| 17 |
|
* subclassable solely for the sake of adding functionality -- there |
| 18 |
|
* are no overridable methods dealing with scheduling or |
| 19 |
|
* execution. However, you can override initialization and termination |
| 20 |
< |
* cleanup methods surrounding the main task processing loop. If you |
| 21 |
< |
* do create such a subclass, you will also need to supply a custom |
| 20 |
> |
* methods surrounding the main task processing loop. If you do |
| 21 |
> |
* create such a subclass, you will also need to supply a custom |
| 22 |
|
* ForkJoinWorkerThreadFactory to use it in a ForkJoinPool. |
| 23 |
< |
* |
| 23 |
> |
* |
| 24 |
> |
* @since 1.7 |
| 25 |
> |
* @author Doug Lea |
| 26 |
|
*/ |
| 27 |
|
public class ForkJoinWorkerThread extends Thread { |
| 28 |
|
/* |
| 46 |
|
* of tasks. To accomplish this, we shift the CAS arbitrating pop |
| 47 |
|
* vs deq (steal) from being on the indices ("base" and "sp") to |
| 48 |
|
* the slots themselves (mainly via method "casSlotNull()"). So, |
| 49 |
< |
* both a successful pop and deq mainly entail CAS'ing a nonnull |
| 49 |
> |
* both a successful pop and deq mainly entail CAS'ing a non-null |
| 50 |
|
* slot to null. Because we rely on CASes of references, we do |
| 51 |
|
* not need tag bits on base or sp. They are simple ints as used |
| 52 |
|
* in any circular array-based queue (see for example ArrayDeque). |
| 58 |
|
* considered individually, is not wait-free. One thief cannot |
| 59 |
|
* successfully continue until another in-progress one (or, if |
| 60 |
|
* previously empty, a push) completes. However, in the |
| 61 |
< |
* aggregate, we ensure at least probablistic non-blockingness. If |
| 61 |
> |
* aggregate, we ensure at least probabilistic non-blockingness. If |
| 62 |
|
* an attempted steal fails, a thief always chooses a different |
| 63 |
|
* random victim target to try next. So, in order for one thief to |
| 64 |
|
* progress, it suffices for any in-progress deq or new push on |
| 77 |
|
* push) require store order and CASes (in pop and deq) require |
| 78 |
|
* (volatile) CAS semantics. Since these combinations aren't |
| 79 |
|
* supported using ordinary volatiles, the only way to accomplish |
| 80 |
< |
* these effciently is to use direct Unsafe calls. (Using external |
| 80 |
> |
* these efficiently is to use direct Unsafe calls. (Using external |
| 81 |
|
* AtomicIntegers and AtomicReferenceArrays for the indices and |
| 82 |
|
* array is significantly slower because of memory locality and |
| 83 |
|
* indirection effects.) Further, performance on most platforms is |
| 201 |
|
long lastEventCount; |
| 202 |
|
|
| 203 |
|
/** |
| 204 |
+ |
* True if use local fifo, not default lifo, for local polling |
| 205 |
+ |
*/ |
| 206 |
+ |
private boolean locallyFifo; |
| 207 |
+ |
|
| 208 |
+ |
/** |
| 209 |
|
* Creates a ForkJoinWorkerThread operating in the given pool. |
| 210 |
+ |
* |
| 211 |
|
* @param pool the pool this thread works in |
| 212 |
|
* @throws NullPointerException if pool is null |
| 213 |
|
*/ |
| 218 |
|
// Remaining initialization is deferred to onStart |
| 219 |
|
} |
| 220 |
|
|
| 221 |
