ViewVC Help

View File | Revision Log | Show Annotations | Download File | Root Listing

root/jsr166/jsr166/src/jsr166e/ForkJoinPool.java

Comparing jsr166/src/jsr166e/ForkJoinPool.java (file contents):
Revision 1.4 by jsr166, Fri Oct 12 16:46:37 2012 UTC vs.
Revision 1.8 by dl, Mon Oct 29 17:23:26 2012 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166e;
8	+
9		import java.util.ArrayList;
10		import java.util.Arrays;
11		import java.util.Collection;
#	Line 17 | Line 18 | import java.util.concurrent.ExecutorServ
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;
#	Line 41 | Line 43 | import java.util.concurrent.locks.Condit
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
#	Line 93 | Line 107 | import java.util.concurrent.locks.Condit
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
#	Line 239 | Line 236 | public class ForkJoinPool extends Abstra
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
#	Line 320 | Line 316 | public class ForkJoinPool extends Abstra
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
#	Line 504 | Line 502 | public class ForkJoinPool extends Abstra
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
#	Line 813 | Line 788 | public class ForkJoinPool extends Abstra
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) {
#	Line 1086 | Line 1083 | public class ForkJoinPool extends Abstra
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		*/
#	Line 1113 | Line 1127 | public class ForkJoinPool extends Abstra
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
1119	<	* much. It must be short enough to release resources during
1120	<	* sustained periods of idleness, but not so short that threads
1121	<	* 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 =
1124	<	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
1128	<	* 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
#	Line 1247 | Line 1256 | public class ForkJoinPool extends Abstra
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
1257	–	final Mutex lock;                          // for registration
1258	–	final Condition termination;               // for awaitTermination
1269		final ForkJoinWorkerThreadFactory factory; // factory for new workers
1270		final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
1261	–	final AtomicLong stealCount;               // collect counts when terminated
1262	–	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		/**
#	Line 1288 | Line 1334 | public class ForkJoinPool extends Abstra
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		/**
#	Line 1301 | Line 1349 | public class ForkJoinPool extends Abstra
1349		*
1350		* @param w the worker's queue
1351		*/
1304	–
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
1358	<	int rs, n = ws.length, m = n - 1;
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
1363		int r = (s << 1) | 1;               // use odd-numbered indices
#	Line 1328 | Line 1377 | public class ForkJoinPool extends Abstra
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		/**
#	Line 1342 | Line 1395 | public class ForkJoinPool extends Abstra
1395		* @param ex the exception causing failure, or null if none
1396		*/
1397		final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
1345	–	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
#	Line 1376 | Line 1434 | public class ForkJoinPool extends Abstra
1434		U.throwException(ex);
1435		}
1436
1379	–
1437		// Submissions
1438
1439		/**
#	Line 1394 | Line 1451 | public class ForkJoinPool extends Abstra
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)) {
#	Line 1424 | Line 1497 | public class ForkJoinPool extends Abstra
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		/**
#	Line 1435 | Line 1544 | public class ForkJoinPool extends Abstra
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;
#	Line 1519 | Line 1628 | public class ForkJoinPool extends Abstra
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
#	Line 1536 | Line 1645 | public class ForkJoinPool extends Abstra
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		}
#	Line 1582 | Line 1691 | public class ForkJoinPool extends Abstra
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
1589	<	}
1590	<	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);
#	Line 1605 | Line 1712 | public class ForkJoinPool extends Abstra
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		*
#	Line 1617 | Line 1724 | public class ForkJoinPool extends Abstra
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();
1621	–	Thread.yield();            // yield before block
1731		while (ctl == currentCtl) {
1623	–	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
#	Line 1915 | Line 2023 | public class ForkJoinPool extends Abstra
2023		}
2024		}
2025
1918	–
2026		/**
2027		* Runs tasks until {@code isQuiescent()}. We piggyback on
2028		* active count ctl maintenance, but rather than blocking
#	Line 1958 | Line 2065 | public class ForkJoinPool extends Abstra
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
#	Line 1990 | Line 2114 | public class ForkJoinPool extends Abstra
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		/**
#	Line 2007 | Line 2145 | public class ForkJoinPool extends Abstra
2145		* @return true if now terminating or terminated
2146		*/
2147		private boolean tryTerminate(boolean now, boolean enable) {
2010	–	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 ||
#	Line 2155 | Line 2299 | public class ForkJoinPool extends Abstra
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
2159	<	this.submitMask = size - 1;     // room for max # of submit queues
2160	<	this.workQueues = new WorkQueue[size];
2161	<	this.termination = (this.lock = new Mutex()).newCondition();
2162	<	this.stealCount = new AtomicLong();
2163	<	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();
2169	–	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
#	Line 2344 | Line 2511 | public class ForkJoinPool extends Abstra
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
#	Line 2424 | Line 2600 | public class ForkJoinPool extends Abstra
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) {
#	Line 2554 | Line 2730 | public class ForkJoinPool extends Abstra
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) {
#	Line 2595 | Line 2771 | public class ForkJoinPool extends Abstra
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
#	Line 2608 | Line 2786 | public class ForkJoinPool extends Abstra
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
#	Line 2629 | Line 2810 | public class ForkJoinPool extends Abstra
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
#	Line 2686 | Line 2868 | public class ForkJoinPool extends Abstra
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		}
2699	–	} finally {
2700	–	lock.unlock();
2884		}
2885	+	return terminated;
2886		}
2887
2888		/**
#	Line 2830 | Line 3014 | public class ForkJoinPool extends Abstra
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();
#	Line 2845 | Line 3032 | public class ForkJoinPool extends Abstra
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		/**

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines