| 83 |
|
* |
| 84 |
|
* When a worker would otherwise be blocked waiting to join a |
| 85 |
|
* task, it first tries a form of linear helping: Each worker |
| 86 |
< |
* records (in field stolen) the most recent task it stole |
| 87 |
< |
* from some other worker. Plus, it records (in field joining) the |
| 88 |
< |
* task it is currently actively joining. Method joinTask uses |
| 86 |
> |
* records (in field currentSteal) the most recent task it stole |
| 87 |
> |
* from some other worker. Plus, it records (in field currentJoin) |
| 88 |
> |
* the task it is currently actively joining. Method joinTask uses |
| 89 |
|
* these markers to try to find a worker to help (i.e., steal back |
| 90 |
|
* a task from and execute it) that could hasten completion of the |
| 91 |
|
* actively joined task. In essence, the joiner executes a task |
| 95 |
|
* technique for implementing efficient futures" SIGPLAN Notices, |
| 96 |
|
* 1993 (http://portal.acm.org/citation.cfm?id=155354). It differs |
| 97 |
|
* in that: (1) We only maintain dependency links across workers |
| 98 |
< |
* upon steals, rather than maintain per-task bookkeeping. This |
| 99 |
< |
* requires a linear scan of workers array to locate stealers, |
| 100 |
< |
* which isolates cost to when it is needed, rather than adding to |
| 101 |
< |
* per-task overhead. (2) It is "shallow", ignoring nesting and |
| 102 |
< |
* potentially cyclic mutual steals. (3) It is intentionally |
| 103 |
< |
* racy: field joining is updated only while actively joining, |
| 104 |
< |
* which means that we could miss links in the chain during |
| 105 |
< |
* long-lived tasks, GC stalls etc. (4) We fall back to |
| 106 |
< |
* suspending the worker and if necessary replacing it with a |
| 107 |
< |
* spare (see ForkJoinPool.tryAwaitJoin). |
| 98 |
> |
* upon steals, rather than use per-task bookkeeping. This may |
| 99 |
> |
* require a linear scan of workers array to locate stealers, but |
| 100 |
> |
* usually doesn't because stealers leave hints (that may become |
| 101 |
> |
* stale/wrong) of where to locate them. This isolates cost to |
| 102 |
> |
* when it is needed, rather than adding to per-task overhead. |
| 103 |
> |
* (2) It is "shallow", ignoring nesting and potentially cyclic |
| 104 |
> |
* mutual steals. (3) It is intentionally racy: field currentJoin |
| 105 |
> |
* is updated only while actively joining, which means that we |
| 106 |
> |
* miss links in the chain during long-lived tasks, GC stalls etc |
| 107 |
> |
* (which is OK since blocking in such cases is usually a good |
| 108 |
> |
* idea). (4) We bound the number of attempts to find work (see |
| 109 |
> |
* MAX_HELP_DEPTH) and fall back to suspending the worker and if |
| 110 |
> |
* necessary replacing it with a spare (see |
| 111 |
> |
* ForkJoinPool.tryAwaitJoin). |
| 112 |
|
* |
| 113 |
< |
* Efficient implementation of these algorithms currently relies on |
| 114 |
< |
* an uncomfortable amount of "Unsafe" mechanics. To maintain |
| 113 |
> |
* Efficient implementation of these algorithms currently relies |
| 114 |
> |
* on an uncomfortable amount of "Unsafe" mechanics. To maintain |
| 115 |
|
* correct orderings, reads and writes of variable base require |
| 116 |
|
* volatile ordering. Variable sp does not require volatile |
| 117 |
|
* writes but still needs store-ordering, which we accomplish by |
| 118 |
|
* pre-incrementing sp before filling the slot with an ordered |
| 119 |
|
* store. (Pre-incrementing also enables backouts used in |
| 120 |
< |
* scanWhileJoining.) Because they are protected by volatile base |
| 121 |
< |
* reads, reads of the queue array and its slots by other threads |
| 122 |
< |
* do not need volatile load semantics, but writes (in push) |
| 123 |
< |
* require store order and CASes (in pop and deq) require |
| 124 |
< |
* (volatile) CAS semantics. (Michael, Saraswat, and Vechev's |
| 125 |
< |
* algorithm has similar properties, but without support for |
| 126 |
< |
* nulling slots.) Since these combinations aren't supported |
| 127 |
< |
* using ordinary volatiles, the only way to accomplish these |
| 128 |
< |
* efficiently is to use direct Unsafe calls. (Using external |
| 129 |
< |
* AtomicIntegers and AtomicReferenceArrays for the indices and |
| 130 |
< |
* array is significantly slower because of memory locality and |
| 131 |
< |
* indirection effects.) |
| 120 |
> |
* joinTask.) Because they are protected by volatile base reads, |
| 121 |
> |
* reads of the queue array and its slots by other threads do not |
| 122 |
> |
* need volatile load semantics, but writes (in push) require |
| 123 |
> |
* store order and CASes (in pop and deq) require (volatile) CAS |
| 124 |
> |
