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root/jsr166/jsr166/src/jsr166y/ForkJoinPool.java

Comparing jsr166/src/jsr166y/ForkJoinPool.java (file contents):
Revision 1.128 by dl, Mon Apr 9 13:11:44 2012 UTC vs.
Revision 1.136 by dl, Mon Oct 29 17:23:34 2012 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	+
9		import java.util.ArrayList;
10		import java.util.Arrays;
11		import java.util.Collection;
#	Line 41 | Line 42 | import java.util.concurrent.locks.Condit
42		* ForkJoinPool}s may also be appropriate for use with event-style
43		* tasks that are never joined.
44		*
45	<	* <p>A {@code ForkJoinPool} is constructed with a given target
46	<	* parallelism level; by default, equal to the number of available
47	<	* processors. The pool attempts to maintain enough active (or
48	<	* available) threads by dynamically adding, suspending, or resuming
49	<	* internal worker threads, even if some tasks are stalled waiting to
50	<	* join others. However, no such adjustments are guaranteed in the
51	<	* face of blocked IO or other unmanaged synchronization. The nested
52	<	* {@link ManagedBlocker} interface enables extension of the kinds of
45	>	* <p>A static {@link #commonPool} is available and appropriate for
46	>	* most applications. The common pool is used by any ForkJoinTask that
47	>	* is not explicitly submitted to a specified pool. Using the common
48	>	* pool normally reduces resource usage (its threads are slowly
49	>	* reclaimed during periods of non-use, and reinstated upon subsequent
50	>	* use).  The common pool is by default constructed with default
51	>	* parameters, but these may be controlled by setting any or all of
52	>	* the three properties {@code
53	>	* java.util.concurrent.ForkJoinPool.common.{parallelism,
54	>	* threadFactory, exceptionHandler}}.
55	>	*
56	>	* <p>For applications that require separate or custom pools, a {@code
57	>	* ForkJoinPool} may be constructed with a given target parallelism
58	>	* level; by default, equal to the number of available processors. The
59	>	* pool attempts to maintain enough active (or available) threads by
60	>	* dynamically adding, suspending, or resuming internal worker
61	>	* threads, even if some tasks are stalled waiting to join
62	>	* others. However, no such adjustments are guaranteed in the face of
63	>	* blocked IO or other unmanaged synchronization. The nested {@link
64	>	* ManagedBlocker} interface enables extension of the kinds of
65		* synchronization accommodated.
66		*
67		* <p>In addition to execution and lifecycle control methods, this
#	Line 93 | Line 106 | import java.util.concurrent.locks.Condit
106		*  </tr>
107		* </table>
108		*
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	–	*
109		* <p><b>Implementation notes</b>: This implementation restricts the
110		* maximum number of running threads to 32767. Attempts to create
111		* pools with greater than the maximum number result in
#	Line 239 | Line 235 | public class ForkJoinPool extends Abstra
235		* when locked remains available to check consistency.
236		*
237		* Recording WorkQueues.  WorkQueues are recorded in the
238	<	* "workQueues" array that is created upon pool construction and
239	<	* expanded if necessary.  Updates to the array while recording
240	<	* new workers and unrecording terminated ones are protected from
241	<	* each other by a lock but the array is otherwise concurrently
242	<	* readable, and accessed directly.  To simplify index-based
243	<	* operations, the array size is always a power of two, and all
244	<	* readers must tolerate null slots. Shared (submission) queues
245	<	* are at even indices, worker queues at odd indices. Grouping
246	<	* them together in this way simplifies and speeds up task
251	<	* scanning.
238	>	* "workQueues" array that is created upon first use and expanded
239	>	* if necessary.  Updates to the array while recording new workers
240	>	* and unrecording terminated ones are protected from each other
241	>	* by a lock but the array is otherwise concurrently readable, and
242	>	* accessed directly.  To simplify index-based operations, the
243	>	* array size is always a power of two, and all readers must
244	>	* tolerate null slots. Shared (submission) queues are at even
245	>	* indices, worker queues at odd indices. Grouping them together
246	>	* in this way simplifies and speeds up task scanning.
247		*
248		* All worker thread creation is on-demand, triggered by task
249		* submissions, replacement of terminated workers, and/or
#	Line 320 | Line 315 | public class ForkJoinPool extends Abstra
315		*
316		* Trimming workers. To release resources after periods of lack of
317		* use, a worker starting to wait when the pool is quiescent will
318	<	* time out and terminate if the pool has remained quiescent for
319	<	* SHRINK_RATE nanosecs. This will slowly propagate, eventually
320	<	* terminating all workers after long periods of non-use.
