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 |
22 |
|
* ForkJoinWorkerThreadFactory to use it in a ForkJoinPool. |
23 |
< |
* |
24 |
< |
* <p>This class also provides methods for generating per-thread |
25 |
< |
* random numbers, with the same properties as {@link |
26 |
< |
* java.util.Random} but with each generator isolated from those of |
27 |
< |
* other threads. |
23 |
> |
* |
24 |
|
*/ |
25 |
|
public class ForkJoinWorkerThread extends Thread { |
26 |
|
/* |
130 |
|
|
131 |
|
/** |
132 |
|
* Maximum work-stealing queue array size. Must be less than or |
133 |
< |
* equal to 1 << 30 to ensure lack of index wraparound. |
133 |
> |
* equal to 1 << 28 to ensure lack of index wraparound. (This |
134 |
> |
* is less than usual bounds, because we need leftshift by 3 |
135 |
> |
* to be in int range). |
136 |
|
*/ |
137 |
< |
private static final int MAXIMUM_QUEUE_CAPACITY = 1 << 30; |
137 |
> |
private static final int MAXIMUM_QUEUE_CAPACITY = 1 << 28; |
138 |
|
|
139 |
|
/** |
140 |
< |
* Generator of seeds for per-thread random numbers. |
140 |
> |
* The pool this thread works in. Accessed directly by ForkJoinTask |
141 |
|
*/ |
142 |
< |
private static final Random randomSeedGenerator = new Random(); |
142 |
> |
final ForkJoinPool pool; |
143 |
|
|
144 |
|
/** |
145 |
|
* The work-stealing queue array. Size must be a power of two. |
146 |
+ |
* Initialized when thread starts, to improve memory locality. |
147 |
|
*/ |
148 |
|
private ForkJoinTask<?>[] queue; |
149 |
|
|
162 |
|
private volatile int base; |
163 |
|
|
164 |
|
/** |
165 |
< |
* The pool this thread works in. |
166 |
< |
*/ |
167 |
< |
final ForkJoinPool pool; |
168 |
< |
|
170 |
< |
/** |
171 |
< |
* Index of this worker in pool array. Set once by pool before |
172 |
< |
* running, and accessed directly by pool during cleanup etc |
165 |
> |
* Activity status. When true, this worker is considered active. |
166 |
> |
* Must be false upon construction. It must be true when executing |
167 |
> |
* tasks, and BEFORE stealing a task. It must be false before |
168 |
> |
* calling pool.sync |
169 |
|
*/ |
170 |
< |
int poolIndex; |
170 |
> |
private boolean active; |
171 |
|
|
172 |
|
/** |
173 |
|
* Run state of this worker. Supports simple versions of the usual |
175 |
|
*/ |
176 |
|
private volatile int runState; |
177 |
|
|
182 |
– |
// Runstate values. Order matters |
183 |
– |
private static final int RUNNING = 0; |
184 |
– |
private static final int SHUTDOWN = 1; |
185 |
– |
private static final int TERMINATING = 2; |
186 |
– |
private static final int TERMINATED = 3; |
187 |
– |
|
178 |
|
/** |
179 |
< |
* Activity status. When true, this worker is considered active. |
180 |
< |
* Must be false upon construction. It must be true when executing |
191 |
< |
* tasks, and BEFORE stealing a task. It must be false before |
192 |
< |
* blocking on the Pool Barrier. |
179 |
> |
* Seed for random number generator for choosing steal victims. |
180 |
> |
* Uses Marsaglia xorshift. Must be nonzero upon initialization. |
181 |
|
*/ |
182 |
< |
private boolean active; |
182 |
> |
private int seed; |
183 |
|
|
184 |
|
/** |
185 |
|
* Number of steals, transferred to pool when idle |
187 |
|
private int stealCount; |
188 |
|
|
189 |
|
/** |
190 |
< |
* Seed for random number generator for choosing steal victims |
191 |
< |
*/ |
204 |
< |
private int randomVictimSeed; |
205 |
< |
|
206 |
< |
/** |
207 |
< |
* Seed for embedded Jurandom |
190 |
> |
* Index of this worker in pool array. Set once by pool before |
191 |
> |
* running, and accessed directly by pool during cleanup etc |
192 |
|
*/ |
193 |
< |
private long juRandomSeed; |
193 |
> |
int poolIndex; |
194 |
|
|
195 |
|
/** |
196 |
< |
* The last barrier event waited for |
196 |
> |
* The last barrier event waited for. Accessed in pool callback |
197 |
> |
* methods, but only by current thread. |
198 |
|
*/ |
199 |
< |
private long eventCount; |
199 |
> |
long lastEventCount; |
200 |
|
|
201 |
|
/** |
202 |
|
* Creates a ForkJoinWorkerThread operating in the given pool. |
206 |
|
protected ForkJoinWorkerThread(ForkJoinPool pool) { |
207 |
|
if (pool == null) throw new NullPointerException(); |
208 |
|
this.pool = pool; |
209 |
< |
// remaining initialization deferred to onStart |
209 |
> |
// Note: poolIndex is set by pool during construction |
210 |
> |
// Remaining initialization is deferred to onStart |
211 |
|
} |
212 |
|
|
213 |
< |
// public access methods |
213 |
> |
// Public access methods |
214 |
|
|
215 |
|
/** |
216 |
< |
* Returns the pool hosting the current task execution. |
216 |
> |
* Returns the pool hosting this thread |
217 |
|
* @return the pool |
218 |
|
*/ |
219 |
< |
public static ForkJoinPool getPool() { |
220 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())).pool; |
219 |
> |
public ForkJoinPool getPool() { |
220 |
> |
return pool; |
221 |
|
} |
222 |
|
|
223 |
|
/** |
224 |
< |
