5 |
|
*/ |
6 |
|
|
7 |
|
package jsr166e; |
8 |
+ |
|
9 |
|
import java.util.ArrayList; |
10 |
|
import java.util.Arrays; |
11 |
|
import java.util.Collection; |
18 |
|
import java.util.concurrent.Future; |
19 |
|
import java.util.concurrent.RejectedExecutionException; |
20 |
|
import java.util.concurrent.RunnableFuture; |
21 |
+ |
import java.util.concurrent.ThreadLocalRandom; |
22 |
|
import java.util.concurrent.TimeUnit; |
23 |
|
import java.util.concurrent.atomic.AtomicInteger; |
24 |
|
import java.util.concurrent.atomic.AtomicLong; |
43 |
|
* ForkJoinPool}s may also be appropriate for use with event-style |
44 |
|
* tasks that are never joined. |
45 |
|
* |
46 |
< |
* <p>A {@code ForkJoinPool} is constructed with a given target |
47 |
< |
* parallelism level; by default, equal to the number of available |
48 |
< |
* processors. The pool attempts to maintain enough active (or |
49 |
< |
* available) threads by dynamically adding, suspending, or resuming |
50 |
< |
* internal worker threads, even if some tasks are stalled waiting to |
51 |
< |
* join others. However, no such adjustments are guaranteed in the |
52 |
< |
* face of blocked IO or other unmanaged synchronization. The nested |
53 |
< |
* {@link ManagedBlocker} interface enables extension of the kinds of |
46 |
> |
* <p>A static {@link #commonPool} is available and appropriate for |
47 |
> |
* most applications. The common pool is used by any ForkJoinTask that |
48 |
> |
* is not explicitly submitted to a specified pool. Using the common |
49 |
> |
* pool normally reduces resource usage (its threads are slowly |
50 |
> |
* reclaimed during periods of non-use, and reinstated upon subsequent |
51 |
> |
* use). The common pool is by default constructed with default |
52 |
> |
* parameters, but these may be controlled by setting any or all of |
53 |
> |
* the three properties {@code |
54 |
> |
* java.util.concurrent.ForkJoinPool.common.{parallelism, |
55 |
> |
* threadFactory, exceptionHandler}}. |
56 |
> |
* |
57 |
> |
* <p>For applications that require separate or custom pools, a {@code |
58 |
> |
* ForkJoinPool} may be constructed with a given target parallelism |
59 |
> |
* level; by default, equal to the number of available processors. The |
60 |
> |
* pool attempts to maintain enough active (or available) threads by |
61 |
> |
* dynamically adding, suspending, or resuming internal worker |
62 |
> |
* threads, even if some tasks are stalled waiting to join |
63 |
> |
* others. However, no such adjustments are guaranteed in the face of |
64 |
> |
* blocked IO or other unmanaged synchronization. The nested {@link |
65 |
> |
* ManagedBlocker} interface enables extension of the kinds of |
66 |
|
* synchronization accommodated. |
67 |
|
* |
68 |
|
* <p>In addition to execution and lifecycle control methods, this |
107 |
|
* </tr> |
108 |
|
* </table> |
109 |
|
* |
96 |
– |
* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is |
97 |
– |
* used for all parallel task execution in a program or subsystem. |
98 |
– |
* Otherwise, use would not usually outweigh the construction and |
99 |
– |
* bookkeeping overhead of creating a large set of threads. For |
100 |
– |
* example, a common pool could be used for the {@code SortTasks} |
101 |
– |
* illustrated in {@link RecursiveAction}. Because {@code |
102 |
– |
* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon |
103 |
– |
* daemon} mode, there is typically no need to explicitly {@link |
104 |
– |
* #shutdown} such a pool upon program exit. |
105 |
– |
* |
106 |
– |
* <pre> {@code |
107 |
– |
* static final ForkJoinPool mainPool = new ForkJoinPool(); |
108 |
– |
* ... |
109 |
– |
* public void sort(long[] array) { |
110 |
– |
* mainPool.invoke(new SortTask(array, 0, array.length)); |
111 |
– |
* }}</pre> |
112 |
– |
* |
110 |
|
* <p><b>Implementation notes</b>: This implementation restricts the |
111 |
|
* maximum number of running threads to 32767. Attempts to create |
112 |
|
* pools with greater than the maximum number result in |
236 |
|
* when locked remains available to check consistency. |
237 |
|
* |
238 |
|
* Recording WorkQueues. WorkQueues are recorded in the |
239 |
< |
* "workQueues" array that is created upon pool construction and |
240 |
< |
* expanded if necessary. Updates to the array while recording |
241 |
< |
* new workers and unrecording terminated ones are protected from |
242 |
< |
* each other by a lock but the array is otherwise concurrently |
243 |
< |
* readable, and accessed directly. To simplify index-based |
244 |
< |
* operations, the array size is always a power of two, and all |
245 |
< |
* readers must tolerate null slots. Shared (submission) queues |