* semantics. (Michael, Saraswat, and Vechev's algorithm has |
| 125 |
> |
* similar properties, but without support for nulling slots.) |
| 126 |
> |
* Since these combinations aren't supported using ordinary |
| 127 |
> |
* volatiles, the only way to accomplish these efficiently is to |
| 128 |
> |
* use direct Unsafe calls. (Using external AtomicIntegers and |
| 129 |
> |
* AtomicReferenceArrays for the indices and array is |
| 130 |
> |
* significantly slower because of memory locality and indirection |
| 131 |
> |
* effects.) |
| 132 |
|
* |
| 133 |
|
* Further, performance on most platforms is very sensitive to |
| 134 |
|
* placement and sizing of the (resizable) queue array. Even |
| 153 |
|
private static final Random seedGenerator = new Random(); |
| 154 |
|
|
| 155 |
|
/** |
| 156 |
< |
* The timeout value for suspending spares. Spare workers that |
| 157 |
< |
* remain unsignalled for more than this time may be trimmed |
| 158 |
< |
* (killed and removed from pool). Since our goal is to avoid |
| 159 |
< |
* long-term thread buildup, the exact value of timeout does not |
| 160 |
< |
* matter too much so long as it avoids most false-alarm timeouts |
| 157 |
< |
* under GC stalls or momentarily high system load. |
| 156 |
> |
* The maximum stolen->joining link depth allowed in helpJoinTask. |
| 157 |
> |
* Depths for legitimate chains are unbounded, but we use a fixed |
| 158 |
> |
* constant to avoid (otherwise unchecked) cycles and bound |
| 159 |
> |
* staleness of traversal parameters at the expense of sometimes |
| 160 |
> |
* blocking when we could be helping. |
| 161 |
|
*/ |
| 162 |
< |
private static final long SPARE_KEEPALIVE_NANOS = |
| 163 |
< |
5L * 1000L * 1000L * 1000L; // 5 secs |
| 162 |
> |
private static final int MAX_HELP_DEPTH = 8; |
| 163 |
> |
|
| 164 |
> |
/** |
| 165 |
> |
* The wakeup interval (in nanoseconds) for the first worker |
| 166 |
> |
* suspended as spare. On each wakeup not signalled by a |
| 167 |
> |
* resumption, it may ask the pool to reduce the number of spares. |
| 168 |
> |
*/ |
| 169 |
> |
private static final long TRIM_RATE_NANOS = 200L * 1000L * 1000L; |
| 170 |
|
|
| 171 |
|
/** |
| 172 |
|
* Capacity of work-stealing queue array upon initialization. |
| 189 |
|
final ForkJoinPool pool; |
| 190 |
|
|
| 191 |
|
/** |
| 183 |
– |
* The task most recently stolen from another worker |
| 184 |
– |
*/ |
| 185 |
– |
private volatile ForkJoinTask<?> stolen; |
| 186 |
– |
|
| 187 |
– |
/** |
| 188 |
– |
* The task currently being joined, set only when actively |
| 189 |
– |
* trying to helpStealer. |
| 190 |
– |
*/ |
| 191 |
– |
private volatile ForkJoinTask<?> joining; |
| 192 |
– |
|
| 193 |
– |
/** |
| 192 |
|
* The work-stealing queue array. Size must be a power of two. |
| 193 |
|
* Initialized in onStart, to improve memory locality. |
| 194 |
|
*/ |
| 210 |
|
private int sp; |
| 211 |
|
|
| 212 |
|
/** |
| 213 |
+ |
* The index of most recent stealer, used as a hint to avoid |
| 214 |
+ |
* traversal in method helpJoinTask. This is only a hint because a |
| 215 |
+ |
* worker might have had multiple steals and this only holds one |
| 216 |
+ |
* of them (usually the most current). Declared non-volatile, |
| 217 |
+ |
* relying on other prevailing sync to keep reasonably current. |
| 218 |
+ |
*/ |
| 219 |
+ |
private int stealHint; |
| 220 |
+ |
|
| 221 |
+ |
/** |
| 222 |
|
* Run state of this worker. In addition to the usual run levels, |
| 223 |
|
* tracks if this worker is suspended as a spare, and if it was |
| 224 |
|
* killed (trimmed) while suspended. However, "active" status is |
| 232 |
|
private static final int TRIMMED = 0x08; // killed while suspended |
| 233 |
|
|
| 234 |
|
/** |
| 228 |
– |
* Number of LockSupport.park calls to block this thread for |
| 229 |
– |
* suspension or event waits. Used for internal instrumention; |
| 230 |
– |
* currently not exported but included because volatile write upon |
| 231 |
– |
* park also provides a workaround for a JVM bug. |
| 232 |
– |
*/ |
| 233 |
– |
volatile int parkCount; |
| 234 |
– |
|
| 235 |
– |
/** |
| 235 |
|
* Number of steals, transferred and reset in pool callbacks pool |
| 236 |
|
* when idle Accessed directly by pool. |
| 237 |
|
*/ |
| 251 |
|
|
| 252 |
|
/** |
| 253 |
|
* True if use local fifo, not default lifo, for local polling. |
| 254 |
< |
* Shadows value from ForkJoinPool, which resets it if changed |
| 256 |
< |
* pool-wide. |
| 254 |
> |
* Shadows value from ForkJoinPool. |
| 255 |
|
*/ |
| 256 |
|
private final boolean locallyFifo; |
| 257 |
< |
|
| 257 |
> |
|
| 258 |
|
/** |
| 259 |
|
* Index of this worker in pool array. Set once by pool before |
| 260 |
|
* running, and accessed directly by pool to locate this worker in |