* Returns the index number of the current worker thread in its |
225 |
< |
* pool. The returned value ranges from zero to the maximum |
226 |
< |
* number of threads (minus one) that have ever been created in |
227 |
< |
* the pool. This method may be useful for applications that |
228 |
< |
* track status or collect results on a per-worker basis. |
224 |
> |
* Returns the index number of this thread in its pool. The |
225 |
> |
* returned value ranges from zero to the maximum number of |
226 |
> |
* threads (minus one) that have ever been created in the pool. |
227 |
> |
* This method may be useful for applications that track status or |
228 |
> |
* collect results per-worker rather than per-task. |
229 |
|
* @return the index number. |
230 |
|
*/ |
231 |
< |
public static int getPoolIndex() { |
232 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())).poolIndex; |
231 |
> |
public int getPoolIndex() { |
232 |
> |
return poolIndex; |
233 |
|
} |
234 |
|
|
235 |
< |
// Access methods used by Pool |
235 |
> |
|
236 |
> |
// Runstate management |
237 |
> |
|
238 |
> |
// Runstate values. Order matters |
239 |
> |
private static final int RUNNING = 0; |
240 |
> |
private static final int SHUTDOWN = 1; |
241 |
> |
private static final int TERMINATING = 2; |
242 |
> |
private static final int TERMINATED = 3; |
243 |
> |
|
244 |
> |
final boolean isShutdown() { return runState >= SHUTDOWN; } |
245 |
> |
final boolean isTerminating() { return runState >= TERMINATING; } |
246 |
> |
final boolean isTerminated() { return runState == TERMINATED; } |
247 |
> |
final boolean shutdown() { return transitionRunStateTo(SHUTDOWN); } |
248 |
> |
final boolean shutdownNow() { return transitionRunStateTo(TERMINATING); } |
249 |
|
|
250 |
|
/** |
251 |
< |
* Get and clear steal count for accumulation by pool. Called |
252 |
< |
* only when known to be idle (in pool.sync and termination). |
251 |
> |
* Transition to at least the given state. Return true if not |
252 |
> |
* already at least given state. |
253 |
|
*/ |
254 |
< |
final int getAndClearStealCount() { |
255 |
< |
int sc = stealCount; |
256 |
< |
stealCount = 0; |
257 |
< |
return sc; |
254 |
> |
private boolean transitionRunStateTo(int state) { |
255 |
> |
for (;;) { |
256 |
> |
int s = runState; |
257 |
> |
if (s >= state) |
258 |
> |
return false; |
259 |
> |
if (_unsafe.compareAndSwapInt(this, runStateOffset, s, state)) |
260 |
> |
return true; |
261 |
> |
} |
262 |
|
} |
263 |
|
|
264 |
|
/** |
265 |
< |
* Returns estimate of the number of tasks in the queue, without |
263 |
< |
* correcting for transient negative values |
265 |
> |
* Try to set status to active; fail on contention |
266 |
|
*/ |
267 |
< |
final int getRawQueueSize() { |
268 |
< |
return sp - base; |
267 |
> |
private boolean tryActivate() { |
268 |
> |
if (!active) { |
269 |
> |
if (!pool.tryIncrementActiveCount()) |
270 |
> |
return false; |
271 |
> |
active = true; |
272 |
> |
} |
273 |
> |
return true; |
274 |
|
} |
275 |
|
|
276 |
< |
// Intrinsics-based support for queue operations. |
277 |
< |
// Currently these three (setSp, setSlot, casSlotNull) are |
278 |
< |
// usually manually inlined to improve performance |
276 |
> |
/** |
277 |
> |
* Try to set status to active; fail on contention |
278 |
> |
*/ |
279 |
> |
private boolean tryInactivate() { |
280 |
> |
if (active) { |
281 |
> |
if (!pool.tryDecrementActiveCount()) |
282 |
> |
return false; |
283 |
> |
active = false; |
284 |
> |
} |
285 |
> |
return true; |
286 |
> |
} |
287 |
|
|
288 |
|
/** |
289 |
< |
* Sets sp in store-order. |
289 |
> |
* Computes next value for random victim probe. Scans don't |
290 |
> |
* require a very high quality generator, but also not a crummy |
291 |
> |
* one. Marsaglia xor-shift is cheap and works well. |
292 |
|
*/ |
293 |
< |
private void setSp(int s) { |
294 |
< |
_unsafe.putOrderedInt(this, spOffset, s); |
293 |
> |
private static int xorShift(int r) { |
294 |
> |
r ^= r << 1; |
295 |
> |
r ^= r >>> 3; |
296 |
> |
r ^= r << 10; |
297 |
> |
return r; |
298 |
|
} |
299 |
|
|
300 |
+ |
// Lifecycle methods |
301 |
+ |
|
302 |
+ |
/** |
303 |
+ |
* This method is required to be public, but should never be |
304 |
+ |
* called explicitly. It performs the main run loop to execute |
305 |
+ |
* ForkJoinTasks. |
306 |
+ |
*/ |
307 |
+ |
public void run() { |
308 |
+ |
Throwable exception = null; |
309 |
+ |
try { |
310 |
+ |
onStart(); |
311 |
+ |
pool.sync(this); // await first pool event |
312 |
+ |
mainLoop(); |
313 |
+ |
} catch (Throwable ex) { |
314 |
+ |
exception = ex; |
315 |
+ |
} finally { |
316 |
+ |
onTermination(exception); |
317 |
+ |
} |
318 |
+ |
} |
319 |
+ |
|
320 |
+ |
/** |
321 |
+ |
* Execute tasks until shut down. |
322 |
+ |
*/ |
323 |
+ |
private void mainLoop() { |
324 |
+ |
while (!isShutdown()) { |
325 |
+ |
ForkJoinTask<?> t = pollTask(); |
326 |
+ |
if (t != null || (t = pollSubmission()) != null) |
327 |
+ |
t.quietlyExec(); |
328 |
+ |