318	>	* time out and terminate if the pool has remained quiescent for a
319	>	* given period -- a short period if there are more threads than
320	>	* parallelism, longer as the number of threads decreases. This
321	>	* will slowly propagate, eventually terminating all workers after
322	>	* periods of non-use.
323		*
324		* Shutdown and Termination. A call to shutdownNow atomically sets
325		* a runState bit and then (non-atomically) sets each worker's
#	Line 504 | Line 501 | public class ForkJoinPool extends Abstra
501		}
502
503		/**
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	–	/**
504		* Class for artificial tasks that are used to replace the target
505		* of local joins if they are removed from an interior queue slot
506		* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
#	Line 813 | Line 787 | public class ForkJoinPool extends Abstra
787		}
788
789		/**
790	+	* Version of tryUnpush for shared queues; called by non-FJ
791	+	* submitters after prechecking that task probably exists.
792	+	*/
793	+	final boolean trySharedUnpush(ForkJoinTask<?> t) {
794	+	boolean success = false;
795	+	if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
796	+	try {
797	+	ForkJoinTask<?>[] a; int s;
798	+	if ((a = array) != null && (s = top) != base &&
799	+	U.compareAndSwapObject
800	+	(a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) {
801	+	top = s;
802	+	success = true;
803	+	}
804	+	} finally {
805	+	runState = 0;                         // unlock
806	+	}
807	+	}
808	+	return success;
809	+	}
810	+
811	+	/**
812		* Polls the given task only if it is at the current base.
813		*/
814		final boolean pollFor(ForkJoinTask<?> task) {
#	Line 1047 | Line 1043 | public class ForkJoinPool extends Abstra
1043		ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
1044		}
1045		}
1046	+
1047		/**
1048		* Per-thread records for threads that submit to pools. Currently
1049		* holds only pseudo-random seed / index that is used to choose
#	Line 1085 | Line 1082 | public class ForkJoinPool extends Abstra
1082		public static final ForkJoinWorkerThreadFactory
1083		defaultForkJoinWorkerThreadFactory;
1084
1085	+
1086	+	/** Property prefix for constructing common pool */
1087	+	private static final String propPrefix =
1088	+	"java.util.concurrent.ForkJoinPool.common.";
1089	+
1090	+	/**
1091	+	* Common (static) pool. Non-null for public use unless a static
1092	+	* construction exception, but internal usages must null-check on
1093	+	* use.
1094	+	*/
1095	+	static final ForkJoinPool commonPool;
1096	+
1097	+	/**
1098	+	* Common pool parallelism. Must equal commonPool.parallelism.
1099	+	*/
1100	+	static final int commonPoolParallelism;
1101	+
1102		/**
1103		* Generator for assigning sequence numbers as pool names.
1104		*/
#	Line 1103 | Line 1117 | public class ForkJoinPool extends Abstra
1117		private static final RuntimePermission modifyThreadPermission;
1118
1119		/**
1120	<	* Per-thread submission bookeeping. Shared across all pools
1120	>	* Per-thread submission bookkeeping. Shared across all pools
1121		* to reduce ThreadLocal pollution and because random motion
1122		* to avoid contention in one pool is likely to hold for others.
1123		*/
#	Line 1112 | Line 1126 | public class ForkJoinPool extends Abstra
1126		// static constants
1127
1128		/**
1129	<	* The wakeup interval (in nanoseconds) for a worker waiting for a
1130	<	* task when the pool is quiescent to instead try to shrink the
1131	<	* 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.
1129	>	* Initial timeout value (in nanoseconds) for the thread triggering
1130	>	* quiescence to park waiting for new work. On timeout, the thread
1131	>	* will instead try to shrink the number of workers.
1132		*/
1133	<	private static final long SHRINK_RATE =
1123	<	4L * 1000L * 1000L * 1000L; // 4 seconds
1133	>	private static final long IDLE_TIMEOUT      = 1000L * 1000L * 1000L; // 1sec
1134
1135		/**
1136	<	* The timeout value for attempted shrinkage, includes
1127	<	* some slop to cope with system timer imprecision.
1136	>	* Timeout value when there are more threads than parallelism level
1137		*/
1138	<	private static final long SHRINK_TIMEOUT = SHRINK_RATE - (SHRINK_RATE / 10);
1138	>	private static final long FAST_IDLE_TIMEOUT =  100L * 1000L * 1000L;
1139
1140		/**
1141		* The maximum stolen->joining link depth allowed in method
#	Line 1246 | Line 1255 | public class ForkJoinPool extends Abstra
1255		* empirically works OK on current JVMs.
