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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.*; |
11 |
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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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* ForkJoinPool.ForkJoinWorkerThreadFactory} to use it in a {@code |
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* ForkJoinPool}. |
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* |
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* @since 1.7 |
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* @author Doug Lea |
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*/ |
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public class ForkJoinWorkerThread extends Thread { |
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/* |
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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 |
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* calling pool.sync |
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* calling pool.sync. |
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*/ |
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private boolean active; |
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|
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|
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/** |
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* Index of this worker in pool array. Set once by pool before |
198 |
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* running, and accessed directly by pool during cleanup etc |
198 |
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* running, and accessed directly by pool during cleanup etc. |
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*/ |
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int poolIndex; |
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|
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final boolean shutdownNow() { return transitionRunStateTo(TERMINATING); } |
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|
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/** |
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* Transitions to at least the given state. Returns true if not |
276 |
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* already at least at given state. |
275 |
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* Transitions to at least the given state. |
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* |
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* @return {@code true} if not already at least at given state |
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*/ |
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private boolean transitionRunStateTo(int state) { |
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for (;;) { |
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} |
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|
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/** |
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* Tries to set status to active; fails on contention. |
302 |
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* Tries to set status to inactive; fails on contention. |
303 |
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*/ |
304 |
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private boolean tryInactivate() { |
305 |
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if (active) { |
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* one. Marsaglia xor-shift is cheap and works well. |
317 |
|
*/ |
318 |
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private static int xorShift(int r) { |
319 |
< |
r ^= r << 1; |
320 |
< |
r ^= r >>> 3; |
321 |
< |
r ^= r << 10; |
314 |
< |
return r; |
319 |
> |
r ^= (r << 13); |
320 |
> |
r ^= (r >>> 17); |
321 |
> |
return r ^ (r << 5); |
322 |
|
} |
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|
324 |
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// Lifecycle methods |
376 |
|
/** |
377 |
|
* Performs cleanup associated with termination of this worker |
378 |
|
* thread. If you override this method, you must invoke |
379 |
< |
* super.onTermination at the end of the overridden method. |
379 |
> |
* {@code super.onTermination} at the end of the overridden method. |
380 |
|
* |
381 |
|
* @param exception the exception causing this thread to abort due |
382 |
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* to an unrecoverable error, or null if completed normally |
382 |
> |
* to an unrecoverable error, or {@code null} if completed normally |
383 |
|
*/ |
384 |
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protected void onTermination(Throwable exception) { |
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// Execute remaining local tasks unless aborting or terminating |
386 |
< |
while (exception == null && !pool.isTerminating() && base != sp) { |
386 |
> |
while (exception == null && pool.isProcessingTasks() && base != sp) { |
387 |
|
try { |
388 |
|
ForkJoinTask<?> t = popTask(); |