else if (tryInactivate()) |
329 |
+ |
pool.sync(this); |
330 |
+ |
} |
331 |
+ |
} |
332 |
+ |
|
333 |
+ |
/** |
334 |
+ |
* Initializes internal state after construction but before |
335 |
+ |
* processing any tasks. If you override this method, you must |
336 |
+ |
* invoke super.onStart() at the beginning of the method. |
337 |
+ |
* Initialization requires care: Most fields must have legal |
338 |
+ |
* default values, to ensure that attempted accesses from other |
339 |
+ |
* threads work correctly even before this thread starts |
340 |
+ |
* processing tasks. |
341 |
+ |
*/ |
342 |
+ |
protected void onStart() { |
343 |
+ |
// Allocate while starting to improve chances of thread-local |
344 |
+ |
// isolation |
345 |
+ |
queue = new ForkJoinTask<?>[INITIAL_QUEUE_CAPACITY]; |
346 |
+ |
// Initial value of seed need not be especially random but |
347 |
+ |
// should differ across workers and must be nonzero |
348 |
+ |
int p = poolIndex + 1; |
349 |
+ |
seed = p + (p << 8) + (p << 16) + (p << 24); // spread bits |
350 |
+ |
} |
351 |
+ |
|
352 |
+ |
/** |
353 |
+ |
* Perform cleanup associated with termination of this worker |
354 |
+ |
* thread. If you override this method, you must invoke |
355 |
+ |
* super.onTermination at the end of the overridden method. |
356 |
+ |
* |
357 |
+ |
* @param exception the exception causing this thread to abort due |
358 |
+ |
* to an unrecoverable error, or null if completed normally. |
359 |
+ |
*/ |
360 |
+ |
protected void onTermination(Throwable exception) { |
361 |
+ |
// Execute remaining local tasks unless aborting or terminating |
362 |
+ |
while (exception == null && !pool.isTerminating() && base != sp) { |
363 |
+ |
try { |
364 |
+ |
ForkJoinTask<?> t = popTask(); |
365 |
+ |
if (t != null) |
366 |
+ |
t.quietlyExec(); |
367 |
+ |
} catch(Throwable ex) { |
368 |
+ |
exception = ex; |
369 |
+ |
} |
370 |
+ |
} |
371 |
+ |
// Cancel other tasks, transition status, notify pool, and |
372 |
+ |
// propagate exception to uncaught exception handler |
373 |
+ |
try { |
374 |
+ |
do;while (!tryInactivate()); // ensure inactive |
375 |
+ |
cancelTasks(); |
376 |
+ |
runState = TERMINATED; |
377 |
+ |
pool.workerTerminated(this); |
378 |
+ |
} catch (Throwable ex) { // Shouldn't ever happen |
379 |
+ |
if (exception == null) // but if so, at least rethrown |
380 |
+ |
exception = ex; |
381 |
+ |
} finally { |
382 |
+ |
if (exception != null) |
383 |
+ |
ForkJoinTask.rethrowException(exception); |
384 |
+ |
} |
385 |
+ |
} |
386 |
+ |
|
387 |
+ |
// Intrinsics-based support for queue operations. |
388 |
+ |
|
389 |
|
/** |
390 |
|
* Add in store-order the given task at given slot of q to |
391 |
|
* null. Caller must ensure q is nonnull and index is in range. |
404 |
|
return _unsafe.compareAndSwapObject(q, (i << qShift) + qBase, t, null); |
405 |
|
} |
406 |
|
|
407 |
+ |
/** |
408 |
+ |
* Sets sp in store-order. |
409 |
+ |
*/ |
410 |
+ |
private void storeSp(int s) { |
411 |
+ |
_unsafe.putOrderedInt(this, spOffset, s); |
412 |
+ |
} |
413 |
+ |
|
414 |
|
// Main queue methods |
415 |
|
|
416 |
|
/** |
421 |
|
ForkJoinTask<?>[] q = queue; |
422 |
|
int mask = q.length - 1; |
423 |
|
int s = sp; |
424 |
< |
_unsafe.putOrderedObject(q, ((s & mask) << qShift) + qBase, t); |
425 |
< |
_unsafe.putOrderedInt(this, spOffset, ++s); |
424 |
> |
setSlot(q, s & mask, t); |
425 |
> |
storeSp(++s); |
426 |
|
if ((s -= base) == 1) |
427 |
< |
pool.signalNonEmptyWorkerQueue(); |
427 |
> |
pool.signalWork(); |
428 |
|
else if (s >= mask) |
429 |
|
growQueue(); |
430 |
|
} |
435 |
|
* @return a task, or null if none or contended. |
436 |
|
*/ |
437 |
|
private ForkJoinTask<?> deqTask() { |
322 |
– |
ForkJoinTask<?>[] q; |
438 |
|
ForkJoinTask<?> t; |
439 |
+ |
ForkJoinTask<?>[] q; |
440 |
|
int i; |
441 |
|
int b; |
442 |
|
if (sp != (b = base) && |
443 |
|
(q = queue) != null && // must read q after b |
444 |
|
(t = q[i = (q.length - 1) & b]) != null && |
445 |
< |
_unsafe.compareAndSwapObject(q, (i << qShift) + qBase, t, null)) { |
445 |
> |
casSlotNull(q, i, t)) { |
446 |
|
base = b + 1; |
447 |
|
return t; |
448 |
|
} |
450 |
|
} |
451 |
|
|
452 |
|
/** |
453 |
< |
* Returns a popped task, or null if empty. Called only by |
454 |
< |
* current thread. |
453 |
> |
* Returns a popped task, or null if empty. Ensures active status |
454 |
> |
* if nonnull. Called only by current thread. |
455 |
|
*/ |
456 |
|
final ForkJoinTask<?> popTask() { |
341 |
– |
ForkJoinTask<?> t; |
342 |
– |
int i; |
343 |
– |
ForkJoinTask<?>[] q = queue; |
344 |
– |
int mask = q.length - 1; |
457 |
|
int s = sp; |
458 |
< |
if (s != base && |
459 |
< |
(t = q[i = (s - 1) & mask]) != null && |
460 |
< |
_unsafe.compareAndSwapObject(q, (i << qShift) + qBase, t, null)) { |
461 |
< |
_unsafe.putOrderedInt(this, spOffset, s - 1); |
462 |
< |
return t; |
458 |
> |
while (s != base) { |
459 |
> |
if (tryActivate()) { |
460 |
> |
ForkJoinTask<?>[] q = queue; |
461 |
> |