| 275 |
|
volatile long nextWaiter; |
| 276 |
|
|
| 277 |
|
/** |
| 278 |
+ |
* Number of times this thread suspended as spare |
| 279 |
+ |
*/ |
| 280 |
+ |
int spareCount; |
| 281 |
+ |
|
| 282 |
+ |
/** |
| 283 |
+ |
* Encoded index and count of next spare waiter. Used only |
| 284 |
+ |
* by ForkJoinPool for managing spares. |
| 285 |
+ |
*/ |
| 286 |
+ |
volatile int nextSpare; |
| 287 |
+ |
|
| 288 |
+ |
/** |
| 289 |
+ |
* The task currently being joined, set only when actively trying |
| 290 |
+ |
* to helpStealer. Written only by current thread, but read by |
| 291 |
+ |
* others. |
| 292 |
+ |
*/ |
| 293 |
+ |
private volatile ForkJoinTask<?> currentJoin; |
| 294 |
+ |
|
| 295 |
+ |
/** |
| 296 |
+ |
* The task most recently stolen from another worker (or |
| 297 |
+ |
* submission queue). Not volatile because always read/written in |
| 298 |
+ |
* presence of related volatiles in those cases where it matters. |
| 299 |
+ |
*/ |
| 300 |
+ |
private ForkJoinTask<?> currentSteal; |
| 301 |
+ |
|
| 302 |
+ |
/** |
| 303 |
|
* Creates a ForkJoinWorkerThread operating in the given pool. |
| 304 |
|
* |
| 305 |
|
* @param pool the pool this thread works in |
| 308 |
|
protected ForkJoinWorkerThread(ForkJoinPool pool) { |
| 309 |
|
this.pool = pool; |
| 310 |
|
this.locallyFifo = pool.locallyFifo; |
| 311 |
+ |
setDaemon(true); |
| 312 |
|
// To avoid exposing construction details to subclasses, |
| 313 |
|
// remaining initialization is in start() and onStart() |
| 314 |
|
} |
| 320 |
|
this.poolIndex = poolIndex; |
| 321 |
|
if (ueh != null) |
| 322 |
|
setUncaughtExceptionHandler(ueh); |
| 299 |
– |
setDaemon(true); |
| 323 |
|
start(); |
| 324 |
|
} |
| 325 |
|
|
| 378 |
|
*/ |
| 379 |
|
protected void onTermination(Throwable exception) { |
| 380 |
|
try { |
| 358 |
– |
stolen = null; |
| 359 |
– |
joining = null; |
| 381 |
|
cancelTasks(); |
| 382 |
+ |
while (active) // force inactive |
| 383 |
+ |
active = !pool.tryDecrementActiveCount(); |
| 384 |
|
setTerminated(); |
| 385 |
|
pool.workerTerminated(this); |
| 386 |
|
} catch (Throwable ex) { // Shouldn't ever happen |
| 415 |
|
* Find and execute tasks and check status while running |
| 416 |
|
*/ |
| 417 |
|
private void mainLoop() { |
| 418 |
< |
boolean ran = false; // true if ran task in last loop iter |
| 396 |
< |
boolean prevRan = false; // true if ran on last or previous step |
| 418 |
> |
int misses = 0; // track consecutive times failed to find work; max 2 |
| 419 |
|
ForkJoinPool p = pool; |
| 420 |
|
for (;;) { |
| 421 |
< |
p.preStep(this, prevRan); |
| 421 |
> |
p.preStep(this, misses); |
| 422 |
|
if (runState != 0) |
| 423 |
< |
return; |
| 424 |
< |
ForkJoinTask<?> t; // try to get and run stolen or submitted task |
| 425 |
< |
if ((t = scan()) != null || (t = pollSubmission()) != null) { |
| 404 |
< |
t.tryExec(); |
| 405 |
< |
if (base != sp) |
| 406 |
< |
runLocalTasks(); |
| 407 |
< |
stolen = null; |
| 408 |
< |
prevRan = ran = true; |
| 409 |
< |
} |
| 410 |
< |
else { |
| 411 |
< |
prevRan = ran; |
| 412 |
< |
ran = false; |
| 413 |
< |
} |
| 423 |
> |
break; |
| 424 |
> |
misses = ((tryExecSteal() || tryExecSubmission()) ? 0 : |
| 425 |
> |
(misses < 2 ? misses + 1 : 2)); |
| 426 |
|
} |
| 427 |
|
} |
| 428 |
|
|
| 429 |
|
/** |
| 430 |
< |
* Runs local tasks until queue is empty or shut down. Call only |
| 431 |
< |
* while active. |
| 430 |
> |
* Try to steal a task and execute it |
| 431 |
> |
* |
| 432 |
> |
* @return true if ran a task |
| 433 |
|
*/ |
| 434 |
< |
private void runLocalTasks() { |
| 435 |
< |
while (runState == 0) { |
| 436 |
< |
ForkJoinTask<?> t = locallyFifo? locallyDeqTask() : popTask(); |
| 437 |
< |
if (t != null) |
| 438 |
< |
t.tryExec(); |
| 439 |
< |
else if (base == sp) |
| 440 |
< |
break; |
| 434 |
> |
private boolean tryExecSteal() { |
| 435 |
> |
ForkJoinTask<?> t; |
| 436 |
> |
if ((t = scan()) != null) { |
| 437 |
> |
t.quietlyExec(); |
| 438 |
> |
currentSteal = null; |
| 439 |
> |
if (sp != base) |
| 440 |
> |
execLocalTasks(); |
| 441 |
> |
return true; |
| 442 |
|
} |
| 443 |
+ |
return false; |
| 444 |
|
} |
| 445 |
|
|
| 446 |
|
/** |
| 447 |
< |
* If a submission exists, try to activate and take it |
| 447 |
> |
* If a submission exists, try to activate and run it; |
| 448 |
|
* |
| 449 |
< |
* @return a task, if available |
| 449 |
> |
* @return true if ran a task |
| 450 |
|
*/ |
| 451 |
< |
private ForkJoinTask<?> pollSubmission() { |
| 451 |
> |
private boolean tryExecSubmission() { |
| 452 |
|
ForkJoinPool p = pool; |
| 453 |
|
while (p.hasQueuedSubmissions()) { |
| 454 |
+ |
ForkJoinTask<?> t; |
| 455 |
|
if (active || (active = p.tryIncrementActiveCount())) { |
