27 |
|
* (eventually blocking if none exist). This makes them efficient when |
28 |
|
* most tasks spawn other subtasks (as do most ForkJoinTasks), as well |
29 |
|
* as the mixed execution of some plain Runnable- or Callable- based |
30 |
< |
* activities along with ForkJoinTasks. Otherwise, other |
30 |
> |
* activities along with ForkJoinTasks. When setting |
31 |
> |
* {@code setAsyncMode}, a ForkJoinPools may also be appropriate for |
32 |
> |
* use with fine-grained tasks that are never joined. Otherwise, other |
33 |
|
* ExecutorService implementations are typically more appropriate |
34 |
|
* choices. |
35 |
|
* |
38 |
|
* adding, suspending, or resuming threads, even if some tasks are |
39 |
|
* waiting to join others. However, no such adjustments are performed |
40 |
|
* in the face of blocked IO or other unmanaged synchronization. The |
41 |
< |
* nested <code>ManagedBlocker</code> interface enables extension of |
41 |
> |
* nested {@code ManagedBlocker} interface enables extension of |
42 |
|
* the kinds of synchronization accommodated. The target parallelism |
43 |
< |
* level may also be changed dynamically (<code>setParallelism</code>) |
44 |
< |
* and dynamically thread construction can be limited using methods |
45 |
< |
* <code>setMaximumPoolSize</code> and/or |
46 |
< |
* <code>setMaintainsParallelism</code>. |
43 |
> |
* level may also be changed dynamically ({@code setParallelism}) |
44 |
> |
* and thread construction can be limited using methods |
45 |
> |
* {@code setMaximumPoolSize} and/or |
46 |
> |
* {@code setMaintainsParallelism}. |
47 |
|
* |
48 |
|
* <p>In addition to execution and lifecycle control methods, this |
49 |
|
* class provides status check methods (for example |
50 |
< |
* <code>getStealCount</code>) that are intended to aid in developing, |
50 |
> |
* {@code getStealCount}) that are intended to aid in developing, |
51 |
|
* tuning, and monitoring fork/join applications. Also, method |
52 |
< |
* <code>toString</code> returns indications of pool state in a |
52 |
> |
* {@code toString} returns indications of pool state in a |
53 |
|
* convenient form for informal monitoring. |
54 |
|
* |
55 |
|
* <p><b>Implementation notes</b>: This implementation restricts the |
56 |
|
* maximum number of running threads to 32767. Attempts to create |
57 |
|
* pools with greater than the maximum result in |
58 |
|
* IllegalArgumentExceptions. |
59 |
+ |
* |
60 |
+ |
* @since 1.7 |
61 |
+ |
* @author Doug Lea |
62 |
|
*/ |
63 |
|
public class ForkJoinPool extends AbstractExecutorService { |
64 |
|
|
84 |
|
* Returns a new worker thread operating in the given pool. |
85 |
|
* |
86 |
|
* @param pool the pool this thread works in |
87 |
< |
* @throws NullPointerException if pool is null; |
87 |
> |
* @throws NullPointerException if pool is null |
88 |
|
*/ |
89 |
|
public ForkJoinWorkerThread newThread(ForkJoinPool pool); |
90 |
|
} |
136 |
|
new AtomicInteger(); |
137 |
|
|
138 |
|
/** |
139 |
< |
* Array holding all worker threads in the pool. Array size must |
140 |
< |
* be a power of two. Updates and replacements are protected by |
141 |
< |
* workerLock, but it is always kept in a consistent enough state |
142 |
< |
* to be randomly accessed without locking by workers performing |
143 |
< |
* work-stealing. |
139 |
> |
* Array holding all worker threads in the pool. Initialized upon |
140 |
> |
* first use. Array size must be a power of two. Updates and |
141 |
> |
* replacements are protected by workerLock, but it is always kept |
142 |
> |
* in a consistent enough state to be randomly accessed without |
143 |
> |
* locking by workers performing work-stealing. |
144 |
|
*/ |
145 |
|
volatile ForkJoinWorkerThread[] workers; |
146 |
|
|
156 |
|
|
157 |
|
/** |
158 |
|
* The uncaught exception handler used when any worker |
159 |
< |
* abrupty terminates |
159 |
> |
* abruptly terminates |
160 |
|
*/ |
161 |
|
private Thread.UncaughtExceptionHandler ueh; |
162 |
|
|
186 |
|
/** |
187 |
|
* Head of Treiber stack for barrier sync. See below for explanation |
188 |
|
*/ |
189 |
< |
private volatile WaitQueueNode barrierStack; |
189 |
> |
private volatile WaitQueueNode syncStack; |
190 |
|
|
191 |
|
/** |
192 |
|
* The count for event barrier |
209 |
|
private volatile int parallelism; |
210 |
|
|
211 |
|
/** |
212 |
+ |
* True if use local fifo, not default lifo, for local polling |
213 |
+ |
*/ |
214 |
+ |
private volatile boolean locallyFifo; |
215 |
+ |
|
216 |
+ |
/** |
217 |
|
* Holds number of total (i.e., created and not yet terminated) |
218 |
|
* and running (i.e., not blocked on joins or other managed sync) |
219 |
|
* threads, packed into one int to ensure consistent snapshot when |
220 |
|
* making decisions about creating and suspending spare |
221 |
|
* threads. Updated only by CAS. Note: CASes in |
222 |
< |
* updateRunningCount and preJoin running active count is in low |
223 |
< |
* word, so need to be modified if this changes |
222 |
> |
* updateRunningCount and preJoin assume that running active count |
223 |
> |
* is in low word, so need to be modified if this changes. |
224 |
|
*/ |
225 |
|
private volatile int workerCounts; |
226 |
|
|
229 |
|
private static int workerCountsFor(int t, int r) { return (t << 16) + r; } |
230 |
|
|
231 |
|
/** |
232 |
< |
* Add delta (which may be negative) to running count. This must |
232 |
> |
* Adds delta (which may be negative) to running count. This must |
233 |
|
* be called before (with negative arg) and after (with positive) |
234 |
< |
* any managed synchronization (i.e., mainly, joins) |
234 |
> |
* any managed synchronization (i.e., mainly, joins). |
235 |
|
* @param delta the number to add |
236 |
|
*/ |
237 |
|
final void updateRunningCount(int delta) { |
240 |
|
} |
241 |
|
|
242 |
|
/** |
243 |
< |
* Add delta (which may be negative) to both total and running |
243 |
> |
* Adds delta (which may be negative) to both total and running |
244 |
|
* count. This must be called upon creation and termination of |
245 |
|
* worker threads. |
246 |
|
* @param delta the number to add |
274 |
|
private static int runControlFor(int r, int a) { return (r << 16) + a; } |
275 |
|
|
276 |
|
/** |
277 |
< |
* Increment active count. Called by workers before/during |
278 |
< |
* executing tasks. |
277 |
> |
* Try incrementing active count; fail on contention. Called by |
278 |
> |
* workers before/during executing tasks. |
279 |
> |
* @return true on success |
280 |
|
*/ |
281 |
< |
final void incrementActiveCount() { |
282 |
< |
int c; |
283 |
< |
do;while (!casRunControl(c = runControl, c+1)); |
281 |
> |
final boolean tryIncrementActiveCount() { |
282 |
> |
int c = runControl; |
283 |
> |
return casRunControl(c, c+1); |
284 |
|
} |
285 |
|
|
286 |
|
/** |
287 |
< |
* Decrement active count; possibly trigger termination. |
287 |
> |
* Tries decrementing active count; fails on contention. |
288 |
> |
* Possibly triggers termination on success. |
289 |
|
* Called by workers when they can't find tasks. |