int mask = q.length - 1; |
462 |
> |
int i = (s - 1) & mask; |
463 |
> |
ForkJoinTask<?> t = q[i]; |
464 |
> |
if (t == null || !casSlotNull(q, i, t)) |
465 |
> |
break; |
466 |
> |
storeSp(s - 1); |
467 |
> |
return t; |
468 |
> |
} |
469 |
|
} |
470 |
|
return null; |
471 |
|
} |
473 |
|
/** |
474 |
|
* Specialized version of popTask to pop only if |
475 |
|
* topmost element is the given task. Called only |
476 |
< |
* by current thread. |
476 |
> |
* by current thread while active. |
477 |
|
* @param t the task. Caller must ensure nonnull |
478 |
|
*/ |
479 |
|
final boolean unpushTask(ForkJoinTask<?> t) { |
480 |
|
ForkJoinTask<?>[] q = queue; |
481 |
|
int mask = q.length - 1; |
482 |
|
int s = sp - 1; |
483 |
< |
if (_unsafe.compareAndSwapObject(q, ((s & mask) << qShift) + qBase, |
484 |
< |
t, null)) { |
367 |
< |
_unsafe.putOrderedInt(this, spOffset, s); |
483 |
> |
if (casSlotNull(q, s & mask, t)) { |
484 |
> |
storeSp(s); |
485 |
|
return true; |
486 |
|
} |
487 |
|
return false; |
519 |
|
t = null; |
520 |
|
setSlot(newQ, b & newMask, t); |
521 |
|
} while (++b != bf); |
522 |
< |
pool.signalIdleWorkers(false); |
406 |
< |
} |
407 |
< |
|
408 |
< |
// Runstate management |
409 |
< |
|
410 |
< |
final boolean isShutdown() { return runState >= SHUTDOWN; } |
411 |
< |
final boolean isTerminating() { return runState >= TERMINATING; } |
412 |
< |
final boolean isTerminated() { return runState == TERMINATED; } |
413 |
< |
final boolean shutdown() { return transitionRunStateTo(SHUTDOWN); } |
414 |
< |
final boolean shutdownNow() { return transitionRunStateTo(TERMINATING); } |
415 |
< |
|
416 |
< |
/** |
417 |
< |
* Transition to at least the given state. Return true if not |
418 |
< |
* already at least given state. |
419 |
< |
*/ |
420 |
< |
private boolean transitionRunStateTo(int state) { |
421 |
< |
for (;;) { |
422 |
< |
int s = runState; |
423 |
< |
if (s >= state) |
424 |
< |
return false; |
425 |
< |
if (_unsafe.compareAndSwapInt(this, runStateOffset, s, state)) |
426 |
< |
return true; |
427 |
< |
} |
522 |
> |
pool.signalWork(); |
523 |
|
} |
524 |
|
|
525 |
|
/** |
526 |
< |
* Ensure status is active and if necessary adjust pool active count |
527 |
< |
*/ |
528 |
< |
final void activate() { |
529 |
< |
if (!active) { |
530 |
< |
active = true; |
531 |
< |
pool.incrementActiveCount(); |
532 |
< |
} |
533 |
< |
} |
439 |
< |
|
440 |
< |
/** |
441 |
< |
* Ensure status is inactive and if necessary adjust pool active count |
442 |
< |
*/ |
443 |
< |
final void inactivate() { |
444 |
< |
if (active) { |
445 |
< |
active = false; |
446 |
< |
pool.decrementActiveCount(); |
447 |
< |
} |
448 |
< |
} |
449 |
< |
|
450 |
< |
// Lifecycle methods |
451 |
< |
|
452 |
< |
/** |
453 |
< |
* Initializes internal state after construction but before |
454 |
< |
* processing any tasks. If you override this method, you must |
455 |
< |
* invoke super.onStart() at the beginning of the method. |
456 |
< |
* Initialization requires care: Most fields must have legal |
457 |
< |
* default values, to ensure that attempted accesses from other |
458 |
< |
* threads work correctly even before this thread starts |
459 |
< |
* processing tasks. |
460 |
< |
*/ |
461 |
< |
protected void onStart() { |
462 |
< |
juRandomSeed = randomSeedGenerator.nextLong(); |
463 |
< |
do;while((randomVictimSeed = nextRandomInt()) == 0); // must be nonzero |
464 |
< |
if (queue == null) |
465 |
< |
queue = new ForkJoinTask<?>[INITIAL_QUEUE_CAPACITY]; |
466 |
< |
|
467 |
< |
// Heuristically allow one initial thread to warm up; others wait |
468 |
< |
if (poolIndex < pool.getParallelism() - 1) { |
469 |
< |
eventCount = pool.sync(this, 0); |
470 |
< |
activate(); |
471 |
< |
} |
472 |
< |
} |
473 |
< |
|
474 |
< |
/** |
475 |
< |
* Perform cleanup associated with termination of this worker |
476 |
< |
* thread. If you override this method, you must invoke |
477 |
< |
* super.onTermination at the end of the overridden method. |
478 |
< |
* |
479 |
< |
* @param exception the exception causing this thread to abort due |
480 |
< |
* to an unrecoverable error, or null if completed normally. |
481 |
< |
*/ |
482 |
< |
protected void onTermination(Throwable exception) { |
483 |
< |
try { |
484 |
< |
clearLocalTasks(); |
485 |
< |
inactivate(); |
486 |
< |
cancelTasks(); |
487 |
< |
} finally { |
488 |
< |
terminate(exception); |
489 |
< |
} |
490 |
< |
} |
491 |
< |
|
492 |
< |
/** |
493 |
< |
* Notify pool of termination and, if exception is nonnull, |
494 |
< |
* rethrow it to trigger this thread's uncaughtExceptionHandler |
495 |
< |
*/ |
496 |
< |
private void terminate(Throwable exception) { |
497 |
< |
transitionRunStateTo(TERMINATED); |
498 |
< |
try { |
499 |
< |
pool.workerTerminated(this); |
500 |
< |
} finally { |
501 |
< |
if (exception != null) |
502 |
< |
ForkJoinTask.rethrowException(exception); |
503 |
< |
} |
504 |
< |
} |
505 |
< |
|
506 |
< |
/** |
507 |
< |
* Run local tasks on exit from main. |