| 456 |
< |
ForkJoinTask<?> t = p.pollSubmission(); |
| 457 |
< |
return t != null ? t : scan(); // if missed, rescan |
| 456 |
> |
if ((t = p.pollSubmission()) != null) { |
| 457 |
> |
currentSteal = t; |
| 458 |
> |
t.quietlyExec(); |
| 459 |
> |
currentSteal = null; |
| 460 |
> |
if (sp != base) |
| 461 |
> |
execLocalTasks(); |
| 462 |
> |
return true; |
| 463 |
> |
} |
| 464 |
|
} |
| 465 |
|
} |
| 466 |
< |
return null; |
| 466 |
> |
return false; |
| 467 |
> |
} |
| 468 |
> |
|
| 469 |
> |
/** |
| 470 |
> |
* Runs local tasks until queue is empty or shut down. Call only |
| 471 |
> |
* while active. |
| 472 |
> |
*/ |
| 473 |
> |
private void execLocalTasks() { |
| 474 |
> |
while (runState == 0) { |
| 475 |
> |
ForkJoinTask<?> t = locallyFifo? locallyDeqTask() : popTask(); |
| 476 |
> |
if (t != null) |
| 477 |
> |
t.quietlyExec(); |
| 478 |
> |
else if (sp == base) |
| 479 |
> |
break; |
| 480 |
> |
} |
| 481 |
|
} |
| 482 |
|
|
| 483 |
|
/* |
| 545 |
|
ForkJoinTask<?> t; |
| 546 |
|
ForkJoinTask<?>[] q; |
| 547 |
|
int b, i; |
| 548 |
< |
if ((b = base) != sp && |
| 548 |
> |
if (sp != (b = base) && |
| 549 |
|
(q = queue) != null && // must read q after b |
| 550 |
|
(t = q[i = (q.length - 1) & b]) != null && base == b && |
| 551 |
|
UNSAFE.compareAndSwapObject(q, (i << qShift) + qBase, t, null)) { |
| 580 |
|
|
| 581 |
|
/** |
| 582 |
|
* Returns a popped task, or null if empty. Assumes active status. |
| 583 |
< |
* Called only by current thread. (Note: a specialization of this |
| 548 |
< |
* code appears in popWhileJoining.) |
| 583 |
> |
* Called only by current thread. |
| 584 |
|
*/ |
| 585 |
< |
final ForkJoinTask<?> popTask() { |
| 586 |
< |
int s; |
| 587 |
< |
ForkJoinTask<?>[] q; |
| 588 |
< |
if (base != (s = sp) && (q = queue) != null) { |
| 589 |
< |
int i = (q.length - 1) & --s; |
| 590 |
< |
ForkJoinTask<?> t = q[i]; |
| 591 |
< |
if (t != null && UNSAFE.compareAndSwapObject |
| 592 |
< |
(q, (i << qShift) + qBase, t, null)) { |
| 593 |
< |
sp = s; |
| 594 |
< |
return t; |
| 585 |
> |
private ForkJoinTask<?> popTask() { |
| 586 |
> |
ForkJoinTask<?>[] q = queue; |
| 587 |
> |
if (q != null) { |
| 588 |
> |
int s; |
| 589 |
> |
while ((s = sp) != base) { |
| 590 |
> |
int i = (q.length - 1) & --s; |
| 591 |
> |
long u = (i << qShift) + qBase; // raw offset |
| 592 |
> |
ForkJoinTask<?> t = q[i]; |
| 593 |
> |
if (t == null) // lost to stealer |
| 594 |
> |
break; |
| 595 |
> |
if (UNSAFE.compareAndSwapObject(q, u, t, null)) { |
| 596 |
> |
sp = s; // putOrderedInt may encourage more timely write |
| 597 |
> |
// UNSAFE.putOrderedInt(this, spOffset, s); |
| 598 |
> |
return t; |
| 599 |
> |
} |
| 600 |
|
} |
| 601 |
|
} |
| 602 |
|
return null; |
| 611 |
|
*/ |
| 612 |
|
final boolean unpushTask(ForkJoinTask<?> t) { |
| 613 |
|
int s; |
| 614 |
< |
ForkJoinTask<?>[] q; |
| 615 |
< |
if (base != (s = sp) && (q = queue) != null && |
| 614 |
> |
ForkJoinTask<?>[] q = queue; |
| 615 |
> |
if ((s = sp) != base && q != null && |
| 616 |
|
UNSAFE.compareAndSwapObject |
| 617 |
|
(q, (((q.length - 1) & --s) << qShift) + qBase, t, null)) { |
| 618 |
|
sp = s; |
| 619 |
+ |
// UNSAFE.putOrderedInt(this, spOffset, s); |
| 620 |
|
return true; |
| 621 |
|
} |
| 622 |
|
return false; |
| 705 |
|
ForkJoinWorkerThread v = ws[k & mask]; |
| 706 |
|
r ^= r << 13; r ^= r >>> 17; r ^= r << 5; // inline xorshift |
| 707 |
|
if (v != null && v.base != v.sp) { |
| 708 |
< |
if (canSteal || // ensure active status |
| 709 |
< |
(canSteal = active = p.tryIncrementActiveCount())) { |
| 710 |
< |
int b = v.base; // inline specialized deqTask |
| 711 |
< |
ForkJoinTask<?>[] q; |
| 712 |
< |
if (b != v.sp && (q = v.queue) != null) { |
| 713 |
< |
ForkJoinTask<?> t; |
| 714 |
< |
int i = (q.length - 1) & b; |
| 715 |
< |
long u = (i << qShift) + qBase; // raw offset |
| 716 |
< |
if ((t = q[i]) != null && v.base == b && |
| 717 |
< |
UNSAFE.compareAndSwapObject(q, u, t, null)) { |
| 718 |
< |
stolen = t; |
| 719 |
< |
v.base = b + 1; |
| 720 |
< |
seed = r; |
| 721 |
< |
++stealCount; |
| 722 |
< |
return t; |
| 723 |
< |
} |
| 708 |
> |
ForkJoinTask<?>[] q; int b; |
| 709 |
> |
if ((canSteal || // ensure active status |
| 710 |
> |
(canSteal = active = p.tryIncrementActiveCount())) && |
| 711 |
> |
(q = v.queue) != null && (b = v.base) != v.sp) { |
| 712 |
> |
int i = (q.length - 1) & b; |
| 713 |
> |
long u = (i << qShift) + qBase; // raw offset |
| 714 |
> |
ForkJoinTask<?> t = q[i]; |
| 715 |
> |
if (v.base == b && t != null && |
| 716 |
> |
UNSAFE.compareAndSwapObject(q, u, t, null)) { |
| 717 |
> |
int pid = poolIndex; |
| 718 |
> |
currentSteal = t; |
| 719 |
> |
v.stealHint = pid; |
| 720 |
> |
v.base = b + 1; |
| 721 |