290 |
+ |
* @return true on success |
291 |
|
*/ |
292 |
< |
final void decrementActiveCount() { |
293 |
< |
int c, nextc; |
294 |
< |
do;while (!casRunControl(c = runControl, nextc = c-1)); |
292 |
> |
final boolean tryDecrementActiveCount() { |
293 |
> |
int c = runControl; |
294 |
> |
int nextc = c - 1; |
295 |
> |
if (!casRunControl(c, nextc)) |
296 |
> |
return false; |
297 |
|
if (canTerminateOnShutdown(nextc)) |
298 |
|
terminateOnShutdown(); |
299 |
+ |
return true; |
300 |
|
} |
301 |
|
|
302 |
|
/** |
303 |
< |
* Return true if argument represents zero active count and |
303 |
> |
* Returns true if argument represents zero active count and |
304 |
|
* nonzero runstate, which is the triggering condition for |
305 |
|
* terminating on shutdown. |
306 |
|
*/ |
336 |
|
* @throws SecurityException if a security manager exists and |
337 |
|
* the caller is not permitted to modify threads |
338 |
|
* because it does not hold {@link |
339 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
339 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")}, |
340 |
|
*/ |
341 |
|
public ForkJoinPool() { |
342 |
|
this(Runtime.getRuntime().availableProcessors(), |
344 |
|
} |
345 |
|
|
346 |
|
/** |
347 |
< |
* Creates a ForkJoinPool with the indicated parellelism level |
347 |
> |
* Creates a ForkJoinPool with the indicated parallelism level |
348 |
|
* threads, and using the default ForkJoinWorkerThreadFactory, |
349 |
|
* @param parallelism the number of worker threads |
350 |
|
* @throws IllegalArgumentException if parallelism less than or |
352 |
|
* @throws SecurityException if a security manager exists and |
353 |
|
* the caller is not permitted to modify threads |
354 |
|
* because it does not hold {@link |
355 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
355 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")}, |
356 |
|
*/ |
357 |
|
public ForkJoinPool(int parallelism) { |
358 |
|
this(parallelism, defaultForkJoinWorkerThreadFactory); |
367 |
|
* @throws SecurityException if a security manager exists and |
368 |
|
* the caller is not permitted to modify threads |
369 |
|
* because it does not hold {@link |
370 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
370 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")}, |
371 |
|
*/ |
372 |
|
public ForkJoinPool(ForkJoinWorkerThreadFactory factory) { |
373 |
|
this(Runtime.getRuntime().availableProcessors(), factory); |
379 |
|
* @param parallelism the targeted number of worker threads |
380 |
|
* @param factory the factory for creating new threads |
381 |
|
* @throws IllegalArgumentException if parallelism less than or |
382 |
< |
* equal to zero, or greater than implementation limit. |
382 |
> |
* equal to zero, or greater than implementation limit |
383 |
|
* @throws NullPointerException if factory is null |
384 |
|
* @throws SecurityException if a security manager exists and |
385 |
|
* the caller is not permitted to modify threads |
386 |
|
* because it does not hold {@link |
387 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
387 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")}, |
388 |
|
*/ |
389 |
|
public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) { |
390 |
|
if (parallelism <= 0 || parallelism > MAX_THREADS) |
401 |
|
this.termination = workerLock.newCondition(); |
402 |
|
this.stealCount = new AtomicLong(); |
403 |
|
this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>(); |
404 |
< |
createAndStartInitialWorkers(parallelism); |
404 |
> |
// worker array and workers are lazily constructed |
405 |
|
} |
406 |
|
|
407 |
|
/** |
415 |
|
if (w != null) { |
416 |
|
w.poolIndex = index; |
417 |
|
w.setDaemon(true); |
418 |
+ |
w.setAsyncMode(locallyFifo); |
419 |
|
w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index); |
420 |
|
if (h != null) |
421 |
|
w.setUncaughtExceptionHandler(h); |
424 |
|
} |
425 |
|
|
426 |
|
/** |
427 |
< |
* Return a good size for worker array given pool size. |
427 |
> |
* Returns a good size for worker array given pool size. |
428 |
|
* Currently requires size to be a power of two. |
429 |
|
*/ |
430 |
|
private static int arraySizeFor(int ps) { |
432 |
|
} |
433 |
|
|
434 |
|
/** |
435 |
< |
* Create or resize array if necessary to hold newLength |
435 |
> |
* Creates or resizes array if necessary to hold newLength. |
436 |
> |
* Call only under exclusion. |
437 |
> |
* |
438 |
|
* @return the array |
439 |
|
*/ |
440 |
|
private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) { |
452 |
|
*/ |
453 |
|
private void tryShrinkWorkerArray() { |
454 |
|
ForkJoinWorkerThread[] ws = workers; |
455 |
< |
int len = ws.length; |
456 |
< |
int last = len - 1; |
457 |
< |
while (last >= 0 && ws[last] == null) |
458 |
< |
--last; |
459 |
< |
int newLength = arraySizeFor(last+1); |
460 |
< |
if (newLength < len) |
461 |
< |
workers = Arrays.copyOf(ws, newLength); |
455 |
> |
if (ws != null) { |
456 |
> |
int len = ws.length; |
457 |
> |
int last = len - 1; |
458 |
> |
while (last >= 0 && ws[last] == null) |
459 |
> |
--last; |
460 |
> |
int newLength = arraySizeFor(last+1); |
461 |
> |
if (newLength < len) |
462 |
> |
workers = Arrays.copyOf(ws, newLength); |
463 |
> |
} |
464 |
|
} |
465 |
|
|
466 |
|
/** |
467 |
< |
* Initial worker array and worker creation and startup. (This |
447 |
< |
* must be done under lock to avoid interference by some of the |
448 |
< |
* newly started threads while creating others.) |
467 |
> |
* Initialize workers if necessary |
468 |
|
*/ |
469 |
< |
private void createAndStartInitialWorkers(int ps) { |
470 |
< |
final ReentrantLock lock = this.workerLock; |
471 |
< |
lock.lock(); |
472 |
< |
try { |
473 |
< |
ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps); |
474 |
< |
for (int i = 0; i < ps; ++i) { |
475 |
< |
ForkJoinWorkerThread w = createWorker(i); |
476 |
< |
if (w != null) { |
477 |
< |
ws[i] = w; |
478 |
< |
w.start(); |
479 |
< |
updateWorkerCount(1); |
469 |
> |
final void ensureWorkerInitialization() { |
470 |
> |
ForkJoinWorkerThread[] ws = workers; |
471 |
> |
if (ws == null) { |
472 |
> |
final ReentrantLock lock = this.workerLock; |
473 |
> |
lock.lock(); |
474 |
> |
try { |
475 |
> |
ws = workers; |
476 |
> |
if (ws == null) { |
477 |
> |
int ps = parallelism; |
478 |
> |
ws = ensureWorkerArrayCapacity(ps); |
479 |
> |
for (int i = 0; i < ps; ++i) { |
480 |
> |
ForkJoinWorkerThread w = createWorker(i); |
481 |
> |
if (w != null) { |
482 |
> |
ws[i] = w; |
483 |
> |
w.start(); |
484 |
> |
updateWorkerCount(1); |
485 |
> |
} |
486 |
> |
} |
487 |
|
} |
488 |
+ |
} finally { |
489 |
+ |
lock.unlock(); |
490 |
|
} |
463 |
– |
} finally { |
464 |
– |
lock.unlock(); |
491 |
|
} |
492 |
|
} |
493 |
|
|
533 |
|
private <T> void doSubmit(ForkJoinTask<T> task) { |
534 |
|
if (isShutdown()) |
535 |
|
throw new RejectedExecutionException(); |
536 |
+ |
if (workers == null) |
537 |
+ |
ensureWorkerInitialization(); |
538 |
|
submissionQueue.offer(task); |
539 |
< |