< |
// Public access methods |
| 221 |
> |
// Public access methods |
| 222 |
|
|
| 223 |
|
/** |
| 224 |
< |
* Returns the pool hosting this thread |
| 224 |
> |
* Returns the pool hosting this thread. |
| 225 |
> |
* |
| 226 |
|
* @return the pool |
| 227 |
|
*/ |
| 228 |
|
public ForkJoinPool getPool() { |
| 235 |
|
* threads (minus one) that have ever been created in the pool. |
| 236 |
|
* This method may be useful for applications that track status or |
| 237 |
|
* collect results per-worker rather than per-task. |
| 238 |
< |
* @return the index number. |
| 238 |
> |
* |
| 239 |
> |
* @return the index number |
| 240 |
|
*/ |
| 241 |
|
public int getPoolIndex() { |
| 242 |
|
return poolIndex; |
| 243 |
|
} |
| 244 |
|
|
| 245 |
+ |
/** |
| 246 |
+ |
* Establishes local first-in-first-out scheduling mode for forked |
| 247 |
+ |
* tasks that are never joined. |
| 248 |
+ |
* |
| 249 |
+ |
* @param async if true, use locally FIFO scheduling |
| 250 |
+ |
*/ |
| 251 |
+ |
void setAsyncMode(boolean async) { |
| 252 |
+ |
locallyFifo = async; |
| 253 |
+ |
} |
| 254 |
|
|
| 255 |
|
// Runstate management |
| 256 |
|
|
| 267 |
|
final boolean shutdownNow() { return transitionRunStateTo(TERMINATING); } |
| 268 |
|
|
| 269 |
|
/** |
| 270 |
< |
* Transition to at least the given state. Return true if not |
| 271 |
< |
* already at least given state. |
| 270 |
> |
* Transitions to at least the given state. Returns true if not |
| 271 |
> |
* already at least at given state. |
| 272 |
|
*/ |
| 273 |
|
private boolean transitionRunStateTo(int state) { |
| 274 |
|
for (;;) { |
| 275 |
|
int s = runState; |
| 276 |
|
if (s >= state) |
| 277 |
|
return false; |
| 278 |
< |
if (_unsafe.compareAndSwapInt(this, runStateOffset, s, state)) |
| 278 |
> |
if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, state)) |
| 279 |
|
return true; |
| 280 |
|
} |
| 281 |
|
} |
| 282 |
|
|
| 283 |
|
/** |
| 284 |
< |
* Try to set status to active; fail on contention |
| 284 |
> |
* Tries to set status to active; fails on contention. |
| 285 |
|
*/ |
| 286 |
|
private boolean tryActivate() { |
| 287 |
|
if (!active) { |
| 293 |
|
} |
| 294 |
|
|
| 295 |
|
/** |
| 296 |
< |
* Try to set status to active; fail on contention |
| 296 |
> |
* Tries to set status to active; fails on contention. |
| 297 |
|
*/ |
| 298 |
|
private boolean tryInactivate() { |
| 299 |
|
if (active) { |
| 305 |
|
} |
| 306 |
|
|
| 307 |
|
/** |
| 308 |
< |
* Computes next value for random victim probe. Scans don't |
| 308 |
> |
* Computes next value for random victim probe. Scans don't |
| 309 |
|
* require a very high quality generator, but also not a crummy |
| 310 |
< |
* one. Marsaglia xor-shift is cheap and works well. |
| 310 |
> |
* one. Marsaglia xor-shift is cheap and works well. |
| 311 |
|
*/ |
| 312 |
|
private static int xorShift(int r) { |
| 313 |
|
r ^= r << 1; |
| 337 |
|
} |
| 338 |
|
|
| 339 |
|
/** |
| 340 |
< |
* Execute tasks until shut down. |
| 340 |
> |
* Executes tasks until shut down. |
| 341 |
|
*/ |
| 342 |
|
private void mainLoop() { |
| 343 |
|
while (!isShutdown()) { |
| 344 |
|
ForkJoinTask<?> t = pollTask(); |
