
import java.util.Collection; |
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|
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/** |
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* A thread managed by a {@link ForkJoinPool}. This class is |
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* subclassable solely for the sake of adding functionality -- there |
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< |
* are no overridable methods dealing with scheduling or |
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< |
* execution. However, you can override initialization and termination |
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< |
* methods surrounding the main task processing loop. If you do |
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< |
* create such a subclass, you will also need to supply a custom |
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< |
* ForkJoinWorkerThreadFactory to use it in a ForkJoinPool. |
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> |
* are no overridable methods dealing with scheduling or execution. |
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> |
* However, you can override initialization and termination methods |
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> |
* surrounding the main task processing loop. If you do create such a |
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> |
* subclass, you will also need to supply a custom {@link |
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> |
* ForkJoinWorkerThreadFactory} to use it in a {@code ForkJoinPool}. |
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* |
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* @since 1.7 |
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* @author Doug Lea |
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* which gives threads a chance to activate if necessary before |
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* stealing (see below). |
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* |
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+ |
* This approach also enables support for "async mode" where local |
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+ |
* task processing is in FIFO, not LIFO order; simply by using a |
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+ |
* version of deq rather than pop when locallyFifo is true (as set |
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+ |
* by the ForkJoinPool). This allows use in message-passing |
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+ |
* frameworks in which tasks are never joined. |
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+ |
* |
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|
* Efficient implementation of this approach currently relies on |
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* an uncomfortable amount of "Unsafe" mechanics. To maintain |
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|
* correct orderings, reads and writes of variable base require |
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|
private static final int MAXIMUM_QUEUE_CAPACITY = 1 << 28; |
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|
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/** |
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< |
* The pool this thread works in. Accessed directly by ForkJoinTask |
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> |
* The pool this thread works in. Accessed directly by ForkJoinTask. |
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|
*/ |
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final ForkJoinPool pool; |
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|
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* Activity status. When true, this worker is considered active. |
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* Must be false upon construction. It must be true when executing |