1256		*/
1257
1258	+	volatile long stealCount;                  // collects worker counts
1259		volatile long ctl;                         // main pool control
1260		final int parallelism;                     // parallelism level
1261		final int localMode;                       // per-worker scheduling mode
1262	+	volatile int nextWorkerNumber;             // to create worker name string
1263		final int submitMask;                      // submit queue index bound
1264		int nextSeed;                              // for initializing worker seeds
1265	+	volatile int mainLock;                     // spinlock for array updates
1266		volatile int runState;                     // shutdown status and seq
1267		WorkQueue[] workQueues;                    // main registry
1256	–	final Mutex lock;                          // for registration
1257	–	final Condition termination;               // for awaitTermination
1268		final ForkJoinWorkerThreadFactory factory; // factory for new workers
1269		final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1260	–	final AtomicLong stealCount;               // collect counts when terminated
1261	–	final AtomicInteger nextWorkerNumber;      // to create worker name string
1270		final String workerNamePrefix;             // to create worker name string
1271
1272	+	/*
1273	+	* Mechanics for main lock protecting worker array updates.  Uses
1274	+	* the same strategy as ConcurrentHashMap bins -- a spinLock for
1275	+	* normal cases, but falling back to builtin lock when (rarely)
1276	+	* needed.  See internal ConcurrentHashMap documentation for
1277	+	* explanation.
1278	+	*/
1279	+
1280	+	static final int LOCK_WAITING = 2; // bit to indicate need for signal
1281	+	static final int MAX_LOCK_SPINS = 1 << 8;
1282	+
1283	+	private void tryAwaitMainLock() {
1284	+	int spins = MAX_LOCK_SPINS, r = 0, h;
1285	+	while (((h = mainLock) & 1) != 0) {
1286	+	if (r == 0)
1287	+	r = ThreadLocalRandom.current().nextInt(); // randomize spins
1288	+	else if (spins >= 0) {
1289	+	r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
1290	+	if (r >= 0)
1291	+	--spins;
1292	+	}
1293	+	else if (U.compareAndSwapInt(this, MAINLOCK, h, h | LOCK_WAITING)) {
1294	+	synchronized (this) {
1295	+	if ((mainLock & LOCK_WAITING) != 0) {
1296	+	try {
1297	+	wait();
1298	+	} catch (InterruptedException ie) {
1299	+	Thread.currentThread().interrupt();
1300	+	}
1301	+	}
1302	+	else
1303	+	notifyAll(); // possibly won race vs signaller
1304	+	}
1305	+	break;
1306	+	}
1307	+	}
1308	+	}
1309	+
1310		//  Creating, registering, and deregistering workers
1311
1312		/**
#	Line 1287 | Line 1333 | public class ForkJoinPool extends Abstra
1333		* ForkJoinWorkerThread.
1334		*/
1335		final String nextWorkerName() {
1336	<	return workerNamePrefix.concat
1337	<	(Integer.toString(nextWorkerNumber.addAndGet(1)));
1336	>	int n;
1337	>	do {} while(!U.compareAndSwapInt(this, NEXTWORKERNUMBER,
1338	>	n = nextWorkerNumber, ++n));
1339	>	return workerNamePrefix.concat(Integer.toString(n));
1340		}
1341
1342		/**
#	Line 1300 | Line 1348 | public class ForkJoinPool extends Abstra
1348		*
1349		* @param w the worker's queue
1350		*/
1303	–
1351		final void registerWorker(WorkQueue w) {
1352	<	Mutex lock = this.lock;
1353	<	lock.lock();
1352	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1353	>	tryAwaitMainLock();
1354		try {
1355	<	WorkQueue[] ws = workQueues;
1356	<	if (w != null && ws != null) {          // skip on shutdown/failure
1355	>	WorkQueue[] ws;
1356	>	if ((ws = workQueues) == null)
1357	>	ws = workQueues = new WorkQueue[submitMask + 1];
1358	>	if (w != null) {
1359		int rs, n =  ws.length, m = n - 1;
1360		int s = nextSeed += SEED_INCREMENT; // rarely-colliding sequence
1361		w.seed = (s == 0) ? 1 : s;          // ensure non-zero seed
#	Line 1327 | Line 1376 | public class ForkJoinPool extends Abstra
1376		runState = ((rs = runState) & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN);
1377		}
1378		} finally {
1379	<	lock.unlock();
1379	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1380	>	mainLock = 0;
1381	>	synchronized (this) { notifyAll(); };
1382	>	}
1383		}
1384	+
1385		}
1386
1387		/**
#	Line 1341 | Line 1394 | public class ForkJoinPool extends Abstra
1394		* @param ex the exception causing failure, or null if none
1395		*/
