--- jsr166/src/jsr166e/ForkJoinPool.java 2012/11/21 19:54:32 1.21 +++ jsr166/src/jsr166e/ForkJoinPool.java 2013/02/13 18:30:47 1.56 @@ -51,7 +51,7 @@ import java.util.concurrent.TimeUnit; * dynamically adding, suspending, or resuming internal worker * threads, even if some tasks are stalled waiting to join * others. However, no such adjustments are guaranteed in the face of - * blocked IO or other unmanaged synchronization. The nested {@link + * blocked I/O or other unmanaged synchronization. The nested {@link * ManagedBlocker} interface enables extension of the kinds of * synchronization accommodated. * @@ -99,7 +99,7 @@ import java.util.concurrent.TimeUnit; * *
The common pool is by default constructed with default
* parameters, but these may be controlled by setting three {@link
- * System#getProperty properties} with prefix {@code
+ * System#getProperty system properties} with prefix {@code
* java.util.concurrent.ForkJoinPool.common}: {@code parallelism} --
* an integer greater than zero, {@code threadFactory} -- the class
* name of a {@link ForkJoinWorkerThreadFactory}, and {@code
@@ -440,7 +440,7 @@ public class ForkJoinPool extends Abstra
* Common Pool
* ===========
*
- * The static commonPool always exists after static
+ * The static common Pool always exists after static
* initialization. Since it (or any other created pool) need
* never be used, we minimize initial construction overhead and
* footprint to the setup of about a dozen fields, with no nested
@@ -708,7 +708,7 @@ public class ForkJoinPool extends Abstra
* shared-queue version is embedded in method externalPush.)
*
* @param task the task. Caller must ensure non-null.
- * @throw RejectedExecutionException if array cannot be resized
+ * @throws RejectedExecutionException if array cannot be resized
*/
final void push(ForkJoinTask> task) {
ForkJoinTask>[] a; ForkJoinPool p;
@@ -907,7 +907,7 @@ public class ForkJoinPool extends Abstra
* or any other cancelled task. Returns (true) on any CAS
* or consistency check failure so caller can retry.
*
- * @return false if no progress can be made, else true;
+ * @return false if no progress can be made, else true
*/
final boolean tryRemoveAndExec(ForkJoinTask> task) {
boolean stat = true, removed = false, empty = true;
@@ -952,7 +952,7 @@ public class ForkJoinPool extends Abstra
/**
* Polls for and executes the given task or any other task in
- * its CountedCompleter computation
+ * its CountedCompleter computation.
*/
final boolean pollAndExecCC(ForkJoinTask> root) {
ForkJoinTask>[] a; int b; Object o;
@@ -987,14 +987,13 @@ public class ForkJoinPool extends Abstra
if (t != null) {
(currentSteal = t).doExec();
currentSteal = null;
+ ++nsteals;
if (base - top < 0) { // process remaining local tasks
if (mode == 0)
popAndExecAll();
else
pollAndExecAll();
}
- ++nsteals;
- hint = -1;
}
}
@@ -1021,29 +1020,12 @@ public class ForkJoinPool extends Abstra
s != Thread.State.TIMED_WAITING);
}
- /**
- * If this owned and is not already interrupted, try to
- * interrupt and/or unpark, ignoring exceptions.
- */
- final void interruptOwner() {
- Thread wt, p;
- if ((wt = owner) != null && !wt.isInterrupted()) {
- try {
- wt.interrupt();
- } catch (SecurityException ignore) {
- }
- }
- if ((p = parker) != null)
- U.unpark(p);
- }
-
// Unsafe mechanics
private static final sun.misc.Unsafe U;
private static final long QLOCK;
private static final int ABASE;
private static final int ASHIFT;
static {
- int s;
try {
U = getUnsafe();
Class> k = WorkQueue.class;
@@ -1051,13 +1033,13 @@ public class ForkJoinPool extends Abstra
QLOCK = U.objectFieldOffset
(k.getDeclaredField("qlock"));
ABASE = U.arrayBaseOffset(ak);
- s = U.arrayIndexScale(ak);
+ int scale = U.arrayIndexScale(ak);
+ if ((scale & (scale - 1)) != 0)
+ throw new Error("data type scale not a power of two");
+ ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);
} catch (Exception e) {
throw new Error(e);
}
- if ((s & (s-1)) != 0)
- throw new Error("data type scale not a power of two");
- ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
}
}
@@ -1091,12 +1073,12 @@ public class ForkJoinPool extends Abstra
* to paranoically avoid potential initialization circularities
* as well as to simplify generated code.