signalIdleWorkers(true); |
539 |
> |
signalIdleWorkers(); |
540 |
|
} |
541 |
|
|
542 |
|
/** |
693 |
|
* @throws SecurityException if a security manager exists and |
694 |
|
* the caller is not permitted to modify threads |
695 |
|
* because it does not hold {@link |
696 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
696 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")}, |
697 |
|
*/ |
698 |
|
public Thread.UncaughtExceptionHandler |
699 |
|
setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) { |
705 |
|
old = ueh; |
706 |
|
ueh = h; |
707 |
|
ForkJoinWorkerThread[] ws = workers; |
708 |
< |
for (int i = 0; i < ws.length; ++i) { |
709 |
< |
ForkJoinWorkerThread w = ws[i]; |
710 |
< |
if (w != null) |
711 |
< |
w.setUncaughtExceptionHandler(h); |
708 |
> |
if (ws != null) { |
709 |
> |
for (int i = 0; i < ws.length; ++i) { |
710 |
> |
ForkJoinWorkerThread w = ws[i]; |
711 |
> |
if (w != null) |
712 |
> |
w.setUncaughtExceptionHandler(h); |
713 |
> |
} |
714 |
|
} |
715 |
|
} finally { |
716 |
|
lock.unlock(); |
720 |
|
|
721 |
|
|
722 |
|
/** |
723 |
< |
* Sets the target paralleism level of this pool. |
723 |
> |
* Sets the target parallelism level of this pool. |
724 |
|
* @param parallelism the target parallelism |
725 |
|
* @throws IllegalArgumentException if parallelism less than or |
726 |
< |
* equal to zero or greater than maximum size bounds. |
726 |
> |
* equal to zero or greater than maximum size bounds |
727 |
|
* @throws SecurityException if a security manager exists and |
728 |
|
* the caller is not permitted to modify threads |
729 |
|
* because it does not hold {@link |
730 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
730 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")}, |
731 |
|
*/ |
732 |
|
public void setParallelism(int parallelism) { |
733 |
|
checkPermission(); |
747 |
|
} finally { |
748 |
|
lock.unlock(); |
749 |
|
} |
750 |
< |
signalIdleWorkers(false); |
750 |
> |
signalIdleWorkers(); |
751 |
|
} |
752 |
|
|
753 |
|
/** |
762 |
|
/** |
763 |
|
* Returns the number of worker threads that have started but not |
764 |
|
* yet terminated. This result returned by this method may differ |
765 |
< |
* from <code>getParallelism</code> when threads are created to |
765 |
> |
* from {@code getParallelism} when threads are created to |
766 |
|
* maintain parallelism when others are cooperatively blocked. |
767 |
|
* |
768 |
|
* @return the number of worker threads |
786 |
|
* Setting this value has no effect on current pool size. It |
787 |
|
* controls construction of new threads. |
788 |
|
* @throws IllegalArgumentException if negative or greater then |
789 |
< |
* internal implementation limit. |
789 |
> |
* internal implementation limit |
790 |
|
*/ |
791 |
|
public void setMaximumPoolSize(int newMax) { |
792 |
|
if (newMax < 0 || newMax > MAX_THREADS) |
817 |
|
} |
818 |
|
|
819 |
|
/** |
820 |
+ |
* Establishes local first-in-first-out scheduling mode for forked |
821 |
+ |
* tasks that are never joined. This mode may be more appropriate |
822 |
+ |
* than default locally stack-based mode in applications in which |
823 |
+ |
* worker threads only process asynchronous tasks. This method is |
824 |
+ |
* designed to be invoked only when pool is quiescent, and |
825 |
+ |
* typically only before any tasks are submitted. The effects of |
826 |
+ |
* invocations at other times may be unpredictable. |
827 |
+ |
* |
828 |
+ |
* @param async if true, use locally FIFO scheduling |
829 |
+ |
* @return the previous mode |
830 |
+ |
*/ |
831 |
+ |
public boolean setAsyncMode(boolean async) { |
832 |
+ |
boolean oldMode = locallyFifo; |
833 |
+ |
locallyFifo = async; |
834 |
+ |
ForkJoinWorkerThread[] ws = workers; |
835 |
+ |
if (ws != null) { |
836 |
+ |
for (int i = 0; i < ws.length; ++i) { |
837 |
+ |
ForkJoinWorkerThread t = ws[i]; |
838 |
+ |
if (t != null) |
839 |
+ |
t.setAsyncMode(async); |
840 |
+ |
} |
841 |
+ |
} |
842 |
+ |
return oldMode; |
843 |
+ |
} |
844 |
+ |
|
845 |
+ |
/** |
846 |
+ |
* Returns true if this pool uses local first-in-first-out |
847 |
+ |
* scheduling mode for forked tasks that are never joined. |
848 |
+ |
* |
849 |
+ |
* @return true if this pool uses async mode |
850 |
+ |
*/ |
851 |
+ |
public boolean getAsyncMode() { |
852 |
+ |
return locallyFifo; |
853 |
+ |
} |
854 |
+ |
|
855 |
+ |
/** |
856 |
|
* Returns an estimate of the number of worker threads that are |
857 |
|
* not blocked waiting to join tasks or for other managed |
858 |
|
* synchronization. |
867 |
|
* Returns an estimate of the number of threads that are currently |
868 |
|
* stealing or executing tasks. This method may overestimate the |
869 |
|
* number of active threads. |
870 |
< |
* @return the number of active threads. |
870 |
> |
* @return the number of active threads |
871 |
|
*/ |
872 |
|
public int getActiveThreadCount() { |
873 |
|
return activeCountOf(runControl); |
877 |
|
* Returns an estimate of the number of threads that are currently |
878 |
|
* idle waiting for tasks. This method may underestimate the |
879 |
|
* number of idle threads. |
880 |
< |
* @return the number of idle threads. |
880 |
> |
* @return the number of idle threads |
881 |
|
*/ |
882 |
|
final int getIdleThreadCount() { |
883 |
|
int c = runningCountOf(workerCounts) - activeCountOf(runControl); |
906 |
|
* tuning fork/join programs: In general, steal counts should be |
907 |
|
* high enough to keep threads busy, but low enough to avoid |
908 |
|
* overhead and contention across threads. |
909 |
< |
* @return the number of steals. |
909 |
> |
* @return the number of steals |
910 |
|
*/ |
911 |
|
public long getStealCount() { |
912 |
|
return stealCount.get(); |
929 |
|
* an approximation, obtained by iterating across all threads in |
930 |
|
* the pool. This method may be useful for tuning task |
931 |
|
* granularities. |
932 |
< |
* @return the number of queued tasks. |
932 |
> |
* @return the number of queued tasks |
933 |
|
*/ |
934 |
|
public long getQueuedTaskCount() { |
935 |
|
long count = 0; |
936 |
|
ForkJoinWorkerThread[] ws = workers; |
937 |
< |
for (int i = 0; i < ws.length; ++i) { |
938 |
< |
ForkJoinWorkerThread t = ws[i]; |
939 |
< |
if (t != null) |
940 |
< |
count += t.getQueueSize(); |
937 |
> |
if (ws != null) { |
938 |
> |
for (int i = 0; i < ws.length; ++i) { |
939 |
> |
ForkJoinWorkerThread t = ws[i]; |
940 |
> |
if (t != null) |
941 |
> |
count += t.getQueueSize(); |
942 |
> |
} |
943 |
|
} |
944 |
|
return count; |
945 |
|
} |
948 |
|
* Returns an estimate of the number tasks submitted to this pool |
949 |
|
* that have not yet begun executing. This method takes time |
950 |
|
* proportional to the number of submissions. |
951 |
< |
* @return the number of queued submissions. |
951 |
> |
* @return the number of queued submissions |
952 |
|
*/ |
953 |
|
public int getQueuedSubmissionCount() { |
954 |
|
return submissionQueue.size(); |
957 |
|
/** |
958 |
|
* Returns true if there are any tasks submitted to this pool |