1396		final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1344	–	Mutex lock = this.lock;
1397		WorkQueue w = null;
1398		if (wt != null && (w = wt.workQueue) != null) {
1399		w.runState = -1;                // ensure runState is set
1400	<	stealCount.getAndAdd(w.totalSteals + w.nsteals);
1400	>	long steals = w.totalSteals + w.nsteals, sc;
1401	>	do {} while(!U.compareAndSwapLong(this, STEALCOUNT,
1402	>	sc = stealCount, sc + steals));
1403		int idx = w.poolIndex;
1404	<	lock.lock();
1405	<	try {                           // remove record from array
1404	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1405	>	tryAwaitMainLock();
1406	>	try {
1407		WorkQueue[] ws = workQueues;
1408		if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
1409		ws[idx] = null;
1410		} finally {
1411	<	lock.unlock();
1411	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1412	>	mainLock = 0;
1413	>	synchronized (this) { notifyAll(); };
1414	>	}
1415		}
1416		}
1417
#	Line 1375 | Line 1433 | public class ForkJoinPool extends Abstra
1433		U.throwException(ex);
1434		}
1435
1378	–
1436		// Submissions
1437
1438		/**
#	Line 1393 | Line 1450 | public class ForkJoinPool extends Abstra
1450		for (int r = s.seed, m = submitMask;;) {
1451		WorkQueue[] ws; WorkQueue q;
1452		int k = r & m & SQMASK;          // use only even indices
1453	<	if (runState < 0 || (ws = workQueues) == null || ws.length <= k)
1453	>	if (runState < 0)
1454		throw new RejectedExecutionException(); // shutting down
1455	+	else if ((ws = workQueues) == null || ws.length <= k) {
1456	+	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1457	+	tryAwaitMainLock();
1458	+	try {
1459	+	if (workQueues == null)
1460	+	workQueues = new WorkQueue[submitMask + 1];
1461	+	} finally {
1462	+	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1463	+	mainLock = 0;
1464	+	synchronized (this) { notifyAll(); };
1465	+	}
1466	+	}
1467	+	}
1468		else if ((q = ws[k]) == null) {  // create new queue
1469		WorkQueue nq = new WorkQueue(this, null, SHARED_QUEUE);
1470	<	Mutex lock = this.lock;      // construct outside lock
1471	<	lock.lock();
1472	<	try {                        // recheck under lock
1470	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
1471	>	tryAwaitMainLock();
1472	>	try {
1473		int rs = runState;       // to update seq
1474		if (ws == workQueues && ws[k] == null) {
1475		ws[k] = nq;
1476		runState = ((rs & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN));
1477		}
1478		} finally {
1479	<	lock.unlock();
1479	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
1480	>	mainLock = 0;
1481	>	synchronized (this) { notifyAll(); };
1482	>	}
1483		}
1484		}
1485		else if (q.trySharedPush(task)) {
#	Line 1423 | Line 1496 | public class ForkJoinPool extends Abstra
1496		}
1497		}
1498
1499	+	/**
1500	+	* Submits the given (non-null) task to the common pool, if possible.
1501	+	*/
1502	+	static void submitToCommonPool(ForkJoinTask<?> task) {
1503	+	ForkJoinPool p;
1504	+	if ((p = commonPool) == null)
1505	+	throw new RejectedExecutionException("Common Pool Unavailable");
1506	+	p.doSubmit(task);
1507	+	}
1508	+
1509	+	/**
1510	+	* Returns true if the given task was submitted to common pool
1511	+	* and has not yet commenced execution, and is available for
1512	+	* removal according to execution policies; if so removing the
1513	+	* submission from the pool.
1514	+	*
1515	+	* @param task the task
1516	+	* @return true if successful
1517	+	*/
1518	+	static boolean tryUnsubmitFromCommonPool(ForkJoinTask<?> task) {
1519	+	// Peek, looking for task and eligibility before
1520	+	// using trySharedUnpush to actually take it under lock
1521	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
1522	+	ForkJoinTask<?>[] a; int t, s, n;
1523	+	int k = submitters.get().seed & SQMASK;
1524	+	return ((p = commonPool) != null &&
1525	+	(ws = p.workQueues) != null &&
1526	+	ws.length > (k &= p.submitMask) &&
1527	+	(q = ws[k]) != null &&
1528	+	(a = q.array) != null &&
1529	+	(n = (t = q.top) - q.base) > 0 &&
1530	+	(n > 1 || (int)(p.ctl >> AC_SHIFT) < 0) &&
1531	+	(s = t - 1) >= 0 && s < a.length && a[s] == task &&
1532	+	q.trySharedUnpush(task));
1533	+	}
1534	+
1535		// Maintaining ctl counts
1536
1537		/**
#	Line 1434 | Line 1543 | public class ForkJoinPool extends Abstra
1543		}
1544
1545		/**
1546	<	* Tries to activate or create a worker if too few are active.