246 |
< |
* are at even indices, worker queues at odd indices. Grouping |
247 |
< |
* them together in this way simplifies and speeds up task |
251 |
< |
* scanning. |
239 |
> |
* "workQueues" array that is created upon first use and expanded |
240 |
> |
* if necessary. Updates to the array while recording new workers |
241 |
> |
* and unrecording terminated ones are protected from each other |
242 |
> |
* by a lock but the array is otherwise concurrently readable, and |
243 |
> |
* accessed directly. To simplify index-based operations, the |
244 |
> |
* array size is always a power of two, and all readers must |
245 |
> |
* tolerate null slots. Shared (submission) queues are at even |
246 |
> |
* indices, worker queues at odd indices. Grouping them together |
247 |
> |
* in this way simplifies and speeds up task scanning. |
248 |
|
* |
249 |
|
* All worker thread creation is on-demand, triggered by task |
250 |
|
* submissions, replacement of terminated workers, and/or |
316 |
|
* |
317 |
|
* Trimming workers. To release resources after periods of lack of |
318 |
|
* use, a worker starting to wait when the pool is quiescent will |
319 |
< |
* time out and terminate if the pool has remained quiescent for |
320 |
< |
* SHRINK_RATE nanosecs. This will slowly propagate, eventually |
321 |
< |
* terminating all workers after long periods of non-use. |
319 |
> |
* time out and terminate if the pool has remained quiescent for a |
320 |
> |
* given period -- a short period if there are more threads than |
321 |
> |
* parallelism, longer as the number of threads decreases. This |
322 |
> |
* will slowly propagate, eventually terminating all workers after |
323 |
> |
* periods of non-use. |
324 |
|
* |
325 |
|
* Shutdown and Termination. A call to shutdownNow atomically sets |
326 |
|
* a runState bit and then (non-atomically) sets each worker's |
502 |
|
} |
503 |
|
|
504 |
|
/** |
507 |
– |
* A simple non-reentrant lock used for exclusion when managing |
508 |
– |
* queues and workers. We use a custom lock so that we can readily |
509 |
– |
* probe lock state in constructions that check among alternative |
510 |
– |
* actions. The lock is normally only very briefly held, and |
511 |
– |
* sometimes treated as a spinlock, but other usages block to |
512 |
– |
* reduce overall contention in those cases where locked code |
513 |
– |
* bodies perform allocation/resizing. |
514 |
– |
*/ |
515 |
– |
static final class Mutex extends AbstractQueuedSynchronizer { |
516 |
– |
public final boolean tryAcquire(int ignore) { |
517 |
– |
return compareAndSetState(0, 1); |
518 |
– |
} |
519 |
– |
public final boolean tryRelease(int ignore) { |
520 |
– |
setState(0); |
521 |
– |
return true; |
522 |
– |
} |
523 |
– |
public final void lock() { acquire(0); } |
524 |
– |
public final void unlock() { release(0); } |
525 |
– |
public final boolean isHeldExclusively() { return getState() == 1; } |
526 |
– |
public final Condition newCondition() { return new ConditionObject(); } |
527 |
– |
} |
528 |
– |
|
529 |
– |
/** |
505 |
|
* Class for artificial tasks that are used to replace the target |
506 |
|
* of local joins if they are removed from an interior queue slot |
507 |
|
* in WorkQueue.tryRemoveAndExec. We don't need the proxy to |
788 |
|
} |
789 |
|
|
790 |
|
/** |
791 |
+ |
* Version of tryUnpush for shared queues; called by non-FJ |
792 |
+ |
* submitters after prechecking that task probably exists. |
793 |
+ |
*/ |
794 |
+ |
final boolean trySharedUnpush(ForkJoinTask<?> t) { |
795 |
+ |
boolean success = false; |
796 |
+ |
if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) { |
797 |
+ |
try { |
798 |
+ |
ForkJoinTask<?>[] a; int s; |
799 |
+ |
if ((a = array) != null && (s = top) != base && |
800 |
+ |
U.compareAndSwapObject |
801 |
+ |
(a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) { |
802 |
+ |
top = s; |
803 |
+ |
success = true; |
804 |
+ |
} |
805 |
+ |
} finally { |
806 |
+ |
runState = 0; // unlock |
807 |
+ |
} |
808 |
+ |
} |
809 |
+ |
return success; |
810 |
+ |
} |
811 |
+ |
|
812 |
+ |
/** |
813 |
|
* Polls the given task only if it is at the current base. |
814 |
|
*/ |
815 |
|
final boolean pollFor(ForkJoinTask<?> task) { |
1044 |
|
ASHIFT = 31 - Integer.numberOfLeadingZeros(s); |
1045 |
|
} |
1046 |
|
} |
1047 |
+ |
|
1048 |
|
/** |
1049 |
|
* Per-thread records for threads that submit to pools. Currently |
1050 |
|
* holds only pseudo-random seed / index that is used to choose |
1083 |
|
public static final ForkJoinWorkerThreadFactory |
1084 |
|
defaultForkJoinWorkerThreadFactory; |
1085 |
|
|
1086 |
+ |
|
1087 |
+ |