*/
- static final ForkJoinPool commonPool;
+ static final ForkJoinPool common;
/**
- * Common pool parallelism. Must equal commonPool.parallelism.
+ * Common pool parallelism. Must equal common.parallelism.
*/
- static final int commonPoolParallelism;
+ static final int commonParallelism;
/**
* Sequence number for creating workerNamePrefix.
@@ -1104,8 +1086,8 @@ public class ForkJoinPool extends Abstra
private static int poolNumberSequence;
/**
- * Return the next sequence number. We don't expect this to
- * ever contend so use simple builtin sync.
+ * Returns the next sequence number. We don't expect this to
+ * ever contend, so use simple builtin sync.
*/
private static final synchronized int nextPoolId() {
return ++poolNumberSequence;
@@ -1129,6 +1111,11 @@ public class ForkJoinPool extends Abstra
private static final long FAST_IDLE_TIMEOUT = 200L * 1000L * 1000L;
/**
+ * Tolerance for idle timeouts, to cope with timer undershoots
+ */
+ private static final long TIMEOUT_SLOP = 2000000L;
+
+ /**
* The maximum stolen->joining link depth allowed in method
* tryHelpStealer. Must be a power of two. Depths for legitimate
* chains are unbounded, but we use a fixed constant to avoid
@@ -1257,15 +1244,13 @@ public class ForkJoinPool extends Abstra
volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17;
volatile Object pad18, pad19, pad1a, pad1b;
- /*
+ /**
* Acquires the plock lock to protect worker array and related
* updates. This method is called only if an initial CAS on plock
- * fails. This acts as a spinLock for normal cases, but falls back
+ * fails. This acts as a spinlock for normal cases, but falls back
* to builtin monitor to block when (rarely) needed. This would be
* a terrible idea for a highly contended lock, but works fine as
- * a more conservative alternative to a pure spinlock. See
- * internal ConcurrentHashMap documentation for further
- * explanation of nearly the same construction.
+ * a more conservative alternative to a pure spinlock.
*/
private int acquirePlock() {
int spins = PL_SPINS, r = 0, ps, nps;
@@ -1317,41 +1302,8 @@ public class ForkJoinPool extends Abstra
}
/**
- * Performs secondary initialization, called when plock is zero.
- * Creates workQueue array and sets plock to a valid value. The
- * lock body must be exception-free (so no try/finally) so we
- * optimistically allocate new array outside the lock and throw
- * away if (very rarely) not needed. (A similar tactic is used in
- * fullExternalPush.) Because the plock seq value can eventually
- * wrap around zero, this method harmlessly fails to reinitialize
- * if workQueues exists, while still advancing plock.
- *
- * Additonally tries to create the first worker.
- */
- private void initWorkers() {
- WorkQueue[] ws, nws; int ps;
- int p = config & SMASK; // find power of two table size
- int n = (p > 1) ? p - 1 : 1; // ensure at least 2 slots
- n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8; n |= n >>> 16;
- n = (n + 1) << 1;
- if ((ws = workQueues) == null || ws.length == 0)
- nws = new WorkQueue[n];
- else
- nws = null;
- if (((ps = plock) & PL_LOCK) != 0 ||
- !U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
- ps = acquirePlock();
- if (((ws = workQueues) == null || ws.length == 0) && nws != null)
- workQueues = nws;
- int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
- if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
- releasePlock(nps);
- tryAddWorker();
- }
-
- /**
- * Tries to create and start one worker. Adjusts counts etc on
- * failure.
+ * Tries to create and start one worker if fewer than target
+ * parallelism level exist. Adjusts counts etc on failure.