1546	>	* Tries to create one or activate one or more workers if too few are active.
1547		*/
1548		final void signalWork() {
1549		long c; int u;
#	Line 1518 | Line 1627 | public class ForkJoinPool extends Abstra
1627		* awaiting signal,
1628		*
1629		* @param w the worker (via its WorkQueue)
1630	<	* @return a task or null of none found
1630	>	* @return a task or null if none found
1631		*/
1632		private final ForkJoinTask<?> scan(WorkQueue w) {
1633		WorkQueue[] ws;                       // first update random seed
#	Line 1535 | Line 1644 | public class ForkJoinPool extends Abstra
1644		t = (ForkJoinTask<?>)U.getObjectVolatile(a, i);
1645		if (q.base == b && ec >= 0 && t != null &&
1646		U.compareAndSwapObject(a, i, t, null)) {
1647	<	q.base = b + 1;       // specialization of pollAt
1647	>	if (q.top - (q.base = b + 1) > 0)
1648	>	signalWork();    // help pushes signal
1649		return t;
1650		}
1651		else if (ec < 0 || j <= m) {
#	Line 1580 | Line 1690 | public class ForkJoinPool extends Abstra
1690		}
1691		}
1692		else if (w.eventCount < 0) {      // already queued
1693	<	if ((nr = w.rescans) > 0) {   // continue rescanning
1694	<	int ac = a + parallelism;
1695	<	if (((w.rescans = (ac < nr) ? ac : nr - 1) & 3) == 0)
1696	<	Thread.yield();       // yield before block
1587	<	}
1588	<	else {
1693	>	int ac = a + parallelism;
1694	>	if ((nr = w.rescans) > 0)     // continue rescanning
1695	>	w.rescans = (ac < nr) ? ac : nr - 1;
1696	>	else if (((w.seed >>> 16) & ac) == 0) { // randomize park
1697		Thread.interrupted();     // clear status
1698		Thread wt = Thread.currentThread();
1699		U.putObject(wt, PARKBLOCKER, this);
#	Line 1603 | Line 1711 | public class ForkJoinPool extends Abstra
1711		/**
1712		* If inactivating worker w has caused the pool to become
1713		* quiescent, checks for pool termination, and, so long as this is
1714	<	* not the only worker, waits for event for up to SHRINK_RATE
1715	<	* nanosecs.  On timeout, if ctl has not changed, terminates the
1714	>	* not the only worker, waits for event for up to a given
1715	>	* duration.  On timeout, if ctl has not changed, terminates the
1716		* worker, which will in turn wake up another worker to possibly
1717		* repeat this process.
1718		*
#	Line 1615 | Line 1723 | public class ForkJoinPool extends Abstra
1723		private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
1724		if (w.eventCount < 0 && !tryTerminate(false, false) &&
1725		(int)prevCtl != 0 && !hasQueuedSubmissions() && ctl == currentCtl) {
1726	+	int dc = -(short)(currentCtl >>> TC_SHIFT);
1727	+	long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
1728	+	long deadline = System.nanoTime() + parkTime - 100000L; // 1ms slop
1729		Thread wt = Thread.currentThread();
1619	–	Thread.yield();            // yield before block
1730		while (ctl == currentCtl) {
1621	–	long startTime = System.nanoTime();
1731		Thread.interrupted();  // timed variant of version in scan()
1732		U.putObject(wt, PARKBLOCKER, this);
1733		w.parker = wt;
1734		if (ctl == currentCtl)
1735	<	U.park(false, SHRINK_RATE);
1735	>	U.park(false, parkTime);
1736		w.parker = null;
1737		U.putObject(wt, PARKBLOCKER, null);
1738		if (ctl != currentCtl)
1739		break;
1740	<	if (System.nanoTime() - startTime >= SHRINK_TIMEOUT &&
1740	>	if (deadline - System.nanoTime() <= 0L &&
1741		U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
1742		w.eventCount = (w.eventCount + E_SEQ) | E_MASK;
1743		w.runState = -1;   // shrink
#	Line 1913 | Line 2022 | public class ForkJoinPool extends Abstra
2022		}
2023		}
2024
1916	–
2025		/**
2026		* Runs tasks until {@code isQuiescent()}. We piggyback on
2027		* active count ctl maintenance, but rather than blocking
#	Line 1956 | Line 2064 | public class ForkJoinPool extends Abstra
2064		}
2065
2066		/**
2067	+	* Restricted version of helpQuiescePool for non-FJ callers
2068	+	*/
2069	+	static void externalHelpQuiescePool() {
2070	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue w, q;
2071	+	ForkJoinTask<?> t; int b;
2072	+	int k = submitters.get().seed & SQMASK;
2073	+	if ((p = commonPool) != null &&
2074	+	(ws = p.workQueues) != null &&
2075	+	ws.length > (k &= p.submitMask) &&
2076	+	(w = ws[k]) != null &&
2077	+	(q = p.findNonEmptyStealQueue(w)) != null &&
2078	+	(b = q.base) - q.top < 0 &&
2079	+	(t = q.pollAt(b)) != null)
2080	+	t.doExec();
2081	+	}
2082	+
2083	+	/**
2084		* Gets and removes a local or stolen task for the given worker.