/** Property prefix for constructing common pool */ |
1088 |
+ |
private static final String propPrefix = |
1089 |
+ |
"java.util.concurrent.ForkJoinPool.common."; |
1090 |
+ |
|
1091 |
+ |
/** |
1092 |
+ |
* Common (static) pool. Non-null for public use unless a static |
1093 |
+ |
* construction exception, but internal usages must null-check on |
1094 |
+ |
* use. |
1095 |
+ |
*/ |
1096 |
+ |
static final ForkJoinPool commonPool; |
1097 |
+ |
|
1098 |
+ |
/** |
1099 |
+ |
* Common pool parallelism. Must equal commonPool.parallelism. |
1100 |
+ |
*/ |
1101 |
+ |
static final int commonPoolParallelism; |
1102 |
+ |
|
1103 |
|
/** |
1104 |
|
* Generator for assigning sequence numbers as pool names. |
1105 |
|
*/ |
1127 |
|
// static constants |
1128 |
|
|
1129 |
|
/** |
1130 |
< |
* The wakeup interval (in nanoseconds) for a worker waiting for a |
1131 |
< |
* task when the pool is quiescent to instead try to shrink the |
1132 |
< |
* number of workers. The exact value does not matter too |
1118 |
< |
* much. It must be short enough to release resources during |
1119 |
< |
* sustained periods of idleness, but not so short that threads |
1120 |
< |
* are continually re-created. |
1130 |
> |
* Initial timeout value (in nanoseconds) for the thread triggering |
1131 |
> |
* quiescence to park waiting for new work. On timeout, the thread |
1132 |
> |
* will instead try to shrink the number of workers. |
1133 |
|
*/ |
1134 |
< |
private static final long SHRINK_RATE = |
1123 |
< |
4L * 1000L * 1000L * 1000L; // 4 seconds |
1134 |
> |
private static final long IDLE_TIMEOUT = 1000L * 1000L * 1000L; // 1sec |
1135 |
|
|
1136 |
|
/** |
1137 |
< |
* The timeout value for attempted shrinkage, includes |
1127 |
< |
* some slop to cope with system timer imprecision. |
1137 |
> |
* Timeout value when there are more threads than parallelism level |
1138 |
|
*/ |
1139 |
< |
private static final long SHRINK_TIMEOUT = SHRINK_RATE - (SHRINK_RATE / 10); |
1139 |
> |
private static final long FAST_IDLE_TIMEOUT = 100L * 1000L * 1000L; |
1140 |
|
|
1141 |
|
/** |
1142 |
|
* The maximum stolen->joining link depth allowed in method |
1256 |
|
* empirically works OK on current JVMs. |
1257 |
|
*/ |
1258 |
|
|
1259 |
+ |
volatile long stealCount; // collects worker counts |
1260 |
|
volatile long ctl; // main pool control |
1261 |
|
final int parallelism; // parallelism level |
1262 |
|
final int localMode; // per-worker scheduling mode |
1263 |
+ |
volatile int nextWorkerNumber; // to create worker name string |
1264 |
|
final int submitMask; // submit queue index bound |
1265 |
|
int nextSeed; // for initializing worker seeds |
1266 |
+ |
volatile int mainLock; // spinlock for array updates |
1267 |
|
volatile int runState; // shutdown status and seq |
1268 |
|
WorkQueue[] workQueues; // main registry |
1256 |
– |
final Mutex lock; // for registration |
1257 |
– |
final Condition termination; // for awaitTermination |
1269 |
|
final ForkJoinWorkerThreadFactory factory; // factory for new workers |
1270 |
|
final Thread.UncaughtExceptionHandler ueh; // per-worker UEH |
1260 |
– |
final AtomicLong stealCount; // collect counts when terminated |
1261 |
– |
final AtomicInteger nextWorkerNumber; // to create worker name string |
1271 |
|
final String workerNamePrefix; // to create worker name string |
1272 |
|
|
1273 |
+ |
/* |
1274 |
+ |
* Mechanics for main lock protecting worker array updates. Uses |
1275 |
+ |
* the same strategy as ConcurrentHashMap bins -- a spinLock for |
1276 |
+ |
* normal cases, but falling back to builtin lock when (rarely) |
1277 |
+ |
* needed. See internal ConcurrentHashMap documentation for |
1278 |
+ |
* explanation. |
1279 |
+ |
*/ |
1280 |
+ |
|
1281 |
+ |
static final int LOCK_WAITING = 2; // bit to indicate need for signal |
1282 |
+ |
static final int MAX_LOCK_SPINS = 1 << 8; |
1283 |
+ |
|
1284 |
+ |
private void tryAwaitMainLock() { |
1285 |
+ |
int spins = MAX_LOCK_SPINS, r = 0, h; |
1286 |
+ |
while (((h = mainLock) & 1) != 0) { |
1287 |
+ |
if (r == 0) |
1288 |
+ |
r = ThreadLocalRandom.current().nextInt(); // randomize spins |
1289 |
+ |
else if (spins >= 0) { |
1290 |
+ |
r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift |
1291 |
+ |
if (r >= 0) |
1292 |
+ |
--spins; |
1293 |
+ |
} |
1294 |
+ |
else if (U.compareAndSwapInt(this, MAINLOCK, h, h | LOCK_WAITING)) { |
1295 |
+ |
synchronized (this) { |
1296 |
+ |
if ((mainLock & LOCK_WAITING) != 0) { |
1297 |
+ |
try { |
1298 |
+ |
wait(); |
1299 |
+ |
} catch (InterruptedException ie) { |
1300 |
+ |
Thread.currentThread().interrupt(); |
1301 |
+ |
} |
1302 |
+ |
} |
1303 |
+ |
else |
1304 |
+ |