*/
private void tryAddWorker() {
long c; int u;
@@ -1461,21 +1413,42 @@ public class ForkJoinPool extends Abstra
}
}
- long c; // adjust ctl counts
+ long c; // adjust ctl counts
do {} while (!U.compareAndSwapLong
(this, CTL, c = ctl, (((c - AC_UNIT) & AC_MASK) |
((c - TC_UNIT) & TC_MASK) |
(c & ~(AC_MASK|TC_MASK)))));
- if (!tryTerminate(false, false) && w != null) {
- w.cancelAll(); // cancel remaining tasks
- if (w.array != null) // suppress signal if never ran
- tryAddWorker(); // create replacement
- if (ex == null) // help clean refs on way out
- ForkJoinTask.helpExpungeStaleExceptions();
+ if (!tryTerminate(false, false) && w != null && w.array != null) {
+ w.cancelAll(); // cancel remaining tasks
+ WorkQueue[] ws; WorkQueue v; Thread p; int u, i, e;
+ while ((u = (int)((c = ctl) >>> 32)) < 0 && (e = (int)c) >= 0) {
+ if (e > 0) { // activate or create replacement
+ if ((ws = workQueues) == null ||
+ (i = e & SMASK) >= ws.length ||
+ (v = ws[i]) == null)
+ break;
+ long nc = (((long)(v.nextWait & E_MASK)) |
+ ((long)(u + UAC_UNIT) << 32));
+ if (v.eventCount != (e | INT_SIGN))
+ break;
+ if (U.compareAndSwapLong(this, CTL, c, nc)) {
+ v.eventCount = (e + E_SEQ) & E_MASK;
+ if ((p = v.parker) != null)
+ U.unpark(p);
+ break;
+ }
+ }
+ else {
+ if ((short)u < 0)
+ tryAddWorker();
+ break;
+ }
+ }
}
-
- if (ex != null) // rethrow
+ if (ex == null) // help clean refs on way out
+ ForkJoinTask.helpExpungeStaleExceptions();
+ else // rethrow
ForkJoinTask.rethrow(ex);
}
@@ -1513,13 +1486,19 @@ public class ForkJoinPool extends Abstra
/**
* Full version of externalPush. This method is called, among
* other times, upon the first submission of the first task to the
- * pool, so must perform secondary initialization (via
- * initWorkers). It also detects first submission by an external
- * thread by looking up its ThreadLocal, and creates a new shared
- * queue if the one at index if empty or contended. The plock lock
- * body must be exception-free (so no try/finally) so we
- * optimistically allocate new queues outside the lock and throw
- * them away if (very rarely) not needed.
+ * pool, so must perform secondary initialization. It also
+ * detects first submission by an external thread by looking up
+ * its ThreadLocal, and creates a new shared queue if the one at
+ * index if empty or contended. The plock lock body must be
+ * exception-free (so no try/finally) so we optimistically
+ * allocate new queues outside the lock and throw them away if
+ * (very rarely) not needed.
+ *
+ * Secondary initialization occurs when plock is zero, to create
+ * workQueue array and set plock to a valid value. This lock body
+ * must also be exception-free. Because the plock seq value can
+ * eventually wrap around zero, this method harmlessly fails to
+ * reinitialize if workQueues exists, while still advancing plock.
*/
private void fullExternalPush(ForkJoinTask> task) {
int r = 0; // random index seed
@@ -1530,17 +1509,31 @@ public class ForkJoinPool extends Abstra
r += SEED_INCREMENT) && r != 0)
submitters.set(z = new Submitter(r));
}
- else if (r == 0) { // move to a different index
+ else if (r == 0) { // move to a different index
r = z.seed;
- r ^= r << 13; // same xorshift as WorkQueues
+ r ^= r << 13; // same xorshift as WorkQueues
r ^= r >>> 17;
z.seed = r ^ (r << 5);
}
else if ((ps = plock) < 0)
throw new RejectedExecutionException();
else if (ps == 0 || (ws = workQueues) == null ||
- (m = ws.length - 1) < 0)
- initWorkers();
+ (m = ws.length - 1) < 0) { // initialize workQueues
+ int p = config & SMASK; // find power of two table size
+ int n = (p > 1) ? p - 1 : 1; // ensure at least 2 slots
+ n |= n >>> 1; n |= n >>> 2; n |= n >>> 4;
+ n |= n >>> 8; n |= n >>> 16; n = (n + 1) << 1;
+ WorkQueue[] nws = ((ws = workQueues) == null || ws.length == 0 ?
+ new WorkQueue[n] : null);
+ if (((ps = plock) & PL_LOCK) != 0 ||
+ !U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
+ ps = acquirePlock();
+ if (((ws = workQueues) == null || ws.length == 0) && nws != null)
+ workQueues = nws;
+ int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
+ if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
+ releasePlock(nps);
+ }
else if ((q = ws[k = r & m & SQMASK]) != null) {
if (q.qlock == 0 && U.compareAndSwapInt(q, QLOCK, 0, 1)) {
ForkJoinTask>[] a = q.array;
@@ -1660,12 +1653,14 @@ public class ForkJoinPool extends Abstra
*
* * If not already enqueued, try to inactivate and enqueue the
* worker on wait queue. Or, if inactivating has caused the pool
- * to be quiescent, relay to idleAwaitWork to check for
- * termination and possibly shrink pool.