> |
seed = r; |
| 722 |
> |
++stealCount; |
| 723 |
> |
return t; |
| 724 |
|
} |
| 725 |
|
} |
| 726 |
|
j = -n; |
| 740 |
|
// Run State management |
| 741 |
|
|
| 742 |
|
// status check methods used mainly by ForkJoinPool |
| 743 |
+ |
final boolean isRunning() { return runState == 0; } |
| 744 |
|
final boolean isTerminating() { return (runState & TERMINATING) != 0; } |
| 745 |
|
final boolean isTerminated() { return (runState & TERMINATED) != 0; } |
| 746 |
|
final boolean isSuspended() { return (runState & SUSPENDED) != 0; } |
| 747 |
|
final boolean isTrimmed() { return (runState & TRIMMED) != 0; } |
| 748 |
|
|
| 749 |
|
/** |
| 750 |
< |
* Sets state to TERMINATING, also resuming if suspended. |
| 750 |
> |
* Sets state to TERMINATING, also, unless "quiet", unparking if |
| 751 |
> |
* not already terminated |
| 752 |
> |
* |
| 753 |
> |
* @param quiet don't unpark (used for faster status updates on |
| 754 |
> |
* pool termination) |
| 755 |
|
*/ |
| 756 |
< |
final void shutdown() { |
| 756 |
> |
final void shutdown(boolean quiet) { |
| 757 |
|
for (;;) { |
| 758 |
|
int s = runState; |
| 759 |
+ |
if ((s & (TERMINATING|TERMINATED)) != 0) |
| 760 |
+ |
break; |
| 761 |
|
if ((s & SUSPENDED) != 0) { // kill and wakeup if suspended |
| 762 |
|
if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, |
| 763 |
|
(s & ~SUSPENDED) | |
| 764 |
< |
(TRIMMED|TERMINATING))) { |
| 717 |
< |
LockSupport.unpark(this); |
| 764 |
> |
(TRIMMED|TERMINATING))) |
| 765 |
|
break; |
| 719 |
– |
} |
| 766 |
|
} |
| 767 |
|
else if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, |
| 768 |
|
s | TERMINATING)) |
| 769 |
|
break; |
| 770 |
|
} |
| 771 |
+ |
if (!quiet && (runState & TERMINATED) != 0) |
| 772 |
+ |
LockSupport.unpark(this); |
| 773 |
|
} |
| 774 |
|
|
| 775 |
|
/** |
| 776 |
< |
* Sets state to TERMINATED. Called only by this thread. |
| 776 |
> |
* Sets state to TERMINATED. Called only by onTermination() |
| 777 |
|
*/ |
| 778 |
|
private void setTerminated() { |
| 779 |
|
int s; |
| 783 |
|
} |
| 784 |
|
|
| 785 |
|
/** |
| 786 |
< |
* Instrumented version of park used by ForkJoinPool.awaitEvent |
| 739 |
< |
*/ |
| 740 |
< |
final void doPark() { |
| 741 |
< |
++parkCount; |
| 742 |
< |
LockSupport.park(this); |
| 743 |
< |
} |
| 744 |
< |
|
| 745 |
< |
/** |
| 746 |
< |
* If suspended, tries to set status to unsuspended. |
| 747 |
< |
* Caller must unpark to actually resume |
| 786 |
> |
* If suspended, tries to set status to unsuspended and unparks. |
| 787 |
|
* |
| 788 |
|
* @return true if successful |
| 789 |
|
*/ |
| 790 |
|
final boolean tryUnsuspend() { |
| 791 |
< |
int s = runState; |
| 792 |
< |
if ((s & SUSPENDED) != 0) |
| 793 |
< |
return UNSAFE.compareAndSwapInt(this, runStateOffset, s, |
| 794 |
< |
s & ~SUSPENDED); |
| 791 |
> |
int s; |
| 792 |
> |
while (((s = runState) & SUSPENDED) != 0) { |
| 793 |
> |
if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, |
| 794 |
> |
s & ~SUSPENDED)) |
| 795 |
> |
return true; |
| 796 |
> |
} |
| 797 |
|
return false; |
| 798 |
|
} |
| 799 |
|
|
| 800 |
|
/** |
| 801 |
< |
* Sets suspended status and blocks as spare until resumed, |
| 802 |
< |
* shutdown, or timed out. |
| 803 |
< |
* |
| 763 |
< |
* @return false if trimmed |
| 801 |
> |
* Sets suspended status and blocks as spare until resumed |
| 802 |
> |
* or shutdown. |
| 803 |
> |
* @returns true if still running on exit |
| 804 |
|
*/ |
| 805 |
|
final boolean suspendAsSpare() { |
| 806 |
< |
for (;;) { // set suspended unless terminating |
| 806 |
> |
lastEventCount = 0; // reset upon resume |
| 807 |
> |
for (;;) { // set suspended unless terminating |
| 808 |
|
int s = runState; |
| 809 |
|
if ((s & TERMINATING) != 0) { // must kill |
| 810 |
|
if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, |
| 815 |
|
s | SUSPENDED)) |
| 816 |
|
break; |
| 817 |
|
} |
| 818 |
< |
boolean timed; |
| 819 |
< |
long nanos; |
| 779 |
< |
long startTime; |
| 780 |
< |
if (poolIndex < pool.parallelism) { |
| 781 |
< |
timed = false; |
| 782 |
< |
nanos = 0L; |
| 783 |
< |
startTime = 0L; |
| 784 |
< |
} |
| 785 |
< |
else { |
| 786 |
< |
timed = true; |
| 787 |
< |
nanos = SPARE_KEEPALIVE_NANOS; |
| 788 |
< |
startTime = System.nanoTime(); |
| 789 |
< |
} |
| 790 |
< |
pool.accumulateStealCount(this); |
| 791 |
< |
lastEventCount = 0; // reset upon resume |
| 792 |
< |
interrupted(); // clear/ignore interrupts |
| 818 |
> |
ForkJoinPool p = pool; |
| 819 |
> |
p.pushSpare(this); |
| 820 |
|
while ((runState & SUSPENDED) != 0) { |
| 821 |
< |
++parkCount; |
| 822 |
< |
if (!timed) |
| 821 |
> |
if (!p.tryAccumulateStealCount(this)) |
| 822 |
> |
continue; |
| 823 |
> |
interrupted(); // clear/ignore interrupts |