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* tasks, and BEFORE stealing a task. It must be false before |
| 174 |
< |
* calling pool.sync |
| 174 |
> |
* calling pool.sync. |
| 175 |
|
*/ |
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|
private boolean active; |
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|
|
| 194 |
|
|
| 195 |
|
/** |
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|
* Index of this worker in pool array. Set once by pool before |
| 197 |
< |
* running, and accessed directly by pool during cleanup etc |
| 197 |
> |
* running, and accessed directly by pool during cleanup etc. |
| 198 |
|
*/ |
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|
int poolIndex; |
| 200 |
|
|
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|
final boolean shutdownNow() { return transitionRunStateTo(TERMINATING); } |
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|
| 273 |
|
/** |
| 274 |
< |
* Transitions to at least the given state. Returns true if not |
| 275 |
< |
* already at least at given state. |
| 274 |
> |
* Transitions to at least the given state. |
| 275 |
> |
* |
| 276 |
> |
* @return {@code true} if not already at least at given state |
| 277 |
|
*/ |
| 278 |
|
private boolean transitionRunStateTo(int state) { |
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|
for (;;) { |
| 298 |
|
} |
| 299 |
|
|
| 300 |
|
/** |
| 301 |
< |
* Tries to set status to active; fails on contention. |
| 301 |
> |
* Tries to set status to inactive; fails on contention. |
| 302 |
|
*/ |
| 303 |
|
private boolean tryInactivate() { |
| 304 |
|
if (active) { |
| 315 |
|
* one. Marsaglia xor-shift is cheap and works well. |
| 316 |
|
*/ |
| 317 |
|
private static int xorShift(int r) { |
| 318 |
< |
r ^= r << 1; |
| 319 |
< |
r ^= r >>> 3; |
| 320 |
< |
r ^= r << 10; |
| 316 |
< |
return r; |
| 318 |
> |
r ^= (r << 13); |
| 319 |
> |
r ^= (r >>> 17); |
| 320 |
> |
return r ^ (r << 5); |
| 321 |
|
} |
| 322 |
|
|
| 323 |
|
// Lifecycle methods |
| 375 |
|
/** |
| 376 |
|
* Performs cleanup associated with termination of this worker |
| 377 |
|
* thread. If you override this method, you must invoke |
| 378 |
< |
* super.onTermination at the end of the overridden method. |
| 378 |
> |
* {@code super.onTermination} at the end of the overridden method. |
| 379 |
|
* |
| 380 |
|
* @param exception the exception causing this thread to abort due |
| 381 |
< |
* to an unrecoverable error, or null if completed normally |
| 381 |
> |
* to an unrecoverable error, or {@code null} if completed normally |
| 382 |
|
*/ |
| 383 |
|
protected void onTermination(Throwable exception) { |
| 384 |
|
// Execute remaining local tasks unless aborting or terminating |
| 387 |
|
ForkJoinTask<?> t = popTask(); |
| 388 |
|
if (t != null) |
| 389 |
|
t.quietlyExec(); |
| 390 |
< |
} catch(Throwable ex) { |
| 390 |
> |
} catch (Throwable ex) { |
| 391 |
|
exception = ex; |
| 392 |
|
} |
| 393 |
|
} |
| 394 |
|
// Cancel other tasks, transition status, notify pool, and |
| 395 |
|
// propagate exception to uncaught exception handler |
| 396 |
|
try { |
| 397 |
< |
do;while (!tryInactivate()); // ensure inactive |
| 397 |
> |
do {} while (!tryInactivate()); // ensure inactive |
| 398 |
|
cancelTasks(); |
| 399 |
|
runState = TERMINATED; |
| 400 |
|
pool.workerTerminated(this); |
| 475 |
|
} |
| 476 |
|
|
| 477 |
|
/** |
| 478 |
+ |
* Tries to take a task from the base of own queue, activating if |
| 479 |
+ |
* necessary, failing only if empty. Called only by current thread. |
| 480 |
+ |
* |
| 481 |
+ |
* @return a task, or null if none |
| 482 |
+ |
*/ |
| 483 |
+ |
final ForkJoinTask<?> locallyDeqTask() { |
| 484 |
+ |
int b; |
| 485 |
+ |
while (sp != (b = base)) { |
| 486 |
+ |
if (tryActivate()) { |
| 487 |
+ |
ForkJoinTask<?>[] q = queue; |
| 488 |
+ |
int i = (q.length - 1) & b; |
| 489 |
+ |
ForkJoinTask<?> t = q[i]; |
| 490 |
+ |
if (t != null && casSlotNull(q, i, t)) { |