notifyAll(); // possibly won race vs signaller |
1305 |
+ |
} |
1306 |
+ |
break; |
1307 |
+ |
} |
1308 |
+ |
} |
1309 |
+ |
} |
1310 |
+ |
|
1311 |
|
// Creating, registering, and deregistering workers |
1312 |
|
|
1313 |
|
/** |
1334 |
|
* ForkJoinWorkerThread. |
1335 |
|
*/ |
1336 |
|
final String nextWorkerName() { |
1337 |
< |
return workerNamePrefix.concat |
1338 |
< |
(Integer.toString(nextWorkerNumber.addAndGet(1))); |
1337 |
> |
int n; |
1338 |
> |
do {} while(!U.compareAndSwapInt(this, NEXTWORKERNUMBER, |
1339 |
> |
n = nextWorkerNumber, ++n)); |
1340 |
> |
return workerNamePrefix.concat(Integer.toString(n)); |
1341 |
|
} |
1342 |
|
|
1343 |
|
/** |
1349 |
|
* |
1350 |
|
* @param w the worker's queue |
1351 |
|
*/ |
1303 |
– |
|
1352 |
|
final void registerWorker(WorkQueue w) { |
1353 |
< |
Mutex lock = this.lock; |
1354 |
< |
lock.lock(); |
1353 |
> |
while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1)) |
1354 |
> |
tryAwaitMainLock(); |
1355 |
|
try { |
1356 |
< |
WorkQueue[] ws = workQueues; |
1357 |
< |
if (w != null && ws != null) { // skip on shutdown/failure |
1356 |
> |
WorkQueue[] ws; |
1357 |
> |
if ((ws = workQueues) == null) |
1358 |
> |
ws = workQueues = new WorkQueue[submitMask + 1]; |
1359 |
> |
if (w != null) { |
1360 |
|
int rs, n = ws.length, m = n - 1; |
1361 |
|
int s = nextSeed += SEED_INCREMENT; // rarely-colliding sequence |
1362 |
|
w.seed = (s == 0) ? 1 : s; // ensure non-zero seed |
1377 |
|
runState = ((rs = runState) & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN); |
1378 |
|
} |
1379 |
|
} finally { |
1380 |
< |
lock.unlock(); |
1380 |
> |
if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) { |
1381 |
> |
mainLock = 0; |
1382 |
> |
synchronized (this) { notifyAll(); }; |
1383 |
> |
} |
1384 |
|
} |
1385 |
+ |
|
1386 |
|
} |
1387 |
|
|
1388 |
|
/** |
1395 |
|
* @param ex the exception causing failure, or null if none |
1396 |
|
*/ |
1397 |
|
final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) { |
1344 |
– |
Mutex lock = this.lock; |
1398 |
|
WorkQueue w = null; |
1399 |
|
if (wt != null && (w = wt.workQueue) != null) { |
1400 |
|
w.runState = -1; // ensure runState is set |
1401 |
< |
stealCount.getAndAdd(w.totalSteals + w.nsteals); |
1401 |
> |
long steals = w.totalSteals + w.nsteals, sc; |
1402 |
> |
do {} while(!U.compareAndSwapLong(this, STEALCOUNT, |
1403 |
> |
sc = stealCount, sc + steals)); |
1404 |
|
int idx = w.poolIndex; |
1405 |
< |
lock.lock(); |
1406 |
< |
try { // remove record from array |
1405 |
> |
while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1)) |
1406 |
> |
tryAwaitMainLock(); |
1407 |
> |
try { |
1408 |
|
WorkQueue[] ws = workQueues; |
1409 |
|
if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w) |
1410 |
|
ws[idx] = null; |
1411 |
|
} finally { |
1412 |
< |
lock.unlock(); |
1412 |
> |
if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) { |
1413 |
> |
mainLock = 0; |
1414 |
> |
synchronized (this) { notifyAll(); }; |
1415 |
> |
} |
1416 |
|
} |
1417 |
|
} |
1418 |
|
|
1434 |
|
U.throwException(ex); |
1435 |
|
} |
1436 |
|
|
1378 |
– |
|
1437 |
|
// Submissions |
1438 |
|
|
1439 |
|
/** |
1451 |
|
for (int r = s.seed, m = submitMask;;) { |
1452 |
|
WorkQueue[] ws; WorkQueue q; |
1453 |
|
int k = r & m & SQMASK; // use only even indices |
1454 |
< |
if (runState < 0 || (ws = workQueues) == null || ws.length <= k) |
1454 |
> |
if (runState < 0) |
1455 |
|
throw new RejectedExecutionException(); // shutting down |
1456 |
+ |
else if ((ws = workQueues) == null || ws.length <= k) { |
1457 |
+ |
while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1)) |
1458 |
+ |
tryAwaitMainLock(); |
1459 |
+ |
try { |
1460 |
+ |
if (workQueues == null) |
1461 |
+ |
workQueues = new WorkQueue[submitMask + 1]; |
1462 |
+ |
} finally { |
1463 |
+ |
if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) { |
1464 |
+ |
mainLock = 0; |
1465 |
+ |
synchronized (this) { notifyAll(); }; |
1466 |
+ |
} |
1467 |
+ |
} |
1468 |
+ |
} |
1469 |
|
else if ((q = ws[k]) == null) { // create new queue |
1470 |
|
WorkQueue nq = new WorkQueue(this, null, SHARED_QUEUE); |
1471 |
< |
Mutex lock = this.lock; // construct outside lock |
1472 |
< |
lock.lock(); |
1473 |
< |
try { // recheck under lock |
1471 |
> |
while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1)) |
1472 |
> |
tryAwaitMainLock(); |
1473 |
> |
try { |
1474 |
|
int rs = runState; // to update seq |
1475 |
|
if (ws == workQueues && ws[k] == null) { |
1476 |
|
ws[k] = nq; |
1477 |
|
runState = ((rs & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN)); |
1478 |
|
} |
1479 |
|
} finally { |
1480 |
< |
lock.unlock(); |
1480 |
> |