| 824 |
> |
if ((runState & SUSPENDED) == 0) |
| 825 |
> |
break; |
| 826 |
> |
if (nextSpare != 0) // untimed |
| 827 |
|
LockSupport.park(this); |
| 828 |
< |
else if ((nanos -= (System.nanoTime() - startTime)) > 0) |
| 829 |
< |
LockSupport.parkNanos(this, nanos); |
| 830 |
< |
else { // try to trim on timeout |
| 831 |
< |
int s = runState; |
| 832 |
< |
if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, |
| 833 |
< |
(s & ~SUSPENDED) | |
| 834 |
< |
(TRIMMED|TERMINATING))) |
| 835 |
< |
return false; |
| 828 |
> |
else { |
| 829 |
> |
long startTime = System.nanoTime(); |
| 830 |
> |
LockSupport.parkNanos(this, TRIM_RATE_NANOS); |
| 831 |
> |
if ((runState & SUSPENDED) == 0) |
| 832 |
> |
break; |
| 833 |
> |
long now = System.nanoTime(); |
| 834 |
> |
if (now - startTime >= TRIM_RATE_NANOS) |
| 835 |
> |
pool.tryTrimSpare(now); |
| 836 |
|
} |
| 837 |
|
} |
| 838 |
< |
return true; |
| 838 |
> |
return runState == 0; |
| 839 |
|
} |
| 840 |
|
|
| 841 |
|
// Misc support methods for ForkJoinPool |
| 845 |
|
* used by ForkJoinTask. |
| 846 |
|
*/ |
| 847 |
|
final int getQueueSize() { |
| 848 |
< |
return -base + sp; |
| 848 |
> |
int n; // external calls must read base first |
| 849 |
> |
return (n = -base + sp) <= 0 ? 0 : n; |
| 850 |
|
} |
| 851 |
|
|
| 852 |
|
/** |
| 854 |
|
* thread. |
| 855 |
|
*/ |
| 856 |
|
final void cancelTasks() { |
| 857 |
+ |
ForkJoinTask<?> cj = currentJoin; // try to cancel ongoing tasks |
| 858 |
+ |
if (cj != null) { |
| 859 |
+ |
currentJoin = null; |
| 860 |
+ |
cj.cancelIgnoringExceptions(); |
| 861 |
+ |
try { |
| 862 |
+ |
this.interrupt(); // awaken wait |
| 863 |
+ |
} catch (SecurityException ignore) { |
| 864 |
+ |
} |
| 865 |
+ |
} |
| 866 |
+ |
ForkJoinTask<?> cs = currentSteal; |
| 867 |
+ |
if (cs != null) { |
| 868 |
+ |
currentSteal = null; |
| 869 |
+ |
cs.cancelIgnoringExceptions(); |
| 870 |
+ |
} |
| 871 |
|
while (base != sp) { |
| 872 |
|
ForkJoinTask<?> t = deqTask(); |
| 873 |
|
if (t != null) |
| 895 |
|
// Support methods for ForkJoinTask |
| 896 |
|
|
| 897 |
|
/** |
| 898 |
+ |
* Gets and removes a local task. |
| 899 |
+ |
* |
| 900 |
+ |
* @return a task, if available |
| 901 |
+ |
*/ |
| 902 |
+ |
final ForkJoinTask<?> pollLocalTask() { |
| 903 |
+ |
while (sp != base) { |
| 904 |
+ |
if (active || (active = pool.tryIncrementActiveCount())) |
| 905 |
+ |
return locallyFifo? locallyDeqTask() : popTask(); |
| 906 |
+ |
} |
| 907 |
+ |
return null; |
| 908 |
+ |
} |
| 909 |
+ |
|
| 910 |
+ |
/** |
| 911 |
+ |
* Gets and removes a local or stolen task. |
| 912 |
+ |
* |
| 913 |
+ |
* @return a task, if available |
| 914 |
+ |
*/ |
| 915 |
+ |
final ForkJoinTask<?> pollTask() { |
| 916 |
+ |
ForkJoinTask<?> t = pollLocalTask(); |
| 917 |
+ |
if (t == null) { |
| 918 |
+ |
t = scan(); |
| 919 |
+ |
currentSteal = null; // cannot retain/track/help |
| 920 |
+ |
} |
| 921 |
+ |
return t; |
| 922 |
+ |
} |
| 923 |
+ |
|
| 924 |
+ |
/** |
| 925 |
|
* Possibly runs some tasks and/or blocks, until task is done. |
| 926 |
|
* |
| 927 |
|
* @param joinMe the task to join |
| 928 |
|
*/ |
| 929 |
|
final void joinTask(ForkJoinTask<?> joinMe) { |
| 930 |
< |
ForkJoinTask<?> prevJoining = joining; |
| 931 |
< |
joining = joinMe; |
| 932 |
< |
while (joinMe.status >= 0) { |
| 933 |
< |
int s = sp; |
| 934 |
< |
if (s == base) { |
| 935 |
< |
nonlocalJoinTask(joinMe); |
| 936 |
< |
break; |
| 937 |
< |
} |
| 938 |
< |
// process local task |
| 939 |
< |
ForkJoinTask<?> t; |
| 940 |
< |
ForkJoinTask<?>[] q = queue; |
| 930 |
> |
// currentJoin only written by this thread; only need ordered store |
| 931 |
> |
ForkJoinTask<?> prevJoin = currentJoin; |
| 932 |
> |
UNSAFE.putOrderedObject(this, currentJoinOffset, joinMe); |
| 933 |
> |
if (sp != base) |
| 934 |
> |
localHelpJoinTask(joinMe); |
| 935 |
> |
if (joinMe.status >= 0) |
| 936 |
> |
pool.awaitJoin(joinMe, this); |
| 937 |
> |
UNSAFE.putOrderedObject(this, currentJoinOffset, prevJoin); |
| 938 |
> |
} |
| 939 |
> |
|
| 940 |
> |
/** |
| 941 |
> |
* Run tasks in local queue until given task is done. |
| 942 |
> |
* |
| 943 |
> |
* @param joinMe the task to join |
| 944 |
> |
*/ |
| 945 |
> |
private void localHelpJoinTask(ForkJoinTask<?> joinMe) { |
| 946 |
> |
int s; |
| 947 |
> |
ForkJoinTask<?>[] q; |
| 948 |
> |
while (joinMe.status >= 0 && (s = sp) != base && (q = queue) != null) { |
| 949 |
|
int i = (q.length - 1) & --s; |
| 950 |
|
long u = (i << qShift) + qBase; // raw offset |
| 951 |
< |
if ((t = q[i]) != null && |
| 952 |
< |
UNSAFE.compareAndSwapObject(q, u, t, null)) { |
| 951 |
> |
ForkJoinTask<?> t = q[i]; |
| 952 |
> |
if (t == null) // lost to a stealer |
| 953 |
> |
break; |
| 954 |
> |