| 491 |
+ |
base = b + 1; |
| 492 |
+ |
return t; |
| 493 |
+ |
} |
| 494 |
+ |
} |
| 495 |
+ |
} |
| 496 |
+ |
return null; |
| 497 |
+ |
} |
| 498 |
+ |
|
| 499 |
+ |
/** |
| 500 |
|
* Returns a popped task, or null if empty. Ensures active status |
| 501 |
|
* if non-null. Called only by current thread. |
| 502 |
|
*/ |
| 536 |
|
} |
| 537 |
|
|
| 538 |
|
/** |
| 539 |
< |
* Returns next task. |
| 539 |
> |
* Returns next task or null if empty or contended |
| 540 |
|
*/ |
| 541 |
|
final ForkJoinTask<?> peekTask() { |
| 542 |
|
ForkJoinTask<?>[] q = queue; |
| 543 |
|
if (q == null) |
| 544 |
|
return null; |
| 545 |
|
int mask = q.length - 1; |
| 546 |
< |
int i = locallyFifo? base : (sp - 1); |
| 546 |
> |
int i = locallyFifo ? base : (sp - 1); |
| 547 |
|
return q[i & mask]; |
| 548 |
|
} |
| 549 |
|
|
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|
ForkJoinWorkerThread v = ws[mask & idx]; |
| 607 |
|
if (v == null || v.sp == v.base) { |
| 608 |
|
if (probes <= mask) |
| 609 |
< |
idx = (probes++ < 0)? r : (idx + 1); |
| 609 |
> |
idx = (probes++ < 0) ? r : (idx + 1); |
| 610 |
|
else |
| 611 |
|
break; |
| 612 |
|
} |
| 627 |
|
* @return a task, if available |
| 628 |
|
*/ |
| 629 |
|
final ForkJoinTask<?> pollTask() { |
| 630 |
< |
ForkJoinTask<?> t = locallyFifo? deqTask() : popTask(); |
| 630 |
> |
ForkJoinTask<?> t = locallyFifo ? locallyDeqTask() : popTask(); |
| 631 |
|
if (t == null && (t = scan()) != null) |
| 632 |
|
++stealCount; |
| 633 |
|
return t; |
| 639 |
|
* @return a task, if available |
| 640 |
|
*/ |
| 641 |
|
final ForkJoinTask<?> pollLocalTask() { |
| 642 |
< |
return locallyFifo? deqTask() : popTask(); |
| 642 |
> |
return locallyFifo ? locallyDeqTask() : popTask(); |
| 643 |
|
} |
| 644 |
|
|
| 645 |
|
/** |
| 674 |
|
* |
| 675 |
|
* @return the number of tasks drained |
| 676 |
|
*/ |
| 677 |
< |
final int drainTasksTo(Collection<ForkJoinTask<?>> c) { |
| 677 |
> |
final int drainTasksTo(Collection<? super ForkJoinTask<?>> c) { |
| 678 |
|
int n = 0; |
| 679 |
|
ForkJoinTask<?> t; |
| 680 |
|
while (base != sp && (t = deqTask()) != null) { |
| 695 |
|
} |
| 696 |
|
|
| 697 |
|
/** |
| 698 |
< |
* Returns true if at least one worker in the given array appears |
| 699 |
< |
* to have at least one queued task. |
| 698 |
> |
* Returns {@code true} if at least one worker in the given array |
| 699 |
> |
* appears to have at least one queued task. |
| 700 |
> |
* |
| 701 |
|
* @param ws array of workers |
| 702 |
|
*/ |
| 703 |
|
static boolean hasQueuedTasks(ForkJoinWorkerThread[] ws) { |
| 720 |
|
* Returns an estimate of the number of tasks in the queue. |
| 721 |
|
*/ |
| 722 |
|
final int getQueueSize() { |
| 723 |
< |
int n = sp - base; |
| 724 |
< |
return n < 0? 0 : n; // suppress momentarily negative values |
| 723 |
> |
// suppress momentarily negative values |
| 724 |
> |
return Math.max(0, sp - base); |
| 725 |
|
} |
| 726 |
|
|
| 727 |
|
/** |
| 734 |
|
} |
| 735 |
|
|
| 736 |
|
/** |
| 737 |
< |
* Scans, returning early if joinMe done |
| 737 |
> |
* Scans, returning early if joinMe done. |
| 738 |
|
*/ |
| 739 |
|
final ForkJoinTask<?> scanWhileJoining(ForkJoinTask<?> joinMe) { |
| 740 |
|
ForkJoinTask<?> t = pollTask(); |
| 746 |
|
} |
| 747 |
|
|
| 748 |
|
/** |
| 749 |
< |
* Runs tasks until pool isQuiescent. |
| 749 |
> |
* Runs tasks until {@code pool.isQuiescent()}. |
| 750 |
|
*/ |
| 751 |
|
final void helpQuiescePool() { |
| 752 |
|
for (;;) { |
| 756 |
|
else if (tryInactivate() && pool.isQuiescent()) |
| 757 |
|
break; |
| 758 |
|
} |
| 759 |
< |
do;while (!tryActivate()); // re-activate on exit |
| 759 |
> |
do {} while (!tryActivate()); // re-activate on exit |
| 760 |
> |
} |
| 761 |
> |
|
| 762 |
> |
// Unsafe mechanics |
| 763 |
> |
|
| 764 |
> |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
| 765 |
> |
private static final long spOffset = |
| 766 |
> |
objectFieldOffset("sp", ForkJoinWorkerThread.class); |
| 767 |
> |