+ * to be quiescent, relay to idleAwaitWork to possibly shrink
+ * pool.
*
* * If already enqueued and none of the above apply, possibly
- * (with 1/2 probability) park awaiting signal, else lingering to
- * help scan and signal.
+ * park awaiting signal, else lingering to help scan and signal.
+ *
+ * * If a non-empty queue discovered or left as a hint,
+ * help wake up other workers before return.
*
* @param w the worker (via its WorkQueue)
* @return a task or null if none found
@@ -1676,6 +1671,7 @@ public class ForkJoinPool extends Abstra
if (w != null && (ws = workQueues) != null && (m = ws.length - 1) >= 0) {
int ec = w.eventCount; // ec is negative if inactive
int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
+ w.hint = -1; // update seed and clear hint
int j = ((m + m + 1) | MIN_SCAN) & MAX_SCAN;
do {
WorkQueue q; ForkJoinTask>[] a; int b;
@@ -1697,40 +1693,64 @@ public class ForkJoinPool extends Abstra
}
} while (--j >= 0);
- long c, sc; int e, ns, h;
- if ((h = w.hint) < 0) {
- if ((ns = w.nsteals) != 0) {
- if (U.compareAndSwapLong(this, STEALCOUNT,
- sc = stealCount, sc + ns))
- w.nsteals = 0; // collect steals
- }
- else if (plock != ps) // consistency check
- ; // skip
- else if ((e = (int)(c = ctl)) < 0)
- w.qlock = -1; // pool is terminating
- else if (ec >= 0) { // try to enqueue/inactivate
- long nc = ((long)ec | ((c - AC_UNIT) & (AC_MASK|TC_MASK)));
- w.nextWait = e; // link and mark inactive
- w.eventCount = ec | INT_SIGN;
- if (ctl != c || !U.compareAndSwapLong(this, CTL, c, nc))
- w.eventCount = ec; // unmark on CAS failure
- else if ((int)(c >> AC_SHIFT) == 1 - (config & SMASK))
- idleAwaitWork(w, nc, c);
- }
- else if (w.eventCount < 0) { // block
- Thread wt = Thread.currentThread();
- Thread.interrupted(); // clear status
- U.putObject(wt, PARKBLOCKER, this);
- w.parker = wt; // emulate LockSupport.park
- if (w.eventCount < 0) // recheck
- U.park(false, 0L);
- w.parker = null;
- U.putObject(wt, PARKBLOCKER, null);
- }
- }
- if (h >= 0 || (h = w.hint) >= 0) { // signal others before retry
- w.hint = -1; // reset
- helpSignal(null, h, true);
+ int h, e, ns; long c, sc; WorkQueue q;
+ if ((ns = w.nsteals) != 0) {
+ if (U.compareAndSwapLong(this, STEALCOUNT,
+ sc = stealCount, sc + ns))
+ w.nsteals = 0; // collect steals and rescan
+ }
+ else if (plock != ps) // consistency check
+ ; // skip
+ else if ((e = (int)(c = ctl)) < 0)
+ w.qlock = -1; // pool is terminating
+ else {
+ if ((h = w.hint) < 0) {
+ if (ec >= 0) { // try to enqueue/inactivate
+ long nc = (((long)ec |
+ ((c - AC_UNIT) & (AC_MASK|TC_MASK))));
+ w.nextWait = e; // link and mark inactive
+ w.eventCount = ec | INT_SIGN;
+ if (ctl != c || !U.compareAndSwapLong(this, CTL, c, nc))
+ w.eventCount = ec; // unmark on CAS failure
+ else if ((int)(c >> AC_SHIFT) == 1 - (config & SMASK))
+ idleAwaitWork(w, nc, c);
+ }
+ else if (w.eventCount < 0 && ctl == c) {
+ Thread wt = Thread.currentThread();
+ Thread.interrupted(); // clear status
+ U.putObject(wt, PARKBLOCKER, this);
+ w.parker = wt; // emulate LockSupport.park
+ if (w.eventCount < 0) // recheck
+ U.park(false, 0L); // block
+ w.parker = null;
+ U.putObject(wt, PARKBLOCKER, null);
+ }
+ }
+ if ((h >= 0 || (h = w.hint) >= 0) &&
+ (ws = workQueues) != null && h < ws.length &&
+ (q = ws[h]) != null) { // signal others before retry
+ WorkQueue v; Thread p; int u, i, s;
+ for (int n = (config & SMASK) - 1;;) {
+ int idleCount = (w.eventCount < 0) ? 0 : -1;
+ if (((s = idleCount - q.base + q.top) <= n &&
+ (n = s) <= 0) ||
+ (u = (int)((c = ctl) >>> 32)) >= 0 ||
+ (e = (int)c) <= 0 || m < (i = e & SMASK) ||
+ (v = ws[i]) == null)
+ break;
+ long nc = (((long)(v.nextWait & E_MASK)) |
+ ((long)(u + UAC_UNIT) << 32));
+ if (v.eventCount != (e | INT_SIGN) ||
+ !U.compareAndSwapLong(this, CTL, c, nc))
+ break;
+ v.hint = h;
+ v.eventCount = (e + E_SEQ) & E_MASK;
