| 56 |
|
* maximum number of running threads to 32767. Attempts to create |
| 57 |
|
* pools with greater than the maximum result in |
| 58 |
|
* IllegalArgumentExceptions. |
| 59 |
+ |
* |
| 60 |
+ |
* @since 1.7 |
| 61 |
+ |
* @author Doug Lea |
| 62 |
|
*/ |
| 63 |
|
public class ForkJoinPool extends AbstractExecutorService { |
| 64 |
|
|
| 84 |
|
* Returns a new worker thread operating in the given pool. |
| 85 |
|
* |
| 86 |
|
* @param pool the pool this thread works in |
| 87 |
< |
* @throws NullPointerException if pool is null; |
| 87 |
> |
* @throws NullPointerException if pool is null |
| 88 |
|
*/ |
| 89 |
|
public ForkJoinWorkerThread newThread(ForkJoinPool pool); |
| 90 |
|
} |
| 219 |
|
* threads, packed into one int to ensure consistent snapshot when |
| 220 |
|
* making decisions about creating and suspending spare |
| 221 |
|
* threads. Updated only by CAS. Note: CASes in |
| 222 |
< |
* updateRunningCount and preJoin running active count is in low |
| 223 |
< |
* word, so need to be modified if this changes |
| 222 |
> |
* updateRunningCount and preJoin assume that running active count |
| 223 |
> |
* is in low word, so need to be modified if this changes. |
| 224 |
|
*/ |
| 225 |
|
private volatile int workerCounts; |
| 226 |
|
|
| 229 |
|
private static int workerCountsFor(int t, int r) { return (t << 16) + r; } |
| 230 |
|
|
| 231 |
|
/** |
| 232 |
< |
* Add delta (which may be negative) to running count. This must |
| 232 |
> |
* Adds delta (which may be negative) to running count. This must |
| 233 |
|
* be called before (with negative arg) and after (with positive) |
| 234 |
< |
* any managed synchronization (i.e., mainly, joins) |
| 234 |
> |
* any managed synchronization (i.e., mainly, joins). |
| 235 |
|
* @param delta the number to add |
| 236 |
|
*/ |
| 237 |
|
final void updateRunningCount(int delta) { |
| 240 |
|
} |
| 241 |
|
|
| 242 |
|
/** |
| 243 |
< |
* Add delta (which may be negative) to both total and running |
| 243 |
> |
* Adds delta (which may be negative) to both total and running |
| 244 |
|
* count. This must be called upon creation and termination of |
| 245 |
|
* worker threads. |
| 246 |
|
* @param delta the number to add |
| 276 |
|
/** |
| 277 |
|
* Try incrementing active count; fail on contention. Called by |
| 278 |
|
* workers before/during executing tasks. |
| 279 |
< |
* @return true on success; |
| 279 |
> |
* @return true on success |
| 280 |
|
*/ |
| 281 |
|
final boolean tryIncrementActiveCount() { |
| 282 |
|
int c = runControl; |
| 284 |
|
} |
| 285 |
|
|
| 286 |
|
/** |
| 287 |
< |
* Try decrementing active count; fail on contention. |
| 288 |
< |
* Possibly trigger termination on success |
| 287 |
> |
* Tries decrementing active count; fails on contention. |
| 288 |
> |
* Possibly triggers termination on success. |
| 289 |
|
* Called by workers when they can't find tasks. |
| 290 |
|
* @return true on success |
| 291 |
|
*/ |
| 300 |
|
} |
| 301 |
|
|
| 302 |
|
/** |
| 303 |
< |
* Return true if argument represents zero active count and |
| 303 |
> |
* Returns true if argument represents zero active count and |
| 304 |
|
* nonzero runstate, which is the triggering condition for |
| 305 |
|
* terminating on shutdown. |
| 306 |
|
*/ |
| 379 |
|
* @param parallelism the targeted number of worker threads |
| 380 |
|
* @param factory the factory for creating new threads |
| 381 |
|
* @throws IllegalArgumentException if parallelism less than or |