959 |
|
* that have not yet begun executing. |
960 |
< |
* @return <code>true</code> if there are any queued submissions. |
960 |
> |
* @return {@code true} if there are any queued submissions |
961 |
|
*/ |
962 |
|
public boolean hasQueuedSubmissions() { |
963 |
|
return !submissionQueue.isEmpty(); |
974 |
|
} |
975 |
|
|
976 |
|
/** |
977 |
+ |
* Removes all available unexecuted submitted and forked tasks |
978 |
+ |
* from scheduling queues and adds them to the given collection, |
979 |
+ |
* without altering their execution status. These may include |
980 |
+ |
* artificially generated or wrapped tasks. This method is designed |
981 |
+ |
* to be invoked only when the pool is known to be |
982 |
+ |
* quiescent. Invocations at other times may not remove all |
983 |
+ |
* tasks. A failure encountered while attempting to add elements |
984 |
+ |
* to collection {@code c} may result in elements being in |
985 |
+ |
* neither, either or both collections when the associated |
986 |
+ |
* exception is thrown. The behavior of this operation is |
987 |
+ |
* undefined if the specified collection is modified while the |
988 |
+ |
* operation is in progress. |
989 |
+ |
* @param c the collection to transfer elements into |
990 |
+ |
* @return the number of elements transferred |
991 |
+ |
*/ |
992 |
+ |
protected int drainTasksTo(Collection<ForkJoinTask<?>> c) { |
993 |
+ |
int n = submissionQueue.drainTo(c); |
994 |
+ |
ForkJoinWorkerThread[] ws = workers; |
995 |
+ |
if (ws != null) { |
996 |
+ |
for (int i = 0; i < ws.length; ++i) { |
997 |
+ |
ForkJoinWorkerThread w = ws[i]; |
998 |
+ |
if (w != null) |
999 |
+ |
n += w.drainTasksTo(c); |
1000 |
+ |
} |
1001 |
+ |
} |
1002 |
+ |
return n; |
1003 |
+ |
} |
1004 |
+ |
|
1005 |
+ |
/** |
1006 |
|
* Returns a string identifying this pool, as well as its state, |
1007 |
|
* including indications of run state, parallelism level, and |
1008 |
|
* worker and task counts. |
1049 |
|
* @throws SecurityException if a security manager exists and |
1050 |
|
* the caller is not permitted to modify threads |
1051 |
|
* because it does not hold {@link |
1052 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
1052 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")}, |
1053 |
|
*/ |
1054 |
|
public void shutdown() { |
1055 |
|
checkPermission(); |
1063 |
|
* waiting tasks. Tasks that are in the process of being |
1064 |
|
* submitted or executed concurrently during the course of this |
1065 |
|
* method may or may not be rejected. Unlike some other executors, |
1066 |
< |
* this method cancels rather than collects non-executed tasks, |
1067 |
< |
* so always returns an empty list. |
1066 |
> |
* this method cancels rather than collects non-executed tasks |
1067 |
> |
* upon termination, so always returns an empty list. However, you |
1068 |
> |
* can use method {@code drainTasksTo} before invoking this |
1069 |
> |
* method to transfer unexecuted tasks to another collection. |
1070 |
|
* @return an empty list |
1071 |
|
* @throws SecurityException if a security manager exists and |
1072 |
|
* the caller is not permitted to modify threads |
1073 |
|
* because it does not hold {@link |
1074 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
1074 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")}, |
1075 |
|
*/ |
1076 |
|
public List<Runnable> shutdownNow() { |
1077 |
|
checkPermission(); |
1080 |
|
} |
1081 |
|
|
1082 |
|
/** |
1083 |
< |
* Returns <code>true</code> if all tasks have completed following shut down. |
1083 |
> |
* Returns {@code true} if all tasks have completed following shut down. |
1084 |
|
* |
1085 |
< |
* @return <code>true</code> if all tasks have completed following shut down |
1085 |
> |
* @return {@code true} if all tasks have completed following shut down |
1086 |
|
*/ |
1087 |
|
public boolean isTerminated() { |
1088 |
|
return runStateOf(runControl) == TERMINATED; |
1089 |
|
} |
1090 |
|
|
1091 |
|
/** |
1092 |
< |
* Returns <code>true</code> if the process of termination has |
1092 |
> |
* Returns {@code true} if the process of termination has |
1093 |
|
* commenced but possibly not yet completed. |
1094 |
|
* |
1095 |
< |
* @return <code>true</code> if terminating |
1095 |
> |
* @return {@code true} if terminating |
1096 |
|
*/ |
1097 |
|
public boolean isTerminating() { |
1098 |
|
return runStateOf(runControl) >= TERMINATING; |
1099 |
|
} |
1100 |
|
|
1101 |
|
/** |
1102 |
< |
* Returns <code>true</code> if this pool has been shut down. |
1102 |
> |
* Returns {@code true} if this pool has been shut down. |
1103 |
|
* |
1104 |
< |
* @return <code>true</code> if this pool has been shut down |
1104 |
> |
* @return {@code true} if this pool has been shut down |
1105 |
|
*/ |
1106 |
|
public boolean isShutdown() { |
1107 |
|
return runStateOf(runControl) >= SHUTDOWN; |
1114 |
|
* |
1115 |
|
* @param timeout the maximum time to wait |
1116 |
|
* @param unit the time unit of the timeout argument |
1117 |
< |
* @return <code>true</code> if this executor terminated and |
1118 |
< |
* <code>false</code> if the timeout elapsed before termination |
1117 |
> |
* @return {@code true} if this executor terminated and |
1118 |
> |
* {@code false} if the timeout elapsed before termination |
1119 |
|
* @throws InterruptedException if interrupted while waiting |
1120 |
|
*/ |
1121 |
|
public boolean awaitTermination(long timeout, TimeUnit unit) |
1151 |
|
lock.lock(); |
1152 |
|
try { |
1153 |
|
ForkJoinWorkerThread[] ws = workers; |
1154 |
< |
int idx = w.poolIndex; |
1155 |
< |
if (idx >= 0 && idx < ws.length && ws[idx] == w) |
1156 |
< |
ws[idx] = null; |
1157 |
< |
if (totalCountOf(workerCounts) == 0) { |
1158 |
< |
terminate(); // no-op if already terminating |
1159 |
< |
transitionRunStateTo(TERMINATED); |
1160 |
< |
termination.signalAll(); |
1161 |
< |
} |
1162 |
< |
else if (!isTerminating()) { |
1163 |
< |
tryShrinkWorkerArray(); |
1164 |
< |
tryResumeSpare(true); // allow replacement |
1154 |
> |
if (ws != null) { |
1155 |
> |
int idx = w.poolIndex; |
1156 |
> |
if (idx >= 0 && idx < ws.length && ws[idx] == w) |
1157 |
> |
ws[idx] = null; |
1158 |
> |
if (totalCountOf(workerCounts) == 0) { |
1159 |
> |
terminate(); // no-op if already terminating |
1160 |
> |
transitionRunStateTo(TERMINATED); |
1161 |
> |
termination.signalAll(); |
1162 |
> |
} |
1163 |
> |
else if (!isTerminating()) { |
1164 |
> |
tryShrinkWorkerArray(); |
1165 |
> |
tryResumeSpare(true); // allow replacement |
1166 |
> |
} |
1167 |
|
} |
1168 |
|
} finally { |
1169 |
|
lock.unlock(); |
1170 |
|
} |
1171 |
< |
signalIdleWorkers(false); |
1171 |
> |
signalIdleWorkers(); |
1172 |
|
} |
1173 |
|
|
1174 |
|
/** |
1178 |
|
if (transitionRunStateTo(TERMINATING)) { |
1179 |
|
stopAllWorkers(); |
1180 |
|
resumeAllSpares(); |
1181 |
< |
signalIdleWorkers(true); |
1181 |
> |
signalIdleWorkers(); |
1182 |
|
cancelQueuedSubmissions(); |
1183 |
|
cancelQueuedWorkerTasks(); |
1184 |
|
interruptUnterminatedWorkers(); |