+ if ((p = v.parker) != null)
+ U.unpark(p);
+ if (--n <= 0)
+ break;
+ }
+ }
}
}
return null;
@@ -1750,10 +1770,11 @@ public class ForkJoinPool extends Abstra
*/
private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
if (w != null && w.eventCount < 0 &&
- !tryTerminate(false, false) && (int)prevCtl != 0) {
+ !tryTerminate(false, false) && (int)prevCtl != 0 &&
+ ctl == currentCtl) {
int dc = -(short)(currentCtl >>> TC_SHIFT);
long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
- long deadline = System.nanoTime() + parkTime - 100000L; // 1ms slop
+ long deadline = System.nanoTime() + parkTime - TIMEOUT_SLOP;
Thread wt = Thread.currentThread();
while (ctl == currentCtl) {
Thread.interrupted(); // timed variant of version in scan()
@@ -1768,6 +1789,7 @@ public class ForkJoinPool extends Abstra
if (deadline - System.nanoTime() <= 0L &&
U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
w.eventCount = (w.eventCount + E_SEQ) | E_MASK;
+ w.hint = -1;
w.qlock = -1; // shrink
break;
}
@@ -1776,26 +1798,25 @@ public class ForkJoinPool extends Abstra
}
/**
- * Scans through queues looking for work (optionally, while
- * joining a task); if any present, signals. May return early if
- * more signalling is detectably unneeded.
+ * Scans through queues looking for work while joining a task; if
+ * any present, signals. May return early if more signalling is
+ * detectably unneeded.
*
- * @param task if non-null, return early if done
+ * @param task return early if done
* @param origin an index to start scan
- * @param once if only the origin should be checked
*/
- private void helpSignal(ForkJoinTask> task, int origin, boolean once) {
+ private void helpSignal(ForkJoinTask> task, int origin) {
WorkQueue[] ws; WorkQueue w; Thread p; long c; int m, u, e, i, s;
- if ((u = (int)(ctl >>> 32)) < 0 && (u >> UAC_SHIFT) < 0 &&
+ if (task != null && task.status >= 0 &&
+ (u = (int)(ctl >>> 32)) < 0 && (u >> UAC_SHIFT) < 0 &&
(ws = workQueues) != null && (m = ws.length - 1) >= 0) {
- outer: for (int k = origin, j = once? 0 : m; j >= 0; --j) {
+ outer: for (int k = origin, j = m; j >= 0; --j) {
WorkQueue q = ws[k++ & m];
for (int n = m;;) { // limit to at most m signals
- if (task != null && task.status < 0)
+ if (task.status < 0)
break outer;
if (q == null ||
- ((s = (task == null ? -1 : 0) - q.base + q.top) <= n &&
- (n = s) <= 0))
+ ((s = -q.base + q.top) <= n && (n = s) <= 0))
break;
if ((u = (int)((c = ctl) >>> 32)) >= 0 ||
(e = (int)c) <= 0 || m < (i = e & SMASK) ||
@@ -1803,8 +1824,9 @@ public class ForkJoinPool extends Abstra
break outer;
long nc = (((long)(w.nextWait & E_MASK)) |
((long)(u + UAC_UNIT) << 32));
- if (w.eventCount == (e | INT_SIGN) &&
- U.compareAndSwapLong(this, CTL, c, nc)) {
+ if (w.eventCount != (e | INT_SIGN))
+ break outer;
+ if (U.compareAndSwapLong(this, CTL, c, nc)) {
w.eventCount = (e + E_SEQ) & E_MASK;
if ((p = w.parker) != null)
U.unpark(p);
@@ -1909,7 +1931,6 @@ public class ForkJoinPool extends Abstra
* @param task the task to join
* @param mode if shared, exit upon completing any task
* if all workers are active
- *
*/
private int helpComplete(ForkJoinTask> task, int mode) {
WorkQueue[] ws; WorkQueue q; int m, n, s, u;
@@ -1996,7 +2017,7 @@ public class ForkJoinPool extends Abstra
do {} while ((s = task.status) >= 0 && !joiner.isEmpty() &&
joiner.tryRemoveAndExec(task)); // process local tasks
if (s >= 0 && (s = task.status) >= 0) {
- helpSignal(task, joiner.poolIndex, false);
+ helpSignal(task, joiner.poolIndex);
if ((s = task.status) >= 0 &&
(task instanceof CountedCompleter))
s = helpComplete(task, LIFO_QUEUE);
@@ -2005,7 +2026,7 @@ public class ForkJoinPool extends Abstra
if ((!joiner.isEmpty() || // try helping
(s = tryHelpStealer(joiner, task)) == 0) &&
(s = task.status) >= 0) {
- helpSignal(task, joiner.poolIndex, false);
+ helpSignal(task, joiner.poolIndex);