if (UNSAFE.compareAndSwapObject(q, u, t, null)) { |
| 955 |
|
/* |
| 956 |
< |
* This recheck (and similarly in nonlocalJoinTask) |
| 956 |
> |
* This recheck (and similarly in helpJoinTask) |
| 957 |
|
* handles cases where joinMe is independently |
| 958 |
|
* cancelled or forced even though there is other work |
| 959 |
|
* available. Back out of the pop by putting t back |
| 960 |
< |
* into slot before we commit by setting sp. |
| 960 |
> |
* into slot before we commit by writing sp. |
| 961 |
|
*/ |
| 962 |
|
if (joinMe.status < 0) { |
| 963 |
|
UNSAFE.putObjectVolatile(q, u, t); |
| 964 |
|
break; |
| 965 |
|
} |
| 966 |
|
sp = s; |
| 967 |
< |
t.tryExec(); |
| 967 |
> |
// UNSAFE.putOrderedInt(this, spOffset, s); |
| 968 |
> |
t.quietlyExec(); |
| 969 |
|
} |
| 970 |
|
} |
| 887 |
– |
joining = prevJoining; |
| 971 |
|
} |
| 972 |
|
|
| 973 |
|
/** |
| 974 |
|
* Tries to locate and help perform tasks for a stealer of the |
| 975 |
< |
* given task (or in turn one of its stealers), blocking (via |
| 976 |
< |
* pool.tryAwaitJoin) upon failure to find work. Traces |
| 894 |
< |
* stolen->joining links looking for a thread working on |
| 975 |
> |
* given task, or in turn one of its stealers. Traces |
| 976 |
> |
* currentSteal->currentJoin links looking for a thread working on |
| 977 |
|
* a descendant of the given task and with a non-empty queue to |
| 978 |
< |
* steal back and execute tasks from. Inhibits mutual steal chains |
| 979 |
< |
* and scans on outer joins upon nesting to avoid unbounded |
| 980 |
< |
* growth. Restarts search upon encountering inconsistencies. |
| 981 |
< |
* Tries to block if two passes agree that there are no remaining |
| 982 |
< |
* targets. |
| 978 |
> |
* steal back and execute tasks from. |
| 979 |
> |
* |
| 980 |
> |
* The implementation is very branchy to cope with the potential |
| 981 |
> |
* inconsistencies or loops encountering chains that are stale, |
| 982 |
> |
* unknown, or of length greater than MAX_HELP_DEPTH links. All |
| 983 |
> |
* of these cases are dealt with by just returning back to the |
| 984 |
> |
* caller, who is expected to retry if other join mechanisms also |
| 985 |
> |
* don't work out. |
| 986 |
|
* |
| 987 |
|
* @param joinMe the task to join |
| 988 |
|
*/ |
| 989 |
< |
private void nonlocalJoinTask(ForkJoinTask<?> joinMe) { |
| 990 |
< |
ForkJoinPool p = pool; |
| 991 |
< |
int scans = p.parallelism; // give up if too many retries |
| 992 |
< |
ForkJoinTask<?> bottom = null; // target seen when can't descend |
| 993 |
< |
restart: while (joinMe.status >= 0) { |
| 994 |
< |
ForkJoinTask<?> target = null; |
| 995 |
< |
ForkJoinTask<?> next = joinMe; |
| 996 |
< |
while (scans >= 0 && next != null) { |
| 997 |
< |
--scans; |
| 998 |
< |
target = next; |
| 999 |
< |
next = null; |
| 1000 |
< |
ForkJoinWorkerThread v = null; |
| 1001 |
< |
ForkJoinWorkerThread[] ws = p.workers; |
| 1002 |
< |
int n = ws.length; |
| 1003 |
< |
for (int j = 0; j < n; ++j) { |
| 1004 |
< |
ForkJoinWorkerThread w = ws[j]; |
| 1005 |
< |
if (w != null && w.stolen == target) { |
| 1006 |
< |
v = w; |
| 1007 |
< |
break; |
| 989 |
> |
final void helpJoinTask(ForkJoinTask<?> joinMe) { |
| 990 |
> |
ForkJoinWorkerThread[] ws = pool.workers; |
| 991 |
> |
int n; // need at least 2 workers |
| 992 |
> |
if (ws != null && (n = ws.length) > 1 && joinMe.status >= 0) { |
| 993 |
> |
ForkJoinTask<?> task = joinMe; // base of chain |
| 994 |
> |
ForkJoinWorkerThread thread = this; // thread with stolen task |
| 995 |
> |
for (int d = 0; d < MAX_HELP_DEPTH; ++d) { // chain length |
| 996 |
> |
// Try to find v, the stealer of task, by first using hint |
| 997 |
> |
ForkJoinWorkerThread v = ws[thread.stealHint & (n - 1)]; |
| 998 |
> |
if (v == null || v.currentSteal != task) { |
| 999 |
> |
for (int j = 0; ; ++j) { // search array |
| 1000 |
> |
if (j < n) { |
| 1001 |
> |
if ((v = ws[j]) != null) { |
| 1002 |
> |
if (task.status < 0) |
| 1003 |
> |
return; // stale or done |
| 1004 |
> |
if (v.currentSteal == task) { |
| 1005 |
> |
thread.stealHint = j; |
| 1006 |
> |
break; // save hint for next time |
| 1007 |
> |
} |
| 1008 |
> |
} |
| 1009 |
> |
} |
| 1010 |
> |
else |
| 1011 |
> |
return; // no stealer |
| 1012 |
|
} |
| 1013 |
|
} |
| 1014 |
< |
if (v != null && v != this) { |
| 1015 |
< |
ForkJoinTask<?> prevStolen = stolen; |
| 1016 |
< |
int b; |
| 1017 |
< |
ForkJoinTask<?>[] q; |
| 1018 |
< |
while ((b = v.base) != v.sp && (q = v.queue) != null) { |
| 1019 |
< |
int i = (q.length - 1) & b; |
| 1020 |
< |
long u = (i << qShift) + qBase; |
| 1021 |
< |
ForkJoinTask<?> t = q[i]; |
| 1022 |
< |
if (target.status < 0) |
| 1023 |
< |
continue restart; |
| 1024 |
< |
if (t != null && v.base == b && |