508 |
< |
*/ |
509 |
< |
private void clearLocalTasks() { |
510 |
< |
while (base != sp && !pool.isTerminating()) { |
511 |
< |
ForkJoinTask<?> t = popTask(); |
512 |
< |
if (t != null) { |
513 |
< |
activate(); // ensure active status |
514 |
< |
t.quietlyExec(); |
515 |
< |
} |
516 |
< |
} |
517 |
< |
} |
518 |
< |
|
519 |
< |
/** |
520 |
< |
* Removes and cancels all tasks in queue. Can be called from any |
521 |
< |
* thread. |
522 |
< |
*/ |
523 |
< |
final void cancelTasks() { |
524 |
< |
while (base != sp) { |
525 |
< |
ForkJoinTask<?> t = deqTask(); |
526 |
< |
if (t != null) |
527 |
< |
t.cancelIgnoringExceptions(); |
528 |
< |
} |
529 |
< |
} |
530 |
< |
|
531 |
< |
/** |
532 |
< |
* This method is required to be public, but should never be |
533 |
< |
* called explicitly. It performs the main run loop to execute |
534 |
< |
* ForkJoinTasks. |
535 |
< |
*/ |
536 |
< |
public void run() { |
537 |
< |
Throwable exception = null; |
538 |
< |
try { |
539 |
< |
onStart(); |
540 |
< |
while (!isShutdown()) |
541 |
< |
step(); |
542 |
< |
} catch (Throwable ex) { |
543 |
< |
exception = ex; |
544 |
< |
} finally { |
545 |
< |
onTermination(exception); |
546 |
< |
} |
547 |
< |
} |
548 |
< |
|
549 |
< |
/** |
550 |
< |
* Main top-level action. |
551 |
< |
*/ |
552 |
< |
private void step() { |
553 |
< |
ForkJoinTask<?> t = sp != base? popTask() : null; |
554 |
< |
if (t != null || (t = scan(null, true)) != null) { |
555 |
< |
activate(); |
556 |
< |
t.quietlyExec(); |
557 |
< |
} |
558 |
< |
else { |
559 |
< |
inactivate(); |
560 |
< |
eventCount = pool.sync(this, eventCount); |
561 |
< |
} |
562 |
< |
} |
563 |
< |
|
564 |
< |
// scanning for and stealing tasks |
565 |
< |
|
566 |
< |
/** |
567 |
< |
* Computes next value for random victim probe. Scans don't |
568 |
< |
* require a very high quality generator, but also not a crummy |
569 |
< |
* one. Marsaglia xor-shift is cheap and works well. |
570 |
< |
* |
571 |
< |
* This is currently unused, and manually inlined |
572 |
< |
*/ |
573 |
< |
private static int xorShift(int r) { |
574 |
< |
r ^= r << 1; |
575 |
< |
r ^= r >>> 3; |
576 |
< |
r ^= r << 10; |
577 |
< |
return r; |
578 |
< |
} |
579 |
< |
|
580 |
< |
/** |
581 |
< |
* Tries to steal a task from another worker and/or, if enabled, |
582 |
< |
* submission queue. Starts at a random index of workers array, |
583 |
< |
* and probes workers until finding one with non-empty queue or |
584 |
< |
* finding that all are empty. It randomly selects the first n-1 |
585 |
< |
* probes. If these are empty, it resorts to full circular |
586 |
< |
* traversal, which is necessary to accurately set active status |
587 |
< |
* by caller. Also restarts if pool barrier has tripped since last |
588 |
< |
* scan, which forces refresh of workers array, in case barrier |
589 |
< |
* was associated with resize. |
526 |
> |
* Tries to steal a task from another worker. Starts at a random |
527 |
> |
* index of workers array, and probes workers until finding one |
528 |
> |
* with non-empty queue or finding that all are empty. It |
529 |
> |
* randomly selects the first n probes. If these are empty, it |
530 |
> |
* resorts to a full circular traversal, which is necessary to |
531 |
> |
* accurately set active status by caller. Also restarts if pool |
532 |
> |
* events occurred since last scan, which forces refresh of |
533 |
> |
* workers array, in case barrier was associated with resize. |
534 |
|
* |
535 |
|
* This method must be both fast and quiet -- usually avoiding |
536 |
|
* memory accesses that could disrupt cache sharing etc other than |
537 |
|
* those needed to check for and take tasks. This accounts for, |
538 |
|
* among other things, updating random seed in place without |
539 |
< |
* storing it until exit. (Note that we only need to store it if |
596 |
< |
* we found a task; otherwise it doesn't matter if we start at the |
597 |
< |
* same place next time.) |
539 |
> |
* storing it until exit. |
540 |
|
* |
599 |
– |
* @param joinMe if non null; exit early if done |
600 |
– |
* @param checkSubmissions true if OK to take submissions |
541 |
|
* @return a task, or null if none found |
542 |
|
*/ |
543 |
< |
private ForkJoinTask<?> scan(ForkJoinTask<?> joinMe, |
544 |
< |
boolean checkSubmissions) { |
545 |
< |
ForkJoinPool p = pool; |
546 |
< |
if (p == null) // Never null, but avoids |
547 |
< |
return null; // implicit nullchecks below |
548 |
< |
int r = randomVictimSeed; // extract once to keep scan quiet |
549 |
< |
restart: // outer loop refreshes ws array |
610 |
< |
while (joinMe == null || joinMe.status >= 0) { |
611 |
< |
int mask; |
612 |
< |
ForkJoinWorkerThread[] ws = p.workers; |
613 |
< |
if (ws != null && (mask = ws.length - 1) > 0) { |
614 |
< |
int probes = -mask; // use random index while negative |
543 |
> |
private ForkJoinTask<?> scan() { |
544 |
> |
ForkJoinTask<?> t = null; |
545 |
> |
int r = seed; // extract once to keep scan quiet |