if ((s = task.status) >= 0 && tryCompensate()) {
if (task.trySetSignal() && (s = task.status) >= 0) {
synchronized (task) {
@@ -2046,7 +2067,7 @@ public class ForkJoinPool extends Abstra
do {} while ((s = task.status) >= 0 && !joiner.isEmpty() &&
joiner.tryRemoveAndExec(task));
if (s >= 0 && (s = task.status) >= 0) {
- helpSignal(task, joiner.poolIndex, false);
+ helpSignal(task, joiner.poolIndex);
if ((s = task.status) >= 0 &&
(task instanceof CountedCompleter))
s = helpComplete(task, LIFO_QUEUE);
@@ -2061,29 +2082,22 @@ public class ForkJoinPool extends Abstra
/**
* Returns a (probably) non-empty steal queue, if one is found
- * during a random, then cyclic scan, else null. This method must
- * be retried by caller if, by the time it tries to use the queue,
- * it is empty.
+ * during a scan, else null. This method must be retried by
+ * caller if, by the time it tries to use the queue, it is empty.
* @param r a (random) seed for scanning
*/
private WorkQueue findNonEmptyStealQueue(int r) {
- for (WorkQueue[] ws;;) {
- int ps = plock, m, n;
- if ((ws = workQueues) == null || (m = ws.length - 1) < 1)
- return null;
- for (int j = (m + 1) << 2; ;) {
- WorkQueue q = ws[(((r + j) << 1) | 1) & m];
- if (q != null && (n = q.base - q.top) < 0) {
- if (n < -1)
- signalWork(q);
- return q;
- }
- else if (--j < 0) {
- if (plock == ps)
- return null;
- break;
+ for (;;) {
+ int ps = plock, m; WorkQueue[] ws; WorkQueue q;
+ if ((ws = workQueues) != null && (m = ws.length - 1) >= 0) {
+ for (int j = (m + 1) << 2; j >= 0; --j) {
+ if ((q = ws[(((r + j) << 1) | 1) & m]) != null &&
+ q.base - q.top < 0)
+ return q;
}
}
+ if (plock == ps)
+ return null;
}
}
@@ -2095,37 +2109,34 @@ public class ForkJoinPool extends Abstra
*/
final void helpQuiescePool(WorkQueue w) {
for (boolean active = true;;) {
- ForkJoinTask> localTask; // exhaust local queue
- while ((localTask = w.nextLocalTask()) != null)
- localTask.doExec();
- // Similar to loop in scan(), but ignoring submissions
- WorkQueue q = findNonEmptyStealQueue(w.nextSeed());
- if (q != null) {
- ForkJoinTask> t; int b;
+ long c; WorkQueue q; ForkJoinTask> t; int b;
+ while ((t = w.nextLocalTask()) != null) {
+ if (w.base - w.top < 0)
+ signalWork(w);
+ t.doExec();
+ }
+ if ((q = findNonEmptyStealQueue(w.nextSeed())) != null) {
if (!active) { // re-establish active count
- long c;
active = true;
do {} while (!U.compareAndSwapLong
(this, CTL, c = ctl, c + AC_UNIT));
}
- if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
+ if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null) {
+ if (q.base - q.top < 0)
+ signalWork(q);
w.runSubtask(t);
+ }
}
- else {
- long c;
- if (active) { // decrement active count without queuing
+ else if (active) { // decrement active count without queuing
+ long nc = (c = ctl) - AC_UNIT;
+ if ((int)(nc >> AC_SHIFT) + (config & SMASK) == 0)
+ return; // bypass decrement-then-increment
+ if (U.compareAndSwapLong(this, CTL, c, nc))
active = false;
- do {} while (!U.compareAndSwapLong
- (this, CTL, c = ctl, c -= AC_UNIT));
- }
- else
- c = ctl; // re-increment on exit
- if ((int)(c >> AC_SHIFT) + (config & SMASK) == 0) {
- do {} while (!U.compareAndSwapLong
- (this, CTL, c = ctl, c + AC_UNIT));
- break;
- }
}
+ else if ((int)((c = ctl) >> AC_SHIFT) + (config & SMASK) == 0 &&
+ U.compareAndSwapLong(this, CTL, c, c + AC_UNIT))
+ return;
}
}
@@ -2141,8 +2152,11 @@ public class ForkJoinPool extends Abstra
return t;
if ((q = findNonEmptyStealQueue(w.nextSeed())) == null)
return null;
- if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
+ if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null) {
+ if (q.base - q.top < 0)
+ signalWork(q);
return t;
+ }
}
}
@@ -2171,7 +2185,7 @@ public class ForkJoinPool extends Abstra
* producing extra tasks amortizes the uncertainty of progress and
* diffusion assumptions.