| 382 |
< |
* equal to zero, or greater than implementation limit. |
| 382 |
> |
* equal to zero, or greater than implementation limit |
| 383 |
|
* @throws NullPointerException if factory is null |
| 384 |
|
* @throws SecurityException if a security manager exists and |
| 385 |
|
* the caller is not permitted to modify threads |
| 424 |
|
} |
| 425 |
|
|
| 426 |
|
/** |
| 427 |
< |
* Return a good size for worker array given pool size. |
| 427 |
> |
* Returns a good size for worker array given pool size. |
| 428 |
|
* Currently requires size to be a power of two. |
| 429 |
|
*/ |
| 430 |
|
private static int arraySizeFor(int ps) { |
| 432 |
|
} |
| 433 |
|
|
| 434 |
|
/** |
| 435 |
< |
* Create or resize array if necessary to hold newLength. |
| 436 |
< |
* Call only under exclusion or lock |
| 435 |
> |
* Creates or resizes array if necessary to hold newLength. |
| 436 |
> |
* Call only under exclusion. |
| 437 |
> |
* |
| 438 |
|
* @return the array |
| 439 |
|
*/ |
| 440 |
|
private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) { |
| 723 |
|
* Sets the target parallelism level of this pool. |
| 724 |
|
* @param parallelism the target parallelism |
| 725 |
|
* @throws IllegalArgumentException if parallelism less than or |
| 726 |
< |
* equal to zero or greater than maximum size bounds. |
| 726 |
> |
* equal to zero or greater than maximum size bounds |
| 727 |
|
* @throws SecurityException if a security manager exists and |
| 728 |
|
* the caller is not permitted to modify threads |
| 729 |
|
* because it does not hold {@link |
| 786 |
|
* Setting this value has no effect on current pool size. It |
| 787 |
|
* controls construction of new threads. |
| 788 |
|
* @throws IllegalArgumentException if negative or greater then |
| 789 |
< |
* internal implementation limit. |
| 789 |
> |
* internal implementation limit |
| 790 |
|
*/ |
| 791 |
|
public void setMaximumPoolSize(int newMax) { |
| 792 |
|
if (newMax < 0 || newMax > MAX_THREADS) |
| 826 |
|
* invocations at other times may be unpredictable. |
| 827 |
|
* |
| 828 |
|
* @param async if true, use locally FIFO scheduling |
| 829 |
< |
* @return the previous mode. |
| 829 |
> |
* @return the previous mode |
| 830 |
|
*/ |
| 831 |
|
public boolean setAsyncMode(boolean async) { |
| 832 |
|
boolean oldMode = locallyFifo; |
| 846 |
|
* Returns true if this pool uses local first-in-first-out |
| 847 |
|
* scheduling mode for forked tasks that are never joined. |
| 848 |
|
* |
| 849 |
< |
* @return true if this pool uses async mode. |
| 849 |
> |
* @return true if this pool uses async mode |
| 850 |
|
*/ |
| 851 |
|
public boolean getAsyncMode() { |
| 852 |
|
return locallyFifo; |
| 867 |
|
* Returns an estimate of the number of threads that are currently |
| 868 |
|
* stealing or executing tasks. This method may overestimate the |
| 869 |
|
* number of active threads. |
| 870 |
< |
* @return the number of active threads. |
| 870 |
> |
* @return the number of active threads |
| 871 |
|
*/ |
| 872 |
|
public int getActiveThreadCount() { |
| 873 |
|
return activeCountOf(runControl); |
| 877 |
|
* Returns an estimate of the number of threads that are currently |
| 878 |
|
* idle waiting for tasks. This method may underestimate the |
| 879 |
|
* number of idle threads. |
| 880 |
< |
* @return the number of idle threads. |
| 880 |
> |
* @return the number of idle threads |
| 881 |
|
*/ |
| 882 |
|
final int getIdleThreadCount() { |
| 883 |
|