if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) { |
1481 |
> |
mainLock = 0; |
1482 |
> |
synchronized (this) { notifyAll(); }; |
1483 |
> |
} |
1484 |
|
} |
1485 |
|
} |
1486 |
|
else if (q.trySharedPush(task)) { |
1497 |
|
} |
1498 |
|
} |
1499 |
|
|
1500 |
+ |
/** |
1501 |
+ |
* Submits the given (non-null) task to the common pool, if possible. |
1502 |
+ |
*/ |
1503 |
+ |
static void submitToCommonPool(ForkJoinTask<?> task) { |
1504 |
+ |
ForkJoinPool p; |
1505 |
+ |
if ((p = commonPool) == null) |
1506 |
+ |
throw new RejectedExecutionException("Common Pool Unavailable"); |
1507 |
+ |
p.doSubmit(task); |
1508 |
+ |
} |
1509 |
+ |
|
1510 |
+ |
/** |
1511 |
+ |
* Returns true if the given task was submitted to common pool |
1512 |
+ |
* and has not yet commenced execution, and is available for |
1513 |
+ |
* removal according to execution policies; if so removing the |
1514 |
+ |
* submission from the pool. |
1515 |
+ |
* |
1516 |
+ |
* @param task the task |
1517 |
+ |
* @return true if successful |
1518 |
+ |
*/ |
1519 |
+ |
static boolean tryUnsubmitFromCommonPool(ForkJoinTask<?> task) { |
1520 |
+ |
// Peek, looking for task and eligibility before |
1521 |
+ |
// using trySharedUnpush to actually take it under lock |
1522 |
+ |
ForkJoinPool p; WorkQueue[] ws; WorkQueue q; |
1523 |
+ |
ForkJoinTask<?>[] a; int t, s, n; |
1524 |
+ |
int k = submitters.get().seed & SQMASK; |
1525 |
+ |
return ((p = commonPool) != null && |
1526 |
+ |
(ws = p.workQueues) != null && |
1527 |
+ |
ws.length > (k &= p.submitMask) && |
1528 |
+ |
(q = ws[k]) != null && |
1529 |
+ |
(a = q.array) != null && |
1530 |
+ |
(n = (t = q.top) - q.base) > 0 && |
1531 |
+ |
(n > 1 || (int)(p.ctl >> AC_SHIFT) < 0) && |
1532 |
+ |
(s = t - 1) >= 0 && s < a.length && a[s] == task && |
1533 |
+ |
q.trySharedUnpush(task)); |
1534 |
+ |
} |
1535 |
+ |
|
1536 |
|
// Maintaining ctl counts |
1537 |
|
|
1538 |
|
/** |
1544 |
|
} |
1545 |
|
|
1546 |
|
/** |
1547 |
< |
* Tries to activate or create a worker if too few are active. |
1547 |
> |
* Tries to create one or activate one or more workers if too few are active. |
1548 |
|
*/ |
1549 |
|
final void signalWork() { |
1550 |
|
long c; int u; |
1628 |
|
* awaiting signal, |
1629 |
|
* |
1630 |
|
* @param w the worker (via its WorkQueue) |
1631 |
< |
* @return a task or null of none found |
1631 |
> |
* @return a task or null if none found |
1632 |
|
*/ |
1633 |
|
private final ForkJoinTask<?> scan(WorkQueue w) { |
1634 |
|
WorkQueue[] ws; // first update random seed |
1645 |
|
t = (ForkJoinTask<?>)U.getObjectVolatile(a, i); |
1646 |
|
if (q.base == b && ec >= 0 && t != null && |
1647 |
|
U.compareAndSwapObject(a, i, t, null)) { |
1648 |
< |
if (q.top - (q.base = b + 1) > 1) |
1648 |
> |
if (q.top - (q.base = b + 1) > 0) |
1649 |
|
signalWork(); // help pushes signal |
1650 |
|
return t; |
1651 |
|
} |
1691 |
|
} |
1692 |
|
} |
1693 |
|
else if (w.eventCount < 0) { // already queued |
1694 |
< |
if ((nr = w.rescans) > 0) { // continue rescanning |
1695 |
< |
int ac = a + parallelism; |
1696 |
< |
if (((w.rescans = (ac < nr) ? ac : nr - 1) & 3) == 0) |
1697 |
< |
Thread.yield(); // yield before block |
1588 |
< |
} |
1589 |
< |
else { |
1694 |
> |
int ac = a + parallelism; |
1695 |
> |
if ((nr = w.rescans) > 0) // continue rescanning |
1696 |
> |
w.rescans = (ac < nr) ? ac : nr - 1; |
1697 |
> |
else if (((w.seed >>> 16) & ac) == 0) { // randomize park |
1698 |
|
Thread.interrupted(); // clear status |
1699 |
|
Thread wt = Thread.currentThread(); |
1700 |
|
U.putObject(wt, PARKBLOCKER, this); |
1712 |
|
/** |
1713 |
|
* If inactivating worker w has caused the pool to become |
1714 |
|
* quiescent, checks for pool termination, and, so long as this is |
1715 |
< |
* not the only worker, waits for event for up to SHRINK_RATE |
1716 |
< |
* nanosecs. On timeout, if ctl has not changed, terminates the |
1715 |
> |
* not the only worker, waits for event for up to a given |
1716 |
> |
* duration. On timeout, if ctl has not changed, terminates the |
1717 |
|
* worker, which will in turn wake up another worker to possibly |
1718 |
|
* repeat this process. |
1719 |
|
* |
1724 |
|
private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) { |
1725 |
|
if (w.eventCount < 0 && !tryTerminate(false, false) && |
1726 |
|
(int)prevCtl != 0 && !hasQueuedSubmissions() && ctl == currentCtl) { |
1727 |
+ |
int dc = -(short)(currentCtl >>> TC_SHIFT); |
1728 |
+ |
long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT; |
1729 |
+ |
long deadline = System.nanoTime() + parkTime - 100000L; // 1ms slop |
1730 |
|
Thread wt = Thread.currentThread(); |
1620 |
– |