*
- * So, users will want to use values larger, but not much larger
+ * So, users will want to use values larger (but not much larger)
* than 1 to both smooth over transient shortages and hedge
* against uneven progress; as traded off against the cost of
* extra task overhead. We leave the user to pick a threshold
@@ -2224,61 +2238,71 @@ public class ForkJoinPool extends Abstra
* @return true if now terminating or terminated
*/
private boolean tryTerminate(boolean now, boolean enable) {
- if (this == commonPool) // cannot shut down
+ int ps;
+ if (this == common) // cannot shut down
return false;
+ if ((ps = plock) >= 0) { // enable by setting plock
+ if (!enable)
+ return false;
+ if ((ps & PL_LOCK) != 0 ||
+ !U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
+ ps = acquirePlock();
+ int nps = ((ps + PL_LOCK) & ~SHUTDOWN) | SHUTDOWN;
+ if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
+ releasePlock(nps);
+ }
for (long c;;) {
- if (((c = ctl) & STOP_BIT) != 0) { // already terminating
+ if (((c = ctl) & STOP_BIT) != 0) { // already terminating
if ((short)(c >>> TC_SHIFT) == -(config & SMASK)) {
synchronized (this) {
- notifyAll(); // signal when 0 workers
+ notifyAll(); // signal when 0 workers
}
}
return true;
}
- if (plock >= 0) { // not yet enabled
- int ps;
- if (!enable)
- return false;
- if (((ps = plock) & PL_LOCK) != 0 ||
- !U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
- ps = acquirePlock();
- int nps = SHUTDOWN;
- if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
- releasePlock(nps);
- }
- if (!now) { // check if idle & no tasks
- if ((int)(c >> AC_SHIFT) != -(config & SMASK) ||
- hasQueuedSubmissions())
+ if (!now) { // check if idle & no tasks
+ WorkQueue[] ws; WorkQueue w;
+ if ((int)(c >> AC_SHIFT) != -(config & SMASK))
return false;
- // Check for unqueued inactive workers. One pass suffices.
- WorkQueue[] ws = workQueues; WorkQueue w;
- if (ws != null) {
- for (int i = 1; i < ws.length; i += 2) {
- if ((w = ws[i]) != null && w.eventCount >= 0)
- return false;
+ if ((ws = workQueues) != null) {
+ for (int i = 0; i < ws.length; ++i) {
+ if ((w = ws[i]) != null) {
+ if (!w.isEmpty()) { // signal unprocessed tasks
+ signalWork(w);
+ return false;
+ }
+ if ((i & 1) != 0 && w.eventCount >= 0)
+ return false; // unqueued inactive worker
+ }
}
}
}
if (U.compareAndSwapLong(this, CTL, c, c | STOP_BIT)) {
for (int pass = 0; pass < 3; ++pass) {
- WorkQueue[] ws = workQueues;
- if (ws != null) {
- WorkQueue w;
+ WorkQueue[] ws; WorkQueue w; Thread wt;
+ if ((ws = workQueues) != null) {
int n = ws.length;
for (int i = 0; i < n; ++i) {
if ((w = ws[i]) != null) {
w.qlock = -1;
if (pass > 0) {
w.cancelAll();
- if (pass > 1)
- w.interruptOwner();
+ if (pass > 1 && (wt = w.owner) != null) {
+ if (!wt.isInterrupted()) {
+ try {
+ wt.interrupt();
+ } catch (Throwable ignore) {
+ }
+ }
+ U.unpark(wt);
+ }
}
}
}
// Wake up workers parked on event queue
int i, e; long cc; Thread p;
while ((e = (int)(cc = ctl) & E_MASK) != 0 &&
- (i = e & SMASK) < n &&
+ (i = e & SMASK) < n && i >= 0 &&
(w = ws[i]) != null) {
long nc = ((long)(w.nextWait & E_MASK) |
((cc + AC_UNIT) & AC_MASK) |
@@ -2306,7 +2330,7 @@ public class ForkJoinPool extends Abstra
static WorkQueue commonSubmitterQueue() {
ForkJoinPool p; WorkQueue[] ws; int m; Submitter z;
return ((z = submitters.get()) != null &&
- (p = commonPool) != null &&
+ (p = common) != null &&
(ws = p.workQueues) != null &&
(m = ws.length - 1) >= 0) ?