| 1025 |
< |
UNSAFE.compareAndSwapObject(q, u, t, null)) { |
| 1014 |
> |
// Try to help v, using specialized form of deqTask |
| 1015 |
> |
int b; |
| 1016 |
> |
ForkJoinTask<?>[] q; |
| 1017 |
> |
while ((b = v.base) != v.sp && (q = v.queue) != null) { |
| 1018 |
> |
int i = (q.length - 1) & b; |
| 1019 |
> |
long u = (i << qShift) + qBase; |
| 1020 |
> |
ForkJoinTask<?> t = q[i]; |
| 1021 |
> |
if (task.status < 0) |
| 1022 |
> |
return; // stale or done |
| 1023 |
> |
if (v.base == b) { |
| 1024 |
> |
if (t == null) |
| 1025 |
> |
return; // producer stalled |
| 1026 |
> |
if (UNSAFE.compareAndSwapObject(q, u, t, null)) { |
| 1027 |
|
if (joinMe.status < 0) { |
| 1028 |
|
UNSAFE.putObjectVolatile(q, u, t); |
| 1029 |
< |
return; // back out |
| 1029 |
> |
return; // back out on cancel |
| 1030 |
|
} |
| 1031 |
< |
stolen = t; |
| 1031 |
> |
int pid = poolIndex; |
| 1032 |
> |
ForkJoinTask<?> prevSteal = currentSteal; |
| 1033 |
> |
currentSteal = t; |
| 1034 |
> |
v.stealHint = pid; |
| 1035 |
|
v.base = b + 1; |
| 1036 |
< |
t.tryExec(); |
| 1037 |
< |
stolen = prevStolen; |
| 1036 |
> |
t.quietlyExec(); |
| 1037 |
> |
currentSteal = prevSteal; |
| 1038 |
|
} |
| 946 |
– |
if (joinMe.status < 0) |
| 947 |
– |
return; |
| 1039 |
|
} |
| 1040 |
< |
next = v.joining; |
| 1040 |
> |
if (joinMe.status < 0) |
| 1041 |
> |
return; |
| 1042 |
|
} |
| 1043 |
< |
if (target.status < 0) |
| 1044 |
< |
continue restart; // inconsistent |
| 1045 |
< |
if (joinMe.status < 0) |
| 1043 |
> |
// Try to descend to find v's stealer |
| 1044 |
> |
ForkJoinTask<?> next = v.currentJoin; |
| 1045 |
> |
if (task.status < 0 || next == null || next == task || |
| 1046 |
> |
joinMe.status < 0) |
| 1047 |
|
return; |
| 1048 |
+ |
task = next; |
| 1049 |
+ |
thread = v; |
| 1050 |
|
} |
| 956 |
– |
|
| 957 |
– |
if (bottom != target) |
| 958 |
– |
bottom = target; // recheck landing spot |
| 959 |
– |
else if (p.tryAwaitJoin(joinMe) < 0) |
| 960 |
– |
return; // successfully blocked |
| 961 |
– |
Thread.yield(); // tame spin in case too many active |
| 1051 |
|
} |
| 1052 |
|
} |
| 1053 |
|
|
| 1103 |
|
} |
| 1104 |
|
|
| 1105 |
|
/** |
| 1017 |
– |
* Gets and removes a local task. |
| 1018 |
– |
* |
| 1019 |
– |
* @return a task, if available |
| 1020 |
– |
*/ |
| 1021 |
– |
final ForkJoinTask<?> pollLocalTask() { |
| 1022 |
– |
while (sp != base) { |
| 1023 |
– |
if (active || (active = pool.tryIncrementActiveCount())) |
| 1024 |
– |
return locallyFifo? locallyDeqTask() : popTask(); |
| 1025 |
– |
} |
| 1026 |
– |
return null; |
| 1027 |
– |
} |
| 1028 |
– |
|
| 1029 |
– |
/** |
| 1030 |
– |
* Gets and removes a local or stolen task. |
| 1031 |
– |
* |
| 1032 |
– |
* @return a task, if available |
| 1033 |
– |
*/ |
| 1034 |
– |
final ForkJoinTask<?> pollTask() { |
| 1035 |
– |
ForkJoinTask<?> t; |
| 1036 |
– |
return (t = pollLocalTask()) != null ? t : scan(); |
| 1037 |
– |
} |
| 1038 |
– |
|
| 1039 |
– |
/** |
| 1106 |
|
* Runs tasks until {@code pool.isQuiescent()}. |
| 1107 |
|
*/ |
| 1108 |
|
final void helpQuiescePool() { |
| 1109 |
|
for (;;) { |
| 1110 |
|
ForkJoinTask<?> t = pollLocalTask(); |
| 1111 |
|
if (t != null || (t = scan()) != null) { |
| 1112 |
< |
t.tryExec(); |
| 1113 |
< |
stolen = null; |
| 1112 |
> |
t.quietlyExec(); |
| 1113 |
> |
currentSteal = null; |
| 1114 |
|
} |
| 1115 |
|
else { |
| 1116 |
|
ForkJoinPool p = pool; |
| 1117 |
|
if (active) { |
| 1118 |
+ |
if (!p.tryDecrementActiveCount()) |
| 1119 |
+ |
continue; // retry later |
| 1120 |
|
active = false; // inactivate |
| 1053 |
– |
do {} while (!p.tryDecrementActiveCount()); |
| 1121 |
|
} |
| 1122 |
|
if (p.isQuiescent()) { |
| 1123 |
|
active = true; // re-activate |
| 1128 |
|
} |
| 1129 |
|
} |
| 1130 |
|
|
| 1131 |
+ |
|
| 1132 |
|
// Unsafe mechanics |
| 1133 |
|
|
| 1134 |
|
private static final sun.misc.Unsafe UNSAFE = sun.misc.Unsafe.getUnsafe(); |
| 1135 |
+ |
private static final long spOffset = |
| 1136 |
+ |
objectFieldOffset("sp", ForkJoinWorkerThread.class); |
| 1137 |
|
private static final long runStateOffset = |
| 1138 |
|
objectFieldOffset("runState", ForkJoinWorkerThread.class); |
| 1139 |
+ |
private static final long currentJoinOffset = |
| 1140 |
+ |
objectFieldOffset("currentJoin", ForkJoinWorkerThread.class); |
| 1141 |
+ |
private static final long currentStealOffset = |
| 1142 |
+ |
objectFieldOffset("currentSteal", ForkJoinWorkerThread.class); |
| 1143 |
|
private static final long qBase = |
| 1144 |
|
UNSAFE.arrayBaseOffset(ForkJoinTask[].class); |
| 1145 |
+ |
|
| 1146 |
|
private static final int qShift; |
| 1147 |
|
|
| 1148 |
|
static { |
| 1162 |
|
throw error; |
| 1163 |
|
} |
| 1164 |
|
} |
| 1165 |
+ |
|
| 1166 |
|
} |