| 345 |
< |
if (t != null || (t = pollSubmission()) != null) |
| 345 |
> |
if (t != null || (t = pollSubmission()) != null) |
| 346 |
|
t.quietlyExec(); |
| 347 |
|
else if (tryInactivate()) |
| 348 |
|
pool.sync(this); |
| 369 |
|
} |
| 370 |
|
|
| 371 |
|
/** |
| 372 |
< |
* Perform cleanup associated with termination of this worker |
| 372 |
> |
* Performs cleanup associated with termination of this worker |
| 373 |
|
* thread. If you override this method, you must invoke |
| 374 |
|
* super.onTermination at the end of the overridden method. |
| 375 |
|
* |
| 376 |
|
* @param exception the exception causing this thread to abort due |
| 377 |
< |
* to an unrecoverable error, or null if completed normally. |
| 377 |
> |
* to an unrecoverable error, or null if completed normally |
| 378 |
|
*/ |
| 379 |
|
protected void onTermination(Throwable exception) { |
| 380 |
|
// Execute remaining local tasks unless aborting or terminating |
| 391 |
|
// propagate exception to uncaught exception handler |
| 392 |
|
try { |
| 393 |
|
do;while (!tryInactivate()); // ensure inactive |
| 394 |
< |
cancelTasks(); |
| 394 |
> |
cancelTasks(); |
| 395 |
|
runState = TERMINATED; |
| 396 |
|
pool.workerTerminated(this); |
| 397 |
|
} catch (Throwable ex) { // Shouldn't ever happen |
| 403 |
|
} |
| 404 |
|
} |
| 405 |
|
|
| 406 |
< |
// Intrinsics-based support for queue operations. |
| 406 |
> |
// Intrinsics-based support for queue operations. |
| 407 |
|
|
| 408 |
|
/** |
| 409 |
< |
* Add in store-order the given task at given slot of q to |
| 410 |
< |
* null. Caller must ensure q is nonnull and index is in range. |
| 409 |
> |
* Adds in store-order the given task at given slot of q to null. |
| 410 |
> |
* Caller must ensure q is non-null and index is in range. |
| 411 |
|
*/ |
| 412 |
|
private static void setSlot(ForkJoinTask<?>[] q, int i, |
| 413 |
< |
ForkJoinTask<?> t){ |
| 414 |
< |
_unsafe.putOrderedObject(q, (i << qShift) + qBase, t); |
| 413 |
> |
ForkJoinTask<?> t) { |
| 414 |
> |
UNSAFE.putOrderedObject(q, (i << qShift) + qBase, t); |
| 415 |
|
} |
| 416 |
|
|
| 417 |
|
/** |
| 418 |
< |
* CAS given slot of q to null. Caller must ensure q is nonnull |
| 418 |
> |
* CAS given slot of q to null. Caller must ensure q is non-null |
| 419 |
|
* and index is in range. |
| 420 |
|
*/ |
| 421 |
|
private static boolean casSlotNull(ForkJoinTask<?>[] q, int i, |
| 422 |
|
ForkJoinTask<?> t) { |
| 423 |
< |
return _unsafe.compareAndSwapObject(q, (i << qShift) + qBase, t, null); |
| 423 |
> |
return UNSAFE.compareAndSwapObject(q, (i << qShift) + qBase, t, null); |
| 424 |
|
} |
| 425 |
|
|
| 426 |
|
/** |
| 427 |
|
* Sets sp in store-order. |
| 428 |
|
*/ |
| 429 |
|
private void storeSp(int s) { |
| 430 |
< |
_unsafe.putOrderedInt(this, spOffset, s); |
| 430 |
> |
UNSAFE.putOrderedInt(this, spOffset, s); |
| 431 |
|
} |
| 432 |
|
|
| 433 |
|
// Main queue methods |
| 434 |
|
|
| 435 |
|
/** |
| 436 |
|
* Pushes a task. Called only by current thread. |
| 437 |
< |
* @param t the task. Caller must ensure nonnull |
| 437 |
> |
* |
| 438 |
> |
* @param t the task. Caller must ensure non-null. |