1185 |
< |
signalIdleWorkers(true); // resignal after interrupt |
1185 |
> |
signalIdleWorkers(); // resignal after interrupt |
1186 |
|
} |
1187 |
|
} |
1188 |
|
|
1189 |
|
/** |
1190 |
< |
* Possibly terminate when on shutdown state |
1190 |
> |
* Possibly terminates when on shutdown state. |
1191 |
|
*/ |
1192 |
|
private void terminateOnShutdown() { |
1193 |
|
if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl)) |
1195 |
|
} |
1196 |
|
|
1197 |
|
/** |
1198 |
< |
* Clear out and cancel submissions |
1198 |
> |
* Clears out and cancels submissions. |
1199 |
|
*/ |
1200 |
|
private void cancelQueuedSubmissions() { |
1201 |
|
ForkJoinTask<?> task; |
1204 |
|
} |
1205 |
|
|
1206 |
|
/** |
1207 |
< |
* Clean out worker queues. |
1207 |
> |
* Cleans out worker queues. |
1208 |
|
*/ |
1209 |
|
private void cancelQueuedWorkerTasks() { |
1210 |
|
final ReentrantLock lock = this.workerLock; |
1211 |
|
lock.lock(); |
1212 |
|
try { |
1213 |
|
ForkJoinWorkerThread[] ws = workers; |
1214 |
< |
for (int i = 0; i < ws.length; ++i) { |
1215 |
< |
ForkJoinWorkerThread t = ws[i]; |
1216 |
< |
if (t != null) |
1217 |
< |
t.cancelTasks(); |
1214 |
> |
if (ws != null) { |
1215 |
> |
for (int i = 0; i < ws.length; ++i) { |
1216 |
> |
ForkJoinWorkerThread t = ws[i]; |
1217 |
> |
if (t != null) |
1218 |
> |
t.cancelTasks(); |
1219 |
> |
} |
1220 |
|
} |
1221 |
|
} finally { |
1222 |
|
lock.unlock(); |
1224 |
|
} |
1225 |
|
|
1226 |
|
/** |
1227 |
< |
* Set each worker's status to terminating. Requires lock to avoid |
1228 |
< |
* conflicts with add/remove |
1227 |
> |
* Sets each worker's status to terminating. Requires lock to avoid |
1228 |
> |
* conflicts with add/remove. |
1229 |
|
*/ |
1230 |
|
private void stopAllWorkers() { |
1231 |
|
final ReentrantLock lock = this.workerLock; |
1232 |
|
lock.lock(); |
1233 |
|
try { |
1234 |
|
ForkJoinWorkerThread[] ws = workers; |
1235 |
< |
for (int i = 0; i < ws.length; ++i) { |
1236 |
< |
ForkJoinWorkerThread t = ws[i]; |
1237 |
< |
if (t != null) |
1238 |
< |
t.shutdownNow(); |
1235 |
> |
if (ws != null) { |
1236 |
> |
for (int i = 0; i < ws.length; ++i) { |
1237 |
> |
ForkJoinWorkerThread t = ws[i]; |
1238 |
> |
if (t != null) |
1239 |
> |
t.shutdownNow(); |
1240 |
> |
} |
1241 |
|
} |
1242 |
|
} finally { |
1243 |
|
lock.unlock(); |
1245 |
|
} |
1246 |
|
|
1247 |
|
/** |
1248 |
< |
* Interrupt all unterminated workers. This is not required for |
1248 |
> |
* Interrupts all unterminated workers. This is not required for |
1249 |
|
* sake of internal control, but may help unstick user code during |
1250 |
|
* shutdown. |
1251 |
|
*/ |
1254 |
|
lock.lock(); |
1255 |
|
try { |
1256 |
|
ForkJoinWorkerThread[] ws = workers; |
1257 |
< |
for (int i = 0; i < ws.length; ++i) { |
1258 |
< |
ForkJoinWorkerThread t = ws[i]; |
1259 |
< |
if (t != null && !t.isTerminated()) { |
1260 |
< |
try { |
1261 |
< |
t.interrupt(); |
1262 |
< |
} catch (SecurityException ignore) { |
1257 |
> |
if (ws != null) { |
1258 |
> |
for (int i = 0; i < ws.length; ++i) { |
1259 |
> |
ForkJoinWorkerThread t = ws[i]; |
1260 |
> |
if (t != null && !t.isTerminated()) { |
1261 |
> |
try { |
1262 |
> |
t.interrupt(); |
1263 |
> |
} catch (SecurityException ignore) { |
1264 |
> |
} |
1265 |
|
} |
1266 |
|
} |
1267 |
|
} |
1272 |
|
|
1273 |
|
|
1274 |
|
/* |
1275 |
< |
* Nodes for event barrier to manage idle threads. |
1275 |
> |
* Nodes for event barrier to manage idle threads. Queue nodes |
1276 |
> |
* are basic Treiber stack nodes, also used for spare stack. |
1277 |
|
* |
1278 |
|
* The event barrier has an event count and a wait queue (actually |
1279 |
|
* a Treiber stack). Workers are enabled to look for work when |
1280 |
< |
* the eventCount is incremented. If they fail to find some, |
1281 |
< |
* they may wait for next count. Synchronization events occur only |
1282 |
< |
* in enough contexts to maintain overall liveness: |
1280 |
> |
* the eventCount is incremented. If they fail to find work, they |
1281 |
> |
* may wait for next count. Upon release, threads help others wake |
1282 |
> |
* up. |
1283 |
> |
* |
1284 |
> |
* Synchronization events occur only in enough contexts to |
1285 |
> |
* maintain overall liveness: |
1286 |
|
* |
1287 |
|
* - Submission of a new task to the pool |
1288 |
< |
* - Creation or termination of a worker |
1288 |
> |
* - Resizes or other changes to the workers array |
1289 |
|
* - pool termination |
1290 |
|
* - A worker pushing a task on an empty queue |
1291 |
|
* |
1292 |
< |
* The last case (pushing a task) occurs often enough, and is |
1293 |
< |
* heavy enough compared to simple stack pushes to require some |
1294 |
< |
* special handling: Method signalNonEmptyWorkerQueue returns |
1295 |
< |
* without advancing count if the queue appears to be empty. This |
1296 |
< |
* would ordinarily result in races causing some queued waiters |
1297 |
< |
* not to be woken up. To avoid this, a worker in sync |
1298 |
< |
* rescans for tasks after being enqueued if it was the first to |
1299 |
< |
* enqueue, and aborts the wait if finding one, also helping to |
1300 |
< |
* signal others. This works well because the worker has nothing |
1301 |
< |
* better to do anyway, and so might as well help alleviate the |
1302 |
< |
* overhead and contention on the threads actually doing work. |
1303 |
< |
* |
1304 |
< |
* Queue nodes are basic Treiber stack nodes, also used for spare |
1305 |
< |
* stack. |
1292 |
> |
* The case of pushing a task occurs often enough, and is heavy |
1293 |
> |
* enough compared to simple stack pushes, to require special |
1294 |
> |
* handling: Method signalWork returns without advancing count if |
1295 |
> |
* the queue appears to be empty. This would ordinarily result in |
1296 |
> |
* races causing some queued waiters not to be woken up. To avoid |
1297 |
> |
* this, the first worker enqueued in method sync (see |
1298 |
> |
* syncIsReleasable) rescans for tasks after being enqueued, and |
1299 |
> |
* helps signal if any are found. This works well because the |
1300 |
> |
* worker has nothing better to do, and so might as well help |
1301 |
> |
* alleviate the overhead and contention on the threads actually |
1302 |
> |
* doing work. Also, since event counts increments on task |
1303 |
> |
* availability exist to maintain liveness (rather than to force |
1304 |
> |
* refreshes etc), it is OK for callers to exit early if |
1305 |
> |
* contending with another signaller. |
1306 |
|
*/ |
1307 |
|
static final class WaitQueueNode { |
1308 |
|
WaitQueueNode next; // only written before enqueued |
1309 |
|
volatile ForkJoinWorkerThread thread; // nulled to cancel wait |
1310 |
|
final long count; // unused for spare stack |
1311 |
< |
WaitQueueNode(ForkJoinWorkerThread w, long c) { |
1311 |
> |
|
1312 |
> |
WaitQueueNode(long c, ForkJoinWorkerThread w) { |
1313 |
|
count = c; |
1314 |
|
thread = w; |
1315 |
|
} |
1316 |
< |
final boolean signal() { |
1316 |
> |
|
1317 |
> |
/** |
1318 |
> |