int c = runningCountOf(workerCounts) - activeCountOf(runControl); |
| 906 |
|
* tuning fork/join programs: In general, steal counts should be |
| 907 |
|
* high enough to keep threads busy, but low enough to avoid |
| 908 |
|
* overhead and contention across threads. |
| 909 |
< |
* @return the number of steals. |
| 909 |
> |
* @return the number of steals |
| 910 |
|
*/ |
| 911 |
|
public long getStealCount() { |
| 912 |
|
return stealCount.get(); |
| 929 |
|
* an approximation, obtained by iterating across all threads in |
| 930 |
|
* the pool. This method may be useful for tuning task |
| 931 |
|
* granularities. |
| 932 |
< |
* @return the number of queued tasks. |
| 932 |
> |
* @return the number of queued tasks |
| 933 |
|
*/ |
| 934 |
|
public long getQueuedTaskCount() { |
| 935 |
|
long count = 0; |
| 948 |
|
* Returns an estimate of the number tasks submitted to this pool |
| 949 |
|
* that have not yet begun executing. This method takes time |
| 950 |
|
* proportional to the number of submissions. |
| 951 |
< |
* @return the number of queued submissions. |
| 951 |
> |
* @return the number of queued submissions |
| 952 |
|
*/ |
| 953 |
|
public int getQueuedSubmissionCount() { |
| 954 |
|
return submissionQueue.size(); |
| 957 |
|
/** |
| 958 |
|
* Returns true if there are any tasks submitted to this pool |
| 959 |
|
* that have not yet begun executing. |
| 960 |
< |
* @return {@code true} if there are any queued submissions. |
| 960 |
> |
* @return {@code true} if there are any queued submissions |
| 961 |
|
*/ |
| 962 |
|
public boolean hasQueuedSubmissions() { |
| 963 |
|
return !submissionQueue.isEmpty(); |
| 1187 |
|
} |
| 1188 |
|
|
| 1189 |
|
/** |
| 1190 |
< |
* Possibly terminate when on shutdown state |
| 1190 |
> |
* Possibly terminates when on shutdown state. |
| 1191 |
|
*/ |
| 1192 |
|
private void terminateOnShutdown() { |
| 1193 |
|
if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl)) |
| 1195 |
|
} |
| 1196 |
|
|
| 1197 |
|
/** |
| 1198 |
< |
* Clear out and cancel submissions |
| 1198 |
> |
* Clears out and cancels submissions. |
| 1199 |
|
*/ |
| 1200 |
|
private void cancelQueuedSubmissions() { |
| 1201 |
|
ForkJoinTask<?> task; |
| 1204 |
|
} |
| 1205 |
|
|
| 1206 |
|
/** |
| 1207 |
< |
* Clean out worker queues. |
| 1207 |
> |
* Cleans out worker queues. |
| 1208 |
|
*/ |
| 1209 |
|
private void cancelQueuedWorkerTasks() { |
| 1210 |
|
final ReentrantLock lock = this.workerLock; |
| 1224 |
|
} |
| 1225 |
|
|
| 1226 |
|
/** |
| 1227 |
< |
* Set each worker's status to terminating. Requires lock to avoid |
| 1228 |
< |
* conflicts with add/remove |
| 1227 |
> |
* Sets each worker's status to terminating. Requires lock to avoid |
| 1228 |
> |
* conflicts with add/remove. |
| 1229 |
|
*/ |
| 1230 |
|
private void stopAllWorkers() { |
| 1231 |
|
final ReentrantLock lock = this.workerLock; |
| 1245 |
|
} |
| 1246 |
|
|
| 1247 |
|
/** |
| 1248 |
< |
* Interrupt all unterminated workers. This is not required for |
| 1248 |
> |
* Interrupts all unterminated workers. This is not required for |
| 1249 |
|
* sake of internal control, but may help unstick user code during |
| 1250 |
|
* shutdown. |
| 1251 |
|
*/ |
| 1315 |
|
} |
| 1316 |
|
|
| 1317 |
|
/** |
| 1318 |
< |
* Wake up waiter, returning false if known to already |
| 1318 |
> |
* Wakes up waiter, returning false if known to already |
| 1319 |
|
*/ |
| 1320 |
|
boolean signal() { |
| 1321 |
|
ForkJoinWorkerThread t = thread; |