| 439 |
|
*/ |
| 440 |
|
final void pushTask(ForkJoinTask<?> t) { |
| 441 |
|
ForkJoinTask<?>[] q = queue; |
| 452 |
|
/** |
| 453 |
|
* Tries to take a task from the base of the queue, failing if |
| 454 |
|
* either empty or contended. |
| 455 |
< |
* @return a task, or null if none or contended. |
| 455 |
> |
* |
| 456 |
> |
* @return a task, or null if none or contended |
| 457 |
|
*/ |
| 458 |
< |
private ForkJoinTask<?> deqTask() { |
| 458 |
> |
final ForkJoinTask<?> deqTask() { |
| 459 |
|
ForkJoinTask<?> t; |
| 460 |
|
ForkJoinTask<?>[] q; |
| 461 |
|
int i; |
| 472 |
|
|
| 473 |
|
/** |
| 474 |
|
* Returns a popped task, or null if empty. Ensures active status |
| 475 |
< |
* if nonnull. Called only by current thread. |
| 475 |
> |
* if non-null. Called only by current thread. |
| 476 |
|
*/ |
| 477 |
|
final ForkJoinTask<?> popTask() { |
| 478 |
|
int s = sp; |
| 495 |
|
* Specialized version of popTask to pop only if |
| 496 |
|
* topmost element is the given task. Called only |
| 497 |
|
* by current thread while active. |
| 498 |
< |
* @param t the task. Caller must ensure nonnull |
| 498 |
> |
* |
| 499 |
> |
* @param t the task. Caller must ensure non-null. |
| 500 |
|
*/ |
| 501 |
|
final boolean unpushTask(ForkJoinTask<?> t) { |
| 502 |
|
ForkJoinTask<?>[] q = queue; |
| 510 |
|
} |
| 511 |
|
|
| 512 |
|
/** |
| 513 |
< |
* Returns next task to pop. |
| 513 |
> |
* Returns next task. |
| 514 |
|
*/ |
| 515 |
|
final ForkJoinTask<?> peekTask() { |
| 516 |
|
ForkJoinTask<?>[] q = queue; |
| 517 |
< |
return q == null? null : q[(sp - 1) & (q.length - 1)]; |
| 517 |
> |
if (q == null) |
| 518 |
> |
return null; |
| 519 |
> |
int mask = q.length - 1; |
| 520 |
> |
int i = locallyFifo? base : (sp - 1); |
| 521 |
> |
return q[i & mask]; |
| 522 |
|
} |
| 523 |
|
|
| 524 |
|
/** |
| 596 |
|
} |
| 597 |
|
|
| 598 |
|
/** |
| 599 |
< |
* Pops or steals a task |
| 599 |
> |
* Gets and removes a local or stolen task. |
| 600 |
> |
* |
| 601 |
|
* @return a task, if available |
| 602 |
|
*/ |
| 603 |
|
final ForkJoinTask<?> pollTask() { |
| 604 |
< |
ForkJoinTask<?> t = popTask(); |
| 604 |
> |
ForkJoinTask<?> t = locallyFifo? deqTask() : popTask(); |
| 605 |
|
if (t == null && (t = scan()) != null) |
| 606 |
|
++stealCount; |
| 607 |
|
return t; |
| 608 |
|
} |
| 609 |
|
|
| 610 |
|
/** |
| 611 |
+ |
* Gets a local task. |
| 612 |
+ |
* |
| 613 |
+ |
* @return a task, if available |
| 614 |
+ |
*/ |
| 615 |
+ |
final ForkJoinTask<?> pollLocalTask() { |
| 616 |
+ |
return locallyFifo? deqTask() : popTask(); |
| 617 |
+ |
} |
| 618 |
+ |
|
| 619 |
+ |
/** |
| 620 |
|
* Returns a pool submission, if one exists, activating first. |
| 621 |
+ |
* |
| 622 |
|
* @return a submission, if available |
| 623 |
|
*/ |
| 624 |
|
private ForkJoinTask<?> pollSubmission() { |
| 644 |
|
} |
| 645 |
|
|
| 646 |
|
/** |
| 647 |
< |
* Get and clear steal count for accumulation by pool. Called |
| 647 |
> |
* Drains tasks to given collection c. |
| 648 |
> |
* |
| 649 |
> |
* @return the number of tasks drained |
| 650 |
> |
*/ |
| 651 |
> |
final int drainTasksTo(Collection<ForkJoinTask<?>> c) { |