* Wakes up waiter, returning false if known to already |
1319 |
> |
*/ |
1320 |
> |
boolean signal() { |
1321 |
|
ForkJoinWorkerThread t = thread; |
1322 |
+ |
if (t == null) |
1323 |
+ |
return false; |
1324 |
|
thread = null; |
1325 |
< |
if (t != null) { |
1326 |
< |
LockSupport.unpark(t); |
1327 |
< |
return true; |
1325 |
> |
LockSupport.unpark(t); |
1326 |
> |
return true; |
1327 |
> |
} |
1328 |
> |
|
1329 |
> |
/** |
1330 |
> |
* Awaits release on sync. |
1331 |
> |
*/ |
1332 |
> |
void awaitSyncRelease(ForkJoinPool p) { |
1333 |
> |
while (thread != null && !p.syncIsReleasable(this)) |
1334 |
> |
LockSupport.park(this); |
1335 |
> |
} |
1336 |
> |
|
1337 |
> |
/** |
1338 |
> |
* Awaits resumption as spare. |
1339 |
> |
*/ |
1340 |
> |
void awaitSpareRelease() { |
1341 |
> |
while (thread != null) { |
1342 |
> |
if (!Thread.interrupted()) |
1343 |
> |
LockSupport.park(this); |
1344 |
|
} |
1211 |
– |
return false; |
1345 |
|
} |
1346 |
|
} |
1347 |
|
|
1348 |
|
/** |
1349 |
< |
* Release at least one thread waiting for event count to advance, |
1350 |
< |
* if one exists. If initial attempt fails, release all threads. |
1351 |
< |
* @param all if false, at first try to only release one thread |
1352 |
< |
* @return current event |
1349 |
> |
* Ensures that no thread is waiting for count to advance from the |
1350 |
> |
* current value of eventCount read on entry to this method, by |
1351 |
> |
* releasing waiting threads if necessary. |
1352 |
> |
* @return the count |
1353 |
|
*/ |
1354 |
< |
private long releaseIdleWorkers(boolean all) { |
1355 |
< |
long c; |
1356 |
< |
for (;;) { |
1357 |
< |
WaitQueueNode q = barrierStack; |
1358 |
< |
c = eventCount; |
1226 |
< |
long qc; |
1227 |
< |
if (q == null || (qc = q.count) >= c) |
1228 |
< |
break; |
1229 |
< |
if (!all) { |
1230 |
< |
if (casBarrierStack(q, q.next) && q.signal()) |
1231 |
< |
break; |
1232 |
< |
all = true; |
1233 |
< |
} |
1234 |
< |
else if (casBarrierStack(q, null)) { |
1354 |
> |
final long ensureSync() { |
1355 |
> |
long c = eventCount; |
1356 |
> |
WaitQueueNode q; |
1357 |
> |
while ((q = syncStack) != null && q.count < c) { |
1358 |
> |
if (casBarrierStack(q, null)) { |
1359 |
|
do { |
1360 |
< |
q.signal(); |
1360 |
> |
q.signal(); |
1361 |
|
} while ((q = q.next) != null); |
1362 |
|
break; |
1363 |
|
} |
1366 |
|
} |
1367 |
|
|
1368 |
|
/** |
1369 |
< |
* Returns current barrier event count |
1246 |
< |
* @return current barrier event count |
1369 |
> |
* Increments event count and releases waiting threads. |
1370 |
|
*/ |
1371 |
< |
final long getEventCount() { |
1249 |
< |
long ec = eventCount; |
1250 |
< |
releaseIdleWorkers(true); // release to ensure accurate result |
1251 |
< |
return ec; |
1252 |
< |
} |
1253 |
< |
|
1254 |
< |
/** |
1255 |
< |
* Increment event count and release at least one waiting thread, |
1256 |
< |
* if one exists (released threads will in turn wake up others). |
1257 |
< |
* @param all if true, try to wake up all |
1258 |
< |
*/ |
1259 |
< |
final void signalIdleWorkers(boolean all) { |
1371 |
> |
private void signalIdleWorkers() { |
1372 |
|
long c; |
1373 |
|
do;while (!casEventCount(c = eventCount, c+1)); |
1374 |
< |
releaseIdleWorkers(all); |
1374 |
> |
ensureSync(); |
1375 |
|
} |
1376 |
|
|
1377 |
|
/** |
1378 |
< |
* Wake up threads waiting to steal a task. Because method |
1379 |
< |
* sync rechecks availability, it is OK to only proceed if |
1380 |
< |
* queue appears to be non-empty. |
1378 |
> |
* Signals threads waiting to poll a task. Because method sync |
1379 |
> |
* rechecks availability, it is OK to only proceed if queue |
1380 |
> |
* appears to be non-empty, and OK to skip under contention to |
1381 |
> |
* increment count (since some other thread succeeded). |
1382 |
|
*/ |
1383 |
< |
final void signalNonEmptyWorkerQueue() { |
1271 |
< |
// If CAS fails another signaller must have succeeded |
1383 |
> |
final void signalWork() { |
1384 |
|
long c; |
1385 |
< |
if (barrierStack != null && casEventCount(c = eventCount, c+1)) |
1386 |
< |
releaseIdleWorkers(false); |
1385 |
> |
WaitQueueNode q; |
1386 |
> |
if (syncStack != null && |
1387 |
> |
casEventCount(c = eventCount, c+1) && |
1388 |
> |
(((q = syncStack) != null && q.count <= c) && |
1389 |
> |
(!casBarrierStack(q, q.next) || !q.signal()))) |
1390 |
> |
ensureSync(); |
1391 |
|
} |
1392 |
|
|
1393 |
|
/** |
1394 |
< |
* Waits until event count advances from count, or some thread is |
1395 |
< |
* waiting on a previous count, or there is stealable work |
1396 |
< |
* available. Help wake up others on release. |
1394 |
> |
* Waits until event count advances from last value held by |
1395 |
> |
* caller, or if excess threads, caller is resumed as spare, or |
1396 |
> |
* caller or pool is terminating. Updates caller's event on exit. |
1397 |
|
* @param w the calling worker thread |
1282 |
– |
* @param prev previous value returned by sync (or 0) |
1283 |
– |
* @return current event count |
1398 |
|
*/ |
1399 |
< |
final long sync(ForkJoinWorkerThread w, long prev) { |
1400 |
< |
updateStealCount(w); |
1399 |
> |
final void sync(ForkJoinWorkerThread w) { |
1400 |
> |
updateStealCount(w); // Transfer w's count while it is idle |
1401 |
|
|
1402 |
< |
while (!w.isShutdown() && !isTerminating() && |
1403 |
< |
(parallelism >= runningCountOf(workerCounts) || |
1290 |
< |
!suspendIfSpare(w))) { // prefer suspend to waiting here |
1402 |
> |
while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) { |
1403 |
> |
long prev = w.lastEventCount; |
1404 |
|
WaitQueueNode node = null; |
1405 |
< |
boolean queued = false; |
1406 |
< |
for (;;) { |
1407 |
< |
if (!queued) { |
1408 |
< |
if (eventCount != prev) |
1409 |
< |
break; |
1410 |
< |
WaitQueueNode h = barrierStack; |
1411 |
< |
if (h != null && h.count != prev) |
1299 |
< |
break; // release below and maybe retry |
1300 |
< |
if (node == null) |
1301 |
< |
node = new WaitQueueNode(w, prev); |
1302 |
< |
queued = casBarrierStack(node.next = h, node); |
1303 |
< |
} |
1304 |
< |
else if (Thread.interrupted() || |
1305 |
< |
node.thread == null || |
1306 |
< |
(node.next == null && w.prescan()) || |
1307 |
< |
eventCount != prev) { |
1308 |
< |
node.thread = null; |
1309 |
< |
if (eventCount == prev) // help trigger |
1310 |
< |
casEventCount(prev, prev+1); |
1405 |
> |
WaitQueueNode h; |
1406 |
> |
while (eventCount == prev && |
1407 |
> |
((h = syncStack) == null || h.count == prev)) { |
1408 |
> |
if (node == null) |
1409 |
> |
node = new WaitQueueNode(prev, w); |
1410 |
> |
if (casBarrierStack(node.next = h, node)) { |
1411 |
> |
node.awaitSyncRelease(this); |
1412 |
|
break; |
1413 |
|
} |
1313 |
– |
else |
1314 |
– |
LockSupport.park(this); |
1414 |
|
} |
1415 |
+ |
long ec = ensureSync(); |
1416 |
+ |
if (ec != prev) { |
1417 |
+ |
w.lastEventCount = ec; |
1418 |
+ |
break; |
1419 |
+ |
} |
1420 |
+ |
} |
1421 |
+ |
} |
1422 |
+ |
|
1423 |
+ |
/** |
1424 |
+ |
* Returns true if worker waiting on sync can proceed: |
1425 |
+ |