ws[m & z.seed & SQMASK] : null;
@@ -2320,7 +2344,7 @@ public class ForkJoinPool extends Abstra
ForkJoinTask>[] a; int m, s;
if (t != null &&
(z = submitters.get()) != null &&
- (p = commonPool) != null &&
+ (p = common) != null &&
(ws = p.workQueues) != null &&
(m = ws.length - 1) >= 0 &&
(q = ws[m & z.seed & SQMASK]) != null &&
@@ -2378,7 +2402,7 @@ public class ForkJoinPool extends Abstra
(u = (int)(ctl >>> 32)) >= 0 || (u >> UAC_SHIFT) >= 0)
break;
if (task == null) {
- helpSignal(root, q.poolIndex, false);
+ helpSignal(root, q.poolIndex);
if (root.status >= 0)
helpComplete(root, SHARED_QUEUE);
break;
@@ -2397,7 +2421,7 @@ public class ForkJoinPool extends Abstra
ForkJoinTask>[] a; int m, s, n;
if (t != null &&
(z = submitters.get()) != null &&
- (p = commonPool) != null &&
+ (p = common) != null &&
(ws = p.workQueues) != null &&
(m = ws.length - 1) >= 0 &&
(q = ws[m & z.seed & SQMASK]) != null &&
@@ -2421,23 +2445,11 @@ public class ForkJoinPool extends Abstra
if (t instanceof CountedCompleter)
p.externalHelpComplete(q, t);
else
- p.helpSignal(t, q.poolIndex, false);
+ p.helpSignal(t, q.poolIndex);
}
}
}
- /**
- * Restricted version of helpQuiescePool for external callers
- */
- static void externalHelpQuiescePool() {
- ForkJoinPool p; ForkJoinTask> t; WorkQueue q; int b;
- if ((p = commonPool) != null &&
- (q = p.findNonEmptyStealQueue(1)) != null &&
- (b = q.base) - q.top < 0 &&
- (t = q.pollAt(b)) != null)
- t.doExec();
- }
-
// Exported methods
// Constructors
@@ -2454,7 +2466,7 @@ public class ForkJoinPool extends Abstra
* java.lang.RuntimePermission}{@code ("modifyThread")}
*/
public ForkJoinPool() {
- this(Runtime.getRuntime().availableProcessors(),
+ this(Math.min(MAX_CAP, Runtime.getRuntime().availableProcessors()),
defaultForkJoinWorkerThreadFactory, null, false);
}
@@ -2536,13 +2548,21 @@ public class ForkJoinPool extends Abstra
}
/**
- * Returns the common pool instance.
+ * Returns the common pool instance. This pool is statically
+ * constructed; its run state is unaffected by attempts to {@link
+ * #shutdown} or {@link #shutdownNow}. However this pool and any
+ * ongoing processing are automatically terminated upon program
+ * {@link System#exit}. Any program that relies on asynchronous
+ * task processing to complete before program termination should
+ * invoke {@code commonPool().}{@link #awaitQuiescence}, before
+ * exit.
*
* @return the common pool instance
+ * @since 1.8
*/
public static ForkJoinPool commonPool() {
- // assert commonPool != null : "static init error";
- return commonPool;
+ // assert common != null : "static init error";
+ return common;
}
// Execution methods
@@ -2665,27 +2685,23 @@ public class ForkJoinPool extends Abstra
// In previous versions of this class, this method constructed
// a task to run ForkJoinTask.invokeAll, but now external
// invocation of multiple tasks is at least as efficient.
- List