546 |
> |
ForkJoinWorkerThread[] ws; // refreshed on outer loop |
547 |
> |
int mask; // must be power 2 minus 1 and > 0 |
548 |
> |
outer:do { |
549 |
> |
if ((ws = pool.workers) != null && (mask = ws.length - 1) > 0) { |
550 |
|
int idx = r; |
551 |
+ |
int probes = ~mask; // use random index while negative |
552 |
|
for (;;) { |
553 |
< |
ForkJoinWorkerThread v; |
554 |
< |
// inlined xorshift to update seed |
555 |
< |
r ^= r << 1; r ^= r >>> 3; r ^= r << 10; |
556 |
< |
if ((v = ws[mask & idx]) != null && v.sp != v.base) { |
557 |
< |
ForkJoinTask<?> t; |
558 |
< |
activate(); |
559 |
< |
if ((joinMe == null || joinMe.status >= 0) && |
624 |
< |
(t = v.deqTask()) != null) { |
625 |
< |
randomVictimSeed = r; |
626 |
< |
++stealCount; |
627 |
< |
return t; |
628 |
< |
} |
629 |
< |
continue restart; // restart on contention |
553 |
> |
r = xorShift(r); // update random seed |
554 |
> |
ForkJoinWorkerThread v = ws[mask & idx]; |
555 |
> |
if (v == null || v.sp == v.base) { |
556 |
> |
if (probes <= mask) |
557 |
> |
idx = (probes++ < 0)? r : (idx + 1); |
558 |
> |
else |
559 |
> |
break; |
560 |
|
} |
561 |
< |
if ((probes >> 1) <= mask) // n-1 random then circular |
562 |
< |
idx = (probes++ < 0)? r : (idx + 1); |
561 |
> |
else if (!tryActivate() || (t = v.deqTask()) == null) |
562 |
> |
continue outer; // restart on contention |
563 |
|
else |
564 |
< |
break; |
564 |
> |
break outer; |
565 |
|
} |
566 |
|
} |
567 |
< |
if (checkSubmissions && p.hasQueuedSubmissions()) { |
568 |
< |
activate(); |
569 |
< |
ForkJoinTask<?> t = p.pollSubmission(); |
640 |
< |
if (t != null) |
641 |
< |
return t; |
642 |
< |
} |
643 |
< |
else { |
644 |
< |
long ec = eventCount; // restart on pool event |
645 |
< |
if ((eventCount = p.getEventCount()) == ec) |
646 |
< |
break; |
647 |
< |
} |
648 |
< |
} |
649 |
< |
return null; |
567 |
> |
} while (pool.hasNewSyncEvent(this)); // retry on pool events |
568 |
> |
seed = r; |
569 |
> |
return t; |
570 |
|
} |
571 |
|
|
572 |
|
/** |
573 |
< |
* Callback from pool.sync to rescan before blocking. If a |
574 |
< |
* task is found, it is pushed so it can be executed upon return. |
575 |
< |
* @return true if found and pushed a task |
576 |
< |
*/ |
577 |
< |
final boolean prescan() { |
578 |
< |
ForkJoinTask<?> t = scan(null, true); |
579 |
< |
if (t != null) { |
580 |
< |
pushTask(t); |
661 |
< |
return true; |
662 |
< |
} |
663 |
< |
else { |
664 |
< |
inactivate(); |
665 |
< |
return false; |
666 |
< |
} |
573 |
> |
* Pops or steals a task |
574 |
> |
* @return a task, if available |
575 |
> |
*/ |
576 |
> |
final ForkJoinTask<?> pollTask() { |
577 |
> |
ForkJoinTask<?> t = popTask(); |
578 |
> |
if (t == null && (t = scan()) != null) |
579 |
> |
++stealCount; |
580 |
> |
return t; |
581 |
|
} |
582 |
|
|
669 |
– |
// Support for ForkJoinTask methods |
670 |
– |
|
583 |
|
/** |
584 |
< |
* Scan, returning early if joinMe done |
584 |
> |
* Returns a pool submission, if one exists, activating first. |
585 |
> |
* @return a submission, if available |
586 |
|
*/ |
587 |
< |
final ForkJoinTask<?> scanWhileJoining(ForkJoinTask<?> joinMe) { |
588 |
< |
ForkJoinTask<?> t = scan(joinMe, false); |
589 |
< |
if (t != null && joinMe.status < 0 && sp == base) { |
590 |
< |
pushTask(t); // unsteal if done and this task would be stealable |
591 |
< |
t = null; |
587 |
> |
private ForkJoinTask<?> pollSubmission() { |
588 |
> |
ForkJoinPool p = pool; |
589 |
> |
while (p.hasQueuedSubmissions()) { |
590 |
> |
ForkJoinTask<?> t; |
591 |
> |
if (tryActivate() && (t = p.pollSubmission()) != null) |
592 |
> |
return t; |
593 |
|
} |
594 |
< |
return t; |
594 |
> |
return null; |
595 |
|
} |
596 |
< |
|
596 |
> |
|
597 |
> |
// Methods accessed only by Pool |
598 |
> |
|
599 |
|
/** |
600 |
< |
* Pops or steals a task |
601 |
< |
* @return task, or null if none available |
600 |
> |
* Removes and cancels all tasks in queue. Can be called from any |
601 |
> |
* thread. |
602 |
|
*/ |
603 |
< |
final ForkJoinTask<?> pollLocalOrStolenTask() { |
603 |
> |
final void cancelTasks() { |
604 |
|
ForkJoinTask<?> t; |
605 |
< |
return (t = popTask()) == null? scan(null, false) : t; |
605 |
> |
while (base != sp && (t = deqTask()) != null) |
606 |
> |
t.cancelIgnoringExceptions(); |
607 |
|
} |
608 |
|
|
609 |
|
/** |
610 |
< |
* Runs tasks until pool isQuiescent |
610 |
> |
* Get and clear steal count for accumulation by pool. Called |
611 |
> |
* only when known to be idle (in pool.sync and termination). |
612 |
|
*/ |
613 |
< |
final void helpQuiescePool() { |
614 |
< |
for (;;) { |
615 |
< |
ForkJoinTask<?> t = pollLocalOrStolenTask(); |
616 |
< |
if (t != null) { |
617 |
< |
activate(); |
618 |
< |
t.quietlyExec(); |
619 |
< |
} |
620 |
< |
else { |
621 |
< |
inactivate(); |
622 |
< |
if (pool.isQuiescent()) { |
623 |
< |
activate(); // re-activate on exit |
624 |
< |
break; |
613 |
> |
final int getAndClearStealCount() { |
614 |
> |