| 1327 |
|
} |
| 1328 |
|
|
| 1329 |
|
/** |
| 1330 |
< |
* Await release on sync |
| 1330 |
> |
* Awaits release on sync. |
| 1331 |
|
*/ |
| 1332 |
|
void awaitSyncRelease(ForkJoinPool p) { |
| 1333 |
|
while (thread != null && !p.syncIsReleasable(this)) |
| 1335 |
|
} |
| 1336 |
|
|
| 1337 |
|
/** |
| 1338 |
< |
* Await resumption as spare |
| 1338 |
> |
* Awaits resumption as spare. |
| 1339 |
|
*/ |
| 1340 |
|
void awaitSpareRelease() { |
| 1341 |
|
while (thread != null) { |
| 1375 |
|
} |
| 1376 |
|
|
| 1377 |
|
/** |
| 1378 |
< |
* Signal threads waiting to poll a task. Because method sync |
| 1378 |
> |
* Signals threads waiting to poll a task. Because method sync |
| 1379 |
|
* rechecks availability, it is OK to only proceed if queue |
| 1380 |
|
* appears to be non-empty, and OK to skip under contention to |
| 1381 |
|
* increment count (since some other thread succeeded). |
| 1462 |
|
// Parallelism maintenance |
| 1463 |
|
|
| 1464 |
|
/** |
| 1465 |
< |
* Decrement running count; if too low, add spare. |
| 1465 |
> |
* Decrements running count; if too low, adds spare. |
| 1466 |
|
* |
| 1467 |
|
* Conceptually, all we need to do here is add or resume a |
| 1468 |
|
* spare thread when one is about to block (and remove or |
| 1552 |
|
} |
| 1553 |
|
|
| 1554 |
|
/** |
| 1555 |
< |
* Add a spare worker if lock available and no more than the |
| 1556 |
< |
* expected numbers of threads exist |
| 1555 |
> |
* Adds a spare worker if lock available and no more than the |
| 1556 |
> |
* expected numbers of threads exist. |
| 1557 |
|
* @return true if successful |
| 1558 |
|
*/ |
| 1559 |
|
private boolean tryAddSpare(int expectedCounts) { |
| 1586 |
|
} |
| 1587 |
|
|
| 1588 |
|
/** |
| 1589 |
< |
* Add the kth spare worker. On entry, pool counts are already |
| 1589 |
> |
* Adds the kth spare worker. On entry, pool counts are already |
| 1590 |
|
* adjusted to reflect addition. |
| 1591 |
|
*/ |
| 1592 |
|
private void createAndStartSpare(int k) { |
| 1608 |
|
} |
| 1609 |
|
|
| 1610 |
|
/** |
| 1611 |
< |
* Suspend calling thread w if there are excess threads. Called |
| 1612 |
< |
* only from sync. Spares are enqueued in a Treiber stack |
| 1613 |
< |
* using the same WaitQueueNodes as barriers. They are resumed |
| 1614 |
< |
* mainly in preJoin, but are also woken on pool events that |
| 1615 |
< |
* require all threads to check run state. |
| 1611 |
> |
* Suspends calling thread w if there are excess threads. Called |
| 1612 |
> |
* only from sync. Spares are enqueued in a Treiber stack using |
| 1613 |
> |
* the same WaitQueueNodes as barriers. They are resumed mainly |
| 1614 |
> |
* in preJoin, but are also woken on pool events that require all |
| 1615 |
> |
* threads to check run state. |
| 1616 |
|
* @param w the caller |
| 1617 |
|
*/ |
| 1618 |
|
private boolean suspendIfSpare(ForkJoinWorkerThread w) { |
| 1633 |
|
} |
| 1634 |
|
|
| 1635 |
|
/** |
| 1636 |
< |
* Try to pop and resume a spare thread. |
| 1636 |
> |
* Tries to pop and resume a spare thread. |
| 1637 |
|
* @param updateCount if true, increment running count on success |
| 1638 |
|
* @return true if successful |
| 1639 |
|
*/ |
| 1651 |
|
} |
| 1652 |
|
|
| 1653 |
|
/** |
| 1654 |
< |
* Pop and resume all spare threads. Same idea as ensureSync. |
| 1654 |
> |
* Pops and resumes all spare threads. Same idea as ensureSync. |
| 1655 |
|
* @return true if any spares released |
| 1656 |
|
*/ |
| 1657 |
|