389 |
|
if (t != null) |
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|
t.quietlyExec(); |
391 |
< |
} catch(Throwable ex) { |
391 |
> |
} catch (Throwable ex) { |
392 |
|
exception = ex; |
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|
} |
394 |
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} |
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// Cancel other tasks, transition status, notify pool, and |
396 |
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// propagate exception to uncaught exception handler |
397 |
|
try { |
398 |
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do;while (!tryInactivate()); // ensure inactive |
398 |
> |
do {} while (!tryInactivate()); // ensure inactive |
399 |
|
cancelTasks(); |
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|
runState = TERMINATED; |
401 |
|
pool.workerTerminated(this); |
415 |
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* Caller must ensure q is non-null and index is in range. |
416 |
|
*/ |
417 |
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private static void setSlot(ForkJoinTask<?>[] q, int i, |
418 |
< |
ForkJoinTask<?> t){ |
418 |
> |
ForkJoinTask<?> t) { |
419 |
|
UNSAFE.putOrderedObject(q, (i << qShift) + qBase, t); |
420 |
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} |
421 |
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|
476 |
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} |
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|
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|
/** |
479 |
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* Tries to take a task from the base of own queue, activating if |
480 |
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* necessary, failing only if empty. Called only by current thread. |
481 |
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* |
482 |
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* @return a task, or null if none |
483 |
+ |
*/ |
484 |
+ |
final ForkJoinTask<?> locallyDeqTask() { |
485 |
+ |
int b; |
486 |
+ |
while (sp != (b = base)) { |
487 |
+ |
if (tryActivate()) { |
488 |
+ |
ForkJoinTask<?>[] q = queue; |
489 |
+ |
int i = (q.length - 1) & b; |
490 |
+ |
ForkJoinTask<?> t = q[i]; |
491 |
+ |
if (t != null && casSlotNull(q, i, t)) { |
492 |
+ |
base = b + 1; |
493 |
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return t; |
494 |
+ |
} |
495 |
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} |
496 |
+ |
} |
497 |
+ |
return null; |
498 |
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} |
499 |
+ |
|
500 |
+ |
/** |
501 |
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* Returns a popped task, or null if empty. Ensures active status |
502 |
|
* if non-null. Called only by current thread. |
503 |
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*/ |
537 |
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} |
538 |
|
|
539 |
|
/** |
540 |
< |
* Returns next task. |
540 |
> |
* Returns next task or null if empty or contended |
541 |
|
*/ |
542 |
|
final ForkJoinTask<?> peekTask() { |
543 |
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ForkJoinTask<?>[] q = queue; |
544 |
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if (q == null) |
545 |
|
return null; |
546 |
|
int mask = q.length - 1; |
547 |
< |
int i = locallyFifo? base : (sp - 1); |
547 |
> |
int i = locallyFifo ? base : (sp - 1); |
548 |
|
return q[i & mask]; |
549 |
|
} |
550 |
|
|
607 |
|
ForkJoinWorkerThread v = ws[mask & idx]; |
608 |
|
if (v == null || v.sp == v.base) { |
609 |
|
if (probes <= mask) |
610 |
< |
idx = (probes++ < 0)? r : (idx + 1); |
610 |
> |
idx = (probes++ < 0) ? r : (idx + 1); |
611 |
|
else |
612 |
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break; |
613 |
|
} |
628 |
|
* @return a task, if available |
629 |
|
*/ |
630 |
|
final ForkJoinTask<?> pollTask() { |
631 |
< |
ForkJoinTask<?> t = locallyFifo? deqTask() : popTask(); |
631 |
> |
ForkJoinTask<?> t = locallyFifo ? locallyDeqTask() : popTask(); |
632 |
|
if (t == null && (t = scan()) != null) |
633 |
|
++stealCount; |
634 |
|
return t; |
640 |
|
* @return a task, if available |
641 |
|
*/ |
642 |
|
final ForkJoinTask<?> pollLocalTask() { |
643 |
< |
return locallyFifo? deqTask() : popTask(); |
643 |
> |
return locallyFifo ? locallyDeqTask() : popTask(); |
644 |
|
} |
645 |
|
|
646 |
|
/** |
675 |
|
* |
676 |
|
* @return the number of tasks drained |
677 |
|
*/ |
678 |
< |
final int drainTasksTo(Collection<ForkJoinTask<?>> c) { |
678 |
> |
final int drainTasksTo(Collection<? super ForkJoinTask<?>> c) { |
679 |
|
int n = 0; |
680 |
|
ForkJoinTask<?> t; |
681 |
|
while (base != sp && (t = deqTask()) != null) { |
696 |
|
} |
697 |
|
|
698 |
|
/** |
699 |
< |
* Returns true if at least one worker in the given array appears |
700 |
< |
* to have at least one queued task. |
699 |
> |
* Returns {@code true} if at least one worker in the given array |
700 |
> |
* appears to have at least one queued task. |
701 |
> |
* |
702 |
|
* @param ws array of workers |
703 |
|
*/ |
704 |
|
static boolean hasQueuedTasks(ForkJoinWorkerThread[] ws) { |