int sc = stealCount; |
615 |
> |
stealCount = 0; |
616 |
> |
return sc; |
617 |
> |
} |
618 |
> |
|
619 |
> |
/** |
620 |
> |
* Returns true if at least one worker in the given array appears |
621 |
> |
* to have at least one queued task. |
622 |
> |
* @param ws array of workers |
623 |
> |
*/ |
624 |
> |
static boolean hasQueuedTasks(ForkJoinWorkerThread[] ws) { |
625 |
> |
if (ws != null) { |
626 |
> |
int len = ws.length; |
627 |
> |
for (int j = 0; j < 2; ++j) { // need two passes for clean sweep |
628 |
> |
for (int i = 0; i < len; ++i) { |
629 |
> |
ForkJoinWorkerThread w = ws[i]; |
630 |
> |
if (w != null && w.sp != w.base) |
631 |
> |
return true; |
632 |
|
} |
633 |
|
} |
634 |
|
} |
635 |
+ |
return false; |
636 |
|
} |
637 |
|
|
638 |
+ |
// Support methods for ForkJoinTask |
639 |
+ |
|
640 |
|
/** |
641 |
|
* Returns an estimate of the number of tasks in the queue. |
642 |
|
*/ |
643 |
|
final int getQueueSize() { |
644 |
|
int n = sp - base; |
645 |
< |
return n <= 0? 0 : n; // suppress momentarily negative values |
645 |
> |
return n < 0? 0 : n; // suppress momentarily negative values |
646 |
|
} |
647 |
|
|
648 |
|
/** |
654 |
|
return (sp - base) - (pool.getIdleThreadCount() >>> 1); |
655 |
|
} |
656 |
|
|
729 |
– |
// Per-worker exported random numbers |
730 |
– |
|
731 |
– |
// Same constants as java.util.Random |
732 |
– |
final static long JURandomMultiplier = 0x5DEECE66DL; |
733 |
– |
final static long JURandomAddend = 0xBL; |
734 |
– |
final static long JURandomMask = (1L << 48) - 1; |
735 |
– |
|
736 |
– |
private final int nextJURandom(int bits) { |
737 |
– |
long next = (juRandomSeed * JURandomMultiplier + JURandomAddend) & |
738 |
– |
JURandomMask; |
739 |
– |
juRandomSeed = next; |
740 |
– |
return (int)(next >>> (48 - bits)); |
741 |
– |
} |
742 |
– |
|
743 |
– |
private final int nextJURandomInt(int n) { |
744 |
– |
if (n <= 0) |
745 |
– |
throw new IllegalArgumentException("n must be positive"); |
746 |
– |
int bits = nextJURandom(31); |
747 |
– |
if ((n & -n) == n) |
748 |
– |
return (int)((n * (long)bits) >> 31); |
749 |
– |
|
750 |
– |
for (;;) { |
751 |
– |
int val = bits % n; |
752 |
– |
if (bits - val + (n-1) >= 0) |
753 |
– |
return val; |
754 |
– |
bits = nextJURandom(31); |
755 |
– |
} |
756 |
– |
} |
757 |
– |
|
758 |
– |
private final long nextJURandomLong() { |
759 |
– |
return ((long)(nextJURandom(32)) << 32) + nextJURandom(32); |
760 |
– |
} |
761 |
– |
|
762 |
– |
private final long nextJURandomLong(long n) { |
763 |
– |
if (n <= 0) |
764 |
– |
throw new IllegalArgumentException("n must be positive"); |
765 |
– |
long offset = 0; |
766 |
– |
while (n >= Integer.MAX_VALUE) { // randomly pick half range |
767 |
– |
int bits = nextJURandom(2); // 2nd bit for odd vs even split |
768 |
– |
long half = n >>> 1; |
769 |
– |
long nextn = ((bits & 2) == 0)? half : n - half; |
770 |
– |
if ((bits & 1) == 0) |
771 |
– |
offset += n - nextn; |
772 |
– |
n = nextn; |
773 |
– |
} |
774 |
– |
return offset + nextJURandomInt((int)n); |
775 |
– |
} |
776 |
– |
|
777 |
– |
private final double nextJURandomDouble() { |
778 |
– |
return (((long)(nextJURandom(26)) << 27) + nextJURandom(27)) |
779 |
– |
/ (double)(1L << 53); |
780 |
– |
} |
781 |
– |
|
657 |
|
/** |
658 |
< |
* Returns a random integer using a per-worker random |
784 |
< |
* number generator with the same properties as |
785 |
< |
* {@link java.util.Random#nextInt} |
786 |
< |
* @return the next pseudorandom, uniformly distributed {@code int} |
787 |
< |
* value from this worker's random number generator's sequence |
658 |
> |
* Scan, returning early if joinMe done |
659 |
|
*/ |
660 |
< |
public static int nextRandomInt() { |
661 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())). |
662 |
< |
nextJURandom(32); |
660 |
> |
final ForkJoinTask<?> scanWhileJoining(ForkJoinTask<?> joinMe) { |
661 |
> |
ForkJoinTask<?> t = pollTask(); |
662 |
> |
if (t != null && joinMe.status < 0 && sp == base) { |
663 |
> |
pushTask(t); // unsteal if done and this task would be stealable |
664 |
> |
t = null; |
665 |
> |
} |
666 |
> |
return t; |
667 |
|
} |
668 |
|
|
669 |
|
/** |
670 |
< |
* Returns a random integer using a per-worker random |
796 |
< |
* number generator with the same properties as |
797 |
< |
* {@link java.util.Random#nextInt(int)} |
798 |
< |
* @param n the bound on the random number to be returned. Must be |
799 |
< |
* positive. |
800 |
< |
* @return the next pseudorandom, uniformly distributed {@code int} |
801 |
< |
* value between {@code 0} (inclusive) and {@code n} (exclusive) |
802 |
< |
* from this worker's random number generator's sequence |
803 |
< |
* @throws IllegalArgumentException if n is not positive |
670 |
> |
* Runs tasks until pool isQuiescent |
671 |
|
*/ |
672 |
< |
public static int nextRandomInt(int n) { |
673 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())). |
674 |
< |
nextJURandomInt(n); |
672 |
> |
final void helpQuiescePool() { |