2085		*
2086		* @return a task, if available
#	Line 1988 | Line 2113 | public class ForkJoinPool extends Abstra
2113		8);
2114		}
2115
2116	+	/**
2117	+	* Returns approximate submission queue length for the given caller
2118	+	*/
2119	+	static int getEstimatedSubmitterQueueLength() {
2120	+	ForkJoinPool p; WorkQueue[] ws; WorkQueue q;
2121	+	int k = submitters.get().seed & SQMASK;
2122	+	return ((p = commonPool) != null &&
2123	+	p.runState >= 0 &&
2124	+	(ws = p.workQueues) != null &&
2125	+	ws.length > (k &= p.submitMask) &&
2126	+	(q = ws[k]) != null) ?
2127	+	q.queueSize() : 0;
2128	+	}
2129	+
2130		//  Termination
2131
2132		/**
#	Line 2005 | Line 2144 | public class ForkJoinPool extends Abstra
2144		* @return true if now terminating or terminated
2145		*/
2146		private boolean tryTerminate(boolean now, boolean enable) {
2008	–	Mutex lock = this.lock;
2147		for (long c;;) {
2148		if (((c = ctl) & STOP_BIT) != 0) {      // already terminating
2149		if ((short)(c >>> TC_SHIFT) == -parallelism) {
2150	<	lock.lock();                    // don't need try/finally
2151	<	termination.signalAll();        // signal when 0 workers
2152	<	lock.unlock();
2150	>	synchronized(this) {
2151	>	notifyAll();                // signal when 0 workers
2152	>	}
2153		}
2154		return true;
2155		}
2156		if (runState >= 0) {                    // not yet enabled
2157		if (!enable)
2158		return false;
2159	<	lock.lock();
2160	<	runState |= SHUTDOWN;
2161	<	lock.unlock();
2159	>	while (!U.compareAndSwapInt(this, MAINLOCK, 0, 1))
2160	>	tryAwaitMainLock();
2161	>	try {
2162	>	runState |= SHUTDOWN;
2163	>	} finally {
2164	>	if (!U.compareAndSwapInt(this, MAINLOCK, 1, 0)) {
2165	>	mainLock = 0;
2166	>	synchronized (this) { notifyAll(); };
2167	>	}
2168	>	}
2169		}
2170		if (!now) {                             // check if idle & no tasks
2171		if ((int)(c >> AC_SHIFT) != -parallelism ||
#	Line 2153 | Line 2298 | public class ForkJoinPool extends Abstra
2298		// Use nearest power 2 for workQueues size. See Hackers Delight sec 3.2.
2299		int n = parallelism - 1;
2300		n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8; n |= n >>> 16;
2301	<	int size = (n + 1) << 1;        // #slots = 2*#workers
2157	<	this.submitMask = size - 1;     // room for max # of submit queues
2158	<	this.workQueues = new WorkQueue[size];
2159	<	this.termination = (this.lock = new Mutex()).newCondition();
2160	<	this.stealCount = new AtomicLong();
2161	<	this.nextWorkerNumber = new AtomicInteger();
2301	>	this.submitMask = ((n + 1) << 1) - 1;
2302		int pn = poolNumberGenerator.incrementAndGet();
2303		StringBuilder sb = new StringBuilder("ForkJoinPool-");
2304		sb.append(Integer.toString(pn));
2305		sb.append("-worker-");
2306		this.workerNamePrefix = sb.toString();
2167	–	lock.lock();
2307		this.runState = 1;              // set init flag
2308	<	lock.unlock();
2308	>	}
2309	>
2310	>	/**
2311	>	* Constructor for common pool, suitable only for static initialization.
2312	>	* Basically the same as above, but uses smallest possible initial footprint.