721 |
|
* Returns an estimate of the number of tasks in the queue. |
722 |
|
*/ |
723 |
|
final int getQueueSize() { |
724 |
< |
int n = sp - base; |
725 |
< |
return n < 0? 0 : n; // suppress momentarily negative values |
724 |
> |
// suppress momentarily negative values |
725 |
> |
return Math.max(0, sp - base); |
726 |
|
} |
727 |
|
|
728 |
|
/** |
735 |
|
} |
736 |
|
|
737 |
|
/** |
738 |
< |
* Scans, returning early if joinMe done |
738 |
> |
* Scans, returning early if joinMe done. |
739 |
|
*/ |
740 |
|
final ForkJoinTask<?> scanWhileJoining(ForkJoinTask<?> joinMe) { |
741 |
|
ForkJoinTask<?> t = pollTask(); |
747 |
|
} |
748 |
|
|
749 |
|
/** |
750 |
< |
* Runs tasks until pool isQuiescent. |
750 |
> |
* Runs tasks until {@code pool.isQuiescent()}. |
751 |
|
*/ |
752 |
|
final void helpQuiescePool() { |
753 |
|
for (;;) { |
757 |
|
else if (tryInactivate() && pool.isQuiescent()) |
758 |
|
break; |
759 |
|
} |
760 |
< |
do;while (!tryActivate()); // re-activate on exit |
760 |
> |
do {} while (!tryActivate()); // re-activate on exit |
761 |
> |
} |
762 |
> |
|
763 |
> |
// Unsafe mechanics |
764 |
> |
|
765 |
> |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
766 |
> |
private static final long spOffset = |
767 |
> |
objectFieldOffset("sp", ForkJoinWorkerThread.class); |
768 |
> |
private static final long runStateOffset = |
769 |
> |
objectFieldOffset("runState", ForkJoinWorkerThread.class); |
770 |
> |
private static final long qBase; |
771 |
> |
private static final int qShift; |
772 |
> |
|
773 |
> |
static { |
774 |
> |
qBase = UNSAFE.arrayBaseOffset(ForkJoinTask[].class); |
775 |
> |
int s = UNSAFE.arrayIndexScale(ForkJoinTask[].class); |
776 |
> |
if ((s & (s-1)) != 0) |
777 |
> |
throw new Error("data type scale not a power of two"); |
778 |
> |
qShift = 31 - Integer.numberOfLeadingZeros(s); |
779 |
> |
} |
780 |
> |
|
781 |
> |
private static long objectFieldOffset(String field, Class<?> klazz) { |
782 |
> |
try { |
783 |
> |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
784 |
> |
} catch (NoSuchFieldException e) { |
785 |
> |
// Convert Exception to corresponding Error |
786 |
> |
NoSuchFieldError error = new NoSuchFieldError(field); |
787 |
> |
error.initCause(e); |
788 |
> |
throw error; |
789 |
> |
} |
790 |
|
} |
791 |
|
|
792 |
< |
// Temporary Unsafe mechanics for preliminary release |
793 |
< |
private static Unsafe getUnsafe() throws Throwable { |
792 |
> |
/** |
793 |
> |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
794 |
> |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
795 |
> |
* into a jdk. |
796 |
> |
* |
797 |
> |
* @return a sun.misc.Unsafe |
798 |
> |
*/ |
799 |
> |
private static sun.misc.Unsafe getUnsafe() { |
800 |
|
try { |
801 |
< |
return Unsafe.getUnsafe(); |
801 |
> |
return sun.misc.Unsafe.getUnsafe(); |
802 |
|
} catch (SecurityException se) { |
803 |
|
try { |
804 |
|
return java.security.AccessController.doPrivileged |
805 |
< |
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
806 |
< |
public Unsafe run() throws Exception { |
807 |
< |
return getUnsafePrivileged(); |
805 |
> |
(new java.security |
806 |
> |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
807 |
> |
public sun.misc.Unsafe run() throws Exception { |
808 |
> |
java.lang.reflect.Field f = sun.misc |
809 |
> |
.Unsafe.class.getDeclaredField("theUnsafe"); |
810 |
> |
f.setAccessible(true); |
811 |
> |
return (sun.misc.Unsafe) f.get(null); |
812 |
|
}}); |
813 |
|
} catch (java.security.PrivilegedActionException e) { |
814 |
< |
throw e.getCause(); |
814 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
815 |
> |
e.getCause()); |
816 |
|
} |
817 |
|
} |
818 |
|
} |
749 |
– |
|
750 |
– |
private static Unsafe getUnsafePrivileged() |
751 |
– |
throws NoSuchFieldException, IllegalAccessException { |
752 |
– |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
753 |
– |
f.setAccessible(true); |
754 |
– |
return (Unsafe) f.get(null); |
755 |
– |
} |
756 |
– |
|
757 |
– |
private static long fieldOffset(String fieldName) |
758 |
– |
throws NoSuchFieldException { |
759 |
– |
return UNSAFE.objectFieldOffset |
760 |
– |
(ForkJoinWorkerThread.class.getDeclaredField(fieldName)); |
761 |
– |
} |
762 |
– |
|
763 |
– |
static final Unsafe UNSAFE; |
764 |
– |
static final long baseOffset; |
765 |
– |
static final long spOffset; |
766 |
– |
static final long runStateOffset; |
767 |
– |
static final long qBase; |
768 |
– |
static final int qShift; |
769 |
– |
static { |
770 |
– |
try { |
771 |
– |
UNSAFE = getUnsafe(); |
772 |
– |
baseOffset = fieldOffset("base"); |
773 |
– |
spOffset = fieldOffset("sp"); |
774 |
– |
runStateOffset = fieldOffset("runState"); |
775 |
– |
qBase = UNSAFE.arrayBaseOffset(ForkJoinTask[].class); |
776 |
– |
int s = UNSAFE.arrayIndexScale(ForkJoinTask[].class); |
777 |
– |
if ((s & (s-1)) != 0) |
778 |
– |
throw new Error("data type scale not a power of two"); |
779 |
– |
qShift = 31 - Integer.numberOfLeadingZeros(s); |
780 |
– |
} catch (Throwable e) { |
781 |
– |
throw new RuntimeException("Could not initialize intrinsics", e); |
782 |
– |
} |
783 |
– |
} |
819 |
|
} |