* - on signal (thread == null) |
1426 |
+ |
* - on event count advance (winning race to notify vs signaller) |
1427 |
+ |
* - on Interrupt |
1428 |
+ |
* - if the first queued node, we find work available |
1429 |
+ |
* If node was not signalled and event count not advanced on exit, |
1430 |
+ |
* then we also help advance event count. |
1431 |
+ |
* @return true if node can be released |
1432 |
+ |
*/ |
1433 |
+ |
final boolean syncIsReleasable(WaitQueueNode node) { |
1434 |
+ |
long prev = node.count; |
1435 |
+ |
if (!Thread.interrupted() && node.thread != null && |
1436 |
+ |
(node.next != null || |
1437 |
+ |
!ForkJoinWorkerThread.hasQueuedTasks(workers)) && |
1438 |
+ |
eventCount == prev) |
1439 |
+ |
return false; |
1440 |
+ |
if (node.thread != null) { |
1441 |
+ |
node.thread = null; |
1442 |
|
long ec = eventCount; |
1443 |
< |
if (releaseIdleWorkers(false) != prev) |
1444 |
< |
return ec; |
1443 |
> |
if (prev <= ec) // help signal |
1444 |
> |
casEventCount(ec, ec+1); |
1445 |
|
} |
1446 |
< |
return prev; // return old count if aborted |
1446 |
> |
return true; |
1447 |
> |
} |
1448 |
> |
|
1449 |
> |
/** |
1450 |
> |
* Returns true if a new sync event occurred since last call to |
1451 |
> |
* sync or this method, if so, updating caller's count. |
1452 |
> |
*/ |
1453 |
> |
final boolean hasNewSyncEvent(ForkJoinWorkerThread w) { |
1454 |
> |
long lc = w.lastEventCount; |
1455 |
> |
long ec = ensureSync(); |
1456 |
> |
if (ec == lc) |
1457 |
> |
return false; |
1458 |
> |
w.lastEventCount = ec; |
1459 |
> |
return true; |
1460 |
|
} |
1461 |
|
|
1462 |
|
// Parallelism maintenance |
1463 |
|
|
1464 |
|
/** |
1465 |
< |
* Decrement running count; if too low, add spare. |
1465 |
> |
* Decrements running count; if too low, adds spare. |
1466 |
|
* |
1467 |
|
* Conceptually, all we need to do here is add or resume a |
1468 |
|
* spare thread when one is about to block (and remove or |
1482 |
|
* only be suspended or removed when they are idle, not |
1483 |
|
* immediately when they aren't needed. So adding threads will |
1484 |
|
* raise parallelism level for longer than necessary. Also, |
1485 |
< |
* FJ applications often enounter highly transient peaks when |
1485 |
> |
* FJ applications often encounter highly transient peaks when |
1486 |
|
* many threads are blocked joining, but for less time than it |
1487 |
|
* takes to create or resume spares. |
1488 |
|
* |
1547 |
|
return (tc < maxPoolSize && |
1548 |
|
(rc == 0 || totalSurplus < 0 || |
1549 |
|
(maintainParallelism && |
1550 |
< |
runningDeficit > totalSurplus && mayHaveQueuedWork()))); |
1551 |
< |
} |
1413 |
< |
|
1414 |
< |
/** |
1415 |
< |
* Returns true if at least one worker queue appears to be |
1416 |
< |
* nonempty. This is expensive but not often called. It is not |
1417 |
< |
* critical that this be accurate, but if not, more or fewer |
1418 |
< |
* running threads than desired might be maintained. |
1419 |
< |
*/ |
1420 |
< |
private boolean mayHaveQueuedWork() { |
1421 |
< |
ForkJoinWorkerThread[] ws = workers; |
1422 |
< |
int len = ws.length; |
1423 |
< |
ForkJoinWorkerThread v; |
1424 |
< |
for (int i = 0; i < len; ++i) { |
1425 |
< |
if ((v = ws[i]) != null && v.getRawQueueSize() > 0) { |
1426 |
< |
releaseIdleWorkers(false); // help wake up stragglers |
1427 |
< |
return true; |
1428 |
< |
} |
1429 |
< |
} |
1430 |
< |
return false; |
1550 |
> |
runningDeficit > totalSurplus && |
1551 |
> |
ForkJoinWorkerThread.hasQueuedTasks(workers)))); |
1552 |
|
} |
1553 |
|
|
1554 |
|
/** |
1555 |
< |
* Add a spare worker if lock available and no more than the |
1556 |
< |
* expected numbers of threads exist |
1555 |
> |
* Adds a spare worker if lock available and no more than the |
1556 |
> |
* expected numbers of threads exist. |
1557 |
|
* @return true if successful |
1558 |
|
*/ |
1559 |
|
private boolean tryAddSpare(int expectedCounts) { |
1586 |
|
} |
1587 |
|
|
1588 |
|
/** |
1589 |
< |
* Add the kth spare worker. On entry, pool coounts are already |
1589 |
> |
* Adds the kth spare worker. On entry, pool counts are already |
1590 |
|
* adjusted to reflect addition. |
1591 |
|
*/ |
1592 |
|
private void createAndStartSpare(int k) { |
1598 |
|
for (k = 0; k < len && ws[k] != null; ++k) |
1599 |
|
; |
1600 |
|
} |
1601 |
< |
if (k < len && (w = createWorker(k)) != null) { |
1601 |
> |
if (k < len && !isTerminating() && (w = createWorker(k)) != null) { |
1602 |
|
ws[k] = w; |
1603 |
|
w.start(); |
1604 |
|
} |
1605 |
|
else |
1606 |
|
updateWorkerCount(-1); // adjust on failure |
1607 |
< |
signalIdleWorkers(false); |
1607 |
> |
signalIdleWorkers(); |
1608 |
|
} |
1609 |
|
|
1610 |
|
/** |
1611 |
< |
* Suspend calling thread w if there are excess threads. Called |
1612 |
< |
* only from sync. Spares are enqueued in a Treiber stack |
1613 |
< |
* using the same WaitQueueNodes as barriers. They are resumed |
1614 |
< |
* mainly in preJoin, but are also woken on pool events that |
1615 |
< |
* require all threads to check run state. |
1611 |
> |
* Suspends calling thread w if there are excess threads. Called |
1612 |
> |
* only from sync. Spares are enqueued in a Treiber stack using |
1613 |
> |
* the same WaitQueueNodes as barriers. They are resumed mainly |
1614 |
> |
* in preJoin, but are also woken on pool events that require all |
1615 |
> |
* threads to check run state. |
1616 |
|
* @param w the caller |
1617 |
|
*/ |
1618 |
|
private boolean suspendIfSpare(ForkJoinWorkerThread w) { |
1620 |
|
int s; |
1621 |
|
while (parallelism < runningCountOf(s = workerCounts)) { |
1622 |
|
if (node == null) |
1623 |
< |
node = new WaitQueueNode(w, 0); |
1623 |
> |
node = new WaitQueueNode(0, w); |
1624 |
|
if (casWorkerCounts(s, s-1)) { // representation-dependent |
1625 |
|
// push onto stack |
1626 |
|
do;while (!casSpareStack(node.next = spareStack, node)); |
1506 |
– |
|
1627 |
|
// block until released by resumeSpare |
1628 |
< |
while (node.thread != null) { |
1509 |
< |
if (!Thread.interrupted()) |
1510 |
< |
LockSupport.park(this); |
1511 |
< |
} |
1512 |
< |
w.activate(); // help warm up |
1628 |
> |
node.awaitSpareRelease(); |
1629 |
|
return true; |
1630 |
|
} |
1631 |
|
} |
1633 |
|
} |
1634 |
|
|
1635 |
|
/** |
1636 |
< |
* Try to pop and resume a spare thread. |
1636 |
> |
* Tries to pop and resume a spare thread. |
1637 |
|
* @param updateCount if true, increment running count on success |
1638 |
|
* @return true if successful |
1639 |
|
*/ |
1651 |
|
} |
1652 |
|
|
1653 |
|
/** |
1654 |
< |
* Pop and resume all spare threads. Same idea as |
1539 |
< |
* releaseIdleWorkers. |
1654 |
> |
* Pops and resumes all spare threads. Same idea as ensureSync. |
1655 |
|
* @return true if any spares released |
1656 |
|
*/ |
1657 |
|
private boolean resumeAllSpares() { |
1669 |
|
} |
1670 |
|
|
1671 |
|
/** |
1672 |
< |
* Pop and shutdown excessive spare threads. Call only while |
1672 |
> |
* Pops and shuts down excessive spare threads. Call only while |
1673 |
|
* holding lock. This is not guaranteed to eliminate all excess |