private boolean resumeAllSpares() { |
| 1669 |
|
} |
| 1670 |
|
|
| 1671 |
|
/** |
| 1672 |
< |
* Pop and shutdown excessive spare threads. Call only while |
| 1672 |
> |
* Pops and shuts down excessive spare threads. Call only while |
| 1673 |
|
* holding lock. This is not guaranteed to eliminate all excess |
| 1674 |
|
* threads, only those suspended as spares, which are the ones |
| 1675 |
|
* unlikely to be needed in the future. |
| 1721 |
|
* Possibly blocks the current thread, for example waiting for |
| 1722 |
|
* a lock or condition. |
| 1723 |
|
* @return true if no additional blocking is necessary (i.e., |
| 1724 |
< |
* if isReleasable would return true). |
| 1724 |
> |
* if isReleasable would return true) |
| 1725 |
|
* @throws InterruptedException if interrupted while waiting |
| 1726 |
|
* (the method is not required to do so, but is allowed to). |
| 1727 |
|
*/ |
| 1760 |
|
* attempt to maintain the pool's nominal parallelism; otherwise |
| 1761 |
|
* activate a thread only if necessary to avoid complete |
| 1762 |
|
* starvation. |
| 1763 |
< |
* @throws InterruptedException if blocker.block did so. |
| 1763 |
> |
* @throws InterruptedException if blocker.block did so |
| 1764 |
|
*/ |
| 1765 |
|
public static void managedBlock(ManagedBlocker blocker, |
| 1766 |
|
boolean maintainParallelism) |
| 1822 |
|
|
| 1823 |
|
private static long fieldOffset(String fieldName) |
| 1824 |
|
throws NoSuchFieldException { |
| 1825 |
< |
return _unsafe.objectFieldOffset |
| 1825 |
> |
return UNSAFE.objectFieldOffset |
| 1826 |
|
(ForkJoinPool.class.getDeclaredField(fieldName)); |
| 1827 |
|
} |
| 1828 |
|
|
| 1829 |
< |
static final Unsafe _unsafe; |
| 1829 |
> |
static final Unsafe UNSAFE; |
| 1830 |
|
static final long eventCountOffset; |
| 1831 |
|
static final long workerCountsOffset; |
| 1832 |
|
static final long runControlOffset; |
| 1835 |
|
|
| 1836 |
|
static { |
| 1837 |
|
try { |
| 1838 |
< |
_unsafe = getUnsafe(); |
| 1838 |
> |
UNSAFE = getUnsafe(); |
| 1839 |
|
eventCountOffset = fieldOffset("eventCount"); |
| 1840 |
|
workerCountsOffset = fieldOffset("workerCounts"); |
| 1841 |
|
runControlOffset = fieldOffset("runControl"); |
| 1847 |
|
} |
| 1848 |
|
|
| 1849 |
|
private boolean casEventCount(long cmp, long val) { |
| 1850 |
< |
return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val); |
| 1850 |
> |
return UNSAFE.compareAndSwapLong(this, eventCountOffset, cmp, val); |
| 1851 |
|
} |
| 1852 |
|
private boolean casWorkerCounts(int cmp, int val) { |
| 1853 |
< |
return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val); |
| 1853 |
> |
return UNSAFE.compareAndSwapInt(this, workerCountsOffset, cmp, val); |
| 1854 |
|
} |
| 1855 |
|
private boolean casRunControl(int cmp, int val) { |
| 1856 |
< |
return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val); |
| 1856 |
> |
return UNSAFE.compareAndSwapInt(this, runControlOffset, cmp, val); |
| 1857 |
|
} |
| 1858 |
|
private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) { |
| 1859 |
< |
return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val); |
| 1859 |
> |
return UNSAFE.compareAndSwapObject(this, spareStackOffset, cmp, val); |
| 1860 |
|
} |
| 1861 |
|
private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) { |
| 1862 |
< |
return _unsafe.compareAndSwapObject(this, syncStackOffset, cmp, val); |
| 1862 |
> |
return UNSAFE.compareAndSwapObject(this, syncStackOffset, cmp, val); |
| 1863 |
|
} |
| 1864 |
|
} |