Thread.yield(); // yield before block |
1731 |
|
while (ctl == currentCtl) { |
1622 |
– |
long startTime = System.nanoTime(); |
1732 |
|
Thread.interrupted(); // timed variant of version in scan() |
1733 |
|
U.putObject(wt, PARKBLOCKER, this); |
1734 |
|
w.parker = wt; |
1735 |
|
if (ctl == currentCtl) |
1736 |
< |
U.park(false, SHRINK_RATE); |
1736 |
> |
U.park(false, parkTime); |
1737 |
|
w.parker = null; |
1738 |
|
U.putObject(wt, PARKBLOCKER, null); |
1739 |
|
if (ctl != currentCtl) |
1740 |
|
break; |
1741 |
< |
if (System.nanoTime() - startTime >= SHRINK_TIMEOUT && |
1741 |
> |
if (deadline - System.nanoTime() <= 0L && |
1742 |
|
U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) { |
1743 |
|
w.eventCount = (w.eventCount + E_SEQ) | E_MASK; |
1744 |
|
w.runState = -1; // shrink |
2023 |
|
} |
2024 |
|
} |
2025 |
|
|
1917 |
– |
|
2026 |
|
/** |
2027 |
|
* Runs tasks until {@code isQuiescent()}. We piggyback on |
2028 |
|
* active count ctl maintenance, but rather than blocking |
2065 |
|
} |
2066 |
|
|
2067 |
|
/** |
2068 |
+ |
* Restricted version of helpQuiescePool for non-FJ callers |
2069 |
+ |
*/ |
2070 |
+ |
static void externalHelpQuiescePool() { |
2071 |
+ |
ForkJoinPool p; WorkQueue[] ws; WorkQueue w, q; |
2072 |
+ |
ForkJoinTask<?> t; int b; |
2073 |
+ |
int k = submitters.get().seed & SQMASK; |
2074 |
+ |
if ((p = commonPool) != null && |
2075 |
+ |
(ws = p.workQueues) != null && |
2076 |
+ |
ws.length > (k &= p.submitMask) && |
2077 |
+ |
(w = ws[k]) != null && |
2078 |
+ |
(q = p.findNonEmptyStealQueue(w)) != null && |
2079 |
+ |
(b = q.base) - q.top < 0 && |
2080 |
+ |
(t = q.pollAt(b)) != null) |
2081 |
+ |
t.doExec(); |
2082 |
+ |
} |
2083 |
+ |
|
2084 |
+ |
/** |
2085 |
|
* Gets and removes a local or stolen task for the given worker. |
2086 |
|
* |
2087 |
|
* @return a task, if available |
2114 |
|
8); |
2115 |
|
} |
2116 |
|
|
2117 |
+ |
/** |
2118 |
+ |
* Returns approximate submission queue length for the given caller |
2119 |
+ |
*/ |
2120 |
+ |
static int getEstimatedSubmitterQueueLength() { |
2121 |
+ |
ForkJoinPool p; WorkQueue[] ws; WorkQueue q; |
2122 |
+ |
int k = submitters.get().seed & SQMASK; |
2123 |
+ |
return ((p = commonPool) != null && |
2124 |
+ |
p.runState >= 0 && |
2125 |
+ |
(ws = p.workQueues) != null && |
2126 |
+ |
ws.length > (k &= p.submitMask) && |
2127 |
+ |
(q = ws[k]) != null) ? |
2128 |
+ |
q.queueSize() : 0; |
2129 |
+ |
} |
2130 |
+ |
|
2131 |
|
// Termination |
2132 |
|
|
2133 |
|
/** |
2145 |
|
* @return true if now terminating or terminated |
2146 |
|
*/ |
2147 |
|
private boolean tryTerminate(boolean now, boolean enable) { |
2009 |
– |
Mutex lock = this.lock; |
2148 |
|
for (long c;;) { |
2149 |
|
if (((c = ctl) & STOP_BIT) != 0) { // already terminating |
2150 |
|
if ((short)(c >>> TC_SHIFT) == -parallelism) { |
2151 |
< |
lock.lock(); // don't need try/finally |
2152 |
< |
termination.signalAll(); // signal when 0 workers |
2153 |
< |
lock.unlock(); |
2151 |
> |
synchronized(this) { |
2152 |
> |
notifyAll(); // signal when 0 workers |
2153 |
> |
} |
2154 |
|
} |
2155 |
|
return true; |
2156 |
|
} |
2157 |
|
if (runState >= 0) { // not yet enabled |
2158 |
|
if (!enable) |
2159 |
|
return false; |
2160 |
< |
lock.lock(); |
2161 |
< |
runState |= SHUTDOWN; |
2162 |
< |
lock.unlock(); |
2160 |
> |
while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1)) |
2161 |
> |
tryAwaitMainLock(); |
2162 |
> |
try { |
2163 |
> |
runState |= SHUTDOWN; |
2164 |
> |
} finally { |
2165 |
> |
if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) { |
2166 |
> |
mainLock = 0; |
2167 |
> |
synchronized (this) { notifyAll(); }; |
2168 |
> |
} |
2169 |
> |
} |
2170 |
|
} |
2171 |
|
if (!now) { // check if idle & no tasks |
2172 |
|
if ((int)(c >> AC_SHIFT) != -parallelism || |
2299 |
|
// Use nearest power 2 for workQueues size. See Hackers Delight sec 3.2. |
2300 |
|
int n = parallelism - 1; |
2301 |
|
n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8; n |= n >>> 16; |
2302 |
< |
int size = (n + 1) << 1; // #slots = 2*#workers |
2158 |
< |
this.submitMask = size - 1; // room for max # of submit queues |
2159 |
< |
this.workQueues = new WorkQueue[size]; |
2160 |
< |
this.termination = (this.lock = new Mutex()).newCondition(); |
2161 |
< |
this.stealCount = new AtomicLong(); |
2162 |
< |
this.nextWorkerNumber = new AtomicInteger(); |
2302 |
> |
this.submitMask = ((n + 1) << 1) - 1; |
2303 |
|
int pn = poolNumberGenerator.incrementAndGet(); |
2304 |
|
StringBuilder sb = new StringBuilder("ForkJoinPool-"); |
2305 |
|
sb.append(Integer.toString(pn)); |
2306 |
|
sb.append("-worker-"); |
2307 |
|
this.workerNamePrefix = sb.toString(); |