| 652 |
> |
int n = 0; |
| 653 |
> |
ForkJoinTask<?> t; |
| 654 |
> |
while (base != sp && (t = deqTask()) != null) { |
| 655 |
> |
c.add(t); |
| 656 |
> |
++n; |
| 657 |
> |
} |
| 658 |
> |
return n; |
| 659 |
> |
} |
| 660 |
> |
|
| 661 |
> |
/** |
| 662 |
> |
* Gets and clears steal count for accumulation by pool. Called |
| 663 |
|
* only when known to be idle (in pool.sync and termination). |
| 664 |
|
*/ |
| 665 |
|
final int getAndClearStealCount() { |
| 707 |
|
} |
| 708 |
|
|
| 709 |
|
/** |
| 710 |
< |
* Scan, returning early if joinMe done |
| 710 |
> |
* Scans, returning early if joinMe done |
| 711 |
|
*/ |
| 712 |
|
final ForkJoinTask<?> scanWhileJoining(ForkJoinTask<?> joinMe) { |
| 713 |
|
ForkJoinTask<?> t = pollTask(); |
| 717 |
|
} |
| 718 |
|
return t; |
| 719 |
|
} |
| 720 |
< |
|
| 720 |
> |
|
| 721 |
|
/** |
| 722 |
< |
* Runs tasks until pool isQuiescent |
| 722 |
> |
* Runs tasks until pool isQuiescent. |
| 723 |
|
*/ |
| 724 |
|
final void helpQuiescePool() { |
| 725 |
|
for (;;) { |
| 726 |
|
ForkJoinTask<?> t = pollTask(); |
| 727 |
< |
if (t != null) |
| 727 |
> |
if (t != null) |
| 728 |
|
t.quietlyExec(); |
| 729 |
|
else if (tryInactivate() && pool.isQuiescent()) |
| 730 |
|
break; |
| 733 |
|
} |
| 734 |
|
|
| 735 |
|
// Temporary Unsafe mechanics for preliminary release |
| 736 |
+ |
private static Unsafe getUnsafe() throws Throwable { |
| 737 |
+ |
try { |
| 738 |
+ |
return Unsafe.getUnsafe(); |
| 739 |
+ |
} catch (SecurityException se) { |
| 740 |
+ |
try { |
| 741 |
+ |
return java.security.AccessController.doPrivileged |
| 742 |
+ |
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
| 743 |
+ |
public Unsafe run() throws Exception { |
| 744 |
+ |
return getUnsafePrivileged(); |
| 745 |
+ |
}}); |
| 746 |
+ |
} catch (java.security.PrivilegedActionException e) { |
| 747 |
+ |
throw e.getCause(); |
| 748 |
+ |
} |
| 749 |
+ |
} |
| 750 |
+ |
} |
| 751 |
|
|
| 752 |
< |
static final Unsafe _unsafe; |
| 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; |
| 770 |
|
static final int qShift; |
| 771 |
|
static { |
| 772 |
|
try { |
| 773 |
< |
if (ForkJoinWorkerThread.class.getClassLoader() != null) { |
| 774 |
< |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
| 775 |
< |
f.setAccessible(true); |
| 776 |
< |
_unsafe = (Unsafe)f.get(null); |
| 777 |
< |
} |
| 778 |
< |
else |
| 699 |
< |
_unsafe = Unsafe.getUnsafe(); |
| 700 |
< |
baseOffset = _unsafe.objectFieldOffset |
| 701 |
< |
(ForkJoinWorkerThread.class.getDeclaredField("base")); |
| 702 |
< |
spOffset = _unsafe.objectFieldOffset |
| 703 |
< |
(ForkJoinWorkerThread.class.getDeclaredField("sp")); |
| 704 |
< |
runStateOffset = _unsafe.objectFieldOffset |
| 705 |
< |
(ForkJoinWorkerThread.class.getDeclaredField("runState")); |
| 706 |
< |
qBase = _unsafe.arrayBaseOffset(ForkJoinTask[].class); |
| 707 |
< |
int s = _unsafe.arrayIndexScale(ForkJoinTask[].class); |
| 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 (Exception e) { |
| 782 |
> |
} catch (Throwable e) { |
| 783 |
|
throw new RuntimeException("Could not initialize intrinsics", e); |
| 784 |
|
} |
| 785 |
|
} |