673 |
> |
for (;;) { |
674 |
> |
ForkJoinTask<?> t = pollTask(); |
675 |
> |
if (t != null) |
676 |
> |
t.quietlyExec(); |
677 |
> |
else if (tryInactivate() && pool.isQuiescent()) |
678 |
> |
break; |
679 |
> |
} |
680 |
> |
do;while (!tryActivate()); // re-activate on exit |
681 |
|
} |
682 |
|
|
683 |
< |
/** |
684 |
< |
* Returns a random long using a per-worker random |
685 |
< |
* number generator with the same properties as |
686 |
< |
* {@link java.util.Random#nextLong} |
687 |
< |
* @return the next pseudorandom, uniformly distributed {@code long} |
688 |
< |
* value from this worker's random number generator's sequence |
689 |
< |
*/ |
690 |
< |
public static long nextRandomLong() { |
691 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())). |
692 |
< |
nextJURandomLong(); |
683 |
> |
// Temporary Unsafe mechanics for preliminary release |
684 |
> |
private static Unsafe getUnsafe() throws Throwable { |
685 |
> |
try { |
686 |
> |
return Unsafe.getUnsafe(); |
687 |
> |
} catch (SecurityException se) { |
688 |
> |
try { |
689 |
> |
return java.security.AccessController.doPrivileged |
690 |
> |
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
691 |
> |
public Unsafe run() throws Exception { |
692 |
> |
return getUnsafePrivileged(); |
693 |
> |
}}); |
694 |
> |
} catch (java.security.PrivilegedActionException e) { |
695 |
> |
throw e.getCause(); |
696 |
> |
} |
697 |
> |
} |
698 |
|
} |
699 |
|
|
700 |
< |
/** |
701 |
< |
* Returns a random integer using a per-worker random |
702 |
< |
* number generator with the same properties as |
703 |
< |
* {@link java.util.Random#nextInt(int)} |
704 |
< |
* @param n the bound on the random number to be returned. Must be |
827 |
< |
* positive. |
828 |
< |
* @return the next pseudorandom, uniformly distributed {@code int} |
829 |
< |
* value between {@code 0} (inclusive) and {@code n} (exclusive) |
830 |
< |
* from this worker's random number generator's sequence |
831 |
< |
* @throws IllegalArgumentException if n is not positive |
832 |
< |
*/ |
833 |
< |
public static long nextRandomLong(long n) { |
834 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())). |
835 |
< |
nextJURandomLong(n); |
700 |
> |
private static Unsafe getUnsafePrivileged() |
701 |
> |
throws NoSuchFieldException, IllegalAccessException { |
702 |
> |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
703 |
> |
f.setAccessible(true); |
704 |
> |
return (Unsafe) f.get(null); |
705 |
|
} |
706 |
|
|
707 |
< |
/** |
708 |
< |
* Returns a random double using a per-worker random |
709 |
< |
* number generator with the same properties as |
710 |
< |
* {@link java.util.Random#nextDouble} |
842 |
< |
* @return the next pseudorandom, uniformly distributed {@code double} |
843 |
< |
* value between {@code 0.0} and {@code 1.0} from this |
844 |
< |
* worker's random number generator's sequence |
845 |
< |
*/ |
846 |
< |
public static double nextRandomDouble() { |
847 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())). |
848 |
< |
nextJURandomDouble(); |
707 |
> |
private static long fieldOffset(String fieldName) |
708 |
> |
throws NoSuchFieldException { |
709 |
> |
return _unsafe.objectFieldOffset |
710 |
> |
(ForkJoinWorkerThread.class.getDeclaredField(fieldName)); |
711 |
|
} |
712 |
|
|
851 |
– |
// Temporary Unsafe mechanics for preliminary release |
852 |
– |
|
713 |
|
static final Unsafe _unsafe; |
714 |
|
static final long baseOffset; |
715 |
|
static final long spOffset; |
716 |
+ |
static final long runStateOffset; |
717 |
|
static final long qBase; |
718 |
|
static final int qShift; |
858 |
– |
static final long runStateOffset; |
719 |
|
static { |
720 |
|
try { |
721 |
< |
if (ForkJoinWorkerThread.class.getClassLoader() != null) { |
722 |
< |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
723 |
< |
f.setAccessible(true); |
724 |
< |
_unsafe = (Unsafe)f.get(null); |
865 |
< |
} |
866 |
< |
else |
867 |
< |
_unsafe = Unsafe.getUnsafe(); |
868 |
< |
baseOffset = _unsafe.objectFieldOffset |
869 |
< |
(ForkJoinWorkerThread.class.getDeclaredField("base")); |
870 |
< |
spOffset = _unsafe.objectFieldOffset |
871 |
< |
(ForkJoinWorkerThread.class.getDeclaredField("sp")); |
872 |
< |
runStateOffset = _unsafe.objectFieldOffset |
873 |
< |
(ForkJoinWorkerThread.class.getDeclaredField("runState")); |
721 |
> |
_unsafe = getUnsafe(); |
722 |
> |
baseOffset = fieldOffset("base"); |
723 |
> |
spOffset = fieldOffset("sp"); |
724 |
> |
runStateOffset = fieldOffset("runState"); |
725 |
|
qBase = _unsafe.arrayBaseOffset(ForkJoinTask[].class); |
726 |
|
int s = _unsafe.arrayIndexScale(ForkJoinTask[].class); |
727 |
|
if ((s & (s-1)) != 0) |
728 |
|
throw new Error("data type scale not a power of two"); |
729 |
|
qShift = 31 - Integer.numberOfLeadingZeros(s); |
730 |
< |
} catch (Exception e) { |
730 |
> |
} catch (Throwable e) { |
731 |
|
throw new RuntimeException("Could not initialize intrinsics", e); |
732 |
|
} |
733 |
|
} |