2313	>	*/
2314	>	ForkJoinPool(int parallelism, int submitMask,
2315	>	ForkJoinWorkerThreadFactory factory,
2316	>	Thread.UncaughtExceptionHandler handler) {
2317	>	this.factory = factory;
2318	>	this.ueh = handler;
2319	>	this.submitMask = submitMask;
2320	>	this.parallelism = parallelism;
2321	>	long np = (long)(-parallelism);
2322	>	this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
2323	>	this.localMode = LIFO_QUEUE;
2324	>	this.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
2325	>	this.runState = 1;
2326	>	}
2327	>
2328	>	/**
2329	>	* Returns the common pool instance.
2330	>	*
2331	>	* @return the common pool instance
2332	>	*/
2333	>	public static ForkJoinPool commonPool() {
2334	>	ForkJoinPool p;
2335	>	if ((p = commonPool) == null)
2336	>	throw new Error("Common Pool Unavailable");
2337	>	return p;
2338		}
2339
2340		// Execution methods
#	Line 2342 | Line 2510 | public class ForkJoinPool extends Abstra
2510		}
2511
2512		/**
2513	+	* Returns the targeted parallelism level of the common pool.
2514	+	*
2515	+	* @return the targeted parallelism level of the common pool
2516	+	*/
2517	+	public static int getCommonPoolParallelism() {
2518	+	return commonPoolParallelism;
2519	+	}
2520	+
2521	+	/**
2522		* Returns the number of worker threads that have started but not
2523		* yet terminated.  The result returned by this method may differ
2524		* from {@link #getParallelism} when threads are created to
#	Line 2422 | Line 2599 | public class ForkJoinPool extends Abstra
2599		* @return the number of steals
2600		*/
2601		public long getStealCount() {
2602	<	long count = stealCount.get();
2602	>	long count = stealCount;
2603		WorkQueue[] ws; WorkQueue w;
2604		if ((ws = workQueues) != null) {
2605		for (int i = 1; i < ws.length; i += 2) {
#	Line 2552 | Line 2729 | public class ForkJoinPool extends Abstra
2729		public String toString() {
2730		// Use a single pass through workQueues to collect counts
2731		long qt = 0L, qs = 0L; int rc = 0;
2732	<	long st = stealCount.get();
2732	>	long st = stealCount;
2733		long c = ctl;
2734		WorkQueue[] ws; WorkQueue w;
2735		if ((ws = workQueues) != null) {
#	Line 2593 | Line 2770 | public class ForkJoinPool extends Abstra
2770		}
2771
2772		/**
2773	<	* Initiates an orderly shutdown in which previously submitted
2774	<	* tasks are executed, but no new tasks will be accepted.
2775	<	* Invocation has no additional effect if already shut down.
2776	<	* Tasks that are in the process of being submitted concurrently
2777	<	* during the course of this method may or may not be rejected.
2773	>	* Possibly initiates an orderly shutdown in which previously
2774	>	* submitted tasks are executed, but no new tasks will be
2775	>	* accepted. Invocation has no effect on execution state if this
2776	>	* is the {@link #commonPool}, and no additional effect if
2777	>	* already shut down.  Tasks that are in the process of being
2778	>	* submitted concurrently during the course of this method may or
2779	>	* may not be rejected.
2780		*
2781		* @throws SecurityException if a security manager exists and
2782		*         the caller is not permitted to modify threads
#	Line 2606 | Line 2785 | public class ForkJoinPool extends Abstra
2785		*/
2786		public void shutdown() {
2787		checkPermission();
2788	<	tryTerminate(false, true);
2788	>	if (this != commonPool)
2789	>	tryTerminate(false, true);
2790		}
2791
2792		/**
2793	<	* Attempts to cancel and/or stop all tasks, and reject all
2794	<	* subsequently submitted tasks.  Tasks that are in the process of
2795	<	* being submitted or executed concurrently during the course of
2796	<	* this method may or may not be rejected. This method cancels
2797	<	* both existing and unexecuted tasks, in order to permit
2798	<	* termination in the presence of task dependencies. So the method
2799	<	* always returns an empty list (unlike the case for some other
2800	<	* Executors).
2793	>	* Possibly attempts to cancel and/or stop all tasks, and reject
2794	>	* all subsequently submitted tasks.  Invocation has no effect on
2795	>	* execution state if this is the {@link #commonPool}, and no
2796	>	* additional effect if already shut down. Otherwise, tasks that
2797	>	* are in the process of being submitted or executed concurrently
2798	>	* during the course of this method may or may not be
2799	>	* rejected. This method cancels both existing and unexecuted
2800	>	* tasks, in order to permit termination in the presence of task
2801	>	* dependencies. So the method always returns an empty list
2802	>	* (unlike the case for some other Executors).