private static final long runStateOffset = |
| 768 |
> |
objectFieldOffset("runState", ForkJoinWorkerThread.class); |
| 769 |
> |
private static final long qBase; |
| 770 |
> |
private static final int qShift; |
| 771 |
> |
|
| 772 |
> |
static { |
| 773 |
> |
qBase = UNSAFE.arrayBaseOffset(ForkJoinTask[].class); |
| 774 |
> |
int s = UNSAFE.arrayIndexScale(ForkJoinTask[].class); |
| 775 |
> |
if ((s & (s-1)) != 0) |
| 776 |
> |
throw new Error("data type scale not a power of two"); |
| 777 |
> |
qShift = 31 - Integer.numberOfLeadingZeros(s); |
| 778 |
> |
} |
| 779 |
> |
|
| 780 |
> |
private static long objectFieldOffset(String field, Class<?> klazz) { |
| 781 |
> |
try { |
| 782 |
> |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
| 783 |
> |
} catch (NoSuchFieldException e) { |
| 784 |
> |
// Convert Exception to corresponding Error |
| 785 |
> |
NoSuchFieldError error = new NoSuchFieldError(field); |
| 786 |
> |
error.initCause(e); |
| 787 |
> |
throw error; |
| 788 |
> |
} |
| 789 |
|
} |
| 790 |
|
|
| 791 |
< |
// Temporary Unsafe mechanics for preliminary release |
| 792 |
< |
private static Unsafe getUnsafe() throws Throwable { |
| 791 |
> |
/** |
| 792 |
> |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
| 793 |
> |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
| 794 |
> |
* into a jdk. |
| 795 |
> |
* |
| 796 |
> |
* @return a sun.misc.Unsafe |
| 797 |
> |
*/ |
| 798 |
> |
private static sun.misc.Unsafe getUnsafe() { |
| 799 |
|
try { |
| 800 |
< |
return Unsafe.getUnsafe(); |
| 800 |
> |
return sun.misc.Unsafe.getUnsafe(); |
| 801 |
|
} catch (SecurityException se) { |
| 802 |
|
try { |
| 803 |
|
return java.security.AccessController.doPrivileged |
| 804 |
< |
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
| 805 |
< |
public Unsafe run() throws Exception { |
| 806 |
< |
return getUnsafePrivileged(); |
| 804 |
> |
(new java.security |
| 805 |
> |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
| 806 |
> |
public sun.misc.Unsafe run() throws Exception { |
| 807 |
> |
java.lang.reflect.Field f = sun.misc |
| 808 |
> |
.Unsafe.class.getDeclaredField("theUnsafe"); |
| 809 |
> |
f.setAccessible(true); |
| 810 |
> |
return (sun.misc.Unsafe) f.get(null); |
| 811 |
|
}}); |
| 812 |
|
} catch (java.security.PrivilegedActionException e) { |
| 813 |
< |
throw e.getCause(); |
| 813 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
| 814 |
> |
e.getCause()); |
| 815 |
|
} |
| 816 |
|
} |
| 817 |
|
} |
| 751 |
– |
|
| 752 |
– |
private static Unsafe getUnsafePrivileged() |
| 753 |
– |
throws NoSuchFieldException, IllegalAccessException { |
| 754 |
– |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
| 755 |
– |
f.setAccessible(true); |
| 756 |
– |
return (Unsafe) f.get(null); |
| 757 |
– |
} |
| 758 |
– |
|
| 759 |
– |
private static long fieldOffset(String fieldName) |
| 760 |
– |
throws NoSuchFieldException { |
| 761 |
– |
return UNSAFE.objectFieldOffset |
| 762 |
– |
(ForkJoinWorkerThread.class.getDeclaredField(fieldName)); |
| 763 |
– |
} |
| 764 |
– |
|
| 765 |
– |
static final Unsafe UNSAFE; |
| 766 |
– |
static final long baseOffset; |
| 767 |
– |
static final long spOffset; |
| 768 |
– |
static final long runStateOffset; |
| 769 |
– |
static final long qBase; |
| 770 |
– |
static final int qShift; |
| 771 |
– |
static { |
| 772 |
– |
try { |
| 773 |
– |
UNSAFE = getUnsafe(); |
| 774 |
– |
baseOffset = fieldOffset("base"); |
| 775 |
– |
spOffset = fieldOffset("sp"); |
| 776 |
– |
runStateOffset = fieldOffset("runState"); |
| 777 |
– |
qBase = UNSAFE.arrayBaseOffset(ForkJoinTask[].class); |
| 778 |
– |
int s = UNSAFE.arrayIndexScale(ForkJoinTask[].class); |
| 779 |
– |
if ((s & (s-1)) != 0) |
| 780 |
– |
throw new Error("data type scale not a power of two"); |
| 781 |
– |
qShift = 31 - Integer.numberOfLeadingZeros(s); |
| 782 |
– |
} catch (Throwable e) { |
| 783 |
– |
throw new RuntimeException("Could not initialize intrinsics", e); |
| 784 |
– |
} |
| 785 |
– |
} |
| 818 |
|
} |