2168 |
– |
lock.lock(); |
2308 |
|
this.runState = 1; // set init flag |
2309 |
< |
lock.unlock(); |
2309 |
> |
} |
2310 |
> |
|
2311 |
> |
/** |
2312 |
> |
* Constructor for common pool, suitable only for static initialization. |
2313 |
> |
* Basically the same as above, but uses smallest possible initial footprint. |
2314 |
> |
*/ |
2315 |
> |
ForkJoinPool(int parallelism, int submitMask, |
2316 |
> |
ForkJoinWorkerThreadFactory factory, |
2317 |
> |
Thread.UncaughtExceptionHandler handler) { |
2318 |
> |
this.factory = factory; |
2319 |
> |
this.ueh = handler; |
2320 |
> |
this.submitMask = submitMask; |
2321 |
> |
this.parallelism = parallelism; |
2322 |
> |
long np = (long)(-parallelism); |
2323 |
> |
this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK); |
2324 |
> |
this.localMode = LIFO_QUEUE; |
2325 |
> |
this.workerNamePrefix = "ForkJoinPool.commonPool-worker-"; |
2326 |
> |
this.runState = 1; |
2327 |
> |
} |
2328 |
> |
|
2329 |
> |
/** |
2330 |
> |
* Returns the common pool instance. |
2331 |
> |
* |
2332 |
> |
* @return the common pool instance |
2333 |
> |
*/ |
2334 |
> |
public static ForkJoinPool commonPool() { |
2335 |
> |
ForkJoinPool p; |
2336 |
> |
if ((p = commonPool) == null) |
2337 |
> |
throw new Error("Common Pool Unavailable"); |
2338 |
> |
return p; |
2339 |
|
} |
2340 |
|
|
2341 |
|
// Execution methods |
2511 |
|
} |
2512 |
|
|
2513 |
|
/** |
2514 |
+ |
* Returns the targeted parallelism level of the common pool. |
2515 |
+ |
* |
2516 |
+ |
* @return the targeted parallelism level of the common pool |
2517 |
+ |
*/ |
2518 |
+ |
public static int getCommonPoolParallelism() { |
2519 |
+ |
return commonPoolParallelism; |
2520 |
+ |
} |
2521 |
+ |
|
2522 |
+ |
/** |
2523 |
|
* Returns the number of worker threads that have started but not |
2524 |
|
* yet terminated. The result returned by this method may differ |
2525 |
|
* from {@link #getParallelism} when threads are created to |
2600 |
|
* @return the number of steals |
2601 |
|
*/ |
2602 |
|
public long getStealCount() { |
2603 |
< |
long count = stealCount.get(); |
2603 |
> |
long count = stealCount; |
2604 |
|
WorkQueue[] ws; WorkQueue w; |
2605 |
|
if ((ws = workQueues) != null) { |
2606 |
|
for (int i = 1; i < ws.length; i += 2) { |
2730 |
|
public String toString() { |
2731 |
|
// Use a single pass through workQueues to collect counts |
2732 |
|
long qt = 0L, qs = 0L; int rc = 0; |
2733 |
< |
long st = stealCount.get(); |
2733 |
> |
long st = stealCount; |
2734 |
|
long c = ctl; |
2735 |
|
WorkQueue[] ws; WorkQueue w; |
2736 |
|
if ((ws = workQueues) != null) { |
2771 |
|
} |
2772 |
|
|
2773 |
|
/** |
2774 |
< |
* Initiates an orderly shutdown in which previously submitted |
2775 |
< |
* tasks are executed, but no new tasks will be accepted. |
2776 |
< |
* Invocation has no additional effect if already shut down. |
2777 |
< |
* Tasks that are in the process of being submitted concurrently |
2778 |
< |
* during the course of this method may or may not be rejected. |
2774 |
> |
* Possibly initiates an orderly shutdown in which previously |
2775 |
> |
* submitted tasks are executed, but no new tasks will be |
2776 |
> |
* accepted. Invocation has no effect on execution state if this |
2777 |
> |
* is the {@link #commonPool}, and no additional effect if |
2778 |
> |
* already shut down. Tasks that are in the process of being |
2779 |
> |
* submitted concurrently during the course of this method may or |
2780 |
> |
* may not be rejected. |
2781 |
|
* |
2782 |
|
* @throws SecurityException if a security manager exists and |
2783 |
|
* the caller is not permitted to modify threads |
2786 |
|
*/ |
2787 |
|
public void shutdown() { |
2788 |
|
checkPermission(); |
2789 |
< |
tryTerminate(false, true); |
2789 |
> |
if (this != commonPool) |
2790 |
> |
tryTerminate(false, true); |
2791 |
|
} |
2792 |
|
|
2793 |
|
/** |
2794 |
< |
* Attempts to cancel and/or stop all tasks, and reject all |
2795 |
< |
* subsequently submitted tasks. Tasks that are in the process of |
2796 |
< |
* being submitted or executed concurrently during the course of |
2797 |
< |
* this method may or may not be rejected. This method cancels |
2798 |
< |
* both existing and unexecuted tasks, in order to permit |
2799 |
< |
* termination in the presence of task dependencies. So the method |
2800 |
< |
* always returns an empty list (unlike the case for some other |
2801 |
< |
* Executors). |
2794 |
> |
* Possibly attempts to cancel and/or stop all tasks, and reject |
2795 |
> |
* all subsequently submitted tasks. Invocation has no effect on |
2796 |
> |
* execution state if this is the {@link #commonPool}, and no |