2803		*
2804		* @return an empty list
2805		* @throws SecurityException if a security manager exists and
#	Line 2627 | Line 2809 | public class ForkJoinPool extends Abstra
2809		*/
2810		public List<Runnable> shutdownNow() {
2811		checkPermission();
2812	<	tryTerminate(true, true);
2812	>	if (this != commonPool)
2813	>	tryTerminate(true, true);
2814		return Collections.emptyList();
2815		}
2816
#	Line 2684 | Line 2867 | public class ForkJoinPool extends Abstra
2867		public boolean awaitTermination(long timeout, TimeUnit unit)
2868		throws InterruptedException {
2869		long nanos = unit.toNanos(timeout);
2870	<	final Mutex lock = this.lock;
2871	<	lock.lock();
2872	<	try {
2873	<	for (;;) {
2874	<	if (isTerminated())
2875	<	return true;
2876	<	if (nanos <= 0)
2877	<	return false;
2878	<	nanos = termination.awaitNanos(nanos);
2870	>	if (isTerminated())
2871	>	return true;
2872	>	long startTime = System.nanoTime();
2873	>	boolean terminated = false;
2874	>	synchronized(this) {
2875	>	for (long waitTime = nanos, millis = 0L;;) {
2876	>	if (terminated = isTerminated() ||
2877	>	waitTime <= 0L ||
2878	>	(millis = unit.toMillis(waitTime)) <= 0L)
2879	>	break;
2880	>	wait(millis);
2881	>	waitTime = nanos - (System.nanoTime() - startTime);
2882		}
2697	–	} finally {
2698	–	lock.unlock();
2883		}
2884	+	return terminated;
2885		}
2886
2887		/**
#	Line 2828 | Line 3013 | public class ForkJoinPool extends Abstra
3013		private static final long PARKBLOCKER;
3014		private static final int ABASE;
3015		private static final int ASHIFT;
3016	+	private static final long NEXTWORKERNUMBER;
3017	+	private static final long STEALCOUNT;
3018	+	private static final long MAINLOCK;
3019
3020		static {
3021		poolNumberGenerator = new AtomicInteger();
#	Line 2843 | Line 3031 | public class ForkJoinPool extends Abstra
3031		Class<?> ak = ForkJoinTask[].class;
3032		CTL = U.objectFieldOffset
3033		(k.getDeclaredField("ctl"));
3034	+	NEXTWORKERNUMBER = U.objectFieldOffset
3035	+	(k.getDeclaredField("nextWorkerNumber"));
3036	+	STEALCOUNT = U.objectFieldOffset
3037	+	(k.getDeclaredField("stealCount"));
3038	+	MAINLOCK = U.objectFieldOffset
3039	+	(k.getDeclaredField("mainLock"));
3040		Class<?> tk = Thread.class;
3041		PARKBLOCKER = U.objectFieldOffset
3042		(tk.getDeclaredField("parkBlocker"));
3043		ABASE = U.arrayBaseOffset(ak);
3044		s = U.arrayIndexScale(ak);
3045	+	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3046		} catch (Exception e) {
3047		throw new Error(e);
3048		}
3049		if ((s & (s-1)) != 0)
3050		throw new Error("data type scale not a power of two");
3051	<	ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
3051	>	try { // Establish common pool
3052	>	String pp = System.getProperty(propPrefix + "parallelism");
3053	>	String fp = System.getProperty(propPrefix + "threadFactory");
3054	>	String up = System.getProperty(propPrefix + "exceptionHandler");
3055	>	ForkJoinWorkerThreadFactory fac = (fp == null) ?
3056	>	defaultForkJoinWorkerThreadFactory :
3057	>	((ForkJoinWorkerThreadFactory)ClassLoader.
3058	>	getSystemClassLoader().loadClass(fp).newInstance());
3059	>	Thread.UncaughtExceptionHandler ueh = (up == null)? null :
3060	>	((Thread.UncaughtExceptionHandler)ClassLoader.
3061	>	getSystemClassLoader().loadClass(up).newInstance());
3062	>	int par;
3063	>	if ((pp == null || (par = Integer.parseInt(pp)) <= 0))
3064	>	par = Runtime.getRuntime().availableProcessors();
3065	>	if (par > MAX_CAP)
3066	>	par = MAX_CAP;
3067	>	commonPoolParallelism = par;
3068	>	int n = par - 1; // precompute submit mask
3069	>	n |= n >>> 1; n |= n >>> 2; n |= n >>> 4;
3070	>	n |= n >>> 8; n |= n >>> 16;
3071	>	int mask = ((n + 1) << 1) - 1;
3072	>	commonPool = new ForkJoinPool(par, mask, fac, ueh);
3073	>	} catch (Exception e) {
3074	>	throw new Error(e);
3075	>	}
3076		}
3077
3078		/**

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