1674 |
|
* threads, only those suspended as spares, which are the ones |
1675 |
|
* unlikely to be needed in the future. |
1692 |
|
} |
1693 |
|
|
1694 |
|
/** |
1580 |
– |
* Returns approximate number of spares, just for diagnostics. |
1581 |
– |
*/ |
1582 |
– |
private int countSpares() { |
1583 |
– |
int sum = 0; |
1584 |
– |
for (WaitQueueNode q = spareStack; q != null; q = q.next) |
1585 |
– |
++sum; |
1586 |
– |
return sum; |
1587 |
– |
} |
1588 |
– |
|
1589 |
– |
/** |
1695 |
|
* Interface for extending managed parallelism for tasks running |
1696 |
|
* in ForkJoinPools. A ManagedBlocker provides two methods. |
1697 |
< |
* Method <code>isReleasable</code> must return true if blocking is not |
1698 |
< |
* necessary. Method <code>block</code> blocks the current thread |
1697 |
> |
* Method {@code isReleasable} must return true if blocking is not |
1698 |
> |
* necessary. Method {@code block} blocks the current thread |
1699 |
|
* if necessary (perhaps internally invoking isReleasable before |
1700 |
|
* actually blocking.). |
1701 |
|
* <p>For example, here is a ManagedBlocker based on a |
1721 |
|
* Possibly blocks the current thread, for example waiting for |
1722 |
|
* a lock or condition. |
1723 |
|
* @return true if no additional blocking is necessary (i.e., |
1724 |
< |
* if isReleasable would return true). |
1724 |
> |
* if isReleasable would return true) |
1725 |
|
* @throws InterruptedException if interrupted while waiting |
1726 |
< |
* (the method is not required to do so, but is allowe to). |
1726 |
> |
* (the method is not required to do so, but is allowed to). |
1727 |
|
*/ |
1728 |
|
boolean block() throws InterruptedException; |
1729 |
|
|
1738 |
|
* is a ForkJoinWorkerThread, this method possibly arranges for a |
1739 |
|
* spare thread to be activated if necessary to ensure parallelism |
1740 |
|
* while the current thread is blocked. If |
1741 |
< |
* <code>maintainParallelism</code> is true and the pool supports |
1741 |
> |
* {@code maintainParallelism} is true and the pool supports |
1742 |
|
* it ({@link #getMaintainsParallelism}), this method attempts to |
1743 |
|
* maintain the pool's nominal parallelism. Otherwise if activates |
1744 |
|
* a thread only if necessary to avoid complete starvation. This |
1760 |
|
* attempt to maintain the pool's nominal parallelism; otherwise |
1761 |
|
* activate a thread only if necessary to avoid complete |
1762 |
|
* starvation. |
1763 |
< |
* @throws InterruptedException if blocker.block did so. |
1763 |
> |
* @throws InterruptedException if blocker.block did so |
1764 |
|
*/ |
1765 |
|
public static void managedBlock(ManagedBlocker blocker, |
1766 |
|
boolean maintainParallelism) |
1797 |
|
|
1798 |
|
|
1799 |
|
// Temporary Unsafe mechanics for preliminary release |
1800 |
+ |
private static Unsafe getUnsafe() throws Throwable { |
1801 |
+ |
try { |
1802 |
+ |
return Unsafe.getUnsafe(); |
1803 |
+ |
} catch (SecurityException se) { |
1804 |
+ |
try { |
1805 |
+ |
return java.security.AccessController.doPrivileged |
1806 |
+ |
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
1807 |
+ |
public Unsafe run() throws Exception { |
1808 |
+ |
return getUnsafePrivileged(); |
1809 |
+ |
}}); |
1810 |
+ |
} catch (java.security.PrivilegedActionException e) { |
1811 |
+ |
throw e.getCause(); |
1812 |
+ |
} |
1813 |
+ |
} |
1814 |
+ |
} |
1815 |
+ |
|
1816 |
+ |
private static Unsafe getUnsafePrivileged() |
1817 |
+ |
throws NoSuchFieldException, IllegalAccessException { |
1818 |
+ |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
1819 |
+ |
f.setAccessible(true); |
1820 |
+ |
return (Unsafe) f.get(null); |
1821 |
+ |
} |
1822 |
+ |
|
1823 |
+ |
private static long fieldOffset(String fieldName) |
1824 |
+ |
throws NoSuchFieldException { |
1825 |
+ |
return UNSAFE.objectFieldOffset |
1826 |
+ |
(ForkJoinPool.class.getDeclaredField(fieldName)); |
1827 |
+ |
} |
1828 |
|
|
1829 |
< |
static final Unsafe _unsafe; |
1829 |
> |
static final Unsafe UNSAFE; |
1830 |
|
static final long eventCountOffset; |
1831 |
|
static final long workerCountsOffset; |
1832 |
|
static final long runControlOffset; |
1833 |
< |
static final long barrierStackOffset; |
1833 |
> |
static final long syncStackOffset; |
1834 |
|
static final long spareStackOffset; |
1835 |
|
|
1836 |
|
static { |
1837 |
|
try { |
1838 |
< |
if (ForkJoinPool.class.getClassLoader() != null) { |
1839 |
< |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
1840 |
< |
f.setAccessible(true); |
1841 |
< |
_unsafe = (Unsafe)f.get(null); |
1842 |
< |
} |
1843 |
< |
else |
1844 |
< |
_unsafe = Unsafe.getUnsafe(); |
1712 |
< |
eventCountOffset = _unsafe.objectFieldOffset |
1713 |
< |
(ForkJoinPool.class.getDeclaredField("eventCount")); |
1714 |
< |
workerCountsOffset = _unsafe.objectFieldOffset |
1715 |
< |
(ForkJoinPool.class.getDeclaredField("workerCounts")); |
1716 |
< |
runControlOffset = _unsafe.objectFieldOffset |
1717 |
< |
(ForkJoinPool.class.getDeclaredField("runControl")); |
1718 |
< |
barrierStackOffset = _unsafe.objectFieldOffset |
1719 |
< |
(ForkJoinPool.class.getDeclaredField("barrierStack")); |
1720 |
< |
spareStackOffset = _unsafe.objectFieldOffset |
1721 |
< |
(ForkJoinPool.class.getDeclaredField("spareStack")); |
1722 |
< |
} catch (Exception e) { |
1838 |
> |
UNSAFE = getUnsafe(); |
1839 |
> |
eventCountOffset = fieldOffset("eventCount"); |
1840 |
> |
workerCountsOffset = fieldOffset("workerCounts"); |
1841 |
> |
runControlOffset = fieldOffset("runControl"); |
1842 |
> |
syncStackOffset = fieldOffset("syncStack"); |
1843 |
> |
spareStackOffset = fieldOffset("spareStack"); |
1844 |
> |
} catch (Throwable e) { |
1845 |
|
throw new RuntimeException("Could not initialize intrinsics", e); |
1846 |
|
} |
1847 |
|
} |
1848 |
|
|
1849 |
|
private boolean casEventCount(long cmp, long val) { |
1850 |
< |
return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val); |
1850 |
> |
return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val); |
1851 |
|
} |
1852 |
|
private boolean casWorkerCounts(int cmp, int val) { |
1853 |
< |
return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val); |
1853 |
> |
return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val); |
1854 |
|
} |
1855 |
|
private boolean casRunControl(int cmp, int val) { |
1856 |
< |
return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val); |
1856 |
> |
return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val); |
1857 |
|
} |
1858 |
|
private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) { |
1859 |
< |
return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val); |
1859 |
> |
return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val); |
1860 |
|
} |
1861 |
|
private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) { |
1862 |
< |
return _unsafe.compareAndSwapObject(this, barrierStackOffset, cmp, val); |
1862 |
> |
return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val); |
1863 |
|
} |
1864 |
|
} |