2797 |
> |
* additional effect if already shut down. Otherwise, tasks that |
2798 |
> |
* are in the process of being submitted or executed concurrently |
2799 |
> |
* during the course of this method may or may not be |
2800 |
> |
* rejected. This method cancels both existing and unexecuted |
2801 |
> |
* tasks, in order to permit termination in the presence of task |
2802 |
> |
* dependencies. So the method always returns an empty list |
2803 |
> |
* (unlike the case for some other Executors). |
2804 |
|
* |
2805 |
|
* @return an empty list |
2806 |
|
* @throws SecurityException if a security manager exists and |
2810 |
|
*/ |
2811 |
|
public List<Runnable> shutdownNow() { |
2812 |
|
checkPermission(); |
2813 |
< |
tryTerminate(true, true); |
2813 |
> |
if (this != commonPool) |
2814 |
> |
tryTerminate(true, true); |
2815 |
|
return Collections.emptyList(); |
2816 |
|
} |
2817 |
|
|
2868 |
|
public boolean awaitTermination(long timeout, TimeUnit unit) |
2869 |
|
throws InterruptedException { |
2870 |
|
long nanos = unit.toNanos(timeout); |
2871 |
< |
final Mutex lock = this.lock; |
2872 |
< |
lock.lock(); |
2873 |
< |
try { |
2874 |
< |
for (;;) { |
2875 |
< |
if (isTerminated()) |
2876 |
< |
return true; |
2877 |
< |
if (nanos <= 0) |
2878 |
< |
return false; |
2879 |
< |
nanos = termination.awaitNanos(nanos); |
2871 |
> |
if (isTerminated()) |
2872 |
> |
return true; |
2873 |
> |
long startTime = System.nanoTime(); |
2874 |
> |
boolean terminated = false; |
2875 |
> |
synchronized(this) { |
2876 |
> |
for (long waitTime = nanos, millis = 0L;;) { |
2877 |
> |
if (terminated = isTerminated() || |
2878 |
> |
waitTime <= 0L || |
2879 |
> |
(millis = unit.toMillis(waitTime)) <= 0L) |
2880 |
> |
break; |
2881 |
> |
wait(millis); |
2882 |
> |
waitTime = nanos - (System.nanoTime() - startTime); |
2883 |
|
} |
2698 |
– |
} finally { |
2699 |
– |
lock.unlock(); |
2884 |
|
} |
2885 |
+ |
return terminated; |
2886 |
|
} |
2887 |
|
|
2888 |
|
/** |
3014 |
|
private static final long PARKBLOCKER; |
3015 |
|
private static final int ABASE; |
3016 |
|
private static final int ASHIFT; |
3017 |
+ |
private static final long NEXTWORKERNUMBER; |
3018 |
+ |
private static final long STEALCOUNT; |
3019 |
+ |
private static final long MAINLOCK; |
3020 |
|
|
3021 |
|
static { |
3022 |
|
poolNumberGenerator = new AtomicInteger(); |
3032 |
|
Class<?> ak = ForkJoinTask[].class; |
3033 |
|
CTL = U.objectFieldOffset |
3034 |
|
(k.getDeclaredField("ctl")); |
3035 |
+ |
NEXTWORKERNUMBER = U.objectFieldOffset |
3036 |
+ |
(k.getDeclaredField("nextWorkerNumber")); |
3037 |
+ |
STEALCOUNT = U.objectFieldOffset |
3038 |
+ |
(k.getDeclaredField("stealCount")); |
3039 |
+ |
MAINLOCK = U.objectFieldOffset |
3040 |
+ |
(k.getDeclaredField("mainLock")); |
3041 |
|
Class<?> tk = Thread.class; |
3042 |
|
PARKBLOCKER = U.objectFieldOffset |
3043 |
|
(tk.getDeclaredField("parkBlocker")); |
3044 |
|
ABASE = U.arrayBaseOffset(ak); |
3045 |
|
s = U.arrayIndexScale(ak); |
3046 |
+ |
ASHIFT = 31 - Integer.numberOfLeadingZeros(s); |
3047 |
|
} catch (Exception e) { |
3048 |
|
throw new Error(e); |
3049 |
|
} |
3050 |
|
if ((s & (s-1)) != 0) |
3051 |
|
throw new Error("data type scale not a power of two"); |
3052 |
< |
ASHIFT = 31 - Integer.numberOfLeadingZeros(s); |
3052 |
> |
try { // Establish common pool |
3053 |
> |
String pp = System.getProperty(propPrefix + "parallelism"); |
3054 |
> |
String fp = System.getProperty(propPrefix + "threadFactory"); |
3055 |
> |
String up = System.getProperty(propPrefix + "exceptionHandler"); |
3056 |
> |
ForkJoinWorkerThreadFactory fac = (fp == null) ? |
3057 |
> |
defaultForkJoinWorkerThreadFactory : |
3058 |
> |
((ForkJoinWorkerThreadFactory)ClassLoader. |
3059 |
> |
getSystemClassLoader().loadClass(fp).newInstance()); |
3060 |
> |
Thread.UncaughtExceptionHandler ueh = (up == null)? null : |
3061 |
> |
((Thread.UncaughtExceptionHandler)ClassLoader. |
3062 |
> |
getSystemClassLoader().loadClass(up).newInstance()); |
3063 |
> |
int par; |
3064 |
> |
if ((pp == null || (par = Integer.parseInt(pp)) <= 0)) |
3065 |
> |
par = Runtime.getRuntime().availableProcessors(); |
3066 |
> |
if (par > MAX_CAP) |
3067 |
> |
par = MAX_CAP; |
3068 |
> |
commonPoolParallelism = par; |
3069 |
> |
int n = par - 1; // precompute submit mask |
3070 |
> |
n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; |
3071 |
> |
n |= n >>> 8; n |= n >>> 16; |
3072 |
> |
int mask = ((n + 1) << 1) - 1; |
3073 |
> |
commonPool = new ForkJoinPool(par, mask, fac, ueh); |
3074 |
> |
} catch (Exception e) { |
3075 |
> |
throw new Error(e); |
3076 |
> |
} |
3077 |
|
} |
3078 |
|
|
3079 |
|
/** |